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Biomedical subjects

S Seeger

Publications and source records attributed to S Seeger.

12 recordsLinked to original sources
PubMed2001

Metabolites from the biodegradation of pharmaceutical residues of ibuprofen in biofilm reactors and batch experiments.

The three metabolites hydroxyibuprofen (OH-Ibu), carboxyibuprofen (CA-Ibu), and carboxyhydratropic acid (CA-HA), also known from human metabolism of ibuprofen, could be identified in biodegradation experiments. Identification was based on EI mass spectra and comparison with literature data. Detection was performed by selective MS-MS measurements by GC-ion-trap MS and online methylation. Ibuprofen (Ibu), OH-Ibu, and CA-Ibu could be detected with a signal-to-noise ratio of 10:1 at a concentration of 2 nmol L(-1), CA-HA at 0.5 nmol L(-1). Degradation experiments in both biofilm reactors (BFR) and batch experiments with activated sludge (BAS) reveal OH-Ibu as the major metabolite under oxic conditions, and CA-HA under anoxic conditions. CA-Ibu was found under oxic and anoxic conditions almost only in the BAS. The metabolites together do not account for more than 10% of the initial concentration of Ibu.

Biodegradation, Environmental↗
PubMed2001

Cellular localization of human relaxin-like factor in the cyclic endometrium and placenta.

We have studied the cellular localization of the relaxin-like factor (RLF) in the histologically normal cyclic endometrium collected from days 3--26 of the menstrual cycle. RLF transcripts and protein were detected in the luminal and glandular epithelium and in stromal cells at all stages of the cyclic endometrium. Increased expression of RLF was observed in endometrial tissues in the proliferative as compared to the secretory phase, suggesting that oestrogens affect RLF gene activity in the human endometrium. The cellular localization of RLF transcripts and protein was also determined in first trimester placental tissues obtained from normal and ectopic tubal implantation sites and in third trimester placentae of normal and pre-eclamptic pregnancies. In first trimester placenta, weaker expression of RLF was observed in the syncytiotrophoblast as compared to the underlying cytotrophoblast. Extravillous trophoblast cells constitutively expressed RLF. Trophoblast cells were the main source of RLF in the human placenta and trophoblastic RLF gene activity was unaffected by either the site of implantation or the invasive properties of the cytotrophoblast as demonstrated by samples from patients with tubal implantation and pre-eclampsia respectively. Decidual cells weakly expressed RLF. The presence of unprocessed and cleaved immunoreactive RLF in term placenta was determined by Western analysis. The above results suggest a functional role for both RLF isoforms within normal placental tissue.

Adult↗
PubMed2000

Forbidden light detection from single molecules

We present a new concept for ultrasensitive detection of surface-generated fluorescence which is made possible by a new optical module. The detection method leads to an enhancement in fluorescence collection efficiency to more than 65% of the total of emitted light, whereas high-aperture microscope objectives are able to collect 44% at best. Moreover, by employing this new optical module, the detection volume can be restricted to approximately 10(-17) L. This allows for an exceptional discrimination of bulk-generated against surface-generated fluorescence, which may be of great value when surface-binding processes are monitored. We demonstrate the performance of the new detection system by detecting single fluorescent molecules and by determining antigen concentrations down to 5 fmol.

Journal Article↗
PubMed1999

Fluorimetric multiparameter cell assay at the single cell level fabricated by optical tweezers.

A fluorimetric multi-parameter cell sensor at the single cell level is presented which makes it possible to observe the physiological behavior of different cell lines, different physiological parameters, and statistical data at the same time. Different cell types were immobilized at predefined positions with high accuracy using optical tweezers and adhesion promoting surface layers. The process is applicable to both adherent and non-adherent cells. Coating of the immobilization area with mussel adhesive protein was shown to be essential for the process. Intracellular proton and calcium concentrations in different cell classes were simultaneously imaged and the specific activation of T lymphocytes was demonstrated. This method should be especially useful for drug screening due to the small sample volume and high information density.

Adhesives↗
PubMed1998

Counting of single protein molecules at interfaces and application of this technique in early-stage diagnosis.

The fluorescence-based detection and counting of single protein molecules after specific binding to antibodies at interfaces is presented. A diode laser was used as the excitation source. The unspecific binding at the interface has been reduced to a level of only 0.1% of the maximum signal level. At present, the detection limit of this molecule-counting process is in the range of 10(-17) mol/L, and the dynamic range of the signal corresponds to 7 orders of magnitude of antigen concentration, but these values are not limiting. As a preliminary application in early-stage diagnosis, we have investigated the detection of a single cardiac actin molecule in human plasma, which is of interest in myocardial infarction diagnosis.

Actins↗
PubMed1998

Optical tweezers in pharmacology.

Current applications of optical tweezers in pharmacology are presented. The manufacture of cellular biosensor arrays employing optical tweezers is reviewed. Using this technique, a new approach to cellular drug screening, based on single cells patterned with the laser tweezers was introduced. Specific stimulation of different immobilized, viable cells could be shown simultaneously. Furthermore, the usefulness of optical tweezers for analyzing the interactions of ligands with cellular membrane receptors is demonstrated. The laser tweezers could successfully be used to compare neuron interactions with glycoproteins of the extracellular matrix by applying the optical tweezers as picotensometer. The forces of interactions between polystyrene beads coated with different proteins of the extracellular matrix and the cell membrane receptors of cerebellar neurons from postnatal day 6 (P6) mice were measured. When antibodies to the extracellular matrix proteins were added, forces were significantly reduced for the corresponding antigens but not for the other glycoproteins. This proved the specificity of the measured interactions. Information regarding the receptor anchorage of tenascin-C could be deduced.

Animals↗
PubMed1994

The laser microbeam trap as an optical tool for living cells.

Pulsed ultraviolet lasers coupled into a microscope can be used for micromanipulation of cells and subcellular structures. In addition, continuous infrared lasers can be used as ultrafine optical tweezers (or synonymously: optical trap). The pulsed UV lasers (for example excimer lasers or nitrogen lasers) can be used as optical scalpels for the preparation of protoplasts from plant root hairs. The precise microdissection of chromosomes with the laser microbeam provides access to chromosome segments where a specific gene is supported to be localized. From such segments, specific DNA libraries can be prepared for the search after such genes or markers in their environment. With the optical trap contact between effector cells of the immune system and their target cells can be established in a very simple and gentle way. The kinetics of the attack of a natural killer on an erythroleukemia cell can be studied from the first seconds after contact. Isolated plant cells as well as cells in a plant embryo tissue can be perforated and DNA or fluorescent molecules can be injected. From the temperature dependence of laser induced membrane lesions one can obtain predictions on laser induced cell fusion, which can be performed at slightly modified irradiation conditions under total microscopic control. Since focusing into the depth of a cell with an accuracy of better than a micrometer is possible, one can work on subcellular structures in the interior of a cell without opening it. For example, in rapeseed protoplasts subcellular structures such as mitochondria or chloroplasts can be perforated or moved out of their original position. Interestingly, such structures find their way back into the original position after the laser is switched off. From their speed one can obtain estimates on intracellular viscoelasticity.

Animals↗
PubMed1991

Application of laser optical tweezers in immunology and molecular genetics.

Optical tweezers, based on a compact diode pumped Nd:YAG laser providing 350 mW at 1,064 nm coupled into a Zeiss IM 35 microscope, were used to sort CD4+ T cells into a capillary for further mechanical handling and to establish contact between single human natural killer (NK) cells and human erythroleukemia cells (K562) as targets. After contact and a lag phase of a few tens of seconds, the target cell starts to change its morphology and membrane blebbing occurs. The kinetics of the attack of the NK cell on K562 cells is not straightforward but governed by temporal oscillations in the shape of the target cell (zeosis). In a second application, the optical tweezers are combined with a UV laser microbeam based on a pulsed UV laser and with flow cytometry and sorting. With the pulsed laser, segments of sorted chromosome 1 of the chinese hamster karyotype (CHV 79) can be easily micro-dissected and subsequently collected using the optical tweezers. This allows preparation of a few hundred chromosome segments per day without mechanical contact and in an absolutely sterile way and thus may provide an interesting basic technique in any type of genome sequencing project.

Animals↗
PubMed1975

[Effect of intraaortic-ballon-counterpulsation on the changes of myocardial blood flow following coronary artery stenosis and occlusion (author's transl)].

To prove the effectiveness of the IABP in case of impending myocardial infarction in one series of experiments myocardial blood flow changes due to IABP in dogs with stenosis of the left circumflex coronary artery (LC) were investigated using tracer microspheres. In a control series the left anterior descending artery (LAD) was occluded. In acute LAD occlusion the IABP caused an increase of blood flow in the epicardial layer. In case of LC stenosis there was a far greater increase in blood flow by the IABP most prominent in the endocardial layer. Our experiments indicate that the IABP seems to be effective in impending myocardial infarction.

Animals↗