The Dynamics of Ca2+ Ions within the Solvation Shell of Calbindin D9k

The encounter of a Ca2+ ion with a protein and its subsequent binding to specific binding sites is an intricate process that cannot be fully elucidated from experimental observations. We have applied Molecular Dynamics to study this process with atomistic details, using Calbindin D9k (CaB) as a model protein. The simulations show that in most of the time the Ca2+ ion spends within the Debye radius of CaB, it is being detained at the 1st and 2nd solvation shells. While being detained near the protein, the diffusion coefficient of the ion is significantly reduced. However, due to the relatively long period of detainment, the ion can scan an appreciable surface of the protein. The enhanced propagation of the ion on the surface has a functional role: significantly increasing the ability of the ion to scan the protein's surface before being dispersed to the bulk. The contribution of this mechanism to Ca2+ binding becomes significant at low ion concentrations, where the intervals between successive encounters with the protein are getting longer. The efficiency of the surface diffusion is affected by the distribution of charges on the protein's surface. Comparison of the Ca2+ binding dynamics in CaB and its E60D mutant reveals that in the wild type (WT) protein the carboxylate of E60 function as a preferred landing-site for the Ca2+ arriving from the bulk, followed by delivering it to the final binding site. Replacement of the glutamate by aspartate significantly reduced the ability to transfer Ca2+ ions from D60 to the final binding site, explaining the observed decrement in the affinity of the mutated protein to Ca2+

Heat or Insulation: Behavioral Titration of Mouse Preference for Warmth or Access to a Nest

In laboratories, mice are housed at 20–24°C, which is below their lower critical temperature (≈30°C). This increased thermal stress has the potential to alter scientific outcomes. Nesting material should allow for improved behavioral thermoregulation and thus alleviate this thermal stress. Nesting behavior should change with temperature and material, and the choice between nesting or thermotaxis (movement in response to temperature) should also depend on the balance of these factors, such that mice titrate nesting material against temperature. Naïve CD-1, BALB/c, and C57BL/6 mice (36 male and 36 female/strain in groups of 3) were housed in a set of 2 connected cages, each maintained at a different temperature using a water bath. One cage in each set was 20°C (Nesting cage; NC) while the other was one of 6 temperatures (Temperature cage; TC: 20, 23, 26, 29, 32, or 35°C). The NC contained one of 6 nesting provisions (0, 2, 4, 6, 8, or 10g), changed daily. Food intake and nest scores were measured in both cages. As the difference in temperature between paired cages increased, feed consumption in NC increased. Nesting provision altered differences in nest scores between the 2 paired temperatures. Nest scores in NC increased with increasing provision. In addition, temperature pairings altered the difference in nest scores with the smallest difference between locations at 26°C and 29°C. Mice transferred material from NC to TC but the likelihood of transfer decreased with increasing provision. Overall, mice of different strains and sexes prefer temperatures between 26–29°C and the shift from thermotaxis to nest building is seen between 6 and 10 g of material. Our results suggest that under normal laboratory temperatures, mice should be provided with no less than 6 grams of nesting material, but up to 10 grams may be needed to alleviate thermal distress under typical temperatures

New Abundant Microbial Groups in Aquatic Hypersaline Environments

We describe the microbiota of two hypersaline saltern ponds, one of intermediate salinity (19%) and a NaCl saturated crystallizer pond (37%) using pyrosequencing. The analyses of these metagenomes (nearly 784 Mb) reaffirmed the vast dominance of Haloquadratum walsbyi but also revealed novel, abundant and previously unsuspected microbial groups. We describe for the first time, a group of low GC Actinobacteria, related to freshwater Actinobacteria, abundant in low and intermediate salinities. Metagenomic assembly revealed three new abundant microbes: a low-GC euryarchaeon with the lowest GC content described for any euryarchaeon, a high-GC euryarchaeon and a gammaproteobacterium related to Alkalilimnicola and Nitrococcus. Multiple displacement amplification and sequencing of the genome from a single archaeal cell of the new low GC euryarchaeon suggest a photoheterotrophic and polysaccharide-degrading lifestyle and its relatedness to the recently described lineage of Nanohaloarchaea. These discoveries reveal the combined power of an unbiased metagenomic and single cell genomic approach

Competing Activities of Heterotrimeric G Proteins in Drosophila Wing Maturation

Drosophila genome encodes six alpha-subunits of heterotrimeric G proteins. The Gαs alpha-subunit is involved in the post-eclosion wing maturation, which consists of the epithelial-mesenchymal transition and cell death, accompanied by unfolding of the pupal wing into the firm adult flight organ. Here we show that another alpha-subunit Gαo can specifically antagonize the Gαs activities by competing for the Gβ13F/Gγ1 subunits of the heterotrimeric Gs protein complex. Loss of Gβ13F, Gγ1, or Gαs, but not any other G protein subunit, results in prevention of post-eclosion cell death and failure of the wing expansion. However, cell death prevention alone is not sufficient to induce the expansion defect, suggesting that the failure of epithelial-mesenchymal transition is key to the folded wing phenotypes. Overactivation of Gαs with cholera toxin mimics expression of constitutively activated Gαs and promotes wing blistering due to precocious cell death. In contrast, co-overexpression of Gβ13F and Gγ1 does not produce wing blistering, revealing the passive role of the Gβγ in the Gαs-mediated activation of apoptosis, but hinting at the possible function of Gβγ in the epithelial-mesenchymal transition. Our results provide a comprehensive functional analysis of the heterotrimeric G protein proteome in the late stages of Drosophila wing development

Twenty years of stereotype threat research: A review of psychological mediators

This systematic literature review appraises critically the mediating variables of stereotype threat. A bibliographic search was conducted across electronic databases between 1995 and 2015. The search identified 45 experiments from 38 articles and 17 unique proposed mediators that were categorized into affective/subjective (n = 6), cognitive (n = 7) and motivational mechanisms (n = 4). Empirical support was accrued for mediators such as anxiety, negative thinking, and mind-wandering, which are suggested to co-opt working memory resources under stereotype threat. Other research points to the assertion that stereotype threatened individuals may be motivated to disconfirm negative stereotypes, which can have a paradoxical effect of hampering performance. However, stereotype threat appears to affect diverse social groups in different ways, with no one mediator providing unequivocal empirical support. Underpinned by the multi-threat framework, the discussion postulates that different forms of stereotype threat may be mediated by distinct mechanisms

Deciphering the Role of RND Efflux Transporters in Burkholderia cenocepacia

Burkholderia cenocepacia J2315 is representative of a highly problematic group of cystic fibrosis (CF) pathogens. Eradication of B. cenocepacia is very difficult with the antimicrobial therapy being ineffective due to its high resistance to clinically relevant antimicrobial agents and disinfectants. RND (Resistance-Nodulation-Cell Division) efflux pumps are known to be among the mediators of multidrug resistance in Gram-negative bacteria. Since the significance of the 16 RND efflux systems present in B. cenocepacia (named RND-1 to -16) has been only partially determined, the aim of this work was to analyze mutants of B. cenocepacia strain J2315 impaired in RND-4 and RND-9 efflux systems, and assess their role in the efflux of toxic compounds. The transcriptomes of mutants deleted individually in RND-4 and RND-9 (named D4 and D9), and a double-mutant in both efflux pumps (named D4-D9), were compared to that of the wild-type B. cenocepacia using microarray analysis. Microarray data were confirmed by qRT-PCR, phenotypic experiments, and by Phenotype MicroArray analysis. The data revealed that RND-4 made a significant contribution to the antibiotic resistance of B. cenocepacia, whereas RND-9 was only marginally involved in this process. Moreover, the double mutant D4-D9 showed a phenotype and an expression profile similar to D4. The microarray data showed that motility and chemotaxis-related genes appeared to be up-regulated in both D4 and D4–D9 strains. In contrast, these gene sets were down-regulated or expressed at levels similar to J2315 in the D9 mutant. Biofilm production was enhanced in all mutants. Overall, these results indicate that in B. cenocepacia RND pumps play a wider role than just in drug resistance, influencing additional phenotypic traits important for pathogenesis

Recruitment and Activation of Pancreatic Stellate Cells from the Bone Marrow in Pancreatic Cancer: A Model of Tumor-Host Interaction

BACKGROUND AND AIMS: Chronic pancreatitis and pancreatic cancer are characterised by extensive stellate cell mediated fibrosis, and current therapeutic development includes targeting pancreatic cancer stroma and tumor-host interactions. Recent evidence has suggested that circulating bone marrow derived stem cells (BMDC) contribute to solid organs. We aimed to define the role of circulating haematopoietic cells in the normal and diseased pancreas. METHODS: Whole bone marrow was harvested from male β-actin-EGFP donor mice and transplanted into irradiated female recipient C57/BL6 mice. Chronic pancreatitis was induced with repeat injections of caerulein, while carcinogenesis was induced with an intrapancreatic injection of dimethylbenzanthracene (DMBA). Phenotype of engrafted donor-derived cells within the pancreas was assessed by immunohistochemistry, immunofluorescence and in situ hybridisation. RESULTS: GFP positive cells were visible in the exocrine pancreatic epithelia from 3 months post transplantation. These exhibited acinar morphology and were positive for amylase and peanut agglutinin. Mice administered caerulein developed chronic pancreatitis while DMBA mice exhibited precursor lesions and pancreatic cancer. No acinar cells were identified to be donor-derived upon cessation of cerulein treatment, however rare occurrences of bone marrow-derived acinar cells were observed during pancreatic regeneration. Increased recruitment of BMDC was observed within the desmoplastic stroma, contributing to the activated pancreatic stellate cell (PaSC) population in both diseases. Expression of stellate cell markers CELSR3, PBX1 and GFAP was observed in BMD cancer-associated PaSCs, however cancer-associated, but not pancreatitis-associated BMD PaSCs, expressed the cancer PaSC specific marker CELSR3. CONCLUSIONS: This study demonstrates that BMDC can incorporate into the pancreas and adopt the differentiated state of the exocrine compartment. BMDC that contribute to the activated PaSC population in chronic pancreatitis and pancreatic cancer have different phenotypes, and may play important roles in these diseases. Further, bone marrow transplantation may provide a useful model for the study of tumor-host interactions in cancer and pancreatitis

Severe traumatic injury during long duration spaceflight: Light years beyond ATLS

Traumatic injury strikes unexpectedly among the healthiest members of the human population, and has been an inevitable companion of exploration throughout history. In space flight beyond the Earth's orbit, NASA considers trauma to be the highest level of concern regarding the probable incidence versus impact on mission and health. Because of limited resources, medical care will have to focus on the conditions most likely to occur, as well as those with the most significant impact on the crew and mission. Although the relative risk of disabling injuries is significantly higher than traumatic deaths on earth, either issue would have catastrophic implications during space flight. As a result this review focuses on serious life-threatening injuries during space flight as determined by a NASA consensus conference attended by experts in all aspects of injury and space flight

Determinants of consumers’ intentions to share knowledge and intentions to purchase on s-commerce sites: incorporating attitudes toward persuasion attempts into a social exchange model

This research explores s-commerce users’ intentions to purchase and to share knowledge by incorporating ‘attitudes toward persuasion attempts,’ ‘ease of use,’ and ‘perceived usefulness’ into a social exchange theory model. A survey using an on-site purposive sampling technique was used to recruit the respondents, and an interception technique was used to approach the consumers. A total of 471 Korean consumers participated in this research. Based on 471 Korean social-commerce users, our results reveal that social exchange belief factors and a site’s usability affect user satisfaction, which subsequently affects users’ intentions to purchase and to share knowledge. In addition, attitudes toward persuasion attempts moderate the effect of satisfaction on users’ purchase intentions. Keywords: social exchange theory, attitudes toward persuasion attempts, intention to share knowledge, social exchange belief