Hypovitaminosis D is prevalent among elderly patients entering a nursing home with secondary hyperparathyroidism and apparently increased bone turnover present in patients with circulating 25(OH)D levels below 50 nmol/L. Bone density measurements showed that a majority of the individuals entering a nursing home are osteoporotic. There is a positive association between 25(OH)D levels and bone mass and a negative association between 25(OH)D levels and a history of fracture.

Vitamin D metabolism in elderly individuals can be compromised by several mechanisms. We previously described reduced concentrations of 1,25-dihydroxyvitamin D [1,25(OH)2D] in 30% of elderly nursing home residents. The present study assesses the effect of vitamin D supplementation on 25-hydroxyvitamin D [25(OH)D] and 1,25(OH)2D. We performed a double-blind study in which 30 elderly nursing home residents were randomly given either 50 micrograms vitamin D or a placebo daily for 6 wk. Vitamin D metabolites, immunometrically assayed parathyroid hormone (IRMA-PTH), ionized calcium, and bone Gla hormone (BGP) were measured in serum at baseline and biweekly for 6 wk. Serum 25(OH)D concentrations increased significantly (P less than 0.0001) over the 6 wk in the treatment group but were unchanged in the placebo group. Serum 1,25(OH)2D, ionized calcium, BGP, and PTH were not significantly altered by the supplement. We conclude that vitamin D supplementation results in an increase in circulating 25(OH)D but not 1,25(OH)2D; however, the long-term effect on bone mineral metabolism remains unclear.

Transglutaminase activity is present in human peripheral lymphocytes and is enhanced up to 15-fold within (1)(2)(3). Transglutaminase (TGase), a Ca2+-dependent enzyme that catalyzes the crosslinking of proteins through y-glutamyle-lysine bridges, was recently found to play a role in Ca2+_ mediated crosslinking of erythrocyte proteins (4). Several reports have noted an increase in the influx of Ca2+ soon after treatment of cells with mitogens (5-6), and indeed Ca2+ ionophore itself (A 23187) was found to exhibit mitogenic properties (7). However, the necessity of early Ca2+ influx for the induction of blastogenesis has recently been questioned (8).In the present study, we have explored the possibility that TGase may be involved in crosslinking of lymphocyte membrane sites and that these phenomena may be related to mitogen-induced lymphocyte activation. (9). Cells were washed twice in phosphate-buffered saline (pH 7.2) (10) and suspended at a concentration of 10 X 106 cells/ml in RPMI medium containing heat-inactivated fetal calf serum (20%). Ten milliliters of the cell suspension was added to 25 ml (bed volume) of Sephadex G-10 (in a 50-ml plastic syringe) that had been equilibrated with the cell-suspension medium. After incubation for 30 min at 370, cells were eluted with 50 ml of RPMI 1640 containing fetal calf serum (20%). Approximately 50% of the cells were recovered in this eluate, and they contained less than 1% of macrophages as determined by nonspecific esterase staining (11).Cell Lines. MOLT, a human T-cell line, and RPMI 1788 and RPMI 6237, human B-cell lines, were obtained from Associated Biomedic Systems, Inc. MPC-li, a murine myeloma cell line, was obtained from S. D. Litwin, Cornell University Medical College. Cells were cultured as described (12).Mitogen-Induced Lymphoblasts. Cells were exposed during incubation to Con A (2 gg/ml) or PHA (2 ,ug/ml), or were treated with neuraminidase and galactose oxidase before culturing as follows: cells (20 X 106/ml) in phosphate-buffered saline were incubated with neuraminidase (50 units/ml) and galactose oxidase (4 units/ml) at 370 for 30 min with shaking, followed by two washings with phosphate-buffered saline to remove excess reagents.Mitogen-treated cells (1 X 106/ml), suspended in RPMI 1640 medium containing heat-inactivated fetal calf serum (5%), were cultured at 37°in a 95% air/5% CO2 atmosphere for 72 hr. In the [3H]thymidine incorporation studies, aliquots (0.2 ml) were incubated in flat-bottom microwells and [3H]thymidine incorporation (2 Ci/mmol, 2 ,uCi/well) during 52-72 hr of incubation was determined (13).Incubation of Cells with Mitogens. To determine the effects of mitogen treatment of cells on TGase activity, cell preparations (10 X 106/ml) in RPMI 1640, containing 5% heat-inactivated fetal calf serum, were treated with varying concentrations of phytomitogens, and the mixtures were incubated at 37°in a 95% air/5% CO2 atmosphere for 30 min. After incubation, the cells were diluted with ice-cold phosphate-buffered saline Abbreviations...

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