Uncertainty in and around biophysical modelling: insights from interdisciplinary research on agricultural digitalization.

Agricultural digitalization is providing growing amounts of real-time digital data. Biophysical simulation models can help interpret these data. However, these models are subject to complex uncertainties, which has prompted calls for interdisciplinary research to better understand and communicate modelling uncertainties and their impact on decision-making. This article develops two corresponding insights from an interdisciplinary project in a New Zealand agricultural research organization. First, we expand on a recent Royal Society Open Science journal article (van der Bles et al. 2019 Royal Society Open Science 6, 181870 (doi:10.1098/rsos.181870)) and suggest a threefold conceptual framework to describe direct, indirect and contextual uncertainties associated with biophysical models. Second, we reflect on the process of developing this framework to highlight challenges to successful collaboration and the importance of a deeper engagement with interdisciplinarity. This includes resolving often unequal disciplinary standings and the need for early collaborative problem framing. We propose that both insights are complementary and informative to researchers and practitioners in the field of modelling uncertainty as well as to those interested in interdisciplinary environmental research generally. The article concludes by outlining limitations of interdisciplinary research and a shift towards transdisciplinarity that also includes non-scientists. Such a shift is crucial to holistically address uncertainties associated with biophysical modelling and to realize the full potential of agricultural digitalization.

Farm-specific carbon footprinting to the farm gate for agricultural co-products using the OVERSEER® model.

The user inputs to OVERSEER® Nutrient Budgets (Overseer) allow farm-specific greenhouse gas (GHG) emissions to be estimated. Since the development of the original model, life cycle assessment standards (e.g. PAS 2050) have been proposed and adopted for determining GHG or carbon footprints, which are usually reported as emissions per unit of product, for example, per kg milk, meat or wool. New Zealand pastoral farms frequently generate a range of products with different management practices. A robust system is required to allocate the individual sources of GHGs (e.g. methane, nitrous oxide, direct carbon dioxide and embodied carbon dioxide emissions for inputs used on the farm) to each product from a farm. This paper describes a method for allocating emissions to co-products from New Zealand farms. The method requires allocating the emissions, first, to an animal enterprise, separating the emissions between breeding and trading animals, and then allocating to a specific product to give product (e.g. milk, meat, wool, velvet) footprints from the 'cradle-to-farm-gate'. The meat product was based on live-weight gain. Procedures were adopted so that emissions associated with rearing of young stock used in live-weight gain systems, both as a by-product or a primary product could be estimated. This allows the possibility of total emissions for a meat product to be built up from contributing farms along the production chain.

The effects of allergens in outdoor air on both atopic and nonatopic subjects with airway disease.

BACKGROUND: Reports on air pollution and asthma exacerbations have been inconsistent, although effects of airborne allergen can be spectacular. With no generalized test for allergen in air, it is not known how far allergen is responsible for nonepidemic exacerbations of the disease. METHODS: Two hundred and ninety-seven patients using bronchodilators aged 18-64 years attending a London practice provided serum samples and were asked to report any acute respiratory events over the coming months. Small particles with a mean aerodynamic diameter <10 microm (PM(10)) were collected using a high volume sampler on the roof of the practice. The ability of airborne particles to bind IgE from the patients was compared for particles sampled on the weekend before their reported exacerbation with particles sampled on the weekend 2 weeks before or after. RESULTS: Exacerbations were associated with a 25% increase in IgE binding to particles collected on the previous weekend compared with the control weekends (95% confidence interval: 10-43%; P = 0.00089). This increase was not higher in patients with positive skin tests or in those sensitized to grass or tree pollens. CONCLUSIONS: Airborne allergen is an important cause of exacerbations even in those with 'intrinsic' asthma. It is important to identify the allergens responsible, as some of these may be controllable. Interpretation of associations of asthma exacerbations with other air pollutants is difficult in the light of these findings.

Interventions for primary vesicoureteric reflux.

BACKGROUND: Vesicoureteric reflux (VUR) results in urine passing, in a retrograde manner, up the ureter. Urinary tract infections (UTIs) have been considered the main cause of permanent renal parenchymal damage in children with reflux. Management of these children has been directed at preventing infection by antibiotic prophylaxis and/or surgical correction of reflux. Controversy remains as to the optimum strategies. OBJECTIVES: To evaluate the benefits and harms of different treatment options for primary VUR. SEARCH STRATEGY: Randomised controlled trials (RCTs) were identified from the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, reference lists of articles and abstracts from conference proceedings. Date of last search: June 2006 SELECTION CRITERIA: Any treatment of VUR including surgery, antibiotic prophylaxis of any duration, non-invasive techniques and any combination of therapies. DATA COLLECTION AND ANALYSIS: Two authors independently searched the literature, determined study eligibility, assessed quality, extracted and entered data. For dichotomous outcomes, results were expressed as relative risk (RR) and 95% confidence intervals (CI). Data were pooled using the random effects model. MAIN RESULTS: Eleven studies (1148 children) were identified. Seven compared correction of VUR (by surgery or endoscope) plus antibiotics for 1-24 months with antibiotics alone, two compared antibiotics with no treatment and two compared different materials for endoscopic correction of VUR. Risk of UTI by 2, 5 and 10 years was not significantly different between surgical and medical groups (2 years RR 1.07, 95% CI 0.32 to 2.09; 5 years RR 0.99, 95% CI 0.79 to 1.26; 10 years RR 1.06, 95% CI 0.78 to 1.44). Combined treatment resulted in a 50% reduction in febrile UTI by 10 years (RR 0.54, 95% CI 0.55 to 0.92) but no concomitant reduction in risk of new or progressive renal damage by 10 years (RR 1.03, 95% CI 0.53 to 2.00). In two small studies no significant differences in risk for UTI (RR 0.75, 95% CI 0.15 to 3.84) or renal damage (RR 1.70, 95% CI 0.36 to 8.07) were found between antibiotic prophylaxis and no treatment. AUTHORS' CONCLUSIONS: It is uncertain whether the treatment of children with VUR confers clinically important benefit. The additional benefit of surgery over antibiotics alone is small at best. Assuming a UTI rate of 20% for children with VUR on antibiotics for five years, nine reimplantations would be required to prevent one febrile UTI, with no reduction in the number of children developing any UTI or renal damage.

School-based education programmes for the prevention of child sexual abuse.

BACKGROUND: Child sexual abuse is a significant problem that requires an effective means of prevention. OBJECTIVES: To assess: if school-based programmes are effective in improving knowledge about sexual abuse and self-protective behaviours; whether participation results in an increase in disclosure of sexual abuse and/or produces any harm; knowledge retention and the effect of programme type or setting. SEARCH STRATEGY: Electronic searches of Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, PsycINFO, CINAHL, Sociological Abstracts, Dissertation Abstracts and other databases using MESH headings and text words specific for child sexual assault and randomised controlled trials (RCTs) were conducted in August 2006. SELECTION CRITERIA: RCTs or quasi-RCTs of school-based interventions to prevent child sexual abuse compared with another intervention or no intervention. DATA COLLECTION AND ANALYSIS: Meta-analyses and sensitivity analysis, using two imputed intraclass correlation coefficients (ICC) (0.1, 0.2), were used for four outcomes: protective behaviours, questionnaire-based knowledge, vignette-based knowledge and disclosure of abuse. Meta-analysis was not possible for retention of knowledge, likelihood of harm, or effect of programme type and setting. MAIN RESULTS: Fifteen trials measuring knowledge and behaviour change as a result of school-based child sexual abuse intervention programmes were included. Over half the studies in each initial meta-analysis contained unit of analysis errors. For behaviour change, two studies had data suitable for meta-analysis; results favoured intervention (OR 6.76, 95% CI 1.44, 31.84) with moderate heterogeneity (I(2)=56.0%) and did not change significantly when adjustments using intraclass coefficients were made. Nine studies were included in a meta-analysis evaluating questionnaire-based knowledge. An increase in knowledge was found (SMD 0.59; 0.44, 0.74, heterogeneity (I2=66.4%). When adjusted for an ICC of 0.1 and 0.2 the results were SMD 0.6 (0.45, 0.75) and 0.57 (0.44, 0.71) respectively. Heterogeneity decreased with increasing ICC. A meta-analysis of four studies evaluating vignette-based knowledge favoured intervention (SMD 0.37 (0.18, 0.55)) with low heterogeneity (I(2)=0.0%) and no significant change when ICC adjustments were made. Meta-analysis of between-group differences of reported disclosures did not show a statistically significant difference. AUTHORS' CONCLUSIONS: Studies evaluated in this review report significant improvements in knowledge measures and protective behaviours. Results might have differed had the true ICCs from studies been available or cluster-adjusted results been available. Several studies reported harms, suggesting a need to monitor the impact of similar interventions. Retention of knowledge should be measured beyond 3-12 months. Further investigation of the best forms of presentation and optimal age of programme delivery is required.

Specialist home-based nursing services for children with acute and chronic illnesses.

BACKGROUND: Specialist paediatric home-based nursing services have been proposed as a cost-effective means of reducing trauma resulting from hospital admissions, while enhancing primary care and reducing length of hospital stay. OBJECTIVES: To evaluate specialist home-based nursing services for children with acute and chronic illnesses. SEARCH STRATEGY: Electronic searches were made of CENTRAL (Cochrane Central Register of Controlled Trials) 2005 (Issue 2); MEDLINE (1966 to August 2005); EMBASE (1980 to August 2005); PsycINFO (1887 to August 2005); CINAHL (1982 to August 2005); Sociological Abstracts (1963 to August 2005). Optimally sensitive search strategies for randomised controlled trials (RCTs) were combined with medical subject headings and text words specific for ambulatory paediatrics, nursing outreach and 'hospital in the home', and no language restrictions were applied. SELECTION CRITERIA: RCTs of children aged 0-18 with acute or chronic illnesses allocated to specialist home-based nursing services compared with conventional medical care. Outcomes included utilisation of health care, physical and mental health, satisfaction, adverse health outcomes and costs. DATA COLLECTION AND ANALYSIS: Meta-analysis was not appropriate because of the clinical diversity and lack of common outcomes measures MAIN RESULTS: 1655 titles yielded 5 RCTs with a total of 771 participants. Participants, interventions and outcomes were diverse. No significant differences were reported in health outcomes; two studies reported improvements in child and parental anxiety; one study reported no significant difference in readmissions; two studies reported significantly fewer bed days; increased satisfaction was reported ; home care was more costly for service providers, but less expensive for parents. AUTHORS' CONCLUSIONS: While current research does not provide definitive support for specialist home-based nursing services in reducing access to hospital services or length of stay, preliminary results show no adverse impact on physical health outcomes and a number of papers reported improved satisfaction with home-based care. Further trials are required, measuring health, satisfaction, service utilisation and long-term costs.

Intravenous secretin for autism spectrum disorder.

BACKGROUND: Secretin is a gastro-intestinal hormone which has been presented as an effective treatment for autism based on anecdotal evidence. OBJECTIVES: To determine if intravenous secretin:1. improves the core features of autism (social interaction, communication and behaviour problems); 2. improves the non-core aspects of behaviour or function such as self injurious behaviour;3. improves the quality of life of affected individuals and their carers; 4. has short term and long term effects on outcome; 5. causes harm. SEARCH STRATEGY: Results of electronic searches of CENTRAL, MEDLINE, EMBASE, PsycINFO, CINAHL, ERIC, HealthStar and Sociofile (1998 - March 2005) were independently examined by two authors. Reference lists of trials and reviews were searched; experts and trialists were contacted to find unpublished studies. SELECTION CRITERIA: Randomised controlled trials of intravenous secretin comparing secretin with a placebo treatment in children or adults diagnosed with autism spectrum disorders, where at least one standardised outcome measure was reported. DATA COLLECTION AND ANALYSIS: Fourteen studies met inclusion criteria. All outcome data were continuous. Where trials used cross-over designs, analysis was conducted on results from first treatment phase, allowing combined analysis with parallel design trials. Where standardised assessment tools generated scores as outcome measures, comparisons were made between means of these scores. Where baseline means were reported, differences between treatment and control were determined to assess possible bias. Where mean change from baseline was reported, this was used in preference to post-treatment scores for meta-analyses or forest plots. As meta-analysis was possible for only one outcome (Childhood Autism Rating Scale), it was impossible to use sensitivity or subgroup analyses to assess impact of study quality, clinical differences in the intervention, or clinically relevant differences between groups, such as age or presence of gastrointestinal symptoms. MAIN RESULTS: Twenty-five established standardised outcome measures were reported to assess core features of autism, communication, behaviour, visio-spatial skills, affect and adverse events within fourteen included studies. No more than four studies used any one outcome measure similarly. Outcomes were reported between three and six weeks. RCTs of efficacy of secretin in autism have not shown improvements for core features of autism. AUTHORS' CONCLUSIONS: There is no evidence that single or multiple dose intravenous secretin is effective and as such it should not currently be recommended or administered as a treatment for autism. Further experimental assessment of secretin's effectiveness for autism can only be justified if methodological problems of existing research can be overcome.

Interventions for primary vesicoureteric reflux.

BACKGROUND: Vesicoureteric reflux (VUR) results in urine passing, in a retrograde manner, up the ureter. Urinary tract infections (UTIs) have been considered to be the main cause of permanent renal parenchymal damage in children with reflux. Therefore management of these children has been directed at preventing infection by antibiotic prophylaxis and/or surgical correction of reflux. However controversy remains as to the optimum strategies for management of children with primary VUR. OBJECTIVES: To evaluate the benefits and harms of the different treatment options for primary VUR. SEARCH STRATEGY: Published and unpublished randomised controlled trials (RCTs) were identified from the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, reference lists of articles and abstracts from conference proceedings. SELECTION CRITERIA: RCTs were included if they compared any treatments of VUR including surgery (open and closed techniques), antibiotic prophylaxis of any duration, non-invasive techniques such as bladder training and any combination of therapies. DATA COLLECTION AND ANALYSIS: Two reviewers independently searched the literature, determined trial eligibility, assessed quality, extracted and entered data. For dichotomous outcomes, results were expressed as relative risk (RR) and 95% confidence intervals (CI). Data were pooled using the random effects model. MAIN RESULTS: Ten trials involving 964 evaluable children comparing long-term antibiotics and surgical correction of VUR with antibiotics (seven trials), antibiotics with no treatment (one trial) and different materials for endoscopic correction of VUR (two trials) were identified. Risk of UTI by 1-2 and 5 years was not significantly different between surgical and medical groups (by 2 years RR 1.07, 95% CI 0.55 to 2.09; by 5 years RR 0.99; 95% CI 0.79 to 1.26). Combined treatment resulted in a 60% reduction in febrile UTI by 5 years (RR 0.43, 95% CI 0.27 to 0.70) but no concomitant significant reduction in risk of new or progressive renal damage at 5 years (RR 1.05, 95% CI 0.85 to 1.29). In one small study no significant differences in risk for UTI or renal damage were found between antibiotic prophylaxis and no treatment. REVIEWERS' CONCLUSIONS: It is uncertain whether the identification and treatment of children with VUR confers clinically important benefit. The additional benefit of surgery over antibiotics alone is small at best. Assuming a UTI rate of 20% for children with VUR on antibiotics for five years, nine reimplantations would be required to prevent one febrile UTI, with no reduction in the number of children developing any UTI or renal damage.

How accurate is dimercaptosuccinic acid scintigraphy for the diagnosis of acute pyelonephritis? A meta-analysis of experimental studies.

UNLABELLED: The purpose of this study was to evaluate the performance of dimercaptosuccinic acid (DMSA) scintigraphy in the diagnosis of acute pyelonephritis and to compare the test performance of the standard technique, planar DMSA, with the newly introduced technique, SPECT DMSA. METHODS: All published animal studies in which DMSA scintigraphy was compared with histopathology, the reference standard for acute pyelonephritis, were identified using a comprehensive search strategy with the MEDLINE and EMBASE databases. Test performances of all DMSA methods and SPECT versus planar DMSA were analyzed using summary receiver operating characteristic (sROC) curves. RESULTS: Seven studies were identified, including 2 of SPECT DMSA. Problems in study design or reporting were common, with numerical errors in 4 studies. Overall, at a sensitivity of 86%, specificity was estimated to be 91%. Detection of acute pyelonephritis was at a lower threshold for SPECT than for planar DMSA (sensitivity/specificity values of 97%0/66% compared with 82%/ 97%), and the overall test performance of SPECT was not demonstrably better than that of planar DMSA. When applied to a group of children with a prevalence of renal damage of 40%, this means that 98% of children with abnormal planar DMSA scans will have renal damage, whereas only 65% of those with abnormal SPECT scans will have renal damage. Planar and SPECT DMSA will miss 11% and 3% of children with renal damage, respectively. Out of 100 children in the hypothetical group with 40% experiencing renal damage, SPECT will identify 6 extra true cases of renal damage at the expense of 19 extra false positives, when compared with planar DMSA. CONCLUSION: Published studies of DMSA test performance are few in number and have significant methodologic problems that should be avoided in future studies. DMSA, particularly the planar technique, performs well for the diagnosis of acute pyelonephritis. Using test performance criteria, SPECT DMSA alone has not been shown to be preferable to the established planar method and will result in a small number of true-positives at the expense of a larger number of false-positives.

Prenatal screening in the first trimester of pregnancy.

Prenatal screening for fetal abnormalities in an accepted part of modern obstetric management. Improvements on current screening procedures need to address increased diagnostic efficacy and earlier diagnosis. This study evaluates diagnostic efficacy of PAPP-A and F beta-hCG in the detection of first trimester pregnancy abnormalities, including Down syndrome (DS). Of 731 pregnant volunteers, obtained from a mature age population undergoing chorionic villus sampling (CVS), 17 DS and 11 compromised (six numerical (excluding sex chromosome) aneuploidies, five spontaneously failed) pregnancies were detected. Application of an algorithm, which combines PAPP-A and F beta-hCG levels with material age, detected 66.6 per cent of DS pregnancies for a five per cent false positive rate. Similarly, for a 1-2 per cent recall rate, 72.2 per cent of compromised pregnancies were detected. This report supports the notion that prenatal screening at 9-12 weeks of pregnancy is achievable with PAPP-A and F beta hCG quantitation. Whereas mid-gestational screening targetted the detection of fetal abnormalities, screening earlier in pregnancy will detect other pregnancy-related abnormalities, in addition to aneuploidy.

Initial contractile response of isolated rat heart cells to halothane, enflurane, and isoflurane.

BACKGROUND: In several beating cardiac muscle preparations, a short-lived increase in twitch tension or amplitude has been observed when they were exposed abruptly to solutions containing halothane or enflurane. As exposure to the anesthetics was continued, the expected negative inotropic effect became evident after the short-lived increase in twitch. No such increase in twitch has been reported during exposure to isoflurane. It has been hypothesized that this short-lived increase in twitch is caused by an enhancement of calcium release from the sarcoplasmic reticulum, but other mechanisms have not been excluded. METHODS: Freshly isolated, single rat ventricular cells were stimulated to beat at room temperature and abruptly exposed to solutions containing halothane (0.25-0.64 mM), enflurane (0.69-1 mM), or isoflurane (0.31-0.54 mM). During these exposures, twitch amplitude was measured and intracellular calcium concentration was followed using the calcium-sensitive dye indo-1. In some experiments, the whole-cell patch-clamp technique was used to measure membrane current. In addition, in several cells the sarcoplasmic reticulum calcium content was assessed through the response to brief pulses of caffeine. RESULTS: Both the twitch amplitude and the intracellular calcium transient were increased temporarily in cells abruptly exposed to halothane or enflurane. No such behavior was found with isoflurane. After continued exposure to all three agents, both the twitch amplitude and the calcium transient were less than control. During the beats exhibiting an increase in twitch, no alteration in the relation between cell length (twitch amplitude) and the intracellular calcium transient was found compared with control conditions. In addition, the temporary increase in twitch amplitude occurred in cells contracting under voltage-clamp control when halothane was introduced, and it was not associated with any increase in the calcium current. The sarcoplasmic reticulum calcium content at the time of the halothane-induced increase in twitch also was not increased. CONCLUSIONS: The short-lived increase in twitch after abrupt exposure to halothane or enflurane is related to increased intracellular calcium during the beat and not to any changes in myofilament sensitivity to calcium. Because these results eliminate most alternative explanations for this phenomenon, the authors conclude that halothane, and probably also enflurane, increases the fraction of calcium released from the sarcoplasmic reticulum with each heart beat. Isoflurane appears to lack this action.

Trophoblast antigen levels in the first trimester of a trisomy 22 pregnancy.

We report trophoblast antigen (pregnancy-associated plasma protein-A, PAPP-A; free beta-human chorionic gonadotrophin, F beta hCG) expression in a trimosy 22 pregnancy. Maternal concentrations of these antigens were depressed prior to detection of abnormalities by ultrasonography. Immunohistochemical findings were consistent with depressed marker expression.

Volatile anesthetic effects on sarcoplasmic reticulum Ca content and sarcolemmal Ca flux in isolated rat cardiac cell suspensions.

BACKGROUND: Cardiac cellular Ca metabolism is central to the control of the inotropic state of the heart and is altered in various ways by the volatile anesthetics halothane, enflurane and isoflurane. Specifically, differences among the agents regarding their effect on the uptake and release of Ca from the sarcoplasmic reticulum (SR) have been found, but the nature of such differences is not yet certain. At the sarcolemma, the effects of the anesthetics on the peak Ca current generally are believed to be similar among the three agents, but their impact on other aspects of sarcolemmal Ca transport is less understood. The authors sought to measure the direct action of these agents on SR Ca content and, in the same preparation, to provide a measure of Ca transfer across the sarcolemma during sustained depolarizations. METHODS: In stirred suspensions of quiescent rat cardiac cells, the effects were measured of halothane, enflurane, and isoflurane on changes in quin2Ca fluorescence produced by the addition of caffeine (10 mM) and by depolarization with increased extracellular K+. The peak of the fluorescence response to caffeine, which is due to a sudden release of Ca from the SR into the cytoplasm, was used as an index of SR Ca content. Analysis of the fluorescence increase that occurred after increasing extracellular K+ from 5 mM to 30 mM in the presence of caffeine provided a measure of net Ca influx across the sarcolemma during sustained depolarizations. RESULTS: The Ca channel blocker nitrendipine maximally inhibited 77% of the initial net Ca influx during 30 mM K+ depolarization, indicating that most of this influx involves L-type Ca channels. Of the volatile anesthetics, isoflurane (2.6 vol% or 0.57 mM) and enflurane (4.3 vol% or 1.25 mM) inhibited initial net Ca influx during K depolarization significantly more than halothane (1.7 vol% or 0.50 mM), which had no apparent effect. Isoflurane caused no transient change in cytoplasmic Ca concentration and had no effect on the SR Ca content of these quiescent cells. Enflurane (4.3 vol%) caused a significant reduction in SR Ca content. CONCLUSIONS: As previously reported, halothane depleted the SR of Ca in quiescent rat cardiac cells, and the present results indicate that enflurane had a similar effect. However, isoflurane did not produce any SR Ca depletion and thus must not significantly alter the balance between SR Ca efflux and uptake in these quiescent cells. The different effects of the three volatile anesthetics on a Ca influx largely carried by L-type Ca channels stand in contrast to the reported findings of similar inhibition of peak L-channel current among the three agents. This result may indicate a differential action (at least in the case of halothane) on peak and steady-state Ca currents.

Effect of halothane on arrhythmogenic responses induced by sympathomimetic agents in single rat heart cells.

The combination of catecholamines and halothane has long been recognized as arrhythmogenic. The purpose of this study was to evaluate whether the mechanism of this interaction originates at the single cell level. The incidence of spontaneous contractile waves occurring between stimulated beats (interbeat waves), early aftercontractions, and late aftercontractions was measured in rat myocytes exposed to sympathomimetics with and without halothane. Each of these endpoints in single cells has the potential to produce arrhythmias in multicellular preparations. Interbeat waves and late aftercontractions were observed with isoproterenol (1 X 10(-7) M) and norepinephrine (1-3 X 10(-7) M). The incidence of these phenomena was significantly reduced in the presence of 0.30 mM halothane. Early aftercontractions occurred in the presence of isoproterenol (1 X 10(-7) M), norepinephrine (1-3 X 10(-7) M), and phenylephrine (5-10 X 10(-6) M). There was a statistically significant decrease in the incidence of early aftercontractions in the presence of 0.30 mM halothane. These results indicate that the mechanism behind the clinically observed increased arrhythmogenicity of catecholamines with halothane does not arise at the level of single ventricular cells because halothane inhibited sympathomimetic-induced arrhythmogenic activity in this model. The probable mechanisms rather include altered impulse propagation, which might lead to phenomena such as reentry.

The action of halothane on spontaneous contractile waves and stimulated contractions in isolated rat and dog heart cells.

The cell length of single, isolated rat and dog heart cells was monitored during exposure to halothane-containing solution to define the cellular mechanism of halothane's negative inotropic effect. Spontaneous contractile waves, which reflect spontaneous Ca release from the sarcoplasmic reticulum (SR) in resting rat heart cells, exhibited a significant increase in frequency and a decrease in amplitude in the presence of halothane 0.27 mM (0.9 vol%) and 0.55 mM (1.7 vol%). Electrically stimulated dog and rat heart cells abruptly exposed to halothane (0.47-0.55 mM or 1.5-1.7 vol%) revealed a transient increase in twitch amplitude (significantly different from control). Twitch amplitude then declined to values significantly below control as halothane exposure continued. This decrease in twitch reached 42 +/- 13% (mean +/- SD) of control in rat cells and 50 +/- 14% in dog cells beating at 60 beats per min. In dog cells the magnitude of the transient increase in twitch amplitude was greater at faster beating rates compared with lower rates in the same cells (P less than 0.01) and the transient increase was insensitive to verapamil. Halothane 0.55 mM (1.7 vol%) also significantly accelerated the rate of decline in the twitch amplitude of successive beats in rat cells stimulated after a rest interval (negative staircase). The findings regarding spontaneous contractile waves indicate a direct effect of halothane at the SR in resting cells, occurring independently of any changes in the slow inward current. The halothane-induced changes in beating cells can be explained by an enhancement of Ca release from the SR with an eventual reduction of SR Ca stores.

The effect of halothane on the free intracellular calcium concentration of isolated rat heart cells.

The free intracellular calcium concentration of suspensions of isolated rat heart cells was monitored during sequential exposures to halothane and caffeine to evaluate cellular mechanisms of the negative inotropic effect of halothane. The calcium-sensitive, fluorescent dye quin2 was used as the indicator of free intracellular calcium. The acute addition of halothane in concentrations greater than or equal to 0.062 mM (0.19 vol%) to suspensions of quiescent rat heart cells at 37 degrees C caused a transient (approximately 1.5 min) increase in free intracellular calcium concentration. The intracellular calcium concentration after the decay of this transient was not detectably different from that prior to the addition of halothane. Neither the reduction of extracellular calcium from 1 mM to 100 nM, nor the prior addition of verapamil (5 microM) decreased this halothane-induced calcium transient. The transient was completely blocked by the prior addition of 10 mM caffeine, which depletes the sarcoplasmic reticulum of calcium. Also, the prior addition of halothane caused a reduction in the calcium transient due to caffeine. The depression of the caffeine-induced calcium transient by halothane was independent of the time interval (up to 4 min) between the additions of halothane and caffeine. These results indicate that halothane causes a net loss of calcium from the sarcoplasmic reticulum of quiescent rat heart cells. Thus, halothane has a direct effect at the sarcoplasmic reticulum, probably an enhancement of calcium release, which may explain its depression of myocardial contractility.

Mistakes in diagnosing non-accidental injury: 10 years' experience.

Fifty children who were referred to the child abuse team in Leeds over the 10 years 1976-86 with suspected non-accidental injury were found to have conditions which mimicked non-accidental injury. These included impetigo (nine children) and blue spots (five children). Five children who presented with multiple bruising had haemostatic disorders. Eight children had disorders of the bone. Five children had been previously abused physically. Four showed evidence of neglect. One had evidence of non-accidental injury as well as the condition mimicking abuse. It is emphasised that when child abuse is suspected a sensitive and thorough assessment should be carried out by a paediatrician who is experienced in this.

The electrophysiologic actions of lidocaine and bupivacaine in the isolated, perfused canine heart.

To discriminate between the electrophysiologic and arrhythmogenic effects of lidocaine and those of bupivacaine, isolated, perfused canine hearts were exposed to toxic concentrations of the drugs. The preparations included the sinus node and right atrium, and, in some cases, the AV node and interventricular septum as well. Action potentials were recorded from these areas, and right atrial twitch amplitude and spontaneous rate and rhythm were monitored. Heart rate was depressed in a dose-dependent manner by both drugs, as was atrial twitch amplitude. In the absence of arrhythmias, the spontaneous rate decreased less than 30% with lidocaine up to 50 micrograms/ml, and with bupivacaine up to 5 micrograms/ml. The twitch depression reflected a potency ratio for bupivacaine (mol. wt. 288) to lidocaine (mol. wt. 234) on a mass basis of 8.1:1. The most prominent arrhythmia found was sinoatrial block, which was caused by both drugs with a potency ratio for bupivacaine to lidocaine of 15.4:1 and was reversed by 0.02 microgram/ml norepinephrine. Sinus arrhythmias, block of retrograde conduction from AV node to atrium, and irregular rhythms originating within the AV node were observed with both drugs at concentrations similar to those which produced sinoatrial block. The atrial action potential revealed decreased upstroke velocity, overshoot, and height with both lidocaine and bupivacaine, with potency ratios (bupivacaine:lidocaine) ranging from 15:1 to 26:1. In septal cells, both drugs depressed upstroke velocity, and bupivacaine lengthened action potentials by up to 14%, but lidocaine did not. The major difference between bupivacaine and lidocaine in this study was the higher potency of the former agent with respect to electrophysiologic end-points.

Coupled sodium-calcium transport in cultured chick heart cells.

In cultured embryonic chick heart cells, alterations of extracellular Na (Nao) and Ca (Cao), intracellular Na (Nai) and Ca, extracellular pH, and membrane potential resulted in changes in Na and Ca contents that were consistent with sarcolemmal Na-Ca exchange. 24Na efflux measurements revealed a large ouabain-insensitive component, one-third of which was inhibited by removal of Cao. Incubating the cells in Na-free solution resulted in a rapid, 1.5- to 2-fold increase in total cell Ca that remained elevated for at least 15 min. Cells exposed for 15 min to Nao less than or equal to 20 mM became maximally loaded with Ca, whereas Ca loading fell off sharply at values of Nao greater than 20 mM. The movement of Na against its electrochemical gradient was shown to be associated with Ca accumulation. During Na-K pump inhibition (in 10(-4) M ouabain), Na initially rose 2- to 3-fold to a level below its equilibrium value; then, lowering Cao for 30 min from 1.25 to 0.75 mM caused a 26% elevation in Nai, whereas raising Cao from 1.25 to 2.7 mM resulted in a 25% fall in Nai against its electrochemical gradient. These data are consistent with Nai being maintained by a Na-Ca exchange during Na-K pump inhibition. In the presence of ouabain (10(-4) M), Ca uptake into intracellular organelles, e.g., mitochondria, was suggested by an increase in total cell Ca as well as the occurrence of mitochondrial matrix granules, which were shown qualitatively by X-ray analysis to contain Ca. Although matrix granules also occurred in mitochondria during Na-free incubation, they did not contain detectable amounts of Ca when examined under identical conditions of fixation and analysis.