PubMed Health⌕ Search

Biomedical subjects

M C Burleigh

Publications and source records attributed to M C Burleigh.

10 recordsLinked to original sources
PubMed1992

Collagen types I and III, collagen content, GAGs and mechanical strength of human atherosclerotic plaque caps: span-wise variations.

Measurements of total collagen, of the ratio of collagen types III/(I+III) and of sulphated glycosaminoglycans (GAGs) were compared with mechanical strength for individual ulcerated and non-ulcerated human aortic plaque caps and with intima adjacent to the plaques. The distributions of the collagen type ratio were similar for both ulcerated and non-ulcerated plaque caps but different from that of the adjacent intima. The proportions of different collagen types were not related to fracture stress and are thus unlikely to affect the potential to ulcerate. The distributions of the sulphated GAGs showed lower amounts for the plaque caps compared with the nearby intima, with the centres of ulcerated plaque caps having the lowest values. Total collagen had higher values in the peripheries of plaque caps compared with the nearby intima, but was distinctly lower in the centres of ulcerated plaque caps. Plaque caps appeared to require a higher collagen content than adjacent intima to support a given level of mechanical strength, suggesting that while collagen production had occurred in the plaque caps it was not as efficiently organized to resist fracture as a similar amount of collagen in the adjacent intima. Ulcerated plaque caps are notable for much larger transverse (centre vs. periphery) gradients of connective tissue constituents than for non-ulcerated plaque caps. The development of these transverse gradients may be a critical aspect in determining the propensity of a plaque to ulcerate.

Aortic Diseases↗
PubMed1987

Biochemical characterization of individual normal, floppy and rheumatic human mitral valves.

Human mitral valves (32 floppy and 17 rheumatic) obtained at surgery were analysed and compared with 35 normal (autopsy) valves. Total amounts of collagen, proteoglycan and elastin were increased approx. 3-fold in floppy and rheumatic valves. The water content of rheumatic cusps was lower than normal. The most significant changes in floppy valves were the 59% increase in mean value of the proteoglycan content, a large increase in the ease of extractability of proteoglycans from 26.7 to 57.2% of the total and a 62% increase in mean value of the elastin content in the anterior cusps. Normal human mitral valve cusps contained a mean proportion of 29.3 (and chordae 26.6) type III collagen (as % of total types III + I collagen), the values increasing significantly to 33.2 and 36.3% respectively in chronic rheumatic disease. The ratio observed in floppy valves depended on the extent of secondary surface fibrosis, which could be demonstrated histologically; in valve cusps with considerable secondary fibrosis, the percentage of type III increased significantly (to 34.4%), whereas it decreased significantly (to 25.2%) when fibrosis was negligible. It is concluded that the ratio of collagen types in floppy valves reflects the extent of secondary fibrosis rather than the pathogenesis of the disrupted collagen in the central core of the valve.

Amino Acids↗
PubMed1977

The degradation of articular collagen by neutrophil proteinases.

The action of the serine proteinase (EC 3.4.21--)of human neutrophil leucocytes, elastase and cathepsin G, on cartilage and tendon was investigated. With cartilage, both enzymes first degraded the proteoglycan, then solubilized collagen by an attack on the terminal peptides, destroying the inter- and intramolecular cross-links. There was little degradation of the helical region of the type II collagen. Elastase also solubilized type I collagen from tendon, though this was less susceptible than cartilage collagen, and attacked the terminal peptides and perhaps the helical region of type I skin collagen in solution. Cathepsin G had little or no effect on type I collagen of skin or tendon. Since massive infiltration of joint tissues by neutrophil leucocytes is a prominent feature of inflammatory joint disease, it may well be that elastase and cathepsin G make a significant contribution to the tissue damage that occurs.

Achilles Tendon↗
PubMed1975

Collagenase and other proteinases in the cornea of the retinol-deficient rat.

1. Enzymes that may contribute to liquefaction of the cornea in retinol-deficient animals and in man have been studied using rat cornea. The established technique of culturing tissue fragments and determining the activity of collagenase (EC 3-4-24-3) and other enzymes in the medium after different periods of culture was used. 2. A collagenolytic system was detected in the media from cultures of rat corneas. This system probably consists of at least two enzymes, a collagenase and a neutral proteinase. 3. Both proteolytic and specific collagenolytic activity were greater in media from retinol-deficient rat corneas. The hydroxyproline level increased in parallel with the increase in enzyme activity. 4. In the final stages of retinol deficiency the cornea is invaded by granulocytes and other cells of the blood and we suggest that destruction of cornea collagen may be due largely to the activity of the enzymes from these cells.

Animals↗
PubMed1974

A specific collagenase from rabbit fibroblasts in monolayer culture.

1. Explants of rabbit skin and synovium in tissue culture secreted a specific collagenase into their culture media. Primary cultures of fibroblast-like cells, which were obtained from these tissues and maintained in culture for up to 14 subculture passages, also secreted high activities of a specific collagenase into serum-free culture medium. Secretion of enzyme activity from the cell monolayer was at constant rate for over 100h and continued for up to 8 days in serum-free culture medium. The enzymic activity released was proportional to the number of cells in the monolayer. 2. The fibroblast collagenase was maximally active between pH7 and 8. At 24 degrees C the collagenase decreased the viscosity of collagen in solution by 60%. The collagen molecule was cleaved into three-quarters and one-quarter length fragments as demonstrated by electron microscopy of segment-long-spacing crystallites (measured as native collagen molecules aligned with N-termini together along the long axis), and by polyacrylamide-gel electrophoresis of the denatured products. The collagenase hydrolysed insoluble collagen, reconstituted collagen fibrils and gelatin, but had no effect on haemoglobin or Pz-Pro-Leu-Gly-Pro-d-Arg (where Pz=4-phenylazobenzyloxycarbonyl). 3. The fibroblast collagenase was partially purified by gel filtration and the molecular weight was estimated as 38000. The activity of the partially purified enzyme was stimulated by 4-chloromercuribenzoate, inhibited by EDTA, cysteine, 1,10-phenanthroline and serum, but was unaffected by di-isopropyl phosphorofluoridate, Tos-LysCH(2)Cl and pepstatin. 4. Long-term cell cultures originating from rabbit skin or synovium from rabbits with experimentally induced arthritis also secreted specific collagenase. Human fibroblasts released only very small amounts of collagenase.

Animals↗
PubMed1974

Cathepsin B1. A lysosomal enzyme that degrades native collagen.

1. Experiments were made to determine whether the purified lysosomal proteinases, cathepsins B1 and D, degrade acid-soluble collagen in solution, reconstituted collagen fibrils, insoluble collagen or gelatin. 2. At acid pH values cathepsin B1 released (14)C-labelled peptides from collagen fibrils reconstituted at neutral pH from soluble collagen. The purified enzyme required activation by cysteine and EDTA and was inhibited by 4-chloromercuribenzoate, by the chloromethyl ketones derived from tosyl-lysine and acetyltetra-alanine and by human alpha(2)-macroglobulin. 3. Cathepsin B1 degraded collagen in solution, the pH optimum being pH4.5-5.0. The initial action was cleavage of the non-helical region containing the cross-link; this was seen as a decrease in viscosity with no change in optical rotation. The enzyme also attacked the helical region of collagen by a mechanism different from that of mammalian neutral collagenase. No discrete intermediate products of a specific size were observed in segment-long-spacing crystalloids (measured as native collagen molecules aligned with N-termini together along the long axis) or as separate peaks on gel filtration chromatography. This suggests that once an alpha-chain was attacked it was rapidly degraded to low-molecular-weight peptides. 4. Cathepsin B1 degraded insoluble collagen with a pH optimum below 4; this value is lower than that found for the soluble substrate, and a possible explanation is given. 5. The lysosomal carboxyl proteinase, cathepsin D, had no action on collagen or gelatin at pH3.0. Neither cathepsin B1 nor D cleaved Pz-Pro-Leu-Gly-Pro-d-Arg. 6. Cathepsin B1 activity was shown to be essential for the degradation of collagen by lysosomal extracts. 7. Cathepsin B1 may provide an alternative route for collagen breakdown in physiological and pathological situations.

Carbon Radioisotopes↗
PubMed1974

The interaction of alpha2-macroglobulin with proteinases. Binding and inhibition of mammalian collagenases and other metal proteinases.

1. Experiments were performed to determine whether the specific collagenases and other metal proteinases are bound and inhibited by alpha(2)-macroglobulin, as are endopeptidases of other classes. 2. A specific collagenase from rabbit synovial cells was inhibited by human serum. The inhibition could be attributed entirely to alpha(2)-macroglobulin; alpha(1)-trypsin inhibitor was not inhibitory. alpha(2)-Macroglobulin presaturated with trypsin or cathepsin B1 did not inhibit collagenase, and pretreatment of alpha(2)-macroglobulin with collagenase prevented subsequent reaction with trypsin. The binding of collagenase by alpha(2)-macroglobulin was not reversible in gel chromatography. 3. The collagenolytic activity of several rheumatoid synovial fluids was completely inhibited by incubation of the fluids with alpha(2)-macroglobulin. 4. The collagenase of human polymorphonuclear-leucocyte granules showed time-dependent inhibition by alpha(2)-macroglobulin. 5. The collagenolytic metal proteinase of Crotalus atrox venom was inhibited by alpha(2)-macroglobulin. 6. The collagenase of Clostridium histolyticum was bound by alpha(2)-macroglobulin, and inhibited more strongly with respect to collagen than with respect to a peptide substrate. 7. Thermolysin, the metal proteinase of Bacillus thermoproteolyticus, was bound and inhibited by alpha(2)-macroglobulin. 8. It was shown by polyacrylamidegel electrophoresis of reduced alpha(2)-macroglobulin in the presence of sodium dodecyl sulphate that synovial-cell collagenase, clostridial collagenase and thermolysin cleave the quarter subunit of alpha(2)-macroglobulin near its mid-point, as do serine proteinases. 9. The results are discussed in relation to previous work, and it is concluded that the characteristics of interaction of the metal proteinases with alpha(2)-macroglobulin are the same as those of other proteinases.

Animals↗