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Biomedical subjects

K Tamura

Publications and source records attributed to K Tamura.

At least 1,495 records · Page 83Linked to original sources
PubMedDate not supplied

Experimental gastric carcinogenesis related to Helicobacter pylori.

In this paper, we present our research on the lipid A of Helicobacter pylori, an experimental study using the Mongolian gerbil model and experimental carcinogenesis using the mouse model to evaluate roles of host factors and bacterial factors which are related to the pathogenicity of Helicobacter pylori including gastric carcinogenesis. Future study on bacterial factors and host factors may give more insight into the role of Helicobacter pylori in gastric carcinogenesis.

Animals↗
PubMedDate not supplied

Chemopreventive effects of curcumin on glandular stomach carcinogenesis induced by N-methyl-N'-nitro-N-nitrosoguanidine and sodium chloride in rats.

The modifying effects of pure curcumin on glandular stomach carcinogenesis were investigated during the post-initiation phase in male Wistar rats treated with N-methyl-N'-nitro-N-nitrosoguanisine (MNNG) and sodium chloride. A total of 110 male 6-week-old rats were divided into four groups. Groups 1-3 (consisting of 30 rats/group) were given MNNG in their drinking water at a concentration of 100 ppm and simultaneously fed a diet supplemented with 5% NaCl for 8 weeks. They were then fed a diet containing either 0.2% (group 1) or 0.05% (group 2) pure curcumin or kept on a basal diet alone (group 3) for 55 weeks. The rats of the curcumin-treated groups (groups 1 and 2) were then switched to the basal diet for the following 4 weeks before sacrifice. Group 4 (20 rats) served as a non-treatment control. The total incidence of combined atypical hyperplasias and adenocarcinomas in the glandular stomachs was rather lower in groups 1 (93%) and 2 (90%) than in group 3 (100%), albeit without statistical significance. However, the mean number of atypical hyperplasias or adenocarcinomas of the glandular stomachs in group 1 (4.70) was significantly less than the value of group 3 (7.17) (p<0.05). Thus, the development of cancerous and precancerous lesions in the glandular stomach was decreased by exposure to pure curcumin. The present results indicate that the compound exerts chemopreventive effects, when given during the post-initiation phase of glandular stomach carcinogenesis in rats.

Adenocarcinoma↗
PubMedDate not supplied

Age-related trend in circadian rhythm of electrocardiographic sinusal R-R intervals in clinically healthy subjects.

It is a clinical observation that human HR shows a tendency to bradycardia with advancing age. In addition, there is experimental evidence that heart rate (HR) shows a circadian rhythm (CR) in healthy humans. Because of this background, the present study is devoted to investigate how the CR of the electrocardiographic sinusal R-R intervals (SRRI) changes its properties as a function of chronological age in healthy humans. The study was performed on 170 clinically healthy Japanese, ranging in age from 12 to 83 years (mean age +/- SD = 43 +/- 15 years), who were monitored in their electrocardiogram over the day-night span. An opposite age-related trend was detected for two properties of SRRI CR, i.e., mesor (positive trend) and amplitude (negative trend). Accordingly, the SRRI CR can be classified as an "amphiclinous rhythm", i.e., a rhythm in which the cardiac interbeat duration shows a progressive increase of its daily mean value along with a progressive deamplification of its oscillatory extent. Furthermore, the rhythm is characterized by a progressive anticipation in time of its oscillatory maximum of duration with advancing age. The findings suggest that the biological clocks regulating the HR CR in human beings undergo a resetting of their mechanisms of tonic, amplitude and phasic modulation as a function of age. The clock-mediated readjustment of the HR CR may be regarded as one of the mechanisms for explaining the bradycardia that is associated with the aging process in human beings.

Adolescent↗
PubMedDate not supplied

Cytotoxic effects of a new antitumor antibiotic, FK973, in malignant glioma.

A novel antitumor antibiotic, 11-acetyl-8-carbamoyloxymethyl-4-formyl-14-oxa-1, 11-diazatetracyclo [7.4.1.0(2,7).0(10,12] tetradeca-2,4,6-trien-6,9-diyl diacetate, FK973, was obtained as a fermentation product from Streptomyces sandaensis. This drug showed excellent cytotoxic effects on human glioblastoma and medulloblastoma and murine glioma (203 glioma) cells. The antitumor effects were also observed in ACNU-resistant glioma cells. The median survival time (MST) of MG models was 15 days. When they were treated with FK973, their MST was prolonged to 21 days. FK973 showed no apparent damage to murine brain cells.

Animals↗
PubMedDate not supplied

Experimental studies of a hybrid artificial esophagus combined with autologous mucosal cells.

Preliminary results, obtained using an artificial esophagus combined with autologous mucosal cells in dogs, are reported. The authors' prosthesis is a silicone tube coated with freeze dried collagen sponge. Cells infiltrate this collagen layer and synthesize new tissue, which will become the neoesophagus. The silicone tube imparts rigidity to the prosthesis and prevents infection, leakage, and dislocation of the prosthesis at the anastomotic site. After formation of the epithelized neoesophageal lumen, the silicone tube drops into the stomach as the result of peristalsis in response to food. Eventually, no artificial prosthesis remains in place, and the defect is replaced by ingrowing tissue. This process was shortened by mucosal cell seeding. Before replacement, the authors harvested oral mucosal (OM) cells, cultured them for 10 days, and seeded them in the collagen layer of the prosthesis just after anastomosis. The neo-esophageal lumen was formed 1 week after the operation without any local complications, infection, leakage, or stenosis, and 2 weeks later the firm, epithelized neoesophagus was completed. OM cell seeding accelerated not only epithelization, but also regeneration of mesenchymal tissue. Parallel with this, transmission electron microscopy showed that most of the cells in the neoesophagus exhibited large nuclei and prominent rough endoplasmic reticulum, indicative of active collagen production.

Animals↗
PubMedDate not supplied

Functional and metabolic effects of bucladesine (dibutyryl cyclic AMP) in the working rat heart preparation: comparison with dopamine.

The effects of bucladesine (10(-4) and 3 x 10(-4) M) on cardiac function and energy metabolism were investigated in comparison with those of dopamine (3 x 10(-6) and 10(-5) M) in the working rat heart preparation. Bucladesine dose-dependently increased systolic pressure, cardiac work and coronary flow, but scarcely changed heart rate or cardiac output at 78 cm H2O perfusion pressure. Dopamine increased systolic pressure to a similar extent as bucladesine and also increased heart rate, cardiac work and coronary flow, but did not change cardiac output. Neither drug caused any changes in energy metabolites. At reduced perfusion pressure (15 cm H2O), bucladesine increased systolic pressure, coronary flow and cardiac output, but caused a decrease (at 10(-4) M) or a negligible change (at 3 x 10(-4) M) in heart rate. At 10(-4) M, there was only a slight change in energy metabolism, but at 3 x 10(-4) M, anaerobic metabolism was enhanced. Dopamine decreased systolic pressure and coronary flow and increased heart rate and cardiac work. Cardiac output increased transiently and, thereafter, decreased. Dopamine also enhanced anaerobic metabolism at both doses. The results suggest that both drugs exert similar effects at normal perfusion pressure, but after reduction of perfusion pressure, some differences occur between the two drugs, presumably due to acceleration of the heart rate and subsequent increase in cardiac work by dopamine.

Adenosine Triphosphate↗
PubMedDate not supplied

Effects of chronic oral administration of a new beta-blocker, bopindolol, on serum lipoprotein concentrations and blood pressure of spontaneously hypertensive rats.

The effects of chronic oral administration of bopindolol (twice daily for 12 weeks beginning at 5 weeks of age) on serum lipoprotein concentrations, blood pressure and heart rate, were studied in spontaneously hypertensive rats. They were compared with those of two other beta-blockers. Bopindolol and propranolol (15 mg/kg) attenuated the increase in heart rate. Pindolol produced a similar, gradual change in heart rate, but only after the 6th week of treatment. Propranolol and bopindolol attenuated the development of hypertension, whereas pindolol showed no such effect. Pindolol and bopindolol produced a significant increase in high-density lipoprotein cholesterol concentration, but did not produce an increase in serum creatine phosphokinase activity. Administration of these drugs in an acute regimen at 10 weeks of age, provoked changes in blood pressure and heart rate, reflecting partial agonist activities of varying degree, in agreement with the results obtained in chronic experiments with regard to serum lipoprotein concentrations. Pindolol (5 mg/kg) provoked a larger decrease of blood pressure without decrease of heart rate, while the decrease of blood pressure after bopindolol (5 and 15 mg/kg) was associated with a decrease of heart rate. It was concluded that bopindolol is a beta-adrenergic blocking agent with a mild partial agonist activity and devoid of adverse effects on lipid metabolism.

Adrenergic beta-Antagonists↗
PubMedDate not supplied

Application of the avidin-biotin-complex method for the light microscopic analysis of lymphocyte subsets with monoclonal antibodies on air-dried smears.

A study was undertaken of the application of the avidin-biotin-peroxidase complex (ABC) method to the monoclonal antibody MAbs staining of mononuclear cells in hematologic and cytodiagnostic materials. Satisfactory cell morphology and immunoreactivity of surface antigens were observed when the slides were fixed in 80% acetone in phosphate-buffered saline or in 60% acetone in 0.03 M citric acid buffer solution (pH 5.4). Unstained air-dried preparations could be preserved for two weeks at room temperature in a desiccator and for one year at -70 degrees C after fixation. An excellent immunoreaction, even with a weak surface antigen, was observed by inhibition of endogenous peroxidase after the secondary antibody reaction; reactions of weak antigens tended to be obscured when the inhibition was performed before the first antibody reaction. Use of the Giemsa stain as a counterstain made it possible to readily observe the cell morphology; therefore, white blood cell analysis could be performed simultaneously when peripheral blood smears were studied. The positive rate of immunoreaction by an immunofluorescent method was well correlated with that obtained by the ABC method. The ABC method proved to be an excellent immunocytochemical technique for detecting cell surface antigens with high sensitivity and specificity; furthermore, it is useful for cell morphology studies and yields permanent preparations.

Antibodies, Monoclonal↗
PubMedDate not supplied

Two histologic types of early gastric carcinoma and their cytologic presentation.

A study was made of 119 case of early gastric carcinomas as to age, sex, histologic cell types, depth of penetration of the cancer, metastasis to the regional lymph nodes and cellular changes of the mucosa near the foci of center. Two distinctly different cellular types were identified. One was the intestinal type, and the other was a diffusely infiltrated, mixed-cell type that was termed the "gastric" type. In both sexes, the intestinal type occurred in the older age group while the gastric type was noted in the younger age group. Once the cancer had penetrated through the muscularis mucosae, there was a sudden, increased incidence of metastasis to the regional lymph nodes regardless of the cellular type. While still confined to the mucosae, only one case of early gastric carcinoma, one of the gastric type, had metastasized to the regional lymph nodes. On this histologic basis, cytologic characteristics of two types of gastric carcinoma are summarized, and the importance of their recognition is emphasized.

Adenocarcinoma↗
PubMedDate not supplied

Diagnosis of chronic lymphocytic thyroiditis (nodular presentation) by needle aspiration.

Needle aspiration was performed on 40 patients with a diagnosis of chronic lymphocytic thyroiditis, and the cytologic findings are described. Clinically, 32 patients had a nodular lesion or lesions, and 8 had diffuse enlargement of the thyroid. A 20-ml glass syringe and an 18-gauge needle were used to aspirate the lesions, and smears were stained according to the Wright-Giemsa technique. Diagnostic material was obtained in 36 patients, and in 4 the aspirate was unsatisfactory. There was good correlation between cytologic findings and antibody tests. Thirteen patients underwent surgical excision of the lesions, and the diagnosis was confirmed histologically. In one patient, the histopathologic diagnosis was chronic lymphocytic thyroiditis and thyroid adenoma. The latter component was not recognized initially on the cytologic specimen. The abundant cellular material obtained in the early nodular forms may correspond to a cellular phase of the disease as opposed to a later fibrotic phase. The evaluation of the epithelial-lymphoid ratio is stressed, and substantial alteration of this ratio may suggest an association of chronic lymphocytic thyroiditis with other thyroid lesions, benign or malignant.

Adolescent↗
PubMedDate not supplied

Protective effect of pacing on reperfusion-induced ventricular arrhythmias in isolated rat hearts.

OBJECTIVES: To determine whether pacing would have a protective effect similar to preconditioning on reperfusion-induced ventricular arrhythmias and whether this protective effect would be induced by pacing-induced myocardial ischemia. DESIGN: Isolated rat hearts (n = 36) were perfused by the Langendorff technique and the working heart mode. Global ischemia was induced for 10 mins followed by reperfusion for 15 mins. The control group had no pacing, while in the other groups, the hearts were electrically paced three times at 300, 400 and 600 beats/min, respectively, for 5 mins with 1 min intervals between pacings. MAIN RESULTS: The incidence of reperfusion-induced ventricular fibrillation in controls was 100%, whereas that in the 300, 400 and 600 beats/min groups was reduced to 67% (not significant), 50% (P < 0.03) and 30% (P < 0.01), respectively. The mean duration of reperfusion-induced ventricular fibrillation was also significantly reduced in the 300, 400 and 600 beats/min groups compared with the control group. Coronary flow during pacing in the 400 and 600 beats/min groups, but not the 300 beats/min group, was reduced significantly compared with controls. In the 300 beats/min group, oxygen tension of the coronary effluent during pacing was decreased significantly, and proton production and lactate release of coronary effluent during pacing were increased significantly compared with the control group. CONCLUSIONS: Pacing exerted a protective effect similar to preconditioning against reperfusion-induced ventricular arrhythmias. Pacing-induced mild myocardial ischemia, in which coronary flow was maintained, may be involved in the mechanism of this protective effect.

Animals↗
PubMedDate not supplied

Telehygiene system for preventive chronopharmacology in space and remote areas on earth.

A chronobiologic computerized modular health care (telehygiene) system for humans in extraterrestrial space 1) monitors and analyzes physiologic blood pressure, heart rate and other variation, including that in tumor markers; 2) recognizes earliest risk elevation by dynamic changes in the 'usual value' range (trend and rhythm alteration); 3) prompts timely and timed treatment for cardiovascular and emotional disease and malignancy prevention, and 4) serves for health improvement; the information from the system can also help optimize shift-work schedules for peak performance and provides endpoints of interest in basic science. The system exploits the chronome, a genetically anchored, habitat-synchronized structure of multifrequency rhythms and trends which is now documented (by longitudinal data series) to respond to magnetic disturbance in the solar system, with consequences expressed in catastrophic illness that is best prevented. Such a system, rated by peers as being of highest priority, could complement classical tools such as the stethoscope, proposed by the U.S. Johnson Space Center representative for use on the moon.

Aerospace Medicine↗
PubMedDate not supplied

Comparison of blood pressure, heart rate and activity between normotensive and spontaneously-hypertensive rats.

Blood pressure, heart rate and physical activity in spontaneously hypertensive rats (SHR) were measured and compared with those of Wistar Kyoto rats (WKY) to see how these parameters vary with age and whether we can find a marker of essential hypertension among these variables. An automatic telemetric system was employed to measure these variables. In SHR, blood pressure and physical activity increased with age, but heart rate decreased. In WKY, neither blood pressure nor physical activity showed significant changes, but heart rate decreased with age. The 24h mean values of blood pressure, heart rate and physical activity were significantly higher in SHR than in WKY. The mean values of blood pressure, heart rate and physical activity were higher during nighttime than during daytime in both SHR and WKY. Circadian MESOR and amplitude of blood pressure increased simultaneously in SHR. These results are compatible with the concept that an increased amplitude of blood pressure may predict subsequent development of essential hypertension.

Aging↗
PubMedDate not supplied

Differences in some circadian patterns of cardiac arrhythmia, myocardial infarctions and other adverse vascular events.

BACKGROUND: Results from unpublished data on the incidence of adverse vascular events and from several published studies are reevaluated chronobiologically. METHODS AND RESULTS: Cosinor methods indicate 1. a circadian variation in the incidence of paroxysmal supraventricular tachycardia (PST), of broadly classified ventricular arrhythmia (VAr), and of atrial fibrillation (AF); 2. a statistically significant difference in the timing of the circadian rhythm of PST and VAr versus that of AF; and 3. a further difference in the timing of these rhythms from that in the incidence of myocardial infarctions (MI). Electrocardiographic records for spans longer than 24h show the extent of day-to-day variability in circadian characteristics of the given patient and indicate the presence of even lower-frequency components, notably along the scale of a week, that may underlie weekly and half-weekly patterns of morbidity and mortality. CONCLUSION: Beyond alterations in the about 1-Hz periodicity of the heart, predictable changes along the scales of the day and the week may constitute a clue to the etiopathology of a given condition and provide a basis for treatment timing. The assessment of unfavorable changes in the lower frequency components may provide a lead time long enough to prompt the institution of preventive, rather than curative, intervention.

Animals↗
PubMedDate not supplied

Alpha 1-adrenoceptor-blocking activity of ofloxacin and ciprofloxacin in isolated vascular smooth muscles.

Using vascular strips from dogs and rabbits, we investigated whether the hypotensive action of ofloxacin enantiomers could be ascribed to effects on vascular smooth muscle. (+)-Ofloxacin, (-)-ofloxacin, (+/-)-ofloxacin and ciprofloxacin competitively inhibited contractions induced by norepinephrine or phenylephrine in dog mesenteric artery and rabbit aortic smooth muscles, without affecting the maximum contractions, whereas they did not affect contractions induced by high KCl. (-)-Ofloxacin did not affect the contractions induced by prostaglandin F2 alpha, 5-hydroxy-tryptamine, U46619 and angiotensin II. Pretreatment with (-)-ofloxacin protected alpha 1-receptors of rabbit aortas from the irreversible blockade by phenoxybenzamine. Any action on the vascular endothelium or intracellular Ca release was not involved in the vasorelaxing action of the drugs. The results suggest that these drugs have an antagonistic action on alpha 1-adrenoceptors in vascular smooth muscles and that this action is, at least partly, responsible for the hypotensive action.

Animals↗