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Biomedical subjects

A M Municio

Publications and source records attributed to A M Municio.

At least 55 records · Page 3Linked to original sources
PubMed1984

The microviscosity of liver plasma membranes of rats fed with oleoylanilide.

Oleoylanilide was administered orally to groups of rats according to different patterns. Oleoylanilide was perfused at different concentrations through rat liver. Oleoylanilide was added to isolated hepatocytes. Oleoylanilide was added to plasma-membrane preparations. Membrane preparations were obtained after experiments performed in vivo and perfusion experiments and, by using 1,6-diphenylhexa-1,3,5-triene as fluorescence probe, the fluorescence polarization parameter was measured, from which the microviscosity (eta) was calculated. In all cases the microviscosity decreased markedly. Addition of oleoylanilide to hepatocyte preparations and to isolated membranes produced the same effect, increasing the fluidity of the membranes. These data suggest that oleoylanilide partitions into the membrane, disordering some lipid interactions.

Anilides↗
PubMed1984

Effect of Escherichia coli lipopolysaccharide on the glucagon and insulin binding to isolated rat hepatocytes.

Number and affinity constant of low affinity binding sites of insulin and glucagon to isolated hepatocytes decreased when the cells were incubated with Escherichia coli 0111:B4 lipopolysaccharide. This effect agrees with a non-specific binding of lipopolysaccharide to hepatocytes, similar to the well-recognized non-specific binding of albumin. Also, binding of different lectins to their glycoprotein receptors did not affect the [14C]lipopolysaccharide interaction with the cell membrane surface. Endotoxin depresses gluconeogenesis from lactate when the precursor was incubated with the cells for short time intervals. The longer the preincubation interval with lipopolysaccharide, the higher the inhibition of gluconeogenesis in the absence and in the presence of glucagon. The effect of endotoxin was also studied on the glucagon-induced synthesis of cyclic AMP and the glucagon binding. Levels of cyclic AMP and hormone binding decreased with increasing both endotoxin concentrations and preincubation intervals at which cells were in contact with endotoxin.

Animals↗
PubMed1984

Regulatory mechanisms of fatty acid isomers on adenylate cyclase activity from Ceratitis capitata brain.

The regulatory properties of saturated and unsaturated fatty acids on membrane-bound preparations of adenylate cyclase from Ceratitis capitata brains have been investigated. Saturated long-chain fatty acids do not exhibit any significant modification of the enzyme activity of the enzyme preparations but the presence of one, two or three double bonds in the 18C chain provokes an inhibitory effect. Binding of oleate and linoleate to the membrane enzyme preparation is non-specific and simply stoichiometric in the range of concentrations examined. Studies of cis and trans isomers of the double-bond isomers, 18:1(n-9) and 18:1(n-11), reveal the higher inhibitory effect of the cis isomers on membrane-bound adenylate cyclase of the insect brain. The inhibitory effect of cis-vaccinate in the basal conditions of the enzyme assay is identical to the effects obtained in the presence of GTP and octopamine. Insect membrane preparations were labeled with 1,6-diphenyl-1,3,5-hexatriene as fluorescent probe and treated with cis and trans 18:1(n-9) and 18:1(n-11). The fluorescence polarization parameter was measured, from which the microviscosity of the preparations was calculated; microviscosity of the membranes treated with both cis isomers decreased in a clear extent whereas it is not influenced by the trans isomers.

Adenylyl Cyclases↗
PubMed1984

The fluidity of plasma membranes from ethanol-treated rat liver.

Male Wistar rats were maintained for 35-40 days on a liquid diet containing 36% of calories as ethanol. Ethanol was replaced by carbohydrates in the isocaloric diet fed to control animals. The effect of ethanol consumption has been studied on the fluorescence polarization of rat liver plasma membranes and artificial lipid vesicles and on the lipid composition of the membranes. Fluorescence polarization in both membranes and vesicles was determined using DPH and TMA-DPH as fluorescence markers; from these data, the polarization term (ro/r-l)-1 and flow activation energy (delta E) were calculated. The ethanol consumption induces a more fluid environment within the membrane core of liver plasma membranes; the ethanol-fed rat membranes are more resistant to the in vitro effect of ethanol disordering the membrane structure. Vesicles obtained with lipids from either control membranes or ethanol-fed rat membranes were treated with ethanol and the changes in polarization paralleled to those exhibited by the membranes. The absence of phase transitions and of delta E changes was also shown in temperature-dependence studies. The lower cholesterol content found in ethanol-fed rat plasma membranes might be responsible for observed variations in the microviscosity.

Animals↗
PubMed1984

Stabilization of pericardial tissue by glutaraldehyde.

The effect of glutaraldehyde on pericardial tissue has been studied with special reference to the degree of chemical modification, thermal stability and enhancement of the resistance to proteolytic digestion. The nature of the cross-links depends on time and reagent concentration. At least two populations of lysine and hydroxylysine residues can be distinguished on the basis of their reactivity against the aldehyde. The appearance of these families is not dependent on the structural integrity of the tissue. The time course of the tissue modification is not modified by removing lipids and proteoglycans from the biomaterial. Highest thermal stability is obtained by long-term modification at low reagent concentration.

Aldehydes↗
PubMed1983

Effect of fatty acid anilides on the generation of arachidonic acid by human polymorphonuclear leukocytes.

The addition of oleoylanilide or linoleylanilide to human polymorphonuclear leukocytes induces a time- and dose-dependent generation of arachidonic acid. Half-maximal effect is caused by a dose of 0.2 mg linoleylanilide/ml. Fatty acid anilides also produce a time- and dose-dependent inhibition of the synthesis of triacylglycerol. Half-maximal effect is caused by 1 microgram linoleylanilide/ml. These results indicate that fatty acid anilides, which have been found in the illegal cooking oil which intoxicated thousands of Spaniards, alter lipid metabolism in human polymorphonuclear leukocytes.

Anilides↗
PubMed1983

Lipogenesis in liver, lung and adipose tissue of rats fed with oleoylanilide.

Oleoylanilide was administered orally to groups of rats according to different patterns. Subcellular fractionation of liver, lung and adipose tissue was then carried out in order to study the main enzyme activities involved in the lipogenesis. The observed findings indicate that adipose tissue and lung are the main target organs for the anilide, adipose tissue being involved in a general decrease of the enzyme activities, whereas transacylation reaction exhibits the most marked depletion of all the enzyme activities in the lung. The enzyme activities in liver were not markedly affected by this oral administration, although some data support the existence of a latent liver toxicity. These data suggest that oleoylanilide has the capacity to alter lipid metabolism of lung and adipose tissue to a considerable extent, whereas no major effect was produced in the liver. This different organ response could be related to the lymphatic gland via absorption of the substance.

Adipose Tissue↗
PubMed1983

cAMP-dependent protein kinases from the insect Ceratitis capitata.

Among the components of the two cyclic nucleotide system of Ceratitis capitata pharate adults, two cAMP-dependent protein kinase activities have been identified and purified through a sequence of chromatographic procedures. The properties of both protein kinases, A-1 and A-2, were studied and characterized in comparison with those of other sources. Protein kinase A-2 from Ceratitis capitata corresponds to type I from mammals mainly concerning about the dissociating effect of histones. Protein kinase A-2 exhibited a molecular weight of 39,000 in the presence of cAMP, whereas in the absence of the cyclic nucleotide two components of 80,000 and 159,000 were present and attributed to the forms RC and R2C2, respectively. Protein kinase activities A-1 and A-2 were markedly inhibited by increasing ionic strength whereas the activity (-cAMP/+cAMP) ratio for protein kinase A-2 increased versus NaCl concentration. Histones H1 and H2B were the best substrates for both A-1 and A-2 activities; the high mobility group of insect proteins (HMG) were also notably phosphorylated by A-2 preparation. Among the cyclic nucleotides assayed for the protein kinase activity A-2, cAMP induced a high activation at the lowest concentrations although high cAMP concentrations decreased the protein kinase activity, possibly through binding to the catalytic site. The protein kinase A-2 preparations exhibited a complex kinetics due to the presence of two forms with different affinity for ATP; these forms may be related to the aggregation properties of the enzyme.

Animals↗
PubMed1983

Labelled lipids distribution following [3H]glycerol injection to pregnant rabbits.

1. The time dependent variation in specific activity of serum triglycerides and phospholipids has been studied following an intravenous pulse-labelling with 2-[3H]glycerol to pregnant rabbits. 2. The specific activity of triglycerides varied according to the gestation time and the maximal values of specific activity shifted to shorter times when gestation progressed to term. 3. The specific activity of serum phospholipids was higher in pregnant animals and increased with gestation time. 4. Concentrations and specific activities of both triglycerides and phospholipids were investigated in serum of pregnant and fetal rabbits at term. Concentrations of both lipid classes were notably higher in the fetal blood than in the maternal one. 5. The results were discussed on the basis of changes in hepatic biosynthesis of phosphatidic acid. Also, it was suggested a high drainage of either lipids or their degradation products by the feto-placental unit at the end of pregnancy. 6. Levels and specific activities of maternal and fetal lipids from liver and lung were also examined. The different metabolic roles of the main tissues involved in triglyceride and phospholipid metabolism were discussed.

Animals↗
PubMed1982

Effects of palmitoyl-CoA on the structure-function of the fatty acid synthetase complex from Ceratitis capitata.

1. The effects of palmitoyl-CoA on the structure and enzyme activity of the fatty acid synthetase from the insect Ceratitis capitata have been examined. 2. The acyl-CoA derivative increases the helical content of the protein from 45 to 60% and inhibits the enzyme activity of the complex. 3. Bovine serum albumin, calf thymus histone H1 and phospholipids protect the enzyme from the inactivation by palmitoyl-CoA. Phospholipids increase also the ellipticity at 220 nm in the enzyme complex. 4. The results obtained show a non specific character for the inhibition and are interpreted in terms of the detergent properties of the long-chain acyl-CoA derivatives.

Acyl Coenzyme A↗
PubMed1982

Effect of proteolytic and lipolytic enzymes on the adenylate cyclase activity from brain membranes of Ceratitis capitata.

1. The effect of various proteolytic enzymes was assayed on the adenylate cyclase activity in purified brain membrane preparations from the insect Ceratitis capitata. Trypsin, chymotrypsin, papain, thermolysin, elastase, subtilisin and prot. XIV were examined. 2. Trypsin treatment, at 37 degrees C, decreased the adenylate cyclase activity even in the presence of GppNHp that protects the activity from the thermal inactivation. 3. Residual basal, GppNHp- and F(-)-stimulated activities were similar when membrane preparations were preincubated either in the presence or in the absence of GppNHp and F-. 4. All proteolytic activities assayed on the brain membrane preparations, excepting papain, exerted an inhibition of adenylate cyclase in basal conditions. 5. The inhibition was stronger in the presence of F- than in the presence of other regulators. 6. Papain showed also a notable inhibition of adenylate cyclase in the presence of F-. 7. Phospholipase A2 treatment decreased both basal and stimulated activity; however, F(-)-sensitive activity was less affected than basal and GppNHp-sensitive activity. F(-)-stimulated activity was less affected by phospholipase A2 than either basal or GppNHp-stimulated activities. 8. Phospholipids are, then, essential for the highest basal activity, although the relationship between catalytic and nucleotide-regulatory components was unaffected by this treatment.

Adenylyl Cyclases↗
PubMed1981

Fluorescence studies on the lipoprotein complex of the fatty acid synthetase from the insect Ceratitis capitata.

The fatty acid synthetase complex from the insect Ceratitis capitata forms a stable lipoprotein complex. The intrinsic fluorescence of the complex was studied by observing the emission spectra with different excitation wavelengths, both in the native complex and after temperature with sodium cholate and sodium dodecyl sulfate. The excitation spectrum of the native form also was recorded. The fluorescence behavior of the native enzyme showed two families of tryptophan residues. Cholate influenced the fluorescence, suggesting that phospholipids are the conformational support at this level. The two families of fluorescing tryptophan residues were similarly accessible to quenching by acrylamide. Thermal changes in the fluorescence characteristics were observed; warming caused a decrease in the quantum yield as well as a red shift in the emission maximum. The high fluorescence remaining after the thermal transition suggested that the lipid-protein interaction was affected but maintained shielding of the fluorophore by the lipids. Fluorescent probe molecules 1,6-diphenyl-hexa-1,3,5-triene (DPH) and dansylphosphatidylethanolamine (DPE) also were used. DPH uptake was temperature dependent, with a middle point consistent with the thermal conformation transition, indicating that internal lipids are nonrandomly distributed within the complex. DPE uptake did not reach the saturation of the complex, suggesting that its solubilization sites would be located on the lipoprotein surface.

Animals↗
PubMed1981

Fatty acid synthetase complex from the insect Ceratitis capitata. Structural studies.

The involvement of lipids in the structure and the activity of the fatty acid synthetase from the insect Ceratitis capitata has been previously established. Lipid-protein interactions were examined by circular dichroism. A thermal transition for both the structure and the activity of the enzyme complex takes place at about 50 degrees C; as the temperature is raised alpha-helix content decreases considerably and, concomitantly, the enzyme undergoes a marked inactivation. After 180 min at 37 degrees C, the secondary structure of the enzyme complex is 20% alpha-helix, 33% beta structure and 47% of not ordered structure against 43%, 26% and 31% as respective percentages for the native form of the complex. Lipolytic digestion of the complex was carried out with either lipase or phospholipase A2 or a mixture of both enzymes. Any of the lipolytic treatments induces a decrease of [theta]220 and the simultaneous digestion with lipase plus phospholipase during 90 min account for a limit structure with 8% of alpha-helix. The secondary structure of the complex after treatment with proteolytic enzymes, trypsin or chymotrypsin, had 15% alpha-helix, 20% beta structure and 57% of not ordered structure. The preservation of the alpha-helix content indicates that lipids protect certain of the bonds cleavable in the absence of lipids. The structural organization of the complex was studied through sequences of lipolytic and proteolytic treatments; final organization was dependent on the initial lipolytic digestion in agreement with the peptide bond shielding by the lipid component. Nitration of the complex with tetranitromethane modified almost completely all tyrosine residues of the polypeptide chains.

Animals↗