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At least 451 records · Page 25Linked to original sources
PubMed1993

Benzodiazepine antagonism of thyrotrophin-releasing hormone receptors: biphasic actions on growth hormone secretion in domestic fowl.

Benzodiazepines are pharmacological agents widely used for their anxiolytic and anticonvulsant properties. However, as these drugs are known to antagonize the binding and action of thyrotrophin-releasing hormone (TRH) in pituitary tissue, the possibility that they may modulate GH secretion was investigated in domestic fowl, in which TRH is a GH-releasing factor. Chlordiazepoxide (an antagonist of central-type benzodiazepine receptors) had no significant effect on the basal release of GH from incubated chicken pituitary glands, but at concentrations > 10 mumol/l chlordiazepoxide suppressed somatotroph responsiveness and sensitivity to TRH stimulation. At this concentration, chlordiazepoxide competitively displaced the binding of [3H]3-methyl-histidine2-TRH ([3H]MeTRH) to chicken pituitary membranes. The prior incubation of pituitary glands with chlordiazepoxide had no significant effect on the number of [3H]MeTRH-binding sites, which were also unaffected by the administration of chlordiazepoxide in vivo. However, contrary to its effects in vitro, chlordiazepoxide reduced basal GH secretion in vivo, whilst potentiating the GH response to systemic TRH challenge. These results demonstrate benzodiazepine antagonism of TRH-binding sites in domestic fowl and a biphasic modulation of GH secretion, which may be mediated through opposing actions at pituitary and central sites.

Animals↗
PubMed1993

pGlutamylglutamylprolineamide modulation of growth hormone secretion in domestic fowl: antagonism of thyrotrophin-releasing hormone action?

Pyroglutamyglutamylprolineamide (pGlu-Glu-ProNH2) is a tripeptide with structural and immunological similarities to thyrotrophin-releasing hormone (TRH; pGlu-His-ProNH2). Since TRH stimulates GH secretion in domestic fowl, the possibility that pGlu-Glu-ProNH2 may also provoke GH release was investigated. Unlike TRH, pGlu-Glu-ProNH2 alone had no effect on GH release from incubated chicken pituitary glands and did not down-regulate pituitary TRH receptors. However, pGlu-Glu-ProNH2 suppressed TRH-induced GH release from pituitary glands incubated in vitro and competitively displaced [3H]methyl3-histidine2-TRH from pituitary membranes. Systemic injections of pGlu-Glu-ProNH2 had no significant effect on basal GH concentrations in conscious birds, but promptly lowered circulating GH levels in sodium-pentobarbitone anaesthetized fowl. Submaximal GH responses of conscious and anaesthetized birds to systemic TRH challenge were, however, potentiated by prior or concomitant administration of pGlu-Glu-ProNH2. These results demonstrate, for the first time, that pGlu-Glu-ProNH2 has biological activity, with inhibitory and stimulatory actions within the avian hypothalamo-pituitary axis. These results indicate that pGlu-Glu-ProNH2 may act as a TRH receptor antagonist within this axis.

Animals↗
PubMed1993

Thyrotrophin-releasing hormone-induced growth hormone secretion in domestic fowl: concomitant stimulation of dopamine turnover in the medial basal hypothalamus.

Thyrotrophin-releasing hormone (TRH) stimulates GH secretion in domestic fowl by actions at pituitary and central nervous system sites. The possibility that this central action might be mediated by hypothalamic catecholamines or indoleamines was therefore investigated. When TRH was administered into the lateral ventricles of anaesthetized fowl the concentration of 3,4-dihydroxyphenylacetic acid (DOPAC, a metabolite of dopamine (DA)) in the medial basal hypothalamus (MBH) was increased within 20 min. The concentrations of MBH noradrenaline (NA), DA, serotonin (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) were, however, unaffected by the intra-cerebroventricular (i.c.v.) administration of TRH, although the MBH concentrations of somatostatin and TRH were concomitantly reduced. A rapid increase in DA release into MBH extracellular fluid and its metabolism to DOPAC was also observed after i.c.v. or i.v. administration of TRH, in birds in which the MBH was perfused in vivo with Ringer's solution. Microdialysate concentrations of NA, 5-HT and 5-HIAA were not, however, affected by central or peripheral injections of TRH. Diminished GH responses to i.v. TRH challenge occurred in birds pretreated with reserpine (a catecholamine depletor), alpha-methyl-paratyrosine (a DA synthesis inhibitor) and pimozide (a DA receptor antagonist). These results therefore provide evidence for the involvement of a hypothalamic dopaminergic pathway in the induction of GH release following the central or peripheral administration of TRH. In contrast with its inhibitory actions at peripheral sites, DA would appear to have a central stimulatory role in regulating GH release in birds.

Amines↗
PubMed1998

Autoregulation of central and peripheral growth hormone receptor mRNA in domestic fowl.

Growth hormone (GH) regulates numerous cellular functions in many different tissues. A common receptor is believed to mediate these tissue-specific effects, suggesting that post-receptor signalling molecules or tissue sensitivity to GH may differ between tissues. Tissue sensitivity depends upon the abundance of GH receptors (GHRs), thus tissue-specific GHR regulation could enable tissue-specific GH actions. The comparative autoregulation of GHR gene transcription in central (whole brain or hypothalami) and peripheral (liver, bursa, spleen and thymus) tissues was therefore examined in domestic fowl. In all tissues, a 4.4 kb GHR gene transcript that encodes the full-length GHR was identified. The abundance of this transcript was inversely related to endogenous GH status; it was lower in males with high circulating concentrations of GH and higher in females with lower basal concentrations of plasma GH. The abundance of this transcript was also rapidly downregulated in response to a bolus systemic injection of recombinant chicken GH, designed to mimic an episodic burst of endogenous GH release. This autoregulatory response was observed within 2 h of GH administration and was of greater magnitude in the brain than in peripheral tissues. Intracerebroventricular injections of GH also downregulated GHR gene expression in the brain, although hepatic GHR transcripts were unaffected 24 h after central administration of GH. In contrast, the induction of hyposomatotropism by passive GH immunoneutralization increased the abundance of the GHR transcript in the thymus, but not in other central (brain) or peripheral (bursa, liver) tissues. GH is not the sole regulator of GHR abundance, however; hypersomatropism induced by hypothyroidism was associated with an increase in GHR mRNA. The expression of the GHR gene in the domestic fowl would thus appear to be autoregulated by GH in a tissue-specific way.

Animals↗
PubMed1993

A natural outbreak of Newcastle disease in guinea-fowl (Numida meleagris galeata) in Nigeria.

A natural outbreak of Newcastle disease (ND) was reported in a flock of guinea-fowl in Nigeria, affecting 1,029 birds of which 250 (24.3%) died. Paralysis of the legs and wings, coughing, sneezing, white diarrhoea and complete cessation of egg production were observed. Serum samples collected at the onset and during the course of the disease had high ND antibody titres. ND virus was isolated from a pool of brain tissues from diseased guinea-fowl. The ND virus isolate was characterised as a velogenic strain.

Animals↗
PubMed2006

The magnum-isthmus junction of the fowl oviduct participates in the formation of the avian-type shell membrane.

Avian eggs possess a shell membrane in the shape of an asymmetrical ellipsoid and with a limiting membrane that is a smooth layer of homogeneous, dense materials. We describe the role of the magnum-isthmus junction (MIJ) of the oviduct in the formation of the avian-type shell membrane in the domestic fowl Gallus domesticus. The narrow width of the lumen at the MIJ indirectly participates in the determination of the asymmetrical ellipsoid shape of eggs that are encased by the egg-white layer and subsequently by the peri-albumen layer (PL) and the shell membrane. The PL reacts with Alcian blue and exists between the egg white and the limiting membrane. It is added to the ovulating egg at the MIJ and covers the outermost surface of the egg-white layer. The function of the PL is to provide a smooth surface by covering the irregular surface of the egg-white layer. The materials of the PL consist of an Alcian blue-positive polysaccharide (or glycoprotein) of 240 kDa and five proteins of 135, 116, 72, 49, and 46 kDa. The isolated materials have an affinity to bind with the egg-white mass. An antiserum against quail PL materials stains the domestic fowl PL and secretory cells of the luminal epithelium at the MIJ, and cross-reacts with the molecules of 240, 135, and 116 kDa.

Animals↗
PubMed1985

Loss of sensitivity to ACTH of adrenocortical cells isolated from maturing domestic fowl.

Maturation of domestic fowl corticosteroidogenesis was evaluated using purified adrenocortical cells. Basal corticosterone production decreased steadily from 2 days to 26 weeks after hatching. However, maximally stimulated corticosterone production was not changed. In contrast, the half-maximal steroidogenic concentrations (ED50 values or effective doses for 50% maximal effect) of ACTH analogs increased approximately 40 times by 26 weeks, but the ED50 values of 8-bromo-cyclic AMP and pregnenolone were not changed. This suggests that adrenocortical cell sensitivity to ACTH decreases with maturation of the domestic fowl.

Adrenal Cortex↗
PubMed1975

Fowl cholera: immunologic and werologic response in turdeys to live Pasteruella multocida vaccine administered in the drinking water.

Live fowl cholera vaccine administered in drinking water induced immunity in young turkeys against a challenge of a different immunogenic type of Pasteurella multocida; this is referred to as cross-immunity. Serum from the vaccinated birds induced passive cross-immunity in chicks and turkeys; this demonstrated that the cross-immunity induced with the drinking water vaccine was associated with the humoral system. Results of serologic tests with agar grown P. multocida indicate that agglutinins and precipitins are not associated with the induced cross-immunity. A live culture of P. multodica previously reported to induce cross-immunity in mature turkeys without causing adverse effects when administered in the drinking water, killed 6 of 45 (13 per cent) poults in the present study; this demonstrated that young turkeys are more susceptible to fowl cholera than mature turkeys.

Administration, Oral↗
PubMed1980

Effects of microwave and various combinations of ambient temperature and humidity exposures on off-host survival of northern fowl mites.

When northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), were removed from their host and exposed to ambient temperatures ranging from -15 to 49 C with uncontrolled relative humidity (RH) or to temperatures ranging from .3 to 38 C with an RH of ca. 75%, mites lived longest at 4 C. However, temperatures between .3 and 26 C were also conducive to survival. Temperatures above 43 C killed the mites in less than 5 hr; mites exposed to -15 C lived up to 5 days. A constant humidity of ca. 75% was most beneficial to the mites when temperatures ranged from 33 to 38 C. Manipulation of ambient temperature and RH would be effective in exterminating the northern fowl mites on inanimate objects. Mites exposed for different periods to microwave energy at a net power ranging between 165 to 430 kw/m2 were not selectively heated to temperatures above the temperatures of the containers, nor did the irradiation have any other lethal effects on the mites.

Animals↗
PubMed1981

Application phenomena and efficacy of concentrated acaricide dusts for northern fowl mite control on caged laying hens.

Fluorescent pigments were used to measure plumage coverage when caged laying hens were dusted for northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), control. Carriage type electrostatic or high velocity backpack equipment produced superior coverage 2 hr posttreatment when the rates of 454 g (1 lb) dust per 100 or 500 hens was employed. A redistribution of dust was noted 48 hr posttreatment, and a subsequent experiment demonstrated that this phenomenon resulted from intracage cross contamination dependent upon bird caging density. Carbaryl 80% wettable powder (WP) at 454 g/1600 hens and tetrachlorvinphos 50% WP at 454 g/1000 hens provided northern fowl mite control for 11 and 5 weeks posttreatment, respectively.

Animals↗
PubMed1982

Comparisons of permethrin formulations and application methods for northern fowl mite control on caged laying hens.

Formulations of permethrin (Ectiban), a synthetic pyrethroid, as an emulsifiable concentrate (EC), wettable powder (WP), and dust were nearly equally effective for 9 or more weeks for control of the northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), on caged laying hens under environmentally controlled conditions. The permethrin was applied to the vent area as .05% active ingredient (AI) spray of the diluted EC or WP at 40 ml per bird, .1% AI mist of the diluted EC at 20 ml per bird, and 4.5 g per bird of the .25% AI dust. Dilute sprays of .05% permethrin prepared from the EC and WP and applied at 40 ml per bird were more effective in a commercial caged-laying hen house for northern fowl mite control than were .5% sprays of tetrachlorvinphos (Rabon), Ravap, and carbaryl (Sevin). Satisfactory mite control was obtained with .6% permethrin prepared from the EC and misted at the rate of 2.5 ml per bird. Low volume, high concentration misting of permethrin was a promising method for mite control with satisfactory control achieved with .2% AI at 5 ml per bird and .6% AI at 2.5 ml per bird.

Aerosols↗
PubMed1983

Control of the northern fowl mite on inanimate objects by fumigation: field studies.

Field studies were conducted to determine the efficacies of methyl bromide and sulfur dioxide as fumigants for northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), on egg flats and egg cases. Both fumigants killed the mites within 24 hr; however, sulfur dioxide had a repulsive irritating odor, which was retained in the cardboard egg flats and egg crates and persisted for several days after exposure to the gas. When used in accordance with the manufacturer's recommendations for fumigating enclosed trailers and vans to control insects that attack food products, methyl bromide gave excellent control of northern fowl mites infesting inanimate materials.

Animals↗
PubMed1984

A new in-cage treatment system for control of northern fowl mites on laying hens.

Commercially available plastic and other types of flexible tubing were tested to determine their relative permeability to an emulsifiable concentrate (EC) of permethrin acaricide. Bioassays employing northern fowl mites, Ornithonyssus sylviarum (Canestrini and Fanzago), indicated that .3 mg permethrin/cm2 surface area penetrated vinyl plastic tubing that had been filled with 42.5% active ingredient EC for 14 days. Vinyl tubing circuits were installed in wire poultry cages, either in the form of suspended loops or woven through the rear cage wall, and permethrin EC was introduced by means of a small pump. Significant reductions in northern fowl mite populations on hens caged therein were apparent after 48 days posttreatment. This approach has merit as a long-term, labor-economical form of mite control on caged poultry.

Animals↗
PubMed1984

Effect of parathyroid hormone on total phosphate and inorganic phosphate in blood, plasma, and urine of domestic fowl.

Previous work has shown that parathyroid hormone causes the kidneys of domestic fowl to secrete inorganic phosphate (Pi) into the urine. Secreted Pi is not derived directly from plasma Pi. The objective of the present study was to determine if direct or indirect correlations exist between the urinary Pi excretion rate and the concentration of phosphate in plasma or whole blood. Parathyroid hormone dissolved in gelatin carrier vehicle was injected into immature domestic fowl to cause net renal Pi secretion. Control birds were injected with carrier vehicle alone, resulting in net Pi reabsorption. Urine, plasma, and whole blood samples obtained during net Pi secretion were compared with samples obtained during net Pi reabsorption. Each sample was assayed for total and inorganic phosphate. Neither time course nor point by point comparisons of individual samples provided any evidence that secreted Pi is derived from organic phosphate in plasma or whole blood. These experiments suggest that phosphate pools within the kidneys may serve as a source for the Pi that is secreted in response to parathyroid hormone.

Animals↗
PubMed1986

Effects of temperature on reproduction in guinea fowl.

The effects of four temperature regimens on the onset and maintenance of semen and egg production, fertility, hatchability, and feed consumption by guinea fowl were examined. Temperatures of 26.7 and 21.1 C hastened the onset of egg and semen production in guinea fowl. However, egg and semen production rates of guineas exposed to ambient or 15.6 C minimum temperatures eventually increased to the level of those exposed to the higher temperatures. This suggests that it may be possible to initiate production by exposure to a warm environment and then reduce the environmental temperature after egg and semen production has been well established. There were no statistically significant differences in fertility or hatchability. Differences seen in feed conversion were mainly due to delayed onset of egg production in the lower temperature regimens. Thus, it appears that proper winter management of guinea breeders would involve exposure to a warm temperature for some period of time.

Animals↗
PubMed1986

Age-related variations in seminiferous tubule dimensions and germinal and Sertoli cell numbers in guinea-fowl raised under a 14L:10D photoperiod.

Histological studies of testicular development in guinea-fowl (Numida meleagris), raised under a 14L:10D photoperiod from 1 to 70 weeks of age, revealed: rapid increases in the relative volume, diameter, and length of the seminiferous tubules from 8 to 20 weeks but no significant changes thereafter; the appearance at 12 weeks of both mature Sertoli cells and round spermatids, characteristic of puberty; and biphasic increases in the numbers of Sertoli and germinal cells. The numbers of Sertoli cells, Type I spermatocytes, and round spermatids increased rapidly between 8 and 20 weeks; thereafter the numbers of Sertoli cells and Type I spermatocytes increased slowly but significantly, whereas the number of round spermatids was static. This indicated that age-related changes in meiotic yields could occur in adult guinea-fowl maintained under a 14L:10D photoperiod.

Aging↗
PubMed1986

Intraduodenal glucose infusions do not affect food intake in the fowl.

A series of experiments was performed to examine the role of the duodenum in food intake regulation in the fowl. In each of the experiments, birds were surgically fitted with intraduodenal cannulae. In Experiments 1 to 6, Single Comb White Leghorn (SCWL) or Rock Cornish cockerels were infused with isosmotic glucose, urea, or saline solutions. Glucose had no effect on food intake as compared with the saline and urea control treatments. In the final experiment, food intake of splanchnicectomized SCWL cockerels was contrasted to that of sham-operated controls, following intraduodenal glucose infusions. No difference between the denerved and intact birds was observed. The duodenum of the fowl, unlike the mammal, does not appear to play a significant role in food intake regulation.

Animals↗
PubMed1989

Histological study on seminal plasma absorption and spermiophagy in the epididymal region of domestic fowl.

Absorption of seminal plasma and spermiophagy in the fowl epididymal region were studied ultrastructurally and histochemically. Epithelial cells of the rete testis had sparse coated vesicles and rarely showed spermiophagy. Many macrophages in the lumen of the rete testis actively phagocytosed spermatozoa. Nonciliated cells in the proximal efferent ductules had well-developed microvilli, coated vesicles, numerous tubular structures, and lysosomes in their apical cytoplasm. They rarely contained fragments of spermatozoa. Intense alkaline phosphatase activity was observed at the luminal borders of these cells. Ciliated cells had no features indicating active absorption of seminal plasma. Epithelial cells of the connecting ductules and epididymal duct had numerous microvilli, a few vesicles, and small lysosomes. They did not contain spermatozoa. Intense acid phosphatase activity was observed on the luminal and lateral surfaces of the epithelial cells of the connecting ductules and epididymal duct. After injection of horseradish peroxidase into the excurrent ducts, a large amount of reaction product was detected in the vesicles and tubular structures of the nonciliated cells of the proximal efferent ductules. These results suggest that the absorption of seminal plasma occurred mainly in the efferent ductules, and that spermiophagy by macrophages occurred in the rete testis in the fowl epididymal region.

Absorption↗