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B B Boycott

Publications and source records attributed to B B Boycott.

At least 37 records · Page 2Linked to original sources
PubMed1987

Alpha ganglion cells in mammalian retinae.

Retinae from species of six orders of mammals (table 1) were processed by an on-the-slide neurofibrillar staining method to establish whether alpha-type ganglion cells are generally present in placental mammals. Alpha cells of the domestic cat, where they were first defined as a type, are used as a standard of reference. Alpha cells were found in all the twenty species examined; characteristically they have the largest somata and large dendritic fields with a typical branching pattern. In keeping with the common morphology there are inner and outer stratifying subpopulations and therefore a presumptive 'on-centre' and 'off-centre' responsiveness to light. Depending on the species, alpha cells form between 1 and 4% of the ganglion-cell population and their dendritic fields cover the retina three to four times. The morphology of alpha ganglion cells, and many of their quantitative features, are conserved in mammals coming from different habitats and having a wide variety of behaviours. Because it is known different habitats and having a wide variety of behaviours. Because it is known from the cat that alpha ganglion cells have brisk-transient or Y receptive fields it is possible that all placental mammals possess this physiological system.

Animals↗
PubMed1987

Cone connections of the horizontal cells of the rhesus monkey's retina.

The presence in the rhesus monkey's retina of a second morphological type of horizontal cell (H2), described by Kolb et al. (1980), is confirmed. Both types of cell are here further described. Their cone connections are quantified and compared with those of mammals and other vertebrates. The dendrites and axons of the H2 type of cell contact only cones as do the dendrites of the H1 cell (originally described by Polyak (1941)) which has an axon contacting only rods. The dendrites of foveal H2 cells contact between 11 and 14 cones; those of H1 contact 7. The number of cones that each type of cell contacts increases with increasing distance from the fovea, so that, by 5-6 mm eccentricity, H2-type cells synapse with between 20 and 30 cones, and the H1 cells with 12-15. The qualitatively estimated coverage factors of each are 3 or 4; every cone synapses with more than one of both types. Neither type of horizontal cell makes chromatically specific connections that are anatomically recognizable, unlike the situation in some teleostean and turtle retinae. Individual horizontal cells, particularly those connected to foveal cones, may have different ratios of chromatic input. At equivalent eccentricities, up to about 6 mm from the fovea, the dendritic fields of H2 horizontal cells are about twice the size of H1 cells and contact about twice the number of cones. These relative differences are closely similar to those of the cat's horizontal cells and it is suggested that they are a basic feature of most placental mammals. The organization of foveal cone fibres within Henle's layer is described. The distribution of primate cone telodendria, gap junctions and synapses in the outer plexiform layer are briefly reviewed and compared with those of other vertebrate retinae.

Animals↗
PubMed1984

A neurofibrillar method stains solitary (primary) cilia in the mammalian retina: their distribution and age-related changes.

Richardson's reduced silver method, developed for the staining of autonomic nerve fibres in the mammalian intestine, is shown consistently to stain solitary (primary) cilia and diplosomes of the cells of the retinae of cats and rabbits. The cilia comprise a centriole, a basal body and an axoneme with a 9 + 0 complement of microtubules. Probably all retinal cells possess a cilium during their development but, contrary to previous reports, not all retain the axoneme after birth. Axonemes are absent from horizontal, bipolar, microglia, Müllerian, and probably some other glial, cells; all of which showed paired centrioles (diplosomes) after staining. Photoreceptor, amacrine, interplexiform, displaced amacrine and ganglion cells have each one cilium. These differences between cell types persist, without significant change, in the retina of adult rabbits up to the age of 2 years, and in the cat up to 5 years. The alpha-type ganglion cells of the cat are an exception. In 4 to 8-week-old kittens they are all ciliated, like other types of ganglion cells. But by two years about 30% of central area alpha-cells lack an axoneme. Individual cells may have only diplosomes, unusual dispositions of the centrioles in the perikaryal cytoplasm, or even show complete loss of the whole ciliary apparatus. By 5 years of age the proportion of those alpha-cells showing unusual arrangements has increased to approximately 70%, while less than 5% of the other types of ganglion cells are so affected. Cilia of peripheral alpha-cells change at a different rate and by 5 years of age are approximately like the 2-year-old central area population.

Aging↗
PubMed1983

A spatial analysis of on- and off-ganglion cells in the cat retina.

Using reduced silver staining methods it was possible to stain all alpha-ganglion cells of the cat retina. The dendritic trees of alpha-cells are unistratified in either of two laminae within the inner plexiform layer. This stratification difference was shown physiologically to correspond to the on-off dichotomy. For all alpha-cells recorded, the dendritic field was covered by the corresponding receptive field centre. In addition the general shape of the receptive field centre corresponded to the shape of the dendritic field. The size of the dendritic tree was always smaller than the receptive field centre. The topographical distribution of on- and off-alpha cells could be studied. They were found to occur in about equal numbers. Both on- and off-alpha-cell perikarya form a regular lattice and both lattices are superimposed independently. The dendritic branches of neighbouring alpha-cells overlap and each retinal point is covered by the dendritic field of at least one on- and one off-alpha-cell. After horseradish peroxidase (HRP) injection into the lateral geniculate nucleus all beta-cells were labelled. In this way it is shown that about 55% of all ganglion cells are beta-cells. The mosaic of on- and off-beta-cells was studied from the HRP-labelled material. It is commonly assumed that beta-cells are associated with the resolution of fine detail in the cat visual system. The mosaic of beta-cells imposes some constraints and permits some predictions to be made with respect to the cat's visual discrimination.

Action Potentials↗
PubMed1981

Matching populations of amacrine cells in the inner nuclear and ganglion cell layers of the rabbit retina.

In rabbit retina, neurofibrillar methods stain two populations of amacrines whose cell before are located on either side of the inner plexiform layer: one in the ganglion cell layer and the other at the inner margin of the inner nuclear layer. The stained amacrines in the ganglion cell layer have the distinctive cytology of "coronate" amacrines described from Nissl-stained retina (Vaney, '80a) and account from about 85% of the displaced amacrines in the rabbit retina. The coronate amacrines have a streak topography similar to that of the ganglion cells; they comprise about 32% of the neurons in the ganglion cells layer although their proportion increases with eccentricity from the visual streak. The cytology of the neurofibrillar stained amacrines in the inner nuclear layer resembles that of the displaced amacrines and their densities are almost equal. The cell bodies of the stained amacrines are smaller than those of the displaced amacrines but larger than most others in the inner nuclear layer; they account for some 2% of the neurons in the amacrine sublayer. Although the cell bodies of both populations are distributed rather evenly, the mosaic of the inner nuclear layer cells is more regular than that of the ganglion layer cells. We propose that the two populations of amacrines stained by neurofibrillar methods correspond to the acetylcholine synthesizing cells labelled by Masland and Mills ('79).

Animals↗
PubMed1981

Morphology and topography of on- and off-alpha cells in the cat retina.

Neurofibrillar staining methods were found to stain all alpha cells of the cat retina completely, that is the perikaryon, the axon and the dendritic branches. The dendrites of the alpha cells in vertical sections were found to be unistratified and to occupy two narrow strata in the outer half of the inner plexiform layer. This difference in branching level could also be observed in whole-mount preparations and it has been demonstrated in the preceding paper (Peichl & Wässle 1981) that it corresponds to the physiological on-off dichotomy. Thus the topographical distribution of on- and off-alpha cells could be studied. They are found to occur in about equal numbers. Both on- and off-alpha cell perikarya form a regular lattice and both lattices are superimposed independently. The dendritic branches of neighbouring alpha cells overlap and each retinal point is covered by the dendritic field of at least one on- and one off-alpha cell. The dendritic trees of on-alpha cells seem to have more small branches and are on the average smaller than those of off-alpha cells. The density of alpha cells was found to peak in the central area whence it continuously decreased towards the retinal periphery.

Animals↗
PubMed1981

Morphology and mosaic of on- and off-beta cells in the cat retina and some functional considerations.

The beta type of ganglion cell can be subdivided in Golgi-stained whole mounts of the cat retina according to the branching level of the dendritic tree in the inner plexiform layer. The dendritic branching level of on-beta cells is nearer to the cell body; that of off-beta cells is about 10 micrometers further outwards. After horseradish peroxidase (HRP) injection into the lateral geniculate nucleus all beta cells were labelled. In this way it is shown that about 55% of all ganglion cells, irrespective of retinal topography, are beta cells. The spatial distribution of on- and off-beta cells was studied from the HRP-labelled material. On-beta cells form a lattice with regular inter-cell spacings; off-beta cells are also regularly arrayed. The two lattices are superimposed independently of each other. Beta cells are commonly assumed to be associated with the resolution of fine detail in the cat vision system. The mosaic of beta cells imposes some constraints and permits some predictions to be made with respect to the cat's visual discrimination.

Animals↗
PubMed1978

Morphological types of horizontal cell in the retina of the domestic cat.

Two morphologically distinct types of horizontal cell are described from Golgi-stained whole mounts of the cat retina. They are referred to as A-type and B-type cells. The two types differ in their dendritic branching pattern, their overall size and the absence or presence of an axon. At every retinal position the dendrites of B-type cells branch more densely and overlap each other more frequently than do the dendrites of A-type cells. At equivalent retinal positions the dendritic field size of A-type cells is greater than that of B-type cells by a factor of about 1.5. Only B-type cells have an axon, which branches at the end into a large axon terminal system. The axons have no preferred direction of orientation. The stain-ability of horizontal cells by different Golgi methods is discussed.

Animals↗
PubMed1978

Receptor contacts of horizontal cells in the retina of the domestic cat.

The terminal aggregations of A- and B-type horizontal cells, stained by the Golgi-Colonnier method, have been analysed. The pattern of the aggregations is regular and is shown to be in register with the cone mosaic. Both tyes of horizontal cell are in contact with at least 80% of the cones above their dendritic fields. Therefore, the different horizontal cell classes cannot be selective for a special kind of cone but must have at least 60% of the cone input in common. Each A-type horizontal cell makes contacts with between 120 and 170 cones, and each B-type horizontal cell with 60-90 cones. An individual A-type horizontal cell occupies an average of 20% of the lateral elements of the triads in a cone pedicle, but an individual B-type cell fills only some 13%. Each and every cone is connected with several of both types of horizontal cell. An estimation of the number of rods converging onto a single axon terminal system showed that it could be as many as 3000.

Animals↗
PubMed1978

Topography of horizontal cells in the retina of the domestic cat.

Neurofibrillar methods stain a class of horizontal cells in the cat retina which are shown to be identical with the A-type horizontal cell of Golgi-staining. Thus all of the A-type cells of a single retina can be observed. On this basis the changes in density and dendritic field size of A-type horizontal cells with respect to retinal eccentricity were measured. The decrease in density from centre to periphery is balanced by a corresponding increase in size of the dendritic field. Consequently each retinal point--independent of retinal position--is covered by the dendritic fields of three of four A-type horizontal cells. The nuclei and nucleoli of B-type horizontal cells could also be recognized in neurofibrillar-stained material and thus their distribution was determined. The density ratio B-type: A-type is 2.8 +/- 0.4 and does not vary much from the centre to the periphery of the retina. Each retinal point is also covered by four B-type horizontal cells. Thus a single cone can contact a maximum of eight horizontal cells. The rate of density decrease from centre to periphery is closely similar in cones and horizontal cells but greater in ganglion cells.

Animals↗
PubMed1974

The morphological types of ganglion cells of the domestic cat's retina.

1. Three distinct morphological types of cat retinal ganglion cells have been identified and categorized as alpha, beta and gamma. Alpha ganglion cells have dendritic field diameters from 180 to 1000 mum; beta, about 25 to 300 mum; gamma, 180 to 800 mum, possibly more.2. The dimensions of the alpha and beta ganglion cell dendritic fields increase monotonically from the central area outwards to the periphery; those of the gamma cells do not. Seemingly a spectrum of sizes of the gamma cells is found at most locations in the retina.3. All three morphological types of ganglion cells are found in the central area.4. Possible further anatomical types of ganglion cells are discussed. Correlations are suggested between the morphological category alpha cells and the physiological class Y cells; between beta cells and the X cells and between the gamma cells and the W cells.

Animals↗