Biomedical subjects
David R Jones
Publications and source records attributed to David R Jones.
Combined bronchial sleeve resection and repair of partial anomalous pulmonary venous return.
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A systematic review of systematic reviews and meta-analyses of animal experiments with guidelines for reporting.
To maximize the findings of animal experiments to inform likely health effects in humans, a thorough review and evaluation of the animal evidence is required. Systematic reviews and, where appropriate, meta-analyses have great potential in facilitating such an evaluation, making efficient use of the animal evidence while minimizing possible sources of bias. The extent to which systematic review and meta-analysis methods have been applied to evaluate animal experiments to inform human health is unknown. Using systematic review methods, we examine the extent and quality of systematic reviews and meta-analyses of in vivo animal experiments carried out to inform human health. We identified 103 articles meeting the inclusion criteria: 57 reported a systematic review, 29 a systematic review and a meta-analysis, and 17 reported a meta-analysis only. The use of these methods to evaluate animal evidence has increased over time. Although the reporting of systematic reviews is of adequate quality, the reporting of meta-analyses is poor. The inadequate reporting of meta-analyses observed here leads to questions on whether the most appropriate methods were used to maximize the use of the animal evidence to inform policy or decision-making. We recommend that guidelines proposed here be used to help improve the reporting of systematic reviews and meta-analyses of animal experiments. Further consideration of the use and methodological quality and reporting of such studies is needed.
The effect of laparoscopy on the IGF system in patients diagnosed with acute cholecystitis.
OBJECTIVE: IGFs and IGF binding proteins in the circulation are subject to modulation by a number of catabolic states including inflammation, trauma and surgery. We sought to determine the impact of laparoscopy on the IGF system in patients diagnosed with acute cholecystitis. DESIGN: The components of the IGF system, cortisol, glucose and insulin concentration in both the serum and urine of patients were compared to those from a healthy group of subjects. An additional comparison was made between pre- and post-laparoscopically assisted patients. PATIENTS: Thirty patients diagnosed with acute cholecystitis and 81 matched controls were included in the study. MEASUREMENTS: Radioimmunoassays were used to determine the IGF-I, IGF-II, insulin and cortisol concentrations. The concentration of IGFBP-3 was measured using an immunoradiometric assay. The GOD-PAP method was used to determine the glucose concentration. Gel filtration chromatography was performed to calculate the IGF binary/ternary complex ratio. The amount of sialic acid in IGFBP-3 was determined by affinity chromatography. The presence of IGFBPs in serum was determined by both immunoblotting and ligandblotting. RESULTS: The concentrations of circulating IGF-I, IGF-II and IGFBP-3 were significantly reduced in pre-operative patients compared to healthy subjects. No further reductions were observed post-laparoscopy. Immunoblotting and ligandblotting demonstrated a decreased amount of IGFBP-3 in both pre- and post-operative patients compared to healthy subjects. Increased levels of IGFBP-2 and IGFBP-1 were observed in pre-operative patients compared to healthy subjects, but laparoscopy did not cause further elevation. No alteration in the IGF binary/ternary complex ratio was witnessed between any of the study groups. A significant increase in the sialic acid content of IGFBP-3 was seen in both patient groups when compared to healthy subjects. The level of urinary cortisol was significantly increased in post-operative patients, whereas the urinary IGF-I concentration was decreased compared to healthy subjects. CONCLUSIONS: Our results indicate that acute cholecystitis causes several significant changes in the circulating IGF system. Laparoscopy, however, does not aggravate such changes, but elevates urinary cortisol.
Systemic NF-kappaB activation in blood cells of breast cancer patients.
There is a well-established role for reactive oxygen and nitrogen species, chronic inflammation and immune response in the pathogenesis of breast cancer. Complex interactions between breast cancer cells and surrounding blood vessels are prerequisites for cancer growth and invasion. Reports in the literature concerning the systemic response to, and the effect of, common breast cancer therapy on NF-kappaB and antioxidative defence enzyme expression and activity under clinical conditions are scarce. We determined these parameters in whole blood cell lysate from 16 women with breast cancer before and after combined (cyclophosphamide, doxorubicin, 5-fluorouracil; CAF) therapy and compared the results with 16 healthy women. Significantly higher levels of NF-kappaB and Mn-SOD (both their protein level and their activity) were found in breast cancer patients before and after CAF therapy, in comparison with healthy women. In parallel measurements, no change in the level or activity of catalase (CAT) was detected. According to our findings, it appears that breast cancer creates conditions that increase the level of hydrogen peroxide in the circulating cells and that the applied CAF therapy fails to compensate, therefore creating systemic conditions that favour survival and invasion of breast cancer cells.
The effects of depth, temperature and food ingestion on the foraging energetics of a diving endotherm, the double-crested cormorant (Phalacrocorax auritus).
Avian divers are confronted with a number of physiological challenges when foraging in cold water, especially at depth. Besides the obvious constraint imposed by the necessity to return to the surface for gas exchange, cold water temperatures and a reduction in body insulation due to the increase in pressure with dive depth will elevate the energetic costs of foraging in these endotherm divers. The complex effect that depth has on the diving energetics of aquatic birds has largely been ignored. To date, no study has assessed the impact of depth on diving energetics over a significant depth range, naturally encountered by the diver. We used open-circuit respirometry to study the energetic requirements of a foot-propelled pursuit diver, the double-crested cormorant (Phalacrocorax auritus albociliatus), when diving in a shallow (1 m) and deep (10 m) dive tank and when resting in air and water. We also investigated the modifying effects of air or water temperature and feeding status on the costs associated with diving and resting. Of all factors investigated, dive depth exercised the strongest influence on diving metabolic rate. Diving to 10 m depth increased metabolic rate on average by 22% when compared with shallow diving. Declining temperatures in air and water significantly elevated metabolic rate of cormorants resting in air and water as well as during diving. Feeding before resting in water or diving increased metabolic rate by 5-8% for at least 2 h. Cormorants maintained an elevated stomach temperature (>42 degrees C) when resting in water and during diving, even at cold temperatures. The elevated dive costs during deep diving, when compared with shallow diving, are most likely a consequence of the increased thermoregulatory costs associated with a greater heat loss to the water at depth. Nevertheless, our study shows that dive costs in double-crested cormorants are similar to those of other foot-propelled avian divers.
Effect of dietary zinc on the levels and distribution of Fatty acids and vitamin A in blood plasma chylomicrons.
The aim of this work was to explore the effects of a low- and high-zinc diet and vitamin Aon the distribution of fatty acids in chylomicrons. Mongolian Gerbils were fed a basal diet (for 3 wk) containing 8 or 38 mg zinc/kg of feed (low-zinc group [termed LZ group] and saturated zinc group [termed SZ group], respectively). The following day, the animals were given sunflower oil containing 50 nmol vitamin A. The results showed that the concentration of zinc in blood plasma was similar in both groups. The amount of plasma chylomicrons was lower in the LZ group than in the SZ group (p < 0.001). The concentration of retinol in blood plasma was lower in the LZ group than in the SZ group (p < 0.01). However, the results demonstrated an increase in the blood plasma retinol concentration in the LZ group compared to the SZ group when calculated per milligram of plasma chylomicrons (p < 0.01). In plasma chylomicrons, fatty acids corresponding to 16:0, 16:1, 17:0, 17:1, 18:0, 18:1, 18:2, 18:3, 20:0, 21:0, and 20:4 were detected. The fatty acid distribution was similar in both groups. There was no major difference in the concentration of fatty acids in plasma chylomicrons between both experimental groups, except for 20:4 (a lower amount was found in the SZ group). Our results show that dietary zinc influences both the amount of chylomicrons in blood plasma and the concentrations of retinol and arachidonic acid in chylomicrons.
Alterations in anti-oxidative defence enzymes in erythrocytes from sporadic amyotrophic lateral sclerosis (SALS) and familial ALS patients.
BACKGROUND: Overproduction of nitric oxide (NO) and hydrogen peroxide (H(2)O(2)) may be an important factor in the pathogenesis of amyotrophic lateral sclerosis (ALS). Owing to their ability to permeate through biological membranes, excess NO and H(2)O(2) may be present in the media surrounding motor neurones. Anti-oxidative defence enzymes (ADEs) in erythrocytes are capable of detoxifying reactive oxygen species (produced endogenously or exogenously), but may also be structurally modified and inactivated by reactive oxygen and nitrogen species. Both balanced and coordinated ADE activities are of utmost importance for their correct physiological function. METHODS: We determined activity of the following ADEs: copper-zinc superoxide dismutase (CuZn SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR) in erythrocytes from sporadic ALS patients [SALS (-/+)], familial ALS patients with the Leu144Phe mutation in the SOD1 gene [FALS (+/+)], asymptomatic carriers with the Leu144Phe mutation in the SOD1 gene (+/-), and control subjects (-/-). We also examined the in vitro effect of diethyldithiocarbamate (DDC) on CuZn SOD activity in erythrocytes from FALS patients, SALS patients and control subjects. RESULTS: The influence of the Leu144Phe mutation and/or disease was apparent for ADE activities measured in all three patient groups. The SOD1 gene mutation decreased CuZn SOD and GSH-Px activity (two-way ANOVA, significant mutation effect). We noted that the disease also contributed to decreased CuZn SOD activity in SALS patients in comparison with the control group (two-way ANOVA, mutation and disease effect). The disease also influenced CAT and GR activity. CAT activity was decreased in both SALS and FALS patients. In all three patient groups, GR activity was higher than in the control group. Finally, DDC inhibited CuZn SOD activity in erythrocytes from control subjects, FALS (Leu144Phe) patients and SALS patients; however, its effect was more pronounced and significant in FALS patients. CONCLUSIONS: Changes in erythrocyte ADE activities suggest that oxidative stress, involved in the motor neurone pathogenesis of SALS and FALS, also has systemic effects. Differences in ADE systems between the study groups revealed the presence of different types of oxidative pressure, indicating the potential additional benefit of individually designed anti-oxidant cocktail therapies.
Additive and multiplicative covariate regression models for relative survival incorporating fractional polynomials for time-dependent effects.
Relative survival is used to estimate patient survival excluding causes of death not related to the disease of interest. Rather than using cause of death information from death certificates, which is often poorly recorded, relative survival compares the observed survival to that expected in a matched group from the general population. Models for relative survival can be expressed on the hazard (mortality) rate scale as the sum of two components where the total mortality rate is the sum of the underlying baseline mortality rate and the excess mortality rate due to the disease of interest. Previous models for relative survival have assumed that covariate effects act multiplicatively and have thus provided relative effects of differences between groups using excess mortality rate ratios. In this paper we consider (i) the use of an additive covariate model, which provides estimates of the absolute difference in the excess mortality rate; and (ii) the use of fractional polynomials in relative survival models for the baseline excess mortality rate and time-dependent effects. The approaches are illustrated using data on 115 331 female breast cancer patients diagnosed between 1 January 1986 and 31 December 1990. The use of additive covariate relative survival models can be useful in situations when the excess mortality rate is zero or slightly less than zero and can provide useful information from a public health perspective. The use of fractional polynomials has advantages over the usual piecewise estimation by providing smooth estimates of the baseline excess mortality rate and time-dependent effects for both the multiplicative and additive covariate models. All models presented in this paper can be estimated within a generalized linear models framework and thus can be implemented using standard software.
Inhibition of phosphatidylinositol 3-kinase/Akt and histone deacetylase activity induces apoptosis in non-small cell lung cancer in vitro and in vivo.
OBJECTIVE: Resistance to histone deacetylase inhibitors in non-small cell lung cancer is mediated in part through activation of nuclear factor-kappaB through a phosphatidylinositol 3-kinase/Akt-dependent pathway. We hypothesize that inhibition of phosphatidylinositol 3-kinase/Akt will sensitize non-small cell lung cancer cells to histone deacetylase inhibitor-induced apoptosis. METHODS: Tumorigenic non-small cell lung cancer cell lines H157, H358, H460, and A549 were treated with nothing, the histone deacetylase inhibitor butyrate, the phosphatidylinositol 3-kinase/Akt inhibitor LY294002, or both compounds. Nuclear factor-kappaB activity was assessed by reporter gene assays and reverse transcriptase-polymerase chain reaction of the nuclear factor-kappaB dependent genes cIAP-2, Bfl/A1, and MnSOD. Whole cell extracts were immunoblotted for phospho-Akt, Akt, and phospho-ser/thr-Akt substrate. Cell death and apoptosis were measured by crystal violet staining, caspase-3 activity, and DNA fragmentation. A549 non-small cell lung cancer xenografts were created in athymic nude mice, and tumor growth was assessed after treatments as noted above. Explanted tumors underwent terminal deoxynucleotide transferase-mediated dUTP nick-end labeling and Western blot analyses for apoptosis assessment and drug target validation, respectively. RESULTS: Butyrate activated nuclear factor-kappaB-dependent transcription, and LY294002 abrogated this effect. Combined treatment induced more apoptosis and cell death in vitro compared with either drug alone as measured by caspase-3, DNA fragmentation, and clonogenic survival. Combined butyrate and LY294002 was tumoristatic in vivo, but all other xenografts grew. This decreased tumor growth correlated with more apoptosis in the xenografts treated with combined therapy. Tumor levels of phospho-Akt and acetylated histone H3 were decreased and increased, respectively, in xenografts treated with combined therapy. CONCLUSIONS: Combined histone deacetylase inhibitor and phosphatidylinositol 3-kinase/Akt pathway inhibition sensitized non-small cell lung cancer xenografts to apoptosis. Further investigations of this combined therapy are warranted as new pharmacologic phosphatidylinositol 3-kinase/Akt pathway inhibitors are developed.
Necrophysiological determination of blood pressure in fishes.
Bony fishes have an elastic chamber between the heart and aorta, the bulbus arteriosus, which has unique mechanical properties. On inflation, the isolated bulbus is initially very stiff but soon becomes extremely compliant yielding a steady (plateau) pressure upon further inflation, which appears to be similar in any given species. Here we show that the plateau pressure correlates with mean blood pressure determined in vivo. Consequently, inflation of the bulbus can be used to determine blood pressure in the living animal from recordings made after it is dead.
How vague is vague? A simulation study of the impact of the use of vague prior distributions in MCMC using WinBUGS.
There has been a recent growth in the use of Bayesian methods in medical research. The main reasons for this are the development of computer intensive simulation based methods such as Markov chain Monte Carlo (MCMC), increases in computing power and the introduction of powerful software such as WinBUGS. This has enabled increasingly complex models to be fitted. The ability to fit these complex models has led to MCMC methods being used as a convenient tool by frequentists, who may have no desire to be fully Bayesian. Often researchers want 'the data to dominate' when there is no prior information and thus attempt to use vague prior distributions. However, with small amounts of data the use of vague priors can be problematic. The results are potentially sensitive to the choice of prior distribution. In general there are fewer problems with location parameters. The main problem is with scale parameters. With scale parameters, not only does one have to decide the distributional form of the prior distribution, but also whether to put the prior distribution on the variance, standard deviation or precision. We have conducted a simulation study comparing the effects of 13 different prior distributions for the scale parameter on simulated random effects meta-analysis data. We varied the number of studies (5, 10 and 30) and compared three different between-study variances to give nine different simulation scenarios. One thousand data sets were generated for each scenario and each data set was analysed using the 13 different prior distributions. The frequentist properties of bias and coverage were investigated for the between-study variance and the effect size. The choice of prior distribution was crucial when there were just five studies. There was a large variation in the estimates of the between-study variance for the 13 different prior distributions. With a large number of studies the choice of prior distribution was less important. The effect size estimated was not biased, but the precision with which it was estimated varied with the choice of prior distribution leading to varying coverage intervals and, potentially, to different statistical inferences. Again there was less of a problem with a larger number of studies. There is a particular problem if the between-study variance is close to the boundary at zero, as MCMC results tend to produce upwardly biased estimates of the between-study variance, particularly if inferences are based on the posterior mean. The choice of 'vague' prior distribution can lead to a marked variation in results, particularly in small studies. Sensitivity to the choice of prior distribution should always be assessed.
Dextromethorphan to dextrorphan urinary metabolic ratio does not reflect dextromethorphan oral clearance.
Dextromethorphan urinary metabolic ratio is widely used to determine the CYP2D6 phenotype, but its utility to reflect subtle differences in catalytic activity is unclear. We evaluated the capability of dextromethorphan urinary metabolic ratio to predict dextromethorphan oral clearance as a measure of CYP2D6 activity. Data from 10 healthy extensive metabolizers of CYP2D6 were given 30 mg of dextromethorphan hydrobromide orally on two occasions. Blood and urine samples were collected for 72 h. Dextromethorphan and dextrorphan were determined in urine by high-performance liquid chromatography with fluorescence detection and in serum by liquid chromatography-mass spectrometry. The urinary metabolic ratio was very weakly correlated with dextromethorphan oral clearance (r = 0.24; p = 0.04). In contrast, the dextromethorphan oral clearance was highly correlated with the dextromethorphan to dextrorphan area under the concentration-time curve ratio (r = 0.84; p = 0.005) and the 3-h (r = 0.60; p = 0.003), 4-h (r = 0.72, p < 0.001), 6-h (r = 0.67; p < 0.001), and 8-h (r = 0.74; p < 0.001) dextromethorphan to dextrorphan serum ratios. Assuming an effect size of 30%, the number of volunteers required for crossover and cross-sectional studies using the urinary metabolic ratio as the CYP2D6 index was calculated to be 56 and 524, respectively, whereas 14 and 60 subjects are needed if oral clearance is used. Considering the required sample size and the low correlation with oral clearance, urinary metabolic ratio is not recommended as the primary outcome variable in studies requiring the detection of modest changes in CYP2D6 activity.
Differential mechanism-based inhibition of CYP3A4 and CYP3A5 by verapamil.
The genetic basis for polymorphic expression of CYP3A5 has been recently identified, but the significance of CYP3A5 expression is unclear. The purpose of this study is to quantify the capability of verapamil, a mechanism-based inhibitor of CYP3A, and its metabolites to inhibit the activities of CYP3A4 and CYP3A5, and to determine whether CYP3A5 expression in human liver microsomes alters the inhibitory potency of verapamil. Testosterone 6beta-hydroxylation or midazolam 1'-hydroxylation was used to quantify CYP3A activity. The possibility that verapamil and its metabolites form metabolic-intermediate complex (MIC) with CYP3A was assessed using dual beam spectrophotometry. Verapamil and N-desalkylverapamil (D617) were found to have little inhibitory effect on cDNA-expressed CYP3A5 activity and did not form a MIC with cDNA-expressed CYP3A5 as indicated by the appearance of the characteristic peak at 455 nm. At 50 microM, norverapamil showed time-dependent inhibition of CYP3A5 (30%), but to a much lesser extent compared with that of CYP3A4 (80%). The estimated values of the inactivation parameters k(inact) and K(I) of norverapamil were 4.53 microM and 0.07 min(-1) for cDNA-expressed CYP3A5, and 10.3 microM and 0.30 min(-1) for cDNA-expressed CYP3A4. Human liver microsomes that expressed CYP3A5 were less inhibited by both verapamil and norverapamil. The inactivation efficiency of verapamil and norverapamil was 30 times and 45 times lower, respectively, for CYP3A5-expressing microsomes compared with CYP3A5-non-expressing microsomes. These findings indicate that the presence of variable CYP3A5/CYP3A4 expression in the liver may contribute to the interindividual variability associated with verapamil-mediated drug interactions.
Phosphorylation of glycosyl-phosphatidylinositol by phosphatidylinositol 3-kinase changes its properties as a substrate for phospholipases.
Phosphatidylinositol 3-kinases (PI3K) phosphorylate the 3-position of the inositol ring of phosphatidylinositol-4,5-bisphosphate to produce phosphatidylinositol-3,4,5-trisphosphate. It is not clear whether PI3K can phosphorylate the inositol group in other biomolecules. We sought to determine whether PI3K was able to use glycosyl-phosphatidylinositol (GPI) as a substrate. This phospholipid may exist either in free form (GPIfree) or forming a lipid anchor (GPIanchor) for the attachment of extracellular proteins to the plasma membrane. We demonstrate the specific PI3K-mediated phosphorylation of the inositol 3-hydroxyl group within both types of GPI by incubating this phospholipid with immunoprecipitated PI3K. The phosphorylated product behaves in HPLC as a derivative of a PI3K lipid product. To our knowledge, this is the first demonstration that PI3K uses lipid substrates other than phosphoinositides. Further, we show that this has potential functional consequences. When GPIfree is phosphorylated, it becomes a poorer substrate for GPI-specific phospholipase D, but a better substrate for phosphatidylinositol-specific phospholipase C. These phosphorylation events may constitute the basis of a previously undescribed signal transduction mechanism.
High dose melphalan in the treatment of advanced neuroblastoma: results of a randomised trial (ENSG-1) by the European Neuroblastoma Study Group.
BACKGROUND: High dose myeloablative chemotherapy ("megatherapy"), with haematopoietic stem cell support, is now widely used to consolidate response to induction chemotherapy in patients with advanced neuroblastoma. PROCEDURE: In this study (European Neuroblastoma Study Group, ENSG1), the value of melphalan myeloablative "megatherapy" was evaluated in a randomised, multi-centre trial. Between 1982 and 1985, 167 children with stages IV and III neuroblastoma (123 stage IV > 1 year old at diagnosis and 44 stage III and stage IV from 6 to 12 months old at diagnosis) were treated with oncovin, cisplatin, epipodophyllotoxin, and cyclophosphamide (OPEC) induction chemotherapy every 3 weeks. After surgical excision of primary tumour, the 90 patients (69% of the total) who achieved complete response (CR) or good partial response (GPR) were eligible for randomisation either to high dose melphalan (180 mg per square meter) with autologous bone marrow support or to no further treatment. RESULTS: Sixty-five (72%) of eligible children were actually randomised and 21 of these patients were surviving at time of this analysis, with median follow-up from randomisation of 14.3 years. Five year event-free survival (EFS) was 38% (95% confidence interval (CI) 21-54%) in the melphalan-treated group and 27% (95% CI 12-42%) in the "no-melphalan" group. This difference was not statistically significant (P = 0.08, log rank test) but for the 48 randomised stage IV patients aged >1 year at diagnosis outcome was significantly better in the melphalan-treated group-5 year EFS 33% versus 17% (P = 0.01, log rank test). CONCLUSIONS: In this trial, high dose melphalan improved the length of EFS and overall survival of children with stage IV neuroblastoma >1 year of age who achieved CR or GPR after OPEC induction therapy and surgery. Multi-agent myeloablative regimens are now widely used as consolidation therapy for children with stage IV disease and in those with other disease stages when the MYCN gene copy number in tumour cells is amplified. Because they are more toxic, complex, and costly these combination megatherapy regimens should be compared with single agent melphalan in randomised clinical trials.
New considerations for IGFBP-3 determination in human serum.
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A Bayesian approach to evaluating net clinical benefit allowed for parameter uncertainty.
BACKGROUND AND OBJECTIVE: Although randomized controlled trials (RCTs) are conducted to establish whether novel interventions work on average in the patient population, there is a growing desire to move to a more individualized approach to evaluation. The potential benefits and harms of a treatment policy may differ between individuals. If these benefits and harms are not evaluated distinctly, and in a quantitative framework, transparency can be lost in the decision-making process. METHODS: Glasziou and Irwig have outlined the concept of net clinical treatment benefit for identifying the patients for whom the potential benefits of treatment outweigh the possible side effects. This study revisits the decision whether to use warfarin to treat atrial fibrillation. In this analysis, RCT and various sorts of observational data are synthesized. RESULTS: This reanalysis brings into question the conclusions of the original analysis on who would benefit from warfarin; however, caution is advised, due to limitations in the quality of life data available. CONCLUSION: A fully realized Bayesian implementation of the model is presented. This provides a framework for including uncertainty related to the estimation of all model parameters, and permits both direct probability statements and credible intervals for specific patient groups to be expressed.