Project description:Nitrous oxide (N(2)O) is a major radiative forcing and stratospheric ozone-depleting gas emitted from terrestrial and aquatic ecosystems. It can be transformed to nitrogen gas (N(2)) by bacteria and archaea harboring the N(2)O reductase (N(2)OR), which is the only known N(2)O sink in the biosphere. Despite its crucial role in mitigating N(2)O emissions, knowledge of the N(2)OR in the environment remains limited. Here, we report a comprehensive phylogenetic analysis of the nosZ gene coding the N(2)OR in genomes retrieved from public databases. The resulting phylogeny revealed two distinct clades of nosZ, with one unaccounted for in studies investigating N(2)O-reducing communities. Examination of N(2)OR structural elements not considered in the phylogeny revealed that the two clades differ in their signal peptides, indicating differences in the translocation pathway of the N(2)OR across the membrane. Sequencing of environmental clones of the previously undetected nosZ lineage in various environments showed that it is widespread and diverse. Using quantitative PCR, we demonstrate that this clade was most often at least as abundant as the other, thereby more than doubling the known extent of the overall N(2)O-reducing community in the environment. Furthermore, we observed that the relative abundance of nosZ from either clade varied among habitat types and environmental conditions. Our results indicate a physiological dichotomy in the diversity of N(2)O-reducing microorganisms, which might be of importance for understanding the relationship between the diversity of N(2)O-reducing microorganisms and N(2)O reduction in different ecosystems.
Project description:At present, a lack of consensus exists regarding the clinical impact of osteoporosis on alveolar bone metabolism during implant osseointegration. While limited preclinical and clinical evidence demonstrates a negative influence of osteoporosis on dental extraction socket healing, no preclinical studies offer data on the results of implant placement in 6-mo-old, ovariectomized (OVX) Sprague-Dawley rats. This study aimed to investigate the outcomes of dental tooth extraction socket healing and implant placement in a rodent model of osteoporosis following daily vehicle (VEH) or abaloparatide (ABL) administration. Micro-CT and histologic analysis demonstrated signs of delayed wound healing, consistent with alveolar osteitis in extraction sockets following 42 d of healing in both the VEH and ABL groups. In a semiquantitative histological analysis, the OVX-ABL group demonstrated a tendency for improved socket regeneration with a 3-fold greater rate for moderate socket healing when compared to the OVX-VEH group (43% vs 14%), however, this finding was not statistically significant (p=.11). No significant differences were observed between vehicle and test groups in terms of implant outcomes (BMD and bone volume/total volume) at 14- and 21-d post-implant placement. Abaloparatide (ABL) significantly increased BMD of the femoral shaft and intact maxillary alveolar bone sites in OVX animals, demonstrating the therapeutic potential for oral hard tissue regeneration. The present model involving estrogen-deficiency-induced bone loss demonstrated an impaired healing response to dental extraction and implant installation.
Project description:N2O-reducing bacteria have been examined and harnessed to develop technologies that reduce the emission of N2O, a greenhouse gas produced by biological nitrogen removal. Recent investigations using omics and physiological activity approaches have revealed the ecophysiologies of these bacteria during nitrogen removal. Nevertheless, their involvement in anammox processes remain unclear. Therefore, the present study investigated the identity, genetic potential, and activity of N2O reducers in an anammox reactor. We hypothesized that N2O is limiting for N2O-reducing bacteria and an exogeneous N2O supply enriches as-yet-uncultured N2O-reducing bacteria. We conducted a 1200-day incubation of N2O-reducing bacteria in an anammox consortium using gas-permeable membrane biofilm reactors (MBfRs), which efficiently supply N2O in a bubbleless form directly to a biofilm grown on a gas-permeable membrane. A 15N tracer test indicated that the supply of N2O resulted in an enriched biomass with a higher N2O sink potential. Quantitative PCR and 16S rRNA amplicon sequencing revealed Clade II nosZ type-carrying N2O-reducing bacteria as protagonists of N2O sinks. Shotgun metagenomics showed the genetic potentials of the predominant Clade II nosZ-carrying bacteria, Anaerolineae and Ignavibacteria in MBfRs. Gemmatimonadota and non-anammox Planctomycetota increased their abundance in MBfRs despite their overall lower abundance. The implication of N2O as an inhibitory compound scavenging vitamin B12, which is essential for the synthesis of methionine, suggested its limited suppressive effect on the growth of B12-dependent bacteria, including N2O reducers. We identified Dehalococcoidia and Clostridia as predominant N2O sinks in an anammox consortium fed exogenous N2O because of the higher metabolic potential of vitamin B12-dependent biosynthesis.
Project description:Nitrous oxide (N2O), a potent greenhouse gas in the atmosphere, is produced mostly from aquatic ecosystems, to which algae substantially contribute. However, mechanisms of N2O production by photosynthetic organisms are poorly described. Here we show that the green microalga Chlamydomonas reinhardtii reduces NO into N2O using the photosynthetic electron transport. Through the study of C. reinhardtii mutants deficient in flavodiiron proteins (FLVs) or in a cytochrome p450 (CYP55), we show that FLVs contribute to NO reduction in the light, while CYP55 operates in the dark. Both pathways are active when NO is produced in vivo during the reduction of nitrites and participate in NO homeostasis. Furthermore, NO reduction by both pathways is restricted to chlorophytes, organisms particularly abundant in ocean N2O-producing hot spots. Our results provide a mechanistic understanding of N2O production in eukaryotic phototrophs and represent an important step toward a comprehensive assessment of greenhouse gas emission by aquatic ecosystems.
Project description:A large variety of aquatic animals was found to emit the potent greenhouse gas nitrous oxide when nitrate was present in the environment. The emission was ascribed to denitrification by ingested bacteria in the anoxic animal gut, and the exceptionally high N(2)O-to-N(2) production ratio suggested delayed induction of the last step of denitrification. Filter- and deposit-feeding animal species showed the highest rates of nitrous oxide emission and predators the lowest, probably reflecting the different amounts of denitrifying bacteria in the diet. We estimate that nitrous oxide emission by aquatic animals is quantitatively important in nitrate-rich aquatic environments like freshwater, coastal marine, and deep-sea ecosystems. The contribution of this source to overall nitrous oxide emission from aquatic environments might further increase because of the projected increase of nitrate availability in tropical regions and the numeric dominance of filter- and deposit-feeders in eutrophic ecosystems.
Project description:BackgroundThis study compared the safety and efficacy of nitrous oxide (N2O)/midazolam and N2O/promethazine for dental treatment of uncooperative children.Materials and methodsIn this randomized, cross-over, clinical trial investigation Eighteen healthy uncooperative children with a pair of similar teeth requiring the same treatment were included. Combination of N2O/midazolam was given in one visit, where N2O/promethazine was administrated in the other appointment for each patient in a cross-over manner. Oxygen saturation and heart rate as well as behavior parameters according to Houpt behavior scales were recorded. Postoperatively, patients' anxiety and parents' satisfaction were assessed by visual analog score and a questionnaire, respectively. Data were analyzed using Wilcoxon' s signed rank test and Paired t-tests with a P value set at 0.05.ResultsPhysiologic parameters were within normal limit in both groups. Children in midazolam group were significantly deeper sedated compared to other groups. In the first phase, children sedated with midazolam behaved superiorly in comparison to promethazine, while there was no difference at the final phase of the treatment between the two groups.ConclusionBoth of the drug combinations resulted in acceptable, efficient, and safe sedation outcomes.
Project description:Although the interaction between anxiety and attention is considered crucial for learning and performance in mathematics, few studies have examined these cognitive and affective predictors in a single framework or explored the role of sustained attention in promoting children's arithmetic performance, using traditional linear analyses and latent profile analysis (LPA). In this paper, state anxieties (in a math test and in an attention test situation), general anxiety traits, sustained attention (performance-based test and attention deficit/hyperactivity disorder (ADHD) self-ratings) and math achievement of 403 fourth and fifth graders (55.8% girls) were assessed. A negative correlation between state anxiety prior to the math test and arithmetic achievements was identified, even when controlling for other non-math related state anxieties and general anxiety. Sustained attention was a strong predictor of arithmetic achievement and functioned as a moderator in the anxiety-performance link. LPA identified six distinct profiles that revealed a complex relationship with arithmetic fluency. The weakest achievement was found for a specific math anxiety subgroup. The findings highlight the important role of the interaction of anxiety and sustained attention in children's ability to perform math and enable new conclusions about the specific nature of math anxiety. Implications for future research are discussed.