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Biomedical subjects

M Bara

Publications and source records attributed to M Bara.

80 records · Page 5Linked to original sources
PubMedDate not supplied

Membrane potential and input resistance in syncytiotrophoblast of human term placenta in vitro.

Direct measurements of electrical potential and input resistance were performed on the syncytial membrane facing maternal blood. The potentials varied according to the external potassium ion levels and, to a lesser extent, with sodium ion concentrations. Ouabain provoked a rapid and consistent depolarization which indicates an electrogenic component. Amiloride slightly hyperpolarized the membrane, confirming the predominant role of potassium ions in the control of the diffusional component of the membrane potential. The electrical potential revealed in this study might play a part in the maternofetal transport of ions.

Antimetabolites↗
PubMedDate not supplied

Ethanol effect on the ionic transfer through isolated human amnion. I. Preventive and antagonistic actions of some nutrients and of their synthetic congeners.

The inhibition of the placental transfer of nutrients was studied in the pathogenesis of the fetal alcohol syndrome. Ethanol reduces the ionic transfer through the human amnion. In this study, the preventive and antagonistic actions of natural nutrients (Mg2+, Ca2+, taurine, homotaurine, gamma-aminobutyric acid) and of their synthetic congeners (Ca2+-taurinate, Ca2+-acetyltaurinate, Ca2+-acetylhomotaurinate) were observed on the amniotic conductance which was modified by ethanol. All the molecules, except Mg, demonstrated protective actions on the fetal side. The effect varied with the molecule and its concentration. An absolute protective effect was obtained on the maternal side with Ca2+-acetylhomotaurinate and Ca2+-taurinate. Some molecules, which have protective actions, had no opposing actions (homotaurine), or inversely (Mg2+), only Ca2+-acetylhomotaurinate exhibited both a preventive and an opposing action against ethanol. These results show the interest of studying synthetic molecules for prevention of fetal alcoholism.

Acamprosate↗
PubMedDate not supplied

Investigations on the action of neurotoxic agents present in the urine of patients suffering from hepatitis. (Biological test).

Injecting urine obtained from patients suffering from hepatitis (acute and chronic-active), into the dorsal lymph sac of 336 frogs, the authors repeatedly observed serious motor disturbances, which caused the death of animals, in proportion of 66%. Histologically, in the treated animals grave neuronal lesions appear (reaching sclerosis and disintegration of motor neurons) at the level of the midbrain, pons and medulla oblongata, attaining the highest degree in the motor zones of the ventral horns, of the spinal cord. In the control group (200 frogs), treated in the same manner with urine originating from healthy persons, the mortality was only 6%. It is concluded that in the active stage of hepatites, in the urine of the patients cytolytic substances of a definite neurotoxic action appear, which is manifest by motor disorders and grave dystrophic lesions of the brainstem and spinal cord.

Animals↗
PubMedDate not supplied

Magnesium and thermoregulation. I. Newborn and infant. Is sudden infant death syndrome a magnesium-dependent disease of the transition from chemical to physical thermoregulation?

The sudden infant death syndrome (SIDS) remains a leading cause of death during the first year. The common epidemiological and pathological data which characterize SIDS include the curve for age at death (with 3 months as modal age), the stigmata of early maternal intrauterine injury, the seasonal predominance in winter, and the absence of an adequate cause of death at autopsy. Some data characterize risk factor subgroups: for example low socioeconomic level, environmental pollution, stress, and mistakes in baby care. Symptoms before death may be lacking, they may be common and non-specific, or rarely they may be acute, corresponding to "apparent life-threatening events" (ALTE). SIDS may be a magnesium-dependent disease of the transition from chemical to physical thermoregulation. This theory originates from a synthesis of our present knowledge of SIDS, maternal magnesium status, and thermoregulation in the baby. It is consistent with all the epidemiological and pathological prerequisites characterizing SIDS. It eliminates the hiatus between relatively minor thermal stress and induced lethal thermal stroke. Logical scepticism about the role of an implausible lethal superacute magnesium deficiency is no longer justified with regard to well established chronic marginal magnesium deficiency. Further experimental and clinical research will be interesting, i.e. ex vivo studies on brown adipose tissue (BAT) and magnesium deficiency under various conditions of thermal exposure. But even now the theory leads to three therapeutic consequences: (1) the need to define the importance of magnesium deficiency in diagnosis and treatment of ALTE; (2) an assessment of the use of new techniques of rewarming (i.e. extracorporeal circulation) in hypothermia cases to distinguish cot death from "apparent death"; (3) investigation of the prevention of SIDS with magnesium through a blinded and randomized multicentre prospective cooperative study of magnesium supplementation in pregnant and lactating women, followed not only in the mother, fetus, and neonate at birth, but also through the first year of life.

Body Temperature Regulation↗
PubMedDate not supplied

Relationship between magnesium, cancer and carcinogenic or anticancer metals.

It is known that carcinogenesis induces Mg distribution disturbances which cause Mg mobilization through blood cells and Mg depletion in non-neoplastic tissues. Mg deficiency seems to be carcinogenic in cases of some particular haemolymphoreticular diseases only, more often, in cases of solid tumors, it inhibits carcinogenesis. Both carcinogenesis and Mg deficiency increase the plasma membrane permeability and fluidity. The regulation of Mg cellular and subcellular distribution is very important in cancer research. If the Mg level is normal in histones, and particularly in H1 and in nucleic acids on the N7 site of the guanine, it can protect against carcinogenesis. On the other hand, if it is abnormally high it can generate the left-handed Z DNA which is correlated with carcinogenesis. The carcinogenic action of Mg may be linked with some effects on sulfur amino-acid metabolism, growth and the immune system. Although Mg antagonizes certain carcinogenic metals, this is not one of its general properties. Our studies on human amniotic membranes show that Mg acts as a competitive antagonist on 2 or 3 weak carcinogens, Pb and Cd, but not on Co. Mg is a non-competitive antagonist of Ni and is devoid of action on As, both of which are powerful carcinogens. All carcinogenic metals (As, Ni, Cr, Cd, Co, Pb, except Be) reduce the total conductance (Gt). Reversibly all cocarcinogens increase Gt or do not modify it. However, both anticancer and carcinogenic metals reduce Gt. Thus the main target in the relationship between Mg and metals in carcinogenesis is either membrane as regards Pb and Cd, or nucleus as regards Pt, Ga, Co and Ni. The ideal treatment of Mg disturbances in carcinogenesis should control the factors which regulate cellular and subcellular Mg distribution in neoplastic tissues as well as those which avoid Mg depletion in extra malignant tissues.

Animals↗
PubMedDate not supplied

Comparative studies of Ca N-acetylhomotaurinate and Ca N-acetyltaurinate. II. Preventive and opposing actions of the acute ethanol depletive effect on the ionic transfer through the isolated human amnion.

Ethanol reduces the ionic paraplacental transfer through the human amnion. This effect is exerted on the cationic paracellular pathway, the coupling between two adjacent epithelial cells, the monovalent cation pump and the antiport system. In this study, the preventive and opposing actions of two taurine and homotaurine derivatives (Ca N-acetyltaurinate: ATACa, Ca N-acetylhomotaurinate: AOTACa) were observed. One the maternal side, ATACa and AOTACa demonstrated protective actions on cationic paracellular pathways and on the Na/K-ATPase pump with AOTACa only. On the fetal side, the effect of ATACa was limited to the sodium paracellular pathway. This effect was total at 5 mM. On the maternal side, ATACa and AOTACa exhibited an opposing action on the same components of the conductance. But on the fetal side, ATACa increased the ethanol effect and AOTACa exerted an antagonistic effect on the cation pump only. These results indicate that two closely related molecules may have different effects on a membranous ethanol model.

Acamprosate↗