No abstract

The TEX 86 (tetraether index of 86 carbon atoms) sea surface temperature proxy has been increasingly applied in the reconstruction of Mesozoic and Cenozoic ocean temperatures. However, the archaeal lipids that compose TEX 86 indices, glycerol dialkyl glycerol tetraethers (GDGTs), can derive from water column production, terrestrial sources, and/or within sediments. TEX 86 -sea surface temperature estimates can also be influenced by non-temperature factors, such as growth phase and nutrient levels. Here we show that the weighted average of cyclopentane moieties, known as the Ring Index (RI), can be used to determine if TEX 86 temperature estimates are influenced by non-thermal factors and/or deviate from modern analogues. We demonstrate that RI and TEX 86 indices from the published global core top data set and mesocosm cultures are significantly correlated, as predicted through the influence of temperature on lipid biochemistry. We further show that when RI and TEX 86 indices in modern or ancient records deviate from the modern global TEX 86 -RI relationship, GDGT distributions are not solely controlled by environmental temperature and/or TEX 86 -based temperature reconstructions are questionable.

No abstract

Exercise showed the beneficial effects on mental health in depressed sufferers, whereas, its underlying mechanisms remained unresolved. This study utilized the chronic unpredictable stress (CNS) animal model of depression to evaluate the effects of exercise on depressive behaviors and spatial performance in rats. Furthermore, we tested the hypothesis that the capacity of exercise to reverse the harmful effects of CNS was relative to the hypothalamo-pituitary-adrenal (HPA) system and brain-derived neurotrophic factor (BDNF) in the hippocampus. Animal groups were exposed to CNS for 4 weeks with and without access to voluntary wheel running. Stressed rats consumed significantly less of a 1% sucrose solution during CNS and exhibited a significant decrease in open field behavior. On the other hand, they showed impaired spatial performance in Morris water maze test 2 weeks after the end of CNS. Further, CNS significantly decreased hippocampal BDNF mRNA levels. However, voluntary exercise improved or even reversed these harmful behavioral effects in stressed rats. Furthermore, exercise counteracted a decrease in hippocampal BDNF mRNA caused by CNS. In addition, we also found that CMS alone increased circulating corticosterone (CORT) significantly and decreased hippocampal glucocorticoid receptor (GR) mRNA. At the same time, exercise alone increased CORT moderately and did not affect hippocampal GR mRNA levels. While, when both CNS and exercise were combined, exercise reduced the increase of CORT and the decrease of GR caused by CMS.The results demonstrated that: (1) exercise reversed the harmful effects of CNS on mood and spatial performance in rats and (2) the behavioral changes induced by exercise and/or CNS might be associated with hippocampal BDNF levels, and in addition, the HPA system might play different roles in the two different processes.