bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of Heart Activity in the Terrestrial SlugLimax Maximusby the Feeding Motor Program, Small Cardioactive Peptides and Stimulation of Buccal Neuron B1
Authors: Welsford Ian G. , Prior David J. 
Published: April 2021

ABSTRACTActivation of the feeding motor program (FMP) increases the force of ventricular contractions in heart/central nervous system (CNS) preparations of the terrestrial slug Limax maximus (Linnaeus). The FMP-induced increase in ventricular activity requires innervation of the heart by abdominal ganglion nerves N9 and Nil. Application of the small cardioactive peptides SCPA and SCPB to isolated preparations of the heart causes dose-dependent increases in the force of ventricular contractions. In addition, the SCPs induce rhythmic contractions in quiescent heart preparations. The effects of the SCPs appear to be specific in that the neuropeptide FMRFamide has an inhibitory effect on ventricular activity. SCP-like and FMRFamide-like immunoreactive material is found in the heart, kidney and pericardium and in the nerves that innervate these organs. Unilateral intracellular stimulation of buccal neuron Bl, which contains SCP-like and FMRFamide-like immunoreactive material, mimics the FMP-and SCP-induced increases in ventricular activity. The effect of B1 on ventricular activity is frequency dependent and requires innervation of the heart by Nil. These results are consistent with the hypothesis that the SCPs are involved in feeding-related alterations in heart activity in Limax and that the control of this effect involves neuron Bl.
Actions Of Putative Amino Acid Neurotransmitters On The Neuropile Arborizations Of Locust Flight Motoneurones
Authors: Dubas F. 
Published: April 2021

ABSTRACTTo characterize the receptors for putative amino acid neurotransmitters present on the dendritic arborizations of flight motoneurones in Locusta migratoria, the effects of pressure applications of glutamate, γ-aminobutyric acid (GABA), aspartate, taurine, glycine and cysteine were studied using an animal preparation in which neuropile intracellular recordings could be made during expression of the flight motor output. A majority of cells responded to glutamate, GABA, aspartate and taurine. At resting potential, glutamate and GABA caused, in different cells, a depolarization, a hyperpolarization or, in a few cells, a biphasic response, all accompanied by a decrease in the size of the evoked and spontaneous postsynaptic potentials (PSPs). At spiking threshold, the responses were always hyperpolarizing. Activation of a chloride conductance mediated the effects of both glutamate and GABA. In some cells, the response to glutamate or GABA desensitized during long-lasting applications, but in most cells the amplitude of the response did not decrease during applications lasting several minutes. Responses to aspartate and glutamate had identical reversal potentials and cross-desensitized. Responses to GABA and taurine had more negative reversal potentials and did not cross-desensitize with those elicited by glutamate or aspartate. Only a few neurones responded to applications of glycine or cysteine at resting potential; they responded with an inhibition of spiking at depolarized potentials. These data suggest that a variety of amino acid receptors are present on the neuropile arborizations of flight motoneurones.
The Function of the Urinary BladderIn Vivoin the Freshwater Rainbow Trout
Authors: Curtis B. James , Wood Chris M. 
Published: April 2021

ABSTRACTTwo different approaches were employed to examine the possible urine storage and ionoregulatory functions of the urinary bladder in vivo in the freshwater trout. An indirect approach, using non-catheterized fish, involved ‘spot sampling’ from the bladder to determine urine composition and measurement of PEG-4000 release into surrounding water to quantify urination events. The direct approach employed a new external catheterization technique to collect naturally discharged urine. Both methods demonstrated that trout urinate in intermittent bursts at 20–30 min intervals, and that natural urine flow rate is at least 20% lower and urinary Na+ and Cl− excretion rates at least 40 % lower than those determined by the traditional internal bladder catheter technique. The urine is stored for approximately 25 min prior to discharge, and significant ionic reabsorption via the bladder epithelium occurs during this period; a small residual volume is always likely to be retained. We conclude that previous studies using internal bladder catheterization have underestimated the ionoregulatory effectiveness of the entire renal system by preventing the function of the urinary bladder.
Olfactory Cues Perceived at the Home Loft are not Essential for the Formation of a Navigational Map in Pigeons
Authors: Waldvogel Jerry A. , Phillips John B. 
Published: April 2021

ABSTRACTDeflector lofts consist of a ‘pinwheel’ arrangement of four stationary deflector panels attached to the sides of a cube-shaped cage. These panels are made of wood and Plexiglas and rotate incoming winds in either a clockwise or counterclockwise direction. When released at a distant site, homing pigeons (Columba livia) raised in deflector lofts exhibit a shift in orientation relative to controls which corresponds to the clockwise or counterclockwise rotation of winds in their loft, suggesting the involvement of wind-borne olfactory cues in pigeon navigation. As part of a long-term study designed to test whether orientation cues other than odors might also be involved in creating the deflector-loft effect, we carried out experiments in upstate New York, USA, in which deflector lofts were modified to reverse the direction of light reflected from the Plexiglas panels while leaving the rotation of winds unchanged. The results indicate that the orientation of pigeons raised as permanent residents of these altered deflector lofts is not influenced by reflected light cues; i.e. they exhibit the same orientation bias as birds raised in the lofts with normal panels. This is in direct contrast to our previous findings that non-resident pigeons kept in the altered lofts for short periods exhibit a reversal of initial orientation compared to birds from the lofts with normal panels. However, when permanent-resident birds are prevented from having a direct view of the horizon sky by the addition of ‘anti-cheating’ slats (which prevent the birds from seeing beyond the end of each panel), the deflections are either greatly reduced or eliminated entirely, contrary to the predictions of olfactory navigation models. This disappearance of the deflector-loft effect in the presence of anti-cheating slats suggests that the positions of the deflector panels in the two experimental lofts must be differentially influencing important visual orientation cues reaching the birds housed inside. We believe that these cues are probably derived from polarized skylight emanating from the horizon, and that the obstruction of specific regions of horizon skylight by the deflector panels in the two experimental lofts is responsible for a miscalibration of the pigeon’s sun compass. This miscalibration, in turn, generates the orientation bias observed for deflector-loft birds. Our findings force us to conclude that, at least for pigeons raised in New York (and perhaps those from other geographical locations as well), olfactory cues perceived at the home loft do not contribute to the formation of the navigational map.
Studies on the Fauna of an Algerian Hot Spring
Authors: Mason I. L. 
Published: April 2021

ABSTRACT
Many exaggerated statements have been made, and too often uncritically repeated, concerning the temperatures at which animals and plants have been found in hot springs. To throw light on this subject, the author undertook two expeditions—in the summer of 1937 and the winter of 1938–9—to study the hot springs at Hammam Meskoutine, Algeria.
The Evolution of Activity Capacity
Authors: Bennett Albert F. 
Published: April 2021

ABSTRACT
The capacities of animals for activity (burst speed, maximal exertion, endurance) are examined in relation to their selective importance in extant populations and the pattern of their evolution in major animal taxa.
Activity capacities have been demonstrated to be both heritable and highly variable in natural populations and hence susceptible to natural selection. Some field studies have demonstrated significant positive associations between activity capacities, particularly burst speed, and survivorship; other studies have not. The potential for such selection therefore clearly exists, although it may not operate in all populations.
Comparative studies of major taxa have linked endurance capacities to maximal rates of oxygen consumption; speed and exertion are correlated with capacities for anaerobic metabolism, either the catabolism of phosphagens or the production of lactic acid or octopine, depending on taxon. In vertebrates, the primitive metabolic pattern involved the use of aerobic metabolism to support moderate swimming performance, supplemented by bursts of activity fuelled through lactic acid production. Because of much greater locomotor costs, the transition of vertebrates onto land entailed a decrease in endurance, which was greatly expanded again only after the evolution of the higher rates of aerobic metabolism characteristic of the birds and mammals. These greater aerobic capacities may have been selected for thermoregulatory reasons and/or for increased activity capacity itself.
Effect of Exercise on Amino Acid Concentrations in Skeletal Muscle and Plasma
Authors: Henriksson Jan 
Published: April 2021

ABSTRACT
Protein is not normally an important energy fuel for exercising muscle. In spite of this, there is a significant increase in the rate of amino acid catabolism during exercise. This is secondary to the exercise-induced increase in several metabolic processes, such as hepatic gluconeogenesis and the citric acid cycle, where amino acid carbon is utilized. The suppression of protein synthesis during an exercise bout leaves amino acids available for catabolism. There is some evidence that basal amino acid concentrations in plasma and muscle may be higher in trained than in untrained individuals. In the rat, the concentration of free amino acids is higher in slow-twitch than in fast-twitch muscles. With short-term exercise, the transamination of glutamate by alanine aminotransferase leads to increased levels of alanine in muscle and plasma, and an increased release of alanine from the muscle. At the same time, the muscle and plasma glutamate concentrations are markedly decreased. The plasma glutamine level is elevated with short-term exercise, but changes in muscle glutamine concentration are more variable. With prolonged exercise, there is a depletion of the plasma amino acid pool, which may be explained by an increased consumption in organs other than muscle. With the exception of alanine, we found, however, that the muscle levels of free amino acids are kept stable throughout a 3.5-h exercise period. There is a significant activation of branched-chain amino acid metabolism with prolonged exercise, and the current data indicate that this is more pronounced in endurance-trained subjects than in untrained controls.
Patterns of Metabolic Recovery from Exercise in Amphibians and Reptiles
Authors: Gleeson Todd T. 
Published: April 2021

ABSTRACT
The physiological responses of amphibians and reptiles undergoing vigorous exercise are qualitatively similar to those of other vertebrates. Oxygen consumption increases rapidly to rates that are three-to 10-fold the rates at rest. The aerobic response to graded exercise in locomoting reptiles and amphibians is for the most part linear. Oxygen transport by the cardiovascular system during exercise is accomplished by factorial increases in heart rate and oxygen extraction from arterial blood in a fashion similar to that in mammals. Increments in stroke volume during exercise are small or in some cases negative. The influence of temperature or of intracardiac shunting on the cardiovascular function of active amphibians and reptiles is poorly understood. These aerobic responses to exercise are accompanied by robust anaerobic contributions to energy metabolism, resulting in significant lactate accumulation and glycogen depletion. The rate of lactate accumulation during exercise is generally greater in reptiles than in amphibians, but in all cases is so rapid that the only significant substrate source to support anaerobic energy production is muscle glycogen. Vigorous behavior in these animals is therefore limited to some degree by the maintenance and replenishment of muscle glycogen stores. Whereas data from rats and dogs suggest that most lactate is oxidized to CO2 following exercise, amphibians and reptiles appear to use lactate as a substrate for immediate muscle glycogen replenishment. Data from a variety of amphibians and lizards demonstrate that lactate removal following activity and glycogen replenishment are stoichiometrically and temporally related. Studies employing isotopically labelled compounds in intact frogs and lizards indicate that most lactate is resynthesized to glycogen during recovery. In vivo studies suggest skeletal muscle as the site for glycogenesis from lactate, and in vitro studies from many laboratories demonstrate a gluconeogenic capacity in skeletal muscle of lizards, frogs and salamanders. The liver appears to play no significant role in recovery metabolism in any of these classes. Data from lizard muscle suggest that oxidative fiber types have the most significant gluconeogenic capacity, and that the process may be stimulated by the hormonal milieu that exists following exercise. Whereas the recovery metabolism of many mammals seems to facilitate the rapid return of acid-base balance via lactate oxidation, the strategy of lactate removal employed by amphibians and reptiles provides for a mechanism of immediate muscle glycogen replenishment and consequently a reestablished capacity for subsequent activity.
Cardiovascular and Respiratory Control Mechanisms During Exercise: an Integrated View
Authors: Turner Duncan L. 
Published: April 2021

ABSTRACTExercise can impose an immense stress upon many physiological systems throughout the body. In order that exercise performance may be optimally maintained, it is essential that a profound and complex series of responses is coordinated and controlled. The primary site for coordination is the central nervous system, whereas control mechanisms (both feedback loops and feedforward activation) involve complex sensory information, often in the form of neural coding but also in the form of blood-borne chemical signals, a number of levels of peripheral and central integration and, finally, the efferent branches of the nervous system coursing via sympathetic and parasympathetic nerves to target sites of action.The neurohumoral control of the cardiorespiratory responses to exercise has received intense attention for over two decades and some particularly important steps forward in its understanding have occurred within the last 10 years. The initial fast increase (phase 1) in cardiovascular and ventilatory flow parameters are brought about by neurally mediated muscle mechanoreceptor feedback reflexes and a feedforward ‘central motor command’. The blood pressure operating point is also raised by a combination of these two neural mechanisms. Fine control of the matching of cardiac output to ventilation may occur by means of a feedforward ventilatory control of cardiac origin. During the slower phase of adjustment (phase 2), the neurally mediated mechanisms are augmented by a cohort of humorally mediated feedback reflexes involving muscle and vascular chemoreceptors as well as being supported by central neural reverberation. A steady state of cardiorespiratory responses is achieved (phase 3) by an amalgamation of neural and humoral, i.e. ‘neurohumoral’, control mechanisms, which then must further modulate the cardiorespiratory responses to exercise in the face of increasing competition from other basic physiological requirements, such as thermoregulation and fluid homeostasis.The myriad of subtle modifications in the basic blueprint found throughout the vertebrates illustrates the flexibility of the principal design and also how it can be applied to an extraordinary number of specific ecophysiological niches.
The Ionic Basis of the Hypo-Osmotic Depolarization in Neurons From the Opisthobranch Mollusc Elysia Chlorotica
Authors: Quinn R. H. , Pierce S. K. 
Published: April 2021

ABSTRACT
The resting potential of identified cells (Parker cells) in the abdominal ganglion of Elysia chlorotica (Gould) depolarizes by about 30 mV in response to a 50% reduction in osmolality and returns to the original potential in 20 min. Cell volume recovery requires approximately 2 h. Thus, recovery of the resting potential is not dependent on recovery of cell volume. The hypo-osmotic depolarization persists following inhibition of the electrogenic Na+/K+-ATPase with ouabain, and the levels of extracellular K+ and Cl− have little effect on the magnitude of the depolarization, while decreasing extracellular Na+ concentration produces a depolarization of only 10 mV. This suggests that the hypo-osmotic depolarization in Parker cells results mostly from increased relative permeability to Na+. Following transfer from 920 to 460mosmolkg−1, Na+, Cl− and proline betaine leave the cells while intracellular K+ is conserved. Loss of intracellular Na+ and conservation of intracellular K+ are dependent on active transport by the Na+/K+-ATPase. Na+ and proline betaine leave the cells with a time course that is much longer than that of the hypo-osmotic depolarization. Unlike the other solutes, most of the reduction in intracellular Cl− concentration occurs coincidentally with the hypo-osmotic depolarization. However, unlike the hypo-osmotic depolarization, bulk loss of Cl− does not require the reduction in osmolality, only the reduction in extracellular ion concentrations. There is no apparent relationship between membrane depolarization and the regulation of intracellular osmolytes in Elysia neurons following hypo-osmotic stress.
Wing Movements Associated With Collision-Avoidance Manoeuvres During Flight in the Locust Locusta Migratoria
Authors: Robertson R. Meldrum , Reye David N. 
Published: April 2021

ABSTRACT
Flying locusts will try to avoid colliding with objects directly in their flight path. This study investigated the wing movements and behaviour patterns associated with collision avoidance. Tethered locusts were flown in a wind tunnel. Targets were transported at different speeds either directly towards the head of the animal or to one side of the midline but parallel to it. Changes in the form of the wingbeat for each of the wings were monitored using either a video camera or a high-speed ciné camera. Animals attempted to avoid an impending collision by making movements interpreted here as (a) increasing lift to fly over the object, (b) gliding and extending the forelegs to land on the object, and (c) steering to one side of the object. Steering was monitored by observation of abdominal movements. Steering to one side of an approaching target was reliably associated with an earlier and more pronounced pronation of the wings on the inside of the turn. Also, in the middle of the downstroke, the forewings were markedly asymmetrical. On the outside of the turn, the forewing was more elevated and separate from the hindwing. On the inside of the turn, the forewing was more depressed and often came down in conjunction with, or in advance of, the hindwing on that side. The forewing asymmetry correlated with the position of the target such that most attempted turns were in the direction that would take the animal around the closest edge. High-speed cinematography showed that the asymmetry was caused both by changes in the timing of the two wings and by changes in the angular ranges of the wingbeats. We propose that these changes in the form and timing of the wingbeats are likely to have swung the flight force vector around the long axis of the body to produce a banked turn around the closest edge of the object.
A Paradoxical Problem in Insect Communication: Can Bush Crickets Discriminate Frequency?
Authors: Hartley J. C. , Stephen R. O. 
Published: April 2021

ABSTRACT
Many bush crickets (Tettigoniidae) produce calls that consist of trains of transient high-frequency pulses (Fig. 1). Each pulse is generated by a file tooth on one wing being struck by a plectrum on the other, causing the wing resonator to produce harmonic transients each composed of only two or three cycles of oscillation. In animals, high-frequency sound can only be detected by means of some form of auditory filter, since the refractory period of the nervous system restricts direct measurement using periodicity to frequencies below 1 kHz. The necessity of using a filter produces a paradoxical situation with these brief transients. If the bandwidth of a tuned filter is such that frequency can be accurately discriminated, the response time may exceed the duration of the signal and then there would be no output. To respond to such a signal, the filter bandwidth must be increased but then frequency information is lost.
Comparison of Messenger RNA Pools in Active and Dormant Artemia Franciscana Embryos: Evidence for Translational Control
Authors: Hofmann Gretchen E. , Hand Steven C. 
Published: April 2021

ABSTRACT
In response to environmental anoxia, embryos of the brine shrimp Arteimia franciscana enter a dormant state during which energy metabolism and development are arrested. The intracellular acidification that correlates with this transition into anaerobic dormancy has been linked to the inhibition of protein synthesis in quiescent embryos. In this study, we have addressed the level of control at which a mechanism mediated by intracellular pH might operate to arrest protein synthesis.
Two independent lines of evidence suggest that there is an element of translational control when protein synthesis is arrested in dormant embryos. First, as determined by in vitro translation techniques, there were no significant quantitative differences in mRNA pools in dormant as compared to actively developing embryos. In addition, fluorography of the translation products showed that there are no large qualitative changes in mRNA species when embryos become dormant. These data suggest that there was no net degradation of mRNA pools in dormant embryos and that protein synthesis may therefore be controlled more strongly at translation than at transcription. Second, polysome profile studies showed that dormant embryos possess reduced levels of polysomes relative to those found in cells of active embryos. The disaggregation of polysomes is an indication that the initiation step in protein synthesis is disrupted and is further evidence that the mechanism involved in protein synthesis arrest in dormant Artemia involves translational control.