Biomedical subjects

T Henning

Publications and source records attributed to T Henning.

11 recordsLinked to original sources

PubMed2002

Identification of iron sulphide grains in protoplanetary disks.

Sulphur is depleted in cold dense molecular clouds with embedded young stellar objects, indicating that most of it probably resides in solid grains. Iron sulphide grains are the main sulphur species in cometary dust particles, but there has been no direct evidence for FeS in astronomical sources, which poses a considerable problem, because sulphur is a cosmically abundant element. Here we report laboratory infrared spectra of FeS grains from primitive meteorites, as well as from pyrrhotite ([Fe, Ni](1-x)S) grains in interplanetary dust, which show a broad FeS feature centred at approximately 23.5 micrometres. A similar broad feature is seen in the infrared spectra of young stellar objects, implying that FeS grains are an important but previously unrecognized component of circumstellar dust. The feature had previously been attributed to FeO. The observed astronomical line strengths are generally consistent with the depletion of sulphur from the gas phase, and with the average Galactic sulphur/silicon abundance ratio. We conclude that the missing sulphur has been found.

Journal Article↗

PubMed2001

Formation and spectroscopy of carbides.

We review the evidence for carbides in space both from infrared spectroscopy and direct measurements on presolar grains extracted from primitive meteorites. The paper includes a discussion of the structural properties of silicon carbide and metal carbides and their formation routes from the gas phase. In addition, we present spectroscopic data in the infrared, which are required for a better understanding of astronomical spectra.

Astronomical Phenomena↗

PubMed2001

Limited tryptic hydrolysis of pea legumin: molecular mass and conformational stability of legumin-T.

The investigation of hydrodynamic and thermodynamic properties and the determination of the molecular mass of legumin-T, the product of limited tryptic hydrolysis of the 11-S-globulin from pea seeds, was carried out to ascertain the structural relationship to globulin-T's from other legumin-like proteins. The obtained legumin-T preparation has a molecular mass M(W)=260+/-10 kDa and M(S,D)=270+/-20 kDa. The secondary structure of legumin-T is characterised by a high percentage of beta-sheet conformation, comparable to that of native legumin and a reduced percentage of helical conformation. The conformational stability of legumin-T evaluated by equilibrium unfolding in the presence of guanidinium chloride was only slightly reduced in comparison to the native legumin, whereas the calorimetrically determined denaturation enthalpy and Gibbs energy of denaturation were found to be increased for legumin-T. These physicochemical properties are very similar to those of faba bean legumin-T.

Calorimetry↗

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

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

Growth and form of planetary seedlings: results from a microgravity aggregation experiment.

The outcome of the first stage of planetary formation, which is characterized by ballistic agglomeration of preplanetary dust grains due to Brownian motion in the free molecular flow regime of the solar nebula, is still somewhat speculative. We performed a microgravity experiment flown onboard the space shuttle in which we simulated, for the first time, the onset of free preplanetary dust accumulation and revealed the structures and growth rates of the first dust agglomerates in the young solar system. We find that a thermally aggregating swarm of dust particles evolves very rapidly and forms unexpected open-structured agglomerates.

Models, Theoretical↗

PubMed1998

Carbon in the universe.

Carbon is a major player in the evolutionary scheme of the universe because of its abundance and its ability to form complex species. It is also a key element in the evolution of prebiotic molecules. The different forms of cosmic carbon are reviewed ranging from carbon atoms and carbon-bearing molecules to complex, solid-state, carbonaceous structures. The current state of knowledge is assessed on the observational and laboratory fronts. Fundamental astrophysical implications are examined as well as the impact of these studies on the hitherto poorly understood physical and chemical properties of carbon materials in space.

Astronomical Phenomena↗

PubMed1998

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.

Biosensing Techniques↗

PubMed1997

Structural and functional changes of faba bean legumin during super-limited tryptic hydrolysis.

The influence of a super-limited tryptic hydrolysis on physicochemical and surface functional properties of faba bean legumin has been studied using size-exclusion HPLC, SDS-PAGE, UV and fluorescence spectroscopy, fluorescence probe techniques, surface tension measurements as well as determination of emulsifying activity index (EAI) and emulsion droplets diameter (D). The extent of legumin hydrolysis comprised the range between about 14 and 60 split peptide bonds per molecule resulting in a stepwise decrease of legumin molecular weight to 240 kDa (legumin-T) via discrete intermediates with characteristic subunit patterns. These changes are accompanied by an increase in the surface hydrophobicity and the exposure of aromatic chromophores. No differences were found in the surface tension between the variously hydrolyzed legumin samples. Best emulsifying properties (highest EAI and lowest D values) were attained after a rather low tryptic hydrolysis (about 30 split peptide bonds per mol). Further hydrolysis impaired the emulsifying parameter which were, however, higher (EAI) or lower (D) than those for native legumin.

Amines↗

PubMed1995

Coagulation of grains and gas-grain interactions.

Three-dimensional off-lattice Monte Carlo simulations have been used to simulate the production of interstellar dust analogues on the computer. At first, the two rather well known extreme cases of ballistic growth, i.e. particle-cluster (BPCA) and cluster-cluster aggregation (BCCA) were investigated. In a second step, we included rotation of the clusters during the growth process. Following this, gas particles were deposited on these aggregates taking variable sticking probabilities due to the growth of monolayers into account. This is of interest to the problem of molecular abundances in dark clouds.

Computer Simulation↗

PubMedDate not supplied

Evaluation in rural practice of a rapid group B streptococcus screening test.

Group B streptococcus (GBS) is the leading cause of infant mortality from infection. A rapid screening immunoassay for GBS was evaluated in a rural obstetrical population and was found to have an unacceptably low specificity (90%) and sensitivity (50%). With a culture proven GBS colonization rate of 6.8%, the positive predictive value of the rapid screening test was only 27%, and the negative predictive value was 96%. Current recommendations for routine vaginal cultures, on all women based on urban research data with high maternal colonization rates (15%-23%) and high prematurity rates (15%-40%) are reviewed in relation to this community's low colonization and prematurity rates.

Adolescent↗