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101.
Biochemical similarity among serologically distinct flagellins of Campylobacter jejuni 总被引:1,自引:0,他引:1
Irving Nachamkin Ruth-Hogue Angeletti Michael B. Prystowsky 《FEMS microbiology letters》1988,51(2-3):149-152
Abstract We describe a simplified method for obtaining highly purified flagellin, suitable for biochemical analysis using HPLC-gel permeation. Amino acid composition and N-terminal sequence analyses were performed on flagellins from serologically distinct isolates. The amino acid composition of flagellin from 10 strains was very similar. The N-terminal amino acid sequence is highly conserved. Significant sequence homology was found with flagellin of Bacillus subtilis . 相似文献
102.
G.W. Skyring 《FEMS microbiology letters》1988,53(2):87-94
Abstract Simultaneous measurements of sulfate reduction and acetate oxidation using 35 S and 14 C tracers showed that acetate was the main energy substrate for the sulfate-reducing bacteria in Lake Eliza sediments. Sulfate reduction rates calculated from acid-volatile sulfide data only, correlated with acetate oxidation at around 0.5:1. However, the rates calculated from acid-volatile plus pyrite sulfur data correlated with acetate oxidation at a ratio of around 1:1. Molybdate completely inhibited sulfate reduction but acetate oxidation was not totally inhibited. From 10 to 15% of acetate oxidation was not attributable to the sulfate-reducing bacteria. There was rapid accumulation of acetate, within the first 12 h of incubation. Acetate, propionate and butyrate accumulated in the presence of molybdate. 相似文献
103.
H. S. Bachelard R. S. Badar-Goffer K. J. Brooks S. J. Dolin P. G. Morris 《Journal of neurochemistry》1988,51(4):1311-1313
We report the first measurement of the free intracellular calcium level in an actively metabolising intact cerebral tissue preparation. To this end, we applied the recently developed 19F-nuclear magnetic resonance calcium chelator, 5,5'-F2-1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (5FBAPTA), in superfused cerebral cortical slices to give values for the intracellular Ca2+ concentration of 350 and 480 nM, at external calcium concentrations of 1.2 and 2.4 mM, respectively. Under both conditions, the intracellular Ca2+ concentration was increased by depolarisation using a high external K+ concentration. Interleaved 31P spectra showed that the presence of the 5FBAPTA had a deleterious effect on the metabolic state of the tissue with an external Ca2+ concentration of 1.2 mM, but normal viability was maintained using 2.4 mM. 相似文献
104.
Aromatic l-Amino Acid Decarboxylase Activity of the Rat Retina Is Modulated In Vivo by Environmental Light Maria Hadjiconstantinou 总被引:3,自引:1,他引:2
Zvani Rossetti Christopher Silvia Dimitrij Krajnc Norton H. Neff 《Journal of neurochemistry》1988,51(5):1560-1564
Aromatic L-amino acid decarboxylase (AAAD) activity of rat retina is low in animals placed in the dark. When the room lights are turned on, activity rises for almost 3 h and reaches values that are about twice the values found in the dark. A study of the kinetics of the enzyme revealed that the apparent Km values for L-3,4-dihydroxyphenylalanine and pyridoxal-5'-phosphate were unchanged in light- and dark-exposed animals, whereas the Vmax increased in the light. Treating the animals with cycloheximide before exposure to light prevented the increase of enzyme activity. Immunotitration with antibodies to AAAD suggested that more enzyme molecules are present in the light than in the dark. When the room lights are turned off AAAD activity drops rapidly at first and then more slowly, suggesting that at least two processes are responsible for the fall of enzyme activity. Exposure to short periods of dark followed by light results in a rapid increase of AAAD activity. Mixing homogenates from light- and dark-exposed rats results in activity values that are less than expected, suggesting the presence of an endogenous inhibitor(s). These studies demonstrate that AAAD activity is modulated in vivo. 相似文献
105.
Preincubation of brain membranes with phospholipase A2 (PLA2) has been shown previously to affect the binding characteristics of various recognition sites associated with the gamma-aminobutyric acid (GABA) receptor complex. In the present study, we have investigated the effects of PLA2 (from Naja naja siamensis venom) on the functional activity of the GABA receptor/chloride ion channel. PLA2 (0.001-0.02 U/mg protein) preincubation decreased pentobarbital-induced 36Cl- efflux and muscimol-induced 36Cl- uptake in rat cerebral cortical synaptoneurosomes. The effect of PLA2 was prevented by EGTA and two nonselective PLA2 inhibitors, mepacrine and bromophenacyl bromide. The removal of free fatty acids by addition of bovine serum albumin both prevented and reversed the effect of PLA2. Products of the catalytic activity of PLA2, such as the unsaturated free fatty acids, arachidonic and oleic acids, mimicked the effect of PLA2. However, the saturated fatty acid, palmitic acid, and lysophosphatidyl choline had no effect on pentobarbital-induced 36Cl- efflux. Because unsaturated free fatty acids are highly susceptible to peroxidation by oxygen radicals, the role of oxygen radicals was investigated. Xanthine plus xanthine oxidase, a superoxide radical generating system, mimicked the effect of PLA2, whereas the superoxide radical scavenger, superoxide dismutase, diminished the effects of PLA2 and arachidonic acid on pentobarbital-induced 36Cl- efflux. Similarly, the effect of PLA2 was also inhibited by methanol (1 mM), a scavenger of the hydroxyl radical, and by catalase. These data indicate that exogenously added PLA2 induces alterations in membrane phospholipids, possibly promoting the generation of oxygen radicals and fatty acid peroxides which can ultimately modulate GABA/barbiturate receptor function in brain. 相似文献
106.
Dale L. Birkle Pawels Kurian Pierre Braquet Nicolas G. Bazan 《Journal of neurochemistry》1988,51(6):1900-1905
We have investigated the effects of the specific platelet-activating factor (PAF; 1-alkyl-2-acetyl-glycerophosphocholine) antagonist BN52021 on free fatty acid (FFA) and diacylglycerol (DG) accumulation and on the loss of fatty acids from phosphatidylinositol-4,5-bisphosphate (PIP2) in mouse brain. Mice were pretreated with BN52021 (10 mg/kg, i.p.) 30 min before electroconvulsive shock (ECS) or postdecapitation ischemia. These procedures cause rapid breakdown of PIP2 and accumulation of FFA and DG. Lipid extracts were prepared from microwave-fixed cerebrum and fractionated by TLC, and the fatty acid methyl esters were prepared by methanolysis and quantified by capillary GLC. In saline or vehicle (dimethyl sulfoxide)-treated mice, ECS caused marked accumulation of FFA and DG and loss of mainly stearic (18:0) and arachidonic (20:4) acids from PIP2. BN52021 pretreatment of ECS-treated mice decreased the accumulation of free palmitic (16:0), 18:0, 20:4, and docosahexaenoic (22:6) acids with no effect on the fatty acids in DG or the loss of PIP2. BN52021 had no effect on basal levels of FFA, DG, or PIP2. One minute of postdecapitation ischemia induced PIP2 loss and accumulation of FFA and DG. BN52021 attenuated the accumulation of free 20:4 and 22:6 acids, decreased the content of oleic (18:1), 20:4, and 22:6 acids in DG, but had no effect on PIP2 loss. These data indicate that BN52021 reduces the injury-induced activation of phospholipase A2 and lysophospholipase, which mediate the accumulation of FFA in brain, while having a negligible effect on phospholipase C-mediated degradation of PIP2. 相似文献
107.
Significant differences in the thermal stability of benzodiazepine receptors were found in cerebral cortical membranes prepared from the long-sleep (LS) and short-sleep (SS) selected mouse lines. Thus, benzodiazepine receptors from LS mice were heat inactivated (55 degrees C) at a significantly faster rate than those from SS mice. Although gamma-aminobutyric acid (GABA) reduced the rate of heat inactivation in both lines, the more rapid rate of inactivation in the LS line was maintained. Furthermore, the potency of GABA to enhance [3H]flunitrazepam binding decreased threefold in membranes from LS mice as the incubation temperature was increased from 0 degrees to 37 degrees C, but was unaltered in membranes from SS mice. These differences in the biophysical properties of the benzodiazepine/GABA receptor chloride channel complex ("supramolecular complex"), together with a higher KD for t-[35S]butylbicyclophosphorothionate in membranes from LS compared to SS mice, suggest that the supramolecular complex may modulate the differential sensitivity to some depressants and convulsants in these lines. 相似文献
108.
109.
The biology of mycorrhiza in the Ericaceae 总被引:6,自引:4,他引:2
110.
High temperature (45°C) inhibits seed germinition and seedling sunflower ( Helianthus annuus L. cv. Mirasol). Treatment of imbibed seeds at 45°C for more than 48 h induces a secondary dormancy, which is associated with progressive decrease of germination ability at optimal temperature (25°C) as well as with abnormal seedling growth. Ethylene (55μl l−1 ) and 2-chloroethylphosphonic acid (ethephon) (2.5 m M ) improve germination of thermodormant seeds at 25°C. but the abnormal growth of the seedlings remains. O2 -enriched atmosphere and dry storage improve germination and normal seedling growth. The induction of thermodormancy in sunflower seeds seems associated with loss of their ability to convert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene. Possible effects of high temperature on membranes and ethylene forming enzyme (EFE) are discussed. 相似文献