Bone metabolic and hormonal characteristics of Australian Antarctic expeditioners

Summary: Serum 25(OH)D levels decline without sunlight exposure. We studied 120 expeditioners to Antarctica to determine the skeletal and hormonal responses to sunlight deprivation. With emerging vitamin D insufficiency, serum calcium decreased, PTH increased, and bone loss at the proximal femur was observed. Baseline serum 25(OH)D levels >100 nmol/L prevented vitamin D insufficiency. Introduction: Vitamin D stores deplete without adequate sunlight exposure unless supplementation is provided. We studied 120 healthy adults who spent a year in Antarctica as a model for sunlight deprivation to define the timing and magnitude of the skeletal and hormonal responses to emerging vitamin D insufficiency. Methods: Fasting blood samples were assessed at baseline, 6 and 12 months for serum 25-hydroxyvitamin D (25(OH)D), osteocalcin (OC), bone formation (P1NP) and resorption (CTx), PTH and calcium. Lumbar spine and proximal femur BMD was measured using DXA. Differences over time were determined using repeated measures ANOVA. Percent changes were expressed as (Delta value/(value A +value B)/2)x100. Relationships between outcome measures were determined using Spearman's correlations. Results: Vitamin D insufficiency (<50 nmol/L) was observed in 85% of expeditioners by 6 months when serum calcium decreased and PTH increased (p<0.01). By 12 months, OC increased by 7.4±3.0% (p<0.05), and BMD decreased by 1.0±2.0% at the total proximal femur (p<0.05). For those with vitamin D sufficiency at baseline (>50 nmol/L), sunlight deprivation produced vitamin D insufficiency within 4 months unless baseline values were >100 nmol/L. Conclusion: Supplementation may be necessary for expeditioners with limited access to UV light.

Lesion, and haematologic and serum characteristics of Weddell seals (Leptonychotes weddellii) sampled in McMurdo Sound, Antarctica

We examined and collected biomedical samples from Weddell seals (Leptonychotes weddellii) during studies of post-breeding-season foraging behaviour of adults and movements of weaned pups as a complement to ongoing studies on the ecology and population dynamics of the McMurdo seals (Stewart et al. 2000, 2003). Here we report on Weddell seal health assessments conducted during the 1996/97, 1997/98 and 1998/99 breeding seasons at the Delbridge Islands (77.68°S, 166.50°E), McMurdo Sound, Antarctica. Our objectives were to compile baseline biomedical data for Weddell seals in McMurdo Sound, and to identify infectious and non-infectious diseases affecting the population. Development of such a database, including information on normal background morbidity and mortality, is an important first step in evaluating natural versus anthropogenic impacts on population health (Geraci et al. 1999; Reddy et al. 2001). These data will be integral to international studies of southern ocean pinnipeds that seek to evaluate the influence of biotic and abiotic factors on the ecology of these apex predators.