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L Rakic

Publications and source records attributed to L Rakic.

At least 37 records · Page 2Linked to original sources
PubMed1994

Desensitization of c-fos mRNA expression in rat brain following cortical lesions.

The effect of cortical lesions on the c-fos mRNA expression in adult rat brain was studied using in situ hybridization and Northern blot analysis. It was observed that the single cortical lesion evoked a rapid increase in the content of c-fos mRNA in whole brain. However, when rats received a second and third cortical injury 4 and 8 h after the first one, there was reduced elevation of c-fos mRNA after the second (60%) and third (75%) injuries in comparison with those seen after a single cortical lesion. These results represent the desensitization period during which the induction of c-fos mRNA by repeated cortical lesions was decreased. On the contrary, when animals were treated with a fourth cortical lesion 24 h after the first injury, with recovery for 16 h after the third one, the levels of c-fos mRNA were again elevated to a degree almost comparable to that seen after the single injury alone. The anatomical distribution of c-fos mRNA-expressing cells after cortical lesions revealed a large increase of hybridization to a heterogeneous population of hippocampal neurons including small cells of stratum granulosum in the dentate gyrus and larger cells within hippocampal stratum pyramidale. A dramatic labeling of neurons with c-fos riboprobe in frontoparietal and piriform cortex was also observed but with predominantly localized hybridization to c-fos mRNA on the damaged side of the cortex following the first and second cortical injury. However, hippocampal distribution of c-fos mRNA-containing cells was bilateral as a result of polysynaptic potentials evoked by cortical lesions.

Animals↗
PubMed1994

Effect of cerebellar stimulation on EEG power spectra in the acute model of epilepsy.

Experiments were performed to investigate the effects of cerebellar stimulation on epilepsy induced by parenteral administration of penicillin, in rats without or with the lesion of sensorimotor cortex. There were no differences in the EEG activity of the same experimental animal after the first and subsequent penicillin treatments (at least 7 days later). The electrical stimulation (duration of 5-10 min) of the lateral cerebellar nucleus was applied repetitively 135-315 min after penicillin administration, when the EEG power spectra markedly increased. The cerebellar stimulation evoked the decrease of the mean total EEG power spectra, but the effects were temporary. The EEG power spectra were significantly lower (P < 0.05) during the period of 150-330 min after penicillin treatment in experimental sessions with applied cerebellar stimulation in comparison to the experimental sessions without such stimulation. The residual effects (if any) of cerebellar stimulation on the EEG activity in the later period, 345-600 after penicillin treatment were not significant (P > 0.05). Cerebellar stimulation had the same effect among unlesioned animals and animals with prior cortical lesion in the acute model of epilepsy.

Animals↗
PubMed1993

Temporal and spatial preferences of c-fos mRNA expression in the rat brain following cortical lesion.

The expression of the proto-oncogene c-fos is increased in neuronal cells by a number of stimuli and the usefulness of this gene as a marker of neuronal activity has been demonstrated. The temporal and spatial expression of c-fos mRNA following the induction of a unilateral cortical lesion have been investigated in the rat brain by Northern blot analysis and in situ hybridization histochemistry. It was observed that the lesion evoked a rapid increase (20-fold) in the content of c-fos mRNA in the ipsilateral cortex, whereas in the contralateral cortex c-fos mRNA expression was more modest (7-fold). In the whole hippocampus a large and very rapid increase (17-fold) of c-fos mRNA expression was detected. The effect of a cortical lesion on Ca2+ uptake and membrane potential was also investigated. Using synaptosomes as a model system, we have provided evidence that Ca2+ entry via membrane depolarization increases in coordination with c-fos gene expression in neuronal cells. The principal conclusions from this study are that cortical lesions induce transient expression of the c-fos gene in specific neuronal cells of the rat brain.

Animals↗
PubMed1990

Sport activity and personality as elements in preventing cancer and coronary heart disease.

Results are reported for 3 groups of healthy male probands, 318 in each group, matched for age and personality type on the Personality-Stress Questionnaire. One group was actively engaged in sports, one had discontinued former sporting activities, and one group had never taken part in regular sports. Follow-up after 13 yr. showed lowest mortality in those actively engaged in sport, highest mortality in those who had given up sport, with those who had never been engaged in sport intermediate. Prophylactic behaviour therapy was shown to reduce mortality of those who had given up sport to a significant extent but not to affect degree of retinal sclerosis.

Adult↗
PubMed1989

Brain plasticity after corpus callosum transection in the newborn rat.

The importance of afferent fibers in the final shaping of the central nervous system has been well established in several papers. In order to study how much one can influence cortical development by changing afferent input to the cortex cerebri, we transected corpus callosum in rats at 2 or 3 postnatal days. Equal numbers of lesioned and control animals were transcardially perfused with mixed aldehydes at postnatal day 6 (P-6) or P-14. Brain tissue was processed for Golgi impregnation, Nissl stain, and quantitative electron microscopic analysis. Morphometric image analysis (MOP 3) of the primary sensory area did not show significant differences with respect to cortical depth and total and apical dendritic length. The cross-sectional area and maximal diameter of neuronal cell bodies were smaller in P-14-lesioned animals. Ultrastructural analysis of the cortex revealed that synaptic density was not reduced in lesioned animals. In conclusion, early in development, rat brain can compensate for major changes in the commissural afferent system.

Animals↗
PubMed1987

Monoamine-containing neurons in the Aplysia brain.

The localization of monoamine-containing neurons in the CNS of Aplysia depilans has been studied by fluorescent histochemistry (the glyoxylic acid condensation method) and microspectrofluorimetry. Yellow fluorescent nerve cells and fibers show the emission maximum at 515-520 nm which corresponds to that of serotonin fluorophore in a model system. Green fluorescent nerve cells have the emission maximum at 485 nm which corresponds to that of catecholamine. Central catecholamine-containing neurons were found in cerebral, buccal, pedal and unpaired abdominal ganglia. The majority of them were revealed in cerebral ganglia (about 40). Serotonin-containing neurons are abundant in cerebral and pedal ganglia. More than 30 serotonin-containing nerve cells were localized in cerebral ganglia. In the right pedal ganglion approximately 100 neurons were revealed; in the left one about 150. In the abdominal ganglion all nerve cells of this chemical type (except one) are located in the right hemiganglion. The results are summarized in corresponding schemes.

Abdomen↗
PubMed1987

Catecholamine-containing neurons in the peripheral nervous system of Aplysia.

Numerous green-fluorescent neurons have been revealed by means of the glyoxylic acid histochemical method in cryostat sections of several organs of two Adriatic aplysiid gastropods, Aplysia depilans and A. fasciata. Catecholamine-containing perikarya and their processes have been found to be especially abundant in the vaginal portion of the large hermaphrodite duct, in the penis and its sheath, and in the gill. In the reproductive organs, two subpopulations of catecholamine-containing neurons could be distinguished according to their size and location. Axons of larger neurons formed bundles which seemed to project at the CNS.

Animals↗
PubMed1984

[Compensation of anisocoria in cats following transection of the optic tract: the role of subcortical commissures].

Experiments were carried out on cats with unilateral optic tract transection and cerebral commissures. The data obtained indicate that destruction of the afferent part of the pupillary reflex by optic transection led to reversible anisocoria. In cats with combined transection of the optic tract and teleencephalic, diencephalic and mesencephalic commissures, such a rehabilitation did not occur. In contrast, section of telencephalic commissures alone was immaterial for the processes of compensation of papillary system function. The data obtained attest to an important role of subcortical commissures in compensation of anisocoria after destruction of the afferent arc of the papillary reflex to light.

Afferent Pathways↗
PubMed1981

Biogenic monoamines in early embryos of sea urchins.

Indolylalkylamine determination was performed on the eggs and embryos of six species of sea urchins, using several fluorometric techniques, including the fluorescence of a substance itself and the fluorescence of its condensation products after treatment with orthophthaldialdehyde and ninhydrin. The serotonin-like substance of sea urchin embryos as well as of adults was shown to consist of at least two components, of which the major one is tryptamine or its derivative with a substituting group at aminonitrogen. Further, serotonin was found to be present at all developmental stages investigated. although at much lower concentrations. The results of this study suggest a regulatory role of 'prenervous' tryptamine in the early embryogenesis of the sea urchin.

Animals↗
PubMed1979

[Sensitivity of fragmented and stratified sea urchin embryos to cytotoxic neuropharmacological preparations].

The red half embryos and related quarter embryos (yolk and pigment) of Arbacia lixula, obtained by means of centrifugation of the eggs in sucrose gradient, retain the normal level of sensitivity and supersensitivity to cytotoxic neuropharmaca, antagonists of biogenic monoamines. The white half embryos and clear quarter embryos practically lack supersensitivity whereas the granular quarter embryos restore it to the initial level. The non-pigmented blastomers of stratified embryos are characterized by somewhat weakened supersensitivity. A suggestion is put forward that the supersensitive embryos of A. lixula possess a sensibilizing factor which couples the supersensitivity receptors with the processes of cell division and moves together with the yolk granules upon centrifugation. This factor is not observed in the Strongylocentrotus granularis embryos lacking evident supersensitivity.

Amphetamines↗
PubMedDate not supplied

Comparative caustic and biological activity of trichloroacetic and glycolic acids on keratinocytes and fibroblasts in vitro.

OBJECTIVES: Beside their causticity, the biological mechanism by which trichloroacetic acid (TCA) and glycolic acid (GA), two agents extensively used for chemical peeling, might act remains unknown. The purpose of this study was to examine in vitro the effect of TCA and GA on human keratinocytes and the influence of the released epithelial mediators on collagen and matrix metalloproteinases (MMPs) production by human dermal fibroblasts. METHOD: Cultured keratinocytes were treated by TCA and GA at 10 mg/ml brought to pH 3, 5 and 7, and the conditioned media neutralized to pH 7 were added to human normal skin fibroblasts. RESULTS: TCA was cytotoxic for keratinocytes at each tested pH. The conditioned medium depressed protein and collagen synthesis and the expression of MMPs when added to fibroblasts as did also TCA when added directly to fibroblasts. GA was not cytotoxic for keratinocytes at neutral pH and the conditioned medium obtained at each pH applied to fibroblasts did not alter protein, collagen nor MMPs production while causing an elevated secretion of IL-6. CONCLUSION: TCA exerts a toxic effect on keratinocytes and fibroblasts while GA does not alter the metabolism of fibroblasts but induces the secretion of IL-6.

Caustics↗
PubMedDate not supplied

[Mechanism of the protective action of acetylcholine and serotonin against their cytotoxic antagonists].

By means of biological testing on supersensitive embryos of the sea-urchin Arbacia lixula, it has been shown that the eggs and embryos of the sea-urchin Paracentrotus lividus incubated in solutions of cytotoxic neuropharmacological drugs (cholino- and serotoninolytics), accumulate the latter. During the first (rapid) stage of binding, a level is reached which is 2-6 times higher than the external concentration; during the second stage of binding, this level gradually increases up to the values which are 8-12 times higher than the external concentration. The protecting action of exogenous acetylcholine and serotonin against the drugs studied does not inhibit their accumulation in embryonic cells. Therefore this protecting action is due to the decrease in the sensitivity of embryos to neurophysiological drugs. The protecting effect of endogenous factor produced by eggs and embryos is associated with the inhibition or abolition of the second stage of binding of cytotoxic neuropharmacological drugs.

Acetylcholine↗
PubMedDate not supplied

[Differential diagnosis of a red nose].

A red nose is a semiological sign shared in common by a series of diseases. The differential diagnosis is important to establish. A careful clinical examination often allows to reach the precise diagnosis. A skin biopsy is required when erythema is accompanied by a cutaneous infiltration suggesting some granulomatous and tumoral processes.

Diagnosis, Differential↗