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1.
Timothy J. French Anthony W. Good T. Norman Palmer Mary C. Sugden 《Bioscience reports》1985,5(9):729-734
The in vivo effects of dexamethasone administration on liver and extrahepatic tissue carnitine concentrations were assessed in 48-h-starved rats. In heart and kidney, but not in liver, dexamethasone significantly increased total carnitine concentration. Acute (2.5 h) treatment with 2-tetradecylglycidate (TDG), a specific inhibitor of carnitine palmitoyl transferase 1, not only increased total hepatic carnitine concentrations, but also permitted an effect of dexamethasone (a further increase in hepatic carnitine concentration). The results are discussed in terms of acute (substrate-mediated) and chronic (hormonal) control of carnitine turnover. 相似文献
2.
The effect of substrate modification on binding of porcine pancreatic alpha amylase: hydrolysis of modified amylose containing D-allose residues 总被引:1,自引:0,他引:1
A modified amylose containing 10% of tritiated D-allose residues has been hydrolyzed by porcine pancreatic alpha amylase (PPA). This reaction produced a number of radioactive oligosaccharides of low molecular weight, including modified mono-, di-, and tri-saccharides, as well as larger products. Analysis of these products by chemical and enzymic methods identified D-allose, two isomers of modified maltose, and isomers of modified maltotriose. These results may be interpreted in terms of current PPA models to indicate that D-allose residues may be productively bound at all five subsites of the active site of the enzyme. The distribution of modified residues in these products, however, further suggests that productive binding of D-allose at the subsite where catalytic attack occurs (subsite 3) is less favorable than binding of D-glucose. These results are compared with results of a series of PPA substrates having modifications at C-3 and at other positions. Trends observed in enzyme hydrolysis of these modified substrates reflect factors that contribute to PPA catalysis, with respect to steric, electronic, and hydrogen-bonding interactions between enzyme and substrate. 相似文献
3.
Josiah?P. Zayner Chloe Antoniou Alexander?R. French Ronald?J. Hause Jr. Tobin?R. Sosnick 《Biophysical journal》2013,105(4):1027-1036
To investigate the relationship between a protein’s sequence and its biophysical properties, we studied the effects of more than 100 mutations in Avena sativa light-oxygen-voltage domain 2, a model protein of the Per-Arnt-Sim family. The A. sativa light–oxygen–voltage domain 2 undergoes a photocycle with a conformational change involving the unfolding of the terminal helices. Whereas selection studies typically search for winners in a large population and fail to characterize many sites, we characterized the biophysical consequences of mutations throughout the protein using NMR, circular dichroism, and ultraviolet/visible spectroscopy. Despite our intention to introduce highly disruptive substitutions, most had modest or no effect on function, and many could even be considered to be more photoactive. Substitutions at evolutionarily conserved sites can have minimal effect, whereas those at nonconserved positions can have large effects, contrary to the view that the effects of mutations, especially at conserved positions, are predictable. Using predictive models, we found that the effects of mutations on biophysical function and allostery reflect a complex mixture of multiple characteristics including location, character, electrostatics, and chemistry. 相似文献
4.
L D Foil T R Klei R I Miller G E Church C S Foil D D French J N Smith 《The Journal of parasitology》1987,73(2):320-326
Seasonal changes in density and spatial distribution of Onchocerca cervicalis microfilariae were studied in ventral-midline skin of 15 infected pony mares in southern Louisiana. Triple running mean analysis of data over a 13-mo period indicated that a distinct pattern exists in total microfilariae population density and in microfilariae occurrence in different levels of the dermis. Microfilariae density reaches peak levels in the spring followed by a 58% decrease in the summer, a 19% increase in the fall, and a decrease to the lowest numbers in the winter. Microfilariae were found in all levels of the skin during the spring, summer, and fall but were not found in the superficial layers of the dermis during the winter months. The population density of Culicoides variipennis, a demonstrated vector of O. cervicalis, appeared to have seasonal fluctuations similar to the changes in microfilarial density. Harmonic wave analysis of microfilariae density data in individual ponies showed that all individuals did not follow the population trend. 相似文献
5.
Dietary linoleic acid is required for development of experimentally induced alcoholic liver injury 总被引:5,自引:0,他引:5
We had previously hypothesized that linoleic acid (LA) was essential for development of alcoholic induced liver injury in our rat model. Male Wistar rats were fed a nutritionally adequate diet (25% calories as fat) with ethanol (8-17 g/kg/day). The source of fat was tallow (0.7% LA), lard (2.5% LA) or tallow supplemented with linoleic acid (2.5%). Liver damage was followed monthly by obtaining blood for alanine aminotransferase assay and liver biopsy for assessment of morphologic changes. Enzyme and histologic changes (fatty liver, necrosis and inflammation) in the tallow-linoleic acid-ethanol fed animals were more severe than in the lard-ethanol group. The tallow ethanol group did not show any evidence of liver injury. Our results strongly support our hypothesis that LA is essential for development of alcoholic liver disease in our rat model. 相似文献
6.
Myosin cross-bridge orientation in rigor and in the presence of nucleotide studied by electron spin resonance. 总被引:3,自引:2,他引:1
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The tilt series electron spin resonance (ESR) spectrum from muscle fibers decorated with spin labeled myosin subfragment 1 (S1) was measured from fibers in rigor and in the presence of MgADP. ESR spectra were measured at low amplitude modulation of the static magnetic field to insure that a minimum of spectral lineshape distortion occurs. Ten tilt series ESR data sets were fitted simultaneously by the model-independent methodology described in the accompanying paper (Burghardt, T. P., and A. R. French, 1989. Biophys. J. 56:525-534). By this method the average and standard error in the mean of order parameters for the probe angular distribution were calculated for the two states of the fiber investigated. The average order parameters were used to reconstruct the probe angular distribution in two dimensions, one angular dimension corresponding to a polar angle measured relative to the fiber axis, and the other a torsional angular degree of freedom of the probe. We find that the probe angular distributions for the rigor and MgADP states of the fiber differ such that the rigor distribution is broader and shifted relative to the distribution in the presence of MgADP. The shape of the rigor distribution suggests the presence of two probe orientations, one similar to that in the presence of MgADP, and another at a different orientation. The shape of the distribution in the presence of MgADP suggests that the binding of the nucleotide to the rigor cross-bridge shifts the spin population into a more homogeneous one by causing a cross-bridge rotation. 相似文献
7.
Primary structure and androgen regulation of a 20-kilodalton protein specific to rat ventral prostate 总被引:3,自引:0,他引:3
K C Ho R Snoek V Quarmby D H Viskochil P S Rennie E M Wilson F S French N Bruchovsky 《Biochemistry》1989,28(15):6367-6373
Nuclear and cytosolic forms of a 20-kdalton rat ventral prostate protein were purified and partially sequenced from their N-termini. Isolated nuclei were treated with micrococcal nuclease and extracted in 0.6 M NaCl, and proteins were separated by affinity chromatography on Matrex gel green A, ammonium sulfate fractionation, and fast protein liquid chromatography on Superose 12. The 43 amino acid N-terminal sequence of the nuclear 20-kdalton protein was identical with the cytosolic protein except it lacked 7 N-terminal amino acids present in the cytosolic form. The DNA sequence of a full-length complementary DNA clone isolated from a ventral prostate gt11 library extended the N-terminal sequence of the cytosolic form by an additional nine amino acids from the predicted initiation methionine. The cDNA included the nucleotide sequence for the 43 amino acid N-terminal sequence of the purified 20-kdalton protein and predicted molecular weights of 16,686, 17,521, and 18,650, respectively, for the nuclear, cytoplasmic, and nonprocessed proteins. Northern blot analyses of reproductive tract tissue RNAs using the 20-kdalton protein cDNA as probe revealed a single mRNA species of 0.92 kb detectable only in extracts of rat ventral prostate. Expression of the 0.92-kb mRNA was androgen dependent since the mRNA was undetectable in extracts obtained 4 days after castration and was restored 16 h after restimulation with androgen. 相似文献
8.
9.
A study of GDP binding to purified thermogenin protein from brown adipose tissue. 总被引:1,自引:0,他引:1
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1. The binding of GDP to purified thermogenin protein was studied by using fluorescence spectroscopy and equilibrium dialysis. 2. GDP binding to thermogenin diminished fluorescence emission in a concentration-dependent manner that exhibited saturation. 3. Kd values for binding of nucleoside di- and tri-phosphates were lower than those for nucleoside monophosphates. 4. The GDP-induced fluorescence quenching was decreased by increasing pH, but the apparent Kd was unaltered by pH changes. 5. Equilibrium dialysis showed a Kd change from 3 to 6 microM when the pH was increased from 6.6 to 8.5. 6. The apparent pK of the fluorescence changes induced by pH (8.3) was identical with the apparent pK of the GDP-binding response. 7. The data are consistent with the existence of protonated and non-protonated forms of thermogenin protein that both bind GDP. 相似文献
10.
Effects of nutritional status and acute variation in substrate supply on cardiac and skeletal-muscle fructose 2,6-bisphosphate concentrations. 总被引:3,自引:3,他引:0
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Vasopressin was found to be an effective inhibitor of protein labelling in isolated liver cells. Its effect shows the following distinct characteristics: (1) in contrast with alpha-adrenergic agonists, its effect is observable under a wide range of cellular Ca2+-loading conditions; (2) it is not influenced by the nutritional state of the animal. The lack of vasopressin effect on valine production, and its ability to decrease protein labelling from near-saturation concentrations of [3H]valine, indicate that the observed variations in protein labelling reflect actual changes in the rate of protein synthesis. The action of vasopressin is primarily exerted on the initiation step of protein synthesis and this effect is accompanied by a decreased activity of eukaryotic initiation factor 2. Activators of protein kinase C showed similar but not additive effects on protein synthesis, as did vasopressin. It seems plausible to conclude that protein kinase C activation may play an important regulatory role in hepatic protein synthesis as a transducer of hormonal and perhaps other type of signals. 相似文献