Parathyroid hormone production in vitro by human parathyroid cells transformed by Simian virus 40

Cells froma human parathyroid adenoma were infected with simian virus 40 and maintained through 13 subcultures in monolayer tissue culture. For more than 9 months, these "transformed" cells contimed to produce parathyroid hormone which was identified by radioimmunoassay and density-gradient ultra centrifugation.     

Viral RNA subunits in cells transformed by RNA tumor viruses

Single-stranded 35S and 20S viral RNA species are synthesized in virus-producing mouse and rat cells transformed by the murine sarcoma virus. A transformed hamster cell line that does not produce virus synthesizes 35S, but not 20S viral RNA.     

Antigenic material: persistence in hypersensitive cells

Radioactivity derived from injections of tritiated tetanus toxin was observed in lymphocytes and macrophages for as long as 9 months after injection into immunized mice. These labeled cells became highly vacuolated and attracted eosinophils and lymphocytes when the animals were reinjected with specific antigen.     

Tumor DNA structure in plant cells transformed by A. tumefaciens

Crown gall tumors are induced in plants by infection with the soil bacterium Agrobacterium tumefaciens. Because the tumor induction involves transfer of a portion of the tumor-inducing (Ti) plasmid DNA from the bacterium to the plant cells, this system is of interest for the study of genetic exchange as well as tumor induction. The boundaries of the transferred DNA (T-DNA) have been cloned from transformed plant cells of tobacco. Detailed mapping with restriction enzymes and nucleotide sequence analysis of two independent clones were used to study the molecular structure of the ends of the T-DNA. One clone contains the two ends of the T-DNA joined together; the other contains one end of the T-DNA joined to repetitive plant DNA sequences. These studies provide direct evidence that the T-DNA can be integrated into the plant genome. In addition, the data suggest that in the plant, T-DNA can be tandemly repeated. Sequence analysis of the junction of crown gall clone 1 reveals several direct repeats as well as an inverted repeat; these structures may be involved in the transfer of the DNA from Agrobacterium to plant cells.     

Observed ozone response to variations in solar ultraviolet radiation

During the winter of 1979, the solar ultraviolet irradiance varied with a period of 13.5 days and an amplitude of 1 percent. The zonal mean ozone values in the tropics varied with the solar irradiance, with an amplitude of 0.25 to 0.60 percent. This observation agrees with earlier calculations, although the response may be overestimated. These results imply changes in ozone at an altitude of 48 kilometers of up to 12 percent over an 11-year solar cycle. Interpretation of ozone changes in the upper stratosphere will require measurements of solar ultraviolet radiation at wavelengths near 200 nanometers.     

In vitro and in vivo consequences of VLA-2 expression on rhabdomyosarcoma cells

Cloned integrin alpha 2 subunit complementary DNA was expressed on human rhabdomyosarcoma (RD) cells to give a functional VLA-2 (alpha 2 beta 1) adhesion receptor. The VLA-2-positive RDA2 cells not only showed increased adhesion to collagen and laminin in vitro, but also formed substantially more metastatic tumor colonies in nude mice after either intravenous or subcutaneous injection. These results show that a specific adhesion receptor (VLA-2) can markedly enhance both experimental and spontaneous metastasis. In contrast to the metastasis results, there was no difference in either the in vitro growth rate or apparent in vivo tumorigenicity of RD and RDA2 cells.     

Lymphoma growth in vivo: electronic discrimination between tumor and stroma cells

Moloney lymphoma cells are larger than normal cells of mouse spleen, lymph-node, and thymus. Use of electronic cell-size anaylsis in conjunction with specific immunocytolysis permits difjerential counting of host and tumor cells. Increase of lymphoma cells occurs first in spleen and then in lymph nodes; in thymus it occurs only during the terminal stages of tumor growth.     

拟南芥花粉体外和体内2种萌发差异的比较研究

[目的]比较拟南芥花粉体外和体内2种萌发的差异。[方法]以模式植物拟南芥作为研究对象,采用荧光显微镜观察比较2种体外萌发培养基的萌发率差异并比较体外萌发率和体内萌发率的差异。[结果]花粉在固体培养基上的萌发率平均为51.01%,而在液体培养基上萌发率平均为83.97%;在体外,液体萌发培养基优于固体萌发培养基,液体培养基萌发率较固体培养基萌发率高,稳定;体内萌发较体外萌发稳定,萌发率高,平均萌发率为94.00%。[结论]研究结果为检测花粉活力提供了一个有效的检测标准,为拟南芥花粉的生物学研究提供理论与方法。     

Lymphokine production by cultured human T cells transformed by human T-cell leukemia-lymphoma virus-I

Cell-free conditioned media from human T cells transformed by human T-cell leukemia-lymphoma virus (HTLV-I) were tested for the production of soluble biologically active factors, including several known lymphokines. The cell lines used were established from patients with T-cell leukemia-lymphoma and from human umbilical cord blood and bone marrow leukocytes transformed by HTLV-I in vitro. All of the cell lines liberated constitutively one or more of the 12 biological activities assayed. These included macrophage migration inhibitory factor (MIF), leukocyte migration inhibitory factor (LIF), leukocyte migration enhancing factor (MEF), macrophage activating factor (MAF), differentiation inducing factor (DIF), colony stimulating factor (CSF), eosinophil growth and maturation activity (eos. GMA), fibroblast activating factor (FAF), gamma-interferon and, in rare instances, T-cell growth factor (TCGF). Some cell lines produced interleukin 3 (IL-3), platelet-derived growth factor (PDGF), or B-cell growth factors (BCGF). Such cells should prove useful for the production of lymphokines and as sources of specific messenger RNA's for their genetic cloning.     

高毒力杀蝗绿僵菌的紫外线诱变选育

以金龟子绿僵菌M105复壮菌株M1053为出发菌株,通过紫外线诱变选育,获得Pr1酶活是出发菌株1.36倍的诱变株M105-52。经测定,诱变株的遗传性能稳定,紫外线抗性和杀蝗毒力均有显著提高。     

Antigenic changes in lymph-node cells after administration of antiserum to thymus cells

Mice of the RIII and C57BL strains were treated with rabbit antiserum to thymus (ATS), and cells of their lymph nodes were analyzed serologi-cally at intervals after treatment. While lymph-node cells of untreated mice were sensitive to the cytotoxic effect of isoantibodies against the theta antigen, lymph-node cells of ATS-treated mice showed a significantly reduced sensitivity. Three days after ATS treatment lymph-node cells of most mice were completely refractory to the cytotoxic effect of theta antibodies. Administration of normal rabbit serum elicited only a slight reduction of the sensitivity of lymph-node cells to the cytotoxic effect of theta antibodies. The results support the hypothesis that ATS treatment selectively affects a population of thymus-dependent circulating lymphocytes.     

A similarity between viral defense and gene silencing in plants

Gene silencing in plants, in which an endogenous gene is suppressed by introduction of a related transgene, has been used for crop improvement. Observations that viruses are potentially both initiators and targets of gene silencing suggested that this phenomenon may be related to natural defense against viruses. Supporting this idea, it was found that nepovirus infection of nontransgenic plants induces a resistance mechanism that is similar to transgene-induced gene silencing.     

Site-specific integration of H-ras in transformed rat embryo cells

A karyotypic analysis was performed on seven independently derived clones of primary rat embryo cells transformed by the ras oncogene plus the cooperating oncogene myc. The transfected oncogenes were sometimes present in amplified copy number, with heterogeneity in the levels of amplification. Some chromosomal features, such as aberrantly banding regions and double-minute chromosomes, typical of cells carrying amplified genes, were also seen in three of the seven cell lines. Underlying this heterogeneity there was an unexpected finding. All seven lines showed a common integration site for ras on the q arm of rat chromosome 3 (3q12), though some lines also had other sites of integration. In four of the lines integration of ras was accompanied by deletion of the p arm of chromosome 3 or its possible translocation to chromosome 12.     

Contraction of granulation tissue in vitro: similarity to smooth muscle

Strips of granulation tissue from three different experimental models contract in vitro when treated with substances that induce contraction of smooth muscle. Because the fibroblasts in such tissues have some ultrastructural features typical of smooth muscle, our findings indicate that fibroblasts are able to modulate toward a cell type that is morphologically and functionally close to smooth muscle.     

英汉文化差异与英语教学

生活环境、民族价值观、民族性格和民族生活习俗是英汉文化的主要差异。弄清这些差异,对英语学习大有裨益。     

气调包装结合紫外线预处理保鲜施氏鲟鱼片

为延长施氏鲟鱼片的保鲜期,以未经过紫外线照射预处理的鲟鱼片进行气调包装(MAP)保鲜作为对照组,研究鲟鱼片经紫外线预处理5、10和15 min后进行MAP的保鲜效果.结果表明,鲟鱼片经紫外线处理10 min可以杀灭其表面98%的原始细菌,再用50%CO2+10%O2+40%N2进行MAP,在1℃、(92±3)%相对湿度下贮藏,可抑制pH和总挥发性盐基氮(TVB-N)含量的增加,鲟鱼片的贮藏期达到28 d,与对照组相比延长了4-6 d,但贮藏后期紫外线处理组鲟鱼片的感官品质略有降低.     

Inhibition of interferon-gamma may suppress allograft reactivity by T lymphocytes in vitro and in vivo

The addition to mixed-leukocyte reactions of monoclonal antibodies to interferon-gamma abrogated alloantigen recognition and induction of cytotoxic T lymphocytes by inducing early and highly effective suppressor T lymphocytes. This inhibitory activity was not confined to in vitro models, since daily injection of the antibodies into CBA/J mice blocked the usual rejection of allogenic tumor cells.