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Biomedical subjects

T Parker

Publications and source records attributed to T Parker.

At least 19 recordsLinked to original sources
PubMed2006

Deletion of chromosome 13 detected by conventional cytogenetics is a critical prognostic factor in myeloma.

In myeloma, the prognostic impact of different strategies used to detect chromosome 13 deletion (Delta13) remains controversial. To address this, we compared conventional cytogenetics and interphase fluorescence in situ hybridization (iFISH) in a large multicenter study (n=794). The ability to obtain abnormal metaphases was associated with a poor prognosis, which was worse if Delta13, p53 deletion or t(4;14) was present, but only Delta13 remained significant on multivariate analysis. Patients with Delta13, by either cytogenetics or iFISH, had a poor prognosis. However, when cases with Delta13 detectable by both cytogenetics and iFISH were separated from those detected by iFISH only, the poor prognosis of iFISH-detectable Delta13 disappeared; their outcome matched that of patients with no detectable Delta13 (P=0.115). Addition of ploidy status to iFISH-Delta13 did not affect the prognostic value of the test. Indeed both cytogenetics and iFISH Delta13 divided both hyperdiploidy and nonhyperdiploidy into two groups with similar prognoses, indicating that the poor prognosis of ploidy is entirely due to its association with Delta13. We conclude that Delta13 detected by metaphase analysis is a critical prognostic factor in myeloma. Absence of Delta13, even in those patients yielding only normal or no metaphases, is associated with a relatively good prognosis.

Adult↗
PubMed2006

Validity of foot-to-foot bioelectrical impedance analysis in overweight and obese children and parents.

AIM: The aim of this study was to evaluate the validity of foot-to-foot bioelectrical impedance analysis (FF-BIA) in the measurement of body composition in overweight and obese children and their parents by comparison to dual-energy X-ray absorptiometry (DXA). METHODS: Seventeen, 7-12 year old overweight and obese children (6 boys, 11 girls) and 17 parents (5 fathers, 12 mothers) were evaluated for body composition with FF-BIA and DXA. Measures of percent body fat (PBF), fat mass (FM) and fat free mass (FFM) derived from FF-BIA and DXA were compared. Measures of validity were determined by Pearson correlations between FF-BIA and DXA, paired t-tests to assess mean differences, as well as biases and limits of agreement using the Bland Altman tests. RESULTS: FF-BIA produced estimates of body composition that were highly correlated with DXA in overweight and obese children and parents. For children, the correlations for PBF, FM, and FFM were 0.85, 0.97, and 0.94, respectively. For parents, the correlations for PBF, FM, and FFM were 0.92, 0.97, and 0.91, respectively. However, mean differences between FF-BIA and DXA were significant in children but not in parents. Bland-Altman tests of agreement showed moderate to large within-subject differences in body composition variables between FF-BIA and DXA. CONCLUSIONS: FF-BIA is strongly related to DXA in the measurement of body composition in both overweight and obese preadolescent children and parents, but the two measures may not be used interchangeably. Although FF-BIA may lack the precision to assess small changes in body composition in overweight and obese individuals, it is appropriate for epidemiological use.

Absorptiometry, Photon↗
PubMed2004

Localization and physical property experiments conducted by Opportunity at Meridiani Planum.

The location of the Opportunity landing site was determined to better than 10-m absolute accuracy from analyses of radio tracking data. We determined Rover locations during traverses with an error as small as several centimeters using engineering telemetry and overlapping images. Topographic profiles generated from rover data show that the plains are very smooth from meter- to centimeter-length scales, consistent with analyses of orbital observations. Solar cell output decreased because of the deposition of airborne dust on the panels. The lack of dust-covered surfaces on Meridiani Planum indicates that high velocity winds must remove this material on a continuing basis. The low mechanical strength of the evaporitic rocks as determined from grinding experiments, and the abundance of coarse-grained surface particles argue for differential erosion of Meridiani Planum.

Extraterrestrial Environment↗
PubMed2004

The Opportunity Rover's Athena science investigation at Meridiani Planum, Mars.

The Mars Exploration Rover Opportunity has investigated the landing site in Eagle crater and the nearby plains within Meridiani Planum. The soils consist of fine-grained basaltic sand and a surface lag of hematite-rich spherules, spherule fragments, and other granules. Wind ripples are common. Underlying the thin soil layer, and exposed within small impact craters and troughs, are flat-lying sedimentary rocks. These rocks are finely laminated, are rich in sulfur, and contain abundant sulfate salts. Small-scale cross-lamination in some locations provides evidence for deposition in flowing liquid water. We interpret the rocks to be a mixture of chemical and siliciclastic sediments formed by episodic inundation by shallow surface water, followed by evaporation, exposure, and desiccation. Hematite-rich spherules are embedded in the rock and eroding from them. We interpret these spherules to be concretions formed by postdepositional diagenesis, again involving liquid water.

Atmosphere↗
PubMed2004

The Spirit Rover's Athena science investigation at Gusev Crater, Mars.

The Mars Exploration Rover Spirit and its Athena science payload have been used to investigate a landing site in Gusev crater. Gusev is hypothesized to be the site of a former lake, but no clear evidence for lacustrine sedimentation has been found to date. Instead, the dominant lithology is basalt, and the dominant geologic processes are impact events and eolian transport. Many rocks exhibit coatings and other characteristics that may be evidence for minor aqueous alteration. Any lacustrine sediments that may exist at this location within Gusev apparently have been buried by lavas that have undergone subsequent impact disruption.

Atmosphere↗
PubMed2004

Quality of life changes following peripheral blood stem cell transplantation and participation in a mixed-type, moderate-intensity, exercise program.

The purpose of this investigation was to evaluate the impact of undertaking peripheral blood stem cell transplantation (PBST) on quality of life (QoL), and to determine the effect of participating in a mixed-type, moderate-intensity exercise program on QoL. It was also an objective to determine the relationship between peak aerobic capacity and QoL in PBST patients. QoL was assessed via the CARES questionnaire and peak aerobic capacity by a maximal graded treadmill test, pretransplant (PI), post transplant (PII) and following a 12-week intervention period (PIII). At PII, 12 patients were divided equally into a control or exercise intervention group. Undergoing a PBST was associated with a statistically but not clinically significant decline in QoL (P<0.05). Following the intervention, exercising patients demonstrated an improved QoL when compared with pretransplant ratings (P<0.01) and nonexercising transplant patients (P<0.05). Moreover, peak aerobic capacity and QoL were correlated (P<0.05). The findings demonstrated that exercise participation following oncology treatment is associated with a reduction in the number and severity of endorsed problems, which in turn leads to improvements in global, physical and psychosocial QoL. Furthermore, a relationship between fitness and QoL exists, with those experiencing higher levels of fitness also demonstrating higher QoL.

Adolescent↗
PubMed2003

Influence of postweaning social isolation in the rat on brain development, conditioned behavior, and neurotransmission.

There is substantial evidence that early life events influence brain development and subsequent adult behavior and play an important role in the causation of certain psychiatric disorders including schizophrenia and depression. The underlying mechanism of the effects of these early environmental factors is still not understood. It is a challenge to attempt to model early environmental factors in animals to gain understanding of the basic mechanisms that underlie the long-term effects. This paper reviews the effects of rearing rats from weaning in social isolation and reports some recent results indicating hippocampal dysfunction. Isolation rearing in rats from weaning produces a range of persistent behavioral changes in the young adult, including hyperactivity in response to novelty and amphetamine and altered responses to conditioning. These are associated with alterations in the central aminergic neurotransmitter functions in the mesolimbic areas and other brain regions. Isolation-reared rats have enhanced presynaptic dopamine (DA) and 5-HT function in the nucleus accumbens (NAC) associated with decreased presynaptic 5-HT function in the frontal cortex and hippocampus. Isolation-reared rats have reduced presynaptic noradrenergic function in the hippocampus, but have enhanced presynaptic DA function in the amygdala. These neurochemical imbalances may contribute to the exaggerated response of the isolated rat to a novel stimulus or to stimuli predictive of danger, and isolation-induced behavioral changes. These changes have neuroanatomical correlates, changes which seem to parallel to a certain degree those seen in human schizophrenia. A greater understanding of the processes that underlie these changes should improve our knowledge of how environmental events may alter brain development and function, and play a role in the development of neuropsychiatric disorders.

8-Hydroxy-2-(di-n-propylamino)tetralin↗
PubMed2003

Total energy expenditure and body composition changes following peripheral blood stem cell transplantation and participation in an exercise programme.

The purpose of this investigation was to assess changes in total energy expenditure (TEE), body weight (BW) and body composition following a peripheral blood stem cell transplant and following participation in a 3-month duration, moderate-intensity, mixed-type exercise programme. The doubly labelled and singly labelled water methods were used to measure TEE and total body water (TBW). Body weight and TBW were then used to calculate percentage body fat (%BF), and fat and fat-free mass (FFM). TEE and body composition measures were assessed pretransplant (PI), immediately post-transplant (PII) and 3 months post-PII (PIII). Following PII, 12 patients were divided equally into a control group (CG) or exercise intervention group (EG). While there was no change in TEE between pre- and post-transplant, BW (P<0.01) and FFM (P<0.05) significantly decreased during the same period. Participation in the exercise programme led to increases in TEE to levels that were both higher than pre- and post-transplant measures (P<0.01). By PIII, the exercising patients also showed gains in FFM (P<0.01) in association with a reduction in %BF (P<0.05). Exercise has a functionally important role in preserving and increasing skeletal mass in the rehabilitation phase of cancer patients.

Adipose Tissue↗
PubMed2003

Effect of high vegetable protein diets on urinary calcium loss in middle-aged men and women.

OBJECTIVE: To determine the effect of high-protein diets, which have recently been promoted for their health benefits, on urinary calcium losses and bone turnover in older subjects. DESIGN: Randomized controlled cross-over study. SETTING: Teaching hospital and university. SUBJECTS: Twenty hyperlipidemic men and postmenopausal women (age 56+/-2 y) completed the study. INTERVENTION: One-month test and control phases during which subjects consumed equi-energy metabolic diets high in calcium (1578 and 1593 mg/day, respectively). On the test diet 11% of total dietary energy from starch in the control bread was replaced by protein (wheat gluten), resulting in 27% of energy from protein on the test diet vs 16% on the control diet. MAIN OUTCOME MEASURE: Urinary calcium excretion. RESULTS: Compared with the control diet, at week 4, the test diet increased mean (+/-s.e.m.) 24 h urinary output of calcium (139+/-15 vs 227+/-21 mg, P=0.004). The treatment difference in urinary calcium loss correlated with the serum anion gap as a marker of metabolic acid production (r=0.57, P=0.011). Serum calcium levels were marginally lower 2.41+/-0.02 vs 2.38+/-0.02 mmol/l (P=0.075), but there was no significant treatment difference in calcium balance, possibly related to the high background calcium intake on both diets. CONCLUSION: In the presence of high dietary calcium intakes the vegetable protein gluten does not appear to have a negative effect on calcium balance despite increased urinary calcium loss.

Adult↗
PubMed2002

Elastin: a representative ideal protein elastomer.

During the last half century, identification of an ideal (predominantly entropic) protein elastomer was generally thought to require that the ideal protein elastomer be a random chain network. Here, we report two new sets of data and review previous data. The first set of new data utilizes atomic force microscopy to report single-chain force-extension curves for (GVGVP)(251) and (GVGIP)(260), and provides evidence for single-chain ideal elasticity. The second class of new data provides a direct contrast between low-frequency sound absorption (0.1-10 kHz) exhibited by random-chain network elastomers and by elastin protein-based polymers. Earlier composition, dielectric relaxation (1-1000 MHz), thermoelasticity, molecular mechanics and dynamics calculations and thermodynamic and statistical mechanical analyses are presented, that combine with the new data to contrast with random-chain network rubbers and to detail the presence of regular non-random structural elements of the elastin-based systems that lose entropic elastomeric force upon thermal denaturation. The data and analyses affirm an earlier contrary argument that components of elastin, the elastic protein of the mammalian elastic fibre, and purified elastin fibre itself contain dynamic, non-random, regularly repeating structures that exhibit dominantly entropic elasticity by means of a damping of internal chain dynamics on extension.

Acoustic Stimulation↗
PubMed2001

Effects of central noradrenaline depletion by the selective neurotoxin DSP-4 on the behaviour of the isolated rat in the elevated plus maze and water maze.

RATIONALE: Social isolation of the rat from weaning influences behaviour following central noradrenaline (NA) depletion by the selective neurotoxin N-(2-chloroethyl)-N-ethyl-2-bromobenzylamine (DSP-4). OBJECTIVES: The study characterised the effects of DSP-4 on the behaviour of isolates in the elevated plus maze and water maze. METHODS: Male Lister hooded rats were reared singly or in groups after weaning. Two weeks postweaning, the rats were injected with DSP-4 (25 mg/kg, i.p.) or saline. From week 4, rats were tested in the plus maze and in the water maze. RESULTS: DSP-4 significantly reduced cortical and hippocampal NA but had no effect on hypothalamic NA. Isolation rearing alone had no significant effects on behaviour in the elevated plus maze but enhanced retention of platform placement in the water maze as measured by increased entries to the platform annulus during the probe test. DSP-4 in group-reared rats increased activity in the open arms and increased general activity in the elevated plus maze with no effect on water maze performance. DSP-4-treated isolates spent less time in the open arms and were hypoactive in the plus maze compared to group-reared DSP-4-treated rats, and had impaired retention of spatial memory in the water maze compared to isolate controls. CONCLUSIONS: DSP-4 treatment had an 'anxiolytic' effect in group-reared rats in the elevated plus maze. In the water maze, isolation rearing enhanced retention of spatial information, an effect normalised by NA depletion. The results demonstrate the importance of noradrenergic function in the regulation of responsiveness to environmental cues.

Animals↗
PubMed2001

Lactic acid-stabilised albumin for microsphere formulation and biomedical coatings.

Microspheres of ovalbumin (OVA) ranging from 1 to 15 microm were prepared by emulsifying an aqueous solution of albumin in soya oil at room temperature then raising the temperature to 45 degrees C for 30 min, prior to harvesting of the microspheres. Production of OVA nanospheres with size less than 500 nm was achieved by desolvation from aqueous albumin solutions using acetone. In both cases, lactic acid was added to the starting albumin solution to stabilise the resulting particles. Utilisation of an endogenous substance avoids the use of chemical crosslinking agents such as glutaraldehyde and associated toxicological concerns. Protein coating of knitted Dacron vascular grafts was performed by impregnation of the textile structure with lactic acid-stabilised ovalbumin nanospheres thereby providing a surface potentially resistant to blood platelet adhesion but conducive to endothelialisation. Protein release testing carried out in PBS at 37 degrees C revealed that approximately 60% of the original albumin coating was retained by the Dacron graft material after 4 days and remained at this level for upto 4 weeks. Apart from the formulation of albumin microspheres for drug delivery, diagnostic applications and coating of biomedical textiles, the process of albumin stabilisation using lactic acid may be usefully applied to improve protein immobilisation on a wide range of biomaterial surfaces.

Blood Vessel Prosthesis↗
PubMed2001

Consultative exercise on dose assessments.

A summary is given of a meeting held at Sussex University, UK, in October 2000, which allowed the exchange of ideas on methods of assessment of dose to the public arising from potential authorised radioactive discharges from nuclear sites in the UK. Representatives of groups with an interest in dose assessments were invited, and hence the meeting was called the Consultative Exercise on Dose Assessments (CEDA). Although initiated and funded by the Food Standards Agency, its organisation, and the writing of the report, were overseen by an independent Chairman and Steering Group. The report contains recommendations for improvement in co-ordination between different agencies involved in assessments, on method development and on the presentation of data on assessments. These have been prepared by the Steering Group, and will be taken forward by the Food Standards Agency and other agencies in the UK. The recommendations are included in this memorandum.

Environmental Exposure↗
PubMed2001

High-protein diets in hyperlipidemia: effect of wheat gluten on serum lipids, uric acid, and renal function.

BACKGROUND: The metabolic effects of diets high in vegetable protein have not been assessed despite much recent interest in the effect of soy proteins in reducing serum cholesterol. OBJECTIVE: We assessed the metabolic effects of diets high in vegetable protein (specifically, wheat gluten) on serum lipids, uric acid concentrations, and renal function. DESIGN: Twenty hyperlipidemic men and women consumed isoenergetic test (high-protein) and control metabolic diets for 1 mo in a randomized crossover design. In the high-protein diet, 11% of the total dietary energy from starch in the control bread was replaced by vegetable protein (wheat gluten), resulting in 27% of total energy from protein compared with 16% in the control diet. In other respects, the 2 diets were identical. RESULTS: Compared with the control, the high-protein diet resulted in lower serum concentrations of triacylglycerol (by 19.2 +/- 5.6%; P = 0.003), uric acid (by 12.7 +/- 2.0%; P < 0.001), and creatinine (by 2.5 +/- 1.1%; P = 0.035) and higher serum concentrations of urea (by 42.2 +/- 5.8%; P < 0.001) and a higher 24-h urinary urea output (by 99.2 +/- 17.2%; P < 0.001). No significant differences were detected in total or HDL cholesterol or in the renal clearance of creatinine. LDL oxidation, assessed as the ratio of conjugated dienes to LDL cholesterol in the LDL fraction, was lower with the high-protein diet (by 10.6 +/- 3.6%; P = 0.009). CONCLUSIONS: High intakes of vegetable protein from gluten may have beneficial effects on cardiovascular disease risk by reducing oxidized LDL, serum triacylglycerol, and uric acid. Further studies are required to assess the longer-term effects on renal function.

Adult↗
PubMed2001

A randomised controlled trial of high versus low long chain triglyceride whole protein feed in active Crohn's disease.

BACKGROUND: Polymeric feeds have shown variable efficacy in active Crohn's disease (CD) with remission rates from 36% to 82%. Meta-analyses of elemental, peptide, and whole protein feeds have shown a strong negative correlation between remission rate in CD and the long chain triglyceride (LCT) content of the feed. We performed a randomised controlled double blind trial in patients with active CD comparing two single whole protein feeds with LCT supplying 5% or 30% of the total energy. METHODS: Fifty four patients with active CD (Crohn's disease activity index (CDAI) >200, serum C reactive protein (CRP) 10 mg/l) were randomised to a high or low LCT feed for three weeks. The total amount of energy supplied by fat was identical in the two feeds. Remission was defined as a CDAI < or =150 and response as a fall in CDAI of > or =70 or a CRP <10 mg/l. RESULTS: Overall remission rate by intention to treat was 26% for the low LCT feed and 33% for the high LCT feed (p=0.38). Response was achieved in 33% with the low LCT and in 52% with the high LCT feed (p=0.27). CRP <10 mg/l was achieved in 30% in the low LCT and 33% in the high LCT group (p=0.99). Thirty nine per cent (21/54) of patients withdrew before three weeks because of inability to tolerate the diet. Excluding patients unable to tolerate the diet, remission rates were 46% for low LCT and 45% for high LCT (p=0.99). DISCUSSION: This trial has shown no difference in the effect of low and high LCT whole protein feeds in active CD. The previously reported correlation between LCT content of diet and response in active CD is unlikely to be due to LCT itself and may be due to some other component of high LCT feeds.

Acute Disease↗
PubMed2001

Influence of postweaning social isolation in the rat on brain development, conditioned behaviour and neurotransmission.

There is substantial evidence that early life events influence brain development and subsequent adult behaviour and play an important role in the causation of certain psychiatric disorders including schizophrenia and depression. The underlying mechanism of the effects of these early environmental factors is still not understood. It is a challenge to attempt to model early environmental factors in animals to gain understanding of the basic mechanisms that underlie the long-term effects. This paper reviews the effects of rearing rats from weaning in social isolation and reports some recent results indicating hippocampal dysfunction. Isolation rearing in rats from weaning produces a range of persistent behavioural changes in the young adult, including hyperactivity in response to novelty and amphetamine and altered responses to conditioning. These are associated with alterations in the central aminergic neurotransmitter functions in the mesolimbic areas and other brain regions. Isolation-reared rats have enhanced presynaptic dopamine (DA) and 5-HT function in the nucleus accimbens (NAC) associated with decreased presynaptic 5-HT function in the frontal cortex and hippocampus. Isolation-reared rats have reduced presynaptic noradrenergic function in the hippocampus, but have enhanced presynaptic DA function in the amygdala. These neurochemical imbalances may contribute to the exaggerated response of the isolated rat to a novel stimulus or to stimuli predictive of danger, and isolation-induced behavioural changes. These changes have neuroanatomical correlates; changes which seem to parallel to a certain degree those seen in human schizophrenia. A greater understanding of the processes that underlie these changes should improve our knowledge of how environmental events may alter brain development and function, and play a role in the development of neuropsychiatric disorders.

Animals↗
PubMed2000

Conditional up-regulation of MHC class I in skeletal muscle leads to self-sustaining autoimmune myositis and myositis-specific autoantibodies.

In the human inflammatory myopathies (polymyositis and dermatomyositis), the early, widespread appearance of MHC class I on the surface of muscle cells and the occurrence of certain myositis-specific autoantibodies are striking features. We have used a controllable muscle-specific promoter system to up-regulate MHC class I in the skeletal muscles of young mice. These mice develop clinical, biochemical, histological, and immunological features very similar to human myositis. The disease is inflammatory, limited to skeletal muscles, self-sustaining, more severe in females, and often accompanied by autoantibodies, including, in some mice, autoantibodies to histidyl-tRNA synthetase, the most common specificity found in the spontaneous human disease, anti-Jo-1. This model suggests that an autoimmune disease may unfold in a highly specific pattern as the consequence of an apparently nonspecific event-the sustained up-regulation of MHC class I in a tissue-and that the specificity of the autoantibodies derives not from the specificity of the stimulus, but from the context, location, and probably the duration of the stimulus. This model further suggests that the presumed order of events as an autoimmune disease develops needs to be reconsidered.

Animals↗