PubMed Health⌕ Search

Biomedical subjects

V M France

Publications and source records attributed to V M France.

16 recordsLinked to original sources
PubMed1983

Degenerative changes and detection of plasminogen in fetal membranes that rupture prematurely.

Amniochorion obtained at caesarean section and vaginal delivery, at 34-36 weeks gestation and at term, have been studied by electron microscopy and immunofluorescence for evidence of amniotic epithelial degenerative changes and the presence of plasminogen. When delivery was by caesarean section between 34-36 weeks, electron microscopy revealed no degenerative changes in four cases, but in two cases they were widespread. All but one membrane obtained at term showed only minimal amniotic epithelial cell degenerative changes, but extensive change was seen when delivery was premature after premature membrane rupture. Plasminogen was seen in amniotic epithelium proportional to the degree of cell degeneration; it was absent from healthy membranes. These findings demonstrate that degenerative changes are extensively present in membranes that rupture prematurely, particularly before the onset of premature labour, and suggest a role for plasminogen in membrane rupture.

Epithelium↗
PubMed1981

Ouabain binding to isolated frog gastric mucosa.

Inhibition of gastric acid secretion by the cardiac glycoside, ouabain, is considerably reduced by elevating external K+ as first shown by Davenport (Proc. Soc. Exp. Biol. Med. 110: 613-615, 1962). To determine the possible role of K+ in this effect, we measured [3H]ouabain binding in isolated bullfrog gastric mucosa. Uptake of the labeled drug showed two components: one that saturated at 0.36 pmol ouabain per milligram wet weight and one that was linear with the external ouabain concentration. The former component is considered to represent specific binding to Na+-K+-ATPase; activity of this enzyme system in mucosal homogenates was 0.2 mumol per milligram protein per hour. Increase of K+ in the nutrient bathing solution from 3 to 30 mM, or replacement of Na+ by K+ in the secretory bathing solution, largely reversed inhibition of acid secretion by ouabain but did not affect maximum specific binding. The results fit a model in which Na+-K+-ATPase is normally required in oxyntic cells to maintain a high K+ level, which in turn supports exchange of K+ for H+ at the apical surface.

Animals↗
PubMed1979

Cation transport across the guinea-pig placenta perfused in situ.

1. The guinea-pig placenta perfused in situ via the umbilical circulation has been used to measure unidirectional fluxes of Na from mother to fetus, and in the reverse direction, with 24Na and 22Na. There was no significant difference between the two fluxes, each being 22 mumole.min-1. 2. Ouabain 10(-5) M in the perfusion fluid had no detectable effect on radioisotopic movements of Na in either direction. 3. Unidirectional fluxes of 42K in both directions were approximately equal at 1.7 mumole.min-1 mother fetus and 1.8 mumole.min-1 in the reverse direction, despite a K concentration of 3.4 mM on the maternal side and 5.0 mM on the fetal side of the placenta. 4. Extraction of 42K and 86Rb from the perfusion fluid was inhibited by 43% by 10(-5) M-ouabain in the fluid. This effect was largely due to a reduction of isotope uptake by the placental tissue. 5. The relative permeabilities of the placenta, mother to fetus, were Rb approximately K (3.2) greater than Na (1.0) greater than Li (0.55). 6. Under the experimental conditions, the electrical potential difference between perfusion fluid and maternal blood was 6 mV (fetus negative). It was shifted towards the positive by a low Na fluid. 7. The results suggest the presence of a dominant Na-K pump (active component towards mother) sited at the maternal-facing membrane of the syncytiotrophoblast together with a subsidiary pump oriented in the opposite direction and probably sited together with a subsidiary pump oriented in the opposite direction and probably sited at the fetal-facing membrane of the syncytiotrophoblast. 8. A high proportion of Na movement particularly towards the fetus is probably passive, occurring through water-filled spaces, whilst K movement is more dependent on active transport.

Animals↗
PubMed1976

Active sodium uptake by the skin of foetal sheep and pigs.

1. Simultaneous measurements of unidirectional sodium fluxes across foetal skin incubated in vitro with identical solutions ([Na] = 150 mM) bathing either side showed a flux ratio (influx/efflux) of 1-40+/-0-08 in twenty-seven sheep skins, which was significantly different from unity (P less than 0-001). The gestational ages ranged from 47 to 98 days (term = 147 days). Similar experiments on eight foetal pig skins at 58 days gestation (term = 114-118 days) gave a mean flux ratio of 1-10 +/- 0-03 (P less than 0-02). 2. Unidirectional sodium fluxes measured with dilute Ringer solution on the outside (mucosal) surface ([Na]0 = 100mM) gave influx to efflux ratios of 0-86 +/- 0-09 in seventeen sheep (P less than 0-05) and 1-07 +/- 0-26 in five foetal pigs; the value predicted for passive movement was 0-67. 3. Incubation with inhibitors, ouabain (10-4 M) or dinitrophenol (DNP) (10-4 M) gave a flux ratio for sodium which was not significantly different from unity in the absence of a gradient, or from 0-67 when the concentration gradient was applied. 4. Sequential measurement of unidirectional diffusional fluxes of tritiated water across foetal skin gave flux ratios of 0-98 +/- 0-02 in six sheep skins and 1-06 +/- 0-11 for four pig skins in control conditions. When the outside solution was diluted to give an osmotic gradient of 100 m-osmole. kg-1 across the skin a flux ratio of 0-95 +/- 0-07 was obtained for seven sheep and was not measured in pig skin. Hormones and inhibitors had no effect on the diffusional flux ratio for water in the presence or absence of an osmotic gradient. 5. Lysine vasopressin (ADH) (200 mu./ml.) increased influx and efflux of water in the presence and, to a lesser extent in the absence of an osmotic gradient in sheep skin. In pig skin prolactin (1 u./ml.) increased both influx and efflux, but ADH had no effect on diffusional water fluxes. 6. ADH increased sodium influx in sheep skin slightly but vasotocin (5-5 mu./ml.) was more potent, particularly in the presence of an opposing diffusion gradient. Vasotocin (55 mu./ml.) reduced sodium influx in pig skin ADH had no effect on influx or efflux and prolactin reduced sodium influx and efflux. Ouabain and DNP generally reduced permeability to both sodium and water in sheep skin but had no effect in pig skin.

Animals↗
PubMed1976

The effect of hormones and of an osmotic gradient on the structure and properties of mammalian foetal urinary bladder in vitro.

1. Water and isotope fluxes were measured by incubating urinary bladders of foetal pigs and sheep in vitro in the presence and absence of a concentration and osmotic gradient. The structure of the urinary bladder of foetal pigs under various conditions was studied by electron microscopy. Its ultrastructure was found to be closely similar to that of foetal sheep. 2. Antidiuretic hormone (ADH) (0-2 U. ml-1) enhanced the enlargement of intercellular spaces caused by dilute mucosal medium in pig bladders; prolactin (1 u. ml-1) prevented osmotic dilatation of the intercellular spaces. 3. The hydraulic conductivity, Lp, was estimated to be 0-5 X 10 (-7) cm.s-1atm-1 in sheep and pigs at about 100 days gestation; the ratio of osomotic to diffusional permeability, (LpRT/VW)/PD, in the presence and absence of ADH, was 2-1 and 1-6 respectively. These are similar to the values found in fish gills. 4. Prolactin reduced bulk flow of water to zero in seven out of eight bladders investigated. Incubation with ADH or vasotocin (55 mu. ml-1) in the presence of prolactin restored water flux to 22% and 45% of control values respectively. 5. There was no significant net flux of sodium from mucosa to serosa in pig bladder except in the presence of prolactin. No net flux of sodium occurred from mucosal to serosal side of pig or sheep bladders in the presence of an adverse electrochemical gradient, although in sheep the permeability ratio was significantly greater than one. 6. The diffusional flux ratio for water remained unity under all conditions; vasotocin increased unidirectional fluxes and prolactin reduced them. The flux ratios were unaffected by the direction of bulk fluid flow, probably because diffusion was rapid compared to flow: the ratio of diffusional flux to volume flow was between 11 and 18.

Animals↗
PubMed1974

Structure and function in urinary bladder of foetal sheep.

1. The structure and function of the epithelial lining of the urinary bladder of sheep foetuses was investigated by electron microscopic studies made in conjunction with a series of experiments in which the permeability of the bladder to sodium and water was measured in vitro. Measurements were made at gestational ages ranging from 50 to 141 days (term = 147 days) Osmolarity and electrolyte concentrations of urine found in the foetal bladder were also measured.2. The development of tight junctions between the bladder epithelial cells was investigated by incubating the tissue with solutions containing 1 mM-LaCl(3) on the mucosal surface. No penetration of the junctions by lanthanum was observed in foetuses of 90 days or older. In younger bladders, the epithelial layer was stripped by treatment with lanthanum, but tight junctions appeared to be fully developed in early bladders incubated without lanthanum.3. The surface structure of the luminal (mucosal) plasmalemma was fully developed at 50 days.4. Unidirectional fluxes of labelled sodium and water were measured with identical solutions bathing the two surfaces of the bladder wall. No net water movement occurred; the mean ratio of efflux to influx in nine bladders was 1.002 +/- 0.039 (S.E. of mean). Under these conditions, the flux ratio for sodium was 1.735 +/- 0.143 (S.E. of mean) in twelve bladders.5. Antidiuretic hormone (ADH) had no effect on net water movement but reduced the net efflux of sodium so that the flux ratio became 1.285 +/- 0.255 (S.E. of mean) n = 8. ADH also had a striking effect on the structure of the epithelium, causing marked swelling of the intercellular spaces. The tight junctions remained an effective barrier to lanthanum penetration under these conditions; lanthanum was not observed in the enlarged spaces.

Animals↗