Tropical marine climate during the late Paleozoic ice age using trace element analyses of brachiopods

The late Paleozoic ice age can be considered an important analogue to the modern ice age, but comparisons between the two time intervals have been hampered by the difficulty of resolving climatic changes that occur over short (e.g., seasonal) time scales in the Paleozoic record. As a first step toward overcoming these limitations, this study employed Mg/Ca trace element ratios sampled across the growth bands of six specimens of the brachiopod Composita to assess differences in tropical marine mean temperature and seasonality in Viséan and Moscovian time. These time intervals bracket the onset of the late Paleozoic ice age, which occurred in mid-Serpukhovian time, and thus provide a snapshot of climate changes from a greenhouse to an icehouse world. Shells were screened for diagenetic alteration by cathode luminescence and by comparing the values of Mn, Sr, Na, and B to those reported for modern brachiopods. In addition, a ⁸⁷Sr/⁸⁶Sr value, measured for one specimen, agreed with a published strontium isotope curve for the late Paleozoic Era. Both the mean and range of Mg/Ca values were larger in Viséan than Moscovian time, suggesting colder and less seasonal temperatures during the late Paleozoic ice age. The decline in seasonality was due to a greater proportional reduction of maximum values (which presumably represent summer temperatures) than minimum values. These relative differences between the pre-ice age and ice age tropical climate provide a first step toward understanding the broad patterns of seasonal-scale changes in temperature during a critical time in Earth's history.     

Do stable nitroxide radicals catalyze or inhibit the degradation of hyaluronic acid?

Reactive oxygen-derived species and particularly OH radicals can degrade hyaluronic acid (HA), resulting in a loss of viscosity and a subsequent decrease in its effectiveness as a joint-lubricating agent. The production of OH in the vicinity of HA can be catalyzed by bound redox-active metals, which participate in the Haber-Weiss reaction. Damage to HA can also occur as a result of hypochlorite formed by myeloperoxidase (MPO). The protective reagents commonly used to inhibit oxidative stress-induced degradation of HA include antioxidative enzymes, such as SOD and catalase, chelators that coordinate metal ions rendering them redox-inactive, and scavengers of radicals, such as OH, as well as nonradical reactive species. In recent years, stable cyclic nitroxides have also been widely used as effective antioxidants. In many cases, nitroxide antioxidants operate catalytically and mediate their protective effect through an exchange between their oxidized and reduced forms. It was anticipated, therefore, that nitroxides would protect HA from oxidative degradation as well. On the other hand, nitroxides serve as catalysts in many oxidation reactions of alcohols, sugars and polysaccharides, including hyalouronan. Such opposite effects of nitroxides on oxidative degradation are particularly intriguing and the aim of the present study was to examine their effect on HA when subjected to diverse forms of oxidative stress. The results indicate that nitroxides protect HA from OH radicals generated enzymatically or radiolytically. The protective effect is attributable neither to the scavenging of OH nor to the oxidation of reduced metal, but to the reaction of nitroxides with secondary carbohydrate radicals-most likely peroxyl radicals.     

Preferential synthesis of a membrane-associated protein by free polyribosomes (Short Communication)

Isolated free polyribosomes from rat liver appear to synthesize NADPH–cytochome c reductase in vitro four times as efficiently as do membrane-bound polyribosomes. The observed synthesis by the latter could result from contamination with free polyribosomes, but an alternative explanation is also suggested.     

Identification of a new series of non-peptidic NK3 receptor antagonists

The identification and structure-activity relationships of 2-aminomethyl-1-aryl cyclopropane carboxamides as novel NK₃ receptor antagonists are reported. The compound series was optimized to give analogues with low nanomolar binding to the NK₃ receptor and brain exposure, leading to activity in vivo in the senktide-induced hypoactivity model in gerbils.     

Residential Exposure to Road and Railway Noise and Risk of Prostate Cancer: A Prospective Cohort Study

Background

Few modifiable risk factors for prostate cancer are known. Recently, disruption of the circadian system has been proposed to affect risk, as it entails an inhibited melatonin production, and melatonin has demonstrated beneficial effects on cancer inhibition. This suggests a potential role of traffic noise in prostate cancer.

Methods

Road traffic and railway noise was calculated for all present and historical addresses from 1987–2010 for a cohort of 24,473 middle-aged, Danish men. During follow-up, 1,457 prostate cancer cases were identified. We used Cox Proportional Hazards Models to calculate the association between noise exposure and incident prostate cancer. Incidence Rate Ratios (IRR) were calculated as crude and adjusted for smoking status, education, socioeconomic position, BMI, waist circumference, physical activity, calendar year, and traffic noise from other sources than the one investigated.

Results

There was no association between residential road traffic noise and risk of prostate cancer for any of the three exposure windows: 1, 5 or 10-year mean noise exposure before prostate cancer diagnosis. This result persisted when stratifying cases by aggressiveness. For railway noise, there was no association with overall prostate cancer. There was no statistically significant effect modification by age, education, smoking status, waist circumference or railway noise, on the association between road traffic noise and prostate cancer, although there seemed to be a suggestion of an association among never smokers (IRR: 1.16; 95% CI: 1.00–1.36).

Conclusion

The present study does not support an overall association between either railway or road traffic noise and overall prostate cancer.     

A genome-wide metabolic QTL analysis in Europeans implicates two loci shaped by recent positive selection

We have performed a metabolite quantitative trait locus (mQTL) study of the (1)H nuclear magnetic resonance spectroscopy ((1)H NMR) metabolome in humans, building on recent targeted knowledge of genetic drivers of metabolic regulation. Urine and plasma samples were collected from two cohorts of individuals of European descent, with one cohort comprised of female twins donating samples longitudinally. Sample metabolite concentrations were quantified by (1)H NMR and tested for association with genome-wide single-nucleotide polymorphisms (SNPs). Four metabolites' concentrations exhibited significant, replicable association with SNP variation (8.6×10(-11)相似文献   

Elemental variability in the coralline alga Lithophyllum yemenense as an archive of past climate in the Gulf of Aden (NW Indian Ocean)

This study presents the first algal thallus (skeleton) archive of Asian monsoon strength and Red Sea influence in the Gulf of Aden. Mg/Ca, Li/Ca, and Ba/Ca were measured in Lithophyllum yemenense from Balhaf (Gulf of Aden) using laser ablation inductively coupled plasma mass spectrometry, and Mg/Ca ratio oscillation was used to reconstruct the chronology (34 y). Oscillations of element rates corresponding to the algal growth between 1974 and 2008 were compared with recorded climate and oceanographic variability. During this period, sea surface temperatures (SST) in Balhaf recorded a warming trend of 0.55°C, corresponding to an increase in Mg and Li content in the algal thallus of 2.1 mol‐% and 1.87 μmol‐%, respectively. Lithophyllum yemenense recorded decadal SST variability by Li/Ca, and the influence of the Pacific El‐Niño Southern Oscillation on the NW Indian Ocean climate system by Ba/Ca. Additionally, algal Mg/Ca, Li/Ca, and Ba/Ca showed strong and significant correlations with All Indian Rainfall in the decadal range indicating that these proxies can be useful for tracking variability in the Indian monsoon system, possibly due to changes of the surface wind system, with deep water upwelling in summer, and a distinct seasonality.