Male rabbits were injected daily for 14 days with prednisone 2 mg/ kg. The content and metabolism of collagen and glycosaminoglycans, the content of RNA, DNA, fat and water and the 125I-albumin permeability were investigated in the skin and in the intima-media layer of the aorta. A saline injected group served as control. Since prednisone induced a decrease in body weight, a starvation group with a similar weight loss was included. Following injections of prednisone the protocollagen proline hydroxylase activity, 0.45 m NaCl soluble hydroxyproline, total hydroxyproline, dialysable 14C-hydroxyproline and non-dialysable 14C-hydroxyproline fractions were reduced in the skin. In the aorta, only the total 14C-hydroxyproline synthesis was decreased. Furthermore there was a decrease in 14C-proline incorporation and the alpha-amino nitrogen content in the skin as well as a decrease in the RNA content in the skin and the aorta.
Acid glycosaminoglycans were measured in the tissues of a virtually untreated 83-year-old woman with myxoedema. Intercellular oedema was demonstrated histologically in the tongue, myocardium, striated muscles, and in the skin. Tissue oedema was absent in two female control patients. All tissues from the patient with myxoedema, apart from the stomach, showed high concentrations of hyaluronic acid, but there was no consistent elevation of chondroitin-4,6-sulphate, heparan sulphate or dermatan sulphate. The accumulation of hyaluronic acid might contribute to the oedema formation in myxoedema.
Male albino rabbits of the Danish country strain, 5 months of age, were divided into two groups. One group of animals was killed 180 days after a single mechanical dilatation injury of the thoracic aorta. A second group of untreated controls was killed at ages of 150, 165, 180, 210, 330, and 450 days. Glycosaminoglycans, uptake of <sup>35</sup>S-sulphate, collagen, uptake of <sup>125</sup>I-albumin, and vascular histochemistry and morphology were analyzed in the thoracic aorta. In the injured aortae the dry weight and the total amounts of hexosamine, hyaluronic acid, chondroitin-4,6-sulphate, dermatan sulphate, heparan sulphate, and hydroxyprohne were increased. The concentration of hyaluronic acid decreased, whereas the concentration of dermatan sulphate increased. The concentrations of chondroitin-4,6-sulphate and heparan sulphate were unchanged. The total uptake of <sup>35</sup>S-sulphate into the sulphated proteoglycans as well as the uptake of <sup>125</sup>I-albumin were increased. The light microscopical examination showed thickening of the intima, medial changes with fibrosis, accumulations of proteoglycans, calcifications, formation of cartilage, and ossified tissue with haematopoiesis. In the uninjured thoracic aorta the only significant change during ageing was an increase in the total amount of hyaluronic acid and a decrease of the <sup>35</sup>S-sulphate incorporation into the chondroitin-4,6-sulphate in the aorta. No morphological or histochemical alterations were observed during ageing. Spontaneous lesions were observed in 2 out of 55 aortas. It may be concluded that injury and ageing are reflected quite differently in the thoracic aorta of the rabbits. The observations may be of relevance to the interpretation of the alterations in human arterial diseases involving processes of injury and repair as well as ageing.
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