Changes and tracking of physical activity across seven years in Mexican-American and European-American mothers.

Longitudinal changes in physical activity among 129 Mexican-American (mean age 30.8; SD = 5.6) and 97 European-American (mean age 31.2; SD = 5.4) women were studied. Two physical activity recall interviews were administered at baseline and 7 years later. At baseline, European-American women reported more vigorous leisure activity (p < .005) than Mexican-Americans, and Mexican-Americans reported more moderate work activity (p < .02) than European-Americans. Virtually all components of physical activity increased significantly over the 7 years. Pearson tracking correlations for total energy expenditure were about r = 0.30. The finding that both groups increased physical activity overtime was unexpected and was unrelated to a reduction in the number of preschool children in the homes over time.

Thyroid hormone resistance and increased metabolic rate in the RXR-gamma-deficient mouse.

Vitamin A and retinoids affect pituitary-thyroid function through suppression of serum thyroid-stimulating hormone (TSH) levels and TSH-beta subunit gene expression. We have previously shown that retinoid X receptor-selective (RXR-selective) ligands can suppress serum TSH levels in vivo and TSH-beta promoter activity in vitro. The RXR-gamma isotype has limited tissue distribution that includes the thyrotrope cells of the anterior pituitary gland. In this study, we have performed a detailed analysis of the pituitary-thyroid function of mice lacking the gene for the RXR-gamma isotype. These mice had significantly higher serum T4 levels and TSH levels than did wild-type (WT) controls. Treatment of RXR-gamma-deficient and WT mice with T3 suppressed serum TSH and T4 levels in both groups, but RXR-gamma-deficient mice were relatively resistant to exogenous T3. RXR-gamma-deficient mice had significantly higher metabolic rates than did WT controls, suggesting that these animals have a pattern of central resistance to thyroid hormone. RXR-gamma, which is also expressed in skeletal muscle and the hypothalamus, may have a direct effect on muscle metabolism, regulation of food intake, or thyrotropin-releasing hormone levels in the hypothalamus. In conclusion, the RXR-gamma isotype appears to contribute to the regulation of serum TSH and T4 levels and to affect peripheral metabolism through regulation of the hypothalamic-pituitary-thyroid axis or through direct effects on skeletal muscle.

Characterization of anti-lymphocyte antibodies in inflammatory bowel disease.

Sera from patients with inflammatory bowel disease (IBD) showing broad lymphocytotoxic or lymphocyte-binding activity were subjected to additional analysis to further characterize their properties. Lymphocytotoxins appear to be antibodies predominantly of IgM class as determined by [1] 2-mercaptoethanol sensitivity, [2] serum fractionation by sucrose density gradient sedimentation, Sephadex G-200 filtration, and DEAE ion exchange chromatography, and [3] absorption by anti-Ig immunoadsorbent columns. Lymphocyte-binding antibody was found to be IgG, IgA, and IgM, as determined by indirect immunofluorescent staining of acetone-fixed lymphocytes. Individual IBD sera showed marked variability in occurrence of cytotoxic and binding antibodies when tested against the same donor panel of lymphocytes. These studies emphasize the marked heterogeneity of anti-lymphocyte antibodies occurring in IBD.

Replication of bacteriophage phiX-174 in a mutant of Escherichia coli defective in the dnaE gene.

Strains of E. coli bearing a temperature-sensitive mutation at the dnaE locus were unable to support growth of bacteriophage varphiX-174 at 43 degrees while permitting normal growth at 30 degrees . The dnaE gene product was implicated in all stages of varphiX-174 DNA replication. Differences were observed between a double mutant (pol A(-), dnaE(ts)) and a single mutant (pol A(+), dnaE(ts)) in the ability to synthesize parental replicating form and its subsequent replication. The implications of these observations are discussed in terms of the relationship between DNA polymerases-I and -III.