bluuebunny/crossref_metadata_2025_split huggingface dataset:
Curve Walking in Freely Moving Crayfish (Procambarus Clarkii)
Authors: Domenici Paolo , Jamon Marc , Clarac François 
Published: April 2021

ABSTRACT
The curve walking of freely moving crayfish trained to walk along a curved path during homing behaviour was investigated using a video-analysis system. The leg kinematics and leg phase relationships, as well as the relationship between stepping patterns and body axis rotation measured relative to external references, were studied.
The anterior and posterior extreme positions of the power stroke (AEP and PEP, respectively) and step amplitudes were analysed. As in a previous study on crayfish curve walking on a treadmill, PEPs were more posterior in outer legs (the legs on the outside of the turn) than in the inner legs. As a result, outer legs showed larger step amplitudes than inner legs. Leg kinematics varied within each walking sequence. AEP leg angles (the angles between the body and leg axes at the AEP) tended to decrease over time for inner legs and increase for outer legs. This leg angle drift was present mainly in the anterior legs and it suggests that these legs did not completely compensate for the body rotation after each step. In addition, leg angle asymmetries in a direction opposite to that of leg angle drift were observed at the start of each curve-walking sequence, suggesting that the extensive training (3 weeks) may have allowed crayfish to anticipate the leg angle drift.
The rotational component of curve walking showed a discontinuous pattern, with the animal’s body axis turning towards the inside of the curve only periodically. Analysis of cross-correlation functions showed that the angular acceleration of the body axis in the direction of the turn occurred during the power strokes of inner legs 2 and 5 and outer leg 4. While the tripod formed by these three legs showed in-phase relationships, the legs of the corresponding contralateral tripod (outer legs 2 and 5 and inner leg 4) were not in phase. We hypothesize that inner legs 2 and 5 and outer leg 4 act synergically causing the inward body rotation observed in curve-walking crayfish and that some of the asymmetries found in step geometry may be a passive phenomenon due to the body rotation.
Orthodromically and Antidromically Evoked Local Field Potentials in the Crayfish Olfactory Lobe
Authors: Sandeman D. C. , Sandeman R. E. 
Published: April 2021

ABSTRACT
A local field potential, consistent in form and duration, can be recorded from the olfactory lobe of crayfish following electrical stimulation of the outer flagellum of the antennule. The field potential is reversibly blocked by perfusion of the brain with low-[Ca2+] saline or γ-aminobutyric acid and, to a lesser extent, histamine. Paired shocks to the antennule and antidromic electrical stimulation of olfactory lobe output neurones also partially block the field potential. Comparing the field potential with simultaneously recorded intracellular responses of olfactory interneurones reveals a coincidence between excitatory and inhibitory effects in the interneurones and the appearance of identifiable components of the field potential. We interpret the field potential to reflect the response of neural elements in the olfactory lobe to orthodromic activity in the axons of the olfactory receptor neurones on the antennule. We conclude from the blocking experiments that the greater part of the field potential stems from neurones in the olfactory lobe that are postsynaptic to olfactory receptor neurones. As such, it provides a robust indication of olfactory neurone activity.
The Impact of Endurance Training on Arterial Plasma K+ Levels and Swimming Performance of Rainbow Trout
Authors: Holk Karin , Lykkeboe Gunnar 
Published: April 2021

ABSTRACT
Arterial plasma K+ and lactate concentrations ([K+]a and [lactate]a), as well as blood oxygenation status, were measured in relation to increasing swimming speeds in rainbow trout Oncorhynchus mykiss. Neither [K+]a nor [lactate]a changed at swimming speeds below 1.5 BL s−1, where BL is total body length. Between 1.5 and 2.0 BL s−1, [K+]a started to increase, and above 2.0 BL s−1 both [K+]a and [lactate]a increased with swimming speed. Training shifted the onset of these increases to higher swimming speeds and increased the critical swimming speed (Ucrit) from 2.4 to 3.0 BL s−1. Blood oxygen content showed no changes in control fish, whereas in trained fish it increased by 22 % at the final swimming speed. From the [K+]a data, we suggest that no loss of K+ occurred from the working muscle at low swimming speeds, allowing an unlimited endurance, whereas moderate and higher speeds were probably associated with a loss of K+ from the working muscles, indicating a limited endurance.
Tissue and Whole-Body Extracellular, Red Blood Cell and Albumin Spaces in the Rainbow Trout as a Function of Time: A Reappraisal of the Volume of the Secondary Circulation
Authors: Bushnell P. G. , Conklin D. J. , Duff D. W. , Olson K. R. 
Published: April 2021

ABSTRACT
[58Co]EDTA, [51Cr]RBC and [125I]albumin spaces in the whole body and 28 tissue samples were examined at timed intervals over 16 h in rainbow trout Oncorhynchus mykiss. [58Co]EDTA space (which approximates extracellular fluid volume; ECF) in fins, skin, gallbladder and eye are reported for the first time. After a 16 h equilibration, ECF volume was large (376–726 µl g−1 wet tissue mass) in kidney, swimbladder, skin and fins, moderate (219–313 µl g−1 wet tissue mass) in stomach, skull, spleen, liver, intestine, gills, eye and cecum, and small (53–181 µl g−1 wet tissue mass) in red muscle, fat, brain, gallbladder and white muscle. Whole-body ECF was 387±10.6 µl g−1 (mean ± S.E.M.; N=11). [51Cr]RBC space relative to [58Co]EDTA space was large in spleen, liver, intestine and gill, and low in skin, fins, stomach and skull. Whole-body [51Cr]RBC space was 9.9±0.6 µl g−1 body mass (N=17). Blood volume calculated from [51Cr]RBC space at 16 h and a dorsal aortic hematocrit of 24.5 % was 40.4 µl g−1 body mass. Whole-body [125I]albumin space at 16 h was 118.0±7.4 µl g−1 body mass (N=6), which resulted in an estimated blood volume of 156.6 µl g−1 body mass, nearly four times that estimated from the [51Cr]RBC space. Tissue hematocrits, calculated from [125I]albumin and [51Cr]RBC spaces, were significantly lower than dorsal aortic hematocrit in all tissues except spleen, kidney and liver. [58Co]EDTA and [51Cr]RBC spaces reached equilibrium in nearly all tissues within 1 h, whereas [125I]albumin continued to accumulate in many tissues up 24 h. The disparity between [125I]albumin distribution kinetics compared with the kinetics of [58Co]EDTA and [51Cr]RBC distribution, as well as the accumulation of [125I]albumin in tissues not known to have a secondary circulation, indicates that [125I]albumin is a poor marker of plasma volume in trout and that previous studies based on [125I]albumin clearance from the plasma have overestimated both the volume and the turnover rate of the secondary system. Revised estimates of secondary circulation volume, based on [58Co]EDTA distribution rate, indicate that it is no more than 10–20 % of the volume of the primary circulation.
Neuromuscular Sensitivity to Hydrogen Sulfide in the Marine Invertebrate Urechis Caupo
Authors: Julian David , Dalia Wendy E. , Arp Alissa J. 
Published: April 2021

ABSTRACT
Hydrogen sulfide (HS) is a well-known inhibitor of aerobic respiration via its reversible binding of mitochondrial cytochrome c oxidase, but recent studies have suggested that HS may have other non-respiratory actions. We have studied the effects of HS on spontaneous and evoked contractions in vitro under hypoxic and anoxic conditions in nerve–muscle preparations from the echiuran worm Urechis caupo. Contraction amplitude in response to electric field stimulation under anoxic conditions was completely abolished by HS within minutes in a classic dose–response relationship (Kd=31 mmol l−1, r2=0.86). Exposure of body wall and esophagus to HS in vitro for up to 6 h demonstrated that the contraction amplitude and frequency of spontaneous activity were relatively insensitive to anoxia, but that the sensitivity to HS was similar to that seen in field-stimulated muscle (Kd=2.7–32 mmol l−1). The toxic effects of HS were reversible, with almost complete recovery under anoxic conditions within the first hour. These data indicate that HS at millimolar concentrations can directly inhibit muscle contraction. Although the mechanism of this action is unknown, it does not appear to involve metabolic pathways or oxygen transport.
Cell Volume Regulation In Proximal Renal Tubules From Trout (Salmo Trutta)
Authors: Kanli Hilde , Norderhus Eli 
Published: April 2021

ABSTRACT
Regulatory volume decrease (RVD) following hypo-osmotic stimulation was studied using videometric methods in isolated proximal renal tubules from trout (Salmo trutta). The relative tubule diameter increased by 132.0±4.8 % (maximum swelling within 1 min at 15 and 25 °C and within 4 min at 10 °C) following a change from iso-osmotic (290 mosmol kg−1) to hypo-osmotic (160 mosmol kg−1) Ringer’s solution. The tubule diameter subsequently decreased to approximately one-quarter of the maximal value. Ouabain (1 mmol l−1) reduced cell swelling and inhibited the RVD response by 28.0±10.5 %. Furthermore, increasing the bath K+ concentration by 30 mmol l−1 inhibited RVD by 76.5±3.6 %. The K+ channel blocker quinine, but not Ba2+ (1 and 2 mmol l−1), significantly decreased the RVD response (by 25.0±5.4 and 72.3±5.1 % at 0.1 and 0.5 mmol l−1, respectively). Similarly, increasing the Cl− concentration in the bath from 47 to 102 mmol l−1 induced a significant reduction (45.2±7.9 %) in RVD. The RVD response was also markedly reduced (by 54.7±5.3 %) by the Cl− channel blocker indacrinone (MK-196; 0.5 mmol l−1), but only marginally by 5-nitro-2-(3-phenylpropylamino)benzoic acid (NPPB; 1, 5, 8 and 10 µmol l−1). Addition of the K+/Cl− symport inhibitor furosemide (0.1 mmol l−1) resulted in a 39.8±3.9 % inhibition of RVD. This inhibition could be completely overcome by simultaneous administration of 1 µmol l−1 tributyltin (anion exchanger) and furosemide.
Chelation of either extracellular (1 mmol l−1 EGTA) or both extra- and intracellular Ca2+ (1 mmol l−1 EGTA, 10 µmol l−1 A23187) had no effect on this RVD process. Furthermore, as measured using the fluorescent dye Fura-2/AM, there was no increase in the intracellular free Ca2+ concentration upon hypo-osmotic stimulation. Administration of the 5-lipoxygenase antagonist ETH 615-139 (20 µmol l−1), however, induced a 60 % inhibition of RVD. Simultaneous addition of ETH-615 and either the K+ ionophore gramicidin (0.5 mmol l−1) or the anion exchanger tributyltin (1 µmol l−1) could not reverse the ETH 615-139 inhibition. Finally, administration of the cycloxygenase inhibitor indomethacin had only a small, but significant, effect on RVD.
We conclude that RVD following hypo-osmotic swelling is in these cells a temperature- and ouabain-sensitive process that appears to be the result of K+ efflux through quinine-sensitive, Ba2+-insensitive K+ channels and Cl− efflux through an MK-196- and furosemide-sensitive Cl− conductance that is relatively unaffected by NPPB. This KCl efflux seems to be regulated by eicosanoids produced by the 5-lipoxygenase. Arachidonic acid metabolites from the cycloxygenase pathway are not involved in this process. Similarly, neither extra-nor intracellular Ca2+ appears to be important for the signalling of RVD.
Experimental Approaches Towards Interpreting Dolphin-Stimulated Bioluminescence
Authors: Rohr Jim , Latz Michael I. , Fallon Stewart , Nauen Jennifer C. , Hendricks Eric 
Published: April 2021

ABSTRACT
Flow-induced bioluminescence provides a unique opportunity for visualizing the flow field around a swimming dolphin. Unfortunately, previous descriptions of dolphin-stimulated bioluminescence have been largely anecdotal and often conflicting. Most references in the scientific literature report an absence of bioluminescence on the dolphin body, which has been invariably assumed to be indicative of laminar flow. However, hydrodynamicists have yet to find compelling evidence that the flow remains laminar over most of the body. The present study integrates laboratory, computational and field approaches to begin to assess the utility of using bioluminescence as a method for flow visualization by relating fundamental characteristics of the flow to the stimulation of naturally occurring luminescent plankton.
Laboratory experiments using fully developed pipe flow revealed that the bioluminescent organisms identified in the field studies can be stimulated in both laminar and turbulent flow when shear stress values exceed approximately 0.1 N m−2. Computational studies of an idealized hydrodynamic representation of a dolphin (modeled as a 6:1 ellipsoid), gliding at a speed of 2 m s−1, predicted suprathreshold surface shear stress values everywhere on the model, regardless of whether the boundary layer flow was laminar or turbulent. Laboratory flow visualization of a sphere demonstrated that the intensity of bioluminescence decreased with increasing flow speed due to the thinning of the boundary layer, while flow separation caused a dramatic increase in intensity due to the significantly greater volume of stimulating flow in the wake. Intensified video recordings of dolphins gliding at speeds of approximately 2 m s−1 confirmed that brilliant displays of bioluminescence occurred on the body of the dolphin. The distribution and intensity of bioluminescence suggest that the flow remained attached over most of the body. A conspicuous lack of bioluminescence was often observed on the dolphin rostrum and melon and on the leading edge of the dorsal and pectoral fins, where the boundary layer is thought to be thinnest. To differentiate between effects related to the thickness of the stimulatory boundary layer and those due to the latency of the bioluminescence response and the upstream depletion of bioluminescence, laboratory and dolphin studies of forced separation and laminar-to-turbulent transition were conducted. The observed pattern of stimulated bioluminescence is consistent with the hypothesis that bioluminescent intensity is directly related to the thickness of the boundary layer.
Mechanisms of Acid–Base Regulation in Migrant Sea Lampreys (Petromyzon Marinus) Following Exhaustive Exercise
Authors: Wilkie Michael P. , Couturier Jennifer , Tufts Bruce L. 
Published: April 2021

ABSTRACT
The life cycle of the sea lamprey (Petromyzon marinus) is characterized by a terminal upstream spawning migration that may be associated with brief bursts of high-intensity swimming. Such activity usually leads to pronounced blood acid–base disturbances in fishes, but lampreys rapidly correct these perturbations within 1 h. In the present study, patterns of post-exercise H+ excretion and ion movements were followed in sea lampreys to test the hypothesis that dynamic manipulation of Na+versus Cl− movements across the animal’s body surface, presumably at the gills, accounted for the rapid restoration of blood pH following exercise. The first hour of post-exercise recovery in sea lampreys was associated with marked stimulation of (equivalent to base uptake), which approached −500 μmol kg−1 h−1. After 1 h, patterns had returned to resting rates. Analyses of net Na+ and Cl− movements suggested that elevated net Cl− losses, which greatly exceeded net Na+ losses, accounted for most of the . Subsequent experiments, using radiotracers (22Na+, 36Cl−), indicated that differential increases in Cl−versus Na+ permeability accounted for the greater post-exercise Cl− losses and the corresponding stimulation of net proton excretion. Finally, metabolic acid budget analyses confirmed our hypothesis that rapid excretion of metabolic protons was the primary means used by sea lampreys to correct post-exercise extracellular acidosis.
The electric organ discharge of pulse gymnotiforms: the transformation of a simple impulse into a complex spatio-temporal electromotor pattern
Authors: Caputi Angel Ariel 
Published: April 2021

ABSTRACT
An understanding of how the nervous system processes an impulse-like input to yield a stereotyped, species-specific electromotor output is relevant for electric fish physiology, but also for understanding the general mechanisms of coordination of effector patterns. In pulse gymnotids, the electromotor system is repetitively activated by impulse-like signals generated by a pacemaker nucleus in the medulla. This nucleus activates a set of relay cells whose axons descend along the spinal cord and project to electromotor neurones which, in turn, project to electrocytes. Relay neurones, electromotor neurones and electrocytes may be considered as layers of a network arranged with a lattice hierarchy. This network is able to coordinate a spatio-temporal pattern of postsynaptic and action currents generated by the electrocyte membranes. Electrocytes may be innervated at their rostral face, at their caudal face or at both faces, depending on the site of the organ and the species. Thus, the species-specific electric organ discharge patterns depend on the electric organ innervation pattern and on the coordinated activation of the electrocyte faces. The activity of equally oriented faces is synchronised by a synergistic combination of delay lines. The activation of oppositely oriented faces is coordinated in a precise sequence resulting from the orderly recruitment of subsets of electromotor neurones according to the ‘size principle’ and to their position along the spinal cord. The body of the animal filters the electric organ output electrically, and the whole fish is transformed into a distributed electric source.
Plasticity of feedback inputs in the apteronotid electrosensory system
Authors: Bastian Joseph 
Published: April 2021

ABSTRACT
Weakly electric fish generate an electric field surrounding their body by means of an electric organ typically located within the trunk and tail. Electroreceptors scattered over the surface of the body encode the amplitude and timing of the electric organ discharge (EOD), and central components of the electrosensory system analyze the information provided by the electroreceptor afferents. The electrosensory system is used for electrolocation, for the detection and analysis of objects near the fish which distort the EOD and for electrocommunication. Since the electric organ is typically located in the tail, any movement of this structure relative to the rest of the body alters the EOD field, resulting in large changes in receptor afferent activity. The amplitude of these reafferent stimuli can exceed the amplitudes of near-threshold electrolocation signals by several orders of magnitude. This review summarizes recent studies of the South American weakly electric fish Apteronotus leptorhynchus aimed at determining how the animals differentiate self-generated or reafferent electrosensory stimuli from those that are more behaviorally relevant. Cells within the earliest stages of central electrosensory processing utilize an adaptive filtering technique which allows the system preferentially to attenuate reafferent as well as other predictable patterns of sensory input without degrading responses to more novel stimuli. Synaptic plasticity within the system underlies the adaptive component of the filter and enables the system to learn to reject new stimulus patterns if these become predictable. A Ca2+-mediated form of postsynaptic depression contributes to this synaptic plasticity. The filter mechanism seen in A. leptorhynchus is surprisingly similar to adaptive filters described previously in mormyrid weakly electric fish and in elasmobranchs, suggesting that this mechanism may be a common feature of sensory processing systems.
Plasticity of the electric organ discharge: implications for the regulation of ionic currents
Authors: Zakon Harold , McAnelly Lynne , Smith G. Troy , Dunlap Kent , Lopreato Gregory , Oestreich Joerg , Few W. Preston 
Published: April 2021

ABSTRACT
Weakly electric fish emit electric organ discharges (EODs) to locate objects around themselves and for communication. The EOD is generated by a simple hierarchically organized, neurophysiologically accessible circuit, the electromotor system. A number of forms of plasticity of the EOD waveform are initiated by social or environmental factors and mediated by hormones or neurotransmitters. Because the behavior itself is in the form of electric discharges, behavioral observations easily lead to testable hypotheses about the biophysical bases of these plasticities. This allows us to study ionic channels in their native cellular environments, where the regulation of various parameters of these currents have obvious functional consequences. In this review, we discuss three types of plasticity: a rapidly occurring, long-lasting, N-methyl-D-aspartate (NMDA)-receptor-dependent increase in baseline firing frequency of neurons in the pacemaker nucleus that underlies a readjustment of the baseline EOD frequency after long bouts of the jamming avoidance response; a rapidly occurring diurnal change in amplitude and duration of the EOD pulse that depends in part on modulation of the magnitude of the electrocyte Na+ current by a protein kinase; and a slowly occurring, hormonally modulated tandem change in pacemaker firing frequency and in the duration of the EOD pulse in which changes in EOD pulse duration are mediated by coordinated shifts in the activation and inactivation kinetics of the electrocyte Na+ and K+ currents.
Development and regeneration of the electric organ
Authors: Zakon Harold H. , Unguez Graciela A. 
Published: April 2021

ABSTRACT
The electric organ has evolved independently from muscle in at least six lineages of fish. How does a differentiated muscle cell change its fate to become an electrocyte? Is the process by which this occurs similar in different lineages? We have begun to answer these questions by studying the formation and maintenance of electrocytes in the genus Sternopygus, a weakly electric teleost. Electrocytes arise from the fusion of fully differentiated muscle fibers, mainly those expressing fast isoforms of myosin. Electrocytes briefly co-express sarcomeric proteins, such as myosin and tropomyosin, and keratin, a protein not found in mature muscle. The sarcomeric proteins are subsequently down-regulated, but keratin expression persists. We investigated whether the maintenance of the electrocyte phenotype depends on innervation. We found that, after spinal cord transection, which silences the electromotor neurons that innervate the electrocytes, or destruction of the spinal cord, which denervates the electrocytes, mature electrocytes re-express sarcomeric myosin and tropomyosin, although keratin expression persists. Ultrastructural examination of denervated electrocytes revealed nascent sarcomeres. Thus, the maintenance of the electrocyte phenotype depends on neural activity.