Isolation of Ovulation-inducing Factors in the Seminal Plasma of Bactrian Camel (Camelus bactrianus) by DEAE-cellulose Chromatography

Ovulation in the Bactrian camel ( Camelus bactrianus ) depends upon the ovulation-inducing factor in the seminal plasma; however, little research has been conducted to isolate and identify the factor. The current study attempts to isolate and identify the bioactive fractions from the seminal plasma of Bactrian camel. The seminal plasma was fractionated by diethylamino-ethylcellulose (DEAE)-cellulose chromatography and five protein fractions were obtained. The bioactive of each fraction was estimated by rat pituitary tissue culture in vitro and by the intramuscular injection of the bioactive fraction to the female camels in vivo . The concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary culture media before and 6 h after the addition of each fraction and in the peripheral blood plasma collected from the camel immediately before and hourly after the injection of the active fraction were measured by radioimmunoassay. The results demonstrated that the third fraction (L3) had the bioactive potential to stimulate the release of LH in vitro from 11.82 ± 1.77 to 25.63 ± 3.84 mIU/ml after the addition of L3 to the culture media. The in vivo concentrations of LH in the blood plasma of the camel increased from 6.43 ± 0.14 before to 15.50 ± 2.64 ng/ml 6 h after injection of L3. However, the concentrations of FSH did not show any significant changes either in vitro or in vivo . The results clearly demonstrated the existence of LH-releasing associated fractions in the seminal plasma that appears to be separated by DEAE-cellulose matrix and the isolated L3 fraction might be the ovulation-inducing factor or one of its components.     

Hormonal Response of Female Goats to Active Immunization against a Recombinant Human Inhibin α-subunit, and establishment of an Enzyme-linked Immunosorbent Assay for Caprine Follicle-stimulating Hormone

The effect of selective immunosuppression of endogenous inhibin in goats on FSH, LH, progesterone and estradiol-17β profiles was studied during the breeding and nonbreeding seasons. Eighteen adult female Boer goats were immunized against the recombinant human inhibin α-subunit (hINH-α). With the exception of estradiol, which was determined by radio-immunoassay (RIA), all plasma hormone concentrations were determined by ELISA. The ELISA for FSH presented in this paper was established in the authors' laboratory, based on an existing RIA. Mean basal concentrations of FSH were not affected by immunosuppression of endogenous inhibin, nor was there a difference in the amplitude of the pre-ovulatory FSH surge. Immunization against inhibin appears to eliminate the slight secondary rise of FSH occurring 12–20 h after the major surge associated with ovulation. The LH profiles of the immunized goats were characterized by lower basal concentrations both before and after the pre-ovulatory LH surge which itself was reduced by 50% in immunized does. By contrast, concentrations of circulating estradiol were significantly elevated after inhibin-immunization. Progesterone profiles were not affected. Extending immunization into the anoestrous season by a booster injection of hINH-α, implicating oestrus induction with a progestagen and eCG, produced no discernible differences in FSH and LH profiles in comparison with nonimmunized control goats. The findings suggest that in goats, paracrine factors may play a more significant role in controlling follicular activity than a feedback mechanism acting via the pituitary.     

Luteinizing hormone in the bovine pars tuberalis: secretion in response to luteinizing hormone releasing hormone and intracellular isoforms

The objective of this study was to examine the physiological characteristics of gonadotropes in the bovine (b) pars tuberalis as assessed by their ability to release Luteinizing Hormone (LH) in response to LH-Releasing Hormone (LHRH) and the intracellular distribution of LH isoforms. At slaughter, the stalk median eminence and associated pars tuberalis as well as the anterior pituitary gland were collected from each of 7 castrate males. Each stalk median eminence and pituitary gland was mid-sagitally sectioned and weighed. One half of each tissue was immediately frozen and subsequently homogenized to determine the intracellular distribution of bLH isoforms. Tissue extracts were desalted by flow dialysis against water and chromatofocused on pH 10.5-7.0 gradients. The remaining half of the pituitary was sliced with a Staddie-Riggs slicer. The pituitary slices and the remaining half of the stalk median eminence were perifused (0.1 ml/min) for a total of 360 min with effluent samples (1.0 ml) collected every 10 min. At 130 min tissues were stimulated with 5 x 10(-8) M LHRH. Concentrations of LH in the effluent samples and the fractions collected from chromatofocusing were determined by radioimmunoassay. The release of LH in response to LHRH was 43.9% and 47.0% above basal secretion for the pars tuberalis and pituitary, respectively, suggesting similar degrees of responsiveness. Pars tuberalis and pituitary extracts resolved into nine LH isoforms during chromatofocusing and were coded with letters beginning with the most basic form. No differences (P greater than .05) were observed in distribution of LH isoforms between the pars tuberalis and the pituitary gland.(ABSTRACT TRUNCATED AT 250 WORDS)     

山羊垂体门脉和颈静脉血样同时收集法的建立

本文描述了一种实用的山羊垂体门脉和颈静脉血样同时收集法。试验中应用该法收集了１９例山羊垂体门脉和颈静脉血样，并对其中７例血样分别进行血浆ＧｎＲＨ和ＬＨ水平的检测，然后根据两种血样红细胞压积比值曲线校正ＧｎＲＨ测值。结果表明，手术后颈静脉血浆的ＬＨ平均水平与手术前差异不显著（Ｐ＞０．０５）；两种血浆样品的激素测值分别反映了ＧｎＲＨ和ＬＨ的水平及其相应关系。因而认为，本试验所建立的采样法既能收集山羊垂体门脉血样，又能保持垂体的正常内分泌功能，对于内分泌学的研究有重要的应用价值。     

The effect of pulsatile gonadotropin-releasing hormone and estradiol administration on luteinizing hormone and follicle-stimulating hormone concentrations in pituitary stalk-sectioned ovariectomized pony mares

Hourly pulses of gonadotropin-releasing hormone (GnRH) or bi-daily injections of estradiol (E2) can increase luteinizing hormone (LH) secretion in ovariectomized, anestrous pony mares. However, the site (pituitary versus hypothalamus) of positive feedback of estradiol on gonadotropin secretion has not been described in mares. Thus, one of our objectives involved investigating the feedback of estradiol on the pituitary. The second objective consisted of determining if hourly pulses of GnRH could re-establish physiological LH and FSH concentrations after pituitary stalk-section (PSS), and the third objective was to describe the declining time trends of LH and FSH secretion after PSS. During summer months, ovariectomized pony mares were divided into three groups: Group 1 (control, n = 2), Group 2 (pulsatile GnRH (25 μg/hr), n = 3), and Group 3 (estradiol (5 mg/12 hr), n = 3). All mares were stalk-sectioned and treatment begun immediately after stalk-section. Blood samples were collected every 30 min for 8 h on the day before surgery (DO) and 5 d post surgery (D5) to facilitate the comparison of gonadotropin levels before and after pituitary stalk-section. Additionally, jugular blood samples were collected every 12 hr beginning the evening of surgery, allowing for evaluation of the gonadotropin secretory time trends over the 10 d of treatment. On Day 10, animals were euthanized to confirm pituitary stalk-section and to submit tissue for messenger RNA analysis (parallel study). Plasma samples were assayed for LH and FSH by RIA. Mean LH secretion decreased from Day 0 to Day 5 in Groups 1 and 3, whereas LH secretion tended (P < 0.08) to decrease in Group 2 mares. On Day 5, LH was higher (P < 0.01) in Group 2 (17.26 ± 3.68 ng/ml; LSMEANS ± SEM), than either Group 1 (2.65 ± 4.64 ng/ml) or group 3 (4.28 ± 3.68 ng/ml). Group 1 did not differ from Group 3 on Day 5 (P < 0.40). Similarly, mean FSH levels decreased in all groups after surgery, yet Group 2 mares had significantly (P < 0.001) higher FSH concentrations (17.66 ± 1.53 ng/ml) than Group 1 or Group 3 (8.34 ± 1.84 and 7.69 ± 1. 63 ng/ml, respectively). Regression analysis of bi-daily LH and FSH levels indicated that the time trends were not parallel. These findings indicate: 1) Pituitary stalk-section lowered LH and FSH to undetectable levels within 5 d after surgery, 2) pulsatile administration of GnRH (25 μg/hr) maintained LH and FSH secretion, although concentrations tended to be lower than on Day 0, and 3) E2 did not stimulate LH or FSH secretion.     

Biological and immunological luteinizing hormone activity and blood metabolites in postpartum Brahman cows

Multiparous Brahman cows were assigned by order of calving and sex of calf to groups to be fed to maintain body condition score (BCS) of 6 or greater (M; n = 10) or to lose BCS (L; n = 10). Blood samples were collected weekly for progesterone analysis and at 15, 30 and 45 d after parturition at 15-min intervals for 6 h for determination of immunological (ILH) and biological (BLH) luteinizing hormone. Serum concentrations of ILH were determined using a double antibody RIA procedure, whereas BLH was determined using a rat interstitial cell-testosterone bioassay (RICT). By 45 d after parturition 7 of 10 M cows had returned to estrus. Therefore, comparisons between groups were made on d 15 and 30 postpartum. Cows in the M group had a shorter (P less than .001) interval to first estrus (46.7 d) than did L cows (91.2 d). The concentrations of bioactive and immunoactive LH were parallel between d 15 and 30 postcalving. However, a day x treatment interaction (P less than .05) showed that episodic BLH concentrations (ng/ml) decreased with day postpartum in L, but increased in M cows from d 15 to 30 postcalving. Likewise, relative biological activity, as measured by B:I ratios, decreased between d 15 and 30 in L cows, whereas it increased in M cows during the same period (B:I x day interaction; P less than .05).(ABSTRACT TRUNCATED AT 250 WORDS)     

阉割对公马促性腺激素细胞及血中促性腺激素水平的影响

利用免疫组织化学和形态计测学的方法 ,观察了 7匹公马和 6匹在 1～ 2岁期间被摘除了睾丸的阉割马的脑垂体前叶促性腺激素 (GTH )细胞的数量和面积 ,同时利用放射免疫分析方法检测了血浆中垂体促卵泡激素 (FSH)和垂体促黄体激素 (L H)的水平。结果表明 ,公马阉割后 GTH细胞的数量和在垂体前叶实质细胞中的百分率并没有发生明显改变 ,但 GTH细胞的面积却明显增加 ,血中 GTH水平也明显升高。研究结果提示 ,处在生长发育期的马睾丸可能抑制脑垂体中 GTH细胞的合成与储存 ,也抑制 GTH的释放     

山羊GnRH和促性腺激素的释放特点

通过外科手术分别连续收集活体山羊中黄体期及早卵泡期的垂体门脉血样和外周血样，经放射免疫测定，山羊中黄体期和早卵泡期的促性腺激素释放激素（ＧｎＲＨ）、促黄体生成素（ＬＨ）和促卵泡素（ＦＳＨ）均呈波动式释放。在早卵泡期，ＦＳＨ单位时间内波动次数和血浆平均水平显著高于中黄体期；ＧｎＲＨ与ＬＨ的波动型基本一致，ＦＳＨ的变化不太规则。表明山羊垂体促性腺激素的释放受丘脑下部ＧｎＲＨ的调节，但ＦＳＨ似乎还存在其他调节机理。     

Effect of GnRH and its antagonist (Antarelix) on LH release from cultured bovine anterior pituitary cells

In the following investigations, the LH secretion of cells from pituitaries in heifers on days 16-18 of their oestrous cycle (n = 14) was analysed. Cells were dissociated with trypsin and collagenase and maintained in a static culture system. For the estimation of LH release, the cells were incubated with various concentrations of mammalian GnRH (Lutrelef) for 6 h. To determine the action of Antarelix (GnRH antagonist), the cells were preincubated for 1 h with concentrations of 10(-5) or 10(-4) M Antarelix followed by 10(-6) M GnRH coincubation for a further 6 h. At the end of each incubation, the medium was collected for LH analysis. Parallel, intracellular LH was qualitatively detected by immunocytochemistry. Changes in the intensity of LH staining within the cells in dependence of different GnRH concentrations were not observed, but a significant increase LH secretion in pituitary cells was measured at 10(-6) M GnRH. Antarelix had no effect on basal LH secretion at concentrations of 10(-4) and 10(-5) M. After coincubation of pituitary cells with Antarelix and GnRH, Antarelix blocked the GnRH-stimulated LH secretion with a maximal effect of 10(-4) M, but the staining of immunoreactive intracellular LH was detected at approximately the same level compared to the pituitary cells treated with exogenous GnRH alone. These data demonstrate that Antarelix is effective in influencing the GnRH-stimulated LH secretion of pituitary cells in vitro. After administration of Antarelix in vivo, the GnRH-stimulated LH secretion of cultured pituitary cells was not inhibited.     

Ovine luteinizing hormone: isoforms in the pituitary during the follicular and luteal phases of the estrous cycle and during anestrus.

Pituitaries were collected from late follicular phase (n = 5), mid-luteal phase (n = 5), and anestrous ewes (n = 4) to assess changes in intrapituitary LH heterogeneity at selected reproductive states. After homogenization, an aliquot of each pituitary extract was desalted by flow dialysis against water and chromtofocused on a pH 10.5 to 4.0 gradient. Concentrations of LH in pituitary extracts and chromatofocusing fractions were determined by RIA. The LH in pituitary extracts resolved into 13 isoforms during chromatofocusing, which were coded with letters beginning with the most basic isoform. Follicular and mid-luteal phase ewes exhibited similar distributions of intrapituitary LH among its isoforms. Relative to follicular and luteal phase ewes, anestrous ewes had lower percentages of isoforms D and E as well as higher percentages of isoforms G, H, J and K. Isoform F, the predominant molecular form of LH, constituted a similar percentage in all treatment groups (P > .05). Thus, the distribution of intrapituitary LH among its isoforms did not change significantly between the mid-luteal and follicular phases of the estrous cycle, but higher percentages of the weakly basic and acidic forms of LH were present during anestrus. These observations suggest that intrapituitary LH heterogeneity changes minimally throughout the estrous cycle of ewes during the breeding season.     

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。     

Determination of optimal time for mating by artificial insemination with chilled semen using luteinizing hormone surge as an indicator in beagles.

Artificial insemination (AI) was conducted using the second fraction of semen, which was collected from 15 male dogs, diluted to a total sperm count of 100x10(6) for each insemination with egg-yolk Tris (eyT) citrate acid buffer and incubated at 4 degrees C for 48 hours. Luteinizing hormone (LH) surge was detected to determine the optimal time for mating using canine LH assay kits. Artificial insemination using 100x10(6) sperm was performed on the fourth and sixth days or the fifth and seventh days after the LH surge. The conception rates were 33% (4/12) and 89% (8/9), respectively; the whelping rates also showed similar results. Serum LH and follicle stimulating hormone (FSH) concentrations were measured in nine dogs, and the mean LH concentration (+/- standard deviation) at LH surge was 15.77+/-7.66 ng/ml. The time of the LH surge detected by the canine LH assay kit was very similar to that measured by radioimmunoassay (RIA).     

Characterization of a monoclonal antibody which detects luteinizing hormone from diverse mammalian species

The present study describes the development and characterization of a monoclonal antibody (518B7) generated against bovine LH (bLH). Although 518B7 was extremely specific for LH, very low species specificity was observed. A RIA using this antibody and radioiodinated equine LH (eLH) showed good sensitivity for all mammalian LH preparations tested, with the exception of human LH (15%, relative to the eLH reference standard). Activities of most mammalian LH's ranged between approximately 50-200%. Much less activity was detected with reptilian LH (less than 1.5%). Amphibian and avian LH fractions were essentially inactive. The reactivities of LH alpha and beta subunits from a variety of mammals clearly showed that the antibody reacts with the beta subunit. Sensitive RIAs were also developed utilizing 125I-bovine and 125I-rat LH. Interestingly, all hormone preparations which showed sufficient reactivity for statistical analysis within the dose ranges used in the present study (0.01-1000 ng/tube) produced a displacement curve parallel to the reference standard. We have also validated the use of 518B7 in detecting LH in serum. Parallel dilution curves relative to purified LH reference standards were observed with equine and bovine serum samples and equine pituitary extract. High (average 94%) recoveries were also seen with bovine serum with known amounts of exogenously added bLH. Similar patterns of LH secretion were detected with a RIA based upon 125I-bLH and 518B7 and a previously described polyclonal antibody-based RIA in bovine serum samples during estrus. Thus, a monoclonal antibody for LH has been produced which can be used to develop sensitive and specific RIAs in many different mammalian species.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of estradiol,progesterone, and nutrition on concentrations of gonadotropins and GnRH receptors,and abundance of mRNA for GnRH receptors and gonadotropin subunits in pituitary glands of beef cows

Nutritionally induced anovulatory cows (n = 28) were used to determine the effect of steroids on regulation of synthesis and secretion of gonadotropins. Anovulatory cows were ovariectomized and received intravaginal inserts containing estradiol (E2), progesterone (P4), E2 and P4 (E2P4), or a sham intravaginal insert (C) for 7 d. Concentrations of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) were quantified in serum and E2 and P4 were quantified in plasma. Cows were exsanguinated within 1 to 2 h after removal of intravaginal inserts and pituitary glands were collected and stored at -80 degrees C until messenger ribonucleic acid (mRNA) for gonadotropin-releasing hormone receptor (GnRH-R) and gonadotropin subunits, pituitary content of GnRH-R, and LH and FSH were quantified. Pituitary glands from five proestrous cows were harvested to compare gonadotropin characteristics between ovariectomized, anovulatory cows and intact cows. Plasma concentrations of E2 were greater (P < 0.05) in E2-treated cows than in sham-treated cows. Concentrations of P4 were greater (P < 0.05) in cows treated with P4 than in sham-treated cows. Mean serum concentrations of LH and FSH were not significantly influenced by steroid treatments. However, frequency of LH pulses of ovariectomized, nutritionally induced anovulatory cows was increased (P < 0.05) by treatment with E2 and amplitude of LH pulses was greater (P < 0.05) in cows treated with E2 or P4 than in cows treated with E2P4 or sham-treated. Quantity of mRNA for LHbeta in the pituitary gland was greater when cows were treated with P4. Concentrations of LH in the pituitary gland were not affected by steroid treatments; however, pituitary concentrations of FSH were less (P < 0.1) in E2 cows than in sham-treated cows. The number of GnRH-R was increased (P < 0.05) in cows treated with E2, but P4 treatment did not influence the number of GnRH-R. Abundance of mRNA for GnRH-R, common alpha-subunit, and FSHbeta were not affected by treatments. Pituitary concentrations of LH were greater (P < 0.05) and concentrations of FSH were less (P < 0.05) in proestrous cows than in ovariectomized, anovulatory cows treated with or without steroids. Abundance of mRNA for GnRH-R, common alpha-subunit, LHbeta and FSHbeta were similar for proestrous and anovulatory cows. We conclude that treatment of nutritionally induced anovulatory cows with progesterone and estradiol may cause pulsatile secretion of LH.     

Pituitary responsiveness to GnRH, hypothalamic content of GnRH and pituitary LH and FSH concentrations immediately preceding puberty in gilts

To determine whether pituitary concentrations of luteinizing hormone (LH), follicle-stimulating hormone (FSH) or hypothalamic content of gonadotropin releasing hormone (GnRH) change before puberty, 40 prepubertal gilts averaging 7 mo of age were slaughtered before or on the second, third or fourth day after relocation and boar exposure. Some gilts responded to relocation and boar exposure as indicated by swollen vulvae, turgid uteri and enlarged ovarian follicles at the time of slaughter. Pituitary concentrations of LH and FSH and hypothalamic content of GnRH were similar between gilts that responded to relocation and boar exposure and gilts that did not respond. In addition, boar exposure and relocation had no effect on pituitary concentrations of LH and FSH or on hypothalamic content of GnRH. To determine whether pituitary responsiveness to GnRH changes before puberty, a third experiment was conducted in which 72 gilts were injected with 400 micrograms of GnRH either before or on the second, third or fourth day after relocation and boar exposure. In gilts that subsequently responded (i.e., ovulated) as a result of relocation and boar exposure, pituitary responsiveness to GnRH was reduced as compared with gilts that failed to ovulate after relocation and boar exposure. Peak concentrations of serum LH after GnRH injection were 4.6 +/- 1.3 vs 9.8 +/- .8 ng/ml for responders vs nonresponders. Peak serum FSH after GnRH injection was also lower for responders than for nonresponders (29.5 +/- 4.2 vs 41.2 +/- 2.4 ng/ml). When compared with controls, relocation and boar exposure did not significantly affect GnRH-induced release of LH and FSH.(ABSTRACT TRUNCATED AT 250 WORDS)     

Leptin: a metabolic signal affecting central regulation of reproduction in the pig

The discovery of the obesity gene and its product, leptin, it is now possible to examine the relationship between body fat and the neuroendocrine axis. A minimum percentage of body fat may be linked to onset of puberty and weaning-to-estrus interval in the pig. Adipose tissue is no longer considered as only a depot to store excess energy in the form of fat. Recent findings demonstrate that numerous genes, i.e., relaxin, interleukins and other cytokines and biologically active substances such as leptin, insulin-like growth factor-I (IGF-I), IGF-II and Agouti protein are produced by porcine adipose tissue, which could have a profound effect on appetite and the reproductive axis. Hypothalamic neurons are transsynaptically connected to porcine adipose tissue and may regulate adipose tissue function. In the pig nutritional signals such as leptin are detected by the central nervous system (CNS) and translated by the neuroendocrine system into signals, which regulate appetite, hypothalamic gonadotropin-releasing hormone (GnRH) release and subsequent luteinizing hormone (LH) secretion. Furthermore, leptin directly affects LH secretion from the pituitary gland independent of CNS input. Changes in body weight or nutritional status are characterized by altered adipocyte function a reduction in adipose tissue leptin expression, serum leptin concentrations and a concurrent decrease in LH secretion. During pubertal development serum leptin levels, hypothalamic leptin receptor mRNA and estrogen-induced leptin gene expression in fat increased with age and adiposity in the pig and this occurred at the time of expected puberty. In the lactating sow serum and milk leptin concentrations were positively correlated with backfat thickness and level of dietary energy fed during gestation as well as feed consumption. Although, these results identify leptin as a putative signal that links metabolic status and neuroendocrine control of reproduction, other adipocyte protein products may play an important role in regulating the reproductive axis in the pig.     

Monoclonal antibody based sandwich enzyme-linked immunosorbent assay for chicken growth hormone.

1. Monoclonal antibodies which bind to different epitopes of chicken growth hormone (cGH) were used to develop a homologous sandwich enzyme-linked immunosorbent assay (ELISA). 2. The first antibody, which is species specific, was immobilised on microtitre plates and concentrations of cGH in biological fluids were estimated by revealing bound hormone using a second, biotinylated monoclonal antibody. 3. The sensitivity was 0.024 ng/ml, which is at least ten-fold greater than current radioimmunoassays (RIA) and there was no cross-reactivity to other chicken pituitary hormones or to growth hormone from other species. 4. The accuracy and precision of the assay were similar to RIA, and the growth hormone concentrations measured in plasma samples by both RIA and this new ELISA showed a high degree of correlation. 5. The assay takes only 4 h using pre-coated plates which can be stored at 4 degrees C in sucrose. The advantages of being rapid and non-isotopic make this method attractive to both research and industrial laboratories.     

日粮能量对乌鸡外周血清促性腺激素与垂体分泌促性腺激素的影响

采用体外细胞培养和放射免疫测定法（RIA）测定日粮能量对鸟鸡外周血清促性腺激素与垂体分泌促性腺激素的影响。日粮能量处理：低能Ⅱ组、低能I组、对照组、高能I组、高能Ⅱ组;体外培养垂体细胞组分：高能组、对照纽、低能组。结果显示,血清中FSH含量,对照组与高能Ⅱ组相比差异显著（P〈0．05）,与低能I、Ⅱ组相比差异极显著（P〈0．01）;血清中LH含量,对照组与高能I组、高能Ⅱ组组间差异显著（P〈0．05）;低能Ⅱ组与高能I组、低能Ⅱ组与高能Ⅱ组、低能I组与高能I组、低能I组与高能Ⅱ组组间差异极显著（P〈0．01）;单层垂体细胞中FSH含量,高能组和对照组与低能组比差异显著（P〈0．05）;单层垂体细胞中LH含量,高能组与低能组比较差异极显著（P〈0．01）,对照组与低能组比较差异不显著。结果表明,日粮能量对处理体外培养乌鸡垂体细胞分泌FSH、LH有促进作用。     

Concentrations of luteinizing hormone, follicle stimulating hormone and prolactin following transection of the pituitary stalk in ovariectomized ewes

Two experiments (Spring and Fall) were conducted in ovariectomized ewes to determine changes in pituitary hormone secretion immediately after pituitary stalk-transection. Ewes underwent either pituitary stalk-transection (SS), sham-transection (SH) or administration of anesthesia only (AO). Stalk-transected, but not sham-operated or anesthetized ewes had polyuria and polydipsia for 7 to 14 days after surgery. Concentrations of luteinizing hormone (LH), follicle stimulating hormone (FSH) and prolactin were measured in peripheral blood samples collected every 10 minutes for a six-hour period. Results were comparable for each season. During the six hours following surgery or removal from anesthesia, concentrations of LH declined in all ewes, but more slowly in SS ewes. No differences in patterns or mean concentrations of FSH were observed. Immediately after surgery, concentrations of prolactin were elevated, then declined in SH and SS ewes. The decrease was greater in SH than SS ewes. Data are consonant with the view that hypothalamic inhibition as well as LHRH stimulation regulate gonadotropin release by the pituitary.     

Failure of neuropeptide y to modulate the release of LH and prolactin by cultured bovine pituitary cells

Possible direct effects of neuropeptide Y (NPY) on dispersed and cultured cells of the anterior lobe (AL) of the bovine pituitary were investigated. AL tissue from steers was enzymatically dissociated into individual cells, preincubated for 18 hr and then incubated in suspension cultures for 2 hr or 24 hr with either NPY, gonadotropin-releasing hormone (GnRH) or both. Release of luteinizing hormone (LH) and prolactin (PRL) into medium was quantified by radioimmunoassay and expressed as hormone released per 100,000 cells. Basal release of LH averaged 38 and 86 ng for 2 hr and 24 hr respectively while that of PRL averaged 118 and 438 ng for the same incubation periods. Addition of NPY did not alter (P>.05) basal release of LH or PRL for either duration of incubation. Also, NPY did not affect (P>.05) release of LH in response to GnRH. In summary, this study indicated that NPY, at in vitro dosages of .01 to 100nM, does not modulate the release of LH or PRL at the pituitary level in castrate cattle.