bluuebunny/crossref_metadata_2025_split huggingface dataset:
Perturbation of the Motor System in Freely Walking Cockroaches I. Rear Leg Amputation and the Timing of Motor Activity in Leg Muscles
Authors: Delcomyn Fred 
Published: April 2021

ABSTRACTThe effects of amputation of a rear leg on the pattern of motor activity in the legs of freely walking cockroaches (Periplaneta americana L.) were studied. Amputation affected both the frequency and the timing (phase) of motor bursts during a stepping cycle. Bursts in the stump of an amputated rear leg and in the contralateral (intact) rear leg often occurred at two or three times the frequency of bursts in the other legs. The remaining legs also showed multiple bursting during some steps. Amputation affected the phase of motor bursts in two different ways. First, for every leg pair, phase was more variable after amputation, whether or not the mean phase was affected. Second, for some leg pairs, the mean phase itself was altered. During most steps, the timing of motor bursts in the stump of the amputated leg was walking-speed-dependent relative to bursts in the anterior legs. In contrast, the timing of bursts in the stump relative to bursts in the legs across the body from it showed no such speed-dependent timing. Timing between bursts in pairs of intact legs also showed either speed-dependent or speed-independent effects, depending on the pair under consideration. The effects of amputation were not consistent. After loss of a leg, bursts in some leg pairs occurred synchronously in some insects and alternately in others. Even in single insects there were cases in which the timing between bursts in two legs switched from one value to another during walking. These effects of amputation were manifest during slow walking only. At higher speeds, the timing of motor bursts in different pairs of legs was consistently closer to that seen during walking in intact insects. Three conclusions are drawn from these results, (i) During slow walking, sensory feedback from the legs helps maintain the timing of adjacent ipsilateral leg pairs, but has little influence on contralateral pairs, (ii) During slow walking, either sensory input is quite variable, or it has variable effects on the motor pattern, (iii) During fast walking, sensory input from the legs seems to play a minimal role, if any, in the timing of the motor pattern of walking.
A Suboesophageal Ganglion Cell Innervates Heart And Retrocerebral Glandular Complex In The Locust
Authors: Bräunig Peter 
Published: April 2021

ABSTRACTThe suboesophageal ganglion of the migratory locust Locusta migratoria contains a pair of large neurosecretory cells located posteriorly, close to the sagittal plane. By means of double labelling, it is shown that the cells are immunoreactive to bovine pancreatic polypeptide. Using a combination of electrophysiological, neuroanatomical and immunocytochemical methods, it is shown that the neurones project into the corpora cardiaca with ascending anterior axons and into the lateral cardiac nerve cords with posterior axons that descend into the thoracic and abdominal nerve cord.
Long-Term GrowthIn Vitroof Isolated, Fully Differentiated Neurones from the Central Nervous System of an Adult Insect
Authors: Howes E. A. , Cheek T. R. , Smith P. J. S. 
Published: April 2021

ABSTRACTA method is described for the isolation and growth in vitro of fully differentiated neurones from the thoracic ganglia of adult cockroaches. The presence of insect blood in the culture system is shown to promote growth. The morphology of the growing neurones and the plasticity of the branching processes are described and growth rates are measured. Using a fluorescent Ca2+ indicator dye, changes of intracellular calcium levels in the growing neurones in response to K+ depolarization have been measured. The results, indicating the presence of voltage dependent Ca2+ channels on neuronal processes in vitro, show that neurones can be maintained in a functional state for several weeks by this technique. Such preparations could prove useful for studying a variety of physiological and pharmacological properties of neurones, including the mechanisms controlling growth, synapse formation and neuronal interactions with other cell types.
A Model of the Mechanism of Sound Production in Cicadas
Authors: Bennet-Clark H. C. , Young D. 
Published: April 2021

ABSTRACT
Dried cicada bodies of the species Cyclochila australasiae and model cicadas made from a miniature earphone driving a plastic cavity were used to study the acoustics of sound production in male cicadas. A model cicada with shape and dimensions similar to those of the abdomen of a male C. australasiae resonates at the natural song frequency of the species (4.3 kHz). The abdominal air sac of C. australasiae also resonates at frequencies close to the natural song frequency when excited by external sounds. In an atmosphere of chlorofluorocarbon (CFC) gas, the resonant frequency is lowered in keeping with the decrease in velocity of sound in the CFC gas. At the model’s resonant frequency, the driving earphone dissipates more electrical power with the cavity attached than without the cavity. The cavity of the model cicada acts as a narrow-band acoustic acceptance filter, tuned to the natural song frequency. When the miniature earphone emits brief clicks, mimicking those produced by the natural tymbal mechanism, the model cicada produces sound pulses that vary in duration and shape according to the number and timing of the clicks. A coherent train of two or three resonant clicks results in a long slowly-decaying sound pulse similar to that in the natural song. The natural song frequency can be predicted from the dimensions of the abdominal cavity and the tympana in C. australasiae using a simple equation for the resonant frequency of a Helmholtz resonator. This equation also predicts the song frequency of Macrotristria angularis and Magicicada cassini, but it fails with the low-frequency song of Magicicada septendecim. This discrepancy can be accounted for by the unusually thick tympana of M. septendecim, which tend to lower the resonant frequency of the system. We conclude that the abdomen of male cicadas forms a Helmholtz resonator, the components of which are the large air sac as the cavity and the tympana as the neck of the resonator. We suggest that cicada sound production depends on the coupling of two resonators, that of the tymbal and that of the abdominal air sac, from which sound is radiated through the tympana. The coupled resonator system would produce the long sound pulses required for stimulating a sensitive sharply tuned auditory organ.
N-Methyl-D-Aspartate (NMDA) and Non-Nmda (Metabotropic) Type Glutamate Receptors Modulate the Membrane Potential of the Schwann Cell of the Squid Giant Nerve Fibre
Authors: Evans Peter D. , Reale Vincenzina , Merzon Rosa Maria , Villegas Jorge 
Published: April 2021

ABSTRACT
L-Glutamate application can produce three different responses in the membrane potential of the Schwann cell of the tropical squid, Sepioteuthis sepioidea, which appear to be mediated by three pharmacologically distinct classes of receptor. A class of non-NMDA-type receptors, with some similarities to metabotropic glutamate receptors, mediates the development of a rapid and long-lasting hyperpolarization. Two pharmacologically distinct classes of NMDA-type receptor are present. One mediates the development of a slow depolarization accompanied by a long-lasting change in responsiveness of the Schwann cell. The second produces rapid depolarizing responses during the period of this changed responsiveness. All three types of receptor can be activated by dipeptides containing excitatory amino acids.
In vitro Interactions Between Oxygen and Carbon Dioxide Transport in the Blood of the Sea Lamprey (Petromyzon Marinus)
Authors: Ferguson R. A. , Sehdev N. , Bagatto B. , Tufts B. L. 
Published: April 2021

ABSTRACT
In vitro experiments were carried out to examine the interactions between oxygen and carbon dioxide transport in the blood of the sea lamprey. Oxygen dissociation curves for whole blood obtained from quiescent lampreys had Hill numbers (NH) ranging from 1.52 to 1.89. The Bohr coefficient for whole blood was −0.17 when extracellular pH (pHe) was considered, but was much greater (−0.63) when red blood cell pH (pHi) was considered. The pHi was largely dependent on haemoglobin oxygen-saturation and the pH gradient across the red blood cell membrane was often reversed when was increased and/or was lowered. The magnitude of the increase in pHi associated with the Haldane effect ranged from 0.169 pH units at 2.9 kPa to 0.453 pH units at a of 0.2 kPa. Deoxygenated red blood cells had a much greater total CO2concentration than oxygenated red blood cells, but the nonbicarbonate buffer value for the red blood cells was unaffected by oxygenation. Plasma was not significantly different under oxygenated or deoxygenated conditions. Partitioning of CO2 carriage in oxygenated and deoxygenated blood supports recent in vivo observations that red blood cell CO2 carriage can account for much of the difference between arterial and venous blood. Together, the results also suggest that oxygen and carbon dioxide transport may not be tightly coupled in the blood of these primitive vertebrates. Finally, red cell sodium concentrations were dependent on oxygen and carbon dioxide tensions in the blood, suggesting that sodium-dependent ion transport processes may contribute to the unique strategy for gas transport in sea lamprey blood.
The Effect of a Glutamate Uptake Inhibitor on Axon-Schwann Cell Signalling in the Squid Giant Nerve Fibre
Authors: Evans Peter D. , Reale Vincenzina , Merzon Rosa Maria , Villegas Jorge 
Published: April 2021

ABSTRACT
The glutamate uptake blocker p-chloromercuriphenylsulphonic acid (PCMS) (100μmoll−1) does not block any of the membrane potential changes induced by the application of L-glutamate to the adaxonal Schwann cells of the giant axon of the tropical squid Sepioteuthis sepioidea. This indicates that these potential changes are not due to the activation of an electrogenic glutamate uptake system and supports the idea that they are due to the activation of specific glutamate receptors. The presence of PCMS (100μmol 1−1) reduces the activity of the glutamate uptake system sufficiently for the extracellular level of axonally released glutamate to exceed the threshold for the activation of the NMDA-type glutamate receptors in this preparation.
Isolation of a Neuropeptide From Locust Corpus Cardiacum Which Influences Ileal Transport
Authors: Audsley Neil , Mcintosh Chris , Phillips John E. 
Published: April 2021

ABSTRACT
Schistocerca gregaria ion-transport peptide (Scg-ITP) was isolated from aqueous extracts of the corpus cardiacum by a four-step procedure, utilizing reverse-phase high-performance liquid chromatography for separation and stimulation of a Cl−-dependent short-circuit current (Isc) across locust ilea as the bioassay. Scg-ITP has an unblocked N terminus and an apparent relative molecular mass of 7700. Thirty-one residues (of an estimated 65) were identified by sequence analysis. Scg-ITP is structurally related to a crustacean family of neuropeptides which includes the crustacean hyperglycaemic hormones from the shore crab Carcinus maenas and the crayfish Orconectes limosus and moult-inhibiting hormone and vitellogenesis-inhibiting hormone from the lobster Homarus americanus. Scg-ITP has no sequence homology with neuroparsins (Nps). Nps are the only other neuropeptides isolated to date that might regulate reabsorption in an insect hindgut (rectum).
Lack of Correlation Between Cardiac Myoglobin Concentration and in vitro Metmyoglobin Reductase Activity
Authors: Bailey John R. , Driedzic William R. 
Published: April 2021

ABSTRACT
Myoglobin (Mb) is an intracellular protein found in red skeletal muscle and heart. It binds oxygen reversibly and enhances oxygen consumption, especially under conditions of low oxygen availability (Bailey et al. 1990; Wittenberg and Wittenberg, 1989). A variety of biochemical and biophysical experiments reveals that Mb functions by facilitating the diffusion of oxygen from the extracellular space to the mitochondria (Wittenberg and Wittenberg, 1989). Each molecule of Mb contains a single iron atom which may bind to one molecule of O2 when the iron is in the ferrous state (i.e. Mb-Fe2+). Mb-Fe2+ undergoes spontaneous oxidation in vitro to the ferric state (Mb-Fe3+), known as metmyoglobin (metMb), which cannot bind O2. Autoxidation occurs for myoglobin isolated from numerous sources with a half-time of the order of hours under conditions approximating in vivo pH, ionic strength and temperature (e.g. Kitahara et al. 1990; Tajima and Shikama, 1987; Livingstone et al. 1986). It is generally accepted that spontaneous autoxidation must occur in vivo-, however, metmyoglobin accumulation under physiological conditions has never been reported. Since the turnover time for Mb may exceed several months (Hickson and Rosenkoetter, 1981), a mechanism must exist to reconvert metMb to Mb and any failure in this mechanism could impair oxygen delivery to the mitochondria. Reduction of metMb has been observed in isolated, perfused rat and sea raven hearts following treatment with NaNO2, which oxidizes Mb (Tamura et al. 1980; Bailey and Driedzic, 1988). Two fundamentally different enzyme mechanisms have been proposed to account for metMb reduction in vivo.
Effects of Serotonin on Circulation and Respiration in the Rainbow Trout Oncorhynchus Mykiss
Authors: Fritsche Regina , Thomas Serge , Perry Steve F. 
Published: April 2021

ABSTRACT
The effects of serotonin (5-hydroxytryptamine; 5-HT) on continuously recorded dorsal and ventral aortic blood pressures, (PDA, PVA), arterial oxygen tension arterial carbon dioxide tension extracellular pH (pHa), buccal pressure (Pbuccal) and plasma catecholamine levels were investigated in rainbow trout, Oncorhynchus mykiss. Intra-arterial injections of serotonin (50–250 nmol kg−1) caused a rapid decrease in PDA and an increase in PVA, suggesting vasoconstriction of the branchial vasculature. The blood pressure changes were accompanied by a reduction in (approximately 3–8 kPa depending on the dose injected), an increase in (approximately 0.03–0.07 kPa) and a decrease in pHa (approximately 0.02–0.12 pH units). These changes, indicative of impaired gas transfer, occurred despite obvious hyperventilation based on measurements of buccal pressure. After pre-treatment with the serotonergic receptor antagonist methysergide, injections of 100nmolkg−1 serotonin caused an increase in a reduction in and an increase in pHa. Methysergide treatment did not affect the usual serotonin-induced hyperventilation or the reduction in PDA but did abolish the rise in PVA; indeed, PVA was lowered significantly by serotonin after methysergide treatment. This reduction in PVA was eliminated by pre-treatment of fish with the combination of methysergide and sotalol (β-adrenoceptor antagonist), suggesting an adrenergic component to the overall blood pressure response. Analysis of plasma catecholamines after injection of serotonin revealed that high doses (50, 100, 250 nmol kg−1) caused significant increases in concentrations of both noradrenaline and adrenaline.
We conclude that the cardio-respiratory effects of exogenous serotonin injections are complex and arise from several integrated responses, including the direct action of serotonin on receptors within the branchial and systemic vasculatures, indirect action on ganglionic receptors, and the stimulation of catecholamine release from adrenergic nerves and/or chromaffin cells.
Deciphering The Hippocampal Polyglot: the Hippocampus as a Path Integration System
Authors: McNAUGHTON B. L. , Barnes C. A. , Gerrard J. L. , Gothard K. , Jung M. W. , Knierim J. J. , Kudrimoti H. , Qin Y. , Skaggs W. E. , Suster M. , Weaver K. L. 
Published: April 2021

ABSTRACT
Hippocampal ‘place’ cells and the head-direction cells of the dorsal presubiculum and related neocortical and thalamic areas appear to be part of a preconfigured network that generates an abstract internal representation of two-dimensional space whose metric is self-motion. It appears that viewpoint-specific visual information (e.g. landmarks) becomes secondarily bound to this structure by associative learning. These associations between landmarks and the preconfigured path integrator serve to set the origin for path integration and to correct for cumulative error. In the absence of familiar landmarks, or in darkness without a prior spatial reference, the system appears to adopt an initial reference for path integration independently of external cues. A hypothesis of how the path integration system may operate at the neuronal level is proposed.
Circadian and Circannual Programmes in Avian Migration
Authors: Gwinner Eberhard 
Published: April 2021

ABSTRACT
In migratory birds, endogenous daily (circadian) and annual (circannual) rhythms serve as biological clocks that provide the major basis for their temporal orientation. Circannual rhythms are responsible for the initiation of migration both in autumn and spring. This function of timing migrations is particularly important for birds that spend the winter close to the equator where the environment is too constant or irregular to provide accurate timing cues. In addition, circannual rhythms produce programmes that determine both the temporal and the spatial course of migration. In Sylvia warblers, the time programmes controlling autumn migration are organized in a species-or population-specific manner. It has been proposed that, in first-year migrants, the time programme for autumn migration plays a major role in determining migratory distance, thus providing the vector component in a mechanism of vector navigation. It is not yet clear, however, whether this programme does indeed determine migratory distance or whether it only provides the temporal framework within which other factors determine how far a bird flies. Evidence against the first alternative comes from findings indicating that migratory activity can be drastically modified by a constellation of rather specific, but highly relevant, factors and that the resulting changes in migratory activity are not compensated by subsequent increases or decreases of migratory activity.
In normally day-active but nocturnally migrating birds, circannual signals cause alterations in the circadian system leading to the development of nocturnal activity. Although the nature of these signals is unknown, there is evidence that changes in the diurnal pattern of melatonin secretion by the pineal gland are associated with, and possibly causally involved in, the waxing and waning of nocturnal activity. These changes in the melatonin pattern presumably also affect general synchronization properties of the circadian system to Zeitgebers in such a way that circadian rhythms adjust faster to new conditions after long transmeridian flights.
Metabolic Constraints on Long-Distance Migration in Birds
Authors: Klaassen Marcel 
Published: April 2021

ABSTRACT
The flight range of migrating birds depends crucially on the amount of fuel stored by the bird prior to migration or taken up en route at stop-over sites. However, an increase in body mass is associated with an increase in energetic costs, counteracting the benefit of fuel stores. Water imbalance, occurring when water loss exceeds metabolic water production, may constitute another less well recognised problem limiting flight range. The main route of water loss during flight is via the lungs; the rate of loss depends on ambient temperature, relative humidity and ventilatory flow and increases with altitude. Metabolite production results in an increased plasma osmolality, also endangering the proper functioning of the organism during flight. Energetic constraints and water-balance problems may interact in determining several aspects of flight behaviour, such as altitude of flight, mode of flight, lap distance and stop-over duration. To circumvent energetic and water-balance problems, a bird could migrate in short hops instead of long leaps if crossing of large ecological barriers can be avoided. However, although necessitating larger fuel stores and being more expensive, migration by long leaps may sometimes be faster than by short hops. Time constraints are also an important factor in explaining why soaring, which conserves energy and water, occurs exclusively in very large species: small birds can soar at low speeds only. Good navigational skills involving accurate orientation and assessment of altitude and air and ground speed assist in avoiding physiological stress during migration.
The Geographical Scale Factor in Orientation of Migrating Birds
Authors: Alerstam Thomas 
Published: April 2021

ABSTRACT
Migration routes of birds throw light on orientation performance at different geographic scales, over distances ranging from a few kilometres to more than 104 km. Detailed knowledge about the flight routes may be used to test predictions about optimal orientation according to theoretical principles and about the use of compasses based on celestial or magnetic cues. Ringing recoveries demonstrate that the migratory journey of many species, such as the wheatear and willow warbler, is divided into successive legs with different main orientation. Autumn and spring migration routes are often different, sometimes diverging on a continental scale. Aerial radiotracking of whooping cranes in North America and satellite tracking of brent geese migrating from Iceland across the Greenland ice cap point to the significant role of large-scale topography for the shaping of migration routes. Compass and position control are also required, e.g. during long passages across featureless sea or ice, but how these elements are integrated into the birds’ orientation system remains unclear. Radar studies from the Arctic Ocean illustrate the importance of map projections for interpreting flight paths and suggest that birds accomplish approximate great circle orientation. Gradual course changes shown by migrating knots monitored by radar in Scandinavia are at variance with expected changes if the birds were to use a star, sun or magnetic compass over longer distances. Accurate recording of short flight segments shows how flying birds respond to visual, audible and electromagnetic cues, and also documents orientation precision and capacity to integrate rapidly shifting courses into a consistent resulting orientation. Analyses of flight patterns are crucial for understanding how birds find and follow their migration routes over different ranges of geographical scale.
Central Monoaminergic Responses to Salinity and Temperature Rises in Common Carp
Authors: Boeck Gudrun De , Nilsson Göran E. , Vlaeminck Andrea , Blust Ronny 
Published: April 2021

ABSTRACT
Juvenile common carp, Cyprinus carpio, were exposed to increased levels of salinity (1 % NaCl) at 25 °C and 30 °C. Levels of the monoamine neurotransmitters dopamine (DA) and serotonin (5-HT) and their metabolites dihydroxyphenylacetic acid and 5-hydroxyindoleacetic acid were determined in different brain parts. Whereas the elevated temperature only resulted in higher levels of the metabolites, increased salinity caused increased levels of DA and 5-HT as well. Increased levels appeared after the first day of exposure and most effects were further enhanced after 1 week in 1 % NaCl. Increases in DA and 5-HT levels were most pronounced in the hypothalamus, which is the major integrative centre controlling the release of hormones. Thus, one possible role of these changes in neurotransmitter metabolism could be to control the release of prolactin and cortisol, two major hormones involved in the regulation of ion homeostasis in teleosts.