Biomedical subjects

T Ohta

Publications and source records attributed to T Ohta.

At least 901 records · Page 50Linked to original sources

PubMed1992

Isolation of 2 novel RFLP markers and their localization at 2q35 by microdissection and subsequent enzymatic amplification.

We previously constructed a chromosome 2q-specific genomic library and isolated a number of microclones. In the present study, we first analyzed with Southern hybridization whether any of the microclones represent restriction fragment length polymorphisms (RFLPs), and then tried to map RFLP markers physically, using the recently developed chromosome microdissection/enzymatic amplification method. Of 13 clones analyzed, two were RFLP markers; a clone, pM2C83, showed a four-allele MspI RFLP, and the other, pM2C8, a two-allele RsaI RFLP. In order to assign the two polymorphic markers, two chromosomal segments, 2q32-q35 and 2q35-qter, on the chromosome 2 from a karyotypically normal person were microdissected, and the DNA from each segment was amplified with the polymerase chain reaction (PCR) using marker sequence-specific primers. With this method, both of the clones were assigned to 2q35. These two RFLP markers must be useful for linkage analysis of genetic diseases whose loci are at around 2q35.

Base Sequence↗

PubMed1992

Effect of SMS 201-995 on exocrine pancreatic secretion in a patient with external pancreatic fistula.

The effect of SMS 201-995 on pancreatic exocrine function was studied. The SMS 201-995 was administered to a patient with an artificial external pancreatic fistula following pancreaticoduodenectomy. Variations in pancreatic exocrine function were assessed by determining the volume and components of the fistula fluid during the following periods: 5 d prior to SMS 201-995 administration, for 5 d during actual administration, and for 5 d after it had been discontinued. The SMS 201-995 was administered by subcutaneous injection of 100 micrograms every 12 h for the first 2 d and then 100 micrograms every 6 h for 3 d. This experiment demonstrated that SMS 201-995 has a strong inhibitory effect on pancreatic exocrine function, markedly reducing the amount of fistula fluid and the production of amylase, total protein, and bicarbonate.

Female↗

PubMed1992

Argyrophilic nucleolar organizer region counts in exocrine pancreatic tumors.

We enumerated the number of Ag-NORs in normal pancreatic ducts and exocrine pancreatic tumors to assess their cellular activity. Our results indicate that the mean number of Ag-NOR counts increased stepwise in the following order: normal pancreatic duct (1.26), serous cystadenoma (1.27), mucinous cystadenoma (1.65), mucinous cystadenocarcinoma (2.29), noninvasive intraductal variant of mucin-producing papillary adenocarcinoma (3.16), and a common type of invasive duct cell adenocarcinoma (3.78). These results suggest that cellular proliferative activity is low in normal pancreatic ducts and serous cystadenoma, intermediate in mucinous cystadenoma, and high in mucinous cystadenocarcinoma and duct cell adenocarcinoma. In addition, mucinous cystadenocarcinoma has significantly lower Ag-NOR counts than duct cell adenocarcinoma. We conclude that a clear quantitative difference between the Ag-NOR content of tumor cells of serous cystadenoma, mucinous cystadenoma, mucinous cystadenocarcinoma, and duct cell adenocarcinoma reflects the underlying different biologic behavior (chiefly, grade of malignancy) of these lesions.

Carcinoma, Intraductal, Noninfiltrating↗

PubMed1992

Enhancing effects of heterocyclic amines and beta-carbolines on the induction of chromosome aberrations in cultured mammalian cells.

The effects of post-treatment with heterocyclic amines and beta-carbolines on the induction of chromosome aberrations were studied in Chinese hamster CHO K-1 cells and SV40-transformed excision repair-deficient human XP2OSSV cells. The number of chromosome aberrations induced by UV and MMC were increased by post-treatment with Trp-P-1 and Trp-P-2, in both the presence and the absence of S9 mix. A alpha C, MeA alpha C, Glu-P-1, Glu-P-2, IQ, MeIQ, harman and harmine increased chromosome aberrations only in the presence of S9 mix. Glu-P-2, IQ, MeIQ, harman, and harmine did not induce chromosome aberrations by themselves at the concentrations used in this study. Trp-P-1, Trp-P-2, A alpha C, MeA alpha C and Glu-P-1 were weak clastogens by themselves, but at much higher concentrations than those at which they increased the induction of chromosome aberrations in cells pretreated with UV or MMC. Therefore, the increases in chromosome aberrations were not considered to be additive.

Amines↗

PubMed1992

Daily activity and persistent sleep-wake schedule disorders.

1. Patients with disorders of entrainment to external time cues such as delayed sleep phase syndrome (DSPS) and non-24-hour sleep-wake syndrome (HNS) were treated with non-pharmacological interventions and/or pharmacological agents. 2. Resetting the circadian clock with chronotherapy was easy in all DSPS patients, but it was not as easy to maintain the reset rhythm without additional therapy. Triazolam was effective in treating the phase delay that reappeared after chronotherapy. 3. Vitamin B12 (methylcobalamin) was strikingly effective in some patients with DSPS or HNS. 4. All the adolescent patients who complained of inability to attend school finally returned to their classes after treatment. Maintaining the reset rhythm in adolescent patients was easier than in adults.

Adolescent↗

PubMed1992

Microdissection of human chromosomal regions 8q23.3-q24.11 and 2q33-qter: construction of DNA libraries and isolation of their clones.

Human chromosomal regions 8q23.3-q24.11 and 2q33-qter were microdissected, DNAs from the regions were amplified with the primer-linker method of polymerase chain reaction (PCR), and their DNA libraries were constructed by cloning into pUC19. The primer-linker PCR involved Sau3AI digestion of microdissected chromosomal DNAs, ligation of the digests to a 10mer DNA linker and 24mer primer, filling the recessed 3' ends, and PCR amplification using the 24mer DNA as a primer. A total of 3.5 x 10(4) pUC19 recombinants (8q library) from the 8q region and 5.0 x 10(4) pUC clones (2q library) from the 2q region were obtained. From the 8q library, 60 pUC clones were selected, while 88 pUC-clones were selected from the 2q library. These clones were Southern blot analyzed on hybrid cell panels with or without human chromosome 8 or 2. Twelve (20%) of the 60 8q-derived clones were unique DNA sequences, and 9 were subjected to deletion analysis in the genomic DNA of two patients, one with trichorhino-phalangeal syndrome (TRPS) type I and the other with TRPS type II, both with del(8) (q23.3q24.13). Five of the 9 pUC clones tested showed a one-copy density in both patients, an indication that the clones map to the region deleted in both patients. Screening a genomic DNA library constructed in the phage revealed a clone with a 9.4-kb insert and a one-copy density in both patients. From the 2q library, 15 (17%) of the 88 pUC clones obtained were unique sequences. When a phage library was screened, 8 clones were obtained: 4 were identical and 2 were overlapping sequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Abnormalities, Multiple↗

PubMed1992

A statistical examination of hypervariability in complementarity-determining regions of immunoglobulins.

To determine the relative importance of gene conversion followed by natural selection and of natural selection for point mutation in generating variability in immunoglobulins, the numbers of synonymous and nonsynonymous substitutions in immunoglobulin sequences of various subgroups were estimated for complementarity-determining regions (CDRs) and for framework regions (FRs). Both the number of synonymous substitutions and the number of nonsynonymous substitutions in the CDR were found to exceed the corresponding numbers in the FR. Therefore, gene conversion is likely to be an important mechanism for providing variability in the CDR of immunoglobulins. The correlation coefficients between the number of synonymous substitutions and the number of nonsynonymous substitutions and between the substitution number in the CDR and that in the FR were found to be very low. Again, gene conversion is thought to be responsible for this finding.

Animals↗

PubMed1992

Gene conversion generates hypervariability at the variable regions of kallikreins and their inhibitors.

The two mechanisms for generating hypervariability at the reactive center of serine proteases and their inhibitors are gene conversion followed by natural selection and natural selection for point mutation. One way to clarify the effects of these two mechanisms is to calculate separately the number of nonsynonymous substitutions and that of synonymous substitutions at the variable regions and at the conserved regions. Our data analysis shows that not only the number of nonsynonymous substitutions but also the number of synonymous substitutions at the variable regions exceed the corresponding numbers at the conserved regions. Thus gene conversion has provided needed variability at the variable regions of serine proteases and their inhibitors. Natural selection has helped perpetuate such variability.

Animals↗

PubMed1992

Mechanism of allosteric transition of bacterial L-lactate dehydrogenase.

The allosteric behaviour of L-lactate dehydrogenase (L-lactate:NAD+oxidoreductase, EC 1.1.1.27, LDH) from Bifidobacterium longum aM101-2 was studied by means of the subunit hybridization technique as well as X-ray crystallography. Homotropic allosteric response of the LDH activity was found against the concentration of its substrate, pyruvate. Heterotropic allosteric activation of the enzyme was induced by the addition of fructose 1,6-bisphosphate (FBP). Two mutant enzymes, which had either altered sensitivity to FBP or altered substrate specificity from pyruvate to oxaloacetate, were made by site-directed mutagenesis. Hybrid LDHs, between the wild and the mutant LDHs, were made by in vivo subunit hybridization using double transformation of Escherichia coli with two plasmids carrying either the gene of wild or mutant LDH. Introduction of only one desensitized mutant subunit to the LDH changed the characteristic of the wild enzyme to that of the mutant LDH. Kinetic studies on hybrid enzymes consisting of subunits having different substrate specificity indicated that there was a strong cooperative interaction among subunits. These results strongly support the idea that the allosteric change of the LDH fits the concerted-symmetry model proposed by Monod, Wyman, and Changeux. We analysed the crystallographic structure of the LDH having low affinity to substrate at 1.9 A resolution. By the comparison of the structure with that of other LDHs, we concluded that the conformational transition of the LDH was mainly caused by concerted rotations of subunits.

Allosteric Regulation↗

PubMed1992

Growth hormone stimulates cortical bone formation in immature hypophysectomized rats.

Daily subcutaneous injections of rat derived growth hormone to immature, hypophysectomized rats stimulated significant increases in body weight gain, serum osteocalcin, skeletal alkaline phosphatase and incorporation of radioactive thymidine and proline into the compact bone of femurs and tibiae. Equimolar doses of insulin-like growth factor-II did not produce similar biological effects. The data support the contention that growth hormone at equimolar concentration is a stronger osteogenic agent than is insulin-like growth factor-II in vivo.

Alkaline Phosphatase↗

PubMed1992

Lipoprotein-containing apolipoprotein A-I: sex-related quantitative and qualitative changes in this lipoprotein subspecies after ingestion of fat.

We investigated the postprandial changes of two species of lipoproteins containing apolipoprotein (apo)A-I: lipoprotein containing apo A-I but no apo A-II (LpA-I), and lipoprotein containing apo A-I and apo A-II (LpA-I/A-II). These lipoproteins were isolated from 10 men and 11 women at 0, 4, and 6 h after they had eaten butter. In LpA-I, the concentrations of all lipids except triglyceride were increased at 4 and 6 h in the women. In the men all lipids were increased only at 4 h. The increase of apo A-I concentration was found at 6 h only in the women. In LpA-I/A-II, the concentrations of all lipids were increased at 4 h and only phospholipid (PL) was increased at 6 h in the women. In the men, free cholesterol and PL were increased at 4 and 6 h. The increases of apo A-I and apo A-II concentrations were found at 4 and 6 h only in the men. These results suggest that the postprandial changes are sex-related and may relate to the different incidence of atherosclerotic cardiovascular disorders.

Adult↗

PubMed1992

Hyperphosphorylation of cytokeratins 8 and 18 by microcystin-LR, a new liver tumor promoter, in primary cultured rat hepatocytes.

Microcystin-LR (MC-LR), an inhibitor of protein phosphatases 1 and 2A, is a potent tumor promoter in rat liver initiated with diethylnitrosamine. To understand its biochemical process in hepatocytes, primary cultured rat hepatocytes were treated with MC-LR. MC-LR (1 microM) induced phosphorylation of various proteins. Two 55 and 49 kDa proteins were phosphorylated at a 3-fold higher rate than other proteins, and these proteins were identified to be cytokeratins 8 and 18 respectively, by immunoprecipitation and Western blot analysis using monoclonal anti-cytokeratin 8 and 18 antibodies. The basic cytokeratins 8 and 18 showed pI 6.4 and 5.4 respectively, in two-dimensional gel electrophoresis. MC-LR dose dependently increased phosphorylation of cytokeratins 8 and 18 in a cell-free system by incubation with a cytosolic fraction of rat liver containing both protein kinases and protein phosphatases 1 and 2A, and with [gamma-32P]ATP. Cytokeratins 8 and 18 were target proteins for phosphorylation induced by inhibition of protein phosphatases 1 and 2A, in vitro and in rat hepatocytes. Thus, the treatment of rat hepatocytes with MC-LR induced hyperphosphorylation of cytokeratins 8 and 18 associated with morphological changes, indicating that intermediate filament networks were rearranged in the cytoplasm. The hyperphosphorylation of cytokeratins is a significant biochemical process associated with liver tumor promotion.

Animals↗

PubMed1992

Theoretical study of near neutrality. II. Effect of subdivided population structure with local extinction and recolonization.

There are several unsolved problems concerning the model of nearly neutral mutations. One is the interaction of subdivided population structure and weak selection that spatially fluctuates. The model of nearly neutral mutations whose selection coefficient spatially fluctuates has been studied by adopting the island model with periodic extinction-recolonization. Both the number of colonies and the migration rate play significant roles in determining mutants' behavior, and selection is ineffective when the extinction-recolonization is frequent with low migration rate. In summary, the number of mutant substitutions decreases and the polymorphism increases by increasing the total population size, and/or decreasing the extinction-recolonization rate. However, by increasing the total size of the population, the mutant substitution rate does not become as low when compared with that in panmictic populations, because of the extinction-recolonization, especially when the migration rate is limited. It is also found that the model satisfactorily explains the contrasting patterns of molecular polymorphisms observed in sibling species of Drosophila, including heterozygosity, proportion of polymorphism and fixation index.

Animals↗

PubMed1992

Simulation study of a multigene family, with special reference to the evolution of compensatory advantageous mutations.

We investigate the evolution of a multigene family incorporating the forces of drift, mutation, gene conversion, unequal crossing over and selection. The use of simulation studies is required due to the complexity of the model. Selection is modeled in two modes: positive selection as a function of the number of different beneficial alleles and negative selection against deleterious alleles. We assume that gene conversion is unbiased, and that all mutations are initially deleterious. Compensation between mutants creates beneficial and neutral alleles, and allowances are made for compensatory mutations either within or between the members of a multigene family. We find that gene conversion can enhance the rate of acquisition of compensatory advantageous mutations when genes are redundant.

Alleles↗

PubMed1992

Cloning and characterization of the inversion breakpoint at chromosome 2q35 in a patient with Waardenburg syndrome type I.

We described cloning and characterization of an inversion breakpoint of chromosome 2 inv(2)(q35q37.3) observed in a patient with Waardenburg syndrome type I (WSI). Genomic cosmid clones containing the HuP2 gene, which was considered as a candidate for WSI, were isolated from a library constructed from the patient DNA. One of the clones contained the inversion breakpoint and revealed signals at both 2q35 and 2q37 by fluorescent in situ hybridization (FISH), indicating disruption of the HuP2 gene by the inversion. Our result further supports that the HuP2 gene is a candidate for Waardenburg syndrome type I and is located at q35.

Base Sequence↗

PubMed1992

A simple and efficient amplification method of DNA with unknown sequences and its application to microdissection/microcloning.

An alternative method for amplification of DNA with unknown sequences was developed. This involves the direct ligation of a primer oligodeoxyribonucleotide itself to restricted DNA fragments with unknown sequences to be amplified by PCR. The oligonucleotide need not be phosphorylated and need not be annealed with its complementary oligonucleotide in advance for ligation. The ligation reaction seems to be independent of the concentration of unknown DNA, proceeds in short time, and is efficient. The ligation efficiency was more than 30% at a low concentration, 10 fg/microliters, of DNA. This method was applied to a microdissection/microcloning of the short arm of human chromosome 2. Of 65 clones screened for the highly repetitive sequences with total human genomic DNA, eleven (17%) were positive. Their inserts ranged in size from 150 to 1,200 bp (average, 460 bp). In Southern blot analysis, thirty consecutive clones all detected signals common to both total human genomic DNA and mouse-human hybrid cell DNA containing only chromosome 2 of human origin. Among them, 24 (80%) were unique sequences, and 6 (20%) were multi-copy (or intermediate-repeat) sequences. Thus, this method is simple and efficient, and provides an alternative way to amplify unknown DNA.

Base Sequence↗

PubMed1992

Synchronous cancer of the biliary tract and pancreas associated with anomalous arrangement of the pancreaticobiliary ductal system.

A 58-year-old man on abdominal ultrasonography and CT had an irregularly elevated lesion at the neck of the gallbladder and a cyst of approximately 6.5 cm in diameter at the pancreatic tail. Percutaneous transhepatic cholangiography revealed a 2-cm shadow defect at the neck of the gallbladder and an irregular, translucent 30 x 12 mm lesion in the intrapancreatic bile duct. Total pancreatectomy and extended cholecystectomy with regional lymph node dissection was performed. An anomalous arrangement of the pancreaticobiliary ductal system (AAPBD) was demonstrated by postoperative contrast radiography of resected specimen. The lesions of the gallbladder and common bile duct were papillary adenocarcinoma. In addition, papillary adenocarcinoma was limited almost entirely to the mucosal layer of the main pancreatic duct and its branches, from the junction of the common bile duct and pancreatic duct to the pancreatic tail. The three tumors were not continuous. The cyst at the pancreatic tail was a pseudocyst. This case represents synchronous cancer of the gallbladder, common bile duct, and pancreas associated with AAPBD.

Adenocarcinoma, Papillary↗

PubMed1992

Histological features and interphase nucleolar organizer regions in hyperplastic, dysplastic and neoplastic epithelium of intrahepatic bile ducts in hepatolithiasis.

Neoplastic transformation occurs in the intrahepatic biliary tree in hepatolithiasis. The present study aimed to clarify the neoplastic processes by correlating the histological features of the bile duct lesions with counts of interphase argyrophilic nucleolar organizer regions (AgNORs), which reflect cell proliferative activity. We studied 55 cases of hepatolithiasis and 25 normal autopsy livers. The biliary epithelial lesions in hepatolithiasis were divisible into hyperplasia, dysplasia and neoplasia. These lesions were found in bile ducts containing calculi. All cases of hepatolithiasis showed a varied degree of hyperplasia. Additionally, eight cases showed dysplasia, five non-invasive intraductal adenocarcinoma and 10 invasive adenocarcinoma. Cases of non-invasive and invasive carcinoma frequently harboured areas of dysplasia, and areas of dysplasia and non-invasive carcinoma, respectively. The mean and standard deviation of the number of interphase AgNORs in the normal and abnormal biliary epithelium showed a step-wise increase in the following order: normal (1.32 +/- 0.36), hyperplasia (1.52 +/- 0.37), dysplasia (2.28 +/- 0.56), non-invasive carcinoma (3.23 +/- 1.00), and invasive carcinoma (3.72 +/- 0.77). These histological and cell kinetic observations suggest that, in hepatolithiasis, carcinogenesis in bile duct epithelial cells progresses in a multi-step manner, through hyperplasia, dysplasia, non-invasive adenocarcinoma and invasive adenocarcinoma.

Adenoma, Bile Duct↗