Josep G. Llaurado

Connective tissue composition of human coronary artery and its relationship to divalent cation context.

* Present Address: Biomedical Engineering Group, Marquette University and Marquette School of Medicine, Milwaukee, and Veterans Administration Center, Wood, Wisconsin, 53193 Supported by Grants USPHS HE-07762 and N-ONR 551 (54) Physiological and clinical considerations of coronary artery blood flow usually treat resistance of the bed as a function of smooth muscle activity, modified by pathological processes in the arterial wall and by mechanical effects of the contracting myocardium. However, normal connective tissue structure of an artery plays a role in its distensibility, since connective tissue elements represent over one-half the dry weight of arterial walf and account for passive tension in the wall without the expenditure of energy2. The relative amounts of collagen and elastin influence this passive distensibility by affecting the tension-strain relationship in the wall2, 3, the collagen fibers being much less &dquo;stretchable&dquo; than the elastin fibers. Scott et al4 in a study on coronary blood flow in dogs suggested that one cause of the gradually declining rate of fall of resistance in the coronary bed as flow rate increased might be a gradual approach to the limit of distensibility of this bed. Previous studies on connective tissue content of various arteries in normal’ and hypertensive5 dogs have shown that the coronary artery has the highest collagen to elastin ratio (C/E) of all arteries studied, this ratio having been suggested as an index of passive distensibility due to connective tissue structure. If a high C/E also obtains in the human coronary artery it might have clinical implications in that structurally the degree of coronary vasodilation could be limited. The present report is concerned with the quantities of collagen and elastin in the human coronary artery as compared to its vessel of origin, the ascending aorta. In addition concentrations of three divalent cations, viz., calcium, magnesium and zinc, were determined in many of the same specimens to assess whether these elements bear any relationship to connective tissue composition.

Some observations on the effects of time curtailing on the parameters of decaying exponentials fitted to biomedical data

Abstract Digital-computer methods allow for resolution of certain experimental response curves versus time into a sum of exponentials without prolonging the actual experiment until a straight-line part of the curve appears. This report indicates that mean parameter values (exponential coefficients and factors) for exponential fittings to experimental curves of 22Na outflow from squirrel monkey brain biopsies undergo no statistically significant difference when the points belonging to the second half-hour of the experiment were not used. This result might be extended to other sets of experimental data. Some practical implications of this finding are: (a) economy in time for the recording of experimental data, (b) better survival possibilities for biological tissues kept under precarious conditions, (c) reassurance for records which could not be carried out to completion.