Diversity and Range of Amphibians of the Yukon Territory

Four amphibian species occur in the Yukon: Western Toad (Bufo boreas; first verified record in 1961), the Boreal Chorus Frog (Pseudacris maculata, first record in 1995), the Columbia Spotted Frog (Rana luteiventris, first record in 1993), and the Wood Frog (Rana sylvatica; first record in 1933). The Western Toad is restricted to the Liard Basin in five geographically separated areas. Breeding sites have been located on the lower Coal River and vicinity. The Boreal Chorus Frog has been documented from a small area of the lower La Biche River valley near the Yukon-British Columbia-Northwest Territories border. The Columbia Spotted Frog occurs in two widely separated areas, at Bennett Lake in the southwest and in the Liard Basin in the southeast. The Wood Frog is widespread below treeline. Limited survey efforts continue to hinder our knowledge of amphibian distribution. Erratum included

Rapid Multiplexed Data Acquisition: Application To Three-Dimensional Magnetic Field Measurements In A Turbulent Laboratory Plasma

Multiplexing electronics have been constructed to reduce the cost of high-speed data acquisition at the Swarthmore Spheromak Experiment (SSX) and Redmond Plasma Physics Laboratory. An application of the system is described for a three-dimensional magnetic probe array designed to resolve magnetohydrodynamic time scale and ion inertial spatial scale structure of magnetic reconnection in a laboratory plasma at SSX. Multiplexing at 10 MHz compresses 600 pick-up coil signals in the magnetic probe array into 75 digitizer channels. An external master timing system maintains synchronization of the multiplexers and digitizers. The complete system, calibrated and tested with Helmholtz, line current, and magnetofluid fields, reads out the entire 5 x 5 x 8 probe array every 800 ns with an absolute accuracy of approximately 20 G, limited mainly by bit error. (C) 2003 American Institute of Physics

Surface structure and spectroscopy of charge-density wave materials using scanning tunneling microscopy

The Scanning tunneling microscope (STM) has been used to study the effects of Fe doping on the charge-density wave (CDW) structure in NbSe{sub 3} and 1T-TaS{sub 2}. In NbSe{sub 3} small amounts of Fe reduce both CDW gaps by 25--30% and change the relative CDW amplitudes of the high and low temperature CDWs. The CDW amplitudes remain strong on all three chains of the surface unit cell with no evident disorder. In 1T-Fe{sub 0.05}Ta{sub 0.95}S{sub 2} the Fe introduces substantial disorder in the CDW pattern, but the local CDW amplitude remains strong. The CDW energy gap is reduced by approximately 50% and the resistive anomaly at the commensurate-incommensurate transition is removed. The STM in both the image and spectroscopy modes can detect subtle changes in CDW structure due to impurities

Carbon-Carbon bond forming reactions of organotransition metal enolate complexes

Abstract -Metal enolates play an important role in stereoselective organic synthesis. Their chemistry is affected profoundly by the metal counterion associated with the enolate fragment. In order to expand the potential of replacing main group with transition metal moieties in such species, methods have been developed for the synthesis of a number of stable, characterizable "late" transition metal ql-(C)-enolate complexes having the general structure LM-CH2COR (M = Mo, W, Re). The chemistry of these materials (e.g., functional transformations of the organic carbonyl group, transfer of the enolate moietry to organic substrates such as aldehydes and alkynes) has been investigated. The scope and mechanisms of the enolate reactions will be discussed in detail. The reaction of organic enolates with carbon electrophiles (e.g., alkyl halides, organic carbonyl compounds) gives rise to compounds containing new carbon-carbon bonds; reaction with heteroatom electrophiles results in the formation of oxidized products? There has been much interest recently in developing methods for carrying out these transformations with high stereoselectivity.3 Historically, most enolate research has focused on salts involving alkali metal anions. More recently, research efforts have been extended to enolates associated with organic cations, main group metals, and transition metals. In the transition metal area, enolates involving the so-called "early" metals (to the left of chromium, molybdenum and tungsten) have seen extensive investigationi4 in general these complexes have 0-bonded structures A in Scheme 1. This paper describes the synthesis and chemistry of middle-and late transition metal enolates, which have seen less investigation. It was our hope that such species would be more likely to have Cbound structure B, and also to react with both electrophilic and non-electrophilic species (e.g., by insertion rather than nucleophile-electrophile mechanisms). SYNTHESIS, CHARACTERIZATION AND FUNCTIONAL GROUP TRANSFORMATIONS OF TUNGSTEN AND MOLYBDENUM ENOLATES The well-known nucleophilic anionic metal salts5 Na[(qS-C5R5)(C0)3M] (M = Mo, W, R=H, Me), on treatment with a-chloroketones and esters, provide good yields of enolates 1 -8, as shown in Scheme 2. These are thermally stable complexes that may be isolated by conventional chromatographic and recrystallization methods; they have been characterized fully by elemental analysis and spectroscopic techniques. Preparation of these materials on a multi-gram scale in a one-pot procedure is possible by treatment of W(CO)6 or Mo(C0)6 with NaCp, followed by addition of the a-chlorocarbonyl compound to the resulting metal anion solution. The stability of the tungsten-carbon bond in tungsten ester enolates, fiist suggested several years ago by the work of Green and his coworkers6, has allowed us to carry out a wide range of transformations on the organic carbonyl group. Thus the reactions shown in Scheme 3 proceed in good yield, and lead to stable tungsten enolates containing ester, amide and even carboxylic acid and acid chloride functionality

Quantifying normal human brain metabolism using hyperpolarized [1– 13 C]pyruvate and magnetic resonance imaging

Hyperpolarized 13 C Magnetic Resonance Imaging ( 13 C-MRI) provides a highly sensitive tool to probe tissue metabolism in vivo and has recently been translated into clinical studies. We report the cerebral metabolism of intravenously injected hyperpolarized [1– 13 C]pyruvate in the brain of healthy human volunteers for the first time. Dynamic acquisition of 13 C images demonstrated 13 C-labeling of both lactate and bicarbonate, catalyzed by cytosolic lactate dehydrogenase and mitochondrial pyruvate dehydrogenase respectively. This demonstrates that both enzymes can be probed in vivo in the presence of an intact blood-brain barrier: the measured apparent exchange rate constant (k PL ) for exchange of the hyperpolarized 13 C label between [1– 13 C]pyruvate and the endogenous lactate pool was 0.012 ± 0.006 s −1 and the apparent rate constant (k PB ) for the irreversible flux of [1– 13 C]pyruvate to [ 13 C]bicarbonate was 0.002 ± 0.002 s −1 . Imaging also revealed that [1– 13 C]pyruvate, [1– 13 C]lactate and [ 13 C]bicarbonate were significantly higher in gray matter compared to white matter. Imaging normal brain metabolism with hyperpolarized [1– 13 C]pyruvate and subsequent quantification, have important implications for interpreting pathological cerebral metabolism in future studies

Hyperpolarized13c mri of tumor metabolism demonstrates early metabolic response to neoadjuvant chemotherapy in breast cancer

Purpose: To compare hyperpolarized carbon 13 (13C) MRI with dynamic contrast material–enhanced (DCE) MRI in the detection of early treatment response in breast cancer. Materials and Methods: In this institutional review board–approved prospective study, a woman with triple-negative breast cancer (age, 49 years) underwent13C MRI after injection of hyperpolarized [1–carbon 13 {13C}]-pyruvate and DCE MRI at 3 T at baseline and after one cycle of neoadjuvant therapy. The13C-labeled lactate-to-pyruvate ratio derived from hyperpolarized13C MRI and the pharmacokinetic parameters transfer constant (Ktrans) and washout parameter (kep ) derived from DCE MRI were compared before and after treatment. Results: Exchange of the13C label between injected hyperpolarized [1-13C]-pyruvate and the endogenous lactate pool was observed, catalyzed by the enzyme lactate dehydrogenase. After one cycle of neoadjuvant chemotherapy, a 34% reduction in the13C-labeled lactate-to-pyruvate ratio resulted in correct identification of the patient as a responder to therapy, which was subsequently confirmed via a complete pathologic response. However, DCE MRI showed an increase in mean Ktrans (132%) and mean kep (31%), which could be incorrectly interpreted as a poor response to treatment. Conclusion: Hyperpolarized13C MRI enabled successful identification of breast cancer response after one cycle of neoadjuvant chemotherapy and may improve response prediction when used in conjunction with multiparametric proton MRI

The Golgin GMAP210/TRIP11 Anchors IFT20 to the Golgi Complex

Eukaryotic cells often use proteins localized to the ciliary membrane to monitor the extracellular environment. The mechanism by which proteins are sorted, specifically to this subdomain of the plasma membrane, is almost completely unknown. Previously, we showed that the IFT20 subunit of the intraflagellar transport particle is localized to the Golgi complex, in addition to the cilium and centrosome, and hypothesized that the Golgi pool of IFT20 plays a role in sorting proteins to the ciliary membrane. Here, we show that IFT20 is anchored to the Golgi complex by the golgin protein GMAP210/Trip11. Mice lacking GMAP210 die at birth with a pleiotropic phenotype that includes growth restriction, ventricular septal defects of the heart, omphalocele, and lung hypoplasia. Cells lacking GMAP210 have normal Golgi structure, but IFT20 is no longer localized to this organelle. GMAP210 is not absolutely required for ciliary assembly, but cilia on GMAP210 mutant cells are shorter than normal and have reduced amounts of the membrane protein polycystin-2 localized to them. This work suggests that GMAP210 and IFT20 function together at the Golgi in the sorting or transport of proteins destined for the ciliary membrane