Biomedical subjects

J V Zappia

Publications and source records attributed to J V Zappia.

5 recordsLinked to original sources

PubMed1988

Development of the supraoptic decussation in the chick (Gallus gallus).

The developing supraoptic decussation (SOD), a major interhemispheric tract in birds, has been implicated in both transfer of visual information and in the modulation of brain asymmetry. Moreover little is known of its morphology during development. We have examined the development of the chick SOD, which consists of three subregions; dorsal, ventral and subventral SOD. In the dorsal SOD the total number of fibres reach 968,000 on the 19th day of incubation (E-19), falling to 570,000 by the 8th day after hatching (P-8). In the ventral SOD, the number of fibres at E-19 reach 660,000, followed by a gradual reduction in their number to about 490,000 at P-22. In the subventral SOD the number of fibres estimated was 87,000 at E-15 falling to about 36,000 P-1. Compared with adult levels, there is, respectively, a drop in the number of fibres of 44%, 25% and 69% in the dorsal, ventral and subventral SOD during development. At E-19 in both the dorsal and ventral SOD there is qualitative evidence of axonal loss; disrupted axonal profiles, increased extracellular space and cells containing lysosomal cytoplasmic inclusions indicative of macrophages. Differences were also observed in the pattern of myelination, the dorsal, ventral and subventral SOD were shown to myelinate at different rates. Thus, in a single named tract, the SOD, there are major differences in the onset, rate and extent of fibre loss and myelogenesis within its three subregions. The functional implications of these differences are considered.

Animals↗

PubMed1987

Sex differences and reversal of brain asymmetry by testosterone in chickens.

The study examined the effect of testosterone on the asymmetry of visual discrimination performance of young chicks. Two-week-old chicks were tested on the pebble floor visual discrimination task. Male chicks were found to have brain asymmetry for visual discrimination learning, since chicks tested binocularly, or tested monocularly using their right eye system, have superior learning performance compared to chicks tested monocularly using their left eye system. Control female chicks were not found to have brain asymmetry. Testosterone treatment (12.5 mg of testosterone oenanthate on day 2 posthatch) reversed the pattern of brain asymmetry observed in control males but not females. In addition, asymmetry of visual discrimination learning is demonstrated in both male and female chicks after unilateral intracranial treatment with monosodium glutamate.

Animals↗

PubMed1986

The influence of testosterone on the sex-dependent structural asymmetry of the medial habenular nucleus in the chicken.

The volume of the left and right medial habenular nuclei of male and female chicks was analysed for evidence of structural asymmetry. The influence of exogenous testosterone on habenular asymmetry was also examined. Male and female chickens were injected intramuscularly with either testosterone enanthate or an oil vehicle on day 2 (15 animals per group) and were perfused at days 5, 12, and 19 respectively. Paraffin sections (8 microns) containing the medial habenular nucleus were stained with cresyl violet and both left and right medial habenular nuclei were measured by planimetry. In control chicks, males had structural asymmetry at day 12, whereas females did not show any structural asymmetry. Testosterone did not appear to influence asymmetry in the male chick but induced structural asymmetry at all three ages in the female to favour the right hemisphere. This study demonstrates a role for testosterone in influencing structural asymmetry of a nucleus in the vertebrate brain.

Animals↗

PubMed1985

Visual deficits following intraocular treatment of chicks with glutamate or kainic acid.

After intraocular treatment with kainate or glutamate, chicks were tested for visual discrimination performance, pecking aim, bead detection, optokinetic response and pupillary response. Kainate at an amount of 6 nmol per eye impaired performance in all of the tests except pupillary response. No effects were seen after 0.6 nmol of kainic acid. Glutamate at 6000 nmol impaired performance on all tests but the optokinetic and pupillary response. Although glutamate caused less severe deficits in visual behaviour than the high dose of kainate, cellular organization of the retina, at least in some regions, was more disrupted in these animals. Glutamate at 600 nmol caused a late onset defect in visual discrimination performance but no effects on optokinetic response.

Animals↗

PubMed1983

Light experience during development affects asymmetry of forebrain function in chickens.

The chicken brain has asymmetry of forebrain function of attack and copulation behaviors. This study reports that this asymmetry, revealed by intracranial injections of glutamate, is affected by light exposure. Eggs were incubated in 3 forced-draught incubators matched for noise, humidity and temperature control, so that light and laboratory noise were the only systematic variables. All eggs were incubated in darkness for the first 17 days of incubation after which they were allocated to one of 3 incubating conditions, L+S+, L-S+, L+S-, where + or - indicates the presence or absence of light (L) or laboratory noise (S). Light exposure was necessary to establish lateralization of attack and copulation, sound was not since only the L+S+ and L+S- groups were lateralized. The lateralization of auditory habituation was not affected by these incubating conditions. Further experiments established that on day 19 of incubation exposure for 4 h to a light of constant intensity produced lateralization. 1 h exposure to a light of constant intensity or to a flickering light (1.7 Hz) failed to produce lateralization. Examination of the data for individuals suggests that light exposure synchronizes the direction of lateralization rather than generates its presence. Environmental and genetic factors interact to produce the lateralization of attack and copulation.

Acoustic Stimulation↗