Seismic evidence for a cold serpentinized mantle wedge beneath Mount St Helens.

Mount St Helens is the most active volcano within the Cascade arc; however, its location is unusual because it lies 50 km west of the main axis of arc volcanism. Subduction zone thermal models indicate that the down-going slab is decoupled from the overriding mantle wedge beneath the forearc, resulting in a cold mantle wedge that is unlikely to generate melt. Consequently, the forearc location of Mount St Helens raises questions regarding the extent of the cold mantle wedge and the source region of melts that are responsible for volcanism. Here using, high-resolution active-source seismic data, we show that Mount St Helens sits atop a sharp lateral boundary in Moho reflectivity. Weak-to-absent PmP reflections to the west are attributed to serpentinite in the mantle-wedge, which requires a cold hydrated mantle wedge beneath Mount St Helens (<∼700 °C). These results suggest that the melt source region lies east towards Mount Adams.

Issues and implications in the selection of blood glucose monitoring technologies.

Over the last 2 decades assay technology originating in the laboratory has been adapted for the special situation of in vitro blood glucose monitoring in the home, at work or play, or at the bedside. The availability of blood glucose monitoring devices has had a significant impact on the treatment of diabetes, especially with respect to involving the patients in their treatment. The unique requirements of this type of testing have led to novel developments in sample acquisition techniques, analyte detection, measurement techniques, and error detection. The performance of these in vitro devices in terms of accuracy and imprecision is largely dependent on factors that contribute to variation in response that are related to testing with blood samples outside of the laboratory. These factors include, for example, variations in environmental conditions, the variability of hematocrit and oxygen concentrations of the blood, and the fact that the blood is used undiluted. Therefore, the technologies used have been selected, developed, optimized, and calibrated to minimize the impact of these factors. The technologies also must be capable of providing accurate, reproducible results over the large range of clinical interest from the hypoglycemic range to glucose concentrations 10 to 15 to 20 times greater. However, when selecting a technology there are invariably some trade-offs to consider. Thus, the products must be optimized to balance performance, reliability, and cost. Examples are discussed.

Adaptation of microvolume EMIT assays for theophylline, phenobarbital, phenytoin, carbamazepine, primidone, ethosuximide, and gentamicin to a CentrifiChem chemistry analyzer.

We have developed microvolume EMIT procedures for theophylline, phenobarbital, phenytoin, carbamazepine, primidone, ethosuximide, and gentamicin using a centrifugal analyzer (CentrifiChem and Pipettor 1000) to reduce the manufacturer's recommended manual reagent consumption by one-sixth. In addition to developing the EMIT procedure, the performance of the analyzer and pipettor were verified. The analyzer and pipettor are capable of producing within-run precision at a 3-microliters sample volume and 210-microliters analyzer cuvette volume equal to or less than 1.5%. The performance of the EMIT procedures on the analyzer yielded spike drug recoveries of 90.8 to 106.1% for drug concentrations throughout the calibration concentration range of each assay. The percent error on standard reference material of the National Bureau of Standards ranged from a +12.0% to a -0.6% for ethosuximide, phenobarbital, phenytoin, and primidone. Patient comparison data yielded slopes from 0.930 to 1.110 for all assays. The other important feature of the adapted EMIT assay is its simplicity for use on a routine basis.

Observation of a variant creatine kinase isoenzyme in sera and breast tumor cytosols.

A variant creatine kinase (CK) isoenzyme was identified in the sera of some patients who had advanced adenocarcinoma of the breast, stomach, and large intestine. A similar variant isoenzyme, together with a high concentration of CK-BB isoenzyme, was identified in some breast tumor cytosols. The variant creatine kinase activity in both sera and tumor cytosols was unaffected by antibodies specific for both the CK-M and DK-B subunits. This indicates that DK-MB isoenzyme determinations are currently best performed by electrophoretic rather than immunologic technics.

Determination of the backbone structure of nucleic acids and nucleic acid oligomers by laser Raman scattering.

Raman spectra of fibers of DNA that have been prepared in the A, B, and C forms are presented and compared with Raman spectra of DNA and RNA in dilute solution. It is shown that the phosphate vibrations in the region 750-850 cm(-1) are very sensitive to the specific conformation of the phosphate group in the backbone chain and are virtually independent of all ohter factors. Thus, a very simple method for the determination of the specific conformation of the backbone chain of nucleic acids, at least so far as the sugar-phosphate chain is concerned, appears available. The method is applied to short oligomers and dimers of ribonucleosides. It is found that at low temperatures, at pH 7, the phosphate group goes into the geometry of the A conformation when the stacking forces between the bases are sufficiently strong.