Possible glimpses into early speciation: the effect of ovarian fluid on sperm velocity accords with post-copulatory isolation between two guppy populations.

Identifying mechanisms of reproductive isolation is key to understanding speciation. Among the putative mechanisms underlying reproductive isolation, sperm-female interactions (post-mating-prezygotic barriers) are arguably the hardest to identify, not least because these are likely to operate at the cellular or molecular level. Yet sperm-female interactions offer great potential to prevent the transfer of genetic information between different populations at the initial stages of speciation. Here, we provide a preliminary test for the presence of a putative post-mating-prezygotic barrier operating between three populations of Trinidadian guppies (Poecilia reticulata), an internally fertilizing fish that inhabits streams with different levels of connectivity across Trinidad. We experimentally evaluate the effect of female ovarian fluid on sperm velocity (a predictor of competitive fertilization success) according to whether males and females were from the same (native) or different (foreign) populations. Our results reveal the potential for ovarian fluid to act as a post-mating-prezygotic barrier between two populations from different drainages, but also that the strength of this barrier is different among populations. This result may explain the previous finding that, in some populations, sperm from native males have precedence over foreign sperm, which could eventually lead to reproductive isolation between these populations.

Development of acute kidney injury during continuous infusion of vancomycin in septic patients.

PURPOSE: Few data are available on the occurrence of renal failure during continuous infusion of vancomycin in critically ill patients. METHODS: We reviewed the data of all patients admitted to the intensive care unit (ICU) between January 2008 and December 2009 in whom vancomycin was given as a continuous infusion for more than 48 h in the absence of renal replacement therapy. We collected data on the doses of vancomycin and blood concentrations during therapy. Acute kidney injury (AKI) was defined as a daily urine output <0.5 ml/kg/h and/or an increase in the serum creatinine of ≥0.3 mg/dl from baseline levels during vancomycin therapy or within 72 h after its discontinuation. Multivariable logistic regression analysis was performed to identify predictors of AKI. RESULTS: Of 207 patients who met the inclusion criteria, 50 (24 %) developed AKI. These patients were more severely ill, had lower creatinine clearance at admission, were more frequently exposed to other nephrotoxic agents, had a longer duration of therapy, and had higher concentrations of vancomycin during the first 3 days of treatment (C(mean)). The C(mean) was independently associated with early AKI (within 48 h from the onset of therapy) and the duration of vancomycin administration with late AKI. CONCLUSIONS: AKI occurred in almost 25 % of critically ill patients treated with a continuous infusion of vancomycin. Vancomycin concentrations and duration of therapy were the strongest variables associated with the development of early and late AKI during therapy, respectively.