Porcine-specific hemoglobin saturation measurements.

The determination of O(2) consumption by using arteriovenous O(2) content differences is dependent on accurate oxyhemoglobin saturation measurements. Because swine are a common experimental species, we describe the validation of CO-oximeter for porcine-specific oxyhemoglobin saturation. After developing a nonlinear mathematical model of the porcine oxyhemoglobin saturation curve, we made 366 porcine oxyhemoglobin saturation determinations with a calibrated blood-gas analyzer and a porcine-specific CO-oximeter. There was a high degree of correlation with minimal variability (r(2) = 0.99, SE of the estimate = 5.2%) between the mathematical model and the porcine-specific CO-oximeter measurements. Bland-Altman comparison showed that the CO-oximeter measurements were biased slightly lower (-0.4 vol%), and the limits of agreement (+/-2 SD) were 0.7 and -1.5 vol%. This is in contrast to a 10-20 vol% error if human-specific methods were used. The results show excellent agreement between the nonlinear model and CO-oximeter for porcine-specific oxyhemoglobin saturation measurements. In contrast, comparison of the porcine-specific oxyhemoglobin saturations with saturations obtained by using human methods highlights the necessity of species-specific measurement methodology.     

On the relation between gene flow theory and genetic gain

In conventional gene flow theory the rate of genetic gain is calculated as the summed products of genetic selection differential and asymptotic proportion of genes deriving from sex-age groups. Recent studies have shown that asymptotic proportions of genes predicted from conventional gene flow theory may deviate considerably from true proportions. However, the rate of genetic gain predicted from conventional gene flow theory was accurate. The current note shows that the connection between asymptotic proportions of genes and rate of genetic gain that is embodied in conventional gene flow theory is invalid, even though genetic gain may be predicted correctly from it.     

Outgassing Losses of Toluene and m-Xylene Evaluated by 14C-Based Mass Balances for Laboratory Bioventing Simulations

Mixtures of toluene, ethylbenzene, and the xylenes spiked with ¹⁴C-labeled toluene or m-xylene were added to bench-scale bioventing simulation columns filled with hydrocarbon-contaminated subsurface soils. After 2 to 4 weeks of incubation during which air was pumped through the column at rates of at least 2?ml·min^?1·kg^?1 between 54 and 84% of the radiolabel was recovered in traps as outgassed parent compound from four columns sterilized with gamma-irradiation. In contrast, seven nonsterilized but otherwise identically treated (except for inorganic nitrogen addition) columns lost less than 0.4% (and one column lost 0.7%) of the radiolabel through outgassing of the parent compound. Nonsterilized columns lost 40 to 61% of the radiolabel as ¹⁴CO₂, whereas gamma-irradiated columns usually lost only trace amounts of ¹⁴C in this form. Biologically active columns also retained much larger fractions than sterilized columns of the radiolabel in the subsoil in forms, possibly microbial biomass, from which it could be recovered by wet oxidation. Addition of 10 or 40?mg/kg of mineral nitrogen had no consistent effect on bioventing performance.     

Acute and chronic effects of an aromatase inhibitor on territorial aggression in breeding and nonbreeding male song sparrows

Many studies have demonstrated that male aggression is regulated by testosterone. The conversion of testosterone to estradiol by brain aromatase is also known to regulate male aggression in the breeding season. Male song sparrows (Melospiza melodia morphna) are territorial not only in the breeding season, but also in the nonbreeding season, when plasma testosterone and estradiol levels are basal. Castration has no effect on nonbreeding aggression. In contrast, chronic (10 day) aromatase inhibitor (fadrozole) treatment decreases nonbreeding aggression, indicating a role for estrogens. Here, we show that acute (1 day) fadrozole treatment decreases nonbreeding territoriality, suggesting relatively rapid estrogen effects. In spring, fadrozole decreases brain aromatase activity, but acute and chronic fadrozole treatments do not significantly decrease aggression, although trends for some behaviors approach significance. In gonadally intact birds, fadrozole may be less effective at reducing aggression in the spring. This might occur because fadrozole causes a large increase in plasma testosterone in intact breeding males. Alternatively, estradiol may be more important for territoriality in winter than spring. We hypothesize that sex steroids regulate male aggression in spring and winter, but the endocrine mechanisms vary seasonally.     

Electronic properties of some inorganic solids

A simple bonding model previously used to calculate cohesive energies is used to calculate electronic properties of simple solids. The model assumes that AB compounds of CN6 or 8 are completely ionic and that CN4 compounds, and metals, are completely covalent. It is then possible to calculate the electronic chemical potential, the work function and the average energy gap between filled and empty bands in insulators, semiconductors and conductors.     

Differences in biophysical properties of nucleus accumbens medium spiny neurons emerging from inactivation of inward rectifying potassium currents

Inward rectifying potassium (K_IR) currents in medium spiny (MS) neurons of nucleus accumbens inactivate significantly in ~40% of the neurons but not in the rest, which may lead to differences in input processing by these two groups. Using a 189-compartment computational model of the MS neuron, we investigate the influence of this property using injected current as well as spatiotemporally distributed synaptic inputs. Our study demonstrates that K_IR current inactivation facilitates depolarization, firing frequency and firing onset in these neurons. These effects may be attributed to the higher input resistance of the cell as well as a more depolarized resting/down-state potential induced by the inactivation of this current. In view of the reports that dendritic intracellular calcium levels depend closely on burst strength and spike onset time, our findings suggest that inactivation of K_IR currents may offer a means of modulating both excitability and synaptic plasticity in MS neurons.