A quantitative evaluation of aerosol generation during cardiopulmonary resuscitation.

It is unclear if cardiopulmonary resuscitation is an aerosol-generating procedure and whether this poses a risk of airborne disease transmission to healthcare workers and bystanders. Use of airborne transmission precautions during cardiopulmonary resuscitation may confer rescuer protection but risks patient harm due to delays in commencing treatment. To quantify the risk of respiratory aerosol generation during cardiopulmonary resuscitation in humans, we conducted an aerosol monitoring study during out-of-hospital cardiac arrests. Exhaled aerosol was recorded using an optical particle sizer spectrometer connected to the breathing system. Aerosol produced during resuscitation was compared with that produced by control participants under general anaesthesia ventilated with an equivalent respiratory pattern to cardiopulmonary resuscitation. A porcine cardiac arrest model was used to determine the independent contributions of ventilatory breaths, chest compressions and external cardiac defibrillation to aerosol generation. Time-series analysis of participants with cardiac arrest (n = 18) demonstrated a repeating waveform of respiratory aerosol that mapped to specific components of resuscitation. Very high peak aerosol concentrations were generated during ventilation of participants with cardiac arrest with median (IQR [range]) 17,926 (5546-59,209 [1523-242,648]) particles.l-1 , which were 24-fold greater than in control participants under general anaesthesia (744 (309-2106 [23-9099]) particles.l-1 , p < 0.001, n = 16). A substantial rise in aerosol also occurred with cardiac defibrillation and chest compressions. In a complimentary porcine model of cardiac arrest, aerosol recordings showed a strikingly similar profile to the human data. Time-averaged aerosol concentrations during ventilation were approximately 270-fold higher than before cardiac arrest (19,410 (2307-41,017 [104-136,025]) vs. 72 (41-136 [23-268]) particles.l-1 , p = 0.008). The porcine model also confirmed that both defibrillation and chest compressions generate high concentrations of aerosol independent of, but synergistic with, ventilation. In conclusion, multiple components of cardiopulmonary resuscitation generate high concentrations of respiratory aerosol. We recommend that airborne transmission precautions are warranted in the setting of high-risk pathogens, until the airway is secured with an airway device and breathing system with a filter.

Quantitative evaluation of aerosol generation during manual facemask ventilation.

Manual facemask ventilation, a core component of elective and emergency airway management, is classified as an aerosol-generating procedure. This designation is based on one epidemiological study suggesting an association between facemask ventilation and transmission during the SARS-CoV-1 outbreak in 2003. There is no direct evidence to indicate whether facemask ventilation is a high-risk procedure for aerosol generation. We conducted aerosol monitoring during routine facemask ventilation and facemask ventilation with an intentionally generated leak in anaesthetised patients. Recordings were made in ultraclean operating theatres and compared against the aerosol generated by tidal breathing and cough manoeuvres. Respiratory aerosol from tidal breathing in 11 patients was reliably detected above the very low background particle concentrations with median [IQR (range)] particle counts of 191 (77-486 [4-1313]) and 2 (1-5 [0-13]) particles.l-1 , respectively, p = 0.002. The median (IQR [range]) aerosol concentration detected during facemask ventilation without a leak (3 (0-9 [0-43]) particles.l-1 ) and with an intentional leak (11 (7-26 [1-62]) particles.l-1 ) was 64-fold (p = 0.001) and 17-fold (p = 0.002) lower than that of tidal breathing, respectively. Median (IQR [range]) peak particle concentration during facemask ventilation both without a leak (60 (0-60 [0-120]) particles.l-1 ) and with a leak (120 (60-180 [60-480]) particles.l-1 ) were 20-fold (p = 0.002) and 10-fold (0.001) lower than a cough (1260 (800-3242 [100-3682]) particles.l-1 ), respectively. This study demonstrates that facemask ventilation, even when performed with an intentional leak, does not generate high levels of bioaerosol. On the basis of this evidence, we argue facemask ventilation should not be considered an aerosol-generating procedure.

A quantitative evaluation of aerosol generation during supraglottic airway insertion and removal.

Many guidelines consider supraglottic airway use to be an aerosol-generating procedure. This status requires increased levels of personal protective equipment, fallow time between cases and results in reduced operating theatre efficiency. Aerosol generation has never been quantitated during supraglottic airway use. To address this evidence gap, we conducted real-time aerosol monitoring (0.3-10-µm diameter) in ultraclean operating theatres during supraglottic airway insertion and removal. This showed very low background particle concentrations (median (IQR [range]) 1.6 (0-3.1 [0-4.0]) particles.l-1 ) against which the patient's tidal breathing produced a higher concentration of aerosol (4.0 (1.3-11.0 [0-44]) particles.l-1 , p = 0.048). The average aerosol concentration detected during supraglottic airway insertion (1.3 (1.0-4.2 [0-6.2]) particles.l-1 , n = 11), and removal (2.1 (0-17.5 [0-26.2]) particles.l-1 , n = 12) was no different to tidal breathing (p = 0.31 and p = 0.84, respectively). Comparison of supraglottic airway insertion and removal with a volitional cough (104 (66-169 [33-326]), n = 27), demonstrated that supraglottic airway insertion/removal sequences produced <4% of the aerosol compared with a single cough (p < 0.001). A transient aerosol increase was recorded during one complicated supraglottic airway insertion (which initially failed to provide a patent airway). Detailed analysis of this event showed an atypical particle size distribution and we subsequently identified multiple sources of non-respiratory aerosols that may be produced during airway management and can be considered as artefacts. These findings demonstrate supraglottic airway insertion/removal generates no more bio-aerosol than breathing and far less than a cough. This should inform the design of infection prevention strategies for anaesthetists and operating theatre staff caring for patients managed with supraglottic airways.

The risk of cancer in primary care patients with hypercalcaemia: a cohort study using electronic records.

BACKGROUND: The risk of cancer with hypercalcaemia in primary care is unknown. METHODS: This was a cohort study using calcium results in patients aged ⩾40 years in a primary care electronic data set. Diagnoses of cancer in the following year were identified. RESULTS: Participants (54 267) had calcium results: 1674 (3%) were ⩾2.6 mmol l(-1). Hypercalcaemia was strongly associated with cancer, especially in males: OR 2.92, 95% CI 2.17-3.93, P=<0.001; positive predictive value (PPV) 11.5%; females: OR 1.86, 95% CI 1.39-2.50, P<0.001: PPV 4.1%. CONCLUSIONS: Hypercalcaemia is strongly associated with cancer in primary care, with men at most risk, despite hypercalcaemia being more common in women.

An international, prospective, multicenter evaluation of the combination of AdvanDx Staphylococcus QuickFISH BC with mecA XpressFISH for detection of methicillin-resistant Staphylococcus aureus isolates from positive blood cultures.

Sepsis caused by Staphylococcus aureus is a major health problem worldwide. Better outcomes are achieved when rapid diagnosis and determination of methicillin susceptibility enable early optimization of antimicrobial therapy. Eight large clinical laboratories, seven from the United States and one from Scotland, evaluated the combination of the Staphylococcus QuickFISH BC and the new mecA XpressFISH assay (both AdvanDx, Woburn, MA, USA) for the detection of methicillin-resistant S. aureus in positive blood cultures. Blood cultures flagged as positive by automated blood culture instruments and demonstrating only Gram-positive cocci in clusters on Gram stain were tested by QuickFISH, a 20-min assay. If only S. aureus was detected, mecA XpressFISH testing followed. The recovered S. aureus isolates were tested by cefoxitin disk diffusion as the reference method. The QuickFISH assay results were concordant with the routine phenotypic testing methods of the testing laboratories in 1,211/1,221 (99.1%) samples and detected 488/491 S. aureus organisms (sensitivity, 99.4%; specificity, 99.6%). Approximately 60% of the samples (730) contained coagulase-negative staphylococci or nonstaphylococci as assessed by the QuickFISH assay and were not tested further. The 458 compliant samples positive exclusively for S. aureus by the QuickFISH assay were tested by the mecA XpressFISH assay, which detected 209 of 211 methicillin-resistant S. aureus organisms (sensitivity, 99.1%; specificity, 99.6%). The mecA XpressFISH assay also showed high reproducibility, with 534/540 tests performed by 6 operators over 5 days achieving reproducible results (98.9% agreement). The combination of the Staphylococcus QuickFISH BC and mecA XpressFISH assays is sensitive, specific, and reproducible for the detection of methicillin-resistant S. aureus and yields complete results in 2 h after the blood culture turns positive.

Effect of financial incentives on delivery of alcohol screening and brief intervention (ASBI) in primary care: longitudinal study.

INTRODUCTION: Alcohol screening and brief intervention (ASBI) is effective but underprovided in primary care. Financial incentives may help address this. This study assesses the impact of a local pay-for-performance programme on delivery of ASBI in UK primary care. METHODS: Longitudinal study using data from 30 general practices in north-west London from 2008 to 2011 with logistic regression to examine disparities in ASBI delivery. RESULTS: Of 211 834 registered patients, 45 040 were targeted by the incentive (cardiovascular conditions or high risk; mental health conditions), of whom 65.7% were screened (up from a baseline of 4.8%, P < 0.001), compared with 14.7% of non-targeted patients (P < 0.001). Screening rates were lower after adjustment in younger patients, White patients, less deprived areas and in patients with mental health conditions (P < 0.05). Of those screened, 11.5% were positive and 88.6% received BI. Men and White patients were significantly more likely to screen positive. Women and younger patients were less likely to receive BI. 30.1% of patients re-screened were now negative. However, patients with mental health conditions were less likely to re-screen negative than those with cardiovascular conditions. CONCLUSION: Financial incentives appear to be effective in increasing delivery of ASBI in primary care and may reduce hazardous and harmful drinking in some patients. The findings support universal rather than targeted screening.

Effectiveness of providing financial incentives to healthcare professionals for smoking cessation activities: systematic review.

OBJECTIVE: Financial incentives are seen as one approach to encourage more systematic use of smoking cessation interventions by healthcare professionals. A systematic review was conducted to examine the evidence for this. METHODS: Medline, Embase, PsychINFO, Cochrane Library, ISI Web of Science and sources of grey literature were used as data sources. Studies were included if they reported the effects of any financial incentive provided to healthcare professionals to undertake smoking cessation-related activities. Data extraction and quality assessment for each study were conducted by one reviewer and checked by a second. A total of 18 studies were identified, consisting of 3 randomised controlled trials and 15 observational studies. All scored in the mid range for quality. In all, 8 studies examined smoking cessation activities alone and 10 studied the UK's Quality and Outcomes Framework targeting quality measures for chronic disease management including smoking recording or cessation activities. Five non-Quality and Outcomes Framework studies examined the effects of financial incentives on individual doctors and three examined effects on groups of healthcare professionals based in clinics and general practices. Most studies showed improvements in recording smoking status and smoking cessation advice. Five studies examined the impact of financial incentives on quit rates and longer-term abstinence and these showed mixed results. CONCLUSIONS: Financial incentives appear to improve recording of smoking status, and increase the provision of cessation advice and referrals to stop smoking services. Currently there is not sufficient evidence to show that financial incentives lead to reductions in smoking rates.

Effect of financial incentives on ethnic disparities in smoking cessation interventions in primary care: cross-sectional study.

BACKGROUND: Smoking cessation interventions are underprovided in primary care. Financial incentives may help address this. However, few studies in the UK have examined their impact on disparities in the delivery of smoking cessation interventions. METHODS: Cross-sectional study using 2007 data from 29 general practices in Wandsworth, London, UK. We used logistic regression to examine associations between disease group [cardiovascular disease (CVD), respiratory disease, depression or none of these diseases], ethnicity and smoking outcomes following the introduction of the Quality and Outcomes Framework in 2004. RESULTS: Significantly, more CVD patients had smoking status ascertained compared with those with respiratory disease (89 versus 72%), but both groups received similar levels of cessation advice (93 and 89%). Patients with depression or none of the diseases were less likely to have smoking status ascertained (60% for both groups) or to receive advice (80 and 75%). Smoking prevalence was high, especially for patients with depression (44%). White British patients had higher rates of smoking than most ethnic groups, but black Caribbean men with depression had the highest smoking prevalence (62%). CONCLUSIONS: Smoking rates remain high, particularly for white British and black Caribbean patients. Extending financial incentives to include recording of ethnicity and rewarding quit rates may further improve smoking cessation outcomes in primary care.

Loneliness and vascular biomarkers: the Dublin Healthy Ageing Study.

BACKGROUND: Loneliness has been associated with poor physical health and a link has been suggested between the presence of loneliness, cardiovascular health and inflammatory markers. OBJECTIVE: To investigate the association between vascular disease biomarkers and loneliness in a community-dwelling non-demented elderly population. DESIGN: cross-sectional community based assessment. PARTICIPANTS: 466 subjects with mean age 75.45 (SD, 6.06) years. 208 (44.6%) were male. RESULTS: Higher levels of HbA1c, but not other vascular biomarkers were independently associated with being lonely. CONCLUSION: Loneliness was associated with raised levels of HbA1c in a community dwelling elderly population. The mechanism for this association has yet to be elucidated but may reflect an abnormal stress response in people who are lonely.

Loneliness and cognition in older people: the Dublin Healthy Ageing study.

INTRODUCTION: While several studies have found a link between impaired cognition and social isolation, few have examined the relationship between cognition and loneliness. Loneliness has been thought to increase the risk of development of Alzheimer's dementia. AIM: The aims of this study were to explore the relationship between loneliness and cognition and to determine whether specific cognitive domains are associated with loneliness. DESIGN: Cross-sectional community-based study. PARTICIPANTS: This study included 466 community-dwelling subjects with mean age 75.45 (SD 6.06) years, of which 208(44%) were males. RESULTS: Loneliness was significantly associated with impaired global cognition independent of social networks and depression. The domains of psychomotor processing speed and delayed visual memory were specifically associated with self-reported loneliness. CONCLUSION: This cross-sectional study demonstrated an association between loneliness and specific aspects of cognition independent of depression, social networks and other demographics. The mechanism for this association is unclear and warrants further investigation.

Serum and salivary IgE, IgA, and IgG4 antibodies to Dermatophagoides pteronyssinus and its major allergens, Der p1 and Der p2, in allergic and nonallergic children.

Allergic rhinitis (AR) is a public health problem with high prevalence worldwide. We evaluated levels of specific IgE, IgA, and IgG4 antibodies to the Dermatophagoides pteronyssinus (Dpt) house dust mite and to its major allergens (Der p1 and Der p2) in serum and saliva samples from allergic and nonallergic children. A total of 86 children were analyzed, from which 72 had AR and 14 were nonallergic healthy children. Serum IgE and serum/salivary IgG4 levels to Dpt, Der p1, and Der p2 were higher in allergic children whereas serum/salivary IgA levels to all allergens were higher in nonallergic children. IgE levels positively correlated with IgG4 and IgA to all allergens in allergic children, while IgA levels negatively correlated with IgG4 to Dpt and Der p1 in nonallergic children. In conclusion, mite-specific IgA antibodies predominate in the serum and saliva of nonallergic children whereas mite-specific IgE and IgG4 are prevalent in allergic children. The presence of specific IgA appears to have a key role for the healthy immune response to mucosal allergens. Also, specific IgA measurements in serum and/or saliva may be useful for monitoring activation of tolerance-inducing mechanisms during allergen specific immunotherapeutic procedures, especially sublingual immunotherapy.

Associations between holotranscobalamin, vitamin B12, homocysteine and depressive symptoms in community-dwelling elders.

BACKGROUND: Vitamin B12 and homocysteine have been shown to be associated with depression or depressive symptoms, but the relationship has not been universal. Both vitamin B12 and homocysteine may exert an effect via vascular mechanisms; it is possible that other mechanisms apply. Holotranscobalamin is a novel, more accurate measure of tissue vitamin B12. OBJECTIVES: To examine associations between vitamin B12, serum folate, holotranscobalamin, homocysteine and depressive symptoms in a sample of healthy elderly. METHODS: Cross-sectional, observational community based study. RESULTS: Lower levels of holotranscobalamin and vitamin B12 were associated with higher levels of depressive symptoms when controlled for Mini-mental state examination scores and psychosocial and cardiovascular risk factors. Homocysteine was not associated with depressive symptoms when biological and psychosocial covariates were included. CONCLUSIONS: It is possible that low levels of vitamin B12 or holotranscobalamin are associated with depressive symptoms via mechanisms other than vascular pathology.

Is convalescent plasma futile in COVID-19? A Bayesian re-analysis of the RECOVERY randomized controlled trial.

BACKGROUND: Randomized trials are generally performed from a frequentist perspective, which can conflate absence of evidence with evidence of absence. The RECOVERY trial evaluated convalescent plasma for patients hospitalized with coronavirus disease 2019 (COVID-19) and concluded that there was no evidence of an effect. Re-analysis from a Bayesian perspective is warranted. METHODS: Outcome data were extracted from the RECOVERY trial by serostatus and time of presentation. A Bayesian re-analysis with a wide variety of priors (vague, optimistic, sceptical, and pessimistic) was performed, calculating the posterior probability for: any benefit, an absolute risk difference of 0.5% (small benefit, number needed to treat 200), and an absolute risk difference of one percentage point (modest benefit, number needed to treat 100). RESULTS: Across all patients, when analysed with a vague prior, the likelihood of any benefit or a modest benefit with convalescent plasma was estimated to be 64% and 18%, respectively. The estimated chance of any benefit was 95% if presenting within 7 days of symptoms, or 17% if presenting after this. In patients without a detectable antibody response at presentation, the chance of any benefit was 85%. However, it was only 20% in patients with a detectable antibody response at presentation. CONCLUSIONS: Bayesian re-analysis suggests that convalescent plasma reduces mortality by at least one percentage point among the 39% of patients who present within 7 days of symptoms, and that there is a 67% chance of the same mortality reduction in the 38% who are seronegative at the time of presentation. This is in contrast to the results in people who already have antibodies when they present. This biologically plausible finding bears witness to the advantage of Bayesian analyses over misuse of hypothesis tests to inform decisions.

Walking and talking: an investigation of cognitive-motor dual tasking in multiple sclerosis.

BACKGROUND: Deficits in motor functioning, including walking, and in cognitive functions, including attention, are known to be prevalent in multiple sclerosis (MS), though little attention has been paid to how impairments in these areas of functioning interact. OBJECTIVES: This study investigated the effects of performing a concurrent cognitive task when walking in people with MS. Level of task demand was manipulated to investigate whether this affected level of dual-task decrement. METHOD: Eighteen participants with MS and 18 healthy controls took part. Participants completed walking and cognitive tasks under single- and dual-task conditions. RESULTS: Compared to healthy controls, MS participants showed greater decrements in performance under dual-task conditions in cognitive task performance, walking speed and swing time variability. In the MS group, the degree of decrement under dual-task conditions was related to levels of fatigue, a measure of general cognitive functioning and self-reported everyday cognitive errors, but not to measures of disease severity or duration. CONCLUSIONS: Difficulty with walking and talking in MS may be a result of a divided attention deficit or of overloading of the working memory system, and further investigation is needed. We suggest that difficulty with walking and talking in MS may lead to practical problems in everyday life, including potentially increasing the risk of falls. Clinical tools to assess cognitive-motor dual-tasking ability are needed.

Laser and other light therapies for the treatment of acne vulgaris: systematic review.

BACKGROUND: Acne is common and can lead to scarring of the skin, as well as to psychological distress and reduced self-esteem. Most topical or oral treatments for acne are inconvenient and have side-effects. Laser and other light therapies have been reported to be convenient, safe and effective in treating acne. OBJECTIVES: To carry out a systematic review of randomized controlled trials of light and laser therapies for acne vulgaris. METHODS: We searched the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, CINAHL, PsycInfo, LILACS, ISI Science Citation Index and Dissertation Abstracts International for relevant published trials. RESULTS: We identified 25 trials (694 patients), 13 of light therapy and 12 of light therapy plus light-activated topical cream (photodynamic therapy, PDT). Overall, the results from trials of light alone were disappointing, but the trials of blue light, blue-red light and infrared radiation were more successful, particularly those using multiple treatments. Red-blue light was more effective than topical 5% benzoyl peroxide cream in the short term. Most trials of PDT showed some benefit, which was greater with multiple treatments, and better for noninflammatory acne lesions. However, the improvements in inflammatory acne lesions were not better than with topical 1% adapalene gel, and the side-effects of therapy were unacceptable to many participants. CONCLUSIONS: Some forms of light therapy were of short-term benefit. Patients may find it easier to comply with these treatments, despite the initial discomfort, because of their short duration. However, very few trials compared light therapy with conventional acne treatments, were conducted in patients with severe acne or examined long-term benefits of treatment.

Outcome measures in acne vulgaris: systematic review.

BACKGROUND: Clinical trials require valid and reliable outcome measures to facilitate the interpretation and communication of results, and the secondary use of data for systematic reviews. There are numerous tools available to assess the severity of acne vulgaris in clinical trials, and extensive debate about the merits of these. OBJECTIVES: To review the literature about investigator-assessed outcome measures used in clinical trials for acne vulgaris; and to evaluate the measurement properties of these tools. METHODS: A systematic literature review was conducted of articles outlining and evaluating investigator-assessed outcome measures for acne. RESULTS: Thirty-one papers met the criteria for inclusion in the literature review, including nine papers proposing a novel means of assessing acne, and five evaluating existing outcome measures. Variable attempts had been made to evaluate these tools. CONCLUSIONS: The array of evaluation tools used in acne trials prohibits good secondary analysis of trial data, and complicates the interpretation of study results, potentially compromising clinical care. Existing outcome measures need to be assessed further and agreement reached about which should be used more widely. Other innovative methods of assessing acne should also be explored.

Early Warning Scores do not accurately predict mortality in sepsis: A meta-analysis and systematic review of the literature.

OBJECTIVES: Early Warning Scores are used to evaluate patients in many hospital settings. It is not clear if these are accurate in predicting mortality in sepsis. We performed a systematic review and meta-analysis of multiple studies in sepsis. Our aim was to estimate the accuracy of EWS for mortality in this setting. METHODS: PubMED, CINAHL, Cochrane, Web of Science and EMBASE were searched to October 2016. Studies of adults with sepsis who had EWS calculated using any appropriate tool (e.g. NEWS, MEWS) were eligible for inclusion. Study quality was assessed using QUADAS-2. Summary estimates were derived using HSROC analysis. RESULTS: Six studies (4298 participants) were included. Results suggest that EWS cannot be used to predict which patients with sepsis will (positive likelihood ratio 1.79, 95% CI 1.53 to 2.11) or will not die (negative likelihood ratio 0.59, 95% CI 0.45 to 0.78). Two studies were rated as low risk of bias and one as unclear risk of bias on all domains. The other three studies were judged at high risk of bias in one domain. CONCLUSION: Early Warning Scores are not sufficiently accurate to rule in or rule out mortality in patients with sepsis, based on the evidence available, which is generally poor quality.

Relating gastric scintigraphy and symptoms to motility capsule transit and pressure findings in suspected gastroparesis.

BACKGROUND: Wireless motility capsule (WMC) findings are incompletely defined in suspected gastroparesis. We aimed to characterize regional WMC transit and contractility in relation to scintigraphy, etiology, and symptoms in patients undergoing gastric emptying testing. METHODS: A total of 209 patients with gastroparesis symptoms at NIDDK Gastroparesis Consortium centers underwent gastric scintigraphy and WMCs on separate days to measure regional transit and contractility. Validated questionnaires quantified symptoms. KEY RESULTS: Solid scintigraphy and liquid scintigraphy were delayed in 68.8% and 34.8% of patients; WMC gastric emptying times (GET) were delayed in 40.3% and showed 52.8% agreement with scintigraphy; 15.5% and 33.5% had delayed small bowel (SBTT) and colon transit (CTT) times. Transit was delayed in ≥2 regions in 23.3%. Rapid transit was rarely observed. Diabetics had slower GET but more rapid SBTT versus idiopathics (P ≤ .02). GET delays related to greater scintigraphic retention, slower SBTT, and fewer gastric contractions (P ≤ .04). Overall gastroparesis symptoms and nausea/vomiting, early satiety/fullness, bloating/distention, and upper abdominal pain subscores showed no relation to WMC transit. Upper and lower abdominal pain scores (P ≤ .03) were greater with increased colon contractions. Constipation correlated with slower CTT and higher colon contractions (P = .03). Diarrhea scores were higher with delayed SBTT and CTT (P ≤ .04). CONCLUSIONS & INFERENCES: Wireless motility capsules define gastric emptying delays similar but not identical to scintigraphy that are more severe in diabetics and relate to reduced gastric contractility. Extragastric transit delays occur in >40% with suspected gastroparesis. Gastroparesis symptoms show little association with WMC profiles, although lower symptoms relate to small bowel or colon abnormalities.

Inducible gene expression in transgenic Xenopus embryos.

The amphibian Xenopus laevis has been successfully used for many years as a model system for studying vertebrate development. Because of technical limitations, however, molecular investigations have mainly concentrated on early stages. We have developed a straightforward method for stage-specific induction of gene expression in transgenic Xenopus embryos [1] [2]. This method is based on the Xenopus heat shock protein 70 (Xhsp70 [3]) promoter driving the expression of desired gene products. We found that ubiquitous expression of the transgene is induced upon relatively mild heat treatment. Green fluorescent protein (GFP) was used as a marker to monitor successful induction of gene expression in transgenic embryos. We used this method to study the stage specificity of Wnt signalling function. Transient ectopic Wnt-8 expression during early neurulation was sufficient to repress anterior head development and this capacity was restricted to early stages of neurulation. By transient over-expression at different stages of development, we show that frizzled-7 disrupted morphogenesis sequentially from anterior to posterior along the dorsal axis as development proceeds. These results demonstrate that this method for inducible gene expression in transgenic Xenopus embryos will be a very powerful tool for temporal analysis of gene function and for studying molecular mechanisms of vertebrate organogenesis.