Structure and molecular mechanism of a nucleobase-cation-symport-1 family transporter

The nucleobase-cation-symport-1 (NCS1) transporters are essential components of salvage pathways for nucleobases and related metabolites. Here, we report the 2.85-angstrom resolution structure of the NCS1 benzyl-hydantoin transporter, Mhp1, from Microbacterium liquefaciens. Mhp1 contains 12 transmembrane helices, 10 of which are arranged in two inverted repeats of five helices. The structures of the outward-facing open and substrate-bound occluded conformations were solved, showing how the outward-facing cavity closes upon binding of substrate. Comparisons with the leucine transporter LeuT(Aa) and the galactose transporter vSGLT reveal that the outward- and inward-facing cavities are symmetrically arranged on opposite sides of the membrane. The reciprocal opening and closing of these cavities is synchronized by the inverted repeat helices 3 and 8, providing the structural basis of the alternating access model for membrane transport.     

Distribution of mercury species in soil from a mercury-contaminated site

The distribution of mercury species was determined in soil from a site with Hg contamination. Mercury contamination was primarily confined to the top 40 cm of soil, and the concentration of total Hg ranged from 0.5 to 3000 µg Hg g^?1. Of total Hg present, we determined that 91% was inorganic, 0.01% organic (as methyl Hg), and 6% elemental Hg. Furthermore, of total inorganic Hg present, 85% was in the insoluble mercuric sulfide form. Thus, of total Hg present in soil at this contaminated site, 91% was in the relatively insoluble HgS and Hg⁰ forms.     

The Solar Acoustic Spectrum and Eigenmode Parameters

The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances of the sun from data sets lasting 36 days. The frequency resolution of a single data set is 0.321 microhertz. For frequencies averaged over the azimuthal order m, the median formal error is 0.044 microhertz, and the associated median fractional error is 1.6 x 10(-5). For a 3-year data set, the fractional error is expected to be 3 x 10(-6). The GONG m-averaged frequency measurements differ from other helioseismic data sets by 0.03 to 0.08 microhertz. The differences arise from a combination of systematic errors, random errors, and possible changes in solar structure.     

Clinical and clinicopathologic features of dogs that consumed foodborne hepatotoxic aflatoxins: 72 cases (2005-2006)

OBJECTIVE: To characterize clinical signs, clinicopathologic features, treatments, and survival in dogs with naturally acquired foodborne aflatoxicosis. DESIGN: Retrospective case series. ANIMALS: 72 dogs that consumed aflatoxin-contaminated commercial dog food. PROCEDURES: Medical records of affected dogs were reviewed. Between December 2005 and March 2006, dogs were identified as having foodborne aflatoxin hepatotoxicosis on the basis of the history of consumption of contaminated food or characteristic histopathologic lesions (subject dog or a recently deceased dog in the same household or kennel). Recorded information included signalment, clinical features, clinicopathologic test results, treatments, and survival. Data were analyzed by survival status. RESULTS: Most dogs were of large breeds from breeding kennels. No significant differences were found in age or weight between 26 (36%) survivor dogs and 46 (64%) nonsurvivor dogs. Severity of clinical signs varied widely; 7 dogs died abruptly. In order of onset, clinical features included anorexia, lethargy, vomiting, jaundice, diarrhea (melena, hematochezia), abdominal effusion, peripheral edema, and terminal encephalopathy and hemorrhagic diathesis. Common clinicopathologic features included coagulopathic and electrolyte disturbances, hypoproteinemia, increased serum liver enzyme activities, hyperbilirubinemia, and hypocholesterolemia. Cytologic hepatocellular lipid vacuolation was confirmed in 11 dogs examined. In comparisons of clinicopathologic test results between survivor and nonsurvivor dogs, only granular cylindruria (7/21 dogs) consistently predicted death. Best early markers of aflatoxicosis were low plasma activities of anticoagulant proteins (protein C, antithrombin) and hypocholesterolemia. Despite aggressive treatment, many but not all severely affected dogs died. CONCLUSIONS AND CLINICAL RELEVANCE: Serum liver enzyme activities and bilirubin concentration were unreliable early markers of aflatoxin hepatotoxicosis in dogs. Hypocholesterolemia and decreased plasma protein C and antithrombin activities may function as exposure biomarkers.     

Nutritional responses in rainbow trout (Oncorhynchus mykiss) fed diets with different physical qualities at stable or variable environmental conditions

Rainbow trout with initial body weight 1144 g were fed two diets with high (feed A) or low (feed B) water stability for 6 weeks. During the last 2 weeks either stable or fluctuating oxygen saturation, salinity and temperature was introduced. High water stability of the feed was associated with harder pellets, less dust formation and less broken pellets compared to feed with low water stability. During the first 4 weeks, feed intake was 23% higher in trout fed diet B than in those fed diet A. Fluctuating environment resulted in a severe drop in feed intake for both dietary groups. At termination of the trial, stomachs of trout fed feed B contained mashed pellets and free water and oil. Stomachs of trout fed feed A contained more intact pellets and little fluid. The apparent digestibility of protein, starch, dry matter and energy was highest in feed A. The apparent digestibility of P and Zn was highest at stable environment, and the absorption of P was highest from feed A. In conclusion, physical quality affected the nutritional value of the feeds, and differences in nutritional value at stable or fluctuating environment appeared to be related to feed intake.     

A new ornithological record,Pechora Pipit Anthus gustavi Swinhoe,1863,from Xinjiang

On 15 September,2010,a Pechora Pipit Anthus gustavi Swinhoe was found in the Hami prefecture(41°13’N and 93°29’E,1,143 m a.s.l.),Xinjiang,during the period of a comprehensive scientific survey in Lop Nur region.The bird,which was photographed,is a new avian record for Xinjiang.The pipit reproduces in northern Eurasia,mainly in wide meadows and low hills,and can be found in open forests and nearby residential areas in the process of on migration.The species is an insectivore and is a rare migrant or vagrant in Xinjiang.The geographical distribution,character,habitat,ecological habit and subspecies of the Pechora Pipit were discussed in this paper.     

Competitive exclusion of Yersinia enterocolitica biotype 4, serotype O:3 by Yersinia enterocolitica biotype 1A,serotype O:6,30 in tissue culture and in pigs

AIMS: To study the adhesion properties of a biotype 4, serotype O:3 (human pathogenic) strain of Yersinia enterocolitica and to determine if adhesion in vitro and colonisation in vivo can be prevented by competition with a biotype 1A, serotype O:6,30 (non-pathogenic) strain. To study interaction between Y. enterocolitica biotype 4, serotype O:3 and cultured epithelial cells using the synthetic tripeptide arginine-glycine-aspartic acid (RGD).

METHODS: The human intestinal epithelial (HEp-2) cell line was used for in vitro studies. Inocula of Y. enterocolitica biotype 4, serotype O:3 radiolabelled using tritium were incubated with HEp-2 cells and RGD tripeptide, or with Y. enterocolitica biotype 1A, serotype O:6,30 sequentially or concurrently, then washed and lysed, and radioactivity measured to determine the effect of RGD on adhesion, and competitive exclusion of pathogenic by non-pathogenic bacteria. For in vivo studies, two groups of 5-week-old piglets (n=5/group) were sequentially inoculated orally with 5x10⁹ colony forming units (cfu) of either a non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica followed by a pathogenic biotype 4, serotype O:3 strain, or vice versa. Pigs were monitored for carriage of strains using bacterial culture and a multiplex polymerase chain reaction (PCR).

RESULTS: The RGD tripeptide significantly inhibited adherence of the pathogenic Y. enterocolitica strain to cultured epithelial cells, suggesting that adhesion involved the RGD tripeptide sequence. The non-pathogenic biotype 1A, serotype O:6,30 strain of Y. enterocolitica prevented adhesion of the pathogenic strain to cells in vitro when allowed to adhere first. Pathogenic Y. enterocolitica was consistently isolated from rectal swabs from 80-100% of pigs on all sampling occasions but not from oral swabs after 14 days in pigs first inoculated with the non- pathogenic strain or at 26 days in pigs first inoculated with the pathogenic strain.

CONCLUSIONS: A non-pathogenic strain of Y. enterocolitica reduced adhesion of a human pathogenic strain in vitro but not in vivo.