Biomedical subjects

M Tauc

Publications and source records attributed to M Tauc.

59 records · Page 4Linked to original sources

PubMed1983

Different localizations of Met-enkephalin-like immunoreactivity in rat forebrain and spinal cord using hydrogen peroxide and Triton X-100. Light microscopic study.

The histological distribution of met-enkephalin-like immunoreactivity was studied in the forebrain (particularly the striatum) and the spinal cord of the rat using the indirect peroxidase-labelled antibody method. In most experiments, vibratome sections of formaldehyde-fixed tissues and purified antibodies were used. The search for optimal conditions for the immunohistochemical reaction lead us to establish that met-enkephalin-containing perikarya of both untreated and colchicinized animals were better demonstrated when tissue were pre-treated with diluted hydrogen peroxide only. The additional treatment of these sections with Triton X-100 (or some other detergents) resulted in the near disappearance of the perikaryal immunoreactivity; on the contrary, numerous met-enkephalin containing nerve fibres and varicosities were then demonstrated in the same region. Using only the hydrogen peroxide treatment, we found numerous met-enkephalin-containing perikarya in the medial and ventral regions of the neostriatum. This distribution was prolonged caudally by the existence of a prominent group of stained somata in the ventral putamen-central nucleus of the amygdala. When intraventricular injections of colchicine were used, positive perikarya were more numerous within the striatum (the globus pallidus excepted) but their distribution was largely the same as in non injected animals. However, some new groups of somata were stained in this case in the forebrain (in the lateral septum, the olfactory tubercle and the hypothalamus particularly). In control animals only few met-enkephalin-containing perikarya were observed in the dorsal horn of the spinal cord when H2O2 pretreatment was used alone and they were numerous only when intraspinal injections of colchicine were performed. Met-enkephalin-containing fibres and varicosities, which were scattered in the whole neostriatum in the conditions used above, became very numerous when the tissue sections were incubated in the presence of Triton X-100. Their density increased markedly from the latero-dorsal to the medio-ventral regions but, in addition, an organization under the form of islands of stronger immunoreactivity was also evidenced. These islands were more numerous ventrally in the anterior neostriatum and in the central region of the "putamen." The dense plexus of immunoreactive nerve fibers forming "tube-like structures" which was always observed in the paleostriatum and in the cranial medial forebrain bundle (islands of Calleja) appeared more diffuse when detergents were used.(ABSTRACT TRUNCATED AT 400 WORDS)

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PubMed1983

Met-enkephalin-like immunoreactivity in rat forebrain and spinal cord using hydrogen peroxide and Triton X-100. Ultrastructural study.

Using two immunocytochemical methods, we have shown in light microscopy that the met-enkephalin-like immunoreactivity within striatum and spinal cord of the rat is differentially distributed in either perikarya or nerve terminals according to the technical conditions used [1]. The present electron microscopic study has been undertaken in order to elucidate the subcellular localization of immunoprecipitates according to the same technical conditions. In the neostriatum, numerous met-enkephalin-containing perikarya were stained (principally at the level of rough endoplasmic reticulum) when tissue sections were treated with hydrogen peroxide (H2O2) only, prior to the immunocytochemical procedure. However, injections of colchicine were required to demonstrate perikarya in the dorsal horn of the spinal cord. At variance with previous results, numerous dendritic profiles and nerve terminals were also reactive in this condition. Neurotubules, mitochondria, large granular vesicles (LGVs) and small synaptic vesicles were stained within these structures. The addition of a low concentration of Triton-X-100 (0.02%) in the first incubation medium often resulted in the disappearance of most perikarya and in the staining of only LGVs in nerve terminals. The addition of a higher concentration of Triton-X-100 (0.1%) produced diffusion of immunoprecipitates at the level of nerve terminals, which was probably responsible for the increased intensity of staining and, subsequently, for the better demonstration of fibre varicosities in light microscopy. On the contrary, the disappearance of reactive perikarya seemed to result from the diffusion of the non-protected peptide out of the cytoplasm. The diverse ultrastructural localizations of met-enkephalin-like immunoreactivity in striatum and spinal cord are finally discussed in light of intrinsic connections or afferents described in the literature.

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PubMedDate not supplied

Histofluorescence analysis of several systems of catecholaminergic nerve fibres within the rat neostriatum revealed by either restricted lesions of the substantia nigra or gamma-hydroxybutyrate.

The glyoxylic acid fluorescence technique was applied to the study of catecholamine fibres in the caudate-putamen (neostriatum) of control and experimental adult rats. Cryostat or vibratome sectioning procedures were used; in the last case, either incubations of brain slices in gamma-methyl-noradrenaline or pre-treatment of animals with gamma-hydroxybutyrate were performed, in order to increase the intensity of fluorescence. In control animals and in the contralateral side of rats lesioned in the substantia nigra, the fluorescence of the dense plexus of dopamine nerve fibres appeared under the form of densely packed varicosities. However, some regions differed from the ordinary fluorescence of the neostriatum by their stronger intensity and more visible varicosities. They were located principally in the ventro-medial regions bordering either the nucleus accumbens, the dorsal nucleus interstitialis striae terminalis and the ventricle in the anterior part, or the amygdala, the globus pallidus and the ventricle in the posterior part. Moreover, islands of stronger fluorescence also were observed in the head of the caudate-putamen along the dorsal and lateral corpus callosum, as well as scattered in the central region. These particular neostriatal structures might correspond to a separate system of ascending dopamine nerve fibres. Therefore, restricted electrolytic lesions of the substantia nigra pars compacta were undertaken in order to study the morphology of the remaining catecholaminergic fibres in the ipsilateral neostriatum. In largely denervated areas, different types of fluorescent axons were evident. Presumed noradrenergic nerve fibres characterized by a very coarse appearance and closed varicosities were rare. They contrasted markedly with numerous delicate fibres which might belong to several dopaminergic systems. Both first types exhibited long, clearly visible intervaricose segments and ovoid triangular varicosities. The second type, which was thicker and more strongly fluorescent, probably formed the islands observed in unlesioned striata. The third type had very closed, small spherical varicosities and poorly fluorescent intervaricose segments. Dopamine nerve fibres of the same morphology were described previously in the neocortex [43,44] and the possibility of a common origin for nerve fibres of the same type is discussed. When rats were treated with the anaesthetic gamma-hydroxybutyrate, all the dopamine nerve fibres appeared to develop a strong fluorescence within the neostriatum, but more fluorescent islands were always visible. Additionally, some swollen fluorescent fibres were seen; these could be abnormal dopamine fibres whose metabolism had been pathologically altered by the drug.

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PubMedDate not supplied

Embryonic renal collecting duct cell differentiation is influenced in a concentration-dependent manner by the electrolyte environment.

BACKGROUND: During kidney development, the embryonic collecting duct (CD) epithelium develops into a heterogeneously composed epithelium consisting of principal and intercalated cells. It is unknown by which molecular mechanism the different cell types arise. We have experimental evidence that the electrolyte environment is involved in the process of terminal cell differentiation. METHODS: Embryonic CD epithelia from neonatal rabbit kidneys were microsurgically isolated and maintained in gradient perfusion culture for 13 days under serum-free conditions. Controls were maintained in the same medium (Iscove's modified Dulbecco's medium; IMDM) on basal and luminal sides. Experimental series were performed with IMDM only on the basal side, while on the luminal side IMDM with increasing concentrations of NaCl was used. Finally, the development of principal and intercalated cell features was registered by immunohistochemical labeling with markers specific for adult CD cells. RESULTS: Immunohistochemical markers show that the differentiation pattern is quite different when the embryonic CD epithelia are cultured in IMDM only as compared with specimens kept in IMDM supplemented with 3-24 mmol/l NaCl on the luminal cell side. First signs of changes in development were seen when low doses of 3-6 mmol/l NaCl were added. CONCLUSIONS: We conclude that facultative protein expression in embryonic CD epithelium is influenced by the electrolyte environment and starts to be upregulated after administration of unexpectedly low doses of 3-6 mmol/l NaCl added to the luminal perfusion culture medium and increases in a concentration-dependent manner.

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PubMedDate not supplied

Electrolyte environment modulates differentiation in embryonic renal collecting duct epithelia.

The influence of electrolytes on the development of renal principal and intercalated collecting duct cells is unknown. Consequently embryonic collecting duct epithelia were exposed to different electrolyte concentrations, and their degree of differentiation was registered by immunohistochemical methods. Embryonic collecting duct epithelia were isolated from neonatal rabbit kidneys and placed on tissue carriers. The apical urine and the basal serum compartments were simulated in a gradient culture container. The two sides of the epithelium were each constantly superfused with medium for 13 days. In controls the medium on both apical and basal side was standard Iscove's modified Dulbecco's Medium (IMDM) with 112 mmol/l Na+ and 85 mmol/l Cl-. In experimental series the NaCl concentration at the basal side of the epithelium was increased up to 137 mmol/l Na+ and 99 mmol/l Cl- as found in the serum of neonatal rabbits. Light microscopy revealed morphologically faultless epithelia following gradient perfusion culture in standard and NaCl-adapted IMDM. The development of principal and intercalated cell features was monitored with the monoclonal antibodies 703, 503, PCD9, and peanut lectin. Cells immunopositive for monoclonal antibody 703, for example, increased from less than 10% in controls to more than 80% in NaCl-adapted IMDM. It is a new finding that the development of collecting duct cell features is influenced by the extracellular electrolyte environment.

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