Biomedical subjects

A J Bailey

Publications and source records attributed to A J Bailey.

At least 19 recordsLinked to original sources

PubMed1997

Chemistry of collagen cross-linking: biochemical changes in collagen during the partial mineralization of turkey leg tendon.

With age, the proximal sections of turkey leg tendons become calcified, and this phenomenon has led to their use as a model for collagen mineralization. Mineralizing turkey leg tendon was used in this study to characterize further the composition and cross-linking of collagen in calcified tissues. The cross-link profiles of mineralizing collagen are significantly different from those of other collagenous matrices with characteristically low amounts of hydroxylysyl-pyridinoline and the presence of lysyl-pyridinoline and pyrrolic cross-links. However, the presence of the immature cross-link precursors previously reported in calcifying tissues was not supported in the present study, and was found to be due to the decalcification procedure using EDTA. Analysis of tendons from young birds demonstrated differences in the cross-link profile which indicated a higher level of hydroxylation of specific triple-helical lysines involved in cross-linking of the proximal tendon. This may be related to later calcification, suggesting that this part of the tendon is predestined to be calcified. The minimal changes in lysyl hydroxylation in both regions of the tendon with age were in contrast with the large changes in the cross-link profile, indicating differential hydroxylation of the helical and telopeptide lysine residues. Changes with age in the collagen matrix, its turnover and thermal properties in both the proximal and distal sections of the tendon clearly demonstrate that a new and modified matrix is formed throughout the tendon, and that a different type of matrix is formed at each site.

Age Factors↗

PubMed1997

Increased expression of promatrix metalloproteinase-9 and neutrophil elastase in canine dilated cardiomyopathy.

OBJECTIVE: Canine dilated cardiomyopathy, commonly affecting Doberman pinschers, results in extracellular matrix remodelling within the myocardium. The aim of this study was to examine the proteolytic activity in myocardium from Doberman pinschers with dilated cardiomyopathy. METHODS: Samples of myocardium, obtained rapidly post mortem from the left ventricular free wall of Dobermans with dilated cardiomyopathy, clinically normal Dobermans and control dogs (non-Dobermans), were examined for proteolytic activity using substrate gel zymography. Gels were analysed by scanning densitometry. RESULTS: Promatrix metalloproteinase-9 activity was significantly increased in all Doberman myocardium when compared to controls. A significant increase in an enzyme, identified to be neutrophil elastase by inhibition of its activity by Elastatinal and Western blotting, was also detected in all Dobermans when compared to controls. CONCLUSIONS: The results indicate that promatrix metalloproteinase-9 and neutrophil elastase, both of which are implicated in inflammatory responses, are present in significantly elevated levels in Doberman dilated cardiomyopathy and are raised in clinically normal Dobermans. Both proteolytic enzymes degrade a wide variety of connective tissue components and thus the increased levels found may play an important role in the structural remodelling seen in the myocardium and subsequent heart failure. Increased proteolytic enzyme levels in clinically normal Dobermans may be indicative of the predisposition of the breed to dilated cardiomyopathy.

Animals↗

PubMed1997

Biomechanical and biochemical study of a standardized wound healing model.

Standardized protocols were developed for use in a detailed investigation into the biomechanical and biochemical properties of a dermal wound healing model in the rat. The use of a rapid freezing method at -80 degrees C minimized the detrimental effects of freezing on the biomechanical properties of the tissue and also allowed for convenient inter-laboratory collaboration to be performed. The methodology described allowed for the simultaneous and reproducible measurement of tensile strength, collagen cross-linking and proteolytic enzyme activity. Increases in the tensile properties of the tissue with time were consistent with an active process of remodelling process as indicated by changes in the cross-link and enzyme profiles. Initially the granulation tissue was comparatively rich in the keto-imine cross-link hydroxylysino-keto-norleucine, which was later replaced by the aldimine cross-link dehydro-hydroxy-lysinonorleucine. The mature cross-link histidino-hydroxy-lysinonorleucine was not observed within the granulation tissue at any stage and was also absent in aged control skin. A peak of matrix metalloproteinase-9 activity was observed at early timepoints (48 hr) and then decreased rapidly to normal levels and is consistent with an acute inflammatory response. In contrast matrix metalloproteinase-2 activity peaked later (3 days) and then decreased gradually, consistent with its role as one of the predominant enzymes involved in the remodelling process. The results described validate the animal model used and emphasize its potential for use in combined biomechanical and biochemical studies of acute wound healing.

Animals↗

PubMed1997

Expression of gelatinases within the trabecular bone compartment of ovariectomized and parathyroidectomized adult female rats.

Ovariectomized (ovx) and parathyroidectomized (ptx) rat models of disturbed bone metabolism have been widely used in evaluating bone changes resulting from hormonal depletion, and are characterized by elevated and depressed bone turnover, respectively. We report here the expression of gelatinases extracted from native trabecular bone in these models. Nine-month-old female Sprague-Dawley rats were sacrificed after 3 weeks following ovx or 10 days post ptx to determine the influence of these procedures on the levels of proximal tibial bone tissue gelatinases. Identification and quantitation of these enzymes were performed via gelatin gel zymography of native tissue extracts and laser densitometry of developed gels, respectively. In the ptx model, a reduction in tissue levels of pro- and active-MMP-2 and a 45 kDa activated fragment was seen, whereas ovx exhibited significant increases in these enzymes. The MMPs are therefore clearly under the influence of factors known to modulate bone remodeling in vivo. The study of MMP levels directly extracted from bone using these experimental models may assist in developing management regimes for metabolic bone diseases through the use of drugs aimed at controlling turnover.

Animals↗

PubMed1997

Biochemical evidence for altered subchondral bone collagen metabolism in osteoarthritis of the hip.

Osteoarthritis (OA) of the hip is invariably viewed as a disease primarily affecting the articular cartilage. Data presented in this report, however, demonstrate changes in the metabolic activity of the underlying trabecular bone tissue, the processes of which may represent a significant factor in the pathogenesis of hip OA. Trabecular bone tissue from OA subjects expressed significantly more matrix metalloproteinase (MMP)-2 (gelatinase A, 72 kDa type IV collagenase) when compared to age-matched osteoporotic (OP) and normal bone tissue. Alkaline phosphatase was also significantly elevated in OA bone tissue. The combination of increased MMP-2 and alkaline phosphatase indicates heightened collagen turnover in the subchondral bone compartment of osteoarthritic hips. The data obtained from this study warrant a closer investigation into the significance of these changes in OA and emphasize the multifactorial elements of the whole joint in the whole joint in the overall disease process.

Age Factors↗

PubMed1997

Analysis of collagen status in premenopausal nulliparous women with genuine stress incontinence.

OBJECTIVE: To determine if differences exist in the collagen status of premenopausal nulliparous women with genuine stress incontinence compared with continent controls. DESIGN: Thirty-six premenopausal nulliparous women with urodynamically-proven genuine stress incontinence were compared with 25 controls. All the women studied had a periurethral vaginal biopsy taken of approximately 30-50 mg in wet weight. This biopsy was then analysed to determine the collagen content, the type I:III collagen ratio and the collagen cross-link content. SETTING: A tertiary referral urodynamic unit. RESULTS: The nulliparous women with genuine stress incontinence had significantly less collagen in their tissues (P < 0.0001) compared with the continent controls. In addition, there was a decreased ratio of type I to type III collagen (P = 0.0008), and the cross-link content was also significantly reduced in the women with genuine stress incontinence (P < 0.0001). CONCLUSION: Genuine stress incontinence is present in a significant number of women before childbirth. The aetiology of their incontinence appears to be due to a defect in their connective tissue, with both a quantitative and qualitative reduction in their collagen.

Adolescent↗

PubMed1997

Do subchondral bone changes exacerbate or precede articular cartilage destruction in osteoarthritis of the elderly?

Research into the aetiology of osteoarthritis has for several decades been concentrated on the destruction of the articular cartilage, the initiating events being believed to be changes in the proteoglycans and subsequently in the supporting collagenous framework, whereafter the disease is irreversible. Recent evidence has supported an old contention that the underlying bone may be involved, namely, increased technetium scintigraphy correlated with increased severity of the osteoarthritis as demonstrated by joint narrowing, and a demonstration of increased metabolism of cancellous bone collagen compared to age-matched controls. These studies have not been able to answer the question of the primary initiating event: does increased bone metabolism initiate cartilage destruction or vice versa? However, recent detailed studies on animal models, particularly the macaque, have demonstrated that in this case thickening of the subchondral bone precedes fibrillation of the cartilage, which is possibly due to increased resistance of the bone to compression. Further, MRI studies on the guinea pig suggest that the initial site of activity is at the ligament bone insertion site, prior to endochondral bone sclerosis. We propose that the biomechanics of the joint are perturbed by the loss of tension from the ligament following trauma, leading to remodelling of the subchondral bone. Certainly in humans damage to the cruciate ligament often results in osteoarthritis. It may be that subclinical damage also ultimately results in osteoarthritis. Although the results from animal models will need to be treated with caution, the concept that bone ligament changes precede articular cartilage destruction should lead to a redirection of research, and perhaps therapy, for this important and cruelly disabling disease.

Aged↗

PubMed1996

Changes in metabolism of collagen in genitourinary prolapse.

BACKGROUND: Genitourinary prolapse is a common problem, the pathophysiology of which is unknown. METHODS: We analysed vaginal-epithelial tissue from premenopausal women with genitourinary prolapse and compared them with controls. FINDINGS: We found that genitourinary prolapse is associated with a reduction in total collagen content and a decrease in collagen solubility. Both intermediate intermolecular cross-links and advanced glycation cross-links were increased in prolapse tissue. Collagen turnover, as indicated by matrix metalloproteinase activity, was up to four times higher in prolapse tissue. Collagen-type ratios, mature cross-link pyridinoline and total elastin content were similar in both prolapse and control tissues. Increased collagenolytic activity causes loss of collagen from prolapse tissue. INTERPRETATION: Based on these findings, we have identified a probable mechanism for genitourinary prolapse. Development of agents to inhibit collagenolytic activity may help in the treatment of this condition.

Adult↗

PubMed1996

The role of glycation cross-links in diabetic vascular stiffening.

Previous studies have shown that biomechanical analysis of aorta from diabetic subjects reveals a marked increase in stiffness compared to aorta from age-matched control subjects. In the present paper we have proposed that this increased stiffness can be attributed to glycation-induced inter-molecular cross-links based on a direct analysis of the two known glycation cross-links, the fluorescent pentosidine and the non-fluorescent NFC-1. There was a significant difference in the increase in concentration of both cross-links with increasing age for both the intima (p < 0.0025) and the media (p < 0.0005) from the diabetic compared to the control subjects, but no correlation with the mature enzymic cross-link hy droxylysyl-pyridinoline. Finally, we have obtained a significant correlation of stiffness with both glycation cross-links (NFC-1, r = 0.86; p < 0.005 and pentosidine r = 0.75, p < 0.05), but the concentration of NFC-1 is about 50 times greater than that of pentosidine, indicating that it is the major glycation cross-link responsible for the stiffening of the aorta.

Adult↗

PubMed1996

Interactions of elastin and aorta with sugars in vitro and their effects on biochemical and physical properties.

Stiffening of blood vessel walls occurs in the early stages of atherosclerosis, and this process is known to occur earlier in diabetic subjects. The effect could be due, in part, to glycation. Although collagen is responsible for ensuring the ultimate tensile strength of the tissue, elastin largely determines the compliance of the vessel wall in the normal physiological range of pressures and this appears to be closely matched to haemodynamic requirements. Changes in elastin are therefore likely to affect optimal function of the tissue. We have investigated the susceptibility of elastin to glycation and effects of glycation on its mechanical and physicochemical properties. We found that purified elastin and a collagen-elastin preparation from the porcine thoracic aorta rapidly incorporated glucose and ribose, the extent increasing linearly with increasing concentration and reaching a maximum after 7 days at 37 degrees C. Biochemical analysis showed that about one of the five lysines available per elastin monomer was glycated after 12 days incubation at a sugar concentration of 250 mmol/l. In long-term incubations glycation was associated with the appearance of the advanced glycation end products, the fluorescent cross-link pentosidine and the non-fluorescent putative cross-link NFC-1. In both purified elastin and the whole elastin-collagen matrix the slope of the force-extension curve increased significantly with glycation. The greatest increase in stiffness was observed in the elastin-collagen preparation after ribose incubation (250 mmol/l for 1 month), where the slope, at large strain, increased by 56 +/- 19% (mean +/- SD, n = 12). The diameter of the tissue at 1 N force also changed: for elastin there was an increase in length of approximately 5%, but for the elastin-collagen there was a decrease of similar magnitude indicating that glycation introduces differential strains within the fibrous protein matrix. Potentiometric titration demonstrated that glycation was associated both with loss of basic groups and shifts in pK of the acidic groups, which indicated changes in the environment of the charge groups due to conformational rearrangements. Changes in ion binding were dependent on pH, and were consistent with a reduction in effective anionic charge. Calcium binding to elastin was increased at acid pH, but decreased at higher pH. We suggest that these effects are not only due to changes in the charge profile, but also in the conformation of the molecule resulting from glycation of the charged lysine and arginine side-chain residues.

Amino Acid Sequence↗

PubMed1996

Long-term survival in small cell lung cancer: the case for a standard definition. Medical Research Council Lung Cancer Working Party.

OBJECTIVES: This paper investigates whether a particular time point can be recommended as the standard definition for long-term survival (LTS) in small cell lung cancer (SCLC). DESIGN: A review of the literature specifically referring to long-term survival in SCLC in the title. Individual and updated survival data from 2196 patients entered into six Medical Research Council (MRC) SCLC randomised trials to investigate changes in the hazard, or risk of death, over time. Examination of subgroups to identify different hazard patterns. SETTING: World-wide literature and patients recruited to SCLC trials conducted by the MRC Lung Cancer Working Party (LCWP). SUBJECTS: Papers accessed through computerised literature and hand searches and 2196 patients from six randomised clinical trials in SCLC conducted by the MRC LCWP. RESULTS: In all, 111 publications were identified by the literature searches. Although the majority defined LTS as 2 years, the definitions ranged from 18 months to greater than 5 years. There thus appears to be no agreed standard definition. The daily hazard was plotted for the large series of patients entered into the MRC LCWP SCLC trials to observe any patterns of change. There was an approximately constant daily hazard of 0.0035 during the first 2 years from randomisation, and following a transitional period, there was a further approximately constant, but smaller, daily hazard of 0.00035 from 3 years onwards. When subgroups of patients were examined this transition to a lower risk was observed in patients with limited disease, but patients with extensive disease remained at a high constant hazard throughout. It is suggested that 3 years should be adopted as the standard definition of LTS in SCLC, and that studies should always report limited and extensive stage patients separately.

Aged↗

PubMed1996

Randomized trial of palliative two-fraction versus more intensive 13-fraction radiotherapy for patients with inoperable non-small cell lung cancer and good performance status. Medical Research Council Lung Cancer Working Party.

In patients with non-metastatic but inoperable non-small cell lung cancer that is locally too extensive for radical radiotherapy (RT), but who have good performance status, it is important to determine whether thoracic RT should be the minimum that is required to palliate thoracic symptoms or whether treatment should be more intensive, with the aim of prolonging survival. A total of 509 such patients from 11 centres in the UK between November 1989 and October 1992 were admitted to a trial comparing palliative versus more intensive RT with respect to survival and quality of life. They were allocated at random to receive thoracic RT with either 17 Gy in two fractions (F2) 1 week apart (255 patients) or 39 Gy in 13 fractions (F13) 5 days per week (254 patients). Survival was better in the F13 group, the median survival periods being 7 months in the F2 group compared with 9 months in the F13 group, and the survival rates 31% and 36% at one year and 9% and 12% at 2 years, respectively (hazard ratio = 0.82; 95% CI0.69-0.99). There was a suggestion of a trend towards greater benefit in fitter patients. Metastases appeared earlier in the F2 group. As recorded by patients using the Rotterdam Symptom Checklist, the commonest symptoms on admission were cough, shortness of breath, tiredness, lack of energy, worrying and chest pain. These were more rapidly palliated by the F2 regimen. Psychological distress was generally lower in the F13 group. Three patients (two F13, one F2) exhibited evidence of myelopathy. As recorded by patients using a diary card, 76% of the F2 compared with 81% of the F13 patients had dysphagia associated with their RT. This was transient, lasting for a median of 6.5 days in the F2 group compared with 14 days in the F13 group. In conclusion, the F2 regimen had a more rapid palliative effect. In the F13 group, although treatment-related dysphagia was worse, survival was longer.

Aged↗

PubMed1996

Glycation of collagen: the basis of its central role in the late complications of ageing and diabetes.

The most serious late complication of ageing and diabetes mellitus follow similar patterns in the dysfunction of retinal capillaries, renal tissue, and the cardiovascular system. The changes are accelerated in diabetic patients owing to hyerglycaemia and are the major cause of premature morbidity and mortality. These tissues and their optimal functioning are dependent on the integrity of their supporting framework of collagen. It is the modification of the properties by glycation that results in many of the damaging late complications. Initially glycation affects the interactions of collagen with cells and other matrix components, but the most damaging effects are caused by the formation of glucose-mediated intermolecular cross-links. These cross-links decrease the critical flexibility and permeability of the tissues and reduce turnover. In contrast to the renal and retinal tissue, the cardiovascular system also contains a significant proportion of other fibrous connective tissue protein elastin, and its properties are similarly modified by glycation. The nature of these glycation cross-links is now being unravelled and this knowledge is crucial in any attempt to inhibit these deleterious glycation reactions.

Aging↗

PubMed1995

Biochemical changes in the collagenous matrix of osteoporotic avian bone.

No detailed biochemical analysis has been carried out of the compositional changes in the collagen matrix of avian bone in relation to increased bone fragility in osteoporosis. We have shown that osteoporosis in avian bone is certainly not just a simple loss of apatite and collagen, but involves significant changes in the biochemistry of the collagen molecule and consequently in the physical properties of the fibre. The decreased mechanical strength and the change in the thermal stability can be directly related to changes in post-translational modifications, i.e. lysine hydroxylation and the intermolecular cross-link profile. The increased hydroxylation and change in cross-linking are consistent with increased turnover of the collagen, possibly in an attempt to initiate a repair mechanism which, in fact, leads to an acceleration in the increase in fragility of the bone. Clearly there are post-translational modifications of the newly synthesized collagen in avian osteoporosis, and these changes may play a role in the pathogenesis of the disease.

Animals↗

PubMed1995

The kinetics of the thermal denaturation of collagen in unrestrained rat tail tendon determined by differential scanning calorimetry.

This paper shows that the position and shape of the denaturation endothem of collagen fibrils are governed by the kinetics of an irreversible rate process. This was proved by measuring the rate of denaturation in rat tail tendons held isothermally at different temperatures, thereby determining rate constant characteristics such as the activation enthalpy and entropy and predicting endotherm position and shape therefrom. Comparison with actual scanning results showed good correspondence. Isothermal measurements of the rate of collagen denaturation, measured continuously using a calorimetric method, were used to determine rate constants for collagen denaturation in tendons immersed in water and 0.5 M acetic acid. The temperature dependence of the rate constants were fitted to the three rate process models, previously examined theoretically: the D and z formulation, the Arrhenius equation and the absolute rate theory. For example, in water the activation enthalpy was 0.518 (+/- 0.016) Mj mol-1 and the activation entropy 1.485 (+/- 0.049) kj mol-1 K-1, while in acetic acid the corresponding figures were 1.306 (+/- 0.099) Mj mol-1 and 4.142 (+/- 0.323) kj mol-1 K-1. These characteristics are discussed in terms of the thermal activation of a region of the molecule, the co-operative unit. The ratio of the activation enthalpy to the calorimetry enthalpy of denaturation indicated a co-operative unit that was 66 (+/- 5) residues long when fibrils were swollen in acetic and the collagen molecules acted essentially independently. On the other hand the intact fibrils in water gave a co-operative unit of 26 (+/- 1) residues long. The reason for the reduction in size of the co-operative unit is that it is surrounded, and therefore stabilized by other molecules in the fibre. It is interesting to note that the suggested co-operative unit lies almost entirely within the "gap" zone of the collagen fibril in its quarter-staggered arrangement of molecules. We believe that the co-operative unit would be represented by a domain that is free of stabilising hydroxyproline residues. Indeed such a domain exists near the C terminus of the triple helix from Gly877 to Pro941, i.e. 65 residues. In acetic acid, activation is similar to that of collagen molecules in solution. All the inter alpha-chain hydrogen bonds in the co-operative unit are broken and the separate chains in this short region are free to flail around under the action of thermal collisions relatively unimpeded by intermolecular interactions.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1995

Non-enzymic glycation of fibrous collagen: reaction products of glucose and ribose.

Non-enzymic glycation of collagen involves a series of complex reactions ultimately leading to the formation of intermolecular cross-links resulting in changes in its physical properties. During analysis for the fluorescent cross-link pentosidine we identified the presence of an additional component (Cmpd K) in both glucose and ribose incubations. Cmpd K was formed more quickly than pentosidine in glucose incubations and more slowly than pentosidine in ribose incubations. Cmpd K represented 45% of the total fluorescence compared with 15% for pentosidine in glucose incubations and 25% of the total fluorescence compared with 30% for pentosidine in the ribose incubations. Cmpd K is not an artefact of in vitro incubations, as it was shown to be present in dermal tissue from diabetic patients. Subsequent high-resolution h.p.l.c. analysis of glucose-incubated collagen revealed Cmpd K comprise two components (K1 and K2). Further, a similar analysis of Cmpd K from the ribose incubations revealed two different components (K3 and K4). These differences indicate alternative mechanisms for the reactions of glucose and ribose with collagen. The amounts of these fluorescent components and the pentosidine cross-link determined for both glucose and ribose glycation were found to be far too low (about one pentosidine molecules per 200 collagen molecules after 6 months incubation with glucose) to account for the extensive cross-linking responsible for the changes in physical properties, suggesting that a further additional series of cross-links are formed. We have analysed the non-fluorescent high-molecular-mass components and identified a new component that increases with time of in vitro incubation and is present in the skin of diabetic patients. This component is present in sufficient quantities (estimated at one cross-link per two collagen molecules) to account for the changes in physical properties occurring in vitro.

Adolescent↗

PubMed1995

Interdisciplinary integration for quality improvement: the Cleveland Veterans Affairs Medical Center Firm System.

BACKGROUND: Many of the characteristics of Firm Systems lend themselves to the application of principles of continuous quality improvement (CQI). A Firm System is defined as two or more parallel practices organized on the principle of continuity of relationships between patients and an interdisciplinary group of health care professionals and trainees. Firm Systems are organized around the care of the patient or customer and emphasize access, continuity, and quality of care. CASE STUDY: The Firm System was implemented at the Cleveland Veterans Affairs Medical Center (VAMC) not as a CQI initiative per se, but as an effort to coordinate the processes involved in the delivery of patient care. The primary goals of this implementation were to improve the quality of patient care, medical education, and health care research. The main strategy to deal with problems caused by uncoordinated care were to move from a departmental approach to an integrated interdisciplinary approach. This approach represented a paradigm shift within the organization that extended to planning, documentation, and the general work environment. Most important, the institution had leaders who were committed to the Firm System and willing to authorize resources to ensure its success. CONCLUSION: VA hospitals are ideal settings for Firm Systems because they provide longitudinal, comprehensive care with a centralized, prepaid payment mechanism, and they have well-developed information systems that allow the random assignment of patients to Firms. Recommendations to others interested in implementing Firm Systems include creation of a written plan that can gain general support; identification of resources needed for successful implementation; remembering that the patient is the most important customer, as well as that complex systems have many customers; monitoring of performance; and the importance of randomizing patients and providers.

Continuity of Patient Care↗

PubMed1995

Abnormal collagen cross-linking in the cartilage of a diastrophic dysplasia patient.

The abnormal organization of the cartilage collagen in diastrophic dysplasia is not generally reflected in the levels of the major stabilizing cross-link, hydroxylysyl-pyridinoline. However, in one case there was a marked decrease in the pyridinoline concomitant with the appearance of two unknown components in the cross-link region of the chromatogram. A decrease in cross-linking of this magnitude could lead to mechanically weakened cartilage. Insufficient material was available to characterize these unknown components. The disorganization of cartilage in some cases of diastrophic dysplasia could therefore be due to post-translational modifications, including defective cross-linking.

Amino Acids↗