Blood LH level and induced ovulation after hCG and PMSG treatment in ovarian quiescent cattle

Ovarian quiescent cattle bearing follicle with palpable size were treated with single intramuscular injection of 750-6,000 IU of human chorionic gonadotrophin (hCG) in 13 cases and 1,000-2,000 IU of pregnant mare serum gonadotrophin (PMSG) in 5 cases. Changes of blood luteinizing hormone (LH) level, estrus and ovulation after the treatments were examined. After the hCG treatment LH level became slightly high from 0.2-0.6 ng/ml of pre-treatment to 0.3-1.9 ng/ml of post-treatment and maintained the level up to ovulation without the ovulatory LH surge. Ovulation was induced about 36 hr after the treatment in 12 cases. The ovulations were all silent ovulations. After the PMSG treatment LH level became slightly high from 0.6 ng/ml of pre-treatment to 1.3 ng/ml of post-treatment and the level lasted until the ovulatory LH surge. The ovulatory LH surge occurred about 39 hr after the PMSG treatment in 4 cases with a peak of about 32 ng/ml. Ovulation was induced about 74 hr after the treatment in all 5 cases. Four cases showed estrus but one in which the LH surge could not be confirmed did silent estrus preceding the induced ovulations. It was demonstrated that hCG induced ovulation without the LH surge but PMSG induced the ovulatory LH surge and the subsequent ovulation in ovarian quiescent cattle.     

Plasma Testosterone in Bulls: Seasonal Variation

Levels of peripheral plasma testosterone and LH were studied in 4 bulls hourly during a 12 hr. sampling period at 5 times of the year. The average plasma testosterone levels were significantly lower in October (1.8 ng/ml, Ρ < 0.001) and December (2.5 ng/ml, Ρ < 0.05) than in February, June and August (3.5, 3.7 and 3.7 ng/ml respectively). LH showed a slight fluctuation during the day, with values ranging between 0.8 and 3.8 ng/ml, but underwent no significant seasonal variation. A significant increase in average plasma testosterone was observed 1 hr. after the LH peaks (P < 0.001).     

Fasting-induced changes in ovulation rate, plasma leptin, gonadotropins, GH, IGF-I and insulin concentrations during oestrus in ewes

The aim of this experiment was to study the changes in the hormonal status and ovulation rate (OR) evoked by starvation during the follicular phase of the oestrous cycle in ewes. To achieve this goal, 12 female crossbreed sheep were synchronized and then half of them were fasted from the 12th to the 16th day of the oestrous cycle. On the 16th day, analysis of hormones and insulin-like growth factor-I (IGF-I) were performed in 10-min intervals. Then, on the 6th day of the following oestrous cycle, the OR in all ewes was determined by laparoscopy. Fasting reduced significantly (P < 0.05) the OR in ewes (1.25 +/- 0.50) in comparison with control (1.75 +/- 0.50). The drop in the OR was coincident with a significant (P < 0.001) decrease in the plasma concentration and pulse amplitude of leptin (0.29 +/- 0.08 ng/ml versus control 0.53 +/- 0.14 ng/ml), the plasma level of luteinizing hormone (LH) (0.19 +/- 0.06 IU/l versus 0.25 +/- 0.09 IU/l in control; P < 0.05) and the mean frequency of LH pulses (2.0/h versus 2.5/h in control). Fasting resulted also in a significant (P < 0.05) decrease in the plasma concentration and pulse amplitude of follicle stimulating hormone (FSH) in comparison with the control. Simultaneously, a significant (P < 0.001) drop in the IGF-I concentration in the fasted ewes (4.78 +/- 0.91 ng/ml) was found in comparison with control (7.63 +/- 1.85 ng/ml). Also the level of insulin were significantly (P < 0.001) lower in the fasted (178.99 +/- 39.08 pM/l respectively) than in the control sheep (302.66 +/- 49.01 pM/l respectively). Meanwhile, a double increase in the growth hormone (GH) pulses frequency and an augmentation in its plasma concentrations as a result of starvation was found. The obtained results shows that the acute fasting exerts an inhibitory effect on the ovulation rate in ewes coincident with suppression in leptin, FSH and LH secretion and changes in signalization mediated by GH.     

Nutritionally induced relationships between insulin levels during the weaning-to-ovulation interval and reproductive characteristics in multiparous sows: I. Luteinizing hormone, follicle development, oestrus and ovulation

To get more insight in how insulin secretion patterns and corresponding insulin-like growth factor-1 (IGF-1) levels are related to luteinizing hormone (LH) secretion, follicle development and ovulation, 32 multiparous sows were fed either a dextrose plus lactose-containing diet at 4 h intervals (DL; each 150 g/day) or an isocaloric control diet at 12 h intervals (CTRL; containing soybean oil) during the weaning-to-ovulation interval (WOI). Insulin parameters (basal, peak levels and mean insulin) and IGF-1 levels during the WOI were similar for both treatments, but the insulin secretion pattern differed (related with feeding frequency and meal sizes). Oestrus and ovulation characteristics were not influenced by treatment. The LH surge was higher in CTRL compared with DL sows (3.73 vs 3.00 ng/ml; p = 0.03). Average diameter (6.5 vs 6.1 mm; p = 0.08) and uniformity (CV: 11 vs 15%, p = 0.02) of follicles ≥3 mm at day 4 after weaning was higher in CTRL compared with DL sows. Basal insulin levels were positively related with follicle diameter at ovulation (β = 0.05 mm/(μU/ml); p = 0.04) and negatively related with LH surge level (β = -0.07 (ng/ml)/(μU/ml); p = 0.01). Insulin area under the curve (AUC) (β = 0.037 (ng/ml)/1000 μU; p = 0.02) and IGF-1 levels (β = 0.002 (ng/ml)/(ng/ml); p < 0.01) were positively related to basal LH level around the LH surge. From these data, we conclude that insulin and IGF-1 levels during the WOI are related to LH secretion and follicle development. Not only the absolute level of insulin seems important, but also the pattern within a day in which insulin is secreted seems to affect LH secretion and development of pre-ovulatory follicles.     

Oestrous Behaviour and Timing of Ovulation in Relation to Onset of Oestrus and LH Peak in Mithun (Bos frontalis) Cows

The objectives of the study were to evaluate the oestrus behaviour and to determine the timing of ovulation in relation to onset of oestrus and the pre-ovulatory LH surge in mithun (Bos frontalis). For this purpose, the blood samples collected at 15-min intervals for 9 h period following onset of oestrus and thereafter, at an interval of 2 h till 4 h post-ovulation for three consecutive cycles from 12 mithun cows were assayed for plasma LH and progesterone. Ovulation was confirmed by palpation of ovaries per rectum at hourly intervals. Various signs of behavioural oestrus were also recorded. The common signs of oestrus and their frequency of occurrence in mithuns were following and mounting by male mithuns (100%), standing to be mounted (100%), frequent urination (62.33%), raising of tail (65.23%), swelling of vulva (54.26%) and congestion of vulvar mucous membrane (69.87%). The pre-ovulatory LH surges consisted of several pulses (2.92 +/- 0.26 pulses/animal; range, 1-4). The mean (+/-SEM) peak level of LH for individual mithun varied from 6.99 +/- 0.44 to 12.69 +/- 2.10 ng/ml and the mean pooled LH peak concentration was 9.10 +/- 0.60 ng/ml. The highest peak (highest amplitude of LH during LH surge) was 10.83 +/- 0.76 ng/ml (range, 8.07-16.49 ng/ml). The duration of LH surge was 6.98 +/- 0.22 h (6-8 h). Onset of LH surge was at 1.23 +/- 0.17 h post-oestrus onset (range, 0.25-2.25 h). Mean plasma progesterone stayed low (<0.24 ng/ml) during the entire duration of sampling. Ovulation occurred at 26.92 +/- 0.31 (range, 26-29 h) after the onset of oestrus and 18.63 +/- 0.35 h (range, 17-20.75 h) after the end of LH surge. The occurrence of the highest LH peaks within a narrow time frame of 2- to 5-h post-oestrus onset in mithuns could have contributed to the animals ovulating within a narrow time interval. These results are very promising from a practical standpoint of potential success when AI program in this species is implemented in a big way. Furthermore, the results of the occurrence of LH pulses during pre-ovulatory LH surges, which are required for ovulation in this species of animals, is unique and species specific.     

Comparison of luteinizing hormone and steroid hormone secretion during the peri- and post-ovulatory periods in Mangalica and Landrace gilts

The objective of this study was to determine plasma concentrations of luteinizing hormone (LH), progesterone (P4) and estradiol-17beta (E2) in Mangalica gilts (M), a Hungarian native breed, and compare them with Landrace gilts (L) during the peri- and post-ovulatory periods. The estrous cycle of gilts was synchronised by Regumate feeding, and ovulation was induced with a gonadotropin-releasing hormone (GnRH) agonist. Blood sampling was carried out via indwelling jugular catheters three times a day and in 2-h intervals during a 16-h period after the GnRH application. The concentrations of LH, E2 and P4 were determined by immunoassays. Gilts of both breeds showed a typical gonadotropin and gonadal hormone secretion pattern. Preovulatory E2 peaks were observed on day 2 (M) and day 4 (L) after the last Regumate feeding. Highest E2 concentration was different between M and L breeds (46.5 +/- 5.7 vs. 26.0 +/- 6.8 pg/ml, P < 0.05). Maximum LH levels measured up to 6 h after GnRH were not different between M and L breeds (11.5 +/- 4.1 vs. 6.6 +/- 2.3 ng/ml). Both LH amounts during surge (41.1 +/- 15.9 vs. 27.5 +/- 6.1 ng/ml) and total over LH release (73.4 +/- 22.2 vs. 50.0 +/- 8.7 ng/ml) did not differ significantly between M and L breeds. P4 concentrations started to rise on day 6 after Regumate feeding and increased significantly from 0.6 +/- 0.3 and 0.7 +/- 0.4 ng/ml to maximal 14.0 +/- 2.4 and 11.3 +/- 2.1 ng/ml in M and L breeds, respectively. Mean P4 secretion was higher in M on days 10-15 (12.9 +/- 2.6 vs. 9.3 +/- 2.2 ng/ml; P<0.05). At the same time the number of corpora lutea was lower in M compared to L (10.3 +/-1.5 vs. 17.8 +/- 5.0, P<0.05). In our experiment, there was no evidence that differences in the secretion of analysed hormones during the peri- and post-ovulatory periods are a possible cause of usually lower fecundity in Mangalica gilts.     

湖羊和考力代羊公羔垂体－性腺轴系内分泌活动的差异

用放射免疫方法测定了湖羊和考力代羊公羔从初生到１８０日龄垂体内ＬＨ总量，血浆ＬＨ和睾酮浓度的变化。结果表明：湖羊从初生到９０日龄垂体内ＬＨ总量迅速上升（Ｐ＜０．０１），以后呈下降趋势；血浆ＬＨ浓度０～２０日龄较低（０．８９～１．０３ｍＩｕ／ｍｌ），３０日龄开始上升，９０日龄达到峰值（２．３４ｍＩＵ／ｍｌ），以后呈下降趋势。血浆睾酮从４０日龄起迅速上升，１２０日龄达到２．７３ｎｇ／ｍｌ，以后维持于高水平（２．３４～４．４４ｎｇ／ｍｌ）。考力代羊０～１８０日龄垂体内ＬＨ总量呈持续上升趋势（Ｐ＜０．０１），血浆ＬＨ水平０～８０日龄维持较低水平（０．５２±０．９９ｍＩｕ／ｍｌ），以后呈上升趋势；血浆睾酮水平０～１３０日龄很低（０．１９～１．１３ｎｇ／ｍｌ），１４０日龄开始上升。两品种比较，０～９０日龄湖羊垂体内的ＬＨ总量，血浆ＬＨ及睾酮水平均高于考力代羊。提示湖羊公羔性成熟早与其生后早期垂体合成和释放ＬＨ水平高有关。     

The adenohypophyseal response and effect of GnRh (Dirigestran inj. Spofa) administration in cows in the postpartum period

Radioimmunological investigation (RIA) of the level of pituitary FSH in the peripheral blood of cows after parturition demonstrated that this level increased successively. The FSH value of 32.93 +/- 3.71 ng per 1 ml, recorded the fourth to sixth day post partum, increased to as much as 57.78 +/- 40.98 ng per 1 ml 40 days after parturition. The LH level changed only slightly over the same period (from 1.12 +/- 0.21 ng per ml to 1.72 +/- 1.15 ng per ml). The concentration of progesterone in the blood of the cows was about 0.40 ng per ml during the first 15 days after parturition, but from the 25th day post partum it trebled, on an average (1.53 +/- 1.19 - 1.59 +/- 1.25 ng per ml). The response of the adenohypophysis of the cows to the administration of 200 micrograms of synthetic gonadoreline (spec. Dirigestran inj. Spofa) increased with increasing length of time from parturition. FSH concentration increased less markedly during the first 28 days p.p. and this increase was not uniform in time (the average increase was 1.5 to three times); in the later period the highest increase 300-500% was recorded, as a rule, 120 minutes after GnRH administration. The situation was similar in the increase in LH concentration in peripheral blood, but after the 26th day post partum the average increase in LH accounted for 500 to 600%. The concentration of progesterone in peripheral blood increased by more than 300%, on an average, from the 25th day after parturition. This testifies to the first post partum ovulation and to the formation of a new yellow body in the majority of cows under study.(ABSTRACT TRUNCATED AT 250 WORDS)     

Adenohypophyseal receptors for LHRH, pituitary content of gonadotropins and plasma concentrations of LH in cyclic, pregnant and postpartum beef cows

Adenohypophyseal concentrations of LHRH receptors, pituitary content of LH and FSH, and plasma concentrations of LH were determined in thirty Hereford, Angus or Hereford-Angus heifers that were randomly assigned by breed and weight to five periods including day 3 of the estrous cycle (CY), pregnant day 120 (P120), 200 (P200), 275 (P275), or day 2 postpartum (PP). Jugular blood samples were collected at 10-min intervals for 8 hr from all cows. Within 2 hr after completion of blood sampling, animals were slaughtered and the pituitary gland frozen at −196 C. LH pulse frequency/8 hr was reduced (P<.05) during gestation (.5, .2, and 1.5 ± .5/8 hr, for P120, P200, and P275, respectively) and PP (.5 ± .5/8 hr) compared to CY (7.8 ± .5/8 hr). Frequency of LH pulses/8 hr was not different (P>.1) among P120, P200 or PP periods but was different (P<.05) between P200 and P275. There were no differences in LH pulse height (P>.1) among periods; however, pulse amplitude was greatest (P<.05) at P120 (1.3 ± .2 ng/ml) and lowest between P200 and PP (.6 to .8 ± .2 ng/ml). Baseline concentrations of plasma LH did not differ (P>.1) among P and PP periods (.3 ± .1 ng/ml), but were lower (P<.05) than in CY animals (.7 ± .1 ng/ml). Concentration of adenohypophyseal LHRH receptors was approximately two-fold greater (P<.05) at P120 (25.85 ± 2.2 fmol/mg) than at all other periods (9.5 to 14.9 ± 2.2 fmol/mg). Pituitary content of LH was greatest at P120 (1.56 ± .11 ug/mg) and lowest (P<.05) at P275 and PP (0.46 to 0.52 ± .11 ug/mg). Pituitary content of FSH was greatest (P<.05) in P (12.7 to 17.0 ± 1.4 ug/mg) and PP (18.3 ± 1.4 ug/mg) vs CY (5.0 ± 1.4 ug/mg) cows and increased from P120 to PP (P<.05). Results indicate that physiological changes occurring during gestation may have an effect on subsequent function of the adenohypophysis in beef cows.     

Peri-oestrus hormone profiles and follicle growth in lactating sows with oestrus induced by intermittent suckling.

This study describes follicle dynamics, endocrine profiles in multiparous sows with lactational oestrus compared with conventionally weaned sows (C). Lactational oestrus was induced by Intermittent Suckling (IS) with separation of sows and piglets for either 12 consecutive hours per day (IS12, n = 14) or twice per day for 6 h per occasion (IS6, n = 13) from day 14 of lactation onwards. Control sows (n = 23) were weaned at day 21 of lactation. Pre-ovulatory follicles (> or =6 mm) were observed in 100% of IS12, 92% of IS6 and 26% of C sows before day 21 of lactation and in the remaining 74% C sows within 7 days after weaning. All sows with pre-ovulatory follicles showed oestrus, but not all sows showed ovulation. Four IS6 sows and one IS12 sow developed cystic follicles of which two IS6 sows partially ovulated. Follicle growth, ovulation rate and time of ovulation were similar. E(2) levels tended to be higher in IS sows (p = 0.06), the pre-ovulatory LH surge tended to be lower in IS12 (5.1 +/- 1.7 ng/ml) than in C sows (8.4 +/- 5.0 ng/ml; p = 0.08) and P(4) levels were lower in IS12 and IS6 than in C sows (at 75 h after ovulation: 8.8 +/- 2.4 ng/ml vs 7.0 +/- 1.4 ng/ml vs 17.1 +/- 4.4 ng/ml; p < 0.01). In conclusion, sows with lactational oestrus induced by IS are similar to weaned sows in the timing of oestrus, early follicle development and ovulation rates, but the pre-ovulatory LH surge and post-ovulatory P(4) increase are lower.     

Induction of ovulation in the prepuberal gilt by pulsatile administration of gonadotropin releasing hormone

An attempt was made to induce precocious puberty in gilts approximately 164 days of age by stimulating a luteinizing hormone (LH) secretory pattern similar to that which occurs before normal onset of puberty. Hourly iv administration of 1 μg synthetic gonadotropin releasing hormone (GnRH) for 7 or 8 days resulted in a mean serum LH concentration of 1.7 ± .3 ng/ml in three treated gilts compared with .9 ± .1 ng/ml in three control gilts (P<.08). Serum LH peak frequency was also greater (P<.05) in treated (3.4 ± .5 peaks/4 hr) than in control gilts (1.2 ± .1 peaks/4 hr), but serum LH peak amplitude was not altered (P>.33) by GnRH treatment. All treated gilts displayed estrus and ovulated within 6 days after treatment began, and all control gilts remained prepuberal throughout the study (P=.05). Only one of the three treated gilts displayed a normal estrous cycle and reovulated after treatment. Precocious ovulation but not puberty was induced in gilts by hourly administration of 1 μg synthetic GnRH, indicating that the pituitary and ovaries of 164-day-old gilts are competent and that final sexual maturation occurs at the hypothalamic level.     

Characterization of gonadotropic and ovarian steroid hormones during the periovulatory period in high ovulating select and control line gilts

Cyclic gilts from Control (C, randomly selected, n = 11) and Relax Select (RS, nine generations of selection for increased ovulation rate followed by seven generations of relaxed or random selection, n = 9) lines of the University of Nebraska Gene Pool population (derived from 14 different breeds) were utilized to characterize differences in gonadotropic and ovarian steroid hormones during preovulatory and postovulatory phases of the estrous cycle. Blood samples were collected during four periods (0500, 1100, 1700 and 2300) daily beginning 2 d prior to anticipated estrus (d -2, d 18 of a 20-d estrous cycle), and continuing through d 4 postestrus (d 0 = 1st of standing estrus). Sampling within a period consisted of five blood samples at 15-min intervals. All plasma samples were analyzed for concentrations of follicle stimulating hormone (FSH) and luteinizing hormone (LH). Neither mean LH nor peak concentration of LH during the preovulatory surge differed between genetic lines (P greater than .10). Concentrations of FSH increased faster (line X period, P less than .05) and tended (P less than .1) to peak at a higher concentration in RS (.88 ng/ml) than in C (.54 ng/ml) gilts (P less than .05) during the 12 h preceding the FSH and LH preovulatory peaks. The second FSH surge began approximately 24 h after the preovulatory FSH peak. Peak FSH concentrations were observed at 42 h in both lines (1.46 vs 1.74 ng/ml for C and RS gilts, respectively). The higher FSH concentration in RS gilts established during the preovulatory surge was maintained through the second FSH surge (P less than .01). No line differences were detected in plasma concentrations of estradiol-17 beta and progesterone.     

Plasma progesterone levels during oestrous cycle and their relationship with the ovulation rate in Red Sokoto (Maradi) goats

Twenty-five 2-3-year-old cycling does weighing 17-25 kg were obtained from semi-nomadic farmers and managed under controlled conditions while simulating the traditional management system. Oestrus was synchronized using progestogen impregnated vaginal pessaries. Blood samples were collected daily for progesterone assay from the day of pessary withdrawal up to one complete oestrous cycle. Oestrus was checked twice daily using vasectomized bucks. Ovulation rate was determined by direct observation of the ovaries following laparotomy on day 5-7 of the oestrous cycle. Following oestrus synchronization, mean ovulation rate was 1.68 +/- 0.13. Mean oestrous cycle length and duration of oestrus were 21.30 +/- 0.28 days and 21.37 +/- 0.24 hours respectively. Plasma progesterone concentrations ranged from non-detectable levels on the day of oestrus to 5.2 +/- 0.28 ng ml at mid-cycle. The duration of elevated progesterone level (greater than 2 ng/ml) was about 12 days. The peak progesterone values did not differ between animals with different ovulation rates. However, the plasma progesterone concentration during the early cycle (days 0-6) was significantly lower in the single ovulators compared with others. There were no major differences in plasma progesterone levels during the oestrous cycle of Red Sokoto does with different ovulation rates.     

Effect of Naloxone on Serum Luteinizing Hormone Concentration in Anovulatory Holstein Cows During the Early Postpartum Period

This experiment was conducted to investigate the effect of naloxone (NAL), an opioid receptor antagonist, on pituitary LH secretion in anovulatory Holstein cows during the early postpartum period when cows were expected to be in negative net energy balance. Twenty-three cows (11 primiparous) received either saline (n = 12) or 1 mg/kg BW NAL i.v. (n = 11) on Day 14 or 15 postpartum. Jugular blood samples were collected at 15-min intervals for 2 hr before and 2.5 hr after NAL or saline. All cows received 3 ug gonadotropin releasing hormone (GnRH) at 2.5 hr post-NAL or -saline and blood collection was continued for 1 hr. Mean serum progesterone concentration was 0.33 ± 0.2 ng/ml. Mean net energy balance for all cows was -5.5 ± 0.6 Mcal/day. Naloxone caused a transient increase (P < 0.05) in serum LH concentrations in both primi- and multiparous cows within 45 min after administration. In contrast, serum LH concentrations remained unchanged in saline-treated cows. GnRH increased (P < 0.05) LH and there was no effect of treatment. These results suggest that modulation of LH secretion, at least in part, may be mediated via endogenous opioids in dairy cows before first postpartum ovulation.     

Estimated pregnancy length from ovulation to parturition in the bitch and its influencing factors: a retrospective study in 162 pregnancies

An accurate timing of parturition is very useful for managing canine parturition. It is generally accepted that parturition in bitches occurs between 64 and 66 days after the luteinizing hormone peak. In this retrospective study, we determined pregnancy length in different breeds and its influencing factors dating it from the estimated day of ovulation (EDO), defined as the day when peripheral plasma level of progesterone (P4) reaches 6 ng/ml. From January 2001 to December 2006, 162 pregnancies in 151 bitches of 53 different breeds were followed. Different parameters concerning the bitch, the litter, the type of semen and the type of reproduction were studied. The mean estimated pregnancy length in the bitch from EDO to parturition was 63.1±2.1 days. The main influencing factors for the pregnancies studied were the breed, the size of the bitch and the number of puppies within the litter.     

西农萨能奶山羊妊娠期外周血浆孕酮、17β──雌二醇和皮质醇的变化

采用放射免疫分析法测定了１４只西在萨能奶山羊妊娠期外周血浆孕酮（Ｐ４）、１７β－雌二醇（１７β－Ｅ２）和皮质醇（Ｆ）水平。血浆Ｐ４水平在配种当日为０．５ｎｇ／ｍｌ，以后升高，妊娠２０天时为４．７ｎｇ／ｍｌ。在妊娠３０－５０天，Ｐ４水平有所下降，最低值在４０天，为３２ｎｇ／ｍｌ，Ｐ４水平从６０天开始一直维持在６．２ｎｇ／ｍｌ左右，到妊娠结束时降低到０．６ｎｇ／ｍｌ。血浆１７ｐ－Ｅ２水平在配种后保持稳定，从妊娠４０天开始稳定上升，在妊娠结束时达到峰值７９．８ｐｇ／ｍｌ，血浆下水平在配种后呈波动式下降，到妊娠６０天变为波动式升高，并在妊娠结束时达到峰值１７ｎｇ／ｍｌ。前言西农萨能奶山羊是经过数１０年选育的高产品种，在国内享有盛名。关于西农萨能奶山羊初情期［１］、发情周期［２，３］、分娩期［４］以及非繁殖季节［５］的内分泌状况已有研究报告，但对其妊娠期的内分泌变化迄今尚无资料。为了研究西农萨能奶山羊妊娠期主要生殖激素的变化情况，给奶山羊妊娠生理学及妊娠病理学提供基础资料，我们应用放射免疫分析法（ＲＩＡ）分析了西农萨能奶山羊妊娠期外周血浆孕酮（Ｐ４）、１７β－雌二醇（１７β－Ｅ２）和皮质醇（Ｆ）的水平。材料和方法在西?     

Serum leptin concentrations, luteinizing hormone and growth hormone secretion during feed and metabolic fuel restriction in the prepuberal gilt

Two experiments were conducted to determine 1) the effect of acute feed deprivation on leptin secretion and 2) if the effect of metabolic fuel restriction on LH and GH secretion is associated with changes in serum leptin concentrations. Experiment (EXP) I, seven crossbred prepuberal gilts, 66 +/- 1 kg body weight (BW) and 130 d of age were used. All pigs were fed ad libitum. On the day of the EXP, feed was removed from four of the pigs at 0800 (time = 0) and pigs remained without feed for 28 hr. Blood samples were collected every 10 min from zero to 4 hr = Period (P) 1, 12 to 16 hr = P 2, and 24 to 28 hr = P 3 after feed removal. At hr 28 fasted animals were presented with feed and blood samples collected for an additional 2 hr = P 4. EXP II, gilts, averaging 140 d of age (n = 15) and which had been ovariectomized, were individually penned in an environmentally controlled building and exposed to a constant ambient temperature of 22 C and 12:12 hr light: dark photoperiod. Pigs were fed daily at 0700 hr. Gilts were randomly assigned to the following treatments: saline (S, n = 7), 100 (n = 4), or 300 (n = 4) mg/kg BW of 2-deoxy-D-glucose (2DG), a competitive inhibitor of glycolysis, in saline iv. Blood samples were collected every 15 min for 2 hr before and 5 hr after treatment. Blood samples from EXP I and II were assayed for LH, GH and leptin by RIA. Selected samples were quantified for glucose, insulin and free fatty acids (FFA). In EXP I, fasting reduced (P < 0.04) leptin pulse frequency by P 3. Plasma glucose concentrations were reduced (P < 0.02) throughout the fast compared to fed animals, where as serum insulin concentrations did not decrease (P < 0.02) until P 3. Serum FFA concentrations increased (P < 0.02) by P 2 and remained elevated. Subcutaneous back fat thickness was similar among pigs. Serum IGF-I concentration decreased (P < 0.01) by P 2 in fasted animals compared to fed animals and remained lower through periods 3 and 4. Serum LH and GH concentrations were not effected by fast. Realimentation resulted in a marked increase in serum glucose (P < 0.02), insulin (P < 0.02), serum GH (P < 0.01) concentrations and leptin pulse frequency (P < 0.01). EXP II treatment did not alter serum insulin levels but increased (P < 0.01) plasma glucose concentrations in the 300 mg 2DG group. Serum leptin concentrations were 4.0 +/- 0.1, 2.8 +/- 0.2, and 4.9 +/- 0.2 ng/ml for S, 100 and 300 mg 2DG pigs respectively, prior to treatment and remained unchanged following treatment. Serum IGF-I concentrations were not effected by treatment. The 300 mg dose of 2DG increased (P < 0.0001) mean GH concentrations (2.0 +/- 0.2 ng/ml) compared to S (0.8 +/- 0.2 ng/ml) and 100 mg 2DG (0.7 +/- 0.2 ng/ml). Frequency and amplitude of GH pulses were unaffected. However, number of LH pulses/5 hr were decreased (P < 0.01) by the 300 mg dose of 2DG (1.8 +/- 0.5) compared to S (4.0 +/- 0.4) and the 100 mg dose of 2DG (4.5 +/- 0.5). Mean serum LH concentrations and amplitude of LH pulses were unaffected. These results suggest that acute effects of energy deprivation on LH and GH secretion are independent of changes in serum leptin concentrations.     

Pituitary Hormone Responses to Luteal Regression after Administration of Prostaglandin F2α-Analogue

As an experiment to elucidate the canine luteal function maintenance system, a PGF2alpha-analogue, fenprostalene (PGF-F), was administered 24 and 54 days after ovulation to induce luteal regression, and the responses of luteinizing hormone (LH) and prolactin (PRL), which are considered to support the canine corpus luteum, were investigated. The plasma progesterone (P(4)) level was rapidly decreased, by which the plasma PRL level was increased, but no change was observed in the plasma LH level. The decrease in the plasma P(4) level after PGF-F administration may have induced positive feedback to the superior system, and stimulated secretion of the pituitary hormones. These findings suggested that the canine corpus luteum is maintained by PRL, not by LH.     

Canine plasma cortisol (hydrocortisone) measured by radioimmunoassay: clinical absence of diurnal variation and results of ACTH stimulation and dexamethasone suppression tests.

A radioimmunoassay for plasma cortisol (hydrocortisone) was developed and validated for sensitivity, specificity, accuracy, precision, and parallelism. Steroids were extracted with ethyl ether, and cortisol was purified by gel column chromatography prior to assay. [1,2-3H] cortisol and a commercially available sheep antibody to cortisol-21-hemisuccinate were used. Free steriods were separated from bound steroids by centrifugation after adsorption to dextran-coated charcoal. Plasma cortisol was measured by this technique in 6 normal dogs. Circadian rhythm of cortisol secretion was not detected in samples obtained by venipuncture at 8 different hours on 3 separate days, suggesting that adrenal function tests may be started in clinical patients at any time of day. Resting plasma cortisol concentrations averaged 19.4+/-3.0 (SD) ng/ml and ranged from nondetectable (less than 3 ng/ml) to 77.5 ng/ml. Of 144 canine plasma samples, 95% contained less than 50 ng of cortisol/ml. Intramuscular injection of 2.2 units of adrenocorticotropic hormone/kg of body weight caused detectable increase in plasma cortisol concentrations; maximum response (68.3 to 111.6 ng/ml) occurred 1 to 2 hours after injection. Oral administration of dexamethasone suppressed plasma cortisol to nondetectable concentrations for 32 hours in all 6 dogs.     

Neonatal hemiorchidectomy of bulls alters plasma growth hormone levels and advances onset of pubertal testosterone secretion

Bovine GH and testosterone profiles were determined in plasma collected at 20 min intervals during 3 hr bleeding periods on day 25 of life and every 15 days thereafter in six intact (I) Holstein bull calves and in six others which had been hemiorchidectomized (HO) at 10 days of age. In I bulls average plasma GH concentrations varied between 7.9 and 14.5 ng/ml (P greater than 0.05) until 130 days of age, after which the GH level gradually rose (P = 0.007) to a maximum of 19.4 ng/ml on day 205 of life. Episodic release of GH was apparent in 55 day-old and older I bulls and in HO bulls of all ages. Plasma GH concentrations in HO bulls were higher than in I bulls 15 and 30 days after surgery (P = 0.07), at which times the levels in HO bulls averaged 19.6 and 22.5 ng/ml and in I bulls 10.3 and 10.2 ng/ml, respectively. Plasma GH in HO bulls again exceeded that of I bulls at ages of 130-190 days (P = 0.04). Plasma testosterone was virtually nondetectable before 130 days of age in I bulls but thereafter exhibited the typical episodic pattern. In HO bulls, plasma testosterone concentrations began to rise 15 to 30 days before those in I bulls, resulting in an age X treatment interaction (P less than 0.0001). Furthermore, average testosterone levels were higher (P = 0.07) in HO than I bulls at 235 and 250 days of age.(ABSTRACT TRUNCATED AT 250 WORDS)