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131.
The formation of new root apices from small groups of cells with different cellular patterns has been simulated using an existing model based on growth tensors. To generate an apex, a steady growth field was used. The pattern of cells evolved to approach the steady state. Two extreme types of progressions have been obtained : one leading to an apex with a single or a few apical cells, and the other to an apex with a quiescent centre. The change of structure while applying a steady growth tensor indicates that development may involve a succession of discrete growth tensors. 相似文献
132.
Abundance and composition of nematode fauna were examined in the benthic microbial mats and upper sediment layer of the littoral
of acidified (pH 4.6 to 5.7) lakes.
Nematodes constituted from 58% to 90% of all the invertebrates present (excluding protozoans and rotifers). In the examined
material, the majority of nematodes was represented by 3 taxa of which Ironus was found specifically associated with the mats. It was concluded that the persistence of benthic mats may be linked to the
metabolic activity of the associated nematode fauna. 相似文献
133.
Phosphorylation of Synaptic Membrane Glycoproteins: The Effects of Ca2+ and Calmodulin 总被引:1,自引:0,他引:1
Synaptic membranes were incubated with [gamma-32P]ATP, and glycoproteins were isolated by affinity chromatography on concanavalin A agarose. Glycoproteins accounted for 1.5-2.5% of the total 32P incorporated into synaptic membrane proteins. Ca2+ and calmodulin enhanced the phosphorylation of synaptic membrane glycoproteins approximately threefold. In the presence of Ca2+ and calmodulin, the rate of glycoprotein dephosphorylation was also increased three- to four-fold. Gel electrophoretic analysis identified several synaptic membrane glycoproteins that incorporated 32P, with the most highly labeled glycoprotein under basal phosphorylating conditions having an apparent Mr of 205,000 (gpiii). Ca2+ and calmodulin produced a marked increase in the phosphorylation of a glycoprotein with an apparent Mr of 180,000 (gpiv) and lesser increases in the labeling of three other glycoproteins. Membranes that had been labeled with [gamma-32P]ATP were extracted with Triton X-100 under conditions that yield a detergent-insoluble residue enriched in postsynaptic structures. The Triton X-100 insoluble residue accounted for 20-25% of the 32P associated with synaptic membrane glycoproteins. Gpiv and other glycoproteins, the phosphorylation of which was stimulated by calmodulin, were located exclusively in the Triton X-100 insoluble residue, whereas gpiii and other calmodulin-insensitive glycoproteins partitioned predominantly into the Triton X-100-soluble fraction. Phosphopeptide maps and phosphoamino acid analysis of gpiv isolated from synaptic membranes and a postsynaptic glycoprotein of apparent Mr of 180,000 (gp180) isolated from synaptic junctions indicated that the former protein was identical to the previously identified postsynaptic-specific gp180. In addition to phosphoserine and phosphothreonine, gpiv also contained phosphotyrosine, identifying it as a substrate for tyrosine-protein kinase as well as for Ca2+/calmodulin-dependent protein kinase. 相似文献
134.
Krystyna M. Urbanska 《Biodiversity and Conservation》1995,4(7):679-695
Ecological restoration trials in high-alpine sites require sampling of indigenous plant populations. This problem is discussed briefly in relation to initial genetic diversity in the restoration material. The further part of the paper deals with restoration trials in the Swiss Alps and their assessment.The plots, set in machine-graded downhill ski runs, were revegetated with transplants of alpine species used in various combinations. Safe-site conditions were simulated with biodegradable wood-fibre mats. Surveys carried out in plots aged four to seven years focused on plant species inventory and age-state structure of mixed stands. The alpha diversity assessment included speices number and the associated aspects. The consistent increase in species number, the number of plant families represented, and range of life-forms was apparently independent of the restoration timing. The age-state structure of the mixed stands was characterized by a considerable increase in the range of age-state classes and, in particular, a regular appearance of younger variants. These changes clearly indicate development of self-sustaining plant communities influenced by reproduction of the transplants and extensive immigration. It is proposed that age-state structure be called delta diversity and included in a routine assessment of post-restoration status of both single plant populations and mixed stands. 相似文献
135.
Mutations were induced in tissue-cultured wasabi (Wasabia japonica Matsumura) by treating in vitro-derived shoot tips with either γ-rays or X-rays at 0, 10, 20, 40 or 80 Gy. Doses of up to 40 Gy of either γ- or X-ray treatments
resulted in a survival rate of more than 60% in culture after 3 mo. The use of γ- or X-rays at doses between 10 Gy and 40 Gy
to induce mutation in W. japonica resulted in an alteration of the growth and allyl isothiocyanate (AITC) content of multiple shoots after 3 mo. in culture
on Murashige and Skoog medium containing 5 μM N6-benzyladenine (BA). Putative mutants from the 40 Gy treatments of either γ- or X-rays exhibited a reduction in shoot weight,
number, and height, whereas treatments of either γ-rays or X-rays at 10 Gy and 20 Gy doses showed no significant differences
in shoot growth. All shoots treated with 80 Gy were either necrotic or irregenerable, while those treated with 40 Gy produced
deformed leaves, from both types of ionizing radiation. Concentrations of AITC were measured by the use of gas chromatography-mass
spectrometry (GC-MS). The accumulation of AITC was shown to decrease when doses increased in both γ- and X-ray treatments,
compared with the controls. Positive responses were solely occurred at 18 mo. after transfer of in vitro rooted shoots to the shade house. The survival rate, rhizome weight and AITC content of plants derived from shoots treated
with 20 Gy or 40 Gy of either γ-rays or X-rays were significantly greater than those of the controls. 相似文献
136.
Physiological activity of 1-amino-2-phenylethylphosphonic acid,a substrate analogue of phenylalanine
1-Amino-2-phenylethylphosphonie acid (PheP) retards growth inSpirodela oligor-rhiza causing morphological malformations, inhibits chlorophyll synthesis in progeny fronds, and markedly stimulates L-phenylalanine ammonia-lyase (PAL) activityin vivo and inhibits itin vitro; in prolonged experiments ribonuclease activity is stimulated. PheP severely inhibits anthocyanin synthesis in seedlings of red cabbage, with moderate inhibition of PAL activityin vivo; chlorophyll synthesis and growth of the seedlings are little affected. 相似文献
137.
Paul F. Torrence Wei Xiao Guiying Li Shahrzad Khamnei Krystyna Lesiak Avudaiappan Maran 《Nucleosides, nucleotides & nucleic acids》2013,32(3-5):1073-1076
Abstract A novel method is described to selectively cleave RNA by harnessing the 2-5A-dependent ribonuclease. 相似文献
138.
Krystyna Bogucka Lech Wojtczak 《Biochemical and biophysical research communications》1976,71(1):161-167
The intermembrane compartment of rat liver mitochondria contains high molecular weight compounds, most likely proteins, complexing magnesium ions. Compound/s/ of about 150 000 daltons has a low affinity /Kd 0.37 mM/ and a high binding capacity of 300 ng atoms Mg/mg protein; compound/s/ of about 100 000 daltons is characterized by a very high affinity towards magnesium /Kd of the order of magnitude of 0.001 mM/ and a low capacity of about 20 ng atoms Mg/mg protein. 相似文献
139.
Agnieszka Markowska Irena Bruzgo Krystyna Midura-Nowaczek 《International journal of peptide research and therapeutics》2008,14(3):215-218
Eight peptides of the general formula X-d-Ser-AA-Arg-Y where X = H, Ac; AA = Ala, Gly and Y = OH, NH2 were obtained and tested for their effect on the amidolytic activities of urokinase, thrombin, plasmin, and trypsin. 相似文献
140.
Advances in soil microbial ecology and the biodiversity 总被引:3,自引:0,他引:3
Tsutomu Hattori Hisayuki Mitsui Hideki Haga Norio Wakao Shuichi Shikano Krystyna Gorlach Yasuhiro Kasahara Adel El-Beltagy Reiko Hattori 《Antonie van Leeuwenhoek》1997,72(1):21-28
Recent studies on the colony formation of soil bacteria opened the way to categorize soil bacteria into colony forming curve (CFC) groups of different growth rates. A bacterial culture collection comprising organisms from every CFC group is called an ecocollection. Outlines of ECs of paddy soil 1992 and grassland soil 1987 and 1992 were described. Phylogenetic studies by 16S rDNA sequencing showed a great diversity of culture strains of the ecocollections (EC). A set of alternative concepts was proposed; the active and the quiescent forms of bacterial cells in soil. The former is able to be cultivated and thus counted by the plate method, while the latter is not unless it transforms into the former. Based on the results several points required for extensive cataloguing of soil bacteria were noted. 相似文献