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31.
S Millar D C Hayward C A Read M J Browne R V Santelli F Garcia Vallejo M T Pueyo A Zaha D M Glover F J Lara 《Gene》1985,34(1):81-86
We have constructed a library of recombinant phage containing DNA from salivary gland chromosomes of Rhynchosciara americana. We have isolated phage from this library that carry sequences homologous to cDNA clones that hybridize in situ to the DNA puffs at the polytene chromosome regions C3 and C8. This has enabled us to demonstrate a 16-fold amplification of the genomic DNA sequences at these regions during DNA-puffing. At the C8 site there is a sequence element that has characteristics of 'scrambled' moderately repetitive DNA. This is located within 3 kb from the gene encoding a 1.95-kb mRNA. We have assayed restriction fragments from the two DNA puffs for Ars activity in yeast. The only strong Ars activity is associated with a part of the moderately repetitive DNA element from the C8 puff which is not present at this site in all animals. 相似文献
32.
33.
Abstract By using an extension to group N streptococci of a contransformation procedure we have introduced 4 different-sized cryptic plasmids for Streptococcus lactis into the plasmid-free S. lactis IL1403. A mixture of 4 cryptic plasmids with an indicator plasmid (pHV1301) conferring erythromycin resistance was used for IL1403 protoplast transformation. Under such conditions, 41.5% of the erythromycin-resistant transformants were contransformed with one of the cryptic plasmids in addition to pHV1301. Indicator plasmid pHV1301 was later spontaneously segregated from doubly transformed cells. This protocol should be very useful for constructing lactic streptococcal strains bearing any phenotypically cryptic plasmid. 相似文献
34.
The isolation and restriction mapping of a miniplasmid from the Actinomycete Nocardia corallina 总被引:1,自引:0,他引:1
Abstract A variety of plasmids has been identified as covalently closed circular and linear DNA in certain Actinomycetes, such as Streptomyces . This paper describes the first isolation and characterisation of a plasmid from the genus Nocardia . The plasmid pKU100 isolated from Nocardia corallina is a cccDNA molecule, 2.7 kb in length. This plasmid has been mapped with a wide variety of restriction enzymes and contains a number of unique restriction sites making it suitable for development as a cloning vector. 相似文献
35.
Synopsis Laboratory studies were conducted on 15 schools of blackchin shiners, Notropis heterodon, to determine if they altered their structure in response to changing environmental demands. The hypothesis tested was that fish schools should sacrifice a flat, hydrodynamically efficient structure in favour of an unobstructed visual field in the presence of a predator by staggering in the vertical plane. Ten schools were exposed for two weeks to a simple environment with only a current. For the next two-week period a predator was added. Five control schools were exposed to the simple environment for both two-week periods. Six of the ten treated schools increased their staggering in the vertical dimension as predicted while none of the control schools changed. This result was suggestive that hydrodynamic advantages were sacrificed. Respirometer experiments indicated these fish were capable of achieving some hydrodynamic benefits from schooling but these benefits may be a function of fish size. 相似文献
36.
Kaoru Miyazaki Keisuke Mashima Nobuhiko Yamashita Jinpei Yamashita Takekazu Horio 《In vitro cellular & developmental biology. Plant》1985,21(1):62-66
Summary We have previously reported the transformation by Rous sarcoma virus of a cloned epithelial cell line (BRL) established from
Buffalo rat liver by H. Coon. The nontransformed (BRL) and transformed (RSV-BRL) cells grew at comparable rates in culture,
whereas only the transformed cells were tumorigenic in vivo. We report here on the existence in rat and mouse sera of a growth
inhibitor for the nontransformed BRL cells. The transformed BRL cells (RSV-BRL) were insensitive to this inhibitor. The inhibitory
activity was not prominent in sera from other species of animals tested except for rabbit; this serum inhibited the growth
of RSV-BRL cells more strongly than that of BRL cells. The growth inhibitor was partially purified from rat serum. It is a
protein free of lipid and has a molecular weight of about 220 000. The inhibitor could be separated into three components
of pI 4.6, 5.2 (major) and 5.6 by isoelectric electrophoresis.
EDITOR'S STATEMENT Although compelling theoretical arguments sometimes can be made for the likely existence of growth-inhibitory
substances of physical relevance in the control of cell proliferation, experiments aimed at identifying and studying such
factors often are difficult to design and interpret, and little strong data exists to suggest that growth-inhibitory substances
are important regulatorsin vivo. The information presented in this paper represents a start toward developing a useful system for studying growth-inhibitory
factor. David W. Barnes 相似文献
37.
Summary Studies on intercalary regeneration in several organisms have shown that a regenerate is formed when surfaces of different positional value along the proximo-distal axis are opposed. One of the main problems posed by this phenomenon is to know which piece contributes to the building of the regenerate. In the present work we have studied this problem in planarians using chimaeras made between pieces of different body levels, irradiated or not, of the sexual and asexual races ofDugesia(S)mediterranea that differ in a chromosomal marker.The results found show very clearly that intercalary regenerates in planarians are formed by cells coming from both pieces (stumps), and that irradiated pieces keep the positional values and interact with non-irradiated pieces to restore the missing parts. This means that distal and proximal transformation do actually occur at the same time during intercalary regeneration in planarians. The implications of these results as regards to the origin of cells in the regenerate and to present models of intercalary regeneration are discussed. 相似文献
38.
P. D. S. Caligari J. Brown R. J. Abbott 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1986,73(2):218-222
Summary A number of unselected potato (Solanum tuberosum L.) clones were grown at two locations (a seed site and a ware site) in three consecutive years. The repeatability of total yield and yield components in the first two clonal years was compared with the same characters recorded in the third clonal year. Selection for yield in the first clonal year was only marginally more effective than a random reduction in number of genotypes, while selection in the second clonal year appeared to be somewhat more effective as judged by performance in the third clonal year. The inefficiency of selection in the first clonal year was ascribed, at least in part, to the inaccuracy of yield assessment as well as the carry-over effect of the mother tubers. Correlations of total yield were higher between different years in the same location than between different locations. Selection under growing conditions suitable for production of seed tubers tended to result in selection of early maturing clones which would not necessarily be optimal for ware growing conditions. 相似文献
39.
Jacques Hille Frank Verheggen Peter Roelvink Henk Franssen Ab van Kammen Pim Zabel 《Plant molecular biology》1986,7(3):171-176
Summary Plant cells are sensitive to the antibiotic bleomycin, a DNA damaging glycopeptide. A bleomycin resistance determinant, located on transposon Tn5 and functional in bacteria, has been cloned in a plant expression vector and introduced into Nicotiana plumbaginifolia using Agrobacterium tumefaciens. The expression of this determinant in plant cells confers resistance to bleomycin and allows selection of transformed plant cells. 相似文献
40.
Dr. Hans-Joachim Gabius Katalin Vehmeyer Reinhild Engelhardt Gerd A. Nagel Friedrich Cramer 《Cell and tissue research》1986,246(3):515-521
Summary A tumor model system of clones of myeloproliferative sarcoma virus (MPV)-transformed rat fibroblasts (NRK) with different growth properties and metastatic potential was studied. The relationship between metastatic behavior and composition of carbohydrate-binding proteins (lectins) was analyzed by affinity chromatography. The metastatic variant differs qualitatively from its parental clone in the presence of galactoside-binding proteins at apparent molecular weights of 80 kDa, 70 kDa, 22 kDa, 18 kDa and 16 kDa and of a fucose-binding protein at apparent molecular weight of 42 kDa. The -glucosyl-binding proteins at apparent molecular weights of 67 kDa and 53 kDa and a galactoside-binding protein of apparent molecular weight of 34 kDa, however, are not detectable in the metastatic variant in comparison to its parental clone. In this respect the parental clone shows closer resemblance to the clone 5–8#1 with different growth properties and low metastatic potential than to its own metastatic variant. Furthermore, only the parental clone has a melibiose- and a mannan-binding protein of an apparent molecular weight of 64 kDa and 14 kDa, respectively. Rosette formation as model system for intercellular interaction reveals differences in the inhibition pattern with sugar between the two clones 5–8#1 and 5–20#20, whereas the metastatic variant 5–20#20 (s) exhibits drastically reduced capability to form rosettes. Initial experiments demonstrate the feasibility of drug targeting to transformed fibroblasts via carbohydrate-binding proteins. 相似文献