Body Bending Research Articles

Rapid phenotypic changes in Caenorhabditis elegans under uranium exposure

Pollutants can induce selection pressures on populations, and the effects may be concentration-dependant. The main ways to respond to the stress are acclimation (i.e. plastic changes) and adaptation (i.e. genetic changes). Acclimation provides a short-term response to environmental changes and adaptation can have longer-term implications on the future of the population. One way of studying these responses is to conduct studies on the phenotypic changes occurring across generations in populations experimentally subjected to a selective factor (i.e. multigenerational test). To our knowledge, such studies have not been performed with uranium (U). Here, the phenotypic changes were explored across three generations in experimental Caenorhabditis elegans populations exposed to different U-concentrations. Significant negative effects of U were detected on survival, generation time, brood size, body length and body bend. At lower U-concentrations, the negative effects were reduced in the second or the third generation, indicating an improvement by acclimation. In contrast, at higher U-concentrations, the negative effects on brood size were amplified across generations. Consequently, under high U-concentrations acclimation may not be sufficient, and adaptation of individuals would be required, to permit the population to avoid extinction. The results highlight the need to consider changes across generations to enhance environmental risk assessment related to U pollution.

A rat-like robot for interacting with real rats

SUMMARYWe developed a novel small rat-like robot calledWasedaRat No.4(WR-4) to interact with real rats. WR-4 can perform both rearing (rising up on its hind limbs) and rotating (body bending during movement) actions faster than live mature rats. After robot–rat interaction involving rearing and body grooming (body cuddling and head curling) actions of WR-4, real rats showed more activity and greater interest in the robot. Similar results evident from rat–rat interaction suggest that a rat-like robot is able to interact with rats in the same way as real rats. Furthermore, lower variances between the rat subjects in robot–rat interaction reveals that a rat-like robot can more effectively impact rat's behavior in a controllable, predictable way.

Emergence of the advancing neuromechanical phase in a resistive force dominated medium

Undulatory locomotion, a gait in which thrust is produced in the opposite direction of a traveling wave of body bending, is a common mode of propulsion used by animals in fluids, on land, and even within sand. As such, it has been an excellent system for discovery of neuromechanical principles of movement. In nearly all animals studied, the wave of muscle activation progresses faster than the wave of body bending, leading to an advancing phase of activation relative to the curvature toward the tail. This is referred to as "neuromechanical phase lags" (NPL). Several multiparameter neuromechanical models have reproduced this phenomenon, but due to model complexity, the origin of the NPL has proved difficult to identify. Here, we use perhaps the simplest model of undulatory swimming to predict the NPL accurately during sand-swimming by the sandfish lizard, with no fitting parameters. The sinusoidal wave used in sandfish locomotion, the friction-dominated and noninertial granular resistive force environment, and the simplicity of the model allow detailed analysis, and reveal the fundamental mechanism responsible for the phenomenon: the combination of synchronized torques from distant points on the body and local traveling torques. This general mechanism should help explain the NPL in organisms in other environments; we therefore propose that sand-swimming could be an excellent system with which to generate and test other neuromechanical models of movement quantitatively. Such a system can also provide guidance for the design and control of robotic undulatory locomotors in complex environments.

Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of <em>Caenorhabditis elegans</em>' Locomotion

The nematode Caenorhabditis elegans is a versatile model organism for biomedical research because of its conservation of disease-related genes and pathways as well as its ease of cultivation. Several C. elegans disease models have been reported, including neurodegenerative disorders such as Parkinson's disease (PD), which involves the degeneration of dopaminergic (DA) neurons (1). Both transgenes and neurotoxic chemicals have been used to induce DA neurodegeneration and consequent movement defects in worms, allowing for investigations into the basis of neurodegeneration and screens for neuroprotective genes and compounds (2,3). Screens in lower eukaryotes like C. elegans provide an efficient and economical means to identify compounds and genes affecting neuronal signaling. Conventional screens are typically performed manually and scored by visual inspection; consequently, they are time-consuming and prone to human errors. Additionally, most focus on cellular level analysis while ignoring locomotion, which is an especially important parameter for movement disorders. We have developed a novel microfluidic screening system (Figure 1) that controls and quantifies C. elegans' locomotion using electric field stimuli inside microchannels. We have shown that a Direct Current (DC) field can robustly induce on-demand locomotion towards the cathode ("electrotaxis") (4). Reversing the field's polarity causes the worm to quickly reverse its direction as well. We have also shown that defects in dopaminergic and other sensory neurons alter the swimming response (5). Therefore, abnormalities in neuronal signaling can be determined using locomotion as a read-out. The movement response can be accurately quantified using a range of parameters such as swimming speed, body bending frequency and reversal time. Our work has revealed that the electrotactic response varies with age. Specifically, young adults respond to a lower range of electric fields and move faster compared to larvae (4). These findings led us to design a new microfluidic device to passively sort worms by age and phenotype (6). We have also tested the response of worms to pulsed DC and Alternating Current (AC) electric fields. Pulsed DC fields of various duty cycles effectively generated electrotaxis in both C. elegans and its cousin C. briggsae (7). In another experiment, symmetrical AC fields with frequencies ranging from 1 Hz to 3 KHz immobilized worms inside the channel (8). Implementation of the electric field in a microfluidic environment enables rapid and automated execution of the electrotaxis assay. This approach promises to facilitate high-throughput genetic and chemical screens for factors affecting neuronal function and viability.

Microfluidic-based Electrotaxis for On-demand Quantitative Analysis of <em>Caenorhabditis elegans</em>' Locomotion

The nematode Caenorhabditis elegans is a versatile model organism for biomedical research because of its conservation of disease-related genes and pathways as well as its ease of cultivation. Several C. elegans disease models have been reported, including neurodegenerative disorders such as Parkinson's disease (PD), which involves the degeneration of dopaminergic (DA) neurons 1. Both transgenes and neurotoxic chemicals have been used to induce DA neurodegeneration and consequent movement defects in worms, allowing for investigations into the basis of neurodegeneration and screens for neuroprotective genes and compounds 2,3. Screens in lower eukaryotes like C. elegans provide an efficient and economical means to identify compounds and genes affecting neuronal signaling. Conventional screens are typically performed manually and scored by visual inspection; consequently, they are time-consuming and prone to human errors. Additionally, most focus on cellular level analysis while ignoring locomotion, which is an especially important parameter for movement disorders. We have developed a novel microfluidic screening system (Figure 1) that controls and quantifies C. elegans' locomotion using electric field stimuli inside microchannels. We have shown that a Direct Current (DC) field can robustly induce on-demand locomotion towards the cathode ("electrotaxis") 4. Reversing the field's polarity causes the worm to quickly reverse its direction as well. We have also shown that defects in dopaminergic and other sensory neurons alter the swimming response 5. Therefore, abnormalities in neuronal signaling can be determined using locomotion as a read-out. The movement response can be accurately quantified using a range of parameters such as swimming speed, body bending frequency and reversal time. Our work has revealed that the electrotactic response varies with age. Specifically, young adults respond to a lower range of electric fields and move faster compared to larvae 4. These findings led us to design a new microfluidic device to passively sort worms by age and phenotype 6. We have also tested the response of worms to pulsed DC and Alternating Current (AC) electric fields. Pulsed DC fields of various duty cycles effectively generated electrotaxis in both C. elegans and its cousin C. briggsae 7. In another experiment, symmetrical AC fields with frequencies ranging from 1 Hz to 3 KHz immobilized worms inside the channel 8. Implementation of the electric field in a microfluidic environment enables rapid and automated execution of the electrotaxis assay. This approach promises to facilitate high-throughput genetic and chemical screens for factors affecting neuronal function and viability.

Endurance exercise does not protect the decrease in bone associated with Type 1 diabetes in adult rats

Streptozotocin (STZ) induced type 1 diabetes mellitus (T1DM) decreases trabecular bone volume in mice. This study investigated the potential protective effects of endurance training (ET) on bone in STZ‐induced T1DM adult rats. Sixty four 8‐week old Sprague‐Dawley rats were randomly divided into 4 groups of 16: non‐T1DM sedentary (CS) and exercised (CX), T1DM sedentary (DS) and exercised (DX). Blood glucose was maintained at 9–15 mmol/L using subcutaneously implanted insulin pellets (Linplant, Linshin Canada, Inc.). ET was at ~75% VO2max for 1 h/d, 5 d/wk for 10 wk. Areal and volumetric bone mineral density (aBMD and vBMD; excised femur) was measured using dual‐energy x‐ray absorptiometry (DXA; QDR 4500A) and micro computed tomography (μCT; Aloka LCT200); bone strength was estimated using μCT. Two‐way ANOVA was used to test for diabetes and exercise differences; significance was set at P<0.05. T1DM had lower body weight (20.0%), aBMD (8.6%), cortical vBMD (1.6%), and bending (12.4%) and torsional strength (13.4%) vs control (P<0.001) with no differences in trabecular vBMD. Exercise also decreased body weight (4.7%) vs sedentary (P=0.019). These results suggest that 10 wk of ET does not have bone protective effects and T1DM rats have lower aBMD and vBMD than control, which may be secondary to effects on body weight. Funded by CIHR.

Inhibitions on the behavior and growth of the nematode progeny after prenatal exposure to sulfonamides at micromolar concentrations

Sulfonamides are one typical antibiotic which is an emerging hazardous material to the ecological stability due to their continuously application and biological effects to non-target organisms. The parent–progeny transgenerational effects need investigations to indicate their long-term consequences. Currently, we tested the transgenerational effects of sulfadiazine (SD), sulfapyridine (SP) and sulfamethazine (SMZ) on L3 larva of Caenorhabditis elegans. The nematodes were exposed to aqueous sulfonamides at micromolar concentrations for 96h, and then the effects on the behavior and growth in the exposed parent and unexposed progeny were measured. Results showed that SD, SP and SMZ inhibited three behavior indicators including body bending frequency (BBF), reversal movement (RM) and Omega turn (OT), and the growth indicator (body length, BL). Behavior indicators showed higher sensitivities than the growth indicator, and BBF had the highest sensitivity among the behavior indicators. Moreover, the effects of sulfonamides were also observed in the unexposed progeny with partially rescued or more severe inhibitions on the indicators. The behavior also showed higher sensitivity than the growth in the progeny. The transgenerational effects of sulfonamides indicated that parental exposure can multiply the harmful effects of antibiotic pollution in following generations and their potential ecological risks at environmental concentrations were further raised.

Postsynaptic ERG Potassium Channels Limit Muscle Excitability to Allow Distinct Egg-Laying Behavior States inCaenorhabditis elegans

Caenorhabditis elegans regulates egg laying by alternating between an inactive phase and a serotonin-triggered active phase. We found that the conserved ERG [ether-a-go-go (EAG) related gene] potassium channel UNC-103 enables this two-state behavior by limiting excitability of the egg-laying muscles. Using both high-speed video recording and calcium imaging of egg-laying muscles in behaving animals, we found that the muscles appear to be excited at a particular phase of each locomotor body bend. During the inactive phase, this rhythmic excitation infrequently evokes calcium transients or contraction of the egg-laying muscles. During the serotonin-triggered active phase, however, these muscles are more excitable and each body bend is accompanied by a calcium transient that drives twitching or full contraction of the egg-laying muscles. We found that ERG-null mutants lay eggs too frequently, and that ERG function is necessary and sufficient in the egg-laying muscles to limit egg laying. ERG K(+) channels localize to postsynaptic sites in the egg-laying muscle, and mutants lacking ERG have more frequent calcium transients and contractions of the egg-laying muscles even during the inactive phase. Thus ERG channels set postsynaptic excitability at a threshold so that further adjustments of excitability by serotonin generate two distinct behavioral states.

Stationary Detection of the Pedestrian?s Intention at Intersections

This paper focuses on stat ionary detect ion of the pedestrian's intention to enter the traffic lane at intersections. We use an Interacting Multiple Model Extended Kalman Filter (IMM-EKF) based tracking approach as basic method to recognize this. In addition, we propose a novel Motion Contour image based HOG-like descriptor (MCHOG) in combination with Support Vector Machine (SVM) classification that reaches the decision at an accuracy of 99 % within the initial step at the curb of smart infrastructure. MCHOG implicitly comprises the body language of gait initiation, especially the body bending and the spread of legs. As a result of a case study at laboratory conditions we present Receiver Operating Characteristic (ROC) performance data and an evaluation of the span of time necessary for recognition. While MCHOG in special cases indicates detection of the intention before the whole body moves, on average it allows for detection of gait initiation within 6 frames at a frame rate of 50 Hz and an accuracy of 80%. In addition to a comprehensive evaluation under laboratory conditions we demonstrate feasibility of the methods in a real world intersection scenario and we show the gain which we achieve with MCHOG compared to the IMM-EKF approach.

A kinematic model of Kármán gaiting in rainbow trout

A mechanistic understanding of how fishes swim in unsteady flows is challenging despite its prevalence in nature. Previous kinematic studies of fish Kármán gaiting in a vortex street behind a cylinder only report time-averaged measurements, precluding our ability to formally describe motions on a cycle-by-cycle basis. Here we present the first analytical model that describes the swimming kinematics of Kármán gaiting trout with 70-90% accuracy. We found that body bending kinematics can be modelled with a travelling wave equation, which has also been shown to accurately model free-stream swimming kinematics. However, free-stream swimming and Kármán gaiting are separated in the parameter space; the amplitude, wavelength and frequency values of the traveling wave equation are substantially different for each behavior. During Kármán gaiting, the wave is initiated at the body center, which is 0.2L (where L is total body length) further down the body compared with the initiation point in free-stream swimming. The wave travels with a constant speed, which is higher than the nominal flow speed just as in free-stream swimming. In addition to undulation, we observed that Kármán gaiting fish also exhibit substantial lateral translations and body rotations, which can constitute up to 75% of the behavior. These motions are periodic and their frequencies also match the vortex shedding frequency. There is an inverse correlation between head angle and body angle: when the body rotates in one direction, the head of the fish turns into the opposite direction. Our kinematic model mathematically describes how fish swim in vortical flows in real time and provides a platform to better understand the effects of flow variations as well as the contribution of muscle activity during corrective motions.

Effects of lateral morphology on swimming performance in two sturgeon species

Fish express a high degree of diversity in morphology, which is closely related to behaviors such as swimming ability. The effect of morphology on swimming performance is explored using geometric morphometric analyses and classic critical swimming speed (Ucrit) tests in Chinese sturgeon Acipenser sinensis and Siberian sturgeon A. baerii. It was found that A. sinensis is a stronger swimmer compared to A. baerii, with an average 25% higher Ucrit (expressed in body lengths per second). In A. sinensis, the depth and length of the snout and the trailing edge length of the dorsal fin were negatively correlated with Ucrit, whereas the height of the trunk anterior, the leading edge length of the dorsal fin and anal fin, and the length and width of the ventral lobe were positively related to Ucrit; similar relationships between Ucrit and morphological characters of the anterior trunk, dorsal fin, anal fin and caudal fin were found in A. baerii. Moreover, although the degree of upward bending of the snout of A. baerii was negatively related to Ucrit, there was a positive relationship between the length of the caudal peduncle and Ucrit as well as between the dorsal tail lobe and Ucrit. In addition, the streamline index (SI) was calculated by comparing landmark coordinates on the trunk displayed in the relative warp, with its corresponding point on the NACA (the U.S. National Advisory Committee for Aeronautics) airfoil shape. SI showed that the body shape in RW1 of the A. baerii with more swimming capacity was more approximate to the NACA 0016 airfoil shape, but there was no such symmetry for A. sinensis, possibly due to body bending caused by stiffness.

Transgenerational effects of heavy metals on L3 larva of Caenorhabditis elegans with greater behavior and growth inhibitions in the progeny

Heavy metals are ubiquitous environmental pollutants, and their toxic effects have been widely studied. However, their transgenerational effects between parent and progeny at environmental relevant concentrations need further investigations. Currently, L3 stage of Caenorhabditis elegans was exposed to aqueous metals (Cd, Cu, Pb and Zn) at environmentally realistic concentrations for 96h. The whole exposure time covered the formation of sperm, ovum and eggs. Subsequently the behavior and growth indicators were measured. The parent nematodes were then bleached to gain synchronized eggs, which were cultured under non-toxic conditions to L3 stage when the same indicators were measured in the progeny. The parent suffered concentration-dependent inhibitions on behavior and growth. Based on the median effective concentration (EC50) values, body bending frequency showed relatively higher sensitivity than other behavior indicators. The inhibitions on growth and behavior of progeny were more severe than those of the parent, based on their respective EC50 values. Interestingly, Cd was not the most toxic metal in either parent or progeny according to EC50 values, but its EC50 ratios between parent and progeny (EC50, parent/EC50, progeny) were the most significant, indicating its greatest transgenerational effects. The results demonstrated the higher sensitivity of L3 larva stage of C. elegans in the transgenerational effect studies than other life stages used before. Our findings suggested that parental exposure to heavy metals can multiply their harmful effects in following generations.

고무 마운트로 이산 지지되는 플로팅 슬래브 궤도의 실모형 실내 실험에서의 정적 및 저주파 대역 동적 거동

Recently, with increasing social interests on noise and vibration induced by railway traffic, the application of floating slab track that can efficiently reduce the railway vibration is increasing. In this study, to more accurately understand the dynamic behavior of the floating slab track, a laboratory mock-up test has been performed, and the static and dynamic behaviors at frequency range near the system resonance frequency were explored. Based on the test results, the design of the floating slab track and the structural analysis model used in the design have been verified. The analytic and test results demonstrate that the dominant frequency of the floating slab track occurs at the frequencies between vertical rigid body mode natural frequency and bending mode natural frequency, and the dominant deformation mode is close to the bending mode. This suggests that in the design of the floating slab track, the bending rigidity of the slab and the boundary conditions at slab joints and slab ends should be taken into consideration. Also, the analytic results by the two-dimensional finite element analysis model using Kelvin-Voigt model, such as static and dynamic deflections and force transmissibility, are found in good agreement with the test results, and thus the model used in this study has shown the reliability suitable to be utilized in the design of the floating slab track.

Toxicity of Sodium Fluoride to Caenorhabditis elegans

ObjectiveTo investigate the toxic effect of sodium fluoride (NaF) on the nematode Caenorhabditis elegans (C. elegans). MethodsAdult C. elegans were exposed to different concentrations of NaF (0.038 mmol/L, 0.38 mmol/L, and 3.8 mmol/L) for 24 h. To assess the physiological effects of NaF, the brood size, life span, head thrashes, and body bend frequency were examined. Reactive oxygen species (ROS) and cell apoptosis were detected as parameters of biochemical response. The gene expressions were determined by real-time polymerase chain reaction (PCR) to assess the molecular-level response. ResultsAt the physiological level, the brood size of C. elegans exposed to 0.038 mmol/L, 0.38 mmol/L, and 3.8 mmol/L concentrations of NaF were reduced by 6%, 26%, and 28% respectively in comparison with the control group. The maximum life spans of C. elegans exposed to 0.038 mmol/L, 0.38 mmol/L, and 3.8 mmol/L concentrations of NaF were reduced by 3 days and 5 days, respectively. Head thrashes and body bend frequency both decreased with increasing concentrations of NaF. At the biochemical level, the production of ROS and the incidence of cell apoptosis increased with increasing concentrations of NaF(P<0.05). At the molecular level, different concentrations of NaF exposure raised the expression of stress-related genes, such as hsp16.1, sod-3, ctl-2, dhs-28, gst-1, and cep-1. ConclusionNaF exposure could induce multiple biological toxicities to C. elegans in a concentration-dependent manner. These toxicities may be relevant to the oxidative stress induced by increased ROS production and accumulation in C. elegans.

Keeping track of worm trackers

C. elegans is used extensively as a model system in the neurosciences due to its well defined nervous system. However, the seeming simplicity of this nervous system in anatomical structure and neuronal connectivity, at least compared to higher animals, underlies a rich diversity of behaviors. The usefulness of the worm in genome-wide mutagenesis or RNAi screens, where thousands of strains are assessed for phenotype, emphasizes the need for computational methods for automated parameterization of generated behaviors. In addition, behaviors can be modulated upon external cues like temperature, O(subscript)2(/subscript) and CO(subscript)2(/subscript) concentrations, mechanosensory and chemosensory inputs. Different machine vision tools have been developed to aid researchers in their efforts to inventory and characterize defined behavioral "outputs". Here we aim at providing an overview of different worm-tracking packages or video analysis tools designed to quantify different aspects of locomotion such as the occurrence of directional changes (turns, omega bends), curvature of the sinusoidal shape (amplitude, body bend angles) and velocity (speed, backward or forward movement).

Neurotoxicological evaluation of microcystin-LR exposure at environmental relevant concentrations on nematode Caenorhabditis elegans

Previous studies have not examined the adverse effects of microcystin-LR (MC-LR) at environmental relevant concentrations on the development and functions of nervous system. The neurotoxic effects of MC-LR exposure on neurotransmitter systems were investigated in Caenorhabditis elegans. After exposing L1 larvae to 0.1, 1, 10, and 100 μg l(-1) of MC-LR for 8 and 24 h, the adverse effects on GABAergic, cholinergic, serotonergic, dopaminergic, and glutamatergic neurons were examined. The expression levels of genes required for development and functions of GABAergic neurons were further investigated. Body bend frequency and head thrash frequency decreased significantly after MC-LR exposure for 8 h at concentrations more than 1 μg l(-1) and after MC-LR exposure for 24 h at concentrations more than 0.1 μg l(-1). Loss of GABAergic neurons increased significantly in a dose-dependent manner after MC-LR exposure at concentrations more than 0.1 μg l(-1). In contrast, no obvious neuronal losses or morphologic changes were observed in cholinergic, serotonergic, dopaminergic, and glutamatergic neurons in MC-LR-exposed nematodes. Quantitative real-time PCR assay further showed that expression levels of unc-30, unc-46, unc-47, and exp-1 genes required for development and function of GABAergic neurons decreased significantly in nematodes exposed to MC-LR at concentrations more than 0.1 or 1 μg l(-1). MC-LR at environmental relevant concentrations caused neurobehavioral defects, which may be largely due to the neuronal loss and the alterations of expression level of genes required for GABAergic neurotransmitter system in C. elegans.

Hip geometry in diabetic women: Implications for fracture risk

ObjectiveWomen with type 2 diabetes mellitus (T2DM) have a higher risk of fractures despite increased bone mineral density (BMD) as compared to women without diabetes. We hypothesized that bone strength is diminished in women with T2DM after accounting for lean body mass, which may contribute to their increased fracture risk. MethodsParticipants from Women's Health Initiative Observational Study were included in this cross-sectional study. These analyses include 3 groups of women: 1) T2DM women on diet or oral hypoglycemic agents (n=299); 2) T2DM women on insulin therapy (with or without oral agents) (n=128); and 3) Non-diabetic control women (n=5497). Hip structural analyses were done using the validated Beck's method on hip scans from dual energy x-ray absorptiometry (DXA). We compared BMD and section modulus (bending strength) at the narrow neck with and without correcting for total body DXA lean body mass. ResultsWomen in all three groups were of similar ages (63.7, 64.6 and 64.2years, respectively) and heights, but those with T2DM were heavier, with greater lean body weight vs controls (P<.001). In both diabetic groups, absolute BMD and section modulus were higher compared with controls. However, after adjusting for total lean body weight, diabetic women on insulin had significantly lower BMD and section modulus. ConclusionAdjusted for lean body weight, the BMD and bending strength in the femoral neck are significantly lower in insulin-treated diabetic women vs controls. This may represent altered adaptation of bone modeling and explain the higher fracture risk in patients with T2DM.

Undulatory Locomotion of Caenorhabditis elegans on Wet Surfaces

The physical and biomechanical principles that govern undulatory movement on wet surfaces have important applications in physiology, physics, and engineering. The nematode Caenorhabditis elegans, with its highly stereotypical and functionally distinct sinusoidal locomotory gaits, is an excellent system in which to dissect these properties. Measurements of the main forces governing the C. elegans crawling gait on lubricated surfaces have been scarce, primarily due to difficulties in estimating the physical features at the nematode-gel interface. Using kinematic data and a hydrodynamic model based on lubrication theory, we calculate both the surface drag forces and the nematode's bending force while crawling on the surface of agar gels within a preexisting groove. We find that the normal and tangential surface drag coefficients during crawling are ∼222 and 22, respectively, and the drag coefficient ratio is ∼10. During crawling, the calculated internal bending force is time-periodic and spatially complex, exhibiting a phase lag with respect to the nematode's body bending curvature. This phase lag is largely due to viscous drag forces, which are higher during crawling as compared to swimming in an aqueous buffer solution. The spatial patterns of bending force generated during either swimming or crawling correlate well with previously described gait-specific features of calcium signals in muscle. Further, our analysis indicates that one may be able to control the motility gait of C. elegans by judiciously adjusting the magnitude of the surface drag coefficients.

Challenging zebrafish escape responses by increasing water viscosity

Escape responses of fishes have long been studied as a model locomotor behavior in which hypothesized maximal or near-maximal muscle power output is used to generate rapid body bending. In this paper we present the results of experiments that challenged zebrafish (Danio rerio) to perform escape responses in water of altered viscosity, to better understand the effects that the fluid mechanical environment exerts on kinematics. We quantified escape kinematics using 1000 frames s(-1) high-speed video, and compared escape response kinematics of fish in three media that differed in viscosity: 1 mPa s (normal water), 10 mPa s and 20 mPa s (20 times normal water viscosity). We hypothesized that because viscosity is increased but not density there will be a different effect on kinematic variables resulting from unsteady (acceleration-dependent) hydrodynamic forces and steady (velocity-dependent) ones. Similarly, we hypothesized that the kinematics of stage 1 will be less affected by viscosity than those of stage 2, as higher angular velocities are reached during stage 1 resulting in higher Reynolds numbers. Our results showed a significant overall effect of viscosity on escape response kinematics but the effect was not in accordance with our predictions. Statistical tests showed that increasing viscosity significantly decreased displacement of the center of mass during stage 1 and after 30 ms, and decreased maximum velocity of the center of mass, maximum angular velocity and acceleration during stage 1, but increased time to maximum angular acceleration and time to maximum linear velocity of the center of mass. Remarkably, increasing water viscosity 20 times did not significantly affect the duration of stage 1 or stage 2.

Effects of Liraglutide on Caenorhabditis elegans

Aims: C. elegans was used as a model organism to study effects of glucagon-like peptide-1 (GLP-1) analogue liraglutide, which is known to have neuroprotective effects, on glucose driven changes of lifespan and neuronal function. The short lifespan, good accessibility and strong homologies between human and C. elegans insulin signal transduction system offers excellent opportunities to study molecular mechanisms being responsible for these changes. In C. elegans, high glucose conditions impair neuronal function and reduce lifespan, likely driven by formation of advanced glycation end products (AGEs). In addition, GLP-1 homologue can be found in C. elegans. Aim of the study was to study effects of liraglutide on C. elegans with respect to lifespan and neuronal function under standard (ST) and high glucose (HG) conditions. Relative head motility, body angular velocity and body bending frequency were used as a parameter of neuronal function or damage, respectively.