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J Regidor

Publications and source records attributed to J Regidor.

13 recordsLinked to original sources
PubMed1995

Afferents to different layers of the dorsolateral isocortex in rats.

Fluorescent somatopetal tracers were used to infiltrate, by diffusion rather than injections, the dorsolateral cortex of one hemisphere in rats. In different animals the tracers penetrated into the cortex to different depths. We found several interesting features of the commissural system: first, there were no areas without commissural neurons. At least a few labelled cell bodies were present in a single-cell layer also in "acallosal" cortical areas. Secondly, there is a considerable variety of laminar distribution patterns of labelled perikarya in different areas. Thirdly, some cortical fields, which cytoarchitecturally appear uniform, can be subdivided according to different distributions of cell bodies with commissural projections. Fourthly, when only supragranular layers were infiltrated, labelled cell bodies were present mainly in the supragranular layers of the contralateral cortex. Infiltration of the first layer alone did not label any neurons in the contralateral cortex but did label neurons in layer VIb ipsilaterally. In the subcortex, the labelled perikarya were found in the structures already known to project directly to the cortex. In rats with the tracer restricted mainly to the supragranular layers, a conspicuously reduced labelling was found in the basal forebrain and the thalamus. In the thalami of those animals, labelled neurons were found only in paralamellar nuclei. The high sensitivity of the tracer used, together with infiltration of the entire dorsolateral cortex, allows us to conclude that probably all sources of innervation of the isocortex in rats have been seen.

Afferent Pathways↗
PubMed1994

Anti-inflammatory drugs suppress injury-induced NADPH-d activity in CA1 pyramidal neurones.

Inducibility of NADPH-diaphorase (NADPH-d) or nitric oxide synthase (NOS) has been demonstrated in pyramidal neurones of the hippocampus, but the mechanisms of this induction are not known. The present study aimed to assess the role of anti-inflammatory drugs in injury-induced production of NADPH-d/NOS in CA1 pyramidal neurones. We found that either a steroid, dexamethasone or a non-steroid, indomethacin, prevents induction of these enzymes. We also found that NO is not necessary for the induction. None of the three drugs used had detectable effect on the neurones which contain constitutive NADPH-d/NOS.

Animals↗
PubMed1993

Bilateral induction of NADPH-diaphorase activity in neocortical and hippocampal neurons by unilateral injury.

Unilateral injury of the cerebral cortex or hippocampus induced a bilateral appearance of NADPH-diaphorase in some pyramidal neuronal and glial cells of both structures. Only in the cerebral cortex, near the needle track, did some V layer pyramidal neurons contain so much of this enzyme that they looked to be stained by the Golgi method. The induction of NADPH-diaphorase in a subset of cortical and hippocampal neurons in both hemispheres after unilateral injections of either cysteamine or artificial cerebro-spinal fluid suggests the existence in the isocortex and the hippocampus of a selective signalling system which may play a role in recovery of function following local brain damage.

Animals↗
PubMed1993

NADPH-diaphorase (NOS) is induced in pyramidal neurones of hippocampal slices.

We found NADPH-diaphorase (presumably identical with nitric oxide synthase) in pyramidal neurones of the hippocampus in slices that stayed in a chamber for 30 min or longer. In some instances parallel slices showed normal membrane properties when studied electrophysiologically. In freshly made slices the pyramidal neurones were not stained. Thus, after induction of the enzyme, the hippocampal pyramidal neurones can synthesize nitric oxide which may serve as a retrograde messenger in long-term potentiation. The enzyme may also play a role in cell loss seen in slices which stayed in a chamber for 9-22 h before fixation.

Animals↗
PubMed1993

NOS neurones lie near branchings of cortical arteriolae.

We show that numerous neurones labelled for NADPH-diaphorase, which synthetize nitric oxide, lie near branching points of the arteriolae which descend through the cerebral cortex from its pial surface. This spatial relationship suggests the possibility of neural control of cortical blood flow by the NADPH-diaphorase neurones, possibly mediated by the rapid action of nitric oxide.

Amino Acid Oxidoreductases↗
PubMed1993

Cortical projections of the thalamic mediodorsal nucleus in the rat. Definition of the prefrontal cortex.

Deposits of somatopetal tracers, that filled the entire dorsolateral cortex of one hemisphere, labelled only a few cell bodies in the thalamic mediodorsal nucleus (MD). Further experiments served to confirm the existence of strong projections from MD to the mesial and suprarhinal areas of the frontal cortex. Thus, only a very small proportion of the MD neurones in the rat projects outside the cortical areas described first by Leonard (1969). We conclude that at least in the rat, cortical projections of the MD are selective enough to be used as the basis for definition of the prefrontal cortex.

Animals↗
PubMed1992

Bilateral thalamocortical projection in hedgehogs: evolutionary implications.

In adult hedgehogs with large unilateral cortical deposits of fluorescent somatopetal tracers, labelled perikarya were found not only in the ipsilateral but also contralateral thalamus. An exceptionally large number of contralaterally labelled neurons was seen in the ventrolateral nucleus, also at a considerable distance from the midline. Deposits of one of two different tracers in the frontoparietal cortex of each hemisphere appear to label different perikarya in each ventrolateral nucleus. This projection to the contralateral cortex in hedgehogs does not resemble thalamo-cortical connections in either adult or developing brains of other mammalian species. Among amniotes, only in pigeons have contralateral projections from the thalamus to the telencephalon been described. The somatosensorimotor system of hedgehogs may be the only known mammalian remnant of primitive vertebrate thalamocortical organization. Whether primitive or derived, the bilateral thalamocortical projection in hedgehogs shows that hedgehog brains cannot be uncritically taken to represent brains of primate ancestors.

Animals↗
PubMed1987

Vertical ascending connections in the isocortex.

Different fluorescent tracers were applied to the surface of the cortex of rats, marmosets and one hedgehog. Irrespective of the kind of tracer and the depth of penetration, some perikarya of layer VI were labelled in each specimen and in all cortical regions. In the rat almost all labelled neurons were packed in sublayer VIb, in the marmoset such cells were dispersed throughout layer VI, whereas in the hedgehog the degree of their segregation to sublayer VIb was intermediate. Additional experiments in the rat indicated that most of the medium-sized neurons in the VIb layer project to layer I, that most of the perikarya projecting to the thalamus are localized in sublayer VIa, that different neurons project to the thalamus and to the surface of the cortex, and that only very few perikarya in deep parts of layers III and V and of sublayer VIa send axons or axon collaterals to layers I and II.

Animals↗
PubMed1987

Architectonics of the thalamus in the echidna (Tachyglossus aculeatus): search for the mediodorsal nucleus.

Architectural characteristics of the thalamus in echidnas and rats were compared in sections stained to reveal cell bodies, myelin, acetylcholinesterase, succinate dehydrogenase and cytochrome oxidase. Numerous species differences were noticed: in general, the thalamus is architecturally more homogeneous in echidnas than in rats, especially anteriorly. In this report we emphasize the presence of a relatively large structure localized in the anteromediodorsal part of the thalamus in echidnas. This structure, previously shown to project to the frontal cortex, contains very small amounts of acetylcholinesterase and the oxidative enzymes; in this respect it resembles the mediodorsal nucleus of rats. The same properties make this formation different from the anterodorsal and anteroventral nuclei in rats, the equivalents of which could not be identified in echidnas. The anteromediodorsal region of the thalamus in echidnas consists chiefly of two cytoarchitecturally different regions: the medial, 'polymorphic' part contains relatively small, densely packed, multiform perikarya, whereas the lateral, 'monomorphic' part is characterised by larger, sparse neurons with little cytoplasm and round, large, empty-looking nuclei in which the nucleolus is clearly seen. We conclude tentatively that this brain structure of echidnas corresponds to the mediodorsal nucleus in placental species. Further studies of connections and chemical properties will be essential to determine the degree of correspondence of the presumed 'frontal lobe system' in echidnas to that in other mammals.

Animals↗
PubMed1981

A method for the study of the spatial distribution of the neuronal dendritic tree using a universal stage.

The use of a microscope equipped with a universal stage with 4 rotation axes, drawing tube and photographic system for the 3-dimensional study of neuronal morphology is considered. Two-dimensional projections of the neuronal tree are obtained by rotating the stage, and the application of coordinate transformations results in 3-dimensional mapping of neuronal topography. Algorithms used for these transformations are presented and the method applied to Golgi-impregnated neurons of the cerebral cortex of adult lizards. The advantages, limitations and sources of error of this method are discussed.

Animals↗