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Biomedical subjects

A J Wilson

Publications and source records attributed to A J Wilson.

At least 55 records · Page 3Linked to original sources
PubMed1999

Transoral fusion with internal fixation in a displaced hangman's fracture.

STUDY DESIGN: A case is reported in which late displacement of a "hangman's fracture" was managed by transoral C2-C3 fusion by using bicortical iliac crest graft and a titanium cervical locking plate. OBJECTIVES: To review the management of unstable fractures of the axis and to study other reports of transoral instrumentation of the cervical spine. SUMMARY OF BACKGROUND DATA: Undisplaced fractures of the axis are considered to be stable injuries. Although late displacement is unusual, it can lead to fracture nonunion with persisting instability and spinal cord dysfunction. In this situation, an anterior fusion of the second and third cervical vertebrae is preferred to a posterior fusion from the atlas to the third cervical vertebra, which would abolish lateral rotation between C1 and C2. METHODS: The literature on hangman's fractures was reviewed. Clinical and radiographic details of a case of C2 instability were recorded, and the particular problems posed by late displacement were considered. RESULTS: There are no other reports of transoral instrumentation of the cervical spine. A sound fusion of C2-C3 was obtained without infection or other complications. Good neck movement returned by 6 months after surgery. CONCLUSION: Undisplaced fractures of the axis are not always stable. The transoral route allows good access for stabilization of displaced hangman's fractures. In special circumstances, a locking plate may prove useful in securing the bone graft. The cervical spine locking plate can be inserted transorally with no complications and by using standard instrumentation.

Aged↗
PubMed1999

An artefact desynchroniser for use with visual evoked potential stimulators.

When recording visual evoked potentials elicited by a CRT raster display, driven from a frame-synchronised stimulus generator, artefacts caused by magnetic fields originating from the CRT field coils may seriously contaminate the recordings. This interference cannot be removed by signal averaging as it is time locked to the frame rate of the CRT. The circuit described here effectively desynchronises the interference, enabling the signal averaging process to reduce the artefact without the bandwidth restriction and resultant distortion of the recording which would be caused by lowpass filtering.

Electronics, Medical↗
PubMed1999

Colonic epithelial cell activation and the paradoxical effects of butyrate.

Butyrate may have paradoxical effects on epithelial cells of similar origin. This study aimed to examine the hypothesis that one mechanism that dictates a cell's response to butyrate is its state of activation. First, the responses to 24 h exposure to butyrate (1-2 mM) of normal and neoplastic human colonic epithelial cells activated by their isolation and primary culture, and of colon cancer cell lines, LIM1215 and Caco-2, were examined. In primary cultures of normal and cancer cells, butyrate had no effect on alkaline phosphatase activities but significantly suppressed urokinase receptor expression by a mean +/- SEM of 30 +/- 12% and 36 +/- 9%, respectively. Interleukin-8 secretion was suppressed by 44 +/- 7% in normal cells (P < 0.05) but was unchanged in cancer cells. In contrast, the cell lines significantly increased alkaline phosphatase activities by >50%, urokinase receptor expression >2-fold and interleukin-8 secretion >3-fold in response to butyrate. Secondly, the effect of butyrate on Caco-2 cells was examined with or without prior exposure to a specific activating stimulus [tumour necrosis factor alpha (TNF alpha)]. Interleukin-8 secretion increased by 145 +/- 23% and 132 +/- 17% on 24 h exposure to 2 mM butyrate or 0.1 microM TNF alpha alone, respectively. However, in cells pre-treated with TNF alpha, butyrate significantly inhibited secretion by 34 +/- 7% below unstimulated levels. The response to butyrate of urokinase receptor, whose expression was not stimulated by TNF alpha, was unchanged. These effects were mimicked by trichostatin A, an inhibitor of histone deacetylase, suggesting that butyrate's paradoxical effects may have been operating by the same mechanism. In conclusion, some of the paradoxical effects of butyrate do not appear to represent inherent differences between normal and transformed cells. Rather, the response may be determined by the state of activation of the cells.

Adult↗
PubMed1999

Quantitative analysis of the plain radiographic appearance of unicameral bone cysts.

RATIONALE AND OBJECTIVES: The authors determine the features that distinguish the radiographic appearance of unicameral bone cysts (UBC) from other solitary lesions of bone and to develop an ordered differential of similar-appearing lesions. MATERIALS AND METHODS: Seven hundred nine cases of solitary bone lesions, including 40 UBCs, were analyzed according to demographic, anatomic, and plain radiographic features. Vector analysis of both classic and new groups of features was performed to determine the sensitivity and specificity of radiographs for UBC and an ordered differential based on radiographic features. RESULTS: The features of the UBCs in this study compared favorably with those in the literature. The male:female ratio was 3.3:1, with an average age of 15 +/- 13 years. Age ranges and lesion diameters were similar for both sexes. Thirty-three of the 40 (83%) UBCs were in long bones, and seven were in the pelvis or calcaneus. All 40 UBCs were geographic, medullary, and lytic. None had an associated soft-tissue mass. Fifty-five percent had pathologic fractures, and 10% had fallen fragment signs. Ninety-eight percent had no cortical break, and 88% had well-defined margins. CONCLUSION: Classic descriptions of UBCs can be refined to improve sensitivity without sacrificing specificity. The best vector in this study had a sensitivity of 80% and a specificity of 93% and included these radiographic features: metaphyseal, diaphyseal, or flat bone location, geographic, lytic, medullary-based, no matrix, no satellite lesions, no subarticular extension, no soft-tissue mass, no cortical break, and central location in long bones. An ordered differential diagnosis, starting with the most likely lesion, includes enchondroma, aneurysmal bone cyst, fibrous dysplasia, nonossifying fibroma, Brodie abscess, and chondrosarcoma.

Adolescent↗
PubMed1999

Detection of live Trypanosoma cruzi in tissues of infected mice by using histochemical stain for beta-galactosidase.

The pathogenesis of tissue damage in chronic Trypanosoma cruzi infection has been a subject of long-standing debate. Conventional staining methods reveal a paucity of parasites in tissues from chronically infected individuals, which has led to the theory that the pathologic findings may be primarily autoimmune in origin. Immunostaining for T. cruzi antigens or in situ PCR methods show evidence for parasite components in chronic tissues; however, these methods do not address whether the stained material represents parasite debris or live organisms. An improved method for detecting intact T. cruzi in tissues was developed by making a genetically engineered strain that expresses Escherichia coli beta-galactosidase. The expression of this enzyme allows the detection of T. cruzi in tissues by using the histochemical stain 5-bromo-4-chloro-3-indolyl-beta-D-galactopyranoside (X-Gal). The technique was used to monitor tissue parasitism and its relation to pathologic findings in the mouse model of Chagas' disease. Parasites were easily visible as bright blue structures in skeletal muscle, heart, bladder, peripheral nerve, liver, spleen, adrenal gland, brain, and adipose tissue in acutely infected mice. The number of viable parasites diminished >100-fold when tissues from 3-week-infected mice were compared with those from 10-month-infected mice. However, even at the lower level, parasites were clearly recognizable in sections of skeletal muscle and bladder at the 10-month time point. Inflammation remained robust in skeletal muscle, bladder, and sciatic nerve despite the near disappearance of parasites, suggesting three possibilities: exuberant host reactions to the few remaining parasites, autoimmune inflammation, or reactions to retained parasite antigens in the tissues.

3T3 Cells↗
PubMed1999

Cervical spine tomography with an angiographic C-arm.

Phantom studies were performed to develop a technique for linear tomography of the craniocervical junction with a digital fluoroscopic angiographic C-arm unit. Section thicknesses were similar to those used at conventional tomography, and the radiation dose was lower. C-arm tomography was possible with a 6-second exposure and a 40 degrees arc. C-arm tomography is a practical method for decreasing patient turnaround time.

Angiography, Digital Subtraction↗
PubMed1999

Interleukin-8 stimulates the migration of human colonic epithelial cells in vitro.

The migration of colonic epithelial cells (restitution) is an important event in the repair of mucosal injuries. Interleukin-8 (IL-8) is a physiological initiator of the chemotactic migration of leucocytes. This study aimed to determine whether IL-8 had a similar effect on migration in an in vitro model of wounded colonic epithelium. Cell migration over 24 h was assessed in circular wounds made in confluent monolayers of the human colon cancer cell line LIM1215. This migration was stimulated in a concentration-dependent manner by IL-8, with maximal effects of approx. 1.75-fold above basal migration. The motogenic effect of IL-8 was mediated independently of effects on cell proliferation. In contrast, it was partially dependent upon gene transcription and protein synthesis and involved the activation of pertussis-toxin-sensitive G-proteins. The short-chain fatty acids, acetate, propionate, butyrate and valerate, the activator of protein kinase C (phorbol-12-myristate-13-acetate) and tumour necrosis factor-alpha (TNF-alpha) all stimulated the secretion of IL-8. However, only the motogenic effect of TNF-alpha was dependent upon IL-8. In conclusion, IL-8 stimulated cell migration in an in vitro model of colonic epithelium, whereas the motogenic effect of at least one physiologically relevant factor was dependent upon an increase in its endogenous levels. If IL-8 stimulates colonic epithelial restitution in vivo, this would have ramifications for the control of repair processes following wounding of the colonic mucosa.

Cell Division↗
PubMed1999

Compliance by collaboration: effectively addressing problems of treatment adherence.

BACKGROUND: Poor treatment compliance is a major problem in general practice. GPs need to develop strategies to identify and manage this problem as part of their clinical skills. OBJECTIVES: This paper provides an overview of the frequency and underlying causes of poor treatment compliance, highlighting strategies that can be utilised for its enhancement and promoting an understanding of the cycle of motivational change as it may apply to treatment compliance. DISCUSSION: General practitioners should consider the use of multiple strategies to manage adherence problems. General practitioners should develop an individualised understanding of why a patient does not adhere to appropriate treatment.

Australia↗
PubMed1998

Triple-injection wrist arthrography: unidirectional communications are due to technical factors.

One justification for triple-injection wrist arthrography is detection of unidirectional interjoint communication that might escape notice if only a single joint were injected. To determine whether the direction of 1-way communications is related to the choice of the first joint injected, the authors prospectively randomized 100 wrists undergoing consecutive single-contrast, fluoroscopically controlled arthrograms into 2 well-matched groups. One group received the initial injections into the midcarpal and distal radioulnar joints and the other group received the initial injection into the radiocarpal joint. Two unidirectional radial capsular communications with the radiocarpal joint were detected on delayed midcarpal joint injection. No other unidirectional communications were found. No statistically significant difference was found between the midcarpal and radiocarpal study groups. Thus, the first joint injected appears to be a major determinant in demonstrating unidirectional communications between wrist compartments.

Adult↗
PubMed1998

A search for type 1 diabetes susceptibility genes in families from the United Kingdom.

Genetic analysis of a mouse model of major histocompatability complex (MHC)-associated autoimmune type 1 (insulin-dependent) diabetes mellitus (IDDM) has shown that the disease is caused by a combination of a major effect at the MHC and at least ten other susceptibility loci elsewhere in the genome. A genome-wide scan of 93 affected sibpair families (ASP) from the UK (UK93) indicated a similar genetic basis for human type 1 diabetes, with the major genetic component at the MHC locus (IDDM1) explaining 34% of the familial clustering of the disease (lambda(s)=2.5; refs 3,4). In the present report, we have analysed a further 263 multiplex families from the same population (UK263) to provide a total UK data set of 356 ASP families (UK356). Only four regions of the genome outside IDDM1/MHC, which was still the only major locus detected, were not excluded at lambda(s)=3 and lod=-2, of which two showed evidence of linkage: chromosome 10p13-p11 (maximum lod score (MLS)=4.7, P=3x10(-6), lambda(s)=1.56) and chromosome 16q22-16q24 (MLS=3.4, P=6.5x10(-5), lambda(s)=1.6). These and other novel regions, including chromosome 14q12-q21 and chromosome 19p13-19q13, could potentially harbour disease loci but confirmation and fine mapping cannot be pursued effectively using conventional linkage analysis. Instead, more powerful linkage disequilibrium-based and haplotype mapping approaches must be used; such data is already emerging for several type 1 diabetes loci detected initially by linkage.

Adolescent↗
PubMed1998

A male-female bias in type 1 diabetes and linkage to chromosome Xp in MHC HLA-DR3-positive patients.

It is generally assumed that the male:female (M:F) ratio in patients with type 1 (insulin-dependent) diabetes mellitus (IDDM) is 1. A recent survey, however, revealed that high incidence countries (mainly European) have a high M:F ratio and low incidence ones (Asian and African) have a low M:F ratio. We have now analysed the M:F ratio according to genotype at the major locus, the major histocompatibility complex (MHC; IDDM1). There are two main IDDM1 susceptibility haplotypes, HLA-DR3 and -DR4, which are present in 95% of Caucasian cases. We report here that in medium/high incidence Caucasian populations from the United States of America, United Kingdom and Sardinia (1307 cases), the bias in male incidence is largely restricted to the DR3/X category of patients (X not = DR4) with a M:F ratio of 1.7 (P=9.3x10(-7)), compared with a ratio of 1.0 in the DR4/Y category (Y;DR3). This is additional evidence for significant heterogeneity between the aetiology of 'DR4-associated' and 'DR3-associated' diabetes. We analysed linkage of type 1 diabetes to chromosome X, and as expected, most of the linkage to Xp13-p11 was in the DR3/X affected sibpair families (n=97; peak multipoint MLS at DXS1068=3.5, P=2.7x10(-4); single point MLS=4.5, P=2.7x10(-5)). This is evidence for aetiological heterogeneity at the IDDM1/MHC locus and, therefore, in the search for non-MHC loci in type 1 diabetes, conditioning of linkage data by HLA type is advised.

Adolescent↗
PubMed1998

Induction of resistance to azole drugs in Trypanosoma cruzi.

Trypanosoma cruzi is the protozoan parasite that causes Chagas' disease, a frequently fatal illness affecting the heart and gastrointestinal systems. An estimated 16 million to 18 million people in Latin America and 50,000 to 100,000 people in the United States are infected with this pathogen. Treatment options for T. cruzi infections are suboptimal due to the toxicities and limited effectiveness of the available drugs. Azole antimicrobial agents have been discovered to have antitrypanosomal activity by inhibition of ergosterol synthesis. The triazole itraconazole was recently shown to produce a parasitologic cure rate of 53% in chronically infected patients (W. Apt et al., Am. J. Trop. Med. Hyg. 59:133-138, 1998), a result which may lead to more use of this family of drugs for the treatment of T. cruzi infections. In the experiments reported on here, resistance to azoles was induced in vitro by serial passage of mammalian-stage parasites in the presence of fluconazole for 4 months. These parasites were cross resistant to the other azoles, ketoconazole, miconazole, and itraconazole. They remained susceptible to benznidazole and amphotericin B. The azole-resistant phenotype was stable for more than 2 months of in vitro serial passage without fluconazole. In addition, the parasites resisted treatment in mice receiving ketoconazole. The rapid development of azole resistance in T. cruzi in vitro suggests that resistance to azole drugs has the potential to occur in patients and may pose an impediment to the progress being made in the treatment of T. cruzi infection.

Animals↗
PubMed1998

Mechanical loading stimulates bone formation by reactivation of bone lining cells in 13-week-old rats.

The bone formation that occurs in response to mechanical stimulation is generally considered to be a means by which bone adapts to changes in its mechanical environment. We have previously shown that the expression of genes for bone matrix proteins is maximal 72 h after a single 5-minute episode of loading of tail vertebrae of 13-week-old female rats, that the predominant increase in mineralization occurs after 3 days, and that the osteogenic response to mechanical stimulation is not dependent on prior bone resorption. We have now investigated the cellular correlates of this osteogenic response. No proliferation was detected, by pulse or flash labeling, in the trabecular bone surface cells of animals killed 1 h to 10 days after the loading episode. Ultrastructural examination revealed that most of the cells covering the trabecular bone surface of control vertebrae were flat bone lining cells. After mechanical stimulation, the trabecular bone surface cells developed ultrastructural features of osteoblastic differentiation and activity, with acquisition of an increasingly cuboidal shape, rounded nuclei, and abundant rough endoplasmic reticulum. Morphometric analysis of the mean cell area, mean nuclear area, and cell and nuclear height showed that they were all maximal 48 h after loading. By 120 h after loading, the appearances of bone surface cells had reverted to those of control vertebrae. Thus, mechanical loading appears to activate lining cells, with a temporal sequence that correlates with bone matrix production.

Analysis of Variance↗