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Biomedical subjects

D F van de Wiel

Publications and source records attributed to D F van de Wiel.

At least 19 recordsLinked to original sources
PubMed2001

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.

Age Factors↗
PubMed1998

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.

Animals↗
PubMed1993

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.

Anestrus↗
PubMed1992

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)

Animals↗
PubMed1988

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.

Journal Article↗
PubMed1988

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.

Animals↗
PubMed1988

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)

Animals↗
PubMed1988

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.

Animals↗
PubMed1987

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.

Animals↗
PubMed1987

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.

Aging↗
PubMed1987

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.

Animals↗
PubMed1983

[Improvement of fertility status in dairy farms by using the milk progesterone test].

On nine farms comprising a total number of 370 cows, studies were done for two years to determine whether the reproductive status (RS) could be improved by systematic performance of the milk progesterone test. Milk samples were taken on the day of insemination (day 0), day 8 and day 21 to verify oestrus detection, the observation of ovarian dysfunction and the early diagnosis of (non-)pregnancy. The RS on these nine farms increased from thirty-six to fifty-four, which was mainly due to the reduction of the number of inseminations required for each conception (from 2.1 to 1.7). On ten farms selected by a similar method, on which reproduction was supervised by the veterinary practitioner, the RS increased from forty-seven to fifty-five, which increase was particularly due to inseminations carried out sooner after calving. The RS of ten herds which served as controls, increased from forty-one to forty-seven. An analysis of costs showed that the costs using the progesterone test were estimated to be equivalent to the expense of supervising a reproductive dairy herd health programme. A diagnosis negative for pregnancy based on three milk samples tested was correct in 98 per cent of the cases. A diagnosis positive for pregnancy was correct in 90 per cent of the cases. When a death rate of 8 per cent of the embryos within three weeks after conception is taken into account, the proportion will also be 98 per cent. Summarizing, it is concluded that systematic performance of the milk progesterone test provides an attractive method of improving reproduction on those farms which do not take part in veterinary supervision of reproductive dairy herd health programmes.

Animals↗
PubMed1983

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.

Animals↗
PubMed1982

[Progesterone and estrogen concentrations in the peripheral blood of heifers in relation to the course of calving].

Concentrations of progesterone (P), free (E1) and conjugated (E1S) oestrone and free (E2) and conjugated (E2S) oestradiol-17 beta were determined in plasma samples from twenty-five heifers of three different breeds (Holstein, Meuse-Rhine-Yssel, Dutch Friesian). The blood of the animals was sampled once weekly from the jugular vein during the period from the 29th to the 9th day before parturition. Findings in five heifers were not included in analysis because of malpresentation of the calf. Nine of the remaining twenty heifers had difficulties in calving and nine others, partially the same animals, gave birth to dead calves. The total period of sampling was divided into three periods of seven days and, within each period, the direct relationship between hormone levels and ease of calving was examined. For this purpose hormone concentrations were corrected within each period, for a number of days prepartum, breed, sex of calf, birth weight, length of gestation and season of calving, when these were significant. Only the effect of birth weight of male calves on P, the effect of season on E2S and that of days on E1 and E2 in period 3 (15-9 days before parturition) were significant. As a rule, there were only small, non-significant differences in corrected hormone concentrations between heifers with and those without dystocia. A comparison of average concentrations between heifers which gave birth to a stillborn calf and heifers giving birth to a living calf showed similar results. Measurements on the calves suggested that dystocia was more likely to be caused by an oversized calf than it was by abnormalities in hormone levels in these cases.

Animals↗
PubMed1979

Oestrus control and early pregnancy diagnosis in the swamp buffalo: comparison of enzymeimmunoassay and radioummunoassay for plasma progesterone.

A preliminary study has been undertaken, in order to investigate the suitability of a progesterone assay in blood plasma for oestrus control and pregnancy diagnosis in the swamp buffalo (Bubalus bubalis ). Progesterone was determined both by radioimmunoassay (RIA) and by enzymeimmunoassay (EIA). Values obtained by EIA were considerably lower than values obtained by RIA. This may be partly due to the fact that only RIA values were corrected for procedural losses. Blood samples were taken on day 1 (= day of insemination) and on days 24, 27 and 30 after insemination (p.i.). Additional samples from pregnant animals were taken around day 170 p.i.. Normal progesterone values during oestrus were lower than 0.5 ng/ml, and generally the same low values were found in case of non-pregnancy at days 24, 27 and 30 p.i.. Pregnant animals showed in all cases progesterone concentrations higher than 0.5 ng/ml at days 24, 27 and 30, as well as around day 170 p.i.. These preliminary results indicate that the analysis of progesterone in plasma may be suitable for fertility control in the swamp buffalo. Furthermore we suggest that a modified EIA method can be used as a simple and rapid oestrus detection test under field conditions.

Journal Article↗
PubMed1978

Fertility control in cattle by use of the "milk progesterone test".

The development and validation of a radioimmunoassay for progesterone in cow's milk is described. Control of the temperature during storage of the milk and also during the sample incubation procedure appeared to be a critical requirement with respect to reduction of nonspecific binding of tritiated progesterone. Ranges of milk progesterone levels were established during pregnancy as well as during the luteal and the follicular phase of the oestrus and of pregnancy in three trials on two experimental farms. The mean accuracy with respect to the diagnosis "pregnant", "non-pregnant" or "not in oestrus" were 84.0, 97.6, and 100%, respectively. By leaving out of account all animals with high progesterone values (greater than 10 ng. ml(-1)) on day 1 (= day of insemination) the accuracy of the diagnosis "pregnant" was improved to 87.1%.

Animals↗
PubMed1978

Radioimmunoassay for porcine prolactin: plasma levels during lactation, suckling and weaning and after TRH administration.

A sensitive heterologous radioimmunoassay for porcine prolactin (pPRL) has been developed. Anti-ovine prolactin antibody was raised in rabbits which allowed a final dilution of 1:500 000. The separation of free and antibody bound [125I]pPRL is based on the double antibody solid phase system. The assay is specific for pPRL. There is no cross-reaction with pLH, pFSH and pTSH; little cross-reaction (1.35%) was found with pGH. The smallest detectable amount was 0.08 ng per tube. During lactation high plasma levels are found with great fluctuations. After weaning the plasma PRL levels fall to basal within a few hours. After thyrotrophin-releasing hormone (TRH) administration plasma concentrations increase within a few minutes.

Animals↗