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Biomedical subjects

H Masaki

Publications and source records attributed to H Masaki.

At least 271 records · Page 15Linked to original sources
PubMed1986

Purification and properties of epithelial growth inhibitor (EGI) from human platelets: its separation from type beta transforming growth factor (TGF-beta).

We previously reported that sera from various kinds of animals contain a protein(s) capable of inhibiting the growth of the non-malignant epithelial cell line derived from Buffalo rat liver (BRL). In the present study, a similar epithelial cell-specific growth inhibitor (EGI) was purified to homogeneity from an acid-ethanol extract of human platelets. During purification, EGI was separated from the major component of type beta transforming growth factor (TGF-beta), which can stimulate the colony formation of the non-malignant fibroblastic cell line derived from rat kidney (NRK) in soft agar in the presence of epidermal growth factor (EGF). The purified EGI had an Mr of 27,000, and was composed of two subunits identical in Mr. It significantly inhibited the growth in monolayer cultures of three non-malignant epithelial cell lines, BRL, MDCK (from Madin-Darby canine kidney) and BSC-1 (from African green monkey kidney), at doses lower than 40 pg/ml in medium containing 10% fetal calf serum. Its inhibitory activity was stable against heating at 90 degrees C for 3 min, but not against treatment with 50 mM dithiothreitol. In addition, TGF-beta was also partially purified from the same extract. The purified TGF-beta did not show any inhibitory activity toward the growth of BRL, MDCK, BSC-1, or NRK.

Blood Platelets↗
PubMed1986

Primary structures of the ColE2-P9 and ColE3-CA38 lysis genes.

The lysis genes of plasmids ColE2-P9 and ColE3-CA38 were identified by DNA sequencing and electrophoretic analysis of the products of both wild type and artificially introduced ochre mutant genes. The E2 and E3 lysis genes had identical primary structures and were shown to encode 47 amino acids with a calculated molecular weight of 4,861, which is much smaller than that proposed previously for the ColE3-CA38 lysis protein. They are homologous with ColDF13 gene H, except in their 3'-portions. The nine C-terminal amino acids of the E2 and E3 lysis proteins proved to be non-essential for the lysis phenotype.

Amino Acid Sequence↗
PubMed1985

Colicin E3 and its immunity genes.

A DNA segment of plasmid ColE3-CA38 was cloned into pBR328 and its nucleotide sequence was determined. This segment contains the putative promoter-operator region, the structural genes of protein A (gene A) and protein B (gene B) of colicin E3, and a part of gene H. Just behind the promoter region, there is an inverted repeat structure of two 'SOS boxes', the specific binding site of the lexA protein. This suggests that the expression of colicin E3 is regulated directly by the lexA protein. Genes A and B face the same direction, with an intergenic space of nine nucleotides between them. ColE3-CA38 and ColE1-K30 are homologous in their promoter-operator regions, but hardly any homology was found in their structural genes. On the other hand, ColE3-CA38 is fairly homologous to CloDF13 throughout the regions sequenced, with some exceptions including putative receptor-binding regions. By deletion mapping of the immunity gene and recloning of gene B, it was shown genetically that protein B itself is the actual immunity substance of colicin E3. It was also found that the expression of E3 immunity partially depends on the recA function. Thus, we propose two modes of expression of E3 immunity: in the uninduced state, only a slight amount of protein B is produced constitutively to protect the cell from being attacked by the exogenous colicin; and in the SOS-induced state, a large amount of protein B is produced to protect the protein synthesis system of the host cell from ribosome inactivation by endogenously produced colicin E3.

Amino Acid Sequence↗
PubMed1985

Structure and expression of the ColE2-P9 immunity gene.

The primary structure and expression of the ColE2-P9 immunity gene (imm) were investigated. The imm gene is located behind the colicin gene (col) in the same orientation with an intergenic space of two base pairs. Although the imm gene was transcribed primarily in response to the SOS function of the host cell as well as the col gene, the immunity phenotype also appeared to be expressed by only a slight level of leaky transcription without an evident promoter. On comparing the ColE2-P9 sequence with those of relevant plasmids, a highly homologous sequence with the immE2 gene was found downstream of the immE3 gene of ColE3-CA38, and thus, an evolutional relationships could be deduced among some E-group Col plasmids.

Amino Acid Sequence↗
PubMed1984

Determination of the stable isotope of nitrite flux in the blood of mice by gas chromatography-mass spectrometry with selected ion monitoring.

A simple and reliable method for the determination of the stable isotope of nitrite (15NO2) flux in the blood of mice is described. It is based on the reaction of 15NO2 with 1-hydrazinophthalazine in acidic solution to form [15N]tetrazolophthalazine, a stable compound which can be extracted with an organic solvent and then determined by gas chromatography-mass spectrometry with selected ion monitoring using the pentafluorobenzoyl ester of 2,4-dinitro-6-sec.-butylphenol as an internal standard. Amounts of 0.2-10 micrograms of 15NO2 can be determined. The detection limit of 15NO2 was 0.1 microgram/ml. This is a specific method for 15NO2. The procedure for determining 15NO2 in the blood of mice involves extraction with solvent, followed by further clean-up by alumina column chromatography; the detection limit is 0.05 microgram. With the new technique we were able to perform a metabolic fate study of nitrite in the blood of mice following a single oral dose of 15NO2 or the stable isotope of nitrate (15NO3).

Animals↗