Mode of action hypothesis testing in chemical safety assessments using metabolomics as supporting evidence: Phenobarbital and cyclobutrifluram metabolomics profile comparison.

In long term rodent studies administering Cyclobutrifluram (TYMIRIUM® Technology), a new agrochemical, there was a slight elevation of incidence of hepatocellular carcinomas in male CD-1 mice that was within the historical control range but appeared to be dose responsive. Cyclobutrifluram's ability to activate mouse constitutive androstane receptor (CAR) mediated gene transcription was confirmed in vitro, therefore a 28-day dietary toxicity study was conducted in vivo in male CD-1 mice to assess the CAR activation mode of action hypothesis of Cyclobutrifluram along with phenobarbital, a known CAR activator. In addition to other end points comprehensive (polar and lipidomic) hybrid metabolomics analyses were performed on terminal plasma and liver samples following 2-, 7- and 28-days dietary exposure to cyclobutrifluram and phenobarbital. The data generation and quality assessments were performed in line with the principles of the MEtabolomics standaRds Initiative in Toxicology (MERIT).First the full annotated feature set was used to compare the metabolomic changes induced by the administration of the two test substances using Shared and Unique Structures plots. This gave a comprehensive overview of the similarity of the two effect profiles showing good correlation and demonstrated that no other, alternative effect signatures were detected. Then the phenobarbital induced differentially abundant metabolites were selected, compared to the literature and their direction of change was assessed in cyclobutrifluram profiles, finding good agreement. Both approaches concluded that the metabolomics data supports the CAR activation hypothesis. Comparison of the metabolomic effect profiles can be a line of evidence in mode of action hypothesis testing in the chemical risk assessment process.

Attitudes of anesthetists towards an anesthesia-led nurse practitioner model for low-risk colonoscopy procedures: a cross-sectional survey.

BACKGROUND: The mounting pressure on the Australian healthcare system is driving a continual exploration of areas to improve patient care and access and to maximize utilization of our workforce. We hypothesized that there would be support by anesthetists employed at our hospital for the design, development, and potential implementation of an anesthesia-led nurse practitioner (NP) model for low-risk colonoscopy patients. METHODS: We conducted a cross-sectional, mixed methods study to ascertain the attitudes and acceptability of anesthetists towards a proposed anesthesia-led NP model for low-risk colonoscopy patients. An online survey using commercial software and theoretical questions pertaining to participants' attitudes towards an anesthesia-led NP model was e-mailed to consultant anesthetists. Participants were also invited to participate in a voluntary 20-min face-to-face interview. RESULTS: A total of 60 survey responses were received from a pool of 100 anesthetists (response rate = 60%, accounting for 8.04% margin of error). Despite the theoretical benefits of improved patient access to colonoscopy services, most anesthetists were not willing to participate in the supervision and training of NPs. The predominant themes underlying their lack of support for the program were a perception that patient safety would be compromised compared to the current model of anesthesia-led care, the model does not meet the Australian and New Zealand College of Anesthetists guidelines for procedural sedation and analgesia, and the program may be a public liability prone to litigation in the event of an adverse outcome. Concerns about consumer acceptance and cost-effectiveness were also raised. Finally, participants thought the model should be pilot tested to better understand consumer attitudes, logistical feasibility, patient and proceduralist attitudes, clinical governance, and, importantly, patient safety. CONCLUSIONS: Most anesthetists working in a single-center university hospital did not support an anesthesia-led NP model for low-risk colonoscopy patients. Patient safety, violations of the current Australian and New Zealand College of Anesthetists guidelines on procedural sedation, and logistical feasibility were significant barriers to the acceptance of the model. TRIAL REGISTRATION: Australian and New Zealand Clinical Trials Registry, 12619001036101.

Cerebral oximetry to reduce perioperative morbidity.

The use of cerebral oximetry to guide intraoperative management has been shown to improve patient outcomes in cardiac surgery. This pilot trial assessed the feasibility of performing a similar study of outcome in patients over the age of 70 years undergoing non-cardiac surgery. Patients over the age of 70 years undergoing total knee or hip arthroplasty or bowel resection surgery were randomly assigned to have cerebral oximetry values monitored (intervention group) or not monitored (control) while under general anaesthesia. Indicators of proof of concept were: rate of complications, rate of cerebral desaturation, relationship between cerebral desaturation and complications, and anaesthetist response to cerebral desaturation. Forty patients were recruited and randomised to a control group (n=20) or an intervention group (n=20). The proportion of the study population who had a complication was 40% (95% confidence interval [CI] 26% to 55%). Cerebral desaturation (<75% of baseline) occurred in only two patients (5.0% (CI 1.4% to 16%)), one in each group, and neither of those patients recorded a complication. Changes to anaesthetic management on the basis of cerebral oximetry values occurred in only two patients in the intervention group (10% (CI 2.8% to 30%)). Maintenance of cerebral oximetry values appeared to be closer to baseline in the intervention group than in the control group but this difference was not significant (P=0.15). Our results indicated that complications occurred frequently in the study population but did not appear to be associated with cerebral desaturation events. These findings do not support a larger intervention study using the current study population.

A mechanism for the anti-fibrogenic effects of the pregnane X receptor (PXR) in the liver: inhibition of NF-kappaB?

The liver is susceptible to chronic damage through exposure to a variety of toxins (e.g. alcohol) and viruses (e.g. hepatitis C). Obesity, autoimmune diseases (e.g. autoimmune hepatitis) and a variety of genetic diseases (e.g. Wilson's disease) also lead to chronic liver damage. This damage results in scarring fibrogenesis, structural disruption and functional impairment of the organ. Recent work suggests that there is cross-talk between the PXR and NF-kappaB pathways. This cross-talk may explain the observation that PXR activators inhibit liver fibrosis in in vitro and in vivo animal models of the disease. This reveiw will focus on the two transcription factors and their potential interaction.

Pacemaker-driven tachycardia induced by electrocardiograph monitoring in the recovery room.

Monitoring devices are known to induce tachycardia in minute-ventilation rate-responsive pacemakers. This is because some monitoring devices measure the same parameter as do the pacemakers (change in thoracic impedance). Hence, the biological signal to the pacemaker is increased and is misconstrued as increased minute ventilation causing tachycardia which resolves when the monitoring device is removed. Whilst this could occur for all minute-volume rate responsive pacemakers, most reported interactions have been with the Telectronics META series. We present a case of an interaction between a Telectronics Tempo DR pacemaker (St. Jude Medical) and an Agilent Patient Care System (Philips). Failure to recognise the true nature and cause of such tachycardias may lead to mismanagement of the patient, including the inappropriate use of cardio-active medications.

Supplementary oxygenation with the laryngeal mask airway: a comparison of four devices.

The provision of supplementary oxygen via the laryngeal mask airway used in the recovery room is important for patient safety. Several devices have been described for this purpose, but these studies have not included an accurate measurement of the most clinically important variable, the end-tidal oxygen concentration. We constructed an artificial model of spontaneous ventilation to compare the efficacy and safety of four devices; a circuit filter, a Hudson mask, the 'T-bag' device and a T-piece. We combined the use of oximetry with a pneumotachograph to provide a continuous picture of the oxygen delivery characteristics of the devices at flow rates of 2, 4 and 8 l.min-1. The performances of the T-bag and the T-piece were superior to those of the filter and Hudson mask, with end-tidal oxygen concentrations of 46.1%, 45.8% and 35.4%, 34.8%, respectively, at 8 l.min-1. Single point assessments of oxygen delivery, such as peak inspired oxygen concentration, may overestimate the efficacy of test devices.

Knowledge of cardiopulmonary resuscitation protocols and level of anaesthetic training.

Inadequate recall of resuscitation protocols has contributed to poor performance of resuscitation in simulation studies. We asked, does the level of anaesthesia training affect knowledge of cardiopulmonary resuscitation protocols? We used a questionnaire that covered the areas of basic life support, advanced adult life support and paediatric life support. The proportions of correct answers were hospital medical officers 50%, junior registrars 62%, senior registrars 84% and consultants 42%. The consultant group performed worse than all other groups for the basic life support and advanced life support questions. We suggest yearly resuscitation training for all anaesthetists and anaesthesia trainees.

The threonine-sensitive homoserine dehydrogenase and aspartokinase activities of Escherichia coli K12. Distribution and accessibility to antibodies of some epitopes of the bifunctional enzyme.

In the presence of l-threonine, the allosteric effector, most of the antigenic determinants situated in the aspartokinase region of the wild-type enzyme become unavailable to the antibodies raised against a fragment of the enzyme containing this region and devoid of homoserine dehydrogenase activity. The cross-reactivities of the antibodies raised against this fragment (extracted from a nonsense mutant) and a fragment endowed with homoserine dehydrogenase activity but devoid of aspartokinase activity (obtained by limited proteolysis) with the corresponding antigens were studied. The conclusion is drawn that the two fragments, which share an overlapping sequence of molecular weight about 17,000, share at least two antigenic determinants.

Deoxyribonucleic acid hybridization analysis of the defective bacteriophage carried by strain 15 of Escherichia coli.

Evidence from several laboratories indicates that strain 15 of Escherichia coli is lysogenic for a defective phage. When lysates from induced cultures were centrifuged in CsCl, three bands were obtained. In order of decreasing density, these bands contained tailless particles, complete phages, and a second band of complete phages, in a ratio of 65.7:28.6:5.7. Reassociation rate measurements were used to establish that the molecular weights of the deoxyribonucleic acid (DNA) species from the phages in the first two bands are similar. A smaller genome is postulated in the complete phages from the minor band. Hybridization experiments revealed extensive homology between the DNA species from all three phage bands, thus suggesting that the complete and tailless particles are not different at the genetic level. The DNA from each phage band was also shown to hybridize almost completely with DNA from either E. coli 15T(-) or a reportedly cured derivative of 15T(-). In contrast, only about 25% of each phage DNA was able to react with DNA from E. coli strains B and K-12 C-600.

Intramolecular heterogeneity of the deoxyribonucleic acid of temperate bacteriophages.

Spectral changes accompanying the thermal denaturation of phage deoxyribonucleic acid suggested that lambda is not unique in possessing large-scale intramolecular heterogeneity and nucleotide clustering; instead, lambda seems to share this property with other enteric phages.

Thermal stability of Escherichia coli-Salmonella typhimurium deoxyribocleic acid duplexes.

Single-stranded, labeled deoxyribonucleic acid (DNA) fragments from Escherichia coli were incubated at 60 and 66 C with a large excess of single-stranded, unlabeled DNA fragments from E. coli and Salmonella typhimurium. The resulting reassociated DNA was adsorbed to hydroxylapatite and eluted in a series of washes at increasing temperatures. The thermal stability of the reassociated DNA was determined by means of this procedure. Neither the extent of reassociation nor stability of the reassociated E. coli DNA was affected by increasing the incubation temperature from 60 to 66 C. The double-stranded molecules resulting from the reassociation of E. coli DNA with S. typhimurium DNA had a markedly lower thermal stability than reassociated E. coli DNA. More reassociation occurred between E. coli and S. typhimurium at 60 C than at 66 C. In addition, the product of interspecies reassociation occurring at 66 C had a higher thermal stability than that occurring at 60 C. Preliminary results indicate that the decreased thermal stability of the interspecies duplex is in part the result of unpaired bases.

Thermal chromatography of DNA-DNA reactions.

Genetic relationships among bacteriophages and bacteria have been investigated using an extension of the DNA-agar technique. Thermal elution profiles, each characteristic of a specific DNA-DNA reaction, have been obtained from reactions involving homologous and heterologous DNAs. A sizable portion of the DNA of lysogenic (or semilysogenic DNA) viruses has been shown to be homologous to the DNA of their bacterial hosts. These homologies are contained in numerous sequences throughout the viral DNAs. Furthermore, DNA homologies exist among most temperate phage DNAs as well as with their respective hosts.