紫外线对4个Bt亚种活性的影响

用培养24h的苏云金杆菌,经稀释处理,显微计数,然后将定量的菌液涂布于平板上,用紫外线对4个Bt亚种(Bt-1.897,Bt-1.903,Bt-1.905,Bt-1.959)进行不同照射时间处理后,再于平板上培养24h,结果表明:Bt-1.897在紫外线处理15min仍然还有活性,Bt-1.903在紫外线处理12min基本上全部失活,Bt-1.905和Bt-1.959这2个菌株在紫外线处理12min时还有活性,但在处理15min后全部失活。说明不同种的苏云金杆菌对紫外线的抗性有一定差异。经紫外线处理后Bt-1.897、Bt-1.903、Bt-1.905、Bt-1.959各自有部分菌落发生明显的变异,菌落大小明显小于原始菌落,并且发生变异的菌落呈现出新的颜色,经涂片后在油镜下观察发现,其菌体要比原始菌体小,为明显的变异菌株。     

Herpes-type virus and chromosome marker in normal leukocytes after growth with irradiated Burkitt cells

Cultured cells derived from male patients with Burkitt's lymphoma and harboring herpes-type virus particles were lethally irradiated. These irradiated cells induced normal peripheral leukocytes of female infants to grow within 2 to 4 weeks after mixed cultivation. Cells of a line free of this agent failed to stimulate growth. If either type of cell was cultured separately, it did not survive under the experimental conditions. Herpes-type viral antigen and C-group chromosomal marker previously described in cultured Burkitt cells were found in all of the female cell cultures that were obtained.     

The RAD9 gene controls the cell cycle response to DNA damage in Saccharomyces cerevisiae

Cell division is arrested in many organisms in response to DNA damage. Examinations of the genetic basis for this response in the yeast Saccharomyces cerevisiae indicate that the RAD9 gene product is essential for arrest of cell division induced by DNA damage. Wild-type haploid cells irradiated with x-rays either arrest or delay cell division in the G2 phase of the cell cycle. Irradiated G1 and M phase haploid cells arrest irreversibly in G2 and die, whereas irradiated G2 phase haploid cells delay in G2 for a time proportional to the extent of damage before resuming cell division. In contrast, irradiated rad9 cells in any phase of the cycle do not delay cell division in G2, but continue to divide for several generations and die. However, efficient DNA repair can occur in irradiated rad9 cells if irradiated cells are blocked for several hours in G2 by treatment with a microtubule poison. The RAD9-dependent response detects potentially lethal DNA damage and causes arrest of cells in G2 until such damage is repaired.     

玉米幼芽提取物对小鼠皮肤UVA照射损伤的保护作用

研究了玉米幼芽提取物(extract of maize plumule,EMP)对长波紫外线(UVA)损伤的小鼠皮肤超微结构、抗氧化酶活性及脂质过氧化作用的影响。结果表明,UVA模型小鼠真皮细胞内出现空泡变性,线粒体肿胀、嵴减少,粗面内质网和核周间隙扩张;表皮细胞微绒毛减少,细胞固缩,细胞核染色质边集。EMP保护的小鼠皮肤细胞损伤程度明显减轻,结构基本正常。EMP可显著提高UVA辐射小鼠皮肤组织中的SOD活性(P<0.01)及CAT活性(P<0.05),降低MDA含量(P<0.05),与VC的抗氧化作用一致。表明EMP能够抵抗UVA对皮肤组织的氧化损伤。     

Purification and characterization of mouse hematopoietic stem cells

Mouse bone marrow hematopoietic stem cells were isolated with the use of a variety of phenotypic markers. These cells can proliferate and differentiate with approximately unit efficiency into myelomonocytic cells, B cells, or T cells. Thirty of these cells are sufficient to save 50 percent of lethally irradiated mice, and to reconstitute all blood cell types in the survivors.     

辐照保藏食品技术及其应用现状与发展前景

较详细地介绍了辐照技术在食品保藏上的应用和优点 ,以及电离辐射对食品营养成份和活细胞的影响 ,从不同角度说明了辐照食品的卫生安全性 ,肯定了经 1 0kGy以下剂量辐照的食品不会产生任何有害物质 ;并对辐照保藏食品技术的应用现状及发展前景进行了初步地探讨     

Selection of auxotrophic bacterial mutants by tritium-labeled thymidine

A method is proposed for the efficient isolation of auxotrophic mutants of cells of diverse origin by the use of radioactive materials. An example is described in which mutants of Escherichia coli B were selected by growing irradiated cells in the presence of tritium-labeled thymidine.     

Inhibition of lipolytic action of growth hormone and glucocorticoid by ultraviolet and x-radiation

Addition of catecholamines or growth hormone plus glucocorticoid activates lipolysis in isolated white-fat cells of the rat. If the fat cells were irradiated just before the addition of growth hormone and glucocorticoid, their lipolytic action was abolished. However, irradiation did not affect the activation of lipolysis by catecholamines.     

Bone marrow-derived lymphoid cells (B cells): functional depletion with cobra factor and fresh serum

Treatment of rat spleen cells with cobra factor and fresh rat serum provided a simple, rapid means of functionally eliminating complement receptor lymphocytes. Cells able to differentiate into plaque-forming cells in a syngeneic, irradiated host were diminished, but cells able to induce a graft-versus-host reaction were not diminished. There was no effect on plaque-forming cells from an immune spleen.     

Ultraviolet irradiation of DNA in vitro and in vivo produces a 3d thymine-derived product

A new thymine-derived product was separated from DNA irradiated with utlraviolet light in vitro and in vivo. This compound was mistaken to be thymine homodiner (T=T) by other workers because it is chromatographically indistinguishable from T=T in most eluents. It has absorbancy maximums at 312, 312, and 300 millimicrons in neutral, pH 2, and pH 11 aqueous solutions, respectively. When it is irradiated in aqueous solution with wavelengths of 360 and 313 millimicrons its spectrum reverts to one similar to that of thymine. Therefore, at least three thymine-derived products can be detected in ultraviolet irradiated DNA, namely the homodimer, a material with absorbancy maximum at 312 millimicrons, and a "minor" product suggested by others to be a dimer of cytosine and thymine. In cells, the latter two are formed in aboult equal amounts. While these three products were shown to exist in the acid hydrolyzates of ultraviolet irradiated DNA, a material with absorbancy maximum at about 310 millimicrons was demonstrated to form in ultraviolet irradiated DNA without further treatment. The magnitude of this spectral increase varied directly with the incrcase in the adenine-thymine contents in the DNA as shlown by differential transmittance spectra of the irradiated Micrococcus lysodeikticus, calf thymus, Bacillus cereus, and Hemophilus influenzae DNA.     

Germ cell chimerism: absence in parabiotic frogs

Embryos of the leopard frog deprived of primordial germ cells by treatment with ultraviolet light were joined in parabiosis with normal, unirradiated embryos. The irradiated member of the pair was not colonized by germ cells from its normal partner. Unlike the primordial germ cells of birds and mammals, the germ cells of frog embryos are not carried by the circulating blood.     

Protection against malaria by vaccination with sporozoite surface protein 2 plus CS protein.

The circumsporozoite (CS) protein has been the target for development of malaria sporozoite vaccines for a decade. However, immunization with subunit vaccines based on the CS protein has never given the complete protection found after immunization with irradiated sporozoites. BALB/c mice immunized with irradiated Plasmodium yoelii sporozoites produced antibodies and cytotoxic T cells against a 140-kilodalton protein, sporozoite surface protein 2 (SSP2). Mice immunized with P815 cells that had been transfected with either SSP2 or CS genes were partially protected, and those immunized with a mixture of SSP2 and CS transfectants were completely protected against malaria. These studies emphasize the importance of vaccine delivery systems in achieving protection and define a multi-antigen sporozoite vaccine.     

低剂量中子对庭院菊花(Chrysanthemum morifolium Ram.)生长的作用

通过实验，以庭院菊花的Ｓｐｒａｙ菊花品种作母系，对其进行低剂量核分裂中子照射，发现照射组与非照射组生根率有明显差异。基于实验结果，提出促进生长及抑制生长的原因都在于细胞的死亡，得出了低剂量核分裂中子对庭院菊花生长产生毒物兴奋效应的结论，并阐述了产生机理。     

Graft versus host inhibition: fetal liver and thymus cells to minimize secondary disease

Long-lived radiation chimeras were produced in mice diflering at the major histocompatibility locus. Survival occurred in lethally irradiated recipients inoculated with allogeneic fetal liver and allogeneic fetal thymus cells in combination. The survival rate was equal or superior to that of mice with transplanted syngeneic fetal, neonatal, or adult hematopoietic cells.     

Prevention of allogeneic bone marrow graft rejection by H-2 transgene in donor mice

Rejection of bone marrow grafts in irradiated mice is mediated by natural killer (NK) cells and is controlled by genes linked to the major histocompatibility complex (MHC). It has, however, not been possible to identify the genes or their products. An MHC class I (Dd) transgene introduced in C57BL donors prevented the rejection of their bone marrow by NK cells in irradiated allogeneic and F1 hybrid mice expressing the Dd gene. Conversely, H-2Dd transgenic C57BL recipients acquired the ability to reject bone marrow from C57BL donors but not from H-2Dd transgenic C57BL donors. These results provide formal evidence that NK cells are part of a system capable of rejecting cells because they lack normal genes of the host type, in contrast to T cells, which recognize cells that contain abnormal or novel sequences of non-host type.     

SOD对紫外辐射受损的苏云金芽孢杆菌作用的研究

探讨了超氧化物歧化酶 (SOD)等自由基清除剂对苏云金芽孢杆菌紫外辐射的影响。结果表明 ,SOD、绞股蓝皂甙等自由基清除剂能够明显地提高紫外辐射损伤细胞的存活率 ,并且SOD的保护作用表现为防护与恢复两种不同的作用。又通过细胞电泳与琼脂糖凝胶电泳发现紫外辐射后其细胞膜及质粒DNA均受到了明显的损伤 ;SOD对细胞膜损伤有一定的恢复作用 ,而对DNA不表现恢复效应。由此认为 :紫外线对细胞膜及DNA均有损伤 ,SOD恢复作用的主要部位在细胞膜而不是DNA分子。为进一步确定SOD的作用以及利用自由基清除剂制备高效的Bt农药提供了理论基础。     

Delayed hypersensitivity: bone marrow as the source of cells in delayed skin reactions

Adult Lewis rats were thymectomized, irradiated, and restored with bone marrow from allogeneic (or F(1)) donors. They were passively sensitized to tuberculin by a subsequent transfer of Lewis lymph node cells and were given intradermal skin tests with tuberculoprotein. In 24-hour skin reactions the majority of cells, in successive experiments, were shown to be allogeneic (or F(1)) with the use of isoantibody against the antigens of the transplanted marrow cells and by the indirect fluorescent antibody technique. Our results demonstrate that the non-specific cells making up a large proportion of the infiltrating elements in tuberculin skin reactions probably originate in the bone marrow.     

Focal antibody production by transferred spleen cells in irradiated mice

Lethally irradiated mice were injected with small numbers of normal spleen cells and then immunized with sheep erythrocytes. Antibody activity was found in their spleens in localized areas whose number corresponded to the number of spleen cells injected. When sheep and pig erythrocytes were injected together, antibody against each was found in separate areas. Each area may consist of the progeny of a single precursor cell, restricted to forming a single antibody.     

Low-level x-ray damage to amphibian erythrocytes

In vitro x-irradiation of frog and Amphiuma erythrocytes caused cytophysiological damage to part of the cell population. There was a significant decrease in the percentage of normal cells and some hemolysis. Changes were also observed in the electrical capacitance and potassium-42 uptake of irradiated erythrocytes.     

Repression of colony formation reversed by antiserum to mouse thymocytes

Marrow cells derived from C57BL/6 mice form many fewer splenic colonies in irradiated C57BL/6 x C3H F1 hybrid recipients than in irradiated C57BL/6 recipients (repression of colony formation). This effect is reversed by treatment of the hybrid recipients with active antiserum to mouse thymocytes. The repression phenomenon cannot readily be explained in immunological terms; hence the effect of the antilymphocyte serum on this phenomenon may not result from immunosuppression in the usual sense.