Measuring honey bee feeding rhythms with the Beebox, a platform for nectar foraging insects.

In honey bees, most studies of circadian rhythms involve a locomotion test performed in a small tube, a tunnel, or at the hive entrance. However, despite feeding playing an important role in honey bee health or fitness, no demonstration of circadian rhythm on feeding has been performed until recently. Here, we present the BeeBox, a new laboratory platform for bees based on the concept of the Skinner box, which dispenses discrete controlled amounts of food (sucrose syrup) following entrance into an artificial flower. We compared caged groups of bees in 12h-12h light/dark cycles, constant darkness and constant light and measured average hourly syrup consumption per living bee. Food intake was higher in constant light and lower in constant darkness; mortality increased in constant light. We observed rhythmic consumption with a period longer than 24h; this is maintained in darkness without environmental cues, but is damped in the constant light condition. The BeeBox offers many new research perspectives and numerous potential applications in the study of nectar foraging animals.

Regulation of feeding dynamics by the circadian clock, light and sex in an adult nocturnal insect.

Animals invest crucial resources in foraging to support development, sustenance, and reproduction. Foraging and feeding behaviors are rhythmically expressed by most insects. Rhythmic behaviors are modified by exogenous factors like temperature and photoperiod, and internal factors such as the physiological status of the individual. However, the interactions between these factors and the circadian clock to pattern feeding behavior remains elusive. As Drosophila, a standard insect model, spends nearly all its life on food, we rather chose to focus on the adults of a non-model insect, Agrotis ipsilon, a nocturnal cosmopolitan crop pest moth having structured feeding activity. Our study aimed to explore the impact of environmental cues on directly measured feeding behavior rhythms. We took advantage of a new experimental set-up, mimicking an artificial flower, allowing us to specifically monitor feeding behavior in a naturalistic setting, e.g., the need to enter a flower to get food. We show that the frequency of flower visits is under the control of the circadian clock in males and females. Feeding behavior occurs only during the scotophase, informed by internal clock status and external photic input, and females start to visit flowers earlier than males. Shorter duration visits predominate as the night progresses. Importantly, food availability reorganizes the microstructure of feeding behavior, revealing its plasticity. Interestingly, males show a constant number of daily visits during the 5 days of adult life whereas females decrease visitations after the third day of adult life. Taken together, our results provide evidence that the rhythmicity of feeding behavior is sexually dimorphic and controlled by photoperiodic conditions through circadian clock-dependent and independent pathways. In addition, the use of the new experimental set-up provides future opportunities to examine the regulatory mechanisms of feeding behavior paving the way to investigate complex relationships between feeding, mating, and sleep-wake rhythms in insects.

Student Procrastination on an E-learning Platform: From Individual Discounting to Group Behavior.

Most applied research on delay discounting has focused on substance use disorders, eating, or gambling. In comparison, the issue of procrastination has received little interest from quantitative behavior analysts. In the present study, conducted on an e-learning platform, a group of 295 psychology students completed a series of four tests. The students could choose the day and hour on which they completed the tests, the deadline for each test being separated from the previous one by a period of 30 days. Most students completed the test in the last days before the deadline. The group response profile across days, reminiscent of fixed-interval scalloping, was well described formally by a hyperbola, replicating previous results by Howell et al. (2006). Also, the students' individual degree of procrastination showed stability across tests, in accordance with the notion of discounting as a persistent behavioral trait, and was negatively correlated with the students' grades. Finally, the shape of the scallop observed at the group level was consistent with a lognormal density of individual degrees of impulsivity, as measured by people's delay-discounting parameter.

The Behavioral Economics of Alcohol Demand in French and American University Students.

BACKGROUND: Behavioral economic approaches have revealed several characteristics of alcohol demand (e.g., intensity, elasticity, and essential value) in university students; however, these approaches have not yet examined alcohol demand among students outside of the United States. The current study examined alcohol demand among student samples in the United States and France using a hypothetical alcohol purchase task (APT) and a novel APT Choice task, in which nonalcoholic beverages were concurrently available at a fixed low price. METHODS: Participants at each site (United States, n = 132; France, n = 132) were asked to complete an Internet-based survey including the APT, APT Choice, Alcohol Use Disorders Identification Test, Daily Drinking Questionnaire, and Drinking Motives Questionnaire-Revised Short Form. Group demand functions were produced for each of the 2 samples in both country-specific and standardized drink units, and the exponential demand equation was fitted to each of the APT and APT Choice demand curves. Slope analyses were performed on the Non-Alcoholic Cross-Price demand to assess substitutability. RESULTS: APT data revealed that in both samples, alcohol price and consumption were inversely related and demand measures were significantly associated with other alcohol measures. In addition, the availability of a nonalcoholic alternative reduced alcohol demand in both samples, with evidence of substitutability revealed by increases in cross-price consumption. CONCLUSIONS: Low-cost alcohol is associated with increased alcohol consumption in both French and U.S. university students, and concurrent availability of a nonalcoholic beverage within the APT both reduces alcohol demand and demonstrates behavioral economic substitutability. These findings will inform future studies investigating behavioral and environmental factors underlying transcultural differences and specific prevention efforts.

A portable system for studying discrete-trial group choice.

Whether groups of people or animals behave optimally in relation to resources is an issue of interest to psychology, ecology, and economics. In behavioral ecology, the simplest model of optimal group choice is the ideal free distribution (IFD). The IFD model has been tested in humans with discrete or continuous inputs and through manual or automated procedures (e.g., Kraft, Baum, & Burge, 2002; Madden, Peden, & Yamagushi, 2002). Manual procedures tend to be time consuming, however, whereas automated procedures typically require access to a computer network. In this article, we describe a new automated system for discrete-trial tests of the IFD model. Our protocol involves a single computer connected to a digital projector (for stimulus presentation) and a network of gamepads (for registering choices). The system is comparatively inexpensive, easy to install, easy to transport, and it permits the automated collection of group data in minimal time. We show that the data generated through this protocol are comparable to those previously reported in the IFD literature.

An assessment of fixed interval timing in free-flying honey bees (Apis mellifera ligustica): an analysis of individual performance.

Interval timing is a key element of foraging theory, models of predator avoidance, and competitive interactions. Although interval timing is well documented in vertebrate species, it is virtually unstudied in invertebrates. In the present experiment, we used free-flying honey bees (Apis mellifera ligustica) as a model for timing behaviors. Subjects were trained to enter a hole in an automated artificial flower to receive a nectar reinforcer (i.e. reward). Responses were continuously reinforced prior to exposure to either a fixed interval (FI) 15-sec, FI 30-sec, FI 60-sec, or FI 120-sec reinforcement schedule. We measured response rate and post-reinforcement pause within each fixed interval trial between reinforcers. Honey bees responded at higher frequencies earlier in the fixed interval suggesting subject responding did not come under traditional forms of temporal control. Response rates were lower during FI conditions compared to performance on continuous reinforcement schedules, and responding was more resistant to extinction when previously reinforced on FI schedules. However, no "scalloped" or "break-and-run" patterns of group or individual responses reinforced on FI schedules were observed; no traditional evidence of temporal control was found. Finally, longer FI schedules eventually caused all subjects to cease returning to the operant chamber indicating subjects did not tolerate the longer FI schedules.

Social reinforcement delays in free-flying honey bees (Apis mellifera L.).

Free-flying honey bees (Apis mellifera L.) reactions were observed when presented with varying schedules of post-reinforcement delays of 0 s, 300 s, or 600 s. We measured inter-visit-interval, response length, inter-response-time, and response rate. Honey bees exposed to these post-reinforcement delay intervals exhibit one of several patterns compared to groups not encountering delays, and had longer inter-visit-intervals. We observed no group differences in inter-response time. Honey bees with higher response rates tended to not finish the experiment. The removal of the delay intervals increased response rates for those subjects that completed the trials.

"Beetrack": a software for 2D open field locomotion analysis in honey bees.

"Beetrack" is a complete software designed to analyze the 2D locomotor behavior of four simultaneous honey bees moving in petri dishes. Several dependent variables can be measured: traveled distance, number of jumps and % of immobility. A spatial analysis can also be performed to detect if the bees are using preferentially one part of the box. The software has been successfully tested with eight honey bees and promise to be an interesting tool in the pharmacology field.

Ethanol self-administration in free-flying honeybees (Apis mellifera L.) in an operant conditioning protocol.

BACKGROUND: This study examines the effect of ethanol (EtOH) on continuous reinforcement schedules in the free-flying honeybee (Apis mellifera L.). As fermented nectars may be encountered naturally in the environment, we designed an experiment combining the tools of laboratory research with minimal disturbance to the natural life of honeybees. METHODS: Twenty-five honeybees were trained to fly from their colonies to a fully automated operant chamber with head poking as the operant response. Load size, intervisit interval, and interresponse times (IRTs) served as the dependent variables and were monitored over the course of a daily training session consisting of many visits. Experimental bees were tested using an ABA design in which sucrose only was administered during condition A and a 5% EtOH sucrose solution was administered during condition B. Control bees received sucrose solution only. RESULTS: Most bees continued to forage after EtOH introduction. EtOH significantly reduced the load size and the intervisit interval with no significant effect on IRTs. However, a look on individual data shows large individual differences suggesting the existence of different kinds of behavioral phenotypes linked to EtOH consumption and effects. CONCLUSIONS: Our results contribute to the study of EtOH consumption as a normal phenomenon in an ecological context and open the door to schedule-controlled drug self-administration studies in honeybees.

The effect of pymetrozine (Plenum WG-50) on proboscis extension conditioning in honey bees (Apis mellifera: Hybrid var. Buckfast).

Experiments are designed to examine the effects of pymetrozine (Plenum WG-50), a recent systemic pesticide of the pyridine-azomethin family, on Pavlovian conditioning of harnessed foragers. In one set of experiments bees learned a task in which they associated a conditioned stimulus with feeding. A second set of experiments required the bees to learn a discrimination task. Within each experiment, bees received 5 µl of sucrose only, the recommended field dose of Plenum (5 µL of .3 gL(-1), .16 gL(-1) of pymetrozine measured), or 100 times the field dose of Plenum WG 50 thirty minutes prior to training (5 µL of 30 gL(-1), 14 gL(-1) of pymetrozine measured). The Plenum WG 50 was diluted with .88 M sucrose to facilitate the drinking of the pesticide. In addition to varying the concentration, we also investigated the effect of Plenum WG 50 on bees confined to an observation hive and a hive located outside. The results indicated that prior exposure to Plenum WG 50 affected Pavlovian conditioning only when bees were exposed to 100 times the recommended dosage.

A paradigm for operant conditioning in blow flies (Phormia terrae novae Robineau-Desvoidy, 1830).

An operant conditioning situation for the blow fly (Protophormia terrae novae) is described. Individual flies are trained to enter and reenter a hole as the operant response. Only a few sessions of contingent reinforcement are required to increase response rates. When the response is no longer followed by food, the rate of entering the hole decreases. Control procedures revealed that rate of responding is not a simple overall result of feeding or of aging. The flies entered into the hole only if the response was required to obtain the food.

From foraging to operant conditioning: a new computer-controlled Skinner box to study free-flying nectar gathering behavior in bees.

The experimental study of nectar foraging behavior in free-flying bees requires the use of automated devices to control solution delivery and measure dependent variables associated with nectar gathering. We describe a new computer-controlled artificial flower and provide calibration data to measure the precision of the apparatus. Our device is similar to a "Skinner box" and we present data of an experiment where various amounts of a 50% sugar solution are presented randomly to individual bees. These data show large individual variations among subjects across several dependent variables. Finally, we discuss possible applications of our device to problems in behavioral sciences.

Efeitos de planos nutricionais e de fontes de metionina sobre o desempenho, rendimento e composição de carcaças de frangos de corte / Effects of nutritional plans and methionine sources on broilers performance, carcass yield, and carcass composition

Para avaliar os efeitos de dois diferentes planos nutricionais de aminoácidos sulfurados totais (AAST) e de duas fontes de metionina nas rações de frangos de corte, foi realizado um experimento com 840 frangos machos, da linhagem agRoss 308. Os tratamentos foram definidos pelos planos nutricionais de AAST (normal e reduzido) e pelas fontes de metionina (DL-metionina e metionina hidroxianáloga - MHA) usadas nas rações. O delineamento experimental foi o inteiramente ao acaso, em arranjo fatorial 2x2, (duas fontes de metionina x dois planos nutricionais de AAST). Não foram encontradas diferenças entre os tratamentos para o consumo de ração, ganho de peso, viabilidade, rendimento de carcaça, porcentagem de peito e composição das carcaças e vísceras. As aves que receberam as rações com o plano normal de AAST apresentaram melhor conversão alimentar, e as que receberam ração contendo DL-metionina tiveram menor porcentagem de gordura abdominal. Concluiu-se que a substituição da DL-metionina pela MHA não afetou o desempenho, que o plano nutricional normal melhorou a conversão alimentar dos frangos de corte e que as fontes de metionina e os planos nutricionais de AAST não influenciaram o rendimento e a composição da carcaça e vísceras de frangos de corte.

To evaluate the effects of two different nutritional plans for total sulfur amino acids (TSAA), and two methionine sources in the diets of broiler chickens, an experiment was conducted with 840 male broiler line agRoss 308. The treatments were defined by nutritional plans of TSAA (normal and low) and the methionine sources (DL-methionine and methionine hydroxy-analogue - MHA) used in the diets. The experimental design was completely randomized in a factorial scheme 2X2, (two methionine sources x two levels of nutrition plans TSAA). No differences were found between treatments for ration consumption, weight gain, viability, carcass yield, and carcass composition. The broilers that received the diets with the TSAA normal level had better feed conversion, and those that received diets containing DL-methionine had lower abdominal fat percentages. It was concluded that the substitution of DL-methionine by MHA did not affect the performance of broilers, whereas the normal nutrition plan improved feed conversion of broiler chickens as well as methionine sources and TSAA nutritional plans did not influence the carcass yield and carcass composition of broiler chickens.

Redundancy of single diagnostic test evaluation.

Diagnostic research and diagnostic practice frequently do not cohere. Studies commonly evaluate whether a single test discriminates between disease presence and absence, whereas in practice a test is always judged in the context of other information. This study illustrates drawbacks of single-test evaluation and discusses principles of diagnostic research. We used data on 140 patients suspected of pulmonary embolism who had an inconclusive ventilation-perfusion lung scan. We evaluated three tests: partial pressure of oxygen in arterial blood (PaO2), x-ray film of the thorax, and leg ultrasound. On the basis of single-test evaluations, ultrasound was most informative. Given a prior probability of 0.27, it had a much better combination of positive and negative predictive value (0.71 and 0.21, respectively) relative to thorax x-ray (0.33 and 0.11) and PaO2 (0.35 and 0.27). The combination of positive and negative likelihood ratio was also more promising for ultrasound (7.3 and 0.7) than for thorax x-ray (1.3 and 0.3) and PaO2 (1.3 and 0.9). As the tests are always performed after the history and physical, we judged their added value using multivariable logistic modeling with receiver operating characteristic (ROC) analyses. The ROC areas of the model, including history and physical, with additional PaO2, thorax x-ray, or ultrasound, were 0.75, 0.77, 0.81, and 0.81, respectively, which indicated similar added value of thorax x-ray and ultrasound. Application of the models to patient subgroups also yielded added predictive value for thorax x-ray film. Thus, the results of single-test evaluations may be very misleading. As no diagnosis is based on one test, single-test evaluations have limited value in diagnostic research and only have relevance in the context of screening and the initial phase of test development. Diagnostic research should always apply an approach of constructing, extending, and validating diagnostic models in agreement with routine clinical work-up using logistic regression analyses.

Sample size calculation in economic evaluations.

A simulation method is presented for sample size calculation in economic evaluations. As input the method requires: the expected difference and variance of costs and effects, their correlation, the significance level (alpha) and the power of the testing method and the maximum acceptable ratio of incremental effectiveness to incremental costs. The method is illustrated with data from two trials. The first compares primary coronary angioplasty with streptokinase in the treatment of acute myocardial infarction, in the second trial, lansoprazole is compared with omeprazole in the treatment of reflux oesophagitis. These case studies show how the various parameters influence the sample size. Given the large number of parameters that have to be specified in advance, the lack of knowledge about costs and their standard deviation, and the difficulty of specifying the maximum acceptable ratio of incremental effectiveness to incremental costs, the conclusion of the study is that from a technical point of view it is possible to perform a sample size calculation for an economic evaluation, but one should wonder how useful it is.

Application of treatment thresholds to diagnostic-test evaluation: an alternative to the comparison of areas under receiver operating characteristic curves.

Diagnostic tests are often evaluated by comparison of the areas under receiver operating characteristic (ROC) curves. In this study the authors compared this approach with a more direct method that takes into account consequences of a diagnosis. Data from a prospective study of diagnosis of pulmonary embolism were used for a motivating example. Using multivariable logistic regression analysis, three diagnostic models were built and compared based on their ROC curves. Although model 1 (0.706) and model 2 (0.702) had the same ROC-curve area, they performed differently when risks and benefits of subsequent decisions were considered by applying the treatment probability threshold. Models 1 and 3 (0.611) had substantially different ROC-curve areas but performed similarly taking into account the therapeutic consequences. This demonstrates that comparison of diagnostic tests using the areas under the ROC curves may lead to erroneous conclusions about therapeutic usefulness. To correspond to daily practice, it would be more appropriate to also consider the clinical implications in evaluating diagnostic tests. This is made feasible by explicit definition and application of a treatment threshold.

The role of a decision rule in symptomatic pulmonary embolism patients with a non-high probability ventilation-perfusion scan.

BACKGROUND: In order to improve the use of information contained in the medical history and physical examination in patients with suspected pulmonary embolism and a non-high probability ventilation-perfusion scan, we assessed whether a simple, quantitative decision rule could be derived for the diagnosis or exclusion of pulmonary embolism. METHODS: In 140 consecutive symptomatic patients with a non-high probability ventilation-perfusion scan and an interpretable pulmonary angiogram, various clinical and lung scan items were collected prospectively and analyzed by multivariate stepwise logistic regression analysis to identify the most informative combination of items. RESULTS: The prevalence of proven pulmonary embolism in the patient population was 27.1%. A decision rule containing the presence of wheezing, previous deep venous thrombosis, recently developed or worsened cough, body temperature above 37 degrees C and multiple defects on the perfusion scan was constructed. For the rule the area under the Receiver Operating Characteristic curve was larger than that of the prior probability of pulmonary embolism as assessed by the physician at presentation (0.76 versus 0.59; p = 0.0097). At the cut-off point with the maximal positive predictive value 2% of the patients scored positive, at the cut-off point with the maximal negative predictive value pulmonary embolism could be excluded in 16% of the patients. CONCLUSIONS: We derived a simple decision rule containing 5 easily interpretable variables for the patient population specified. The optimal use of the rule appears to be in the exclusion of pulmonary embolism. Prospective validation of this rule is indicated to confirm its clinical utility.

[Costs of diagnosis and treatment for pulmonary embolism lower due to application of consensus strategy]. / Kosten van diagnostiek en behandeling wegens longembolie lager door toepassing van de consensusstrategie.

OBJECTIVE: To compare the costs of diagnosis and treatment of patients clinically suspected of pulmonary embolism, before and after the adoption of the Dutch consensus for the diagnosis of pulmonary embolism. DESIGN: Study of the records, followed by a prospective study with a follow-up lasting 6 months. SETTING: Academic Medical Centre and Slotervaart Hospital, Amsterdam, the Netherlands. METHOD: Data were collected on 120 patients from the preconsensus period and on 452 patients examined according to the consensus strategy. This established the average patterns of medical consumption of patients before and after adoption of consensus. The mean costs per patient were then estimated. RESULTS: Diagnosis and treatment of a patient according to the consensus strategy on the basis of our estimates were considerably less expensive than non-protocolled diagnosis and treatment (Dfl. 4,413 as against Dfl. 5,115 per patient). This difference mainly resulted from shorter hospital stays owing to more rapid completion of the diagnosis. Considering the large number of annual hospital admissions in the Netherlands in connection with this diagnosis, savings of up to Dfl. 26 million would appear possible if the consensus were followed nationwide. CONCLUSION: Considerable amounts are involved in the diagnosis and treatment of pulmonary embolism in the Netherlands. Accordingly, further research into possibilities to make these more efficient would appear advisable.

Simulation models in the planning of health care facilities: an application in the case of neonatal extracorporeal membrane oxygenation.

OBJECTIVES: To investigate whether modelling techniques can be used in the planning of health care facilities for patients requiring neonatal extracorporeal membrane oxygenation (ECMO). METHODS: In a micro-simulation model the number of patients that will have to be referred to facilities abroad is estimated for any number of neonatal ECMO patients presenting annually for treatment in The Netherlands, and any number of ECMO facilities. The inputs to the model consist of the number of ECMO facilities, the number of patients presenting annually, the duration of treatment and the date on which patients present for ECMO treatment. The model is estimated on data from The Netherlands for 1992, during which 29 patients were treated in three facilities. Several future scenarios are modelled, principally one in which a potential increase to 56 patients per year is foreseen. RESULTS: The model indicates that, if such an increase takes place, no additional ECMO facilities will be necessary in The Netherlands if between three and four referrals annually to centres outside the region (or abroad) are considered acceptable and feasible. In that situation, it is expected that on 22 occasions each year two patients will be treated simultaneously, for a total of 81 days. On ten occasions, all three facilities will be occupied at the same time, for 21 days in total. On 199 days, at least one of the facilities will be occupied. CONCLUSION: The current study shows that the acceptability and feasibility of patient referrals to ECMO centres abroad is an important issue which health care planners will have to consider. The study also shows that modelling techniques can provide information that is useful to policy-makers in the planning of health care facilities.

The cost-effectiveness of diagnostic strategies in patients with suspected pulmonary embolism.

The cost-effectiveness of various diagnostic strategies in patients with clinically suspected pulmonary embolism (PE) was analysed using a modelling approach. In 451 consecutive patients with clinically suspected PE data on the performance of diagnostic tests were collected prospectively in two large teaching hospitals in Amsterdam, The Netherlands. The ventilation-perfusion lung scan was used as the primary diagnostic test in all patients. In patients with a non-diagnostic lung scan result the performance of a clinical decision rule, a D-dimer test, and ultrasonography of the leg veins was evaluated with pulmonary angiography as the gold standard. It was estimated that the strategy recommended by a 1992 Dutch consensus meeting costs about Dfl 4400 per patient and that 97.02% of the patients can be expected to survive the first 6 months after the primary PE. The nation-wide annual costs for the diagnosis and treatment of patients by this strategy were estimated at 163 million Dutch Guilders. Subsequently, the costs and effects of alternative strategies were evaluated in a modelling approach, and compared with those of the consensus strategy. One strategy was selected that produces the best results in terms of survival and leads to considerable savings as compared with the consensus strategy. In this strategy subsequently a ventilation-perfusion scan, a clinical decision rule, a D-dimer test, a pulmonary angiography and leg ultrasonography are performed. Patients with a high probability ventilation-perfusion scan, an abnormal angiography or leg ultrasound test are treated, whereas treatment is withheld in patients with a normal ventilation-perfusion scan, a normal clinical decision rule, a negative D-dimer test, a normal angiography, or a normal leg ultrasound test. This strategy will have to prove its value and usefulness in clinical practice in a subsequent prospective validation phase.