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Biomedical subjects

W Baumann

Publications and source records attributed to W Baumann.

At least 19 recordsLinked to original sources
PubMed2006

UV/Vis spectra and solubility of some naphthoquinones, and the extraction behavior of plumbagin from Plumbago scandens roots in supercritical CO2.

The solubility of 1,4-naphthoquinone, plumbagin, lawsone, and juglone in supercritical carbon dioxide was determined spectroscopically at 40 degrees C, and in the pressure range 8-18 MPa. Their solubilities at 12 MPa were between 0.3 and 10 g L(-1). Plumbagin from Plumbago scandens L. roots was extracted at 40 degrees C and 20 MPa. The extracted plumbagin mass fraction was up to 0.2% in fresh roots but down to about 0.006% in aged roots. n-Hexane and chloroform extraction of such aged roots indicates that the older and dryer the roots are, the stronger they bind plumbagin. Reversed-phase HPLC indicated a relatively pure plumbagin extract with supercritical carbon dioxide.

Carbon Dioxide↗
PubMed2005

Dipole moments of 4'-aminoflavonol fluorescent probes in different solvents.

Electrooptical absorption measurements (EOAM) were used to measure the dipole moments of the normal form of 4'-(dimethylamino)-3-hydroxyflavone (FME), and 4' N-(15-azacrown-5)-3-hydroxyflavone (FCR) in 1,4-dioxane, toluene, and cyclohexane. With these probes excited-state intramolecular proton transfer (ESIPT) takes place. For comparison, the dipole moments of 4'-(dimethylamino)-3-metoxyflavone (FME3ME), for which ESIPT is lacking, were measured, too. For all three probes the ground (micro(g)) and excited Franck-Condon state (micro(e)FC) electrical dipole moments are parallel to each other and also parallel to the transition dipole moment. The electrical dipole moments of FCR, FME, and FME3ME in their ground state have values within the range (12.0-17.7) x 10(-30) C m. Upon optical excitation, the dipole moments increase by (41.9-52.9) x 10(-30) C m. The value of the change of the dipole moment vector delta(a)micro with excitation to the Franck-Condon state and the value of the vector micro(e)FC for FCR and FME are practically independent on the solvent polarity. From this point of view and due to large values of the dipole moments FCR and FME are very promising probes for the investigation of the distribution of the local polarity in biological systems using site-selective excitation of the different sites. Our steady-state fluorescence studies on FME and FCR have demonstrated a high spectral sensitivity of the normal form to such solvent characteristics as polarity.

Journal Article↗
PubMed2005

Evaluation of the concept of heterology in a monoclonal antibody-based ELISA utilizing direct hapten linkage to polystyrene microtiter plates.

A series of new heterologous haptens has been synthesized and used as coating haptens in an antigen-immobilized immunoassay with a monoclonal antibody against atrazine. Coating was achieved by covalently linking the different haptens to a glutaraldehyde network directly bound to the polystyrene surface of a standard 96-well microtiter plate. With the assay designed in the antigen-immobilized format with direct chemical linkage of the hapten to the solid polystyrene surface well-defined hapten densities were achieved in all experiments. The results of different experiments with different coating haptens were comparable. Using different heterologous haptens it appears that the concept of heterology is applicable in this case and can be used to enhance the sensitivity of an immunoassay in the coating-hapten format.

Antibodies, Monoclonal↗
PubMed2001

Multiparametric microsensor chips for screening applications.

The identification of drug targets for pharmaceutical screening can be greatly accelerated by gene databases and expression studies. The identification of leading compounds from growing libraries is realized by high throughput screening platforms. Subsequently, for optimization and validation of identified leading compounds studies of their functionality have to be carried out, and just these functionality tests are a limiting factor. A rigorous preselection of identified compounds by in vitro cellular screening is necessary prior to using the drug candidates for the further time consuming and expensive stage, e.g. in animal models. Our efforts are focused to the parallel development, adaptation and integration of different microelectronic sensors into miniaturized biochips for a multiparametric, functional on-line analysis of living cells in physiologically environments. Parallel and on-line acquisition of data related to different cellular targets is required for advanced stages of drug screening and for economizing animal tests.

Biocompatible Materials↗
PubMed2001

An immunoassay for terbutryn using direct hapten linkage to a glutaraldehyde network on the polystyrene surface of standard microtiter plates.

2-Aminobutylamino-4-ethylamino-6-isopropylamino-1,3,5-triazine (ABA-atrazine) has been synthesized and used as a coating hapten in an immunoassay with a monoclonal antibody against terbutryn. Coating was achieved by covalently linking ABA-atrazine to a glutaraldehyde polymer network directly bound to the polystyrene surface of a standard 96-well microtiter plate. The assay was carefully optimized. In particular, the coating hapten concentration had a strong effect on the ELISA sensitivity. By including a pre-incubation step a low test midpoint (IC50-value) of 0.130 microg L(-1) was achieved. As far as we are aware this is the most sensitive ELISA for terbutryn yet reported. The coating-hapten-format presented is proposed as generally applicable, because the glutaraldehyde-modified microtiter plate surface enables stable immobilization of a broad variety of coating haptens.

Antibodies, Monoclonal↗
PubMed2001

Simultaneous measurement of cellular respiration and acidification with a single CMOS ISFET.

In vivo, the pH value and oxygen partial pressure are the most important physico-chemical parameters in the microenvironment of human tissues. In vitro, the extracellular acidification rate of cell cultures is an indicator of global cellular metabolism, while the rate of oxygen consumption is a measure of mitochondrial activity. Earlier approaches had the disadvantage that these two values had to be measured with two separate sensors at different loci within the tissue or cell culture. Furthermore, conventional Clark-type oxygen sensors are not very compatible for miniaturisation, making it impossible to measure at small cell volumes or even at the single cell level. We have, therefore, developed an ISFET based sensor structure which is able to measure both pH and oxygen partial pressure. This sensor structure was tested in vitro for simultaneous records of cellular acidification and respiration rates at the same site within the cell culture. This sensor is manufactured by a CMOS-process.

Biosensing Techniques↗
PubMed2001

[Challenges in social medicine counseling and expert assessment].

The services of expert testimony and professional consultation in sociomedicine are considerably challenged. It is not so much the question of maintaining their traditional functions but of developing them in order to maintain at least the status quo. These challenges consist for example of the lack of a scientific basis for the complex function of allocation, piloting and control of medical resources. Some new approaches are offered by the ICIDH, by new instruments of medical assessment and by quality management including "evidence-based medicine". Furthermore the services of expert testimony must bridge the gap between patients and social services in a way which is satisfactory for the population. Nevertheless, these services must maintain strict independence.

Evidence-Based Medicine↗
PubMed2001

Approach to a multiparametric sensor-chip-based tumor chemosensitivity assay.

Although not widely practiced by oncologists, in vitro tumor chemosensitivity assays (TCA) have proved to increase the lifetime of tumor patients in prospective clinical trials. By individualizing cancer therapy, they can support the clinician's decision which is usually based on empirically retrieved data and thereby prevent inadequate chemotherapy. We present the first results of a new sensor-chip-based technology which might be useful for a multiparametric TCA. In particular, the aspect of dynamic on-line data generation on intact cellular specimens is a major difference to alternative assays. A series of experiments has been performed on cell lines and human tumor explants. Cell cultures and tumor tissue explants were placed on miniaturized silicon and glass sensor chips. The sensor data currently analyze metabolic profiles (rates of extracellular acidification and cellular oxygen consumption) and changes in cell morphology (monitoring of electric impedance). With the cell lines, drug-associated cellular signals have been detected with all three parameters, while primary explants so far caused metabolic responses only. In particular, cellular respiration or mitochondrial activity seems to be a most sensitive indicator of acute cytotoxic effects. The experimental results were achieved using different test versions. Besides giving a status report, the theoretical potential and current problems of sensor chip technology in TCA is discussed.

Acetaldehyde↗
PubMed2000

[Cp2V] migration along an octatetrayne chain: from the monometallic complex (Cp2V(2-4eta-tBuC triple bond C2-C triple bond CC triple bond CtBu)] to the dimetallic complex.

The oxidative addition of one equivalent of [Cp2V] (4) to the tetrayne ligand tBuC triple bond CC triple bond CC triple bond CC triple bond CtBu (5) gives the monometallic complex [Cp2V(3-4eta-tBuC triple bond C-C2-C triple bond CC triple bond CtBu)] (7). Compound 7 reacts further with a second equivalent of [Cp2V] to give the dimetallic complex [(Cp2V)2(1-2eta:7-8eta-tBuC2-C triple bond CC triple bond C-C2tBu)] (8), which involves a shift of the first coordinated [Cp2V] unit from the internal C3-C4 to the external C1-C2 positions on the alkynyl ligand. Compound 8 is also directly obtained by the addition of two equivalents of [Cp2V] to 5. Reversibly, reaction of 8 with 5 leads to 7. This exchange reaction between 7 and 8 by adding successively 5 and 4 has been monitored by EPR spectroscopy. By contrast, the oxidative addition of one or two equivalents of [Cp2V] to the tetrayne ligand PhC triple bond CC triple bond CC triple bond CC triple bond CPh (6) gives the homodimetallic complex [(Cp2V)2(1-2eta:7-8eta-PhC2-CC triple bond CC triple bond C-C2-Ph)] (9). Both monometallic and dimetallic complexes 7, 8, and 9 have been characterized by X-ray diffraction. Magnetic moment measurements for 8 and 9 from 300 to 4 K indicated a weak antiferromagnetic J exchange coupling of -12.5 and -4.1 cm(-1), respectively.

Journal Article↗
PubMed2000

Different C-C coupling reactions of permethyltitanocene and permethylzirconocene with disubstituted 1,3-butadiynes

Herein we describe different C-C coupling reactions of permethyltitanocene and -zirconocene with disubstituted 1,3-butadiynes. The outcomes of these reactions vary depending on the metals and the diyne substituents. The reduction of [Cp2*MCl2] (Cp* = C5Me5; M = Ti, Zr) with Mg in the presence of disubstituted butadiynes RC triple bond C-C triple bond CR' is suitable for the synthesis of different C-C coupling products of the diyne and the permethylmetallocenes, and provides a new method for the generation of functionalized pentamethyl-cyclopentadienyl derivatives. For M = Zr and R = R' = tBu, the reaction gives, by a twofold activation of one pentamethylcyclopentadienyl ligand, the complex [Cp*Zr[-C(=C=CHtBu)-CHtBu-CH2-eta5-C5Me3-CH2-]] (3), containing a fulvene ligand that is coupled to the modified substrate (allenic subunit). When using the analogous permethyltitanocene fragment "Cp2*Ti", the reaction depends strongly on the substituents R and R'. The coupling product of the butadiyne with two methyl groups of one of the pentamethylcyclopentadienyl ring systems, [Cp*Ti[eta5-C5Me3-(CH2-CHR-eta2-C2-CHR'-CH2)]], is obtained with R = R' = tBu (4) and R = tBu, R' = SiMe3 (5). In these complexes one pentamethylcyclopentadienyl ligand is annellated to an eight-membered ring with a C-C triple bond, which is coordinated to the titanium center. A different activation of both pentamethylcyclopentadienyl ligands is observed for R = R' = Me, resulting in the complex [[eta5-C5Me4(CH2)-]Ti[-C(=CHMe)-C(=CHMe)-CH2-eta5-C5Me4]] (6), which displays a fulvene as well as a butadienyl-substituted pentamethylcyclopentadienyl ligand. The influence exerted by the size of the metal is illustrated in the reaction of [Cp2*ZrCl2] with MeC triple bond C-C triple bond CMe. Here the five-membered metallacyclocumulene complex [Cp2*Zr(eta4-1,2,3,4-MeC4Me)] (7) is obtained. The reaction paths found for R = R' = Me are identical to those formerly described for R = R' = Ph.

Journal Article↗
PubMed2000

Ketorolac versus prednisolone versus combination therapy in the treatment of acute pseudophakic cystoid macular edema.

OBJECTIVE: To evaluate the efficacy of ketorolac tromethamine 0.5% ophthalmic solution, prednisolone acetate 1.0% ophthalmic solution, and ketorolac and prednisolone combination therapy in the treatment of acute, visually significant, cystoid macular edema (CME) occurring after cataract extraction surgery. DESIGN: Randomized, double-masked, prospective trial. PARTICIPANTS: Twenty-eight patients who had undergone cataract extraction and in whom clinical CME developed within 21 to 90 days after cataract surgery. METHODS: Patients were randomized to topical therapy with ketorolac (group K), prednisolone (group P), or ketorolac and prednisolone combination therapy (group C) four times daily. Treatment was continued until CME resolved or for 3 months, whichever occurred first. Treatment was then tapered over 3 weeks. Examinations were monthly and included Snellen visual acuity, contrast sensitivity, Amsler grid, slit-lamp examination, dilated fundus examination, and fluorescein angiography. RESULTS: Twenty-six of 28 patients completed the study. Patients were enrolled an average of 48 days after surgery. The average improvements in Snellen visual acuity were as follows: 1.6 lines in group K, 1.1 lines in group P, and 3.8 lines in group C. This reached statistical significance for all visits when group C was compared with group P, and for visits 4 and 5 when group C was compared with group K. Group C reached a mean change of two lines or more by visit 2; at no time did either group K or P reach a mean two-line improvement. At no time was a significant difference detected between group K and P with regard to visual acuity or change from baseline. A two-line or more improvement in Snellen acuity was achieved in 16 of 26 patients (61%). Analysis by group revealed four of eight patients (50%) in group P, six of nine patients (67%) in group K, and eight of nine patients (89%) in group C who had achieved a two-line or more improvement. In patients who did improve two lines or more, improvement occurred an average of 2.75 months after initiating therapy in group P, 1.43 months in group K, and 1.33 months in group C. Improvements in contrast sensitivity and leakage on fluorescein angiography tended to mirror improvements in Snellen acuity. CONCLUSIONS: Treatment of acute, visually significant pseudophakic CME with ketorolac and prednisolone combination therapy appears to offer benefits over monotherapy with either agent alone. Patients were more likely to experience recovery of two lines or more of visual acuity. Patients treated with combination therapy or ketorolac monotherapy responded more quickly than did patients treated with prednisolone alone.

Acute Disease↗
PubMed2000

Non-invasive measurement of cell membrane associated proton gradients by ion-sensitive field effect transistor arrays for microphysiological and bioelectronical applications.

The pH in the cellular microenvironment (pH(M)) is an important regulator of cell-to-cell and cell-to-host interactions. Additionally the extracellular acidification rate of a cell culture is an important indicator of global cellular metabolism. In a new approach a biocompatible ion-sensitive field effect transistor (ISFET)-array was developed to measure the pH(M) close to a surface and the global extracellular acidification rate at the same time. This ISFET-array is part of a new multiparametric microsensor chip. The paper highlights some basic applications of this method for in-vitro measurements. Using a fluid perfusion system for cell culture media, it is possible to measure the pH(M) of few (five to ten) adherent tumor cells in a distance of 10-100 nm from the cell plasma membrane. Experiments showed a pH(M)-value of 6.68 +/- 0.06 pH. Further experiments suggest that both the low pH, and the extracellular acidification rate of the examined tumor cell line are mainly built up by glycolysis.

Biosensing Techniques↗
PubMed1999

An ISFET-algal (Chlamydomonas) hybrid provides a system for eco-toxicological tests.

A cellular sensoring system was designed in which metabolism-dedicated pH-ISFETs and the unicellular green alga Chlamydomonas reinhardtii as a biological component, were combined. The system permits on-line detection of pH changes caused by the metabolic and photosynthetic activities of the cells. Photosynthetic activity results in a basification of the medium caused by uptake of CO2. In darkness, an acidification of the medium, resulting from the production of CO2 by degradation of starch was observed. Both, acidification and basification, are sensitive indicators for the physiological activity of the alga. Experiments using inhibitors of energy metabolism or photosynthesis illustrate the utility of this system for an on-line monitoring of substances of eco-toxicological importance.

Animals↗
PubMed1999

Polar drug residues in sewage and natural waters in the state of Rio de Janeiro, Brazil.

The drug residues of lipid regulators, anti-inflammatories and some drug metabolites have been detected in raw sewage, treated waste water and river water in the state of Rio de Janeiro, Brazil. These residues are mainly derived from humans via excretion. The median concentrations in the effluents of sewage treatment plants (STPs) of most drugs investigated in this study ranged from 0.1 to 1 microgram/l. The removal rates of individual drugs during passage through a Brazilian STP varied from 12 to 90%. As a consequence of the incomplete removal of these residues during passage through a STP, rivers were also found to be contaminated. Median concentrations ranged from between 0.02 and 0.04 microgram/l in river water, whereas the maximum values were observed to be up to 0.5 microgram/l.

Animals↗
PubMed1999

Synthesis of non proteinogenic dipeptides by asymmetric hydrogenation.

N-Boc protected non-proteinogenic dipeptides with D,L- and L,L-configuration were prepared by catalytic asymmetric hydrogenation of the corresponding dehydrophenylalanyl-(L)-phenylalanine derivatives. The configuration of the new stereogenic centre depends first of all on the catalyst configuration and is less influenced by the substrate configuration. Diastereomeric excesses in the range of 80-96% de could be increased up to 99% by recrystallization. Analytical data of selected new compounds are given.

Dipeptides↗
PubMed1998

Monitoring of cellular signalling and metabolism with modular sensor-technique: the PhysioControl-Microsystem (PCM).

Microsensors provide instruments particularly suited for the noninvasive analysis of cell and tissue cultures. The outstanding benefit lies in the passive behaviour of continuously working transducers, which in turn allows the dynamic recording of function-specific cellular processes. The microsensor system presented in this paper is a modular arrangement of various planar and non-planar sensor elements surrounding small cell culture chambers. An optic access to the cultures (e.g. for high resolution light microscopy and spectro-photometric techniques) enables a parallel and comparative data acquisition. The system was originally designed for biomedical research in chemotherapy and pharmacology but it proved to be an effective device both for toxicological and environmental research.

Biosensing Techniques↗
PubMed1998

On-line control of cellular adhesion with impedance measurements using interdigitated electrode structures.

Critical parameters to be assessed in cell culture are the number of viable cells and cell viability. Growth, product formation, toxicity effects and the overall success of cell culture can depend largely on these. With interdigitated electrode structures (IDES) adherent cells are cultured directly on a pair of interdigitated electrodes, and the impedance of the system gives insight into the adhesive behaviour of the cells. The signal is influenced by the changes in number, growth and morphological behaviour of adherently growing cells, mainly owing to the insulating effects of the cell membranes. Five different cell lines are used, and their divergent behaviour is monitored over a period of four days, from inoculation of the cells to killing of the cells at the end of the experiments. Even when the cells from close monolayers, great fluctuations in the impedance signal can be observed. Nevertheless, for a more complete description of cellular systems, other parameters, such as acidification and respiration, have to be included in the measuring system.

Biosensing Techniques↗