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Biomedical subjects

M Maillard

Publications and source records attributed to M Maillard.

At least 19 recordsLinked to original sources
PubMed1991

Ion channels involved in the presynaptic hyperexcitability induced by herpes virus suis in rat superior cervical ganglion.

Rat superior cervical ganglia infected with herpes virus suis (pseudorabies virus) display a spontaneous bursting activity of still unknown origin. Previous intracellular recordings from the ganglionic neurons combined with pharmacological studies showed that the postganglionic action potentials are induced by acetylcholine release spontaneously from the preganglionic nerve. In this study we investigated whether the acetylcholine release is caused by mechanisms which are dependent on action potentials spontaneously generated on the preganglionic nerve or by mechanisms which occur without any changes in the excitability of presynaptic fibers. Simultaneous intra- and extracellular recordings from the ganglion cells and from the preganglionic nerve, respectively, were performed 32-38 h after the inoculation of herpes virus suis (strain Aujeszky) into the anterior chamber of one eye of the rat. Tetrodotoxin, well known to prevent the generation of action potentials by blocking the fast sodium channels, completely and reversibly abolished, whereas the potassium channel blockers 4-aminopyridine and apamin, enhanced the spontaneous, bursting activity at pre- and postsynaptic levels. The nicotinic receptor antagonist hexamethonium abolished the postsynaptic discharges and reduced the preganglionic activity by 50%. Pre- and postsynaptic electrical activities were suppressed in low calcium Krebs' solution, demonstrating that extracellular calcium is required not only for acetylcholine release but also for triggering the presynaptic action potentials. It is concluded that in the infected ganglia the spontaneous acetylcholine release is due to the generation of action potentials in the preganglionic nerve. Voltage-gated sodium and calcium channels contribute to the presynaptic electrogenesis, while the latter appears to be damped by the activation of voltage- and calcium-dependent potassium channels. Possible factors as well as mechanisms inducing such an increase in excitability are discussed.

4-Aminopyridine↗
PubMed1991

[Indications of lithium plasma levels in professional practice. Average of a 7-year follow-up].

With a mean follow-up duration of 7 years, the retrospective analysis of 57 charts of lithiotherapy shows that: Better results are observed when the lithium blood level reactus 0.87 mmoles/l. In that case, the best lithiotherapy indication is the major recurrent long cycles depression. We also propose as lithiotherapy indication in order of efficacy: 1--The maniac-depressive psychosis (P.M.D.) in its mixed form. 2--The schizo-affective troubles. The curative and preventive lithium efficacy is on favour of the diagnosis of recurrent endogenous psychiatric disease.

Adult↗
PubMed1989

Partially N-desulfated heparin as a non-anticoagulant heparin: some physico-chemical and biological properties.

A partially N-desulfated preparation of heparin (UFH) obtained by thermally inactivating heparinic acid for 24 hours at 50 degrees C (TIHA) was examined for its physico-chemical and biological properties in vitro and in vivo. TIHA has a molecular weight of 14,700 and 27% remaining N-sulfate groups (UFH = 17,500; 100% N-sulfate groups). TIHA has no anticoagulant activity measurable by conventional amidolytic or clotting tests. However, in a rabbit stasis-induced thrombosis model and using two different thrombogenic stimuli (Feiba and PCC(Konyne)/RVV), TIHA afforded a dose-dependent (1.0-2.5 mg/kg) protection sufficient to impair thrombosis (UFH: fully effective at 0.13 mg/kg). TIHA did not produce any bleeding at supramaximal antithrombotic dosage in a rat tail bleeding and a rabbit ear blood loss model and it did not augment ADP-induced aggregation of platelets. In contrast, a completely N-desulfated derivative of UFH (Inoue and Nagasawa, Carbohydr. Res. 46, 87-95, 1976) also lacking measurable in vitro activity was completely inactive in vivo. The results in this study suggest that TIHA may be considered as a non-anticoagulant heparin still retaining antithrombotic activity and also with lower haemorrhagic effect than UFH.

Adenosine Diphosphate↗
PubMed1989

Wheat germ agglutinin (WGA) reduces ADH-induced water flow and induces cell surface changes in epithelial cells of frog urinary bladder.

The functional and structural changes induced by apical wheat germ agglutinin (WGA) 100 micrograms/ml exposure on frog urinary bladder have been investigated and the possible correlations between these effects discussed. Bladders, apically exposed to WGA for 30 min to 3 hr exhibit a marked reduction of their response to antidiuretic hormone (ADH) challenge and of their hydrosmotic reactivity. Structural changes triggered by WGA treatment are: 1. apical invaginations of the plasma membrane, interpreted as endocytotic in nature, taking into account the results of carbohydrate cytochemical detection and horseradish peroxidase (HRP) exposure: 2. cytoskeleton disorganization and microvilli collapse. These phenomena do not interfere with cortical granule traffic and are independent of ADH challenge: they occur in ADH-stimulated bladders as well as in bladders at rest. These findings could be interpreted as follows: binding of the divalent lectin WGA to its coat specific receptors would induce changes in the apical membrane structure which in turn could provoke disorganization and disruption of apical cytoskeletal elements associated with plasma membrane. Reduction of bladder response to ADH challenge could result from a reduced recycling of aggrephores, as they are associated with cytoskeletal elements in the subapical cytoplasm. Collapse of microvilli and endocytotic events also could result from apical cytoskeleton disruption, as microvilli are sustained by bundles of actin filaments interconnected with apical cytoskeletal filaments and as plasma membrane is associated with apical cytoskeleton. However, these two last events evidently occur in ADH-challenged or non-challenged bladders.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1985

Neurohypophysial peptides depress cholinergic transmission in a mammalian sympathetic ganglion.

The actions of arginine-vasopressin (AVP) and oxytocin (OXT) were investigated in the rat superior cervical ganglion (SCG). At micromolar concentrations AVP decreased the amplitude of fast excitatory postsynaptic potentials (f-EPSPs) evoked by preganglionic stimulation and in many cells depolarized the postsynaptic membrane. Both effects were reversibly abolished by a potent vasopressor antagonist. The peptide decreased the frequency of spontaneous miniature EPSPs and the quantal content of the f-EPSPs without affecting the sensitivity of the ganglion cells to acetylcholine. OXT exerted the same effects as AVP but was less powerful. It was concluded that neurohypophysial peptides exert a dual pre- and post-synaptic action mediated by specific receptors.

Action Potentials↗
PubMed1985

Twisted architectures in cell-free assembled collagen gels: study of collagen substrates used for cultures.

Reprecipitated fibrils from collagen solutions assemble into aggregates often showing a remarkable twisted structure. We first observed these aggregates in collagen gels prepared to facilitate culture of epithelial cells. We verified that these structures form in the absence of cells and correspond to a process of self-assembly. Studies on reconstructed fibrils of collagen are generally based on the examination of thin specimens mounted onto coated grids prepared for electron microscopy. We rather applied the classical methods of fixation, embedding and ultramicrotomy, which allowed us to analyze the structure of these aggregates, several microns in diameter. Our gels were prepared from 2.5 mg/ml tropocollagen solutions usually chosen for cell and organ cultures. The time required to obtain twisted architectures, in these aggregates, depends on temperature and the presence of factors such as fetal calf serum proteins. Twist is observed at two different levels of organization. Microfibrils are gathered into twisted bundles which condense into cross-striated fibrils. These fibrils themselves aggregate and show a mutual twist whose orientation is left-handed as is the twist observed within each microfibril bundle. Several models of these architectures are presented. Planar twist, cylindrical twist and toroidal twist are described and their relation to the structure of certain liquid crystals is considered. Examples of orthogonal packing also have been observed. These structures obtained in vitro are very close to patterns already described in vivo in numerous collagen matrices.

Animals↗
PubMed1979

[Acquired von Willebrand's syndrome associated with malignant lymphoma].

The sudden development of multiple bleeding episodes in a 63-year-old patient with malignant lymphoma was shown to be due to the presence of an acquired von Willebrand syndrome, characterized by a prolonged bleeding time and low levels of the factors VIII: C, VIIR:Ag and VIII:Rcof. Crossed immunoelectrophoresis demonstrated diminution of the factor VIII portion with least anodic mobility. Mixing experiments of the patient's and normal plasma revealed a weak (T/2: 4.5 hours) inhibitory activity against the factors VIII:C, VIIIR:Ag and VIII:Rcof. After infusion of 800 units of cryoprecipitate there was rapid destruction (T/2: less than 1 hour) of infused factors VIII: C and VIIIR:Ag and no correction of the bleeding time. Chemotherapy resulted in disappearance of the lymphoma and the hemostatic defect, and its discontinuation in their reappearance. The weak inhibitory activity of the patient's plasma does not fully account for the factor VIII levels observed and other pathophysiological mechanisms, such as adsorption of factor VIII to the malignant lymphocytes, must be considered.

Antigens↗
PubMed1977

The energy metabolism of the leukocyte. IX. Changes in the concentration of the coenzymes NAD, NADH, NADP, and NADPH in polymorphonuclear leukocytes during phagocytosis of Staphylococcus albus and due to the action of phospholipase C.

The determination of the coenzymes NAD+, NADH, NADP+ and NADPH, by the use of a method of enzymatic cycling, demonstrates that the enzymes responsible for the stimulations found during the phagocytosis of Staphylococcus albus are NADH and NADPH oxidase of human leukocytes and NADPH oxidase in the case of guinea pig leukocytes. The effects of serum, of the bacterial strain used and of phospholipase C are also discussed.

Animals↗
PubMed1977

Leucocyte energy metabolism. VII. Respiratory chain enzymes, oxygen consumption and oxidative phosphorylation of mitochondria isolated from leucocytes.

A new method for the destruction of cell membrane with heparin and for the subsequent isolation of mitochondria from different types of leucocytes (polymorphonuclear leucocytes (PMN) and lymphocytes of human blood, PMN and macrophages of guinea pig peritoneal exudates) is presented. This method is less traumatic to the mitochondria than the usual mechanical procedures. The activites of several enzymes of the respiratory chain were estimated. Oxygen consumption was measured with oxyhaemoglobin as oxygen donor and reaction rate indicator. The integrity of the mitochodria can be demonstrated by the determination of the acceptor control index; the existence of a coupled phosphorylation of ADP to the respiration is clearly demonstrated in all type of cells studied; the ADP/O ratios with several substrates, near to the theoretical values, could be estimated in mitochondria preparation of lymphocytes (normal and leukaemic) and of macrophages. The highest oxidative ratios were found in leukaemic cells.

Animals↗