Biogeochemistry of hypersaline microbial mats illustrates the dynamics of modern microbial ecosystems and the early evolution of the biosphere

Photosynthetic microbial mats are remarkably complete self-sustaining ecosystems at the millimeter scale, yet they have substantially affected environmental processes on a planetary scale. These mats may be direct descendents of the most ancient biological communities in which even oxygenic photosynthesis might have developed. Photosynthetic mats are excellent natural laboratories to help us to learn how microbial populations associate to control dynamic biogeochemical gradients.     

Comparative ecology of H2 cycling in sedimentary and phototrophic ecosystems

The simple biochemistry of H₂ is critical to a large number of microbial processes, affecting the interaction of organisms with each other and with the environment. The sensitivity of each of these processes to H₂ can be described collectively, through the quantitative language of thermodynamics. A necessary prerequisite is to understand the factors that, in turn, control H₂ partial pressures. These factors are assessed for two distinctly different ecosystems. In anoxic sediments from Cape Lookout Bight (North Carolina, USA), H₂ partial pressures are strictly maintained at low, steady-state levels by H₂-consuming organisms, in a fashion that can be quantitatively predicted by simple thermodynamic calculations. In phototrophic microbial mats from Baja California (Mexico), H₂ partial pressures are controlled by the activity of light-sensitive H₂-producing organisms, and consequently fluctuate over orders of magnitude on a daily basis. The differences in H₂ cycling can subsequently impact any of the H₂-sensitive microbial processes in these systems. In one example, methanogenesis in Cape Lookout Bight sediments is completely suppressed through the efficient consumption of H₂ by sulfate-reducing bacteria; in contrast, elevated levels of H₂ prevail in the producer-controlled phototrophic system, and methanogenesis occurs readily in the presence of 40 mM sulfate. This revised version was published online in August 2006 with corrections to the Cover Date.     

Reverse flux through cardiac NADP(+)-isocitrate dehydrogenase under normoxia and ischemia

Little is known about the role of mitochondrial NADP(+)-isocitrate dehydrogenase (NADP(+)-ICDH) in the heart, where this enzyme shows its highest expression and activity. We tested the hypothesis that in the heart, NADP(+)-ICDH operates in the reverse direction of the citric acid cycle (CAC) and thereby may contribute to the fine regulation of CAC activity (Sazanov and Jackson, FEBS Lett 344: 109-116, 1994). We documented a reverse flux through this enzyme in rat hearts perfused with the medium-chain fatty acid octanoate using [U-(13)C(5)]glutamate and mass isotopomer analysis of tissue citrate (Comte et al., J Biol Chem 272: 26117-26124, 1997). In this study, we assessed the significance of our previous finding by perfusing hearts with long-chain fatty acids and tested the effects of changes in O(2) supply. We showed that under all of these conditions citrate was enriched in an isotopomer containing five (13)C atoms. This isotopomer can only be explained by substrate flux through reversal of the NADP(+)-ICDH reaction, which is evaluated at 3-7% of flux through citrate synthase. Small variations in reversal fluxes induced by low-flow ischemia that mimicked hibernation occurred despite major changes in contractile function and O(2) consumption of the heart as well as citrate and succinate release rates and tissue levels. Our data show a reverse flux through NADP(+)-ICDH and support its hypothesized role in the fine regulation of CAC activity in the normoxic and O(2)-deprived heart.     

The importance of isometric maximum strength and peak rate-of-force development in sprint cycling

This study was designed to investigate the relationship of whole-body maximum strength to variables potentially associated with track sprint-cycling success. These variables included body composition, power measures, coach's rank, and sprint-cycling times. The study was carried out in 2 parts. The first part (n = 30) served as a pilot for the second part (n = 20). Subjects for both parts ranged from international-caliber sprint cyclists to local-level cyclists. Maximum strength was measured using an isometric midthigh pull (IPF). Explosive strength was measured as the peak rate-of-force development (IPRFD) from the isometric force-time curve. Peak power was estimated from countermovement (CMJPP) and static vertical jumps (SJPP) and measured by modified Wingate tests. Athletes were ranked by the U.S. national cycling coach (part 1). Sprint times (from a standing start) were measured using timing gates placed at 25, 82.5, 165, 247.5, and 330 m of an outdoor velodrome (part 2). Maximum strength (both absolute and body-mass corrected) and explosive strength were shown to be strongly correlated with jump and Wingate power. Additionally, maximum strength was strongly correlated with both coach's rank (parts 1 and 2) and sprint cycling times (part 2). The results suggest that larger, stronger sprint cyclists have an advantage in producing power and are generally faster sprint cyclists.     

An Integrated Global Analysis of Compartmentalized HRAS Signaling

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Population change in hyper-oceanic liverworts before and after hydroelectric power development: a preliminary study

Introduction. The best sites for oceanic bryophytes are typically in ravines that offer good potential for hydroelectric power (HEP) development. This preliminary study is the first to investigate population change in oceanic bryophytes of conservation concern at a site subject to HEP development.

Methods. Populations of five hyperoceanic liverworts were measured, Aphanolejeunea microscopica, Drepanolejeunea hamatifolia, Harpalejeunea molleri, Jubula hutchinsiae and Radula voluta, at two time periods, before and after HEP installation.

Results. Spanning almost four years, results reveal a dynamic system, with significant change in fine-scale distribution patterns, including many colony extinctions and colonisations. About 23% of colony losses of A. microscopica, D. hamatifolia and H. molleri appeared to result from exclusion by larger bryophytes, involving at least 17 species, in particular Ctenidium molluscum.

Conclusions. Inference with regards to effects of the HEP is not advised from this type of preliminary before and after study, based at a single site without controls. Given rapid recent growth of small HEP development and the enormous future potential, both in Britain and around the world, it is important to build upon this work and undertake comprehensive studies to detect possible impacts on bryophytes of conservation concern.     

The nocturnal larvae of a specialist folivore perform better on Chromolaena odorata leaves from a shaded environment

Increasing evidence suggests that individuals of the same plant species occurring in different microhabitats often show a degree of phenotypic and phytochemical variation. Consequently, insect herbivores associated with such plant species must deal with environment‐mediated changes or variability in the traits of their host plants. In this study, we examined the effects of habitat condition (shaded vs. full‐sun habitats) on plant traits and leaf characteristics of the invasive alien plant, Chromolaena odorata (L.) King & Robinson (Asteraceae). In addition, the performance was evaluated in two generations of a specialist folivore, Pareuchaetes insulata (Walker) (Lepidoptera: Erebidae: Arctiinae), on leaves obtained from both shaded and full‐sun habitats. The study was done in an area where the insect was introduced as a biological control agent. Leaves growing in shade were less tough, had higher water and nitrogen content, and lower total non‐structural carbohydrate, compared with leaves growing in full sun. Plants growing in shade had longer leaves and were taller, but above‐ground biomass was significantly reduced compared with plants growing in full sun. In both generations (parents and offspring), P. insulata developed faster and had larger pupal mass, increased growth rate, and higher fecundity when reared on shaded foliage compared with full‐sun foliage. Although immature survival and adult longevity did not differ between habitats, Maw's host suitability index indicated that shaded leaves were more suitable for the growth and reproduction of P. insulata. We suggest that the benefits obtained by P. insulata feeding on shaded foliage are associated with reduced toughness and enhanced nitrogen and water content of leaves. These results demonstrate that light‐mediated changes in plant traits and leaf characteristics can affect insect folivore performance.     

Will "Combined Prevention" Eliminate Racial/Ethnic Disparities in HIV Infection among Persons Who Inject Drugs in New York City?

It has not been determined whether implementation of combined prevention programming for persons who inject drugs reduce racial/ethnic disparities in HIV infection. We examine racial/ethnic disparities in New York City among persons who inject drugs after implementation of the New York City Condom Social Marketing Program in 2007. Quantitative interviews and HIV testing were conducted among persons who inject drugs entering Mount Sinai Beth Israel drug treatment (2007–2014). 703 persons who inject drugs who began injecting after implementation of large-scale syringe exchange were included in the analyses. Factors independently associated with being HIV seropositive were identified and a published model was used to estimate HIV infections due to sexual transmission. Overall HIV prevalence was 4%; Whites 1%, African-Americans 17%, and Hispanics 4%. Adjusted odds ratios were 21.0 (95% CI 5.7, 77.5) for African-Americans to Whites and 4.5 (95% CI 1.3, 16.3) for Hispanics to Whites. There was an overall significant trend towards reduced HIV prevalence over time (adjusted odd ratio = 0.7 per year, 95% confidence interval (0.6–0.8). An estimated 75% or more of the HIV infections were due to sexual transmission. Racial/ethnic disparities among persons who inject drugs were not significantly different from previous disparities. Reducing these persistent disparities may require new interventions (treatment as prevention, pre-exposure prophylaxis) for all racial/ethnic groups.     

Investigating biological activity spectrum for novel quinoline analogues

The lack of the wide spectrum of biological data is an important obstacle preventing the efficient molecular design. Quinoline derivatives are known to exhibit a variety of biological effects. In the current publication, we tested a series of novel quinoline analogues for their photosynthesis-inhibiting activity (the inhibition of photosynthetic electron transport in spinach chloroplasts (Spinacia oleracea L.) and the reduction of chlorophyll content in Chlorella vulgaris Beij.). Moreover, antiproliferative activity was measured using SK-N-MC neuroepithelioma cell line. We described the structure-activity relationships (SAR) between the chemical structure and biological effects of the synthesized compounds. We also measured the lipophilicity of the novel compounds by means of the RP-HPLC and illustrate the relationships between the RP-HPLC retention parameter logK (the logarithm of capacity factor K) and logP data calculated by available programs.