The coronary arterial system was characterized by its input impedance determined in systole and diastole from impulse response functions in five dogs. The impulse response technique was verified on a known hydraulic system. A second confirmation was obtained on the circumflex artery: reflected pulses were correlated with site of reflections generated by occlusions. The impulse response indicates discrete reflections, superimposed on the tail of the response, resulting from diffuse reflections. Input impedance was calculated from Fourier analysis of the impulse response. Characteristic impedance was 1.0 +/- 0.2 X 10(9) Pa X s X m-3 (0.13 +/- 0.02 mmHg X ml-1 X min) and impedance at 0 Hz was 2.6 +/- 0.8 X 10(9) Pa X s X m-3. No significant differences between systole and diastole were found in both characteristic impedance and impedance at 0 Hz. It is concluded that the coronary system consists of a proximal part that can be described with the three-element windkessel and a distal part not seen by oscillatory pressure or flow perturbations, which depends on the phase of cardiac contraction.

This study was performed to elucidate the effects of cardiac contraction on coronary pressure-flow relations. On the basis of the waterfall mechanism, a lumped model of the coronary arterial system is presented consisting of a proximal (epicardial) compliance, a coronary resistance, and an intramyocardial compliance. A "back"-pressure, assumed to be proportional (constant k) to left ventricular pressure, impedes flow. From steady-state measurements of circumflex coronary artery flow and inflow pressure, together with left ventricular pressure, the values of the three model parameters and the constant k have been estimated. In the control condition proximal compliance is found to be 1.7 X 10(-12) m4s2kg-1, intramyocardial compliance 110 X 10(-12)m4s2kg-1, and resistance 7.5 X 10(9) kgm-4s-1. The proportionality constant k is close to unity. Effects of changes in left ventricular pressure and inflow pressure and the effect of vasoactive drugs on the parameters are also investigated. Changes in coronary resistance are always opposite to changes in intramyocardial compliance. Sensitivity analysis showed that epicardial compliance plays its major role during isovolumic contraction and relaxation; resistance plays a role throughout the cardiac cycle but is more important in diastole than in systole, whereas intramyocardial compliance plays a role in systole and in early diastole.

Labeled leucine, serine, galactose, glucosamine and sulphate were administered to rat stomachs in a perfusion system. Sections of the gastric fundus were studied by light microscopic autoradiography. Five categories of mucous cells were distinguished and their glycoprotein synthetic activity was measured in autoradiographs by counting silver grains over each category. During their differentiation, while migrating from the isthmus of the fundic glands to the free luminal surface, the surface mucous cells (SMC) showed an increase in incorporation of all precursors used. Differences between the incorporation patterns of the various precursors, in cells of different ages, suggest that structural development runs ahead of functional activity, and that the latter continues up to the very moment the cell is shed from the surface. Sulphate was incorporated at a considerably lower rate by the SMC of the free surface than by the foveolar SMC, in which by cytochemical staining strongly acidic glycoproteins were shown. Since the mucous neck cells incorporated all precursors at a low rate, these cells apparently do not play an important role in gastric mucus synthesis. They did not incorporate sulphate, which is consistent with histochemical observations.

No abstract

Although a clinical dose of carbenoxolone has no effect on HCI and pepsin secretion,9 its precipitation of glycoproteins from the gastric lumen'0 is also a complicaiting factor.When, after several weeks of carbenoxolone administration, a new steady state has been reached in long-term experiments, an increased rate of secretion is impossible without a higher rate of glycoprotein synthesis in the mucinproducing gland cells of the stomach. We therefore compared the rate of radioactive sugar and amino acid incorporation in the cells of the superficial gastric epithelium of rats treated with carbenoxolone (three weeks) and of control rats by measuring the radioactivity per cell in autoradiographs. The radioactive precursors were administered in a vascular perfusion system of the rat stomach ex vivo."1 12