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Biomedical subjects

R C Bray

Publications and source records attributed to R C Bray.

At least 55 records · Page 3Linked to original sources
PubMed1997

Anterior knee pain: a review.

OBJECTIVE: To establish whether there is consensus in the areas of definition, classification, assessment, diagnostic tests, and management of anterior knee pain. DATA SOURCES: A Medicine search for the years 1988-1995 was performed using the terms patellofemoral joint, knee joint and pain, injury and rehabilitation, and anterior knee pain. In addition, references from selected papers were examined. STUDY SELECTION: A total of 77 references specifically related to anterior knee pain were reviewed in the areas of definition, classification, assessment, diagnostic tests, and management. Although a small number of these papers were analytic in their study design, most of the papers reviewed were descriptive. DATA EXTRACTION: Definitive statements on anterior knee pain in the areas noted herein were extracted and summarized. Similar statements were then grouped as indicative of general consensus. Independent and divergent statements were also summarized for each area of anterior knee pain. DATA SYNTHESIS: Most of the literature related to anterior knee pain is subjective in nature and demonstrates limited consensus among experts. There is no generally accepted definition or classification of anterior knee pain. There was some agreement on the assessment, use of diagnostic tests, and management of anterior knee pain, but there are no definitive or objective management outcome criteria. CONCLUSIONS: The scientific literature on anterior knee pain is sparse. This review supports a need for the development of consensus guidelines for anterior knee pain. A consensus approach to anterior knee pain could result in the more efficient use of high-yield diagnostic tests, the use of more effective and standardized protocols for assessment and treatment, increased patient satisfaction, and recommendations on fitness counseling and early prevention.

Diagnostic Tests, Routine↗
PubMed1997

Serial ultrasonographic imaging evaluation of the patellar tendon after harvesting its central one third for anterior cruciate ligament reconstruction.

The purpose of this study was to assess ultrasonographic image changes in the patellar tendon after removal of its central one third for anterior cruciate ligament reconstruction. Fourteen patellar tendons in 14 patients were assessed preoperatively and at 2 weeks, 4 weeks, 2 months, 6 months, and 12 months postoperatively. With time, the entire donor tendon became enlarged, hypoechoic, and inhomogeneous compared with the presurgical state. Tendons enlarged maximally in anteroposterior thickness by 2 months and then began to diminish, remaining two times their original anteroposterior thickness by 12 months and never returning to their preoperative appearance. The margins of the defect became indistinct over time. In the donor patellar tendon, abnormal echogenicity was profound and persisted up to 1 year after surgery. Ultrasonographic imaging has the ability to evaluate the postoperative patellar tendon over time and to monitor the normal changes seen with healing.

Adult↗
PubMed1996

Properties of xanthine dehydrogenase variants from rosy mutant strains of Drosophila melanogaster and their relevance to the enzyme's structure and mechanism.

Xanthine dehydrogenase, a molybdenum, iron-sulfur flavoenzyme encoded in the fruit fly Drosophila melanogaster by the rosy gene, has been characterised both from the wild-type and mutant files. Enzyme assays, using a variety of different oxidising and reducing substrates were supplemented by limited molecular characterisation. Four rosy strains showed no detectable activity in any enzyme assay tried, whereas from four wild-type and three rosy mutant strains, those for the [E89K], [L127F] and [L157P]xanthine dehydrogenases (in all of which the mutation is in the iron-sulfur domain), the enzyme molecules, although present at different levels, had extremely similar or identical properties. This was confirmed by purification of one wild-type and one mutant enzyme. [E89K]xanthine dehydrogenase. These both had ultraviolet-visible absorption spectra similar to milk xanthine oxidase. Both were found to be quite stable molecules, showing very high catalytic-centre activities and with little tendency to become degraded by proteolysis or modified by conversion to oxidase or desulfo forms. In three further rosy strains, giving [G353D]xanthine dehydrogenase and [S357F]xanthine dehydrogenase mutated in the flavin domain, and [G1011E]xanthine dehydrogenase mutated in the molybdenum domain, enzyme activities were selectively diminished in certain assays. For the G353D and S357F mutant enzymes activities to NAD+ as oxidising substrate were diminished, to zero for the latter. In addition for [G353D]xanthine dehydrogenase, there was an increase in apparent Km values both for NAD+ and NADH. These findings indicate involvement of this part of the sequence in the NAD(+)-binding site. The G1011E mutation has a profound effect on the enzyme. As isolated and as present in crude extracts of the files, this xanthine dehydrogenase variant lacks activity to xanthine or pterin as reducing substrate, indicating an impairment of the functioning of its molybdenum centre. However, it retains full activity to NADH with dyes as oxidising substrate. Mild oxidation of the enzyme converts it, apparently irreversibly, to a form showing full activity to xanthine and pterin. The nature of the group that is oxidised is discussed in the light of redox potential data. It is proposed that the process involves oxidation of the pterin of the molybdenum cofactor from the tetrahydro to a dihydro oxidation state. This conclusion is fully consistent with recent information [Romäo, M. J., Archer, M., Moura, I., Moura. J.J.G., LeGall, J., Engh, R., Schneider, M., Hof, P. & Huber, R. (1995) Science 270. 1170-1176) from X-ray crystallography on the structure of a closely related enzyme from Desulfovibrio gigas. It is proposed, that apparent irreversibility of the oxidative activating process for [G1011E]xanthine dehydrogenase, is due to conversion of its pterin to the tricyclic derivative detected by these workers. The data thus provide the strongest evidence available, that the oxidation state of the pterin can have a controlling influence on the activity of a molybdenum cofactor enzyme. Implications regarding pterin incorporation into xanthine dehydrogenase and in relation to other molybdenum enzymes are discussed.

Amino Acid Sequence↗
PubMed1996

Evidence favoring molybdenum-carbon bond formation in xanthine oxidase action: 17Q- and 13C-ENDOR and kinetic studies.

The reaction mechanism of the molybdoenzyme xanthine oxidase has been further investigated by 13C and 17O ENDOR of molybdenum(V) species and by kinetic studies of exchange of oxygen isotopes. Three EPR signal-giving species were studied: (i) Very Rapid, a transient intermediate in substrate turnover, (ii) Inhibited, the product of an inhibitory side reaction with aldehyde substrates, and (iii) Alloxanthine, a species formed by reaction of reduced enzyme with the inhibitor, alloxanthine. The Very Rapid signal was developed either with [8-13C]xanthine or with 2-oxo-6-methylpurine using enzyme equilibrated with [17O]H2O. The Inhibited signal was developed with 2H13C2HO and the Alloxanthine signal by using [17O]H2O. Estimates of Mo-C distances were made, from the anisotropic components of the 13C-couplings, by corrected dipolar coupling calculations and by back-calculation from assumed possible structures. Estimated distances in the Inhibited and Very Rapid species were about 1.9 and less than 2.4 A, respectively. A Mo-C bond in the Inhibited species is very strongly suggested, presumably associated with side-on bonding to molybdenum of the carbonyl of the aldehyde substrate. For the Very Rapid species, a Mo-C bond is highly likely. Coupling from a strongly coupled 17O, not in the form of an oxo group, and no coupling from other oxygens was detected in the Very Rapid species. No coupled oxygens were detected in the Alloxanthine species. That the coupled oxygen of the Very Rapid species is the one that appears in the product uric acid molecule was confirmed by new kinetic data. It is concluded that this oxygen of the Very Rapid species does not, as frequently assumed, originate from the oxo group of the oxidized enzyme. A new turnover mechanism is proposed, not involving direct participation of the oxo ligand group, and based on that of Coucouvanis et al. [Coucouvanis, D., Toupadakis, A., Lane, J. D., Koo, S. M., Kim, C. G., Hadjikyriacou, A. (1991) J. Am. Chem. Soc. 113, 5271-5282]. It involves formal addition of the elements of the substrate (e.g., xanthine) across the Mo = S double bond, to give a Mo(VI) species. This is followed by attack of a "buried" water molecule (in the vicinity of molybdenum and perhaps a ligand of it) on the bound substrate carbon, to give an intermediate that on intramolecular one-electron oxidation gives the Very Rapid species. The latter, in keeping with the 13C, 17O, and 33S couplings, is presumed to have the 8-CO group of the uric acid product molecule bonded side-on to molybdenum, with the sulfido molybdenum ligand retained, as in the oxidized enzyme.

Animals↗
PubMed1996

Coloured microsphere assessment of blood flow to knee ligaments in adult rabbits: effects of injury.

Coloured microspheres were used to determine standardized blood flow in an established model of medial collateral ligament injury in the adult rabbit knee. Resting blood flow in the ligament was ascertained to be on the order of 0.68 +/- 0.08 ml/min/100 g (mean +/- SEM) in normal rabbit knees, although errors in flow estimates of this magnitude may be quite high. In healing medial collateral ligament, however, flow had increased markedly 3 weeks after injury (21.45 +/- 5.48 ml/min/100 g). Flows in sham-operated control medial collateral ligaments were not significantly increased compared with those in control normal ligaments. Six weeks after injury, blood flow in the ligament remained elevated (16.90 +/- 3.20 ml/min/100 g) and was similarly elevated in other neighbouring joint tissues (i.e., ipsilateral synovial fat pad). The increase in flow to ipsilateral noninjured articular tissues did not persist beyond 6 weeks, but flow in the healing medial collateral ligament scar tended to remain elevated after 17 weeks (4.20 +/- 1.79 ml/min/100 g), although this did not achieve statistical significance. We conclude from these data that it is possible to measure the increase in blood flow in injured and healing articular tissues using the coloured microspheres technique and that ligament injury is a potent stimulus for increasing blood flow. Coloured microsphere measurements of blood flow to joint connective tissues may offer a valuable approach to future investigations of joint injury and arthritis.

Animals↗
PubMed1996

Normal and healing ligament vascularity: a quantitative histological assessment in the adult rabbit medial collateral ligament.

Normal and healing adult rabbit medial collateral ligaments (MCL) have been assessed for microvascular anatomy using a quantitative image analysis methodology. MCL preparation by ink-gelatin perfusion enabled acceptable visualisation of microvascular channels within the tissue. Fifteen adult rabbits were studied; 3 normal rabbits formed an external time-zero control group; 12 animals received a standardised gap injury to the right MCL. The ligament injury was permitted to heal for 3, 6, 17 or 40 wk (3 animals in each healing group). Results confirmed that the normal MCL is hypovascular (about 1.46% vascularity by area) and that microvascular channels are highly organised and oriented longitudinally deep within the tissue. Healing MCL scar becomes twice as vascular as normal ligament early on, but returns to near normal values by 40 wk. Microvascular channels appear less organised in scar than in contralateral controls, but remodel with time. The directional scatter and spatial extent of ligament microvascular channels is quantifiable in normal and healing tissues.

Animals↗
PubMed1995

Properties of rabbit liver aldehyde oxidase and the relationship of the enzyme to xanthine oxidase and dehydrogenase.

The properties of the molybdenum iron-sulfur flavoprotein, aldehyde oxidase from rabbit livers, have been further investigated in comparison with bovine milk xanthine oxidase. In agreement with earlier work, the ultraviolet/visible spectra indicate that the flavin and iron-sulfur centres of the enzymes are quite similar to one another. The molybdenum centres have been compared by EPR spectroscopy of molybdenum(V) and regarding re-insertion of the sulfido ligand of molybdenum into the desulfo enzyme forms. The pH optimum for sulfide insertion is approximately 2 lower for aldehyde oxidase than for xanthine oxidase. A detailed comparison of molybdenum(V) EPR signals has been made for the signals known as Arsenite, Slow and Rapid. Computer simulation of spectra in 1H2O and 2H2O, at 9 and 35 GHz was used. Slow signals from the two enzymes are scarcely distinguishable from one another. Under the conditions used, aldehyde oxidase yielded only the Rapid type 2 signal, whereas xanthine oxidase gives both the Rapid type 1 and 2 signals. The nature of the structural difference between the Rapid type 1 and type 2 signal-giving species is discussed. It is concluded that the molybdenum centres of xanthine oxidase and aldehyde oxidase are indeed similar to one another and that such differences as exist between their molybdenum(V) EPR signals and re-sulfuration properties are related to differences only in the substrate-binding sites. N-terminal amino acid analyses have been performed on peptides obtained by trypsin cleavage of aldehyde oxidase. Comparison with a sequence previously deduced [Wright, R. M., Vaitaitis, G. M., Wilson, C. M., Repine, T. B., Terada, L. S. & Repine, J. E. (1993) Proc. Natl Acad. Sci. USA 90, 10690-10694] makes it clear that the latter is not, as was assumed, that of a xanthine dehydrogenase but of an aldehyde oxidase. In contrast to the situation with xanthine oxidase, attempts to convert non-proteolysed aldehyde oxidase to a dehydrogenase form by treatment with dithiothreitol were unsuccessful. The reason for this is considered in the light of sequence data in the literature. The location of the NAD(+)-binding site is discussed, and the sequence data are also discussed in relation to the molybdenum, iron-sulfur and substrate-binding sites.

Aldehyde Oxidase↗
PubMed1995

Patellar tendinitis: MR imaging features, with suggested pathogenesis and proposed classification.

PURPOSE: To characterize the magnetic resonance (MR) imaging features of patellar tendinitis. MATERIALS AND METHODS: Fifteen patients with a clinical diagnosis of patellar tendinitis underwent gadolinium-enhanced MR imaging of the knee. RESULTS: Grades of patellar abnormality, based on findings in the enthesial region at MR imaging, correlated with signs of increasing fibrovascular repair: grade 1 (n = 4), enhancing area adjacent to patellar apex, with marginal zone of intermediate signal intensity, and a patellar apical chondral-bone avulsion; grade 2 (n = 5), same signs as grade 1 damage but without avulsion; grade 3 (n = 6), homogeneous, nonenhancing area of intermediate signal intensity adjacent to the patellar apex seen on all images. Changes were most obvious posteriorly and involved the central and medial thirds of the tendon. Chronic injury to the medial retinaculum was a common associated finding. CONCLUSION: Patellar tendinitis demonstrates a consistent spectrum of changes at MR imaging that can aid understanding of the origin and treatment of damage.

Adolescent↗
PubMed1995

Exercise loading of tendons and the development of overuse injuries. A review of current literature.

This review examines recent studies on the effects of exercise on tendons in animal models. Although tendon adaptation to exercise has been described using histology, morphometry, ultrasonography and molecular biology, precise measurements of excess tendon loading during exercise protocols have not been reported. Only a few studies have attempted to evaluate the mechanical strength of exercised tendons. The long term effect of exercise on tendons appears to be positive, but researchers have suggested that periods of mechanical weakness occur in tendons during adaptation to loading conditions. Studies documenting changes associated with the terminal state of pathological tendons are also summarised. Unfortunately, there are no descriptions of tendon tissue in the early stages of overuse injury. Since blood flow is commonly implicated in the emergence of tendinitis, the final section covers recent work on blood flow and tendon physiology. Related research identifying cellular mediators (hyperthermia, hypoxia, and oxidative stress) involved in the development of tendinitis is also presented. Suggestions for further research into exercise loading and the development of tendon overuse injuries are made.

Adaptation, Physiological↗
PubMed1994

Multiple states of the molybdenum centre of dimethylsulphoxide reductase from Rhodobacter capsulatus revealed by EPR spectroscopy.

The dimethylsulphoxide reductase of Rhodobacter capsulatus contains a pterin molybdenum cofactor molecule as its only prosthetic group. Kinetic studies were consistent with re-oxidation of the enzyme being rate limiting in the turnover of dimethylsulphoxide in the presence of the benzyl viologen radical. EPR spectra of molybdenum(V) were generated by reducing the highly purified enzyme under a variety of conditions, and with careful control it was possible to generate at least five clearly distinct EPR signals. These could be simulated, indicating that each corresponds to a single chemical species. Structures of the signal-giving species are discussed in light of the EPR parameters and of information from the literature. Three of the signals show coupling of molybdenum to an exchangeable proton and, in the corresponding species, the metal is presumed to bear a hydroxyl ligand. One signal with gav 1.96 shows a very strong similarity to a signal for the desulpho form of xanthine oxidase, while two others with gav values of 1.98 show a distinct similarity to signals from nitrate reductase of Escherichia coli. These data indicate an unusual flexibility in the active site of dimethylsulphoxide reductase, as well as emphasising structural similarities between molybdenum enzymes bearing different forms of the pterin cofactor. Interchange among the different species must involve either a change of coordination geometry, a ligand exchange, or both. The latter may involve replacement of an amino acid residue co-ordinating molybdenum via O or N, for a cysteine co-ordinating via S. Since the two signals with gav 1.96 were obtained only under specific conditions of reduction of the enzyme by dithionite, it is postulated that their generation may be triggered by reduction of the pteridine of the molybdenum cofactor from a dihydro state to the tetrahydro state.

Binding Sites↗