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PubMed2003

Guinea-pig interpubic joint (symphysis pubica) relaxation at parturition: underlying cellular processes that resemble an inflammatory response.

BACKGROUND: At term, cervical ripening in coordination with uterine contractions becomes a prerequisite for a normal vaginal delivery. Currently, cervical ripening is considered to occur independently from uterine contractions. Many evidences suggest that cervical ripening resembles an inflammatory process. Comparatively little attention has been paid to the increased flexibility of the pelvic symphysis that occurs in many species to enable safe delivery. The aim of this study was to investigate whether the guinea-pig interpubic joint relaxation process observed during late pregnancy and parturition resembles an inflammatory process. METHODS: Samples of pubic symphysis were taken from pregnant guinea-pigs sacrificed along gestation, parturition and postpartum. Serial sections of paraffin-embedded tissues were used to measure the interpubic distance on digitalized images, stained with Giemsa to quantify leukocyte infiltration and to describe the vascular area changes, or studied by the picrosirius-polarization method to evaluate collagen remodeling. P4 and E2 serum levels were measured by a sequential immunometric assay. RESULTS: Data showed that the pubic relaxation is associated with an increase in collagen remodeling. In addition, a positive correlation between E2 serum levels and the increase in the interpubic distance was found. On the other hand, a leukocyte infiltration in the interpubic tissue around parturition was described, with the presence of almost all inflammatory cells types. At the same time, histological images show an increase in vascular area (angiogenesis). Eosinophils reached their highest level immediately before parturition; whereas for the neutrophilic and mononuclear infiltration higher values were recorded one day after parturition. Correlation analysis showed that eosinophils and mononuclear cells were positively correlated with E2 levels, but only eosinophilic infiltration was associated with collagen remodeling. Additionally, we observed typical histological images of dissolution of the connective tissue matrix around eosinophils. CONCLUSION: The present study shows that a timely regulated influx of infiltrating leukocytes is associated with an extensive collagen remodeling process that allows the pubic separation for a normal delivery in guinea-pig. Thus, the findings in this study support the hypothesis that the guinea-pig pubic symphyseal relaxation at parturition resembles an inflammatory process.

Animals↗
PubMed1988

Effect of preparturient 17 beta-estradiol and relaxin on parturition and pup survival in the rat.

This study examined the requirement for 17 beta-estradiol (E) and relaxin (R) during the preparturient period (approximately the last 30 h of gestation) for normal parturition and pup survival in the rat. On the evening of day 21 of pregnancy, primiparous Sprague-Dawley rats were bilaterally ovariectomized or sham operated and fitted with Silastic capsules containing one of four doses of E (6.0, 11.4, 45.6, or 68.4 micrograms in sesame oil) or sesame oil only. These rats were also injected sc with either 200 micrograms highly purified porcine R dissolved in 200 microliter 5% beeswax in corn oil or R vehicle three times (approximately 8 to 10-h intervals) beginning at ovariectomy. The durations of straining and delivery were increasingly prolonged with increasing doses of E in the ovariectomized groups that received E but no R. In rats that received the two highest doses of E there was a reduction in the percentage of pups born alive and a reduction in pups surviving on day 2 postpartum, and one or two undelivered fetuses were retained in utero in some animals 3 days postpartum. The administration of R with the two highest doses of E restored all parturition parameters to values not different from those of intact controls. In the absence of both E and R, all measured parturition parameters were abnormal, and administration of R in the absence of E only partially restored them to control values. Two major conclusions are drawn. First, E treatment alone to pregnant rats ovariectomized on day 21 fails to elicit normal parturition; indeed, with increasing doses of E, parturition parameters and pup survival become increasingly adversely affected. Second, R treatment of E-treated ovariectomized rats during the immediate preparturient period restores parturition parameters and pup survival to the levels of intact sham-operated controls.

Animals↗
PubMed1975

Radioimmunoassay of plasma relaxin levels throughout pregnancy and at parturition in the pig.

Relaxin concentrations in peripheral plasma have been measured throughout pregnancy and immediately following parturition in the pig by radioimmunoassay. Gestation ranged from 114-117 days. Relaxin concentrations remained below 2 ng/ml during the first 100 days of pregnancy and then rose gradually to a mean of 11.9 ng/ml by 3 days before parturition. At this time, relaxin levels began to rise more rapidly and over the next 2 days increased to a mean concentration of 44.0 ng/ml by 30 h before parturition. Relaxin concentrations then increased sharply to a mean of 145.6 ng/ml by 14 h before parturition. This maximum was followed be a rapid decrease to a mean of 42.4 ng/ml by 2 h before parturition. At one day following parturition, relaxin levels were less than 1 ng/ml.

Animals↗
PubMed1998

Studies on the role of ACTH in the regulation of adrenal responsiveness and the timing of parturition in the ovine fetus.

A dramatic late-gestation increase in fetal plasma cortisol concentrations is critical for the timing of parturition in the sheep. This increase appears to depend upon an intact hypothalamo-pituitary unit and is characterised by increasing responsiveness of the fetal adrenal gland to ACTH. ACTH has been postulated as the critical determinant of the late-gestation cortisol increase; however, recent evidence has suggested that other factors, including the ACTH precursor, pro-opiomelanocortin, may also be involved. To further define the role of ACTH in determining the timing of parturition and the responsiveness of the fetal adrenal gland, intact (INT/ACTH) and hypophysectomised (HX/ACTH) fetuses received a continuous infusion of ACTH(1-24) from the time of surgery (approximately 115 days gestational age (GA)) at a rate we have previously shown to generate normal fetal cortisol concentrations and term parturition in HX fetuses. A third group of saline-infused intact fetuses (INT/SAL) served as the control group. Adrenal responsiveness was assessed by cortisol responses to ACTH(1-24) challenges at 120, 130 and 140 days GA. There were no differences between the three groups of fetuses in the timing of parturition, the late-gestation increase in cortisol concentrations or the size of the adrenal cortex. In both INT/SAL and INT/ACTH fetuses, there were significant increases in basal immunoreactive-ACTH concentrations with advancing GA, although no such increase was observed in HX/ACTH fetuses. The proportion of total ACTH immunoreactivity present in low molecular weight (LMW) forms in INT/ACTH fetuses was greater than that in INT/SAL fetuses, while the level of LMW ACTH in HX/ACTH fetuses was intermediate. Both ACTH(1-24)-infused groups of fetuses had dramatically enhanced adrenal responsiveness to ACTH(1-24) at all GAs tested when compared with INT/SAL fetuses and there was a correlation (in rank order) between the proportion of LMW ACTH immunoreactivity and adrenal responsiveness. From these observations it appears that there is a separate regulation of adrenal responsiveness from basal cortisol concentrations and that an increase in basal cortisol concentrations can occur in the absence of an increase in basal ACTH concentrations. Furthermore, an increase in adrenal responsiveness does not appear to predict the timing of parturition nor basal cortisol concentrations. Taken together with previous studies it appears that ACTH plays an essential role in maintaining the growth of the fetal adrenal and enhancing its responsiveness, but a late-gestation increase in ACTH concentrations is not required to regulate basal cortisol concentrations or the timing of parturition.

Adrenal Glands↗
PubMed1990

Control of prostaglandin-induced parturition in sows by injection of the beta-adrenergic blocking agent carazolol or carazolol and oxytocin.

Although parturition commonly is induced in swine with prostaglandin F2 alpha or one of its analogs, variation in response to the treatment is large. The purpose of this investigation was to more precisely terminate parturition. Two experiments were conducted. Sows all received prostaglandin analog followed, 20 h later, by different doses of the beta-adrenergic blocking agent carazolol and(or) oxytocin. Treatment with 3 mg of carazolol alone caused parturition to commence within 2.6 +/- .23 (SEM) h after injection. Parturition was complete in 2.0 +/- .13 h and proceeded smoothly without the necessity of manual assistance. Adding 2.5 I.U. of oxytocin to the 3 mg of carazolol speeded the onset of labor (1.7 +/- .17 h). However, in some cases parturition was interrupted and the time passing between the birth of the first and the last piglet was prolonged to 2.5 +/- .28 h. We conclude that by applying carazolol 20 h after a prostaglandin analog, parturition in swine may be terminated very effectively.

Adrenergic beta-Antagonists↗
PubMed1998

Body condition at parturition and postpartum weight gain influence luteal activity and concentrations of glucose, insulin, and nonesterified fatty acids in plasma of primiparous beef cows.

Effects of body condition score (BCS) at parturition and postpartum weight gain on luteal activity and concentrations of glucose, insulin, and NEFA in plasma were evaluated during the breeding season in 242 primiparous beef cows over 3 yr (Y) at three locations (L). At approximately 90 d prepartum, cows were blocked by breed, expected calving date, and BCS and randomly assigned to diets so that cows would calve in BCS of 4, 5, or 6. At calving, cows were blocked by breed, calving date, and BCS and randomly allotted to gain .45 (M) or .90 (H) kg/d, from parturition to the start of breeding (postpartum nutrition; PPN). During the 60-d breeding season, weekly blood samples were obtained from cows, and progesterone, insulin, glucose, and NEFA were quantified. Progesterone concentrations greater than 1 ng/mL for more than 1 wk indicated luteal activity. To determine the possible value of blood constituents as predictors of luteal activity, categorical data analyses were performed. Cows with greater BCS at parturition had greater concentrations of glucose during breeding (P < .07). Similarly, PPN influenced glucose at the beginning of breeding, but the differences were minimal after d 28 (PPN x day; P <.001). Cows with greater BCS at parturition and M-PPN had greater concentrations of insulin during the breeding season (BCS x PPN; P < .02). Cows with a BCS of 6 at parturition had the lowest concentrations of NEFA; however, cows on H-PPN had greater concentrations of NEFA (BCS x PPN; P < .03). Location, BCS, PPN, and day affected luteal activity (P < .002). Location differences in luteal activity were associated with the interval from calving to the start of breeding. In general, a greater percentage of cows with BCS of 5 or 6 at calving had luteal activity by the end of the breeding season. Concentrations of metabolites in blood during breeding were not predictive of luteal activity. We conclude that BCS at parturition and postpartum nutrition influence concentrations of glucose, insulin, and NEFA in blood and the onset of luteal activity in primiparous beef cows.

Animals↗
PubMed1983

Intramammary infections in primigravid heifers near parturition.

Mammary secretion from 32 primigravid heifers was obtained aseptically to determine frequency of bacterial isolation and incidence of intramammary infection near parturition. Quarter samples were collected 14 and 7 days prior to expected parturition, at parturition, and 7 and 14 days postparturition. Analysis of culture data indicated that 77.1% of samples were bacteriologically negative, and 15.7% contained coagulase negative staphylococci, 4.4% streptococci other than Streptococcus agalactiae, 3.8% coliforms, .8% coagulase positive staphylococci, and .1% Corynebacterium bovis. Frequency of bacterial isolation was highest in samples obtained prior to and at parturition. Thirty-five of 128 quarters were infected at parturition. Twenty-six of the 35 infections were caused by coagulase negative staphylococci, 4 by streptococci other than Streptococcus agalactiae, 4 by coliforms, and 1 by coagulase positive staphylococci. Twenty infections were observed during the early postpartum period. Coagulase negative staphylococcal infections decreased markedly. However, the number and type of primary pathogen infections during early lactation were similar to those at parturition.

Animals↗
PubMed1998

Sources of intramammary infections from Staphylococcus aureus in dairy heifers at first parturition.

The study objective was to identify probable sources and modes of transmission of 91 Staphylococcus aureus isolates obtained from the colostrum of 76 heifers at parturition. Sources cultured were milk (including colostrum), heifer body sites (teats, muzzle, rectum, vagina, and lacteal secretions), and environmental sites (bedding, insects, housing, water, feedstuffs, humans, nonbovine animals, air, and equipment). Staphylococcus aureus isolates were characterized by 63 phenotypic traits. A similarity coefficient was calculated by herd to identify the S. aureus that most closely resembled the S. aureus obtained from heifer colostrum. Staphylococcus aureus from a heifer's colostrum was compared with all preexisting S. aureus isolates from that heifer's herd. Isolates that were > or = 90% similar were considered to be identical. Because 30 (of the 91) S. aureus isolates from heifer colostrum were collected prior to environmental sampling, only 61 S. aureus isolates from heifer colostrum were available for comparison among all three sources. Possible sources of S. aureus from heifer colostrum at parturition were milk (70%, 43 of 61 isolates), heifer body sites (39%, 24 of 61), environmental sites (28%, 17 of 61), or no identified source (16%, 10 of 61). Three heifers with intramammary infection (IMI) from S. aureus at parturition had the same S. aureus on their teats prior to parturition. Milk was the only source identified for 41% (25 of 61) of isolates from heifer colostrum. Isolates from heifer body sites were the only source identified for 5% (3 of 61) of heifer colostrum isolates. Staphylococcus aureus from the environment was never the sole possible source for S. aureus from heifer colostrum. Data suggest that the major sources of S. aureus IMI in heifers at parturition are milk and heifer body sites. Contact among heifers may be an important mode of transmission of S. aureus leading to IMI in heifers at parturition.

Animals↗
PubMedDate not supplied

Gene knockout mice in the study of parturition.

OBJECTIVE: To review recent studies of parturition control in mice with relevance to understanding the control of human parturition. METHODS: Assimilation of published studies of gene knockout mice with mutations in neuropeptides, prostaglandin synthetic enzymes and receptors, and other molecules implicated in parturition. RESULTS: The central role of prostaglandins in murine labor is demonstrated by mice with gene mutations at multiple levels of the prostaglandin synthetic pathway. In addition, novel molecules such as steroid 5 alpha-reductase are found to play an essential role in the progression of labor. Surprisingly, deficiency of neuropeptides such as oxytocin and corticotropin-releasing hormone have little effect on parturition. CONCLUSION: Molecular genetic analyses in mice provide an efficient way to define molecules critical for murine parturition. Extrapolation of the importance of these molecules to human parturition provides the next challenge.

3-Oxo-5-alpha-Steroid 4-Dehydrogenase↗
PubMed1992

[The physiology of natural parturition in cows].

In the year 1990 free parturitions of 339 cows were followed on three farms; these parturitions were compared with the last parturitions of these cows when the tender's assistance was available. The spontaneous free parturitions were followed in the open air in litter boxes which were located outside the barns where the groups of about twenty highly pregnant cows and heifers were housed for two months before their parturitions all the year round irrespective of the weather conditions. In addition to direct continuous observations, a host of zooveterinary data filed for these groups of animals were evaluated, concerning particularly those animals which could not be directly followed for the time reasons. Through direct observations the time schedule of the given parturition was evaluated and recorded above all, including all changes in the behaviour of the cow itself, and also behavioural changes in the group of animals or the behaviour of particular groups of animals toward each other. Applying the same criteria, the behaviour of born calves toward the mother, behaviour of calves toward each other and their behaviour toward other breeding cows was evaluated. The method of disinterested observation was used, this means the principle of noninterference with the most actions observed, with the exception of such situations that could result in the calf death. Another principle was to minimize through these observations all negative effects that could influence the behaviour of individual animals and also the behaviour of the whole group.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2006

Real-time ultrasound measure of the fetal eye (vitreous body) for prediction of parturition date in small ponies.

Ultrasonographic fetal eye measures have been used to estimate gestational age of the fetus in light horse mares. However, fetal eye measures have not been published for smaller pony breeds. This study was conducted to develop reference ranges for ultrasonographic measures of fetal eyes in small ponies for the purpose of predicting days before parturition (DBP) when breeding or ovulation dates are unknown. Twenty-three Shetland-type pony mares were studied across one (n = 10) or two (n = 13) gestations in 2004 (18 pregnancies) and 2005 (18 pregnancies). Measurements of fetal eyes were obtained during transrectal ultrasound examination. Examinations were conducted once monthly in a field situation beginning in December (2003) or August (2004) until mares foaled (March through July). The length (from sclera to sclera) and width (from retina to cornea) of the vitreous body were measured. For the 273 examinations in which gestation age was greater than 2 months, eye measures were obtainable in 248 (91%). Mixed-effects linear regression modeling was used to account for serial growth measures within pregnancy, repeated measurements across mares, and unbalanced study design. Independent variables evaluated included vitreous body length, vitreous body width, the ratio of length to width, parity, and mare height at the withers at parturition. Eye length was the best single predictor of days before parturition, with almost no additional predictive value of the other variables considered. Our resulting regression equation is: days before parturition=265.16-0.21*(vitreous body length in mm)(2). This study suggests that measure of the fetal eye is a practical on-farm procedure for estimating days before parturition in small ponies.

Animals↗
PubMed2003

Accuracy of canine parturition date prediction using fetal measurements obtained by ultrasonography.

The length of canine gestation is 65 days from the luteinizing hormone (LH) surge. Early and accurate determination of canine gestational age is useful for predicting and managing parturition. We performed a retrospective study on fetal measurements obtained by transabdominal ultrasonographic examination of 83 bitches (32 breeds) to estimate gestational age. Gestational age was estimated using two published tables correlating either (1). embryonic vesicle diameter (EVD), crown-rump length (CRL), body diameter (BD), and biparietal diameter (HD) to the LH surge in mid-gestational beagles or (2). BD and HD to parturition in late-gestation retrievers. Parturition date was predicted by obtaining the difference between the gestational age estimate and 65 days. Bitches were divided into four body weight (BW) groups based on nonpregnant body weight: small ( 9-20 kg), large (>20-40 kg), and giant (>40 kg). Mean+/-S.D. litter size (LS) was calculated for each BW group. The BW groups were then divided into small, average, or large LS groups. The accuracy of the prediction was not affected by LS but was affected by maternal body weight for small and giant BW groups only. When adjusted for weight, the accuracy of prediction within +/-1 day and +/-2 day intervals was 75 and 87%, respectively. Using stepwise logisitic regression, the most accurate prediction of parturition date was obtained when fetuses were measured at 30 days after the LH surge, regardless of body weight or LS. Parturition date predictions made after 39 days of gestation using only biparietal and BD fetal measurements were <50% accurate within +/-2 days.

Animals↗
PubMed2002

Sows intramammarily inoculated with Escherichia coli at parturition. II. Effects on the densities of MHC class II(+), CD4(+) and CD8(+) cells in the mammary gland.

The aim of this study was to determine the density of MHC class II, CD4 and CD8 positive cells in mammary glands of sows around parturition, and whether the densities were altered following intramammary inoculation with Escherichia coli prior to parturition. Also, animals developing clinical disease after inoculation were compared with animals not developing clinical disease. Fourteen cross-bred primiparous sows were subject to intramammary inoculation with E. coli bacteria 24h before estimated parturition. Mammary gland biopsies were collected and clinical observations were made. Four sows were categorised as clinically ill based on general condition, body temperature and gross mammary affection. There were no changes in density of MHC class II, CD4 and CD8 positive cells in non-inoculated glands around parturition, while significant changes in densities were shown in inoculated glands. Here, the density of MHC class II, CD4 and CD8 positive cells reached a peak at 72 h post-inoculation (p<0.01). In sows developing clinical disease, there was a tendency to an over all lower density (p=0.07) of MHC class II positive cells in inoculated glands compared with sows not developing clinical disease. When comparing the categories with respect to the density of CD4 and CD8 positive cells, the sows developing clinical disease showed a higher density (p=0.03) of CD4 and CD8 positive cells in inoculated glands than sows not developing disease. No differences were shown between categories in non-inoculated glands. It is concluded that the density of MHC class II, CD4 and CD8 positive cells seems to be unaltered around parturition. However, there is a rapid increase in density of these cells following intramammary inoculation with E. coli. Also, the data suggest that there is a difference between sows developing and sows not developing clinical disease after inoculation with respect to the increase in density of MHC class II, CD4 and CD8 positive cells in the mammary gland.

Animals↗
PubMedDate not supplied

Hormones, IgG and lactose changes around parturition in plasma, and colostrum or saliva of multiparous sows.

Blood, colostrum and saliva samples were serially taken from 6 multiparous sows from day 109 of gestation until day 3 postpartum. Plasma was assayed for oestradiol-17beta (E2), progesterone (P4), prolactin (PRL), cortisol, immunoglobulin G (IgG) and lactose. Colostrum was assayed for E2, P4, IgG and lactose. Lactoserum, obtained after ultra centrifugation of colostrum, was assayed for PRL. Saliva was assayed for cortisol. Time-related variations in hormone, IgG and lactose concentrations measured in plasma were parallel to those measured in colostrum, lactoserum or saliva. However, the concentrations were higher in colostrum or lactoserum and lower in saliva than in plasma. Ratios of concentrations of cortisol in saliva and PRL in lactoserum over those in plasma did not vary with time and averaged 0.2 and 1.6, respectively. Conversely, the ratios of concentrations of E2 and P4 in colostrum over those in plasma varied with time (P < 0.05) but were quite constant before the end of parturition, averaging 2.7 and 3.6, respectively. The ratios of concentrations of IgG and lactose in colostrum over those in plasma also varied with time (P < 0.05). The concentrations of hormones in plasma on the one hand and in colostrum, lactoserum or saliva on the other hand were significantly correlated but correlations varied with time (PRL across periods: r = 0.31; cortisol across periods: r = 0.60; E2 during parturition: r = 0.83; P4 before parturition: r = 0.82; P4 during parturition: r = 0.67). The present results indicate that around parturition, assays of hormones in colostrum or saliva can be used to study the hormonal status of sows. Furthermore, variations in colostrum and plasma concentrations of IgG and lactose are good indicators of the transition from colostrum to milk synthesis.

Animals↗
PubMed2006

Changes of sex hormone-binding globulin/SHBG expression in the hypothalamo-hypophyseal system of rats during pregnancy, parturition and lactation.

Sex hormone-binding globulin (SHBG) is expressed in hypothalamic magnocellular neurons. High co-localization rates of SHBG with oxytocin have been observed in the hypothalamus, indicating that SHBG plays a role in pregnancy, parturition and lactation. Further studies have shown that hypothalamic SHBG expression is malleable to changing steroid conditions. In this study, we have examined SHBG levels in the supraoptic and paraventricular hypothalamic nuclei and in the posterior pituitary lobe of late pregnant, parturient and early lactating rats by IN SITU hybridization, immunocytochemistry, and ELISA. Immunocytochemical and biochemical analysis showed that the SHBG levels increased during late pregnancy in hypothalamic nuclei. During parturition, SHBG levels fell in the magnocellular nuclei but increased in the posterior pituitary lobe. SHBG levels increase again during lactation. At day six of lactation, there was no significant difference in SHBG levels compared to normal cycling female rats, which served as control in this study. IN SITU hybridization showed increased SHBG mRNA signal during late pregnancy. The highest SHBG expression was observed during parturition. Our data indicate that hypothalamic SHBG expression changes during pregnancy, parturition and lactation, parallel to ovarian steroid and co-localized OT levels. This may in part be linked to known steroid actions on synthesis and secretion of magnocellular hypothalamic peptide hormones, important for the control of parturition and lactation.

Animals↗
PubMed2006

Comparison of the accuracy of two ultrasonographic measurements in predicting the parturition date in the bitch.

OBJECTIVES: To compare the accuracy of two ultrasonographic measurements, inner chorionic cavity diameter and biparietal diameter, for the prediction of parturition date in small and medium size bitches. The effects of litter size and fetal sex ratio on the accuracy of the prediction were also investigated. METHODS: Ultrasonographic examinations were performed on pregnant bitches and, depending on the stage of pregnancy, the inner chorionic cavity diameter and biparietal diameter were measured. The mean value of the data of each structure was calculated and the predicted day of parturition was obtained by the application of equations derived from growth curves we previously developed for different size bitches. RESULTS: The parturition term was predicted with similar accuracy during early gestation, by the measurement of inner chorionic cavity diameter, as well as during late gestation, by the measurement of biparietal diameter. Litter size affected only biparietal diameter accuracy, whereas fetal sex ratio did not influence the estimation of the day of parturition. CLINICAL SIGNIFICANCE: Inner chorionic cavity diameter and biparietal diameter were equally reliable parameters in obtaining a reasonably accurate prediction of parturition date at any gestational period at which a bitch is examined.

Animals↗
PubMed2003

Pineal gland (melatonin) affects the parturition time, but not luteal function and fetal growth, in pregnant rats.

The purpose of the present study was to investigate the role of pineal gland (melatonin) on parturition time, luteal function, and fetal growth in pregnant rats. Cycling rats were subjected to pinealectomy or sham operation under ether anesthesia; and pinealectomized rats immediately underwent implantation of a melatonin capsule (PINX + Mel group) or a vehicle-containing capsule (PINX group), and sham operated rats also underwent implantation of a vehicle-containing capsule (control group). All rats were maintained under the same photoperiod conditions (14 L:10 D) and were induced pregnancy. Blood samples were obtained on days 7, 12, 15, 17, 19, and 21 of pregnancy to measure serum progesterone concentrations, and parturition times were recorded on days 22 and 23. In the next experiment, pregnant PINX rats received subcutaneous injection of melatonin (10 microg/body) at 08:00 h (PINX + 8 h group) or at 20:00 h (PINX + 20 h group) from day 15 to the end of pregnancy, and parturition times were recorded. Parturition times of rats in the PINX group, the PINX + Mel group or the PINX + 8 h group, but not the PINX + 20 h group, were significantly different compared with those in the control group. Pinealectomy or melatonin implantation did not affect serum progesterone concentrations during pregnancy or the number and weight of fetuses or corpora lutea. The present results indicate that pineal gland (melatonin rhythm) synchronizing with photoperiodic rhythm is likely to be an important determinant of parturition time, but it does not affect progesterone production or fetal growth in pregnant rats.

Animals↗
PubMed2004

Effects of parity and body condition at parturition on endocrine and reproductive parameters of the cow.

The effect of parity (multiparous vs primiparous) and body condition score (BCS; <3.0 or > or =3.0, lean vs fat) at parturition on metabolic and endocrine profiles from 1 month before to 2 months after parturition were studied in 42 Holstein cows grazing on improved pastures. BCS and milk production were determined every 2 weeks. Non-esterified fatty acids (NEFA), beta-hydroxy-butyrate (BHB), insulin, IGF-I, leptin, thyroxine (T4) and 3,3',5-tri-iodothyroinine (T3) were determined in plasma every 10 days. Progesterone was determined three times per week after parturition. Primiparous cows had a lower BCS during the early postpartum period and produced less milk than multiparous animals. Primiparous cows had higher NEFA concentrations and they presented more samples with BHB concentrations of >1 mmol/l than multiparous cows. Multiparous cows had higher T3, T4 and IGF-I concentrations, while fat cows had higher leptin and IGF-I concentrations. All hormone concentrations were diminished in the first week postpartum. Primiparous cows and fat cows presented a steeper decay of IGF-I and leptin around parturition than multiparous cows and lean cows. While thyroid hormones and IGF-I showed increasing concentrations from approximately day 30, leptin concentrations remained low until the end of the experimental period. The initiation of ovarian cyclicity was delayed in primiparous cows and especially in primiparous lean cows, consistent with longer intervals from parturition to first service and to conception. The endocrine signals most likely to inform the reproductive axis regarding a negative energy balance were IGF-I and leptin.

3-Hydroxybutyric Acid↗