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Biomedical subjects

R K Schenk

Publications and source records attributed to R K Schenk.

At least 55 records · Page 3Linked to original sources
PubMed1987

[Personal experiences with uncemented prostheses].

Experience with different types of non-cemented total hip endoprostheses is critically discussed. Three radiological criteria of a good result indicated: the presence of radiolucent lines, cancellous transformation, and a particular appearance and thickness of the cortex. The radiological changes and clinical results make it possible to draw a 'survival curve' for each type of implant. This series shows that unsatisfactory results have been due mostly to primary diaphyseal, distal fixation of the prosthetic stem. The CLS prosthesis, with mainly metaphyseal primary anchorage, is presented. Discussion of the radiologically and histologically established response of bone.

Adult↗
PubMed1985

Matrix compartments in the growth plate of the proximal tibia of rats.

The cartilaginous matrix in the growth plate of the proximal tibia of rats is subdivided into various compartments according to criteria established by electron microscopic examination. In conventionally fixed specimens, the arrangement of collagen fibrils was analyzed by transmission and scanning electron microscopy. Distribution of proteoglycans and relations between matrix and cells were studied after fixation in media containing cationic dyes. Matrix compartments are best characterized by the density and arrangement of their collagen fibrils. On the other hand, proteoglycans are distributed almost homogenously all over the matrix. Each chondrocyte is surrounded by a thin envelope of proteoglycans, the pericellular matrix. Adjacent to this is a layer dominated by the content and order of its collagen fibrils, the territorial matrix. Its inner part covers the pericellular matrix with a thin net of intersecting fibrils. The outer part unites the cells of each column by a sheath of tightly packed longitudinal fibrils. This distinction is only possible in the longitudinal parts of the territorial matrix, whereas in the transverse septa both layers fuse into a common network. The interterritorial matrix is interposed between the columnar units and thus represents the central part of the longitudinal septa. Mineralization is restricted to the interterritorial matrix and matrix vesicles are coincidentally found in the same compartment. During growth, this structural organization undergoes a permanent and relatively fast remodeling, a process that is discussed in view of possible cell matrix interactions.

Animals↗
PubMed1984

Cartilage ultrastructure after high pressure freezing, freeze substitution, and low temperature embedding. I. Chondrocyte ultrastructure--implications for the theories of mineralization and vascular invasion.

Electron microscopic examination of epiphyseal cartilage tissue processed by high pressure freezing, freeze substitution, and low temperature embedding revealed a substantial improvement in the preservation quality of intracellular organelles by comparison with the results obtained under conventional chemical fixation conditions. Furthermore, all cells throughout the epiphyseal plate, including the terminal chondrocyte adjacent to the region of vascular invasion, were found to be structurally integral. A zone of degenerating cells consistently observed in cartilage tissue processed under conventional chemical fixation conditions was not apparent. Hence, it would appear that cell destruction in this region occurs during chemical processing and is not a feature of cartilage tissue in the native state. Since these cells are situated in a region where tissue calcification is taking place, the implication is that the onset and progression of cartilage calcification are, at least partially, controlled by the chondrocytes themselves. The observation that the terminal cell adjacent to the zone of vascular invasion is viable has important implications in relation to the theory of vascular invasion. This may now require reconceptualization to accommodate the possibility that active cell destruction may be a precondition for vascular invasion.

Animals↗
PubMed1984

Cartilage ultrastructure after high pressure freezing, freeze substitution, and low temperature embedding. II. Intercellular matrix ultrastructure - preservation of proteoglycans in their native state.

The extracellular matrix of epiphyseal cartilage tissue was preserved in a state believed to resemble closely that of native tissue following processing by high pressure freezing, freeze substitution, and low temperature embedding (HPF/FS). Proteoglycans (PG) were preserved in an extended state and were apparent as a reticulum of fine filamentous threads throughout the matrix. Within this network, two morphologically discrete components were discernible and identified with the carbohydrate and protein components of PG molecules. Numerous points of contact were clearly visible between components of the PG network and cross-sectioned collagen fibrils and also between PG components and chondrocytic plasmalemmata. These observations provide direct morphological indication that such relationships may exist in native epiphyseal cartilage tissue.

Animals↗
PubMed1983

Ruthenium hexammine trichloride (RHT)-mediated interaction between plasmalemmal components and pericellular matrix proteoglycans is responsible for the preservation of chondrocytic plasma membranes in situ during cartilage fixation.

Treatment of cartilage tissue with the cationic dye ruthenium hexammine trichloride (RHT) prior to fixation has been shown to prevent the detachment of chondrocytic plasmalemmata from the pericellular matrix and the aqueous extraction of proteoglycans during the subsequent fixation procedures. However, plasmalemmal rupture is prevented only by the simultaneous addition of RHT and the dialdehydic fixative glutaraldehyde. It is proposed that RHT forms an electrostatic cross-linkage between anionic components within the chondrocytic plasmalemma and proteoglycans of the pericellular matrix; experimental support for this hypothesis is presented. The precise nature of the plasmalemmal components with which RHT interacts is unknown. However, since their anionic properties are apparently lost following treatment with chondroitinase ABC, it seems likely that they represent chondroitin sulfate groups of membrane intercalated proteoglycans.

Animals↗
PubMed1982

Synthesis of cartilage matrix by mammalian chondrocytes in vitro. I. Isolation, culture characteristics, and morphology.

We describe the isolation and the ultrastructural characteristics of adult bovine articular chondrocytes in vitro. Slices of bovine articular cartilage undergo sequential digestions with pronase and collagenase in order to release cells. Chondrocytes are plated at high density (1 x 10(5) cells/cm2) in culture dishes or roller bottles with Ham's F-12 medium, supplemented with 10% fetal bovine serum. Before culture, chondrocytes are freed of surrounding territorial matrix. Within the first few days of culture they re-establish a territorial matrix. As time progresses, chondrocytes synthesize both territorial and extraterritorial matrices. The matrices are rich in collagen fibrils and ruthenium red-positive proteoglycans. These features are most apparent in mass roller cultures in which aggregates of cells and matrix appear as long streaks and nodules. This morphology reveals an organization of chondrocytes and their matrices that is similar to that of the parent articular cartilage in vivo.

Animals↗
PubMed1977

Differential staining of calcified tissues in plastic embedded microtome sections by a modification of Movat's pentachrome stain.

Movat's pentachrome I stain has been adapted and modified as a stain for undecalcified bone sections. After embedding in methyl methacrylate, this procedure yields consistently good results, with an excellent and colorful contrast between mineralized and unmineralized compartments of both cartilage and bone. In addition, osteoblasts, osteoclasts, and other cells and tissue components can easily be differentiated. The staining properties of the lacunar wall surrounding the osteocytes are considered to reflect various states of osteocytic activity. The method is especially useful for the study of bone growth and bone repair, and as a stain for conventional histomorphometry and computer-assisted image analysis in bone biopsies.

Animals↗
PubMed1977

Sodium etidronate in the treatment of Paget's disease of bone. A study of long-term results.

Subjects (109) with symptomatic Paget's disease of bone were treated with 5, 10, or 20 mg of sodium etidronate (EHDP)/kg body weight - day for 6 to 24 months. Significant decreases in serum alkaline phosphatase and urinary hydroxyproline were noted after 6 months of therapy; no significant further improvement resulted after prolonged therapy. Some patients maintained biochemical remission after withdrawal of EHDP but others showed a relapse, related primarily to the pretreatment severity. Clinical improvement was noted in 61% of the patients. Similar findings were seen after a second course of EHDP. No side-effects were noted in patients treated with 5 mg of EHDP/kg body weight - day. In patients treated with 10 or 20 mg of EHDP/kg body weight - day, severe diarrhea, bone pain, and nontraumatic fractures were noted in 3, 13, and 12 patients respectively. Quantitative histomorphometry showed mineralization delay in patients receiving 10 or 20 mg of EHDP/kg body weight - day but not in those receiving 5 mg/kg body weight - day. Five milligrams of EHDP/kg body weight - day was effective and appears to be safer than the higher doses.

Adult↗
PubMed1976

[Some structural and functional peculiaritis of the growing skeleton and their significance in fracture healing (author's transl)].

The following properties of the growing skeleton are discussed in relation to fracture healing: (1) The pronounced reaction of periosteum and endosteum and their part in the correction of deformities, and the vascular pattern of cortical bone; (2) the microscopical structure and the vascular supply of the growth plate, with reference to their significance in injuries; (3) the involvement of growth plate and growing articular cartilage in the modeling of the end of long bones and in the correction of angular deformitis.

Bone Development↗