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Biomedical subjects

M Sekiguchi

Publications and source records attributed to M Sekiguchi.

At least 451 records · Page 25Linked to original sources
PubMed1988

Chronic toxicity of muroctasin in mice.

The chronic toxicity of N2-[(N-acetylmuramoyl)-L-alanyl-D-isoglutaminyl]-N6-stearoyl-L-lysine (MDP-Lys(L-18), muroctasin), a synthetic muramyl dipeptide, was investigated in mice. Leukocytosis and immunologically activated appearances of splenic white pulp and lung were seen in mice, when treated with MDP-Lys(L18) for 26 weeks. Furthermore, inflammation around the injection site and synovial epithelium hyperplasia of the tarsal joint occurred in higher incidence in the high dose group. These changes were similar to those seen in the subacute toxicity study with mice.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1987

NMDA-receptors on Purkinje cell dendrites in guinea pig cerebellar slices.

The Mg2+-dependent depolarizing action of N-methyl-D-aspartate (NMDA) was intrasomatically investigated, in comparison with quisqualate (QA), in Purkinje cells in cerebellar slices from adult guinea pigs. NMDA applied iontophoretically to the proximal dendritic region (about 100 micron from the Purkinje cell soma) induced depolarizations and spike firings in about the half of the Purkinje cells tested in nominal Mg2+-free medium (contaminated with 4-11 microM Mg2+), and 1 mM Mg2+ almost completely blocked this NMDA action. Application of NMDA onto the distal dendritic region (about 200 micron from the soma) caused no depolarization at all even in the Mg2+-free medium. QA applied onto either the proximal or distal dendritic region consistently showed Mg2+-independent depolarizations. The amplitude of NMDA-induced depolarization in the Mg2+-free medium was non-linearly related to the membrane potential, i.e. smaller at a hyperpolarized potential level. 2-Amino-5-phosphonovalerate blocked the NMDA action partially but more selectively than the QA action, while the reverse was the case for glutamic acid diethylester. These results suggest that the Mg2+-dependent, NMDA-sensitive receptor, which is distinct from the QA receptor and probably similar to the well-known NMDA receptor, is present on the proximal dendrite of the cerebellar Purkinje cell of the guinea pig.

Animals↗
PubMed1987

Excitatory action of N-acetylaspartylglutamate on Purkinje cells in guinea pig cerebellar slices: an intrasomatic study.

The action of N-acetylaspartylglutamate (NAAG) on Purkinje cell somata in guinea pig cerebellar slices was intracellularly investigated in comparison with L-aspartate (Asp) and L-glutamate (Glu). A synthetic NAAG sample used was confirmed not to be contaminated with free Glu and Asp. NAAG, applied by either iontophoresis or superfusion, dose-dependently depolarized Purkinje cell somata, and iontophoretically applied NAAG decreased the membrane resistance in voltage- and Mg2+-dependent manners, like Asp or Glu. Relative depolarizing potencies seemed to be Glu greater than NAAG not equal to Asp in the presence of external Mg2+ and Asp greater than NAAG greater than or equal to Glu in the absence of Mg2+. In addition to this selective blocking effect of Mg2+, 2-amino-5-phosphonovalerate (APV) antagonized the actions of NAAG and Asp more strongly than that of Glu, while 2-amino-4-phosphonobutyrate showed rather non-selective antagonisms. The reversal potential of the NAAG action was at about 10 mV and similar to that of the action of Asp or Glu. These results suggest that NAAG itself is excitatory to guinea pig cerebellar Purkinje cells and is likely to be acting on Asp- and APV-sensitive, Mg2+-dependent receptors on cerebellar Purkinje cells.

Animals↗
PubMed1987

Electrophysiological and pharmacological actions of N-acetylaspartylglutamate intracellularly studied in cultured chick cerebellar neurons.

The electrophysiological and pharmacological actions of N-acetylaspartylglutamate (NAAG) in cultured chick cerebellar neurons were intracellularly investigated in comparison with L-aspartate (ASP) and L-glutamate (GLU). Iontophoretically applied NAAG dose-dependently induced depolarizations associated with increases in spike discharge and changes in membrane conductance. Relative excitatory potencies seemed to be GLU greater than ASP greater than or equal to NAAG. The voltage-dependent increase in input resistance observable in the presence of Mg ions was most notable for ASP, moderate for NAAG and least for GLU. The reversal potential of NAAG-induced depolarization was at about 0 mV and similar to that for ASP or GLU, indicating primary concern of Na+/K+-conductances to the NAAG action. Mg ions depressed the actions of ASP and NAAG more strongly than the GLU action. 2-Amino-5-phosphonovalerate (APV) and D-alpha-aminoadipate antagonized the actions of ASP and NAAG more effectively than the GLU action. 2-Amino-4-phosphonobutyrate (APB) and glutamic acid diethylester showed rather non-selective antagonisms to NAAG, ASP and GLU. These results suggest that NAAG is excitatory to cultured chick cerebellar neurons and functionally resembles ASP or is intermediate between ASP and GLU, and may also support the suggested candidacy of NAAG for a neurotransmitter in the CNS.

Action Potentials↗
PubMed1987

Molecular cloning and nucleotide sequence of the mutT mutator of Escherichia coli that causes A:T to C:G transversion.

The Escherichia coli mutator gene mutT, which causes A:T----C:G transversion, was cloned in pBR 322. mutT+ plasmids carry a 0.9 kb PvuII DNA fragment derived from the E. coli chromosome. Specific labelling of plasmid-encoded proteins by the maxicell method revealed that mutT codes for a polypeptide of about 15,000 daltons. The protein was overproduced when the mutT gene was placed under the control of the lac regulatory region on a multicopy runaway plasmid. The nucleotide sequence of the mutT gene was determined by the dideoxy method.

Amino Acid Sequence↗
PubMed1987

Replication intermediate of a hybrid plasmid carrying the replication terminus (ter) site of R 6K as revealed by agarose gel electrophoresis.

A 4.32 kb DNA fragment, on which the DNA replication terminus (terR) site of plasmid R 6K was located, was inserted into the unique EcoRI site of plasmid pUC9. To detect replication intermediate molecules with a replication fork halted at the terR site, a cell DNA extract was digested with EcoRI, electrophoresed through an agarose gel and stained with ethidium bromide. In addition to two major bands, one derived from vector DNA and the other from the ter insert fragment, two extra minor bands were detected. Following DNA-DNA hybridization and electron microscopic observation we concluded that the two minor bands corresponded to the two Y-shaped molecules, produced from the theta-shaped intermediate molecules by EcoRI digestion.

DNA Replication↗
PubMed1987

A newly discovered tRNA(1Asp) gene (aspV) of Escherichia coli K12.

We report a new tRNA(1Asp) gene near the dnaQ gene, which is located at 5 min on the Escherichia coli linkage map. We named it aspV. The sequence corresponding to the mature tRNA is identical with that of the two previously identified tRNA(1Asp) genes (aspT and aspU), but there is no homology in the sequences of their 3'- and 5'-flanking regions.

Base Sequence↗
PubMed1987

An infant with dilated cardiomyopathy confirmed as myocarditis by endomyocardial biopsy.

A case of an 11-month-old infant who was incidentally diagnosed as having myocarditis by right and left ventricular endomyocardial biopsy is reported. This patient was admitted because of heart failure. Chest X-ray showed cardiomegaly and an electrocardiogram revealed decreased voltage with right atrial and right ventricular overloading. A dilated left ventricle with poor ejection fraction was shown in an echocardiogram. Dilated cardiomyopathy was the initial diagnosis since there was no episode of preceding viral infection or evidence of an inflammatory process in routine laboratory investigations. However, the biopsy findings, including massive infiltration of inflammatory cells and myocyte degeneration, indicated myocarditis. To our knowledge, this is the youngest patient in whom myocarditis has been confirmed by endomyocardial biopsy.

Biopsy↗
PubMed1987

Isolation of a human X chromosome-linked gene essential for progression from G1 to S phase of the cell cycle.

The tsBN462 cell line, a temperature-sensitive (ts) mutant isolated from the hamster cell line, BHK21/13, cannot progress into S phase at 39.5 degrees C, following the release from isoleucine deprivation. The mutant cells were transfected with high molecular weight (HMW) DNA from human KB cells, and several human DNA bands were found to be conserved through three cycles of ts+ transformation. Conserved human DNA was isolated from the cosmid library of the secondary ts+ transformant (K-1-1), using 32P-labelled total human DNA as a probe. The isolated human DNA covers about 70 kb of human DNA flanked with hamster DNA, and originates from the human X chromosome. The middle part (56 kb) of the isolated human DNA was conserved through the primary, secondary and tertiary ts+ transformation, without gross rearrangement.

Animals↗
PubMed1987

Expression of the truncated E. coli O6-methylguanine methyltransferase gene in repair-deficient human cells and restoration of cellular resistance to alkylating agents.

We have constructed a truncated E. coli O6-methylguanine methyltransferase (MT) gene (ada gene) to express the MT activity for O6-methylguanine and O4-methylthymine but not for methylphosphotriester in human cells and transferred it into Mer- HeLa MR cells. The transfectant cells expressed the truncated E. coli MT were resistant to alkylating agents as same as the transfectant cells with the intact ada gene in cell killing, sister-chromatid exchange induction and host-cell reactivation of adenovirus 5. These results strongly suggest that methylphosphotriester may not contribute to the biological effect of alkylating agents in human cells.

Alkylating Agents↗
PubMed1987

Isolation and characterization of the active cDNA of the human cell cycle gene (RCC1) involved in the regulation of onset of chromosome condensation.

The human RCC1 gene was cloned after DNA-mediated gene transfer into the tsBN2 cell line, which shows premature chromosome condensation at nonpermissive temperatures (39.5-40 degrees C). This gene codes for a 2.5-kb poly(A)+ RNA that is well conserved in hamsters and humans. We isolated 15 cDNA clones from the Okayama-Berg human cDNA library, and found two that can complement the tsBN2 mutation with an efficiency comparable to that of the genomic DNA clone. The base sequences of these two active cDNA clones differ at the 5' proximal end, yet both have a common open reading frame, encoding a protein of 421 amino acids with a calculated molecular weight of 44,847 and with seven homologous repeated domains of about 60 amino acids. This human RCC1 gene was located to human chromosome 1 using sorted chromosomal fractions.

Animals↗
PubMed1987

Human testicular germ cell tumors in vitro and in athymic nude mice.

Four cell lines derived from pure and mixed types of human testicular germ cell tumors in vitro and in nude mice were examined by light and electron microscopies. The NEC8 and NEC15 cell lines in vitro were composed of embryonal carcinoma cells with potentiality of trophoblastic differentiation. All of the tumors formed in nude mice by both cell lines were pure embryonal carcinomas. On the other hand, the NEC14 and ITO-II cell lines showed morphological differentiation from embryonal carcinoma cells to trophoblastic cells and to yolk sac tumor cells in vitro. In nude mice, these cell lines formed mixed tumors which consisted of embryonal carcinoma, yolk sac tumor, immature teratoma or trophoblastic cells. Our data suggest that some embryonal carcinomas have multipotentiality of morphological differentiation but that others have little such potentiality.

Animals↗
PubMed1987

Production of alpha-fetoprotein by human germ cell tumors in vivo and in vitro.

The production of alpha-fetoprotein (AFP) by human germ cell tumors was studied in surgical specimens, cultured cells and transplanted tumors in nude mice. AFP was detected most frequently in yolk sac (endodermal sinus) tumors, and it was also detected, though only occasionally, in embryonal carcinomas and in teratomas. AFP-positive cells in teratomas presented a glandular or hepatoid appearance. Our experimental data suggest that AFP production in embryonal carcinomas is due to the functional expression of yolk sac differentiation preceding its morphologic expression. Although the transplanted tumors maintained the productivity of AFP, the cultured cells were not successful in maintaining a continuous AFP production.

Adult↗