Donald H. Barron

Thermal aspects of uterine blood flow in nonpregnant sheep

Abstract Thermocouples were implanted in the uterine cavity and aorta of 1 normal and 4 ovariectomized ewes. A temperature difference of 0.2 to 0.4° C. between cavity of uterus and aorta, characteristic of these sheep, was reduced to 0.05° C. 1.5 hours after administration of 1 to 2 mg. of estrone. In 2 acute experiments, the uterine blood flow was measured by a direct method. Flows between 100 and 1,150 grams of blood per kilogram uterus per minute were inversely related to differences in temperature between uterine cavity and aorta. Alterations in the temperature difference between the uterus and the blood coming to it appear to result from a dissociation between the rate of heat loss from this organ and its rate of heat production. The thermal technique appears to be useful as a qualitative bioassay in continuous, long-term studies of uterine blood flow in waking animals.

Temperature differences in reproductive tract of nonpregnant ewe

The effect of estrogens, epinephrine, oxytocin and pituitrin on blood flow through the uterus, cervix vagina, uterine surface uterine vein as well as aorta, liver and cavity of the rumen were measured in waking ewes using thermocouples encased in polyvinyl catheters. Estrone, estradiol and estriol administration led to a reduction in temperature difference between the aorta and reproductive organs. The response was greatest in the temperature of the uterine cavity. The temperature differences between the liver, and cavity of the rumen were unaffected. After the infusion of epinephrine, oxytocin or pituitrin into estrogen-treated ewes, there was an increase in temperature difference compared with the aorta. This may have been caused by the reduction of blood flow to the uterus.

Umbilical blood flow in late gestation: A comparison of simultaneous measurements with two different techniques

Abstract The umbilical blood flow of the fetus in utero has been estimated in near-term ewes by two methods based on different assumptions and techniques: (1) by equating it with the quotient of the decrease in maternal oxygen consumption which followed interruption of the umbilical circulation divided by the umbilical venoarterial oxygen difference and (2) by the diffusion equilibrium technique using antipyrine as the test substance. The results obtained are in good agreement. The mean values are 278 and 274 ml. per kilogram per minute, respectively.

Paul Zweifel, pioneer fetal physiologist

SummaryThe demonstration by Paul Zweifel a hundred years ago (1876) that the fetus in utero consumes oxygen marks the beginning of the modern era of research on foetal physiology. The circumstances which led to the demonstration are reviewed, and its importance acknowledged anew as a tribute to Zweifels many contributions to obstetrics and gynecoloy.

Uterine blood flow, oxygen consumption, and maternal plasma estradiol and progestins following fetal death

Fetuses of 42 near-term sheep were killed while they were in utero. Uterine blood flow, oxygen consumption, A-V O2, and maternal arterial plasma concentrations of estradiol and progestins were observed for the next 4 hours. There was an immediate (88 per cent) fall in oxygen consumption; blood flow decreased by 50 per cent within 30 minutes. Hormone concentrations changed, but only after 2 hours. Circulatory changes appeared to be related to local changes within the uterus, particularly to decomposition of the chorioallantoic membrane. This relationship was best seen in the experiments in which one of a set of twins was killed. The experiments are in accord with the theory that the rate of uterine blood is not directly related to acute changes in respiratory gases nor to plasma concentrations of certain hormones.

An automated collecting and measuring device for uterine blood flow studies

Abstract Blood was collected in a plastic beaker as it flowed from catheters in the uterine veins of anesthetized sheep. The weight of the blood was monitored continuously on a potentiometric recorder. Signals from a retransmitting potentiometer attached to the slide wire of this recorder were sampled every 15 seconds and compared with each previous sample. By this means, the differential of the weight, or the rate of weight change, was recorded on a second instrument. Application of the device was demonstrated in experiments in which extremely high uterine blood flow rates were produced by progesterone and estrogen therapy and by manipulation of the uterus. Rapid, marked reductions in rate of uterine blood flow occurred following administration of oxytocin to one pregnant and three nonpregnant ewes.