Biomedical subjects

T Shishido

Publications and source records attributed to T Shishido.

At least 109 records · Page 6Linked to original sources

PubMed1997

Functional myocardial perfusion abnormality induced by left ventricular asynchronous contraction: experimental study using myocardial contrast echocardiography.

OBJECTIVES: The aim of this study was to clarify how myocardial perfusion is impaired by asynchronous contraction. BACKGROUND: False septal hypoperfusion is noted in some patients with left bundle branch block. METHODS: Eight dogs were examined with epicardial pacing at the left ventricular posterior wall, the right ventricular anterior wall and, as a control, the right atrial appendage. The pacing rate was 80, 110 and 150 beats/min (bpm). Myocardial perfusion was assessed by contrast echocardiography. RESULTS: Left ventricular pacing at 80 and 110 bpm did not change systolic wall thickening or contrast intensity at the pacing site, although an early excitation notch was noted at the pacing site. However, at 150 bpm, systolic thickening was impaired (23.3 +/- 4.2% vs. 37.0 +/- 2.6% during atrial pacing, p < 0.05), and the peak intensity ratio of the pacing site to the ventricular septum was significantly decreased (24.1 +/- 5.7% vs. 37.0 +/- 2.8% at a pacing rate of 80 bpm, p < 0.01). The peak intensity ratio correlated with systolic wall thickening at the pacing site (y = 0.413 x -0.028, r = 0.81, p < 0.0001). However, right ventricular pacing did not change either systolic thickening or the peak intensity ratio at any pacing rate, although an early excitation notch was noted on the ventricular septum. CONCLUSIONS: Wall motion abnormalities after early excitation vary depending on the pacing mode. When tachycardia induces regional wall motion abnormalities, the ventricular wall of the pacing site is functionally hypoperfused.

Animals↗

PubMed1997

Perirenal pseudolymphoma: a case report.

A right nephrectomy was performed on a 51 year-old female with a tumor surrounding the right kidney since the possibility of malignant lymphoma could not be excluded based on radiography or a needle biopsy. An immunohistological examination of the surgically-resected specimen confirmed a diagnosis of pseudolymphoma. A pseudolymphoma involving the urinary tract is rare, and this is only the second reported case of pseudolymphoma in the perirenal space.

Female↗

PubMed1997

Dynamic vagosympathetic interaction augments heart rate response irrespective of stimulation patterns.

We previously demonstrated that tonic stimulation of either the sympathetic or the vagal nervous system augmented the dynamic heart rate response to the other of the two systems. We characterized the phenomenon as bidirectional augmentation of heart rate regulation. The question remained unanswered, however, as to whether such augmentation could occur under simultaneous dynamic stimulation of the two systems. The transfer characteristics from nerve stimulation to heart rate were well described by linear systems analysis, although no attention was paid to the aphasic nature of the stimuli in relation to each R-R interval. When we stimulated the two nerves with statistically independent Gaussian white noises, gain of the transfer function increased by 63.2 +/- 47.4% relative to individual stimulation (P < 0.05). When we stimulated the two nerves with mutually reciprocal Gaussian white noises, gain of the transfer function increased by 54.9 +/- 49.1% (P < 0.05). Thus simultaneous dynamic stimulation of the sympathetic and vagal systems bidirectionally augmented heart rate regulation irrespective of the pattern of the stimulation signals.

Animals↗

PubMed1997

Inhibition of NO synthesis minimally affects the dynamic baroreflex regulation of sympathetic nerve activity.

The purpose of this investigation was to examine the role of nitric oxide (NO) in the dynamic baroreflex regulation of cardiac sympathetic nerve activity. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses before and after the intravenous administration of NG-monomethyl-L-arginine. We characterized the dynamic properties relating carotid sinus pressure input to sympathetic nerve activity by means of a transfer function analysis. NG-monomethyl-L-arginine decreased the corner frequency of the transfer function (0.100 +/- 0.054 vs. 0.074 +/- 0.035 Hz; P < 0.05), whereas other parameters such as the steady-state gain and transmission lag time remained unchanged. Although cursory examination of these findings would suggest a possible contribution of NO in the dynamic baroreflex regulation of sympathetic nerve activity, quantitative assessment of the transfer function reveals only a minimal effect on the baroreflex regulation of arterial pressure, particularly under closed-loop conditions. We conclude that NO noticeably affects the dynamic baroreflex regulation of sympathetic nerve activity. However, it may not significantly affect arterial pressure regulation through central modulation of the carotid sinus baroreflex.

Animals↗

PubMed1997

Inhibition of NO synthesis does not potentiate dynamic cardiovascular response to sympathetic nerve activity.

We examined whether the inhibition of nitric oxide (NO) synthesis potentiates the dynamic sympathetic regulation of the cardiovascular system through the baroreflex. In anesthetized rabbits, we imposed random pressure perturbations on the isolated carotid sinuses to evoke random changes in sympathetic nerve activity (SNA). We estimated the transfer functions from SNA to both aortic pressure (AoP) and heart rate (HR). The inhibition of NO synthesis by NG-monomethyl-L-arginine (L-NMMA, 40 mg/ kg) altered neither the transfer function from SNA to AoP nor that from SNA to HR. In contrast, sodium nitroprusside (3-6 micrograms.kg-1.min-1) significantly decreased the steady-state gain (40.3 +/- 11.7% of the control, P < 0.05) of the transfer function from SNA to AoP without affecting the HR responses. We conclude that the basal release of NO may have a role in the tonic blood pressure regulation, whereas it may not be involved in the dynamic sympathetic regulation of AoP or HR through the baroreflex.

Animals↗

PubMed1997

Closed-loop identification of carotid sinus baroreflex open-loop transfer characteristics in rabbits.

In the circulatory system, a change in blood pressure operates through the baroreflex to alter sympathetic efferent nerve activity, which in turn affects blood pressure. Existence of this closed feedback loop makes it difficult to identify the baroreflex open-loop transfer characteristics by means of conventional frequency domain approaches. Although several investigators have demonstrated the advantages of the time domain approach using parametric models such as the autoregressive moving average model, specification of the model structure critically affects their results. Thus we investigated the applicability of a nonparametric closed-loop identification technique to the carotid sinus baroreflex system by using an exogenous perturbation according to a binary white-noise sequence. To validate the identification method, we compared the transfer functions estimated by the closed-loop identification with those estimated by open-loop identification. The transfer functions determined by the two identification methods did not differ statistically in their fitted parameters. We conclude that exogenous perturbation to the baroreflex system enables us to estimate the open-loop baroreflex transfer characteristics under closed-loop conditions.

Animals↗

PubMed1997

Vagal stimulation decreases left ventricular contractility mainly through negative chronotropic effect.

Although an increase in vagal tone is known to slow heart rate (HR), whether it also depresses left ventricular contractility through mechanisms independent of the bradycardic effect remains unknown. The chief aim of this investigation, therefore, was the separation of the observed vagally mediated depression of ventricular contractility into direct and indirect vagal effects, the latter resulting via negative chronotropism. In 12 anesthetized, sympathectomized open-chest rabbits, we measured left ventricular contractility through determination of the end-systolic elastance (Ees). We found that tonic vagal stimulation administered at 0, 5, and 10 Hz decreased both HR (226.9 +/- 39.7, 201.9 +/- 25.7, and 171.3 +/- 18.5 beats/min, respectively; P = 0.0003) and Ees (109.5 +/- 25.7, 85.1 +/- 34.1, and 71.9 +/- 33.1 mmHg/ml, respectively; P = 5 x 10(-6)) in a frequency-dependent fashion. However, we observed that as long as HR was kept constant through fixed-rate atrial pacing, vagal stimulation resulted in little or no change in Ees. Thus we conclude that the negative inotropic effect of vagal stimulation is attributable primarily to its negative chronotropic effect when sympathetic tone is minimal.

Animals↗

PubMed1997

Severe diastolic dysfunction with preserved energy conversion efficiency after countershock.

The left ventricular (LV) mechanical performance and the LV myocardial oxygen consumption (VO2)-to-pressure-volume area (PVA; LV total mechanical energy index) relationship were measured in isovolumic contraction of isolated blood-perfused dog hearts before and after direct current (DC) countershocks. At a constant LV volume, DC shocks increased LV end-diastolic pressure progressively and strikingly with the progression of myocardial edema and a marked prolongation of the time constant of LV pressure decay. In contrast, DC shocks changed neither the slope of the LV end-systolic pressure-volume relationship nor the contractile efficiency (the slope of the Vo2-PVA relationship). The oxygen cost of contractility (the slope of the relationship between PVA-independent VO2 and LV contractility) increased 27% after DC shocks. However, the magnitude of this change was considerably smaller than that previously reported in postischemic stunned myocardium (123%), suggesting that the adverse effect of DC shocks on the energy cost of excitation-contraction coupling is relatively minor. Thus, despite the severe diastolic dysfunction, DC shocks do not substantially impair either the efficiency of cross-bridge cycling or calcium cycling. Myocardial interstitial edema is more likely a potential mechanism of diastolic dysfunction after DC shocks.

Animals↗

PubMed1997

Interstitial norepinephrine level by cardiac microdialysis correlates with ventricular contractility.

Although a cardiac microdialysis technique has made it possible to estimate myocardial interstitial norepinephrine (NE) levels, whether such levels reflect the local NE concentration that would regulate ventricular contractility remains unknown. If such levels indicate locally regulating NE concentration, then ventricular contractility should be a unique function of the interstitial NE level regardless of how the latter is altered. To examine this hypothesis, we altered the interstitial NE level endogenously by stimulating the cardiac sympathetic nerves at 1 and 2 Hz while monitoring ventricular contractility. We also altered the interstitial NE level exogenously by means of intravenous NE infusions at 10 and 40 micrograms.kg-1.h-1. The basal NE levels did not differ between the stimulation and the infusion experiments (42.9 +/- 11.2 vs. 40.1 +/- 6.2 pg/ml, means +/- SE). The slopes of regression lines relating ventricular contractility and interstitial NE level were also not different between the two experiments [1.13 +/- 0.20 vs. 1.17 +/- 0.20%/(pg/ml), means +/- SE]. We conclude that the interstitial NE level estimated by cardiac microdialysis reflects the local NE concentration regulating ventricular contractility.

Animals↗

PubMed1997

Infected subdural effusion associated with resolving subdural hematoma--case report.

A 70-year-old male presented with rapid neurological deterioration and fever 3 months after suffering a closed head trauma. He underwent craniotomy for possible subdural empyema based on computed tomography and clinical findings. Dural incision revealed an outer membrane typical of chronic subdural hematoma which covered a clear, yellowish fluid containing Campylobacter fetus. Histological examination confirmed the capsule of the hematoma, with a necrotic focus infiltrated by neutrophils. Administration of intravenous imipenem and topical tobramycin and cefalothin achieved total resolution of his neurological deficits. Development of the infected subdural effusion was probably secondary to bacterial infection in the pre-existing chronic subdural hematoma in the resolving stage. The presence of the hematoma capsule always carries the risk of development of an infectious focus.

Aged↗

PubMed1997

[A case of vesical endometriosis associated with Wunderlich syndrome].

A case of vesical endometriosis associated with unilateral renal agenesis and uterus didelphys (Wunderlich syndrome) is reported. A 20-year-old unmarried woman visited the gynecologic department with dysmenorrhea. She was referred to us because a bladder mass was detected on abdominal ultrasonography. She had no episode of gross hematuria. Cystoscopy revealed a finger tip-sized cystic mass dark red to dark blue in color. Computerized tomography and magnetic resonance imaging demonstrated right renal agenesis and uterus didelphys. The mass was located at the ureterovesical pouch and protruded into the bladder. Partial cystectomy, right hysterectomy and right salpingo-oophorectomy were performed. Histopathological diagnosis was endometriosis. The patient was treated with 400 mg danazol for 6 months has had no recurrence and regular menstruation.

Adult↗

PubMed1997

Estimation of arterial mechanical properties from aortic and tonometric arterial pressure waveforms.

Although arterial mechanical properties have been evaluated using arterial input impedance, the relative difficulty in accurate flow measurement made the value of impedance somewhat limited. To develop an alternative method to evaluate arterial mechanical properties, we analyzed the aortic pressure (AoP)-radial arterial pressure (RAP) relationship because of relative ease in obtaining peripheral pressure waveform by tonometry. In 8 patients we simultaneously recorded aortic root and radial arterial pressure waveforms. We calculated the transfer function from AoP to RAP. We then fitted the transfer function to a model of a lossless uniform elastic tube terminated with a modified Windkessel model. The fact that the model transfer function predicted AoP from RAP waveform with considerable accuracy indicated that the model represented the arterial mechanical properties well. We conclude that we can estimate the arterial mechanical properties by the pressure-pressure transfer function analysis.

Adolescent↗

PubMed1996

Differential production of interleukin-6 and its close relation to liver metastasis in clones from murine P815 mastocytoma.

Interleukin-6 (IL-6)-producing abilities of plastic-adherent and plastic-non-adherent P815 clones were investigated in connection with the liver metastasis. Most adherent clones produced IL-6 at high level (over 10 ng/10(5) cells per 48 h), and they coincided with highly liver-metastatic clones. The remaining adherent and all the non-adherent clones tested produced IL-6 at low level (under 1.5 ng/10(5) cells), and they coincided with the low or non-liver-metastatic clones. The IL-6 production was greatly enhanced by IL-1 alpha, but not by IL-6, tumor necrosis factor-alpha or interferon-gamma.

Animals↗

PubMed1996

Inhibition of liver metastasis of human gastric carcinoma by angiogenesis inhibitor TNP-470.

The anti-tumor and anti-metastatic effects of TNP-470, an angiogenesis inhibitor, and mitomycin C (MMC), a representative anti-neoplastic agent, were investigated using our established liver-metastasizing gastric carcinoma line, AZ-H5c. AZ-H5c was injected into the spleen of nude mice which had been randomly divided into 4 groups; a control group given saline solution, a group receiving 15 mg/kg TNP-470, a group receiving 30 mg/kg TNP-470 and a group receiving 2 mg/kg MMC. TNP-470 was given s.c. on alternate days for 5 weeks from day 10 after intrasplenic injection, and MMC was administered intraperitoneally (i.p.) once a week from day 10 after intrasplenic injection. In the control group, liver metastasis developed in 13 of 16 mice (81%). Liver metastasis developed in 6 of 11 mice (55%) receiving MMC. In contrast, liver metastasis developed in 4 of 8 mice (50%) receiving 15 mg/kg TNP-470, and in 0 of 14 mice (0%) receiving 30 mg/kg TNP-470. However, TNP-470 had no effect on the tumor growth. These results indicate that the angiogenesis inhibitor TNP-470 has a strong inhibitory activity against in vivo liver metastasis of human gastric carcinoma.

Animals↗

PubMed1996

Bidirectional augmentation of heart rate regulation by autonomic nervous system in rabbits.

Although the characteristics of the static interaction between the sympathetic and parasympathetic nervous systems in regulating heart rate (HR) have been well established, how the dynamic interaction modulates the HR response remains unknown. We therefore investigated dynamic interaction by estimating the transfer function from nerve stimulation to HR using a band-limited Gaussian white-noise technique. The transfer function relating dynamic sympathetic stimulation to HR had characteristics of a second-order low-pass filter. Simultaneous tonic vagal stimulation at 5 and 10 Hz increased gain of the transfer function by 55.0 +/- 40.1 and 80.7 +/- 50.5%, respectively (P < 0.05). The transfer function from dynamic vagal stimulation to HR had characteristics of a first-order low-pass filter. Simultaneous tonic sympathetic stimulation at 5 and 10 Hz increased the gain by 18.2 +/- 17.9 and 24.1 +/- 18.0%, respectively (P < 0.05). Thus interaction augmented dynamic gain bidirectionally, even though it affected mean HR antagonistically. By virtue of this interaction, the autonomic nervous system appears to extend its dynamic range of operation.

Animals↗

PubMed1996

Neural arc of baroreflex optimizes dynamic pressure regulation in achieving both stability and quickness.

The baroreflex loop consists of a fast neural arc and a slow mechanical arc. We hypothesized that the neural baroreflex arc compensates the slow mechanical response and thus improves the quality of blood pressure regulation. We estimated the open-loop transfer characteristics of the neural baroreflex arc (HP), i.e., from carotid sinus pressure to sympathetic nerve activity (SNA), and that of the effective peripheral baroreflex arc (Hp), i.e., from SNA to arterial pressure, in anesthetized rabbits. The gain of Hn was constant below 0.12 +/- 0.057 Hz and increased with a slope of 6.1 +/- 0.06 dB/octave above its frequency up to 1 Hz. In contrast, the gain of Hp was constant below 0.071 +/- 0.03 Hz and decreased with a slope of -11.0 +/- 1.48 dB/octave above the frequency. These data indicate that Hn accelerates slow peripheral responses in the frequency range of 0.1-1 Hz. Although too much acceleration in the high-frequency range could result in instability of the system, numerical analysis of the closed-loop baroreflex response indicated that the neural arc optimized arterial pressure regulation in achieving both stability and quickness.

Animals↗

PubMed1995

Abrupt augmentation of ST segment elevation associated with successful reperfusion: a sign of diminished myocardial salvage.

To investigate the significance of abrupt augmentation of ST segment elevation immediately after reperfusion, 36 patients with an initial acute anterior myocardial infarction successfully treated with thrombolysis were studied. Immediately after reperfusion was performed, 17 (47%) patients showed abrupt augmentation of ST segment elevation of anterior area (E group), and 19 (53%) patients did not (N group). The time to reperfusion was not significantly different between the two groups. In the E group the peak level of creatine kinase MB isozyme was higher (p < 0.05) than in the N group. The left ventricular ejection fraction (EF) did not increase in the E group from acute to chronic phase. However, in the N group EF increased significantly. The difference in EF in the chronic phase was significant between the two groups (p < 0.05). The infarcted regional wall motion (RWM) did not increase in the E group, whereas in the N group it increased markedly (p < 0.05). In addition, the infarcted RWM in the chronic phase was worse in the E group than in the N group (p < 0.05). Abrupt augmentation of ST segment elevation associated with successful reperfusion appears to reflect diminished myocardial salvage.

Aged↗

PubMed1995

A novel translocation involving chromosomes 2, 9, 14, and 22 in chronic myeloid leukemia.

A 46-year-old man with chronic myelogenous leukemia was found to have a new complex translocation. In chronic phase, all of the bone marrow cells had a rearrangement of a t(2;9;14;22) (p21;q34;q32;q11). Southern blot analysis of leukocyte DNA revealed rearrangement of the breakpoint cluster region (bcr) within the 5.8-Kb bcr. The patient eventually died in blast crisis 28 months later. The cytogenetic findings of bone marrow cells showed a 46,XY,t(2;9;14;22)(p21;q34;q32;q11),add(1p),del(3q) karyotype in blast crisis.

Chromosome Banding↗