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Biomedical subjects

K Morimoto

Publications and source records attributed to K Morimoto.

At least 595 records · Page 33Linked to original sources
PubMed1985

Repair of O6-propylguanine and O6-butylguanine in DNA by O6-alkylguanine-DNA alkyltransferases from rat liver and E. coli.

DNA substrates containing O6-n-butylguanine, O6-iso-butylguanine, O6-n-propylguanine and O6-iso-propylguanine were prepared by reaction of calf thymus DNA with the appropriate N-alkyl-N-nitrosourea. These substrates were used to test the ability of O6-alkylguanine-DNA alkyltransferases from Escherichia coli and rat liver to remove such alkyl groups from the O6-position of guanine. It was found that all of these adducts were removed by the alkyltransferases, but the branched alkyl chain iso-butyl- and iso-propyl adducts were removed very slowly. Also, when tested with a DNA substrate containing both O6-n-propylguanine and O6-iso-propylguanine, the alkyltransferases removed almost all of the n-propyl-adduct before the iso-propyl-adduct was attacked. Both alkyltransferases showed a decreasing rate of reaction as the size of the alkyl group increased, but there was a significant difference between the rat liver and E. coli alkyltransferase in the relative rates. The rat liver alkyltransferase repaired O6-methylguanine more slowly than the E. coli protein, but was considerably more rapid than the bacterial equivalent when acting on n-propyl- and n-butyl-adducts. The relative rates of repair were methyl much greater than ethyl greater than n-propyl greater than n-butyl greater than iso-propyl, iso-butyl for the E. coli alkyl-transferase and methyl greater than ethyl, n-propyl greater than n-butyl greater than iso-propyl, iso-butyl greater than 2-hydroxyethyl for the rat liver protein. These results indicate that differential rates of repair may contribute to the relative risks of carcinogenesis and mutagenesis by exposure to alkylating agents of different size and that rates of repair may be species specific and must be determined from specific measurements rather than extrapolated from data on other organisms.

Animals↗
PubMed1985

Calcium-dependent interaction of actin filaments with actin binding protein in the presence of calmodulin and caldesmon.

Caldesmon, calmodulin-, and actin-binding protein of chicken gizzard did not affect the process of polymerization of actin induced by 0.1 M KCl. Caldesmon binds to F-actin, thus inhibiting the gelation action of actin binding protein (ABP; filamin). Low shear viscosity and flow birefringence measurements revealed that in a system of calmodulin, caldesmon, ABP, and F-actin, gelation occurs in the presence of micromolar Ca2+ concentrations, but not in the absence of Ca2+. Electron microscopic observations showed the Ca2+-dependent formation of actin bundles in this system. These results were interpreted by the flip-flop mechanism: in the presence of Ca2+, a calmodulin-caldesmon complex is released from actin filaments on which ABP exerts its gelating action. On the other hand, in the absence of Ca2+, caldesmon remains bound to actin filaments, thus preventing the action of ABP.

Actins↗
PubMed1985

Immunohistochemical investigation of cerebral ischemia in gerbils.

Experimental cerebral ischemia was produced in gerbils by occlusion of the right common carotid artery in the neck. The evolution of the ischemic lesions was followed from five minutes to six hours by using the immunohistochemical techniques for tubulin and creatine kinase BB-isoenzyme. The earliest lesion was found in the subiculum-CA1 and CA2 regions of the hippocampus in five minutes. There was loss of staining in the apical dendrites and perikarya of the pyramidal cells. The earliest lesion in the cerebral cortex, visible in ten minutes, was a laminar loss of staining for tubulin. Evolution of the ischemic lesions in the thalamus and caudoputamen was delayed. However, in two hours widespread ischemic lesions were seen there. Evolution of the ischemic lesions was slightly slower with the reaction for creatine kinase BB-isoenzyme as compared to the reaction for tubulin, but was far more sensitive than hematoxylin-eosin staining. The distribution of ischemic lesions detected by the immunohistochemical method compared to ischemic areas detected by an India ink perfusion study suggested that both the extent of regional ischemia and regional difference in tissue vulnerability were contributing factors for the emergence of early ischemic lesions. The mechanism for prompt disappearance of the immunohistochemical reaction for tubulin is not clear, but the present investigation demonstrates the usefulness of the immunohistochemical technique for detecting early ischemic lesions and provides a possible biochemical mechanism for cellular damage after ischemic insults.

Animals↗
PubMed1985

Purification of astroprotein (astrocyte-specific cerebroprotein) by reversed-phase C-1 HPLC.

A method for purification of astroprotein (an astrocyte-specific cerebroprotein) with HPLC is described. A linear gradient from 30 to 70% acetonitrile in 0.1% trifluoroacetic acid (pH 2.2) was applied to the reversed-phase C-1 (particle size 10 micron) column. Cerebroproteins from the crude extract from human glioma were clearly separated by this procedure. Highly purified astroprotein was homogeneous by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and has immunoreactivity to antiserum against astroprotein. Reversed-phase C-1 HPLC offers advantages over previously available preparative techniques in the higher purity and better separation time of the products.

Chromatography, High Pressure Liquid↗
PubMed1985

Effect of non-ionic surfactants in a polyacrylic acid gel base on the rectal absorption of [Asu1,7]-eel calcitonin in rats.

The effect of non-ionic surfactants in a polyacrylic acid gel base on the rectal absorption of [Asu1,7]-eel calcitonin, a calcitonin analogue, was studied in rats. Absorption was enhanced by a microenema which used a polyacrylic acid gel base, but it was reduced by the incorporation of polysorbate 80 (0.1-5% v/v). The incorporation of polyoxyethylene 9 lauryl ether (0.1-5% v/v) in the polyacrylic acid gel base enhanced the absorption. Rectal administration in the base containing 0.5% v/v polyoxyethylene 9 lauryl ether required a dose of the calcitonin 2-3 times greater than an intramuscularly administered dose to achieve an equivalent hypocalcaemic effect.

Acrylic Resins↗
PubMed1985

Enhancement of nasal absorption of insulin and calcitonin using polyacrylic acid gel.

The effects of polyacrylic acid gel on the nasal absorption of insulin and [Asu1,7]-eel calcitonin were investigated in rats. The nasal administration of insulin (1 IU kg-1) in polyacrylic acid gel at 0.1 and 1% w/v showed maximum hypoglycaemic effects at 30 min and 1 h after administration, respectively. However, the nasal administration of insulin in carboxymethyl cellulose (1% w/v) solution had no hypoglycaemic effect at the same dose. When [Asu1,7]-eel calcitonin (10 U kg-1) was administered nasally in polyacrylic acid gel (0.1% w/v), a prominent hypocalcaemic effect was observed during the first 30 min. Nasal administration of [Asu1,7]-eel calcitonin in saline had no hypocalcaemic effect at the same dose. The results indicate that the polyacrylic acid gel base significantly enhanced the absorption of insulin and [Asu1,7]-eel calcitonin via the nasal cavity.

Absorption↗
PubMed1985

Synthesis of prostaglandin E2 and F2 alpha in human tonsillar lymphocytes.

Although prostaglandins (PGs), especially PGE2 and PGF2 alpha, are thought to be associated with inflammation, there have been no papers dealing with the synthesis of PGE2 and PGF2 alpha in human tonsillar lymphocytes. The features of PG synthesis in lymphocytes were investigated by incubating cells with radiolabelled precursors. Synthesis of PGE2 was greater than that of PGF2 alpha in tonsillar lymphocytes. PGE2 was the predominant product in the tonsillar lymphocytes of the recent infection group. There was no significant difference between T and B lymphocytes in the ratio of PGE2 and PGF2 alpha formed. A significant increase in PGE2 formed with bradykinin was found in the tonsillar hypertrophy group. The possible role of PGs in the pathogenesis and mechanism of releasing free fatty acid PG precursors from cell membranes was discussed.

Adolescent↗
PubMed1985

Surgical correction of subglottic stenosis in children. A follow-up study.

In general, subglottic stenosis in children is one of the most difficult problems to treat surgically. Six patients, aged 4-9, requiring a tracheostomy due to severe subglottic stenosis are reviewed. Decannulation was difficult to perform in these cases. All children in this series underwent surgical correction of subglottic stenosis. Patients had been successfully decannulated with no evidence of recurrent stenosis and were followed up for a period of 2-9 years. Our cases which were followed up for 2-9 years address the issue raised by opponents of surgical correction of subglottic stenosis in children, namely the consideration that the laryngeal growth potential may be adversely affected by surgery.

Child↗
PubMed1985

Studies of the repair of O6-alkylguanine and O4-alkylthymine in DNA by alkyltransferases from mammalian cells and bacteria.

O6-Methylguanine in DNA is repaired by the action of a protein termed O6-alkylguanine-DNA alkyltransferase (AT) which transfers the methyl group to a cysteine residue in its own sequence. Since the cysteine which is methylated is not regenerated rapidly, if at all, the capacity for repair of O6-methylguanine is limited by the number of molecules of the AT available within the cell. The level and inducibility of the AT differed greatly in different mammalian cell types and species with the highest levels in human tissues and in liver and the lowest levels in brain. Only a small induction occurred in rat liver in response to exposure to alkylating agents. In E. coli such exposure increased the activity more than 100-fold. The At was not specific for methyl groups but also removed ethyl, 2-hydroxyethyl, n-propyl, isopropyl and n-butyl groups from the O6-position in DNA. The protein isolated from E. coli removed methyl groups much more rapidly than the larger alkyl groups but the mammalian AT isolated from rat liver showed much less difference in rate with adducts of different size. Ethyl and n-propyl groups were removed by the rat liver AT only three to four times more slowly than methyl groups. Another important difference between the bacterial and mammalian ATs is that the bacterial protein was also able to remove methyl groups from the O4-position of thymine in methylated DNA or poly(dT) but the AT from rat liver or human fibroblasts did not repair O4-methylthymidine.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1985

Immunohistochemical investigation of cerebral ischemia during recirculation.

Immunohistochemical methods for the determination of tubulin, creatine kinase BB-isoenzyme, and astroprotein-glial fibrillary acidic protein were used to investigate recovery of the ischemic lesion after temporary occlusion of a common carotid artery in the gerbil and the evolution of the postischemic lesion following reperfusion. One group of gerbils was followed from 15 minutes to one month after an ischemic period of 30 minutes, and another group was examined after 7 days following an ischemic period of 5 to 30 minutes. It was found that the postischemic lesion, visualized as loss of the immunohistochemical reaction for tubulin and creatine kinase BB-isoenzyme, evolved within 60 minutes after reperfusion in the hippocampus and cerebral cortex and within 3 hours in the caudoputamen and thalamus. Resolution of the preexisting ischemic lesion was possible only after an ischemic period of less than 10 minutes in the cerebral cortex and caudoputamen and less than 15 minutes in the thalamus. In the CA1-CA2 region of the hippocampus, the ischemic lesion already existed after an ischemic period of 5 minutes and was mostly irreversible. The immunohistochemical method of testing for different cellular and subcellular components was very useful for investigation of cerebral ischemia and may also be advantageous for investigation of other pathophysiological conditions of the nervous system.

Animals↗
PubMed1985

[Successful treatment of mediastinal seminoma with combination chemotherapy of cis-diamminedichloroplatinum (CDDP), vinblastine (VBL), and bleomycin (BLM)].

Complete response (CR) has been achieved in a case of advanced mediastinal seminoma using PVB therapy (CDDP, VBL, BLM). A 21-year-old man visited our department with the complaint of superior vena cava syndrome. Chest X-ray film, ultrasonography and CT scan revealed a large anterior mediastinal mass. Histological proof of mediastinal seminoma was obtained by needle biopsy. The patient was treated with a combination chemotherapy, consisting of CDDP, VBL and BLM according to Einhorn's PVB regimen. After three courses of this regimen, complete disappearance of the tumor was obtained. The patient underwent further radiation treatment (Linac: 4,000 rad), as a salvage therapy, at the anterior mediastinum, and has since been doing well without any sign of recurrence for a follow-up period of nine months.

Adult↗
PubMed1985

CT diagnosis of abdominal lymph node metastases in hepatocellular carcinoma.

CT scanning is useful for diagnosing abdominal lymph node metastasis. Using this technique, histologically confirmed abdominal lymph node metastases were detected in nine of 49 patients (33 autopsy cases and 16 laparotomy cases) with hepatocellular carcinoma (hepatoma). Among the 49 patients, three had periportal (6.1%), six peripancreatic (12.2.%) and six para-aortic adenopathies (12.2%). Two of the patients had adenopathy at all three sites. Retrospectively, CT detected two periportal, four peripancreatic and all six para-aortic adenopathies. Most of the hepatomas with adenopathy showed infiltrative growth; tumour thrombosis of the portal vein was a common complication.

Abdominal Neoplasms↗
PubMed1985

[A carcinogens--methods for detecting environmental muta/carcinogens].

The major causes of cancer in the developed countries are now thought to be environmental or man-made factors. Because most carcinogens are also mutagens, the detection and identification of muta/carcinogens to humans seem to be very important in the environmental sciences. We describe here, i) in vitro and in vivo short-term assays for muta/carcinogens in the environment, ii) possible method for monitoring human exposure to muta/carcinogens, and iii) some trials for estimating human risk for the development of cancers due to environmental mutagens.

Abnormalities, Drug-Induced↗