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Biomedical subjects

T Niki

Publications and source records attributed to T Niki.

At least 91 records · Page 5Linked to original sources
PubMed1987

Tetraethylammonium induced coronary spasm in isolated perfused rabbit heart: a hypothesis for the mechanism of coronary spasm.

The vasoactive effect of tetraethylammonium, which is known to reduce potassium conductance of the membrane of arterial smooth muscle cells, was tested on large epicardial coronary arteries in isolated perfused rabbit hearts. These hearts were perfused selectively through the right and left coronary arteries. Left coronary angiography was performed using Krebs-Henseleit solution containing phenolsulfonphthalein under constant pressure, and the epicardial electrogram was recorded. In 59 of 114 hearts 30 mmol.litre-1 tetraethylammonium induced severe constriction of the left epicardial coronary artery, which was associated with electrocardiographic ST segment elevation in some cases. The induced spasm was prevented by diltiazem (200 nmol.litre-1), glyceryl trinitrate (2 mumol.litre-1), or nicorandil (10 mumol.litre-1), but not by phentolamine (1 mumol.litre-1) or atropine (1 mumol.litre-1). In hearts in which tetraethylammonium did not induce spasm, subsequent addition of ergonovine (100 nmol.litre-1) or alkalinisation of the perfusate (pH 7.65-7.70) provoked spasm. The tetraethylammonium induced spasm resembled the coronary spasm seen in patients with variant angina and was a reproducible in vitro model of coronary spasm. These observations support the hypothesis that the primary defect in patients with coronary spasm is decreased potassium permeability of the membrane of coronary arterial smooth muscle cells.

Animals↗
PubMed1986

Properties of Plasma Membrane Isolated from Chilling-Sensitive Etiolated Seedlings of Vigna radiata L.

Plasma membrane was isolated in a uniform population and with a high purity from chilling-sensitive etiolated young seedlings of Vigna radiata (mung bean) utilizing an aqueous two polymer phase separation system and subsequent sucrose density gradient. The isolated plasma membrane was associated with vanadate-sensitive and KNO(3)-insensitive ATPase. The ATPase has high specificities both for substrate and Mg(2+) ion with optimum pH at 6.5. It was slightly stimulated by monovalent anions, especially Cl(-). Proton ionophores such as gramicidin D and carbonyl cyanide p-trifluoromethoxyphenylhydrazone did not stimulate the enzyme activity. The ATPase is apparently latent and highly stimulated by the addition of detergents such as Triton X-100. A maximum stimulation was achieved by the addition of 0.02% Triton X-100. After treatment with proteinase K in an isotonic buffer solution, the enzyme activity was less affected, whereas the peptides were specifically digested. Based on these facts, the isolated plasma membrane vesicles appear to be tightly sealed and in a right-side-out orientation. The plasma membrane ATPase had two inflection points at higher (18.9 degrees C) and lower (6.7 degrees C) temperatures on the Arrhenius plots of the activity. The lower inflection temperature apparently coincided with that of the anisotropy parameter of embedded 1,6-diphenyl-1,3,5-hexatriene, indicating that the membrane bound ATPase activity was affected by a phase transition of membrane lipids and/or temperature-dependent conformational changes in the enzyme molecules per se. Considering the fact that the plant material used here is highly sensitive to chilling temperatures and injured severely by exposure to temperatures below 5 degrees C for a relatively short period, the thermotropic properties of membrane molecules are considered to be involved in the mechanism of chilling injury.

Journal Article↗
PubMed1986

Isolation and Characterization of Tonoplast from Chilling-Sensitive Etiolated Seedlings of Vigna radiata L.

Tonoplasts were isolated in a high purity from etiolated young seedlings of Vigna radiata L. (mung bean) utilizing a sucrose density gradient system. The excised hypocotyls were homogenized in a sorbitol-buffer system and the 3,600 to 156,000g pellets obtained after the differential centrifugations were suspended in a sorbitol medium and loaded on a linear sucrose density gradient. After centrifugation at 89,000g for 2 hours, tonoplasts were banded at the sample load/sucrose interface. Assessed by electron microscopy and marker enzymes, the purity and the quantity were found to be sufficient for biochemical and biophysical analyses. The tonoplasts were associated with NO(3) (-)-sensitive and vana-date-insensitive ATPase. The tonoplast ATPase was stimulated by proton ionophores such as carbonyl cyanide p-trifluoromethoxyphenyl-hydrazone and gramicidin D, suggesting a proton-pumping enzyme. In the presence of ATP and Mg(2+), a proton gradient was formed in the isolated tonoplast vesicles as assessed by fluorescence quenching of quinacrine. The tonoplasts contained several kinds of mannosylated or glycosylated glycoproteins and a major protein (65 kilodaltons) which was unique to the membranes.

Journal Article↗
PubMed1985

[Stress pulsed Doppler echocardiography in the evaluation of diastolic left ventricular function].

The effect of sublingual nifedipine on left ventricular (LV) function was assessed by analyzing LV inflow velocity patterns using pulsed Doppler echocardiography (PDE) and radioisotope (RI) angiography in 23 patients with hypertrophic cardiomyopathy (HCM), 13 with hypertensive heart disease (HHD) and 24 with ischemic heart disease (IHD). The results were as follows: LV inflow velocity pattern and M-mode echocardiography after the administration of nifedipine (Study-I). The deceleration time (DT) of the diastolic rapid filling wave was shortened after nifedipine in HCM and HHD, but not in IHD. The acceleration time (AT) of the diastolic rapid filling wave and the A/D ratio (amplitude of an atrial contraction wave/amplitude of a diastolic rapid filling wave) were not significantly changed in all groups. Peak negative Vcf was significantly improved after nifedipine in HCM, but unchanged in the other groups. Fractional shortening and peak Vcf did not change in all groups. LV inflow velocity pattern and RI angiography after nifedipine (Study-II). The mean LV rapid filling rate (V1) based on the LV volume curve by multi-gated blood pool scans increased during nifedipine in HCM and HHD, but other diastolic indices, such as the peak filling rate and 1/3 filling fraction, were unchanged. The DT-V1 relationship during nifedipine shifted toward the right and downward in HCM and HHD. In IHD, however, this relationship shifted toward the left and downward in cases with reduced LV function (V1 less than 1.0 EDC/sec), but toward the right and downward in patients whose LV function was maintained (V1 greater than or equal to 1.0 EDC/sec). Nifedipine therapy was associated with an improved LV filling in nearly all cases of HCM and HHD, and in some cases of IHD. PDE and RI angiography are useful for evaluating LV diastolic function during sublingual nifedipine in various heart diseases.

Cardiomegaly↗
PubMed1985

[Genesis of protodiastolic extra heart sound in mitral stenosis: a phono-, apex-, echo- and cineangiographic study].

To clarify the genesis of a protodiastolic extra heart sound (S3') which was occasionally recorded at about the beginning of a diastolic rumble in mitral stenosis (MS), phono-, apex- and echocardiography were performed for 33 patients with MS, and left ventricular (LV) cineangiography was performed for eight of them. The patients were classified as S3'(+) and S3'(-) groups, according to whether they had S3'. Results were as follows: The S3' was synchronous with the rapid filling (RF) wave of the apexcardiogram (ACG). Its amplitude was proportional to the size of the RF wave. The RF wave was significantly sharper in the S3'(+) group as compared with that of the S3'(-) group. The S3' always appeared after onset of dispersion of dots in the velocity pattern of blood flow at the mitral valve orifice according to pulsed Doppler echocardiography. There was no significant difference between the S3'(+) and S3'(-) groups in the region of the mitral valve orifice according to two-dimensional echocardiography, and at the peak rate of change of the LV dimension during diastole as determined by M-mode echocardiography. The peak rate of change of the long-axis dimension of the LV during diastole as determined by cineangiography was significantly greater in the S3'(+) group than in the S3'(-) group. However, there was no significant difference between the two groups regarding the peak rate of change in the short-axis dimension of the LV during diastole as determined by cineangiography. The amplitude of the early diastolic dip of the interventricular septum (IVS) was significantly greater in the S3'(+) group as compared with that of the S3'(-) group. The amplitude of the S3' and the size of the RF wave correlated positively with the amplitude of the early diastolic dip of the IVS in pts with atrial fibrillation. Fractional shortening of the LV ascertained by M-mode echocardiography was significantly greater in the S3'(+) group than in the S3'(-) group. The end-systolic dimension of the LV tended to be less in the former than in the latter group. In conclusion, the S3' in MS was considered to be a third heart sound. Expansion along the long-axis of the LV and its sudden change in early diastole may account for the genesis of the S3', and this expansion may be accentuated by restoring force and active diastolic suction of the LV, and by velocity, direction and spread toward the cardiac apex of the stenotic mitral jet flow.

Adult↗
PubMed1985

[Apical mid-diastolic rumble in hypertrophic cardiomyopathy: a pulsed Doppler echocardiographic study].

To investigate the mechanism of an apical mid-diastolic rumble in hypertrophic cardiomyopathy (HCM), we recorded left ventricular (LV) inflow velocity patterns using pulsed Doppler echocardiography and apexcardiography for 10 HCM patients with rumble and 20 HCM patients without rumble. Controls consist of 17 normal subjects, three patients with complete atrioventricular block and two patients with artificial right ventricular pacemakers. The LV inflow velocity profiles were analyzed in terms of acceleration time (AT) and deceleration time (DT) of the rapid filling wave, and the ratio of peak velocity of the atrial contraction wave to that of the rapid filling wave (A/D ratio). The results were as follows: The apical mid-diastolic murmur in HCM had a crescendo-decrescendo character mainly of medium frequency, and increased in intensity after the inhalation of amyl nitrite. All patients with rumble had asymmetric septal hypertrophy and the five of these had LV outflow obstruction. In six of the 10 patients with rumble, mild mitral regurgitation was detected. In HCM with rumble, the AT tended to be shorter than that of HCM without rumble, but it was significantly longer than the AT of normal subjects. In HCM with rumble, the DT was significantly shorter than that of HCM without rumble, but it was significantly longer than the DT of normal subjects. There was no significant difference in the A/D ratio between the HCM with rumble and the normal subjects, but the A/H ratio of the apexcardiogram was significantly increased in HCM with rumble as compared with those of HCM without rumble and of the normal subjects. The LV dimension was significantly decreased in HCM with rumble as compared with those of HCM without rumble and the normal subjects. Peak negative VCF was significantly decreased in HCM with rumble as compared with that of HCM without rumble. But there was no significant difference in this parameter between HCM with rumble and the normal subjects. In simultaneous recordings of apical mid-diastolic rumble and LV inflow velocity patterns, the rumble appeared to start after the beginning of the diastolic rapid filling wave and to stop before or at the end of the diastolic rapid filling wave. In patients with complete atrioventricular block and with artificial right ventricular pacemakers, the apical mid-diastolic rumble appeared when the P wave was during the rapid filling phase of the left ventricle.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Phase I study of cilostazol. Safety evaluation at increasing single doses in healthy volunteers.

The safety and blood concentrations of the novel synthetic platelet aggregation inhibitor cilostazol (6-[4-(1-cyclohexyl-1H-tetrazol-5-yl)butoxy]-3,4-dihydro-2(1H)-qui nolinone, OPC-13013) were determined in eight healthy volunteers. The drug was orally administered to the subjects once at successive dose increments of 25, 50, 75, 100, 150, 200 and 300 mg/body. Subjective complaints were headache at 75 mg/body in 1 of 4 subjects and dull headache at 75 mg/body in 2 of 4. Each of these symptoms was also seen at higher doses in 1 to 2 of 4 subjects. Clinical laboratory values, blood pressure and heart rate were normal. Blood concentrations of the drug peaked after 3 to 4 h, the levels declining with half-lives of 2.6 to 3.2 h in the alpha-phase and 19.5 to 25.5 h in the beta-phase. The decline was generally prompt. The average peak concentrations were 283.7, 663.4, 540, 823.6, 1110.4, 1129.2 and 1623.9 mg/ml at the above doses, respectively. The effect of food on the blood concentration was also studied; however, the areas under the curve did not indicate significant differences between the fed and fasted subjects.

Adult↗
PubMed1984

Distribution of capillary nonperfusion in early-stage diabetic retinopathy.

Using composite super-wide fluorescein angiography, 152 eyes with nonproliferative diabetic retinopathy were evaluated for capillary nonperfusion. Four basic types of eyes were distinguished according to the location of capillary nonperfusion: peripheral type 4 eyes, midperipheral type 93 eyes, central type 40 eyes and generalized type 15 eyes. The rate of enlargement of nonperfused area was more rapid in peripheral type, midperipheral type, central type and the generalized type in the ascending order. Eyes belonging to midperipheral and central types evolved into other, usually generalized type during the course of observation. There is a positive correlation between the initial site of occurrence of capillary nonperfusion and its progression in nonproliferative diabetic retinopathy. A proper recognition of the typing is claimed to be of prognostic value.

Adolescent↗
PubMed1984

Characteristics of non-sustained ventricular tachycardia detected by ambulatory electrocardiography.

We analyzed non-sustained ventricular tachycardia (VT) observed during ambulatory electrocardiographic (ECG) monitoring in 21 subjects. The rate of VT was 160.7 +/- 2.3 beats/min and showed a moderate positive correlation (r = 0.61, p less than 0.01) with the preceding heart rate (81.8 +/- 1.0 beats/min). The prematurity index of VT was 1.118 +/- 0.015 and showed a moderate inverse correlation with the rate of VT (r = -0.64, p less than 0.01). The vulnerability index was 0.713 +/- 0.009. These indices of prematurity showed a wide distribution and the prematurity of ventricular ectopic beats may not be so significant as previously documented. The incidence of VT was higher in the morning and the evening and was reduced by sleep. The most frequent type of VT (25-/day) was observed only in patients with VT predominantly occurring during the day. We have therefore postulated that these diurnal variations in the frequency of VT may have important therapeutic and prognostic implications. In this study, we used the classification of VT based on the focus, the diurnal variation and the frequency of the tachycardia. Ambulatory ECG monitoring is useful in distinguishing the various types of VT and it is important to separate the various types of VT into several subgroups in order to classify grade the severity of VT.

Adult↗
PubMed1984

[Noninvasive studies of dynamic left ventricular outflow obstruction in patients with sigmoid septum].

In order to evaluate the clinical significance of the markedly protruding interventricular septum into the left ventricular (LV) cavity (sigmoid septum), we performed non-invasive studies including amyl nitrite (AN) inhalation in 21 patients (pts) with two-dimensional echocardiographic (2DE) documentations. LV outflow tract (LVOT) obstruction was determined by the presence at least three of the following findings at rest or during AN inhalation: 1) a loud apical ejection systolic murmur (ESM), 2) a midsystolic dip in the carotid pulse, 3) systolic anterior motion (SAM) of the mitral valve (MV) or chordae tendineae, and 4) systolic semiclosure of the aortic valve (AV). The 21 pts were subdivided into six pts (group I) with resting (two pts) or provocative (four) obstruction, and 15 pts (group II) without obstruction. Their ages ranged from 40 to 85 years with an average of 65. No pt had evidence of hypertrophic cardiomyopathy. Results were as follows: In five pts of group I a long ESM with a mid-systolic peak was recorded near the apex. After AN inhalation, this murmur was markedly intensified. On the contrary, all pts of group II had a short and early systolic murmur, which was not markedly intensified by AN. In contrast to group II, group I pts had a significantly smaller LV end-diastolic dimension, a smaller LVOT dimension, higher percent thickening of the LV posterior wall, higher fractional shortening and decreased aorto septal angle (the angle between the anterior aortic wall and the interventricular septum by 2DE). On 2DE, each pt of group I showed significant narrowing between the protruded septum and the hypercontractile LV posterior wall with the papillary muscle. Anteriorly shifted chordae tendineae noted as the SAM on the M-mode echocardiogram might also play an important role on the genesis of obstruction. The signs of LVOT obstruction at rest disappeared following oral administration of propranolol in two pts of group I. These observations suggested that LVOT obstruction might occur in some pts with sigmoid septum and the hypercontractile state, and that a systolic murmur observed in this condition should be differentiated from a functional murmur in the aged or a systolic murmur in hypertrophic obstructive cardiomyopathy.

Adult↗
PubMed1984

[Mechanism of an early diastolic posterior motion of the interventricular septum in patients with mitral stenosis: with special reference to left ventricular inflow velocity pattern].

The mechanism of an early diastolic posterior motion of the interventricular septum (IVS) was investigated by means of M-mode, two-dimensional and pulsed Doppler echocardiographies in 53 patients with pure mitral stenosis (MS). Velocity patterns of the blood flow at the inflow tract of the left ventricle (LVIT) were classified into three types as previously reported (cf. Fig.3). The results obtained were as follows: The mitral valve orifice area (MVA) was significantly smaller in patients with type III of the LVIT flow velocity pattern than in patients with type I (p less than 0.001). An amplitude ("a") of the posterior IVS motion in systole (P1) was significantly diminished in type III (4.2 +/- 1.1 mm) than in type I (6.6 +/- 1.5 mm) (p less than 0.001). An amplitude ("b") of the posterior IVS motion in early diastole (P3) showed a significant increase in type III (7.5 +/- 1.2 mm) than in type I (5.2 +/- 1.5 mm) (p less than 0.001). Difference of the amplitude between P1 and P3 ("a-b") was significantly greater in type III (-3.4 +/- 1.1 mm) than in type I (1.4 +/- 0.9 mm) (p less than 0.0001). MVA was correlated statistically with "a" (r = 0.58, p less than 0.001), "b" (r = -0.38, p less than 0.01) and "a-b" (r = 0.80, p less than 0.0001). Deformity of the left ventricular cavity due to the flattened IVS in early diastole was observed in severe MS with an augmented septal P3 dip. A case of severe MS with type III velocity pattern and an augmented P3 dip showed type II velocity pattern and a decreased P3 dip after the attack of acute myocardial infarction. These findings suggested a close relationship between type III of the LVIT flow velocity pattern and the prominent septal P3 dip. The importance of diastolic suction of the left ventricle in producing an early diastolic posterior motion of IVS (P3) was discussed.

Biomechanical Phenomena↗
PubMed1984

[Left ventricular function in patients with right ventricular overload evaluated by exercise echocardiography: comparison of pulmonary hypertension and atrial septal defects].

To evaluate left ventricular function in patients (pts) with right ventricular overload, exercise echocardiographic studies using a bicycle ergometer were performed for seven pts with pulmonary hypertension (PH), two with cor pulmonale (CP) and 16 with atrial septal defects (ASD), and the results were compared with those of 10 (control I) and 27 (control II) normal persons. These subjects were categorized in two study groups; study I consisting of PH, CP and control group I with an exercise workload of 25 watts for 3 min; and study II consisting of ASD and control group II with an exercise workload of 50 watts for 3 min. The results were as follows: M-mode echocardiography revealed that: During exercise, the stroke volume (SV) was increased with a significant decrease of left ventricular end-systolic dimension (LVDs), but without a change in left ventricular end-diastolic dimension (LVDd) in control groups I and II, with a marked increase of LVDd and a slight decrease of LVDs in the ASD group. By contrast, the SV in the PH group tended to decrease during exercise with a slight decrease of LVDd, but without a significant change in LVDs. Right ventricular dimension (RVD) was significantly increased during exercise in the PH group, but was decreased in the ASD group. In control groups I and II, RVD did not change during exercise. In ASD, and control groups I and II, the peak velocity of circumferential fiber shortening (Vcf) was increased during exercise, and the peak negative Vcf was significantly decreased. However, these parameters exhibited impaired responses during exercise in the PH group. Abnormal interventricular septal (IVS) motion at rest tended to become normal during exercise in 12 of 16 pts with ASD. In all pts with PH, however, IVS motion did not change substantially during exercise. There were similar parameter responses between the PH and CP groups. Two-dimensional echocardiography showed that: The left ventricular short-axis view demonstrated a diastolic left ventricular configuration which changed from oblique to relatively circular orientation during exercise in the ASD group. In four of five pts with PH, the diastolic configuration of the left ventricle was oblique because of a loss of the normal curvature of the IVS at rest and during exercise. The diastolic left ventricular configuration improved during exercise in only one pt with PH, with slightly elevated pulmonary arterial systolic pressure as in the ASD group.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1984

[Left ventricular diastolic filling patterns in hypertrophic cardiomyopathy and myocardial infarction: studies by pulsed doppler echocardiography and multi-gated blood pool scans].

Relationship between various parameters of the left ventricular inflow velocity patterns by pulsed Doppler echocardiography and the early diastolic mean filling rate (V1) by multi-gated blood pool scans was evaluated. The materials consist of 26 patients with hypertrophic cardiomyopathy (HCM), 24 with old myocardial infarction (MI), seven with hypertensive heart disease (HHD), seven with dilated cardiomyopathy (DCM), seven with ischemic heart disease (IHD), and 16 normal subjects (N). The results were as follows: 1. Acceleration time (AT) and deceleration time (DT) were significantly prolonged in HCM (120 +/- 20 msec, 147 +/- 23 msec), MI (102 +/- 17 msec, 124 +/- 21 msec), HHD (105 +/- 11 msec, 141 +/- 17 msec) and IHD (111 +/- 16 msec, 122 +/- 20 msec) compared with those of normals (89 +/- 20 msec, 106 +/- 18 msec). 2. V1 was significantly decreased in HCM (1.14 +/- 0.28 sec-1), MI (0.68 +/- 0.24 sec-1), HHD (0.73 +/- 0.12 sec-1), DCM (0.67 +/- 0.30 sec-1) and IHD (1.03 +/- 0.29 sec-1) compared with that of normals (1.48 +/- 0.28 sec-1). 3. There were significant negative correlations between V1 and AT or DT in HCM, IHD with slightly impaired diastolic filling and normals. However, there were significant positive correlations between V1 and AT or DT in MI and DCM. These findings suggested that left ventricular diastolic filling is impaired in both HCM and MI, and that DT-V1 relationship is useful for differentiating HCM characterized by the "chamber stiffness" from MI characterized by the "myocardial stiffness".

Adolescent↗
PubMed1984

[Phono- and echocardiographic studies of the genesis of mitral valve prolapse in patients with funnel chest].

Two-dimensional echocardiograms (2-DE) and phonocardiograms (PCG) were used to clarify the genesis of mitral valve prolapse (MVP) and mitral regurgitation (MR) in 44 patients with funnel chest. These patients were categorized in three groups on the basis of the fronto-sagittal index (FSI) as determined from chest radiographs; 17 as mild, 15 as moderate and 12 as severe funnel chest. Their ages ranged from 5 to 65 years and averaged 24 years. MVP was diagnosed using the long-axis view of the 2-DE, and MR was diagnosed phonocardiographically including provocative test using angiotensin II. The results were as follows: In 44 patients with funnel chest, 20 (45%) had MVP and 15 (34%) had MR, respectively. The incidence of MVP increased directly in proportion to the severity of index, but the incidence of MR did not. In the short-axis view of the left ventricle at the level of the papillary muscles, there was more marked flattening of the interventricular septum than of the left ventricular posterior wall, resulting in deformity of the left ventricular geometry. A distortion index (DI) was used to quantify the degree of distortion of left ventricular shape, calculated as follows: DI = (R-r)/r, where R and r were radii of the curvatures of the interventricular septum and the left ventricular posterior wall, respectively. The DI in end-diastole (DId) and end-systole (DIs) increased in proportion to the severity of funnel chest. Patients were subdivided into four groups on the basis of DId. Incidence of MVP increased in proportion to the degree of distortion of the left ventricular shape. There was, however, no significant difference in the incidence of MR among the four groups. Patients were subdivided; one group of 13 under 14 years of age; another, 31 over 15 years old. The incidence was much higher in the latter than the former, but the incidence of MVP increased in proportion to the severity of funnel chest in both groups. MR was complicated by MR in nearly all cases in the latter group, but none had MR in the former. The DI of patients, whose FSI improved with surgery, apparently improved in addition to the disappearance and/or improvement of their MVP and MR. However, patients whose FSI did not improve with surgery showed little change in DI and persistence of MVP and/or MR.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗