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W Umrath

Publications and source records attributed to W Umrath.

10 recordsLinked to original sources
PubMed1981

An improved technique for the freeze-fracture of cell cultures grown as monolayers.

An improved and rapid procedure for the freeze-fracture of cell cultures grown as monolayers is described. No additional equipment than normally used for freeze-fracturing is necessary and cell culture conditions are as usual on plastic dishes. Cells are grown on a plastic foil membrane so that they can be viewed with a light microscope. If necessary, while viewing with a binocular microscope, specimen holders are glued to the foil membrane over selected areas of the culture. The specimen holders with the attached cell culture are dissected out and processed for freeze-fracturing in a BIOETH 2005. Fracture planes occur along the cell surface as well as through entire cells. Analysis of corresponding fracture faces is possible.

Animals↗
PubMed1981

Interpretation of morphological data obtained by freeze-fracturing at very low temperatures.

In freeze-fracture replication the greatest variety of methods exists for the fracturing process itself. The present stage of knowledge allows to evaluate fracture faces obtained by freeze-cleaving at temperatures down to 4 K. Under condensation free conditions the possibility for artefact formation will be restricted to the fracturing and replication process. Experiments on model systems and complex biological systems show that many fine structural details seen on freeze-fractured replicas have to be interpreted as the result of a multi-event process involving plastic deformation, elastic recontraction, collapse phenomena and thermal load induced alterations during replica formation. With some structures the degree of deformation may be reduced by chemical fixation procedures.

Cell Membrane↗
PubMed1979

The structure of tight junctions in human thyroid tumors. A systematic freeze-fracture study.

Tight junctions of normal human epithelium comprise 6--8 intramembranous ridges. Tight junctions of adenomas and one case of follicular carcinoma were morphologically identical with normal controls. Another follicular carcinoma (clinically less malignant than the case mentioned above), however, showed loss of junctional polarity with spreading of ridges on lateral cell membranes. One case of papillary carcinoma (clinically low malignancy) displayed only focal attenuations of the tight junction belt. Another more malignant tumor of the same histologic type showed breaks of ridges and focal interruptions of the tight junction meshwork. Cell membranes of two anaplastic carcinomas of high malignancy were completely devoid of tight junction ridges. We conclude that tight junction alterations are not necessarily implicated in malignant transformation and that they correspond with tumor differentiation rather than directly with a single parameter of thyroid tumor malignancy.

Adenocarcinoma↗