Perinatal morbidity among women with a previous caesarean delivery (PRISMA trial): a cluster-randomised trial.

BACKGROUND: Women with a previous caesarean delivery face a difficult choice in their next pregnancy: planning another caesarean or attempting vaginal delivery, both of which are associated with potential maternal and perinatal complications. This trial aimed to assess whether a multifaceted intervention, which promoted person-centred decision making and best practices, would reduce the risk of major perinatal morbidity among women with one previous caesarean delivery. METHODS: We conducted an open, multicentre, cluster-randomised, controlled trial of a multifaceted 2-year intervention in 40 hospitals in Quebec among women with one previous caesarean delivery, in which hospitals were the units of randomisation and women the units of analysis. Randomisation was stratified according to level of care, using blocked randomisation. Hospitals were randomly assigned (1:1) to the intervention group (implementation of best practices and provision of tools that aimed to support decision making about mode of delivery, including an estimation of the probability of vaginal delivery and an ultrasound estimation of the risk of uterine rupture), or the control group (no intervention). The primary outcome was a composite risk of major perinatal morbidity. This trial was registered with ISRCTN, ISRCTN15346559. FINDINGS: 21 281 eligible women delivered during the study period, from April 1, 2016 to Dec 13, 2019 (10 514 in the intervention group and 10 767 in the control group). None were lost to follow-up. There was a significant reduction in the rate of major perinatal morbidity from the baseline period to the intervention period in the intervention group as compared with the control group (adjusted odds ratio [OR] for incremental change over time, 0·72 [95% CI 0·52-0·99]; p=0·042; adjusted risk difference -1·2% [95% CI -2·0 to -0·1]). Major maternal morbidity was significantly reduced in the intervention group as compared with the control group (adjusted OR 0·54 [95% CI 0·33-0·89]; p=0·016). Minor perinatal and maternal morbidity, caesarean delivery, and uterine rupture rates did not differ significantly between groups. INTERPRETATION: A multifaceted intervention supporting women in their choice of mode of delivery and promoting best practices resulted in a significant reduction in rates of major perinatal and maternal morbidity, without an increase in the rate of caesarean or uterine rupture. FUNDING: Canadian Institutes of Health Research (CIHR, MOP-142448).

No. 355-Physiologic Basis of Pain in Labour and Delivery: An Evidence-Based Approach to its Management.

OBJECTIVE: To review the evidence relating to nonpharmacological approaches in the management of pain during labour and delivery. To formulate recommendations for the usage of nonpharmacological approaches to pain management. OPTIONS: Nonpharmacological methods available for pain management during labour and delivery exist. These should be included in the counselling and care of women. EVIDENCE: PubMed and Medline were searched for articles in French and English on subjects related to "breastfeeding," "pain," "epidural," "anaesthesia," "analgesia," "labour," "labor," and combined with "gate control theory," "alternative therapies," "massage," "position," "mobility," "TENS," "bathing," "DNIC," "acupuncture," "acupressure," "sterile water injection," "higher center," "control mind," "cognitive structuring," "holistic health," "complementary therapy(ies)," "breathing," "relaxation," "mental imagery," "visualization," "mind focusing," "hypnosis," "auto-hypnosis," "sophrology," "mind and body interventions," "music," "odors," "biofeedback," "Lamaze," "Bonapace," "prenatal training," "gymnastic," "chanting," "haptonomy," "environment," "transcutaneous electrical stimulus-stimulation," "antenatal education," "support," "continuous support," "psychosocial support," "psychosomatic medicine," "supportive care," "companion," "intrapartum care," "nurse," "midwife(ves)," "father," "doula," "caregiver," " hormones," "oxytocin," "endorphin," "prolactin," "catecholamine," "adrenaline," and "noradrenaline" from 1990 to December 2015. Additional studies were identified by screening reference lists from selected studies and from expert suggestions. No language restrictions were applied. VALIDATION METHODS: The quality of the evidence is rated using the criteria described in the Report of the Canadian Task Force on Preventive Health Care. Recommendations for practice are ranked according to the method described in this report. BENEFITS, RISKS, AND COST: The nonpharmacological method encourages an incremental approach to pain management that contributes to reduced interventions through optimal use of the woman's neurophysiologic and endocrine resources and a better understanding of the physiology of stress and pain during labour. GUIDELINE UPDATE: The guideline will be reviewed 5 years after publication to decide whether all of part of the guideline should be updated. However, if important new evidence is published prior to the 5-year cycles, the review process may be accelerated for a more rapid update of some recommendations. SPONSORS: This guideline was developed with resources funded by The Society of Obstetricians and Gynaecologists of Canada. SUMMARY STATEMENTS: RECOMMENDATIONS.

Characterization of the cyanobacteria and associated bacterial community from an ephemeral wetland in New Zealand.

New Zealand ephemeral wetlands are ecologically important, containing up to 12% of threatened native plant species and frequently exhibiting conspicuous cyanobacterial growth. In such environments, cyanobacteria and associated heterotrophs can influence primary production and nutrient cycling. Wetland communities, including bacteria, can be altered by increased nitrate and phosphate due to agricultural practices. We have characterized cyanobacteria from the Wairepo Kettleholes Conservation Area and their associated bacteria. Use of 16S rRNA amplicon sequencing identified several operational taxonomic units (OTUs) representing filamentous heterocystous and non-heterocystous cyanobacterial taxa. One Nostoc OTU that formed macroscopic colonies dominated the cyanobacterial community. A diverse bacterial community was associated with the Nostoc colonies, including a core microbiome of 39 OTUs. Identity of the core microbiome associated with macroscopic Nostoc colonies was not changed by the addition of nutrients. One OTU was highly represented in all Nostoc colonies (27.6%-42.6% of reads) and phylogenetic analyses identified this OTU as belonging to the genus Sphingomonas. Scanning electron microscopy showed the absence of heterotrophic bacteria within the Nostoc colony but revealed a diverse community associated with the colonies on the external surface.

Lung-volume controlled computerised tomography in real-life acute severe asthma.

OBJECTIVE: It is not known how airway structure is altered during real-life acute asthma exacerbations. The aim of this study was to examine changes in airway structure during acute asthma exacerbations and at convalescence by using lung-volume controlled high resolution computerised tomography (HRCT). METHODS: Eight subjects with acute asthma exacerbation admitted to hospital were recruited. HRCT was performed within 72 h of admission (n = 8) and repeated after 8 weeks of convalescence (n = 7). Individual airways were carefully matched on acute and convalescent CT data sets for comparisons of airway parameters. A novel methodology was employed for standardisation of lung volumes to permit valid comparisons of lung imaging. Measurements of bronchial cross sectional airway area (Aa) and bronchial luminal area (Ai) for each matched airway were obtained using a validated program. RESULTS: The airway wall thickness was analysed as wall area (WA) calculated as a percentage: WA% = WA/Aa × 100. Wilcoxon signed-rank testing was used to compare acute and convalescent asthma and Spearman's correlation to examine associations. Airway lumen (Ai) areas were similar in both acute and stable asthma phases (6.6 ± 3.1 mm(2) versus 7.2 ± 3.8 mm(2) p = 0.8). However, the airway wall was significantly thickened during acute asthma exacerbations compared to convalescence (62 ± 4% versus 55 ± 7%; p = 0.01). There was no correlation between airway structure dimensions and lung function measurements. CONCLUSIONS: This is the first study to demonstrate an increase in airway wall thickness during real-life acute asthma exacerbation. However, narrowing of the airway lumen area was variable and will require larger studies able to detect small differences. These results suggest that airway wall thickening linked to mucosal inflammation is likely to characterise acute asthma in vivo but that changes in the airway lumen accompanying bronchoconstriction may be more heterogeneous.

Nonpharmacologic approaches for pain management during labor compared with usual care: a meta-analysis.

OBJECTIVES: To assess the effects of nonpharmacologic approaches to pain relief during labor, according to their endogenous mechanism of action, on obstetric interventions, maternal, and neonatal outcomes. DATA SOURCE: Cochrane library, Medline, Embase, CINAHL and the MRCT databases were used to screen studies from January 1990 to December 2012. STUDY SELECTION: According to Cochrane criteria, we selected randomized controlled trials that compared nonpharmacologic approaches for pain relief during labor to usual care, using intention-to-treat method. RESULTS: Nonpharmacologic approaches, based on Gate Control (water immersion, massage, ambulation, positions) and Diffuse Noxious Inhibitory Control (acupressure, acupuncture, electrical stimulation, water injections), are associated with a reduction in epidural analgesia and a higher maternal satisfaction with childbirth. When compared with nonpharmacologic approaches based on Central Nervous System Control (education, attention deviation, support), usual care is associated with increased odds of epidural OR 1.13 (95% CI 1.05-1.23), cesarean delivery OR 1.60 (95% CI 1.18-2.18), instrumental delivery OR 1.21 (95% CI 1.03-1.44), use of oxytocin OR 1.20 (95% CI 1.01-1.43), labor duration (29.7 min, 95% CI 4.5-54.8), and a lesser satisfaction with childbirth. Tailored nonpharmacologic approaches, based on continuous support, were the most effective for reducing obstetric interventions. CONCLUSION: Nonpharmacologic approaches to relieve pain during labor, when used as a part of hospital pain relief strategies, provide significant benefits to women and their infants without causing additional harm.

Ancient RNA? RT-PCR of 50-year-old RNA identifies peach latent mosaic viroid.

The preservation of macromolecules is at best haphazard. Modern techniques have improved the detection of ancient DNA and proteins, but there is little information on the preservation of RNA. Fifty-year-old dried leaf material showing symptoms of peach calico disease was used successfully in RT-PCRs to amplify peach latent mosaic viroid (PLMVd) RNA and the mRNA for the large subunit of ribulose 1,5-bisphosphate carboxylase (rubisco). These results indicate that naked RNA may be preserved, under suitable conditions, for at least 50 years. The results are discussed in the context of ancient DNA and proteins and the process of fossilization.

Preventable obstetrical interventions: how many caesarean sections can be prevented in Canada?

Public health authorities have been alarmed by the progressive rise in rates of Caesarean section in Canada, approaching one birth in three in several provinces. We aimed therefore to consider what were preventable obstetrical interventions in women with a low-risk pregnancy and to propose an analytic framework for the reduction of the rate of CS. We obtained statistical variations of CS rates over time, across regions, and within professional practices from MED-ÉCHO, the Quebec hospitalization database, from 1969 to 2009. Data were extracted from a recent systematic review of the cascade of obstetrical interventions to calculate the population-attributable fractions for each intervention associated with an increased probability of CS. We thereby identified expectant management (as an alternative to labour induction) and planned vaginal birth after CS as the leading strategies for potentially reducing rates of CS in women at low risk. For vaginal birth after CS, an increase to its 1995 level could lower the current CS rate of 23.2% (2009 to 2010) to 21.0%. Other alternatives to obstetrical interventions with a potential for lowering CS rates included non-pharmacological pain control methods (such as continuous support during childbirth) in addition to usual care, intermittent auscultation of the fetal heart (instead of electronic fetal monitoring), and multidisciplinary internal quality assessment audits. We believe, therefore, that the concept of preventable CS is supported by empirical evidence, and we identified realistic strategies to maintain a CS rate in Quebec near 20%.

Les autorités en matière de santé publique ont été alarmées par la hausse graduelle des taux de césarienne (CS) au Canada (près d'une naissance sur trois dans plusieurs provinces). Nous avons donc cherché à identifier les interventions obstétricales qui pouvaient être évitées chez les femmes qui connaissent une grossesse les exposant à de faibles risques, ainsi qu'à proposer un cadre analytique pour la réduction du taux de CS. Les variations statistiques, entre 1969 et 2009, des taux de CS avec le temps, d'une région à l'autre et en fonction des pratiques professionnelles ont été tirées de MED-ÉCHO (la base de données sur l'hospitalisation au Québec). Des données ont été tirées d'une récente analyse systématique de la cascade d'interventions obstétricales en vue de calculer les fractions étiologiques du risque pour chacune des interventions associées à une probabilité accrue de CS. Nous avons ainsi identifié la prise en charge non interventionniste (à titre de solution de rechange au déclenchement du travail) et l'accouchement vaginal planifié après CS comme étant les principales stratégies pouvant permettre la réduction des taux de CS chez les femmes exposées à de faibles risques. Pour ce qui est de l'accouchement vaginal après CS, une hausse jusqu'à son niveau de 1995 pourrait faire passer le taux actuel de CS de 23,2 % (de 2009 à 2010) à 21,0 %. Parmi les solutions de rechange aux interventions obstétricales qui présentent le potentiel d'abaisser les taux de CS, on trouvait les méthodes non pharmacologiques de maîtrise de la douleur (comme l'offre d'un soutien continu pendant l'accouchement) s'ajoutant aux soins habituels, l'auscultation intermittente du cœur fœtal (plutôt que le monitorage électronique du fœtus) et les audits internes multidisciplinaires de la qualité. Nous estimons donc que le concept de la CS évitable est soutenu par des données empiriques et nous avons identifié des stratégies réalistes permettant d'assurer le maintien, au Québec, d'un taux de CS se situant près de 20 %.

New Virus Diagnostic Approaches to Ensuring the Ongoing Plant Biosecurity of Aotearoa New Zealand.

To protect New Zealand's unique ecosystems and primary industries, imported plant materials must be constantly monitored at the border for high-threat pathogens. Techniques adopted for this purpose must be robust, accurate, rapid, and sufficiently agile to respond to new and emerging threats. Polymerase chain reaction (PCR), especially real-time PCR, remains an essential diagnostic tool but it is now being complemented by high-throughput sequencing using both Oxford Nanopore and Illumina technologies, allowing unbiased screening of whole populations. The demand for and value of Point-of-Use (PoU) technologies, which allow for in situ screening, are also increasing. Isothermal PoU molecular diagnostics based on recombinase polymerase amplification (RPA) and loop-mediated amplification (LAMP) do not require expensive equipment and can reach PCR-comparable levels of sensitivity. Recent advances in PoU technologies offer opportunities for increased specificity, accuracy, and sensitivities which makes them suitable for wider utilization by frontline or border staff. National and international activities and initiatives are adopted to improve both the plant virus biosecurity infrastructure and the integration, development, and harmonization of new virus diagnostic technologies.

Laryngeal penetration and aspiration in individuals with stable COPD.

BACKGROUND AND OBJECTIVE: Swallowing is closely coordinated with breathing but in COPD altered synchronization may predispose patients to a breach of the upper airway protective mechanisms. However, aspiration during swallow has never been shown in COPD. We examined penetration of liquid material into the airway of patients with COPD and correlated it with breathing-swallow patterns. METHODS: A case-control study was performed. Patients with COPD (n = 16) were matched with normal control subjects (n = 15). Sub-mandibular videofluoroscopy was carried out during swallow of graduated volumes of barium to detect penetration (contrast enters the airway and may contact vocal folds) and aspiration (contrast passes glottis). Respiration was monitored simultaneously to gauge synchronization. Hospitalization and mortality were assessed after 36 months. RESULTS: Penetration/aspiration scores were higher in patients with COPD (3.3 ± 0.7 vs 1.6 ± 0.4 in healthy controls, P = 0.03; mean ± SE). Penetration with aspiration was observed in 4/16 patients with COPD versus 1/15 controls (P = 0.07). Penetration with or without aspiration was found in 6/16 patients (P = 0.04). Inspiration-swallow-expiration patterns were favoured in individuals with COPD (P = 0.02). Penetration/aspiration was associated with higher respiratory rates (P = 0.01), reduced hyoid elevation (P = 0.04), post-swallow larynx penetration (P = 0.05) and oxygen desaturation (P = 0.01). There was a trend for the penetration/aspiration group to have an adverse outcome. CONCLUSIONS: Upper airway protective mechanisms may be flawed in COPD, possibly through reduced coordination of breathing with swallowing. This abnormality may contribute to COPD morbidity in a subgroup of patients.

Rare Case of Dynamic Thoracic Outlet Syndrome Resolved by an Isolated Subclavius Posticus Muscle Resection: A Case Report.

CASE: We reported a dynamic neurogenic left thoracic outlet syndrome (TOS) with a permanent abduction of the fifth left finger. Preoperative magnetic resonance imaging (MRI) assessed the presence of subclavius posticus muscle (SPM). Because of a nonoperative treatment failure, we performed a brachial plexus neurolysis and SPM resection. Immediate postoperative assessment showed an immediate disappearance of the Wartenberg sign. CONCLUSION: SPM constitutes an underestimated cause of TOS. A careful MRI reading is necessary to make correct diagnosis. Nonoperative treatment includes physiotherapy and can be proposed in first instance. When nonoperative treatment fails, brachial plexus exploration with release of the SPM may result in resolution of symptoms.

Lung diffusing capacity in adult bronchiectasis: a longitudinal study.

BACKGROUND: Recent studies described a progressive decline in lung volumes in adult bronchiectasis. Interstitial lung disease is also a feature of bronchiectasis, but whether this is associated with a decline in lung diffusing capacity (measured as the diffusing capacity of the lung for carbon monoxide [D(LCO)]) is not well known. OBJECTIVE: To assess longitudinal decline in diffusing capacity of the lung for carbon monoxide (D(LCO)) in adult bronchiectasis. METHODS: Sixty-one subjects had a detailed baseline clinical and laboratory assessment, then were followed regularly with clinical and lung-function assessment for a median 7 years. RESULTS: Baseline spirometry demonstrated mild obstructive lung disease, with a mean FEV(1) of 72% of predicted, mean forced vital capacity 87% of predicted, and normal D(LCO) (mean D(LCO) 88% of predicted, and mean D(LCO) adjusted for alveolar volume [D(LCO)/V(A)] 100% of predicted). There was an accelerated decline in D(LCO) and D(LCO)/V(A) over the 7-year period. The median D(LCO) decline was 2.9% of predicted per year (95% CI 2.3-4.1% of predicted per year). The median D(LCO)/V(A) decline was 2.4% of predicted per year (95% CI 2.1-4.0% of predicted per year). There was a significant relationship between D(LCO) decline and age and decline in FEV(1). CONCLUSIONS: In our cohort of patients with bronchiectasis there was a progressive D(LCO) decline.

Fungal diversity in canopy soil of silver beech, Nothofagus menziesii (Nothofagaceae).

Adventitious roots in canopy soils associated with silver beech (Nothofagus menziesii Hook.f. (Nothofagaceae)) form ectomycorrhizal associations. We investigated the extent to which canopy ectomycorrhizal communities contribute to overall diversity of ectomycorrhizal fungi associated with silver beech. Hyphal ingrowth bags were buried for 12 months in canopy and terrestrial soils of five trees at one site. We used amplicon sequencing of the nuclear ribosomal internal transcribed spacer 2 region (ITS2) to assess diversity of both ectomycorrhizal and non-ectomycorrhizal OTUs in hyphal ingrowth bags. There was a significant difference in ectomycorrhizal fungal community diversity between the terrestrial and canopy hyphal ingrowth bag communities. Ectomycorrhizal community composition of the terrestrial and canopy environments was also significantly different. Some ectomycorrhizal taxa were significantly differentially represented in either the terrestrial or canopy environment. The hyphal ingrowth bags also accumulated non-ectomycorrhizal species. The non-ectomycorrhizal fungi also had significantly different diversity and community composition between the canopy and terrestrial environments. Like the ectomycorrhizal community, some non-ectomycorrhizal taxa were significantly differentially represented in either the terrestrial or canopy environment. The canopy soil microhabitat provides a novel environment for growth of ectomycorrhizal adventitious roots and enables the spatial partitioning of ectomycorrhizal and non-ectomycorrhizal fungal diversity in the forest.

Dual-energy X-ray absorptiometry is the method of choice to assess body composition in COPD.

BACKGROUND AND OBJECTIVE: Mortality and morbidity in COPD have been related to reduced FEV1 as well as indices of body composition. Different techniques used to evaluate body composition may vary in accuracy, particularly in conditions with altered fluid balance such as COPD. We hypothesized that direct measurement of fat-free mass index (FFMI) by dual-energy X-ray absorptiometry (DEXA) would provide superior assessment of body composition in COPD. METHODS: We measured body composition in 31 patients with COPD randomly selected from a teaching hospital clinic. To estimate total body water (TBW) and FFMI, skin-fold anthropometry, bioelectrical impedance analysis (BIA) with Schols and Lukaski equations as well as DEXA, total body potassium by whole-body gamma-counting (TBK) and in vivo neutron activation analysis were used. Combined body composition methods providing precise estimations of TBW were used for comparisons. Bland-Altman analyses, ANOVA and chi2-testing were used to examine data. RESULTS: Mean BMI was 27.6 +/- 5.34 kg/m2 (mean +/- SD). Estimations of TBW were similar using Schols BIA or by using combined body composition methods. FFMI did not vary significantly between grades of COPD severity but was significantly different when assessed using DEXA and other methods. Calculated FFM hydration was significantly different from the fixed hydration factor used to calculate FFMI from BIA TBW (P < 0.05). CONCLUSION: The Schols BIA method incorporates a fixed hydration factor that may lead to an erroneous estimation of FFMI with ensuing clinical implications. DEXA can be used to obtain accurate and comprehensive assessments of body composition and should be the preferred investigation in COPD.

Twitter as a Potential Disaster Risk Reduction Tool. Part I: Introduction, Terminology, Research and Operational Applications.

Twitter, a popular communications platform, is identified as contributing to improved mortality and morbidity outcomes resulting from the 2013 Hattiesburg, Mississippi EF-4 Tornado. This study describes the methodology by which Twitter was investigated as a potential disaster risk reduction and management tool at the community level and the process by which the at-risk population was identified from the broader Twitter user population. By understanding how various factors contribute to the superspreading of messages, one can better optimize Twitter as an essential communications and risk reduction tool. This study introduces Parts II, III and IV which further define the technological and scientific knowledge base necessary for developing future competency base curriculum and content for Twitter assisted disaster management education and training at the community level.

Twitter as a Potential Disaster Risk Reduction Tool. Part II: Descriptive Analysis of Identified Twitter Activity during the 2013 Hattiesburg F4 Tornado.

BACKGROUND: This article describes a novel triangulation methodological approach for identifying twitter activity of regional active twitter users during the 2013 Hattiesburg EF-4 Tornado. METHODOLOGY: A data extraction and geographically centered filtration approach was utilized to generate Twitter data for 48 hrs pre- and post-Tornado. The data was further validated using six sigma approach utilizing GPS data. RESULTS: The regional analysis revealed a total of 81,441 tweets, 10,646 Twitter users, 27,309 retweets and 2637 tweets with GPS coordinates. CONCLUSIONS: Twitter tweet activity increased 5 fold during the response to the Hattiesburg Tornado.  Retweeting activity increased 2.2 fold. Tweets with a hashtag increased 1.4 fold. Twitter was an effective disaster risk reduction tool for the Hattiesburg EF-4 Tornado 2013.

Twitter as a Potential Disaster Risk Reduction Tool. Part III: Evaluating Variables that Promoted Regional Twitter Use for At-risk Populations During the 2013 Hattiesburg F4 Tornado.

INTRODUCTION: Study goals attempt to identify the variables most commonly associated with successful tweeted messages and determine which variables have the most influence in promoting exponential dissemination of information (viral spreading of the message) and trending (becoming popular) in the given disaster affected region. METHODS: Part II describes the detailed extraction and triangulation filtration methodological approach to acquiring twitter data for the 2013 Hattiesburg Tornado. The data was then divided into two 48 hour windows before and after the tornado impact with a 2 hour pre-tornado buffer to capture tweets just prior to impact. Criteria-based analysis was completed for Tweets and users. The top 100 pre-Tornado and post-Tornado retweeted users were compared to establish the variability among the top retweeted users during the 4 day span.  RESULTS: Pre-Tornado variables that were correlated to higher retweeted rates include total user tweets (0.324), and total times message retweeted (0.530).  Post-Tornado variables that were correlated to higher retweeted rates include total hashtags in a retweet (0.538) and hashtags #Tornado (0.378) and #Hattiesburg (0.254). Overall hashtags usage significantly increased during the storm. Pre-storm there were 5,763 tweets with a hashtag and post-storm there was 13,598 using hashtags. CONCLUSIONS: Twitter's unique features allow it to be considered a unique social media tool applicable for emergency managers and public health officials for rapid and accurate two way communication.  Additionally, understanding how variables can be properly manipulated plays a key role in understanding how to use this social media platform for effective, accurate, and rapid mass information communication.

Twitter as a Potential Disaster Risk Reduction Tool. Part IV: Competency-based Education and Training Guidelines to Promote Community Resiliency.

Twitter can be an effective tool for disaster risk reduction but gaps in education and training exist in current public health and disaster management educational competency standards.  Eleven core public health and disaster management competencies are proposed that incorporate Twitter as a tool for effective disaster risk reduction.  Greater funding is required to promote the education and training of this tool for those in professional schools and in the current public health and disaster management workforce.

Changes in the activities of antioxidant enzymes in response to virus infection and hormone treatment.

Activities of enzymes involved in the detoxification of reactive oxygen species (catalase, glutathione reductase, peroxidase and superoxide dismutase (SOD)) were examined in the leaves of Phaseolus vulgaris L. var. Top Crop treated with plant hormones and infected with a non-lesion-forming isolate of white clover mosaic potexvirus (WClMV). The activities of catalase, glutathione reductase and SOD rapidly declined after infection while peroxidase activity was enhanced. These changes occurred before the rapid increase (5 days) in WClMV replication. A mild chlorosis appeared 7-10 days after inoculation but necrosis was never observed on inoculated leaves. Plants treated with dihydrozeatin, salicylic acid and jasmonic acid prior to WClMV inoculation showed elevated catalase, glutathione reductase, and peroxidase activity, while SOD activities remained the same as in water-treated controls. These treatments all inhibited virus replication with enzyme activities remaining near control levels. We propose that a decline in free radical scavenging capacity may be required before a rapid increase in virus replication can take place. Treatments increasing the ability of the plant to scavenge reactive oxygen species may hinder virus replication. A possible role for reactive oxygen species as a requirement for virus replication is discussed.