A 50 000-dalton anorexigenic protein from urine

A potent, homogeneous, 50 kDa protein which transiently depresses food intake of rats up to 24 h after injection was isolated from rat urine. It was prepared from an ethanolic benzoic acid precipatate of urine. The material was subjected to DEAE-Sephacel chromatography, whereupon four fractions (DEAE pools a, b, c, and d) were obtained. The latter three contained anorexigenic activity. DEAE pools b and c were subjected to further purification on colums of Sephacryl S-300 eluted with buffer containing 8 M urea. One of the subfractions of DEAE pool b contained only one protein as judged by polyacrylamide gel electrophoresis in sodium dodecyl sulfate. This protein had a molecular weight of 50,000 and was active in reducing 24 h food intake at a dose of 130 μg/100 g bodyweight.     

Carbon-nanotube-modified electrodes for the direct bioelectrochemistry of pseudoazurin

The bioelectrochemistry of the blue copper protein, pseudoazurin, at glassy carbon and platinum electrodes that were modified with single-wall carbon nanotubes (SWNTs) was investigated by multiple scan rate cyclic voltammetry. The protein showed reversible electrochemical behavior at both bare glassy carbon electrodes (GCEs) and SWNT-modified GCEs (SWNT|GCEs); however, direct electrochemistry was not observed at any of the platinum electrodes. The effect of the carbon nanotubes at the GCE was to amplify the current response 1000-fold (nA at bare GCE to μA at SWNT|GCE), increase the apparent diffusion coefficient D _app of the solution-borne protein by three orders of magnitude, from 1.35 × 10⁻¹¹ at bare GCE to 7.06 × 10⁻⁸ cm² s-1 at SWNT|GCE, and increase the heterogeneous electron transfer rate constant k _s threefold, from 1.7 × 10⁻² cm s⁻¹ at bare GCE to 5.3 × 10⁻² cm s⁻¹ at SWNT|GCE. Pseudoazurin was also found to spontaneously adsorb onto the nanotube-modified GCE surface. Well-resolved voltammograms indicating quasi-reversible faradaic responses were obtained for the adsorbed protein in phosphate buffer, with I _pc and I _pa values now greater than corresponding values for solution-borne pseudoazurin at SWNT|GCEs and with significantly reduced ΔE _p values. The largest electron transfer rate constant of 1.7 × 10⁻¹ cm s⁻¹ was achieved with adsorbed pseudoazurin at the SWNT|GCE surface in deaerated buffer solution consistent with its presumed role in anaerobic respiration of some bacteria.     

Effects of emissions from different type of residential heating upon cyclic guanosine monophosphate (cGMP) in blood platelets of residents

We hypothesized that different types of residential heating would be associated with different levels of indoor carbon monoxide (CO) and further that this might result in a differential in the concentration of cyclic 3′:5′ guanosine monophosphate (cGMP) in blood platelets in exposed residents. Individuals, who were recruited from homes using different fuel for heating, donated a venous blood sample in the winter and in the summer. In the winter the median blood platelet cGMP value for the group using liquid propane gas (LPG) was 65% higher than for the group using piped natural gas for heating (p <0.001). Also in the group using LPG, the median concentration of cGMP in the winter was 39% higher than the summer median (p?<?0.003). The mean indoor concentrations of CO were measured over a period of 1 week during the winter and were <1 ppm. We conclude that observed differences were associated with emissions from different types of heating but that CO exposure alone is too low to explain these.     

Reservoir Condition Pore-scale Imaging of Multiple Fluid Phases Using X-ray Microtomography

X-ray microtomography was used to image, at a resolution of 6.6 µm, the pore-scale arrangement of residual carbon dioxide ganglia in the pore-space of a carbonate rock at pressures and temperatures representative of typical formations used for CO₂ storage. Chemical equilibrium between the CO₂, brine and rock phases was maintained using a high pressure high temperature reactor, replicating conditions far away from the injection site. Fluid flow was controlled using high pressure high temperature syringe pumps. To maintain representative in-situ conditions within the micro-CT scanner a carbon fiber high pressure micro-CT coreholder was used. Diffusive CO₂ exchange across the confining sleeve from the pore-space of the rock to the confining fluid was prevented by surrounding the core with a triple wrap of aluminum foil. Reconstructed brine contrast was modeled using a polychromatic x-ray source, and brine composition was chosen to maximize the three phase contrast between the two fluids and the rock. Flexible flow lines were used to reduce forces on the sample during image acquisition, potentially causing unwanted sample motion, a major shortcoming in previous techniques. An internal thermocouple, placed directly adjacent to the rock core, coupled with an external flexible heating wrap and a PID controller was used to maintain a constant temperature within the flow cell. Substantial amounts of CO₂ were trapped, with a residual saturation of 0.203 ± 0.013, and the sizes of larger volume ganglia obey power law distributions, consistent with percolation theory.     

Limnological regime shifts caused by climate warming and Lesser Snow Goose population expansion in the western Hudson Bay Lowlands (Manitoba,Canada)

Shallow lakes are dominant features in subarctic and Arctic landscapes and are responsive to multiple stressors, which can lead to rapid changes in limnological regimes with consequences for aquatic resources. We address this theme in the coastal tundra region of Wapusk National Park, western Hudson Bay Lowlands (Canada), where climate has warmed during the past century and the Lesser Snow Goose (LSG; Chen caerulescens caerulescens) population has grown rapidly during the past ~40 years. Integration of limnological and paleolimnological analyses documents profound responses of productivity, nutrient cycling, and aquatic habitat to warming at three ponds (“WAP 12”, “WAP 20”, and “WAP 21″), and to LSG disturbance at the two ponds located in an active nesting area (WAP 20, WAP 21). Based on multiparameter analysis of ²¹⁰Pb‐dated sediment records from all three ponds, a regime shift occurred between 1875 and 1900 CE marked by a transition from low productivity, turbid, and nutrient‐poor conditions of the Little Ice Age to conditions of higher productivity, lower nitrogen availability, and the development of benthic biofilm habitat as a result of climate warming. Beginning in the mid‐1970s, sediment records from WAP 20 and WAP 21 reveal a second regime shift characterized by accelerated productivity and increased nitrogen availability. Coupled with 3 years of limnological data, results suggest that increased productivity at WAP 20 and WAP 21 led to atmospheric CO₂ invasion to meet algal photosynthetic demand. This limnological regime shift is attributed to an increase in the supply of catchment‐derived nutrients from the arrival of LSG and their subsequent disturbance to the landscape. Collectively, findings discriminate the consequences of warming and LSG disturbance on tundra ponds from which we identify a suite of sensitive limnological and paleolimnological measures that can be utilized to inform aquatic ecosystem monitoring.     

Carbon labelling influences on consumers’ behaviour: A system dynamics approach

This paper proposes a system dynamics approach to model consumers’ responses to carbon labelled products by showing how the number of consumers is varied visually. Three categories of the consumers are defined, i.e., potential, ordinary and loyal consumers, to reflect their different preferences to the carbon labelled products. Two case scenarios are presented to demonstrate the application of the proposed approach, in which the consumers’ preferences to the carbon labelled and non-labelled milk, as well as the carbon labelled milk with different fat contents are simulated. The result shows that both of the two scenarios have the similar variation in the number of the defined consumers, and especially the number of loyal consumer accounts for the largest proportion. In addition, public awareness, education level, critical premium and perceived consumer effectiveness are identified as key factors to have an impact on the purchasing behaviour. The limitations of this approach are then discussed, laying a foundation for further work.     

Observation of superoxide production during catalysis of Bacillus subtilis oxalate decarboxylase at pH 4

This contribution describes the trapping of the hydroperoxyl radical at a pH of 4 during turnover of wild-type oxalate decarboxylase and its T165V mutant using the spin-trap BMPO. Radicals were detected and identified by a combination of EPR and mass spectrometry. Superoxide, or its conjugate acid, the hydroperoxyl radical, is expected as an intermediate in the decarboxylation and oxidation reactions of the oxalate monoanion, both of which are promoted by oxalate decarboxylase. Another intermediate, the carbon dioxide radical anion was also observed. The quantitative yields of superoxide trapping are similar in the wild type and the mutant while it is significantly different for the trapping of the carbon dioxide radical anion. This suggests that the two radicals are released from different sites of the protein.     

A NOTE ON THE UNUSUAL CRUSTACEAN COMMUNITY OF A TEMPORARY POOL IN THE NORTHERN CAPE

Summary

A temporary pool in a dry stream bed traversing Grootvloer Pan in the Northern Cape was inhabited by fifteen branchiopod and calanoid copepod crustacean species. There was an unusually high number of congeneric species in the pool; in the class Branchiopoda, five Streptocephalus species and four Daphnia species were collected. In addition, two species of the calanoid genus Metadiaptomus were identified. The high species richness was not related to habitat diversity, pool size or difference in body size of each species. Three species (Streptocephalus purcelli, S. gracilis and Metadiaptomus capensis) had previously been collected only from the winter-rainfall areas of the Cape. Episodic flooding in the Northern Cape in 1988 may have resulted in the unusual community in the Grootvloer temporary pool.