Characterization of flavonoid--biomembrane interactions

The flavonoids comprise a large group of polyphenolic compounds that are ubiquitous in vegetables, berries, and fruits, and they have been shown to possess antioxidative activity. The interactions between flavonoids and membranes composed of dipalmitoylphosphatidylcholine (DPPC) have been studied by means of noncovalent immobilized artificial membrane (IAM) chromatography. We have also investigated flavonoid-induced calcein release from fluid egg phosphatidylcholine (EPC) vesicles. Flavonoids with more hydroxyl groups showed longer retention delays in the IAM studies, suggesting stronger interactions between the flavonoids, which are rich in hydroxyl groups, and the DPPC membrane interface. We also observed an inverse correlation between the number of hydroxyl groups in the flavonoids and their capacity to induce calcein leakage through fluid EPC bilayer membranes (the more nonpolar flavonoids caused more calcein leakage). Rhamnetin and morin, however, both showed marked activity for the DPPC membrane interface and caused significant membrane leakage. Both polar and nonpolar forces were shown to have a significant impact on the flavonoid/biomembrane interactions.     

Identification and discrimination of Staphylococcus aureus strains using matrix-assisted laser desorption/ionization-time of flight mass spectrometry

Staphylococcus aureus is an important human pathogen frequently resistant to a wide range of antibiotics. Methicillin-resistant S. aureus (MRSA) strains are common nosocomial pathogens that pose a world-wide problem. Rapid and accurate discrimination between methicillin-sensitive S. aureus (MSSA) and methicillin-resistant S. aureus is essential for appropriate therapeutic management and timely intervention for infection control. We report here the application of matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS) for monitoring the bacterial fingerprints expressed by two well characterized S. aureus strains ATCC 29213 (MSSA) and ATCC 43330 (MRSA). Consistent strain-specific data were obtained from subcultures analyzed over a period of three months as well as after changing the growth media from Mueller-Hinton to blood agar indicating the reliability of the method. The bacterial fingerprints of these two strains were compared to independent clinical isolates of S. aureus. A uniform signature profile for MRSA could not be identified. However, the bacterial fingerprints obtained proved to be specific for any given strain. This study demonstrates that MALDI-TOF MS is a powerful method for rapid identification of clonal strains of S. aureus, which might be useful for tracking nosocomial outbreaks of MRSA and for epidemiologic studies of infections diseases in general.     

Miniaturized real-time monitoring system for L-lactate and glucose using microfabricated multi-enzyme sensors.

A miniaturized on-line monitoring system for the detection of L-lactate and glucose is presented. The system is based on a microfabricated multi-enzyme silicon sensor chip with flow channels integrated on the chip. The sensors were fabricated in containment technology. They were characterized in test solutions. The cross-talking behaviour was investigated and was found to be practically negligible. The linear measurement ranges of both glucose and lactate sensors were large enough for most practical applications. As a result of the miniaturization the analyte consumption could be reduced to a few nmol min(-1). The system was equipped with a microdialysis probe whose recovery was 45% for lactate and 37% for glucose in test solutions using a flow rate of 3 microl min(-1). Lower flow rates of 0.5 microl min(-1) resulted in recoveries of over 90%. The long-term stability of the system was acceptable. Initial measurements have also been performed in vitro using human blood serum.     

The Bielefeld teaching program in zoo biology

The teaching program in zoo biology of the University of Bielefeld offers a 4-week course that aims at providing special knowledge of zoos and zoo animals from theoretical, educational, and applied points of view. The course includes 1 week each of seminar-type lectures, a 1-week visit to one particular zoo, “comparative” 1-day visits to different zoos, and reports and seminars to be given by the participants. During the “zoo week” the students are required to select one of the exhibits and to make full-day behavioral observations of the animals. Requirements include seminar talks, a protocol about the observations, and the design of a label.     

Cell-Type Specific Four-Component Hydrogel

In the field of regenerative medicine we aim to develop implant matrices for specific tissue needs. By combining two per se, cell-permissive gel systems with enzymatic crosslinkers (gelatin/transglutaminase and fibrinogen/thrombin) to generate a blend (technical term: quattroGel), an unexpected cell-selectivity evolved. QuattroGels were porous and formed cavities in the cell diameter range, possessed gelation kinetics in the minute range, viscoelastic properties and a mechanical strength appropriate for general cell adhesion, and restricted diffusion. Cell proliferation of endothelial cells, chondrocytes and fibroblasts was essentially unaffected. In contrast, on quattroGels neither endothelial cells formed vascular tubes nor did primary neurons extend neurites in significant amounts. Only chondrocytes differentiated properly as judged by collagen isoform expression. The biophysical quattroGel characteristics appeared to leave distinct cell processes such as mitosis unaffected and favored differentiation of sessile cells, but hampered differentiation of migratory cells. This cell-type selectivity is of interest e.g. during articular cartilage or invertebral disc repair, where pathological innervation and angiogenesis represent adverse events in tissue engineering.