The effect of season and latitude on in vitro vitamin D formation by sunlight in South Africa

AIMS: To assess the effect of season and latitude on the in vitro formation of previtamin D3 and vitamin D3 from 7-dehydrocholesterol (7-DHC) by sunlight in two cities in South Africa, Cape Town and Johannesburg. METHODS: An in vitro study utilising vials containing 7-DHC, which were exposed to sunlight for a period of 1 hour between 8:00 and 17:00 on 1 day a month for a year. Previtamin D3 and vitamin D3 were separated from 7-DHC by high-performance liquid chromatography, and the amounts formed were calculated with the use of external standards. RESULTS: A marked seasonal variation in vitamin D3 production was noted in Cape Town, with very little being formed during the winter months of April through September. In Johannesburg, in vitro formation changed little throughout the year, and was similar to that found in Cape Town during the summer. During sunlit hours, vitamin D3 production was maximal at midday and small quantities were still being formed between 8:00 and 9:00, and between 16:00 and 17:00 during the summer. During winter in Cape Town, peak formation at midday was less than one-third of that in Johannesburg, and negligible amounts were formed before 10:00 and after 15:00. CONCLUSIONS: The previously documented seasonal variation in serum 25-hydroxyvitamin D recorded in patients in Johannesburg is probably a consequence of the increased clothing worn and the decreased time spent out of doors during winter, rather than decreased ultraviolet radiation reaching the earth. The limited in vitro formation of vitamin D3 during winter in Cape Town may have clinical implications insofar as the management of metabolic bone diseases like rickets and osteoporosis is concerned. Breast-fed infants resident in the area are likely to suffer from vitamin D deficiency rickets unless vitamin D supplements are provided, or the mothers are encouraged to take their children out of doors.     

Variations in posteroanterior stiffness in the thoracolumbar spine: preliminary observations and proposed mechanisms

BACKGROUND AND PURPOSE: Evaluation of posteroanterior (PA) movement in the spine is commonly used in the clinic, but little is known about the mechanisms involved. The purposes of this study were to examine variations in PA stiffness along the thoracolumbar spine and to investigate possible factors that might determine the pattern of stiffness. SUBJECTS: Twenty-one pain-free volunteers (10 male, 11 female), aged 18 to 41 years (mean age=26.6, SD=7.5), participated. METHODS: Posteroanterior stiffness was measured at 5 locations (L4, L1, T10, T7, T4), together with various subject characteristics. RESULTS: Mean PA stiffness varied among locations, with the greatest stiffness at L4 (13.3 N/mm) and the lowest stiffness at L1 (10.4 N/mm). A relatively small, but important, proportion (22% or less) of the variance in stiffness data at some vertebral levels was accounted for by the variables describing subject characteristics. CONCLUSION AND DISCUSSION: Posteroanterior stiffness varies along the spine in a manner consistent with the nature of support for the spine. The observed pattern of variation of PA stiffness along the spine appears to be influenced by some factors other than those relating to the spine.     

Subcellular site of expression and route of vaccination influence pulmonary eosinophilia following respiratory syncytial virus challenge in BALB/c mice sensitized to the attachment G protein

The attachment glycoprotein (G) of respiratory syncytial virus (RSV) is synthesized as two mature forms: a membrane-anchored form and a smaller secreted form. Mutant cDNAs were constructed that encoded one or the other form of the protein and were expressed in recombinant vaccinia viruses (rVV). Mice were immunized with rVV by dermal scarification or i.p. injection to determine the contribution of the membrane-anchored and secreted forms of the G protein on the augmentation of pulmonary pathology seen following RSV challenge. Mice scarified with rVV expressing the membrane-anchored G protein had a markedly reduced pulmonary eosinophilic response following RSV challenge compared with mice scarified with rVV expressing either wild-type or secreted G protein. The induction of pulmonary eosinophilia in rVV-primed mice was also dependent upon the route of vaccination. An eosinophilic response was not observed in any groups of mice immunized i.p. with rVV expressing any of the different forms of the G protein. The difference in pulmonary pathology observed between dermal scarification or i.p. vaccinated mice was not reflected in a difference in cytokine production by splenocytes from vaccinated and challenged mice restimulated with RSV in vitro. Both groups produced significant levels of IL-4 and IL-5. These data suggest that the local APCs and lymphoid environment, together with the form of the G protein, influence pulmonary pathology following RSV challenge.     

Cytotoxicity-associated effects of reactive oxygen species on endothelin-1 secretion by pulmonary endothelial cells

In this study bovine pulmonary artery endothelial cells (BPAEC) were used as a model system to investigate the effects of the hypoxanthine-xanthine oxidase (HXXO) oxygen radical donor system on ET-1 secretion into pulmonary vasculature. Incubation of BPAEC with HXXO for 4 h caused a significant reduction in ET-1 secretion, which was significantly offset by allopurinol or catalase, but not by Cu/Zn superoxide dismutase (SOD). ET-1 secretion was also reduced by H2O2, and this effect was again significantly offset by catalase. XO alone also reduced ET-1 secretion, but to a significantly lesser degree than did HXXO, and this effect was not offset by allopurinol, catalase, or SOD. None of the oxidant treatments were associated with a loss of immunoreactive ET-1 from endothelial cell medium containing synthetic peptide. The HXXO- and H2O2-mediated reductions in ET-1 secretion were accompanied by evidence of reduced cell viability. This loss of viability was absent when cells were treated with HXXO + catalase, allopurinol, or mercaptopropionyl glycine, but not when SOD was present. We conclude that under conditions of oxidative stress, the pulmonary vascular endothelium responds by secreting less ET-1. This may be relevant to its vasodilator functions in the pulmonary vasculature, which would therefore be compromised when the endothelium is exposed to oxidant stress.     

Intra-articular empyema due to Staphylococcus caprae following arthroscopic cruciate ligament repair

Complaints of racism from visible-minority students at dalhousie medical school led to a study of the problem. Nancy Robb reports that the results surprised some people.     

A genetic system involving superoxide causes F1 necrosis in wheat (T. aestivum L.)

A genetic system in wheat is described in which F1 produced by crossing a drought tolerant cultivar C306 and high yielding cultivar WL711 exhibits leaf necrosis leading to the death of the plant. The mechanism underlying hybrid necrosis is not yet known. The hybrid exhibited a higher level of superoxide anion compared to the healthy leaves of parents at similar developmental stages. This increase in superoxide generation preceded necrotic lesion formation and displayed a gradient from the leaf tip to base. The leaf tip where necrotic lesions make their first appearance exhibited a higher level of superoxide compared to the base. Superoxide anion thus appears to play a vital role in necrosis of leaves in F1 hybrid. This genetic system can be a model system for understanding cell death in higher plants.