Biomedical subjects

A Privat

Publications and source records attributed to A Privat.

At least 127 records · Page 7Linked to original sources

PubMed1994

Adenovirus insertion encoding the Lac Z gene in human nervous cells in primary dissociated cultures.

Primary dissociated cultures of human fetal central nervous system cells were prepared and inoculated at different days in vitro with adenovirus that contained a reporter gene encoding beta-galactosidase. At various time intervals, the cultures were processed for characterization with X-gal histochemistry and additional immunostaining with neurofilament (NF), GABA and glial fibrillary acidic protein (GFA-P). We observed that NF (+) and GABA (+) neuronal as well as GFA-P (+) glial cells could express beta-galactosidase activity after inoculation. The labeling was detected up to 3 months after virus treatment. In addition, neurons cultivated for three months were found to be still permissive for virus infection. We can conclude that adenovirus may be considered as a potential vector to transfer genes to nerve cells.

Adenoviruses, Human↗

PubMed1994

[Experimental medullary lesions: prevention of the extension of secondary lesions and formation of glial scarring].

Early treatment of spinal cord lesions is undertaken following two lines of research carried in adult rats: First, the reduction of secondary lesions, immediately after the trauma, second, the prevention of glial scar formation in the following days. In the first case, after a photochemical focal lesion at thoracic level (T8), a specific, non competitive antagonist of NMDA, TCP, is injected systemically. The result is the reduction of the extent of the lesion, as measured in serial coronal sections, the improvement of the performance in two functional tests of hindlimb function, and the improvement of somatosensory evoked potentials. In the second case, the spinal cord of rats were hemisected at thoracic level (T8-T9), and a suspension of liposomes containing a cholesterol derivative (7 beta-OH cholesteryl-oleate) was administered through a sub dural catheter, 2 days after the section. Histological investigations evidenced a reduction of astrocyte hyperplasia and hypertrophy, together with the blocking of the expression of a cell adhesion molecule, the so-called polysialic N-CAM. This resulted, within 5 weeks after the lesion, in the growth of axons in the denervated dorsal horn, below hemisection originating from the contralateral side. In conclusion, these two experimental studies constitute the basis for a coherent strategy of treatment in spinal cord traumatic lesions. Their sequential application could even improve the functional outcome of spinal cord lesions. However, these two research lines do not exclude other associated treatments such as the local applications of growth factors, which can potentiate both neuron survival and axonal sprouting.

Animals↗

PubMed1993

Neurotoxic effect of the anti-HIV drug D-aspartate beta-hydroxamate for rat primary neuronal cultures: attenuation by N-methyl-D-aspartate (NMDA) antagonists.

The anti-tumor drug D-aspartate beta-hydroxamate (D-A beta H), selectively destroys HIV-1 infected peripheral blood mononuclear cells, but produces anorexia and nausea during prolonged treatment to AIDS patients. Consequently, based on the structural similarity between D-A beta H and the excitotoxins L-aspartate and NMDA, we have investigated the potential neurotoxic action and pharmacology of D-A beta H and of a series of chemically related anti-tumor drugs on rat primary neuronal/glial cultures. In this aim, after a 30 min exposure to D-A beta H (1-2 mM), cortical neurons were selectively destroyed within 24 h. The stereoisomer L-A beta H (0.5-2 mM) was highly neurotoxic for both glial and neuronal cells in mixed cultures but demonstrated no toxicity in glial cell cultures alone. Furthermore, for a series of D-A beta H analogues, VHS.121 and VHS.122 demonstrated a reduced but significant neurotoxicity, whereas VHS.124 and VHS.125 showed no significant neurotoxic effect, and in the case of VHS.125 also prevented D-A beta H and glutamate-mediated neurotoxicity. The related anti-tumor drugs L- or D-glutamate gamma-monohydroxamate or keto-glutamate gamma-monohydroxamate (< or = 2 mM) were not neurotoxic for cortical neurons. The neurotoxic effect of D-A beta H and L-A beta H was attenuated by the NMDA antagonists MK-801, TCP, memantine, ifenprodil, pentamidine and CGS-19755. alpha-Difluoromethylornithine, an inhibitor of polyamine biosynthesis, also protected cultures against the neurotoxicity of L-A beta H and D-A beta H.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1993

Protection by BTCP of cultured dopaminergic neurons exposed to neurotoxins.

This study presents 'in vitro' evidence for a protection of cultured dopaminergic neurons against the toxicity of 6-hydroxydopamine (6-OHDA) and 1-methyl-4-phenylpyridinium (MPP+) by pretreatment with BTCP, a selective and potent dopamine (DA) uptake blocker. Moreover, we show that, at low concentration (10 nM), treatment with MPP+, which is more selective than 6-OHDA for dopaminergic neurons, is followed by some regeneration of these neurons.

1-Methyl-4-phenylpyridinium↗

PubMed1993

Neuropeptide Y-producing neurons of the arcuate nucleus regenerate axons after surgical deafferentation of the mediobasal hypothalamus.

Dorsolateral and ventomedial surgical deafferentiation of the hypothalamus were used to study the capacity of different types of neuropeptide Y-containing axons afferent to the dorsal hypothalamus to regenerate through surgical lesions. The kinetics of the postlesional responses of transected neuropeptide Y-axons was studied on 30-40 microns thick vibratome sections, either (i) by light or electron microscopy after peroxidase immunostaining for neuropeptide Y or (ii) by confocal microscopy after double fluorescence immunostaining for neuropeptide Y and for glial fibrillary acidic protein. The dorsolateral cut was found to sever 2 main pathways containing neuropeptide Y axons located, respectively, below the bed nucleus of the stria terminalis and in the perifornical region. In both regions transected fibers were found to abut onto the surgical lesion, but even 45 days after the lesion, they were very rarely observed to penetrate into the astroglial scar forming along the lesion. The ventromedial cut was found to sever numerous neuropeptide axons that originate in the underlying arcuate nucleus. Seven to 15 days after the lesion neuropeptide Y fibers located below this type of cut presented a dramatic increase in both their numerical density and their immunostaining intensity. With increasing post-surgery times, an increased number of neuropeptide Y fibers was observed to penetrate and to cross the lesional scar formed by densely packed astrocytic processes. Electron microscope observations further demonstrated that 45 days after the lesion, numerous neuropeptide Y-immunoreactive axonal profiles were included in the scar matrix, which appeared to be mainly composed of closely interdigitating astrocytic processes containing dense bundles of filaments. These data indicate that, in contrast to other neuropeptide Y neurons innervating the dorsal hypothalamus, neuropeptide Y neurons of the arcuate nucleus regenerate axons through the astroglial scar produced by a surgical lesion placed in the ventromedial hypothalamus.

Animals↗

PubMed1993

Reactive astrocytes involved in the formation of lesional scars differ in the mediobasal hypothalamus and in other forebrain regions.

The fine organization of lesional scars was studied in adult rats at the level of 2 types of surgical cuts aimed at deafferentating the dorsal hypothalamus from its neuropeptide-Y innervation. These included: (i) lesions located dorsolateral to the dorsal hypothalamus, which were shown to form a permanent obstacle to the regeneration of transected neuropeptide-Y-fibers, and (ii) lesions located in the ventromedial hypothalamus, where transected neuropeptide-Y-fibers were shown to penetrate and eventually cross the lesional area. Double labeling immunocytochemistry and conventional electron microscopy were used to identify various molecules produced by reactive astrocytes and to visualize their ultrastructural organization within the scars, respectively. In the different portions of the dorsolateral scars, the large majority of reactive astrocytes was characterized by a strong immunoreactivity to glial fibrillary acidic protein, vimentin, and embryonic (polysialylated) NCAM. Intense laminin-immunoreactivity was also observed over large patches included in the scar. Electron microscope observations further indicated that the matrix of the scar was mainly composed of tightly packed astrocytic perikarya and processes connected by extended gap junctions. All around the extracellular and perivascular spaces, these astrocyte profiles were bordered by a thick basal lamina. Only scarce axonal profiles were detected in the core of the scar, most of which exhibited degenerative features. In the ventromedial hypothalamic scars, reactive astrocytes were found to exhibit intense immunoreactivity to both glial fibrillary acidic protein and vimentin. On the other hand, only slight immunostaining to embryonic NCAM and laminin were associated with this type of lesional scar. At the ultrastructural level, the main differences with the dorsolateral scars concerned (i) the gap junctions, which were less frequent and involved shorter portions of adjacent membranes; (ii) the basal lamina, which was essentially localized to the perivascular spaces; and (iii) the axonal profiles, which were frequently observed throughout the scar matrix. These data indicate that reactive astrocytes that formed the glial scar differ in the mediobasal hypothalamus and in other forebrain regions. This provides strong support for the hypothesis that the regeneration of neuropeptide-Y axons through a mediobasal hypothalamic surgical cut depends mainly on the particular organization of the astroglial scar.

Animals↗

PubMed1993

Evidence for nonsynaptic serotonergic and noradrenergic innervation of the rat dorsal horn and possible involvement of neuron-glia interactions.

We investigated the synaptic incidence of the contacts established by serotonergic and noradrenergic descending fibers in the dorsal horn of the rat spinal cord. Serial electron microscopic sections were performed. Synapses were scarce. The majority of serotonergic and noradrenergic varicosities (more than 60%) are characterized by nonsynaptic contacts. Numerous glial profiles, and particularly astrocytic profiles, were observed in apposition with serotonergic and noradrenergic varicosities. The proportion of astroglia was higher around serotonergic and noradrenergic varicosities devoid of synaptic specialization. The length of the contact between immunoreactive nonsynaptic varicosities and astrocytes was twice as long as that between synaptic varicosities and astrocytes. Thus, the modulation of sensitive messages by serotonin and noradrenaline through pauci-synaptic varicosities in the dorsal horn of the spinal cord could be an example of the concept of "volume transmission" [Fuxe and Agnati (1991) Volume Transmission in the Brain: Novel Mechanisms for Neural Transmission, Advances in Neuroscience, Vol. 1, pp. 1-9.] in the central nervous system. Analysis of the microenvironment of serotonergic and noradrenergic varicosities led us to make the hypothesis that glial cells, particularly astrocytes, could play some role in volume transmission.

Animals↗

PubMed1993

Effects of neonatal adrenalectomy on 5-HT and TRH-like immunoreactivity in the rat spinal cord.

This study investigated the effects of neonatal unilateral adrenalectomy on the serotonin- (5-HT) and thyrotropin-releasing hormone-like immunoreactivities (TRH-LI) in the intermediolateral cell column (IML) of the rat spinal cord where the sympathetic preganglionic neurons innervating the adrenal medulla are located. The density of the innervation was measured by a computer-assisted image analysis. Two weeks after the lesion, only one rat (1/3) showed a 30% decrease of 5-HT-LI in the ipsilateral IML, although no modifications were observed for TRH-LI. At 1 month, we observed a variable decrease of 19% to 30% for either 5-HT- or TRH-LI in the ipsilateral IML. However, one animal (1/3) showed nonsignificant modifications. At 3 months, we showed a 17% mean loss of 5-HT-LI and TRH-LI in the ipsilateral IML. However, the decreases of 5-HT-LI and TRH-LI did not always appear similar. These results appear different from those obtained after neonatal removal of the superior cervical ganglion.

Adrenalectomy↗

PubMed1993

Thienylphencyclidine protection for the spinal cord of adult rats against extension of lesions secondary to a photochemical injury.

The purpose of this study was to evaluate treatment with the N-methyl-D-aspartate antagonist thienyl-phencyclidine (TCP) after spinal cord injury for its behavioral, electrophysiological, morphological, and immunohistochemical effects. Five minutes after a photochemical lesion was produced in rats at the T-8 level, the animals received TCP (1 mg/kg, intravenously) or TCP vehicle (saline). The animals were evaluated on Day 18 for neurological recovery by testing motor and sensory functions. The TCP-treated group showed less neurological impairment than the untreated group (p < 0.05 for inclined-plane stability and withdrawal reflex to extension). Somatosensory evoked potential testing was performed on Days 21 to 23 and the wave amplitude between the onset and P1 in the TCP-treated group was higher than in the untreated group (p < 0.05). Mean arterial blood pressure was not significantly modified after TCP injection. Morphometric studies of the lesion area in cross section revealed a significantly reduced spinal cord infarction in the TCP-treated group (p < 0.05). Immunohistochemical evaluation of the spinal cord in lumbar area showed an increased level of serotonin immunoreactivity in the dorsal horn of animals treated by TCP. These results demonstrate the efficacy of TCP in reducing secondary lesions after spinal cord injury in rats.

Animals↗

PubMed1993

[Spinal cord injuries: comments on preventive and curative strategy].

Research for the cure for paralysis caused by spinal cord injury has followed three complementary lines: Limitation of secondary lesions; the use of antagonists of excitatory amino acids has proven affective in reducing the extent of the lesions. Control of the glial scar; an oxygenated derivative of cholesterol can reduce the proliferation of reactive astrocytes and their hypertrophy, and permit the regrowth of axons in a denervated territory. Transplantation of embryonic neurons below the lesion allows to reinnervate denervated sites and reestablish reflex functions.

Humans↗

PubMed1992

Pre- and post-natal ontogeny of thyrotropin-releasing-hormone in the rat spinal cord: an immunocytochemical study.

This work aimed at providing by means of immunocytochemical techniques a detailed study of the ontogeny of thyrotropin-releasing hormone (TRH) in the spinal cord of the rat. We report the first appearance of TRH-immunoreactive fibers in the ventral funiculus of thoracic and lumbar levels at embryonic day 17. At embryonic day 18, fibers penetrated the ventral gray matter towards the central canal. At embryonic day 19, the first immunoreactive fibers were seen in the intermediolateral cell column at upper thoracic levels. This region was invaded at lower thoracic levels on the day of birth. At this time, TRH-immunoreactive axodendritic synapses were observed in the ventral horn and in the intermediolateral cell column. Immunoreactivity increased in these regions until post-natal day 21 when the adult pattern of TRH immunoreactivity was established in the sympathetic nuclei and in the ventral horn. However, a transient TRH-like immunoreactivity was detected in lamina IIi of the dorsal horn between post-natal days 14 and 30: at ultrastructural level, immunoreactive varicosities were seen to establish axodendritic synapses. In conclusion, TRH is one of the earliest peptidergic systems established in the spinal cord and it presents extensive temporal and topographical similarities with the serotonergic system with which it could be colocalized.

Animals↗

PubMed1992

Spinal dopaminergic system of the rat: light and electron microscopic study using an antiserum against dopamine, with particular emphasis on synaptic incidence.

The mapping of the spinal dopaminergic innervation has been performed in the adult rat using an anti-dopamine antiserum. Immunoreactive fibers were detected with the light microscope in the dorsal horn (mainly in laminae III-IV), in the intermediolateral cell column (IML), in the peri-ependymal region and in the ventral horn. The ultrastructural analysis of dopaminergic innervation showed mainly axodendritic contacts and fewer axosomatic ones. In the ventral horn and the IML, the pattern of dopaminergic innervation exhibited a majority of classical synapses. In the dorsal horn, dopaminergic innervation was partly non-synaptic (at cervical level), whereas numerous axodendritic synapses were observed at thoraco-lumbar level. Previous studies described the non-synaptic organization of serotonergic and noradrenergic projections in the dorsal horn. It is thus hypothesized that the monoaminergic systems, involved in pain modulation within the dorsal horn, act partly through volume transmission. In contrast, these systems would modulate the motor and autonomic functions through classical synapses.

Animals↗

PubMed1992

Inhibition of locus coeruleus neurons by the phencyclidine analog, N-[1-(2-benzo(b)thiophenyl)cyclohexyl]piperidine: evidence for potent indirect adrenoceptor agonist properties.

The effects of the phencyclidine derivative, N-[1-(2-benzo(b)thiophenyl)cyclohexyl]piperidine (BTCP), on the electrical activity of noradrenaline (NA) neurons of the locus coeruleus (LC) were studied in halothane-anesthetized rats. Systemic administration of BTCP potently inhibited LC neurons (ID50 of 1.1 +/- 0.1 mg/kg i.v.). This effect was mimicked by local microejection of BTCP into the LC. Both the systemic and local effects of BTCP were blocked by alpha 2-adrenoceptor antagonists and prevented by prior depletion of catecholamines with reserpine. These and other data suggest that BTCP behaves as a potent indirect NA agonist (i.e. via NA re-uptake and/or release systems).

Animals↗

PubMed1992

Pre- and postnatal development of noradrenergic projections to the rat spinal cord: an immunocytochemical study.

Using immunocytochemistry with a specific antiserum against noradrenaline, the pre- and postnatal development of noradrenergic (NA) projections to the rat spinal cord was studied from embryonic day 16 (E16) to adulthood (the day following nocturnal mating being considered as E0). In this study, pregnant animals were pre-treated with the MAO inhibitor pargyline (200 mg/kg i.p.), whereas postnatal animals received 100 mg/kg. In vibratome sections, noradrenaline-immunoreactive (NA-IR) axons were seen to invade the spinal cord at E16, at cervical and upper thoracic levels, from the ventral funiculus. At E18, small caliber NA-IR fibers were present in the ventral horn at all cord levels, and some fibers were seen in the intermediolateral cell column (IML) at thoracic level. The growth of axons towards the dorsal horn became noticeable by postnatal day 0 (P0). At P3, fine beaded and radially orientated NA-IR fibers were observed at all levels. The pattern of NA innervation of the dorsal horn was similar to that of the adult by P7. The segregation of noradrenaline immunoreactivity in the ventral and dorsal horns, the IML and the periependymal area was more obvious at all levels by P14 and P20. From P30 the NA innervation was similar to that found in the adult spinal cord. Thus, noradrenaline, like serotonin, was present early in the spinal cord before the onset of specific functions. In addition to and prior to its transmitter function, it might play a trophic role in the neurogenesis of the spinal cord.

Aging↗

PubMed1992

Alterations in spinal cord excitatory amino acid receptors in amyotrophic lateral sclerosis patients.

Excitatory amino acids (EAA) have been implicated in the pathogenesis of amyotrophic lateral sclerosis (ALS). We have analyzed the distribution of the N-methyl-D-aspartate (NMDA) 1-(1-(2-thienyl)-cyclohexyl) piperidine (TCP), kainate and alpha-amino-3-hydroxy-5-methyl-4 isoxazole propionic acid (AMPA) quisqualate subtypes of EAA receptors using quantitative receptor autoradiography in the cervical and thoracic spinal cords of patients who have died with ALS, and of controls. We observed that in control spinal cords [3H]TCP/NMDA binding sites were located both in the ventral and dorsal horns with the highest densities being situated in lamina II. [3H]AMPA and [3H]kainate binding sites were present almost exclusively in the substantia gelatinosa of the dorsal horn. In ALS, the distribution of these 3 types of receptors was unchanged, but [3H]TCP/NMDA binding was decreased both in the dorsal and ventral horns. [3H]kainate binding was possibly decreased in substantia gelatinosa, of ALS cords. However, the limited sample size available for [3H]kainate binding did not permit statistical analysis. [3H]AMPA binding sites were unaltered in ALS. These results indicate that there is a preferential reduction in NMDA receptors in ALS. We suggest that should an excitotoxic mechanism be involved in the pathogenesis of ALS, then NMDA receptors may be the target of this effect.

Adult↗

PubMed1992

Serotoninergic, noradrenergic, and peptidergic innervation of Onuf's nucleus of normal and transected spinal cords of baboons (Papio papio).

We have investigated with light and electron microscope immunocytochemistry the aminergic and peptidergic innervation of Onuf's nucleus in adult baboons. This nucleus, located in the ventrolateral part of the sacral spinal cord (S2 and S3), is considered to control urethral and anal sphincters and penile muscles. By comparison of intact and transected spinal cords, we have found that serotoninergic innervation has two origins: first, supraspinal, innervating the whole nucleus, with a possible predominance in the dorsal half; and second, intraspinal, corresponding to the ventral half of the nucleus. Thyrotropin-releasing hormone innervation appears largely coincident with serotonin, both in intact and transected spinal cords. Noradrenaline is exclusively of supraspinal origin, as attested by its disappearance below the level of the section. Substance P, calcitonin gene-related peptide, and Leu- and Met-enkephalin, which profusely innervate Onuf's nucleus, are on the contrary not affected by the transection. They most likely originate from the cord itself or the dorsal root ganglia. Thus, Onuf's nucleus innervation in the baboon arises both from supraspinal and intraspinal sources. The present study provides an anatomical basis for both voluntary and reflex controls of excretory and sexual functions in a primate. The same neurotransmitter (serotonin) according to its cell origin and discrete topography could exert different influences upon the same effector system.

Animals↗

PubMed1992

TCP enhances the survival of human fetal spinal cord cells in culture.

Dissociated cell cultures were prepared from human spinal cords of 7-10-week-old fetuses. After 10 weeks progressive neuronal necrosis was observed in controls whereas N/1-(2-thienyl)cyclohexyl/piperidine (TCP) enhanced the survival time of the cells. After 21 weeks the number of gamma-aminobutyric acid (GABA)ergic and neuron specific enolase (NSE)-stained neurons was higher in the TCP-treated cultures than in controls. TCP appears to be a promising drug for long term survival of neurons.

Biomarkers↗

PubMed1992

5-Hydroxytryptamine, substance P and thyrotropin-releasing hormone synapses in the intermediolateral cell column of the rat thoracic spinal cord.

Serotonin-, substance P-, and thyrotropin-releasing hormone-immunoreactive profiles were studied in the intermediolateral cell column at the thoracic level of the rat spinal cord with light- and electron-microscopic immunocytochemistry. For each transmitter, a dense immunoreactive deposit was observed with the light microscope. At ultrastructural level, morphologically identified synapses amounted to 47% of all serotonergic varicosities, to 49% for substance P and 50% for thyrotropin-releasing hormone. Synapses appeared both symmetrical and asymmetrical. In each case, these synapses were mainly axodendritic (98%). These synaptic connections could mediate the physiological influence of these 3 substances in the spinal cord on the cardiovascular system.

Animals↗