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G Raisman

Publications and source records attributed to G Raisman.

At least 109 records · Page 6Linked to original sources
PubMed1979

Muscarinic receptofs in the central nervous system of the rat. III. Postnatal development of binding of [3H]propylbenzilylcholine mustard.

The postnatal development of muscarinic receptors has been studied in 7 selected areas from the brains of 1-17-day-old rats by counting silver grains in light microscope autoradiographs of the specific (atropine-sensitive) binding of [3H]propylbenzilylcholine mustard in cryostat sections. A major part of the adult receptor density is present at 1 day of age, a time when only a small fraction of the adult number of synapses has yet been formed. Of the areas studied the hypoglossal nucleus is the most precocious in muscarinic receptor development, and the dentate gyrus the latest (associated with the late development of the dentate granule cells). The pattern of receptor distribution changes with development. The caudate-putamen first develops receptor in patches, beginning at the lateral (ventricular) surface. The pontine nuclei develop receptor in a medial to lateral sequence. The maturation of the adult laminar pattern of the olfactory bulb depends on the alignment of cells (especially the mitral cells). The neocortex initially has uniform labelling throughout its depth, and later the labelling in layer 4 becomes relatively less dense (probably associated with the ingrowth of afferent fibres). The hippocampal formation first develops receptor evenly over the pyramidal cell dendrites; later receptor appears over the newly formed dentate stratum moleculare and becomes much reduced over the hippocampal stratum lucidum and stratum lacunosum-moleculare (probably associated with the ingrowth of afferent fibres from the dentate gyrus and entorhinal area). In the cerebellum muscarinic receptor is found only in the lobules which receive the primary vestibular afferents. In the neonate it is present in the granular layer, but this later disappears and is replaced by the adult pattern of labelling in the molecular layer.

Aging↗
PubMed1979

Muscarinic receptors in the central nervous system of the rat. IV. A comparison of the effects of axotomy and deafferentation on the binding of [3H]propylbenzilylcholine mustard and associated synaptic changes in the hypoglossal and pontine nuclei.

The reaction of axotomy has been studied in the rat hypoglossal nucleus by quantitative electron microscopical counts of numbers of synapses and by changes in muscarinic receptors assessed by counting silver grains in light microscope autoradiographs of the specific (atropine-sensitive) binding of [3H]propylbenzilylcholine mustard in cryostat sections. For the first 5 days after unilateral peripheral hypoglossal nerve axotomy the muscarinic ligand binding falls to 50% of control levels and then shows no further fall for up to 30 days. Synapse numbers decrease progressively over the first 10 days after operation, by which time they reach 50% of normal. Thus receptor changes reach completion at a time when synapse loss is still continuing. Later, both muscarinic ligand binding and synapse numbers recover to an extent which depends at least in part on the effectiveness of the peripheral nerve regeneration, suggesting that both the receptor and synapse changes may be dependent upon neuromuscular contacts. The reactions of muscarinic receptors to axotomy and deafferentation have been studied in the rat basilar pontine nuclei. Cerebellectomy, which causes axotomy of the pontine neurones and also removes their postsynaptic targets (the granule cells), causes no change in pontine muscarinic receptor over the first week after operation. This differs from the rapid fall in hypoglossal muscarinic receptors induced by axotomy. At longer survivals after cerebellectomy there is a partial loss of pontine muscarinic receptors associated with atrophy of the pontine neurones. Destruction of the neocortical afferents causes a loss of at least half of the synapses in the pontine neuropil. However, the light microscopic autoradiographic study revealed no obvious changes in the dentisy or distribution of the pontine muscarinic receptors from 4 days to more than 6 months after operation.

Afferent Pathways↗
PubMed1978

Electron microscope autoradiographic evidence for specific transneuronal transport in the mouse accessory olfactory bulb.

The distribution of radioactive material was examined autoradiographically 8 h after application of [3H] proline to the vomeronasal organ in mice. Labelled material was transported along the axons of the vomeronasal nerves to their terminals in the glomerular layer of the accessory olfactory bulb (AOB). A lesser but consistent amount of radioactivity was found in the external plexiform layer (EPL) of the AOB. Electron microscopic autoradiography was used to determine which of the components of the EPL contained this labelled material. The method of proportional grain counts showed that the highest concentration of silver grains lay over the mitral cell dendrites, which are the elements immediately postsynaptic to the vomeronasal nerve axons. However, a fairly high proportion of grains also lay over the peripheral processes of granule cells. By application of a method of 'crossfire analysis' (which is explained in detail) it was possible to show that the observed grain distribution is best explained by the assumption that the radioactive material is confined to mitral cells, and the labelling over granule cell processes is due to crossfire from these sources. Im one animal at 5 days after [3H]proline administration label was found to have extended from mitral cells to granule cells, suggesting that the transsynaptically transported radioactive material, which was confined to the mitral cells at 8 h, may have become further redistributed at longer survivals. In a control experiment, [3H]proline was applied directly to the surface of the AOB. This gave rise to a completely different distribution of radioactivity in the EPL: radioactive material was present in all tissue components.

Animals↗
PubMed1978

Inhibition by puromycin of transneuronal transport in the mouse accessory olfactory bulb.

Application of [3H]proline to the vomeronasal organ (VNO) in mice results in the transport of labelled material along the vomeronasal axons to their terminals in the glomerular layer of the accessory olfactory bulb (AOB). In addition labelled material leaves the vomeronasal nerve terminals and is found over the external plexiform layer (EPL), where a previous electron microscopic autoradiographic study showed that it is preferentially accumulated in mitral cells. Grain densities over the glomerular layer and the EPL were counted in light micrographs. After subtracting background, the overall density of grains in the EPL is about 10% of that over the glomerular layer at 6 h after administration of [3H]proline to the VNO (5 mice). In a further 7 mice, puromycin (or saline) was applied directly to the AOB at hourly intervals during the 6 h after [3H]proline administration. Under these circumstances the labelling in the EPL is only 2--4% of that in the glomerular layer (9% for the 2 saline controls). These observations are evidence that a major part of the transsynaptic transfer mechanism is dependent on protein synthesis, and also favour the view that free amino acids are an important component of the material transferred.

Animals↗
PubMed1978

Replacement of receptor neurones after section of the vomeronasal nerves in the adult mouse.

Eight days after vomeronasal nerve section or removal of the accessory olfactory bulb, the majority of receptor cells of the vomeronasal neuroepithelium degenerate and disappear, leaving a regular framework consisting of supporting cells and their radial processes. The cell clusters at the boundaries of the epithelial sheet (which have been shown to be actively dividing in the normal, unoperated adult mouse) are also spared. The epithelium is subsequently repopulated by receptor cells appearing first in the basal part of the receptor cell layer and later occupying the full width of the receptor layer. These cells are anatomically fully differentiated receptor cells with normal sensory dendrites. Their axons form conspicuous intraepithelial neuromatous masses. Administration of [3H]thymidine on days 10-20 postoperatively labels some clusters of supporting cells and virtually all of the receptor cells, indicating that the repopulation of the epithelium is due to new formation of receptor cells.

Animals↗
PubMed1978

Cell division in the vomeronasal organ of the adult mouse.

Using [3H]thymidine labelling we could demonstrate the presence of a population of dividing cells in the vomeronasal neurosensory epithelium of the adult mouse. These cells are localised in the regions of the epithelium adjacent to its boundaries with the ciliated respiratory epithelium. With increasing survival times after thymidine administration, the labelled cells become situated progressively further away from the boundary region. The cluster of cells with labelled nuclei forms a loose column, consisting of labelled receptor cells, but in addition the immediately overlying supporting cell nuclei are also labelled. By 56 days after thymidine administration the cluster of labelled cells is separated from the epithelial boundary by a distance equivalent to about one-fifth of the total width of the epithelial sheet. There is little further change in position at 102 days. It is not clear to what extent this represents a turnover process as opposed to a continuing growth of the epithelium by accretion at the edges.

Animals↗
PubMed1978

What hope for repair of the brain?

The consequences of axonal injuries in the adult nervous system depend on the location of the axons: complete anatomical and functional repair can occur in the peripheral but not the central nervous system. A quantitative electron microscopical comparison of the reactions to axonal injuries in a peripheral site (the superior cervical sympathetic ganglion) and in a central site (the septal nuclei) in adult rats shows that in both cases the denervated postsynaptic sites are reinnervated by new formation of synapses. However, in the ganglion it is the originally severed axons which form the new synapses (regeneration), whereas in the septum the new synapses arise from local, undamaged axons and the cut axons do not reestablish their original contacts. Failure of regeneration in the central site is probably due to the fact that the growing axon sprouts are incapable of finding a pathway to the denervated tissues. Since the observations indicate that the neuropil of the central nervous system is capable of highly efficient synapse formation after injury, true repair of central nervous system damage might be possible if methods could be devised for dealing with the "pathway" problem.

Animals↗
PubMed1978

The neuroanatomical search for sexual dimorphism.

In the rat preoptic area, there is a region of neuropil which shows anatomical differences between males and females. Destruction of this area does not prevent ovulation. Destruction of the suprachiasmatic nuclei prevents spontaneous cyclic ovulation in female rats, but ovulation can be induced by mating in such animals. The rats with suprachiasmatic lesions also showed major disturbances in the normal diurnal timing of many bodily functions. The ovulatory disturbance caused by suprachiasmatic lesions may be due to a defect in the normal timing mechanism for the facilitatory action of progesterone on LH secretion.

Animals↗
PubMed1976

A quantitative comparison of the formation of synapses in the rat superior cervical sympathetic ganglion by its own and by foreign nerve fibres.

The rat superior cervical sympathetic ganglion (SCG) has about 36,000 neurones in a volume of about 1 cu.mm. There are about 8.8 X 10(6) synapses, and 6000-9000 preganglionic axons. Section of the preganglionic chain causes a loss of 93% of the synapses. In the denervated SCG there are 0.6 X 10(6) remaining ('intrinsic') synapses, and a proportion of the synaptic sites are identifiable as vacated synaptic thickenings (3 X 10(6) per SCG, as compared with 0.5 X 10(6) in the normal intact SCG). After deducting the intrinsic synapses, this indicates that each preganglionic axon forms about 1100 (900-1400) synapses. After freezing the preganglionic chain, subsequent axonal regeneration restores synapse numbers to 85% of normal (7.5 X 10(6) synapses per SCG). After anastomotic repair by suture of the cut ends of the preganglionic chain (a necessary control for the foreign nerve anastomoses), the SCG contains only 60% of the normal complement of synapses (5.2 X 10(6) synapses per SCG). The results of this anastomosis are very variable. However, in individual ganglia the numbers of synapses are directly correlated with the numbers of axons which reach the SCG. After deducting the intrinsic synapses it can be calculated that each axon forms about 700 synapses. This is probably an underestimation of the numbers which would be achieved at longer survival times. After anastomosis of the vagal nerve into the denervated SCG there are about 4.4 X 10(6) synapses per SCG. Morphologically the majority have axon terminals with large dense cored vesicles, and it is likely that these belong to the axons of the parasympathetic preganglionic neurones in the dorsal motor nucleus of the vagus. A smaller population of axon terminals are devoid of large dense cored vesicles; their origin is unknown. The dorsal motor nucleus of the vagus has between 1000 and 2000 neurones. After deducting the intrinsic synapses, this indicates that each axon may form up to 1900-3800 synapses. To the extent that other, unidentified vagal fibres also contribute to the synapses found after this anastomosis, this figure is an overestimate. After anastomosis of the hypoglossal nerve into the denervated SCG, there are 1.5 X 10(6) synapses per SCG. A morphologically distinctive type of axon terminal is found, and it is argued that this may belong to a special category of skeletomotor neurones located in the caudoventral part of the hypoglossal nucleus and distinguished by pseudocholinesterase staining. There are about 600 of these neurones, which would indicate that they form about 1500 synapses per axon (after deducting the numbers of intrinsic synapses). The majority of the hypoglossal neurones do not form intraganglionic synapses; this suggests that although the possession of a cholinergic mechanism may be necessary for axons to be able to form ganglionic synapses, it is not in itself sufficient. For each of the types of anastomosis, the numbers of vacated thickenings are inversely proportional to the numbers of synapses...

Acetyltransferases↗
PubMed1975

Retrograde transport of horseradish peroxidase in the magnocellular neurosecretory system of the rat.

Horseradish peroxidase (HRP) was injected into the pituitary in adult rats. After 2-3 days, the neurones of the supraoptic nuclei, the magnocellular parts of the paraventricular nuclei, and the various accessory neurosecretory hypothalamic nuclei showed accumulation of HRP. The HRP reaction product consisted of fine, discrete cytoplasmic granules, and in electron micrographys it was seen to be located in the lysosome-like dense bodies of 0.4-0.6 mum diameter which are normally present in the cytoplasm of the neurosecretory neuron.es. Very little reaction product was found in the neurosecretory axons. Reaction product was also found in the hypothalamic arcuate nuclei. This was the result of an endogenous peroxidase-like activity, since it occurred in control animals which had not received HRP. This endogenous reaction product is non-neuronal. Morphologically, it takes the form of distinctive clusters of coarse granules which are seen in electron micrographs to be characteristic angular bodies of 0.7-1.0 mum diameter located in the cytoplasm of astrocytes or their processes.

Animals↗