Biomedical subjects

H Stam

Publications and source records attributed to H Stam.

95 records · Page 6Linked to original sources

PubMedDate not supplied

Intracoronary infusion of small doses of nifedipine lowers regional myocardial O2-consumption without altering regional myocardial function.

Intracoronary infusion of low doses (0.1-0.3 microgram X kg-1) of nifedipine caused dose-dependent decreases in regional myocardial O2-consumption, without significant changes in any of its major global hemodynamic determinants: heart rate, left ventricular systolic and end-diastolic pressure and maxLVdP/dt. Furthermore, regional myocardial function was unaltered. It is suggested that nifedipine decreased myocardial O2-consumption by a direct effect on myocardial metabolism. Some of the possible mechanisms involved are discussed.

Animals↗

PubMedDate not supplied

Effect of fasting and streptozotocin-diabetes on the coronary flow in isolated rat hearts: A possible role of endogenous catecholamines and prostaglandins.

The coronary flow rate of retrogradely perfused hearts from fasted (group I) and streptozotocin-diabetic rats (group II) is increased when compared with the flow rate of control, fed animals (group III). The enhanced coronary flow is absent when hearts of groups I and II are perfused in the presence of indomethacin (1 microgram/ml) in the perfusion fluid and the lowest flow rates are observed after depletion of the endogenous catecholamines by reserpin. Hearts from groups I and II showed a marked increase in prostaglandin-release which was counteracted both in the presence of indomethacin (1 microgram/ml) and by reserpin-pretreatment. The results suggest that the increased coronary flow rates in hearts from fasted and streptozotocin-diabetic rats are mediated by an effect of released endogenous catecholamines on coronary vascular smooth muscle and by a catecholamine-induced release of vasodilatory, prostaglandin-like substances.

Animals↗

PubMedDate not supplied

Metabolic consequences of Sephadex-induced reduction of coronary flow in isolated rat heart.

With a polysaccharide microsphere suspension (Sephadex), coronary flow of isolated perfused rat hearts was reduced by approximately 70%. During this Sephadex-induced ischemia, the energy charge and creatine phosphate content of the myocardial tissue dropped significantly, while total nucleoside and lactate release from the heart increased. During hypoxia (30% O2), changes in high-energy phosphate content and lactate and nucleoside release were similar to the changes induced by ischemia. During hypoxia, coronary flow rate was increased by 47%. Thus, Sephadex-induced reduction of coronary flow could be a useful model in studies of metabolic change during ischemia.

Adenine Nucleotides↗

PubMedDate not supplied

Interpretation of changes in spirographic and flow-volume variables after operative treatment in bilateral vocal cord paralysis.

In 13 patients, who underwent a superolateralization of a vocal cord after bilateral vocal cord paralysis, we studied pre- and postoperatively spirometric dynamic and static lung volumes and variables from maximal expiratory and maximal inspiratory flow-volume (MEFV and MIFV) curves. The effects of surgical treatment on these variables have been established by comparing the statistical significance of the changes post- versus preoperative. A significant increase was found in the vital capacity and a significant decrease in the indices associated with the dynamic variability of the obstruction. The most significant changes were found in peak inspiratory flow and peak expiratory flow, and in the inspiratory defined dynamic estimates, as forced inspiratory volume in 1 second and maximal voluntary ventilation at a frequency of 30 c X min-1. Significant correlations, however, were found to exist only for the changes within the group of flow-volume indices and for those within the group of spirographic variables. This led us to the conclusion that for the diagnosis of this type of upper airway obstruction these measurements are additive, reflecting different aspects of airway mechanics.

Adult↗

PubMedDate not supplied

The components of the carbon monoxide diffusing capacity in man dependent on alveolar volume.

The effect of alveolar volume (VA) on diffusing capacity for carbon monoxide (DL), membrane conductance (Dm) and pulmonary capillary blood volume (Qc) was investigated in 39 normal volunteers to study alveolar membrane expansion and capillary volume recruitment. DL/VA was related to alveolar volume breathing air and 95% oxygen respectively. Both relations appeared to be linear with a negative slope and were used to calculate Dm and Qc as a function of VA. The relation between Dm and VA resulted in: Dm = kVAx, where x characterizes the kind of membrane expansion with increasing alveolar volume, when we assume Dm = kA/delta. In this equation, A is the membrane area and delta the membrane thickness. In 36% of our subjects, x was nearly 0.67, which corresponds to an isotropic expansion of diffusion area with alveolar volume without changes in delta. In 41%, x was between 0.67 and 1. We hypothesized that, in these subjects, either some decrease of delta or some recruitment of alveoli was superimposed on the area increase according to x = 2/3. In recruitment, a proportional increase of diffusion area with alveolar volume is assumed, which means x = 1. Subjects over the age of 50 years (n = 12) showed greater variation in the value of x, which was greater than 1.3 in three and less than 0.6 in a further three. The relation between Qc and VA was best described by a second order polynomial, characterized by a maximum above 50% of VAmax. With lung expansion, either a recruitment of capillaries or a better contact between blood and air could occur up to that maximum. Where Qc was decreasing with further rise of VA, we assumed compression of capillaries by stretching of pulmonary tissue.

Adolescent↗