Spatial distribution and seasonal variation in 18 O/ 16 O of modern precipitation and river water across the conterminous USA

We report a quantitative analysis of regional differences in the the oxygen isotope composition of river water and precipitation across the USA because data are now available to undertake a more geographically and temporally extensive analysis than was formerly possible. Maps of modern, mean annual Δ 18 O values for both precipitation (Δ 18 O PPT ) and river water (Δ 18 O RIV ) across the 48 contiguous states of the USA have been generated using latitude and elevation as the primary predictors of stable isotope composition while also incorporating regional and local deviations based on available isotopic data. The difference between these two maps was calculated to determine regions where Δ 18 O RIV is significantly offset from local Δ 18 O PPT . Additional maps depicting seasonal and extreme values for Δ 18 O RIV and Δ 18 O PPT were also constructed. This exercise confirms the presence of regions characterized by differences in Δ 18 O RIV and Δ 18 O PPT and specifically identifies the magnitude and regional extent of these offsets. In particular, the Great Plains has Δ 18 O RIV values that are more positive than precipitation, while much of the western USA is characterized by significantly lower Δ 18 O RIV values in comparison with local Δ 18 O PPT . The most salient feature that emerged from this comparison is the ‘catchment effect’ for the rivers. Because river water is largely derived from precipitation that fell upstream of the sample locality (i.e. at higher elevations) Δ 18 O RIV values are often lower than local Δ 18 O PPT values, particularly in catchments with high-elevation gradients. Seasonal patterns in the isotopic data substantiate the generally accepted notion that amplitudes of Δ 18 O variation are greatly dampened in river water relative to those of local precipitation. Copyright © 2005 John Wiley & Sons, Ltd.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/49284/1/5876_ftp.pd

A luteinizing hormone receptor intronic variant is significantly associated with decreased risk of Alzheimer's disease in males carrying an apolipoprotein E ε4 allele

Genetic and biochemical studies support the apolipoprotein E (APOE) ε4 allele as a major risk factor for late-onset Alzheimer's disease (AD), though ~50% of AD patients do not carry the allele. APOE transports cholesterol for luteinizing hormone (LH)-regulated steroidogenesis, and both LH and neurosteroids have been implicated in the etiology of AD. Since polymorphisms of LH beta-subunit (LHB) and its receptor (LHCGR) have not been tested for their association with AD, we scored AD and age-matched control samples for APOE genotype and 14 polymorphisms of LHB and LHCGR. Thirteen gene-gene interactions between the loci of LHB, LHCGR, and APOE were associated with AD. The most strongly supported of these interactions was between an LHCGR intronic polymorphism (rs4073366; lhcgr2) and APOE in males, which was detected using all three interaction analyses: linkage disequilibrium, multi-dimensionality reduction, and logistic regression. While the APOE ε4 allele carried significant risk of AD in males [p = 0.007, odds ratio (OR) = 3.08(95%confidence interval: 1.37, 6.91)], ε4-positive males carrying 1 or 2 C-alleles at lhcgr2 exhibited significantly decreased risk of AD [OR = 0.06(0.01, 0.38); p = 0.003]. This suggests that the lhcgr2 C-allele or a closely linked locus greatly reduces the risk of AD in males carrying an APOE ε4 allele. The reversal of risk embodied in this interaction powerfully supports the importance of considering the role gene-gene interactions play in the etiology of complex biological diseases and demonstrates the importance of using multiple analytic methods to detect well-supported gene-gene interactions

The effect of oestradiol implants on regional and total bone mass: a three year longitudinal study

Objective: Although there is evidence from cross-sectional studies that percutaneous oestrogen administration protects against menopausal bone loss, few longitudinal data are available. We have examined the effect of 3 years' treatment with percutaneous oestradiol on total body calcium, spinal trabecular bone mineral density and radial bone mineral content in post-menopausal women. Design and patients: Twenty-nine post-menopausal women, aged 37–55 years, who had undergone hysterectomy and had experienced the onset of menopausal symptoms within the previous 2 years, were studied before and for 3 years during hormone replacement with oestradiol implants, given at approximately 6-monthly intervals. Measurements: Total body calcium was measured by prompt gamma neutron activation analysis, spinal trabecular bone mineral density by quantitative computed tomography and radial bone mineral content by single-photon absorptiometry. Results: There was a significant increase in the mean total body calcium, spinal trabecular bone mineral density and radial bone mineral content over the 3 years of the study. The mean (± SEM) percentage change per annum was +2 4% (±0.8) for total body calcium (P <0 01), + 3.3% (±0.6) for spinal trabecular bone mineral density (P < 0.001) and +12% (± 0.6) for radial bone mineral content (P < 0 05). Conclusions: Percutaneous oestradiol replacement therapy prevents menopausal bone loss and is associated with a sustained and significant increase in total body calcium, spinal trabecular bone mineral density and radial bone mineral content over a 3-year treatment period. Oestradiol implants thus have skeletal effects comparable to those of oral or transdermal oestrogens