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Biomedical subjects

A Friedland

Publications and source records attributed to A Friedland.

9 recordsLinked to original sources
PubMed2000

Mikheyev-smirnov-wolfenstein effects in vacuum oscillations

We point out that for solar neutrino oscillations with the mass-squared difference of Deltam(2) approximately 10(-10)-10(-9) eV(2), i.e., in the so-called vacuum oscillation range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle straight theta and pi/2-straight theta are not equivalent, making it necessary to consider the entire physical range of the mixing angle 0</=straight theta</=pi/2 when determining the allowed values of the neutrino oscillation parameters.

Journal Article↗
PubMed1999

Severe microcirculatory abnormalities elicited by E. coli hemolysin in the rabbit ileum mucosa.

Decreased capillary flow and heterogeneity of microvascular perfusion are hallmarks of septic circulatory disturbances, and the gastrointestinal mucosa is considered to be particularly prone to such abnormalities. We investigated the impact of Escherichia coli hemolysin (HlyA), a medically relevant pore-forming bacterial toxin, on the mucosal microvasculature in a constant-flow blood-perfused rabbit ileum model. Microsensor techniques were employed to assess spatial distribution of mucosal hemoglobin oxygenation and relative mucosal hemoglobin content, as well as mucosal-arterial PCO(2) gap. Administration of low doses of HlyA (0.005 to 0.1 hemolytic units [HU]/ml) into the mesenteric artery provoked a transient vasoconstrictor response. Whereas physiological mucosal oxygenation is homogeneous, severe heterogeneity in capillary blood flow distribution appeared, paralleled by a marked increase in the mucosal-arterial PCO(2) gap. In addition, HlyA provoked a dose-dependent increase in relative hemoglobin concentration (rel Hb(conc)) values and edema formation, suggesting postcapillary vasoconstriction and capillary leakage. The observed changes occurred while fully maintaining mesenteric oxygen delivery. We conclude that low doses of HlyA may elicit severe mucosal microcirculatory disturbances in the rabbit ileum under maintenance of global hemodynamics, reminiscent of septic perfusion abnormalities. Pore-forming bacterial toxins may thus be considered as contributors to splanchnic mucosal damage under conditions of severe infection and sepsis.

Animals↗
PubMed1976

Factors affecting human percutaneous penetration of methotrexate and its analogues in vitro.

Factors affecting the percutaneous penetration of methotrexate (MTX) and its analogues through excised human skin were studied. With application of 0.05% MTX solution to the epidermis, 0.07% of the applied dose was recovered in the epidermis and less than 0.005% penetrated completely through the skin. The percent of drug which penetrated remained constant from 0.05% to 2.0% MTX and was also unchanged by increasing incubation temperature from 28 degrees C to 37 degrees C. Cellophane tape stripping of stratum corneum following drug incubation removed essentially all the MTX that had been measured in whole epidermis. Binding of MTX was localized to the outermost layers of the stratum corneum. With removal of the stratum corneum prior to drug incubation, 25% of the applied MTX penetrated through the skin. Various vehicles were tested to determine their effect on MTX percutaneous absorption. Dimethylsulfoxide (80%), dimethylacetamide (25%), or retinoic acid (0.1%) had no effect on penetration. Maximum enhancement of penetration by 25-fold and 143-fold was obtained with retinoic acid (saturated solution in aqueous ethanol) and C-10-methylsulfoxide (2.5%), respectively. The penetration of lipid-soluble derivatives of MTX was also tested. The compound that penetrated best was the dimethyl ester of dichloro-MTX with a 3-fold increase in penetration over MTX.

Acetamides↗