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Biomedical subjects

Andrew Carr

Publications and source records attributed to Andrew Carr.

At least 55 records · Page 3Linked to original sources
PubMed2004

Microsatellite association mapping of a primary osteoarthritis susceptibility locus on chromosome 6p12.3-q13.

OBJECTIVE: To test a high density of microsatellite markers from within a primary osteoarthritis (OA) locus on chromosome 6 for association with OA as a means of narrowing and focusing our search for the susceptibility gene. METHODS: One hundred forty-six families, each with 2 or more women concordant for primary OA (ascertained by total hip replacement), were genotyped for 36 microsatellite markers from within a narrow interval at 6p12.3-q13 which we had previously shown to be linked to OA. Each marker was tested for linkage and for association, the latter by means of the transmission disequilibrium test and by a case-control analysis. RESULTS: The highest 2-point logarithm of odds (LOD) score was 4.8, with 11 markers having LOD scores > or =2.0. Several markers demonstrated evidence of association, in particular, a cluster of markers positioned within or near the functional candidate gene BMP5. CONCLUSION: Our linkage data reinforce the evidence of a major susceptibility locus on chromosome 6. We had previously failed to detect an association with BMP5 using gene-based single-nucleotide polymorphisms. The association data reported here prompt us to speculate that the chromosome 6 susceptibility may be coded for by cis-acting polymorphism in the regulatory elements of this gene, rather than by variation in its protein coding sequence.

Arthroplasty, Replacement, Hip↗
PubMed2003

An objective lipodystrophy severity grading scale derived from the lipodystrophy case definition score.

HIV lipodystrophy can be objectively diagnosed using a score derived from the 10 parameters in the HIV lipodystrophy case definition (LDCD). Lipodystrophy severity remains subjectively determined by physical examination and patient assessment. Regional dual-energy x-ray absorptiometry (DEXA) and single-slice abdominal computed tomography (CT) scanning are objective but are gender-dependent body composition measures. The LDCD score may provide a means of generating an objective and lipodystrophy grading/severity scale applicable to both men and women. Total and regional clinical lipodystrophy severity scores (generated using the HIV Outpatient Study [HOPS] scale: nil (0), mild (1), moderate (2), and severe (3) lipoatrophy or fat accumulation in 8 body regions) were correlated with objective measures of LD (LDCD score, DEXA, abdominal CT) and metabolic (lipid, glycemic, acid-base) parameters known to correlate significantly with lipodystrophy severity. Analysis was based on 417 lipodystrophic adults and 371 controls recruited to the HIV LDCD study. Correlation coefficients were used to compare physician and patient assessments (rPhysician, rPatient) with objective LD measures and metabolic parameters. The strongest objective correlate of total clinical lipodystrophy severity was the LDCD score (rPhysician = 0.641 [95% CI, 0.584-0.698]; rPatient = 0.620 [95% CI, 0.561-0.678]), whereas the strongest imaging correlate (trunk:limb fat ratio on DEXA) was significantly lower (rPhysician = 0.483 [95% CI, 0.420-0.546]; rPatient = 0.475 [95% CI, 0.412-0.538]; P < 0.001). The LDCD score also yielded significantly greater correlations with 7 of the 8 metabolic parameters than did clinical lipodystrophy severity scores. Based on quartiles of physician-rated severity, the LDCD scores were categorized to allow for rating of lipodystrophy as absent (LDCD score < 0), grade 1 (0-9.9), grade 2 (10-14.9), grade 3 (15-22.9), and grade 4 (>or=23). In conclusion, the LDCD score is the best objective measure of lipodystrophy severity and, in contrast to DEXA and CT, it is also gender independent. Subjective assessment of lipodystrophy severity could possibly be abandoned in cross-sectional studies. The LDCD score and its derived lipodystrophy grading scale merit prospective evaluation.

Adult↗
PubMed2003

Application of multiplexed capillary electrophoresis with laser-induced fluorescence (MCE-LIF) detection for the rapid measurement of endogenous extracellular signal-regulated protein kinase (ERK) levels in cell extracts.

Multiplexed (96-lane) capillary electrophoresis with laser-induced fluorescence (MCE-LIF) detection was used for the rapid analysis of extracellular signal-regulated protein kinase (ERK) levels from in vitro cell extracts. The levels of ERK enzyme in cell extracts were determined by monitoring the conversion of a fluorescent-labeled peptide substrate to a phosphorylated fluorescent-labeled peptide product using MCE-LIF. The incorporation of a fluorescent internal standard was found to improve the precision of the analysis. The enzyme assay conditions including substrate concentration, reaction time and enzyme linear range were rapidly optimized using the MCE-LIF approach for both direct and immunoprecipitation-based ERK assays. The levels of ERK from in vitro cell extracts stimulated with angiopoietin 1 (Ang1*) were determined using the MCE-LIF approach. The advantages of MCE-LIF for developing and applying enzyme assays, as well as the figures of merit for the direct and immunoprecipitation ERK assays, are discussed.

Cell Extracts↗
PubMed2003

Prospective evaluation of the effects of antiretroviral therapy on body composition in HIV-1-infected men starting therapy.

OBJECTIVE: Little prospective data are published on the natural history of HIV-associated lipodystrophy (HIVLD) in individuals beginning their first antiretroviral regimen. To investigate this a study was designed to explore changes in body composition occurring with antiretroviral therapy. STUDY DESIGN: A non-randomized, prospective, exploratory study of 40, HIV-infected men, naive to treatment, beginning antiretroviral therapy. Regular assessments of body composition, and metabolic and immunological parameters were performed. RESULTS: Mean follow-up was 96 (SD 45) weeks of therapy. There were increases in limb fat, central abdominal fat and lean mass over the initial 24 weeks of therapy followed by a selective, progressive loss of limb fat from week 24. There was a median 13.6% [interquartile range (IQR), 0.9-26.3] loss of limb fat per year from week 24 onwards. Treatment with stavudine, higher baseline HIV RNA, higher baseline 'T' score and lower week 24 lean mass were associated with higher rate of limb fat loss from week 24. In multivariate analysis, treatment with stavudine was the strongest independent factor associated with rate of limb fat loss (P = 0.05). Hypercholesterolaemia developed early in treatment, whereas hypertriglyceridaemia, hyperinsulinaemia and decreased bone mineral density developed later. The largest changes in CD4 cell counts and HIV viral load, seen early into treatment, were associated with gain rather than loss of fat. CONCLUSIONS: This is the first prospective study demonstrating that treatment with antiretrovirals results in progressive, selective loss of limb fat. Loss of limb fat occurred after the period of most intense immune restoration, making an immune aetiology unlikely.

Adipose Tissue↗
PubMed2003

Brief report: incubation and duration of specific symptoms at acute retroviral syndrome as independent predictors of progression to AIDS.

The incubation and duration of acute retroviral syndrome (ARS) have been associated with progression to AIDS. We assessed the independent effect of specific symptoms at ARS on the rate of progression to AIDS or a CD4+ count of <200 cells/mm3 in 70 ARS patients. The incubation and duration of ARS features were stratified on their medians. The Cox regression model was used to calculate the adjusted relative hazard (ARH) of progression. Short incubations of fever (ARH = 5.8, P = 0.004), fatigue (ARH = 2.7, P = 0.06), and myalgia (ARH = 3.8, P = 0.04) were associated with faster disease progression, as was the long duration of most symptoms (ARH range: 3.1-8.1, P < 0.03 to P < 0.001). Pathogenetic mechanisms involved in the incubation of ARS features may be associated with progression to AIDS.

Acute Disease↗
PubMed2003

Lactic acidemia in infection with human immunodeficiency virus.

Lactic acidosis in patients infected with the human immunodeficiency virus was initially identified as a rare complication of therapy with nucleoside analog reverse transcriptase inhibitors (NRTIs). The only patient group that appears to be at greater risk is pregnant women. More recently, milder elevations in lactate (i.e., lactic acidemia or hyperlactatemia) have been found to be more common and to be associated with numerous illnesses. Mild asymptomatic lactic acidemia is common, but it appears to lead to more severe illness only rarely. This suggests that routine measurement of plasma lactate should be limited to patients with previous acidemia who reinitiate NRTI therapy and to pregnant women. For symptomatic lactic acidemia (generally >5 mmol/L), NRTIs and other antiretroviral therapy should be ceased. Currently, asymptomatic lactic acidemia should not be treated and should not lead to a change in antiretroviral therapy.

Acidosis, Lactic↗
PubMed2003

False negative HIV-1 proviral DNA polymerase chain reaction in a patient with primary infection acquired in Thailand.

BACKGROUND: Qualitative HIV-1 proviral DNA PCR tests have three main diagnostic applications. These include direct detection of viral sequences in the pre-seroconversion window period which may be positive up to 8 days prior to the development of HIV specific antibodies; resolution of indeterminate HIV serological tests and in the diagnosis of neonates born to seropositive mothers where maternal antibodies may be detectable for up to 15 months past partum. METHODS: A total of three serial specimens from a single patient following symptomatic primary HIV-1 infection were assessed by commercially available serological assays for antibodies to HIV and HIV-1 antigen and nucleic acid amplification assays for proviral DNA (Amplicor HIV-1 test, Roche Molecular Systems, CA, USA) and RNA (HIV MONITOR ver1.5, Roche Molecular Systems) according to manufacturers recommendations. A subsequent modified PCR protocol for HIV proviral DNA was performed which included modified primers (SK145/SKCC1B) and altered thermal cycling parameters. RESULTS: We describe a case of HIV infection acquired in Thailand by heterosexual transmission, where a commercially available HIV proviral DNA PCR assay remained negative despite a typical evolving serological profile consistent with seroconversion. CONCLUSION: These data support the use of HIV DNA PCR tests only as a second line supplemental test to licensed standard HIV diagnostic testing strategies, and should be used with care in cases where non-B subtype infection is a possibility.

AIDS Serodiagnosis↗
PubMed2003

Chemokine receptor genotype and response to interleukin-2 therapy in HIV-1-infected individuals.

Interleukin-2 therapy is an immune-based treatment for HIV-1-infected individuals with declining CD4(+) T cell counts. Intravenous IL-2 produces an elevation of circulating CD4(+) T cells, but with a varying degree of effectiveness in individual patients. IL-2 is also known to increase the expression of chemokine receptors, coreceptors for HIV-1. Allelic variation in chemokine receptor genes can markedly affect the course of HIV disease; consequently, we analyzed CCR5 and CCR2B genotypes among a cohort of HIV-1-infected individuals that received IL-2 therapy. DNA was extracted from treated individuals and genotyping was performed using PCR followed by allele-specific detection or cleavage of the amplified product. Samples from 47 trial participants (25 CIV-IL-2 group; 22 placebo group) were analyzed for CCR5 and CCR2B genotype. We report that CCR5 Delta 32 heterozygous individuals had a greater CD4(+) T cell response to continuous intravenous IL-2 (CIV-IL-2) treatment than those homozygous for the wild-type allele (median = 427 vs 237 cells/mm(3); P = 0.03). This study highlights the importance of interactions between IL-2 and CCR5; at the clinical level, it argues for assessment of chemokine receptor genotype in IL-2 and perhaps other immune-based therapy trials.

Adolescent↗
PubMed2003

Greater reversal of CD4+ cell abnormalities and viral load reduction after initiation of antiretroviral therapy with zidovudine, lamivudine, and nelfinavir before complete HIV type 1 seroconversion.

In a prospective open-label study, 41 male subjects received nelfinavir, zidovudine, and lamivudine stratified as either: early stage (ES; negative/indeterminate Western blot; n = 19) or late stage (LS; positive Western blot; n = 22) primary HIV-1 infection. Despite higher median baseline HIV-1 RNA levels and lower CD4(+) cell numbers in the ES subjects, a significantly greater decline in viral load (-3.46 vs. -2.83 log(10) copies/ml; p = 0.023) and increase in CD4(+) cell number (+85 vs. +41 cells/month increase, p = 0.01) were observed over the first 3 months of therapy such that both groups had comparable results at 1 year. The proportion with HIV-1 RNA < 50 copies/mL at 1 year was similar (9 of 19 ES subjects and 11 of 22 LS subjects by intention-to-treat analysis). Memory CD4(+) cell numbers, and activated CD4(+) percentages, were also significantly improved in ES subjects. Despite poorer prognostic markers at baseline ES subjects achieved responses similar to those of LS subjects after 1 year of treatment.

Anti-HIV Agents↗
PubMed2003

Cardiovascular risk factors in HIV-infected patients.

Highly active antiretroviral therapy (HAART) commonly leads to persistent dyslipidemia and insulin resistance that appear likely to confer an increased incidence of cardiovascular disease (CVD). Both protease inhibitors (PIs) and, to a lesser extent, nucleoside analog reverse transcriptase inhibitors (NRTIs) appear to be involved, through direct metabolic effects of PIs and an indirect effect of PI and NRTI-related lipodystrophy. Several studies have found a variable relationship between CVD incidence and HAART, but these studies were not prospective and may not have been adequately powered. A variety of treatment strategies have been evaluated for dyslipidemia and insulin resistance, including lifestyle changes, drugs, and antiretroviral switching, but their relative safety, efficacy and roles are unclear. Although treatment of dyslipidemia and insulin resistance is commonly recommended, it should be remembered that such therapy is likely to be of greater benefit in those with a greater perceived CVD risk (i.e., multiple risk factors) and the lowest risk of HIV disease progression.

Adult↗
PubMed2003

HIV lipodystrophy: risk factors, pathogenesis, diagnosis and management.

HIV lipodystrophy is a heterogeneous syndrome, which has yet to be objectively defined, comprising peripheral lipoatrophy, central fat accumulation and lipomata, along with hyperlipidaemia, insulin resistance and lactic acidaemia. Both nucleoside analogues and protease inhibitors are involved, but there are also host factors that probably place some patients at greater risk. The pathogenesis is increasingly understood, with evidence of interference of several regulatory proteins such as sterol regulatory enhancer binding protein-1, the proteasome, mitochondrial DNA polymerase gamma and GLUT-4. Along with the issues of cosmesis and stigmatization, a principal clinical concern that arises with lipodystrophy is a possible increased risk of accelerated atherosclerosis. A variety of therapeutic interventions, designed to limit these risks, are under evaluation, but none is conclusively shown to be of value.

HIV-Associated Lipodystrophy Syndrome↗
PubMed2003

Practical applications of the HIV lipodystrophy case definition.

Diagnosis of HIV-associated lipodystrophy (LD) has been limited by the absence of a validated case definition and the frequent lack of objective body composition measures. An international, objective, case-control study recruited HIV-infected, adult outpatients free of active AIDS, and a case definition model for LD was developed. The relative merits and limitations of this definition as a practical tool for the long-term monitoring of a patient's LD status over the duration of clinical treatment are discussed.

Adult↗
PubMed2003

HIV lipodystrophy case definition using artificial neural network modelling.

OBJECTIVE: A case definition of HIV lipodystrophy has recently been developed from a combination of clinical, metabolic and imaging/body composition variables using logistic regression methods. We aimed to evaluate whether artificial neural networks could improve the diagnostic accuracy. METHODS: The database of the case-control Lipodystrophy Case Definition Study was split into 504 subjects (265 with and 239 without lipodystrophy) used for training and 284 independent subjects (152 with and 132 without lipodystrophy) used for validation. Back-propagation neural networks with one or two middle layers were trained and validated. Results were compared against logistic regression models using the same information. RESULTS: Neural networks using clinical variables only (41 items) achieved consistently superior performance than logistic regression in terms of specificity, overall accuracy and area under the ROC curve. Their average sensitivity and specificity were 72.4 and 71.2%, as compared with 73.0 and 62.9% for logistic regression, respectively (area under the ROC curve, 0.784 vs 0.748). The discriminating performance of the neural networks was largely unaffected when built excluding 13 parameters that patients may not have readily available. The average sensitivity and specificity of the neural networks remained the same when metabolic variables were also considered (total 60 items) without a clear advantage against logistic regression (overall accuracy 71.8%). The performance of networks considering also body composition variables was similar to that of logistic regression (overall accuracy 78.5% for both). CONCLUSIONS: Neural networks may offer a means to improve the discriminating performance for HIV lipodystrophy, when only clinical data are available and a rapid approximate diagnostic decision is needed. In this context, information on metabolic parameters is apparently not helpful in improving the diagnosis of HIV lipodystrophy, unless imaging and body composition studies are also obtained.

Absorptiometry, Photon↗