UWSA1-4 Flashcards

Question

Celiac Disease S&S

Answer 1

This patient, with persistent diarrhea, bloating, and weight loss, has typical symptoms of celiac disease. Celiac disease is often associated with dermatitis herpetiformis, which causes grouped vesicles, papules, and urticaria on the extensor surfaces of the elbows, knees, sacrum, and buttocks. The lesions are extremely pruritic and are caused by cross-reactivity of anti-gliadin IgA antibodies with transglutaminase at the dermal basement membrane. Skin biopsy will show microabscesses at the dermal papillary tips, which coalesce to form subepidermal blisters. Immunofluorescence staining for IgA confirms the diagnosis.

Answer 2

Celiac disease is often associated with dermatitis herpetiformis, which causes grouped vesicles, papules, and urticaria on the extensor surfaces of the elbows, knees, sacrum, and buttocks. The lesions are extremely pruritic and are caused by cross-reactivity of anti-gliadin IgA antibodies with transglutaminase at the dermal basement membrane. Skin biopsy will show microabscesses at the dermal papillary tips, which coalesce to form subepidermal blisters. Immunofluorescence staining for IgA confirms the diagnosis.

Answer 3

In the small bowel, celiac disease causes marked villous atrophy in a background of diffuse enteritis. CD8+ T-cell lymphocytes infiltrate the small intestine surface epithelium, and a wide range of inflammatory cells (CD4+ T-cell lymphocytes, plasma cells, macrophages, eosinophils, and mast cells) take up residence in the lamina propria.

Answer 4

Crohn disease

Answer 5

polycystic ovary syndrome (PCOS), a common endocrine disorder in women that is associated with an elevated LH/FSH ratio and ovarian hyperresponsiveness to LH. Because LH stimulates the ovarian theca cells to produce androgens, patients with PCOS usually have hyperandrogenism, which can be diagnosed clinically (eg, acne, hirsutism) or biochemically (ie, high testosterone level) Elevated androgen levels and an unbalanced LH/FSH ratio both inhibit the maturation and release of a single dominant ovarian follicle (ie, ovulation). Therefore, patients with PCOS are typically anovulatory and develop multiple, smaller follicles that arrest in development. These follicles eventually degenerate and accumulate fluid, causing the classic appearance of bilaterally enlarged, polycystic ovaries.

Answer 6

Lesch-Nyhan syndrome caused by an X-linked recessive defect in hypoxanthine-guanine phosphoribosyltransferase (HGPRT). The HGPRT enzyme participates in the purine salvage pathway by catalyzing the conversion of hypoxanthine and guanine to inosine monophosphate and guanosine monophosphate, respectively. Deficiency of this enzyme causes decreased purine salvage, increased purine synthesis, hyperuricemia, and hyperuricuria.

Answer 7

Characteristic features include self-mutilating behavior (eg, finger and lip biting), mild intellectual disability, involuntary movements (eg, dystonia), delayed motor development, nephrolithiasis, and gout. Parents may also report a "frost" on the skin under the affected child's diaper due to hyperuricuria. Treatment with allopurinol decreases uric acid levels and therefore relieves symptoms related to gout and urolithiasis, but this treatment has little effect on neurological symptoms.

Answer 8

tetracyclines (eg, doxycycline) and the aminoglycosides (eg, streptomycin)

Answer 9

macrolide antibiotic that binds to the 50s prokaryotic ribosomal subunit and blocks the translocation step by preventing tRNA release from the donor site after peptide bond formation.

Answer 10

Chloramphenicol binds to the 50s prokaryotic ribosomal subunit and blocks peptidyltransferase action, thereby preventing new peptide bond formation.

Answer 11

Rifampin blocks prokaryotic mRNA synthesis by bacterial RNA polymerase. Typically used in combination with other antibiotics to minimize bacterial resistance, rifampin treats active tuberculosis and prevents meningitis caused by Neisseria meningitidis or Haemophilus influenzae.

Answer 12

Puromycin is an aminonucleoside antibiotic that has a structure analogous to aminoacyl-tRNA. In prokaryotes, it leads to the premature release of unfinished polypeptide chains as polypeptidyl-puromycin derivatives.

Answer 13

Muscarinic agonist

Answer 14

Muscarinic antagonist

Answer 15

Acetylcholinesterase inhibitor

Answer 16

alpha-adrenergic receptor agonist (α1 \> α2)

Answer 17

peripheral blood smear shows macrocytosis and a hypersegmented neutrophil.

Answer 18

This patient has fatigue, peripheral neuropathy, and atrophic glossitis. The peripheral blood smear shows macrocytosis and a hypersegmented neutrophil. In addition, she has a history of autoimmune thyroiditis (the most common cause of hypothyroidism in developed countries). In light of her current symptoms, this patient most likely has pernicious anemia due to autoimmune destruction of gastric mucosa. Over time, this damage results in chronic atrophic gastritis, causing profound hypochlorhydria and leading to a compensatory increase in serum gastrin levels (antral G cell gastrin secretion is inhibited by hydrochloric acid). In addition, the loss of intrinsic factor-secreting parietal cells leads to depletion of vitamin B12 stores and eventual deficiency. Vitamin B12 deficiency causes hematologic (eg, macrocytic anemia) and neurologic (eg, peripheral neuropathy, combined degeneration of ascending and descending spinal tracts) manifestations. Pernicious anemia occurs most commonly in patients age \>50, but it can be seen more frequently in younger patients with other autoimmune disorders.

Answer 19

Vitamin B12 deficiency causes hematologic (eg, macrocytic anemia) fatigue, peripheral neuropathy, and atrophic glossitis and neurologic (eg, peripheral neuropathy, combined degeneration of ascending and descending spinal tracts) manifestations.

Answer 20

Pernicious anemia is due to autoimmune destruction of gastric mucosa (parietal cells). Production of gastric acid is diminished, leading to a compensatory increase in gastrin release. Secretion of gastric intrinsic factor is also lost, leading to vitamin B12 deficiency. Over time, this damage results in chronic atrophic gastritis, causing profound hypochlorhydria and leading to a compensatory increase in serum gastrin levels (antral G cell gastrin secretion is inhibited by hydrochloric acid). In addition, the loss of intrinsic factor-secreting parietal cells leads to depletion of vitamin B12 stores and eventual deficiency. Vitamin B12 deficiency causes hematologic (eg, macrocytic anemia) and neurologic (eg, peripheral neuropathy, combined degeneration of ascending and descending spinal tracts) manifestations. Pernicious anemia occurs most commonly in patients age \>50, but it can be seen more frequently in younger patients with other autoimmune disorders.

Answer 21

Secretin is produced by S cells of the duodenal mucosa in response to passage of gastric acid through the pylorus.

Answer 22

Varicoceles are dilations of the spermatic vein pampiniform plexus that are common in adults. They tend to arise on the left side as the left gonadal vein is one of the longest veins in the body and drains into the left renal vein at a perpendicular angle. The pressure within the left renal vein is also higher due to compression between the aorta and the superior mesenteric artery ("nutcracker effect"). This increased pressure in the left gonadal vein results in valve leaflet failure and retrograde blood flow toward the testis on standing. When the patient is recumbent, much of the blood returns to systemic circulation and the varicocele diminishes in size. A varicocele can present as a vague fullness or as a large, compressible mass likened to a "bag of worms." It does not transilluminate light. Some individuals are asymptomatic; others experience aching pain relieved with recumbency, testicular atrophy, or reduced fertility (due to blood stasis and/or increased scrotal temperature).

Answer 23

Varicoceles are dilations of the spermatic vein pampiniform plexus that are common in adults. They tend to arise on the left side as the left gonadal vein is one of the longest veins in the body and drains into the left renal vein at a perpendicular angle. The pressure within the left renal vein is also higher due to compression between the aorta and the superior mesenteric artery ("nutcracker effect"). This increased pressure in the left gonadal vein results in valve leaflet failure and retrograde blood flow toward the testis on standing. When the patient is recumbent, much of the blood returns to systemic circulation and the varicocele diminishes in size. A varicocele can present as a vague fullness or as a large, compressible mass likened to a "bag of worms." It does not transilluminate light. Some individuals are asymptomatic; others experience aching pain relieved with recumbency, testicular atrophy, or reduced fertility (due to blood stasis and/or increased scrotal temperature)

Answer 24

The pressure within the left renal vein is also higher due to compression between the aorta and the superior mesenteric artery

Answer 25

A varicocele can present as a vague fullness or as a large, compressible mass likened to a "bag of worms." It does not transilluminate light. Some individuals are asymptomatic; others experience aching pain relieved with recumbency, testicular atrophy, or reduced fertility (due to blood stasis and/or increased scrotal temperature).

Answer 26

Hydroceles are peritoneal fluid collections that accumulate between the parietal and visceral layers of the tunica vaginalis. Hydroceles can be small or quite large, with pain increasing with the mass size. Although communicating hydroceles can change in size with positional changes, the fluid within a hydrocele is easily transilluminated

Answer 27

Varicoceles are dilations of the spermatic vein pampiniform plexus that enlarge with standing and regress with lying down. Patients may be asymptomatic or experience aching pain relieved with recumbency, testicular atrophy, or reduced fertility.

Answer 28

acanthosis nigricans, a reactive skin condition characterized by brown to black, velvety thickened plaques that tend to arise in flexural regions such as the axillae or back of the neck. Acanthosis nigricans is most commonly associated with benign conditions such as insulin resistance or obesity. However, it can also signal the presence of malignancy within the gastrointestinal (GI) tract (eg, stomach, liver) or lungs. When acanthosis nigricans appears suddenly, spreads quickly, or involves the mucous membranes or palms and soles, the likelihood of malignancy increases. It has been postulated that malignancy and hyperinsulinemia cause acanthosis nigricans by influencing growth factor production.

Answer 29

Adrenal insufficiency can present with fatigue and weight loss, and it is associated with hyperpigmentation due to increased secretion of ACTH and melanocyte-stimulating hormone in response to inadequate cortisol levels.

Answer 30

rare autosomal dominant disease characterized by pigmented mucocutaneous macules (eg, perioral pigmentation) and hamartomatous polyps in the GI tract. Progressive growth can lead to malignant transformation.

Answer 31

may be associated with a number of nutritional deficiencies, including iron, vitamin B12, folate, and other nutrients.

Answer 32

Mechanical prosthetic valves are thrombogenic, and patients are at risk of valve thrombosis and systemic thromboembolic complications. In patients with mechanical mitral valve replacement, long-term anticoagulation with a vitamin K antagonist (eg, warfarin) is recommended to reduce the risk of thromboembolic complications. Vitamin K is essential for the gamma-carboxylation of coagulation factors II, VII, IX and X. It is converted into an "inactive" form during the process and reactivated by the enzyme vitamin K epoxide reductase. Warfarin competitively inhibits this enzyme, depleting the body of biologically active vitamin K. This interferes with the vitamin K-dependent synthesis of active clotting factors.

Answer 33

(eptifibatide, abciximab, tirofiban)

Answer 34

clopidogrel, ticagrelor, prasugrel

Answer 35

Alirocumab is a monoclonal antibody against PCSK9 (increases availability of LDL receptors on hepatocyte membranes, resulting in increased LDL clearance from the circulation.)

Answer 36

Most prostate cancers are androgen-dependent. Androgen deprivation therapy, either by surgical orchiectomy or pharmacologic suppression of testosterone production, can slow progression of the disease and relieve symptoms (eg, bone pain). Leuprolide is a gonadotropin-releasing hormone (GnRH) analog. It has agonist properties when administered in a pulsatile fashion and can cause a rise in LH and testosterone release on initial administration. However, continuous GnRH effect, whether from a GnRH infusion or long-term leuprolide use, suppresses pituitary LH release (Choice E) and leads to reduced production of testosterone by Leydig cells. The lower levels of circulating testosterone produce a clinical effect similar to surgical orchiectomy.

Answer 37

Flutamide, a nonsteroidal agent used in the treatment of prostate cancer, acts as a competitive testosterone receptor inhibitor. Prevention of androgen-receptor binding blocks the stimulatory effect of androgens on the primary tumor and metastases.

Answer 38

During the first three months of embryonic development, precursor melanocytes migrate from the neural crest to the dermis and then the epidermis. Once established in the epidermis, the precursor cells differentiate into melanocytes. Identifiable melanosomes appear within the melanocytes of the fetal epidermis by eight to ten weeks of gestational age.

Answer 39

Originating from the tissues of the posterior yolk sac, primordial germ cells similarly migrate to the gonadal ridge during the fifth and sixth weeks of embryonic development. (Like melanocytes, germ cells may stray from the migration route and take up residence in different organs or tissues, which accounts for the development of melanocytic and germ cell tumors in unusual locations.) As oogonia, the germ cells undergo numerous mitoses and then meiosis, finally arresting as primary oocytes in meiotic prophase. As undifferentiated spermatogonia, the germ cells proliferate in the basal compartment, with some giving rise to primary spermatocytes.

Answer 40

Conotruncal (outflow tract) defects are common in infants with DGS and include persistent truncus arteriosus, tetralogy of Fallot, and interrupted aortic arch. In utero, a wall normally divides the single truncal root into a separate pulmonary artery and ascending aorta. Persistent truncus arteriosus occurs when this septum does not form, leading to branching of the aorta, pulmonary arteries, and coronary arteries from a single arterial trunk. This defect can lead to cyanosis and heart failure if it is not surgically corrected.

Answer 41

DiGeorge syndrome (DGS) is caused by a chromosome 22q11.2 deletion and results in failed development of the third and fourth pharyngeal pouches during week 4 of embryogenesis. Consequently, individuals with DGS have defective T cell-mediated immunity due to an absent or hypoplastic thymus (absent thymic shadow), tetany or seizures secondary to absent parathyroid glands (hypocalcemia), and defects in the heart and great vessels.

Answer 42

Conotruncal cardiac defects Abnormal facies Thymic aplasia/hypoplasia Cleft palate Hypocalcemia (seizures or tetany)

Answer 43

IgA and IgG and IgE Activated CD4 cells express CD40 ligand (CD40L), which stimulates B cells to undergo class-switch recombination. Defects in CD40L signaling prevent B cells from producing significant amounts of immunoglobulin other than IgM (hyper-IgM syndrome), leading to recurrent sinopulmonary, gastrointestinal, and opportunistic infections The 5 major types of immunoglobulin are distinguished by different amino acid sequences in their heavy chain (alpha, delta, epsilon, gamma, mu). Unstimulated B cells constitutively express mu and delta heavy chains and generate only IgM and IgD. In order to generate other immunoglobulin types, B cells must undergo costimulation by CD40 ligand (CD40L), which is expressed on the surface of activated CD4 cells. Binding of CD40L to CD40 triggers activated B cells to undergo class-switch recombination, which replaces the mu heavy chain with alpha, epsilon, or gamma depending on concurrent cytokines released by the activated CD4 cell. This leads to the production of IgA (alpha heavy chain), IgE (epsilon heavy chain), or IgG (gamma heavy chain). Because CD40L is required for B cells to class-switch from IgM to other major immunoglobulin types, defects in CD40L signaling result in elevated IgM and no significant IgA, IgE, or IgG. This rare disorder is called hyper-IgM syndrome and is characterized by recurrent sinopulmonary, gastrointestinal, and opportunistic (eg, Pneumocystis jiroveci) infections. Although interaction between B and T cells is impaired in this condition, overall B and T cell quantities tend to be normal.

Answer 44

An error in CD40 signaling from t cells to b cells The 5 major types of immunoglobulin are distinguished by different amino acid sequences in their heavy chain (alpha, delta, epsilon, gamma, mu). Unstimulated B cells constitutively express mu and delta heavy chains and generate only IgM and IgD. In order to generate other immunoglobulin types, B cells must undergo costimulation by CD40 ligand (CD40L), which is expressed on the surface of activated CD4 cells. Binding of CD40L to CD40 triggers activated B cells to undergo class-switch recombination, which replaces the mu heavy chain with alpha, epsilon, or gamma depending on concurrent cytokines released by the activated CD4 cell. This leads to the production of IgA (alpha heavy chain), IgE (epsilon heavy chain), or IgG (gamma heavy chain).

Answer 45

DNA methylation refers to the addition of methyl groups to nucleotide residues (often adenine and cytosine) by the enzyme DNA methyltransferase. In eukaryotes, cytosine-guanine dinucleotide repeats (CpGs) in the promoter region of genes are preferentially methylated as part of the epigenetic code – a heritable form of gene regulation not reliant on changes in the genetic code itself. The methylation of cytosine residues in CpGs prevents transcription factors from binding to the promoter, effectively silencing transcription of genes not required by terminally differentiated somatic cells. It can also be pathologic; an example includes malignancies in which selective methylation downregulates tumor suppressor genes. In contrast to eukaryotes, the methylation of adenine and cytosine residues in prokaryotic DNA helps the cell distinguish its DNA from foreign DNA. Unmethylated foreign DNA is destroyed as part of a cellular defense mechanism. Adenine residues may also be methylated shortly after DNA replication, allowing mismatch repair enzymes to distinguish between old and new strands.

Answer 46

Low transcriptional activity due to methylation

Answer 47

β-Glucocerebrosidase Gaucher disease

Answer 48

Autosomal recessive

Answer 49

Glucocerebroside

Answer 50

Hepatosplenomegaly Pancytopenia Bone pain/osteopenia

Answer 51

X-linked recessive

Answer 52

α-Galactosidase A

Answer 53

Globotriaosylceramide

Answer 54

Angiokeratomas Peripheral neuropathy Glomerulopathy

Answer 55

Autosomal Recessive

Answer 56

β-Hexosaminidase A

Answer 57

GM2 (ganglioside)

Answer 58

Macular cherry-red spot Progressive neurodegeneration

Answer 59

Autosomal recessive

Answer 60

Sphingomyelinase

Answer 61

Sphingomyelin

Answer 62

Macular cherry-red spot Progressive neurodegeneration Hepatosplenomegaly

Answer 63

Galactocerebrosidase

Answer 64

Galactocerebroside & psychosine

Answer 65

Progressive neurodegeneration Peripheral neuropathy Optic atrophy

Answer 66

Arylsulfatase A

Answer 67

Cerebroside sulfate

Answer 68

Progressive neurodegeneration Peripheral neuropathy

Answer 69

Autosomal Recessive

Answer 70

Autosomal Recessive

Answer 71

Autosomal recessive

Answer 72

Gaucher Disease

Answer 73

Gaucher disease is the most common lysosomal storage disorder. It is an autosomal recessive condition resulting from β-glucocerebrosidase deficiency. Accumulation of the glycolipid glucocerebroside in lysosomes of macrophages results in the cardinal finding of "wrinkled tissue paper" on microscopy. These Gaucher cells are found throughout the body. In addition, accumulation of lipid-laden macrophages in the liver and spleen leads to hepatosplenomegaly. The enlarged spleen breaks down blood cells faster than they are produced, resulting in anemia, thrombocytopenia, and leukopenia (pancytopenia). Blood cell production may also be impaired from bone marrow infiltration. The pathologic lipid accumulation also triggers the release of lysosomal proteolytic enzymes and inflammatory mediators that are destructive to bone. Affected patients have osteopenia, collapse of the bony cortex, and bone infarction. The compromised vascular supply of the bone can present as bone pain crises and later progress to pathologic fractures and avascular necrosis (osteonecrosis). This patient's clinical and radiographic findings are suggestive of avascular necrosis.

Answer 74

Gaucher Disease Accumulation of the glycolipid glucocerebroside in lysosomes of macrophages results in the cardinal finding of "wrinkled tissue paper" on microscopy. These Gaucher cells are found throughout the body.

Answer 75

Fabry disease, a disorder of α-galactosidase A deficiency, can initially present with severe extremity pain. Deposition of globotriaosylceramide in nerve tissue causes a peripheral neuropathy that manifests as a burning sensation.

Answer 76

Metachromatic leukodystrophy is caused by a deficiency of arylsulfatase A, an enzyme responsible for metabolism of the myelin glycolipid cerebroside sulfate. Accumulation of this substrate causes central and peripheral nervous system demyelination, leading to neurologic regression, seizures, and ataxia.

Answer 77

Glucose-6-phosphatase deficiency causes von Gierke disease, an autosomal recessive glycogen storage disorder that presents in infancy. Typical features include hepatomegaly, hypoglycemia, and lactic acidosis

Answer 78

Tay-Sachs disease (hexosaminidase A deficiency) and Niemann-Pick disease (sphingomyelinase deficiency) present in infancy with neurologic degeneration and cause death in early childhood secondary to respiratory infection and failure. Funduscopic examination reveals a characteristic, cherry-red macular spot.

Answer 79

accumulated substrate Niemann-Pick includes hepatosplenomegaly and Tay-Sachs does not The histology for diagnosing Tay-Sachs disease and Niemann-Pick disease also differs. Niemann-Pick disease’s histological diagnosis is most notable for its lipid laden macrophages. In other words, under the microscope and histology slides, doctors can see a patient’s macrophage with an unusual large amount of lipids inside them, known as foam cells. Unlike Niemann-Pick disease, Tay-Sachs disease is notable for its lysosomes with onion skin for histology – literally, the lysosomes in the cells look like onions with multiple circular peel layers in it!

Answer 80

Ip3 ## Footnote This patient with coffee ground emesis, orthostatic hypotension, and tachycardia likely has a brisk upper gastrointestinal hemorrhage due to excessive ibuprofen use. His sympathetic tone has increased in an effort to prevent circulatory failure from hypovolemia, causing vasoconstriction (eg, cool, clammy skin) and tachycardia. The 2 major mediators of the sympathetic response are epinephrine and norepinephrine. These catecholamines function by stimulating adrenergic cell surface receptors. The adrenergic receptor responsible for arteriolar constriction and increasing blood pressure is the alpha-1 receptor. This receptor functions via the phosphatidylinositol second messenger system. When a catecholamine binds to the alpha-1 receptor, Gq protein becomes stimulated and activates phospholipase C. Phospholipase C then releases inositol triphosphate (IP3) and diacylglycerol (DAG) from membrane phospholipids. IP3 liberates calcium stored in the endoplasmic reticulum and DAG activates protein kinase C, ultimately leading to smooth muscle contraction.

Answer 81

S-adenosylmethionine (SAM) is produced by condensation of methionine with ATP. SAM functions as a methyl group donor in several reactions requiring methyl transfer. In the adrenergic system, SAM is required for the conversion of norepinephrine to epinephrine by the enzyme phenylethanolamine-N-methyltransferase. This enzymatic reaction predominantly occurs in the adrenal medulla and is upregulated by cortisol.

Answer 82

Infliximab

Answer 83

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine produced by activated macrophages and T cells in response to inflammatory stimuli (eg, infection, injury). TNF-alpha stimulates signaling pathways (eg, nuclear factor–κB) that lead to local and systemic inflammatory reactions through the following mechanisms: Local: Increased expression of adhesion molecules on endothelial cells, leading to recruitment of leukocytes (eg, neutrophils, macrophages). Stimulation of phagocytosis Systemic: Induces fever (prostaglandin-mediated effect), acute phase responses (eg, elevated C-reactive protein), anorexia/cachexia, and increased leukocyte production. Triggers release of additional pro-inflammatory cytokines (eg, IL-1, IL-6)

Answer 84

Excessive TNF-alpha activity is implicated in the pathogenesis of a variety of chronic inflammatory conditions (eg, rheumatoid arthritis, Crohn disease) and is an important target for therapeutic agents (eg, TNF-alpha inhibitors).

Answer 85

Infliximab and adalimumab are monoclonal antibodies that bind TNF-alpha and prevent it from associating with its cell-surface receptors, thus blocking proinflammatory effects. Another TNF-alpha inhibitor is etanercept, a recombinant TNF-alpha receptor fusion protein that acts as a decoy receptor, binding TNF-alpha and keeping it away from functional receptors.

Answer 86

Imatinib inhibits BCR-ABL1 tyrosine kinase, the abnormal gene product associated with chronic myeloid leukemia.

Answer 87

Natalizumab, a monoclonal antibody against integrin, interferes with leukocyte adhesion and subsequent migration into tissue. Natalizumab can be used to treat multiple sclerosis and Crohn disease, but is associated with increased risk of progressive multifocal leukoencephalopathy.

Answer 88

Tacrolimus decreases T-cell activation and proliferation by inhibiting calcineurin and blocking transcription of IL-2. It is used to prevent rejection following solid organ transplantation and to treat severe atopic dermatitis.

Answer 89

Angina pectoris

Answer 90

This patient has stable angina (ie, angina pectoris), which is characterized by chest pain that develops with exertion and resolves within 1–2 minutes of rest. Stable angina can progress to acute coronary syndrome (ie, unstable angina or myocardial infarction), which is caused by occlusion of the coronary vasculature, typically by a thrombus. The thrombus arises secondary to increased platelet deposition and clotting factor activity at the site of a disrupted atherosclerotic plaque. Patients with stable angina should be started on aspirin to reduce the occurrence of adverse cardiovascular events. Aspirin impairs prostaglandin synthesis by irreversibly inhibiting cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2). COX-1 is expressed in most tissues and regulates normal cellular processes (eg, gastric protection, platelet function). By inhibiting COX-1 in platelets, aspirin prevents the synthesis of thromboxane A2 (TXA2), a potent stimulator of platelet aggregation and vasoconstriction. This helps reduce the risk of occlusive thrombus formation.

Answer 91

Ductus venosus

Answer 92

In utero, blood flows from the placenta into the fetus via the umbilical vein. The blood then flows to the fetal liver, where it may be diverted into the inferior vena cava (IVC) via the ductus venosus. The ligamentum teres and ligamentum venosum are the remnants of the umbilical vein and ductus venosus in adults, respectively. The umbilical vessels are commonly used for central vascular access and resuscitation of a critically ill neonate. These procedures take advantage of the fact that complete closure of the ductus venosus does not occur until approximately 1 week after birth, although this structure is closed functionally within hours of birth. An umbilical venous catheter passes through the umbilical vein and ductus venosus until the tip reaches the IVC at the junction of the right atrium.

Answer 93

In the fetus, the foramen ovale allows blood to pass from the right atrium directly into the left atrium, bypassing the lungs. Lung inflation at the time of birth decreases right heart pressure relative to left heart pressure, causing closure of the foramen ovale. The foramen ovale is obliterated in most adults, with the fossa ovale as its remnant.

Answer 94

Culture of this patient's bronchoalveolar lavage fluid shows a conidial head consistent with Aspergillus fumigatus, a fungus ubiquitous in the environment (eg, soil) worldwide. In culture, Aspergillus has a characteristic microscopic morphology, with conidial heads (fruiting structures) that project from septate hyphae on exposure to air. The conidial head is composed of a supportive conidiophore (hyphal stalk) and terminal vesicle with radiating phialides that bear infectious conidia (spores). The conidia disseminate in the air and spread the organism. Inhalation of conidia may lead to pulmonary disease in certain individuals. In patients with a history of tuberculosis, Aspergillus can colonize preexisting lung cavities. Multiplication of fungal elements within these cavities can lead to formation of an aspergilloma (ie, fungus ball), which may cause chronic cough and occasional hemoptysis (due to eroded blood vessels). Treatment includes antifungal therapy and surgical excision.

Answer 95

Aspergillus (fungus ball=aspergilloma)

Answer 96

Actinomyces israelii is a bacterium that colonizes the mouth and classically causes cervicofacial abscesses following trauma (eg, tooth extraction). Gross examination of fluid drained from infected sites typically shows yellow "sulfur" granules, which are microscopically composed of aggregates of branching, gram-positive rods.

Answer 97

Candida albicans is a yeast that typically causes mucocutaneous infections in immunocompetent hosts. Widespread disease occurs only in immunocompromised patients, and microscopic examination would show budding yeast and pseudohyphae

Answer 98

Reactivation of latent Mycobacterium tuberculosis infection may cause cough and hemoptysis, but culture would grow acid-fast bacilli (appear pink-purple with acid-fast stain).

Answer 99

Pneumocystis jirovecii is a ubiquitous fungal organism that causes opportunistic pneumonia in HIV-positive patients with CD4 counts \< 200/mm3. Microscopic examination of sputum or bronchoalveolar lavage fluid shows cup- or disc-shaped organisms; it cannot be cultured.

Answer 100

Transformation

Answer 101

Transformation Conjugation Transduction

Answer 102

Direct uptake of naked DNA from the environment

Answer 103

One-way transfer of chromosomal or plasmid DNA Donor cell F factor DNA codes for sex pilus Bacteria that lack F factor serve as recipient cells

Answer 104

Transfer of DNA by bacteriophage: * Generalized transduction: Packaging of random bacterial genes into virion during lytic infection * Specialized transduction: Packaging of specific bacterial genes near the viral insertion site during lysogenic infection

Answer 105

Transposons mediate the transfer of genetic information from one location in the genome to another (eg, from a plasmid to chromosomal DNA). This process is **not** directly responsible for organism-to-organism genetic transfer, but moving a gene from chromosome to plasmid readies it for conjugative transfer.