bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Directionally Sensitive Motion Detecting Neurone in the Brain of A Moth
Authors: Rind F. Claire 
Published: April 2021

ABSTRACT
In the moth, Manduca sexta, a pair of neurones, one on each side of the brain, were characterized morphologically and physiologically as descending interneurones, selective for horizontal motion over a large area of the moth’s visual field. Their cell bodies and dendritic processes are located in the protocerebrum of the brain. Their axons, 12–15μm in diameter, project down the ipsilateral connective, branching profusely on the ipsilateral side of the suboesophageal, prothoracic and pterothoracic ganglia. Each neurone responds to movement over either retina. Their preferred directions are from front to back across the ipsilateral eye and back to front over the contralateral one. Movement in the opposite direction supresses their usual ‘resting’ discharge. The neurones are particularly sensitive to movements within the frontal, ventral visual field. Each neurone responds repeatedly, for up to 5 h, to a stimulus oscillating back and forth across the retinae. The response is not diminished during concurrent wing flapping. An increase in the velocity of stimulus movement produces a proportional increase in firing frequency. For stripes of 2·5 cm wavelength and subtending 32° at the eye, the maximum response occurs at a velocity of 3cm/s which gives a contrast frequency of 1-2 Hz. The latency of the neurone’s response, measured from its axon as it enters the pterothoracic ganglion, depends on at least two factors: light intensity and the speed of stimulus movement. The neurone gives a directional response to stripes of period 6·4° in bright light. The response falls to 16· in dim light. At night, in dim light, the latency of response is much reduced and the threshold light intensity, necessary for a directional response, decreases by two orders of magnitude.
Hormonal Influence on Diurnal Glycogen Rhythms in Rat Skeletal Muscles
Authors: IV C. W. Saubert , Armstrong R. B. 
Published: April 2021

ABSTRACT
Normal, diabetic, and sympathectomized rats were killed at intervals during a 12h light (6a.m. to 6p.m.)/12h dark cycle to determine (1) the patterns of diurnal glycogen rhythms in skeletal muscle fibre types, and (2) if the absence of insulin or the catecholamines epinephrine and norepinephrine abolished these rhythms. Normal rat muscles lost and restored 40–60 % of their glycogen stores during one 24-h cycle. Glycogen losses were linear between 6.30 a.m. (acrophase time for all muscles) and 8.30a.m. and between 8.30a.m. and nadir points (4.30 p.m. to 8.30 p.m.), but the rates of loss were non-uniform between these time frames and among fibre types. All muscles had similar linear restoration rates. Glycogen stores in most muscles from diabetic and sympathectomized rats exhibited changes similar to those seen in normal animals. Skeletal muscle fibre types have notable and non-uniform diurnal glycogen rhythms that should be considered in the design of metabolic and exercise experiments. These rhythms do not appear to be regulated, either differentially or in toto, either by insulin or by the catecholamines epinephrine and norepinephrine.
An Analysis of Waving Behaviour: an Alternative Motor Programme for the Thoracic Appendages of Decapod Crustacea
Authors: Pasztor V. M. , Clarac F. 
Published: April 2021

ABSTRACT
Decapod Crustacea display a slow metachronal rhythm of the third maxillipeds and pereiopod pairs one to four when undisturbed in the natural habitat. The dactyl tips are lifted off the substrate, and the unweighted limbs promote and remote at a slow frequency (range for all species 9–30min− 1). Movement is limited to the T-C joint. This behaviour, called waving, has been observed in many macrurans and an analogous activity, limited to the third maxillipeds, has been seen in several brachyurans. Analysis of EMGs shows: (a) the promotor activity increases in strength during a burst due to facilitation and motoneurone recruitment; (b) the rhythm period is stable throughout long waving sessions; (c) the promotor and remotor strokes are of equal duration and co-vary with period. Ipsilateral coupling is strong, with equal phases between adjacent limbs of 0· 05. The metachronal wave can pass anteriorly or posteriorly along an ipsilateral row. Bilateral coupling is weak. The two sides maintain equal frequency, and antiphasic coordination between the two ipsilateral sets of limbs is favoured. Possible functions for waving include gill grooming and supplementary gill ventilation. Comparisons between waving and other rhythmical motor programmes are discussed. Waving is an alternative programme for the walking legs, and is expressed when proprioceptive feedback is reduced.
Coupled Neuronal Oscillators in the Snail Lymnaea Stagnalis: Endogenous Cellular Properties and Network Interactions
Authors: Egelhaaf M. , Benjamin P. R. 
Published: April 2021

ABSTRACT
The role of endogenous cellular properties and network interactions due to electrotonic coupling were investigated in two bilateral populations of 2–7 peripheral neurones (‘Peripheral Bursters’) in the snail Lymnaea stagnalis.
These cells are endogenously capable of bursting. Their burst frequency does not depend on the level of steady membrane polarization. Short hyperpolarizing current pulses injected during the bursting cycle induce phase advance and no phase delay in subsequent cycles, the phase advance being a function of the phase of stimulus application. Phase response and inter-burst interval curves have been constructed for short hyperpolarizing current pulses. Their shape depends on the intensity and sign of tonically injected current. This property of Peripheral Bursters is one reason for the independence of period duration from membrane polarization. Coordination of burst activity of Peripheral Bursters has been studied as a function of coupling strength : whereas homolateral cells are relatively strongly electrotonically coupled and always burst synchronously, thus forming a single oscillatory unit, heterolateral cells are only weakly electrotonically coupled. Accordingly, they show more variable, though coordinated, patterns of activity. Most commonly, periods with 1:1 entrainment alternate with periods with 1:2 entrainment. The duration and frequency of occurrence of either mode of entrainment are highly variable in different preparations.
Fine Structure and Mechanical Properties of the Catch Apparatus of the Sea-Urchin Spine, A Collagenous Connective Tissue with Muscle-Like Holding Capacity
Authors: Hidaka Michio , Takahashi Keiichi 
Published: April 2021

ABSTRACT
The catch apparatus (CA) of the sea-urchin spine has been known to have a muscle-like holding property, though it is composed mainly of extracellular collagen fibres. An electron microscopic study has been made on the CA of the sea urchin, Anthocidaris crassispina, with special reference to its content of muscle cells and to structural changes of the collagen components on elongation of the CA. The stretch resistance of the CA in a highly extensible state and in a very inextensible state was also measured. Although very thin smooth muscle cells were found scattered among the collagen fibres in the CA, the difference in the passive tension was greater than the estimated stress which could be generated by the muscle cells in the CA by three orders of magnitude. The collagen fibrils remained undeformed but slid along one another during the length change of the CA. The present results suggest that the cohesive force between the collagen fibrils rather than the contractile activity of the muscle cells plays a significant role in determining the mechanical properties of the CA.
Locomotory Stresses in the Limb Bones of Two Small Mammals: The Ground Squirrel and Chipmunk
Authors: Biewener Andrew A. 
Published: April 2021

ABSTRACT
Peak stresses acting in limb bones should increase with increasing size if the forces acting on the bones increase in direct proportion to the animal’s body weight. This is a direct consequence of the scaling of limb bone geometry over a wide range in size in mammals. In addition, recent work has shown that the material strength of bone is similar in large and small animals. If the assumptions in this analysis are correct, large animals would have a lower safety factor to failure than small animals. The purpose of this study was to measure peak stresses acting in the limb bones of small animals during locomotion and compare the results with similar measurements available for larger animals. Locomotory stresses acting in the fore and hindlimb bones of two rodents, the ground squirrel (Spermophilus tridecem-lineatus) and chipmunk (Tamais striatus), were calculated using ground force recordings and measurements of limb position taken from high speed x-ray cine films. Peak (compressive) stresses calculated to act in the bones of these animals (—31 to —86MN/m2) are similar in magnitude to those determined for much larger mammals. The more proximal bones of the fore and hindlimb, the humerus and femur, were found to develop stresses ( — 31 to —42MN/m2) significantly lower than those acting in the more distal bones of each limb: the radius, ulna and tibia (—58 to —86MN/m2). All of the long bones from both species, except their femora, were found to be loaded principally in bending. The caudal cortices of each bone developed a peak compressive stress, whereas the cranial cortices were loaded in tension. Various features of the musculo-skeletal organization and manner of locomotion in these rodents are considered to explain how animals of different size maintain a uniform safety factor to failure.
Effects of Certain Physico-Chemical Agents On the Mechanical Properties of the Catch Apparatus of the Sea-Urchin Spine
Authors: Hidaka M. 
Published: April 2021

ABSTRACT
The catch apparatus (CA), a collagenous connective tissue which connects the sea-urchin spine to the test, is known to undergo a remarkable change in its mechanical properties. Effects of various physico-chemical factors on the mechanical properties of the CA have been investigated in order to characterize the linkages which are responsible for determining the mechanical properties of the CA. The stress-strain relations obtained by stretching the specimen at a slow constant speed, 7 μm s−1, were taken as a measure of the viscous resistance of the CA. The viscous resistance of the CA depended largely on the pH and the ionic strength of the medium. It increased with increasing pH and with decreasing ionic strength. The viscous resistance was markedly reduced in a Ca-free medium containing 5mm-EGTA. It is suggested that linkages sensitive to low pH and those mediated by Ca2+ play a significant role in determining the mechanical properties of the CA.
Stick Insect Locomotion On A Walking Wheel: Interleg Coordination of Leg Position
Authors: Dean Jeffrey , Wendler Gernot 
Published: April 2021

ABSTRACT
Continuous measurements of anterior-posterior leg position recorded from stick insects walking on a wheel were tested for relationships among spatial and temporal parameters of leg coordination. This analysis revealed that the protraction of middle and rear legs is guided by the ipsilateral front and middle legs respectively. Protraction endpoint for each rear leg shows a significant positive correlation with the simultaneous position of the ipsilateral middle leg (Figs 1, 2; Table 1). An analogous, but somewhat weaker, correlation exists between the protraction endpoint of each middle leg and the position of the ipsilateral front leg.
This coordination of spatial parameters was tested experimentally by manipulating the position of the forward leg. When a middle leg is restrained in various positions, the ipsilateral rear leg adjusts its protraction endpoint accordingly (Fig. 3). However, its retraction endpoint does not undergo parallel shifts; consequently, step amplitude, protraction duration, and step frequency all change as a function of middle leg position. When a sinusoidal movement is imposed on either a middle or front leg, the adjacent, caudal leg continuously adjusts its protraction endpoint according to the momentary position of the forward leg (Fig. 4). This adjustment is again accompanied by changes in step amplitude and step period, changes which may affect all five unrestrained legs.
The anterior-posterior leg position measured in our experiments primarily reflects the angle of the coxo-thoracic joint; this angle is monitored by hair rows and hairplates located on the coxa (Wendler, 1964; Baessler, 1965). Modifying these external proprioceptive inputs revealed both inter-and intrasegmental control functions. The caudally situated hair rows are important for measuring the small variations in the position of the target leg which occur during normal walking. Immobilization of these hairs on a middle leg causes the mean protraction endpoint of the ipsilateral rear leg to shift forward (Fig. 5: 01 versus C) and reduces or eliminates the step by step correlation of this protraction endpoint with middle leg position (Table 1). The additional immobilization of the cranially situated hairplates usually leads to a caudal shift in the protraction endpoint of the ipsilateral rear leg (Fig. 5: 02 versus 01) and reduces any residual correlation (Table 1). The actual position of the protraction endpoint reflects an integration of intersegmental signals representing the position of the target leg and intrasegmental signals from the sensory hairs on the protracting leg. Both operations may affect the duration of protraction in both the operated target leg and the adjacent, caudal leg.
Potassium Metabolism in Seawater Teleosts : I. The Use of 86Rb as a Tracer for Potassium
Authors: Sanders Martin J. , Kirschner Leonard B. 
Published: April 2021

ABSTRACT
Comparison of the movements of rubidium and potassium between blood and tissues, and between blood and external medium, was undertaken in seawater adapted rainbow trout (Salmo gairdneri) and sculpin (Leptocottus armatus). Qualitative observations suggested that the two ions behaved similarly in exchanges within both fish. More than 90 % of an injected dose of both ions disappeared from the blood within 1 h. Complete equilibration of both required about 5 h, and the decrease in blood concentration during the last 4h followed similar kinetics. After injection and equilibration of 86Rb into trout the specific activity of most tissue pools (c.p.m. 86Rb /μeq tissue K) was close to that of blood (c.p.m. Rb/µeq plasma K). Skeletal muscle was the sole exception; its specific activity was less than 15 % that of plasma even 4–5 h after injection. Injection of ouabain into trout caused cells to lose both 86Rb and K at similar rates. The same thing occurred when [K] in the external medium was raised abruptly.
Exchanges of the two ions between blood and the external medium were also similar. Both ions were extruded and taken up rapidly across the gills. Double-labelling (86Rb and 42K fluxes measured simultaneously) showed that JK/JRb = l·27 for both influx and efflux in trout. The same value was obtained for effluxes in sculpin. Exposing sculpin to seawater lacking Na and K caused both 42K and 86Rb efflux to fall by 75–80%; 86Rb efflux decreased similarly in trout. Alkali metal-free sea water also caused the voltage across the trout gill to change from +10 mV to −20 mV, and in the sculpin from +25 mV to −25 mV. Addition of either Rb or K to the ion-deficient medium partially repolarized the gill in both fish. Repolarization was slightly greater after K repletion than after Rb repletion.
These observations suggest that 86Rb is an adequate tracer for potassium movement in seawater-adapted fish. The gills of trout and sculpin are a little more permeable to K than to Rb, and Rb fluxes must be multiplied by 1·3 to provide accurate estimates of transbranchial K movement. The quantitative relationship between JK and JRb within the animal was not established, but some data suggest that cell membranes in fish, like the gills, are somewhat more permeable to K than to Rb.
3H-Ouabain Binding Autoradiography in the Abdominal Nerve Cord of the Hawk Moth, Manduca Sexta
Authors: Rubin Andrew L. , Stirling Charles E. , Stahl William L. 
Published: April 2021

ABSTRACT
Ouabain, a specific inhibitor of the Na+,K+-ATPase, was used to study localization of this enzyme in the abdominal nerve cord of the hawk moth, Manduca sexta. Treatment of nerve cords with urea was necessary to permit access of ouabain to binding sites within the nerve cord, probably due to opening of the perineurial barrier. Specific, saturable 3H-ouabain binding below 10 μM was observed in the urea-treated nerve cord, and the total number of specific binding sites was 17·8 pmol/mg protein and those sites were half-occupied (KD) at 1·8 μM-ouabain. The urea treatment did not alter the total number of 3H-ouabain binding sites in this tissue. Localization of the 3H-ouabain binding sites was studied by light microscopic autoradiography. Potassium, an established inhibitor of ouabain binding, at 50 mm blocked 3H-ouabain binding in abdominal ganglia by 59%. The majority of ouabain binding sites in the ganglion are in the neuropil, consistent with the high transport requirement in active nerve processes of small diameter. Significant, but lower binding than found in the neuropil was present in the ganglionic perineurium and this structure may be involved in the transport of sodium from the haemolymph into the neural extracellular space.
Physiological Consequences of Severe Exercise in the Inactive Benthic Flathead Sole (Hippoglossoides Elassodon): a Comparison With the Active Pelagic Rainbow Trout (Salmo Gairdneri)
Authors: Turner Jeffrey D. , Wood Chris M. , Hōbe Helve 
Published: April 2021

ABSTRACT
Chronically cannulated flathead sole were subjected to 10 min of either moderate or exhausting burst exercise and monitored over a 12 h recovery period. Acid-base disturbances were more severe after exhausting exercise, but ionic and haematological changes were the same in the two treatments. Most effects were qualitatively similar to those previously described in severely exercised rainbow trout (Turner, Wood & Clark, 1983). Specific differences are discussed and related to the different external environments (sea water vs fresh water), exercise capabilities and ecologies of the two species. The most striking divergence occurred in lactate (La−) and metabolic proton dynamics. Post-exercise La− levels in white muscle in sole were less than half those in trout but declined much more slowly. In contrast to the situation in trout, muscle [La−] remained significantly elevated and a large muscle to blood La− gradient persisted even after 12 h recovery. Blood [La−] underwent only minimal elevation (&lt; 2 mequiv l−1), and blood metabolic proton load greatly exceeded ΔLa− throughout the recovery period, effects directly opposite those in trout. This observed excess of over ΔLa− in the blood of exercised sole is probably not due to a preferential removal mechanism, because and ΔLa− disappeared from the blood at similar rates after an intra-arterial infusion of lactic acid in resting animals. It is therefore argued that the phenomenon reflects a differential release of the two metabolites from the white muscle of the sole, La− being strictly retained in the muscle for gluconeogenesis in situ.
The Circulatory Response to Acute Hypoxia in Octopus
Authors: wells M. J. , wells J. 
Published: April 2021

ABSTRACT
Octopus vulgaris can regulate its oxygen uptake in a closed respirometer down to a of less than 70 mmHg. As the tankwater falls the hearts slow down. Pulse amplitudes and mean pressures fall in the afferent branchial vessels and in the dorsal aorta. Despite behavioural changes – expansion of the interbrachial web and extension of the arms -that might imply this, the proportion of the total oxygen uptake attributable to cutaneous respiration (less than 13%) does not alter as the external falls. The response of the hearts to a low is not affected by severing the nerve supply from the central nervous system, or by removal of the heart ganglia. It is evidently determined by oxygen lack and not by the accumulation of CO2 or other metabolites, since the same effects are achieved by placing the animals in water where the has been reduced by boiling. The conclusion that regulation does not depend upon circulatory responses to hypoxia is considered in the light of recent work on the changes in blood oxygen affinity associated with acute hypoxia in cephalopods.
Studies of Ammonia in the Rainbow Trout Physico-Chemical Parameters, Acid-Base Behaviour and Respiratory Clearance
Authors: Cameron James N. , Heisler Norbert 
Published: April 2021

ABSTRACT
Ammonia (NH3) is only slightly more soluble (+3·4%) in the plasma of rainbow trout than in water, and its pK′ is only 0·14 units higher than in fresh water at 15 °C. Determination of these physico-chemical parameters together with measurements of blood and water pH and total ammonia concentrations allowed calculation of the mean resting partial pressure gradient across the gills (54 × 10−s6Torr) and estimation of the gill permeability coefficient (D = 1·3 × 10−5cm−1).
Under normal resting conditions of low external NH3 and pH, diffusive movement of NH3 appears to account adequately for ammonia excretion in the rainbow trout; 90 ± 10% of the excreted ammonia appears to originate from the blood, rather than from de novo synthesis of ammonia in the gills.
During the high external ammonia treatments, the fish reached a steady state with a net inward ammonia gradient, which could be accounted for by a counter-balancing Na+/NH4+ exchange. Ammonium salt infusions or injections which stimulate Na+ influx are not sufficient demonstrations of Na+/NH4+ exchange, since acidosis is produced, and alternate interpretations of the Na+ flux stimulation are possible, such as enhanced Na+/H+ exchange.
Allometry of Quadrupedal Locomotion: the Scaling of Duty Factor, Bonecurvature and Limb Orientation to Body Size
Authors: Biewener Andrew A. 
Published: April 2021

ABSTRACT
Measurements of the chord length (∝ M0·31) and diameter (∝ M0·35) of the femora, tibiae, humeri and radii from 32 species of mammals, ranging in approximate body mass from 0·020– 3500 kg, support previous data which show that mammalian long bones scale close to geometric similarity. Scaling of peak stresses based on these measurements of limb bone geometry predicts that peak stress increases ∝ M0·28, assuming that the forces acting on a bone are directly proportional to an animal’s weight. Peak locomotory stresses measured in small and large quadrupeds contradict this scaling prediction, however, showing that the magnitude of peak bone stress is similar over a range of size. Consequently, a uniform safety factor is maintained. Bone curvature (∝ M−0·09) and limb bone angle relative to the direc tion of ground force (∝ M−0·07) exhibit a slight, but significant, decrease with increasing body mass. Duty factor measured at the animal’s trot-gallop transition speed does not change significantly with body size. The moment arm ratio of ground force to muscular force exerted about a joint was found to decrease dramatically for horses as compared to ground squirrels and chipmunks. This six-fold decrease (∝ M−0·23) provides preliminary data which appear to explain, along with the decrease in bone curvature and angle, the similar magnitudes of peak bone stress developed during locomotion in different sized animals. The crouched posture adopted by small quadrupeds while running may allow greater changes in momentum (when accelerating or decelerating) or a decrease in the forces exerted on their limbs.