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Biomedical subjects

G Engelhardt

Publications and source records attributed to G Engelhardt.

At least 37 records · Page 2Linked to original sources
PubMed1995

Metabolism of the Fusarium mycotoxins zearalenone and deoxynivalenol by yeast strains of technological relevance.

The Fusarium mycotoxin zearalenone (ZEA), added at a level of 2 micrograms/ml, was reduced stereoselectively by cultures of Candida tropicalis, Torulaspora delbrückii, Zygosaccharomyces rouxii, and 7 Saccharomyces strains to both alpha- and beta-zearalenol. In contrast, only alpha-zearalenol was produced from ZEA by Pichia fermentans and several yeast strains of the genera Candida, Hansenula, Brettanomyces, Schizosaccharomyces, and Saccharomycopsis. No glucose conjugates of ZEA (zearalenone-4-beta-D-glucopyranoside) were detected. The trichothecene mycotoxin deoxynivalenol (DON) was not metabolized by any of the yeast strains that were used for analysis.

Beer↗
PubMed1995

Meloxicam: a potent inhibitor of adjuvant arthritis in the Lewis rat.

The effects of meloxicam, piroxicam, diclofenac and tenidap on the swelling of hind paws, radiologically-detectable bone and cartilage destruction of hind paws, increase in spleen weight, increase in erythrocyte sedimentation rate and changes in serum protein composition in male Lewis rats with adjuvant arthritis were studied following once-daily oral administration of these drugs for 21 days. All the drugs dose-dependently inhibited hind paw swelling. For equal activity against hind paw swelling caused by the secondary reaction, the required daily dose of piroxicam was about twice that of meloxicam; those of diclofenac and tenidap were about 3.5 and 60 times higher respectively. The bone and cartilage destruction induced by adjuvant arthritis were inhibited by meloxicam at low daily doses and by piroxicam at doses approximately four times those of meloxicam. Diclofenac and tenidap had only a weak effect on radiologically-detectable lesions when administered at doses sufficient to reduce paw swelling. Meloxicam also had a dose-dependent corrective effect on the systemic changes which occur in adjuvant arthritic rats, e.g. increase in spleen weight, increase in erythrocyte sedimentation rate and changes in serum protein composition. Piroxicam produced similar effects, at 3-4 times higher doses. Diclofenac and tenidap did not show comparable effects when administered at appropriate doses. These findings indicate that the action of meloxicam and piroxicam differs from that of diclofenac and tenidap in adjuvant arthritis in the Lewis rat. At oral doses which significantly reduce edema formation, only meloxicam and piroxicam showed a significant effect on systemic parameters of adjuvant disease in the Lewis rat.

Animals↗
PubMed1995

Anti-inflammatory, analgesic, antipyretic and related properties of meloxicam, a new non-steroidal anti-inflammatory agent with favourable gastrointestinal tolerance.

The anti-inflammatory, analgesic and antipyretic properties of the new non-steroidal anti-inflammatory agent, meloxicam, were investigated in a variety of animal models and compared with the properties of piroxicam, diclofenac, indomethacin and several other NSAIDs. With respect to the total effect of a single oral dose, the anti-exudative effect of meloxicam on carrageenan-induced oedema in the rat exceeded that of all the NSAIDs included in the comparison. Additionally, meloxicam showed the greatest potency of all the compounds examined with respect to adjuvant-induced arthritis in the rat, the granuloma pouch model and the cotton pellet test in the rat. Unlike indomethacin, in the carrageenan pleurisy model in the rat, meloxicam caused both a dose-dependent reduction in exudate volume and also inhibition of leucocyte migration. Meloxicam showed a strong and lasting effect on inflammatory pain in the rat. Like other NSAIDs, but unlike dipyrone, meloxicam had no effect in the hot plate and tail clamp tests, which are used to identify weak central analgesic effects. Unlike dipyrone and like indomethacin, meloxicam had no effect in a model of visceral distention pain. In common with other NSAIDs, meloxicam had no influence on the body temperature of normothermic rats in the anti-inflammatory dose range, but did reduce yeast-induced fever in the rat in a dose-dependent manner. Like piroxicam, meloxicam had a uricosuric effect on rats treated with oxonic acid. Low-dose meloxicam inhibited both bradykinin-induced and PAF-induced bronchospasm in the guinea-pig, but had no effect on acetylcholine-induced bronchospasm. Piroxicam had greater ulcerogenic effects in the rat stomach than meloxicam. The therapeutic range of meloxicam in the rat, with regard to inhibition of adjuvant arthritis, was several times greater than that of piroxicam, indomethacin, diclofenac and naproxen.

Animals↗
PubMed1995

Debonding orthodontic ceramic brackets by ultrasonic instrumentation.

Breakage of ceramic brackets because of brittleness may cause such problems as aspiration of fragments and injury by flying debris. Portions remaining on the tooth must be laboriously ground off with a handpiece. This study investigated a potential method of lowering the force required to remove ceramic brackets, i.e., use of an ultrasonic chisel. Ceramic brackets were bonded to extracted incisors and canines. The degree of cure of a light-activated cement was systematically varied with different exposure times to a curing light. The brackets were sheared from the teeth with a universal testing machine and a chisel tip on a Cavitron. The ultrasonic chisel markedly reduced the force required to debond the brackets; however, the time of application averaged 16.6 seconds. Reducing the degree of cure of the cement had only a slight effect on the time required and the forces generated. This method of debonding is not recommended without further development.

Ceramics↗
PubMed1993

1-Methyl-2-pyrrolidinone (NMP) does not induce structural and numerical chromosomal aberrations in vivo.

1-Methyl-2-pyrrolidinone induces aneuploidy in yeast, but only under special treatment conditions. Other genotoxic effects have not been found in vitro, and in vivo no data are available in the literature. Therefore, NMP was investigated in the mouse micronucleus test and the Chinese hamster bone marrow test for structural and numerical chromosomal aberrations. These tests can detect both types of alterations as demonstrated by appropriate positive control substances (cyclophosphamide, vincristine sulfate and benomyl). NMP at single oral doses up to 3800 mg/kg body weight (approximately 80% of the LD50) did not lead to an increase either in micronucleated erythrocytes or in structural or numerical chromosomal aberrations when bone marrow was sampled 16, 24 and 48 h after treatment in the micronucleus test or after 24 and 48 h for karyotype analysis.

Animals↗
PubMed1993

Characterization of sodium cations in dehydrated faujasites and zeolite EMT by 23Na DOR, 2D nutation, and MAS NMR.

Sodium cations localized at crystallographically distinct cation sites in dehydrated zeolites were characterized using 23Na double rotation, two-dimensional nutation, and magic-angle-spinning nuclear magnetic resonance spectroscopy. The new DOR NMR technique has been applied at different magnetic field strengths to determine the quadrupole parameters of the overlapping quadrupole patterns. In the NMR spectra of dehydrated NaY and NaEMT two signals of sodium cations were identified, a low-field gaussian line at -12 +/- 1 ppm and a high-field quadrupole pattern, with an isotropic chemical shift of -8 +/- 1 ppm and a quadrupole coupling constant of about 4 MHz. By comparison of the 23Na MAS NMR intensities of these signals with the population of the cation sites determined by XRD and by calculation of the electric field gradients, the former signal was attributed to sodium cations at the sites SI and the latter one to sodium cations at the sites SI' as well as SII in faujasite and zeolite EMT. This assignment has further been confirmed by 23Na MAS NMR studies of dehydrated HNaY and BaNaY zeolites.

Cations↗
PubMed1992

27Al and 23Na double-rotation NMR of sodalites.

The 27Al NMR spectra of calcium tungstate aluminate sodalite (CAW), Ca8[Al12O24](WO4)2, and the 23Na NMR spectra of sodium aluminosilicate sodalites of general composition Na9[Si6Al6O24]A2 with A = B(OH)4- (SBS), SCN- (SRS) and A2 = SO4(2-) (SSS), MoO4(2-) (SMS) have been measured using magic-angle spinning (MAS) and double-rotation (DOR) techniques. Rotor synchronized pulse excitation is applied in the DOR experiments. Dramatic line narrowing is observed in the DOR spectra of all samples. The 27Al DOR NMR spectra of CAW measured at 9.4 and 11.7 T and spinning rates of 800-1150 Hz of the outer and 5 kHz of the inner rotor show seven sharp central lines accompanied by a manifold of spinning sidebands. These lines correspond to the seven crystallographically inequivalent Al sites of the CAW framework derived from X-ray structure analysis. From the difference of the line positions in the 9.4 and 11.7 T spectra the quadrupole coupling constant, QCC, quadrupole induced shift, sigma qs, and isotropic chemical shift, delta cs, of each Al site have been calculated. QCC values in the range of 5 to 9 MHz are obtained which reflect the strong tetragonal distortion of the AlO4 tetrahedra in CAW. delta cs shows only small changes in the range between 74.4 and 77.2 ppm. A tentative assignment of all lines to the distinct Al sites is derived from the correlation between QCC and a "shear strain parameter" describing quantitatively the distortion of the AlO4 tetrahedra.(ABSTRACT TRUNCATED AT 250 WORDS)

Aluminum↗
PubMed1990

Distribution of [14C]meloxicam in joints of rats with adjuvant arthritis.

Using the new non-steroidal anti-inflammatory agent meloxicam (Mel), comparative investigations on pharmacokinetics and metabolism show good agreement between results in man and in the rat. To demonstrate preferential localization of the compound in inflamed sites, the distribution of the radiolabelled compound in arthritic joints of rats was studied using autoradiography. For that purpose an arthritis-inducing antigen was given to male albino rats. Twenty one days after antigen injection, all animals were given [14C]Mel orally. At three different times after receiving the labelled compound, the animals were sacrificed under anaesthesia. Tissue sections from each leg of each animal were taken for autoradiography. Sections were stained after film exposure using Masson-Goldner staining. The radiolabelled compound was preferentially localized in the areas which stained for inflamed connective tissue. The distribution pattern described persists beyond 24 h post-application. The figures indicate a highly efficient distribution of the radioactivity into chronically inflamed tissue of the hind foot-pads. Since negligible radioactivity was found in the front foot-pads, it is concluded that uptake into inflamed tissue is favoured.

Animals↗
PubMed1990

Biological activity of the main metabolites of meloxicam.

Meloxicam (Mel) is a new non-steroidal anti-inflammatory drug (NSAID) which was selected with regard to its remarkable efficacy in adjuvant arthritis of the rat. Similar to the situation in man, three main metabolites were identified in rat urine which are rapidly excreted since they are not detectable in blood, where only the parent compound was found. The latter is practically not eliminated in urine. Since it has been proposed that the nephrotoxicity of NSAIDs is due to inhibition of prostaglandin E2 (PG) biosynthesis, the aim of the study was to determine whether the metabolites can contribute to the known effects of the parent compound in this pathway. For this purpose, PG-biosynthesis was measured in vitro using a radiochemical technique with an enzyme preparation from bull seminal vesicles. In an in vivo assay the effect of the compounds against kaolin-induced oedema in the rat hind paw was determined. In the test systems described, the efficacy of Mel has been demonstrated. In contrast to this finding, the metabolites in relevant doses showed neither in vitro nor in vivo effects. From the results it can be concluded that the metabolites do not change renal blood flow and therefore have no capability for nephrotoxicity. These findings are in accordance with the observations in the rat kidney during subacute and chronic toxicity studies, where no nephrotoxic effects could be detected after therapeutic doses.

Animals↗
PubMed1988

Determination of ergosterol as a measure of fungal growth using Si 60 HPLC.

In order to determine to fungal growth of Fusarium graminearum 480, a method was developed for the extraction and estimation of ergosterol, a sterol specific for fungi. This method includes the direct saponification of bound ergosterol to fungal mycelia followed by n-hexane extraction and quantification using. High performance liquid chromatography (HPLC) with UV-detection. This procedure proved to be superior compared with other methods, since the yield of ergosterol yields was higher (up to 40%). n-Hexane extracts contained minor impurities which interfered with the UV-detection and the retention time of the compound was halved using Si 60 HPLC. The protein and ergosterol contents in F. graminearum cultures increased proportionally over a 3-week incubation period. The fungal formation of the mycotoxin zearalenone started at a level of 50 mg/kg ergosterol and increased rapidly in the stationary phase of growth, which was characterized by decreasing rates of ergosterol formation.

Chromatography, High Pressure Liquid↗
PubMed1988

Assessment of the potential germ cell mutagenicity of industrial and plant protection chemicals as part of an integrated study of genotoxicity in vitro and in vivo.

An approach is described that enables the germ cell mutagenicity of chemicals to be assessed as part of an integrated assessment of genotoxic potential. It is recommended, first, that the genotoxicity of a chemical be defined by appropriate studies in vitro. This should involve use of the Salmonella mutation assay and an assay for the induction of chromosomal aberrations, but supplementary assays may be indicated in specific instances. If negative results are obtained from these 2 tests there is no need for the conduct of additional tests. Agents considered to be genotoxic in vitro should then be assessed for genotoxicity to rodents. This will usually involve the conduct of a bone marrow cytogenetic assay, and in the case of negative results, a genotoxicity test in an independent tissue. Agents found to be non-genotoxic in vivo are regarded as having no potential for germ cell mutagenicity. Agents found to be genotoxic in vivo may either be assumed to have potential as germ cell mutagens, or their status in this respect may be defined by appropriate germ cell mutagenicity studies. The basis of the approach, which is supported by the available experimental data, is that germ cell mutagens will be evident as somatic cell genotoxins in vivo, and that these will be detected as genotoxins in vitro given appropriate experimentation. The conduct of appropriate and adequate studies is suggested to be of more value than the conduct of a rigid set of prescribed tests.

Animals↗
PubMed1987

Production of mycotoxins by Fusarium species isolated in Germany. 2. Time course of deoxynivalenol and 3-acetyldeoxynivalenol formation by Fusarium graminearum in different liquid media.

Several semisynthetic liquid media were examined for the large-scale production of deoxynivalenol (DON) und 3-acetyldeoxynivalenol (AcDON) by Fusarium graminearum 183. Only in three of the eight media used could high toxin yields of DON and AcDON be detected. The maximum levels of DON in a medium according to Miller were 3 mg/l and of AcDON 32 mg/l. In glucose-yeast extract-peptone (GYEP) medium containing 1% glucose, the AcDON concentrations reached 33 mg/l and the DON yields were 19 mg/l. In a rice flour liquid medium, however, the mean levels of AcDON and DON increased to 170 mg/l and 9 mg/l, respectively. The maximum amounts observed were 480 mg/l for AcDON and 65 mg/l for DON. The addition of trifluoracetic acid sodium salt or malonic acid, which are suggested to cause an accumulation of acetyl-CoA by inhibiting enzymes of the tricarboxylic acid cycle, did not stimulate the toxin formation.

Culture Media↗
PubMed1987

Extensive glomerular immaturity associated with renal tubular acidosis, nephrogenic diabetes insipidus and nephrocalcinosis.

Neonatal renal failure and glomerular immaturity have been described in 1983. The present paper describes 3 cases with the same histological features. However, follow-up of the patients during 14, 18 and 4 years, respectively, showed the following: The histologic immaturity may be followed by maturation. Thus, late maturation may be a term more suitable to designate this constellation. Renal failure may not necessarily ensue, at least not during early infancy. In the 3 cases presented in this report, the histological finding is associated with renal tubular acidosis, renal diabetes insipidus and nephrocalcinosis. The association of transient glomerular immaturity (or late glomerular maturation) and renal tubular acidosis may enhance the development of nephrocalcinosis.

Acidosis, Renal Tubular↗
PubMed1987

In vivo screening of glutathione related detoxification products in the early state of drug development.

Glutathione (GSH) adducts and consecutive degradation products thereof are indications of reactive intermediates during drug metabolism. As demonstrated with the analgesic SX-PP 16 (4-amino-3,5-dibromacetanilide), however, interactions of a drug with GSH can be detected by labelling the GSH-stores with labelled cysteine, and consecutive administration of the unlabelled drug even at therapeutic doses. The GSH-adducts are sensitively and specifically traced by HPLC, applying column-switching and a combination of diode-array- and radioactivity detection. This approach seems to be much more sensitive than a classical GSH-depletion study. The structure of the main metabolite of SX-PP 16 (46% of urinary excretion) was elucidated as 3-bromo-4-amino-5-mercapturyl-acetanilid.

Acetanilides↗
PubMed1987

Effect of corticosteroids on the toxic pulmonary oedema induced by nitrogen dioxide inhalation in the rat.

Various corticoid derivatives administered by inhalation or intraperitoneally were investigated for a preventive effect on the pulmonary oedema of the rat induced by the 30-min inhalation of 100-105 ppm NO2. After inhalational administration in the form of an aqueous aerosol, dexamethasone-21-isonicotinate showed a considerably greater efficacy than beclomethasone-17,21-dipropionate or dexamethasone-21-dihydrogen phosphate. With prophylactic intraperitoneal administration dexamethasone (free alcohol), dexamethasone-21-dihydrogen phosphate and 6 alpha-methylprednisolone-21-dihydrogen succinate had to be given in much higher doses than dexamethasone-21-isonicotinate to achieve the same effects on the toxic pulmonary oedema.

Adrenal Cortex Hormones↗