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PubMed1992

Evaluation of an on-farm blood progesterone test for predicting the day of parturition in cattle.

An on-farm blood progesterone enzymeimmunoassay (EIA) was evaluated as a diagnostic test to predict the time of calving within a 24-hour period in near-term dairy cows. Blood samples were taken daily from 45 cows beginning 5 days prior to their expected due dates until calving, and plasma was stored at -20 degrees C until all cows had calved. The EIA test was performed on frozen-thawed plasma samples, and progesterone concentrations were determined to be low (positive test for calving within 24 hours) or high (negative test for calving within 24 hours). Sensitivity, specificity and predictive value of the EIA to accurately determine parturition within 24 hours were 86.7, 90.8 and 75.0%, respectively. The EIA correctly predicted the day of parturition in 168 of 187 (89.8%) plasma samples. Ten additional cows were similarly monitored except the EIA was performed on whole blood immediately after collection, and the sensitivity, specificity and predictive value of the test were 80.0, 97.6 and 88.9%, respectively. The day of parturition was correctly predicted in 49 of 52 (94.2%) whole blood samples. More than 95% of the cows calved within 24 hours when their plasma progesterone reached < 1.3 ng/ml. When results of the EIA were compared with those of a radioimmunoassay (RIA), the EIA findings were used to correctly classify 190 of 232 (81.9%) plasma samples as having low (< 2.0 ng/ml) or high (>/= 2.0 ng/ml) concentrations of progesterone. The EIA test was found to be a quick, practical means of estimating progesterone concentrations in bovine plasma or whole blood and was a useful test for predicting the day of parturition in cows.

Journal Article↗
PubMed1979

Studies on the effects of altered timing of parturition in the rat.

Manipulation of the length of gestation with two different agents has been compared and contrasted in the rat. Single subcutaneous injection of 1 mg/rat of PGF 2 alpha on day 19 of gestation caused premature parturition of at least 24 hours in 55% of treated rats. Premature parturition was associated with perinatal death and cannibalism of delivered pups. Subcutaneous implantation of pellets of naproxen over days 20-23 of gestation prolonged gestation to 24 days and synchronized onset of parturition compared to placebo-treated controls. Post-mature onset of delivery, in contrast, was associated with increased birth weight of pups and a survival rate of 90%. Post-mature pup deaths were restricted to the last pups delivered, i.e. longest gestation. The potential utility of naproxen for manipulation of time of parturition in domestic animals is suggested.

Animals↗
PubMed1984

Neuronal/glial plasticity in the supraoptic dendritic zone: dendritic bundling and double synapse formation at parturition.

The magnocellular neurosecretory cells of the supraoptic nucleus increase production and release of oxytocin and/or vasopressin under such conditions as parturition, lactation and dehydration. These stimuli have been shown to result in increased direct apposition of neuronal membranes and the formation of double synapses (one presynaptic terminal contacting two postsynaptic elements) within the supraoptic nucleus at the level of the cell bodies. These morphological changes are due to the retraction of the thin glial processes which are normally interposed between adjacent neurons. The present study was undertaken to ascertain whether, and to what extent, neuronal/glial plasticity occurs in the dendritic zone (i.e. the ventral glial laminar area) of the supraoptic nucleus. The instances of two or more dendrites with membrane in direct apposition (dendritic bundles), the number of dendrites per bundle, the amount of dendritic membrane in direct apposition and the percentage of dendrites contacted by double synapses were quantified at the ultrastructural level in virgin female, prepartum (21 days of gestation), postpartum (day of parturition) and lactating rats. All parameters measured varied significantly with the hormone demand states created by pregnancy and lactation, apparently due to glial retraction. Moreover, in the 2-24 h period between pre- and postpartum there was a significant increase in the number of dendrites per bundle, dendritic membrane in direct apposition and the percentage of dendrites contacted by double synapses. This time course corresponds to the known increased release of oxytocin and vasopressin at parturition. These findings constitute the first demonstration that dendritic bundles and double synapses occur in the ventral glial lamina/dendritic zone of the supraoptic nucleus and vary under the physiological conditions of pregnancy, parturition and lactation.

Animals↗
PubMed1988

Hypothalamic opioid mechanisms controlling oxytocin neurones during parturition.

The influences of opioids on oxytocin secretion and parturition were investigated in the rat. Morphine, administered centrally or peripherally, severely delays the course of established parturition. This delay is accompanied by reduced plasma oxytocin levels and is overcome by treatment either with the opioid antagonist naloxone, or by infusion of oxytocin. An endogenous opioid regulatory mechanism inhibiting oxytocin secretion becomes activated immediately prior to and during parturition. This mechanism does not operate earlier in pregnancy or during normal lactation and is not seen in nonpregnant animals. Naloxone acutely speeds up the course of established parturition, an effect accompanied by greatly elevated plasma oxytocin levels. The mechanisms underlying opioid regulation of oxytocin neurones were investigated at two sites. Precipitated withdrawal from chronic morphine treatment causes hypersecretion of oxytocin. This response is mediated by greatly enhanced electrical activity in the perikarya of oxytocin neurones indicating the presence of opioid receptors on oxytocin neurones and/or on their afferent input. Opioid receptors are also present in the neurohypophysis where they exert direct and noradrenaline mediated effects on secretion from oxytocin terminals in vitro.

Animals↗
PubMed2005

Progesterone receptor isoform (A/B) ratio of human fetal membranes increases during term parturition.

OBJECTIVE: The role of progesterone in the control of human parturition remains unsettled. Because there is no systemic progesterone withdrawal before the onset of labor, a 'functional progesterone withdrawal' has been proposed to be operative before human parturition. This may be accomplished by a change in the density of the progesterone receptor (PR) isoforms in myometrium and fetal membranes. The purpose of our study was to determine if spontaneous term labor is associated with changes of PR isoforms (PR-A and PR-B) in the fetal membranes. STUDY DESIGN: Fetal membranes were obtained from women undergoing elective cesarean delivery at term (not in labor group), and from women with a vaginal delivery (labor group). The expression of PR isoforms was assessed by Western blot analysis of amnion and chorio-decidua. Densitometric analysis of PR-A/PR-B ratio was performed. Immunohistochemistry with specific antibodies to PR-A and PR-B was done. Nonparametric statistics were used for analysis. RESULTS: 1) The predominant isoform of PR in women not in labor was PR-B, and PR-A in patients in labor. The ratio of PR-A/PR-B in fetal membranes was significantly higher in women in labor than in those not in labor (for amnion, median 4.3, range [0.9-8.4] vs median 0.4, range [0.3-2.6], P < .001; for chorio-decidua, median 2.0, range [1.1-19.2] vs median 1.2, range [0.1-2.0], P < .05). 2) Fetal membranes expressed both types of PR. 3) Immunohistochemistry showed the presence of PR-A and PR-B in the cytoplasm of amnion epithelial cells, chorion trophoblast, and decidual cells. CONCLUSION: Human parturition at term is associated with changes in PR isoforms in the fetal membranes and, thus, a local 'functional progesterone withdrawal' may operate in human parturition through this mechanism.

Blotting, Western↗
PubMed1997

Inhibition and augmentation of progesterone production during pregnancy: effects on parturition in rhesus monkeys.

OBJECTIVES: Uterine quiescence during mammalian pregnancy is attributed to progesterone. However. systemic progesterone levels remain elevated in primates before parturition. Epostane, a selective 3beta-hydroxysteroid dehydrogenase inhibitor, and progesterone (with or without epostane) were administered to late pregnant rhesus monkeys to clarify the role of progesterone in primate parturition. STUDY DESIGN: On days 122 to 132 of gestation (term 167 days), 11 rhesus monkeys (Macaca mulatta) with timed pregnancies were divided into three treatment groups: (1) epostane alone (10 mg/kg subcutaneously), (2) epostane with progesterone subcutaneously in Silastic silicone rubber capsules, and (3) progesterone implants only with no surgical instrumentation. Maternal and fetal blood and amniotic fluid were sampled for progesterone, estrone, estradiol, cortisol, testosterone, androstenedione, dehydroepiandrosterone, dehydroepiandrosterone sulfate, and amniotic fluid was sampled for prostaglandins E2 and F2alpha. Uterine activity was monitored continuously by electromyography and intraamniotic pressure. Cervical status was assessed by a modified Bishop's score. Production of prostaglandins E2 and F2alpha by amnion was determined by tissue superfusion. The group of three noninstrumented monkeys, which received only progesterone Silastic silicone rubber implants subcutaneously at 146 to 148 days, were observed until spontaneous vaginal delivery. RESULTS: Epostane reduced maternal and fetal progesterone levels by 75% and 50%, respectively, followed by increased uterine activity and cervical ripening within 24 hours and vaginal delivery within 48 hours. Amniotic fluid progesterone decreased to undetectable levels. Progesterone implants prevented the epostane-induced decrease in maternal and fetal progesterone levels and the associated myometrial and cervical changes until the implants were removed. Alterations in other steroid hormones were consistent with inhibition of 3beta-hydroxysteroid dehydrogenase. Amniotic prostaglandin E2 production was increased sixfold by epostane (p < 0.05) but did not reach the high levels normally seen at spontaneous parturition. Animals that received progesterone implants alone had markedly elevated circulating progesterone concentrations yet were delivered spontaneously at term (range 163 to 167 days). CONCLUSIONS: Progesterone withdrawal induces preterm labor and delivery (which can be blocked by progesterone substitution) but exogenous progesterone, even in substantial quantities, does not prevent parturition at term.

Amniotic Fluid↗
PubMed1999

The tumor necrosis factor alpha and its soluble receptor profile in term and preterm parturition.

OBJECTIVE: The common terminal pathway of parturition describes the anatomic, biochemical, endocrine, and clinical events present in the fetus and mother in both term and preterm labor. Labor at term is thought to result from physiologic activation of this pathway, whereas preterm labor is the result of pathologic activating events. The purpose of this study was to determine whether physiologic and pathologic activation could be discerned by the analysis of a cytokine-receptor signaling system. Tumor necrosis factor alpha and its soluble receptors were used as probes because of their pivotal role in the regulation of several processes activated during parturition. Soluble receptors are thought to buffer the biologic and potentially deleterious effects of tumor necrosis factor alpha in pathologic conditions. STUDY DESIGN: The in vivo concentrations of tumor necrosis factor alpha and its soluble receptors were studied in patients in term labor and preterm labor. Amniotic fluid was retrieved from 175 women and tumor necrosis factor alpha, tumor necrosis factor receptor 1, and tumor necrosis factor receptor 2 concentrations were measured by highly sensitive immunoassays. Patients were classified in the following groups: (1) term labor (n = 29), (2) term not in labor (n = 29), (3) preterm labor leading to term delivery (n = 34), (4) preterm labor without infection resulting in preterm delivery (n = 34), (5) preterm labor with intra-amniotic infection (n = 23), and (6) second trimester (n = 26). RESULTS: Tumor necrosis factor alpha and tumor necrosis factor receptor 1 concentrations decreased with advanced gestational age (r = -0.51 and r = -0.7; P <.01 for each). (1) Patients in spontaneous term labor had a higher median concentration of tumor necrosis factor alpha than those at term not in labor (median, 6.4 pg/mL; range, 2.4->500 pg/mL vs median, 4.1 pg/mL; range, 1.1-22.7 pg/mL; P <.01) but had lower concentrations of tumor necrosis factor receptor 1 (median, 3.2 ng/mL; range, 1.3-9.1 ng/mL vs median, 4.2 ng/mL; range, 1.6-8.3; P <.001) and tumor necrosis factor receptor 2 (median, 5.5 ng/mL; range, 0.73-12.8 ng/mL vs median, 6.8 ng/mL; range, 2.9-12.9 ng/mL; P <.01). (2) In contrast, patients with preterm labor leading to preterm delivery had higher concentrations of tumor necrosis factor alpha (median, 12.3 pg /mL; range, 1.5->500 pg/mL vs median, 4.8 pg/mL; range, 1-60.9 pg/mL; P <.01), tumor necrosis factor receptor 1 (median, 8.8 ng/mL; range, 2.5-38 ng/mL vs median, 6.2 ng/mL; range, 1.4-28 ng/mL; P <.05), and tumor necrosis factor receptor 2 (median, 8.5 ng/mL; range, 3.5-45.4 ng/mL vs median, 6.1 ng/mL; range, 1.99-14.1 ng/mL; P <.01) than patients with preterm labor who delivered at term. (3) Microbial invasion of the amniotic cavity was associated with dramatic increases in the concentrations of tumor necrosis factor alpha (median, 93.5 pg/mL; range, 1.2->500 pg/mL) and its soluble receptors tumor necrosis factor receptor 1 (median, 8.8 ng/mL; range, 2.1-36.7 ng/mL) and tumor necrosis factor receptor 2 (median, 11.8 ng/mL; range, 3.4-46. 3 ng/mL), concentrations that were significantly higher than in those with preterm labor who delivered at term and those who delivered preterm but were not infected. CONCLUSION: The tumor necrosis factor alpha and tumor necrosis factor alpha soluble receptor profiles are different in term and preterm parturition. Our observations provide support for the thesis that preterm parturition is a pathologic condition. Increased tumor necrosis factor alpha soluble receptor concentrations may attenuate the deleterious effects of the excess of tumor necrosis factor alpha found in pathologic labor.

Amniotic Fluid↗
PubMed1997

Oxytocin and its receptor in pregnancy and parturition: current concepts and clinical implications.

OBJECTIVE: To present our current understanding of oxytocin and its receptors during pregnancy and parturition and their potential clinical applications. DATA SOURCES: A MEDLINE search was conducted for pertinent articles from 1966 to October 1996 related to oxytocin and its receptor and their clinical implications during pregnancy and parturition. Review articles, book chapters, and published trials were also searched. METHODS OF STUDY SELECTION: Only references in English that were deemed relevant were used. When possible, human data and sometimes animal data pertinent to understanding the interaction of oxytocin and its receptors were selected. TABULATION, INTEGRATION, AND RESULTS: Oxytocin is synthesized in the hypothalamus and in many reproductive tissues during pregnancy, whereas the receptors are synthesized in reproductive tissues. The genes for oxytocin and its receptors are on chromosomes 20 and 3, respectively. Oxytocin and its receptors are regulated by sex steroids and by oxytocin itself. The paracrine and autocrine mechanisms regulating oxytocin and its receptor within the fetoplacental-uterine unit are central to the control of uterine contractions and parturition. Such current understanding provides the basis for appropriate oxytocin regimens to induce or augment labor, to inhibit preterm labor by blockade of oxytocin receptors, and to achieve cervical ripening. CONCLUSION: Advances in our knowledge of oxytocin and its receptor have provided rational and sound principles for current concepts about their role in parturition, the appropriate use of oxytocin to stimulate the pregnant uterus or ripen the cervix, and the use of oxytocin antagonist to inhibit uterine contractions and preterm labor.

Chromosomes, Human, Pair 20↗
PubMed1998

The sensory but not muscular pelvic nerve branch is necessary for parturition in the rat.

In the rat the pelvic nerve consists of a viscerocutaneous (sensory) branch which receives information from pelvic viscera and the midline perineal region, and a somatomotor (muscular) branch which innervates the ilio- and pubococcygeous muscles. To investigate the contribution of these branches to the parturition process, the length of gestation and course of delivery were closely monitored in 43 pregnant, Wistar-strain rats randomly assigned to five groups: untreated control animals, animals in which the somatomotor branch of the pelvic nerve was bilaterally sectioned on Day 14 of gestation, animals in which the viscerocutaneous branch of the pelvic nerve was bilaterally sectioned on Day 14 of gestation, animals treated similarly to the previous group but with young delivered by C-section at term, and sham-operated controls. Sectioning the viscerocutaneous branch seriously disrupted parturition and resulted in major dystocia and a high percentage of stillbirths in all females. In contrast, sectioning the somatomotor branch had no apparent effect on parturition and no significant differences were found between females of this group and sham or control dams on any of the measures recorded. It is concluded that the viscerocutaneous branch of the pelvic nerve is vital for the normal course of parturition in the rat but that the somatomotor branch plays little role, if any.

Abdominal Muscles↗
PubMed2000

The induction of parturition in the bitch using sodium cloprostenol.

The objectives of this studies were to determine a continuous low-dose treatment regimen for the administration of sodium cloprostenol to the bitch that did not cause polydipsia, and whether this treatment would induce normal and timed parturition in bitches during late pregnancy. Non-pregnant greyhound bitches (n=18) received sodium cloprostenol subcutaneously, via a miniosmotic pump, at dose rates of 0.875 to 4.5 microg/kg/24 h, for 7 days (Days 0 to 7). Daily water intake was measured from Day -2 to Day 9. Polydipsia was observed in bitches treated with the higher dose rates but not in bitches treated with the lowest dose rate of 0.875 microg/kg/24 h. In the second experiment, pregnant greyhound bitches received sodium cloprostenol at dose rates of 1 (n=4), 2 (n=1) and 3 microg/kg/24 h (n=1), on Day 57 of pregnancy. Polydipsia was observed in bitches treated at the higher dose rates of 2 and 3 microg/kg/24 h, but not in the bitches treated at the lower dose rate of 1 microg/kg/24 h. These treatments resulted in the successful induction of parturition. Parturition was associated with a decrease in plasma progesterone concentrations, a reduction in body temperature, and an increase in plasma concentrations of 13,14-dihydro-15-keto prostaglandin F2alpha. The first puppy was born 37.7 +/- 2.9 h after the start of treatment (range 28 to 46 h). The duration of whelping was approximately 15.7 +/- 2.2 h (range 10 to 24 h). The litter size was 9.2 +/- 0.8 pups (range 6 to 12 pups), and the puppy survival rate was 6.0 +/- 0.8 per litter (range 4 to 9 pups). This study demonstrated that the administration of sodium cloprostenol in continuous low dose for 24 h is an effective treatment for the induction of parturition in bitches during late pregnancy. This treatment resulted in the birth of healthy pups, with minimal or no side effects to the bitch.

Animals↗
PubMed2002

Ultrasonic measurements of second and third trimester fetuses to predict gestational age and date of parturition in captive and wild spotted hyenas Crocuta crocuta.

Parturition in spotted hyenas (Crocuta crocuta) is a fascinating event to witness, as females of this species are highly masculinized and give birth through a penis-like clitoris. Furthermore, shortly after birth, a high rate of aggression occurs between littermates that can sometimes end in siblicide. To study these events thoroughly, an accurate estimate of the date of parturition is necessary. To this end, we performed transabdominal ultrasounds every 20-30 days in five captive spotted hyenas of known gestational age, beginning approximately 30 days after mating. We measured the femur length (FL), abdominal circumference (AC), and biparietal diameter (BPD) of eight fetuses from Days 42 to 100 of their 110 days of gestation. FL proved to be the most effective measurement, as it correlated well with gestational age and was easy to obtain consistently. The relationship between estimated gestational age (EGA) and FL is described by the equation: [EGA = 37.3 + (14.0 x FL)]. AC also correlated well with EGA, but was more difficult to measure than FL. Measuring BPD became increasingly difficult as pregnancies advanced beyond 70 days of gestation. Because gestational age is often not known in captive and free-ranging spotted hyenas, measuring fetal FL ultrasonographically is a rapid and reliable way to determine an approximate date of parturition. This technique proved invaluable when used to track and monitor a free-ranging spotted hyena during the days just before and after parturition.

Abdomen↗
PubMed1998

Comparison of the expression of two immediate early gene proteins, FosB and Fos in the rat preoptic area, hypothalamus and brainstem during pregnancy, parturition and lactation.

Medial preoptic area (MPA), supraoptic nucleus (SON), magnocellular (MaPVN) and parvocellular (PaPVN) paraventricular hypothalamic nuclei, and mesencephalic lateral tegmentum (MLT) are involved in maternal behavior, parturition and lactation. This study investigated the FosB and Fos immunoreactivity in these regions of virgin, pregnant, parturient, lactating, and lactating-arrested rats. The patterns of FosB and Fos expression were compared between the sections taken from the same animals. Quantitative immunohistochemistry revealed a significant increase in the numbers of FosB-positive neurons in the MPA, SON, MaPVN, and MLT of parturient and lactating females as compared with pregnant or virgin animals. In lactating rats, the numbers of FosB-positive neurons in the MPA, PaPVN, and MLT were increased, but the numbers in the SON and MaPVN were decreased as compared with parturient females. Many Fos-positive neurons were also seen in parturient and lactating rats, and the patterns of Fos expression in each region were quite similar to those of FosB. Moreover, double-labeling immunohistochemistry revealed that: (1) many FosB-positive nuclei were observed in oxytocin and vasopressin neurons of the SON and PVN in parturient rats; (2) within FosB-positive neurons, 89.5% in the MPA, 86.8% in the MLT of parturient rats, and 92% in the MPA and 90.8% in the MLT of lactating animals were also Fos-positive. Only a small number of FosB and Fos-positive neurons were seen in females that were killed in the early stage of parturition. Removal of the litters immediately after parturition completely eliminated FosB and Fos expression in each region in the dams. Taken together, the present results suggest that FosB expression is co-involved with Fos in the neural activation during parturition and lactation in rats.

Animals↗
PubMed2000

Induction of parturition with prostaglandin f2 alpha as a possible model to study impaired reproductive performance in the dairy cow.

Parturitions were induced in five cows, 2 weeks before term using prostaglandin (PG) F(2alpha). Two i.m. injections were performed with an interval of 24 h. All cows calved within 5 days (average 2.7 days) after the first injection of PGF(2alpha). Out of five cows, four had retained fetal membranes (RFM). Each animal was sampled for bacteriological examination using uterine biopsies twice a week during 42 days postpartum (PP). Jugular vein blood samples were withdrawn for PGF(2alpha)-metabolite and progesterone analyses five times per day during the first week PP and eight times per 24 h during the 2nd and 3rd weeks PP. From the 4th week, the sampling interval was reduced back to five times per day. From the 5th week PP, the sampling was reduced to two times per day and sampling was terminated after day 46 PP. Only morning samples were used for progesterone analyses. From day 10 PP, ultrasonography (US) was performed every 3rd day until day 39 PP for detection of ovarian activity and follicular dynamics. The highest incidence of bacteriological species was found during the first 3 weeks PP. After the 5th week of collection, all animals were free from bacteria. The species of bacteria found were Arcanobacterium (Actinomyces) pyogenes, Escherichia coli, alpha-hemolytic streptococcae and Pasteurella multocida. Immediately after parturition, very high levels of the PG-metabolite were seen in all animals, with a sharp decrease to line of significance around days 9-12 PP. Small increases above the line of significance were detected up to day 27 PP in cows with RFM, and after that time the levels were considered to be at baseline. Low levels of progesterone were seen in four animals during the whole experimental time. In one animal, an increase was seen on day 43 PP, which was maintained until the end of the experimental period on day 46 PP. Based on US, follicular waves were detected in all animals during the experimental period. In three animals, three non-ovulatory follicular waves were detected and in two animals, four non-ovulatory follicular waves were detected during 39 days of ultrasound sessions. Based on progesterone levels, only one animal was considered to have ovulated around day 40 PP. Results from the present study indicate that reproductive performance of cows after PG-induced parturitions differs from those of spontaneous cases of RFM. Differences regarding the resumption of ovarian activity were also observed between previous studies of dexamethasone-induced parturitions and the present study.

Actinomyces↗
PubMed1970

The roles of pregn-5-ene-3 beta, 20 alpha-diol and 20 alpha-hydroxy steroid dehydrogenase in the control of progesterone synthesis preceding parturition and lactogenesis in the rat.

1. The activity of 20alpha-hydroxy steroid dehydrogenase in rat ovarian corpora lutea increased at least 50-fold between 2 days before and 2 days after parturition, and then fell gradually during lactation. The activity of 3beta-hydroxy Delta(5)-steroid dehydrogenase decreased by 50% at parturition but remained constant at other times. 2. The 20alpha-hydroxypregn-4-en-3-one/progesterone concentration ratio in the ovary fell tenfold between 1 day before and 1 day after parturition, in contrast with the increase of the ratio for these steroids in plasma. 3. Pregnenolone was metabolized in intact cells or cell-free systems either to pregn-5-ene-3beta,20alpha-diol and then to 20alpha-hydroxypregn-4-en-3-one by 20alpha-hydroxy steroid dehydrogenase and 3beta-hydroxy Delta(5)-steroid dehydrogenase respectively, or directly to progesterone by the latter enzyme. The relative activities of these pathways appeared to reflect the relative amounts of the two enzymes and the concentrations of their respective coenzymes NADPH and NAD(+). 4. From these and other observations it was concluded that the cessation of progesterone secretion, which precedes parturition and lactogenesis at the end of pregnancy, is partly due to the redirected metabolism of pregnenolone away from progesterone and towards 20alpha-hydroxypregn-4-en-3-one as the secreted end product. This is primarily the consequence of the sharp increase in the activity of 20alpha-hydroxy steroid dehydrogenase. This mechanism is super-imposed on the already declining rate of net Delta(4)-steroid release by the ovary. 5. A relationship of these pathways to subcellular compartments of luteal cells is proposed.

Animals↗
PubMed1997

Radiotelemetrically recorded blood pressure and heart rate changes in relation to plasma catecholamine levels during parturition in the conscious, unrestrained goat.

The aim of this study was to investigate the extent of sympathetic nervous system activation during parturition in four unrestrained goats. Chronically implanted radiotelemetry devices registered heart rate and arterial blood pressure around the clock and blood was sampled for determination of plasma adrenaline and noradrenaline concentrations before, during and after labour. Two goats delivered two kids after moderately intensive abdominal contractions. A third goat had dystocia, and was treated with prostaglandin F2 alpha. One normal kid and one mummified foetus were delivered manually. After milking, a third kid was born spontaneously. The fourth goat experienced severe abdominal contractions and delivered one kid. Mean blood pressure was 69 +/- 2 mmHg the day before parturition, increased gradually during the labour pains, and reached a maximal value of 120 +/- 7 mmHg when the head of the first kid was visible (P < or = 0.05). Heart rate was 134 +/- 4 beats min-1 the day before parturition and peaked when the first kid was born (159 +/- 6 beats min-1, P < or = 0.05), as did plasma adrenaline concentration (from 0.4 +/- 0.2 nmol L-1 to 2.7 +/- 1.2 nmol L-1, P < or = 0.05). The concentration of noradrenaline increased from 4.8 +/- 2.3 nmol L-1 to 12.2 +/- 8.4 nmol L-1 (P < or = 0.05), when the head of the first kid was visible. Expulsion of the second and third kids caused relatively smaller increases in blood pressure, heart rate and catecholamines than those seen with the first born kid. It is concluded that changes in pressure, heart rate and catecholamines during parturition are related to the different phases of labour and not to its duration or severity.

Animals↗
PubMed2002

Redistribution of the sheep neonatal Fc receptor in the mammary gland around the time of parturition in ewes and its localization in the small intestine of neonatal lambs.

Maternal immunity is mediated exclusively by colostral immunoglobulins in ruminants. As the neonatal Fc receptor (FcRn) is suggested to be involved in the transport of immunoglobulin G (IgG) in the mammary gland, we cloned this receptor from sheep and analysed its expression in the mammary gland around the time of parturition and also in the small intestine from the newborn lamb. FcRn heavy-chain mRNA was detected (by using in situ hybridization) exclusively in the acinar and ductal epithelial cells in mammary gland biopsies both before and after parturition. Immunohistochemistry revealed that the cytoplasm of the epithelial cells of the acini and ducts in the mammary gland biopsies stained homogeneously before parturition. A remarkable difference was observed in the pattern after lambing, where the apical side of the cells was strongly stained. The presence of the FcRn in the acinar and ductal epithelial cells of the mammary gland, and the obvious change in distribution before and after parturition, indicate that the FcRn plays an important role in the transport of IgG during colostrum formation in ruminants. Immunohistochemical analysis detected a strong apical and a weak basal FcRn signal in the duodenal crypt cells of a neonatal lamb, which have been previously demonstrated to secrete IgG1 in newborn ruminants. The FcRn was not detected in the duodenal enterocytes, which absorb intact IgG from the colostrum in a non-specific manner. These data suggest that FcRn is involved in IgG1 secretion in ruminant epithelial cells.

Amino Acid Sequence↗
PubMed1980

Influence of photoperiod on the time of parturition in the rat. I. --Effect of the length of daily illumination on normal or adrenalectomized animals.

Four groups of normal rats have been studied to elucidate the effect on the time of birth of four different light regimes applied throughout pregnancy (day 1: beginning of pregnancy). The results showed that the time of parturition (onset of expulsion) depended on the light treatment: the longer the duration of the daily illumination, the longer pregnancy lasted. With a 14 hrs light regime, the births occurred during two main periods: 50 p. 100 before 8 p.m. on day 22 of pregnancy and 36 p. 100 between 5 a.m. and 1 p.m. on day 23. With 8 h of light per day, 69 p. 100 of the rats delivered before 9 p.m. on day 22 and 85 p. 100 before 5 a.m. of day of pregnancy. On the other hand, only 22 and 49 p. 100 of the rats gave birth at the same periods under a 20 hrs light regime. Parturition under a completely dark photoperiod occurred mainly before day 23 of pregnancy and with a different rhythm than those of the preceding groups. The influence of maternal adrenalectomy on the time of parturition was determined using two light regimes (14 or 20 hrs of light per day). Under those conditions, the length of pregnancy was modified; parturition occurred earlier in adrenalectomized than in the normal rats submitted to the same light regime. These results suggest that the effect of light on the time of birth in the rat involves adrenal gland secretions.

Adrenalectomy↗
PubMed1983

A critical period in the onset of parturition in rats and uterine sensitivity to estradiol and progesterone.

The purpose of this paper was to impair normal parturition in rats in order to measure tissue levels of progestins and estrogens and compare these results with those of normal parturition in rats. Abnormal parturition was obtained by injection of isotonic saline into the uterine lumen of pregnant rats at the end of pregnancy or by handling the uterus. After each of these treatments on day 21 of pregnancy, parturition was impaired in 70 to 98% of the rats. When the treatments were carried out earlier or later in pregnancy, there was little or no impairment. Our results indicate transient discrepancies in plasma and tissue levels of steroids 6 h after treatment on day 21: 20 alpha-HP concentrations increased in treated rats compared to controls (uteri: 470%; p less than 0.01; ovaries: 89%; p less than 0.001); concomitantly, there was a sharp rise in P concentrations in uteri (+ 74% : p less than 0.05) and ovaries (+ 52%; p less than 0.05). Inversely, uterine concentrations of E2 decreased 6 h after treatment compared to controls (- 30%; p less than 0.05), although there was a transient rise of E2 in the ovaries (+ 30%; p less than 0.05). Twenty-four hours later, E2 concentrations were always lower in the uteri (- 30%; p less than 0.01). No change in E2 levels was noted in the uteri or ovaries of either the control or treated rats. The physiological significance of these changes and their consequences on uterine reactivity at term have been discussed. The data demonstrate that day 21 was a critical period in the parturient activity of the rat uterus which appears to be primarily affected by uterine levels of E2 between days 21 and 22 of pregnancy.

20-alpha-Dihydroprogesterone↗