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991.
Cell division in cell suspension cultures can be completely blocked by the growth retardant tetcyclacis at a concentration of 10-4 mol l-1. In rice cells it has been demonstrated that the growth inhibition can be completely overcome by application of cholesterol independent of the duration of pretreatment with tetcyclacis. In suspension cultures of maize and soybean, too, the effect of tetcyclacis on cell division was neutralized by adding cholesterol. Other plant sterols, stigmasterol, campesterol and sitosterol were active in a decreasing order. Modifications in the cholesterol perhydro-cyclopentanophenanthrene-ring system indicate that the hydroxyl group at C-3 and the double bond between C-5 and C-6 in ring B are required for the activity. In contrast, gibberellic acid as well as ent-kaurenoic acid could not compensate retardant effects. Likewise, tetcyclasis did not change the level of gibberellins in rice cells as shown by radioimmunoassay. Thus, it is concluded that in cell suspension cultures sterols play a more important role in cell division than gibberellins.Abbreviation GAx
gibberelin Ax 相似文献
992.
Carp (Cyprinus carpio) hemoglobin readily autoxidizes in blood smears. Quantification of Soret-band absorbance in individual erythrocytes by means of scanning cytophotometry therefore requires more elaborate methods of preparation of blood samples. Of the fixatives that have been tested, suspension of whole blood in isotonic salt solutions containing glutaraldehyde was most suitable. Glutaraldehyde-fixed red blood cells are totally resistant to hemolysis. In the course of fixation, hemoglobin is transformed to methemoglobin. Spectrophotometry indicated extensive similarities between glutaraldehyde-fixed carp methemoglobin and human methemoglobin. In aqueous solutions, the intensity of the Soret-peak was pH-dependent. The allosteric modifier organic polyphosphate caused an R----T transition, resulting in increased molar extinctions. Dried preparations showed Soret-spectra that were not influenced from either pH or organic polyphosphate concentration of the aqueous suspensions in which the erythrocytes had been stored. The same was true for slide preparations of cyanomethemoglobin, easily derived from methemoglobin on addition of potassium cyanide. In the absence of oxygen fresh blood cells from carp slowly transform their hemoglobin into deoxyhemoglobin. Spectra of the intermediate stages of deoxygenation, Hb4(O2)3, Hb4(O2)2 and Hb4(O2), as well as mixtures of these intermediates, could be monitored. 相似文献
993.
G Ponsin A M Gotto G Utermann H J Pownall 《Biochemical and biophysical research communications》1985,133(3):856-862
Several isoforms of apoprotein A-I [apoA-I], the major apoprotein of high density lipoproteins [HDL], have been described. We compared the in vivo and in vitro properties of normal human apoA-I with those of apoA-I [Lys107----0]. Fluorescence and circular dichroic spectra showed that deletion of Lys107 decreases apoprotein self-association. In vivo metabolic studies in the rat indicated that the interaction of apoA-I [Lys107----0] with HDL was lower than normal. We conclude that deletion of Lys107 results in a reorganization of the apoprotein structure that decreases its potential to form hydrophobic associations. 相似文献
994.
The receptor for asialoglycoproteins was isolated from murine liver and was purified by means of biospecific chromatography on sepharose-Asialo-orosomucoid. The obtained receptor with an absorption maximum at 277 nm binds to the nonreducing terminal galactosyl residues of glycoproteins similar to the receptors from liver of other mammalians. The interaction between this receptor and desialylated glycoproteins requires the presence of calcium. The dependence of specific binding on the concentration of [125I]acialo-orosomucoid used as a ligand gives a saturating curve. The dissociation constant for the receptor-ligand complex is 0.4 X 10(-9) M. Similar to asialo-orosomucoid, the receptor binds the p-aminophenyl-beta-D-galactopyranoside derivatives of bovine serum albumin, ovalbumin and acid alpha-glucosidase synthesized by us earlier. Possible use of the asialoglycoprotein receptor as a highly specific carrier transporting the modified acid alpha-glucosidase to hepatocyte lysosomes is discussed. 相似文献
995.
A González-Fernández J Sans P Aller C de la Torre 《Cell biology international reports》1985,9(3):237-243
Bromosubstitution for most of the S period in synchronous populations of Allium cepa L. meristematic cells resulted in a delay in the late S-G2 transition point where protein synthesis is needed for later mitotic entrance to occur. This retardation in the position of the transition point was not accompanied by the expected delay in the entrance into mitosis, suggesting that such protein synthesis is a requisite, but not a timer for prophase triggering. 相似文献
996.
M E Porter J M Scholey D L Stemple G P Vigers R D Vale M P Sheetz J R McIntosh 《The Journal of biological chemistry》1987,262(6):2794-2802
We have used an in vitro assay to characterize some of the motile properties of sea urchin egg kinesin. Egg kinesin is purified via 5'-adenylyl imidodiphosphate-induced binding to taxol-assembled microtubules, extraction from the microtubules in ATP, and gel filtration chromatography (Scholey, J. M., Porter, M. E., Grissom, P. M., and McIntosh, J. R. (1985) Nature 318, 483-486). This partially purified kinesin is then adsorbed to a glass coverslip, mixed with microtubules and ATP, and viewed by video-enhanced differential interference contrast microscopy. The microtubule translocating activity of the purified egg kinesin is qualitatively similar to the analogous activity observed in crude extracts of sea urchin eggs and resembles the activity of neuronal kinesin with respect to both the maximal rate (greater than 0.5 micron/s) and the direction of movement. Axonemes glide on a kinesin-coated coverslip toward their minus ends, and kinesin-coated beads translocate toward the plus ends of centrosome microtubules. Sea urchin egg kinesin is inhibited by high concentrations of SH reagents ([N-ethylmaleimide] greater than 3-5 mM), vanadate greater than 50 microM, and [nonhydrolyzable nucleotides] greater than or equal to [MgATP]. The nucleotide requirement of sea urchin egg kinesin is fairly broad (ATP greater than GTP greater than ITP), and the rate of microtubule movement increases in a saturable fashion with the [ATP]. We conclude that the motile activity of egg kinesin is indistinguishable from that of neuronal kinesin. We propose that egg kinesin may be associated with microtubule-based motility in vivo. 相似文献
997.
Merocyanine 540 (MC 540) has been reported to interact specifically with excitable plasma membranes in live cells [3]. Here we show that the MC 540 fluorescence staining pattern previously believed to be characteristic of viable myotubes [3] is observed in formaldehyde-fixed cells. In contrast, viable myotubes show an MC 540 fluorescence staining pattern that is characteristic of cell surface staining (no internal structures fluoresce). The specific I-band and H-zone fluorescence of isolated myofibrils is also consistent with the interpretation that the fluorescence patterns previously reported for viable myotubes are in fact characteristic of cells with disrupted plasma membranes. Time-course observations of MC 540 and trypan blue staining of myotubes suggest that when plasma membrane integrity is lost, MC 540 fluorescence can be visualized inside the cell 5-10 min before trypan blue absorbance. Thus the trypan blue viability assay can be misleading when applied to myotubes. 相似文献
998.
999.
1000.
F García J Sánchez J Planas 《Comparative biochemistry and physiology. A, Comparative physiology》1987,87(4):947-950
1. Male quails submitted 20 and 120 days to a low iron diet (7 ppm) were compared to female laying quails, exposed for 30 days to the same low iron regime, in order to compare the response of the iron metabolic control under a single (erythropoiesis) or a doubled (erythropoiesis and egg formation) iron demand. 2. Iron deposit in storage organs, the classical hematology and the intestinal iron absorption were analyzed in these animals. 3. In males, after 120 days, the iron deposits were reduced 50 and 75%, but hematological values (hematocrit and hemoglobin concentration) were normal, although in laying quails, after 30 days, an anemic condition was evident in both blood parameters and iron deposits, provoking an iron deficient erythropoiesis. 4. The enhancement of the intestinal iron uptake, confirms the anemic character of these birds. 相似文献