Search PubMed⌕ Search

Biomedical subjects

J Bear

Publications and source records attributed to J Bear.

25 records · Page 2Linked to original sources
PubMed1986

An outline of continuum modeling of brain tissue mechanics.

Modern, very sensitive, and noninvasive devices (strain-gauges, accelerometers, etc) detect deformations and motions in the order of a few microns. The observation that the rise in intracranial pressure produces measurable suture strain suggests that noninvasive determination of mechanical parameters in the intracranial cavity, such as density, velocity, pressure, energy, and their time rates, is clearly possible. Based on the above premise, and utilizing the concept of representative elementary volume (REV), this paper presents the conceptual part of a theory that defines the mechanical behavior of the brain and skull under various conditions. The systematic review of brain tissue mechanics leads to a continuum model of a mixed stress-displacement boundary value type, which defines the dynamics of the visco-elastic brain tissue in mathematical terms.

Biomechanical Phenomena↗
PubMed1982

Inhibition by tumor-promoting phorbol esters of procollagen synthesis in promotable JB6 mouse epidermal cells.

The JB6 mouse epidermal cell line has been developed to study promotion of neoplastic transformation in vitro. Treatment of JB6 cells with 12-O-tetradecanoylphorbol 13-acetate (TPA) or other tumor promoters resulted in the irreversible acquisition by JB6 cells of tumorigenicity in nude mice and anchorage-independent growth in soft agar. As previously reported, one of the biochemical responses that occurs during TPA treatment is a greater than 75% reduction in a mannose-labeled glycoprotein with an apparent molecular weight of 180,000. This TPA-sensitive glycoprotein has now been identified on the basis of collagenase and pepsin sensitivity as procollagen pro-alpha 1(I) chain. [3H]proline labeling also demonstrated a parallel decrease in the 150,000 procollagen pro-alpha 2(I) component. Two nonphorbol promoters, mezerein and epidermal growth factor, were also active in decreasing procollagen synthesis. Promotion-sensitive and promotion-resistant clonal derivatives of JB6 showed similar basal levels of collagen synthesis as well as similar degrees of TPA-dependent procollagen loss indicating that the collagen decrease may be necessary but is not sufficient to produce the promotion response. Comparison of chemically transformed mouse epidermal cell lines with paried nontransformants suggests the reduced procollagen synthesis is a stably acquired phenotypic change and may therefore be involved in maintenance of the transformed phenotype as well as in its induction.

Animals↗
PubMed1979

The association of HLA--B8 with atrophic thyroiditis.

One-hundred-and-forty-seven patients with autoimmune thyroiditis were studied with respect to HLA antigens as they related to various clinical features. HLA--B8 was found to be significantly increased among 59 patients with atrophic thyroiditis (57% vs. 26% for controls) but was identical to controls in 88 patients with goitrous thyroiditis (26%). No relation was found in either group between B8 and thyroid autoantibody titer or, in the case of goitrous thyroiditis, the rate of progression of the disease. Thus a link seems to be established between Graves' disease and atrophic thyroiditis in that both are significantly associated with HLA-B8. This study stresses the need to take clinical features into consideration when examining for HLA/disease associations.

Atrophy↗