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P Helin

Publications and source records attributed to P Helin.

71 records · Page 4Linked to original sources
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Effects of intermittent and continuous hypoxia on the aortic wall in rabbits.

Male albino rabbits were exposed to intermittent nitrogen breathing every 30 sec for 5 sec, 15 min daily over a period of 3 weeks, and every 30 sec for 5 sec over a period of 10 hr. A third group of animals was exposed continuously to 8% oxygen breathing for 2 weeks. Neither intermittent not continuous hypoxia induced gross or microscopic alteration in the aorta. The effects of hypoxia upg which hypoxia was distributed than upon the total period or the degree of hypoxia. Exposure to hypoxia over a short period stimulated the synthesis of glycosaminoglycans, whereas distribution of the hypoxia over a longer period resulted in a reduction in the amount of glycosaminoglycans, probably secondary to an inhibition of the synthesis. Similarly, continuous exposure to 8% oxygen for a longer period decreased the aortic content of collagen. The alterations in the glycosaminoglycans and collagen induced by hypoxia may cause changes in the passage of macromolecules through the aortic wall. The changes may also influence the mechanical properties of the aorta and lead to impaired healing of vascular injury.

Animals↗
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Seasonal variations in the susceptibility of the aortic wall to atherosclerosis. Biochemical studies of glycosaminoglycans and collagen of rabbit atherosclerosis.

The aortic content of glycosaminoglycans and collagen as well as the uptake of [125 I] albumin were studied in 53 male albino rabbits during hair-shedding and outside the period of hair-shedding to elucidate the previously reported resistance to experimental arteriosclerosis during the shedding period [1]. The concentration of hyaluronic acid was highest during hair shedding, decreasing towards the non-shedding period. The content of dermatan sulphate, chondroitin-4, 6-sulphate and hydroxyproline was lowest during sheeding and highest outside the sheeding period. Accordingly, the incorportation of [35 S] sulphate in chondroitin -4, 6-sulphate and the dermatan plus heparan sulphate fraction was increased outside shedding, consistent with a stimulated synthesis. The concentration of hyaluronic acid was negatively correlated to the uptake of [125I] albumin, and the dermatan sulphate content was positively correlated to the content of hydroxyproline. The higher concentration of hyaluronic acid during the period of shedding may improve the elastic properties as well as the ability of the aortic wall to absorbe the haemodynamic strain involved in the vascular injury of this type of experimental arteriosclerosis [2]. The decrease in the concentration of hyaluronic acid simultaneously with an increase in the aortic content of collagen as well as of chondroitin-4, 6-sulphate and dermatan sulphate may imply a greater stiffness of the aorta resulting in a higher susceptibility to injury. The relationship between hyaluronic acid and [125 I] albumin is consistent with an importance of hyaluronic acid to the susceptibility of the arterial wall to deposition of macromolecules such as the lipids. Our observations represent an example of endogenous conditioned variations in the aortic content of glycosaminoglycans and hydroxyproline accompanied by a variation in the susceptibility to experimental arteriosclerosis.

Albumins↗