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Biomedical subjects

T Mitsuoka

Publications and source records attributed to T Mitsuoka.

At least 127 records · Page 7Linked to original sources
PubMed1987

Interactive negative chronotropic actions of adenosine and verapamil on the canine sinus node in vivo.

To study the interaction between adenosine and verapamil, adenosine (3 mumol/kg) was administered rapidly into the right atrium before and following verapamil (0.2 mg/kg, i.v.) in 25 pentobarbital anesthetized dogs divided into 4 groups: I (n = 7) - intact dogs; II (n = 6) - dogs pretreated with atropine (0.2 mg/kg, i.v.); III (n = 6) - dogs pretreated with propranolol (1 mg/kg, i.v.) and IV (n = 6) - bilateral stellectomized and cervical vagotomized dogs. Arterial blood pressure, standard lead II ECG, as well as right atrial, right ventricular and His bundle electrograms were continuously monitored and recorded. The negative chronotropic effect of adenosine was determined as the maximal prolongation in sinus cycle length (SCL). Verapamil maximally prolonged SCL by 70 +/- 14 msec (p less than 0.005) in Group I, 39 +/- 15 msec (0.1 greater than p greater than 0.005) in Group II, 86 +/- 18 msec (p less than 0.01) in Group III and by 100 +/- 12 msec (p less than 0.001) in Group IV. In Group I, control dogs, adenosine increased SCL by 82 +/- 21 msec before vs. 185 +/- 35 msec 15 minutes after verapamil, respectively (p less than 0.05). This potentiating effect of verapamil was completely abolished by atropine and markedly attenuated by propranolol. In stellectomized + vagotomized dogs, adenosine-verapamil interaction was more complex. In this group adenosine prolonged sinus cycle length maximally by 270 +/- 41 msec before verapamil, but following verapamil this effect of adenosine was transiently attenuated with a maximal sinus cycle length prolongation of only 165 +/- 24 msec (10 minutes following verapamil) (p less than 0.05, vs. before verapamil). These data indicate that the autonomic nervous system modulate the interactive negative chronotropic effects of adenosine and verapamil in the canine sinus node. Hence, the adenosine-verapamil interaction has clinical implications for conditions in which release of adenosine is increased (e.g. myocardial ischemia) or adenosine is administered in the presence of verapamil.

Adenosine↗
PubMed1987

Vagal component in the chronotropic and dromotropic actions of adenosine and ATP.

Several studies indicate that the vagus plays an important modulating role in the electrophysiologic actions of exogenous adenosine and ATP in the heart of certain mammalian species. In addition, extracellular adenosine can enhance the depressant effects of the vagus on the heart. These findings have immediate clinical implication with regard to the use of adenosine and ATP as antiarrhythmic agents as well as the mechanism of cardiac arrhythmias associated with high vagal tone and/or elevate extracellular adenosine levels.

Adenosine↗
PubMed1987

Factors influencing the incidence and severity of swine-serum-induced bile duct lesion in mice.

The detailed histopathology of the swine-serum (SS)-induced bile duct lesion and some factors influencing the incidence and severity of the lesion were examined. The lesion was expressed as an eosinophilic and proliferative cholangitis affecting almost the full length of the biliary tract. It appears to be a useful new model of bile duct diseases. The co-existence of sufficient anti-SS antibody together with repeated injection of SS were necessary to produce this lesion. The lesion could be induced reproducibly by intraperitoneal injection of 0.05 to 0.2 ml of swine serum twice a week for 4 weeks in young BALB/c mice.

Animals↗
PubMed1987

Adenosine mediates the negative chronotropic action of adenosine 5'-triphosphate in the canine sinus node.

ATP exerts pronounced electrophysiologic effects in the mammalian heart. The present study tested the hypothesis that the negative chronotropic action of ATP in the canine sinus node is dependent on its degradation to adenosine. Increasing doses of the following compounds were administered in the sinus nodal artery of 12 open chest dogs (either sex, 30-35 kg) anesthetized with pentobarbital (30 mg/kg i.v.): adenosine, ATP, alpha,beta methylene-ATP (AMPCPP) and beta,gamma methylene-ATP (AMPPCP). Right atrial, His bundle and right ventricular electrograms as well as Lead II ECG and systemic arterial blood pressure were monitored continuously and recorded. The depressant effects of test compounds on the sinus node were assessed from the prolongation of sinus cycle length and the duration of junctional escape rhythm which they induced. Data were used to plot dose-response curves for the four test compounds. The order of potency was adenosine greater than or equal to ATP greater than or equal to AMPPCP much greater than AMPCPP = 0. In 3 of 12 dogs the emergence of junctional escape rhythm was observed after the highest dose of either adenosine, ATP or AMPPCP. In addition, aminophylline, a selective competitive inhibitor of adenosine at P1-purinoceptor site, reduced the effects of maximal doses of adenosine, ATP and AMPPCP by 52 +/- 7, 67 +/- 8 and 72 +/- 6%, respectively (each, P less than .05; AMPPCP vs. adenosine, P less than .05). The present data indicate that the negative chronotropic action of ATP is due to its rapid catabolism to adenosine and the action of adenosine at P1-purinoceptor sites.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine↗
PubMed1986

Effects of adenosine and adenosine 5'-triphosphate on ventricular escape rhythm in the canine heart.

The effects of adenosine and adenosine 5'-triphosphate (ATP) on ventricular escape rhythms were studied in 16 closed chest dogs after electroablation of the His bundle region. All dogs exhibited complete atrioventricular (AV) block and stable ventricular escape rhythm with a mean cycle length of 1,210 +/- 80 ms and a QRS width of 91 +/- 5 ms. Physiologic AV sequential pacing was operative during experiments and was interrupted for rapid (less than or equal to 1 second) administration of either adenosine or ATP (3 mumol/kg) into the right atrium. Adenosine and ATP effectively depressed ventricular escape rhythms in a similar manner both qualitatively and quantitatively (cycle length from 1,210 +/- 80 to 1,764 +/- 132 ms and from 1,274 +/- 84 to 2,000 +/- 150 ms, respectively; each p less than 0.01). These effects were not significantly altered by either physostigmine (an acetylcholinesterase inhibitor) or atropine (a muscarinic cholinergic blocker), but were slightly attenuated by propranolol (a beta-adrenoceptor blocker). In the presence of autonomic blockade, the adenosine transport blocker dipyridamole markedly enhanced the depressant effects of adenosine and ATP. The adenosine competitive antagonist aminophylline reversed the action of dipyridamole. Thus, both adenosine and ATP depress ventricular escape rhythms in vivo, independent of the autonomic nervous system. Moreover, the effects of ATP can be accounted for in large part by its rapid breakdown to adenosine.

Adenosine↗
PubMed1986

Comparison of the fecal microflora in rural Japanese and urban Canadians.

The fecal microflora of nine rural healthy Japanese and eight urban healthy Canadians was examined. The two populations ate typical Japanese and western diets, respectively. The numbers of eubacteria (P less than 0.01), bifidobacteria (P less than 0.05), bacilli (P less than 0.01), lactobacilli and veillonellae and the frequency of occurrence of bifidobacteria were higher in the Japanese than in the Canadians. Higher numbers of bacteroides and lecithinase-negative clostridia were found in the Canadians. Twenty-three genera and over 75 species or biovars were isolated from the feces of Japanese and 18 genera and over 66 species or biovars from the Canadians. The numbers of Bacteroides vulgatus (P less than 0.05), Clostridium coccides (P less than 0.001), and C. tertium (P less than 0.05) and the incidence of B. uniformis (P less than 0.01), C. innocuum (P less than 0.05), and Bacillus spp. (P less than 0.01) were significantly lower in the Japanese than in the Canadians. In contrast, the numbers of Eubacterium aerofaciens (P less than 0.001), and the incidence of Bifidobacterium adolescentis biovar b (P less than 0.01) and Bacillus subtilis (P less than 0.01) were significantly higher in the Japanese than in the Canadians. These findings suggest that significant reductions in anaerobic gram-positive bacilli and increased numbers of bacteroides and clostridia in the feces were induced by the intake of a western diet.

Canada↗
PubMed1986

Effect of moxalactam on human fecal microflora.

Five healthy male adults received 2 g of moxalactam every 12 h for 7 days. The alterations of fecal microflora were investigated before, during, and after treatment with moxalactam. On day 7 of treatment, the number of total bacteria was decreased in all subjects. There was marked suppression of the obligate anaerobic bacteria and enterobacteria to undetectable levels, but the counts of Streptococcus spp. and Lactobacillus spp. increased. On day 7, two subjects had Clostridium innocuum and Clostridium ramosum in their feces but not Clostridium difficile. On day 7 after treatment, the counts of Streptococcus spp., enterobacteria, Lactobacillus spp., and Clostridium spp. in all subjects were still not normal.

Adult↗
PubMed1986

Optimum pacing mode for patients with angina pectoris.

A within patient double blind prospective study of symptoms and exercise tolerance was designed to determine the preferred pacing mode in 10 patients with programmable dual chamber pacemakers who also had angina pectoris. Patients were randomly allocated to one month in each of the following modes: ventricular pacing at 70 beats/min (VVI) or atrioventricular synchronous upper rate 150 beats/min (DDD 150) or 100 beats/min (DDD 100). Medications were unchanged throughout the study; none was taking beta blockers. At the end of each month patients underwent an exercise test. During each month patients recorded symptoms and their preferred pacing mode. DDD 100 was the preferred mode (seven patients). There was significantly less chest pain with this mode than with either of the other modes. There were significantly more episodes of dizziness in VVI, and two patients who developed pacemaker syndrome were unable to complete the pacing period. Three patients developed angina during exercise testing in DDD 150. Atrial synchronous ventricular pacing is better than ventricular pacing for the control of symptoms in patients with angina pectoris provided that the upper atrial tracking rate is limited.

Aged↗
PubMed1986

Mouse strain difference in bile duct lesions induced by swine serum injections.

The mouse strain difference in bile duct lesions was studied on male A/J, BALB/c, C57BL/6, C3H/He, DBA/2 and DDY mice 4 weeks old given intraperitoneal injections of swine serum (0.05 or 0.2 ml per mouse) twice a week for 4 weeks. The hepatic lesions were restricted to the portal tract. Biliary epithelial cells showed hypertrophy and hyperplasia, and eosinophilic and homogeneous or needle-shaped material appeared in the cytoplasm of such hypertrophied epithelial cells and in the ductular lumen. Around these damaged biliary epithelia, eosinophil leukocyte and plasma cell infiltration with proliferation of collagen fibres was commonly detected. These changes became more apparent with increasing size of bile duct. Such histopathological characteristics of hepatic lesions were essentially the same in all strains, but the severity showed a clear strain difference: the lesion was marked in the DDY, A/J and BALB/c strains, moderate in C3H/He and slight in C57BL/6 and DBA/2. A high production of anti-swine-serum antibodies associated with a marked increase in the number of mouse IgG-producing lymphocytes in the spleen was detected in the strains showing the marked hepatic lesions.

Animals↗
PubMed1986

Histopathology of streptozotocin-induced diabetic DBA/2N and CD-1 mice.

Histopathological examinations were carried out on female DBA/2N and CD-1 mice which were autopsied 4 and 12 weeks after six daily intraperitoneal injections of streptozotocin (SZ). Histopathological changes related to SZ treatment were found in the pancreas, liver and kidneys. Little difference was observed between the two strains in the histological changes of the pancreas (a decrease in size of the islets, and degranulation and a decrease in the number of B cells) and liver (hypertrophy of hepatocytes and cytoplasmic invagination into hepatocyte nuclei). With regard to the changes in the kidneys, DBA/2N mice showed characteristic inclusions positive to periodic acid-Schiff reagent in the distal tubule epithelial cells, while CD-1 mice showed remarkable luminal dilatation and epithelial cell deformation of distal tubules. SZ-induced diabetes had no influence on the development of spontaneous cardiovascular lesions in DBA/2N mice under the present experimental conditions.

Animals↗
PubMed1986

Colonization resistance against Pseudomonas aeruginosa in gnotobiotic mice.

Gnotobiotic (GB) mice were colonized with various groups of intestinal bacteria to determine which members of the indigenous flora would exert colonization resistance against Pseudomonas aeruginosa. P. aeruginosa was cultured from the faeces at levels of 10(3)-10(4) cells/g in GB mice inoculated with either the combination of bacteroides and clostridia obtained from conventional (CV) mice or the combination of bacteroides, lactobacilli and clostridia obtained from limited flora mice. The combination of lactobacilli and clostridia from CV mice also did not eliminate P. aeruginosa from GB mice. However, P. aeruginosa was not detected in the faeces of GB mice by 14 days after inoculation with the combination of bacteroides, lactobacilli and clostridia obtained from CV mice. Thus, a complex indigenous flora consisting of bacteroides, lactobacilli and certain clostridia obtained from CV mice but not clostridia obtained from limited flora mice is required to exert complete colonization resistance against P. aeruginosa in GB mice.

Animals↗
PubMed1986

Isolation of Clostridium difficile from various colonies of laboratory mice.

An attempt was made to isolate Clostridium difficile from a total of 565 mice from nine different conventional mouse colonies and six different specified-pathogen-free mouse colonies. C. difficile was isolated from all the conventional colonies but from none of the specified-pathogen-free colonies. Ampicillin injected intraperitoneally increased the isolation rate of C. difficile from mouse faeces to 63.6% compared with 19.4% from untreated mice.

Animals↗
PubMed1986

Development of spontaneous tongue calcification and polypoid lesions in DBA/2NCrj mice.

Calcified tongue lesions were observed in 4- to 8-week-old DBA/2NCrj mice, the highest frequency being reached at 6 weeks of age. Calcification was initially observed in the superficial longitudinal muscles and these lesions were distributed segmentally under the dorsolateral mucous epithelium in the middle portion of the lingual body. After calcification, marked inflammation was observed in the same lesion. Finally, the swollen tissue elevated the covering mucous epithelium and produced polypoid lesions.

Animals↗
PubMed1986

Development of heart and aortic lesions in DBA/2NCrj mice.

The development of heart and aortic lesions was investigated in 3- to 8-week-old DBA/2NCrj mice. In the heart, small foci of myocardial calcification and severe calcification with subsequent inflammation were observed. Severe lesions were restricted to the myocardium below the right ventricular epicardium. Small foci of myocardial calcification were found from 4 to 8 weeks of age with almost the same frequency. The incidence of severe calcification showed a drastic increase between 6 and 7 weeks of age. Aortic lesions were observed from 3 weeks of age and characterized by focal calcification of the smooth muscle cells and elastic laminae. The frequency of aortic calcification was about 50% and not age-related.

Animals↗
PubMed1986

Sinus node function after selective elimination of sympathetic influences on the sinus node area of the dog.

Six-hydroxydopamine (6OHDA) was injected directly into the subepicardium of the sinus node area in an attempt to damage sympathetic nerve terminals in the sinus node. The changes in sinus node function were observed for 4 weeks. The predominant rhythm was of sinus origin throughout the observation period. The sinus rate progressively decreased from 145.1 +/- 14.2 to 76.2 +/- 12.1 beats/min during the first week after injection of 6OHDA. The sinus rate remained at this level for 2 weeks, followed by a gradual increase to 89.3 +/- 18.2 beats/min 4 weeks after injection of 6OHDA. These sinus rates were only significantly different from control dogs through the 14th postoperative day. The sinus rate was considerably increased by intravenous atropine injections 5 to 7 days after the injection of 6OHDA into the sinus node area. The sinus node recovery time was much longer in dogs with an injection of 6OHDA than that in the control dogs throughout the observed period. These results suggest that elimination of the sympathetic influences on the sinus node can be achieved by direct injection of 6OHDA into the sinus node area in the dog, and that sinus node function can be depressed by decreasing sympathetic tone alone, in the absence of an intrinsic dysfunction of the sinus node.

Animals↗
PubMed1985

The intestinal microflora of infants: fecal flora of infants with vitamin K deficiency.

The fecal flora of 10 infants with vitamin K deficiency (VKD) and 10 healthy infants was examined. All the infants were breast-fed. In the infants with VKD, the total counts (P less than 0.01) and the numbers of bifidobacteria (P less than 0.001) were lower than in the healthy infants, whereas bacteroides, veillonella and enterococci were present in greater numbers in the feces of infants with VKD. The incidence of the Bacteroides fragilis group was higher (P less than 0.05) in the infants with VKD than in the healthy infants. A significant reduction (P less than 0.05) in Bifidobacterium breve was shown in the infants with VKD. The data emphasize the abnormal flora in infants with VKD.

Feces↗