bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Neural Basis of Escape Swimming Behaviour in the Squat Lobster Galathea Strigosa
Authors: Sillar Keith T. , Heitler William J. 
Published: April 2021

ABSTRACT
The anatomy and physiology of neurones underlying escape swimming behaviour in the squat lobster, Galathea strigosa, have been investigated, and the results are discussed in the context of the evolution of decapod escape behaviour. In contrast to crayfish, hermit crabs and a number of other related decapods, Galathea does not possess a giant fibre system for escape. Fast flexor motor neurones (FFs) and fast extensor motor neurones (FEs) have been shown, by cobalt backfilling, to be homologous with crayfish FFs and FEs in number, size and distribution of somata. A small degree of intersegmental and interspecific variation is noted. The flexor inhibitor (FI) neurone is described in terms of its central anatomy, peripheral function and peripheral branching pattern. In each of these respects the neurone is found to be homologous with the crayfish FI The neurone homologous with the crayfish motor giant (MoG) in its soma size and position is found to be a typical FF in Galathea. This ‘MoGH’ contrasts with the crayfish MoG in having central neuropilar arborization and in lacking axonal branches in the connectives. These differences can be accounted for by the absence of cord giant axons.
Pressure-Induced Changes in Ca2+-Channel Excitability inParamecium
Authors: Otter T. , Salmon E. D. 
Published: April 2021

ABSTRACTThe behaviour of swimming Paramecium is markedly affected by hydro-static pressure (50-200atm, 1 atm = 101 325Pa). To investigate whether pressure might alter behaviour by acting directly on specific ion channels that mediate the behavioural responses, we examined the effects of K+, Na+ and Ba2+ ions on swimming speed and the reversal response during pressurization and decompression. If pressure acted on the channels that transport these ions, then the pressure-induced responses of swimming Paramecium should be exaggerated or diminished, according to which ions were present in the experimental buffer. Pressurization to 100 atm in standard buffer inhibited the brief reversal of swimming direction that occurred at atmospheric pressure when a paramecium encountered the wall of the pressure chamber. To determine whether pressure impaired mechanoreceptor function or directly blocked the Ca2+-channels that control ciliary reversal, we added Ba2+ or Na+ to standard buffer to induce multiple spontaneous reversals. Pressurization blocked these reversals, suggesting that channel opening is directly inhibited by pressure. Decom-pression in standard buffer elicited momentary ciliary reversal and backward swimming. Buffers with a high ratio of K+ to Ca2+ suppressed this response, and the decompression-induced reversal was exaggerated in the presence of Ba2+ or Na+, consistent with the effects that these ions are known to have on Paramecium’s reversal response. These data imply that, upon decompression, the Ca2+-channels that mediate ciliary reversal open transiently. In addition to blocking the reversal response, pressurization slowed forward swimming. By examining the response to pressurization of Paramecium immobilized by Ni2+, we found that hydrostatic pressure apparently slows swimming by reorientating the direction of ciliary beat.
The Mechanical Power Output of A Tettigoniid Wing Muscle During Singing and Flight
Authors: Josephson Robert K. 
Published: April 2021

ABSTRACT
The mesothoracic wings of tettigoniid insects are used in song production and flight; the metathoracic wings in flight only. In Neoconocephalus triops the wing stroke frequency during flight is about 25 Hz ; the frequency during singing about 100 Hz. The twitch duration of mesothoracic, first tergocoxal (Tcxl) wing muscles is only about one-half the duration of the upstroke or downstroke portion of the wing cycle. During tethered flight the Tcxl muscles are activated on each cycle with short bursts of action potentials, each burst typically containing four action potentials. Activating the muscles with brief, tetanizing bursts increases the duration of muscle activity and the mechanical power output per wing cycle above that obtainable with single twitch contractions of the muscle. The mechanical power output was determined for mesothoracic Tcxl muscles undergoing sinusoidal length change and stimulated phasically in the length cycle. At 25 Hz, the power at optimum muscle strain and optimum stimulus phase was 5 Wkg-1 at 30 °C for muscles activated with a single stimulus per cycle and about 33 W kg-1 for muscles activated with bursts of stimuli in the normal pattern of flight. The maximum power output at 100 Hz, the singing frequency, was 18 W kg-1. This was achieved with a single stimulus per wing cycle. From published values of oxygen consumption by tettigoniids during singing, it is concluded that the efficiency of conversion of metabolic to mechanical power during singing is about 3 %.
Temperature Acclimation: Influence on Transient Outward and Inward Currents in an Identified Neurone of Helix Pomatia
Authors: Zečević Dejan , Levitan Herbert , Pašlć Mira 
Published: April 2021

ABSTRACT
To gain insight into the mechanisms underlying compensatory changes in excitability induced by thermal acclimation we examined the effects of short-term and long-term temperature transition on a transient outward potassium current (A-current) and the transient inward current in an identified neurone (Br) of the land snail Helix pomatia. The A-current in neurones from snails acclimated to 20°C was suppressed by cooling to 3°C, with a Q10 of 4.5 between 10°C and 20°C. This is consistent with suppression of the ability of these neurones to fire repetitively at low temperatures. Neurones acclimated to low temperature (5°C) partially recovered their ability to fire repetitively, but exhibited no A-current, at this temperature. Neither the equilibrium potential for the A-current (EA), the steadystate inactivation parameters of the A-current (Bo), nor the ratio of the time constants of A-current activation and inactivation (τA/τB) were affected by cooling, leading to the conclusion that the reduction of the A-current by cooling was due to a decrease in the A-current activation parameters (GAA∞). Cooling reduced the maximum peak inward current, with a Q10 of 2, in neurones from warm-acclimated animals. After acclimation to 5°C, maximum peak inward current partially recovered. Cooling neurones from warm-acclimated animals slowed the time course of the recovery of inward current from inactivation. Acclimation to the cold caused a partial, compensatory shortening of the inactivation removal process.
Characteristics of Mechanoreceptors in the Air-Breathing Organ of the Holostean Fish, Amia Calva
Authors: Milsom William K. , Jones David R. 
Published: April 2021

ABSTRACT
Single nerve fibre discharge was recorded from mechanoreceptors associated with the air-breathing organ in double-pithed specimens of the bowfin, Amia calva L. These receptors were innervated by the vagus nerve and although their exact location was difficult to determine, most appeared to be located along the anterio-ventral wall of the single lung. All receptors increased tonic discharge with step increases in lung volume, above a threshold level, and were slowly adapting. There was a dynamic, rate-sensitive burst of activity associated with lung inflation and a dynamic, rate-sensitive inhibition of discharge associated with deflation. These responses were qualitatively similar to those of the tonic stretch receptors found in fish swimbladder and mammalian gut. All receptors were insensitive to changes in intrapulmonary partial pressures of oxygen and carbon dioxide. These observations suggest that receptors capable of transducing the rate, as well as the degree, of inflation and deflation are associated with primitive lungs, and may have arisen from tonic gut receptors.
Spontaneous Efferent Activity in Branches of the Vagus Nerve Controlling Heart Rate and Ventilation in the Dogfish
Authors: Barrett D. J. , Taylor E. W. 
Published: April 2021

ABSTRACT
Efferent activity was recorded from cranial nerves in the decerebrate dogfish (Scyliorhinus canicula) before and after injection of paralysing drugs. The recordings were made from the mandibular (Vth) and glossopharyngeal (IXth) nerves and the branchial (respiratory) and cardiac branches of the vagus (Xth) nerve. All the respiratory branches (Vth, IXth and Xth) and both cardiac branches fired rhythmic bursts of activity, synchronous with ventilation, which continued (at a higher rate) following paralysis, indicat-ing that they originated in the CN S rather than arising reflexly from stimula-tion of pharyngeal mechanoreceptors. A burst of activity in the Vth nerve was followed by a burst in the IXth then, after a 30-ms delay, simultaneous bursts in the three respiratory branches of the Xth. The bursts in the bran-chial cardiac branches had a fixed phase relationship with activity in the respiratory branches, the onset of each burst preceding that in the im-mediately adjacent branch (branchial III), whereas the bursts in the visceral cardiac branches had a variable phase relationship with all other branches. The branchial cardiac branches alone contained units which fired sporadi-cally between the bursts and increased their rate of firing during hypoxia. Both the bursting and non-bursting units responded to mechanical stimula-tion of the gill area. Separate oscillatory inputs driving the Vth, IXth and Xth respiratory motoneurones and an excitatory input to the bursting car-diac vagal motoneurones from expiratory motoneurones or the respiratory rhythm generator are implied by these relationships. The sporadically firing units in the branchial cardiac nerves clearly receive non-oscillatory inputs.
The Location of Cardiac Vagal Preganglionic Neurones in the Brain Stem of the Dogfish Scyliorhinus Canicula
Authors: Barrett D. J. , Taylor E. W. 
Published: April 2021

ABSTRACT
The locations, within the brain stem, of vagal efferent preganglionic neurones with axons in the two pairs of cardiac vagal rami of the dogfish have been defined by the retrograde intra-axonal transport of horseradish peroxidase (HRP). HRP was applied to the cardiac rami in one of two ways: either as crystals placed on the cut central end of the nerve or as a dried concentrated solution administered into the nerve on the tip of a fine pin. No difference was observed in the number of labelled cell bodies identified using either method. Labelled branchial cardiac vagal motoneurones were found ipsilaterally in the medial division of the vagal motor column, in the lateral division of the vagal motor column, and scattered between these two locations. In contrast, visceral cardiac vagal motoneurones were confined to the ipsilateral medial division of the vagal motor column. We suggest that the dual location of cell bodies supplying axons to the branchial cardiac branch of the vagus may represent a separation of function with respect to the two types of activity conducted by this nerve. Cardiac efferent fibres are confined in their exit from the brain to a middle group of vagal rootlets. This corresponds to the topographical representation of cardiac efferent somata within the extent of the vagal motor column.
The Characteristics of Cardiac Vagal Preganglionic Motoneurones in the Dogfish
Authors: Barrett D. J. , Taylor E. W. 
Published: April 2021

ABSTRACTPreganglionic vagal motoneurones supplying the heart of the dogfish have been located in the medulla by antidromic stimulation of the central cut end of the branchial cardiac branch of the vagus. They supplied axons with conduction velocities between ·75 and 16·3 ms-1, which is similar to mam-malian B fibres. Motoneurones were found in two locations: the rostromedial (N=5) and lateral (N = 12) divisions of the vagal motor column. Their measured depths and rostrocaudal distributions with respect to obex corresponded with the location of branchial cardiac motoneurones determined by horseradish peroxidase (HRP) histochemistry. All the neurones located in the rostromedial division of the vagal motor column were spontaneously rhythmically active. Their activity contributed to the rhythmic, respiratory-related bursts in peripheral recordings of efferent activity from the branchial cardiac vagus. They could be induced to fire in a prolonged burst by mechanical stimulation of the gill arches. The neurones located lateral to the rostromedial division of the vagal motor column could be divided into three categories : (1) spontaneously, continuously active cells which could be induced to fire more frequently by mechanoreceptor stimulation, (2) silent cells which could be induced to fire by mechanoreceptor stimulation, (3) silent cells which did not respond to mechanoreceptor stimulation. It is concluded, from the response of the medial and two categories of lateral cells to mechanoreceptor stimulation (which results in a transient bradycardia), that branchial cardiac motoneurones from both these central locations exert a chronotropic influence on the heart.
Contractile Performance of Cephalopod Hearts Under Anoxic Conditions
Authors: Driedzic William R. 
Published: April 2021

ABSTRACT
The cephalopod circulatory system includes an efferent systemic ventricle and two afferent branchial hearts. Branchial hearts lack coronary arteries and thus must be nourished by only venous blood. During routine metabolism in normoxic water, oxygen availability to branchial hearts is only a small percentage of that to the systemic heart; during hypoxic excursions the venous oxygen content may, at least transiently, approach zero (Johansen, Brix & Lykkeboe, 1982; Houlihan, Innes, Wells & Wells, 1982). The extreme difference in oxygen delivery to these tissues suggests that branchial hearts are better able to meet their energetic demands through anaerobic metabolism than are systemic hearts. This hypothesis was tested by following isometric force development of the cardiac tissue of the cuttlefish, Sepia officinalis, during cyanide poisoning. Experiments were also conducted with the systemic heart of Octopus vulgaris, in order to allow a comparison between a decapod and an octapod.
Continuous Recording of Arterial Blood in Octopus Vulgaris During Progressive Hypoxia and Movement
Authors: Smith P. J. S. , Duthie G. G. , Wells M. J. , Houlihan D. F. 
Published: April 2021

ABSTRACT
The respiratory and acid-base status of the blood of animals continually changes in response to variations in internal and external conditions. Attempts to monitor transitory changes by repetitive sampling techniques can, however, lead to an unacceptable level of blood loss. An external circulatory shunt in which blood is continuously removed from one vessel, passed across monitoring electrodes and reintroduced into an appropriate second vessel would obviate this problem. Such a system has been developed to continuously monitor blood gas parameters and pH in fish (Belaud, Trotter & Peyraud, 1979; Thomas & Le Ruz, 1982). The present study attempts to apply a similar technique to an invertebrate, Octopus vulgaris.
Ocular Freezing Avoidance in Antarctic Fish
Authors: Turner Jeffrey D. , Schrag Joseph D. , Devries Arthur L. 
Published: April 2021

ABSTRACT
A series of experiments was undertaken to determine the underlying mechanism of ocular freezing avoidance in a variety of antarctic fish. The three possible mechanisms that were examined include the depression of the freezing point through (1) colligative or (2) non-colligative means or (3) the supercooling of the ocular fluids. The ocular fluids of antarctic fish, like those of most vertebrates, are slightly hypotonic with respect to plasma and contain very low levels of serum proteins. The chief means of ocular freezing avoidance appears to involve supercooling of the ocular fluids. The presence of suitable barriers to prevent ice propagation into the eye has been demonstrated both in vitro and in vivo.
Multisegmental Integration and Divergence of Afferent Information from Single Tactile Hairs in A Cricket
Authors: Hustert R. 
Published: April 2021

ABSTRACT
The long tactile hairs of crickets contribute to intersegmental receptive fields of interneurones that integrate input from different types of tactile mechano-sensory hairs. Afferent input from the identified long hairs studied converges on a group of multisegmental interneurones of the abdominal and thoracic ganglia. Conversely, the input from each tactile hair receptor diverges to several multisegmental interneurones and also to motoneurones of their own and neighbouring segments. The interneurones have spike initiating zones in each ganglion they reach. Spikes initiated by hair afferents can travel caudally and rostrally in an interneurone. These interneurones spreading tactile information from single sensory cells to several ganglia are not suited for fine discrimination of sources of touch which could elicit specific somatotopically oriented motor behaviour of the cricket. More specific pathways from long tactile hairs to motoneurones exist in abdominal and thoracic segments.
The Development of the Locust Jumping Mechanism : II. Energy Storage and Muscle Mechanics
Authors: Gabriel Julie M. 
Published: April 2021

ABSTRACT
In an escape jump, the adult locust extensor tibiae muscle produces more than twice the specific energy output of the fourth instar muscle. If forced to jump repeatedly, the extensor muscles of hoppers and adults produce the same specific energy output. In escape jumping, specific energy production increases with age within an instar, but this does not seem to be the case in repeated jumping over a 10-min period. Adult locusts have thicker cuticle, including thicker semilunar processes, than hoppers. They also have relatively larger extensor apodemes. The cuticle thickness of all instars increases with age up to apolysis or maturity. The fourth instar extensor muscle has a lower angle of pennation and relatively longer muscle fibres than the adult muscle. The stiffness of the semilunar processes increases with age both within and between instars,’so that the mature adult leg has the highest energy storage capacity. To produce the required amount of energy storage, the adult muscle fibres must shorten slightly more than those of the fourth instar, but they must produce more than twice the force per unit area. The strain on the apodeme is similar in adults and hoppers, and greater at the distal than at the proximal end.
Neurohormonal Modulation of theLimulusHeart: Amine Actions on Neuromuscular Transmission and Cardiac Muscle
Authors: Watson Winsor H. , Hoshi Toshinori , Colburne John , Augustine George J. 
Published: April 2021

ABSTRACTThe responses of Limulus cardiac neuromuscular junctions and cardiac muscle cells to four endogenous amines were determined in order to identify the cellular targets underlying amine modulation of heartbeat amplitude. The amines increased the amplitude of the Limulus heartbeat, with dopamine (DA) being more potent than octopamine, epinephrine or norepinephrine. The effect of DA on heartbeat amplitude was not blocked by phentolamine. DA enhanced the contractility of deganglionated heart muscle, with time course and dose-dependence similar to its effect on the intact heart. The amines also enhanced neuromuscular transmission, with time course and dose-dependence similar to their effects upon the intact heart. The amplitude of unitary excitatory junction potentials (EJPs) and frequency of miniature excitatory junction potentials (mEJPs) were increased by DA, while mEJP amplitude was unchanged. Thus DA, and probably the other amines, had a presynaptic effect. Combined actions upon cardiac muscle and cardiac neuromuscular transmission account for the ability of these amines to increase the amplitude of the Limulus heartbeat.
Light-Dependent Eye Coupling During The Optokinetic Response Of The Crab Carcinus Maenas (L.)
Authors: Nalbach H.-O. , Thier P. , Varjú D. 
Published: April 2021

ABSTRACT
The movements of both distal eye stalks in the horizontal plane, elicited by optokinetic stimuli, have been recorded simultaneously. A panorama was split into two separate halves and was either oscillated around the animal in a sinusoidal fashion or displaced in a stepwise manner. Both eyes could be stimulated independently. The stimuli on both sides differed either (a) in the illumination, or (b) in the total amount of light impinging upon the eyes or (c) in the relative phase of the sinusoidal stimuli to either eye. As the illumination decreases the optokinetic response weakens. If one eye has no or only weak optokinetic input, it will be driven by the other eye. The response mediated by the contralateral optokinetic stimulus diminishes if the amount of light impinging upon the driven eye is increased. There is a logarithmic relationship between the response of the driving eye and that of the driven eye. The possible biological significance of these relationships is seen in the enhanced coupling at low light intensities. The variable strength of coupling and possible roles of movable eyes are discussed.
The Recovery From a Transient Inhibition of the Oxidative Metabolism of the Photoreceptors of the Drone (Apis Mellifera ♂)
Authors: Dimitracos S. A. , Tsacopoulos M. 
Published: April 2021

ABSTRACT
In the honey-bee drone retina (Apis mellifera) oxidative metabolism is carried out largely by the photoreceptors. We have studied the effects of a transient inhibition of this metabolism, by recording receptor potential simultaneously with measurements of local and extracellular [K+] ([K+]o), using O2-and K+-sensitive microelectrodes. When the retina was subjected to anoxia or exposed to Na-amobarbital (amytal), the photoreceptors depolarized by about 30 my, in parallel with an increase of [K+]o of up to 30 mmol 1−1, and the receptor potential was abolished in 2–3 min. The reduction of the receptor potential followed the beginning of anoxia with a delay, which we define as a ‘resistance’ of the photoreceptors to anoxia. The resistance to anoxia was greater if the photoreceptors were stimulated with only low intensity light flashes, suggesting that the effects of anoxia are due to the progressive consumption of a substance stored in the photoreceptors. This substance is probably ATP. When O2 was reintroduced, or amytal washed out, oxidative metabolism rapidly resumed. [K+]o quickly decreased and, after a large undershoot, returned to the baseline in less than 5 min. There was in parallel a repolarization of the photoreceptors, followed by recovery of the receptor potential. About 5 min after réintroduction of O2, when the [K+]o, the membrane potential and the amplitude and kinetics of the receptor potential had completely recovered, exposure of the retina to a second anoxia suppressed the receptor potential faster than had the first anoxia. Full recovery of the resistance to anoxia thus takes longer (by about 10 min) than recovery of the electrical properties of the photoreceptor cells. The amplitude of the extra oxygen consumption measured after a flash of light recovered in parallel with the resistance to anoxia.