Properties of purified squalene-hopene cyclase from Bacillus acidocaldarius

The squalene-hopene cyclase from Bacillus acidocaldarius cytoplasmic membrane, was purified to homogeneity by solubilization with Triton X-100, chromatography on DEAE-cellulose, phenyl Sepharose and two gel-filtration columns. The enzyme monomer had a molecular mass of 75 kDa. The sequence of the first 23 amino acids was determined by Edman degradation. The enzyme activity was efficiently inhibited by n-alkyldimethylammonium halides with alkyl chain lengths between 12 and 18 C atoms. Inhibition was also observed with (5-hydroxycarvacryl)trimethylammonium chloride 1-piperidine carboxylate, dodecyldimethylamine N-oxide, azasqualene and farnesol. Competitive inhibition with dodecyltrimethylammonium bromide, (5-hydroxycarvacryl)trimethylammonium chloride 1-piperidine carboxylate and dodecyldimethylamine N-oxide was demonstrated by Lineweaver-Burk plots.     

Fluorescent probes in model membranes. II. monolayer studies of 2,2′-(vinylenedi-p-phenylene)bisbenzoxazole, d-3-aminodesoxyequilenin and n-octadecylnaphthyl-2-amino-6-sulfonic acid with host-lipid tetradecanoic acid

Film studies at the air-water interface have been carried out for pure films of 2,2′-(vinylenedi-p-phenylene)bisbenzoxazole (VPBO), d-3-aminodesoxy-equlenin (EQ) and N-octadecylnapthyl-2-amino-6-sulfonic acid (ONS), and for mixed films with tetradecanoic acid for the first two fluorescent probes. Pure film isotherms indicate highly rigid non-monomolecular films for both VPBO and EQ, revealing the presence of strong intermolecular forces. In mixed films with tetradecanoic acid VPBO rapidly segregates with resultant film loss over a wide concentration range. EQ, however, can be stabilized by the host-lipid at low concentrations. This, coupled with an ability to only slightly affect the host-lipid liquid-condensed/liquid-expanded phase change, suggests that EQ can be regarded as “non-perturbing” and should be retained in condensed lipid phases.ONS, because of its unusual polar headgroup, resembled hexadecanoic acid more than octadecanoic acid. While difficulties in spreading ONS precluded the study of mixed films, the indications are that it would be a satisfactory expanded lipid state probe if mixing can be brought about.     

Incorporating benthic community changes into hydrochemical-based projections of coral reef calcium carbonate production under ocean acidification

Coral Reefs - The existence of coral reefs is dependent on the production and maintenance of calcium carbonate (CaCO3) framework that is produced through calcification. The net production of CaCO3...     

Can we rely on forest reserves for primate conservation?

Tropical forests contain much of the world's biodiversity, yet their rate of decline is increasing. The strategy most frequently used to protect this biodiversity is to make parks and reserves. While there is a great deal of research on the effectiveness of parks for protecting biodiversity, there is little research on how well extractive reserves conserve biodiversity. Here, we evaluate the effectiveness of four forest reserves in western Uganda at maintaining populations of primates and compare census data from the reserves to data from the neighbouring well‐protected Kibale National Park. The relative abundance of the five most common primates in the park was approximately four times that of the forest reserves. In the forest reserves, evidence of new human encroachment was seen every 500 m, while in the park it was seen every 100,000 m. Two recommendations emerge from our research: (i) for forest reserves, such as those studied here, to have conservation value for primates, extraction must be reduced and (ii) until the long‐term viability of the populations in forest reserves can be ascertained, they should not be considered in estimates of the sizes of endangered species protected ranges.     

The miR-30 MicroRNA Family Targets smoothened to Regulate Hedgehog Signalling in Zebrafish Early Muscle Development

The importance of microRNAs in development is now widely accepted. However, identifying the specific targets of individual microRNAs and understanding their biological significance remains a major challenge. We have used the zebrafish model system to evaluate the expression and function of microRNAs potentially involved in muscle development and study their interaction with predicted target genes. We altered expression of the miR-30 microRNA family and generated phenotypes that mimicked misregulation of the Hedgehog pathway. Inhibition of the miR-30 family increases activity of the pathway, resulting in elevated ptc1 expression and increased numbers of superficial slow-muscle fibres. We show that the transmembrane receptor smoothened is a target of this microRNA family. Our results indicate that fine coordination of smoothened activity by the miR-30 family allows the correct specification and differentiation of distinct muscle cell types during zebrafish embryonic development.     

Thermal ecology and baseline energetic requirements of a large‐bodied ectotherm suggest resilience to climate change

1. Most studies on how rising temperatures will impact terrestrial ectotherms have focused on single populations or multiple sympatric species. Addressing the thermal and energetic implications of climatic variation on multiple allopatric populations of a species will help us better understand how a species may be impacted by altered climates.
2. We used eight years of thermal and behavioral data collected from four populations of Pacific rattlesnakes (Crotalus oreganus) living in climatically distinct habitat types (inland and coastal) to determine the field‐active and laboratory‐preferred body temperatures, thermoregulatory metrics, and maintenance energetic requirements of snakes from each population.
3. Physical models showed that thermal quality was best at coastal sites, but inland snakes thermoregulated more accurately despite being in more thermally constrained environments. Projected increases of 1 and 2°C in ambient temperature result in an increase in overall thermal quality at both coastal and inland sites.
4. Population differences in modeled standard metabolic rate estimates were driven by body size and not field‐active body temperature, with inland snakes requiring 1.6× more food annually than coastal snakes.
5. All snakes thermoregulated with high accuracy, suggesting that small increases in ambient temperature are unlikely to impact the maintenance energetic requirements of individual snakes and that some species of large‐bodied reptiles may be robust to modest thermal perturbations under conservative climate change predictions.

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Mouse model systems of autism spectrum disorder: Replicability and informatics signature

Phenotyping mouse model systems of human disease has proven to be a difficult task, with frequent poor inter‐ and intra‐laboratory replicability, particularly in behavioral domains such as social and cognitive function. However, establishing robust animal model systems with strong construct validity is of fundamental importance as they are central tools for understanding disease pathophysiology and developing therapeutics. To complete our studies of mouse model systems relevant to autism spectrum disorder (ASD), we present a replication of the main findings from our two published studies of five genetic mouse model systems of ASD. To assess the intra‐laboratory robustness of previous results, we chose the two model systems that showed the greatest phenotypic differences, the Shank3/F and Cntnap2, and repeated assessments of general health, activity and social behavior. We additionally explored all five model systems in the same framework, comparing all results obtained in this three‐yearlong effort using informatics techniques to assess commonalities and differences. Our results showed high intra‐laboratory replicability of results, even for those with effect sizes that were not particularly large, suggesting that discrepancies in the literature may be dependent on subtle but pivotal differences in testing conditions, housing enrichment, or background strains and less so on the variability of the behavioral phenotypes. The overall informatics analysis suggests that in our behavioral assays we can separate the set of tested mouse model system into two main classes that in some aspects lie on opposite ends of the behavioral spectrum, supporting the view that autism is not a unitary concept.     

Contribution of Val/Ile87 residue in the extracellular domain in agonist-induced current responses of the human and rat P2X7 receptors

Purinergic Signalling - The P2X7 receptor (P2X7R) is an ATP-gated cation channel with a critical role in many physiological and pathological processes, and shows prominent functional differences...