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D Ehrlich

Publications and source records attributed to D Ehrlich.

At least 73 records · Page 4Linked to original sources
PubMed1985

The effects of binocular and monocular occlusion on the number of optic nerve axons containing degenerative organelles.

In this study chicks were incubated in the dark and then reared for 2 days with either none, one or both eyes occluded. Cross-sections of the optic nerves were examined for profiles of axons containing accumulations of degenerative organelles. There were significantly more organelle-containing axons in the non-occluded and monocularly occluded birds compared with the binocularly occluded birds. There was no significant difference between the non-occluded and monocular group. Furthermore, there was no significant difference between the occluded and non-occluded eyes of monocular birds. We propose that the rise in organelle-containing axons during development reflects a phenomenon involved in the linking of the eyes, and that visual input to a single eye is sufficient to hasten this process.

Animals↗
PubMed1985

Sex-dependent structural asymmetry of the medial habenular nucleus of the chicken brain.

An investigation of structural asymmetry in the avian brain was conducted on the epithalamic medial habenular nucleus of the chicken. Twelve male and ten female two-day-old chickens were used for a morphometric evaluation of asymmetry. The medial habenular nucleus was measured from paraffin-wax-embedded, 8 micron-thick sections by use of a semiautomatic image analyser. The volumes of the right and left medial habenula of each animal were statistically analysed ('within animal experimental design'). The right medial habenula in males showed significant group asymmetry. In contrast, females failed to demonstrate group bias in favour of either hemisphere. However, individual females were lateralised, with either a larger right or left medial habenula. Although individuals of both sexes were lateralised, there was no significant sex difference in volume in either the right or left medial habenula. We propose that sex-linked structural asymmetry may be influenced by steroid hormonal effects in the central nervous system, and that such asymmetry could be more prevalent in the non-mammalian vertebrate brain than previously considered.

Animals↗
PubMed1985

Myelogenesis and estimation of the number of axons in the anterior commissure of the chick (Gallus gallus).

By use of light- and electron microscopy the anterior commissure of the chick was studied at different times during development. Between the 19th day of incubation and the 35th day after hatching the cross-sectional area of the anterior commissure, as determined from mid-sagittal sections, undergoes a 6-fold increase in size. Thereafter the area remains fairly constant. The total number of fibres in the anterior commissure was estimated to be 89000. The full complement of fibres is already present by the 19th day of incubation. Myelogenesis occurs mainly between the 19th day of incubation and the 35th day after hatching, concomitant with the increase in cross-sectional area. From the 35th day after hatching, myelinated fibres comprise approximately 40% of the total number of fibres. The median diameter of unmyelinated fibres is about 0.35-0.40 micron. The median diameters of myelinated axons and fibres are 0.8-1.0 micron and 1.1-1.3 micron, respectively.

Animals↗
PubMed1985

Visual deficits and retinotoxicity caused by the naturally occurring anthelmintics, Embelia ribes and Hagenia abyssinica.

The naturally occurring anthelmintics, Embelia ribes (Enkoko) and Hagenia abyssinica (Kosso), have been reported to possibly cause optic atrophy among the Ethiopian population. In this study we found retinal pathology and defects in visual behavior in chicks treated with Enkoko, Kosso, or embelin, a crystalline extract of E. ribes. The chicks were fed orally with a high dose of 0.25 g (5 g/kg) or a low dose of 0.025 g (0.5 g/kg) per day of Enkoko or Kosso, beginning on Day 2 of life. The high dose for Enkoko was administered for 1 or 5 days, while that for Kosso was administered for 1 or 9 days. For the low dose of both Enkoko and Kosso, the dosing regime was for a period of 1, 4, or 9 days. Embelin was administered at a dose of 0.001 g (0.02 g/kg) per day for 9 days. Control chicks were force fed an equivalent amount of chick feed. Treatment with Enkoko or Kosso significantly reduced the ability of chicks to detect a moving bead introduced into the peripheral field of vision. The degree of constriction of the visual field for detection was dependent upon the total amount of drug administered. Performance on a visual discrimination task, which required discrimination of feed grains from pebbles, was also impaired in chicks treated with total doses of 0.200 and 0.250 g of Enkoko or Kosso. Thus, the extent of deficit in visually guided tasks was found to be dose dependent. The visual deficits observed in Enkoko-treated chicks were mimicked by embelin, which suggests that embelin may be responsible for the visual defects. Anatomical evidence of degeneration of ganglion cells was found in retinae exposed to high doses of Enkoko (1.25 g) and Kosso (2.25 g). However, no retinal lesions were detected in chicks following treatment with cumulative doses of less than 0.25 g of Enkoko or Kosso. Similarly, retinal pathology was not observed in embelin-exposed retinae.

Administration, Oral↗
PubMed1985

Evidence for self-absorption of terminals by developing axons of retinal ganglion cells in the chick.

The appearance of membrane-bound degenerative organelles in chick optic nerve axons was studied at the electron microscopic level. A semiquantitative analysis revealed a sharp increase in the number of axons containing accumulations of such organelles during the second day after hatching. In dark-reared chicks this increase was retarded, suggesting the presence of a light-influenced event in the early post-hatch period.

Animals↗
PubMed1984

The course of axons of retinal ganglion cells within the optic nerve and tract of the chick (Gallus gallus).

Small laser lesions placed in the posthatch chicken retina resulted in axotomy and then death of all ganglion cells located in a sector peripheral to the primary damage. With the use of silver techniques, the patterns of degenerating retinal fibers in the optic nerve, chiasm, and optic tract were examined. In the proximal part of the optic nerve, radial retinal lesions resulted in a sheet of degenerating axons along the rostrocaudal extent of the nerve. The position of degenerating axons was related to the site of their entry in the optic nerve head with an overlapping distribution of degenerating fibers entering the optic nerve head from equivalent points from the temporal and nasal sides. In the optic chiasm, the distribution of fibers was similar to that seen in the proximal part of the optic nerve. In the optic tract there was a similar mixing of fibers from opposite sides of the retina. The ventral, nasal and temporal retinal fibers lay in the superficial part of the tract whereas the fibers from the nasal and temporal dorsal retina ran in the deeper, medial aspect of the tract. The central-to-peripheral axes of the retina were mapped along the rostrocaudal axis of the tract. As the tract approached the tectum degenerating fibers from single retinal lesions did not always remain together. In the case of a lesion in the ventral nasal retina, degenerating fibers split into two bundles located at opposite ends of the tract only to reunite at their terminal regional at the caudal pole of the tectum.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

An atlas of the primary visual projections in the brain of the chick Gallus gallus.

The localisation of the primary visual centres in the chick mesencephalon and diencephalon was determined by autoradiographic anterograde transport and degeneration techniques. Strong visual projections were found in the tectum, lateral anterior thalamic nucleus, lateroventral geniculate nucleus, superficial synencephalic nucleus, external nucleus, ectomammillary nucleus, tectal grey, dorsolateral anterior thalamus, rostrolateral part, and the pretectal optic area. Weaker retinal projections were found in the ventrolateral thalamus, two subregions of the dorsolateral anterior thalamus, lateral part, diffuse pretectal nucleus, dorsolateral anterior thalamus, magnocellular part, and the hypothalamus. An atlas of the retinal projections was constructed from sections.

Animals↗
PubMed1984

Topography of primary visual centres in the brain of the chick, Gallus gallus.

In a previous paper (Ehrlich and Mark, '83b) the primary visual centres of the chick were described. In this paper patterns of retinotopy are examined by means of silver degeneration and autoradiographic techniques following discrete laser lesions of the retina. Well-defined and complete retinotopic maps are found in each of the following visual centres: tectum, lateral anterior thalamus, lateroventral geniculate nucleus, superficial synencephalic nucleus, ectomammillary nucleus, and tectal grey. In the dorsolateral anterior thalamus, pars lateralis, and external nucleus there is some evidence of a retinotopic innervation, yet not as well defined as those nuclei mentioned previously. Retinotopic maps were not observed in other retinorecipient regions. These include the ventrolateral thalamus, dorsolateral anterior thalamus, magnocellular part and rostrolateral part, pretectal optic area, and diffuse pretectal nucleus. Within the lateroventral geniculate, lateral anterior thalamus, superficial synencephalic nuclei, and the tectal grey, the ventral to dorsal retinal axis is mapped along the rostrocaudal axis, the reverse of the orientation seen in the tectum, which may have implications for explanations of how retinotopic maps are formed. The poor retinotopy n dorsolateral anterior thalamus, lateral part, is discussed with respect to the view that it may be the avian homologue of the mammalian lateral geniculate nucleus.

Animals↗
PubMed1984

Composition of the supraoptic decussation of the chick (Gallus gallus). A possible factor limiting interhemispheric transfer of visual information.

In the chick the supraoptic decussation consists of dorsal, ventral, and subventral subregions. The dorsal region contains about 580000 axons of which 24% are myelinated. The mean diameters of unmyelinated and myelinated fibers are 0.31 micron and 1.0 micron, respectively. The ventral region contains about 520000 axons of which only 0.53% are myelinated. The mean diameters of unmyelinated and myelinated fibers are 0.35 micron and 1.09 micron, respectively. A small proportion of unmyelinated fibers has regions of localized expansions. The subventral region, the smallest subregion, contains about 31000 fibers of which 20% are myelinated. The mean diameters of unmyelinated and myelinated axons are 0.31 micron and 1.15 micron, respectively. On the basis of the interhemispheric channels available to the visual system it is argued that visual information must be modified to some extent prior to its transfer.

Animals↗
PubMed1983

Retinotopy in the optic chiasm of chicks and its significance in an undesirable complication of lesioning the supraoptic decussation.

Following discrete lesions of the chick retina, the distribution of degenerating retinal ganglion cell axons in the optic chiasm was examined. A feature of particular interest was the dorsal aspect of the optic chiasm which was found to contain fibres originating from the superior temporal retina. The significance of this finding is discussed in relation to possible damage to the optic chiasm resulting as a consequence of sectioning the supraoptic decussation.

Animals↗
PubMed1983

Asymmetry in the chicken forebrain during development and a possible involvement of the supraoptic decussation.

During the first week of post-hatch life, the chicken forebrain is asymmetrically susceptible to the action of cycloheximide. Between days 2 to 8 treatment of the left hemisphere, but not the right, causes long-lasting changes in behaviour. The right hemisphere is susceptible on days 10 and 11. These developmental events may be related to a significant loss of fibres in the supraoptic decussation, which occurs around the same time.

Animals↗
PubMed1982

Laser-induced defects of retinal development in chick embryos.

Retinae of 8-day-old chick embryos were exposed to laser beam irradiation and examined after hatching. The most prominent feature in the irradiated area was the presence of rosettes consisting of photoreceptors surrounded by an orderly arrangement of outer plexiform layer, inner nuclear layer and inner plexiform layer. The histological character of these rosettes raises questions of regeneration of retinal cells that have apparently withdrawn from the mitotic cycle and also the possibility of the regeneration of ganglion cell axons.

Animals↗
PubMed1982

Composition of the tectal and posterior commissures of the chick (Gallus domesticus).

In chick, the tectal and posterior commissures form a continuous band of axons lying in the dorsal aspect of the meso-diencephalon. In midline sagittal sections, two zones can be clearly defined. The rostral zone (RZ) contains about 290,000 axons of which 32% are myelinated. The caudal zone (CZ) contains about 911,000 fibers of which 12% are myelinated. The majority of unmyelinated fibers in RZ and CZ are between 0.15 and 0.40 micrometers in diameter. The majority of myelinated fibers in both RZ and CZ are less than 1 micrometer in diameter. It is likely that RZ corresponds to the posterior commissure while CZ corresponds to the tectal commissure.

Animals↗
PubMed1981

Regional specialization of the chick retina as revealed by the size and density of neurons in the ganglion cell layer.

On the basis of both morphological criteria and survival after ganglion cell axotomy, three populations of cells can be recognized in the ganglion cell layer of the chick retina. These are: 1) Irregularly shaped cells, which are not affected by axotomy and lack Nissl stain. They comprise about 5% of the total cell population and are probably glial cells. 2) Small cells which have a distinctive teardrop-shaped perikarya, stain for Nissl substance, and are not affected by axotomy. They occur with a uniform density of about 4,000 cells/mm2 across the entire retina and comprise 30-35% of the total number of cells in the ganglion cell layer. It is suggested that these cells are displaced amacrine cells. 3) Cells which stain strongly for Nissl substance and disappear after axotomy. These cells comprise 60-65% of the population of cells in this layer. The density of the latter cells varies throughout the retina. A high-density region in the central area extends into the superior-temporal retina. This high-density region corresponds to a position in the lateral visual field extending into the infero-frontal field. The total number of these cells agrees with the reported number of the optic nerve fibres in the chick, (Rager and Rager, '78); therefore they are presumably ganglion cells. The size distribution of the presumptive ganglion cells varies in different parts of the retina. The only previous study of the distribution and size of cells in the ganglion cell layer of the avian retina did not distinguish between ganglion cells and displaced amacrine cells (Binggeli and Paule, '69). The present results are therefore likely to be a more accurate description of the total number of ganglion cells, the regional variations in their density, and the characteristics of their size than previously reported.

Animals↗
PubMed1980

Kainic acid destroys displaced amacrine cells in post-hatch chicken retina.

Laser-induced axotomy of chicken retinal ganglion cells leads to the death of the cells. This leaves intact a population of small neurons in the retinal ganglion cell layer which accounts for 30-35% of the total cells in that layer. The cells which are resistant to axotomy are destroyed by intraocular injection of kainic acid, whereas ganglion cells are not killed. We suggest that the population of small, axotomy-resistant, kainic acid-sensitive neurons corresponds to the displaced amacrine cells reported by other workers.

Animals↗
PubMed1977

Fiber counts of regenerating peripheral nerves in axolotls and the effect of metamorphosis.

Counts have been made of myelinated and unmyelinated fibers in the sixteenth nerve root of the axolotl, before, during and after regeneration following nerve section. There is no loss of myelinated fibers. Many collateral sprouts are formed and eventually withdrawn. Regeneration during metamorphosis is similar but there is more sprouting. There is no fiber loss from cut nerves in metamorphosis. This suggests that rising thyroid hormone levels are not in themselves detrimental to nerves without peripheral connections. Other factors that may govern cell loss in limb development are discussed.

Ambystoma↗