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Biomedical subjects

M Geffard

Publications and source records attributed to M Geffard.

At least 73 records · Page 4Linked to original sources
PubMed1992

Autoanti-phosphatidylinositide antibodies specifically inhibit noradrenaline effects on Ca2+ and Cl- channels in rat portal vein myocytes.

High levels of circulating autoantibodies (auto-Ab) directed against phosphatidylinositides have been identified in the sera of patients with malignant tumors. These polyclonal autoantibodies had higher avidity and specificity for phosphatidylinositol (PtdIns) than for the other phosphatidylinositides. Effects of the auto-Ab were studied in smooth muscle myocytes in the PtdIns-involving transduction mechanism triggered by activation of alpha 1-adrenoceptors. Noradrenaline activated a Ca(2+)-dependent Cl- current through the Ca(2+)-releasing action of inositol 1,4,5-trisphosphate (InsP3) and enhanced the Ca2+ channel current through a diacylglycerol and protein kinase C-dependent mechanism. External applications of auto-Ab (0.03-0.3 mg/ml) were without effect on noradrenaline-induced responses whereas intracellular applications (0.0004-0.012 mg/ml) inhibited both Cl- current activation and Ca2+ channel current stimulation. Intracellular applications of IgG from healthy donors had no effect on noradrenaline-induced responses. When anti-PtdIns Ab were preincubated with PtdIns the inhibition of the noradrenaline-induced responses on Ca2+ and Cl- channels was not observed. Autoanti-PtdIns Ab inhibited also the acetylcholine-activated Cl- current, confirming that the acetylcholine response was mediated through the phosphatidylinositol breakdown. In contrast, the autoanti-PtdIns Ab were ineffective against the transduction pathway after beta-adrenoceptor activation. Therefore, these results suggest that the biological effect of autoanti-PtdIns Ab results from a specific binding to membrane PtdIns or PtdIns metabolites and thereby prevented InsP3 and diacylglycerol production. These autoanti-PtdIns Ab appear to be a new specific tool to identify the role of phosphatidylinositides in intracellular transduction processes.

Acetylcholine↗
PubMed1992

Transplantation of embryonic serotonin immunoreactive neurons into the transected spinal cord of adult monkey (Macaca fascicularis).

Five adult monkeys (Macaca fascicularis) underwent a total section of the spinal cord at the thoracic level (T6). Four of them received a daily treatment with cyclosporin (10 mg/kg). Ten days later, two animals treated with cyclosporin and one without cyclosporin received at T8 and T10 levels an injection of a cell suspension prepared from the rhombencephalon of a 40-day-old macaque embryo. Two control animals received one injection of Hank's balanced salt solution. The animals were sacrificed after 2 months (one grafted and one control) and 3 months (two grafted and one control), and their spinal cord was processed for the immunocytochemical detection of serotonin using light and electron microscopy. After 2 months of survival, serotonergic neurons had survived and developed within the transplant. Three months after transplantation, in the animal treated with cyclosporin, serotonergic neurons were found to survive with their axons growing into the host grey matter and establishing axosomatic and axodendritic synapses in the ventral horn. If the graft was isolated in the white matter no fibers were seen invading the grey matter.

Animals↗
PubMed1992

Identification and immunochemical characterization of IgA in sera of patients with mammary tumors.

It has been reported that several types of human cancer are associated with elevated levels of class-A immunoglobulins (Ig) and IgA-containing immune complexes. Moreover, most previous work has come up against the lack of IgA reactivity for chemically defined antigen (Ag). To overcome this, we first evaluated possible immunological binding in sera of patients with mammary tumors or malignant hematologic diseases and controls on a mouse monoclonal anti-idiotypic antibody (Ab2), internal image of conjugated benzo(a)pyrene (BP) coated on well plates. Using this indirect ELISA, a statistically highly significant immunological binding was found in sera of patients with mammary tumors of every grade, type and size. This immunological binding was linked to the IgA isotype. Second, we performed competition experiments between a BP conjugate coated on well-plates and anti-anti-"BP-like" antibodies (Ab) previously incubated with rabbit idiotypic antibodies (Ab1) directed against conjugated BP. A part of these anti-anti-BP-like Ab, raised in rabbits immunized with human IgA of patients with mammary tumors, recognized the Ag-combining site of polyclonal Ab1, previously developed in a rabbit immunized with BP conjugates. It appears that part of the human Ig from sera of patients with mammary tumors shares common idiotopes with rabbit polyclonal Ab1 raised against conjugated BP.

Age Factors↗
PubMed1992

Immunocytochemical mapping of noradrenergic projections to the rat spinal cord with an antiserum against noradrenaline.

The mapping of noradrenergic innervation was performed in transverse and longitudinal sections of the adult rat spinal cord using noradrenaline immunocytochemistry. Noradrenergic fibres and terminals were distributed in the dorsal horn (mainly in the superficial part), in the vicinity of the different groups of motoneurons, and concentrated in the intermediolateral cell column and around the central canal. The ultrastructural study showed principally axodendritic synapses in the ventral horn and in the intermediolateral cell column. Fewer axosomatic synapses were detected. In the dorsal horn, noradrenaline-innervation was predominantly non-synaptic. It is hypothesized that the noradrenergic modulation of nociception is not mediated through classical synapses. The concept of 'volume transmission' can explain such an influence. Conversely, noradrenaline may be involved in the control of locomotion and automatic functions through conventional synapses.

Animals↗
PubMed1992

Fate of B1-B2 and B3 rhombencephalic cells transplanted into the transected spinal cord of adult rats: light and electron microscopic studies.

Embryonic cell suspensions (14-day embryos) containing either B3 or B1-B2 serotonergic cell groups were obtained by microdissection of specific rhombencephalic regions and transplanted into the transected spinal cord of adult male Sprague-Dawley rats. After 3 months of survival, the animals were sacrificed and the spinal cords processed for the immunocytochemical detection of serotonin (5-HT). 5-HT-immunoreactive fibers from B1-B2-grafted cells were selectively distributed in the ventral horn and the intermediolateral cell column (IML) where they established conventional synaptic contacts. However, B3 5-HT cells grew and extended their processes into the dorsal horn where in addition we observed scarce synaptic contacts as in the normal spinal cord. These results suggest that the specificity of the 5-HT innervation of the spinal cord by grafted neurons is due, at least partly, to the presence of local mechanisms mediating guidance and cell recognition, possibly operating in conjunction with preexisting substrate pathways.

Animals↗
PubMed1992

Intensification of labelings of the immunogold silver staining method by gold toning.

We evaluated the applicability of the gold toning procedure to the immunogold silver staining method using monoclonal antibody against dopamine. Immunolabeling was examined in the rat substantia nigra at light and electron microscopic levels. Vibratome sections of fixed midbrains were incubated with anti-dopamine antiserum and then with 5 nm colloidal gold bound to goat anti-mouse immunoglobulin. Silver staining of these sections produced a light brown immunolabeling. After the sections were processed by gold toning, the labeling became intense black. At a light microscopic level, these high contrast signals were retained after the sections were osmicated and embedded in Epon. At an electron microscopic level, signal-to-noise ratio was high, and the positive staining could easily be verified at a low-power magnification. The technique described here, the gold-toned immunogold silver staining method, provides high contrast signals and is much more sensitive than immunogold silver staining alone. This method, therefore, has great potential for use in immunohistochemical analysis of the central nervous system.

Animals↗
PubMed1992

Curative effects of all-trans-retinoic acid on rat sarcomas.

The effects of all-trans-retinoic acid (all-trans-RA) on benzo(a)pyrene [B(a)P]-induced malignant sarcomas in Sprague-Dawley female rats were evaluated. Ninety-eight days after B(a)P administration, all-trans-RA was daily injected to animals with or without clinically palpable tumors. The growth of tumors was slowed down compared with controls. Magnetic resonance imaging analyses showed that all-trans-RA-treated rat tumors presented early necrotic areas. Animal survival was slightly increased. Anti-phosphatidylinositol autoantibody levels which were significantly higher in B(a)P-treated rat sera were not modified by all-trans-RA treatment.

Animals↗
PubMed1992

First characterization of 6-hydroxytryptamine in the rat midbrain by using specific antibodies.

The visualization of serotonin, 5-methoxytryptamine, and tryptamine in the rat midbrain has been made possible by the development of antibodies raised against these conjugated molecules. It has been suggested that 6-hydroxytryptamine (6-HT) might also be a neurotransmitter in this region. To test this hypothesis, 6-HT was synthesized and antibodies were raised in the rabbit. The high avidity (IC50 = 5 x 10(-9) M) and specificity [cross-reactivity ratio between 6-HT-glutaraldehyde (G)-bovine serum albumin (BSA) and 5-HT-G-BSA, the most immunoreactive compound, was 1,500] rendered these antibodies reliable tools for specific molecular detection of 6-HT in the G-fixed tissues. In the dopaminergic region, 6-HT immunoreactivity was noted in the substantia nigra but was particularly intense in the red nuclei, where it seems to be localized in the magnocellular division in the form of large 6-HT neurons. In contrast, there were few 6-HT neurons in the raphe nuclei. Thus, 6-HT may be a new putative neurotransmitter existing in the red nuclei, in addition to the other neurotransmitters already described in this region, in the nigro-rubral pathway, and in the rubral projection from the dorsal raphe nuclei. 6-HT is possibly implicated in motor control and might exert hallucinogenic properties as do other 6-hydroxylated indoleamines.

Animals↗
PubMed1992

Maturation and fine structure of thalamic reticular neurons transplanted into the adult rat CNS.

This work was undertaken to determine whether or not cell suspension transplants provide a promising vehicle for the in vivo study of neuronal development. Cell suspensions of rat fetal tissue that contained both reticular (RT) and ventrobasal primordia were transplanted into the excitotoxically lesioned somatosensory thalamus of adult rats. The fine structure of transplanted GABAergic RT neurons that were identified by immunocytochemistry was investigated 5 days to 7 months following transplantation. The dissociation and transplantation of the tissue results in disruption of the extracellular matrix and alteration of cellular interactions which could introduce major changes in neuronal maturation. Our results show that maturation of transplanted GABAergic RT neurons was comparable to normal and that they were able to establish and receive, with one exception, usual sets of connections. In contrast, disruption of the tissue was responsible for the definitive loss of organotypic characteristics and the emergence of abnormal connections, especially synaptic connections from somatosensory afferents, the functional significance of which will be important to determine.

Animals↗
PubMed1992

Combined use of silver staining of the retrograde tracer WGAapoHRP-Au and pre-embedding immunocytochemistry for electron microscopy: demonstration of dopaminergic terminals in synaptic contact with striatal neurons projecting to the substantia nigra in the rat.

We investigated the applicability of the pre-embedding immunoperoxidase technique to WGAapoHRP-Au retrograde tracing. After injection of the tracer into the substantia nigra of rat, the brain was fixed and cryostat sections were immunostained for dopamine. The sections were osmicated and silver-stained to amplify the colloidal gold particles. Products of both the immunoperoxidase staining and the silver staining could be detected and distinguished by electron microscopy at low magnification. The ultrastructure was so well preserved that synaptic characteristics could be investigated. Dopaminergic terminals were demonstrated to synapse with striatal neurons projecting to the substantia nigra.

Animals↗
PubMed1991

Visualization of a protein involved in seric immune complexes of patients with epithelial tumors having elevated levels of anti-'benzo[a]pyrene-like' IgA.

Many authors have previously described that several types of human cancer were associated with elevated levels of IgA and IgA-containing immune complexes. We have recently identified and characterized IgA directed against a "benzo[a]pyrene-like' antigen in sera of patients with mammary tumors. Circulating immune complexes from these sera were precipitated and analysed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A 18-20-kDa protein was found closely associated with high levels of anti-'benzo[a]pyrene-like' IgA in sera of patients having a proliferative pathology.

Antibodies, Monoclonal↗
PubMed1991

Dopamine-immunoreactive neurones in the central nervous system of the pond snail Lymnaea stagnalis.

The distribution of dopamine and dopamine-immunoreactive neurones was studied in the central nervous system of the snail Lymnaea stagnalis. The results from immunocytochemical labelling were compared with those from the application of the glyoxylic acid fluorescence method and 6-hydroxydopamine-induced pigment labelling. Comparisons were also made between the number of dopamine immunoreactive neurones and the dopamine content of the ganglia, measured by high-performance liquid chromatography. Dopamine immunocytochemistry proved to be superior to the other two histochemical techniques in terms of specificity and sensitivity. The 6-hydroxydopamine-induced pigment labelling failed to prove a useful tool for the in vivo identification of all dopamine-containing neurones. The distribution and number of dopamine-immunoreactive neurones and levels of biochemically measured dopamine in specific ganglia showed a close correspondence. By using the results of the dopamine immunocytochemistry and glyoxylic acid technique, a detailed map of dopamine-containing neurones was constructed. Dopamine-containing inter- and intra-ganglionic axon tracts were also demonstrated. The mapping of dopamine-containing neurones will facilitate further neurophysiological analysis of dopaminergic neural mechanisms in Lymnaea.

Animals↗
PubMed1991

Electronmicroscopic detection of the axonal coexistence of serotonin and substance P in B1-B2 raphé cells transplanted into the transected spinal cord of adult rats.

One week after a complete spinal cord transection at the thoracic (T8) level in adult rats, a suspension of rhombencephalic embryonic (day 14) cells containing the B1-B2 serotonergic groups was injected below the section. After a survival period of one month, the spinal cord was processed for an ultrastructural dual immunocytochemical detection of serotonin (5-HT) and substance P (SP). It was shown by ultrastructural dual immunolabeling that 5-HT and SP coexist in the same axon terminals of transplanted cells.

Animals↗
PubMed1991

Antibody responses of mice exposed to low-power microwaves under combined, pulse-and-amplitude modulation.

Irradiation by pulsed microwaves (9.4 GHz, 1 microsecond pulses at 1,000/s), both with and without concurrent amplitude modulation (AM) by a sinusoid at discrete frequencies between 14 and 41 MHz, was assessed for effects on the immune system of Balb/C mice. The mice were immunized either by sheep red blood cells (SRBC) or by glutaric-anhydride conjugated bovine serum albumin (GA-BSA), then exposed to the microwaves at a low rms power density (30 microW/cm2; whole-body-averaged SAR approximately 0.015 W/kg). Sham exposure or microwave irradiation took place during each of five contiguous days, 10 h/day. The antibody response was evaluated by the plaque-forming cell assay (SRBC experiment) or by the titration of IgM and IgG antibodies (GA-BSA experiment). In the absence of AM, the pulsed field did not greatly alter immune responsiveness. In contrast, exposure to the field under the combined-modulation condition resulted in significant, AM-frequency-dependent augmentation or weakening of immune responses.

Animals↗
PubMed1991

Quantitative image analysis with densitometry for immunohistochemistry and autoradiography of receptor binding sites--methodological considerations.

Major technical progress in the development of computer-based image analysis has made possible the entry of autoradiography and immunohistochemistry into a new era where quantification by densitometry has become easily accessible. Autoradiography could become quantitative and displayed adequate reproducibility with the help of emulsion-coated films and the use of scales of standards of known radioactivity exposed and analyzed in parallel to the tissue sections. Immunohistochemistry after revelation by a color-based enzymatic technique can also become quantitative, providing that standardization of the crucial steps of the procedure and calibration through a parallel treatment of a scale of antigen standards can be ensured. Such an approach is described here in the rat with reference to tyrosine hydroxylase (TH), the main synthesizing enzyme for catecholamines, and with dopamine (DA) itself, a catecholaminergic neurotransmitter. The different parts of the procedure, which can influence the results, such as the fixation of the animals by perfusion and the evaluation of the fluctuations via the calibration curve, are discussed in detail. Biological validation of the proposed procedure is described by reference to experiments already well documented biochemically, such as the induction effect of reserpine on TH in the rat locus coeruleus and the depleting effect of alpha-methyltyrosine (AMPT), a well-known blocker of TH activity, on rat striatal DA content. Finally the importance of restricting the measurements to the (pseudo)linear portion of the calibration curve is illustrated by the autoradiographic identification of the differential intrastriatal repartition of the dopaminergic D1 and D2 receptor sites, particularly the dual patch-matrix compartments.

Animals↗
PubMed1991

The role of 5-hydroxytryptophan (5-HTP) in the regulation of the sleep/wake cycle in parachlorophenylalanine (p-CPA) pretreated rat: a multiple approach study.

In the rat, the insomnia which follows the administration of parachlorophenylalanine (p-CPA), a serotonin synthesis inhibitor, is transiently reversed either by intra-cisternal injection of L-5-HTP or by an associated injection of 5-HTP and an L-aromatic-acid-decarboxylase inhibitor (benserazide). Histochemical, immunohistochemical and chemical investigations showed that 5-HTP administration does not lead to a detectable increase in cerebral 5-HT. These findings suggest that the restoration of sleep after p-CPA treatment could be mediated by the central action of 5-HTP.

5-Hydroxytryptophan↗
PubMed1991

Serotonergic innervation of the dorsal horn of rat spinal cord: light and electron microscopic immunocytochemical study.

The ultrastructure of serotonergic projections to the dorsal horn of the rat spinal cord has been investigated, using a highly specific polyclonal antiserum. The highest concentrations of immunoreactive profiles were found in lamina I and the outer part of lamina II (IIo). Intermediate concentrations were found in laminae III and IV, while the inner part of lamina II (IIi) was almost devoid of immunoreactivity. Whereas 60% of the profiles show at least one varicosity studded with synaptic vesicles, only one-fifth of the latter contributes to classical synapses, the remaining profiles being devoid of a facing postsynaptic density. The results are compared with those in the literature and our own results relative to other regions of the cord. It is concluded that the pauci-synaptic projections to the dorsal horn could correspond to a diffuse influence of serotonin, the targets for which are determined by the corresponding serotonergic receptors.

Animals↗