Uteroplacental O2 uptake: continuous measurements during uterine quiescence and contractions.

To determine the constancy of uteroplacental O2 uptake (VO2) during uterine quiescence and both spontaneous and oxytocin-induced uterine contractions, we have developed a method to measure VO2 continuously and reproducibly. In seven ewes during uterine quiescence, total uterine blood flow (Qut) averaged 200 ml X min-1 X kg uterine contents-1, with intra-animal SD of 18 min X min-1 X kg-1 and interanimal SD of 86 ml X min-1 X kg-1. Uterine arteriovenous O2 content difference averaged 4.

Regional anatomy of the term human placenta.

We have studied regional anatomical variability in four term placentae, comparing both whole placental regions and intralobar zones and plates. In addition, we have emphasized the need for careful selection of the area to be sampled, rather than strictly randomized sampling of the whole placenta. A unique contribution is our quantitative data for a number of structures of the several intralobar zones and plates.

Vasopressin dose-response effects on fetal vascular pressures, heart rate, and blood volume.

To determine the effects of circulating arginine vasopressin (AVP) on fetal arterial pressure, venous pressure, heart rate, and blood volume, we infused graded amounts of AVP into chronically catheterized fetal sheep at 122-136 days gestation (term 145-150 days). Plasma AVP concentrations increased by 6.5 +/- 3.

Temperature effects on oxygen affinity of human fetal blood.

In an effort to understand the effects of temperature changes on fetal oxygenation, the temperature effects were measured on oxygen affinity of whole blood from term human fetuses. The blood obtained was tonometered at delivery in two flasks gassed with 95% N2 (+ 5% CO2 or 20.9% + 5% CO2, and mixed aliquots from each flask in different proportions to obtain samples for analysis of PO2 and percent saturation.

Mathematical model of fetal circulation and oxygen delivery.

To better understand the fetal circulation and its regulation we constructed a dynamic model of fetal circulation as a transport system. The fetal vascular system is divided into 16 compartments which incorporate the peculiarities of the fetal circulation that produce a difference in oxygen concentration in blood supplying the upper and lower body. Recently published data is used to provide a firm experimental base for the model.

Amniotic fluid volume and fetal swallowing rate in sheep.

To investigate amniotic fluid (AF) dynamics and volume regulatory mechanisms, we measured the concentration of radioiodinated (125I) serum albumin (RISA), 51Cr-labeled red blood cells (Cr-RBC), and 103Ru-labeled microspheres after injection into the amniotic cavity and determined AF volume and fetal swallowing rate in 22 singleton pregnant sheep. Under normal conditions 2-3 h were required for complete mixing of RISA and Cr-RBC within AF; however, when the fetus was dead only 3-5 h were required. AF volume of 17 sheep on the 5th postoperative day averaged 975 +/- 128 ml by RISA and 986 +/- 130 ml by Cr-RBC.

The relation of maternal blood volume to plasma renin activity in the pregnant rabbit.

Blood volume, estradiol 17 beta and estrone concentrations, and plasma renin activity were determined weekly in 26 chronically catheterized nonanesthetized rabbits during pregnancy and after delivery. We determined blood volume by 99technetium, and plasma volume by the microhaematocrit method. The values for whole blood volume were 52.

A comparison of sheep and human fetal oxygen delivery systems with use of a mathematical model.

Human fetal cardiac output measured with ultrasound is only about 60% of that found in the sheep. We modified a previously developed mathematical model of the fetal circulation and oxygen delivery in sheep for the human in order to study several differences. The model predicts that a human fetus can maintain its oxygen delivery with a relatively low cardiac output because of its relatively high fetal hemoglobin concentration, as compared with that of the sheep fetus.

Maternal and fetal responses to exercise during pregnancy.

Exercise has numerous effects on the pregnant woman, the developing fetus, and the placenta. In turn, pregnancy affects the ability to perform physical activity. During pregnancy, increased metabolism at rest results almost exclusively from the gestational increase in mass.

Regional cerebral blood flow: studies in the fetal lamb during hypoxia, hypercapnia, acidosis, and hypotension.

In order to determine the relative roles of O2 tension and content, CO2 tension, hydrogen ion concentration, arterial blood pressure, and cardiac output in the regulation of fetal cerebral blood flow (CBF), we used radioactively labeled microspheres to measure flow to 20 major brain regions in 24 chronically catheterized fetal lambs. We continually monitored fetal heart rate and blood pressure, and periodically measured arterial PO2, PCO2, pH, and hematocrit. In addition to CBF measurements during control periods, we measured CBF during: 1) hypoxia (O2 content less than 6 ml X dl-1; O2 tension less than 15 torr) induced by having the ewe breathe a gas mixture with low O2 concentration, 2) hypercapnia (PCO2 greater than 50 torr) induced by increasing the maternal inspired CO2, 3) acidosis and alkalosis (7.

Placental anatomy and diffusing capacity in guinea pigs following long-term maternal hypoxia.

To determine the relation of placental structure to placental diffusing capacity (DPCO), we exposed Hartley guinea pigs to 12 or 14 per cent O2 from day 15 of gestation to near term (64 days). At that time we measured DPCO and fetal body and placental weights. In addition, we used stereological techniques to measure placental parameters important to diffusing capacity.

Acute embolization of the uteroplacental circulation: uterine blood flow and placental CO diffusing capacity.

In an effort to determine to what extent the fetal sequalae following repeated embolization result from decreased area of placental exchange or from decreased uterine blood flow, we injected microspheres into the uterine circulation of the pregnant ewe. We measured total UBF continuously and sampled fetal blood gases in 6 chronically instrumented ewes following repeated injections of 1 to 2 million 25 mu microspheres into the common internal iliac artery at 30 min intervals. Embolization resulted in an immediate 25 to 30% drop in uterine flow, with partial recovery to about 85% of its control value within 30 min after injection.

The interactions of exercise and pregnancy: a review.

Increasing numbers of women engage in relatively strenuous exercise during pregnancy. The interaction of the increased metabolic demands of physical activity with those of pregnancy is poorly understood. We review what is known and what is not known of the extent to which pregnancy affects a woman's ability to perform strenuous activity and the degree to which exercise affects the pregnant woman, the fetus, and the infant.

[Anti-Legionella pneumophila antibody titers in blood from children and adults with lung diseases of unknown etiology].

175 sera from children and 101 sera from adults both with respiratory illness of unknown origin were collected between September 1980 and February 1983 and studied by using the indirect immunofluorescence test for Legionnaires' disease. By using the criteria of the Center for Disease Control for a positive (fourfold increase in titer over 128 during convalescence) or presumptive (single titer greater than or equal to 256) serological test, 8 samples from adults (7.92%) and 11 samples from children (6.

Brainstem auditory evoked responses in the newborn lamb. Studies during postnatal development and acute hypoxia.

Brainstem auditory evoked responses (BAER) have been studied in several species and have provided a neurophysiologic 'window' into brainstem function. We have pursued further studies in the newborn lamb and adult sheep. BAER amplitude increased as the stimulus intensity increased from 45 to 95 dB and as the click frequency decreased from 88.

Maternal blood volume and cardiac output during pregnancy: a hypothesis of endocrinologic control.

During the course of gestation the increase of maternal total blood volume and cardiac output may result from two mechanisms acting in concert: 1) the production of several hormones by the fetus and the placenta, and 2) the uteroplacental circulation acting as an arteriovenous shunt. Plasma volume appears to increase as a consequence of renal Na+ reabsorption and water retention, which result from increased aldosterone production via the renin-angiotensin system, as a consequence of placental estrogen production. This estrogen production in turn results from increasing availability of the estrogen substrate dehydroepiandrosterone (chiefly from the fetal adrenal gland).

Exercise responses in pregnant sheep: oxygen consumption, uterine blood flow, and blood volume.

In an attempt to explore the acute maternal responses to exercise we measured oxygen consumption, uterine blood flow, and blood volume in 13 chronically catheterized pregnant sheep at rest and while exercising on a treadmill. With maximal exercise O2 consumption increased 5.6 times, from a resting value of 5.

Exercise responses in pregnant sheep: blood gases, temperatures, and fetal cardiovascular system.

In an effort to examine the effects of maternal exercise on the fetus we measured maternal and fetal temperatures and blood gases and calculated uterine O2 consumption in response to three different treadmill exercise regimens in 12 chronically catheterized near-term sheep. We also measured fetal catecholamine concentrations, heart rate, blood pressure, cardiac output, blood flow distribution, blood volume, and placental diffusing capacity. Maternal and fetal temperatures increased a mean maximum of 1.

Placental exchange area in guinea pigs following long-term maternal exercise: a stereological analysis.

We have used stereological techniques to measure the peripheral labyrinth exchange area of the guinea pig placenta in groups of animals which were exercised 0, 15, 30, 45, or 60 min daily throughout pregnancy. The surface area of the maternal lacunae in the peripheral labyrinth decreased linearly as a function of exercise duration, and the maternal volumes of each exercised group were consistently lower, but not linearly. Placental diffusing capacity for carbon monoxide decreased as a function of exercise duration (r = - 0.

Fetal growth and placental diffusing capacity in guinea pigs following long-term maternal exercise.

To determine the critical level of maternal exercise which produces effects on fetal weight and placental diffusing capacity, we measured the relationship between increasing levels of exercise and its effect on the fetus. Hartley guinea pigs with dated pregnancies were exercised on a treadmill (9.7 m/min at a 6.