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Biomedical subjects

F Yamamoto

Publications and source records attributed to F Yamamoto.

At least 235 records · Page 13Linked to original sources
PubMed1984

Calcium and cardioplegia. The optimal calcium content for the St. Thomas' Hospital cardioplegic solution.

The relationship between the calcium content of the St. Thomas' Hospital cardioplegic solution and the degree of tissue protection it affords has been characterized by means of an isolated working rat heart preparation subjected to normothermic ischemic arrest. With a 3 minute period of preischemic infusion of solutions containing calcium chloride concentrations of 0, 0.6, 1.0, 1.1, 1.2, 1.3, 1.4, and 2.4 mmol/L and 35 minutes of normothermic ischemic arrest, postischemic creatine kinase leakage was 562.3 +/- 26.7, 64.8 +/- 12.1, 63.3 +/- 9.9, 37.5 +/- 5.4, 33.4 +/- 3.1, 41.2 +/- 4.1, 58.6 +/- 7.4, and 65.7 +/- 9.1 IU/15 min/gm dry weight, respectively. The postischemic recovery of aortic flow was 0%, 29.2% +/- 6.8%, 29.0% +/- 3.3%, 45.8% +/- 4.9%, 55.5% +/- 1.4%, 38.5% +/- 2.7%, 27.8% +/- 8.6%, and 19.5 +/- 7.1%, respectively. The results indicate optimal protection with a calcium concentration of 1.2 mmol/L and a rapid decline in protection with even small changes in concentration either side of the optimum. The hazard of total absence of calcium was confirmed by the induction of the calcium paradox. This study shows that under normothermic conditions a calcium concentration of 1.2 mmol/L is optimal for the St. Thomas' Hospital solution. This study reinforces the importance of undertaking dose-response studies for all components of all cardioplegic solutions.

Animals↗
PubMed1984

Calcium antagonists and hypothermia: the temperature dependency of the negative inotropic and anti-ischemic properties of verapamil in the isolated rat heart.

Using an isolated rat heart preparation under both aerobic and ischemic conditions we have characterized the temperature dependency of the slow calcium channel-blocking drug verapamil. In the first series of studies, isolated working rat hearts were subjected to global ischemia at 37 degrees, 34 degrees, 31 degrees, 29 degrees, 27 degrees, 25 degrees, and 20 degrees C. The duration of ischemic arrest was adjusted so that in the control group the postischemic recovery of function (aortic flow) was approximately 50% of its preischemic value. Ischemic times were therefore 35, 50, 55, 60, 80, 100, and 130 min, respectively. In all cases hearts were subjected to 3 min preischemic infusion with St. Thomas' cardioplegic solution with or without added verapamil (1.1 mumol/liter). At 37 degrees C verapamil increased recovery by 36.6 +/- 4.8%; this increased to 57.4 +/- 6.0% at 34 degrees C. Below 34 degrees C, however, additional protection was progressively lost, so that at 27 degrees C or below verapamil contributed no significant additional protection. In separate aerobic perfusion studies with paced Langendorff-prepared hearts with intraventricular balloons, verapamil (0.2 mumol/liter) was shown to depress pressure development by up to 76% at 37 degrees C; this increased to 92% at 34 degrees C, but thereafter the drug's negative inotropic effects declined, so that at 24 degrees C and below there was no significant difference in developed pressure between the control and drug-treated groups. On the basis of these and other studies, the argument is advanced that by some mechanism common to both hypothermia and verapamil, the anti-ischemic and negative inotropic effects of verapamil are rendered redundant under conditions of hypothermia.

Aerobiosis↗
PubMed1983

Detection of cellular receptors for Sendai virus in mouse tissue sections.

We have established a method for detecting virus receptors in the tissue sections and have been able to clarify the distribution of cellular receptors for Sendai virus in various mouse organs, including trachea, esophagus, large intestine and cerebrum. The virus receptors were detected in ciliated cells of the trachea, as to be expected for a pneumotropic virus. The lamina propria and connective tissue of the mouse esophagus and large intestine, immediately under the epithelium, contained an abundance at virus receptors, but very few were detected in the epithelium of these organs. In mouse cerebrum, the cells lining the ventricles had a large number of virus receptors.

Animals↗
PubMed1983

Calcium antagonists and myocardial protection: diltiazem during cardioplegic arrest.

Using an isolated rat heart preparation as a model of cardiopulmonary bypass and ischemic arrest, the effects of the addition of the calcium antagonist, diltiazem, to St. Thomas' cardioplegic solution were investigated. Under conditions of normothermic ischemic arrest (37 degrees C, 35 min), the addition of diltiazem improved the protective properties of the St. Thomas' cardioplegic solution. Moreover, studies with varying concentrations produced a bell-shaped dose-response curve for diltiazem with its optimal concentration at 0.5 mumoles/liter (0.21 mg/liter) when postischemic recovery of aortic flow was improved from 53.2 +/- 4.3% to 79.2 +/- 4.4% (p less than 0.01) and postischemic creatine kinase leakage was reduced by approximately 40%. Despite this marked additional protection when ischemic arrest was normothermic, diltiazem afforded no improvement in protection under conditions of hypothermic (20 degrees C, 180 min) ischemic arrest.

Animals↗
PubMed1983

Nifedipine and cardioplegia: rat heart studies with the St Thomas' cardioplegic solution.

The ability of nifedipine to enhance myocardial protection was assessed using an isolated rat heart model of cardiopulmonary bypass and ischaemic cardiac arrest. With normothermic ischaemic arrest (35 min, 37 degrees C), nifedipine addition improved the protective properties of the St Thomas' cardioplegic solution. Optimal protection was observed with 0.075 mumol nifedipine X litre-1, where post-ischaemic recovery of aortic flow was improved from 47.9 +/- 5.2% to 76.7 +/- 2.9% (P less than 0.001) and creatine kinase leakage was reduced by approximately 50%. Despite the marked additional protection under normothermic conditions the drug was unable to improve contractile recovery after a period of hypothermic ischaemic arrest (150 min, 20 degrees C) although it did allow a significant reduction (22%) in creatine kinase leakage. In other studies, the ability of nifedipine to replace the cardioplegic solution was examined. Under normothermic conditions, it showed a good ability to protect against ischaemia, but this protection did not match that afforded by the St Thomas' cardioplegic solution. Under hypothermic conditions the drug failed to substitute for the cardioplegic solution, suggesting that a common modality between hypothermia and nifedipine-induced protection.

Animals↗
PubMed1983

Cardioplegia and slow calcium-channel blockers. Studies with verapamil.

The ability of dl-verapamil to enhance myocardial protection when given before, during, or after myocardial ischemia was assessed with the use of an isolated working rat heart model of cardiopulmonary bypass and ischemic cardiac arrest. Under conditions of normothermic ischemic arrest (30 minutes at 37 degrees C), the addition of verapamil enhanced the protective properties of the St. Thomas' Hospital cardioplegic solution. Optimal protection was observed with verapamil concentrations of 0.5 mg/L (1.09 mumol/L) of cardioplegic solution. Under these conditions, postischemic enzyme leakage was reduced by 32.2% and the postischemic recovery of aortic flow was improved by 18.7%. Despite the additional protection at normothermia, the drug at several concentrations appeared unable to improve functional recovery after an extended period of hypothermic arrest (150 minutes at 20 degrees C), although under these conditions its inclusion in the cardioplegic solution could substantially reduce enzyme leakage. In other studies, the ability of various doses of verapamil alone as a substitute for the cardioplegic solution was examined. At the optimal dose (again 0.5 mg/L), and under normothermic conditions, verapamil alone was a good protection against ischemic injury, although this protection did not match that afforded by the St. Thomas' Hospital cardioplegic solution. In similar studies under hypothermic conditions, the drug failed to afford tissue protection, perhaps indicating some common modality between hypothermia and verapamil-induced protection. Pretreatment with verapamil (0.1 mg/L) prior to ischemia offered moderate additional protection, but its use during reperfusion failed to enhance overall recovery.

Animals↗
PubMed1982

Comparative studies on the distribution mode of orthomyxo-virus and paramyxo-virus receptor possessing cells in mice and birds.

Many experimental studies have shown that orthomyxo- and para-myxoviruses may be pneumotropic, but not enterotropic in mammals. On the other hand, these viruses are both pneumotropic and enterotropic in avian species. We have devised a new method for detecting virus receptor possessing cells (VRPC) in tissue sections. VRPC could be detected in the cells lining the airways of both mice and birds. The mode of distribution of VRPC in mouse digestive system differed remarkedly from that in avian digestive system. VRPC were not found in the epithelium of mouse digestive systems whereas the epithelium of bird digestive system were abundant in VRPC. When the large intestines from mice or duck undergoing laparotomy and inoculated directly into intestine with influenza virus were examined, viral antigen was detected in the epithelial cell of duck colon, but not in mouse intestines. From the study utilizing the new method, it could be concluded that the distribution mode of VRPC is one of the most important factors determining the virus tissue specificity.

Animals↗
PubMed1982

The 'pricking' method. A new efficient technique for mechanically introducing foreign DNA into the nuclei of culture cells.

Using the thymidine kinase gene-containing plasmid pTK-1 and the mouse fibroblast thymidine kinase-deficient LTK- cell line, we obtained results indicating that the plasmid molecules suspended in the external medium were introduced into the nuclei by pricking cells on the nuclei with a microneedle. Approx. 25% of the cells pricked in the presence of the plasmid pTK-1 showed TK gene expression, and 2% of the cells became stable TK+ transformants. This 'pricking' method is applicable for introducing DNA into cell nuclei and is more efficient than the conventional calcium phosphate transformation method.

Animals↗
PubMed1982

Occurrence of uronic acid in lipopolysaccharides of Vibrionaceae.

The occurrence of uronic acid as a sugar constituent of lipopolysaccharides (LPS) in Vibrionaceae was demonstrated for the first time. More than 100 strains were examined. Of five genera constituting Vibrionaceae, i.e., Vibrio, Aeromonas, Plesiomonas, Photobacterium, and Lucibacterium, the latter three contained uronic acid in LPS of all of their constituting members examined, while it was totally lacking in Aeromonas LPS so far tested. Only the members of genus Vibrio were found to be divided into uronic acid-containing and -lacking groups; V. parahaemolyticus, V. alginolyticus, V. fisheri, V. costicola, Beneckea ('Vibrio'), and V. fluvialis belonged to the former, while all four biotypes of V. cholerae regardless of their serotypes, V. vulnificus and V. anguillarum, belonged to the latter group. The uronic acid content of V. parahaemolyticus O1 to O12 LPS ranged from 1.6 to 4.2%. The uronic acid residue released from V. parahaemolyticus O1, O4, O10, and O12 LPS by heating in 5% acetic acid at 100 C for 2 hr was identified as galacturonic acid; in particular, that from O12 LPS was characterized as D-galacturonic acid.

Aeromonas↗