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Biomedical subjects

G Raisman

Publications and source records attributed to G Raisman.

At least 91 records · Page 5Linked to original sources
PubMed1983

The distribution of Thy-1 antigen in the P.N.S. of the adult rat.

The distribution of the cell surface glycoprotein Thy-1 in the P.N.S. of adult rats was examined using immunohistochemical and experimental techniques. In the hypoglossal nerve the pattern of Thy-1 labelling suggested the antigen was on the plasma membrane of all axons, not only in their major myelinated course but also on their fine terminal branches and at the motor end plate itself. Similarly in other peripheral nerves examined [phrenic and vagus nerves, dorsal and ventral roots, and both the preganglionic and postganglionic trunks of the superior cervical ganglion (SCG) and the submandibular ganglion] Thy-1 was always associated with axons, but the resolution obtained with immunohistochemical techniques was not in itself sufficient to exclude the possibility that the antigen was on the surface of the ensheathing Schwann cell where it apposed the axons. However, in the hypoglossal nerve the antigen was found to accumulate proximal to a ligation of the nerve, suggesting it was made by the neurons and transported down the nerve by axoplasmic flow. This impression was supported by examining neuronal cell bodies in the SCG, dorsal root ganglia and submandibular ganglion, all of which contain readily detectable cytoplasmic Thy-1. In the SCG this cytoplasmic antigen was shown to include the pool of newly synthesized Thy-1. It was increased by treatment of the ganglion with colchicine, and decreased by cycloheximide. Conversely, treatment of hypoglossal nerve trunk with colchicine did not lead to the appearance of the antigen around the non-neuronal perikarya. It is therefore concluded that in those parts of the adult rat P.N.S. examined, Thy-1 is made by neurons and occurs generally on the plasma membrane of axons.

Animals↗
PubMed1983

Mossy fibre projections into and out of hippocampal transplants.

Hippocampal primordia taken from one day old postnatal rats and grown for 1 month in the hippocampus of adult rat hosts developed hippocampal pyramids, dentate granule cells, and specific patterns of mossy fibres. In 26 cases where certain boundary conditions were precisely met, the transplant mossy fibres crossed into the host and ramified for a distance of from 0.5 mm to no more than 1 mm in the stratum oriens of the host field CA1. They formed a layer 35 micron thick adjacent to the host CA1 pyramidal cell layer. The necessary boundary conditions were: (1) direct (and "unscarred") contact between the neuropil of the transplant and the host field CA1, (2) that the hilar (and not the molecular) aspect of the transplanted dentate granule cell lamina faced the host CA1 pyramids, and (3) that some of the interface was devoid of transplant hilar cells or CA3-type pyramids interposed between the transplant dentate granules and the host CA1 pyramids. In 3 cases a converse connection was found--viz. the host mossy fibres entered the transplant. In these cases the transplants consisted entirely of pyramidal cells (with no dentate granule cells of their own), and the part of the transplant receiving the host mossy fibres was embedded directly in the host mossy fibre pathway. For the dentato-hippocampal mossy fibre system, therefore, it is shown that postsynaptic targets in the adult mammalian brain can receive specific patterns of innervation from growing axons derived from a transplant, and that cut central axons of the same type can grow and form target-specific terminal arborizations in a transplant.

Animals↗
PubMed1983

Density of Thy-1 on axonal membrane of different rat nerves.

The density of the cell surface antigen, Thy-1, has been measured on the axonal plasma membrane of the optic and hypoglossal nerves, and on the sympathetic (preganglionic) chain of the superior cervical ganglion in the rat. For each, the amount of Thy-1 in a standard length of nerve was determined. The amount of axonal plasma membrane in a similar length was then measured by use of a computer graphics system which determined the total length of membrane in electron micrographs of cross sections of nerve. The axons of the two peripheral nerves were found to have a similar density (1100-1500 molecules/microns2) of Thy-1 on their surface, and this was two- to threefold higher than the density on axons of optic nerve (500 molecules/microns2). These figures indicate that the density of Thy-1 on the surface of these axons is somewhat lower than that found on the cells of the lymphoid system. Moreover, contrary to the impression gained from previous determinations of Thy-1 levels, axons in the peripheral nervous system do not necessarily have a lower density of Thy-1 on their surface than do those of the central nervous system.

Animals↗
PubMed1983

Estimation of Thy-1 in cryostat sections of nervous tissue.

The conventional assay for measuring cell surface antigens--the quantitative absorption of antibody by tissue homogenates--proved inadequate when used to determine the level of Thy-1 glycoprotein in rat nerves and peripheral ganglia. In this paper we report that the binding of 125I-labelled Fab fragments of a monoclonal anti-Thy-1 antibody to cryostat sections is sufficiently sensitive to give consistent estimates of the Thy-1 level on single samples of even small nerves. Observed levels of Thy-1 were generally higher than had previously been thought, and in particular we found no nerves totally lacking the antigen. The lowest levels (6-10 pmol/mg protein) were in peripheral nerves with a large motor component. Autonomic and sensory nerves had higher levels (15-20 pmol/mg protein). The highest levels were on the optic nerve (34 pmol/mg protein), superior cervical sympathetic ganglion (40 pmol/mg protein), and the cerebellar vermis (46 pmoles/mg protein; the only brain region examined in this study). From a practical point of view, the cryostat assay has the advantage that measurements of Thy-1 can be done on sections from the same series as is used for immunohistochemical localisation.

Animals↗
PubMed1982

Astrocyte cultures from adult rat brain. Derivation, characterization and neurotrophic properties of pure astroglial cells from corpus callosum.

It has not as yet been routinely possible to derive primary cultures of glial cells from adult rat brain tissue even when adopting strategies that have proven successful with perinatal tissue. We now report that in response to a surgical lesion and a period of postoperative 'priming' in vivo, proliferating cultures of astroglial cells can be derived from the normally quiescent glia of the corpus callosum region of the adult rat brain. In such cultures the predominance of astroglia and the virtual absence of oligodendroglia and neurons has been established by the use of a variety of cell-type specific antisera. Fibroblasts, the only other cell type identified, when not numerous could be successfully eliminated by treatment of the cultures with anti-Thy-1 antibodies and guinea pig complement. Pure astroglial cells from adult brain have been sub-cultured and maintained for up to 4 months in vitro, providing suitable quantities of cells for studies on the trophic interaction between glia and neurons. In long-term culture the adult astrocytes maintain a flattened undifferentiated morphology but readily assume a stellate shape with long branching processes upon the addition of a crude homogenate from bovine pituitary.

Animals↗
PubMed1981

Effects of spinal cord transection on synapse numbers and biochemical maturation in rat lumbar sympathetic ganglia.

The effects of interruption of descending central pathways on the morphological and biochemical ontogeny of peripheral sympathetic ganglia were examined in the sixth lumbar (L6) sympathetic rat ganglia. Previous studies defined the normal maturation of presynaptic choline acetyltransferase (CAT) activity, postsynaptic tyrosine hydroxylase (T-OH) activity, and total protein in the L6 ganglion. In the present investigations ganglion synapse numbers and adrenergic neuron numbers were examined in transected and sham-operated littermate controls 6 weeks after surgery at 10 days of age and correlative biochemical studies were performed. Spinal transection resulted in a reduction in synapse number on ganglion cell bodies (53.5% reduction) and neuronal processes (55.8% reduction). This abnormality in synapse number was associated with a reduction of CAT activity to 56% of control. Although T-OH activity also failed to develop normally and was 25% of control, there was no associated alteration in adrenergic neuron number. These studies suggest that descending central pathways regulate the maturation of presynaptic cholinergic terminals (and hence synapse number) in sympathetic ganglion and that CAT activity serves as an accurate marker for these terminals. Additionally, the ontogeny of ganglion T-OH activity is altered by central lesions and this effect is not secondary to a decrease in adrenergic neuron number.

Animals↗
PubMed1980

Synapse formation after injury in the adult rat brain: preferential reinnervation of denervated fimbrial sites by axons of the contralateral fimbria.

The dorsolateral quadrant of the lateral septal nucleus receives projections from both the ipsilateral and the contralateral fimbria. In the adult rat the effect of fimbrial lesions on synapse formation has been studied by a quantitative electron microscopic analysis of the various types of synapses present, using electron-dense degeneration to identify fimbrial fibre terminals. In this area, the fimbrial axons from both sides together account for about 30% of the total number of synapses and they terminate mainly on dendritic spines. The ipsilateral fimbria forms twice as many synapses as the contralateral fimbria. When one fimbria is cut and time left for the degeneration to be removed, the numbers of synapses are restored to normal levels and the remaining fimbria acquires, on both sides of the septum, a number of synapses equal to the sum of the two individual fimbria, This suggests that the axons of the surviving fimbria have completely reinnervated the denervated postsynaptic sites formerly occupied by the cut fimbria of the other side, effectively excluding non-fimbrial axon terminals, even though the latter constitute the majority (70%) of the synaptic terminals in the region. When both fimbria are cut the numbers of synapses are once again restored to normal levels. However, since there are now no fimbrial axons left, the denervated fimbrial postsynaptic sites must this time have been reinnervated by non-fimbrial axons. Reinnervation by non-fimbrial axons is numerically equally effective in reclaiming the denervated sites, although when compared to the reinnervation by fimbrial axons, the removal of degenerating terminals is somewhat slower, and among the reinnervating terminals there is a much higher incidence of axon terminals making more than one synaptic contact in the plane of section. Thus, fimbrial axons, when present, have the ability to exclude the reinnervation of denervated fimbrial sites by non-fimbrial axons, despite the fact that the latter are both more numerous and also clearly capable of reinnervating those sites when no fimbrial axons are present. Two possible mechanisms are discussed: a spatial preference based on the geometrical arrangements in the neuropil, and a temporal preference based on the relative rates of response of the fimbrial vs the non-fimbrial axons.

Animals↗
PubMed1980

Age-related changes in the neurosensory epithelium of the mouse vomeronasal organ: extended period of postnatal growth in size and evidence for rapid cell turnover in the adult.

The total number of neurosensory cells in the mouse vomeronasal organ was estimated during postnatal development by counting the cell density and measuring the total volume of the neurosensory cell layer. There is a 43% increase in neurosensory cell number between 1 and 4 months of age, followed by a 21% fall in cell number between 4 and 8 months. There is no further significant change in cell number between 8 and 18 months of age. Cell division was shown to be occurring in the vomeronasal organ of animals at 7 months of age by labelling dividing cells with [3H]thymidine continuously administered by means of implanted 'osmotic pumps'. At least 1 in 6 cells were labelled by 12 days of thymidine administration, indicating a turnover time of 2--3 months for the whole epithelium. This raises the general problem of how a fixed central nervous system accommodates a changing peripheral input.

Age Factors↗
PubMed1980

Synapse formation in the rat superior cervical ganglion during normal development and after neonatal deafferentation.

Ten per cent of the adult number of synapses are present in the neonatal rat superior cervical sympathetic ganglion on day 1 (day of birth taken as day 0). Synapses are formed rapidly over the first postnatal week, and then more slowly, reaching 80% of adult numbers by the end of the third week. Adult numbers are present at the end of the third month. Prominent axosomatic synapses are present for the first two weeks of life, but disappear later. Of the adult numbers of synapses, 20-40% are already present on days 2 and 4, and transection of the preganglionic chain on these days causes disappearance of all synapses by 2 days after operation. However, by 2 months after operation the numbers of synapses are the same as in unoperated ganglia from rats of the same age. Unoccupied postsynaptic densities were not seen either in normal development or after lesions.

Afferent Pathways↗
PubMed1979

Quantitative electron microscopic evidence for reinnervation in the adult rat interpeduncular nucleus after lesions of the fasciculus retroflexus.

The method of electron dense degeneration has been used to make a quantitative study of the projection from the habenula through the fasciculus retroflexus (FR) to the interpeduncular nucleus (IPN) in the rat. The IPN si a midline structure onto which the right and left fasciculi converge. In the rostral part of the IPN the fascicular axons from each side form synapses throughout the mediolateral extent of the ventral two-thirs of the nucleus. In the caudal part of the IPN the fascicular axons from each side terminate to an equal extent in two discrete, parasagittal zones, situated one on side in the mid-mediolateral extent of the IPN. These zones contain clusters of neurons located along the course of a characteristic row of arterioles and venules penetrating the IPN from its ventral surface. In both rostral and caudal parts of the IPN the fascicular axons form single synaptic contaerpeduncular neurons, but caudally, in the two parasagittal zones they also form crest synapses. Crest synapses are only found in this part of the IPN. In crest synapses two presynaptic terminals form markedly asymmetrical contacts with the parallel opposing sides of an attenuated dendritic appendage (the crest). After unilateral fascicular lesions only one member of a pair of axon terminals contacting a crest degenerates. After bilateral fascicular lesions, however, there are many instances in which both members of a crest pair degenerate. This indicates that the axon terminals from the right and left fasciculi are segregated at the level of the crests, in such a way that one terminal comes from the right fasciculus and one from the left. At longer survivals after unilateral or bilateral fasciculus lesions the degeneration is completely removed, but crest synapses are still present, indicating that the presence of fascicular axons is not necessary for the maintenan ce of crests in the IPN. To investigate the effects of chronic deafferentation, the left fasciculus was destroyed and, after a survival of at least six weeks (sufficient for all degeneration to be removed) the right fasciculus was destroyed one day before killing. Under these conditions there are many crests in which both axon terminals show degeneration. The proportion of such doubly degenerating crest synapses is similar to that found after acute (1 day) bilateral lesions, indicating that axons from the right fasciculus have reinnervated sites formerly occupied by the left fasciculus. We conclude that during normal development there is some constraint which prevents both sides of a crest being innervated by axons from the fasciculus of the same side of the brain, but that this constraint is not effective after unilateral fascicular lesions in the adult.

Afferent Pathways↗
PubMed1979

Dissociation of spontaneous and mating induced ovulation by frontal hypothalamic deafferentations in the rat.

Different types of anterior hypothalamic deafferentations have been used to investigate the nervous pathways involved in spontaneous and mating-induced ovulation in the rat. Knife cuts which circumscribed the suprachiasmatic nuclei on all but their ventral surface and either their rostral or caudal poles prevented spontaneous ovulation, but the rats were sexually receptive (copulation plugs and sperm in the smear), and mating induced ovulation. Similar types of cut extended dorsally so as to sever the continuity between the preoptic area and the mediobasal hypothalamus also prevented spontaneous ovulation, and although these rats were also receptive, mating did not induce ovulation. Two possible explanations are considered: either (i) that difference between the effects of the two types of cut is a direct function of the differing proportions of gonadotrophic hormone-containing axons severed, or (ii) cuts in the region of the suprachiasmatic nuclei specifically impair a mechanism for the maintenance of diurnal rhythms, to which the abnormality in gonadotrophin control is secondary.

Afferent Pathways↗
PubMed1979

Decentralization of the superior cervical ganglion in neonates impairs the development of the innervation of the iris. A quantitative ultrastructural study.

The superior cervical sympathetic ganglion was decentralized unilaterally by section of the preganglionic chain in 2- or 4-day-old rats. Twenty-one days post-operatively the dilator muscle of the iris was examined electron microscopically. Quantitative estimates demonstrated that there was a reduction both in the numbers of axon bundles and of individual axons in the iris innervated by the deafferented ganglion as compared with its fellow of the contralateral control side.

Animals↗
PubMed1979

Muscarinic receptors in the central nervous system of the rat. I. Technique for autoradiographic localization of the binding of [3H]propylbenzilylcholine mustard and its distribution in the forebrain.

[3H]Propylbenzilylcholine mustard ([3H]PrBCM) is a synthetic, potent muscarinic antagonist, which binds specifically and irreversibly by means of a covalent linkage to muscarinic receptors. Ten micrometer coronal cryostat sections taken through unfixed rat brain at the level of the maximum extent of the caudate nucleus were mounted on glass slides and incubated with 2.4 nM [3H]PrBCM at 30 degrees C for 25 min. They showed a total binding of 3250 pmol/g protein, of which 2130 pmol/g protein was sensitive to pretreatment with 10-6 M atropine. The specific (atropine-sensitive) binding was saturable. Saturation was reached at 15 min, with a rate constant of 1.3 x 106 M-1 sec-1. Binding was unaffected by drugs acting at nicotinic receptors (D-tubocurarine, hexamethonium), or by physostigmine, but was inhibited by muscarinic drugs (pilocarpine, oxotremorine, 3-quinuclidinylbenzilate). Postfixation for 15 min in Carnoy's fixative reduced the specific binding by 10% and the non-specific by 50%. Prefixation (i.e. before incubation with [3H]PrBCM) with any fixatives containing formaldehyde largely prevented specific binding, but a range of concentrations of glutaraldehyde (2% to 0.05%) caused only small reductions in specific binding (e.g. 0.1% glutaraldehyde caused only a 6% reduction). Clear, regionally specific patterns of localization of specific label in light microscope autoradiographs could be obtained from cryostat sections prefixed with 0.1% glutaraldehyde, incubated with 2.4 nM [3H]PrBCM for 15 min at 30 degrees C, and postfixed for 15 min in Carnoy's solution. Of the 105 forebrain areas studied 12 had grain counts between 6 and 9 times the non-specific level and a further 30 had counts 4 to 6 times non-specific. The higher grain counts were in the external plexiform layer of the olfactory bulb, anterior olfactory nucleus, olfactory tubercle, pyriform cortex, stratum radiatum of the hippocampus, stratum moleculare of the dentate gyrus, lateral amygdaloid nucleus, cortico-amygdaloid transition zone, anteroventral thalamic nucleus, hypothalamic supraoptic nucleus, caudate-putamen, nucleus accumbens, and in laminae 3 and 6 of the neocortex (parietal region). There were high grain densities over the choroid plexus the lateral but not the third or fourth ventricles.

Animals↗
PubMed1979

Muscarinic receptors in the central nervous system of the rat. II. Distribution of binding of [3H]propylbenzilylcholine mustard in the midbrain and hindbrain.

The distribution of muscarinic receptors has been studied in the rat midbrain and hindbrain by counting silver grains in light microscope autoradiographs of the specific (atropine-sensitive) binding of [3H]propylbenzilylcholine mustard in cryostat sections. Of the 78 areas studied 6 had grain counts between 6 and 9 times the nonspecific level ("high"), and a further 15 had counts 4-6 times non-specific ("intermediate"). The basilar pontine nuclei and the ventral nuclei of the lateral lemniscus had high counts. Among the cranial nerve motor nuclei the facial and hypoglossal nuclei had high counts and the motor trigeminal nucleus and nucleus ambiguus had medium counts. The interpeduncular nucleus as a whole had low counts but there were two bands of intense staining on each side around the entry zone of the bundles of afferent cholinergic fibres from the habenula. Intermediate levels of binding occurred over the inferior colliculus and the superficial and intermediate grey layers of the superior colliculus. The molecular layer of the vestibulocerebellar vermis was distinctly labelled.

Animals↗