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Biomedical subjects

R Takaki

Publications and source records attributed to R Takaki.

At least 19 recordsLinked to original sources
PubMed2001

[Evaluation of time dependency of the acetazolamide effect on cerebral hemodynamics as measured by 99mTc-ECD single-photon emission computed tomography].

PURPOSE: Kuwabara et al. have examined the cerebral artery dilation with acetazolamide (ACZ) challenge test using PET. And, they reported that ACZ reaction came out time dependently. We have developed a unique SPECT's method using Technetium-99m ethyl cysteinate dimer (99mTc-ECD) to verify the results obtained by Kuwabara et al. METHOD: 1000 MBq of 99mTc-ECD was exactly divided into three syringes. Each of which was intravenous infused (i.v.) at rest, 7.5, and 20 minutes after ACZ administration. Data collection was started using dynamic SPECT immediately after 99mTc-ECD i.v. at rest. Using necessary data only, SPECT images representing each of the three 99mTc-ECD i.v. was reconstructed. SPECT counts were obtained by the ROI method from each images to calculate relative CBF from rest to 7.5 and 20 minutes after ACZ administration. RESULT: The 18 hemispheres of nine patients in the negative control group in whom ACZ was not loaded. CBF was stable during the three evaluation. The measurement error our method was estimated as small. The 18 hemispheres of nine patients in the positive control group who has normal vasodilatory reserve, CBF was increased by 26.2 +/- 8.1% at 7.5 minutes and 29.3 +/- 13.1% at 20 minutes after ACZ administration. Seven patients with and chronic stage unilateral internal carotid artery severe stenosis and/or occlusion were evaluated as the test group. Case of unaffected side, CBF was increased by 17.6 +/- 6.9% at 7.5 minutes and 24.8 +/- 11.3% 20 minutes after ACZ administration. And, increase rate of CBF in the affected side was 2.8 +/- 1.6% at 7.5 minutes and 17.3 +/- 5.0% at 20 minutes after ACZ administration. In the affected side, timing of the maximum CBF increase caused by ACZ was remarkably delayed. CONCLUSION: Our method based on 99mTc-ECD SPECT also revealed delayed cerebral artery dilation in the affected side. It was suggested that ACZ reaction came out time dependently, as reported by Kuwabara et al.

Acetazolamide↗
PubMed2000

A three-dimensional model of the human pulmonary acinus.

A three-dimensional (3-D) model of the human pulmonary acinus, a gas exchange unit, is constructed with a labyrinthine algorithm generating branching ducts that fill a given space completely. Branching down to the third respiratory bronchioles is generated with the proposed algorithm. A subacinus, a region supplied by the last respiratory bronchiole, is approximated to be a set of cubic cells with a side dimension of 0.5 mm. The labyrinthine algorithm is used to determine a pathway through all cells only once, except at branching points with the smallest path lengths. In choosing each step of a pathway, random variables are used. Resulting labyrinths have equal mean path lengths and equal surface areas of inner walls. An alveolus can be generated by attaching alveolar septa, 0.25 mm long and 0.1 mm wide, to the inner walls. Total alveolar surface area and numbers of alveolar ducts, alveolar sacs, and alveoli in our 3-D acinar model are in good accordance with those reported in the literature.

Algorithms↗
PubMed1999

A three-dimensional model of the human airway tree.

A three-dimensional (3D) model of the human airway tree is proposed using a deterministic algorithm that can generate a branching duct system in an organ. The algorithm is based on two principles: 1) the amount of fluid delivery through a branch is proportional to the volume of the region it supplies; and 2) the terminal branches are arranged homogeneously within the organ. These principles define the basic process of branching: generation of the dimensions and directionality of two daughter branches is governed by the properties of the parent branch and the region the parent supplies. The algorithm is composed of nine basic rules and four complementary rules. When the contour of an organ and the position of the trunk are specified, branches are successively generated by the algorithm. Applied to the human lung, the algorithm generates an airway tree that consists of approximately 54,000 branches. Its morphometric characteristics are in good agreement with those reported in the literature. The algorithm and the 3D airway model are useful for studying the structure-function relationship in the lung.

Algorithms↗
PubMed1999

[Simulations of bronchial displacement owing to solitary pulmonary nodules].

On the basis of elasticity dynamics, we constructed mathematical models of bronchial displacements caused by well-differentiated adenocarcinoma and inflammatory pulmonary nodules. We simulated bronchial displacement with a three-dimensional model of the airway tree that we constructed. One-hundred sixty simulations of cancerous and inflammatory displacements were performed, where 20 nodule centers were placed in the right upper lobe in the three-dimensional bronchial model and four different sizes (30 mm, 37.5 mm, 45 mm, and 60 mm) of original lesions were assumed which contracted to nodules of 15 mm in diameter. The three-dimensional simulation images were highly similar to the cancerous or inflammatory nodules in the clinical images. Angles and distances in simulated structures between respective branches and the nodule center were measured. The mean value of angles of branches whose distance from the nodule center was within a range of 6 mm to 12 mm was in good accordance with the value obtained theoretically. Discrimination between cancer and inflammation was successfully carried out by examining the distance dependency of the angles. We concluded that the measurement of angles of linear structures surrounding a pulmonary nodule would be useful for its differential diagnosis.

Diagnosis, Differential↗
PubMed1997

Primary adenocarcinoma in the urethrorectal fistula.

A 60-year-old Japanese man was hospitalized because of urinary leakage from the anus on October 3, 1994. Retrograde urethrography detected a fistula between the bulbous urethra and the rectum. Urethrocystoscopy revealed a tumor on the urethrorectal fistula. Tumor biopsy showed a well differentiated adenocarcinoma. Cystourethrectomy with fistulectomy, and ileal conduit urinary diversion were performed. Pathological examination revealed primary adenocarcinoma in the fistula with invasion to the prostatic urethra and bladder wall. The patient showed no evidence of a recurrence as of August, 1996.

Adenocarcinoma↗
PubMed1996

Malignant mesenchymoma arising from the prostate in Gardner's syndrome.

The first case of a primary malignant mesenchymoma arising from the prostate in Gardner's syndrome is reported. The neoplasm occurred in a 40-year-old man with a chief complaint of urinary retention. Biopsy findings were primary malignant mesenchymoma. Total cystectomy and lymphadenectomy were performed, but the patient died due to multiple metastases within 6 months. He had undergone a colectomy for polyposis coli 17 years earlier and had mandibular osteomas. This was the first case of malignant mesenchymoma arising from the prostate in Gardner's syndrome.

Abdominal Neoplasms↗
PubMed1995

The endocrine pancreas of spontaneously diabetic db/db mice: microangiopathy as revealed by transmission electron microscopy.

Abnormalities in ultrastructures of islet capillaries were detected in db/db mice, with the visual inspection and morphometry of electron micrographs. The observed changes are: (1) capillary scarcity; (2) increase in the mean and diversity of capillary size; (3) pericapillary edema and fibrosis; (4) hypertrophy of the pericyte and abundance therein of actin-like microfilaments; and (5) luminal irregularity. Changes (2), (3) and (4) are conceived to indicate hyperperfusion, capillary hypertension and secondary vascular response. In particular, such pericyte changes were found to be shared by other organs whose capillaries are susceptible to diabetic complications.

Animals↗
PubMed1994

Reinnervation of allografted pancreatic islets in the rat liver.

Rat pancreatic islets were allografted in the liver and were studied morphologically in order to evaluate possible reinnervation. Islets isolated from rat pancreas were allotransplanted in the liver of streptozocin-induced diabetic rats via the portal vein. Electron microscopy revealed nerve endings with synaptic vesicles in the transplanted islets 100 days after transplantation, whereas axons in the islets appeared to degenerate several hours after isolation and prior to transplantation. These findings suggest that the nerve endings observed in the transplanted islets regenerate from nerves that innervate the recipient's liver. The tissue specimens were also investigated immunohistochemically using antityrosine hydroxylase antibody, and histochemically by the modified Karnovsky and Roots' method for visualizing acetylcholinesterase. Some nerve endings in the transplanted islets reacted positively to antityrosine hydroxylase antibody. Acetylcholinesterase was visualized in other nerves. These results indicate that norepinephrine- and acetylcholinesterase-containing nerves may reinnervate the transplanted islets.

Acetylcholinesterase↗
PubMed1993

Chemopreventive effects of tamoxifen in ethyl methanesulphonate-induced rat mammary carcinogenesis.

Ethyl methanesulphonate (EMS), an alkylating agent and a potent mutagen, has been shown to be an effective carcinogen for the induction of mammary carcinoma in female Wistar King A rats. We therefore utilized this new system to assess the effects of tamoxifen (TAM) on mammary carcinogenesis. In Group A rats, given EMS orally for a period of 12 weeks, mammary carcinomas were first detected at the 13th week and were found in all surviving rats at the 20th week. The concomitant administration of TAM for 4 weeks, in Group B rats, retarded the development of the tumors significantly. There was a significant reduction in the incidence of estrogen receptor (ER)-positive tumors in the rats previously exposed to TAM; 100% in Group A versus 50% in Group B. Neither the progesterone receptor (PgR) nor androgen receptor (AR) status of the tumors were significantly different between these two groups. The inhibitory effects of TAM on tumor induction was also observed when TAM treatment started after EMS administration, though the intensity was smaller than that in Group B. These findings suggest the preventive action of TAM on EMS-induced mammary carcinogenesis, and indicate that this tumor system may provide a feasible model for research on chemoprevention and hormone therapy using an antiestrogen for human mammary carcinoma.

Animals↗
PubMed1993

Suppression of ventricular premature contractions continues after the washout of antiarrhythmic drugs.

The effects of the washout of antiarrhythmic drugs on the frequency of ventricular premature contraction (VPC) were investigated in 64 patients (VPCs > 2000/day). Included were patients on mexiletine (300-600 mg/day; 23 patients), disopyramide (300-600 mg/day; 19 patients) and atenolol (50 mg/day; 22 patients). Holter monitoring was repeated before, during and after the treatment with the above 3 drugs and the efficacies of the drugs were evaluated based on the spontaneous variability before the treatment. VPC reduction exceeding the calculated spontaneous variability during drugs therapy (drug-responders) and after the washout of the drugs (wash-responders) was noted in 17 (63%) and 3 (13%) of the mexiletine group; 11 (58%) and 5 (26%) of the disopyramide group; and 13 (59%) and 8 (36%) of the atenolol group, respectively. For the entire group of 64 patients, wash-responders were noted significantly (p < 0.05) more among drug-responders (14 of 41 patients; 34%) than drug-nonresponders (2 of 23 patients; 9%). Therefore, the antiarrhythmic effects of drugs observed during drugs therapy seem to continue even after the discontinuation of antiarrhythmic drugs in 34% of patients those whose VPC reduction exceeded the spontaneous variability (drug-responders).

Adult↗
PubMed1993

Hemodynamic effects of milrinone in patients with congestive heart failure--short- and long-term follow up studies.

The hemodynamic effects of milrinone (Mil) were studied in 11 patients with congestive heart failure (CHF) and New York Heart Association (NYHA) functional class II-IV before and after a 2-week treatment. The plasma concentration of Mil was also determined and its pharmacokinetics analyzed. The effect of a placebo was examined before the initiation of the treatment. At the onset, the hemodynamic effects of a single oral dose of Mil (7.5 mg) were evaluated. Mil increased the cardiac index significantly (p < 0.05) 4 h after administrations from 2.3 +/- 0.4 to 2.9 +/- 0.6 L/min/m2. The pulmonary capillary wedge pressure (PCW) was lowered significantly by Mil (p < 0.05) between 0.5 and 4 h after administration. After a 2-week treatment, the baseline PCW dropped (p < 0.05) and the NYHA functional class improved in 10 patients. One patient remained in the same class (II). The improved NYHA class was maintained in 6 patients tested after a mean interval of 16 +/- 3 months. Single oral administration of Mil (7.5 mg) induced hemodynamic improvements after 2-week treatment and the drug also induced similar improvements even after the chronic oral therapy with Mil for 16 +/- 3 months. Pharmacokinetic analysis showed a significant increase in the area under the curve after 2 weeks of treatment. We conclude that Mil decreases the PCW and probably increases the cardiac index and thus improves the symptoms and NYHA functional class in patients with CHF.

Aged↗
PubMed1993

Pure progressive autonomic failure presenting severe orthostatic hypotension.

A 59-year-old woman showed chronic progressive autonomic failure consisting of orthostatic hypotension and dyshidrosis. No signs of Parkinsonism, cerebellar or peripheral neuropathy were observed. Autonomic nervous function tests and findings of biopsied sural nerve suggested that this case had both sympathetic and parasympathetic dysfunctions, mainly postganglionic. A decrease in the total peripheral resistance and no increase in the heart rate on standing seemed to be the mechanism of orthostatic hypotension in this case. We conclude that pure PAF can be recognized as a distinct clinical syndrome of systematic degeneration of the autonomic nervous system.

Autonomic Nervous System Diseases↗
PubMed1993

[Serial changes in QT interval during acute myocardial infarction: comparison of QT interval changes of reperfused cases and non-reperfused cases].

The serial changes in QT intervals during the course of acute myocardial infarction are of interest from the standpoint of the electrocardiogram itself, the development of ventricular tachyarrhythmias, residual cardiac function, and the prognosis of the patients. However, only sparse literature has dealt with this issue because it is difficult to obtain ECGs for analysis, and multiple factors influence the QT interval including the degree of reperfusion, electrolyte imbalance, hemodynamic changes and drugs which alter the QT interval. The ECGs of patients with acute myocardial infarction who underwent reperfusion therapy were analyzed: Sixteen consecutive patients were enrolled in this study, 9 with TIMI grade II and III (TIMI: the thrombolysis in myocardial infarction study group criteria) and 7 with TIMI grade 0, myocardial infarction with (9) and without (7) reperfusion. Patients with collaterals, TIMI grade I, hypertrophic cardiomyopathy, electrolyte imbalance, Ia antiarrhythmic drugs, beta adrenoreceptor blockades, atrial fibrillation, and intraventricular conduction disturbances were excluded from the study. Serial ECG recordings were performed at 3, 6, 9, 12, 24, 48, and 72 hours after the onset of myocardial infarction. One week after and one month after the onset, the ECGs were recorded. Patients who exhibited reocclusion on their arteriograms in the chronic phase were also excluded from the study. Measurements of the QT intervals were performed at the ischemic lead (II in the standard limb lead in inferior infarction and V2 in anteroseptal infarction), and values were averaged from 5 consecutive QRS complexes according to Lepeschkin's method and corrected using Bazett's method. The left ventricular ejection fraction (LVEF) and percent fractional shortening (FS) in segments 2, 3, 4 or 5 were calculated from the ventriculogram in the chronic phase. The QT interval revealed a lengthening with its peak within 12 hours after the onset and it became shorter thereafter in reperfused patients. In patients without reperfusion, the QT interval became progressively prolonged without showing a peak point, up to one month. LVEF and FS were significantly higher values in patients with reperfusion than in those without reperfusion. In conclusion, in patients with reperfusion, the QT interval was transiently prolonged and later shortened with improved LVEF and FS than in patients without reperfusion.

Adult↗
PubMed1992

QT interval shortening and ST elevation in intracoronary ECG during PTCA.

Percutaneous transluminal coronary angioplasty (PTCA) can provide a unique model of transient and reversible myocardial ischemia. The aim of this study was to assess the serial changes in QT interval during elective PTCA-induced transient ischemia. The serial changes in QT interval before, during, and after PTCA of the left anterior descending artery (LAD) were measured in patients who showed ST elevation in intracoronary electrocardiogram. Twelve consecutive patients who showed ST-segment elevation during PTCA-induced ischemia anterior precordial leads of the electrocardiogram (ECG) were enrolled in the present study. Target lesions for PTCA were all in the LAD. There were six patients with angina pectoris, two with non-Q-wave infarction, and four with Q-wave myocardial infarction. During balloon inflation, QTc interval shortened in both intracoronary ECG (ic-ECG) (0.472 +/- 0.013 vs 0.436 +/- 0.014) and surface ECG (0.462 +/- 0.012 vs 0.438 +/- 0.011). However, a significant shortening of the QT interval was more rapidly observed in the ic-ECG (20 s) than in the surface ECG (40 s). We conclude that the QT interval in both ic-ECG and surface ECG becomes shortened in PTCA-induced myocardial ischemia, and that the ic-ECG might be a good probe for detecting survived viable myocardium in the infarcted zone.

Aged↗
PubMed1992

Periodicity of insulin secretion comprises multiple cycles with different duration in perfused rat islets.

Insulin secretion from pancreatic islets has been found to be periodic by in vivo and in vitro experiments. The pacemaker which regulates the periodicity may be localized in the central nervous system or in the pancreas, though the precise location and the mechanisms of generating pacing have not been determined. In order to solve these problems, we examined the period of secretory cycles of insulin in isolated islets using a prolonged perfusion system, and investigated the effects of glucose and other agents on these periods. Isolated islets from male Wistar rats were enclosed in a millipore holder and were perfused with MEM containing 1 mg/ml glucose at a flow rate of 0.3 ml/min for 240 min. The effluent was collected at 1-min intervals to measure insulin secretion. The results were analyzed by the maximum entropy method to demonstrate the periodicity of insulin secretion. When islets were perfused with 1 mg/ml glucose, the periodicity comprised five cycles with different duration: 71.5 +/- 14.6 min, 29.8 +/- 3.4 min, 19.2 +/- 1.5 min, 11.6 +/- 2.1 min and 4.3 +/- 0.4 min. This indicates the presence of a pacemaker within the islets, although, in vivo, participation of a higher center to control periodicity has to be taken into account. Further, the presence of a long cycle (71.5 +/- 14.6 min) of insulin secretion which previously has only been observed in vivo was first demonstrated in this in vitro study. The cycles were consistent even in islets which were desensitized to glucose by cultivating in a high glucose medium for 5 days before perfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Activity Cycles↗