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Biomedical subjects

K Conway

Publications and source records attributed to K Conway.

45 records · Page 3Linked to original sources
PubMed1984

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. A computer-implemented finite element method was used to solve the non-linear model equations reiteratively. For the Gierer-Meinhardt model, initial activation (varying in size over two orders of magnitude) of one point on the disc's edge was sufficient to generate the primary gradient. Various parts of the disc were removed (remaining only as diffusible space) from the morphogen-producing cycle to investigate the effects of cells dropping out of the cycle due to cell death or malfunction (single point removed) or differentiation (center removed), as occur in the Xenopus eye rudiment. The resulting patterns had the same general shape and amplitude as normal gradients. Nor did a two-fold increase in disc size affect the pattern-generating ability of the model. Disc fragments bearing their primary gradient patterns were fused (with gradients in opposite directions, but each parallel to the fusion line). The resulting patterns generated by the model showed many similarities to results of "compound eye" experiments in Xenopus. Similar patterns were obtained with the model of Kauffman's group (1978), but we found less stability of the pattern subject to simulations of central differentiation. However, removal of a single point from the morphogen cycle (cell death) did not result in any change. The sensitivity of the Kauffman et al. model to shape perturbations is not surprising since the model was originally designed to use shape and increasing size during growth to generate a sequence of transient patterns. However, the Gierer-Meinhardt model is remarkably stable even when subjected to a wide range of perturbations in the diffusible space, thus allowing it to cope with normal biological variability, and offering an exciting range of possibilities for reaction-diffusion models as mechanisms underlying the spatial patterns of tissue structures.

Animals↗
PubMed1984

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. F1 hybrid mice resulting from a cross between A/J and BALB/cByJ mice had levels of activity intermediate to the parental strains, indicating additive inheritance of this genetic difference.

Animals↗
PubMedDate not supplied

Nursing management of MS patients receiving interferon beta-1b therapy.

In 1993, recombinant interferon beta-1b (Betaseron, Berlex Laboratories) was approved by the Food and Drug Administration as a treatment for relapsing-remitting multiple sclerosis (MS). Betaseron is the first therapeutic agent licensed for use with therapeutic patients with MS in more than 20 years. Many patients and their families have expressed great interest in obtaining information about this agent. In response, MS centers throughout the United States have developed Betaseron training programs. This article describes how rehabilitation nurses can educate patients and families about Betaseron.

Adjuvants, Immunologic↗
PubMedDate not supplied

The involvement of heterochromatic damage in nickel-induced transformation.

Nickel ions produce selective damage in heterochromatic regions of chromosomes. Male Chinese hamster embryo cells, which have heterochromatin along the entire long arm of the X-chromosome, exhibit an unusually high incidence of nickel-induced transformation compared with female cells of the same species. However, 3-methylcholanthrene, a carcinogen that produces a random distribution of chromosome damage, transforms female and male cells equally. Other species that do not have as much heterochromatin on the X-chromosome exhibit similar incidences of nickel-induced tumors in males and females. Four out of five of the male nickel-transformed Chinese hamster cell lines exhibit a deletion of the heterochromatic long arm of the X-chromosome as the only common karyotypic aberration. This result indicates that a deletion of a heterochromatic chromosomal region may be an important feature of the nickel-induced carcinogenic process. All of the male nickel transformed cells lines are able to form tumors in athymic nude mice.

Animals↗
PubMedDate not supplied

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. However, there were some definite racial differences. These included level of social support, use of prayer in coping, and use of nonprescription drugs; the black elderly engaged in these latter behaviors more frequently.

Black or African American↗