Biomedical subjects

I Haller

Publications and source records attributed to I Haller.

At least 19 recordsLinked to original sources

PubMed2001

Effect of cardiolipin oxidation on solid-phase immunoassay for antiphospholipid antibodies.

Diagnostic assays for antiphospholipid antibodies are routinely performed on microtitre plates coated with cardiolipin. Here we show that contact between cardiolipin and NUNC-Immuno plates leads to extensive oxidation, generating a series of peroxy-cardiolipins which were identified by electrospray ionization mass spectrometry. To investigate the impact of oxidation on the antibody assay. cardiolipin was resolved into 12 molecular species, including oxidized species and non-oxidized species with different degrees of unsaturation. All 12 species reacted under anaerobic conditions with serum from patients with primary antiphospholipid syndrome. Immune reactivity was similar for tetralinoleoyl-cardiolipin, trilinoleoyl-oleoyl-cardiolipin, and peroxycardiolipins, but somewhat lower for tristearoyl-oleoyl-cardiolipin. Oxidative treatment of cardiolipin with air, cytochrome c, or Cu2+/tert-butylhydroperoxide, either before or during the assay, did not enhance immune reactivity. Similar results were obtained with a monoclonal IgM from lupus-prone mice, that binds cardiolipin in the absence of protein cofactors. We conclude that the solid-phase assay for antiphospholipid antibodies can be supported by various oxidized and non-oxididized molecular species of cardiolipin.

Adult↗

PubMed2000

Energy balance, viral burden, insulin-like growth factor-1, interleukin-6 and growth impairment in children infected with human immunodeficiency virus.

OBJECTIVE: To determine the relationship between energy metabolism and growth abnormalities in HIV-infected children and to assess clinical or laboratory characteristics which may be contributing factors to their growth impairment. DESIGN: A comparative study. METHODS: We measured energy intake by inpatient calorie count/outpatient 24 h food recalls, resting energy expenditure by indirect calorimetry, total energy expenditure by the doubly-labeled water technique, iron metabolism, protein metabolism, and lipid metabolism markers as well as CD4 count, viral load, insulin-like growth factor-1 (IGF-1), serum interleukin-6 (IL-6), and whole blood stimulated IL-6 levels in prepubertal congenitally HIV-infected children with normal and impaired growth patterns. RESULTS AND CONCLUSIONS: Differences in energy expenditures were not found between normal and growth-impaired HIV-infected children. Energy intake but not energy expenditure was significantly reduced when HIV-infected children were compared to expected normal values for age and gender. Advanced HIV clinical disease, severe immune suppression, increased viral burden, increased IL-6 activity, decreased total serum protein, and decreased IGF-1 levels were more likely to be found in HIV-infected children with growth impairment in comparison with HIV-infected children with normal growth.

Adolescent↗

PubMed1998

Substrate inhibition of D-amino acid transaminase and protection by salts and by reduced nicotinamide adenine dinucleotide: isolation and initial characterization of a pyridoxo intermediate related to inactivation.

D-Amino acid transaminase, a pyridoxal phosphate (PLP) enzyme, is inactivated by its natural substrate, D-alanine, concomitant with its alpha-decarboxylation [Martinez del Pozo, A., Yoshimura, T., Bhatia, M. B., Futaki, S., Manning, J. M., Ringe, D., and Soda, K. (1992) Biochemistry 31, 6018-6023; Bhatia, M. B., Martinez del Pozo, A., Ringe, D., Yoshimura, T., Soda, K., and Manning, J. M. (1993) J. Biol. Chem. 268, 17687-17694]. beta-Decarboxylation of d-aspartate to d-alanine leads also to this inactivation [Jones, W. M., van Ophem, P. W., Pospischil, M. A., Ringe, D., Petsko, G., Soda, K., and Manning, J. M. (1996) Protein Sci. 5, 2545-2551]. Using a high-performance liquid chromatography-based method for the determination of pyridoxo cofactors, we detected a new intermediate closely related to the inactivation by d-alanine; its formation occurred at the same rate as the inactivation and upon reactivation it reverted to PLP. Conditions were found under which it was characterized by ultraviolet-visible spectral analysis and mass spectroscopy; it is a pyridoxamine phosphate-like compound with a C2 fragment derived from the substrate attached to the C'-4 of the pyridinium ring and it has a molecular mass of 306 consistent with this structure. In the presence of d-serine, slow accumulation of a quinonoid intermediate is also related to inactivation. The inactivation can be prevented by salts, which possibly stabilize the protonated aldimine coenzyme complex. The reduced cofactor, nicotinamide adenine dinucleotide, prevents D-aspartate-induced inactivation. Both of these events also are related to formation of the novel intermediate.

Alanine↗

PubMed1997

Structure of chain d of the gigantic hemoglobin of the earthworm.

The extracellular hemoglobin of the earthworm has four major O2-binding chains, a, b, c and d, together with additional non-heme structural chains that are required for assembly. Although the abc trimer self-associates extensively at least to (abc)10, addition of chain d results in the formation of a discrete 280 kDa complex corresponding to (abcd)4. Thus a primary function of chain d is to cap the abc association and convert an abc trimer that binds O2 with weak cooperativity to a highly cooperative (abcd)4 complex. Amino-acid sequences of the major globin chains a, b, c have been determined previously by peptide and cDNA analysis. However, the peptide sequence reported for the major chain d (Shishikura, F., Snow, J.W., Gotoh, T., Vinogradov, S.N. and Walz, D.A. (1987) J. Biol. Chem., 262. 3123-3131), has a calculated molecular mass 134-167 Da higher than masses for components of chain d determined by mass spectrometry (Owrby, D.W., Zhu, H., Schneider, K., Beavis, R.C., Chait, B.T. and Riggs, A.F. (1993) J. Biol. Chem. 268, 13539-13547). Reverse-phase HPLC confirms the presence of two distinct polypeptides, d1 and d2, together with d'1, a variant of d1, cDNA derived amino acid sequences have been determined for chains d'1 and d2 by application of the polymerase chain reaction with primers based on the NH2-terminal sequences and oligo-dT. Each of the two cDNA-derived sequences has 140 residues and they differ by 28 substitutions. The data show that the sequence originally reported had been derived from peptides generated from both polypeptides.

Amino Acid Sequence↗

PubMed1994

Anti-tumor necrosis factor antibody treatment of recurrent bacteremia in a baboon model.

Timely intervention in recurrent episodes of sepsis poses a major problem in intensive care, because the diagnosis is often made after the onset of sepsis, delaying the initiation of treatment. There are only a few animal models that cover this situation. We have developed a baboon model of recurrent bacteremia (3 x 2 h intravenous infusion of 1 x 10(8) CFU Escherichia coli/kg), which leads to late organ failure. In this model (tested on 16 animals) we began anti-tumor necrosis factor antibody treatment (BAYX 1351; Bayer AG, 7.5 mg/kg or saline placebo) after the first bacteremic episode (+4 h), which significantly (p < .05) protected animals from death, none out of eight (100% survival), in the treatment group in contrast to four animals out of eight died (50% survival) in the placebo group. This effect was also reflected in improved organ function and in attenuated cytokine and plasminogen activator inhibitor release. From these studies we conclude that the delayed application of anti-tumor necrosis factor antibodies in recurrent bacteremia is a powerful tool for preventing septic death.

Animals↗

PubMed1987

Evaluation of ciprofloxacin alone and in combination with other antibiotics in a murine model of thigh muscle infection.

The therapeutic efficacies of ciprofloxacin and some comparative drugs were evaluated in a model of thigh muscle infection in neutropenic mice. Ciprofloxacin was found to be highly effective against all gram-negative and gram-positive bacteria tested. Combinations of ciprofloxacin and either gentamicin or beta-lactam antibiotics exhibited additive or slightly synergistic effects against the Enterobacteriaceae and gram-positive isolates. Azlocillin was found to increase significantly the efficacy of ciprofloxacin against Pseudomonas aeruginosa. Antagonistic interactions with vancomycin, which impaired the bactericidal activity of ciprofloxacin against Streptococcus faecalis, were observed only in vitro but not in vivo, whereas erythromycin also slightly reduced the therapeutic efficacy of ciprofloxacin in vivo.

Animals↗

PubMed1986

Comprehensive evaluation of ciprofloxacin in combination with beta-lactam antibiotics against Enterobacteriaceae and Pseudomonas aeruginosa.

1-cyclopropyl-6-fluoro-1, 4-dihydro-4-oxo-7-piperazine-1-ylquinoline-3-carboxylic acid (ciprofloxacin, Bay o-9867, Bay q-3939) was evaluated by checkerboard assay in combination with ampicillin, ticarcillin, mezlocillin, azlocillin, piperacillin, cefamandole, cefoxitin, cefotaxime, and ceftazidime. A total of 220 clinical isolates of enterobacteriaceae and Pseudomonas aeruginosa (11 species, 20 strains each) were examined. Predominantly additive combination effects were seen with all antibiotic combinations tested. Synergy was obtained with only a few test strains while antagonistic drug interactions were not observed at all. Time-kill experiments which were performed to assess the bactericidal activities, confirmed these findings. The antibiotic combinations were also evaluated in vivo using a model of experimental thigh muscle infection in neutropenic mice. In-difference or additive therapeutic effects resulted when the beta-lactam compounds and ciprofloxacin were given in combination at doses which were also effective alone. Subinhibitory doses of azlocillin and mezlocillin, on the other hand, appeared to increase the efficacy of ciprofloxacin. The influence of various application schedules was examined by time-kill experiments and in mice. Sequential administration of the drugs at intervals of 2 h did not alter the combination effects regardless of the sequence of administration.

Animals↗

PubMed1986

Distribution of [14C]-ciprofloxacin in experimentally induced intramuscular abscesses of rats.

Wistar rats were infected by injection of 0.05 ml of a dense oily suspension of Staphylococcus aureus into the posterior thigh muscles of the hind leg. Three days later, solid abscesses had formed which were characterized by a peripheral accumulation of polymorphocytes and incipient central necrosis. At this time, 10 mg/kg of [14C]-ciprofloxacin (1-cyclopropyl-6-fluoro-1,4-dihydro-4-oxo-7-piperazin-1-ylquino line-3-carboxylic acid, Bay o 9867; designated tradename: Ciprobay) were administered intravenously. The animals were sacrificed at various time intervals after treatment and the distribution of radioactivity was examined by whole-body autoradiography. Five min after administration of ciprofloxacin, the radioactivity was found to be differentially distributed among all organs and tissues, but no radioactivity was detectable in the abscess. Beginning from 1 h post appl., increasing relative amounts of radioactivity were seen inside the abscesses. The relative enrichment as compared to the surrounding muscle tissue was most pronounced after 5 h, indicating that the radioactivity was eliminated more rapidly from the muscle than from the abscess. Some radioactivity was still present in the abscess 8 h after treatment of the animals. The comparison of autoradiograms and corresponding histological sections revealed a distinct affinity of [14C]-ciprofloxacin and/or its potential radioactive metabolites to the areas of inflammatory cellular infiltrates.

Abscess↗

PubMed1985

Mode of action of clotrimazole: implications for therapy.

Ergosterol is an essential constituent of the fungal cytoplasmic membrane. Clotrimazole and other azoles interfere with the ergosterol biosynthesis in a concentration-dependent fashion. Although low concentrations exhibit only a partially inhibitory effect, high concentrations may completely block ergosterol synthesis. Reduction of fungal growth and inhibition of growth and fungicidal action during prolonged incubation are the corresponding effects at the cellular level that are a consequence of ergosterol depletion. The inoculum effect, the influence of the incubation period, and the influence of nutrient media, three factors that often complicate susceptibility testing in vitro, can also be explained by the mode of action of azole compounds. Another interesting characteristic of azole antifungals was revealed by the observation that hyphae and pseudomycelia of Candida albicans are much more susceptible to azoles than are yeast cells. Even 1% of the minimum inhibitory concentration of clotrimazole may totally inhibit mycelial growth in vitro. This may be of clinical importance, since germination was reported to enhance adherence of C. albicans to buccal and vaginal epithelial cells.

Azoles↗

PubMed1985

A model to show the role of extracellular beta-lactamases in mediating staphylococcal resistance.

Considerable amounts of extracellular beta-lactamase are liberated from penicillin-resistant staphylococci into the surrounding medium. The accumulation of exoenzyme in conventional in-vitro test systems may result in rapid inactivation of hydrolysable antibiotics, while in vivo the concentration of extracellular beta-lactamase varies depending on the site of infection. Using a new open test model designed to eliminate the effect of exoenzyme, it could be shown that resistance of beta-lactamase-producing staphylococci to mezlocillin as seen in the broth dilution test was mediated predominantly by the extracellular beta-lactamase fraction. Animal experiments suggested that mezlocillin may exhibit a therapeutic effect against beta-lactamase-producing staphylococci under certain conditions in vivo which prevent build-up of exoenzyme.

Animals↗

PubMed1985

Penetration of antibiotics through cell culture monolayers.

Commercial tissue culture chambers were modified in such a way that they contained two portions of medium separated by a horizontal membrane. When grown on this membrane, Vero (monkey kidney) cells formed continuous cell monolayers. By comparing the penetration of antibiotics through monolayer-covered and cell-free membranes, the retention brought about by the cell layer could be measured. Only minor differences were seen between oxacillin, mezlocillin and ciprofloxacin. Penetration of polymyxin B through the cell layer proved to be reduced by about 40% in comparison to oxacillin.

Animals↗

PubMed1985

Comprehensive evaluation of ciprofloxacin-aminoglycoside combinations against Enterobacteriaceae and Pseudomonas aeruginosa strains.

The in vitro activities of antibiotic combinations containing ciprofloxacin and either gentamicin, sisomicin, netilmicin, amikacin, or tobramycin were evaluated by checkerboard assay (agar dilution method). A total of 220 strains of Enterobacteriaceae and Pseudomonas aeruginosa (11 species, 20 strains each) were tested. Synergistic or antagonistic effects were observed in less than 1% of the tests performed; they appeared to represent method-dependent fluctuations rather than true antibiotic interactions. No significant differences among the five aminoglycosides tested were seen. Time-kill experiments performed with three representative strains of Escherichia coli and Serratia marcescens showed additive combination effects with respect to the kill rates and inhibition of bacterial regrowth. Exposure of Serratia strains to either ciprofloxacin or gentamicin before the addition of the second drug had little influence on the combination effects observed. No antagonistic drug interactions were seen in vivo when combination therapy with ciprofloxacin and gentamicin was evaluated in a model of E. coli thigh muscle infection in neutropenic mice. Comparable therapeutic effects were obtained, regardless of whether the two compounds were administered simultaneously or sequentially at 1- or 2-h intervals.

Aminoglycosides↗

PubMed1984

Importance of extracellular and cell-bound beta-lactamase in mediating resistance of Staphylococcus aureus to mezlocillin.

Most penicillin-resistant staphylococci release a considerable portion of their beta-lactamase into the surrounding medium. Accumulation of this exoenzyme in conventional susceptibility test systems may result in a rapid inactivation of hydrolyzable antibiotics. Since under in vivo conditions the concentration of extracellular beta-lactamase should depend on the site of infection, susceptibility of Staphylococcus aureus to mezlocillin, a broad-spectrum penicillin, was measured in an open test model which prevented build-up of exoenzyme. The staphylococcal cells were immobilized and incubated between two membrane filters, and the excreted beta-lactamase was washed out by a constant flow of broth containing the antibiotic. Two test strains which produced large amounts of extracellular beta-lactamase and which were found to be resistant in the broth dilution test proved to be susceptible to mezlocillin in the open test model. This indicates that resistance to mezlocillin as measured by the broth dilution method was mediated predominantly by the extracellular enzyme fraction. Experiments performed with small infective doses in a model of peritoneal infection in leukopenic mice suggest that mezlocillin exhibits a therapeutic effect against beta-lactamase-producing staphylococci under certain in vivo conditions in which build-up of extracellular beta-lactamase does not occur.

Animals↗

PubMed1983

The combined action of azlocillin and sisomicin in a model simulating the in vivo serum kinetics.

The in vivo serum kinetics of azlocillin and sisomicin were simulated in a new in vitro test model. A strong synergistic effect against Pseudomonas aeruginosa resulted when both compounds were administered simultaneously and eliminated according to their individual half-life values, even when the decreasing drug concentrations exceeded the MICs for only a short period of time. When applied at intervals, neither pretreatment with azlocillin nor with sisomicin blocked the antibacterial activity of the combination partner.

Azlocillin↗

PubMed1982

Combined action of decreasing concentrations of azlocillin and sisomicin on Pseudomonas aeruginosa as assessed in a dynamic in vitro model.

The effect of decreasing concentrations of azlocillin and sisomicin on Pseudomonas aeruginosa was examined. Logarithmically growing bacterial cultures were incubated in an ultrafiltration cell, and after adding the antibiotics, the culture medium was diluted every 20 min without any decrease in cell density. The turn-over of medium resulted in the elimination of azlocillin with a half-life of 75 min. This simulated serum kinetics in vivo. When testing sisomicin, small amounts of this agent were added during every dilution step to achieve a half-life of 120 min. Growth conditions were comparable in all experiments. The simultaneous combination of azlocillin and sisomicin resulted in strong synergism as assessed by higher killing rates and more prolonged growth inhibition of surviving bacteria. Comparable results were observed when both drugs were added at intervals of 40 min. When applied at intervals of 120 min, the combined effect of azlocillin and sisomicin was reduced, but still superior to the effect of double the concentration of each compound alone. Thus, neither pre-treatment with azlocillin nor with sisomicin impaired the antibacterial activity of the combination partner. This seems to be of clinical importance since the agents may be administered at different times during combined therapy.

Azlocillin↗

PubMed1982

In vitro activity of the two principal oxidative metabolites of metronidazole against Bacteroides fragilis and related species.

Metronidazole and its two principal oxidative metabolites were tested in vitro against 20 clinical isolates of the Bacteroides fragilis group. Both metabolites were bactericidal, and the exhibited 65 and 5%, respectively, of the inhibitory effect of metronidazole. Additive or weak synergistic effects resulted in combination with the parent compound.

Bacteroides fragilis↗

PubMed1982

In vitro activity of modern penicillins and cephalosporins against enterococci.

The in vitro activity of nine penicillin and cephalosporin antibiotics against enterococci was compared by MIC determination and killing curve experiments. To inhibit 90% of the 143 clinical isolates tested the following drug concentrations were required: mezlocillin, 1--2 micrograms/ml; azlocillin, 2 micrograms/ml; piperacillin, 4 micrograms/ml; cefazedone, 16 micrograms/ml; cefazolin and cefoperazone, 32 micrograms/ml; ticarcillin, 64 micrograms/ml. Cefotaxime and lamoxactam proved to be almost ineffective at 128 micrograms/ml which was the highest concentration tested. In killing curve experiments a reduction of viable cell count by 2--3 logs was achieved with all antibiotics except cefotaxime and lamoxactam. In general, the acylureido-penicillins exhibited a better bactericidal activity than the cephalosporins.

Cephalosporins↗

PubMed1982

[Actual resistance of Staphylococcus aureus: beta-Lactamase production and susceptibility to various penicillins and erythromycin (author's transl)].

The actual resistance of Staphylococcus aureus from different clinics in Bielefeld was examined on the basis of 155 strains freshly isolated from clinical specimens during a period of two months. Sensitivity of these strains was assessed by minimum inhibitory concentrations (MICs) as determined by agar dilution method. As expected oxacillin proved to be the most effective compound according to its stability to beta-lactamases. Ampicillin and amoxicillin were nearly as active as penicillin G, while propicillin exhibited a higher activity than penicillin G against those strains which were moderately sensitive to penicillin G. Mics of erythromycin were similar to those of propicillin and most of the highly penicillin resistant strains proved to be resistant to erythromycin too. When comparing the acylureidopenicillins and ticarcillin nearly identical MIC values resulted for azlocillin, mezlocillin and piperacillin; ticarcillin was found to be slightly less active. The qualitative assay for beta-lactamase activity performed after induction with methicillin demonstrated strong correlation between presence or absence of beta-lactamases and sensitivity of the bacteria to penicillin G. beta-lactamase activity could be found in almost all strains with MIC greater than or equal to 0.25 micrograms/ml for penicillin G. These results are discussed with respect to the recommendations for susceptibility testing.

Erythromycin↗