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21.
Hans Thijs Julie Garde Theo Goosen Brian Tomsett Klaas Swart Christa Heyting Henk W. J. Broek 《Molecular & general genetics : MGG》1995,247(3):343-350
We have examined polarity of meiotic gene conversion in the niiA-niaD gene cluster of Aspergillus nidulans in two-point crosses. The type and position of the mutations represented by the niaD alleles and the correlation between the relative frequency of gene conversion and the physical position of these mutations were determined. We show that polarity of meiotic gene conversion is 5 to 3 (transcribed strand) within the niaD gene. Additional crosses involving a niiA allele and a niaD allele show little polarity of gene conversion, which suggests that the recombination events leading to restoration of the niaD gene are initiated upstream of the coding region of the niaD gene but within the niiA-niaD gene cluster, possibly within the intergenic promoter region. 相似文献
22.
Klaus Peter Zulka Norbert Milasowszky Christa Lethmayer 《Biodiversity and Conservation》1997,6(1):75-88
To assess the biodiversity potential of an ungrazed and a grazed inland salt meadow in the Seewinkel (Eastern Austria), spider assemblages were recorded by pitfall trapping for 1 year. Both species assemblages consisted, to a large extent, of rare species of conservation interest. The species assemblage of the grazed site was dominated by Pardosa agrestis, but highly specific halotopobiontic species also occurred in higher numbers. Halotolerant species were also present in the ungrazed meadow, but their individual number was much lower. The species composition of this site reflects the more balanced microclimatical situation of the high sward. Comparison of the two assemblages with 207 other meadow spider assemblages of Central Europe shows a separated position, especially of the grazed site assemblage. High similarities with assemblages of meadows with a similar vegetation structure indicate a high importance of management. Considering the high proportion of rare species on both sites, the best management of the salt meadow and pan shores of the Seewinkel should combine areas of light grazing with ungrazed areas. However, the proportion of these parts and the intensity of grazing still remains to be determined by quantitative experiments. 相似文献
23.
Liedtke Christa; Polsakiewicz Monika; Hartmann Ingrid; Peters Petra; Volkmann Dieter; Scherer Gnther F.E. 《Journal of experimental botany》1997,48(6):1215-1221
The vacuolar membrane, the tonoplast, is a proteinrich membranehitherto only few proteins in it have been identified. As anapproach for the identification of tonoplast proteins by monoclonalantibodies (MABs), purified tonoplast from cress roots (Lepidiumsativum L.) were used for immunization and plasma membranesas a control membrane to test the absence of antigen. The MABTOP 35 identified a glycoprotein of about 35 kDa in purifiedtonoplast of cress roots. Triton X-114 phase separation showedthat it was a hydrophobic integral membrane protein. In immunocytochemistrythe MAB TOP 35 strongly labelled the vacuolar membrane. Theabsence of cell wall or plasma membrane labelling by TOP 35indicates a distinct biosynthetic pathway of this protein tothe vacuolar membrane in plants. Key words: Immnocytochemistry, Lepidium sativum, monoclonal antibody, secretion, vacuole 相似文献
24.
Martin H. Spalding Christa Critchley Govindjee William L. Orgren 《Photosynthesis research》1984,5(2):169-176
Carbon dioxide concentration during growth is commonly not considered to be a factor influencing the photochemical properties of plants. It was observed that fluorescence induction in Chlamydomonas reinhardii cells grown at air levels of CO2 was both qualitatively and quantitatively different from that of cells grown at 5% CO2. In the two cell types, measured at equivalent chlorophyll and irradiance levels, the fluorescence intensity and the ratio of the levels of peak fluorescence (Fp) to that of the initial fluorescence (Fo) were much lower in the air-adapted than in the 5% CO2 adapted cells. The maximum fluorescence (Fmax) in the presence of diuron was also lower for air-adapted cells. Roughly twice the light input was required for the air-adapted cells to give a fluorescence induction transient and intensity equivalent to that of the 5% CO2-adapted cells. Similar properties were observed in several other unicellular green algae and in cyanobacteria. Chlamydomonas grown under variable CO2 concentrations exhibit significant differences in photosynthetic carbon metabolism and are presumed to have altered energy requirements. The observed variation in fluorescence induction may be due to changes in the properties of the thylakoid reactions (e.g. cyclic electron flow) of Chlamydomonas cells, which may, in turn, be due to a response to the altered energy requirements. 相似文献
25.
Hartmut Beug Steven Palmieri Christa Freudenstein Hanswalter Zentgraf Thomas Graf 《Cell》1982,28(4):907-919
Chicken erythroblast cell strains and a cell line transformed by ts mutants of avian erythroblastosis virus (AEV) terminally differentiate when shifted to the nonpermissive temperature (42°C). The differentiated cells resemble mature erythrocytes with respect to morphology and ultrastructure, expression of differentiation-specific cell-surface antigens, pattern of protein synthesis and hemoglobin content. Terminal differentiation is dependent on conditions favoring the differentiation of normal erythroid progenitor cells, including an erythropoietin-like factor. Colonies of ts AEV cells grown at 42°C in semisolid medium resemble erythrocyte colonies derived from normal erythroid progenitor cells. The colonies obtained were comparable in size or slightly larger than the late erythroid precursor (CFU-E) colonies. These results suggest that AEV-transformed cells are blocked at a stage of differentiation that is more advanced than that of the uninfected target cells. ts AEV cells are irreversibly committed to terminal differentiation within 20 to 30 hr after shift to 42°C. 相似文献
26.
The investigation of some Heterotheca species afforded three new cadinane angelicates, in addition to several known compounds. The structures are elucidated by spectroscopic methods. The chemotaxonomic situation is discussed briefly. 相似文献
27.
Ferdinand Bohlmann Karl-Heinz Knoll Christa Zdero Pradip Kumar Mahanta Michael Grenz Albert Suwita Dorothea Ehlers Ngo Le Van Wolf-Rainer Abraham Arvind Anant Natu 《Phytochemistry》1977,16(7):965-985
Investigation of about 50 Senecio species has afforded many new substances, in addition to known compounds. Present in these plants are 23 fura 相似文献
28.
The aerial parts of the South African composite Printzia laxa contain two manoyl oxides and three clerodane derivatives together with two further acids, which belong to a new type of diterpene, biogenetically closely related to the clerodanes. The structures have been elucidated by spectroscopic methods. The constituents may indicate some relationship of Printzia to the tribe Astereae. 相似文献
29.
The investigation of two species of Lasthenia afforded two new guaianolides and a new bisabolone derivative, in addition to already known compounds. The presence of an eremophilenic acid in these plants is remarkable. The results are discussed chemotaxonomically, since the tribal position of this genus is still debated. 相似文献
30.
Investigation of a further 27 Euryops species affords, besides known compounds, 55 new furanoeremophilanes together with several other compounds. The configuration of six furanoeremophilanes earlier given as 10β-H has to be changed to 10α-H. Furthermore 9 new eremophilenes were isolated; the configurations of four compounds of this type isolated before have had to be changed. One of the eremophilenes is esterified with 3-methylpent-3(E)-enoic acid, not found before in nature. Two hemiacetals, which are probable precursors of the furanoerephilanes, and a corresponding lactone are also present. Furthermore two benzylic esters, cis-caryophyllene, a bicyclo-germacrene derivative, and a new oplopanone derivative have been found. The structures are elucidated mainly by spectroscopic methods together with some chemical transformations. From the chemotaxonomic viewpoint, the high concentration of very variable furanoeremophilanes may be important. The proposed differentiation into sections however can not be clearly correlated with the chemical constituents, though some taxonomic conclusions seem to be supported by the chemical evidence. 相似文献