牛脾转移因子的提取工艺研究

目的：比较从牛脾中提取活性ＴＦ的不同方法。方法：分别利用Ｌａｗｒｅｎｃｅ－－透析法、Ｌａｗｒｅｎｃｅ－超滤法、超离心－超滤法提取,再以蛋白反应、红外及紫外扫描予以鉴定比较。结果：Ｌａｗｒｅｎｃｅ－超滤法和超离心－超滤法效果较好。结论：工业化生产中应采用Ｌａｗｒｅｎｃｅ－超滤法。     

The distribution of Iberian gypsophilous flora as a criterion for conservation policy

Within the EU territory, gypsum habitats with a peculiar flora are exclusively restricted to the eastern half of the Iberian Peninsula. The Habitats Directive considers the scrublands belonging to the Gypsophiletalia order as priority habitats (habitats 1,520). Although these scrublands do not represent the only kind of vegetation associated with gypsum outcrops, they tend to occur together with other types of communities that grow exclusively on this substrate. As far as vascular flora is concerned, there are some species that grow exclusively on Iberian gypsums and are accordingly included in the Spanish Red List. Besides, given the fragmentary character and punctuated location of these outcrops, the protection of this Iberian habitat and its flora is, therefore, an enormous challenge for any preservation policy. The disjunct distribution of the flora faithfully reflects this geological feature of gypsum areas. Consequently, a proper and detailed knowledge of the distribution of the gypsophilous vascular flora can be very useful in formulating an efficient preservation policy for these habitats. Using the checklist of the Iberian gypsophilous flora, we collected a wide data base with records of distribution arranged into 10 × 10 km UTM grids. For each of the 1,241 grids where at least one gypsophyte was recorded we reckoned a series of parameters in order to determine the priority level of the flora for preservation purposes. These parameters were specific richness, gypsophily level, continuous and discontinuous rarity and endangered level. Our analyses reveal serious gaps in the Spanish network of protected sites with gypsophilous flora, the most important being located in the Hoya de Baza.     

Plasmids in avirulent strains of Agrobacterium.

Twelve strains of Agrobacterium radiobacter isolated from naturally occurring crown galls or soil were found to be avirulent on sunflower, tomato, Kalanchoe, and carrot. Eleven strains contained plasmids of molecular weights 77 X 10(6) to 182 X 10(6) as determined by electron microscopy. One strain contained only a smaller plasmid (50 X 10(6) daltons). Several strains had both large and small (ca. 11 X 10(6) daltons) plasmids; one strain contained two large plasmids (112 X 10(6) and 136 X 10(6) daltons). Hybridization reactions of virulence plasmids from Agrobacterium tumefaciens strains C58 and A6 with plasmids from each of the A. radiobacter strains revealed that some A. radiobacter plasmids had less than 10% homology to either the C58 or A6 plasmids. Plasmids from some strains had approximately 50% homology with the C58 plasmid, but only one A. radiobacter plasmid contained more than 10% homology to the A6 plasmid. The presence of large plasmids in A. radiobacter strains did not correlate with sensitivity to agrocin 84; however, the utilization of the amino acid derivatives octopine and nopaline was generally correlated to partial base sequence homology to the C58 plasmid. We conclude that all large plasmids found in Agrobacterium strains are not virulence associated, although they may share base sequence homology with a virulence-associated plasmid. Further, plasmids from tumorigenic strains may be more closely related by base sequence homology to plasmids from nonpathogenic strains than to plasmids from other pathogenic strains.     

Dolomite flora of the Baetic Ranges glades (South Spain)

The vegetation growing on special types of rocks has long attracted the attention of botanists and ecologists. In this respect, interest in serpentine soils has led to the publication of a number of monographs on their flora and vegetation. The high levels of heavy metals, in particular of Ni, and the low proportion of Ca/Mg are generally held responsible for the severe restrictions limiting flora development on this kind of rocks. Although researchers have also studied other types of unusual bedrocks such as gypsum outcrops, little work has been done on dolomites. This is surprising because dolomites share certain features with serpentines (they are both rocks rich in Mg). This paper deals with the flora peculiar to the dolomites of the Baetic Ranges, one of the richest territories in Europe as far as flora is concerned. A number of botanists with experience in the study of this very particular flora have joined together to make a list of the plants peculiar to the dolomites. Our catalogue includes 144 species with a variable degree of “dolomitophily”, the score of which ranging from 1 to 3, the maximal value. A comparison of the taxonomical spectrum of this catalogue with the one found in territories where dolomites are dominant or with other areas of serpentines reveals that there is a given deviation or bias in favour of some families. A similar comparison between biotypes also leads to the observation that, as usually happens on ultramafic rocks, hemicryptophytes tend to be dominant on dolomites. In addition, we show that the proportion of Ca/Mg catalogued for different kinds of soils could be a key element in explaining the restrictions which dolomites and serpentines impose on plants. In dolomites this proportion shows an intermediate position (2.19) between soils derived from limestones (11.30) and serpentines (0.84) in the study area.     

Promotion of DNA renaturation by a non-DNA factor in crown call tumor DNA preparation.

A 5400-fold excess of tobacco crown gall tumor DNA increased the renaturation rate of $\text{Agrobacterium tumefaciens}$ DNA, whereas, the same excess of healthy plant DNA had no effect on the rate or kinetics of renaturation. Since deoxyribonuclease treatment of the tumor DNA did not remove its ability to accelerate renaturation, the tumor tissue contains a non-DNA factor that increases the rate of renaturation of $\text{A. tumefaciens}$ DNA.     

Stable incorporation of plasmid DNA into higher plant cells: the molecular basis of crown gall tumorigenesis

Evidence is presented that crown gall tumors are caused by the incorporation of part of a virulence plasmid carried by the inciting bacterium, Agrobacterium tumefaciens. The rate of reassociation of labeled plasmid DNA was slightly accelerated in the presence of tobacco crown gall tumor DNA, but not normal tobacco DNA. Treatment of tumor DNA with DNAase abolished the acceleration. To determine whether all plasmid sequences are represented in tumor DNA, the labeled plasmid DNA was separated into specific fragments after digestion with restriction endonuclease Sma I. Renaturation rates for DNA from bands 1, 2, 7, 8, 9, 12 and 14 were not affected by tumor DNA. DNA from band 3 showed a slight rate increase in the presence of tumor DNA, indicating 21–27 copies of 14–18% of the DNA sequences in this (doublet) band. The band 3 doublet was separated by electrophoresis into bands 3a and 3b. Tumor DNA had little effect on the rate of reassociation of labeled band 3a DNA. Band 3b DNA renatured rapidly in the presence of tumor DNA, and its rate increase indicated that approximately 18 copies of 40% of band 3b DNA sequences are present per diploid tumor cell. This amounts to 3.7 × 10⁶ daltons of foreign genetic information and represents a contribution of 0.0011% to the DNA content of the tumor cell. The relationship between this plant tumor and virally induced animal tumor systems is discussed.