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S Geuna

Publications and source records attributed to S Geuna.

At least 37 records · Page 2Linked to original sources
PubMed2001

Evidence of very early neuronal migration from the olfactory placode of the chick embryo.

Cell migration from the olfactory neuroepithelium is a very peculiar phenomenon in the development of the nervous system. In this paper, we provide evidence that, in the chick embryo, migration of cells from the olfactory neuroepithelium begins earlier than previously reported, namely at the same time as the first olfactory placode differentiation, that occurs several hours before the superficial ectodermal invagination that gives rise to the olfactory pit. Moreover, we provide evidence that very early migrating cells express the HuC/D RNA-binding protein antigen, a specific neuronal marker. These observations refocus our knowledge on the very first developmental stages of olfactory neuroepithelium.

Animals↗
PubMed2001

Confocal imaging of HuC/D RNA-binding proteins in adult rat primary sensory neurons.

HuC/D RNA-binding proteins are antigens that are specifically expressed in nerve cells. In the present study, immunocytochemistry and laser confocal microscopy were used to study the cellular distribution of HuC/D RNA-binding proteins in adult rat primary sensory neurons. Colocalization with the protein gene product 9.5 (PGP 9.5) was used to identify sensory neurons. Confocal laser imaging showed that HuC/D antigens are expressed in the cytoplasm of all rat primary sensory neurons. Most neurons also showed anti-HuC/D immuno-positivity in the nucleus. The demonstration of the ubiquitous expression of HuC/D antigens in primary sensory neurons gives us a possible explanation for the severe pathological lesions observed in dorsal root ganglia in association with the paraneoplastic Hu Syndrome.

Animals↗
PubMed2000

Appreciating the difference between design-based and model-based sampling strategies in quantitative morphology of the nervous system.

Quantitative morphology of the nervous system has undergone great developments over recent years, and several new technical procedures have been devised and applied successfully to neuromorphological research. However, a lively debate has arisen on some issues, and a great deal of confusion appears to exist that is definitely responsible for the slow spread of the new techniques among scientists. One such element of confusion is related to uncertainty about the meaning, implications, and advantages of the design-based sampling strategy that characterize the new techniques. In this article, to help remove this uncertainty, morphoquantitative methods are described and contrasted on the basis of the inferential paradigm of the sampling strategy: design-based vs model-based. Moreover, some recommendations are made to help scientists judge the appropriateness of a method used for a given study in relation to its specific goals. Finally, the use of the term stereology to label, more or less expressly, only some methods is critically discussed.

Animals↗
PubMed2000

Nerve repair by means of vein filled with muscle grafts I. Clinical results.

Peripheral nerve lesions with a long segment defect need a grafting conduit to heal. Although autogenous nerve grafting is still considered the best method for bridging nerve defects, several alternative types of conduits (biological and synthetic) have been studied. We have demonstrated in previous experimental research in rats that a graft made using a vein (providing a guide for nerve regeneration) filled with fresh skeletal muscle (to prevent vein collapse and support axon regeneration) gave similar results to traditional nerve grafts. On this basis, we decided to use the muscle-vein-combined grafts in clinical cases. From 1993 to 1997, this technique was applied for bridging both sensory and mixed nerve defects (21 cases). We report good results in 85% of our cases with a minimum follow-up of 14 months. These results, obtained on nerve defects ranging from 0.5 to 6 cm in length, seem to be superior to those reported with other kinds of artificial or biological conduits.

Adolescent↗
PubMed2000

Nerve repair by means of vein filled with muscle grafts. II. Morphological analysis of regeneration.

The morphological features of regeneration in long-distance (3 cm) muscle-vein-combined grafts were experimentally investigated in the rat sciatic nerve by means of light and electron microscopy. In the early phases of regeneration (14 days after surgery), many regenerating nerve fibers were detected along the muscle-vein-combined graft. Six months after surgery, quantitative morphometrical analysis of myelinated nerve fibers showed that both the total number and density of myelinated nerve fibers were significantly greater in regenerated nerves than in control nerves. The contrary appeared true for the mean fiber size, with fiber size significantly smaller in regenerated nerves. Ultrastructural observations allowed the description of some peculiar aspects of the relationship between muscle fibers, nerve fibers, and Schwann cells in both early and late phases of regeneration.

Animals↗
PubMed2000

Tissue specificity in rat peripheral nerve regeneration through combined skeletal muscle and vein conduit grafts.

Diffusible factors from the distal stumps of transected peripheral nerves exert a neurotropic effect on regenerating nerves in vivo (specificity). This morphological study was designed to investigate the existence of tissue specificity in peripheral nerve fiber regeneration through a graft of vein filled with fresh skeletal muscle. This tubulization technique demonstrated experimental and clinical results similar to those obtained with traditional autologous nerve grafts. Specifically, we used Y-shaped grafts to assess the orientation pattern of regenerating axons in the distal stump tissue. Animal models were divided into four experimental groups. The proximal part of the Y-shaped conduit was sutured to a severed tibial nerve in all experiments. The two distal stumps were sutured to different targets: group A to two intact nerves (tibial and peroneal), group B to an intact nerve and an unvascularized tendon, group C to an intact nerve and a vascularized tendon, and group D to a nerve graft and an unvascularized tendon. Morphological evaluation by light and electron microscopy was conducted in the distal forks of the Y-shaped tube. Data showed that almost all regenerating nerve fibers spontaneously oriented towards the nerve tissue (attached or not to the peripheral innervation field), showing a good morphological pattern of regeneration in both the early and late phases of regeneration. When the distal choice was represented by a tendon (vascularized or not), very few nerve fibers were detected in the corresponding distal fork of the Y-shaped graft. These results show that, using the muscle-vein-combined grafting technique, regenerating axons are able to correctly grow and orientate within the basement membranes of the graft guided by the neurotropic lure of the distal nerve stump.

Animals↗
PubMed2000

Morphological analysis of peripheral nerve regenerated by means of vein grafts filled with fresh skeletal muscle.

Clinical data have shown that a vein segment filled with fresh skeletal muscle can be considered a good autologous grafting conduit for the repair of peripheral nerve lesions. In this study, the long-term morphological organization of rat sciatic nerve fibers regenerated along a muscle-vein-combined graft conduit is further analysed by light and electron microscopy. Regenerated nerve fibers were organized into fascicles of various sizes that were clearly delimited by perineurial-like shells made by long and thin cytoplasmic processes of perineurial-like bipolar cells and by densely packed collagen fibrils. Grafted skeletal muscle fibers were still detectable among nerve fiber fascicles. However, in spite of the persistence of skeletal muscle along the graft, regenerated nerve fibers showed a good morphological pattern of regeneration, providing further evidence that the muscle-vein-combined grafting technique represents an effective surgical alternative to the classical fresh nerve autograft for the repair of peripheral nerve defects.

Animals↗
PubMed2000

Verification of the two-dimensional disector, a method for the unbiased estimation of density and number of myelinated nerve fibers in peripheral nerves.

Quantification of the number of myelinated fibers in peripheral nerves is a common requirement in quantitative morphology. This parameter provides important information on the consequences of various physiological, pathological and experimental conditions on the nerve structure and is one of the main indicators of success of peripheral nerve repair. In this paper, the theoretical rationale for the application of stereological principles to obtain unbiased estimates of the density and total number of myelinated fibers in peripheral nerves is discussed and a simple stereological method is described. The method is applied together with a systematic random sampling scheme, that was optimized for the purposes of the present study, and with sampling scheme analysis by calculating the coefficient of error (CE). The stereological method, which consists of a two-dimensional variation of the classical disector procedure (two-dimensional disector), and the sampling scheme are verified by comparing estimates with the true density and total number of myelinated fibers in peripheral nerve trunks where true values have been accurately determined by extensive counting. The verification of the 2-D disector method, both of normal and regenerated nerves, showed that estimates of density and total number of myelinated nerve fibers are unbiased. The method also proved to be efficient (time-saving): Estimation of density and total number of myelinated fibers in a single nerve takes about 2-3 hours.

Animals↗
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↗