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Biomedical subjects

M Conradi

Publications and source records attributed to M Conradi.

16 recordsLinked to original sources
PubMed2006

Colloids on free-standing smectic films.

We study the structure of a free-standing smectic-A film around a micron-size polystyrene colloid adsorbed onto the film. We find that a colloid or a cluster of colloids is surrounded by an optically distinct and radially decorated meniscus ending with a sharp edge. The observed strong and finite-range attraction between the adsorbed colloids is driven by the fusion of menisci. We interpret the structure of the smectic meniscus in terms of a model dominated by the surface free energy and we argue that the characteristic appearance of the meniscus is due to layer undulations.

Adsorption↗
PubMed2005

Test of clock model in ellipsometric study of thin and thick free-standing films of an antiferroelectric liquid crystal.

The temperature dependences of the ellipsometric parameters in a weak dc external field are studied in thin and thick free-standing films of MHPOBC. The results for thin films consisting of two, three, and four layers are analyzed within the discrete phenomenological model. We find very good quantitative agreement between the theory and experiment, which indicates an odd-even effect. We find that the XY structures are stable for an odd number of layers, whereas planar, Ising-like structures are stable for an even number of layers. The experiments on thick (several tens of layers) films show a combination of bulklike and free-surface behavior. This is most pronounced at high temperatures, where the interior of the film is not tilted, whereas the layers at the air interfaces show qualitatively similar temperature dependance of the ellipsometric parameters as in the four-layer film.

Journal Article↗
PubMed2004

Structures and phase transitions in thin free standing films of an antiferroelectric liquid crystal.

The premises of a discrete mean-field model for polar smectic liquid crystals are tested by analyzing the ellipsometric experiments on two, three, and four-layer freestanding films of MHPOBC. The measured temperature dependences of the ellipsometric parameters in a weak dc external field are compared to the predictions of a simple clock model. A very good quantitative agreement is found indicating an odd-even effect: XY structures are stable for odd and Ising-like structures for an even number of layers.

Computer Simulation↗
PubMed2004

Sediment quality in the Guadalquivir estuary: lethal effects associated with the Aznalcóllar mining spill.

Monitoring from 1998 to 2001 has assessed the impact of the Aznalcóllar mining spill on the sediment quality in the Guadalquivir estuary. Chemical analysis has been completed with biological effects measured in different organisms. The toxicity of sediments obtained from dilutions of toxic mud and from environmental stations affected by the accidental spill was tested using the amphipod Ampelisca brevicornis and the clam Scrobicularia plana. The results obtained show that amphipods are more sensitive to the accidental spill than the clams. A dilution of clean sediment by more than 1.8% of toxic mud produced 100% mortality of amphipods. In GR2 station is detected toxicity to amphipods but not to clams. The rest of the environmental stations show no toxicity. Toxicity to amphipods in GR2 station decreased along time (from 50% to 60% of mortality in 1998 to 10 to 15% in 2001) and it can be associated with a recovery of the areas impacted by the accidental spill.

Accidents↗
PubMed2002

Structure and dynamics of freely suspended film of the smectic-C*alpha phase in an external transverse electric field.

We present a theoretical analysis of static and dynamic properties of freely suspended films of the smectic-C*alpha phase in an external electric field, applied along the smectic layers. The analysis is performed within the "clock" model, where the interactions up to next-nearest neighbors are considered. The calculated critical electric field for the unwinding of the smectic-C*alpha phase is of the order of several 100 V/mm and strongly depends on the interlayer interactions. The calculated relaxation rates of the eigenfluctuations of a system of N layers are in the kilohertz range for phase fluctuations and several megahertz for amplitude fluctuations.

Journal Article↗
PubMed1994

Synthesis of fluorescent derivatives of 7-methylguanine through reaction with 2-aryl-substituted malondialdehydes: analysis by HPLC with fluorescence detection.

Fluorescent derivatives of 7-methylguanine were prepared through reaction with 2-aryl-substituted-malondialdehydes and analysed by reversed-phase HPLC with fluorescence detection. Reaction of carbons 1 and 3 of the malondialdehyde molecule at the N1 and N2 positions of 7-methylguanine yielded fluorescent tricyclic structures. Two novel fluorescent derivatives of 7-MeG were obtained, namely, 7-(3,4-dimethoxyphenyl)-10-oxo-1-methyl-9,10-dihydropyrimido[1,2- alpha]purine (yield 15-34%) and 7-(1-naphthyl)-10-oxo-1-methyl-9,10- dihydropyrimido[1,2-alpha]purine (yield 56-70%) after reaction with 3,4-dimethoxyphenylmalondialdehyde and 1-naphthylmalondialdehyde, respectively which were characterized by IR, NMR, MS and UV and fluorescence spectroscopy. The fluorescence intensity of the derivatives was found to be 10-20-fold higher than the intrinsic fluorescence of 7-methylguanine. Concentration versus fluorescence intensity curves exhibit linearity in the picomole to nanomole range. The 2-aryl-substituted malondialdehydes were used to analyse the concentration of 7-methylguanine in neutral hydrolysates obtained from calf thymus DNA samples alkylated with dimethyl sulfate. The results obtained indicate their potential as reagents for the analysis of alkylated guanines in biological samples. Molecular modeling calculations were carried out to generate lowest energy spatial configurations. The results obtained indicated that the aryl-substituents on the malondialdehyde moiety do not lie in the same plane as the tricyclic moiety of the fluorescent derivatives with implications for their fluorescence properties.

Chromatography, High Pressure Liquid↗
PubMed1994

Development of a 32P-postlabelling method for the analysis of 2'-deoxyguanosine-3'-monophosphate and DNA adducts of methylglyoxal.

A 32P-postlabelling assay was developed for the analysis of adducts arising from the reaction of 2'-deoxyguanosine-3'-monophosphate with the 1,2-dicarbonyl compound methylglyoxal, a major mutagen in several foodstuffs, in particular, instant and brewed coffee. The 32P-postlabelling reaction was optimized by testing various parameters such as the kinetics of phosphorylation by T4 polynucleotide kinase, substrate concentration-dependent labelling efficiency and the concentration of the various ingredients of the phosphorylation reaction. The sensitivity to the 3'-monophosphate dephosphorylation activity of nuclease P1 was also studied. Four isomeric reaction products were separated by HPLC, structurally characterized and identified as 3-(2'-deoxy-beta-D-erythro-pentafuranosyl)-6,7-dihydro-6,7-dihydro xy-6- methylimidazo[2,3-b]purine-9(8H)one. The same adducts could be detected from calf thymus DNA that had been reacted in vitro with methylglyoxal. DNA adducts were isolated after enzymatic digestion to mononucleotides followed by nuclease P1 digestion of normal nucleotides. The total level of methylglyoxal-DNA adducts obtained was 5.7 +/- 1.7 (n = 15) adducts/10(6) nucleotides. The 32P-postlabelling method was further validated by the detection of adducts of methylglyoxal in DNA from freshly isolated and stimulated human lymphocytes exposed in vitro. The concentrations of the adducts detected in these samples were 8.2 +/- 0.9 (n = 3) adducts/10(7) nucleotides and 1.5 +/- 0.1 (n = 3) adducts/10(6) nucleotides after treatment with 1.5 and 3.0 mM methylglyoxal respectively.

Animals↗
PubMed1986

Pulmonary reaction associated with transfusion of plasma containing anti-5b.

A patient developed an acute respiratory distress syndrome with lung infiltrates during a transfusion of plasma. The transfused plasma was shown to contain a potent leucocyte agglutinating antibody of IgG type with anti-5b specificity, reactive with the patient's cells. A review of the literature on similar transfusion-related syndromes showed an association with more of less well-defined white cell antibodies, mainly in the donors' plasma. The majority of donors were multiparous women. The anti-5b in our donor was demonstrated only by granulocyte agglutination technique, as previously described antibodies in the five system. A long incubation procedure (20-25 h) seemed to be optimal for granulocyte agglutination.

Aged↗
PubMedDate not supplied

[Tocolysis with fenoterol suppositories--a comparison with oral administration of fenoterol tablets].

A new application form of fenoterol (Partusisten) as 15 mg suppositories from Boehringer Ingelheim was tested for its tocolytic effect, tolerance and the main side effects under usual clinical conditions in a prospective study in 50 pregnant patients with premature labour in 24-36th week of gestation. During one week's treatment 25 pregnant women received 3 to 4 15 mg fenoterol suppositories and 25 patients 6 to 8 5 mg fenoterol tablets. Beginning on the second day of treatment until the end of therapy in both groups a reduction of the uterine activity of at least 50 percent was achieved. The uterine relaxant effect was sufficient until 3 to 4 hours after the application of fenoterol tablets and 6 to 8 hours after the application of fenoterol suppositories. Side effects were mainly limited to cardiovascular complaints, restlessness and tremor, and we found no significant difference between tablets and suppositories. The maternal heart rate reached its highest level on the second day of treatment. Fenoterol suppositories can be recommended in all cases, where an oral tocolytic therapy is not possible e.g. in cases of vomiting or before operations. Here the application of fenoterol suppositories can replace in some cases the intravenous infusion of fenoterol.

Administration, Oral↗
PubMedDate not supplied

[Various aspects of Parkinson syndrome in the aged].

The author defines this syndrome with symptoms and diagnostics and describes its aetiopathogenesis, pathological and anatomical changes in the patient, course, treatment and epidemiology as well as primary and secondary measures to prevent it.

Aged↗