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Biomedical subjects

T Yamaya

Publications and source records attributed to T Yamaya.

42 records · Page 3Linked to original sources

Resistance to acetohydroxamate acquired by slow adaptive increases in urease in cultured tobacco cells.

Urease activity of tobacco XD cells (1U cells) had undergone a 4-fold increase (4U cells) during a year of growth on urea (Skokut and Filner 1980 Plant Phvsiol 65: 995-1003). A clone of 4U cells gave rise to 12U cells during another year of growth on urea. The doubling time of 12U cells on urea is 2.2 days, compared to about 4 days for 1U cells, while 1U and 12U cells double in 2 days on nitrate. Acetohydroxamic acid (AHA), a specific inhibitor/reversible inactivator of jack bean urease, affects tobacco cell urease similarly. Fifty per cent inhibition of growth by AHA occurred at 20 micromolar in 1U cells growing on urea and at 165 micromolar in 12U cells growing on urea, but at 600 micromolar for either 1U or 12U cells growing on nitrate. When 12U cells were grown on urea with 100 micromolar AHA, extractable urease activity decreased 80% within 2.5 hours and remained at this level for 2 weeks; the doubling time increased to 3.7 days, and intracellular urea rose 2-fold, compared to 12U cells grown on urea without AHA. Urease of 12U cells inactivated by AHA in vivo could be reactivated to its pre-AHA level by incubation at 30 C after extraction and separation from free AHA. AHA inhibited incorporation of (15)N from [(15)N]urea into Kjeldahl nitrogen in the cells, in spite of the increased intracellular urea. These results indicate that AHA acts primarily by inhibiting urease action, rather than by inhibition of formation of urease protein or of uptake of urea. Because 12U cells are 8 times more tolerant of AHA than 1U cells, it is likely that growth on urea in the presence of AHA should select strongly for cells with high urease.

Journal Article↗

Changes in lymphocytes as an early sign of relapse in adult acute leukemia.

This study was undertaken to find out some clue to detect early relapse of adult acute leukemia which had been in remission. Laboratory data such as LDH, erythrocyte sedimentation, or immunoglobulin level did not show any difference at the time of relapse from the remission period. Complete blood count with reticulocyte count was evaluated every two weeks retrospectively for 12 weeks before relapse. No significant change was observed at the time of relapse. However, both the percentage and absolute number of peripheral lymphocytes significantly increased, whereas percentages of both T and B cells markedly decreased at the time of relapse, suggesting some derangement of lymphocyte function. Results in bone marrow culture did not yield any remarkable difference. It was suggested from this study that it is the time of prerelapse of adult acute leukemia when lymphocytes show an increase in either percentage or absolute number in the patients who are followed under their maintenance therapy schedule.

Adolescent↗

Characteristics of Nitrate Reductase-inactivating Proteins Obtained from Corn Roots and Rice Cell Cultures.

Nitrate reductase (NR)-inactivating proteins from corn roots (Wf-9 x 38-11) and rice cell suspension cultures were tested against a partially purified NR obtained from corn leaves (W64A x W182E). The corn protein was purified 921-fold and the rice protein, 1,660-fold using standard purification procedures. Approximate molecular weight values were 75,000 for the corn protein, and 150,000 for the rice protein as determined by Sephadex G-100 gel filtration. The Sephadex-treated proteins were characterized by electrophoresis on polyacrylamide gels. With a running pH of 9.4 the corn protein remained at the origin whereas the rice protein migrated with an R(F) value of 0.49. With a running pH of 4.0 the corn protein migrated with an R(F) value of 0.25. With the corn protein the activities of NR inactivation and hydrolysis of azocasein were detected in the same protein band. The rice protein, however, had no associated protease activity. From sodium dodecyl sulfate gel electrophoresis, there was one major protein band with an estimated molecular weight of 66,000 in corn protein. In rice protein four bands were observed with estimated molecular weights of 73,000, 66,000, 62,500, and 58,500, respectively.Both inactivators had an inhibitory effect on NADH-NR and NO(3) (-) induced NADH-cytochrome c reductase activities but they had less influence on the activities of FMNH(2)-NR and reduced methylviologen-NR. Inactivation of rice cell NR by rice inactivator was reversed by addition of NADH. Inactivation of corn leaf NR by rice inactivator was inhibited by the simultaneous addition of NADH, but rice inactivator-inactivated corn leaf NR could not be reactivated by NADH.

Journal Article↗

Action of Corn and Rice-inactivating Proteins on a Purified Nitrate Reductase from Chlorella vulgaris.

When nitrate reductase (NR) purified from Chlorella was incubated with NR-inactivating proteins purified from corn roots and rice cell suspension cultures or with trypsin there was a loss in NADH-NR and NADH cytochrome c reductase (NADH-CR) activities with time whereas the reduced methylviologen NR (MV-NR) remained active. When NADH-NR and NADH-CR activities were inactivated completely by the incubation with corn protein, the major protein band obtained by polyacrylamide gel electrophoresis shifted from an R(F) value of 0.12 to an R(F) of 0.25 and reduced MV-NR activity moved to the new position on the gel. When NADH-NR and NADH-CR activities were partially inactivated by the corn protein, NADH-NR activity was detected in an intermediate position (R(F) value of 0.18). Incubation with trypsin also caused a change in the NR protein migration pattern (R(F) value of 0.20). This protein band also had reduced MV-NR activity. Thus, the corn inactivator degrades NR in a fashion similar to but not identical with trypsin. The incubation of NR with rice inactivating protein resulted in a loss of NADH-NR but had no effect on the migration of NR protein or on the reduced MV-NR activity or mobility suggesting that the rice protein binds to Chlorella NR.

Journal Article↗

Activation of nitrate reductase by extracts from corn scutella.

NADH-nitrate reductase (NR) from the primary leaves and root tips of corn seedlings (var. W64A x W182E) were activated by extracts from corn scutella. The activator extracted in potassium phosphate buffer (pH 7.5) or 80% (v/v) ethanol and fractionated by Dowex 1 (acetate) and Dowex 50 (H(+)) resins was recovered in the cationic fraction. The activator was not detected in extracts from shoots, roots, or endosperm of the seedlings. It activated the nitrate-induced cytochrome c reductase of NR complex but had slight inhibitory effects on the activities of FMNH(2)-NR and reduced methylviologen-NR. In addition the activator inhibited the activities of purified NR-inactivating proteins from corn roots (var. Wf9 x 38-11) and rice cell cultures.

Journal Article↗