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Biomedical subjects

M Bara

Publications and source records attributed to M Bara.

At least 73 records · Page 4Linked to original sources
PubMed1988

The magnesium, calcium, sodium, potassium and chloride contents of the term human placenta.

The ion content of the human term placenta was determined. When ordered decreasingly according to their placental content, the series of ions was: Na greater than Cl greater than K greater than Ca greater than Mg. These levels, plotted as a function of the tissue dry weight, showed an exponential distribution. Using Cl as an extracellular marker, Na and K cellular concentrations were evaluated. The equilibrium potentials derived from these values were very different from the measured syncytial membrane potential or from the value usually recorded in non-innervated tissues.

Calcium↗
PubMed1988

Relationship between magnesium, carcinogenic metals and ionic permeability of the human amnion.

The effects of the well established carcinogenic metals or metalloids (As, Be, Cr, Ni), hypothetically carcinogenic but well-established cocarcinogenic metals (Cd, Pb, Co) and weak co-carcinogenic metals (Al, Cu, Fe, Zn) and the antagonism between Mg and these metals were studied on the ionic transfer through the isolated human amnion. The ionic transfer is estimated by the measure of the membrane potential (delta psi), the cationic number transference t+ and the ionic fluxes (F1, F2). All carcinogenic metals increase delta psi (+) and reduce t+, F1 and F2. Mg has an opposite action with regard to Cd, Pb and Ni, but may act as a co-carcinogenic agent by increasing the effects of Al, Cu and Zn.

Aluminum↗
PubMed1985

Comparative study of the effects of two tocolytic agents (magnesium sulfate and alcohol) on the ionic transfer through the isolated human amnion.

The effects of two tocolytic agents (MgSO4 and ethanol) on ionic transfer through the isolated human amnion were observed and compared. The ionic transfer was estimated by conductance and ionic flux measurements. MgSO4 increased the ionic conductance (Gt) on the fetal side; it also increased the ionic fluxes from fetus to mother and from mother to fetus, but it decreased the flux ratio. Ethanol decreased Gt in both directions as well as the ionic fluxes; the flux ratio, however, remained constant. Thus, the two tocolytic agents (MgSO4 and ethanol) show a negative effect on ionic transfer through the human amnion.

Amnion↗
PubMed1985

[Comparison of the effects of taurine and magnesium on electrical characteristics of artificial and natural membranes. IV. Effects on different components of the paracellular and cellular conductances of the human amnion].

The ionic conductance, Gt, through the isolated human amnion is the sum of several conductances: Gt = Gp + Gc + Gs. Gp, the paracellular conductance is: Gp = Gj + Gjc (Gj is due to the intercellular channel and Gjc due to the electrical coupling factor); Gc, the cellular conductance is: Gc = Gc1. Gc2/Gc1 + Gc2 with Gc1 = GAC + GAC1 and Gc2 = GM + GM1, GAC and GM being the dependent conductances on amniotic cavity (AC) and maternal (M) sides; GAC1 and GM1 being the leak conductances on AC and M. Gp and Gc are due to epithelial cell layer and Gs (conductance in a series) is due to the other layers. The utilization of metabolic inhibitors (ouabain, amiloride, DNP) allows one to split up Gt into various components. In this study, the action of magnesium and taurine (TA) was studied on the various conductances in Hanks' solution modified by metabolic inhibitors. In Hanks' solution: + ouabain, Mg and TA increased GAC1 and GM1; - + amiloride, Mg increased GAC and GM but TA had no effect; - + ouabain + amiloride, Mg and TA increased GK. In this way, Mg appears to have an action on the ATPase and on the regulation of the Na+ and K+ channels, but TA has no effect on the ATPase but TA appears to govern the viability of the Na+ and K+ channels. Moreover, TA and Mg have a compensatory effect on GAC1, GM1 and Gjc in Hanks' solution, but their actions are not cumulative.

Adenosine Triphosphatases↗
PubMed1985

[Comparison of the effects of taurine and magnesium on electrical characteristics of artificial and natural membranes. V. Study on the human amnion of the antagonism between magnesium, taurine and polluting metals].

The effects of metal pollutants (Pb, Cd, Hg, As) were studied on strips of human amnion isolated from the placental zone put in between two Ussing chambers with Hanks' solution at 37 degrees C and pH 7.4. The total conductance Gt through the human isolated amnion was decreased on the fetal side by Pb and As; on the maternal side by Cd, Hg and As. When Gt was decreased by metal pollutants, Mg or taurine (TA) were added in the external medium to induce an antagonism between Mg or TA and metal pollutants. The addition of Mg increased significantly the Gt reduced by Pb, Cd and Hg, but had no effect on the Gt reduced by As. The addition of taurine increased significantly the Gt reduced by Cd and Hg, but had no effect on the Gt reduced by Pb and As. Dixon's kinetics (Gt as a function of the Mg or TA concentration when the metal pollutant concentration increased) indicate that there is a competitive inhibition between Mg-Pb and Mg-Cd (the inhibition constant Ki is lower with Pb (= 2.5) than with Cd (= 11.4) and suggests a greater antagonism between Mg-Pb than between Mg-Cd). Moreover, there appears to be a noncompetitive inhibition between Mg-Hg, TA-Cd and TA-Hg. These results indicate that Mg and TA, on the fetal side, exert an action on the same sites and that, on the maternal side, their action takes place on the same sites and also on different ones. Also, TA can be considered as a partial magnesium agonist, at least in the human amnion.

Air Pollutants↗
PubMed1985

Monovalent cations transfer through isolated human amnion: a new pharmacological model.

Transfer of monovalent cation through the isolated human amnion consists of different factors: paracellular, coupling, ATPase dependent cellular transfer, leak cellular transfer. Understanding this transfer permits testing of the action of various substances. Physiological substances (Mg, taurine) increase ionic transfer and there is a vicarious effect between Mg and taurine. The tocolytic agents MgSO4 and ethanol do not exhibit a good effect on the transfer: decrease with ethanol; equality between entry and exit fluxes with MgSO4. On the other hand, amphotericin B increases mother-to-fetus transfer. Polluting metals (Pb, Cd, Hg, As) dramatically reduce exchanges and almost completely inhibit amnion permeability. Ingestion of ethanol also exhibits a dramatic effect on the exchange between mother and fetus through the amnion. Study of ionic transfer in vitro can be considered a pharmacological model to investigate the modifications of mother-fetus exchanges by various substances.

Amnion↗
PubMed1985

Magnesium level in drinking water and cardiovascular risk factor: a hypothesis.

Water hardness can no longer be considered as the most reliable "water factor' with regard to the cardiovascular risk observed in epidemiologic studies. Only two out of three studies have shown a reverse correlation between cardiovascular mortality and water hardness. But studies carried out on the water Mg level alone, as opposed to those on water hardness (Ca + Mg) have all shown a reverse correlation between cardiovascular mortality and the Mg level. In developed countries, the Mg intake is often marginal and the Mg intake coming from drinking water represents the critical factor through which the Mg intake is deficient or satisfactory. Thus, Mg deficiency, either experimental or in man facilitates cardiovascular pathology. The importance of the Mg intake in drinking water is both quantitative and qualitative. Water containing Mg is better and more quickly absorbed than dietary Mg. This particular availability might help to understand why an adequate water Mg level may determine a better state of health, even without any Mg deficiency. Epidemiological data in man and experimental data in rats have demonstrated that the intake of water containing a sufficient amount of Mg may prevent arterial hypertension and correlated ionic and nervous disturbances. Indirectly the water Mg level also interferes in the leakage of food-borne Mg during cooking. There is an inverse correlation between the Mg loss in the cooked food and the Mg level of the cooking water itself. Mg appears to be an antagonist of noxious polluting agents (e.g. in the human amnion, Mg is a competitive inhibitor of Pb and Cd). It is not advisable to enrich water in Mg in the course of the processing since its corrosivity index would also increase. The best pathway is probably to neutralize corrosive water by filtration on calibrated grains of earth-alkaline metals (Neutralite or Magno or Akdolit) to ensure the highest possible Mg/Ca ratio, with the best anticorrosive power.

Animals↗
PubMed1984

Potassium, magnesium and membranes. Review of present status and new findings.

The interactions between magnesium, potassium and various membranes were examined. The different membranes chosen were: artificial, erythrocyte, cardiac, muscular, nervous, gallbladder, urinary bladder, mitochondrial and human amniotic. In general, Mg++ and K+ act on the cellular adhesion and on the stability of the membrane by forming bonds between the charges of the lipids and the proteins. Mg++ acts on the passive K+ transfer either by activation or inhibition. In addition, Mg++ acts on the K+ active transfer: the presence of Mg++ is essential to maintain the activity of the membrane (Na+K) adenosine triphosphatase (ATPase).

Amnion↗
PubMed1983

Comparative study of the human amnion, chorion and chorioamnion permeability to monovalent cations.

Amnion, chorion and chorioamnion from human term placenta were mounted between two Ussing chambers. The monovalent cation transfer was estimated by potentials (dilution, bi-ionic) and conductance measurements. This study revealed that amnion and chorioamnion discriminate the monovalent cations (the sequence is: Rb = Cs = K greater than Na greater than Li), while the chorion does not discriminate these cations. This discrimination relies on the size of the sites on the cell membrane and in intercellular spaces. The monovalent cation conductance for the three layers is gA greater than gC = gCA, and reveals that the chorioamnion properties derive in part from the properties of the isolated amnion (cationic discrimination) and those of the isolated amnion + chorion (size of sites and hydration pathways). The transfer is dependent on the three membranes' orientation and corresponds to fetal needs; the conductance ratio (g mother-fetus/g fetus-mother) is always superior to 1 when the two sides are bathed by the same medium.

Amnion↗
PubMed1979

[Transfer of monovalent cations across the isolated human amniotic membrane].

When the conductance and the bi-ionic potential are measured in vitro, monovalent cations are transferred according to a simple diffusion mechanism across the amnion (from the inside to the outside of the amniotic cavity or in the reverse direction) in channels with neutral or negative fixed sites. For equal concentration, the permeability to K+ is superior to that of Na+.

Amnion↗
PubMed1978

[Permeability of the isolated human amniotic membrane to divalent cations].

Membrane potential and resistance recordings, in vitro, show that Mg++ does not pass through the amnion from the inside of the amniotic compartment to the outside of the amniotic membrane. Mg++ may become fixed on the surface or in the midst of the amniotic membrane. However, Mg++ diffuses in the opposite direction. Ca++, Ba++, Sr++ diffuse in both directions across the amniotic membrane.

Amnion↗