In: Septic Shock2 Nov 2014
With the revised system, it became apparent that the age of the myocardial cells grown in this primary cell culture system had an important relationship to the sensitivity of the myocardial cell response to the depressant stimulus. Simply stated, the sensitivity of the myocardial cells both to drugs (eg, verapamil) and to serum changes as the cells mature. In the early stages of development (days 4 to 6), the cells are sensitive to a variety of stimuli. As the cells mature (days 7 to 9), they become resistant to these same stimuli. This change in maturation of the heart cells is associated with a decrease in the intrinsic beating rate of these heart cells. We have been careful to choose culture dishes with the following characteristics: a regular rhythm; vigorous contractility; and cells that have not grown to confluence.
Using cells with these characteristics, the assay for myocardial depressant activity is conducted as follows. Young cells (days 4 to 6) are useful for screening patient samples. During this period, the cells are sensitive to relatively low concentrations of pharmacologic agents (eg, verapamil), and the beating myocytes are depressed by sera with relatively weak depressant capability. If negative results (ie, failure to depress the myocardial cells at least 20 percent) are obtained with a patients serum using these younger sensitive cells, such a serum would be deemed “MDS negative.” The older cells (days 7 to 9) are less sensitive and therefore more specific for MDS activity. If a patients serum was positive on early sensitive cells, the assay was always repeated on older, less sensitive (more specific) myocytes. If positive on these cells, a patient was considered a definite positive. Each patient judged “MDS positive” had to depress older myocardial cells (seven to nine days in culture) on at least two of four occasions, including two different Petri dishes of myocardial cells in culture.
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