Integrating NHANES and toxicity forecaster data to compare pesticide exposure and bioactivity by farmwork history and US citizenship

BACKGROUND

Farmworkers in the United States, especially migrant workers, face unique barriers to healthcare and have documented disparities in health outcomes. Exposure to pesticides, especially those persistent in the environment, may contribute to these health disparities.

OBJECTIVE

Quantify differences in pesticide exposure bioactivity by farmworker category and US citizenship status.

METHODS

We queried the National Health and Nutrition Examination Study (NHANES) from 1999-2014 for pesticide exposure biomarker concentrations among farmworkers and non-farmworkers by citizenship status. We combined this with toxicity assay data from the US Environmental Protection Agency's (EPA's) Toxicity Forecaster (ToxCast). We estimated adverse biological effects that occur across a range of human population-relevant pesticide doses.

RESULTS

In total, there were 844 people with any farmwork history and 23,592 non-farmworkers. Of 12 commonly detectable pesticide biomarkers in NHANES, 2,4-dichlorophenoxyacetic acid (OR = 3.76, p = 1.33 × 10-6) was significantly higher in farmworkers than non-farmworkers. Farmworkers were 1.15 times more likely to have a bioactive pesticide biomarker measurement in comparison to non-farmworkers (adjusted OR = 1.15, 95% CI: 0.87, 1.51). Non-U.S. citizens were 1.39 times more likely to have bioactive pesticide biomarker concentrations compared to people with U.S. citizenship (adjusted OR 1.39, 95% CI: 1.17, 1.64). Additionally, non-citizens were significantly more exposed to bioactive levels of β-hexachlorocyclohexane (BHC) (OR = 8.10, p = 1.33 × 10-6), p,p-DDE (OR = 2.60, p = 0.02), and p,p'-DDT (OR = 7.75, p = 0.01).

IMPACT STATEMENT

Farmworkers are a vulnerable population due to social determinants of health and occupational exposures. Here, we integrate US population chemical biomonitoring data and toxicity outcome data to assess pesticide exposure by farmwork history and citizenship. We find that farmworkers and those without US citizenship are significantly more likely to be exposed to concentrations of pesticides which are bioactive in toxicological assays. Thus, farmworkers employed in the US but who are not citizens could be at increased risk of harm to their health due to pesticides. These findings are important to shape evidence-based policies in regulatory science to promote worker safety.

Integrating NHANES and Toxicity Forecaster Data to Compare Pesticide Exposure and Bioactivity by Farmwork History and US Citizenship

Introduction

Farmworkers in the United States, especially migrant workers, face unique barriers to healthcare and have documented disparities in health outcomes. Exposure to pesticides, especially those persistent in the environment, may contribute to these health disparities.

Methods

We queried the National Health and Nutrition Examination Study (NHANES) from 1999-2014 for pesticide exposure biomarker concentrations among farmworkers and non-farmworkers by citizenship status. We combined this with toxicity assay data from the US Environmental Protection Agency's (EPA's) Toxicity Forecast Dashboard (ToxCast). We estimated adverse biological effects that occur across a range of human population-relevant pesticide doses.

Results

In total, there were 1,137 people with any farmwork history and 20,205 non-farmworkers. Of the 14 commonly detectable pesticide biomarkers in NHANES, 2,4-dichlorophenol (OR= 4.32, p= 2.01×10 -7 ) was significantly higher in farmworkers than non-farmworkers. Farmworkers were 1.37 times more likely to have a bioactive pesticide biomarker measurement in comparison to non-farmworkers (adjusted OR=1.37, 95% CI: 1.10, 1.71). Within farmworkers only, those without U.S. citizenships were 1.31 times more likely to have bioactive pesticide biomarker concentrations compared those with U.S. citizenship (adjusted OR 1.31, 95% CI: 0.75, 2.30). Additionally, non-citizen farmworkers were significantly more exposed to bioactive levels of β -hexachlorocyclohexane (BHC) (OR= 8.50, p= 1.23×10 -9 ), p,p-DDE (OR= 2.98, p= 3.11×10 -3 ), and p,p'-DDT (OR= 10.78, p= 8.70×10 -4 ).

Discussion

These results highlight pesticide exposure disparities in farmworkers, particularly those without U.S. citizenship. Many of these exposures are occurring at doses which are bioactive in toxicological assays.

To Sobol or not to Sobol? The effects of sampling schemes in systems biology applications

Computational and mathematical models in biology rely heavily on the parameters that characterize them. However, robust estimates for their values are typically elusive and thus a large parameter space becomes necessary for model study, particularly to make translationally impactful predictions. Sampling schemes exploring parameter spaces for models are used for a variety of purposes in systems biology, including model calibration and sensitivity analysis. Typically, random sampling is used; however, when models have a high number of unknown parameters or the models are highly complex, computational cost becomes an important factor. This issue can be reduced through the use of efficient sampling schemes such as Latin hypercube sampling (LHS) and Sobol sequences. In this work, we compare and contrast three sampling schemes - random sampling, LHS, and Sobol sequences - for the purposes of performing both parameter sensitivity analysis and model calibration. In addition, we apply these analyses to different types of computational and mathematical models of varying complexity: a simple ODE model, a complex ODE model, and an agent-based model. In general, the sampling scheme had little effect when used for calibration efforts, but when applied to sensitivity analyses, Sobol sequences exhibited faster convergence. While the observed benefit to convergence is relatively small, Sobol sequences are computationally less expensive to compute than LHS samples and also have the benefit of being deterministic, which allows for better reproducibility of results.

Risk factors for increased COVID-19 case-fatality in the United States: A county-level analysis during the first wave

The ongoing COVID-19 pandemic is causing significant morbidity and mortality across the US. In this ecological study, we identified county-level variables associated with the COVID-19 case-fatality rate (CFR) using publicly available datasets and a negative binomial generalized linear model. Variables associated with decreased CFR included a greater number of hospitals per 10,000 people, banning religious gatherings, a higher percentage of people living in mobile homes, and a higher percentage of uninsured people. Variables associated with increased CFR included a higher percentage of the population over age 65, a higher percentage of Black or African Americans, a higher asthma prevalence, and a greater number of hospitals in a county. By identifying factors that are associated with COVID-19 CFR in US counties, we hope to help officials target public health interventions and healthcare resources to locations that are at increased risk of COVID-19 fatalities.

Modulation of Bacterial Fitness and Virulence Through Antisense RNAs

Regulatory RNAs contribute to gene expression control in bacteria. Antisense RNAs (asRNA) are a class of regulatory RNAs that are transcribed from opposite strands of their target genes. Typically, these untranslated transcripts bind to cognate mRNAs and rapidly regulate gene expression at the post-transcriptional level. In this article, we review asRNAs that modulate bacterial fitness and increase virulence. We chose examples that underscore the variety observed in nature including, plasmid- and chromosome-encoded asRNAs, a riboswitch-regulated asRNA, and asRNAs that require other RNAs or RNA-binding proteins for stability and activity. We explore how asRNAs improve bacterial fitness and virulence by modulating plasmid acquisition and maintenance, regulating transposon mobility, increasing resistance against bacteriophages, controlling flagellar production, and regulating nutrient acquisition. We conclude with a brief discussion on how this knowledge is helping to inform current efforts to develop new therapeutics.

Spatial Organization and Recruitment of Non-Specific T Cells May Limit T Cell-Macrophage Interactions Within Mycobacterium tuberculosis Granulomas

Tuberculosis (TB) is a worldwide health problem; successful interventions such as vaccines and treatment require a 2better understanding of the immune response to infection with Mycobacterium tuberculosis (Mtb). In many infectious diseases, pathogen-specific T cells that are recruited to infection sites are highly responsive and clear infection. Yet in the case of infection with Mtb, most individuals are unable to clear infection leading to either an asymptomatically controlled latent infection (the majority) or active disease (roughly 5%-10% of infections). The hallmark of Mtb infection is the recruitment of immune cells to lungs leading to development of multiple lung granulomas. Non-human primate models of TB indicate that on average <10% of T cells within granulomas are Mtb-responsive in terms of cytokine production. The reason for this reduced responsiveness is unknown and it may be at the core of why humans typically are unable to clear Mtb infection. There are a number of hypotheses as to why this reduced responsiveness may occur, including T cell exhaustion, direct downregulation of antigen presentation by Mtb within infected macrophages, the spatial organization of the granuloma itself, and/or recruitment of non-Mtb-specific T cells to lungs. We use a systems biology approach pairing data and modeling to dissect three of these hypotheses. We find that the structural organization of granulomas as well as recruitment of non-specific T cells likely contribute to reduced responsiveness.

Male fetal sex affects uteroplacental angiogenesis in growth restriction mouse model†

Abnormally increased angiotensin II activity related to maternal angiotensinogen (AGT) genetic variants, or aberrant receptor activation, is associated with small-for-gestational-age babies and abnormal uterine spiral artery remodeling in humans. Our group studies a murine AGT gene titration transgenic (TG; 3-copies of the AGT gene) model, which has a 20% increase in AGT expression mimicking a common human AGT genetic variant (A[-6]G) associated with intrauterine growth restriction (IUGR) and spiral artery pathology. We hypothesized that aberrant maternal AGT expression impacts pregnancy-induced uterine spiral artery angiogenesis in this mouse model leading to IUGR. We controlled for fetal sex and fetal genotype (e.g., only 2-copy wild-type [WT] progeny from WT and TG dams were included). Uteroplacental samples from WT and TG dams from early (days 6.5 and 8.5), mid (d12.5), and late (d16.5) gestation were studied to assess uterine natural killer (uNK) cell phenotypes, decidual metrial triangle angiogenic factors, placental growth and capillary density, placental transcriptomics, and placental nutrient transport. Spiral artery architecture was evaluated at day 16.5 by contrast-perfused three-dimensional microcomputed tomography (3D microCT). Our results suggest that uteroplacental angiogenesis is significantly reduced in TG dams at day 16.5. Males from TG dams are associated with significantly reduced uteroplacental angiogenesis from early to late gestation compared with their female littermates and WT controls. Angiogenesis was not different between fetal sexes from WT dams. We conclude that male fetal sex compounds the pathologic impact of maternal genotype in this mouse model of growth restriction.

The GRE in Public Health Admissions: Barriers, Waivers, and Moving Forward

In the wake of COVID-19, there is an urgent need for a diverse public health work force to address problems presented or exacerbated by the global pandemic. Educational programs that create our work force both train and shape the makeup of access through graduate applications. The Graduate Record Exam has a number of standing issues, with additional barriers created by the pandemic. We trace the GRE waiver movement over several years, focusing on the gradual adoption in CEPH accredited programs and the rapid expansion of temporary waivers as a response to testing access. Going forward, we need to consider gaps in waivers during the pandemic and how this data can be used to shape our future use of the GRE.

Vancomycin-Resistant Enterococcus Acquisition in a Tertiary Care Hospital: Testing the Roles of Antibiotic Use, Proton Pump Inhibitor Use, and Colonization Pressure

Background

Vancomycin-resistant Enterococcus (VRE) is a leading cause of healthcare-associated infections, and asymptomatic colonization precedes infection. VRE continues to spread despite widespread application of pathogen-specific control guidelines. A better understanding of the risk factors for transmission is needed.

Methods

A retrospective matched case-control study was performed from June 2013 through December 2016 in a single institution. Patients in 6 intensive care units, 1 hematology and oncology unit, and 1 bone marrow transplant unit were screened by means of rectal swab sampling on admission and weekly thereafter. Case patients had a negative swab sample followed by a positive sample >3 days after admission. Controls were closely matched to case patients based on time from admission to the second swab sample, unit in which the second sample was obtained, and date of admission. Comorbidity data, procedures, healthcare settings and exposures, culture data, and duration of antibiotic and proton pump inhibitor (PPI) therapy were abstracted from the electronic medical record. A multivariable risk factor model for conversion was generated using purposeful selection.

Results

A total of 551 case patients were matched with controls. The largest modifiable effects on VRE acquisition were ≥1 day of vancomycin therapy (odd ratio, 1.98; P < .001), ≥1 day of aerobic antibiotic therapy (1.90; P < .001), and a dose-dependent effect of PPI therapy (odds ratio per day of therapy, 1.09; P < .001). Colonization pressures from patients identified to be carriers and placed in contact precautions did not confer increased risk.

Conclusions

Decreasing PPI use and preventing the inappropriate initiation of antibiotic therapy are modifiable targets to decrease VRE transmission in the hospital.

LytTR Regulatory Systems: A potential new class of prokaryotic sensory system

The most commonly studied prokaryotic sensory signal transduction systems include the one-component systems, phosphosignaling systems, extracytoplasmic function (ECF) sigma factor systems, and the various types of second messenger systems. Recently, we described the regulatory role of two separate sensory systems in Streptococcus mutans that jointly control bacteriocin gene expression, natural competence development, as well as a cell death pathway, yet they do not function via any of the currently recognized signal transduction paradigms. These systems, which we refer to as LytTR Regulatory Systems (LRS), minimally consist of two proteins, a transcription regulator from the LytTR Family and a transmembrane protein inhibitor of this transcription regulator. Here, we provide evidence suggesting that LRS are a unique uncharacterized class of prokaryotic sensory system. LRS exist in a basal inactive state. However, when LRS membrane inhibitor proteins are inactivated, an autoregulatory positive feedback loop is triggered due to LRS regulator protein interactions with direct repeat sequences located just upstream of the -35 sequences of LRS operon promoters. Uncharacterized LRS operons are widely encoded by a vast array of Gram positive and Gram negative bacteria as well as some archaea. These operons also contain unique direct repeat sequences immediately upstream of their operon promoters indicating that positive feedback autoregulation is a globally conserved feature of LRS. Despite the surprisingly widespread occurrence of LRS operons, the only characterized examples are those of S. mutans. Therefore, the current study provides a useful roadmap to investigate LRS function in the numerous other LRS-encoding organisms.

Dynamic balance of pro- and anti-inflammatory signals controls disease and limits pathology

Immune responses to pathogens are complex and not well understood in many diseases, and this is especially true for infections by persistent pathogens. One mechanism that allows for long-term control of infection while also preventing an over-zealous inflammatory response from causing extensive tissue damage is for the immune system to balance pro- and anti-inflammatory cells and signals. This balance is dynamic and the immune system responds to cues from both host and pathogen, maintaining a steady state across multiple scales through continuous feedback. Identifying the signals, cells, cytokines, and other immune response factors that mediate this balance over time has been difficult using traditional research strategies. Computational modeling studies based on data from traditional systems can identify how this balance contributes to immunity. Here we provide evidence from both experimental and mathematical/computational studies to support the concept of a dynamic balance operating during persistent and other infection scenarios. We focus mainly on tuberculosis, currently the leading cause of death due to infectious disease in the world, and also provide evidence for other infections. A better understanding of the dynamically balanced immune response can help shape treatment strategies that utilize both drugs and host-directed therapies.

Intraperitoneal nanotherapy for metastatic ovarian cancer based on siRNA-mediated suppression of DJ-1 protein combined with a low dose of cisplatin

Herein, we report an efficient combinatorial therapy for metastatic ovarian cancer based on siRNA-mediated suppression of DJ-1 protein combined with a low dose of cisplatin. DJ-1 protein modulates, either directly or indirectly, different oncogenic pathways that support and promote survival, growth, and invasion of ovarian cancer cells. To evaluate the potential of this novel therapy, we have engineered a cancer-targeted nanoplatform and validated that DJ-1 siRNA delivered by this nanoplatform after intraperitoneal injection efficiently downregulates the DJ-1 protein in metastatic ovarian cancer tumors and ascites. In vivo experiments revealed that DJ-1 siRNA monotherapy outperformed cisplatin alone by inhibiting tumor growth and increasing survival of mice with metastatic ovarian cancer. Finally, three cycles of siRNA-mediated DJ-1 therapy in combination with a low dose of cisplatin completely eradicated ovarian cancer tumors from the mice, and there was no cancer recurrence detected for the duration of the study, which lasted 35 weeks.

Horizontally Acquired Biosynthesis Genes Boost Coxiella burnetii's Physiology

Coxiella burnetii, the etiologic agent of acute Q fever and chronic endocarditis, has a unique biphasic life cycle, which includes a metabolically active intracellular form that occupies a large lysosome-derived acidic vacuole. C. burnetii is the only bacterium known to thrive within such an hostile intracellular niche, and this ability is fundamental to its pathogenicity; however, very little is known about genes that facilitate Coxiella's intracellular growth. Recent studies indicate that C. burnetii evolved from a tick-associated ancestor and that the metabolic capabilities of C. burnetii are different from that of Coxiella-like bacteria found in ticks. Horizontally acquired genes that allow C. burnetii to infect and grow within mammalian cells likely facilitated the host shift; however, because of its obligate intracellular replication, C. burnetii would have lost most genes that have been rendered redundant due to the availability of metabolites within the host cell. Based on these observations, we reasoned that horizontally derived biosynthetic genes that have been retained in the reduced genome of C. burnetii are ideal candidates to begin to uncover its intracellular metabolic requirements. Our analyses identified a large number of putative foreign-origin genes in C. burnetii, including tRNA^Glu2 that is potentially required for heme biosynthesis, and genes involved in the production of lipopolysaccharide—a virulence factor, and of critical metabolites such as fatty acids and biotin. In comparison to wild-type C. burnetii, a strain that lacks tRNA^Glu2 exhibited reduced growth, indicating its importance to Coxiella's physiology. Additionally, by using chemical agents that block heme and biotin biosyntheses, we show that these pathways are promising targets for the development of new anti-Coxiella therapies.

Accumulation and expression of multiple antibiotic resistance genes in Arcobacter cryaerophilus that thrives in sewage

We explored the bacterial diversity of untreated sewage influent samples of a wastewater treatment plant in Tucson, AZ and discovered that Arcobacter cryaerophilus, an emerging human pathogen of animal origin, was the most dominant bacterium. The other highly prevalent bacteria were members of the phyla Bacteroidetes and Firmicutes, which are major constituents of human gut microbiome, indicating that bacteria of human and animal origin intermingle in sewage. By assembling a near-complete genome of A. cryaerophilus, we show that the bacterium has accumulated a large number of antibiotic resistance genes (ARGs) probably enabling it to thrive in the wastewater. We also determined that a majority of ARGs was being expressed in sewage, suggestive of trace levels of antibiotics or other stresses that could act as a selective force that amplifies multidrug resistant bacteria in municipal sewage. Because all bacteria are not eliminated even after several rounds of wastewater treatment, ARGs in sewage could affect public health due to their potential to contaminate environmental water.

Emergence of New sRNAs in Enteric Bacteria is Associated with Low Expression and Rapid Evolution

Non-coding small RNAs (sRNAs) are critical to post-transcriptional gene regulation in bacteria. However, unlike for protein-coding genes, the evolutionary forces that shape sRNAs are not understood. We investigated sRNAs in enteric bacteria and discovered that recently emerged sRNAs evolve at significantly faster rates than older sRNAs. Concomitantly, younger sRNAs are expressed at significantly lower levels than older sRNAs. This process could potentially facilitate the integration of newly emerged sRNAs into bacterial regulatory networks. Furthermore, it has previously been difficult to trace the evolutionary histories of sRNAs because rapid evolution obscures their original sources. We overcame this challenge by identifying a recently evolved sRNA in Escherichia coli, which allowed us to determine that novel sRNAs could emerge from vestigial bacteriophage genes, the first known source for sRNA origination.

Friend or Foe-Light Availability Determines the Relationship between Mycorrhizal Fungi, Rhizobia and Lima Bean (Phaseolus lunatus L.)

Plant associations with root microbes represent some of the most important symbioses on earth. While often critically promoting plant fitness, nitrogen-fixing rhizobia and arbuscular mycorrhizal fungi (AMF) also demand significant carbohydrate allocation in exchange for key nutrients. Though plants may often compensate for carbon loss, constraints may arise under light limitation when plants cannot extensively increase photosynthesis. Under such conditions, costs for maintaining symbioses may outweigh benefits, turning mutualist microbes into parasites, resulting in reduced plant growth and reproduction. In natural systems plants commonly grow with different symbionts simultaneously which again may interact with each other. This might add complexity to the responses of such multipartite relationships. We experimented with lima bean (Phaseolus lunatus), which efficiently forms associations with both types of root symbionts. We applied full light and low-light to each of four treatments of microbial inoculation. After an incubation period of 14 weeks, we quantified vegetative aboveground and belowground biomass and number and viability of seeds to determine effects of combined inoculant and light treatment on plant fitness. Under light-limited conditions, vegetative and reproductive traits were inhibited in AMF and rhizobia inoculated lima bean plants relative to controls (un-colonized plants). Strikingly, reductions in seed production were most critical in combined treatments with rhizobia x AMF. Our findings suggest microbial root symbionts create additive costs resulting in decreased plant fitness under light-limited conditions.

Coxiella burnetii and Leishmania mexicana residing within similar parasitophorous vacuoles elicit disparate host responses

Coxiella burnetii is a bacterium that thrives in an acidic parasitophorous vacuole (PV) derived from lysosomes. Leishmania mexicana, a eukaryote, has also independently evolved to live in a morphologically similar PV. As Coxiella and Leishmania are highly divergent organisms that cause different diseases, we reasoned that their respective infections would likely elicit distinct host responses despite producing phenotypically similar parasite-containing vacuoles. The objective of this study was to investigate, at the molecular level, the macrophage response to each pathogen. Infection of THP-1 (human monocyte/macrophage) cells with Coxiella and Leishmania elicited disparate host responses. At 5 days post-infection, when compared to uninfected cells, 1057 genes were differentially expressed (746 genes up-regulated and 311 genes down-regulated) in C. burnetii infected cells, whereas 698 genes (534 genes up-regulated and 164 genes down-regulated) were differentially expressed in L. mexicana infected cells. Interestingly, of the 1755 differentially expressed genes identified in this study, only 126 genes (~7%) are common to both infections. We also discovered that 1090 genes produced mRNA isoforms at significantly different levels under the two infection conditions, suggesting that alternate proteins encoded by the same gene might have important roles in host response to each infection. Additionally, we detected 257 micro RNAs (miRNAs) that were expressed in THP-1 cells, and identified miRNAs that were specifically expressed during Coxiella or Leishmania infections. Collectively, this study identified host mRNAs and miRNAs that were influenced by Coxiella and/or Leishmania infections, and our data indicate that although their PVs are morphologically similar, Coxiella and Leishmania have evolved different strategies that perturb distinct host processes to create and thrive within their respective intracellular niches.

Genome rearrangements can make and break small RNA genes

Small RNAs (sRNAs) are short, transcribed regulatory elements that are typically encoded in the intergenic regions (IGRs) of bacterial genomes. Several sRNAs, first recognized in Escherichia coli, are conserved among enteric bacteria, but because of the regulatory roles of sRNAs, differences in sRNA repertoires might be responsible for features that differentiate closely related species. We scanned the E. coli MG1655 and Salmonella enterica Typhimurium genomes for nonsyntenic IGRs as a potential source of uncharacterized, species-specific sRNAs and found that genome rearrangements have reconfigured several IGRs causing the disruption and formation of sRNAs. Within an IGR that is present in E. coli but was disrupted in Salmonella by a translocation event is an sRNA that is associated with the FNR/CRP global regulators and influences E. coli biofilm formation. A Salmonella-specific sRNA evolved de novo through point mutations that generated a σ⁷⁰ promoter sequence in an IGR that arose through genome rearrangement events. The differences in the sRNA pools among bacterial species have previously been ascribed to duplication, deletion, or horizontal acquisition. Here, we show that genomic rearrangements also contribute to this process by either disrupting sRNA-containing IGRs or creating IGRs in which novel sRNAs may evolve.

A diversity of Antibiotic-resistant Staphylococcus spp. in a Public Transportation System

OBJECTIVES

Our goal was to determine the diversity and abundance of Staphylococcus bacteria on different components of a public transportation system in a mid-sized US city (Portland, Oregon) and to examine the level of drug resistance in these bacteria.

METHODS

We collected 70 samples from 2 cm × 4 cm sections from seven different areas on buses and trains in Portland, USA, taking 10 samples from each area. We isolated a subset of 14 suspected Staphylococcus spp. colonies based on phenotype, and constructed a phylogeny from16S rRNA sequences to assist in identification. We used the Kirbye-Bauer disk diffusion method to determine resistance levels to six common antibiotics.

RESULTS

We found a range of pathogenic Staphylococcus species. The mean bacterial colony counts were 97.1 on bus and train floors, 80.1 in cloth seats, 9.5 on handrails, 8.6 on seats and armrests at bus stops, 3.8 on the underside of seats, 2.2 on windows, and 1.8 on vinyl seats per 8 cm(2) sample area. These differences were significant (p < 0.001). Of the 14 isolates sequenced, 11 were staphylococci, and of these, five were resistant to penicillin and ampicillin, while only two displayed intermediate resistance to bacitracin. All 11 isolates were sensitive to trimethoprim-sulfamethoxazole, vancomycin, and tetracycline.

CONCLUSIONS

We found six different strains of Staphylococcus, and while there were varying levels of drug resistance, we did not find extensive levels of multidrug-resistant bacteria, and no S. aureus was found. We found floors and cloth seats to be areas on buses and trains that showed particularly high levels of bacteria.

Relationship between sample size and the definition of equivalence in non-inferiority drug studies

Statistical testing of clinical trial data leads to acceptance of a hypothesis if a test of the opposite (null) hypothesis (H0) fails to reach a critical probability value. The usual aim is to demonstrate that a new treatment is superior to a comparator, whence H0 is that the two treatments are the same. By contrast, in studies designed to show that a new treatment is equivalent to an existing therapy, the same principle is satisfied by an amended null hypothesis, that the treatments differ by more than a defined amount. This reversal entails subtle but important logical and practical problems which affect particularly the calculation of sample size. The choice of the limits used to define equivalence is critical to the calculation of sample size in a manner not previously discussed, and in the interpretation of data in relation to the probability of Type I and Type II errors. Investigators, regulatory bodies and institutional ethics committees must ensure that the range of values chosen to indicate equivalence is clinically appropriate and be aware of the effect of this decision on possible errors in accepting or rejecting H0.

Is the Australian HREC system unsustainable?

The Australian HREC system is now highly centralised and subject to national guidelines in an attempt to assure consistency of decision-making and of ethical standards. The penalty has been greatly increased paperwork and reporting requirements which many committees feel burdensome. In addition, many Committees may be under-resourced. However, I argue that though it is timely to reassess the current directions it is an exaggeration to claim that the system is in danger of collapse.

A review of Clinical Terms Version 3 (Read Codes) for speech and language record keeping

There may be bugs, there may be viruses, but computers are here to stay. Access to computers may vary greatly from 'seen one once' to daily usage. However, with an increasing dependence on electronic records, even the most remote therapist will ultimately be faced with computerization. To make this process as painless as possible some commonality in approach is logical. A common vocabulary, for instance, would ensure that dysphasia in Cape Town is the same as dysphasia in Dundee. This is great in theory but is Clinical Terms Version 3 (Read Codes) (CTV3) sufficient to encode records in clinical practice? It is to this end that the Speech and Language Therapy Department at Burton Hospital took part in a multidisciplinary project with the NHS Centre for Coding and Classification (NHS CCC). (NHS CCC became the NHS Information Authority, Coding and Classification on 1 April 1999.) Their CTV3 offers a standardized clinical terminology. An audit of patient case-notes found that 78% of the terms used by therapists were available in CTV3. Although there are many issues raised concerning electronic patient records, CTV3 presented as a potential vocabulary for recording patient information in this acute setting.

The role of Ca2+ stores in the muscarinic inhibition of the K+ current IK(SO) in neonatal rat cerebellar granule cells

Cerebellar granule neurons (CGNs) possess a standing outward potassium current (IK(SO)) which shares many similarities with current through the two-pore domain potassium channel TASK-1 and which is inhibited following activation of muscarinic acetylcholine receptors. The action of muscarine on IK(SO) was unaffected by the M2 receptor antagonist methoctramine (100 nM) but was blocked by the M3 antagonist zamifenacin, which, at a concentration of 100 nM, shifted the muscarine concentration-response curve to the right by around 50-fold. Surprisingly, M3 receptor activation rarely produced a detectable increase in [Ca2+]i unless preceded by depolarization of the cells with 25 mM K+. Experiments with thapsigargin and ionomycin suggested that the endoplasmic reticulum Ca2+ stores in CGNs were depleted at rest. In contrast, cerebellar glial cells in the same fields of cells possessed substantial endoplasmic reticulum Ca2+ stores at rest. Pretreatment of the cells with BAPTA AM, thapsigargin or the phospholipase C (PLC) inhibitor U-73122 all blocked the muscarine-induced Ca2+ signal but had little or no effect on muscarinic inhibition of IK(SO). Raising [Ca2+]i directly with ionomycin caused a small but significant inhibition of IK(SO). It is concluded that muscarine acts on M3 muscarinic acetylcholine receptors both to inhibit IK(SO) and to mobilize Ca2+ from intracellular stores in CGNs. While the mobilization of Ca2+ occurs through activation of PLC, this does not seem to be the primary mechanism underlying muscarinic inhibition of IK(SO).

Implications of pulse pressure as a predictor of cardiac risk in patients with hypertension

Previously we demonstrated that pulse pressure is a strong risk factor for coronary events in male hypertensive subjects in the MRC Mild Hypertension Trial, whereas stroke is best predicted by mean blood pressure. In this study, we have assessed the implications of this finding in the treatment of mild essential hypertension. We examined the relationship between diastolic blood pressure and both coronary disease risk and stroke when these events were predicted by the above blood pressure measures using an empirical linear model and multivariate logistic regression models that contained data from the MRC trial. Under these circumstances, the predicted stroke risk increased progressively with increasing values of diastolic blood pressure, but in both empirical and formal statistical models, the predicted risk of a coronary event exhibited a J-shaped relationship with diastolic blood pressure. These results suggest that if coronary event risk in mild essential hypertension is predicted by pulse pressure then it may increase at low values of diastolic blood pressure, in contrast to stroke risk, which declines continuously as diastolic blood pressure falls within the physiological range. This raises the possibility that different sequelae of hypertension are best predicted by different measures of blood pressure and that the effect of treatment on stroke and coronary events in some circumstances may be discordant.

A functional role for the two-pore domain potassium channel TASK-1 in cerebellar granule neurons

Cerebellar granule neurons (CGNs) are one of the most populous cells in the mammalian brain. They express an outwardly rectifying potassium current, termed a "standing-outward" K(+) current, or IK(SO), which does not inactivate. It is active at the resting potential of CGNs, and blocking IK(SO) leads to cell depolarization. IK(SO) is blocked by Ba(2+) ions and is regulated by activation of muscarinic M(3) receptors, but it is insensitive to the classical broad-spectrum potassium channel blocking drugs 4-aminopyridine and tetraethylammonium ions. The molecular nature of this important current has yet to be established, but in this study, we provide strong evidence to suggest that IK(SO) is the functional correlate of the recently identified two-pore domain potassium channel TASK-1. We show that IK(SO) has no threshold for activation by voltage and that it is blocked by small extracellular acidifications. Both of these are properties that are diagnostic of TASK-1 channels. In addition, we show that TASK-1 currents expressed in Xenopus oocytes are inhibited after activation of endogenous M(3) muscarinic receptors. Finally, we demonstrate that mRNA for TASK-1 is found in CGNs and that TASK-1 protein is expressed in CGN membranes. This description of a functional two-pore domain potassium channel in the mammalian central nervous system indicates its physiological importance in controlling cell excitability and how agents that modify its activity, such as agonists at G protein-coupled receptors and hydrogen ions, can profoundly alter both the neuron's resting potential and its excitability.

Inhibition of neuronal KV potassium currents by the antidepressant drug, fluoxetine

1. The effect of the antidepressant drug, fluoxetine on neuronal delayed rectifier (KV) potassium (K) currents was investigated using perforated-patch whole-cell electrophysiological recording methods. 2. Fluoxetine was an effective inhibitor of KV currents in cerebellar granule neurons (CGNs) and also inhibited recombinant KV1.1 channels expressed in Chinese hamster ovary (CHO) cells. 3. Fluoxetine had an IC50 of 11 microM in CGNs but was slightly less potent on KV1.1 channels (IC50=55 microM). Interestingly, fluoxetine was a much more potent inhibitor of KV1.1 expressed in mammalian cells than has been found previously for the same homomeric channel expressed in Xenopus oocytes. 4. At concentrations that produced around 50% block, the shape of the KV currents in the presence of fluoxetine was simply scaled down when compared to control currents. 5. The effect of fluoxetine on KV currents in CGNs was neither voltage-dependent nor dependent on the channels being in their open state. Both of these observations suggest that fluoxetine does not act as a simple open channel blocking agent. 6. It is concluded that block of KV currents in mammalian neurons can occur at therapeutic levels of fluoxetine. This could lead to an increase in neuronal excitability and this effect may contribute to the therapeutic antidepressant action of fluoxetine.

Pulse pressure as a risk factor for cardiovascular events in the MRC Mild Hypertension Trial

OBJECTIVES

The aim of this study was to determine whether pulse pressure is a risk factor for coronary artery disease using data from the MRC trial of treatment of mild hypertension, and whether the effect of anti-hypertensive drug therapy on pulse pressure may be a determinant of outcome in treated patients.

METHODS

Logistic regression and Cox regression analyses were used to compare systolic and diastolic blood pressure, pulse pressure and mean blood pressure as predictors of coronary events and stroke in the MRC Mild Hypertension Trial. The effects of anti-hypertensive drug treatment with bendrofluazide and propranolol on pulse pressure were assessed using 1-year follow-up data. Event rates in the placebo-treated group and responses to anti-hypertensive treatment were measured in quartiles of age-adjusted entry pulse pressure. A 'four-corners' analysis was performed, with subjects divided into the upper and lower halves of the distributions of systolic and diastolic blood pressure at entry.

RESULTS

Pulse pressure was a stronger predictor of coronary events than systolic, diastolic or mean blood pressure in males by logistic regression. Pulse pressure was similar to systolic pressure as a coronary event predictor on Cox regression. Stroke was predicted most strongly by mean blood pressure. Fatal and non-fatal coronary event rates increased progressively in ascending quartiles of age-adjusted pulse pressure, but there was also a strong correlation with systolic blood pressure. The values of partial logistic regression coefficients in models containing both systolic and diastolic blood pressure also supported a role for pulse pressure in predicting coronary events and for mean blood pressure in predicting stroke. Coronary risk, but not stroke, was inversely related to diastolic blood pressure in the four-corners analysis. In a Cox model, regressions of coronary event probability on systolic blood pressure at entry were significantly and inversely related to diastolic blood pressure categorized in quartiles. Bendrofluazide but not propranolol decreased pulse pressure significantly and was associated with a reduction in cardiovascular events overall, but no definite relationship between the effect of drugs on pulse pressure and specific responses to treatment was seen.

CONCLUSION

Pulse pressure is a strong risk factor for coronary events in untreated hypertensive male subjects in the MRC Mild Hypertension Trial, whereas stroke is best predicted by mean blood pressure. Bendrofluazide and propranolol have different effects on pulse pressure which may be related to their relative efficacy in the treatment of hypertension, but this possibility requires further study in more suitable populations.

Impaired endothelium-dependent and independent dilatation of forearm resistance arteries in men with diet-treated non-insulin-dependent diabetes: role of dyslipidaemia

1. We measured endothelium-dependent and independent dilatation of forearm resistance arteries in 29 men with diet-treated non-insulin-dependent diabetes mellitus and 18 age- and sex-matched control subjects. None of the diabetic patients had hypercholesterolaemia, overt hypertension or microproteinuria. 2. We examined endogenous and exogenous nitric oxide-mediated vasodilatation by measuring forearm blood flow with venous occlusive plethysmography after administration of acetylcholine (7.5 and 15 micrograms/min) and sodium nitroprusside (3 and 10 micrograms/min), respectively, into the brachial artery. NG-monomethyl-L-arginine was also infused to study the inhibition of basal and stimulated release of nitric oxide. 3. The vasodilatory response to acetylcholine, expressed as area under curve, was significantly decreased in the diabetic patients compared with the control subjects (P = 0.019). NG-monomethyl-L-arginine significantly reduced basal (P < 0.001) and acetylcholine-stimulated blood flow (P < 0.02) in both groups. The vasodilatory response (also expressed as area under curve) to sodium nitroprusside was significantly less (P = 0.044) in the diabetic patients than in the control subjects. 4. In the diabetic patients, impaired vasodilatory responses to acetylcholine were significantly correlated with higher serum triacylglycerols (P = 0.048) and lower high-density lipoprotein-cholesterol concentrations (P = 0.007); the association with high-density lipoprotein was independent of age, glycated haemoglobin and blood pressure. Sodium nitroprusside responses were not correlated with lipid and lipoprotein concentrations. 5. We conclude that there is impaired endothelial and smooth muscle cell function in men with diet-treated non-insulin-dependent diabetes mellitus uncomplicated by overt hypertension or microproteinuria. Endothelial dysfunction may be related to diabetic dyslipidaemia and associated metabolic disturbances.

Measurement of blood pressure may be affected by an interaction between subject and observer based on gender

Retrospective studies have suggested that blood pressure (BP) may be affected by a covert gender interaction between patient and observer, which is most marked for female patients and male observers. Such an effect could be one of the determinants of the "white coat' response. We have assessed this interaction in a prospective study in 56 hospital outpatients (31 males, 25 females) in whom supine and erect BP and heart rate were measured by two male and two female subjects, and by an automatic sphygmomanometer when no persons were present. Supine systolic BP (SBP) was related to age, and fell progressively over three measurements. Absolute BP was less in females but the fall on repeated measurement was significantly greater than in males. When absolute BP was analysed by patient and observer sex, no significant interaction was present. BP measured by automatic sphygmomanometry was less than the value obtained clinically. Absolute BP showed no significant interaction with observer and patient sex, but the difference between machine and age-adjusted clinical measurements for SBP was significantly greater in female patients when BP was measured by male observers. However, this effect dissipated on repeated measurement. These data suggest that a transient gender interaction can contribute to the white-coat effect, especially in female patients when BP is measured by a male observer.

Adjustment of the apparent benefits of treatment on stroke risk in the MRC mild hypertension trial using data from the placebo-treated group

Clinical trials show that drug treatment significantly decreases stroke risk in hypertension. The benefit as measured in clinical trials may be affected by changes of blood pressure at entry and by departure from randomised treatment, but the magnitude of such effects is disputed. We have assessed benefit from reduction of stroke using data from the MRC Trial of mild to moderate hypertension, taking these factors into account, and have studied the likely effect of recent guidelines. The original analysis suggested that 850 patients needed treatment for 1 year to prevent one stroke. Under the more conservative of two assumptions made about the effect of treatment, this falls to 695 patients when allowance is made for reduction of stroke in placebo group patients withdrawn and actively treated, to 680 patients when allowance is made for the fall in blood pressure after entry, and to 556 patients with allowance for both. When benefit is assessed in patients whose entry diastolic blood pressure was > or = 100 mm Hg, 557 patients require treatment annually per stroke saved and this is decreased to 360 patients when allowance is made for withdrawal and active treatment of placebo group patients. These results suggest that benefit from reduction of stroke was underestimated in the MRC trial and that this is likely to be present in most trials. Changes to diagnostic criteria for hypertension in new management guidelines are likely to have significant effects on the number of patients treated per stroke prevented.

Heart mass and blood pressure have separate genetic determinants in the New Zealand genetically hypertensive (GH) rat

OBJECTIVE

To determine associations between cardiovascular parameters and genotype in 205 F2 rats of both sexes and lineages from reciprocal crosses made between rats of the New Zealand genetically hypertensive (GH) and Brown Norway (BN) rat strains.

METHODS

Systolic tail blood pressure, mean arterial blood pressure, pulse rate, heart mass, body mass and relative heart mass were determined for each rat in the age range 17-19 weeks, and DNA polymorphisms were examined for the guanylyl cyclase A (GCA), angiotensin converting enzyme (ACE) and renin (REN) genes.

RESULTS

The phenotypic data indicated the presence of genes on the X and Y chromosomes that affected blood pressure. The GH GCA allele, in males only, and the GH ACE allele, in females only, both cosegregated with increased blood pressure. The ACE effect was confined to rats of one lineage only, namely those with GH grandfathers. A cosegregation of the GH REN allele with decreased blood pressure was also detected in females with BN grandfathers. In contrast, the GH REN allele cosegregated with a smaller heart in males only, whereas the GH ACE allele cosegregated with a larger heart both in males and in females. In males this was the consequence of a decrease in body mass with no change in absolute heart mass, whereas in females there were changes in both of these parameters.

CONCLUSIONS

The results show that cardiac hypertrophy and blood pressure have independent genetic determinants in the GH rat, and indicate the importance of sex in determining the phenotypic expression of genes underlying cardiovascular pathology.

Economic comparison of drug and lifestyle treatment of cardiovascular risk factors in high-risk patients

1. Lifestyle interventions are routinely used in the treatment of cardiovascular risk factors in individual patients but their cost-effectiveness relative to drug treatment is largely unknown. 2. Drug treatment is effective at normalizing risk factors and is known to decrease morbidity and mortality though costs may be high. Lifestyle interventions carry a significant potential to reduce expenditure on drugs, but prospective studies on cost-effectiveness of lifestyle interventions favour drug treatment. 3. According to current evidence, lifestyle intervention in high-risk patients is not more cost-effective than drug treatment.

Blood pressure, 'white-coat' pressor responses and cardiovascular risk in placebo-group patients of the MRC Mild Hypertension trial

OBJECTIVE AND PATIENTS

To study the relationship between blood pressure and cardiovascular risk in 8654 patients randomly assigned to receive placebo in the Medical Research Council Mild Hypertension trial; 339 patients had a cardiovascular event during 5 years of follow-up.

RESULTS

Tracking of blood pressure and regression of blood pressure to and from the mean were demonstrated. Cardiovascular risk was related independently and positively to blood pressure, smoking and cholesterol, and inversely to low-normal plasma sodium. The relationship with blood pressure was stronger when measurements were made at entry to the trial by nurses and weaker when measurements were made by doctors.

DISCUSSION

One reason for this finding was that blood pressure increased at entry and, because the rise was greater in females, in whom the risk was lower than in males, a low-risk group predominated in the upper part of the blood pressure distribution. Another reason was that the rise itself conferred little or no cardiovascular risk. This rise might be a 'white-coat' response, because the increase in blood pressure in individuals correlated with the subsequent decrease after entry.

CONCLUSION

If the rise is a 'white-coat' effect and if, as the present study suggests, it is common and relatively free from risk, then changes are needed in the design of placebo-controlled trials and in the management of hypertension.

Remodelling of resistance arteries by treatment with enalapril in the New Zealand genetically hypertensive rat

1. New Zealand genetically hypertensive (GH) rats were treated with enalapril from the age of 4 to 10 weeks and the effects of treatment on the structure of mesenteric resistance arteries (MRA) was measured by use of stereological analysis of stained sections and by myograph techniques. 2. Tail-cuff blood pressure (BP) was measured weekly and intra-arterial BP recorded just before MRA were either fixed by perfusion or mounted on a myograph. 3. Stereological techniques (Cavalieri and optical dissector) were used to determine media and lumen volume, fraction of smooth muscle (SM) within the media and SM cell density. For MRA mounted on the myograph, lumen diameter, media thickness, active tension and active pressure were recorded. 4. BP was significantly (P < 0.0001) lowered by enalapril throughout the experiment. Intraarterial BP and left ventricular (LV) mass were also significantly lower in the enalapril treated GH rats (P < 0.0001). 5. Stereological measurements showed that enalapril treatment significantly (P < 0.0001) reduced media volume by 50%, doubled lumen volume (P < 0.0001), reduced the fraction of SM in the media (P < 0.04), and had no effect on the number of SM cell layers or on SM cell density. 6. Myograph measurements showed a decrease in the ratio media thickness/lumen diameter which was accompanied by a decrease in maximum active tension and pressure development. 7. In the GH rat early treatment with enalapril causes a true loss of medial tissue that is not simply due to rearrangement of existing media around an enlarged lumen.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of sex-related changes in blood pressure at entry to the MRC trial on prediction of cardiovascular risk

1. Using the MRC trial placebo group as the data source, we examined relationships between cardiovascular risk, gender, and blood pressure (BP) at screening, on entry to the trial, and after 3 months of follow up. 2. Blood pressure on entry to the trial (162/98 mmHg) was significantly higher than at the second screening (154/95 mmHg) visit and at 3 months (144/91 mmHg). The entry BP was higher, and the changes from screening to entry and from entry to 3 months were greater in females. Females had a low cardiovascular risk, but because of the greater changes of BP at entry they were over-represented at the top of the entry BP distribution, whereas males were over-represented at the bottom. The result of these effects was that the relationship between cardiovascular risk and entry BP was shifted to the right and was flatter than the corresponding curves measured at screening or after 3 months of follow up. 3. In consequence, the severity of hypertension in the trial population was overestimated from measurement of BP at entry, and the capacity of trial entry BP to predict cardiovascular risk was weakened. 4. BP on entry to the MRC Trial was affected by a pressor effect that diminished the value of BP as a cardiovascular risk factor because it differentially affected sub-populations by gender.

Stereological studies on mesenteric resistance artery structure in New Zealand genetically hypertensive and control rats

1. Stereological methods were used to quantitate and compare the structure of mesenteric resistance arteries (MRA) in New Zealand genetically hypertensive (GH) rats aged 4, 10 and 16 weeks and their normotensive control strain (N). 2. Blood pressure (BP) (tail-cuff and intra-arterial) were recorded before the vessels were fixed by perfusion and embedded in Technovit Kulzer GmbH D-6393, Wehrheim, Germany). 3. Media and lumen volumes were measured on transverse sections (TS), by the Cavalieri method, and numbers of smooth muscle (SM) cells were estimated by the optical disector method. 4. There were no significant differences in lumen volume per unit vessel length between GH and age-matched N groups at any age. However, at 10 and 16 weeks volume in GH groups was 9-10% lower than their respective N groups. 5. Media volume per unit vessel length increased in GH rats at all ages. The media/lumen ratio also increased in GH at all ages. 6. Smooth muscle cell density (SM cell number per unit volume of media) decreased in GH rats at all ages, i.e. there was no evidence of hyperplasia. 7. Blood pressure (tail-cuff and intra-arterial) significantly increased in GH rats at 4 weeks of age and also at 10 and 16 weeks. 8. These results show that media volume is increased in GH early in life, is not due to hyperplasia, but may be due to hypertrophy of the SM cells, an increase in the amount of extracellular matrix or a combination of both.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cilazapril on the structure of mesenteric resistance arteries of New Zealand genetically hypertensive and normotensive control rats

1. New Zealand genetically hypertensive (GH) rats and their normotensive controls (N) rats between the ages of 10 and 16 weeks were treated with cilazapril in the diet for 6 weeks. 2. Systolic blood pressure (SBP; tail-cuff) was measured weekly and intra-arterial blood pressure (BP) was measured at the end of the treatment period. 3. The effect of cilazapril on the structure of mesenteric resistance arteries (MRA) was evaluated by both stereological and myographic techniques. 4. Cilazapril lowered SBP significantly throughout the treatment period (16 weeks; GH with cilazapril 135 +/- 5 vs GH 216 +/- 9 mmHg, P < 0.001; N cilazapril 91 +/- 6 vs N 137 +/- 3 mmHg, P < 0.001); intra-arterial BP was also significantly lowered. 5. Bodyweight (BW) of treated GH rats was significantly lower than that of untreated GH at 16 weeks (P < 0.01; t-test); however, the weight of treated N rats was not significantly affected. Ventricular mass was reduced by cilazapril in GH and N rats (GH 259 +/- 10 vs 306 +/- 11, P < 0.001; N 171 +/- 3 vs 195 +/- 4 mg/100 g BW, P < 0.001). 6. Lumen volume of MRA was not significantly affected by cilazapril in either strain; media volume was reduced by 14% in both strains and the media/lumen ratio was significantly reduced. Vascular smooth muscle cell density significantly increased in cilazapril-treated GH rats.