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Biomedical subjects

R Mizuno

Publications and source records attributed to R Mizuno.

At least 37 records · Page 2Linked to original sources
PubMed2000

Effects of VEGF on Ca(2+)-transient in cultured lymphatic endothelial cells and mechanical activity of isolated lymph vessels.

We investigated the effects of vascular endothelial growth factor (VEGF(165)) on [Ca(2+)](i)-transient in cultured lymphatic endothelial cells (LEC) and mechanical activity of isolated dog thoracic ducts. VEGF (0.1-10 ng/ml) caused a dose-dependent increase of the [Ca(2+)](i) in LEC. Pretreatment with 10(-5) M genistein or 5x10(-6) M herbimycin A produced a significant reduction of the VEGF-induced [Ca(2+)](i)-transient. In the presence of 10(-6) M thapsigargin, VEGF caused no significant effect on the [Ca(2+)](i)-transient. Pretreatment with Ca(2+)-free solution containing 0.1 mM EGTA produced no significant effect on the peak increase of [Ca(2+)](i) induced by 0.1 or 10 ng/ml VEGF, but significantly depressed the sustained part of [Ca(2+)](i) observed at the higher concentration of VEGF. The VEGF (0.1-10 ng/ml) caused a significant dilation of the isolated lymph vessels with intact endothelium, which were precontracted with U46,619. The 10 ng/ml VEGF-induced dilation was significantly reduced by 3 x 10(-5) M N(omega)-nitro-L-arginine methyl ester (L-NAME). The action of L-NAME was inhibited by the simultaneous application of 10(-3) M L-arginine. Mechanical rubbing of the endothelium also caused significant inhibition of the VEGF-induced dilation. The findings suggest that VEGF(165) may activate the receptor-related tyrosine kinase and cause the release of Ca(2+) from the inositol 1,4, 5-triphosphate-sensitive intracellular Ca(2+) stores in LEC. VEGF(165) also produces endothelium-dependent nitric oxide-mediated dilation of the precontracted isolated lymph vessels.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1999

Spontaneous rupture of splenic hamartoma: a case report.

Splenic hamartomas are rare. The authors report a case of spontaneously ruptured splenic hamartoma in a 5-month-old boy. This rupture led to the death of the child. If abdominal pain is present and a mass is palpated, the splenic hamartoma should be managed surgically in an expeditious manner. There have been only two known previous reports of spontaneous rupture of splenic hamartoma in adults, but none in children.

Hamartoma↗
PubMed1999

Ultrasonic tissue characterization in patients with dilated cardiomyopathy: comparison with findings from right ventricular endomyocardial biopsy.

AIM: The clinical usefulness of integrated backscatter (IB) imaging was compared with right ventricular endomyocardial biopsy for assessing myocardial damage in patients with dilated cardiomyopathy (DCM). METHODS: We examined 15 patients with DCM and 20 healthy controls. In addition to the conventional M-mode echocardiographic parameters, we determined the cyclic variation in IB values (CV-IB) obtained from parasternal short axis views of the left ventricle just under the transducer for both the interventricular septum (IVS) and the left ventricular posterior wall (PW). The per cent fibrosis area (%) and the transverse diameter of myocytes (microm) were measured in right ventricular endomyocardial biopsy specimens by computer image analysis. To analyze the relationship between pathological findings and CV-IB, we divided patients into four subgroups on the basis of the pathological characteristics of endomyocardial biopsy specimens as follows: degeneration dominant group (n = 5), fibrosis dominant group (n = 5), dilated phase hypertrophic cardiomyopathy (n = 2), and mixed type (n = 3). RESULTS: CV-IB in the IVS and the PW was lower in patients with DCM (8.8 +/- 2.9, 8.3 +/- 2.7 dB, respectively) than in normal subjects (14.4 +/- 2.9, 13.6 +/- 2.6 dB, respectively). Biopsy findings showed a mean per cent fibrosis area of 24.0 +/- 12.3%, and a mean myocyte diameter of 14.3 +/- 2.9 microm in patients with DCM. CV-IB was correlated with both of these findings: per cent fibrosis area (r = -0.56 in IVS, r = -0.56 in PW) and myocyte diameter (r = 0.67 in IVS, r = 0.71 in PW). CV-IB was decreased in all DCM subgroups compared with normal subjects, but there was no significant difference between subgroups. CONCLUSIONS: CV-IB was correlated with both the extent of fibrosis in myocardial tissue and the myocyte diameter. These findings suggest that ultrasonic tissue characterization is a good indicator of the severity of fibrosis and myocyte atrophy in patients with DCM.

Biopsy↗
PubMed1999

Involvement of ATP-sensitive K(+) channels in spontaneous activity of isolated lymph microvessels in rats.

Physiological roles of ATP-sensitive K(+) channels for spontaneous activity in isolated rat mesenteric lymph microvessels (maximum diameter approximately 80-150 microm) were investigated. The lymph microvessels were cannulated with glass micropipettes and pressurized at a perfusion pressure of 6 cmH(2)O. Changes in the diameter and frequency of spontaneous contractions in the lymphatics were measured with videomicroscopy. Pinacidil (K(+)-channel opener) inhibited the spontaneous activity. In the presence of glibenclamide (selective ATP-sensitive K(+)-channel blocker; 10(-7) and 10(-6) M) and tetraethylammonium (TEA; nonselective K(+)-channel blocker; 10(-4) and 10(-3) M), the pinacidil-induced inhibition of the spontaneous contractions in lymph microvessels was significantly reversed. Glibenclamide and TEA themselves, however, did not affect the frequency of spontaneous activity in the lymph microvessels. These results suggest that ATP-sensitive K(+) channels are involved in the regulation of spontaneous activity in the smooth muscles of isolated lymph microvessels of rat mesenteries.

Adenosine Triphosphate↗
PubMed1999

Flow reduces the amplitude and increases the frequency of lymphatic vasomotion: role of endothelial prostanoids.

Fluid dynamic forces have substantial effects on the movement of lymph and activity of lymph vessels. The effect of increases in intraluminal flow on spontaneous pumping activity of isolated collecting lymphatics has not yet been characterized in a condition in which the intraluminal pressure is constant. Thus, in afferent lymph microvessels isolated from rat iliac lymph nodes, changes in maximum (Dmax) and minimum (Dmin) diameter to increases in perfusate flow were investigated in the presence of a constant perfusion pressure of 6 cmH2O. Intraluminal flow was elicited by increases in the difference between outflow and inflow pressures (Pdiff, from 0 to 6 cmH2O). Diameters were measured by videomicroscopy. In response to increases in perfusate flow, Dmax and Dmin of lymphatics decreased from 157.5 +/- 6.1 to 90.9 +/- 5.6 micron and from 91.9 +/- 5.3 to 66.3 +/- 3.6 micron, respectively, whereas vasomotion frequency increased from 18.0 +/- 0.7 min(-1) to 23.4 +/- 1.1 min(-1) (at Pdiff of 4 cmH2O). Removal of extracellular Ca2+ abolished spontaneous diameter oscillations; under these conditions the passive diameter of lymphatics was 216.0 +/- 7.1 micron and did not change in response to increases in perfusion. In the absence of endothelium, flow-induced changes in Dmax, Dmin, and oscillation frequency were eliminated. Nomega-nitro-L-arginine methyl ester, an inhibitor of nitric oxide synthase, did not affect flow-induced changes in diameter of lymphatics. In contrast, indomethacin, an inhibitor of prostaglandin synthesis, or SQ-29,548, a PGH2/thromboxane A2 (PGH2/TxA2) receptor blocker, inhibited the perfusion-induced reduction of Dmax and Dmin of lymphatics and also the increase in the frequency of vasomotion. These findings suggest that the sensitivity of lymphatic endothelium to increases in intraluminal flow could provide an important local intrinsic mechanism for the control of lymphatic resistance by release of constrictor prostanoids PGH2/TxA2.

Animals↗
PubMed1999

Atrial involvement in patients with progressive systemic sclerosis: relationship between ultrasonic tissue characterization of the atrium and interatrial conduction.

OBJECTIVE: The aim of this study was to assess atrial lesions using ultrasonic tissue characterization and to determine the contribution of atrial lesions to the interatrial electromechanical coupling conduction time in patients with progressive systemic sclerosis (PSS). METHODS: Twenty patients with PSS and 20 age-matched healthy controls were evaluated. The cyclic variation in integrated backscatter value (CV-IB) was measured at the interatrial septum (IAS) from apical four chamber view. M-modes of ventricular long axis motion along with phono- and electrocardiograms were recorded simultaneously at the right lateral (RT) and left lateral (LT) sites of the atrioventricular (AV) rings and central fibrous body (CFB) in the apical four-chamber view. Intervals from the P wave on ECG to the echocardiographic onset of atrial contraction as a point of inflection in long axis M-mode echocardiogram were measured at the RT and LT sites of AV rings and CFB (P-RT, P-LT, P-SEP, respectively). Interatrial electromechanical coupling conduction time was determined as [(P-LT) - (P-RT)]. RESULTS: In patients with PSS compared to normal controls, P-RT, P-SEP, P-LT, and interatrial conduction time were greater, while CV-IB in IAS decreased. Furthermore, CV-IB in IAS correlated well with interatrial conduction time (r = 0.7, p < 0.01) in patients with PSS. CONCLUSIONS: Interatrial electromechanical coupling times may be prolonged due to atrial tissue damage in patients with PSS.

Adult↗
PubMed1998

Infant temperament and child-rearing stress: birth order influences.

The relationship between an infant's temperamental difficulty and the mother's child-rearing stress was investigated in a sample of 128 children. Children's temperament was assessed by the Revised Infant Temperament Questionnaire (RITQ) at 6-7 months, and by the Toddler Temperament Scale (TTS) at 18 months. The mothers' child-rearing stress was assessed by a self-report questionnaire. At the children's age of 18 months, mothers of difficult children reported higher child-rearing stress than mothers of easy children. Although difference in the level of child-rearing stress reflecting birth order was not evident at either 6-7 months or 18 months, the proportion of child-rearing stress which could be explained by the children's temperament was highest for mothers of first-borns when their children were 18 months old.

Birth Order↗
PubMed1998

[A resected case of malignant peripheral nerve sheath tumor (MPNST) necessary to distinguish from Askin tumor].

We have treated a patient with malignant peripheral nerve sheath tumor (MPNST) for 7 years by interdisciplinary therapy. The diagnosis and treatment are reported with the clinical course so far. A 20-year-old man underwent surgical resection of a tumor on the left side of the chest in 1990, and a diagnosis of Askin tumor was made. In 1993, the disease recurred in the left axilla and was surgically resected. The surgical specimen was investigated histologically, and a diagnosis of MPNST was made instead of Askin tumor. Recently, a tumor began to grow in the left pleural cavity and was surgical resected. The tumor tissue contained both cells with oval and long spindle nuclei, which were intermingled with each other. Immunohistochemically, the tumor cells were positive for vimentin and some of them were positive for S100 protein. Because electron microscopy showed cytoplasmic processes on the tumor cell and basal lamina-like structures, a diagnosis of recurrent MPNST was made. Because this lesion resembled Askin tumor in its clinical manifestations and histological characteristics, differential diagnosis from Askin tumor was necessary. When a malignant soft tissue tumor arising from the mediastinum or chest walls is detected, immunohistochemical and electron microscopic studies should be performed. The diagnosis should be based on the overall findings including the location and clinical data.

Adult↗
PubMed1998

Magnetic resonance velocity mapping of transtricuspid velocity profiles in dilated cardiomyopathy.

To investigate the velocity profiles and jet sizes of transtricuspid inflow by magnetic resonance imaging (MRI), we examined seven dilated cardiomyopathy (DCM) patients (mean age 37 +/- 15 years) and 20 normal subjects (mean age 32 +/- 7 years). We used a Siemens Magnetom Impact Expert (1.0 T) together with a surface receiver coil. Electrocardiographic gating, triggered by the R wave, was performed. Cine gradient echo images were obtained in the short axis of the right ventricle. Velocity mapping of right ventricular inflow was obtained at peak early diastolic filling. Velocity profile curves across the tricuspid inflow were obtained at 1-cm intervals from the tricuspid ring up to 3 cm into the cavity. Maximum/mean velocities in both groups were 1.1 +/- 0.1 at the ring level, unchanged at 1 cm from the tricuspid ring, and thereafter increased to 1.4 +/- 0.3 at 2 cm and 1.5 +/- 0.3 at 3 cm as peak velocity fell. Jet cross-sectional area was 10.4 +/- 2.1 cm2 at the ring level, and was unchanged at the 3-cm level in the normal subjects. However, in patients with DCM it was smaller than that in normals, and decreased in proportion to the distance from the tricuspid ring. Thus, tricuspid inflow velocity showed a relatively flat profile at the tricuspid ring and tip levels, becoming more dispersed at 2 and 3 cm from the ring. The cross-sectional area of the right ventricular inflow jet in the DCM patients was small and decreased in proportion to the distance from the tricuspid ring, although it appeared to be relatively constant in normal subjects.

Adult↗
PubMed1998

Contribution of long axis motion of left ventricular outflow to calculation of left ventricular stroke volume.

Stroke volume can be calculated by using noninvasive Doppler techniques. The products of pulsed Doppler stroke distance of left ventricular outflow and left ventricular outflow area can often be used to calculate stroke volume. However, left ventricular outflow also moves longitudinally toward the apex of the ventricle during systole, so that zero velocity flow cannot be detected by the usual pulsed Doppler studies. We evaluated the contribution of these zero velocity flow to the noninvasive estimation of left ventricular stroke volume in 20 patients with left ventricular disease and in 20 age matched healthy controls. Left ventricular stroke distance was calculated by summing the Doppler stroke distance and the outflow long axis motion. The percentage of zero velocity flow for total stroke volume was calculated in each group. Cardiac output was also measured by thermo-dilution technique. The percentage of zero velocity flow for total noninvasive stroke volume in patients with left ventricular disease was 2.5 +/- 1.1 ml (4.0 +/- 1.5%), significantly lower than in normal subjects, 3.6 +/- 1.0 ml (5.5 +/- 1.5%) (p < 0.05). These long axis motions are significantly reduced, especially in left ventricular disease. Amplitudes of the left ventricular outflow long axis motion were correlated with Doppler stroke distance in all (r = 0.54, p < 0.01). In patients with myocardial infarction, stroke volume by thermo-dilution methods and calculated stroke volume showed good correlation both only by Doppler stroke distance (y = 1.044x + 0.547, r = 0.968) and by Doppler and long axis motion (y = 0.989x + 0.521, r = 0.974). Compared with stroke volume measured by thermodilution method, stroke volume calculated only by Doppler stroke distance was underestimated. We thus demonstrated the influence of zero velocity flow on left ventricular outflow both in patients with left ventricular disease and in normal subjects.

Adult↗
PubMed1998

Estimation of the right ventricular volume and ejection fraction by transthoracic three-dimensional echocardiography. A validation study using magnetic resonance imaging.

AIMS: To validate the use of three-dimensional transthoracic echocardiography compared with the magnetic resonance imaging for determination of right ventricular volume and ejection fraction. METHODS AND RESULTS: We recorded transthoracic echocardiographic images starting from the apical four-chamber view in which the RV is clearly visualized in 15 healthy volunteers. The scanning plane of the RV was obtained by the rotational scanning technique in 2 degree angular increments for three-dimensional reconstruction. The RV volumes in end-diastole and end-systole were calculated using a Tomtec three-dimensional reconstruction computer. We also assessed the RV by cine magnetic resonance imaging using the Siemens Magnetom Impact Expert (1.0 T). Cine gradient echo images were obtained in the short axis of the RV. The RV volume at each phase was calculated by Simpson's method. We also calculated the RV ejection fraction. The RV volumes in end-diastole and end-systole were 111 +/- 22 ml and 52 +/- 13 ml, respectively as determined by three-dimensional echo, and 115 +/- 18 ml and 55 +/- 14 ml determined by MRI. The right ventricular volumes at end-diastole and end-systole determined by three-dimensional echo were correlated with the volumes determined by MRI (r = 0.94 and 0.97, respectively, p < 0.001). The RV ejection fraction determined by three dimensional echo was also correlated with the ejection fraction determined by MRI (r = 0.90, p < 0.01). CONCLUSIONS: Three-dimensional transthoracic echocardiography provided reliable calculations of the right ventricular volume and ejection fraction.

Adult↗
PubMed1998

Assessment of the normal adult right ventricular diastolic function using M-mode echocardiographic measurement of tricuspid ring motion.

Right ventricular function can be evaluated echocardiographically by assessing the longitudinal motion of the tricuspid ring recorded in the apical four chamber view. In this study, we applied this technique to assess the right ventricular diastolic function in 10 healthy Japanese men (mean age: 28 +/- 6 years; age range: 20-43 years). Echocardiographic studies were performed with a phased-array imaging system using a 2.5 MHz probe. Tricuspid ring motion was measured by two-dimensional echo guided M-mode echocardiogram of the right lateral tricuspid ring. The excursion of the tricuspid ring during early diastole (DS; mm) and the peak rate of change of the excursion (dS/dt; mm/sec) were measured. We also assessed the right ventricular function by cine magnetic resonance imaging (MRI). Cine gradient echo images were obtained along the short axis of the right ventricle. The right ventricular volume at each phase of the cardiac cycle was calculated by Simpson's method and time-volume curves were constructed. The peak filling rate (dV/dt; ml/s) was determined from these time-volume curves. The dS was 12.8 +/- 2.5 mm, dS/dt was 132 +/- 27 mm/sec and dV/dt was 269 +/- 66 ml/s. There were significant positive correlations between dS and dV/dt (r = 0.80, P < 0.01), and between dS/dt and dV/dt (r = 0.45, P < 0.05). Based on our results, M-mode echocardiographic measurements of tricuspid ring motion may be used to assess the right ventricular diastolic function.

Adult↗
PubMed1998

Regulation of the vasomotor activity of lymph microvessels by nitric oxide and prostaglandins.

It was shown previously that the presence of endothelium modulates spontaneous vasomotion of small lymphatic vessels. In the present study, we aimed to elucidate the nature of endothelium-derived factors, produced in basal conditions and in response to agonists, that affect the smooth muscle tone of lymph microvessels in vitro. Afferent lymph microvessels were isolated from rat iliac lymph nodes, cannulated with glass micropipettes, and pressurized (6 cmH2O), and changes in their diameter were investigated with video microscopy. In resting conditions, isolated lymph vessels exhibited spontaneous constrictions and dilations. The maximum and minimum diameters (Dmax and Dmin) were 149.8 +/- 2.9 and 85.8 +/- 3.6 microns, respectively. Acetylcholine (ACh, 10(-7) to 10(-5) M) and sodium nitroprusside (SNP, 10(-8) to 10(-6) M) temporarily abolished diameter oscillations, increasing the diameter of lymphatics dose dependently. For example, 10(-5) M ACh and 10(-6) M SNP increased the diameter (Dmax) by 15.2 +/- 2.2 and 25.0 +/- 2.7 microns, respectively. Treatment of vessels with NG-nitro-L-arginine (10(-4) M) significantly reduced the amplitude of diameter oscillations and nearly completely eliminated ACh-induced dilation of lymph microvessels, whereas SNP (10(-6) M) elicited a significantly greater dilation (55.6 +/- 7.5 microns). Arachidonic acid (AA, 10(-8) to 10(-6) M) constricted (up to 50 microns), whereas prostaglandin E2 (PGE2, 10(-9) to 10(-7) M) dilated (up to 40 microns), lymphatic vessels. Indomethacin (10(-5) M) increased both Dmax and Dmin and completely inhibited AA-induced constrictions, but did not affect PGE2-induced dilations of lymph microvessels. AA-induced constrictions of lymphatics were converted into dilations after treatment with SQ-29,548, a selective PGH2-thromboxane A2 (PGH2-TxA2, 10(-6) M) receptor antagonist, whereas PGE2-induced dilations were not affected. We conclude that endothelial nitric oxide and prostaglandins are important modulators of lymphatic vasomotion, hence pumping activity of lymph microvessels in vivo.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1998

Apical hypertrophy with massive myocardial fibrosis: comparison with electrocardiographic changes.

We report the case of a 48-year-old woman with apical hypertrophy with massive myocardial fibrosis. She was admitted to our hospital because of general malaise. Echocardiographic examination showed asymmetrical apical hypertrophy, and an electrocardiogram showed a giant negative T wave on V3-V6. Right ventricular endomyocardial biopsy revealed massive myocardial fibrosis. Apical hypertrophy can lead to disorders that vary in severity, including rare massive myocardial fibrosis.

Biopsy↗