Biomedical subjects

D M van Winkle

Publications and source records attributed to D M van Winkle.

4 recordsLinked to original sources

PubMed2000

Propidium iodide compares favorably with histology and triphenyl tetrazolium chloride in the assessment of experimentally-induced infarct size.

Quantitative assessment of infarct size after histology processing or by tetrazolium staining requires long reperfusion times to facilitate the delineation of the injured tissue. We evaluated the nucleic acid stain propidium iodide as an alternate technique for assessment of infarct size because it does not require extended reperfusion and is accomplished with more simple tissue processing. Eight mice underwent 45 min of coronary artery occlusion and 24 h of reperfusion, after which propidium iodide was administered and allowed to circulate for 15 min. Hearts were excised, sliced into transverse slices approximately 620 micro m thick, and photographed for determination of infarction with propidium iodide. Slices were processed by standard histology techniques, and infarction was evaluated using classical criteria of necrosis. In four other mice, infarct size was assessed by both triphenyl tetrazolium chloride and propidium iodide staining. A total of 46 slices were analysed and infarction was described as a percentage of the cross-sectional area of the slice. The correlation (r=0.94), orthogonal regression line (y=0.9x+1.8), and the percentage of the cross-section infarcted (histology 17.5+/-3.0%v propidium iodide 18.5+/-3.0%), demonstrates that infarct size assessment after propidium iodide staining or histology processing yields the same results. Similarly, propidium iodide measurement of infarct size was comparable to that obtained with TCC staining (22.5+/-4.1%v 25.4+/-5.4%, respectively, r=0.84). We conclude that propidium iodide staining yields accurate infarct size assessment and is a simpler alternative to tetrazolium staining or histologic processing.

Animals↗

PubMed1999

Met5-enkephalin protects isolated adult rabbit cardiomyocytes via delta-opioid receptors.

In rats and rabbits, endogenous opioid peptides participate in ischemic preconditioning. However, it is not known which endogenous opioid(s) can trigger cardioprotection. We examined preconditioning-induced and opioid-induced limitation of cell death in isolated, calcium-tolerant, adult rabbit cardiomyocytes. Cells were subjected to simulated ischemia by pelleting and normothermic hypoxic incubation. Preconditioning was elicited with 15 min of simulated ischemia followed by 15 min of resuspension and reoxygenation. All cells underwent 180 min of simulated ischemia. Cell death was assessed by trypan blue permeability. Morphine protected cells, as did preconditioning; naloxone blocked the preconditioning-induced protection. Exogenous Met5-enkephalin (ME) induced protection, but exogenous beta-endorphin did not. ME-induced protection was blocked by the delta-selective antagonist naltrindole. Additionally, two other proenkephalin products, Leu5-enkephalin and Met5-enkephalin-Arg-Phe, provided protection equipotent to ME. These data suggest that one or more proenkephalin products interact with delta-opioid receptors to endogenously trigger opioid-mediated protection.

Animals↗

PubMed1997

High spinal anesthesia does not alter experimental myocardial infarction size or ischemic preconditioning.

OBJECTIVE: The role of the central nervous system in the development of myocardial infarction and ventricular fibrillation in virgin and ischemically preconditioned myocardium was investigated. DESIGN: Infarct size and ventricular arrhythmias were assessed after regional ischemia-reperfusion. Animals were randomly assigned to four groups: (1) preconditioned, central nervous system intact; (2) nonpreconditioned, nervous system intact; (3) preconditioned, nervous system blocked; and (4) nonpreconditioned, nervous system blocked. Differences in hemodynamics and infarct size were assessed with analysis of variance, and differences in ventricular fibrillation were assessed with the Kruskal-Wallis test. SETTING: Experiments were performed in the Anesthesiology Research Laboratory at a medical center. PARTICIPANTS: Anesthetized open-chest New Zealand white rabbits were used for these studies. INTERVENTIONS: Rabbits underwent 30 minutes of coronary artery occlusion and 3 hours of reperfusion. The central nervous system was blocked with total spinal anesthesia. Ischemic preconditioning was elicited with 5 minutes of coronary artery occlusion and 10 minutes of reperfusion. Infarction was assessed with tetrazolium and expressed as a percentage of the risk zone (mean +/- SEM). MEASUREMENTS AND MAIN RESULTS: Preconditioning resulted in infarct size limitation compared with the control (8% +/- 4% v 43% +/- 5%; p < 0.001) and delayed the onset of fibrillation (15.5 minutes v 11 minutes; p = 0.001). Spinal blockade neither altered nonpreconditioned infarct size nor attenuated preconditioning (32% +/- 7% v 8% +/- 3%; p = 0.04), but it was associated with ventricular fibrillation in 24/25 rabbits as compared with 6/14 rabbits without blockade. In blocked animals, preconditioning resulted in a decreased duration of fibrillation (2.5 minutes v 12.5 minutes; p = 0.0004). However, spinal blockade eliminated the preconditioning-induced delay in fibrillation (10 minutes v 12 minutes; p = NS). CONCLUSIONS: It is concluded that (1) activation of efferent sympathetic nerves is not necessary for ischemic preconditioning; (2) preconditioning delays the onset of ventricular arrhythmias; and (3) spinal blockade exacerbates ischemia-induced ventricular arrhythmias.

Anesthesia, Spinal↗

PubMed1994

"Normothermic range" temperature affects myocardial infarct size.

OBJECTIVES: This study tested the hypothesis that small changes in temperature above the hypothermic range may alter myocardial infarct size after acute coronary occlusion-reperfusion. A secondary hypothesis, that a correlation between temperature and infarct size may be independent of an associated change of heart rate, was also evaluated. METHODS: Eighteen pentobarbitone-anaesthetised, open chest rabbits underwent 30 min coronary artery occlusion and 3 h reperfusion at blood temperatures ranging from 35-42 degrees C, achieved and maintained using surface methods (not paced, group NP). In a second group of 11 animals, heart rate was held constant across the same range of temperatures (paced, group P), before and throughout coronary artery occlusion-reperfusion. Infarct sizes were assessed by the tetrazolium method. RESULTS: Target temperature was effectively controlled over the duration of the experimental protocol to within +/- 0.25 degrees C. Area at risk did not vary with temperature. Infarct size, normalised to area at risk, was correlated with temperature in both groups (infarct size = 7.9 x temp-250.0, r = 0.75, p = 0.0003, group NP; infarct size = 11.7 x temp-404.5, r = 0.88, p = 0.0004, group P). There was no significant difference between the slopes of these two lines (p = 0.18), indicating that the positive correlation between infarct size and temperature is not related to changes of heart rate. CONCLUSION: Temperatures in the range of 35-42 degrees C affect myocardial infarct size significantly, independent of heart rate.

Animals↗