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81.
Michael Gjedde Palmgren Marianne Sommarin Peter Ulvlskov Peter Leth Jørgensen 《Physiologia plantarum》1988,74(1):11-19
Plasma membrane vesicles were purified from 8-day-old oat ( Avena sativa L. cv. Brighton) roots in an aqueous polymer two-phase system. The plasma membranes possessed high specific ATPase activity [ca 4 μmol P1 (mg protein)−1 min−1 at 37°C]. Addition of lysophosphatidylcholine (lyso-PC) produced a 2–3 fold activation of the plasma membrane ATPase, an effect due both to exposure of latent ATP binding sites and to a true activation of the enzyme. Lipid activation increased the affinity for ATP and caused a shift of the pH optimum of the H+ -ATPase activity to 6.75 as compared to pH 6.45 for the negative H+ -ATPase. Activation was dependent on the chain length of the acyl group of the lyso-PC, with maximal activition obtained by palmitoyl lyso-PC. Free fatty acids also activated the membrane-bound H+ -ATPase. This activation was also dependent on chain length and to the degree of unsaturation, with linolenic and arachidonic acid as the most efficient fatty acids. Exogenously added PC was hydrolyzed to lyso-PC and free fatty acids by an enzyme in the plasma membrane preparation, presumably of the phospholipase A type. Both lyso-PC and free fatty acids are products of phospholipase A2 (EC 3.1.1.4) action, and addition of phospholipase A2 from animal sources increased the H+ -ATPase activity within seconds. Interaction with lipids and fatty acids could thus be part of the regulatory system for H+ -ATPase activity in vivo, and the endogenous phospholipase may be involved in the regulation of the H+ -ATPase activity in the plasma membranne. 相似文献
82.
In the subarctic moss Dicranum elongatum Schleich & Schwaegr., the level of total lipids and triacylglycerols (TAG) was high in late winter and spring and low in autumn and winter. Four-week exposure of field material to continuous light (135μmol m−2 s−1 ) at 1°C resulted in a considerable increase in the amount of TAG in the autumn material acclimated to low temperatures and rhythmic light in the field. In contrast, the same treatment did not cause any increase in TAG in the spring material, acclimated to low temperatures and continuous light in the field. Results from experiments, in which moss cultivated for 4 months at 9°C on 12-h photoperiods (135μmol m−2 s−1 ) was kept for 3 weeks at low temperatures (9°C and −3°C) either in continuous light (135 or 70 μmol m−2 s−1 ) or with 12-h photoperiods (135 μmol m−2 s−1 ), indicated that the TAG level was higher at higher light intensity. At 9°C it was also higher in continuous light of both intensities than in rhythmic light. These results strongly suggest that decreasing irradiance and decreasing daylength limits the accumulation of TAG in D. elongatum during autumn in the subarctic. 相似文献
83.
Cholesterol and cholesteryl ester concentrations and cholesteryl ester fatty acid substituents have been measured during the first 10 weeks of life in tissues of normal and dystrophic mice. In normal Swiss and 129ReJ(+/?) mice the concentrations of both cholesterol and cholesteryl esters remain essentially constant in liver, increase in brain and fall sharply in both thigh (mixed fiber type muscles) and chest muscles (predominantly slow oxidative muscles) over this period. In all cases the concentration of free cholesterol exceeds that of esterified cholesterol. In dystrophic mice, similar patterns are found in brain and liver. In both thigh and chest muscles, however, the developmental pattern is significantly different. After an initial decrease the concentrations of cholesterol and cholesteryl esters increase rapidly with the largest increase occurring in the concentration of cholesteryl esters which by 10 weeks of age exceeds the concentration of cholesterol in chest muscle. During the same period the pattern of esterified fatty acids changes gradually in dystrophic tissues towards an increasing ratio of unsaturated/saturated fatty acids. By 10 weeks of age this ratio is significantly higher in dystrophic tissues than normal in all tissues tested. 相似文献
84.
Brian Rodrigues Michael R. Spooner David L. Severson 《Molecular and cellular biochemistry》1992,116(1-2):33-37
An exogenous [3H]triolein emulsion was hydrolyzed by intact cardiac myocytes with functional LPL located on the cell surface. This surface-bound LPL could be released into the medium when cardiac myocytes were incubated with heparin. Incubation of cardiac myocytes with VLDL, or the products of TG breakdown, oleic acid or 2-monoolein, did not increase LPL activity in the medium. However, incubation of cardiac myocytes with either VLDL or oleic acid for > 60 min did reduce heparin-releasable LPL activity. In the heart, this inhibitory effect of FFA could regulate the translocation of LPL from its site of synthesis in the cardiac myocyte to its functional site at the capillary endothelium.Abbreviations LPL
lipoprotein lipase
- TG
triacylglycerol
- FFA
free fatty acids
- VLDL
very-low density lipoprotein 相似文献
85.
R. J. de Antueno R. C. Cantrill Y. -S. Huang S. K. Raha M. Elliot D. F. Horrobin 《Molecular and cellular biochemistry》1992,116(2):153-161
The present study examines the time dependent effects of n-6 and n-3 polyunsaturated fatty acids on liver microsomal lipid metabolism in FVB mice fed a diet supplemented with a mixture of free fatty acids (mainly 18:3n-6 and 20:5n-3) at 25 mg/g diet. Significant changes in the fatty acid composition of total liver and microsomal lipids were observed after 7 days on the diets. Thereafter, some animals remained on the same diet while others were fed a diet supplemented with hydrogenated coconut oil (HCO). With the exception of 20:5n-3 which showed a slower recovery, establishment of the HCO pattern was rapid indicating that the diet-induced changes could be easily reversed. The unsaturation index, the cholesterol/phospholipid ratio and the microviscosity of the microsomal membranes were not affected by these dietary manipulations. Unsaturated fatty acid supplementation reduced the activity of 9 desaturase by 50%. Feeding the HCO diet to mice previously fed the EPA/GLA diet led to a progressive increase in 9 desaturase activity, reaching 80% of the day zero values after 14 days. The monoene content of hepatic total lipids reflected, in most cases, the changes in enzyme activity. This study shows that a low dose of a n-3 and n-6 free fatty acid mixture increases the quantities of members of the n-3 family, without loss of n-6 fatty acids in microsomal membranes and modifies the activity of 9 desaturase without altering the microsome physicochemical parameters. 相似文献
86.
Kiyoshi Terao Emiko Ito Motoko Oarada Misako Ohkusu Katsukiyo Yazawa Yuzuru Mikami Kazuei Igarashi 《Mycopathologia》1992,119(2):115-125
An exotoxin (HS-6) produced by Nocardia otitidiscaviarum isolated from certain lesions of cutaneous nocardiosis of a male 82-year-old patient induced severe injuries in the pancreas, liver, stomach, small intestine, heart, thymus and kidney of male ICR mice. Mice given Nocardia-free preparation of HS-6 at a dose of 1 mg/kg of body weight developed several autophagic vacuoles in the pancreas and liver within 20 min after the i.p. injection. Thereafter, the autophagic vacuoles increased in number and size with time. About 24 hr after the administration of HS-6, the liver showed marked accumulation of fat droplets in the cytoplasm of the hepatocytes. Although they contained abundant autophagic vacuoles in the regions of RER, there were no lipomatoses in the acinar cells of the pancreas, those of the chief cells and smooth muscle cells of the stomach, Paneth cells, goblet cells, smooth muscle cells of the small intestine, and plasma cells in the digestive tract. Biochemical examinations revealed that HS-6 had no significant effect on the protein synthesis of reticulocytes. Inoculation of the Nocardia into the mouse peritoneal cavities caused marked granulomatoses in the pancreas, liver and regional lymph nodes, but did not develop autophagic vacuoles in RER regions of these organs. 相似文献
87.
The utilization of some amino acids, added at 1 mM and 10 mM concentrations, as the sole combined nitrogen sources by Frankia sp. strain CpI1, has been investigated. Glutamine, like NH
4
+
, provided rapid growth without N2 fixation. Histidine at 1 mM yielded poor N2-fixing activity but better cell growth than N2. Aspartate, glutamate, alanine, proline, each at 1 mM concentration, supported similar levels of N2 fixation and growth. Growth on 10 mM glutamate, proline, or histidine resulted in poor N2-fixing activity and poor cell growth. Cells grown on 10 mM alanine had about half the N2-fixing activity of cells grown on N2 but growth was good. Aspartate at 10 mM concentration, however, stimulated N2-fixing activity dramatically and promoted faster growth. Enzyme analysis suggested that asparate is catabolized by glutamate-oxaloacetate transaminase (GOT), since GOT specific activity was induced, and aspartase activity was not detected, in cells grown on aspartate as the sole combined nitrogen source. Thinlayer chromatography (TLC) of metabolites extracted from N2-grown cells fed with [14C]-aspartate showed that label was rapidly accumulated mainly on aspartate and/or glutamate, depending on the cells' physiological state, without detectable labeling on fumarate or oxaloacetate (OAA). These findings provide evidence that aspartate is catabolized by GOT to OAA which, in turn, is rapidly converted to -ketoglutarate through the TCA cycle and then to glutamate by GOT or by glutamate synthase (GOGAT). The stimulation of N2 fixation and growth by aspartate is probably caused by an increased intracellular glutamate pool. 相似文献
88.
The mechanism responsible for the initial steps in the anaerobic degradation of trans-cinnamate and -phenylalkane carboxylates by the purple non-sulphur photosynthetic bacterium Rhodopseudomonas palustris was investigated. Phenylacetate did not support growth and there was a marked CO2 dependence for growth on acids with greater side-chain lengths. Here, CO2 was presumably acting as a redox sink for the disposal of excess reducing equivalents. Growth on benzoate did not require the addition of exogenous CO2. Aromatic acids with an odd number of side-chain carbon atoms (3-phenylpropionate, 5-phenylvalerate, 7-phenylheptanoate) gave greater apparent molar growth yields than those with an even number of side-chain carbon atoms (4-phenylbutyrate, 6-phenylhexanoate, 8-phenyloctanoate). HPLC analysis revealed that phenylacetate accumulated and persisted in the culture medium during growth on these latter compounds. Cinnamate and benzoate transiently accumulated in the culture medium during growth on 3-phenylpropionate, and benzoate alone accumulated transiently during the course of trans-cinnamate degradation. The transient accumulation of 4-phenyl-2-butenoic acid occurred during growth on 4-phenylbutyrate, and phenylacetate accumulated to a 1:1 molar stoichiometry with the initial 4-phenylbutyrate concentration. It is proposed that the initial steps in the anaerobic degradation of trans-cinnamate and the group of acids from 3-phenylpropionate to 8-phenyloctanoate involves -oxidation of the side-chain.Abbreviation 3-PP
3-phenylpropionic acid
- 4-PB
4-phenylbutyric acid
- 5-PV
5-phenylvaleric acid
- 6-PH
6-phenylhexanoic acid
- 7-PH
7-phenylheptanoic acid
- 8-PO
8-phenyloctanoic acid
- 4-P2B
4-phenyl-2-butenoic acid
- GC/MS
Gas chromatography/Mass spectrometry
- HPLC
High-pressure liquid chromatography 相似文献
89.
Rainer Voigt Jelle Atema 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1992,171(5):673-683
1. | We determined the spectral tuning properties of 47 chemoreceptor cells of the antenna of Homarus americanus to amino acids and other compounds. Tests with 17 single compounds at 10-4 M showed 40 of 47 cells responded best to hydroxyproline, 4 cells to taurine and 3 cells to betaine. Mean tuning breadth (H-metric) doubled with 10 fold increase in concentration. |
2. | In hydroxyproline-best cells the mean threshold for hydroxyproline (Hyp) was found between 10-7 M and 10-8 M. An equimolar mixture of the 17 compounds generated a shallower stimulus-response function with thresholds similar to Hyp function (mixture suppression). Hyp-best cells were relatively narrowly tuned, often with arginine or leucine as second best stimuli. |
3. | Thus, physiologically the second antenna of H. americanus is a major chemoreceptor organ. It is more than any of the 5 chemoreceptor organs studied so far dominated by a single best-cell type (Hyp). Receptor cell composition of antennae resembles that of antennules more than legs or maxillipeds. Hyp-best cells in antennae and lateral antennules have similar tuning spectra. |
4. | Our cell tuning studies argue for independent receptors for all amino acids tested. We conclude that diversity of receptor cell tuning is created by cell-specific blends of receptors. At the organ level, differences in organ tuning result from different blends of receptor cells. |
90.
Thomas L. Pazdernik Matthew Layton Stanley R. Nelson Fred E. Samson 《Neurochemical research》1992,17(1):11-21
This overview presents data showing that glucose use increases and that excitatory amino acids (i.e., glutamate, aspartate), taurine and ascorbate increase in the extracellular fluid during seizures. During the cellular hyperactive state taurine appears to serve as an osmoregulator and ascorbate may serve as either an antioxidant or as a pro-oxidant. Finally, a unifying hypothesis is given for seizure-induced brain damage. This unifying hypothesis states that during seizures there is a release of excitatory amino acids which act on glutamatergic receptors, increasing neuronal activity and thereby increasing glucose use. This hyperactivity of cells causes an influx, of calcium (i.e. calcium stress) and water movements (i.e., osmotic stress) into the cells that culminate in brain damage mediated by reactive oxygen species.Special issue dedicated to Dr. Frederick E. Samson 相似文献