In: Septic Shock1 Nov 2014
The procedure can be summarized as follows. Spontaneously beating rat myocardial cells grown in a Petri dish were placed on a dissecting microscope stage. The growth medium was removed from the Petri dish supernatant and replaced by control physiologic medium employing 20 percent heat-inactivated newborn calf serum (20 percent serum, 58 percent Dulbeccos BBS-K, and 22 percent Medium 199). The cells were allowed to equilibrate for 15 min. Baseline values for extent of myocardial cell shortening (contraction) were obtained. Then 2 ml of 20 percent patient serum (control or test) plus physiologic medium was placed on the cells and allowed to equilibrate for 15 min.
The percentage of depression of myocardial cell contractility was calculated as decrease in extent of shortening with test serum divided by extent of shortening with control serum. A positive assay for MDS was defined as 20 percent or greater depression of myocardial cell contractility (vs control) that was consistent and reproducible on two or more occasions. Any sample that failed to depress contractility 20 percent or more was considered negative. This 20 percent cutoff was chosen because it appears to provide good discrimination between normal control or critically ill control serum and patients with septic shock who have MDS activity. fully
Myocardial Cell Assay Reproducibility
A previous publication has described a revised method of assaying the extent and velocity of mammalian (rat) myocardial cell contraction in vitro. The revised method used a closed-loop electronic tracking system to quantify the distance traveled by a latex bead affixed to the myocardial cell membrane. This system represented very accurately the distance and distance per unit time (velocity) of the myocardial cell membrane during contraction and relaxation.
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