The effect of mature plant resistance in sugar beet (Beta vulgaris spp. vulgaris) on survival, fecundity and behaviour of green peach aphids (Myzus persicae).

Several studies have shown the negative effects of mature plant resistance (MPR) on aphids in sugar beet, which is correlated to the formation of black deposits in their stomach. However, the underlying mechanism of MPR still needs to be elucidated, by understanding the toxicity effects of MPR on aphids and the role of the plant phenological stage and the environment. Here, we report that MPR in sugar beet does not only affect Myzus persicae mortality rate and the formation of a black deposit in the aphid stomach, but also aphid fecundity and behaviour. In addition, experiments in climate-controlled and field settings showed quantitative variation in MPR to M. persicae between six genotypes of sugar beet. Our results indicate that environmental effects, such as temperature, play a major role in MPR and underscore the importance of proper climate-controlled experiments for investigating MPR. In climate-controlled experiments, 83.3% of aphids on old leaves developed a black deposit, in contrast to only 16.8% of aphids on young leaves. This shows that not only plant age, but also leaf age plays a major role in the intensity of MPR. Further research will be needed to identify the underlying mechanism, before MPR can be used as a viable and sustainable solution to aphid pests in sugar beet.

CALIMA: The semi-automated open-source calcium imaging analyzer.

BACKGROUND AND OBJECTIVE: Ever since its discovery, calcium imaging has proven its worth in discovering new insights into the mechanisms of cellular communication. Yet, the analysis of the data generated by calcium imaging experiments demands a large amount of time from researchers. Tools enabling automated and semi-automated analysis are available, but often they allow automating only a part of the data analysis process. Therefore, we developed CALIMA (https://aethelraed.nl/calima), a free and open-source standalone software tool that provides an opportunity to quickly detect cells, to obtain the calcium spikes, and to determine the underlying network structure of neuronal cell cultures. METHODS: Owing to the difference of Gaussians algorithm applied for the cell detection, CALIMA is able to detect regions of interest (ROIs) quickly. The z-scoring algorithm provides a means to set the requirements for spike detection, and the neuronal connections can be reconstructed by analyzing the cross-correlation between the cellular activity. We evaluated CALIMA's reliability, speed, and functionality with a special focus on neuronal cell detection and network reconstruction. The evaluation was performed by using real-life data such as a known example dataset (cultured primary rat cortical neurons, University of Pennsylvania) and by analyzing video graphic footage of in vitro brain cell samples (SH-SY5Y neuroblastoma cultures, one sample with synchronous neuron firing). The obtained results were compared to the corresponding outcomes observed on same datasets for other similar software solutions. Moreover, we compared the results of segmentation and peak detection analysis, the ones obtained using CALIMA and those acquired manually. RESULTS: CALIMA was able to detect the cells in the cultures within seconds. The average sensitivity was 82% across the datasets checked, comparing favorably with the alternative software solutions. Using the correct parameters, CALIMA's Ca-spikes detection sensitivity reached 96%. Lastly, neuronal networks were reconstructed by combining the data on the ROI's activity and the cell's positions, finding the most likely inter-cell connections. CONCLUSIONS: We found that CALIMA proved to be a robust and fast tool to analyze the data of experiments for the digital reconstruction of the neuronal cellular network while being able to process the analysis steps with minimal user input required and in a time efficient manner.

USE OF GREEN MANURE CROPS AND SUGAR BEET VARIETIES TO CONTROL HETERODERA BETAE.

Although it is less studied than the white beet cyst nematode (Heterodera schachtii), the yellow beet cyst nematode (H. betae) has been found in many countries in Europe. For example in The Netherlands, France and Spain. H. betae causes yield losses on sandy soils. A high infestation can result in loss of complete plants. In The Netherlands, this nematode is especially found in the south eastern and north eastern part, where it occurs on 18% and 5% of the fields, respectively. From a project of the Dutch Sugar beet Research Institute IRS (SUSY) on factors explaining differences in sugar yield, this nematode was one of the most important factors reducing sugar yields on sandy soils. Until 2008, the only way to control H. betae was by reducing the number of host crops in the crop rotation. Host crops are crops belonging to the families of Cruciferae, Chenopodiaceae, Polygonaceae, Caryophyllaceae and Leguminosea. In order to find more control measures, research was done to investigate the host status of different green manure crops and the resistance and tolerance of different sugar beet varieties to H. betae. White mustard (Sinapis alba) and oil seed radish (Raphanus sativus spp. oleiferus) varieties resistant to H. schachtii were investigated for their resistance against H. betae. A climate room trial and a field trial with white mustard and oil seed radish were conducted in 2007 and 2008, respectively. Results show that H. betae could multiply on susceptible white mustard and susceptible oil seed radish, but not on the H. schachtii resistant varieties. In climate room trials in 2009, 2010 and 2011 and field trials in 2010, 2011 and 2012, the effect of different sugar beet varieties on the multiplication of H. betae and the effect of H. betae on yield at different infestation levels was investigated. Sugar beet varieties with resistance genes to H. schachtii (from Beta procumbens or B. maritima) were selected. Varieties with resistance genes from these sources were not totally resistant to H. betae, but limited the multiplication of this nematode in comparison with susceptible varieties considerably. Only the varieties with resistance genes from B. maritima gave higher yields in comparison with susceptible varieties. Growing these varieties was already profitable from very light infestation levels (75 eggs and larvae/100 ml soil) of H. betae. Therefore, resistant cruciferous green manure crops and resistant and tolerant sugar beet varieties are good tools for growers to control H. betae.

Intracranial radiosurgery in the Netherlands. A planning comparison of available systems with regard to physical aspects and workload.

Different planning and treatment systems for intracranial stereotactic radiosurgery available in the Netherlands are compared. The systems for intracranial radiosurgery include: Gamma Knife, Cyberknife, Novalis, and Tomotherapy. Electronic data of 5 patients was transferred to all participating centres and treatment plans were generated according to 2 different prescription protocols. For this study, plans were also generated for a conventional linac. Even systems with a high resolution (Gammaknife and Novalis) have conformity indices in violation with RTOG guidelines (CI > 2.5) when target volumes of <0.5 cc are treated. For medium sized targets (0.5-1 cc) all systems performed reasonably well, but for the different systems a large range of conformity indices was seen (1.1 to 3.7). The differences are partly system dependent but depend also on specific planning choices made. For larger target volumes (> 1 cc), all systems perform well. The workload of the different techniques was comparable although the treatment times were usually longer for Gamma Knife radiosurgery. We conclude that small targets should be treated by dedicated systems, larger volumes (> 0.5-1 cc) can also be treated using conventional treatment systems equipped with a MLC.

Development of a criterion for repositioning a relocatable stereotactic frame using depth helmet measurements.

Based on 95% confidence intervals in the normal distribution, a criterion was developed for a relocatable stereotactic frame depth helmet measurement. The method for obtaining such a criterion is described. The criterion states that, if more than two points deviate more than 1.5 mm the frame should be repositioned.

Always on a Friday? Time pattern of referral for spinal cord compression.

For patients with spinal cord compression, radiotherapy should be initiated as soon as possible to optimize the chances for restoration of neurological function. The speed of referral in the region of our radiotherapy institution with nine general hospitals was analysed based on a tumour and treatment-related registry. From January 1987 to December 1997, 443 patients were treated. All patients were seen and treated on the day of referral. Significantly more referrals took place on Friday, 30%, compared with 12% on Monday, 17% on Tuesday, 15% on Wednesday, 20% on Thursday, 5% on Saturday and 1% on Sunday (p < 0.002). This difference was the same for patients whether they were formerly treated in our institution (n = 242) or not (n = 201). No significant difference was found between different categories of patients (p = 0.28). These data are discussed with the referring physicians to encourage speed of diagnosis and referral.

Electrical impedance tomography in the assessment of extravascular lung water in noncardiogenic acute respiratory failure.

STUDY OBJECTIVES: To establish the value of electrical impedance tomography (EIT) in assessing pulmonary edema in noncardiogenic acute respiratory failure (ARF), as compared to the thermal dye double indicator dilution technique (TDD). DESIGN: Prospective clinical study. SETTING: ICU of a general hospital. PATIENTS: Fourteen ARF patients. INTERVENTIONS: In order to use the TDD to determine the amount of extravascular lung water (EVLW), a fiberoptic catheter was placed in the femoral artery. MEASUREMENTS AND MAIN RESULTS: Fourteen consecutive ARF patients receiving mechanical ventilation were measured by EIT and TDD. EIT visualizes the impedance changes caused by the ventilation in two-dimensional image planes. An impedance ratio (IR) of the ventilation-induced impedance changes of a posterior and an anterior part of the lungs was used to indicate the amount of EVLW. For the 29 measurements in 14 patients, a significant correlation between EIT and TDD (r = 0. 85; p < 0.001) was found. The EIT reproducibility was good. The diagnostic value of the method was tested by receiver operator characteristic analysis, with 10 mL/kg of EVLW considered as the upper limit of normal. At a cutoff level of the IR of 0.64, the IR had a sensitivity of 93%, a specificity of 87%, and a positive predictive value of 87% for a supranormal amount of EVLW. Follow-up measurements were performed in 11 patients. A significant correlation was found between the changes in EVLW measured with EIT and TDD (r = 0.85; p < 0.005). CONCLUSION: We conclude that EIT is a noninvasive technique for reasonably estimating the amount of EVLW in noncardiogenic ARF.

A meta-analysis of three decades of validating thoracic impedance cardiography.

OBJECTIVE: To provide a meta-analysis of current literature concerning the validation of thoracic impedance cardiography (TIC) and to explain the variations in the reported results from the differences in the studies. DATA SOURCES: A computer-assisted search of English-language, German, and Dutch literature was performed for the period January 1966 to April 1997. Moreover, references from review articles were obtained. STUDY SELECTION: A total of 154 studies comparing measurements of cardiac output or related variables obtained from TIC and a reference method were analyzed. DATA EXTRACTION: Articles were classified by differences in TIC methodology, reference method, and subject characteristics. Fisher's Zf transformed correlation coefficients were used to compare results. Data were pooled using the random-effects method. DATA SYNTHESIS: An overall pooled r2 value of .67 (95% confidence interval, 0.64-0.71) was found. However, the correlation was higher in repeated-measurement designs than in single-measurement designs (r2 = .53; 95% confidence interval, 0.43-0.62). Further research using analysis of variance revealed a significant influence of the reference method and the subject characteristics on the correlation coefficient. The correlation was significantly better in animals than in cardiac patients. Subgroup analysis revealed that TIC correlated significantly better to the indirect Fick method than to echocardiography in healthy subjects. No significant influence of the applied TIC methodology was found. DISCUSSION: The overall r2 value of .67 indicates that TIC might be useful for trend analysis of different groups of patients. However, for diagnostic interpretation, a r2 value of .53 might not meet the required accuracy of the study. Great care should be taken when TIC is applied to the cardiac patient. However, because the applied reference method was of significant influence, differences between TIC and the reference method are incorrectly attributed to errors in TIC alone.

A meta-analysis of published studies concerning the validity of thoracic impedance cardiography.

UNLABELLED: Our aim was to provide a meta-analysis of the literature concerning the validation of thoracic impedance cardiography (TIC) and to explain variations in reported results from differences in the studies. One hundred fifty-four studies (164 Fisher's Z-transformed correlation coefficients) comparing measurements of cardiac output or related parameters from TIC and a reference method were analyzed. Papers were classified according to differences in TIC methodology, reference method, and subject characteristics. Pooling using the random-effects method yielded an overall correlation of r = 0.82 (95% confidence interval: 0.80-0.84). ANOVA revealed a significant influence of the reference method and the subject characteristics on the correlation coefficient. In cardiac patients, the correlation was significantly decreased. No influence of the applied TIC methodology was found. CONCLUSION: TIC might be useful for trend analysis of different groups of patients. However, since the reference method was of significant influence, differences between TIC and the reference method are incorrectly attributed to TIC alone.

Towards a theoretical understanding of stroke volume estimation with impedance cardiography.

In electrical impedance cardiography, Kubicek's formula is often used to measure stroke volume from thoracic impedance variations synchronously to heart activity. To calculate stroke volume from impedance variations, the so-called outflow problem should be adequately solved. This outflow problem refers to the joint causes of impedance change due to blood entering the aorta from the heart, as well as blood leaving the aorta due to arterial runoff. The aim of this study was to investigate the Kubicek formula as a solution of the outflow problem. Kubicek's formula was theoretically investigated using a simple model of the volume-conducting properties of the thorax (two-cylinder model), as well as the hemodynamics of the systemic circulation (three-element "windkessel" model). The mathematical analysis showed that the outflow problem was not solved by the Kubicek formula. Moreover, this theoretical result was experimentally confirmed.

The influence of extravascular lung water on cardiac output measurements using thoracic impedance cardiography.

The purpose of this study was to investigate the influence of pulmonary oedema as measured with the double indicator dilution technique on the accuracy of cardiac output (CO) measurement using thoracic impedance cardiography (TIC) compared with thermodilution in thirteen sepsis patients. Differences in the Kubicek and Sramek-Bernstein equation with respect to pulmonary oedema were explored theoretically and experimentally. From a parallel two cylinder model a hypothesis can be derived that CO determined with the Kubicek equation is oedema independent, whereas CO determined using the Sramek-Bernstein equation is oedema dependent. Experimentally, CO determined using Kubicek's equation correlated better with thermodilution CO (r = 0.75) than CO determined with the Sramek-Bernstein equation (r = 0.25). The effect of oedema on the accuracy of TIC was investigated by comparing the differences in the CO of impedance and thermodilution to the extravascular lung water index. For the Kubicek equation the difference was not influenced by oedema (r = 0.04, p = 0.84), whereas for the Sramek-Bernstein equation the difference was affected by oedema (r = 0.39, p = 0.05). Thus, the effects of pulmonary oedema on the accuracy of TIC measurements can better be understood with the parallel cylinder model. Moreover, the Kubicek equation still holds when pulmonary oedema is present, in contrast to the Sramek-Bernstein equation.

Thoracic geometry and its relation to electrical current distribution: consequences for electrode placement in electrical impedance cardiography.

In thoracic impedance cardiography (TIC) measurements the neck electrodes are often positioned at the basis of the neck, close to the neck-thorax transition. Theoretically, this neck-thorax transition will cause inhomogeneities in the current density and potential distribution. This was simulated using a 3D finite element method, solely representing the geometrical neck-thorax transition. The specific conductivity was 7 10(-3) (omega cm)-1 and the injected current was 1 mA. As expected, the model generated inhomogeneities in the current distribution at the neck-thorax transition, which reached as far as 5 cm into the neck and 20 cm into the thorax. These results are supported by in vivo measurements performed in 10 young male subjects, in which the position of the neck electrodes was varied. A two-way ANOVA revealed that the stroke volume of the lowest neck position was significantly different from the other positions. Small shifts in the position of the neck electrode resulted in large changes in impedance and stroke volume (127 to 82 ml for the Kubicek equation). To standardise the electrode position, the authors strongly recommend placement of the neck electrodes at least 6 cm above the clavicula.

An electrically isolated balanced wideband current source: basic considerations and design.

At relatively high frequencies, the application of an alternating current through the body or a body segment results in electromagnetic stray fields which reduce the amount of current actually injected into the tissue under study. This radiation effect can be reduced by use of a symmetrical configuration current source. The symmetry of such an arrangement, however, depends on the stray capacitances of the source with respect to surrounding equipment. To minimise these effects, it is required that the source is electrically isolated from the surrounding equipment and the subject under study. In this manner stray capacitances with respect to elements of the current source are reduced. In such a configuration common mode voltages to the input amplifier of the measuring system are also reduced. The paper describes design considerations and the implementation of a wideband current source capable of injecting alternating current in the order of 300 microARMS into biological tissue having impedances up to 1 k omega. Current stabilisation is obtained by means of a control circuit which measures the actual current passing through the tissue under study. Leakage currents arising from shielding and stray capacitances are compensated for. The usable frequency range is between 4 kHz and 1024 kHz and current stability is better than 0.2%. Through the use of a symmetrical, floating circuit a configuration is obtained which substantially reduces stray effects. The current source is connected to other circuits by means of two isolation ports: (1) a transformer coupling for the carrier frequency; and (2) an opto-coupler to transfer a phase reference signal obtained from current measurement. The current amplitude can be modulated by controlling the reference input to the control loop by means of a third auxiliary isolation port for transfer of the modulating signal.

A wideband high common mode rejection ratio amplifier and phase-locked loop demodulator for multifrequency impedance measurement.

Design considerations and implementation of a multifrequency measuring channel for application in the field of bio-impedance measurement are discussed in this paper. The input amplifier has a differential configuration which is electrically isolated from the remaining circuits. Transformer coupling provides improved common mode rejection when compared to non-isolated input stages. The frequency characteristic of the section between input and demodulator is flat within +/- 0.1 dB between 4 kHz and 1024 kHz. The synchronous demodulator is based on a wideband switched video amplifier. In contrast to commonly used lock--in techniques, the carrier for demodulation is recovered from the input signal by means of a phase-locked loop. This method ensures zero phase shift with respect to the input signal and improves the accuracy of measurement. The system has been developed primarily for thoracic impedance cardiography (TIC) but has also successfully been applied in the field of total body bio-impedance analysis (BIA). At present an electrical impedance tomograph is under development based on the instrumentation described. Results regarding the measurement range and accuracy are given and some recordings of patient data are shown.

Estimation of non-cardiogenic pulmonary oedema using dual-frequency electrical impedance.

The study investigates the effects of non-cardiogenic oedema, especially the accumulation of protein in extracellular fluid, on thoracic impedance and proposes a new method of oedema measurement based on an impedance ratio from a dual-frequency measurement. In vitro measurements in a cell containing an albumin-in-saline solution yield a resistance increase when the albumin concentration increases. Subsequently, 13 patients having acute respiratory failure are measured. The single-frequency Z0 measurements and the proposed impedance ratio are compared with extravascular lung water (EVLW) determined by the double indicator dilution method. The single-frequency measurement correlates poorly with EVLW (r = -0.24, p = 0.56). In some patients, a total thoracic impedance increase is found with increasing EVLW. The correlation between the impedance ratio and EVLW is r = -0.79 (p < 0.0005). The ratio decreases as EVLW increases. Thus, when oedema is measured using bio-impedance, cardiogenic and non-cardiogenic oedema yield different results. It is well recognised that cardiogenic oedema decreases total thoracic impedance. In non-cardiogenic oedema, however, protein accumulation causes an impedance increase. The decrease in the impedance ratio as EVLW increases can be explained by the accumulation of albumin in the extracellular compartment.

The inaccuracy of Kubicek's one-cylinder model in thoracic impedance cardiography.

The validity of a one- and a two-cylinder model, underlying thoracic impedance cardiography (TIC), was investigated by studying the length dependence of the impedance parameters Z0, (dZ/dt)min, and stroke volume (SV). It can be shown that, within a one-cylinder model, all parameters are directly proportional to the length, whereas, if the volume conduction of the thorax and the neck are modeled separately, Z0 and (dZ/dt)min are expected to be linear dependent and SV will be nonlinear upon the length. The expectations were compared to results from in vivo measurements. Two electrode arrays were studied, in which the caudal recording electrode position was varied; SV was calculated using Kubicek's equation. Except for small distances, the results showed a nearly linear relation between the parameters and the length. Regression analysis of the linear part revealed statistically significant intercepts (p < 0.05). Neither the intercept nor the nonlinear part can be explained by a one-cylinder model, whereas a model consisting of two cylinders serially connected describes the experimental results accurately. Thus SV estimation based on a one-cylinder model is biased due to the invalid one-cylinder model. Corrections for the Kubicek-equation need to be developed in future research using this two-cylinder model.

Long-term evaluation of Bennett's fracture. A comparison between open and closed reduction.

18 patients with Bennett's fracture were evaluated after a mean follow-up period of 10.7 years. Treatment consisted of closed reduction and K-wire fixation in seven cases and open reduction with osteosynthesis in 11 cases. Overall, symptoms were few and restricted mobility of the thumb could not be demonstrated. The strength of the affected hand was decreased in all patients regardless of the type of treatment. Osteoarthritis was found to correlate with the quality of reduction of the fracture, but had developed in almost all cases even after exact reduction. Exact reduction, either by the open or closed method, should be the aim of treatment of Bennett's fracture.