Biomedical subjects

F W Keeley

Publications and source records attributed to F W Keeley.

At least 55 records · Page 3Linked to original sources

PubMed1991

Biochemical study of repair of induced osteochondral defects of the distal portion of the radial carpal bone in horses by use of periosteal autografts.

Periosteal autografts were used for repair of large osteochondral defects in 10 horses aged 2 to 3 years old. In each horse, osteochondral defects measuring 1.0 x 1.0 cm2 were induced bilaterally on the distal articular surface of each radial carpal bone. Control and experimental defects were drilled. Periosteum was harvested from the proximal portion of the tibia and was glued into the principal defects, using a fibrin adhesive. Control defects were glued, but were not grafted. Sixteen weeks after the grafting procedure, the quality of the repair tissue of control and grafted defects was assessed biochemically. Total collagen content and the proportion of type-II collagen were determined. Galactosamine and glucosamine contents also were determined. From these measurements, contents of chondroitin and keratan sulfate and total glycosaminoglycan, and galactosamine-to-glucosamine ratio were calculated. All biochemical variables were compared with those of normal equine articular cartilage taken from the same site in another group of clinically normal horses. Total collagen content was determined on the basis of 4-hydroxyproline content, using a colorimetric method. The proportions of collagen types I and II in the repair tissue were assessed by electrophoresis of their cyanogen bromide-cleaved peptides on sodium dodecyl sulfate slab gels. Peptide ratios were computed and compared with those of standard mixtures of type-I and type-II collagens. Galactosamine and glucosamine contents were determined by use of ion chromatography. In general, the biochemical composition of repair tissue of grafted and nongrafted defects was similar, but clearly differed from that of normal articular cartilage.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Response of aortic elastin synthesis and accumulation to developing hypertension and the inhibitory effect of colchicine on this response.

One of the well-known consequences of established hypertension is an increase in connective tissue proteins in the walls of the large arterial blood vessels. Using renal clip and Dahl salt-sensitive rat models of systemic hypertension, we investigated the effect of developing hypertension on elastin production and accumulation in rat aorta. In both models of hypertension, increased accumulation of arterial elastin appeared coincidentally with, and was proportional to, elevation of blood pressure. In spite of large increases in absolute amounts of elastin, the proportion of elastin present in the vessel wall remained essentially constant from the earliest stage of the response. These changes in elastin synthesis and accumulation took place in the absence of evidence of cell proliferation. Treatment of Dahl rats with colchicine during development of hypertension affected blood pressure rise only marginally but abolished the vascular hypertrophic response. Our results suggest that the response of elastin production to increased blood pressure is rapid and sensitive, and that the stimulus for increased synthesis is an increase in wall stress. The striking effect of colchicine may indicate a role of elements of the cytoskeleton in the perception of stress by the vascular smooth muscle cells or in the transduction of that stress into increased production of connective tissue proteins.

Animals↗

PubMed1990

Pattern of accumulation of elastin and the level of mRNA for elastin in aortic tissue of growing chickens.

Synthesis and accumulation of elastin in many elastic tissues begins in the last third of fetal development, reaches a maximum shortly after birth, and then declines rapidly. For the aorta of the chick and the pig and the ligamentum nuchae and lung of the sheep, it has been shown that increased levels of elastin production with fetal development are correlated with increased levels of elastin mRNA in the tissue, measured both by cell-free translation and by hybridization to cDNA probes. In this study we examine the relationship between insoluble elastin accumulation and message levels for tropoelastin in aortic tissue of chickens during posthatching development and growth. Whether evaluated by cell-free translation or by dot blot hybridization, steady state levels of tropoelastin message increase to a maximum at 2 weeks after hatching, and then fall rapidly with further development and growth. This pattern correlates well with production of insoluble elastin by the aorta, determined either by direct measurements of synthesis or by rate of accumulation of insoluble elastin. The data indicate that the major site of regulation of elastin production is pretranslational throughout the entire period of development and growth of the chicken aorta.

Animals↗

PubMed1990

Type IV Ehlers-Danlos syndrome presenting as sudden infant death.

A previously healthy 5-month-old female infant presented with sudden death due to spontaneous subarachnoid hemorrhage associated with minor multifocal visceral hemorrhages. The clinical diagnosis had been sudden infant death syndrome. Although the family history was noncontributory and other features of type IV Ehlers-Danlos syndrome (EDS) were absent, the pattern of hemorrhage was consistent with this type of connective tissue disorder. The diagnosis was confirmed after postmortem analysis of skin and aorta showed less than 5% type III collagen (normal greater than 15%). Extensive literature review failed to find any other reported cases of sudden death in infancy due to intracranial hemorrhage in patients with previously unsuspected type IV EDS. The authors suggest that collagen analysis should be performed in cases of unexplained multifocal spontaneous hemorrhage in infancy so that this rare diagnosis will not be missed.

Collagen↗

PubMed1990

Alterations in elastin and collagen related to the mechanism of progressive pulmonary venous obstruction in a piglet model. A hemodynamic, ultrastructural, and biochemical study.

We created an animal model to understand better the pathogenesis and underlying mechanism of progressive central pulmonary venous (PV) obstruction, a condition not amenable to current therapy. Twenty piglets underwent banding of their PVs, 18 had a sham operation, and 12 were nonoperated controls. After 1, 3, and 6 weeks hemodynamic data were obtained and correlated with ventricular weights, PV and pulmonary artery (PA) distensibilities (at 1 week), morphometric structural and ultrastructural analyses, and biochemical assessment of elastin determined gravimetrically (and by desmosine level at 1 week), collagen, and elastase activity. At 1 week, PV banding was associated with increased PV compliance (p less than 0.05). At 3 weeks, an increased PA pressure (Ppa) (p less than 0.05) was observed, unaccompanied by a rise in PV pressure (Pcw). In the PV, however, there was breakdown of the internal elastic lamina with apparent migration of smooth muscle cells from media to subendothelium. At 6 weeks, a rise in Pcw (p less than 0.01), a further rise in Ppa (p less than 0.01), and right ventricular hypertrophy (p less than 0.005) were observed. We also observed mild PV intimal thickening (p less than 0.01), complete degradation of elastic laminae (p less than 0.05), and an increase in collagen assessed morphometrically (p less than 0.01). The banding procedure resulted in an overall increase in PV elastin synthesis and in the proportion of elastin determined gravimetrically (p less than 0.05 for both) but not by desmosine level, suggesting the possibility of poor cross-linking of elastin, which might account for the early increased distensibility of the PV. However, our assay could not detect an increase in elastase activity associated with either the increased distensibility or the ultrastructural changes of elastin degradation. The increased Ppa was not associated with significant PA biochemical or structural changes. We speculate that in response to distal venous obstruction, early remodeling of the PVs increases distensibility, protecting the lung from venous congestion and blunting a rise in Pcw. PA hypertension precedes the rise in Pcw, likely because of reflex vasoconstriction. The subsequent modest rise in Pcw is already associated with extensive fibrosis of the PV, suggesting a reason for unsuccessful current therapy and a need for consideration of earlier assessment and intervention.

Animals↗

PubMed1990

Factors affecting the production of insoluble elastin in aortic organ cultures.

Aortic organ and cell culture systems have made important contributions to the understanding of the synthesis and accumulation of elastin in arterial tissues. However, methods used to quantitate production of elastin have been diverse, and evaluations of different culture conditions have not been made. In this study we describe a convenient and reproducible organ culture system for the assay of insoluble elastin synthesis. Under optimum incubation conditions, insoluble elastin is produced in organ culture at rates approximating in vivo accumulation rates. The assay is stable under a wide variety of incubation conditions, although elastin production is sensitively inhibited by acidification of the incubation medium. Alterations in intracellular calcium concentration had little effect on elastin production. In contrast, manipulations of sodium ion concentration, including treatment with ouabain or monensin, depressed elastin production. Except at high doses, pharmacological or humoral agents, including non-steroidal anti-inflammatory agents, alpha and beta adrenergic agonists, cyclic nucleotides, theophylline or aminophylline, and histamine, generally had only small effects on elastin production in this organ culture system.

Animals↗

PubMed1990

Biochemical analysis of normal articular cartilage in horses.

Articular cartilage specimens from the distal articular surface of 32 radiocarpal bones from 24 2- to 5-year-old horses were analyzed. The total collagen content was determined on the basis of the 4-hydroxyproline content, using a colorimetric method. A method for estimating the proportions of types-I and -II collagen by measuring spectrophotometric densities of specific cyanogen bromide peptide bands from mixtures of types-I and -II collagen on sodium dodecyl sulfate-polyacrylamide gels was used. The cyanogen bromide peptides representative of each collagen types-I and -II were identified. The peptide ratios were then computed for each of several standards of type-I and -II mixtures. A standard curve was derived from the correlation between these ratios and the corresponding proportions of type-II collagen in standard mixtures. Galactosamine and glucosamine content (hexosamines) were measured by ion chromatography. The galactosamine-to-glucosamine ratio, chondroitin sulfate and keratan sulfate values, and total glycosaminoglycan content were derived from the measured hexosamine content. The total collagen content averaged 556 mg/g (55.6 mg/100 mg) of tissue (dry weight, [dw]). Type-II collagen was the major collagen type in normal articular cartilage specimens. The ratio of the area under the alpha 1 (II)CB10 peak to the area under the alpha 1 (I)CB 7,8 + alpha 1 (II)CB11 peak was a second-order polynomial function of the proportion of type-II collagen in the specimens. The mean galactosamine and glucosamine content were 20.6 mg/g and 7.9 mg/g (dw), respectively. The mean galactosamine-to-glucosamine ratio was 3.74 +/- 0.62.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1989

Adaptations of carotid arteries of young and mature rabbits to reduced carotid blood flow.

Adaptive responses of rabbit common carotid arteries were examined after 70-80% reductions in blood flow produced by ipsilateral external carotid artery ligation. These flow reductions elicited growth inhibition of arterial wall tissue in immature rabbits. Specifically, experimental carotid arteries exhibited DNA levels significantly lower, by 35%, than contralateral control arteries 1 mo after external carotid ligation. Lower elastin contents (38%) were also observed, although collagen contents were not affected. These changes were accompanied by a relative reduction in wall mass of 30% and a 31% reduction in internal diameter. Adult rabbits exhibited decreased internal diameter (21%) after flow reduction, but no significant change in vessel mass or wall constituents was observed. Early diameter reductions were vasoconstrictor in origin, but the vessel functioned as a smaller artery rather than as a partially constricted normal vessel after 1 mo, i.e., both maximally dilated and maximally constricted diameters were reduced. A reduction in endothelial cell number was detected for the narrowed vessels. Manipulation of local flow conditions indicated that the vessels responded to changes in mean blood flow rather than the pulsatile component of flow.

Adaptation, Biological↗

PubMed1988

Altered elastin and collagen synthesis associated with progressive pulmonary hypertension induced by monocrotaline. A biochemical and ultrastructural study.

Changes in elastin and collagen synthesis in the pulmonary artery wall, assessed both biochemically and ultrastructurally, were related to the development of progressive pulmonary hypertension induced by the toxin monocrotaline. Male Sprague-Dawley rats (200 to 225 gm) were injected subcutaneously in the hind flank with either monocrotaline (60 mg/kg) or an equivalent volume of saline and studied 8, 16 and 28 days later. At each time point, the right ventricle and left ventricle with septum were separated and weighed to follow the development of right ventricular hypertrophy. The hilar pulmonary artery was assessed by light microscopy for medial hypertrophy and by electron microscopy for changes in the endothelium, subendothelium and media. The mainstem pulmonary artery was used to determine synthesis of elastin and collagen by in vitro incorporation of [14C]proline into nonelastin, [14C]hydroxyproline into collagen, and [3H]valine into cyanogen bromide-insoluble elastin. In addition, total content of insoluble elastin was determined by weight of the residue after cyanogen bromide digestion and of collagen by total hydroxyproline content in sodium dodecyl sulfate and cyanogen bromide extracts. Eight days after monocrotaline injection, there was pulmonary artery endothelial swelling and a significant decrease in the number of myoendothelial junctions (p less than 0.05) associated with a decreased proportion of amorphous elastin in the media (p less than 0.01). Sixteen days after monocrotaline injection, a decrease in the proportion of elastin in the media was still evident (p less than 0.01) despite an apparent increase in insoluble elastin synthesis. Moreover, the amorphous elastin was distributed preferentially in small islands rather than in laminae (p less than 0.05). Twenty-eight days after monocrotaline injection, medial and right ventricular hypertrophy had developed (p less than 0.05 and p less than 0.01, respectively). At the same time, there was a striking increase in both insoluble elastin synthesis and total insoluble elastin content (p less than 0.01 for both) and an increase in collagen synthesis and total collagen content (p less than 0.05 for both). In addition, the ratio of insoluble elastin synthesis to collagen synthesis was greater than in controls (p less than 0.01), whereas the ratio of total insoluble elastin to total collagen did not change. On ultrastructural analysis, the proportion of amorphous elastin in the vessel wall relative to other elements remained low (p less than 0.01) and was distributed throughout the media as increased numbers of small islands (p less than 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

Durability of regenerated articular cartilage produced by free autogenous periosteal grafts in major full-thickness defects in joint surfaces under the influence of continuous passive motion. A follow-up report at one year.

An autogenous graft of tibial periosteum was sutured (with its cambium layer facing into the joint) to the base of a five by ten-millimeter full-thickness defect in the patellar groove of each of forty-five adolescent rabbits. The rabbits were randomly treated postoperatively by either four weeks of immobilization in a cast, intermittent active motion in a cage, or two weeks of continuous passive motion. One year postoperatively, the regenerated tissue from each rabbit was analyzed macroscopically, histologically, histochemically, and biochemically. Gross degenerative changes were seen in 57 per cent of the rabbits that had been immobilized in a cast, in 73 per cent of the rabbits that had been allowed intermittent active motion, and in 22 per cent of the rabbits that had been subjected to continuous passive motion (p less than 0.05). Out of a possible score of 7.0 points for the nature of the regenerated tissue, the scores for the three groups were: immobilization in a cast, 4.1 points; intermittent active motion, 4.0 points; and continuous passive motion, 5.9 points (p greater than 0.05). Out of a possible perfect combined score of 10.0 points for the structural characteristics of the regenerated tissue, the cast-immobilization group scored 3.8 points; the intermittent active-motion group, 2.5 points; and the continuous passive-motion group, 6.4 points (p less than 0.001). The total scores for freedom from cellular changes of degeneration, a perfect score being 5.0 points, were: immobilization in a cast, 2.4 points; intermittent active motion, 2.3 points; and continuous passive motion, 3.9 points (p less than 0.01). Degenerative changes in the adjacent cartilage, which were noted in 42 and 46 per cent of the knees in the immobilization and intermittent active-motion groups, respectively, were not found in the knees that had been subjected to continuous passive motion (p less than 0.05). The total indices, which were derived by combining the scores for all categories (maximum, 24.0 points), revealed that the index for the continuous passive-motion group was significantly better than the index for either of the other two groups: immobilization in a cast, 12.9 points; intermittent active motion, 11.2 points; and continuous passive motion, 19.2 points (p less than 0.0005).(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1988

An inherited connective tissue disease in the horse.

The hyperextensible, fragile skin of two related horses was compared with the skin of eight normal horses. Skin sections were examined by light microscopy and transmission electron microscopy. The deep dermal layer of the dorsal abdomen was much thinner in the affected horses, and contained bundles of collagen fibers which were more loosely packed. Within individual fibers, the fibrils were frequently curved and nonparallel rather than straight and parallel. Both of the affected animals had a greater range of fibril diameters than a normal horse. They had some unusually thick fibrils with very irregular outlines in cross-sections, not observed in the normal animal. Other skin samples were subjected to acetic acid extraction, pepsin digestion, amino acid analysis and polyacrylamide gel electrophoresis. In the skin of the two affected horses, the proportion of total extracted collagen which was acid-soluble was twice as high as in two normal horses. Collagen types I and III were present in similar proportions in normal and affected horses, and the collagen chains were of normal molecular weights. The disorder resembles the group described by Minor (Minor RR: Am J Pathol 98: 226, 1980) as 'dominant collagen packing defect I' which has been reported in dogs, mink, and cats, and which shares features with Ehlers Danlos Syndrome I, II, and III in man. The pedigree data available for these horses suggest an autosomal recessive mutation, but are also consistent with autosomal dominant inheritance.

Animals↗

PubMed1987

Age differences in the effect of hydrocortisone on the synthesis of insoluble elastin in aortic tissue of growing chicks.

Glucocorticoids have been shown by others to increase the synthesis of elastin both in aortic tissue of embryo chicks and in cells derived from fetal ligamentum nuchae. This report describes the effects of hydrocortisone on the production of elastin in aortic tissue of developing chick embryos and chicks. While the effect of hydrocortisone on elastin synthesis is stimulatory in the 14 day chick embryo and the day-old chick, the same dose of this glucocorticoid has no effect on elastin production in the 7 day old chick and significantly inhibits synthesis of elastin in the 14 day old chick. These age-related alterations in elastin production in response to hydrocortisone cannot be attributed to an effect of the steroid on the pool size of the radioactively labelled amino acid used to measure elastin synthesis.

Aging↗

PubMed1986

The effect of developing hypertension on the synthesis and accumulation of elastin in the aorta of the rat.

This report describes an investigation of the effects of developing hypertension on the synthesis and accumulation of insoluble elastin in the thoracic aorta of young rats. Uninephrectomized male rats were made hypertensive by administration of deoxycorticosterone acetate and addition of 1% NaCl to their drinking water. Divergence of systolic blood pressures between treated and control animals and hypertrophy of the vessel began after about 2 weeks of treatment. Coincident with the appearance of hypertrophy, there was an increased accumulation of insoluble elastin in the aorta and a large increase in the capacity of the aortic tissue to synthesize elastin. However, in spite of continued increases in blood pressure and vessel hypertrophy, this effect on elastin synthesis and accumulation was transient. The results of this study suggest that synthesis of elastin in aortic tissue of young rats is highly sensitive to alterations in blood pressure.

Animals↗

PubMed1986

The chondrogenic potential of free autogenous periosteal grafts for biological resurfacing of major full-thickness defects in joint surfaces under the influence of continuous passive motion. An experimental investigation in the rabbit.

A rectangular graft of autogenous tibial periosteum was sutured (with its cambium layer facing into the joint) onto the base of a five by ten-millimeter full-thickness defect in the patellar groove of each of 143 adolescent and adult rabbits. The rabbits were managed postoperatively by either immobilization, intermittent active motion, continuous passive motion for two weeks, or continuous passive motion for four weeks. When the animals were killed four weeks postoperatively, the contour of the patellar groove had been restored in all of the rabbits in the group that had had four weeks of continuous passive motion, and the newly formed tissue in all of the defects in this group had the gross, histological, and histochemical appearance of smooth, intact hyaline articular cartilage. Histologically, the nature of the tissue that had formed, as well as its surface regularity, structural integrity, and bonding to the adjacent cartilage, were significantly better in the group that had had four weeks of continuous passive motion than in any of the other groups. The results were significantly worse when the orientation of the periosteal graft was reversed (that is, when it had been sutured into the defect with the cambium layer of the graft facing the subchondral bone rather than into the joint) or when no periosteal graft was used. Biochemical analyses revealed that, in the group that had had four weeks of continuous passive motion, the total hexosamine content, the levels of chondroitin sulphate and keratan sulphate, and the ratio of galactosamine to glucosamine were all comparable with the values for normal articular cartilage. In contrast, in the groups that were treated by immobilization, intermittent active motion, or two weeks of continuous passive motion, as well as in the adult rabbits, the content of the first three of these substances was significantly less than normal. In the groups that were treated by immobilization, intermittent active motion, or two weeks of continuous passive motion, 32 to 47 per cent of the total collagen was type II, while in the group that had had four weeks of continuous passive motion, 93 per cent of the total collagen was type II. These results demonstrate that, under the influence of continuous passive motion, free autogenous periosteal grafts can repair a large full-thickness defect in a joint surface by producing tissue that resembles articular cartilage grossly, histologically, and biochemically, and that contains predominantly type-II collagen.

Animals↗

PubMed1985

A method for quantitative analysis of ratios of types I and II collagen in small samples of articular cartilage.

Currently available methods for quantitative analysis of type II collagen in studies of articular cartilage repair either require much larger samples than are available or are inaccurate and unreliable. A method of determining the percentage of type II collagen in small samples of articular cartilage (100 to 200 micrograms) by measuring the spectrophotometric densities of specific cyanogen bromide peptide bands from mixtures of types I and II collagen on sodium dodecyl sulfate-polyacrylamide gels has been developed and found to be accurate and very reliable. The ratio of the area under the alpha 1(II)CB10 peak to the area under the alpha 1(I)CB7,8 + alpha 1(II)CB11 peak was function of the proportion of type II collagen in the sample. Since the ratio was independent of the quantity of sample loaded onto the gel, it was not affected by moderate losses of sample. This method should therefore be useful in the fields of collagen research and particularly valuable to those investigating the repair and regeneration of articular cartilage.

Animals↗

PubMed1985

The effect of induced atherosclerosis on the synthesis of elastin in chick aortic tissue.

Atherosclerosis was induced in growing chickens by the administration of a diet containing elevated levels of cholesterol and vitamin D3. The effect of this diet on the accumulation of insoluble elastin and the synthesis of soluble and insoluble elastin in the thoracic aortas of these animals was measured. Although the diet resulted in significant increases in levels of cholesterol, 25-OH vitamin D3 and calcium in plasma, increased levels of cholesterol and calcium in aortic tissue, and histological evidence of aortic lipid deposition, there were no detectable differences between experimental and control animals in either the rate or the time course of accumulation of total insoluble elastin in the thoracic aorta, or in the rate and time course of synthesis of soluble and insoluble elastin. These data suggest that, at least in this model, any effect of atherosclerosis on aortic elastin production must be either small or so localized as to be not measurable by the methods used.

Animals↗

PubMed1985

Identification and quantitation of alpha 2-HS-glycoprotein in the mineralized matrix of calcified plaques of atherosclerotic human aorta.

alpha 2-HS-glycoprotein (HSGP) is a minor constituent of plasma with negative acute-phase reactant properties. HSGP has been shown previously to accumulate in the mineralized matrix of bone and dentin to concentrations substantially higher than those present in plasma. In addition, HSGP has also been found in experimentally induced dermal calcifications in animals. Here we show that HSGP is occluded in the organic matrix of pathological calcifications of atherosclerotic human aortic tissue in a concentration approximately 7-fold greater than that found in plasma.

Aorta↗

PubMed1984

Cartilage in the Atlantic hagfish, Myxine glutinosa.

Light and electron microscopic observations and biochemical analysis of the lingual cartilages from the Atlantic hagfish, Myxine glutinosa, reveal two different types of cartilage, designated types 1 and 2, respectively. The anterior and medial lingual are type 1, while the posterior lingual cartilage is type 2. Chondrocytes in type 1 cartilage are similar to those found in other vertebrate cartilages. The presence within the Golgi elements of material that resembles a component of the extracellular matrix suggests the involvement of active chondrocytes in the synthesis of the matrix. The matrix of the type 1 cartilage contains fibrils arranged to form concentric lamellae in the territorial matrix and irregularly arranged, branched fibrils in the interterritorial matrix. Biochemical analysis of the type 1 cartilage reveals that it is composed primarily of a cyanogen bromide (CNBr)-insoluble protein of unique composition that we have termed " myxinin ." Myxinin appears to be similar, but not identical, to lamprin . Type 2 cartilage bears no resemblance to any other known vertebrate cartilage. The principal cells are hypertrophied and are characterized by masses of cytoplasmic filaments. The appearance of the organelles in smaller nest cells suggests that nest cells are active in the production of some of the matrix, which consists primarily of collagen. Microfibrils and a basal lamina-like material are also present. Biochemical analysis of the type 2 cartilage reveals that the CNBr-insoluble material is different from myxinin . Comparisons of lamprey and hagfish cartilages prompt the concept that these two agnathans probably followed long-independent evolutionary histories.

Animals↗