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Biomedical subjects

I Hamamoto

Publications and source records attributed to I Hamamoto.

At least 19 recordsLinked to original sources
PubMed1995

Assessment of hepatic viability during cold ischemic preservation.

A reliable and easy method for assessing the viability of a cold ischemia-preserved donor liver prior to transplantation into the recepient is needed. Based on an earlier study, we hypothesized that liver free fatty acid (FFA) leakage into the preservation fluid may be a useful, atraumatic indicator of irreversible ischemic injury. The aim of the present study was to determine the time course and magnitude of liver FFA release into the preservation solution and its correlation with the duration of cold ischemic preservation compatible with survival after transplantation. Rat livers (n = 48) were flushed and preserved with University of Wisconsin (UW) solution at 4 degrees C for 0, 12, 24, and 48 h. Thereafter, half of the livers were analyzed for preservation fluid FFA (gas-liquid chromatography) and protein. The other half were perfused with Krebs-Henseleit (KH) solution at 37 degrees C for 1 h. Bile secretion and liver enzyme release (SGOT, SGPT, and LDH) were measured in addition to perfusate FFA and protein. Total FFA in the preservation fluid was 24 micrograms/g wet tissue after 12 h; it increased sharply 2.6-fold after 24 h and 3.7-fold after 48 h of preservation. Bile production was normal after 12 h of preservation but fell by 20% and 54% after 24 h and 48 h, respectively. LDH release rose from a value of 20 U/l at 0 time to 120 U/l and 260 U/l after 24 h and 48 h of preservation. These results suggest that liver viability declines sharply between 12 and 24 h of cold ischemic preservation, which corresponds with a sharp decrease in the 1-week survival from 100% to 33% after 12 h and 24 h, respectively, of cold ischemic preservation. We conclude that measuring FFA and LDH in the preservation solution of donor livers may be a useful means of assessing the quality of the cold-preserved liver before insertion into the recipient. We also speculate that a "threshold" FFA level in the UW preservation fluid indicating irreversible damage may be in the order of 35 micrograms total FFA/g liver. Studies on the clinical applicability of our findings are currently under way.

Adenosine↗
PubMed1995

Prediction of the early prognosis of the hepatectomized patient with hepatocellular carcinoma with a neural network.

The early prognosis of the hepatectomized patients with hepatocellular carcinoma was determined preoperatively with a perceptron-type neural network. The neural network was trained with the preoperative data of 54 example cases with the early prognosis, successful or died of hepatic dysfunction, as teaching signals. After learning these examples, the neural network came to give a precise prediction to the example data except for one case. With the learned neural network, the outcomes of the hepatectomy of 11 patients (10 successful; 1 died) were predicted prospectively with 100% precision. The usefulness of the neural network for the prediction was determined.

Adult↗
PubMed1995

Comparison of warm and cold ischemia of the canine small intestine.

Warm and cold ischemia-reperfusion injuries to canine small intestine was compared. In the warm ischemic model, the superior mesenteric artery of mongrel dogs was clamped for 2 h and then released (group A). As a cold ischemia model, canine small intestines were harvested with cold lactated Ringer solution, preserved for 24 h in cold LR solution and then autotransplanted (group B). After ischemia and during reperfusion, activities of maltase (MAL), myeloperoxides (MPO), xanthine dehydrogenase (XD) and xanthine oxidase (XO) were measured as well as hypoxanthine (HX) concentration. MAL activities were not changed during warm or cold ischemia, whereas it was remarkably decreased after revascularization in both the groups. Neutrophil infiltration after reperfusion was shown by the increase of MPO activities to 8 and 1.5 U/mg protein in groups A and B respectively from a normal value of 0.35 U/mg protein. During warm ischemia, %XO (XO/XD + XO) was increased from 18.4 to 84.9% for 2 h. In contrast, %XO was not changed for 24 h of cold ischemia. Tissue accumulation of HX was increased 2.8 times from a normal value of 1.06, 2 h after warm ischemia, but there was almost neither accumulation of HX nor the conversion of XD to XO in 24 h cold ischemia. It was observed that warm and cold ischemia caused similar injury after reperfusion in spite of the striking difference in the conversion of XD to XO and accumulation of HX. Thus, it is suggested that the XO system is not always necessary for ischemia-reperfusion injury.

Animals↗
PubMed1994

Can adenine nucleotides predict primary nonfunction of the human liver homograft?

Sixty-eight primary liver grafts were analyzed to see whether adenine nucleotides (AN: ATP, ADP, and AMP) or purine catabolites (PC: adenosine, inosine, hypoxanthine, and xanthine) of tissue or effluent can predict primary graft nonfunction. AN, PC, and nicotinamide adenine dinucleotide, oxidized form (NAD+) of the tissue before (pretransplant) and after graft reperfusion (post-transplant) and of the effluent were analyzed. The graft outcome was classified into two groups (group A: successful, n = 64; group B: primary nonfunctioning, n = 4). No significant differences were observed in pretransplant measurements between groups A and B, whereas ATP, ADP, total AN, total AN + total PC (T) and NAD+, in post-transplant tissues, were significantly higher in group A. Xanthine in the effluent was significantly higher in group B than in group A. ATP, ADP, total AN, T, and NAD+ in post-transplant tissue were significantly associated with primary graft nonfunction by logistic regression analysis.

Adenine Nucleotides↗
PubMed1993

Effect of nutritional status on hypothermic liver perfusion.

The effect of nutritional status on livers preserved either by simple cold storage or by hypothermic perfusion was studied using isolated rat liver perfusion model. Livers either form fed or fasted rats were preserved for 18 hours by simple cold storage procedure with UW solution, or continuously perfused for 12 hours at 5 or 20 degrees C. Each liver was assessed by one hour normothermic reperfusion following preservation period. Fasted livers in each preservation procedure demonstrated deterioration of hepatocytes more than fed livers assessed by AST, ALT and LDH liberation into perfusate. PNP in the perfusion procedures showed no difference between fasted and fed livers. Slight sinusoidal lining cells changes and vacuolization in hepatocytes were preferential in all groups. Patchy areas of hepatocytic discoloration were often seen in fasted group in each preservation procedure. The nutritional status of hepatic graft is important in both simple storage and continuous perfusion preservation method.

Animals↗
PubMed1993

Evaluation of oxygen necessity during hypothermic liver perfusion.

Need of oxygen by the liver during hypothermic perfusion was evaluated using isolated perfusion model. Livers were perfused by a continuous perfusion system with oxygen saturated perfusate or nitrogen saturated perfusate, or simply stored for 12 hours at 5 degrees C. Quality of individual liver was assessed at one hour after normothermic reperfusion. Tissue edema was significant in all experimental groups, but the extent of which was much higher in nitrogen and simple cold storage groups. AST, ALT, LDH and PNP in the perfusate at the end of normothermic reperfusion were significantly higher in nitrogen and simple storage groups and those of oxygen group were similar to the control. Tissue adenine nucleotide and purine catabolite concentration in oxygen group was almost identical to the control at the end of hypothermic preservation, while ATP and energy charge in nitrogen and simple cold storage groups were significantly low. Conjugated dienes before and after reperfusion showed no difference in any groups, indicating no involvement of free radical injury on reperfusion in this asanguineous perfusion model. These results suggest that continuous supply of oxygen is necessary for liver preservation even though the temperature is lowered to inhibit cellular metabolism.

Animals↗
PubMed1993

Isolated perfusion of rat livers: effect of temperature on O2 consumption, enzyme release, energy store, and morphology.

The effect of temperature on isolated rat liver perfusion was studied. Livers were perfused for 12 hours with oxygenated Krebs-Henseleit solution at 5, 10, 15, 20, 25 and 30 degrees C, followed by one hour normothermic reperfusion. After each perfusion, oxygen consumption, liver enzyme release, tissue swelling, energy metabolism and histopathological abnormalities were determined. Compared to the oxygen consumption at 37 degrees C, that of 25, 10 and 5 degrees C was 47%, 16% and 12%, respectively. When the liver was perfused at 30 degrees C, higher enzyme release and lower energy status was observed. Tissue swelling was significant only with livers perfused at 5, 10 and 30 degrees C. After normothermic reperfusion, liver injury indicated by enzyme release and bile production was remarkable with 30 degrees C liver, and that of the other groups was essentially the same as the control. ATP of 5, 25 and 30 degrees C liver was significantly lower than the control. Histopathological examination demonstrated abnormalities of sinusoidal cells and hepatocytes in livers perfused at 25 degrees C and 30 degrees C Thus higher temperature (25 degrees C to 30 degrees C) during continuous perfusion were found to induce liver damage. Moderate hypothermia between 10 degrees C and 20 degrees C maintained structure and function of rat livers rather well. These results suggest that, when a machine perfusion of the liver is attempted, a wider temperature range, higher than the conventional, needs to be taken into consideration.

Alanine Transaminase↗
PubMed1993

Rat liver lipids during ex vivo warm and cold ischemia and reperfusion.

Rat livers were flushed and stored ex vivo in Krebs-Henseleit buffer at 37 degrees C for 3 hr or in University of Wisconsin solution at 2 degrees C for 48 hr. After this they were perfused with recirculated Krebs-Henseleit solution at 37 degrees C for 1 hr. Levels of phospholipids (PL), free fatty acids (FFA), and conjugated dienes were determined at various times during ischemia and after 1 hr of reperfusion. After 3 hr warm ischemia, total PL content decreased by about 30% primarily because of decreases in phosphatidylcholine and phosphatidylethanolamine. One hour of reperfusion normalized PL levels. Total PL content was unchanged up to 48 hr of cold ischemia because of offsetting alterations in levels of PL classes. FFA accumulation during warm ischemia was about half that during cold ischemia. Conjugated diene concentration increased fivefold during warm ischemia but was unchanged during cold ischemia. Low PL levels and FFA accumulation along with production of conjugated dienes suggest that lipid oxidation is a major mechanism of PL degradation during warm, but not cold, ischemia of the liver.

Animals↗
PubMed1993

Effects of ionic strength and pH on the dissociation constant between NADPH-adrenoferredoxin reductase and adrenoferredoxin.

The dissociation constant between NADPH-adrenoferredoxin reductase and adrenoferredoxin was measured at various ionic strengths (0.05-0.25) and pHs (6.6-8.2) by means of a kinetic method involving pyridoxal 5'-phosphate. For each ionic strength, the maximum dissociation constant was obtained at pH 7.4. It ranged from 8.34 (ionic strength = 0.05) to 169 nM (ionic strength = 0.25) at pH = 7.4. At each pH, the dissociation constant increased along with the increase in ionic strength.

Adrenodoxin↗