Adaptations to nitrogen availability drive ecological divergence of chemosynthetic symbionts.

Bacterial symbionts, with their shorter generation times and capacity for horizontal gene transfer (HGT), play a critical role in allowing marine organisms to cope with environmental change. The closure of the Isthmus of Panama created distinct environmental conditions in the Tropical Eastern Pacific (TEP) and Caribbean, offering a "natural experiment" for studying how closely related animals evolve and adapt under environmental change. However, the role of bacterial symbionts in this process is often overlooked. We sequenced the genomes of endosymbiotic bacteria in two sets of sister species of chemosymbiotic bivalves from the genera Codakia and Ctena (family Lucinidae) collected on either side of the Isthmus, to investigate how differing environmental conditions have influenced the selection of symbionts and their metabolic capabilities. The lucinid sister species hosted different Candidatus Thiodiazotropha symbionts and only those from the Caribbean had the genetic potential for nitrogen fixation, while those from the TEP did not. Interestingly, this nitrogen-fixing ability did not correspond to symbiont phylogeny, suggesting convergent evolution of nitrogen fixation potential under nutrient-poor conditions. Reconstructing the evolutionary history of the nifHDKT operon by including other lucinid symbiont genomes from around the world further revealed that the last common ancestor (LCA) of Ca. Thiodiazotropha lacked nif genes, and populations in oligotrophic habitats later re-acquired the nif operon through HGT from the Sedimenticola symbiont lineage. Our study suggests that HGT of the nif operon has facilitated niche diversification of the globally distributed Ca. Thiodiazotropha endolucinida species clade. It highlights the importance of nitrogen availability in driving the ecological diversification of chemosynthetic symbiont species and the role that bacterial symbionts may play in the adaptation of marine organisms to changing environmental conditions.

Modeling Trans-Spinal Direct Current Stimulation in the Presence of Spinal Implants.

Trans-spinal direct current stimulation (tsDCS) is a technique considered for the treatment of corticospinal damage or dysfunction. TsDCS aims to induce functional modulation in the corticospinal circuitry via a direct current (DC) generated an electric field (EF). To ensure subject safety, subjects with metallic implants are generally excluded from receiving neural dc stimulation. However, spinal injuries often require spinal implants for stabilization. Our goal was to investigate implant imposed changes to EF and current density (CD) magnitude during tsDCS. We simulated the EF and CD, generated by tsDCS in the presence of spinal rods for two electrode configurations and four implant locations along the spinal cord. For each scenario, a no-implant condition was computed for comparison. We assessed changes in EF and CD at the implant location and the EF inside the spinal cord. Our results show that implant presence was able to influence peak CD, compared to the no-implant condition. Nonetheless, the highest calculated CD levels were a factor six lower than those thought to lead to hazardous tissue-damaging effects. Additionally, implant presence did not considerably affect the average EF inside the spinal cord. Our findings do therefore not indicate potentially unsafe CD levels, or significant alterations to stimulation intensity inside the spinal cord, caused by a spinal implant during tsDCS. Our results are relevant to the safety of transcutaneous spinal stimulation applied in the presence of metallic spinal implants.

Modeling trans-spinal direct current stimulation for the modulation of the lumbar spinal motor pathways.

OBJECTIVE: Trans-spinal direct current stimulation (tsDCS) is a potential new technique for the treatment of spinal cord injury (SCI). TsDCS aims to facilitate plastic changes in the neural pathways of the spinal cord with a positive effect on SCI recovery. To establish tsDCS as a possible treatment option for SCI, it is essential to gain a better understanding of its cause and effects. We seek to understand the acute effect of tsDCS, including the generated electric field (EF) and its polarization effect on the spinal circuits, to determine a cellular target. We further ask how these findings can be interpreted to explain published experimental results. APPROACH: We use a realistic full body finite element volume conductor model to calculate the EF of a 2.5 mA direct current for three different electrode configurations. We apply the calculated electric field to realistic motoneuron models to investigate static changes in membrane resting potential. The results are combined with existing knowledge about the theoretical effect on a neuronal level and implemented into an existing lumbar spinal network model to simulate the resulting changes on a network level. MAIN RESULTS: Across electrode configurations, the maximum EF inside the spinal cord ranged from 0.47 V m-1 to 0.82 V m-1. Axon terminal polarization was identified to be the dominant cellular target. Also, differences in electrode placement have a large influence on axon terminal polarization. Comparison between the simulated acute effects and the electrophysiological long-term changes observed in human tsDCS studies suggest an inverse relationship between the two. SIGNIFICANCE: We provide methods and knowledge for better understanding the effects of tsDCS and serve as a basis for a more targeted and optimized application of tsDCS.

Sleep quality in pregnancy during treatment with Bryophyllum pinnatum: an observational study.

INTRODUCTION: Poor sleep quality in pregnancy is frequent. A treatment with sedatives is problematic due to possible adverse effects for mother and embryo/foetus. In the present study, we investigated the sedative effect of Bryophyllum pinnatum, a phytotherapeutic medication used in anthroposophic medicine. In previous clinical studies on its tocolytic effect, B. pinnatum showed a good risk/benefit ratio for mother and child. A recent analysis of the prescribing pattern for B. pinnatum in a network of anthroposophic physicians revealed sleep disorders as one of the most frequent diagnoses for which these preparations are prescribed. MATERIALS AND METHODS: In this prospective, multi-centre, observational study, pregnant women suffering from sleep problems were treated with B. pinnatum (350mg tablets, 50% leaf press juice, Weleda AG, Arlesheim, dosage at physician's consideration). Sleep quality, daily sleepiness and fatigue were assessed with the aid of standardised questionnaires, at the beginning of the treatment and after 2 weeks. Possible adverse drug reactions perceived by the patients during the treatment were recorded. RESULTS: The number of wake-ups, as well as the subjective quality of sleep was significantly improved at the end of the treatment with B. pinnatum. The Epworth Sleeping Scale decreased, indicating a decrease of the tiredness during the day. There was, however, no evidence for prolongation of the sleep duration, reduction in the time to fall asleep, as well as change in the Fatigue Severity Scale after B. pinnatum. No serious adverse drug reactions were detected. CONCLUSION: B. pinnatum is a suitable treatment of sleep problems in pregnancy. The data of this study encourage further clinical investigations on the use of B. pinnatum in sleep disorders.

The assembly-activating protein promotes capsid assembly of different adeno-associated virus serotypes.

Adeno-associated virus type 2 (AAV2) capsid assembly requires the expression of a virally encoded assembly-activating protein (AAP). By providing AAP together with the capsid protein VP3, capsids are formed that are composed of VP3 only. Electron cryomicroscopy analysis of assembled VP3-only capsids revealed all characteristics of the wild-type AAV2 capsids. However, in contrast to capsids assembled from VP1, VP2, and VP3, the pores of VP3-only capsids were more restricted at the inside of the 5-fold symmetry axes, and globules could not be detected below the 2-fold symmetry axes. By comparing the capsid assembly of several AAV serotypes with AAP protein from AAV2 (AAP-2), we show that AAP-2 is able to efficiently stimulate capsid formation of VP3 derived from several serotypes, as demonstrated for AAV1, AAV2, AAV8, and AAV9. Capsid formation, by coexpressing AAV1-, AAV2-, or AAV5-VP3 with AAP-1, AAP-2, or AAP-5 revealed the ability of AAP-1 and AAP-2 to complement each other in AAV1 and AAV2 assembly, whereas for AAV5 assembly more specific conditions are required. Sequence alignment of predicted AAP proteins from the known AAV serotypes indicates a high degree of homology of all serotypes to AAP-2 with some divergence for AAP-4, AAP-5, AAP-11, and AAP-12. Immunolocalization of assembled capsids from different serotypes confirmed the preferred nucleolar localization of capsids, as observed for AAV2; however, AAV8 and AAV9 capsids could also be detected throughout the nucleus. Taken together, the data show that AAV capsid assembly of different AAV serotypes also requires the assistance of AAP proteins.

Genetic basis and risk factors for infectious and noninfectious diseases in US Holsteins. I. Estimation of genetic parameters for single diseases and general health.

Health data collected from 1996 to 1999 from 177 herds in Minnesota and Wisconsin were analyzed to establish genetic basis for infectious and noninfectious diseases. Three types of health traits were targeted. First, available infectious conditions were used to identify animals that are superior in their general immunity (including innate immunity) for infectious diseases. Generalized immunity may be thought of as a combination of immune responses to a variety of immune system challenges. Second, single infectious and noninfectious diseases were analyzed separately. Third, infectious reproductive diseases as one category of related conditions, and cystic ovary disease as one category of 3 related noninfectious ovary disorders were studied. Data were analyzed using a threshold model that included herd, calving year, season of calving, and parity as cross-classified fixed factors; and sire and cow within sires as random effects. Days at risk and days in milk at the beginning of a record were included by fitting the days as continuous covariates in the model. A heritability value of 0.202 +/- 0.083 was estimated for generalized immunity. Heritability values of 0.141 and 0.161 were estimated for uterine infection and mastitis, respectively. Heritability of single noninfectious disorders ranged from 0.087 to 0.349. The amount of additive genetic variance recovered in the underlying scale of noninfectious disorders tended to zero when combining multiple conditions. The study supports combining infectious diseases into categories of interest but we do not recommend the same approach for noninfectious disorders.

Genetic variation in bovine mononuclear leukocyte responses to dexamethasone.

The objective of this study was to determine whether bovine mononuclear leukocytes exhibit genetic variability prior to and after a glucocorticoid hormone challenge in vivo. Test animals included 60 pedigreed Holstein bulls treated on 3 consecutive days with dexamethasone and 5 untreated control bulls. Eight indicator traits of leukocyte responsiveness to dexamethasone included the percentages of circulating B cells, T cells (CD4, CD8, and workshop cluster 1 molecule expressed by bovine gammadelta T cell), major histocompatibility complex (MHC) I and II expressing cells, and mean expressions of surface MHC I and MHC II on circulating cells. Blood for this work was collected from each test bull 10 times before, during, and after dexamethasone administration, with corresponding samples taken for control bulls. Random regression models with treatment-specific serial correlation were applied to the leukocyte data sets to estimate genetic and nongenetic sources of variation in baseline and recovery aspects of the traits. All traits responded predictably to glucocorticoid challenge. Genetic variation was observed in baseline measurements of all traits, with heritability estimates ranging from 0.21 +/- 0.03 to 0.60 +/- 0.06. Genetic variation in linear recovery from nadir values following dexamethasone administration was significant only for percentage CD4, percentage CD8, and for surface expression of MHC II. The genetic covariance between basal and linear recovery was positive and significant for percentage CD4, percentage CD8, and MHC II expression. The bovine lymphocyte antigen DRB3.2 locus accounted for significant proportions of total variation in percentage MHC II cells and MHC I expression. These results suggest that genetic variability exists for important basal and glucocorticoid-modified phenotypes of bovine mononuclear leukocytes, implying that immunocompetence traits impacted by this stress hormone may be enhanced by genetic selection.

Correlations among body condition scores from various sources, dairy form, and cow health from the United States and Denmark.

The objectives of this study were to estimate genetic correlations among body condition scores (BCS) from various sources, dairy form, and measures of cow health. Body condition score and dairy form evaluated during routine type appraisal was obtained from the Holstein Association USA, Inc. A second set of BCS was obtained from Dairy Records Managements Systems (DRMS) and was recorded by producers that use PCDART dairy management software. Disease observations were obtained from recorded veterinarian treatments in several dairy herds in the United States. Estimated breeding values for diseases in Denmark were also obtained. Genetic correlations among BCS, dairy form, and cow health traits in the United States were generated with sire models. Models included fixed effects for age, DIM, and contemporary group. Random effects included sire, permanent environment, herd-year season for health traits, and error. Predicted transmitting abilities (PTA) for BCS and dairy form were correlated with estimated breeding values for disease in Denmark. The genetic correlation estimate between BCS from DRMS and BCS from the Holstein Association USA, Inc., was 0.85. The genetic correlation estimate between BCS and a composite of all diseases in the United States was -0.79, and PTA for BCS was favorably correlated with an index of resistance to disease other than mastitis in Denmark (0.27). Dairy form was positively correlated with a composite of all diseases in the United States (0.85) and was unfavorably correlated with an index for resistance to disease other than mastitis in Denmark (-0.29). Adjustment for protein yield PTA had a minimal affect on correlations between PTA for BCS or dairy form and disease in Denmark. Selection for higher body condition or lower dairy form with continued selection for yield may slow deterioration in cow health as a correlated response to selection for increased yield.

Genetics of health traits in Holstein cattle.

Incidences of 22 health related traits were analyzed for 11,008 lactation records provided by 21st Century Genetics. Traits were analyzed both individually and grouped into one of five health categories. Significant sources of variation included herd-year, lactation, cow, and sire effects. Genetic parameters were estimated with multiple-trait REML. Repeatability and heritability estimates were low to moderate. Estimates ranged from .09 to .57 for repeatability and from .02 to .21 for heritability when individual traits were pooled by health category. Reproductive and respiratory traits were the least heritable (less than .10); mammary and locomotive traits were slightly higher (less than .20); and digestive category was most heritable (.21). Genetic correlations of mature equivalent milk with number of inseminations and other reproductive problems were positive (antagonistic), but those with incidences of other health problems were negative. Phenotypic correlations among mature equivalent milk and fat with individual health traits and categories of health traits were small and mostly near zero. Genetic correlations among health traits were positive except for reproduction with mammary and respiratory traits. Phenotypic correlations among health traits were near zero. Results suggest that selection for reduction of health problems is possible. If selection is practiced for improved health, these health traits should be properly weighted relative to production and other traits by the appropriate economic value. Evaluation of animals for health problems should be done on a multiple-trait basis.