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[en] Objective: To explore the spectra and mechanism of human HPRT gene mutation induced by ⁶⁰Co γ-rays and its relation with anti-tumor effect of radiation. Methods: Single cell clone culturing, two-way screening count, multiplex PCR amplification and electrophoresis technique were used. Results: (1) When doses were increasing, cell plating efficiency reduced and mutation frequency increased. (2) The most frequent spontaneous mutations were point mutation (92.3%) and gamma-ray-induced mutation, including mainly partial deletion and point mutation (61.7% and 38.3%, respectively). (3) There were deletion mutations in all 9 exons of HPRT gene and the most of gamma-ray-induced mutations were chain deletion with multiplex exons (97.9%). Conclusion: The spectra of spontaneous and gamma-ray-induced mutants were different. The bigger changes in genetic structure are related to the antitumor mechanism of radiation

[en] Objective: To explore a new method for developing the efficiency of human umbilical cord blood (UCB) cells engraftment, and further understand the growth characteristic of hematopoietic stem cells (HSC) in vivo. Methods: Sublethally irradiated severe combined immunodeficient (SCID) mice were transplanted i.v. with UCB cells which had been cryo-preserved at -80 degree C. The human cells in recipient mice were detected by flow cytometry and CFU-GM assay. Results: In contrast to the single transplantation, scheduled engraftment of similar numbers of UCB cells resulted in a proportionally obvious increase in the percentages of CD45⁺, CD34⁺ cells produced in SCID mouse bone marrow (BM). When the donor cells were reduced to 20 percent, an identical reconstitution of both hematopoietic and part of immunologic functions was achieved. Conclusion: Scheduled engraftment improves the repopulating ability of HSC, which would provide a novel way for clinical cord blood engraftment in adult objects

[en] Objective: To investigate the effects of tumor necrosis factor α(TNFα) on the bone marrow (BM) hematopoietic progenitor cells (HPCs) in irradiated mice and the radioprotection of TNFα on BM HPCs. Methods: TNFα was injected into the mice before irradiation. Peripheral WBC, BM mononuclear cells (MNCs), CFU-S, CFU-Mix and hematopoietic reconstitution ability were examined on lethally irradiated mice with or without TNFα pre-treatment. Surface marker and c-Kit⁺ of BM stem cells was analyzed with flow cytometry. Results: The mice with TNF α treatment were markedly higher than those without TNFα treatment in number of WBC, BM MNCs, CFU-S, and CFU-Mix in vitro and in the percentage of BM c-Kit⁺ cells. The life span of the former was longer than that of the latter. In hematopoietic reconstitution, the above criteria of the recipient mice given the BM cells derived from donor mice of pre-irradiation TNFα treatment were remarkable superior to those given the donor without TNFα treatment. Conclusion: Pre-irradiation treatment has obviously radioprotective effect on the BM HPCs. The experiment provides a novel approach to lessening BM hematopoietic arrest caused by chemotherapy and radiotherapy in tumor patients, and is of great significance in clinical application

[en] Objective: To study the relation between changes in expression of endothelial nitric oxide synthase (eNOS) in brain vascular endothelial cells and acute radiation-induced cerebral edema after ⁶⁰Co gamma knife irradiation with a high dose. Methods: The right caudate nucleus of rats were irradiated with 200 Gy ⁶⁰Co gamma knife. the rats were sacrificed within 14 days after irradiation. By a light microscopy, electron microscopy, immunohistochemistry and in situ hybridization, the authors studied the formation and development of acute radiation-induced cerebral edema as well as the expression of eNOS in brain vascular endothelial cells. Results: Acute radiation-induced cerebral edema was observed morphologically 2 hours after irradiation and peaked on day 3 after irradiation. The expression of eNOS in brain vascular endothelial cells markedly increased 2 hours after irradiation, which could be consistently visualized during the acute developmental phase of radiation-induced cerebral edema. Conclusion: The increased expression of eNOS may be related to the formation and development of acute radiation-induced cerebral edema after ⁶⁰Co gamma knife irradiation with a high dose

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[en] Regular monitoring of solar erythemal ultraviolet (UV) irradiance at Toravere (Estonia) was performed in two years with notably different weather conditions in summer (herein the months May-August). Erythemal UV characteristics were compared and their dependence on meteorological conditions was studied. The erythema] doses over the first half of the summer were similar for both years, but over the second half the dose for 1999 was 28% higher. The strongest affecting factor in both summers was low cloudiness. Its partial correlation with the daily UV doses in the extremely cloudy summer of 1998 (-0.70) was not much higher than in the fine weather summer of 1999 (-0.65) when the noon solar elevation contributed two times more than in cloudy 1998 (about 0.6 and 0.3). The contribution of total ozone was close to zero in 1998 and quite weak (-0.44) in 1999. The daily distributions of erythemal UV index values in case of moderate partial cloudiness often give higher values than in clear sky conditions and the daily doses are higher. (author)