East Greenland and Barents Sea polar bears (Ursus maritimus): adaptive variation between two populations using skull morphometrics as an indicator of environmental and genetic differences

A morphometric study was conducted on four skull traits of 37 male and 18 female adult East Greenland polar bears (Ursus maritimus) collected 1892-1968, and on 54 male and 44 female adult Barents Sea polar bears collected 1950-1969. The aim was to compare differences in size and shape of the bear skulls using a multivariate approach, characterizing the variation between the two populations using morphometric traits as an indicator of environmental and genetic differences. Mixture analysis testing for geographic differentiation within each population revealed three clusters for Barents Sea males and three clusters for Barents Sea females. East Greenland consisted of one female and one male cluster. A principal component analysis (PCA) conducted on the clusters defined by the mixture analysis, showed that East Greenland and Barents Sea polar bear populations overlapped to a large degree, especially with regards to females. Multivariate analyses of variance (MANOVA) showed no significant differences in morphometric means between the two populations, but differences were detected between clusters from each respective geographic locality. To estimate the importance of genetics and environment in the morphometric differences between the bears, a PCA was performed on the covariance matrix derived from the skull measurements. Skull trait size (PC1) explained approx. 80% of the morphometric variation, whereas shape (PC2) defined approx. 15%, indicating some genetic differentiation. Hence, both environmental and genetic factors seem to have contributed to the observed skull differences between the two populations. Overall, results indicate that many Barents Sea polar bears are morphometrically similar to the East Greenland ones, suggesting an exchange of individuals between the two populations. Furthermore, a subpopulation structure in the Barents Sea population was also indicated from the present analyses, which should be considered with regards to future management decisions.     

Muscular ETB receptors develop postnatally and are differentially distributed in specific segments of the rat vasculature.

The endothelin/endothelin-receptor system is a key player in the regulation of vascular tone in mammals. We raised and characterized an antiserum against rat ETB receptor and investigated the distribution of ETB receptors in different vascular beds during postnatal development (day 0 through day 28) and in the adult rat. We report the tissue-specific and age-dependent presence of vasoconstrictor ETB receptors. At the time of birth, vascular smooth muscle cells from all tissues examined did not exhibit ETB receptor immunoreactivity. The occurrence of ETB receptor immunoreactivity in the postnatal development was time dependent and started in small coronary and meningeal arteries at day 5, followed by small mesenteric arteries as well as brachial artery and vein at day 14. At day 21, ETB receptors were present in the media of muscular segments of pulmonary artery, large coronary arteries, and intracerebral arterioles. At day 28, ETB receptor immunoreactivity was evident in interlobular renal arteries, vas afferens, and efferens. Large renal arteries, mesenteric artery, and elastic segments of pulmonary arteries, as well as coronary and mesenteric veins, did not exhibit ETB receptor immunoreactivity. These data demonstrate the age-dependent and tissue-specific presence of ETB receptors, mainly on arterial smooth muscle cells in the vascular system of the rat.     

Murine Norovirus: An Intercurrent Variable in a Mouse Model of Bacteria-Induced Inflammatory Bowel Disease

Murine norovirus (MNV) has recently been recognized as a widely prevalent viral pathogen in mouse colonies and causes disease and mortality in mice with impaired innate immunity. We tested the hypothesis that MNV infection would alter disease course and immune responses in mice with inflammatory bowel disease (IBD). FVB.129P2-Abcb1a^tm1Bor N7 (Mdr1a−/−) mice develop spontaneous IBD that is accelerated by infection with Helicobacter bilis. As compared with controls, Mdr1a−/− mice coinfected with MNV4 and H. bilis showed greater weight loss and IBD scores indicative of severe colitis, demonstrating that MNV4 can modulate the progression of IBD. Compared with controls, mice inoculated with MNV4 alone had altered levels of serum biomarkers, and flow cytometric analysis of immune cells from MNV4-infected mice showed changes in both dendritic cell (CD11c⁺) and other nonT cell (CD4⁻ CD8⁻) populations. Dendritic cells isolated from MNV4-infected mice induced higher IFNγ production by polyclonal T cells in vitro at 2 d after infection but not at later time points, indicating that MNV4 infection enhances antigen presentation by dendritic cells early after acute infection. These findings indicate that acute infection with MNV4 is immunomodulatory and alters disease progression in a mouse model of IBD.Abbreviations: DC, dendritic cell; IBD, inflammatory bowel disease; IP, IFNγ–inducible protein; MCP, macrophage chemotactic protein; MLN, mesenteric lymph node; MNV, murine norovirus; TNF, tumor necrosis factorThe genus Norovirus of the family Caliciviridae contains a large number of single-stranded, positive-sense RNA viruses that infect vertebrates, and strains have been identified in humans, cattle, swine, and (most recently) mice.^19,29,34 Murine noroviruses (MNV) are recently recognized pathogens that can cause lethal infection in immunocompromised mice that lack innate immunity.¹⁹ However, MNV did not cause clinical disease in wild-type mice or many other strains of immunodeficient mice, including those lacking the recombination-activating gene (Rag−/−) and inducible nitric oxide synthase deficient mice.^19,35,37 MNV was reported recently to be widespread in laboratory mice and may persist in immunocompetent animals, depending on the strain of MNV used.^15,16,25 Studies in Rag−/− mice and B-cell–deficient strains showed that the acquired immune system plays an important role in the clearance of MNV.^6,19,37 MNV has tropism for dendritic cells (DCs),³⁶ which are important in the presentation of antigens to T cells in draining lymph nodes and in the pathogenesis of inflammatory bowel disease (IBD). Therefore, MNV is a potential confounder for in vivo immunology studies, including murine models of IBD.Idiopathic IBD, which encompasses both ulcerative colitis and Crohn disease, is a widely studied disorder that affects approximately 1.4 million people in the United States.²⁰ Although the precise cause of human IBD has not been elucidated, studies with mouse models have demonstrated that abnormal host responses of the innate and adaptive immune systems to intestinal microbiota are important in the pathogenesis of IBD.^28,38 DCs are the sentinels of the intestinal mucosal barrier and have a pivotal role in the initiation of IBD in response to microbial ligands.³⁹ Alterations in DC responses could lead to persistence of bacterial infection, aberrant activation of the acquired immune system, and (ultimately) tissue damage.³⁸Viral stimulation of DCs leads to activation of adaptive immune responses,¹⁷ including effector T cells, and as demonstrated with murine coronavirus (mouse hepatitis virus), intercurrent viral infections in mice can alter the phenotype of mouse models of human disease.¹⁰ Additional evidence suggests that intercurrent viral infection may enhance disease in human IBD patients.^12,18 Whether infection with MNV alters DC function and, therefore, influences the progression of IBD in mouse models is unclear.Many mouse models of intestinal inflammation develop IBD that is driven by bacterial flora.^9,28 Helicobacter spp. have been shown to drive this process in several mouse models including IL10-deficient, SMAD3-deficient, severe combined immunodeficiency and T-cell–deficient mice.^4,5,13,23 FVB.129P2-Abcb1a^tm1Bor (Mdr1a−/−) mice develop spontaneous IBD that is accelerated by infection with Helicobacter bilis.^21,22 In this report, we tested the hypothesis that infection with MNV can modulate IBD in this mouse model of bacterial-induced disease. We demonstrate that intercurrent MNV4 infection accelerates the progression of bacterial-induced IBD in the Mdr1a−/− mouse and alters the immune responses in this mouse model of IBD.     

Spatiotemporal dynamics of the bacterial microbiota on lacustrine Cladophora glomerata (Chlorophyta)

The branched periphytic green alga Cladophora glomerata, often abundant in nearshore waters of lakes and rivers worldwide, plays important ecosystem roles, some mediated by epibiotic microbiota that benefit from host‐provided surface, organic C, and O₂. Previous microscopy and high‐throughput sequencing studies have indicated surprising epibiont taxonomic and functional diversity, but have not included adequate consideration of sample replication or the potential for spatial and temporal variation. Here, we report the results of 16S rRNA amplicon‐based phylum‐to‐genus taxonomic analysis of Cladophora‐associated bacterial epibiota sampled in replicate from three microsites and at six times during the open‐water season of 2014, from the same lake locale (Picnic Point, Lake Mendota, Dane Co., WI, USA) explored by high‐throughput sequencing studies in two previous years. Statistical methods were used to test null hypotheses that the bacterial community: (i) is homogeneous across microsites tested, and (ii) does not change over the course of a growth season or among successive years. Results indicated a dynamic microbial community that is more strongly influenced by sampling day during the growth season than by microsite variation. A surprising diversity of bacterial genera known to be associated with the key function of methane‐oxidation (methanotrophy), including relatively high‐abundance of Crenothrix, Methylomonas, Methylovulum, and Methylocaldum–showed intraseasonal and interannual variability possibly related to temperature differences, and microsite preferences possibly related to variation in methane abundance. By contrast, a core assemblage of bacterial genera seems to persist over a growth season and from year to year, possibly transmitted by a persistent attached host resting stage.     

The Relationship of Rapid Weight Gain in Infancy to Obesity and Skeletal Maturity in Childhood

Objective: Children with birth weight appropriate for gestational age (AGA) who also demonstrate rapid weight gain in infancy have a greater risk of being overweight or obese during childhood. A concurrent advancement in skeletal maturity would account for their greater size and would, therefore, not necessarily pose a threat of greater risk during adolescence and early adulthood. This study aims to determine whether children with rapid weight gain during infancy have advanced skeletal maturity during childhood. Research Methods and Procedures: One hundred and ninety‐three African children (boys = 108; girls = 85) of normal birth weight and gestational age were assessed from birth to 9 years. Body composition was assessed at 9 years of age by whole‐body DXA, and skeletal maturity was assessed using the Tanner‐Whitehouse II technique. Rapid weight gain in infancy was defined as a +0.67 change in weight‐for‐age Z‐score between birth and 2 years. Results: Rapid weight gain was experienced by over 20% of the sample. Children with rapid weight gain were significantly lighter at birth and significantly taller, heavier, and fatter throughout childhood. Chronological age and Tanner‐Whitehouse II technique skeletal ages at 9 years were not significantly different between groups or between sexes within groups. Discussion: Because AGA children with rapid weight gain have a greater risk of overweight and obesity but are not advanced in skeletal maturity, later adolescent adjustments toward average weight and fatness values are unlikely. The identification and monitoring of such children is of importance in reducing their risk of morbidity.     

Rate variation among nuclear genes and the age of polyploidy in Gossypium

Molecular evolutionary rate variation in Gossypium (cotton) was characterized using sequence data for 48 nuclear genes from both genomes of allotetraploid cotton, models of its diploid progenitors, and an outgroup. Substitution rates varied widely among the 48 genes, with silent and replacement substitution levels varying from 0.018 to 0.162 and from 0.000 to 0.073, respectively, in comparisons between orthologous Gossypium and outgroup sequences. However, about 90% of the genes had silent substitution rates spanning a more narrow threefold range. Because there was no evidence of rate heterogeneity among lineages for any gene and because rates were highly correlated in independent tests, evolutionary rate is inferred to be a property of each gene or its genetic milieu rather than the clade to which it belongs. Evidence from approximately 200,000 nucleotides (40,000 per genome) suggests that polyploidy in Gossypium led to a modest enhancement in rates of nucleotide substitution. Phylogenetic analysis for each gene yielded the topology expected from organismal history, indicating an absence of gene conversion or recombination among homoeologs subsequent to allopolyploid formation. Using the mean synonymous substitution rate calculated across the 48 genes, allopolyploid cotton is estimated to have formed circa 1.5 million years ago (MYA), after divergence of the diploid progenitors about 6.7 MYA.     

A convenient model of severe, high incidence autoimmune gastritis caused by polyclonal effector T cells and without perturbation of regulatory T cells

Autoimmune gastritis results from the breakdown of T cell tolerance to the gastric H(+)/K(+) ATPase. The gastric H(+)/K(+) ATPase is responsible for the acidification of gastric juice and consists of an α subunit (H/Kα) and a β subunit (H/Kβ). Here we show that CD4(+) T cells from H/Kα-deficient mice (H/Kα(-/-)) are highly pathogenic and autoimmune gastritis can be induced in sublethally irradiated wildtype mice by adoptive transfer of unfractionated CD4(+) T cells from H/Kα(-/-) mice. All recipient mice consistently developed the most severe form of autoimmune gastritis 8 weeks after the transfer, featuring hypertrophy of the gastric mucosa, complete depletion of the parietal and zymogenic cells, and presence of autoantibodies to H(+)/K(+) ATPase in the serum. Furthermore, we demonstrated that the disease significantly affected stomach weight and stomach pH of recipient mice. Depletion of parietal cells in this disease model required the presence of both H/Kα and H/Kβ since transfer of H/Kα(-/-) CD4(+) T cells did not result in depletion of parietal cells in H/Kα(-/-) or H/Kβ(-/-) recipient mice. The consistency of disease severity, the use of polyclonal T cells and a specific T cell response to the gastric autoantigen make this an ideal disease model for the study of many aspects of organ-specific autoimmunity including prevention and treatment of the disease.     

Inhibition of Retinoic Acid Biosynthesis by the Bisdichloroacetyldiamine WIN 18,446 Markedly Suppresses Spermatogenesis and Alters Retinoid Metabolism in Mice

Knowledge of the regulation of testicular retinoic acid synthesis is crucial for understanding its role in spermatogenesis. Bisdichloroacetyldiamines strongly inhibit spermatogenesis. We reported previously that one of these compounds, WIN 18,446, potently inhibited spermatogenesis in rabbits by inhibiting retinoic acid synthesis. To understand how WIN 18,446 inhibits retinoic acid synthesis, we characterized its effects on human retinal dehydrogenase ALDH1A2 in vitro as well as its effects on retinoid metabolism in vivo using mice. WIN 18,446 strongly and irreversibly inhibited ALDH1A2 in vitro. In vivo, WIN 18,446 treatment completely abolished spermatogenesis after 4 weeks of treatment and modestly reduced adiposity in mice fed a chow diet. Effects of WIN 18,446 on retinoid concentrations were tissue-dependent. Although lung and liver retinyl ester concentrations were lower in WIN 18,446-treated animals, adipose retinyl ester levels were increased following the treatment. Interestingly, animals treated with WIN 18,446 had significantly higher circulating retinol concentrations compared with control mice. The effect on spermatogenesis by WIN 18,446 was not prevented by simultaneous treatment with retinoic acid, whereas effects on other tissues were partially or completely reversed. Cessation of WIN 18,446 treatment for 4 weeks reversed most retinoid-related phenotypes except for inhibition of spermatogenesis. Our data suggest that WIN 18,446 may be a useful model of systemic acquired retinoic acid deficiency. Given the effects observed in our study, inhibition of retinoic acid biosynthesis may have relevance for the treatment of obesity and in the development of novel male contraceptives.     

Narrow host range of some streptococcal R plasmids

Nine R plasmids originally harbored by Streptococcus faecalis (pIP614, pIP655, pIP685, pIP686, pIP 1075, pIP1017),S. faecium (pIP716, pIP991), and group B Streptococcus (pMV120) wild-type hosts were transferred by conjugation into various recipients in order to study the extent of their intraspecies, interspecies, and intergeneric host range. Recipients were streptococci of groups A, B, C, D (S. faecalis, S. faecium, S. durans, S. bovis), and G, S. sanguis, two S. pneumoniae strains (encapsulated and nonencapsulated), and two strains of different genera, Staphylococcus aureus and Listeria inocua. The plasmids carried different antibiotic resistance markers: tetracycline, high levels of gentamicin and kanamycin or of streptomycin and kanamycin, and chloramphenicol. These R plasmids displayed narrow host ranges. They transferred into S. faecalis recipients and plasmid DNA could be detected in these transconjugants. Occasionally, the R plasmids also transferred into one or more other recipients, but no detectable plasmid DNA could be demonstrated in the new hosts.