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K Madsen

Publications and source records attributed to K Madsen.

85 records · Page 5Linked to original sources
PubMed1983

Specific binding of growth hormone to isolated chondrocytes from rabbit ear and epiphyseal plate.

Chondrocytes were isolated from rabbit ear, epiphyseal and rib cartilage, and their ability to bind 125I-labeled human growth hormone (hGH) was investigated. The total binding of hormone to ear chondrocytes increased with time until 4-6 h, whereas non-specific binding did not increase. Total binding was 1-3% of total counts added, and non-specific binding was 10-20% of total binding. Unlabeled hGH, bGH and oPRL competed with the binding of labeled hGH in a dose-dependent manner with half-maximal binding at concentrations of 10-20 ng/ml (hGH) and 100 ng/ml (bGH and oPRL). The two latter hormones displaced almost all specific binding of hGH at higher concentrations. Ear chondrocytes from newborn to 4 week old rabbits all showed specific binding of hGH with no clear age dependence. Rib chondrocytes, on the other hand, showed very little specific binding. Epiphyseal chondrocytes from newborn animals yielded intermediate binding values. The finding of specific hGH binding by cultured chondrocytes supports the concept of a direct effect of GH on chondrocytes.

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PubMed1983

X-ray microanalysis of cultured chondrocytes.

Methodological aspects of X-ray microanalysis of cultured chondrocytes from rabbit auricular cartilage were investigated. The cells were grown on a Formvar-film covered carbon specimen holder with a hole, which allowed examination in STEM. Several different fluids for washing away the culture medium from the cells were used. The effect of these fluids on the elemental composition of the cells was studied. The composition of cultured chondrocytes was compared with that of auricular chondrocytes in situ. Washing with 0.3 M sucrose gave the most satisfactory results. Subsequently, the specimen holders could be frozen in liquid nitrogen and the cells freeze-dried. The effects of human growth hormone on rabbit chondrocytes were investigated by X-ray microanalysis and transmission electron microscopy. Although no ultrastructural effects of hormone treatment could be observed, marked changes in the elemental concentrations in nucleus and cytoplasm of the chondrocytes were detected.

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PubMed1979

Comparison of the in vitro effects of colchicine and its derivative colchiceine on chondrocyte morphology and function.

Colchiceine is a colchicine-metabolite which has been reported to inhibit axonal transport although not binding to brain tubulin. In the present study, colchiceine was shown not to depolymerize cytoplasmic microtubules, nor to mimic other effects of colchicine on the ultrastructure of cultured chondrocytes. In addition, the synthesis of proteoglycans was inhibited by colchicine but slightly stimulated by colchiceine. These results support the idea that the disturbances in cultured chondrocytes caused by colchicine are specifically related to a loss of cytoplasmic microtubules.

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PubMed1978

Proteoglycans synthesized by fetal guinea pig chondrocytes in culture.

Short term cultures were carried out with chondrocytes and tissue fragments from fetal guinea pig epiphyseal cartilage. Proteoglycans were isolated from these cultures and their properties were compared with those of proteoglycans from adult hyaline cartilage. It was concluded that the proteoglycans synthesized in culture were essentially similar to those present in cartilage matrix in vivo. The authors therefore suggest that fetal guinea pig chondrocytes cultured in monolayer or as aggregates in suspension constitute a useful system for the study of synthesis and secretion of proteoglycans.

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PubMedDate not supplied

Growth hormone stimulates the proliferation of cultured chondrocytes from rabbit ear and rat rib growth cartilage.

The effect of growth hormone (GH) on various growth processes is generally considered to be indirect, mediated by GH-dependent plasma factors--somatomedins--which are produced mainly in the liver. In vitro, somatomedins stimulate a number of processes that apparently are associated with cell growth. It has been difficult, however, to induce skeletal growth by the administration of somatomedins in vivo. Daily injections of a partially purified somatomedin preparation failed to induce accumulated longitudinal bone growth using the intravital marker tetracycline or by measuring the nose-to-tail length. Administration of insulin-like growth factor I (IGF I) which is probably identical to somatomedin C, to hypophysectomized rats has been reported to increase the width of the epiphyseal plate. But although this suggests an in vivo effect of IGF I on longitudinal bone growth, such an effect has not been directly demonstrated. Recently, we reported that local administration of human GH (hGH) into the proximal cartilage growth plate of the tibia of hypophysectomized rats stimulated longitudinal bone growth on the side injected with the hormone. Furthermore, we have identified specific binding sites for hGH in cultured chondrocytes from rabbit ear and epiphyses. Here, we show that hGH, but not the structurally related polypeptides ovine prolactin or human prolactin, stimulates DNA synthesis in chondrocytes from rabbit ear and from rat rib growth plate, cultured in a chemically defined medium without the addition of serum. Our results suggest that GH directly initiates proliferation in mammalian chondrocytes.

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