Biomedical subjects

Uwe Marx

Publications and source records attributed to Uwe Marx.

7 recordsLinked to original sources

PubMed2006

Physical and biological properties of barium cross-linked alginate membranes.

We describe the manufacture of highly stable and elastic alginate membranes with good cell adhesivity and adjustable permeability. Clinical grade, ultra-high viscosity alginate is gelled by diffusion of Ba2+ followed by use of the "crystal gun" [Zimmermann H. et al., Fabrication of homogeneously cross-linked, functional alginate microcapsules validated by NMR-, CLSM- and AFM-imaging. Biomaterials 2003;24:2083-96]. Burst pressure of well-hydrated membranes is between 34 and 325kPa depending on manufacture and storage details. Water flows induced by sorbitol and raffinose (probably diffusional) are lower than those caused by PEG 6000, which may be related to a Hagen-Poiseuille flow. Hydraulic conductivity, L(p), from PEG-induced flows ranges between 2.4x10(-12) and 6.5x10(-12) m Pa(-1)s(-1). Hydraulic conductivity measured with hydrostatic pressure up to 6 kPa is 2-3 orders of magnitude higher and decreases with increasing pressure to about 3x10(-10) m Pa(-1)s(-1) at 4kPa. Mechanical introduction of 200 microm-diameter pores increases hydraulic conductivity dramatically without loss of mechanical stability or flexibility. NMR imaging with Cu2+ as contrast agent shows a layered structure in membranes cross-linked for 2h. Phase contrast and atomic force microscopy in liquid environment reveals surface protrusions and cavities correlating with steps of the production process. Murine L929 cells adhere strongly to the rough surface of crystal-bombarded membranes. NaCl-mediated membrane swelling can be prevented by partial replacement of salt with sorbitol allowing cell culture on the membranes.

Alginates↗

PubMed2006

A human lymph node in vitro--challenges and progress.

Extracorporeal human lymphatic organs are expected to be excellent tools in the study of human molecular and cellular bases of the immunologic balance and tissue harmony. A rational approach and process to design a device and a procedure to recreate the human lymph node environment in vitro is described with emphasis on T-cell activation. Based on this approach, a bioreactor and a process supporting self-assembly of human lymphatic tissues due to proper emulation of human architecture and homeostasis could be developed.

Bioreactors↗

PubMed2004

Linker peptide and affinity tag for detection and purification of single-chain Fv fragments.

The peptide tag GATPQDLNTML, corresponding to amino acids 46-56 of the human immunodeficiency virus type 1 (HIV-1) capsid protein p24, is the linear epitope of the murine monoclonal antibody CB4-1. This antibody shows high affinity (KD = 1.8 x 10(-8) M) to the free epitope peptide in solution. The original p24 peptide tag and mutant derivatives were fused to the C terminus of a single-chain antibody (scFv) and characterized with respect to sensitivity in Western blot analyses and behavior in purification procedures using affinity chromatography. The p24 tag also proved to be a suitable alternative to the (Gly4Ser)3 linker commonly used to connect single-chain antibody variable regions derived from a heavy (VH) and light chain (VL). Binding of CB4-1 antibody to the p24 tag was not hampered when the tag was located internally in the protein sequence, and the specific antigen affinity of the scFv was only slightly reduced. All scFv variants were solubly expressed in Escherichia coli and could be purified from the periplasm. Our results highlight the p24 tag as a useful tool for purifying and detecting recombinantly expressed scFvs.

Affinity Labels↗

PubMed2003

Intracellular transport of plant toxins ricin and viscumin from different plasma membrane sites.

Binding of ricin and viscumin to paraformaldehyde fixed cell surface has been studied by confocal laser scanning microscopy (CLSM). Both toxins were labeled with different fluorochromes to allow for their identification after being applied jointly. The experiments indicated that viscumin and ricin bind to different cell receptors. Viscumin bound to the very periphery of the cells including lamellapodia and cell contact regions. Labeled ricin became localized in surface clusters located close to the cell body. The binding of toxins to the cell membrane was completely inhibited by 100 mmol/l lactose and in the presence of unlabeled homological toxins 500 times in abundance of the fluorochromed toxins. The experiments indicate that uptake and intracellular transport of ricin and viscumin starts from different membrane sites.

3T3 Cells↗

PubMed2002

Detection of isolated mistletoe lectin chains in plant extracts.

New test systems which allow to detect with high sensitivity the presence of isolated subunits in mistletoe extracts subunits are proposed. Interaction of monoclonal antibodies MNA5 and mouse anti-MLA (mistletoe lectin I A-chain) immune serum with panel of synthetic octapeptides linked to the surface of polyethylene pins have been analyzed. Two main immunogenic epitopes in MLA, AETHL and DGVFNNP, were found. The second sequence can be part of the MNA5 antibody epitope as shown by antigenic prediction. Possible role of the isolated A- and B-chains of mistletoe lectins in pharmacological effects of plant extracts is discussed.

Animals↗

PubMed2002

Comparison between the mechanisms of action of plant toxins ricin and viscumin on the stage of intracellular dissociation.

Pharmacological effects of mistletoe extracts are determined by the concentration of three toxic lectins: mistletoe lectin I (MLI, or viscumin), MLII, MLIII. These proteins, as well as ricin, belong to ribosome-inactivating proteins type 2 (RIP2). However, the extracts from the plant Ricinus communis, containing ricin, are highly toxic. Ricin is about 30 times more effective in cell culture than viscumin. The dissociation of subunits and the transmembrane transport of catalytic subunit into the cytoplasm are needed to obtain the cytotoxic effect of RIP2. In this paper, hybridomas producing monoclonal antibodies against catalytic subunits of ricin and viscumin are described. Monoclonal antibodies against different epitopes, including one localized in intra-subunit area of catalytic subunits of ricin and viscumin, do not inhibit the enzymatic activity of these proteins in cell-free system. These hybridomas are resistant to the cytotoxic action of native toxins. Protective effect of antibodies are about the same for both toxins, though the dissociation of the subunits of ricin is more effective. The causes of the differences in activity of plant toxins as pharmacological agents, and the importance of above mentioned epitopes for neutralizing antibodies at the clinical applications of mistletoe extracts are discussed.

Animals↗

PubMed1994

[Production of monoclonal antibodies in chicken eggs]

The possibility to produce monoclonal antibodies in chicken eggs was shown. Knowledge of biochemical and biophysical parameters of eggs were the basic of the experiments. The cell clones produced 0.1 mg/ml of antibodies in the egg fluid. This method can be a alternative to the monoclonal antibody production in mouse ascites or in bioreactors.

Journal Article↗