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Biomedical subjects

M Tada

Publications and source records attributed to M Tada.

At least 433 records · Page 24Linked to original sources
PubMed1989

Nature and site of phospholamban regulation of the Ca2+ pump of sarcoplasmic reticulum.

The rapid removal of Ca2+ ions from the cytosol, necessary for the efficient relaxation of cardiac muscle cells, is performed by the Ca2+-pumping ATPase of the sarcoplasmic reticulum. The calcium pump is activated by cyclic AMP- and calmodulin-dependent phosphorylation of phospholamban, an integral membrane protein of the sarcoplasmic reticulum. Using a heterobifunctional crosslinking agent which can be cleaved and photoactivated, we provide evidence for a direct interaction between the two proteins. Only the non-phosphorylated form of phospholamban interacts with the ATPase, demonstrating that phospholamban is an endogenous inhibitor that is removed from the ATPase by phosphorylation. Non-phosphorylated phospholamban interacts only with the calcium-free conformation of the ATPase and is released when it is converted to the calcium-bound state. We localized the site of interaction to a single peptide isolated after cyanogen bromide cleavage of the ATPase. The peptide derives from a domain just C-terminal to the aspartyl phosphate of the active site. This domain is unique to ATPases of the sarcoplasmic reticulum in that it has no homology with any other phosphorylation-type ion pump. The domain occurs in both slow- and fast-twitch isoforms of the ATPase, even though phospholamban is not expressed in fast-twitch muscles.

Adenosine Triphosphatases↗
PubMed1989

Slow/cardiac sarcoplasmic reticulum Ca2+-ATPase and phospholamban mRNAs are expressed in chronically stimulated rabbit fast-twitch muscle.

Fast-twitch extensor digitorum longus muscles of the rabbit were subjected to chronic low-frequency stimulation during different time periods. Changes in the relative amounts of mRNAs encoding fast and slow/cardiac Ca2+-ATPase isoforms were assessed through the use of an RNase-protection assay. Stimulation-induced increases in slow cardiac Ca2+-ATPase and phospholamban mRNAs were quantified by mRNA hybridization. Prolonged stimulation resulted in an exchange of the fast with the slow/cardiac Ca2+-ATPase isoform mRNAs. The exchange was complete after 72 d of stimulation as compared with normal slow-twitch soleus muscle. The tissue content of phospholamban mRNA reached levels similar to that found in normal slow-twitch soleus muscle by the same time. The conversion of the sarcoplasmic reticulum coincided with the fast-to-slow troponin C isoform transition, previously investigated in the same muscles.

Animals↗
PubMed1989

[Definition of the adaptation of endoscopic surgery for early gastric cancer. Special examination on the relationship between the histological differentiation of the intramucosal gastric cancer and the lymph node metastasis].

Out of five hundred and nineteen surgically resected lesions which were histologically shown to be intramucosal gastric cancer, 247 were well differentiated, 98 were moderately differentiated, and 176 were poorly differentiated lesions. The incidence of lymph node metastasis in the 247 well differentiated, 98 moderately differentiated, and 176 poorly differentiated intramucosal adenocarcinomas were 0.8% (= 2/247), 2.1% (= 2/98), and 8% (14/176), respectively. The cumulative survival rate of 5 years after gastrectomy was 94.2% for the 247 well, 93.3% for the 98 moderately, and 93.7% for the 176 poorly differentiated adenocarcinomas. A pathological study on the atypism of the gland of the cancer and the condition of the proprial space under the cancer cells was conducted on 100 lesions of well differentiated adenocarcinomas in order to define the criteria of non-surgical endoscopic removal resection for early gastric cancer. Out of the 100 lesions mentioned above, there were only two well differentiated adenocarcinomas with lymph node metastasis in which the boundary between the epithelium of the cancer and the proprial space under the cancer was very unclear and the interstitial space in the propria under the cancer was very small. On the other hand, we have resected 73 intramucosal gastric cancers using the endoscopic surgical method called strip biopsy since 1984, and have followed up these cases. The cancers resected by strip biopsy, and were histologically intramucosal well differentiated adenocarcinomas shown to have a moderately maintained interstitial space under the cancer cells. And, up to the present, there has been no incidence of recurrence after strip biopsy for the 73 lesions mentioned above. According to these results, we have defined the criterion for early gastric cancer endoscopic surgery, as follows. Intramucosal cancer which is shown to be well differentiated adenocarcinoma with a moderately maintained interstitial space under the cancer cells is considered to be sufficient for non-surgical endoscopic resection.

Aged↗
PubMed1989

Expression and site-specific mutagenesis of phospholamban. Studies of residues involved in phosphorylation and pentamer formation.

Full-length cDNAs encoding either dog cardiac or rabbit skeletal muscle phospholamban were expressed transiently in COS-1 cells. The expressed protein displayed the mobility of a pentamer when dissolved in sodium dodecyl sulfate and separated in polyacrylamide gels, and of a monomer when boiled prior to polyacrylamide gel separation. Site-specific mutagenesis was used to analyze the roles of several amino acids in the structure and function of the protein. Ser16 and Thr17 were shown to be phosphorylated uniquely by cAMP- and calmodulin-dependent protein kinases, respectively, confirming earlier observations on the native protein (Simmerman, H. K. B., Collins, J. H., Theibert, J.L., Wegener, A.D., and Jones, L.R. (1986) J. Biol. Chem. 261, 13333-13341). Arg13 and Arg14 were shown to be essential for both types of phosphorylation, and Arg9 was shown to be essential for calmodulin-dependent phosphorylation. In studies of pentamer stability, mutation of Gln22-Gln23 to Ala-Ala or Glu-Glu, of Gln26-Asn27 to Glu-Asp, or of Gln29-Asn30 to Glu-Asp had no effect on thermal stability of the pentamer, suggesting that hydrogen bonding involving these residues in domain IB is not important for pentamer stability. By contrast, mutation of Cys36, Cys41, and Cys46 in transmembrane domain II to Ser, Ala, or Phe diminished the stability of the pentamer when microsomal proteins were dissociated in sodium dodecyl sulfate and separated by polyacrylamide gel electrophoresis. In particular, the Cys41 to Phe mutant existed as a monomer at ambient temperature. These results suggest that the intramembranous cysteine residues are important for pentamer formation even though they are not disulfide-bonded.

Amino Acid Sequence↗
PubMed1989

Characterization of a monoclonal antibody to guinea pig peritoneal macrophages that inhibits phagocytosis of unopsonized zymosan: structural and functional similarities of the antigen to human and mouse CR3.

A monoclonal antibody, anti-Z-1, was established by fusion of spleen cells from mice immunized with guinea pig thioglycollate-induced peritoneal macrophages (TGC-M phi s) with mouse myeloma cells, P3-X63-Ag8-6.5.3. The Fab' fragments of anti-Z-1 bound to almost all of the TGC-M phi s with a high association constant (6.0 +/- 0.8) X 10(8) M-1, and effectively inhibited phagocytic activities of the cells for unopsonized zymosan and serum-treated zymosan. On the contrary, neither the phagocytic activity for rabbit IgG antibody-sensitized sheep erythrocytes nor that for periodate-treated sheep erythrocytes was inhibited by anti-Z-1. Immunoprecipitation analysis revealed that the antigen recognized by anti-Z-1, which was named Z-1 antigen, consists of a polypeptide chain with a molecular weight of 140,000 (alpha chain) noncovalently associated with a polypeptide chain of 95,000 (beta chain). The epitope with which anti-Z-1 reacts was found to be on the alpha chain by Western blotting. Furthermore, it was found that Z-1 antigen solubilized from the cells with nonionic detergent was capable of binding to unopsonized zymosan, suggesting that Z-1 antigen may function as a receptor for zymosan. These findings show the structural and functional similarities of Z-1 molecules on guinea pig peritoneal macrophages to the third complement receptor on human and mouse leukocytes.

Animals↗
PubMed1989

Possible involvement of a 95-kDa protein phosphorylation in phorbol 12-myristate 13-acetate-induced suppression of zymosan phagocytosis in guinea pig macrophages.

Recently, we characterized a surface antigen (Z-1) of guinea pig macrophages by monoclonal anti-Z-1 antibody. The Z-1 antigen consists of two different polypeptide chains; alpha (140 kDa) and beta (95 kDa). This antigen is closely correlated with the phagocytic activity of the cells for zymosan and presumably functions as a receptor for zymosan. In the present study, the effect of phorbol 12-myristate 13-acetate (PMA) on the function of Z-1 was examined. Incubation of ortho-[32P]phosphate-labeled macrophages with PMA greatly increased the phosphorylation of the beta subunit of Z-1 but not that of the alpha subunit. Optimal phosphorylation was observed when cells were incubated with 300 ng/ml of PMA for 60-120 min. The PMA-induced phosphorylation was markedly suppressed by treatment of the macrophages with H-7, an inhibitor of protein kinase C. A chemotactic peptide, N-formyl-Met-Leu-Phe (fMLP) also caused phosphorylation of the beta subunit. Unlike PMA, fMLP maximized the phosphorylation within 30 s. Purified Z-1 was an excellent substrate for the exogenously added protein kinase C only in the presence of both Ca2+ and phosphatidylserine. H-7 completely inhibited the in vitro phosphorylation. These data suggest that the beta subunit of Z-1 is phosphorylated by protein kinase C. The phosphorylation of Z-1 by PMA and fMLP coincided with inhibition of zymosan phagocytosis. A linear relationship was obtained between the level of phosphorylation of Z-1 and the degree of inhibition of zymosan phagocytosis induced by PMA. Thus, the results suggest that zymosan uptake is negatively regulated by protein kinase C-mediated phosphorylation of the beta subunit of Z-1.

Animals↗
PubMed1989

Renin expression in the kidney and brain is reciprocally controlled by captopril.

The tissue distribution of rat renin mRNA was examined. Sensitive RNase protection analyses demonstrated that renin mRNA are produced by the extra-renal tissues such as adrenal, brain, liver, lung, pituitary and testis. In response to sodium depletion and captopril treatment, the expression of mRNAs encoding rat renin were in a tissue-specific manner. The level of kidney renin mRNA remarkably increased in sodium-depleted rats treated with captopril, whereas that of brain renin mRNA definitely decreased. No significant change in the level of liver renin mRNA was observed after the same treatment. These results suggest that the expression of cerebral renin is regulated by physiological stimuli independent of its extra-cerebral expression.

Animals↗
PubMed1989

Attenuation of neutrophil function by inhibitors of arachidonate metabolism reduces the extent of canine myocardial infarction.

To assess the role of neutrophils and arachidonate metabolites in evolving myocardial infarction, the effect of inhibitors of arachidonate metabolism on the extent of myocardial damage and neutrophil function was examined in a 90-minute occlusion/5-hour reperfusion model of canine myocardial infarction. A thromboxane A2 synthetase inhibitor, CV-4151, and a lipoxygenase inhibitor, AA-861, greatly reduced the infarct size. They also attenuated the production of chemoattractant leukotriene B4 and chemotactic activity of neutrophils isolated from peripheral circulation. Under these conditions, both the increases in peripheral leukocyte count and neutrophil infiltration in ischemic myocardium were inhibited. These results indicate that the inhibition of 2 pathways of arachidonate metabolism may decrease infiltration of activated neutrophils in ischemic myocardium by attenuating chemotactic function of neutrophils, resulting in reduction of the extent of myocardial infarction.

Animals↗
PubMed1989

Regulation of the Ca2+ pump ATPase by cAMP-dependent phosphorylation of phospholamban.

Ca2+ transients in myocardial cells are modulated by cyclic AMP-dependent phosphorylation of a protein in the sarcoplasmic reticulum. This protein, termed phospholamban, serves to regulate the Ca2+ pump ATPase of this membrane, thus altering the mode of Ca2+ transients and the myocardial contractile response. Elucidating the structure of phospholamban and its intimate interaction with the Ca2+ pump ATPase should provide the basis for understanding, at the molecular level, how the cAMP system contributes to excitation-contraction coupling in muscle cells.

Adenosine Triphosphatases↗
PubMed1989

2-Deoxy-2-[18F]fluoro-D-galactose as an in vivo tracer for imaging galactose metabolism in tumors with positron emission tomography.

The feasibility of 2-deoxy-2-[18F]fluoro-D-galactose ([ 18F]FdGal) for imaging galactose metabolism in tumors with positron emission tomography (PET), was investigated using two hepatomas, Yoshida sarcoma, or glioma in rats, and mouse mammary carcinoma. In hepatoma-bearing rats the highest uptake of [18F]FdGal was observed in the liver followed by the kidney and tumor. The tumor uptake increased with time, and the high uptake ratios of tumor to organ were observed except for the liver and kidney. Tumor uptake was also measured in all tumors. As main metabolites in all tumors, [18F]FdGal 1-phosphate and UDP-[18F]FdGal were found by HPLC. Two hepatomas showed a slightly higher uptake and a larger percentage of UDP derivative than the other three tumors. By autoradiography the brain tumor was visualized clearly. These results indicate that [18F]FdGal has potential as a tracer for imaging galactose metabolism in tumors with PET.

Animals↗
PubMed1989

Regulation of myocardial Ca2+-ATPase and phospholamban mRNA expression in response to pressure overload and thyroid hormone.

The sarcoplasmic reticulum (SR) and the contractile protein myosin play an important role in myocardial performance. Both of these systems exhibit plasticity--i.e., quantitative and/or qualitative reorganization during development and in response to stress. Recent studies indicate that SR Ca2+ uptake function is altered in adaptive cardiac hypertrophy and failure. The molecular basis (genetic and phenotypic) for these changes is not understood. In an effort to determine the underlying causes of these changes, we characterized the rabbit cardiac Ca2+-ATPase phenotype by molecular cloning and ribonuclease A mapping analysis. Our results show that the heart muscle expresses only the slow-twitch SR Ca2+-ATPase isoform. Second, we quantitated the steady-state mRNA levels of two major SR Ca2+ regulatory proteins, the Ca2+-ATPase and phospholamban, to see whether changes in mRNA content might provide insight into the basis for functional modification in the SR of hypertrophied hearts. In response to pressure overload hypertrophy, the relative level of the slow-twitch/cardiac SR Ca2+-ATPase mRNA was decreased to 34% of control at 1 week. The relative Ca2+-ATPase mRNA level increased to 167% of control after 3 days of treatment with thyroid hormone. In contrast, in hypothyroid animals, the relative Ca2+-ATPase mRNA level decreased to 51% of control at 2 weeks. The relative level of phospholamban mRNA was decreased to 36% in 1-week pressure overload. Hyperthyroidism induced a decrease to 61% in the phospholamban mRNA level after 3 days of treatment, while hypothyroidism had virtually no effect on phospholamban mRNA levels. These data indicate that the expression of SR Ca2+-ATPase and phospholamban mRNA may not be coordinately regulated during myocardial adaptation to different physiological conditions.

Animals↗
PubMed1989

Preparation and characterization of antibodies against 3,2'-dimethyl-4-aminobiphenyl-modified DNA.

Polyclonal antibodies for 3,2'-dimethyl-4-aminobiphenyl (DMAB)-DNA adducts were obtained from the sera of rabbits immunized with N-OH-DMAB-modified DNA. Using the enzyme linked immunosorbent assay (ELISA), these antibodies were shown to recognize DNA modified by N-OH-DMAB and N-hydroxy-4-aminobiphenyl, but not unmodified DNA, 2-acetylaminofluorene- or 4-nitroquinoline-1-oxide-modified DNA, free aminobiphenyl or DMAB derivatives. Using competitive ELISA with DMAB-modified denatured DNA, a 50% inhibition of antibody antigen binding was caused by 7 fmol of DMAB adducts applied to each assay well as an inhibitor. Native DNA bearing adducts was associated with 50% inhibition in the range of 22-90 fmol/asay well, depending on the levels of modification. The adducts recognized by the antibody were shown to be stable against treatment of heat or alkali denaturation. Optimal conditions for the detection of adducts in DNA from the rat organs exposed to DMAB were established by means of competitive ELISA, using alkaline-denatured DNA as an inhibitor. Thus, as little as 5 fmol adducts in 1 microgram of DNA could be detected. Indirect immunofluorescence staining indicated that anti-DMAB-DNA antibodies bound specifically to nuclear components of rat fibroblast 3Y1 cells treated with N-OH-DMAB. The intensity of the fluorescence was proportional to the dose of carcinogen administered. The antibodies should be helpful for use in studies on the formation of adducts and their removal in cells and tissues after DMAB administration.

Aminobiphenyl Compounds↗
PubMed1989

Role of free radicals and neutrophils in canine myocardial reperfusion injury: myocardial salvage by a novel free radical scavenger, 2-octadecylascorbic acid.

To define the role of oxygen free radicals and neutrophil involvement in evolving myocardial reperfusion injury, we evaluated the effect of 2-octadecylascorbic acid (CV-3611), a novel free radical scavenger, on neutrophil function and the extent of myocardial damage resulting from 90 min of ischaemia followed by 5 h of reperfusion in an experimental model of myocardial infarction. Dogs were randomly assigned to receive CV-3611 (5 mg.kg-1.[5 min]-1, intravenously) just before the onset of reperfusion. Infarct size, as a percent of area at risk, was reduced by 60% in CV-3611 treated group as compared with control, at 16.7(SEM 3.1)% v 41.5(4.5)%, p less than 0.01. Administration of CV-3611 markedly reduced function of neutrophils isolated from peripheral circulation during reperfusion ex vivo as estimated by free radical generation (ferricytochrome c reduction and luminol enhanced chemiluminescence), chemotactic activity, and aggregation induced by A23187. Under these conditions, the enhancement in neutrophil infiltration and free radical generation (luminol enhanced chemiluminescence) in myocardium within area at risk, especially in the border zone between viable and irreversible injured myocardium, was markedly reduced. Haemodynamic profiles were similar between control and CV-3611 treated group. These results suggest that activated neutrophils, especially their generation of oxygen free radicals, contribute to reperfusion induced myocardial injury.

Animals↗
PubMed1989

Differential diagnosis of AH109A tumor and inflammation by radioscintigraphy with L-[methyl-11C]methionine.

For the evaluation of tumor imaging with L-[methyl-11C]methionine (11C-Met), a basic study on the differentiation of tumor from inflammation with 11C-Met and a comparison of the diagnostic value of the image with that obtained using 67Ga citrate, a conventional scintigraphic agent, are important. 11C-Met accumulations into inflammatory lesions, AH109A tumor and normal tissues of rats were examined by means of a tissue distribution study. Aseptic inflammatory lesions on the back of Donryu rats induced by croton oil and 1.5% carrageenan showed significantly lower accumulations of 11C-Met than the AH109A tumor. Histologically, croton oil induced granulomatous inflammation and carrageenan, acute exudative inflammation. Whole-body autoradiography with 14C-Met, a substitute for 11C-Met, was negative in the carrageenan lesion and showed a slightly increased activity at the periphery of the croton oil lesion, in contrast with the high tumor activity. Whole-body autoradiography with 67Ga citrate was performed to compare the imaging ability with that of 14C-Met; it showed high activities in the tumor, bone, and intestine, and a broad increased activity at the periphery of the croton oil lesion, but was negative in the carrageenan lesion. 11C-Met accumulations in the inflammations were very low and clinical application with positron emission tomography, should be useful for the differential diagnosis of tumor from inflammation.

Animals↗
PubMed1989

Rapid and sensitive response of carbon-11-L-methionine tumor uptake to irradiation.

Evaluation of cancer treatments by the measurement of tumor size is an unsatisfactory method for the observation of the radiobiologic response of the tumor. After 20 Gy single-dose irradiation of 60Co to rat tumor AH109A, the L-[methyl-11C] methionine tumor uptake, the microscopic extension of tumor necrosis and the shrinkage of tumor were compared quantitatively. L-[Methyl-11C]methionine uptake fell to 54 +/- 19% of non irradiated tumor at 12 hr after irradiation. Necrosis extended 49 +/- 7% of total tissue volume after 3 days. Tumor volume decreased 48 +/- 12% 10 days after irradiation. L-[Methyl-11C]methionine uptake by tumor showed a sharp and rapid linear decrease after irradiation and the response of the uptake to irradiation preceded the extension of necrosis and tumor shrinkage. We conclude that radiation effect on the tumor may be evaluated immediately after irradiation by the measurement of L-[methyl-11C]methionine uptake and thus clinical application of positron emission tomography may give a benefit to the patients undergoing radiotherapy.

Animals↗