Omi, a recessive mutation on chromosome 10, is a novel allele of Ostm1

Large-scale N-ethyl-N-nitrosourea (ENU) mutagenesis has provided many rodent models for human disease. Here we describe the initial characterization and mapping of a recessive mutation that leads to degeneration of the incisors, failure of molars to erupt, a grey coat colour, and mild osteopetrosis. We mapped the omi mutation to chromosome 10 between D10Mit214 and D10Mit194. The Ostm1 gene is a likely candidate gene in this region and the grey-lethal allele, Ostm1 ^gl , and omi mutations fail to complement each other. We show that om/om mice have reduced levels of Ostm1 protein. To date we have not been able to identify the causative mutation. We propose that omi is a novel hypomorphic mutation affecting Ostm1 expression, potentially in a regulatory element.     

Human sleep‐wake cycles in the high arctic: Effects of unusual photoperiodicity in a natural setting

Abstract

Studies of human circadian rhythms are typically conducted in artificial environments that are low in ecological validity. In the current study, six subjects and the field director lived in temporal isolation in a completely natural environment with constant daylight (a high Arctic research camp) for six weeks. Detailed daily sleep logs were kept. In keeping with past findings, five of the six subjects developed a free‐running sleep‐wake cycle longer than 24 hours. Unlike past results, the isolated subjects did not exhibit any synchronicity in their rhythms. There was a high degree of intersubject variability in circadian patterns. The findings have important implications for the comparison of the results of laboratory and field investigations of sleep‐wake cycles.     

Gender Differences in Homicide of Neonates,Infants, and Children under 5 y in South Africa: Results from the Cross-Sectional 2009 National Child Homicide Study

BackgroundHomicide of children is a global problem. The under-5-y age group is the second largest homicide age group after 15–19 y olds, but has received little research attention. Understanding age and gender patterns is important for assisting with developing prevention interventions. Here we present an age and gender analysis of homicides among children under 5 y in South Africa from a national study that included a focus on neonaticide and infanticide.ConclusionsHomicide of children is an extreme form or consequence of violence against children. This national study provides one of the first analyses of neonaticide and infanticide by age and gender and shows the failure of reproductive and mental health and social services to identify and help vulnerable mothers. Multi-sectoral prevention strategies are needed.     

Leaf Decomposition in a Dry Season Irrigation Experiment in Eastern Amazonian Forest Regrowth

Leaf-litter decomposition is a major component of carbon and nutrient dynamics in tropical forest ecosystems, and moisture availability is widely considered to be a major influence on decomposition rates. Here, we report the results of a study of leaf-litter decomposition of five tree species in response to dry-season irrigation in a tropical forest regrowth stand in the Brazilian Amazon; three experiments differing in the timing of installation and duration allowed for an improved resolution of irrigation effects on decomposition. We hypothesized that decomposition rates would be faster under higher moisture availability in the wet season and during dry-season irrigation periods in the treatment plots, and that decomposition rates would be faster for species with higher quality leaves, independent of treatment. The rates of decomposition ( k ) were up to 2.4 times higher in irrigated plots than in control plots. The highest k values were shown by Annona paludosa (0.97 to 1.26/yr) while Ocotea guianensis (0.73 to 0.85/yr) had the lowest values; intermediate rates were found for Lacistema pubescens (0.91 to 1.02/yr) and Vismia guianensis (0.91 to 1.08/yr). These four tree species differed significantly in leaf-litter quality parameters (nitrogen, phosphorus, lignin, and cellulose concentrations, as well as lignin:nitrogen and carbon:nitrogen ratios), but differences in decomposition rates among tree species were not strictly correlated with leaf-litter quality. Overall, our results show that dry-season moisture deficits limit decomposition in Amazonian forest regrowth.     

Safe To Walk? Neighborhood Safety and Physical Activity Among Public Housing Residents

Background

Despite its health benefits, physical inactivity is pervasive, particularly among those living in lower-income urban communities. In such settings, neighborhood safety may impact willingness to be regularly physically active. We examined the association of perceived neighborhood safety with pedometer-determined physical activity and physical activity self-efficacy.

Methods and Findings

Participants were 1,180 predominantly racial/ethnic minority adults recruited from 12 urban low-income housing complexes in metropolitan Boston. Participants completed a 5-d pedometer data-collection protocol and self-reported their perceptions of neighborhood safety and self-efficacy (i.e., confidence in the ability to be physically active). Gender-stratified bivariate and multivariable random effects models were estimated to account for within-site clustering. Most participants reported feeling safe during the day, while just over one-third (36%) felt safe at night. We found no association between daytime safety reports and physical activity among both men and women. There was also no association between night-time safety reports and physical activity among men (p = 0.23) but women who reported feeling unsafe (versus safe) at night showed significantly fewer steps per day (4,302 versus 5,178, p = 0.01). Perceiving one''s neighborhood as unsafe during the day was associated with significantly lower odds of having high physical activity self-efficacy among both men (OR 0.40, p = 0.01) and women (OR 0.68, p = 0.02).

Conclusions

Residing in a neighborhood that is perceived to be unsafe at night is a barrier to regular physical activity among individuals, especially women, living in urban low-income housing. Feeling unsafe may also diminish confidence in the ability to be more physically active. Both of these factors may limit the effectiveness of physical activity promotion strategies delivered in similar settings.     

Reach specific use of spawning habitat by adult green sturgeon (Acipenser medirostris) under different operation schedules at Red Bluff Diversion Dam

Mature green sturgeon, Acipenser medirostris, enter rivers along the western coast of North America in late winter to late spring and migrate upriver to spawning sites. After spawning, they may leave the river or spend the summer and autumn holding in deep pools before departing from the river with the onset of winter rains. Evidence exists that the seasonal Red Bluff Diversion Dam (RBDD) was an obstacle to the upriver migration of green sturgeon in the Sacramento River in Central California. We compared the migratory movements of green sturgeon under three different dam operation schedules, including post‐decommissioning, to assess the impact of this management action. The proportion of green sturgeon carrying acoustic transmitters that moved above the RBDD was higher when the gates were closed on June 15, one month later than the historical closure date of May 15, and increased again after the dam was decommissioned. The application of statistical analyses (generalized linear and additive mixed models) to the detection records of green sturgeon highlighted an improvement in connectivity after dam decommissioning. The data also indicate that interannual variation in river condition is an important driver of sturgeon presence on the spawning grounds.     

Inhibition of hydrogen peroxide release from activated macrophages by prior ingestion of erythrocytes or haemoglobin

Abstract Production of hydrogen peroxide by mouse peritoneal macrophages activated with Corynebacterium parvum was induced by incubating the cells with opsonised zymosan. H₂O₂ release was reduced by 47% when macrophages were preincubated with opsonised sheep erythrocytes. A significant decrease also occurred when the cells were preincubated with heat-denatured haemoglobin, but not when preincubated with opsonised erythrocyte ghosts, even though the latter were taken up by the macrophages. The ability of macrophages in an infected lesion to destroy microorganisms may therefore be impaired by ingestion of extravasated erythrocytes.     

Laser light-scattering evidence for an altered association of beta B1-crystallin deamidated in the connecting peptide

Deamidation is a prevalent modification of crystallin proteins in the vertebrate lens. The effect of specific sites of deamidation on crystallin stability in vivo is not known. Using mass spectrometry, a previously unreported deamidation in beta B1-crystallin was identified at Gln146. Another deamidation was investigated at Asn157. It was determined that whole soluble beta B1 contained 13%-17% deamidation at Gln146 and Asn157. Static and quasi-elastic laser light scattering, circular dichroism, and heat aggregation studies were used to explore the structure and associative properties of recombinantly expressed wild-type (wt) beta B1 and the deamidated beta B1 mutants, Q146E and N157D. Dimer formation occurred for wt beta B1, Q146E, and N157D in a concentration-dependent manner, but only Q146E showed formation of higher ordered oligomers at the concentrations studied. Deamidation at Gln146, but not Asn157, led to an increased tendency of beta B1 to aggregate upon heating. We conclude that deamidation creates unique effects depending upon where the deamidation is introduced in the crystallin structure.     

Identification of the catalytic motif of the microbial ribosome inactivating cytotoxin colicin E3

Colicin E3 is a cytotoxic ribonuclease that specifically cleaves 16S rRNA at the ribosomal A-site to abolish protein synthesis in sensitive Escherichia coli cells. We have performed extensive mutagenesis of the 96-residue colicin E3 cytotoxic domain (E3 rRNase), assayed mutant colicins for in vivo cytotoxicity, and tested the corresponding E3 rRNase domains for their ability to inactivate ribosome function in vitro. From 21 alanine mutants, we identified five positions where mutation resulted in a colicin with no measurable cytotoxicity (Y52, D55, H58, E62, and Y64) and four positions (R40, R42, E60, and R90) where mutation caused a significant reduction in cytotoxicity. Mutations that were found to have large in vivo and in vitro effects were tested for structural integrity through circular dichroism and fluorescence spectroscopy using purified rRNase domains. Our data indicate that H58 and E62 likely act as the acid-base pair during catalysis with other residues likely involved in transition state stabilization. Both the Y52 and Y64 mutants were found to be highly destabilized and this is the likely origin of the loss of their cytotoxicity. The identification of important active site residues and sequence alignments of known rRNase homologs has allowed us to identify other proteins containing the putative rRNase active site motif. Proteins that contained this active site motif included three hemagglutinin-type adhesins and we speculate that these have evolved to deliver a cytotoxic rRNase into eukaryotic cells during pathogenesis.