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Biomedical subjects

D Ashby

Publications and source records attributed to D Ashby.

At least 19 recordsLinked to original sources
PubMed2001

Progressive human immunodeficiency virus-specific immune recovery with prolonged viral suppression.

The degree of immune recovery achievable with anti-human immunodeficiency virus (HIV) therapy remains to be established. The effects of potent antiretroviral therapy, including ritonavir and saquinavir, on immune function were studied for a prolonged period in 41 patients. After 96 weeks, 88% of patients had plasma HIV RNA levels below the limit of quantitation. There were continuous increases in CD4 lymphocyte counts and in CD4:CD8 ratios over time. About half the patients developed lymphoproliferative responses to HIV p24 antigen, and nearly all developed responses to phytohemagglutinin. This occurred in parallel with increases in interleukin-12 production and expression of CD28 on CD8 lymphocytes, despite potential antiproliferative effects of protease inhibitors. Transient increases in virus load were temporally associated with loss of proliferative responses. The improved immune function, including HIV-specific immunity in many subjects, demonstrates the potential reversibility of HIV-induced immunodeficiency and does not identify a limit to immune recovery.

Anti-HIV Agents↗
PubMed2001

Lack of effect of serum amyloid A (SAA) on the ability of high-density lipoproteins to inhibit endothelial cell adhesion molecule expression.

Studies have been conducted to determine whether the ability of high density lipoproteins (HDL) to inhibit the cytokine-induced expression of vascular cell adhesion molecule-1 (VCAM-1) in endothelial cells is altered by the presence in HDL of the acute phase reactant, serum amyloid-A (SAA). Preparations of HDL(3) were isolated on two separate occasions from the plasma of each of 19 patients: the first was collected before and the second 3 days after undergoing coronary artery bypass graft surgery. Whereas the preoperative HDL(3) sample contained no SAA, in the postoperative sample SAA accounted for an average of 42% of the HDL(3) protein. The preoperative HDL(3) and postoperative, SAA-enriched HDL(3) were identical in terms of their ability to inhibit the tumour necrosis factor-alpha (TNF-alpha)-induced expression of VCAM-1 in human umbilical vein endothelial cells (HUVECs). To assess the effect of having an even greater SAA enrichment of HDL(3), samples of HDL(3) were incubated with purified SAA, which displaced almost all of the apoAI and about 40% of the apoAII from the HDL(3). This in vitro SAA-enriched HDL(3) inhibited the TNF-alpha-induced expression of VCAM-1 in HUVECs in a concentration dependent manner, which was identical to that of the unmodified HDL(3). The presence of SAA did not alter the cell-surface binding of HDL(3) to endothelial cells. It has been concluded that the presence of SAA in HDL has no effect on the ability of these lipoproteins either to inhibit the expression of VCAM-1 in endothelial cells or to bind to proteins on the endothelial cell surface.

Apolipoprotein A-I↗
PubMed2000

Evidence-based medicine as Bayesian decision-making.

We review two recent trends: the emergence of evidence-based medicine and the growing use of Bayesian statistics in medical applications. Evidence-based medicine requires an integrated assessment of the available evidence, and associated uncertainty, but there is also an emphasis on decision-making, for individual patients, or at other points in the health-care system. This demands consideration of the values and costs associated with potential outcomes. We argue that the natural statistical framework for evidence-based medicine is a Bayesian approach to decision-making that incorporates an integrated summary of the available evidence and associated uncertainty with assessment of utilities. We outline a practical agenda for further development.

Bayes Theorem↗
PubMed2000

WD40 repeat proteins striatin and S/G(2) nuclear autoantigen are members of a novel family of calmodulin-binding proteins that associate with protein phosphatase 2A.

Protein phosphatase 2A (PP2A) is a multifunctional serine/threonine phosphatase that is critical to many cellular processes including development, neuronal signaling, cell cycle regulation, and viral transformation. PP2A has been implicated in Ca(2+)-dependent signaling pathways, but how PP2A is targeted to these pathways is not understood. We have identified two calmodulin (CaM)-binding proteins that form stable complexes with the PP2A A/C heterodimer and may represent a novel family of PP2A B-type subunits. These two proteins, striatin and S/G(2) nuclear autoantigen (SG2NA), are highly related WD40 repeat proteins of previously unknown function and distinct subcellular localizations. Striatin has been reported to associate with the post-synaptic densities of neurons, whereas SG2NA has been reported to be a nuclear protein expressed primarily during the S and G(2) phases of the cell cycle. We show that SG2NA, like striatin, binds to CaM in a Ca(2+)-dependent manner. In addition to CaM and PP2A, several unidentified proteins stably associate with the striatin-PP2A and SG2NA-PP2A complexes. Thus, one mechanism of targeting and organizing PP2A with components of Ca(2+)-dependent signaling pathways may be through the molecular scaffolding proteins striatin and SG2NA.

3T3 Cells↗
PubMed2000

Randomized controlled trials in cystic fibrosis (1966-1997) categorized by time, design, and intervention.

The improved prognosis of cystic fibrosis (CF) over the last three decades has been associated with an increased use of a range of treatments, but it is important that the use of an individual treatment is based on evidence. Well-designed randomized controlled trials (RCTs) are a robust method for evaluating the effectiveness of such treatments. We have developed a register of RCTs in CF and have studied when they were performed, their design, and what interventions were investigated. We identified 506 RCTs; 37.5% were identified solely as abstract reports in conference proceedings. There has been about a 30-fold increase in the number of RCTs in CF since 1966. A high proportion of the RCTs (72.7%) had a sample size of 30 or less, and only 8.7% were multicenter trials. Reporting of study design was poor: in 51.4% the report did not state whether there was any blinding in the trial design; 53.6% of studies were of crossover design. The most common interventions studied were antibiotic treatments and physiotherapy, but a number of commonly used therapies had been evaluated only in a small number of patients. Although the number of RCTs of interventions in CF patients has increased over the last 25 years, the sample sizes of these trials are generally too small to indicate whether the intervention was effective, and very few were multicenter. Future RCTs in CF are more likely to provide clinically useful answers if higher numbers of patients are recruited into large, well-designed multicenter trials. This should be a priority of the organization of future research in CF.

Cystic Fibrosis↗
PubMed2000

Ursodeoxycholic acid for cystic fibrosis-related liver disease.

BACKGROUND: Cystic fibrosis-related liver disease peaks in adolescence with up to 20% of patients developing chronic liver disease. Early changes in the liver may ultimately result in end stage liver disease with patients needing transplantation. One therapeutic option currently used is ursodeoxycholic acid. OBJECTIVES: To assess the effectiveness of ursodeoxycholic acid in cystic fibrosis liver disease. SEARCH STRATEGY: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group trials register, and contacted drug companies. Date of the most recent search of the Group's specialised register: June 1999. SELECTION CRITERIA: Randomised and quasi-randomised trials of use of ursodeoxycholic acid for at least three months compared with placebo or no additional treatment in people with cystic fibrosis. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial eligibility and quality. MAIN RESULTS: Three trials involving 118 patients were included. The complex study design used in two trials meant that data could only be analysed for subsets of patients. There was no difference in weight change (weighted mean difference -0.496, 95% confidence interval -1.545 to +0.553) based on 30 patients from two trials. Improvement in biliary excretion was reported in only one study and no significant change after treatment was shown. Long term outcomes such as death or need for liver transplantation were not reported. REVIEWER'S CONCLUSIONS: There are few trials assessing the effectiveness of ursodeoxycholic acid. There is insufficient evidence to justify is its routine use in cystic fibrosis.

Cholagogues and Choleretics↗
PubMed2000

Oral steroids for cystic fibrosis.

BACKGROUND: In cystic fibrosis, airway obstruction and recurrent respiratory infection leads to inflammation and eventually long term lung damage, (bronchiectasis), respiratory failure and death. Inflammation occurs early in the disease process, hence the rationale for the use of anti-inflammatory agents such as oral steroids. OBJECTIVES: To assess the effectiveness of oral steroids in management of respiratory complications cystic fibrosis with particular regard to lung function and occurrence of adverse events. We aimed to to examine short term use for a respiratory exacerbation separately (up to 30 days) from long term anti-inflammatory use (greater than 30 days). SEARCH STRATEGY: We searched The Cochrane Cystic Fibrosis and Genetic Disorders Group specialist trials register. Date of the most recent search of the Group's specialised register: November 1999. SELECTION CRITERIA: All randomised or pseudorandomised trials comparing oral corticosteroids given for a period of five to 30 days for treatment of an exacerbation or for more than 30 days used long term, with placebo or no additional therapy in patients with cystic fibrosis. DATA COLLECTION AND ANALYSIS: Two reviewers independently assessed trial eligibility and quality. MAIN RESULTS: Three trials were identified studying a total of 354 patients. Two of these were long term trials with four year follow up whilst one had follow up to 12 weeks only. There was a lack of data on our predefined outcomes with common outcomes examined at different time-points and also variations in the presentation of common outcomes. A meta-analysis was not possible. Oral corticosteroids at a prednisolone equivalent dose of 1 mg/kg alternate days appear to slow the progression of lung disease in cystic fibrosis. At 24 months from commencement, 70.4% patients treated with 1mg/kg prednisolone on alternate days had an increase in per cent predicted forced vital capacity (FVC) compared to 41.6% patients treated with placebo. The mean absolute change in per cent predicted forced expiratory volume at one second (FEV1) 48 months from commencement was -2% in the 1 mg/kg alternate days prednisolone group but -6% in the placebo group. In the long term, this benefit needs to be weighed against the occurrence of adverse events. Linear growth retardation was observed as early as six months from start of treatment in the 2 mg/kg alternate days prednisolone group and from 24 months of treatment in the 1 mg/kg alternate days prednisolone group. Occurrence of adverse events, particularly glucose abnormalities, cataracts and growth retardation resulted in early termination of one of the four year studies ( approximately approximately Eigen 1995 approximately approximately ), with the group taking 2 mg/kg prednisolone on alternate days being stopped first but followed by the 1 mg/kg alternate days. REVIEWER'S CONCLUSIONS: Oral corticosteroids at a prednisolone equivalent dose of 1-2 mg/kg alternate days appear to slow the progression of lung disease in CF but this benefit needs to be weighed against the occurrence of adverse events, in particular, development of cataracts and effect on linear growth. A risk/benefit analysis of low-dose alternate days corticosteroids would be important and the role of short term use of oral steroids should be more fully evaluated.

Anti-Inflammatory Agents↗
PubMed2000

Orthodontic treatment for posterior crossbites.

BACKGROUND: 'Posterior crossbite' occurs when the top back teeth bite inside the bottom back teeth. When it affects one side of the mouth the lower jaw may have to move to one side to allow the back teeth to meet together. This movement may have long term effects on the growth of the teeth and jaws. It is unclear what causes posterior crossbites and they may develop or improve at any time from when the baby teeth come into the mouth to when the adult teeth come through. Several treatments have been recommended to correct them. Some treatments widen the upper teeth whilst others are directed at treating the cause of the posterior crossbite e.g. breathing problems or sucking habits. Most treatments have been used at each stage of dental development. OBJECTIVES: The aim of this review was to identify and evaluate orthodontic treatments used to expand the maxillary dentition and / or correct posterior crossbites. SEARCH STRATEGY: All randomised and controlled clinical trials identified from the Cochrane Controlled Trials Register according to the Oral Health Group Search Strategy and stored in the Cochrane Collaboration Oral Health Group Database of Clinical Trials, a MEDLINE search using the Mesh term and free text words, hand searching the British, European and American journals of orthodontics and Angle Orthodontist, and the bibliographies of papers and review articles which reported the outcome of orthodontic treatment to expand the maxillary dentition and/or correct a posterior crossbite that were published as abstracts or papers between 1970 and 1997 in English. SELECTION CRITERIA: All randomised and controlled clinical trials published as full papers or abstracts which reported quantitative data on the outcomes crossbite correction, molar and/or canine expansion, signs and symptoms of temporomandibular joint dysfunction or respiratory disease. DATA COLLECTION AND ANALYSIS: Data were extracted without blinding to the authors, treatments used or results obtained. The first named authors of randomised and controlled clinical trials were written to in an attempt to establish the method of randomisation / allocation and identify unpublished studies. Odds ratio, 95% confidence intervals, relative risk, relative risk reduction, absolute risk reduction, and the number need to treat were calculated for event data. The weighted mean difference and 95% confidence intervals were calculated for continuous data. MAIN RESULTS: Using the search strategy 7 randomised and 5 controlled clinical trials were identified but following correspondence with the authors, 3 of the randomised and 1 of the controlled clinical trials were reclassified giving 5 randomised and 7 controlled clinical trials for inclusion in the review. Trials comparing occlusal grinding in the primary dentition with/without an upper removable expansion appliance in the mixed dentition versus no treatment, banded versus bonded rapid maxillary expansion, banded versus bonded slow maxillary expansion, transpalatal arch with/without buccal root torque and an upper removable expansion appliance versus quad-helix were identified. Occlusal grinding in the primary dentition with/without the addition of an upper removable expansion plate, in the mixed dentition for those children who did not respond to grinding, was shown to be effective in preventing a posterior crossbite in the primary dentition from being perpetuated to the mixed and permanent dentitions. No evidence of a difference in treatment effect (molar and canine expansion) between the test and control intervention was found in the trials which compared banded versus bonded rapid maxillary expansion, banded versus bonded slow maxillary expansion, transpalatal arch with/without buccal root torque, or upper removable expansion appliance versus quad-helix. (ABSTRACT TRUNCATED)

Adult↗
PubMed2000

Reliability of percentage ideal weight for height.

AIMS: To assess the reliability of percentage ideal weight for height (%WFH) as a measure in children. METHODS: Forty two dietitians calculated %WFH of six children. Eleven of the 42 repeated the calculations. RESULTS: Interexaminer estimates varied by 16.5 to 40 percentage points (mean 27.8). Intraexaminer variability was also large. CONCLUSIONS: %WFH is an unreliable measure of nutritional status.

Body Height↗
PubMed1999

An investigation of the effects on children of tooth extraction under general anaesthesia in general dental practice.

OBJECTIVE: To describe the morbidity related to general anaesthesia provided in general dental practices for the extraction of teeth in school children. DESIGN: Observational study supported by structured questionnaires and interviews. SETTING: Three general dental practices in a Lancashire health district and children's homes. SUBJECTS: 80 children aged 5-15 years undergoing extractions under general anaesthesia. MAIN OUTCOME MEASURES: Observed demeanour of the children prior to, during and immediately after the surgical procedures. Reported morbidity during the following 24 hours and 1 month later. RESULTS: 92% of the children complained of symptoms associated with the surgery under general anaesthesia. Distress was noted in 16 (20%) patients during the induction of 26 (33%) during recovery. Continued crying was reported for 24 (39%) during the journey home and for 23 (37%) once home had been reached. Other symptoms included nausea, vomiting, sickness and prolonged bleeding. Six reported psychological trauma 1 month after; three had nightmares, two had continuing bad memories and one was depressed for several days. CONCLUSION: Morbidity following extractions under general anaesthesia in general dental practice is common and has distressing consequences for the young patients and their carers.

Adolescent↗
PubMed1999

Dynamic correlation of apoptosis and immune activation during treatment of HIV infection.

T cells from HIV infected patients undergo spontaneous apoptosis at a faster rate than those from uninfected patients, are abnormally susceptible to activation induced cell death (AICD), and undergo increased apoptosis in response to Fas receptor ligation. These observations have led to the hypothesis CD4 T cell apoptosis may be a mechanism of CD4 T cell depletion and the pathogenesis of AIDS. Successful treatment of HIV infected patients is accompanied by quantitative and qualitative improvements in immune function reflecting at least partial reversibility of the underlying pathogenesis of HIV. In this report we correlate improvements in markers of immune function with a decrease in apoptosis, and changes in its regulation. Therapy with nelfinavir plus saquinavir in combination with two nucleoside analogue inhibitors of reverse transcriptase dramatically reduces plasma viremia and increases CD4 T cell counts. Coincident with these improvements, CD38 and HLA-DR coexpression on both CD4 and CD8 T cells decrease, and CD45RA and CD62L coexpression increase. Furthermore, spontaneous apoptosis decreases in both CD4 and CD8 T cells (CD4 apoptosis 17.4 vs 2.6%, P=0.005; CD8 apoptosis 15.0 vs 1.0%, P<0.001), as does both Fas mediated apoptosis (CD4 apoptosis 19.0 vs 3.5%, P=0.03; CD8 apoptosis 13.7 vs 1.5%, P=0.002) and CD3 induced AICD (CD4 apoptosis 13.7 vs 3.2%, P=0.001; CD8 apoptosis 29 vs 2.2%, P=0.08). Changes in apoptosis are not associated with changes in Fas receptor expression, but are significantly correlated with changes in activation marker profiles. Although this suggests a possible regulatory role for the apoptosis inhibitory protein FLIP, direct assessment did not reveal quantitative differences in FLIP expression between apoptosis resistant PBL's from HIV negative patients, and apoptosis sensitive PBL's from HIV positive patients. These findings support the hypothesis that apoptosis mediates HIV induced CD4 T cell depletion, but indicate the need for further studies into the molecular regulation of HIV induced apoptosis.

Adolescent↗
PubMed1998

Time to publication as full reports of abstracts of randomized controlled trials in cystic fibrosis.

OBJECTIVES: To determine 1) what proportion of abstracts of randomized controlled trials (RCTs) presented at international conferences on cystic fibrosis (CF) are published as full reports, 2) time to publication, and 3) factors that might delay or prevent publication. METHODS: At the end of 1995, the Cochrane CF Group's register of RCTs contained 199 abstracts describing 180 RCTs. Abstracts were identified by handsearching 44 abstract books of three international CF conferences over a 30-year period. We searched the register for subsequent full reports of these RCTs and used survival analysis to investigate time to publication. Using the log-rank test, we examined 1) whether there is a difference in time to publication between reports where the investigators concluded that the test treatment was as effective as or better than the control treatment, and reports where it was not, and 2) whether there is a difference in time to publication according to sample size. RESULTS: Thirty-two percent of the 178 abstracts analyzed were subsequently published in full. Survival analysis indicated that the proportions published before 12 months, 2 years, and 5 years were 8.1%, 29%, and 40% respectively. No difference in time to publication was identified when the abstracts were stratified according to conclusions or sample size; no significant association (P > 0.05) existed between time to publication and both sample size and conclusions together. CONCLUSION: Only a small proportion of abstracts of RCTs presented at international conferences on CF are followed by full publication, and usually only after several years. Therefore, many potentially valuable studies do not reach a wide audience. However, we found no consistent factors which might delay or prevent publication.

Abstracting and Indexing↗
PubMed1997

Tutorial in biostatistics Bayesian data monitoring in clinical trials.

Many clinical trials organizations use regular interim analyses to monitor the accruing results in large clinical trials. In disease areas such as cancer, where survival is usually a major outcome variable, ethical considerations may lead to a stipulated requirement for data monitoring of mortality. This monitoring has frequently taken the form of limiting interim analyses to be few in number, and specifying an extreme p-value of, for example, p < 0.001 or p < 0.01 as grounds for early termination of the trial. Group-sequential methods are also used. However, none of these approaches formally assesses the impact that the results of a clinical trial may have upon clinical practice. Thus a trial might be terminated early because of apparent treatment benefits, but might fail to influence sceptical clinicians to modify their future treatment policy. We discuss the application of Bayesian methods, including the use of uninformative, sceptical and enthusiastic priors, and demonstrate that the necessary calculations are both straightforward to perform and easy to interpret statistically and clinically. Methods are illustrated with interim analyses of a clinical trial in oesophageal cancer.

Bayes Theorem↗
PubMed1997

Respiratory syncytial virus genotypes and disease severity among children in hospital.

OBJECTIVES: To determine the spectrum of N and G genotypes of respiratory syncytial virus (RSV) causing respiratory tract infection and whether particular genotypes are associated with severity of infection. PATIENTS AND METHODS: Nasopharyngeal aspirates (NPAs) were obtained from 114 infants with acute respiratory tract infection due to RSV over two seasons. Viral mRNA was extracted from NPAs or cultured virus, reverse transcribed, and the cDNA amplified by the polymerase chain reaction using primers directed to parts of the N and G gene respectively. Amplicons were separately digested with four different restriction endonucleases for each gene. The fragments were separated by agarose gel, electrophoresis, and the electrophoretic patterns used to assign the various genotypes. Disease severity was assessed as very mild (upper respiratory tract signs only), mild (coryza and signs of lower respiratory tract infection), moderate (requiring nasogastric or intravenous fluids), and severe (requiring oxygen or ventilation). RESULTS: Five of the six known N genotypes were detected, but NP4 and NP2 were found most frequently. There was no association between N genotype and disease severity. Six G (SHL) genotypes were detected. Significantly (p = 0.04) more of the infants infected with the SHL2 genotype had severe or moderate disease. CONCLUSIONS: During the seasonal peaks of RSV respiratory tract infection at least 10 different RSV genotypes cocirculated. While there is no association between N genotypes and disease severity, infection with the SHL2 G genotype appears to result in moderate to severe disease.

Acute Disease↗
PubMed1996

A Bayesian approach to Weibull survival models--application to a cancer clinical trial.

In this paper we outline a class of fully parametric proportional hazards models, in which the baseline hazard is assumed to be a power transform of the time scale, corresponding to assuming that survival times follow a Weibull distribution. Such a class of models allows for the possibility of time varying hazard rates, but assumes a constant hazard ratio. We outline how Bayesian inference proceeds for such a class of models using asymptotic approximations which require only the ability to maximize the joint log posterior density. We apply these models to a clinical trial to assess the efficacy of neutron therapy compared to conventional treatment for patients with tumours of the pelvic region. In this trial there was prior information about the log hazard ratio both in terms of elicited clinical beliefs and the results of previous studies. Finally, we consider a number of extensions to this class of models, in particular the use of alternative baseline functions, and the extension to multi-state data.

Bayes Theorem↗