Search PubMed⌕ Search

Biomedical subjects

V H Perry

Publications and source records attributed to V H Perry.

At least 163 records · Page 9Linked to original sources
PubMed1989

Hippocampal specialization of food-storing birds.

In a study of 52 individuals belonging to 35 species or subspecies of passerine birds it was shown that the volume of the hippocampal complex relative to brain and body size is significantly larger in species that store food than in species that do not. Retrieval of stored food relies on an accurate and long-lasting spatial memory, and hippocampal damage disrupts memory for storage sites. The results suggest, therefore, that food-storing species of passerines have an enlarged hippocampal complex as a specialization associated with the use of a specialized memory capacity. Other life-history variables were examined and found not to be correlated with hippocampal volume.

Animals↗
PubMed1989

Absence of Wallerian Degeneration does not Hinder Regeneration in Peripheral Nerve.

Wallerian degeneration of the distal stump of a severed peripheral nerve involves invasion by myelomonocytic cells, whose presence is necessary for destruction of myelin and for initiating mitosis in Schwann cells (Beuche and Friede, 1984). Degeneration of the distal ends of the axons themselves is assumed to occur by autolytic mechanisms. We describe a strain of mice (C57BL/6/Ola) in which leucocyte invasion is slow and sparse. In these mice, confirming Beuche and Friede, myelin removal is extremely slow. A new finding is that axon degeneration is also very slow. This is a consequence of lack of recruitment of myelomonocytic cells for if such recruitment is prevented in other mouse strains by a monoclonal antibody against the complement type 3 receptor (Rosen and Gordon, 1987) axon degeneration is again slowed. We have also, surprisingly, found that nerve regeneration in the C57BL/6/Ola mice is not impeded by the presence of largely intact axons in the distal stump and absence of recruited cells, myelin debris and the absence of Schwann cell mitosis.

Journal Article↗
PubMed1988

The axon initial segment as a possible determinant of retinal ganglion cell dendritic geometry.

In wholemounted retinae of cat, rat and monkey, in which ganglion cells were retrogradely labelled with horseradish peroxidase, a quantitative analysis of the direction of the axon initial segment with respect to the optic disc and of the relationship between the axon initial segment and the direction and distribution of primary dendrites was performed on the class of largest ganglion cells. The results show the following. (1) In all 3 species, the majority of primary dendrites of ganglion cells are directed away from the axon initial segment. (2) Primary dendrites arise with a greater frequency from the region of the cell body opposite to the axon initial segment than close to it. (3) In cat the direction of the axon initial segments show less variance in their initial direction with respect to the optic disc than in rat or monkey. In adult cats the nucleus of alpha-ganglion cells occupies a central position. In the kitten the position of the nucleus is eccentric and lies in a part of the cell body opposite to the axon initial segment. The nucleus moves to a central position over the next 3 weeks. The position of the axon initial segment is discussed as a possible determinant of ganglion cell dendritic geometry.

Animals↗
PubMed1988

Dendritic competition: competition for what?

A lesion to the retina of a newborn rat results in the retrograde degeneration of ganglion cells in a sector of retina peripheral to the lesion. The dendritic tree of ganglion cells bordering the region depleted of ganglion cells have their dendrites preferentially directed into this area. We have examined the factors which play a role in this rearrangement of the dendritic tree. The results show that the lesion in neonates selects for or produces a population of cells with the axon directed away from the depleted area and primary dendrites directed towards the depleted area. The abnormal dendritic bias cannot be accounted for solely on the basis of a decrease in contact inhibition since a reduction in the density of all ganglion cells by 30% prior to making the retinal lesion does not attenuate the abnormal dendritic bias into the depleted area. The abnormal dendritic bias is present in animals operated on up to 15 days of age postnatally but not in more mature animals. The abnormal dendritic bias develops prior to the formation of a large number of synapses in the inner nuclear layer. Our results cannot be easily accounted for by competition for synaptic contacts or a loss of contact inhibition as previously suggested. We propose that chemotropic factors produced within the area depleted of ganglion cells induce the abnormal dendritic bias and the number of synaptic contacts may limit the size of the dendritic field.

Aging↗
PubMed1988

Ibotenic acid induced demyelination in the central nervous system: a consequence of a local inflammatory response.

We examined the effects of injections of ibotenic acid into the medial septum (MS), dorsal lateral geniculate nucleus (dLGN), caudate-putamen (CP) or fornix-fimbria (FF) on fibres close to the injection site. Injections into the MS and dLGN resulted in demyelination. The area of demyelination correlated with the area of maximal gliosis. The major cell type in the area of gliosis were cells of haemopoietic origin, as revealed by using monoclonal antibodies (Mabs). Demyelination was not observed in the CP or FF. Axonal transport in fibres en passage through the dLGN lesion was also disrupted following injections of horseradish peroxidase (HRP) into the eye contralateral to the lesion. These results show that when ibotenic acid induces cell death it can secondarily damage myelin sheaths and disrupt axonal transport in areas containing diffuse fibre systems. We suggest that this is due to a non-specific effect of the inflammatory response.

Animals↗
PubMed1988

Functional lamination in the ganglion cell layer of the macaque's retina.

Close to the fovea of the primate retina the ganglion cell layer is at its maximal thickness and several layers of cells deep. In whole-mount preparations in which the ganglion cells had been retrogradely labelled to reveal the dendritic trees we have studied the distribution of the different ganglion cell types across the depth of the ganglion cell layer. The ganglion cells which project to the parvocellular layers (P ganglion cells) are found more vitread than those which project to the magnocellular layers (M ganglion cells). The cells which project to the midbrain lie in the outer part of the ganglion cell layer among the M cells and adjacent to the inner plexiform layer. Within the P and M classes of ganglion cell the On-centre cells lie more vitread than the Off-centre cells. These results are discussed with relation to the proportions of different cell types sampled with intraocular recordings from ganglion cells and the possible significance for the development of different types of ganglion cell.

Animals↗
PubMed1988

The lengths of the fibres of Henle in the retina of macaque monkeys: implications for vision.

In Golgi preparations of retinae from macaque monkeys the lengths of the fibres of Henle from photoreceptors, and Müller's fibres were measured. It was shown that the lengths of Müller's fibres provide a good estimate of the lengths of adjacent fibres of Henle of photoreceptors. The fibres form a radiate pattern with respect to the fovea. They are longest at the fovea and their length decreases in a systematic way with distance from the fovea. The implications of the fibre length are considered with respect to the relationship between the ganglion cell distribution and central magnification factors. We show that even when the functional offset introduced by the fibres of Henle and by bipolar and ganglion cells is taken into account there is not a constant proportional relationship between ganglion cells and central magnification factors. The representation of the central few degrees of the visual field on the striate cortex is greater than would be predicted on the basis of the ganglion cell density for the central retina.

Animals↗
PubMed1988

Conditions for optic axon outgrowth.

A series of studies is described which show that retinal axon outgrowth can be stimulated by the close proximity of an appropriate target region. The suggestion is offered that, in normal development, optic axons first follow cues available at the surface of the brainstem, but once they reach a target region, ramify there in response to the presence of a target-derived factor.

Animals↗
PubMed1988

Plasma membrane receptors of the mononuclear phagocyte system.

Plasma membrane receptors control macrophage activities such as growth, differentiation and activation, migration, recognition, endocytosis and secretion. They are therefore important in a wide range of physiological and pathological processes including host defence, inflammation and repair, involving all systems of the body including the arterial wall and nervous system. The versatile responsiveness of these cells to various stimuli depends on their ability to express a large repertoire of receptors, some restricted to macrophages and closely related cells, others common to many cell types. This volume contains reviews of the macrophage receptors that are best characterized and deals with aspects of signal transduction and function of the actin cytoskeleton. Our introduction is designed to place these topics in perspective. We summarize features of constitutive and induced mononuclear phagocyte distribution within the body and consider receptor expression and macrophage responses in the context of cell heterogeneity associated with its complex life history. We classify receptors discussed in detail in other chapters, list ligand-binding properties that are not as well defined, and briefly review general features of receptor function in macrophages. An understanding of macrophage receptor biology should bring insights into the contribution of these cells to physiology and disease and result in an improved ability to manipulate activities within the mononuclear phagocyte system.

Animals↗
PubMed1987

Modulation of CD4 antigen on macrophages and microglia in rat brain.

Mononuclear phagocytes which express the HIV entry receptor CD4 have been implicated as possible sites of virus replication in brain, but there is still considerable uncertainty as to which cells in the CNS express CD4 Ag. Although it is not susceptible to HIV infection the rat provides a model to define expression of the CD4 Ag on MO in brain. We report that the CD4 epitopes W3/25 and OX35 are found only on monocytes, MO, microglia, and occasional lymphocytes and not on neurons, other glia, or endothelium. CD4 Ag levels are modulated during microglial differentiation, after reactivation after local inflammation, and within the intact blood brain barrier. MO and microglia also express other potential plasma membrane binding and entry sites for HIV viz Fc and complement receptors that are regulated independently of CD4.

Animals↗
PubMed1987

The macrophage response to central and peripheral nerve injury. A possible role for macrophages in regeneration.

Using mAbs and immunocytochemistry we have examined the response of macrophages (M phi) after crush injury to the sciatic or optic nerve in the mouse and rat. We have established that large numbers of M phi enter peripheral nerves containing degenerating axons; the M phi are localized to the portion containing damaged axons, and they phagocytose myelin. The period of recruitment of the M phi in the peripheral nerve is before and during the period of maximal proliferation of the Schwann cells. In contrast, the degenerating optic nerve attracts few M phi, and the removal of myelin is much slower. These results show the clearly different responses of M phi to damage in the central and peripheral nervous systems, and suggest that M phi may be an important component of subsequent repair as well as myelin degradation.

Animals↗
PubMed1987

Ganglion cell dendritic structure and retinal topography in the rat.

The dendritic field size, the distribution of the dendrites relative to the cell body, and the overall shape of the dendritic field of type I ganglion cells in the rat retina were analyzed. These features of neuronal structure were related to the topography of the rat retina. As in the cat, the cell bodies of type I ganglion cells are arranged in a nonrandom mosaic. Previous work has demonstrated that the density of type I cells in the rat retina does not covary with the density of all ganglion cells. Type I dendritic field size varies over the retina; the increase in dendritic field size is accounted for better by the decrease in type I density than by the decrease in overall ganglion cell density. The center of the dendritic field of most type I cells is displaced in the plane of the retina from the cell body. Unlike in carnivore retina (Schall and Leventhal: J. Comp. Neurol. 257:149-159, '87), the dendritic fields in the rat are not displaced down the ganglion cell density gradient. Rather, there is a tendency for the dendritic trees, especially in temporal retina, to be displaced toward dorsal retina. Most of the dendritic fields are elongated, but the degree of elongation is less than that observed in carnivore or primate retina. Unlike in carnivore and primate retina (Leventhal and Schall: J. Comp. Neurol. 220:465-475, '83; Schall et al.: Brain Res. 368:18-23, '86), there is no relationship between dendritic tree orientation and position relative to any point on the retina in the rat.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1987

An investigation into the role of ganglion cells in the regulation of division and death of other retinal cells.

The patterns of cell death and division are described in the normal postnatal rat retina and following transection of the optic nerve on the day of birth. Optic nerve transection on the day of birth results in the rapid degeneration of the ganglion cells. Mitosis at the outer retinal surface ceases first in the temporal retina, then in the nasal retina and becomes progressively more restricted to peripheral regions. Mitotic activity was not affected by the loss of ganglion cells. Cell death takes place in a wave passing from the ganglion cell to the inner nuclear to the outer nuclear layer. The time course of cell death is not affected by the loss of ganglion cells following optic nerve transection, and there is no significant increase in the number of cells which degenerate in the inner nuclear layer. The effects of removing a major postsynaptic target of local circuit neurones appears to be less pronounced than has been reported for relay neurones.

Age Factors↗
PubMed1987

Target regions enhance the outgrowth and survival of ganglion cells in embryonic retina transplanted to cerebral cortex in neonatal rats.

In embryonic mouse retina transplanted to occipital cortex of neonatal rats, ganglion cells do not project axons into the host cortex, although they may survive up to but not beyond 6 weeks post-transplantation. By contrast, if embryonic tectum or diencephalon is transplanted along with the retina, ganglion cells exhibit vigorous outgrowth to specific regions of the co-transplant and are able to survive for at least 14 weeks.

Age Factors↗
PubMed1986

Cell surface changes in the developing optic nerve of mice.

A recently defined antibody to a cell surface protein, M6, inhibits neurite outgrowth in culture (Lagenaur, Fushiki, and Schachner: Soc. Neurosci. Abstr. 10:739, '84). In the developing mouse, the antibody stains all parts of the primary optic pathway at birth. Over the next week, staining is lost from the proximal segment of the optic nerve and a week later from the more central part of the nerve. By contrast staining persists through adulthood in the optic fiber layer of the retina. This means that single axons in the mature optic nerve express the antigen over only the proximal few millimeters of their course and over their terminal region. The results are discussed in relation to the overall maturation of the optic pathway and to the processes of membrane maturation and myelination.

Animals↗
PubMed1986

Retinal ganglion cell dendritic fields in old-world monkeys are oriented radially.

We analyzed the dendritic field morphology of 297 ganglion cells from peripheral regions of monkey retina. Most of the dendritic fields were elongated, and there was a significant tendency for the dendritic fields to be oriented radially, i.e., like the spokes of a wheel with the fovea at the hub. An overrepresentation of radial orientations in the peripheral retina of primates might explain why humans are best able to detect stimuli which are oriented radially using peripheral vision.

Animals↗