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Biomedical subjects

N Tamura

Publications and source records attributed to N Tamura.

At least 271 records · Page 15Linked to original sources
PubMed1988

[Dual-energy subtraction radiography of the breast].

Dual-energy projection radiography was applied to breast examination. To perform the dual-energy subtraction radiography using a digital radiography unit, high and low-energy exposures were made at an appropriate time interval under differing X-ray exposure conditions. Dual-energy subtraction radiography was performed in 41 cancer patients in whom the tumor shadow was equivocal or the border of cancer infiltration was not clearly demonstrated by compression mammography, and 15 patients with benign diseases such as fibrocystic disease, cyst and fibroadenoma. In 21 cases out of the 41 cancer patients, the dual-energy subtraction radiography clearly visualized the malignant tumor shadows and the border of cancer infiltration and the daughter nodules by removing the shadows of normal mammary gland. On the other hand, benign diseases such as fibrocystic disease and cyst could be diagnosed as such, because the tumor shadow and the irregularly concentrated image of mammary gland disappeared by the dual-energy subtraction. These results suggest that this new technique will be useful in examination of breast masses.

Breast Neoplasms↗
PubMed1987

Determination of C4b.C4-bp complex formed by the activation of classical complement pathway using an enzyme-linked immunosorbent assay.

We developed a quantitative enzyme-linked immunosorbent assay (ELISA) for the detection of C4b.C4-bp complex by incubating the sample on anti-C4-bp-coated plate and then developing with HRP-labeled anti-C4. The amount of C4b.C4-bp complex, generated in vivo by the interaction of purified C4b with C4-bp or normal human serum with aggregated human IgG, was measured by the ELISA. The complex, however, rapidly decreased in serum by the action of factor I. Six out of the 100 plasma samples from patients with various diseases were found positive in the ELISA. One plasma sample from a patient with SLE showed high level of C4b.C4-bp complex with decreased levels of factor I, C4, C4-bp and CH50. These results suggest that the detection of C4b.C4-bp complex is useful for monitoring the diseases in which the classical pathway activation is expected.

Arthritis, Rheumatoid↗
PubMed1987

The mechanism of action of decay-accelerating factor (DAF). DAF inhibits the assembly of C3 convertases by dissociating C2a and Bb.

DAF is a 70,000-Mr membrane protein that inhibits the amplification of the complement cascade on the cell surface, and protects cells from damage by complement. The precise mechanism of action of DAF is not entirely clear. Purified DAF was incorporated into the membrane of EAC4b cells. EAC4b2 and EDAF AC4b2 cells were prepared with radiolabeled C2. The same amount of labeled C2 bound to both cells, showing that DAF does not prevent the binding of C2 zymogen to C4b. After adding Cl, the radioactivity of bound C2 dissociated more rapidly from EDAF AC4b cells than from EAC4b cells. In EAC4b cells, bound C2 was converted to C2a, which gradually dissociated into the supernatants. In the DAF-treated cells, on the other hand, a large amount of C2a rapidly appeared in the supernatants and only a small amount of C2a remained on the cells. In a similar experiment using EhuAC4b, DAF on human erythrocyte membrane also dissociated the C2a from the cells. These results were confirmed by hemolytic assay and the accelerated decay of C2a caused the rapid depletion of C2 from the fluid phase. In addition, we found that DAF functions on the alternative pathway C3 convertase, C3bBb in the same manner. Thus, DAF, which associates with C4b and C3b in the membrane, acts on C2a and Bb, but not on intact C2 and B, and dissociates them rapidly from the binding sites, thereby preventing the assembly of the classical and alternative pathways C3 convertases.

Animals↗
PubMed1987

Identification and characterization of leukotriene C4 and D4 receptors on a cultured smooth muscle cell line, BC3H-1.

We studied the characteristics of the leukotriene (LT) C4 and D4 receptors on a cultured smooth muscle cell line, BC3H-1. Specific [3H]LTC4 binding to the cell membrane was greater than 80% of total binding and saturable at a density of 3.96 +/- 0.39 pmol/mg protein, with an apparent dissociation constant (Kd) of 14.3 +/- 2.0 nM (n = 9). The association and dissociation of [3H]LTC4 binding were rapid and apparent equilibrium conditions were established within 5 min. Calculated Kd value of [3H]LTC4 binding from the kinetic analysis was 9.9 nM. From the competition analysis, calculated Ki value of unlabeled LTC4 to compete for the specific binding of [3H]LTC4 was 9.2 nM and was in good agreement with the Kd value obtained from the Scatchard plots or kinetic analysis. The rank order of potency of the unlabeled competitors for competing specific [3H]LTC4 binding was LTC4 much greater than LTD4 greater than LTE4 greater than FPL-55712. The maximum number of binding sites (Bmax) of [3H]LTD4 in the membrane of BC3H-1 cell line was about 11 times lower than that of the [3H]LTC4. The calculated values of Kd and Bmax of [3H]LTD4 binding were 9.3 +/- 0.8 nM and 0.37 +/- 0.04 pmol/mg protein, respectively (n = 3). The rank order of potency or the unlabeled competitors for competing specific [3H]LTD4 binding was LTD4 = LTE4 greater than FPL-55712 much greater than LTC4. These findings demonstrate that BC3H-1 cell line possess both LTC4 and LTD4 receptors with a predominance of LTC4 receptors. Thus BC3H-1 cell line is a good model to study the regulation of LTC4 and LTD4 receptors.

Animals↗
PubMed1987

A solid-phase anti-C3 assay for detection of immune complexes in six distinguished forms.

A solid-phase anti-C3 assay detecting immune complexes associated with C3 fragments is described. Two monoclonal antibodies against C3 fragments are used; one recognizes an epitope expressed on C3b, C3c and C3i, the other recognizes an epitope expressed on C3dg and iC3b. Combining these monoclonal anti-C3s with antibodies against class-specific immunoglobulins in enzyme-linked immunosorbent assay (ELISA), immune complexes (ICs) are detected in six distinguished forms; C3b-IgG-IC, iC3b/C3dg-IgG-IC, C3b-IgA-IC, iC3b/C3dg-IgA-IC, C3b-IgM-IC and iC3b/C3dg-IgM-IC. About three-fourths of the plasma samples from patients with active SLE or IgA-nephritis were found positive in one or more types of ICs. IgA-type ICs were found very frequently in patients with autoimmune or renal diseases.

Antibodies, Monoclonal↗
PubMed1987

Effects of platelet activating factor on the chemotaxis of normodense eosinophils from normal subjects.

Highly purified eosinophils were obtained from normal subjects, and their chemotactic responses to platelet activating factor (PAF) were evaluated. PAF induced both eosinophil chemotactic and chemokinetic responses, and was 100 fold more potent eosinophil chemotactic factor as compared to eosinophil chemotactic factor of anaphylaxis. On the other hand, leukotriene B4 did not show any eosinophil chemotactic activity. A selective PAF antagonist, BN52021, inhibited eosinophil chemotaxis in a dose dependent manner. Preincubation of eosinophils with PAF induced the deactivation of eosinophils for further chemotactic responses to PAF. These findings suggest that PAF is a potent chemotactic factor for normal eosinophils.

Adult↗
PubMed1987

A specific radioreceptor assay for leukotriene C4 and the measurement of calcium ionophore-induced leukotriene C4 production from human leukocytes.

A highly specific radioreceptor assay (RRA) for leukotriene (LT) C4 using BC3H-1 cell membrane as a source of LTC4 receptors was developed and demonstrated its use in the measurement of calcium ionophore A23187-induced LTC4 production from purified eosinophils, neutrophils, and mononuclear cells. Unlabeled LTC4 competed for the specific [3H]LTC4 binding to the BC3H-1 cell membranes in a dose-dependent manner. Under the experimental conditions used in this study, the calculated IC50 value of unlabeled LTC4 was 27.2 +/- 1.2 nM (n = 5). The sensitivity of the method for LTC4 was 0.6 pmol. The cross-reactivities of LTD4, LTE4, and FPL 55712 were negligible. The recovery of the exogenously added LTC4 with eosinophils was greater than 90% in both the presence and the absence of calcium ionophore A23187. Calcium ionophore induced 73.0 +/- 17.0 ng of LTC4 production/10(6) eosinophils (n = 8), and this was about 20-40 times more than those from neutrophils and from mononuclear cells.

Calcium↗
PubMed1987

Characterization of three monoclonal antibodies against C3 with selective specificities.

We raised 15 mouse monoclonal antibodies against human C3 from two separate fusions. Mouse plasmacytoma cells were fused with spleen cells from mice immunized either with a mixture of C3, C3b and C3c, or with a mixture of C3dg and C3d. Three of the 15 monoclonals were characterized in detail. N-7A reacted with native C3 as well as C3b and C3c. Two other monoclonals, C-5G and G-3E, recognized neoantigenic determinants on C3c and C3dg, respectively. In ELISA, C-5G reacted with C3b and C3c but not with native C3 nor with C3dg; and on the other hand G-3E reacted only with C3dg. The selective specificities of these monoclonals were further confirmed in a binding assay to C3 fragments formed on cellular intermediates. C-5G bound exclusively to EC3b, and G-3E bound to EiC3b, EC3dg and EC3d. N-7A bound only very poorly to EC3b. C-5G inhibited both the haemolytic activity of C5 convertase and also the CR1-mediated rosette formation of B-enriched peripheral mononuclear cells with EC3b. G-3E inhibited the CR2-mediated EC3dg-rosette formation of Raji cells. These monoclonals, with selective specificities, can distinguish the state of activation and degradation of the C3 molecule.

Antibodies, Monoclonal↗
PubMed1987

C4 nephritic factor in a patient with chronic glomerulonephritis.

C4 nephritic factor (C4NeF) was found in the serum of a patient with chronic glomerulonephritis, whose C3 level was quite low (less than 1% of normal). C4NeF prevented the intrinsic decay of C4b2a enzyme and prolonged the half life of the C4b2a from several minutes to more than 1 h in the solid and fluid phase. The C4NeF activity was associated with a protein fraction immunochemically identified as the IgG3 subclass and it bound specifically to the EAC142 cells. In addition, the patient's serum contained C3-cleaving activity, probably C4b2a, C4NeF complex, which may have lowered the level of C3 in the patient's serum. Spontaneously, the titer of C4NeF decreased, while the level of C3 increased.

Chronic Disease↗
PubMed1986

An immunoglobulin G inhibiting lactate dehydrogenase activity.

We found extremely low (6 U/l) serum lactate dehydrogenase (LDH, EC 1.1.1.27) activity in a patient with uterine myoma. The patient's serum inhibited purified LDH isoenzymes. One milliliter serum neutralized 73 U purified LDH-1 isoenzyme, equivalent to 300-500-fold the amount of LDH in 1 ml of normal serum. The serum inhibitor was purified by ordinary procedures using chromatographies and identified as IgG which contains both kappa- and lambda-chains. The IgG is very unique in showing higher affinity to the H- than M-subunit of the LDH tetramer, in contrast with the IgGs already reported. After removal of the myoma, the anti-LDH activity gradually decreased with a half-life of 20 days corresponding to that of IgG and finally almost disappeared. This indicates a possibility that the myoma cells produce some factors such as B-cell growth and differentiation factors.

Chromatography↗