bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrical and Chemical Synapses Between Giant Interneurones and Giant Flexor Motor Neurones of the Hermit Crab (Pagurus Pollicaris)
Authors: Stephens Philip J. 
Published: April 2021

ABSTRACT
An examination is made of the characteristics of the synapses between the single pair of giant interneurones (GIs) and the giant flexor motor neurones (GFMNs) in the fused thoracic-abdominal (TA) ganglion of the hermit crab Pagurus pollicaris. There is an electrical synapse between each GI and its ipsilateral GFMN. Evidence for this includes (a) dye (Lucifer Yellow CH) coupling between the two neurones, (b) a short synaptic (0·2 ms) delay between spikes in the two axons, (c) the ability to pass hyperpolarizing current between the two neurones and (d) the sensitivity of the connection to bath applications of N-ethylmaleimide. This synaptic connection is rectifying, since a GFMN spike does not provoke an action potential in the GI. There is a connection between the GI and the contralateral GFMN. Data indicating that this synaptic connection is chemical includes (a) a synaptic delay of between 0·6 and 0·8 ms, (b) transmission is easily and irreversibly fatigued, (c) the synapse is insensitive to N-ethylmaleimide and (d) there is no dye coupling between the two neurones. Branches of the GFMN come in close proximity with the GI on both sides of the TA ganglion. However, it is not known whether there is a direct connection or an intervening neurone between the GI and the contralateral GFMN.
The Organization and Role During Locomotion of the Proximal Musculature of the Cricket Foreleg I. Anatomy and Innervation
Authors: Laurent Gilles , Richard Daniel 
Published: April 2021

ABSTRACT
The structure of the proximal segments of the cricket (Gryllus bimaculatus) foreleg, together with the associated musculature and its innervation are described. The morphology of 50 motor neurones involved in the control of this musculature has been revealed using backfilling techniques with cobalt, horseradish peroxidase and Lucifer Yellow.
The ‘ball and socket’ pleurocoxal joint is moved by three sets of anatomical antagonists (promotor-remotor, abductor-adductor, anterior-posterior rotator muscles) inserted on each side of the three axes of rotation.
The axial coxotrochanteral joint is moved by the intrinsic levator and the depressor muscles; these depressors are composed of an intrinsic (coxotrochanteral) and a ‘double’ (pleurotrochanteral) subgroup.
The double depressors, and all the muscles inserting on the trochantin (promotors) or the anterior coxal rim (adductor, abductors, anterior rotators) are supplied by at least eighteen neurones, whose axons run in nerve 3.
The muscles that insert on the posterior coxal rim (remotors, posterior rotators) are innervated by at least twelve similar neurones whose axons run in nerve 4.
The intrinsic coxal muscles are supplied by branches of nerve 5 (ten motor neurones to the levators, two to the depressors).
Three presumably common inhibitors, and one Dorsal Unpaired Median (DUM) neurone have also been found.
Effective and Morphometric Oxygen-Diffusing Capacity of the Gills of the Elasmobranch Scyliorhinus Stellaris
Authors: Piiper Johannes , Scheid Peter , Perry Steven F. , Hughes George M. 
Published: April 2021

ABSTRACT
Calculations of the effective O2 conductance (diffusing capacity or transfer factor, Deff) of fish gills, obtained from experimental data on gill O2 exchange, were compared with the predicted O2-exchange properties of gill models based on morphometric measurements of the elasmobranch, Scyliorhinus stellaris. Deff was calculated from O2 uptake and in gill water and blood, using a modified Bohr integration technique. In the morphometric gill model, O2 conductance was considered for both the water-blood tissue barrier (Dm) and the interlamellar water (Dw). Dm was calculated from the total secondary lamellar surface area, the harmonic mean water-blood barrier thickness, and an assumed Krogh O2-diffusion constant for gill tissue. Dw was estimated from the dimensions of the interlamellar spaces, the mean respiratory water flow velocity, and the diffusion coefficient of O2 in water.
The ratio Dm/Dw was 1·84 in quiescently resting, 1·68 in resting alert, and 1·47 in swimming fish, showing that diffusion across interlamellar water was somewhat more important than that across the water-blood barrier in limiting the diffusive O2 transfer between water and blood. The total morphometric diffusing capacity, Dmorph, estimated by the combined membrane-and-water diffusing capacity, Dm+w, which is defined as l/Dm+w= 1/Dm+1/Dw, was similar to Deff, the ratio Dm+w/ Deff being 1·64 for quiescently resting, 1-02 for resting alert, and 0·92 for swimming fish. The good agreement between the effective and morphometric D estimates validates the approach, and leaves, at least for the alert and swimming fish, little space for functional inhomogeneities, which are expected to reduce Deff as compared to Dm+w.
Primary Cultures of Muscle From Embryonic Locusts (Locusta Migratoria, Schistocerca Gregaria): Developmental, Electrophysiological and Patch-Clamp Studies
Authors: Duce J. A. , Usherwood P. N. R. 
Published: April 2021

ABSTRACTPrimary cultures of muscle tissue from 10-day-old embryos of Locusta migratoria and 11-day-old embryos of Schistocerca gregaria have been grown and maintained in 5+4 insect medium and Grace’s insect medium. Myofibres grown in 5+4 medium reached maximum size after about 5 weeks in culture and could be maintained for 2–3 months. They were often branched and rarely striated in appearance. Those grown in Grace’s medium reached maximum size within 3 weeks and could be maintained for about 4 weeks in toto. They were striated and resembled, at least superficially, locust myofibres in vivo. Patch-clamp recordings from myofibre cultures grown in 5+4 medium, either on the myofibres or from excised membrane patches, indicated the presence of a diffusely-distributed population of receptors for L-glutamate. 10−6moll−1 concanavalin A blocked the desensitization of these receptors. The glutamate receptors gated large conductance channels which had reversal potentials of about 0mV. The amplitude of the channel current was sensitive to the concentration of calcium in the membrane environments.
Myofibrillar ATPase Activity in the Carp Cyprinus Carpio: Interactions Between Starvation and Environmental Temperature
Authors: Heap S. P. , Watt P. W. , Goldspink G. 
Published: April 2021

ABSTRACT
The myofibrillar ATPase activity of the epaxial white muscle was measured in carp Cyprinus carpio L. acclimated to 10°C or 28°C. As previously reported, cold acclimation was associated with an increase in the ATPase specific activity and a decrease in the thermostability. The water content of the white muscle was significantly higher in cold-acclimated fish than in warm-acclimated fish (P&lt; 0·002). Starvation for 10 weeks resulted in a significant increase in the white muscle water content of both warm- and cold-acclimated fish (P&lt; 0·002). When carp were starved, the ability of the myofibrillar ATPase to show thermal compensation disappeared. Previously acclimated fish, when starved, showed steady alterations of the myofibrillar ATPase activity to a level mid-way between the acclimated extremes. Refeeding resulted in a gradual return to the normal acclimated level.
Plasma Catecholamines in the Lesser Spotted Dogfish and Rainbow Trout at Rest and During Different Levels of Exercise
Authors: Butler P. J. , Metcalfe J. D. , Ginley S. A. 
Published: April 2021

ABSTRACT
The hypothesis that there is an increase in plasma catecholamines during exercise in fish and that they play an important role in the cardiovascular adjustments during exercise was investigated in the lesser spotted dogfish and rainbow trout. In resting fish plasma catecholamines were at a concentration of 10−9–10−8 mol I−1. During spontaneous swimming in the dogfish, adrenaline increased by 3·3 times to l·9× 10−8mol I−1 and noradrenaline increased by 2·3 times to 3·2× 10−8mol I−1. In rainbow trout swimming at a steady 1 body lengths−1 (Ls−1) in a water channel, the levels of both amines decreased to approximately 25% of the resting values. When swimming to apparent exhaustion at approximately 2Ls−1, adrenaline was 10 times the resting value at 1·4× 10−8mol I−1, whereas noradrenaline was 2·2 times the resting value at 2·3 × 10−8mol l−1. Only after repeated burst swimming for 2–3 min did the levels of plasma catecholamines increase substantially above the resting values. In the dogfish, both amines were at 10−7moll−1, whereas in the rainbow trout, noradrenaline was at 8·5× 10−8mol I−1 and adrenaline was at 2× 10−7mol l−1.
These levels were compared with the concentrations of catecholamines used by other workers to elicit changes in the branchial vasculature, gas exchange at the gills or gas transport to the tissues. In lesser spotted dogfish, the levels of adrenaline and noradrenaline present in the plasma during spontaneous swimming have 80% and 50% of maximum effect on gill blood vessels, respectively, whereas in rainbow trout the levels present when swimming to apparent exhaustion have approximately 20 % of maximum effect on the branchial vasculature. The levels present in the trout after repeated burst swimming have 40% of maximum effect on blood vessels in the gills. The difference between the dogfish and the trout may be related to the lack of innervation of the gill blood vessels in the former. Enhancement of gas exchange across the gills of rainbow trout can be demonstrated by using adrenaline at the concentration found after repeated burst swimming. It is possible, however, that the concentration of adrenaline found in the plasma of trout after swimming to apparent exhaustion may cause an increase in the concentration of oxygen in arterial blood, thus enhancing oxygen delivery to the tissues.
It therefore appears that, in rainbow trout, only the levels of plasma catecholamines attained during repeated burst swimming are likely to have clear effects on oxygen delivery to the tissues. Burst swimming is powered by the white anaerobic muscle fibres, so oxygen delivery during the exercise will not be of value. An elevated supply of oxygen after such exercise could well be important, although it is not certain to what extent a fish would engage in repeated burst swimming for several minutes in its natural environment.
Intracellular and Extracellular Acid-Base Status and H+ Exchange with the Environment After Exhaustive Exercise in the Rainbow Trout
Authors: Milligan C. Louise , Wood Chris M. 
Published: April 2021

ABSTRACT
Exhaustive exercise induced a severe short-lived (0–1 h) respiratory, and longer-lived (0–4 h) metabolic, acidosis in the extracellular fluid of the rainbow trout. Blood ‘lactate’ load exceeded blood ‘metabolic acid’ load from 1–12 h after exercise. Overcompensation occurred, so that by 8–12 h, metabolic alkalosis prevailed, but by 24 h, resting acid-base status had been restored. Acid-base changes were similar, and lactate levels identical, in arterial and venous blood. However, at rest venous RBC pHi was significantly higher than arterial (7·42 versus 7·31). After exercise, arterial RBC pHi remained constant, whereas venous RBC pHi fell significantly (to 7·18) but was fully restored by 1 h. Resting mean whole-body pHi, measured by DMO distribution, averaged approx. 7·25 at a pHe of approx. 7·82 and fell after exercise to a low of 6·78 at a pHe of approx. 7·30. Whole-body pHi was slower to recover than pHe, requiring up to 12 h, with no subsequent alkalosis. Whole-body ECFV decreased by about 70 ml kg−1 due to a fluid shift into the ICF. Net H+ excretion to the water increased 1 h after exercise accompanied by an elevation in ammonia efflux. At 8–12 h, H+ excretion was reduced to resting levels and at 12–24 h, a net H+ uptake occurred. Lactate excretion amounted to approx. 1 % of the net H+ excretion and only approx. 2% of the whole blood load. Only a small amount of the anaerobically produced H+ in the ICF appeared in the ECF and subsequently in the water. By 24 h, all the H+ excreted had been taken back up, thus correcting the extracellular alkalosis. The bulk of the H+ load remained intracellular, to be cleared by aerobic metabolism.
Hormonally Mediated Reprogramming of Muscles and Motoneurones During the Larval-Pupal Transformation of the Tobacco Hornworm, Manduca Sexta
Authors: Weeks Janis C. , Truman James W. 
Published: April 2021

ABSTRACT
The larval-pupal transformation of Manduca sexta results from an exposure to ecdysteroids in the absence of juvenile hormone (the commitment pulse), followed by a larger exposure to ecdysteroids (the prepupal peak) with a reappearance of juvenile hormone (JH). The prepupal ecdysteroid peak triggers the degeneration of abdominal muscles, and the dendritic regression and death of identified moto-neurones. The present experiments examined the role of the commitment pulse in the larval-pupal reprogramming of these cells. The commitment pulse did not overtly affect the muscles and motoneurones, but it switched their hormonal responsiveness; before the commitment pulse, exposure to ecdysteroids in the presence of JH had no effect on the larval cells, whereas after the commitment pulse the same treatment caused regression and death. Thus, JH lost its ability to prevent pupal development. Furthermore, treatment with ecdysteroids in the absence of JH before the commitment pulse promoted pupal development much less effectively than did the same treatment given after the commitment pulse, indicating that the commitment pulse facilitates the subsequent responsiveness to ecdysteroids. Thus, the commitment pulse covertly causes both qualitative and quantitative changes in the hormonal sensitivity of the larval muscles and motoneurones.
The Effects of Sensory Manipulation Upon Interlimb Coordination During Fast Walking in the Cockroach
Authors: Tang Twen Poh , Macmillan David L. 
Published: April 2021

ABSTRACT
A re-examination of fast stepping in free-walking cockroaches showed that there was considerable variation in the alternating tripod gait. Small load increments applied to the whole animal significantly reduced this variability and concentrated the range and speed of movements used. Animals suspended above oiled glass surfaces moved their legs in normal gait patterns indicating that mechanical coupling via the substrate was not a critical factor for normal high-speed coordination. Increasing the viscosity of the oil produced the same reduction in variability found with load increment so the change cannot be due to increased mechanical coupling. Increasing the viscosity of the oil under one leg alone resulted in concentration over the whole pattern so the result was not considered to be due to viscosity changes. The changes seen in artificial loading situations were mimicked in natural loading situations such as walking up a slight incline. The functional significance of the phenomenon for the stability of the rapidly moving animal is considered and the role of load afference in biasing central pattern generators to produce a continuous range of functional output is discussed.
Pulmonary Mechanics and the Work of Breathing in the Semi-Aquatic Turtle, Pseudemys Scripta
Authors: Vitalis Timothy Z. , Milsom William K. 
Published: April 2021

ABSTRACT
Measurements of pulmonary mechanics on anaesthetized specimens of the aquatic turtle Pseudemys scripta (Schoepff) indicate that the static pulmonary mechanics of the total respiratory system are determined primarily by the mechanics of the body wall rather than those of the lungs. This is also true under the dynamic conditions of pump ventilation at low pump frequencies. As pump frequency increases, the work required to inflate the multicameral lungs of the turtle begins to contribute an increasing portion to the total mechanical work required to produce each breath as measured from pressure volume loops. The rise in the work performed on the lungs results from an increase in the non-elastic, flow-resistive forces which must be overcome during ventilation. The primary bronchus to each lung is the most likely site of flow resistance. There is also a small elastic component to the work required to ventilate the lungs associated with movement of the intrapulmonary septa and the striated muscle surrounding the lungs. The contribution of the work required to distend the body cavity as a percentage of the total mechanical work required to generate each breath remains relatively unchanged with increasing ventilation frequency, indicating that the majority of the forces to be overcome in the body wall are elastic in nature. For a constant rate of minute pump ventilation, as frequency increases, the work done per minute to overcome elastic forces decreases, while that done to overcome non-elastic forces begins to rise. These opposing trends produce an optimum combination of pump volume and frequency at which the rate of mechanical work is minimum.
Kinetics of Oxygen Uptake and Release by Red Blood Cells of Chicken and Duck
Authors: Phu D. Nguyen , Yamaguchi K. , Scheid P. , Piiper J. 
Published: April 2021

ABSTRACT
The specific conductance (G) for O2 transfer by red blood cells (RBCs) of chicken and muscovy duck was measured using the experimental (stopped-flow) and analytical techniques (RBC model) previously applied to human RBC (Yamaguchi, Nguyen Phu, Scheid & Piiper, 1985). Avian RBCs behaved similarly to human RBCs: G values were of similar magnitude; G for O2 uptake decreased with time and increasing O2 saturation; G for O2 release at high levels of dithionite decreased slightly with decreasing O2 saturation; G for O2 release was higher than G for O2 uptake. The deoxygenation kinetics of oxyhaemoglobin in solution was similar for both avian species.
The G measured for O2 release at high dithionite concentration, considered to represent a good approximation to intra-erythrocyte O2 diffusion conductance, averaged (in mmol min-1 Torr-1 ml-1 RBC) 0·33 for chicken and 0·25 for duck (at 41°C, pH of the suspension = 7·5, O2 saturation range 0·4-0·8). These species differences can be explained by differences in cell size, the RBC volume averaging 104, μm3 in the chicken and 155 μm3 in the duck. Compared with human RBCs, the G estimates for avian RBCs are somewhat smaller than would be predicted from size differences, which can be explained by the discoid shape of mammalian RBCs which constitutes an advantage compared with the ovoid avian RBC.
Chemoreception In Sea Anemones: Betaine Stimulates The Pre-Feeding Response In Urticina Eques and u. Felina
Authors: Boothby Kate M. , Mcfarlane Ian D. 
Published: April 2021

ABSTRACT
Chemical stimulation can evoke complex behaviour patterns in sea anemones. In pre-feeding behaviour a diffusible component of food causes the oral disc to expand and the column to extend and bend from side to side. These movements may increase the chance of catching nearby food (Pollock, 1883). The response is coordinated by the ectodermal slow conduction system (SSI). In Urticina eques, food extracts that excite the pre-feeding response evoke a low-frequency series of SSI pulses; and electrical stimulation of the SSI, in the absence of food, causes pre-feeding movements (McFarlane, 1970). The SSI, the SS2 (an endodermal slow system) and a through-conducting nerve net (TCNN) are the three known conducting systems that appear to coordinate sea anemone behaviour (McFarlane, 1982). Other conducting systems have been proposed (e.g. Lawn & Ross, 1982) but not confirmed.
The Effect of Screening Pigment Migration on Spectral Sensitivity in a Crayfish Reflecting Superposition Eye
Authors: Bryceson Kim P. 
Published: April 2021

ABSTRACT
In crayfish, there is some evidence that visual pigments in the eye affect the spectral sensitivity, both at the receptor level (Goldsmith & Fernandez, 1968; Kong & Goldsmith, 1977) and in the optic fibres (Woodcock & Goldsmith, 1970). However, there is a discrepancy between the absorption spectrum of rhodopsin as measured by microspectrophotometry (λmax is 530–550 nm, Goldsmith, 1978) and published measurements of spectral sensitivity [e.g. electroretinogram (ERG) peaks of 565–570 nm (Kennedy & Bruno, 1961) and intracellular recordings of 556 nm and 600–620 nm (Nosaki, 1969) and 538–634 nm (Waterman & Fernandez, 1970)]. Woodcock & Goldsmith (1970) suggested that sensitivity maxima in the orange and red were due to the non-alignment of the stimulating beam with the optical axis of the cell, thereby allowing light to filter obliquely through red and brown proximal screening pigment surrounding the rhabdom. Goldsmith (1978) showed (theoretically) that the red-brown proximal screening pigments of crayfish and lobster are indeed capable of shifting the effective absorption of the rhabdoms enough to account for the discrepancy between the absorption peak of the visual pigment and the published measurements of spectral sensitivity. However, the effect on spectral sensitivity of the migration of the proximal screening pigment has not been documented.
Short Communication Aquatic Prey Capture in Fishes: Experimental and Theoretical Approaches
Authors: Lauder George V. 
Published: April 2021

ABSTRACT
In our attempts to understand how animals work, the diversity of animal design and the physiological basis of animal behaviour it is common to make theoretical models of animal function and to conduct experiments to test these models. Experimental analyses often provide a direct test of competing models, evaluate the accuracy of assumptions of models and, at a more descriptive level, simply provide increased observational precision. On the other hand, theoretical models may play an important heuristic role in suggesting new experiments and may provide a general predictive framework within which research can progress.
Changes in Membrane Potential during Adaptation to External Potassium Ions in Paramecium Caudatum
Authors: Oka Takashi , Nakaoka Yasuo , Oosawa Fumio 
Published: April 2021

ABSTRACT
When Paramecium are transferred from the solution to which they have been adapted to a solution of a different K+ concentration, they initially change their swimming behaviour and then gradually recover normal swimming. This adaptation to the new solution takes 2–3 h. We found that in the process of adaptation there was a change in membrane potential: transfer of the cells to a lower K+ concentration caused depolarization of the potential, whereas transfer to a higher concentration produced a hyperpolarization. In both cases, the change in potential was followed by a gradual repolarization to the original value in the control solution. During adaptation, the intracellular concentration of K+ did not change much. It is probable that the cells change their membrane potential towards a constant level by controlling the membrane conductance for K+.