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.

Neuromagnetic oscillations predict evoked-response latency delays and core language deficits in autism spectrum disorders

Previous studies have observed evoked response latency as well as gamma band superior temporal gyrus (STG) auditory abnormalities in individuals with autism spectrum disorders (ASD). A limitation of these studies is that associations between these two abnormalities, as well as the full extent of oscillatory phenomena in ASD in terms of frequency and time, have not been examined. Subjects were presented pure tones at 200, 300, 500, and 1,000 Hz while magnetoencephalography assessed activity in STG auditory areas in a sample of 105 children with ASD and 36 typically developing controls (TD). Findings revealed a profile such that auditory STG processes in ASD were characterized by pre-stimulus abnormalities across multiple frequencies, then early high-frequency abnormalities followed by low-frequency abnormalities. Increased pre-stimulus activity was a 'core' abnormality, with pre-stimulus activity predicting post-stimulus neural abnormalities, group membership, and clinical symptoms (CELF-4 Core Language Index). Deficits in synaptic integration in the auditory cortex are associated with oscillatory abnormalities in ASD as well as patient symptoms. Increased pre-stimulus activity in ASD likely demonstrates a fundamental signal-to-noise deficit in individuals with ASD, with elevations in oscillatory activity suggesting an inability to maintain an appropriate 'neural tone' and an inability to rapidly return to a resting state prior to the next stimulus.

Missing and delayed auditory responses in young and older children with autism spectrum disorders

Background: The development of left and right superior temporal gyrus (STG) 50 ms (M50) and 100 ms (M100) auditory responses in typically developing (TD) children and in children with autism spectrum disorder (ASD) was examined. Reflecting differential development of primary/secondary auditory areas and supporting previous studies, it was hypothesized that whereas left and right M50 STG responses would be observed equally often in younger and older children, left and right M100 STG responses would more often be absent in younger than older children. In ASD, delayed neurodevelopment would be indicated via the observation of a greater proportion of ASD than TD subjects showing missing M100 but not M50 responses in both age groups. Missing M100 responses would be observed primarily in children with ASD with language impairment (ASD + LI) (and perhaps concomitantly lower general cognitive abilities).

Methods: Thirty-five TD controls, 63 ASD without language impairment (ASD − LI), and 38 ASD + LI were recruited. Binaural tones were presented. The presence or absence of a STG M50 and M100 was scored. Subjects were grouped into younger (6–10 years old) and older groups (11–15 years old).

Results: Although M50 responses were observed equally often in older and younger subjects and equally often in TD and ASD, left and right M50 responses were delayed in ASD − LI and ASD + LI. Group comparisons showed that in younger subjects M100 responses were observed more often in TD than ASD + LI (90 versus 66%, p = 0.04), with no differences between TD and ASD − LI (90 versus 76%, p = 0.14) or between ASD − LI and ASD + LI (76 versus 66%, p = 0.53). In older subjects, whereas no differences were observed between TD and ASD + LI, responses were observed more often in ASD − LI than ASD + LI. Findings were similar when splitting the ASD group into lower- and higher-cognitive functioning groups.

Conclusion: Although present in all groups, M50 responses were delayed in ASD. Examining the TD data, findings indicated that by 11 years, a right M100 should be observed in 100% of subjects and a left M100 in 80% of subjects. Thus, by 11 years, lack of a left and especially right M100 offers neurobiological insight into sensory processing that may underlie language or cognitive impairment.

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.