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Biomedical subjects

S Geuna

Publications and source records attributed to S Geuna.

36 records · Page 2Linked to original sources
PubMed1998

Morphological and morphometrical changes in dorsal root ganglion neurons innervating the regenerated lizard tail.

The variations occurring in neurons from dorsal root ganglia that provide innervation to the regenerated tail of the lizard (vicarious ganglia) are analysed. Vicarious ganglion neurons, when compared to control ganglion neurons (i.e. ganglia from the same animal that were not involved in the reinnervation process), show a size increase of the soma (cell hypertrophy) which applies to all cell types and subtypes. No statistically significant differences in the relative percentage of neurofilament-poor (type D) and neurofilament-rich (type L) neurons were found between vicarious dorsal root ganglia compared to controls in all animals. On the contrary, within L neuron sub-types, a statistically significant increase in sub-type L2 (very rich in neurofilaments), and the appearance of sub-type L3 neuron which is not detectable in controls, were demonstrated in vicarious dorsal root ganglia. In spite of these variations in size and percentage distribution, no structural and ultrastructural differences of the various cell types and sub-types are detectable, except for the appearance of the sub-type L3 neurons. However, this neuron sub-type might not be considered specific of hypertrophy since the same morphological features have been observed, in normal conditions, in lizard dorsal root ganglia from cervical and lumbar spinal levels that provide innervation to limb plexuses.

Animals↗
PubMed1998

Morphometrical analysis of types and sub-types of neurons in dorsal root ganglia of the lizard Podarcis sicula.

In the present study, we conducted a morphometrical analysis of the different types and sub-types of lizard DRG neurons at various spinal levels. This analysis demonstrated significant differences in size distribution among the various neuron types and sub-types, as well as a significant shift to greater values in neurons from the dorsal root ganglia at the cervical and the lumbar spinal levels. The results are critically evaluated in relation to methodological issues, and the implications of these findings are discussed.

Animals↗
PubMed1998

Types and sub-types of neurons in dorsal root ganglia of the lizard Podarcis sicula: a light and electron microscope study.

A morphological analysis of types and sub-types of neurons from dorsal root ganglia at different spinal levels was carried out by combined light and electron microscopy in Podarcis sicula. Two neuron types were recognized: small dark cells (type D) and large light cells (type L). Type L cells were further sub-divided into three sub-types (L1, L2, L3) on the basis of entity and distribution of neurofilaments. Percentage distribution of neuron types did not vary in relation to the spinal level. On the contrary, differences were found in the percentage of the three type L neuron sub-types; a higher percentage of cells very rich in neurofilaments (L2, L3) was found in dorsal root ganglia from the cervical and the lumbar spinal levels. Results are discussed in relation to the spinal-level-related extent of innervation territory of dorsal root ganglia.

Animals↗
PubMed1998

Smooth muscle cell hypertrophy and hyperplasia in the partially obstructed gut of the rat: a quantitative evaluation.

Partial surgical stenosis of the gut induces smooth muscle cell hypertrophy and hyperplasia in the loops upstream from the obstruction in a few days. In the present study we report a quantitative evaluation of these phenomena in the circular smooth muscle layer of the small intestine of the rat 7 days after a subtotal stenosis. In the loops upstream from the obstruction, lumen diameter and muscle wall thickness were found to be increased in comparison with downstream tracts. Morphometrical analysis showed that cross-sectional profile areas of smooth muscle cells, within the circular layer of upstream loops, significantly increased in size. Moreover, smooth muscle underwent a marked cell hyperplasia; in fact, estimates of the number of smooth muscle cell nuclear profiles turned out to be from 2.0 to 3.8 times greater in upstream loops than in downstream loops. The relation between the degree of lumen dilatation and the degree of the increase of the circular muscle layer thickness and of hypertrophic and hyperplastic response is discussed.

Animals↗
PubMed1997

Nucleo-plasmic index variability in dorsal root ganglion neurons of the lizard (Podarcis sicula) during neuronal hypertrophy.

The nucleo-plasmic index was investigated in lizard dorsal root ganglion neurons from different spinal levels (cervical, thoracic, lumbar and caudal) in normal conditions, as well as in caudal dorsal root ganglion (DRG) neurons innervating the regenerated lizard tail (caudal hypertrophic ganglia). Results showed no statistically significant difference in the distribution of nucleo-plasmic index values in DRGs from different spinal levels providing sensory innervation to peripheral territories of different size. On the contrary, in the caudal hypertrophic ganglia, a significant shift towards lower values of the nucleo-plasmic index was observed. This observation suggests that this 'old', and merely morphological, parameter could be regarded as a good and simple marker for the study of neuronal hypertrophy considered as a dynamic response of neurons to variations of the innervation territory.

Animals↗
PubMed1995

Stressors, stress and stress consequences during long-duration manned space missions: a descriptive model.

Keeping crew members in good health is a major factor in the success or failure of long-duration manned space missions. Among the many possible agents that can affect the crew's general well-being, stress is certainly one of the most critical because of its implications on human health and performance, both physical and mental. Nevertheless, very few studies have been performed on this fundamental issue and none of them has addressed it in its entirety, considering its diverse physical and psychological aspects. In this work, a descriptive model is proposed to expound the mechanism and sequence of events which mediate stress. A critical analysis of the information provided by past manned spaceflights and by dedicated research performed in analogous environments is presented, and an extrapolation of the available data on human stress in such extreme conditions is proposed. Both internal and external stressors have been identified, at physical and psychosocial levels, thus providing the basis for their early detection and preventive reduction. The possible negative consequences of stress that may lead to disease in crewmembers are described. Finally, the most effective instruments which may be of help in reducing space-related human stress and treating its negative consequences are suggested.

Adaptation, Psychological↗
PubMed1995

DNA neosynthesis in Auerbach plexus ganglia isolated from the rat hypertrophic gut: an electrophoretic analysis.

We analysed using electrophoresis the total genomic DNA extracted from isolated Auerbach plexus ganglia of the hypertrophic duodenum upstream from a partial experimental stenosis. Results indicated the presence of two extra-bands migrating below the high molecular weight DNA. suggesting that DNA amplification is the basic mechanism of the DNA neosynthesis previously observed in myenteric neurons.

Animals↗
PubMed1992

[Satellite cells of te dorsal root ganglia in neuronal hypertrophy].

Amputation of the lizard tail is followed by its complete regeneration over a period of six-eight months. The new tail is innervated only by the last three pairs of spinal nerves upstream from the plane of amputation, since no nerve cells are present in the regenerated. The corresponding dorsal root ganglia increase in volume (hypertrophic ganglia) and most of their sensory neurons become hypertrophic. Satellite cells belonging to this hypertrophic ganglia increase in number. This paper describes an autoradiographic study, after administration of tritiated thymidine, of the hypertrophic dorsal root ganglia of the lizard during tail regeneration. We evaluated the number of satellite cells which neo-synthetize DNA ("labeling index = LI%) and are therefore suitable to undergo cell division. The LI% was significatively increased in hypertrophic ganglia when compared to internal control ganglia (not directly involved in the reinnervation process) and normal ganglia (lizards with intact tails). The comparison between internal control ganglia and normal ganglia showed higher LI% values in the formers, although this difference was not statistically significative. These results are in line with those obtained by other authors and suggest that satellite cells of dorsal root ganglia can undergo cellular proliferation also in the adult, especially in particular experimental conditions.

Animals↗
PubMed1992

[Hyperplasia of the intestinal smooth muscle tissue proximal to a partial surgical stenosis: an autoradiographic study].

Hypertrophy of the smooth muscle wall of the rat small intestine occurs in the loops upstream from a partial surgical stenosis. This phenomenon is due both to cell hypertrophy and cell proliferation (hyperplasia). The thickness of the muscular layers reached its maximum after ten days from the intervention and then was maintained over the following days. Hyperplasia of the smooth muscle tissue has been demonstrated by means of autoradiography after administration of tritiated-thymidine. This investigation revealed the presence of 37%-44.5% of heavily labeled smooth muscle nuclei, index of active DNA neo-synthesis. On the contrary, no labeled nuclei were observed in the downstream tract as well as in the small intestine of the controls. These results, together with those obtained by other researchers, confirms that the smooth muscle tissue can undergo cell proliferation under particular conditions and that this phenomenon is often associated with the hypertrophic process.

Animals↗
PubMed1991

Electrophoretic analysis of neuronal genomic DNA from hypertrophic spinal ganglia during lizard tail regeneration.

Cytoplasmic and nuclear hypertrophy in neurons from the last 3 pairs of sensory ganglia left in situ cranially to the plane of amputation occurs during lizard tail regeneration. Cytophotometry after Feulgen staining demonstrated the presence of some neurons, from hypertrophic ganglia, whose quantity of DNA exceeded the diploid level (hyperdiploid neurons). In the present work agarose gel electrophoresis of total genomic DNA extracted from hypertrophic ganglia showed one or two bands migrating below the high molecular weight DNA, pointing to a selective amplification of discrete DNA segments.

Amputation, Surgical↗
PubMed1988

DNA content in neurons of Auerbach's plexus under experimental conditions in adult rats.

Some nerve cells of the Auerbach's myenteric plexus of the intestine of the adult rat, which hypertrophied following a surgically induced stenosis, began DNA synthesis unrelated to mitotic division. The cytophotometric analysis confirmed and quantified the amount of synthesis revealed by autoradiography with tritiated thymidine uptake. Numerous nerve cells show a DNA content exceeding the diploid level. Only a few of these show twice the diploid content. The significance of the DNA synthesis is discussed.

Animals↗
PubMedDate not supplied

A stereological study of long-term regeneration of rat severed sciatic nerve repaired by means of muscle-vein-combined grafts.

This study is a stereological analysis, by the 2-D dissector method, on the long-term regeneration of myelinated nerve fibers of the rat sciatic nerve repaired by muscle-vein-combined graft, a surgical technique that has been shown to be a valid tool for the repair of peripheral nerve defects with substance loss. Quantitative analysis showed that the total number and mean density of regenerated myelinated nerve fibers was significantly higher than in control nerves. The contrary was true for fiber mean size. The morpho-quantitative parameters of regenerated fibers from nerves repaired by the muscle-vein-combined graft were similar to those observed in rats where nerve defects were repaired by direct nerve suture thus confirming the validity of this surgical technique.

Animals↗