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Biomedical subjects

E Decuypere

Publications and source records attributed to E Decuypere.

At least 217 records · Page 12Linked to original sources
PubMed1988

Effect of temperature during induced moulting on plumage renewal and subsequent production.

1. Four groups of 18 cages each containing 4 brown laying hybrids aged 79 weeks were formed by two levels of restriction of a moulting diet (lasting for 29 d) being applied at two moulting temperatures (11 degrees C and 29 degrees C, lasting for 56 d). 2. Low temperature-low feeding resulted in greatly retarded growth of remiges, but the final extent was similar in all 4 groups, and reached 4 to 5 new primaries (median value). Body-plumage of hens moulted at 11 degrees C was 25% heavier than of hens moulted at 29 degrees C. 3. Second year production variables (rate of laying, egg mass, efficiency of food utilisation) were greatly influenced by moulting temperature (low moulting temperature performing better), but not by feeding rate. 4. The persistence of the improved food utilisation is related to energetic consequences of improved plumage renewal during moulting at the lower temperature, which can be seen as an acclimatization effect.

Animals↗
PubMed1988

Hypothalamic hormones that release growth hormone stimulate hepatic 5'-monodeiodination activity in the chick embryo.

Plasma GH, tri-iodothyronine (T3), thyroxine (T4) and liver 5'-monodeiodination (5'-D) activity were measured in 18-day-old chick embryos injected with thyrotrophin-releasing hormone (TRH) and human pancreatic growth hormone releasing factor (hpGRF). Injections of 0.1 and 1 microgram TRH and 1.5 micrograms hpGRF increased the concentration of plasma GH while injection of 15 micrograms hpGRF had no effect. Concentrations of plasma T3 were raised after injection of TRH or hpGRF. Injections of TRH but not of hpGRF raised the concentration of plasma T4. The increases in concentration of plasma T3 after injection of TRH or hpGRF were parallelled by increases in liver 5'-D activity. An injection of 0.25 micrograms T4 significantly raised the concentration of T4 in plasma but had no effect on plasma T3 or liver 5'-D activity. It is concluded that the release of chicken GH by TRH or hpGRF is responsible for the observed increase in plasma concentration of T3 and liver 5'-D activity.

Animals↗
PubMed1988

One-step purification of chicken growth hormone from a crude pituitary extract by use of a monoclonal immunoadsorbent.

The immunization of mice with an affinity-purified glycoprotein preparation from chicken pituitary tissue yielded several monoclonal antibodies towards the recently described glycosylated variant of chicken GH. As all these antibodies recognize the classical (non-glycosylated) GH molecule equally well, they provide a suitable tool for the development of both a specific immunoadsorbent and an assay method. This paper deals with the surprising purification power of the immunoadsorbent that was produced with one of the monoclonal antibodies. The resulting preparation was more than 99% pure as assessed by reversed phase high-performance liquid chromatography and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, so that no further purification steps were needed before the determination of the amino acid sequence of the material. The efficiency of the purification protocol as determined by a homologous, monoclonal antibody-based radioimmunoassay was virtually absolute. Moreover, the affinity-purified GH preparation was a mixture representing the multiple molecular forms of pituitary chicken GH, including both oligomeres and glycosylated GH. The purified preparations were finally used to demonstrate the hepatic 5'-monodeiodinase-stimulating activity of GH in the chicken embryo (results not shown), in order to prove that the biological activity of the molecule had not been damaged by elution from the immunoadsorbent.

Amino Acids↗
PubMed1987

Glycosylated chicken growth hormone.

In an attempt to raise monoclonal antibodies to chicken pituitary glycoprotein hormones, mice were immunized with the concanavalin A-adsorbed components of a hypophyseal extract. Fusions of these spleen cells with myeloma cells repeatedly yielded hybridoma lines secreting antibodies that recognized specifically the pituitary caudal acidophils, known as the somatotropes. This paper reveals the existence of a glycosylated counterpart of the well-established holoprotein form of chicken growth hormone, similar to what has been established for human growth hormone and prolactin.

Animals↗
PubMed1987

The influence of methimazole on the thyrotrophic and peripheral activity of thyrotrophin and thyrotrophin-releasing hormone in the chick embryo and growing chicken.

Plasma concentrations of thyroxine (T4) and triiodothyronine (T3) were profoundly depressed both in chick embryos and growing chickens after methimazole (MMI) treatment. There was no response of T4 and T3 levels to TRH or TSH injections in the MMI group, either in embryos or growing chickens. Peroxidase activity measured in the thyroid gland was significantly higher in embryos and growing chickens treated with MMI. However, neither TRH nor TSH affected this activity 2 hr after injection in either control or the MMI-treated group. Hepatic 5'-monodeiodinase activity was significantly stimulated in the MMI-treated groups of embryos and growing chickens but only when additional sulphydryl groups (DTT) were provided. In embryos, monodeiodination activity 2 hr after TSH injection was not significantly different from control values for either DTT-stimulated or unstimulated conditions within the control and MMI-infused groups. However, in both control and MMI-treated embryos monodeiodination activity significantly increased 2 hr after TRH injection. In the growing chickens, monodeiodination activity 2 hr after TRH or TSH injection was not significantly different from control values in either stimulated or unstimulated conditions of each group.

Animals↗
PubMed1987

Plasma concentrations of growth hormone and somatomedin C in dwarf and normal chickens.

Sex-linked dwarf chicks, offspring from the mating of heterozygous sires with dwarf females, were used in this study. On days 18 and 20 of incubation, plasma concentrations of growth hormone (GH) and somatomedin C (Sm-C) did not differ between normal chicks and those of the dw-dwdw genotype. After hatching, Sm-C concentrations in normal chicks remained comparable to the embryo values for up to 1 week, but those in dwarf chicks were lower. After 3 weeks Sm-C increased greatly in the controls, whereas in dwarf birds it was far less pronounced up to 18 weeks of age and only increased to control levels on week 12. GH was low during incubation and increased sharply after hatching in normal and dwarf chicks. After 3 weeks and up to 18 weeks, GH levels were higher in dwarf chicks, except at week 12 when they decreased to control concentrations.

Animals↗
PubMed1987

Effects of hyper- or hypothyroid status on growth, adiposity and levels of growth hormone, somatomedin C and thyroid metabolism in broiler chickens.

Relatively few methods involving dietary manipulation of thyroid status have been used to study the effect of that status on growth and body composition as well as on changes in hormone levels and metabolism. The present work examines the influence of either a hyperthyroid status (induced by feeding triiodothyronine: T3 or thyroxine: T4) or a hypothyroid status (induced by feeding methimazole: MMI) on growth, feed consumption and body composition as well as on changes in thyroid hormone levels and metabolism and in hormone levels of the somatotroph axis of broiler chickens. MMI depressed growth but increased fatness. Long-term administration of thyroid hormones decreased both growth and fat deposition, T3 being more effective than T4. The reduced growth of MMI-treated birds was not only related to the hypothyroid state but also to decreased somatomedin C (Sm-C) production, although growth hormone (GH) levels remained high. Thyroid hormone-treated birds showed slightly depressed GH levels but unchanged Sm-C levels. MMI induced an increase in hepatic 5'-monodeiodination activity, while T3 and T4 reduced that activity. The T4 administered was largely eliminated as inactive reverse T3. Both of the statuses (hypothyroid and hyperthyroid) profoundly changed peripheral thyroid hormone metabolism and influenced GH/Sm-C relationships, but in the opposite way. Hormonal changes could be related to the observed changes in growth and adiposity of broiler chickens and illustrate the negative correlation between T3 and body fat.

Adipose Tissue↗
PubMed1987

Growth hormone stimulates the peripheral conversion of thyroxine into triiodothyronine by increasing the liver 5'-monodeiodinase activity in the fasted and normal fed chicken.

Normal fed and 2 days fasted Warren chickens were injected intravenously with 100 micrograms of ovine growth hormone (GH) and ovine prolactin and plasma concentrations of thyroid hormones were assayed prior and up to 2 h after injection. Fasting alone decreases T3, but increases T4. An injection of GH resulted in increases of plasma T3 concentrations in two fasting experiments by 40% (after 3/4 h) and 104% (after 1 h). In normal fed animals no increase is observed in the first experiment, whereas a 35% increase occurs in the second one. An injection of 100 micrograms prolactin does not influence T3 in normal fed or fasting animals. Both GH and prolactin, however, may decrease plasma concentrations of T4. In a separate experiment 50 micrograms and 200 micrograms of GH raised the decreased T3 levels after fasting by 39% and 60% respectively 1 h after injection and by 24 and 61% respectively in normal fed chicken, whereas prolactin was ineffective in this regard. Using Hisex chickens, the influence of an injection of 100 micrograms GH on plasma concentrations of thyroid hormones could be confirmed. At the same time GH increases the liver 5'-monodeiodinase activity by 330% after 1 h and by 147% after 2 h. The peroxidase activity is not influenced in normal fed chickens, but GH decreases this activity in food deprived animals after 1 h and 2 h. It is concluded that ovine GH, but not prolactin, stimulates the peripheral conversion of T4 into T3 in both normal fed and food deprived chicken and that this effect is dose dependent.

Animals↗
PubMed1987

A new approach to recording plumage deterioration.

1. Recording methods for the scoring of plumage wear are reviewed. 2. A new technique, distinguishing between feather tracts, the surface to which damage occurs and the degree of degradation to the feathers themselves is elaborated: a 5 step scale for degradation is applied to all appropriate fractions of 6 feather regions. After correcting for the normal feather weight in the respective areas, all 6 area values are summed to constitute an overall index of body plumage wear (IBPW).

Animals↗
PubMed1987

Effect of exogenous LH on plasma concentrations of progesterone and oestradiol in relation to the cessation of egg laying induced by different moulting methods.

Artificially induced cessation of egg laying caused regression of the reproductive tract in hens, as well as changes in circulating concentrations of sex steroids. Hens were bled at several stages during and after artificial moult induced by fasting or overfeeding a diet low in calcium or high in zinc. Hens received a single injection of 200 i.u. of horse LH at Day 0, 7, 21, 35 and 77 (Exp. 1) or Day 0, 8, 23, 35 and 71 (Exp. 2) after start of the treatment to induce moult. Blood samples were taken before and 20, 40 and 60 min (Exp. 1) or 15, 30 and 45 min (Exp. 2) after LH injection. Hens which were fasted or given the diet high in zinc had low plasma progesterone concentrations and the response to LH was reduced or delayed. In hens fed low calcium the reduction in plasma progesterone was less pronounced and the responsiveness to LH was more or less maintained. Conversely, there was no response of oestradiol to LH in laying hens. However, oestradiol concentrations increased in moulting hens after LH injection, due to the high oestradiol secretion from the small white follicles, since all yolky follicles were atretic.

Animals↗
PubMed1987

Effect of corticosterone on circulating concentrations of corticosterone, prolactin, thyroid hormones and somatomedin C and on fattening in broilers selected for high or low fat content.

Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and somatomedin C were measured in 28-day-old fat and lean lines of broilers produced by selection for high and low concentrations of very low density lipoproteins (VLDL). The effects of daily injections of corticosterone on the concentrations of these hormones and on fattening were compared in the two lines. The selection procedure had no effect on the concentrations of any of the hormones. However, daily rhythms in concentrations of plasma corticosterone, tri-iodothyronine (T3) and prolactin were less often observed in the fat line than in the lean line. No differences were seen between lines in the daily rhythms in plasma thyroxine (T4) and somatomedin C. Daily injections of 2500 micrograms corticosterone/kg body weight, in both lines, depressed mean concentrations of plasma prolactin, T3 and somatomedin C and body weight. This dose of corticosterone also increased abdominal fat pad and liver weights expressed as a percentage of body weight. The liver and fat pad responses to 2500 micrograms corticosterone in both lines were greater when the steroid was injected at the end rather than towards the beginning of the 14-h daily photoperiod. There was no difference between the lines in the fattening response to corticosterone. Lower doses of 100 and 500 micrograms corticosterone per day did not induce fattening or affect concentrations of plasma prolactin. They did, however, depress concentrations of plasma T3. Concentrations of plasma T4 were increased in both lines treated with 2500, but not with 100 or 500 micrograms corticosterone, towards the beginning of the daily photoperiod.(ABSTRACT TRUNCATED AT 250 WORDS)

Adipose Tissue↗
PubMed1987

Endocrinology of the avian embryo: an overview.

The full endocrine system is developed during the embryonic stages of the domestic fowl and probably in all avian species. This involves the genesis and differentiation of endocrine cells and progressive acquisition of interactions between endocrine tissues leading to integrated series of control systems. The embryonic endocrine organs produce hormones with a variety of physiological roles (including homeostatic, homeorhetic, and anticipatory). The present chapter provides an overview of the recent advances in the endocrinology of the avian embryo. Particular attention is focused on the general phenomenon of endocrine development and on the ontogeny of the hypothalamo-pituitary (growth hormone)-somatomedin-growth axis, the hypothalamo-pituitary-thyroid axis, and the hormones of calcium homeostasis.

Animals↗
PubMed1986

Growth, protein synthesis and plasma concentrations of growth hormone, thyroxine and triiodothyronine in dwarf, control and growth-selected strains of broiler-type domestic fowl.

Body weight, tissue weight and plasma hormone concentrations were determined at 1, 3, 6, 12 and 21 weeks of age in two dwarf strains and one control strain of broiler chickens. Protein synthesis, accretion and degradation rates were determined in the control strain with age. Within each strain, plasma growth hormone (GH) concentrations were greater at 1 and 3 weeks of age and consequently decreased with age. Plasma GH concentrations were greater in the sex-linked dwarf chicken during pubescence and maturity (12 and 21 weeks) compared to the autosomal dwarf and control chickens. Circulating concentrations of 3,5,3' triiodothyronine (T3) were depressed by 70% in sex-linked dwarf birds compared to controls, while thyroxine concentrations did not differ at most time points. These findings support the suggestion that sex-linked dwarf chickens have reduced peripheral conversion of T4 to T3.

Aging↗
PubMed1986

Thyroid function in newborn lambs: influence of prolactin and growth hormone.

Lambs originating from Suffolk, Milksheep and Texel crossbreeds were injected with saline, 500 micrograms ovine prolactin or 500 micrograms ovine GH within 30 min of parturition (n = 10). Birth weight was negatively correlated with plasma concentrations of reverse tri-iodothyronine (rT3) but not with thyroxine (T4), free T4 (expressed as the free thyroxine index) or cortisol. At birth, T3 and T4 plasma concentrations were high and remained high during the 3-h observation period. After 3 h a significantly lower rT3 concentration was found. The cortisol concentration at birth was also high (100-400 nmol/l) but decreased rapidly to basal values after 1 h. An injection of 500 micrograms prolactin after parturition did not influence the hormonal parameters studied except for rT3 where, after 2 h, lower plasma concentrations were found compared with controls. Growth hormone raised T3 levels from 4.80 +/- 0.44 (S.E.M.) nmol/l at birth to 6.74 +/- 0.42 nmol/l at 1 h after birth (P less than 0.01) and to 6.51 +/- 0.42 nmol/l after 2 h (P less than 0.05). At both times these values were significantly (P less than 0.001) different from saline-injected controls. GH decreased rT3 from 6.77 +/- 0.71 nmol/l at birth to 5.42 +/- 0.54 nmol/l after 1 h (P less than 0.05) and to 5.10 +/- 0.45 nmol/l after 2 h (P less than 0.01; values were also significantly different from saline controls at P less than 0.05 and less than 0.005 respectively). At the same time total and free T4 concentrations were increased. No influence of prolactin or GH injection on plasma cortisol concentrations was seen.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Effect of a single injection of prolactin on the serum concentrations of thyroid hormones and corticosterone and liver monodeiodinase in the domestic fowl before and after hatching.

The influence of an intravenous injection of ovine prolactin on the liver monodeiodinase activity and serum concentrations of thyroid hormones and corticosterone was studied in Hisex embryos and chicks after hatching. An injection of 1 and 10 micrograms ovine prolactin into 18-day-old chick embryos increased serum concentrations of tri-iodothyronine (T3) five- and eightfold respectively after 2 h. At the same time serum concentrations of thyroxine (T4) and reverse T3 (rT3) were decreased in the chick embryo, but only with 10 micrograms prolactin. This was accompanied by a doubling of the liver monodeiodinase activity. Serum concentrations of corticosterone, however, were not influenced by the prolactin injections. In the 5-day-old chicken, serum concentrations of T3, rT3, T4 and liver T4-5'-monodeiodinase activity were not influenced by 1 or 10 micrograms prolactin. Serum concentrations of corticosterone after injection of 1 or 10 micrograms prolactin were doubled compared with controls. These results are compatible with a prolactin-induced shift from a T4-5-monodeiodination into a T4-5'-monodeiodination in the liver at the end of incubation. This effect, however, is not mediated through a prolactin-induced corticosterone release.

Animals↗
PubMed1985

Long-term effect of incubation temperatures on production parameters and changes in luteinizing hormone and gonadal steroids during the onset of lay in the hen.

Earlier studies demonstrated that different incubation temperatures (33.8 or 37.8 C) from Day 17 of incubation until hatching resulted in differences in postnatal growth rate and hormonal parameters. These studies were repeated and extended to the reproduction period. The onset of egg laying was significantly delayed by 5 days in the 33.8 C group compared to the 37.8 C group. No differences in percent egg production were found between the groups after 3 or 5 months of production: however, mean egg weight was significantly reduced in the 33.8 C group by 1.9 and 1.8 g over 3 and 5 months of production, respectively. Serum concentrations of luteinizing hormone (LH), estradiol (E2), estrone (E1), progesterone (P4), and testosterone (T) were measured weekly at the same time of day approximately 4 weeks before to 4 weeks after the onset of lay. The changes in levels of all hormones over the period studied were identical for both experimental groups. Luteinizing hormone, T, and E2, but not E1 and P4, were different before and after onset of lay in both groups. There were no significant correlations between hormonal levels before onset of lay and production traits for individual hens. In the 33.8 C group, after onset of lay, significant positive correlations were observed between serum E2 and egg production and serum LH and egg production; however, these correlation coefficients were not significant in the 37.8 C group. Significant negative correlation coefficients were observed in both groups between serum E2 after onset of lay and age at first egg.

Animals↗