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Biomedical subjects

A Kamiya

Publications and source records attributed to A Kamiya.

At least 217 records · Page 12Linked to original sources
PubMed1982

Ultrastructural changes in the endothelial surface of the canine carotid artery induced by wall shear stress load.

To study the morphological changes in the endothelial surface of the artery induced by wall shear stress load, an arterio-venous shunt was constructed between the common carotid artery and the external jugular vein in 21 dogs. The ultrastructural changes in the endothelial surface were observed by scanning electron microscopy after the measurement of the hemodynamic parameters. In acute experiments (3 days or 1 week postoperative), the clear ultrastructural changes, such as the disturbance of the smooth folds, the find transverse wrinkles, the small spindle swellings, the splitting of the intercellular junction of the endothelial cells and occasionally the desquamation of the endothelial cells, were significantly observed as proportional to the elevated flow rate ratio (fs/fc, fs: flow rate of the shunted artery, fc: flow rate of the control artery). In subacute experiments (2 or 4 weeks postoperative), the small spindle swellings were observed in the shunted artery with high flow rate ratio. In chronic experiments (5 or 6 months postoperative), these changes were less proportional to the flow rate ratio. These morphological changes were significant in the disturbance of the endothelial barrier in acute experiments and they were significant in adaptive regulatory change in the chronic experiments. These support our previous observation (Am. J. Physiol. 239, H14-21, 1980). The possibility of the wall shear stress for atherogenesis was discussed.

Animals↗
PubMed1980

Adaptive regulation of wall shear stress to flow change in the canine carotid artery.

To study the adaptive response of the vascular wall to blood flow changes, an arteriovenous shunt was constructed between the common carotid artery and the external jugular vein in 12 dogs. Six to eight months postoperatively, the arterial internal radius (r) was determined by angiography and/or the use of pressure-volume relationship. The results showed that r increased with increased flow load (f) and vice versa. Wall shear rate (gamma) was calculated from gamma = 4f/(tau r3), assuming laminar flow. The value of gamma, initially proportional to f, had recovered almost to the control level (within 15%) due to the vessel dilatation or atrophy during the chronic experiment, when f was less than 4 times the control. Transendothelial protein permeability, evaluated at the T-1824-stained surface by a reflectometric method, also showed a close correlation with wall shear (r = 0.934). A local autoregulatory mechanism of wall shear stress involving protein turnover in the vascular wall is suggested.

Adaptation, Physiological↗
PubMed1980

Mechanism of renal distribution of aminoglycoside antibotics.

The renal accumulation of dibekacin, one of the aminoglycoside antibiotics, was pharmacokinetically analyzed and the mechanism of the renal accumulation of these antibiotics was investigated. The remaining amounts of dibekacin in the kidneys were adequately expressed by the bi-exponential equation. There was no possibility of a covalent bond between dibekacin and the renal tissue components. The renal accumulation of the aminoglycoside antibiotics was explained in terms of the two successive processes, renal tubular reabsorption and electrostatic interaction between these antibiotics and the tissue components. In other words, these antibiotics were reabsorbed at the renal tubules and transported into renal tubular epithelial cells and bound to the tissue components by electrostatic force. The electrostatic interaction also played an important role in increasing the acute toxicities of aminoglycoside antibiotics.

Aminoglycosides↗
PubMed1979

Transcapillary passage of albumin, effects of tissue cooling and of increases in filtration and plasma colloid osmotic pressure.

'Initial' clearance of radiolabelled serum albumin was measured in the perfused, maximally vasodilated muscle vascular bed of rat hindquarters during tissue cooling, during increases in filtration and during changes in serum colloid osmotic pressure. Albumin clearance during ordinary serum perfusion at isogravimetry amounted to 0.03 ml/min times 100 g, increasing linearly with filtration rate to some 0.07 ml/min times 100 g at 0.5 ml/min times 100 g of filtration. During cooling from 36 degrees C to 14 degrees C both CFC and initial albumin clearance at isogravimetry decreased some 40%, in due proportion to the increased viscosity of the fluid. Increases of the colloid osmotic pressure of the perfusate correspondingly increased both the isogravimetric capillary pressure and 'initial' albumin clearance during isogravimetry.--It is concluded that even during isogravimetry the transmicrovascular albumin passage is to about 70 per cent due to filtration, and only some 30 per cent of transport at ordinary serum colloid osmotic pressure takes place by diffusion, both events presumably via 'large pores'. There was no evidence that transendothelial vesicular transport should to any significant extent contribute to the passage of albumin from vessels to tissue.

Animals↗
PubMed1978

Simultaneous measurements of capillary diffusion and filtration exchange during shifts in filtration-absorption and at graded alterations in the capillary permeability surface area products (PS).

The diffusion exchange of Cr-EDTA, using the single injection indicator diffusion method, was followed simultaneously with estimations of the capillary filtration capacity (CFC) in an "isogravimetric" rat hindquarter preparation during artificial perfusion and maximal dilatation. Measurements were performed at constant flow and during 1) shifts in filtration-absorbtion, 2) alterations of perfused capillary wall area (graded rarification of capillary network by microsphere injection) and 3) during alterations of permeability (i.a. infusion of histamine). At maximal vasodilatation CFC was 0.037 +/- 0.001 ml/min X mmHg X 100 g and PS for Cr-EDTA 5.67 +/- 0.13 ml/min X 100 g. During filtration or absorbtion, Cr-EDTA transfer from vessels to interstitium changed only slightly but the situation may well be different for solute transfer from interstitium to vessels. Alterations in capillary wall area resulted in proportional changes in PS for Cr-EDTA while the CFC changes were always relatively smaller. Histamine increased CFC some threefold with a marked increase in protein transfer, while PS for Cr-EDTA increased only marginally. This histamine effect could be ascribed mainly to an increase in the number of large pores which, because of their relative paucity, are of little importance for small molecular diffusion exchange but highly important for convective and macromolecular exchange.

Absorption↗