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At least 1,675 records · Page 93Linked to original sources
PubMed1987

The effect of age on egg production in the domestic hen.

The effect of age on egg production was investigated in the domestic fowl. The rate of egg production was reduced with increasing age and the incidence of thin-shelled and cracked eggs was markedly increased. Older hens which remained in lay produced fewer but larger eggs than the younger birds. The ovaries of these two groups of hens were of similar appearance but the largest preovulatory follicle and the oviduct were significantly heavier in the older birds. No differences in the circulating levels of progesterone or estradiol were apparent between the young and old birds but the activity of the renal 25-hydroxycholecalciferol 1 alpha-hydroxylase was found to be significantly reduced with age. Circulating levels of total and ionized calcium were very similar in the young and old laying birds, plasma ionized calcium levels being markedly depressed during egg shell calcification in both groups. The decreased rate of ovulation in the older birds and the increase with age in the size of the follicles ovulated is thought to be associated with a reduced rate of recruitment of follicles for rapid growth followed by a prolonged period of follicular growth and development. The poor calcification of egg shell in old birds would appear to be due to some dysfunction of the shell gland, possibly associated with reduced synthesis of 1,25-dihydroxycholecalciferol by the kidney. The maintenance of plasma ionized calcium concentrations does not appear to be of primary importance in this respect.

25-Hydroxyvitamin D3 1-alpha-Hydroxylase↗
PubMed1991

Humoral factor mediates acetylcholine-induced endothelium-dependent relaxation of chicken aorta.

A superfusion cascade system was used to determine whether endothelium-dependent vasorelaxation induced by acetylcholine (ACh) is mediated by a humoral factor(s) in the domestic fowl. An abdominal aorta (5 cm in length) with intact endothelium, excised from the donor bird, was mounted in an organ bath and perfused with avian Ringer solution. The vasorelaxing activity of the effluent was determined by an endothelium-denuded aortic ring (bioassay ring) equilibrated and precontracted with phenylephrine (PHE) (10(-6) M). The effluent (containing PHE) from the donor aorta with intact endothelium did not significantly change the PHE-induced tension of the bioassay rings. ACh (10(-6) M), when added to the perfusion medium that runs through the control polyethylene tubing, produced further contraction of the PHE-precontracted endothelium-denuded bioassay rings, whereas ACh caused relaxation of the rings when added to the perfusate that passes through the endothelium-intact donor aorta. The ACh-induced relaxation of the bioassay ring was slightly potentiated by superoxide dismutase (100 U/ml). Hemoglobin (10(-5) M) increased the basal tension of the bioassay rings and completely inhibited the ACh-induced relaxation of the rings. These results suggest that ACh-induced relaxation of fowl aorta is, at least partially, mediated by a humoral factor(s) that resembles endothelium-derived relaxing factor demonstrated in mammals.

Acetylcholine↗
PubMed1991

Participation of the cytoskeleton in avian granulosa cell steroidogenesis.

Cytochalasin B (CB) and the more specific cytochalasin D (CD), disruptors of microfilament polymerization, and colchicine, an inhibitor of microtubule polymerization, were studied for their effects on cAMP and steroid production in granulosa cells of domestic fowl. Each agent was incubated with freshly dispersed cells from the largest preovulatory follicle of laying hens taken 3-4 hr before expected ovulation. Total content (cells + medium) of cAMP and steroids was measured by established radioimmunoassays. CB dose dependently inhibited basal as well as LH- and forskolin-stimulated cAMP generation and diminished basal, LH- and 25-hydroxycholesterol (25-OHC)-supported progesterone production. Conversely, CD potentiated LH- and forskolin-promoted cAMP generation as well as LH- and 25-OHC-stimulated progesterone synthesis. Neither drug had any influence on metabolism of pregnenolone to progesterone. Colchicine had no effect on cyclic AMP generation, yet it suppressed progesterone synthesis by inhibiting the conversion of pregnenolone to progesterone. beta-Lumicolchicine, a colchicine analog that does not depolymerize microtubules, had no such effect. The results suggest that microfilaments are involved in steroidogenesis at two sites, namely, the adenylate cyclase-cAMP system, and cholesterol conversion to pregnenolone; whereas microtubules act on the conversion of pregnenolone to progesterone.

Aminoglutethimide↗
PubMed1992

Use of slow-release pellets to administer calcitriol to avian embryos: effects on plasma calcium, magnesium, and phosphorus.

Calcitriol (1,25-dihydroxycholecalciferol) was administered to embryos of domestic fowl by slow-release pellets inserted into eggs on Day 10 of incubation. Mortality among embryos receiving 10 pg/day was no different from that of controls, but mortality among embryos receiving 100-1000 pg/day was elevated in later stages of incubation. Concentrations of calcium in plasma did not vary over the course of incubation among surviving embryos receiving carrier, but concentrations of magnesium and inorganic phosphorus declined with time. All doses of calcitriol elicited increases in plasma Ca and Mg on Day 12, and embryos may have responded also with a dose-dependent hypophosphatemia. The increases in plasma Ca and Mg were not sustained for the remainder of incubation, but the hypophosphatemia seemingly was of longer duration. This study demonstrates a new procedure for administering hormones to avian embryos and reveals that embryonic chickens respond in the expected manner to very small quantities of calcitriol.

Age Factors↗
PubMed1988

Alarm signals in birds: the role of testosterone.

In the laboratory and under semi-naturalistic conditions, male domestic fowl (Gallus gallus) produce more alarm calls in response to predatory birds flying overhead than females. This study tests the hypothesis that testosterone is a factor in the control of aerial alarm call production. Birds were castrated early in life and tested as adults in the laboratory. Aerial predators were simulated by cardboard silhouettes drawn overhead. Blood samples were taken at intervals and plasma testosterone levels were measured by radioimmunoassay. Each subject was tested in four conditions: with an empty Silastic implant, with a testosterone-filled implant, with an additional testosterone implant, and after removal of the implants. Results show that the presence of testosterone increases the production of aerial alarm calls, and that removal of the hormone supply results in a drop in calling rate. As a control a second vocal system, food calling, was considered. In contrast with alarm calling, there was no correlation between testosterone levels and variation in food-call production. We conclude that testosterone plays a specific role in activation of the production by cockerels of vocalizations that signal the presence of aerial predators.

Animals↗
PubMed1991

Sterilisation of avian embryos with busulphan.

The chemosterilant drug busulphan (1, 4-butanediol dimethane sulphonate) has been applied to embryos of the domestic fowl at doses of from 1 to 500 micrograms after 48 hours incubation. Direct application caused a number of teratological effects. These could be avoided by injecting the drug in sesame oil directly into the yolk. Embryos treated in this way could be sterilised with an efficiency of over 95 per cent with minimal side effects to the young embryo. The technique provides a method for destroying primordial germ cells that will facilitate studies of germ cell/stroma interactions in the gonad and facilitate the production of transgenic birds.

Abnormalities, Drug-Induced↗
PubMed1975

Gas transport efficacy of gills, lungs and skin: theory and experimental data.

The general functional principles encountered in respiratory organs of vertebrates are investigated. Generally three steps are involved in external gas exchange in vertebrates: (1) convective transport by flow of external respiratory medium, air or water (=ventilation); (2) transfer of gas between external respiratory medium and blood by diffusion (=medium/blood transfer); (3) convective transport by blood flow (=perfusion). According to the arrangement of external medium flow relative to capillary blood flow four construction principles may be distinguished: (a) counter-current system (fish gills), (b) cross-current system (avian lungs), (c) ventilated pool system (mammalian lungs), and (d) infinite pool system (amphibian skin). The gas transfer performance of these systems is analyzed in terms of conductances, relative partial pressure differences and limitations attributable to ventilation. to medium/blood transfer and to perfusion. The theory is applied to analysis of gas exchange data obtained in an elasmobranch fish, domestic fowl, dog and a lungless salamander. The analysis shows that, despite distinct differences in maximum efficiencies of these systems, the differences in efficiency values actually attained are much less pronounced, and may be even less marked when taking functional inhomogeneities into account which are neglected in this study.

Animals↗
PubMed1976

Pulmonary arteriovenous anastomoses in the avian lung: do they exist?

A search for pulmonary arteriovenous anastomoses was made in 15 adult domestic fowls using Lycopodium spores and microspheres. The diameter of the spores and microspheres ranged from about 10 to 33 mum. To dilate any pulmonary arteriovenous anastomoses, the birds were warmed to induce panting, killed with chloroform, or injected intravenously with papavarine. The spores or microspheres were injected either into the jugular vein under anaesthesia, or into the pulmonary artery after death. After the pulmonary arterial injections, the effluent from the pulmonary vein, and histological sections of the lungs, were examined for spores or microspheres. When injections were made into the jugular vein, blood smears from the pulmonary veins, left atrium, and the aorta, as well as histological sections of the lungs and other organs were inspected. The results of all these experiments showed that no spores or microspheres were ever found on the venous side of the pulmonary circulation, indicating absence of pulmonary arteriovenous anastomoses.

Animals↗
PubMed1982

Morphometrics of the avian lung. 2. The wild mallard (Anas platyrhynchos) and graylag goose (Anser anser).

The lungs of 5 wild mallard ducks (Anas platyrhynchos) and 5 feral graylag geese (Anser anser) of mean body weight 1.04 and 3.84 kg, respectively, were fixed in situ by intratracheal infusion of 2.3% glutaraldehyde, pH 7.4 and total osmolarity 350 mOsm, at a pressure head of 25 cm, and analysed by standard morphometric techniques. The following data apply to both lungs together, in the fixed state, the first value relating to Anas and the second to Anser in each case: lung volume, 30.4 and 95.3 cm3; volume of exchange tissue, 12.32 and 38.50 cm3; volume of capillary blood, 4.06 and 12.49 cm3; surface area of blood-gas (tissue) barrier per unit body weight, 28.56 and 23.10 cm2/g; surface area of the blood-gas (tissue) barrier per unit volume of lung, 977 and 932 cm2/cm3; surface area of blood-gas (tissue) barrier per unit volume of exchange tissue, 241 and 230 mm2/mm3; harmonic mean thickness of tissue barrier, 0.133 and 0.118 microns; arithmetic mean thickness of tissue barrier, 0.903 and 0.887 microns; harmonic mean thickness of plasma layer, 0.369 and 0.322 microns; mean total morphometric pulmonary diffusing capacity per unit body weight, 3.85 and 3.59 ml O2/min/mm Hg/kg. These morphometric parameters of Anas and Anser are compared with those reported in the literature for the domestic fowl (Gallus gallus), the budgerigar (Melopsittacus undulatus), the house sparrow (Passer domesticus), and the violet-eared hummingbird (Colibri coruscans). The lungs of these six avian species show progressively advancing adaptations, from Gallus, through Anser, Anas, Melopsittacus and Passer, to Colibri, which appear to be consistent with the energetic characteristics of these birds.

Animals↗
PubMed1983

Gas exchange, blood gases and acid-base status in the chick before, during and after hatching.

To study the transition from chorioallantoic to pulmonary gas exchange in birds, blood gases and acid--base variables were measured in chicks of domestic fowl before, during and after hatching. Measurements were made in samples of 'venous' blood (from allantoic arteries or the right ventricle, respectively) entering the gas exchanger (chorioallantois or lungs, respectively) and arterialized blood (from allantoic veins or the left ventricle, respectively) leaving the gas exchanger. Also, O2 uptake was measured and blood flow of the gas exchanger was determined according to the Fick principle. During the last days of incubation PO2 decreased PCO2 increased in both arterialized and 'venous' blood, but the changes of pH were small due to a concomitant increase in bicarbonate concentration, in accordance with the results of previous studies. After external pipping and hatching pronounced hypocapnia developed, but the respiratory alkalosis was partiallY compensated by a transitory non-respiratory reduction of bicarbonate. In spite of arterial hypoxia at the end of incubation and some loss of blood during hatching, blood O2 transport was not seriously impaired during pipping and hatching as revealed by 'venous' blood gases. The blood gases and pH of 17-day-old chicks were close to those of adult chickens.

Acid-Base Equilibrium↗
PubMed1985

Effects of changes in tidal volume on avian intrapulmonary chemoreceptor discharge.

It has been suggested that avian intrapulmonary CO2-sensitive receptors (IPC) may be capable of monitoring the rate and extent of CO2 washout from the lung during spontaneous breathing. The purpose of this study was to analyse IPC discharge activity (using computerised bin-averaging and counting techniques) in spontaneously breathing domestic fowl when VT was elevated from resting levels. This was accomplished by administration of almitrine (2 mg X kg-1 i.v.), a respiratory stimulant drug that has been shown to have a specific long-lasting stimulatory action on carotid body chemoreceptors. Unanaesthetized decerebrate chickens were tracheotomized and single unit activity was recorded from 14 IPC. When VT progressively increased following administration of almitrine (with little or no change in TI or TE), IPC activity increased in a linear relationship with the increased VT. IPC activity in expiration was also increased, and the delay period before the onset of IPC discharge in inspiration was shortened. It is concluded that IPC discharge is increased when VT is elevated in the spontaneously breathing chicken and hence the IPC are capable of monitoring the extent of each ventilatory effort. It is well known that IPC have strong inhibitory effects on ventilatory motor output and conceivably they could originate reflexogenic information to the respiratory centres in response to intrapulmonary PCO2 changes. The latter could arise from changes in CO2 delivery by the mixed venous blood or from changes in the extent of CO2 washout with each breath.

Almitrine↗
PubMed1989

Changes in eggshell water vapour conductance during shell formation in the chicken.

Time-related changes in shell porosity and eggshell water vapour conductance were measured in uterine eggs of the domestic fowl (Gallus domesticus) from 10 h in uterus to oviposition. Measurements were carried out in artificially-aborted eggs. It was found that the eggshell water vapour conductance decreased to a minimum level at 15 h in uterus. This coincided with increases in shell thickness and shell porosity as power functions of uterine time. From that time on, water vapour conductance increased as a power function of uterine time to the final value prior to oviposition. Thus, eggshell water vapour conductance is determined by different rates of dynamic changes in shell porosity and shell thickness in the course of shell calcification. The final conductance is reached about 2 h before oviposition.

Animals↗
PubMedDate not supplied

Metabolic responses of chicken embryos and hatchlings to altered O2 environments.

The oxygen consumption (MO2) response over a 4 h period of exposure to altered ambient O2 (air, 10, 15, 40, 60, 80 and 100%), helium (He) and sulfur hexafluoride (SF6) environments was determined for young (12 days old) and late (16 and 18 days old) embryos, externally pipped (EP) eggs and just hatched chicks (hatchlings) of the domestic fowl. The young embryos were insensitive to hyperoxic gas mixtures and to He exposure, while the late embryos increase their MO2 in hyperoxic environments, independently of O2 concentration, and also in a He atmosphere. Both the young and late embryos responded to SF6 exposure with decreasing MO2, as SF6 reduces O2 diffusivity through the eggshell. The MO2 of EP eggs and hatchlings in He and SF6 varied very widely, the effects of altered diffusivity being insignificant. In hypoxic environments in which the MO2 decreased, the fall of MO2 became smaller as embryos developed and particularly after they pipped the shell and hatched. In an atmosphere of 10% O2, the MO2 of all embryos in the egg before hatching decreased to below 10% of the control after 4 h, while in hatchlings the MO2 remained above 80% of the control. As all embryos in situ in the egg depend entirely or partly on diffusion in order to obtain O2, this emphasizes the limitation of the diffusive process. A 4 h exposure to 10% O2 was lethal for embryos in the egg even if they had pipped the shell and were breathing air with the lungs.

Animals↗
PubMed1986

Hypermetropia in dark reared chicks and the effect of lid suture.

Two experimental groups of domestic fowl chicks were reared in darkness. One group was normal (DR) and the second had unilateral lid closure (DRC). A control group was reared in normal illumination (LR). The optical components of the eye were examined by retinoscopy, keratometry and phacometry while physical measurements were made using ultrasonography and micrometry. The DR chicks developed a significant hyperopia (+3.11 D) compared to the LR chicks (+0.65 D), attributed to a significant decrease in corneal height and lens thickness. A significant increase in the anteroposterior axis of the DR chicks tends to reduce the dark induced hyperopia. Lid closure in the DRC chicks increases the hyperopic effect by +3.07 D due to additional corneal flattening. These results reinforce our proposal of the chick eye as a model for research in the various forms of ametropia.

Animals↗
PubMed1976

The drinking response of the chicken to peripheral and central administration of angiotensin II.

Intravenous injection of Ang II (val5 angiotensin II amide) elicited an immediate drinking response in the domestic fowl which lasted at least 20 minutes. The minimal dosage needed was 300 mug. Intracranial injection of 10 mug Ang II through cannulas implanted in the anterior diencephalon caused a significant increase in water intake. The minimal intracranial dosage of Ang II which evoked drinking was 2.5 mug. Intracranial injection of isotonic KCl inhibited the drinking response induced by intravenously injected Ang II when administered simultaneously. This suggests that drinking caused by both intravenous or intracranial injection of Ang II is activated through identical brain regions. The positive drinking response of the chicken is repeated concecutive intracranial injections of Ang II declined from the first injection through the following ones.

Angiotensin II↗
PubMed1986

Central and peripheral effects of serotonin on the immobility response in chickens.

The effects of low and high doses of serotonin on tonic immobility (TI) duration and susceptibility in 10- and 45-day-old chickens were examined. High doses of serotonin reduced the number of inductions required to produce TI, regardless of the subject's age. In contrast, low and high doses of serotonin produced biphasic increases and decreases in TI duration in 10-day-old birds, but there were no apparent effects on immobility duration by either dose of this drug in older chickens. These results are discussed in terms of the formation of the blood-brain barrier in domestic fowl and the differential peripheral versus central actions by serotonin on TI susceptibility and response duration.

Age Factors↗
PubMed1996

A complement factor B-like cDNA clone from the zebrafish (Brachydanio rerio).

An important molecule in the activation of the complement system in vertebrates is factor B, a serine protease with a molecular mass of 95,000. Factor B and the complement component C2 are thought to have arisen by gene duplication. In mammals and in Xenopus the factor B gene is linked to the major histocompatibility complex (MHC), whereas in domestic fowl it segregates independently of the MHC. Here we describe the isolation of a cDNA clone coding for factor B in the zebrafish, Brachydanio rerio. The deduced protein sequence exhibits a characteristic mosaic structure consisting of the short consensus repeat (SCR), the von Willebrand factor, and the serine protease domains. The estimated time of factor B and C2 divergence (approximately 350 million years ago), combined with the fact that C2 has thus far been found only in mammals, suggest that the factor B-C2 gene duplication occurred after the divergence of mammal-like reptiles from other reptiles and hence also birds. After the duplication, the C2 component evolved significantly faster than factor B.

Amino Acid Sequence↗
PubMed1991

Stress--mechanisms of immunosuppression.

Stress, a term commonly used to describe varied phenomena, should be restricted to describe an adaptive response by an animal to threats to homeostasis. The threats to homeostasis are called stressors. Stressors include a variety of physical, psychological, chemical, or infectious causes that are modified by intrinsic and extrinsic factors. Examples of modifiers include stressor severity, duration, novelty, host genetics and immune status. What may be a stressor to an animal in one situation, when modified, may not be a stressor in another situation. Mechanisms of stress once thought to involve a single pathway described by Seyle as the General Adaptation Syndrome, have been rejected. Four pathways, some incompletely defined, have been implicated in modulation of the immune system. They include autonomic nervous system, the hypothalamic adrenal axis, extra-adrenal pathways involving neuropeptides and neurotransmitters and neuroimmunological mediators. The mechanisms of stress-induced immunosuppression resistance are poorly defined in domestic fowl and will require careful experimentation linking defined stressors with altered physiological responses that affect specific immune function and result in increased disease susceptibility.

Adaptation, Physiological↗