Effects of active immunization against GnRH on serum LH, inhibin A, sexual development and growth rate in Chinese female pigs.

Surgical castration of young female pigs is common practice in Chinese pig farming today. The purpose of the present study is to investigate anti-GnRH immunization as a practical alternative to surgical castration for female pigs. Thirty-six Chinese female crossbred pigs (Chinese Yanan x Yorkshire) were selected from 12 litters, three pigs from each litter, at the age of 10-13 weeks. One pig from each litter was immunized with 62.5 microg D-Lys6-GnRH-tandem-dimer peptide conjugated to ovalbumin in Specol adjuvant at Week 0 (0 week post-vaccination, wpv), and a booster vaccination was given 8 weeks later (8 wpv). Its intact and castrate littermates (surgically castrated at the time of weaning, i.e. at 6 weeks of age) were administered the vehicle and served as controls. Antibody titers, serum LH and inhibin A were determined at the day of first vaccination, every 4 weeks thereafter and at the day of slaughter (18 wpv). At slaughter, ovaries were inspected for the presence of follicles and corpora lutea, and ovarian and uterine weights were recorded. Ten of twelve immunized pigs responded well to the immunization (immunocastrated animals), while the remaining two pigs responded poorly (nonresponders). Antibody titres in immunocastrated animals steadily increased after immunization, became maximal at 12 wpv and remained high until slaughter. Serum LH levels were reduced (P < 0.05) in immunocastrated pigs as compared to intact controls and surgical castrates. Serum inhibin A levels decreased after vaccination, and equaled surgical castrate levels from 8 wpv until the end of the experiment. Ovarian and uterine weights (1.3 +/- 0.2 and 43.9 +/- 11.4 g, respectively; mean +/- S.E.M.) were significantly lower (P < 0.05) in immunocastrates than in intact controls (9.4 +/- 1.1 and 390.9 +/- 67.2 g, respectively). Antibody titers were significantly lower (P < 0.05) in nonresponders than in immunocastrated pigs from 12 wpv to slaughter. Ovarian and uterine weights were similar in nonresponders and in intact controls. Macroscopically, no follicular structures were found in ovaries of immunocastrated pigs, while large follicles or corpora lutea were observed in the ovaries of both nonresponders and intact controls. Although not significant, immunocastrates had a numerically higher average daily gain than surgical castrates and intact controls (0.74 +/- 0.04 versus 0.66 +/- 0.04 versus 0.66 +/- 0.03 kg per day, respectively; mean +/- S.E.M., P = 0.09). Results obtained in the present study demonstrate that anti-GnRH immunization can be an attractive alternative to surgical castration for Chinese crossbred female pigs. Our results also question the beneficial effect of surgical castration on growth as compared to intact controls.

Different regulation of rat 5-HT(2A) and rat 5-HT(2C) receptors in NIH 3T3 cells upon exposure to 5-HT and pipamperone.

The 5-HT(2A) and 5-HT(2C) receptors belong to the same subtype of the G-protein coupled receptor family and have several agonist and antagonist ligands in common. To gain more insight into the differences in the regulation of the two receptors, we studied the effect of agonist and antagonist pre-treatment on radioligand receptor binding and 5-HT-induced inositol phosphate formation on rat 5-HT(2A) and rat 5-HT(2C) receptors stable expressed in NIH 3T3 cells. We compared short (15 min) and prolonged (48 h) pre-treatment of the cells with the natural agonist, 5-HT and with the antagonist pipamperone, which can be readily washed out. The rat 5-HT(2C) receptor showed an agonist-induced down-regulation (decrease in B(max) of labelled agonist and antagonist binding) and desensitisation (decrease in 5-HT-induced inositol phosphate formation and potency of 5-HT). Antagonist pre-treatment induced an increase in rat 5-HT(2C) receptor-mediated inositol phosphate formation as well as increased agonist and antagonist radioligand binding. These findings are consistent with the classical model of G-protein coupled receptor regulation. In contrast, the rat 5-HT(2A) receptor expressed in the same host cell behaved differently, unlike the classical model. Pre-treatment with 5-HT for 15 min and 48 h did not change receptor levels measured by radioligand binding, but the signal transduction response (inositol phosphate formation) was significantly reduced. Pre-treatment with the antagonist pipamperone for 15 min and 48 h caused an increase in antagonist radioligand binding but a reduction in agonist radioligand binding and a decrease in inositol phosphate formation and potency of 5-HT. Hence, the rat 5-HT(2A) receptor apparently undergoes agonist desensitisation without down-regulation of the total receptor number. Antagonist pre-treatment causes a paradoxical desensitisation, possibly by uncoupling of the receptor from G-proteins. The uncoupled receptor does not bind 5-HT in the nanomolar range but retains its antagonist binding properties. Paradoxical antagonist-induced desensitisation of rat 5-HT(2A) receptors has also been observed in vivo.

Secretion of biologically active glycoforms of bovine follicle stimulating hormone in plants.

We chose the follicle stimulating hormone (FSH), a pituitary heterodimeric glycoprotein hormone, as a model to assess the ability of the plant cell to express a recombinant protein that requires extensive N-glycosylation for subunit folding and assembly, intracellular trafficking, signal transduction and circulatory stability. A tobacco mosaic virus (TMV) based transient expression system was used to express a single-chain (sc) version of bovine FSH in the tobacco related species Nicotiana benthamiana. Preparations of periplasmic proteins from plants infected with recombinant viral RNA contained high levels of sc-bFSH, up to 3% of total soluble proteins. Consistently, in situ indirect immunofluorescence revealed that the plant cell secreted the mammalian secretory protein to the extracellular compartment (EC). By mass spectrometric analysis of immunoaffinity purified sc-bFSH derived from EC fractions, we found two species of the plant paucimannosidic glycan type, truncated forms of complex-type N-glycans. Stimulation of cAMP production in a CHO cell line expressing the porcine FSH receptor acknowledged the native-like structure of sc-bFSH and a sufficient extent of N-glycosylation required for signal transduction. Furthermore, in superovulatory treatments of mice, sc-bFSH displayed significant in vivo bioactivity, although much lower than that of pregnant mare serum gonadotropin. We conclude that plants may have a broad utility as hosts for the recombinant expression of proteins even where glycosylation is essential for function.

Active immunization against gonadotrophin-releasing hormone in Chinese male pigs.

We have investigated, under the normal conditions of local Chinese pig farming, castration of young male pigs by vaccination with a newly developed vaccine against gonadotrophin releasing hormone (GnRH). Because of the very early onset of puberty, long fattening period and relatively harsh circumstances in Chinese pig production, an investigation of the endocrine response of Chinese breeds to this type of vaccination was of particular interest. Fifteen crossbred boars (Yorkshire x Yanan) from three different litters were randomly assigned to three groups of five animals each. The first group was immunized at 13 weeks of age with a GnRH tandem dimer OVA-conjugate in Specol and received a booster immunization 8 weeks later. The second group was injected with Specol alone and served as untreated controls. The remaining group was surgically castrated at the time of weaning (at 6 weeks of age). Pigs were fed ad libitum from weaning onwards. All animals were slaughtered at 31 weeks of age. Immunized boars had undetectable or low serum testosterone (0.09 +/- 0.12 ng/ml), low fat androstenone (0.05 +/- 0.01 microg/g) levels and very low testes weights (19.1 +/- 4.3 g). Intact controls had much higher serum levels of testosterone (9.76 +/- 4.81 ng/ml), fat androstenone levels (2.26 +/- 0.87 microg/g) and testes weights (114.3 +/- 29.41 g) at slaughter. Both the immunized and castrated group grew significantly faster than intact boars (p < 0.01). Average daily gains in immunized, castrated and intact animals were 0.69 +/- 0.08, 0.63 +/- 0.05 and 0.42 +/- 0.07 kg (mean +/- SD), respectively. The present data demonstrate for the first time that the newly developed anti-GnRH vaccine works very well under practical Chinese pig farming conditions, and can be an attractive alternative to surgical castration.

Effects of recent and reference antipsychotic agents at human dopamine D2 and D3 receptor signaling in Chinese hamster ovary cells.

RATIONALE: Central dopamine D2 receptor blockade is an essential property of antipsychotic agents in the treatment of schizophrenia. However, for certain of the newer antipsychotics (e.g., sertindole), the in vitro D2 receptor binding affinity does not correlate with in vivo central dopamine antagonism. OBJECTIVE: This study aimed to investigate the effect and potency of haloperidol, pipamperone, clozapine, risperidone, sertindole, zotepine, olanzapine, and quetiapine on signaling pathways of human dopamine D2S and D3 receptors expressed in Chinese hamster ovary cells and to relate this to their dopamine antagonist potency in vivo. METHODS: Chinese hamster ovary cells, stably expressing high levels of hD2S and hD3 receptors were cultured: dopamine-stimulated [35S]-GTPgammaS binding was investigated in cell membrane preparations, and forskolin-induced cAMP formation was measured in intact cells. RESULTS: The antipsychotic agents inhibited dopamine-stimulated [35S]-GTPgammaS binding mediated by hD2S and hD3 receptors with potencies equal to their receptor binding affinities. The antipsychotics reversed dopamine inhibition of cAMP formation (equally well detectable with both hD2S and hD3 receptors) dose dependently at both receptors. Partial agonist effects were not observed with any of the antipsychotics. Antagonistic potencies of haloperidol, risperidone, and pipamperone in the cAMP test were equal to their receptor binding affinities. Sertindole and olanzapine were more than ten times less potent dopamine antagonists in the intact cell assay than in the assay using cell membranes; the other compounds showed less marked potency differences. CONCLUSIONS: Olanzapine and sertindole were less efficacious dopamine antagonists in intact cell assays, possibly due to avid uptake in cells. For sertindole, the weak hD2S receptor antagonism in intact cells corresponded to a weak in vivo central dopamine antagonism assessed in rats. However, for olanzapine, hD2S receptor binding affinity correlated better with its in vivo dopamine antagonist potency. Such discrepancies may be further explained by relative differences of the compounds in penetrating into the brain.

High-level expression of biologically active recombinant bovine follicle stimulating hormone in a baculovirus system.

Superovulation treatment of cows can benefit from the application of very pure recombinant bovine FSH (rbFSH), which is produced in nonmammalian cells. rbFSH is completely free of LH, and therefore can possibly reduce the variability in the results of superovulation. Furthermore, it does not contain brain-tissue-derived proteins and, when produced under serum-free conditions, it is free of other mammalian substances or potentially infectious material. We have produced rbFSH in insect cells, with the ultimate aim of inducing superovulation in cattle. Sf21 insect cells were coinfected with two recombinant baculoviruses, containing the cDNAs of bovine FSH alpha- and beta-subunits respectively. High levels of production of bioactive rbFSH were obtained after cloning cDNA that contained a major part of the 3' untranslated region of the bFSH beta gene. Maximum production of rbFSH 1-5 micrograms/ml (as measured by immunoassay) was obtained 70-90 h after infection. The recombinant material was highly potent in two in vitro bioassays, giving biological activities of 13 IU/ml (Y1 cell rounding assay), 22 IU/ml (Y1 cell cAMP assay), and 23 IU/ml (bovine oocyte maturation inhibition assay), and had a lower but significant activity of 6 IU/ml in the rat Sertoli cell assay. rbFSH was purified by immunoaffinity chromatography, using a monoclonal antibody directed against the human FSH beta-subunit. The purified heterodimer appeared to be homogeneous by SDS-PAGE, whereas the free beta-subunit appeared as a doublet, possibly indicating differently glycosylated forms. Intact heterodimer and both subunits were further identified by western blot analysis, and showed apparent molecular masses of 20 kDa (alpha-subunit), 23 kDa (beta-subunit) and 32.5 kDa (heterodimer). This insect-cell-produced rbFSH did not bind to wheat germ agglutinin, thus indicating that glycosidic side-chains may not contain terminal sialic acid. The relevance of a large 3' untranslated region in bFSH beta cDNA to the level of production of rbFSH, and the possible implications of the pattern of glycosylation for the biological activity of the recombinant hormone are discussed.

Post-weaning anoestrus in primiparous sows: LH patterns and effects of gonadotropin injection and boar exposure.

Post-weaning anoestrus was studied in eighteen primiparous sows, selected from a breed showing a high proportion of anoestrous sows. The sows were studied from late lactation, through weaning at day 29 post-partum (p.p.), until day 21 post-weaning (p.w.). Blood samples were taken once daily, and frequently (every ten minutes) on several days before and after weaning. Out of a total of ten anoestrous sows, three were exposed to a boar and seven were given gonadotropins (PG600) on day 21 p.w.. Serial blood samples were analysed for LH only and daily samples were additionally analysed for oestradiol-17 beta and progesterone, by validated radioimmunoassay procedures. Analysis of variance of the basal level, pulse frequency, pulse amplitude and mean level of LH showed, retrospectively, that during lactation the basal and mean levels of LH were significantly lower in anoestrous than in oestrous sows (P < or = 0.05). Furthermore, the post-weaning basal and mean levels of LH were also significantly lower in anoestrous than in oestrous sows (P < or = 0.05). However, because of the small number of oestrous animals (n = 3), these results should be interpreted with caution. Exposure of anoestrous sows to a boar did not result in oestrus and/or ovulation within seven days, but did increase LH pulse frequency. Injection of gonadotropins resulted in an LH surge, oestrus and ovulation in only three sows, but oestradiol levels were increased in six sows. From our experiments and from reports in the literature we conclude that a lowered secretion of LH may play a role in the aetiology of post-weaning anoestrus in the sow.

Pubertal development in the male pig: effects of treatment with a long-acting gonadotropin-releasing hormone agonist on plasma luteinizing hormone, follicle stimulating hormone and testosterone.

The effects of a long-acting gonadotropin-releasing hormone (GnRH) agonist, [D-Trp6]-GnRH (GnRH-A) on developmental profiles of plasma luteinizing hormone (LH), follicle stimulation hormone (FSH) and testosterone (T), and pituitary responsiveness to exogenous GnRH were studied in male Dutch Landrace x Large White crossbred pigs from 1 to 30 wk of age. Group 1 control animals (control; n = 12) were injected subcutaneously in the neck with vehicle at 1 and 16 wk of age. Group 2 animals (early treatment; n = 10) were injected with 600 micrograms [D-Trp6]-GnRH at 1 wk and with vehicle at 16 wk. Group 3 animals (late treatment; n = 8) were injected with vehicle and 3 mg GnRH-A at 1 and 16 wk, respectively. Group 4 animals (early plus late treatment; n = 9) were injected at both 1 and 16 wk with GnRH-A. Blood was collected by brachiocephalic puncture at weekly or biweekly intervals, and through brachiocephalic cannulae, to determine longitudinal profiles of LH, FSH and T, and plasma gonadotropin responses to intravenous injection of GnRH (0.1 microgram/kg), respectively. In control animals, LH and FSH declined over the first 5 wk of postnatal life and peaked again at 10-14 wk. Levels of both hormones were basal from 18 to 30 wk. Plasma T was high in the first week, declined progressively over the next few weeks and remained low until 24 wk when a transient increment was noted. The LH and FSH responses to acute GnRH stimulation were similar at 7 and 14 wk and declined significantly at 23 wk of age.(ABSTRACT TRUNCATED AT 250 WORDS)

Reproductive performance of Nili-Ravi buffaloes after a single injection of GnRH early post partum.

Sixty dairy buffaloes (second to fourth lactation) from a large buffalo farm were used to compare the effects of single intramuscular injections of 100 micrograms gonadotrophin releasing hormone (GnRH), 250 micrograms GnRH or saline given on day 14 post partum. The buffaloes had calved at the end of the breeding season (December). Milk samples for progesterone determination were taken at the time of injection and then three times a week either until first insemination or until around day 90 post partum. GnRH given at 14 days post partum resulted in quicker completion of uterine involution, earlier resumption of ovarian activity, shorter intervals between calving and conception and a better first service conception rate in non-suckled dairy buffaloes. Differences between the results obtained by a GnRH dose level of 100 micrograms and 250 micrograms were non-significant. In the post-treatment period cases of prolonged luteal activity were common in all groups of buffaloes. Therefore the sequential administration of GnRH and prostaglandin is suggested for the management of post-partum reproductive activity in problem herds.

Effects of morphine and naloxone on plasma levels of LH, FSH, prolactin and growth hormone in the immature male pig.

The effects of acute i.v. administration of gonadotrophin-releasing hormone (GnRH; 0.1 micrograms/kg), morphine (3 mg/kg) and/or naloxone (0.5 mg/kg) on LH and FSH secretion was evaluated in young male pigs (approximately 6 weeks old) with venous brachiocephalic cannulae. The effects of morphine and/or naloxone treatments on prolactin and GH were also evaluated. The influence of morphine on hypophysial hormone secretion was also examined 2 days after castration. Animals treated with morphine and/or naloxone were compared with saline-injected control animals. Injection of GnRH induced 400 and 50% increases in LH and FSH respectively. Morphine and/or naloxone did not influence LH secretion in intact or castrated animals. Morphine suppressed (P less than 0.01) FSH levels 40-60 min after injection whereas naloxone had no effect. Castration eliminated morphine-induced suppression of FSH. Injection of morphine followed by naloxone resulted in acutely raised (P less than 0.05) FSH concentrations. Morphine induced a threefold increase (P less than 0.01) in prolactin within 30 min of injection and naloxone inhibited the effect of morphine. Levels of GH were increased (P less than 0.01) 20 min after morphine treatment and this increase was delayed when naloxone was given immediately after morphine. Naloxone alone did not affect prolactin or GH secretion. Castration caused increases in LH (P less than 0.05) and FSH (P less than 0.01), did not influence prolactin or GH, and reduced plasma testosterone to undetectable (less than 1.0 nmol/l) levels. These results suggest that in young male pigs the hypothalamic-hypophysial axis is responsive to GnRH and gonadal negative feedback.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolactin in the developing pig.

Prolactin (PRL) was determined in plasma of fetal pigs from 40 days post coitum (d.p.c.) onwards. Values increased in the last 3 wk of the gestational period and reached 10 ng/ml at term. Immunoreactive lactotropes could be identified as early as 31 d.p.c. Lactotrope development appeared to be biphasic, with no apparent increase in cell number in the 51-75 d.p.c. period. Sex differences in volume percentage of lactotropes and plasma PRL levels were observed in the 71-75 d.p.c. period. Pituitary PRL content increased 20-fold between 95 d.p.c. and term and 10-fold between birth and 6 wk. Volume percentage of lactotropes did not change from birth to 6 wk. In the postnatal period, plasma PRL concentrations were high in the first 1-2 wk and they decreased thereafter. Lower stable values were observed until about 10 wk, when PRL concentrations began to increase. Prepubertal peak levels were observed in the 10- to 16-wk period and a pubertal peak was observed at 20-22 wk. No significant differences between plasma PRL profiles of males and females were observed in the postnatal period. Castrated males, however, had consistently lower plasma PRL concentrations than intact boars. Cryptorchid boars had PRL concentrations comparable to intact boars. The PRL profile, in relation to the pattern of gonadal development, suggests a role for PRL in gonadal development of the pig.

A simple enzymeimmunoassay of milk progesterone for monitoring fertility in dairy buffaloes.

A simple, sensitive, direct (without extraction) enzymeimmunoassay (EIA) was usec to determine progesterone levels in whole milk samples of 400 Nili-Ravi dairy buffaloes. The mean progesterone values 22 d after A.I. were significantly higher in pregnant (16.6 +/- 9.2 ng/ml) than nonpregnant (below 5 ng/ml) animals. The mean progesterone values were below 0.34 +/- 0.12 (the detection limit) both at estrus and in cases of clinically diagnosed inactive ovaries, 3.18 +/- 1.9 at proestrus, 2.25 +/- 1.2 postestrus and 13.22 +/- 6.74 at Day 10 of the estrous cycle. Twenty buffaloes confirmed pregnant for 2 to 3 mo, had a mean value of 20.3 +/- 4.5 ng/ml. The EIA test is very reliable in the selection of nonpregnant buffaloes (100 %) and the confirmation of inactive ovaries and of estrus. Differential diagnosis of inactive or active ovaries can be made by analyzing two milk samples at a 7-d interval.

Influence of season and social environment on basal and thyrotropin releasing hormone-induced prolactin secretion in the adult domestic boar.

Basal and TRH-induced PRL secretions were investigated for adult Landrace boars housed in two social environments. Socially nonrestricted boars (N = 4) were individually penned adjacent to ovariectomized gilts that were hormonally induced into estrus every 3 weeks, while socially restricted boars (N = 4) were individually kept in pens with solid walls. In February, May and August all boars were fitted with jugular catheters for serial blood sampling which took place 2 h prior to and 4 h following in iv injection of TRH (1 microgram/kg). Mean pre-injection serum PRL concentration was not influenced by either month or social environment. The PRL response to TRH injection, however, was influenced by both factors. The magnitude of the PRL response (peak delta value) increased (month, P less than 0.01) progressively in both groups of boars from February through August and was greater (P less than 0.05) in the nonrestricted versus the restricted boars in August. The total amount of PRL secreted was also maximal and greater in the socially nonrestricted boars in August (month x social group, P less than 0.05). These results indicate that TRH-induced and not basal PRL secretion is influenced by both season and social interaction of boars.

Chronic GnRH administration in prepubertal male pigs. A model to evaluate the effects of GnRH treatment in cryptorchidism.

The effect of chronic pulsatile low-dose GnRH treatment on the juvenile testis and associated structures was evaluated in relation to hormonal parameters in the peripheral blood in the pig. Starting at 8 weeks of age, male pigs (crossbreds of Dutch Landrace and Yorkshire breeds) were injected 6 times daily im with 0, 75 or 250 ng GnRH/kg body weight during 4 weeks. Immediately after the treatment period, a GnRH stimulation test with 750 ng GnRH/kg iv was carried out. Samples for plasma LH, FSH, testosterone and 5 alpha DHT measurement were obtained weekly (basal level) and after GnRH stimulation. The pigs were castrated at 12 weeks of age and the weights and lengths of the testis, epididymis and cremaster muscle were recorded. Intratesticular testosterone and 5 alpha DHT concentrations were determined, and the testis and epididymis were evaluated for histological changes. Basal plasma hormone concentrations, intratesticular androgen concentrations and the response of the pituitary gland to stimulation had not been affected by GnRH treatment. Pigs receiving the higher treatment dose of GnRH showed less increase in testosterone levels in response to the stimulation dose at 12 weeks of age than the other pigs. Morphologically, no changes were observed in the epididymis and cremaster muscle after GnRH treatment and no signs of reactivation of structures that can provoke testicular descent could be seen. The development of the seminiferous epithelium was more advanced in the GnRH-treated groups, apparently in a dose-dependent manner.

Development of a sensitive enzymeimmunoassay (EIA) for progesterone determination in unextracted bovine plasma using the second antibody technique.

A simple direct enzymeimmunoassay (EIA) on microtiter plates for plasma progesterone using the second antibody coating technique and horseradish peroxidase (HRP) as the enzyme label (EIA-HRP) is described and compared with an identical EIA procedure which employed alkaline phosphatase (AP) as the enzyme label (EIA-AP). The assays used antiserum raised against progesterone-7-carboxyethlthioether-BSA in rabbits. Both systems were further compared with the conventional direct progesterone radioimmunoassay (RIA) in regular use. The enzymes HRP and AP were coupled to progesterone-6 beta-hydroxy-hemisuccinate by a mixed anhydride method. While the precision of EIA-HRP was comparable to RIA, the sensitivity in terms of the lowest detection limit obtained in EIA-HRP was about 10 times better than that seen in RIA. Progesterone estimates from plasma samples in EIA-HRP showed good correlation (r = 0.94) with the RIA values and the levels measured in the two systems were identical. Progesterone estimates from plasma samples in EIA-AP were at least three times higher than those obtained by either EIA-HRP or RIA. Thus, only the EIA-HRP but not the EIA-AP was suitable for the reliable direct measurement of progesterone in plasma.

Feedback regulation of gonadotropic hormone secretion in neonatal pigs.

The effect of castration and of administration of charcoal-treated porcine follicular fluid (pFF) containing inhibin-like activity on plasma concentration of gonadotropic hormones was studied in neonatal pigs. Plasma follicle-stimulating hormone (FSH) concentration averaged 25.1 +/- 1.5 ng/ml (mean +/- SEM) in 1-wk-old females and gradually declined to 20.2 +/- 0.7 ng/ml 6 wk later. Ovariectomy did not significantly influence plasma FSH concentration. In males, concentration averaged 8.0 +/- 0.7 ng/ml before castration but rose significantly within 2 days after castration. Injection of luteinizing hormone-releasing hormone (LHRH) did not influence plasma FSH concentrations in intact males, but did in females and in 7-wk-old males castrated at 1 wk. Plasma luteinizing hormone (LH) concentrations in 1-wk-old females (2.2 +/- 0.4 ng/ml) gradually declined and were not influenced by castration. Concentrations of plasma LH in 1-wk-old male piglets (2.8 +/- 0.7 ng/ml) were not significantly influenced by castration within 2 days but were significantly higher 6 wk later. LHRH induced a significant rise in plasma LH concentrations in all animals. Injection of pFF resulted in a decline of plasma FSH concentrations in intact and castrated males and in intact females, but did not influence plasma LH concentrations. These data demonstrate a sex-specific difference in the control of plasma FSH, but not in plasma LH concentration in the neonatal pig. Plasma FSH concentrations, but not plasma LH concentrations, are suppressed by testicular hormones in 1-wk-old piglets. Plasma FSH concentrations can be suppressed in both neonatal male and female pigs by injections of pFF.

An international collaborative study on the First International Standard of bovine luteinizing hormone for immunoassay.

An ampouled freeze-dried preparation of bovine pituitary luteinizing hormone (bLH), coded EHC-bLH-1, has been evaluated in an international collaborative study and shown to be suitable and sufficiently stable to serve as a standard for bLH. Eight laboratories provided immunoassay data, one laboratory provided receptor assay data, and bioassay data were obtained from 4 laboratories. The geometric mean potency estimate obtained by immunoassays, expressed as milliunits of the USDA bLH-B-5 preparation per ampoule, was 25.6, which is consistent with the result obtained by in-vivo bioassays. The geometric mean estimate obtained by receptor assays or by in-vitro bioassays was lower, i.e. 13.2 milliunits per ampoule. The reason for this discrepancy is currently under investigation. With the authorization of the Expert Committee on Biological Standardization of the World Health Organization this preparation was established in 1985 as the International Standard for Luteinizing Hormone, Bovine, for Immunoassay with a unitage of 25 mi.u. per ampoule.

Ontogeny of hypothalamic pituitary function in the pig: pituitary thyrotrophin in the fetus and neonate.

Thyrotrophin in individual pituitaries obtained from fetal and prepubertal pigs was quantified by homologous radioimmunoassay (RIA) and heterologous radioreceptor assay (RRA). Relative evolution of pituitary TSH contents and concentrations with age were in good agreement as measured by both assay systems although the quantity of TSH detected by RRA appeared consistently lower than that measured by RIA. Thyrotrophin was first detected in pituitaries of fetal pigs at day 75 of gestation. Thereafter the pituitary content of TSH increased to approximately 45 micrograms/pituitary in the oldest group tested (6 weeks of age). The pituitary TSH concentration rose sharply until birth (114 +/- 1 day post coitum) and thereafter remained increased at a concentration of approximately 400 ng/mg wet weight.

The ontogeny of hypothalamic pituitary function in the pig. I. Pituitary LH and FSH in the fetus and neonate.

Pituitaries were collected from fetal and postnatal pigs from day 55 p.c. until 6 weeks after birth at closely spaced intervals. LH and FSH in individual pituitaries were quantified by both homologous RIA and homologous RRA. No significant difference was found between results obtained by RIA and RRA. Both LH and FSH are first detected by RIA and RRA in the porcine fetal pituitary at 75 days p.c. Thereafter both LH and FSH pituitary content rises until term. LH pituitary concentration in both male and female fetuses and FSH pituitary concentration in males exhibit a peak just before birth. FSH pituitary concentration in females rises until birth and thereafter remains elevated. A statistically significant sex difference was found postnatally with regard to FSH content and concentration but not for LH.

Oocyte maturation inhibitor, inhibin and steroid concentrations in porcine follicular fluid at various stages of the oestrous cycle.

Oocyte maturation inhibitor (OMI), inhibin, progesterone and oestradiol 17 beta concentrations were measured in fluid collected from small (less than 3 mm), medium size (3-6 mm) and large (greater than 6 mm) porcine ovarian follicles, which were obtained on Days 5, 10, 15 and 18 of the oestrous cycle and at 24 h after the onset of oestrus. Concentrations of OMI decreased with increasing follicle diameter (P less than 0.05), independent of the stage of the oestrous cycle. Concentrations of inhibin showed a tendency to decrease with increasing follicle diameter on Days 10, 15 and 18, but not on Day 5 of the cycle. Concentrations of OMI and inhibin in the largest follicles were low before the onset of oestrus, and were essentially unaltered 24 h later. A positive correlation was found between OMI and inhibin concentrations, whereas the correlation between inhibin concentration and log (progesterone concentrations) was negative.