Opposing effects of PGI2 and TXA2 limit clot formation. LT are linear molecules produced from arachidonic acid by the 5-lipoxygenase (5-LOX) pathway. They mediate allergic response. Their synthesis is inhibited by cortisol and not by aspirin.
glycosphingolipids, and eicosanoids. PLA2 = phospholipase A2; = sulfate ion; NSAID = nonsteroidal anti-inflammatory drugs.
Choose the ONE best answer.
7.1. Aspirin-exacerbated respiratory disease (AERD) is a severe reaction to nonsteroidal anti-inflammatory drugs (NSAID) characterized by bronchoconstriction 30 minutes to several hours after ingestion. Which of the following statements best explains the symptoms seen in patients with AERD? NSAID:
A. inhibit the activity of the cystic fibrosis transmembrane conductance regulator protein, resulting in thickened mucus that block airways.
B. inhibit cyclooxygenase but not lipoxygenase, resulting in the flow of arachidonic acid to leukotriene synthesis.
C. activate the cyclooxygenase activity of prostaglandin H2 synthase, resulting in increased synthesis of prostaglandins that promote vasodilation.
D. activate phospholipases, resulting in decreased amounts of dipalmitoylphosphatidylcholine and alveolar collapse (atelectasis).
Correct answer = B. NSAID inhibit cyclooxygenase but not lipoxygenase, so any arachidonic acid available is used for the synthesis of bronchoconstricting leukotrienes. NSAID have no effect on the cystic fibrosis (CF) transmembrane conductance regulator protein, defects in which are the cause of CF. Steroids, not NSAID, inhibit phospholipase A2. Cyclooxygenase is inhibited by NSAID, not activated. NSAID have no effect on phospholipases.
7.2. An infant, born at 28 weeks’ gestation, rapidly gave evidence of respiratory distress. Clinical laboratory and imaging results supported the diagnosis of infant respiratory distress syndrome. Which of the following statements about this syndrome is true?
A. It is unrelated to the baby’s premature birth.
B. It is a consequence of too few type II pneumocytes.
C. The lecithin/sphingomyelin ratio in the amniotic fluid is likely to be high (>2).
D. The concentration of dipalmitoylphosphatidylcholine in the amniotic fluid would be expected to be lower than that of a full-term baby.
E. It is an easily treated disorder with low mortality.
F. It is treated by administering surfactant to the mother just before she gives birth.
Correct answer = D. Dipalmitoylphosphatidylcholine (DPPC or, dipalmitoyl lecithin) is the lung surfactant found in mature, healthy lungs. Respiratory distress syndrome (RDS) can occur in lungs that make too little of this compound. If the lecithin/sphingomyelin (L/S) ratio in amniotic fluid is ≥2, a newborn’s lungs are considered to be sufficiently mature (premature lungs would be expected to have a ratio <2). The RDS would not be due to too few type II pneumocytes, which would simply be secreting sphingomyelin rather than DPPC at 28 weeks’ gestation. The mother is given a glucocorticoid, not surfactant, prior to giving birth (antenatally). Surfactant would be administered to the baby postnatally to reduce surface tension.
7.3. A 10-year-old boy was evaluated for burning sensations in his feet and clusters of small, red-purple spots on his skin. Laboratory studies revealed protein in his urine. Enzymatic analysis revealed a deficiency of αgalactosidase, and enzyme replacement therapy was recommended. The most likely diagnosis is: