PubMed Health⌕ Search

Biomedical subjects

J M Girault

Publications and source records attributed to J M Girault.

26 records · Page 2Linked to original sources
PubMed1988

Thymotaxin: a thymic epithelial peptide chemotactic for T-cell precursors.

The embryonic thymus is seeded by invading hemopoietic precursor cells that differentiate intrathymically into T lymphocytes. We have recently reported that avian thymic epithelial cells secrete chemotactic peptides, which provoke oriented migration of hemopoietic precursor cells in vitro. The established rat thymic epithelial cell line IT-45 R1 produced a polypeptide that resolves as a single band in the region of 11 kDa on NaDodSO4/polyacrylamide gels. This molecule, which we have named thymotaxin, induced a chemotactic response in a subpopulation of hemopoietic cells from juvenile rat bone marrow. Responding cells were generated by short-term coculture of rat bone marrow hemopoietic cells with mouse bone marrow stroma in a steroid-free medium. Cells selected in a chemotactic chamber have a lymphoid or blast cell morphology. The phenotype of the responding cells is Thy-1+, CD4- [corrected] and CD8-. In contrast, CD8 T-lymphocyte differentiation antigen was expressed after coculture with embryonic thymic monolayers, suggesting that the responding cells correspond to the precursors colonizing the thymus.

Animals↗
PubMed1987

Haloperidol-succinylglycyl[125I]iodotyrosine, a novel iodinated ligand for dopamine D2 receptors.

A novel radioiodinated ligand of the butyrophenone type has been synthesized for the quantification and characterization of dopamine D2 receptors. This haloperidol-derived ligand, haloperidol-succinylglycyl[125I]iodotyrosine ([125I]HSGTI), binds rapidly (equilibrium is reached within 30 min, at 10 pM and 37 degrees C) and with high affinity (Kd = 0.3 nM) to bovine striatal membranes. Its pharmacology, determined by competitive displacement with dopaminergic and non-dopaminergic drugs, is characteristic of binding to dopamine D2 receptors.

Aminoacridines↗
PubMed1987

Beta-adrenergic receptors of cerebellar astrocytes in culture: intact cells versus membrane preparation.

Experiments were carried out to assess: the influence of culture conditions on the expression of beta-adrenergic receptors in intact glial cells from the central nervous system; and the extent to which quantitation of receptor sites in membrane preparations reflects the receptor population of the whole cells they are derived from. Cerebellar astrocytes were chosen for this study since essentially one receptor subtype, the beta 2 one, is present in adult cerebellum. Intact, attached cerebellar astrocytes exhibit only one class of binding sites for the beta-adrenergic antagonist, [3H]CGP 12177. Replating of the astrocytes after a few days of culture in vitro induces an up-regulation of the receptors. This effect is particularly important when astrocytes are maintained for 6 days in the presence of horse serum, a condition that favors cellular differentiation. Only 30-50% of the beta-adrenergic receptors of the intact cells can be detected on membrane preparations. When membranes are prepared from astrocytes grown either in the presence of horse serum or under chemically controlled medium (i.e. under differentiation promoting conditions) two classes of binding sites for [125I](-)-iodocyanopindolol are revealed. Several hypotheses, mainly related to the morphology of the cells, may provide an explanation for such differences. Studies of the pharmacological specificity of receptors of membrane fractions show that cerebellar astrocytes cultured in vitro exhibit both beta 1 and beta 2 receptor subtypes. The beta 1 subtype receptors are slightly more abundant when astrocytes are grown in fetal calf serum (FCS), a condition under which they exhibit a polygonal, poorly differentiated morphology. When culture conditions favor cellular differentiation, more receptors of the beta 2 subtype are seen, which can be related to what is observed in the adult in vivo where the astrocytes exhibit a differentiated morphology.

Animals↗
PubMed1982

The effect of pituitary removal on pain regulation in the rat.

The effects of hypophysectomy (HX) on pain regulation in basal and in various stressful situations were investigated in the rat. Pain sensitivity was assessed by measuring the thresholds of 3 nociceptive reactions (tail withdrawal, vocalization, vocalization afterdischarge) following electrical stimulation of the tail. The completeness of HX and the integrity of hypothalamus were verified in each HX rat. (1) Baseline pain thresholds were lower in HX rats than in sham-operated animals; (2) naloxone (Nx) hyperalgesia was only slightly altered by HX; (3) different types of stress induced different types of changes in nociception i.e. analgesia or hyperalgesia. The influence of HX varied according to the stress: it increased hyperalgesia, reduced analgesia, or had no effect at all. These results indicate that in the rat: (i) the pituitary participates in the regulation of basal pain sensitivity, probably through analgesic factors; (ii) Nx hyperalgesia results essentially from an antagonism of endogenous opioids originating in the CNS and not in the pituitary; and (iii) the pain regulatory processes engaged in adaptation to stressful stimuli involve the CNS and the pituitary in variable proportions depending upon the nature of the stress.

Animals↗
PubMed1979

Serotonin antagonists and central hyperthermia produced by biogenic amines in conscious rabbits.

Previous studies have shown that the hyperthermia produced by intracerebroventricular injection of 5-hydroxytryptamine (5-HT) to conscious rabbits was antagonized by cyproheptadine and increased by LSD. Other putative antagonists, i.e. cinanserin, methiothepin, 2-bromo LSD, methysergide and dimetiotazine are investigated in the present report. Cinanserin and methiothepin resembeld cyproheptadine, 2-bromo LSD had almost the same effects as LSD and methysergide exhibited a mixed pattern of action, being depressant or potentiating as a function of dose. Dimetiotazine had no specific action. Cinanserin, however, differed from cyproheptadine in selectively antagonizing and early component of the 5-HT rise, unmasking an important fall and leaving a late hyperthermic component unaffected, thus disclosing three distinct effects of 5-HT action. The cinanserin, methiothepin and methysergide antagonism of the 5-HT-induced temperature rise was greater than the antagonism of the noradrenaline (NA)-induced rise. Methiothepin and methysergide inhibited both the 5-HT and DA hyperthermia; cinanserin--like cyproheptadine--was more effective on the 5-HT rise. The potentiation of the 5-HT temperature rise by 2-bromo LSD and methysergide was more developed than was the potentiation of the NA and DA rises. The effects of the drugs studied on 5-HT action argue in favour of the existence of several types of central 5-HT receptors. The dissociation observed between the antagonism to 5-HT and that to DA does not favour a mediation of DA hyperthermia by 5-HT; antiserotonin drug antagonism of DA hyperthermia is more simply accounted for by interactions at the level fo specific DA receptors. The potentiation of the 5-HT-induced temperature rise by 2-bromo LSD and methysergide might result from an antagonism of the hypothermic component. As with LSD, 2-bromo LSD and methysergide alone also produced hyperthermia, the origin of which is briefly discussed.

Animals↗