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Biomedical subjects

G A Murrell

Publications and source records attributed to G A Murrell.

At least 55 records · Page 3Linked to original sources
PubMed1994

Denatured muscle as a nerve conduit: a functional, morphologic, and electrophysiologic evaluation.

This experimental study evaluated denatured skeletal muscle and denatured epineural basement membrane tube as conduits to bridge defects in rat sciatic nerve. A 1-cm segment of sciatic nerve was resected in 48 rats. In Group I (control), the segment was discarded; in Group 2, the segment was reimplanted orthotopically; in Group 3, the defect was bridged by denatured (liquid nitrogen frozen and thawed) muscle; and in Group 4, the resected nerve segment was denatured as in Group 3, the axons removed, and the resulting epineural basement membrane tube used as a conduit. Functional assessment was carried out with the sciatic functional index (SFI). Histologic examination of the graft was made at 1.5, 2, 2.5, 3, and 6 months postoperatively. At 6 months, a Grass neurostimulator was used to determine the minimal voltage necessary to elicit ankle motion. Hind-foot ulceration and/or toe loss occurred in all groups, but less commonly in the rats with denatured muscle and denatured nerve conduits. Both Groups 3 and 4 achieved a macroscopic appearance of nerve at 45 days. However, the denatured conduits were longer and narrower than in standard nerve grafts. In the distal nerve, a mixture of axonal regeneration and degeneration was seen in Groups 2 to 4. By 6 months, the microscopic appearance of the nerve grafts, conduits, and distal nerves was that of normal nerve, with no differences between the groups. Active plantar flexion following electrical stimulation was observed in Groups 2 to 4 at 6 months.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Hip fusion in young adults. Using a medial displacement osteotomy and cobra plate.

Eight consecutive patients, mean age 17.25 years, underwent a medial displacement osteotomy and hip arthrodesis with a nine-hole Cobra plate. A transverse innominate osteotomy facilitated medial displacement of the femoral head and acetabulum. Alignment of the lower limb at 25 degrees flexion, neutral abduction, and neutral rotation was assisted by a long-limbed protractor and Steinmann pins placed in both anterior superior iliac spines. The greater trochanter was reattached to the Cobra plate so that hip abductor function could be restored should the fusion ever be converted to an arthroplasty. No postoperative immobilization was required. All patients had radiographic evidence of union by 12 months. One patient had a postoperative brachial plexus neuropraxia that resolved at three months. One patient required an ipsilateral femoral lengthening for limb-length inequality secondary to collapse of his femoral head before hip fusion. At a mean follow-up interval of 2.8 years (range, one to 4.5 years), all patients had significant improvements in pain (p < 0.05), function (p < 0.01), and gait (p < 0.01). The average preoperative Harris Hip Score of 45 points +/- 8 points (mean +/- SEM) improved to 84 points +/- 2 points (p < 0.01).

Activities of Daily Living↗
PubMed1993

Achilles tendon healing: a correlation between functional and mechanical performance in the rat.

The pathogenesis and treatment of rupture of the Achilles tendon remain a source of controversy. This study presents the results of a biomechanical, functional, and morphological evaluation of a group of rats that had division and repair of the Achilles tendon. A total of 46 rats were used: 18 for biomechanical testing, 18 for functional evaluation, and 10 for histology. Morphological examination revealed an early inflammatory response with loose connective tissue formation that was replaced gradually by fibroblasts and a collagenous matrix. The functional evaluation (Achilles functional index [AFI]) was made from measurements of the hind pawprints of walking rats. Division and repair of the Achilles tendon produced a significant functional impairment (mean [+/- SEM] AFI = -87 +/- 8; p < 0.001), which gradually improved with healing time. The load to failure for the repaired tendons consistently improved with healing time, in a manner similar to the functional recovery. The average deformation (repair/control) varied considerably and was not related to healing time. The stiffness of the repaired tendons increased with healing time and was 60% of the corresponding control side by day 15. The major finding of this study was a strong correlation between the AFI and the failure load of the healing tendon-bone constructs (250-300 g group, r = 0.97, p < 0.001; 325-375 g group, r = 0.96, p < 0.001).

Achilles Tendon↗
PubMed1993

An assessment of the reliability of the Scoliometer.

Accurate noninvasive measurements of spinal curvature are crucial in planning treatment and assessing curve progression in adolescent idiopathic scoliosis. An inter-rater agreement trial and an intrarater agreement trial were undertaken to estimate the reliability of axial rotation measurement using the Scoliometer (Orthopedic Systems, Inc., Haywood, California). In the inter-rater trial, two orthopedic surgeons and two orthopedic surgery residents independently measured the thoracic and lumbar axial rotations of 22 patients with idiopathic scoliosis using the Scoliometer. In the intrarater, trial a single orthopedic surgeon measured the thoracic and lumbar axial rotations of 25 patients on four separate occasions with the Scoliometer. Inter-rater agreement using the Scoliometer to estimate the magnitude of the hump (in centimeters) in the thoracic and lumbar regions was poor (intraclass correlation coefficient, Rho = 0.57 and Rho = 0.76 for the thoracic and lumbar regions, respectively). Inter-rater agreement using the Scoliometer to estimate the degree of axial trunk rotation was better (Rho = 0.81 and Rho = 0.82 for the thoracic and lumbar regions, respectively). Intrarater agreement using this device to estimate the magnitude of the hump (in centimeters) in the thoracic and lumbar regions was good (Rho = 0.90 and Rho = 0.84 for the thoracic and lumbar regions, respectively). Intrarater agreement using the Scoliometer to estimate the degrees of curvature was outstanding (Rho = 0.995 and Rho = 0.998 for the thoracic and lumbar regions, respectively). These results indicate that the Scoliometer can be a reliable noninvasive method for repetitively assessing spinal axial rotation when used by a single trained observer.

Adolescent↗
PubMed1993

Achilles tendon injuries: a comparison of surgical repair versus no repair in a rat model.

Controversy exists regarding the treatment of Achilles tendon ruptures. The aim of this study was to determine whether surgical repair of the rat Achilles tendon offered any biomechanical, functional, or morphological advantage over no repair. Thirty-two male Sprague-Dawley rats were randomly allocated into four groups: (1) sham operated (skin incision only), (2) no repair (complete division of the Achilles tendon and plantaris tendon without repair), (3) internal splint (plantaris left intact), and (4) Achilles repair (with a modified Kessler-type suture). Functional performance was determined from the measurements of hindpaw prints utilizing the Achilles Functional Index. On day 15, the animals were killed, and biochemical and histological evaluations were performed on both the injured and uninjured Achilles tendon constructs. All groups subjected to Achilles tendon division had a significant initial functional impairment that gradually improved so that by day 15 there were no functional or failure load impairments in any group. The injured tendons in all three groups subjected to Achilles tendon division had a 13-fold increase in the cross-sectional area and were less stiff and more deformable than uninjured and sham-operated tendons on day 15 (P < .001). The magnitude of the biomechanical and morphological changes at postoperative day 15 and the initial impairment and rate of functional recovery were similar for no repair, internal splint, and Achilles repair groups. In summary, this study demonstrates that surgical repair of the Achilles tendon in the rat does not offer any advantage over nonoperative management.

Achilles Tendon↗
PubMed1992

The Achilles Functional Index.

The literature regarding the management of spontaneous rupture of the Achilles tendon is controversial and confusing. The relative infrequency of the condition in any one center prohibits the completion of well-designed clinical studies. Many of the disputes could be addressed and innovations tested if an appropriate animal model were available. We present a method for evaluating Achilles tendon function from measurements of the prints, preserved in bromphenol-blue-impregnated photocopying paper, of the hindfeet of walking rats. The stimulus for this study was derived from de Medinaceli's method for assessing the functional condition of rat sciatic nerves (de Medinaceli L, Freed WJ, Wyatt RJ: An index of the functional condition of rat sciatic nerve based on measurements made from walking tracks. Exp Neurol 77:634-643, 1982). Four variables were measured from these walking tracks, and comparisons between the damaged (experimental) and intact (normal) side were converted to proportional deficits. The relative contribution of each parameter to the overall deficit was determined by multiple linear regression analysis, and the variables were weighted accordingly to obtain an "Achilles Functional Index" (AFI). A sham operation produced no functional deficit, whereas animals subjected to a 0.5-cm midsubstance Achilles tendon defect demonstrated a markedly impaired AFI. Animals with repaired transected Achilles tendons also demonstrated a significant, but less severely impaired AFI. The functional deficit in this repair group returned to control values by postoperative day 15, whereas animals with a defect remained impaired at day 15. Furthermore, an excellent correlation was found between the functional recovery and biomechanical properties (ultimate failure load) of the healing tendon (r = 0.94; p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Achilles Tendon↗
PubMed1992

The functional recovery of peripheral nerves following defined acute crush injuries.

This study evaluates the effect of crushing load on functional recovery of the sciatic nerve. Male Sprague-Dawley rats were divided into five groups: sham operation, resected sciatic nerve, and 100 g (13 mm Hg/mm2), 500 g (50 mm Hg/mm2), and 15,000 g (1,000 mm Hg/mm2) of sciatic crush load (groups 1-5). In groups 3-5, a 5-mm segment of sciatic nerve was crushed for 10 min using a specially designed crushing device. Motor functional recovery was assessed from hind-limb walking tracks by calculating a sciatic functional index. There was no detectable functional deficit in the group receiving sham operations, while the resected sciatic nerve group exhibited complete dysfunction for the full duration of the experiment. All groups subjected to crush exhibited an initial deficit that gradually recovered to normal by day 14 (100-g crush), day 39 (500-g crush), and day 53 (15,000-g crush). Histological changes were also related to the initial crushing load and the length of the recovery period. Results indicate that the crushing device described is able to administer an adjustable, defined crush injury to the rat sciatic nerve, and that the functional deficit resulting from such an injury can be easily monitored with a sciatic functional index. The rate of recovery of crushed nerves was directly related to the initial load. All crushed nerves recovered in this experiment, even after the application of a 15,000-g load for 10 min.

Animals↗
PubMed1992

The informed consent treatment report.

A brief history of informed consent and introduction of the "Informed Consent Treatment Report" (ICTR) is presented. The ICTR is a document developed in 1984 that combines the requirements of informed consent and the elements of good treatment planning and presentation to achieved improved patient and practice management. An outline of the parts and sections of the ICTR is included as a guide for preparing an informed consent and treatment planning document.

Dental Records↗
PubMed1992

Scientific comment. Basic science of Dupuytren's disease.

At a cellular level, the major phenomenon in Dupuytren's contracture is an increase in proliferating fibroblasts, rather than an alteration in the type of fibroblasts. The collagen and glycosaminoglycan changes observed in the tissues of Dupuytren's contracture are likely to be secondary to changes in fibroblast density. Oxygen free radicals released from narrowed microvessels and from the fibroblasts themselves may play a role in stimulating fibroblast proliferation. Messina's experiments with continuous distraction and the success of limited fasciotomy indicate a role for physical forces in the pathogenesis of Dupuytren's contracture. The mechanism whereby physical events stimulate biochemical changes are undetermined, but preliminary investigations suggest that electrical fields and ion channels may be important. The future of Dupuytren's contracture rests with the delineation of these chemical and physical processes and their application and rigorous testing in the clinical setting.

Cell Division↗
PubMed1992

An insight into Dupuytren's contracture.

Dupuytren's contracture is a deforming, fibrotic condition of the palmar fascia which has confounded clinicians and scientists since the early descriptions by Guillaume Dupuytren in 1831. It predominantly affects elderly, male caucasians, has a hereditary predisposition and has strong associations with diabetes, alcohol consumption, cigarette smoking and HIV infection. The major morphological features are an increase in fibroblasts, particularly around narrowed fibroblasts; a finding consistent with localised ischaemia. During ischaemia, adenosine triphosphate (ATP) is converted to hypoxanthine and xanthine, and endothelial xanthine dehydrogenase to xanthine oxidase (alcohol also mediates this change, a finding of particular relevance given the association of Dupuytren's contracture with alcohol intake). Xanthine oxidase catalyses the oxidation of hypoxanthine to xanthine and uric acid with the release of superoxide free radicals (O2-), hydrogen peroxide (H2O2) and hydroxyl radicals (OH.). These free radicals are highly reactive, with half-lives in the order of milliseconds and are toxic in high concentrations. A potential for free radical generation in Dupuytren's contracture was elicited by finding a sixfold increase in hypoxanthine concentrations in Dupuytren's contracture compared with control palmar fascia. In vitro studies affirmed the toxic effects of oxygen free radicals to Dupuytren's contracture fibroblasts, but also showed that, at lower concentrations (concentrations similar to those likely to occur in Dupuytren's contracture), free radicals had a stimulatory effect on fibroblast proliferation. Cultured fibroblasts were found to release their own O2-. These endogenously released free radicals were also found to be important in fibroblast proliferation. The collagen changes of Dupuytren's contracture were examined. The results established that fibroblast origin was unimportant, but that inhibition of type I collagen production at high fibroblast density accounted for the increase in type III/I collagen ratios observed by previous investigators. These biochemical and morphological observations throw new light on Dupuytren's contracture. They suggest that age, genetic and environmental factors may contribute to micro vessel narrowing with consequent localised ischaemia and free radical generation. Endothelial xanthine oxidase derived free radicals may both damage the surrounding stroma and stimulate fibroblasts to proliferate. Proliferating fibroblasts lay down and contract collagen in lines of stress.Progressive fibroblast proliferation and deposition of collagen is likely to encourage further microvessel narrowing with a positive feedback effect consistent with the progressive nature of the condition.

Capillaries↗
PubMed1991

The collagen changes of Dupuytren's contracture.

In Dupuytren's contracture there is an increase in the ratio of type III to type I collagen. The objective of this study was to determine if fibroblasts from patients with Dupuytren's contracture have an intrinsic aberration in collagen production or whether local factors govern the collagen changes in Dupuytren's contracture. Using a new collagen micro-method, we found that fibroblasts cultured from palmar fascia affected by Dupuytren's contracture produced similar collagen to fibroblasts derived from the palmar fascia of age- and sex-matched patients with carpal tunnel syndrome. Furthermore, the collagen changes of Dupuytren's contracture could be reproduced in all cell lines by increasing fibroblast density. At high fibroblast density, type I collagen production was inhibited: a finding that could account for the increased types III/I collagen ratio in Dupuytren's contracture. These results suggest that a genetic defect in collagen production is unlikely and that the important phenomenon is an increase in fibroblast density.

Collagen↗
PubMed1991

The role of the fibroblast in Dupuytren's contracture.

Ultrastructural, immunohistochemical, and biochemical studies to date show that the fibroblast in Dupuytren's contracture is identical to palmar fascia fibroblasts in patients unaffected by Dupuytren's contracture, and to all other fibroblasts. The major difference relating to fibroblasts is that in Dupuytren's contracture there are more of them, and they are clustered around narrowed microvessels. It is probable that these two phenomena are linked because recent studies indicate a greater potential for ischemia-induced oxygen free radical generation in Dupuytren's contracture, and because oxygen free radicals in these concentrations can stimulate fibroblast proliferation. The major source of oxygen free radicals is likely to be from microvascular endothelial xanthine oxidase-catalyzed reactions. These observations also account for many of the epidemiologic associations of Dupuytren's contracture, because (1) age, race, and diabetes are associated with microvessel narrowing and (2) age, diabetes, alcohol consumption, HIV infection, cigarette smoking, and trauma are associated with increased free radical generation. Nonsteroidal anti-inflammatory drugs and allopurinol are two agents that decrease oxygen free radical release and may inhibit or prevent Dupuytren's contracture.

Collagen↗
PubMed1990

Modulation of fibroblast proliferation by oxygen free radicals.

The major unexplained phenomenon in fibrotic conditions is an increase in replicating fibroblasts. In this report we present evidence that oxygen free radicals can both stimulate and inhibit proliferation of cultured human fibroblasts, and that fibroblasts themselves release superoxide (O2.-) free radicals. Fibroblasts released O2.- in concentrations which stimulated proliferation, a finding confirmed by a dose-dependent inhibition of proliferation by free radical scavengers. Oxygen free radicals released by a host of agents may thus provide a very fast, specific and sensitive trigger for fibroblast proliferation. Prolonged stimulation may result in fibrosis, and agents which inhibit free radical release may have a role in the prevention of fibrosis.

Cell Division↗
PubMed1990

Cell-controlling factors in Dupuytren's contracture.

The search for the causative factors in Dupuytren's disease has historically progressed form gross anatomical dissection, through microscopical tissue studies, to the biochemistry of the collagen produced. But these elements are merely the end products of cellular activity - not revealing the factors responsible for the changes in cellular activity. Recent biochemical investigations suggest that a number of conditions including localized microvascular ischemia and high alcohol concentrations transform the "benign" xanthine dehydrogenase of endothelial cells to the oxygen-free radical-releasing xanthine oxidase. Oxygen-free radicals are highly reactive species with half-lives in the order of milliseconds capable of both damaging the surrounding peri-microvasculature and stimulating fibroblast proliferation. It is this stimulation of fibroblast proliferation in the palmar fascia that is the key event in the pathogenesis of Dupuytren's contracture.

Dupuytren Contracture↗
PubMed1990

Aetiology of Dupuytren's contracture.

Dupuytren's contracture is a fascinating, deforming, fibrotic condition of the palmar fascia which has confounded clinicians and scientists for centuries. The aim of this paper is to place in perspective the longstanding associations of age, sex, race, hereditary factors, diabetes and alcohol consumption with the more recent novel investigations at the cellular level. In concert, the findings indicate that a number of factors may lead to the narrowing of palmar fascia microvessels, with localized ischaemia and oxygen free radical release. Oxygen free radicals are likely to damage the surrounding stroma, and stimulate fibroblast proliferation. Proliferating fibroblasts lay down collagen and contract in the lines of stress. The process is likely to encourage further microvessel ischaemia with a positive feedback effect that is consistent with the progressive nature of the condition.

Dupuytren Contracture↗
PubMed1989

Dupuytren's contracture. Fine structure in relation to aetiology.

The fine structure of palmar fascia from patients with Dupuytren's contracture (DC) was compared with that from patients with carpal tunnel syndrome (CTS). In contrast to previous assumptions, the ultrastructure of fibroblasts both in vivo and in vitro from DC and CTS appeared identical, indicating that myofibroblasts are not specific to DC. The major differences between DC and CTS were: 1) a sixfold and fortyfold increase in fibroblast density in cord and nodular areas of DC compared with CTS; 2) a more disorganised pattern of collagen fibrils in DC; and 3) markedly narrowed microvessels surrounded by thickened, laminated basal laminae and proliferating fibroblasts in DC compared with CTS. To account for these morphological changes a hypothesis is presented which proposes that oxygen-free radicals cause pericytic necrosis and fibroblastic proliferation. This hypothesis provides a potential avenue for therapy of DC and other fibrotic conditions.

Aged↗
PubMed1989

Complete denture esthetics.

Complete denture esthetics can no longer be considered solely a function of tooth selection and arrangement or the colors and contours of the denture bases. Denture esthetics must also include the entire face in which the expressions of inner feelings, personality, comfort, image, well-being, and perceptions of past dental experiences are all very evident. These hard and soft components all contribute to the complete denture esthetic result; they are inseparable and should be given every consideration when developing a successful complete denture esthetic restoration. Both the patient and the dentist must understand this interrelationship for optimal success.

Denture Design↗