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    Histopathologic effects of meconium on human umbilical artery and vein: In vitro study
    (Parthenon Publishing Group Ltd, 1997) Kafkasli A.; Belfort M.A.; Giannina G.; Vedernikov Y.P.; Schaffner D.L.; Popek E.J.
    Objective: To determine the histopathologic effects of meconium on human umbilical artery and vein. Methods: Umbilical cords from six patients with uncomplicated, singleton, term gestations were obtained immediately after delivery. One centimeter segments from each cord were flushed, isolated, placed in either modified Krebs solution alone or modified Krebs solution with various concentrations (1%, 10%, or 25%) of fresh meconium, and then incubated at pH 7.2, temperature 37°C, PCO2 50-55 mmHg, PO2 40-45 mmHg for 1, 6, 12, or 24 h. The specimens were then fixed, stained, and examined under light microscopy. Results: Umbilical arteries exhibited focal vacuolation of the endothelium after exposure of the cord to meconium. Umbilical veins revealed: 1) endothelial loss proportionate to the meconium concentration at all intervals (P < 0.05), 2) increased density or focal absence of the internal elastic lamina, and 3) focal loss of myocyte nuclei. Rare nonpigmented macrophages and increased mast cells were identified in the Wharton's jelly. Conclusions: Exposure to meconium in vitro results in histopathologic changes in the umbilical artery and vein. © 1997 Wiley-Liss, Inc.
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    In vitro comparison of four tocolytic agents, alone and in combination
    (1994) Saade G.R.; Taskin O.; Belfort M.A.; Erturan B.; Moise K.J.; Jr.
    Objective: To compare the tocolytic effects or magnesium sulfate, ritodrine, terbutaline, and nifedipine on human myometrial strips. Methods: Myometrial strips were suspended in organ chambers for isotonic measurements and contracted with KCl. Strips from nonpregnant patients were used to obtain concentration-response curves. Myometrial strips from pregnant uteri were then exposed to the molar concentrations causing 50% relaxation in the nonpregnant tissues. Results: In strips from nonpregnant patients, nifedipine was found to be the most potent tocolytic. Using strips from nonlaboring patients, nifedipine caused relaxation similar to ritodrine, and both were more effective than magnesium sulfate or terbutaline. Combinations were more effective than single agents. These agents were found to be equally less effective in myometrial strips from laboring patients. Conclusions: Nifedipine, alone or in combination, relaxes myometrial strips more effectively than the other agents studied. Myometrial strips from laboring patients are more resistant to inhibition, with none of the agents being superior. © 1994 by The American College of Obstetricians and Gynecologists.