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Biomedical subjects

K Takakura

Publications and source records attributed to K Takakura.

At least 487 records · Page 27Linked to original sources
PubMed1976

Radiation effects of poly(L-glutamic acid) and poly(L-lysine) in the helix-coil transitional state.

The degradation of poly(L-glutamic acid) and poly(L-lysine) by X-rays and ultraviolet radiation has been studied at various pH values, including the helix-coil transition region. It was found that X-rays cause maximum degradation in the transition region for both polypeptides, indicating that the efficiency of degradation is affected not only by the secondary structure but also by some other factors related to the transition. On the contrary, the degradation by monochromatic ultraviolet 2537 A radiation showed a strong dependence on helix content of PLGA, suggesting that degradation occurs more effectively in the helical form than in the coil form. Theoretical calculations were made to approximate the pH dependence of degradation, assuming different cross sections for the peptide bonds in helix, coil, and junctions between helical and coil regions.

Molecular Conformation↗
PubMed1976

New approach to brain tumour chemoradiotherapy with cellular synchronization by colcemid.

Cellular synchronization using Colcemid as pretreatment for combined chemoradiotherapy was investigated. C6 rat brain tumour was cultured in RPMI medium containing 10(-5)-10(-7) Mol. of Colcemid for 24 hours. The basic cell kinetics were analysed with a Pulse Cytophotometer, which facilitated the analysis of tumour cell cycle phase distribution according to the DNA content. The effect of Colcemid depended on the concentration, and the minimal concentration showing continuous blocking during 48 hours after removal of the drug was 10(-6) Mol. G1 fraction of 2 C DNA content was reduced from 74% to 36%. G2-M phase of 4 C DNA content increased from 9% to 28%. S phase cells increased from 17% to 31%. Polyploid cells in the Tetraploid cell cycle could be recognized. The remaining 36% of cells within the GO + G1 peak of 2 C DNA content were considered to be diploid GO cells.

Brain Neoplasms↗
PubMed1975

Adjuvant immunotherapy for malignant brain tumors in infants and children.

Immune deficiency of immunocompetent cells or of humoral factors are essential causes of tumor growth. The authors have investigated the transfer of immunocompetent cells - allogeneic bone marrow cell transfusion and white blood cell intracranial infusion - for the treatment of 11 malignant gliomas in infants and children as an adjuvant to surgery, radiation and/or chemotherapy. Ten cases, from 3 months to 11 years, received bone marrow cell transfusion. Two medulloblastomas and 3 pontine gliomas are dead. Five cases are alive and well 37-65 months following surgery. Among these two posterior fossa neoplasms, a medulloblastoma and a glioblastoma have survived 46 and 65 months, respectively. One cerebral glioblastoma received allogeneic white blood cells infused locally into the tumor bed: it recurred 1 year following surgery, chemotherapy, and immunotherapy. Cytolysis of the tumor cells by sensitized lymphoid cells were demonstrated in this case. The role of immunotherapy should be limited at the present time to adjuvant therapy until its effect on tumor growth is statistically confirmed. The results so far are promising, and improvement of the immunological approach in treating malignant brain tumors is under way.

Bone Marrow Cells↗