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Biomedical subjects

D Wolff

Publications and source records attributed to D Wolff.

At least 73 records · Page 4Linked to original sources
PubMed1982

Modification on ion transport in lipid bilayer membranes by the insecticides DDT and DDE.

In order to elucidate the mechanism of action of organochlorine insecticides on the ion transport in biological membranes, we have studied the effect of DDT and its analog DDE on the structural parameters of phosphatidylethanolamine (PE) planar bilayers. DDT and DDE increases the conductance induced by the hydrophobic ions tetraphenylarsonium (TPhAs+) and tetraphenylborate (TPhB-) in lipid bilayers. Neither DDT nor DDE alters the surface potential of PE monolayers. On the other hand, these organochlorine compounds increase only slightly the electric capacitance of the bilayers. These results are compatible with the hypothesis that these insecticides increase the fluidity of the membrane.

Anions↗
PubMed1982

Inhibition of the active transport of D-glucose and L-tyrosine by DDT and DDE in the rat small intestine.

1. The effect of DDT and DDE on the active transport of D-glucose and L-tyrosine was studied in everted sacs of small intestine. 2. DDT and DDE (10(-5) and 10(-4) M) inhibit the active transport of D-glucose and L-tyrosine. 3. These organochlorine compounds also inhibit the (Na+ + K+)-ATPase from the same tissue, to about the same extent. 4. These results suggest that the inhibition of the active transport is due to an action of DDT and DDE on the sodium pump.

Animals↗
PubMed1980

Protocol-dependence of equivalent circuit parameters of toad urinary bladder.

Determinations o- current-voltage relationships are widely employed in the characterization of epithelial sodium transport. In order to determine the protocol dependence of transport parameters in the toad urinary bladder, studies were carried out in the presence and absence of amiloride, an inhibitor of active sodium transport. With symmetric positive and negative perturbations of the transepithelial electrical potential difference delta psi (0 leads to +/- 100 mV) for 30 sec, the amiloride-sensitive current-voltage (ia-delta psi) relationship was near linear over the range -75 leads to +100 mV, indicating constancy of the conductance ka and the apparent electromotive force "ENa", lumped parameters of the standard electrical equivalent circuit model of the active transport system. With a reverse protocol (+/- 100 leads to 0 mV) or 15 min perturbations the ia-delta psi relationships were highly nonlinear. Nonlinearity reflected voltage dependence of parameters: perturbations that increased active transport decreased "ENa" and increased ka, as evaluated from 10 sec perturbations of delta psi; slowing of active transport produced the converse changes. These effects are usefully analyzed in both quasi-steady states and true steady states by means of a detailed equivalent circuit incorporating the significant ionic currents across each plasma membrane. Precise understanding of the significance of ka and "ENa" will require characterization of the partial ionic conductances on perturbation of delta psi.

Amiloride↗
PubMed1980

Analgesic activity of the naturally occurring heptapeptide [Met]enkephalin-Arg6-Phe7.

[Met]Enkephalin-Arg6-Phe7 is an opiate-like peptide normally found in the the adrenal gland and brain that has analgesic (antinociceptive) activity when administered directly into the cerebral ventricles of mice. On a molar basis, [Met]-enkephalin-Arg6-Phe7, with a median effective dose (ED50) of 38.5 nmol/mouse, is 8 times more potent than [Met]enkephalin. As with [Met]enkephalin, analgesic activity is blocked by naloxone and intravenous administration does not produce characteristic opiate effects in tests for analgesic, antidiuretic, or antidiarrheal activity. These findings suggest that [Met]enkephalin-Arg6-Phe7 may be at least as important as the enkephalins in the postulated enkephalin system mediating pain and analgesia.

Analgesics↗
PubMed1980

Production of timed pregnant mice by utilization of the Whitten effect and a simple cage system.

Pregnant female mice with an impregnation time of 4 hours were achieved by utilizing the Whitten effect and a simple caging system. The cage consisted of a mobile wire-lattice which divided a plastic cage into two compartments to separate the females from the male but still allowed some contact. A synchronization time of 72 hours succeeded in an average copulation rate of 28.1 +/- 5.39% when the procedure was conducted in the forenoon.

Animals↗
PubMed1978

An outbreak of pneumocystis pneumonia in children with acute lymphocytic leukemia.

Between Jan 1 and Oct 31, 1975, a cluster of ten cases of pneumocystis pneumonia occurred in children with acute lymphocytic leukemia (ALL) at the James Whitcomb Riley Hospital for Children in Indianapolis. The risk of infection appeared to be related to the intensity of chemotherapy. Furthermore, illness developed in nine of the ten patients between 30 and 100 days after initiation of therapy, suggesting a period of heightened susceptibility to infection. An indirect immunofluorescent test was used to detect antipneumocystis antibodies in serum samples collected from patients with pneumocystis pneumonia and their contacts. Members of the Riley Hospital staff who had close contact with infected children had a higher prevalence of elevated antibody titers (7/12) than other staff members (2/22; P = .004) or parents of infected patients (0/8; P = .01). This suggests that transmission of pneumocystis may occur within the hospital environment.

Adolescent↗
PubMed1977

Kinetics of bidirectional active sodium fluxes in the toad bladder.

The kinetics of isotopic Na+ flows was studied in urinary bladders of toads from the Dominican Republic. Initial studies of the potential dependence of passive serosal to mucosal 22Na+ efflux demonstrated the absence of isotope interaction and/or other coupling with passive Na+ flow. The electrical current I and mucosal to serosal 22Na+ influx were then measured with transmembrane potential clamped at deltapsi=0, 25, 50, 75 or 100 mV. Subsequent elimination of active Na+ transport with mucosal amiloride permitted calculation of the rates of active Na+ transport JaNa and active and passive influx leads to JaNa and leads to JpNa. The results indicate that for Dominican toad bladders mounted in chambers only Na+ contributes significantly to transepithelial active ion transport; hence JaNa=Ja. Ja was abolished at deltapsi=E=96.3+/-1.9 (S.E.) mV. As deltapsi approached E, active efflux comes from Ja became demonstrable. At deltapsi=100 mV, comes from Ja exceeded leads to Ja, so that Ja was negative. Experimental values of leads to Ja agreed well with theoretical values predicted by a thermodynamic formulation: leads to Jaexp=0.985 leads to Jatheor (r=0.993). The dependence of leads to Ja on deltapsi is curvilinear.

Amiloride↗