A novel low mol wt inositol phosphoglycan antagonist of insulin action of oxidative glucose metabolism in isolated rat adipocytes was partially purified from normal human plasma and shown to be increased in type II diabetic plasma. It was characterized chemically as a myo-inositol phosphoglycan containing a cyclic 1,2-phosphate. This antagonist, termed fraction V3, is now shown to inhibit the action of an inositol glycan insulin pH 2.0 mediator that stimulates pyruvate dehydrogenase phosphatase in a similar manner to insulin. In addition, fraction V3 inhibits stimulation of the pyruvate dehydrogenase (PDH) phosphatase by Mg2+, the enzyme's required metal, and by spermine, a polyamine. Fraction V3 does not inhibit active PDH itself. The inhibitory effect is dose dependent and apparently noncompetitive or nonsurmountable for the insulin inositol glycan pH 2.0 mediator, thus comparing kinetically with its insulin antagonistic action on intact adipocytes. Its inhibitory action on PDH phosphatase is dose dependent and competitive for Mg2+ stimulation of the phosphatase. Additionally, fraction V3 is shown to inhibit stimulation by Mg2+ of cloned recombinant PDH phosphatase catalytic subunit. Inhibition by fraction V3 of Mg(2+)-stimulated PDH phosphatase and its cloned catalytic subunit helps explain its mechanism of action to inhibit insulin-stimulated oxidative glucose metabolism in adipocytes and its potential clinical significance in insulin resistance.
Abstract-Although progress has been made in the development of submillimeter-wave monolithic integrated circuits, the evaluation of these circuits still relies on test fixtures, which makes testing expensive and time consuming. Based on a W-band prototype, a micromachined on-wafer probe covering frequencies 500-750 GHz is built to simplify submillimeter-wave integrated circuits testing. This paper demonstrates the repeatability and the robustness of this terahertz micromachined on-wafer probe.
A micromachined on-wafer probe is designed, fabricated and measured at W-Band as a proof of concept for probes operating at submillimeter wavelengths. A fabrication process is developed to create devices that combine a waveguide probe with a GSG probe tip on a 15 μm silicon substrate. This device is housed in a metal machined waveguide block that provides mechanical support for the probe and connection to a waveguide flange. Load-cell measurements show a DC contact resistance below 0.07 Ω with a force of 1 mN. A two-tier TRL calibration characterizes the operation of the electromagnetic design and an insertion loss of 1.75 dB is achieved; this is comparable with commercial probes operating in the same band.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.