Ion Transport in Isolated Rabbit Ileum : III. Chloride fluxes

Unidirectional Cl fluxes across in vitro segments of rabbit ileum have been determined both in the absence and in the presence of an electrochemical potential gradient. The results indicate that Cl transport in this preparation can be attributed to purely passive forces uninfluenced by solvent drag or exchange diffusion. Furthermore, on the basis of this and previous studies, it has been demonstrated that the sum of the partial ionic conductances of Na and Cl accounts for at least 90 per cent of the total tissue conductance.     

Effect of Actinomycin D on Virus-induced Ribonucleic Acid Polymerase Formation in Foot-and-Mouth Disease Virus-Infected Baby Hamster Kidney Cells

Actinomycin D, at a concentration that inhibits cellular ribonucleic acid (RNA) synthesis, inhibited the production of foot-and-mouth disease virus-induced RNA polymerase in baby hamster kidney cells. Inhibition was proportional to exposure time and reached 85% when actinomycin D was added 90 min before infection. Polymerase production was inhibited to the same extent in growth and minimal media, and the kinetics of its appearance were slightly different than in untreated cells. Enzyme preparations from actinomycin-treated cells having one-third to one-tenth the activity of untreated samples gave products with RNA profiles similar to those of controls. The 37S viral peak, 20S ribonuclease-resistant peak, and 26 to 28S peaks were present in all cases. Actinomycin D did not consistently inhibit virus production in either medium. Insulin did not prevent the actinomycin induced inhibition of polymerase and virus production from occurring.     

OXIDATIVE AND HYDROLYTIC ENZYMES IN THE NEPHRON OF NECTURUS MACULOSUS : Histochemical, Biochemical, and Electron Microscopical Studies

The distribution of oxidative and hydrolytic enzyme activities along the nephron of Necturus maculosus Rafinesque was studied histochemically. The proximal tubule possessed all the demonstrable enzyme activities associated with the hexose-monophosphate shunt and glycolysis, but lacked detectable succinic dehydrogenase and cytochrome oxidase activities. Krebs cycle enzymes other than succinic dehydrogenase were easily detectable. The distal tubule, on the other hand, possessed no detectable hexose-monophosphate shunt enzyme activities, but all demonstrable glycolytic and Krebs cycle enzymes and cytochrome oxidase were present in high activity. These data indicate that the proximal tubule of Necturus probably cannot depend, as can the distal tubule, on the Krebs cycle and cytochrome system to provide energy for its transport processes, an inference supported, in general, by available physiological evidence. The question of the importance of the hexose shunt to proximal tubular function arises. Evidence is presented that the proximal tubular blood supply is primarily venous in nature, a hypothesis which would correlate well with its anaerobic metabolic pattern. In addition, the absence of cytochrome oxidase and succinic dehydrogenase from the proximal tubular cells implies either that they possess very few mitochondria, or that their mitochondria have a very unusual enzymatic pattern. Electron microscopical observations and data obtained from the measurement of the enzyme activities of homogenates of Necturus kidney are presented which indicate that the second hypothesis is more probably correct.     

IS SUICIDE PREVENTABLE?

Among 500 cases of suicide analyzed in Stockholm, fewer than a third were associated with depression. Most forms of psychiatric disease were represented. Nevertheless, most persons give some warning before attempting suicide, and these warnings should be the signal for preventive action. Centers with trained personnel could prevent many suicides, if the potential victims were recognized and referred early enough. Laymen too should be educated to recognize potential suicide and help avert it.