Progesterone In Peripheral Blood Research Articles

Transfer of Day 11 ruptured embryos can prevent luteolysis in recipient mares

Previous studies transferring Day 11 embryos to Day 11 or 12 recipient mares and then manually crushing the transferred embryo 24 hours later resulted in 83% (5/6) and 100% (6/6) mares, respectively, entering a period of luteostasis. Undertaking manual reduction 12 hours post transfer resulted in 100% (5/5) of Day 11 recipient mares becoming luteostatic. This work suggested that the mare could recognise the presence of an embryo within the uterus after only a short period of time. The present experiment aimed to shorten the window of the presence of an intact embryo still further by evaluating the ability of ruptured or damaged Day 11 embryos transferred to recipient mares to initiate a period of luteostasis. A total of sixteen Day 11 embryos were flushed from the uteri of donor mares. Embryos were moved to a petri dish containing 5mL of Vigro Hold Plus Solution where they were measured and graded. The intact embryos were ruptured using two 100µm diameter acupuncture needles, ensuring the blastocoele fluid was released into the medium. The ruptured embryo and the medium were then transferred to recipient mares at Day 11 (n = 8) or 12 (n = 8) post ovulation using a standard embryo transfer technique. Control Day 11 (n = 8) and 12 (n = 8) recipient mares received 5mL of Vigro Hold Plus. All recipient mares were monitored on alternate days post transfer using a combination of ultrasonography,including assessment of the corpus luteum using colour Doppler, and serial blood serum samples assayed for progesterone in peripheral blood to determine if, and when, they returned to oestrus. Mares with a functional corpus luteum with blood flow and progesterone levels >1ng/mL up to 25 post ovulation were deemed to have entered a period of luteostasis and at this time point luteolysis was achieved by administration of an i.m injection of prostaglandin. Transfer of the ruptured embryo and medium resulted in significantly more Day 12 recipients entering a period of luteostasis compared to Day 11 recipients (75% vs. 12.5%; 6/8 vs. 1/8; P= 0.04, respectively). Day 11 and 12 control recipient mares that received only medium had an incidence of luteostasis of 12.5% (1/8) in each group. Hence the presence of medium containing blastocoele fluid, a ruptured capsule and trophoblast within the uterus can prevent luteolysis around the time of maternal recognition of pregnancy (MRP) in the mare. If all or only some of the components of the ruptured Day 11 embryo are required to initiate luteostasis needs further study. If the mechanisms underlying luteostasis with this model mirror those of the MRP signal in pregnant mares this study also raises questions about the duration of the MRP signal and how long embryo migration within the uterus is needed to prevent luteolysis.

Ovarian function in women with type 1 diabetes mellitus

To study the hormonal and ovulatory ovarian function in women with type 1 diabetes mellitus 180 patients of reproductive age with type 1 diabetes were examined. Basal-bolus insulin therapy received 146 patients (81.1 %), insulin pomp therapy received 34 women (18.9 %). Examination included: determination of blood glucose level and glycated hemoglobin, content of FSH, LH, prolactin, estradiol, total and free testosterone, and progesterone in peripheral blood by enzyme-linked immunosorbent assay, determination of autoantibodies against ovarian tissue by indirect immunofluorescence, pelvic ultrasonography. Ovarian insufficiency was present in 62.2 % of women surveyed. An association of ovarian insufficiency with the glycemia level, glycosylated hemoglobin and the dose of insulin was found. There was no dependence of ovarian function and insulin regimens or the severity of microvascular complications of diabetes. Patients with type 1 diabetes had an increase of ovarian volume and the number of antral follicles compared with those in healthy women. These patients exhibit elevated levels of LH, estradiol and free testosterone in peripheral blood. Ovarian volume increased correlated with the presence and severity microvascular complications of diabetes and the dose of insulin. Autoantibodies against ovarian tissue were found only in 3.6 % women of type 1 diabetes mellitus.

A field study to unravel factors that are significantly associated with the secretory activity of the corpus luteum during the first three postpartum cycles in high yielding dairy cows, based on the amount of steroidogenic and endothelial cells present in the luteal tissue.

Fourteen multi- and eight primiparous high-yielding dairy cows were followed from the first till the fourth ovulation postpartum. Cows were randomly divided into two groups and supplemented with soybean (group I; n = 11) or rapeseed meal (group II; n = 11). Both groups were subjected to a biopsy sampling of the corpus luteum (CL) at cycle day 9. The luteal capillary network (visualized by Bandeiraea simplicifolia) was denser in cycles 2 and 3 (p = 0.0005). The same was seen for the surface occupied by steroidogenic cells (visualized by 3β-hydroxysteroiddehydrogenase) (p = 0.0001). The peripheral blood progesterone concentration showed an increasing trend with increasing cycle number and was higher in primiparous cows (p = 0.013), which had also larger glands on cycle day 9. The area occupied by endothelial cells was positively correlated with the area occupied by steroidogenic cells (r = 0.59; p < 0.0001). Both the areas occupied by endothelial and by steroidogenic cells were negatively correlated with the blood concentration of nonesterified fatty acids (NEFAs) (respectively, r = -0.377; p = 0.004 and r = -0.355; p = 0.007). We can conclude that primiparous cows generally have higher peripheral progesterone levels during the first three cycles after calving which is associated with a larger CL. In comparison with those of the first post-partum cycle, corpora lutea of cycles 2 and 3 have a denser capillary network and a larger area of steroidogenic cells, while these are only associated with a trend of higher peripheral progesterone concentrations.

71 EFFECTS OF A CONTROLLED DIETARY EXPOSITION TO ZERALENONE ON SELECTED REPRODUCTIVE PARAMETERS IN DAIRY COWS

Whole plant corn silage is an important component of dairy cow nutrition. Growing conditions in a moderate climate, as are present in large parts of Europe and North America, are often beneficial for mould contaminations to occur. Very commonly, varieties of Fusarium spp. grow on the corn plant producing the non-steroidal estrogenic mycotoxin zearalenone (ZEN). Numerous studies have shown that ZEN massively interacts with the porcine reproductive system. Nevertheless, only a few studies have assessed the possible effects on dairy cows, most publications being field studies following accidental exposure. Therefore, it was aim of the present study to assess the effects of a controlled dietary exposition on selected reproductive parameters in dairy cows. The chosen exposure concentration was within the range of the ‘Commision Recommendation on the presence of deoxynivalenol, zearalenone, ochratoxin A, T-2 and HT-2 and fumonisins in products intended for animal feeding’ of the European Union. Corn plants were artificially inoculated with Fusarium spp. and the silage obtained from the whole plant was analysed to determine to which degree the silage contained ZEN. Thirty Holstein Friesian cows and heifers (aged between 2 years 3 months and 5 years at calving) were allocated to 3 groups with 10 animals each: control (CTL), uncontaminated silage; ZEN 50, silage with 0.25 mg of ZEN/day; and ZEN 100, silage with 0.5 mg of ZEN/day. The contaminated rations were distributed by automated feeding stations to ensure an equal uptake. Feeding began 7 days post-parturition. Blood samples were obtained twice weekly for 12 weeks and were analyzed regarding the progesterone level via radioimmunoassay. At the same time, the oestrous cycle was monitored by ultrasonography. Furthermore, the size of the corpus luteum (CL) was measured 7 ± 2 days after the third ovulation. Simultaneously, the luteal blood flow was documented via Doppler ultrasonography. The peripheral blood progesterone level (xgeom. ± CV; CTL: 9.3 ± 1.7; ZEN 50: 8.5 ± 1.6; ZEN100: 7.1 ± 1.5) did not differ among groups. Furthermore, it was not possible to detect differences in luteal blood flow, size of the CL (mean ± SD; CTL: 6.4 ± 1.7 cm2; ZEN50: 5.9 ± 1.3 cm2; ZEN 100: 5.0 ± 1.0 cm2) or the ratio of luteal size and size of the area supplied with blood (CTL: 0.1 ± 0.1; ZEN 50: 0.1 ± 0.0; ZEN 100: 0.1 ± 0.1). Although the mean length of the oestrous cycles (n = 60; distributed among groups) did not differ among groups (CTL: 24.0 ± 1.7 days; ZEN 50: 27.2 ± 1.6 days; ZEN 100: 27.7 ± 1.4 days), it was possible to detect an interaction between the age of the animal and the treatment regarding the cycle length in tendency (P &lt; 0.07) by two-way ANOVA. The results of the present study indicate that, independent of the age of the animal, exposure to ZEN even within recommended dosages might result in an endocrine disruption in dairy cows. A larger sample size would contribute to the verification of these findings. Further analyses regarding the peripheral level of 17β-estradiol as well as molecular examinations are under progress.

Feeding soybean meal increases the blood level of isoflavones and reduces the steroidogenic capacity in bovine corpora lutea, without affecting peripheral progesterone concentrations

Thirty-three Holstein-Friesian cows were followed from 14 days pre partum until the fourth ovulation post partum. Housing conditions and basic ration were identical for all animals. Concentrates were individually supplemented according to the daily milk production level, using two different types of protein rich concentrates: soybean meal and rapeseed meal. Soybean and rapeseed meal are known to be respectively high and low in isoflavones. Cows were randomly divided into three groups and blocked for parity. Group I (n=11) was supplemented with soybean meal and acted as control group. Groups II (n=11) and III (n=11) were respectively supplemented with soybean and rapeseed meal and were subjected to a biopsy sampling of the corpus luteum at day 9 of the first three postpartal estrous cycles.Soybean meal supplementation to lactating dairy cows (1.72kg on average) induced an increase in the blood concentration of equol, dihydrodaidzein, o-desmethylangolensin in both soy groups and resulted in a reduced area occupied by steroidogenic (P=0.012) and endothelial cells (P=0.0007) in the luteal biopsies. Blood concentrations of equol and glycitein were negatively correlated with the areas occupied by steroidogenic (r=−0.410 with P=0.0002, respectively r=−0.351 with P=0.008) and endothelial cells (r=−0.337 with P=0.01, respectively r=−0.233 with P=0.085) in the 3 first estrous cycles. The latter however did not affect the diestrous peripheral blood progesterone concentration.

Immunohistochemical and histochemical identification of proteins and carbohydrates in the equine endometrium: Reaction patterns in the cycling mare

Little is known about the stage of estrus cycle-dependent variations of uterine secretions of the more and most published results were based on evaluation of uterine flushings. Hence, the aim of this study was to define patterns of expression of different endometrial proteins throughout the estrus cycle using newly established immunohistochemical methods and endometrial biopsies. Therefore, endometrial biopsies were collected from three mares on defined days of the estrus cycle with known concentrations of estradiol and progesterone in serum. The proteins uteroglobin, uteroferrin, calbindin(D9k) and uterocalin were examined using polyclonal antibodies. Furthermore glycogen was identified using the PAS-reaction prior to and after a-amylase digestion. During the estrus cycle expression of the examined proteins, as well as glycogen, revealed a typical, progesterone-dependent pattern. In the early- and mid-interestrus there is a simultaneous increase in expression of uterocalin and glycogen staining intensity associated with increasing concentrations of progesterone in peripheral blood. The maximal expression of calbindin(D9k) was also in association with high levels of circulating progesterone in mid-interestrus. In contrast, secretion of both uteroglobin and uteroferrin was simultaneously associated with the decrease in circulating concentrations of progesterone in mid-to late-interestrus. However, it has to be emphasized that distinct among mare differences were obvious. This new method enables pathologists to interpret changes in the uterine secretion pattern associated with fertility reducing diseases by using a single endometrial biopsy

Comparison of the Immulite and RIA assay methods for measuring peripheral blood progesterone levels in Greyhound bitches

Determination of optimal breeding time in bitches earmarked for single insemination only is based on measurement of peripheral blood serum or plasma progesterone concentration. In this paper a comparison is made between radioimmune assay (RIA) and chemoluminescent assay (Immulite) for determination of P4 concentrations in the bitch. The Immulite assay is shown to be an accurate and reliable method for serum or plasma P4 measurement. It compares favourably with other methods in terms of turn-around time, cost and accessibility for veterinarians in practice.

Anastomosis between Ovarian and Mesenteric Veins in Sheep: Induction of a Physiological Hyperstimulation of the Ovary

Progesterone (P4) and estradiol 17β are essential for the dialogue between the ovary and the hypothalamohypophysial system. Immunization against steroids, although a valuable tool, displays limits. We propose a straightforward method to suppress steroids from the peripheral circulation by using the liver to catabolize steroids, through an anastomosis of the ovary to the mesenteric vein. Twelve mature cycling Ile-de-France ewes were unilaterally ovariectomized during the breeding season and subsequently randomly assigned to be anastomosed (n= 6; A) or sham-operated (n= 6; SO) on Day 10 of a synchronized estrous cycle. The ovarian vein was anastomosed to the superior mesenteric vein and all collateral veins to the ovarian vein were ligatured. Sham-operated ewes had only their collateral vein ligatured without anastomosis. Four days following surgery, ewes from both treatments were injected with PGF-2α and autopsied between 9 and 14 days following surgery. Blood progesterone and estradiol 17β were measured daily from Day 4 before surgery until 7 days after castration. Estradiol levels measured at the level of the ovarian vein indicated that anastomosis allowed normal ovarian activity in all but 1 ewe in which collateral veins to the ovarian duct had developed. In the 5 A ewes, progesterone in peripheral blood decreased to low levels the day following surgery but this fall was not accompanied by an increase in estradiol. Estradiol levels measured at the output of the liver from hepatic vein were lower in A ewes (46.6 pg/ml) than in the ovarian vein of SO ewes (334.1 pg/ml). Ovarian hypertrophy was observed in 5 A ewes in which numerous large follicles were observed. These results indicate that the experimental model is functional and permits the study of the stimulation and hyperstimulation of the ovary and the control of the terminal follicular growth in the endocrine environment of the animal itself.

LH and progesterone concentrations during diestrus in the mare and the effect of hCG

The temporal association between circulating concentrations of LH and progesterone was studied by collecting blood samples from 4 mares at 15-min intervals for 12h on Days 3, 8 and 13 of diestrus. Luteinizing hormone appeared to be secreted in an episodic fashion on Days 8 and 13, but on Day 3 of the cycle discrete pulses of LH were detected in only 1 mare. Episodic progesterone secretion was detected on all days of sampling. No correlation was observed between LH and progesterone concentrations. Intravenous administration of 1,500 IU hCG to mares resulted in significantly elevated circulating concentrations of progesterone in 3 of the 4 mares. These results suggest that exogenous LH can be luteotrophic for the mare corpus luteum but that there was little temporal relationship between endogenous circulating LH and progesterone in peripheral blood.

Oxytocin and bovine parturition: a steep rise in endometrial oxytocin receptors precedes onset of labor.

Oxytocin receptors were measured in myometrium and intercaruncular endometrium of cows during pregnancy and parturition. Concentrations of estradiol-17 beta, estrone, and progesterone in peripheral blood were also measured. Receptor concentrations in the endometrium rose almost 200-fold from Day 20 to term (p < 0.0001, ANOVA), from 40 +/- 11 to 7300 +/- 1430 fmol/mg protein. Myometrial receptor concentrations increased 10-fold from 180 +/- 36 fmol/mg on Day 20 to 1850 +/- 360 fmol/mg protein at term (p < 0.0001, ANOVA). During labor, endometrial receptors (6600 +/- 1300 fmol/mg) remained at prelabor values, whereas myometrial receptor concentrations had decreased to 1190 +/- 316 fmol/mg (not significant) and declined further postpartum. Plasma concentrations of progesterone declined from 4-5 ng/ml to about 2 ng/ml between Days 250 and 282 and dropped to < 0.2 ng/ml shortly before delivery. Plasma concentrations of estrone and estradiol-17 beta were below 10-20 pg/ml until Day 230. Estrone concentrations were significantly (p < 0.05) increased by Day 250 and estradiol-17 beta by Day 270, and then both rose rapidly. During labor, plasma estrone was 1135 +/- 245 pg/ml and plasma estradiol-17 beta was 226 +/- 131 pg/ml. The molar ratio of estrone and estradiol-17 beta to progesterone rose from less than 0.01 to 4.4 during labor, and was correlated with oxytocin receptor concentrations in endometrium (r = 0.5160, p < 0.001), but not those in myometrium (r = 0.0122). The regulation of oxytocin receptors by ovarian hormones in the two tissues may therefore differ.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravulvo-submucosal injections of luprostiol may reach corpora lutea by a local, unilateral pathway in cattle

Fifteen ewes were assigned as they came into estrus to the following randomized treatment groups: 1) Vehicle (1 ml corn oil + vehicle Na2CO3 buffer), 2) Estradiol-17β + vehicle and 3) Estradiol-17β + PGE2 (500 μg) in Na2CO3 buffer (5 ewes/treatment group). Prostaglandin E2 was given through an intrauterine cannula every four hours from days 8 through 15 postestrus. PGE2 prevented a luteolytic dose of estradiol-17β given on days 9 and 10 from causing a precious luteolysis. PGE2 maintained concentrations of progesterone in peripheral blood (days 8 through 15) and weights and concentrations of progesterone in corpora lutea on day 15 postestrus of ewes receiving estradiol-17β. It is concluded that chronic intrauterine infusions of PGE2 can prevent an estradiol-17β-induced premature luteolysis.

Antagonists of embryo-derived platelet-activating factor prevent implantation of mouse embryos

Inhibitors of platelet activation, alprazolam, iloprost and SRI 63-441, were used to demonstrate the necessity of embryo-derived platelet-activating factor (PAF) activity for the establishment of pregnancy in mice. In a splenectomized mouse bioassay 6 micrograms alprazolam inhibited, for 3 h, the thrombocytopenia induced by 0.1 micrograms PAF; 4 micrograms iloprost and 0.5 microgram SRI 63-441 were effective for 6 and 12h respectively. The administration of 2 micrograms iloprost/30 g body weight on Days 1 and 4 of pregnancy and twice daily on Days 2 and 3 caused a 50% reduction (P less than 0.0005) in the number of implantation sites in the uterus at Day 8 of pregnancy, without affecting (P greater than 0.05) the number of corpora lutea. A similar reduction in the number of implantation sites was achieved with 20 micrograms SRI 63-441/30 g body weight/day. The reduction in implantation rate was evident on Day 5 of pregnancy by visualizing the implantation sites with pontamine sky blue. SRI 63-441 had no effect on peripheral blood progesterone concentrations from Day 1 to Day 9 of pregnancy, and did not appear to inhibit implantation by blocking the preimplantation surge of oestradiol. The number and morphology of blastocysts flushed from the uterus of Day 4 inhibitor-treated mice was not different (P greater than 0.05) from the controls. The cleavage rate and morphology of embryos cultured from the 2-cell to blastocyst stage in media containing SRI 63-441 or iloprost (10 micrograms/ml) were normal, precluding a gross toxic effect. Simultaneous administration of 1 microgram PAF-acether to treated animals re-established pregnancy rates to levels not significantly different (P greater than 0.05) from the controls.

Prostaglandin E 2 (PGE 2) inhibits an IUD-induced premature luteolysis in sheep

Fifteen ewes were assigned as they came into estrus to one of three randomized treatment groups: 1. Sham IUD + Vehicle, 2. IUD + Vehicle, and 3. IUD + PGE2 in Vehicle. An IUD was inserted adjacent to the luteal-bearing ovary of unilaterally ovariectomized ewes on day 3 postestrus. Vehicle (Na 2CO 3) or PGE 2 (500 μg) in vehicle was given every 4 hours intrauterine through an indwelling uterine cannula from day 3 postestrus until ewes returned to estrus. Luteolysis was advanced in both the Sham IUD and IUD groups receiving vehicle. An IUD-induced premature luteolysis was prevented by PGE based on daily concentrations of progesterone in peripheral blood and the extended interestrous interval. It is concluded that chronic intrauterine injections of PGE2 (500 μg) every four hours can prevent an IUD-induced premature luteolysis. It is also concluded that an IUD-induced premature luteolysis is not necessarily through uterine distention.

Inhibition of an IUD-induced precocious luteolysis by prostaglandin E 1 (PGE 1) in sheep

Fifteen ewes were assigned as they came into estrus to one of three randomized treatment groups: 1. Sham IUD + Vehicle, 2. IUD + Vehicle or 3. IUD + PGE 1 in vehicle. An IUD was inserted adjacent to the luteal-bearing ovary on day 3 postestrus. Prostaglandin E 1 (500 μg) in vehicle (Na 2CO 3) or vehicle was given intrauterine through an indwelling uterine cannula every four hours from day 3 postestrus until ewes returned to estrus. Precocious estrus was induced in both the sham IUD groups receiving vehicle. Prostaglandin E 1 prevented an IUD-induced premature luteolysis based on daily concentrations of progesterone in peripheral blood and the interestrous interval. It is concluded that an IUD-induced premature luteolysis is not necessarily via physical distention by the IUD. It is also concluded that chronic intrauterine infusions of PGE 1 can prevent an IUD-induced premature luteolysis.

Effects of prostaglandin E 2 (PGE 2) on estradiol-17β-induced luteolysis in the nonpregnant ewe

Fifteen ewes were assigned as they came into estrus to the following randomized treatment groups: 1) Vehicle (1 ml corn oil + vehicle Na 2CO 3 buffer), 2) Estradiol-17β + vehicle and 3) Estradiol-17β + PGE 2 (500 μg) in Na 2CO 3 buffer (5 ewes/treatment group). Prostaglandin E 2 was given through an intrauterine cannula every four hours from days 8 through 15 postestrus. PGE 2 prevented a luteolytic dose of estradiol-17β given on days 9 and 10 from causing a precious luteolysis. PGE 2 maintained concentrations of progesterone in peripheral blood (days 8 through 15) and weights and concentrations of progesterone in corpora lutea on day 15 postestrus of ewes receiving estradiol-17β. It is concluded that chronic intrauterine infusions of PGE 2 can prevent an estradiol-17β-induced premature luteolysis.

Cloprostenol-induced luteolysis in the marmoset monkey (Callithrix jacchus).

A single intramuscular injection of 0.5 micrograms cloprostenol was not luteolytic on Day 6 or 7 of the ovarian cycle (N = 3), but was luteolytic in some animals (3/5) on Day 8 and 9 and luteolytic in all 23 animals treated between Days 10 and 17 of the ovarian cycle, and in 7 animals treated between Days 19 and 43 of pregnancy. Luteal function was monitored by measurement of progesterone in peripheral blood using a simple and rapid non-extraction assay. There was a dramatic fall in peripheral blood progesterone to less than 10 ng/ml within 24 h of cloprostenol injection; progesterone remained at this low level until the day after post-treatment ovulation. The interval from cloprostenol injection to ovulation in animals treated between Days 8 and 17 was 10.7 +/- 0.3 days. A similar interval was found in pregnant animals. Embryos recovered from the uterus after cloprostenol treatment were morphologically normal (23/24).

The influence of pregnancy on PGF 2α secretion in cattle. I. Concentrations of 15-keto-13,14-dihydroprostaglandin F 2α and progesterone in peripheral blood of recipients of transferred embryos

Three experiments were performed to study the influence of viable or formalin-killed embryos, transferred late in the oestrous cycle, on the maintenance of the corpus luteum and prostaglandin production by the uterus. In Experiment 1, day-12 to day-16 embryos were transferred to synchronous recipients (± 24h) on day 12 to day 17. All five recipients of formalin-killed embryos and nine recipients of viable embryos exhibited a decline in progesterone to baseline levels (0.8 ng/ml) which was followed by oestrus in some of them. In a further nine animals, subsequently shown to be pregnant, luteal phase levels of progesterone were maintained. In six animals (not pregnant at day 42) progesterone levels were maintained for varying periods following transfers between days 13 and 17. In Experiment 2, progesterone and 15-keto-13,14-dihydroprostaglandin F 2α (PGFM) concentrations were determined in plasma samples collected hourly for 15 days from seven animals receiving fresh or formalin-killed embryos on day 16 or 17. Marked hour-to-hour changes in progesterone concentrations were seen in all animals initially and persisted in those in which luteal phase levels were maintained. In three cows progesterone concentrations declined to baseline levels during the period of hourly sampling. Progesterone levels were maintained in the others although they subsequently declined in two cases. In all seven cows a large PGFM peak (189–828 pg/ml) was associated with surgical transfer. The luteolysis in three recipients was associated with a series of PGFM peaks (165–396 pg/ml) whereas only occasional single peaks were observed in those cows in which luteal phase concentrations of progesterone were maintained. In Experiment 3 the cause of the PGFM peak associated with surgery was investigated. While extensive manipulation of the genital tract, at different times in the cycle, or oxytocin injections on day 16 had little effect on PGFM concentrations, a peak (310–1000 pg/ml) was observed immediately after the intravenous injection of sodium thiopentone. It was concluded that the corpus luteum can be maintained by the introduction of a viable embryo as late as day 17 of the cycle and that the decline in progesterone concentration at luteolysis is associated with a series of PGFM peaks which were absent or reduced in animals in which progesterone levels were maintained.

Initiation of asymmetrical ovarian estradiol secretion in the primate ovarian cycle after luteectomy.

We investigated the onset of asymmetrical ovarian function in rhesus monkeys after luteectomy, a procedure that has been shown to synchronize the initiation of new follicle growth. Monkeys underwent laparotomy for luteectomy 17–19 days after the spontaneous onset of menses. Subsequent laparotomy for ovarian inspection and ovarian venous blood collection was performed on days 1, 3, or 5 after luteectomy and on day 16 to determine the location of the new corpus luteum. Femoral blood was collected daily beginning 8 days after the onset of menses for the measurement of hormones. Luteectomy was followed by an abrupt decline in serum progesterone levels, the early onset of menses, and a prompt transient rise in FSH concentrations in all monkeys. The patterns of LH, FSH, 17β- estradiol, and progesterone in peripheral blood of monkeys that maintained ovulatory cycles, as indicated by midcycle type preovulatory gonadotropin surges 12.3 ±2.1 days after luteectomy, contained elevations of serum progesterone and an i...

A method to evaluate various parameters of progesterone production in beef cows, using the levels of progesterone in peripheral blood sampled on specific days of the oestrous cycle

Progesterone concentrations were determined in blood samples taken sequentially each day during 85 oestrous cycles in six beef cows. The sum of progesterone levels in sequential daily samples for a complete oestrous cycle varied considerably between cycles within cows (range 30–150 ng), and the means of cycles differed markedly between cows (range 36–60 ng). There was a typical pattern of daily progesterone levels throughout the oestrous cycle, and marked fluctuations were evident when the sum of daily progesterone levels for each cycle were plotted sequentially against time. Significant correlations and linear regression equations are described for the relationship between the sum of daily progesterone levels for a complete cycle and the mean concentration of progesterone in various combinations of daily samples. Furthermore, significant correlations were also obtained between the sum of daily progesterone levels and the maximum daily progesterone level obtained ( r = 0.87; P < 0.001), the number of daily progesterone values greater than 2 ng/ml of blood ( r = 0.89; P < 0.001) and the mean of daily progesterone levels for days 7–15 of the cycle ( r = 0.91; P < 0.001). An ability to gain an estimate of these parameters of progesterone production from a small number of blood samples collected at strategic times during the cycle would facilitate the examination of the relationships between the environment, progesterone level, and the subsequent fertility in a greater number of animals, and so provide for a more precise measure of the effects of experimental treatments.

Hypothalamic ventromedial nucleus and hormonal regulation of estrous rhythm in the rat.

An experiment was performed to determine whether the ventromedial nucleus (VMN) lesions could modify the duration of the estrous cycle by altering ovarian progesterone secretion. In the 1st group of rats small bilateral stereotaxic lesions were performed on the VMN by passing a 2 mA cathodic current for 7 seconds through a .25 mm diameter teflon-insulated platinum unipolar electrode. 41 of 88 rats retained a 4-day cyclicity. 16 were sacrificed in the morning of estrus of their 3rd postoperative cycle to monitor estrous rhythm stability. The remaining rats were used for progesterone radioimmunoassay. 43 rats exhibited a 24-hour delay in cycle length postoperatively. A 2nd group was composed of 29 unoperated 4-day cyclers and 28 sham-VMN- and 18 DMN-lesioned 4-day cyclic females all of whom maintained 4-day cycles after surgery. Peripheral blood progesterone decreased from the morning of Diestrous 1 to that of Diestrous 2 in both unoperated and small VMN-lesioned 4-day cyclic females. Blood progesterone levels remained constant during the same period in unoperated 5-day cyclic females. The levels however increased in small VMN-lesioned 5-day cyclic animals reaching a higher level on the morning of Diestrous 2 than in unoperated 5-day cyclers (p less than .01). Results confirm that partial lesioning of the VMN causes a 24-hour cycle prolongation in about 50% of 4-day cyclic female rats.