Hasil untuk "physics.acc-ph"

P. A. Shore, B. Brodie, H. Ca

Parenterally administered drugs are secreted directly into the gastric juice. The concentration ratio (concentration of drug in gastric juice divided by concentration in plasma) depends on the dissociation constant of the drug. Thus strong acids appear in gastric juice in negligible concentration, weak acids and weak bases in measurable amount and stronger bases in highest concentration. The stronger bases appear in a limiting concentration ratio of about 40 to 1 when gastric juice flow is maximal, the limitation apparently being due to complete clearance by the gastric mucosa. The pattern of drug secretion can be explained by the concept that the membrane separating plasma from gastric juice has the characteristics of a lipoid membrane that allows the passage of drugs in their undissociated form while restricting passage of dissociated form.

Zhenhua Sun, Weihai Ni, Zhi Yang et al.

S. Jamasb, S. Collins, Rosemary L. Smith

Michael S. Jensen, D. Bainton

Although previous workers have established that the pH of the phagocytic vacuole of the polymorphonuclear (PMN) leukocyte changes from neutral to acid, the time course of conversion has not been investigated. The present experiments were initiated to study pH changes immediately after phagocytosis. Peritoneal exudates were induced in rats; 4 h later, yeast stained with pH indicators was injected intraperitoneally, and the exudate was retrieved at 30-s intervals and examined by light microscopy. Results revealed that (a) within 3 min, pH dropped to ∼6.5, as indicated by the change in color of neutral red-stained yeast; (b) within 7–15 min, pH dropped progressively to ∼4.0, as indicated by color change in bromcresol green-stained yeast; (c) pH did not fall below 4, since no color change was observed up to 24 h when bromphenol blue-stained yeast was used. The finding that intravacuolar acidity increases rapidly after phagocytosis is undoubtedly important with respect to PMN leukocyte function in killing and digesting microorganisms, for many PMN leukocyte granule enzymes (i.e., peroxidase and lysosomal enzymes) are activated at acid pH (∼4.5). It follows that temporal changes in pH and maximal pH depression should be considered in studies of intraleukocytic microbicidal mechanisms, since a defect in these factors could result in impaired PMN leukocyte function.

K. Meyer‐Rosberg, Scott, D. Rex et al.

R. Vaughan, S. Bauer, L. Wise

D. Prusky, N. Yakoby

Hai Lin, P. Heřman, J. Lakowicz

L. D. Shrode, H. Tapper, S. Grinstein

N. Raghunand, R. Gillies

N. Raghunand, C. Howison, A. Sherry et al.

Yongsheng Han, G. Hadiko, M. Fuji et al.

T. Lapidot, S. Harel, B. Akiri et al.

Y. J. Lee, T. Miyahara, T. Noike

O. Kawamura, M. Aslam, Tanya Rittmann et al.

M. L. Kremer

S. George, B. Lund, T. Brocklehurst

H. Eagle

Iuliana Gatej, M. Popa, M. Rinaudo

John T Mongan, D. Case