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.

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.

[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.

Adsorption of PCDD/F on MWI fly ash

The removal of polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/F) from waste incinerator off-gas is a costly task, because a considerable part of the PCDD/F may exist in the gas phase (often 50-100% around 200 degrees C). The volatile fraction passes the particle filter and the subsequent gas cleaning equipment, so that an additional unit is needed to remove the gaseous PCDD/F from the flue gas. Moreover, dioxins and furans can accumulate in some parts of the equipment in a way that they can act as a latent source. In this work, we investigate the possibility to adsorb the PCDD/F at the fly ash particles and to remove them during the filtration. The gas/particle partitioning of the PCDD/F depends on the temperature, the vapor pressure, the particle size, the particle number density and on the physical and chemical properties of the particle surface. These relationships are investigated by model calculations and by pilot scale experiments (500 Nm3/h) which employ one selected hexachlorinated dioxin congener. At room temperature, approx. 90% of the HxCDD are found in the particulate phase, while at 135 degrees C that portion is only 10%. This means that at ambient temperatures, the gas/particle partitioning of the dioxin corresponds well to the sublimation equilibrium. At higher temperatures, it is much different from the sublimation equilibrium and the apparent adsorption enthalpy is smaller than the enthalpy of sublimation. This observation is in agreement with literature data. From the above experiments and from similar literature data, the efficiency of fly ash particles as a sink for PCDD/F can be evaluated. The data suggest that the adsorption rate is not the limiting factor for the transfer into the particulate phase. The important factors appear to be the chemical composition of the fly ash and the temperature.

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.

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.

[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.

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.

Microsensor-aided measurements of cellular signalling and metabolism on tumor cells. The cell monitoring system (cms(R))

Microsensors provide instruments particularly suited for the rapid, noninvasive and on-line analysis of cell and tissue cultures. The microsensor system presented in this paper is a modular arrangement of various planar and nonplanar sensor elements for the measurement of physiological parameters of cell cultures. An optic access to the cultures (e.g. for light microscopy and spectrophotometric techniques) is also provided for a parallel and comparative data acquisition. The system was originally designed for biomedical research in chemotherapy (predicative chemotherapy assays) and pharmacology but it turned out to be also an effective tool for toxicological and environmental research.

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.

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.

How Long Have Nonlinear Effects Been Known in the Field of Catalysis?

The similarities and differences between nonlinear effects in asymmetric synthesis (see diagram), predicted 60 years ago by W. Langenbeck, and the long-known amplification phenomenon in stoichiometric reactions with chiral starting materials are discussed.