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A Haug

Publications and source records attributed to A Haug.

At least 37 records · Page 2Linked to original sources
PubMed1988

Frictional resistance to motions of bimane-labelled spinach calmodulin in response to ligand binding.

The single cysteinyl residue 26 of spinach calmodulin was labelled with the thiol-specific bimane fluorescence probe. Following application of stoichiometric quantities of Ca2+ or aluminum ions to the protein, temperature-dependent fluorescence changes (anisotropy, lifetime) could be monitored via the label. From these data the Y function could be constructed which, as a function of temperature, seems to consist of two linear regions which intersect at the critical temperature, Tc. From the Y function the thermal coefficient, b(T), of the frictional resistance to fluorophore rotation could be determined. b(T) was dependent on the type and stoichiometry of the ligand(s) bound to calmodulin. Changes of the thermal coefficient apparently resulted in part from ligand-triggered structural pertubations transmitted over a considerable distance to calmodulin region I, the site of the fluorophore.

Aluminum↗
PubMed1988

Polycation binding to isolated lipopolysaccharide from antibiotic-hypersusceptible mutant strains of Escherichia coli.

Lipopolysaccharide (LPS) samples isolated from a parent and two antibiotic-hypersusceptible mutant strains of Escherichia coli were analyzed for polycation affinity and level of binding. Purified salts of the LPSs from the parent strain, UB1005, and from one of the mutant strains, DC1, bound similar amounts of sodium and magnesium, but the samples from the second mutant strain, DC2, had significantly greater amounts of counterions bound per phosphate than did the other two isolates. The 31P nuclear magnetic resonance spectra indicated that, compared with LPS from the parental strain, the sample from strain DC1 was similar but the DC2 sample contained fewer diphosphodiester and more diphosphomonoester groups. Motion within the lipid A head group regions of the magnesium salts of the three isolates was dramatically different, as revealed by an electron spin resonance probe. The binding of the cations to the LPS aggregates was measured by the displacement of this cationic spin probe from the LPS samples. The polycations polymyxin, gentamicin, and spermine displaced more probe from samples of the two mutant strains than from that of the parental strain. The sample from the most antibiotic-susceptible strain, DC2, had the highest affinity for all the polyvalent cations tested. The results indicate that antibiotic hypersusceptibility can result from at least two distinct alterations in LPS structure. The decrease in diphosphodiesters and increase in diphosphomonoesters in the LPS of the DC2 sample resulted in more acidic phosphate moieties and a more antibiotic-susceptible cell. In contrast, the alterations in the LPS of DC1 that resulted in antibiotic hypersusceptibility of the cell were not in the phosphate substituents. In both mutants, however, hypersusceptibility resulted in an alteration in LPS structure that increased the affinity of the molecules for polycations.

Acylation↗
PubMed1988

Enhanced binding of polycationic antibiotics to lipopolysaccharide from an aminoglycoside-supersusceptible, tolA mutant strain of Pseudomonas aeruginosa.

The lipopolysaccharide (LPS) of the aminoglycoside-supersusceptible Pseudomonas aeruginosa tolA mutant PAO1715 was compared with its parent strain PAO1670 and tol+ revertant PAO1716. Electrophoretic separation of purified LPSs from the three isolates showed similar LPS banding patterns. Analysis of the Western blots of these LPSs from the three isolates with O-antigen-specific monoclonal antibody indicated that the ladder pattern consisted of doublet bands, which presumably reflected a modification of core or lipid A; the level of one of the bands in the doublet was in much lower amounts in the isolate from the tolA mutant than in that from the parent or revertant. Results of competitive displacement experiments, in which the cationic spin probe 4-dodecyldimethylammonium-1-oxyl-2,2,6,6-tetramethylpiperidine bromide was displaced from its LPS-binding site by polycations, revealed that the tolA mutant had a much higher affinity for gentamicin, polymyxin, Ca2+, and Mg2+ than did the parent or revertant. The order of affinity for all samples was polymyxin B much greater than gentamicin C much greater than Ca2+ greater than Mg2+. Both gentamicin and polymyxin induced rigidification of all of the LPS samples, but for the sample from the tolA mutant, rigidification occurred at substantially lower concentrations. Dansyl polymyxin titration experiments with intact cells demonstrated that the increased affinity of the LPS from the tolA mutant for polycations was reflected in an increase in the affinity of binding to the cell. Together these data suggest that the tolA mutant is supersusceptible to aminoglycosides by virtue of an LPS change which increases the binding affinity of the LPS for polycations, including gentamicin.

Anti-Bacterial Agents↗
PubMed1988

Bordetellae and charcoal horse blood agar: inactivation of antibiotics in agar during prolonged incubation for susceptibility testing.

We examined the degree of inactivation of 22 antibiotics caused by prolonged incubation at 36 degrees C of agar plates during agar dilution susceptibility testing of Bordetellae. Fresh antibiotic-containing plates of charcoal horse blood agar and plates which had been held at 36 degrees C for 2 or 3 days prior to inoculation were inoculated with strains of Bordetella pertussis and Bordetella parapertussis and incubated for 2 days. Then the MICs were compared. Most antibiotics showed a loss of activity of up to four dilution steps after prolonged incubation. Further studies with other slow-growing organisms and other complex media are needed.

Agar↗
PubMed1987

Aluminum-induced conformational changes in calmodulin alter the dynamics of interaction with melittin.

Studies were undertaken to examine the impact of aluminum-induced structural changes in bovine brain calmodulin on the protein's interface region with melittin, a model for calmodulin's target enzymes. Both steady-state and time-dependent fluorescence characteristics of the single tryptophanyl residue of melittin were employed to derive information on aluminum-related changes in the fluorophore's microenvironment. In the presence of stoichiometric amounts of aluminum ions, calmodulin's target region with melittin appears to be more polar than that with aluminum absent. As a result, upon association of melittin with aluminum-calmodulin, the enhancement of helical arrays is less pronounced. The fluorophore's average microenvironment also is modified such that its apparent lifetime is shortened when aluminum is present. In the presence of aluminum ions, the solvation structure of calmodulin is possibly changed, which may be unfavorable for a proper fit between calmodulin and target proteins.

Aluminum↗
PubMed1987

Lipoprotein lipases, lipoproteins and tissue lipids in rats fed fish oil or coconut oil.

The effect of fish oil and coconut oil on plasma lipoproteins and lipoprotein-catabolizing enzymes [lipoprotein lipase (LPL) and hepatic endothelial lipase (HL)] was studied in rats. Male rats were fed for 4 wk purified diets containing equienergetic, amounts of either coconut oil (group A), coconut oil:fish oil, 50:50 (group B) or fish oil (group C). Whole plasma triacylglycerol, cholesterol and phospholipid concentrations were appreciably lower in group C than in group A, mainly due to a fall in very low density lipoprotein (VLDL) and subgroup 2 of high density lipoprotein (HDL2), with less consistent changes in LDL and HDL3. VLDL components of group B were also considerably lower than corresponding ones in group A. LPL and HL activities were about 50% lower in groups B and C than in group A. Increased hepatic triacylglycerol and cholesterol concentrations were observed in groups B and C. It is suggested that the decrease in LPL and HL activity of fish oil-fed rats may be an adaptive response to the low concentration of the substrate (triacylglycerols) for these enzymes.

Animals↗
PubMed1987

Susceptibility of Bordetella pertussis and Bordetella parapertussis to 24 antibiotics.

The susceptibility of Bordetella pertussis (28 strains) and Bordetella parapertussis (6 strains) to 24 antibiotics (penicillin and cephalosporin derivatives, erythromycin, josamycin, cotrimoxazole, imipenem, aztreonam and fosfomycin) was studied by means of the agar dilution method using charcoal horse blood agar. Piperacillin and mezlocillin showed the highest activity (MIC 0.0039-0.00781 micrograms/ml) against B. pertussis while B. parapertussis was most susceptible to piperacillin (0.03125-0.0625 microgram/ml), mezlocillin and latamoxef (0.125-0.25 microgram/ml).

Anti-Bacterial Agents↗
PubMed1986

Physical properties of short- and long-O-antigen-containing fractions of lipopolysaccharide from Escherichia coli 0111:B4.

Aggregates of short- and long-chain O-antigen-containing fractions of lipopolysaccharide were analyzed by electron spin resonance probing to reveal differences in their physical properties. The fluidities of the lipid regions of the two fractions were quite similar, although the long-chain lipopolysaccharide aggregates appeared to be more hydrated as reflected by the polarity determined with a lipid probe. In contrast, the head-group region of the long-chain fraction was dramatically more mobile than that of the short-chain sample. The binding of polycations (e.g., polymyxin B, spermine) to lipopolysaccharide aggregates was measured by the partitioning of a cationic spin probe. Less probe was displaced from the long-chain fraction and unseparated lipopolysaccharide than from the short-chain fraction by the addition of cations, suggesting that the long O-antigen masks anionic sites on lipopolysaccharide. These results indicate that the aggregate shape and reactivity of lipopolysaccharide are affected by O-antigen length. Thus, the biological activity of lipopolysaccharide may be modulated directly by the presence of O-antigen and indirectly by the effects of O-antigen on the lipopolysaccharide aggregate structure.

Antigens, Bacterial↗
PubMed1986

Hypercholesterolaemia, hypotriacylglycerolaemia and increased lipoprotein lipase activity following orchidectomy in rats.

Plasma lipoproteins, faecal cholesterol excretion, and activities of lecithin: cholesterol acyltransferase (LCAT) hepatic lipase (HL), and lipoprotein lipase (LPL) were determined in castrated rats, in rats treated with testosterone propionate after castration, and in sham-operated controls. Compared to control rats, whole-plasma total cholesterol (TC) rose, and triacylglycerols (TG) fell in castrated rats, but were normalized by androgen substitution. VLDL components tended to be reduced, whereas HDL2 components rose following castration. In general, testosterone substitution normalized the alterations induced by castration. Adipose tissue LPL was higher in castrated rats than in control rats, whereas activities of HL and LCAT were not significantly affected by the treatments. Hepatic cholesterol concentration, and faecal excretion of cholesterol and bile acids were not significantly altered by the treatments. Considering all 3 groups together, there was a significant positive correlation between the concentration of plasma cholesterol and cholesterol in liver, between plasma HDL2-cholesteryl esters and hepatic cholesterol, and also between HL and faecal cholesterol excretion. The results suggest that short term castration of rats causes increased levels of lipoprotein lipase and thereby brings about a lowering of VLDL and an increased concentration of LDL and HDL2. These effects are reflected in hypotriacylglycerolaemia and hypercholesterolaemia.

Animals↗
PubMed1985

A pH titration study on the ionic bridging within lipopolysaccharide aggregates.

The packing of lipopolysaccharide aggregates from rough strains of Escherichia coli was examined at different pH values. Lipopolysaccharide head-group motion, measured with an electron spin resonance probe, was found to be dependent on pH, and indicated the existence of multiple ionizable groups. Lipopolysaccharide from a rough (Ra) and a heptose-less (Re) mutant were more rigid at pH 5 than at pH 10.5. In addition, head-group mobility of the magnesium salt of Ra lipopolysaccharide was substantially less than that of the sodium salt at pH 7.0, whereas at high pH (pH 12) the two salts were equally fluid. Changes in head-group packing were also reflected in pH-dependent changes in the phase transition measured with differential scanning calorimetry. The enthalpy of the transition, delta Ht, for the sodium salt of Re lipopolysaccharide was greatest at pH 7.5 and approached zero in both the acidic and the basic pH ranges. We propose that fixed charges in the core and lipid A regions significantly influence lipopolysaccharide head-group motion and the lipopolysaccharide aggregation state. Furthermore, ionic bridging among phosphate groups dramatically rigidifies head group interactions in the neutral to acidic pH ranges.

Calorimetry, Differential Scanning↗
PubMed1985

Effects of aspirin, indomethacin, and sodium salicylate on human erythrocyte membranes as detected with electron spin resonance spectroscopy.

Electron spin resonance spectroscopy of probed samples was used to determine the structural changes in human erythrocyte membranes prior to and at intervals following ingestion of either 10 grains acetylsalicylic acid, 10 grains sodium salicylate, or 50 mg indomethacin by both male and female subjects. Analysis of erythrocytes from female subjects indicated a time-dependent disordering of the membrane over the eight hour period following aspirin ingestion while the cells of male subjects showed a slight membrane ordering over the same time period. Erythrocytes drawn from females at the beginning of the menstrual cycle showed the greatest amount of membrane disordering at one hour following aspirin ingestion, but by eight hours, the membrane structure had returned to that of control. The time dependent disordering in membrane structure of cells from females in the middle of the menstrual cycle was biphasic. Ingestion of indomethacin induced only slight membrane changes in both male and female subjects over the times examined. Ingestion of sodium salicylate by either men or women did not induce significant changes in erythrocyte membrane order. Washed erythrocytes when mixed with salicylate, aspirin, or indomethacin were either identical to control cells or slightly more ordered. This study suggests that aspirin-induced alterations in membrane structure may depend upon steroid hormone levels.

Aspirin↗
PubMed1985

Effect of orchidectomy and testosterone substitution on enzyme activities and DNA content in rat liver and epididymal fat.

Orchidectomy of rats resulted in increased concentration and whole organ amount of DNA both in the epididymal fat pad and liver. Liver hexokinase (HK) and phosphofructokinase (PFK) activities were raised after orchidectomy, but were normalized by testosterone substitution. Several glycolytic enzymes, and fumarase and aspartate aminotransferase were increased by orchidectomy in epididymal fat. Most of the enzyme changes tended to normalize after testosterone administration. Activities of NADPH generating enzymes were increased after orchidectomy both in liver and epididymal fat. When related to DNA, several enzyme activities in both tissues fell following castration. However, liver HK, PFK and NADPH generating enzymes, as well as epididymal fat HK and isocitrate dehydrogenase were elevated after castration also when related to DNA. The results suggest that the influence of testosterone on cell proliferation is organ-specific. The observed enzyme alterations after orchidectomy might partly explain fat accumulation and hyperlipoproteinemia encountered in castrates.

Amino Acids↗
PubMed1985

Responses of plasma apolipoproteins to gonadectomy and androgen substitution in male rats.

To obtain information on testosterone effects on plasma apolipoproteins, the amount and composition of apo-proteins in lipoproteins of 5 density classes (VLDL, LDL, HDL2b, HDL2a, HDL3) was estimated in 3 groups of adult male rats: normal control rats, castrated rats, and rats injected daily with testosterone propionate (200 micrograms/day) for one week after castration. Apoproteins were separated by sodium dodecylsulfate polyacrylamide gel electrophoresis after ultracentrifugation of plasma, and determined colorimetrically. Total amount of apoprotein carried in LDL (d = 1.006-1.063 g/ml) and HDL2b (d = 1.063-1.100 g/ml) was higher in castrated than in control rats, but was not significantly different from controls in testosterone substituted rats. LDL apo B and HDL2b apo E were higher in castrated than in normal rats; control levels were observed in androgen substituted rats. Except for a greatly increased relative amount of HDL2b apo E, and a decreased percentage of HDL2b apo A-I in castrated rats, there were no significant alterations by castration of apoprotein composition of the lipoproteins. The results raise the question whether the androgenic state might affect processes related to the effects of plasma LDL apo B and HDL apo E.

Androgens↗
PubMed1985

Plasma lipoprotein distribution, faecal cholesterol excretion, and activities of lipoprotein lipase, hepatic lipase and lecithin:cholesterol acyltransferase in rats fed diets rich in sucrose or sunflower oil.

Plasma HDL2 has been suggested to carry cholesterol to the liver for subsequent excretion in the bile and faeces. The enzymes lipoprotein lipase (LPL), hepatic lipase (HL) and lecithin:cholesterol acyltransferase (LCAT) have been implicated in the centripetal cholesterol transport. Activities of these enzymes, the amount of faecal cholesterol excretion and the level of plasma lipoproteins were determined in male rats fed for 4 weeks on purified diets in which the sunflower oil:sucrose ratio was either 0.03 (group a) or 1.01 (group b). Whole plasma triacylglycerols (TG), unesterified cholesterol (UC) and phospholipids (PL) were highest in group (a). The concentration of cholesteryl esters (CE) was similar in the two groups. Protein, TG and UC of VLDL, and TG, UC, CE and PL of HDL2 were higher in group (a) than in group (b). The HDL3-protein and TG were lowest in group (a). Thus, total weight of VLDL and HDL2 were increased, and HDL3 reduced in group (a), which had also increased activities of HL and adipose tissue LPL. Activity of LCAT was lower, and faecal excretion of cholesterol was reduced by about 50% in group (a) compared to group (b). Accordingly, in the rat increased plasma levels of HDL2 are not necessarily indicative of increased faecal cholesterol excretion.

Animals↗
PubMed1984

Organic acids prevent aluminum-induced conformational changes in calmodulin.

At a molar excess of 10:1 for [citrate]/[calmodulin], citrate can prevent aluminum binding to calmodulin when present in the protein solution in micromolar concentration, as determined by fluorescence and circular dichroism spectroscopy. In contrast, citrate is only partially effective in restoring calmodulin to its native structure once the aluminum-calmodulin complex (3:1) is formed, as measured by the alpha-helix content of the protein. Considering the magnitude of the stability constant of the citrate-aluminum chelate, citrate and perhaps other carboxylic acids may protect calmodulin, and thus cells, from toxic aluminum ions.

Aluminum↗
PubMed1984

Estimation of lipoprotein and apoprotein distribution in rat plasma by cumulative density ultracentrifugation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis.

Lipoprotein distribution in rat plasma determined after sequential ultracentrifugation (requiring 8 days of centrifugation to separate lipoproteins in five density classes), was compared to estimates based upon cumulative density ultracentrifugation (46 hr of ultracentrifugation). In general comparable values were obtained by the two methods with regard to protein, total cholesterol, cholesteryl ester, free cholesterol, and triacylglycerol distribution. However, the HDL3 protein concentration found by sequential ultracentrifugation was only about 50% of that found after the cumulative procedure. Apolipoproteins in lipoproteins isolated by the two methods were well separated by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Color of the stained bands was extracted and read photometrically. A linear standard curve was obtained with albumin. Absorbance corresponding to 1 microgram/ml was 0.057. Below d = 1.100 g/ml (HDL2b) the two ultracentrifugation methods gave comparable results for all apoproteins. In contrast to this the level of apo A-I, apo E, and apo A-IV in the more dense types of HDL was higher when estimated by cumulative than by sequential ultracentrifugation. In HDL3 isolated by sequential ultracentrifugation the apo A-IV, apo E, and apo A-I concentrations were 51, 31, and 45% respectively, of values found after cumulative ultracentrifugation. The results indicate that cumulative density ultracentrifugation, followed by colorimetric determination of apoproteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, is a useful approach when studying lipoprotein distribution in rat plasma.

Animals↗
PubMed1984

Plasma lipoprotein responses to castration and androgen substitution in rats.

To elucidate plasma testosterone/lipoprotein relationships in a controlled animal experiment, whole-plasma lipid concentration and amount of lipoprotein components in five density classes were determined in three groups of rats: normal control rats, short-term castrated rats, and rats treated with testosterone propionate after castration. Compared to control rats, whole-plasma total cholesterol, free cholesterol (FC), cholesteryl-ester (CE), and phospholipids (PL) rose in castrated rats but were normalized in rats receiving androgen substitution. There were no group differences in whole-plasma triacylglycerol concentration. The levels of protein, FC, and CE in LDL (d = 1.006 to 1.063 g/mL) and HDL2b (d = 1.063 to 1.100 g/mL) of castrated rats were appreciably higher than in LDL and HDL2b of control rats. In androgen-substituted rats the level of LDL and HDL2b protein, FC, CE, and PL were all reduced to normal or subnormal levels. The esterified fraction of cholesterol in whole plasma was increased by androgen treatment. There were no significant group differences in VLDL (d less than 1.006 g/mL), HDL2a (d = 1.100 to 1.125 g/mL) or in HDL3 (d = 1.125 to 1.210 g/mL). The results suggest that short-term castration of rats is followed by hyperlipoproteinemia due to lack of testosterone and that the lipoprotein changes mainly reside in LDL and the less-dense type of HDL.

Animals↗