Stretch of the myocardium influences the shape and amplitude of the intracellular Ca(2+)([Ca(2+)](i)) transient. Under isometric conditions stretch immediately increases myofilament Ca(2+) sensitivity, increasing force production and abbreviating the time course of the [Ca(2+)](i) transient (the rapid response). Conversely, muscle shortening can prolong the Ca(2+) transient by decreasing myofilament Ca(2+) sensitivity. During the cardiac cycle, increased ventricular dilation may increase myofilament Ca(2+) sensitivity during diastolic filling and the isovolumic phase of systole, but enhance the decrease in myofilament Ca(2+) sensitivity during the systolic shortening of the ejection phase. If stretch is maintained there is a gradual increase in the amplitude of the Ca(2+) transient and force production, which takes several minutes to develop fully (the slow response). The rapid and slow responses have been reported in whole hearts and single myocytes. Here we review stretch-induced changes in [Ca(2+)](i) and the underlying mechanisms. Myocardial stretch also modifies electrical activity and the opening of stretch-activated channels (SACs) is often used to explain this effect. However, the myocardium has many ionic currents that are regulated by [Ca(2+)](i) and in this review we discuss how stretch-induced changes in [Ca(2+)](i) can influence electrical activity via the modulation of these Ca(2+)-dependent currents. Our recent work in single ventricular myocytes has shown that axial stretch prolongs the action potential. This effect is sensitive to either SAC blockade by streptomycin or the buffering of [Ca(2+)](i) with BAPTA, suggesting that both SACs and [Ca(2+)](i) are important for the full effects of axial stretch on electrical activity to develop.

Actin Cytoskeleton↗

PubMedDate not supplied

Geographic studies of pediatric cancer near hazardous waste sites.

The incidence of pediatric (i.e., 0-17 y of age) cancers in North Carolina was studied for the years 1990-1993 in counties and ZIP-code areas that contained a National Priorities List hazardous-waste site. We analyzed the areas to determine if there was an excess incidence of cancer among the pediatric population. We used geographic information systems technology to address-match and map the cancer cases, along with county and National Priorities List hazardous waste-site location. No significantly elevated cancer incidence rates were found at the county level. Two ZIP-code areas had statistically significant elevations in cancer incidence (p < .05). Only 3 of the cancer cases we mapped resided within a 1.6-km (1 mi) buffer zone of a National Priorities List hazardous-waste site. These 3 cases were not in the ZIP-code areas that had increased incidence rates. The small numerators throughout the study led us to question the accuracy of the assessment of underlying rates. The general capabilities of the geographic information systems, as well as advantages and limitations of the system, are discussed. As an exploratory study, this study serves as a springboard into more in-depth environmental-health hypotheses and more-specific investigations of point sources of hazardous exposures.

Adolescent↗

PubMedDate not supplied

The certification of cocaine and benzoylecgonine in a human urine standard reference material.

The concentrations of cocaine and benzoylecgonine (BE) in Standard Reference Material (SRM) 1508, cocaine and metabolites in freeze-dried human urine, were determined at the National Institute of Standards and Technology (NIST, formerly NBS) by two independent methods. For cocaine, one method was based on gas chromatography/mass spectrometry (GC/MS); the other was based on high-performance liquid chromatography (HPLC). For BE, one method was based on GC/MS; the other was based on flow injection analysis/thermospray mass spectrometry (FIA/MS). The results for each pair of methods were statistically evaluated. Concentrations were determined in the SRM for three levels of cocaine and three levels of benzoylecgonine. Methylecgonine, although present in the material, was not determined. For cocaine, the concentrations were 90, 263, and 429 ng/mL of human urine. For BE, the concentrations were 103, 259, and 510 ng/mL of human urine.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Determination of 3-quinuclidinyl benzilate (QNB) and its major metabolites in urine by isotope dilution gas chromatography/mass spectrometry.

In response to the scheduled destruction of U.S. military stockpiles of the hallucinogenic agent 3-quinuclidinyl benzilate (QNB), a specific confirmatory test for human exposure to QNB was developed. The amount of the parent compound in the urine as well as the two major metabolites, 3-quinuclidinol (Q) and benzilic acid (BA), was determined because the relationship between QNB dose and levels of QNB and its metabolites in human urine is not known. QNB was determined in urine samples spiked at a target level of 0.5 ng/mL, and the metabolites BA and Q were determined at a target level of 5 ng/mL. The method uses solid-phase extraction to isolate each analyte from the urine and isotope dilution gas chromatography/mass spectrometry for quantitation. Each analyte is converted to its trimethylsilyl derivative for analysis. The analytical method was tested on eight different urine samples spiked with known amounts of the analytes near the target levels, at 10 times the target levels, and blank (unspiked) urine samples. The variabilities in the method are for the most part evenly distributed between three imprecision categories: GC/MS measurement, sample preparation, and the urine samples. The total imprecision (1 standard deviation) of a single measurement is about 15% of the value for each analyte.

Gas Chromatography-Mass Spectrometry↗

PubMedDate not supplied

Effects of primary allogeneic tooth transplants on rejection of skin allografts in rabbits.

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Animals↗

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Diffusion hyperoxia following preoxygenation.

Several minutes of 100 percent O2 breathing prior to inhalation induction with 79 percent N23 results in consistently higher PaO2 values during the first 10 minutes compared with prior air breathing. The theoretic maximum concentrating action of N2O uptake upon O2 is approximately the same (60 torr) regardless of gas breathed before induction.

Adult↗

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The inverted type: homosexuality as a theme in James Merrill's prophetic books.

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Female↗

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Who wants to know?

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Breast Neoplasms↗