Antagonistic effect of magnesium chloride on the nickel chloride-induced inhibition of DNA replication in Chinese hamster ovary cells.

The degree of inhibition of semiconservative DNA replication induced by nickel chloride (NiCl2) was analyzed by radiolabeled-thymidine incorporation alone or with cesium chloride (CsCl) density gradient centrifugation. The onset and duration of this Ni2+-induced inhibition was time- and concentration-dependent, but the degree of inhibition was not. A maximal reduction in the rate of DNA synthesis was observed within the first hour of treatment with 2.

Coping with the stress of medical problems among black and white elderly.

This is a preliminary study looking at the coping responses of a group of black and white urban elderly women to the stressful event of a medical problem. Cognitive and active coping responses, as well as social support, were explored. Findings revealed these women were similar in many of the ways in which they responded to the stress of medical problems.

Application of reaction-diffusion models to cell patterning in Xenopus retina. Initiation of patterns and their biological stability.

We have examined the behavior of two reaction-diffusion models, originally proposed by Gierer & Meinhardt (1972) and by Kauffman, Shymko & Trabert (1978), for biological pattern formation. Calculations are presented for pattern formation on a disc (approximating the geometry of a number of embryonic anlagen including the frog eye rudiment), emphasizing the sensitivity of patterns to changes in initial conditions and to perturbations in the geometry of the morphogen-producing space. Analysis of the linearized equations from the models enabled us to select appropriate parameters and disc size for pattern growth.

Strain differences among inbred mice in protein kinase C activity.

A protein kinase was identified in mouse organs whose activity is strictly dependent on the presence of Ca++ and phosphatidylserine when assayed at pH 6, and thus has the characteristics of protein kinase C. The relative order of specific activities was brain greater than spleen greater than lung greater than heart, an order similar to that found previously for rat organs. Mice from seven strains had the same level of protein kinase C activity, but strain A/J had half as much activity in each organ as did the other strains.

Demonstration of a polarizing signal that reverses future retinotectal patterns across Nuclepore filter barriers, in Xenopus embryonic eye.

We have studied the interactions which occur in surgically disarranged eye rudiments by recombining a left anterior half-eye graft from a donor Xenopus embryo with a right host posterior half eye, across a variety of physical barriers, at embryonic stages 31 or 32. The anterior half-eye graft and barrier were removed 18 h later at stage 38, and the host posterior half-eye was allowed to reconstitute a whole eye whose visuotectal projection could be mapped electrophysiologically after metamorphosis. Anteroposteriorly reversed maps and double-anterior twinned maps that are characteristic of anterior half-eyes, were found in 50-65% of cases in each of the experimental series using no barrier (N = 16), or using Nuclepore filter barriers (N = 47), including 5 of 8 cases when a filter of 0.

Arousal of sexual and aggressive contact by exposure to stressors in albino rats.

Since certain forms of aggressive and sexual activity are associated with elevated adrenal steroid activity, the hypothesis explored here was whether subjection to a stressful environment which is known to elevate adrenal output would arouse both sexual and aggressive behavior. Accordingly, 24 male Sprague-Dawley rats were subjected to either physical restraint and heat or a nonstress control environment for 13 days. Following this treatment Ss were tested for sexual and aggressive behavior.