3H-labeled dibenzyldimethylammonium ion, applied as an indicator for the potential differences across the plasma membrane, enters the Ehrlich ascites-tumor cell during 2 h to an apparent steady-state concentration about twice that of the suspending medium. In the presence of valinomycin, the distribution ratio reached was increased to about four, the cells meanwhile undergoing a substantial los...

A system has been described in which the penetration of Rickettsia tsutsugamushi (Karp strain) into tissue culture cells can be quantitated, and the factors affecting this process studied. The results indicated that rickettsial penetration in vitro depended largely on the viability of the organisms. Certain components of the fluid environment such as the divalent cations and protein were found ...

At the present time very little information is available about the survival of typhus rickettsiae in fluid media. Data on this point are of value, however, in the solution of a number of problems which arise. The data presented in this report were not collected with the idea of making a detailed investigation of various media but simply to assess the value of media in common use for work in exp...

1. The seven bacterial viruses of the T group, active against E. coli, are much more rapidly inactivated by heat when suspended in 0.1 N solutions of sodium salts than when suspended in broth. 2. The kinetics of this inactivation whether in salt solutions or in broth are those of a first order reaction. 3. The rate of inactivation of phage T5 in 0.1 N NaCl at 37 degrees C. can be greatly decrea...

Measurements of cytosolic pH (pHi) 36Cl fluxes and free cytosolic Ca2+ concentration ([Ca2+]i) were performed in the clonal osteosarcoma cell line UMR-106 to characterize the kinetic properties of Cl-/HCO3- (OH-) exchange and its regulation by pHi and [Ca2+]i. Suspending cells in Cl(-)-free medium resulted in rapid cytosolic alkalinization from pHi 7.05 to approximately 7.42. Subsequently, the ...

A medium for consistent induction of aggregation of Azospirillum brasilense cells was developed and used to study the effects of chemical and physical factors as well as extracellular components involved in this phenomenon. Growth of A. brasilense strain Cd in a high C:N medium using fructose and ammonium chloride as C and N sources, respectively, resulted in flocculation visible to the naked e...

The reversible aggregation of red blood cells (RBC) into linear and three-dimensional structures continues to be of basic science and clinical interest: RBC aggregation affects low shear blood viscosity and microvascular flow dynamics, and can be markedly enhanced in several clinical states. Until fairly recently, most research efforts were focused on relations between suspending medium composi...

1. The pH-activity relationship of invertase has been studied in vivo and in vitro under identical external environmental conditions. 2. The effect of changing (H(+)) upon the sucroclastic activity of living cells of S. cerevisiae and of invertase solutions obtained therefrom has been found, within experimental error, to be identical. 3. The region of living yeast cells in which invertase exert...