English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Postischemic ventricular myocardial dysfunction, termed stunning, is characterized by a persistent but ultimately reversible depression of contractile function. The present study was undertaken to investigate the possibilities that reduced contractile force in stunning is due to a decrease in maximal tension-generating capability or to a decrease in the Ca2+ sensitivity of the myofilaments. The experiments combine an in vivo open-chest porcine heart model of stunning (n = 5) with in vitro measures of myocyte myofilament calcium sensitivity from these same hearts. Regional myocardial function in the left anterior descending coronary artery (LAD) perfusion bed of porcine hearts was measured with transmural ultrasonic crystals. The protocol was 45 minutes of low-flow LAD ischemia at 40% of control flow, followed by 30 minutes of postischemic reperfusion at control aerobic flow. Percent systolic wall thickening decreased to 8 +/- 5% of control during ischemia (p &lt; 0.05) and returned to 38 +/- 8% of control in the postischemic stunned state (p &lt; 0.05). Serial endocardial biopsies were obtained from the preischemic and postischemic myocardium in the LAD perfusion bed and from the aerobically perfused myocardium in the circumflex bed. The biopsies were mechanically disrupted, and myocyte-sized preparations of permeabilized myocardium were attached to a force transducer and a length-changing device to allow for direct measurement of steady-state tension-pCa (i.e., -log[Ca2+]) relations. The pCa for half-maximal activation of tension, i.e., pCa50, in LAD myocardium decreased from 5.88 +/- 0.05 before ischemia to 5.69 +/- 0.03 after ischemia (p &lt; 0.05); however, maximal Ca(2+)-activated tension and the slope of the tension-pCa relation were unaffected by the ischemic episode.(ABSTRACT TRUNCATED AT 250 WORDS)

Altered calcium sensitivity of isometric tension in myocyte-sized preparations of porcine postischemic stunned myocardium.