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Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 703 records · Page 39Linked to original sources
PubMed1994

Limited diffusibility of gene products directed by a single nucleus in the cytoplasm of multinucleated myofibres.

Two types of beta-galactosidase genes, whose products are distributed in the nucleus (N beta-gal) or cytoplasm (C beta-gal), were injected with fructose intramuscularly into the quadriceps of adult mice. Regionally restricted and overlapped distributions of both gene products were observed in the myofibres. These findings indicate that N beta-gal is incorporated into the nucleus responsible for its synthesis and that C beta-gal becomes located in the vicinity of the nucleus after its synthesis. This restricted location of C beta-gal in myofibres remained unchanged during the development of infant mouse muscle. Thus, the gene products directed by the nucleus of myofibres seem to show limited diffusibility, suggesting a universal localization of subcellular domains in myofibres.

Animals↗
PubMed1994

On hypervariability at the reactive center of proteolytic enzymes and their inhibitors.

The pattern of synonymous and nonsynonymous substitutions at the reactive center of proteases (kallikrein) and their inhibitors (alpha 1-antitrypsin and serpin) was examined. In the case of alpha 1-antitrypsin, the proportion of different nonsynonymous sites exceeds that of different synonymous sites at the reactive center for sequence pairs of recent duplication. The result indicates that the positive selection has operated after duplication to increase functional diversity. In the cases of kallikrein, serpin, and remote sequence pairs of alpha 1-antitrypsin, the proportion of different synonymous sites at the reactive center exceeds that of different synonymous sites at the remaining region. The result indicates that gene conversion followed by natural selection is working. On the whole, it is concluded that hypervariability of amino acids at the reactive center is generated by an interaction among natural selection, random genetic drift, point mutation, and gene conversion. Gene duplication may provide potential for them to interact.

Animals↗
PubMed1994

Fermentation conditions for efficient production of thermophilic protease in Escherichia coli harboring a plasmid.

Escherichia coli TG1, transformed with an expression plasmid pAQN carrying the aqualysin I (AQI) gene derived from Thermus aquaticus YT-1 under the control of the tac promoter, was cultivated under various conditions in order to find fermentation conditions for the efficient production of the thermophilic protease, AQI. The amount of AQI produced was closely related to the growth phase at the time of isopropyl-beta-D-thiogalactopyranoside (IPTG) induction, and the highest production was obtained when it was added during the exponential growth phase. The addition of yeast extract had a greater effect on AQI production than did Polypeptone or casamino acids, and AQI productivity increased from 1.1 x 10(3) kU/g to 2.7 x 10(3) kU/g cells when 2 g/l yeast extract was supplied. Furthermore, the specific growth rate improved from 0.35 h-1 to 0.89 h-1 when 5 g/l yeast extract was supplied. The culture temperature also affected AQI gene expression. When the temperature was shifted from 37 degrees C to 34 degrees C at the time of IPTG induction, 19 kU/ml enzymatically active AQI was obtained, corresponding to a 28% increase over the amount produced in a batch culture without a shift. This is about a 44-fold higher yield than was obtained from the original strain, T. aquaticus YT-1.

Biotechnology↗
PubMed1994

Expression of transforming growth factor-alpha and its receptor during human liver development and maturation.

We investigated the expression of transforming growth factor-alpha (TGF-alpha) and its receptor during human liver development and maturation, using immunohistochemistry. In the fetal liver, strong immunoreactivity for TGF-alpha and its receptor was noted in intrahepatic bile duct cells of various developmental stages; moderate immunoreactivity for TGF-alpha and mild immunoreactivity for TGF-alpha receptor were found in immature hepatocytes. In the postnatal liver, reactivity for TGF-alpha in hepatocytes decreased gradually and was negative or only weakly positive in the adult liver, while reactivity for TGF-alpha receptor in hepatocytes increased gradually and was strongly positive in the adult liver. In contrast, immunoreactivity of TGF-alpha and its receptor in intrahepatic bile duct cells persisted in the postnatal liver and was positive in the adult liver. These data suggest that the system of TGF-alpha and its receptor has an important role in the proliferation and differentiation of intrahepatic biliary cells and hepatocytes in the fetal liver. The decreasing expression of TGF-alpha in hepatocytes in the postnatal liver may indicate that proliferative activity of hepatocytes gradually decreases with liver maturation. The presence of TGF-alpha and its receptor in intrahepatic bile ducts in the postnatal liver suggests that the system of TGF-alpha and TGF-alpha receptor is operative postnatally.

Adolescent↗
PubMed1994

Chemical induction of quadruple and octuple chromosomes in Chinese hamster CHO-K1 cells and relationship between their three-dimensional structure and spatial distribution of BrdU-labeled chromatids.

Double endoreduplication of Chinese hamster CHO-K1 cells that exhibited quadruple chromosomes at metaphase was induced by a combination of rotenone and ammonium vanadate treatments. Analysis of sister chromatid differential staining patterns (using 5-bromo-2'-deoxyuridine) revealed that approximately 50% of the quadruple chromosomes did not keep the scheme of "outside replication" of DNA. Based on the ratio of the staining patterns observed, we suggest that the two diplochromosomes forming a quadruple chromosome are held together by a physical link connecting the two original chromatids. Metaphases with octuple chromosomes were also produced by the same treatment. Each chromosome constituting an octuple chromosome was longer and thinner than ordinary metaphase chromosomes. This suggests incomplete chromosome condensation at metaphase. The majority of octuple chromosomes showed the eight constituent chromosomes to be so enmeshed that a planar alignment could not be observed in air-dried preparations.

Aneuploidy↗
PubMed1994

Exostosis of the posterior clinoid process.

We report an unusual case of exostosis arising from the lateral aspect of the posterior clinoid process. Its presence should be considered in approaching the parasellar regions.

Arteries↗
PubMed1994

Recurrence of intrahepatic stones after an end-to-side choledochojejunostomy.

The risk factors for the recurrence of intrahepatic stones after an end-to-side choledochojejunostomy were investigated, along with the outcome following the treatment of such stones. Thirty-two patients with intrahepatic stones underwent an end-to-side choledochojejunostomy, and a complete lithotomy was achieved in 26 of them. The follow-up which ranged from 5-19 years after surgery revealed that eight patients developed a recurrence of intrahepatic stones, and their clinical and cholangiographic findings were thus reviewed. Recurrent stones were associated with onset of symptoms at a younger age and were predominantly located in the intrahepatic bile ducts. Recurrence was also associated with severe intrahepatic bile duct dilatation. Six of the eight patients developed recurrent stones more than 5 years after a complete lithotomy. One of these patients died of liver cirrhosis while two died of acute obstructive suppurative cholangitis. Five patients underwent cholangioscopic lithotomy through the jejunostomy for their recurrent stones, and a complete lithotomy was accomplished in three of them. These findings indicate the necessity of performing a hepatectomy in such patients whenever possible, and also emphasize the need for a long-term follow-up after a complete lithotomy with an end-to-side choledochojejunostomy. In addition, any recurrent stones should be treated promptly by a cholangioscopic lithotomy through a jejunostomy.

Adult↗
PubMed1994

Pancreatic resection for periampullary carcinoma in the elderly.

The effect of pancreatic resection for periampullary carcinoma in the elderly was studied by comparing the pre- and perioperative factors affecting survival in 102 patients less than 70 years of age (group A) with those in 28 patients 70 years and older (group B). Concomitant cardiac and pulmonary diseases were significantly more frequent in group B (P < 0.05), but the difference in routine laboratory data was not significant. The overall operative mortality was 7% (7/102) in group A and 18% (5/28) in group B, while the actuarial 5-year survival rates were 31% in group A and 23% in group B, these differences not being significant. A multivariate analysis using a logistic model showed that blood loss was the greatest risk factor for early postoperative death in the elderly patients, whereas anastomotic dehiscence and postoperative bleeding were significant factors in the younger patients. Thus, we conclude that age is not a contraindication to pancreaticoduodenectomy which offers the only hope for long-term survival in patients with periampullary carcinoma; however, meticulous dissection to minimize blood loss is especially important in elderly patients.

Actuarial Analysis↗
PubMed1994

Three-dimensional studies on the structure of the tissue surrounding the superior mesenteric artery.

The anatomy and topography of tissue surrounding the superior mesenteric artery were examined histopathologically, and the structure surrounding the superior mesenteric artery (SMA) was reconstructed with data from histologic examination and three-dimensional analyses. Specimens were obtained from three autopsy cases without abnormalities, two surgically resected cases of cancer of the pancreatic head, and one autopsy case of cancer of the pancreatic head. The endothelium or basal membrane of blood and lymph vessels were identified immunohistochemically, and the distribution of lymph nodes, blood vessels, lymph vessels, and collagen fibers was determined. The superior mesenteric plexus was found to be a relatively dense structure with a thickness of about 2 mm, composed of collagen fibers and connective tissue, which concentrically enveloped the small arteries, the superior mesenteric artery, nerve bundles, and capillaries. Lymph vessels larger than a few micrometers in diameter were often found outside of the plexus, and this plexus contained no lymph nodes in any sections. The three-dimensional study of the modes of spread along the superior mesenteric artery of pancreatic cancer revealed two types of spread: the tumor extends mainly by neural invasion, and the tumor extends mainly by lymph node metastases. These morphologic features suggest that lymphatic flow in the vicinity of the superior mesenteric artery passes primarily outside of the plexus, and complete excision of lymph nodes close to the superior mesenteric artery with preservation of the superior mesenteric plexus is feasible if there is no neural invasion into retropancreatic tissues.

Biomarkers↗
PubMed1994

Superficial-type adenomas and adenocarcinomas of the colon and rectum: a comparative morphological study.

BACKGROUND/AIMS: It has been uncertain whether colorectal carcinomas preferentially arise on preexisting adenomas or de novo. However, from a morphological viewpoint, it seems unlikely that pedunculated or exophytic malignant polyps progress to the deeply ulcerated advanced carcinomas usually found clinically. METHODS: The morphological features of 26 nonpolypoid, superficial-type colorectal tumors (17 adenomas and 9 adenocarcinomas) were compared to clarify the developmental route of colorectal carcinomas. RESULTS: The adenomas and adenocarcinomas were very similar in size and gross appearance; however, examination of the surface appearances of unsectioned tumors by dissecting microscopy was helpful for distinguishing the two. Histologically, no adenomatous tissue was found in any case of superficial-type adenocarcinoma. Five of the nine adenocarcinomas, even including those of small size, invaded the submucosal layer, and two showed lymph node metastasis. CONCLUSIONS: These findings suggest that superficial-type adenocarcinomas show rapid growth and aggressive behavior. We suggest that this type of carcinoma may not progress by the adenoma-to-carcinoma pathway but that it may arise from a very small superficial-type adenoma.

Adenocarcinoma↗
PubMed1994

Giant neurinoma occupying the holocervical and upper thoracic regions: case report.

We report a case with a giant spinal neurinoma located between the foramen magnum and fifth thoracic levels. The patient did not develop any neurologic symptoms until 16 years after the onset of hydrocephalus. The latter, successfully treated with a ventriculoperitoneal shunt, was associated with a cerebrospinal fluid protein of 400 mg/dL and was in all probability the first sign of the spinal cord tumor.

Aged↗
PubMed1994

Rapid inactivation of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), a potent mutagen in chlorinated drinking water, by sulfhydryl compounds.

The mutagenic activity of 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), which is formed during chlorination of drinking water, was effectively inhibited by sulfhydryl compounds such as cysteine, cysteamine, glutathione, dithiothreitol and 2-mercaptoethanol. Preincubation of 0.5 micrograms MX with 15 micrograms cysteine (molar ratio 1:37) in a phosphate buffer (pH 6.0-8.0) at 37 degrees C for 15 min prior to exposure of bacterial cells depleted the mutagenic activity of MX. Together with the result showing a change in the UV spectra, it is suggested that sulfhydryl compounds inactivate MX by direct chemical interaction before MX induces DNA damage. On the other hand, a variety of antioxidants other than the sulfhydryl compounds showed no inhibitory effects. Investigation using structural analogs of cysteine revealed that the thiol moiety was indispensable for antimutagenic activity and the amino moiety appeared to enhance the MX-inactivating reaction of the SH group.

Antimutagenic Agents↗
PubMed1994

Recommendations for the performance of bacterial mutation assays.

At the International Workshop on the Standardisation of Genotoxicity Test Procedures, in Melbourne (27-28 February 1993), the current international guidelines for the correct conduct of bacterial mutation assays were considered, and the major differences between them were examined. An attempt was made to construct a scientifically based, internationally harmonized protocol. The main points of agreement were as follows. The consensus opinion was that there are currently insufficient data to justify a preference for either the preincubation or plate-incorporation methodologies as the initial test. Whichever method is used there was consensus agreement that the bacterial test battery should consist of S. typhimurium TA1537, TA1535, TA98 and TA100. There was also consensus that the 3 strains TA97a, TA97 and TA1537 could be used interchangeably. Although it was not possible to achieve a consensus, the majority of the working group members agreed that strains for the detection of mutagens acting specifically on AT base pairs should be routinely included within the test battery. These strains may be S. typhimurium TA102 or E. coli WP2 strains (WP2 pKM101 and WP2 uvrA or WP2 uvrA pkM101). With regard to study design it was universally agreed that 5 doses of test compound should be used in each experiment, and a majority agreement was obtained for 3 plates per dose. The use of 2 plates per dose is acceptable ONLY if the experiment is repeated. It is recommended that the negative controls may consist of solvent control alone provided that historical data are available to demonstrate lack of effect of the solvent in question. Positive control compounds should be included in all experiments, although the nature of these control compounds need not be specified in the guidelines. There was consensus agreement that for non-toxic freely soluble test agents, an upper limit of 5 mg/plate should be tested (5 microliters per plate for liquids). For insoluble or toxic compounds, the recommendations were the same as those for other in vitro tests (see appropriate paper). A consensus agreement was reached on the need to carry out further tests if equivocal results are obtained in the initial test, although it was generally agreed that the design of the repeat study should be left flexible. As there are little or no data to support the use of an exact repeat assay, a majority of the group recommended that negative results in the first test should be further investigated by either conducting a modified repeat (e.g. S9 titration) or by conducting the alternative methodology.(ABSTRACT TRUNCATED AT 400 WORDS)

Biotransformation↗
PubMed1994

Vasoactive intestinal peptide released by acetylcholine in the dog ileum.

Release of vasoactive intestinal peptide (VIP) in response to acetylcholine (ACh) was characterized in the dog ileum using cholinergic antagonists. In blood-perfused ileum, ACh (2-200 nmol/min) produced a dose-dependent increase in venous VIP output, which was slightly reduced by hexamethonium (10 nmol/min) and blocked by hexamethonium and atropine (10 nmol/min) in combination. In isolated ileal tissues containing the submucous or myenteric plexus, excess KCl (75 mM), veratridine (0.1 mM) and ACh (0.1 mM) evoked the release of VIP. ACh-induced VIP output was decreased slightly by hexamethonium (0.1 mM), and blocked by atropine (0.1 mM) or pirenzepine (0.1 mM). Dimethylphenylpiperazinium (0.1 mM) also caused a small increase in VIP output sensitive to hexamethonium in the ileal tissues containing either the submucous or myenteric plexus. It is concluded that ACh evokes the release of VIP from VIP-containing neurons of the submucous and myenteric plexuses in the dog ileum mainly through the activation of M1 muscarinic receptors.

Acetylcholine↗
PubMed1994

Effects of the umuDC, mucAB, and samAB operons on the mutational specificity of chemical mutagenesis in Escherichia coli: I. Frameshift mutagenesis.

The specificity of frameshift mutations induced by several classes of chemical mutagens was determined using a collection of mutant E. coli lacZ genes. This collection can detect each of five kinds of specific frameshift events by scoring Lac+ revertant colonies. In addition, the mutational spectra were characterized in backgrounds carrying plasmids that encode the umuDC, mucAB, or samAB operon. 4-Nitroquinoline 1-oxide (4-NQO) and furylfuramide (AF-2) induced efficiently -1G, -2(C-G), and +1A frameshift mutations. 4-NQO and AF-2 differed in the ability for the induction of -1A and +1G frameshifts. +1A and -1A frameshift mutations induced by 4-NQO or AF-2 were enhanced by the introduction of the mucAB plasmid, and, to a lesser extent, the umuDC plasmid. The enhancing effect of the umuDC or mucAB plasmid on -1G and -2(C-G) frameshifts was weak or else not observed. 9-Aminoacridine was a potent inducer of +1G, -1G and -1A frameshifts, whereas ICR-191 induced all types of frameshift mutations. A mutation enhancing effect was observed only on ICR-191-induced +1A frameshift mutations by the introduction of the mucAB plasmid. Mitomycin C caused no appreciable induction of frameshift mutations to the tester strains without plasmid. However, all types of frameshifts, except -1G, were induced in the strains carrying the mucAB plasmid. N-methyl-N'-nitro-N-nitrosoguanidine induced all types of frameshift mutations. The mucAB plasmid enhanced mutagenesis in strains designed to detect the addition or loss of A.T base pair, indicating that the formation of +1A and -1A frameshifts was partly dependent on an error-prone SOS repair. Any frameshift mutagenesis was not affected by the samAB plasmid. In general, frameshifts in adenine runs were enhanced more preferentially by the mucAB and umuDC plasmids than frameshifts at runs of guanine were.

4-Nitroquinoline-1-oxide↗
PubMed1994

Effects of the umuDC, mucAB, and samAB operons on the mutational specificity of chemical mutagenesis in Escherichia coli: II. Base substitution mutagenesis.

Mutational spectra induced by different classes of chemical mutagens including two ultraviolet-mimetic mutagens, an alkylating agent, intercalators, a crosslinking agent, and base analogs were characterized by means of a set of mutant lacZ genes in E. coli. These strains can be used to detect each of two types of transition and four types of transversion, simply by measuring the number of Lac+ revertant colonies. 4-Nitroquinoline 1-oxide induced G.C-->A.T, G.C-->C.G, or G.C-->T.A changes almost equally, whereas furylfuramide and mitomycin C induced only G.C-->A.T transitions and G.C-->T.A transversions, respectively. No base substitutional mutations were detected by the treatment with 9-aminoacridine. A weak stimulation of G.C-->A.T transitions by ICR-191 was observed. Both the G.C-->A.T and A.T-->G.C transitions were induced by N-methyl-N'-nitro-N-nitrosoguanidine and N4-aminocytidine. 5-Azacytidine was a specific inducer of G.C-->C.G transversions. In addition, a comparative study of mutational specificity was performed in the strains bearing either the umuDC, mucAB, or the samAB operon on a multicopy plasmid. Regardless of the kind of mutagen, G.C-->T.A transversions were greatly potentiated by the introduction of plasmids in the order of pGW1700 (mucAB) > pSE117 (umuDC) > or = pYG8011 (samAB). Besides G.C-->T.A transversions, the introduction of pGW1700, but not pSE117 and pYG8011, enhanced the mutations of A.T-->C.G and A.T-->T.A transversions. The mucAB plasmid also enhanced the G.C-->A.T transitions and G.C-->C.G transversions induced by some mutagens.

Aminacrine↗
PubMed1994

Pancreatic trypsinogen and cathepsin B in human pancreatic carcinomas and associated metastatic lesions.

Expression of pancreatic trypsinogen and cathepsin B in 23 surgically resected pancreatic ductal adenocarcinomas was evaluated immunohistochemically, using a monoclonal antibody against human pancreatic trypsinogen and a polyclonal antibody against human cathepsin B. Fifteen of 20 invasive tubular adenocarcinomas (75%) expressed pancreatic trypsinogen in a coarse granular pattern located in the supranuclear cytoplasm of the carcinoma cells. In addition, metastatic lesions, including those in peripancreatic lymph nodes and neural plexuses, expressed pancreatic trypsinogen. In contrast, three intraductal (non-invasive) papillary adenocarcinomas did not express pancreatic trypsinogen. Cathepsin B expression was recognised in 14 of 20 invasive tubular adenocarcinomas (70%) in a fine granular pattern located diffusely in the cytoplasm of the carcinoma cells, while none of the three intraductal papillary adenocarcinomas had detectable cathepsin B. These findings suggest that pancreatic invasive ductal adenocarcinomas express pancreatic trypsinogen and cathepsin B immunoreactive peptides, raising the possibility that pancreatic trypsinogen and cathepsin B may act independently of each other in the process of carcinoma invasion and metastasis, like other different classes of proteases involved in the proteolytic modification of the matrix barrier.

Adult↗