Showing papers on "Retinal ganglion cell published in 1977"

Magnification in striate cortex and retinal ganglion cell layer of owl monkey: a quantitative comparison.

Abstract: Magnification, the relative size of the neural representation of a portion of the visual field, decreases more rapidly with increasing visual field eccentricity in striate cortex than in the retinal ganglion cell layer of the owl monkey (Aotus trivirgatus); the proportion of the cells in striate cortex devoted to central vision is much larger than the comparable proportion of retinal ganglion cells. Magnification in striate cortex is a power function of magnification in the retinal ganglion cell layer. A formula for convergence (ganglion cells to cortical neurons) follows from this relationship.

Foveal sparing. New anatomical evidence for bilateral representation of the central retina.

Abstract: • The pattern of retinal ganglion cell projections to the dorsal lateral geniculate nuclei has been demonstrated with horseradish peroxidase neuronography. A 1°-wide strip centered on the vertical meridian has been found in which ipsilaterally and contralaterally projecting ganglion cells intermingle. This strip expands to a width of 3° at the fovea, since mixing of horseradish peroxidase-labeled and unlabeled ganglion cells was found in a band approximately 0.5° wide along both the nasal and temporal rims of the foveola. These labeled ganglion cells rimming the foveal pit in Its entirety represent a possible anatomical basis for "foveal sparing." ( Arch Ophthalmol 95:1445-1447, 1977)

The identification of two intra-axonally transported polypeptides resembling myosin in some respects in the rabbit visual system.

Abstract: Two polypeptides (M1 and M2) which co-sediment with F-actin in an ATP-reversible way have been detected in extracts of tissue from the rabbit visual system. Both polypeptides resemble skeletal muscle myosin in their ATP-sensitive co-sedimentation with actin, while they resemble the heavy chain of myosin and the lighter polypeptide of erythrocyte spectrin in their electrophoretic mobilities. (The estimated molecular weights are: MI congruent to 195,000; myosin congruent 200,000; M2 and spectrin congruent to 220,000). M1 and M2 were labeled in the cell bodies of the retinal ganglion cells with a radioactive amino acid and subsequently recovered in tissues (optic nerve, optic tract, lateral geniculate nucleus, and superior colliculus) containing segments of the retinal ganglion cell axons. The temporal sequence of labeling M1 and M2 in these tissues indicated that both polypeptides were synthesized in the cell bodies of retinal ganglion cells and subsequently transported down their axons at different maximum velocities. The estimated velocities were: M1, 4-8 mm per day; and M2, 2-4 mm per day.

Abnormal development of the suprachiasmatic nuclei of the hypothalamus in a strain of genetically anophthalmic mice.

Abstract: In the anophthalmic mutant of the mouse the optic primordia are "genetically enucleated" well before the usual emergence of retinal ganglion cell axons (Silver and Hughes, '74). In eyeless animals, a portion of the mediobasal hypothalamus and one of its constituent nuclear pairs, nucleus suprachiasmaticus (SCN), were markedly abnormal in the embryo and adult. It has been reported that the ventral portion of the SCN receives a substantial, direct retinal innervation (Moore and Lenn, '72) and that these nuclei may mediate several light-induced hormonal and behavioral circadian rhythms (Stetson and Whitmyre, '76). During day 13 of mutant embryogenesis, just prior to the time of optic chiasm formation in normal animals, a large portion of ependyma and adjacent brain tissue herniated into the lumen of the would-be suprachiasmatic region of the third ventricle. In 70% of the animals examined histologically during the latter phase of development and as adults, regulation occurred and the brains were largely comparable with those of controls. However, in the remaining mutant mice, the overall size of either, or sometimse both, SCN was much reduced. The basal (but not the apical) dendrites of SCN neurons failed to develop fully. Some basal dendrites normally invade the optic chiasm below. In several mutant animals one or the other SCN had greatly increased numbers of cells, while the contralateral one had diminished numbers. These observations suggest that regular formation of the suprachiasmatic region of the hypothalamus and especially the suprachiasmatic nuclei, may depend during development upon the presence of the eye or the subjacent optic axons.

The perfused cat eye: a model in neurobiologic research.

Abstract: The viability of an arterially perfused mammalian eye preparation is demonstrated in (1) electrophysiological recordings of multineuronal responses (electroretinogram, optic nerve action potential) as well as of signals from single cells (ganglion cells, horizontal cells, pigment epithelium), and (2) in a quantitative analysis of the fine structure of the retina. The possibilities of assessing the function of the retina at several levels of information processing and of controlling the biochemical input without systemic effects favor pharmacologic studies in vitro. Results from our research on cholinergic transmission in the cat retina are presented, revealing reversible effects of physostigmine, atropine, scopolamine and mecamylamine on the activity of ganglion cells.

Interactions between rod and cone systems in the goldfish retina.

Abstract: Signals from both the rod and the cone receptor systems converge upon the same retinal ganglion cell, but only one or the other of these systems appears to be effective at any particular level of adaptation. In this report we provide evidence that the change from one receptor system to the other is not simply due to the two systems having nonoverlapping dynamic ranges; rather, there is a distance-dependent interaction between the two systems.