bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri:III. Renal ionic fluxes
Authors: Vermette M. G. , Perry S. F. 
Published: April 2021

ABSTRACT
Rainbow trout were infused continuously for 24 h with epinephrine in order to evaluate the effects of elevated circulating levels of epinephrine on selected renal variables. Pronounced effects of epinephrine included elevation of urine flow rate and concomitant increases in the excretion of all measured electrolytes (Na+, Cl−, K+, Ca2+, inorganic phosphate) with the exception of ammonium and bicarbonate ions. Significant reductions in the tubular reabsorption of Na+ and Cl− also contributed to enhanced excretion of these ions. Similarly, epinephrine affected the tubular handling of NH4+ and HCO3− with NH4+ secretion decreasing and HCO3− reabsorption increasing. We speculate that the stimulation of HCO3− reabsorption was a consequence of elevated tubular H+ secretion. Such a mechanism may be important to permit plasma HCO3− retention during periods of internal acidosis. The results are discussed with reference to the role of the fish kidney in regulating acid-base disturbances and the possible interactive effects of elevated epinephrine.
Course-Control, Metabolism and Wing Interference During Ultralong Tethered Flight in Drosophila Melanogaster
Authors: Götz Karl G. 
Published: April 2021

ABSTRACT
Tethered flight in a 3-day-old female Drosophila was sustained for 32·2 h with only short interruptions during uptake of sucrose solution. The course-control reactions derived from the difference of the wingbeat amplitudes on either side have been used to simulate the rotatory displacement of the surrounding landmarks during a comparable turn in free flight. Stabilization of a target in the preferred area of the visual field requires continuous visual attention. A rate of about 5 course-correcting manoeuvres per second was maintained throughout the experiment. Drosophila seems to be able to cover long distances in search of a favourable habitat.
Flight-specific carbohydrate consumption is equivalent to a metabolic power input per body weight of about 18 W N−1. The tethered fly produces about 40 % of the lift required to sustain hovering flight. The resulting mechanochemical efficiency of about 0·04-0·07 is within the expected order of magnitude for flying insects. Expenditure of reserve substances may account for the difference between the comparatively low power input of about 7 W N−1, derived from carbohydrate uptake in the first hours of flight (Wigglesworth, 1949), and the actual metabolic turnover of about 21 WN−1, derived from oxygen consumption during this period (Laurie-Ahlberg et al. 1985).
Weis-Fogh’s ‘clap and fling’, a widespread lift-generating process exploiting the aerodynamic wing interference at the dorsal end of the wingbeat, was in action throughout the flight. However, there were two significant modifications (as first conceived by Ellington, 1980) : (1) during ‘clap’, there is a progress of wing contact from the leading to the trailing edge, which is likely to ‘squeeze’ a thrust-generating jet of air to the rear; (2) during ‘fling’, there is a progress of wing separation in the same direction, which is described as a ‘peel’ resembling the progressive separation of two plastic foils pulled apart against forces of mutual attraction. The wings of the test fly survived about 23 million such peels without damage. Increasing airspeed decreases the intensity of ‘clap and fling’ in Drosophila : results obtained in the wind tunnel show the transition to a ‘near clap and fling’, lacking mutual wing contact.
Salinity Acclimation and Intestinal Salt Transport in the Flounder: the Role of the Basolateral Cell Membrane
Authors: Gibson J. S. , Ellory J. C. , Lahlou B. 
Published: April 2021

ABSTRACT
Intestinal absorption of Na+ and Cl−, measured using bidirectional tracer fluxes, is higher in saltwater (SW)-acclimated flounders than in freshwater (FW)-acclimated ones. Removal of the selective permeability of the apical cell membrane by application of amphotericin B to the mucosal solution enhances the difference in Na+ transport, whilst the difference in Cl− absorption is lost. Transepithelial resistance and were similar between the two groups of fish, whilst , was always greatest in SW-acclimated tissues, even after mucosal application of amphotericin. Analysis of the present results and previous work suggests that the principal acclimatory changes following salt adaptation occur in the basolateral cell membrane, and that both the Na+,K+-ATPase activity and the basolateral cell membrane permeability to Cl− are increased in the SW-acclimated tissues.
The Tuned Singing Burrow of Mole Crickets
Authors: Bennet-Clark H. C. 
Published: April 2021

ABSTRACT
During burrow digging by the mole cricket Scapteriscus acletus Rehn and Hubbard, the burrow is enlarged and shaped in a series of digging cycles, each lasting 1–2 min, and song chirps are produced after every cycle. The song becomes up to 18 dB louder and acoustically purer during burrow building. The shape of the song pulse envelope changes so that its average power density becomes greater and its build-up and decay become more gradual.
The forewings show a single resonance of the harp (Cu 1 cell) regions at 2·5-3·0kHz: the normal song carrier frequency is 2·5-2·7kHz. Removal of the outer parts of the forewings does not affect the radiated sound power.
The singing burrow has an exponential horn opening at the soil surface and an internal bulb. The calculated cut-off frequency of the horn is 1·34 kHz and that of the first resonance is 2·5-2·7 kHz. The volume of the bulb is close to that required to tune the throat: obliteration of the burrow bulb causes a substantial decrease in the radiated sound pressure levels before singing ceases.
The horn mouth acts as a finite sound source, with large acoustic reactance. The acoustics of the burrow were measured with a small doublet source inserted at the position at which the cricket sings. At this position, the burrow resonates at 2·75-3 kHz, with a quality factor (Q), measured both by the –3 dB bandwidth and by the build-up and decay of tone bursts, of 2·5-2·7. The sound pressure produced by the doublet source is up to 24 dB louder when it is in the burrow than when it is in free air. Further in or out from the insect’s singing position, the effective gain of the burrow is reduced and other resonances and anti-resonances are observed. Obliteration of the burrow bulb reduces the effective gain of the burrow by 6–10 dB and the burrow ceases to resonate at 2·75 kHz.
It is proposed that the tuned burrow acts as a resistive load on the vibrating harps, so allowing good coupling between the small wings and the surrounding medium while allowing a pure carrier frequency to be radiated.
Walking and Surface Film Locomotion in Terrestrial and Semi-Aquatic Spiders
Authors: Shultz Jeffrey W. 
Published: April 2021

ABSTRACT
The walking and surface film locomotion of a terrestrial spider, Lycosa rabida Walckenaer, and a semi-aquatic spider, Dolomedes triton (Walckenaer), are compared. Stepping patterns during locomotion on a solid substrate resemble an alternating tetrapod in both species. L. rabida retains elements of the terrestrial gait when moving on water: propulsive thrusts are concentrated at the tarsi and intra-segmental legs step in alternation. However, protraction/retraction (p/r) values are generally greater and phase values of adjacent ipsilateral legs are lower compared to values for walking animals. D. triton shows greater behavioural specialization for aquatic locomotion: propulsive forces are generated along the length of the leg, intrasegmental legs move in synchrony and leg 4 (which is not used for propulsion on water) functions in yaw correction. Changes in p/r value and ipsilateral phase accompanying the transition from a solid substrate to the water surface are similar to those found in L. rabida. The fact that coordination within a segment and coordination between segments can be altered independently in both proximate and evolutionary time suggests that interleg coupling in spiders is governed by two distinct mechanisms: intrasegmental and intersegmental mechanisms. It is suggested that proximate changes in p/r value and ipsilateral phase in both spiders may be the effect of sensory modulation of similar motor control mechanisms and that certain specializations for aquatic locomotion in D. triton (such as yaw corrective movements of leg 4) are derived from elements of the primitive terrestrial motor programme.
The effects of temperature and pH on the contractile properties of skinned muscle fibres from the terrapin, Pseudemys scripta elegans
Authors: Mutungi G. , Johnston I. A. 
Published: April 2021

ABSTRACT
Fibre types in the iliofibularis muscle of the freshwater terrapin Pseudemys scripta elegans have been characterized on the basis of their histochemical characteristics, nerve endings and contractile properties. Three types of focally innervated fibres are present, corresponding to the fast glycolytic (Fg), fast oxidative glycolytic (FOG) and slow oxidative (SO) fibre types of other vertebrates. Single fibres or small bundles of fibres representing each histochemical type were identified on the basis of their light scattering properties under dark-field illumination. Fibres were detergent-skinned using Brij 58, and their maximum isometric tension (Po) and unloaded contraction velocity (Vo) were determined by the slack test method. At 15 °C, fast glycolytic fibres generated maximum isometric tensions of 184 ± 5 kN m−2 and Vo values of 5·5 ± 0·3 muscle lengths per second (Los−1). Slow oxidative fibres produced tensions of 70·6±3kNm−2 and had Vo values of 1·3 Los−1. Tensions and Vo values of fast oxidative glycolytic fibres were between those of Fg and SO fibres. The force-velocity (P-V) characteristics of slow oxidative fibres were studied at 5° and 15°C. Points below 0·6 Po on the curves could be fitted by a linear form of Hill’s equation. Maximum contraction velocities (Vmax) extrapolated from the P–V relationship were 0·62 Los−1 at 5°C and 0·91 Los−1 at 15°C. The curvature of the P-V relationship was relatively independent of temperature over the range 5 to 15°C. Values for Hill’s constant a/P0 were 0·29 and 0·33 at 5°C and 15°C, respectively. The temperature dependence of P0 and contraction velocity at near zero load (Vi) were studied at constant pH, and under conditions designed to simulate the changes in intracellular pH which occur with temperature in vivo (ΔpH/ΔT = –0·0186). Changes in pH in the range 6·6 to 7·8 had no effect on either tension or V, at temperatures between 0° and 20°C. However, below and above this pH range, both tension and V, were depressed. It is concluded that pH changes within the normal physiological range (6·7–7·8) have no effect on the temperature dependence of P0 and Vi.
Hagfish (Eptatretus stouti) erythrocytes show minimal chloride transport activity
Authors: Ellory JC , Wolowyk MW , Young JD 
Published: April 2021

ABSTRACT
Capnophorin (Band 3) is the major red cell transport protein, present in human erythrocyte membranes at 1 × 106 copies per cell. Under physiological conditions, the transporter is capable of moving 50 mol (Cl−/HCO3−) 1 cells−1 min−1 (Knauf, 1979), this high rate being necessary for carriage of CO2 in normal respiration (Wieth et al. 1982). In the present paper we demonstrate that, in contrast to the situation in all other vertebrate species studied except the lamprey (Ohnishi & Asai, 1985), capnophorin activity in hagfish red cells is very limited, amounting to only 40 μmol Cl− transported 1 cells-1 min-1 at 11 °C, the environmental temperature of this species. Five experimental approaches were used to characterize this transporter in hagfish red cells: pH regulation in lightly buffered medium; 36C1− uptake; 36C1− efflux; effects of H2DIDS (dihydro-4,4-diisothiocyanostilbene 2,2-disulphonic acid), a specific capnophorin inhibitor (Knauf, 1979); and sodium dodecyl sulphate (SDS) polyacrylamide gel electrophoresis (PAGE).
Regeneration of Feathers After Thyroid Feeding
Authors: Hosker Anne 
Published: April 2021

ABSTRACT
It may be concluded from these experiments that excessive doses of thyroid cause (a) moulting, followed by rapid regeneration of depigmented feathers in mature birds ; (b) depigmentation of growing feathers followed by increased melanisation in young birds, giving a white and black bar ; (c) accelerated growth rate in all feathers, regardless of the region considered or the age of the bird ; (d) stimulation of the papillae of plucked feathers causing rapid regeneration from each papilla.
From the variability in the measurements recorded, liver feeding appears to have no definite effect upon feather growth, but a slight stimulating effect upon the papillae causing them to regenerate.
In cases of lack of external signs of regeneration of feathers for some months after plucking in normal or liver-fed birds, the papilla regenerates a rudimentary calamus, or lies quiescent beneath cornified tissue which acts as a calamus, until the next moult, or until some substance with an accelerating influence upon feather growth (e.g. thyroid) is administered.
Calcium-Dependent Action Potentials in the Second-Order Neurones of Cockroach Ocelli
Authors: Mizunami Makoto , Yamashita Shigeki , Tateda Hideki 
Published: April 2021

ABSTRACT
The ionic basis of the action potential in the large second-order neurones (L-neurones) of the ocellus of the cockroach, Periplaneta americana, was studied. L-neurones generated action potentials, usually once, at the off-set of hyperpolarizing light responses, or at the termination of hyperpolarizing current stimuli. The action potential was blocked by replacing saline Ca2+ with Mg2+ but maintained when Ba2+ was substituted. A block was produced by 2 mmol l−1 Cd2+ or 20 mmol l−1 Co2+. The peak amplitude of the action potential increased by 26 mV for a 10-fold increase in external Ca2+ concentration, at concentrations below 1·8 mmol l−1. The action potential was not affected by sodium-free saline or by 3×l0−6moll−1 tetrodotoxin (TTX). These observations suggest that calcium ions are the major carrier for the inward current of the action potential. This finding supports the suggestion that the off-set responses of hyperpolarizing visual neurones of both vertebrates and invertebrates have a common ionic mechanism, including voltage-sensitive calcium currents.
Lactate Uptake by Toadfish Hepatocytes: Passive Diffusion is Sufficient
Authors: Walsh Patrick J. 
Published: April 2021

ABSTRACT
Mechanisms of hepatic lactate uptake were studied in the gulf toadfish, Opsanus beta by following the accumulation of [l4C]lactate by isolated hepatocytes in vitro. Uptake rates were linear for up to 5 s at external lactate concentrations of 1 and 20 mmol 1−1. 5-s uptake rates for several concentrations in the physiological range (i.e. 0 2-20 mmol 1−1) yielded a linear double reciprocal plot (1/v VS l/[lactate]) that passed through the origin. Lactate uptake was not inhibited by known inhibitors of carrier-mediated lactate transport (e.g. 5 mmol 1−1 α-cyano-4-hydroxycinnamate; 10 mmol 1−1 pyruvate), and was not stereospecific for L-( +)-lactate. These observations indicate that lactate uptake is by passive diffusion in toadfish hepatocytes. Lactate uptake by toadfish hepatocytes further differed from lactate uptake by mammalian tissues in that rates were not altered by changes in either pHe (6·5−8·0) or [Na+]e (3−151 mmol 1−1). Rates of lactate conversion to glucose and CO2 were measured and compared to uptake rates, and it appears that rates of lactate metabolism are not limited by passive diffusion. These results are discussed in relation to rates of lactate uptake and metabolism in mammalian hepatocytes.
Electric fish approach stationary signal sources by following electric current lines
Authors: Schluger James H. , Hopkins Carl D. 
Published: April 2021

ABSTRACT
African electric fish of a pulse species, Brienomyrus brachyistius (Mormyridae), housed singly in a large, circular arena, were presented with electrical stimuli which mimicked a conspecific intruder. Stimuli were produced with either dipolar or bipolar electrodes in three different geometries. We tracked the unconditioned approach response paths taken by the fish and compared tracks for each of the geometries. The results suggest that B. brachyistius can determine neither the distance nor the direction of an electric dipole from afar, but that they do manage to find the source by maintaining a precise alignment of their body axis parallel to the direction of the local electric field vector (parallel to current lines) while swimming. This behaviour ultimately leads to the current source. We propose that this behaviour may be a simple mechanism mediating the approach response of one electric fish to another.
Bird Migration Across a Strong Magnetic Anomaly
Authors: Alerstam Thomas 
Published: April 2021

ABSTRACT
Migratory flights of birds across a strong magnetic anomaly were recorded by tracking radar and, during the daytime, by simultaneous visual observations. The anomaly in central Sweden is about 12 km long and a few kilometres wide, with the total magnetic intensity at low altitude exceeding the normal field by up to 60 %, according to aeromagnetic measurements. Migrants change altitude, most often by starting to descend, to a significantly greater extent over those parts of the anomaly where the magnetic field intensity is abnormally high, and particularly where the magnetic inclination is steepest, than over other parts of the study area and at another study area with a normal geomagnetic field. The descents lasted on average about 2min, with a mean angle of descent of 2·6°, leading to a height loss of about 100 m before level flight was resumed. Flock formations were repeatedly broken up during these temporary descents. The changes in flight altitude were associated with gradients in magnetic inclination along the birds’ flight paths across the anomaly. This supports the possibility that birds use the geomagnetic field and associated gradients for continuous guiding and recording of migration. Additional visual observations of migrating birds at the lowest altitudes over the magnetic anomaly suggest that birds sometimes become briefly disturbed (clear weather) or disoriented for longer periods, because of difficulties in finding their way out of the anomaly area (poor visibility).
On the termination of ingestive behaviour by the medicinal leech
Authors: Lent C. M. , Dickinson M. H. 
Published: April 2021

ABSTRACT
Hungry leeches, Hirudo medicinalis, ingest blood meals averaging 890% of their mass in 29min. Ingestion is terminated as a result of distension of the body: experimentally distending leeches as they feed causes an immediate cessation of ingestion and inhibits any subsequent biting behaviour; if distension is circumvented by various experimental procedures, leech ingestive periods are prolonged significantly. Ingestion is not terminated as a result of fatigue, chemical cues or mass change. Distension also underlies satiation, for removing blood from the crops of recently fed leeches qualitatively alters their satiated behaviour to biting. Biting is not a defensive reaction to injury.
In rostral ganglia, impulses of the serotonergic Retzius (RZ) and LL neurones evoke the physiological components of ingestion. Localized warming of the prostomial lip induces impulses in these large effector neurones. Distending the body wall tonically hyperpolarizes the RZ and LL cells. This inhibitory response to distension is conducted from the mid-body to the anterior neurones via the ventral nerve cord. Distensive inhibition antagonizes the synaptic excitation evoked in RZ and LL neurones by thermal stimulation. Thus, a stimulus which evokes feeding synaptically excites 5-HT neurones and a stimulus which terminates ingestion inhibits them. The integration of these inputs controls the expression of leech feeding behaviour and these connections match precisely a model proposed to regulate the ingestive behaviour of blowflies.
Functioning of identified snail neurones in electric fields
Authors: Ierusalimsky V. N. , Balaban P. M. 
Published: April 2021

ABSTRACT
In both silent and spontaneously active neurones of the snail Helix lucorum, depolarization and spikes were elicited by low-frequency (0·1 Hz) sinusoidal currents applied to the bath solution. Threshold voltage gradients had a range of 1–10 V m−1, which is less than gradients in the nervous tissue during synchronous activation of the neurones. It is shown that the same neurone can generate spikes in response to opposite directions of polarizing currents. Thresholds of spontaneously active neurones to extracellular currents were significantly lower than thresholds of silent cells. A simple quantitative method for evaluation of the transmembrane voltage drop evoked by an electric field is presented. The role of neuronal branches in the response was studied by electrophysiological and morphological methods.
Laboratory studies of homing orientation in the eastern red-spotted newt, Notophthalmus viridescens
Authors: Phillips J. B. 
Published: April 2021

ABSTRACT
The orientation behaviour of adult male eastern red-spotted newts (Notophthal-mus viridescens) was studied in laboratory tests. Newts were collected from ponds located 10-30 km from the laboratory, and housed in water-filled, all-glass aquaria located in a greenhouse or outdoors adjacent to the laboratory building. The aquaria were aligned on the magnetic north-south axis. Newts were tested in a dry, enclosed arena in four magnetic fields: the ambient magnetic field (magnetic north at North) and three altered fields (magnetic north rotated to East, West or South). Newts tested during January-March exhibited weak bimodal magnetic orientation along the axis of the holding tank. However, during the spring migratory period (April until early May), the bimodal response shifted to coincide with the direction of the pond from which the newts had been collected. Much stronger unimodal orientation was elicited by elevating the water temperature to 33-34°C immediately prior to testing. If newts were held in a training tank with an artificial shoreline at one end and exposed to elevation of water temperature after several days of stable water temperatures, they exhibited unimodal shoreward orientation and did not show the seasonal switch to homing behaviour observed in the earlier tests. If, however, the elevation of water temperature followed a period of fluctuating water temperature (over a 20°C range), the newts exhibited strong unimodal orientation in the direction of the pond from which they had been collected. These results suggest that newts possess a navigational system that enables them to home from distances in excess of 20 km. Moreover, these experiments provide the first opportunity to examine the sensory basis of navigational ability in any animal under controlled laboratory conditions.