Search PubMed⌕ Search

Biomedical subjects

R Matthews

Publications and source records attributed to R Matthews.

115 records · Page 7Linked to original sources
PubMedDate not supplied

Analysis of thiol-containing compounds in biological samples by capillary zone electrophoresis.

A new method for the determination of reduced and oxidized glutathione by using capillary zone electrophoresis was developed and compared with the N-(1-pyrenyl)maleimide high-performance liquid chromotography method. The tissue samples were obtained from C57BL/6 mice and homogenized in deionized water. The detection wavelength was set at 214 nm. A 50-cm effective length x 75 microns i.d. uncoated fused silica capillary with a 10 mM phosphate buffer at pH 7.5 was used for the experiment. Samples were introduced by pressure injection for 5s. The voltage for separation was at 20 kV. Between runs, the capillary was regularly washed with 0.1 N NaOH and deionized water, followed by reconditioning with running buffer. The present method was shown to be reproducible and is convenient in that a derivatization step is not required. The method has been used to measure glutathione levels in biological samples and the results show good agreement with those obtained by high-performance liquid chromotography.

Animals↗
PubMedDate not supplied

Quantitative two-dimensional echocardiographic assessment of regional wall motion during transient ischemia and reperfusion in the rat.

Nonlethal myocardial ischemia produces profound and long-lasting effects on regional ventricular function and metabolism (myocardial stunning) and protects against myocardial infarction from subsequent prolonged ischemia (ischemic preconditioning). Two-dimensional echocardiography (2DE) is an essential tool for quantitative analysis of regional and global left ventricular (LV) function during myocardial ischemia and reperfusion and the study of these phenomena. However, the inability to perform 2DE in the open-chest rat heart has seriously limited the use of this model. To investigate the effect of transient coronary occlusion on segmental wall motion and LV geometry, we employed a 20 MHz intravascular ultrasound catheter placed on the epicardial surface of the rat heart (n = 15) to yield 2DE images suitable for quantitative analysis. Three 2-minute left coronary occlusions were made, separated by 5 minutes of reperfusion, with imaging during occlusion and at 5 and 60 minutes of reperfusion. Ischemic and nonischemic wall thicknesses, LV cross-sectional area, estimated LV volume, and the fractional changes of these parameters were measured. In eight animals these values were also compared with necropsy measurements of wall thickness, LV cross-sectional area, and volume. LV and right ventricular structures were well visualized in short-axis cross-sectional images in all animals, and images suitable for quantitative analysis were obtained in 92% of the periods. Coronary occlusion caused immediate, marked LV cavitary expansion, which rapidly returned to normal by 5 minutes of reperfusion. Active systolic thickening of the anterior wall at baseline (47% +/- 3%) became passive thinning during occlusion (-6% +/- 2%) and recovered partially, to 30% +/- 3% at 5 minutes of reperfusion and 42% +/- 4% at 60 minutes (p < 0.0005 at 5 minutes of reperfusion vs baseline; p not significant at 60 minutes). Recovery of thickening after 5 minutes of reperfusion was not different after the first versus third occlusion (23% +/- 4% vs 30% +/- 3%; p = 0.19). Measurements made by 2DE correlated well with those made by necropsy, although wall thickness was slightly thicker by 2DE. We conclude that epicardial echocardiography with an intravascular ultrasound catheter provides quantifiable 2DE images in this model and yields accurate information on segmental wall thickening and ventricular geometry not available by other techniques. Left coronary occlusion in the rat is associated with marked global and segmental LV expansion, which rapidly reverses with reperfusion. Postischemic regional wall motion abnormalities are present after coronary occlusion as brief as 2 minutes and can be measured accurately. The effect of multiple brief occlusions is not cumulative.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Reducing perinatal transmission of HIV: early diagnosis and interventions during pregnancy.

This article reviews the New York State regulations regarding expedited testing of newborns for exposure to HIV. Included is a review of statistics as well as the medical and obstetric management of HIV positive pregnant women, including route of delivery. The professional responsibility of midwives, physicians, and other clinicians regarding maternal and neonatal health care is emphasized, especially in states without expedited testing.

Female↗
PubMedDate not supplied

Evaluation of a genus-specific monoclonal antibody in an amplified enzyme-linked immunoassay in the detection of Chlamydia in urine samples from men.

In this study, the authors used amplified enzyme-linked immunoassay (IDEIA Chlamydia test) on urine samples of 623 male patients attending a sexually transmitted disease clinic. They compared the results with routine urethral cell culture isolation, which showed a sensitivity and specificity of 72.6% and 98.6%, respectively. The sensitivity was significantly higher (79.7%) in patients with clinical evidence of urethritis as compared with those without such evidence (59%). The use of first-catch, early-morning urine may improve the sensitivity of the test.

Antibodies, Monoclonal↗
PubMedDate not supplied

Rapid incidental phosphorus transfers from grassland.

In Britain, frequent rainfall means that there is a high potential for rapid, direct (incidental) losses of phosphorus (P) to occur after fertilizer or manure application. However, despite the known contribution of P to the eutrophication of water bodies in Britain, such incidental transfers have received little experimental attention. To rectify this, we used lysimeter plots (each 3 x 10 m) to investigate incidental transfers in a composite of overland and lateral subsurface flow (0-27 cm) following the application of different P sources. The treatments used were triple super phosphate (TSP), dairy slurry (Slurry), an equal mix of TSP plus slurry (TSP + Slurry), and no P (Zero P). The treatments were applied to wet soil at a rate of 29 kg ha(-1). In the following 169 h, 48.8 mm rainfall (intensity < or =3 mm h(-1)) resulted in total phosphorus (TP) exports between 1.8 and 2.3 kg ha(-1). A single 4-h period (with overland flow) accounted for 33 to 46% of overall loads from the P-amended treatments. Concentrations in discharge from TSP + Slurry and TSP peaked at 11000 microg TP L(-1) (67-68% as reactive P < 0.45 microm (RP<0.45). Slurry peaked at 7000 microg TP L(-1), 66% as particulate TP (>0.45 microm) and 20% as RP<0.45. Even in subsurface flow, concentrations exceeded 3000 microg TP L(-1) for all P-amended treatments. Incidental TP concentrations in plot discharge were up to 110-fold higher than those considered eutrophic in inland waters. We suggest that targeting short-term management decisions for P applications is the most immediately viable method to mitigate P loss and benefit the environment.

Biological Availability↗