Simulation of intraluminal gas transport processes in the microcirculation

Intraluminal resistance to gas transport between the microcirculation and tissue was neglected for a half-century following the early work of Krogh. In recent years it has come to be understood that this neglect is seriously in error. This paper reviews the background for the long period of misdirection, and progress in placing the simulation of gas transport processes on a more accurate, quantitative basis.

Angiogenic vascular growth in the rat peritoneal disseminated tumor model

The objective of this study was to provide the first quantitative measurements of the process of vascular growth in the rat peritoneal disseminated tumor model in both arteriolar and venular systems. Male Fischer 344 rats were injected intraperitoneally with 1 x 10(7) cells of colon carcinoma cell line (RCN-9). Three to eleven days after tumor cell inoculation, the rats were subjected to intravital microscopic observation of the mesenteric microcirculation. Accompanying tumor growth, mesenteric windows showed a marked neovascularization. The branching pattern of the vascular network was analyzed based on Horton's law of bifurcation. Arterioles and venules were given an order of branching separately according to the Strahler's nomenclature, and the number of vessel segments (N) having the same order number was counted. A vascular density index (VDI) and a bifurcation ratio (BR) were calculated from a semilogarithmic plot of the vessel density (dividing N by the vascularized area) against vessel order. Values of the VDI in venules (3.1 +/- 0.3 in the tumor-free rats, mean +/- SEM, n = 6) were found to be larger than those in arterioles (1.8 +/- 0.2). These values in both arterioles and venules showed a significant increase with time after the tumor cell inoculation (in venules, 12.3 +/- 1.1 at 9-11 days after the tumor cell inoculation; in arterioles, 5.7 +/- 0.7). Moreover, the rate of increase in the venular VDI was larger than that of the arteriolar VDI. The arteriolar BR remained almost constant (3.8 +/- 0.2 for the tumor-free rats and 4.1 +/- 0.1 for 9-11 days after tumor cell inoculation), whereas the venular BR showed an increase with time (3.0 +/- 0.1 and 3.8 +/- 0.2, respectively). In conclusion, a marked angiogenesis was observed in the mesentery of the rats bearing peritoneal tumors. Neovascularization was found to occur predominantly in the venular system.

Antithrombotic activity of a symmetrical triglyceride with eicosapentaenoic acid and gamma-linolenic acid in guinea pig mesenteric microvasculature

The antithrombotic effect of a synthetic symmetrical triglyceride having eicosapentaenoic acid (EPA) at positions 1 and 3, and gamma-linolenic acid (GLA) at position 2 was investigated. Administration of the triglyceride significantly increased thrombus formation time and thrombotic occlusion time induced by light irradiation and a fluorescent dye in guinea pigs after 14 days administration compared to that of soybean oil. The antithrombotic effect of the triglyceride was similar to that of EPA ethyl ester. Administration of the triglyceride increased GLA, dihomo-gamma-linolenic acid (DGLA) and EPA contents in plasma and the liver, and the ratio of DGLA to arachidonic acid. These results might be responsible for this antithrombotic effect.

[A case of traumatic aneurysm of the thoracic aorta with severe chronic compression of the trachea]

A case of successfully treated traumatic aneurysm of the thoracic aorta with severe major air way compression was reported. A 38-year-old man, who had a history of blunt chest trauma in a traffic accident twenty years ago, complained of asthma-like coughing chest CT scan and angiogram showed a saccular aneurysm of desending aorta compressing the isthmus of the trachea and the esophagus severely. Resection of the aneurysm and prosthetic graft replacement was undertaken successfully with the aid of F-F bypass. The trachea and the esophagus were well decompressed and the patient recovered well with no complaints.

Subpressor dose of angiotensin II increases susceptibility to the haemodynamic injury of blood pressure in Dahl salt-sensitive rats

OBJECTIVE

To investigate the effects of subpressor doses of angiotensin II (Ang II) on the progression of renal injuries in Dahl salt-sensitive (Dahl-S) rats with hypertension.

METHODS

Rats were fed a high-salt (4% NaCl) diet and given an Ang II infusion (10 or 50 ng/kg per min, subcutaneously) for 4 weeks.

RESULTS

The plasma Ang II concentration achieved in the high-dose Ang II infusion was lower than that in low-salt (0.3% NaCl) normotensive rats. The Ang II infusion did not affect systolic blood pressure, cardiac hypertrophy or weight of thoracic aorta. However, the high-dose Ang II infusion increased proteinuria by 58%, enhanced the urinary N-acetyl-beta-D-glucosaminase index by 77% and reduced the glomerular filtration rate by 37%. The impaired renal function was associated with a progression of glomerulosclerotic lesions. Neither tubular nor arterial lesions were exacerbated. The infusion did not influence prostacyclin production or urinary cyclic GMP excretion.

CONCLUSION

A subpressor dose of Ang II infusion impairs renal function with progression of glomerulosclerosis, and these alterations may be due to increased susceptibility of the glomerulus in Dahl-S rats to Ang II-induced injuries. Such a mechanism might underlie a predisposition to hypertension-induced organ damage seen in Dahl-S rats with salt-induced hypertension.

The relationship between the pharmacological effect of amitriptyline based on an improved forced-swimming test and plasma concentration in rats

The relationship between the plasma concentration of amitriptyline (AMI) and its pharmacological effect was investigated in rats. The plasma concentration of AMI was maintained constantly from 5 h to 7 d after intraperitoneal infusion by the implantation of an osmotic minipump with an adjusted release rate of 20 mg/kg/d of AMI. Neither the plasma or brain concentrations of AMI in a 24-h infusion group were significantly different as compared with those in the 7-d group. The pharmacological effect of AMI was measured by our improved forced-swimming test. When AMI (dose of 20 and 50 mg/kg/d) was infused, the pharmacological effect in both infusion groups of rats was increased significantly at each dose in comparison to that of the control rats (p < 0.05). With 10 mg/kg/d infusion, the effect in the 7-d group increased significantly as compared with that of the control (p < 0.05), although the effect in the 24-h group did not change. The effect was increased in both groups with an increase of dose. When the effect was plotted to the area under the plasma concentration-time curve (AUC), the effect approached a limiting value (12 micrograms/ml.h). Therefore, it was suggested that 12 micrograms.ml/h as the AUC for AMI was enough to obtain a maximum AMI pharmacological effect in rats. From these results, we concluded that the AUC for AMI may be a useful index to evaluate its pharmacological effect, rather than the plasma concentration.

Long-term infusion of kallikrein attenuates renal injury in Dahl salt-sensitive rats

We investigated whether long-term infusion of kallikrein would attenuate renal injury in salt-induced hypertension in Dahl salt-sensitive rats. A subdepressor dose of purified rat urinary kallikrein (700 ng/d IV) was infused by osmotic minipump for 4 weeks in male Dahl salt-sensitive rats fed a high salt (2% NaCl) diet. This dose did not affect the time-dependent elevation of blood pressure; however, urinary protein excretion was significantly decreased, and glomerular filtration rate was increased. These beneficial effects were reflected morphologically by an attenuation of glomerulosclerotic lesions and tubular injury seen in the hypertensive Dahl salt-sensitive rats. Kallikrein infusion increased urinary excretion of bradykinin and stimulated excretion of cyclic GMP, suggesting that the kallikrein-kinin-prostaglandin and nitric oxide axes were enhanced by rat urinary kallikrein infusion. The alterations induced by kallikrein infusion were potentiated by the concomitant administration of the angiotensin-converting enzyme inhibitor alacepril. These studies indicated that long-term replacement with rat tissue kallikrein attenuates renal injury in hypertensive Dahl salt-sensitive rats.

Visualization of renal microcirculation in isolated Munich-Wistar rat kidneys: effects of endothelin-1 on renal hemodynamic activity

The aim of the present study was to visualize the superficial glomeruli of the Munich-Wistar (MW) rat and to characterize the responses of the renal microvasculature to endothelin-1 (ET-1). We first examined the distribution of superficial glomeruli of the MW rat compared to that in a control strain (Wistar rat). Secondly, we examined the effects of ET-1 on the renal microcirculation of the MW rat. The right kidney was perfused with a Krebs-Ringer solution containing fluorescein isothiocyanate dextran (FITC-dextran) and was visualized under an epi-illuminated fluorescence microscope system. Changes in perfusion pressure and diameter of the microvessels accompanying the administration of ET-1 (10 fmole-300 pmole) were measured. The number of superficial glomeruli was greater in the MW rat than in the Wistar rat. ET-1 had long-lasting and dose-dependent pressor effects. Perfusion pressure showed a 3.5-fold increase compared with the control, and the afferent arterioles showed greater dose-dependent vasoconstriction than the efferent arterioles. These findings suggest that the MW rat is a useful animal model for the study of renal microcirculation and that the renal microcirculation is extremely sensitive to ET-1.

Mechanistic analysis of renal protection by angiotensin converting enzyme inhibitor in Dahl salt-sensitive rats

OBJECTIVE

To investigate whether and how renin-angiotensin inhibition attenuates renal injury seen in salt-induced hypertension in Dahl salt-sensitive (Dahl-S) rats.

METHODS

Dahl-S rats fed a high-salt (4% sodium chloride) diet for 6 weeks were treated with the angiotensin converting enzyme (ACE) inhibitor alacepril or the angiotensin receptor antagonist losartan for 4 weeks. Functional and morphological alterations in the kidney were investigated.

RESULTS

Alacepril decreased systolic blood pressure (SBP). This SBP reduction was associated with the attenuation of cardiac and aortic wall hypertrophy and that of proteinuria and urinary N-acetyl-beta-D-glucosaminidase excretion. Kidney injuries, e.g. glomerular, arterial and tubular damage, were improved with alacepril treatment. Losartan decreased SBP to the same extent as alacepril, but neither renal function nor morphological structure was improved as was the case with alacepril. The response of the renal eicosanoid system to alacepril was inadequate, but cyclic GMP excretion, an indicator of nitric oxide formation, was significantly enhanced and lipid peroxidation in the kidney was decreased.

CONCLUSIONS

The beneficial effects of ACE inhibition on the renal injury in Dahl-S rats outrange those induced by the receptor antagonism. This might be due to multiple factors including an increased vasodepressor eicosanoid system, enhanced nitric oxide formation and possible inhibition of oxygen radical generation in the injured renal tissues.

Regulation of Ca2+ entry in rat aortic smooth muscle cells in primary culture

We characterized Ca2+ entry in rat aortic smooth muscle cells (SMCs) maintained in primary culture by measuring uptake of 45Ca2+ or Mn2+ from a normal balanced salt solution and the extracellular Ca(2+)-induced increase in the intracellular Ca2+ concentration ([Ca2+]i) in a medium [high pH (pH 8.8)/high Mg2+ (20 mM) medium containing a sarcoplasmic reticulum Ca(2+)-ATPase inhibitor, thapsigargin] that inhibits removal of Ca2+ from the cytoplasm. Such measurements in the presence or absence of a dihydropyridine (DHP) calcium channel antagonist (PN200-110) or hyperpolarizing agent (valinomycin) revealed that DHP-sensitive voltage-gated Ca2+ channels (VGCCs) are activated in these SMCs under resting conditions and that DHP-sensitive Ca2+ entry occurs mostly via these VGCCs. We found that receptor stimulation by endothelin-1 in these SMCs resulted in activation of neither DHP-sensitive nor -insensitive Ca2+ entry, but rather resulted in marked suppression of the former. Utilizing the DHP-sensitive extracellular Ca(2+)-induced increase in [Ca2+]i as a monitor of activity of the DHP-sensitive VGCCs, we investigated the effects of protein kinase activators and phosphatase inhibitors on the regulation of these VGCCs. We found that the DHP-sensitive VGCCs were inhibited by endothelin-1 through the activation of protein kinase C. We also found that they were inhibited by 8Br-cGMP, okadaic acid, and calyculin A.

Thrombolytic activity of YM866, a novel modified tissue-type plasminogen activator, in a photochemically induced platelet-rich thrombosis model

We compared the thrombolytic activity of a novel modified tissue-type plasminogen activator (t-PA; del 92-173, 275Arg-->Glu), YM866, with that of t-PA in a platelet-rich thrombosis model. Thrombus was induced in guinea pig mesenteric artery by irradiation with filtered light in combination with intravenous (i.v.) administration of fluorescent dye. When occlusion by the thrombus extended to 99% of the luminal area of the vessel, test drug (YM866, t-PA, or saline) was administered by i.v. bolus injection under heparinization. Both YM866 and t-PA exhibited dose-dependent thrombolytic activity; however, the improvement in occlusion rate and the incidence of successful thrombolysis induced by YM866 were three times higher than those induced by t-PA. With YM866 1 mg/kg, alpha 2-plasmin inhibitor levels decreased significantly to 58% of saline group values, but no change was noted in fibrinogen levels. YM866 antigen levels at this dose were seven times higher than those of t-PA. These results suggest that YM866 in single bolus injection is a thrombolytic agent superior to t-PA in platelet-rich thrombi without systemic fibrinolytic activation and that this efficacy is due to the prolonged half-life (t1/2) of the drug.

New dihydropyridine calcium channel antagonist, pranidipine, attenuates hypertensive renal injury in Dahl salt-sensitive rats

Interest in the cardiovascular protective effects of calcium channel antagonists has increased in the past decade. We investigated prevention of vascular wall remodeling by the long-acting calcium channel antagonist pranidipine in 12-week-old Dahl salt-sensitive (SS) rats with high-salt-induced (4% NaCl) hypertension. Six-week pranidipine treatment (60 mg/kg chow) decreased systolic blood pressure (SBP) by 22% in SS rats. This BP reduction was associated with decreases in cardiac mass and weight of the aortic wall. Glomerular filtration rate (GFR) was increased by 33%, but this did not lead to a decrease in urinary protein or NAG excretion. Morphologic investigation demonstrated striking resolution of arterial injury (medial necrosis and/or hyperplasia, inflammatory cell infiltration, and thrombus formation) by 87% after pranidipine treatment. Glomerular sclerosis was also attenuated by 61%, whereas tubular injury was improved by only 28%. These morphologic changes were reflected in the findings that the capacity of kidney homogenate for generating lipid peroxides was significantly decreased and that collagen levels and pattern type became similar to those of normotensive salt-resistant (SR) rats. Pranidipine also attenuated hypertensive vasculopathy in small arteries of the middle cerebral arteries. Thus, the calcium channel antagonist pranidipine can attenuate the vascular injury that occurs in salt-induced hypertension, a promising property that implicates its clinical usage, particularly in essential hypertension with cardiovascular complications.

Vasoconstrictors and renal protection induced by beta 1-selective adrenoceptor antagonist bisoprolol

We investigated the role of the vasoconstrictors endothelin-1 (ET-1) and thromboxane in renal protection by the beta 1-selective adrenoceptor antagonist, bisoprolol, in Dahl salt-sensitive rats (Dahl S) and salt-resistant rats (Dahl R). Six-week bisoprolol treatment (20 mg/kg chow) reduced systolic blood pressure (SBP) by 14% in Dahl S rats fed a high-salt (4% NaCl) diet. This BP reduction was accompanied by a decrease in aortic wall thickness. ET-1 and thromboxane released from renal cortex was significantly decreased by 17 and 30% with bisoprolol, respectively. Other prostaglandin synthesis was unaffected. Renal function such as proteinuria, N-acetyl-beta-D-glucosaminidase (NAG) excretion, and glomerular filtration rate (GFR) was not influenced by bisoprolol. Morphologic investigation showed that bisoprolol significantly improved glomerular sclerosis by 29% and attenuated arterial damage by 71%, although tubular injury was not affected. The more severe the glomerulosclerotic lesions, the greater the generation of thromboxane and ET. The arterial lesions were positively correlated to thromboxane generation. These data indicate that long-term bisoprolol treatment reduces vasoconstrictive ET-1 and thromboxane generation and that these alterations may be partly responsible for the amelioration of glomerular and arterial injury in Dahl S rats.

Flow-induced changes in shape and cytoskeletal structure of vascular endothelial cells

Changes in shape and cytoskeletal structure of vascular endothelial cells induced by fluid-imposed shear stress were studied in vivo and in vitro. In in vivo experiments, aortic tissue specimens including the flow dividers of the branching of the left subclavian artery and the aortic intercostal ostium were obtained and their endothelial cell shapes were observed using the scanning electron microscope. It was found that the shape and orientation of endothelial cells were strongly affected by blood flow conditions. In in vitro cell culture experiments, porcine aortic endothelial cells were cultured on glass coverslips and extracellular matrix coated (ECM coated) glass coverslips and exposed to shear stress using a parallel plate flow chamber. When we applied a shear stress of 2 Pa for 24 hrs, the rearrangement of F-actin filaments occurred within 3 hrs and preceded the cell shape change in the early stage after shear exposure. The endothelial cells on ECM-coated coverslips exhibited more elongated cell shapes even under no-flow conditions. After exposure to shear stress, the endothelial cells on ECM-coated glass showed more retarded elongation and orientation to the direction of flow than those on no-coated glass, suggesting that the anchorage to the substrate was enhanced by ECMs.

Antihypertensive property and renal protection by shichimotsu-koka-to extract in salt-induced hypertension in Dahl strain rats

We determined whether or not the kampo formula, Shichimotsu-koka-to extract, attenuates the development of salt-induced hypertension and provides renal protection against hypertensive injury in Dahl salt-sensitive (Dahl S) rats. A six-week treatment using this formula dose-dependently decreased the systolic blood pressure in Dahl S rats fed a high-salt (2% NaCl) diet. This blood pressure reduction was associated with a decrease in the thickness of the aortic wall. Renal function was not altered with this treatment; however, glomerular sclerotic lesions in the kidney were significantly attenuated. Neither arterial nor tubular lesions were affected. These data suggest that Shichimotsukoka-to extract exhibits an antihypertensive effect which is associated with partial resolution of glomerular sclerosis in the kidney.

Tissue distribution and metabolism of amitriptyline after repeated administration in rats

Plasma concentration, tissue distribution, and metabolism of amitriptyline (AMI) in rats pretreated with AMI (20 mg/kg/day, ip dose, for 7 days; treated) were compared with control rats. Plasma concentrations of AMI after intravenous administration (2 and 10 mg/kg) to the treated rat were significantly higher than those to the control rat in both doses. The difference in the plasma concentration between both groups may be caused by a change of tissue distribution of AMI, because the blood cell-to-plasma concentration ratio and the tissue-to-blood concentration ratio values for various tissues in the treated rat were smaller than those in the control, respectively. The plasma unbound fraction of AMI in the treated rat was significantly smaller (p < 0.05). alpha 1-Acid glycoprotein concentration in plasma of the treated rat was approximately twice that in the control rat. These results suggest that the decrease of tissue distribution of AMI in the treated rat may be caused by the decrease in the plasma unbound fraction of AMI with the increase of alpha 1-acid glycoprotein in plasma. The area under the plasma concentration-time curve for AMI and its main metabolite, nortriptyline, in the treated rat after intraportal administration of AMI was 1/3 and 3-fold those in the control rats, respectively. On the other hand, the hepatic intrinsic clearance (CLH,Int) of the unbound drug in the treated rat was approximately twice that of the control, suggesting that the increase of the (CLH,Int) by repeated administration of AMI may result in the induction of oxidative metabolism.

Flow injection determination of glucose, bile acid and ATP using immobilized enzyme reactor and chemiluminescent assay of NAD(P)H

We have developed a chemiluminescent flow injection method for analysis of bile acid, glucose and ATP using the chemiluminescent assay of NADH using 1-methoxy-5-methylphenazinium methyl sulphate (1-MPMS)/isoluminol(IL)/microperoxidase (m-POD) system and immobilized enzyme reactors such as 3 alpha-hydroxysteroid dehydrogenase, glucose-dehydrogenase, hexokinase and glucose-6-phosphate dehydrogenase. The standard curves were obtained in the range of 5-100 pmol for bile acid, 0.5-5.0 nmol for glucose and 10(-7)-10(-5) mol/L for ATP. The coefficient of variation for each assay was not more than 4.1% for bile acid, 2.3% for glucose and 5.3% for ATP, respectively.

Morphological changes of endothelial cells after exposure to fluid-imposed shear stress: differential responses induced by extracellular matrices

Effects of extracellular matrices (ECMs) and fluid-imposed shear stress on the cell shape and the cytoskeletal structure of microfilaments were studied in cultured porcine aortic endothelial cells (PAECs). The PAECs were cultured until confluent on non-coated or on ECM-coated glass coverslips. The components of ECM used were type IV collagen, heparan sulfate, chondroitin sulfate and dermatan sulfate. The PAECs cultured on the mixed ECMs showed marked elongation and segmental orientation with randomly distributed cell axis even under a no-flow static condition, and the microfilaments were mostly observed in parallel with the cell axis. After shear flow exposure (2 Pa, 24-48 hrs), the PAECs on non-coated glass were significantly elongated and oriented to the flow direction, however the PAECs on ECM-coated glass showed more retarded responses than the ones on non-coated glass, indicating that the anchorage to the substrate was enhanced by ECMs. The stress fibers were reorganized in accordance with the cell shape and oriented to the flow direction. These findings suggest that ECM may act together with shear stress to modify and maintain the endothelial cell configuration.

Effects of physical exercise on the elasticity and elastic components of the rat aorta

To evaluate the effects of exercise on aortic wall elasticity and elastic components, young male rats underwent various exercise regimes for 16 weeks. In the exercised rats, the aortic incremental elastic modulus decreased significantly when under physiological strain. The aortic content of elastin increased significantly and the calcium content of elastin decreased significantly in the exercised group. The accumulated data from the exercised and sedentary groups revealed that the elastin calcium content was related positively to the incremental elastic modulus. We concluded that physical exercise from an early age decreases the calcium deposit in aortic wall elastin and that this effect probably produced in the exercised rats a distensible aorta.

Time course changes in cytoskeletal structures of cultured endothelial cells exposed to shear stress

Changes in patterns of microfilament distribution were analyzed using cultured porcine aortic endothelial cells under shear flow. Within the elongated endothelial cells after shear flow exposure (20 dyne/cm2, 0-24 h), F-actin filaments were mainly observed as stress fibers. After 24 h exposure, the fluorescence intensity of rhodamine-phalloidin-stained cells was enhanced, indicating the increase in F-actin content. It was suggested that not only F-actin distribution but also the content may be affected by shear stress at the early stage of exposure.

Changes in the microstructure of cultured porcine aortic endothelial cells in the early stage after applying a fluid-imposed shear stress

Time course changes in the cell shape and in the patterns of microfilament distribution were analyzed quantitatively using cultured porcine aortic endothelial cell monolayers before and after a shear flow exposure. Geometrical parameters of the cell and of the microfilament were measured on fluorescent photomicrographs of the cells stained with rhodamine-phalloidin. After the shear flow exposure (20 dyn cm-2, 0-24 h), the endothelial cells on glass were elongated and oriented to the direction of the flow. Under the no-flow condition, F-actin filaments were mainly localized at the periphery of the cell, although some filaments were seen in the more central portion. The angles of the filaments were randomly distributed. After 3 h, the stress fiber-like structure of an F-actin bundle was formed in the central part of the cells, and these filaments were oriented to the direction of the flow. The degree of orientation increased as the time of exposure to shear stress became longer. This change in F-actin preceded cell elongation and orientation; these changes were statistically significant only after 6 h. After 24 h, peripheral filaments were again observed, and the fluorescence intensity of rhodamine-phalloidin-stained cells was enhanced. These findings suggest that the redistribution of F-actin filaments is one of the early cellular responses to the onset of shear stress and that it is one of the most important factors controlling cell elongation and orientation to the direction of the flow.

Platelet thrombi produced on cultured endothelial cells by the dye/light method

Platelet adhesion and aggregation were induced on cultured endothelial cells using the fluorescent dye/light method. A cone-and-plate apparatus was newly developed to observe interactions between platelets and cultured endothelial cells under a shear flow condition. The platelet deposition grew on the light-irradiated area of the cells. Degree of endothelial cell injury induced by the dye/light reaction seemed to depend on the dye concentration. Application of either aspirin or indomethacin significantly inhibited the growth of platelet aggregation, but was not effective for the platelet adhesion to endothelial cells. The platelet thrombi were formed on endothelial cells without their denudation. It was found by transmission electron microscopy that platelets directly adhered to endothelial cells which were not seriously damaged. This thrombus model is expected to be applicable to some physiological and pharmacological studies investigating platelet-endothelial cell interaction and mechanism of platelet thrombus formation in blood vessels.

A packed-bed reactor utilizing porous resin enables high density culture of hepatocytes

To enable high density culture of hepatocytes for use as a hybrid artificial liver support system or a bioreactor system, a packed-bed reactor using collagen-coated reticulated polyvinyl formal (PVF) resin was applied to a primary culture of hepatocytes. Cubic PVF resins (2 x 2 x 2 mm, mean pore size: 100, 250 or 500 microns) were used as supporting substrates to immobilize hepatocytes. Two hundred and fifty cubes were packed in a cylindrical column, and 2.6-11.3 x 10(7) hepatocytes were seeded in the column by irrigating with 3 ml of the medium containing hepatocytes. Perfusion culture experiments using this packed-bed reactor, as well as monolayer cultures using conventional collagen-coated petri dishes as control experiments, were performed. Sufficient amounts of hepatocytes were found to be immobilized in the reticulated structure of the PVF resins. The highest density of immobilized hepatocytes attained with PVF resin was 1.2 x 10(7) cells/cm3 PVF, which showed levels of ammonium removal and urea-N secretion comparable to those in the monolayer culture. It is concluded that the packed-bed reactor system utilizing PVF resin is a promising process for developing a bioreactor or a bioartificial organ using hepatocytes.

[Assessment of left ventricular function with ESS-ESVI relationship in patients undergoing aortic valve replacement for aortic regurgitation]

Aortic valve replacement (AVR) for aortic regurgitation (AR) results in the reduction of left ventricular dimensions. But postoperative death or congestive heart failure may occur in patients with left ventricular dysfunction. Pre- and postoperative stress (ESS)-volume (ESVI) relationship by M-mode echocardiography was examined in 30 patients undergoing AVR. Postoperatively, 23 patients (Group A) achieved a normal left ventricular dimension (LVDd less than 55 mm, LVDs less than 45 mm) and 7 patients (Group B) had persistent left ventricular dilation (LVDd greater than or equal to 55 mm, LVDs greater than or equal to 45 mm). Correlation between preoperative ESS and ESVI was significant (r = 0.92, p less than 0.001), and the ESS/ESVI was greater in Group A of 1.62 +/- 0.29 kdy/cm2/ml/m2 than in Group B of 1.18 +/- 0.19 kdy/cm2/ml/m2 (p less than 0.001). Three patients with ESVI greater than 180 ml/m2 and ESS/ESVI less than 1.2 kdyn/cm2/ml/m2 died after operation. Echocardiographic variables correlated with ESS/ESVI were ESVI (r = -0.57), FS (r = -0.53) and CSA (r = -0.47). The changes in LVDs (delta Ds) after AVR correlated with ESS/ESVI in 12 patients with severe left ventricular dilatation. Postoperative left ventricular function could be predicted by ESS-ESVI relationship by preoperative DBcAMP infusion test. ESS/ESVI is sensitive to changes in the left ventricular contractility. The patients with ESVI greater than 180 ml/m2 and ESS/ESVI less than 1.2 kdyn/cm2/ml/m2 may result in poor prognostic outcome.

Vasoconstrictor effects of endothelin-1 on myocardium microcirculation studied by the Langendorff perfusion method: differential sensitivities among microvessels

An intravital fluorescence microscope system was used to investigate the pharmacological effects of endothelin-1 (ET-1) on the coronary microcirculation in the isolated beating hearts of rats. The heart was perfused by retrograde aortic steady flow with an oxygenated Krebs-Ringer solution containing FITC-dextran. Changes in diameters of coronary microvessels accompanying the cumulative injection of ET-1 in the perfusate were observed and recorded with a video camera system. Coronary perfusion pressure was also measured during each experiment. Bolus injections of ET-1 (1-300 pmole) elicited a dose-dependent increase in perfusion pressure from 54 +/- 6 mm Hg (mean +/- SEM; n = 10, before the ET-1 injection) to 144 +/- 9 mm Hg (n = 8, at the ET-1 dose of 300 pmole). A dose-dependent narrowing of microvessels was also observed. This vasoconstriction was especially prominent in small-sized arterioles; the maximum vasoconstriction of the smaller arterioles was significantly higher than that of the larger arterioles (P less than 0.05). The response induced by ET-1 dose of 3-10 pmole was significantly larger in arterioles than in postcapillary venules in the diameter range between 10 and 40 microns. The vasoconstriction produced by ET-1 was inhomogeneous. Some part of bifurcations of arterioles showed a prominent localized vasoconstriction, and occasionally showed a complete luminal obstruction. Such a segmental vasospasm might be attributed to localized sensitivities of arterioles to ET-1. These findings suggest that ET-1 may have an important role in governing the coronary resistance and regulating the capillary flow in the myocardium.

Cyclic GMP stimulates Na+/Ca2+ exchange in vascular smooth muscle cells in primary culture

We examined the effect of cGMP on Na+/Ca2+ exchange in rat aortic smooth muscle cells (VSMCs) in primary culture. The intracellular Ca2+ concentration [( Ca2+]i) was raised by adding ionomycin to VSMCs incubated at high extracellular pH (pH0) (pH0 = 8.8) and high extracellular Mg2+ (Mg2+0) (Mg2+0 = 20 mM), conditions that inhibit activity of the sarcolemmal Ca2+ pump. 45Ca2+ efflux observed under these conditions was mostly extracellular Na+ (Na+0)-dependent and thus presumably catalyzed by the Na+/Ca2+ exchanger. Brief treatment of VSMCs with 8-bromo-cGMP or atrial natriuretic peptide increased this Na+0-dependent 45Ca2+ efflux by about 50%. The 8-bromo-cGMP treatment did not significantly influence total cell Na+, membrane potential, and cell pH. Conversely, when VSMCs were loaded with Na+ and then exposed to a Na+0-free medium, the rate of 45Ca2+ uptake into VSMCs increased as cell Na+ increased. Prior treatment of VSMCs with 8-bromo-cGMP accelerated 45Ca2+ uptake by up to 60% without influencing Na+ loading itself. Treatment of VSMCs with 25 microM 2,5-di-(tert-butyl)-1,4-benzohydroquinone, an inhibitor of the sarcoplasmic reticulum Ca(2+)-ATPase, induced a transient elevation of [Ca2+]i. 8-Bromo-cGMP stimulated the rate of recovery phase of this Ca2+ transient measured in the high pHo/high Mg2+o medium. All these results indicate that cGMP stimulates Na+/Ca2+ exchange in VSMCs.

Emigration of activated leukocytes augments transvascular permeability in mesenteric venules of rat

Effects of leukocyte adhesion and emigration on the microvascular permeability were analyzed by the combined use of high resolution transilluminated intravital microscopy and the epiilluminated fluorescent tracer imaging. After stimulating leukocytes by topical application of PAF-LPS or fMLP solution on the mesentery of a rat, a dynamic process of leukocyte emigration was visualized under high resolution transilluminated microscopic observation. When considerable emigration of leukocytes was observed, the same microvasculature was subjected to a permeability study to visualize the diffusional process of the FITC-labeled macromolecules under an epiilluminated fluorescent microscope. Dye diffusion was accelerated in the PAF-LPS or fMLP-treated group, and also a distinctly spotty leakage was observed in venules where successive adhesion and emigration of leukocytes were observed.

[Interposition graft technique for the treatment of AAE (annuloaortic ectasia) with aortic regurgitation: surgical results]

Interposition graft technique had been used exclusively in 8 consecutive patients with AAE and AR. Two patients with severely dilated left ventricle (CTR 65, 80%, LVDd 93, 83 mm, LVDs 86, 68 mm), and 1 patient complicated with the postoperative mediastinitis died in the perioperative period, 10, 145 and 135 days after surgery, respectively. In the remaining 5 patients, excellent clinical improvement was observed with the reduction of CTR and echo-cardiographic findings without formation of hematoma, pseudoaneurysm, and leak from the suture lines on DSA and CT.

Effects of endothelin-1 on coronary microcirculation in isolated beating hearts of rats

An intravital fluorescence videomicroscope system was used to investigate the pharmacological effects of endothelin-1 (ET-1) on the coronary microcirculation in isolated beating hearts of rats. The heart was perfused by retrograde aortic steady flow with an oxygenated Krebs-Ringer solution containing FITC-dextran. Cumulative injections of ET-1 (1-30 pmol) elicited a dose-dependent increase in perfusion pressure from 52 +/- 15 mm Hg (mean +/- SEM; n = 6) before the ET-1 injection to 104 +/- 23 mm Hg at the ET-1 dose of 30 pmol. A dose-dependent narrowing of microvessels was also observed on a monitor screen. This diffuse vasoconstriction was especially prominent in small arterioles; the maximum vasoconstriction of the smaller arterioles was significantly higher than that of the larger arterioles. These findings suggest that ET-1 may have an important role in governing the coronary resistance and regulating the capillary flow in myocardium.

[Familial cardiac myxoma with multiple and contralateral recurrence]

This report described a familial recurrent cardiac myxoma involving mother and daughter. The mother, at 27 year of age, had developed recurrent multiple myxomas in both left and right atrium and right ventricle 4 years after surgical excision of left atrial myxoma. Excision was successful and remains well without signs of recurrence 9 years postoperatively. In an asymptomatic 13-year-old daughter, a recurrent left atrial myxoma was found 3 years after the excision of right atrial myxoma by echocardiographic follow-up at 6 month intervals. Excision of left atrial myxoma was performed and histology showed the essentially the same findings as primary myxoma without signs of malignancy. From an experience of this familial recurrent myxoma and a review of 38 cases of 17 familial cardiac myxoma, it is recommended that wide excision of tumor including surrounding tissues, thorough search for multiple heterotopic tumors at surgery, close postoperative echocardiographic follow-up for at least 5 years, and examination of skin and breast tumor, and endocrine disorder for "complex" myxoma.

[Reconstruction of radicular arteries in the total replacement of thoracoabdominal aorta]

A technique of reconstructing low intercostal, high lumbar arteries and Adamkiewicz artery is described to prevent paraplegia following operations on the thoracoabdominal aorta. A graft with a side branch is anastomosed proximally and a side branch to the distal thoracic aorta after reinforcement of the stumps under the partial bypass. Applying a clamp on the main graft, flow through the side branch and true lumen of the aneurysm is reestablished and bypass is terminated. The main graft, extended with a Y-graft, is anastomosed to common iliac arteries after proximal suture-ligation to perfuse the lower extremities. Splanchnic arteries are reconstructed according to DeBakey's technique which is followed by trimming of the thoracoabdominal aorta incising longitudinally with a clamp applied on the 1st side branch. Edges of the trimmed aneurysm are sutured to the slit of the graft from the right common iliac artery reconstructing intercostal, lumbar arteries and Adamkiewicz artery from the level of L2 upwards to T4 or more. As a final step, the graft is sutured to the 1st side branch allowing perfusion distally to the right lower extremity and the main graft to the splanchnic arteries and left lower extremity after division of a Y-graft right branch. The technique minimizes ischemic time for reconstruction of the aortic branches and enables complete reconstruction of the radicular arteries.

Application of the micropipette technique to the measurement of cultured porcine aortic endothelial cell viscoelastic properties

The viscoelastic deformation of porcine aortic endothelial cells grown under static culture conditions was measured using the micropipette technique. Experiments were conducted both for control cells (mechanically or trypsin detached from the substrate) and for cells in which cytoskeletal elements were disrupted by cytochalasin B or colchicine. The time course of the aspirated length into the pipette was measured after applying a stepwise increase in aspiration pressure. To analyze the data, a standard linear viscoelastic half-space model of the endothelial cell was used. The aspirated length was expressed as an exponential function of time. The actin microfilaments were found to be the major cytoskeletal component determining the viscoelastic response of endothelial cells grown in static culture.

A high density culture of hepatocytes using a reticulated polyvinyl formol resin

To enable high density culture of hepatocytes to be used as a hybrid artificial liver support or bioreactor system, collagen coated reticulated polyvinyl formal (PVF) resin (a filter material with a porosity of more than 80%) was used for the primary culture of hepatocytes. Stationary and perfusion culture experiments using PVF resin and monolayer culture were performed as control experiments. Due to the porous structure of the substrate material, hepatocytes were able to penetrate the reticulated pores of the PVF resin, and adhere to and spread on its surface. The densities of hepatocytes attained with PVF were about 10 times as high as those in the monolayer culture using conventional collagen coated Petri dishes. Hepatocytes immobilized in the PVF resin showed viability, as assessed by glutamic pyruvic transaminase (GPT) activity in the medium. Perfusion culture with PVF resin showed stable, high level metabolism, ammonium removal, and urea secretion comparable to the monolayer culture. It is concluded that perfusion culture with PVF resin is useful in attaining a high density culture of hepatocytes.

Effect of wall shear rate on thrombogenesis in microvessels of the rat mesentery

The role of hemodynamics on platelet thrombus formation was studied in venules and arterioles of the rat mesentery. Thrombus formation was induced by the fluorescent dye/light method for examination of the following factors: 1) the effect of wall shear rate on thrombus initiation, 2) the effect of wall shear rate on the growth of thrombi, and 3) the relation between platelet thrombus initiation and intraluminal velocity profile. The range of wall shear rate was up to approximately 1,000 1/sec in venules and from 640 to 2,900 1/sec in arterioles. Platelet thrombus initiation occurred more rapidly at higher wall shear rate in venules and at lower wall shear rate in arterioles. Thrombus initiation time was shortest around a wall shear rate of 900 1/sec in venules and around 700 1/sec in arterioles. Thrombus growth rate in venules was greatest at a wall shear rate of 1,500-2,000 1/sec. Thrombus initiation and its relation to blood flow was also examined in branched and curved microvessels. In these vessels platelet thrombi were also first initiated at the sites of higher wall shear rate in venules and of lower wall shear rate in arterioles.

[Significance of raphe in congenitally bicuspid aortic valve]

The decrease of rheumatic aortic regurgitation (AR) is observed due to the relative increase of non-rheumatic aortic valvular diseases since 1980. Among 240 patients who had undergone aortic valve replacement (AVR) including combined valvular diseases up to March 1989, the congenitally bicuspid aortic valve was responsible for AR and stenosis (AS) in 33 patients (13.8%) and were divided according to the presence of a raphe. In the raphe (+) group (n = 15), infective endocarditis (IE) (n = 5), prolapse of the aortic valve, mainly non-coronary cusp (n = 5), and thickening with contraction of cusp (n = 4) were the cause of AR. Calcification of the cusp was seen in 2 older (greater than 59 yrs) patients. In the raphe (-) group (n = 18), IE (n = 2), contraction of cusps (n = 2) in the relatively younger (less than 48 yrs) were the cause of AR. Rest of the patients exhibited severe AS due to the calcification of cusps except a case who showed IE with AR in the calcified cusp. Although not generally recognized, the bicuspid valve with a raphe, less tendency to deposit calcium, is an important cause of pure AR severe enough to warrant AVR. The bicuspid valve without raphe, as already recognized, prones to develop severe calcification and AS in later life.

Inhibitory effects of mold oil including gamma-linolenate on platelet thrombus formation in mesenteric microvessels of the rat

Diet including mold oil from a lipid accumulative fungus, containing gamma-linolenic acid, showed an inhibitory effect on thrombus formation in the microvessels of rats by the light/dye method of the authors. Male Wistar rats were fed for 3 to 4 weeks with two series of experimental diets and were examined for thrombus formation. The thrombus formation times to totally occlude, ts, were 347 sec for (mold + soybean)-oil and 236 sec for (palm + soybean)-oil in the first series of diets and 1288 sec for mold oil, 538 sec for olive oil and 575 sec for safflower oil in the second series of diets. Fatty acid composition of plasma, erythrocyte and liver lipids showed an increase in arachidonate content with the diet including the mold oil. Higher arachidonate content seem favorable in inhibiting thrombus formation with increasing PGI2 formation. In terms of the level of lipid hydroperoxides, indicated as a desaturation index of constituent fatty acids, the higher desaturation index with safflower oil gave shorter ts, which suggested some oxygen derived free radicals from polyunsaturated fatty acids were involved in the mechanism of thrombogenesis study by this method.

Value of vectorcardiography in predicting progress in dilated cardiomyopathy

Sixteen of 75 patients with dilated cardiomyopathy (DCM) died during a mean follow-up period of 39.7 months. In non-survivors, the cardiothoracic ratio and the left ventricular end-diastolic dimensions were greater, the left ventricular end-diastolic pressures were more elevated, and the cardiac index was lower than in the survivors at the time of initial diagnosis. There were no significant differences between survivors and non-survivors in the magnitude of the maximum QRS and T vectors or in the maximum T angle. In the non-survivors, the maximum QRS vector was directed more posteriorly and the width/length ratio of the loop in the horizontal plane was smaller than in survivors. The QRS loop in the horizontal plane was often distorted in non-survivors or showed a bizarre figure-of-eight configuration. It appears that in DCM a marked posterior displacement of a QRS loop that is narrow and distorted or is in a bizarre figure-of-eight configuration in the horizontal plane indicates an unfavorable prognosis.

[Simplified operative technique for thoracoabdominal dissecting aneurysm]

A graft with branches is used to reconstruct the extensively dissected thoracoabdominal aorta. Anastomoses of the proximal end of the main graft distal to the left subclavian artery and the side branch to the distal aneurysmal descending thoracic aorta were first undertaken after the preparation of both ends under the iliac vein-artery partial bypass. A main graft with a Y graft extension was anastomosed distally to iliac arteries. This permits the blood flow within the aneurysm and the main graft to the extremities until splanchnic and spinal cord arteries have individually been transferred to the main graft. Ischemic time of the splanchnic and spinal cord arteries, using this technique, can be minimized within 10 minutes to each in the total replacement of descending thoracic and abdominal aorta.

Performance of a new hybrid artificial liver support system using hepatocytes entrapped within a hydrogel

To develop a hybrid artificial liver support system (ALSS), the authors constructed a rotating-disk type ALSS using hepatocytes entrapped within a calcium alginate hydrogel. This module was designed in imitation of the gas-liquid contactor that uses the same principle. Forty disks with film-shaped hydrogel were mounted to a horizontal rotating axis and were kept in contact with blood. The concentration of hepatocytes in the gel varied from 1.9 X 10(9) to 1.7 X 10(10) cells/L gel. Entrapping hepatocytes within hydrogel kept the hepatocytes viable, and results of in vitro experiments showed ammonium metabolism and urea synthesis. The results of ex vivo perfusion experiments using cats with acute hepatic insufficiency indicated that this module had the ability to replace liver function in vivo.

Sex difference of the metabolic disposition of clioquinol in rats

The order of plasma levels of clioquinol and its conjugates in male rats after intraduodenal administration of 32.7 mumol/kg dose of clioquinol was clioquinol sulfate (C-Sul) greater than glucuronide (C-Glu) much greater than clioquinol, whereas that in female rats was C-Glu greater than C-Sul much greater than clioquinol. Total (urine + bile) recovery was almost the same among male and female rats. The percentage of excretion amounts of C-Sul (urine + bile) to the total excretion amounts for 24 h in male rats after intravenous administration of clioquinol was about twice that in female rats, while the percentage of excretion amounts of C-Glu to the total excretion amounts in male rats was smaller than that in female rats. In intravenous administration of 16.4 mumol/kg dose of C-Glu, C-Sul and clioquinol other than C-Glu were found in bile and urine of male and female rats. The percentage of excretion amounts of C-Sul and C-Glu (urine + bile) to the total excretion amounts was similar among male and female rats, respectively. In intravenous administration of 16.4 mumol/kg dose of C-Sul, C-Glu and clioquinol other than C-Sul were found in bile and urine of male and female rats, and the percentage of excretion amounts of C-Sul (urine + bile) to the total excretion amounts in male rats was 1.3 fold that in female rats.(ABSTRACT TRUNCATED AT 250 WORDS)

[Interposition graft method in the treatment of aortic regurgitation associated with aneurysm of the ascending aorta]

Interposition graft method, total replacement of the ascending aorta with a valved conduit and reimplantation of the coronary artery by an interposed graft with some modifications, had been exclusively used for the treatment of aortic regurgitation associated with an aneurysm of the ascending aorta in consecutive 7 cases. Clinical improvement is apparent and postoperative angiographic study revealed a satisfactory coronary and aortic appearance with no leakage, pseudoaneurysm formation nor compression of the graft. This technique proved to be a reliable and safe method for the treatment of aortic regurgitation associated with an aneurysm of the ascending aorta with no mortality nor modality.

Effects of exercise training on biochemical and biomechanical properties of rat aorta

The authors studied the effect of prolonged physical exercise on the mechanical properties of rat aorta in relation to the amounts and qualities of arterial connective tissue fibrous proteins. Twelve male rats were divided into two groups: 6 sedentary rats (S) and 6 training rats (T), which were forced to swim from nine weeks to twenty-five weeks of age. The ultimate tensile stress and the ultimate tensile extension ratio of ring specimens at the descending thoracic aorta were larger in T than in S (192.3 +/- 47.9 g/mm2, mean +/- SD, vs 147.8 +/- 26.0, p less than 0.05; 3.52 +/- 0.13 vs 3.18 +/- 0.27, p less than 0.05; respectively). The elasticity parameter, calculated by fitting stress-strain curves to exponential function in the stress level of 0-20 g/mm2, was lower in T than in S (1.79 +/- 0.15 vs 2.13 +/- 0.24, p less than 0.01). The contents of elastin (alkali-insoluble elastin preparation) and collagen were higher in T than in S (0.44 +/- 0.11 g/g dry aorta vs 0.30 +/- 0.06, p less than 0.05; 0.15 +/- 0.04 g/g dry aorta vs 0.11 +/- 0.04, NS, respectively). Although the aortic calcium content did not significantly change in the training rats (T 1.17 +/- 0.23 mg/g dry aorta, S 0.95 +/- 0.34), the content of calcium in elastin was lower in T than in S (1.75 +/- 0.51 mg/g dry elastin vs 2.63 +/- 1.00, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Changes in lipid peroxide concentrations in plasma and tissues by repeated administration of clioquinol to neonatal rats

The changes in lipid peroxide concentrations in plasma and tissues after subcutaneous administration of clioquinol to clioquinol-sensitive (S-rats) and -resistant neonatal rats (R-rats) were investigated. When a fixed dose of 150 mg/kg/d of clioquinol was given to R-rats for 14 d after birth, no significant difference in lipid peroxide concentrations in plasma, liver, kidney, brain and spinal cord at 5, 10 and 15 d was observed between clioquinol-treated and untreated rats. However, with increasing doses of clioquinol to R-rats every 5 d (150----300----600 mg/kg/d), the lipid peroxide concentrations at 15 d were higher in plasma, brain and spinal cord of clioquinol-treated rats than in those of untreated rats. These results suggested that repeated administrations of large doses of clioquinol to rats increased the lipid peroxides in nerve tissues. With S-rats at 5 d after birth, the lipid peroxide concentrations in liver were approximately twice those in R-rats regardless of the clioquinol administration.

Velocity profiles of blood flow in microvessels measured by ten channels' dual-sensor method

Ten channels' dual-sensor method newly developed was applied to the measurement of velocity profiles in arterioles and venules in the rat mesentery. In some experiments, red blood cells (RBC), labelled in vitro with a fluorescein isothiocyanate (FITC), were injected to compare the velocity profiles obtained by the RBC visualization technique with those measured by the dual-sensor method. It was found that the velocity profile of the FITC labelled RBC in straight microvessels was blunt as compared to a parabola. The centerline velocity measured by the dual-sensor method was smaller than that of the FITC labelled RBC by about 20%. The velocity profiles were also measured at the curved arterioles and venules as well as at the bifurcation and the confluence. It was found that the velocities were higher along the inner wall at the curved portion and along the outer wall at the bifurcation of arterioles.

Microhemodynamics of blood flow in narrow glass capillaries of 9 to 20 micrometers; the Fahraeus effect

Velocities of the red blood cell (RBC) and the suspending medium in glass capillaries of 9 to 20 micron were measured under microscopic observation. The effects of physical factors such as driving pressure, capillary diameter, hematocrits and RBC deformability on flow velocities were studied using freshly drawn blood of the rat resuspended in phosphate buffered saline solution in the hematocrit range between 5 and 12.5%. These RBC suspensions were made to flow through the test glass capillaries under known negative driving pressures. Ratios of capillary hematocrit to feed hematocrit taken as measures of the Fahraeus effect showed almost constant value of about 0.74. While, ratios of capillary hematocrit to discharge hematocrit showed a characteristic dependence on capillary diameter, showing minimal values at about 13 micron in capillary diameter. The same hematocrit ratios were found to be well correlated with values of wall shear rates estimated from the relative RBC velocities.

Role of red blood cells in the coronary microcirculation during cold blood cardioplegia

The role of red blood cells during cold blood cardioplegia was studied using an intravital microscope in 13 isolated canine hearts perfused with diluted blood containing potassium chloride. The coronary microcirculation on the left ventricular epicardial surface was observed while the perfusate temperature was varied between 37 degrees C and 10 degrees C. Considerable sludging of red blood cells occurred during hypothermia. The percentage of capillaries perfused by red blood cells (percentage change) significantly decreased as perfusate temperature was reduced (100, 56, and 31% at 37, 20, and 10 degrees C respectively). This was caused by occlusion of microvessels due to sludging and by functional closure due to hypothermia. There was incomplete recovery of perfusion of capillaries at the end of rewarming (60%). The diameters of venules were reduced to 76% of control value at 10 degrees C because of the decrease in the numbers of feeding capillaries, but this value returned to 91% at the end of rewarming. Coronary vascular resistance (mmHg.ml-1.min-1 (kPa.s.litre-1] significantly decreased from 2.0(0.2) at 37 degrees C to 1.2(0.12) at 10 degrees C, but it increased to 2.4(0.24) at the end of rewarming. The finding in this study that sludging occurred which was slow to clear is a definite disadvantage of perfusion with red blood cells during hypothermia.