Target-dependent sexual differentiation of a limbic-hypothalamic neural pathway.

Neural pathways between sexually dimorphic forebrain regions develop under the influence of sex steroid hormones during the perinatal period, but how these hormones specify precise sex-specific patterns of connectivity is unknown. A heterochronic coculture system was used to demonstrate that sex steroid hormones direct development of a sexually dimorphic limbic-hypothalamic neural pathway through a target-dependent mechanism. Explants of the principal nucleus of the bed nuclei of the stria terminalis (BSTp) extend neurites toward explants of the anteroventral periventricular nucleus (AVPV) derived from male but not female rats. Coculture of BSTp explants from male rats with AVPV explants derived from females treated in vivo with testosterone for 9 d resulted in a high density of neurites extending from the BSTp to the AVPV explant, as was the case when the BSTp explants were derived from females and the AVPV explants were derived from males or androgen-treated females. These in vitro findings suggest that during the postnatal period testosterone induces a target-derived, diffusible chemotropic activity that results in a sexually dimorphic pattern of connectivity.

Role of iron in the pathogenesis of Mycobacterium avium infection in mice.

Mycobacterial infections are of serious concern to HIV-infected patients, and take a heavy toll of such patients. Mycobacterium avium is the most common opportunistic bacterial infection in patients with AIDS. The overload of iron in serum has been implicated in the pathogenicity of a number of bacterial infections. Since iron storage in cells such as macrophages is increased in AIDS, the role of iron as a possible factor in the pathogenesis of M. avium infection was examined. Supplementing iron to normal laboratory chow resulted in accelerated M. avium infection in mice inoculated earlier with the same organism. The bacterial loads in liver, spleen and lungs were approximately 12-fold higher in mice receiving iron supplementation compared with control groups. This is attributed to an increased percentage saturation of iron in the sera of the mice, thus making more iron available for the replication of bacteria. The addition of beef fat to the diet, together with high iron supplementation, further enhanced the infection. Using smaller inocula, mice receiving chow supplemented with high iron and fat developed disseminated M. avium infection faster than control mice. The results provide strong evidence that iron may play a major role in the pathogenesis of M. avium infection.

Short- and long-term effects of calcitonin and calcium administration on blood calcium, magnesium and inorganic phosphorus in post menopausal osteoporosis.

This paper studies the effects of the administration of calcitonin (CT) and Ca on post menopausal osteoporosis, immediately (short-term) and after three months (long-term) of treatment, on total and ionic calcium (Ca), magnesium (Mg), inorganic phosphorus (Pi), calcitonin (CT) and parathyroid hormone (PTH) in plasma. The short-term results show a decrease in total and ionic Ca and Pi four hours after the beginning of the treatment; at seven hours, only Pi varies. A decrease in the total and ionic Ca was observed after three months of CT treatment (long-term effects). No hormonal (PTH and CT) variations were found either in the short or the long-term. However, the PTH/CT ratio decreased significantly during the experiment and this may be an important factor in explaining the long-term Ca variations.