Data-model comparison of soil–water δ 18 O at a temperate site in N. Spain with implications for interpreting speleothem δ 18 O

An understanding of how seasonal and longer-term d18O signals in meteoric precipitation (d18Op) are modified by percolation through soils is essential to link temporal changes in speleothem d18O to surface climatic conditions. This study focuses on modifications that occur in a relatively thick soil above a temperate cave site (La Garma, N. Spain). Monthly soil-water d18O (d18Osw) values at a depth of 60 cm through the year is only 14% of the range in d18Op, implying substantial homogenisation and attenuation of seasonal signals. A striking feature is that d18Osw values at 60 cm depth are lowest in summer and highest in winter, the opposite (anti-phase) to that observed in rainfall. Soil-water residence times of up to circa 6 months in the upper 60 cm of soil, and a matrix flow, piston-type infiltration behaviour with mixing is inferred. Evaporative effects on recovered soil-water d18O are minimal at this wet temperate site, in contrast with published results from arid and semi-arid sites. A soil-water model is presented to estimate monthly d18Osw as a function of air temperature and d18Op, incorporating effects such as variations in the amount of infiltrated water, changes in the ratio between evaporation and transpiration, mixing with antecedent soil moisture and small enrichments in 18O linked to evaporation and summer moisture deficits. Our model reproduces the observed d18Osw results, and produces d18Osw outputs in excellent agreement with d18O data for two monitored drip-water sites at La Garma cave that exhibit seasonal d18O variability. We conclude that simple evapotranspiration models that permit infiltration during months that have a positive hydrological balance only tend to under-estimate summer rainfall contributions. Overall, the study provides an improved framework for predicting d18Osw trends at temperate sites such as La Garma that have a relatively thick soil cover, as well as for understanding seasonal ranges and trends in d18O in cave drip-sites

Distribution and Abundance of MAAs in 33 Species of Microalgae across 13 Classes

We provide a direct comparison of the distribution and abundance of mycosporine-like amino acids (MAAs) in a diverse range of microalgal cultures (33 species across 13 classes) grown without supplementary ultraviolet radiation (UV). We compare the MAAs in cultures with those present in characterised natural phytoplankton populations from the English Channel. We detected 25 UV absorbing compounds including at least two with multiple absorption maxima. We used LC-MS to provide chemical characterisation of the six most commonly occurring MAAs, namely, palythene, palythine, mycosporine-glycine, palythenic acid, porphyra-334 and shinorine. MAAs were abundant (up to 7 pg MAA cell−1) in 10 species, with more minor and often unknown MAAs in a further 11 cultures. Shinorine was the most frequently occurring and abundant MAA (up to 6.5 pg cell−1) and was present in all but two of the MAA-containing species. The study provides further insight into the diversity and abundance of MAAs important from an ecological perspective and as potential source of natural alternatives to synthetic sunscreens

Evaluation of NFKB1A variants in patients with knee osteoarthritis

A key feature of osteoarthritis (OA) is articular cartilage loss mediated by numerous catabolic factors including pro-inflammatory cytokines. Cytokine expression is modulated by the nuclear factor κB (NF-κB) family of transcription factors that are in turn, regulated by the inhibitor of NF-κB IκBα encoded by NFKB1A. We examined eight, previously reported common germline polymorphisms to determine whether NFKB1A variants are associated with knee OA. Eight common single-nucleotide polymorphisms (SNPs) across the NFKB1A gene were genotyped in 189 cases with knee OA and 197 healthy controls. Allele, genotype and haplotype frequencies were compared between case and control groups and stratified according to gender due to the increased prevalence of female OA. Serum concentrations of four biochemical markers elevated in OA were compared with genotype for each knee OA case. None of the SNPs showed an association with knee OA; however, stratification of the data for gender showed an increased frequency of the rs8904 variant allele in the female knee OA case group (P = 0.02). Six common haplotypes were identified (H1–H6). H6 was marginally more prevalent in the knee OA group (P = 0.05). The rs8904 variant was associated with increased levels of hyaluronan (HA), a marker of synovial inflammation at 12 and 24 months compared to baseline levels. The nearby rs696 variant demonstrated increased levels of C-reactive protein (CRP) at 12 months and HA at 12 and 24 months. A reduction in CRP levels at 12 months was observed for the rs2233419 variant. These findings provide evidence for the association of NFKB1A variants and knee OA