Elastin Fraction Research Articles

Vasa vasorum in the tunica media and tunica adventitia of the porcine aorta

Vasa vasorum supply both the tunica adventitia and the tunica media of major arteries with nutrients and oxygen. We estimated the density of von Willebrand factor-positive profiles of vasa vasorum visible in transversal histological sections of 123 tissue samples collected from five anatomical positions in the porcine aortae of growing pigs (n=25). The animals ranged in age from 0 to 230 days. The tunica media of the thoracic aorta had a greater vasa vasorum density, with microvessels penetrating deeper towards the lumen than in the abdominal aorta. The density of vasa vasorum gradually decreased with age in both the media and the adventitia. The relative depth into which the vasa vasorum penetrated and where they branched remained constant during the ageing and growth of the media. The ratio of the tunica media and tunica adventitia thicknesses did not change in the single aortic segments during ageing. The media of older animals received fewer but equally distributed vasa vasorum. A greater density of vasa vasorum in the media was correlated with greater media thickness and a greater elastin fraction (data on elastin taken from another study on the same samples). Immunohistochemical quantification revealed deeper penetration of vasa vasorum towards the adluminal layers of the tunica media that were hitherto reported to be avascular. The complete primary morphometric data, in the form of continuous variables, have been made available as a supplement. Mapping of the vasa vasorum profile density and position has promising illustrative potential for studies on atherosclerotic and inflammatory neovascularization, aortic aneurysms, and drug distribution from arterial stents in experimental porcine models.

Segmental and age differences in the elastin network, collagen, and smooth muscle phenotype in the tunica media of the porcine aorta

The porcine aorta is often used in studies on morphology, pathology, transplantation surgery, vascular and endovascular surgery, and biomechanics of the large arteries. Using quantitative histology and stereology, we estimated the area fraction of elastin, collagen, alpha-smooth muscle actin, vimentin, and desmin within the tunica media in 123 tissue samples collected from five segments (thoracic ascending aorta; aortic arch; thoracic descending aorta; suprarenal abdominal aorta; and infrarenal abdominal aorta) of porcine aortae from growing domestic pigs (n=25), ranging in age from 0 to 230 days. The descending thoracic aorta had the greatest elastin fraction, which decreased proximally toward the aortic arch as well as distally toward the abdominal aorta. Abdominal aortic segments had the highest fraction of actin, desmin, and vimentin positivity and all of these vascular smooth muscle markers were lower in the thoracic aortic segments. No quantitative differences were found when comparing the suprarenal abdominal segments with the infrarenal abdominal segments. The area fraction of actin within the media was comparable in all age groups and it was proportional to the postnatal growth. Thicker aortic segments had more elastin and collagen with fewer contractile cells. The collagen fraction decreased from ascending aorta and aortic arch toward the descending aorta. By revealing the variability of the quantitative composition of the porcine aorta, the results are suitable for planning experiments with the porcine aorta as a model, i.e. power test analyses and estimating the number of samples necessary to achieving a desirable level of precision. The complete primary morphometric data, in the form of continuous variables, are made publicly available for biomechanical modeling of site-dependent distensibility and compliance of the porcine aorta.

Multi-scale biomechanical remodeling in aging and genetic mutant murine mitral valve leaflets: insights into Marfan syndrome.

Mitral valve degeneration is a key component of the pathophysiology of Marfan syndrome. The biomechanical consequences of aging and genetic mutation in mitral valves are poorly understood because of limited tools to study this in mouse models. Our aim was to determine the global biomechanical and local cell-matrix deformation relationships in the aging and Marfan related Fbn1 mutated murine mitral valve. To conduct this investigation, a novel stretching apparatus and gripping method was implemented to directly quantify both global tissue biomechanics and local cellular deformation and matrix fiber realignment in murine mitral valves. Excised mitral valve leaflets from wild-type and Fbn1 mutant mice from 2 weeks to 10 months in age were tested in circumferential orientation under continuous laser optical imaging. Mouse mitral valves stiffen with age, correlating with increases in collagen fraction and matrix fiber alignment. Fbn1 mutation resulted in significantly more compliant valves (modulus 1.34±0.12 vs. 2.51±0.31 MPa, respectively, P<.01) at 4 months, corresponding with an increase in proportion of GAGs and decrease in elastin fraction. Local cellular deformation and fiber alignment change linearly with global tissue stretch, and these slopes become more extreme with aging. In comparison, Fbn1 mutated valves have decoupled cellular deformation and fiber alignment with tissue stretch. Taken together, quantitative understanding of multi-scale murine planar tissue biomechanics is essential for establishing consequences of aging and genetic mutations. Decoupling of local cell-matrix deformation kinematics with global tissue stretch may be an important mechanism of normal and pathological biomechanical remodeling in valves.

Possible involvement of increased glycoxidation and lipid peroxidation of elastin in atherogenesis in haemodialysis patients

Glycoxidation and lipid peroxidation products accumulate in collagen of various tissues in haemodialysis patients with end-stage renal disease (ESRD). The purpose of this study was to test the hypothesis that increased glycoxidation and lipid peroxidation of aortic elastin is implicated in the cardiovascular complications, particularly atherosclerosis, of chronic haemodialysis patients. Post-mortem aortic samples were obtained from 16 deceased subjects, including chronic haemodialysis patients (group 1 n=6, age 64.7+/-11.4 years) and control subjects (group 2 n=10, age 61.1+/-10.4 years). The samples were divided into three vessel wall sites: atherosclerotic intima, lesion-free intima, and media. They were sequentially treated with 0.01 M phosphate-buffered saline, collagenase, and elastase to obtain three fractions, namely soluble (SF), collagen (CF), and elastin (EF) fractions, respectively. Using spectrophotofluorometry, the pentosidine- and malondialdehyde (MDA)-linked fluorescence of these fractions was measured at wavelengths 335/385 and 390/460 (excitation/emission), respectively. Samples from haemodialysis patients (group 1) exhibited a significant increase in both pentosidine- and MDA-linked fluorescence of EF in atherosclerotic intima, lesion-free intima, and media samples, compared with samples from control subjects (group 2). In group 1, the levels of pentosidine- and MDA-linked fluorescence of EF were highest in atherosclerotic intima among the three aortic sites. Interestingly, in both groups, the levels of pentosidine- and MDA-linked fluorescence of EF were significantly higher than those of CF in all aortic sites. There was a strong correlation between the levels of pentosidine- and MDA-linked fluorescence in CF and EF for all aortic sites. In group 1, the pentosidine- and MDA-linked fluorescence levels of EF correlated significantly with the duration of haemodialysis in lesion-free intima and media. Our study provides the first biochemical evidence for a close link between aortic elastin glycoxidation and lipid peroxidation. In addition, we demonstrated high levels of these products in the aortic elastin of haemodialysis patients with ESRD. Our findings support the hypothesis that modification of aortic elastin by glycoxidation and lipid peroxidation may contribute to the development of vascular complications, particularly atherosclerosis, in patients with end-stage renal failure.

The Inhibitory Effect of Cacao Liquor Crude Polyphenols(CLP) on Experimental Arteriosclerosis with Calcification in Rat Soft Tissue.

Cacao liquor crude polyphenols (CLP) contained potent anti-oxidants, such as catechin, and their oligomers. An investigation was conducted on the effects of CLP on experimental arteriosclerosis with calcification in rats, induced by giving vitamin D2 (2.5 × 105 I.U./kg) for the first 4 consecutive days with an atherogenic diet (2% cholesterol, 1.5% cholic acid, 0.1% methylthiouracil). The diet was prepared using a vitamin E deficient diet. CLP inhibited the increase of serum lipid peroxides, the increase of calcium (Ca) in the aorta, the increase of Ca and inorganic phosphorus (P) in the aortic elastin fraction, or in the renal Ca and P of the arteriosclerotic rats. Previously, vitamin E and vitamin K2 showed anti-calcification and radical scavenging activities under the above experimental conditions without vitamin E deficiency. Moreover, CLP reduced lipid peroxides in plasma and in tissue induced by vitamin E deficiency, without maintaining vitamin E levels. It is suggested that the inhibitory effects of CLP on the accumulation of Ca and P in the aorta or kidney were partially due to an anti-oxidant activity.

Quantitative changes of elastin, fibrillin and collagen in abdominal aortic aneurysms

To examine quantitative changes of elastin, fibrillin and collagen in abdominal aortic aneurysms, including ruptured abdominal aortic aneurysms (RAAA), inflammatory abdominal aortic aneurysms (IAAA) and abdominal aortic aneurysms (AAA) were measured. Items measured included the desmosine content of the aorta (desmosine 1) or of the elastin fraction (desmosine 2), fibrillin content in the aorta, hydroxyproline in the aorta, collagen percent and elastin percent, and were compared with control samples from the nonaneurysmal aortic segments. The elastin contents (desmosine 2) in RAAA, IAAA and AAA were significantly lower than those of controls. The content of the desmosine 2 from IAAA and AAA did not show a negative association with Ca. The fibrillin contents of the aorta from RAAA, IAAA and AAA were significantly higher than those of controls. The collagen content in the RAAA aorta was significantly higher than that of controls. There was a correlation of the ratio of fibrillin to elastin components (fibrillin/desmosine 1 or fibrillin/desmosine 2 or fibrillin/elastin%) and the ratio of collagen to elastin components (collagen/desmosine 1 or collagen/desmosine 2 or collagen/elastin%). These results indicated that increasing fibrillin and collagen might be a complementary result of decreasing elastin crosslinks in the aorta. This phenomenon was markedly in RAAA.

Qualitative change in the elastin from the calcified portion of human artery

To examine the qualitative changes of elastin and the aorta related to calcification of human arteries, biochemical properties were measured, including calcium (Ca), phosphorus (P) and magnesium (Mg) contents in the aorta or in the elastin fraction in calcification, cholesterol content in atherosclerosis, desmosine content of cross-link, free thiol contents (free SH/total SH) and hydrophobic properties in the elastin fraction from the calcified portion, adjacent sites and another normal artery. The results from different sites of the calcified abdominal artery are as follows: The contents of Ca, P and Mg in aorta and the elastin fraction from the calcification site were higher than those at other sites. Moreover, Ca in the aorta and elastin fraction correlated positively with P and Mg. The content of cholesterol in the calcification site was the same as at other sites and did not correlate with Ca, P or Mg. The content of desmosine in the calcification site was significantly lower than that in different sites. In addition, its content was negatively associated with Ca and P in the elastin fraction and with the aortic Mg. The content of free thiol in the calcification site was similar to the other sites and correlated negatively with Ca and P in the aorta. The hydrophobicity in the calcification was similar to that at other sites, and was negatively associated with Ca and Mg in the elastin fraction.

Effect of 2-Methylimidazole on the Mechanical, Biochemical, and Morphological Properties of the Rat Aorta by Its Chronic Treatment along Maturation.

To examine whether the retention of imidazole analogues in the organ rich with elastic connective tissue can be of toxicological significance, the effect of 14C labeled 2-methylimidazole (2MI) as a model compound on the mechanical, biochemical, and morphological properties of the rat aorta, together with its irreversible interaction with the tissue macromolecules, was investigated after chronic treatment during maturation (10 and 100 μmol/kg/day for 28 days, from 4 to 8 weeks of age, subcutaneous injection). 1. Aortic extensibility was significantly decreased in 2MI-dose-dependent manner, whereas tensile strength showed an increasing trend. 2. Aortic elastin content was decreased dose-dependently, while collagen content was increased. 3. The low dose of 2MI scarcely altered histological picture of the aortic wall compared to the control group (isotonic saline dosing), but the high dose caused focal disorganization and fragmentation of the medial elastic laminae. Thickness of the aortic media showed a dose-dependent increasing trend. 4. The level of irreversibly bound 2MI-equivalent in elastin fraction was considerably high as compared with that in non-elastin fraction, and was increased dose-dependently. The aortic microautoradiograph showed that [14C]2MI-derived radioactivity occurred in the media, the region rich with elastic fiber. These findings indicate that 2MI affects maturation of the elastic organ materially, and that the effect can be closely linked with the binding of 2MI to elastin. It is possible that the same holds true for some other imidazole-based compounds that are retained in large quantities in the elastic connective tissue.

Properties in elastin of different arteries: cross-links, hydrophobicity and fibronectin in elastin fraction

In order to evaluate the quantitative and qualitative changes of elastin in different arteries, biochemical properties were measured; that is, elastin content, isodesmosine (ID) as cross-links content, free thiol content (free SH/total SH), hydrophobic properties and coexisting fibronectin (FN) content in elastin fraction from different arteries, correlation coefficients of these properties and these their effect with aging were also calculated. The results from different arteries in regard to changes in elastin can be summarized as follows: 1. The basilar artery in the quantitative changes of elastin. There was no correlation of these parameters in the basial artery from the other arteries. 2. The content of ID in the coronary artery was lower than that of the other arteries. The level of ID was negatively associated with aging, FN, elastin and free SH. On the other hand, the level of free SH was positively associated with aging, cholesterol and FN. 3. The contents of free SH, hydrohobicity and FN in elastin from the arch to the thoracic artery were lower than that of the other arteries. Hydrohobicity was negatively correlated with ID, and FN was positively correlated with cholesterol. 4. In the abdominal artery, FN content was higher than that of other arteries. There was a correlation between FN and free SH. However, free SH was inversely associated with elastin, ID and hydrohobicity.

Effects of traditional Chinese medicines (dai-saiko-to, sho-saiko-to and hachimi-zio-gan) on spontaneously diabetic rat (WBN/Kob) with experimentally induced lipid and mineral disorders

To clarify the therapeutic effects of several traditional Chinese medicines to improve disorders of carbohydrate, lipid and mineral metabolism, spontaneously diabetic rats (WBN/Kob) were treated with Vit. D2, 1 x 10(5) I.U./kg b.w./day, for 4 days, and then fed a hyperlipidemic diet containing traditional Chinese medicines for 6 weeks. The following results were obtained: 1) In the diabetic rats, the 3 traditional Chinese medicines further decreased the blood glucose level at 120 min after glucose loading in the glucose tolerance test. 2) The drugs increased the inorganic phosphate in the liver and normalized mineral metabolic disorder. 3) Hachimi-zio-gan decreased the cholesterol content in the kidney, and Sho-saiko-to decreased the cholesterol content in the elastin fraction (elastin-cholesterol) of the kidney. Such experimental results suggest that traditional Chinese medicines may be effective against the pathological conditions of diabetes mellitus that involve disorders of lipid and mineral metabolism.

Change in elastin structure in human aortic connective tissue diseases

Biochemical pathogenesis of the aortic connective tissue diseases (such as, Marfan's syndrome, dissecting aneurysm or aortic aneurysm) was examined by estimating glycoprotein, collagen and elastin contents in the aorta and the intramolecular cross-linking component (isodesmosine) and the intermolecular cross-linking components (cystine, histidinoalanine) in comparison with the control samples obtained from subjects with aortic regurgitation. The elastin content in the aorta and isodesmosine content obtained from the extract of the aortic sample found to be decreased. Ratio of cysteine residues (Cys/Cys-Cys) in the elastin fraction in disease increased. Content of histidinoalanine was found to be decreased. It may be suggested that elastin is maintained in its native nature and shape by intra- and inter-molecular cross-linking bridges, and they are readily denatured by various disease conditions. After elastin was solubilized by elastase, immunoreactive elastin content in those aortic diseases was found to be increased in the human connective tissue. Serum elastase and elastase-like activities tend to increase more than those in the control. These findings may suggest that the change in the structure of elastin would make more susceptible to elastase and other proteolytic enzymes. The reasonable hypothesis may be that molecular defect of fibillin or other constitutional structural glycoproteins produce deficient and functionally incompetent elastin associated microfibrils, and the defect of microfibrils cause to insufficient intra- and inter-molecular cross-links in elastin.

Salt-soluble collagen and elastin in the human aorta and pulmonary artery

Collagen and elastin, the major structural components of blood vessels, have a very low turnover. In disease, this rate may be increased and an elevation of the tissue concentration of the soluble degradation fragments might be anticipated. In this preliminary study the concentration of extractable collagen and elastin in the aorta and pulmonary artery of eight human subjects postmortem was determined. The proportion of pulmonary artery collagen and elastin that was soluble was generally either equal to or greater than that in the abdominal aorta. The fraction of collagen that was salt extractable was larger than the soluble elastin fraction.

Repair of protease-damaged elastin in neonatal rat aortic smooth muscle cell cultures.

The objective of this study was to investigate the elastin repair process in the rat aortic smooth muscle cell culture after proteolytic injury. Although little studied in vivo, elastin repair is thought to occur through a sequential process involving enzymatic removal (debridement) of damaged fibers followed by synthesis of tropoelastin, its subsequent processing, and eventual incorporation into new insoluble elastin. A second repair mechanism of proteolytically damaged elastin in a culture system is reported here. Repair in this system relates directly to restoration of resistance to elastin solubilization by hot alkali. As expected, severe injuries were observed with porcine pancreatic elastase (PPE). Using PPE, only 6% of the elastin, relative to control, was resistant to hot alkali immediately after elastase treatment. 4 wk later, resistance to hot alkali had increased dramatically to a mean of 90%. Repair took longer after injury with 75 micrograms of PPE as compared with 50 micrograms of PPE. The limited elastic fiber proteolysis induced by either human neutrophil elastase or porcine trypsin was repaired in culture within 2 wk. Elastin that had been radiolabeled with [3H]lysine 4-5 wk before injury was converted from a hot NaOH-susceptible to a NaOH-resistant elastin fraction during recovery from PPE injury. At the same time, the frayed elastic fibers that were seen with the electron microscope immediately after PPE treatment were replaced by continuous bands of elastin that resembled those in control cultures. Restoration of NaOH resistance did not require a net increase in total cell layer elastin, suggesting that relatively little new tropoelastin incorporation into the cell layer was required for this type of repair. These results suggested a salvage repair mechanism for proteolytically damaged elastin.

Pharmacological studies of eicosapentaenoic acid ethylester (EPA-E) on high cholesterol diet-fed rabbits

The effects of eicosapentaenoic acid ethylester (EPA-E) at daily doses of 3 and 30 mg/kg (p.o.) on vascular lesions and changes in blood components were investigated in rabbits fed with a 1% cholesterol diet for 12 weeks and partly compared with those given 30 mg/kg/day (p.o.) of ticlopidine. EPA-E at 30 mg/kg significantly improved the reduction in distensibility of isolated thoracic aorta caused by cholesterol diet feeding. Ticlopidine at 30 mg/kg also showed significant but milder improvement. EPA-E at 30 mg/kg, unlike ticlopidine, tended to lower cholesterol content in the thoracic wall and elastin fraction. Although EPA-E did not act on plasma total cholesterol, HDL-cholesterol and triglyceride contents, it tended to mildly reduce platelet aggregability in response to sodium arachidonate and the increased production of TXA2-like activity by platelets. In addition, daily doses of 30 mg/kg EPA-E caused a significant increase in plasma and platelet EPA-E contents without any change in docosahexaenoic acid and arachidonic acid contents. From these results, daily administration of EPA-E to cholesterol diet-fed rabbits caused a remarkable improvement of the reduction in distensibility of isolated thoracic aorta. The mechanism of this improvement by EPA-E appears to depend on the protection of elastic fibers from lipid deposition on the vascular wall.

大動脈エラスチンおよびエラスチン結合脂質

In order to understand the relationship between elastin and atherosclerosis the investigation was undertaken using aorta by measuring amounts of aortic elastin, amino acid analysis of extracted elastin, and elastin binding lipids. Hog aortic elastin was extracted using for several kinds of methods (collagenase, cyanogen bromide (BrCN), NaOH and formic acid methods), and it was considered that the most purified elastin could be obtained by the BrCN method according to the amino acid analysis. The contents of elastin binding lipids showed different levels in each method. In BrCN method the ratio of cholesterol ester and phospholipids were the highest, while the total amounts of lipid levels were the lowest among the four methods. In the analysis of human aorta with atherosclerosis, contents of elastin in the BrCN method increased, and it was considered that the degenerated collagen or pseudoelastin were contaminated in the elastin fraction according to the amino acid analysis. Elastin binding lipid, especially cholesterol ester and phospholipid fraction, increased in the atherosclerotic aorta. These results suggest that the quantitative and qualitative changes of aortic elastin and elastin binding lipids were strongly related to the atherosclerotic development.

Alteration of the extracellular matrix of smooth muscle cells by ascorbate treatment

The protein composition in the extracellular matrix of cultured neonatal rat aortic smooth muscle cells has been monitored over time in culture. The influence of ascorbate on insoluble elastin and collagen has been described. In the absence of ascorbate, the cells accumulate an insoluble elastin component which can account for as much as 50% of the total protein in the extracellular matrix. In the presence of ascorbate, the amount of insoluble collagen increases, while the insoluble elastin content is significantly less. When ascorbate conditions are varied at different times during the culture, the extracellular matrices are altered with respect to collagen and elastin ratios. The decrease in elastin accumulation in the presence of ascorbate may be explained by an overhydroxylation of tropoelastin. Approximately 1 3 of the prolyl residues in the soluble elastin fractions isolated from cultures grown in the presence of ascorbate are hydroxylated. Since the insoluble elastin accumulated in these cultures contain the unique lysine-derived cross-links in amounts comparable to aortic tissue, this culture system proves ideal for studying the influence of extracellular matrix elastin on cell growth and metabolism.

Elastaseの作用の研究(5)

Experimental atherosclerosis was induced in rats by feeding the animal with vit. D2 and atherogenic diet, which was reported previously. In order to examine the mechanism of action of elastase preparation (Eisai, 450 ELU/kg b.w./day), in terms of anti-atherosclerotic effect, calcitonin, an antagonist of vit. D2 in the calcium metabolism, was administered to the experimentally induced athero-sclerotic rats (calcitonin in the form of elcatonin, a derivative of calcitonin, 0.4 MRCU/kg b.w./day, i. m. injection, made by Toyo Jozo Co.).1) In the experimentally induced atheroscle-rosis, serum lipids as well as cholesterol, as the total cholesterol, in the artery and in the heart were increased. Cholesterol levels in the artery and in the heart after the fractionation, mainly present in the elastin fraction, were also increased. For such lipids increasing tendency in the experimental stherosclerosis elastase and calcitonin was tend to decrease their levels.2) In the experimentally induced atheroscle-rosis, the content of the bridge components of lysine origin (isodesmosine, desmosine, merodesmosine, and lysinonorleucine) of the artery was decreased or at least tend to be decreased. Administration of elastase or calcitonin was tend to improve, or normalize such ill tendency.It may be said that elastase and calcitonin have similar mechanism in the anti-atherosclerotic effect, and metabolic regulation of calcium may be partly related.

Variation in proteins of single lesions from the intima of the aorta from a human patient with severe atherosclerosis

A method is presented for grinding and extracting very small samples of tough fibrous tissue from single atherosclerotic lesions of human aortas. Grinding to a powder was easily accomplished while the samples were frozen in liquid nitrogen in a porcelain micromortar. Extractions of the powder were made first in the mortar and then in tapered centrifuge tubes. Salt soluble, dodecyl sulfatemercaptoethanol-urea soluble and hot alkali soluble fractions were obtained, in addition to a hot alkali insoluble elastin residue from each sample. Variation in the protein composition of 23 samples from the lumenal surface of the severely atherosclerotic aorta of a 58-year-old human male were determined. The proteins soluble in the buffered-saline and the dodecyl sulfate—urea soluble polypeptides from each sample were analyzed by dodecyl sulfate—acrylamide gel electrophoresis. The amino acid compositions of the insoluble elastin fractions were determined. The 5 grossly normal intima samples had very similar gel electrophoresis band patterns and amino acid compositions. The 3 samples of necrotic gruel had markedly different dodecyl sulfate—urea soluble polypeptides than either normal or calcified tissue; they also had elastin fractions whose amino acid compositions were unique in that they contained 10 times more serine than elastin fractions from grossly normal intima. The 3 calcified samples had less saline or dodecyl sulfate soluble protein than either grossly normal or necrotic gruel samples, and had very altered elastin fraction compositions characterized by much higher contents of hydroxylysine than grossly normal intima. The elastin fractions of necrotic gruel and calcified tissue samples had little or no isodesmosine or desmosine, suggesting that little of the elastin found in healthy aorta tissue was present.

Hemodynamically-induced increase in soluble collagen in the anastomosed veins of experimental arteriovenous fistulae

External jugular veins that had been subjected to the hemodynamic stresses produced by experimental arteriovenous anastomosis developed 2% increased total protein contents and 17% increased collagen contents. When the stressed veins were homogenized and extracted with saline solutions, statistically significant increases in the saline-soluble proteins and in the saline-soluble collagen (87% and 267%, respectively) were observed. Increased amounts of low molecular weight peptides were found in the extracts. A fraction of these peptides could be degraded by Clostridium collagenase. The saline extract also contained proteins which resembled by their amino-acid composition the acidic structural proteins of the connective tissues. Additonally, in 3 dogs so tested, changes were found in the hydroxylation and glycosylation of lysine from gelatin extracts as well as in the lysine and desmosine contents of the insoluble elastin fractions. This is the first demonstration of a hemodynamically induced increase in the saline solubility of connective tissue proteins in the absence of dietary manipulations.

Texture of elastin gels

Elastin gels which show a filamentous texture have been observed when an elastin fraction was swollen in buffer solutions between pH 5.85 and 8.16. This fraction, previously completely soluble in aqueous solutions, had been obtained during the hydrolysis of bovine ligamentum nuchae and stored for over three years at about 3°C. The diameter of the filaments was about 2 μm and microscopic examination showed that the texture of the gel depended on the protein concentration, pH and the ionic strength of the buffer solution used to cause swelling. Amino acid analysis of this protein fraction showed a slightly higher proportion of lysine and it is considered that the gel is the result of the reformation of a few lysinonorleucine and/or desmosine crosslinkages recreating an insoluble elastin matrix.