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Biomedical subjects

D Waters

Publications and source records attributed to D Waters.

168 records · Page 10Linked to original sources
PubMedDate not supplied

Reversibility and pathohistological basis of left ventricular remodeling in hibernating myocardium.

The phenomenon of left ventricular (LV) remodeling with dilatation, wall thinning, and increased muscle mass has previously been reported in pigs with 7-day myocardial hibernation. This study investigated cellular and extracellular basis and reversibility of the structural LV remodeling with hibernating myocardium. Five groups of pigs were included: Group A: 7-day myocardial hibernation with a fixed coronary stenosis; Group B: 7-day hibernation with subsequent 3-week reperfusion by release of the stenosis; Group C: control group with sham operation; Group D: 24-hour myocardial hibernation to define structural mechanism of initial wall thinning in the hibernating region without confounding factors of cell loss or hypertrophy, Group E: 4-week myocardial hibernation to exclude the possibility of spontaneous regression of LV remodeling with hibernation. LAD flow decreased by 38+/-12% (p<0.01) with a significant decrease in systolic wall thickening at 7 days of hibernation with severe coronary stenosis (Group A). End-diastolic wall thickness decreased by 19% (p<0.01) accompanied by a decrease in myocyte number across the wall (44%) and in myocyte density (24%), a significant increase in myocyte width (17%), a mild increase in interstitial tissues in hibernating region, and significant increases in LV diastolic volume and in LV mass at 7 days. After reperfusion (Group B), LV volume decreased, LV ejection fraction improved, and myocyte hypertrophy regressed with a decreased LV mass index without a significant change in interstitial tissue. LV remodeling progressed with further increases in LV volume, mass, and interstitial fibrosis in 4-week hibernation. In pigs undergoing 24 hours of myocardial hibernation (Group D), end-diastolic LV wall thickness decreased significantly in the hibernating region with a proportional decrease in the transmural myocyte number but without changes in myocyte width, myocyte density, or interstitial tissues. Therefore, progressive gross LV remodeling associated with hibernating myocardium is accompanied by increasing myocyte hypertrophy and interstitial fibrosis. In hibernating myocardial region, wall thinning is proportional to a decreased myocyte number across the LV wall, indicating slippage of myocytes as a preponderant mechanism for the wall thinning. Myocyte hypertrophy develops within 7 days in hibernating myocardium, causing an increase in LV mass. These changes are partially reversible after reperfusion.

Animals↗
PubMedDate not supplied

Comparison of exercise, dipyridamole, adenosine, and dobutamine stress with the use of Tc-99m tetrofosmin tomographic imaging.

PURPOSE: The purpose of this study was to compare defect extent and severity and myocardial uptake with exercise and pharmacologic stress with technetium-99m (Tc-99m) tetrofosmin tomographic myocardial perfusion imaging. BACKGROUND: Detection of stress-induced myocardial perfusion defects depends on both a disparity in blood flow between normal and stenotic vessels and the extraction fraction and linearity of myocardial uptake of the tracer. There are limited clinical data for exercise or pharmacologic stress with Tc-99m tetrofosmin tomographic myocardial perfusion imaging. METHODS: Thirty-one patients with coronary artery disease and 7 with a < 5% likelihood of coronary artery disease underwent on separate days Tc-99m tetrofosmin single-photon emission computed tomographic imaging at rest and after exercise, dipyridamole, adenosine, and dobutamine stress. Images were interpreted by a blinded consensus of 3 experienced readers with a 17-segment model and 5-point scoring system. RESULTS: Compared with exercise, the summed stress score was smaller with dipyridamole (P < .01), and the reversibility score was smaller with both dipyridamole (P < .01) and dobutamine (P < .05), whereas the number of abnormal and reversible segments was less with both dipyridamole (P < .01 and P < .001, respectively) and dobutamine (both P < .05). No significant differences were found in the summed stress or reversibility scores and the number of abnormal or reversible segments between exercise and adenosine. CONCLUSIONS: Compared with exercise, defect extent, severity, and reversibility are less with dipyridamole and dobutamine with Tc-99m tetrofosmin single photon emission computed tomographic imaging.

Adenosine↗
PubMedDate not supplied

Absence of human T-lymphotropic virus types I and II infection in an Ontario hemophilia population.

Two hundred ninety-three serum samples from Ontario hemophiliacs and 200 samples from human immunodeficiency virus-positive blood donors were screened for the presence of antibodies to human T-lymphotropic virus type I (HTLV-I) by enzyme-linked immunosorbent assay, radioimmunoassay, and Western blot techniques. None of the serum samples provided unequivocal positive results, but several samples gave inconclusive results. Of the hemophiliacs with inconclusive serologic results from whom peripheral blood lymphocyte DNA could be obtained, all were negative for HTLV-I and HTLV type II (HTLV-II) sequences as determined by polymerase chain reaction (PCR). PCR was also performed on a lymph node biopsy sample taken from a hemophiliac who developed a rare T-cell lymphoma; the sample was negative for HTLV-I and -II sequences. These results indicate that Ontario hemophiliacs have not been exposed to HTLV-I or HTLV-II.

Adult↗
PubMedDate not supplied

Correlation between plasma physostigmine concentrations and percentage of acetylcholinesterase inhibition over time after controlled release of physostigmine in volunteer subjects.

Five to six subjects ingested doses of controlled-release physostigmine salicylate tablets (9, 12, and 15 mg) followed by sequential blood drawing for measurement of plasma physostigmine concentrations and percentage of acetylcholinesterase (AChE) inhibition. Both plasma physostigmine concentrations and percentage of AChE inhibition demonstrated dose proportionality to three doses of ingested drug. Plasma physostigmine concentrations correlated with percentage of AChE inhibition across time by dose and across all doses and subjects tested. These data should be helpful to physicians in adjusting physostigmine dosing, enabling them to use the relatively simple and widely available AChE assay to approximate plasma physostigmine concentrations.

Adult↗
PubMedDate not supplied

HIV-1 and HIV-2 in Ghana, west Africa: community surveys compared to surveys of pregnant women.

We conducted a population-based serosurvey of HIV-1/2 in 2,410 residents of two urban and two rural areas of southern Ghana, West Africa and compared the results to serosurveys of 1,417 pregnant women. Using conservative criteria, we found the prevalence of HIV-1/2 in community survey adults (> 15 years old) to be 1.5% in women and 1.0% in men. Among pregnant women, the prevalence was 9.3% in one rural area but only 1.0% in other areas. Many samples, especially among the pregnant women were HIV-1 and -2 dual reactive on serology. We attribute the disparity between prevalence in the community survey participants and pregnant women to local socio-economic factors. Women in this area have a tradition of working throughout West Africa as trader/ commercial sex workers. When pregnant or ill, they return to their home villages to be with their families. HIV surveillance programs which rely on pregnant women need to be sure that sampled populations are truly typical of the communities they are intended to represent.

Adolescent↗