In vivo physiological recording from the lateral line of juvenile zebrafish

Hair cells are sensory receptors responsible for transducing auditory and vestibular information into electrical signals, which are then transmitted with remarkable precision to afferent neurons. The zebrafish lateral line is emerging as an excellent in vivo model for genetic and physiological analysis of hair cells and neurons. However, research has been limited to larval stages because zebrafish become protected from the time of independent feeding under European law (from 5.2 days post-fertilization, dpf, at 28.5°C). In larval zebrafish, the functional properties of hair cells, as well as those of other excitable cells, are still immature. We have developed an experimental protocol to record electrophysiological properties from hair cells of the lateral line in juvenile zebrafish. We found that the anaesthetic benzocaine at 50 mg l(-1) was an effective and safe anaesthetic to use on juvenile zebrafish. Concentrations up to 300 mg l(-1) did not affect the electrical properties or synaptic vesicle release of juvenile hair cells, unlike the commonly used anaesthetic MS-222, which reduces the size of basolateral membrane currents. Additionally, we implemented a method to maintain gill movement, and as such respiration and blood oxygenation, via the intubation of > 21 dpf zebrafish. The combination of benzocaine and intubation provides an experimental platform to investigate the physiology of mature hair cells from live zebrafish. More generally, this method would allow functional studies involving live imaging and electrophysiology from juvenile and adult zebrafish. This article is protected by copyright. All rights reserved

Biophysical Properties of Zebrafish Hair Cells

Hair cells are specialized mechanosensory receptors in vertebrates that detect and process auditory and vestibular information with remarkable precision, fidelity and efficiency (Schwander et al., 2010). Most of our knowledge about these cells stems from in vitro preparations using isolated tissue, which creates the need for a relatively simple in vivo vertebrate model to study hair cells. The zebrafish (Danio rerio) is being increasingly used to study the genetic basis of hearing and deafness but also the function and physiology of hair cells (Nicolson, 2005). However, the use of the zebrafish as an in vivo model to study hair cell function is currently limited by our poor understanding of their biophysical properties. The aim of this study was to provide a detailed description of the biophysical properties of zebrafish hair cells both in the lateral line as well as inner ear during early and mature stages of fish development. I have used single cell patch-clamp electrophysiology to measure potassium currents and synaptic transmission in hair cells. I found that hair cells from the lateral line and inner ear show different current types, the expression of which depends upon the position of the cell within the lateral line neuromast or inner ear macula. Moreover, I found that the abundance of hair cell types in the lateral line changes over time, which potentially reflects adaptations to a changing sensory environment for the fish. The synaptic machinery of the lateral line hair cells is comparable in terms of efficiency to its mammalian counterpart, but less sensitive. Lastly, I have also developed an approach to study hair cell properties in vivo in the juvenile fish

What motivates academic dishonesty in students? A reinforcement sensitivity theory explanation

BACKGROUND: Academic dishonesty (AD) is an increasing challenge for universities worldwide. The rise of the Internet has further increased opportunities for students to cheat. AIMS: In this study, we investigate the role of personality traits defined within Reinforcement Sensitivity Theory (RST) as potential determinants of AD. RST defines behaviour as resulting from approach (Reward Interest/reactivity, goal-drive, and Impulsivity) and avoidance (behavioural inhibition and Fight-Flight-Freeze) motivations. We further consider the role of deep, surface, or achieving study motivations in mediating/moderating the relationship between personality and AD. SAMPLE: A sample of UK undergraduates (N = 240). METHOD: All participants completed the RST Personality Questionnaire, a short-form version of the study process questionnaire and a measure of engagement in AD, its perceived prevalence, and seriousness. RESULTS: Results showed that RST traits account for additional variance in AD. Mediation analysis suggested that GDP predicted dishonesty indirectly via a surface study approach while the indirect effect via deep study processes suggested dishonesty was not likely. Likelihood of engagement in AD was positively associated with personality traits reflecting Impulsivity and Fight-Flight-Freeze behaviours. Surface study motivation moderated the Impulsivity effect and achieving motivation the FFFS effect such that cheating was even more likely when high levels of these processes were used. CONCLUSIONS: The findings suggest that motivational personality traits defined within RST can explain variance in the likelihood of engaging in dishonest academic behaviours

Experimental research into uniformity in spreading mineral fertilizers with fertilizer spreader disc with tilted axis

Improving the efficiency in the work process of mineral fertilizer dressing is a topical problem in today’s agricultural industry. The authors have developed a design of the fertilizer spreading tool with a tilted axis and carried out field experiment investigations on it. It has been established by the results of the investigations that the non-uniformity in the spreading of mineral fertilizers along the line of their departure from the fertilizer spreading tool with a tilted axis is most strongly affected by the disc rotation frequency. The obtained results provide for selecting the optimum parameters and modes of operation for the tool under consideration in the situation, when it is installed in fertilizer placing machines. Also, it has been established that increasing the spreading disc rotation frequency in such a tool from 600 to 800 rpm results in the growth of the effective range of mineral fertilizer spreading along the placing line at a level of 10.5 m. Increasing the disc’s angle of inclination to the horizontal plane to 20º results in the rise of the effective fertilizer spreading range at a level of the 48th tray (24 m) inclusive as well as the increase of the distance between the tool and the tray that contains the maximum share of the spread fertilizers (5.1%) to 24 trays (12 m). At a constant rotation frequency of the disc in the tilted-axis fertilizer spreading tool, in all its kinematic modes of operation, an increase in the angle of its disc’s inclination to the horizontal plane results in the rise of the indices representing the distribution of the mineral fertilizers over the trays along the line of their placing. The width of the mineral fertilizer spreading can be controlled by adjusting the rotation frequency of the disc in the tilted-axis fertilizer spreading tool, when it is set at an angle to the horizontal plane, similar to how it is done in state-of-the-art fertilizer placing machines with horizontally positioned discs in their centrifugal spreading tools. The rotation frequency of the disc in the tilted-axis fertilizer spreading tool has the most significant effect on the coefficient of variation incidental to the distribution of the mineral fertilizers along the line of their placing

The coupling between Ca2+ channels and the exocytotic Ca2+ sensor at hair cell ribbon synapses varies tonotopically along the mature cochlea.

The cochlea processes auditory signals over a wide range of frequencies and intensities. However, the transfer characteristics at hair cell ribbon synapses are still poorly understood at different frequency locations along the cochlea. Using recordings from mature gerbils, we report here a surprisingly strong block of exocytosis by the slow Ca(2+) buffer EGTA (10 mM) in basal hair cells tuned to high frequencies (∼30 kHz). In addition, using recordings from gerbil, mouse and bullfrog auditory organs, we find that the spatial coupling between Ca(2+) influx and exocytosis changes from nanodomain in low-frequency tuned hair cells (∼2 kHz). Hair cell synapses have thus developed remarkable frequency-dependent tuning of exocytosis: accurate low-latency encoding of onset and offset of sound intensity in the cochlea's base and submillisecond encoding of membrane receptor potential fluctuations in the apex for precise phase-locking to sound signals. We also found that synaptic vesicle pool recovery from depletion was sensitive to high concentrations of EGTA, suggesting that intracellular Ca(2+) buffers play an important role in vesicle recruitment in both low- and high-frequency hair cells. In conclusion, our results indicate that microdomain coupling plays an important role in the exocytosis of high-frequency hair cells, and suggest a novel hypothesis for why these cells are more susceptible to sound-induced damage than low-frequency cells; high-frequency IHCs must have a low Ca(2+) buffer capacity in order to sustain exocytosis, thus making them more prone to Ca(2+)-induced cytotoxicity. SIGNIFICANCE STATEMENT: In the inner ear, sensory hair cells signal reception of sound. They do this by converting the sound induced movement of their hair bundles present at the top of these cells, into an electrical current. This current depolarizes the hair cell and triggers the calcium-induced release of the neurotransmitter glutamate that activates the postsynaptic auditory fibres. The speed and precision of this process enables the brain to perceive the vital components of sound such as frequency and intensity. We show that the coupling strength between calcium channels and the exocytosis calcium sensor at inner hair cell synapses changes along the mammalian cochlea such that the timing and/or intensity of sound is encoded with high precision

Research into engineering and operation parameters of mineral fertiliser application machine with new fertiliser spreading tools

The output capacity of the machine for top spreading the soil with solid mineral fertilisers can be raised by means of increasing its working width. The authors have carried out field trials and field experiment investigations with the MVU-8 granulated mineral fertilizer spreading machine equipped with two prototype units of the centrifugal fertiliser spreading tool, in which the axis can be tilted at different angles to the vertical line. In accordance with the results of the completed investigations, it has been established that setting the axial tilt angle of the centrifugal operating device in the fertiliser spreading tool within the range of 25–30° provides for achieving a productivity of the combined tractor-implement unit for applying mineral fertilisers at a level of 35–40 ha per working shift hour. The best performance in the fertiliser application with regard to both the working width and the fertiliser placing distribution uniformity is ensured at angles of inclination of the disc in the fertiliser spreading tool with respect to the horizontal plane within the range of 25–30°. At these angles, the uneven distribution of the fertiliser over the working width is equal to 19.2%, the uneven distribution of the fertiliser along the unit’s line of travel is equal to 8.9%, while the deviation in the dosage of the applied fertilisers from the set value is equal to 7.5%

Operational and technological properties of ploughing block-modular machine-and-tractor aggregate

One of the topical directions in the development of agricultural tractor construction can be the formation of machine-and-tractor units according to a modular principle, using technological modules with the driving wheels. The aim of this work is to study the possibilities how to increase the operational and technological indicators of the operation of an agricultural aggregate in a modular aggregation system due to the selection of rational parameters of an elastic-dissipative connection of the energy and the technological modules. The obtained data were processed by statistical methods on a PC, using correlation and dispersion analyses. It has been established by experimental investigation that the operation of a ploughing block-modular aggregate, while ensuring rational rigidity of the connection of its energy and technological modules, is achieved by throttling the hydraulic system of its rear suspension at the level of 75%, characterised by an increase in its performance by 6% and a decrease in the specific fuel consumption by 12.4%. In addition, the level of vertical vibration load of the operator corresponds to the allowed fatigue rate for 8 h of work

Theoretical study on motion of potato tuber on surface of separator

The aim of the study was to determine the optimal design and kinematic parameters of the separator that cleans potatoes from impurities and has a design of the spiral type. The authors have devised a highly efficient design of the spiral type potato heap separator, in which the motion of the potato tubers takes place in the channel formed by two spiral members made in the form of cylindrical spiral springs. In order to substantiate the optimal kinematic and design parameters of the new spiral type potato heap separator, the authors have generated a mathematical model of the motion of a single potato tuber on the cleaning surface formed by two spirals. As a result of solving the obtained analytical expressions, the graphical relations between the parameters of the investigated process of the motion of a single potato tuber body situated between two adjacent spirals have been plotted, which has enabled selecting the optimal design and kinematic parameters of the spiral separator. It has been established in the completed investigation that the angular velocity of rotation of the cleaning rolls has to be within the range of 27 40 rad s -1 in order to ensure the efficient transportation and cleaning of the potato tuber with a diameter of 50 mm that moves on the surface of the spiral with a radius of 75 mm wound from the round bar with a diameter of 15 mm, in case the spirals are mounted with an eccentricity of 10 mm. By analysing the kinematics of motion of the potato tuber on the surface of the spiral type cleaning machine, in case the tuber contacts the spirals at two points, it has been established that the increase of the angular velocity of rotation of the spirals results in the respective growth of the transportation capacity of the cleaning tool, while the separating efficiency at the same time becomes reduced to some extent

Dynamics of Temperature Variation in Soil under Fallow Tillage at Different Depths

One of the important processes taking place during soil surface tillage is the variation of the soil temperature at different depths. The paper presents the results of research into the dynamics of soil temperature variation in terms of such parameters of the soil as its thermal diffusivity and temperature oscillation frequency. It has been established that the temperature oscillation amplitude decreases when the depth increases, following the logarithmic law. In this variation, the temperature difference between the 0–5 cm layer and the adjacent 5–10 cm layer has the greatest value. This circumstance is a favorable factor for the fallow tillage technology, where the soil is regularly cultivated to a depth of no more than 5 cm, in case of a moisture deficit. A decrease in the frequency of the soil temperature oscillations can result in the reduced level of its heating in different layers. In terms of qualitative changes, the reduction in soil thermal diffusivity results in the amplitude of the soil temperature oscillations being lowered and at the same time the maximum of these oscillations being shifted towards a delay

The effect of a lateral airflow created on nozzle tip on the spray droplets deposition

Improved application efficacy of a plant protection products by using a pneumatic device to change the dispersion of spray droplets is depended on the intensity of crosswind. The laboratory investigations of the spraying process of plants by means of the nozzles of a pneumatic system determined the quality indicators of pressure in the injection process of 0.4 MPa – the droplet coating density of 19–46 pcs cm2 –1 for the weighted mean droplet diameters (WMD) in the other experimental variants was within 304–543 μm. These indicators were compared with those for the standard, anti-drift and air injection nozzle types in which the droplet coating density was 23–59 pcs cm2 –1 and the weighted mean droplet diameters (WMD) were in the range of 350 to 485 μm. An analytical dependence was obtained of the influence of the lateral airflow and air pressure in the pneumatic system upon the amount of the deposited spray liquid