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991.
Asparagine was a superior nitrogen source for clavine-alkaloid production in Claviceps purpurea. Its transport into the cell excedded the cell's biosynthetic need for this amino acid. Asparagine entered the cell without degradation. This disturbed the relative pool sizes of various amino acids resulting in a change in the genetically determined ratio at which amino acids were utilized for protein synthesis. Overproduction of alkaloids (4500 mug.ml-1) may be associated with increased availability of tryptophan because of the enhanced assimilation of asparagine-derived ammonia via glutamine synthetase (EC 6.3.1.2). However, ammonium salts in the fermentation broth led to a depression of the alkaloid yield. Partial replacement of the ammonium salt by aspartic acid elevated alkaloid production. 相似文献
992.
H. Dave C. Ramakrishna B. D. Bhatt J. D. Desai 《World journal of microbiology & biotechnology》1994,10(6):653-656
Slop oil, i.e. waste oil from a petrochemical complex, contains at least 240 hydrocarbon components, of which 54% are from C5 to C11 and the rest from C12 to C23. Of 22 isolated bacterial cultures that were able to degrade slop oil, seven could each degrade about 40% of the slop oil, and a mixture of all seven could degrade 50% in liquid medium. Bioaugmentation of soil contaminated with slop oil with the mixed bacterial culture gave up to 70% degradation of slop oil after 30 days. This compares with 40% degradation without bioaugmentation. Bioaugmentation led to a significant increase in counts of bacteria able to degrade slop oil. Wheat sown on bioaugmented soil germinated and grew better than on non-augmented soil and led to increased degradation of slop oil (up to 80%). This indicates the potential of mixed culture for bioremediation. 相似文献
993.
R. S. Jadhav N. V. Thaker A. Desai 《World journal of microbiology & biotechnology》1994,10(3):360-361
An iron-inefficient variety of peanut plant, when grown hydroponically with the catechol siderophore of Rhizobium (peanut isolate), showed increased growth and chlorophyll content compared with plants grown with Fe alone. The siderophore, when used in concentrations less than the concentrations of Fe, was still effective in grwoth promotion, indicating that it might function as a shuttle agent, solubilizing and supplying Fe to the plant. Similar results were also obtained with desferrioxamine B.The authors are with the Department of Microbiology and Biotechnology Centre, Faculty of Science, M.S. University of Baroda, Baroda-390 002, Gujarat, India. 相似文献
994.
Shyamali Mukherjee Sukla Ghos Lisa Rodgers Tultul Nayyar Usha Desai Salil K. Das 《Journal of biochemical and molecular toxicology》1994,9(1):1-7
Toxic oil syndrome (TOS) is caused by ingestion of denatured edible oils. Even though the etiology and pathogenesis of this disease are not fully known, it is quite clear that generation of free radicals caused by ingestion of fatty acid anilides is responsible for the pathogenetic mechanism in many TOS patients. Fatty acid anilides may also alter the free radical status of lungs and erythrocytes; this possibility may shed some light on understanding toxic oil syndrome. The present study describes the effects of oral administration of fatty acid anilides on the activities of major enzymes involved in the oxygen defense systems of lungs and erythrocytes. Feeding fatty acid anilides caused an increase in the superoxide dismutase (SOD) activity in erythrocytes, whereas it caused a decrease in the SOD activity in lungs. GSH-Px activity was not significantly changed in erythrocytes but was decreased in lungs. Although the activity of catalase was increased only by a higher dose in the erythrocytes, it was not affected in the lung at any dosage. Even though the ingestion of fatty acid anilides caused an increase in the SOD activity in the erythrocytes and a decrease in the SOD activity in the lungs, there was an increase in the lipid peroxidation in both cases. The increase in lipid peroxidation in erythrocytes is probably caused by the accumulation of H2O2, and that in the lungs is due to the accumulation of superoxide anion. 相似文献
995.
Beneficial mutation selection balance and the effect of linkage on positive selection 总被引:3,自引:0,他引:3
When beneficial mutations are rare, they accumulate by a series of selective sweeps. But when they are common, many beneficial mutations will occur before any can fix, so there will be many different mutant lineages in the population concurrently. In an asexual population, these different mutant lineages interfere and not all can fix simultaneously. In addition, further beneficial mutations can accumulate in mutant lineages while these are still a minority of the population. In this article, we analyze the dynamics of such multiple mutations and the interplay between multiple mutations and interference between clones. These result in substantial variation in fitness accumulating within a single asexual population. The amount of variation is determined by a balance between selection, which destroys variation, and beneficial mutations, which create more. The behavior depends in a subtle way on the population parameters: the population size, the beneficial mutation rate, and the distribution of the fitness increments of the potential beneficial mutations. The mutation-selection balance leads to a continually evolving population with a steady-state fitness variation. This variation increases logarithmically with both population size and mutation rate and sets the rate at which the population accumulates beneficial mutations, which thus also grows only logarithmically with population size and mutation rate. These results imply that mutator phenotypes are less effective in larger asexual populations. They also have consequences for the advantages (or disadvantages) of sex via the Fisher-Muller effect; these are discussed briefly. 相似文献
996.
Evolution can favor antagonistic epistasis 总被引:2,自引:2,他引:0
The accumulation of deleterious mutations plays a major role in evolution, and key to this are the interactions between their fitness effects, known as epistasis. Whether mutations tend to interact synergistically (with multiple mutations being more deleterious than would be expected from their individual fitness effects) or antagonistically is important for a variety of evolutionary questions, particularly the evolution of sex. Unfortunately, the experimental evidence on the prevalence and strength of epistasis is mixed and inconclusive. Here we study theoretically whether synergistic or antagonistic epistasis is likely to be favored by evolution and by how much. We find that in the presence of recombination, evolution favors less synergistic or more antagonistic epistasis whenever mutations that change the epistasis in this direction are possible. This is because evolution favors increased buffering against the effects of deleterious mutations. This suggests that we should not expect synergistic epistasis to be widespread in nature and hence that the mutational deterministic hypothesis for the advantage of sex may not apply widely. 相似文献
997.
Staines HM Alkhalil A Allen RJ De Jonge HR Derbyshire E Egée S Ginsburg H Hill DA Huber SM Kirk K Lang F Lisk G Oteng E Pillai AD Rayavara K Rouhani S Saliba KJ Shen C Solomon T Thomas SL Verloo P Desai SA 《International journal for parasitology》2007,37(5):475-482
The altered permeability characteristics of erythrocytes infected with malaria parasites have been a source of interest for over 30 years. Recent electrophysiological studies have provided strong evidence that these changes reflect transmembrane transport through ion channels in the host erythrocyte plasma membrane. However, conflicting results and differing interpretations of the data have led to confusion in this field. In an effort to unravel these issues, the groups involved recently came together for a week of discussion and experimentation. In this article, the various models for altered transport are reviewed, together with the areas of consensus in the field and those that require a better understanding. 相似文献
998.
Reduced pepsin A processing of sonic hedgehog in parietal cells precedes gastric atrophy and transformation 总被引:1,自引:0,他引:1
Zavros Y Waghray M Tessier A Bai L Todisco A L Gumucio D Samuelson LC Dlugosz A Merchant JL 《The Journal of biological chemistry》2007,282(46):33265-33274
Sonic hedgehog (Shh) is not only essential to the development of the gastrointestinal tract, but is also necessary to maintain the characteristic acid-secreting phenotype of the adult stomach. Gastrin is the only hormone capable of stimulating gastric acid and is thus required to maintain functional parietal cells. We have shown previously that gastrin-null mice display gastric atrophy and metaplasia prior to progression to distal, intestinal-type gastric cancer. Because reduced levels of Shh peptide correlate with gastric atrophy, we examined whether gastrin regulates Shh expression in parietal cells. We show here that gastrin stimulates Shh gene expression and acid-dependent processing of the 45-kDa Shh precursor to the 19-kDa secreted peptide in primary parietal cell cultures. This cleavage was blocked by the proton pump inhibitor omeprazole and mediated by the acid-activated protease pepsin A. Pepsin A was also the protease responsible for processing Shh in tissue extracts from human stomach. By contrast, extracts prepared from neoplastic gastric mucosa had reduced levels of pepsin A and did not process Shh. Therefore processing of Shh in the normal stomach is hormonally regulated, acid-dependent, and mediated by the aspartic protease pepsin A. Moreover parietal cell atrophy, a known pre-neoplastic lesion, correlates with loss of Shh processing. 相似文献
999.
Receptor for advanced glycation end products expression on T cells contributes to antigen-specific cellular expansion in vivo 总被引:1,自引:0,他引:1
Moser B Desai DD Downie MP Chen Y Yan SF Herold K Schmidt AM Clynes R 《Journal of immunology (Baltimore, Md. : 1950)》2007,179(12):8051-8058
Receptor for advanced glycation end products (RAGE) is an activation receptor triggered by inflammatory S100/calgranulins and high mobility group box-1 ligands. We have investigated the importance of RAGE on Ag priming of T cells in murine models in vivo. RAGE is inducibly up-regulated during T cell activation. Transfer of RAGE-deficient OT II T cells into OVA-immunized hosts resulted in reduced proliferative responses that were further diminished in RAGE-deficient recipients. Examination of RAGE-deficient dendritic cells did not reveal functional impairment in Ag presentation, maturation, or migratory capacities. However, RAGE-deficient T cells showed markedly impaired proliferative responses in vitro to nominal and alloantigens, in parallel with decreased production of IFN-gamma and IL-2. These data indicate that RAGE expressed on T cells is required for efficient priming of T cells and elucidate critical roles for RAGE engagement during cognate dendritic cell-T cell interactions. 相似文献
1000.
Sherri Sheinfeld Gorin Alfred R Ashford Rafael Lantigua Manisha Desai Andrea Troxel Donald Gemson 《Implementation science : IS》2007,2(1):1-6