Development of parasympathetic and sympathetic reflexes controlling heart rate, vascular pressures, and blood flows was investigated in fetal lambs weighing 300-5,800 g (65-165 days' gestation). Cardiovascular responses to veratridine injections, atrial stretching, bilateral cervical vagotomy, and cholinergic blockade with atropine were used to test parasympathetic activities. Responses to propranolol and phenoxybenzamine were used to test beta- and alpha-adrenergic activities. Autonomic ganglionic blockade and stimulation provided additional information on both cholinergic and adrenergic systems. Fetal responses to various tests were compared to those of the mother. Results show: a) little parasympathetic tone on resting heart rate and other circulatory functions exists prior to fetal maturity; b) despite the feeble resting tone, the parasympathetic system is capable of exerting significant control when stimulated in both premature and mature fetuses, the capability increases as fetus approaches term; c) alpha- and beta-adrenergic tone in control of resting heart rate and peripheral circulation exists in early fetal life and increases as the fetus reaches maturity, and both adrenergic receptors respond strongly to stimuli in immature, premature, and mature fetuses; d) in immature fetuses, veratridine does not elicit a vagally mediated reflex; instead, it produces a centrally mediated alpha- and beta-adrenergic stimulation; e) the fetal cardiovascular response to any given test is dampened by the existence of the various vascular shunts, the umbilicoplacental circulation and, possibly, by incomplete maturation of vasomotor tone.
Changes in resting cardiac output (CO), stroke volume (SV), and systemic vascular resistance (SVR) during neonatal growth were studied in chronically instrumented lambs from the 1st to 5th wk of age; adult nonpregnant sheep values measured simultaneously were used as standard reference. Neonatal responses to autonomic agonists and antagonists were also investigated. Total CO increased linearly with neonatal growth, but decreased strikingly when expressed per weight unit; at 5 wk of age, CO/kg was still significantly higher than the adult value. SV also increased with neonatal growth but did not change when related to body weight; at 5 wk of age, SV/kg values were still higher than those of adult sheep. SVR changed reciprocally to CO. The decrease in CO/kg during neonatal growth paralleled the progressive decline in heart rate (HR). Beta receptor stimulation increased neonatal CO markedly and the increment was the same from the first through the fifth neonatal week. Beta blockade had insignificant effects, but cholinergic blockade produced moderate CO increases.
Background: The primary objective of this study was to determine if elevated antiphospholipid antibody titers were correlated with the presence of preeclampsia/eclampsia, systemic lupus erythematosus (SLE), placental insufficiency, and a prolonged length of stay (PLOS), in women who delivered throughout Florida, USA.
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