Biomedical subjects

Fumihiko Kajiya

Publications and source records attributed to Fumihiko Kajiya.

At least 19 recordsLinked to original sources

PubMed2006

Prediction of functional recovery of 60-minute warm ischemic hearts from asphyxiated canine non-heart-beating donors.

BACKGROUND: Cardiac function of non-heart-beating donors (NHBDs) is uncertain due to severe myocardial damage. We developed an isolated myocardial perfusion system to resuscitate NHBD hearts and attempted to predict functional recovery of 60-minute warm ischemic hearts by analyzing systolic and diastolic functions. METHODS: Hypoxic cardiac arrest was induced in 8 mongrel dogs without any pre-treatments. After 60-minute ischemia, intracoronary microthrombi were flushed out by retrograde blood cardiopledia with tissue-type plasminogen activator. Coronary arteries were initially perfused from the aortic root with tepid hyperkalemic blood (20 mmol/liter) at low pressure (20 mm Hg) for the first 60 minutes and then with normothermic blood for the next 60 minutes. After 120 minutes of reperfusion, pre-load was increased for ejection against an after-load of 80 mm Hg. Pressure-volume loops were recorded to obtain the end-systolic pressure-volume relationship (ESPVR) and end-diastolic pressure-volume relationship (EDPVR). Stroke volume at a given pre-load was calculated from averaged ESPVR, EDPVR and after-load identical to an averaged baseline value. The Frank-Starling relationship was obtained and cardiac status was classified according to Forrester's hemodynamic sub-set. RESULTS: End-systolic elastance decreased significantly to about 60% of baseline and the time constant of isovolumic relaxation was prolonged significantly by about 20%. Cardiac index was decreased to about 50% and cardiac status was classified in the Forrester III or IV sub-set. CONCLUSIONS: The extent of functional recovery of NHBD hearts is predictable by cardiac output. Although 120 minutes of recovery time may be short for 60-minute ischemic damage, this system may be feasible to predict post-transplant cardiac function before transplantation.

Animals↗

PubMed2006

Celsior preserved cardiac mechanoenergetics better than popular solutions in canine hearts.

BACKGROUND: Better protective effects of Celsior on cardiac function than the other conventional solutions have been reported in acute experiments and in clinical trials for at-risk patients. However, no study has yet precisely elucidated how these preservation solutions affect cardiac mechanoenergetics. Therefore, we evaluated the effects of St. Thomas' Hospital solution No. 2, University of Wisconsin solution, and Celsior on left ventricular contractility (Emax: end-systolic pressure-volume ratio) and oxygen consumption. METHODS: We used 32 canine excised cross-circulated hearts. Twenty-three hearts served as donor hearts after hypothermic ischemia with one of the three solutions, and the remaining 9 served as controls. After arrest with each solution, the hearts were preserved for 4 hours at 4 degrees C. Then, we measured left ventricular pressure, volume, and oxygen consumption to obtain Emax and the relation between ventricular pressure-volume area (a measure of total mechanical energy) and oxygen consumption. We also evaluated the oxygen cost of Emax by changing Emax with calcium administration. RESULTS: Celsior did not significantly affect E(max) (6.3 +/- 2.4 in control versus 5.3 +/- 1.3 mm Hg.mL(-1).100 g with Celsior) nor the oxygen cost of Emax (1.2 +/- 0.6 versus 1.6 +/- 0.5 mL O2.mL.mm Hg(-1).beat(-1).100 g(-2), respectively). In contrast, St. Thomas' Hospital and University of Wisconsin solutions significantly decreased Emax (4.5 +/- 1.1 and 3.5 +/- 0.9 mm Hg.mL(-1).100 g, respectively) and increased the oxygen cost of Emax (2.5 +/- 0.8 and 2.4 +/- 0.9 mL O2.mL.mm Hg(-1).beat(-1).100 g(-2), respectively) compared with control and Celsior-preserved hearts. The slope and intercept of the oxygen consumption versus pressure-volume area relation showed no significant difference among the four groups. CONCLUSIONS: Celsior showed better protective effects on cardiac mechanoenergetics than St. Thomas' Hospital and University of Wisconsin solutions in the acute phase of heart transplantation.

Animals↗

PubMed2005

Iris movement mediates vascular apoptosis during rat pupillary membrane regression.

In the course of mammalian lens development, a transient capillary meshwork known as the pupillary membrane (PM) forms, which is located at the pupil area; the PM nourishes the anterior surface of the lens and then regresses to make the optical path clear. Although the involvement of apoptotic process has been reported in the PM regression, the initiating factor remains unknown. We initially found that regression of the PM coincided with the development of iris motility, and iris movement caused cessation and resumption of blood flow within the PM. Therefore, we investigated whether the development of the iris's ability to constrict and dilate functions as an essential signal that induces apoptosis in the PM. Continuous inhibition of iris movement with mydriatic agents from postnatal day 7 to day 12 suppressed apoptosis of the PM and migration of macrophage toward the PM, and resulted in the persistence of PM in rats. The distribution of apoptotic cells in the regressing PM was diffuse and showed no apparent localization. These results indicated that iris movement induced regression of the PM by changing the blood flow within it. This study suggests the importance of the physiological interactions between tissues-in this case, the iris and the PM-as a signal to advance vascular regression during organ development, and defines a novel function of the iris during ocular development in addition to the well-known function, that is, optimization of light transmission into the eye.

Animals↗

PubMed2005

Systemic nitric oxide production rate during hemodialysis and its relationship with nitric oxide-related factors.

BACKGROUND/AIMS: Nitric oxide (NO) plays a key role in the regulation of vascular tone and controls both local and systemic hemodynamics. Here, we estimated systemic NO production rates of hemodialysis (HD) patients, based on the time course of plasma concentration of nitrate (an oxidative end product of NO) and investigated possible roles of NO-related factors. METHODS: We measured plasma concentrations of nitrate, L-arginine (a substrate of NO synthase: NOS), asymmetric dimethylarginine (ADMA, an endogenous NOS inhibitor), tetrahydrobiopterin (BH4, a NOS cofactor), dihydrobiopterin (BH2, an oxidized form of BH4) and oxidized low-density lipoprotein (oxyLDL; an index of oxidative stress) before and after 30-min and 4-hour HD (n = 10). RESULTS: The time-averaged NO production rate during HD was estimated by fitting the time course of plasma nitrate concentration with a single-compartment model (4.00 +/- 0.82 micromol/min, 4.99 +/- 1.08 micromol/kg/h). The L-arginine/ADMA ratio (L-arginine availability) after 30-min HD showed a positive correlation with the NO production rate (p < 0.05). CONCLUSION: The systemic NO production rate during HD could be estimated by the single-compartment analysis. The L-arginine/ADMA ratio seems to play an important role in the regulation of the NO production during HD.

Arginine↗

PubMed2005

Evaluation of bioavailability of nitric oxide in coronary circulation by direct measurement of plasma nitric oxide concentration.

Although bioavailability of NO in the coronary circulation is commonly evaluated by acetylcholine (ACh)-induced vasodilation, a change in plasma NO concentration and its relation to the flow response after injection of ACh are still unknown. Thus, we directly measured the concentration of NO in the coronary sinus by using a catheter-type NO sensor for coronary sinus. An NO-sensitive sensor was located and fixed in a 4-Fr catheter with a soft tip for protection of vascular wall. After calibration with an NO-saturated pure water, the catheter-type NO sensor was located in the coronary sinus in anesthetized dogs. The coronary flow velocity (CFV) was measured with a Doppler guide wire. Intracoronary injection of ACh (0.4 and 1.0 microg/kg) increased plasma NO concentration in a dose-dependent manner (3-10 nM). Although ACh increased CFV by 95%, there was no significant difference between the two ACh doses. After ACh, the peak value of plasma NO concentration was observed significantly later than CFV. N(G)-methyl-L-arginine (NO synthase inhibitor) decreased basal NO concentration by 3 nM and suppressed the ACh-induced NO synthesis with no significant change in average peak velocity. We conclude that production of NO in the coronary circulation can be evaluated in the coronary sinus. Although ACh increases both CFV and NO concentration, CFV dose not reflect NO concentration in terms of magnitude and time course. Direct measurement of plasma NO concentration by the catheter-type NO sensor is useful to evaluate bioavailability of NO in the coronary circulation.

Acetylcholine↗

PubMed2005

Beneficial effect of hydroxyfasudil, a specific Rho-kinase inhibitor, on ischemia/reperfusion injury in canine coronary microcirculation in vivo.

OBJECTIVES: We examined whether hydroxyfasudil, a specific Rho-kinase inhibitor, exerts cardioprotective effect on coronary ischemia/reperfusion (I/R) injury and, if so, whether nitric oxide (NO) is involved. BACKGROUND: Recent studies have demonstrated that Rho-kinase is substantially involved in the pathogenesis of cardiovascular diseases; however, it remains to be examined whether it is also involved in ischemia/reperfusion (I/R) injury. METHODS: Canine subepicardial small arteries (SA, >or=100 microm) and arterioles (A, <100 microm) were observed by a charge-coupled device intravital microscope during I/R. Coronary vascular responses to endothelium-dependent (acetylcholine, intracoronary [IC]) and -independent (papaverine, IC) vasodilators were examined after I/R under the following four conditions: control (n = 7), NO synthase inhibitor alone (N(G)-monomethl-L-arginine [L-NMMA], IC, n = 4), hydroxyfasudil alone (IC, n = 7), and hydroxyfasudil plus L-NMMA (n = 7). RESULTS: Hydroxyfasudil significantly attenuated serotonin (IC)-induced vasoconstriction of SA (-7 +/- 1% vs. 2 +/- 1%, p < 0.01). Coronary I/R significantly impaired coronary vasodilation to acetylcholine after I/R (SA, p < 0.05; and A, p < 0.01 vs. before I/R) and L-NMMA further reduced the vasodilation, whereas hydroxyfasudil completely preserved the responses. The vasoconstriction by L-NMMA after I/R was significantly improved by hydroxyfasudil in both-sized arteries (both p < 0.01). Expression of endothelial nitric oxide synthase (eNOS) protein in the ischemic endocardium of left anterior descending coronary artery area (as determined by Western blotting) significantly decreased (79 +/- 4%) compared with the nonischemic endocardium of LCX area (100 +/- 7%), which was improved by hydroxyfasudil (105 +/- 6%, p < 0.01). Hydroxyfasudil significantly reduced myocardial infarct size, and hydroxyfasudil with L-NMMA also reduced the infarct size compared with L-NMMA alone. CONCLUSIONS: Hydroxyfasudil exerts cardioprotective effects on coronary I/R injury in vivo, in which NO-mediated mechanism may be involved through preservation of eNOS expression.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗

PubMed2005

Involvement of aldosterone and mineralocorticoid receptors in rat mesangial cell proliferation and deformability.

We demonstrated recently that chronic administration of aldosterone to rats induces glomerular mesangial injury and activates mitogen-activated protein kinases including extracellular signal-regulated kinases 1/2 (ERK1/2). We also observed that the aldosterone-induced mesangial injury and ERK1/2 activation were prevented by treatment with a selective mineralocorticoid receptor (MR) antagonist, eplerenone, suggesting that the glomerular mesangium is a potential target for injuries induced by aldosterone via activation of MR. In the present study, we investigated whether MR is expressed in cultured rat mesangial cells (RMCs) and involved in aldosterone-induced RMC injury. MR expression and localization were evaluated by Western blotting analysis and fluorolabeling methods. Cell proliferation and micromechanical properties were determined by [3H]-thymidine uptake measurements and a nanoindentation technique using an atomic force microscope cantilever, respectively. ERK1/2 activity was measured by Western blotting analysis with an anti-phospho-ERK1/2 antibody. Protein expression and immunostaining revealed that MR was abundant in the cytoplasm of RMCs. Aldosterone (1 to 100 nmol/L) dose-dependently activated ERK1/2 in RMCs with a peak at 10 minutes. Pretreatment with eplerenone (10 micromol/L) significantly attenuated aldosterone-induced ERK1/2 phosphorylation. Aldosterone (100 nmol/L) treatment for 30 hours increased [3H]-thymidine incorporation and decreased the elastic modulus, indicating cellular proliferative and deforming effects of aldosterone, respectively. These aldosterone-induced changes in cellular characteristics were prevented by pretreatment with eplerenone or an ERK (MEK) inhibitor, PD988059 (100 micromol/L). The results indicate that aldosterone directly induces RMC proliferation and deformability through MR and ERK1/2 activation, which may contribute to the pathogenesis of glomerular mesangial injury.

Aldosterone↗

PubMed2005

Direct measurement of nipradilol-derived nitric oxide in the vascular wall of canine femoral arteries.

Nipradilol (NP: 3,4-dihydro-8-[2-hydroxy-3-isopropylamino]propoxy-3-nitroxy-2H-1-benzopyran) shows not only beta-adrenoreceptor-blocking effects but also nitroglycerin-like vasodilatory action. We aimed to directly measure NP-derived nitric oxide (NO) in the vascular wall. An NO-sensitive microelectrode was inserted into the vascular media (the vasodilatory action site of NO) of isolated perfused canine femoral arteries. Each vessel was perfused with 15 microM NP in the presence or absence of 1 mM N-ethylmaleimide (NEM; a thiol alkylator). Intravascular-wall NO concentration increased 181+/-34 nM during NP perfusion (P<0.001 vs basal, n=10) with an average base-to-peak reaction time of 1.5+/-0.1 min (P<0.0001, n=8). Concomitant perfusion of NEM with NP attenuated the intravascular-wall NO production significantly (P<0.0001 vs NP only). It is concluded that NP is metabolized to NO in the vascular wall of an isolated canine femoral artery in large part through a metabolic process involving thiols with a base-to-peak reaction time of about 1.5 min.

Adrenergic beta-Antagonists↗

PubMed2005

Cardiac hemodynamics, coronary circulation and interventional cardiology.

Microcirculation is the functional end of the coronary circulation and it plays a key role in the regulation of coronary blood flow, both on the local and global scales. A good understanding of its function under physiological and pathophysiological conditions is crucial but, because of its micro-scale, access to this part of the coronary circulation is extremely difficult and requires a considerable amount of innovation and new technologies. Dynamics of the coronary circulation provide the true vehicle by which blood supply reaches the myocardium- coronary vasculature is only the conducting component of that vehicle. It is highly unlikely that the pulsatile nature of the flow, the capacitance of the conducting vessels and the constant pounding of coronary vasculature by surrounding tissue are not part of the design, regulation, and function of the coronary circulation. Interventions, whether to assess or to correct coronary stenosis, continue to be the main clinical avenue to dealing with coronary heart disease. Clinical decisions rely heavily on the ability to determine the true morphology of an occlusive lesion, to predict the future course of that lesion and to assess the functional toll on coronary blood supply which it will inflict at each stage.

Animals↗

PubMed2005

Digital radiographic quantification of myocardial blood flow around a transmyocardial laser channel in rabbit hearts.

BACKGROUND: A mechanism underlying the benefits of transmyocardial laser revascularization (TMLR) has been presumed to be improvement in perfusion. We evaluated myocardial blood flow around a laser channel using digital radiography combined with a 3H-labeled desmethylimipramine ([3H]DMI) deposition. METHODS AND RESULTS: A laser channel was created in the left ventricular wall using a YAG-laser in 6 non-ischemic rabbit hearts. After 8 weeks, [3H]DMI(1.11 MBq) was injected into the left atrium and the TMLR-treated myocardium was sectioned. Another 6 hearts were examined as controls. We measured [3H]DMI density in arbitrary units with digital radiography in the channel remnant, the surrounding area and a remote area. Flow distribution was quantified by the coefficient of variation of flows (CV). The surrounding area had the highest density (p < 0.001) and the lowest CV (p < 0.001), and had higher density (p < 0.001) and lower CV (p < 0.001) than the controls. There was no transmural difference in the density in all domains. The CV increased with depth in the remote area, as well as in controls (p < 0.001), but there was no transmural difference in the surrounding area. CONCLUSIONS: The TMLR increases myocardial blood flow and decreases flow heterogeneity in the surrounding area. The disappearance of transmural difference in flow heterogeneity might indicate the remodeling of microcirculation to improve regional oxygen delivery.

Animals↗

PubMed2005

Role of asymmetrical dimethylarginine in renal microvascular endothelial dysfunction in chronic renal failure with hypertension.

We examined whether endothelial function of the renal microcirculation was impaired in a model of chronic renal failure (CRF), and further assessed the role of asymmetrical dimethylarginine (ADMA) and its degrading enzyme, dimethylarginine dimethylaminohydrolase (DDAH), in mediating the deranged nitric oxide (NO) synthesis in CRF. CRF was established in male mongrel dogs by subtotal nephrectomy, and the animals were used in experiments after a period of 4 weeks. The endothelial function of the renal afferent and efferent arterioles was evaluated according to the response to acetylcholine, using an intravital needle-lens charge-coupled device camera. Intrarenal arterial infusion of acetylcholine (0.01 microg/kg/min) elicited 22+/-2% and 20+/-2% dilation of the afferent and efferent arterioles in normal dogs. In dogs with CRF, this vasodilation was attenuated (afferent, 12+/-2%; efferent, 11+/-1%), and the attenuation paralleled the diminished increments in urinary nitrite+nitrate excretion. In the animals with CRF, plasma concentrations of homocysteine (12.2+/-0.7 vs. 6.8+/-0.4 micromol/l) and ADMA were elevated (2.60+/-0.13 vs. 1.50+/-0.08 micromol/l). The inhibition of S-adenosylmethionine-dependent protein arginine N-methyltransferase by adenosine dialdehyde decreased plasma ADMA levels, and improved the acetylcholine-induced changes in urinary nitrite+nitrate excretion and arteriolar vasodilation. Acute methionine loading impaired the acetylcholine-induced renal arteriolar vasodilation in CRF, but not normal dogs, and the impairment in CRF dogs coincided with the changes in plasma ADMA levels. Real-time polymerase chain reaction revealed downregulation of the mRNA expression of DDAH-II in the dogs with CRF. Collectively, these results provide direct in vivo evidence of endothelial dysfunction in canine CRF kidneys. The endothelial dysfunction was attributed to the inhibition of the NO production by elevated ADMA, which involved the downregulation of DDAH-II. The deranged NO metabolic pathway including ADMA and DDAH is a novel mechanism for the aggravation of renal function.

Acetylcholine↗

PubMed2005

Increased pulmonary heme oxygenase-1 and delta-aminolevulinate synthase expression in monocrotaline-induced pulmonary hypertension.

Monocrotaline (MCT), a pyrrolizidine alkaloid plant toxin, is known to cause pulmonary hypertension (PH) in rats. Recent findings suggest that pulmonary inflammation may play a significant role in the pathogenesis in MCT-induced PH. Heme oxygenase-1 (HO-1), the rate-limiting enzyme in heme catabolism, is known to be induced by various oxidative stresses, including inflammation and free heme, and its induction is thought essential in the protection against oxidative tissue injuries. In this study, we examined expression of HO-1 as well as non-specific delta-aminolevulinate synthase (ALAS1), the rate-limiting enzyme in heme catabolism and biosynthesis, respectively, in a rat model of PH produced by subcutaneous injection of MCT (60 mg/kg). MCT treatment caused infiltration of inflammatory cells, fibrosis of the interstitium, and pulmonary arterial wall thickening with marked elevation of right ventricular (RV) pressure, which are characteristics of MCT-induced PH. Gene expression of tumor necrosis factor-alpha (TNF-alpha) as well as DNA binding activity of nuclear factor-kappaB (NF-kappaB) increased at 1 week after MCT treatment, reached a maximum at 2 weeks, and then decreased to the pretreatment level at 3 weeks. HO-1 expression was markedly increased at 1 week, and continued to increase by 3 weeks following MCT treatment, both at transcriptional and protein levels in the mononuclear cells in the lung. ALAS1 mRNA levels in the lung also significantly increased at 2 weeks after MCT treatment. These findings suggest that pulmonary HO-1 expression was presumably induced by proinflammatory cytokine(s) in MCT-treated rats, resulting in the derepression of heme-repressible ALAS1 expression, and that HO-1 induction plays a significant role as an inflammatory factor in this condition.

5-Aminolevulinate Synthetase↗

PubMed2004

Regression of capillary network in atrophied soleus muscle induced by hindlimb unweighting.

Little is known about the mechanisms responsible for the adaptation and changes in the capillary network of hindlimb unweighting (HU)-induced atrophied skeletal muscle, especially the coupling between functional and structural alterations of intercapillary anastomoses and tortuosity of capillaries. We hypothesized that muscle atrophy by HU leads to the apoptotic regression of the capillaries and intercapillary anastomoses with their functional alteration in hemodynamics. To clarify the three-dimensional architecture of the capillary network, contrast medium-injected rat soleus muscles were visualized clearly using a confocal laser scanning microscope, and sections were stained by terminal deoxynucleotidyltransferase-mediated dUTP nick-end labeling (TUNEL) and with anti-von Willebrand factor. In vivo, the red blood cell velocity of soleus muscle capillaries were determined with a pencil-lens intravital microscope brought into direct contact with the soleus surface. After HU, the total muscle mass, myofibril protein mass, and slow-type myosin heavy chain content were significantly lower. The number of capillaries paralleling muscle fiber and red blood cells velocity were higher in atrophied soleus. However, the mean capillary volume and capillary luminal diameter were significantly smaller after HU than in the age-matched control group. In addition, we found that the number of anastomoses and the tortuosity were significantly lower and TUNEL-positive endothelial cells were observed in atrophied soleus muscles, especially the anastomoses and/or tortuous capillaries. These results indicate that muscle atrophy by HU generates structural alterations in the capillary network, and apoptosis appears to occur in the endothelial cell of the muscle capillaries.

Animals↗

PubMed2004

Normal distribution of ventricular pressure-volume area of arrhythmic beats under atrial fibrillation in canine heart.

We previously found the frequency distribution of the left ventricular (LV) effective afterload elastance (E(a)) of arrhythmic beats to be nonnormal or non-Gaussian in contrast to the normal distribution of the LV end-systolic elastance (E(max)) in canine in situ LVs during electrically induced atrial fibrillation (AF). These two mechanical variables determine the total mechanical energy [systolic pressure-volume area (PVA)] generated by LV contraction when the LV end-diastolic volume is given on a per-beat basis. PVA and E(max) are the two key determinants of the LV O(2) consumption per beat. In the present study, we analyzed the frequency distribution of PVA during AF by its chi(2), significance level, skewness, and kurtosis and compared them with those of other major cardiodynamic variables including E(a) and E(max). We assumed the volume intercept (V(0)) of the end-systolic pressure-volume relation needed for E(max) determination to be stable during arrhythmia. We found that PVA distributed much more normally than E(a) and slightly more so than E(max) during AF. We compared the chi(2), significance level, skewness, and kurtosis of all the complex terms of the PVA formula. We found that the complexity of the PVA formula attenuated the effect of the considerably nonnormal distribution of E(a) on the distribution of PVA along the central limit theorem. We conclude that mean (SD) of PVA can reliably characterize the distribution of PVA of arrhythmic beats during AF, at least in canine hearts.

Animals↗

PubMed2004

Dynamics of flow velocities in endocardial and epicardial coronary arterioles.

The subendocardium is the most vulnerable area of the left ventricle to the effects of hypoperfusion and ischemia. Despite this well-acknowledged observation, the mechanisms underlying this susceptibility are not elucidated, although numerous explanations including differences in transmural distribution of hemodynamics, metabolism, and wall stresses have been proposed. Our goal was to make dynamic measurements of endocardial and epicardial flow velocities, which reflect hemodynamic and wall stresses, to approach this problem. We measured blood flow velocities in subendocardial and subepicardial coronary arterioles of in vivo beating canine hearts using a high-speed, charge-coupled device, intravital videomicroscope with a rod-probe lens. Subendocardial flow was characterized by remarkable systolic flow-velocity reversal (systolic slosh ratio, 84%; measurable velocity of retrograde flow, faster than -40 mm/s), which contrasted to predominant forward-flow velocity during systole in the subepicardial arterioles (systolic slosh ratio, 25%; maximum velocity, approximately -20 mm/s; P < 0.0005 and 0.05 vs. subendocardial arterioles, respectively). We speculate that this retrograde flow is "wasteful," because this volume must be refilled during the subsequent diastole, which thereby detracts from the net perfusion as well as the time for perfusion. Accordingly, we also believe that the retrograde systolic blood flow contributes to the vulnerability of the subendocardium to ischemia.

Animals↗

PubMed2004

Exogenous NO suppresses flow-induced endothelium-derived NO production because of depletion of tetrahydrobiopterin.

Exogenous nitric oxide (NO) suppresses endothelium-derived NO production. We were interested in determining whether this is also the case in flow-induced endothelium-derived NO production. If so, then is the mechanism because of intracellular depletion of tetrahydrobiopterin [BH4; a cofactor of NO synthase (NOS)], which results in superoxide production by uncoupled NOS? Isolated canine femoral arteries were perfused with 100 microM S-nitroso-N-acetylpenicillamine (SNAP; an NO donor) and/or 64 microM BH4. Perfusion of SNAP suppressed flow-induced NO production, which was evaluated as a change in the slope of the linear relationship between perfusion rate and NO production rate (P < 0.02 vs. control; n = 7). Subsequent BH4 perfusion returned the slope to the control level. Concomitant perfusion of SNAP and BH4 retained the control-level NO production (n = 7). Concomitant perfusion of SNAP and 4,5-dihydroxy-1,3-benzene disulfonic acid (Tiron; 1 mM; a membrane-permeable superoxide scavenger) also retained the control-level NO production (n = 7), whereas perfusion of Tiron after SNAP could not return the NO production to the control level (P < 0.02 vs. control; n = 7). We also found a significant decrease in BH4 concentration in the endothelial cells after SNAP perfusion. In conclusion, these results indicate that exogenous NO suppresses the flow-induced, endothelium-derived NO production by superoxide released from uncoupled NOS because of intracellular BH4 depletion.

Animals↗

PubMed2004

Direct observation of epicardial coronary capillary hemodynamics during reactive hyperemia and during adenosine administration by intravital video microscopy.

Using high-resolution intravital charge-coupled device video microscopy, we visualized the epicardial capillary network of the beating canine heart in vivo to elucidate its functional role under control conditions, during reactive hyperemia (RH), and during intracoronary adenosine administration. The pencil-lens video-microscope probe was placed over capillaries fed by the left anterior descending artery in atrioventricular-blocked hearts of open-chest, anesthetized dogs paced at 60-90 beats/min (n = 17). In individual capillaries under control conditions, red blood cell flow was predominant during systole or diastole, indicating that the watershed between diastolic arterial and systolic venous flows is located within the capillaries. Capillary flow increased during RH and reached a peak flow velocity (2.1 +/- 0.6 mm/s), twice as high as control (1.2 +/- 0.5 mm/s), with enhancement of intercapillary cross-connection flow and enlargement of diameter (by 17%). With adenosine, capillary flow velocity significantly increased (1.8 +/- 0.7 mm/s). However, the increase in volumetric capillary flow with adenosine estimated from red blood cell velocity and diameter was less than the increase in arterial flow, whereas that during RH was nearly equivalent to the increase in arterial flow. There was a time lag of approximately 1.5 s for refilling of capillaries during RH, indicating their function as capacitance vessels. In conclusion, the coronary capillary network functions as 1) the major watershed between diastolic-dominant arterial and systolic-dominant venous flows, 2) a capacitor, and 3) a significant local flow amplifier and homogenizer of blood supply during RH, but with adenosine the increase in capillary flow velocity was less than the increase in arterial flow.

Adenosine↗

PubMed2004

Kinetic study on the elastic change of vascular endothelial cells on collagen matrices by atomic force microscopy.

The elasticity of vascular endothelial cells (HUVEC) was measured with an atomic force microscopy (AFM, Olympus), and analyzed by applying the Hertz model, and those data were compared with ones reported by us previously. The latter elasticity data were measured with AFM Instruments (Seiko) on the basis of the Young's modulus of gelatin gel, which was obtained from the measurement with a tensile tester. The elasticity of HUVEC was concluded to depend on the culture period. The elasticity of the cells cultured on type IV collagen for longer than 4 days led to average elasticity values higher than ca. 10(4)Pa. Moreover, the scattered values of elasticity decreased eminently in the AFM measurement of the cells at room temperature. A few cells, however, appeared to adhere long and tensely on matrix, which seems to one of reasons for relatively high elasticity in our previous works. The possibility of such high elasticity was considered to change in cell adhesion, anchoring on matrix during a long culture period.

Cell Adhesion↗