Biomedical subjects

E Decuypere

Publications and source records attributed to E Decuypere.

At least 199 records · Page 11Linked to original sources

PubMed1990

Ontogeny of the effect of purified chicken growth hormone on the liver 5' monodeiodination activity in the chicken: reversal of the activity after hatching.

The ontogeny of the effect of chicken growth hormone (c-GH) on the liver 5' monodeiodination (5'-D) activity was studied in chickens starting from 14-day-old embryos until 5-week-old chickens. Ten micrograms of the purified hormone was injected intravenously and after 2 hr, blood and liver samples were taken. In all embryonic stages tested, c-GH stimulated the peripheral thyroxine (T4) to triiodothyronine (T3) conversion as demonstrated by the increased plasma T3 level and liver 5'-D activity while the plasma reverse T3 (rT3) level was decreased. In chicks 1 day after hatching, GH was still able to increase the plasma T3 level and the liver 5'-D activity. However, in 2-day-old chicks, this stimulation had completely disappeared, while the control value of the plasma T3/T4 ratio was considerably higher than the day before. The effect of c-GH injection gradually turned into a decrease of 5'-D activity and plasma T3 in 5- and 7-day-old chicks. Further on, no effect of c-GH could be found in 2- to 4-week-old growing chickens, but in 5-week-old GH-injected animals the plasma T4 and rT3 level decreased again, although no significant effect on T3 or liver 5'-D activity could be demonstrated.

Animals↗

PubMed1990

Effects of dietary T3 on growth parameters and hormone levels in normal and sex-linked dwarf chickens.

Tri-iodothyronine (T3) has been administered in the diet, from day of hatch until 8 weeks of age, to sex-linked dwarf and normal chicks of both sexes from a brown-egg slow-growing strain. Feed was supplemented with either 0.1 ppm or 0.5 ppm T3. A significant genotype by treatment interaction was observed on body weight: the effect of T3 in males was significantly positive for dwarfs and null for normals, the effect in females was null for dwarfs and significantly negative for normals. Feed efficiency was rather decreased by the treatment in both genotypes. Abdominal fatness was decreased in a dose-dependent manner in both genotypes, while rectal temperature was raised in dwarf chicks only. Plasma T3 was raised to normal levels in dwarfs receiving 0.1 ppm exogenous T3, while the 0.5 ppm dose yielded hyperthyroid levels. Plasma GH levels were decreased in a dose-dependent manner by the T3 treatment, the effect being larger in dwarfs. Surprisingly, plasma IGF-I was unchanged in spite of the GH decrease, whatever the genotype or the sex. It was concluded that exogenous T3 alone can have a stimulatory effect on growth in dwarfs but can not fully restore a normal growth rate. Both T3 and IGF-I are important for a normal growth and the relationship between T3 and IGF-I production should be further investigated in order to better understand the physiological modifications due to the sex-linked dwarf gene.

Abdomen↗

PubMed1990

Impaired peripheral T3 production but normal induced thyroid hormone secretion in the sex-linked dwarf chick embryo.

Plasma concentrations of thyroxine (T4), triiodothyronine (T3) and chicken GH (cGH), together with hepatic 5'-monodeiodination (5'-D) activity, were measured in normal (Dw) and dwarf chick (dw) embryos at incubation d 18. An injection of 10 micrograms of ovine GH (oGH) raised plasma concentrations of T3 in Dw embryos after 1 and 2 h and stimulated hepatic 5'-D activity after 2 h. A non-specific increase in T4 was also observed after 1 h in Dw animals probably due to the heterologous nature of the injection. These effects were not observed in dw embryos. An injection of 1 microgram of TRH was able to increase cGH levels after 15 min in Dw embryos, whereas the the observed increase in the dw group was not significant. In Dw embryos, 0.01, 0.1 and 1 microgram of TRH increased plasma concentrations of T3 in a dose-dependent way, whereas in dw embryos, no reaction to the TRH injections was seen, except for the highest dose used. Contrary to this observation, T4 was increased to the same level in both Dw and dw embryos following TRH injections. An injection of 1 microgram of ovine CRH increased corticosterone after 0.5 h and elevated T3 and T4 after 2 h to the same extent in Dw and dw embryos. It is concluded that the thyrotrophic activities of TRH and oCRH and the corticotropic activity of oCRH do not differ between normal and sex-linked dwarf embryos. However TRH and GH were unable to stimulate the T4-T3 conversion in the liver of dw embryos, presumably due to the lack of hepatic GH receptors in these animals.

Animals↗

PubMed1990

The effect of thyroid hormone status on plasma glucose-insulin interrelationship in broiler chickens.

The aim of the present experiments was to study the plasma glucose-insulin relationship in eu-, hypo- or hyperthyroid broiler chickens. None of the thyroid states modified the fasting plasma glucose and insulin levels. Hypothyroid chickens exhibited a normal glucose tolerance and a normal glucose-induced insulin release after oral glucose (2 g/kg body weight) administration compared to euthyroid chickens. In contrast, hyperthyroid chickens exhibited an improved glucose tolerance accompanied by a lower insulin release. Insulin injections at a concentration of 0.1 U/kg body weight was only hypoglycemic in hyperthyroid chickens, which confirms the observation that these chickens are more sensitive to insulin. From this study it can be suggested that alterations in body composition according to thyroid status are at least partly mediated by changes in the control of carbohydrate metabolism by pancreatic hormones.

Animals↗

PubMed1990

Accumulation of zinc in egg yolk, ovarian follicles and organs after forced resting by high dietary zinc.

1. Eighteen Warren SSL hens of 71 weeks of age were forced-moulted by ad libitum feeding of a high-zinc diet (10,000 ppm zinc for 2 days followed by 5,000 ppm zinc-supplement diet for 4 days). From the start of the treatment, eggs were collected and 3 hens were slaughtered on days 0, 2, 3, 4, 5 and 6 of the study. 2. Zinc analyses were carried out on the different components of the eggs and on liver, pancreas, kidney, different yolky follicles of the ovary and various segments of the oviduct. 3. Seven-, six- and threefold increases in zinc concentration were found in pancreas, liver and kidney, respectively. 4. The shell gland and isthmus, but not the magnum, also showed slight but significant increases in Zn content. 5. Zinc accumulation was also high and almost identical in ovarian follicles F1 to F4 but slightly less in F5 and F6 follicles. 6. In the egg, a significant increase in zinc concentration was only observed in the yolk.

Animals↗

PubMed1990

Effect of the sex-linked dwarf gene on circulating levels of 17 beta-estradiol, progesterone and luteinising hormone in the laying hen.

1. The sex-linked dwarf gene did not appear to affect the LH, progesterone (P4) and oestradiol 17-beta (E2) levels around the onset of lay in a sample of White Leghorn hens. 2. A longer interval between oviposition and subsequent ovulation was suggested in dwarf layers by a slower decrease in the P4 plasma concentration after the preovulatory peak and is consistent with the increased oviposition interval already described. 3. A higher ratio of E2/P4 basal levels was found in dwarf layers; this is consistent with their lower number of fast-growing follicles and with their reduced laying rate. 4. Lipid mobilisation was modified in dwarf layers (as shown by their reduced abdominal fattiness); although plasma concentrations of triglycerides were normal, unusual correlations between plasma triglycerides, E2 basal concentrations and body weight were recorded.

Animals↗

PubMed1990

Seasonal variations in prolactin, growth hormone and thyroid hormones and the prolactin surge at ovulation do not affect litter size of ewes during pregnancy in the oestrous or the anoestrous season.

Injection of bromocriptine from 5 days before until 5 days after mating clearly suppressed the periovulatory prolactin surge in ewes in the anoestrous and oestrous season but did not change the litter size significantly. Progesterone, GH, TSH or thyroid hormone concentrations were not influenced by the bromocriptine treatment. The progesterone concentrations were lower during the first weeks after mating in the anoestrous season compared to the oestrous season, while there was no difference between pregnant and non-pregnant ewes. During later gestation this seasonal difference was only observed in the non-pregnant ewes. At the same time there was a clear difference between pregnancy and non-pregnancy in both seasons. The prolactin, GH and thyroid hormone values also varied significantly during gestation. Since these patterns are identical in pregnant and non-pregnant ewes, the fluctuations are due to environmental factors and not to pregnancy or altered progesterone concentrations. In the anoestrous season prolactin, GH, T4 and T3 levels were higher than in the breeding season, while rT3 showed the opposite pattern. The TSH concentration did not differ between the two seasons. These results suggest that seasonal variations in prolactin, GH and thyroid hormones or the periovulatory prolactin surge do not affect litter size of ewes during pregnancy in the oestrous or the anoestrous season.

Animals↗

PubMed1989

Thyrotropic activity of the ovine corticotropin-releasing factor in the chick embryo.

An injection of several doses of ovine corticotropin-releasing factor (oCRF) was made into an allantoic blood vessel of 18-day-old chick embryos. All doses used (0.5, 1, 2, and 5 micrograms) induce a quick increase of plasma corticosterone concentrations after 15 and 30 min and 1 and 2 hr and this in a dose-dependent manner with the high doses having a prolonged effect lasting up to 2 hr. An increase in plasma levels of thyroxine (T4) and triiodothyronine (T3) was observed after 1 and 2 hr. After the oCRF injection, no stimulation of the hepatic 5'-monodeiodination activity was observed and there was no increase, but even a small decrease in the T3 to T4 ratio could be calculated. It was therefore concluded that oCRF in the chick embryo has a thyrotropic effect presumably by stimulating the release of thyrotropin from the pituitary.

Adrenocorticotropic Hormone↗

PubMed1989

Evidence for chicken GH as the only hypophyseal factor responsible for the stimulation of hepatic 5'-monodeiodination activity in the chick embryo.

The influence of an intravenous injection of chicken growth hormone (cGH), a total chicken pars distalis (PD) extract, and a PD extract depleted of cGH by immunoadsorption was studied in the 18-d-old chick embryo. Plasma concentrations of triiodothyronine (T3), thyroxine (T4), and hepatic 5'-monodeiodination (5'-D) activity were measured. An injection of total PD extract raised plasma T3, T4, and 5'-D activity, whereas a PD extract depleted of GH only increased plasma T4. The amount of cGH present in the PD extracts, as measured by homologous cGH radioimmunoassay, increased T3 and raised liver 5'-D, but had no effect on plasma T4. The effect on liver 5'-D was more pronounced with cGH than with a total PD extract, whereas the effect on plasma T3 was somewhat less pronounced. It was concluded that cGH increased the peripheral conversion of T4 into T3 in the chick embryo, whereas a PD extract depleted of cGH was purely thyrotropic. The PD extract also seemed to have 5'-D-suppressing activity.

Animals↗

PubMed1989

Effect of the sex-linked dwarf gene on thyrotrophic and somatotrophic axes in the chick embryo.

Plasma concentrations of thyroxine (T4), triiodothyronine (T3), reversed triiodothyronine (rT3), and insulin-like growth factors I and II (IGF-I, IGF-II) together with peripheral 5'-monodeiodination activity were measured in both normal and sex-linked dwarf embryos between day 14 of incubation and day 1 posthatch. Plasma T4 levels increased gradually during embryonic development while T3 concentrations remained low until day 20, when a sharp increase was observed. rT3 levels also increased from day 14 and dropped on day 20 when T3 levels started to increase. 5'-monodeiodination activity was high on day 14 of incubation, decreased thereafter, and showed an increase at the time of air sac penetration together with increased T3 levels. At this stage, differences between normal and dwarf embryos were observed; the latter had lower nonsignificant 5'-Monodeiodination activity and lower (P less than 0.01) plasma T3 levels. Plasma IGF-II levels were high during the whole embryonic period studied. Dwarf embryos had lower (P less than 0.05) IGF-II levels at the time of hatching. IGF-I levels were high on days 14 and 16, declined afterwards, and started to increase again around hatching. With the exception of T3 and IGF-II levels, introduction of the dwarf gene did not cause major changes in the hormonal parameters studied. This may explain the identical body weight at hatching.

Animals↗

PubMed1989

Relationship between the thyroidal and gonadal axes during the estrous cycle of ewes of different breeds and ages.

In order to define the patterns of TSH, T4, T3, rT3, GH and cortisol during the estrous cycle of sheep, pluriparous and primiparous ewes were synchronized with progestagen-impregnated pessaries (Veramix) at the start of the normal breeding season. After the pessaries were removed (day 0), daily blood sampling was carried out in cannulated ewes during the ovulatory cycle. Hormonal analyses of TSH, T4, T3, rT3, GH, cortisol, LH and progesterone (P) were performed by RIA. P and LH levels during the cycle were conform to the literature and were not different between the primiparous and pluriparous ewes of different breeds used in this study. Neither age nor breed influenced the hormone patterns. A significant negative correlation was found between TSH and P during the cycle, although the correlation between P and T4 was not significant; during the estrous period, low P levels were paralleled by high T4 levels, whereas the reverse was observed during the luteal phase. Higher T3 levels and T3/T4 ratios were observed during the luteal phase. No obvious pattern of rT3 and cortisol during the cycle was found. The GH concentration increased during the 17 days of the cycle. A positive correlation with P was calculated. During the estrous cycle obvious changes in thyroid hormones, GH and TSH occurred. However, this study shows no causal relationship between the thyroid and the gonadal axes.

Animals↗

PubMed1989

Effects of feather wear and temperature on prediction of food intake and residual food consumption.

Heat production, which accounts for 0.6 of gross energy intake, is insufficiently represented in predictions of food intake. Especially when heat production is elevated (for example by lower temperature or poor feathering) the classical predictions based on body weight, body-weight change and egg mass are inadequate. Heat production was reliably estimated as [35.5-environmental temperature (degree C)] x [Defeathering (=%IBPW) + 21]. Including this term (PHP: predicted heat production) in equations predicting food intake significantly increased accuracy of prediction, especially under suboptimal conditions. Within the range of body weights tested (from 1.6 kg in brown layers to 2.8 kg in dwarf broiler breeders), body weight as an independent variable contributed little to the prediction of food intake; especially within strains its effect was better included in the intercept. Significantly reduced absolute values of residual food consumption were obtained over a wide range of conditions by using predictions of food intake based on body-weight change, egg mass, predicted heat production (PHP) and an intercept, instead of body weight, body-weight change, egg mass and an intercept.

Animals↗

PubMed1989

Effect of plumage renewal after induced moulting on subsequent laying efficiency and persistence.

1. Brown egg layers and dwarf broiler breeder females were force-moulted by different diets. The relationship between the extent of feather replacement and subsequent laying performance was studied. Some brown hens were subjected to metabolic experiments in order to compare post-moult heat production in relation to moulting success. 2. The extent of moulting had a clear effect on the post-moult heat production, and the differences were still present after 6 months in the second year of laying. 3. The extent of feather renewal during moulting showed high and very significant rank correlations with efficiency of food utilisation during the subsequent laying cycle. These correlations were generally higher than those of other features of the moulting procedure (body-weight-loss, minimum weight, duration of pause in laying). 4. The long-term energetic implications of the extent of moulting play an important role in subsequent performances and the persistence of lay during the following year is related to the extent of feather replacement.

Animals↗

PubMed1989

Developmental changes in the corticosterone response to corticotrophin and in the adrenal corticosterone content of rapid and slow growing strains of chickens (Gallus domesticus).

1. The high sensitivity of the immature domestic fowl to corticotrophin (ACTH) has been confirmed. The minimal effective dose was age-dependent, and decreased from 2 IU/kg BW in 1-d-old chicks to 0.4 IU/kg BW in 12-d-old chicks. 2. Increasing doses of ACTH evoked similar maximal corticosterone responses but the time to return to basal values increased with increasing dose of ACTH in both a broiler and layer strain. 3. Maximal corticosterone responses to ACTH occurred earlier in hatched chicks compared with embryos, and were delayed in embryos and young chicks of the layer strain compared to those of the broiler strain. 4. Strain differences in basal concentrations of corticosterone as well as in the response to ACTH occurred at a time when there were differences in the corticosterone content of the adrenals.

Adrenal Glands↗

PubMed1988

Changes in progesterone metabolism in the chicken hypothalamus during induced egg laying stop and molting.

In the present study, we have established and validated a radioenzyme assay which permits us to quantify progesterone metabolism in the chicken brain. Progesterone metabolism was then studied in five brain areas obtained by microdissection from the telencephalon (part of the lobus paraolfactorius immediately rostral to the preoptic area), the preoptic area, and the hypothalamus. Three metabolites of progesterone were produced in large amounts in these brain regions and were quantified in this study: 5 beta-pregnane-3,20-dione (5 beta-DHP) as well as its metabolite 3 alpha-hydroxy-5 beta-pregnane-20-one (5 beta,3 alpha-ol) and 5 alpha-pregnane-3,20-dione (5 alpha-DHP). The unmetabolized progesterone was also recovered and quantified. The 5 beta-reduction of progesterone (production of 5 beta-DHP and 5 beta,3 alpha-ol) was very active but its 5 alpha-reduction (production of 5 alpha-DHP) was almost absent in the lobus paraolfactorius. An opposite pattern of metabolism was found in the preoptic area and the hypothalamus (higher 5 alpha- but lower 5 beta-reductase activity). The changes in progesterone metabolism in these brain areas were then studied in groups of hens submitted to induced egg laying stop and molting. A significant decrease in progesterone 5 alpha-reduction was found in the median hypothalamus of hens during the period of molt. Simultaneously, the experimental procedures induced significant decreases in the production of 5 beta-DHP by the lobus paraolfactorius, anterior, and medial hypothalamus but induced a significant increase in the production of this metabolite in the preoptic area. These changes are likely to be involved in the control of reproductive functions including sexual behavior and secretion of luteinizing hormone-releasing hormone, and a number of possible causal mechanisms are presented. These should now be tested experimentally especially in view of the very limited information which is now available on the biological effects of the metabolites of progesterone.

3-Hydroxysteroid Dehydrogenases↗

PubMed1988

Thyrotropic and peripheral activities of thyrotrophin and thyrotrophin-releasing hormone in the chick embryo and adult chicken.

The influence of an intravenous injection of thyrotrophin-releasing hormone (TRH) and bovine thyrotrophin (TSH) on circulating levels of thyroid hormones and the liver 5'-monodeiodination (5'-D) activity is studied in the chick embryo and the adult chicken. In the 18-day-old chick embryo, an injection of 1 microgram TRH and 0.01 I.U. TSH increase plasma concentrations of triiodothyronine (T3) and of thyroxine (T4). TRH, however, preferentially raises plasma levels of T3, resulting in an increased T3 to T4 ratio, whereas TSH preferentially increases T4, resulting in a decreased T3 to T4 ratio. The 5'-D-activity is also stimulated following TRH but not following TSH administration. The increase of reverse T3 (rT3) is much more pronounced following the administration of TSH. In adult chicken an injection of up to 20 micrograms of TRH never increased plasma concentrations of T4, but increases T3 at every dose used together with 5'-D at the 20 micrograms dose. TSH on the other hand never increased T3 or 5'-D, but elevates T4 consistently. It is concluded that TSH is mainly thyrotropic in the chick embryo or adult chicken whereas TRH is responsible for the peripheral conversion of T4 into T3 by stimulating the 5'-D-activity. The involvement of a TRH induced GH release in this peripheral activity is discussed.

Animals↗

PubMed1988

Thyroid hormone response to thyrotropin releasing hormone after cold treatment during pre- and postnatal development in the domestic fowl.

The purpose of the present study was to compare the effect of periodic cooling during the establishment of a functional pituitary-thyroid axis at days 11-14 of incubation and at other developmental stages, on the subsequent thyroid hormone response to thyrotropin releasing hormone (TRH). In the first and second experiment chick embryos were cooled for 6 hr/day to 30 degrees C from day 11 till 14 and from day 15 till 18 respectively, whereas control groups were incubated throughout at 37.8 degrees C. In both experiments the thyroxine (T4) response upon TRH in 19 day-old embryos was higher in the previously cold treated embryos, according to the percentages of increase. However, the higher T4 response in the cold treated animals disappeared in 1 or 7 day-old chicks hatched from the 2nd experiment, but remained present in chicks of the same ages in the 1st experiment. In a third experiment the T4 response to TRH injection immediately and 3 and 8 days after a temperature treatment (25 degrees C or 12 degrees C) for one week on four weeks old broiler chickens was found to be similar in both temperature groups. In all experiments there was a concomitant triiodothyronine (T3) increase after TRH injection, but differences between experimental groups were observed at days 15 and 19 of incubation and immediately after the postnatal temperature treatment. As an overall conclusion the results indicate that cold treatment only during the establishment of the hypothalamo-hypophysial control of thyroid function can have a long lasting effect by enhancing the T4 response to TRH injection.

Animals↗

PubMed1988

Role of ovarian steroids in the control of moult induction in laying fowls.

1. Thirty-five Warren SSL hens were selected on the basis of variation in moulting response following a force-moult at 81 weeks of age. Fourteen hens were from a group which returned to layers mash ad libitum from day 9, while 21 came from a group with dietary restriction prolonged to day 28. Blood samples were taken on days 23 and 36, and hormone concentrations were measured. Moulting was recorded on days 0, 11, 23, 36, 52 and 68. 2. Progesterone (P4) but not oestradiol (E2) inhibited moulting during egg laying and the sharp fall in P4 concentration when laying ceased was a primary factor in the induction of moulting. 3. Thyroxine (T4) concentrations were closely correlated with all criteria of plumage renewal, but not with the onset of moulting. Although T4 was closely correlated with subsequent feather growth it is questionable whether T4 is a primer of moult-induction independent of P4. 4. Feathers which were pulled out required 12 +/- 2 d to be replaced beyond the feather-papillae stage. For remiges this timing was similar regardless of whether hens were moulting or still laying. The timing was similar for remiges and body-feathers in moulting hens, but the reappearance of body-feathers in laying hens was slightly delayed.

Animals↗