Search PubMed⌕ Search

Biomedical subjects

G Martin

Publications and source records attributed to G Martin.

At least 343 records · Page 19Linked to original sources
PubMed1986

Relation between power spectrum time course during ventricular fibrillation and electromechanical dissociation. Effects of coronary perfusion and nifedipine.

To relate the evolution of ventricular fibrillation (VF) to the haemodynamic recovery after cardioversion, we characterized the differences in the ECG power spectrum (PS) time course, among different types of VF: under control conditions, with previous administration of nifedipine and on cardiopulmonary bypass (CPB). In the first few seconds VF showed a PS with a narrow peak between 8 and 15 Hz and its higher harmonics, suggesting some organization and regularity. In the following 40 seconds, the arrhythmia accelerated slightly, maintaining an organized spectrum. Afterwards, the PS became slow and irregular, losing its initial characteristics after 60 seconds. Conversely, VF on CPB maintained its organized PS, over a prolonged period. Previous administration of 0.32, 0.64 mg kg-1 of nifedipine maintained the initial characteristics of the PS for 90 and 150 seconds. Similar results were obtained with previous autonomic blockade. In another group of dogs, defibrillation was performed after successive periods of VF, to study electromechanical dissociation (EMD). In all control dogs, EMD was observed after 90 seconds of VF. Pretreatment with nifedipine postponed EMD until 120-150 seconds and was not observed in dogs on CPB. The PS time course during VF seems a reliable method of analyzing and quantifying the different types of VF. It could be related with the onset of EMD, reflecting the metabolic alterations that happen during VF. Nifedipine could delay the ischaemic effects during VF and increase the possibility of successful cardiac resuscitation.

Animals↗
PubMed1986

Monoclonal antibodies for the prevention of graft-versus-host disease and marrow graft rejection. The depletion of T cell subsets in vitro and in vivo.

One of the major complications of allogeneic bone marrow transplantation is graft-versus-host disease. This can be avoided by removing the mature T cells from the marrow, most conveniently by the use of monoclonal antibodies. However, T cell purging results in an increased tendency for the recipient to reject the donor marrow. We have developed monoclonal antibodies to L3/T4 and Lyt-2 that specifically deplete functional T cell subsets in mice. We demonstrate that such reagents can be used to control both graft-versus-host disease and marrow rejection in mouse models of bone marrow transplantation across one-haplotype or two-haplotype major histocompatibility differences. Such strategies to abrogate host resistance, by administration of anti-T-cell monoclonal antibodies to the recipient, may complement marrow T cell purging for human allogeneic bone marrow transplantation.

Animals↗
PubMed1986

The action of a dopamine (DA1) receptor agonist, fenoldopam in human vasculature in vivo and in vitro.

This study was designed to investigate dopaminergic mechanisms in human vasculature using the selective vascular dopamine receptor agonist fenoldopam in vivo and in vitro. In vivo, forearm blood flow was measured plethysmographically and in vitro isolated rings of human blood vessels from a variety of sites were used for tissue bath studies. Intra-arterial fenoldopam markedly increased forearm blood flow, this effect was antagonised by (R) sulpiride, a vascular dopamine (DA1) antagonist, but not by metoclopramide, a neuronal (DA2) antagonist, or by guanethidine, an adrenergic neurone blocking agent. In vitro, fenoldopam relaxed preconstricted human renal, mesenteric and lumbar arteries, but not saphenous vein in a concentration dependent manner. (RS) sulpiride and SCH 23390 competitively antagonised this effect. These studies demonstrate the presence of a vasodilatory vascular dopamine receptor in man both in vivo and in vitro.

Adolescent↗
PubMed1986

Immunohistological identification of cell subsets in human gingiva after local treatment for gingivitis or periodontitis.

The cellular infiltrate present in human diseased gingiva was analyzed in biopsies from 12 patients with gingivitis or periodontitis. The samples studied had been obtained in the course of surgery at inflammatory sites remaining after institution of periodontal treatment. Histological and immunological techniques were used to identify macrophages, B-cells, plasma-cells, T-cells and T cell subsets, as well as cells expressing class II HLA membrane antigens. T-cells appeared as the predominant population, but plasma-cells were also visualized in nearly all samples. Both OKT4+ and OKT8+ cells were seen in all cases, the latter being more numerous in periodontitis patients. Interdigitating-like cells were observed, positively labelled for class II antigens, as well as macrophages which were more numerous in periodontitis patients. These results suggest the participation of all components of the immune response in gingival disease, in a way resembling chronic recurrent inflammatory diseases.

Adolescent↗
PubMed1985

Gap-like junctions between neuron cell bodies and glial cells of crayfish.

Data reported up to now on neuron-glia relationships, show that neuron cell bodies and glial cells are separated by a narrow intercellular cleft which is considered as the microenvironment of the nervous system, and where neuron-glia exchange occurs. We present here evidence that neuron perikarya and ensheathing glial cells of the abdominal ganglia of the crayfish communicate through gap-like junctions. These junctions could constitute short circuits for ionic exchange between neuron perikarya and glial cells, probably with some degree of electrotonic coupling between neurons and glia. In the preparation described here, the intercellular cleft would play only a secondary role in neuron-glia communication.

Animals↗
PubMed1985

Histogenesis of olfactory neuroblastoma. I. Electron microscopy of typical human case.

"Olfactory neuroblastoma" covers several types of esthesioneurogenic tumors such as esthesioneuroepithelioma, esthesioneuroblastoma and others. They are thought to be of olfactory mucosal origin and present with typical light microscopical "neurogenic features" e.g. rosettes and/or axon production. Some cases have been analyzed ultrastructurally and contained membrane bound granula like others tumors of the APUD system, originating from the neural crest. Furthermore neuronal differentiation of various degrees has been described. The human case of this contribution did not contain rosettes, but axons could be demonstrated in considerable number by silver impregnation. Electron microscopy could demonstrate the presence of dendritic processes with microtubuli and filaments as well as abundance of secretory granules of 1800 A. The comparison with the up to now published findings shows that the production of dense core granules is the most constant ultrastructural feature in these tumors; however, additional ultrastructural features in typical human cases as here presented, earlier experimental results and few human descriptions show, that DCV production is not essential for olfactory neuroblastoma. This might shed new light on the histogenesis of these tumors.

Actin Cytoskeleton↗
PubMed1985

Human vascular smooth muscle responses mediated by alpha 2 mechanisms in vivo and in vitro.

The effects of compounds with alpha 2-agonist and alpha 2-antagonist properties on human forearm blood flow and on isolated human arterial segments have been studied. The findings from these studies in vivo and in vitro did not provide evidence in support of the hypothesis that postsynaptic alpha 2-receptors mediate smooth muscle contraction in the tissues under investigation. The constriction of the forearm vascular bed in response to low intra-arterial doses of idazoxan (RX 781094), an alpha 2-antagonist, provides evidence for a physiological role for a presynaptic alpha 2 autoregulatory mechanism. The variability of the forearm vascular responses to higher doses of idazoxan highlights the pitfalls that may have misled previous authors in their interpretation of the results of similar studies. A U-shaped dose-response curve to compounds with mixed alpha 2- and alpha 1-antagonist properties may be constructed, which emphasizes the importance of the dose-dependent selectivity of these antagonists at alpha 2- and alpha 1-receptors. The effect of idazoxan on the responses of arterial segments in vitro to exogenous catecholamines was dependent on the integrity of the endothelium, and provides evidence that alpha 2-receptors may mediate release of the endothelium-derived relaxing factor.

Adrenergic alpha-Agonists↗