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J L Williams

Publications and source records attributed to J L Williams.

At least 127 records · Page 7Linked to original sources
PubMed1997

Measurements of permeability in human calcaneal trabecular bone.

2.36 cm diameter cores of trabecular bone (n = 22), oriented in the mediolateral direction, were obtained from fresh-frozen calcanei of 16 cadavers ranging in age from 32 to 89 yr. The cores were defatted and tested to determine values for permeability along the cylinder axis. Permeability values (0.4-11 x 10(-9)m2) were found to be strongly correlated with specimen porosity (78-92%) through a linear relationship (r2 = 0.91). These results provide essential information for the biphasic or poroelastic modeling of fluid-filled trabecular bone at this location.

Adult↗
PubMed1997

Surveillance of Barrett's esophagus: a need for guidelines?

Barrett's esophagus carries a 10-15% lifetime risk of malignant change, and dysplasia may be an early indication of such transformation. Endoscopic surveillance is widely practised but guidelines have not been established. A questionnaire regarding surveillance protocols was sent to all consultants in the Trent Region performing endoscopy (n = 79), of whom 58 (73%) replied. Surveillance is performed by 52 clinicians (90%), but the interval varies between 1 and 3 years. Routine biopsies are only taken by 38 (65%), of which 74% are taken randomly. Detection of low-grade dysplasia would lead 32 (62%) to reduce the surveillance interval. For high-grade dysplasia, a reduced surveillance interval or surgery is advocated by 36 (69%) and 13 (25%), respectively. Most clinicians (74%) discontinue surveillance at age 70 or 75. Surveillance of Barrett's esophagus is variable, especially in the presence of dysplasia. No surveillance guidelines are available, but most respondents (79%) believe these would help.

Adenocarcinoma↗
PubMed1997

Symmetrical synovial fluid cell cytokine messenger RNA expression in rheumatoid arthritis: analysis by reverse transcription/polymerase chain reaction.

To investigate the complex intra-articular immune activity in rheumatoid arthritis (RA), we analysed the expression of a wide range of cytokine mRNAs in synovial fluid cells from patients with rheumatoid arthritis. To minimize in vitro artefact, mRNA was rapidly extracted from synovial fluid leucocytes taken from single joints of seven patients and simultaneously from both knee joints of four patients. Expression of interleukin (IL) 1 beta, IL-2, IL-4, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, tumour necrosis factor-alpha and interferon-gamma (IFN-gamma) was detected using the reverse transcription/polymerase chain reaction. The expression of cytokines varied between patients. IFN-gamma mRNA was detected in 60% of the patients and IL-4 mRNA in 10%. Cytokine expression in both knees was very similar. These results suggest that T-cell activity in RA is detectable using sensitive techniques and that the intra-articular immunopathology of RA is systemically very similar.

Adult↗
PubMed1997

Biomechanical comparison of fixation methods in transverse olecranon fractures: a cadaveric study.

OBJECTIVES/HYPOTHESIS: Our null hypothesis was that no difference in fracture displacement would be detected between traditional monofilament wire and Kirschner wire placement versus three modified tension-band techniques for transverse olecranon fractures. STUDY DESIGN: A nested form of the repeated measures design with twenty-two paired embalmed elbows (subjects grouped by sex and nested within the fracture method). METHODS: Transverse osteotomies were created at the olecranon and stabilized with four techniques. One hundred cycles of loading were applied to achieve a peak flexion bending moment at the fracture of nine newton-meters. At the onset of testing, the triceps tendon was anchored at an initial elbow flexion angle of 70 degrees. RESULTS: When using a monofilament figure-eight loop, oblique Kirschner wire placement into the anterior ulnar cortex provided greater resistance to tensile force than intramedullary Kirschner wires (p = 0.04). With intramedullary Kirschner wire placement, 1.6-millimeter-diameter braided cable in both figure-eight (p < 0.0001) and circular loop (p < 0.0001) designs allowed less fracture displacement than did the 1.0-millimeter-diameter monofilament wire. There was no difference between figure-eight and circular loop configurations when using braided cable (p = 0.98). CONCLUSIONS: In transverse noncomminuted olecranon fractures, fixation with monofilament wire is superior with Kirschner wire placement into the anterior ulnar cortex. With intramedullary Kirschner wires, fixation using braided cable is significantly improved over that with monofilament wire. When using braided cable, figure-eight and circular loop designs allow similar displacements. Braided cable or anterior cortical Kirschner wire purchase increases the stability of fixation over that achieved with the traditional method.

Adult↗
PubMed1997

Dwarfism in Dexter cattle is not caused by the mutations in FGFR3 responsible for achondroplasia in humans.

Dexter cattle carry a genetic defect causing a dwarf phenotype in the heterozygotes (Dx+/-), while homozygotes (Dx+/+) are stillborn with extreme shortening of limbs and gross craniofacial defects and are described as 'bulldog' calves. The heterozygous phenotype has been likened to achondroplastic dwarfism in humans (ACH), which has recently been shown to be the result of mutations in the transmembrane region of the fibroblast growth factor receptor 3 (FGFR3) gene. We have sequenced the transmembrane region of bovine FGFR3 from normal Dexter cattle (Dx-/-) and bulldog calves (Dx+/+). The sequence from both is identical and therefore excludes mutations in the trans-membrane region of FGFR3 as the cause of Dexter dwarfism.

Achondroplasia↗
PubMed1997

Probability-based structural parameters from three-dimensional nuclear magnetic resonance images as predictors of trabecular bone strength.

The mechanical competence of trabecular bone is a function of its apparent density and three-dimensional (3D) distribution. Three-dimensional structure is typically inferred from histomorphometry and stereology on a limited number of two-dimensional anatomic sections. In this work 3D nuclear magnetic resonance (NMR) images of anisotropic trabecular bone from the distal radius were analyzed in terms of a series of new structural parameters which are obtainable at relatively crude resolution, i.e., in the presence of substantial partial volume blurring. Unlike typical feature extraction techniques requiring image segmentation, the method relies on spatial autocorrelation analysis, which is based on the probability of finding bone at specified locations. The structural parameters were measured from high-resolution images (78x78x78 microm3 voxels) of 23 trabecular bone specimens from the distal radius. Maximum-likelihood bone volume fractions (BVF) were calculated for each voxel and a resolution achievable in vivo (156x156x391 microm3 voxels) was simulated by averaging BVF's from neighboring voxels. The parameters derived from the low-resolution images were found to account for 91% of the variation in Young's modulus. The results suggest that noninvasive assessment of the mechanical competence of trabecular bone in osteoporotic patients may be feasible.

Biomechanical Phenomena↗
PubMed1997

Low power, type II errors, and other statistical problems in recent cardiovascular research.

Frequently in biomedical literature, measurements are considered "not statistically different" if a statistical test fails to achieve a P value that is < or = 0.05. This conclusion may be misleading because the size of each group is too small or the variability is large, and a type II error (false negative) is committed. In this study, we examined the probabilities of detecting a real difference (power) and type II errors in unpaired t-tests in Volumes 246 and 266 of the American Journal of Physiology: Heart and Circulatory Physiology. In addition, we examined all articles for other statistical errors. The median power of the t-tests was similar in these volumes (approximately 0.55 and approximately 0.92 to detect a 20% and a 50% change, respectively). In both volumes, approximately 80% of the studies with nonsignificant unpaired t-tests contained at least one t-test with a type II error probability > 0.30. Our findings suggest that low power and a high incidence of type II errors are common problems in this journal. In addition, the presentation of statistics was often vague, t-tests were misused frequently, and assumptions for inferential statistics usually were not mentioned or examined.

Analysis of Variance↗
PubMed1997

Glenohumeral joint translations before and after total shoulder arthroplasty. A study in cadavera.

UNLABELLED: The purpose of the present study was to examine the motions of natural and prosthetically reconstructed glenohumeral joints without capsular contracture in the laboratory to obtain a better understanding of joint motion as it may relate to failure of the implant. Seven joints from fresh-frozen human cadavera were instrumented with a six-degrees-of-freedom magnetic tracking device to study patterns of translation and rotation with and without the application of simulated muscle forces (active and passive models). The specimens were tested before and after reconstruction of the joint with use of modified operative techniques and implants that had from zero to five millimeters of radial mismatch between the humeral head and glenoid components. The natural and reconstructed joints had similar patterns of translation, with larger rotations and translations observed in the passive model. On the average, the active translations of the natural joints were best reproduced by the reconstructed joints with less conforming articulations. The mean active translation in the natural joints was 1.5 millimeters along the anterior-posterior axis and 1.1 millimeters along the superior-inferior axis. The active translations in the reconstructed joints were observed to increase consistently as the conformity of the components decreased: the mean active anterior-posterior translations ranged from 0.3 millimeter for conforming components to 1.7 millimeters for components with a five-millimeter radial mismatch, and the mean active superior-inferior translations ranged from 0.4 to 1.1 millimeters. The patterns of translation during passive motions were less consistent, presumably because of the influence of capsular ligaments and because the translations were large enough for the articular surface of the humeral head to lose contact with the articular surface of the glenoid component. CLINICAL RELEVANCE: Glenohumeral translations during active motions were found to depend on articular conformity, which indicates that the choice of implants may have important consequences for normal motions. Totally conforming designs may impose a degree of restraint to translations that is higher than that in the natural joint. The patterns of translation may influence the longevity of the joint replacement with respect to stability, loosening of the glenoid component, and wear of the components.

Aged↗
PubMed1997

Effect of desonide ointment, 0.05%, on the hypothalamic-pituitary-adrenal axis of children with atopic dermatitis.

Desonide ointment has demonstrated a good safety and efficacy profile during the many years it has been used in treating dermatoses. However, there have been no controlled clinical trials to evaluate its systemic safety when used in treating children. Suppression of the hypothalamic-pituitary-adrenal (HPA) axis can occur after repeated application of topical corticosteroids. In general, the degree of suppression of the HPA axis function is related to the daily dosage of steroid given, the duration of its administration, the extent of body surface covered, and the potency of the corticosteroid. This study sought to determine the comparative effects of 0.05 percent desonide and 2.5 percent hydrocortisone ointments on the HPA axis of children with atopic dermatitis. There was no suppression of early morning cortisol in either treatment group. The ACTH-stimulated mean cortisol values after four weeks of treatment were not significantly different from the baseline values for either treatment group. We conclude that neither 0.05 percent desonide ointment nor 2.5 percent hydrocortisone ointment compromised the HPA axis of children with atopic dermatitis treated topically for four weeks.

Administration, Topical↗
PubMed1996

Kinematics of the glenohumeral joint: influences of muscle forces, ligamentous constraints, and articular geometry.

Despite recent interest in the study of shoulder kinematics, there is considerable controversy in the literature regarding translations at the glenohumeral joint. The purpose of this study was to investigate the key factors that control shoulder motions, thus leading to a better understanding of joint function. Translation and rotation patterns were studied in fresh-frozen glenohumeral joints of human cadavers with a six-degrees-of-freedom magnetic tracking device. Shoulders were positioned from maximal internal to external rotation at several arm positions (various elevations and planes of motion). In order to determine the effect of muscle forces, joints were positioned both actively and passively. Additionally, articular surface geometry and ligament origin-insertion wrap lengths were measured to assess their influences on joint kinematics. When joints were positioned passively, large translations were observed at the extremes of motion. With active positioning, muscle forces tended to limit humeral head translations, principally by restricting rotational ranges of motion. However, when data from the passive model were reanalyzed by considering only the rotational ranges of motion seen actively, no significant differences in translation were found between the two models. Joint conformity was found to have a significant influence on translations during active positioning but not during passive positioning. Glenohumeral ligament wrap lengths, however, correlated with translations when joints were positioned passively but not when positioned actively. Findings from this study emphasize the importance of muscle forces in keeping the humeral head centered in the glenoid. Although large translations are possible, they can be achieved only with increases in rotational ranges of motion associated with the removal of muscle force. Additionally, joint conformity appears to play a role in controlling translations during active motions, whereas capsular constraints become more important during passive motions.

Aged↗
PubMed1996

Bronchopulmonary foregut malformation mimicking neuroblastoma.

We report the case of a patient with an unusual, complex bronchopulmonary foregut malformation. The malformation included an extralobar sequestration, an esophageal duplication cyst, and a gastric duplication cyst. Postnatal imaging suggested a fetal adrenal neuroblastoma.

Adrenal Gland Neoplasms↗
PubMed1996

Altered expression of class I major histocompatibility antigens on bovine cells infected with the protozoan parasite Theileria annulata.

Theileria annulata infection is controlled by MHC class I restricted cytotoxic T cell killing of infected cells. The long term persistence of parasite suggests that it employs a mechanism to avoid immune surveillance. In this paper we describe the modification of BoLA class I antigens on the surface of Theileria annulata transformed lymphoblastoid cells. The extent of modification is different between individuals varying from extensive to undetectable.

Animals↗
PubMed1996

The spin trap reagent PBN attenuates degeneration of 5-HT neurones in rat brain induced by p-chloroamphetamine but not fenfluramine.

Dark Agouti rats injected with either p-chloroamphetamine (PCA; 2.5 mg/kg i.p.) or fenfluramine (15 mg/kg i.p.) had substantial decreases (approximately 50%) in the concentration of 5-HT and 5-HIAA and binding of [3H]paroxetine in the cerebral cortex 7 days later. This indicates that both compounds had produced neurodegeneration of 5-HT axon terminals. Two doses of alpha-phenyl-N-tert-butyl nitrone (PBN; 150 mg/kg i.p.) 130 min apart had no effect on cortical 5-HT content or [3H]paroxetine binding. However, when PBN (150 mg/ kg) was given 10 min before and 120 min after PCA (2.5 mg/kg) it attenuated the PCA-induced neurodegeneration. In contrast, PBN was without significant effect on the fenfluramine-induced damage. Changes in rectal temperature following either the neurotoxins or neurotoxins+ PBN were no more than +/-1 degree C of saline-injected control rats. These data indicate that PCA, like MDMA, probably induces neurotoxic degeneration because of the formation of catechol or quinone metabolites and subsequent reactive tree radical formation. Such a mechanism does not appear to explain fenfluramine-induced damage to 5-HT neurones.

Animals↗