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81.
Adaptation to salt in the cyanobacterium Nostocmuscorum, is composed of a few mechanisms which together lead to the generation of a salt-tolerant cell. The initial mechanism combines a stimulation of photosynthetic activity with the accumulation of sucrose as an osmoregulator. The secondary mechanism involves the adaptation of N2 fixation activity and protein biosynthesis. The adaptation is most efficient in response to NaCl-induced stress and functions only partially under stress induced by either KCl or a nonionic osmoticum such as mannitol. 相似文献
82.
Rachel Gabbay-Azaria Mordechay Schonfeld Shoshana Tel-Or Rachel Messinger Elisha Tel-Or 《Archives of microbiology》1992,157(2):183-190
Intracellular ion concentration and respiratory activity in the marine cyanobacterium Spirulina subsalsa was analyzed during cell transition from saline to hypersaline medium. During salt upshock, an early phase of Na+ and Cl- influx was observed, followed by an adaptation phase where both Na+ and Cl- were excluded from the cell. Respiration in intact cells was enhanced during salt upshock. S. subsalsa spheroplasts exhibited a high rate of O2 uptake, which was further enhanced in cells grown in hypersaline medium, upon addition of NaCl to the assay mixture. This effect was found to be specific to sodium ions. Plasma membrane fractions from cells grown in hypersaline medium exhibited a high rate of cytochrome oxidase activity, which was further stimulated by NaCl, and was sensitive to DCCD. Immunoblot analysis of Spirulina plasma membrane polypeptides with anti-cytochrome oxidase serum demonstrated high content of 53.4 kDa polypeptide of cytochrome oxidase, which was enriched in membranes obtained from hypersaline Spirulina cells. The enhanced respiration, and more specifically the enrichment of cytochrome oxidase activity in salt-adapted cells in situ, as well as its stimulation by NaCl in vitro and inhibition by DCCD, suggest that cytochrome oxidase is involved in the extrusion of sodium ions from cells of the salt-tolerant Spirulina subsalsa.Abbreviations DCCD
dicyclohexylcarbodiimide
- CCCP
carbonylcyanide m-chlorophenyl hydrazone
- TMPD
N, N, N, N, tetramethyl p-phenylenediamine dichloride 相似文献
83.
Manganese nutrition effects on tomato growth, chlorophyll concentration, and superoxide dismutase activity 总被引:2,自引:0,他引:2
The effects of Mn nutrition of tomato (Lycopersicon esculentum Mill.) seedlings on Mn-, Fe- and CuZn-superoxide dismutase (SOD, EC 1.15.1.1) enzymatic activities, metal translocation, chlorophyll concentration, and plant growth were tested using a bioassay system consisting of chelator-buffered nutrient culture with Mn2+ activities set to pMn (-log activity of Mn2+) of 6.6, 7.6, 8.6, and 9.6. The two middle levels resulted in optimal plant growth, whereas the two extreme levels resulted in a gradual decrease in chlorophyll concentration and slower plant growth. At the end of the experiment, 26 days after transfer to the Mn treatments, significant differences in shoot Mn concentration were manifested, from 10.5 mg kg(-1) in plants grown in pMn 9.6 to 207.4 mg kg(-1) in plants grown in pMn 6.6. Other element concentrations in the leaf suggest that growth inhibition and chlorophyll synthesis were affected primarily by manganese deficiency and excess. Twenty days after transfer of plants to the Mn treatments Mn-, Fe- and CuZn-SOD activities were assayed in young expanded leaf tissues by electrophoresis running gel. Whereas chloroplastic CuZn-SOD activity did not differ among Mn treatments, the cytosolic CuZn-SOD and mitochondrial Mn-SOD activities increased in both Mn-excess and Mn-deficient plants. 相似文献
84.
Elisha P. Renne 《Medical anthropology quarterly》2001,15(1):127-129
. Plague of Paradoxes: AIDS, Culture, and Demography in Northern Tanzania. Philip W. Setel. Chicago: University of Chicago Press, 1999.308 pp. 相似文献
85.
86.
Janina Braatz Hans-Joachim Harloff Nazgol Emrani Chirlon Elisha Lars Heepe Stanislav N. Gorb Christian Jung 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2018,131(4):959-971
Key message
This study elucidates the influence of indehiscent mutations on rapeseed silique shatter resistance. A phenotype with enlarged replum-valve joint area and altered cell dimensions in the dehiscence zone is described.Abstract
Silique shattering is a major factor reducing the yield stability of oilseed rape (Brassica napus). Attempts to improve shatter resistance often include the use of mutations in target genes identified from Arabidopsis (Arabidopsis thaliana). A variety of phenotyping methods assessing the level of shatter resistance were previously described. However, a comparative and comprehensive evaluation of the methods has not yet been undertaken. We verified the increase of shatter resistance in indehiscent double knock-down mutants obtained by TILLING with a systematic approach comparing three independent phenotyping methods. A positive correlation of silique length and shatter resistance was observed and accounted for in the analyses. Microscopic studies ruled out the influence of different lignification patterns. Instead, we propose a model to explain increased shattering resistance of indehiscent rapeseed mutants by altered cell shapes and sizes within the contact surfaces of replum and valves.87.
Michael J. Pocklington John R. Jenkins Elisha Orr 《Molecular & general genetics : MGG》1990,220(2):256-260
Summary Low concentrations of novobiocin are toxic to permeable yeast cells, but do not inhibit type II topoisomerase activity. Furthermore, the enzyme does not bind specifically to novobiocin-Sepharose. These observations are in agreement with genetical analyses. Mutations at a single locus that confer novobiocin resistance and temperature sensitivity exhibit a similar phenotype to cells treated with novobiocin, but are not topoisomerase II mutants. 相似文献
88.
89.
Experimental investigation of protein structure and dynamics by spectroscopic methods using external probes requires attachment of a probe to a well-defined site and preparation of pure samples. Measurements of efficiency of nonradiative excitation energy transfer can yield very detailed information about the structure of proteins, provided that two different probes are selectively attached to well-defined sites. We have used specific protection of ε-amino groups using tert-butylazidoformate at high pH for covalent attachment of the fluorescent probe 2-naphthoxyacetic acid at the α-amino group of bovine pancreatic trypsin inhibitor (BPTI). The product is a chromatoraphically homogenous protein derivative that contains the probe at a dye to protein ratio of 1:1, specifically located at the N-terminus, and and that retains its full biological activity. The HPLC tryptic peptide map of BPTI has been analyzed, and all the peptide fragments have been identified. Analysis of tryptic fragments of the labled BPTI derivative showed that it was selectively labeled at the N-terminal amino acid. The probe absorbs in the 310–325-nm range, which is spectrally distinct from the absorption of the protein, and has a monoexponetial fluorescence decay. These and other charactristics make this probe a good energy donor in transfer-efficiency measurements. 相似文献
90.
The mechanism of iron uptake in the chrysophyte microalga Dinobryon was studied. Previous studies have shown that iron is the dominant limiting elements for growth of Dinobryon in the Eshkol reservoir in northern Israel, which control its burst of bloom. It is demonstrated that Dinobryon has a light-stimulated ferrireductase activity, which is sensitive to the photosynthetic electron transport inhibitor DCMU and to the uncoupler CCCP. Iron uptake is also light-dependent, is inhibited by DCMU and by CCCP and also by the ferrous iron chelator BPDS. These results suggest that ferric iron reduction by ferrireductase is involved in iron uptake in Dinobryon and that photosynthesis provides the major reducing power to energize iron acquisition. Iron deprivation does not enhance but rather inhibits iron uptake contrary to observations in other algae. 相似文献