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Biomedical subjects

Y Hama

Publications and source records attributed to Y Hama.

At least 109 records · Page 6Linked to original sources
PubMed1983

A two-dimensional analysis of regional myocardial function in the dog.

The pattern of left ventricular contraction or relaxation is not uniform and also changes depending on hemodynamic states. Accordingly, the measurement of myocardial segment length only may have limitations for the analysis of regional myocardial function, and a two-dimensional analysis of regional myocardial function was developed and characterized by utilizing measurement of regional myocardial surface area on the epicardial surface. In eight anesthetized open-chest dogs, the relationship between regional myocardial function and total cardiac function was examined. The extent of the reduction of regional myocardial surface area during the ejection phase or during the systolic phase correlated more closely with stroke volume over wide ranges of left ventricular end-diastolic pressure, aortic pressure, left ventricular contractility, and heart rate (r = 0.75 - 0.96) than the shortening of myocardial segment length alone. Thus, the results demonstrated that regional myocardial function estimated by the measurement of regional myocardial surface area represents total cardiac function more accurately than myocardial segment length over wide ranges of hemodynamic states despite the changes in the left ventricular contraction and relaxation pattern.

Animals↗
PubMed1981

Analysis of the Radiorespirometric pattern after administration of [U-14C] glucose to Ehrlich ascites tumor-bearing mice.

Ehrlich ascites tumor-bearing mice were subjected to 14CO2 radiorespirometric analysis after administration of [U-14C]glucose, and the results were compared with the levels of host liver glycolytic enzyme activities and the uptake of the radioactivity into the liver. After IP administration of [U-14C]glucose, there was a progressive decline in respiratory 14CO2 after the transplantation of the Ehrlich ascites tumor cells. The peak time (PT) was about 10 min on day 1, but thereafter was increasingly delayed, and could not be determined on day 13. Peak height (PH) and yield value (YV) were both considerably decreased, and again the magnitudes of the changes increased with the time after transplantation of the tumor cells. Glycolytic enzyme activities in the host liver were at normal levels 13 days after transplantation of the tumor cells. The uptake of the radioactivity into the liver after IP administration of [U-14C]glucose began to decline from day 5 and was 50% the value in normal mice 13 days after transplantation of the tumor cells. THese results indicate that the radiorespirometric patterns with [U-14C]glucose reflects hepatic biochemical changes rather well.

Animals↗
PubMed1981

Radiorespirometric study of glucose metabolism in liver-damaged rats.

Changes in glucose metabolism in rats during feeding with 3-methyl-4-(dimethylamino)azobenzene (3'-Me-DAB) were investigated by radiorespirometry with 14C-labelled carbohydrates as substrates, in relation to the levels of liver glycolytic enzyme activities. Rats were fed on 0.06% 3'-Me-DAB for 7 weeks. Radiorespirometry was carried out by the IP administration of [U-14C] glucose 2.5 micro Ci or [1-14C] acetate 2.0 micro Ci weekly during the experimental period. In the analysis of the radiorespirometric pattern obtained with [U-14C]glucose, the peak time (PT) was markedly shortened at week 4. At week 6 of 3'-Me-DAB feeding, the peak height (PH) and yield value (YV) both increased significantly with concomitant shortening of PT. The duration of the activation in radiorespirometric parameters was paralleled reasonably well by that of glycolytic enzyme activity; the activation of liver glucose-6-phosphate dehydrogenase (G-6-PDH) shortens PT, while the activation of the tricarboxylic acid (TCA) cycle increases YV. This study showed that the radiorespirometric pattern reflected glucose metabolism in the liver well. In conclusion, radiorespirometric analysis with 14C-labelled glucose as a substrate may be useful for the clinical diagnosis of liver diseases.

Animals↗
PubMed1980

Effects of niludipine on regional myocardial blood flow and regional myocardial function in the dog with partial occlusion of the coronary artery.

The effects of bis(2-propoxyethyl)-1,4-dihydro-2,6-dimethyl-4-*3-nitrophenyl)-3,5-pyridine dicarboxylate (niludipine), a newly-synthesized calcium antagonist related in chestical structure to nifedipine, on the ischemic myocardium were studied in eight anesthetized, open-chest dogs, mainly by the simultaneous measurement of regional myocardial blood flow (MBF) and regional myocardial function. The ischemic myocardium was prepared by partial occlusion of the left circumflex coronary artery, and niludipine was given i.v. at a dose of 5 micrograms/kg. MBF was measured by the radioactive microsphere method and regional myocardial function was assessed by measurement of myocardial segment length. Measurements were also taken of aortic pressure, left ventricular pressure, ascending aortic blood flow, and left circumflex coronary blood flow. Niludipine decreased left ventricular contractility, dilated resistance vessels and reduced heart rate. MBF, measured 5 min after the drug was administered, increased in both the ischemic and the non-ischemic myocardium. Improvement in regional myocardial function was observed in the ischemic myocardium 5 min later, when aortic pressure had returned to nearly the pre-administration level. Thus, the results of the study suggest that niludipine improves the balance between myocardial energy supply and demand in the ischemic myocardium when there is little change in aortic pressure, and we concluded that niludipine exerts a beneficial effect on the ischemic myocardium

Animals↗
PubMedDate not supplied

The changes in regional myocardial surface area during coronary occlusion and reperfusion.

For the analysis of regional myocardial function, the measurement of regional myocardial surface area (RMA) was performed on the epicardial surface of myocardial segment lengths in a direction parallel to the superficial myocardial fibers (SLa) and at right angles to the first (SLb). In eight anesthetized dogs with opened-chests, measurements were done during a 60 s left anterior descending coronary artery occlusion and reperfusion. In the ischemic region, coronary occlusion resulted in dyskinesis in RMA, and the reduction of it during the ejection phase (ERA) decreased significantly at 10 s (p less than 0.05) and thereafter (p less than 0.01). Regional myocardial work (EWA) from the pressure-area loops during the ejection phase also decreased significantly at 10 s (p less than 0.05) and thereafter (p less than 0.01). The end-diastolic RMA (EDRMA) increased significantly at 30 s (p less than 0.01) and thereafter (p less than 0.01). In the non-ischemic region, compensatory changes were shown, namely ERA, EWA and EDRMA, increased significantly during occlusion. After reperfusion, recovery to the control level was prompt, and only EDRMA remained the increased value after 30 s (p less than 0.01). Between SLa and SLb, characteristics differed from each other, which suggested that the directional differences of SLs should be considered when regional myocardial function is assessed from unidirectional SL. The changes in RMA reflect both changes of SLa and SLb during coronary occlusion and reperfusion, and were more marked than each SL. Thus, the usefulness of RMA to assess regional myocardial function was demonstrated during coronary occlusion and reperfusion.

Animals↗
PubMedDate not supplied

Successful transcatheter embolization of penetrating aortic ulcer using interlocking detachable coils.

A 54-year-old man with persistent chest pain was hospitalized for hypertension and DeBakey type IIIb aortic dissection. The false lumen of the dissection was almost completely thrombosed; however, a penetrating atherosclerotic ulcer (PAU) was observed 5 weeks later. At that time, we successfully embolized the PAU with a microcatheter and interlocking detachable coils (IDCs). The patient is well with no episodes of relapse in 20 months of follow-up. This case suggests the utility of the microcatheter and IDC system as an alternative to surgery.

Aortic Dissection↗
PubMedDate not supplied

Dopamine, GABA, cholecystokinin and opioids in neuroleptic-induced tardive dyskinesia.

The long-term administration of neuroleptics causes tardive dyskinesia, which closely resembles levodopa-induced dyskinesias, and is brought about through complex mechanisms which are ill-defined. It is generally believed that the pathogenesis of tardive dyskinesia relates closely to the chronic blockade of dopamine receptor sites and that its pathophysiology results from a hypersensitivity of dopamine receptor sites. In the therapeutic management of neuroleptic-induced tardive dyskinesia, in addition to reserpine and lithium, diazepam, baclofen, or gamma-vinyl-gamma-aminobutyric acid have also been advocated. However, the reported beneficial effects of diazepam and GABA-mimetic agents in ameliorating the symptoms of tardive dyskinesia may occur through a mechanism which does not necessarily link transmission involving both dopamine and GABA. The presence of high concentrations of both cholecystokinin and opioids in the striatum also suggests that these peptides not only may influence dopaminergic transmission, but that they may also be relevant to the psychopathology of schizophrenia and to the therapeutic effects of neuroleptics. Indeed, the acute and chronic administration of neuroleptics alters the levels of cholecystokinin and opioids and their receptors in several brain regions including the striatum. However, neuroleptics also alter the biochemical integrity of neurotensin, neuropeptide Y, substance P and somatostatin, which may also play a role in the overall expression of the neuroleptic-induced extrapyramidal reactions.

Adult↗