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M Iwabuchi

Publications and source records attributed to M Iwabuchi.

At least 109 records · Page 6Linked to original sources
PubMed1988

Molecular cloning of cell-type-specific cDNAs exhibiting new types of developmental regulation in Dictyostelium discoideum.

By screening cDNA libraries from NC-4 cells, we have obtained five prespore-specific and two prestalk-specific cDNA clones. The two classes of prespore genes began to be expressed at the tipped aggregate stage: one class was expressed throughout development, while the other was shut off during culmination. Another class of prespore genes was expressed in vegetative cells but only in prespore cells at the later stages. Prestalk-specific genes were first expressed at the tipped aggregate stage concurrently with the two prespore gene classes, indicating the importance of this stage for transcriptional regulation in both prestalk and prespore differentiation. Except for the first prespore gene class, these represent new cell-type-specific genes as to their temporal pattern of expression.

Cloning, Molecular↗
PubMed1988

Disposition and metabolism of [14C]-amezinium metilsulfate in rats.

Disposition and metabolism of [14C]-amezinium metilsulfate (4-amino-6-methoxy-1-phenylpyridazinium methylsulfate, Risumic) were systematically studied in rats after intravenous (5 mg/kg) or oral (20, 100 mg/kg) administration. After oral administration at 20 mg/kg, blood level reached the maximum (Cmax) of 0.65 microgram eq/ml at 3 h (tmax) and decreased with t1/2 of 8.1 h. Levels in plasma and most tissues elevated to the Cmax at 3 h. The liver level was the highest (61 times as high as plasma level) of all examined tissues. Most tissue levels decreased thereafter essentially in parallel with plasma levels. The findings by whole-body autoradiography essentially agreed with those by radiometry. In lactating rats, milk levels were virtually similar to plasma levels. [14C]-Amezinium metilsulfate radioactivity in fetus and fetal blood was around 0.3 microgram eq/g, being about 1/10 level of maternal plasma level. About 24, 72 and 42% were excreted in urine, feces and bile, respectively. Re-absorption of biliary metabolites accounted for about 31%, being about 13% of orally given [14C]-amezinium metilsulfate. Plasma and aorta contained unchanged amezinium and glucuronide of hydroxyl amezinium MIII. In the brain, the major metabolite was O-demethyl amezinium MV and unchanged drug was not detected. Urinary metabolites were largely MIII glucuronide and the unchanged drug. Biliary metabolite was found composed mostly from MIII glucuronide. In feces, MIII and the unchanged amezinium were found. MIII and its glucuronide were novel metabolites which were identified by thin-layer chromatography and mass spectrometry.

Animals↗
PubMed1987

Nuclear protein(s) binding to the conserved DNA hexameric sequence postulated to regulate transcription of wheat histone genes.

Nuclear protein(s) that specifically bind(s) to the upstream hexamer motif, ACGTCA, of wheat histone H3 and H4 genes has (have) been identified. Sequences homologous to this hexamer are found to be conserved in the upstream region of not only wheat histone genes but also other plant and animal histone genes. This suggests a possible role(s) for the hexamer and the nuclear protein(s) in the transcriptional regulation of the wheat histone genes. This hexamer is homologous to the upstream core sequence, TGACGTCA, which is highly conserved in some animal genes whose expression is regulated by cAMP.

Binding, Competitive↗
PubMed1987

Action of ubenimex on aminopeptidase activities in spleen cells and peritoneal macrophages from mice.

The action of ubenimex on aminopeptidase (APase) activity was studied in intact spleen cells and peritoneal macrophages from mice. Ubenimex strongly inhibited hydrolyzing activities against arginine-beta-naphtylamide (Arg-NA), Lys-NA and Pro-NA in both cells. Inhibition of hydrolysis of Leu-NA, Met-NA and Ala-NA was relatively small or not observed. When both cells were incubated in HANKS' solution, hydrolyzing activities against Arg-NA, Lys-NA and Pro-NA were released to the medium, while Leu-NA and Met-NA-hydrolyzing activities were mostly bound. In addition, the Leu-NA-hydrolyzing activity in the spleen cells was kinetically studied. The Arg-NA and Leu-NA-hydrolyzing activities in four fractions prepared from the homogenate of spleen cells were also studied kinetically. From these studies it was suggested that ubenimex inhibits aminopeptidase B and a Pro-NA-hydrolyzing enzyme more effectively than Leu-APase in intact spleen cells and peritoneal macrophages from mice.

Adjuvants, Immunologic↗
PubMed1986

X-linked mutations that give rise to overproduction of glucose-6-phosphate dehydrogenase in Drosophila melanogaster.

Two X-linked mutations that give rise to overproduction of glucose-6-phosphate dehydrogenase (G6PD) were found among the progenies of isogenic strains which had been subjected to selection for high G6PD activity. Mapping of the high-activity factor in these mutants was carried out using car ZwB sw males of low G6PD activity. As a result, the factor mapped 0.02-0.04 unit to the left of the Zw locus. The amount of the G6PD gene was also quantitated utilizing a cloned G6PD gene as a probe, but no significant difference was found between the mutants and low-G6PD activity flies which shared the same X, second, and third chromosomes with the mutants. These findings are consistent with our notion that the mutations might be regulatory mutations, possibly resulting from the insertion of a novel class of transposable genetic elements.

Animals↗
PubMed1985

Efficiency of in vitro transcription of Dictyostelium discoideum actin gene is affected by the nucleotide sequence of the transcription initiation region.

The actin gene of Dictyostelium discoideum is transcribed faithfully but with very low efficiency in a cell-free system containing HeLa cell extract [Takiya, S., Tabata, T., Iwabuchi, M., Hirose, S., & Suzuki, Y. (1984) J. Biochem. (Tokyo) 95, 1367-1377]. Using the same in vitro system, we determined that the promoter activity of the actin 5 gene is 100-200 times weaker than that of the silkworm fibroin gene. To clarify the cause of the low transcription efficiency, various chimeric genes were constructed from the actin and fibroin genes, and their transcription efficiencies were examined in vitro. Both the TATA box and the transcription initiation site of the two natural genes functioned in the transcription of the chimeric genes, the efficiency of which was especially affected by the transcription initiation region. In chimeric genes having the upstream sequence of the actin gene and a downstream sequence including the transcription initiation site of the fibroin gene, the transcription efficiency was higher than one-third of that of the natural fibroin gene. In chimeric genes having the actin transcription initiation region and an upstream sequence of the fibroin gene, the transcription efficiency was as low as that of the natural actin gene. We concluded that the transcription initiation site is a part of the promoter and an essential region for directing faithful and efficient initiation of gene transcription.

Actins↗
PubMed1985

Phylogenetic relationships among eukaryotic kingdoms inferred from ribosomal RNA sequences.

Phylogenetic trees among eukaryotic kingdoms were inferred for large- and small-subunit rRNAs by using a maximum-likelihood method developed by Felsenstein. Although Felsenstein's method assumes equal evolutionary rates for transitions and transversions, this is apparently not the case for these data. Therefore, only transversion-type substitutions were taken into account. The molecules used were large-subunit rRNAs from Xenopus laevis (Animalia), rice (Plantae), Saccharomyces cerevisiae (Fungi), Dictyostelium discoideum (Protista), and Physarum polycephalum (Protista); and small-subunit rRNAs from maize (Plantae), S. cerevisiae, X. laevis, rat (Animalia), and D. discoideum. Only conservative regions of the nucleotide sequences were considered for this study. In the maximum-likelihood trees for both large- and small-subunit rRNAs, Animalia and Fungi were the most closely related eukaryotic kingdoms, and Plantae is the next most closely related kingdom, although other branching orders among Plantae, Animalia, and Fungi were not excluded by this work. These three eukaryotic kingdoms apparently shared a common ancestor after the divergence of the two species of Protista, D. discoideum and P. polycephalum. These two species of Protista do not form a clade, and P. polycephalum diverged first and D. discoideum second from the line leading to the common ancestor of Plantae, Animalia, and Fungi. The sequence data indicate that a drastic change occurred in the nucleotide sequences of rRNAs during the evolutionary separation between prokaryote and eukaryote.

Animals↗
PubMed1985

[Kinetics of etoposide cytotoxicity against mouse P388 leukemia].

The in vitro cytotoxicity of etoposide against mouse P388 leukemia cells was kinetically studied and compared with those of podophyllotoxin, the parent compound, and other antitumor agents. When P388 cells were exposed to etoposide, surviving-cell fraction decreased with etoposide concentration and exposure time. Similar results were obtained with doxorubicin, peplomycin and cisplatin. The cytotoxicity of melphalan was dependent on concentration but scarcely on exposure time. From these data, n in Cn X T = K where T, C and K are exposure time, concentration required for killing 90% of P388 cells and a constant, respectively, was calculated. Etoposide gave an n value of 1.16. n values for doxorubicin, peplomycin and cisplatin, all belonging to the Shimoyama type Ib group where the cytotoxicity of the agent depends on both concentration and exposure time, were 1.29, 1.28 and 3.03, respectively. The n value for melphalan, belonging to the type Ia group where cytotoxicity depends only on concentration, was 54.0. From these results, it was concluded that etoposide is of type Ib. The cytotoxicities of podophyllotoxin, 5-fluorouracil, cytarabine and vinblastine were greatly dependent on exposure time. Podophyllotoxin may be an agent of type II whose cytotoxicity depends only on exposure time.

Animals↗
PubMed1985

Antitumor activity and toxicity of serum protein-bound platinum formed from cisplatin.

When cisplatin was incubated with mouse serum, its cytotoxicity towards P388 leukemia cells decreased with the formation of non-ultrafiltrable or protein-bound platinum. The cytotoxicity of prepared mouse serum protein-bound platinum at 100 microgram/ml (as the cisplatin-equivalent concentration) was less than that of cisplatin at 0.125 microgram/ml. The prepared protein-bound platinum exhibited antitumor activity against colon adenocarcinoma 26 in mice, when administered iv daily for 9 consecutive days at 32 and 64 mg/kg (as the cisplatin-equivalent dose). Cisplatin similarly administered exhibited antitumor activity at daily doses of only 1 and 2 mg/kg. Administration of the protein-bound platinum at such high doses as 32 and 64 mg/kg (as the cisplatin-equivalent dose) caused elevation of serum BUN and reduction of bone marrow cells in mice. After iv administration of cisplatin to mice at 6 mg/kg, ultrafiltrable platinum was detected in the plasma for the first 30 min. Thereafter platinum was found only in protein-bound form. When mice were iv inoculated with colon adenocarcinoma 26 more than 30 min after cisplatin administration, no prolongation of the life span was observed. From these results, it is concluded that mouse serum protein-bound platinum does not contribute significantly to cisplatin antitumor activity and toxicity in mice.

Animals↗
PubMed1984

Sequence analysis of the transcribed and 5' non-transcribed regions of the ribosomal RNA gene in Dictyostelium discoideum.

The nucleotide sequence of Dictyostelium discoideum rDNA extending over almost the entire transcribed region and a part of the 5' non-transcribed spacer region has been determined. Computer analysis revealed that there were several conserved sequences in the 17S, 5.8S and 26S coding regions when compared with the sequences at analogous positions in some eukaryotic rRNA genes. The data also showed that the D. discoideum rDNA contains several extra sequences, which have not been found in other eukaryotes' rDNAs , near the 3' terminus of the 17S coding region and the 5' terminus of the 26S coding region.

Animals↗
PubMed1984

Molecular cloning and nucleotide sequence of a variant wheat histone H4 gene.

To determine whether there is structural variation among histone H4 genes in wheat, one (TH091) of the H4 genes that had been cloned from a wheat genomic DNA library was sequenced and compared with another H4 gene (TH011) which we had described previously [Tabata et al., Nucl. Acids Res. 11 (1983) 5865-5865]. Nucleotide sequence analysis revealed that there are 17 nucleotide replacements in the protein-coding region of two H4 genes, causing only one amino acid substitution: a glycine at position 4 (from the N terminus) in TH011 was replaced by an aspartic acid in TH091. S1 mapping, using total nuclear RNA from germinated seeds, indicated that the H4 gene was transcribed in vivo.

Amino Acid Sequence↗
PubMed1984

Transcription of cloned actin genes of Dictyostelium discoideum in the cell-free system.

Truncated templates of a cloned actin gene (actin 5) of Dictyostelium discoideum were transcribed in a HeLa cell extract from a position indistinguishable from the in vivo initiation site. The efficiency of this accurate transcription, however, was very low compared with that of the adenovirus 2 major late gene in the same system. Transcription of the actin 6 and 8 genes, of which the 5'-flanking regions differ in their base sequences from the corresponding region of the actin 5 gene, was not good in either fidelity or efficiency. When the partially purified RNA polymerase II of D. discoideum was used instead of the HeLa cell extract, no accurate transcription of the actin 5 gene occurred. However, simultaneous addition of RNA polymerase II and HeLa cell extract into the cell-free system caused a shift of the in vitro initiation point of transcription of the actin 5 gene to a position about 20 nucleotides downstream from the presumed in vivo initiation site. The reason for the shift remains unknown, but it is supposed that some factor(s) other than RNA polymerase II are involved in the accurate initiation of transcription and the maintenance of transcription efficiency of the actin genes.

Actins↗