USMLE 20

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rere_girl4ever
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USMLE 20
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2015-03-01 14:46:36
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  1. What is the function of Aldose reductase?
    Converts Glucose to Sorbitol
  2. This enzyme converts glucose to sorbitol.
    Aldose reductase
  3. What is the function of Sorbitol dehydrogenase?
    • a.k.a Polyol dehydrogenase
    • Converts sorbitol to fructose
  4. This enzyme converts sorbitol to fructose.
    Sorbitol dehydrogenase/ Polyol dehydrogenase
  5. Which tissues have only aldose reductase activity?
    • Schwann cells
    • Retina
    • Kidneys
  6. Which tissues have both aldose reductase and sorbitol dehydrogenase?
    • Liver
    • Ovaries
    • Seminal vessicles.
  7. What is tumor lysis syndrome and what complication can arise from it?
    • Occurs when tumors with a high cell turnover are treated with chemotherapy.
    • Complication: ⇧ uric acid. Can precipitate in the distal tubules and collecting ducts due to ↓pH
  8. Describe the triad of Hemolytic Uremic syndrome.
    • Anemia- lethargy, FRAGMENTED RBCS (schistocytes)
    • Thrombocytopenia↓platelets
    • Renal insufficiency⇧BUN/Cr
  9. This pathology is associated with eating undercooked beef.
    Hemolytic uremic syndrome- e.g. hamburgers
  10. Hemolytic uremic syndrome is caused by?
    EHEC 0157;H7
  11. Consumption of raw oysters is associated with?
    Vibrio parahaemolyticus and Vibrio vulnificus
  12. Raw egg consumption is associated with?
    Salmonella gastroenteritis
  13. Canned food is associated with?
    Clostridium botulinum
  14. Which hormones use cGMP as a second messenger?
    • Atrial natriuretic peptide
    • Nitric oxide (endothelium derived relaxing factor)
  15. What causes a lingual thyroid?
    • Failure of the thyroid to MIGRATE downward.
    • It forms within the tongue and is called a lingual thyroid.
  16. What complications could arise from the removal of a lingual thyroid?
    • Sometimes, the lingual thyroid is the only thyroid tissue in the body. If it is removed, significant hypothyroidism occurs
    • Lethargy, feeding problems, constipation, macroglossia, umbilical hernia, dry skin.
  17. Failure of the GnRH-secreting neurons to migrate from the olfactory lobes to the hypothalamus causes?
    Kallmann's syndrome
  18. Failure of the testes to migrate from their intra-abdominal location to the scrotum is called?
    Cryptochordism
  19. Describe the process of Expression cloning.
    • 1. mRNA is used as a template by reverse transcriptase to produce a cDNA strand.
    • 2. The cDNA is then inserted into bacteria-plasmids containing antibiotic resistance genes.
    • 3. The gene is translated into a protein, which is identified using a radiolabeled DNA probe.
    • 4. In order to then be radiolabeled by a DNA probe, the protein must be able to bind DNA.
  20. How can the S3 heart sound best be heard?
    By having the patient lie in the left lateral decubitus position and fully exhale.
  21. What p value indicates statistical significance?
    p<0.05
  22. What are the effects of menopause on bone?
    • Menopause causes accelerated bone loss due to a decrease in estrogen.
    • Estrogens cause increased osteoblastic activity and decreased osteoclastic activity.
  23. What are the effects of smoking on bone?
    • Smokers have significantly lower bone mineral density compared to nonsmokers.
    • Smoking is a major risk factor for osteoporosis and osteoporotic fractures.
  24. What are the effects of body mass index on bone density?
    • High BMI= high bone density
    • Low BMI= low bone density
  25. What are the effects of corticosteroid therapy on bone density?
    • Associated with low bone mineral density
    • Decrease GI absorption of Ca2+
    • Inhibit collagen synthesis by osteoblasts
    • Decrease GnRH -> Hypogonadiam
    • Increase urinary Ca2+ loss
  26. Which race has a higher bone density?
    Black/ African descent.
  27. Describe the sweat produced by patients with Cystic fibrosis.
    High Na+ and Cl- concentrations in sweat
  28. What is the use of Primidone?
    • First-line medication for the treatment of benign essential tremor.
    • Narrow-spectrum anticonvulsant that can be used to treat partial seizures.
  29. What are the active metabolites of Primidone?
    Phenobarbital and phenylethymalonamide
  30. How do integrins work?
    Adhere cells to the basement membrane via binding to fibronectin, collagen and lamin
  31. Which foods contain gluten?
    • Wheat, rye and barley
    • White oats and rice do not
  32. Deposits of IgA at the tips of dermal papillae are characteristic of?
    Dermatitis herpetiformis
  33. Agglutination of sheep or horse RBCs are diagnostic of?
    • Heterophile anitbodies- Positive Monospot test
    • EBV
  34. What amino acid becomes essential in patients with homocystinuria?
    Cysteine
  35. Describe the presentation of a Schwannoma.
    • CN 8- VESTIBULOCOCHLEAR
    • Loss of hearing, balance. Tinnitus (ear ringing), nystagmus, vertigo.
    • CN 7- FACIAL
    • Paralysis of the muscles of facial expression, loss of taste in the anterior 2/3 of the tongue
    • CN 5- TRIGEMINAL
    • Loss of sensation around the mouth and nose, loss of corneal reflex, paralysis of muscles of mastication.
  36. Bilateral acoustic neuromas are associated with?
    Neurofibromatosis type 2
  37. Where are schwannomas usually located?
    At the cerebellopontine angle, which is between the cerebellum and lateral pons
  38. Where does lymph drainage from the scrotum go into?
    Superficial inguinal lymph node
  39. What is the major determinant of whether or not a coronary artery plaque will cause ischemic myocardial injury?
    • The rate at which it occludes the artey.
    • A slowly developing occlusion would allow for the formation of collaterals that could prevent myocardial necrosis
  40. Deficiency of alpha-antitrypsin 1 leads to?
    • Cirrhosis
    • Pacinar emphysemia
  41. What is the function of alpha-1 antitrypsin?
    Inhibits enzymes such as pancreatic trypsin, chymotrypsin, neutrophil elastase
  42. Hepatic adenomas are associated with?
    Young/ middle aged woman who have a lengthy history of oral contraceptive or anabolic steroid use.
  43. Describe the presentation of a hepatic adenoma.
    • Patient complains of abdominal pain in the epigastrum or RUQ.
    • Or individual suddenly collapses because of rupture and intraabdominal bleeding.
    • NORMAL AFP levels
  44. What are the following pressure measurements for each?
  45. How does Hepatitis B virus replicate?
    dSDNA⇨  template + RNAprogeny dsDNA
  46. How do IFN-alpha and IFN-beta acts as antiviral agents?
    Stimulates cells to synthesize antiviral proteins (RNaseL and Protein kinase R) that degrade intracellular mRNA and impair protein synthesis.
  47. What causes acute transplant rejection? What is the onset and what are the histological findings?
    • CD8+ T cells activated against donor's MHC
    • Occurs weeks to months
    • Graft vessels has sense interstitial lymphocytic infiltrate
  48. In this type of transplant rejection, CD8+ T cells are activated against donor's MHCs
    Acute transplant rejection
  49. This transplant rejection occurs weeks to months.
    Acute transplant rejection
  50. In this transplant rejection, graft vessels are dense with intersitial lymphocytic infiltrate.
    Acute transplant rejection
  51. Preformed antibodies against graft ABO antigens are characteristic of this transplant rejection.
    Hyperacute transplant rejection
  52. What causes hyperactue transplant rejection? What is the onset and what are the tissue findings?
    • Cauesd by preformed antibodies against graft ABO antigens.
    • Onset: within minutes
    • Acute thrombosis of the graft's vascular supply ischemia, necrosis
  53. In this transplant rejection, there is acute thrombosis of the graft's vascular supply leading to ischemia and necrosis.
    Hyperacute transplant rejection
  54. This type of leukemia expresses terminal deoxynucleotidyltransferase
    ALL
  55. What are the toxicities of Mannitol?
    • Pulmonary edema
    • Dehydration
    • Contraindicated in anuira (failure of the kidneys to produce urine), CFH
  56. This diuretic causes pulmonary edema.
    Mannitol
  57. This organism is pyrrolidonyl arylamidase positive.
    • Streptococcus pyogenes
    • PRY replaced bacitracin
  58. Colonies produce a narrow zome of beta hemolysis that enhances when plated perpendicular to S.aureus.
    • Steptococcus agalactiae (Group B strep)
    • Positive cAMP test.
  59. What is the most common source of infection with Pseudomonas aeruginosa?
    Water
  60. What is the function of pyruvate dehydrogenase?
    Converts pyruvate into acetyl-CoA in the presence of O2
  61. What happens to the metabolism of pyruvate in the absence of O2 or deficiency of pyruvate dehydrogenase?
    • It is converted to lactate by the enzyme lactate dehydrogenase.
    • Excessive lactate production in these states results in lactic acidosis.
  62. What is the function of lactate dehydrogenase?
    Convrerts pyruvate to lactate
  63. Decribe the findings of pyruvate dehydrogenase deficiency and how do we treat?
    • Neurologic defects, LACTIC ACIDOSIS, ⇧⇧
    • ⇧ serum ALANINE starting during infancy.
    • Tx↑ intake of ketogenic nutrients - Lysine and Leucine
  64. Patient presents with severe pain associated with bowel movements. He sees spots of bright red blood on the toilet paper. Rectal examination reveals a tear of the anal mucosa. Where is this tear most commonly found?
    • Anal fissue
    • Tear in the anal mucosa below the pectinate line, located POSTERIORLY midline distal to dentate line poorly perfused.
  65. Describe the presentation and most common location of an Anal fissure
    • Pain on defecation, blood on toilet paper.
    • Tear in anal mucosa is located posteriorly midline distal to dentate line poorly perfused
  66. This agent used in the treatment of M.tuberculosis requires an acidic environment to exert antimicrobial effects.
    Pyrazinamide
  67. What is the MOA of Pyrazinamide?
    • Mechanism unknown. It is a prodrug that is concerted to the active compound pyrazinoic acid.
    • Requires acidic environment.
  68. What is the MOA of Ethambutol?
    Decrease carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyltransferase.
  69. This drug decreases carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyl transferase
    Ethambutol
  70. What is the importance of Metalloproteinases?
    • Zinc-containing enzymes that degrade the components of the extracellular matrix (collagen, laminin, fibronectin)
    • Essential for proper tissue remodeling during wound healing
  71. What test can be used to differentiate Streptococci from Staphylocci?
    • Catalase test
    • Staphyloccus - catalase positive
    • Streptococcus- catalase negative
  72. DNAse is produced by which microorganism?
    Group A streptococcus- S.pyogenes
  73. Yellow pigment is produced by which microorganism?
    S.aureus
  74. Catalase positive
    Staphylocci
  75. Catalase negative
    Streptococci
  76. Coagulase positive
    Staph aureus
  77. Coagulase negative
    • S.epidermidis- Novobiocin sensitive
    • S.saprophyticus- Novobiocin resistant
  78. Novobiocin sensitive
    S.epidermidis
  79. Novobiocin resistant
    S.saprophyticus
  80. In which patients should the use of ACE inhibitors be avoided and why?
    • Patients with bilateral renal artery stenosis.
    • Patients with RAS depends on ACE mediated efferent arteriole constriction to maintain renal perfusion and GFR.
    • The use of ACE inhibitors can cause Acute renal failure in these patients.
  81. What is the MOA and use of Nafcillin?
    • Penicillinase-resistant penicillins.
    • Resistant to degradation by β lactamases.
    • S.aureus (except MRSA)
  82. What are the loop diuretics and what are their use?
    • Furosemide, Bumetanide, Toresemide
    • USE: Edematous states (HF, cirrhosis, nephrotic syndrome), pulmonary edema, venous and pulmonary congestion 2o to Congestive heart failure.
  83. What are the loop diuretics and what is their mechanism of action?
    • Furosemide, Bumetanide, Toresemide
    • Inhibit Na+-K+-2Cl symporters in the thick ascending limb of the loop of Henle and effectively blocking NA+ and Cl- transport resulting in increased Na+, Cl- and H20 excretion
  84. What causes methemoglobin poisoning?
    Nitrates and Benzocaine cause poisoning by oxidiing Fe2+ to Fe3+

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