Comparison between the uptake of nitrous oxide and nitric oxide in the human nose

The absorption of nitrous oxide(N₂O) during unidirectional flowwas compared with the rate of uptake of nitric oxide (NO). At flowrates of 10, 20, and 60 ml/min from one nostril to the other, with thesoft palate closed, the N₂Oreached a steady-state rate of absorption in 5-15 min. The meansuperficial capillary blood flow (n = 5) calculated from solubility and the steady-state rate ofN₂O absorption ranged from 13.3 to15.9 ml/min. The relation between absorption ofN₂O in the nose and capillaryblood flow fits a ventilation-perfusion model used by others todescribe uptake of inert, soluble gases in the rat nose. By contrast,the rate of uptake of NO gas, which is chemically reactive, is25-31 times as great as predicted by just its blood-to-airpartition coefficient. Exogenous NO (16.9 parts/million) did not induce nasal vasodilation as measured with laser Doppler andN₂O absorption methods. Thedifference between the measured rate of uptake of NO and the rate ofuptake attributable to its partition coefficient in blood at the rateof blood flow calculated from N₂Ouptake is probably due to chemical reaction of NO in mucous secretions, nasal tissues, and capillary blood.

     

Sociality, Mate Choice, and Timing of Mating in American Bison (Bison bison): Effects of Large Males

We studied group size, composition, and mating activities in American bison (Bison bison) during rut on the Delta Junction Bison Range in interior Alaska, USA, in 1996 and 1997. Our purpose was to determine the effects of large males (≥5 yr old) on mating and associated activities. Groups with large males were larger than those containing smaller males. Most groups of bison were mixed‐sex (90%), but large males occurred in only one‐half of all groups. Moreover, females in groups with large males were more likely to copulate than those in groups with smaller males, indicating a female preference for large males. Nevertheless, our results are consistent with large males seeking out adult females for mating rather than vice versa. Mating peaked in mid‐August during both the study years and was highly synchronous. Scent marking was coincident with mating, an outcome consistent with a hypothesis of such behavior triggering ovulation. Scent marking by large male bison occurred in both male–male and male–female contexts, but was associated most often with sexual activities. No differences in group size occurred with changes in weather or among vegetation types occupied by bison. Group size of bison, however, was larger with increasing distance from the forest edge, which likely was a response to predation risk in this predator‐rich environment.     

Trophic convergence drives morphological convergence in marine tetrapods

Marine tetrapod clades (e.g. seals, whales) independently adapted to marine life through the Mesozoic and Caenozoic, and provide iconic examples of convergent evolution. Apparent morphological convergence is often explained as the result of adaptation to similar ecological niches. However, quantitative tests of this hypothesis are uncommon. We use dietary data to classify the feeding ecology of extant marine tetrapods and identify patterns in skull and tooth morphology that discriminate trophic groups across clades. Mapping these patterns onto phylogeny reveals coordinated evolutionary shifts in diet and morphology in different marine tetrapod lineages. Similarities in morphology between species with similar diets—even across large phylogenetic distances—are consistent with previous hypotheses that shared functional constraints drive convergent evolution in marine tetrapods.     

The potential impact of second‐generation biofuel landscapes on at‐risk species in the US

The recent increase in corn ethanol production has drawn attention to the environmental sustainability of biofuel production. Environmental assessments of second‐generation biofuel crops (SGBC) have focused primarily on greenhouse gas emissions and water quality. However, expanding the production of cellulosic biomass resources, especially those that require dedicated agricultural land, is also likely to have impacts on biodiversity. We developed an optimization framework for projecting the spatial pattern of SGBC expansion in the United States and intersected these predictions with occurrence data for at‐risk species. In particular, we focused on two candidate perennial grass feedstocks, Panicum virgatum (switchgrass), and Miscanthus × giganteus (Miscanthus). Tradeoffs between biodiversity and economic profitability are assessed using county level data sets of SGBC yield, agricultural land availability, land rents, and at‐risk species occurrences. Results show that future SGBC expansion is likely to occur outside of the Corn Belt, where conventional biofuel feedstocks are currently grown. The set of at‐risk species that could potentially be impacted is therefore likely to be different from the at‐risk species prevalent in the agroecological landscapes of the Upper Midwest that are dominated by corn and soy production. The total number and type of potentially impacted taxa is influenced by several factors, including the total demand for cellulosic biomass, the type of agricultural land used for production, and the method for defining at‐risk species. SGBC production is also concentrated in fewer counties when a national species conservation constraint is combined with a biofuel production mandate. This analysis provides a foundation for future research on species conservation in bioenergy production landscapes and highlights the importance of incorporating biodiversity into broader environmental assessments of biofuel sustainability.     

Infant Male Circumcision: Healthcare Provider Knowledge and Associated Factors

Background and Objectives

The emerging science demonstrates various health benefits associated with infant male circumcision and adult male circumcision; yet rates are declining in the United States. The American Academy of Pediatrics and the Centers for Disease Control and Prevention recommend that healthcare providers present evidence-based risk and benefit information for infant male circumcision to parent(s) and guardian(s). The purpose of this study was to assess providers’ level of infant male circumcision knowledge and to identify the associated characteristics.

Methods

An online survey was administered to healthcare providers in the family medicine, obstetrics, and pediatrics medical specialties at an urban academic health center. To assess infant male circumcision knowledge, a 17 point summary score was constructed to identify level of provider knowledge within the survey.

Results

Ninety-two providers completed the survey. Providers scored high for the following knowledge items: adverse event rates, protects against phimosis and urinary tract infections, and does not prevent hypospadias. Providers scored lower for items related to more recent research: protection against cervical cancer, genital ulcer disease, bacterial vaginosis, and reduction in HIV acquisition. Two models were constructed looking at (1) overall knowledge about male circumcision, and (2) knowledge about male circumcision reduction in HIV acquisition. Pediatricians demonstrated greater overall infant male circumcision knowledge, while obstetricians exhibited significantly greater knowledge for the HIV acquisition item.

Conclusion

Providers’ knowledge levels regarding the risks and benefits of infant male circumcision are highly variable, indicating the need for system-based educational interventions.