Suppression of the initiation of DNA synthesis as an index of cellular radiosensitivity

A gamma-radiation dose (Di) suppressing DNA synthesis initiation by 35% in primary suspension cultures of mammalian cells, is nearly the same as D0 for survival of clonogenic cells of the same lines and tissues. The extent of DNA synthesis suppression is assessed by impulse 3H-thymidine incorporation in the acid-insoluble fraction of irradiated cells. The values of Di determined in this way for HeLa cells, Ehrlich ascites tumor cells, mouse bone marrow and thymus cells are 2.0, 1.5, 1.5, and 1.0 Gy, respectively; as determined by clonogenic capacity of these cells, Di = 1.9, 2.0, 1.3, and 1.0 Gy, respectively.     

The effect of irradiation on the growth of human laryngeal tumors transplanted under the kidney capsule of immunocompetent mice

A study was made of the influence of gamma-radiation on the growth of human larynx squamous cell carcinoma transplanted under the capsule of the kidney of immunocompetent mice. The transplants were shown to increase in size 6 days after transplantation. Irradiation of animals 24 h after transplantation inhibited considerably the tumor growth. However, the preirradiation (24 h before operation) inhibited the growth of nonirradiated transplants to the same extent as the exposure of mice with the transplanted tumor fragments did: the radiation dose that induced 50% inhibition of the growth was 4.5 Gy and 5.3 Gy, respectively. Preliminary data indicate that tumor fragment of patients with the unfavourable prognosis increase in size and respond to radiation to a lesser extent.     

DNA replication in mammalian cells after the action of physical, chemical or biological factors. VI. The recovery of DNA synthesis in a culture of irradiated cells

The kinetics of DNA synthesis restoration in cultured HeLa cells and in L-929 mouse fibroblasts irradiated by gamma-rays of 60Co with a dose of 10 Gy was studied. Early after irradiation the rate of DNA synthesis in HeLa cells measured with 3H-thymidine incorporation was seen to decrease. Two hours later the incorporation starts to increase to reach the control level 4 hours after irradiation and then becomes even higher than this level. The distribution of cells among phases of the cell cycle measured with flow cytometry undergoes changes. 4-6 hours after irradiation part of S-phase cells increased contributing presumably to the elevating of 3H-thymidine incorporation observed at this time. The restoration of the incorporation was suppressed by inhibitors of protein and RNA synthesis--cycloheximide and actinomycin D. It is suggested that the processes of restoration of DNA synthesis in irradiated cells can be of inducible nature. In irradiated HeLa and L-929 cells the restoration of DNA synthesis is resistant to novobiocin, an inhibitor of DNA replication.     

5-fluorodeoxyuridine induces radioresistant synthesis of DNA and sensitizes HeLa cells to gamma radiation

It was shown that preincubation of HeLa cells with 5-fluorodeoxyuridine (10(-6) M) induced DNA synthesis resistant to gamma-radiation (6 Gy). At the same time, the death rate of exposed cells increased and nucleoid relaxation decreased. The role of DNA synthesis inhibitors in the reproductive death of exposed cells is discussed.     

Mechanism of the cytotoxic action of formaldehyde on cultured mammalian cells

Induction and repair of DNA lesions cell inactivation and repair of potentially lethal damages (PLD) were studied after the treatment of cultured cells with formaldehyde. Formaldehyde induced the appearance of a rapidly sedimentating DNA--membrane complex. This complex may contain up to 50% of choline and no more than 3-5% of leucine or lysine incorporated in the acid insoluble cell fraction, Inhibition of DNA synthesis, induction of single strand DNA breaks and/or alkali-labile sites increased with the raise of formaldehyde concentration. A good correlation is observed between with the raise of formaldehyde concentration. A good correlation is observed between with the raise of formaldehyde concentration. A good correlation is observed between the increasing DNA quantities in the rapid sedimentation complex and the cell lethality.     

Latent autoantibodies to cardiolipin in the blood serum of healthy subjects

Pooled health blood donors' sera were fractionated by gel filtration and/or ion exchange chromatography on strong anion-exchanger. Measurement of anticardiolipin antibodies levels by ELISA method shows that gel filtration at pH 4.05 and 9.2 (complex-degradation conditions) leads to increase in summary levels while after elution at neutral pH such an effect did not appear. Light increasing of anticardiolipin levels was also noted after fractionation on QAE-Sephadex. Data obtained state that anticardiolipin autoantibodies amount in sera is greater than it can be detected by direct measurement in untreated serum samples. Existence of "hidden" anticardiolipin autoantibodies supposes the hypothesis about alternative way of humoral immunity regulation by blocking anti-self antigens activities with serum biopolymers.     

Pre-steady state kinetics of the ferroxidase reaction catalyzed by ceruloplasmin

Analysis of the presteady-state step of the ferroxidase reaction catalyzed by ceruloplasmin revealed that the kinetic curve for the reaction product accumulation versus time is characterized by an induction period, tau, whose value does not change within the pH range of 5.0-7.5. The value of tau decreases with a rise in the enzyme concentration and increases with a rise in the substrate concentration at constant Fe(II) and E0 concentrations. A reaction scheme is proposed which points to the existence of an induction period in the ceruloplasmin-catalyzed ferroxidase reaction. It was shown that the calculated values of tau = f([Fe(II)]0) and tau = f([E]0) obtained through the use of differential equations qualitatively coincide with the corresponding experimental values.     

17个建兰品种光合特性分析

以17个建兰(Cymbidium ensifolium)品种为材料,采用改良的丙酮法提取叶绿素,再通过Arnon丙酮法公式计算光合色素含量,利用捷克FluorCam开放式叶绿素荧光仪测定不同品种的叶绿素荧光参数。结果表明,17个建兰品种的光合色素和叶绿素荧光参数具有不同程度的差异,其中‘铁骨素’(C. ensifolium ‘Tiegusu’)、‘逸红双娇’(C. ensifolium ‘Yihongshuangjiao’)和‘闽南黄蝶’(C. ensifolium ‘Minnanhuangdie’)的光合色素含量高于其他品种,表明这3个品种具有良好的光合效率,吸收光能的能力较强;‘铁骨素’最大荧光产量(Fm)、Kautsky诱导效应最大荧光(Fp)、PS Ⅱ原初光能转化效率(Fv/Fm)和非光化荧光淬灭系数(NPQ)均为最高。综上可知,‘铁骨素’的光合生理特性优于其他品种,可作为优良建兰品种进行种植推广。     

小叶锦鸡儿天然居群叶形态性状变异研究

为揭示小叶锦鸡儿(Caragana microphylla)天然居群叶形态性状的变异规律及其生态适应性特征,该研究以10个小叶锦鸡儿天然居群为对象,通过多重比较、巢式方差分析、相关性分析、聚类分析和主成分分析等方法,对7个叶形态性状进行分析。结果表明：(1)小叶锦鸡儿叶形态性状在居群内和居群间均存在极显著差异(P < 0.01),平均变异系数为10.13%,不同性状的变异幅度为6.23%~12.78%;平均叶形态性状的表型分化系数为43.62%,居群内变异(30.09%)大于居群间变异(24.91%),说明居群内是其叶形态性状变异的主要来源。(2)相关性分析表明,环境因子对小叶锦鸡儿的叶形态性状变异有很大的影响,在地理空间上主要呈现出沿海拔梯度的变异模式;主成分分析的结果显示,小叶宽、叶柄宽和叶柄长对小叶锦鸡儿叶形态变异起主导作用;利用欧式距离对小叶锦鸡儿居群进行UPGMA聚类分析结果显示,基于叶形态性状和环境因子可分别将小叶锦鸡儿10个居群分为3类和2类,Mantel检验结果表明,小叶锦鸡儿的叶形态性状变异不存在地理连续性。研究结果为小叶锦鸡儿的适应性进化和开发利用提供了理论依据。