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Biomedical subjects

M Iwamoto

Publications and source records attributed to M Iwamoto.

At least 271 records · Page 15Linked to original sources
PubMed1990

Effect of isolated C-terminal fragment of theta-toxin (perfringolysin O) on toxin assembly and membrane lysis.

theta-toxin, a thiol-activated cytolysin, binds cholesterol and assembles on plasma membrane during the lytic process. In order to understand the process at the molecular level, two fragments (T1 and T2) were isolated from a nicked toxin obtained by limited proteolysis with trypsin. Although neither the T1 nor T2 fragment has hemolytic activity. T2 has almost the same potential as native theta-toxin in its binding affinity for erythrocytes and in its binding specificity for cholesterol. T2, derived from the C-terminus of the toxin, loses binding activity upon 5,5'-dithiobis(2-nitrobenzoic acid) modification of the thiol group. The T2 fragment was found to abolish the hemolytic activity of theta-toxin completely without any inhibition of theta-toxin binding to erythrocytes. theta-toxin normally appears in polymeric form on membranes, while it remains in monomer form in the presence of the T2 fragment, as judged by sedimentation patterns in sucrose density-gradient centrifugation. These results indicate that without inhibiting binding, the T2 fragment inhibits hemolysis by preventing theta-toxin from aggregating on membranes, a step that might be essential for the lytic process.

Animals↗
PubMed1990

Presence and function of chondroitin-4-sulfate on recombinant human soluble thrombomodulin.

We constructed a human soluble thrombomodulin (sTM) expression vector using the RSV promoter. Recombinant sTM (rsTM) was expressed in CHO cells and was recovered from culture medium by ion exchange chromatography. Two active fractions, designated as rsTM alpha (low salt elution) and rsTM beta (high salt elution), were detected and further purified by immunoaffinity chromatography. Purified rsTM beta contained bound chondroitin-4-sulfate as judged by HPLC detection of the chondroitinase ABC and AC I digestion product, 2-acetamido-2-deoxy-3-O-(beta-D-gluco-4-enepyranosyluronic acid)-4-O-sulfo-D-galactose. The apparent Kd values for thrombin of alpha and beta were 7.4 and 1.4 nM respectively. RsTM beta was more effective at inhibition of thrombin clotting activity and had antithrombin III-dependent anticoagulant activity which was not possessed by rsTM alpha. Both anticoagulant activities were lost after chondroitinase treatment of rsTM beta.

Animals↗
PubMed1990

Dissolution of emboli in rats with experimental cerebral thromboembolism by recombinant human tissue plasminogen activator (TD-2061).

Tissue plasminogen activator (t-PA) is frequently administered clinically as thrombolytic therapy. We injected recombinant t-PA into rats with cerebral 125I-labeled blood clot emboli to evaluate the dissolutive effect of recombinant human single-chain t-PA (rt-PA; TD-2061) on such emboli and to examine the possibility of improving neurological damage in patients with cerebral thrombosis. When rt-PA was given intravenously at a dose of 350,000 IU/kg 2 minutes before embolization, radioactivity in the affected cerebral hemisphere decreased to 20% of that in the vehicle control 2 hours after embolization. A significant decrease in radioactivity in the cerebral hemisphere was also found on the administration of 700,000 IU/kg of rt-PA 30 or 60 minutes after embolization, but not when rt-PA was administered 2 minutes after embolization. Marked inhibition of abnormal behavior such as hemiplegia was seen on treatment with rt-PA 2 minutes before embolization, but not at all when rt-PA treatment was given 30 or 60 minutes after embolization. The findings suggest that rt-PA can dissolve blood clot emboli in cerebral vessels and that prompt thrombolytic therapy is important to minimize neurological dysfunction in cases of cerebral thromboembolism.

Animals↗
PubMed1990

Stimulation by concanavalin A of cartilage-matrix proteoglycan synthesis in chondrocyte cultures.

The effect of concanavalin A on proteoglycan synthesis by rabbit costal and articular chondrocytes was examined. Chondrocytes were seeded at low density and grown to confluency in medium supplemented with 10% fetal bovine serum, and then the serum concentration was reduced to 0.3%. At the low serum concentration, chondrocytes adopted a fibroblastic morphology. Addition of concanavalin A to the culture medium induced a morphologic alteration of the fibroblastic cells to spherical chondrocytes and increased by 3- to 4-fold incorporation of [35S]sulfate and [3H]glucosamine into large chondroitin sulfate proteoglycan that was characteristically found in cartilage. The stimulation of incorporation of labeled precursors reflected real increases in proteoglycan synthesis, as chemical analyses showed a 4-fold increase in the accumulation of macromolecules containing hexuronic acid in concanavalin A-maintained cultures. Furthermore, the effect of concanavalin A on [35S]sulfate incorporation into proteoglycans was greater than that of various growth factors or hormones. However, concanavalin A had smaller effects on [35S]sulfate incorporation into small proteoglycans and [3H]glucosamine incorporation into hyaluronic acid and chondroitinase AC-resistant glycosaminoglycans. Since other lectins tested, such as wheat germ agglutinin, lentil lectin, and phytohemagglutinin, had little effect on [35S]sulfate incorporation into proteoglycans, the concanavalin A action on chondrocytes seems specific. Although concanavalin A decreased [3H]thymidine incorporation in chondrocytes, the stimulation of proteoglycan synthesis could be observed in chondrocytes exposed to the inhibitor of DNA synthesis, cytosine arabinoside. These results indicate that concanavalin A is a potent modulator of proteoglycan synthesis by chondrocytes.

Animals↗
PubMed1990

A modified theta-toxin produced by limited proteolysis and methylation: a probe for the functional study of membrane cholesterol.

A derivative of cytolytic theta-toxin from Clostridium perfringens was prepared by limited proteolytic digestion of the native toxin followed by methylation. Among the chloroform/methanol-extractable, lipid components of sheep and human erythrocytes, the proteinase-nicked and methylated derivative (MC theta) specifically binds to cholesterol. While MC theta retains binding affinity comparable to that of intact toxin, it causes no obvious membrane damage, resulting in no hemolysis at temperatures of 37 degrees C or lower. Using MC theta, we demonstrated the possible existence of high- and low-affinity sites for theta-toxin on sheep erythrocytes at both 37 degrees C and 10 degrees C. The number of high-affinity sites on sheep erythrocytes was estimated to be approximately 3-times larger at 37 degrees C than that at 10 degrees C. In addition, high- and low-affinity sites were demonstrated in human erythrocytes and a lymphoma B cell line, BALL-1 cells. Both binding sites disappear upon simultaneous treatment of cells with sublytic doses of digitonin, suggesting that cholesterol is an essential component of both the high- and low-affinity sites and that the mode of cholesterol existence in plasma membranes is heterogeneous in these cells. Because of its high affinity for membrane cholesterol without causing any obvious membrane changes at physiological temperatures, MC theta may provide a probe for use in the functional study of membrane cholesterol.

Animals↗
PubMed1990

Fibroblast growth factor is an inhibitor of chondrocyte terminal differentiation.

The effects of basic fibroblast growth factor (bFGF) on terminal differentiation of chondrocytes and cartilage-matrix calcification were investigated. Rabbit growth-plate chondrocytes maintained as a pelleted mass in a centrifuge tube produced an abundant proteoglycan matrix during the matrix-maturation stage, yielding a cartilage-like tissue. Thereafter, they terminally differentiated to hypertrophic chondrocytes which produced high levels of alkaline phosphatase. These cells induced extensive calcification of the matrix in the absence of additional phosphate (Kato, Y., Iwamoto, M., Koike, T., Suzuki, F., and Takano, Y. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 9552-9556). Addition of bFGF to the chondrocyte cultures abolished the increases in alkaline phosphatase activity, 45Ca deposition, and the calcium content. These effects were dose-dependent, reversible, and observed in the presence of cytosine arabinoside, an inhibitor of DNA synthesis. The inhibitory effects could be observed only when chondrocytes were exposed to bFGF in a transition period between the matrix-maturation and hypertrophic stages. As chondrocytes differentiated to hypertrophic cells, bFGF became less effective in inhibiting the expression of the mineralization-related phenotypes. The present study also shows that although the rate of [35S]sulfate incorporation into large, chondroitin sulfate proteoglycan in the cell-matrix fraction is very high during the matrix-maturation stage, it abruptly decreases by 90% after terminal differentiation. Furthermore, the terminal differentiation-associated decrease in proteoglycan synthesis was delayed by bFGF. These results provide evidence that bFGF inhibits terminal differentiation of chondrocytes and calcification.

Alkaline Phosphatase↗
PubMed1990

Ocular histopathology and ultrastructure of Morquio syndrome (systemic mucopolysaccharidosis IV A).

Morquio syndrome (mucopolysaccharidosis IV) is a hereditary lysosomal storage disease characterized by dwarfism, spondyloepiphyseal and dental abnormalities, corneal opacification, and normal intelligence. We report the light and electron microscopic features of two patients with mucopolysaccharidosis type IV A (MPS IV A). Variable degrees of mucopolysaccharide deposition were seen in tissue surveyed by light microscopy. Transmission electron microscopy demonstrated fibrillogranular and multimembranous membrane-bound inclusions distributed primarily in the cornea and trabecular meshwork, to a milder degree in the conjunctiva and sclera, and rarely in the retinal pigment epithelium. Our findings indicate that the accumulation of mucopolysaccharide in MPS IV A occurs primarily in the structures of the anterior segment.

Adolescent↗
PubMed1990

Serum IgG from an autoimmune prone mouse C3H/HeJ-gld/gld supports the interleukin-3-dependent cell line through an autocrine mechanism.

C3H/HeJ-gld/gld(C3H/gld) mice have been shown to develop massive lymphadenopathy with autoimmunity. In this study, we tested whether C3H/gld-IgG supports the growth of the IL-3-dependent cell line, FDC-P2/185-4. Serum IgG from C3H/gld mice stimulated FDC-P2/185-4 cells to proliferate. On the other hand, IgG from C3H/HeJ-+/+ did not show such activity. This activity increased with age in both sexes of C3H/gld mice. It was suggested that a monomeric IgG component was responsible for the proliferative activity of C3H/gld mouse sera. The cell-induced growth required Fc gamma receptors on FDC-P2/185-4 cells. FDC-P2/185-4 cells stimulated with C3H/gld-IgG, secreted IL-3, and grew by themselves, indicating an autocrine mechanism. Thus, cytokines produced by serum IgG may play an important role in the development of disease in mice bearing the autosomal recessive mutation gld.

Age Factors↗
PubMed1990

Polyclonal and monoclonal IgGs from MRL/Mp-lpr/lpr mice induce an interleukin-3-dependent cell line to produce interleukin-3 through an Fc gamma-receptor-mediated mechanism.

Serum IgG from autoimmune MRL/MP-lpr/lpr(MRL/l) mice induced IL-3 mRNA, IL-3 synthesis, and cell proliferation in the IL-3-dependent cell line, FDC-P2/185-4. Cell growth, induced by MRL/l-IgG, was suppressed by anti-IL-3 antibody, suggesting an autocrine mechanism. We established hybridomas from the splenocytes of a nonimmunized MRL/l mouse. The mAbs, produced by these hybridomas, also stimulated IL-3 synthesis and cell growth in FDC-P2/185-4 cells. Both anti-IgG-Fc antibody and anti-Fc gamma RII mAb, 2.4G2 suppressed the cell growth induced by these mAbs. Our results suggest that some IgGs of MRL/l mice may induce IL-3 synthesis in cells by binding to Fc receptors.

Animals↗
PubMed1990

1 alpha,25-dihydroxyvitamin D3 stimulates colony formation of chick embryo chondrocytes in soft agar.

The effect of vitamin D metabolites on the growth of chick embryo chondrocytes in soft agar was examined. 1,25-Dihydroxyvitamin D3 [1,25(OH)2D3] at 10(-8)-10(-7) M induced colony formation by chick embryo chondrocytes in soft agar in the presence of 10% fetal bovine serum. Furthermore, 1,25(OH)2D3 increased the number of colonies in the presence of a maximal dose of basic fibroblast growth factor, a potent mitogen for chondrocytes in soft agar. However, 24R,25 (OH)2D3 and other metabolites had little effect on the soft agar growth of chondrocytes in the presence or absence of basic fibroblast growth factor. These results suggest that 1,25(OH)2D3 is an active metabolite which may be involved in supporting cartilage growth.

Agar↗
PubMed1990

Vasodilatory active principles of Sophora flavescens root.

Flavanones vexibinol and kurarinone were isolated from an ethyl acetate extract of Sphora flavescens roots and assayed using isolated rabbit and rat thoracic aorta helical strips. These compounds inhibited KCl and norepinephrine maximum contractions in a concentration-dependent manner in the rat but only KCl contractions in the rabbit. Vexibinol and kurarinone weakly inhibited histamine- and serotonin-induced contractions in the rabbit. The results suggest that these flavanones may inhibit Ca2+ influx through a voltage-dependent Ca2+ channel.

Animals↗
PubMed1990

Bromination, no-carrier-added radiobromination and simultaneously-occurring chlorination by chloramine T.

Factors regulating initial rates of bromination, no-carrier-added radiobromination and simultaneously-occurring chlorination by chloramine T were studied using a neuroleptic drug spiperone as the substrate. Besides the factors such as initial concentrations of chloramine T, substrate and bromide ions, upon which the rates were dependent in first, second or zero-order, the water-acetic acid composition or the hydrogen ion concentration of the solutions, where the reactions took place, was found to play a key role. By controlling these factors, optimal radiobromination conditions, where radiobromination proceeds effectively whilst simultaneously-occurring chlorination is kept from proceeding at a high rate, thus resulting in radiobrominated radiopharmaceuticals of high specific activity (10 Ci/mumol) and high radiochemical and chemical purity, could be fulfilled.

Bromine↗
PubMed1990

Role of 1,25-dihydroxycholecalciferol in growth-plate cartilage: inhibition of terminal differentiation of chondrocytes in vitro and in vivo.

The effects of vitamin D metabolites on alkaline phosphatase [ALPase; orthophosphoric-monoester phosphohydrolase (alkaline optimum), EC 3.1.3.1] activity, a marker of terminal differentiation, in chondrocyte cultures and growth plates in vivo were examined. In cultures of pelleted rabbit growth-plate chondrocytes, 1,25-dihydroxycholecalciferol (1,25-dihydroxyvitamin D3) increased the contents of DNA and macromolecules containing uronic acid (proteoglycans). It also decreased ALPase activity with an ED50 of less than 1 nM. Other vitamin D3 metabolites, such as 24,25-dihydroxycholecalciferol and 25-hydroxycholecalciferol, had little effect on these biochemical parameters. In rachitic growth plates, the uronic acid content was half that in normal growth plates, whereas ALPase activity was 2.5 times that in normal growth plates. Administration of 1,25-dihydroxycholecalciferol at a low dose (0.1 micrograms per kg of body weight) to rachitic rats increased the uronic acid content 1.4-fold and decreased ALPase activity by 40%. This compound, like 24,25-dihydroxycholecalciferol (10 micrograms per kg of body weight), increased the calcium level of the blood. However, administration of 24,25-dihydroxycholecalciferol had little effect on the uronic acid and ALPase contents in growth plates. These observations suggest that 1,25-dihydroxycholecalciferol is a bioactive form of vitamin D that plays an important role in the control of chondrocyte terminal differentiation.

24,25-Dihydroxyvitamin D 3↗
PubMed1990

[Isolation of methicillin-resistant Staphylococcus aureus (MRSA) at the Hokusho Central Hospital--observation during the recent 4 years].

Clinical and bacteriological studies were carried out to investigate the isolation of MRSA from clinical materials, during the 4 years from 1985 to 1988 at the Hokusho Central Hospital. The isolation frequency of MRSA from Staphylococcus aureus increased from 5.6% (3 strains) in 1985 to 50.0% (90 strains) in 1988. MRSA from sputum and pressure sore increased significantly. However MRSA from outpatient and inpatient in the ward for common people were constant, about 20%. Inpatients in the ward for aged person were increased significantly from 13.6% (3 strains) to 67.0% (67 strains). Most of the patients with positive MRSA isolation had background diseases (88.3%) and were bedridden (78.4%). Patients with cerebrovascular disease were 55.9% of all of the cases. But most of the MRSA strains were resistant to CZX, FOM, DMPPC, CMX, CEZ, CZON, CZX, most of the MRSA strains were sensitive to RFP, VCM, MINO, IPM/CS.

Anti-Bacterial Agents↗
PubMed1990

[A case of fatal sepsis due to Vibrio vulnificus].

A 66-year-old male with chronic alcoholic liver injury was admitted on July 27, 1986 to our hospital with complaints of high fever, convulsion and skin erythema. He had consumed raw fish 3 days before, and had a scratch wound over the right arm and left leg because he had slipped in a small stream in the woods the day before admission. He was already in shock state with sepsis of V. vulnificus and DIC on admission. Although the treatment with ABPC, CP, CAZ, MINO for sepsis, and Heparin & Antithrombin III for DIC was immediately begun, he died only 10 hours after admission. On autopsy, the skin lesion revealed phlegmon with necrotizing angitis and the liver showed fatty changes with Mallory's body. The causative organism was detected from the blood and on autopsy from the skin wound, bile juice, liver, spleen, kidney and bone marrow, and its type was determined as a V. vulnificus serovar 4. It was suspected that the route of infection in this case was the raw fish rather than via the wound because the water in which he had been wounded was fresh water and the bacterium was not detected from the water, shells, nor moss existing there.

Aged↗
PubMed1990

Catecholamine levels and their correlation to blood gases in umbilical venous blood obtained by cordocentesis.

The plasma catecholamine concentration was evaluated in umbilical venous blood obtained by cordocentesis performed in 77 fetuses for indications including: nonimmune hydrops; Rh incompatibility; intrauterine growth retardation; polyhydramnios; anomalies; immunological disorders, and possible viral infection. The pH as well as pO2 of the umbilical venous blood showed a notably significant negative correlation with the norepinephrine concentration (r = -0.5607, r = 0.4467); while pCO2 was also significantly correlated with the norepinephrine concentration (r = 0.4955). When the pCO2/pO2 ratio was tentatively put up for comparison, the ratio was undoubtedly better correlated (r = 0.60442) with the fetal norepinephrine concentration than any other biochemical variable. Moreover, the ratio over 2.0 suggests that fetal catecholamine values have reached abnormal levels.

Carbon Dioxide↗
PubMed1990

Potent mitogenic effects of parathyroid hormone (PTH) on embryonic chick and rabbit chondrocytes. Differential effects of age on growth, proteoglycan, and cyclic AMP responses of chondrocytes to PTH.

The effect of PTH on chondrocyte proliferation as a function of cartilage age was examined. PTH[1-34] induced a 12- to 15-fold increase in the efficiency of colony formation in soft agar by chondrocytes from embryonic 13- to 19-d-old chickens and fetal 25-d-old rabbits with a 10-fold increase in their DNA content. It also caused a 2.5-fold increase in [3H]thymidine incorporation into DNA in fetal 25-d-old rabbit chondrocytes. No mitogenic responses to PTH were observed, however, in postnatal 7- to 21-d-old chick chondrocytes or postnatal 21-d-old rabbit chondrocytes. This age dependency was observed only with PTH: fibroblast growth factor, epidermal growth factor, and insulin stimulated chondrocyte proliferation irrespective of cartilage age. The absence of a mitogenic effect in postnatal chondrocytes was not due to a decrease in number or a reduction in affinity of receptors for PTH. PTH also increased [35S]sulfate incorporation into proteoglycans and the cyclic AMP level in fetal and postnatal chondrocytes, but at 100-fold higher concentrations (10(-8)-10(-7) M) than those (10(-10)-10(-9) M) required for the stimulation of cell division. These results suggest that PTH is a potent mitogen for embryonic chondrocytes, and that its mitogenic effect disappears selectively after birth.

Age Factors↗