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Biomedical subjects

R Okamoto

Publications and source records attributed to R Okamoto.

At least 181 records · Page 10Linked to original sources
PubMed1991

Anticancer effects of a Chinese herbal medicine, juzen-taiho-to, in combination with or without 5-fluorouracil derivative on DNA-synthesizing enzymes in 1,2-dimethylhydrazine induced colonic cancer in rats.

Juzen-taiho-to (JTT; [Shi-quan-da-bu-tang], a Japanese modified Chinese herbal prescription) in combination with an anticancer drug UFT (5-fluorouracil derivative) prevented the body weight loss and the induction of the colonic cancer in rats treated with a chemical carcinogen 1,2-dimethylhydrazine (DMH), and suppressed markedly the activity of thymidylate synthetase (TS) involved in the de novo pathway of pyrimidine synthesis in colonic cancer induced by DMH.

Adenocarcinoma↗
PubMed1991

Temporary portal vein arterialization as an attractive option in canine orthotopic partial liver transplantation.

We performed 22 canine orthotopic partial liver transplantations (PLTs) with three different revascularization methods; portal vein arterialization (PVA group, n = 11), hepatic arterial shunt (HAS group, n = 5), and conventional portal vein reperfusion (control group, n = 6). Our purpose was to evaluate the feasibility of PVA as a revascularization technique in PLT assessing the changes in arterial ketone body ratio (KBR) as an index of hepatic energy status. After the first anastomosis (left hepatic vein), the ischemic partial liver graft was revascularized with arterial blood flow shunted from the external iliac artery to the hepatic side of the portal vein (PVA group) or the proper hepatic artery (HAS group). Both anhepatic period and ischemia time were significantly shortened in groups PVA and HAS as compared with those in control. In the PVA group, 10 out of 11 recipients survived for at least 5 days (14.2 +/- 3.8 days, mean +/- SEM), while 3 out of 5 (5.2 +/- 1.0) survived in the HAS group and 4 out of 6 (6.2 +/- 1.3) in the controls. Although portal blood flow during PVA was only about 25% of the total hepatic blood flow at preclamping, the KBR was rapidly restored after PVA and showed almost the same values at preclamping. The KBR values during the arterialization time and initial velocity of KBR recovery in the PVA group were significantly higher than those in the HAS and control groups. These results suggest that PVA presents an attractive option in PLT.

Animals↗
PubMed1991

A new bioabsorbable material for rat orthotopic liver transplantation.

Rat orthotopic liver transplantation was performed using a newly synthesized bioabsorbable material (LA-GA copolymer) cuffs and the ordinary polyethylene cuffs. The LA-GA copolymer cuff which anastomosed the portal vein was patent and developed no collateral veins even after 6 months, keeping the transplanted liver normal. By contrast, the polyethylene cuff-anastomosed portal vein was completely occluded and the collateral veins were highly developed, with the transplanted liver showing the fatty degeneration of hepatocytes and numerous regenerative nodules. It is concluded that the LA-GA copolymer cuff is a suitable material for the short- and long-term study of rat orthotopic liver transplantation.

Anastomosis, Surgical↗
PubMed1991

Susceptibility of neonatal lipoproteins to oxidative stress.

We compared peroxidizability of neonatal and adult lipoproteins exposed to oxidative stress initiated by an azo-compound. Oxygen uptake showed a two-phase pattern, with slow oxygen uptake in the first phase and faster uptake in the second phase. During the first phase, tocopherol was consumed progressively, inhibiting lipid peroxidation by scavenging peroxy radicals. After the tocopherol concentration fell below a critical level, extensive propagation of chain oxidative reactions produced the rapid oxygen uptake in the second phase. In the first phase of neonatal lipoprotein oxidation, a faster oxygen uptake was observed and the length of this phase was shorter than in adults. The oxygen uptake rate in the second phase was smaller in the neonatal lipoproteins. In other words, neonatal lipoproteins were more susceptible to oxidative stress than were adult ones when tocopherol remained in lipoproteins, but after tocopherol depletion the reverse was true. These results were consistent with the finding that in neonatal lipoproteins the tocopherol/lipid ratio was significantly lower (length of the inhibitory phase was closely correlated to the lipoprotein tocopherol content). In addition, the average number of active bisallylic hydrogen atoms, which are considered to determine the relative susceptibility of polyunsaturated fatty acids to oxidation, was significantly smaller (oxygen uptake rate in the second phase was closely correlated to the active bisallylic hydrogen number) in neonatal lipoproteins, and the ratio of active bisallylic hydrogen to tocopherol content (which closely correlated to oxygen uptake rate in the first phase) was also significantly lower compared with the adult ratio. Under physiologic conditions, an intensive oxidation of lipoproteins sufficient to cause lipoprotein tocopherol to fall below critical levels is unlikely to occur.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Purification and properties of a chromosomal beta-lactamase from Klebsiella oxytoca.

A beta-lactamase was purified from Klebsiella oxytoca strain GN10650. The enzyme was chromosomally-mediated and gave a single protein band on polyacrylamide gel electrophoresis. Its pI was 5.34 and its MW was approximately 27,000. The optimal pH and temperature were about 7.0 and 50 degrees C, respectively. The specific activity of the enzyme was 1,207 units per mg of protein for hydrolysis of penicillins and cephalosporins, including cefuroxime, cefotaxime, and aztreonam. The enzyme activity was inhibited by p-chloromercuribenzoate, iodine, ferrous ion, and by clavulanic acid. Rabbit antibodies raised against the purified K. oxytoca enzyme showed no cross-reactivity in neutralization tests with beta-lactamases produced by other species of Gram-negative bacteria.

Ampicillin↗
PubMed1991

Enhanced production of antibiotics by Pecilomyces lilacinus under alkaline conditions associated with morphological change.

The production of the group of peptide antibiotics called No. 1907 by Paecilomyces lilacinus was stabilized and enhanced by mono-spore isolation followed by strain improvement, and the production seemed to be related to a morphological change of the strain. Unstable and a low productivity (below 10 micrograms/ml) of the antibiotics No. 1907 by P. lilacinus was greatly improved up to 140 micrograms/ml by successive mono-spore isolation along with mutagenization. Alkaline conditions caused by adding Na2CO3, K2CO3, NaHCO3 or KHCO3 were essential to obtain high production of the antibiotics following simultaneous morphological change of the cells from filamentous mycelia to round arthroconidia. Resting cell experiments showed that a significant amount of antibiotics (213 micrograms/ml) was synthesized by the filamentous cells along with their morphological change to arthroconidia in the presence of glucose under the alkaline conditions.

Anti-Bacterial Agents↗
PubMed1991

Yearly changes of limb alignment toward varus as measured by the femorotibial angle after total knee arthroplasty.

Total knee arthroplasty was performed in 126 knees of 104 patients, using either the UCI, the Kinematic Anteriorly Joined (K-AJ), or the Kinematic Posterior Cruciate Retention (K-PCR) prosthesis. The average patient age at the time of surgery was 59 years; the average follow-up period was 3.3 years. The UCI device was used in 25 knees, the K-AJ in 75, and the K-PCR in 26. Postoperatively, the femorotibial angle was measured yearly for a period of at least six years on an anteroposterior radiograph of the patient standing on one leg. The cases with the UCI prosthesis, with an average standing FTA of 175 degrees one year postoperatively, showed a gradual change of limb alignment toward varus. In contrast, in the cases with the K-AJ and K-PCR prostheses, with an average standing FTA of 172 degrees one year after surgery, limb alignment remained essentially unchanged throughout a long period of follow-up. The authors recommend that total knee arthroplasty be performed to achieve a postoperative femorotibial angle (standing) as close to 172 degrees as possible, which allows the mechanical axis of the lower extremity to pass through the center of the knee.

Adult↗
PubMed1991

Effects of ulinastatin in experimental acute arterial occlusion in rats.

The effects of ulinastatin (human urinary trypsin inhibitor, UTI) were studied in experimental acute arterial occlusion in rats. The experimental model comprised concurrent cross-clamping of the abdominal aorta and bilateral femoral arteries for 4 hours. Blood was sampled for measurement of the enzymes 2 hours after release of the clamps. The rats were grouped according to method of infusing UTI and/or physiologic saline solution. When UTI was infused continuously from the start of clamping, the plasma creatine phosphokinase and plasma beta-glucuronidase levels were significantly lower than in the control rats (p less than 0.05). The results suggest that UTI prevents the destruction of the lysosomal membrane in acute arterial occlusion.

Acute Disease↗
PubMed1991

In vitro and in vivo antibacterial activities of ME1220 and ME1221, novel cephalosporins.

The antibacterial activities and serum pharmacokinetic properties of ME1220 and ME1221, new aminothiazolylalkoxyiminoacetylcephalosporins having an N-alkylpyridiniumthiomethyl side chain at C-3, were compared with those of cefpirome and ceftazidime. ME1220 and ME1221 exhibited broad antibacterial activity against Gram-positive and Gram-negative bacteria. The in vitro and in vivo activities of ME1220 were similar to cefpirome, while ME1221 was superior to ceftazidime against almost all test organisms except pseudomonas. On intravenous injection in rats, ME1220 and ME1221 were excreted mainly in the urine. ME1221 was excreted moderately in the bile and showed higher serum concentration and AUC than those of ME1220.

Animals↗
PubMed1990

[Thymidine kinase activities in sera and liver tissues during hepatocarcinogenesis in rats treated with 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB)].

It is known that a high incidence of hepatocellular carcinoma in rat liver can be induced with 3'-methyl-4-dimethylaminoazobenzene (3'-MeDAB). In the present study, we investigated serum levels of alpha-fetoprotein (AFP) and thymidine kinase (TK), DNA-synthesizing enzyme in the salvage pathway, and tissue TK and its isozyme activities in the liver of rats treated with 3'-MeDAB. Serum TK activities rose abruptly right after the onset of 3'-MeDAB treatment, peaking after one week and then gradually decreasing. At 3 weeks, though serum TK was decreasing, serum AFP and tissue TK began to increase, and oval cells appeared in the liver. At 5 weeks, though serum TK reached a nadir, serum AFP and tissue TK formed transient peaks, and oval cells occupied a major part of the hepatic lobules with hyperplastic nodules. Thereafter, serum TK continued to increase, and serum AFP and tissue TK, after transiently decreasing, re-increased; at 20 weeks, each value was at high level, and mixed type hepatocarcinoma was observed. The liver TK isozymes were separated into 3 types by DEAE-cellulose column chromatography. A 3'-MeDAB induced a remarkable increase in activity of cytosolic and fetal type isozyme in non-tumorous regions of livers at 5 weeks and tumorous regions at 20 weeks. These results indicate that biochemical changes in 3'-MeDAB-treated rat liver may provide a valuable insight into two step process in hepatocarcinogenesis.

Animals↗
PubMed1990

Isolation and characterization of a new hemagglutinin from the red alga Gracilaria bursa-pastoris.

A new agglutinin has been isolated from the red alga Gracilaria bursa-pastoris by affinity chromatography on a yeast mannan-Cellulofine column. This agglutinin was isolated as a monomeric glycoprotein with a relatively low molecular weight. It had an isoelectric point of 4.7 and contained large amounts of Gly, Asx and Glx. It agglutinated trypsin-treated rabbit erythrocytes at the low concentration of 30 ng/ml. The activity was inhibited only by glycoproteins bearing N-glycans. This agglutinin also showed mitogenic activity for mouse splenic lymphocytes.

Amino Acids↗
PubMed1990

The experimental study on the temporary portal vein arterialization in the canine liver transplantation: preliminary report.

To evaluate the feasibility of temporary portal vein arterialization (PVA) in orthotopic partial liver transplantation (PLT), we performed 5 canine PLTs with PVA assessing the changes in arterial ketone body ratio (AKBR) as an index of hepatic energy status, and measuring portal pressure and flow. After anastomosis of hepatic vein, the graft liver was revascularized with arterial blood shunted from the external iliac artery to the hepatic side of the portal vein. By using this technique, both anhepatic period of the recipient and ischemic time, especially warm ischemic time, of the allograft were markedly shortened (31.0 +/- 4.5 min: Mean +/- SEM). Four out of 5 recipients survived for at least 5 days (13 days in average). The AKBR was restored immediately after PVA and showed almost the same values as those at preclamping and after completion of anastomoses of both portal vein and hepatic artery. No significant difference in portal venous pressure was observed between during PVA and after vascular reconstruction. Portal blood flow during PVA was about one fourth of the total hepatic blood flow at preclamping. These results suggest that PVA can be used as an alternative procedure in PLT.

Anastomosis, Surgical↗
PubMed1990

[Effects of hyperthermochemotherapy on activities of DNA-synthesizing enzymes in 1, 2-dimethylhydrazine (DMH)-induced colon carcinomas in rats].

It has been known that a high incidence of adenocarcinoma in distal colon can be induced by s.c. injection of 1, 2-dimethylhydrazine (DMH) into rats at weekly intervals. We investigated effects of radiofrequency hyperthermia (RF-HT) in combination with anti-cancer drug UFT (a combination of tegafur and uracil) on activities of DNA-synthesizing enzymes, using colon carcinomas induced by DMH treatment in rats. 1) Thymidylate synthetase (TS), DNA-synthesizing enzyme in de novo pathway of pyrimidine metabolism, increased to approximately 7-fold that of normal control colon in DMH-induced colon carcinomas in activity, but was markedly reduced to 48% of that in the carcinomas by administration of UFT. 2) Thymidine kinase (TK) in salvage pathway increased to approximately 8-fold that of the control in the carcinomas in activity, but was markedly reduced to 25% of that in the carcinomas by RF-HT treatment. 3) The TK-isozyme, that was thought to be a fetal type in the intracellularly cytoplasmic fraction and closely involved in rapid DNA replication, increased to approximately 24-fold that of the control in the carcinomas in activity, but was reduced to the nearly same level as that of the control by RF-HT treatment. This isozyme was labile in thermostability and easy to be inactivated in low pH. 4) The activities of TS and TK in the carcinomas were extremely suppressed by UFT administration in combination with RF-HT treatment. These results indicate that hyperthermochemotherapy with UFT may serve as an available treatment for colon carcinomas.

1,2-Dimethylhydrazine↗
PubMed1990

Truncoumbilical bypass of the portal vein in radical resection of biliary tract tumour involving the hepatic duct confluence.

Before combined resection of the right hepatic lobe and the hepatoduodenal ligament, an autogenous external iliac vein was interposed between the root of the portal vein trunk and the umbilical portion of the vein in four patients with biliary tract tumour. The left hepatic arterial pathway was preserved, except in one case in whom resection of this artery was followed by reconstruction. This procedure allowed successful and safe extended right hepatic lobe resection and combined en bloc resection of the hepatoduodenal ligament while preserving hepatic blood perfusion.

Adenoma, Bile Duct↗
PubMed1990

Evaluation of temporary portal vein arterialization: the minimum arterialized blood flow for maintaining liver viability.

The effect of temporary portal vein arterialization (PVA) on hepatic energy metabolism was investigated by changes in the arterial blood ketone body ratio (KBR) and hepatic energy charge (EC) level in 17 dogs. The KBR decreased markedly after clamping the hepatic hilar vessels combining mesocaval shunt and remained at a low level throughout hepatic ischemia. After PVA, the KBR was rapidly restored and maintained at sufficient levels. EC at 60 min after arterialization also recovered to the preclamping level. By reducing the arterial shunt flow, the critical point of arterialized blood flow for maintaining the KBR at high levels was assessed to be about 10% of the total hepatic blood flow (THBF). These findings demonstrate that temporary PVA is an effective method for maintaining the functional capacity of the liver, and that the minimum arterialized blood flow needed to preserve liver viability is only about 10% of the total hepatic blood flow.

3-Hydroxybutyric Acid↗