Clinical characteristics influence in vitro action of 1,25-dihydroxyvitamin D(3) in human marrow stromal cells.

Vitamin D is important for bone health, with low vitamin D levels being associated with skeletal fragility and fractures. Among its other biological activities, 1,25-dihydroxyvitamin D (1,25(OH)(2) D), stimulates the in vitro differentiation of human marrow stromal cells (hMSCs) to osteoblasts, which can be monitored by increases in alkaline phosphatase enzyme activity or osteocalcin gene expression. In this study, we tested the hypotheses that age and clinical attributes of subjects influence in vitro responsiveness of hMSCs to 1,25(OH)(2) D(3) .

Effects of age on parathyroid hormone signaling in human marrow stromal cells.

Human bone marrow stromal cells (hMSCs) have the potential to differentiate into osteoblasts; there are age-related decreases in their proliferation and differentiation to osteoblasts. Parathyroid hormone (PTH), when applied intermittently in vivo, has osteoanabolic effects in a variety of systems. In this study, we compared PTH signaling and osteoanabolic effects in hMSCs from young and old subjects.

The role of non-calcemic analogs of vitamin D in differentiation of cultured rat bone marrow into osteoblast-like cells: age and sex differences.

We have previously demonstrated that rat bone in vivo and rat bone cells in vitro, responded sex-specifically to gonadal steroids in stimulation of the specific activity of the BB isozyme of creatine kinase (CK), a marker for hormonal responsiveness. Pre-treatment with vitamin D analogs up-regulated the sex-specific responsiveness and sensitivity to gonadal steroids. We also found that mice cultured femoral bone marrow (BM) in the presence of dexamethasone (DEX) and 1,25(OH)2D3 (1,25D) or both differentiated into osteoblast-like cells (Obs), which acquired sex-specific responsiveness to gonadal steroids.

Differentiation of cultured mice bone marrow into osteoblast-like cells results in acquisition of sex-specific responsiveness to gonadal steroids.

We have previously demonstrated that mouse skeletal tissue, rat bone as well as rat or human derived bone cells in culture, show a sex-specific response to gonadal steroids in stimulation of the specific activity of the BB isozyme of creatine kinase (CK). This response could be modified by manipulation of the endocrine environment during early postnatal development. Moreover, pretreatment with vitamin D up-regulated the sex-specific responsiveness and sensitivity to gonadal steroids.

Cultural perception of harassment in two groups of medical students: American and Israeli.

The aims of this study were to determine whether harassment occurs in the authors' school, the Sackler Faculty of Medicine at Tel Aviv University, and to address the possible influence of cultural background on the perception of harassment. The unique makeup of the school was utilized, with two separate programs for American and Israeli students trained at the same sites and by the same faculty. A two-part questionnaire was developed that included students' reports on the occurrence of harassment, at what stage of their studies, by whom and its nature as well as demographic data.