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H Sakamoto

Publications and source records attributed to H Sakamoto.

At least 649 records · Page 36Linked to original sources
PubMed1991

Repositioning of an alternative exon sequence of mouse IgM pre-mRNA activates splicing of the preceding intron.

Using a transient expression system of mouse IgM mini-gene constructs in mouse B-cell lines and in fibroblast L cell, we investigated splicing of the IgM transcript. We observed that the efficiency of splicing between exons C4 and M1 (C4-to-M1 splicing), the splicing reaction leading to the production of membrane-bound form (microns) mRNA, was drastically affected by mutations in a specific portion of the downstream exon (M2). The results show that the specific exon M2 sequence activates the C4-to-M1 splicing. This activation was not observed when splicing between exons M1 and M2 was abolished by base substitutions at the splice sites. These results indicate that positioning of the downstream exon is crucial for efficient splicing of the preceding intron.

Animals↗
PubMed1991

Biological significance of gene amplification in carcinogenesis.

K-SAM gene was originally isolated as an amplified gene in a stomach cancer cell line by in-gel DNA renaturation method. K-SAM encodes a membrane receptor with tyrosine kinase and is often amplified in poorly differentiated type of stomach cancer, while c-ERBB-2 is often amplified in well differentiated type of stomach cancer. There are several forms of K-SAM mRNAs which are generated by alternative splicing, and two types of K-SAM protein without transmembrane region. The ligand of K-SAM is considered to be growth factor(s) belonging to fibroblast growth factor (FGF) or heparin binding growth factor (HBFG) family. We have also frequently found amplification of HST-1 or HSTF1 gene in esophageal cancer. HST-1 gene, originally found as a transforming gene, is located on human chromosome 11q13, and it locates 35 kbp apart from its related gene, INT-2. Neither of the genes was expressed even in cancer cells with the co-amplification. By cosmid walking, we have identified at least two genes, designated tentatively as EXP1 and EXP2, on the same amplicon as HST-1 and INT-2, and the mRNAs for EXP1 and EXP2 genes were increased in amounts proportional to the degree of amplification.

Esophageal Neoplasms↗
PubMed1991

Pleomorphic adenoma in the periphery of the lung. Report of a case and review of the literature.

A pleomorphic adenoma of the lung recurred after 9 years. The primary tumor consisted mainly of cartilaginous and fibrous elements with a small area of epithelial cell nests, whereas the second one possessed epithelial cell nests with cartilaginous stroma. Immunohistochemical studies showed that both tumors had neoplastic cells with immunoreactive S100, keratin, actin, vimentin, and glial fibrillary acid protein-positive cytoplasm. The primary tumor, which was resected from the periphery of the lung, was not connected with the trachea or the bronchus macroscopically. To our knowledge, the literature contains only six reports of pleomorphic adenoma in the lung.

Adenoma↗
PubMed1990

Production of endothelin-1 by rat cultured mesangial cells.

We investigated whether ET-1 is synthesized by and released from mesangial cells. ET-1-like immunoreactivity (LI) released into medium increased time-dependently under a serum-free condition. The amounts of ET-1-LI released into the medium was augmented in the presence of fetal calf serum. Reverse-phase HPLC profile of the conditioned media revealed a major component coeluting with standard ET-1. Northern blot analysis of poly(A) +RNA extracted from mesangial cells showed a single major band corresponding to the size of preproET-1 mRNA (2.3 kb). These findings demonstrate that ET-1 is synthesized by and released from rat mesangial cells and suggest a possibility that it acts on their own cells as an autocrine factor.

Animals↗
PubMed1990

Binding of the Drosophila sex-lethal gene product to the alternative splice site of transformer primary transcript.

Somatic sexual differentiation in Drosophila melanogaster is accomplished by a hierarchy of genes of which one, Sex-lethal (Sxl), is required for the functional female-specific splicing of the transcripts of the immediately downstream regulatory gene, transformer (tra). The first exon of the tra primary transcript is spliced to one of two acceptor sites. Splicing to the upstream site yields a messenger RNA which is neither sex-specific nor functional, but that produced after splicing to the downstream acceptor site yields a functional female-specific mRNA. Here we address the question of how the Sxl gene product determines the alternative splicing of tra primary transcripts. One suggestion is that non-sex-specific splicing to the upstream acceptor is blocked in female flies by sex-specific factors, but neither the identity of the female-specific factors nor the mechanism of the blockage has been specified. We have now performed co-transfection experiments in which Sxl complementary DNA and the tra gene are expressed in Drosophila Kc cells. Moreover, we find that female Sxl-encoded protein binds specifically to the tra transcript at or near the non-sex-specific acceptor site, implying that the female Sxl gene product is the trans-acting factor that regulates the alternative splicing.

Animals↗
PubMed1990

Specific inhibitory conformation of dipeptides for chymotrypsin.

Based on the analyzed conformation of a chymotrypsin inhibitor H-delta Phe-Phe-OMe, we have designed a series of diastereomeric phenylalanylphenylalanine methyl esters and derivatives as possible inhibitors. Among the peptides synthesized, H-D-Phe-L-Phe-OMe was found to be very resistant to chymotrypsin in spite of its L-Phe-OMe structure at the C-terminus. It inhibited the enzyme fairly strongly and competitively with Ki = 9.0 x 10(-5) M in the assay using Ac-Tyr-OEt as a substrate. The measurements of the NOEs in high-resolution 1H-NMR analyses indicated the presence of the hydrophobic core built by the intramolecular interaction between the D-Phe-phenyl and ester-methyl groups. It was suggested that this core interacts with the chymotrypsin S2 site (Trp215) and Phe2 with the S1 site. The backbone structure of this dipeptide was assumed to be in an inhibitory conformation that fits the active center of the enzyme.

Amino Acid Sequence↗
PubMed1990

Molecular biology of the hst-1 gene.

The hst-1 gene (or HSTF1 by human gene nomenclature) was originally identified in our laboratory by an NIH/3T3 focus formation assay using DNA from a human gastric cancer. Sequence analysis predicted the hst-1 product to be a novel growth factor with 30-50% homology with six other heparin-binding growth factors: basic and acidic fibroblast growth factors (FGFs), the int-2 protein, FGF5, the hst-2/FGF6 protein and keratinocyte growth factor (KGF). A recombinant hst-1 protein was synthesized in silkworm cells and found to be a potent heparin-binding mitogen for murine fibroblasts and human vascular endothelial cells. Although hst-1 expression cannot be detected in most cancer cells, including gastric cancers, it is expressed in mouse embryos and in some germ cell tumours. Both hst-1 and int-2 are located on band q13.3 of human chromosome 11 within a distance of 35 kbp; in the mouse genome these two genes are separated by less than 20 kbp. They are differentially transcribed in the F9 mouse teratocarcinoma cell line; hst-1 is expressed in undifferentiated stem cells and int-2 in differentiated endodermal cells. The hst-1 and int-2 genes were coamplified in a variety of cancer cells, most notably in more than 50% of oesophageal cancers.

Amino Acid Sequence↗
PubMed1990

Spontaneous and cAMP-dependent induction of a resting phase and neurite formation in cell hybrids between human neuroblastoma cells and thymidine auxotrophs of rat nerve-like cells.

Cell hybrids (BIM) were produced between human neuroblastoma cells (IMR-32) and thymidine auxotrophs (B3T) of rat nerve-like cells (B103) in order to obtain cell lines undergoing stable neuronal differentiation. BIM cells exhibited the growth properties of partial transformation: 1) When the cell growth reached a plateau, BIM cells ceased to proliferate and expressed a differentiated phenotype. The shape of the cells changed from flat to round and they extended neurites. 2) When cultured in methylcellulose, BIM cells formed colonies, indicating that BIM cells have the ability of anchorage-independent growth. By Southern blot analysis, BIM cells had both human and rat types of N-myc genes. The human N-myc genes were amplified, but the extent of the amplification was lower in BIM cells than that in the parental cell line IMR-32. The rat N-myc gene was detected at a similar level in BIM, B3T, B103, and rat fibroblastic cells 3Y1. Therefore, the decrease in amplification of human N-myc genes may be involved in the properties of partial reverse-transformation in BIM cells. When treated with various drugs such as db-cAMP, forskolin, and cAMP with isobutyl-methylxanthine, BIM cells expressed a nerve-like phenotype. These findings indicate that cell hybridization yielded partial normalization of transformed nerve-like cells.

1-Methyl-3-isobutylxanthine↗
PubMed1990

The destructive effects of sclerosant ethanolamine oleate on mammalian vessel endothelium.

Ethanolamine oleate (EO) used widely in sclerotherapy against esophageal varices was studied for its pharmacological effect on blood coagulation and vascular damage in animals. Blood coagulation was completely inhibited by EO at a concentration of 0.31%. EO destroyed the endothelial cells of the vessel of dog and rat within one minute after injection into the vessels. An accumulation of fibrin and platelets on the surface of the damaged vessel was observed electron microscopically. Mural thrombus was formed in a few hours and the thrombus occluded the blood stream in the vein. From these animal experiment, intravasal injection of EO was considered to cause the disappearance of varices by the following two processes: collapse of varices because of occlusion of the blood stream and shrinking of the obstructed thrombus through organization.

Adult↗
PubMed1990

Analysis of rapidly changing EEGs before generalized spike and wave complexes.

Ten epileptic patients who had absence and tonic-clonic seizures were examined. They showed almost generalized 2-5 Hz spike and wave complexes (SWCs) with maxima at the frontal or central locations. Their EEGs were recorded from F3, F4, C3, C4, P3, P4, O1 and O2. One 15 sec EEG epoch, which included the background activity followed by SWCs, was divided into 20 segments. On the basis of Akaike's information criterion obtained from an AR model fitted to each segment by the least squares method, a distance measure between segments was obtained. The 20 segments were classified according to the distance measure with the combined use of both cluster analysis and multidimensional scaling. The power spectrum was also obtained for each segment. There were 2-6 clusters at some locations, always including the largest amplitude locations of the SWCs (the frontal or central locations). The clusters could be grouped into 3 major types, each forming a period: (1) one large cluster distant from the SWCs (the period of background activity); (2) small clusters just before the SWCs (the period just before the SWCs); (3) small clusters during the SWCs (the period of the SWCs). The period just before the SWCs, which occurred earliest at the largest amplitude location, may be a transition state of the background activity to the SWCs. A few segments remote from the SWCs belonged to the small cluster just before or during the SWCs in some patients, thus suggesting that an EEG event similar to EEG changes just before or during the SWCs occurred. The EEG event buried within the background can be considered as a poorly developed epileptiform discharge. A gradual increase or decrease in alpha frequency before the SWCs was found in most patients; this suggests that changes in the level of vigilance occur before SWCs.

Adolescent↗
PubMed1990

Net increase of platelet membrane tyrosine specific-protein kinase activity by phorbol myristate acetate.

Tyrosine protein kinase (TPK) activity in rabbit platelets after stimulation by phorbol myristate acetate (PMA) or thrombin was directly estimated by 32P incorporation from (gamma-32P)ATP (adenosine triphosphate) into synthetic peptide angiotensin II. By PMA-treatment a net increase of TPK activity was obtained, while thrombin acted on the TPK quickly but stimulation was limited within the range attained by the control after lengthy incubation. The responsive TPK to these stimulators was localized mainly in membrane but much less in cytosol. The specific activity of the particulate TPK was low in the sonicate of control ice cold platelets but increased about 6-fold when the platelets were incubated at 37 degrees C. On a brief contact of platelets with PMA at 37 degrees C the TPK was fully activated and reached a maximum value about 130% of the control. Determination of phosphotyrosine phosphatase in the stimulated platelet sonicate revealed that its participation in the above described increase of 32P-incorporation was meagre. The quick response suggested a possible role of TPK in the signal transduction through the platelet cell membrane.

Adenosine Triphosphate↗
PubMed1990

Flow injection of lithium ion using chromogenic 14-crown-4 derivatives as extraction-spectrophotometric reagents.

A system for flow injection of Li+ has been designed, with use of proton-dissociable chromogenic 14-crown-4 derivatives as the extraction-spectrophotometric reagents, and the analytical conditions have been optimised. This flow injection system showed high selectivity for Li+ reflecting the cation-complexing property of the chromogenic crown ethers. The determination of Li+ in the clinical range in blood under a high Na+ background of 130-160 mM was feasible, with a small sample size (50 microliters) and high sampling rate (more than 100 injections per hour), with this method. The proposed extraction-spectrophotometric flow injection system was, therefore, found to be promising for the efficient determination of Li+ in biological samples, such as blood sera, with a high Na+ background.

Autoanalysis↗
PubMed1990

K-sam, an amplified gene in stomach cancer, is a member of the heparin-binding growth factor receptor genes.

DNA fragments amplified in a stomach cancer-derived cell line, KATO-III, were previously identified by the in-gel DNA renaturation method, and a 0.2-kilobase-pair fragment of the amplified sequence was subsequently cloned. By genomic walking, a portion of the exon of the gene flanking this 0.2-kilobase-pair fragment was cloned, and the gene was designated as K-sam (KATO-III cell-derived stomach cancer amplified gene). The K-sam cDNAs, corresponding to the 3.5-kilobase K-sam mRNA, were cloned from the KATO-III cells. Sequence analysis revealed that this gene coded for 682 amino acid residues that satisfied the characteristics of the receptor tyrosine kinase. The K-sam gene had significant homologies with bek, FLG, and chicken basic fibroblast growth factor receptor gene. The K-sam gene was amplified in KATO-III cells with the major transcript of 3.5-kilobases in size. This gene was also expressed in some other stomach cancer cells, a small cell lung cancer, and germ cell tumors.

Amino Acid Sequence↗
PubMed1990

Time-related changes in plasma adrenal steroids during treatment with spironolactone in primary aldosteronism.

Time-related changes in plasma levels of aldosterone, deoxycorticosterone, corticosterone, and cortisol were studied during treatment with spironolactone in 8 patients with primary aldosteronism due to adenomas. Plasma renin activity (PRA), serum sodium and serum potassium were also measured. The patients were treated with spironolactone, 75 to 225 mg daily, and blood samples were withdrawn on days 7, 14, and 21 to 28 of drug administration. Plasma aldosterone concentrations (PAC) were not altered by spironolactone; however, significant increases were observed in plasma deoxycorticosterone on days 21 to 28 and in plasma corticosterone and cortisol on days 14 and 21 to 28. The suppressed PRA values were markedly increased on days 21 to 28 and low levels of serum potassium returned to the normal range on day 7. The lack of increase in PAC, despite a remarkable rise in PRA and serum potassium, suggests biosynthetic inhibition of spironolactone at the sites of 18-hydroxylation and/or 18-oxidation, because of the elevation of deoxycorticosterone and corticosterone.

Adenoma↗