PubMed Health⌕ Search

Biomedical subjects

M Yanaka

Publications and source records attributed to M Yanaka.

4 recordsLinked to original sources
PubMed1990

Effect of blood filling in intramyocardial vessels on coronary arterial inflow.

The influence of the filling condition of the unstressed volume (UV) of intramyocardial vessels on the diastolic coronary arterial pressure-flow relationship was analyzed. UV is defined as the blood volume at zero transmural pressure. In seven anesthetized, paced dogs with induced heart block, coronary artery inflow was occluded so that blood in the UV was displaced into the coronary vein by myocardial contraction. After pacing was turned off, coronary perfusion pressure was increased stepwise to seven target pressures (20-90 mmHg). After reperfusion, left anterior descending coronary arterial (LAD) flow reached an initial quasi-steady level, but great cardiac venous (GCV) flow was absent (UV-unfilled phase). With reappearance of the GCV flow (UV-filled phase), LAD flow decreased to a final steady level. Pressure-flow relationships during both phases were linear (r = 0.97-0.99). The inverse of the slope of the pressure-flow relationship during the UV-filled phase, 0.69 +/- 0.08 mmHg.min.ml-1, was significantly higher than that during the UV-unfilled phase, 0.55 +/- 0.06 mmHg.min.ml-1 (P less than 0.01), although the zero-flow pressure intercepts were similar (18.9 +/- 1.8 mmHg for UV filled vs. 19.9 +/- 2.2 for UV unfilled). These results indicate that diastolic coronary arterial inflow is impeded by a blood volume within intramyocardial vessels that exceeds the UV.

Animals↗
PubMed1989

Analysis of the characteristics of the flow velocity waveforms in left atrial small arteries and veins in the dog.

To clarify the characteristics of the phasic blood velocity pattern in small arteries and veins on the left atrial surface, we used our newly developed fiber-optic laser Doppler velocimeter. We intended particularly to examine the influence of atrial contraction and relaxation on velocity waveforms to obtain some insight into the nature of the mechanical force acting on the atrial intramyocardial vascular beds. In 14 anesthetized open-chest dogs, the left atrial appendage was gently displaced to expose small branches of the artery and vein. Vessels with an outer diameter of about 150-500 microns were chosen for the measurements because their walls are transparent to laser light. The fiber tip (velocity sensor) was fixed on the vessel surface with a drop of cyanoacrylate when good-quality Doppler signals were consistently observed. Additional experiments with three dogs were performed to observe the blood velocities in the atrial artery and vein during arrhythmia. The blood velocity waveform in the artery was similar to the pattern of aortic pressure during ventricular ejection (peak velocity, 18.8 +/- 7.8 cm/sec) but was characterized by a pronounced dip during atrial contraction. The temporal coincidence between the dip formation and atrial contraction was confirmed during atrial flutter with an atrioventricular block. After isoproterenol administration (2 micrograms i.v.), the acceleration rate of the forward flow velocity increased by 176% (p less than 0.05), and reverse flow appeared during atrial contraction in five cases out of eight (p = 0.013). The blood flow velocity in atrial small veins, on the other hand, was predominant during atrial contraction (peak velocity, 15.6 +/- 5.8 cm/sec). Isoproterenol increased the acceleration rate of this forward flow velocity by 121% (p less than 0.01). Nitroglycerin did not change the blood velocity waveform significantly in atrial arteries or in veins. The phase opposition between arterial inflow into and venous outflow from the atrial myocardium indicates that a large portion of the coronary inflow to the atrial myocardium may be stored due to the presence of atrial myocardial vascular capacitance. We conclude that atrial myocardial contraction impedes atrial inflow and promotes venous outflow from atrial capacitance vessels.

Animals↗
PubMed1978

Plasma cell granuloma (inflammatory pseudotumor) of the spinal cord meninges: report of a case.

A case of plasma cell granuloma (inflammatory pseudotumor) arising in the meninges of cervical spinal cord of a 37-year-old Japanese man is presented. The diagnosis was made by analogy with the similar lesions known in the lung. Its histology was characterized by infiltration of three kinds of cells; histiocytes with slight epithelioid appearance, plasma cells with numerous Russell bodies, and lymphocytes. Electron microscopy of the formalin-fixed tissue was useful for the identification of these cells, particularly of histiocytes. Although extrapulmonary plasma cell granulomas have been reported, this is the first case, to our knowledge, of this type "tumor" in the spinal cord meninges. Differential diagnoses have been briefly discussed.

Adult↗