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Biomedical subjects

D F Van de Wiel

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

5 recordsLinked to original sources
PubMed1990

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.

Animals↗
PubMed1988

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.

Animals↗
PubMed1982

Changes in serum FSH concentrations in the pig during development.

Serum FSH concentrations were measured in fetal and prepubertal pigs between 40 days postcoitum and 25 weeks after birth. In addition, serum FSH was estimated in prepubertal, unilaterally cryptorchid, freemartin and castrated pigs. The average serum FSH concentrations in male and female fetuses was low (less than 2 ng/ml) until 80 days p.c. During the remaining fetal period, concentrations in females were elevated (7.9 +/- 0.4 ng/ml) and remained fairly constant after birth (16.3 +/- 0.8 ng/ml). In the male, serum FSH concentrations gradually rose to 22.5 +/- 5.5 ng/ml during the first 3 weeks after birth and declined thereafter. The changes in FSH concentrations in male pigs are reflected in gonadal-development. In contrast, in fetal and prepubertal females, ovarian development seems not to be influenced by changes in serum FSH concentrations. Unilateral cryptorchidism did not affect serum FSH concentrations. After castration, however, concentrations rose significantly. In freemartin pigs concentrations were similar to those in female pigs.

Animals↗
PubMed1982

Response of luteinizing hormone and follicle-stimulating hormone to luteinizing hormone releasing hormone in the fetal pig.

The responses of anesthetised fetal pigs (n=95) and chronically catheterized fetal pigs (n=10) to luteinizing hormone releasing hormone (LHRH) administration (2 micrograms/kg estimated fetal body weight) was investigated. Fetuses were studied at 55, 70, 85, 100, 106 (chronic) and 113 days. Plasma concentrations of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were measured by radioimmunoassay. Blood samples were taken from the umbilical artery (anesthetised fetuses) or carotid artery (catheterized fetuses) every 10 min for 1 h except in the youngest age group. No significant sex difference in the LH response to LHRH treatment was observed. The LH response increased with gestational age; average pretreatment plasma concentrations were below 1.1 ng/ml. No response was observed at 55 days, and the highest response was seen at 113 days when plasma LH concentrations rose to 4.3 +/- 0.7 (mean +/- SEM) ng/ml 40 min after treatment. Pretreatment plasma FSH concentrations at 55 days were 1.6 +/- 0.1 ng/ml and gradually rose in males to 3.2 +/- 0.4 ng/ml at 113 days, which was significantly lower than in females where concentrations averaged 8.1 +/- 2.0 ng/ml. LHRH did not significantly affect FSH concentrations in males, while in females a gradually increasing response was observed; at 113 days plasma FSH was 12.5 +/- 2.9 ng/ml 40 min after treatment. The increase in response to LHRH with age of plasma LH concentrations in both sexes, and of plasma FSH concentrations in females indicates the maturation of the hypothalamo-pituitary system.

Animals↗