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At least 991 records · Page 55Linked to original sources
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↗
PubMed1988

Relationship between endocardial activation of SA valve and right atrium in domestic fowl.

We mapped endocardial activation in the isolated, perfused chicken heart to determine how excitation spreads from the sinoatrial (SA) valve, the avian pacemaker structure, to the atrioventricular (AV) ring. We found activity originating from one of three sites on the right valvule with the upper half of this valvule being the dominant origin. Only one heart exhibited an origin lower on the right valvule. We never observed activity originating from the left valvule. Depending on the valvular origin, two patterns of atrial activation were observed. The dominant pattern emerged from an upper to middle origin on the right valvule and involved two preferential conduction pathways. One pathway followed the right transverse arch and pectinate muscle medially to depolarize the AV ring from a posterior medial direction. Activation along the second pathway traveled caudally along the right valvule and then followed the sinus septum to approach the AV ring from an anterior lateral direction. An atypical pattern resulted from one heart exhibiting a lower origin on the right valvule. In this case, preferential atrial conduction only followed the lower pathway. This could represent an entrance block located cranially in the right valvule preventing normal activation of the right transverse arch and pectinate muscle.

Animals↗
PubMed1995

Fixed patterns of bradycardia during late embryonic development in domestic fowl with C locus mutations.

A predictable late embryonic bradycardia (relative to normal White Leghorn chickens) has been documented in chicken strains with C locus mutations. The basis of the bradycardia remains unknown but clearly is related to a mutation at the C locus, which contains the structural gene for tyrosinase. When compared with the heart rate of normal White Leghorns (approximately 295-305 beats/min from day 8 to day 20 of incubation), ca/ca and other C locus mutants showed a 10-12% reduction in heart rate during the last 4 days of incubation. Embryonic mortality occurred in both mutant and normal strains at an equivalent rate (approximately 23%); a significant bradycardia (when compared with surviving embryos of the same strain) developed on the day before death in White Leghorn but not mutant strains. The bradycardia did not affect embryonic oxygen consumption (approximately 0.2 ml O2.egg-1.min-1 at day 14 and 0.4 ml O2.egg-1.min-1 at day 20), which showed only minor differences between strains that can be attributed to differences in embryonic mass on days 16-20.

Animals↗
PubMed1979

Effect of timing of FICO2 changes on ventilatory period in domestic fowl.

These experiments were conducted to see if the pacing phenomenon found by Kunz and Miller (Respir. Physiol., 22: 167--177, 1974) in the open-loop, unidirectionally ventilated chicken is important in normally breathing birds. In this study, chickens breathed spontaneously through a tracheostomy from a gas source in which the fraction of CO2 (FICO2) could be rapidly changed. A feedback algorithm kept the FICO2 at 0.05 except for a constant duration pulse (approx 0.6 s) of low FICO2 given tau seconds after the beginning of each inspiration. In all birds tested an increase in tau resulted in a proportional increase of both inspiratory period (TI), expiratory period (TE), and the total period (Ttot). Increases in TI were from 0.5 to 1.0 times the increase in tau. Dynamic expeiments showed TI usually changed on the next breath after a step change in tau, and sinusoidal modulation of tau caused concurrent sinusoidal changes in TI, TE, and Ttot. These findings indicate that the phenomenon that produced pacing in the unidirectionally ventilated birds is important to the ventilatory pattern of normal breathing.

Animals↗
PubMed1980

P-wave morphology and atrial activation in the domestic fowl.

The purpose of this study was to define the P-wave morphology in the open chest, anesthetized fowl, and to map the corresponding pattern of atrial epicardial activation. Using back lead electrocardiograms (ECG) recorded between the base of the neck and tail, seven P-wave morphologies were identified. Four of these morphologies were upright, two were inverted, and one was biphasic. Spontaneous conversion from one morphology to another was common. During the most common P-wave morphology, activation of the atrial epicardium was mapped by comparing the onset of up to 68 local electrograms with the onset of the P wave of the ECG. Pacemaker activity was found near the base of the left sinoatrial valve and preferential conduction was demonstrated caudally along the base of that valve and medially along the rostral border of the right atrium. Changes in P-wave morphology were shown to correspond with changing patterns of atrial activation. Spontaneous changes in P-wave morphology and epicardial activation indicate a labile pacemaker region in the bird and suggest a developmental stage of evolution similar to both their reptilian ancestors and to their mammalian counterparts.

Animals↗
PubMed1984

Vagal control of respiratory pattern during hyperpnea in domestic fowl.

Minute volume, tidal volume, and respiratory frequency were measured during hyperpnea induced by exercise, increased body temperature, and CO2 inhalation. Ventilatory characteristics were compared before and after the vagus nerve had been blocked. In normal birds exercise produced increases in both tidal volume and respiratory frequency; hyperthermia produced a typical thermal polypnea consisting of greatly increased respiratory frequency and reduced tidal volume; CO2 inhalation produced increases in tidal volume and respiratory frequency when the birds were euthermic but a slowing of respiratory rate when the birds were hyperthermic. After vagal block these pronounced differences in the pattern of ventilatory response to the various respiratory stimuli were abolished. Instead there was a uniform ventilatory response to all three stimuli consisting mainly of increases in tidal volume combined with small increases in respiratory frequency. It is concluded that in the normal animal control of the varied pattern of ventilatory response to different respiratory stimuli is dependent on vagal fiber activity.

Animals↗
PubMed1978

Autoradiographic localization of androgen-concentrating cells in the brain of the male domestic fowl.

Cells in the male fowl brain which accumulate radioactivity following 3H testosterone (T) administration were identified by autoradiography. Labelled cells were found principally in hypothalamic, limbic and midbrain structures. Marked uptake was observed in the preoptic area (POA) and in the anterior and posterior hypothalamus. There was also a significant amount of labelling in the archistriatum (ARCH), particularly in the nucleus taeniae (Tn), and in the lateral septum. In the midbrain, substantial uptake of labelled hormone was found in the nucleus intercollicularis (ICo). The pattern of accumulation of T in the male fowl was comparable to that for sex hormone uptake in vertebrates in general. Furthermore, accumulation was generally found in areas known to be concerned with sex hormone-dependent functions.

Animals↗
PubMed1983

Synaptonemal complexes and the chromosome complement of domestic fowl, Gallus domesticus.

Synaptonemal complexes (SC's) were compared to their chromosomes by transmission electron microscopy (TEM) of whole-mount spreads from 42 male chickens. Individual macrochromosomal SC's were first identified in heterokaryotypes and later by their centromere index. For all nine macrochromosomes (eight autosomes and the Z sex chromosome), the relative length (rl) of each SC corresponded to that of its mitotic and meiotic chromosome, and the centromere position along each SC corresponded to that of its mitotic chromosome. An idiogram was constructed which included the 30 microchromosomes. The idiogram revealed a graded series of SC lengths with a 30-fold difference between the longest and the shortest SC. Microchromosomal SC's comprised 35% of the genome length.

Animals↗
PubMed1983

Synaptonemal complex analysis of chromosome rearrangements in domestic fowl, Gallus domesticus.

Electron microscopy of synaptonemal complexes in heterokaryotypic Gallus domesticus cockerels revealed that chromosome rearrangements that had been classified by light microscopy as single breaks were in fact reciprocal translocations. A microchromosome provided the centromere for the acentric long arm of chromosome 1 in a rearrangement that had been classified as a centric fission, and microchromosomes were involved in several other rearrangements. The translocation points were mapped in three of the rearrangements.

Animals↗
PubMed1985

Synaptonemal complex analysis of a pericentric inversion in chromosome 2 of domestic fowl, Gallus domesticus.

Electron microscopy of synaptonemal complexes in three Gallus domesticus cockerels that were heterokaryotypic for a pericentric inversion in chromosome 2 revealed a low incidence of homologous pairing and a high incidence of nonhomologous pairing. The significance of these results are related to the finding that heterokaryotypic parents have fertility rates that are normal or above normal and produce only balanced gametes. One cockerel apparently had both normal cells and cells with a heteromorphic bivalent 2 in its germ line.

Animals↗