Biomedical subjects

G Brandes

Publications and source records attributed to G Brandes.

13 recordsLinked to original sources

PubMed1998

Tissue engineering of heart valves--human endothelial cell seeding of detergent acellularized porcine valves.

OBJECTIVE: Tissue engineering of heart valves represents a new experimental concept to improve current modes of therapy in valvular heart disease. Drawbacks of glutaraldehyde fixed tissue valves or mechanical valves include the short durability or the need for life-long anticoagulation, respectively. Both have in common the inability to grow, which makes valvular heart disease especially problematic in children. The aim of this study was to develop a new methodology for a tissue engineered heart valve combining human cells and a xenogenic acellularized matrix. METHODS: Porcine aortic valves were acellularized by deterging cell extraction using Triton without tanning. Endothelial cells were isolated in parallel from human saphenous veins and expanded in vitro. Specimens of the surface of the acellular matrix were seeded with endothelial cells. Analysis of acellularity was performed by light microscopy and scanning electron microscopy. Cell viability following seeding was assayed by fluorescence staining of viable cells. RESULTS: The acellularization procedure resulted in an almost complete removal of the original cells while the 3D matrix was loosened at interfibrillar zones. However the 3D arrangement of the matrix fibers was grossly maintained. The porcine matrix could be seeded with in vitro expanded human endothelial cells and was maintained in culture for up to 3 days to document the formation of confluent cultures. CONCLUSIONS: Porcine aortic valves can be almost completely acellularized by a non-tanning detergent extraction procedure. The xenogenic matrix was reseeded with human endothelial cells. This approach may eventually lead to the engineering of tissue heart valves repopulated with the patients own autologous cells.

Animals↗

PubMed1996

Microfilament system in the microvascular endothelium of the palmar fascia affected by mechanical stress applied from outside.

The effect of externally applied mechanical stress was investigated by thin section electron microscopy of the microvessels in the unaffected palmar fascia in the carpal tunnel syndrome and in patients with Dupuytren's contracture before and after application of a continuous elongation device. In the unaffected palmar fascia the microfilaments of the endothelial cells were connected to a few adherens junctions and focal contacts; stress fibres were absent. In the cord of Dupuytren's disease the microfilaments were increased in quantity. The length ratios of the connections with the lateral and basal cell membrane were significantly higher than in the control group and increased to an even greater extent in the continuously extended fascia. Stress fibres appeared in the endothelial cells of postcapillary venules in the nonextended cord and in the endothelium of both arterioles and venules after extension elongation. the numerous intermediate filaments and the rare microtubules remained unchanged in the endothelial cells of all palmar fasciae analysed. In the endothelial cells of the microvessels the mechanical stress applied from outside mainly affected the contractile component of the cytoskeleton.

Actin Cytoskeleton↗

PubMed1994

The palmar fascia after treatment by the continuous extension technique for Dupuytren's contracture.

After complete elongation using the continuous extension technique the palmar fascia of four patients with Dupuytren's contracture was examined by light and electron microscopy and compared with non-elongated samples from 20 patients at the same clinical stage of the disease. Nodules and cords were no longer clinically recognizable after extension. The tissue contained collagen fibrils of uniform diameter (about 50 nm), densely packed in fibres parallel to the stretching force. Fine filaments (presumably proteoglycans) formed a network which was intermingled with and periodically bound to the collagen fibrils. Fibroblasts and myofibroblasts with an high biosynthetic activity and oxytalan-like microfibrils were aligned along the collagen fibres. The results show that in Dupuytren's disease the contracted palmar fascia reacts to external forces with neoformation and reorientation of all tissue components by myofibroblasts.

Actin Cytoskeleton↗

PubMed1992

Alterations in the morphology of glycoconjugate molecules caused by histochemical procedures: comparison of renal glomeruli and articular cartilage.

The fine structure of the glycoconjugate molecules was investigated in the glomerular capillary wall of the rat kidney fixed by vascular perfusion, and in the human and rat articular cartilage fixed by immersion. Kidney and cartilage were either prefixed in aldehyde alone (group a), or with the addition of Alcian Blue 8 GX (group b), or Alcian Blue and 0.3 M MgCl2 (group c), or Acridine Orange at a low (0.01%) and high (0.1%) concentration (group d). The specimens were postfixed either in OsO4 phosphate or cacodylate, with the exception of some of the samples in group a, for which a solution of potassium ferrocyanide-reduced OsO4 was used (group e). All samples were conventionally dehydrated and embedded in Epon. In addition, some of the tissue samples in group c were cryoprotected, frozen in liquid Freon (-150 degrees C) or in nitrogen slush (-210 degrees C), both postfixed and dehydrated by cryosubstitution, and embedded in Epon (group f). The present investigations demonstrate that some well known extracellular structures such as the laminae rarae of the glomerular basement membrane or the interfibrillar matrix of the articular cartilage can be considerably altered in their morphology by the histological procedures applied. Whereas the precipitated glycoconjugates, as seen after staining with cationic dyes or reduced OsO4 and conventional dehydration, can easily be recognized, the superposition of the extended molecules, as preserved by freezing and substitution, prevents their demonstration in native conformation.

Adolescent↗

PubMed1991

Histochemical localization of glycoconjugates in the palmar aponeurosis of Dupuytren's patients.

Acridine orange added to the primary fixative or reduced osmium tetroxide as postfixative have been used in order to localize by thin section electron microscopy glycoconjugates in the extracellular matrix of the normal palmar aponeurosis as well as in tissues at different stages of Dupuytren's contracture. After use of acridine orange or reduced osmium tetroxide, in the nodule of the active stage an extensive network of fine filaments separated single or small bundles of collagen fibrils from each other. In the cord of the residual stage fixed in presence of acridine orange, the tightly packed collagen fibrils in the central region of the specimens were swollen and had stained material interposed between the single microfibrils. In specimens of the same cord first fixed with glutaraldehyde alone, followed by reduced osmium tetroxide, the disaggregation of collagen fibrils could be seen only occasionally and the intrafibrillar stained glycoconjugates were less evident. Comparable alterations were absent from the normal tissue. The possible reasons of these differences are discussed.

Acridine Orange↗

PubMed1990

The reaction of acridine orange with proteoglycans in the articular cartilage of the rat.

Acridine Orange in concentrations from 0.01% to 0.2% was added to the first fixative solution in order to stain vibratome sections and small blocks of the articular cartilage of 2 month old rats. The interterritorial matrix of the radial or deep zone (zone 3) was examined. It contained reaction products with different morphology depending on the specimens used. In vibratome sections filaments were seen arranged in a homogenous pattern and changing in size with the concentration of the dye: diluted solutions produced finer filaments than concentrated ones. In contrast, in tissue blocks the staining pattern was not altered by different concentrations of Acridine Orange. However, with increase of the distance from the surface of the specimens the size of the filaments gradually decreased and formed a finer network. Since after preincubation with chondroitin ABC lyase only minute reaction products remained, an interaction of the dye with the sulphated glycosaminoglycans of the proteoglycans in the articular cartilage is suggested. The experiments show that by using mainly monocationic monomers of Acridine Orange the proteoglycans can be stained in a more expanded state than with polycationic dye polymers.

Acridine Orange↗

PubMed1978