Evidence that the putative compatible solute 5-dimethylsulfoniopentanoate is an extraction artifact.

A novel gas chromatography-mass spectrometry method for analyzing sulfonium compounds as their S-demethylated silyl derivatives has clarified the origin of 5-dimethylsulfoniopentanoate. This compound, previously reported from flowers of Diplotaxis tenuifolia (L.) DC. (Cruciferae), is generated from glucoerucin during treatment with hot 6 N HCl. Glucoerucin is the characteristic glucosinolate of D. tenuifolia.     

The sodium current underlying action potentials in guinea pig hippocampal CA1 neurons

Neurons were acutely dissociated from the CA1 region of hippocampal slices from guinea pigs. Whole-cell recording techniques were used to record and control membrane potential. When the electrode contained KF, the average resting potential was about -40 mV and action potentials in cells at -80 mV (current-clamped) had an amplitude greater than 100 mV. Cells were voltage-clamped at 22-24 degrees C with electrodes containing CsF. Inward currents generated with depolarizing voltage pulses reversed close to the sodium equilibrium potential and could be completely blocked with tetrodotoxin (1 microM). The amplitude of these sodium currents was maximal at about -20 mV and the amplitude of the tail currents was linear with potential, which indicates that the channels were ohmic. The sodium conductance increased with depolarization in a range from -60 to 0 mV with an average half-maximum at about -40 mV. The decay of the currents was not exponential at potentials more positive than -20 mV. The time to peak and half-decay time of the currents varied with potential and temperature. Half of the channels were inactivated at a potential of -75 mV and inactivation was essentially complete at -40 to -30 mV. Recovery from inactivation was not exponential and the rate varied with potential. At lower temperatures, the amplitude of sodium currents decreased, their time course became longer, and half-maximal inactivation shifted to more negative potentials. In a small fraction of cells studied, sodium currents were much more rapid but the voltage dependence of activation and inactivation was very similar.     

Aberrant fatty acyl alpha-hydroxylation in human neuroblastoma tumor gangliosides

Abnormalities of ganglioside structure characterize the neoplastic state, and aberrant glycosylation has been implicated as underlying many new tumor ganglioside structures. However, variations in ceramide structure can also result in novel tumor gangliosides. To address systematically this aspect of ganglioside metabolism, we have initiated a study of the structures of the ceramide species of an oligosaccharide-homogeneous human tumor-derived ganglioside, GM2. The ganglioside was isolated from neuroblastoma tissue and purified by normal-phase high pressure liquid chromatography. Marked ceramide heterogeneity was observed; 18 individual ceramide species of neuroblastoma GM2 were separated by reversed-phase high pressure liquid chromatography and collected. Their structures were determined by a combination of negative- and positive-ion fast atom bombardment mass spectrometry and collisionally activated dissociation tandem mass spectrometry of the underivatized gangliosides. The striking finding was the detection of alpha-hydroxylation of a significant fraction of each of the major fatty acid species (16:0, 18:0, 20:0, 22:0, and 24:1); alpha-hydroxylated species quantitatively represented almost one-fifth of the total tumor GM2 species. Fatty acyl hydroxylation was also detected in the ceramide of several other human tumor gangliosides. In contrast, as previously known, fatty acyl hydroxylation was not detected in the normal human brain gangliosides GM3, GM2, and GM1. We propose that aberrant fatty acid alpha-hydroxylation is a novel and sometimes quantitatively significant characteristic of human tumor ganglioside metabolism.     

The Acoustic Habitat Hypothesis: An Ecoacoustics Perspective on Species Habitat Selection

Sound is an inherent component of the environment that provides conditions and information necessary for many animal activities. Soniferous species require specific acoustic and physical conditions suitable for their signals to be transmitted, received, and effectively interpreted to successfully identify and utilize resources in their environment and interact with conspecifics and other heterospecific organisms. We propose the Acoustic Habitat Hypothesis to explain how the acoustic environment influences habitat selection of sound-dependent species. We postulate that sound-dependent species select and occupy habitats with unique acoustic characteristics that are essential to their functional needs and conducive to the threshold of sound frequency they produce and detect. These acoustic habitats are based on the composition of biophony, geophony, and technophony in the soundscape and on the biosemiotics mechanisms described in the eco-field hypothesis. The Acoustic Habitat Hypothesis initiates questions of habitat selection that go beyond the physical attributes of the environment by applying ecoacoustics theory. We outline the theoretical basis of the Acoustic Habitat Hypothesis and provide examples from the literature to support its assumptions. The concept of acoustic habitats has been documented in the literature for many years but here, we accurately and extensively define acoustic habitat and we put this concept into a unified theory. We also include perspectives on how the Acoustic Habitat Hypothesis can stimulate a paradigm shift in conservation strategies for threatened and endangered species.     

Colorado animal‐based plague surveillance systems: relationships between targeted animal species and prediction efficacy of areas at risk for humans

Human plague risks (Yersinia pestis infection) are greatest when epizootics cause high mortality among this bacterium's natural rodent hosts. Therefore, health departments in plague‐endemic areas commonly establish animal‐based surveillance programs to monitor Y. pestis infection among plague hosts and vectors. The primary objectives of our study were to determine whether passive animal‐based plague surveillance samples collected in Colorado from 1991 to 2005 were sampled from high human plague risk areas and whether these samples provided information useful for predicting human plague case locations. By comparing locations of plague‐positive animal samples with a previously constructed GIS‐based plague risk model, we determined that the majority of plague‐positive Gunnison's prairie dogs (100%) and non‐prairie dog sciurids (85.82%), and moderately high percentages of sigmodontine rodents (71.4%), domestic cats (69.3%), coyotes (62.9%), and domestic dogs (62.5%) were recovered within 1 km of the nearest area posing high peridomestic risk to humans. In contrast, the majority of white‐tailed prairie dog (66.7%), leporid (cottontailed and jack rabbits) (71.4%), and black‐tailed prairie dog (93.0%) samples originated more than 1 km from the nearest human risk habitat. Plague‐positive animals or their fleas were rarely (one of 19 cases) collected within 2 km of a case exposure site during the 24 months preceding the dates of illness onset for these cases. Low spatial accuracy for identifying epizootic activity prior to human plague cases suggested that other mammalian species or their fleas are likely more important sources of human infection in high plague risk areas. To address this issue, epidemiological observations and multi‐locus variable number tandem repeat analyses (MLVA) were used to preliminarily identify chipmunks as an under‐sampled, but potentially important, species for human plague risk in Colorado.     

GABA increases both the conductance and mean open time of recombinant GABAA channels co-expressed with GABARAP

The single channel properties of recombinant gamma-aminobutyric acid type A (GABA(A))alphabetagamma receptors co-expressed with the trafficking protein GABARAP were investigated using membrane patches in the outside-out patch clamp configuration from transiently transfected L929 cells. In control cells expressing alphabetagamma receptors alone, GABA activated single channels whose main conductance was 30 picosiemens (pS) with a subconductance state of 20 pS, and increasing the GABA concentration did not alter their conductance. In contrast, when GABA(A) receptors were co-expressed with GABARAP, the GABA-activated single channels displayed multiple, high conductances (> or =40 pS), and GABA (> or =10 microM) was able to increase their conductance, up to a maximum of 60 pS. The mean open time of GABA-activated channels in control cells expressing alphabetagamma receptors alone was 2.3 +/- 0.1 ms for the main 30-pS channel and shorter for the subconductance state (20 pS, 0.8 +/- 0.1 ms). Similar values were measured for the 30- and 20-pS channels active in patches from cells co-expressing GABARAP. However higher conductance channels (> or =40 pS) remained open longer, irrespective of whether GABA or GABA plus diazepam activated them. Plotting mean open times against mean conductances revealed a linear relationship between these two parameters. Since high GABA concentrations increase both the maximum single channel conductance and mean open time of GABA(A) channels co-expressed with GABARAP, trafficking processes must influence ion channel properties. This suggests that the organization of extrasynaptic GABA(A) receptors may provide a range of distinct inhibitory currents in the brain and, further, provide differential drug responses.     

Plant one-carbon metabolism and its engineering

The metabolism of one-carbon (C1) units is vital to plants. It involves unique enzymes and takes place in four subcellular compartments. Plant C1 biochemistry has remained relatively unexplored, partly because of the low abundance or the lability of many of its enzymes and intermediates. Fortunately, DNA sequence databases now make it easier to characterize known C1 enzymes and to discover new ones, to identify pathways that might carry high C1 fluxes, and to use engineering to redirect C1 fluxes and to understand their control better.