bluuebunny/crossref_metadata_2025 huggingface dataset:
Metabolic and Enzymatic Heterogeneity in the Liver of the Ureogenic Teleost Opsanus Beta
Authors: Mommsen Thomas P. , Walsh Patrick J.
Published: April 2021

Viable toadfish hepatocytes were separated into distinct subpopulations by gradient centrifugation. Although 3–5 density subpopulations were obtained for each fish, only two metabolically and enzymatically different subpopulations could be discerned. In all cases, hepatocytes with the lowest density (less than 1.040 g ml− 1) were more oxidative in scope, as judged by the activities of mitochondrial enzymes (citrate synthase, aspartate aminotransferase, glutamate dehydrogenase); activities of these enzymes (normalised to cell protein) were on average two-to threefold higher than in subpopulations with higher densities. Lower-density hepatocytes also contained higher levels of the urea cycle enzymes arginase and ornithine carbamoyltransferase. The higher-density subpopulations showed no significant differences from each other in enzymatic activities. Compared with lower-density cells, these hepatocytes had higher activities of two cytosolic enzymes, malate dehydrogenase and glutathione-S-transferase. There was no distinct distribution pattern for alanine aminotransferase and glutamine synthetase. Despite generally lower oxidative enzyme content, higher-density hepatocytes were metabolically more active, with 2.5-to fourfold higher rates of urea synthesis, gluconeogenesis and oxidation of lactate. We conclude that, although the toadfish liver shows distinct enzymatic and metabolic heterogeneity, this heterogeneity is dissimilar to the zonation pattern in the livers of mammals, in that separated toadfish hepatocyte types did not appear to possess exclusive metabolic functions. Notably, all cells were capable of metabolic functions that are strictly localised in mammalian liver. In nitrogen metabolism, glutamine synthetase displays a distribution pattern commensurate with its unique metabolic function in the liver of the ureogenic toadfish. Further, all subpopulations possessed detoxification capabilities as indicated by high levels of glutathione-S-transferase, a ‘phase II’ conjugation enzyme.
Studies on the Regulation of Enzyme Binding During Anoxia in Isolated Tissues ofBusycon Canaliculatum
Authors: Brooks Stephen P. J. , Storey Kenneth B.
Published: April 2021

The role of pH and protein kinase second messengers in triggering or potentiating anoxia-linked changes in enzyme binding to particulate matter were evaluated using in vitro incubations of isolated ventricle strips of Busycon canaliculatum (L.) (Prosobranchia, Melongenidae). Incubating whelks under anoxic conditions for 4h reduced the percentage of phosphofructokinase (PFK), aldolase, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and pyruvate kinase (PK) activity associated with cellular particulate matter. Triose phosphate isomerase, phosphoglycerate kinase, phosphoglyceromutase and enolase showed no changes in enzyme binding when whelks were subjected to anoxic stress in vivo. Incubating isolated ventricle strips in vitro under anoxic conditions simulated the changes seen in vivo in whole, anoxic whelks with respect to the percentage of PFK and PK bound during anoxic stress; both whole-animal studies and isolated tissue studies showed reduced PFK and PK binding after 4 h of anoxic incubation. Tissue pH could be artificially changed by incubating isolated ventricle strips in sea water buffered to a desired pH. This permitted an investigation of the effect of intracellular pH on PFK and PK binding in situ. PFK and PK responded to altered intracellular pH with increased enzyme binding at lower intracellular pH values and decreased enzyme binding at higher intracellular pH values. These binding patterns were exactly the opposite of those observed during anoxia; during anoxia stress, both intracellular pH and the percentage of PFK and PK associated with particulate matter decreased. Addition of the second messenger compounds dibutyryl cyclic AMP, dibutyryl cyclic GMP or phorbol 12-myristate 13-acetate plus the calcium ionophore A23187 had no effect on the percentage of activity bound to subcellular structures measured under either normoxic or anoxic conditions. This study suggests that enzyme binding in vivo is not regulated by changes in intracellular pH or concentrations of protein kinase second messenger compounds during anoxia.
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

The 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

The 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

A 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

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

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

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

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

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

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

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

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

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

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

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

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.
Further Observations on the Effect of De-Afferentation on the Locomotory Activity of Amphibian Limbs
Authors: Gray J. , Lissmann H. W.
Published: April 2021

The extent to which co-ordinated rhythmical patterns of locomotory movement are to be regarded as expressions of intrinsic activity within the central nervous system, and how far they are dependent upon the patterns of impulses received from peripheral sense organs, remains a fundamental problem in general physiology. In previous communications we have discussed this problem with reference to the ambulatory activity of Amphibia (Gray & Lissmann, 1940). We found that when the limbs and body of a toad (Bufo bufo) are desensitized by severance of their sensory nerves, the effect on the locomotory pattern depends to a very marked degree upon the extent to which the process of de-afferentation has been applied to the whole of the somatic musculature. In conformity with the results obtained by previous investigators (Hering, 1893 ; Weiss, 1936) we found that de-afferentation of either one or two limbs did not substantially affect the co-ordinated, diagonal pattern of limb movements. When three limbs were de-afferentated the ambulatory activity of the animal was substantially reduced; nevertheless, the diagonal co-ordination of the limbs was maintained whenever movement occurred. When four limbs were de-afferentated, ambulation was laboured and restricted to a few steps at a time. On the other hand, when de-afferentation was applied to all the spinal nerves II–XI (inclusive) no trace of ambulatory rhythm or of diagonal limb movements was observed, although non-ambulatory responses were obtained from the limbs by labyrinthine or optical stimulation. From these observations we were unable to derive any positive support for the theory, advocated by Weiss (1936), that the power to maintain rhythmical ambulatory limb movements is an intrinsic property of the central nervous system and fundamentally independent of the peripheral sense organs. We see no reason to amend our views, but further consideration is desirable in view of the subsequent publications by Weiss (1941 a, b) which not only stress the conception of an inherent central nervous control of ambulatory rhythms but quote our experiments in its support.
The Co-Ordination of Limb Movements in the Amphibia
Authors: Gray J. , Lissmann H. W.
Published: April 2021

Well-defined myotactic reflexes (retractor-extensor thrusts) can be elicited from the retractor and extensor musculature when these muscles contract against an external resistance. A de-afferentated limb cannot exert a retractor-extensor thrust. A retractor-extensor thrust arising in a forelimb evokes an extensor response in the diagonal hindlimb and a protractor response in the contralateral forelimb. In order that these responses should display themselves with regularity it is necessary to de-afferentate the responding limb; in an intact limb they are often masked by the control exerted by the limb’s own proprioceptive mechanism. In an intact animal a retractor-extensor thrust in a forelimb evokes a ‘placing reaction’ from the ipsilateral hindlimb. This phenomenon is only partially displayed if the hindlimb is de-afferentated. When an intact forelimb responds, by protraction, to passive stretch, the contralateral hindlimb flexes and the ipsilateral hindlimb extends if the latter limbs have been de-afferentated. The individual proprioceptor limb responses integrate to form an adequate picture of the co-ordinated limb movements seen when an intact toad ceases to swim and begins to walk on land. The role of proprioceptor activity in the maintenance of an ambulatory rhythm in a single limb is discussed.
The Neurological Basis of the Locomotory Rhythm in the Spinal Dogfish (Scyllium Canicula, Acanthias Vulgaris)
Authors: Lissmann H. W.
Published: April 2021

Body and fin reflexes in the spinal dogfish, Scyllium canicula and Acanthias vulgaris, are described. A reflex posture can be induced in inactive spinal preparations through localized exteroceptive stimuli. The location of the primary and secondary contraction areas is determined by the site of stimulation. Spinal preparations of Scyllium canicula and Acanthias vulgaris display a persistent locomotory rhythm as long as they are free from contact. Diffuse touch to the ventral surface of a spinal preparation has an inhibitory effect on the swimming movements. Some dogfish remain immobile after the ventral contact has been discontinued, but resume their persistent swimming after application of a gentle exteroceptive stimulus of short duration. Through feeble transitory stimuli any individual swimming stroke can be retarded, temporarily arrested, reversed, accelerated and augmented. The reaction depends on the site of the stimulation and on the momentary phase of the swimming movement at which it is applied. The rhythm emerging after the application of a transitory stimulus is, as a rule, out of phase with the rhythm as recorded prior to the application of the stimulus. Therefore the response cannot be interpreted as resulting from a super-position of an independent automatic rhythm integrating with a reflex, but must be considered as an interaction of two equal and mutually dependent processes.
The Neurological Basis of the Locomotory Rhythm in the Spinal Dogfish (Scyllium Canicula, Acanthias Vulgaris)
Authors: Lissmann H. W.
Published: April 2021

Some of the more striking effects of de-afferentation in the spinal dogfish are diagrammatically represented in Fig. 13.

The persistent locomotory rhythm of a spinal dogfish depends upon afferent excitation. If all afferent excitation is cut off by severance of all dorsal roots, the rhythm is abolished (Fig. 13, 1). The rhythm clearly emerges when about half the number of all the dorsal roots is transected, irrespective whether the anterior or the posterior half of the animal be de-afferentated (Fig. 13, 2 and 3), or whether complete unilateral de-afferentation is executed (Fig. 13, 4). Extensively de-afferentated preparations may exhibit swimming movements after exteroceptive stimulation. These swimming movements do not persist. Preparations de-afferentated except for the tail exhibit after exteroceptive stimulation a static reflex posture. The de-afferentated musculature takes part in both tonic and rhythmic responses as long as it is connected through the spinal cord with normally innervated musculature. In response to electrical stimulation applied to the cord of a spinal dogfish two distinct types of rhythmic response have been evoked. No rhythmic responses have bee obtained through electrical stimulation of the spinal cord in completely de-afferentated preparations. No evidence has been found in support of the view that the swimming rhythm emanates through a spontaneous, automatic activity from the central nervous system.
The Mechanics of Amphibian Locomotion
Authors: Barclay Oliver R.
Published: April 2021

A new type of apparatus is described for measuring the forces exerted on the ground by tetrapods in three orthologonal axes simultaneously. From results obtained with toads and newts an analysis of the mechanics of normal amphibian walking is carried out and several features of Gray’s (1944) analysis of the mechanics of the tetrapod skeleton are confirmed. The introduction into the stride of periods of instability is shown to be related to an increase of the length of the stride and is an adaptation to faster movement. The pattern of couples exerted on the limbs by the extrinsic muscles is calculated for the toad and newt. This is found to be basically the same as that in the cat and in man is shown to be, in several important respects, the most efficient possible. The internal mechanics of the toad forelimb is discussed. It is basically similar to that of both fore- and hindlimbs of the newt. The operation of this type of limb is compared to that of a ‘crank’ mechanism and differs in important respects from that of the mammals.
An Isolated Nerve-Muscle Preparation from Ascaris Lumbricoides
Authors: Baldwin Ernest , Moyle Vivien
Published: April 2021

A technique is described for the preparation from the body wall of Ascaris of semi-isolated strips of muscle. These strips are exposed on one side to the surrounding medium and are suitable for studies of the action of anthelminthic and other drugs upon the exposed musculature. A medium suitable for use in such experiments has been devised and its preparation is described. Media made up to represent the body fluid of Ascaris fail to support physiological activity in the exposed muscle strips, and it seems that this perienteric fluid does not correspond to the true milieu intérieur of this nematode. Some new observations on the nature and composition of the perienteric fluid are presented incidentally in the text.
Disk-Sphere Transformations Produced by Lysins, and Their Reversal, in Systems of Different pH
Authors: Ponder Eric
Published: April 2021

Although sphering almost always occurs at some time before a mammalian red cell haemolyses, the shape change has to be placed in a variable position on the time scale to which the progress of the lytic reaction is referred. In the case of some lysins, e.g. saponin, the shape change is a late event, while in the case of others, e.g. sodium tetradecyl sulphate, it is an early event on the same time scale. In the case of four lysins (sodium taurocholate, sodium tetradecyl sulphate, saponin and digitonin) the amount of lysin required for complete haemolysis increases with increasing pH, but the amount required to produce sphering decreases with decreasing pH. Serum albumin produces a reversal of the disk-sphere transformation brought about by distearyl lecithin, sodium taurocholate, sodium tetradecyl sulphate, saponin and digitonin. Benzene has a weak reversing effect when the spheres are formed as the result of the action of the first three substances mentioned, and cholesterol produces reversal of the shape change only when it is brought about by sodium tetradecyl sulphate. The simple explanation that the reversing agents act by reacting with the lysins and reducing their concentration is not tenable, and the effect of the reversing agents must be regarded as something distinct from their inhibitory effect on the lysin in the system. Some of the substances used can produce the disk-sphere transformation and can even bring about lysis when they are present in such small amounts that they cannot cover the red cell surface. Either the effects produced by each molecule of sphering agent or lysin extend to neighbouring regions on the cell surface and perhaps also into the interior, or sphering and lysis occur as the result of changes at spots on the surface.
Studies in the Development of the Rainbow Trout (Salmo Irideus)
Authors: Smith Sydney
Published: April 2021

The wet and dry weights of a selected population of rainbow trout eggs were determined at intervals from the 1st day after fertilization until the 84th day of incubation at 10° C. The alevin attains its maximum weight at the 65th day, the embryo some 10 days later. The heat production of egg and alevin rises until the 65th day and subsequently fluctuates violently. Fuel values of yolk and embryo samples were measured. The heat production is commensurate with the loss in the total fuel value of the system. Nitrogen excretion of eggs and alevin rises steadily throughout development. It seems probable that only the ammonia fraction is freely diffusible through the chorion. Determinations of the total nitrogen content of embryo and yolk samples demonstrate that the nitrogen excretion observed is sufficient to balance the loss in total nitrogen of the system. The fuel values and excretion measurements are shown to be in accord with the observed loss of dry materials by the egg-alevin system. The significance of this is discussed.
Physiological demands and nutrient intake modulate a trade-off between dispersal and reproduction based on age and sex of field crickets
Authors: Treidel Lisa A. , Clark Rebecca M. , Lopez Melissa T. , Williams Caroline M.
Published: April 2021

Animals adjust resource acquisition throughout life to meet changing physiological demands of growth, reproduction, activity and somatic maintenance. Wing-polymorphic crickets invest in either dispersal or reproduction during early adulthood, providing a system in which to determine how variation in physiological demands, determined by sex and life history strategy, impact nutritional targets, plus the consequences of nutritionally imbalanced diets across life stages. We hypothesized that high demands of biosynthesis (especially oogenesis in females) drive elevated resource acquisition requirements and confer vulnerability to imbalanced diets. Nutrient targets and allocation into key tissues associated with life history investments were determined for juvenile and adult male and female field crickets (Gryllus lineaticeps) when given a choice between two calorically equivalent but nutritionally imbalanced (protein- or carbohydrate-biased) artificial diets, or when restricted to one imbalanced diet. Flight muscle synthesis drove elevated general caloric requirements for juveniles investing in dispersal, but flight muscle quality was robust to imbalanced diets. Testes synthesis was not costly, and life history investments by males were insensitive to diet composition. In contrast, costs of ovarian synthesis drove elevated caloric and protein requirements for adult females. When constrained to a carbohydrate-biased diet, ovary synthesis was reduced in reproductive morph females, eliminating their advantage in early life fecundity over the dispersal morph. Our findings demonstrate that nutrient acquisition modulates dispersal–reproduction trade-offs in an age- and sex-specific manner. Declines in food quality will thus disproportionately affect specific cohorts, potentially driving demographic shifts and altering patterns of life history evolution.
Stimulus-dependent learning and memory in the neotropical ant Ectatomma ruidum
Authors: Riveros Andre J. , Entler Brian V. , Seid Marc A.
Published: April 2021

Learning and memory are major cognitive processes strongly tied to the life histories of animals. In ants, chemotactile information generally plays a central role in social interaction, navigation and resource exploitation. However, in hunters, visual information should take special relevance during foraging, thus leading to differential use of information from different sensory modalities. Here, we aimed to test whether a hunter, the neotropical ant Ectatomma ruidum, differentially learns stimuli acquired through multiple sensory channels. We evaluated the performance of E. ruidum workers when trained using olfactory, mechanical, chemotactile and visual stimuli under a restrained protocol of appetitive learning. Conditioning of the maxilla labium extension response enabled control of the stimuli provided. Our results show that ants learn faster and remember for longer when trained using chemotactile or visual stimuli than when trained using olfactory and mechanical stimuli separately. These results agree with the life history of E. ruidum, characterized by a high relevance of chemotactile information acquired through antennation as well as the role of vision during hunting.
The Analysis of Mixtures of Volatile Fatty Acids
Authors: Gray F. V.
Published: April 2021

In the course of investigating certain aspects of carbohydrate fermentation in the rumen of the sheep it became necessary to estimate the individual concentrations of formic, acetic, propionic and butyric acids in aqueous solutions containing all four components.
The Reactions of Pygosteus Pungitius L. to Toxic Solutions
Authors: Erichsen Jones J. R.
Published: April 2021

An apparatus is described in which small fish (Pygosteus pungitius L.) are confined in a horizontal glass tube, half of which is filled with flowing tap water and half with flowing solution. Solution and water are very sharply differentiated, so that the concentration difference the fish encounter is known. The directions of flow can be rapidly reversed in order to check the result. The movements of the fish are recorded for 7-120 min., according to the degree of toxicity of the substance tested. A negative reaction is shown towards 1% ethyl alcohol, 1/10,000-1/5000 chloroform and 0.1-0.4% formalin (% HCHO). High concentrations of these substances may stupefy the fish so rapidly that a pseudo-positive reaction appears. A sharp negative reaction is displayed towards 0.003-0.001N mercuric chloride; at 0.0003 the reaction is delayed, at 0.0001 is indefinite, and at 0.00004N solution, though of comparatively high toxicity, does not appear to be detected. Zinc sulphate appears to be detected and avoided at concentrations at least as low as 0.0003N. This concentration is of comparatively low toxicity and may be exceeded in streams polluted by effluents from zinc mines. Copper sulphate is only detected and avoided at extremely high concentrations (0.1N). At 0.04N the reaction is vague, and at 0.01-0.001N the fish swim into the solution where they become stupefied and lie motionless, so that the reaction appears positive. Copper salts appear to impair or destroy the stickleback’s ability to distinguish other toxic substances.
Distribution of Glycogen in the Developing Salmon (Salmo Salar L.)
Authors: Daniel R. J.
Published: April 2021

The presence of glycogen has been recorded in the eggs and larvae of teleosts as a result of histochemical methods, notably by Pasteels & Léonard (1935), who included the fertilized eggs of trout (Salmo irideus) in material used to test the efficacy of various fixatives. They reported glycogen in the blastodisc of the trout egg.
Seasonal Cyclical Changes in the Thymus of the Mallard*
Authors: Höhn E. O.
Published: April 2021

In the course of an investigation into seasonal changes in the endocrine organs of wild mallards (Anas platyrhinchas p. (L.)), a striking seasonal cycle was found in the thymus affecting both the amount of thymus tissue and its histological structure. This appears to be the first description of changes of this nature affecting the thymus apart from a statement by Jolly (1913) in connexion with age involution of the thymus in fowls, to the effect that this tissue is much influenced by seasonal and nutritive changes. Aimé (1912) has described a seasonal regeneration of the thymus in turtles, but it will be shown below that this must be regarded as a different type of response from that found in the mallard.