Biomedical subjects

W K Wickham

Publications and source records attributed to W K Wickham.

5 recordsLinked to original sources

PubMed1981

Glucose uptake into plasma membrane vesicles from the maternal surface of human placenta.

Glucose uptake into plasma membrane vesicles from the maternal surface of the human placenta was measured with the Millipore filtration technique. Uptake off D-glucose was dependent on the osmolarity of the incubation medium surrounding the vesicles. Uptake of D-glucose exceeded that of L-glucose. The uptake of D-glucose was not enhanced by placing 100 mM NaCl or NaSCN in the medium outside the vesicles (none inside) at the onset of uptake determinations. D-glucose transport was inhibited by cytochalasin B; phloretin, phlorizin, and 1-fluoro-2,4-dinitrobenzene. D-glucose uptake was inhibited by 2-deoxy-D-glucose, 3-O-methyl-D-glucose and to a lesser extent by D-galactose. It was not inhibited by alpha-methyl-D-glucoside. Cytochalasin B binding to the vesicles was 30% inhibited in the presence of 80 mM D-glucose. The results indicate that the system for facilitated transport of D-glucose at the maternal face of the placenta is distinctly different from that on the brush-border membrane of intestine or renal tubule and more closely resembles that of human erythrocyte.

Cell Membrane↗

PubMed1979

Placental transfer of water and nonelectrolytes during a single circulatory passage.

A bolus of a 14C-labeled nonelectrolyte and tritiated water was injected into the maternal arterial system supplying the uterine circulation. Blood was sampled immediately on the fetal side of the placenta from the umbilical vein. A placental transfer index (PTI) was calculated from the ratio of the tracers in the fetal blood divided by the ratio of the tracers in the injectate. Placental transfer was measured for 11 nonelectrolytes in anesthetized guinea pigs and 8 nonelectrolytes in unanesthetized sheep. Placental transfer in both species was determined by molecular weight and lipid solubility. The PTI measured for the lipophilic solutes antipyrine and 1,6-hexanediol were less than 1, and those for methanol and ethanol were greater than 1. We conclude that placental transfer for water and small (mol wt less than 200) lipid-soluble nonelectrolytes is limited by diffusion as well as by blood flow.

Animals↗

PubMed1978

Pulmonary diffusing capacity in lambs during the early neonatal period.

A rebreathing method was used to make 53 measurements of pulmonary diffusing capacity (DLco) and functional residual capacity (FRC) in 17 newborn lambs during the first 2 days of life. DLco, FRC, and DLco/FRC all increased in studies made at 24--48 hr of age compared to those at 2--4 hr of age: DLco 0.86 +/- 0.18 to 1.52 +/- 0.09 ml/min/torr; FRC 37 +/- 10 to 60 +/- 8 ml and DLco/FRC 2.52 +/- 0.75 to 2.89 +/- 0.37 ml/min/torr/ml X 10(-2). DLco measured using 0.005% CO in the test gas was not different than that measured using 0.5% CO.

Animals↗

PubMed1977

Placental diffusing capacity for carbon monoxide in unanesthetized guinea pigs.

In unanesthetized pregnant guinea pigs 5-7 ml of maternal blood which had been equilibrated with carbon monoxide (CO) was reinfused into the sow's carotid artery. Three serial blood samples were withdrawn from the sow and a single terminal fetal sample obtained for determination of CO content and hemoglobin concentration. Transplacental CO uptake (VCO) was determined as the product of fetal blood CO content and fetal CO space (11.8% of fetal weight). Placental diffusing capacity (DPCO) was calculated by dividing VCO by the mean partial pressure difference between maternal and fetal blood. DPCO (ml-min(-1)/torr) increased significantly with gestational age: 45-50 days = 0.0413, 51-57 days = 0.1092 and 58-68 days = 0.1858. This increase paralleled fetal weight but was not related to placental weight.

Animals↗

PubMed1977

Placental diffusing capacities at varied carbon monoxide tensions.

To test the hypothesis that carbon monoxide transfer across the placenta is, in part, a facilitated process, we have looked for evidence of saturation kinetics for carbon monoxide. In eight pregnant ewes, fetal to maternal carbon monoxide transfer was examined in a preparation in which the fetal side of the placenta was perfused with blood. The carboxyhemoglobin concentrations on the fetal side of the placenta were varied from 4.8 to 70% in 23 measurements. At increased carbon monoxide tensions, the transfer from fetus to mother always decreased. The slope of log rate of carbon monoxide transfer vs. log partial pressure gradient across the placenta was significantly different from 1. Placental membrane diffusing capacity was calculated separately from total placental diffusing capacity which includes hemoglobin reaction rates and erythrocyte membrane diffusion. Placental membrane diffusing capacity decreased at increased carbon monoxide tensions. Placental permeability for urea did not change with increasing carbon monoxide tensions. These results are consistent with the hypothesis that carbon monoxide diffusion in the placenta is, in part, carrier mediated.

Animals↗