USMLE 1 MCQ3

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    <1>A 72-year-old male is noted as having a 9-pound weight loss over the past
    few weeks. His past medical history is significant for oat cell carcinoma of
    the lung, without known metastases, for which he is currently undergoing
    treatment. The patient states that even though his wife is preparing his
    favorite meals, he is not hungry. Which of the following would be the
    best treatment option to improve his eating habits?
    A. Amitriptyline
    B. Megestrol acetate
    C. Methotrexate
    D. Neostigmine
    E. Prochlorperazine

    Answer
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    <2>A 45-year-old homeless man has a chronic cough, a cavitary lesion of the
    lung, and is sputum positive for acid-fast bacilli. Which of the following
    is the principle form of defense by which the patient's body fights this
    infection?
    A. Antibody-mediated phagocytosis
    B. Cell-mediated immunity
    C. IgA-mediated hypersensitivity
    D. IgE-mediated hypersensitivity
    E. Neutrophil ingestion of bacteria


    Answer
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    <3>A researcher is examining the distribution of an ion channel protein in
    the kidney. She incubates slices of kidney tissue in a dilute solution of
    a specific antibody directed against the protein, then uses the
    immunoperoxidase method to localize the ion channel proteins.
    She notes the presence of brown pigment in a population of epithelial
    cells, which on closer examination, have a brush border. The researcher
    concludes that the protein is probably present in cells of the
    A. collecting duct
    B. deep portion of loop of Henle
    C. distal convoluted tubule
    D. glomerulus
    E. proximal convoluted tubule



    Answer
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    <4>A 38-year-old pregnant woman with a past medical history significant for
    chronic hypertension presents with a blood pressure of 158/105 mm Hg. Which
    of the following antihypertensive agents would be most suitable for initial therapy in this patient?
    A. Bumetanide
    B. Fosinopril
    C. Hydrochlorothiazide
    D. Methyldopa
    E. Valsartan



    Answer
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    <5>A 3 year-old boy is brought to a physician because the mother notices tha
    t the child is engaging in less active play and tires easily. During physical
    examination, the pediatrician notices that the child's thighs are larger
    than normal for age and that the child cannot stand up without using his
    arms to help. Further studies demonstrate a defective dystrophin gene in
    the boy. Which of the following people in the child's family is most
    likely to also have this disease?
    A. Father
    B. Father's brother
    C. Mother
    D. Mother's brother
    E. Sister


    Answer
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    <6> The leukocyte pictured above stains intensely with acidic dyes such
    as eosin. Which of the following substances is contained in the crystalline
    core of the granule at the arrow?
    A. Lactoferrin
    B. Major basic protein
    C. Myeloperoxidase
    D. Histamine
    E. Tartrate-resistant acid phosphatase


    Answer
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    <7>A 7-year-old boy is brought to a physician because of a nearly confluent,
    fine, erythematous, macular rash that is most pronounced on his trunk. He
    has had a mild fever for 36 hours, but does not appear very sick, and is
    happily playing when the pediatrician enters the examining room. Physical
    examination demonstrates a reddened throat with tonsillar exudates,
    enlarged cervical nodes including the occipital node, and questionable
    splenomegaly. The mother says that the boy has not been coughing, and
    no Koplik spots are noted. Which of the following is the most likely
    diagnosis?
    A. Bullous pemphigoid
    B. Dermatitis herpetiformis
    C. Herpes simplex
    D. Measles
    E. Rubella



    Answer
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    <8>A child who has had abnormal development of the membranous bones has a
    broad skull with associated facial and dental anomalies. Which other bones
    are most likely to also be affected?

    A. clavicles
    B. Femurs
    C. Metatarsals
    D. Phalanges
    E. Tibias

    Answer
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    <9>A 33-year-old woman presents with fever, vomiting, severe irritative
    voiding symptoms, and pronounced costovertebral angle tenderness.
    Laboratory evaluation reveals leukocytosis with a left shift; blood
    cultures indicate bacteremia. Urinalysis shows pyuria, mild hematuria,
    and gram-negative bacteria. Which of the following drugs would best
    treat this patient's infection?
    A. Ampicillin and gentamicin
    B. Erythromycin
    C. Gentamicin and vancomycin
    D. Phenazopyridine and nitrofurantoin
    E. Tetracycline

    Answer
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    <10>A surgical pathology specimen from a 24-year-old woman seen at a
    reproductive medicine clinic demonstrates a ciliated columnar epithelium.
    From which of the following locations in the female genital tract was the
    biopsy obtained?
    A. Cervix
    B. Endometrium
    C. Fallopian tube
    D. Ovary
    E. Vagina

    Answer
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    <11>In a genotypic male, the testes fail to develop, and do not secrete
    testosterone or Müllerian regression factor. Which of the following best
    describes the in utero reproductive system development of this individual ?
    A. Both male- and female-type internal reproductive tracts and male-type external genitalia
    B. Female-type internal reproductive tract and female-type external genitalia
    C. Female-type internal reproductive tract and male-type external genitalia
    D. Male-type internal reproductive tract and female-type external genitalia
    E. Male-type internal reproductive tract and male-type external genitalia

    Answer
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    <12>A pulmonologist is testing a patient's lung volumes and capacities using
    simple spirometry. Which of the following lung volumes or capacities cannot
    be measured directly using this technique?
    A. Expiratory reserve volume
    B. Functional residual capacity
    C. Inspiratory reserve volume
    D. Tidal volume
    E. Vital capacity

    Answer
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    <13>Contraction of which of the following muscles contributes most to the
    backward movement of the lower jaw during the process of mastication?
    A. Digastric
    B. Lateral pterygoid
    C. Medial pterygoid
    D. Mylohyoid
    E. Temporalis

    Answer
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    <14>A 28-year-old female presents to the doctor complaining of syncopal
    episodes that last a few minutes. She is not taking any medications and
    has no previous medical history. EEG and EKG studies are performed and
    are unremarkable. An echocardiogram shows a single ball-shaped mass
    dangling in the left atrium near the mitral valve. The most likely
    diagnosis is
    A. angiosarcoma
    B. mesothelioma
    C. myxoma
    D. rhabdomyoma
    E. rhabdomyosarcoma

    Answer
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    <15>A patient who has been exhibiting various endocrine abnormalities
    has an MRI scan of the head. This scan reveals a small tumor of the
    pituitary gland. If this tumor expands laterally, which of the following
    nerves will most likely be affected first?
    A. Abducens nerve
    B. Oculomotor nerve
    C. Optic nerve
    D. Trigeminal nerve
    E. Trochlear nerve

    Answer
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    <16>A liver biopsy from a 54-year-old man shows many Mallory bodies. This
    finding is most suggestive of which of the following diseases?
    A. Alcohol abuse
    B. Alpha1-antitrypsin deficiency
    C. Hepatitis A
    D. Hepatitis B
    E. Wilson's disease

    Answer
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    <17>A 27-year-old man has been arrested by the police for hitting, cursing
    at, and verbally berating his wife of 8 years. The wife tells the police he
    also regularly physically whips his 7-year-old son with a leather belt and
    often strikes the boy with his hand. When asked why he does this, he
    responds that this is "how my father treated me, it's how men should act." This represents which of the following types of learning?
    A. Classical conditioning
    B. Cognitive learning
    C. Imprinting
    D. Operant conditioning
    E. Social learning

    Answer
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    <18>A 64-year-old man presents to his doctor with aching, burning pain afte
    r meals. He had been self-medicating for several months with antacids, but
    he found this to be increasingly ineffective. His physician decides to take
    him off the antacids and instead places him on a combination of ranitidine
    and sucralfate. Why is this combination a bad idea?
    A. Ranitidine increases the toxicity of sucralfate
    B. Ranitidine inhibits the action of sucralfate
    C. Sucralfate and ranitidine coprecipitate
    D. Sucralfate increases the toxicity of ranitidine
    E. Sucralfate inhibits the action of ranitidine

    Answer
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    <19>A 42-year-old female presents with a recent onset of fatigue, malaise,
    constipation, and a 12-pound weight gain. On examination, her thyroid is
    firm and enlarged. What laboratory test is most likely to confirm the
    expected diagnosis?
    A. Antithyroid antibodies
    B. Serum thyroid-stimulating hormone (TSH) measurement
    C. Serum thyroxine (T4) measurement
    D. Serum triiodothyronine (T3) measurement
    E. T3 resin uptake

    Answer
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    <20>A 70-year-old man with a history of atrial fibrillation is started on an
    oral anticoagulant. His prothrombin time is monitored on a regular basis. A
    few months into his therapy, he begins treatment for a duodenal ulcer and
    he develops symptoms of a bleeding diathesis. Which of the following ulcer
    medications is most likely responsible for this change in his hemostatic
    status?
    A. Cimetidine
    B. Famotidine
    C. Misoprostol
    D. Omeprazole
    E. Ranitidine

    Answer
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    <21>An elderly woman with a history of multiple oral ulcers presents with
    flaccid bullae on her scalp, face, and trunk. Manual pressure on the skin
    produces separation of the upper layer of the epidermis, followed by
    eventual sloughing of the skin. The patient has been in relatively good
    health until recently, and denies taking any medications. A biopsy of one
    of the skin lesions reveals separation of epithelial cells above the
    basal layer. Autoantibodies to which of the following components would
    most likely be found in this patient?
    A. Epidermal basement membrane proteins
    B. Glycoprotein IIb/IIIa
    C. Intercellular junctions of epidermal cells
    D. Intrinsic factor
    E. Type IV collagen

    Answer
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    <22>A 35-year-old woman notices a change in the appearance of a mole on her
    neck. Physical examination reveals that the lesion is an irregular, nodular,
    superficial mass with a variegated appearance. Biopsy demonstrates a primary malignant tumor. Which of the following factors is most predictive of the patient's long term prognosis?
    A. Circumference of lesion
    B. Darkness of lesion
    C. Degree of color variation
    D. Depth of lesion
    E. Sharpness of border between lesion and adjacent skin

    Answer
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    <23>During embryological development, hematopoiesis occurs in different
    organs at different times. Which of the following are the correct organs,
    in the correct sequence, at which hematopoiesis occurs embryologically?
    A. Amnion, yolk sac, placenta, bone marrow
    B. Placenta, liver and spleen, yolk sac, bone marrow
    C. Placenta, spleen and lymphatic organs, bone marrow
    D. Yolk sac, bone marrow, liver and spleen
    E. Yolk sac, liver, spleen and lymphatic organs, bone marrow

    Answer
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    <24>A 6-month-old boy is brought to the pediatrician by his parents, who are
    first cousins. This is their first child. Physical examination reveals a
    small, thin, lethargic infant with slightly misshapen long bones. His
    features are somewhat coarse. Joint movements are restricted, his corneas
    are clouded, and his gums are underdeveloped. His liver is not enlarged.
    Serum levels of acid hydrolases are found to be elevated. The child most
    likely has a defect in which of the following metabolic activities?
    A. Degradation of dermatan sulfate and heparan sulfate
    B. Degradation of gangliosides
    C. Degradation of glycogen
    D. Degradation of sphingomyelin
    E. Phosphorylation of mannose moieties
    F. Phosphorylation of tyrosine moieties

    Answer
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    <25>A particular association determines membership on the basis of members'
    IQ scores. Only those persons who have documented IQ scores at least 2
    standard deviations above the mean on the Wechsler Adult Intelligence
    Scale (WAIS) are eligible for admission. Of a group of 200 people randomly
    selected from the population at large, how many would be eligible for
    membership to this society?
    A. 1
    B. 2
    C. 3
    D. 4
    E. 5

    Answer
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    <26>5 mL of synovial fluid is aspirated from an inflamed knee joint. The
    fluid is yellow-white and cloudy and contains
    200,000 WBC/mm3 (85% neutrophils). Needle-shaped,
    strongly negatively birefringent crystals are seen both within
    and outside neutrophils. These crystals most likely have which of
    the following compositions?
    A. Basic calcium phosphate
    B. Calcium oxalate
    C. Calcium pyrophosphate dihydrate
    D. Cholesterol
    E. Monosodium urate

    Answer
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    <27>A patient has a painful ulcer on the tip of his tongue. Which of the
    following cranial nerves carries the pain sensation he experiences?
    A. V2
    B. V3
    C. VII
    D. IX
    E. X

    Answer
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    <28>A 30-year-old veterinarian on a cattle ranch presents with a 1-to-2-month
    history of malaise, chills, drenching malodorous sweats, fatigue, and
    weakness. He has anorexia and has lost 15 pounds. He has intermittent
    fevers that range up to 103 F (39.4 C). He complains of visual blurring.
    A physical examination reveals mild lymphadenopathy, petechiae, and a
    cardiac murmur consistent with aortic insufficiency. What is the most
    likely etiologic agent?
    A. Bacillus anthracis
    B. Brucella abortus
    C. Coccidioides immitis
    D. Erysipelothrix rhusiopathiae
    E. Trichinella spiralis

    Answer
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    <29>The parents of a 6-month-old child who was normal at birth bring her
    into the clinic. Since their emigration to the U.S. from Eastern Europe
    soon after her birth, the child has developed diminished responsiveness
    , progressive blindness and deafness, and recently, seizures. Serum levels
    of which of the following compounds would be expected to be decreased in
    both of the parents?
    A. Dystrophin
    B. Hexosaminidase A
    C. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT)
    D. Phenylalanine hydroxylase
    E. Vitamin D3

    Answer
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    <30>A 60-year-old male with angina comes to the emergency room with severe
    chest pain unresponsive to sublingual nitroglycerin. An EKG shows ST
    segment elevation in the anterolateral leads, and thrombolytic therapy
    is initiated. If streptokinase is given to this patient, it may produce
    thrombolysis after binding to which of the following proteins?
    A. Antithrombin III
    B. Fibrin
    C. Plasminogen
    D. Protein C
    E. Thrombomodulin

    Answer
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    <31>The left adrenal vein drains directly into which of the following veins?
    A. Hemiazygos vein
    B. Inferior vena cava
    C. Left renal vein
    D. Splenic vein
    E. Superior mesenteric vein

    Answer
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    <32>A premature infant develops progressive difficulty breathing over the
    first few days of life. Deficient surfactant synthesis by which of the
    following cell types may have contributed to the baby's respiratory problems?
    A. Alveolar capillary endothelial cells
    B. Bronchial mucous cells
    C. Bronchial respiratory epithelium
    D. Type I pneumocytes
    E. Type II pneumocytes

    Answer
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    <33>A surgeon performs an exploratory laparotomy, producing a large incision
    in the patient's abdomen. Poor blood supply to which of the following is
    most likely to cause problems during the healing process?
    A. Adipose tissue
    B. Aponeuroses
    C. Loose connective tissue
    D. Muscle
    E. Skin

    Answer
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    <34>A 1-year-old child develops voluminous watery diarrhea and vomiting. She
    is brought to the pediatrician by her parents and evaluated, then sent home
    with instructions for the parents to give the child an electrolyte
    replacement solution. Which of the following viruses is the most likely
    cause of the child's diarrhea?
    A. Coronavirus
    B. Lymphocytic choriomeningitis virus
    C. Norwalk agent
    D. Orbivirus
    E. Rotavirus

    <35>A 2-year-old child presents to the pediatrician with hematuria.
    Examination reveals hypertension and an abdominal mass. A tumor is localized
    to the right kidney and biopsy reveals a stroma containing smooth and
    striated muscle, bone, cartilage, and fat, with areas of necrosis.
    The gene for this disorder has been localized to which of the following
    chromosomes?
    A. 5
    B. 11
    C. 13
    D. 17
    E. 22
    Answer
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    <36>A newborn baby has a prominent defect at the base of his spine through
    which his meninges and spinal cord protrude. A failure of which of the
    following processes is the most common cause of this type of defect?
    A. Development of primary vertebral ossification centers
    B. Development of the body
    C. Development of the pedicle
    D. Development of the superior articular process
    E. Fusion of the vertebral arches

    Answer
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    <37>A 45-year-old male presents to the physician with muscle cramps,
    perioral numbness, and irritability over the past 3 to 4 months. Lab
    results reveal hypocalcemia, normal albumin level, and hyperphosphatemia
    . Parathyroid hormone level is decreased. Alkaline phosphatase level is
    normal. Which of the following is most likely causing this clinical
    scenario?
    A. Bone metastases
    B. Hashimoto's thyroiditis
    C. Hypervitaminosis D
    D. Hypomagnesemia
    E. Previous subtotal thyroidectomy

    Answer
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    <38>In which of the following organs are fenestrated endothelial cells
    common?
    A. Heart
    B. Liver
    C. Lungs
    D. Pancreas
    E. Stomach

    Answer
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    <39>A macroscopic hepatic change known as nutmeg liver is indicative of
    A. acute left-sided heart failure
    B. acute right-sided heart failure
    C. alcohol toxicity
    D. chronic congestive heart failure
    E. liver cirrhosis

    Answer
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    <40>A 26-year-old man is admitted through the emergency department to the
    hospital for a heroin overdose. His heart rate is 45 beats/min, and his
    blood pressure is 75/40 mm Hg. Which of the following best depicts the
    results from an arterial blood sample ?
    pH PaCO2 (mm Hg) HCO3- (mEq/L)
    A. 7.22 66 26
    B. 7.34 29 15
    C. 7.40 40 24
    D. 7.47 20 14
    E. 7.49 48 35


    Answer
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    <41> The maximum expiratory flow-volume curve shown above is created when
    the patient inhales as much air as possible and then expires with maximum
    effort until no more air can be expired. What is the forced vital capacity
    of this patient?
    A. 1.5 Liters
    B. 2.5 Liters
    C. 3.5 Liters
    D. 4.5 Liters
    E. 6.0 Liters

    Answer
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    <42>A 25-year-old male gets into a brawl outside a bar. During the
    altercation, someone pulls out a gun and shoots him in the head.
    The bullet enters the man's temple and severs his right optic nerve
    completely. He is quickly transported to a nearby emergency room and
    an emergency physician tests his pupillary response by shining a light
    in the right eye. What will the physician most likely find?
    A. No pupillary constriction in the right eye, and no pupillary constriction in the left eye
    B. No pupillary constriction in the right eye, but pupillary constriction in the left eye
    C. Pupillary constriction followed by pupillary dilatation in both eyes
    D. Pupillary constriction in the right eye, and no pupillary constriction in the left eye
    E. Pupillary constriction in both eyes
    F. Pupillary dilatation in both eyes

    Answer
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    <43>A patient complaining of chest pain with exercise is evaluated by
    cardiac catheterization. The left anterior descending (LAD) branch of
    the coronary artery is visualized but the contrast angiography is poor
    . A Doppler-tipped catheter is inserted and the blood velocity is observed
    to increase transiently from 10 cm/sec to 70 cm/sec and then decrease bac
    k to 10 cm/sec as the probe passes a particular location in the artery
    . What was the cause of these changes in velocity measurements?
    A. A coronary artery aneurysm with a cross-sectional area 1/7th the size of the native artery
    B. A coronary artery aneurysm with a cross-sectional area 7 times greater than the native artery
    C. A coronary artery obstruction with a cross-sectional area 1/7th of the size of the native artery
    D. A coronary artery obstruction with a cross-sectional area 7 times greater than the native artery


    Answer
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    <44>Type of blood vessel Fall in blood pressure (mm Hg) (% of total peripheral resistance)
    Aorta and large arteries <1
    Small arteries 10-20
    Arterioles 50
    Capillaries 25
    Venules and small veins 9
    Vena cave <1

    The table above shows the fall in blood pressure that occurs for the
    various types of blood vessels as blood flows from the aorta (100 mm Hg)
    to the right atrium (0 mm Hg). Which of the following types of blood
    vessel is likely to have the highest ratio of wall cross-sectional
    area to lumen cross-sectional area?
    A. Aorta and large arteries
    B. Small arteries
    C. Arterioles
    D. Capillaries
    E. Venules and small veins
    F. Vena cavae

    Answer
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    <45>Evaluation of an infant with a variety of congenital abnormalities
    reveals hypocalcemia due to a lack of parathyroid hormone. On x-ray, the
    thymic shadow is absent. A failure of development and differentiation of
    which of the following embryonic structures would most likely be
    responsible for the observed presentation?
    A. Second pharyngeal arch
    B. Second pharyngeal cleft
    C. Second pharyngeal pouch
    D. Third pharyngeal arch
    E. Third pharyngeal pouch

    Answer
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    <46>A person lifts one foot prior to taking a step. Which of the following
    nerves innervates the muscle group that allows the person to maintain
    balance by holding the weight of his body over the foot remaining on
    the ground?
    A. Femoral nerve
    B. First and second sacral nerves
    C. Obturator nerve
    D. Superior gluteal nerve
    E. Tibial nerve
    Answer
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    <47>A 21-year-old college student from Connecticut with a past history
    of Lyme disease presents with chronic pain and swelling in his right
    knee. He states that he has had problems with the knee for the past
    two years. Which of the following HLA alleles would you expect to
    be present in this individual?
    A. HLA-B9
    B. HLA-B17
    C. HLA-B27
    D. HLA-DR3
    E. HLA-DR4
    Answer
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    <48>Which of the following metabolic processes occurs exclusively in
    the mitochondria?
    A. Cholesterol synthesis
    B. Fatty acid synthesis
    C. Gluconeogenesis
    D. Glycolysis
    E. Hexose monophosphate shunt
    F. Ketone body synthesis
    G. Urea cycle


    Answer
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    49>An alert pediatric intern notices that a neonate with dysmorphic facies
    is twitching abnormally. As he watches, the baby experiences a seizure.
    Stat laboratories indicate a glucose of 90, serum sodium of 140, serum
    potassium of 4.2 and serum calcium of 3.9. Over the next several months,
    the child is admitted to the hospital twice for Candida infections, and
    once for a viral exanthem. Which of the following is the most likely
    diagnosis?
    A. Ataxia telangiectasia
    B. Bruton's hypogammaglobulinemia
    C. DiGeorge syndrome
    D. Severe combined immunodeficiency
    E. Wiskott-Aldrich syndrome
    Answer
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    50>A 2-month-old boy is evaluated for failure to thrive. As the pediatrician
    is examining the patient, she witnesses a seizure. Physical examination
    is remarkable for hepatomegaly, a finding later confirmed by CT scan,
    which also reveals renomegaly. Serum chemistries demonstrate severe
    hypoglycemia, hyperlipidemia, lactic acidosis, and ketosis. Which of
    the following diseases best accounts for this presentation?
    A. Gaucher's disease
    B. McArdle's disease
    C. Niemann-Pick disease
    D. Pompe's disease
    E. von Gierke's disease
    Answer
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    Answer
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    Answers
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    1>The correct answer is B. One of the most common side effects of any antineoplastic therapy is weight loss secondary to decreased appetite and/or nausea and vomiting. Furthermore, weight loss due to decreased food intake tends to occur more frequently in elderly patients receiving antineoplastic therapy. One medication that has consistently helped to increase appetite in such patients is megestrol acetate. This agent is a progestational hormone with antineoplastic properties used in the treatment of advanced carcinoma of the breast and endometrium. Megestrol, when given in relatively high doses, can substantially increase the appetite in most individuals, even those with advanced cancer.
    Amitriptyline (choice A) is a tricyclic antidepressant used in the treatment of depression. There is nothing mentioned in the case study to suggest that the patient is clinically depressed; hence, this agent would provide no benefit.
    Methotrexate (choice C) is an antimetabolite and folic acid antagonist commonly used in various neoplastic disorders and in the treatment of rheumatoid arthritis. Since nausea, vomiting, and ulcerative stomatitis are common side effects of this medication, its usage in this patient would not be recommended.
    Neostigmine (choice D) is a carbamylating acetylcholinesterase inhibitor that would not increase appetite.
    Prochlorperazine (choice E) is a phenothiazine derivative used primarily to control severe nausea and vomiting. This patient is not experiencing nausea. Furthermore, this agent does not possess appetite-stimulating properties.
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    2>The correct answer is B. The principle host defense in mycobacterial infections (such as this patient's tuberculosis) is cell-mediated immunity, which causes formation of granulomas. Unfortunately, in tuberculosis and in many other infectious diseases characterized by granuloma formation, the organisms may persist intracellularly for years in the granulomas, only to be a source of activation of the infection up to decades later.
    While antibody-mediated phagocytosis (choice A) is a major host defense against many bacteria, it is not the principle defense against Mycobacteria.
    IgA-mediated hypersensitivity (choice C) is not involved in the body's defense against Mycobacteria.
    IgE-mediated hypersensitivity (choice D) is not involved in the body's defense against Mycobacteria. It is important in allergic reactions.
    Neutrophil ingestion of bacteria (choice E) is a major host defense against bacteria, but is not the principle defense against Mycobacteria.
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    3>The correct answer is E. The immunoperoxidase method uses horseradish peroxidase to produce a visible pigment when a specific antibody binds to antigenic sites in the tissue. Binding of the antibody to the epithelial cells indicates that the protein in question is being expressed by those cells. The positive immunoperoxidase results obtained here suggests that the channel protein is expressed in proximal convoluted tubular epithelium, since this is the only site in the kidney at which the epithelial cells have a "brush border." The brush border is made of microvilli, which enhance the proximal tubules' ability to reabsorb plasma constituents filtered at the glomeruli.
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    4>The correct answer is D. Pregnant women with chronic hypertension "require" antihypertensive therapy when the diastolic pressure is greater than 100 mm Hg; however, some clinicians may decide to treat patients with diastolic blood pressures less than 100 mm Hg. For the initiation of therapy, methyldopa is still considered to be the agent of choice. Methyldopa is converted intraneuronally to a-methylnorepinephrine, an alpha-2 adrenergic agonist, which is subsequently released. Release of a-methylnorepinephrine in the medulla leads to a decrease in sympathetic outflow, thus lowering blood pressure. Methyldopa has been safely used in the treatment of hypertension during pregnancy; this agent is not associated with the development of teratogenic or other fetal abnormalities.
    Diuretics, such as bumetanide (choice A) and hydrochlorothiazide (choice C), are often avoided since these agents can produce hypovolemia, leading to reduced uterine blood flow. Although these agents can be used during pregnancy, methyldopa and hydralazine are the drugs of choice for hypertension during pregnancy.
    Fosinopril (choice B) is an angiotensin-converting enzyme (ACE) inhibitor that should not be administered to pregnant women, especially in the second or third trimesters. These agents have been associated with severe fetal and neonatal injury, such as hypotension, neonatal skull hypoplasia, anuria, renal failure, and death.
    Along the same lines, the use of the angiotensin II receptor antagonists, such as valsartan (choice E), is not recommended since these agents cause fetal complications similar to the ACE inhibitors.
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    5>The correct answer is D. The disease is Duchenne muscular dystrophy, an X-linked recessive muscular disease usually caused by a deletion involving the dystrophin gene. This defect produces accelerated muscle breakdown leading initially to proximal muscle weakness, then later to generalized weakness that typically begins before age 5. A feature of X-linked recessive diseases is that carrier mothers pass the disease to half their sons; affected fathers can have carrier daughters but not affected sons. Since the mother is presumably normal (because the disease is X-linked), she must be a carrier to have an affected son, and the grandmother must also be a carrier, therefore the mother's brother (maternal uncle) may also have the disease.
    The father's (choice A) side of the family, including the father's brother (choice B), most likely does not carry the defective gene (since they themselves would be affected, and furthermore since the father cannot pass the gene on to a son). It would be extremely unlikely for a carrier female to marry an affected male (and the question does not mention any similar symptoms in the father).
    The mother (choice C) and possibly the sister (choice E) are carriers of, but not affected by, the defective gene.
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    6>The correct answer is B. The cell pictured is an eosinophil, a member of the granulocytic lineage of white blood cells. The crystalline core of the granule contains a protein called the major basic protein, which appears to function in the destruction of parasites. Major basic protein also has deleterious effects on epithelial cells in patients with asthmatic reactions. The light component around the dense crystalline core contains products such as histaminase, arylsulfatase, and other enzymes.
    Lactoferrin (choice A) is found in the specific granules of the neutrophil. It inhibits the growth of bacteria by interfering with iron metabolism.
    Myeloperoxidase (choice C) is found in the azurophilic (large) granule of the neutrophil. This enzyme is also destructive to bacteria, destroying their cell walls.
    Histamine (choice D) is produced by the basophil and the mast cell. The histaminase of the eosinophil regulates the inflammatory reaction of these two cell types.
    Tartrate-resistant acid phosphatase (choice E) is a marker for hairy cell leukemia, a neoplasm of the B lymphocyte line.
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    7>The correct answer is E. This presentation (fine, nonblotchy, truncal rash in a not-very-ill child) is characteristic of rubella, or German measles. IgM specific for rubella can often be detected in serum within 1-2 days of developing the rash. The principal significance of this disease is that it can cause a devastating congenital infection characterized by ocular problems (cataracts, retinopathy, microphthalmos, glaucoma), cardiovascular problems (patent ductus arteriosus, ventricular septal defect, pulmonary stenosis), deafness, thrombocytopenic purpura, hepatosplenomegaly, CNS problems, and bony lesions.
    Bullous pemphigoid (choice A) produces large, tense blisters.
    Dermatitis herpetiformis (choice B) causes recurrent crops of small vesicles or papules.
    Herpes simplex (choice C) is characterized by crops of vesicles on oral or genital sites.
    Measles (choice D) causes a blotchy, maculopapular erythematous rash that begins on the face and spreads downward. Patients with measles are usually much sicker than those with German measles, and Koplik spots maybe seen on the buccal mucosa.
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    8>The correct answer is A. In a syndrome called cleidocranial dysostosis, absence of part of the clavicles accompanies a broad skull, and facial and dental anomalies. Note that you could also have answered this question by noting that of the bones listed, only the clavicles form by intramembranous ossification.
    The femurs (choice B), metatarsals (choice C), phalanges (choice D), and tibias (choice E) are cartilaginous (formed by endochondral ossification) rather than membranous bones.
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    9>The correct answer is A. Acute pyelonephritis is an infectious disease involving the kidney parenchyma and the renal pelvis. Gram-negative bacteria, such as Escherichia coli, Proteus, Klebsiella, and Enterobacter, are the most common causative organisms in acute pyelonephritis. Laboratory evaluation will often reveal leukocytosis with a left shift, and urinalysis typically shows pyuria, varying degrees of hematuria, and white cell casts. Since bacteremia is present, the patient should be hospitalized and empirically started on IV ampicillin and gentamicin. This regimen may be need to be changed, however, once the sensitivity results are available.
    Erythromycin (choice B) and tetracycline (choice E) are both bacteriostatic antibiotics and would not be recommended in a patient with a severe infection, such as acute pyelonephritis with bacteremia.
    Vancomycin (choice C) is primarily used in the treatment of severe gram-positive infections.
    Phenazopyridine (choice D) is a urinary analgesic, and nitrofurantoin (choice D) is a urinary tract anti-infective. Although nitrofurantoin is indicated for the treatment of "mild" cases of pyelonephritis, as well as cystitis, this patient's condition is severe and should be treated with appropriate antibiotics.
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    10>The correct answer is C. The fallopian tube is the only structure in the female genital tract with a ciliated columnar epithelium; the beating of the cilia helps move the egg into the uterus. This fact is also sometimes clinically helpful since dilated and deformed fallopian tubes can be microscopically distinguished from cystic ovarian tumors by the presence of the cilia.
    The cervix (choice A) and vagina (choice E) are lined by squamous epithelium.
    The endometrium (choice B) is lined by columnar epithelium (although a few ciliated cells may be present).
    The covering of the ovary (choice D) is cuboidal epithelium, and cysts within the ovary can be lined by cuboidal or non-ciliated columnar epithelium.
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    11>The correct answer is B. The description is that of gonadal dysgenesis. In the absence of testosterone, the Wolffian ducts will regress and fail to differentiate into normal male internal reproductive tracts. In the absence of Müllerian regression factor, the Müllerian ducts will automatically differentiate into oviducts and a uterus. Differentiation of the male external genitals is dependent on adequate dihydrotestosterone (via an action of 5 a-reductase on testosterone). In the absence of testosterone, female-type external genitalia will develop.
    Selective dysgenesis of the Sertoli cells could produce the situation described in choice A. Normal Leydig cells would secrete testosterone and produce normal male-type internal and external tracts. However, the absence of Müllerian regression factor, which is secreted by the Sertoli cells, would allow formation of female-type internal structures as well.
    Female-type internal reproductive tract and male-type external genitalia (choice C) would not be likely to occur under any circumstances.
    The situation described in choice D could occur with 5 a-reductase deficiency. Normal male-type internal tracts can form because there is no requirement for dihydrotestosterone. Müllerian regression factor will prevent differentiation of female-type internal tracts. Since differentiation of the normal male external genitals requires dihydrotestosterone, 5 a-reductase deficiency will lead to feminization.
    The situation described in choice E is normal, and would not occur in the individual described who has testicular dysgenesis.
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    12>The correct answer is B. The functional residual capacity is the amount of air left in the lungs after a normal expiration. Because this volume cannot be expired in its entirety, it cannot be measured by spirometry. Essentially, lung volume that contains the residual volume, which is the amount of air remaining after maximal expiration (e.g., functional residual capacity and total lung capacity), cannot be measured by spirometry. These volumes can be determined using helium dilution techniques coupled with spirometry or body plethysmography.
    The expiratory reserve volume (choice A) is the volume of air that can be expired after expiration of a tidal volume.
    The inspiratory reserve volume (choice C) is the volume of air that can be inspired after inspiration of a tidal volume.
    Tidal volume (choice D) is the amount of air inspired or expired with each normal breath.
    Vital capacity (choice E) is the volume of air expired after a maximal inspiration
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    13>The correct answer is E. Mastication is a complex process involving alternating elevation, depression, forward movement, and backward movement of the lower jaw. The backward movement step is accomplished by the posterior fibers of the temporalis muscle.
    The digastric (choice A) helps to depress the lower jaw during chewing.
    The lateral pterygoid (choice B) helps to move the lower jaw forward during chewing.
    The medial pterygoid (choice C) helps to elevate the lower jaw during chewing.
    The mylohyoid (choice D) helps to depress the lower jaw during chewing.
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    14>The correct answer is C. The vignette illustrates a typical presentation for a tumor of the heart. Primary cardiac tumors are rare and usually require an intensive work-up to pinpoint the diagnosis. 75% of primary cardiac tumors are benign and among these, myxoma is the most common. The tumors are usually single; the most common location is the left atrium. They may cause syncopal episodes or even shock and death due to obstruction by a "ball valve" mechanism.
    Angiosarcoma (choice A) is a malignant tumor of vascular origin that can occur as a primary cardiac tumor. It is the most common malignant primary cardiac tumor, but it is still very rare. Angiosarcoma usually affects the right side of the heart.
    Mesothelioma (choice B) is a benign tumor of mesothelial origin that can rarely present as a primary cardiac tumor. It is usually a small intramyocardial tumor that presents with disturbances of the conduction system of the heart.
    Rhabdomyoma (choice D) is a benign tumor of muscle origin. It can occur as a primary cardiac tumor, typically in infants and children, in whom it may be associated with tuberous sclerosis. It usually occurs in the ventricles.
    Rhabdomyosarcoma (choice E) is a malignant neoplasm that can also occur as a rare primary cardiac tumor. It is of muscle origin and usually affects the right heart.
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    15>The correct answer is A. The pituitary gland is located in the pituitary fossa within the skull. The floor of this fossa is formed by the sella turcica. The lateral walls of the fossa are formed by the cavernous sinuses. The abducens nerve passes through the cavernous sinus along with the internal carotid artery. As the tumor expands laterally, the first nerve that will be encountered is the abducens nerve, producing a lateral rectus palsy.
    The oculomotor nerve (choice B) lies in the lateral wall of the cavernous sinus. It is further from the pituitary gland than is the abducens nerve.
    The optic nerve (choice C) is anterosuperior to the pituitary gland. Upward expansion of the tumor may compress the optic chiasm.
    The trigeminal nerve (choice D) is found posterior to the cavernous sinus. Two of its three divisions (ophthalmic and maxillary divisions) pass through the lateral wall of the cavernous sinus and are further from the pituitary gland than is the abducens nerve.
    The trochlear nerve (choice E) is also in the lateral wall of the cavernous sinus, and would be affected later if the tumor continued to expand.
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    16>The correct answer is A. Mallory bodies are eosinophilic cytoplasmic inclusions ("alcoholic hyaline") that are found in the largest numbers in alcoholic hepatitis. They were originally considered to be pathognomic of alcohol abuse, but have since been found (in much smaller numbers) in many other liver conditions.
    Alpha1-antitrypsin deficiency (choice B) involvement of the liver is characterized by periodic acid Schiff (PAS)-positive cytoplasmic granules in hepatocytes.
    Hepatitis A (choice C) and hepatitis B (choice D) infections are definitively established with serologic markers.
    In Wilson's disease (choice E), there is excess copper deposition in the liver
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    17>The correct answer is E. In social learning, also known as modeling, behavior is acquired by watching other persons and assimilating their actions into the behavioral repertoire. There is no verbal or cognitive process (choice B) that is involved, no reinforcement (as in operant conditioning; choice D), no pairing of stimuli to get stimulus substitution (as in classical conditioning; choice A), nor any early-life bonding or imprinting (choice C) involved in this type of process. Because behaviors such as spousal abuse, child abuse, and elder abuse are all based on observing and incorporating behaviors from significant others, the person displaying the behaviors does not realize the behaviors are inappropriate and is typically very resistant to change. The fact that the learning is nonverbal and not dependent upon reinforcement contributes to the resistance to change.
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    18>The correct answer is B. Sucralfate is a promising drug that is not presently in widespread use because it is incompatible with H2 antagonists such as cimetidine, ranitidine, famotidine and nizatidine. Sucralfate is aluminum sucrose sulfate, a sulfated disaccharide, which polymerizes and binds to ulcerated tissue. It forms a protective coating against acid, pepsin and bile, giving the tissue a chance to heal. Unfortunately, a low gastric pH is required for polymerization, meaning that sucralfate is incompatible with drugs that reduce gastric acidity, such as H2 blockers and antacids. The moral of the story is that you cannot assume that two medications that are individually helpful in a medical condition will be synergistic. Learning the mechanisms by which the drugs work will help you spot potential interactions and earn you points on the USMLE.
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    19>The correct answer is B. The patient's presentation is consistent with hypothyroidism. Serum thyroid-stimulating hormone (TSH) measurement (choice B) is most likely to confirm the empiric diagnosis. TSH levels usually rise above normal before serum thyroxine (T4; choice C) and serum triiodothyronine (T3; choice D) levels do, even in mild cases of hypothyroidism. Therefore, TSH measurement would be the most accurate test to determine the presence of hypothyroidism regardless of the severity.
    A high titer of antithyroid antibodies (choice A) is characteristic of chronic thyroiditis, which is the most common cause of hypothyroidism. However, detection of these antibodies would not indicate if hypothyroidism was present.
    T3 resin uptake (choice E) measurement is not an accurate test of thyroid function; it is primarily used to exclude various abnormalities in the thyroid-hormone binding proteins.
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    20>The correct answer is A. Warfarin is the oral anticoagulant the patient was most likely taking. This drug is commonly prescribed to patients with atrial fibrillation to prevent the formation of atrial thrombi. Warfarin increases prothrombin time (PT) because it interferes with the synthesis of the vitamin K clotting factors of the liver (II, VII, IX, and X) and therefore necessitates regular monitoring of the PT. Cimetidine is an H2-blocker that inhibits hepatic enzymes, including those that metabolize warfarin. Consequently, coadministration of warfarin and cimetidine results in enhanced warfarin activity, producing pronounced anticoagulation and the bleeding diathesis in the patient in question. Cimetidine has one of the worst side effect profiles of all the H2-blockers and may also result in gynecomastia in men.
    Famotidine (choice B) is an H2-blocker that does not affect liver metabolism.
    Misoprostol (choice C) is a prostaglandin E1 analog used in peptic ulcer disease. It does not affect hepatic metabolism.
    Omeprazole (choice D) is a proton-pump inhibitor used to decrease acid production in patients with peptic ulcer disease or reflux. It does not affect drug metabolism by the liver.
    Ranitidine (choice E) is another H2-blocker. It does not inhibit liver enzymes as strongly as cimetidine does.
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    21>The correct answer is C. Bullae with the cleavage plane above the basal layer of the epidermis suggests pemphigus vulgaris, which is caused by autoantibodies to intercellular junctions of epidermal cells. The autoantibodies decrease the ability of the keratinocytes to adhere to one another, permitting formation of vesicles and bullae. Oral involvement is common, and often precedes the characteristic skin lesions. Separation of the epidermis upon manual stroking of the skin is known as Nikolsky's sign. This sign is present in other disorders such as Stevens-Johnson syndrome, but we are told the woman is not taking any medications, a typical cause of Stevens-Johnson syndrome in the adult population.
    Antibodies to epidermal basement membrane proteins (choice A) are seen in bullous pemphigoid, which is a bullous disease characterized by blisters with a cleavage line between the epidermis and dermis.
    Antibodies to glycoprotein IIb/IIIa (choice B) are seen in autoimmune thrombocytopenic purpura.
    Antibodies to intrinsic factor (choice D) are seen in pernicious anemia.
    Antibodies to Type IV collagen (choice E) are seen in Goodpasture's syndrome.
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    22>The correct answer is D. The lesion is a malignant melanoma. Melanomas can develop either de novo or in an existing mole. Sunlight exposure is a significant risk factor and fair-skinned persons are at increased risk of developing melanoma. The most significant factor for long term prognosis is the depth of the lesion, since the superficial dermis lies about 1 mm under the skin surface, and penetration to this depth is associated with a much higher incidence of metastasis than is seen with a more superficial location.
    The circumference of the lesion (choice A) is much less important than depth, since one form of melanoma (superficial spreading) can still have good prognosis despite large size, if it has not extended to the depth of the superficial dermal lymphatic bed.
    The darkness (choice B) or degree of variation in color (choice C) do not have prognostic significance once melanoma is diagnosed.
    Irregularity, or fuzziness at the border (choice E) of a mole-like lesion is a good clue to potential malignancy, but does not affect prognosis once a melanoma is diagnosed.
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    23>The correct answer is E. By the third week of development, hematopoiesis begins in the blood islands of the yolk sac. Beginning at 1 month of age and continuing until 7 months of age, blood elements are also formed in the liver. Hematopoiesis occurs in the spleen and lymphatic organs between 2 and 4 months, and in the bone marrow after 4 months.
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    24>The correct answer is E. The patient has I-cell disease, also known as mucolipidosis II, which is due to a defective UDP-N-acetylglucosamine-1-phosphotransferase, the enzyme that phosphorylates mannose on enzymes destined for lysosomes. Proteins coded by nuclear DNA are synthesized on cytoplasmic ribosomes, which may be either "free" or associated with the endoplasmic reticulum to form the rough endoplastic reticulum (RER). Proteins synthesized on the RER are transferred into the Golgi apparatus, where they undergo further modifications that determine whether they remain part of the Golgi apparatus, become part of the plasma membrane, or are shipped to lysosomes or mitochondria. Proteins not marked for transport to a specific intracellular site follow the default pathway and are exported into the extracellular compartment. The signal for transport of the acid hydrolases (and probably other enzymes) to the lysosomes is phosphorylation of a terminal mannose moiety on an N-linked oligosaccharide to form mannose 6-phosphate. In I-cell disease, this terminal mannose moiety is not phosphorylated, and the acid hydrolases follow the default pathway and are secreted.
    Deficiency of alpha-L-iduronidase results in lysosomal accumulation of dermatan sulfate and heparan sulfate (choice A) in several conditions such as mucopolysaccharidosis I, Hurler's disease, or Hurler's/Scheie disease.
    Hexosaminidase A deficiency (Tay-Sachs disease) is one example of a condition in which ganglioside accumulation occurs (choice B).
    There are a number of diseases in which glycogen degradation (choice C) is defective. These are collectively termed glycogen storage diseases since they result in abnormal cellular accumulation of glycogen. In Pompe's disease, or type II glycogen storage disease, a lysosomal glucosidase is deficient, resulting in lysosomal glycogen accumulation.
    Deficiency of sphingomyelinase (choice D), an enzyme involved in degradation of sphingomyelin, results in Niemann-Pick disease.
    Phosphorylation of tyrosine moieties (choice F) is unrelated to lysosomes or lysosomal enzymes; however, decreased ability to phosphorylate tyrosine moieties might be associated with diabetes or dwarfism.
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    25>The correct answer is E. 95% of a normally distributed population will fall between plus or minus 1.96 standard deviations from the mean. Since the population is normally distributed with regard to IQ, this means that approximately 2.5% of the population will have IQ scores 2 standard deviations or more above the mean, and 2.5% of the population will have IQ scores 2 standard deviations or more below the mean. 2.5% of 200 people is 5 people.
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    26>The correct answer is E. All the compounds listed can produce crystals in joint fluid, but only monosodium urate (associated with gout) and calcium pyrophosphate dihydrate (associated with CPPD crystal deposition disease, also called pseudogout), and to lesser degree basic calcium phosphate (apatite-associated arthropathy), have a high likelihood of being encountered on a step 1 USMLE exam. The crystals described are those of monosodium urate. Be careful not to answer "uric acid" if that is listed as an alternative choice on an exam, since the sodium salt is the predominant species in vivo.
    Basic calcium phosphate (choice A) is seen in apatite-associated arthropathy and produces spherical clumps of nonbirefringent submicroscopic crystals.
    Calcium oxalate crystals (choice B) are seen in primary oxalosis and are bipyramidal, positively birefringent crystals.
    Calcium pyrophosphate dihydrate crystals (choice C) are a feature of pseudogout and are rod-to-rhomboidal-shaped, weakly positively birefringent crystals.
    Cholesterol crystals (choice D) are seen in chronic and chylous effusions in inflammatory and degenerative arthritis, where they form large, flat, rhomboidal plates with notched corners.
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    27>The correct answer is B. The innervation of the tongue is complex. The mandibular division of the trigeminal nerve (V3) carries general somatic sensation from the anterior two-thirds of the tongue.
    The maxillary division (V2, choice A) carries somatic sensation from the palate, upper gums, and upper lip.
    The facial nerve (VII, choice C) carries taste from the anterior two-thirds of the tongue.
    The glossopharyngeal nerve (IX, choice D) carries sensation and taste from the posterior one-third of the tongue.
    The vagus nerve (X, choice E) carries sensation from the lower pharynx.
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    28>The correct answer is B. Brucella abortus produces a chronic, granulomatous disease with caseating granulomas. Most cases occur in four states (Texas, California, Virginia, and Florida), and are associated with cattle, in which it produces spontaneous septic abortions. Most cases of brucellosis produce mild disease or fevers of unknown origin. However, Brucella spp. can infect the cardiovascular system and cause a localized infection. B. abortus is the most common species to cause endocarditis. The aortic valve is most commonly involved, followed by the mitral valve, and then both valves. Most cases of brucellosis are associated with occupational exposure, in persons such as veterinarians, ranchers, and those who handle carcasses.
    Bacillus anthracis (choice A) is the causative agent for anthrax. It usually produces cutaneous disease (malignant pustule or eschar) at the site of inoculation in handlers of animal skins. It can also produce a severe hemorrhagic pneumonia (Woolsorter's disease) and septicemia. At-risk groups include those who handle animal carcasses or skins.
    Coccidioides immitis (choice C) is a dimorphic fungal disease producing a granulomatous pulmonary syndrome that is more severe in dark-skinned individuals. Disseminated disease occurs most often in Filipinos, Mexicans, and Africans. The infective form is the arthrospore; the diagnostic form in tissue is the spherule containing endospores. The disease is endemic in the San Joaquin River Valley. At-risk groups include military personnel, agricultural workers, construction workers, oil field workers, archaeology students, participants in outdoor sports, and sightseers. Remote infections from fomites (cotton harvested in the Southwestern U.S.) have been reported.
    Erysipelothrix rhusiopathiae (choice D) is a pleomorphic, gram-negative rod that causes a localized skin infection. It is an occupational disease of fishermen, fish handlers, butchers, meat-processing workers, poultry workers, farmers, veterinarians, abattoir workers, and housewives.
    Trichinella spiralis (choice E) is a nematode infection caused by the ingestion of larvae found in undercooked meat. Pork is the most common contaminated meat. However, outbreaks in the northern parts of the U.S. have been associated with eating undercooked infected bear meat. Symptoms include diarrhea, periorbital edema, myositis, fever, and eosinophilia.
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    29>The correct answer is B. This patient has Tay-Sachs disease, an autosomal recessive disorder caused by the deficiency of hexosaminidase A, which leads to the accumulation of ganglioside GM2 in neurons, producing a degenerative neurologic disease. Children appear normal at birth, but then begin to suffer from diminished responsiveness, deafness, blindness, loss of neurologic function, and seizures. A cherry-red spot on the macula may be seen by ophthalmoscopic examination. Death usually occurs by 4 to 5 years of age. There is no therapy. The incidence is higher among Jews of Eastern European descent. Since the parents must be heterozygotes for the mutant hexosaminidase A allele, they would be expected to have diminished levels of the enzyme.
    A defect in the dystrophin (choice A) gene produces Duchenne muscular dystrophy, characterized by onset of weakness in early childhood.
    A severe deficiency in HGPRT (choice C) will lead to Lesch-Nyhan syndrome, characterized by excessive uric acid production, mental retardation, spasticity, self-mutilation, and aggressive, destructive behavior.
    Deficiency of phenylalanine hydroxylase (choice D) results in classic phenylketonuria, a disease in which phenylalanine, phenylpyruvate, phenylacetate, and phenyllactate accumulate in plasma and urine. Clinically, there is a musty body odor and mental retardation.
    Hypophosphatemic rickets is an X-linked dominant condition causing abnormal regulation of vitamin D3 (choice E) metabolism and defects in renal tubular phosphate transport. Symptoms include growth retardation, osteomalacia, and rickets.
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    30>The correct answer is C. The fibrinolytic activity of streptokinase is due to its ability to bind and cleave plasminogen, producing plasmin. Plasmin directly cleaves fibrin, both between and within the fibrin polymers, thus breaking up thrombi and potentially restoring blood flow to ischemic cardiac muscle. This same mechanism of fibrinolysis is shared by urokinase and tissue-plasminogen activator (tPA).
    Antithrombin III (choice A) is a coagulation inhibitor that binds to and inactivates thrombin. Antithrombin III is anticoagulant, not fibrinolyti
  2. wutnext

    wutnext Guest

    can i get answers from 31 to 50
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    Guest Guest

  4. meech

    meech Guest

    TNX FOR THIS SAMPLE BLOCK

    thank you for taking the time to post these questions and answers. they've been a great help. i'm curious to see how i fared with the rest of the questions and tried looking for the answers 31-50. i used the link that "glad" provided but it says that it no longer exists. can you please redirect me? thanks.
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    Guest Guest

    --------------------------------------------------------------------------------
    26The correct answer is A. While it is hard to develop a deficiency in oil-soluble vitamins (A, D, E, K) because the liver stores these substances, deficiency states can be seen in chronic malnutrition (specifically chronic fat deprivation) and chronic malabsorption. Vitamin A is necessary for formation of retinal pigments (deficiency can cause night blindness) and for appropriate differentiation of epithelial tissues (including hair follicles, mucous membranes, skin, bone, and adrenal cortex).
    Vitamin C (choice B), which is water soluble rather than oil soluble, is necessary for collagen synthesis.
    Vitamin D (choice C) is important in calcium absorption and metabolism.
    Vitamin E (choice D) is a lipid antioxidant that is important in the stabilization of cell membranes.
    Vitamin K (choice E) is necessary for normal blood coagulation.
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    27The correct answer is C. The most likely diagnosis is an intracranial meningioma. Meningiomas are slow-growing, benign tumors comprising 15% of intracranial tumors; they are most common in the elderly. They originate from either dura mater or arachnoid and are sharply demarcated from brain tissue. Meningiomas often incite an osteoblastic reaction in the overlying cranial bones. Microscopically, the meningioma cells have a tendency to encircle one another, forming whorls and psammoma bodies. Clinically, they present as mass lesions; seizures may occur. The superior parasagittal surface of the frontal lobes is a favorite site of origin. This can often produce leg weakness, since the leg motor fibers that pass down through the internal capsule originate in parasagittal cortical regions. Treatment of meningiomas is usually surgical.
    Arachnoid cysts (choice A) are formed by splitting of the arachnoid membrane; most arachnoid cysts arise near the Sylvian fissure. They may present with mass effect, but would be unlikely to produce seizures, prominent focal signs, or reactive hyperostosis.
    Glioblastoma multiforme (choice B) is an aggressive malignant astrocytoma that would likely have killed the patient long before 5 years had elapsed.
    Metastatic breast cancer (choice D) would generally look different microscopically (the whorling cell pattern is characteristic of meningioma). It would be unlikely for metastatic cancer to cause a reaction in the overlying bone, or to be present long enough to cause symptoms for 5 years.
    Oligodendrogliomas (choice E) are glial tumors that could produce the described clinical picture, but usually do not cause hyperostosis of the calvarium or exhibit the characteristic whorling cell pattern microscopically
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    28The correct answer is D. The two most common causes of aortic dissection are hypertension and atherosclerosis. An important distinction between the two is that hypertensive dissections generally originate in the ascending aorta, at an intimal surface free of atherosclerosis.
    Dissection secondary to atherosclerosis is typically the consequence of a ruptured aortic aneurysm, which originates in the abdominal aorta at the iliac bifurcation. Dissections due to both hypertension and atherosclerosis generally course through the wall within the media (choice B). They both can involve the entire length of the aorta, and may rupture anywhere along its course (choices A and C). Well recognized sequelae of dissections include rupture through the adventitia, compromise of major arterial branches or the aortic valve, cardiac tamponade, and rapid exsanguination (choice E).
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    29The correct answer is D. Although rare now because of advances in treatment, syphilitic aortitis and aneurysm are still seen, especially in underserved populations. This complication generally occurs 10 to 40 years after initial infection. The vasa vasorum of the aorta undergoes obliterative endarteritis, leading to atrophy of the muscularis and elastic tissues of the aorta and dilatation. Linear calcifications are often seen in the ascending aorta by x-ray. The intimal wrinkling or "tree barking" is also a common feature. Syphilitic aneurysm can be associated with respiratory distress, cough, congestive heart failure and rarely, rupture.
    Atherosclerosis (choice A) is the most common cause of aortic aneurysms. These are most often located in the abdominal aorta, distal to the renal arteries. Intimal wrinkling and linear calcifications are not seen.
    Hypertension (choice B) is usually responsible for dissecting aneurysms located within 10 cm of the aortic valve. Patients present with sudden chest pain, which is usually severe and tearing in nature. The chronic hypertension causes a cystic medial necrosis, allowing the separation of vessel layers.
    Marfan's syndrome, an autosomal dominant connective tissue disorder (choice C) is also associated with dissecting aneurysms, usually of the ascending aorta. The patients are often very tall with arachnodactyly and ligamentous laxity. Their life-span is generally shortened. This patient's description and age are not consistent with this diagnosis.
    Takayasu's arter itis (choice E) is a syndrome characterized by ocular disturbances and weak pulses in the arms. It occurs most frequently in young females. It is considered a giant cell arteritis, and does not cause aneurysms.
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    30The correct answer is E. The disease is progressive supranuclear palsy, a degenerative disorder characterized by ophthalmoplegia, pseudobulbar palsy, axial dystonia, and bradykinesia. The presentation described in the question is typical. The pathologic changes consist of widespread neuronal loss and gliosis in subcortical sites with sparing of the cerebral and cerebellar cortices.
    Pigmented neurons in the substantia nigra (pars compacta) and locus ceruleus (choice A) selectively degenerate in Parkinson's disease.
    In Alzheimer's disease, there is diffuse cortical atrophy (choice B), especially over the association cortex of frontal, temporal, and parietal lobes, with relative sparing of primary sensory and motor areas.
    Selective frontal and temporal lobe atrophy (choice C) is characteristic of Pick's disease.
    The caudate nucleus and putamen undergo severe atrophy (choice D) in Huntington's disease. Cortical atrophy occurs to a lesser extent.
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    31The correct answer is B. Collagen formation begins with transcription of mRNA from appropriate DNA genes in the nucleus. While still within the nucleus, the mRNA is spliced. It is then transported through the cytoplasm to the ribosomes on the rough endoplasmic reticulum. Individual chains are translated on the ribosomes, with the ends feeding into the endoplasmic reticulum lumen. Within the lumen, glycosylation of the individual chains occurs. The material then moves toward the Golgi bodies (whose lumens are connected to the endoplasmic reticulum) where the triple helices of procollagen form. The procollagen is then secreted into the extracellular space, where cleavage of pro-peptides and cross- linking of different triple helices occurs, maturing the collagen.
    The extracellular space (choice A) is the site of procollagen cleavage and cross- linking.
    The nucleus (choice C) is the site of mRNA transcription and splicing.
    The rough endoplasmic reticulum (choice D) is the site of chain translation and glycosylation.
    The smooth endoplasmic reticulum (choice E) does not participate in collagen synthesis
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    32The correct answer is A. The uncus, which is the medial protrusion of the parahippocampal gyrus, is an external structure seen on the ventral surface of the temporal lobe. The amygdala is a collection of nuclei that lies directly beneath the uncus.
    The caudate nucleus (choice B) is a deep nuclear structure that lies lateral to the lateral ventricles.
    The claustrum (choice C) is a thin and elongated nucleus that lies just medial to the insular cortex.
    The hippocampus (choice D) is a nuclear structure that lies in the interior of the parahippocampal gyrus.
    The putamen (choice E) is a nuclear structure that resides lateral to the caudate, and medial to the claustrum.
    The thalamus (choice F) is a deep nuclear structure, caudal to the caudate nucleus.
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    33The correct answer is A. A third heart sound (S3) is a low-pitched sound occurring at the termination of rapid filling. In patients over 40 years of age, the appearance of a third heart sound strongly suggests congestive heart failure. It also occurs in patients with atrioventricular valve incompetence and can be a normal finding in some young athletes.
    A fourth heart sound (S4; choice B) can be a normal finding in some older patients who do not have congestive heart failure.
    Ascites (choice C) can also occur in patients with renal, hepatic, or local conditions not associated with cardiac factors.
    Both orthopnea (choice D) and pulmonary rales (choice E) often occur secondary to heart failure, however, they both are associated with noncardiac disorders as well.
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    34The correct answer is A. Several immunodeficiency disorders have X-linked genetics, including Bruton's agammaglobulinemia, Wiskott-Aldrich syndrome, and some cases of severe combined immunodeficiency diseases. Bruton's agammaglobulinemia is characterized by recurrent respiratory infections caused by pyogenic organisms.
    Common variable immunodeficiency (choice B) is a relatively common, but probably heterogeneous, group of acquired and familial diseases. It is distinct from X-linked (Bruton's) agammaglobulinemia.
    DiGeorge syndrome (choice C) is due to a developmental malformation of the third and fourth pharyngeal pouches leading to failure of the thymus, and sometimes the parathyroids, to develop. Defective cellular immunity and abnormalities of calcium metabolism are typical.
    Hereditary angioedema (choice D) is a usually recessive genetic disease caused by deficiency of C1 esterase inhibitor.
    Isolated IgA deficiency (choice E) can be acquired or genetic, but is not usually X-linked.
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    35>The correct answer is E. The capacity for cooperative play generally does not begin much befo




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    Posted: Sat Aug 13, 2005 11:49 pm Post subject:

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    35>The correct answer is E. The capacity for cooperative play generally does not begin much before the age of 4. Prior to this time (24-30 months), children may play in a parallel fashion, but without real interaction.
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    36>The correct answer is C. Anticipation is a phenomenon in which the phenotype of a disease worsens over successive generations. This has been observed in families affected by a hereditary disorder because of an expansion of unstable sequences of nucleotide repeats (triplet repeat expansion). Clinical features worsen with each successive generation as the number of triplet repeats increases. Huntington disease is caused by expansion of an unstable CAG repeat in a gene encoding a protein called huntingtin, of unknown function. All the unstable triplet-repeat disorders identified so far are associated with neurodegenerative conditions. Other examples are fragile X syndrome, myotonic dystrophy, and Friedreich ataxia.
    FAD (choice A) comprises 5% to 10% of all cases of Alzheimer disease and is due to autosomal dominant mutations of three different genes: amyloid precursor protein (APP) gene, presenilin-1 gene, and presenilin-2 gene. The e4 allele of the gene encoding apolipoprotein E increases the risk for FAD. Unstable repeat expansion is not a cause of FAD.
    The great majority of cases of ALS (choice B)are sporadic. A small subset of familial ALS is caused by mutations in the gene coding for superoxide dismutase on chromosome 21.
    Pick disease (choice D) and progressive supranuclear palsy (choice E) are usually sporadic. The genetic alterations of the very few familial cases reported have not been elucidated.
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    38>The correct answer is E. Terfenadine is the only drug listed that does not cross the blood-brain barrier and therefore does not cause sedation (a bad thing for someone flying an airplane). Other drugs from the same class (piperidines) include astemizole and loratadine.
    All of the other choices have some degree of sedation as a side effect and therefore would not be recommended for someone who is flying an airplane or operating any kind of machinery.
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    39>The correct answer is D. Deficiency of vitamin K produces a clotting disorder characterized by an elevated prothrombin time and easy bleeding, particularly in neonates (hemorrhagic disease of the newborn). The biochemical basis for this hemorrhagic tendency is that glutamate residues on Factors II (Thrombin), VII, IX, and X must be converted to gamma-carboxyglutamate residues (in a vitamin K-requiring reaction) for optimal activity.
    The conversion of homocysteine to methionine (choice A) requires vitamin B12.
    Conversion of methylmalonyl CoA to succinyl CoA (choice B) requires vitamin B12.
    Degradation of cystathionine (choice C) requires vitamin B6.
    Hydroxylation of proline (choice E) requires vitamin C. Vitamin C deficiency can cause easy bruising, but will not prolong the prothrombin time.
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    40>The correct answer is D. Massive dilation of the aortic root with an absence of atherosclerotic vessel lesions strongly suggests a syphilitic aneurysm. These aneurysms are a manifestation of tertiary syphilis and have become very uncommon now, probably due to a combination of deliberate therapy and therapy of undiagnosed disease when antibiotics are given for some other condition. The histologic hallmark of the syphilitic aneurysm is a plasma cell lesion of the small blood vessels (the vasa vasorum) that supply the aorta, and eventually obliterate the small vessel lumina.
    Choice A is a feature of Churg-Strauss syndrome, which is a variant of polyarteritis nodosa that involves vessels smaller than the aorta.
    Choice B is a feature of polyarteritis nodosa, which involves vessels smaller than the aorta.
    Choice C is a feature of cystic medial necrosis, which can cause aortic dissection.
    Choice E is a feature of Mِnckeberg's arteriosclerosis, which involves vessels smaller than the aorta.
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    41>The correct answer is D. The patient is not eating well, as mentioned by her parents, and her weight loss (over 15% of baseline), as well as her school performance and activity level, is consistent with anorexia nervosa. Metatarsal stress fracture is a complication of rigorous prolonged walking or running in this population. While she is malnourished and underweight, she has poor insight and continues to decrease her input and increase her output with prolonged physical activity. The fracture is a complication of increased output beyond the patient's physical limitation.
    Conversion disorder (choice A) is manifested by chronic neurologic pain or deficit without any objective organic cause. This patient's chief complaint is acute pain without any sign of another neurologic deficit.
    Diffuse muscle and joint aches, in conjunction with lack of energy and reduced physical activity, is characteristic of depression (choice B). This patient's pain is localized and she is very active.
    Ruptured or injured tendon of the ankle is a common injury, but the patient does not recall any recent injury, and localization of the pain is not consistent with medial ankle injury (choice C).
    The girl's daily walking in the nearby forest raises suspicion for tick bite (choice E)and Lyme disease with secondary joint pain. Arthritis associated with Lyme disease is generally centered around joints, and does not present as acutely as in this patient.
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    42>The correct answer is C. APGAR is an acronym for appearance, pulse, grimace, activity, and respiration; the APGAR score is taken at 1 minute and 5 minutes after birth. On each parameter, a maximum score of 2 is possible. In this case, one point was taken off for cyanosis of the hands and feet; one point was taken off for irregular respirations. The neonate received the maximum score of 2 for all of the other parameters, leading to an APGAR of 8.
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    43>The correct answer is B. This question requires two logical steps: first, you need to appreciate that the hydrophilic amino acids are more likely to appear on the surface of a protein molecule, while hydrophobic amino acids are most likely be found in its interior. Next, you need to figure out which of the amino acids listed is hydrophilic. If you recall that arginine is a basic amino acid that is positively charged at physiologic pH, you should be able to answer this question right away.
    All of the other choices have neutral side chains and are uncharged at physiologic pH. They would most likely be found in the hydrophobic core of the protein structure. Alanine (choice A), isoleucine (choice C), and leucine (choice D) all have aliphatic side chains; phenylalanine (choice E) and tryptophan (choice F) have aromatic side chains.
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    44>The correct answer is A. The anterior continuation of the cavernous sinus, the superior ophthalmic vein, passes through the superior orbital fissure to enter the orbit. Veins of the face communicate with the superior ophthalmic vein. Because of the absence of valves in emissary veins, venous flow may occur in either direction. Cutaneous infections may be carried into the cavernous sinus and result in a cavernous sinus infection which may lead to an infected cavernous sinus thrombosis. The cavernous sinus is lateral to the pituitary gland and contains portions of cranial nerves III, IV, V1, V2 and VI, and the internal carotid artery.
    The occipital sinus (choice B) is at the base of the falx cerebelli in the posterior cranial fossa. It drains into the confluence of sinuses.
    The sigmoid sinus (choice C) is the anterior continuation of the transverse sinus in the middle cranial fossa. The sigmoid sinus passes through the jugular foramen and drains into the internal jugular vein.
    The superior petrosal sinus (choice D) is at the apex of the petrous portion of the temporal bone and is a posterior continuation of the cavernous sinus. The superior petrosal sinus connects the cavernous sinus with the sigmoid sinus.
    The straight sinus (choice E) is at the intersection of the falx cerebri and the falx cerebelli in the posterior cranial fossa. The straight sinus connects the inferior sagittal sinus with the confluence of sinuses
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    45.The correct answer is E. The baby is probably a victim of sudden infant death syndrome (SIDS). The etiology remains unknown. Rare cases have been witnessed, and some of the SIDS babies give a single small cry, as described in the question stem. Some of these babies were premature at birth and some have upper respiratory infections in the preceding few days before death. Findings at autopsy are subtle and may be absent. The cardiovascular system may show right ventricular hypertrophy, which is possibly secondary to smooth muscle hypertrophy in small pulmonary arteries, and possibly cardiac conduction system abnormalities. Other features include brainstem gliosis (suggesting chronic hypoxia), extramedullary hematopoiesis, and retained periadrenal brown fat.
    A baby with endocarditis (choice A) would be very obviously ill.
    A serious congenital heart defect, such as failure of development of the endocardial cushion (choice B), large interventricular septal defect (choice C), or a mitral value stenosis (choice D) would have been picked up in the comprehensive physical examination at the child's birth.
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    46>The correct answer is C. Patients with AIDS develop a number of neurologic complications, including opportunistic infections, lymphomas, polyneuropathies, and a form of subacute encephalitis. HIV gains access to the CNS through incoming macrophages and may cause a subacute inflammation of the brain parenchyma known as HIV encephalitis. Typical clinical manifestations and histopathologic features of HIV encephalitis are mentioned in the clinical case. The presence of multinucleated giant cells should be emphasized since this is typical of HIV encephalitis. All the other histologic features can be seen in any other form of viral encephalitis.
    Aspergillosis (choice A) is an opportunistic infection caused by Aspergillus species, a ubiquitous fungus found in the environment. Aspergillosis is frequent not only in AIDS, but in many immunocompromised patients. Aspergillus has a specific tropism for blood vessels, causing damage to vessel walls and producing hemorrhagic infarcts in the brain and other organs. The MRI and histopathologic findings rule out Aspergillus infection as the cause of this patient's neurologic condition.
    CMV encephalitis (choice B) is a frequent opportunistic infection affecting AIDS patients. CMV's tropism for epithelial and ependymal cells explains why this virus is found in ependymal and periventricular locations. Typical cytomegalic cells, which contain large purple intranuclear inclusions and granular cytoplasmic inclusions, represent important clues to the diagnosis. The accompanying tissue reaction is similar to that of any viral infection of the brain: lymphocytic infiltration (perivascular cuffing), microglial nodules, and neuronophagia (degenerating neurons surrounded by lymphocytes).
    Mycobacterial infections (choice D), including infections by Mycobacterium tuberculosis and Mycobacterium avium-intracellulare complex, frequently affect AIDS patients. Because of the AIDS epidemic and the emergence of multidrug resistance, the incidence of mycobacterial infections has been increasing in the U.S. Mycobacteria can cause a chronic meningoencephalitis involving the basal surface of the brain or a tuberculoma (a circumscribed lesion consisting of confluent caseating granulomas). Acid-fast bacilli can be demonstrated in these lesions.
    Vacuolar myelopathy (choice E) is a noninfectious complication of obscure pathogenesis involving the spinal cord. It is very similar to subacute combined degeneration pathologically. Vacuolar myelopathy, like subacute combined degeneration, may be related to vitamin B12 deficiency. In this condition, ascending (sensory) tracts in the posterior columns and descending (pyramidal-motor) tracts in the lateral columns degenerate, leading to sensory loss, ataxia, and spastic paraplegia.
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    47>The correct answer is A. Glucose-6-phosphate dehydrogenase (G6PD) deficiency (choice A) is an X-linked recessive disorder that affects the pentose phosphate pathway. The hallmark of X-linked recessive inheritance is an abundance of affected males and an absence of affected females. Males are hemizygous for the X chromosome, so the phenotype is expressed with only one dose of the gene. Females have two copies of the X chromosome, so they appear phenotypically normal although they may carry the recessive allele. Since a male inherits his X chromosome from his mother, if he is affected, she must carry the trait. Other X-linked recessives include Lesch-Nyhan disease, hemophilia A, and Duchenne's muscular dystrophy.
    Leber's hereditary optic neuropathy (choice B) is a relatively common cause of acute or subacute vision loss, especially in young men. It exhibits a mitochondrial inheritance pattern. The hallmark of this pattern is matrilineal inheritance. All of the children of an affected woman will be affected since they receive mitochondrial genes only from the female parent. Affected males do not contribute mitochondria to progeny, so their children will not receive the trait.
    Neurofibromatosis (choice C) shows an autosomal dominant inheritance pattern, so the phenotype will be expressed if the allele is present in one dose. Deleterious autosomal dominants occur at very low frequencies, so affected individuals are almost always heterozygous for the trait. Since the gene is located on an autosome, both male and female progeny can be affected. Other autosomal dominants include Ehlers-Danlos syndrome, Huntington's disease, and osteogenesis imperfecta.
    Sickle cell anemia (choice D) and Tay Sachs disease (choice E) are both inherited as autosomal recessives. For the phenotype of the autosomal recessive to be expressed, the recessive allele must be present in two doses. Both male and female children can be affected. The hallmark feature is that unaffected parents have affected children of both sexes.
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    48>The correct answer is B. Brain herniation can occur either with generalized increased intracranial pressure or as a consequence of a mass lesion of the cranium. Subfalcine herniation occurs when part of one cerebral hemisphere herniates under the falx membrane, which separates the two cerebral hemispheres along the midline of the skull. The gyrus most affected is the cingulate gyrus, which runs along the medial aspect of the cerebral hemisphere, just above the corpus callosum.
    The cerebellar tonsils (choice A) can herniate into the foramen magnum, in a tonsillar herniation. The medulla (choice D) can be compressed by the herniating cerebellar tonsils, producing damage to this structure.
    The medial temporal lobe (choice C) can be damaged in uncal herniation.
    The midbrain (choice E) can be damaged in the course of a uncal herniation.
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    49>The correct answer is D. The tip off for oligodendroglioma is "fried egg" cells, which are tumor cells with round nuclei (the "yolk") and cleared cytoplasm (the "white"). These tumors may contain areas of calcification, hemorrhage, or cysts. They tend to occur in the cerebral hemispheres of middle-aged patients of both sexes, and have a better prognosis (average survival 5 years) than astrocytomas.
    The usual tip-off for choroid plexus papilloma (choice A) is a papillary growth in a ventricle.
    The usual tip-offs for ependymoma (choice B) are pseudorosettes and structures resembling ependymal canals.
    The usual tip-offs for glioblastoma multiforme (choice C) are extreme pleomorphism, necrosis, and hemorrhage.
    The usual tip-offs for pilocytic astrocytoma (choice E) are bipolar cells, and location in the cerebellum of young children.
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    50>The correct answer is B. The ear has a complex sensory nerve supply, which includes all of the nerves listed. A consequence of this complexity is that pain actually originating in other sites (teeth and sinuses are notorious) may be misinterpreted as ear pain or (less commonly) pain originating in the ear may be misinterpreted as arising from other sites. The anterior half of the external ear canal is supplied by the auriculotemporal nerve, which also supplies the facial surface of the upper part of the auricle.
    The auricular branch of the vagus (choice A) supplies the posterior half of the external ear canal.
    The greater auricular nerve (choice C) supplies both surfaces of the lower part of the auricle.
    The lesser occipital nerve (choice D) supplies the cranial surface of the upper part of the auricle.
    The vestibulocochlear nerve (choice E) supplies hearing and motion sense.
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