Impaired respiratory and body temperature control upon acute serotonergic neuron inhibition

Physiological homeostasis is essential for organism survival. Highly responsive neuronal networks are involved, but their constituent neurons are just beginning to be resolved. To query brain serotonergic neurons in homeostasis, we used a neuronal silencing tool, mouse RC::FPDi (based on the synthetic G protein-coupled receptor Di), designed for cell type-specific, ligand-inducible, and reversible suppression of action potential firing. In mice harboring Di-expressing serotonergic neurons, administration of the ligand clozapine-N-oxide (CNO) by systemic injection attenuated the chemoreflex that normally increases respiration in response to tissue carbon dioxide (CO(2)) elevation and acidosis. At the cellular level, CNO suppressed firing rate increases evoked by CO(2) acidosis. Body thermoregulation at room temperature was also disrupted after CNO triggering of Di; core temperatures plummeted, then recovered. This work establishes that serotonergic neurons regulate life-sustaining respiratory and thermoregulatory networks, and demonstrates a noninvasive tool for mapping neuron function.     

Red - green opponent spectral sensitivity: disparity between cancellation and direct matching methods

The spectral sensitivity at the opponent stage of the visual system is traditionally measured by a hue-cancellation procedure. Comparison with a direct hue-matching method shows that cancellation overestimates short-wavelength sensitivity by as much as a factor of 30. The observation implies that different mechanisms control the perception of short-wavelength and long-wavelength redness.     

Wind dispersal of oribatid mites as a mode of migration

Oribatid mites are important colonizers of young soils, but little is known about their immigration pathways. In this study, one often-stated hypothesis was tested quantitatively: that wind is an important dispersal pathway. The aim was (1) to detect wind dispersal in oribatid mites (using sticky traps at different heights above ground level) and to determine factors influencing wind dispersal, (2) to investigate whether oribatids can survive wind dispersal and immigrate by wind into young soils (using mini-pitfall traps in test plots with oribatid-free substrate, active immigration being prohibited) and (3) to find out whether those oribatids are able to colonize young soils (using soil cores from the test plots). The results demonstrate (1) that mainly arboreal oribatid species were dispersed by wind - even at 160 m height - and can therefore be spread over large distances. Nevertheless, about 10% of the wind-dispersed oribatid mites belonged to species able to live in the soil and may therefore be potential colonizers of young soils. The number of specimen and species transported by wind was the highest close to the soil surface and the number of dispersed individuals was mainly influenced by seasonality and humidity. The results also suggest that the probability of a soil oribatid being dispersed by wind depends on its original microhabitat (tree habitats > soil surface > deeper soil layers) and its body weight. It was also shown that soil-dwelling oribatid mites survived wind dispersal and immigrated by wind into the test plots and that colonization of the test plots took at least 2 months longer than immigration. However, colonization success was low during the first 2 years of investigation and only Trichoribates incisellus was found several times in the nutrient-poor substrate. Therefore, wind dispersal is an important migration pathway, especially for arboreal oribatids. We suggest that immigration into young soils most likely occurs by repeated short-distance dispersal. Only some species are able to survive the hostile conditions of wind dispersal as well as of pioneer soils, but those that do are potentially the founders of new populations.     

Thermal oxidation of 9'-cis-neoxanthin in a model system containing peroxyacetic acid leads to the potent odorant beta-damascenone

The potent odorant beta-damascenone was formed directly from 9'-cis-neoxanthin in a model system by peroxyacetic acid oxidation and two-phase thermal degradation without the involvement of enzymatic activity. Beta-damascenone formation was heavily dependent on pH (optimum at 5.0) and temperature, occurring over the two sequential phases. The first was incubation with peroxyacetic acid at 60 degrees C for 90 min, and the second was at above 90 degrees C for 20 min. Only traces of beta-damascenone were formed on application of only one of the two phases. Formate and citrate solutions produced a much better environment for beta-damascenone formation than acetate and phosphate. About 7 microg/L beta-damascenone was formed from 5.8 mg/L 9'-cis-neoxanthin under optimal experimental condition. The detailed pathway by which beta-damascenone is formed remains to be elucidated.     

The potential conservation value of unmowed powerline strips for native bees

The land area covered by powerline easements in the United States exceeds the area of almost all national parks, including Yellowstone. In parts of Europe and the US, electric companies have altered their land management practices from periodic mowing to extraction of tall vegetation combined with the use of selective herbicides. To investigate whether this alternate management practice might produce higher quality habitat for native bees, we compared the bee fauna collected in unmowed powerline corridors and in nearby mowed grassy fields at the Patuxent Wildlife Research Center (MD). Powerline sites had more spatially and numerically rare species and a richer bee community than the grassy fields, although the difference was less pronounced than we expected. Powerline sites also had more parasitic species and more cavity-nesting bees. Bee communities changed progressively through the season, but differences between the site types were persistent. The surrounding, non-grassland landscape likely has a strong influence on the bee species collected at the grassland sites, as some bees may be foraging in the grasslands but nesting elsewhere. Improving habitat for native bees will help ameliorate the loss of pollination services caused by the collapse of wild and managed honeybee populations. This study suggests that powerline strips have the potential to provide five million acres of bee-friendly habitat in the US if utilities more generally adopt appropriate management practices.     

Using segmented regression models to fit soil nutrient and soybean grain yield changes due to liming

Frequently soil-plant relationships and responses are complex combinations of increases-level-decreases consisting of linear segments of differing slope. Segmented regression is very useful to express and quantify such relationships and responses. Fitting segmented regression models to such data, however, remains a challenge. The problem is in estimating the join points and coefficients. We use median functions to express segmented regression models, and estimate the join points by standard estimation routines such as Marquardt, Newton, and doesn’t use derivatives (DUD) methods that are available in statistical software such as SAS. Segmented straight-line models are fit to data reflecting soil Manganese (Mn), Calcium (Ca), Phosphorus (P), and soybean yield changes under different soil pH conditions due to liming. A systematic comparison of the slopes and join points suggests that different mechanisms are limiting soybean yield at different intervals as soil pH increased.     

High pressure liquid chromatographic determination of zearalenone in chicken tissues

A method is reported for the extraction and analysis of zearalenone in chicken fat, heart muscle, and kidney tissue by using high pressure liquid chromatography (HPLC). Zearalenone is extracted with acetonitrile, cleaned up with hexane, and extracted further with ethyl acetate. Zearalenone is determined by HPLC using a reverse phase radial compression separation system, an ultraviolet absorbance detector, and a mobile phase of acetonitrile-water (60 + 40) (v/v). Recoveries of zearalenone added at levels from 50 to 200 ng/g are in the range 82.6-95.1%.