Earth-like Habitable Environments in the Subsurface of Mars.

In Earth's deep continental subsurface, where groundwaters are often isolated for >106 to 109 years, energy released by radionuclides within rock produces oxidants and reductants that drive metabolisms of non-photosynthetic microorganisms. Similar processes could support past and present life in the martian subsurface. Sulfate-reducing microorganisms are common in Earth's deep subsurface, often using hydrogen derived directly from radiolysis of pore water and sulfate derived from oxidation of rock-matrix-hosted sulfides by radiolytically derived oxidants. Radiolysis thus produces redox energy to support a deep biosphere in groundwaters isolated from surface substrate input for millions to billions of years on Earth. Here, we demonstrate that radiolysis by itself could produce sufficient redox energy to sustain a habitable environment in the subsurface of present-day Mars, one in which Earth-like microorganisms could survive wherever groundwater exists. We show that the source localities for many martian meteorites are capable of producing sufficient redox nutrients to sustain up to millions of sulfate-reducing microbial cells per kilogram rock via radiolysis alone, comparable to cell densities observed in many regions of Earth's deep subsurface. Additionally, we calculate variability in supportable sulfate-reducing cell densities between the martian meteorite source regions. Our results demonstrate that martian subsurface groundwaters, where present, would largely be habitable for sulfate-reducing bacteria from a redox energy perspective via radiolysis alone. We present evidence for crustal regions that could support especially high cell densities, including zones with high sulfide concentrations, which could be targeted by future subsurface exploration missions.

Does ultrasonic energy for surgical dissection reduce the incidence of renal transplant lymphocele?

OBJECTIVE: To determine the difference in post-renal transplant lymphocele rate based on the surgical dissection technique for control of lymphatics by examining the historical case group under the direction of a single, university-based surgeon in a retrospective, cohort study. PATIENTS: Five hundred thirty-two consecutive renal transplant patients from January 1994 to December 2009. FINDINGS: Of the 532 cases studied, 259 (48.7%) had suture ligation and 273 (51.3%) employed ultrasonic dissection (UD) for control of lymphatics during renal transplantation. There was no difference found in the rate of lymphocele formation, requiring either percutaneous or surgical drainage, when surgical ties (8.9%) were compared to UD (9.2%; P=.999). Logistic regression analysis showed that the odds ratio for developing a lymphocele was independent of surgical dissection technique. Within the logistic analysis, the prediction for lymphocele was increased 3.29 times for pediatric patients (P=.002) and increased 2.97 times for those who received a living donor graft (P=.001), and there was a trend for those with a history of more than one renal transplant of 2.01 times (P=.079). SUMMARY: Surgical dissection technique was not a factor in the development of post-renal transplant lymphocele. Younger age, living donor transplant, and repeat transplant status were found to be predictive variables for symptomatic lymphoceles requiring drainage, which may be considered when patients present for posttransplant evaluations for laboratory alterations.