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T Masaki

Publications and source records attributed to T Masaki.

At least 289 records · Page 16Linked to original sources
PubMed1994

Changes in annexin I and II levels during the postnatal development of rat pancreatic islets.

The expression patterns and the dynamic changes in content of both annexin I and annexin II in the rat pancreatic islets during postnatal development were investigated by both western blot analysis and immunohistochemistry. Immunohistochemical methods clearly demonstrated the presence of annexins I and II exclusively in pancreatic islets, while exocrine tissues were not stained by anti-annexin antibodies. Pancreatic islets were diffusely stained with no specific differences in distribution between different cell types. The expression of annexin I in pancreatic islets gradually increased with postnatal development. A developmental study of annexins I and II by western blot analysis essentially supported the results obtained by immunohistochemistry. In addition, the increasing expression of two protein tyrosine kinases, epidermal growth factor-receptor/kinase and pp60src, which phosphorylate annexin I and annexin II, respectively, and of protein kinase C, which phosphorylates both proteins, was also shown during postnatal development in rat pancreatic islets. Thus, a relationship between the expression of annexins I and II and the maturation of islet cell function is suggested.

Actins↗
PubMed1994

Hydrolysis of S-2-aminoethylcysteinyl peptide bond by Achromobacter protease I.

The substrate specificity of Achromobacter protease I (API) was examined for S-2-aminoethyl(AE)cysteinyl bonds in Bz-AEC-OMe/OEt, Bz-AEC-NH2, and AE-insulin B chain. The protease hydrolyzed all of the tested AE-cysteinyl bonds at the same rate as that of lysyl bonds. Kinetic parameters were estimated for this hydrolysis reaction.

Alcaligenes↗
PubMed1994

Involvement of annexin I and annexin II in hepatocyte proliferation: can annexins I and II be markers for proliferative hepatocytes?

Annexin is the name of a new family of Ca(2+)-dependent membrane-binding proteins. Eleven types of its related proteins have been reported to date. Among those, annexin I and annexin II have been reported to possess many biological functions in vitro. Its actual role in vivo, however, is yet unknown. The involvement of annexin I and annexin II in the proliferation processes of hepatocytes was examined in the following aspects: (a) hepatocyte proliferation after carbon tetrachloride-induced liver damage, (b) hepatocyte regeneration after partial hepatectomy and (c) postnatal development of hepatocytes. These results showed collectively that annexin I and annexin II were increased in proliferative (or regenerative) hepatocytes, suggesting that both proteins play a certain role in the proliferation event. Furthermore, annexin I- and annexin II-positive hepatocytes always show a wider distribution than that of proliferating cell nuclear antigen or cytokeratin 7-positive hepatocytes, indicating that annexin I and annexin II may be useful markers for detecting not only actively proliferating hepatocytes but also hepatocytes in preproliferative and postproliferative stages.

Animals↗
PubMed1994

Enhanced expression of catalytic subunits of protein phosphatase type 1 and high S-phase fraction in liposarcoma.

The expression of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, was examined in 8 cases of lipoma as a benign tumor and 4 cases of liposarcoma as a malignant tumor using immunohistochemical analysis. Both types of of tumor cells stained positively with antisera against PP1 catalytic subunit isoforms PP1 alpha and PP1 gamma 1 were significantly higher in liposarcoma than in lipoma. Furthermore, liposarcoma showed a markedly high S-phase fraction in the cell cycle of tumor cells, as compared with lipoma. These results suggest that PP1 is involved in the accelerated growth of malignant cells in liposarcoma.

Adult↗
PubMed1994

Enhanced expression of catalytic subunit isoform PP1 gamma 1 of protein phosphatase type 1 in malignant fibrous histiocytoma.

The expression of the three catalytic subunits of protein phosphatase (PP) type 1 and 2A, PP1 alpha, PP1 gamma 1, and PP2AC, was examined in malignant fibrous histiocytoma using immunohistochemical analysis. The percentage of cells stained positively with antiserum against PP1 catalytic subunit isoform PP1 gamma 1 was significantly higher in tumorous region than in non-tumorous region of malignant fibrous histiocytoma. Furthermore, tumorous region showed markedly high S-phase fraction in the cell cycle, as compared to non-tumorous region. These results suggest that PP1 gamma 1 is involved in the accelerated growth of tumor cells in malignant fibrous histiocytoma.

Adult↗
PubMed1994

Elevation of ceruloplasmin activity involved in changes of hepatic metal concentration in primary biliary cirrhosis.

Primary biliary cirrhosis (PBC) patients showed increased ceruloplasmin activity and Cu content in the serum as compared to the control group. Moreover, Cu, Fe, and Zn contents were measured in the livers of autopsied cases. The PBC patients showed increased Cu content and reduced Fe and Zn levels. In PBC cases, Cu transportation via bile is disturbed due to collapse of the interlobular bile ducts and consequently Cu accumulates in the liver. Thus, it is likely that serum ceruloplasmin activity increases to metabolize the accumulated hepatic Cu and that Cu content increases in the serum as a ceruloplasmin-bound form. Furthermore, reduction of Fe and Zn contents in the liver of the PBC patients indicated the possible relationship of ceruloplasmin to Fe and Zn metabolism as well as Cu metabolism.

Cations↗
PubMed1994

[A study of complement fixation test by trinitrophenyl-cap-liposome: application of viral antibody test].

The complement fixation (CF) test is used as one of the diagnostic laboratory procedures for viral infections. The liposome is employed in the immunological method for basic research and we used the trinitrophenyl-cap-liposome (TNP-L) instead of sensitized erythrocyte for CF test. "TNP-L" consists of a plasma membrane of trinitrophenyl bases sensitized with antibody and is dissolved easily by animal complements. Carboxyfluorescein enclosed in liposome is released in fixed quantities according to liposome dissolution. Therefore, as our conclusion, the above CF method has a good agreement to that of sensitized erythrocyte. TNP-L method has advantages to be able to eliminate the individual differences and shorter storage-term of red blood cells and is also satisfactory for utilization with high reproducibility and intra day precision.

Animals↗
PubMed1994

[Feasibility of DNA analysis for prognostic evaluations of colorectal cancer using touch preparations and image cytometry].

The purpose of this study is to demonstrate the applicability of DNA ploidy analysis by using touch preparations obtained from fresh and frozen tissues on the prognostic evaluations of colorectal cancer, especially the development of hepatic metastases. The specimens obtained from surgically resected colorectal carcinomas (32), and hepatic metastases (4), were lightly touched with the slide glasses. Among the 32 patients with colorectal cancers, 7 had synchronous liver metastases, and 5 metastases developed metachronously. After formalin-fixation and Feulgen staining, the DNA analysis was performed by image cytometer (ICM, CAS200R). The data were expressed as the ploidy patterns and DNA indices (p-DNAI: peak DNA index, m-DNAI: mean DNA index), and were correlated very well with those obtained from cytophotometry. The DNA ploidy pattern among the 32 colorectal cancer specimens were Aneuploid(A) in 16, Polyploid (P) in 7, Diploid (D) in 4 and D+P in 5. The cases with synchronous or metachronous liver metastases had a higher m-DNAI (1.74 +/- 0.28) and were Aneuploid in 8, P in 3, and D+P in 1 case. Aneuploidy or Polyploidy predominated among the cases with metachronous liver metastases (4 in 5 cases), with m-DNAI higher than 1.5. Thus, "m-DNA > 1.5" could be a useful prognostic indicator of the high risk group of liver metastases. The liver metastases specimens had Aneuploid and Polyploid patterns in 2 cases each, with m-DNAI ranging from 1.88 to 2.31. DNA ploidy pattern analysis using touch preparations with image cytometry may be useful in determining the prognosis for colorectal cancer.

Adult↗
PubMed1993

Inhibition of tumor growth and metastasis of rodent tumors by the angiogenesis inhibitor O-(chloroacetyl-carbamoyl)fumagillol (TNP-470; AGM-1470).

The effect of the potent angiogenesis inhibitor O-(chloroacetyl-carbamoyl)fumagillol (TNP-470), a semisynthetic analogue of fumagillin, on tumor growth and metastasis was studied using rodent tumors. Injection of TNP-470 s.c. inhibited tumor growth in a dose-dependent manner, and the tumor sizes of B16BL6 melanoma, M5076 reticulum cell sarcoma, Lewis lung carcinoma, and Walker 256 carcinoma were maximally reduced to 16, 10, 17, and 4% of that in the respective control. The activity of TNP-470 upon i.v. injection was slightly weaker than that following s.c. injection. This tendency was observed for all the tumors tested. Injection i.v. (infusion) of TNP-470 increased the life span of Walker 256 carcinoma-bearing rats by 183% over the control, while bolus i.v. injection increased the life span by only 47%. TNP-470 reduced the number of pulmonary metastatic foci of i.v. inoculated B16BL6 melanoma in a dose-dependent manner, and the number of metastatic foci was reduced to 10% of that in the control by treatment with TNP-470 at 60 mg/kg, 3 times/week. The mean survival time of B16BL6 tumor-bearing mice treated with TNP-470 using this regimen was extended by 56% over that of control mice. TNP-470 at 10 mg/kg every day also reduced the number of metastatic foci of M5076 sarcoma in the liver after resection of the tumor from the primary site. Adriamycin at the same dose only slightly reduced the number of metastatic foci, even though TNP-470 and Adriamycin showed roughly equal inhibitory activity against M5076 sarcoma growth. TNP-470 extended the mean survival time of M5076 tumor-bearing mice by more than 100% over that of control mice at 30 mg/kg every 3 days, while Adriamycin extended mean survival times by maximally 20% at 10 mg/kg. These results show that the angiogenesis inhibitor TNP-470 has strong inhibitory activities against in vivo growth and metastasis of a wide variety of tumors.

Animals↗
PubMed1993

Expression of endothelin-1 in the lungs of patients with pulmonary hypertension.

BACKGROUND: Pulmonary hypertension is characterized by an increase in vascular tone or an abnormal proliferation of muscle cells in the walls of small pulmonary arteries. Endothelin-1 is a potent endothelium-derived vasoconstrictor peptide with important mitogenic properties. It has therefore been suggested that endothelin-1 may contribute to increases in pulmonary arterial tone or smooth-muscle proliferation in patients with pulmonary hypertension. We studied the sites and magnitude of endothelin-1 production in the lungs of patients with various causes of pulmonary hypertension. METHODS: We studied the distribution of endothelin-1-like immunoreactivity (by immunocytochemical analysis) and endothelin-1 messenger RNA (by in situ hybridization) in lung specimens from 15 control subjects, 11 patients with plexogenic pulmonary arteriopathy (grades 4 through 6), and 17 patients with secondary pulmonary hypertension and pulmonary arteriopathy of grades 1 through 3. RESULTS: In the controls, endothelin-1-like immunoreactivity was rarely seen in vascular endothelial cells. In the patients with pulmonary hypertension, endothelin-1-like immunoreactivity was abundant, predominantly in endothelial cells of pulmonary arteries with medial thickening and intimal fibrosis. Likewise, endothelin-1 messenger RNA was increased in the patients with pulmonary hypertension and was expressed primarily at sites of endothelin-1-like immunoreactivity. There was a strong correlation between the intensity of endothelin-1-like immunoreactivity and pulmonary vascular resistance in the patients with plexogenic pulmonary arteriopathy, but not in those with secondary pulmonary hypertension. CONCLUSIONS: Pulmonary hypertension is associated with the increased expression of endothelin-1 in vascular endothelial cells, suggesting that the local production of endothelin-1 may contribute to the vascular abnormalities associated with this disorder.

Adult↗
PubMed1993

Distinct subdomains of human endothelin receptors determine their selectivity to endothelinA-selective antagonist and endothelinB-selective agonists.

The endothelin (ET) family of peptides acts via two subtypes of G-protein-coupled heptahelical receptors termed ETA and ETB, which have distinct rank orders of affinity to endothelin receptor agonists and antagonists. To delineate which portions of the receptor molecules determine ligand selectivity, we have constructed a series of chimeras between human ETA and ETB receptors and characterized the chimeric receptors expressed in heterologous cell lines by competitive radioligand binding analysis and by measuring agonist-induced transients of intracellular Ca2+. We demonstrate that the binding determinant for the ETB-selective agonists ET-3, BQ3020, and IRL1620 residues within the region spanning the putative transmembrane helices IV-VI and the adjacent loop regions. In contrast, the transmembrane helices I, II, III, and VII plus the intervening loop regions specify the selectivity for BQ123, an ETA-selective antagonist. BQ123 exhibited no detectable agonistic activity in all wild-type and chimeric receptors tested. A chimeric receptor that has the transmembrane helices IV-VI (and adjacent loops) from the ETB receptor inserted into the remaining regions from the ETA receptor binds both the ETA- and ETB-selective ligands with high affinities. Moreover, BQ123 competitively inhibits the binding of the amino-terminally truncated ETB agonists, 125I-BQ3020 and 125I-IRL1620, to this chimeric receptor, suggesting that BQ123 is a mimic of the carboxyl-terminal linear portion of endothelins. These findings indicate that there are at least two separable ligand interaction subdomains within the endothelin receptors.

Amino Acid Sequence↗
PubMed1993

Enhancement of acetylcholine release in the hippocampus by 6R-L-erythro-5,6,7,8-tetrahydrobiopterin is mediated by 5-hydroxytryptamine.

Recently, we reported that 6R-L-erythro-tetrahydrobiopterin (6R-BH4), a natural cofactor for L-aromatic amino acid hydroxylases, enhances in vivo release of acetylcholine (ACh) in the rat hippocampus: the enhancement was abolished after depletion of brain catecholamines and 5-hydroxytryptamine (5-HT) by pretreatment with reserpine. In the present study, we have used in vivo brain microdialysis to clarify the neuronal mechanism involved in the enhancement of ACh release by 6R-BH4. After depletion of catecholamines by pretreatment of rats with alpha-methyl-p-tyrosine, 6R-BH4 added to the perfusion fluid still induced an increase in extracellular ACh levels monitored by microdialysis as an index of ACh release. In contrast, after depletion of 5-HT by pretreatment with p-chlorophenylalanine, most of the 6R-BH4-induced enhancement was eliminated. Exogenous 5-HT and dopamine (DA) but not noradrenaline added to the perfusion fluid stimulated ACh release with 5-HT being far more potent. Intraperitoneal administration of 5-hydroxytryptophan and L-DOPA also enhanced ACh release, presumably by their conversion to 5-HT and catecholamines, respectively. Administration of 6R-BH4 increased hippocampal 5-HT release, as indicated by increased extracellular levels of the major 5-HT metabolite, 5-hydroxyindoleacetic acid. These results suggest that 6R-BH4 stimulates ACh release in the hippocampus, mainly by augmenting release of 5-HT, a potent stimulator of ACh release, and partly by augmenting release of DA.

5-Hydroxytryptophan↗
PubMed1993

Human smooth muscle myosin heavy chain gene mapped to chromosomal region 16q12.

The partial nucleotide sequence encoding the rod portion of the entire amino acid sequence of human smooth muscle myosin heavy chain (MHC) which corresponds to MYH11, according to Human Gene Mapping nomenclature, has been determined by cloning a complementary DNA (cDNA) and sequencing the cDNA (UMYHSM). Northern blot analysis with the UMYHSM fragment (4.3 Kb) showed that the smooth muscle MHC of the human umbilical artery is expressed in the human umbilical artery, bladder, esophagus and trachea. Southern blot analysis of human genomic DNA from human-mouse or human-Chinese hamster somatic cell hybrids demonstrated that the human smooth muscle MHC was mapped to human chromosome 16. Regional mapping of UMYHSM was performed using human cell lines with partial deletion and trisomy of chromosome 16. As a result, the human smooth muscle MHC gene segregated with 16p11-q12. In situ hybridization of biotin-labeled human smooth muscle MHC probe (UMYHSM fragment) to normal human metaphase chromosome independently showed that the human smooth muscle MHC gene (MYH11) is assigned to chromosome region 16q12. Analysis of early metaphase chromosomes showed that hybridization signals were in 16q12.1. In the human, although skeletal, cardiac, smooth muscle, and nonmuscle MHC genes are mapped to chromosomes 17, 14, 16, and 22, respectively, structural similarities of these MHC genes strongly suggest the common origin of these genes.

Amino Acid Sequence↗
PubMed1993

Arginine-vasopressin increases the release of ET-1 into perfusate of rat mesenteric artery.

The regulatory systems of endogenous endothelin-1 (ET-1) production from intact tissues and the effects of produced ET-1 on vascular tonus by a closed circuit perfusion system of rat mesenteric artery were investigated. It was demonstrated that ET-1 is released from intact mesenteric arterial beds from Wistar rats both under basal conditions and after stimulation with arginine-vasopressin (AVP) (10(-10)-10(-9) M). Furthermore, AVP (10(-10)-10(-9) M) markedly and dose-dependently induced the expression of prepro ET-1 mRNA in the mesenteric arterial beds. Increased release of ET-1 by AVP may contribute to maintaining vascular tonus. Concomitant addition of actinomycin D inhibited the increased expression of prepro ET-1 mRNA and reduced the amount of immunoreactive ET-1 found during the 6-hour perfusate from AVP (10(-10) M)-stimulated and -unstimulated tissues.

Animals↗
PubMed1993

Characterization of phosphoramidon-sensitive metalloproteinases with endothelin-converting enzyme activity in porcine lung membrane.

Endothelin-1 (ET-1), a 21 amino-acid potent vasoconstrictor peptide, is produced from the biologically inactive intermediate big ET-1 via an endoproteolytic cleavage between Trp-21 and Val-22 by endothelin converting enzyme (ECE). cDNA sequence analysis predicts that the two other members of the endothelin family, ET-2 and ET-3, are also generated from the corresponding intermediates called big ET-2 and big ET-3, respectively. The metalloproteinase inhibitor phosphoramidon inhibited the conversion of big ET-1 into mature ET-1 both in vivo and in cultured endothelial cells, suggesting that ECE may be a neutral metalloproteinase. In this study, we solubilized and partially purified ECE from the membrane fraction of porcine lung. Using gel filtration chromatography, we separated two distinct ECE activities, designated M1 (apparent molecular mass approx. 300 kDa) and M2 (approx. 65 kDa). Optimum pH for the cleavage of big ET-1 by M1 and M2 was 7.0 and 7.5, respectively. M1 efficiently converted human big ET-1(1-38) to ET-1, but not human big ET-2(1-37) or human big ET-3(1-41)-amide. In contrast, M2 converted both big ET-1 and big ET-2, but not big ET-3. M1 was inhibited by phosphoramidon (IC50 approx. 1 microM) but not by thiorphan or bacitracin. In contrast, M2 was inhibited by much lower concentrations of phosphoramidon (IC50 approx. 0.3 nM), as well as by thiorphan and bacitracin. ECE activity in M1 was able to bind to a concanavalin A-agarose column and was eluted by alpha-methyl-D-glucoside, indicating that the ECE is glycosylated. From these results, M1 and M2 from the porcine lung membrane are similar to the candidate of ECE in endothelial cells and neutral endopeptidase in kidney (EC 3.4.24.11), respectively. Taken in conjunction with the previous finding that neither thiorphan nor bacitracin affected the conversion of endogenously synthesized big ET-1 in cultured endothelial cells, we conclude that physiologically relevant ECE found in the endothelial cells is more similar to M1 than to M2.

Animals↗
PubMed1993

Malignant potential in flat elevations.

Ninety-nine colonoscopically removed flat elevations were examined. They were divided into two groups: Group 1--flat elevations 1 to 5 mm in diameter (55 cases)--and Group 2--flat elevations 6 to 10 mm in diameter (44 cases). Group 2 had a higher percentage of adenomas (86.4 percent) than Group 1 (67.3 percent). In adenoma cases (flat adenomas), Group 2 tended to show a higher degree of dysplasia. The rates of mild and moderate dysplasia were 83.8 percent and 16.2 percent in Group 1 vs. 1.70 percent and 13.2 percent in Group 2, respectively. Group 2 contained six cases (15.8 percent) of intramucosal carcinoma (severe dysplasia), while there were no cancer cases in Group 1. Both malignancy rate and degree of dysplasia were size dependent; the larger the lesion the more severe the dysplasia. Our study also revealed that small flat elevations tend to contain higher numbers of nonneoplastic lesions than do larger lesions. Increased detection of nonneoplastic lesions seems to have contributed to an overall decline in the malignancy rate of flat elevations in recent reports.

Adenoma↗
PubMed1993

Endothelin-2-converting enzyme from human renal adenocarcinoma cells is a phosphoramidon-sensitive, membrane-bound metalloprotease.

From the membrane fraction of cultured human renal adenocarcinoma (ACHN) cells, two endothelin-2-converting enzymes (ECE-2A and ECE-2B) were solubilized with detergent Lubrol PX and separated by hydrophobic butyl fast-performance liquid chromatography. The pH range of the converting activity of ECE-2B for big endothelin-1 (big ET-1), big ET-2, or big ET-3, was very narrow, and the optimal pH for each substrate was significantly different; the pH optimum for big ET-1 was 6.8 and that for big ET-2 or big ET-3 was 6.4. The ET-converting activity was abolished by phosphoramidon, 1,10-phenanthroline and EDTA but was not inhibited by thiorphan, E-64, leupeptin, PCMS, p-APMSF, or pepstatin A. The conversion efficiency for big ET-2 or big ET-3 by ECE-2B was approximately one-eighth of that for big ET-1. The molecular weight of ECE-2B was estimated to be 400 kDa by gel filtration. Because these characteristics of ECE-2B are very similar to those of ET-1-converting enzyme (ECE-1) in endothelial cells, these results raise the possibility that ECE-2B is identical to ECE-1 and that a single ECE physiologically converts all big ETs to the corresponding ETs in ET-producing cells.

Adenocarcinoma↗