bluuebunny/crossref_metadata_2025_split huggingface dataset:
Modulation of the Buccal Muscle Contraction by Identified Serotonergic and Peptidergic Neurons in the Snail Achatina Fulica
Authors: Yoshida Masayuki , Kobayashi Makoto 
Published: April 2021

ABSTRACT
Serotonergic and peptidergic modulation of buccal muscle contraction at an identified neuromuscular synapse in the African giant snail Achatina fulica was examined. A pair of excitatory motoneurons of the radula protractor was identified in the buccal ganglia and these were named B10 neurons. Pharmacological experiments revealed the B10s to be cholinergic. The serotonergic cerebral neuron v-CDN enhanced B10-evoked contraction of the radula protractor, and it is suggested that this effect is mediated postsynaptically by serotonin released from the v-CDN terminals.
Immunohistochemical analyses revealed that the B10 motoneurons contained an Achatina cardioexcitatory peptide-1 (ACEP-1)-like substance in their cell body, axon and terminals in the radula protractor. From electron microscopic observation, the ACEP-1-like immunoreactive substance was found to be localized in dense-cored vesicles but not in clear vesicles in the nerve terminals. ACEP-1 applied to the radula protractor markedly enhanced B10-evoked contraction of the muscle by increasing the amplitude of excitatory junction potentials (EJPs). The increase of EJP amplitude in the presence of the peptide was probably due to the increased release of acetylcholine from the terminals of B10. It is suggested that the cholinergic motoneuron B10 uses ACEP-1 as an excitatory cotransmitter.
Behavioural and Endocrinological Responses of Mature Male Goldfish to the Sex Pheromone 17α,20β-Dihydroxy-4-Pregnen-3-One in the Water
Authors: Bjerselius R. , Olsén K. H. , Zheng W. 
Published: April 2021

ABSTRACT
The behavioural response of spermiated male goldfish to the sex pheromone 17α,20β-dihydroxy-4-pregnen-3-one (17α,20β-P) in the ambient water was measured using a computerized video-image analysis system. The position and spontaneous locomotor activity of single spermiated male goldfish were continuously recorded in an artificial stream. 17α,20β-P (final concentration 10−11 mol l-1) was supplied to one half and its ethanol carrier to the other half of the test area. The results showed that the fish spent significantly less time in water scented with 17α,20β-P than in control water. Moreover, both the spontaneous locomotor activity and the gonadotropin II concentration in the plasma increased significantly because of contact with 17α,20β-P in the ambient water. The swimming speed was unchanged, whether the fish resided in the 17α,20β-P section or in the section without 17α,20β-P added. In view of the complex dual hormone–pheromone system in goldfish, the possibility of an additional function of 17α,20β-P is discussed. Because the release of the pheromone 17α,20β-P occurs before ovulation and the level then drops drastically, we suggest that the avoidance reaction observed allows the sexually mature male to avoid misdirected courting of non-ovulated females and thus to continue its search for an ovulated female.
Drag Reduction by Wing Tip Slots in a Gliding Harris’ Hawk, Parabuteo Unicinctus
Authors: Tucker Vance A. 
Published: April 2021

ABSTRACT
The anterior-most primary feathers of many birds that soar over land bend upwards and separate vertically to form slotted wing tips during flight. The slots are thought to reduce aerodynamic drag, although drag reduction has never been demonstrated in living birds. Wing theory explains how the feathers that form the tip slots can reduce induced drag by spreading vorticity horizontally along the wing and by acting as winglets, which are used on aircraft to make wings non-planar and to spread vorticity vertically. This study uses the induced drag factor to measure the induced drag of a wing relative to that of a standard planar wing with the same span, lift and speed. An induced drag factor of less than 1 indicates that the wing is non-planar.
The minimum drag of a Harris’ hawk gliding freely in a wind tunnel was measured before and after removing the slots by clipping the tip feathers. The unclipped hawk had 70–90 % of the drag of the clipped hawk at speeds between 7.3 and 15.0 m s-1.
At a wing span of 0.8 m, the unclipped hawk had a mean induced drag factor of 0.56, compared with the value of 1.10 assumed for the clipped hawk. A Monte Carlo simulation of error propagation and a sensitivity analysis to possible errors in measured and assumed values showed that the true mean value of the induced drag factor for the unclipped hawk was unlikely to be more than 0.93. These results for a living bird support the conclusions from a previous study of a feathered tip on a model wing in a wind tunnel: the feathers that form the slotted tips reduce induced drag by acting as winglets that make the wings non-planar and spread vorticity both horizontally and vertically.
A Method For Recording Electrical Activity From the Body Wall Nerve Nets in Sea Anemones
Authors: Cho Kwangwook , Mcfarlane Ian D. 
Published: April 2021

ABSTRACT
Glass microelectrodes were used to record electrical activity from thin rings cut from the column of the sea anemone Calliactis parasitica. This is the first time that pulses have been recorded from the nervous system in the column. Three pulse types were detected, types A, B and C. Type A pulses are probably associated with neurones of the through-conducting nerve net. Type B pulses may be from the endodermal slow conduction system (SS2). Type C pulses have not previously been recorded and are thought to represent activity in a local nerve net. At this stage we cannot positively state whether the recordings are intracellular from endodermal myoepithelial cells or are extracellular from the sub-epithelial region.
Creep Rupture of Wallaby Tail Tendons
Authors: Wang Xiao Tong , Ker Robert F. 
Published: April 2021

ABSTRACT
The tail tendons from wallabies (Macropus rufogriseus) suffer creep rupture at stresses of 10 MPa or above, whereas their yield stress in a dynamic test is about 144 MPa. At stresses between 20 and 80 MPa, the time-to-rupture decreases exponentially with stress, but at 10 MPa, the lifetime is well above this exponential. For comparison, the stress on a wallaby tail tendon, when its muscle contracts isometrically, is about 13.5 MPa. Creep lifetime depends sharply on temperature and on specimen length, in contrast to strength and stiffness as observed in dynamic tests. The creep curve (strain versus time) can be considered as a combination of primary creep (decelerating strain) and tertiary creep (accelerating strain). Primary creep is non-damaging, but tertiary creep is accompanied by accumulating damage, with loss of stiffness and strength. ‘Damage’ is quantitatively defined as the fractional loss of stiffness. A creep theory is developed in which the whole of tertiary creep and, in particular, the creep lifetime are predicted from measurements made at the onset of creep, when the tendon is undamaged. This theory is based on a ‘damage hypothesis’, which can be stated as: damaged material no longer contributes to stiffness and strength, whereas intact material makes its full contribution to both.
Neuromuscular Control and Kinematics of Intermittent Flight in the European Starling (Sturnus Vulgaris)
Authors: Tobalske Bret W. 
Published: April 2021

ABSTRACT
Electromyographic (EMG) and kinematic data were collected from European starlings (Sturnus vulgaris) flying at a range of speeds from 8 to 18 m s−1 in a variable-speed windtunnel. Their flight at all speeds consisted of alternating flapping and non-flapping phases. Wing postures during non-flapping phases included glides, partial-bounds and bounds. Glides were performed proportionally more often within each speed and were longer in duration than either of the other two non-flapping postures, but the percentage of bounds increased markedly with increasing flight speed. The shift from flap-gliding at slow speeds towards flap-bounding at fast speeds was consistent with reducing mean power output relative to continuous flapping.
The starlings often combined more than one non-flapping posture within a single non-flapping period. Transitions between non-flapping postures, as well as transitions between bounds and subsequent flapping, were classified as ‘pull-outs’. Pull-outs consisted of an increase in wingspan but no change in wingtip elevation. The pectoralis and supracoracoideus exhibited electrical activity during glides but not during bounds. The scapulohumeralis caudalis was not active during glides, but this muscle and the supracoracoideus were typically active during partial-bounds and pull-out phases. The scapulohumeralis caudalis occasionally showed activity during bounds, which may reflect its role as a humeral retractor. The frequency and duration of non-flapping intervals in starlings were less during EMG experiments than during non-implanted flights.
During flapping phases, relative intensity and duration of EMG signal and wingbeat frequency increased with flight speed, whereas flapping or non-flapping cycle duration, the percentage of a cycle spent flapping and the number of wingbeats in a cycle were all greatest at 8 m s−1. Wingbeat amplitude was smaller at intermediate speeds, but differences among speeds were not significant. These variables allowed indirect estimates of power output and suggested that minimum power speed for starlings was near 12 m s−1 and that power output increased at both slower and faster speeds. Within windtunnel speeds, muscle activity changed in relation to wingspan at mid-upstroke, wingtip excursion, wingbeat frequency, acceleration, velocity, altitude and horizontal position.
Static Forces and Moments Generated in the Insect Leg: Comparison of a Three-Dimensional Musculo-Skeletal Computer Model With Experimental Measurements
Authors: Full R. J. , Ahn A. N. 
Published: April 2021

ABSTRACT
As a first step towards the integration of information on neural control, biomechanics and isolated muscle function, we constructed a three-dimensional musculo-skeletal model of the hind leg of the death-head cockroach Blaberus discoidalis. We tested the model by measuring the maximum force generated in vivo by the hind leg of the cockroach, the coxa–femur joint angle and the position of this leg during a behavior, wedging, that was likely to require maximum torque or moment production. The product of the maximum force of the leg and its moment arm yielded a measured coxa–femur joint moment for wedging behavior. The maximum musculo-apodeme moment predicted by summing all extensor muscle moments in the model was adequate to explain the magnitude of the coxa–femur joint moment produced in vivo by the cockroach and occurred at the same joint angle measured during wedging. Active isometric muscle forces predicted from our model varied by 3.5-fold among muscles and by as much as 70 % with joint angle. Sums of active and passive forces varied by less than 3.5 % over the entire range of possible joint angles (0–125 °). Maximum musculo-apodeme moment arms varied nearly twofold among muscles. Moment arm lengths decreased to zero and switched to the opposite side of the center of rotation at joint angles within the normal range of motion. At large joint angles (&gt;100 °), extensors acted as flexors. The effective mechanical advantage (musculo-apodeme moment arm/leg moment arm = 0.10) resulted in the six femoral extensor muscles of the model developing a summed force (1.4 N) equal to over 50 times the body weight. The model’s three major force-producing extensor muscles attained 95 % of their maximum force, moment arm and moment at the joint angle used by the animal during wedging.
Reactivation of Ubiquitination in Artemia Franciscana Embryos During Recovery From Anoxia-Induced Quiescence
Authors: Anchordoguy Thomas J. , Hand Steven C. 
Published: April 2021

ABSTRACT
Encysted gastrulae of Artemia franciscana are known to enter a reversible state of quiescence promoted by anoxia, during which the half-life of cytochrome oxidase is prolonged up to 77-fold. This observation suggests that proteolytic pathways within mitochondria are inhibited, and indeed the suppression of the initial step in ubiquitin-mediated proteolysis under anoxia has been reported. Given that active embryos require efficient degradation of macromolecules, we investigated the reactivation of ubiquitination during recovery from anoxia and aerobic acidosis (elevated CO2 levels under aerobic conditions). During 6 h of recovery from anoxia, the levels of ubiquitin-conjugated proteins rose 6.5-fold, reaching 78 % of the pre-anoxia (control) values. Concomitant with the elevation in ubiquitin conjugates was a sharp decline in AMP level, a rise in ATP level and an alkalization of intracellular pH.
Our results suggest that the reinitiation of ubiquitin conjugation is partially dependent on decreasing AMP and/or increasing ATP levels. However, when anoxic embryos were transferred to aerobic acidosis, which promotes a return to control (aerobic) levels of adenylates yet maintains the acidic intracellular pH, 71 % of the total suppression of ubiquitination still remained. This observation reveals a predominant role of intracellular alkalization in the reactivation of ubiquitination during recovery. We suggest that the rapid reversibility of the factors regulating ubiquitin conjugation allows Artemia embryos readily to reinitiate the degradation of proteins via the ubiquitin-mediated pathway during recovery.
The Influence of Tracheal Pressure Changes on the Responses of the Tympanal Membrane and Auditory Receptors in the Locust Locusta Migratoria L.
Authors: Meyer Jens , Hedwig Berthold 
Published: April 2021

ABSTRACT
In resting tethered locusts, the effect of slow changes in tracheal air pressure on peripheral auditory information processing was analysed. The tympanal membrane vibrations, the pressure inside the tracheal system and the summed activity of the auditory receptors were measured simultaneously.
With the membrane in the resting position, laser vibrometry and Fast Fourier Transformation analysis of sound-induced membrane vibrations demonstrated characteristic power spectra at the attachment sites of the high-frequency and low-frequency receptors. The spectra were different above 9 kHz, but very similar in the range 2–9 kHz.
During ventilation, tracheal pressure changed between -500 and 1500 Pa. This caused tympanal membrane peak-to-peak displacements in the range 70–90 μm outwards and 20–30 μm inwards, as measured by means of laser interferometry. For a quantitative analysis, sinusoidal tympanal membrane displacements with amplitudes such as those during natural ventilation could be induced by applying pressure to the tracheal system. There was a sigmoid relationship between the tracheal pressure and the corresponding membrane displacement.
Outward displacements of the tympanal membrane at the attachment site of the elevated process (a-cells) attenuated sound-induced membrane vibrations in the ranges 2–10 kHz and 14–22 kHz and increased them in the ranges 10–14 kHz and 22–25 kHz. At the pyriform vesicle (d-cells), the vibration sensitivity was reduced in the frequency range 2–14 kHz. Sensitivity was enhanced in the range 14–25 kHz.
As a consequence, the detection of acoustic signals was also influenced at the auditory receptor level. Tympanal membrane displacements during acoustic stimulation with 4 kHz sound pulses decreased the summed receptor response by approximately 15 dB. At 16 kHz, an increase of the response equivalent to 7 dB occurred. The effect on the response to white noise was intermediate.
Survival of Intracellular Freezing by the Antarctic Nematode Panagrolaimus Davidi
Authors: Wharton David A. , Ferns Donald J. 
Published: April 2021

ABSTRACT
Animals are usually thought to survive ice formation in their bodies only if the ice is confined to the body cavity and to extracellular spaces. Intracellular ice formation is believed to be fatal. This conclusion is based on studies of the cryopreservation of mammalian cells. Intracellular freezing has been observed in some living insect cells but has not been observed in intact animals. Nematodes are transparent and so the location of ice in their bodies can be observed directly using a cryomicroscope stage. We have observed freezing and melting in all body compartments, including intracellular compartments, of the Antarctic nematode Panagrolaimus davidi. Inoculative freezing from the surrounding water occurs via the body openings, rather than across the cuticle; most frequently it occurs via the excretory pore. Individual nematodes that have frozen intracellularly will subsequently grow and reproduce in culture. Determining the mechanisms by which this nematode survives intracellular freezing could have important applications in the cryopreservation of a variety of biological materials.
An Endogenous Peptide Modulates The Activity Of A Sensory Neurone In The Leech Hirudo Medicinalis
Authors: Wenning Angela , Calabrese Ronald L. 
Published: April 2021

ABSTRACT
Sensory and neurosecretory innervation of each leech excretory complex, a nephridium and its bladder, is accomplished by a single neurone, the nephridial nerve cell (NNC). The NNC monitors the extracellular Cl− concentration, which ranges between 20 and 100 mmol l−1 depending on the physiological state. The NNC contains FMRFamide in its soma and sensory terminals in the nephridium. Bath or focal application of FMRFamide leads to hyperpolarization and decreases the rate of firing of the NNC, suggesting autoregulation of peptide release. Experiments under single-electrode current-clamp and voltage-clamp show that FMRFamide turns off the receptor-specific Cl− current of the NNC, indicating that FMRFamide also modulates the receptor gain.
Electrical Activity, Growth Cone Motility And The Cytoskeleton
Authors: Neely M. Diana , Nicholls John G. 
Published: April 2021

ABSTRACT
The development of the nervous system takes place in two main steps: first an extensive preliminary network is formed and then it is pruned and trimmed to establish the final form. This refinement is achieved by mechanisms that include cell death, selective growth and loss of neurites and the stabilization and elimination of synapses. The focus of this review is on selective neurite retraction during development, with particular emphasis on the role of electrical activity.
In many developing vertebrate and invertebrate neurones, the frequency and duration of ongoing impulse activity determine the final arborizations and the pattern of connections. When impulse traffic is silenced, axons fail to retract branches that had grown to inappropriate destinations in the mammalian visual system, cerebellum and neuromuscular junctions. Similarly, in crustaceans, Drosophila melanogaster and leeches, refinements in axonal morphology during development are influenced by impulse activity. From experiments made in culture, it has been possible to mimic these events and to show a clear link between the density of voltage-activated calcium channels in a neurite and its retraction following stimulation. The distribution of these calcium channels in turn is determined by the substratum with which the neurites are in contact or by the formation of synapses. Several lines of evidence suggest that calcium entry into the growth cone leads to collapse by disruption of actin filaments. One candidate for coupling membrane events to neurite retraction is the microfilament-associated protein gelsolin which, in its calcium-activated state, severs actin filaments. Open questions that remain concern the differential effects of activity on dendrites and axons as well as the mechanisms by which the growth cone integrates information derived from stimuli in the cell and in the extracellular environment.
The Distal Sperm Flagellum: Its Potential For Motility After Separation From The Basal Structures
Authors: Woolley D. M. , Bozkurt H. H. 
Published: April 2021

ABSTRACT
The distal region of the sperm flagellum of Gallus domesticus has been separated and purified. It consists of a 9+2 axoneme, without basal or accessory structures. Such distal segments have been demembranated and then reactivated, either by adding ATP or by releasing ATP photolytically from caged ATP: we find that they are capable of a period of independent motility. Bends form repetitively and travel towards the tip, though it is an abnormal, irregular pattern of beating. It is argued that this motility is not dependent on damage to the flagellum at the fracture site. Evidence is presented that the potential for such motility depends upon the existence of bends on the axoneme before the reactivation. The reactivated motility is short-lived: 50 % of the distal flagellar segments, placed in the reactivating solution, become quiescent and straight within 60 s. However, vigorous beating can be induced in such quiescent segments of axoneme by compressing one end with a glass microneedle. We record, provisionally, that the site of compression does not determine the direction in which bends move along the flagellar segment. The effect of compression in re-initiating motility suggests that a mechanical resistance is necessary, somewhere along the axoneme, for normal, sustained motility; it is proposed that the specialized basal structures, collectively, provide such a resistance in the intact flagellum.
How Should Enzyme Activities be Used in Fish Growth Studies?
Authors: Pelletier Dany , Blier Pierre U. , Dutil Jean-Denis , Guderley Helga 
Published: April 2021

ABSTRACT
The activity of glycolytic and oxidative enzymes was monitored in the white muscle of Atlantic cod Gadus morhua experiencing different growth rates. A strong positive relationship between the activity of two glycolytic enzymes and individual growth rate was observed regardless of whether the enzyme activity was expressed as units per gram wet mass, units per gram dry mass or with respect to muscle protein and DNA content. The most sensitive response to growth rate was observed when pyruvate kinase and lactate dehydrogenase activities were expressed as units per microgram DNA, and this may be useful as an indicator of growth rate in wild fish. In contrast, no relationship between the activities of oxidative enzymes and growth rate was observed when cytochrome c oxidase and citrate synthase activities were expressed as units per gram protein. Apparently, the aerobic capacity of white muscle in cod is not specifically increased to match growth rate.