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Biomedical subjects

E Kobayashi

Publications and source records attributed to E Kobayashi.

At least 253 records · Page 14Linked to original sources
PubMed1995

Mechanical properties of the binary titanium-zirconium alloys and their potential for biomedical materials.

Mechanical properties of titanium-zirconium binary alloys were investigated in order to reveal their possible use for new biomedical materials and to collect useful data for alloy design through a hardness test, a tensile test, and optical microscopy. The hardness of the alloy containing 50% zirconium was approximately 2.5 times as large as the hardness of pure titanium and pure zirconium. Tensile tests showed a similar tendency. No changes between hardness of as cast specimens and as homogenized specimens were observed, nor were changes in microstructures noted. Comparisons between the Ti-6Al-4V alloy and the Ti-Zr-6Al-4V alloy indicated that a titanium-zirconium alloy could provide a base material for a new biomedical alloy. From these results, it was concluded that new alloys for biomedical materials should be designed as titanium-zirconium base alloys.

Alloys↗
PubMed1995

Molecular genetic basis of renal carcinogenesis in the Eker rat model of tuberous sclerosis (Tsc2).

We have recently identified on rat chromosome 10q a germline mutation in the tuberous sclerosis gene (Tsc2), the gene predisposing to renal carcinoma (RC) in the Eker rat. The homozygous mutant condition is lethal at around the 13th day of fetal life. In heterozygotes, RCs invariably develop in the first year of life. Histologically, RCs develop through multiple stages from early preneoplastic lesions (i.e., phenotypically altered tubules) to adenomas. The wild-type allele mutation has been found even in the earliest preneoplastic lesions, fitting Knudson's two-hit hypothesis and supporting the hypothesis that Tsc2 is a tumor suppressor gene. In this study, homozygous deletion of the Ink4 homologue on rat chromosome 5q was observed in 14 of 24 (58%) RC-derived cell lines. This may represent involvement of a second tumor suppressor gene, contributing to tumor progression. Considering previous results of studies of homozygous deletion of the Ifn alpha gene in five of 24 cases (21%) and the Ifn beta gene in one of 24 cases (4%), the order of the genes may be Ink4-Ifn alpha-Ifn beta. Microsatellite instability was not observed in 26 Eker rat tumors.

Amino Acid Sequence↗
PubMed1995

Orthotopic liver retransplantation in rats.

A surgical experience with a method of rate orthotopic liver retransplantation (OLRT), and a preliminary study of immunological responses after OLRT are reported. OLRT was performed on the same recipient after the fist orthotopic liver transplantation (1st-OLT) according to our original (Kamada's) cuff method. Replacement of the portal vein (PV) and infra-hepatic vena cava (IHVC) cuffs was not technically difficult. However, there were no survivors from the first 6 retransplanted rats, mainly due to complications from defective supra-hepatic vena cava (SHVC) anastomoses. Unlike the human intra-abdominal SHVC, the posterior wall of the intra-abdominal SHVC in rats is too short and fragile to perform an end-to-end anastomosis twice between donor and recipient SHVC. For a second group of seven retransplants, a modification of the SHVC anastomosis was made between donor and recipient SHVC in conjunction with the recipient's cuff diaphragm. This enabled reanastomosis to be secure, resulting in the improved 1-week survival after isogenic OLRT (85.7%). This OLRT model has been applied to the fully allogeneic combination for several immunological studies and led to novel findings. Thus, an experimental model of a rat orthotopic liver retransplant model has the potential to allow more valuable insights into the immunological study of chronic rejection, sensitization and chimerism following liver retransplantation.

Anastomosis, Surgical↗
PubMed1995

Recovery from primary deep cerebral venous sinus thrombosis with recanalisation.

A 50-year-old woman with idiopathic deep cerebral sinus and vein thrombosis (DCVT) had cerebellar disturbance prior to impaired consciousness. CT and MRI revealed haemorrhagic infarction in the cerebellum and signal changes suggesting infarction in the thalamus and basal ganglia bilaterally. The straight sinus and internal cerebral vein (ICV) were dense on CT. On angiography, the vein of Galen (VG) and straight sinus were not seen. Following clinical recovery, CT and MRI became normal, and angiography showed recanalization of the VG and ICV. The relationship between cerebellar infarction and DCVT, and signal changes on CT and MRI are discussed.

Basal Ganglia↗
PubMed1995

Renal carcinogenesis in the Eker rat.

The Eker rat hereditary renal carcinoma is an excellent example of a Mendelian dominant predisposition to a specific cancer in an experimental animal. We recently reported that a germline insertion in the rat homologue of the human tuberous sclerosis (TSC2) gene gives rise to the dominantly inherited cancer in the Eker rat model. The function of the TSC2/Tsc2 gene product (called "tuberine" in the human case) is not yet understood, although it contains a short amino acid sequence homologous to the ras family GTPase-activating proteins (GAP3). In the study, we isolated subtracted cDNA clones having increased expression in Eker renal carcinoma cells, using a modified representational difference analysis method to search for additional genes specifically involved in renal carcinogenesis. Here we identified four genes: the third component of the complement (C3) gene, the fos-related antigen I (fra-1) gene, an unknown gene (designated as being expressed in renal carcinoma: erc) and the calpactine I heavy-chain (Annexin II) gene.

Animals↗
PubMed1995

Cosmids and transcribed sequences from chromosome 11q23.

To obtain cosmid markers and transcribed sequences from a specific chromosome region, a series of radiation-reduced hybrids (RHs) containing various regions of human chromosome 11 was prepared from microcell hybrid A9 (neo11) cells containing a normal human chromosome 11 tagged with pSV2neo at 11p11.2. Among 15 radiation hybrid clones isolated, RH(11)-9 which contains a q23 fragment in addition to the neo integration site, was used for the construction of a cosmid library. Cosmid clones having human DNA sequences were screened, and localized by Southern hybridization with the radiation hybrid panel. Fifty-nine cosmids were assigned to 11q23 and 6 cosmids to 11p11.2. Exon amplification proceeded with 23 of the 59 cosmids and 16 putative exons were cloned. Three of them were identical to those constituting a known gene which locates on q23 (ATDC), and the others were unknown. Thus, the RHs containing various subchromosomal fragments of chromosome 11 were useful for constructing region-specific DNA markers. The RH(11)-9 cells and putative exons also facilitate the positional cloning of genes in the 11q23 region.

Animals↗
PubMed1995

Fulminant second-set allograft rejection and endoscopic findings following small bowel transplantation in the rat.

In the presensitized recipient who has been exposed to donor antigens, second-set rejection takes the form of severe hyperacute graft rejection. Second-set allograft rejection was studied following small bowel transplantation in the rat. Heterotopic intestinal grafting was performed from DA (RT1a) donors to PVG (RT1c) recipients 4 weeks after DA skin sensitization. The endoscopic images and histological specimens were compared with those of syngeneic and first-set rejected grafts. Endoscopically, diffuse erosions of the graft were detected from day 1. Mucosal necrosis progressed rapidly, and was accompanied by massive bleeding on days 3-5. These findings were similar to the course of severe necrotizing hemorrhagic enteritis. Histologically, interstitial edema and hemorrhage with massive infiltrations of neutrophils were manifested from day 1. Mesenteric vessels were completely occluded by thrombi on days 3-5. The grafted intestine had became totally necrotic by day 5. Microscopic findings strongly suggested that destructive graft necrosis was due to vascular damage caused by humoral factors. All the presensitized rats (n = 11) died showing systemic septic signs by day 11 after small bowel transplantation. We conclude that lethal hyperacute rejection occurred in presensitized recipients, even when the graft was transplanted heterotopically. Endoscopic evaluation is beneficial for the early diagnosis of graft rejection. Immediate graft removal should be mandatory as a rescue treatment in second-set rejection of the small intestine.

Animals↗
PubMed1995

Significance of elevated urinary human intestinal alkaline phosphatase in Japanese people exposed to environmental cadmium.

Urinary human intestinal alkaline phosphatase (IAP), beta 2-microglobulin (beta 2-MG) and N-acetyl-beta-D-glucosaminidase (NAG) were analyzed in 40 Japanese environmental-cadmium (Cd)-exposed and 40 non-exposed subjects to evaluate early biological markers for Cd-induced renal damage. All urinary indicators were significantly higher in the Cd-exposed subjects than non-exposed subjects. A fourth-order function was fitted for the relationship between beta 2-MG and IAP or NAG. The beta 2-MG concentration corresponding to the inflexion point for IAP was smaller than that for NAG. This result may support the contention that the cells containing IAP are damaged earlier than those containing NAG, and that IAP is a useful marker for detecting renal tubular dysfunction in people moderately exposed to Cd. However, in the stage of severe renal damage, the combination of IAP and beta 2-MG is considered to be more useful.

Acetylglucosaminidase↗
PubMed1995

Evidence that the elevation of soluble MHC class I antigens in the serum precedes the onset of graft-versus-host disease and is correlated with the severity of the disease in rats.

We examined the changes in the levels of soluble major histocompatibility antigen complex (MHC) class I antigens in the serum under a lethal or nonlethal state of graft-versus-host-disease (GVHD) induced by injecting various doses of PVG rat splenic lymphocytes into (DA x PVG)F1 rats. All rats receiving 4 x 10(8) lymphocytes (lethal dose) died on day 20-36 showing typical features of GVHD, while the injection of 4 x 10(7) cells (nonlethal dose) induced no sign of GVHD. When rats were inoculated with a nonlethal dose of lymphocytes prior to the injection of a lethal dose, all rats survived with or without showing transient GVHD. Preceding the onset of GVHD the levels of soluble class I antigens increased significantly to 1094 +/- 487 ng/ml (mean +/- SD, n = 4) from 3 days after the injection of a lethal dose to the time of death, whilst the levels in the nonlethal dose group remained unchanged. Rats with transient GVHD in the preinoculated group showed the increase of soluble class I antigens to the same extent as rats with lethal GVHD, suggesting that GVHD was systemically ongoing. The levels of soluble class I antigens also correlated with the severity of GVHD as judged by daily observation and histological studies. Rats receiving a lethal dose showed destructive alteration of spleen structure and cellular infiltration in the portal area of the liver before the animals started to show signs of GVHD, whereas rats in the nonlethal dose group exhibited no marked change. These data suggest the possibility of serum soluble class I antigens being not only a diagnostic but also a prognostic marker for GVHD.

Animals↗
PubMed1995

Isolation of a 40 kDa immunoinhibitory protein induced by rat liver transplantation.

In certain combinations of donor and recipient rat strains, such as DA (RT1a) donors into PVG (RT1c) recipients, rejection after orthotopic liver transplantation (OLT) is overcome without immunosuppressive drugs, although other organs transplanted between these combinations are promptly rejected. The mechanisms involved in achieving drug-free liver allograft tolerance still remain poorly understood. In the present study, OLT (DA into PVG) serum from various postoperative times was analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis and two unique proteins of 40 kDa and 37 kDa were found to be in large concentrations in 60 day post-OLT serum. These proteins could only be detected at specific times after OLT in the DA into PVG combination and could not be detected in the serum of syngenically transplanted animals (DA into DA) and (PVG into PVG), rejector combinations (DA into LEW) requiring immunosuppressive treatment or induced by other organ transplants. When these proteins were purified and sequenced they were found to have an identical N-terminal sequence which is not listed in sequence databases. Mixed lymphocyte assays revealed that only the 40 kDa protein has a immunosuppressive capability which additionally appears to be donor specific. The 40 kDa protein will aid further in the understanding of how drug-free tolerance is attained in certain liver allografts and may also act as a marker of when treatment with conventional immunosuppressive drugs can be stopped in clinical OLT providing a homologue of the molecule can be found. This possibility appears likely as case reports already exist of patients who have successfully been able to cease treatment with such drugs.

Amino Acid Sequence↗
PubMed1995

A germline insertion in the tuberous sclerosis (Tsc2) gene gives rise to the Eker rat model of dominantly inherited cancer.

The Eker rat hereditary renal carcinoma (RC) is an excellent example of a mendelian dominant predisposition to a specific cancer in an experimental animal. We have previously established a new conserved linkage group on rat chromosome 10q and human chromosome 16p13.3, and shown that the Eker mutation is tightly linked to the tuberous sclerosis (Tsc2) gene. We now describe a germline mutation in the gene encoding Tsc2 caused by the insertion of an approximately 5 kilobase DNA fragment in the Eker rat, resulting in aberrant RNA expression from the mutant allele. The phenotype of tuberous sclerosis in humans differs from that of the Eker rat, except for the occurrence of renal tumours. The Eker rat may therefore provide insights into species-specific differences in tumourigenesis and/or phenotype-specific mutations.

Amino Acid Sequence↗
PubMed1995

Initiation of hepatocarcinogenesis by endogenously formed N-nitrosobis(2-hydroxypropyl)amine, N-nitrosodiethanolamine and N-nitroso-2,6-dimethylmorpholine in rats.

Initiation activities of endogenously formed N-nitrosobis(2-hydroxypropyl)amine (NBHPA), N-nitrosodiethanolamine (NDELA) and N-nitroso-2,6-dimethylmorpholine (NDMM) were investigated in a modified short-term assay for rat hepatocarcinogenesis. Male Wistar rats were fed 1% bis(2-hydroxypropyl)amine, 0.5% diethanolamine or 0.25% 2,6-dimethylmorpholine in the diet plus 0.3% sodium nitrite in the drinking water. Two weeks after starting the experimental regimen they underwent 2/3 partial hepatectomy and were then maintained on the respective diets for a further week. Following a 2 week recovery period on basal diet rats were subjected to a resistant hepatocyte regimen consisting of 0.02% 2-acetylaminofluorene in the diet for 2 weeks and 1 mg carbon tetrachloride/kg body wt by gavage at the midpoint. Initiation activity was assayed by measuring hepatic foci positive for gamma-glutamyltranspeptidase. Numbers of such foci per cm2 were significantly increased in the groups given the secondary amines together with nitrite compared with values for groups given each precursor or nitrite alone. Further, the numbers of lesions were essentially similar to those found in rats given carcinogenic doses of NBHPA, NDELA and NDMM. The results clearly of demonstrate hepatocyte initiation activities of endogenously formed carcinogens, presumably NBHPA, NDELA and NDMM.

Animals↗
PubMed1995

Inhibitory effects of sulfation inhibitors on initiation of pancreatic ductal carcinogenesis by N-nitrosobis(2-oxopropyl)amine in hamsters.

The effects of dehydroepiandrosterone sulfate (DHAS), a typical hydroxysteroid sulfotransferase (HSTase) inhibitor, and of 3'-phosphoadenosine 5'-phosphate (PAP), a nonspecific sulfation inhibitor on N-nitrosobis(2-oxopropyl)-amine (BOP)-induced initiation were examined in a rapid production model for pancreatic carcinomas in hamsters in order to elucidate the involvement of sulfotransferase in the metabolic activation of beta-oxypropylnitrosamines. While neither low nor high doses of DHAS and PAP exerted any significant influence on the incidence of ductal lesions including carcinomas, the high dose of DHAS (350 mg/kg body wt) and a both low (90 mg/kg) and high (180 mg/kg) doses of PAP reduced the mean numbers of pancreatic ductal adenocarcinomas. The high dose of PAP also reduced the number of all ductal lesions combined. The results thus suggest that metabolic activation with STase is involved in BOP-induced pancreatic ductal carcinogenesis in hamsters, and support the hypothesis that BOP is metabolized to beta-hydroxyalkylnitrosamines followed by activation to proximate sulfuric acid esters by HSTase.

Animals↗
PubMed1995

Cloning of the rat homologue of the von Hippel-Lindau tumor suppressor gene and its non-somatic mutation in rat renal cell carcinomas.

Recently, von Hippel-Lindau (VHL) gene mutations were detected in non-inherited, sporadic human renal cell carcinomas (RCs) at a high frequency. In order to determine whether or not the VHL gene is also a critical gene in rat RCs, we cloned and sequenced the rat homologue of human VHL gene and searched for mutations of the VHL gene in rat RCs. Mutations in the VHL gene were not detected in spontaneous RCs of the Eker rat model or in ferric nitrilotriacetate-induced rat RCs using the polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) method. These data indicate that mutation of the VHL tumor suppressor gene is not an event in rat renal carcinogenesis, at least in our present systems.

Amino Acid Sequence↗
PubMed1995

Allelic loss at the tuberous sclerosis (Tsc2) gene locus in spontaneous uterine leiomyosarcomas and pituitary adenomas in the Eker rat model.

Hereditary renal carcinomas (RCs) develop in virtually all Eker rats by the age of one year. Investigation of extra-renal primary tumors co-occurring in Eker rats late in life (at 2 years) additionally revealed enhanced development of hemangiosarcomas of the spleen, uterine leiomyosarcomas and pituitary adenomas, although the demonstrated predilection for these extra-renal tumors was not as complete as with RCs. We identified the germline mutated tuberous sclerosis (Tsc2) gene as the predisposing Eker gene and revealed the tumor suppressor nature of Tsc2 gene function in renal carcinogenesis. In the present study, we examined allelic loss at the Tsc2 gene locus in uterine leiomyosarcomas and pituitary adenomas developing in hybrid F1 rats carrying the Eker mutation as well as in pituitary adenomas from non-carrier rats. We detected loss of heterozygosity in 4 of 11 uterine leiomyosarcomas (36%) and 11 of 31 pituitary adenomas (35%) from Eker rats but in none of 9 pituitary adenomas from non-carrier rats (P < 0.05), suggesting that inactivation of the Tsc2 gene is also a critical event in the pathogenesis of these extra-renal tumors. Our present data indicate that there might be different pathways for tumorigenesis of pituitary adenomas between Eker and

Adenoma↗
PubMed1995

Prevention by methionine of enhancement of hepatocarcinogenesis by coadministration of a choline-deficient L-amino acid-defined diet and ethionine in rats.

The effects of methionine on hepatocarcinogenesis induced by coadministration of a choline-deficient L-amino acid-defined (CDAA) diet and ethionine were examined. F344 male rats were divided into 4 experimental groups. Groups 1 and 2 received the CDAA diet and a choline-supplemented L-amino acid-defined (CSAA)++ diet, respectively. Group 3 received the CDAA diet containing 0.05% ethionine, and group 4 the CDAA diet containing 0.05% ethionine and 0.47% methionine. Animals were killed after 12 weeks of treatment. Histologically, the CDAA diet induced intracellular fat accumulation and foci. In contrast, ethionine caused not only foci, but also hyperplastic nodules, cholangiofibrosis and the proliferation of oval cells without such fat accumulation. Methionine abolished the development of all of the liver lesions induced by coadministration of the CDAA diet and ethionine. To investigate the effects of methionine on induction of c-myc and c-Ha-ras expression, as well as generation of 8-hydroxyguanine (8-OHGua) and 2-thiobarbituric acid-reacting substances (TBARS), by coadministration of the CDAA diet and ethionine, subgroups of 3 to 5 animals were killed at 2, 4, 8, or 11 days after the beginning of the experiment. Coadministration of the CDAA diet and ethionine markedly enhanced the level of expression of c-myc and c-Ha-ras, 8-OHGua formation and TBARS generation as compared with the CDAA or CSAA diet within 11 days, and methionine blocks these actions. These results indicate that addition of methionine prevents the induction of c-myc and c-Ha-ras expression, 8-OHGua formation and TBARS generation, as well as hepatocellular lesions, by coadministration of the CDAA diet and ethionine in rats, and suggest a possible involvement of oxidative stress and gene expression in hepatocarcinogenesis by these agents.

Amino Acids↗