Genetic analysis of the H-2D region using a new intra-D-region recombinant mouse strain

A rare D-region recombination event which gave rise to the B10.RQDB major histocompatibility complex haplotype has been examined to ascertain the nature of the crossover and to determine which class I genes are present in the new alignment of D-region genes. Serologic analysis have shown that the B10 . RQDB major histocompatibility complex recombinant mouse inherited the H-2Dd gene from the B10.T(6R) parental line and the H-2Db gene from the B10.A(2R) parental line, representing the first example of an intra-D-region crossover resulting from an intercross. Previous molecular genetic analyses of the d and b haplotypes revealed structural diversity in the organization of their D-region gene clusters. Hence, the D region is comprised of five class I genes in the d haplotype and only one in the b haplotype. Because allelic relationships among the various D-region genes are not defined, either a homologous or nonhomologous alignment of genes has generated the RQDB crossover. Therefore, the possibility that all three D-region antigen-presenting molecules (Dd, Ld, and Db) might be encoded by the RQDB haplotype was examined. Fluorescence-activated cell sorter and cytotoxic T lymphocyte analyses revealed no detectable levels of H-2Ld cell-surface expression, confirming earlier studies with antibody-mediated cytotoxicity and immunoprecipitation. Southern blot analysis localized the recombination point to within a 1-kb region at the centromeric end of the H-2Ld gene on the B10 . T(6R) chromosome in a region of high homology to the H-2Db gene on the B10 . A(2R) chromosome. Together, these studies define the D region of the RQDB haplotype as containing the five class I genes: Dd, D2d, D3d, D4d, and Db. In addition to providing insight into rare recombination events in the D region, the B10.RQDB mouse should be a useful tool for exploring the function of D-region genes.     

Microbiological quality of frozen shrimp and lobster tail in the retail market.

The microbiological quality of three frozen shrimp products and frozen lobster tail at the retail level was determined. The number of retail units of the four products examined and the geometric means for aerobic plate counts at 30 and 35 degrees C, respectively, were: 1,464 units of cooked, peeled shrimp--13,000 and 7,200 per g; 1,468 units of raw, peeled shrimp--860,000 and 300,000 per g; 1,300 units of raw, in-shell shrimp--800,000 and 300,000 per g; 1,315 units of lobster tail--140,000 and 42,000 per g. Geometric means for coliform, Escherichia coli, and Staphylococcus aureus counts for all products were < 10 per g.     

The effect of deoxyguanosine on human lymphocyte function. II. Analysis of the interference with B lymphocyte differentiation in vitro

The differentiation of normal human peripheral blood B lymphocytes into plasma cells in vitro, studied in mononuclear cells stimulated with PWM or in purified B cells stimulated with a T cell-replacing factor (TRF), can be inhibited by both deoxyguanosine (dGuo) and guanosine. The mechanism underlying this effect, which differs from the in vivo findings in PNP deficiency, was analyzed. dGuo toxicity can be antagonized by hypoxanthine but not by deoxycytidine. PNP-deficient and HGPRT-deficient B lymphocytes are not sensitive to the intoxicating properties of (deoxy)guanosine. Inhibition of PNP activity in normal B lymphocytes by 8-aminoguanosine decreases the sensitivity for dGuo intoxication. Incubation of purified B cells (stimulated with TRF) with dGuo leads to increased intracellular levels of guanosine di- and triphosphate (GDP and GTP), whereas deoxyguanosine triphosphate (dGTP) levels remain low. These observations lead to the conclusion that inhibition of B lymphocyte differentiation by dGuo is brought about by one of the end products of the pathway starting with degradation of dGuo by PNP, followed by guanine salvage by HGPRT, and possibly further phosphorylation of GMP into GDP and GTP. According to this mechanism, B lymphocyte differentiation in PNP deficiency is not sensitive to (deoxy)guanosine; because of the absence of PNP activity, these cells cannot accumulate GMP, GDP, and GTP, and therefore escape dGuo intoxication.     

Validation of tiger beetles as distinct family (Coleoptera: Cicindelidae), review and reclassification of tribal relationships

The higher-level taxonomy of tiger beetles is re-evaluated in light of recent publications based on large taxon sets and a large number of genetic loci. These studies have demonstrated that tiger beetles are a distinct family, Cicindelidae Latreille, sister to the Carabidae Latreille (ground beetles) or Trachypachidae Thomson (false ground beetles) + Carabidae. Recent phylogenies have also recovered consistent patterns in higher-level relationships within the tiger beetles that challenge the traditional taxonomic framework, most of which is more than a century old. These phylogenetic results are reviewed along with concordant morphological characters to create an updated higher-level classification. The subfamily Collyrinae Csiki is not supported by any modern data. We recognize six tribes, Manticorini Laporte (new sense), Megacephalini Laporte (new sense), Collyridini Brullé, Ctenostomatini Laporte, Cicindelini Latreille and the reinstated Oxycheilini Chaudoir (with emended spelling).     

Sixty-Seven Years of Land-Use Change in Southern Costa Rica

Habitat loss and fragmentation of forests are among the biggest threats to biodiversity and associated ecosystem services in tropical landscapes. We use the vicinity of the Las Cruces Biological Station in southern Costa Rica as a regional case study to document seven decades of land-use change in one of the most intensively studied sites in the Neotropics. Though the premontane wet forest was largely intact in 1947, a wave of immigration in 1952 initiated rapid changes over a short period. Overall forest cover was reduced during each time interval analyzed (1947–1960, 1960–1980, 1980–1997, 1997–2014), although the vast majority of forest loss (>90%) occurred during the first two time intervals (1947–1960, 1960–1980) with an annual deforestation rate of 2.14% and 3.86%, respectively. The rate dropped to <2% thereafter and has been offset by forest recovery in fallow areas more recently, but overall forest cover has continued to decline. Approximately 27.9% of the study area is forested currently. Concomitantly, the region shifted from a single contiguous forest to a series of progressively smaller forest fragments with each successive survey. A strong reduction in the amount of core habitat was paralleled by an increased proportion of edge habitat, due to the irregular shape of many forest fragments. Structural connectivity, however, remains high, with an expansive network of >100 km of linear strips of vegetation within a 3 km radius of the station, which may facilitate landscape-level movement for some species. Despite the extent of forest loss, a substantial number of regional landscape-level studies over the past two decades have demonstrated the persistence of many groups of organisms such as birds and mammals. Nonetheless, the continued decline in the quantity and quality of remaining habitat (~30% of remaining forest is secondary), as well as the threat of an extinction debt (or time lag in species loss), may result in the extirpation of additional species if more proactive conservation measures are not taken to reverse current trends–a pattern that reflects many other tropical regions the world over.     

Genome sequence of the marine bacterium Marinobacter hydrocarbonoclasticus SP17, which forms biofilms on hydrophobic organic compounds

Marinobacter hydrocarbonoclasticus SP17 forms biofilms specifically at the interface between water and hydrophobic organic compounds (HOCs) that are used as carbon and energy sources. Biofilm formation at the HOC-water interface has been recognized as a strategy to overcome the low availability of these nearly water-insoluble substrates. Here, we present the genome sequence of SP17, which could provide further insights into the mechanisms of enhancement of HOCs assimilation through biofilm formation.