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81.
W. L. C. Vaz J. Stümpel D. Hallmann A. Gambacorta M. De Rosa 《European biophysics journal : EBJ》1987,15(2):111-115
Fluorescence recovery after photobleaching was used to investigate the translational diffusion of a fluorescent derivative of a membrane-spanning lipid in L
phase multibilayers of 1-palmitoyl-2-oleoylphosphatidylcholine prepared in water and in glycerol. The translational diffusion coefficient in hydrated bilayers (D
w) ranged between 2 and 5x10–8 cm2/s and in glycerinated bilayers (D
g) the range was between 3 and 24×10–10 cm2/s between 10° and 40°C. These results are discussed in terms of models for diffusion in membranes. 相似文献
82.
Biphasic fluence-response curves for phytochrome-mediated kalanchoë seed germination : sensitization by gibberellic Acid 总被引:5,自引:5,他引:0
Rethy R Dedonder A De Petter E Van Wiemeersch L Fredericq H De Greef J Steyaert H Stevens H 《Plant physiology》1987,83(1):126-130
The fluence-response curves for the effect of two red pulses separated by 24 hours on the germination of Kalanchoe blossfeldiana Poelln. cv Vesuv seeds, incubated on gibberellic acid (GA3) are biphasic for suboptimal concentrations. The response in the low fluence range corresponds with a classical red/far-red reversible phytochrome mediated reaction. GA3 induces an additional response in the very low fluence range, which is also phytochrome mediated. The sensitivity to phytochrome-far-red absorbing form (Pfr), however, is increased about 20,000-fold, so that even far-red fluences become saturating. Both in the very low and low fluence response range, the maximal responses induced by saturating fluences are modulated by the GA3 concentration. GA3 having no direct influence on the phytochrome phototransformations, alters the Pfr requirement and determines the responding seed population fraction in the very low and low fluence range. The effet of GA3 appears to be on the transduction chain of the phytochrome signal. 相似文献
83.
M Beauduin J Gueulette B M De Coster M Octave-Prignot S Vynckier A Wambersie 《Comptes rendus des séances de la Société de biologie et de ses filiales》1987,181(1):78-81
RBE of p(34) + Be, p(45) + Be, p(65), + Be, p(75) + Be and d(50) + Be neutron beams produced at the cyclotron "Cyclone" of Louvain-la-Neuve were measured. The biological criterion was the regeneration of the crypts of the intestinal mucosa (50 regenerated crypts per circumference) after abdominal irradiation in mice. Taking the p(65) + Be neutrons as reference, RBE values were found equal to 1.12, 1.07, 1.00 (Ref.), 0.96 and 1.02 respectively. These results are consistent with those published for cell lethality in vitro. However, the RBE variation is smaller than this previously obtained in the laboratory for growth inhibition in Vicia faba. 相似文献
84.
Densities of Drosera intermedia were low in two studied habitats (10–25 ramets m−1 ), a path through a wet heath (short inundation in spring, low soil moisture in summer) and a pool edge (longlasting inundation, high soil moisture in summer). The low densities could be explained by the observed low recruitment and high adult mortality.
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality. 相似文献
The low recruitment resulted from: (1) a high first year mortality of the large number of seedlings that emerged each year in the path population, caused by summer drought and cover with algae after heavy rainfall; (2) the absence in two years out of three of seedling emergence at the pool edge, due to the longlasting inundation. In neither population any seedlings survived to flower; (3) low vegetative reproduction rate.
Adult mortality during the growing season was caused by drought, which did not occur at the pool edge. Rapid senescence in autumn, caused by summer drought on the path and by a rapid submersion after heavy rainfall at the pool edge, was associated with a high winter mortality. 相似文献
85.
Incorporation of the carbocyclic analogue of (E)-5-(2-bromovinyl)-2'-deoxyuridine 5'-triphosphate into a synthetic DNA 总被引:1,自引:0,他引:1
J Sági E De Clercq A Szemz? A Csárnyi T Kovács L Otv?s 《Biochemical and biophysical research communications》1987,147(3):1105-1112
The carbocyclic analogue of (E)-5-(2-bromovinyl)-2'-deoxyuridine, C-BVDU, is a very potent and selective anti-herpes-virus compound. In order to synthesize and study the properties of a DNA that contains C-BVDU, the 5'-triphosphate, C-BVDUTP was prepared and evaluated as a potential substrate of the E. coli Klenow DNA polymerase enzyme. Although C-BVDUTP proved to be a very poor substrate also of this enzyme, it could be incorporated up to 3.6% into the synthetic DNA, poly(dA-dT, C-BVDU). This level of substitution decreased significantly the template activity for DNA and RNA polymerases, as compared to that of poly(dA-dT). 相似文献
86.
Host-plasmid interactions were studied for the broad-host range plasmid, pTJS26, a derivative of RK2. To isolate host and plasmid contributions to the growth dynamics and plasmid stability, separate experiments were performed with host and recombinant cells for two different gram-negative hosts, Pseudomonas putida and Escherichia coli, at two different temperatures, 30 and 37 degrees C. At the lower temperature (30 degrees C) the growth kinetics were not affected by the plasmid, but plasmid instability was observed. At the higher temperature (37 degrees C) growth rates and yields were lower than that for the hosts, but the plasmid was stable. This behavior can be explained by a combination of two phenomena. First, the copy number control mechanism may be temperature sensitive and, second, plasmid segregation may be inefficient. For both E. coli and P. putida the growth dynamics of the recombinant system was dictated by the presence of the plasmid. 相似文献
87.
Tissue-specific expression of porphobilinogen deaminase. Two isoenzymes from a single gene 总被引:18,自引:0,他引:18
B Grandchamp H De Verneuil C Beaumont S Chretien O Walter Y Nordmann 《European journal of biochemistry》1987,162(1):105-110
Porphobilinogen deaminase (hydroxymethylbilane synthase; EC 4.3.1.8), the third enzyme of the heme biosynthetic pathway, catalyzes the stepwise condensation of four porphobilinogen units to yield hydroxymethylbilane, which is in turn converted to uroporphyrinogen III by cosynthetase. We compared the apparent molecular mass of porphobilinogen deaminase from erythropoietic and from non-erythropoietic cells by sodium dodecyl sulfate/polyacrylamide gel electrophoresis and immune-blotting. The results indicate that two isoforms of porphobilinogen deaminase can be distinguished and differ by 2000 Da. Analysis of cell-free translation products directed by mRNAs from human erythropoietic spleen and from human liver demonstrates that the two isoforms of porphobilinogen deaminase are encoded by distinct messenger RNAs. We cloned and sequenced cDNAs complementary to the non-erythropoietic form of porphobilinogen deaminase encoding RNA. Comparison of these sequences to that of human erythropoietic mRNA [Raich et al. (1986) Nucleic Acids Res. 14, 5955-5968] revealed that the two mRNA species differ by their 5' extremity. From the mRNA sequences we could deduce that an additional peptide of 17 amino acid residues at the NH2 terminus of the non-erythropoietic isoform of porphobilinogen deaminase accounts for its higher molecular mass. RNase mapping experiments demonstrate that the two porphobilinogen deaminase mRNAs are distributed according to a strict tissue-specificity, the erythropoietic form being restricted to erythropoietic cells. We propose that a single porphobilinogen deaminase gene is transcribed from two different promoters, yielding the two forms of porphobilinogen deaminase mRNAs. Our present finding may have some relevance for further understanding the porphobilinogen deaminase deficiency in certain cases of acute intermittent porphyria with an enzymatic defect restricted in non-erythropoietic cells. 相似文献
88.
Zenon Steplewski K. Ann Jeglum Carlos Rosales Nancy Weintraub 《Cancer immunology, immunotherapy : CII》1987,24(3):197-201
Summary Lymphoma in dogs resembles human non-Hodgkin's lymphoma in pathological presentation, immunophenotype, and response to therapy, thus representing a good model for comparative studies with human disease. Monoclonal antibodies (MAbs) were derived from mice immunized with a dog lymphoma cell line. Three MAbs were selected for further application in immunophenotyping and immunotherapy. The binding specificities, antigen characterization, and isotypes for these MAbs are described.Supported by NCI grant CA-10815 相似文献
89.
A Miceli D Traversi P De Leo 《Bollettino della Società italiana di biologia sperimentale》1989,65(12):1141-1147
In this study the amount of glucose, sucrose and fructose was determined in the water soluble fraction while cellulose, hemicellulose, pectin and lignin contents were determined in the alcohol insoluble fraction after hydrolysis. Stalks of sweet sorghum (Sorghum vulgare L., var. saccharatum) cv. Vespa, Soave, Roce and MN 1500 at the physiological ripeness stage were used. The results of the analysis of variance with the least significant difference method (LSD, = 0.05) show that cv. Vespa and Roce have a significantly higher total amount of glucose, fructose and sucrose and at the same time, a lower cellulose, pectin, hemicellulose and lignin content then cv. Soave and cv. MN 1500. 相似文献
90.
L De Gara F Tommasi R Liso O Arrigoni 《Bollettino della Società italiana di biologia sperimentale》1989,65(10):959-965
The capacity of ascorbic acid biosynthesis in potato tuber tissue is closely correlated with the ascorbic acid content of the cells: the lower the endogenous content of ascorbic acid, the greater its biosynthesis. At the highest level of ascorbic acid found in the cells, the biosynthetic capacity is virtually zero. In these conditions, adding glucose (the first precursor of ascorbic acid) has no effect whatsoever, whereas adding galactono-gamma-lactone (the last precursor) induces a high rate of ascorbic acid synthesis. It is suggested that AA biosynthesis is subject to a regulatory mechanism "in vivo" which controls an initial step in the biosynthetic pathway. The last step in this pathway, catalyzed by galactone oxidase, is never blocked and, moreover, its activity is greater than that of the preceding steps. 相似文献