Biomedical subjects

E Decuypere

Publications and source records attributed to E Decuypere.

At least 145 records · Page 8Linked to original sources

PubMed1996

Influence of feeding pattern on thyroid hormones in long-term food-restricted rats.

The effect of a long-term 50% food restriction on plasma thyroid hormone levels was studied in adult male rats, which received their reduced daily amount of food either as one meal or 5 different meals. Compared to controls, a long-term food restriction reduced total 24 h-mean plasma T4, T3 and TSH concentrations. The total T4 level was more reduced in rats fed their reduced ration in one meal than in rats given food in several meals. This resulted in a higher T3/T4 ratio in the former group of rats than in the other groups (free access to food; food in several meals). In the control group and in the food-restricted group receiving their food in one meal, significant diurnal variations in total T4, T3 and TSH levels were seen. The T3 rhythm was abolished in food-restricted rats receiving their food spread over several meals, but T4 and TSH rhythms were not. We conclude that total peripheral thyroid hormone levels infood-restricted rats are influenced, not only by the amount of food but also by the feeding pattern.

Animals↗

PubMed1996

Different characteristics in chick embryos of two broiler lines differing in susceptibility to ascites.

1. The relationship between the length of incubation, hatching, hypoxic condition, thyroid hormones and the occurrence of ascites were studied in embryos of 2 broiler lines differing in susceptibility to the ascites syndrome. 2. Both the time of external pipping (ep) and hatching of embryos from the ascites-resistant (AR) broiler line was earlier compared to the ascites-sensitive line (AS). The interval between internal pipping (ip) and ep was the same between the lines, but the interval between ep and hatching was shorter in the resistant line. 3. The T3 and T4 concentrations in plasma of the AS line were lower compared to the AR line. 4. Analyses of partial pressures of oxygen (pO2) and carbon dioxide (pCO2) in the air cell of the egg revealed that at day 18 the AS embryos had lower pO2 and higher pCO2 concentrations compared to the AR embryos. 5. The delay in hatching of the AS embryos might induce a more pronounced and/or extended hypoxic environment, thereby creating an environment that evokes ascites.

Animals↗

PubMed1996

Inhibin and activin have antagonistic paracrine effects on gonadal steroidogenesis during the development of the chicken embryo.

Primary cultures of gonadal cells from chicken embryos were used to explore the paracrine role of inhibin and activin during gonadal development. Fetal testicular and ovarian cells secreted high amounts of immunoactive inhibin. FSH caused a dose-related increase of cAMP and immunoactive inhibin concentrations in testicular cell cultures. Postreceptor signalling through the protein kinase A (PKA) pathway was confirmed by additional experiments with 8-bromo-cAMP, 3-isobutyl-1-methyl-xanthine (MIX), prostaglandins, forskolin, and choleratoxin. The relative ability of these agonists to stimulate cAMP production did not always correlate with their ability to stimulate inhibin secretion. Experiments with phorbol 12-myristate 13-acetate suggested that the regulation of immunoactive inhibin secretion also involves the protein kinase C (PKC) pathway. In addition, it was shown that recombinant human (rh)-inhibin increases the conversion of pregnenolone to androgens whereas rh-activin has the opposite effect. Recombinant human follistatin, an activin-binding protein, antagonized the actions of rh-activin and to a lesser extent those of rh-inhibin. In conclusion, these results show that during the development of the chicken embryo, gonadal inhibin secretion may be regulated by hormones and by local factors such as prostaglandins. Cross talk between the PKA and PKC pathways may be involved in this regulation. Recombinant human inhibin and rh-activin may have antagonistic roles in the paracrine control of gonadal steroidogenesis.

Activins↗

PubMed1996

Effect of recombinant human insulin-like growth factor-II on weight gain and body composition of broiler chickens.

Osmotic minipumps containing either saline or recombinant human insulin-like growth factor-II (IGF-II) were implanted into 4-wk-old female broiler chickens such that the treated chickens received 0.5 mg IGF-II/kg body weight per d. At the end of the trial, no differences in body weight gain or bone length were detected between the treated and control groups. Similarly, there were no differences between the two treatments with respect to heart, spleen, liver, or bursa of Fabricius weight. The relative weight of the abdominal fat pads was greater (P < 0.05) in the birds treated with IGF-II than in the controls, whereas the weight of breast muscle was reduced (P = 0.06) in the birds treated with IGF-II. There was no effect of IGF-II treatment on feed intake or feed conversion efficiency. Plasma growth hormone (GH) levels were acutely depressed by 15 min after IGF-II administration; and also after 2 wk of IGF-II treatment. Plasma triiodothyronine (T3) concentrations were significantly depressed by IGF-II treatment. These results suggest that IGF-II may not stimulate growth in chickens, but can act as a nutrient partitioning agent, either directly or indirectly through altering plasma GH or T3 concentrations.

Adipose Tissue↗

PubMed1996

The use of intermittent lighting in broiler raising. 1. Effect on broiler performance and efficiency of nitrogen retention.

The purpose of the present experiments was to compare the effects of the intermittent lighting schedule (IL) consisting of repeated cycles of 1 h light (L):3 h darkness (D) with a nearly continuous lighting schedule 23L:1D (CL) on the performance of floor-reared male and female broiler chickens. In addition, N balance trials were performed on caged broilers in order to assess their efficiency of dietary N retention. Changing from CL to IL at Day 7 was followed by a temporary reduction in feed intake and BW gain. However, IL males exhibited compensatory growth during the finisher period in such a way that at Day 41 (market age), a similar BW as that of their CL counterparts was attained. In contrast, IL females did not completely attain a BW equal to that of CL females by 41 d of age. Imposing IL reduced feed intake and improved feed conversion. Abdominal fat pad contents of broilers reared under IL were significantly smaller than those of CL broilers. From the N balance trials, it can be inferred that broilers reared under IL have an improved efficiency of dietary N retention, especially during the period of increased growth velocity. Imposing IL at Day 7 is associated with a temporary reduction in BW gain, followed by complete growth compensation of males by Day 41. Female broilers did not restore BW by this age. As a consequence of the altered growth trajectory, the manifestation of the fat growth wave is shifted to an older age together with an enhanced efficiency of N retention.

Adipose Tissue↗

PubMed1996

The use of intermittent lighting in broiler raising. 2. Effects on the somatotrophic and thyroid axes and on plasma testosterone levels.

Male and female broiler chicks were raised separately in nearly continuous lighting [23 h light (L):1 h dark (D), CL] and consumed feed ad libitum. At 7 d of age, the intermittent lighting schedule (1L:3D, IL) was imposed on half of the chicks, whereas the other chicks remained under CL. In addition to performance characteristics, several parameters of the somatotrophic and thyrotrophic axes were studied together with plasma concentrations of testosterone. Males had a higher growth rate than females regardless of the imposed lighting schedule and this pronounced growth difference is reflected by higher plasma concentrations of growth hormone (GH), and a better GH receptor occupancy. Differences in growth rate between sexes could not be attributed to differences in circulating 3,3',5-triiodothyronine (T3) levels or to hepatic deiodination activities. However, from 3 wk of age onwards, males had significantly higher plasma testosterone levels than females. Plasma GH and T3 levels decreased whereas plasma insulin-like growth factor-I and thyroxine levels increased with age in all experimental groups. The age-related decline in plasma GH levels were less pronounced for males than for females. No major changes in other hormonal parameters or deiodination activities could be observed as a result of imposing IL, except for the higher plasma GH levels of IL chickens, and for plasma testosterone concentrations in IL males at Day 41, which were twice the levels found in their CL counterparts. These results therefore suggest that the somatotrophic axis as well as circulating testosterone levels mediate the sex-related differences in growth rate and the compensatory growth as present in males.

Age Factors↗

PubMed1995

Gonadotrophin-regulated production of immunoactive inhibin and androgen by cultured testicular cells from chicken embryos.

To study the potential intragonadal role of inhibin and inhibin-related proteins in the developing gonad, a method was developed to culture testicular cells of chicken embryos. A single-step collagenase/DNase digestion was used to disperse the cells. Except for the primordial germ cells and the erythrocytes, the cells attached well to plastic culture dishes. Moreover, they could easily be grown in the absence of serum or other additives. Inhibin secretion was measured using a heterologous radioimmunoassay validated for use in this species. The fetal testicular cells secreted high amounts of immunoactive inhibin and remained responsive to gonadotrophins. Two different cell populations could be recognized in monolayers of testicular cells: the first population had a fibroblast-like stromal appearance, resembling interstitial cells; the second had an epitheloid appearance and contained large numbers of refractile vacuoles, resembling Sertoli cells. Both cell populations were enriched using a Percoll density gradient. The epitheloid cells displayed a higher capacity to secrete immunoactive inhibin, while the stromal cells were responsible for the bulk of androgen secretion. FSH, but also LH, stimulated inhibin secretion in the epitheloid cells. Although ovine LH was the most potent stimulus for androgen secretion by the stromal cells, ovine FSH was also capable of increasing androgen output in stromal cells and to a lesser extent in epitheloid cells. As the two enriched cell populations were still contaminated by other cell types, this may indicate, as in other species, that FSH-induced paracrine factors are involved in the regulation of androgen secretion in the developing gonad.(ABSTRACT TRUNCATED AT 250 WORDS)

Androgens↗

PubMed1995

Partial food restriction increases hepatic inner ring deiodinating activity in the chicken and the rat.

The effects of a long term partial food restriction were studied in chickens and rats. In chickens the treatment resulted in increased plasma T4 levels while T4 levels in rats remained unchanged. Plasma T3 decreased in both species. In vitro hepatic outer ring deiodinating type I (ORD-I) activity was not influenced by the food restriction, suggesting that the amount of ORD-I enzyme present in the liver remained unchanged. In vitro hepatic inner ring deiodinating type III activity, on the contrary, was greatly increased in both species. This increase may contribute to the decreased circulating T3 levels by increasing the degradation of T3 and diverting the deiodination of T4 to rT3 instead of to T3.

Animals↗

PubMed1995

Passive immunization of insulin-like growth factor (IGF)-1 and of IGF-1 and IGF-2 in chickens.

The effects of passive immunization against IGF-1 either alone, or together with immunization against IGF-2, on growth and metabolism were examined in chickens. Immunization against IGF-1 alone had no effect upon any aspect of growth, carcass composition, efficiency of energy utilization or hormone concentrations studied. Immunization against both IGF-1 and IGF-2 together resulted in a lighter final body weight (P < 0.05) compared with controls. Immunization against both IGFs together decreased abdominal fat content (P < 0.05) and resulted in a heavier mean spleen weight (P < 0.01). The joint immunization was also associated with elevated plasma T3 concentrations. These data may indicate a role for IGF-2, but not for IGF-1, in fat metabolism in chickens.

Adipose Tissue↗

PubMed1995

Influence of long-term simmondsin administration on thyroid hormone levels in adult rats.

Treatment of adult rats for 28 days with 0.50% of simmondsin induced a reduction of food intake of about 40%. The degree of emaciation was the same in simmondsin treated rats (SM) and pair-fed controls (PF). Diurnal variation of plasma thyroid hormone concentrations was determined. The reduction in food intake induced a decrease of mean 24 h plasma T3, T4 and TSH concentrations. Plasma T4 concentrations were decreased more in SM than in PF at almost all times of the day. No difference was seen between SM and PF for plasma T3 and TSH concentrations. Liver outer ring deiodinating activity (type I) remained unchanged compared to controls in PF and SM, but liver inner ring deiodinating activity (type III) was increased 4 fold in both SM and PF. It was concluded that the food intake reduction induced by simmondsin produced a decrease in plasma TSH concentrations which in turn reduced plasma T4 concentrations. Decreased plasma T4 concentrations together with an increased degradation of plasma T3 resulted in lower plasma T3 concentrations.

Acetonitriles↗

PubMed1995

Effect of progressive fasting on physiological criteria of adult Warren SSL hens.

The present study examined the effects of 3 days and 7 days of feed deprivation-as used in artificial moulting programs -on several metabolic criteria in adult Warren SSL hens. Body weight decreased gradually during the fasting period. Abdominal fat pad content decreased only during the first 3 days of fasting and no further during the following 4 days of feed deprivation. The fasting-induced changes in plasma glycerol and uric acid levels confirmed these proportional changes in body composition. In both fed and prolonged fasting (7 days) conditions, glucagon stimulated the in vitro lipolytic activity of abdominal adipose tissue explants. Chicken growth hormone stimulated the in vitro lipolytic activity of adipose tissue from fed but not from hens fasted for 7 days. The relationship between these physiological changes during progressive fasting in the adult hen and energetic and amino acid requirements is discussed.

Adipose Tissue↗

PubMed1995

Developmental changes in immunoreactive inhibin and FSH in plasma of chickens from hatch to sexual maturity.

1. The relationship between immunoreactive inhibin and follicle-stimulating hormone (FSH) was studied in male and female chickens from hatch to sexual maturity. Plasma inhibin was estimated by a heterologous radioimmunoassay validated for use in the chicken. FSH was measured by a recently developed homologous radioimmunoassay. 2. In a cross-sectional study, blood samples and gonads were collected from chickens of both sexes at 1, 3, 5, 7, 14, 21 and 28 d after hatching and subsequently at 14-day intervals until 182 d of age. 3. In the female, plasma progesterone concentration (P4) progressively increased during sexual development. The plasma luteinising hormone (LH) concentration rose during the first week after hatching, and fluctuated thereafter, with troughs at 6 and 14 weeks and peaks at weeks 10 and 18. The plasma inhibin and FSH concentrations remained low until the start of puberty and increased simultaneously thereafter. However, from week 18 on, plasma inhibin continued to rise while plasma FSH fell. Hence, FSH and inhibin were positively correlated before puberty, but developed a negative correlation during sexual maturation. 4. In the male, plasma testosterone and LH concentrations increased 38- and 3.7-fold respectively over the period studied. Inhibin and FSH followed similar time courses and were consequently positively correlated. 5. These results suggest sex differences in the role of inhibin in regulating FSH secretion during development. The FSH-inhibin feedback loop may become operational at the onset of sexual maturity in the hens. In male chickens, the similar pattern of inhibin and FSH secretion suggests that inhibin secretion is driven by FSH.

Aging↗

PubMed1995

Characterization of growth hormone gene expression in the pituitary and plasma growth hormone concentrations during posthatch development in the chicken.

In this study both sexes of two strains of chicken with genetically different growth potentials (broiler- and laying-type) were used to investigate growth hormone (GH) gene expression during posthatch development from day 7 (D7) to D56 by using the in situ hybridization technique and Northern analysis. In pituitaries of both strains a high GH mRNA signal was found as early as D7 by in situ hybridization, showing clear differences in the pattern of gene expression between the two strains. By Northern hybridization sex differences were detectable in all age groups of broilers, with higher levels throughout in males. In layers, however, females showed consistently higher levels compared with males until D21. While signal intensities decreased in the broiler strain during the investigation period, the layer-type strain seemed to express GH mRNA more continuously, reaching significantly (P < 0.01) higher GH mRNA levels than broilers at D56. Plasma GH concentrations ran parallel to GH mRNA in early stages but showed a peak earlier at D14 and decreased after D35 in both sexes and strains. Determination of growth as weekly weight gains, however, proved that a period of rapid growth (at a higher level in both sexes of the broiler strain) at D7 was followed by a strong decrease from D14 to D21. A plateau of constant growth was reached until the end of the observation period with similar rates in both strains and sexes. Analysis of plasma thyroid hormones tri-iodothyronine/thyroxine (T3/T4) showed an increase in T3 concentrations in both strains and sexes in early stages and a decrease thereafter. No clear strain differences were measured. T4 plasma concentrations increased from D7 to D14 in broilers and D21 in layers when a plateau was reached. From the results we conclude that generally there is a good correlation between GH mRNA and plasma GH concentrations in both strains investigated. Neither parameter, however, is coupled directly with the growth rate. Thus the early rapid growth corresponds to relatively low levels of GH mRNA and plasma GH concentrations, but high T3 levels. Later, decreased growth rates are linked to increasing amounts of GH mRNA as well as increasing plasma GH concentrations in both layers and broilers. Towards the end of the observation period there was a strain divergence visible with increased amounts of GH mRNA in layers but a strong reduction in broilers. Moreover, plasma GH concentrations decreased more slowly in layers than in broilers.

Animals↗

PubMed1995

Devazepide reverses the anorexic effect of simmondsin in the rat.

Simmondsin, a glycoside extracted from jojoba meal (Simmondsia chinensis), causes a reduction in food intake after oral administration. To investigate the mechanism by which simmondsin reduces food intake, fasted and free-feeding rats were given simmondsin-supplemented food and simultaneously injected with devazepide, a specific antagonist of peripheral-type cholecystokinin receptors (CCKA receptors). In free-feeding rats, supplementation of food with 0.5% simmondsin caused a reduction in food intake of +/- 40% in the period of 4 h following food presentation. Intraperitoneal injection of 100 micrograms devazepide/kg body weight prevented this effect. In rats fasted for 20 h, the food intake in the 30 min after presentation of food supplemented with 0.15% or 0.50% simmondsin was reduced in a dose-related manner; this was also inhibited by simultaneous application of devazepide. It is suggested that peripheral CCKA receptors are involved in the effect of simmondsin on food intake. However, a direct effect of simmondsin on CCKA receptors has been excluded, since simmondsin was unable to cause contraction of the guinea-pig gallbladder in vitro.

Acetonitriles↗

PubMed1994

Extraction and liquid chromatographic method for the determination of simmondsin in plasma.

A solid-phase method for the extraction of simmondsin from plasma was developed along with a liquid chromatographic method for the quantitative measurement of this compound. The extraction of simmondsin is realised with activated carbon. Chromatography is performed on a 25 x 0.46 cm I.D. RP-18, 5-micron HPLC column with a water-methanol (85:15, v/v) mobile phase and ultraviolet absorbance detection at 217 nm. The limit of detection is 100 ng (using 1 ml of plasma). The linear quantitation range is 0.1-200 micrograms/ml.

Acetonitriles↗

PubMed1994

Growth hormone secretory characteristics of sex-linked dwarf and normal-sized chickens reared on a control or on a 3,3',5-triiodothyronine-supplemented diet.

This study examined the pulsatile presence of growth hormone (GH) in the plasma--which reflects its pulsatile release--of 8-week-old male sex-linked dwarf (dwdw) or normal-sized (Dwdw) chickens from a brown-egg layer strain reared on a control or on a 0.5 ppm triiodothyronine(T3)-supplemented diet. The overall GH mean, amplitude, and baseline levels of control dw chickens were significantly higher than those of control Dw chickens. No differences in peak length or peak frequency between genotypes were observed. Dietary T3 supplementation abolished the pulsatile GH release in both genotypes. T3 treatment depressed the mean GH levels of Dw but not of dw chickens.

Animals↗

PubMed1994

Changes of immunoreactive inhibin, follicle-stimulating hormone, luteinizing hormone, and progesterone in plasma after short-term food deprivation and during the ovulatory cycle of the domestic hen.

The interrelationship between immunoreactive inhibin and follicle-stimulating hormone (FSH) was measured in laying hens after short-term food deprivation and during the ovulatory cycle. Plasma inhibin was estimated by a heterologous radioimmunoassay validated for use in chicken. FSH was measured by a recently developed homologous radioimmunoassay. Ten hens were deprived of food for 10 days (a method to induce artificial moult or to stop egg laying). Blood samples were taken daily via the brachial vein for 10 consecutive days starting on the day of food withdrawal. The data are expressed in relation to the last day of oviposition. Short-term food deprivation, followed by ovarian atrophy, significantly depressed the plasma inhibin and progesterone (P4) concentration. Plasma FSH concentrations significantly increased, while luteinizing hormone (LH) concentrations slightly but not significantly decreased. In another experiment, 6 hens were induced to moult. The control hens (n = 6) were fed ad libitum. On Day 17, the hens were killed and follicular distribution was studied. The atrophy of the large yolky follicles in restricted hens was associated with a significant increase in the number of white follicles. In a third experiment, serial blood samples were taken from hens (n = 15) at 2-hr intervals for 36 hr via a brachial cannula. Plasma immunoreactive inhibin and FSH concentrations did not vary during the ovulatory cycle. LH and P4 increased simultaneously from basal levels to preovulatory peak values 6 hr before ovulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1994

The effect of environmental temperature on episodic growth hormone release of meat-type chickens selected for 6 week body weight or for improved feed efficiency between 3 and 6 weeks of age.

The effect of a high (33 degrees C) compared to a normal (23 degrees C) ambient temperature on the pulsatile release of growth hormone (GH) has been studied in 4-week-old, cannulated male meat-type chickens selected for high body weight (GL line) or for improved feed efficiency (FC line). When reared in the normal temperature environment, overall circulating mean and amplitude GH values of FC chickens were significantly higher than those of GL chickens. There were no differences in GH pulse length or frequency between genotypes. The high rearing temperature completely abolished the pulsatility of GH in the plasma in both lines, but without affecting overall mean GH levels.

Aging↗