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Biomedical subjects

W De Loecker

Publications and source records attributed to W De Loecker.

At least 37 records · Page 2Linked to original sources
PubMed1981

Effects of ionizing irradiation on the estradiol and progesterone receptors in rat mammary tumors.

The determination of estradiol and progesterone receptor concentrations in mammary tumors is useful in predicting the hormone responsiveness. As this assay is carried out on tumor tissue which may have been subjected to radiotherapy, the possibility of an ionizing irradiation affecting the steroid receptor levels in neoplastic tissue should be taken into account. The steroid receptor concentrations are examined in dimethylbenz(a)anthracene-induced tumors of Sprague-Dawley rats. The estradiol and the progesterone receptor titers become reduced significantly after treatment with 20 Gray while an application with 7 Gray does not affect the titer values. After treatment of the tumor with 20 Gray, the steroid receptor concentrations decrease progressively, reaching a maximal reduction 20 to 30 days after exposure. This measured reduction in binding sites seems to be the result of a specific irradiation effect and not due to a possible increase in lytic enzyme levels in the regressing tumors. As radiation treatment affects the receptor concentrations, this should be kept in mind when interpreting the steroid receptor concentrations.

Animals↗
PubMed1979

The effects of cortisol on protein metabolism and on transfer ribonucleic acid methylase activity in rhabdomyosarcoma of rats.

The effects of cortisol on protein metabolism were examined in rhabdomyosarcoma tissue, experimentally provoked in rats by a single intramuscular injection of cobalt powder into the adductor muscle of the hind limb. In vivo treatment of tumour bearing animals with 1 and 10 mg cortisol resulted in a reduced incorporation of [2-14C] glycine into the tumour proteins. In vitro application of 0.01 to 100 micrograms cortisol on tumour slices equally reduced the amino acid incorporation into the proteins. These inhibitions could not be explained by modifications in protein, RNA, DNA content or by changes in the membrane function. The factors inhibiting the amino acid incorporation into tumour proteins could be located in the 105,000 X g supernatant protein fraction. The tumour transfer RNA methylase activity became markedly inhibited by cortisol treatment.

Animals↗
PubMed1979

Interactions between steroidreceptors.

Interactions between the estradiolreceptor and the progesteronereceptor are known to exist in the uterus. The "priming effect" of estradiol is likely to exist also in human and rat mammary tumors. In detecting also the progesteronereceptors along with the estrogenreceptors, one cannot only demonstrate the presence but also the activity of the estrogenreceptor. This finding should improve the response rate of hormonesensitivity to receptorpositivity. However preoperative irradiation possibly induces negative progesteronereceptortiters in human breast tumors.

Animals↗
PubMed1976

The effects of x-irradiation on collagen metabolism in rat skin.

Collagen metabolism in rat skin and the response to X-radiation are studied during three consecutive hair-cycles. Collagen biosynthesis and turnover, assessed by the hydroxylation of [U-14C]-proline, proceeds as a function of the periodic hair-growth phenomenon. A single X-radiation treatment to the skin does not affect the amino-acid composition of collagen, but reduces the proline hydroxylation capacity of the fibroblasts. The initial damage to the tissue, resulting in a reduced collagen concentration of the skin, particularly noticeable after several hair-cycles, is at least partially responsible for the delayed skin lesions after irradiation.

Amino Acids↗
PubMed1976

Fine filaments in lymphatic endothelial cells.

Several and various types of cells contain fine cytoplasmic filaments closely resembling the myofilaments of muscle cells (2, 18, 23, 24). In many of these cells and especially when cultured, it has been demonstrated that some of these filaments react with heavy meromyosin (HMM) in the same way as do the actin filaments of muscle cells (3, 6 7). This suggests that these filaments may be actinoid and form part of a contractile system. As fine intracytoplasmic filaments do occur in lymphatic endothelial cells (2, 14), we undertook an electron microscope investigation of their fine structure and their reaction on incubation with HMM and EDTA. We postulated that lymphatic endothelial cells possess a contractile filamentous system to which these filaments belong.

Animals↗
PubMed1975

Intracytoplasmic filaments in pulmonary lymphatic endothelial cells. Fine structure and reaction after heavy meromyosin incubation.

The cytochemistry and ultrastructure of intracytoplasmic filaments of pulmonary lymphatic endothelial cells of neonatal rabbits were studied by comparison with myofilaments of the peribronchial and pulmonary vascular smooth muscle cells. Two types of endothelial filaments were observed: thin filaments (diameter: 50 A) which lie close to the abluminal cell membrane; and thick filaments (diameter: 90 A) which are dispersed throughout the cell cytoplasm. Following heavy meromyosin (HMM) treatment, characteristic arrowhead complexes formed in the thin lymphatic endothelial filaments as well as in the actin filaments of the smooth muscle cells. There was no detectable reaction of HMM with the thick filaments. After incubation with EDTA, the thin filaments were labile, and the thick filaments became the major filamentous component in the endothelial cells. In smooth muscle cells, the actin myofilaments were also labile while the 100 A filaments were stable. These observations support the hypothesis that the actin-like thin endothelial lymphatic filaments form part of a contractile system, while the thick filaments constitute a plastic cell skeleton. The significance of the contractile system in lymphatic endothelial cells might lie in a mechanism for the active regulation of the endothelial intercellular junction and gaps and hence the permeability of the lymphatic endothelial cell lining.

Actins↗