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Biomedical subjects

M Okuma

Publications and source records attributed to M Okuma.

At least 19 recordsLinked to original sources
PubMed1992

Down-regulation of interleukin 6 receptors of mouse myelomonocytic leukemic cells by leukemia inhibitory factor.

We examined the effect of leukemia inhibitory factor (LIF) on the expression of interleukin 6 receptors (IL-6R) on mouse myelomonocytic leukemic M1 cells. Binding studies using 125I-labeled human and murine IL-6 revealed that LIF caused a decrease in IL-6 binding to M1 cells. The decrease became evident within 1 h, and the maximum decrease was observed at 3-6 h. Scatchard plot analysis revealed that M1 cells had a single class of high affinity receptors for IL-6 and that LIF-induced decrease in IL-6 binding was due to a decrease in the number of IL-6R on the cell surface and not to changes in their affinity. The affinity of IL-6R on M1 cells to human IL-6 (Kd = 2.25 nM) was about 10-fold lower than that to murine IL-6 (Kd = 200 pM). The amount of IL-6 secreted into culture media by M1 cells that were treated with LIF for up to 12 h was not enough to cause receptor down-regulation. Northern blot analysis demonstrated that IL-6R mRNA was down-regulated by LIF treatment, and similar regulation was also observed when the cells were treated with IL-6. The time course of the IL-6R mRNA level was similar to that of IL-6R expression on the cell surface, suggesting that the main mechanism responsible for the loss of high affinity IL-6R was the regulation of IL-6R mRNA. Although the half-life of IL-6R on the cell surface was about 30 min, the addition of LIF reduced it to 16 min, suggesting the existence of an additional mechanism responsible for the loss of high affinity IL-6R on the cell surface.

Animals↗
PubMed1992

Pseudo-high affinity interleukin 2 (IL-2) receptor lacks the third component that is essential for functional IL-2 binding and signaling.

Functional studies of the interleukin 2 receptor (IL-2R) of two (ED515-D and Kit225) IL-2-dependent and three (ED515-I, 3T3-alpha beta 11, and Hut102) IL-2-independent cell lines were done. All of these cell lines appeared to express high as well as low affinity IL-2R. However, ED515-I and 3T3-alpha beta 11, which expressed the IL-2R beta chain, did not bind IL-2 at all when IL-2 binding to their IL-2R alpha chain was blocked with anti-Tac monoclonal antibody, whereas the intermediate affinity binding in ED515-D, Kit225, and Hut102 cells remained. We tentatively called the high affinity IL-2R of the former cells pseudo-high affinity IL-2R. The dissociation constant of pseudo-high affinity IL-2R was higher than that of ordinary high affinity IL-2R. Internalization of cell-bound 125I-IL-2 into ED515-I and 3T3-alpha beta 11 cells was less efficient than that into ED515-D cells. The addition of IL-2 neither promoted cell growth nor upregulated IL-2R alpha chain expression in ED515-I and 3T3-alpha beta 11 cells. Furthermore, tyrosine phosphorylation of the cellular proteins (p120, p98, p96, p54, and p38) was induced or enhanced in response to the addition of IL-2 in ED515-D and Kit225 cells, but not in the cell lines expressing pseudo-high affinity IL-2R. Finally, 125I-IL-2 crosslinking followed by SDS-PAGE analysis showed an 80-kD band corresponding to p65 + IL-2, in addition to bands corresponding to IL-2R alpha and beta chain + IL-2 in cells bearing ordinary high affinity IL-2R but not in cells with pseudo-high affinity IL-2R. Taken together, we consider that another protein whose molecular mass is approximately 65 kD is functionally important in IL-2 binding and subsequent signal transduction and may be the third component of IL-2R.

3T3 Cells↗
PubMed1992

Interleukin-2 (IL-2) induces erythroid differentiation and tyrosine phosphorylation in ELM-I-1 cells transfected with a human IL-2 receptor beta chain cDNA.

The molecular mechanism of erythroid differentiation has been still ill-defined. In this study, we introduced a human interleukin-2 receptor (IL-2R) beta chain cDNA into ELM-I-1 cells which differentiated into hemoglobin-positive cells in the presence of erythropoietin (Epo), and established the transformant which expressed IL-2R beta chain. In this transformant, we revealed that IL-2 induced erythroid differentiation and the same pattern of tyrosine phosphorylation as Epo. These data suggest that tyrosine phosphorylation is involved in signal transduction pathway of erythroid differentiation. It is also implicated that the Epo and IL-2 receptor system share a common signal transduction pathway.

Animals↗
PubMed1992

Platelet adhesion to collagen-coated wells: analysis of this complex process and a comparison with the adhesion to matrigel-coated wells.

The mechanisms of platelet adhesion to collagen type III-coated wells and Matrigel-coated wells were analyzed. The adhesion of 51Cr-labeled platelets to collagen-coated wells showed a biphasic pattern. The early stage of adhesion was inhibited by antibodies against platelet glycoprotein(GP)s Ia/IIa and VI. The later stage of platelet adhesion was inhibited by an antibody against the GPIIb/IIIa complex and a concomitant release of 14C-labeled serotonin was observed. The percentage of adhered platelets was increased when a higher platelet concentration was added in the reaction medium. These results indicated that the adhesion assay of platelets to collagen-coated wells was composed of two reactions: the first one is the platelet-collagen interaction that depends on GPIa/IIa and GPVI on the platelet surface; and the second reaction is the platelet-platelet interaction, platelet aggregation, which depends on GPIIb/IIIa. The adhesion of platelets to Matrigel-coated wells was indicated to involve platelet-Matrigel interactions that were partly dependent on the laminin in the Matrigel solution.

Antibodies, Monoclonal↗
PubMed1992

Use of proton nuclear magnetic resonance spectroscopy of plasma in screening for malignant disease.

In 1986, narrow plasma proton nuclear magnetic resonance (NMR) methyl and methylene line widths were reported to be associated with malignant disease, but more recent studies have not confirmed this relationship. The authors analyzed 106 plasma samples from healthy control subjects and patients with cirrhosis, hepatocellular carcinoma, metastatic liver tumors, other untreated cancers, and hyperlipidemia. NMR spectroscopy was performed using a proton NMR spectrometer operating at 399.65 MHz. A significant difference was found between the mean line widths of the plasma methyl resonances in control subjects and those in patients with cancer or hyperlipidemia. However, no significant difference was found between the mean plasma methylene line widths in control subjects and patients with cancer. Plasma samples from patients with liver disease or hyperlipidemia showed a characteristic methylene spectral pattern. The methylene pattern could be separated into three types: type A had a small peak on the right shoulder of the main peak; type B was a sharp single peak; and type C was a broad single peak. All control subjects had type A pattern; patients with liver disease had type C pattern; and patients who had hyperlipidemia had type B pattern, and hyperlipidemia may affect methyl and methylene line widths in NMR spectra. Because the methyl and methylene levels and their average line widths correlated inversely with triglyceride levels, considering the spectral patterns that indicate hyperlipidemia should decrease false-positive results and make the methyl line width useful for cancer screening.

Adult↗
PubMed1992

Accelerated declining tendency of human T-cell leukemia virus type I carrier rates among younger blood donors in Kumamoto, Japan.

The annual age- and sex-specific human T-cell leukemia virus type I carrier rate of blood donors in Kumamoto, Kyushu, Japan from 1986 to 1990 revealed that the carrier rates of all the age groups below 50 years declined linearly in both sexes (P less than 0.005). Furthermore, the annual declining rates relative to the carrier rates of 16-19-year-old and 20-29-year-old males were higher than those of all of the older males (P less than 0.02), and all female age groups below 50 years had higher relative declining rates than 50-64-year-old females (P less than 0.05). Although several factors, such as a notification program at obstetric clinics, methodological and technical improvement of the assays, wider knowledge of human T-cell leukemia virus type I infection in the latter years, and immigration of individuals from a nonendemic area, might cause an absolute decline of the carrier rate of the blood donors, these factors could not explain the acceleration of the relative declining rate among younger donors. Therefore, this acceleration represents the tendency of the general population.

Adolescent↗
PubMed1992

Analysis of the defective signal transduction mechanism through the platelet thromboxane A2 receptor in a patient with polycythemia vera.

We previously reported a patient with polycythemia vera whose platelets showed subnormal responses to thromboxane A2 (TXA2) (Thromb Haemostas 1987; 57: 158-64). The patient's platelets showed normal binding activity to TXA2 analogues but the generation of second messengers was defective. We further studied the mechanism of this dysfunction in this work. The coupling of TXA2 receptor with its relevant GTP binding protein was examined using STA2(a synthetic TXA2 mimetic)-induced augmentation of GTPase activity as its measure. Only subnormal increase in the GTPase activity of the patient's platelet membrane was found after STA2 stimulation. Down regulation of TXA2 receptor of the patient's platelet also showed abnormal behavior. These results suggested that the defective coupling of TXA2 receptor with GTP binding protein could be included as a cause of defective signal transduction in this patient's platelets. This defect might be due to the abnormality of TXA2 receptor itself if the receptor was down regulated by its phosphorylation through agonist-induced conformational change.

Blood Platelets↗
PubMed1992

Deficiency of P62, a putative collagen receptor, in platelets from a patient with defective collagen-induced platelet aggregation.

Recently, we described a platelet antibody against a putative collagen receptor (P62), which was found in a patient with idiopathic thrombocytopenic purpura (ITP) (Blood 69:1712). We now report a deficiency of the P62 receptor in a young man whose platelets showed defective collagen-induced platelet aggregation. He had a mild bleeding tendency and slight thrombocytopenia. The results of coagulation and fibrinolysis studies were normal. The patient's platelets were partially unresponsive to collagen, although aggregation in response to ADP, thrombin, ristocetin, and calcium ionophore (A23187) was almost normal. Adhesion of his platelets to bovine collagen was markedly reduced. Addition of collagen caused no synthesis of thromboxane (TX)B2 in platelet rich plasma (PRP) from this patient. Furthermore, collagen produced no rise of cytosolic free calcium ([Ca2+]i) in fura2-loaded platelets. In contrast, thrombin caused TXB2 formation and an increase of [Ca2+]i in his platelets. These results suggest defective interaction between the platelets and collagen. The IgG from the ITP-patient induced irreversible aggregation in normal PRP, but caused no aggregation of the young man's platelets. Immunoblot studies showed that normal platelets had antigens with a molecular weight of 62 KDa under reducing conditions and of 57 KDa under nonreducing conditions. In contrast, the young man's platelets had no P62 band, although GPIa/IIa and thrombospondin were normally present. These results indicate that impaired collagen-induced aggregation in the patient's platelets was due to a deficiency of P62 and confirm that P62 may play a crucial role as a collagen receptor in platelet activation.

Adenosine Triphosphate↗
PubMed1992

Bone marrow stromal cells attenuate mitoxantrone cytotoxicity against HL-60 leukemic cells.

We evaluated the effect of cultured human bone marrow (BM) stromal cells on the cytotoxicity of mitoxantrone (MIT) against the HL-60 leukemic cell line. BM-derived fibroblastoid cells (BMFC) suppressed colony formation of HL-60 cells in the absence of MIT. BMFC increased the survival of HL-60 colony-forming cells in the presence of 50 ng/ml MIT. A significant decrease in the drug concentration was not detected on BMFC. Our results suggest that BM stromal cells can modulate the antileukemic effect of an anticancer drug.

Cell Adhesion↗
PubMed1992

Myelodysplastic syndrome (MDS)-associated inhibitory activity on haematopoietic progenitor cells: contribution of monocyte-derived lipid containing macrophages (MDLM).

We studied myelodysplastic syndrome-associated inhibitory activity (MDS-IA), which inhibited colony formation in vitro of normal granulocyte-macrophage progenitors (CFU-GM). When adherent marrow cells were incubated with fetal calf serum for 21-24 d, monocyte-derived lipid containing huge macrophages (MDLM) developed. MDLM from MDS marrow (MDS-MDLMs) and their conditioned medium (MDLM-CM) consistently suppressed the growth of normal CFU-GM colony formation. MDS-IA was active on CFU-GM during the S-phase and relatively resistant to heating. Monoclonal antibody against H subunit (acidic) ferritin and polyclonal antibody against placental ferritin neutralized the inhibitory activity of MDS-MDLMs. In addition, cell lysates of MDS-MDLMs reacted to both monoclonal anti-H subunit ferritin and polyclonal anti-placental ferritin in Western blotting analysis, indicating that the inhibitory activity was predominantly acidic isoferritin. On the other hand, MDLMs obtained from normal bone marrow had a CFU-GM enhancing activity. These results suggest that MDS-MDLMs may be responsible for the suppression of granulopoiesis in patients with MDS and that the suppression may be mediated by soluble factors, notably H subunit isoferritin.

Adolescent↗
PubMed1992

Transient calcium elevation in polymorphonuclear leukocytes triggered by thrombin-activated platelets.

The effect of thrombin-activated platelets and their release products on the intracellular free calcium concentration ([Ca2+]i) of human polymorphonuclear leukocytes (PMNs) was studied by loading PMNs with a fluorescent indicator of calcium, fura-2. [Ca2+]i of PMNs was transiently elevated by thrombin-activated platelets. The supernatant of thrombin-activated platelets also elicited a transient elevation of [Ca2+]i in PMNs. Pretreatment of the supernatant with hexokinase caused a decrease in the transient [Ca2+]i elevation of PMNs, while hexokinase abrogated the [Ca2+]i elevation of PMNs elicited by 80 mumol/l adenosine triphosphate (ATP). Pretreatment of the supernatant with trypsin also decreased the magnitude of the elevation, while trypsin had no effect on the response to ATP. These findings suggest that thrombin-activated platelets induce a transient [Ca2+]i elevation in PMNs by releasing ATP and some trypsin-sensitive factor(s).

Adenosine Triphosphate↗
PubMed1992

Gene analyses of abnormal fibrinogens with a mutation in the gamma chain.

In four abnormal fibrinogens with a point mutation in the gamma chain, all characterized by impaired fibrin polymerization, we identified single base exchanges in the respective mutant gamma chain genes by polymerase chain reaction followed by DNA sequence analysis. These base exchanges accounted for the amino acid substitutions previously reported from our laboratory. They were exchanges of C to T (CGC for gamma Arg-275 to TGC for Cys) in fibrinogen Osaka II, T to G (AAT for gamma Asn-308 to AAG for Lys) in fibrinogen Kyoto I, T to C (ATG for gamma Met-310 to ACG for Thr) in fibrinogen Asahi, and G to T (GAT for gamma Asp-330 to TAT for Tyr) in fibrinogen Kyoto III. These base exchanges were found to reside in exon VIII of the gamma chain gene. Since many abnormal molecules are associated with polymerization defects, unless associated with the impaired release of fibrinopeptides A and/or B, exon VIII of the gamma chain gene may deserve careful study to define the structural alterations.

DNA Mutational Analysis↗
PubMed1992

[Coexistence of myeloma and primary myelodysplastic syndrome (MDS)].

Coexistence of myeloma and MDS was noted in a patient without history of exposure to cytotoxic drugs. A 73-year-old man was admitted because of fever and dyspnea on exertion. A complete blood count revealed macrocytic anemia with hemoglobin 7.1 g/dl, RBC 191 x 10(4)/microliters and MCV 111.2 fl. WBC was 6,000/microliters, with normal differentials. Bone marrow showed erythroid hyperplasia with M/E ratio of 1.36. There were marked tri-lineage cellular abnormalities, which included megaloblastic changes, multinucleated erythroblasts, hypersegmentation of neutrophils, giant neutrophils, and giant platelets. Ringed-sideroblasts were demonstrated in 20% of the erythroblasts. These findings were compatible with MDS. Although plasma cells accounted for only 9.7% of the nucleated marrow cells, there were many immature plasma cells with inclusion bodies, and the patient showed lambda-light chain type monoclonal gammopathy with corresponding Bence Jones protein. Immuno-histochemical staining of the bone marrow biopsy specimen revealed monoclonal growth of lambda-positive plasma cells. A punched-out lesion of the skull eventually developed. These findings suggest existence of myeloma. There have been some reports of coexistence of MDS and myeloma; supporting the idea of pluripotent stem cell origin of the disease. This is the first documentation of such a case in Japan.

Aged↗
PubMed1992

[Sequential changes of specific IgE, IgG4 antibodies and the development of allergic diseases in the first year of life].

Thirty infants who had siblings with major allergy were prospectively followed up to 12 months. Among 15 infants, in whom egg and milk were eliminated by the mother during third trimester and 12 months after birth, three infants developed food allergy. But, among 15 infants without any elimination either by the mother or the infant, 7 infants developed food allergy though this was not statistically significant. Among ten cases with food allergy, eight developed the symptoms during first six months. There were no correlations between allergic symptoms and Total IgE. Also, specific IgG4 did not show significant correlation with specific IgE and allergic symptoms except in several cases. Even though there was no significant decrease of food allergy by elimination of egg and milk during third trimester and 12 months after birth, elimination of egg and milk during that period give some benefit to the infant with strongly positive family history of major allergy under the close observation for growth and development of the infant.

Humans↗
PubMed1992

Phorbol esters up-regulate p55 and down-regulate p75 expression of interleukin-2 receptors in human T cells.

We examined the effects of phorbol esters on the expression of interleukin 2 receptors (IL-2R) in T cell clones. By flow cytometric analysis, we found that phorbol esters up-regulated IL-2R p55 expression, while they down-regulated p75 expression. The expression of IL-2R p55 in T cell clones treated with phorbol esters showed an initial transient and marginal decrease, which was followed by a progressive increase after 6 h of incubation. On the other hand, the expression of IL-2R p75 progressively decreased to a minimum plateau level. Down-regulation of p75 was also revealed in cells treated with diacylglycerols instead of phorbol esters, but there was no up-regulation of p55 in these cells. Moreover, in the presence of cycloheximide, phorbol esters down-regulated p75 expression but did not up-regulate p55 expression. Therefore, it seems that a transient activation of protein kinase C (PKC) is sufficient to down-regulate p75, but not to up-regulate p55, and that a novel protein synthesis is required to increase p55 expression.

Down-Regulation↗