bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mechanics, Power Output and Efficiency of the Swimming Muskrat (Ondatra Zibethicus)
Authors: Fish F. E. 
Published: April 2021

ABSTRACTThe surface swimming of muskrats (Ondatra zibethicus Linnaeus) was studied by forcing individual animals to swim against a constant water current, of velocity ranging from 0·2 to 0·75 ms−1, in a recirculating water channel. Lateral and ventral views of the swimming muskrats were filmed simultaneously for analysis of thrust by the propulsive appendages.Drag measurements and flow visualization on dead muskrats demonstrated that these animals experience large resistive forces due to the formation of waves and a turbulent wake, because of the pressure and gravitational components which dominate the drag force.Biomechanical analysis demonstrated that thrust is mainly generated by alternating strokes of the hindfeet in the paddling mode. A general lengthening of the hindfeet and presence of lateral fringe hairs on each digit increase the surface area of the foot to produce thrust more effectively during the power phase of the stroke cycle. Increased energy loss from drag on the foot during the recovery phase is minimized by configural and temporal changes of the hindfoot. Employing the models developed by Blake (1979, 1980a,b) for paddle propulsion, it was found that as the arc through which the hindfeet were swept increased with increasing velocity the computed thrust power increased correspondingly. However, the frequency of the stroke cycle remained relatively constant across all velocities at a level of 2·5 Hz.Both mechanical and aerobic efficiencies rose to a maximum with increasing swimming velocity. The aerobic efficiency, which examined the transformation of metabolic power input to thrust power output reached a value of 0·046 at 0·75 ms−1. The mechanical efficiency expressing the relationship of the thrust power generated by the paddling hindfeet and laterally compressed tail (Fish, 1982a,b) to the total mechanical power developed by the propulsive appendages increased to a maximum of 0·33 at 0·75 ms−1.I conclude that the paddling mode of swimming in the muskrat is relatively inefficient when compared to swimming modes which maintain a nearly continuous thrust force over the entire propulsive cycle. However, the paddling mode permits the muskrat to generate propulsive forces effectively while swimming at the surface. The evolution of this mode for semi-aquatic mammals represents only a slight modification from a terrestrial type of locomotion.
Development of Swimming Movements and Musculature of Larval Herring (Clupea Harengus)
Authors: Batty R. S. 
Published: April 2021

ABSTRACT
A kinematic analysis was made of swimming of larval herring Clupea harengus L. Swimming style was found to change with growth and development; the amplitude of swimming movements of early post-yolk-sac larvae increases linearly towards the tail, a style of swimming which relies mainly on resistive forces for propulsion. Later, after the caudal and dorsal fins have developed, the swimming style changes, in response to an increase in Reynold’s Number, such that inertial forces are more important. In this type of swimming the amplitude increases more rapidly than linearly towards the tail.
The distribution of red and white muscle fibre types was studied in relation to development. On hatching, red muscle fibres were found to be arranged as a single layer on the outside of the myotomes. They develop into the adult distribution, concentrated at the midline of the flank near the skin, only after the gills and circulation become fully functional.
Lability of Blood Volume in Snakes and its Relation to Activity and Hypertension
Authors: Lillywhite Harvey B. , Smits Allan W. 
Published: April 2021

ABSTRACT
The lability of blood volume and its relationship to locomotor activity was investigated in two species of snakes Elaphe obsoleta, Say and Crotalus viridis, Rafinesque. Repetitive measurements of blood volume, determined from changes in the specific activity of circulating 51Cr-labelled erythrocytes, indicated that 15 min of locomotor activity reduced blood volume by 21 % due to filtration of plasma from capillaries. This magnitude of plasma translocation exceeds that measured in exercising mammals by factors of 2 to 7, depending on the intensity and duration of muscular activity. Activity produced changes in arterial blood pressure, heart rate and haematocrit that were proportionately similar in both species, increasing approximately 57, 85 and 25 %, respectively, above resting values. Arterial infusion of norepinephrine increased arterial pressure by more than 100 % and reduced blood volumes 8·6 and 17·0% in Elaphe and Crotalus, respectively. These data demonstrate that blood volume varies substantially in relation to activity or the hypertensive state of these reptiles. Thus care must be employed in interpreting or comparing reported measurements of blood volume in these and probably other vertebrates.
Functional Conflicts Between Feeding and Gas Exchange in Suspension-Feeding Tadpoles, Xenopus Laevis
Authors: Feder Martin E. , Seale Dianne B. , Boraas Martin E. , Wassersug Richard J. , Gibbs Allen G. 
Published: April 2021

ABSTRACT
Air-breathing tadpoles of Xenopus laevis (Amphibia: Anura) use buccopharyngeal surfaces for both gas exchange and capture of food particles in the water. In dense food suspensions, tadpoles decrease ventilation of the buccopharynx and increase air breathing. The lung ventilatory frequency is elevated even though the rate of oxygen consumption is at or below resting levels, suggesting that the lung hyperventilation reflects compensation for decreased buccopharyngeal respiration rather than an increased metabolic requirement. If tadpoles in hypoxic water are prevented from breathing air, they increase buccopharyngeal respiration at the expense of feeding. Aerial respiration evidently permits the buccopharyngeal surfaces to be used primarily for food entrapment.
Mechanical Properties and Control of Nonmuscular Catch in Spine Ligaments of the Sea Urchin, Strongylocentrotus Franciscanus
Authors: Diab Mohammad , Gilly WM. F. 
Published: April 2021

ABSTRACT
Catch was induced in the spine ligaments of Strongylocentrotus franciscanus (Agassiz) (surrounding muscle and nervous tissue removed) by mechanical agitation. When the catch mechanism is set, the tensile stiffness of urchin ligament can change by nearly an order of magnitude and approaches that of vertebrate tendon. Deflection of a spine in catch through an angle of more than 10° damages the catch mechanism. Setting of catch depends on extracellular calcium. Transglutaminase inhibitors (cadaverine and putrescine) prevent the setting of catch. A model involving Ca-dependent activation of a transglutaminase-like enzyme is discussed as a possible basis for the setting of catch by crosslinking collagen fibrils.
Power output and force-velocity relationship of red and white muscle fibres from the Pacific blue marlin (Makaira nigricans)
Authors: Johnston I. A. , Salamonski J. 
Published: April 2021

ABSTRACT
Single white fibres and small bundles (two to three) of red fibres were isolated from the trunk muscle of Pacific Blue Marlin (50-121 kg body weight). Fibres were chemically skinned with 1 % Brij. Maximum Ca2+-activated force production (Po) was 57 kN m−2 for red fibres and 176 kN m−2 for white fibres at 25 °C. The force-velocity (P-V) characteristics of these fibres were determined at 15 and 25 °C. Points below 0·6 Po on the P-V curve could be fitted to a linear form of Hill’s equation. The degree of curvature of the P-V curve was similar at 15 and 25 °C (Hill’s constant a/P0 = 0·24 and 0·12 for red and white fibres respectively). Extrapolated maximum contraction velocities (Vmax) were 2·5 muscle lengths s−1 (LOS−1) (red fibres) and 5·3 Los−1 (white fibres) at 25 °C. Q10(15-25°C) values for Vmax were 1·4 and 1·3 for red and white fibres respectively. Maximum power output had a similar low temperature dependence and amounted to 13Wkg−1 for red and 57Wkg’ for white muscle at 25 °C. The results are briefly discussed in relation to the locomotion and ecology of marlin.
Differences in temperature dependence of muscle contractile properties and myofibrillar ATPase activity in a cold-temperature fish
Authors: Johnston I. A. , Sidell B. D. 
Published: April 2021

ABSTRACT
Single muscle fibres were isolated from the fast myotomal muscle of the teleost Myoxocephalus scorpius L. and chemically skinned with 1 % Brij. Maximum Ca2+-activated force (Po) increased from 14·5 ± 1·1 N cm-2 at 2°C to 19·1 ± 1·8 N cm-2 at 15 °C (mean ± S.E.). Maximum contraction velocity was determined by Hill’s slack-test method (V0) and by extrapolation from force-velocity (P-V) relationships (Vmax). There was a linear relation between log10 V0 and temperature below 15°C (Q10= 1·9, P&lt;0·01). The force-velocity characteristics of the fibres were determined at 2 °C and 20°C. Points below 0·6 P0 on the P-V curve could be fitted by a linear form of Hill’s equation. Extrapolated Vmax values were 0·55 muscle lengths s-1 (L0s-1) at 2°C and 1·54L0s-1 at 20°C. Curvature of the P-V relationship was independent of temperature. The Mg24-, Ca2+-ATPase activity of Triton-X 100 extracted myofibrils was determined under similar ionic conditions to those used in skinned fibre experiments. (Ionic strength 0·16 mmol1-1, pMgATP2·5). A linear relationship between log10 ATPase and temperature was only obtained below 15 °C {P&lt; 0·001). Above 15 °C, the Q10 for ATPase decreased significantly. The Q10(0-15°C) for ATPase activity (3·9) was significantly higher than for unloaded contraction velocity. Supercontraction of isolated myofibrils to very short sarcomere lengths and differences in the mechanical constraints for crossbridge cycling between the preparations probably account for the lack of proportionality between these two parameters.
The Versatile Synapse
Authors: Pitman Robert M. 
Published: April 2021

ABSTRACT‘Typically’ chemical synaptic transmission takes place when an influx of calcium ions during a presynaptic nerve impulse triggers exocytosis of neurotransmitter substance from synaptic vesicles. The neurotransmitter diffuses across the synaptic cleft and occupies receptors embedded in the subsynaptic membrane. This interaction (directly or via a second messenger) operates characteristic ion channels and produces an increase in the postsynaptic membrane permeability to particular ions. Depending on the ionic species to which the postsynaptic membrane becomes more permeable, the physiological response will be an excitatory or an inhibitory postsynaptic potential. The action of neurotransmitters may be terminated either by enzymic inactivation or by cellular uptake mechanisms.Over the last decade it has become clear that a neurotransmitter substance may exert a number of different actions on a single postsynaptic neurone. These may involve opening or closure of either voltage-independent or voltage-dependent ion channels. It is also possible that in some instances transmitters may act on neuronal biochemical systems to modify the physiology of postsynaptic cells without directly altering their electrical characteristics.Analysis of the postsynaptic actions of neurotransmitter substances has become further complicated by the increasing body of evidence which indicates that more than one transmitter substance (one of which may be a peptide) can be released from a single presynaptic neurone. The significance of such dual transmitter systems has yet to be fully elucidated.The efficacy of transmission across many synapses may be modified by either presynaptic or postsynaptic mechanisms ; both transmitter release and postsynaptic responsiveness may depend on the recent history of a single synapse, on synaptic inputs from other neurones or on circulating neuroactive substances.
The Pattern Of Osmotic Regulation In Larvae Of The Mosquito Culiseta Inornata
Authors: Garrett Margaret , Bradley Timothy J. 
Published: April 2021

Abstract
Larvae of Culiseta inornata (Williston) can survive and complete development in dilutions of sea water ranging from 50–700 mosmol kg-1. The larvae hyperregulate with regard to haemolymph osmotic concentration in dilute media (50–400 mosmol kg−1) and osmoconform when external salinities exceed 400 mosmol kg−1. This pattern of osmoregulation is distinct from that observed in freshwater and saline-water mosquito species. We propose that mosquitoes exhibiting this osmoregulatory pattern should be described as ‘brackish-water’ species. Larvae of Culiseta inornata are able closely to regulate both sodium and chloride ion concentrations in the haemolymph over the full range of salinities tested (50–750mosmolkg−1). The Malpighian tubules produce an isosmotic, potassium-rich fluid. In vitro and in vivo sampling of rectal fluids demonstrates that rectal secretions are isosmotic or only slightly hyperosmotic to the haemolymph and the surrounding saline media, and that they are isotonic with regard to sodium.
Pressure and Water Flow Patterns in the Respiratory Tract of the Bass (Micropterus Salmoides)
Authors: Lauder George V. 
Published: April 2021

Abstract
Instantaneous water velocities in the respiratory tract of bass, Micropterus salmoides (Lacepède), were measured using a fast-responding hot-film anemometer. The flow velocity waveform varied within the buccal cavity, with lower peak velocities at the back than at the front. Flow velocity in both the buccal and opercular cavities varied over the respiratory cycle, and 80 % of signal power in the velocity waveform was between 1 and 10 Hz. Flow within the buccal cavity reached a maximum velocity of 50cms−1 and did not decline to zero, even when differential pressure across the gills was negative. Simultaneous measurement of dimensional changes in the branchial apparatus, pressure and velocity fluctuations showed that gill bar adduction coincides both with the pressure reversal across the gills and with maximum flow velocities in the opercular cavity. The movement of the gill bars during respiration causes flow velocity fluctuation just in front of the primary lamellae and may be an important component of intraoral resistance contributing to the phase differences between pressure and velocity waveforms.
Interneuronal Network Acting on Snail Neurosecretory Neurones (Yellow Cells and Yellow-Green Cells of Lymnaea)
Authors: Benjamin P. R. 
Published: April 2021

Abstract
Neurosecretory cells in Lymnaea are the follower cells of a network of interneurones consisting of four different cell types, three of which are inhibitory and one excitatory. One identified interneurone, the visceral white interneurone (VWI), inhibits the Yellow Cells and Yellow-green Cells, or converts Yellow Cells from single spiking to doubletting or bursting. A second interneurone, RPeDl, has weak inhibitory effects on both types of neurosecretory cells but its main effect is to inhibit the VWI and allow the Yellow Cells to be strongly influenced by spontaneous EPSP inputs (input 3).
Pulmonary Mechanics and the Work of Breathing in the Lizard, Gekko Gecko
Authors: Milsom William K. , Vitalis Timothy Z. 
Published: April 2021

Abstract
Measurements of pulmonary mechanics made on anaesthetized specimens of the Tokay gecko Gekkogecko (Linné), indicate that both static and dynamic pulmonary mechanics are dominated by the mechanics of the body cavity and chest wall. The lungs are relatively large and compliant and offer little resistance to air flow at any of the ventilation frequencies (f) used in this study. The body wall is relatively stiff and becomes less compliant with increasing ventilation frequency and with increasing tidal volume (VT) at the higher frequencies. The vast majority of the work performed in breathing is used to overcome elastic forces in the chest wall resisting lung inflation. This work increases exponentially with increases in volume. As a consequence, in terms of total ventilation, the most economic breathing pattern is a high frequency, low tidal volume pattern in which changes in minute ventilation are most economically produced solely by changes in f. Because reductions in tidal volume drastically reduce alveolar ventilation volume while dead space remains constant, the same arguments do not apply to alveolar minute ventilation . In terms of alveolar minute ventilation, there is an optimum combination of f and VT for each level of VA, with changes in VA being most economically produced by almost equal changes in both f and VT.
Adrenergic Swelling of Nucleated Erythrocytes: Cellular Mechanisms in A Bird, Domestic Goose, and Two Teleosts, Striped Bass and Rainbow Trout
Authors: Nikinmaa Mikko , Huestis Wray H. 
Published: April 2021

ABSTRACT
The mechanism of adrenergic swelling and associated pH changes was investigated in avian (goose) and teleost (striped bass and rainbow trout) erythrocytes.
The swelling of goose red cells was probably caused by Na+/K+/Cl− cotransport and consecutive osmotic flow of water into the cell. Goose red cells swelled when exposed to isoproterenol in the presence of elevated extracellular K+, but not at physiological K+ concentrations. The swelling was quantitatively inhibited by furosemide, and by removing Cl− from the incubation medium, but was not affected by DIDS.
The isoproterenol-induced swelling of fish erythrocytes may be due to loosely coupled Na+/H+ and Cl/HCO3− exchanges. Furosemide did not completely inhibit the swelling of striped bass red cells. The cell volume increased even if K+ was completely removed from the incubation medium. In contrast, both DIDS and amiloride treatment, and the removal of Na+ from the incubation medium, inhibited the volume changes. In fish red cells the swelling is associated with a clear acidification of the medium and alk-alinization of the red cell contents. This phenomenon was most pronounced when the cells were treated simultaneously with DIDS and isoproterenol; the intracellular pH became higher than the extracellular one. Both amiloride and removal of Na+ from the incubation medium prevented the reversal of the transmembrane pH gradient in cells treated simultaneously with DIDS and isoproterenol.
Magnetic Remanence in the Western Atlantic Spiny Lobster, Panulirus Argus
Authors: Lohmann Kenneth J. 
Published: April 2021

ABSTRACT
The magnetic characteristics of 15 western Atlantic spiny lobsters (Panulirus argus) were analysed with a superconducting cryogenic magnetometer. Each specimen possessed a significant natural remanent magnetization (NRM) and isothermal remanent magnetization (IRM), indicating that ferromagnetic material is present. Analyses of the distribution of total remanence and mass-specific remanence indicate that magnetic material is concentrated in the cephalothorax, particularly in tissue associated with the fused thoracic ganglia. Mass-specific remanence and the total quantity of magnetic material in the cephalothorax and abdomen both increase as functions of carapace length.
The NRM is significantly orientated in at least four regions of the body. The NRM of the left half of the posterior cephalothorax is directed posteriorly, while that of the right half is orientated anteriorly. In addition, the NRM of the middle cephalothorax is orientated toward the right side of the animal; the NRM of the telson-uropods region is directed toward the left. The functional significance of these regions of orientated remanence is not known, but such a pattern could result from the ordered alignment of permanently magnetic particles comprising a magnetoreceptor system.
Hearing in Notodontid Moths: A Tympanic Organ with a Single Auditory Neurone
Authors: Surlykke Annemarie 
Published: April 2021

ABSTRACT
Notodontid moths possess paired tympanic organs basically similar to the ears in other noctuoid families, but with a single auditoryA cell. The A cell and the non-auditory B cell were studied anatomically by infusion of C0CI2 and physiologically by recordings from the tympanic nerve. The response of the A cell is determined by intensity parameters and temporal parameters of an ultrasonic stimulus. The notodontid ear is as sensitive as the ears of sympatric noctuids. The directional sensitivity is approximately the same as in noctuids of comparable size (maximal interaural intensity difference of 10–15 dB). The dynamic range of the A cell is about 20–25 dB. Sound levels exceeding the threshold by 30–40dB will saturate the A cells in both ears. Stimuli with different pulse lengths (from 5 to 200 ms, corresponding to pulse repetition rates (PRR) from 100–2·5 Hz), but equal duty cycles (50%) gave a maximum response for pulse lengths lying between 30 and 50 ms. The receptor cell followed the sound pulses in a one-to-one manner even at a PRR of 200 Hz. Notodontid moths seem to show the same ‘bimodal’ evasive behaviour as noctuids. This behaviour can be explained on the basis of intensity parameters, since only low intensity stimuli will give the notodontid directional information. Hence, directional evasive behaviour is expected at low sound pressure levels (SPL), while high SPL (saturating both A cells) should elicit a non-directional evasive behaviour. However, the evasive behaviour could also be explained in terms of time parameters. Hunting bats increase the PRR of their cries when closing in on a prey and the moths may be able to use these time cues for changing their behaviour.
Muscle Function: A Personal View
Authors: Wilkie D. R. 
Published: April 2021

ABSTRACT
We are far more likely to arrive at our destination if we know what it is. For those of us who are interested in how muscles work, the destination is the progressive unification of our knowledge of the physics, chemistry and structure - at all levels - of muscular systems. The same integration is needed to understand other organs, but in my opinion the field of muscle research has progressed further than the others. Optimists that we are, our goal seems almost within our grasp. Perhaps it is just at the rainbow’s end …
The size-principle: a deterministic output emerges from a set of probabilistic connections
Authors: Henneman E. 
Published: April 2021

ABSTRACT
To understand how even a single muscle is controlled, we must understand how a large ensemble of neurones can generate a complex function through the collective action of its members. The orderly recruitment of motoneurones (MNs) and motor units according to their sizes or tensions (Henneman, 1957; Henneman, Somjen & Carpenter, 1965a,b) is the product of collective action, illustrating how hundreds of MNs operate as a functional entity to control a muscle. Fig. 1 reproduces the recruitment of motor units recorded from a rabbit’s diaphragm during a series of progressively stronger inspirations (G. Yasargil, unpublished). With each contraction larger spikes were recorded in orderly sequence, indicating the discharge of larger motor units. Nearly invariant recruitment orders have been recorded from the MNs or muscles of more than 20 species (Henneman & Mendell, 1981).
Control properties of motor units
Authors: De Luca C. J. 
Published: April 2021

ABSTRACT
This review will deal with two evolving concepts which describe and attempt to unify various observations concerning the behaviour of motor units that have been reported during the past decade. The two concepts are: (1) The common drive which describes the behaviour of the firing rates of motor units, and appears to provide a simple schema for controlling motor units; and (2) the firing rate/recruitment interaction which appears to en-hance the smoothness of the force output of a muscle.
The evolution of these concepts has been expedited by the development of recent techniques such as our decomposition technique which enables us accurately to decompose the myoelectric signal into the constituent motor unit action potential trains. For details refer to LeFever & De Luca (1982), Mambrito & De Luca (1983) and Mambrito & De Luca (1984).