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Ian James

Publications and source records attributed to Ian James.

26 records · Page 2Linked to original sources
PubMed2004

Predisposition to abacavir hypersensitivity conferred by HLA-B*5701 and a haplotypic Hsp70-Hom variant.

Susceptibility to a clinically significant drug hypersensitivity syndrome associated with abacavir use seems to have a strong genetic component. We have previously shown that the presence of HLA-B*5701 strongly predicts abacavir hypersensitivity and have identified a potential susceptibility locus within a 300-kb region between the MEGT1 and C4A6 loci in the central MHC. We now report the results of fine recombinant genetic mapping in an expanded patient population of 248 consecutive, fully ascertained, abacavir-exposed individuals in the Western Australian HIV Cohort Study, in which 18 cases of definite abacavir hypersensitivity (7.3%) and 230 tolerant controls were identified. Haplotype mapping within patients with allelic markers of the 57.1 ancestral haplotype suggests a susceptibility locus within the 14-kb Hsp70 gene cluster. HLA-B*5701 was present in 94.4% of hypersensitive cases compared with 1.7% of controls (odds ratio, 960; P < 0.00001). A haplotypic nonsynonymous polymorphism of Hsp70-Hom (HspA1L, resulting from the substitution of residue M493T in the peptide-binding subunit) was found in combination with HLA-B*5701 in 94.4% of hypersensitive cases and 0.4% of controls (odds ratio, 3,893; P < 0.00001). Individuals with abacavir hypersensitivity demonstrated increased monocyte tumor necrosis factor expression in response to ex vivo abacavir stimulation, which was abrogated with CD8(+) T cell depletion. These data indicate that the concurrence of HLA-B*5701 and Hsp70-Hom M493T alleles is necessary for the development of abacavir hypersensitivity, which is likely to be mediated by an HLA-B*5701-restricted immune response to abacavir.

Chromosome Mapping↗
PubMed2004

Alleles of the IL12B 3'UTR associate with late onset of type 1 diabetes.

Carriage of a polymorphism in the 3'untranslated region of the IL12B gene encoding IL-12p40 was investigated in subjects with type 1 diabetes mellitus stratified by age at diagnosis (n = 648) and compared with a population-based control cohort (n = 246) residing in Western Australia. DNA samples were genotyped by polymerase chain reaction-restriction fragment length polymorphism or pyrosequencing. The C allele was more common in patients diagnosed after age 16 years than in controls (29% vs 17%, OR = 2.0, 95% CI = 1.4-2.7, p = 0.00003) or than in patients diagnosed when younger age 16 years (29% vs 22%, OR = 1.4, 95% CI = 1.1-1.9, p = 0.01). This reflected increases in homozygous and heterozygous carriage of the C allele. Heterozygosity was associated with a delayed disease in the late-onset diabetics (p = 0.005; Student's t-test). The effects of IL12B 3'untranslated region alleles on type 1 diabetes mellitus may reflect different levels of p40 available to form p40 homodimer, IL-12 (p35p40), and IL-23 (p19p40).

3' Untranslated Regions↗
PubMed2003

Stabilization versus inhibition of TAFIa by competitive inhibitors in vitro.

Two competitive inhibitors of TAFIa (activated thrombin-activable fibrinolysis inhibitor), 2-guanidinoethylmercaptosuccinic acid and potato tuber carboxypeptidase inhibitor, variably affect fibrinolysis of clotted human plasma. Depending on their concentration, the inhibitors shortened, prolonged, or had no effect on lysis in vitro. The inhibitor-induced effects were both tissue-type plasminogen activator (tPA) and TAFIa concentration-dependent. Inhibitor-dependent prolongation was favored at lower tPA concentrations. The magnitude of the prolongation increased with TAFIa concentration, and the maximal prolongation observed at each TAFIa concentration increased saturably with respect to TAFIa. A theoretical maximal prolongation of 20-fold was derived from a plot of the maximum prolongation versus TAFIa. This represents, for the first time, a measurement of the maximal antifibrinolytic potential of TAFIa in vitro. Because TAFIa spontaneously decays, the stabilization of TAFIa was investigated as a mechanism explaining the inhibitor-dependent prolongation of lysis. Both inhibitors stabilized TAFIa in a concentration-dependent, non-saturable manner. Although their KI values differed by three orders of magnitude, TAFIa was identically stabilized when the fraction of inhibitor-bound TAFIa was the same. The data fit a model whereby only free TAFIa decays. Therefore, the variable effects of competitive inhibitors of TAFIa on fibrinolysis can be rationalized in terms of free TAFIa and lysis time relative to the half-life of TAFIa.

Binding, Competitive↗
PubMed2003

Contribution of nucleoside-analogue reverse transcriptase inhibitor therapy to lipoatrophy from the population to the cellular level.

OBJECTIVES: It has been proposed that the contribution of nucleoside-analogue reverse transcriptase inhibitor (NRTI) therapy to subcutaneous fat wasting involves adipose tissue-specific mitochondrial DNA toxicity. We have investigated the relationships between NRTI therapy, adipocyte mitochondrial DNA content, evidence of toxicity in adipose tissue and fat wasting in Caucasian male Western Australian HIV Cohort study participants. METHODS: Longitudinal mixed effects analysis of fat wasting was undertaken in individuals receiving initial stavudine- or zidovudine-containing highly active antiretroviral measurements). Adipocyte mitochondrial DNA (mtDNA) depletion was also assessed according to current NRTI therapy in 92 subcutaneous fat biopsies from 69 HIV-positive individuals and seven healthy controls, and results were correlated with fat wasting among a subset of patients with biopsy data receiving initial stavudine- or zidovudine-containing HAART (n = 22, 103 DEXA measurements). Confocal microscopy was performed in 22 obtained after initiating/switching NRTI therapy. RESULTS: Stavudine therapy was associated with more severe adipocyte mitochondrial DNA depletion (P < 0.001) and fat wasting over time (P = 0.002) compared with zidovudine therapy in independent analyses. Among patients with concurrent biopsy and longitudinal DEXA data, fat wasting was associated with duration of NRTI therapy (P = 0.001) and adipocyte mtDNA copies/cell (P = 0.01). In this analysis, the significant association between choice of stavudine versus zidovudine and fat wasting (P = 0.03) was lost after adjustment for the effect of mtDNA depletion (P = 0.13). Confocal analysis provided direct evidence of a relationship between severity of adipose tissue toxicity and mitochondrial DNA depletion. No significant effects of HIV protease inhibitor therapy were detected in these analyses. CONCLUSIONS: Severity of subcutaneous fat wasting is primarily determined by choice of NRTI therapy (stavudine versus zidovudine) and by duration of exposure to the relevant NRTI. At the cellular level, evidence is provided that this effect manifests through NRTI-induced mitochondrial DNA depletion.

Adipocytes↗
PubMed2002

Can psychiatric liaison reduce neuroleptic use and reduce health service utilization for dementia patients residing in care facilities.

BACKGROUND: The quality of care and overuse of neuroleptic medication in care environments are major issues in the care of elderly people with dementia. METHOD: The quality of care (Dementia Care Mapping), the severity of Behavioural and Psychological Symptoms (BPSD--Neuropsychiatric Inventory), expressive language skills (Sheffield Acquired Language Disorder scale), service utilization and use of neuroleptic drugs was compared over 9 months between six care facilities receiving a psychiatric liaison service and three facilities receiving the usual clinical support, using a single blind design. RESULTS: There was a significant reduction in neuroleptic usage in the facilities receiving the liaison service (McNemar test p<0.0001), but not amongst those receiving standard clinical support (McNemar test p=0.07). There were also significantly less GP contacts (t=3.9 p=0.0001) for residents in the facilities receiving the liaison service, and a three fold reduction in psychiatric in-patient bed usage (Bed days per person 0.6 vs. 1.5). Residents in care facilities receiving the liaison service experienced significantly less deterioration in expressive language skills (t=2.2 p=0.03), but there were no significant differences in BPSD or wellbeing. CONCLUSION: A resource efficient psychiatric liaison service can reduce neuroleptic drug use and reduce some aspects of health service utilization; but a more extensive intervention is probably required to improve the overall quality of care.

Aged↗
PubMed2002

Early postoperative monocyte deactivation predicts systemic inflammation and prolonged stay in pediatric cardiac intensive care.

OBJECTIVE: Sepsis and systemic inflammatory response syndrome (SIRS) are major causes of morbidity and mortality after cardiopulmonary bypass. Attempts to suppress proinflammatory mediators have failed to improve outcomes in sepsis or in patients undergoing cardiopulmonary bypass. Recent work in adult patients has suggested that the balance between pro- and anti-inflammatory mediators is more important than the level of proinflammatory response alone. This balance may be reflected by the expression of monocyte human lymphocyte antigen (HLA)-DR, with low concentrations indicating an excess of anti-inflammatory stimuli and relative immunodeficiency. We investigated the relationship between monocyte HLA-DR expression and the subsequent development of sepsis/SIRS in children undergoing cardiopulmonary bypass. DESIGN: A prospective, observational, clinical study. SETTING: A tertiary pediatric cardiac center. PATIENTS: Eighty-two infants and children undergoing elective cardiac surgery between March and December 1999. MEASUREMENTS AND MAIN RESULTS: Monocyte HLA-DR expression was assessed before and after surgery and was found to be related to the length of hospital stay and the development of complications including sepsis/SIRS. The inflammatory insult of cardiopulmonary bypass decreased monocyte HLA-DR expression in all children. Lowest concentrations were seen within 72 hrs of surgery and were significantly lower in cases that subsequently required prolonged intensive care support (p <.0001, Mann-Whitney). HLA-DR expression on <60% of circulating monocytes was associated with a greatly increased risk of later (minimum 4 days) development of sepsis/SIRS (odds ratio, 12.9; 95% confidence interval, 3.4-47.5). Low HLA-DR was an independent predictor for the development of sepsis/SIRS after correction for age, bypass time, complexity of surgery, Paediatric Index of Mortality, and surgeon on multiple logistic regression analysis. CONCLUSIONS: Patients with decreased HLA-DR in the early postoperative period represent a subpopulation at greatly increased risk of later sepsis/SIRS. Such patients may benefit from strategies aimed to reduce this risk.

Adolescent↗