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91.
The effects of hyper- and hypo-saline stresses on the levels of various inorganic and organic solutes inUlva lactuca have been recorded. Hypoosmotic stress decreased the tissue concentration of K+, Na+ and Cl- while hyper-osmotic stress caused a transient increase in Na+ and a stable accumulation of K+ and Cl-. The tissue content of -dimethylsulphoniopropionate (-dimethylpropiothetin) responded to changes in salinity. The time course of hypersaline stress showed the -dimethylsulophoniopropionate concentration rose as the Na+ level fell. The levels of free sugars and amino acids, including proline, were relatively low in this alga and did not appear to be important in osmotic adjustment. The possibility that tertiary sulphonium dipolar ions have an analogous role in some algae to glycinebetaine and possibly other quaternary nitrogen compounds in higher plants as cytoplasmic osmotica is discussed briefly.Abbreviations DMSP
-dimenthylsulphomiopropionate
- AFT
apparent free space
- TLE
thin layer electrophoresis
- NPS
ninhydrin positive substances
- TLC
thin layer chromatography 相似文献
92.
Influence of free fatty acid anion on the binding of warfarin to cytoplasmic proteins from rat liver
Louise Charest-Boule Saroj Chakrabarti Jules Brodeur 《Chemico-biological interactions》1980,29(1):85-94
In vitro binding studies have shown that warfarin binds strongly to both ligandins (Y) and Z protein obtained from rat liver cytosol with dissociation constants of 11.7 and 10.1 μM respectively. Increasing concentrations of oleate ion significantly increased the dissociation constant of warfarin with either protein, whereas laurate ion showed the same behavior only with Z protein. On the other hand, the binding of warfarin to liver cytoplasmic proteins in vivo was decreased in 72-h-pre-fasted rats, although such fasting failed to produce any increase in the in vivo levels of the cytoplasmic free fatty acids (FFA). However, based on the results of the in vitro binding study, it is suggested that changes in the composition of hepatic cytoplasmic free fatty acids as a result of fasting could reduce the in vivo binding of warfarin to Y and Z proteins and hence could lead to an increase of unbound warfarin in liver cytosol. 相似文献
93.
Proposed replicative role of the NS polypeptide of vesicular stomatitis virus: structural analysis of an electrophoretic variant. 总被引:10,自引:8,他引:2
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The structural lesion in the temperature-sensitive mutant E1 of the New Jersey serotype of vesicular stomatitis virus has been assigned to the NS protein. Although the packaged wild-type and mutant NS proteins were similarly phosphorylated, the mutant NS protein migrated faster than the wild-type NS protein in polyacrylamide slab gels electrophoresed in the presence of sodium dodecyl sulfate. The resolution appears to be the result of conformational rather than size differences since the two proteins comigrated in polyacrylamide gels which contained 4 M urea in addition to sodium dodecyl sulfate. Peptide maps, obtained by limited proteolysis of 32P-labeled wild-type and mutant NS proteins with Staphylococcus aureus V8 protease and papain, revealed striking differences which suggested that the mutant alteration could involve an aspartic or glutamic acid residue. Since NS proteins obtained from naturally occurring revertants of E1 were indistinguishable from the wild-type protein in all of these analyses, the structural alteration in the mutant NS protein correlates with the functional lesion. Because E1 is defective in the RNA replication pathway at the restrictive temperature, a replicative role is proposed for the NS protein. 相似文献
94.
95.
Michel Roberge Gilles Grondin Louise Larose Adrien R. Beaudoin 《Cell and tissue research》1981,220(4):781-786
Summary Stimulation of the exocrine pancreas by the secretagogue urecholine causes degranulation of the acinar cells. Under in vivo conditions, this degranulation is not uniform throughout the tissue. Indeed some of the acini are almost completely depleted of their granules while others display the appearance of resting acini. A noticeable feature is that all the cells of the same acinus display a comparable degree of degranulation. Moreover, groups of neighbouring acini seem to respond simultaneously suggesting that the secretory stimulus is propagated from one acinus to the other. In vitro stimulation of dispersed acini also showed that some of the acini are more responsive than others indicating that this phenomenon can not be attributed to accessibility of the secretagogue to its receptor. These observations lead us to the concept that the response of the pancreatic acinar cell is controlled at the level of the acinus. 相似文献
96.
97.
Louise Prakash 《Molecular & general genetics : MGG》1977,152(2):125-128
Summary Two rad mutants of yeast, rad10 and rad16, are shown to be defective in the removal of UV-induced pyrimidine dimers since DNAs obtained from irradiated cells following a post-irradiation incubation in the dark still retain UV-endonuclease-sensitive sites. Both rad10 and rad16 mutants are in the same pathway of excision-repair as the rad1, rad2, rad3 and rad4 mutants. 相似文献
98.
Summary Post-meiotic segregation (PMS) results in the formation of mixed genotypes from single meiotic products. A method is described in which single members of tetrads are selected, and these are then tested for their genetic homogeneity. The method is applied to Ustilago maydis using crosses which are heteroallelic for nar 1, the structural gene for nitrate reductase. In the absence of PMS, meiotic products containing a nar
+ recombinant are genetically pure (the equivalent of a 6 mutant: 2 wild-type octad). With PMS, a nar
+ recombinant clone arises in association with a nar
- clone and these are otherwise genetically identical (the equivalent of a 7 mutant: 1 wild type octad). The procedure will make it possible to search for mutant strains which are defective in the correction of mismatched bases in hybrid DNA formed during recombination. Among 26 nar
+ recombinants from a control cross, PMS was detected on 3 occasions. In an equivalent cross, both parents were uvs 3, a mutant defective in the excision of pyrimidine dimers from DNA. Among 43 nar
+ recombinants, 7 arose from PMS. Thus the frequency of PMS for the nar alleles is about 15% and the excision of pyrimidine dimers is probably unrelated to the repair of mismatched bases in hybrid DNA. 相似文献
99.
Dye sensitized photo-oxidation inactivates tyrosinases isolated from Neurospora and Agaricus. The rate of inactivation is enhanced by cyanide and is dependent on pH. 相似文献
100.
G J Howlett P W Dickson H Birch G Schreiber 《Archives of biochemistry and biophysics》1982,215(1):309-318
The molecular weights of a number of 125I-labeled plasma proteins have been determined from an analysis of their sedimentation equilibrium behavior in an air-driven ultracentrifuge. The values obtained agree well with results obtained by other methods. Molecular weights obtained for 125I-labeled bovine serum albumin and the rat serum proteins albumin, α1-acid glycoprotein, and major acute-phase α1-protein were unaffected by the addition of 7% rat plasma. Direct evidence for protein-protein interactions was obtained for mixtures of 125I-labeled rat α1-acid glycoprotein and the plant lectin concanavalin A and for mixtures of 125I-labeled protein A from Staphylococcus aureus and 7% rat plasma. Interactions of a different type were observed when the sedimentation equilibrium profiles of 125I-labeled proteins were determined in concentrated solutions of other proteins. Under these conditions the effects of molecular exclusion or nonideality became significant and low estimates were obtained for the molecular weights of the labeled proteins. Analysis of the data obtained for 125I-labeled bovine serum albumin in concentrated solutions of bovine serum albumin (20–80 mg/ ml) yielded nonideality coefficients in good agreement with literature values. Analysis of the behavior of 125I-labeled rat serum albumin, transferrin, and α1-acid glycoprotein yielded nonideality coefficients and hence activities of these proteins in undiluted rat plasma. 相似文献