Card Set Information

2015-02-03 08:42:15
usmle 8
usmle 2O
Show Answers:

  1. What is positive selection? Where does it occur?
    • Only T cells expressing a TCR that is able to bind self MHC are allowed to survive.
    • Occurs in the thymic cortex.
  2. What is negative selection and where does it occur?
    • T cells posessing TCRs that bind with high affinity to self antigen or self MHC class I/II are eliminated by apoptosis.
    • Occurs in the medulla.
  3. What is somatic hypermutation?
    • DNA coding for the immunoglobulin variable region (idiotype) is mutated randomly at a very high rate.
    • This process results in new immunoglobulins with similar, better or worse affinity for the antigen.
  4. What is affinity maturation?
    B cells which produce antibodies  with increased affinity for the antigen during an immune response predominate in the germinal centers.
  5. Describe the conversion of Pyruvate to glucose in gluconeogenesis.
    • 1. In the mitochondria, Pyruvate is converted to Oxaloacetate by the enzyme Pyruvate carboxylase. Its activity is ↑ by acetyl-CoA and required biotin and ATP.
    • 2. Oxaloacetate is converted to Malate by mitocholdrial malate dehydrogenase to facilitate exit from the mitochondria, in the cytosol, it is converted back to oxaloacetate.
    • 3. In the cytosol, Oxaloacetate is converted to Phosphoenolpyruvate by Phosphoenolpyruvate carboxykinase, which required GTP.
    • 4. In the cytosol, Fructose-1,6-phosphatase converts Fructose-1,6-bisphosphate to Fructose-6-phosphate. This enzyme is activated by citrate and fructose 2,6-bisphosphate.
    • 5. In the ER, glucose-6-phosphate is converted to Glucose by the enzyme glucose-6-phosphatase.
  6. This enzyme in gluconeogenesis requires biotin.
    • Pyruvate carboxylase
    • Pyruvte →Oxaloacetate in mitochondria
  7. This enzyme in gluconeogenesis is activated by acetyl-CoA.
    • Pyruvate carboxylase
    • Pyruvate → Oxaloacetate in mitochondria
  8. What upregulates the activity of Pyruvate carboxylase?
    • Requires biotin, ATP. 
    • Activated by acetyl-CoA
  9. This enzyme in gluconeogenesis requires ATP.
    • Pyruvate carboxylase
    • Pyruvate → Oxaloacetate in mitochondria
  10. Which enzyme does Pyruvate carboxylase bypass?
    • Pyruvate kinase
    • Phosphoenolpyruvate→ Pyruvate

  11. How is Oxaloacetate transported from the mitochondria to the cytosol for further gluconeogenesis?
    Oxaloacetate is converted to malate by mitochondrial malate dehydrogenase to facilitate exit from the mitochondria; in the cytosol, it is converted back to oxaloacetate by cytosol malate dehydrogenase.
  12. What inhibits Oxaloacetate → Malate?
    Ethanol metabolism, which ↑NADH/NAD+ ratio in the liver.
  13. This enzyme in gluconeogenesis requires GTP.
    • Phosphoenolpyruvate carboxykinase
    • Oxaloacetate → Phosphoenolpyruvate
  14. This enzyme in gluconeogenesis is stimulated by citrate.
    • Fructose-1,6-bisphosphatase
    • Fructose-1,6-bisphosphate → Fructose-6-phosphate
  15. This enzyme in gluconeogenesis is inhibited by fructose 2,6-bisphosphate.
    • Fructose-1,6-bisphosphatase
    • Fructose-1,6-bisphosphate→ Fructose-6-phosphate
  16. EBV is associated with an increased incidence of which diseases?
    Nasopharyngeal carcinoma and Burkitt lymphoma
  17. What are the findings of Tay-Sachs disease?
    • Progressive neurodegeneration
    • Developmental delay
    • Cherry red spot on macula
    • Lysosomes with onion skin
  18. What can be given to pregnant women who are at risk of having a premature delivery with fetal lung immaturity?
    • Corticosterioids
    • Cortisol stimulates surfactant production.
  19. This hormone contributes significantly to fetal lung maturation.
  20. What is the affected are in the image below? This is characteristic of which disease?
    Wilson disease- cystic degeneration of putamen and basal ganglia
  21. Label the coronal section of the brain.
    • A- Corpus callosum
    • B-Lateral ventricle
    • C-Internal capsule
    • D- Hippocampus
    • E- Mamillary bodies
    • F- Globus pallidus
    • G- Putamen
    • H- Body of cauate
    • I- Thalamus
  22. What is the function of Leydig cells? What is another name for this type of cell?
    • Leydig/ endocrine cells
    • Secrete testosterone in response to stimulation by LH (which is released by GnRH).
  23. Is testosterone production affected  by temperature?
    NO! Leydig/ endocrine cells are unaffected by temperature.
  24. What happens to the levels of these hormones if Sertoli cell function is impaired: Testosterone, inhibin, FSH, LH
    • Testosterone: Normal
    • Inhibin: ↓
    • FSH: ↓
    • LH: Normal
  25. What hormone is secreted by the Sertoli cells?
    Secrete inhibin → inhibits FSH
  26. Describe the hormonal changes in menopause with resepect to: Estrogen, FSH, LH, GnRH
    • Estrogen: ↓
    • FSH: ↑↑↑
    • LH: ↑
    • GnRH: ↑
  27. Which hormone is specific for menopause?
    Elevated levels of FSH due to loss of negative feedback by ↓estrogen
  28. What breat pathology is seen below?
  29. Describe the presentation of a Fibroadenoma.
    • Small, mobilem firm mass with sharp edges.
    • Increase in size and tenerdness with ↑estrogen (e.g pregnancy and prior to menstration-luteal phase)
  30. What is the target and use of Omalizumab?
    • IgG1 monoclonal antibody that binds IgE to prevent IgE binding to FcεRI
    • Allergic asthma
  31. What is the MOA and use of Trastuzumab?
    • Monclonal antibody against HER2/neu
    • Breast cancer
  32. Which pharyngeal/ aortic arch gives rise to part of the maxillary artery?
    1st Aortic arch
  33. What does the 1st pharyngeal/aortic arch give rise to?
    Part of maxillary artery (branch of external carotid)
  34. Which pharyngeal/ aortic arch gives rise to the  Hyoid artery?
    2nd Aortic arch
  35. Which pharyngeal/ aortic arch gives rise to the Stapedial artery?
    2nd Aortic arch
  36. What does the 2nd pharyngeal/aortic arch give rise to?
    • Stapedial artery
    • Hyoid artery
  37. What does the 3rd pharyngeal/aortic arch give rise to?
    • Common carotid artery
    • Proximal part of internal carotid artery
  38. Which pharyngeal/ aortic arch gives rise to the Common carotid artery?
    3rd Aortic arch
  39. Which pharyngeal/ aortic arch gives rise to the Proximal part of internal carotid artery?
    3rd Aortic arch
  40. What does the 4th pharyngeal/aortic arch give rise to?
    • Aortic arch
    • Proximal part of right subclavian artery
  41. Which pharyngeal/ aortic arch gives rise to the Aortic arch?
    4th Aortic arch
  42. Which pharyngeal/ aortic arch gives rise to the Proximal part of the right subclavian artery?
    4th Aortic arch
  43. What does the 6th pharyngeal/aortic arch give rise to?
    • Proximal part of pulmonary arteries
    • Ductus arteriosus
  44. Which pharyngeal/ aortic arch gives rise to the Ductus arteriosus?
    6th Aortic arch
  45. Which pharyngeal/ aortic arch gives rise to the Proximal part of pulmonary arteries?
    6th Aortic arch
  46. What is the muscle shown below?What artery can be palpated along the inner side of this muscle?
    • Sternocleidomastoid muscle
    • Carotid artery
  47. This defect seen below is associated with which trisomy?
    • Patau (trisomy 13)
    • Cleft lip
  48. Describe the presentation of Patau syndrome.
    • HEAD: Holoprosencephaly, Microcephaly, Micropthalmia, Cleft lip/ palate, Cyclops, malformed/absent nose, Cutis aplasia
    • EXTREMETIES: Polydactaly, Rocker-bottom feet
    • GI: Omphalocele, umbilical hernia, Pyloric stenosis
  49. This defect below is characteristic of which disease?
    • Cutis aplasia- absence of portion of skin
    • Patau syndrome/ Trisomy 13
  50. After administration of vasopressin, urine osmolality increases greater than 50%. What is the pathology?
    • Central DI
    • ↓ADHas a result of a pituitary tumor, autoimmune, trauma, surgery ect
  51. After administration of vasopressin, urine osmolality increases with minimal change of less than 50%. What is the pathology?
    • Nephrogenic DI
    • ADH receptor mutation 2° to hypercalcemia, lithium, demeclocyline
  52. After administration of vasopressin, urine osmolality increases by less than 10%. What is the pathology?
    • Normal: <10% increase
    • Primary polydipsia: <10% increase 
    • Differentiate between urine osmolality (concentration). If normal >800mOsm/L, if polydipsoa >500mOsm/L.
  53. How do we treat Central DI?
    • Intranasal desmopressin acetate
    • Hydration
  54. How do we treat Nephrogenic DI?
    • Hydrochlorothiazide
    • Indomethacin- inhibit prostaglandins (which inhibit ADH)
    • Amiloride- K+ sparing diuretic
  55. What is the use of the Analysis of variance test?
    Checks differences between means of 3 or more groups
  56. What is the use of a t-test?
    Checks differences between means of 2 groups
  57. Electron microscope identifies this glomerular disorder.
    • IgA nephropathy/Berger disease
    • EM- mesangial immune complex deposits
  58. Describe the presentation of IgA nephropathy.
    • Patient presents with painless hematuria (cola colored) DAYS after upper respiratory tract infection
    • (vs APSGN which occurs WEEKS after)
    • RBC casts
    • Associated with gastroenteritis.
    • IF- IgA deposits in mesangium
  59. What causes a Volvulus?
    • Malrotation
    • Failure of the midgut to rotate counterclockwise as it returns to the abdominal cavity.
    • Twisting of a bowel around its mesentery; can lead to obstruction and infarction.
  60. The image below is characteristic of which disorder?
    • Iron deficiency anemia
    • Spoon nails/ koilonycha
  61. Describe the type of anemia in Iron deficiency anemia.
    Microcytic hypochromic
  62. What is the tensilon test?
    • Tensilon/ Edrophonium test
    • Anticholinesterase = ↑Ach
    • Improves muscle activity in Myasthenia gravis ppts
  63. What is type II hypersensitivity disorder?
    IgG, IgM antibodies bind to cell surface antigens → destruction
  64. What type of hypersensitivity is Myasthenia gravis?
    Type II (antibody mediated)
  65. Describe the pathophysiology of Goodpasture's disease?
    • Autoantibodies against alpha-3 type IV collagen
    • Anti-basement membrane antibodies
  66. What causes cystic fibrosis?
    • 3 base pair deletion of Phenylalanine in the Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) gene at aino acid position 508.
    • This mutation impairs posttranslational processing of CFTR, resulting in the shunting of CFTR toward the proteasome for degradation.
  67. What can precipitate a Wenicke encephalopathy?
    Giving IV dextrose without prior thiamine.
  68. What does the arrow below point to?
    Mamillary bodies
  69. What causes coal worker's pneumoconiosis?
    • Prolonged coal dust exposure → macrophages phagocytize dust particles (<2μm) →  release cytokines which induce injury and inflammation 
    • Growth factors stimulate fibroblasts to proliferate and produce collagen (fibrosis)
  70. Describe the cause and presentation of the pathology below.
    • Apple peel atresia/ Jejunal, ileal, colonic atresia
    • Due to vascular accident -> Ischemia/obliteration of segment of bowel
    • Presents with bilious vomiting (greenish-yellowish) after first 24 hrs of life
    • Absence of large segment of small bowel
    • Blind ending proximal jejunum
    • Ileum winds/ spiral around vessel

  71. What causes pagets disease of the bone?
    Excessive osteoclastic resorption
  72. Which factors play an important role in osteoclastic differentiation?
    • M-CSF - Macrophage colony-stimulating factor
    • RANKL- Receptor for activated nuclear factor kappa beta- ligand 
  73. What are the products of pro-opiomelanocortin?
    • ACTH
    • MSH- Melanocyte stimulating hormone
    • Beta-endorphins (opoid peptide- mu, delta, kappa receptors)
  74. What is somatomedin C?
    Refered to as insulin-like growth factor which is released in response to growth hormone.
  75. With which maternal blood types does erythroblastosis fetalis and hemolytic disease of the newborn occur?
    • Maternal blood types A and B: the antibodies (Anti-A and -B) are of the IgM subtype and cannot cross the placenta.
    • In  maternal blood type O, the antibodies are primarily IgG and can cross the placenta to cause fetal hemolysis.
    • In Rh-, the Anti-D antibodies are of IgG and can cross the placenta to cause hemolysis.
  76. At what week of gestation are neural crest cells present in the rectum?
    12th week
  77. At what week of gestation are neural crest cells present in the colon?
    8th week
  78. What genetic mutation is Hirshsprung disease associated with?
    • RET gene mutations
    • Failure of neural crest cell migration
    • Receptor associated Tyrosine kinase
    • MEN2A/2B
  79. What causes orotic aciduria?
    Defect in UMP synthase. Can't convert orotic acid to Uridine monophosphate (UMP)
  80. What is the pathology seen below?
    Horse shoe kidney
  81. What causes a horseshoe kidney?
    • Results from fusion of the inferior poles of both kidneys.
    • As the kidneys ascend from the pelvis during fetal development, horseshoe kidneys get trapped under inferior mesenteric artery.
  82. What does the medullary cord contain?
    B cells, plasma cells
  83. What does the medullary sinuses contain?
    Reticular cells and macrophages
  84. What causes Lynch syndrome?
    • Mutation of DNA mismatch repair genes with subsequent microsatellite instability.
    • Mutation in the genes MSH2 and MLH1 which code for components of the human MutS and MutL homologs.
  85. What are the effects of Radiation therapy?
    Causes apoptosis of tumors via free radical formation and dsDNA breakage.
  86. What is the function of microglia?
    • Microglia (derived from monocytes) move into area of ischemic infarct 3-5 days and they phagocytize fragments of neurons, myelin and debris