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Biomedical subjects

G A Lancaster

Publications and source records attributed to G A Lancaster.

16 recordsLinked to original sources
PubMed2006

Peutz-Jeghers syndrome and screening for pancreatic cancer.

BACKGROUND: Cancer risk, including pancreatic, is high in those with Peutz-Jeghers syndrome (PJS). It has been suggested that such patients should undergo screening for pancreatic cancer. METHODS: The risk of pancreatic cancer in PJS, pancreatic screening and potential screening strategies were reviewed. Cost-effectiveness was assessed according to American Gastroenterology Association guidelines and a risk stratification model proposed by the European Registry of Hereditary Pancreatitis and Familial Pancreatic Cancer. RESULTS: The risk of pancreatic cancer is increased in PJS but screening would cost over US 35,000 dollars per life saved. Risk stratification reduces cost by 100,000 dollars and costs fall to 50,000 dollars per life saved if deaths from other forms of cancer are avoided. CONCLUSION: Screening should be performed only on a research basis to evaluate the benefit and cost-effectiveness in high-risk groups.

Adult↗
PubMed2004

Nutritional impairment in juvenile idiopathic arthritis.

OBJECTIVE: To investigate the relationship between nutritional impairment, measured by body mass index (BMI), expressed as an age- and sex-standardized standard deviation score (BMI SDS), and disease and patient characteristics in a UK cohort of children with juvenile idiopathic arthritis (JIA). A subgroup with available dietary information were analysed separately. METHODS: Important disease and patient characteristics (age, gender, disease subtype, swollen joint count, painful joint count, restricted joint count, treatment and dietary assessment) were assessed as potential explanatory measures of BMI SDS in a multiple linear regression. RESULTS: Data were collected on 123 consecutive patients. Twenty were nutritionally impaired. In multiple regression analysis excluding the dietary data, disease subtype [persistent oligoarthritis and polyarthritis (rheumatoid factor-negative)], five or more joints with reduced range of movement and being younger were associated with lower BMI SDS (P<0.001). When energy and protein intake were included in the analysis for a subgroup of children, the resulting model retained only disease subtype as a predictor of a low BMI SDS (P = 0.013). CONCLUSIONS: In this unselected population of children with JIA, 16% had evidence of undernutrition. The most commonly affected subtype was oligoarthritis, a previously unreported finding. There is no evidence from this study that this nutritional impairment results from inadequate food intake and it is likely that it is multifactorial in aetiology, disease subtype being the most important factor.

Adolescent↗
PubMed2004

Validity and reliability of acoustic analysis of respiratory sounds in infants.

OBJECTIVE: To investigate the validity and reliability of computerised acoustic analysis in the detection of abnormal respiratory noises in infants. METHODS: Blinded, prospective comparison of acoustic analysis with stethoscope examination. Validity and reliability of acoustic analysis were assessed by calculating the degree of observer agreement using the kappa statistic with 95% confidence intervals (CI). RESULTS: 102 infants under 18 months were recruited. Convergent validity for agreement between stethoscope examination and acoustic analysis was poor for wheeze (kappa = 0.07 (95% CI, -0.13 to 0.26)) and rattles (kappa = 0.11 (-0.05 to 0.27)) and fair for crackles (kappa = 0.36 (0.18 to 0.54)). Both the stethoscope and acoustic analysis distinguished well between sounds (discriminant validity). Agreement between observers for the presence of wheeze was poor for both stethoscope examination and acoustic analysis. Agreement for rattles was moderate for the stethoscope but poor for acoustic analysis. Agreement for crackles was moderate using both techniques. Within-observer reliability for all sounds using acoustic analysis was moderate to good. CONCLUSIONS: The stethoscope is unreliable for assessing respiratory sounds in infants. This has important implications for its use as a diagnostic tool for lung disorders in infants, and confirms that it cannot be used as a gold standard. Because of the unreliability of the stethoscope, the validity of acoustic analysis could not be demonstrated, although it could discriminate between sounds well and showed good within-observer reliability. For acoustic analysis, targeted training and the development of computerised pattern recognition systems may improve reliability so that it can be used in clinical practice.

Acoustics↗
PubMed2002

Meta-analysis of method comparison studies.

Methods for the meta-analysis of results from randomized controlled trials are well established. However, there are currently no methods for the meta-analysis of method comparison studies. Here the combination of results from studies comparing two methods of measurement on the same unit of observation is required. We compare standard methods for the pooling of k samples from the same Normal population to those for pooling parameter estimates, in order to estimate the pooled mean difference and 95 per cent limits of agreement. Methods for investigating heterogeneity across studies and for calculating random effects estimates are proposed. We postulate that for published studies either the estimated mean or variance of the difference between measurements will tend to be smaller than for unpublished studies and investigate the evidence for the existence of such publication bias. The methods are illustrated with an example evaluating the accuracy of temperature measured at the axilla compared to the rectum in children.

Axilla↗
PubMed2000

Temperature measured at the axilla compared with rectum in children and young people: systematic review.

OBJECTIVE: To evaluate the agreement between temperature measured at the axilla and rectum in children and young people. DESIGN: A systematic review of studies comparing temperature measured at the axilla (test site) with temperature measured at the rectum (reference site) using the same type of measuring device at both sites in each patient. Devices were mercury or electronic thermometers or indwelling thermocouple probes. STUDIES REVIEWED: 40 studies including 5528 children and young people from birth to 18 years. DATA EXTRACTION: Difference in temperature readings at the axilla and rectum. RESULTS: 20 studies (n=3201 (58%) participants) had sufficient data to be included in a meta-analysis. There was significant residual heterogeneity in both mean differences and sample standard deviations within the groups using different devices and within age groups. The pooled (random effects) mean temperature difference (rectal minus axillary temperature) for mercury thermometers was 0.25 degrees C (95% limits of agreement -0.15 degrees C to 0.65 degrees C) and for electronic thermometers was 0. 85 degrees C (-0.19 degrees C to 1.90 degrees C). The pooled (random effects) mean temperature difference (rectal minus axillary temperature) for neonates was 0.17 degrees C (-0.15 degrees C to 0. 50 degrees C) and for older children and young people was 0.92 degrees C (-0.15 degrees C to 1.98 degrees C). CONCLUSIONS: The difference between temperature readings at the axilla and rectum using either mercury or electronic thermometers showed wide variation across studies. This has implications for clinical situations where temperature needs to be measured with precision.

Adolescent↗
PubMed1990

Identification of deletion and triple alpha-globin gene haplotypes in the Montreal beta-thalassemia screening program: implications for genetic medicine.

We obtained blood samples in a screening program designed to detect beta-thalassemia heterozygotes in Montreal; additional samples were obtained from referred persons. We analyzed DNA for variant numbers of alpha-globin genes, notably the alpha-thalassemia2 (-alpha/), alpha-thalassemia1, (- -/), and triplicated alpha-globin gene (alpha alpha alpha/) haplotypes using restriction enzymes and probes for alpha-globin and zeta-globin gene sequences. We estimated the numbers of Montreal residents of Italian and Greek ethnic origin with -alpha/alpha alpha genotype. Thus, 4.3% of Italians and 1.5% of Greeks, or about 7,500 persons, are estimated to be alpha-thalassemia2, trait (silent carriers), largely (80%) in the -alpha 3.7/type I form. The triplicated alpha-globin gene haplotype was also found. The risk of a severe (alpha-thalassemia1) phenotype associated with inheritance of - -/alpha alpha or -alpha/-alpha genotypes was low and was found predominantly in this study, in persons of Asian ethnic origin. The sample of Asians was too small to estimate carrier frequencies; however, based on results from the beta-thalassemia screening program, we estimated that about 4% of Asians (about 1,300 persons) in Montreal are alpha-thalassemia carriers. We identified persons heterozygous for both beta-thalassemia and alpha-thalassemia mutations. In these double heterozygotes, the effect of the triplicated alpha-globin gene was to make the erythrocyte parameters used for screening (MCV and %HbA2) more deviant from normal whereas deletion of 2 alpha-globin genes tended to normalize the erythrocyte values. These findings have implications for the screening program and reproductive counseling.

Adolescent↗
PubMed1989

Prolidase deficiency: biochemical classification of alleles.

Prolidase (E.C.3.4.13.9) is a homodimeric enzyme encoded at a locus on chromosome 19. Prolidase deficiency is an autosomal recessive disorder with a highly variable clinical phenotype. We purified prolidase to homogeneity from normal human fibroblasts, raised a monospecific rabbit antiserum, and studied biosynthesis of the subunit in normal and prolidase--deficient fibroblasts. Pulse-chase immunoprecipitation experiments showed that the subunit is synthesized and retained in cytosol as a 58-KDa polypeptide. Three types of mutations were identified in six prolidase-deficient cell strains; half conferred a CRM-negative phenotype, while the CRM-positive mutations were of two types, one mutation encoding an enlarged subunit (60 KDa) and the others associated with subunits of normal size. Complementation analysis indicated that these mutations map to one locus. Normal subjects and obligate heterozygotes expressing CRM-negative mutations had thermostable prolidase activity at 50 degrees C in cell extracts, whereas heterozygotes expressing CRM-positive mutations had thermolabile activity under the same condition, implying negative allelic complementation in the putative heterodimer. The occurrence of prolidase-like activity about 5% of normal in amount but with a preference for substrate different from normal, in cells homozygous (or compound) for CRM-negative mutations, identified an alternative cleavage activity not encoded at the prolidase locus. Allelic heterogeneity at the major locus and the amount of alternative peptidase activity encoded elsewhere appear to be determinants of the associated and heterogeneous clinical phenotype.

Alleles↗
PubMed1984

Osteogenesis imperfecta: a heterogeneous morphologic phenotype in cultured dermal fibroblasts.

Osteogenesis imperfecta (OI) is a phenotype with clinical and biochemical heterogeneity. We report here that expression of the OI phenotype extends to the level of dermal fibroblast morphology in vitro. Growth characteristics and morphology of control (n = 6) and OI cell strains (n = 10, representing the four major OI categories, Sillence classification) were compared by measuring the following: (i) days required in culture to reach confluence after plating at uniform density; (ii) cell density at confluence; (iii) width and length of cells (measured on phase contrast micrographs at 300 X magnification). Our results show that: (i) OI fibroblasts take longer (11-27 days, mean 20 days) than control cells (10-19 days, mean 16 days) to reach stationary phase; (ii) all OI phenotypes achieve a lower cell density (0.87 X 10(6) cells/P60, range 0.3-1.6 X 10(6] at stationary phase relative to control cells (2.2 X 10(6) cells/P60, range 1.7-2.6 X 10(6); F4,77 = 56.1, p less than 0.01, indicating that OI cells are larger than normal). Cell shape (expressed as the width : length ratio) was also abnormal in OI cells. (F4,730 = 37.6, p less than 0.01), types I and II OI cells have significantly increased ratios (p less than 0.01) relative to control, type III, and type IV cells. Intra-group phenotypic heterogeneity was also apparent in the OI categories and also within the control population. These findings confirm deviant morphologic phenotypes in OI dermal fibroblasts and further demonstrate interindividual heterogeneity in the expression of genes that determine size and shape of dermal fibroblasts in both OI and normal donors.

Cells, Cultured↗
PubMed1984

Inherited lactic acidosis: correction of the defect in cultured fibroblasts.

We report a case of familial lactic acidosis, lethal in the newborn period. Studies in intact fibroblasts identified a defect in the oxidative pathway of pyruvate metabolism. Although assay of pyruvate dehydrogenase on cell sonicates was not appreciably reduced, flux through the enzyme and other mitochondrial multienzyme dehydrogenases was severely impaired in intact cells. Deficient lactate conversion to carbon dioxide could be repaired by the addition to the incubation medium of electron acceptors such as methylene blue (25 micrograms/ml) or dichlorophenolindophenol (25 micrograms/ml).

Acidosis↗
PubMed1984

Beta-thalassemia disease prevention: genetic medicine applied.

We report here an evaluation of a program for thalassemia-disease prevention, comprising education, population screening for heterozygotes, and reproductive counseling; the evaluation includes cost analysis. A preprogram survey in 1978 of 3,247 citizens in the high-risk communities (85% were high-school students) showed that 88% favored a program but that only 31% considered fetal diagnosis as an acceptable option. Screening in high school or before marriage was preferred by 56%. In a 25-month period (December 1979-December 1982), we screened 6,748 persons, including 5,117 senior high-school students, using MCV/HbA2 indices. The participation rate was 80% in the high-school group. The frequency for beta-thalassemia heterozygosity was 4.7% with 10-fold variation among ethnic groups at risk; the overall frequency for all variants found was 5.4%. We surveyed 60 carriers and 120 noncarriers after screening high-school students (response rate 77%): most carriers told parents (95%) and friends (67%) the test result; and 38% of the carriers' parents (vs. 18% of the noncarriers' parents) were also screened. Carriers would ascertain their spouses' genotype (91%) and approved uniformly (95%) the high-school screening experience and its goal. We performed 11 fetal diagnoses in a 25-month interval (greater than 75% participation in target population) either by fetoscopy and globin-chain analysis or by amniocentesis and genomic DNA analysis; two of three affected fetuses were aborted at parental request, there was one spontaneous abortion (after fetoscopy), and seven live births. The at-risk couples claimed pregnancy would not be contemplated without the fetal-diagnosis option. We analyzed economic costs of the program: cost per case prevented is approximately equal to $ 6,700, slightly less than cost-per-patient-treatment-year or about 4% of undiscounted treatment cost incurred in the first 25 years of life for an affected individual. These findings indicate: collective acceptance of the program, appropriate attitudes among carriers, general acceptance and efficacy of fetal diagnosis, and global cost-effectiveness.

Adolescent↗
PubMed1983

Secreted collagen ratios in normal human and osteogenesis imperfecta skin fibroblasts.

We examined the effects of several variables on the ratio of type I:type III collagen secreted by human caucasian skin fibroblasts in normal and osteogenesis imperfecta (OI) phenotypes. Isotopically labelled collagen extracted from fibroblast medium was analyzed by DEAE-cellulose chromatography and identified by appropriate methods. Type I procollagen was the major form of collagen secreted into the medium by normal cells cultured from one mid-term fetus, infants (n = 3), children (n = 3), adolescents (n = 2), and adults (n = 3). Interstrain differences in collagen production under standardized conditions were significantly greater than intrastrain variation (anova, p = 0.0051). There was no significant alteration in the type I:type III collagen ratio due to variation in: phase of cell growth, doublings (between 13th and 22nd), rate of isotope incorporation, labelling time (24-72 hrs) in the presence of ascorbic acid (50 micrograms/ml), age of donor (with the possible exception of adolescence), and site of biopsy (genital and non-genital sites). Variable conversion of type I procollagen to collagen did not perturb the type I:type III collagen ratio. Cell strains from OI patients (Sillence classification): type I (one strain); type II, III and IV (3 strains each) had greater interstrain than intrastrain variation in the collagen ratio (p = 0.0149). Interstrain differences were greater in OI cell strains relative to normal cell strains (p less than 0.01). In the aggregate, OI cells had significantly lower type I collagen production relative to type III (I/III ratio = 1.18) when compared with normal cells (I/III ratio = 2.90; t test, p less than 0.0001). These findings imply abnormal synthesis, secretion or stability of type I procollagen and greater phenotypic heterogeneity in OI skin fibroblasts relative to normal cells.

Adolescent↗
PubMed1982

Cystinotic and normal fibroblasts: differential protection in cystine-free medium by dithiothreitol.

We studied survival of normal (n=4) and cystinotic (n=3) fibroblast strains in selective (cystine-free) medium, with or without dithiothreitol (DTT)-thiol or disulfide. Cells were plated at low density first in maintenance medium (containing cystine), then washed and exposed to selective medium for 24 hr or longer. Cultures were trypsinized at specified times and the cells counted. Selective medium caused progressive detachment (greater than 90% by 72 hr) of control and cystinotic cells: DTT-disulfide (4 mM) and DTT-thiol (0.5 mM) both protected cystinotic cells (p less than 0.02) but not control cells in selective medium. DTT-thiol (0.5 mM) and DTT-disulfide (4mM) both depleted the intracellular non-protein cystine pool of cystinotic cells to less than 25 percent of pretreatment levels. Cystinotic cells preincubated with cysteamine (1 mM X 4 hr) to deplete the intracellular cystine pool were not protected by DTT-disulfide than with DTT-thiol. These findings imply that mobilization of intracellular cystine protects cystinotic cells in selective medium; cystinotic fibroblasts can utilize DTT-disulfide as well as DTT-thiol to mobilize cystine.

Culture Media↗
PubMed1975

Ontogeny of L-glutamic acid decarboxylase and gamma-aminobutyric acid concentration in human kidney.

GAD activity and GABA, the product of GAD action on L-glutamate, are both prominent in mature human renal cortex. GAD activity is low in fetal kidney but rises several fold preterm to establish the characteristic post-term specific activity. The ontogeny of the initial step in the GABA pathway parallels the need for kidney to accommodate acid-base regulation after birth. PLP coenzyme is required for GAD holoenzyme integrity. Fetal renal GAD was frequently undersaturated with PLP in our series of observations, raising the suggestion that maternal vitamin B6 nutrition is not always adequate.

Age Factors↗