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At least 235 records · Page 13Linked to original sources
PubMed1978

Epileptiform seizures in domestic fowl. VIII. Anticonvulsant activity of primidone and its metabolites, phenobarbital and phenylethylmalonamide.

Primidone is an effective anticonvulsant against seizures induced in epileptic fowl by exposure to intermittent photic stimulation. Epileptic fowl metabolize primidone to phenobarbital. Pretreatment of epileptic fowl with SKF 525A to prevent the metabolism of primidone to phenobarbital indicated that primidone itself had anticonvulsant activity. Phenylethylmalonamide, a second metabolite of primidone, did not have anticonvulsant activity when administered at the same dose as primidone.

Animals↗
PubMed1978

Epileptiform seizures in domestic fowl. IX. Implications of the absence of anticonvulsant activity of ethosuximide in a pharmacological model of epilepsy.

Acute dose--response studies were conducted to determine if ethosuximide had anticonvulsant activity against seizures evoked by stroboscopic stimulation of epileptic fowl and to correlate the observed effects with the concentration of the drug in the plasma. Ethosuximide, in doses that produced mean plasma concentrations of 366 microgram/ml and signs of sedation, did not reduce seizure susceptibility. Twice daily administration of ethosuximide produced mean plasma concentrations of 430 microgram/ml after 36 h without affecting seizure susceptibility even in the presence of marked sedation. Previous studies have shown that epileptic fowl are sensitive to the anticonvulsant effects of phenobarbital, phenytoin, and primidone at plasma concentrations similar to those required in humans. Since ethosuximide has a high specificity against petit mal seizures in humans, the failure of ethosuximide to provide protection indicates that epileptic fowl represent a relatively specific pharmacological model for drugs effective against generalized tonic--clonic and focal cortical epilepsies in humans.

Animals↗
PubMed1986

Regulation of plasma arginine vasotocin in conscious water-deprived domestic fowl.

Radioimmunoassay methods were employed to quantitatively characterize secretion of the avian antidiuretic hormone [arginine vasotocin (AVT)] by the hypothalamo-neurohypophyseal system (HNS) of the conscious domestic fowl in response to chronic dehydration. Water deprivation permitted characterization of AVT secretion in response to the combined stimuli of extracellular hyperosmolality and hypovolemia; the subsequent repletion of extracellular volume permitted separation of potential osmotic and volemic factors involved in the regulation of AVT secretion. In normally hydrated birds, plasma AVT (PAVT) and plasma osmolality (Posm) averaged 2.2 +/- 0.3 microU/ml (10.5 +/- 1.4 pg/ml) and 309.3 +/- 0.7 mosmol/kg H2O, respectively (means +/- SE). With water deprivation, PAVT and Posm of the birds increased in parallel in a curvilinear manner to maxima of 13.1 +/- 0.6 microU/ml (62.4 +/- 2.9 pg/ml) and 346.6 +/- 2.0 mosmol/kg H2O, respectively, at 96 h of dehydration. The isosmotic repletion of extracellular volume at 96 h by acute intravenous infusion failed to alter 96-h PAVT values. The results indicate that AVT secretion is closely linked to the state of hydration during negative fluid balance in the domestic fowl. Analysis of the data indicated that increases in PAVT that occur with dehydration are mediated primarily by extracellular hyperosmolality and that the HNS of the domestic fowl is relatively insensitive to the simultaneous hypovolemia incurred with fluid deprivation.

Animals↗
PubMed2004

Molecular epidemiology of two fowl cholera outbreaks on a free-range chicken layer farm.

Two outbreaks of fowl cholera on a multiage free-range egg farm were investigated. The outbreaks occurred in 1994 and 2002. A total of 22 strains of Pasteurella multocida were available for study, 11 from the 1994 outbreak and 11 from the 2002 outbreak. Lesions typical of acute fowl cholera were seen in the 1994 outbreak, whereas both acute and chronic fowl cholera occurred in the 2002 outbreak. The isolates were examined in an extended phenotypic typing methodology, by a P. multocida-specific polymerase chain reaction (PCR), by the Heddleston somatic serotyping scheme, and by restriction endonuclease analysis (REA) typing using the enzyme HpaII. All 22 strains had the same phenotypic properties, all were confirmed as P. multocida by PCR, all were Heddleston serovar 4, and all had the same REA pattern. The results indicate that these 2 outbreaks were caused by the same clone of P. multocida--despite the 8-year time period between the outbreaks.

Animal Husbandry↗
PubMed1986

Corticotropin-releasing factor stimulates the release of adrenocorticotropin from domestic fowl pituitary cells.

The effect of synthetic ovine CRF on ACTH secretion of dispersed, domestic fowl pituitary cells was investigated. Cells preincubated for 2 h, 16 h, or after 48-h culture were incubated briefly with CRF (up to 4 h). ACTH was bioassayed using isolated rat adrenocortical cells; ACTH-(1-24) served as the standard for expressing the data. Results with 16-h preincubated cells were as follows: CRF induced ACTH secretion in a concentration-dependent manner: ED50 and maximal stimulatory concentrations were 1.0 nM and 5.0 nM, respectively. CRF (10 nM) induced significant ACTH secretion within 10 min of incubation; maximal secretion (370% over basal value) was attained at 2 h. Dexamethasone (DEX) inhibited basal and CRF-induced ACTH secretion in a concentration-dependent manner; half-maximal inhibitory and maximal inhibitory concentrations were approximately 10 nM and 1 microM, respectively. In addition, DEX (10 microM) acutely (within 2 h) inhibited maximal CRF-induced ACTH secretion by 46%. 8-Bromo-cAMP (1 mM) also induced ACTH secretion, and DEX inhibited this secretion with a potency equivalent to that for CRF-induced ACTH secretion. In contrast to the effect of CRF, high concentrations (100 nM) of ovine LHRH, TRH, and synthetic human pancreatic GH-releasing factor (1-32) failed to induce significant ACTH secretion, thus suggesting that the effect of CRF was peptide specific. Domestic fowl pituitary cells cultured for 48 h before treatment also responded to CRF but not to any greater extent than that of 16-h preincubated cells. In contrast to 16-h preincubated cells or 48-h cultured cells, 2-h preincubated cells had high basal values of ACTH secretion that may have partially diminished or masked the actions of CRF. These data suggest that 1) CRF is a potent and specific stimulator of ACTH secretion by domestic fowl pituitary cells and 2) 16-h preincubated cells or 48-h cultured cells are amenable for other in vitro investigations on the regulation of avian ACTH secretion.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed2006

Running over rough terrain: guinea fowl maintain dynamic stability despite a large unexpected change in substrate height.

In the natural world, animals must routinely negotiate varied and unpredictable terrain. Yet, we know little about the locomotor strategies used by animals to accomplish this while maintaining dynamic stability. In this paper, we perturb the running of guinea fowl with an unexpected drop in substrate height (DeltaH). The drop is camouflaged to remove any visual cue about the upcoming change in terrain that would allow an anticipatory response. To maintain stability upon a sudden drop in substrate height and prevent a fall, the bird must compensate by dissipating energy or converting it to another form. The aim of this paper is to investigate the control strategies used by birds in this task. In particular, we assess the extent to which guinea fowl maintain body weight support and conservative spring-like body dynamics in the perturbed step. This will yield insight into how animals integrate mechanics and control to maintain dynamic stability in the face of real-world perturbations. Our results show that, despite altered body dynamics and a great deal of variability in the response, guinea fowl are quite successful in maintaining dynamic stability, as they stumbled only once (without falling) in the 19 unexpected perturbations. In contrast, when the birds could see the upcoming drop in terrain, they stumbled in 4 of 20 trials (20%, falling twice), and came to a complete stop in an additional 6 cases (30%). The bird's response to the unexpected perturbation fell into three general categories: (1) conversion of vertical energy (EV=EP+EKv) to horizontal kinetic energy (EKh), (2) absorption of EV through negative muscular work (-DeltaEcom), or (3) converting EP to vertical kinetic energy (EKv), effectively continuing the ballistic path of the animal's center of mass (COM) from the prior aerial phase. However, the mechanics that distinguish these categories actually occur along a continuum with varying degrees of body weight support and actuation by the limb, related to the magnitude and direction of the ground reaction force (GRF) impulse, respectively. In most cases, the muscles of the limb either produced or absorbed energy during the response, as indicated by net changes in COM energy (Ecom). The limb likely begins stance in a more retracted, extended position due to the 26 ms delay in ground contact relative to that anticipated by the bird. This could explain the diminished decelerating force during the first half of stance and the exchange between EP and EK during stance as the body vaults over the limb. The varying degree of weight support and energy absorption in the perturbed step suggests that variation in the initial limb configuration leads to different intrinsic dynamics and reflex action. Future investigation into the limb and muscle mechanics underlying these responses could yield further insight into the control mechanisms that allow such robust dynamic stability of running in the face of large, unexpected perturbations.

Analysis of Variance↗
PubMed2006

The energetic costs of trunk and distal-limb loading during walking and running in guinea fowl Numida meleagris: I. Organismal metabolism and biomechanics.

We examined the energetic cost of loading the trunk or distal portion of the leg in walking and running guinea fowl (Numida meleagris). These different loading regimes were designed to separately influence the energy use by muscles used during the stance and swing phases of the stride. Metabolic rate, estimated from oxygen consumption, was measured while birds locomoted on a motorized treadmill at speeds from 0.5 to 2.0 m s-1, either unloaded, or with a mass equivalent to 23% of their body mass carried on their backs, or with masses equal to approximately 2.5% of their body mass attached to each tarsometatarsal segment. In separate experiments, we also measured the duration of stance and swing in unloaded, trunk-loaded, or limb-loaded birds. In the unloaded and limb-loaded birds, we also calculated the mechanical energy of the tarsometatarsal segment throughout the stride. Trunk and limb loads caused similar increases in metabolic rate. During trunk loading, the net metabolic rate (gross metabolic rate-resting metabolic rate) increased by 17% above the unloaded value across all speeds. This percentage increase is less than has been found in most studies of humans and other mammals. The economical load carriage of guinea fowl is consistent with predictions based on the relative cost of the stance and swing phases of the stride in this species. However, the available comparative data and considerations of the factors that determine the cost of carrying extra mass lead us to the conclusion that the cost of load carrying is unlikely to be a reliable indicator of the distribution of energy use in stance and swing. Both loading regimes caused small changes in the swing and/or stance durations, but these changes were less than 10%. Loading the tarsometatarsal segment increased its segmental energy by 4.1 times and the segmental mechanical power averaged over the stride by 3.8 times. The increases in metabolism associated with limb loading appear to be linked to the increases in mechanical power. The delta efficiency (change in mechanical power divided by the change in metabolic power) of producing this power increased from 11% in walking to approximately 25% in running. Although tarsometatarsal loading was designed to increase the mechanical energy during swing phase, 40% of the increase in segmental energy occurred during late stance. Thus, the increased energy demand of distal limb loading in guinea fowl is predicted to cause increases in energy use by both stance- and swing-phase muscles.

Animals↗
PubMed2006

The energetic costs of trunk and distal-limb loading during walking and running in guinea fowl Numida meleagris: II. Muscle energy use as indicated by blood flow.

We examined the changes in muscle energy use in guinea fowl running at 1.5 m s-1 either unloaded, or carrying trunk loads equal to 23% of body mass, or loads on their distal legs equal to a total of 5% of body mass. We estimated muscle energy use by measuring blood flow to all of the leg muscles using injected microspheres. Total blood flow to the leg muscles increased by approximately 15% under both loading conditions, which matched the percentage increase in net organismal metabolic rate. Significant increases in energy use (inferred from blood flow) above that found in unloaded birds were found in 12 muscles in trunk-loaded birds, with most of the increases restricted to stance-phase muscles, as predicted. Just three of these muscles, the femerotibialis, the iliotibialis lateralis pars postacetabularis and the fibularis longus accounted for 70% of the increased energy use. Noticeably absent from the group of muscles that increased energy use during trunk loading were several large biarticular muscles that have extensor actions at the hip or ankle, but flexor actions at the knee. We concluded that the low energetic cost of carrying trunk loads in guinea fowl may rely on the activation of a group of muscles that together provide support and propulsion across all the major joints, without producing opposing moments at other joints that could potentially waste energy. The specific leg muscles responsible for the increase in metabolism during trunk loading also suggest that the energy cost of producing mechanical work may be an important determinant of the cost of carrying extra mass on the trunk. During distal-limb loading, eleven leg muscles had significant increases in energy use, but unlike during trunk loading, both stance- and swing-phase muscles had large increases in energy use. This distribution of energy use between stance and swing agrees with the prediction that increased mechanical work determines the cost of limb loading, because a substantial fraction of the increased segmental work during distal-limb loading in guinea fowl has been found to occur during stance.

Animals↗
PubMed2001

Entraining the natural frequencies of running and breathing in guinea fowl (Numida meleagris).

Lung ventilation of tetrapods that synchronize their locomotory and ventilatory cycles during exercise could be economized if the resonant frequency of the respiratory system matched the animal's preferred step frequency. To test whether animals utilize this strategy, the input impedance of the respiratory system of five anesthetized, supine guinea fowl (Numida meleagris) was measured using a forced oscillation technique. The resonant frequency of the respiratory system was 7.12+/-0.27 Hz (N=5, mean +/- S.E.M.). No statistically significant difference was found between the resonant frequency of the respiratory system and the panting frequency used by guinea fowl at rest (6.67+/-0.16 Hz, N=11) or during treadmill locomotion (6.71+/-0.12 Hz, N=8) or to their preferred step frequency (6.73+/-0.09 Hz, N=7) (means +/- S.E.M.). These observations suggest (i) that, at rest and during exercise, panting guinea fowl maximize flow while expending minimal mechanical effort, and (ii) that natural selection has tuned the natural frequencies of the respiratory and locomotor systems to similar frequencies.

Animals↗
PubMed1992

Cardiac musculature of the cranial and caudal venae cavae and the pulmonary vein in the fowl.

The cardiac musculature of cranial and caudal venae cavae and pulmonary vein was examined to clarify its distribution pattern in the fowl using both light and electron microscopies. The musculature was distributed from the heart to the root of subclavian vein in the cranial vena cava, to the cranial margin of the liver in the caudal vena cava, and to the left and right distal pulmonary veins in the pulmonary vein, respectively. Judging from the morphology and distribution pattern in the venous wall, the cardiac musculature in the fowl is thought to share the same phylogenic origin with that in mammals. The ultrastructure of cardiac myocytes including transitional cells in the cranial vena cava and the pulmonary vein resembled that of atrial myocytes. While, the typical specialized myocytes such as Purkinje fiber were found in the caudal vena cava of the fowl.

Animals↗
PubMed1979

Fertilizing capacity and ultrastructure of fowl and turkey spermatozoa before and after freezing.

The fertilizing capacity, motility and ultrastructure of fowl and turkey spermatozoa were examined at various stages of the freezing process. For both species, fertility and motility were depressed after equilibration with dimethyl-sulphoxide at 5 degrees C. After freezing, motility was maintained at 55% for fowl spermatozoa and 40% for turkey spermatozoa; however, fertility was 55% for the fowl and 0% for the turkey. Qualitatively, the damage to the spermatozoa of both species was nearly identical, as revealed by scanning and transmission electron microscopy. The plasmalemma was the primary site of damage. 'Bent' spermatozoa, coiled tails and swollen mitochondria were also present. Damage to the acrosome was only observed in spermatozoa which had been frozen to -180 degrees or -196 degrees C. These changes were attributed to adverse osmotic conditions. Binding of cationic ferritin to the plasmalemma of spermatozoa from both species remained unaltered.

Animals↗
PubMed1980

Fertilizing capacity and morphology of fowl and turkey spermatozoa in hypotonic extender.

The effects of graduated increments of hypotonic Beltsville Poultry Semen Extender (BPSE) on fowl and turkey sperm morphologay, motility, percentage dead and fertility were examined. The morphology of fowl and turkey spermatozoa was adversely affected by decreases in BPSE osmolarity; a reduction of osmolarity of BPSE to below 200 and 140 mosmol adversely affected the fertility of fowl and turkey spermatozoa, respectively. addition of Ficoll to the extender allowed direct observation of the effects of hypotonic BPSE on the sperm plasmalemma. Plasmalemmal swelling, due to the uptake of water, was noted initially at the midpiece. Such plasmalemmal swelling may predipose spermatozoa to further osmotic-induced damage.

Animals↗
PubMed1984

Metabolism of fowl and turkey spermatozoa at low temperatures.

The rate at which fowl and turkey spermatozoa consumed energy (as ATP) in a glutamate-based medium without glucose decreased with temperature by 75-80% over the range 40 to 5 degrees C. The rate of oxygen utilization of these spermatozoa, as a monitor of their rate of energy production, also decreased by 75-80% over the same range of temperature, although sperm ATP levels remained constant. The rate of glycolysis of fowl spermatozoa decreased by a factor of 20 between 40 and 5 degrees C but remained capable of supporting optimal sperm ATP levels. Turkey sperm glycolysis proceeded extremely slowly and was not capable of supporting optimal ATP levels at any temperature investigated. Turkey, but not fowl spermatozoa, therefore require oxygen to maintain optimal energy levels at all temperatures between 5 and 40 degrees C.

Adenosine Triphosphate↗
PubMed1987

Resolution of the sperm motility-stimulating principle of fowl seminal plasma into Ca2+ and an unidentified low molecular weight factor.

It was confirmed, using an objective assay of motility, that fowl seminal plasma restores and stimulates the motility of fowl spermatozoa at 40 degrees C in a dose-dependent manner. By separation of a 100,000 g supernatant of fowl seminal plasma with Sephadex G-15, two peaks of motility-stimulating activity were distinguished. One peak coincided with that of calcium and was absent when calcium was removed from the seminal plasma with Dowex 50. The other peak, which accounted for 44% of motility-stimulating activity, contained a low molecular weight, dialysable factor which remains to be identified.

Animals↗
PubMed1998

Effects of taurine on the motility and intracellular free Ca2+ concentration of fowl spermatozoa in vitro.

The effects of taurine on the motility and intracellular free Ca2+ concentration of fowl spermatozoa were investigated in vitro. The addition of taurine, within the range of 0-5 mmol l(-1), did not appreciably affect the motility of intact fowl spermatozoa. Motility remained almost negligible at 40 degrees C, while vigorous movement was observed at 25 degrees C. Even with the addition of Ca2+ before the addition of taurine, neither stimulation nor inhibition of motility was observed compared with the control (no addition of taurine). Similar results were obtained by the addition of taurine and calyculin A, a specific inhibitor of protein phosphatases. There were no changes in intracellular free Ca2+ concentrations, measured by a fluorescent Ca2+ indicator, fura-2, in taurine-treated spermatozoa. These results suggest that taurine is not involved in the regulation of fowl sperm motility and metabolism by intracellular Ca2+ mobilization in vitro.

Animals↗
PubMedDate not supplied

Construction and immunogenicity studies of recombinant fowl poxvirus containing the S1 gene of Massachusetts 41 strain of infectious bronchitis virus.

The spike 1 (S1) surface glycoprotein of infectious bronchitis virus (IBV) is the major inducer of the generation of virus neutralizing antibodies, and the administration of purified S1 has been shown to elicit a protective immune response against virulent virus challenge. On the basis of these observations, recombinant fowl poxvirus (rFPV) containing a cDNA copy of the S1 gene of IBV Mass 41 (rFPV-S1) was constructed and its immunogenicity and vaccine potential were evaluated. Initially, rFPV-S1 was shown to express the S1 in vito by indirect immunofluorescence staining and western blot analyses. Later, in vivo expression was demonstrated by the detection of IBV-specific serum immunoglobulin G and neutralization antibodies in the sera of chickens immunized with rFPV-S1. That the recombinant virus elicited anti-IBV protective immunity was indicated by the manifested, relatively mild clinical signs of disease, decreased titers of recovered challenge virus, and less severe histologic changes of the tracheas in virulent IBV Mass 41-challenged chickens previously receiving rFPV-S1 as compared with parental fowl poxvirus (FPV)-vaccinated control birds. In contrast, chickens immunized with either recombinant or parental FPV were resistant to a subsequent virulent FPV challenge. As to a preferred method of immunization, wing web administration appeared to be superior to the subcutaneous route because a greater percentage of birds vaccinated by the former protocol exhibited an anti-IBV humoral immune response. Thus, rFPV-S1 has potential as a poultry vaccine against both fowl pox and infectious bronchitis.

Allantois↗
PubMed1975

Episodic release of luteinizing hormone in the domestic fowl.

Plasma luteinizing hormone (LH) levels were measured by radioimmunoassay in serial samples taken from intact adult cockerels, gonadectomized fowl of both sexes and laying hens. By sampling at 30 and 10 min intervals, it was shown that in cockerels LH is released episodically. Each secretory episode lasted 90-120 min and was characterized by a 100-200% rise in LH levels over a period of 10-15 min followed by a more gradual, exponential decline. Mean plasma LH levels were found to be depressed in cockerels as a result of the handling associated with taking blood samples; in cases where LH levels were most depressed, an episodic pattern of secretion could not be demonstrated. In the gonadectomized fowl, an episodic pattern of LH secretion was shown when blood samples were taken at 10 or 5 min intervals. During each secretory episode, which lasted 20-45 min, LH levels rose by 20-60%. It is suggested that the increase in mean plasma LH levels in gonadectomized fowl (30-77 ng/ml) over those in cockerels (7-16 ng/ml) is related to an increase in the frequency of the episodic release of the hormone. Episodic discharges of LH could not be demonstrated in laying hens. In these birds the mean LH levels are low (1-5--2-4 ng/ml) and consequently may be maintained by secretory episodes which are of too low an amplitude to be detectable.

Animals↗
PubMed1990

Participation of tri-iodothyronine and metabolic clearance rate in the inhibition of growth hormone secretion in thyroxine-treated domestic fowl.

Surgical thyroidectomy increases basal and TRH-induced GH concentrations in the peripheral plasma of immature domestic fowl. Replacement therapy with thyroxine (T4; 100 micrograms/kg per day for 7 days, i.m.) suppressed the GH responses to thyroidectomy. Bolus administration of T4 (10 micrograms/kg, i.m.) to thyroidectomized birds promptly lowered the circulating GH concentrations, which remained suppressed for at least 4 h. Chronic (daily injections for 7 days) or acute (one injection) pretreatment of thyroidectomized birds with iopanoic acid (IOP; 40 mg/bird, i.m.) before the bolus administration of T4 attenuated, but did not prevent, inhibition of circulating GH levels by T4. Administration of IOP (40 mg/bird i.m.) 24 h and immediately before the administration of tri-iodothyronine (T3; 3 micrograms/kg, i.m.) or T4 (10 micrograms/kg, i.m.) also failed to suppress thyroidal inhibition of circulating GH concentrations in thyroidectomized birds. Administration of IOP alone had no effect on GH concentrations. Circulating T3 concentrations were not enhanced following the administration of T4 to IOP-treated birds, indicating its inhibition of hepatic monodeiodinase activity. The metabolic clearance rate (MCR) of 125I-labelled chicken GH in the plasma of thyroidectomized fowl was less than that in sham-thyroidectomized birds. Following pretreatment with T4 (100 micrograms/kg per day for 7 days) sham-thyroidectomized and thyroidectomized birds did not differ significantly in their MCR. The GH secretion rate in thyroidectomized birds was similar to that in sham-thyroidectomized birds and in both groups was markedly reduced following pretreatment with T4. These results demonstrate thyroidal inhibition of circulating GH concentrations in fowl.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗