Vibrotactile masking experiments reveal accelerated somatosensory processing in congenitally blind braille readers.

Braille reading is a demanding task that requires the identification of rapidly varying tactile patterns. During proficient reading, neighboring characters impact the fingertip at ∼100 ms intervals, and adjacent raised dots within a character at 50 ms intervals. Because the brain requires time to interpret afferent sensorineural activity, among other reasons, tactile stimuli separated by such short temporal intervals pose a challenge to perception. How, then, do proficient Braille readers successfully interpret inputs arising from their fingertips at such rapid rates? We hypothesized that somatosensory perceptual consolidation occurs more rapidly in proficient Braille readers. If so, Braille readers should outperform sighted participants on masking tasks, which demand rapid perceptual processing, but would not necessarily outperform the sighted on tests of simple vibrotactile sensitivity. To investigate, we conducted two-interval forced-choice vibrotactile detection, amplitude discrimination, and masking tasks on the index fingertips of 89 sighted and 57 profoundly blind humans. Sighted and blind participants had similar unmasked detection (25 ms target tap) and amplitude discrimination (compared with 100 µm reference tap) thresholds, but congenitally blind Braille readers, the fastest readers among the blind participants, exhibited significantly less masking than the sighted (masker, 50 Hz, 50 µm; target-masker delays, ±50 and ±100 ms). Indeed, Braille reading speed correlated significantly and specifically with masking task performance, and in particular with the backward masking decay time constant. We conclude that vibrotactile sensitivity is unchanged but that perceptual processing is accelerated in congenitally blind Braille readers.

Transformation of inorganic and organic arsenic by Alkaliphilus oremlandii sp. nov. strain OhILAs.

Alkaliphilus oremlandii sp. nov. strain OhILAs is a mesophilic, spore-forming, motile, low mole%GC gram positive. It was enriched from Ohio River sediments on a basal medium with 20 mM lactate and 5 mM arsenate and isolated through passage on medium with increased arsenic concentration (10 and 20 mM), tindalization, and serial dilution. The pH optimal for growth was 8.4 and 16S rRNA gene sequence analysis indicated it is most closely related to species in the genus Alkaliphilus (A. crotonoxidans 95%, A. auruminator 95%, A. metalliredigens, 94%). A strict anaerobe, it can ferment lactate via the acrylate pathway as well as fructose and glycerol. A. oremlandii also has respiratory capability, as it is able to use arsenate and thiosulfate as terminal electron acceptors with acetate, pyruvate, formate, lactate, fumarate, glycerol, or fructose as the electron donor. A respiratory arsenate reductase, which is constitutively expressed, has been identified through biochemical and Western blot analyses and confirmed by cloning and sequencing of the gene encoding the structural subunit arrA. The entire arr operon as well as the ars operon have also been identified in the fully annotated genome. A. oremlandii also transforms the organoarsenical 3-nitro-4-hydroxy benzene arsonic acid (roxarsone). Growth experiments and genomic analysis suggest that it couples the reduction of the nitro group of the organoarsenical to the oxidation of either lactate or fructose in a dissimilatory manner, generating ATP via a sodium dependent ATP synthase.

Assessing the occupational performance priorities of people who are homeless.

SUMMARY This study examined retrospective data for 65 participants enrolled in an occupational therapy supportive employment program. The Canadian Occupational Performance Measure (COPM) was used to identify self-perceived occupational performance problems specific to this population. Over half of the identified problems fell in the self-care domain (59%), about one-third (31%) were in the productivity domain and the final 10% were in the leisure domain. Narrative analysis of verbatim goals suggests that these individuals identified different types of self-care and productivity problems than samples in previous studies. The results of this study indicate that the COPM can facilitate person-centered, culturally responsive assessment with individuals who are homeless.

The respiratory arsenate reductase from Bacillus selenitireducens strain MLS10.

The respiratory arsenate reductase from the Gram-positive, haloalkaliphile, Bacillus selenitireducens strain MLS10 was purified and characterized. It is a membrane bound heterodimer (150 kDa) composed of two subunits ArrA (110 kDa) and ArrB (34 kDa), with an apparent K(m) for arsenate of 34 microM and V(max) of 2.5 micromol min(-1) mg(-1). Optimal activity occurred at pH 9.5 and 150 g l(-1) of NaCl. Metal analysis (inductively coupled plasma mass spectrometry) of the holoenzyme and sequence analysis of the catalytic subunit (ArrA; the gene for which was cloned and sequenced) indicate it is a member of the DMSO reductase family of molybdoproteins.

Dissimilatory arsenate reductase activity and arsenate-respiring bacteria in bovine rumen fluid, hamster feces, and the termite hindgut.

Abstract Bovine rumen fluid and slurried hamster feces completely reduced millimolar levels of arsenate to arsenite upon incubation under anoxic conditions. This activity was strongly inhibited by autoclaving or aerobic conditions, and partially inhibited by tungstate or chloramphenicol. The rate of arsenate reduction was faster in feces from a population of arsenate-watered (100 ppm) hamsters compared to a control group watered without arsenate. Using radioisotope methods, arsenate reductase activity in hamster feces was also detected at very low concentrations of added arsenate ( approximately 10 muM). Bacterial cultures were isolated from these materials, as well as from the termite hindgut, that grew using H(2) as their electron donor, acetate as their carbon source, and arsenate as their respiratory electron acceptor. The three cultures aligned phylogenetically either with well-established enteric bacteria, or with an organism associated with feedlot fecal wastes. Because arsenite is transported across the gut epithelium more readily than arsenate, microbial dissimilatory reduction of arsenate in the gut may promote the body's absorption of arsenic and hence potentiate its toxicity.