Search PubMed⌕ Search

Biomedical subjects

E Decuypere

Publications and source records attributed to E Decuypere.

At least 91 records · Page 5Linked to original sources
PubMed2000

Pre-ovulatory follicular characteristics and ovulation rates in different breed crosses, carriers or non-carriers of the Booroola or Cambridge fecundity gene.

Terminal follicular dynamics and ovulation rates (OR) were compared in different local breeds after introducing fecundity genes of different origin. Crossbred ewes which were carriers (F+) or non-carriers (++) of Booroola (BFec) or Cambridge genes (CFec) were included: CambridgexCambridge (CC), CambridgexSuffolk (CS), CambridgexTexel (CT), BooroolaxTexel (BT) and BooroolaxGerman Mutton Merino (BGM). The numbers of small (diameter 2-3.5 mm), medium (diameter >3.5-5.0 mm) and large (diameter >5.0 mm) growing follicles, the maximum diameter before ovulation and the regression and artesia rates of ovarian follicles >/=2 mm in diameter were studied laparoscopically and repeatedly during the last 5 days of an induced oestrous cycle. The ORs were determined one cycle before and two cycles after the repeated laparoscopy. BFec and CFec significantly enhanced the OR of all crossbreeds. Carriers of BFec or CFec did not have significantly different ORs due to any crossbreeding effect. The same observation was made for non-carriers of both Fec gene types. Whatever the crossbreed, the number of small, medium and large growing follicles were similar between carriers and non-carriers in spite of a higher number of ovulating follicles in carriers of both Fec gene types. The diameter of ovulatory follicles did not differ among crossbreds, or between carriers and non-carriers except in the BT (5.2+/-0.2 vs. 6.5+/-0.8 mm, respectively) and CC (6.6+/-0.2 vs. 5.6+/-0.3 mm) ewes.The higher OR in the presence of the Booroola gene was associated with a low atresia rate of large follicles in all crossbreeds (BT: 52+/-8% (F+) vs. 61+/-7% (++); BGM: 51+/-6% vs. 75+/-5%). The high OR of the carriers of the CFec gene seemed to be associated with a lower number of large growing follicles with a lower (P<0.05) atresia rate as compared with Booroola crossbreeds. In conclusion, follicular features were similar between purebred Cambridge and its crossbred CS and CT. In ewes carrying the BFec or CFec gene, the reduction in follicular atresia seemed to be one of the main follicular features implicated in the higher OR.

Animals↗
PubMed2000

The vagus nerve is involved in the anorexigenic effect of simmondsin in the rat.

Simmondsin, 2-(cyanomethylene)-3 hydroxy 4,5 dimethoxy cyclohexyl beta-D-glucoside, from jojoba meal reduces food intake in rats. We investigated the mechanism of action simmondsin, by studying the effects of fasting or of vagotomy on the food intake reduction. The food intake reduction was significantly less in fasted rats than in non-fasted rats. The reduction of food intake was also significantly diminished after vagotomy. The results of the present experiments suggest that simmondsin reduces intake of food in rats through the augmentation of satiety, in part vagally mediated.

Acetonitriles↗
PubMed2000

Complementary DNA cloning and ontogenic expression of pituitary-specific transcription factor of chickens (Gallus domesticus) from the pituitary gland.

Pit-1 is a pituitary-specific POU-domain DNA binding factor, which binds to and transactivates promoters of growth hormone (GH)-, prolactin (PRL)-, and thyroid-stimulating hormone-beta (TSHbeta)-encoding genes. Pit-1 has been identified in several mammalian species. In birds, it has been identified only in the turkey and chicken pituitary. Several (gg) Pit-1 cDNA sequences have been identified in the anterior pituitary of the chicken (Gallus domesticus). As in turkey, three different transcripts (ggPit-1*, ggPit-1beta*, and ggPit-1W*) of the Pit-1 gene were identified. This suggests that the chicken pituitary expresses more variants than reported earlier. Previous studies have concentrated on expressions during posthatch life of the turkey and chicken. The present study has determined the ontogeny of Pit-1 during the embryonic life of the chicken (day 1-day 21 of incubation). The mRNA for Pit-1 was first detected in the pituitary on day 5 of embryonic life. The expression of the mRNA was maintained until hatch. The presence of Pit-1 at this stage of embryonic development suggests that Pit-1 may be physiologically important during embryonic development of birds, as it precedes the gene expression and secretion of GH, PRL, and TSHbeta. A similar sequence for the expression of Pit-1 relative to GH and PRL during embryonic/fetal development has been reported for rodents.

Amino Acid Sequence↗
PubMed2000

A chicken leptin-specific radioimmunoassay.

Recombinant chicken leptin was used to produce an antiserum in order to develop a specific and sensitive radioimmunoassay (RIA) for chicken leptin in plasma and serum. We have used either murine or chicken leptin as tracer and competition curves were performed using recombinant chicken leptin. Variations in leptin plasma levels in different chicken strains and various nutritional states were correlated with the physiological status. Leptin plasma concentrations were regulated by the nutritional state with higher levels in the fed state as compared to the fasted state (3.36 +/- 0. 13 versus 2.78 +/- 0.11 ng/ml) and being dependent upon the age. Higher leptin levels were found in 22 week-old as compared to 15 week-old layer chickens (2.709 +/- 0.172 versus 1.478 +/- 0.102 ng/ml). We have also shown that the multispecies leptin RIA kit (LINCO Inc.) underestimated leptinemia compared to the chicken leptin- specific RIA reported here. In conclusion the RIA developed in the present study is specific to the chicken and thus may be considered as powerful tool for investigating the physiological significance of leptin in chickens.

Animals↗
PubMed2000

Food deprivation and feeding of broiler chickens is associated with rapid and interdependent changes in the somatotrophic and thyrotrophic axes.

1. In several experiments, hormonal changes in the somatotrophic axis, growth hormone (GH) sensitivity to a GH-secretagogue, thyroid hormones and their metabolising enzymes and plasma glucose levels were measured in relation to food deprivation and reinitiation after a single daily meal in 4- to 5-week-old male broiler chickens. 2. Floor-reared male broiler chickens were fed ad libitum or were restricted to a daily food intake of 40 or 45 g per d from the age of 2 weeks onwards. The daily food allowance was consumed in 0.5 h. 3. Food deprivation increased plasma GH concentrations but decreased GH-dependent variables such as plasma insulin-like growth factor-I and 3,3',5-triiodothyronine (T3) concentrations. Hepatic inner ring deiodinating type III activity was markedly elevated, presumably as a consequence of low hepatic GH receptor numbers, and is thought to be the causal mechanism for the low plasma T3 concentrations. Food intake reversed these variables in a time-related manner. 4. GH pulsatility characteristics, as calculated by deconvolution analysis, revealed profound changes between food restricted and ad libitum fed animals. Chickens deprived of food for about 23.5 h were characterised by an enhanced pulsatile GH release as reflected in the higher GH secretory burst amplitude, GH mass per burst, GH production rate and GH pulse frequency. These variables returned very quickly to normal values after refeeding. 5. In summary these experiments taken together demonstrate very clearly the interdependent and time-related changes of the somatotrophic and thyroid axes upon a single meal in previously food-deprived broiler chickens.

Animals↗
PubMed2000

Early and temporary quantitative food restriction of broiler chickens. 2. Effects on allometric growth and growth hormone secretion.

1. An experiment was conducted with male broiler chickens to investigate the effect of different early food restriction programmes on proportional weights and allometric growth coefficients of carcase parts and on pulsatile growth hormone secretion. 2. At 4 d of age the animals were restricted to 80% or 90% of the ad libitum intake for 4 d or 80% for 8 d. When the restriction was finished, all birds received ad libitum food again. 3. On d 1, 8, 11, 14, 21, 28, 35 and 42, from each group 8 birds were weighed, stunned and killed and the weights of the stomachs, liver, heart, sternum, right thigh, right drumstick, breast and abdominal fat pad were determined. On d 29, 30, 31, 32 serial blood samples of 2 birds from each group were taken to determine the plasma growth hormone (GH) content. 4. Only the most severe restriction resulted in a tendency for the stomachs to mature earlier and the thighs to mature later. No other significant effect on the allometric coefficients could be observed. 5. It is concluded that during the restriction the birds give priority to the development of the supply organs such as the stomach, which are more important during early development at the expense of the demand tissues like breast and thigh. 6. No significant differences concerning the GH secretory parameters could be observed.

Animals↗
PubMed2000

Early and temporary quantitative food restriction of broiler chickens. 1. Effects on performance characteristics, mortality and meat quality.

1. An experiment was conducted with broiler chickens to determine the effects of different early food restrictions, strain (Ross 508 and Hybro G) and sex on performance, mortality carcase composition and meat characteristics. 2. Birds were restricted to 80% or 90% of ad libitum intake for 4 d (80%-4 d-group and 90%-4 d-group, respectively) or 80% for 8 d (80%-8 d-group). All restrictions started on d 4. After the periods of restriction, all birds were fed ad libitum. 3. Only the 90%-4 d-group reached a final body weight not significantly different from, but lower than, the ad libitum group. The other restrictions were too severe to allow a sufficient 'catch-up'. 4. No significant differences in food conversion and total carcase fat content between groups were observed. Abdominal fat showed a tendency to increase due to the restrictions induced. 5. There was a slight trend towards a reduced mortality and of 'sudden death syndrome' but no clear effect of food restriction on number of chickens removed with leg problems. There was no significant decrease in uniformity of the flocks due to restriction. 6. The group 80%-8 d had a significant lower yield percentage. Cut-up parts and meat quality were not changed by restriction. Ross birds had a significantly higher proportion of breast meat than Hybro chickens. Meat of female chickens seemed to be paler than that of males, possibly because of the higher proportion of carcase fat. 7. Food restriction did not always give good results. However, a mild restriction (90% for 4 d) may offer some economic advantages over an ad libitum feeding regimen, mainly by reducing mortality.

Adipose Tissue↗
PubMed2000

Modelling the static and dynamic responses of total heat production of broiler chickens to step changes in air temperature and light intensity.

1. The objective of this work was to explore the possibilities of modelling the static and dynamic responses of total heat production of broiler chickens to step changes in temperature and light intensity (light-dark alterations) using compact dynamic model structures. 2. Seventy-seven experiments were performed in an open-circuit respiration chamber to measure the dynamic response of heat production to step variations in temperature and light (on/off). The animal responses were modelled using transfer function model structures. 3. It was demonstrated that the complex process of the dynamic response of heat production of broiler chickens to step changes in air temperature and light-dark alterations can be modelled assuming 1st order dynamics. The coefficient of determination between measured and simulated heat production was on average 0.83 for responses to air temperature and 0.93 for responses to light-dark alterations.

Animals↗
PubMed2000

Altered chicken thyroid hormone metabolism with chronic GH enhancement in vivo: consequences for skeletal muscle growth.

In contrast to most vertebrates, GH reportedly has no effect upon somatic growth of the chicken. However, previous studies employed only one to two dosages of the hormone, and limited evidence exists of a hyperthyroid response that may confound its anabolic potential. This study evaluated the effects of 0, 10, 50, 100 and 200 microgram/kg body weight per day chicken GH (cGH) (0-200 GH) infused i.v. for 7 days in a pulsatile pattern to immature, growing broiler chickens (9-10 birds/dosage). Comprehensive profiles of thyroid hormone metabolism and measures of somatic growth were obtained. Overall (average) body weight gain was reduced 25% by GH, with a curvilinear, dose-dependent decrease in skeletal (breast) muscle mass that was maximal (12%) at 100 GH. This profile mirrored GH dose-dependent decreases in hepatic type III deiodinase (DIII) activity and increases in plasma tri-iodothyronine (T(3)), with bot! h also maximal (74 and 108% respectively) at 100 GH. No effect on type I deiodinase was observed. At the maximally effective dosage, hepatic DIII gene expression was reduced 44% versus controls. Despite dose-dependent, fold-increases in hepatic IGF-I protein content, circulating IGF-I was not altered with GH infusion, suggesting impairment of hepatic IGF-I release. Significant, GH dose-dependent increases in plasma non-esterified fatty acid and glucose, and overall decreases in triacylglycerides were also observed. At 200 GH, feed intake was significantly reduced (19%; P<0.05) versus controls; however, additional control birds pair-fed to this level did not exhibit any responses observed for GH-treated birds. The results of this study support a pathway by which GH impacts on thyroid hormone metabolism beginning at a pretranslational level, with reduced hepatic DIII gene expression, translating to reduced protein (enzyme) ex! pression, and reflected in a reduced level of peripheral T(3)-degrading activity. This contributes to decreased conversion of T(3) to its inactive form, thereby elevating circulating T(3) levels. The hyper-T(3) state leads to reduced net skeletal muscle deposition, and may impair release of GH-enhanced, hepatic IGF-I. In conclusion, GH has significant biological effects in the chicken, but profound metabolic actions predominate that may confound positive, IGF-I-mediated skeletal muscle growth.

Adipose Tissue↗
PubMed2000

Circulating concentrations of inhibin-related proteins during the ovulatory cycle of the domestic fowl (Gallus domesticus) and after induced cessation of egg laying.

Circulating inhibin A, inhibin B, activin A, total immunoreactive inhibin alpha-subunit (ir-alpha inhibin), LH, FSH and progesterone concentrations were measured throughout the normal ovulatory cycle and after cessation of egg laying induced by feed restriction to investigate the potential involvement of inhibins and activins in the ovulatory cycle of the domestic hen. Plasma inhibin A varied significantly (P < 0.05) during the ovulatory cycle; the concentration was highest at the preovulatory LH surge and reached a nadir 10 h later, at about the time the F(2) follicle makes the transition to become the new F(1) follicle. Plasma FSH concentrations did not change significantly throughout the cycle and showed no correlation with inhibin A. Total ir-alpha inhibin concentrations were much higher than those of inhibin A at all stages of the ovulatory cycle and showed no correlation with inhibin A or FSH. Plasma concentrations of inhibin B and of activin A were below the detection limit of the assays in all plasma samples analysed. In the feed restriction study, plasma inhibin A and total ir-alpha inhibin showed little change until the last day of oviposition (day 0) after which they fell significantly (P < 0.05) and remained low to the end of the experiment (approximately 70-78% decrease relative to day -4). Conversely, plasma FSH increased after cessation of laying and was significantly higher (P < 0.05) from day 3 to the end of the study (approximately 50% increase on day 6 relative to day -4). Plasma FSH values were negatively correlated with inhibin A (r = -0.39; P < 0.005) and total ir-alpha inhibin (r = -0.36; P < 0.005). Plasma LH and progesterone also decreased (P < 0.05) during feed restriction. The decrease in LH preceded the terminal oviposition and the associated fall in inhibin A by 2 days; there was a positive correlation between LH and inhibin A (r = 0.35; P < 0.005). Taken together these findings support (i) a role for LH in promoting inhibin A secretion by preovulatory follicles and (ii) an endocrine role for inhibin A secreted by preovulatory follicles in the maintenance of tonic FSH secretion in laying hens.

Activins↗
PubMed2000

Effect of TNF-alpha on LH and IGF-I modulated chicken granulosa cell proliferation and progesterone production during follicular development.

This study demonstrates the effects of recombinant human tumour necrosis factor a (rhTNF-alpha) and conditioned medium of the HD11-transformed chicken macrophage cell line on cultured chicken granulosa cells. Effects were studied on basal, IGF-I- and LH-stimulated progesterone production and cell proliferation. Recombinant human TNF-alpha stimulated basal progesterone production in a dose-dependent manner in the granulosa cells of the largest follicle but had no effect on cells from the third largest follicle. TNF-alpha stimulated and sometimes inhibited progesterone production stimulated by IGF-I and LH alone or in combination depending on the size of the follicle and the concentration of LH or IGF-I applied. However, the inhibitory effect of TNF-alpha was significantly more pronounced in cells from the third largest follicle when high concentrations of IGF-I, LH or a combination of both were applied. TNF-alpha had no effect on basal cell proliferation in both the largest and the third largest follicles, but regulated responses to IGF-I and a combination IGF-I and LH in the cells of the third largest follicle but not those of the largest follicle. The data indicate that the normal hierarchy of follicles is maintained in the chicken ovary through the regulation of the activity of IGF-I and its interaction with LH. Conditioned medium of LPS-activated HD11 macrophages mimicked the effects of TNF-alpha and its interaction with IGF-I and LH on progesterone production and cell proliferation. The observation that the HD11-conditioned medium contained TNF-alpha indicates that TNF-alpha produced by macrophages found in chicken follicles modulates granulosa cell growth and differentiation.

Analysis of Variance↗
PubMed1999

Isolation of plasma membranes and Golgi apparatus from a single chicken liver homogenate.

Chicken liver plasma membranes, minimally contaminated with Golgi apparatus-derived vesicles, were prepared from a low-speed (400 g) pellet by means of flotation in isotonic Percoll solution, followed by a hypotonic wash and flotation in a discontinuous sucrose gradient. Based on the analysis of suitable marker enzymes, alkaline phosphatase and alkaline phosphodiesterase, two plasma membrane fractions were isolated with enrichments, depending on the equilibrium density and marker of 28-97 and with a total yield of 4-5%. Golgi apparatus fractions were prepared by flotation of microsomes, obtained from the same homogenate as the low-speed pellet, in a discontinuous sucrose gradient. The trans-Golgi marker galactosyltransferase was 27-fold enriched in a fraction of intermediate density (d=1.077-1.116 g/ml). Approximately 12% of galactosyltransferase was recovered in the membranes equilibrating d=1.031-1.148 g/ml. Contamination with plasma membrane fragments was low in the light (d=1.031-1.077 g/ml) and intermediate density Golgi vesicles. The isolation of purified plasma membranes and Golgi vesicles from one liver homogenate will enable future studies on receptor cycling between these cell organelles.

Alkaline Phosphatase↗
PubMed1999

Acute pretranslational regulation of type III iodothyronine deiodinase by growth hormone and dexamethasone in chicken embryos.

Both growth hormone (GH) and glucocorticoids are regulators of thyroid hormone metabolism in vertebrates. Studies on chicken embryos demonstrated that intravenous (i.v.) injection of chicken GH or glucocorticoids results in increased plasma 3,3',5-triiodothyronine (T3) concentrations, and this through a reduction of hepatic type III iodothyronine deiodinase (D3) activity. The recent cloning of chicken type I iodothyronine deiodinase (D1) and D3 offers the tools to investigate at what level (pre- or posttranslational) this downregulation of D3 occurs. Eighteen day old chicken embryos were injected with either 0.9% NaCl (control), 50 microg dexamethasone (DEX), or 20 microg cGH per animal. Plasma and tissue samples were taken 5, 10, 30, 60, 120, and 240 min post-injection. Plasma T3 and thyroxine (T4) were determined as well as in vitro hepatic D1 and D3 activities. Hepatic D1 and D3 mRNA levels were measured by both Northern analysis and competitive reverse transcription polymerase chain reaction (RT-PCR). Injection of GH or DEX resulted in a significant increase in plasma T3 when compared to controls within 30 min post-injection. This increase remained until the end of the experiment in the DEX-treated group, but not in the GH group. GH administration had no influence on plasma T4 levels, whereas DEX significantly reduced plasma T4 from 30 min onwards. Hepatic D1 activity and D1 mRNA levels showed no changes. Hepatic D3 activity, however, decreased within 10 min after DEX administration and somewhat slower after GH administration (within 30 min). Hepatic D3 activity remained low for the remainder of the experiment in the DEX-treated group, whereas D3 activity gradually returned to control levels in the GH group. This change in hepatic D3 activity was paralleled by the changes in hepatic D3 mRNA levels (r = 0.88, P = 0.0001) as confirmed by both Northern analysis and competitive RT-PCR. In conclusion, these results demonstrate that in embryonic chicken GH and DEX acutely increase plasma T3 levels by decreasing hepatic D3 activity, a decrease that seems to be regulated predominantly at the pretranslational level. These results are also an indication for the short half life (t(1/2)) of the D3 enzyme. The time lag between the effect of GH and DEX on hepatic D3 mRNA may be due to differences in the mechanism of action between both hormones, a subject that needs further investigation.

Animals↗
PubMed1999

[Metabolic insights and nutrition of poultry].

Excessive specialization and high production requirements place high demands on the metabolism of poultry. A number of metabolic problems, such as disturbances of energy metabolism (affecting mainly hens) and mineral balance (affecting mainly laying hens), affect performance. Nearly all these problems are multifactorial in nature, but diet, and in particular the interaction between diet and phenotype, plays an important role. The problem of ascites in broiler hens is discussed in relation to external and genetic causative factors. Genetic factors can be further subdivided into structural and functional causative factors. This distinction has important consequences. For example, sudden death syndrome can be distinguished as a separate entity. Fatty liver syndrome in laying hens, and gout and urolithiasis in chicks and hens are briefly discussed. Finally, some of the most important or most common skeletal problems affecting poultry, namely, tibial dyschondroplasia, battery fatigue, rickets, and chondrodystrophy, are briefly discussed in the context of the dietary factors that underlie these disorders or which can be used as treatment.

Animal Nutritional Physiological Phenomena↗
PubMed1999

Generation of chicken growth hormone-binding proteins by proteolysis.

A soluble protein that specifically bound growth hormone (GH) was characterized in culture medium of a COS-7 cell line transfected with the cDNA of the full-length chicken GH receptor (cGHR). Incubation of culture medium with 125I-labeled human GH resulted in the formation of a single specific complex with high affinity (KD = 0.36 nM) and apparent molecular weight of 75 kDa. The production of large quantities of GH-binding protein (GHBP) amounting to, per hour, 23% of the cell's GHR, points to the importance of partial proteolysis for GHR turnover. Considerable amounts of GHBP were also detected in a cytosolic fraction. These results strongly suggest that in chicken, as in rabbit and monkey, the GHBP is generated, at least partially, by proteolytic cleavage of the membrane-anchored GHR.

Animals↗
PubMed1999

The regulation of GH-dependent hormones and enzymes after feed restriction in dwarf and control chickens.

The principal objective of this study was to examine the GH-dependency of IGF-I and IGF-II changes in the chicken. To this end, the regulation of GH-dependent hormones and enzymes were studied in undernourished normal and dwarf chickens. The dwarf chickens examined exhibit a Laron-type dwarfism and have been shown to be GH receptor deficient. Thus, they provide an interesting model to determine the GH-dependency of IGF-I and IGF-II changes. Short (1 day) and long-term (7 days) feed restriction was imposed on growing normal and dwarf chickens to follow the subsequent endocrine changes. Since short-term feed restriction of dwarf chickens resulted in decreased plasma IGF-I, it appears that this is not a GH-dependent effect. However, with longer term undernutrition, IGF-I was not decreased in dwarf chickens. So, after a longer restriction period, the regulation of these factors appears to become more GH-dependent. IGF-II was not depressed at all by feed restriction in the dwarf chicken, suggesting a degree of GH-dependency.

Animals↗
PubMed1999

New insights into the mechanism and actions of growth hormone (GH) in poultry.

Despite well documented anabolic effects of GH in mammals, a clear demonstration of such responses in domestic poultry is lacking. Recently, comprehensive dose-response studies of GH have been conducted in broilers during late post-hatch development (8 to 9 weeks of age). GH reduced feed intake (FI) and body weight gain in a dose-dependent manner, whereas birds pair-fed to the level of voluntary FI of GH-infused birds did not differ from controls. The reduction in voluntary FI may involve centrally mediated mechanisms, as hypothalamic neuropeptide Y protein and mRNA were reduced with GH, coincident with the maximal depression in FI. Growth of breast muscle was also reduced in a dose-dependent manner. Circulating IGF-I was not enhanced by GH, despite evidence that early events in the GH signaling pathway were intact. A GH dose-dependent increase in circulating 3,3',5-triiodothyronine(T3) paralleled decreases in hepatic 5D-III monodeiodinase activity, whereas 5'D-I activity was not altered. This confirms that a marked hyperthyroid response to GH occurs in late posthatch chickens, resulting from a decrease in the degradative pathway of T3 metabolism. This secondary hyperthyroidism would account for the decreased skeletal muscle mass (52) and lack of enhanced IGF-I (53) in GH-treated birds. Based upon these studies, it is now evident that GH does in fact have significant effects in poultry, but metabolic responses may confound the anabolic potential of the hormone.

Animals↗