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1.
Hancai Chen James X. Gray Murali Nayudu Michael A. Djordjevic Michael Batley John W. Redmond Barry G. Rolfe 《Molecular & general genetics : MGG》1988,212(2):310-316
Summary R-prime plasmids were constructed from a derivative of Rhizobium strain NGR234 (ANU280) and were shown to contain overlapping genomic DNA segments involved in biosynthesis of exopolysaccharides (EPS). The R-primes originally constructed carried the mutant allele from Tn5-induced EPS-deficient (Exo–) mutant ANU2811. This plasmid-located mutant allele was dominant to the corresponding wild-type allele as merodiploid strains were Exo–. Exo+ revertants occurred at a low rate (1×10-7) and these were shown to result from double reciprocal recombination events, which led to the isolation of R-prime plasmids carrying functional wild-type exo alleles. R-prime plasmids that carry overlapping segments of DNA from parental strain ANU280 complemented 28 of the 30 group 2 Exo– mutants of strain ANU280. Complementation of these Exo– mutants also restored their symbiotic abilities of effective nodulation. Subsequent in vivo recombination between the wild-type alleles located on the R-prime and the corresponding mutated allele on the genome, was used to generate a new family of R-primes, which carried mutations in the exo genes. The 30 group 2 Exo– mutants were classified into 7 distinct genetic groups based upon complementation and physical mapping data. Five of the seven exo loci were gentically linked and located on a 15-kb region of DNA. Mutations at two loci were dominant only when the mutations were R-prime plasmid-located while a mutation at a second locus was cis-dominant to two other exo loci. At least five genes involved in the synthesis of acidic exopolysaccharide synthesis have been identified. 相似文献
2.
Our recent spin trapping studies of free radical generation by ultrasound in aqueous solutions are reviewed. The very high temperatures and pressures induced by acoustic cavitation in collapsing gas bubbles in aqueous solutions exposed to ultrasound lead to the thermal dissociation of water vapor into H atoms and OH radicals. Their formation has been confirmed by spin trapping. Sonochemical reactions occur in the gas phase (pyrolysis reactions), in the gas-liquid interfacial region, and in the bulk of the solution (radiation-chemistry reactions). The high temperature gradients in the interfacial regions lead to pyrolysis products from non-volatile solutes present at sufficiently high concentrations. The sonochemically generated radicals from carboxylic acids, amino acids, dipeptides. sugars, pyrimidine bases. nucleosides and nucleo-tides were identified by spin trapping with the non-volatile spin trap 3.5-dibromo-2.6-dideuterio-4-nitrosobenzenesulfonate. At low concentrations of the non-volatile solutes. the spin-trapped radicals produced by sonolysis are due to H atom and OH radical reactions. At higher concentrations of these non-volatile solutes, sonolysis leads to the formation of additional radicals due to pyrolysis processes (typically methyl radicals). A preferred localization of non-volatile surfactants (compared to analogous non-surfactant solutes) was demonstrated by the detection of pyrolysis radicals at 500-fold lower concentrations. Pyrolysis radicals were also found in the sonolysis of aqueous solutions containing only certain nitrone spin traps. The more hydrophobic the spin trap, the lower the concentration at which the pyrolysis radicals can be observed. The effect of varying the temperature of collapsing transient cavities in aqueous solutions of different rare gases and of N2O on radical yields and on cell lysis of mammalian cells was investigated. 相似文献
3.
Frederick J. Griffin Carol A. Vines Murali C. Pillai Ryuzo Yanagimachi Gary N. Cherr 《Development, growth & differentiation》1996,38(2):193-202
Polyclonal antibodies were generated to the 105 kDa herring sperm motility initiation factor (SMIF) and used to explore the role of SMIF in sperm-egg interaction. Using sodium dodecyl sulfate polyacrylamide gel electrophoresis and immunoblotting with SMIF antibodies, it was demonstrated that SMIF is present as a minor (4–7% of total chorion protein) component of the chorion. The major polypeptides in the chorion migrated at 117 kDa and in a grouping between 48–54 kDa, with other minor bands above and below. The only detectable glycosylated component was the 105 kDa band, which was resolved at two isoelectric points (8.22 and 8.31) after isoelectric focusing gel electrophoresis. Using antibodies to SMIF, fertilization was blocked, sperm motility was inhibited in vitro in the presence of solubilized SMIF and SMIF binding sites on sperm were localized. Lastly, SMIF was localized to the region of the herring egg that encircles the micropyle. 相似文献
4.
Uma Shankar K. S. Murali R. Uma Shaanker K. N. Ganeshaiah K. S. Bawa 《Economic botany》1996,50(3):270-279
Sustainable extraction of non-timber forest products (NTFPs) depends upon harvesting a small fraction of the total productivity. Over-exploitation can lead to a loss of biodiversity, but a low level of extraction, without value addition at the point of origin, is usually not economically feasible for extractors. Extraction and productivity levels per unit area for most non-timber forest products are unknown, nor do we have much information about value addition at various points in the marketing channels. Here we determine extraction and productivity levels for Amla trees (Phyllanthus emblica), which yield fruits that are used for a wide variety of purposes in preparation of various foods, beverages and medicines. We also present preliminary data on the price appreciation of the fruit for one of the processed products. We have determined that the current level of extraction, 60-80% of all fruits at the population level, may have a negative effect on new recruitment. We present a model for value addition that has the potential to enhance income and reduce the level of extraction. This model is currently being implemented by the Soliga community with the assistance of a non-governmental organization. 相似文献
5.
Effect of temperature on the myoglobin-facilitated transport of oxygen in skeletal muscle.
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An analysis of thermal effects on the facilitative transport of oxygen in skeletal muscle fibers is presented. Steady-state mass and energy transport balances are written and solved analytically or numerically using a finite-difference procedure. It is shown that no significant spatial thermal gradients exist due to internal reactions or bulk conduction effects across a muscle fiber. At typical muscle conditions, it is predicted that increased global temperature reduces the fraction of oxygenated myoglobin, increases local oxygen concentrations, and increases the percentage of oxygen flux attributed to oxy-myoglobin. The maximum supportable oxygen consumption rate, mO2max, is defined as the highest consumption rate sustainable without developing anoxic regions at the center of the fiber. By considering only temperature sensitive effects within fibers, mO2max is found to increase slightly with temperature at low temperatures. This increase is due to thermal effects on the diffusion coefficients as opposed to effects associated with the kinetics of the myoglobin-oxygen reaction. If the simulations include the temperature effect associated with oxygen solubility in blood plasma, mO2max decreases with temperature. A sensitivity analysis was performed by varying the values of relevant parameters. The maximum consumption rate was least affected by parameters associated with the kinetic and equilibrium constants and most affected by the diffusion coefficients and the concentration of myoglobin. 相似文献
6.
Chandra M Tschirgi ML Tardiff JC 《American journal of physiology. Heart and circulatory physiology》2005,289(5):H2112-H2119
How different mutations in cardiac troponin T (cTnT) lead to distinct secondary downstream cellular remodeling in familial hypertrophic cardiomyopathy (FHC) remains elusive. To explore the molecular basis for the distinct impact of different mutations in cTnT on cardiac myocytes, we studied mechanical activity of detergent-skinned muscle fiber bundles from different lines of transgenic (TG) mouse hearts that express wild-type cTnT (WTTG), R92W cTnT, R92L cTnT, and Delta-160 cTnT (deletion of amino acid 160). The amount of mutant cTnT is approximately 50% of the total myocellular cTnT in both R92W and R92L TG mouse hearts and approximately 35% in Delta-160 TG mouse hearts. Myofilament Ca2+ sensitivity was enhanced in all mutant cTnT TG cardiac muscle fibers. Compared with the WTTG fibers, Ca2+ sensitivity increased significantly at short sarcomere length (SL) of 1.9 microm (P < 0.001) in R92W TG fibers by 2.2-fold, in R92L by 2.0-fold, and in Delta-160 by 1.3-fold. At long SL of 2.3 microm, Ca2+ sensitivity increased significantly (P < 0.01) in a similar manner (R92W, 2.5-fold; R92L, 1.9-fold; Delta-160, 1.3-fold). Ca2+-activated maximal tension remained unaltered in all TG muscle fibers. However, tension-dependent ATP consumption increased significantly in Delta-160 TG muscle fibers at both short SL (23%, P < 0.005) and long SL (37%, P < 0.0001), suggesting a mutation-induced change in cross-bridge detachment rate constant. Chronic stresses on relative cellular ATP level in cardiac myocytes may cause a strain on energy-dependent Ca2+ homeostatic mechanisms. This may result in pathological remodeling that we observed in Delta-160 TG cardiac myocytes where the ratio of sarco(endo)plasmic reticulum Ca2+-ATPase 2/phospholamban decreased significantly. Our results suggest that different types of stresses imposed on cardiac myocytes would trigger distinct cellular signaling, which leads to remodeling that may be unique to some mutants. 相似文献
7.
AFN-1252 is a potent inhibitor of enoyl-ACP reductase from Burkholderia pseudomallei—Crystal structure,mode of action,and biological activity
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Krishnamurthy Narasimha Rao Anirudha Lakshminarasimhan Sarah Joseph Swathi U Lekshmi Ming-Seong Lau Mohammed Takhi Kandepu Sreenivas Sheila Nathan Rohana Yusof Noorsaadah Abd Rahman Murali Ramachandra Thomas Antony Hosahalli Subramanya 《Protein science : a publication of the Protein Society》2015,24(5):832-840
Melioidosis is a tropical bacterial infection caused by Burkholderia pseudomallei (B. pseudomallei; Bpm), a Gram-negative bacterium. Current therapeutic options are largely limited to trimethoprim-sulfamethoxazole and β-lactam drugs, and the treatment duration is about 4 months. Moreover, resistance has been reported to these drugs. Hence, there is a pressing need to develop new antibiotics for Melioidosis. Inhibition of enoyl-ACP reducatase (FabI), a key enzyme in the fatty acid biosynthesis pathway has shown significant promise for antibacterial drug development. FabI has been identified as the major enoyl-ACP reductase present in B. pseudomallei. In this study, we evaluated AFN-1252, a Staphylococcus aureus FabI inhibitor currently in clinical development, for its potential to bind to BpmFabI enzyme and inhibit B. pseudomallei bacterial growth. AFN-1252 stabilized BpmFabI and inhibited the enzyme activity with an IC50 of 9.6 nM. It showed good antibacterial activity against B. pseudomallei R15 strain, isolated from a melioidosis patient (MIC of 2.35 mg/L). X-ray structure of BpmFabI with AFN-1252 was determined at a resolution of 2.3 Å. Complex of BpmFabI with AFN-1252 formed a symmetrical tetrameric structure with one molecule of AFN-1252 bound to each monomeric subunit. The kinetic and thermal melting studies supported the finding that AFN-1252 can bind to BpmFabI independent of cofactor. The structural and mechanistic insights from these studies might help the rational design and development of new FabI inhibitors. 相似文献
8.
2H2O (99.8%) Ringer's solution greatly reduces the twitch and tetanus of frog sartorius muscle and, as specially shown here, slows the onset features of the mechanical output of the twitch by: (a) increasing the time (LR) from stimulus to start of latency relaxation; (b) slowing the developmet of the latency relaxation, and (c) greatly decreasing the rate of onset of tension development. These changes reflect effects of 2H2O on excitation-contraction coupling and they represent the critical direct effects of 2H2O on muscle since it does not depress either the action potential or the intrinsic myofibrillar contractility. The increase in LR is attributed to slowed inward electrical propagation in the T-tubule. But the critical effect of 2H2O on frog muscle is to greatly depress mobilization of activator Ca2+. The depression of the Ca2+ mobilization and of its effects on the activation of contraction evidently result from (a) a lowered rate of release of Ca2+ from the sarcoplasmic reticulum, as indicated by the slowed development of the latency relaxation, (b) a decreased amount of Ca2+ released in a twitch, and (c) a reduced speed of diffusion of the Ca2+ to the contractile filaments. The depressed mobilization of Ca2+ is apparently the essential cause of 2H2O's general depression of twitch and tetanus output. 相似文献
9.
Ravi babu. Kalahasthi Rajmohan. Hirehal Raghavendra rao Rajan. Bagalur Krishna murthy 《Biomarkers》2013,18(3):241-249
The objectives were to investigate the plasma lipid peroxidation and erythrocyte antioxidants status in workers exposed to nickel. The study groups comprised 69 nickel plating workers and 50 office workers residing in the same city, but away from the place of work of the study group subjects, considered as control group. Urinary nickel concentration was determined by graphite furnace atomic absorption spectrophotometry. The plasma lipid peroxidation and erythrocyte antioxidants were measured by spectrophotmetric methods. The plasma lipid peroxidation level was significantly increased in nickel-platers and their helpers as compared with controls. Erythrocyte antioxidants were significantly decreased in the nickel-platers compared with the controls. The level of plasma lipid peroxidation was positively and erythrocyte antioxidants were negatively and significantly correlated with the urine nickel levels. Multiple regression analysis assessed the oxidative stress associated with nickel and other potential confounding factors such as body mass index, the consumption of green vegetables, coffee, tea, smoking and alcohol consumption. Analysis showed that the lifestyle confounding factors: the consumption of green vegetables, smoking and alcohol, were not significantly associated with oxidative stress. The exposure to nickel, body mass index and coffee consumption were significantly associated with oxidative stress. The results show that the increased plasma lipid peroxidation and decreased erythrocyte antioxidants levels observed in nickel-exposed workers could be used as biomarkers of oxidative stress. 相似文献
10.