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Biomedical subjects

G Stewart

Publications and source records attributed to G Stewart.

At least 37 records · Page 2Linked to original sources
PubMed2001

Renal venous thrombosis with calcification and preservation of renal function.

Two neonates were found on US to have branching linear calcification in the renal parenchyma, right sided in one and bilateral in the other. CT confirmed the presence of branching calcification in the kidneys and demonstrated calcified thrombus in the inferior vena cava in both babies. Antenatal detection of adrenal haemorrhage in one baby and presence of calcification at the age of 3 days in the other indicate that thrombosis probably occurred before birth. The kidneys remained normal in size, and uptake of 99mTc-labelled dimercaptosuccinic acid (99mTc-DMSA) was normal on follow-up examination. The presence of branching calcification and normal renal size probably indicates good prognosis for renal function in neonates in whom renal venous thrombosis is found and may indicate prenatal thrombosis.

Calcinosis↗
PubMed2001

The -590C/T and -34C/T interleukin-4 promoter polymorphisms are not associated with atopic eczema in childhood.

Susceptibility to the development of asthma and other atopic diseases is known to have a genetic component. To date, several studies have linked chromosome 5q31 to asthma and atopy in human beings. This region harbors a cluster of cytokine and growth factor genes, IL-4 presenting as a prime atopy candidate gene, inasmuch as it plays a pivotal role in the atopy pathway. Our approach was to identify polymorphisms within the promoter regions of IL-4 and test their association with atopic eczema. Polymorphisms were typed in a cohort of 76 small nuclear families and 25 triads with childhood atopic eczema. The genotypes were used to test for linkage in the presence of association with atopic eczema. A new polymorphism, -34C/T, was identified and studied with a known polymorphism, -590C/T. On its own, each polymorphism showed no association with atopic eczema. The 2 polymorphisms were used to generate haplotypes, and a significant result was found for the -590C/-34C haplotype. However, after Bonferroni correction for multiple testing, the association became nonsignificant. Neither polymorphism predisposes to early-onset atopic eczema by itself, but suggestive linkage was found for the -590C/-34C haplotype in this study.

Child↗
PubMed2001

Acyl-homoserine lactone production is more common among plant-associated Pseudomonas spp. than among soilborne Pseudomonas spp.

A total of 137 soilborne and plant-associated bacterial strains belonging to different Pseudomonas species were tested for their ability to synthesize N-acyl-homoserine lactones (NAHL). Fifty-four strains synthesized NAHL. Interestingly, NAHL production appears to be more common among plant-associated than among soilborne Pseudomonas spp. Indeed, 40% of the analyzed Pseudomonas syringae strains produced NAHL which were identified most often as the short-chain NAHL, N-hexanoyl-L-homoserine lactone, N-(3-oxo-hexanoyl)-homoserine lactone, and N-(3-oxo-octanoyl)-L-homoserine lactone (no absolute correlation between genomospecies of P. syringae and their ability to produce NAHL could be found). Six strains of fluorescent pseudomonads, belonging to the species P. chlororaphis, P. fluorescens, and P. putida, isolated from the plant rhizosphere produced different types of NAHL. In contrast, none of the strains isolated from soil samples were shown to produce NAHL. The gene encoding the NAHL synthase in P. syringae pv. maculicola was isolated by complementation of an NAHL-deficient Chromobacterium mutant. Sequence analysis revealed the existence of a luxI homologue that we named psmI. This gene is sufficient to confer NAHL synthesis upon its bacterial host and has strong homology to psyI and ahlI, two genes involved in NAHL production in P. syringae pv. tabaci and P. syringae pv. syringae, respectively. We identified another open reading frame that we termed psmR, transcribed convergently in relation to psmI and partly overlapping psmI; this gene encodes a putative LuxR regulatory protein. This gene organization, with luxI and luxR homologues facing each other and overlapping, has been found so far only in the enteric bacteria Erwinia and Pantoea and in the related species P. syringae pv. tabaci.

4-Butyrolactone↗
PubMed2001

Role of Mycobacterium tuberculosis copper-zinc superoxide dismutase.

Superoxide dismutases (SODs) play an important role in protection against oxidative stress and have been shown to contribute to the pathogenicity of many bacterial species. To determine the function of the mycobacterial copper and zinc-cofactored SOD (CuZnSOD), we constructed and characterized Mycobacterium tuberculosis and Mycobacterium bovis BCG CuZnSOD null mutants. Both strains were more sensitive to superoxides and hydrogen peroxide than were their respective parental strains. The survival of M. bovis BCG in unstimulated as well as activated mouse bone marrow-derived macrophages was not affected by the loss of CuZnSOD. The survival of CuZnSOD deficient-M. tuberculosis in guinea pig tissues was comparable to that of its parental strain. These results indicate that the mycobacterial CuZnSOD is not essential for intracellular growth within macrophages and does not detectably contribute to the pathogenicity of M. tuberculosis.

Animals↗
PubMed2001

Epidemiology and diagnosis of meningitis: results of a five-year prospective, population-based study.

Implementation of the advice to give penicillin prior to admission, a fall in the lumbar puncture rate and the introduction into routine use of the meningococcal polymerase chain reaction (PCR) test are factors that have led us to reassess the way meningitis is diagnosed. We examined data for the period 1994-98 from a health district of 800,000 population. Of the 355 cases of meningitis reported, 258 (73%) had either confirmed, probable or possible meningococcal disease. Only 28% of meningococcal cases had received pre-admission benzylpenicillin. The proportion of suspected meningitis cases undergoing lumbar puncture fell over the period. It was 79% in 1994 and 61% in 1998 (p < 0.001). After meningococcal PCR was introduced in 1996, 73 (68%) meningococcal cases were microbiologically confirmed, compared to 72 (48%) before 1996 (p = 0.001). In all cases, age was an independent predictor of meningitis mortality, and for meningococcal cases, age and serogroup were independent predictors. Advice to general practitioners (GPs) to give preadmission benzylpenicillin to any suspected case of meningitis or meningococcal septicaemia should be reinforced regardless of age or whether a rash is present.

Adolescent↗
PubMed2000

The pulvinar sign on magnetic resonance imaging in variant Creutzfeldt-Jakob disease.

BACKGROUND: There is a need for an accurate non-invasive diagnostic test for variant Creutzfeldt-Jakob disease (vCJD). We investigated the sensitivity and specificity of bilateral pulvinar high signal on magnetic resonance imaging (MRI) for the diagnosis of vCJD. METHODS: MRI from patients with vCJD and controls (patients with suspected CJD) were analysed. Scans were reviewed on two separate occasions by two neuroradiologists and scored for the distribution of changes, and likely final diagnosis. Scans from vCJD cases were reassessed to reach a consensus on all abnormalities. FINDINGS: We analysed 36 patients and 57 controls. vCJD patients were correctly identified based on bilateral pulvinar high signal in 29 of 36 and 32 of 36 cases on the first assessment by the two radiologists, and 32 of 36 and 31 of 36 on their second assessment. Bilateral increased pulvinar signal was identified in one of 57 and one of 57 controls on the first assessment and two of 57 and three of 57 controls on the second assessment. These reported changes in controls were graded as minimal/equivocal in six of seven patients and moderate in one (<0.5% of all control assessments). 80% of the assessments in vCJD cases were graded as moderate or substantial. On consensus review, 28 of 36 cases and none of 57 controls had prominent bilateral pulvinar signal-sensitivity 78% (95% CI 60-90%) and specificity 100% (95% CI 94-100%). Other common MRI features of vCJD were medial thalamic and periaqueductal grey matter high signal, and the notable absence of cerebral atrophy. Pulvinar high signal correlated with histological gliosis. INTERPRETATION: In the appropriate clinical context the MRI identification of bilaterally increased pulvinar signal is a useful non-invasive test for the diagnosis of vCJD.

Adolescent↗
PubMed2000

Epithelial Na+ channels and stomatin are expressed in rat trigeminal mechanosensory neurons.

Caenorhabditis elegans MEC-4 and MEC-10 are subunits of the degenerin/epithelial Na+ channel (DEG/ENaC) ion channel superfamily thought to be associated with MEC-2 (a stomatin-like protein) in a mechanotransducing molecular complex in specialized touch sensory neurons. A key question is whether analogous molecular complexes in higher organisms transduce mechanical signals. To address this question, we selected mechanoreceptors of the rat vibrissal follicle-sinus complex in the mystacial pad and the trigeminal ganglia for an immunocytochemical and molecular biological study. RT-PCR of poly(A+) mRNA of rat trigeminal ganglia indicated that alpha-, beta-, and gamma-ENaC and stomatin mRNA are expressed in rat trigeminal ganglia. Using immunocytochemistry, we found that alpha-, beta-, and gamma-ENaC subunits and stomatin are localized in the perikarya of the trigeminal neurons and in a minor fraction of their termination site in the vibrissal follicle-sinus complex, where longitudinal lanceolate endings are immunopositive. We conclude that alpha-, beta-, and gamma-ENaC subunits as well as the candidate interacting protein stomatin are coexpressed in a mammalian mechanoreceptor, a location consistent with a possible role in mechanotransduction.

Animals↗
PubMed2000

Early echocardiographic changes and survival following renal transplantation.

BACKGROUND: Left ventricular hypertrophy, ventricular dilatation and poor systolic function prior to renal transplantation are associated with increased mortality. However, whether the improvement in these echocardiographic indices that is reported to follow renal transplantation improves patient survival has not been investigated. METHODS: We studied 67 patients who underwent renal transplantation in our unit between 1988 and 1990 and in whom echocardiography was performed immediately prior to transplant surgery and 4 months later. Pre- and post-transplantation echocardiographic parameters were compared between the 20 patients who have since died and surviving patients and a descriptive survival analysis was performed. RESULTS: Following transplantation there was no significant change in left ventricular mass index (LVMI) or end diastolic diameter (EDD). End systolic diameter (ESD) improved in 60% of patients (median 3.3 vs 3. 7 cm; P=0.031) as did fractional shortening in 67% (0.33 vs 0.29; P=0.001). However, improvement was not associated with survival benefits. We also found that prior to transplantation, fractional shortening, ESD and EDD were strongly associated with outcome; this was no longer the case following transplantation. In contrast, LVMI provided a stronger association with adverse outcome (albeit of limited statistical significance) following transplantation. CONCLUSIONS: In this Preliminary Report, we conclude that echocardiographic parameters are associated with adverse outcome in patients receiving renal replacement therapy (RRT). Different echocardiographic parameters are associated with adverse outcome before and after renal transplantation and improvement of pre-transplant abnormalities (e.g. poor LV systolic function) following transplantation does not necessarily confer survival benefits. Whether this is a genuine observation or a reflection of the interpretation of echocardiographic measurements in dialysis patients requires further investigation.

Adolescent↗
PubMed1999

Does spinal instrumentation influence the healing process of posterolateral spinal fusion? An in vivo animal model.

STUDY DESIGN: An in vivo sheep model was used to investigate the effect of spinal instrumentation on the healing process of posterolateral spinal fusion. OBJECTIVES: To examine the role of spinal instrumentation during the healing process of posterolateral fusion. SUMMARY OF BACKGROUND DATA: In long bone fractures, internal fixation improves the union rate but does not accelerate the healing process. Spinal instrumentation also improves the fusion rate in spinal arthrodesis. However, it remains unclear whether the use of spinal instrumentation expedites the healing process of spinal fusion. METHODS: Sixteen sheep underwent posterolateral spinal arthrodeses at L2-L3 and L4-L5 using equal amounts of autologous bone. One of those segments was selected randomly to be augmented with transpedicular screw fixation (Texas Scottish Rite Hospital spinal system). The animals were killed at 8 weeks or 16 weeks after surgery. Fusion status was evaluated by biomechanical testing, manual palpation, plain radiography, computed tomography, and histology. RESULTS: Instrumented fusion segments demonstrated significantly higher stiffness than did uninstrumented fusions at 8 weeks after surgery. Radiographic assessment and manual palpation showed that the use of spinal instrumentation improved the fusion rate at 8 weeks (47% versus 38% in radiographs, 86% versus 57% in manual palpation). Histologically, the instrumented fusions consisted of more woven bone than the uninstrumented fusions at 8 weeks after surgery. The 16-week-old fusion mass was diagnosed biomechanically, radiographically, and histologically as solid, regardless of pedicle screw augmentation. CONCLUSION: The current study's results demonstrated that spinal instrumentation creates a stable mechanical environment to enhance the early bone healing of spinal fusion.

Animals↗
PubMed1999

Geographical distribution of variant CJD in the UK (excluding Northern Ireland).

BACKGROUND: The agent that causes variant Creutzfeldt-Jakob disease (variant CJD) is indistinguishable from the causative agent of bovine spongiform encephalopathy (BSE). The transmission route by which human beings are infected has not been established. One hypothesis is that cases of variant CJD have resulted from exposure to the BSE agent via rendering plants involved in the production of meat and bone meal, the main vehicle of the BSE epidemic. METHODS: We identified cases of variant CJD through the National CJD Surveillance Unit, and obtained lifetime residential histories of cases by interviewing a relative. The addresses of all rendering plants in the UK (excluding Northern Ireland) in production in 1988 were available from a survey done in that year. We calculated the distance between each case's place of residence on Jan 1, 1988, and the nearest rendering plant from postcode data, and used data from the 1991 UK census to estimate the population living within various distances of rendering plants. We compared the observed number of cases of variant CJD within a particular distance of a rendering plant with the number expected if there is no association between residential proximity to a rendering plant and the risk of developing variant CJD. FINDINGS: Up to Aug 31, 1998, 26 cases of variant CJD with onset in the UK (Northern Ireland not included) had been identified. The observed and expected numbers of variant CJD cases living within a specified distance of any rendering plant up to 50 km were almost the same. Two plants in the county of Kent each had four cases within 50 km in 1988, significantly more cases than expected (plant A, 1.04 expected; plant B, 0.74 expected). Multiple significance tests were done, so some tests would be expected to appear significant by chance alone. Computer simulations suggested that the observation of four cases of variant CJD living in an area with a population of 1.5 million (the size of Kent) is not unexpected. INTERPRETATION: There is no evidence that people with variant CJD tended to live closer than the population as a whole to rendering plants in the 1980s. The reported cluster of variant CJD cases in Kent is most probably a chance finding.

Abattoirs↗
PubMed1999

Inactivation of ataxia telangiectasia mutated gene in B-cell chronic lymphocytic leukaemia.

BACKGROUND: Patients with the inherited disorder ataxia telangiectasia (A-T) have an increased susceptibility to lymphoid malignancies. In these patients mutations affect both alleles of the A-T gene (ATM). We have looked for mutations in the ATM gene in sporadic cases of B-cell chronic lymphocytic leukaemia (B-CLL). METHODS: 32 cases of B-CLL were analysed by restriction endonuclease fingerprinting to detect mutations within ATM. In six of the cases in which mutations were detected in tumour samples, germline DNA was screened to assess ATM carrier status. The samples in 20 cases were also studied by western blot for abnormal expression of ATM protein. FINDINGS: Expression of the ATM protein was impaired in eight (40%) of the 20 tumours analysed, being absent in three and decreased in five. Mutations within ATM were detected in six (18%) of the 32 patients. These point mutations, deletions, and one insertion were distributed across the coding sequence of ATM. Germline mutations, which indicate ATM carrier status, were found in two of these six patients compared with a frequency within the general population of below 1 in 200. INTERPRETATION: Abnormal expression of ATM protein is a frequent finding in B-CLL. Although the precise function of this protein is unknown, it is thought to have a role in programmed cell death, a deficiency of which would fit with the characteristic phenotype of prolonged cell survival seen in B-CLL tumour cells. Our results also suggest that carriers of ATM mutations may be at a particular risk for the development of B-CLL and this may partly explain the known genetic susceptibility to this disease.

Alleles↗
PubMed1999

Adenosine and pediatric supraventricular tachycardia in the emergency department: multicenter study and review.

STUDY OBJECTIVE: To determine the frequency of successful cardioversion and the adverse effects of adenosine treatment in pediatric emergency department patients with supraventricular tachycardia (SVT). METHODS: This was a multicenter descriptive study with both prospective (convenience sample) and retrospective (chart review) patient entry. The setting was 7 urban pediatric EDs with a yearly census range of 22,000 to 70,000 visits. Pediatric patients 18 years of age and younger who received intravenous adenosine for presumed SVT were eligible. RESULTS: Six investigators from 7 pediatric EDs entered 82 patients with 98 presumed SVT episodes (52 prospective and 46 retrospective) into the study. Twenty-five episodes occurred in children younger than 1 year of age. Eight patients had congenital heart disease, 59 had a history of SVT, 43 were taking cardiac medications (digoxin in 27), 13 had a history of asthma, and 25 presented in compensated cardiogenic shock. A total of 193 intravenous doses of adenosine were administered; doses were classified as low (<.1 mg/kg [n=18]), medium (.1 to <.2 mg/kg [n=116]), or high (>/=.2 mg/kg [n=59]). The dose range was.03 to.5 mg/kg, and only 2 doses were higher than.3 mg/kg. A total of 95 patient-events were determined to be SVT, all but 5 of which were atrioventricular (AV) node-dependent; 3 events were ventricular tachycardia. The overall cardioversion success rate of adenosine was 72% (71/98), and that for AV node-dependent SVT was 79% (71/90). Cardioversion was successful for 4 patient-events at a low dose, 44 at a medium dose, and 23 at a high dose of adenosine. Adverse effects occurred in 22 patients, and no patient had bronchospasm or hemodynamically significant arrhythmia. CONCLUSION: Intravenous administration of adenosine led to successful cardioversion in 72% of pediatric ED patient-events that were presumed to be SVT. A dose range of.1 to.3 mg/kg was found to be most effective. Adenosine was not associated with significant adverse effects.

Adenosine↗
PubMed1999

Hereditary dehydrated and overhydrated stomatocytosis: recent advances.

The hereditary stomatocytoses and allied disorders are genetic defects of the erythrocyte membrane that result in abnormal permeability to the univalent cations Na+ and K+. Although rare, these conditions reflect abnormalities in physiologic mechanisms that are of paramount interest. All cases (as defined here) show increased plasma membrane permeability to Na+ and K+ and, to a greater or lesser degree, stomatocytic morphology. Dehydrated hereditary stomatocytosis, the most common form of hereditary stomatocytosis, is more heterogeneous than previously thought and includes kindreds showing pseudohyperkalemia or perinatal edema, or both. The gene responsible for both dehydrated hereditary stomatocytosis and familial pseudohyperkalemia, a nonhemolytic variant that presents with high plasma K+ levels, has been mapped to 16q23-qter. The cause of overhydrated hereditary stomatocytosis remains elusive despite the manifest lack of the enigmatic protein stomatin in the erythrocyte membrane. In all cases where splenectomy has been performed, this procedure has conferred a marked risk for thrombosis in adult life. This finding stresses the importance of diagnostic distinction between these conditions and hereditary spherocytosis.

Adult↗