bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermodynamic and Hydrodynamic Studies Relating to the Mechanochemical Cycle in the Flagellum of Crithidia Oncopelti
Authors: Holwill M. E. J. , Wais J. 
Published: April 2021

ABSTRACT
The motile response of the flagellum of Crithidia oncopelti to changes in the temperature, pressure and viscosity of the environment were studied. The dependence of beat frequency on temperature and pressure can be interpreted in terms of the theory of reaction rates by making the assumption that the frequency is proportional to the rate constant of a chemical reaction within the flagellum. For viscosities below a characteristic value, which depends on the temperature, increasing the pressure causes a reduction in the beat frequency. At the characteristic value, pressure changes do not affect the frequency while above this value an increase in pressure causes an increase in the frequency. Pressure and temperature changes directly affect chemical reactions within the flagella whereas alterations in viscosity produce changes which can be attributed to a modification of the microtubule sliding rate. The time for which detergent-treated flagella remain active following addition of ATP depends upon the environmental conditions. It appears that these in vitro preparations can convert only a limited amount of chemical energy into mechanical work.
The Energetics of Hovering in the Mandarin Fish (Synchropus Picturatus)
Authors: Blake R. W. 
Published: April 2021

ABSTRACT
The influence of the ground effect on the energetics of hovering in Synchropus picturatus Peters, a negatively buoyant, demersal teleost was studied. Changes in pectoral fin kinematics, the ultimate water velocity in the wake below the fins, the calculated minimum induced thrust and power required to hover are related to the height at which the animal hovers above the substrate. The profile power required to overcome the frictional drag on the fins has been calculated for the case of both a laminar and a turbulent boundary layer over the fins. Reductions in the total power needed to hover (as compared with that required out of ground effect) of 30–60% have been calculated for Synchropus when hovering at commonly observed heights above the bottom. Results are discussed in relation to the hovering flight of birds, insects and helicopters.
Continuous Evaluation of In Fish: Recording and Data Processing
Authors: Belaud Alain , Trotter Yves , Peyraud Claude 
Published: April 2021

ABSTRACT
In the eel (Anguilla anguilla L.), the dorsal and ventral aortas and the subhepatic vein were catheterized to provide an external circulatory shunt. in the shunted blood was continuously recorded using a polarographic measuring device. Spontaneous interruptions in the eel’s ventilatory activity result in rapid changes in . The period of these oscillations is sometimes less than 1 min. However, the response time of the measuring system is so great under the conditions of these experiments that only slow variations of , of a period greater than 5 min, are faithfully recorded. In view of the impractibility of technical improvement in the recording system, a data processing method was developed to reconstitute the real physiological variations from the distorted experimental recordings. Through this method of data correction, it is demonstrated that apnoeic or active ventilatory phases in the eel’s breathing pattern are not triggered by constant low values of . Other physiological applications are suggested.
The Role of Lactic Acid Accumulation in Muscle Fatigue of Two Species of Anurans, Xenopus Laevis and Rana Pipiens
Authors: Putnam Robert W. 
Published: April 2021

ABSTRACT
Fatigue produced a marked increase in the lactic acid content of hind-limb muscles, the blood, and the whole animal. After 15 min of rest there was little decline of lactic acid levels but the animals could be stimulated into about 3 min of intense activity. This re-fatigue produced a further increase in lactic acid levels. Gastrocnemius muscles removed from fatigued frogs and stimulated in vitro were able to generate initial tensions similar to those in control muscles; total tension was about a third of the control value. In vitro stimulation of these muscles from fatigued frogs led to additional accumulation of lactic acid. Fatigue produced little decrease in the glycogen content of muscles in X. laevis but a marked decrease in R. pipiens. Considerable glycogen stores remained even in the muscles of re-fatigued animals. These data show that accumulation of lactic acid in muscle or blood, depletion of glycogen in muscle, or change in blood pH cannot account for fatigue in these species. Possible other causes of fatigue are discussed.
Short Communications How Honey-Bees Know Their Distance From A Near-By Visual Landmark
Authors: Cartwright B. A. , Collett T. S. 
Published: April 2021

ABSTRACT
Insects generally have eyes that are close together and lenses with a very short focal length. In consequence neither stereoscopic nor focus cues can be used to measure the distance of objects that are further than a very few centimetres. To do this insects must rely on information provided by retinal image size or by motion parallax. If an insect knows how large an object appears to be at one distance, it can use image size to compute any other object distance. This method is probably used by some male hoverflies when tracking conspecifics (Collett & Land, 1975). Bulldog ants snap at an image of constant retinal size, and so open their jaws when an appropriately sized prey object comes within range (Via, 1977). The distance of an object can also be specified by the way in which its image travels across the retina or changes size when an insect moves a known distance or at a known speed. To date only stationary locusts have been shown to exploit motion parallax, which they do by performing a specialized side-to-side head and body movement (Wallace, 1959; Collett, 1978). Very little, however, is known about the ways in which freely flying insects measure their distance from stationary objects. We were interested in studying this question in honey-bees because they clearly have a good appreciation of the arrangement of stationary features in their environment, which they will demonstrate all day long as they fly between a food source and their hive. Bees can learn to locate a source of food using near-by landmarks and to do this they must know their distance from such landmarks (Lauer & Lindauer, 1971 ; Anderson, 1977). In this paper we show that honey-bees use both motion parallax and image size or change in image size in determining how far they are from a single landmark.
Measurement of Calcium Ion Concentrations in the Lateral Line Cupulae of Xenopus Laevis
Authors: McGLONE F. P. , Russell I. J. , Sand O. 
Published: April 2021

ABSTRACT
Ion selective microelectrodes were used to measure the distribution of Ca2+ in the cupulae of Xenopus laevis, and to observe the effects of the Ca2+ blocker, La3+, and a Ca2+ chelating agent (EGTA) on the endocupular potential and K+ concentration. Measurements of the endocupular Ca2+ and potential were found to be in the range of 2–30 μM and 55–10 mV respectively, and their relationship indicates that Ca2+ is passively distributed in the cupula. The concentration of endocupular K+ and endocupular potential was found not to be influenced by addition of either 1 mM EGTA or 100 μM–La3+ to the bathing solution.
Neuromuscular Transmission In Peripatus
Authors: Hoyle Graham , Del Castillo José 
Published: April 2021

ABSTRACT
The electrical and mechanical responses of body, leg and jaw muscle of Peripatus to electrical excitation of their motor-nerves were examined. A small twitch was obtained from each muscle, whose strength increased stepwise with increasing stimulus strength. In jaw and body muscles as many as ten increments in height were obtained with increasing stimulus strength. Only a single twitch height was obtained from the claw retractor muscle. Tetanus:twitch ratio under supraminal stimulation was less than 2:1 for jaw muscles, about 50:1 for the claw retractor and about 6:1 for muscles moving the legs. The jaw-muscle twitch duration was 0·6 s, that for the leg muscles 1·2 s and for body muscles about 3·0 s. Large miniature junctional potentials were frequently recorded regardless of electrode location. Responses to neural stimulation consisted of small junctional potentials whose height was progressively increased with increasing stimulus strength, generally with three steps. With repetitive stimulation, facilitation of the second and third junctional potentials occurred, plus summation. A few fibres gave spikes to a single shock : most gave a few spikes sporadically, during repetitive stimulation only. No abrupt tension increments occurred in whole muscles when individual fibres spiked. We saw no evidence for peripheral inhibitory axons. The excitation of Peripatus muscle is by local graded junctional potentials at distributed nerve-on-muscle fibre synapses, together with action potentials. The latter are initiated only by larger junctional potentials compounded of multiple smaller ones summated and/ or facilitated. The details of neuromuscular physiology are not compatible with the phylogenetic status commonly proposed for Peripatus.
Non-Simultaneous Auditory Masking in the Goldfish, Carassius Auratus
Authors: Popper Arthur N. , Clarke Nancy L. 
Published: April 2021

ABSTRACT
Auditory thresholds were determined for 500 Hz pure tone pulses of 15, 25 and 50 ms duration presented leading, following or simultaneously with noise pulses of 50 or 250 ms duration. Masking by the noise decreased : (i) with an increase in tone pulse duration; (ii) with a shortening of the noise pulse duration; and (iii) as the interval between tone and noise pulses was increased from o to 3 50 ms. The effect of the noise was independent of whether the noise led or followed the pure tone. It is suggested that the most significant factor affecting masking was the duration of the interval between tone and noise, and that the site for the interactions between signals is central to the inner ear.
Behavioural and Physiological Aspects of Swimming in Cercariae of the Digenetic Trematode, Proterometra Macrostoma
Authors: Prior David J. , Uglem Gary L. 
Published: April 2021

ABSTRACT
Cyclical swimming behaviour of the cercariae of the digenetic trema-tode, Proterometra macrostoma, involves a highly regular alternating swim-sink sequence. During periods of swimming the cercariae are propelled upward through the water by alternating lateral contractions of the tail. Following each burst of swimming the cercariae passively drift downward. Suction electrode recordings from the tail during swimming reveal that a single biphasic potential precedes each contraction in a burst. The site of initiation of the rhythmic activity is the transverse band at the junction of the furcae and body of the tail. Sensory feedback does not play a major role in maintenance of the rhythm. A burst of swimming can be initiated by tactile stimulation of the tail. At no time is a cercaria refractory to tactile stimulation. The tail of P. macrostoma cercariae is an autonomous locomotor organ specialized for the brief free-living period between emergence from the snail host and infestation of the primary host.
Occlusable Yellow Corneas in Tetraodontidae
Authors: Appleby S. J. , Muntz W. R. A. 
Published: April 2021

ABSTRACT
In three species of brackish-water puffer fish (Tetraodontidae) the corneas are colourless in the dark but become yellow in the light, through the migration of pigment in chromatophore cells lining the corneal margirts. Spectrophotometry indicted the pigment to be a carotenoid. The threshold and time course of pigment migration were determined, and the effects of Unilateral illumination and optic nerve section suggest that the movement is under local control. It is shown that the increase in optical sensitivity obtained by clearing the eye of pigment should be advantageous for fish living in clear water.
Chemical Recognition and Nematocyte Excitation in A Sea Anemone
Authors: Lubbock Roger 
Published: April 2021

ABSTRACT
The response of nematocytes in the anemone Stichodactyla haddoni to contact with complex organic compounds varies according to the substance concerned and in most cases according to the level of accompanying mechanical stimulation. Compounds with a proteinaceous moiety differ in their capacity to excite nematocytes, but usually tend to induce a stronger response than polysaccharides or lipids. Nematocyst discharge against foreign animals appears to be the result of a sophisticated cellular recognition process in which the nematocytes, and/or cells closely associated with them, respond to physical contact with a surface of appropriate chemical composition.
High Density Cell Water in Amphibian Eggs?
Authors: Mild Kjell Hansson , Løvtrup Søren , Forslind Erik 
Published: April 2021

ABSTRACT
The exchange of isotopic water, 2H2O and H218O, has been studied in amphibian eggs. The experiments were carried out with ovarian and body cavity eggs of Rana temporaria and unfertilized eggs of Ambystoma mexicanum. The cytoplasmic diffusion coefficient for H218O was found to be 4·6 × 10− 4 cm2/s, somewhat higher than that for 2H2O, 3·4 × 10−6 cm2/s. The total change in reduced weight, ΔRW;, during the isotope experiments was compared with the total amount of water in the egg cell, m. The ratio &RW/m was significantly higher than would be expected from calculations using ordinary water density values. The results are discussed in terms of different phases of structured cell water.
Neurophysiological Correlates of the Dopaminergic Cilio-Inhibitory Mechanism of Mytilus Edulis
Authors: Catapane Edward J. , Stefano George B. , Aiello Edward 
Published: April 2021

ABSTRACT
The neurophysiological regulation of gill ciliary activity by the CNSof the bivalve mollusc Mytilus edulis was studied by recording electrophysiological activity of the branchial nerve while simultaneously observing ciliary activity of the lateral ciliated cells of the gill by stroboscopic microscopy. The addition of dopamine to the visceral ganglion slowed and stopped ciliary activity by increasing the firing rate of the cilio-inhibitory dopaminergic neurones of the visceral ganglion which innervate the gill. This could be antagonized at the ganglion by pre-applications of ergonovine or methysergide, or by prior treatments of intact animals with the neurotoxin 6-hydroxydopamine. The study confirms earlier work showing the inhibitory functioning of dopaminergic neurones of the CNS and demonstrates the manner in which they may exert their effects.
Haemolymph-Volume Changes in Rhodnius Prolixus During Flight
Authors: Gringorten J. L. , Friend W. G. 
Published: April 2021

ABSTRACT
Exhaustive flight in male Rhodnius prolixus Stål (Hemiptera : Reduviidae) can cause up to a 50% decrease in haemolymph volume. Insects urinate during the flight period which may account for this decrease. The percentage water in the haemolymph does not appear to change substantially during exhaustive flight.
A Novel Mechanism For Salt and Fluid Transport Across Epithelia
Authors: Edwards H. A. 
Published: April 2021

ABSTRACT
Some salt transporting epithelia can absorb inorganic ions from extremely low external concentrations. Salt depleted frogs, for example, can absorb sodium ions from freshwater at concentrations down to 0·01 mM (Krogh, 1939) while freshwater mosquito larvae can maintain haemolymph sodium at 30 mM in external media containing as little as 1·55 × 10−3 mM sodium (Stobbart, 1974). The ability of the frogskin to absorb ions, into the blood, from such low external concentrations has been held to present difficulties (Hansen & Zerahn, 1964) for the classical model, which proposes a passive entry of external sodium ions into the cells and pumping at the inner epithelial membrane (Koefoed-Johnsen & Ussing, 1958). At least two current hypotheses exist to explain how net sodium transport from low external concentrations is achieved. The first postulates an involvement of ion pumps located on the outer epithelial membrane (Hansen & Zerahn, 1964; Leblanc, 1972) and the second that the electrical potential across the outer membrane is large enough to create an inwardly directed electro-chemical gradient to induce a passive entry of sodium ions from media containing as little as 1 mM sodium (Nagel, 1977). This communication proposes an alternative model for unidirectional salt transport from dilute environments which may be applicable to the uptake of cations and anions in a variety of salt absorptive epithelia.
Pharmacological Properties of Axonal Sodium Channels in the Cockroach Periplaneta Americana L.
Authors: Sattelle D. B. , Pelhate M. , Hue B. 
Published: April 2021

ABSTRACT
Voltage-clamp experiments on isolated giant axons of the cockroach Periplaneta americana L. show that chemically synthesized saxitoxin specifically and reversibly blocks the transient inward sodium current without affecting the steady-state outward potassium current. From the concentration dependence of sodium, current suppression it is concluded that individual sodium channels are blocked by single molecules of synthetic saxitoxin which bind reversibly to part of the channel with a dissociation constant of 3·0 × 10−9 M. Synthetic saxitoxin blocks sodium channels in cockroach axons at a lower concentration than tetrodotoxin. Sodium channel block by synthetic saxitoxin is more readily reversed than tetrodotoxin-induced block.
Energy Metabolism of Dragonflies (Odonata: Anisoptera) at Rest and During Endothermic Warm-Up
Authors: May Michael L. 
Published: April 2021

ABSTRACT
Energy metabolism at rest and during pre-flight warm-up was measured in a variety of anisopterous dragonflies. Resting oxygen consumption was similar in its relation to body temperature (Tb) and body mass to that of other insects. At 30 °C, log M = 0·91 log m + 0·44, where M is metabolism (W) and m is body mass (kg). Metabolism during warm-up was calculated both from measurements of Tb and from oxygen consumption. By the former method, log M = 1·01 log m + 2·22 at the maximum Tb attained during warm-up, and log M= 0·90 log m+ 1·87 at Tb = 30 °C. Oxygen consumption measurements mostly gave values of M about 15% higher. Total energy cost of warm-up is directly related to mass, thermal conductance and Tb at takeoff, and inversely related to warm-up rate.
Electrical Interactions Between the Giant Axons of A Polychaete Worm (Sabella Penicillus L.)
Authors: Mellon DeForest , Treherne J. E. , Lane N. J. , Harrison J. B. , Langley C. K. 
Published: April 2021

ABSTRACT
Intracellular recordings demonstrated a transfer of impulses between the paired giant axons of Sabella, apparently along narrow axonal processes contained within the paired commissures which link the nerve cords in each segment of the body. This transfer appears not to be achieved by chemical transmission, as has been previously supposed. This is indicated by the spread of depolarizing and hyperpolarizing voltage changes between the giant axons, the lack of effects of changes in the concentrations of external divalent cations on impulse transmission and by the effects of hyperpolarization in reducing the amplitude of the depolarizing potential which precedes the action potentials in the follower axon.
The ten-to-one attenuation of electronic potentials between the giant axons argues against the possibility of an exclusively passive spread of potential along the axonal processes which link the axons. Observation of impulse traffic within the nerve cord commissures indicates, on the other hand, that transmission is achieved by conduction of action potentials along the axonal processes which link the giant axons. At least four pairs of intact commissures are necessary for inter-axonal transmission, the overall density of current injected at multiple sites on the follower axon being, it is presumed, sufficient to overcome the reduction in safety factor imposed by the geometry of the system in the region where axonal processes join the giant axons.
The segmental transmission between the giant axons ensures effective synchronization of impulse traffic initiated in any region of the body and, thus, co-ordination of muscular contraction, during rapid withdrawal responses of the worm.
Asymmetrical Muscle Activity During Feeding in the Gar, Lepisosteus Oculatus
Authors: Lauder G. V. , Norton S. F. 
Published: April 2021

ABSTRACT
Prey capture in the spotted gar, Lepisosteus oculatus, was studied by high-speed cinematography synchronized with electromyographic recordings of cranial muscle activity. Muscle activity patterns were recorded during each of the three major phases of feeding: the initial strike at the prey, manipulation of the prey following capture, and swallowing. With one exception, the obliquus superioris, all muscles at the strike are active in a bilaterally symmetrical pattern. During the manipulation phase two distinct muscle activity patterns occur: one is characterized by symmetrical activity in the epaxial muscles and obliquus inferioris, the other by complete asymmetry between the right and left sternohyoideus, obliquus superioris, and epaxial muscles. Low-amplitude manipulatory movements are characterized by activity in one side of the sternohyoideus only, all other muscles being generally inactive. The adductor mandibulae and obliquus inferioris are always active symmetrically. Asymmetrical activity in the sternohyoideus, epaxial muscles, and obliquus superioris correlates with lateral head movements during feeding and acts to rotate prey into the preferred orientation for swallowing. The pattern of asymmetrical activity between right and left side muscles is discussed in relation to previous studies of feeding which utilized only unilateral muscle recordings.
Ionic Bases of Resting and Action Potentials in Salivary Gland Acinar Cells of the Snail Helisoma
Authors: Hadley Robert D. , Murphy A. Don , Kater Stanley B. 
Published: April 2021

ABSTRACT
Values for resting and action potentials of Helisoma salivary gland cells are much the same as in most neurones and muscle cells. The resting potential is primarily due to the distribution of potassium ions across the membrane, with a small contribution by an electrogenic sodium pump. Estimated values for intracellular potassium concentration and the relative membrane permeabilities to sodium and potassium ions correspond to similar estimates in other excitable tissues. The inward current of the salivary gland action potential is carried predominantly by calcium ions and possibly serves as a mechanism of calcium entry for stimulus-secretion coupling.
Morphology and Electrophysiology of the Ovulation Hormone Producing Neuro-Endocrine Cells of the Freshwater Snail Lymnaea Stagnalis (L.)
Authors: De Vlieger T. A. , Kits K. S. , Ter Maat A. , Lodder J. C. 
Published: April 2021

ABSTRACT
The ovulation hormone producing neuro-endocrine cells of Lymnaea stagnate, the caudo-dorsal cells (CDC), are comparable to the bag cells of Aplysia. Both cell types are capable of the production of a long-lasting activity (afterdischarge) during which an ovulation hormone is released. The CDC (30 cells in the left cerebral ganglion and 70 cells in the right) are usually electrically silent but an afterdischarge can be brought about in all cells of both groups by direct, repetitive electrical stimulation of single CDC. This is not possible in every preparation, indicating that the CDC can be in different states of excitability.
All cells participate in the afterdischarge and fire approximately synchronously. All CDC are electrotonically connected. Results of experiments in which neurones were injected with horseradish peroxidase suggest that the demonstrated electrotonic connexions between the two opposite groups of CDC are brought about by 10–12 special axons.