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Biomedical subjects

P M George

Publications and source records attributed to P M George.

At least 19 recordsLinked to original sources
PubMed2006

Thyroid hormone resistance: the role of mutational analysis.

The finding of increased thyroxine (T4) and tri-iodothyronine (T3) levels in a patient with normal or increased thyroid-stimulating hormone is unexpected and presents a differential diagnosis between a thyroid-stimulating hormone-secreting pituitary adenoma, generalized resistance to thyroid hormone (RTH) and laboratory artefact. Without careful clinical and biochemical evaluation, errors may occur in patient diagnosis and treatment. In the case of RTH, mutation of the thyroid hormone receptor beta gene results in generalized tissue resistance to thyroid hormone. As the pituitary gland shares in this tissue resistance, euthyroidism with a normal thyroid-stimulating hormone is usually maintained by increased thyroid hormones. To date, we have identified eight pedigrees in New Zealand with mutations in the thyroid hormone receptor beta gene, including two novel mutations. Mutational analysis of the thyroid hormone receptor beta gene allows definitive diagnosis of RTH, potentially avoiding the need for protracted and expensive pituitary function testing and imaging. Mutational analysis also enables family screening and may help to avoid potential misdiagnosis and inappropriate treatment.

DNA Mutational Analysis↗
PubMed2006

A highly informative, multiplexed assay for the indirect detection of hemophilia A using five-linked microsatellites.

BACKGROUND: Hemophilia A is a severe bleeding disorder caused by almost 1000 different known mutations in the F8C gene. Direct mutation analysis is sometimes difficult for this disorder. When a mutation cannot be found, linkage analysis can be used for prenatal and carrier diagnosis. AIM: To develop a rapid and effective system for carrier detection and prenatal diagnosis of hemophilia A based on a single-multiplexed polymerase chain reaction (PCR) reaction utilizing five microsatellite markers. PATIENTS AND METHODS: Two intronic microsatellites and three other markers flanking the factor VIII gene were ascertained, and primers were designed for multiplex PCR amplification. A kindred with Hemophilia A was tested for linkage using the panel of primers, and informativity in the general population was ascertained by testing 50 unrelated females. RESULTS: Co-amplification of all microsatellites was optimized using DNA extracted by standard methods. Rapid detection and sizing of products were carried out using an automated DNA sequencer. The combined microsatellite panel was informative in each of the kindreds tested, and in 100% of the 50 unrelated females (95% CI 94.2-100%). CONCLUSIONS: This method enables the indirect detection of hemophilia A for patients in whom mutations cannot be found, facilitating carrier testing and prenatal analysis. It is rapid and straightforward compared with many other published protocols, and offers a high degree of informativity.

Base Sequence↗
PubMed2006

Urinary VMA, dopamine and the likelihood of neuroblastoma: a preferred way of reporting laboratory results?

BACKGROUND: Neuroblastoma patients may be classified as normal or abnormal depending on reference interval and decision points for urine catecholamine metabolites. We therefore evaluated the utility of positive likelihood ratios (LR+) based on data from patients in whom the diagnosis was suspected. METHODS: Urine samples from 249 patients (122 male, 127 female) suspected of neuroblastoma were assayed for VMA by spectrophotometry and dopamine by HPLC. Ratios of VMA to creatinine (VMA/Cr) and dopamine to creatinine (DA/Cr) were calculated and age-related median scores derived relative to patients without neuroblastoma. Receiver operator characteristic (ROC) curve analysis was undertaken for the ability of median scores to identify neuroblastoma. RESULTS: Of the 249 patients, there were 20 confirmed cases of neuroblastoma, with ages ranging from 0 (congenital tumour) to 8.4 years. From ROC curves, VMA/Cr was found to have an area under the curve 0.96 (95% confidence interval [CI] 0.92-0.98) compared with 0.72 (95% CI 0.66-0.77) for DA/Cr, P=0.001. At the optimal decision point for VMA/Cr, LR+ was 7.2, identifying cases with a sensitivity of 95% and a specificity of 86%, and comparing favourably with published intervals. CONCLUSIONS: VMA/Cr is more accurate than DA/Cr for the diagnosis of neuroblastoma. Reporting LR+ may also be more informative than using reference intervals and decision points.

Catecholamines↗
PubMed2005

Thiopurine methyltransferase and 6-thioguanine nucleotide measurement: early experience of use in clinical practice.

BACKGROUND: Azathioprine and 6-mercaptopurine (6-MP) are well established for the treatment of inflammatory bowel disease (IBD). Assessing thiopurine methyltransferase (TPMT) status has been recommended to reduce the risk of serious toxicity. Measuring red blood cell (RBC) 6-thioguanine nucleotide (6-TGN) concentrations has been recommended for dose adjustment. AIM: To describe the results of measuring TPMT activity and genotype, and 6-TGN concentration in New Zealand. METHODS: Canterbury Health Laboratories provided these analyses for New Zealand. Those with low TPMT activity also underwent genotyping. All results were collated and analysed descriptively. 6-TGN concentrations were correlated with the dose of thiopurine when known. RESULTS: TPMT enzyme activity (range 1-22 U/mL) from 574 patients showed a trimodal distribution. Genotyping results matched this distribution with only mild overlap between (*1/*1) homozygote and (*1/*3) heterozygote groups. One patient without TPMT measurement before therapy had life-threatening neutropenia and was later found to have (*3/*3) genotype. TPMT analysis probably prevented two further such cases. Of 884 6-TGN concentrations (range 0-1434 pmol/10(8) RBC), 41, 39 and 20% were within, below, and above the therapeutic range of 235-450 pmol/10(8) RBC, respectively. Leucopenia was seen in some patients with high 6-TGN. 6-MMP concentrations in 177 patients with low 6-TGN suggested non-compliance in 31, underdosing in 130, and preferential metabolism of 6-MP to 6-methylmercaptopurine in 16. There was poor correlation between azathioprine dose and 6-TGN concentration (r(2) = 0.002), supporting 6-TGN monitoring. CONCLUSIONS: Measurement of TPMT enzyme activity and 6-TGN concentration has been well-integrated into clinical practice. These tests should reduce the risk of toxicity and improve efficacy with thiopurines in patients with IBD.

Azathioprine↗
PubMed2005

Screening for Type 2 diabetes in the accident and emergency department.

AIM: To assess the proportion of patients, aged 40 years and over, attending an inner city accident and emergency department that have Type 2 diabetes, and the proportion previously undiagnosed, and to assess whether the identification of undiagnosed Type 2 diabetes is feasible in this setting. METHODS: Five hundred unselected people participated. All completed a demographic questionnaire regarding risk factors for diabetes. In those without known diabetes, random capillary blood glucose (CBG) was measured. If this was greater than 7.0 mmol/l, patients were asked to return for two fasting blood glucose tests. Diagnosis of diabetes was based on World Health Organization criteria. RESULTS: Of the 500 participating subjects, 73 were already known to have Type 2 diabetes. Of the remaining 427 subjects, 36 had CBG>7.0 mmol/l. All 36 returned for fasting blood tests: 13 fulfilled the diagnostic criteria for Type 2 diabetes, eight for impaired fasting glucose (IFG), and 15 had normal fasting glucose values. The prevalence of Type 2 diabetes was therefore 17.2%, including 2.6% with a new diagnosis, and 14.6% with pre-existing disease; 1.6% were found to have IFG. Body mass index was greater in those with Type 2 diabetes (previously and newly diagnosed) [27.1 (5.15) (mean+/-standard deviation)] vs. 25.8 (4.70) kg/m2; unpaired t-test P=0.0213), and those with Type 2 diabetes were more likely to be of black and minority ethnic origin (57 vs. 28%; chi2 P<0.001) and to have a first-degree family history of diabetes (45 vs. 23%; chi2 P<0.001). CONCLUSIONS: It can be estimated from this survey that, annually, this case-finding methodology could identify 539 (95% CI 249-828) people aged 40 years and over attending our accident and emergency department with previously undiagnosed Type 2 diabetes.

Adult↗
PubMed2004

The molecular mechanisms of congenital hypofibrinogenaemia.

Congenital hypofibrinogenaemia is characterized by abnormally low levels of fibrinogen and is usually caused by heterozygous mutations in the fibrinogen chain genes (alpha, beta and gamma). However, it does not usually result in a clinically significant condition unless inherited in a homozygous or compound heterozygous state, where it results in a severe bleeding disorder, afibrinogenaemia. Various protein and expression studies have improved our understanding of how mutations causing hypo- and afibrinogenaemia affect secretion of the mature fibrinogen molecule from the hepatocyte. Some mutations can perturb chain assembly as in the gamma153 Cys-->Arg case, while others such as the Bbeta Leu-->Arg and the Bbeta414 Gly-->Ser mutations allow intracellular hexamer assembly but inhibit protein secretion. An interesting group of mutations, such as gamma284 Gly-->Arg and gamma375 Arg-->Trp, not only cause hypofibrinogenaemia but are also associated with liver disease. The nonexpression of these variant chains in plasma fibrinogen is due to retention in the endoplasmic reticulum, which in turn leads to hypofibrinogenaemia.

Afibrinogenemia↗
PubMed2004

Genetic screening of patients with familial hypercholesterolaemia (FH): a New Zealand perspective.

Using denaturing high performance liquid chromatography (DHPLC) to screen the LDL receptor gene of people with familial hypercholesterolaemia (FH) in Christchurch, New Zealand, we have identified mutations in 65 patients (44 different mutations, of which 15 are novel). We also test family members of probands for the mutation identified in their relative, allowing diagnosis of affected children and those without classical FH symptoms. This screening programme is helpful to clinicians and benefits FH patients and their families, and has provided us with a pool of LDL receptor variants on which to base research into this disease.

Chromatography, High Pressure Liquid↗
PubMed2004

Trigonelline is not responsible for the acute increase in plasma homocysteine following ingestion of instant coffee.

OBJECTIVE: To determine whether trigonelline contributes to the effect of coffee on homocysteine (Hcy). DESIGN AND INTERVENTIONS: This was a randomised crossover study. Subjects consumed 50 mg trigonelline, 5 g of instant coffee (approximately 50 mg trigonelline) or water, consumed as a single dose in 100 ml, with 1 week between each treatment. Blood samples were drawn fasting and hourly for 8 h. Urine samples were collected pretreatment and every 2 h for 8 h. SETTING: Christchurch Clinical Studies Trust, Christchurch, New Zealand. SUBJECTS: Eight healthy male subjects. RESULTS: Instant coffee raised plasma Hcy concentrations compared with water (P=0.019) and trigonelline (P=0.037). Plasma Hcy concentrations were not different between water and trigonelline treatments (P=0.789). The change in plasma Hcy concentration was higher (mean+/-s.e.) 4 h (0.7+/-0.2 micromol/l, P=0.006), 5 h (0.7+/-0.2 micromol/l, P=0.013) and 7 h (0.7+/-0.2 micromol/l, P=0.024) following coffee consumption. Urinary glycine betaine excretion was increased by coffee but not by trigonelline. CONCLUSION: Ingestion of instant coffee acutely elevated plasma Hcy; however, trigonelline is not responsible for this rise. SPONSORSHIP: Supported by the Health Research Council, the Canterbury Medical Foundation, the Foundation of Research, Science and Technology.

Adult↗
PubMed2004

Fibrinogen Mannheim II: a novel gamma307 His-->Tyr substitution in the gammaD domain causes hypofibrinogenemia.

BACKGROUND: In recent years it has become clear that the molecular investigation of hypofibrinogenemia provides unique insight into regions of the fibrinogen molecule that are important in molecular assembly, secretion and stability. OBJECTIVES: To investigate a case of hypofibrinogenemia at the molecular level. PATIENTS AND METHODS: The study was conducted on a 37-year-old woman from Mannheim, Germany, who had an antigenic plasma fibrinogen concentration of 0.86 g L(-1). Mutation screening was performed by DNA sequencing and the effect of the identified mutation was investigated at the protein level. RESULTS: Analysis of exon 8 of the fibrinogen gamma gene identified a heterozygous CAT-->TAT transition at codon 307. This novel His-->Tyr substitution was not detected when plasma fibrinogen was analyzed by electrospray ionization mass spectrometry. The mutation predicts a mass increase of 26 Da in the gamma chain, but purified gamma chains had a normal mass, indicating non-expression of the gamma(Tyr307) chain in plasma fibrinogen. CONCLUSIONS: This work reports a novel gamma307 His-->Tyr mutation (fibrinogen Mannheim II) that causes hypofibrinogenemia. Crystal structures show that His307 is located immediately adjacent to three residues that have been implicated in fibrin polymerization at the D:D interface. However, the histidine residue appears critical in maintaining structure of the fibrinogen gammaD domain, rather than in determining function.

Adult↗
PubMed2003

Plasma adiponectin in overweight, nondiabetic individuals with or without insulin resistance.

AIM: Adiponectin is a protein produced exclusively by adipocytes with putative insulin-sensitizing and anti-atherogenic properties. This cross-sectional study investigated the relationship between plasma adiponectin and a range of anthropometric, glycaemic, lipid and inflammatory parameters in overweight and obese subjects expressing characteristics of the metabolic syndrome. METHODS: Subjects were selected for the study from a clinical database, if they were non-diabetic, overweight [body mass index (BMI) > 25] and had features of the metabolic syndrome. The subjects were grouped according to BMI (25-30, 31-35 and >35 kg/m2) and then stratified for insulin resistance [homeostasis model assessment (HOMA) %S]. One hundred and ninety-seven patients (109 males and 88 females) were selected for the study by taking an equal number with the highest and lowest HOMA indices from each of the three BMI groups. Plasma adiponectin concentration was measured in duplicate by radioimmunoassay, and the relationship between these levels and the other parameters was investigated using correlation and multiple linear regression analyses. RESULTS: Plasma adiponectin concentration was higher in females than males (median 10.3 vs. 7.1 micro g/ml, p < 0.001) despite being matched for BMI. In both genders, adiponectin levels were inversely related to BMI, waist circumference, percentage body fat, insulin resistance and the fasting plasma concentration of leptin. A direct correlation in both sexes was found between adiponectin levels and high-density lipoprotein (HDL)-cholesterol, apolipoprotein A1 and age. Multiple linear regression analyses showed that the independent determinants of low plasma adiponectin concentrations were gender, age, BMI, insulin resistance and HDL-cholesterol. An association between reduced adiponectin and increased high-sensitivity plasma C-reactive protein concentration was observed only in female subjects and was independent of anthropometric variables. Our observation that adiponectin levels increase with age differs from the majority of other studies and may simply reflect the demographics of the population studied. CONCLUSIONS: This study shows that adiponectin is an important molecular link between obesity, insulin resistance and atherogenic lipoproteins. It is possible that plasma adiponectin concentration may be a convenient marker for identifying subjects with the metabolic syndrome who may progress to impaired glucose tolerance. Longitudinal studies are required in order to verify this clinical application of adiponectin.

Adiponectin↗
PubMed2003

Novel Aalpha chain truncation (fibrinogen Perth) resulting in low expression and impaired fibrinogen polymerization.

A young woman with a history of menorrhagia and easy bruising presented with a functional fibrinogen concentration of 1.8 mg mL(-1), a gravimetric concentration of 3.3 mg mL(-1) and a prolonged thrombin clotting time of 32 s. Both reverse phase analysis and reducing SDS-PAGE revealed a normal profile of Aalpha, Bbeta, and gamma chains. However, non-reducing gels revealed a broadened 340-kDa band, while the 305-kDa band was normal, suggesting a C-terminal truncation of the Aalpha chain. DNA sequencing of all exons and intron boundaries revealed a single heterozygous cytosine deletion at nucleotide 4841 of the Aalpha gene predicting a frameshift and the incorporation of 23 new residues (LMKLPSSTLPQLEKHSQVSSHLC) before termination after residue 517. In agreement with a predicted mass decrease of 9953 Da, the measured mass of the Aalpha(Perth) chain was 56 242 Da, while that of the normal Aalpha(A) chain was 66 189 Da. Tryptic mapping of isolated Aalpha chains revealed a new [M + 2H] ion at 607 m z(-1), corresponding to the predicted penultimate peptide LPSSTLPQLEK. The variant chain was poorly incorporated into plasma fibrinogen at a ratio of Aalpha(Perth)/Aalpha(A) of 0.15 : 1, suggesting the Aalpha(Perth) chain might be out-competed by normal chains during molecular assembly in the hepatocyte. Despite the low expression, polymerization curves showed a decreased V(max) and final turbidity, suggesting the fibrinogen Perth clots are composed of thinner fibers. However, the fibrinolytic rate was very similar to that of the control.

Adult↗
PubMed2003

Haemoglobin Marseille-Long Island and interpretation of HbA1c: which HbA1c result is the "right answer"?

A woman was screened for diabetes using glycated haemoglobin (HbA1c). Vastly different results were obtained by high performance liquid chromatography (45%), immunoassay (2.9%), and affinity chromatography (4.2%) compared with the non-diabetic range of less than 6.4%. Mass spectral studies confirmed the presence a haemoglobin variant, haemoglobin Marseille-Long Island which had confounded interpretation by all methods.

Adult↗
PubMed2002

Macro-alkaline phosphatase due to IgG kappa complex: demonstration with polyethylene glycol precipitation and immunofixation.

An otherwise unexplained, persistently elevated plasma alkaline phosphatase concentration in a 71-year-old woman was found to be attributable to the presence of macro-alkaline phosphatase using polyethylene glycol precipitation. Gel filtration showed two high MW peaks with masses of about 330 kDa and 560 kDa. The alkaline phosphatase (ALP) complex was characterized by immunoelectrophoresis as a complex with IgG with kappa light chains.

Aged↗
PubMed2001

Gamma371 Thr-->Ile substitution in the fibrinogen gammaD domain causes hypofibrinogenaemia.

Six members of a family with hypofibrinogenaemia had fibrinogen concentrations ranging from 0.5 to 1.1 mg/ml and, after sequencing the entire coding region and the intron exon boundaries of all three fibrinogen genes, a single heterozygous ACT-->ATT mutation was identified in the gamma gene. This novel mutation was not detected in normal family members or unrelated controls. The gamma371 Thr-->Ile substitution occurs at a conserved threonine in the gammaD domain, but molecules containing the new isoleucine were not present in circulating fibrinogen. The evidence for this was that purified gamma chains had a normal mass of 48375 Da compared to a control of 48374 Da, and tryptic peptide maps were entirely normal. The mutation predicts a mass increase of 12 Da in peptide T-36, but on mass mapping only the normal [M+2H] ion was detected, at 948 m/z. There was no new signal at 954 m/z that would indicate expression of variant chains. Also the normal 948 m/z signal was at the same intensity in digests from the proposita and controls. Crystal structures show a hydrogen bond from the threonine hydroxyl to the main chain and this case suggests this bond is critical in maintaining the structure of the gammaD domain.

Adult↗
PubMed2001

Implementation of evidence based cardiovascular risk treatments by general practitioners.

AIM: To review general practitioner (GP) implementation of evidence based cardiovascular risk reducing strategies in subjects with coronary heart disease (CHD). METHODS: Audit of patient records of randomly selected GPs. RESULTS: There were 326 subjects with CHD under the care of 21 doctors. Except for smoking, details of lifestyle measures were rarely found in the notes. Advice on diet and exercise was mentioned in 51% and 23.3% of records respectively. Aspirin and beta-blockers were widely used. Of patients with drug untreated values of total cholesterol (TC) and/or TC/HDL exceeding National Heart Foundation (NHF) guidelines, 71% were prescribed lipid-modifying drugs. NHF targets for TC (< or = 5.0 mmol/l) were achieved by 37% and for TC/HDL (< or = 4.5) by 60%. TC remained above 5.5 mmol/L in 120 cases. Lipid results from tests within the last 12 months were found in 60% of cases. CONCLUSIONS: Recording of lifestyle treatments in subjects with CHD appears to be assigned low priority. Cardioprotective treatments were widely used. Cholesterol levels were recorded frequently and of those with values exceeding NHF guidelines, nearly 3/4 were on medication. Recommended targets for lipid parameters were being achieved by <50% of patients. More frequent monitoring could improve this outcome

Adrenergic beta-Antagonists↗