bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reaction–Diffusion Analysis Of The Effects Of Temperature On High-Energy Phosphate Dynamics In Goldfish Skeletal Muscle
Authors: Hubley Mark J. , Locke Bruce R. , Moerland Timothy S. 
Published: April 2021

ABSTRACT
Thermal acclimation results in dramatic changes in the fractional volume of mitochondria within skeletal muscle of teleost fish. We investigated the hypothesis that changes in mitochondrial volume represent a compensatory response to temperature-induced changes in intracellular diffusion coefficients (D) of the high-energy phosphate compounds ATP and creatine phosphate (PCr). Using 31P nuclear magnetic resonance spectroscopy, we determined DPCr and DATP in goldfish (Carassius auratus) skeletal muscle at 25 °C and 5 °C: DPCr was 3.28±0.18×10−6 cm2 s−1 at 25 °C and 2.00±0.09×10−6 cm2 s−1 at 5 °C; DATP was 2.13±0.16×10−6 cm2 s−1 at 25 °C and was estimated to be 1.30×10−6 cm2 s−1 at 5 °C. There was no evidence for an effect of acclimation temperature or fiber type on DATP or DPCr. A mathematical reaction–diffusion model was used to calculate profiles of [ATP], [PCr] and the free energy of ATP hydrolysis (ΔGATP) in activated goldfish muscle fibers at 5 °C and 25 °C. The results showed spatial and temporal constancy of [ATP], [PCr] and ΔGATP in red fibers at both temperatures, regardless of changes in acclimation temperature or mitochondrial density. The model also showed spatial and temporal constancy of [ATP] in white fibers at 5 °C and 25 °C, but gradients in [PCr] and ΔGATP developed in white fibers under all conditions of temperature and acclimation temperature. These gradients were attenuated in cold-acclimated animals by cold-induced increases in mitochondrial density. However, the model shows that the proximal stimulus for temperature-induced changes in mitochondrial volume density in muscle is not a disruption in intracellular diffusion of high-energy phosphates.
Insect Tolerance to A Neurotoxic Polypeptide: Pharmacokinetic and Pharmacodynamic Aspects
Authors: Fishman Lena , Herrmann Rafael , Gordon Dalia , Zlotkin Eliahu 
Published: April 2021

ABSTRACT
Androctonus australis insect toxin (AaIT) is an insect-selective neurotoxic polypeptide from scorpion venom used to probe insect Na+ channels and to design insecticidal recombinant baculoviruses. When injected into susceptible insects (such as flies or cockroaches), nanogram doses of the toxin induce a rapid paralysis within seconds. More tolerant insects respond to microgram doses by developing either a slow progressive paralysis, as in lepidopterous larvae, or a rapid but reversible paralysis, as in Trachyderma philistina, a tenebrionid beetle. Using toxicity and binding assays, microscopy and chromatography, we show that the tolerance of insects to AaIT occurs at both the pharmacokinetic and pharmacodynamic levels. Pharmacokinetic effects occur in Trachyderma philistina in which the toxin undergoes a progressive process of degradation and elimination from the hemolymph, resulting in the loss of 95–97 % of toxin activity 6 h after injection. The pharmacodynamic aspect was demonstrated in studies of the kinetics of binding dissociation of [125I]AaIT from neuronal membranes of susceptible and tolerant insects. Stable binding is shown in susceptible insects such as cockroaches and locusts, which have a dissociation half-time of approximately 9 and 5 min, respectively. This contrasts strongly with the fast half-time of dissociation of 7 s for Spodoptera littoralis larvae and 9 s for Trachyderma philistina, which are both relatively tolerant to AaIT. These differences in binding kinetics may reflect a structural and functional diversity of Na+ channels in different insects that is responsible for their diverse susceptibility to neurotoxic polypeptides.
Polarization Pattern of Freshwater Habitats Recorded by Video Polarimetry in Red, Green and Blue Spectral Ranges and its Relevance for Water Detection by Aquatic Insects
Authors: Horváth Gábor , Varjú Dezsö 
Published: April 2021

ABSTRACT
The reflection-polarization patterns of small freshwater habitats under clear skies can be recorded by video polarimetry in the red, green and blue ranges of the spectrum. In this paper, the simple technique of rotating-analyzer video polarimetry is described and its advantages and disadvantages are discussed. It is shown that the polarization patterns of small water bodies are very variable in the different spectral ranges depending on the illumination conditions. Under clear skies and in the visible range of the spectrum, flat water surfaces reflecting light from the sky are most strongly polarized in the blue range. Under an overcast sky radiating diffuse white light, small freshwater habitats are characterized by a high level of horizontal polarization at or near the Brewster angle in all spectral ranges except that in which the contribution of subsurface reflection is large. In a given spectral range and at a given angle of view, the direction of polarization is horizontal if the light mirrored from the surface dominates and vertical if the light returning from the subsurface regions dominates. The greater the degree of dominance, the higher the net degree of polarization, the theoretical maximum value being 100 % at the Brewster angle for the horizontal E-vector component and approximately 30 % at flat viewing angles for the vertical E-vector component. We have made video polarimetric measurements of differently coloured fruits and vegetables to demonstrate that polarized light in nature follows this general rule. The consequences of the reflection-polarization patterns of small bodies of water for water detection by polarization-sensitive aquatic insects are discussed.
The Kinematics and Performance of Fish Fast-Start Swimming
Authors: Domenici Paolo , Blake Robert W. 
Published: April 2021

ABSTRACT
Fast-starts are brief, sudden accelerations used by fish during predator–prey encounters. The kinematics and performance of fish during fast-start manoeuvres have received a lot of attention since they may determine the outcome of predator–prey interactions in terms of feeding success or survival. We will discuss recent progress on (1) the kinematics of escape responses and feeding strikes, (2) the fast-start performance of species with different body morphologies and from different habitats, and (3) the functional significance of fast-start kinematics and performance within the context of predator–prey interactions.
Opercular Jetting During Fast-Starts by Flatfishes
Authors: Brainerd Elizabeth L. , Page Benjamin N. , Fish Frank E. 
Published: April 2021

ABSTRACT
When attacked by predators, flatfishes perform fast-starts that result in a rapid take-off from the ocean bottom on which they lie. High-speed video recordings of the blind side of flatfishes indicate that they expel a coherent jet of water from the blind-side opercular valve during take-off. Buccal pressure recordings in winter flounder (Pseudopleuronectes americanus) show that a buccal pressure pulse begins 0–20 ms before the beginning of the fast-start and has a range of mean magnitudes for three individuals of 1.6–10.7 kPa. We hypothesize that one function of the opercular jet in flatfishes may be to reduce the effects of Stefan adhesion. Stefan adhesion occurs as the fish lifts its head up rapidly from the ocean bottom, when water must flow into the space forming beneath the fish. Water viscosity opposes this rapid shear, and a suction pressure develops under the fish, making it more difficult for the fish to escape from the bottom. To estimate the magnitude of Stefan adhesion, we simulated fast-starts using a physical model in which a dead flounder was pulled upwards with an acceleration of 95 m s−2. Results from the physical model indicate that up to 35 % of the total force required to lift the head at 20 ms into the start can be attributed to Stefan adhesion. Despite this large adhesion force, previous work has shown that live flatfish do not show improved fast-start performance when Stefan adhesion has been eliminated by starting the fish from an open wire grid. Thus, live fishes are likely to be using behavioral mechanisms to reduce the adhesion force. Both the timing and location along the body of the opercular jet indicate that it is ideally suited to attenuate the effects of Stefan adhesion. Propping the body up on the median fins may also reduce adhesion by increasing the initial distance between the fish and the ocean floor.
Postnatal Development of Body Architecture and Gait in Several Rodent Species
Authors: Eilam David 
Published: April 2021

ABSTRACT
Observations on five species of rodents, vole (Microtus socialis), gerbil (Gerbillus dasyurus), jird (Meriones tristrami), dormouse (Eliomys melanurus) and jerboa (Jaculus orientalis), revealed that, during the period when their neonates share a matching morphology, they also share the same forms of quadruped locomotion (gaits). The order in which the different gaits develop is similar in all species, beginning with the basic gaits of lateral walk and trot. Gaits and body morphology do not undergo further changes in voles, whereas the other species incorporate more specialized gaits later in ontogeny, when the adult body morphology has been attained. Gerbils and jirds incorporate a bounding gait, dormice incorporate galloping and jerboas incorporate bipedal running. Species with more specialized locomotion thus undergo more developmental stages than those with less specialized locomotion. Except for the jerboa, the nesting period was roughly the same for all species, but those with more specialized locomotion exhibited earlier onset of the basic gaits as if condensing their development in order to reach the adult gait within the same nesting period. Consequently, the adult gait emerges approximately 10 days before the end of nesting, regardless of nesting duration. Since growth rate does not seem to account for the differences in morphology and onset of gaits, the heterochrony in the observed species probably stems from differences in the duration of growth, which seems to be the key factor in the diversion from the basic common morphology. The present results reconfirm the traditional generalities of functional morphology derived from cross-species comparisons. In addition, they provide another perspective by comparing form and function within the same individuals in the course of ontogeny.
Interneuronal and Motor Patterns During Crawling Behavior of Semi-Intact Leeches
Authors: Baader A. P. 
Published: April 2021

ABSTRACT
Semi-intact tethered preparations were used to characterize neuronal activity patterns in midbody ganglia of the medicinal leech during crawling. Extra- and intracellular recordings were obtained from identified interneurons and from motor neurons of the longitudinal and circular muscles during crawling episodes. Coordinated activities of nine excitatory and inhibitory motor neurons of the longitudinal and circular muscles were recorded during the appropriate phases of crawling. Thus, during crawling, the leech uses motor output components known to contribute to other types of behavior, such as swimming or the shortening/local bending reflex. Interneurons with identified functions in these other types of behavior exhibit membrane potential oscillations that are in phase with the behavior pattern. Therefore, the recruitment of neuronal network elements during several types of behavior occurs not only at the motor neuron level but also involves interneurons. This applies even to some interneurons that were previously thought to have dedicated functions (such as cells 204 and 208 and the S cell). The function of neuronal circuitries in producing different types of behavior with a limited number of neurons is discussed.
Neural Mechanisms of Adaptive Gain Control in a Joint Control Loop: Muscle Force and Motoneuronal Activity
Authors: Kittmann Rolf 
Published: April 2021

ABSTRACT
An adaptive gain control system of a proprioceptive feedback system, the femur–tibia control loop, is investigated. It enables the joint control loop to work with a high gain but it prevents instability oscillations. In the inactive stick insect, the realisation of specific changes in gain is described for tibial torque, for extensor tibiae muscle force and for motoneuronal activity. In open-loop experiments, sinusoidal stimuli are applied to the femoral chordotonal organ (fCO). Changes in gain that depend on fCO stimulus parameters (such as amplitude, frequency and repetition rate), are investigated. Furthermore, spontaneous and touch-induced changes in gain that resemble the behavioural state of the animal are described.
Changes in gain in motoneurones are always realised as changes in the amplitude of modulation of their discharge frequency. Nevertheless, depending on the stimulus situation, two different mechanisms underlie gain changes in motoneurones. (i) Changes in gain can be based on changes in the strength of the sensorimotor pathways that transmit stimulus-modulated information from the fCO to the motoneurones. (ii) Changes in gain can be based on changes in the mean activity of a motoneurone by means of its spike threshold: when, during the modulation, the discharge of a motoneurone is inhibited for part of the stimulus cycle, then a change in mean activity subsequently causes a change in modulation amplitude and gain.
A new neuronal mechanism is described that helps to compensate the low-pass filter characteristics of the muscles by an increased activation, especially by a sharper distribution of spikes in the stimulus cycle at high fCO stimulus frequencies.
Peripheral Encoding of Moving Sources by the Lateral Line System of a Sit-and-Wait Predator
Authors: Montgomery J. C. , Coombs S. 
Published: April 2021

ABSTRACT
Video-tape recordings of prey-capture behaviour were made to demonstrate that stargazers can detect and capture prey in the dark and to determine the range of prey movement velocities that resulted in prey capture. Electrophysiological recording techniques were then used to determine how an artificial source (a sphere), moving at speeds within the range of recorded prey movement velocities, was encoded by anterior lateral line nerve fibres innervating the preopercular-mandibular canals on the head. A vibrating sphere was also used to measure frequency–response characteristics to determine the bandwidth of response and fibre origin (type of neuromast and location). In order to measure the relevant stimulus parameters likely to govern neural responses, the pressure-gradient pattern produced by the moving sphere was characterised with a pair of miniature hydrophones separated by approximately the same distance as head lateral line canal pores on stargazers. At least four different features of neural response patterns, including direction-dependent changes in the overall envelope of the firing rate pattern, could be predicted on the basis of measured pressure-gradient patterns. The dominant features of both the pressure-gradient and neural response patterns were produced by the wake behind the moving sphere, but behavioural observations indicated that stargazers were responding to the bow of an approaching prey, rather than its wake. Although the form of the wake behind the moving sphere is unlikely to be a good match for the stimulus mediating prey detection, these results clearly establish that pressure-gradient patterns are good predictors of neural response patterns. Thus, similar measurements of pressure-gradient patterns produced by more biologically relevant sources can be used to predict peripheral lateral line responses and stimulus features likely to be of key importance.
Reactivation of Sea-Urchin Sperm Flagella Induced by Rapid Photolysis of Caged ATP
Authors: Tani Tomomi , Kamimura Shinji 
Published: April 2021

ABSTRACT
Sea-urchin sperm flagella in a state of rigor were reactivated by rapid photolysis of caged ATP. After a time lag of 11−17 ms, all bends in the axonemes present during rigor began to be propagated towards the tip as if their propagation had not been interrupted. This result suggests that the site-specific activity of dyneins along the length of the axoneme is preserved even during rigor states when ATP is absent and that regulation of the activity can be restarted immediately with a new cycle of ATP turnover. During the starting transient, pre-existing rigor waves in the distal region were propagated without a change in the maximal shear angle until they disappeared at the tip. This was more evident when the rapid reactivation was triggered in high-viscosity solution, in which only the form of new bends was greatly affected by viscous load. After reactivation, the velocity of microtubule sliding increased and reached a plateau within 28 ms. This time course reflects the rate of force generation by dynein in situ.
5´-Nucleotidase and Alkaline Phosphodiesterase Activities in Trout Gill Localize to Endothelial (Pillar) Cells
Authors: Robertson John C. , Hazel Jeffrey R. 
Published: April 2021

ABSTRACT
Tissue homogenates from rainbow trout gill had three-to fivefold higher specific activity for 5´-nucleotidase (5´NT) and more than twofold greater alkaline phosphodiesterase (APD) activity than liver or kidney homogenates. In isolated plasma membranes, gill 5´NT activity was 3–5 times greater than that of the kidney or liver; gill and kidney plasma membranes had similar APD specific activities, both more than five times that of liver. 5´NT and APD activities were localized by histochemistry to the endothelial (pillar) cells of trout gill secondary lamellae. Staining was consistent with the concentration of both activities at the apical plasma membranes of pillar cells (i.e. at the lamellar microvascular surfaces). This localization may reflect a capacity for processing nucleotide metabolites circulating in the blood, perhaps relating to purinergic regulation of local lamellar hemodynamics. There was no histochemical evidence of either 5´NT or APD activity in the gill epithelial (pavement) cells that interface directly with the environment. In contrast, in trout kidney, both enzyme activities localized to the apical region of tubule epithelial cells. The absence of 5´NT and APD activity in pavement cells reinforces the unique structural and functional character of the gill–environment epithelial barrier. The results indicate that 5´NT and APD activities have particular potential application as markers in efforts to isolate and characterize specific gill plasma membrane fractions.
Contralateral Coordination and Retargeting of Limb Movements During Scratching in the Locust
Authors: Matheson T. 
Published: April 2021

ABSTRACT
Locusts, Schistocerca gregaria, in common with many limbed vertebrates, can make directed scratching movements in response to tactile stimulation. For instance, stimulation of different sites on a wing elicits different movements that are accurately targeted so that the hindleg tarsus passes across the stimulus site. I have analysed these limb movements to define the ability of a locust to target stimulus sites correctly under a range of experimental conditions. In particular, I describe aspects of the behaviour that reveal possible neuronal pathways underlying the responses. These neuronal pathways will be the subject of further physiological analyses.
Limb targeting during scratching is continuously graded in form; different patterns of movement are not separated by sharp transitions. The computation of limb trajectory takes into account the starting posture of the hindleg, so that different trajectories can be used to reach a common stimulus site from different starting postures. Moreover, the trajectories of the two hindlegs moving simultaneously from different starting postures in response to a single stimulus can be different, so that their tarsi converge onto the common stimulus site. Different trajectories can be used to reach a common stimulus site from the same start posture. Targeting information from a forewing is passed not only down the nerve cord to the ipsilateral hindleg but also across the nerve cord, so that the contralateral hindleg can also make directed movements. This contralateral transmission does not rely on peripheral sensory feedback. When the stimulus site moves during a rhythmical scratch, the targeting of subsequent cycles reflects this change. Both ipsilateral and contralateral hindlegs can retarget their movements. The trajectory of a single cycle of scratching directed towards a particular stimulus site can be modified after it has begun, so that the tarsus is redirected towards a new stimulus site.
Modelling Of The Dynamic Relationship Between Arterial Pressure, Renal Sympathetic Nerve Activity And Renal Blood Flow In Conscious Rabbits
Authors: Berger Clive S. , Malpas Simon C. 
Published: April 2021

ABSTRACT
A linear autoregressive/moving-average model was developed to describe the dynamic relationship between mean arterial pressure (MAP), renal sympathetic nerve activity (SNA) and renal blood flow (RBF) in conscious rabbits. The RBF and SNA to the same kidney were measured under resting conditions in a group of eight rabbits. Spectral analysis of the data sampled at 0.4 Hz showed that the low-pass bandwidth of the signal power for RBF was approximately 0.05 Hz. An autoregressive/moving-average model with an exogenous input (ARMAX) was then derived (using the iterative Gauss–Newton algorithm provided by the MATLAB identification Toolbox), with MAP and SNA as inputs and RBF as output, to model the low-frequency fluctuations. The model step responses of RBF to changes in SNA and arterial pressure indicated an overdamped response with a settling time that was usually less than 2 s. Calculated residuals from the model indicated that 79±5 % (mean ± S.D., averaged over eight independent experiments) of the variation in RBF could be accounted for by the variations in arterial pressure and SNA. Two additional single-input models for each of the inputs were similarly obtained and showed conclusively that changes in RBF, in the conscious resting rabbit, are a function of both SNA and MAP and that the SNA signal has the predominant effect. These results indicate a strong reliance on SNA for the dynamic regulation of RBF. Such information is likely to be important in understanding the diminished renal function that occurs in a variety of disease conditions in which overactivity of the sympathetic nervous system occurs.