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71.
72.
Summary Experiments on the survival ofM. phaseoli on cucurbit root pieces were carried out. The sclerotia ofM. phaseoli were almost unaffected by 10 months dry storage in the laboratory. Under dry to moderately moist soil conditions it survived for 2 months with little loss of viability. In wet soils however, the buried root pieces were colonized by other soil microorganisms which prevented the growth ofM. phaseoli. 相似文献
73.
The growth OfRhizoctonia solani in different carbohydrates was studied. The rate of growth of the fungus was traced by taking the dry weights of mycelia obtained from the carbohydrate medium at regular intervals and shifts in the pH were recorded. Different carbohydrate sources had different effects on the growth of the organism. The exoenzymes from the organism were capable of cleaving carbohydrates irrespective of whether the fungus grew in them or not. 相似文献
74.
We have compared regeneration proficiency for cultured explants from different tissues of different ecotypes ofArabidopsis thaliana. Proficiency varies widely with both tissue and ecotype, and is highest when the flux of light during regeneration is low. Analysis of F1 hybrids suggests that high proficiency is dominant to low proficiency. 相似文献
75.
Identification of a cDNA encoding a long form of prolactin receptor in human hepatoma and breast cancer cells 总被引:19,自引:0,他引:19
J M Boutin M Edery M Shirota C Jolicoeur L Lesueur S Ali D Gould J Djiane P A Kelly 《Molecular endocrinology (Baltimore, Md.)》1989,3(9):1455-1461
Human PRL receptor cDNA clones from hepatoma (Hep G2) and breast cancer (T-47D) libraries were isolated by using a rat PRL receptor cDNA probe. The nucleotide sequence predicts a mature protein of 598 amino acids with a much longer cytoplasmic domain than the rat liver PRL receptor. Although this extended region has additional segments of localized sequence identity with the human GH receptor, there is no identity with any consensus sequences known to be involved in hormonal signal transduction. This cDNA will be a valuable tool to better understand the role of PRL in the development and growth of human breast cancer. 相似文献
76.
On the mechanism of action of dexamethasone in a rat mast cell line (RBL-2H3 cells). Evidence for altered coupling of receptors and G-proteins 总被引:1,自引:0,他引:1
D Collado-Escobar H Ali M A Beaven 《Journal of immunology (Baltimore, Md. : 1950)》1990,144(9):3449-3457
Prolonged exposure of rat basophilic leukemia (RBL-2H3) cells, a cultured analog of rat mast cells, to 0.1 microM dexamethasone resulted in global suppression of various stimulatory events in response to Ag and a global enhancement of the same stimulatory events to the adenosine analog, N-(ethylcarboxamide)adenosine (NECA). We had previously shown that Ag and NECA both activate phospholipase C but by different mechanisms; cells that had been treated with cholera or pertussis toxin, for example, responded to Ag but not to NECA with the release of inositol phosphates, increase in levels of cytosolic Ca2+, and secretion. Because the toxins still inhibited the responses to NECA in dexamethasone-treated cells, the effects of dexamethasone may have been exerted at the level of receptor/G-protein coupling rather than at the level of effector systems. Additional evidence for this was the following: 1) NECA-induced hydrolysis of the inositol phospholipids was still enhanced after permeabilizing (with streptolysin O or Staphylococcus alpha-toxin) and washing the cells; 2) the response to the G-protein stimulant, guanosine 5'-(3-O-thio)triphosphate was also enhanced in permeabilized, dexamethasone-treated cells and 3) binding and kinetic studies suggested that the enhanced responsiveness to NECA was attributable in part to an increase in receptor number. The suppressive action of dexamethasone on Ag-induced hydrolysis of inositol phospholipids, however, was readily lost by permeabilizing RBL-2H3 cells. The results indicate, therefore, that treatment with dexamethasone leads to changes in receptor-coupling mechanisms that are either resistant to (i.e., NECA-mediated responses) or reversed by (i.e., Ag-mediated responses) cell permeabilization. 相似文献
77.
Ingestion of licorice or treatment with chemical derivatives of glycyrrhetinic acid (GA), an active principle of licorice, can cause hypertension, sodium retention, and hypokalemia. Although GA has been shown to inhibit 11 beta-hydroxysteroid dehydrogenase, it may not be the only hepatic enzyme affected by this licorice derivative. Therefore, we studied the effects of GA on other major hepatic steroid-metabolizing enzymes from adrenalectomized male rats using aldosterone as the substrate; namely, delta 4-5 alpha- and delta 4-5 beta-reductases and 3 alpha- and 3 beta-hydroxysteroid dehydrogenases (3 alpha- and 3 beta-HSD). From these in vitro studies, we demonstrated that GA does not affect either microsomal 5 alpha-reductase or cytosolic 3 alpha-HSD activity. However, GA is a potent inhibitor of cytosolic 5 beta-reductase; the K(is) and K(ii) were calculated from enzyme kinetic analysis to be 6.79 and 5.41 microM, respectively, using the Cleland equation, indicating that GA is a noncompetitive inhibitor of aldosterone. In addition, GA specifically inhibited microsomal 3 beta-HSD enzyme activity by what appears to be a competitive inhibition mechanism, causing a build-up of the intermediate, 5 alpha-dihydroaldosterone (DHAldo). Thus, this study has indicated that GA has a profound effect on hepatic ring A-reduction of aldosterone. Inhibition of 5 beta-reductase and 3 beta-HSD results in decreased synthesis of both 3 alpha, 5 beta-tetrahydroaldosterone (THAldo) and 3 beta, 5 alpha-THAldo and, hence, accumulation of aldosterone and 5 alpha-DHAldo, both potent mineralocorticoids.(ABSTRACT TRUNCATED AT 250 WORDS) 相似文献
78.
László E. Heszky Zsolt Jekkel Abdel-Hamid Ali 《Plant Cell, Tissue and Organ Culture》1990,21(3):217-226
Reflexed saltmarsh-grass suspension cultures produced by seed callus were frozen to the liquid nitrogen temperature. Cooling rates, cryoprotectants and holding times were taken as a function of transfer temperatures. The highest survival of cells (45%) was found at a freezing rate of 1°C min-1, without cryoprotectant treatments. The cryoprotectants (proline, dimethyl sulphoxide, glycerol), used at different concentrations and transfer temperatures, increased the survival rate. The maximum value was 78% at 12.5% (w/v) of proline with –30°C transfer temperature. Considerable improvement of viability (from 0% to 95%) among the 12.5 and 15.0% (v/v) dimethyl sulphoxide cryopreserved cells was achieved by holding them at – 20°C for 10–30 min before plunging into the liquid nitrogen. A 20 min holding time at 15.0% (v/v) glycerol level and – 30°C transfer temperature significantly enhanced the viability of the explants from 42% to 92%. Plants were successfully regenerated from cells cryopreserved with proline (w/v) and dimethyl sulfoxide (v/v) levels of 12.5 and 15.0%, respectively. 相似文献
79.
Diazotization of primary aromatic amines with isoamyl nitrite in benzene at room temperature was studied employing EPR and spin trapping techniques. Nitrosodurene (ND). 2-methyl-2-nitrosopropane (MNP). and 5,5-dimethyl-pyrroline N-oxide (DMPO) were used as spin trapping agents. Aryl radicals were detected employing ND and MNP. Using DMPO as a spin trap most of the amines produced EPR spectra ascribed to adducts with aniline-type radicals (N-centred radicals). The assignments were verified using 15JN-labeled anilines. Similar spectra of DMPO adducts were recorded from amines treated with benzoyl peroxide or benzophenone plus UV. Possible mechanisms of formation of these adducts (radical trapping versus nucleophilic addition to DMPO followed by oxidation) during treatment of the amines with isoamyl nitrite are discussed. 相似文献
80.
Abstract: 5-Hydroxytryptamine3 (5-HT3 ) receptors are the only known monoamine receptors mediating fast excitatory responses in mammalian neurons. Their primary structure as well as their electrophysiological and pharmacological properties show a phylogenetic relation to nicotinic acetylcholine, GABAA , and glycine receptors. As a prototypical member of this gene superfamily, we investigated the membrane topology of functional homomeric 5-HT3 receptors by using epitope tagging of the channel subunits expressed in heterologous systems. Visualization of 5-HT3 receptors in transfected COS-7 cells, either in western blot (molecular mass 61.2 ± 0.8 kDa) or in situ, was performed with previously characterized antibodies recognizing artificial epitopes as well as with anti-fusion protein antibodies directed against a wild-type receptor intracellular domain. The extracellular location of the distal C-terminal tagged domain demonstrates the presence of a fourth transmembrane domain in 5-HT3 serotonin-gated channels. In this region, the significant homology between members of this class of neurotransmitter-gated channels suggests strongly that they have a common transmembrane organization basically different from glutamate-gated and ATP-gated channels. 相似文献