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Biomedical subjects

M Flieger

Publications and source records attributed to M Flieger.

At least 19 recordsLinked to original sources
PubMed2005

Oligosaccharides produced by submerged cultures of Claviceps africana and Claviceps sorghi.

Oligosaccharides produced by submerged cultures of C. africana and C. sorghi were isolated by semipreparative HPLC. Structure of 6-O-beta-D-fructofuranosyl-D-glucopyranose (blastose), 1,6-bis-O-(beta-D-fructofuranosyl)-alpha-D-glucopyranoside (neokestose) and two sugar alcohols, 1-O-beta-D-fructofuranosyl-D-mannitol (fructosylmannitol) and 1,6-bis-O-(beta-D-fructofuranosyl)-D-mannitol (bisfructosylmannitol) was determined by NMR spectrometry. MALDI TOF MS analysis revealed molecular ions [M+Na]+ that indicate the presence of other tetra- and pentasaccharides (m/z = 689.4 and 851.5, respectively) and corresponding sugar alcohol (m/z = 691.4). Rapid conversion of sucrose into series of oligosaccharides and corresponding sugar alcohols was observed in all tested strains.

Chromatography, High Pressure Liquid↗
PubMed2004

Preparation of nanoparticles by electrocoagulation from soluble exopolysaccharide produced by Claviceps viridis.

Electrocoagulation is an evolving technology that has been effectively applied for wastewater treatment but its applications in biotechnology and nanotechnology are very limited. This method was applied for the preparation of nanoparticles from soluble exopolysaccharide (EPS) produced by Claviceps viridis in a submerged batch culture. A cathode/anode pair electrode (Al or Fe) system was used for determination of the separation rates of electrocoagulation and the yields of EPS nanoparticles production. The separation rates of 0.170 +/- 0.003 mg EPS/sec (Fe electrodes) and 0.250 +/- 0.003 mg EPS/sec (Al electrodes) were calculated for voltage gradient 1 V/1 cm of electrodes distance and were constant during experiments. The specific yield of EPS nanoparticles production based on the consumed electric power was dependent on the material of the electrodes and its value was determined as 0.71 +/- 0.01 mg EPS/W for Fe electrodes and 0.91 +/- 0.01 mg EPS/W for Al electrodes, respectively.

Chemical Precipitation↗
PubMed2004

Physiological dendrogram of Claviceps spp. based on sucrose metabolism in submerged cultures and its comparison with phylogenetic tree.

Sixteen isolates of Claviceps spp. were analyzed for the production of polysaccharides, oligosaccharides, and sucrose metabolism under conditions of submerged fermentation. Physiological markers calculated by the Verhulst-Pearl law were used for hierarchical cluster analysis. Low correlation was found between physiologically based dendrogram and phylogenetic analysis constructed from an alignment of rDNA sequences. To confirm the intraspecific uniformity of physiological markers three isolates of C. africana from different hosts and locations were included. The influence of genotype, physiological variability, environmental location and habitat on metabolite production is discussed.

Claviceps↗
PubMed2003

Biodegradable plastics from renewable sources.

Plastic waste disposal is a huge ecotechnological problem and one of the approaches to solving this problem is the development of biodegradable plastics. This review summarizes data on their use, biodegradability, commercial reliability and production from renewable resources. Some commercially successful biodegradable plastics are based on chemical synthesis (i.e. polyglycolic acid, polylactic acid, polycaprolactone, and polyvinyl alcohol). Others are products of microbial fermentations (i.e. polyesters and neutral polysaccharides) or are prepared from chemically modified natural products (e.g., starch, cellulose, chitin or soy protein).

Bacteria↗
PubMed2003

Kinetics of soluble glucan production by Claviceps viridis.

Among 18 tested strains of Claviceps spp., 7 produced significant amounts of exocellular polysaccharide (EPS). The maximum production of EPS was found in fermentation broth of Claviceps viridis. The kinetics of growth, substrate consumption, and EPS production in the batch, aerobic, submerged culture of this fungus were investigated in detail. The experimental data were processed by a simple mathematical model describing mass balance of growth, substrate consumption, formation of intermediates, and production of EPS. The parameters of the model were estimated from data obtained in cultivation performed in flasks and two laboratory fermentors of different size. Physiological similarity was obtained during process scale-up in volumetric ratio 1:100. The sugar consumption efficiency (52%) and observed EPS productivity (1.9 kg/m3 per d) were comparable with literature data.

Biomass↗
PubMed2002

Psychoactive tryptamines from basidiomycetes.

The review lists natural sources, i.e. strains and species of fungi producing predominantly psychoactive tryptamines (indolealkylamines), their chemical structure and properties, toxic effects on the man and psychic symptoms of intoxication. It describes the biosynthesis and production of some tryptamines by the mycelial culture of Psilocybe bohemica Sebek, a survey of methods for their analysis and isolation. It evaluates the worldwide use and abuse of psychoactive fungi as sources of drugs in general and in the Czechia in particular during the last two and a half decades.

Basidiomycota↗
PubMed2001

Stereospecificity and stereoselectivity of flobufen metabolic profile in male rats in vitro and in vivo: phase I of biotransformation.

Flobufen (F) is the original nonsteroidal antiinflammatory drug (NSAID) containing two enantiomers. The aim of this investigation was to elucidate the biotransformation pathway of F at chiral level in phase I of biotransformation. Stereoselectivity and stereospecificity of the respective enzymes were studied in male rats in vitro (microsomal and cytosolic fractions, hepatocytes suspension) and in vivo. The rac-F, (+)-R-F and (-)-S-F were used as substrates. Amounts of F enantiomers, 4-dihydroflobufen diastereoisomers (DHF) and other metabolites (M-17203, UM) were determined with a chiral HPLC method in two chromatographic runs on R,R-ULMO and allyl-terguride bonded columns. Stereoselective biotransformation of the two enantiomers of F was observed at all tested levels and significant bidirectional chiral inversion of enantiomers of F was observed in hepatocytes. Mean enantiomeric ratios of F concentrations (S-/R-), after rac-F incubations, ranging from 1.09 in cytosolic fraction to 18.23 in hepatocytes. Stereospecificity of the respective F reductases was also observed. (2R;4S)-DHF and (2S;4S)-DHF are the principal metabolites of F in microsomes and hepatocytes. Neither DHF diastereoisomers nor M-17203 were found in cytosolic fraction. Only the nonchiral metabolite, M-17203, was found in all urine and feces samples after oral administration of F.

Animals↗
PubMed2001

The epitope recognized by pan-HLA class I-reactive monoclonal antibody W6/32 and its relationship to unusual stability of the HLA-B27/beta2-microglobulin complex.

A broadly used pan-HLA class I-reactive monoclonal antibody W6/32 is believed to recognize a conformational epitope dependent on association between heavy chains and beta2-microglobulin (beta2m). However, in the present study we report that W6/32 does recognize at least some free HLA class I heavy chains under the partially denaturating conditions of nonreducing Western blotting, namely nearly all HLA-B allelic products. Furthermore, we confirm and largely extend our previous observation that complexes of beta2m with heavy chains of a few HLA class I allelic forms (most notably HLA-B27) exhibit unusual resistance to dissociation by SDS, which is reminiscent of MHC class II molecules. In addition, our data indicate the existence of covalent (disulfide-linked) heterodimers of certain HLA class I heavy chains (namely Cw1 and Cw4) and beta2m.

Animals↗
PubMed2001

Complex interaction of ergovaline with 5-HT2A, 5-HT1B/1D, and alpha1 receptors in isolated arteries of rat and guinea pig.

Vascular effects of ergovaline mediated by 5-hydroxytryptamine(HT)2A, 5-HT1B/1D, and alpha1 receptors were studied in isolated arterial preparations of rat and guinea pig. In rat tail artery ergovaline behaved as a potent contractile partial agonist showing an agonist potency (pEC50) of 8.86 +/- 0.03, a maximum response (Emax) of 59 +/- 2% with respect to 5-HT, and a partial agonist affinity (pK(P)) of 8.51 +/- 0.06. Ergovaline was equipotent with ergotamine (pEC50, 8.69 +/- 0.07; Emax, 52 +/- 4%; pK(P), 8.36 +/- 0.11). Contractile responses to ergovaline and ergotamine were surmountably antagonized by the 5-HT2A receptor antagonist ketanserin (3 nM). Antagonist affinity (apparent pA2) for ketanserin against ergovaline and ergotamine was 9.19 +/- 0.08 and 9.36 +/- 0.17, respectively. Ergovaline showed extremely slow on-set and off-set kinetics in rat tail artery. The construction of cumulative concentration-response curves required about 4 h, and the contractile response to ergovaline (30 nM), which completely abolished the subsequent contractile response to 5-HT (10 nM to 1 mM), could not be reversed by wash-out. In guinea pig iliac artery moderately precontracted with prostaglandin F2alpha (0.05 to 0.5 microM) ergovaline behaved as an agonist (pEC50, 7.71 +/- 0.10) with a potency similar to that of 5-HT (pEC50, 7.60 +/- 0.05). The contractile response to ergovaline was inhibited by the 5-HT1B/1D receptor antagonist GR127935 (10 nM). The apparent pA2 value for GR127935 against ergovaline was 8.90 +/- 0.12. Ergovaline (10 nM) produced no contractile response in guinea pig iliac artery when added before the PGF2alpha-induced precontraction but caused insurmountable blockade of the contractile response to the 5-HT1B/1D receptor agonist 5-carboxamidotryptamine (5-CT). The apparent pA2 value for ergovaline against 5-CT was 8.56 +/- 0.18. In rat thoracic aorta ergovaline (2 microM) activated alpha1 adrenoceptors only with low efficacy (Emax, 12 +/- 3%) but surmountably antagonized norepinephrine-induced contractions with a pK(P) of 7.07 +/- 0.12. It is concluded that the powerful constrictor effect of ergovaline mediated by activation of vascular 5-HT2A and 5-HT1B/1D receptors may explain the vascular symptoms of fescue toxicosis observed in livestock grazing tall fescue pastures infected with the endophytic fungus Neotyphodium coenophialum.

Animals↗
PubMed2000

Strong association of HLA-B27 heavy chain with beta 2-microglobulin.

Monoclonal antibody TG1 recognizes specifically antigens HLA-B27, B7, B22 and B17 on cell surface in cytotoxicity and cytofluorometry tests. When cell detergent extracts were subjected to SDS PAGE under mild conditions (no heating and no reduction of the sample) followed by Western blotting, TG1 detected exclusively a complex of B27 heavy chains with beta(2)-microglobulin (as a 50 kDa band) whereas the other B-locus antigens (B7, B22, B17) were detected as free 43 kDa heavy chains under the same conditions. When the samples were boiled prior to SDS PAGE, TG1 detected again the 43 kDa free heavy chains of B7, B22 and B17 but no zone corresponding to B27 could be detected indicating that the epitope in free B27 chains is more sensitive to denaturation by SDS. Thus, our main finding is that the interaction of HLA-B27 heavy chain with beta(2)-microglobulin appears to be stronger than that of the other HLA-B chains. The resistance of the HLA-B27/beta(2)-microglobulin complex to the SDS dissociation is strikingly similar to the behavior of MHC class II molecules under similar conditions. Thus, it may be speculated that HLA-B27 complexes can be also more stable than other MHC class I molecules under more physiological dissociative conditions (e.g. in endosomal compartments). This feature might potentially influence antigen presentation by HLA-B27 and contribute to the well known disease linkage of HLA-B27.

Animals↗
PubMed2000

Chemoraces and habitat specialization of Claviceps purpurea populations.

We studied genetic variability of 100 isolates of Claviceps purpurea by using randomly amplified polymorphic DNA (RAPD), an EcoRI restriction site polymorphism in the 5.8S ribosomal DNA (rDNA), the alkaloids produced, and conidial morphology. We identified three groups: (i) group G1 from fields and open meadows (57 isolates), (ii) group G2 from shady or wet habitats (41 isolates), and (iii) group G3 from Spartina anglica from salt marshes (2 isolates). The sclerotia of G1 isolates contained ergotamines and ergotoxines; G2 isolates produced ergosine and ergocristine along with small amounts of ergocryptine; and G3 isolates produced ergocristine and ergocryptine. The conidia of G1 isolates were 5 to 8 microm long, the conidia of G2 isolates were 7 to 10 microm long, and the conidia of G3 isolates were 10 to 12 microm long. Sclerotia of the G2 and G3 isolates floated on water. In the 5.8S rDNA analysis, an EcoRI site was found in G1 and G3 isolates but not in G2 isolates. The host preferences of the groups were not absolute, and there were host genera that were common to both G1 and G2; the presence of members of different groups in the same locality was rare. Without the use of RAPD or rDNA polymorphism, it was not possible to distinguish the three groups solely on the basis of phenotype, host, or habitat. In general, populations of C. purpurea are not host specialized, as previously assumed, but they are habitat specialized, and collecting strategies and toxin risk assessments should be changed to reflect this paradigm shift.

Alkaloids↗
PubMed1999

High-performance liquid chromatography study of the enantiomer separation of chrysanthemic acid and its analogous compounds on a terguride-based stationary phase.

The direct enantioseparation of chrysanthemic acid [2,2-dimethyl-3-(2-methylpropenyl)-cyclopropanecarboxylic acid] and its halogen-substituted analogues was systematically studied by HPLC using a terguride-based chiral stationary phase in combination with a UV diode array and chiroptical detectors. Isomers with (1R) configuration always eluted before those with (IS) configuration. The elution sequence of cis- and trans-isomers was strongly affected by mobile phase pH, whereas the enantioselectivity remained the same. Conditions for the separation of all the enantiomers were also examined. This method was used for monitor the hydrolytic degradation products of Cyfluthrin (Baythroid) in soil under laboratory conditions.

Chromatography, High Pressure Liquid↗
PubMed1999

Direct resolution of optically active isomers on chiral packings containing ergoline skeleton. 6. Enantioseparation of profens.

The enantioselective behaviour of some underivatized 2-arylpropionic acids (profens) and flobufen by HPLC using a terguride-based chiral stationary phase was tested. X-ray analysis of crystals of the chiral selector and its complexes with naproxen allowed a deeper insight into the enantiodiscriminative process. The column stability and reproducibility, and the potential of the packing for semipreparative scale separations were also determined. A method for determining flobufen enantiomers and metabolites in plasma samples is described.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1997

Ergot alkaloids--sources, structures and analytical methods.

Natural sources, i.e. fungal strains and species producing ergot alkaloids (EA), are surveyed together with the chemical structures of EA and a list of new natural EA discovered in the last three decades. Other topics include new efficient chromatographic methods (HPLC) for the separation and isolation of new natural EA and also immunological methods of EA detection.

Chromatography, High Pressure Liquid↗
PubMed1997

Neuroimmunomodulation of natural killer (NK) cells by ergot alkaloid derivatives.

Ergot alkaloids (EAs), products of Claviceps spp., are widely used in various fields of clinical medicine (neurology, psychiatry, endocrinology). In the present work we studied the neuroimmunomodulative effect of EAs on activation of NK cells and their signalling pathways. Furthermore, the killing capability of rat NK cells in vitro was examined in the presence of glycosidic derivatives of elymoclavine, agroclavine, and liposome-encapsulated EAs. The engagement of appropriate NK cell membrane receptors by EAs cause an indirect enhancement of adenylyl cyclase system through inhibition of G-protein al,2-subunit (up to 50 % of control values). All of the tested EAs enhanced the rat NK cell-mediated cytotoxic activity in vitro, particularly against target cells of astrocyte origin (C-6 glioma). The present results argue for a possible EA immunomodulatory role of cell-mediated immunity in tumour regression processes.

Animals↗
PubMed1994

Fast atom bombardment mass spectrometry of elymoclavine glycosides.

A series of nine naturally occurring and/or semi-synthetic elymoclavine mono- and oligoglycosides containing various sugar units was investigated by fast atom bombardment, high-resolution measurements and linked scans. The fragmentations of the [M+H]+ and [M+Na]+ ions are described and their different contributions to the structure elucidation are discussed.

Carbohydrate Sequence↗