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Biomedical subjects

K Nagata

Publications and source records attributed to K Nagata.

At least 919 records · Page 51Linked to original sources
PubMed1985

Collagen can modulate cell interactions with fibronectin.

We have examined the effects of soluble collagen on the function of fibronectin in baby hamster kidney (BHK) cells. Collagen and its purified alpha1(l) chain noncompetitively inhibited cell spreading on substrates precoated with fibronectin or a 75,000-D cell-binding fragment of fibronectin. Neither preincubation of cells with collagen followed by washing nor the addition of collagen to previously spread cells had any inhibitory effect on cell spreading, which indicates a requirement for the concurrent presence of collagen during the process of spreading. Treatment of collagen or alpha1(l) chain with collagenase abolished the inhibitory effect on fibronectin-mediated cell spreading. However, direct attachment of BHK cells to fibronectin-coated or 75,000-D fragment-coated substrates was not inhibited by collagen or by the alpha1(l) chain. Moreover, the binding of [3H]fibronectin or the 3'-75,000-D fragment to cell surfaces was not inhibited by the presence of soluble collagen, whereas soluble fibronectin inhibited binding. Although the binding of [3H]fibronectin-coated beads to BHK cell surfaces was also not inhibited by collagen, the phagocytosis of such beads was inhibited by the presence of collagen. On the other hand, soluble fibronectin partially inhibited the binding of fibronectin-coated beads but did not inhibit phagocytosis of the beads that did bind. The mechanism of the inhibition of fibronectin function by collagen and the possible interactions of two different kinds of receptors on the cell surface are discussed.

Animals↗
PubMed1985

Cellular mechanisms in in vivo production of gamma interferon induced by lipopolysaccharide in mice infected with Mycobacterium bovis BCG.

Infection of mice with Mycobacterium bovis BCG sensitizes them for immune induction of interferon (IFN)-gamma by specific antigen. These mice were found also to respond to lipopolysaccharide (LPS) and concanavalin A (Con A) with high level production of IFN-gamma in the circulation, which was not observed in control mice. In this study, we compared the IFN-gamma response to LPS with that to Con A in an attempt to clarify the cellular mechanisms responsible for in vivo LPS-induced IFN-gamma production. Consequently, (i) the responses to LPS and Con A differed in the kinetics, that to LPS having a longer lag period. (ii) Spleen cells taken from infected mice produced little IFN-gamma in response to LPS, but they showed a higher IFN-gamma response to Con A than those from control mice. (iii) By treating infected mice with immunosuppressive drugs or antibodies to T and natural killer cells before challenge with the inducers, it was indicated that different cellular systems are involved in the IFN-gamma responses to LPS and to Con A.

Animals↗
PubMed1985

Characterization of mitochondrial aspartate aminotransferase from the liver of pyridoxine-deficient rats.

The properties of crude and purified mitochondrial aspartate aminotransferase preparations from pyridoxine-deficient and control rat livers were compared. The preparations from the two sources showed very similar behaviors on heat treatment, electrophoresis and chromatofocusing, and had similar molecular weights, but their visible absorption spectra and circular dichroism properties were different. These results suggest that mitochondrial aspartate aminotransferase from pyridoxine-deficient and control rat livers have very similar properties, but differ somewhat in conformation in the region of the pyridoxal phosphate binding site.

Animals↗
PubMed1985

Changes in K+,Na+-sensitive actin gelation factor during the differentiation of myeloid leukemia cells.

A homodimer protein consisting of two 38,000 dalton peptides was isolated from a murine leukemia cell line (M1). The binding molar ratio of the 38K-dimer protein to purified skeletal muscle actin was saturated at 1:3, and when the 38K-dimer/actin ratio exceeded 1:12, gelation occurred. This gelation was completely inhibited by the presence of either 10 mM KCl or 20 mM NaCl. The protein induced actin filament bundling, which required a higher 38K-dimer/actin ratio and was not affected by the presence of monovalent cations. During the differentiation of Ml cells, the sensitivity of the 38K protein to monovalent cations was decreased; that is 20 mM KCl or 50 mM NaCl was required to inhibit the gelation by the 38K protein isolated from differentiated cells. On the other hand, the intracellular K+ content of Ml cells decreased from 70 +/- 5 mM to 18 +/- 3 mM, and Na+ increased from 10 +/- 5 mM to 40 +/- 10 mM during the differentiation. These findings suggest that the differentiation brought about conditions favourable for the 38K protein to induce actin gelation, and in turn, the locomotive and phagocytic activities which were induced only after differentiation in this cell line.

Animals↗
PubMed1985

Purification and characterization of seven distinct forms of liver microsomal cytochrome P-450 from untreated and inducer-treated male Wistar rats.

A total of nine forms of cytochrome P-450 were purified to homogeneity from liver microsomes of male Wistar rats. They were P-451 I and P-451 II from untreated rats, P-450 II and P-450 III from phenobarbital-treated rats, MC-P-448 L and MC-P-448 H from 3-methylcholanthrene-treated rats, and P-452, P-448 L, and P-448 H from 3,4,5,3',4'-pentachlorobiphenyl-treated rats. Among them, MC-P-448 L and MC-P-448 H were indistinguishable from P-448 L and P-448 H, respectively, with regard to electrophoretic, spectral, catalytic and immunochemical properties, and thus seven forms were distinct hemoproteins. The minimal molecular weight of each form was as follows: P-451 I (49,000), P-451 II (52,000), P-450 II (52,000), P-450 III (53,500), P-452 (48,000), P-448 L (56,000), P-448 H (54,000). Judging from the oxidized absolute spectra, P-448 H was a high-spin form and the others were of low-spin type. In a reconstituted system, N-demethylations of benzphetamine and aminopyrine were catalyzed by most of the forms at comparable rates. On the other hand, the activities for the oxidations of benzo[a]pyrene, 7-ethoxycoumarin, biphenyl, and estradiol-17 beta varied greatly among the forms of cytochrome P-450. The most efficient catalysts were as follows: P-448 L and P-451 II for benzo[a]pyrene 3-hydroxylation; P-448 L for 7-ethoxycoumarin O-deethylation; P-448 L, P-451 II, and P-448 H for biphenyl 4-hydroxylation; P-448 L and P-448 H for biphenyl 2-hydroxylation; and P-451 II and P-448 H for estradiol 2-hydroxylation. P-451 I, P-450 II, and P-450 III were somewhat poorer catalysts in metabolizing all the substrates except for benzphetamine and aminopyrine, but their substrate specificities were still distinguishable from one another. Of all the purified cytochrome P-450's, P-452 showed the least ability to metabolize all the substrates. Judging from the properties, it appears that six forms in male Wistar rats correspond to the distinct forms of cytochrome P-450 in Long-Evans and/or Sprague-Dawley rats reported by other workers, but P-451 I is a new constitutive isozyme in Wistar rats.

Animals↗
PubMed1985

The multiplicity of human pancreatic secretory trypsin inhibitor.

Four forms of pancreatic secretory trypsin inhibitor (PSTI; A1, A2, B, and C) were purified from human pancreatic juice. According to sequence results, the primary structure of B was different from that reported earlier (Greene, L.J., et al. (1976) Method Enzymol. 45, 813-825) at two positions, i.e. Asn21----Asp21, Asp29----Asn29. A1 and A2 were deamidated forms of B judging from peptide mappings with Staphylococcus aureus V8 protease. Gln45 in B was replaced by Glu in A1 and Gln51 in B was replaced by Glu in A2. C was an inhibitor lacking five amino acid residues from the amino terminal of B. B and C inhibited human cationic trypsin activity stoichiometrically with similar dissociation constants, but A1 and A2 showed poorer trypsin inhibitory activity than B and C.

Amino Acid Sequence↗
PubMed1985

Site-specific DNA binding of nuclear factor I: analyses of cellular binding sites.

Nuclear factor I is a cellular site-specific DNA-binding protein required for the efficient in vitro replication of adenovirus DNA. We have characterized human DNA sequences to which nuclear factor I binds. Three nuclear factor I binding sites (FIB sites), isolated from HeLa cell DNA, each contain the sequence TGG(N)6-7GCCAA. Comparison with other known and putative FIB sites suggests that this sequence is important for the binding of nuclear factor I. Nuclear factor I protects a 25- to 30-base-pair region surrounding this sequence from digestion by DNase I. Methylation protection studies suggest that nuclear factor I interacts with guanine residues within the TGG(N)6-7GCCAA consensus sequence. One binding site (FIB-2) contained a restriction endonuclease HaeIII cleavage site (GGCC) at the 5' end of the GCCAA motif. Digestion of FIB-2 with HaeIII abolished the binding of nuclear factor I. Southern blot analyses indicate that the cellular FIB sites described here are present within single-copy DNA in the HeLa cell genome.

Base Sequence↗
PubMed1985

Topographic electroencephalographic study with power ratio index mapping in patients with malignant brain tumors.

A variant of electroencephalogram (EEG) power spectral mapping called power ratio index (PRI) mapping was used to monitor 15 patients with malignant brain tumors. This index is generated by dividing the low frequency (delta, theta) power by the high frequency (alpha, beta) power. Because the nonparoxysmal effect of a brain tumor on the EEG is reflected as a relative loss of high frequency power and a gain in low frequency power, utilization of the PRI has the effect of placing the epicenter of the "power dysfunction" coincident with the epicenter of the tumor.

Adult↗
PubMed1985

A monovalent cation-sensitive actin-binding factor in a myeloid leukemia cell line.

Cell extracts of a murine leukemia cell line, M1, apparently contain three kinds of actin-gelation factors; a filamin-like protein, and 38K-dimer and 105K-dimer proteins. Unlike gelation by the filamin-like protein, gelation by the latter two proteins is inhibited by low concentrations of KCl. Our study of the 38K protein has been reported elsewhere (Takagi, K. et al., J. Biochem. Tokyo 97, 605-616, 1985). We here describe the purification and characterization of the 105K protein. The 105K protein differs from the alpha-actinin group of proteins in its antigenicity, peptide components and Ca2+-insensitivity. The saturated binding ratio of the protein to purified skeletal muscle actin is 1:8; when this ratio exceeds 1:20, gelation takes place. This gelation is inhibited completely by the presence of 25 mM KCl. Electron microscopy revealed that, in the absence of KCl, the 105K protein/actin mixture forms short actin bundles that are accompanied by a meshwork of short single filaments. The presence of 25 mM KCl did not prevent actin-bundling, but the bundles became longer and the meshwork of short filaments was no longer present.

Actins↗
PubMed1985

Purification and characterization of two forms of DNA polymerase alpha from mouse FM3A cells: a DNA polymerase alpha-primase complex and a free DNA polymerase alpha.

Two forms of DNA polymerase alpha, alpha 1 and alpha 2, have been partially purified from mouse FM3A cells by discriminating one form from the other on the basis of the association of primase activity. The primase activity in the most purified alpha 1 fraction co-sedimented with the DNA polymerase activity in a glycerol gradient, and almost no primase activity was detected in the most purified alpha 2 fraction. The primase activity associated with DNA polymerase alpha was assayed indirectly by measuring ATP-dependent DNA synthesis with poly (dT) as template. Characterization of the assay system was performed with the purified alpha 1. The system was absolutely dependent on the presence of ATP and a divalent cation. Mn2+ was much more effective than Mg2+, and 5-fold higher activity was observed with Mn2+ than with Mg2+ at their optimal concentrations. The primase activity assayed by the above system showed sensitivity to (NH4)2SO4 very similar to that of free primase reported by Tseng and Ahlem (J. Biol. Chem. 258, 9845-9849, 1983). The activity was inhibited by more than 50% by 20 mM (NH4)2SO4. alpha 1 and alpha 2 were very similar as DNA polymerases in their sensitivity to several inhibitors and their preference for template-primers, except that alpha 1 had a slightly greater preference for poly (dT) X (rA)10 than alpha 2 did. The major difference between the two forms was observed in their S values, 8.2 and 6.4 S for alpha 1 and alpha 2, respectively.

Animals↗
PubMed1985

Unique induction of cytochrome P-450 isozymes in rat liver microsomes by treatment with 3,4,5,3',4'-pentachlorobiphenyl and its effect on testosterone metabolism.

Pretreatment of male Wistar rats with 3,4,5,3',4'-pentachlorobiphenyl (PenCB), a potent 3-methylcholanthrene-type inducer, increased selectively 7 alpha-but strongly repressed 2 alpha-, 6 beta- and 16 alpha-hydroxylations of testosterone in the liver microsomes. To understand this unique phenomenon, the testosterone metabolism by three isozymes (P-452, P-448 L and P-448 H) of cytochrome P-450 purified from Wistar rats treated with PenCB was studied in a reconstituted system. For comparison 4 other isozymes (P-451 I, P-451 II, P-450 II and P-450 III) of cytochrome P-450 from untreated and phenobarbital-treated rats were also studied. In addition, the contribution of cytochrome P-450's to testosterone hydroxylation was examined by an immune complex inhibition of the activity and by a determination of the individual cytochrome P-450 in microsomes using antibodies. In the reconstituted system, 7 alpha-hydroxylation of testosterone was catalyzed almost exclusively by P-452, with the exception of P-451 I. On the other hand, the 6 beta-hydroxylation was catalyzed by most of the cytochrome P-450's tested at considerably lower rates. Among the seven forms, P-451 II was the most effective catalyst for 2 alpha- and 16 alpha-hydroxylations, with equally high turnover numbers, while other forms showed only low or no activity for either or both hydroxylations. The microsomal activity of 7 alpha-hydroxylation in PenCB-treated rats was inhibited almost completely by anti-P-452. A partial inhibition of the 16 alpha-hydroxylation was achieved by anti-P-451 II and anti-P-452 while the 6 beta-hydroxylation was insensitive to anti-P-451 II but slightly sensitive to anti-P-452. The activity of 2 alpha-hydroxylation was not detected in the liver microsomes from PenCB-treated rats. Immunochemical quantitation showed that in the microsomes from PenCB-treated rats, P-451 II, P-452, P-448 L and P-448 H accounted for 4.1, 3.6, 31.6 and 62.8%, respectively, of the total cytochrome P-450 (2.69 nmol/mg protein). On the other hand, the microsomal cytochrome P-450 in untreated rat livers (0.83 nmol/mg protein) consisted of 62.7% as P-451 II, less than 1% as P-452 and the remainder as P-451 I and other unknown forms.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1985

Inductive effect on hepatic enzymes and toxicity of congeners of PCBs and PCDFs.

The present paper describes a marked induction of liver microsomal cytochrome P-450 and cytosolic DT-diaphorase to cause possible disorder of steroid homeostasis and promotion of carcinogenicity of 4-nitroquinoline N-oxide (4-NQO) in rats by pretreatment with 3,4,5,3',4'-pentachlorobiphenyl (PenCB) or 2,3,4,7,8-pentachlorodibenzofuran (PenCDF). The animals were sacrificed 5 days after the pretreatment. These induction experiments showed that 7 alpha-hydroxylation of both progesterone and testosterone in liver microsomes was selectively increased to a great extent, but hydroxylations at the 2 alpha-, 6 beta- and 16 alpha-positions were depressed, together with 5 alpha-reduction. From the same microsomes, three of the strongly induced P-450 isozymes, i.e., high- and low-spin P-448s and P-452, were purified. The last isozyme was most responsible for 7 alpha-hydroxylation of testosterone. The pretreatment, also increased activity of DT-diaphorase and reduction of 4-NQO about 10-fold in liver 9000g supernatants. This reduction of 4-NQO was solely catalyzed by DT-diaphorase and the only product was 4-hydroxylaminoquinoline N-oxide, a proximate carcinogen, indicating that the pretreatment strongly increased production of a proximate carcinogen from 4-NQO. Such an enhancement of the metabolic activation of 4-NQO by the pretreatment was also observed to some extent in the lung and the skin. Persistency of PenCB and PenCDF in the liver of rats was also discussed.

4-Nitroquinoline-1-oxide↗
PubMed1985

A study on the osseous elements in malignant fibrous histiocytoma of bone.

By studying histochemically and ultrastructurally a case of malignant fibrous histiocytoma (MFH) of bone with neoplastic osteoid elements, the distinction of the tumor from osteosarcoma was discussed. MFH was likely to originate from undifferentiated mesenchymal cells that induced a histiocytic line of differentiation, and some histiocytes seemed to be transformed into well differentiated fibroblastic cells which accordingly differentiated into fibroblasts and osteoblasts. This may explain the existence of the osseous elements in MFH. Sarcoma showing the bimodal--histiocytic and fibroblastic--differentiation should be diagnosed as malignant fibrous histiocytoma, even if it contains tumorous osteoid; it must be clearly distinguished from osteosarcoma, in which the various cells only on a fibroblastic line of differentiation can be identified and the osteoblasts are the predominant cells.

Acid Phosphatase↗
PubMed1985

In vitro and in vivo inhibitory effects of propentofylline on cyclic AMP phosphodiesterase activity.

1-(5'-Oxohexyl)-3-methyl-7-propylxanthine (propentofylline), a vasoactive agent, was investigated for its in vitro and in vivo inhibitory effects on cyclic AMP phosphodiesterases activity. Soluble cyclic AMP phosphodiesterases from the cerebral cortex, heart muscle, descending aorta and platelet showed two Km values, high and low. The low Km values were in the range of 2.1-3.0 mumol/l and the high Km values were 111, 28.7, 30.2 and 18.7 mumol/l, respectively. Propentofylline inhibited the enzyme from the 4 tissues noncompetitively. Ki values for the low and high Km cyclic AMP phosphodiesterases were 83.4-135 and 107-188 mumol/l, respectively. In the four tissues, the enzyme inhibitory effect of propentofylline was 1/4 to 1/10 times that of 3-isobutyl-1-methylxanthine (IBMX) but 3-9 and 6-17 times as potent as those of theophylline and caffeine, respectively. The in vivo cyclic AMP phosphodiesterase inhibitory effect of propentofylline was determined in mice using an elevation of plasma cyclic AMP levels as a measure. When given both singly and in combination with isoprenaline (isoproterenol), propentofylline was a potent inhibitor of cyclic AMP phosphodiesterase in the case of intravenous administration.

3',5'-Cyclic-AMP Phosphodiesterases↗