Tail Deformities Research Articles

Adverse effect of cylindrospermopsin on embryonic development in zebrafish (Danio rerio).

Eutrophication of freshwater bodies increases the occurrence of toxic cyanobacterial blooms. The cyanobacterial toxin cylindrospermopsin (CYN) is receiving great interest due to its increasing presence in waterbodies. However, the toxic effects of CYN on zebrafish development are poorly understood, especially the toxicological mechanism, which is still unclear. In this study, we examined the adverse effects of CYN on embryonic development in zebrafish. CYN (2-2000 nM) exposure decreased embryos survival rate, hatching rate, body length and eye size in a concentration-dependent manner and caused abnormalities in embryo morphology, including pericardial edema, spinal curvature, tail deformity, uninflated swim bladder, cardiac and vascular defects. CYN at concentrations of 20 nM or higher significantly increased ROS level and promoted cell apoptosis in zebrafish embryos. To preliminarily elucidate the potential mechanism of zebrafish developmental toxicity caused by CYN, we examined the expression of oxidative stress- and apoptotic-related genes. CYN could promote the expression of oxidative stress-related genes (SOD1, CAT and GPx1) and induce changes in transcriptional levels of apoptotic-related genes (p53, Bax and Bcl-2). Taken together, CYN induced adverse effects on zebrafish embryos development, which may associate with oxidative stress and apoptosis. These outcomes will advance our understanding of CYN toxicity, environmental problems and health hazards caused by climate changes and eutrophication.

Toxicity of PM2.5 Based on a Battery of Bioassays

To accurately evaluate the biotoxicity of PM2.5, PM2.5 samples from winter fog-haze days, winter normal days, and summer days in Changzhou were selected for evaluation based on the acute toxicity of luminescent bacteria and zebrafish embryos and the cytotoxicity of human lung adenocarcinoma cells in vitro (A549). The three atmospheric conditions and the physical and chemical indicators were also evaluated using correlation analysis. The PM2.5 samples showed either acute or developmental toxicity during all three periods. The toxicity unit (TU) of the luminescent bacteria for the winter fog-haze days, winter normal days, and summer days were 1.74 (toxic), 1.19 (toxic), and 0.92 (slightly toxic), respectively. The maximum TU of the zebrafish embryos was for winter normal days (TU=1.14, toxic) followed by winter fog-haze days (TU=0.79, slightly toxic), and summer days (TU=0, non-toxic). The highest TU of A549 was for winter fog-haze days (TU=0.61, toxic) followed by summer days (TU=0.38, toxic) and winter normal days (TU=0.31, toxic). With respect to developmental toxicity, with the exception of summer day samples, the PM2.5 samples from the other two periods had detrimental effects on the development of zebrafish embryos, mainly showing pericardial edema, a bent notochord, and tail deformity. The average toxicity (AvTx), toxic print (TxPr), and most sensitive test (MST) indices showed that the PM2.5 samples from winter fog-haze days and winter normal days exhibited toxicity, while samples from the summer days showed slight toxicity; PM2.5 samples from winter fog-haze days had the highest level of comprehensive toxicity. In addition, luminescent bacteria were the most sensitive to PM2.5 samples, followed by zebrafish embryos and A549. The results of chemical analysis and biological toxicity tests show that the pollutants contained in PM2.5 have a biological toxicity effect, which can provide a basis for the comprehensive assessment of PM2.5 biological toxicity and human health risks.

Exposure to the azo dye Direct blue 15 produces toxic effects on microalgae, cladocerans, and zebrafish embryos.

Aquatic pollution caused by dyes has increased together with the growth of activities using colorants such as the textile, leather, food, and agrochemicals industries. Because most popular azo dyes are synthesized from benzidine, a carcinogenic compound, a threat to aquatic biota could be expected. The use of single species for toxicity assessment provides limited data, so a battery of test organisms, including representatives of different trophic levels such as algae, zooplankters, and fish, could undoubtedly provide more information. Therefore, our study was aimed at evaluating the toxic effect of the azo dye Direct blue 15 (DB15) on a battery of bioassays using a primary producer (Pseudokirchneriella subcapitata), a primary consumer (Ceriodaphnia dubia), and a secondary consumer (Danio rerio). P. subcapitata was more sensitive to DB15 (IC50 = 15.99 mg L-1) than C. dubia (LC50: 450 mg L-1). In the algae exposed to DB15, chlorophyll-a and -b were significantly increased, and carotenoids were reduced. The concentrations of protein, carbohydrates, and lipids per cell in P. subcapitata exposed to all DB15 concentrations were significantly higher than that measured in control. At 25 mg L-1 of DB15, survival, total progeny, and the number of released clutches were significantly decreased, and the start of reproduction was delayed in C. dubia. DB15 did not induce lethal or sublethal effects in D. rerio embryos at any of the tested concentrations from 24 to 72 h post-fertilization (hpf), but from 96 to 144 hpf, the larvae exposed to 100 and 500 mg L-1 developed yolk sac edema, curved tail, and skeletal deformations. After 144 hpf, DB15 produced a significant increase in embryos without a heartbeat, as the concentration of dye raised. The textile-used, azo dye DB15, caused toxic effects of different magnitude on microalgae, cladocerans, and zebrafish embryos; for this reason, the discharge of this colorant into waterbodies should be regulated to prevent environmental impacts.

Retrospective Evaluation of The Result of Fixation of Lateral Humeral Condyle Fractures by K-Wires versus Cannulated Screws in Children

Background: fractures of the lateral condyle of the humerus represent the second most common type of fracture of the elbow in children. Although this injury is seen at all ages, it is predominately observed in children aged between 5 and 10 years. Objective: the purpose of this study is retrospective evaluation of the results of fixation of lateral humeral condyle by K-wires versus cannulated screws in children by assessment of: 1-Time to full union. 2-Range of motion.3- Percentage of complications. 4-According to Hardacre criteria. Patients and methods: a retrospective study for evaluation of the result of fixation of lateral humeral condyle fractures in children by K-wires vs cannulated screws. Our series was conducted in Al-Azher University Hospitals. 20 patients with humeral condyle fractures were treated by K-wires and cannulated screws. Results: in group A patients presented by complications as following: extension lag 1 (10%), delayed union (healing at 3–6 months) 1 (10%), revision 1 (loss of reduction at the 3rd day of operation and required revision using pin fixation) (10%), fish tail deformity 0 (0%) and 7 (70%) had no complications. While in group B: extension lag 1 (10%), delayed union 2 (20%), nonunion 1 (10%) (Not healed at greater than 6 months and reoperated using bone graft and pin fixation), revision 0 (0%), fish tail deformity 1 (10%), pin tract infection 1 (10%) and 4 (40%) had no complications. Conclusion: our study supports that screw fixation may be a viable option, with no nonunions and fewer complications than pin fixation.

Analysis of Hydrodynamic Lubrication Considering the Self-Acceleration of a Liquid Conducting Film at Rail–Armature Interface

In a railgun, the melting of the armature as a result of great frictional and Joule heating forms a liquid conducting film over the rail–armature contact surfaces. The magnetic field was concentrated in the trailing surface of the armature and liquid film due to the velocity skin effect. Electromagnetic forces in the longitudinal direction acting on the armature and liquid film could cause a self-acceleration in the film. However, the magnetic lateral force in the film squeezes the armature legs against the rails in the transverse direction. Thus, a diverging film, with a minimum thickness at the leading edge, forms at the rail–armature interface due to easier tail deformation than head for traditional C-shaped armature legs. This paper attempts to investigate the effect of self-acceleration in this diverging film on hydrodynamic lubrication and compared with the traditional lubrication model. Total pressure distribution considering uniform and nonuniform film accelerations is investigated, respectively. It is found that the film’s self-acceleration can generate the positive pressure, strengthening the total pressure distribution. Furthermore, conditions for generating positive pressure distribution under different film accelerations are analyzed and discussed. The results show that the film acceleration can decrease the minimum film’s slope that produces a positive pressure distribution. Total pressure distribution can maintain positive at thinner film when the film acceleration is considered.

Manipulation of gut microbiota during critical developmental windows affects host physiological performance and disease susceptibility across ontogeny.

Colonization of gut microbiomes during early life can shape metabolism and immunity of adult animals. However, most data are derived from antibiotic-treated or germ-free laboratory mammals. Furthermore, few studies have explored how microbial colonization during critical windows influences a suite of other fitness-related traits in wild animals. This study tested whether hatching constitutes a critical developmental window for gut microbiome colonization in wild-caught amphibians and whether perturbations to gut microbiota at hatching shape fitness-related traits of larval growth, metabolism, metamorphosis and disease susceptibility. We sterilized wood frog eggs and then inoculated them with microbes from differing sources, including from another species (bullfrogs) that differ in disease resistance and life history. We measured development, growth and metabolic rates through metamorphosis among individuals from each microbial treatment. A separate group was exposed to an LD50 dose of ranavirus-an emerging disease-to test for microbiome effects on disease susceptibility. We also quantified rates of deformities to test for microbial treatment effects on overall health. Manipulation of microbiota on eggs altered the trajectory of gut microbiome communities across larval ontogeny, though disruption appeared to be transitory. While microbiome structure converged among the treatments by metamorphosis, the effects of disruption on host phenotypes persisted. Larvae inoculated with the bullfrog gut microbiota exhibited accelerated growth and development rates compared to controls. By contrast, sterilized larvae maintained in sterile water for several days after hatching exhibited greater disruption to their gut microbiota across ontogeny, as well as altered metabolism, more tail deformities, and were more likely to die when exposed to an LD50 dose of ranavirus compared to the other treatments. These results suggest perturbations to the microbiota during critical developmental windows can alter the trajectory of the gut microbiome, and have long-term effects on fitness-related traits in larval amphibians. These results suggest that explicit tests of how changes in the composition and abundance of the microbial community shape phenotypes across ontogeny in amphibians could shed light on host-microbe interactions in wildlife, as well as inform conservation efforts to mitigate emerging diseases.

Occurrence of whirling disease symptoms in cultured common carp in Basrah, Iraq

A total of 128 fish samples including 70 Cyprinus carpio Linnaeus, 1758, 10 Leuciscus vorax (Heckel, 1843), 40 Oreochromis aureus (Steindachner, 1864) and eight Planiliza abu (Heckel, 1843) were collected during the period from November 2016 to May 2017. Seven different localities (floating cages, earthen ponds and natural water) in Basrah were investigated. Among some detected fish diseases, whirling disease symptoms was reported for the first time in Iraq in April 2017, from two C. carpio cultured in earthen fish ponds of Marine Science Centre, University of Basrah. The infested fish were dwarfed, with abnormal big head and small body. Grossly signs of the diseases represent fins and tail deformities in addition to open ulcers and losing of scales, and necrosis of skin and muscles. Internally, fish suffered of muscles ecchymosis and vertebral deformities. Histological sections revealed that the spinal cord had healthy structure.

Acmella oleracea (L) R. K. Jansen Reproductive Toxicity in Zebrafish: An In Vivo and In Silico Assessment.

The plant species Acmella oleracea L. is used in the north of Brazil for the treatment of a range of illnesses, such as tuberculosis, flu, cough, and rheumatism and as an anti-inflammatory agent; besides, hydroethanolic formulations with this species are popularly used as a female aphrodisiac agent. However, currently, there are no studies performed evaluating its effect on embryonic development. Hence, this research aimed to evaluate the effects of the hydroethanolic extract of A. oleracea (EHFAo) on the reproductive performance (parental) and embryonic development (F1 generation) of zebrafish, at concentrations of 50, 100, and 200 μg/L. Histopathology of parental gonads after 21 days of exposure to EHFAo reveals few alterations in the ovaries and testes, not impairing the reproduction; an increase of eggs deposition was observed in animals treated with EHFAo at the highest concentrations. Nevertheless, concerning the embryonic development of F1, teratogenic effects were observed including tail deformation, cardiac and yolk edema, scoliosis, and growth retardation; these alterations were more prominent in the groups born from progenitors exposed to the highest concentrations (100 and 200 μg/L.); but only the occurrence of yolk and cardiac edema had a statistically significant difference when compared to the control group. The chromatographic analysis shows that spilanthol (affinin) was the primary compound found in the EHFAo. Hence, in silico assessment was performed to evaluate the pharmacokinetic and toxicological properties of this molecule and 37 metabolites derived from it. Overall, our data show that the treatment caused no detrimental changes in progenitors regarding their gonads or fertility but caused some potentially teratogenic activity in embryos, which may be due to the action of spilanthol's metabolites M3, M6, M7, M8, M16, M28, and M31.

2,4-Dichlorophenoxyacetic acid herbicide effects on zebrafish larvae: development, neurotransmission and behavior as sensitive endpoints.

Assessment of pesticides toxicity using zebrafish early life stages is relevant for aquatic systems safety. This study aimed to evaluate the short-term effects of 2,4-dichlorophenoxyacetic acid (2,4-D) on zebrafish (Danio rerio) embryos from 3h post fertilization to 96hpf. A set of 2,4-D concentrations ranging from 0.32 to 80mg/L were tested and median lethal concentration (LC50) at 96-h was calculated as 2.86mg/L. A sub-teratogenic concentrations range from 0.02 to 0.8mg/L was then used to assess effects at ontogenic, biochemical, and behavioral levels. The main developmental defects were tail deformities and pericardial edema at concentrations equal or above 0.32mg/L. Cholinesterase activity (at 96hpf) and larvae swimming behavior (at 120hpf) were affected even at the lowest tested dose (0.02mg/L). The behavior analysis was a sensitive endpoint, with a decrease in the swimming distance of exposed larvae during light period. The effect of 2,4-D in ChE was translated by an inhibition of the enzyme activity in all treated groups. These findings demonstrate that 2,4-D can alter the cholinergic system by affecting ChE activity which may be involved in the locomotion reduction of exposed larvae and emphasize the potential of neurotransmission and behavioral endpoints as early warning signs of herbicides contamination in aquatic ecosystems.

Exposure to dilute concentrations of bupropion affects zebrafish early life stages

Psychiatric pharmaceuticals are one of the most prescribed active substances globally. Bupropion (BPP) is an antidepressant that acts via inhibition of norepinephrine and dopamine reuptake. It has been found in various water matrices, and thus its effects on aquatic organisms must be studied. The present study aimed to evaluate the acute toxic effects of BPP on zebrafish (Danio rerio) early life stages. For developmental analysis, organisms were exposed for 168 h to concentrations ranging from 0 to 82000 μg/L. Two other experiments were performed by exposing embryos to a wide range of concentrations (from 0 to 50000 μg/L) in order to evaluate BPP effects on embryonic behavior, using the Zebrabox and testing at the biochemical level (acetylcholinesterase, glutathione-S-transferase, lactate dehydrogenase and catalase). Developmental analysis indicated that BPP had low acute toxicity with a calculated 168 h-LC50 of 50346 μg/L. Concentrations equal to or above 44800 μg/L elicited several effects such as hatching delay, edemas and tail deformities. However, concentrations from 7300 μg/L upwards elicited equilibrium alteration. Behavioral analysis showed that BPP affected zebrafish locomotor behavior by decreasing activity at 0.6 μg/L, increasing activity at 8.8 and 158 μg/L, and decreasing activity at 50000 μg/L. Biochemical analysis showed an increase of AChE activity at 158 and 2812 μg/L, an increase in GST at the highest concentrations, CAT alteration and increase of LDH at 0.6, 2812 and 50000 μg/L. We can conclude that BPP affects zebrafish early life stages at environmental concentrations.

Developmental toxicity of the triazole fungicide cyproconazole in embryo-larval stages of zebrafish (Danio rerio).

Cyproconazole is a triazole fungicide used to protect a diverse range of fruits, vegetables, and grain crops. As such, it has the potential to enter aquatic environments and affect non-target organisms. The objective of this study was to assess the acute toxicity of the triazole fungicide cyproconazole to zebrafish embryos by assessing mortality, developmental defects, morphological abnormality, oxidative respiration, and locomotor activity following a 96-h exposure. Zebrafish embryos at 6-h post-fertilization (hpf) were exposed to either a solvent control (0.1% DMSO, v/v), or one dose of 10, 25, 50, 100, 250, and 500μM cyproconazole for 96h. Data indicated that cyproconazole exhibited low toxicity to zebrafish embryos, with a 96-h LC50 value of 90.6μM (~ 26.4mg/L). Zebrafish embryos/larvae displayed a significant decrease in spontaneous movement, hatching rate, and heartbeats/20s with 50, 100, and 250μM cyproconazole exposure. Malformations (i.e., pericardial edema, yolk sac edema, tail deformation, and spine deformation) were also detected in zebrafish exposed to ≥ 50μM cyproconazole, with significant increases in cumulative deformity rate at 48, 72, and 96hpf. In addition, a 20-30% decrease in basal and oligomycin-induced ATP respiration was observed after 24-h exposure to 500μM cyproconazole in embryos. To determine if cyproconazole affected locomotor activity, a dark photokinesis assay was conducted in larvae following 7-day exposure to 1, 10, and 25μM cyproconazole in two independent trials. Activity in the dark period was decreased for zebrafish exposed to 25μM cyproconazole in the first trial, and hypoactivity was also observed in zebrafish exposed to 1μM cyproconazole in a second trial, suggesting that cyproconazole can affect locomotor activity. These data improve understanding of the toxicity of cyproconazole in developing zebrafish and contribute to environmental risk assessments for the triazole fungicides on aquatic organisms. We report that, based on the overall endpoints assessed, cyproconazole exhibits low risk for developing fish embryos, as many effects were observed above environmentally-relevant levels.

Zebrafish embryos exposed to deltamethrin exhibit abnormalities despite induced expression of related genes (you, you-too, momo and u-boot)

Evaluation of the toxic effects of a widely used synthetic pyrethroid, deltamethrin (DM), was carried out in this study. This pesticide is preferred for pest control because of its low environmental persistence and toxicity. We investigated the expression pattern of four genes, namely, you ( you), yot ( you-too), momo ( mom) and ubo ( u-boot) during early development of zebrafish, that is, from 12 hpf to 48 hpf stages. These stages are selected as most of the important developmental aspects take place during this period. All four genes are known to play a vital role in development of notochord and somites. To understand the effect of DM on development, embryos of 4 hpf stage were exposed to two concentrations (100 and 200 µg/L) of DM, and observations were made at 12, 24 and 48 hpf stages. Our earlier studies have shown phenotypic abnormalities such as notochord bending, tail deformation, yolk sac and pericardial edema, lightening of body and eye pigmentation and interfered in somite patterning, during these stages of development. Understanding the relationship of phenotypic abnormalities with these four genes has been our primary objective. These four genes were analyzed by Reverse transcription (RT)-polymerase chain reaction and intensity of the bands has shown induction in their expression after exposure to the toxicant. In spite of the expression of genes, it was noticed that DM caused abnormalities. It can be said from the results that translational pathway could have been affected.

Monitoring wastewater discharge from the oil and gas industry using passive sampling and Danio rerio bioassay as complimentary tools

Produced water (PW) represents the largest volume waste stream in oil and gas production operations from most offshore platforms. PW is difficult to monitor as releases are rapidly diluted and concentrations can reach trace levels. The use of passive samplers can over come this. Here polyethylene (PE) was calibrated for a diverse range of PW pollutants. Zebrafish were exposed to dilutions of PW and passive sampler extracts in order to investigate the relationship between freely dissolved chemical concentrations and acute toxic effects. The raw PW had an LC50 of 13% (percentage of PW in the standardized zebrafish medium). Observed non-viable deformations to embryos (at 5 hpf) included heart and yolk edema, head, spine and tail deformations. The dose-response relationship of lethal effects showed that if 0.0041 g of PE is exposed to this PW, then extracted, 50% of exposed D. rerio will suffer lethal effects. The sum of tested freely dissolved concentrations that led to 50% lethal effects (mortality and non-viable deformations) was 2.32 × 10−4 mg/L for PW and 7.92 × 10−2 mg/L for PE. This implies that exposure to raw PW was more toxic than exposure to PE extracts. This toxicity was attributed both to the presence of contaminants as well as PW salinity. Passive samplers are able to detect very low freely dissolved pollutant concentrations which is important for assessing the spatial dilution of PW releases. Bioassays provide complimentary information as they account for all toxic compounds including those that are not taken up by passive samplers.

High mortality in aquatic predators of mosquito larvae caused by exposure to insect repellent.

In the face of mosquito-borne disease outbreaks, effective mosquito control is a primary goal for public health. Insect repellents, containing active compounds such as DEET and picaridin, are a first defence against biting insects. Owing to widespread use and incomplete sewage treatment, these compounds are frequently detected in surface waters, but their effects on aquatic taxa such as mosquito larvae or their naturally occurring aquatic predators are poorly understood. We investigated the effects of environmentally realistic concentrations of commercial products containing DEET and picaridin on survivorship of mosquito larvae, and their potential indirect effects on survival of larval salamanders, a major predator of mosquito larvae. Larval mosquitos were not affected by exposure to repellents containing DEET or picaridin. We found no larval salamander mortality in control and DEET treatments, but mortality rates in picaridin treatments ranged from 45 to 65% after 25 days of exposure. Salamander larvae exposed to repellents containing picaridin began to display tail deformities and impaired development four days after the experiment began. Our findings suggest the possibility that environmentally realistic concentrations of picaridin-containing repellents in surface waters may increase the abundance of adult mosquitos owing to decreased predation pressure.

Occurrence of whirling disease symptoms in cultured common carp in Basrah, Iraq

A total of 128 fish samples including 70 Cyprinus carpio Linnaeus, 1758, 10 Leuciscus vorax (Heckel, 1843), 40 Oreochromis aureus (Steindachner, 1864) and eight Planiliza abu (Heckel, 1843) were collected during the period from November 2016 to May 2017. Seven different localities (floating cages, earthen ponds and natural water) in Basrah were investigated. Among some detected fish diseases, whirling disease symptoms was reported for the first time in Iraq in April 2017, from two C. carpio cultured in earthen fish ponds of Marine Science Centre, University of Basrah. The infested fish were dwarfed, with abnormal big head and small body. Grossly signs of the diseases represent fins and tail deformities in addition to open ulcers and losing of scales, and necrosis of skin and muscles. Internally, fish suffered of muscles ecchymosis and vertebral deformities. Histological sections revealed that the spinal cord had healthy structure.

Toxic effects of cyhalofop-butyl on embryos of the Yellow River carp (Cyprinus carpio var.): alters embryos hatching, development failure, mortality of embryos, and apoptosis.

As a universal environmental contaminant, the herbicide cyhalofop-butyl is considered to have infested effects on the embryonic development of aquatic species. The present study focused on an assessment of the impacts of cyhalofop-butyl on Yellow River carp embryos. It was found that cyhalofop-butyl inhibited the hatching of the embryos, and the hatching rate decreased with higher concentrations of the herbicide. The mortality rate was increased on exposure to cyhalofop-butyl and was significantly higher in the 1.6 and 2mg/L treatment groups over 48h. All of the embryos of the 2mg/L treatment group died within the 48h post-hatching stage. And the transcription of several embryos related to apoptosis was also influenced by cyhalofop-butyl exposure. Further, cyhalofop-butyl exposure leads to a series of morphological changes (pericardial edema, tail deformation, and spine deformation) in embryos, which were consistent with significant modifications in the associated genes. These results provided a scientific basis for further studies into the effects of cyhalofop-butyl on aquatic organisms.

Design, Modeling, and Integration of a Flexible Universal Spatial Robotic Tail

This paper presents the novel design of a bioinspired robot capable of generating spatial loading relative to its base. By looking to nature at how animals utilize their tails, a bioinspired structure is developed that utilizes a redundant serial chain of rigid links to mimic the continuous deformation of a biological tail. Individual links are connected by universal joints to enable a spatial robot workspace capable of generating spatial loading comprised of pitch, yaw, and roll direction contributions. Two sets of three cables are used to create two actuated segments along the robot. A dynamic model of the robot is derived using prescribed cable displacement trajectories as inputs to determine the resulting joint angle trajectories and cable tensions. Sensors are integrated on-board the robot to calculate joint angles and joint velocities in real-time for use in feedback control. The loading capabilities of the robot are analyzed, and an experimental prototype is integrated and demonstrated.

Developmental toxicity of deltamethrin and 3-phenoxybenzoic acid in embryo–larval stages of zebrafish (Danio rerio)

Synthetic pyrethroids are the major insecticides used widely in agriculture and household pest control. Deltamethrin (DM), a widely used type II pyrethroid insecticide, is a relatively potent neurotoxicant. 3-Phenoxybenzoic acid (PBA) is the major metabolite formed due to metabolism of DM. In order to illustrate the toxic response of zebrafish embryos/larvae to DM and PBA the present research was carried out. For this 4hpf embryos were treated with two concentrations of DM (100 and 200 μg/L) for 48 h and PBA (1000 and 2000 μg/L) for 96 h or 99.9% ethanol (solvent control). Early life stage parameters were observed at specified time points. DM-treated embryo/larvae exhibited increased mortality, delay in hatching time, decrease in percentage of hatched embryos, increase of heartbeat rate and decrease in blood flow; lightening of body and eye pigmentation in a dose dependent manner. Pericardial and yolk sac edema along with were also caused by DM. Along with these crooked notochord, tail deformation was noticed in hatched and unhatched embryos. In case of PBA treated embryos and larvae, increased embryos/larvae length and yolk sac size were observed. Other abnormalities like edema (yolk sac and pericardial), decreased eye and body pigmentation were also observed but in some embryos only. These were not as severe as observed in parental compound indicating that DM is more toxic than its metabolite PBA. The data contributes to a better understanding of the potential consequences of fish exposed to DM and PBA.

Flapping foil power generator performance enhanced with a spring-connected tail

The flexibility effects on the performance of a flapping foil power generator are numerically studied by using the immersed boundary-lattice Boltzmann method at a Reynolds number of 1100. The flapping foil system consists of a rigid NACA0015 foil undergoing harmonic pitch and plunge motions and a passively actuated flat plate pinned to the trailing edge of the rigid foil. The flexibility is modeled by a torsional spring model at the conjuncture of the rigid foil and the tail. Here, a parametric study on mass density and natural frequency is conducted under the optimum kinematic condition of the rigid system identified from the literature and numerical simulations made for reduced frequency f* = 0.04–0.24 and pitch amplitude θ0 = 40°–90°. Four typical cases are discussed in detail by considering time histories of hydrodynamic loads and tail deformations under the optimal and non-optimal kinematic conditions. Results show that under the rigid-system optimal kinematic condition, a tail with appropriate mass density (μ = 0.60) and resonant frequency ( fr*=1.18) can improve the maximum efficiency by 7.24% accompanied by an increase of 6.63% in power compared to those of a rigid foil with a rigid tail. This is because the deflection of the tail reduces the low pressure region on the pressure surface (i.e., the lower surface during the upstroke or the upper surface during the downstroke) caused by the leading edge vortex after the stroke reversal, resulting in a higher efficiency. At high flapping frequencies, a spring-connected tail ( fr*=0.13) eliminates the large spike in the moment observed in high stiffness cases, reducing the power required for the pitch motion, resulting in 117% improvement in efficiency over that with a rigid tail at a reduced frequency of 0.24.

Driving Force for Spontaneous Perforation of Bilayers Formed by Ionic Amphiphiles in Aqueous Salt.

Spontaneous perforation of amphiphilic membranes is important in both living matter and technology because of an impact on functions of biological membranes and shape transitions of self-assembling structures. Nevertheless, no definite molecular mechanism has been established so far even for simple ionic surfactant systems. We show that spontaneous perforation of a bilayer formed by an ionic amphiphile is driven by electrostatics. Creation of large pores with a concave-convex geometry of the rim is promoted by lower electrostatic free energy than that for a flat nonperforated bilayer. The opposite effect comes from the elasticity of the hydrocarbon tails of the amphiphile that prefer flat geometry of a nonperforated bilayer. The balance between electrostatics and tail deformation controls the appearance of pores; this balance is modulated by added salt that screens the electrostatic interactions. We illustrate the proposed mechanism with the aid of classical aggregation model that has been extended by including an analytical description of the electrostatic contribution for the toroidal rim of a pore. Numerical solution of the linearized Poisson-Boltzmann equation confirms the role of electrostatic forces in formation of pores. For the ionic surfactants of CnTAB family, we predict shape transitions including bilayer perforations and formation of branched micellar networks induced by changing salinity or temperature and demonstrate the effect of surfactant's molecular parameters on these transitions.