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Biomedical subjects

P F Davis

Publications and source records attributed to P F Davis.

At least 37 records · Page 2Linked to original sources
PubMed1991

Dissociation of the tibial component in total knee replacements.

Dissociation of the polyethylene component from its metal backing in total knee arthroplasty is a recognized problem regarding the patella. Two cases of dissociation of the metal-backed tibial component from its polyethylene articulating surface presented symptoms of prosthesis failure: persistent pain, swelling, sensations of instability, and gait difficulty. Investigations ruled out prosthesis malalignment, loosening, and sepsis. Precise diagnosis of dissociation of the tibial component was made by diagnostic arthroscopy.

Adult↗
PubMed1990

The collagenous protein with elastin crosslinks from Descemet's membrane is not related to type VIII collagen.

A collagen-like insoluble protein containing the elastin cross-links (desmosine and isodesmosine) has been isolated from Descemet's membrane. Recently type VIII collagen (endothelial collagen) has been shown to be a major constituent of this membrane. Biochemical studies suggest that these two proteins are unrelated. The cyanogen bromide peptide maps show negligible similarity. Antiserum raised against oxalic acid digests of elastin (alpha-elastin) did not react against an oxalic acid digests of type VIII collagen but did show some reaction against the cross-linked preparation. Immunofluorescent localization has demonstrated the presence of type VIII collagen in trachea but a desmosine cross-linked collagen could not be isolated from this tissue.

Amino Acids↗
PubMed1990

Type VI collagen in experimental atherosclerosis.

Diffuse intercellular immunofluorescence staining of type VI collagen was found in the experimentally thickened vascular wall and in control blood vessel tissues as well, superimposed by more intense staining around basement membranes. While the basement membrane staining disappeared in advanced mural thickenings, the diffusely distributed network of type VI collagen remained.

Aneurysm↗
PubMed1990

Distribution of type VIII collagen in tissues: an immunohistochemical study.

Type VIII collagen was first detected as a secretion product of diverse endothelial cell cultures, including those derived from aorta, arteries and veins. Initial studies of its tissue distribution (using a monoclonal antibody) showed it to be present in a restricted number of tissues and failed to find it in the vasculature. Recently, type VIII collagen was shown (using monospecific polyclonal antibodies) to be a component of large blood vessels with predominant localization in the subendothelium. We applied an improved immunofluorescence technique using these antibodies to define the tissue distribution of type VIII collagen. We show that it is a component of arterioles and venules in muscle, heart, kidney, spleen, liver and lung and is also found in connective tissue layers around hair follicles, around nerve bundles in muscle, in the dura of the optic nerve, in cornea and sclera, and in the perichondrium of cartilaginous tissues. This collagen variant appears to have a wider distribution than originally assumed. It is a macromolecular component of the subendothelium, possibly a constituent of the vascular intimal basement membrane.

Animals↗
PubMed1990

Distribution of type IV collagen, laminin, nidogen and fibronectin in the haemodynamically stressed vascular wall.

Changes in the extracellular matrix of haemodynamically stressed blood vessel walls were studied by immunofluorescence histochemistry in venous-pouch aneurysms fashioned on the site of the common carotid artery of nine sheep. Tissues from the thickened walls of the experimental aneurysms were examined from 11 to 98 months post-operatively for changes in the distribution of the basement membrane components type IV collagen, laminin, nidogen and fibronectin. In the younger aneurysms, there was an increase of the basement membrane components in the thickened area. Very little basement membrane was detected in older aneurysms. Diffuse staining for fibronectin was noted in aneurysms of all ages. Thick deposits of basement membrane material were observed in calcified tissues. The changes in the matrix proteins were similar to alterations occurring during the development of atherosclerosis in human vascular tissue.

Aneurysm↗
PubMed1989

Immunolocalization of type VIII collagen in vascular tissue.

Type VIII collagen was first detected in the culture medium of aortic endothelial cells. Subsequently its synthesis by a number of other cell lines was demonstrated. Its presence in vascular tissue is reported here. It is a component of sheep aorta and carotid artery but could not be demonstrated in the jugular vein. It is principally localized in the subendothelial region but this can only be demonstrated after pretreatment of the tissue with proteases. Thus type VIII collagen is a constituent of blood vessels.

Animals↗
PubMed1989

Reversed-phase liquid chromatography of elastin peptides.

Soluble fragments of elastin are frequently present in biological tissue in small amounts. Because of their hydrophobic character, these peptides are not well resolved by a number of conventional techniques. However, their separation should be possible by reversed-phase chromatography. A wide range of columns, gradients and solvents were evaluated. Two systems are described. One was a C18 liganded silica column eluted isocratically by gravity flow. Some degree of size fractionation was achieved with larger peptides being eluted with methanol and smaller ones with isopropanol. The second system uses a pressurized elution from another C18 ligand column. A concave gradient of trifluoroacetic acid-acetonitrile with a decreasing acetonitrile concentration was optimal. Similar resolution of peptides produced by a variety of digestion methods was obtained with the lower-molecular-mass peptides eluting in the middle of the gradient.

Animals↗
PubMed1989

The biochemical composition of hemodynamically stressed vascular tissue: the insoluble elastin of experimental arteriovenous fistulae.

Arteriovenous fistulae between the external jugular vein and the common carotid artery were surgically fashioned in eight sheep. The altered hemodynamics produced morphological changes similar to those observed in human atherosclerosis. The elastica is a major mural component and undergoes considerable structural variation during lesion development. The most significant biochemical changes in the elastin occur in the experimental vein region. These include a quantitative loss particularly in the midregion of the vein and a decrease in the concentration of up to 20% of the crosslinks (desmosine and isodesmosine). There is an increase in the cholesterol content of the elastin purified from both experimental artery and vein. The bound phospholipid was higher in the experimental artery and in the dilated experimental vein. There was a significant time-dependent loss of elastin in the stressed venous tissue.

Amino Acids↗
PubMed1989

An improved immunofluorescence technique for the histological examination of blood vessel tissue.

Autofluorescence of elastic fibres in blood vessel samples is a common interference with the specific fluorescence of FITC-conjugated antibodies. Counterstaining with eriochrome black T changed the yellow-green colour of elastic fibres to dark red, thus turning a disturbing feature into a useful reference background. A second counterstain, p-phenylenediamine, visualized cell nuclei as an amber colour. To demonstrate the improvement of this staining technique, cryosections from blood vessel samples, derived from control veins, arteries and experimental aneurysms of different ages (15 to 99 month old) in 5 sheep, were stained with antibodies against procollagen III, collagen type IV, laminin, and nidogen. The specific distribution of these connective tissue components could now be related to the location of the elastic fibres and the cells (cell nuclei).

Aneurysm↗
PubMed1989

Urinary excretion of connective tissue protein markers in arterial disease.

In diseases of major arteries there is an increased turnover of connective tissue components. This implies a greater excretion of fragments of collagen and elastin. The changes for each of these may be useful in further delineating the nature of the disease. In a preliminary study, the urine of 10 Marfan's syndrome patients was analyzed. The hydroxyproline (collagen) concentration was up to eight times higher than that of control subjects. The desmosine (elastin) crosslink concentration was either normal or slightly reduced in these patients. The mean of the ratio of hydroxyproline to desmosine was nearly seven times higher in the patients.

Arteries↗
PubMed1989

Scanning electron microscopic study of hemodynamically induced tears in the internal elastic lamina of rabbit arteries.

A scanning electron microscopic investigation of tears in the internal elastic lamina of the afferent artery of experimental arteriovenous fistulae was undertaken to determine their site of initiation and to elucidate their nature. Carotid-jugular arteriovenous fistulae and contralateral common carotid arteriotomies were performed in rabbits sacrificed from two to 63 days post-operatively. Following de-endothelialization, scanning electron microscopy of the internal elastic lamina revealed predominantly transverse straight tears with sharp margins. Even in chronic fistulae the tears retained their sharp margins despite their propagation. No evidence of repair was observed. The tears commenced by rupture of the elastic trabeculae traversing the fenestrae. Enzymatic digestion of the internal elastic lamina did not resemble the hemodynamically induced tears and no evidence of elastolytic enzyme activity was detected. The tears suggest that the abnormally stressed elastic tissue has undergone some structural alteration leading to a reduction in its tensile strength.

Animals↗
PubMed1988

The biochemical composition of haemodynamically stressed vascular tissue. III. The collagen composition of experimental arteriovenous fistulae.

The external jugular vein and the common carotid artery were anastomosed in 8 sheep. Morphological changes similar to those observed in human atherosclerosis are produced particularly in the venous tissue. There is a significant increase in the collagen content of the dilated mid-segment of the experimental vein. Also there is a positive correlation between post-operative age and the amount of collagen, especially in the distal region of the artery and in the proximal and middle regions of the vein. In both the control and experimental veins the amino acid composition of collagen was very similar. However, the arterial preparations did not exhibit the same degree of purity. Most of the collagen was the type I variant (approx. 80% in arteries and 70% in veins). In the sham-operated veins about 30% of the collagen was type III but it was nearer 17% in the control arteries. Whilst experimental and control arteries had similar proportions of type III collagen, there was a 30% reduction in the experimental veins. Although there was no significant correlation between the proportion of any of the genetic types of collagen and the post-operative age of the animals, there was a strong correlation for the increment in type I in all regions of the experimental vein as a function of time.

Amino Acids↗
PubMed1986

The biochemical composition of haemodynamically-stressed vascular tissue. Part 2. The concentrations of protein and connective tissue components in the salt extracts of experimental arteriovenous fistulae.

Arteriovenous fistulae were fashioned between the right external jugular vein and the right common carotid artery in seven experimental sheep, which were then grazed for periods up to 4.25 years. Since the morphological changes in the tissue resemble human atherosclerosis, some of the changes in the extractable protein components in this model were studied. In the experimental venous tissue there was a 1.5-2.5 fold increase in salt-soluble protein. The concentration of extractable collagen was 1.5 times higher in the salt extracts of the experimental veins. The concentration of elastin in the extracts from experimental venous tissue was higher than for the sham-operated veins but the experimental arteries yielded lower levels than the contralateral arteries.

Animals↗
PubMed1985

The biochemical composition of haemodynamically stressed vascular tissue. Part 1. The lipid, calcium and DNA concentrations in experimental arteriovenous fistulae.

Experimental arteriovenous anastomoses were fashioned between the external jugular vein and the common carotid artery in sheep. The altered haemodynamics induced morphological changes, particularly in the venous tissue. Many of these alterations were similar to those seen in human atherosclerosis. Some of the biochemical compositional changes that occurred in such tissues are reported here. Whilst the serum cholesterol level was unaltered during the post-operative period, there was an increase in the free and total cholesterol content of the experimental vein but not of the artery. The serum triglyceride level approximately doubled but the tissue triglyceride rose on only the arterial side of the shunt. There was a decrease in the triglyceride level in the experimental vein. The calcium content showed a slight decrease in both experimental arterial and venous tissue although the drop was not statistically significant. The DNA concentration which was assayed so as to provide a measure of the cell density was about 1.5-2.0 times higher in the arterial tissue.

Animals↗
PubMed1985

Salt soluble cross-linked elastin: formation and composition of fibers.

Cross-linked elastin has been isolated from the salt extract of sheep vascular tissue by means of hydrophobic interaction chromatography on a column of decyl-agarose. Dialysis of the dimethylformamide and sodium dodecyl sulphate column eluates against distilled water produced a precipitate that was fibrous and that resembled insoluble elastin fibers. As judged by amino acid analyses and SDS-polyacrylamide gel electrophoresis, this precipitation resulted in further purification of the soluble cross-linked elastin. Similar chromatography and precipitation of oxalic acid solubilized cross-linked elastin (alpha-elastin) produced identical results.

Amino Acids↗
PubMed1984

Comparison of nonenzymatic glycosylation of arterial and venous collagens.

The extent of nonenzymatic glycosylation of collagen isolated from sheep carotid arteries and jugular veins was compared. It was found that the level of this modification in the arterial collagen was about 2.7 times higher than that in the venous collagen. Arteriovenous fistulae were established between the common carotid artery and external jugular vein on one side only of six sheep. Sham arteriotomy and phlebotomy were performed on the contralateral vessels. Although there was an increase in the concentration of these ketoamine-linked hexoses in all the tissue samples assayed, a difference of between two- and three-fold was maintained between the arterial and venous tissue. The relationship of this finding to the development of vascular complications and to the level of circulating reducing sugar is discussed.

Amines↗