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N D Binder

Publications and source records attributed to N D Binder.

24 records · Page 2Linked to original sources
PubMed1979

Distribution of ionic sulfate, lithium, and bromide across the sheep placenta.

Salts of sulfate, lithium, and bromine were injected or infused intravenously into ewes in the last trimester of gestation. Ewes and fetuses had indwelling catheters; most fetuses were nephrectomized. Concentrations were measured in paired maternal and fetal samples over periods of 4--14 days. Maternal excretion of sulfate was too rapid to permit near equilibration of fetal and maternal plasma concentrations; the results, however, did not support the existence of a large potential difference across the exchange barrier. The concentrations of Li+ (given by continuous infusion) and 82Br- in maternal plasma did not change rapidly. The concentrations of these tracers in fetal plasma rose until they were nearly equal to the maternal plasma concentrations. Steady-state transplacental potentials, calculated by use of the Nernst equation, were 5.2 +/- 2.0 (SEM) mV (n = 26) for Li+ and -2.2 +/- 0.8 (SEM) mV (n = 10) for Br-. Nernst potentials calculated from previously measured maternal and fetal plasma concentrations of Na+, K+, Mg2+, and Cl- were +0.4, +3.6, +0.5, and -1.4 mV. We concluded that, of the total potential difference of about -50 mV (fetus negative) between the fetal lamb and the ewe, only a few mV are dropped across the placental exchange barrier.

Animals↗
PubMed1979

Diffusion permeability and ultrafiltration-reflection-coefficients of Narand Cl- in the near-term placenta of the sheep.

Experiments were performed on unanaesthetized ewes in the last third of pregnancy. Fetuses and ewes had indwelling vascular catheters. In some of the experiments fetal urine was drained to the exterior by means of an indwelling vesicular catheter. Placental diffusion permeabilities were measured with 22Na+ and 36Cl- injected into eight fetuses. Volumes of distribution of Na+ and Cl- in the conceptus were Na+: 548 +/- 24, Cl-: 760 +/- 51 (ml/kg fetal wt +/- SEM). Diffusion permeabilities were Na+: 5.2 X 10(-3) +/- 0.3 X 10(-3), Cl-: 9.8 X 10(-3) +/- 0.9 X 10(-3) (ml.s-1.kg-1 +/- SEM). Ultrafiltration-reflection-coefficients of Na+ and Cl- in the placental exchange barrier were measured 17 times in seven fetuses with vesicular catheters. The transplacental e.m.f. was estimated from these results, on the assumption that the individual reflection-coefficients of Na+ should correlate with those of Cl-. The best estimate was -1.0 mV (fetus negative), and the best estimates of the placental reflection-coefficients were Na+: 0.83 and Cl-: 0.79. There was a reliable negative correlation (P < 0.01) between the calculated reflection-coefficients and the osmolality of the urine secreted by the fetus. This suggested that the concentration of vasopressin in fetal plasma affects the membrane characteristics of the placenta. The mean total osmotic force across the placental barrier of the sheep in these experiments was calculated to be 260 Pa (2 mmHg).

Animals↗
PubMed1978

The transplacental potential difference as distinguished from the maternal-fetal potential difference of the guinea-pig.

1. We measured the differences in electrical potential between mother and fetus in the guinea-pig. The fetus was 33 +/- 2 (S.E. of mean) mV negative with respect to the mother. 2. Salts of bromine, sulphate, rubidium, and lithium were injected into pregnant sows and blood samples were obtained from the sows and their fetuses at various times after injection. The transplacental electrical potentials at which each of these ions would be in electrochemical equilibrium across the placental exchange barrier were calculated from the Nernst equation and the concentrations in maternal and fetal plasmas. 3. The differences in transplacental electrical potential calculated from the steady-state concentrations of these ions in maternal and fetal plasmas were within 1 mV of zero. 4. These observations are consistent with a very small difference in electrical potential across the placental exchange barrier itself, and the generation of a potential difference between mother and fetus at a site other than the exchange barrier.

Animals↗
PubMedDate not supplied

Electrophysiology of extrafetal membranes.

This paper reviews some of the equations that apply to the electrophysiology of the extrafetal membranes, and stresses the limitations that may apply to the use of these equations. A literature review of experimental data on potential differences between the fetus, the extrafetal fluid compartments and the mother leads to the conclusion that the transplacental potential difference is no more than a few millivolts and that, in some species, there is an electrical generator outside the placenta.

Animals↗