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Biomedical subjects

Y Imamura

Publications and source records attributed to Y Imamura.

At least 415 records · Page 23Linked to original sources
PubMed1984

Production of monoclonal antibodies to islet cell surface antigens using hybridization of spleen lymphocytes from non-obese diabetic mice.

Non-obese diabetic mice display a syndrome with dramatic clinical and pathological features similar to those of Type 1 (insulin-dependent) diabetes in man. Circulating autoantibodies to the surface of islet cells were demonstrated in some of these mice by a protein A radioligand assay. To produce monoclonal antibodies to islet cell surface antigens, therefore, we took the spleens of non-obese diabetic mice, transferred the spleen cells into non-immunized recipient mice, which were made immunologically incompetent by a large dose of X-irradiation, and then fused their lymphocytes with FO mouse myeloma cells. After screening the resultant hybrids, one stable hybridoma (3A4) that produced a monoclonal antibody (IgG1) specifically bound to the surface of islet cells was obtained. The purified monoclonal antibody was bound to the surface of transplantable Syrian golden hamster insulinoma cells sevenfold more than control antibody. Adsorption of the antibody on mouse spleen lymphocytes or thymocytes resulted in only a slight decrease in 125I-protein A binding to insulinoma cells. This antibody also reacted with the surface of mouse and rat islet cells, but not with that of rat spleen cells or hepatocytes. A spectrophotometric assay for peroxidase activity demonstrated that six times more peroxidase bound to insulinoma cells incubated with the antibody than to cells treated with control antibody. Furthermore, this antibody could be visually detected in the immunoenzymatic labelling of the surface of insulinoma cells. In summary, we have developed a novel method of producing monoclonal antibodies to the surface of islet cells for probing into the pathogenesis of Type 1 diabetes.

Animals↗
PubMed1984

Molecular basis of ornithine transcarbamylase deficiency lacking enzyme protein.

We report an ornithine transcarbamylase(OTC)-deficient male patient who had no detectable immunoreactive materials but did have active mRNA for OTC-related protein. The total absence of OTC activity in the liver of the patient was caused by a complete lack of immunoreactive material, as determined by Ouchterlony double immunodiffusion, single radial immunodiffusion, and sodium dodecylsulphate-polyacrylamide gel electrophoresis of immunoprecipitate and of liver homogenate. However, mRNA coding for the precursor of OTC was clearly detected in autopsy specimens of the patient's liver as well as of controls in a cell-free translation system consisting of rabbit reticulocyte lysates and [35S]methionine. The labelled precursor of OTC synthesized in vitro with mRNA from the patient could be transported into rat liver and kidney mitochondria and processed to form a protein with a molecular weight indistinguishable from mature OTC, suggesting that there was no defect in the protein structure necessary for its transport into mitochondria. These results suggest that the primary defect of the OTC deficiency was located in the structural gene and that the labile OTC-related protein, after being synthesized with its mRNA, was degraded too rapidly to be detected by the method used.

Amino Acid Metabolism, Inborn Errors↗
PubMed1984

Two different types of inactive renin in human plasma: molecular and kinetic properties.

We separated inactive renin in human plasma into two types, adsorbed and non-adsorbed, by chromatography on a concanavalin A-Sepharose column. About 75% of fresh plasma inactive renin was adsorbed to the column, and the rest passed through it. Non-adsorbed and adsorbed inactive renins were partially purified. Non-adsorbed inactive renin had a molecular weight of 48000 and an isoelectric point of 5.44. Adsorbed inactive renin had a molecular weight of 46000 and isoelectric points of 5.56 and 5.80. After activation with trypsin, both activated inactive renins were similar with respect to molecular weight (45000), thermostability, Km value (0.56 mumol/l) and pH profile. But pI values of both activated inactive renins differed. These results indicate that there exist in human plasma two different types of inactive renin which differ in carbohydrate composition.

Chemical Phenomena↗
PubMed1984

Effect of temperature and added ligands on the susceptibility of Ca2+,Mg2+-adenosine triphosphatase of the sarcoplasmic reticulum to trypsin.

Sarcoplasmic reticulum membranes were subjected to limited proteolysis by trypsin under various conditions and the products were analyzed with SDS-polyacrylamide gel electrophoresis. Besides the fragments well characterized in the literature, i.e. A, B, A1, and A2 [Thorley-Lawson, D.A. & Green, N.M. (1977) Biochem. J., 167, 739] of Mr 55,000, 45,000, 30,000, and 20,000, respectively, two closely related fragments derived from fragment A1, and another migrating a little faster than these (Mr 27,000-28,000), were produced at 35 degrees C. Appearance of these smaller fragments was accompanied by the disappearance not only of A1 but also of A2. This subfragmentation was prevented at 0 degrees C, so that a large amount of A1 fragment was accumulated. Ca2+ and AMP-P(NH)P, alone or in combination, also affected the susceptibility of the ATPase protein to tryptic digestion, resulting in a marked stabilization of A1 and A2 fragments. These findings afforded us a basis of devising a procedure for efficient production of these fragments, which would serve as useful starting materials for protein chemical analyses of this enzyme. The observed changes in susceptibility to proteolytic digestion are consistent with our current knowledge on the conformational changes of this ATPase.

Animals↗
PubMed1984

Conformational change of Ca2+,Mg2+-adenosine triphosphatase of sarcoplasmic reticulum upon binding of Ca2+ and adenyl-5'-yl-imidodiphosphate as detected by trypsin sensitivity analysis.

Ca2+-Mg2+-ATPase of sarcoplasmic reticulum was subjected to trypic digestion under various conditions and the cleavage patterns were compared. The first tryptic cleavage to yield the NH2-terminal A-fragment (Mr approximately equal to 55,000) and COOH-terminal B-fragment (Mr approximately equal to 45,000) [Thorley-Lawson, D.A. & Green, N.M. (1977) Biochem. J. 167, 739-748] was little affected by adding ligands such as Ca2+ and AMP-P(NH)P. On the other hand, subsequent splitting of A-fragment into A1 (Mr approximately equal to 30,000) and A2 (Mr approximately equal to 20,000), and further cleavages giving rise to three smaller fragments of Mr approximately equal to 27,000-28,000 (A1a, A1b, and C) [Saito, K., et al. (1984) J. Biochem. 95, 1297] were profoundly affected by these ligands. A difference in cleavage sites was noted depending on Ca2+ ion concentration; thus, A1b and C were the major components remaining after digestion in the presence and absence of Ca2+, respectively. AMP-P(NH)P markedly stabilized both A1 and A2 fragments, but the effect was much more prominent when Ca2+ was simultaneously present on the transport site. These findings suggest that conformational changes of the ATPase molecule upon binding of Ca2+, AMP-P(NH)P, or both are accompanied by corresponding changes in the susceptibility to tryptic digestion. Fragments A1 and A2 were both quite stable and fragmentation did not proceed beyond A1, when sarcoplasmic reticulum membranes were treated with trypsin at 0 degrees C. Significant further fragmentation of A1 was observed only above 20 degrees C, suggesting a conformational transition of the ATPase protein around that temperature.

Adenosine Triphosphate↗
PubMed1984

Suppressor T cell chronic lymphocytic leukaemia associated with red cell hypoplasia.

A case of T cell chronic lymphocytic leukaemia (CLL) with red cell hypoplasia and neutropenia is reported. WBC was 10.0 X 10(9)/l with 78% being T lymphocytes. These T lymphocytes were positive for Fc gamma receptor and had OKT8 and Leu 2a antigens on the cell surfaces. They suppressed both erythroid and granulocyte-macrophage colony formation in normal bone marrow cultures and suppressed immunoglobulin production by normal B lymphocytes in vitro. Though the myeloid cells were preserved in the bone marrow and the values of serum immunoglobulins were within normal limits, it can be estimated from these results that red cell hypoplasia and neutropenia were partially due to the suppression of haemopoietic precursor cells by leukaemic T lymphocytes.

Aged↗
PubMed1984

Plasma levels of proinsulin, insulin and C-peptide in chronic renal, hepatic and muscular disorders.

Proinsulin, insulin and C-peptide levels were investigated in chronic renal, hepatic and muscular disorders. The proinsulin levels in human plasma were determined by radioimmunoassay using insulin-degrading enzyme (IDE). The fasting levels of proinsulin in 29 patients with chronic renal failure (0.95 +/- 0.05) were significantly higher than those in 10 patients with liver cirrhosis (0.46 +/- 0.04), six with muscular dystrophy (0.37 +/- 0.02) and 52 normal subjects (0.24 +/- 0.02 ng/ml, mean +/- S.E.). The fasting levels of insulin and C-peptide in chronic renal failure were also the highest among these groups. The insulin levels in liver cirrhosis and muscular dystrophy were significantly greater than those in normal subjects and increased molar ratios of proinsulin to total insulin immunoreactivity in chronic renal failure were observed. These results suggest that the kidney, liver and muscle are related to circulating insulin levels and that the kidney plays a particularly important role in circulating proinsulin levels. It can be concluded that increases in these peptides are due to a hypersecretion of B-cells, a decreased degradation or excretion.

C-Peptide↗
PubMed1984

[Effects of estrogen, progesterone and androgen on autoradiograms of the immature rat uterus].

Endometrial cancer is more frequent in patients at a postmenopausal age, when the ovarian secretion of androgens instead of estrogens seems to be relatively increased. In clinical or experimental medicine, progesterones are widely used for the treatment of endometrial cancer, probably because they have an antiestrogenic action and cause differentiation of cancer cells from the proliferative phase. The effects of testosterone(T), progesterone(P), and/or 17 beta-estradiol(E) on the incorporation of 3H-thymidine in autoradiograms were investigated in immature rats. The autoradiogram revealed many grains due to 3H-thymidine in the endometrial epithelium, stroma, and the myometrium in the immature rat 30 hours after E-injection. T alone markedly induced the DNA synthesis in the stroma and the myometrium, but not in the epithelium. T displayed a synergistic interaction with E in both the stroma and the myometrium with a slight increase in thymidine incorporation into the epithelium. P alone induced DNA synthesis in the stroma and the myometrium. Simultaneous injection of E and P also produced the same result as that when P alone was injected. P markedly inhibited DNA synthesis due to E in the epithelium. Autoradiograms of the immature rat uterus provide basic support for the rationality of P therapy for cancer or adenomatous hyperplasia of the endometrium.

Androgens↗
PubMed1984

Accessory cells distinct from macrophages in lymphocyte proliferation of cynomolgus monkeys.

Mononuclear cells of cynomolgus monkeys were separated into four distinct fractions based on their buoyant density on discontinuous gradients of Percoll. Cells of the lightest density (fraction I) were enriched for macrophages and B cells, whereas cells from the denser fractions (fractions II-IV) consisted mainly of T cells, especially in fraction IV up to 88%. Cells of moderate density (fractions II and III) could respond better to T cell mitogens than unfractionated cells. In contrast, cells of fraction I not only failed to respond to mitogens, but also exerted an inhibitory effect on lymphocyte proliferation, indicating that macrophages might suppress the response in cynomolgus monkeys. Cells alone having the heaviest density (fraction IV), although enriched for T cells, also showed no significant response. However, addition of mitomycin C-treated fraction II or III resulted in partial restoration in the proliferative response of this fraction. Further examination revealed that the accessory activity resided in the non-adherent, nonphagocytic, non-E rosette-forming and Fc receptor-negative cells with moderate density, suggesting the presence of accessory cells distinct from monocyte/macrophage lineage in cynomolgus monkeys.

Animals↗
PubMed1983

Modification of batroxobin with activated polyethylene glycol: reduction of binding ability towards anti-batroxobin antibody and retention of defibrinogenation activity in circulation of preimmunized dogs.

Amino groups of batroxobin (Bothrops atrox thrombic protease) were modified with 2,4-bis(O-methoxypolyethylene glycol)-6-chloro-s-triazine (activated PEG2). The modified batroxobin had the reduced binding ability towards anti-batroxobin antibody but retained its enzymic activity in vitro and in vivo. Administration of modified batroxobin in which 29% of the total amino groups in the molecule had been modified, to beagle dogs preimmunized with native batroxobin gave rise to a marked reduction of the fibrinogen level in plasma, accompanied with an increased level of fibrinogen (fibrin) degradation products, FDP. On the other hand, no reduction of fibrinogen level was observed when native batroxobin instead of modified batroxobin was injected to immunized dogs.

Animals↗
PubMed1983

Acetaminophen-aluminum hydroxide interaction in rabbits.

Acetaminophen-aluminum hydroxide interaction was investigated in a crossover study using six rabbits. Blood samples were collected at various time intervals for up to 6 hr following the oral administration of acetaminophen alone or in combination with aluminum hydroxide. Aluminum hydroxide at a 40-mg/kg dose did not appear to affect the rate and extent of acetaminophen absorption. The influence of aluminum hydroxide on gastric emptying could be compromised by gastric absorption of acetaminophen, resulting in a negligible effect on the overall bioavailability of acetaminophen.

Acetaminophen↗
PubMed1983

A Burkitt-type 8;14 translocation in a case of plasma cell leukemia.

In a 50-year-old patient with plasma cell leukemia, the leukemic cells were found to have a 14q+ marker chromosome derived from the same translocation as that seen in Burkitt's lymphoma, namely, t(8;14)(q24;q32). A 14q+ marker has been reported so far in 13 cases of plasma cell dyscrasia, but only in 3 of them was the origin of the extra material on the 14q+ identified by banding analysis. The present case is the first one shown to involve a 14q+ marker derived from a Burkitt-type 8;14 translocation. Of particular interest is the association of the 8;14 translocation with lymphoid malignancies of the B-cell lineage.

Chromosomes, Human, 13-15↗
PubMed1983

Two cases of acute promyelocytic leukemia with variant translocations: the importance of chromosome No. 17 abnormality.

Two patients with acute promyelocytic leukemia (APL) were found to have chromosomal translocations in their leukemic cells; one had a 46,XX,t(7;17)(q36;q22) and another a 46,XY,t(1;17)(p36;q21) karyotype. These two cases of APL seem to be the first involving variant translocations instead of the standard t(15q+; 17q-) translocation. The present cases strongly suggest that the rearrangement of chromosome #17, which occurs in bands of the q21-22 region of the long arm, is crucially important in the pathogenesis of APL.

Adult↗