bluuebunny/crossref_metadata_2025_split huggingface dataset:
Analysis of Mechanisms of Spiking in Normally ‘Non-Spiking’ Motoneurone Somata in Crayfish
Authors: Czternasty Gerard , Kado Raymond T. , Bruner Jan 
Published: April 2021

ABSTRACTThe soma membrane of the abdominal giant motor neurone (MoG) of the crayfish was studied by use of current injection and by measurements of total and local membrane current under voltage-clamp. Depolarization of the soma from the recorded resting potential (about −70 mV) did not produce a regenerative potential. Sodium and calcium currents were observed under voltage-clamp. It was shown that the sodium spike cannot develop at the usual resting potential since sodium channels are already partially inactivated; the spike can appear after the removal of inactivation by a hyperpolarizing prepulse. It was also shown that an early outward current prevents the Ca2+ regenerative potential; the potential can appear after inactivation of this outward current by a depolarizing prepulse.
Mechanics of six-legged runners
Authors: Full R. J. , Tu M. S. 
Published: April 2021

ABSTRACT
Six-legged pedestrians, cockroaches, use a running gait during locomotion. The gait was defined by measuring ground reaction forces and mechanical energy fluctuations of the center of mass in Blaberus discoidalis (Serville) as they travelled over a miniature force platform. These six-legged animals produce horizontal and vertical ground-reaction patterns of force similar to those found in two-, four-and eight-legged runners. Lateral forces were less than half the vertical force fluctuations. At speeds between 0.08 and 0.66 ms−1, horizontal kinetic and gravitational potential energy changes were in phase. This pattern of energy fluctuation characterizes the bouncing gaits used by other animals that run. Blaberus discoidalis attained a maximum sustainable stride frequency of 13 Hz at 0.35 ms-1, the same speed and frequency predicted for a mammal of the same mass. Despite differences in body form, the mass-specific energy used to move the center of mass a given distance (0.9 J kg−1 m−1) was the same for cockroaches, ghost crabs, mammals and birds. Similarities in force production, stride frequency and mechanical energy production during locomotion suggest that there may be common design constraints in terrestrial locomotion which scale with body mass and are relatively independent of body form, leg number and skeletal type.
Observations on the Compound Eyes of the Deep-Sea Ostracod Macrocypridina Castanea
Authors: Land M. F. , Nilsson D.-E. 
Published: April 2021

ABSTRACT
Macrocypridina lives at depths of 800 m, where residual daylight is very weak. It has a pair of mobile apposition compound eyes with large lenses, wide rhabdoms and high acceptance angles, all of which contribute to a calculated sensitivity comparable with the superposition eyes of deep-water decapod crustaceans. The axes of the 27 ommatidia in each eye are not uniformly distributed in space, with a modest acute zone in the anteroventral region. Here the interommatidial angles are about 6°, compared with 20° at the rear of the eye.
The eyes make two kinds of spontaneous movements: large slow rotations of up to 50° around a transverse axis, and a superimposed 2 Hz tremor with an amplitude of 5 °.
Response Characteristics of Four Wide-Field Motion-Sensitive Descending Interneurones IN Apis Melufera
Authors: Ibbotson Michael R. , Goodman Lesley J. 
Published: April 2021

ABSTRACT
The anatomical projections and directional tuning of four descending interneurones sensitive to wide-field motion over the compound eyes are described. The cells are slow to adapt, resistant to habituation and their responses are dependent on the contrast frequency of the periodic patterns used as stimuli. Two of the cells (DNIV2 and DNIV4) are maximally stimulated by movement around the longitudinal axis of the bee (simulated roll), one (DNII2) by movement around the horizontal axis (simulated pitch) and one (DNVI1) by movement around the vertical axis (simulated yaw). The cells are binocular, their directional response being shaped by the interaction of the inputs from each eye. The cells which respond predominantly to roll (DNIV2 and DNIV4) have their arborizations restricted to the ipsilateral side of the brain and thoracic ganglia, i.e. the side which contains the cell soma. The cell responding to pitch (DNII2) has its arborizations distributed bilaterally, invading similar regions of the neuropile in both sides of the brain and thoracic ganglia. The cell which responds to yaw (DNVI1) has its major dendritic field in the ipsilateral side of the brain and descends into the thoracic ganglia in the contralateral side. The majority of its arborizations in the thoracic ganglia are confined to the contralateral neuropile.
Force Maintenance with Reduced Ability to Shorten Actively in Barnacle Striated Muscle
Authors: Iwamoto H. , Muraoka A. , Goto A. , Sugi H. 
Published: April 2021

ABSTRACT
Fibres from adductor scutorum muscle of a barnacle Tetraclita squamosa were made to contract isometrically by electrical stimulation, and the change in the ability to shorten actively during the mechanical responses was examined by suddenly allowing the fibres to shorten under a very small load (&lt;3 % of the force immediately before shortening) at various times after the onset of stimulation. The shortening velocity (Vsl) was nearly constant during stimulation. After the cessation of stimulation, shortening velocity decreased steeply while isometric force decayed slowly, indicating that isometric force was maintained with reduced ability to shorten actively. Similar results were obtained when the maximum rate of force redevelopment following a quick release was measured at various times during the mechanical response to electrical stimulation. In these fibres, but not in fibres from frog skeletal muscle, a quick restretch following a quick release could restore the force to a level similar to that observed without a quick release. These results, together with those above, indicated a reduced cross-bridge cycling rate during the relaxation phase of mechanical responses of barnacle fibres to electrical stimulation. During electrical stimulation, Vsl showed less dependence on [Ca2+]o than was shown by isometric force. These results are discussed in connection with the mechanism of force maintenance with reduced cross-bridge cycling rate.
Cytoplasmic pH recovery in acid-loaded haemocytes of squid (Sepioteuthis lessoniana)
Authors: Heming T. A. , Vanoye C. G. , Brown S. E. , Bidani A. 
Published: April 2021

ABSTRACT
Cytoplasmic pH (pHi) of haemocytes of bigfin reef squid (Sepioteuthis lesso-niana Lesson) was determined with the fluorescent probe, 2′,7′-biscarboxyethyl-5,6-carboxyfluorescein (BCECF). The pHi of haemocytes suspended in nominally HCO3−-free medium (extracellular pH 7.4) averaged (±S.E.) 7.32±0.02. Intracellular pH was independent of external Na+ concentration and varied only slightly with changes in extracellular pH (pHe) (ΔpHi/ΔpHe=0.16 over the pHe range 6.8–7.8). Addition of weak acids (sodium propionate, potassium acetate) to haemocyte suspensions resulted in a rapid decrease in pHi. Haemocyte pHi then recovered with an average half-time of 3–4 min. Recovery of pHi was independent of external Na+ concentration and insensitive to amiloride, but was abolished by N-ethylmaleimide (NEM). These results argue against the involvement of plasma membrane Na+/H+ exchange or other Na+-dependent transport mechanisms in the pHi recovery of acid-loaded haemocytes. The results suggest that there is an NEM-sensitive proton extrusion mechanism in the plasma membrane of squid haemocytes.
Modelling Muscle Power Output in a Swimming Fish
Authors: Altringham John D. , Johnston Ian A. 
Published: April 2021

ABSTRACT
Intact, electrically excitable fibre bundles were isolated from the fast and slow myotomal muscle of the bullrout (Myoxocephalus scorpius L.). Power output was measured under conditions simulating their activity in a fish swimming at different speeds. Preparations were subjected to sinusoidal length changes of ±5% of resting length, and stimulated briefly during each cycle. The number and timing of stimuli were adjusted at each cycle frequency to maximise power output. Maximum power was produced at 5–7 Hz for fast fibres (25–35 W kg−1) and 2 Hz for slow fibres (5–8 Wkg−1). Under these conditions, pre-stretch of active muscle provides an important mechanism for storing potential energy for release during the shortening part of the cycle.
Backbone Mechanics of the Blue Marlin Makaira Nigricans (Pisces, Istiophoridae)
Authors: Hebrank John H. , Hebrank Mary R. , Long John H. , Block Barbara A. , Wainwright Stephen A. 
Published: April 2021

ABSTRACT
Over most of its length, the backbone of the blue marlin, like that of all other istiophorids, contains enlarged and flattened neural and hemal spines and zygapophyses, all of which span the intervertebral joints. These plates of bone restrict dorso-ventral bending of the backbone but their arrangement permits a high degree of lateral flexion. The spines and zygapophyses also appear to be important in stabilizing the relatively large intervertebral joints against axial compression and lateral shearing during bending. Although bone is an elastic material, these overlapping structures are not arranged so as to contribute to elastic recoil of the backbone during normal swimming movements.
An Identified Set of Local Nonspiking Interneurones which Control the Activity of Abdominal Postural Motoneurones in Crayfish
Authors: Toga Tetsuo , Takahata Masakazu , Hisada Mituhiko 
Published: April 2021

ABSTRACT
Several interneurones have been reported to be involved in the control of activity of abdominal postural motoneurones in crayfish (Miall and Larimer, 1982a; Larimer and Jellies, 1983). These interneurones are mostly interganglionic, except for two (each encountered only once) which are local (Jellies and Larimer, 1985). The two local interneurones were found to be nonspiking, as reported in a variety of motor control systems of arthropods (Siegler, 1985). In the abdominal posture system, however, it is still unknown to what extent this type of neurone participates in the control of motoneurone activity. In this study, we repeatedly encountered and identified a set of local nonspiking interneurones which could control the postural motoneurone activity in the same fashion in different preparations.
Discontinuous Turning Reaction during Escape in Soldier Crabs
Authors: Nalbach Hans-Ortwin 
Published: April 2021

ABSTRACT
In many animals, the approach of an object is perceived visually and elicits an escape reaction (Dill, 1974). The escape is often aimed directly away from the threat. In some cases, however, the animal heads towards a nearby refuge, or another preferred place. Blue crabs, for instance, escape from the shore into deeper water (Woodbury, 1986). When ghost crabs are threatened while foraging far away from their burrow, they may change their heading erratically during escape in response to the visually perceived movement of the approaching object (Vannini, 1980). Soldier crabs (Mictyris longicarpus Latreille) face a similar problem because they live on estuarine mud flats and have no permanent burrows. They may react to an approaching person at a distance of 29–33 m, i.e. when the person has a vertical angular size of 2.2–3.2° at the eye of the crab. This illustrates the high vertical visual acuity across the acute zone of the ‘flat-world type crab’ Mictyris (Zeil et al. 1986). Usually, they can avoid being caught by ‘screwing’ themselves into the substratum with astonishing speed (Cameron, 1966). On hard substrata, however, they have to escape. Unlike ghost crabs (Burrows and Hoyle, 1973), soldier crabs are slow, with a maximum velocity of about 10 cm s−1. This may be a consequence of their habit - atypical of brachyurans - of walking exclusively forwards (Sleinis and Silvey, 1980). During escape, soldier crabs walk on a straight path away from the approaching object and usually change their direction only in response to changes of the approach direction of the threatening object. I observed that when one walks around a soldier crab on a circular path at some distance, it still walks along straight paths and changes direction by making abrupt turns from time to time.
Recovery of Chloride Uptake in Sea Wateradapted Rainbow Trout (Salmo Gairdneri) after Transfer to Fresh Water
Authors: Battram John C. , Eddy F. B. 
Published: April 2021

ABSTRACT
The ability of rainbow trout (Salmo gairdneri Richardson) to acclimate to sea water or partially diluted sea water has been studied many times (Houston, 1959; Parry, 1960; Eddy and Bath, 1979; Prunet and Boeuf, 1985). However, the reverse transition from sea water (SW) to fresh water (FW) has been less well studied. The transition from a hyperosmotic medium to a hypo-osmotic medium reverses the burden on the osmoregulatory organs, i.e. the gills and the kidney. SW teleost fish normally show net salt (NaCl) efflux, whereas FW fish need to acquire salt from the medium. Recent work on salmon (Salmo salar) transferred from SW to FW (Talbot and Potts, 1989; Talbot et al. 1989; Potts et al. 1989) has described the changes in sodium balance, osmoregulation and renal function in adult and juvenile fish. Potts et al. (1985) showed that salmon are capable of taking up sodium immediately on transfer to FW. Chloride uptake via the gills of FW fish is of equal importance to sodium uptake, and the two ions are thought to be transported independently (Maetz and Garcia-Romeu, 1964). This paper examines the changes in chloride transport that occur during the transition from SW to FW.
Directional variant and invariant hearing thresholds in the rainbow trout (Salmo Gairdneri)
Authors: Schellart Nico A. M. , Buwalda Rob J. A. 
Published: April 2021

ABSTRACT
The gas-filled bladder, the fish middle-ear analogue, transforms sound pressure (p) into pulsations, which generate displacement waves with body-fixed orientation that stimulate the nearby labyrinths. Moreover, in addition to this indirect stimulation, the otolith organs are stimulated directly by the particle motion vector (v) in line with the source. For pure tones the vector sum of both stimulations results in elliptical displacement orbits, which are nearly identical for left and right ears. We hypothesize that these orbits are centrally analysed, either by breakdown into the original, direct and indirect components, the segregation hypothesis, or by analysis of their characteristic form and orientation, the orbit hypothesis. This provides fish with spatial hearing. Analysing the orbit form and orientation would constitute an essentially monaural mechanism of directional hearing that should show strong and characteristic azimuthal anisotropies. To investigate these anisotropies we have studied the rainbow trout Salmo gairdneri psychophysically with respect to directional-detection and directional-masking paradigms involving heart rate conditioning. We employed superpositioning of standing waves in a large tank for total control of a probe signal and a narrow-band noise masker.
With a sinusoidal p and v probe and a p and v (omnidirectional) noise masker, or with a pure v probe and a (‘uni’directional) p noise masker, trout proved to be equally sensitive to all directions. Only when the indirect stimulation was mimicked by a v stimulus, were we able to demonstrate anisotropy. This indicates that trout indeed use the orbit lengths in the detection and masking tasks. The results can be explained if binaural convergence plays a role, under the assumption that left and right orbits differ appreciably. This might be the case if the divergence in orientation between the indirect stimulations reaching the right and left labyrinths were much larger than would be expected from the geometrical relationships between the two labyrinths and the swimbladder.
Control of optomotor responses by descending deviation detector neurones in intact flying locusts
Authors: Hensler K. , Rowell C. H. F. 
Published: April 2021

ABSTRACT
Neural control of optomotor responses in Locusta migratoria was studied using a newly developed preparation of intact, tethered, flying locusts. The preparation could perform normal flight behaviour and head movements while neurones in the neck connectives were recorded and stimulated intracellularly.
Course deviations simulated by an artificial horizon caused optomotor reactions, e.g. steering by the wings (monitored as steering reactions in M97 and M127, first basalar muscles of fore- and hindwings, respectively) and compensatory head movements. Intracellular recordings were made from two identified descending deviation detector neurones, PI(2)5 and DNC. Both neurones coded direction specifically for course deviations. Electrical activation of either neurone in tethered flight at frequencies of up to 230 Hz elicited steering in M97 and M127 and head rolling with latencies of less than 20 ms. These reactions were of the same quality and strength as compensatory head rolling and steering in M97 and M127 following horizon rolling of about 40°. This demonstrates directly a role of PI(2)5 and DNC in course control.
Scaling of atp-supplying enzymes, myofibrillar proteins and buffering capacity in fish muscle: Relationship to locomotory habit
Authors: Somero G. N. , Childress J. J. 
Published: April 2021

ABSTRACT
Pelagic fishes with an ability to swim in strong bursts have previously been shown to have large size-dependent increases (positive allometric scaling exponents) in the activities of glycolytic enzymes in white skeletal muscle. This scaling of glycolytic activity has been hypothesized to provide the anaerobic power supporting the size-independence of relative burst swimming speeds (body lengths s−1) in these fishes. This paper presents tests of several predictions of this hypothesis, using different-sized individuals of two pelagic teleosts, the kelp bass (Paralabrax clathratus) and the freshwater rainbow trout (Salmo gairdneri), and a flatfish, the Dover sole (Microstomus pacificus). In the two pelagic species, an increase in body size was accompanied by an increase in activities in white muscle (i.u. g wet mass of muscle−1) of lactate dehydrogenase (LDH), an indicator of potential for anaerobic glycolysis, and creatine phosphokinase (CPK), an enzyme that helps maintain stable ATP concentration during muscular activity. Activities of citrate synthase (CS), an indicator of the potential for aerobic metabolism, decreased with size. In the flatfish, activities of all enzymes in white muscle decreased with body size, a trend proposed to reflect lack of adaptive value of strong burst swimming ability in this benthic fish. Activities of LDH and CS were size-independent in brain of flatfish, indicating that the scaling patterns observed in the muscle of this species were related to muscle function, not to common, organism-wide changes with size. In white muscle of P. clathratus, total protein and soluble protein concentrations and buffering capacity increased with body size in parallel, but myofibrillar protein was size-independent. These results suggest that the capacity for anaerobically powered work and the maximal potential to generate force scale only modestly in relation to total body mass and therefore do not appear to be functionally related to the pattern of glycolytic scaling. Thus, these data support the hypothesis that the functional role of the strongly positive scaling of glycolytic enzymes in the white muscle of pelagic fish is to provide increased power during burst swimming in larger-sized fishes.
A vibration-sensitive descending statocyst interneurone in the crayfish Procambarus Clarkii
Authors: Nakagawa H. , Hisada M. 
Published: April 2021

ABSTRACT
An interneurone specifically sensitive to substratum vibration was identified in the crayfish circumoesophageal connective. The interneurone, called B1 in this paper, received excitatory input from the statocysts on both sides. Electrical stimulation of the statocyst nerve elicited several spikes in the interneurone with latencies that depended on which side was stimulated. B1 responded phasically to artificial bending of the statocyst sensory hairs. The response was similar to that of the phasic-type receptor in the statocyst. The morphology of B1 was studied by an intracellular staining technique using nickel chloride and subsequent silver intensification. The interneurone projects its neurite arborization to the dorsal part of the deutocerebrum and parolfactory lobe on both sides, where the statocyst primary afferents also project. The overlapping of central projections, together with the properties of the response of B1; suggests that the interneurone receives excitatory input from the phasic-type receptors and transmits information about phasic body movement, but not static positional information, to the posterior ganglia. Branches of B1 also project to the antennal and tegumentary lobes ipsilateral to the axon. B1 may receive additional mechanosensory information from the cuticular sensory hairs on the antennae and the cephalic body surface.
The Effect Of Iodoacetate On The Electrical Potential And On The Oxygen Uptake Of Frog Skin
Authors: Francis W. L. , Gatty O. 
Published: April 2021

ABSTRACT
The relationship between the maintenance of the electrical potential difference across frog skin and the oxygen consumption of the skin has been investigated by Mansfield (1910), Lund (1925, 1926, 1928), Lund & Moorman (1931), Francis & Pumphrey (1933), Francis (1933, 1934), Taylor (1935), Boell & Taylor (1933), and Ponder & Macleod (1937). These workers investigated the effects of varying temperatures and varying concentrations of cyanide, oxygen, sulphide, carbon monoxide, butyl alcohol, amyl alcohol, and of various carbamates. The objective of the present work has been to use the somewhat more specific respiratory inhibitor iodoacetate to trace further the oxidative biochemistry of frog skin in so far as it is concerned with the maintenance of the electrical potential difference and to be able to cover all statements made by adequate tests of statistical significance and thereby to eliminate troubles arising from the variability of the skins.
Experimental Studies On The Sexual Cycle Of The South African Clawed Toad (Xenopus Laevis). II
Authors: Bellerby C. W. 
Published: April 2021

ABSTRACT
When maintained at an optimum nutritional level both sexes of the South African clawed toad (Xenopus laevis) grow at a normal rate in the complete absence of light, or after removal of the eyes. No detectable atrophic changes take place in the ovaries and testes of eyeless animals after 18 months or in the gonads of male and female toads kept in absolute darkness for 7 months. No evidence is provided by the experiments to show that light is essential for the maintenance of reproductive activity in X. laevis or that seasonal variation in light intensity or wave-length plays any part in the control of the sexual cycle under natural conditions.