Biomedical subjects

S Imaoka

Publications and source records attributed to S Imaoka.

At least 73 records · Page 4Linked to original sources

PubMed1998

Tissue distributions of CYP2D1, 2D2, 2D3 and 2D4 mRNA in rats detected by RT-PCR.

The tissue distributions of four isoforms (CYP2D1/5, 2D2, 2D3 and 2D4/18) in rat CYP2D subfamily were investigated. Twelve kinds of tissue (liver, kidney, brain, lung, heart, spleen, adrenal gland, small intestine mucosa, bladder, testis, ovary and gonecystis) were removed from Sprague-Dawley male and female rats. The expression of CYP2D mRNA in these tissues was detected by RT-PCR. Specific primers were designed to recognize the four isoforms individually. In liver, kidney and small intestine mucosa, the mRNA expression of all four CYP2D isoforms was detected as high-intensity PCR products. mRNA of CYP2D1/5 was expressed in all tissues used in this study except the brain, although the intensity of PCR products varied among tissues. mRNAs of CYP2D2 and CYP2D3 were mainly expressed in liver, kidney and small intestine mucosa, which were exposed to xenobiotics such as drugs, food components and environmental contaminations. mRNA of CYP2D4/18 was expressed in liver, kidney, small intestine mucosa and brain. In brain, only mRNA of CYP2D4/18 was expressed. CYP2D4/18 mRNA was also expressed in ovary, testis and gonecystis. The tissue distributions help to clarify the differences in physiological and pharmacological functions between CYP2D isoforms.

Animals↗

PubMed1998

Strain differences in CYP3A-mediated C-8 hydroxylation (1,3,7-trimethyluric acid formation) of caffeine in Wistar and Dark Agouti rats. Rapid metabolism of caffeine in debrisoquine poor metabolizer model rats.

We observed significant strain differences [Dark Agouti (DA) > Wistar] in 1,3,7-trimethyluric acid formation (C-8 hydroxylation) during caffeine metabolism, though not in N-demethylations, in adult male DA and Wistar rats. In contrast, adult female and immature male rats of both DA and Wistar strains did not show significant differences in activity levels of C-8 hydroxylation. Kinetic studies using liver microsomes revealed that adult male DA rats have a larger Vmax for C-8 hydroxylation than do Wistar rats. Troleandomycin (TAO), known as a cytochrome P450 (CYP) 3A inhibitor, and an anti-rat CYP3A2 polyclonal antibody effectively reduced C-8 hydroxylation by rat liver microsomes in a concentration-dependent manner, suggesting that C-8 hydroxylation in rats is mediated largely by an isoform(s) of the CYP3A subfamily. Troleandomycin and the antibody did not inhibit the N-demethylations of caffeine by rat liver microsomes. Treatment of rats with CYP3A inducers caused a marked increase in C-8 hydroxylase activity. These results indicate that the rat CYP3A subfamily is capable of catalyzing C-8 hydroxylation of caffeine as is the case for human CYP3A4. The results of western blotting analysis using anti CYP3A antiserum showed that the staining intensity of the protein band in DA rat liver microsomes was higher than that in Wistar rat liver microsomes. We concluded that marked sex-dependent strain differences in C-8 hydroxylation of caffeine between Wistar and DA rats are due to the differences in the levels of expression of CYP3A in these strains of rats.

Aging↗

PubMed1998

Activation of the beta-catenin gene by interstitial deletions involving exon 3 in primary colorectal carcinomas without adenomatous polyposis coli mutations.

Among 222 primary colorectal cancers we examined, 58 showed no detectable APC mutations by the protein truncation test. We screened those 58 tumors for somatic mutations in the beta-catenin gene. Although amino acid substitutions in serine or threonine residues in exon 3 had been reported, we found no such mutations; however, in seven tumors, we detected somatic interstitial deletions of 234-760 bp, each of which included all or part of exon 3. Short nucleotide sequences at both ends of each deletion were either identical or complementary, indicating that repeated or inversely repeated sequences were involved in the somatic rearrangements. Reverse transcription-PCR experiments using RNAs isolated from three of these seven tumors detected transcripts that lacked exon 3, in addition to the normal transcript. In one of these cases, we confirmed accumulation of aberrant beta-catenin protein in cytoplasm and nuclei of cancer cells by Western and immunohistochemical analyses. This result suggested that, in the absence of a peptide encoded by exon 3, beta-catenin is stabilized and has a dominant oncogenic effect on colorectal tumorigenesis.

Carcinoma↗

PubMed1998

Allelic imbalance of insulin-like growth factor II gene expression in cancerous and precancerous lesions of the liver.

Allelic imbalance of the insulin-like growth factor II (IGF II) gene expression is often seen in hepatocellular carcinoma (HCC). To investigate the role of allelic imbalance in hepatocarcinogenesis, we have studied allelic expression status of the IGF II gene in dysplastic nodules, which are precancerous lesions of HCC, as well as in HCCs of different histological grade, and the influence of the allelic imbalance on IGF II gene expression has also been examined. Allelic imbalance was observed in 3 of 7 dysplastic nodules, in 7 of 9 well-differentiated HCCs, and in 8 of 9 moderately differentiated HCCs. IGF II gene expression level, which was studied by a semiquantitative reverse-transcriptase polymerase chain reaction (RT-PCR), was significantly higher (3.6-fold) in the dysplastic nodules than the control livers, but a significant increase in the IGF II gene expression was not observed in well- and moderately differentiated HCCs as compared with the control livers. These results demonstrate that the allelic imbalance of the IGF II gene expression is seen in the early stage (precancerous lesions) of hepatocarcinogenesis. Association of the allelic imbalance with an increased expression of the IGF II gene in the precancerous lesions might suggest a possible involvement of an IGF II autocrine loop in the pathogenesis of these lesions.

Alleles↗

PubMed1998

Limited surgery for early gastric cancer in cardia.

BACKGROUND: Because there are some difficulties with the diagnosis of invasion or the endoscopic resection technique, almost all gastric tumors are resected surgically. Surgeons now are performing a limited operation for early gastric cancer of the upper stomach (EGCUS) without lymph node metastasis. This paper discusses and evaluates the surgical technique and the results of the limited operation for EGCUS. PATIENTS AND METHODS: Since 1988, a total of 34 patients with EGCUS, diagnosed as intramucosal invasion, have undergone a limited operation--fundectomy--which includes a limited proximal gastrectomy, a limited lymph node dissection, and a procedure preserving the vagal nerve. The surgical risk, postoperative complications, and survival rates of the fundectomy patients (group A) were compared with those of patients undergoing a total gastrectomy for EGCUS (group B). RESULTS: Blood loss was lower in group A (300+/-193 mL) than in group B (555+/-316 mL) (P <.05). The incidence of postoperative pancreatic fistula also was lower in group A (0%) than in group B (15.0%) (P <.05). All patients in both groups (except one who died of a cerebral infarction) are alive without recurrence. CONCLUSION: Compared to the results of a total gastrectomy, performance of a limited fundectomy for EGCUS decreased surgical risk and postoperative complications without decreasing the survival rate.

Adult↗

PubMed1998

Indications for hepatectomy for hepatocellular carcinoma - what stage of the disease is the best indication for surgery?

To determine the clinical and tumor stage of hepatocellular carcinoma (HCC) that is the best indication for surgery, the postoperative long-term outcomes of patients who underwent hepatic resection were examined retrospectively. Of 975 patients with HCC who underwent regional therapy, 384 patients (39%) received hepatic resection (HR), 534 (55%) had transcatheter arterial chemoembolization (TACE), and the remaining 57 (6%) received percutaneous ethanol injection (PEI) into the tumor. The criteria defined by liver Cancer Study Group of Japan was used for staging and liver functional reserve (i.e., clinical staging). In the 133 patients with stage I HCC, there were no significant differences among the survivals of the HR, TACE, and PEI groups. In the 314 patients with stage II HCC, the 5- and 7-year survival rates were 51% and 46% in the HR group, 23% and 10% in the TACE group, and 0% and 0% in the PEI group. The survival of the HR group was significantly better than the survivals of the TACE and PEI groups (P < 0.001). The 5- and 10-year survivals of the stage II HCC patients who had HR were 64% and 47% in the clinical stage I (i.e., good liver function) group, significantly better than the 5; and 10-year survivals (32% and 23%) in the clinical stage II (i.e., bad liver function) group (P < 0.0001). Patients with good liver function in stage II are expected to have better survival and are considered to be the most suitable for HR.

Aged↗

PubMed1998

Intraoperative cytodiagnosis for detecting a minute invasion of the portal vein during pancreatoduodenectomy for adenocarcinoma of the pancreatic head.

During pancreatoduodenectomy for adenocarcinoma of the pancreatic head, we frequently encountered cases in which the superior mesenteric-portal venous confluence (SMPVC) was involved with cancer. With regard to the indication of the concomitant SMPVC resection, as suggested by recent papers, a better long-term outcome would be expected if the cancer invasions were limited to the tunica adventitia or media of the SMPVC wall. Since this raised fears whether such a small SMPVC invasion was always detectable by macroscopic inspection alone, we have performed an intraoperative cytology on the touch smear of the exposed SMPVC wall for 23 patients with pancreatic head cancer. All of their SMPVCs were separated from the pancreatic head and appeared to be intact at a macroscopic level. As a result of the cytologic examination, however, 7 patients (30%) were newly diagnosed as having cancer cells on the SMPVC wall, and they received an additional resection of the SMPVC. Postoperative histology indicated that cancer invasion into the SMPVC wall was present in 6 of the 7 patients, and that the cancer invasions were limited in the tunica adventitia in 5 patients and to the tunica media in 1 patient. Thus, in order not to miss the chance of cure by SMPVC resection, our intraoperative cytology on the touch smear of the SMPVC is worth performing more actively on the macroscopically intact-looking SMPVC during resection of pancreatic cancer.

Adenocarcinoma↗

PubMed1998

Evidence that immature rat liver is capable of participating in steroidogenesis by expressing 17alpha-hydroxylase/17,20-lyase P450c17.

Steroid hydroxylase cytochrome P450c17 has been previously purified from microsomal fractions of immature rat livers. In this study, we investigated the expression of P450c17 in rat livers to understand a role of steroidogenesis in the extrasteroidogenic tissue. Upon immunoblot analysis utilizing liver microsomes from rats, P450c17 was detected in 1 and 3 week old rats but not in adult rats. Data from immunohistochemical studies also showed a similar age-dependent expression of P450c17 and indicated that P450c17 detected in immature rat livers is localized in cells surrounding interlobular veins. This age-dependent expression of P450c17 in rat livers was observed in both sexes. Upon enzymatic analysis utilizing microsomal fractions from livers, levels of 17alpha-hydroxylase and 17,20-lyase activity for pregnenolone and progesterone increased by 3 weeks and dramatically reduced at 7 weeks, which is consistent with the expression level of P450c17. These data clearly indicate that P450c17 is expressed in immature rat liver to produce 17alpha-hydroxysteroids and C19-steroids. Based upon immunoblot analysis, the expression level of P450c17 in immature rat livers was approximately one third of that in testis. Compared expression level of P450c17 and total volume of organs between liver and testis, the total amount of steroid metabolites produced by liver P450c17 could be greater than that produced by gonadal P450c17. Because of the absence of P450c17 in rat adrenal glands, rat liver could be the major site for producing 17alpha-hydroxysteroids and C19-steroids in this particular period of life. Although physiological products formed by P450c17 in liver and their roles remain to be elucidated, this study suggests a large capacity of prepubertal rat liver for participating the production of steroid hormones and a putative importance of 17alpha-hydroxysteroids and C19-steroids, such as cortisol and androstendione, which are generally believed to be minor components of steroid hormones in rodents.

Animals↗

PubMed1998

Down-regulation of focal adhesion kinase, pp125FAK, in endothelial cell retraction during tumor cell invasion.

Although endothelial cell retraction is required before tumor cell invasion, its molecular mechanism still remains obscure. We previously demonstrated that conditioned medium (CM) derived from a human pancreatic cancer cell line, PSN-1, induced endothelial cell retraction and facilitated tumor cell invasion. To investigate the molecular change of events in the transduction of extracellular signals during endothelial cell retraction, we examined the effect of the CM derived from PSN-1 cells on the tyrosine phosphorylation in endothelial cells. Immunoblot analyses revealed that the PSN-1 CM decreased tyrosine phosphorylation of a 120-130 kD protein, and induced the concomitant down-regulation of focal adhesion kinase, pp125FAK, during endothelial cell retraction in time- and dose-dependent fashions. These changes preceded endothelial cell retraction and were reversible after removal of the CM. Further quantitative densitometric analyses demonstrated that the extent of decrease in tyrosine phosphorylated 120-130 kD protein during the endothelial cell retraction was likely to be proportional to that of the down-regulation of pp125FAK. A tyrosine phosphorylated 120-130 kD protein immunoprecipitated by anti-phosphotyrosine antibody immunoreacted with anti-pp125FAK antibody. These results suggested that decreased amount of a tyrosine phosphorylated 120-130 kD protein probably due to the down-regulation of pp125FAK might be associated with the signal transduction pathway in the endothelial cells during their retraction. Furthermore, these findings were also observed in the CM from another four human cancer cell lines, suggesting the down-regulation of pp125FAK in endothelial cells during tumor cell invasion.

Animals↗

PubMed1998

Presence of a threshold for promoting effects of phenobarbital on diethylnitrosamine-induced hepatic foci in the rat.

The dose dependence of the hepatopromoting effects of phenobarbital (PB) was investigated in a rat liver medium-term bioassay (Ito test) to elucidate a practical threshold level. F344 rats were given a single i.p. injection of diethylnitrosamine (200 mg/kg body wt) and subjected to two-thirds partial hepatectomy at week 3. Commencing 2 weeks from the start, PB at doses of 0, 1, 2, 4, 7.5, 15 or 500 p.p.m. in experiment 1 and 0, 0.01, 0.1 or 0.5 p.p.m. in experiment 2 were fed to the rats for 6 weeks. Experiment 3 was conducted to confirm previous data using the same medium-term bioassay, with PB at doses of 0, 1, 2, 4, 7.5, 15, 30, 60, 125, 250 or 500 p.p.m. fed to the rats. All surviving animals were killed at week 8 in these experiments and their livers were immunohistochemically examined for expression of glutathione S-transferase placental form (GST-P). Quantitative values for GST-P-positive foci in the liver were increased dose dependently in rats given 60-500 p.p.m. PB. However, those for doses in the range 1-7.5 p.p.m. demonstrated a decrease as compared with the control group (0 p.p.m.), with significant differences observed for 1 and 2 p.p.m.. The results for 15-30 and 0.01-0.5 p.p.m. were comparable with the control values. Examination of transforming growth factor-alpha (TGF-alpha)-positive foci also produced similar results to those for GST-P in experiment 1. Immunohistochemical staining of TGF-alpha and GST-P using serial liver sections demonstrated that the TGF-alpha-positive foci comprised a sub-population of the GST-P-positive lesions, being approximately 1/8-1/10th as common in livers of animals treated with PB. TGF-alpha-positive foci were almost always negative on immunostaining for TGF-beta. Western blotting for proteins CYP2B1, 2C6 and 3A2 revealed a good correlation between changes in GST-P-positive foci and CYP3A2 protein expression. The finding of inhibition effects at low doses of PB confirms the presence of a threshold level for promoting effects by PB on liver carcinogenesis in rats.

Animals↗

PubMed1998

[The physiological role of P450-derived arachidonic acid metabolites].

Arachidonic acid is metabolized to biologically active substances by three major enzyme systems including cyclooxygenases, lipoxygenases and cytochrome P450s. The third pathway, P450-dependent pathway, includes allylic oxidation, omega-hydroxylation, and epoxidation of arachidonic acid. Of these metabolites, the physiological role of 20-hydroxyeicosatetraenoic acid (20-HETE) produced by CYP4A isoforms has been extensively studied. 20-HETE affects ion transport, constricts blood vessels and participates in tubuloglomerular feed back. Increased production of 20-HETE is a major factor in elevating blood pressure in spontaneously hypertensive rats (SHR). We have found that CYP4A2 level in SHR is much higher than that of normotensive rat. Recently, factors of endothelial origin other than nitric oxide and prostaglandins were reported. Inhibitors of P450-dependent arachidonic acid metabolism greatly reduce the vasodilator effect and this factor is speculated to be an epoxide of arachidonic acid. We have isolated CYP2C23 from rat kidney and have found that it produces arachidonic acid epoxides. We have investigated changes in the CYP2C23 levels in physiological and pathophysiological conditions. Multiple pathways of arachidonic acid metabolism by P450 have been reported and the diverse properties of these metabolites and the wide distribution of the P450 system make them prime candidates for participation in regulatory mechanisms of the circulation and transporting epithelia.

8,11,14-Eicosatrienoic Acid↗

PubMed1998

[Inhibition of cytochrome P450 by nitric oxide].

Nitric oxide (NO) reacts with iron, superoxide, thiols and oxygen. Although NO reversibly interacts with the heme-iron of P450, the pathophysiological role of this interaction remains to be elucidated. We found that hepatic levels of P450 markedly decreased in endotoxemic rats, particularly when the rate of NO generation was increased. To determine the possible role of NO in the modulation of the structure and function of P450, changes in the levels and activities of P450 isozymes were determined in liver microsomes from normal and endotoxemic rats. Electron spin resonance analysis revealed that incubation of microsomes with the NO donor NOC-7 rapidly generated NO-P450 adducts. Microsomal levels of NO-P450 adducts increased and peaked at 10 min after incubation and decreased thereafter; it disappeared completely within 60 min. In contrast, microsomal levels of the low-spin ferric form and CO-differential spectrally detectable P450 rapidly decreased during the initial 10 min; the signal intensity for P450 recovered thereafter. Western blot analysis using specific antibodies against CYP3A2 and CYP2C11 isozymes revealed no detectable degradation of these isoforms. Effect of NO on the catalytic activity of the enzymes was also determined by using testosterone as the substrate. The hydroxylation activity in microsomes rapidly decreased during the initial 10 min and disappeared slowly thereafter. These results suggested that NO might form dissociable complexes with the heme moiety of P450 and irreversibly inactivate them. The mechanism for P450 inactivation by NO and the role of NO-P450 interaction in the pathogenesis of liver injury in endotoxemia are discussed.

Animals↗

PubMed1998

[Our initial experience with SMANCS in TAE for liver cancer].

To evaluate the efficacy and adverse reaction of SMANCS, we reviewed 10 cases treated by TAE with SMANCS among 896 cases treated by TAE for liver cancer during the past three years at our institute. Our criteria for using SMANCS were as follows: a) reduced effectiveness of past TAE with Lipiodol, hydrophilic drugs and gelatin sponge; b) sufficient caliber and blood flow in the hepatic artery; and c) good hepatic function. The 1- and 2-year survival rates after treatment with SMANCS were 50% and 25%, respectively. The 3- and 5-year survival rates after initial treatment (first TAE, etc.) were 40% and 20%, respectively. There were no significant complications in clinical course, however, subsequent hepatic arteriogram often showed arterial change that may interfere with further regional therapy for the liver.

Adult↗

PubMed1998

cis-Diamminedichloroplatinum induces peroxisomes as well as CYP4A1 in rat kidney.

Effects of cis-diamminedichloroplatinum (cisplatin) on rat kidney were investigated. Clinical parameters in rat urine and blood were studied. Blood urea nitrogen (BUN) and creatinine in blood and K+ in urine increased, but Na+ in urine decreased. Contents of total P450 and metabolic activities towards lauric acid and arachidonic acid in rat renal microsomes were not changed by cisplatin treatment. The levels of P450 isozymes (CYP4A1, 4A2, 4A8 and 2C23) were determined in rat renal microsomes by immunoblotting. The levels of CYP4A2 and 4A8 which are lauric acid omega-hydroxylases were not changed, but the levels of CYP2C23 and 4A1 were increased significantly by cisplatin treatment. Effects of clofibrate, a typical inducer for CYP4A1, on rat kidney were compared with those of cisplatin. Clofibrate induced palmitoyl CoA oxidase (a marker enzyme of peroxysome), CYP4A1, and CYP4A2 and reduced triglyceride level in plasma. Cisplatin had similar effects to clofibrate and induced peroxysomes as well as CYP4A1, although the effects were at a lesser extent than those of clofibrate. The induction levels of CYP4A1 correlated with increased levels of BUN. The present findings suggest that induction of P450 by cisplatin may take part in the renal injury or nephrotoxicity of cisplatin.

Animals↗

PubMed1998

Isolation and characterization of a novel human pancreas-specific gene, pancpin, that is down-regulated in pancreatic cancer cells.

By means of the differential display method, we isolated a novel human gene that is expressed specifically in pancreas. The cDNA, designated "pancpin," contained an open reading frame of 1,215 nucleotides encoding a 405 amino acid protein, showing a high degree of similarity to serine protease inhibitors belonging to the serpin superfamily. To investigate its possible role in pancreatic carcinogenesis, we looked for genetic alterations of this gene in pancreatic cancer cell lines and primary pancreatic cancer tissues. Expression of pancpin was barely detectable in any of the four pancreatic cancer cell lines examined, and very weak also in 10 of 13 pancreatic cancer tissues. A somatic missense mutation at codon 221 was found in two of 16 primary pancreatic cancers. These findings indicate that down-regulation of pancpin expression may play a significant role in development or progression of pancreatic cancer.

Amino Acid Sequence↗

PubMed1998

[Pre- and/or postoperative adjuvant therapy for hepatocellular carcinoma].

Pre- and/or postoperative adjuvant therapy for hepatocellular carcinoma (HCC) is discussed. There is a high recurrence rate of HCC of up to 50% or more within three years after hepatectomy. More than 80% of those recurrences are in the form of intrahepatic metastases. Therefore it is extremely important to administer successful adjuvant therapy to prevent intrahepatic recurrence. There are two types of intrahepatic recurrence: simple dissemination from the primary focus of HCC; and newly developed HCC in the remnant liver. TAE is one option for preoperative adjuvant therapy to prevent intrahepatic recurrence. Postoperative adjuvant chemotherapy via the hepatic artery has occasionally been administered, but it is not yet established as an effective adjuvant therapy. However, a report by Muto et al showed that retinoid administration can prevent intrahepatic recurrence of newly developed HCC after hepatectomy. On the other hand, adjuvant therapy must not be tooaggressive, because: 1) HCC develops mainly in cirrhotic liver (with poor liver function); and 2) locoregional therapy for intrahepatic recurrence results in good survival rats even after detection of an established recurrence.

Antineoplastic Agents↗

PubMed1998

[A measure to continue intra-arterial infusion chemotherapy long-term for locally advanced pancreatic cancer].

For locally advanced non-resectable cancer of the pancreas, we have routinely performed intra-arterial chemotherapy: Each catheter is placed in the splenic artery and gastroduodenal artery during laparotomy, and a mixture of Methotrexate and Angiotensin-II is infused within 30 minutes. This treatment is repeated weekly at our outpatient clinic as long as possible. However, obstruction of the catheter or corresponding artery is the major cause of interruption of treatment. The present paper reports a case in which intra-arterial chemotherapy was possible by repeated catheterization for the catheter obstruction. A 54-year-old woman with non-resectable pancreatic cancer underwent catheter placement during laparotomy, but they became occluded one month later. Another catheter was placed into the common hepatic artery by the Seldinger method. After this catheter was occluded again, another catheter was placed into the inferior pancreaticoduodenal artery via the superior mesenteric artery by the Seldinger method. By repeating this catheter placement, we succeeded in continuing the intra-arterial chemotherapy, and the patient has remained alive (30 postoperative months) without losing her quality of life.

Angiotensin II↗

PubMed1998

[Adjuvant intra-arterial chemotherapy with gastrin receptor antagonist after hepatic resection in colorectal cancer metastasis].

The aim of this study was to determine whether chemo-endocrine therapy after the resection of liver metastasis from colorectal cancer would prevent recurrence in the remnant liver and prolong survival. Eleven colorectal cancer patients underwent hepatic resection for liver metastasis. Subsequently, they were administered Proglumide gastrin antagonist 1,200 mg/day + 5'-DFUR 800 mg/day for 2 years. In seven of them, MMC 6-10 mg and ADM 20 mg were infused intra-arterially every two weeks alternately for one year. In four of them, 5-FU 250 mg/day was infused for seven days continuously intra-arterially every two weeks for one year. Recurrence in the remnant liver occurred in four of 11 patients. All of these patients underwent repeated hepatectomy. The mean disease-free survival in the remnant liver was 37 months and the five-year survival rate was 91%. These results indicate that intra-arterial chemotherapy with gastrin receptor antagonist might be effective for adjuvant therapy in patients with resectable liver metastasis from colorectal cancer.

Antineoplastic Combined Chemotherapy Protocols↗