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Biomedical subjects

A J Hall

Publications and source records attributed to A J Hall.

At least 37 records · Page 2Linked to original sources
PubMed2002

Epilepsy, cysticercosis, and toxocariasis: a population-based case-control study in rural Bolivia.

OBJECTIVE: To assess the relationship between epilepsy and infection with Taenia solium and Toxocara canis with a case-control study, in the rural area of the Cordillera Province, Bolivia. METHODS: A preliminary two-phase door-to-door prevalence survey determined the prevalence of epilepsy and identified cases and control subjects. At least two control subjects per case were selected, matching on sex, age, and community of residence. Cases and control subjects were assessed serologically for antibodies against T. canis by ELISA and against T. solium by enzyme-linked immunoelectrotransfer blot (EITB). RESULTS: The prevalence survey found 130 confirmed cases of epilepsy, of which 113 were eligible for the case-control study (59 partial seizures and 54 generalized seizures). Two hundred thirty-three control subjects were selected. Multivariable analysis for a matched case-control study was carried out. There was an association between EITB positivity for T. solium and epilepsy with an OR of 1.85 (95% CI 0.99 to 3.4) for all cases. A stronger association was found in those with partial epilepsy with a late onset of disease (15 years and older), where the OR was 3.66 (95% CI 1.10 to 12.10). A positive association was also found with T. canis for all cases with an OR of 2.70 (95% CI 1.41 to 5.19). This increased for those with late-onset partial epilepsy to an OR of 18.22 (95% CI 2.10 to 158.10). CONCLUSION: This finding suggests that both neurocysticercosis and toxocariasis may in part explain the higher prevalence of epilepsy, particularly partial epilepsy, in developing countries.

Adult↗
PubMed2002

Adrenocortical responsiveness in southern elephant seal mothers and pups during lactation and the effect of scientific handling.

We examined the cortisol responses to chemical and physical restraint stress in southern elephant seal Mirounga leonina females and their pups at three stages during lactation. In anaesthetised females the serum cortisol levels changed moderately during the 45-min sampling period following restraint, with average peaks at 23 min after anaesthetic administration. Overall, cortisol was relatively low 2 days postpartum and increased throughout lactation. In physically restrained pups serum cortisol increased rapidly after capture; the response was milder at age 2 days than at 11 days and 21 days. Levels were higher in female pups than in males. In order to test whether cortisol levels and/or responses became chronically (i.e. days to weeks) altered due to restraint, we compared the cortisol response at a late stage of lactation between three groups of mother-pup pairs previously given different levels of chemical (mothers) or physical (pups) restraint stress: control (not handled previously), moderate treatment (previously handled twice), and high treatment (previously handled 3-4 times). Pups of the three treatment groups showed similar adrenocortical responses suggesting no chronic effect of repeated physical restraint, despite the clear acute effects. Mothers of the control and moderate treatment groups showed similar cortisol responses; however, mothers of the high treatment group showed significantly attenuated responses. This indicated that elephant seals tolerated moderate degrees of handling disturbance; however, repeated (3-4) chemical immobilisations in lactating females may reduce their adrenocortical responsiveness for a period of days or weeks.

Adrenal Cortex↗
PubMed2002

Development and application of an indirect competitive enzyme-linked immunoassay for aflatoxin m(1) in milk and milk-based confectionery.

High-titer rabbit polyclonal antibodies to aflatoxin M(1) (AFM1) were produced by utilizing AFM1-bovine serum albumin (BSA) conjugate as an immunogen. An indirect competitive enzyme-linked immunosorbent assay was standardized for estimating AFM1 in milk and milk products. To avoid the influence of interfering substances present in the milk samples, it was necessary to prepare AFM1 standards in methanol extracts of certified reference material (CRM) not containing detectable AFM1 (< 0.05 ng/g). The reliability of the procedure was assessed by using CRM with AFM1 concentrations of < 0.5 and 0.76 ng/g. Also, assays of milk samples mixed with AFM1 ranging in concentration between 0.5 and 50 ng/L gave recoveries of > 93%. The relative cross-reactivity with aflatoxins (AF) and ochratoxin A, assessed as the amount of AFM1 necessary to cause 50% inhibition of binding, was 5% for AFB1 and much less for AFB2, AFG1, and AFG2; there was no reaction with ochratoxin A. AFM1 contamination was measured in retail milk and milk products collected from rural and periurban areas in Andhra Pradesh, India. Of 280 milk samples tested, 146 were found to contain < 0.5 ng/mL of AFM1; in 80 samples it varied from 0.6 to 15 ng/mL, in 42 samples from 16 to 30 ng/mL, and in 12 samples from 31 to 48 ng/mL. Most of the milk samples that contained high AFM1 concentrations were obtained from periurban locations. The results revealed a significant exposure of humans to AFM1 levels in India and thus highlight the need for awareness of risk among milk producers and consumers.

Aflatoxin M1↗
PubMed2002

Environmental factors as determinants of malaria risk. A descriptive study on the northern coast of Peru.

We conducted a series of studies on the northern Pacific coast of Peru to determine environmental risk factors for malaria. We report in this paper the results of both a descriptive study of incidence and a prevalence survey of malaria. Both studies showed that the area was at low risk for malaria. The malaria incidence rate was 40/1000 p.a. during the study period, and the prevalence of infection was 0.9% (95% CI: 0.4-1.7) before and 1.4% (95% CI: 0.8-2.2) after the high incidence period. However, the risk of malaria varied according to season, village and even house within a single village. Incidence rates increased from February (2.6/1000 p.a.) to May (12.9/1000 p.a.) and decreased during the second part of the year. Most of the cases were clustered in four villages that constituted only 21% of the total population of the area. Houses where multiple cases were recorded were often located near a source of water. Our observations suggested that environmental factors, and particularly the presence of water for irrigation around villages and houses, played a major role in determining the risk of malaria. These observations were extended through an entomological study and a case-control study, to be published elsewhere.

Adolescent↗
PubMed2002

Modelling kiwifruit budbreak as a function of temperature and bud interactions.

This paper presents two models of budbreak on canes of 'Hayward' kiwifruit (Actinidia deliciosa). A conventional 'chill unit' (CU) type model is compared with an alternative 'loss of potential' (LOP) approach, which assumes that the number of buds developing in spring depends on climate and node position-dependent bud-to-bud interactions that vary in duration and intensity. Both models describe how temperature, and application of a dormancy-breaking chemical, determine the overall amount of budbreak for whole canes. However, the LOP model does so by describing patterns of budbreak along canes. To do this, the cumulative influence of distal neighbours is assumed to cause a progressive fall in the capacity for bud development over the autumn-winter period, an influence that gets stronger as temperature rises. The LOP model also assumes that the rate of decline varies along the cane, as a function of some inherent bud property. These two factors mean that buds towards the base of the cane break less often under the suppressive influence of distal neighbours, while low temperature ('chilling') increases budbreak by diminishing the intensity of suppression relative to bud development rate. Under this scenario, dormancy-breaking chemicals (such as hydrogen cyanamide, HC) enhance budbreak by diminishing the duration of suppression. Models were calibrated using daily temperature series and budbreak proportion data from a multi-year regional survey, and were then tested against independent data sets. Both models were run from a fixed start date until the time budbreak was almost complete, or until a standard date. The fitted models described 87 % of variation in amount of budbreak due to site, year, HC and node position effects in the original data set. Results suggest that the correlation between chilling and the amount of budbreak can be interpreted as a population-based phenomenon based on interaction among buds.

Actinidia↗
PubMed2001

Determination of phenytoin in plasma by molecularly imprinted solid-phase extraction.

A molecularly imprinted polymer (MIP) using phenytoin as template and methacrylamide as the functional monomer was prepared. The selectivity was measured by comparing capacity factors of phenytoin and other structurally related compounds. The polymer was evaluated as a selective sorbent in molecularly imprinted solid-phase extraction (MISPE). Several washing solvents were tested to study their ability to disrupt the non-specific interactions occurring between the sample and the polymer matrix and the role of water in the recognition process was also investigated. It was shown that the key step of successful sample extraction is the right choice of the washing solvent. Plasma samples spiked with phenytoin were analyzed by the MISPE methodology developed in this work. Method validation (intra- and inter-day precision, recovery, specificity) was carried out. The calibration curve showed good linearity in the 2.5-40 microg/ml range corresponding to therapeutically relevant plasma levels. The intra- and inter-day precision values were below the 15% limit established for bioanalytical methods. The results showed that the method could be successfully applied for the determination of phenytoin in plasma samples.

Anticonvulsants↗
PubMed2001

Cancer in the Gambia: 1988-97.

We describe the incidence of cancer in The Gambia over a 10-year period using data collected through the Gambian National Cancer Registry. Major problems involved with cancer registration in a developing country, specifically in Africa are discussed. The data accumulated show a low overall rate of cancer incidence compared to more developed parts of the world. The overall age standardized incidence rates (ASR) were 61.0 and 55.7 per 100 000 for males and females, respectively. In males, liver cancer was most frequent, comprising 58% of cases (ASR 35.7) followed by non-Hodgkin lymphoma, 5.4% (ASR 2.4), lung 4.0%, (ASR 2.8) and prostate 3.3% (ASR 2.5) cancers. The most frequent cancers in females were cervix uteri 34.0% (ASR 18.9), liver 19.4% (ASR 11.2), breast 9.2% (ASR 5.5) and ovary 3.2% (ASR 1.6). The data indicate that cancers of the liver and cervix are the most prevalent cancers, and are likely to be due to infectious agents. It is hoped that immunization of children under 1 year against hepatitis B will drastically reduce the incidence of liver cancer in The Gambia.

Adolescent↗
PubMed2001

Target analogue imprinted polymers with affinity for folic acid and related compounds.

Two approaches to synthesize molecularly imprinted polymers with affinity for folic acid and other substituted pteridines have been compared. In the first approach, the folic acid analogue methotrexate was used as template and functional monomers capable of generating selective binding sites were searched in a miniaturized screening system based on binding assessment in the batch mode. Highest selectivity was seen using 2-vinylpyridine as functional monomer, which was confirmed in the chromatographic mode for a batch synthesized on a gram scale. However, the retentivity and selectivity of this phase were insufficient for anticipated applications. In a second approach, using methacrylic acid as the functional monomer, organic soluble inhibitors for the enzyme dihydrofolate reductase were used to develop sites complementary toward the pteridine substructure. This resulted in materials showing enhanced selectivity for substituted pteridines when evaluated by HPLC. Thus, methotrexate and leucovorine were selectively retained in mobile phases of either low or high aqueous content, thus showing the typical bimodal retention behavior of previously reported MIPs. In organic mobile-phase systems, the inhibitor used as template had an influence on the retentivity and selectivity of the MIP. The polymer imprinted with trimethoprim retained all folic acid analogues strongly and showed the highest selectivity among the MIPs in an organic mobile-phase system. This was supported by Scatchard analysis resulting in biphasic plots and a quantitative yield of high-energy binding sites. All templates were shown to associate strongly with MAA in CDCl(3), the strength of association correlating roughly with the template basicity and the selectivity observed in chromatography. Nonparallel complexation-induced shifts indicated formation of 1:2 template monomer complexes at concentrations corresponding to those of the prepolymerization solutions.

Folic Acid↗
PubMed2001

A case-control study of autism and mumps-measles-rubella vaccination using the general practice research database: design and methodology.

BACKGROUND: An association between mumps-measles-rubella (MMR) vaccination and the onset of symptoms typical of autism has recently been suggested. This has led to considerable concern about the safety of the vaccine. METHODS: A matched case-control study using data derived form the United Kingdom General Practice Research Database. Children with a possible diagnosis of autism will be identified from their electronic health records. All diagnoses will be validated by a detailed review of hospital letters and by using information derived from a parental questionnaire. Ten controls per case will be selected from the database. Conditional logistic regression will be used to assess the association between MMR vaccination and autism. In addition case series analyses will be undertaken to estimate the relative incidence of onset of autism in defined time intervals after vaccination. The study is funded by the United Kingdom Medical Research Council. DISCUSSION: Electronic health databases offer tremendous opportunities for evaluating the adverse effects of vaccines. However there is much scope for bias and confounding. The rigorous validation of all diagnoses and the collection of additional information by parental questionnaire in this study are essential to minimise the possibility of misleading results.

Age of Onset↗
PubMed2001

Characterization of baboon (Papio hamadryas) milk proteins.

The major proteins of baboon milk were identified as beta-lactoglobulin (beta LG), alpha-lactalbumin (alpha LA), lysozyme, lactoferrin, casein, and albumin by immobiline isoelectric focusing, SDS-PAGE, immunoblotting of gels with rabbit antisera to human alpha LA, lysozyme, and albumin and bovine beta LG and casein, and N-terminal sequencing of proteins blotted from gels. The first 30 N-terminal residues of baboon beta LG are identical to those of macaque (Macaca fasicularis) beta LG except for a (D/N) polymorphism at residue 2. The complete cDNA sequence and derived amino acid composition of beta LG were elucidated using RT-PCR amplification of poly(A)+ mRNA purified from lactating mammary gland. Baboon beta LG consists of 168 amino acid residues (M(r) 20,750) and is the longest beta LG identified to date. beta LG and alpha LA polymorphisms with three (A, B, and C) and two (A and B) variants, respectively, were detected by immobiline IEF, pH 4-6, of individual baboon milk samples at varying stages of lactation.

Albumins↗
PubMed2001

Atypical retinal microvasculopathy after bone marrow transplantation.

OBJECTIVE: Typical early ischaemic retinal microvascular changes with cotton wool spots after allogeneic bone marrow transplantation (BMT) are well recognised. In the study an atypical non-ischaemic late retinopathy is described. METHODS: Sequential cases of late retinal microvasculopathy following allogeneic BMT were reviewed. Demographic features and clinical and angiographic data were collected. RESULTS: Of 399 patients undergoing allogeneic BMT between 1992 and 1999, eight eyes of four patients developed atypical retinopathy. All patients were male and the age range was 27-50 (mean 37.5) years. The indications for BMT were acute lymphoblastic leukaemia (two patients), chronic myeloid leukaemia (one patient) and chronic lymphocytic leukaemia (one patient). Two patients had conditioning regimens including irradiation. All had cyclosporine and methotrexate as graft-versus-host disease prophylaxis. All but one had cyclophosphamide and busulphan as conditioning treatment. One had interferon. No patients had sustained hypertension or diabetes mellitus. Atypical retinopathy was identified 13-62 (mean 50) months after BMT and clinical features consisted of microaneurysms (MA; 4/4), hard exudates (1/4) and macular oedema (1/4). No patient had cotton wool spots. The median acuity was 6/5. Angiographic features were MA (4/4), late leak (2/4) and peripheral (1/4) or central (1/4) ischaemia. One patient underwent focal photocoagulation for macular oedema. CONCLUSION: Retinal microvascular incompetence (without cotton wool spots) with good vision may occur in a small number of patients as a late complication of allogeneic BMT

Adult↗
PubMed2001

Nd:YAG laser iridotomy in uveitic glaucoma.

PURPOSE: To determine the survival of Nd:YAG laser peripheral iridotomy in those patients with angle closure glaucoma and iris bombé associated with uveitis. METHODS: A retrospective review was performed on 11 patients of the Ocular Immunology Clinic of the Royal Victorian Eye and Ear Hospital who presented with uveitis, iris bombé due to extensive posterior synechiae and angle closure glaucoma. The date of iridotomy and where possible the degree of inflammation were noted, as was the date of failure of the iridotomy. A control group was constructed consisting of 65 patients who presented with acute angle closure glaucoma without a history of uveitis, who underwent Nd:YAG peripheral iridotomyThe survival of the peripheral iridotomies in the two groups was calculated using Kaplan-Meier survival analysis. Median survival was compared using log rank test. RESULTS: In the study group of 11 patients, 28 iridotomies were performed on 15 eyes; of these 28 iridotomies, 17 failed. Using Kaplan-Meier survival analysis the median time to failure was 85 days. In the control group of 65 patients, 66 iridotomies were performed on 66 eyes. None of the iridotomies in the control group failed. There was a significant difference in the survival of the Nd:YAG iridotomies (P = 0.00015) between groups. CONCLUSION: There is a high early failure rate of Nd:YAG iridotomies in patients with angle closure glaucoma and iris bombé associated with uveitis.

Adult↗