Relationships of maternal–fetal plasma steroid and amniotic fluid electrolyte levels to uterine myoelectrical activity during late gestation in sheep

1984 ◽  
Vol 62 (12) ◽  
pp. 2377-2382 ◽  
Author(s):  
D. D. Kitts ◽  
C. R. Krishnamurti
Keyword(s):  
Amniotic Fluid ◽  
Electrical Activity ◽  
Direct Relationship ◽  
Temporal Changes ◽  
Late Gestation ◽  
Myoelectrical Activity ◽  
Bipolar Electrodes ◽  
Fetal Plasma ◽  
Uterine Contractions ◽  
Uterine Electrical Activity

Paired bipolar electrodes were implanted in the corpus and uterotubal junctions in pregnant ewes. The temporal changes in uterine myoelectrical activity were monitored in conjunction with maternal and fetal plasma steroid and amniotic fluid electrolytes to evaluate the mechanisms regulating the prepartal uterine contractions in the ewe. Increases in total uterine myoelectrical activity were significant (P < 0.001) at both uterine locations as term approached, although significant (P < 0.01) variation existed between individual animals. Significant correlations between maternal progesterone (P < 0.05) and maternal and fetal estrogens (P < 0.01) and uterine myoelectrical activity were observed. The decline in maternal progesterone to levels of 2.03 ± 0.4 ng/mL and concomitant increases in both maternal and fetal total estrogens (199.3 ± 4.7 and 262.5 ± 11.0 pg/mL, respectively) resulted in a relatively high maternal estrogen/progesterone ratio just prior to parturition and corresponded to an approximate fivefold increase in total uterine electrical activity. Fetal cortisol concentrations were not significantly correlated with uterine myoelectrical activity; however, a positive correlation (P < 0.05) between fetal cortisol and maternal estrogen/progesterone ratios was obtained. The results of this study demonstrate a direct relationship between changes in the maternal estrogen/progesterone ratios and frequency and patterns of uterine electrical signals just prior to parturition, which may be ultimately triggered by the surge in fetal corticosteroid production.

Distribution of acute-phase alpha 2-macroglobulin in rat fetomaternal compartments

1983 ◽  
Vol 245 (2) ◽  
pp. E138-E142
Author(s):  
D. E. Panrucker ◽  
P. C. Lai ◽  
F. L. Lorscheider
Keyword(s):  
Amniotic Fluid ◽  
Acute Phase ◽  
Fetal Liver ◽  
Maternal Serum ◽  
Yolk Sac ◽  
Late Gestation ◽  
Early Gestation ◽  
Fetal Plasma ◽  
Maternal Liver ◽  
Metrial Gland

Rat acute-phase alpha 2-macroglobulin (AP alpha 2M) concentration was measured by radioimmunoassay in maternal serum, fetal plasma, maternal liver, fetal liver, and amniotic fluid as a function of gestational and neonatal age. The concentration profiles of AP alpha 2M in maternal serum and fetal plasma displayed two peaks, one in early gestation and another during late gestation. Synthesis of AP alpha 2M was confirmed by the immunoprecipitation of [35S]methionine incorporated into cultures of selected tissues. The following observations were made. 1) Maternal serum concentrations of AP alpha 2M were higher than those observed in fetal plasma in early gestation. This was attributable to a high level of maternal AP alpha 2M synthesis in metrial gland which was absent in liver and moderate in yolk sac. 2) In late gestation fetal plasma concentrations of AP alpha 2M greatly exceeded those observed in maternal serum. This could be explained by the pronounced synthesis of AP alpha 2M in fetal liver that was not apparent in maternal liver or yolk sac. 3) During labor, a transient increase in AP alpha 2M concentration was observed in maternal serum and fetal plasma. 4) During lactation a moderately elevated maternal serum concentration of AP alpha 2M was maintained. 5) Amniotic fluid concentration of AP alpha 2M was very low throughout gestation, which indicated that the fetal glomerulus was relatively impermeable to this large protein. It is concluded that in early gestation a principal maternal source of AP alpha 2M appears to be the metrial gland, whereas in late gestation fetal liver is a major source of AP alpha 2M appearing in fetal plasma from where some of this macroglobulin is speculated to be transported to the maternal circulation.

Prepartum adrenocortical maturation in the fetal foal: responses to ACTH1–24

1994 ◽  
Vol 142 (3) ◽  
pp. 417-425 ◽  
Author(s):  
M Silver ◽  
A L Fowden
Keyword(s):  
Amniotic Fluid ◽  
Plasma Cortisol ◽  
Critical Period ◽  
Maternal Plasma ◽  
Significant Rise ◽  
Late Gestation ◽  
Plasma Acth ◽  
Fetal Plasma ◽  
Period 2 ◽  
Time To Delivery

Abstract The present study was carried out on 19 chronically catheterized mares and fetuses in late gestation (term >320 days). In six animals which were monitored up to the time of delivery of a live foal, plasma and amniotic fluid cortisol concentrations remained low until 4–5 days before parturition when there was a rapid, significant rise (P<0·05) which was not accompanied by any corresponding changes in maternal plasma cortisol. Circulating fetal ACTH concentrations became more variable close to delivery and ANOVA revealed no significant increases during this critical period, although a negative correlation between plasma ACTH and time to delivery was observed (P<0·05). Tests on fetal adrenal responsiveness to exogenous ACTH1–24 were carried out on ten animals. Before 295 days of gestation no significant increases in fetal plasma cortisol above its basal level of 20–30 nmol/l could be elicited by ACTH, administered as a single i.v. injection (1–2 μg/kg). By 304 ± 3 days (mean ± s.e.m.) small but significant (P<0·05) increments in plasma cortisol were detected after ACTH, while in the oldest group (313 ±2 days) significant (P<0·01) 50–60% increments were seen throughout the test period (2 h). Only one fetus was tested within 3 days of delivery and here a fourfold rise in plasma cortisol was evoked by ACTH. When changes in endogenous levels of circulating ACTH and cortisol were monitored every 15 min over 1·5- to 2-h periods in late gestation, rises in ACTH were only accompanied by concomitant increases in plasma cortisol in fetuses within 5 days of delivery (correlation coefficient r=0·58, P<0·01). Before this time, plasma cortisol concentrations remained at basal levels irrespective of any fluctuations in plasma ACTH. These findings indicate that the adrenal cortex of the fetal foal is relatively quiescent and insensitive to ACTH for most of the latter part of gestation, but that a short rapid escalation in circulating cortisol precedes its delivery. Journal of Endocrinology (1994) 142, 417–425

Predominance of l-dopa in fetal plasma and the amniotic fluid during late gestation in the rat

1984 ◽  
Vol 149 (8) ◽  
pp. 880-883 ◽  
Author(s):  
Dan Peleg ◽  
Lydia A. Arbogast ◽  
Edna Peleg ◽  
Nira Ben-Jonathan
Keyword(s):  
Amniotic Fluid ◽  
Late Gestation ◽  
Fetal Plasma

scholarly journals Development of Myometrial Electrical Activity during the First Half of Pregnancy in the Sheep

1984 ◽  
Vol 37 (3) ◽  
pp. 153 ◽  
Author(s):  
JN Sigger ◽  
R Harding ◽  
A Bailey
Keyword(s):  
Electrical Activity ◽  
Progressive Increase ◽  
Myoelectrical Activity ◽  
Plasma Progesterone ◽  
Uterine Activity ◽  
Uterine Contractions ◽  
Pregnant Sheep ◽  
Low Amplitude

Uterine myoelectrical activity was recorded in seven pregnant sheep covering the period between 13 and 75 days post-coitum. Activity in the myometrium was present at day 13 and took the form of intermittent spikes of low amplitude. Bursts of spikes of irregular duration became noticeable between days 25 and 40 but most were not coordinated throughout the myometrium. Coordinated bursts of myoelectrical activity, which could be recorded at several sites simultaneously, first appeared between 40 and 65 days. These bursts had similar characteristics to the myoelectrical activity associated with uterine contractions during the last third of gestation. The myoelectrical activity showed a progressive increase in amplitude during the first half of gestation. There was no relationship between plasma progesterone levels and the increase in amplitude or appearance of coordinated bursts of uterine activity.

Fetal vascular pressure and heart rate responses to nonlabor uterine contractions

1986 ◽  
Vol 251 (2) ◽  
pp. R409-R416 ◽  
Author(s):  
R. A. Brace ◽  
D. S. Brittingham
Keyword(s):  
Heart Rate ◽  
Amniotic Fluid ◽  
Venous Pressure ◽  
Fluid Pressure ◽  
Late Gestation ◽  
Cardiovascular Changes ◽  
Uterine Contractions ◽  
Pregnant Sheep ◽  
On Line ◽  
Pressure Changes

The purpose of this study was to determine whether there are changes in fetal arterial pressure, venous pressure, or heart rate during nonlabor uterine contractions (i.e., contractures) in late gestation pregnant sheep. To do this, amniotic fluid pressure was continuously recorded using on-line computer techniques and subtracted from fetal arterial and venous pressures. With randomly selected data, there were no statistically significant changes with time in the fetal variables. However, when averaged with respect to time of the contractures, fetal arterial and venous pressures increased significantly during the contractures, and heart rate decreased. In addition, there were small but statistically significant decreases in each of the three fetal variables just before the contractures. Blocking the fetal autonomic nervous system eliminated the decreases in the variables before the contractures as well as the decrease in heart rate during the contractures, but arterial and venous pressure increased normally. Infusion of 1 liter of warmed saline into the amniotic space did not alter the fetal cardiovascular or amniotic fluid pressure changes during contractures. In summary, there are significant fetal cardiovascular changes during nonlabor uterine contractions, and these are consistent with a translocation of fetal blood from the placenta into the fetal body. Although the cause of fetal cardiovascular changes just before the contractures is unknown, they suggest but do not prove that the fetus may provide the signal for the nonlabor uterine contractions to occur.

scholarly journals Source of Inhibin in Ovine Fetal Plasma and Amniotic Fluid during Late Gestation: Half-Life of Fetal Inhibin1

1997 ◽  
Vol 57 (2) ◽  
pp. 347-353 ◽  
Author(s):  
S. Miller ◽  
S. Wongprasartsuk ◽  
I. R. Young ◽  
M. E. Wlodek ◽  
J. R. McFarlane ◽  
...  
Keyword(s):  
Amniotic Fluid ◽  
Half Life ◽  
Late Gestation ◽  
Fetal Plasma ◽  
Ovine Fetal

Concentrations of prolactin in the plasma of fetal sheep and in amniotic fluid in late gestation and during dexamethasone-induced parturition

1983 ◽  
Vol 99 (1) ◽  
pp. 107-114 ◽  
Author(s):  
I. C. McMillen ◽  
G. Jenkin ◽  
J. S. Robinson ◽  
G. D. Thorburn
Keyword(s):  
Amniotic Fluid ◽  
Late Gestation ◽  
Fetal Sheep ◽  
Indwelling Catheters ◽  
Low Concentration ◽  
Fetal Plasma ◽  
High Concentrations

The concentration of prolactin in samples of fetal plasma and amniotic fluid collected from sheep with indwelling catheters has been measured by radioimmunoassay. There was considerable variation between animals in the concentration of prolactin in fetal plasma which ranged from <2 μg/l to >50 μg/l. In five out of eight fetuses which were sampled at intervals throughout the last 30 days of pregnancy, there was an increase in the concentration of prolactin in the plasma before parturition. The concentration of prolactin in amniotic fluid was consistently low (approximately 1 μg/l). Induction of premature parturition by intrafetal infusion of dexamethasone was accompanied by an increase in the concentration of prolactin in only one of three fetuses infused. These results indicated that prolactin is present in fetal plasma but that an increase in prolactin in fetal plasma before the onset of parturition does not always occur. The low concentration of prolactin in amniotic fluid contrasts with the high concentrations of this hormone found in the amniotic fluid of the primate.

Noninvasive high-resolution electromyometrial imaging of uterine contractions in a translational sheep model

2019 ◽  
Vol 11 (483) ◽  
pp. eaau1428 ◽  
Author(s):  
Wenjie Wu ◽  
Hui Wang ◽  
Peinan Zhao ◽  
Michael Talcott ◽  
Shengsheng Lai ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Magnetic Resonance Images ◽  
Electrical Activation ◽  
Current Clinical Practice ◽  
Sheep Model ◽  
Activation Patterns ◽  
Uterine Contractions ◽  
Spatial Specificity ◽  
Uterine Electrical Activity ◽  
Pressure Catheter

In current clinical practice, uterine contractions are monitored via a tocodynamometer or an intrauterine pressure catheter, both of which provide crude information about contractions. Although electrohysterography/electromyography can measure uterine electrical activity, this method lacks spatial specificity and thus cannot accurately measure the exact location of electrical initiation and location-specific propagation patterns of uterine contractions. To comprehensively evaluate three-dimensional uterine electrical activation patterns, we describe here the development of electromyometrial imaging (EMMI) to display the three-dimensional uterine contractions at high spatial and temporal resolution. EMMI combines detailed body surface electrical recording with body-uterus geometry derived from magnetic resonance images. We used a sheep model to show that EMMI can reconstruct uterine electrical activation patterns from electrodes placed on the abdomen. These patterns closely match those measured with electrodes placed directly on the uterine surface. In addition, modeling experiments showed that EMMI reconstructions are minimally affected by noise and geometrical deformation. Last, we show that EMMI can be used to noninvasively measure uterine contractions in sheep in the same setup as would be used in humans. Our results indicate that EMMI can noninvasively, safely, accurately, robustly, and feasibly image three-dimensional uterine electrical activation during contractions in sheep and suggest that similar results might be obtained in clinical setting.

Function curve of the membranes that regulate amniotic fluid volume in sheep

2005 ◽  
Vol 289 (1) ◽  
pp. H146-H150 ◽  
Author(s):  
Job Faber ◽  
Debra Anderson ◽  
Roger Hohimer ◽  
Qin Yang ◽  
George Giraud ◽  
...  
Keyword(s):  
Amniotic Fluid ◽  
Absorption Rate ◽  
Plasma Renin ◽  
Fluid Volume ◽  
Natural Rate ◽  
Fetal Plasma ◽  
Amniotic Fluid Volume ◽  
Urine Production ◽  
Rate Of Absorption ◽  
Vascular Catheters

Seven singleton 120-day fetal lambs were prepared with a shunt from the lung to the gastric end of the esophagus, a bladder catheter, and multiple amniotic fluid and vascular catheters. The urachus was ligated. Beginning 7 days later, amniotic fluid volumes were determined by drainage, followed by replacement with 1 liter of lactated Ringer (LR) solution. Urine flow into the amnion was measured continuously. In 14 of 27 experiments, amniotic fluid volumes were determined again 2 days after the inflow into the amnion had consisted of urine only and in 13 experiments after the inflow of urine had been supplemented by an intraamniotic infusion of LR solution. Intramembranous absorption was calculated from the inflows and the changes in volume between the beginning and end of each experiment. The relations between absorption rate and amniotic fluid volume, the “function curves,” were highly individual. Urine production during the infusion of LR solution did not decrease, fetal plasma renin activity decreased ( P < 0.001), and amniotic fluid volume increased by 140% [SE (27%), P < 0.005], but the increase in the amniochorionic absorption rate of 411% [SE (48%), P < 0.001] was greater ( P < 0.005) than the increase in volume. Each of the seven fetuses was proven capable of an average intramembranous absorption rate that exceeded 4.5 liters of amniotic fluid per day. During the infusion of LR solution, the increase in the rate of absorption matched the rate of infusion (both in ml/h), with a regression coefficient of 0.75 ( P < 0.001). Thus, even for large amniotic fluid volumes, volume is not limited by the absorptive capacity of the amniochorion, and, at least in these preparations, the position of the function curve and not the natural rate of inflow was the major determinant of resting amniotic fluid volume.

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