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Biomedical subjects

R Yasuda

Publications and source records attributed to R Yasuda.

14 recordsLinked to original sources
PubMed1992

Factor I-dependent inactivation of human complement C4b of the classical pathway by C3b/C4b receptor (CR1, CD35) and membrane cofactor protein (MCP, CD46).

Proteolytic inactivation of C4b is a crucial step for regulation of the classical complement pathway. A plasma protease factor I and membrane cofactors, C3b/C4b receptor (CR1) and membrane cofactor protein (MCP), participate in the regulation of cell-bound C4b although the physiological potency of these cofactors remains unknown. We have examined the optimal conditions of the factor I-mediated C4b regulatory system using purified cofactors. CR1 being a cofactor at a cofactor/C4b ratio less than 0.1 (w/w), fluid phase C4b, and methylamine-treated C4 (C4ma) were degraded by factor I into C4bi: minimal Cd4 was generated in the fluid phase. Liposome-bound C4b (LAC4b), on the other hand, was degraded into C4c and C4d. CR1 showed two optimal pHs (6.0 and 7.5) for fluid phase C4b, but one (6.0) for LAC4b, and in both cases low conductivity conditions enhanced the C4bi generation. CR1 cofactor activity was barely influenced by the NP-40 concentration. On the other hand, MCP degraded C4b and C4ma, as a factor I-cofactor, more efficiently into C4c and C4d. Though MCP cofactor activity, like that of CR1, was enhanced under low conductivity conditions, it has only one optimal pH, 6.0, in both fluid and solid phases. Furthermore, as in the case of C3b cleavage, a sufficient NP-40 concentration to solubilize membrane was needed for MCP to express full cofactor activity for C4b, in contrast to CR1. MCP was less potent for C4b inactivation than for C3b inactivation, while CR1 acted as a slightly more effective cofactor for C4b cleavage than for C3b cleavage.(ABSTRACT TRUNCATED AT 250 WORDS)

Antigens, CD↗
PubMed1991

A covalent dimer of complement C4b serves as a subunit of a novel C5 convertase that involves no C3 derivatives.

A C intermediate, LAC14, was prepared from TNP-aminocaproyl liposomes sensitized with anti-TNP antibody (Ab) and purified human C1 and C4. LAC14, containing radiolabeled C4, was analyzed by SDS-PAGE followed by autoradiography, and yielded a 210-kDa band and a predominant 400-kDa band. The 210-kDa band consisted of monomeric C4b bound to low molecular mass acceptors. The 400-kDa band was comprised of a 200-kDa moiety, as well as beta- and gamma-chains of C4. The 200-kDa moiety contained neither C1 nor sensitizing Ab, but it was largely decreased by treatment with NH2OH to the 90-kDa moiety with the mobility corresponding to the alpha'-chain of C4b. A covalent dimer of C4b, therefore, is the predominant form of C4b deposited on liposomes sensitized with antibody. The C4b-C4b dimer formed rapidly (within 5 min) followed by slow dissociation into monomers. The LAC14 bearing the C4b dimer but not the monomer was lysed, although with relatively low efficiency, by the addition of oxyC2 and EDTA-supplemented C3-deficient serum (C3DS), and, furthermore, LAC142 possessed the ability to convert C5 into C5a and C5b. Moreover, lysis was inhibited not by anti-C3 Ab but by anti-C4 Ab. In other experiments, the dimer served as an element of C3 convertase, as well. These findings imply that the C4b dimer, when complexed with C2, expresses C3/C5 convertase activity without participation of C3, and may provide a molecular mechanism whereby sera from patients with complete C3 deficiency retain the ability to induce C-mediated cytolysis.

Autoradiography↗
PubMed1991

[A case report of resected double primary lung cancers in the same one segment].

A 68-year-old man with hypertension was admitted to the Shiga Kenritsu Seijinbyo Center for further examinations, because abnormal opacity in the right upper lung field was accidentally revealed by chest X-ray. Chest CT demonstrated two separate mass shadows, one 31 X 27 mm, the other 10 X 10 mm in size, both of which were located in the posterior segment of right lung. Specimens from transbronchial biopsy of the larger mass was histologically diagnosed as adenocarcinoma. He underwent right upper lobectomy with hilar and mediastinal lymph nodes resections. Postoperative patho-histological study showed the larger mass to be poorly differentiated adenocarcinoma, the smaller one, small cell carcinoma respectively, and no continuity between the two masses. Lymph nodes metastasis were negative. Any malignancy was not detected by brain CT, abdominal CT and any other gastro-intestinal examinations, and he was diagnosed to have double primary lung cancers in the same one segment. In this report, we discussed the diagnosis and treatment of double primary lung cancers, and reviewed the literatures.

Adenocarcinoma↗
PubMed1990

[A statistical study on the orthodontic patients in Meikai University Hospital].

We analyzed statistically two thousand orthodontic patients in Meikai University Hospital (formerly Josai Dental University Hospital) who have undergone treatment since the establishment of the hospital (1970-1985). By classifying the data in various ways, we obtained the following statistics; 1) The number of new patients increased quickly after the first class graduated from our university; 2) The number of patients from six to fifteen years old was the largest, with the peak being nine years old; 3) For the time of the first visit, many new patients came during spring and summer vacations, and a few junior high school and high school students came just season before taking their entrance examination; 4) The female sex predominated in most age groups; however, among patients in their twenties, the male sex was predominant, and in recent years the male ratio tended to increase; 5) Most patients came from a radius of less than 20 km from the hospital (mostly from along Tohbu railway line), with few from beyond 30 km; 6) Anterior crossbite and anterior crowding cases were many, particularly, young patients comprised many of the anterior crossbite cases; and in adult patients large overjet cases increased with the advance of age.

Adolescent↗
PubMed1977

C-Terminal peptidyl-L-proline hydrolase activity of Aspergillus acid carboxypeptidase.

Aspergillus saitoi acid carboxypeptidase hydrolyzed C-terminal peptidyl-L-proline bonds and released the C-terminal proline from Z-Gly-Pro-Leu-Gly-Pro and Z-Gly-Pro at pH 3.3. Proline liberated by the enzymic reaction was measured by a sensitive colorimetric ninhydrin method in glacial acetic acid at 513 nm. A Km value of 1.0 mM and a kcat value of 0.09 s-1 for Z-Gly-Pro-Leu-Gly-Pro hydrolysis, and a Km value of 5.0 mM and a kcat value of 0.0045 s-1 for Z-Gly-Pro hydrolysis were calculated from Lineweaver-Burk plots.

Amino Acid Sequence↗