Linking tree genetics and stream consumers: isotopic tracers elucidate controls on carbon and nitrogen assimilation.

Leaf litter provides an important nutrient subsidy to headwater streams, but little is known about how tree genetics influence energy pathways from litter to higher trophic levels. Despite the charge to quantify carbon (C) and nitrogen (N) pathways from decomposing litter, the relationship between litter decomposition and aquatic consumers remains unresolved. We measured litter preference (attachments to litter), C and N assimilation rates, and growth rates of a shredding caddisfly (Hesperophylax magnus, Limnephilidae) in response to leaf litter of different chemical and physical phenotypes using Populus cross types (P.

Microchip separations of protein biotoxins using an integrated hand-held device.

We report the development of a hand-held instrument capable of performing two simultaneous microchip separations (gel and zone electrophoresis), and demonstrate this instrument for the detection of protein biotoxins. Two orthogonal analysis methods are chosen over a single method in order to improve the probability of positive identification of the biotoxin in an unknown mixture. Separations are performed on a single fused-silica wafer containing two separation channels.

Laser-induced dispersed fluorescence detection of polycyclic aromatic compounds in soil extracts separated by capillary electrochromatography.

Polycyclic aromatic hydrocarbons (PAHs) and nitrogen containing aromatic compounds (NCACs) are characterized in soil extracts and laboratory standards by capillary electrochromatography (CEC) with laser-induced dispersed fluorescence (LIDF) detection using a liquid-nitrogen cooled charge-coupled device detector. The LIDF detection technique provides information on compound identity and, when coupled with the high separation efficiencies of the CEC technique, proves useful in the analysis of complex mixtures. Differences in fluorescence spectra also provide a means of identifying co-eluting compounds by using deconvolution algorithms.

Separation of related opiate compounds using capillary electrochromatography.

Capillary electrophoretic separations have been investigated for six controlled narcotic analgesic compounds having related structures. Owing to the similar charge-to-mass ratios of these compounds, capillary zone electrophoresis failed to provide a satisfactory separation, whereas a baseline-resolved separation was achieved in 10 min using micellar electrokinetic chromatography. Column efficiencies of 40,000-150,000 plates/m were obtained with a 50 cm long, 50 microm inner diameter (ID) capillary using 50 mM sodium dodecyl sulfate (SDS) in a 50 mM borate solution containing 12% isopropanol.

Selective trace enrichment by immunoaffinity capillary electrochromatography on-line with capillary zone electrophoresis - laser-induced fluorescence.

Limited by the lack of a sensitive, universal detector, many capillary-based liquid-phase separation techniques might benefit from techniques that overcome modest concentration sensitivity by preconcentrating large injection volumes. The work presented employs selective solid-phase extraction by immunoaffinity capillary electrochromatography (IACEC) to enhance detection limits. A model analyte, fluorescein isothiocyanate (FITC) biotin, is electrokinetically applied to a capillary column packed with an immobilized anti-biotin-IgG support.

Imaging of Pressure- and Electrokinetically Driven Flows through Open Capillaries.

A new tool for imaging both scalar transport and velocity fields in liquid flows through microscale structures is described. The technique employs an ultraviolet laser pulse to write a pattern into the flow by uncaging a fluorescent dye. This is followed, at selected time delays, by flood illumination with a pulse of visible light which excites the uncaged dye.

Upper respiratory tract disease and mycoplasmosis in desert tortoises from Nevada.

A population of desert tortoises (Gopherus agassizii) at Yucca Mountain (Nevada, USA) was monitored during four sampling periods using enzyme-linked immunosorbent assays (ELISA) to determine the percentage of individuals that had been exposed to Mycoplasma agassizii, a causative agent of upper respiratory tract disease. Respiratory tract disease has been considered a significant factor in the decline of desert tortoise populations in the Mojave Desert (USA). Few differences between sexes in ELISA values or percentages testing positive were noted.

Gradient elution in capillary electrochromatography.

In analogy to pressure-driven gradient techniques in high-performance liquid chromatography, a system has been developed for delivering electroosmotically driven solvent gradients for capillary electrochromatography (CEC). Dynamic gradients with submicroliter per minute flow rates are generated by merging two electroosmotic flows that are regulated by computer-controlled voltages. These flows are delivered by two fused-silica capillary arms attached to a T-connector, where they mix and then flow into a capillary column that has been electrokinetically packed with 3-μm reversed-phase particles.

Automated capillary electrochromatography: reliability and reproducibility studies.

The routine application of capillary electrochromatography (CEC) is demonstrated by incorporating 75 microns I.D. capillaries packed with 3 microns octadecylsilica (ODS) particles into a commercial CZE instrument.

Multiplex spectroscopy: determining the transition moments and absolute concentrations of molecular species.

A procedure is described that uses two spectroscopic techniques, absorption and infrared degenerate four-wave mixing, in tandem (multiplex) to measure the transition dipole moments and absolute concentrations of molecular species in situ. The method is demonstrated by the measurement of the relative transition moments and concentrations of two dissimilar sample gas components, hydrogen chloride and nitrogen dioxide, but is applicable to a wide variety of molecules and, thus, can provide new information for transient molecular species. Further, difficulties in obtaining quantitative information through techniques such as laser-induced fluorescence, coherent anti-Stokes Raman scattering, and degenerate four-wave mixing spectroscopies can be overcome when a multiplex approach is used.

Induction of cytochromes P-450 2B and 3A in mice following the dietary administration of the novel cognitive enhancer linopirdine.

The effects of the novel cognitive enhancer linopirdine [3,3-bis(4-pyridinylmethyl)-1-phenylindolin-2-one] on hepatic cytochromes P-450 (CYP) and linopirdine metabolism were determined in female mice fed 0, 10, 50, and 250 mg/kg/day of linopirdine in the diet for 4, 7, 14, and 28 days. Linopirdine induced CYP maximally by day 4 only at the highest dose, as demonstrated by significant (p < 0.05) increases in total spectral CYP and liver weight.

Determination of amantadine in human plasma by capillary gas chromatography using electron-capture detection following derivatization with pentafluorobenzoyl chloride.

A specific, sensitive, and accurate capillary gas chromatographic method for the quantitation of amantadine in human plasma is described. Amantadine and the internal standard, rimantadine were extracted from plasma under alkaline conditions into toluene. Both compounds were derivatized with pentafluorobenzoyl chloride.

Detection of trace molecular species using degenerate four-wave mixing.

Spectroscopies that make use of laser light have provided an important tool to modern researchers for the nonintrusive analysis of chemical systems. The strengths and limitations of these spectroscopic techniques often determine the viability of scientific investigations. The unique properties of degenerate four-wave mixing, a nonlinear optical technique, have recently been found to provide powerful capabilities for a wide range of applications.

Influence of food on the oral absorption and bioavailability of moricizine.

Moricizine, a unique Class I antiarrhythmic agent, was orally administered with and without a meal to 24 healthy male subjects to determine the effect of food on moricizine absorption and bioavailability. Relative to the fasting state, a standardized breakfast delayed the time to peak plasma moricizine concentration (1.2 vs.

Nasal administration of a cognition enhancer provides improved bioavailability but not enhanced brain delivery.

Compound 1 [3,3-bis(4-pyridylmethyl)-1-phenylindolin-2-one] is an experimental cognition-enhancing drug now being developed for cognitive disorders. Oral bioavailability of 1 in rats was less than 10% of the dose. Nasal dosing improved bioavailability to greater than 50%.

Two-dimensional imaging of OH in flames by degenerate four-wave mixing.

Degenerate four-wave mixing is used to produce two-dimensional images of OH distributions in atmosphericpressure flames. The phase-conjugated images from single laser pulses exhibit excellent signal-to-noise ratios and illustrate that degenerate four-wave mixing has outstanding potential as a multidimensional diagnostic for combustion environments.

Measurement of OH rotational temperatures in a flame using degenerate four-wave mixing.

Temperatures have been measured in a laminar premixed propane-air diffusion flame using degenerate four-wave mixing (DFWM) of the OH radical. The spectra were recorded simultaneously with laser-induced fluorescence through the (0, 0) band of the OH A(2)Sigma-X(2)II transition. Individual rotational lines are more clearly resolved in the DFWM spectrum than in the laser-induced fluorescence spectrum, although both are power broadened at laser intensities of 1-2 MW/cm(2) at 307 nm.

Use of a charge-coupled device camera for broadband coherent anti-Stokes Raman scattering measurements.

The use of an unintensified charge-coupled device (CCD) camera for the acquisition of broadband CARS signals is demonstrated. The CCD camera offers significant advantages compared to intensified, linear photodiode array (PDA) detectors that are generally used for broadband CARS measurements. These advantages include higher spectral resolution and improved instrument function, larger dynamic range, and a 2-D format.

High-performance liquid chromatographic method for the determination of tiflamizole in plasma.

A sensitive, specific, high-performance liquid chromatographic procedure was developed for the measurement of plasma tiflamizole levels. Acidic plasma samples were extracted with three volumes of ether. The ether extracts were combined and evaporated to dryness.

Tiflamizole elimination from plasma in rheumatoid arthritis.

Tiflamizole is a fluorinated diarylamidazole sulfone nonsteroidal anti-inflammatory drug not metabolized or excreted in urine. Its mean (+/- SD) elimination t 1/2 from plasma was 21.6 +/- 9 days (range 11.