BRCA2 function in DNA binding and recombination from a BRCA2-DSS1-ssDNA structure

Mutations in the BRCA2 (breast cancer susceptibility gene 2) tumor suppressor lead to chromosomal instability due to defects in the repair of double-strand DNA breaks (DSBs) by homologous recombination, but BRCA2's role in this process has been unclear. Here, we present the 3.1 angstrom crystal structure of a approximately 90-kilodalton BRCA2 domain bound to DSS1, which reveals three oligonucleotide-binding (OB) folds and a helix-turn-helix (HTH) motif. We also (i) demonstrate that this BRCA2 domain binds single-stranded DNA, (ii) present its 3.5 angstrom structure bound to oligo(dT)9, (iii) provide data that implicate the HTH motif in dsDNA binding, and (iv) show that BRCA2 stimulates RAD51-mediated recombination in vitro. These findings establish that BRCA2 functions directly in homologous recombination and provide a structural and biochemical basis for understanding the loss of recombination-mediated DSB repair in BRCA2-associated cancers.     

Detection and measurement of benzimidazole resistance alleles in Haemonchus contortus using real-time PCR with locked nucleic acid Taqman probes

Benzimidazole resistance is a common problem in parasitic nematodes of ruminants and early detection is vital if its spread is to be monitored and controlled. Real time PCR offers a fast and reliable method for rapid detection and measurement of resistance allele frequencies. In Haemonchus contortus a single nucleotide polymorphism at codon 200 of the beta-tubulin gene (TTC to TAC), causing a phenylalanine to tyrosine amino acid substitution, has been shown to be involved in many cases of resistance. Locked nucleic acid (LNA) Taqman probes have been used in this work to detect and measure the frequency of resistance alleles in individual and multiple H. contortus. Detection of resistant genotypes using LNA Taqman probes in individual H. contortus is simpler and more reliable than with previously described assays. Measurement of the frequency of resistant alleles in populations of H. contortus was achieved by using the cycle threshold (C(t)) values and a standard curve derived from populations with known allele frequencies. Results using the LNA probes on individual and multiple worms gave similar results to the allele specific PCR. The sensitivity of the LNA assay on multiple nematodes allowed reliable detection of > or = 10% resistance allele frequency. Using the final fluorescence method, it was possible to differentiate populations with approximately 0, 5 and 10% resistance allele frequencies.     

Holding wild Snow crab,Chionoecetes opilio: effects of stocking density and feeding on survival and injury

In this study the effects of different stocking densities on survival, injury and weight of captive male snow crab were examined. The first experiment (I) was carried out in square plastic tanks (700 L) with stocking densities of 100 (L), 150 (M) and 200 kg m^?3 (H) for 30 days. In a second experiment (II) snow crabs were kept at a stocking density of 50 kg m^?3 and were either fed (F) or not fed (S) for the same period of 35 days. The last experiment (III), was carried out with stocking densities of 25 kg m^?3 for 21 days with two groups, one with inactivated claw and one without rubber bands, with three replicates per treatment. In the first experiment mortality (H = 27, M = 26 and L = 36%) and occurrence of injuries (H = 27, M = 20 and L = 16%) were high in all groups. The weight loss during the experimental period was; H = 15.3, M = 10.9 and L = 15.5 g, and was not significant different between the groups. In experiment II the mortality (F = 13% and S = 14%) and injuries were lower (F = 12% and S = 17%). The average weight increased in the fed treatment and decreased in the starved treatments. In the last experiment there was no mortality in any of the groups and the levels of injury were low (5% and 7%). The results show that adult male snow crab cannot be stored at densities equal to or higher than 25 kg m^?3 for 3 weeks without risk of mortality.     

Measuring density effects on growth and survival of two size classes of juvenile sea urchins (Strongylocentrotus droebachiensis) held in sea‐based holding systems and impacts on holding system design and management

Assessing density in intensive sea urchin culture systems by measuring the percentage coverage of available surface area is an effective means of calculating the available space within a holding system, the proximity of the animals in the system to each other and the probable effects of the stocking density. The results of this study show that density plays a critical role in regard to both somatic growth (increase in test diameter measured in millimetres) as well as mortality of juvenile sea urchins ranging in size from 5 mm to 26 mm test diameter (the size range tested in the current experiments). These effects appear to be greater for smaller urchins. The critical percentage coverage densities are in the order of 50%‐60% coverage for juvenile sea urchins, and the authors advise farmers growing Strongylocentrotus droebachiensis to maintain stocking densities below this point and to reduce the stocking densities as and when stocks reach these critical density points. Percentage cover must be constantly monitored as the results from this study indicate that the growth rates of juvenile urchins can alter percentage coverage rapidly and reductions in density may be required as frequently as every 3‐4 months at the early juvenile stage. Holding system design should take these factors into account and incorporate a method of rapidly reducing stocking densities with minimal stress and handling of sea urchin stocks.     

Chitosan as a wall material for a microencapsulated delivery system for Macrobrachium rosenbergii (de Man) larvae

Chitosan has been widely accepted as a wall material for preparing microcapsules of various purposes in human medicine. The possibility of using chitosan as a wall material for microencapsulating nutrients and drugs for aquaculture purposes, specifically to Macrobrachium rosenbergii larvae was evaluated in this study. Two types of chitosan-coated microcapsules were prepared using either acetone (MEC-A) or NaOH (MEC-N) as the cross-linking agents. They were compared with a microbound diet relative to total leaching of nutrients and free amino acids (FAA). Among the microcapsules, MEC-N showed the lowest level of total leaching of nutrients (23.3%) during 5 h of immersion in seawater and released 65% FAA after 60 min. During laboratory trials, 75% larvae had accepted the MEC-N capsule. The results of the study suggest that chitosan can be used as a wall material for preparing microcapsules to deliver drugs and nutrients to M. rosenbergii larvae.     

Endocarditis caused by Corynebacterium sp in a dog

Mitral valve bacterial endocarditis, caused by Corynebacterium sp, was diagnosed in a dog. The bacteria had characteristics unlike those commonly recognized for most species of Corynebacterium. The primary source of bacteremia was suspected to be a pilonidal cyst of the sacrum. The dog was treated with a first-generation cephalosporin for 6 weeks, and the pilonidal cyst was surgically removed. Physical examination 1 year after initial examination revealed no abnormalities other than a cardiac murmur. On echocardiographic examination 1 year after treatment, the vegetative lesion was still present; however, chamber dimensions had returned to normal. Wall thickness and contractility remained increased.     

Variability in the antinutritional constituents in greengram Vigna radiata

Five greengram varieties, viz. Mg 161, M₃, Co₂, Pusa 8793 and Pusa baisakhi, were analyzed for phytic acid, tannic acid and trypsin activity. Significant varietal variation in tannin (310 to 400 mg percent), phytic acid (201.33 to 265.33 mg percent) and trypsin inhibitor activity (55.74 to 97.70 TIU/mg) were observed.     

Geochemical conditions in groundwater systems: Implications for the attenuation of agricultural nitrate

Nitrate resulting from nitrogen fertilisers used in Agriculture is a widespread contaminant of shallow groundwater and causes adverse effects on human, animal and ecosystem health. In order to evaluate the full extent of groundwater nitrate contamination, and how it might evolve in time, it is essential to understand controls on aquifer assimilative capacity. This level of understanding will also help to better target policies and incentives aimed at controlling the amount of nitrate entering downstream water systems.The potential for nitrate attenuation in groundwater was assessed by examining the concentration and distribution pattern of electron donors such as dissolved organic carbon (DOC), ferrous iron, and redox indicators such as dissolved oxygen (DO) and Eh in 57 monitoring bores on the lower Burdekin coastal floodplain, one of Queensland's and Australia's premier irrigation districts. Nitrate concentrations ranged from 0.1 to 14.4 mg/L NO₃-N but were mostly undetectable in bores close to the coast. Groundwater age dates suggest that while there are nitrate ‘hot spots’ in certain areas, some or most of the nitrate is being consumed on its way to the ocean. Low nitrate concentrations were coupled with high ferrous concentrations. The low DO concentrations (<2 mg/L) and high ferrous concentrations found in 55% of the bores indicate that redox conditions are suitable for nitrate attenuation by either denitrification or dissimilatory nitrate reduction to ammonium. The reducing environment may be associated with the high DOC concentrations (up to 82 mg C/L) found in these groundwaters. Furthermore, high levels of ferrous iron found in the Ayr area combined with the wide spread geographical distribution of DOC indicate that these areas have a high potential for sustaining geochemical processes that reduces nitrate levels. The distribution of geochemical indicators also suggests that the shallower depths (<15 m) of the groundwater systems have more potential for nitrate reduction than the deeper depths. The map identifying areas within the lower Burdekin with most potential for denitrification is a valuable first step in helping to understand and manage the fate of nitrate entering the groundwater.     

Surface deterioration of wood-flour polypropylene composites by weathering trials

The market for wood-fiber plastic composites (WPCs) is expanding rapidly in many countries including Japan, where WPCs are mainly used for exterior products. In such applications, WPCs undergo undesirable color change, chalking, and shrinkage and swelling, and accordingly there is a need to better understand the mechanisms responsible for the weathering of WPC and develop methods of improving their weathering resistance. In this study, weatherability of WPC was assessed by natural and accelerated weathering trials. Discoloration (whitening) of WPC during exposure was caused by degradation of both wood and plastic. Darker color pigments as additives improved the color stability of WPC; however, chalking on the surfaces still occurred. The color stability of WPC was improved by application of exterior coatings. Preweathering of WPC (before coatings were applied) increased the absorption of coatings by the WPC and had a positive effect on the color stability and prevented chalking of the composites. Parts of this study were presented at the IUFRO XXII World Congress Meeting, Brisbane, August 2005 and the IAWPS 2005, Yokohama, November 2005