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Biomedical subjects

M Hagenah

Publications and source records attributed to M Hagenah.

23 records · Page 2Linked to original sources
PubMed1990

The role of pneumolysin in ocular infections with Streptococcus pneumoniae.

Pneumolysin, a cytolytic protein produced by Streptococcus pneumoniae, has many properties which suggest it may be an important virulence factor in pneumococcal ocular infections. To directly test this possibility, we have constructed pneumolysin-negative strains of S. pneumoniae and compared their virulence with that of the wild type in a rabbit model of intracorneal infection. A pneumolysin-negative strain produced by chemical mutagenesis (probably a point mutant) was found to be no less virulent than the parent strain. However, a strain bearing a deletion in the pneumolysin gene showed greatly reduced virulence. This strain produced less pathology while showing significantly higher bacterial counts. These results suggest that a property of the pneumolysin molecule other than its cytolytic (hemolytic) activity may be involved in its pathogenic mechanism of action. This property may be the ability to activate complement, known to be a function of pneumolysin, which results in influx of PMNs, reducing the bacterial counts but also producing tissue damage.

Animals↗
PubMed1990

[Application of experimental findings of cryopreservation of animal tissue to results of cryopreservation of human tissue].

In order to compare the results after experimental corneal cryopreservation of porcine corneas to human tissue we cryopreserved several human corneas that were not suitable for transplantation. The corneas were frozen in a medium containing 2% chondroitin sulfate, 15% DMSO, and 20% fetal calf serum in MEM-medium to -196 degrees C and thawed at 37 degrees C in a waterbath. Subsequently they were kept in organ culture for 24 h. After vital staining with trypan blue and alizarin red S they were evaluated morphometrically. Endothelial cell densities after the experiment ranged between 47% and 64% of the endothelial cell counts revealed before cryopreservation. Human corneal endothelium showed enlargement of single nucleated cells, and large numbers of giant cells with one or two nuclei but only few multinucleated giant cells and only few necrotic spots compared to porcine tissue in which multinucleated giant cells and large necrotic areas were a frequent finding. We conclude that human corneal endothelium is less sensitive to the freeze-thaw trauma than porcine tissue. Porcine tissue can be used as a susceptible model for the development of new methods of corneal cryopreservation.

Adult↗
PubMed1989

[Experimental studies of the correlation of morphologic endothelial cell findings and endothelial pump function].

In our experiments corneal endothelial cell morphology after Alizarin Red and Trypan Blue staining and endothelial pump function in a perfusion chamber were investigated. As a model for morphologically degenerated tissue we used corneas that had been cryopreserved with two different methods. In control groups 1) fresh, 2) one day organ cultured and 3) corneas without endothelium were evaluated. Morphologic evaluation showed degenerations (enlarged mononucleated cells, giant cells, disseminated necrotic areas) in cryopreserved corneas as compared with control groups. However, in perfusion experiments morphologically damaged tissue showed the same deswelling pattern as organ-cultured corneas. The results show that a morphologic evaluation seems to be a more precise criterion for the quality of the tissue than the investigation of the corneal pump function in a perfusion chamber.

Animals↗
PubMed1987

[Cryopreservation of porcine corneas with chondroitin sulfate].

A new method for cryopreservation of porcine corneoscleral discs has been developed. Instead of the widely used cryoprotectant DMSO, chondroitin sulfate was applied as a cryoprotectant for the first time. Post-thawing evaluation was done after short-term tissue culture. Central cell counts showed a mean endothelial cell density of 2430 cells/mm2 (+/- 383) after freezing with a combination of 2% chondroitin sulfate and 20% fetal calf serum. Corneae which were cryopreserved with DMSO using the method established by Capella and Kaufman showed a mean endothelial cell density of 1672 cells/mm2 (+/- 617). These experiments demonstrated significant cryoprotective properties of chondroitin sulfate. In addition to its application in refrigerated corneal storage at 4 degrees C and organ culture at 32 degrees C, this substance may also be useful in cryopreservation.

Animals↗