bluuebunny/crossref_metadata_2025 huggingface dataset:
Feeding And Excretion In The Scorpion Paruroctonus Mesaensis: Water And Material Balance
Authors: D.Yokota Stanley
Published: April 2021

Scorpions feed by a process involving the external grinding and digestion of prey, with the ingestion of only the soluble fraction. The water obtained from the prey represents the most important source of water intake for scorpions inhabiting arid regions, placing great importance on the animals’ ability to utilize prey water effectively. The scorpionParuroctonus mesaensis (Stahnke) was found to ingest a mean of 88 % of the body water of selected prey. However, the scorpion loses 0·37 ml of its own body water per ml of prey water extracted, resulting in a net water gain of 0·51 ml water for every ml of prey water. Fluid uptake by the scorpion has been ascribed to a pharyngeal pumping mechanism. Direct measurements of the suction generated by the pharynx yielded a minimal estimate of its pumping capability of 130 mmHg.

The uptake and excretion of nitrogen and electrolytes by Paruroctonus mesaensis on a diet of Tenebrio molitor adults were also analysed. Almost all the potassium ingested was excreted, whereas most of the sodium and chloride were retained, possibly serving to expand haemolymph volume. Assuming a steady state for nitrogen, it was estimated that the net utilizable water obtained from prey, that is the water intake minus the excretory water necessitated by nitrogen excretion, was equivalent to about 35 % of the initial prey water or 69 % of the water ingested.
Characterization Of The Intermittent Breathing Pattern In Xenopus Laevis
Authors: Boutilier Robert G.
Published: April 2021

Xenopus laevis exhibits an extensive repertoire of breathing patterns during voluntary diving-emergence behaviour. In experiments where animals surfaced to breathe at a blowhole fitted with a pneumotachograph, two noticeably different patterns of breathing were observed. In the first (burst breathing), long periods of diving were periodically interrupted by short visits to the surface when a discrete series of evenly spaced ventilations occurred. On other occasions, the same animal might rise to the surface and begin ventilating its lungs, not in discrete bursts, but intermittently over a long period of time (a breathing bout). Minute ventilation during a breathing burst was more than double that of a bout and represents a more active diving-emergence behaviour on the part of the animal. Regulation of the amount of gas exchanged in both breathing styles appears to be due to manipulation of the temporal pattern of lung ventilations (i.e. the breathhold durations), rather than to an alteration in the overall depth of breathing; the latter is possible to some extent, however, through adjustments in the composition of individual ventilations.
Maintenance of Isolated Smooth Muscle Cells of the Ctenophore Mnemiopsis
Authors: Stein P. G. , Anderson P. A. V.
Published: April 2021

Progress toward understanding the physiology of smooth muscle has been slow for several reasons. In most smooth muscle tissues, the cells are extremely small, electrically coupled to one another, often spontaneously active and complexed with large amounts of inelastic connective tissue. The technical problems posed by these factors are numerous and have been reviewed extensively (Tomita, 1970; Anderson, 1977; Attwell & Cohen, 1977; Beeler & McGuigan, 1978). It is clear that the nature of the tissue severely limits the types of experiments which can be performed and the interpretation of any data obtained. Recent efforts to circumvent these problems have increasingly focused on the development of isolated, single cell models. Thus far, isolated cells from Bufo (Bagby et al. 1971; Fay & Delise, 1973; Singer & Walsh, 1980), Mytilus (Ishii & Takahashi, 1982), Beroe (Hernandez-Nicaise, Mackie & Meech, 1980; Hernandez-Nicaise, Bilbaut, Malaval & Nicaise, 1982; Nicaise, Hernandez-Nicaise & Malaval, 1982) and Mnemiopsis (Anderson, 1984; Stein & Anderson, 1984) have been studied. These preparations have eliminated many of the complicating variables mentioned above and they have allowed the first simplified examination of smooth muscle cellular physiology.
The Physiology of Wandering Behaviour in Manduca Sexta: I. Temporal Organization and the Influence of the Internal and External Environments
Authors: Dominick Oliver S. , Truman James W.
Published: April 2021

A stereotyped series of behavioural changes occurs in preparation for pupation in Manduca sexta. Feeding declines over an 8-h period, after which the larva coats its body with a labial gland secretion. The animal then begins a 10-to 30-h wandering behaviour during which it constructs a pupation chamber underground. Wandering behaviour starts during a specific temporal gate which is determined by an internal circadian timer. The scotophase of the day prior to wandering has the major influence on the timing of internal processes which activate the behaviour. Wandering duration is correlated with larval size, reflecting a possible influence of juvenile hormone. The larva appears to be irrevocably committed to begin wandering by an event that occurs about 15 h previously, a time that corresponds to the second of three prothoracicotropic hormone (PTTH) pulses and the accompanying elevation of ecdysteroids as measured by Gilbert et al. (1981). We conclude that both the initiation and duration of wandering behaviour are governed primarily by processes which are internal to the larva.
The Orientation of Pigeons at Gravity Anomalies
Authors: Lednor A. J. , Walcott C.
Published: April 2021

The means by which homing pigeons determine the direction to their home loft when released in unfamiliar territory remains a mystery. Hypotheses involving the sun (Matthews, 1953, 1955), Coriolis force and the earth’s magnetic field (Yeagley, 1947, 1951), inertial cues (Barlow, 1964, 1966), infrasound (Kreithen & Quine, 1979), have been advanced but currently there is no strong empirical support for any of these hypotheses. Recently Papi (see Papi, 1976; Papi et al. 1980 for reviews) and Wallraff (1980) have proposed that olfactory cues are the basis of the pigeons’ position-finding ability but not all investigators are convinced by the evidence (see e.g. Able, 1980; Keeton, 1980; Schmidt-Koenig, 1979; Walcott & Lednor, 1983).
Nematocyst Inactivation During Feeding in Hydra Littoralis
Authors: Ruch R. J. , Cook C. B.
Published: April 2021

Hydra littoralis uses stenotele nematocysts for prey-killing. Unused stenoteles are retained when prey-killing ceases. This inactivation results from an accumulation of soluble factors in the surrounding medium, and ends when hydra are placed in fresh culture solution. The inactivation factors are most probably released from the hydra during nematocyst discharge since stenotele activity is reduced by KCl solutions containing nematocyst factors and is enhanced by prey homogenate.
Correlations between structure and function in the design of the bat lung: a morphometric study
Authors: Maina J. N. , King A. S.
Published: April 2021

The lungs of five species of bat Pipistrellus pipistrellus, Miniopterus minor (Peters), Tadarida mops (De Blainville), Cynopterus brachyotis (Muller) and Cheiromeles torquatus (Horstield) have been analysed by morphometric techniques. The mean body weight (W) ranged from 5 g in Pipistrellus pipistrellus to 173g in Cheiromeles torquatus; the lung volume (VL) ranged from 0·3 cm3 in Pipistrellus to 10 cm3 in Cheiromeles. The volume densities or the main components of the bat lung, namely the parenchyma [Vv(p,L)] (the gas exchange region) and the nonparenchyma [Vv(np,L)], were closely similar, the Vv(p,L) constituting a mean value of 84·2% and the Vv(np,L) 15·8% in the five species. The VL, the surface area of the blood-gas (tissue) barrier (St), the pulmonary capillary blood volume (Vc), and the total morphometric pulmonary diffusing capacity were all strongly correlated with body weight. The harmonic mean thickness of the blood-gas (tissue) barrier (τht) and the surface density of the blood-gas (tissue) barrier [Sv(t,p)] were poorly correlated with W. The bats had a remarkably higher VL than either birds or terrestrial mammals. The Vc in the bat lung was similar to that in the bird lung but higher than that of the terrestrial mammals. The bats had a more extensive St than either the birds or the terrestrial mammals. In the bats the τht was thicker than in the birds but thinner than that of the terrestrial mammals. These pulmonary structural adaptations culminated in a higher in the bat than either in the birds or in the terrestrial mammals. The superior morphometric properties of the bat lung coupled with the established physiological adaptations may help to explain how the bat lung is capable of providing the immense amount of oxygen demanded by flight.
Analysis of contact-rehydration in terrestrial gastropods: osmotic control of drinking behaviour
Authors: Prior David J.
Published: April 2021

Contact-rehydration in slugs is mediated by a specific behavioural pattern in which dehydrated slugs move onto a moist surface, assume a flattened posture while water is absorbed through the surface of the foot and move off once they are rehydrated. ‘Drinking behaviour’ is initiated when slugs have been dehydrated to the threshold leyel of 60–70% of initial body weight (IBW). Drinking behaviour is terminated once slugs have rehydrated to their individual rehydration set-points. The mean ‘rehydration set-point’ for Limax is 93·6 ± 12·2% IBW (±S.D.). Slugs can achieve their individual set-point regardless of the extent of initial dehydration. Drinking behaviour can be initiated by injections of hyperosmotic mannitol solution and terminated by injections of dilute saline. This indicates that variation in the osmolality of the haemolymph is involved in the control of the behavioural sequence.
Analysis of contact-rehydration in terrestrial gastropods: absorption of 14C-inulin through the epithelium of the foot
Authors: Prior D. J. , Uglem G. L.
Published: April 2021

Contact-rehydration in terrestrial slugs involves a specific drinking behaviour during which water is rapidly absorbed through the integument of the foot. When dehydrated slugs were placed on wet filter paper containing 14C-inulin, they displayed the characteristic drinking posture and absorbed both water and 14C-inulin. Samples of haemolymph from dehydrated slugs after 12 min of contact-rehydration contained about 6µg of 14C-inulin 100 mg−1 of haemolymph (0·24 mmol l−14C-inulin in the substrate). The haemolymph of hydrated slugs however contained no detectable radioactivity after 12 min on the filter paper. Electron microscopy revealed that the intercellular spaces between the epithelial cells of the foot were reduced in dehydrated slugs, but were rapidly enlarged during contact-rehydration. It is concluded that contact-rehydration in terrestrial slugs is mediated by bulk flow of water through an epithelial paracellular pathway in the integument of the foot.
Momentum and Energy in the Wake of a Pigeon (Columba Livia) in Slow Flight
Authors: Spedding G. R. , Rayner J. M. V. , Pennycuick C. J.
Published: April 2021

A technique is described whereby the vortex wake of birds in slow forward flight may be investigated with a view towards testing some of the assumptions and predictions of existing theoretical models of bird flight. Multiflash stereophotogrammetry was used to analyse the wake as a pigeon passed through a cloud of neutrally-buoyant helium bubbles.

All photographs obtained support the hypothesis that the wake is composed of a chain of discrete, small-cored vortex rings. This being the case, velocity profiles taken from sections through the wake allow us to estimate the momentum in the wake as represented by vortex rings.

The momentum in the wake appears to be approximately half that required for weight support in unaccelerated, level flight. The possible causes and consequences of this paradoxical result are discussed.
The Search for Principles of Neuronal Organization
Authors: Burrows M.
Published: April 2021

To say that the brain is complex is to state the obvious, and yet from that statement inevitably comes the realization that there will be no single explanation of how it works. Our understanding is likely to accumulate by the identification of general principles of organization at many levels. Recognizing the necessity for an interdisciplinary approach, this conference dealt with developmental, anatomical, physiological and biochemical levels of explanation. The deliberately intimate size of the conference prevented the inclusion of many exciting molecular neurobiological studies.
Relationships Between Neuronal Structure and Function
Authors: Miller John P. , Jacobs Gwen A.
Published: April 2021

The geometry and electrical properties of a neurone determine how synaptic inputs and endogenously generated currents are integrated and transformed into the signals it transmits to other cells. The dependence of neuronal integration upon dendritic geometry has been studied extensively over the last three decades, both by experimentalists and by theoreticians. We review some of the general principles that have emerged from this work, and summarize recent studies that serve to illustrate these principles. The discussion is organized around the analysis of neuronal structure at three different levels. At the ‘macroscopic’ level, we show how the dendritic branching structure of an identified interneurone in the cricket cereal afferent system determines the directional sensitivity within its receptive field. At the ‘microscopic’ level, we illustrate the dependence of synaptic efficacy upon dendritic length, and demonstrate a very surprising result: that the extension (or ‘growth’) of a dendrite out beyond the point of a synaptic contact can increase the efficacy of that synapse. At the ‘ultrastructural’ level, we show how the structural and electrical properties of dendritic spines might have profound effects upon synaptic integration.
Roles for Electrical Coupling in Neural Circuits as Revealed by Selective Neuronal Deletions
Authors: Marder Eve
Published: April 2021

Understanding fully the operation of a neural circuit requires both a description of the individual neurones within the circuit as well as the characterization of their synaptic interactions. These aims are often particularly difficult to achieve in neural circuits containing electrically-coupled neurones. In recent years two new methods (photoinactivation after Lucifer Yellow injection and intracellular injection of pronase) have been employed to delete selectively single neurones or small groups of neurones from neural circuits. These techniques have been successfully used in the analysis of circuits containing electrically-coupled neurones. In several systems new roles for electrical synapses in the integrative function of neural circuits have been proposed.

In the nervous systems of both the leech and lobster it is now thought that synaptic interactions previously thought to be direct are mediated through an interposed, electrically-coupled neurone. In the pyloric system of the stomatogastric ganglion of the lobster, Panulirus interruptus, the Lucifer Yellow photoinactivation technique has permitted a separate analysis of the properties of several electrically-coupled neurones previously thought quite similar. We now know that the Anterior Burster (AB) interneurone and the Pyloric Dilator (PD) motor neurones, which together act as the pacemaker ensemble for the pyloric network, differ in many regards including (a) their intrinsic ability to generate bursting pacemaker potentials, (b) their neurotransmitters, (c) their sensitivity to some neurotransmitters and hormones, (d) the neural inputs they receive and (e) their pattern of synaptic connectivity.

These results will be discussed in the context of the role of electrical coupling in neuronal integration.
Local Interneurones and Local Interactions in Arthropods
Authors: Siegler M. V. S.
Published: April 2021

As their name implies, local interneurones arborize within anatomically restricted regions of a nervous system, and the connections that they make establish local circuits. In arthropods, they may arborize wholly within a segmental ganglion, or within a specialized region of the brain. Local interneurones can be divided into two physiological types: spiking and nonspiking. In segmental ganglia, spiking local interneurones are largely responsible for the local processing of primary sensory inputs, whereas non-spiking ones play a major role in the control and coordination of motor neurone activity at the segmental level. By contrast, in the brain, primary visual inputs are processed mainly by non-spiking interneurones.

Local interactions between neurones may occur in three ways: by the graded release of transmitter, by the presynaptic modulation of spike-evoked PSPs and by the ‘conventional’ mechanism where spike frequency is translated across a synapse as the summed amplitude of discrete spikeevoked PSPs. Although graded synaptic transmission is the only mechanism so far described for the local interactions of non-spiking interneurones, it is not limited to them. It may occur also in non-spiking neurones specialized to transmit graded signals over long distances, or in local, intraganglionic regions of motor neurones or long interneurones. The ability of spiking neurones to exert graded effects may depend upon input and output synapses being intermingled on their fine branches, at sites relatively distant from the region of spike initiation. Since these synapses are widely distributed over the neurones, local intraganglionic interactions can be seen as the summed effect of many, yet more restricted local interactions. Restricted local interactions also may occur within parts of non-spiking interneurones, but this is a conjecture, based on modelling studies, and upon considerable EM evidence for serial and reciprocal synapses in most other types of arthropod neurones.
Sustained Responses to Brief Stimuli: Swimming in Xenopus Embryos
Authors: Roberts Alan , Dale N. , Soffe S. R.
Published: April 2021

Prolonged responses to brief triggering or releasing stimuli are commonplace in animal behaviour. The initiation of locomotion is an example but hypotheses for the central nervous origin of locomotory rhythms generally do not explain how activity is sustained. After a brief review, which suggests that positive feedback excitation could be involved, evidence fromXenopus embryos is considered. Here a brief skin stimulus can evoke long episodes of swimming even in curarized embryos. Feedback excitation provides a possible explanation for sustaining fictive swimming. This hypothesis is evaluated by simulation of simple neuronal networks using a physiologically realistic digital computer modelling programme. The results from simulations suggest that: (1) positive feedback excitation could sustain activity either in central pattern generators for locomotion or in postural motor systems and (2) that the model networks tested here are not appropriate to produce the pattern of motor output from the Xenopus embryo spinal cord.
How Does The Lamprey Central Nervous System Make The Lamprey Swim?
Authors: Grillner Sten , Wallén Peter
Published: April 2021

The lamprey spinal cord, in isolation or with the brainstem, can be used in vitro. The motor patterns underlying the swimming movements can be elicited by: (1) a pharmacological activation of a specific type of neuronal receptor (NMDA-receptor), that may in other systems give rise to an unstable membrane potential, (2) by stimulation of the brainstem or (3) by tactile activation of skin regions left innervated. In the latter case the initiation of ‘fictive’ swimming is partially caused by a release of a transmitter activating NMDA-receptors, as judged by the effect of NMDA-receptor blockers. The central pattern generator (CPG) is strongly influenced by feedback from mechanosensitive elements, which at least partially reside within the spinal cord. The edge cell in the lamprey spinal cord serves as an intraspinal mechanoreceptor.

The ability to generate a coordinated motor output is distributed, since spinal cord sections down to 1-5-2 segments can be made to generate alternating activity. Motor neurones receive an approximately synchronous alternating excitatory and inhibitory drive in each swim cycle and do not appear to be part of the CPG. Motor neurones supplying different parts of the body wall on the same side of a body segment have different morphology with ramifications around different descending axons. The input drive signal during fictive locomotion to motor neurones located close to each other but with different morphological characteristics may differ substantially with regard to the y-relationship (±25 %) and the shape of the oscillation. This implies that even at a segmental level motor neurones may be further subdivided, and furthermore that the ipsilateral network generating the drive signal to ipsilateral motor neurones generates a more complex and individualized output than previously assumed. Motor neurones are not part of the rhythm-generating circuit. The large identifiable interneurones are not required for rhythmic activity to occur although they may be phasically active in the swim cycle. The small segmental interneurones have not yet been completely characterized. Many are phasically active during ‘fictive locomotion’ and lack an apparent axon. Their phase relationships in relation to the burst patterns vary over the entire swim cycle.
Changes of Membrane Currents During Learning
Authors: Alkon Daniel L.
Published: April 2021

In searching for cellular mechanisms by which nervous systems store learned information, it is helpful to differentiate properties which are genetically programmed from those which are conferred by the interaction of an organism with its environment. With mechanisms of learning, as with those underlying developmental transformations, a chronology must be reconstructed - a sequence of processes which arise as a consequence of preceding conditions. To construct such a chronology, the cellular site at which learned information is stored must be accessible to analysis so that we may watch it during sequential transformations, and so that we can measure with appropriate morphological, biophysical and biochemical techniques the nature and magnitude of the critical changes.
Ligand Activity in the Clearance of Metals from the Blood of the Crayfish (Austropotamobius Pallipes)
Authors: Lyon R. , Taylor Marina , Simkiss K.
Published: April 2021

The rate at which metal ions are cleared from the blood of the crayfish Austropotamobius pallipes can be described as the sum of fast and slow exponential processes. The rate constants of these processes were determined and discussed in terms of ligand chemistry. The half life (t1/2) of the fast component shows a typical Irving-Williams series for the various metals. This is interpreted as showing that the retention of metals in the blood is due to binding to protein ligands. The concentrations of metals in the various tissues also reflect their binding characteristics. Class (a) metals (Ca and Sr) become associated with oxygen donors in the exoskeleton and stomach. Class (b) and borderline metals become bound to nitrogen and sulphur donor ligands in the hepatopancreas. The rapid disappearance of Cd2+ and Zn2+ from the blood can be attributed to specific ligands in the hepatopancreas.
On the Nervous Regulation of Gill Blood Flow in the Dogfish (Scyliorhinus Canicula)
Authors: Metcalfe J. D. , Butler P. J.
Published: April 2021

The motor innervation of the gill blood vessels of the dogfish Scyliorhinus canicula L. has been investigated by electrical stimulation of (1) the branchial branches of the IXth and Xth cranial nerves in isolated perfused 1st holobranch preparations and (2) both Xth cranial nerves in whole anaesthetized fish. The observed vascular responses to nerve stimulation appear to be entirely due to contraction of the striated muscles of the gill arch and not to any direct motor innervation of the major gill blood vessels since the responses were blocked only by the drug pancuronium, which blocks striated muscle motor end-plates. The specificity of pancuronium for the motor end-plate of striated muscle in the dogfish was established by showing that it did not block nervous transmission across the cardiac ganglia.

The results from the nerve stimulation studies have been investigated further by pharmacological studies on isolated perfused gill preparations. Acetylcholine produces an atropine-sensitive increase in resistance to perfusion, while both adrenalin and noradrenalin decrease the resistance to perfusion.
Ionic Basis of Action Potential Propagation Along two Classes of ‘Giant’ Axons In the Ophiuroid, Ophiopteris Papillosa
Authors: Tuft Pamela J. , Gilly WM. F.
Published: April 2021

Electrical activity was recorded from the radial nerve cord with extracellular suction electrodes. Spontaneous unitary spikes are 20–50 μV in amplitude with a duration of about 10 ms. Compound action potentials evoked by brief electrical shocks consist of two distinct fast spikes followed by a much slower wave of activity. Fast spikes are graded in amplitude to a maximal level, with little change in time course, over a considerable range of stimulus intensities. The larger of the two fast spikes (spike 1) has a lower threshold and higher conduction velocity: 139 ± 14·3 cms−1 (mean±s.D., N=6) vs 55 ± 7·4cms−1 for spike 2. Spike 1 is reversibly eliminated by replacement of Na with choline in the bathing medium; spike 2 is unaffected. Spike 2 is reduced in amplitude by removal of Ca from the bathing medium; spike 1 is unaffected. Cadmium (2–10 mmol l−1) reversibly blocks spikes 1 and 2. Tetrodotoxin (TTX, l–2 μmol l−1) does not affect either spike. These results support the existence of at least two classes of relatively large axons. Type 1 axons, generating spike 1, rely on a TTX-insensitive Na action potential, whereas type 2 axons may utilize a Ca action potential. Each spike represents summed activity of a relatively small number of axons probably arranged in bundles. The nature of morphological pathways involved in ophiuroid neural conduction is discussed.
Initiation of Feeding Motor Output By an Identified Interneurone in the Snail Lymnaea Stagnalis
Authors: Mccrohan C. R.
Published: April 2021

The cerebral ventral 1 (CV1) cells of Lymnaea are located in the cerebral ganglia, and have axonal projections to the buccal ganglia. Maintained depolarization of a CV1 neurone leads to initiation, maintenance and modulation of rhythmic feeding motor output from buccal and cerebral ganglia. The CV1 cells receive rhythmic synaptic inputs, in phase with feeding cycles, which probably originate from buccal rhythm-generating interneurones. CV1 cells initiate feeding cycles independently of the buccal slow oscillator (SO) neurone, previously described. The possible roles of CV1 and SO are discussed.
Venous Return and Cardiac Filling in Varanid Lizards
Authors: Johansen Kjell , Burggren Warren W.
Published: April 2021

The duration of ventricular diastole relative to the cardiac cycle length is much shorter (46%) in varanids than in mammals (>70%). Atrial systolic pressures were high (15–20 cmH2O), and atrial contraction was apparent in pressure waveforms from the ventricular cavum arteriosum and cavum pulmonale. Atrial contraction coincides with the short period of ventricular diastole and represents the filling agent for the ventricular cava. Increased central venous flow coincides with ventricular contraction, which by reducing the intrapericardial pressure will promote the expansion and filling of the atria and central veins, implying a suctional element of cardiac filling. Inspiration during spontaneous breathing will reduce central venous pressure, steepen the pressure gradient towards the heart and aid flow towards central veins. There is a positive correlation between the systolic level of central venous pressure and cardiac cycle duration.
The Contribution of Nasal Countercurrent Heat Exchange to Water Balance in the Northern Elephant Seal, Mirounga Angustirostris
Authors: Huntley Anthony C. , Costa Daniel P. , Rubin Robert D.
Published: April 2021

Elephant seals fast completely from food and water for 1-3 months during terrestrial breeding. Temporal countercurrent heat exchange in the nasal passage reduces expired air temperature (Te) below body temperature (Tb) Ata mean ambient temperature of 13·7 °C, Te is 20·9 °C. This results in the recovery of 71·5 % of the water added to inspired air. The amount of cooling of the expired air (Tb–Te) and the percentage of water recovery varies inversely with ambient temperature. Total nasal surface area available for heat and water exchange, located in the highly convoluted nasal turbinates, is estimated to be 720 cm2 in weaned pups and 3140 cm2 in an adult male. Nasal temporal countercurrent heat exchange reduces total water loss sufficiently to allow maintenance of water balance using metabolic water production alone.
Circulation Time, Blood Reserves and Extracellular Space in a Cephalopod
Authors: O’Dor R. K. , Wells M. J.
Published: April 2021

Octopus vulgaris Cuvier has a fully enclosed blood system that includes large blood sinuses behind the eyes and around the gut. Experiments on the response of the hearts in exercise and hypoxic stress (Wells, 1979; Wells & Wells, 1983) and the response of the system to drugs or extracts from neurosecretory systems that discharge into the bloodstream (Wells & Mangold, 1980; Wells, 1983) have revealed a number of situations in which it would be useful to know the mean circulation time, the minimal number of heartbeats needed for blood to return to the hearts, and/or the extent to which the sinuses constitute a reserve of blood which can be mobilized in times of stress.
Gill Na+/H+ and Cl−/HCO3− Exchange Systems Evolved Before the Vertebrates Entered Fresh Water
Authors: Evans David H.
Published: April 2021

Recent studies have demonstrated that the transport mechanisms for Na+ and Cl−uptake across freshwater fish gills (i.e. Na+/H+, Na+/NH4+ and C1−/HCO3− exchange systems) also occur in the branchial epithelium of marine teleosts and elasmobranchs, despite the presumed NaCl load in these hypo-regulating fishes (Evans, 1973, 1975a, 1977, 1982; Evans, Kormanik & Krasny, 1979). It was originally proposed (Evans, 1975b) that this occurrence was a remnant of the freshwater ancestry of the marine fishes. However, this proposition is based upon the assumption that the primary function of the system is NaCl regulation by freshwater organisms, and that the carrier which favoured the excretion of unwanted acid, nitrogen and base arose secondarily, as a means to maintain approximate electroneutrality across the epithelial membrane. The alternative proposition, viz, that acid/base regulation and nitrogen excretion by marine ancestors of the vertebrates were the driving forces for the origin of these ionic exchange systems, is an intriguing one, especially since a corollary is that the branchial transport systems necessary for NaCl regulation in fresh water actually arose before they were ‘needed’. One way to test this proposition is by examining the role that external Na+ and Cl− play in the excretion of H+, ammonia, and base by hagfishes, the only chordate group which has apparently never entered fresh water, and which represent the only modern relatives of the primitive chordates that predated the entry of the vertebrates into fresh water (Hardisty, 1979).
Calcium Enables Photoreceptor Pigment Migration in A Mutant Fly
Authors: Howard Jonathon
Published: April 2021

Upon bright illumination, pigment granules in the photoreceptors of the fly compound eye migrate transversely toward the rhabdomeres (Kirschfeld & Franceschini, 1969). The granules absorb light passing down the rhabdomeric light guide, thereby reducing the light available to the visual pigment. This light-regulating mechanism is found in a number of invertebrate eyes (Stavenga, 1979) and has been termed the ‘longitudinal pupil’ (Franceschini, 1972).
pH Profile Along The Gut of the Silver Eel and its Modification During Seawater Acclimation
Authors: Gilles-Baillien M. , Meister M. F. , Kirsch R. , Gillard CH.
Published: April 2021

It is generally accepted that the gut plays an essential role in the water economy of marine and seawater-acclimated teleosts, water losses being balanced by continuous ingestion of drinking water (e.g. Maetz, 1970). Desalting of the ingested sea water (SW) takes place in the oesophagus, which is very permeable to Na and Cl but relatively impermeable to water, and Na, Cl and water resorption continues in the intestine (Hirano, Morisawa, Ando & Utida, 1976; Kirsch & Meister, 1982). Since 1930, it has been believed that the intestinal fluids of marine teleosts are alkaline (Smith, 1930). This has since been confirmed by Hickman (1968) for the rectal fluid of SW-adapted southern flounders and by Oide (1973) for SW-adapted Japanese eels, whose intestinal fluid was shown to have an average pH of 8·7. Oide has also shown that an increase in the pH of the bathing medium results in greater water movement across everted eel intestine. Hence the alkalinity of intestinal fluid has been invoked as a possible factor involved in water and salt resorption in marine or in SW-adapted teleosts. However, the precise role, or the origin, of this alkalinity has not been elucidated. Moreover, pH measurements in samples collected from dead animals and exposed to the air should always be considered with extreme care, especially in this case, since alkaline pH values are somewhat uncommon in biological fluids.
Analysis of the Scaphognathite Ventilatory Pump in the Shore Crab Carcinus Maenas II. Pumping Efficiency and Metabolic Cost
Authors: Wilkens J. L. , Wilkes P. R. H. , Evans J.
Published: April 2021

The water pumping efficiency and the metabolic costs of the scaphog-nathites (SC), the gill ventilating water pumps, of shore crabs have been measured. The ratio of dynamic stroke volume to static pumping chamber volume, measured over the range of ventilation frequencies (fr) of 60−300 beats min-1, shows the water pumping efficiency to be 85%. Despite this high efficiency, the pump appears to become leaky at low FR. Reflux of water back through the pumping chamber was demonstrated by artificially increasing the pressure gradient across the SC chamber at normal fR.

The oxygen requirements of actively beating SCs, the ventilatory fraction of total metabolism, was measured by comparing oxygen consumption before and after SC ablation. The cost of ventilation for resting crabs is 30% of total . The oxygen requirement for a single SC beat is 0·032μmolO2 kg-1. The high ventilatory fraction of total may be one factor contributing to the low metabolic scope of most crustaceans.
Analysis Of The Scaphognathite Ventilatory Pump in the Shore Crab Carcinus Maenas III. Neuromuscular Mechanisms
Authors: Mercier A. Joffre , Wilkens Jerrel L.
Published: April 2021

The motor output pattern to one of the ventilatory muscles of the scaphognathite (SC) in the shore crab, Carcinus rnaenas, was analysed from extracellular nerve recordings. During ‘forward mode’ bursting, an increase in the burst rate of L2b motor neurones is accompanied by an increase in the average intraburst firing frequency. The number of action potentials per burst, although variable, does not change consistently as a function of burst rate.

The influence of individual aspects of the motor pattern on isotonic contractions of muscle L2b was examined. Increasing the intraburst frequency leads to greater contraction and work output, and allows the muscle to lift heavier loads. This effect is correlated with an increase in the level of postsynaptic depolarization, due, at least in part, to greater summation of EPSPs. Increasing the burst rate alone also enhances muscle contraction and work, and results in greater depolarization. This latter effect appears to involve an accumulation of short-term facilitation, which becomes more acute as the time interval between the bursts is progressively shortened. In addition, contraction and depolarization are augmented by increasing the number of impulses per burst or the number of axons recruited.

These observations indicate some aspects of the motor output pattern which are appropriately modified to accommodate the changes in force and work demands which accompany a change in gill ventilation rate.
Matching of muscle properties and motoneurone firing patterns during early stages of development
Authors: Vrbová G. , Navarrete R. , Lowrie M.
Published: April 2021

In adults, muscle fibres match the functional requirements of the motoneurone that supplies them. During early stages of postnatal development of the rat neither muscle fibre properties, nor activity patterns of motoneurones supplying fast and slow muscles have completed their differentiation. Nevertheless, even at this early stage of development the muscles have characteristic properties that are well matched to the activity patterns of immature motoneurones. With further development differentiation of motoneurone activity and muscle fibre properties goes hand in hand. If during this period of linked differentiation, connections between the motoneurones and muscle fibres are disrupted, the development of fast muscles is permanently impaired.
Motoneurone task groups: coping with kinematic heterogeneity
Authors: Loeb G. E.
Published: April 2021

Physiological principles of motor control have generally been based on linear servocontrol theories in which transducers of force, length and velocity are used to provide feedback to the motor actuators. Within the past few years, recordings of the activity of motoneurones and proprioceptors during normal motor behaviour have indicated a diversity that is not consistent with any one theory of motor control. This paper examines the heterogeneity of kinematic conditions under which muscles are called on to perform, and attempts to correlate this with the effects of various fusimotor states on the activity of the muscle spindle afferents, the major sensory signal source in most feedback control schemes. The concept of ‘task groups’ is proposed, in which functional groups of alpha and gamma motoneurones and spindle afferents are programmed to achieve optimal control over relatively restricted but more linear parts of their operating curves. Such a functional compartmentalization of the motor apparatus is thus consistent with several different theories of servocontrol, although it remains unclear whether such conceptual mechanisms are actually embodied in the highly complex neural circuitry present in the spinal cord and higher motor centres.
Fuels and pathways as designed systems for support of muscle work
Authors: Hochachka P. W.
Published: April 2021

Muscle in all animals relies upon four potential sources of energy: ATP hydrolysis, phosphagen hydrolysis, fermentations or oxidative metabolism. Although the relative contributions of different fuels varies greatly in different organisms, in none is there a simple reliance on stored ATP. Muscle work therefore requires a balance between rates of utilization and formation of ATP, a provision supplied by one of the three remaining fuels and metabolic pathways. Useful endogenous fuels must be storable at high level, and rapidly mobilizable with minimal perturbation of [ATP] and with minimal end-product effects on pH, charge or osmotic balance. In addition to displaying these properties, good exogenous fuels must be transferable at high rates between depot sites and muscle; actual flux rates of exogenous fuels depend upon respective ATP yields and are lowest for fuels which most amplify the yield of ATP per mol substrate oxidized. Subtrate flux rates must be matched with O2 flux rates and with rates of endogenous substrate mobilization in order that the right energy-yielding pathways are activated at the right times. Of various control possibilities, an effective competition for ADP (and possibly Pi) seems at this time to be the dominant strategy for assuring integration of aerobic and anaerobic ATP-yielding pathways.
Metabolic indicators of fibre recruitment in mammalian muscles during locomotion
Authors: Armstrong R. B. , Laughlin M. H.
Published: April 2021

Fast-twitch-oxidative-glycolytic (FOG), fast-twitch-glycolytic (FG) and slow-twitch-oxidative (SO) fibres are distributed within and among physiological extensor muscles in mammals in predictable patterns. Deep muscles and the deep portions of extensor muscles are primarily composed of SO and FOG fibres, and the more peripheral portions of the muscles have higher concentrations of FG fibres. During terrestrial locomotion, the fibres are recruited in this same general order from postural standing through high speed running to jumping (i.e. during standing deep SO fibres are active and during locomotion there is a progressive peripheral recruitment of fibres from SO to FOG to FG). Several metabolic indicators may be used to map these fibre recruitment patterns, including glycogen loss in fibres, metabolic enzyme changes during training at different speeds, and distribution of blood flow within and among the muscles. Concerning the latter, during standing in rats blood flows in the hindlimb muscles are directly proportional to the SO fibre populations in the muscles. However, during locomotion the elevations in blood flow over pre-exercise are a function of the populations of FOG fibres in the muscles. Blood flows in the peripheral white portions (FG fibres) of extensor muscles are not significantly elevated until the rats run at high speeds, when the FG fibres presumably are recruited. During swimming, when flexor muscles are relatively more active than extensor muscles (as compared with terrestrial locomotion), blood flows in the flexors are correspondingly higher. Thus, there exists a clear ‘biological economy’ in the matching of blood flow to the specific fibres that are active within and among muscles during exercise.
The maximum forces exerted by animals
Authors: Alexander R. M.
Published: April 2021

This paper reviews the maximum forces exerted by animals in a wide range of activities including running, jumping, swimming and biting. Most of the data refer to vertebrates and arthropods, ranging in size from 0·5-mg fleas to 3-tonne elephants. Maximum forces exerted on the environment give values of (force/body weight) which lie, in most cases, between 0-5 body mass−1/3 (kg) and 20 body mass−1/3. Maximum forces exerted by major muscle groups give values of (force/body weight) in most cases between 10 body mass− /3 and 50 body mass−1/3.
Sustained force development: specializations and variation among the vertebrates
Authors: Johnston I. A.
Published: April 2021

The kinds of muscle fibre that are recruited for sustained force production by different vertebrates are described. Although aerobic metabolism always accounts for a significant proportion of their ATP turnover, no single characteristic such as colour, number and form of motor endplates, membrane properties, myosin isotype or contraction speed is diagnostic of such muscles. As mechanical power output increases, there is a tendency for a decrease in fatigue resistance with repetitive usage and an increase in both aerobic capacity and the fraction of energy requirements derived from glycolysis.
The role of compliance in mammalian running gaits
Authors: McMahon T. A.
Published: April 2021

The running gaits used by both bipedal and quadrupedal animals are reviewed and contrasted. At high speeds, bipeds use both ordinary running, in which the legs move opposite one another, and hopping. Quadrupeds generally use the trot or its variations at moderate speeds, and first the canter and then the gallop as speed increases. Running in both bipeds and quadrupeds generally involves at least one aerial phase per stride cycle, but certain perturbations to running including running in circles, running under enhanced gravity, running on compliant surfaces and running with increased knee flexion (Groucho running) can reduce the aerial phase, even to zero.

A conceptual model of running based on the idea that an animal rebounds from the ground like a resonant mass-spring system may be used to compare the various gaits. The model makes specific predictions which show that galloping is generally faster than cantering, pronking or trotting, and requires lower peak vertical forces on the legs while also giving a smoother ride. Even so, trotting might be preferred to galloping at low and moderate speeds for the same reason that normal running is preferred to Groucho running - the more compliant gait offers a smoother ride and lower vertical ground-reaction forces on the feet, but this can only be obtained at a high cost of increased metabolic power.
Properties of the muscle proteins - a comparative approach
Authors: Perry S. V.
Published: April 2021

One of the striking features of muscle systems is the wide range in properties they exhibit. This adaptability of muscle to its physiological role is a consequence of the specialization that occurs by the normal process of development and the ability to adapt further to the functional demands when the normal developmental changes are assumed to be complete - a property often referred to as plasticity.
Malleability of the motor system: a comparative approach
Authors: Goldspink G.
Published: April 2021

The various ways in which the power output of muscles can be changed are described. As a result of exercise and growth, force production is increased by an increase in the cross-sectional area of the fibres. This is associated with changes in the rate of synthesis and degradation of muscle proteins which lead to build up of the myofibrils. These then split longitudinally when they reach a critical size. This process is repeated so that the number of myofibrils increases very considerably. Also, during growth, the displacement is increased by increasing the length of the muscles. To do this more sarcomeres are produced in series along the length of the fibres. This is induced by stretch which also encourages fibre growth in girth as well as in length. Yet another way of changing the power output of a muscle is to change the types of muscle fibres (motor units) within the muscle. Fibre type transformation has been shown to occur with cross innervation and stimulation but it does not usually occur with exercise training. It has been possible, however, to change the fibre type proportions in young animals. Also, by combining stretch with stimulation, it has been possible for instance to make the fast glycolytic fibres add on fast oxidative type sarcomeres or even slow oxidation type sarcomeres. Interestingly, fibre transformation also occurs in some species of fish during acclimation to low temperatures in that the specific myofibrillar ATPase activity is increased. This means that the reduction in power output due to decreased temperature is to some extent compensated for by an increase in the intrinsic rate of shortening. EMG studies of fish swimming at different temperatures have shown that the acclimated fish can swim faster and can derive more aerobic sustainable power as a result of this change.
Myosin isoenzymes as molecular markers for muscle physiology
Authors: Whalen R. G.
Published: April 2021

Myosin is a major component of skeletal muscle and it plays a central role in determining the physiological performance of adult tissue. Developing muscles contain myosin molecules which are different from the adult forms, and these isoenzymes have been found to be characteristic markers of the diverse physiological and pathological states of muscle tissue. The differences between these isoenzymes may be demonstrated by protein chemical, immunochemical and genetic evidence. The study of the sequential transitions between isoenzymes represents a means for characterizing the dynamic nature of muscle development, and neuronal and hormonal influences have been identified which contribute to the regulation of these transitions. The perspectives for future work include genetic studies, elucidation of the pathways relating extracellular signals to changes in gene expression, and the possibility that studies of myosin isoenzymes might further understanding of muscle pathology.