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Biomedical subjects

A Atkinson

Publications and source records attributed to A Atkinson.

At least 37 records · Page 2Linked to original sources
PubMed1996

Plasma glycocalicin levels are not elevated in patients with a history of transient ischaemic event and are normal in aspirinated normal volunteers.

Glycocalicin (GC) is the soluble portion of platelet membrane protein GP1b, and may be cleaved from the platelet surface during platelet activation. Previous study has indicated that plasma glycocalicin/platelet (GC/plt) levels are elevated in patients presenting with acute stroke. The present study was undertaken to determine the GC/plt levels in patients being treated for transient ischaemic episodes, to assess whether the elevated GC/plt level in acute stroke is due to a detectable, constitutive premorbid state of platelet activation. In sixteen consecutive patients attending a vascular surgery clinic, GC levels were measured on a citrated plasma sample, and corrected for circulating platelet count. Since 15 of 16 patients were taking aspirin when seen at clinic, a control study was undertaken to assess the effect of aspirin on sequential plasma GC/plt levels measured over 10 days--5 pre and post daily aspirin for 5 days, 4 acting as non-aspirinated controls. Plasma GC/plt levels in normal plasma were 21.6 +/- 8.0 fg; mean +/- SD. In the 16 patients the GC/plt levels were 13.1 fg/plt; SD 5.4, range 2.9-24.3. All platelet counts were in the normal range in all patients involved. While a masking effect due to aspirin cannot be completely ruled out, these studies indicate that plasma GC/plt level is not useful as a predictor of acute stroke in the premorbid population.

Aspirin↗
PubMed1996

Effects of age on energy expenditure and substrate oxidation during experimental overfeeding in healthy men.

Relatively little is known about the influence of age on energy regulation during energy imbalance. We compared the effects of overfeeding on changes in energy expenditure, substrate oxidation, and energy deposition between young men (age 23.7 +/- 1.1 [SEM] years) and older men (age 70.0 +/- 7.0) of normal body weight who were leading unrestricted lives. Changes in total energy expenditure, resting energy expenditure (REE), the thermic effect of feeding (TEF), respiratory quotient (RQ), and body energy content were determined in response to overeating by 4.09 +/- 0.07 Megajoule (MJ)/day for 21 days in 16 healthy subjects consuming a typical diet. After excluding data from one young subject with unusual results and adjusting for individual differences in excess energy intake, there was a tendency towards a smaller increase in REE in older men compared to the young men (p = .07) which was accounted for by their lower fat-free mass (p = .016). There was also a significantly smaller increase in resting energy expenditure averaged over fasting and fed states (i.e, REE + TEF) with overfeeding in older men than in young men (p < .01). Combined, these smaller increases in energy expenditure with overfeeding in the older subjects averaged an estimated 365 kilojoule (kJ)/day (8.9% of the excess energy intake) (p < .02). There were also significant effects of age on fasting RQ (p < .001) and the change in RQ with overfeeding (p < .001), but no significant increase in energy expenditure for physical activity and thermoregulation with overfeeding in either age-group. These results are consistent with the suggestion that older individuals experience both a reduction in the ability to increase energy expenditure, and an alteration in the pattern of substrate utilization, in response to overfeeding. These changes may promote cumulative increases in body energy during normal cycles of positive energy balance unless compensated for by adaptive variations in energy intake.

Adult↗
PubMed1995

In vitro conversion of environmental estrogenic chemical bisphenol A to DNA binding metabolite(s).

In the present study we have investigated the ability of bisphenol A to be converted to reactive metabolite(s) and its potential to bind to DNA. In this in vitro study we show that bisphenol A is oxidized by 70% to bisphenol o-quinone. The evidence for the formation of bisphenol o-quinone was shown by UV, IR and GC-MS. The new product, bisphenol o-quinone, had a maximum UV absorption at 386 nM, the appearance of an IR characteristic of unsaturated carbonyl (1690 cm-1) and a mass of 242. The chemical reaction of deoxyguanosine monophosphate (dGMP) or DNA with bisphenol o-quinone produced 6-8 adducts. The in vitro incubation of DNA with bisphenol A in the presence of peroxidase activation system also produced one major and seven minor adducts. The chromatographic mobilities of major DNA adducts four and six formed by bisphenol A in the presence of peroxidase activation system closely matched those of spots four and six obtained by chemical reaction between DNA or dGMP with bisphenol o-quinone. Based on these data it appears that bisphenol A is converted to DNA binding metabolites in vitro. Whether irreversible binding of bisphenol A to DNA through metabolic activation may be responsible for some of the toxic effects produced by bisphenol A is not clear.

Benzhydryl Compounds↗
PubMed1995

In vivo DNA adduct formation by bisphenol A.

We have previously shown that bisphenol A (BPA) is oxidized to bisphenol-o-quinone in the presence of activation system and that the chemical reaction of DNA or deoxyguanosine 3'-monophosphate (dGMP) with bisphenol-o-quinone produces adducts. In the present study, using the 32P-postlabeling technique, we have investigated the in vivo DNA adduct formation by BPA by examining covalent modification in DNA. Administration of a single or multiple dose of 200 mg/kg of BPA to CD1 male rats produced two major and several minor adducts in liver DNA. The two major in vivo adducts matched the adduct profile of DNA or dGMP-bisphenol-o-quinone. To determine how BPA may be converted to DNA-binding metabolites, adducts were examined after incubation of DNA with BPA in the presence of a microsomal activation system. The in vitro incubation of BPA with DNA in the presence of a microsomal activation system revealed one major adduct and several minor adducts. The formation of adducts in DNA by BPA in the presence of a microsomal activation system was drastically decreased by known inhibitors of cytochrome P450. Adduct formation in DNA when cumene hydroperoxide or NADPH was used as a cofactor showed adducts with similar chromatographic mobilities as those from the reaction of dGMP-bisphenol-o-quinone. These data demonstrate that BPA is capable of binding covalently to DNA. DNA binding can be inhibited by the inhibitors of cytochrome P450. One of the DNA-binding metabolite(s) both in vitro and in vivo may be bisphenol-o-quinone. Covalent modifications in DNA by in vivo exposure of BPA may be a factor in the induction of hepatotoxicity.

Animals↗
PubMed1993

The use of music in curriculum evaluation.

This article outlines the importance of curriculum evaluation and discusses some reasons for it. In particular, it is concerned with the role of reflection. The article further examines how music can be used as an aid to evaluate a course.

Curriculum↗
PubMed1993

Increased oxidative stress in the liver of mice treated with trichloroethylene.

In this study the trichloroethylene treatment-associated production of oxidative stress in mouse liver by measurements of changes in oxygen consumption, the disappearance of beta-nicotinamide adenine dinucleotide reduced form (NADPH), and the rate of malondialdehyde formation have been investigated. The treatment of mice with trichloroethylene (TCE), trichloroacetic acid (TCA), a metabolite of TCE, or clofibrate, a peroxisome proliferator, resulted in an increase in the oxygen consumption of liver microsomes compared to the values of the untreated controls. A maximum increase in the level of oxygen consumption in liver microsomes was observed in the mice treated with TCE, followed by clofibrate and TCA treatments. All three agents also increased the rate of NADPH oxidation in mice liver microsomes compared with untreated controls. NADPH oxidation was increased four fold by TCE or clofibrate (38 or 37 nmol/min) and two fold by TCA treatment (17 nmol/min) over that of the control animals (9 nmol/min). The concentration of malondialdehyde was higher in all three treated groups in comparison with control values. Malondialdehyde levels were elevated by 227%, 191%, and 118% by treatment with TCE, clofibrate, and TCA, respectively. Increases in the levels of oxygen consumption, NADPH disappearance, and malondialdehyde production in microsomes from liver of mice treated chronically with TCE or TCA are all indicative of elevated levels of oxidative stress. Increased oxidative stress may be involved in the induction of TCE-associated hepatotoxicity.

Animals↗
PubMed1989

Recent developments in the molecular genetics and biology of self-incompatibility.

A summary of recent work on molecular aspects of self-incompatibility in Nicotiana alata is presented. The amino acid sequences of style proteins corresponding to different S-alleles of N. alata have a high level of homology in some regions and are variable in other regions. The regions of homology include N-terminal sequences as well as most of the glycosylation sites and cysteine residues. The glycosyl substituents may consist of a number of 'glycoforms'. The isolated style S-glycoproteins inhibit in vitro growth of pollen tubes. The S-glycoproteins tested inhibited the growth of pollen of several S-genotypes, and there was some specificity in the interaction. Heat treatment of the isolated S-glycoproteins dramatically increased their activity as inhibitors of pollen tube growth, although the specificity in the interaction was lost. The nature of the S-allele products in pollen is not yet established.

Alleles↗
PubMed1989

Pragmatic and explanatory trials in the evaluation of the experimental National Health Service nursing homes.

This paper reviews the issues which arose in the design of a randomized controlled trial of three experimental National Health Service nursing homes. Problems associated with the implementation of the trial included ethical issues, choice of sample size and recruitment of subjects to the trial, choice and validity of measures of outcome, evaluation of outcomes and replicability of findings. The distinction between explanatory and pragmatic trials is shown to overcome some of these problems.

Aged↗
PubMed1989

The implementation of a multicentred randomized controlled trial in the evaluation of the experimental National Health Service nursing homes.

This paper reviews the implementation of a pragmatic multicentred randomized controlled trial in the evaluation of three experimental nursing homes. The organization of services for the care of elderly people varied between the three centres, and each used different criteria for selecting subjects for the trial and different methods of seeking informed consent. Data presented show that in each centre two truly randomized samples have been selected. However, differences between centres, in the characteristics of selected subjects, reflect the implementation of the trials in each of the centres. These findings emphasize the importance of good collaboration between health professionals providing the service, an independent research team, and the establishment of rigorous criteria for inclusion and exclusion of subjects at the outset.

Aged↗
PubMed1989

Measurement of outcomes within a multicentred randomized controlled trial in the evaluation of the experimental NHS nursing homes.

This paper reports outcome data from a multicentred randomized controlled trial (RCT) undertaken as part of the evaluation of the experimental NHS nursing homes. A small sample size within centres and differential non-response due to death and physical or mental frailty limits the statistical power of this trial and biases subject-reported outcomes toward the views of elderly people who were less frail. There were no significant differences in survival or personal well-being, or changes in behavioural ability, mental state or perceived health status between propositi and controls. There were significant differences in the views of responding propositi and controls suggesting that the experimental NHS nursing homes were preferred by residents. The results of this pragmatic trial suggest that there is no evidence to conclude that NHS nursing homes should not be provided as NHS continuing-care accommodation. Policy decisions should also take account of the other studies undertaken as part of the evaluation. Further research is needed to develop more appropriate outcome measures for this client group.

Aged↗
PubMed1989

Sequence variability of three alleles of the self-incompatibility gene of Nicotiana alata.

Three alleles of the self-incompatibility gene of Nicotiana alata have been cloned and sequenced. A comparison of the sequences shows a surprisingly low level of homology (56%) and the presence of defined regions of homology and variability. The homologous regions include the N-terminal sequence, most of the cysteine residues and glycosylation sites, as well as other blocks throughout the sequence. We interpret these conserved regions as "framework" and nonconserved regions as "hypervariable," following the terminology used to describe analogous regions in the IgG supergene family. The low level of overall homology forms the basis of a general method for isolating S-allele-specific cDNAs. Allele-specific antibodies can be generated using synthetic peptides corresponding to one of the variable regions. When applied to sections of the pistil, these antibodies label the intercellular matrix in the stigma and transmitting tissue of the style and the cell walls in the epidermis of the placenta. HindIII digestion of genomic DNA generates a characteristic pattern of S-gene fragments for each genotype. These restriction fragment length polymorphisms can be used to assign S-genotype to progeny arising from breeding experiments.

Alleles↗
PubMed1988

Should QALYs be programme-specific?

One reason for the development of quality adjusted life years (QALYs) is to facilitate comparison across health care programmes in terms of productivity per unit of expenditure. However, some approaches to QALY measurement have also been developed using 'programme-specific' dimensions of quality of life. Using data, from a longitudinal trial of long-term care for elderly people, it is shown in this paper that an 'across-programme' method of quality of life measurement is less sensitive to changes in elderly people's health states than programme-specific methods more commonly used in the field of evaluating long-term care. It is argued that the same problem is likely to arise in evaluating care for other common chronic conditions like mental handicap, chronic conditions of childhood and terminal cancer. It is concluded that more work should be carried out comparing across-programme and programme-specific measures of quality of life, otherwise it will be difficult to determine whether certain groups in society are being discriminated against in health service resource allocation due to an insensitive across-programme measure of outcome.

Activities of Daily Living↗
PubMed1988

QALYS and long-term care for elderly people in the UK: scales for assessment of quality of life.

QALYs have developed in the UK as a tool for comparing the outcome of health care procedures in a single index over time. This tool can then be used, along with information on costs of procedures, in decision-making about health service resource allocation. It is shown that the attributes of disability and distress, on which QALYs are presently based in the UK, are insensitive to changes in the health status of elderly people in long-term care when compared to other measures of quality of life which are frequently used in studies of older people. Thus, if the use of QALYs increases, they should be based on attributes appropriate to the groups studied, otherwise certain groups may be discriminated against in health service resource allocation owing to the use of an insensitive measure of outcome.

Aged↗