Appendectomy and Clostridium difficile colitis:Relationships revealed by clinical observations and immunology

Advances in understanding the interaction between the human immune system and the microbiome have led to an improved understanding of the function of the vermiform appendix as a safe-house for beneficial bacteria in the colon.These advances have been made despite long standing clinical observations that the appendectomy is a safe and effective procedure.However,more recent clinical data show that an appendectomy puts patients at increased risk for recurrent Clostridium difficile(C.difficile)-associated colitis,and probably other diseases associated with an altered microbiome.At the same time,appendectomy does not apparently put patients at risk for an initial onset of C.difficile-associated colitis.These clinical observations point toward the idea that the vermiform appendix might not effectively protect the microbiome in the face of broad spectrum antibiotics,the use of which precedes the initial onset of C.difficile-associated colitis.Further,these observations point to the idea that historically important threats to the microbiome such as infectious gastrointestinal pathogens have been supplanted by other threats,particularly the use of broad spectrum antibiotics.

Oxygen isotopic variations in modern cetacean teeth and bones： implications for ecological, paleoecological, and paleoclimatic studies

The oxygen isotope ratios （δ18O） preserved in marine sediments have been widely used to reconstruct past ocean temperatures. However, there remain significant uncertainties associated with this method, owing to assumptions about the δ18O of ancient seawater which affects the temperature inferred from sediment δ18O records. In this study, oxygen isotope compositions of phosphate in teeth and bones from five different modem cetacean species, including sperm whale, pygmy sperm whale, short-finned pilot whale, killer whale, and Cuvier＇s beaked whale, and three fossil whales were determined. The data were used to assess whether the oxygen isotope ratios of biogenic phosphate （δ18Op） from cetaceans are a reliable proxy for the oxygen isotopic composition of ocean water （δ18Ow）. The δ18Op values of modem cetaceans range from 15.5 ‰ to 21.3 ‰, averaging （19.6 ‰ ±0.8 ‰） （n = 136）.Using a greatly expanded global cetacean δ18Op dataset, the following regression equation is derived for cetaceans： δ18Ow = 0.95317 （4-0.03293） δ18Op- 17.971 （＋0.605）, r = 0.97253. The new equation, when applied to fossil teeth and bones, yielded reasonable estimates of ancient seawater δ18Ow values. Intra-tooth isotopic variations were observed within individual teeth. Among the selected species, the killer whale （O. orca） has largest intra-tooth δ18Op preference and migratory the lowest δ18Op values and the variation, reflecting its habitat behavior. The results show that oxygen isotope analysis of phosphate in cetacean teeth and dense ear bones provides a useful tool for reconstructing the oxygen isotopic composition of seawater and for examining environmental preferences （including migratory behavior） of both modem and ancient whales.

Lymphocyte phenotypes in wild-caught rats suggest potential mechanisms underlying increased immune sensitivity in post-industrial environments

The immune systems of wild rats and of laboratory rats can been utilized as models of the human immune system in pre-industrial and post-industrial societies, respectively. In this study, lymphocyte phenotypes in wild rats were broadly characterized, and the results were compared to those obtained by us and by others using cells derived from various strains of laboratory rats. Although not expected, the production of regulatory T cells was not apparently different in wild rats compared to laboratory rats. On the other hand, differences in expression of markers involved in complement regulation, adhesion, signaling and maturation suggest increased complement regulation and decreased sensitivity in wild-caught rats compared to laboratory rats, and point toward complex differences between the maturation of T cells. The results potentially lend insight into the pathogenesis of post-industrial epidemics of allergy and autoimmune disease.