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Biomedical subjects

Y Mitsui

Publications and source records attributed to Y Mitsui.

At least 271 records · Page 15Linked to original sources
PubMed1987

Heparan sulfate and heparin as a potentiator or a suppressor of growth of normal and transformed vascular endothelial cells.

The effects of glycosaminoglycans (GAGs), especially heparan sulfate, on human and porcine vascular endothelial cell growth in the presence of 10% fetal bovine serum (FBS) or so-called heparin-binding growth factors, acidic FGF (aFGF) or basic FGF (bFGF), were investigated in a series of studies in order to clarify their role in cell proliferation. The promotion of normal cell growth by aFGF was suppressed by heparan sulfate but enhanced by heparin, while growth promotion by bFGF was suppressed by both GAGs. Chondroitin sulfate and hyaluronic acid showed no significant suppression of promotion, even at much higher concentrations. The growth of spontaneously transformed cells was enhanced by heparan sulfate or heparin in the presence of 10% FBS or aFGF, while growth promotion in the presence of bFGF was suppressed by both GAGs. From these results, we concluded that heparan sulfate and heparin are not always functional analogs and that in some cases they exert opposite actions on the modulation of normal endothelial cell growth. The findings that heparan sulfate enhanced the growth of transformed cells but suppressed the growth of normal cells in the presence of 10% FBS or aFGF were consistent with those of our previous studies on human fibroblasts, confirming the occurrence of some common alterations in the signal transduction system or cell surface upon cellular transformation. The role of heparan sulfate in the modulation of endothelial cell proliferation in vivo is also discussed.

Cell Division↗
PubMed1987

Hyaluronate synthetase inhibition by normal and transformed human fibroblasts during growth reduction.

To establish the relation of glycosaminoglycan synthesis to cell proliferation, we investigated the synthesis of individual glycosaminoglycan species by intact cells and in a cell-free system, using normal and transformed human fibroblasts under differing culture conditions. Reducing serum concentration brought about a marked decline in the synthesis of hyaluronate (HA) as well as cell proliferation on both normal and transformed cells. Both HA synthesis and proliferation decreased with increasing cell densities markedly (in inverse proportion to cell density) in normal cells but gradually in transformed cells. This noticeable congruity of the changes in HA synthesis and proliferation indicates that the change in HA synthesis is related primarily to cell proliferation rather than to cell density or cellular transformation. Examination of HA synthesis in a cell-free system demonstrated that the activity of HA synthetase also fluctuated in conjunction with cell proliferation. Furthermore, growth-reduced cells (except crowded transformed cells) inhibited cell-free HA synthesis and this inhibition was induced coincidentally with a decrease in both HA synthetase activity and proliferation. These findings suggest that the change in HA synthesis is significant in the regulation of cell proliferation.

Cell Division↗
PubMed1987

Elastic properties and beta-sheet structure of connectin threads.

Connectin is a very long and flexible protein of striated muscle, linking myosin filaments to z discs in a sarcomere. Isolated native connectin in solution frequently forms elastic threads upon concentration of the solution, by side-by-side association of molecules. An X-ray diffraction study was performed to examine the presence of beta-sheet structure in artificially prepared threads. The elastic properties of such threads were measured at various temperatures. Negative temperature dependence of the elastic coefficient suggests that the elasticity of connectin threads is due to deformation of the three-dimensional structure and not to rubber-like behavior.

Animals↗
PubMed1986

Crystallization and preliminary X-ray studies of recombinant murine interferon-beta.

Recombinant murine interferon-beta produced in Escherichia coli was purified and crystallized in an orthorhombic space group C222(1) with a = 61.67 A, b = 55.62 A, and c = 92.16 A. The crystals with a slight tendency for orientational disorder around the c axis diffract at least up to 3.3-A resolution. The crystallizability and the fact that the crystallographic asymmetric unit contains only one molecule of murine interferon-beta strongly indicate that the present preparation (Matsuda, S., Utsumi, J., and Kawano, G. (1986) J. Interferon Res., in press) of recombinant murine interferon-beta is predominantly homogeneous with respect to chemical, tertiary, and quaternary structures.

Animals↗
PubMed1986

Local and overall conformations of DNA double helices with the A - T base pairs.

Raman spectra have been observed of two different poly[d(A-T)].poly[d(A-T)] fibers, whose X-ray diffractions were confirmed to be purely of A and B forms. A number of spectral differences were found between the A and B forms of this DNA duplex, and they were ascribed to local conformational differences in the adenosine, thymidine and phosphodiester portions. The ascription was made on the basis of a separate series of Raman examinations on six crystals involving adenosine or thymidine, and fifteen other nucleotide crystals, whose structures are all known by previous crystallographic works. By taking these structure-spectrum correlations thus obtained into account, a Raman spectroscopic investigation was made of a few double-helical DNAs in aqueous solutions. It has been concluded that both poly[d(A-T)].poly[d(A-T)] and poly(dA).poly(dT) have a C2'endo-anti adenosine, C2'endo-anti thymidine, a b-type mainchain (beta = 160 +/- 15 degrees, gamma = 45 +/- 15 degrees, delta = 140 +/- 10 degrees) and an a2-type mainchain (beta = 210 +/- 10 degrees, gamma = 45 +/- 15 degrees, delta = 140 +/- 10 degrees) not only in low-salt medium but also in 6.6 M CsF solutions, where beta, gamma and delta are the torsion angles around O5'-C5', C5'-C4' and C4'-C3' axes, respectively. Poly(rA).poly(dT), on the other hand, was considered to have a heteronomous duplex structure, in which the poly(rA) strand has a C3'endo-anti adenosine and a1-type mainchain (beta = 175 +/- 25 degrees, gamma = 45 +/- 15 degrees, delta = 80 +/- 10 degrees) whereas the poly(dT) strand has a C2'endo-anti thymidine and b-type mainchain.

Adenosine↗
PubMed1986

The magician's forceps phenomenon in exotropia under general anaesthesia.

Prifinium bromide was administered for eight weeks to three patients with exotropia. Under general anaesthesia active discharges from the lateral rectus muscles were demonstrated by electromyography. When a slight adductive force was applied to the straight or the master eye, active discharge from the lateral rectus of the associate eye disappeared in all patients, and this eye moved in the direction of orthophorisation. The discharge reappeared when the master eye was released from the forced adduction. From these results the authors concluded that proprioception is involved in the magician's forceps phenomenon discovered by Mitsui in exotropic patients in 1978.

Adolescent↗
PubMed1986

Change in activity of an adenosine triphosphate-stimulated glucocorticoid receptor translocation promoter in the cytosol and nucleus of rat liver under various physiological conditions.

Rat liver contains an ATP-stimulated translocation promoter (ASTP), which is not a receptor and which enhances nuclear binding of activated receptor-glucocorticoid complex in the presence of ATP. Studies were made on changes in ASTP activity under various conditions to elucidate its physiological role in the action of glucocorticoid hormone. ASTP activity in the cytosol fraction increased markedly after adrenalectomy. Conversely, 30 min after a single injection of dexamethasone it decreased and then gradually increased. The increase in ASTP activity after adrenalectomy was inhibited by actinomycin D or cycloheximide. With decrease in ASTP activity in the cytosol fraction after the administration of glucocorticoids, activity appeared in the nuclear fraction 30 min after injection and then decreased. Thus, after the dexamethasone injection, the changes in ASTP activity in the cytosol and nuclei were similar to but not coincident with those in the glucocorticoid receptor. These results suggest, but do not prove, that ASTP is translocated or binds to nuclei with activated receptor-glucocorticoid complexes. From these results, we consider that ASTP may be an integral part of the regulatory mechanism for the action of steroid hormones and may influence specific gene expression by increasing nuclear binding of the activated complex.

Adenosine Triphosphate↗
PubMed1986

The nature of reverse phase reflex eye movement.

The unusual phenomenon of reverse phase reflex eye movement was first described by Ishikawa. In this study the reflex frequency response was examined by electrooculography. In typical cases a reflex was observed by repeated forced duction up to 9 Hz. As a result it was postulated that proprioception is usually involved in reverse phase reflex eye movement, because visual eye movement cannot respond to a movement beyond 1 Hz. When the lag-times between the peaks of forced duction in one eye and those of the reflex movement in the other were measured, they were almost zero or even negative at high frequencies of forced duction as 6 and 9 Hz. This phase advance of the reflex movement was explained only when the receptor of the reflex had a dynamic response, because 90 degrees phase advance results in a reflex through such a receptor. The primary ending of muscle spindle represents such a receptor. The magician's forceps phenomenon as first discovered by Mitsui in exotropia is supposed to be a blocking reflex through the tendon organ. The transmission lag-times of both reflexes can be as short as 20 msec, but must be slightly longer to consider them to be monosynaptic.

Adolescent↗
PubMed1985

X-ray crystallographic and chromatographic characterization of the crystals of Ca2+-calmodulin complexed with bee venom melittin.

Crystals of calmodulin complexed with both Ca2+ and melittin, a peptide from bee venom, have been grown from 2-methyl-2,4-pentanediol solution by using the hanging drop method of vapour diffusion. The crystals belong to space group P2(1)2(1)2(1) with a = 97.3(9) A, b = 56.5(0) A, c = 33.4(9) A and Z = 4. Analyses of the dissolved crystals by high performance liquid chromatography show that the crystals contain a 1:1 complex of calmodulin and melittin. An asymmetric unit contains one such complex and the solvent content of the crystals is 47.5% (v/v).

Animals↗
PubMed1985

Histone H1 in G1 arrested, senescent, and Werner syndrome fibroblasts.

Histone H1 content and synthesis were examined in normal, Werner-syndrome, and transformed fibroblasts. Analysis of 3H-lysine incorporation indicated that senescent cells, but not G1-arrested young cells, had a lower ratio of molar synthesis of H1 histone to nucleosome histones than did growing young cells or gamma-ray-transformed cells. Furthermore, a biochemical study of histone H1 content plotted as a function of DNA synthesis activity and an immunocytological study using antiserum against histone H1 revealed that senescent cells had a lower histone H1 content than did young cultures at all stages of cell proliferation. Werner syndrome skin fibroblasts at early passage, however, had amounts of histone H1 comparable to those of age-matched normal control fibroblasts. We conclude that a decline, with increasing passage number, in content and synthesis of H1 histone relative to nucleosomal histones (Mitsui et al., 1980) was not simply due to passage-related accumulation of G1-arrested cells, but actually reflected age specific changes of cultured human fibroblasts. The depletion of histone H1 in the chromatin of senescent cells is a possible cause of DNA strand breakage or relaxation of gene repression.

Cell Cycle↗
PubMed1985

Cell surface changes in senescent and Werner's syndrome fibroblasts: their role in cell proliferation.

Cell surface is known to participate in the regulation of cell proliferation through interaction with adjacent cell surfaces or the extracellular matrix, or both. A clinical survey of the Werner syndrome suggests some disorders in glycosaminoglycan metabolism. Also, the skin fibroblasts derived from the patients with WS have a reduced proliferation capacity. We here examined, in vitro and in vivo, alterations of the cell-surface properties of WS cells and aging human fibroblasts. Cell-surface negative charges, examined by electrophoretic mobility of dispersed single cells in buffer, were seen to decline steadily as a function of cumulative population doublings. A strict linear relationship was found between electrophoretic mobility (micron/sec/V/cm) and number of cells harvested at each passage in all cell lines examined. The slope of this line in cells from donors of different ages indicated that WS fibroblasts resemble cells from much older normal controls. The same conclusion was drawn from our previous study of Con A-mediated red cell adsorption, which was confirmed as reflecting an alteration of cell-surface coat negative charge. Electrophoretic mobility after treatment of cell surface with degradative enzymes showed that the cell-surface negative charges were attributable to sialic acid, chondroitin sulphates, hyaluronic acid, and heparan sulphate. Two-dimensional electrophoresis of 3H-glucosamine incorporated glycosaminoglycans (GAGs) revealed that heparan sulphate was the main component of GAGs on the fibroblast cell surface and that the relative amount of heparan sulphate among GAGs on the cell surface increased in vitro with the number of passages. Growth kinetics of fibroblasts on sheets of fixed cells treated with a fixative (glutaraldehyde) and degradative enzymes were examined to elucidate the role of cell-surface GAGs in the regulation of cell proliferation. Cell growth was inhibited 40% when the fibroblasts were cultured on the fixed sheets of late passage cells. Treatment of the fixed cell sheets with heparitinase or nitrous acid resulted in complete recovery from the growth inhibition. Cell growth on sheets of fixed cells derived from young, middle, and senescent fibroblasts showed that the surface of the senescent cells had the greatest inhibitory effect. These inhibitory effects of fixed cell sheets correlated well with both the amount of heparan sulphate relative to the total GAGs on the surface and to the saturation density of cell growth at each passage. These findings strongly suggest that heparan sulphate, or its complex, on the cell surface is involved in the regulation of cell proliferation.(ABSTRACT TRUNCATED AT 400 WORDS)

Adolescent↗
PubMed1985

Appearance of extrachromosomal circular DNAs during in vivo and in vitro ageing of mammalian cells.

Appearance of extrachromosomal circular DNAs with in vivo and in vitro cellular ageing was examined by using a new technique of mica-press-adsorption for electron microscopy. The size distribution and the copy number of circular DNA complexes varied, depending on the cellular age. Extrachromosomal circular DNA complexes of variable length of more than 0.5 microns or 1.5 kilobase (kb) appeared during in vivo ageing of rat lymphocytes and in vitro ageing of cultured human lung fibroblasts. A restricted size class of circular forms of less than 0.5 microns in contour length was amplified in human skin fibroblasts from aged normal or Werner's syndrome subjects. These circular DNA molecules are suggested to be products of DNA rearrangements or gene amplification occurring in the chromosome.

Aging↗
PubMed1985

Growth-coupled changes in glucosaminoglycans (heparan sulfate and hyaluronic acid) in normal and transformed human fibroblasts.

Changes in glycosaminoglycans (GAGs) were investigated in relation to cell density, growth and transformation of human fibroblasts. Relative amounts (percentages of the total GAGs) of heparan sulfate (HS) increased and those of hyaluronic acid (HA) decreased in growth-reduced (serum-starved, exogenous HS-treated and dense) cultures of normal (WI-38) cells. In contrast, transformed (WI-38 CT-1) cells exerted such GAG changes only in serum-starved cultures, but not in HS-treated or dense cultures. These results indicate that the changes in glucosaminoglycans (G1cAGs) (HS and HA) is coupled exclusively with cell growth.

Animals↗