Uworld28 Flashcards

Question

What are the traits for hep b virus

Answer 1

Hep B virus has a partially double-stranded DNA genome and contains a viral DNA polymerase with reverese transcriptase activity. Reverse transcriptase serves as a crucial step in viral replication; it converts transcribed positive sense single stranged RNA into the partially dsDNA genome of viral progeny.

Answer 2

massive cerebrospinal fluid inflammatory cytokine release in response to bacterial cell wall components. Treatment with dexamethasone prior to antibiotic therapy has been shown to reduce inflammation and decrease the risk of adverse outcomes (eg, seizures, focal neurologic deficits) and death. Other forms of bacterial meningitis do not seem to benefit from glucocorticoid treatment.

Answer 3

type III HSR to nonhuman proteins characterized by vasculitis resulting from tissue deposition of circulating immune complexes. Clinical findings: fever, pruritic skin rash, arthralgias, and low serum C3 and C4 complement levels.

Answer 4

The enzyme 5-alpha reductase converts testosterone to dihydrotestosterone, which drives development of external male genitalia. Genotypic males (XY) with 5-alpha reductase def develop female external genitatlia but have internal male genital ducts (eg, vas deferens) instead of internal female genital ducts (eg, uterus)

Answer 5

characterized by excessive intestinal iron absorption with deposition of iron in parenchymal tissues. Cardiac manifestations include diastolic dysfunction (initial), dilated cardiomyopathy (later) and conduction system disease (eg, sinus node dysfunction)

Answer 6

small (usually <1cm), erythematous epidermal lesions with adherent scale that are the result of chronic sun exposure. Histo: keratinocyte atypia, hyperkeratosis, and parakeratosis. A small percentage of actinic keratoses progress to invasive squamous cell carcinoma, therefore, frequent monitoring is necessary

Answer 7

snRNPs are important components of the spliceosome, a molecule which removes introns from pre-mRNA during processing within the nucleus. Spinal muscular atrophy is a disorder caused by mutations in the SMN1 gene, resulting in impaired assembly of snRNPs in lower motor neurons. Infants often have flaccid paralysis due to degeneration of anterior horn cells in the spinal cord.

Answer 8

the A2-OS interval. A shorter intercal indicates more severe stenosis. Other findings can include a diastolic rumbling murmura with presystolic accentuation due to left-atrial contraction.

Answer 9

the result of a missense mutation in which valine replaces glutamate in the hemoglobin beta-globin chain. This occurs due to a single nucleotide substitution in DNA, specifically GAG --> GTG

Answer 10

Pleural fluid normally enters the pleural space via filtration from the systemic circulation, primarily from the intercostal microvessels of the parietal pleura, and exists the pleural space via stomata in the parietal pleura that drain into the parietal pleura lymphatics.

Answer 11

Black pigment stones arise from conditions that increase the amount of unconjugated bilirubin in bile, which promotes calcium bilirubinate precipitation. This may occur in the setting of chronic hemolysis (eg, sickle cell anemia, beta-thalassemia, hereditary spherocytosis) and increased enterohepatic cycling of bilirubin (eg, ileal disease)

Answer 12

Conjugation is a form of horizontal gene transfer that involves the formation of a pilus and the direct passing of genetic material from one bacterium to another. It is a common source of antibiotic resistance and environmental adaptation. The other forms of bacterial horizontal gene transfer are transduction (viral vector) and transformation (uptake of free DNA).

Answer 13

Cytochrome c is a mitochondiral enzyme that activates caspases and indirectly brings about cell death through intrinsic pathway apoptosis.

Answer 14

characterized by excessive intake of free water, leading to hyponatremia and production of larege volumes of dilute urine. Water restriction normalizes serum sodium levels and increases urine osmolality.

Answer 15

frequently develops in patients with metabolic syndrome (eg, obesity, dyslipidemia, insulin resistance) and can progress to cirrhosis due to chroic inflammation and hepatocyte injury.

Answer 16

caused by a chronic infection by Trypanosoma cruzi and causes secondary achalasia due to destruction of the submucosal (Meissner) and myenteric (Auerbach) plexus. Other manifestations can include nonischemic cardiomyopathy and megacolon.

Answer 17

the difference in event rate between a control group and a treatment group (ie, the percentage of patients improved by treatment) ARR= control rate - treatment rate

Answer 18

involves a neutral stimulus being repeatendly paired with a non-neutral stimulus that elicits a reflexive, unconditioned response. Over time, the formerly neutral stimulus is able to evoke a conditioned response by itself in absence of the non-neutral stimulus.

Answer 19

decreased respiratory rate, pupillary constriction (ie, miosis) and depressed mental status. Hypothermia, hypotension, and decreased tidal volume are also common findings.

Answer 20

Beta blockers act as competitive antagonists for endogenous catecholamines; therefore, toxicity presents with hypotension, bradycardia, bronchospasm, and hypoglycemia. The hypotension and hypoglycemia contribute to altered mental status.

Answer 21

the total cross-sectional area of all the airways at that level. Airway resistance is high in the trachea and reached a peak in the medium sized bronchi, where total cross-sectional area ia at a minimum. Airway resistance then progressively decreases as total cross-sectional area increases through the smaller bronchioles, terminal bronchioles, and alveoli.

Answer 22

results from an exaggerated immunologic response to an inhaled antigen (eg, mold, animal protein), and presents with cough and dysnpea of variable acuity. Bronchoalveolar lavage typically shows high relative lymphocyte count (eg, >20%), which helps support the diagnosis.

Answer 23

the intercostal nerves that derive from the ventral nerve rami A nerve block can be used to control pain from these areas when opioids are ineffective, contraindicated, or have intolerable adverse effects.

Answer 24

caused by a lesion in the ocular parasympathetic (constriction) or sympathetic (dilation) pathways. In this patient, aniscocria increases in bright light, indicating that the larger right pupil is unable to constrict due to a defect in the right parasympathetic pathway.

Answer 25

an inflammatory increase in vascular and pleural membrane permeability. Such effusions are exudative by Light criteria, typically with relatively high pleural fluid protein and lactate dehydrogenase concentrations. Tuberculosis pleural effusions typically demonstrate a lymphocyte-predominant leukocyte pattern.

Answer 26

two distinct mechanisms: negatively by binding of the repressor protein to the operator locus and positively by cAMP-CAP binding upstream from the promoter region. Constitutive expression of the structural genes of the lac operon occurs with mutations that impair the binding of the repressor protein (Lac I) to its regulatory sequence in the operator region.

Answer 27

a delayed-type HSR. Initially, Langerhans cells travel to regional lymph nodes and present haptens to naive T cells, leading to clonal expansion. On reexposure to the hapten, sensitized T cells cause tissue destruction that manifests as pruritic erythema, vesicles, and/or bullae 2-3 days after exposure.

Answer 28

a dating error (eg, inaccurate gestational age). The maternal serum quadruple screen assesses for risk of congenital defects and fetal aneuploidy and includes measurement of alpha-fetoprotein levels, which are dependent on gestational age. alpha fetoprotein is decreased in Down syndrome and Edwards (trisomy 18)

Answer 29

characterized by liver failure and encephalopathy following salicylate (aspirin) administration in children with a febrile illness. Aspirin induced mitochondrial dysfunction causes impaired fatty acid metabolism and microvesicular steatosis of the liver.

Answer 30

single stranded flavivirus transmitted by mosquitoes, most commonly in the summer. Most infections are asymptomatic or may present with a flu-like illness (West Nile fever), often with a maculopapular or morbilliform rash. Neuroinvasive disease manifests as meningitis, encephalitis, or asymmetric flaccid paralysis; patients may have parkinsonian features (eg, tremor)

Answer 31

decreasing urine sodium excretion (thereby increasing circulating blood volume) and increasing the sensitivity of the vasculature to endogenous vasoconstrictors (eg, norepinephrine)

Answer 32

ADH acts on the medullary segment of the collecting duct to increase urea and water reabsorption, allowing for the production of maximally concentrated urine.

Answer 33

organized by selecting a group of people (ie, cohort) determining their exposure status, and then following them over time for development of the disease of interest.

Answer 34

locally-acting substances (eg, adenosine, nitric oxide) that trigger coronary arteriolar vasodilation. Pharmacologic arteriolar vasodilatorys (eg, adenosine, dipyridamole) mimic the vasodilation that occurs with exercise and may cause redistribution of blood flow from ischemic to nonischemic areas of myocardium (ie, coronary steal).

Answer 35

an antimycobacterial agent that specifically inhibits the synthesis of mycolic acids, which are essential components of the mycobacterial peptidoglycan cell wall. Without mycolic acids, the mycobacateria lose their acid-fastness and become unable to synthesize new cell walls or multiply.

Answer 36

a rare AR disorder of de novo pyrimidine synthesis that occurs due to a defect in uridine 5'-monophosphate (UMP) synthase. Children typically present with developmental delay, megaloblastic anemia, and large amounts of urinary orotic acid. Uridine supplementation can improve symptoms as uridine is converted to UMP via nucleoside kinases.

Answer 37

The quadriceps muscle group is connected to the patella, which is attached to the tibial tubercle by the patellar ligament. Repetitive quadriceps contraction (eg, jumping) in adolescents can result in Osgood-Schlatter disease, which is characterized by focal anterior knee pain and swelling due to chronic avulsion of the tibial tubercle.

Answer 38

Oral leukoplakia is a potentially premalignant lesion; the risk for progression to invasive carcinoma is related to the degree of dysplasia.

Answer 39

bone marrow failure due to multipotent hematopoietic stem cell destruction. Cases are often triggered by meds, radiation, toxins, or viruses, Meds-induced AA can be due to dose-dependent bone marrow damage (eg, chemotherapy, immunosuppressive drugs) or idiosyncratic reactions (eg, antiseizure meds, sulfonamides, nifedipine) that may occur at any point during or after therapy.

Answer 40

non IgE mediated reaction that causes inflammation and eosinophilic infiltration of the distal colon. Classic presentation is in early infancy with painless, blood streaked stools that resolve with dietary avoidance of the offending food protein (eg, cow's milk)

Answer 41

results from overly rapid correction of chronic hyponatremia. Clinical features: quadriplegia, pseudobulbar palsy, and reduced level of consciousness. MRI: focal demyelination of the pons

Answer 42

the fast emergence of mycobacterial antibiotic resistance from rapid, selective gene mutations. Isoniazid monotherapy may be used for patients who have a positive PPD and a negative chest x-ray (ie, no evidence of clinical disease)

Answer 43

the number of true negatives divivded by the total number of subjects confirmed as not having the disease TN = (specificity)*(number of patients confirmed without the disease) FP= (1-specificity)*(number of patients confirmed without the disease)

Answer 44

lower peak and average drug levels, which can help reduce toxicity.

Answer 45

measures how much a treatment reduces the risk of an unfavorable outcome. Two methods to calculate it are: RRR= (Riskcontrol - Risktreatment)/ Riskcontrol RRR= 1- relative risk

Answer 46

neutrophil recruitment and activation leading to the release of cytotoxic granules that kill bacteria but also cause liquefying necrosis of surrounding tissue.

Answer 47

a common complication of hip fracture and/or arthroplasty because of the proximity of the sciatic nerve to the hip joint. Injury to the sciatic nerve in the pelvis causes neurological deficits across the sciatic nerve (knee flexion), common peroneal nerve (dorsiflexion, numbness of the calf and dorsal foot), and tibial nerve (plantar flexion, ankle reflex)

Answer 48

glomeruli, Bowman space, proximal tubules, loop of Henle, and distal convoluted tubules.

Answer 49

the collecting system of the kidney (eg, collecting tubules and ducts, major and minor calyces, renal pelvis, ureters)

Answer 50

classically presents in premature infants with increased work of breathing and hypoxia at birth due to surfactant deficiency. Poor alveolar compliance leads to widespread atelectasis and decreased functional residual capacity. Airway resistance is often increased due to lung inflammation and edema.

Answer 51

Enterohemorrhagic E colic is primarily contracted after eating undercooked ground beef. EHEC produces Shiga toxin, which causes hemorrhagic colitis and can lead to hemolytic-uremic syndrome. HUS is characterized by acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia; children age <10 are at greatest risk.

Answer 52

characterized by absent submucosal and myenteric ganglion cells in the distal colon. Contrast enema classically shows a narrowed aganglionic segment (most commonly rectosignmoid) with an abrupt transition zone to the dilated, histologically normal proximal colon.

Answer 53

a form of chronic kidney disease caused by prolonged, heavy intake of nonsteroidal anti-inflammatory drugs and/or acetaminophen. Pathologic characteristics include chronic interstitial nephritis and papillary necrosis.

Answer 54

an extrapyramidal side effect of antipsychotic medication characterized by inner restlessness and an inability to sit or stand in one position. Treatment involves a reduction in the antipsychotic dose, if possible, or the addition of a beta blocker or benzodiazepine.

Answer 55

a parasomnia characterized by dream-enactment behaviors due to a loss of atonia during REM sleep. Most patients with idiopathic RBD eventually develop a disorder of alpha-synuclein neurodegeneration, most commonly Parkinson disease,

Answer 56

an increase in pulse pressure, a slight decrease in diastolic pressure, and the characteristic isolated systolic hypertension commonly seen in the elderly population.

Answer 57

A complete atrioventricular (AV) canal defect is comprosed of an atrial septal defect, a ventricular septal defect, and a common AV valve.

Answer 58

The toxins secreted by these organism modify electrolyte handling by enterocytes but do not cause cell death; therefore, no erythrocytes or leukocytes are typically noted on stool microscopy.

Answer 59

IgE-binding monoclonal antibodies (eg, omalizumab) are effective in treating asthma that remains uncontrolled despite optimal therapy with bronchodialtors and inhaled corticosteroids. IgE binding monoclonal antibodies reduce airway inflammation by blocking the binding of IgE to the IgE receptors on mast cells and preventing the release of proinflammatory substances, including histamine and leukotrienes.

Answer 60

disruption of vitamin-K producing intestinal flora.

Answer 61

Because tumors with defective DNA mismatch repair generate high levels of neoatntigens, they are particularly dependent on adaptations (eg, overexpression of immune checkpoints) to avoid cytotoxic T cell destruction. Treatment with immune checkpoint inhibitors restore anti tumor cytotoxic T cell activity and often dramatically reduce tumor burden.

Answer 62

Polymerase chain reaction is used to amplify small fragments of DNA (eg, genes, exons, noncoding regions) by repeated replication. It requires primers that are complementary to the regions of DNA flanking the segment of interest. Thermostable DNA polymerase, deoxynucleotide triphosphates, and a source DNA template strand are also necessary.

Answer 63

The posterior cruciate ligament attaches proximally to the medial femoral condyle (anterolateral surface) and distally to the posterior aspect of the intercondylar area of the tibia. It prevents posterior displacement of the tibia relative to the femur when the knee is flexed.

Answer 64

Myocardial infarction may be complicated by acute left ventricular failure and cardiogenic shock. In cardiogenic shock, increased LV end diastolic pressure is transmitted backward to cause increased pulmonary capillary wedge pressure (evidenced by pulmonary edema) and increased central venous pressure. There is markedly decreased cardiac output, which causes hypotension and decreased coronary perfusion pressure.

Answer 65

Peripheral edema results from the accumulation of fluid in the interstitial spaces. Factors that promote edema include elevated capillary hydrostatic pressure, decreased plasma oncotic pressure, and impaired lymphatic drainage. In chronic heart failure, increased lymphatic drainage initially offsets factors favoring edema, temporarily delaying edema development.

Answer 66

characterized by focal tubular epithelial necrosis with denuding of the basement membrane. Most patients experience tubular re-epithelization and regain normal renal function.

Answer 67

Beta blockers decrease AV nodal conduction, leading to an increased AV nodal refractory period. This correleates to PR interval prolongation on ECG.

Answer 68

The hep B surface antigen of hep B virus must coat the hep D antigen of hep D virus before it can infect hepatocytes and multiply.

Answer 69

Presbyopia and skin wrinkles are age related changes. Presbyopia occurs due to denaturation of structural proteins within the lens, leading to loss of lens elasticity which can result in improved vision in patients with mild myopia. Decreased synthesis and increased breakdown of collagen and elastin contribute to the development of skin wrinkles.

Answer 70

adrenal cortical hyperplasia due to excess of the adrenal cortex by ACTH. The classic, non salt wasting form presents in boys age 2-4 with early virilization, accelerated linear growth, and elevated levels of 17-hydroxyprogesterone and androgens

Answer 71

low doses of exogenous corticosteroids to suppress excess ACTH secretion, which reduces production of androgens by the adrenal cortex.

Answer 72

Advances hypoxic lund disease (eg, chronic obstructive pulmonary disease, interstitial lung disease, obesity hypoventilation syndrome) is a common cause of pulmonary hypertension (ie, increased right ventricular afterload). The increase in pulmonary arterial pressure mainly results from chronic and diffuse hypoxic vasoconstriction, with a lesser degree of vascular remodeling than in (primary) pulmonary arterial hypertension.

Answer 73

The ureters run in close proximity to the pelvic lymph nodes and the uterine artery in the female pelvis, which predisposes them to injury during pelvic surgery.

Answer 74

Bilateral vestibular schwannomas. NF2 is a dominantly inherited disorder caused by mutations of the NF2 gene on chromosome 22.

Answer 75

APP (ch.21), presenilin 1 and presenilin 2