Changes In Elastin Research Articles

Postnatal development of rat lung. Changes in lung lectin, elastin, acetylcholinesterase and other enzymes.

The development of rat lung from a primitive gas-exchange organ to the mature respiratory organ is in large part a postnatal phenomenon that has been well characterized by morphological and morphometric methods. The alveolarization of the lung is achieved during the first 3 weeks of life. Cholinergic innervation of rat lung also appears postnatally. We have monitored the presence or activity of several proteins during postnatal rat lung development. Newborn-rat lung contains negligible amounts of acetylcholinesterase, but the specific activity of acetylcholinesterase reaches adult values by postnatal day 10-11. Neonatal-rat lung does not contain significant amounts of beta-galactoside-binding protein [Powell (1980) Biochem. J.187, 123-129]. The activity of this endogenous lung lectin was apparent at about day 6, was maximal between days 10 and 13 before declining 8-10-fold to reach adult values. Elastin has been implicated from morphological evidence as critical to lung restructuring. We have quantified the amount of desmosine and isodesmosine per g wet wt. of lung. The concentration of elastin, by this criterion, was low and stationary until postnatal day 7; a dramatic increase in elastin concentration occurred between days 10 and 20, when adult values were reached. The peak of lung-lectin activity was coincident with the maturation of acetylcholinesterase and the beginning of rapid elastin cross-linking. The specific activities of angiotensin-converting enzyme, carbonic anhydrase, choline kinase and glucose 6-phosphate dehydrogenase were also monitored.

Age-related changes in elastic fibers and elastin of lung.

The effect of age on the lung elastic tissue of inbred BALB/c mice were studied. Static compliance of excised lungs increased with age. Morphometrically determined total elastic fiber length increased with lung expansion in age- and sex-matched mice (r = 0.83, P smaller than 0.001), indicating an axial extension of elastic fibers. However, total elastic fiber length of aging lungs fixed at a distending pressure of 15 cm H2O showed no significant change despite an age-related increase in lung volume (male, r = 0.96, P smaller than 0.001; female, r = 0.95 P smaller than 0.001). The correlative finding of decreased elastin content (r = -0.87, P smaller than 0.001) indicates that there is a loss of elastic fibers in the aging lung. It is suggested that the absence of pseudoelastin fibers, as demonstrated by histochemical techniques, accounts for the observed differences in elastin content of aging human and mouse lungs.

Passive mechanics and connective tissue composition of canine arteries.

Passive mechanics and connective tissue composition of canine arteries.

ヒト大動脈コラーゲンとエラスチンの加齢変化

ヒト大動脈コラーゲンとエラスチンの加齢変化

ACCOUNTING FOR NATURAL TENSION IN THE MECHANICAL TESTING OF HUMAN SKIN

A low-pressure suction device has previously been used to obtain quantitative information on the mechanical properties of human skin. Reducing the raw data from this technique was complicated by the fact that the skin is already biaxially loaded in the natural state and a rational basis on which to compare results obtained from different subjects was not available. Using a strain gauged pretension device, a procedure for determining the natural state tension and extension fields in the skin has been developed. The natural tension was then relaxed in the direction of testing and the suction device used to determine the two-dimensional skin tension-extension ratio response of the skin at a constant testing rate. The data from a number of subjects have been used to develop a new multidimensional stress-strain theory in terms of two material constants that are related to basic material characteristics of the dermis and are uniquely determinable regardless of the natural state stress field. Tests performed on the upper backs of 23 healthy adult males were used to investigate the variations in the material constants with age and sun-exposure habits. Age variations were found to corroborate earlier studies, and variations with sun exposure habits were related to known dermal collagen and elastin changes due to ultraviolet radiation. The apparent sensitivity of the testing procedure to physiologic state variables holds out the hope that mechanical properties characterization will be a useful tool in the evaluation of the severity of certain pathologic states and the effect of therapy.

Factors affecting the proteolytic degradation of elastin.

Studies in our laboratory have been concerned with aspects of the interaction of elastin with pancreatic elastase in efforts to assess intrinsic and extrinsic factors which might be involved in the regulation of elastolysis in vivo. Previous studies by others have clearly shown that elastase-elastin interactions are principally governed by ionic forces distributed between the cationic enzyme and the presumably anionic substrate. Our studies have now shown that most of the dicarboxylic amino acids in elastin are amidated, rendering elastin a cationic protein containing very few negatively charged side chains. Further, we have demonstrated that elastin can be rendered highly anionic by complex formation with amphiphilic agents such as fatty acids, bile salts, and detergents. These complexes are much more susceptible to elastolysis than elastin, itself. Evidence has also been obtained that these agents induce conformational changes in insoluble elastin, reflected in losses in elasticity of elastic fibers. Additional studies have shown that the formation of sedimentable elastin-elastase complexes seem not only to be unrelated, but, possibly, counterproductive to peptide bond scission in elastin. Further, both elastolysis and enzyme binding relationships are markedly influenced by calcium ions and by amphiphilic elastin ligands.

ヒト大動脈エラスチン

Elastin was isolated from the thoracic aorta of humans of different ages, sclerotic and nonsclerotic, and studied qualitatively and quantitatively. Sum of collagen and elastin contents of normal aorta showed progressive increasing with age, except for the groups younger than 20 years old, which showed a fall. But proportion of collagen to elastin concentration remained constant in wide age range in the aorta, though markedly diminished with advancing age in the pulmonary artery.The susceptibility of aortic elastin to elastase was expressed as percent solubilized protein N of total elastin N, incubated with elastase in pH8.7 borate buffer under shaking at 37°C for 14 hours. These results showed progressively diminished values with advancing age, but there was no significant difference in the values between sclerotic area and adjacent normal area of the same aorta.Activating by ultraviolet light, the fluorescent spectrum of the solubilized aortic elastin was drawed, using spectrophotofluorometer. Of three fluorescent substances recognised, one showed age-related increasing tendency after 40 years old, whose activation/fluorescence maxima was at 336/400nm. And the intensity of the fluorescence of aortic elastin was not influenced by sclerotic changes.Elastase solubilized aortic elastin was chromatographed using Sephadex-G-100 column. All the samples of aortic elastin showed two peaks, Fraction A with larger molecular weight, and Fraction B with smaller molecular weight. The ratio of A/A+B showed increasing age trend, except for a case of 75 years old, which showed a fall. Elastin from sclerotic area showed higher A/A+B ratio than adjacent normal area of the same aorta.As carbohydrate components of glycoproteins in the elastin fraction from the aorta, hexoses, hexosamines, methylpentose and sialic acid were analyzed. The proportion of the total sugar in elastin fraction showed age related increasig tendency. Of carbohydrate moiety in elastin, hexoses showed definitely increasing tendency with age, but reverse was true in hexosamines.Higher total cholesterol and also ester cholesterol levels in elastin fraction from aorta were proved in sclerotic portion, comparing with adjacent normal portion.From these results it was highly probable that these changes in elastin during aging and atherosclerosis might offer the conditions, attributable to atherogenesis.

Age related and atherosclerotic changes in aortic elastin.

A point we wish to make is the fact that although there has been a great deal of work on dietary fats and their effects on plasma lipids and the effects of these lipids on the development of fatty plaques in the arterial wall, there has been remarkably little effort put into the attempt to find out what components of the arterial connective tissue are damaged at the site of the fatty or calcified plaques, or which of the normal components of the wall are particularly susceptible to fat deposition or calcification. Other questions to be dealt with are how these components of the wall are normally protected and why the damage is so sharply localized.