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Biomedical subjects

A Ohashi

Publications and source records attributed to A Ohashi.

At least 109 records · Page 6Linked to original sources
PubMed1986

Localization of enzyme for heme attachment to apocytochrome c in yeast mitochondria.

Fractionation of yeast mitochondria by controlled hypotonic treatment revealed that the enzyme for heme attachment to apocytochrome c was localized in mitochondrial inner membrane. Trypsin digestion of mitoplasts resulted in a considerable loss of enzymatic activity, whereas the enzyme in intact mitochondria resisted the digestion. Triton X-100 solubilized the enzyme from the membrane but high concentration of salt did not. These results reveal that the enzyme for heme attachment is localized in mitochondrial inner membrane facing the cytoplasmic surface.

Apoproteins↗
PubMed1986

[Localization of radiolabeled antibody to carcinoembryonic antigen in patients with gastrointestinal carcinoma].

Present study was undertaken to investigate accumulation of radiolabeled antibody to CEA in CEA-producing tumor and possibility of radioimmunodetection of cancer with antibody. Nine patients with gastric carcinoma and seventeen colorectal carcinoma were studied. Antibody to CEA were produced in horse by immunization with CEA purified from hepatic metastasis of colorectal carcinoma. The purified antibodies were labeled with 125I or 131I. The patients who entered these studies received radioactive antibodies to CEA intravenously 24-48 hours prior to operation. Radioactivity in tumor tissues and normal mucosal tissues obtained at the operation was counted by gamma-scintillation counter. In four patients with liver metastasis from colorectal carcinoma, external photoscanning was also performed for radioimmunodetection of cancer with 131I-labeled antibody to CEA. The results were as follows. The mean ratio of 125I-uptake of cancer tissue to that of normal mucosal tissue was 3.28 +/- 1.52 (n = 26), and ratio to peripheral blood, liver, skin and fat tissue was 1.91 +/- 1.32, 2.90 +/- 1.47, 5.70 +/- 3.28 and 12.86 +/- 8.48, respectively. Tumor tissue showed the highest uptake. Accumulation of radiolabeled antibody to CEA in tumor tissue was higher in patients with relatively high serum CEA level. High level of circulating CEA did not hinder accumulation of radiolabeled antibody to CEA in tumor tissue. In two out of four patients with liver metastasis from colorectal carcinoma, the tumor location was successfully demonstrated by external photoscanning using gamma-camera. The information obtained in the present study provided possibility of direct radioimmunodetection and immunochemotherapy.

Adult↗
PubMed1982

Import of proteins into mitochondria. The precursor of cytochrome c1 is processed in two steps, one of them heme-dependent.

The apoprotein of yeast cytochrome c1 is made outside the mitochondria as a larger precursor which is then processed in at least two steps. In the first step, it is transported across both mitochondrial membranes and converted by a matrix-localized protease to an intermediate form whose molecular weight is between that of the precursor and the mature form. The intermediate form is bound to the outer face of the inner membrane. This first step requires an energized mitochondrial inner membrane, but no heme. In the second step, the intermediate form is converted to the mature cytochrome. This second step requires heme; it is blocked in a heme-deficient mutant or in wild type cells treated with an inhibitor of heme synthesis. Import of cytochrome c1 into mitochondria thus proceeds via two distinct heme-free precursors and at least two maturation steps, one of them dependent on heme.

Cytochrome c Group↗
PubMed1982

Imported mitochondrial proteins cytochrome b2 and cytochrome c1 are processed in two steps.

Cytochrome b2 of yeast is located in the space between the inner and outer mitochondrial membranes whereas cytochrome c1 is bound to the outer face of the mitochondrial inner membrane. Both proteins are made outside the mitochondria as larger precursors that are processed to their mature forms in two steps. In the first step, at least a segment of the precursor polypeptide chain penetrates into the mitochondrial matrix and is cleaved to an intermediate form by a matrix-localized soluble protease. This step requires an electrochemical gradient across the mitochondrial inner membrane. In the second step, the intermediate form is converted to the mature form. For cytochrome c1, this second step requires heme. Import of these two cytochromes thus involves a "detour" across the inner membrane.

Biological Transport↗
PubMed1982

[Physiological effects and antitumor efficiency of ACNU in postoperative patients with stomach cancer--an evaluation of the treatment combined with FT-207 or 5-FU dry syrup].

In 26 patients with cancer of the stomach, bone marrow function, cell mediated immunity and plasma CEA level were examined after administration of ACN-U. ACNU was given intravenously and intermittently with 5-FU given orally daily. Results 1) Delayed myelosuppression was observed in every cases and reached to the nadir in 2-7 weeks after ACNU administration. 2) Bone marrow suppression and recovery therefrom were observed earlier in platelet counts than in RBC and WBC counts. 3) Suppression of cell mediated immunity was not observed later than 4 weeks after ACNU administration. 4) Plasma CEA level decreased or stopped to increase after ACNU administration in 5 out of 8 patients having a high CEA level before treatment. 5) Regression of tumor size was observed in 4 out of 5 patients in whom a tumor was palpable. Conclusion ACNU has a strong antitumor activity and may be more effective if combined with antimetabolite agent, such as 5FU. Total dosage of ACNU given safely in one series was considered to be 150-200mg. Next series of ACNU administration should be started after restoration of platelet counts more than 100,000/mm3 was obtained.

Antineoplastic Agents↗
PubMed1981

HLA and rheumatoid arthritis in the Japanese.

Sixty-three Japanese patients with rheumatoid arthritis (RA) were typed for HLA-A, -B, and -DR locus specificities. A significant association was found only with increased frequency of HLA-DR4 in the patients (71.4%) compared with controls (41.8%) (corrected P = 0.007, relative risk = 3.5). No association was found with HLA-A9 or HLA-Bw54, which are in linkage disequilibrium with HLA-DR4 in the Japanese. The association between HLA-DR4 and RA observed in these Japanese patients has also been demonstrated in the white population.

Adult↗
PubMed1980

Stimulation of in vitro mitochondrial protein synthesis by yeast cytoplasmic extracts is caused by guanyl nucleotides.

Micromolar concentrations of GDP or GTP stimulate protein synthesis by isolated yeast mitochondria 3- to 10-fold even if alpha-ketoglutarate and an ATP-regenerating system are present. No stimulation is observed with GMP, UTP, CTP, TTP, and the nonhydrolyzable GTP analogues guanyl(beta, gamma-methylene) diphosphate and guanyl imidodiphosphate. This stimulatory effect of exogenously added guanyl nucleotides may answer the long standing question why protein synthesis by isolated mitochondria is so slow. It can also explain previous reports by two other laboratories that a high speed supernatant from yeast cells stimulates protein synthesis by isolated mitochondria. The supernatant contains nondialyzable GMP which is converted to GDP under the conditions used for assaying mitochondrial protein synthesis. The stimulatory effect of high speed supernatants is abolished by 5'-nucleotidase (which degrades GMP) or by trypsin (which destroys supernatant protein(s) necessary for converting GMP to GDP). No evidence was obtained that the stimulatory effect of high speed supernatants was caused by precursors to cytoplasmically made cytochrome c oxidase subunits.

5'-Nucleotidase↗
PubMed1980

A spatio-temporal filter approach to synchronous brain activities.

This paper presents a mathematical mechanism for neuronal synchronization in oscillatory brain activities on the basis of the layer structures with recurrent inhibition. To begin with, a linear theory reveals that the recurrent inhibition tends to cause a synchronous uniform oscillation if the loop delay increases, and that an oscillating neuron recruits neighboring neurons by delivering synchronous inputs through the recurrent inhibition loop if the frequency is that of the selfexcitatory oscillation. Then, a quasilinearized dual wave model (DWM), employing the two-sinusoids plus bias input describing functions (TSBDF), shows the competitive relationship between the synchronous oscillation and a spatial wave that is introduced to represent normal brain activity patterns. Results of computer simulations conform well to the predictions of the DWM. Thus, synchronous brain activities are suggested to be the result of the spatio-temporal filter characteristics of the brain layer structures, modified by the neural nonlinearity.

Brain↗
PubMed1979

Unique requirements for template primers of DNA polymerase beta from rat ascites hepatoma AH130 cells.

The optimal condition for the rat DNA polymerase beta activity with (rA)n . (dT)12-18 as a template-primer was determined. The activity was remarkably affected by the concentration of the primer, (dT)12-18' and the mixing ratio of (dT)12-18 to (rA)n. DNA polymerase beta requires higher primer concentration (Km = 11.1 microM with respect to 3'-OH of the primer) than DNA polymerase gamma (Km = 0.04 microM) or oncornaviral DNA polymerase (Km = 0.08 microM) and the enzyme represented the maximum activity in the base ratio of 2:1 with (dT)12-18 and (rA)n suggesting the difference in reaction mechanisms of these enzymes. Under the optimized conditions, the specific activity of the near homogeneous preparation of DNA polymerase beta was 1,000,000 units per mg protein.

Animals↗
PubMed1979

Inhibitory effects of 9-beta-D-arabinofuranosylguanine 5'-triphosphate and 9-beta-D-arabinofuranosyladenine 5'-triphosphate on DNA polymerases from murine cells and oncornavirus.

The effects of the newly synthesized compound 9-beta-D-arabinofuranosylguanine 5'-triphosphate (ara-GTP) on the activity of DNA polymerases from mouse cells and oncornavirus were compared with those of 9-beta-D-arabinofuranosyladenine 5'-triphosphate. Ara-GTP did not replace deoxyguanosine 5'- triphosphate as substrate for these DNA polymerases but inhibited the activities of DNA polymerase alpha, beta, and gamma and viral DNA polymerase. DNA polymerase alpha was more sensitive than DNA polymerases beta and gamma and viral DNA polymerase to inhibition by ara-GTP. The inhibitions by ara-GTP and 9-beta-D-arabinofuranosyladenine 5'-triphosphate were due to competition or partial competition 5'-triphosphate were due to competition or partial competition with deoxynucleoside triphosphate with the same base. The inhibition constant (Ki) and the mode of inhibition of nucleotide incorporation varied depending on the combination of inhibitor, substrate(s), and enzyme species.

Animals↗