bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Effects of the Wingbeat Cycle on Respiration in Black-Billed Magpies (Pica Pica)
Authors: Boggs Dona F. , Jenkins Farish A. , Dial Kenneth P. 
Published: April 2021

ABSTRACT
Interclavicular and posterior thoracic airsac pressures, tracheal airflows and pectoralis muscle activity were recorded simultaneously to determine the effect of the wingbeat cycle upon the function of the respiratory system. The effects of the wingbeat cycle on the relative positions of thoraco-abdominal skeletal structures were also assessed using high-speed X-ray cinematography of magpies Pica pica flying in a windtunnel.
We found that the furcula bends laterally on the downstroke and recoils medially on the upstroke, as previously described for starlings, and that the coraco-sternal joint (the most consistently visible point on the sternum for digitization) is displaced dorsally during the downstroke and ventrally, with respect to the vertebral column, during the upstroke. In magpies, there are generally three wingbeat cycles during a respiratory cycle. When downstroke occurs during inspiration, its compressive effect reduces the inspiratory subatmospheric airsac pressure by an average of 92 % (0.35 kPa), whereas when upstroke occurs during expiration its expansive effect can reduce the expiratory supra-atmospheric airsac pressure by 63 % (0.23 kPa). Corresponding changes occur in tracheal airflow. Changes in respiratory parameters during short flights with respect to resting values include a doubling of tidal volume and a tripling of respiratory frequency.
We conclude that the wingbeat cycle can have a substantial impact on respiratory system function in the flying magpie, and that this represents a mechanical basis for breathing patterns and patterns of phasic coordination between wingbeat and respiratory cycles that may result in minimal interference and maximal assistance from the wingbeat upon the respiratory cycle.
Hearing and Hunting in red Bats (Lasiurus Borealis, Vespertilionidae): Audiogram and ear Properties
Authors: Obrist Martin K. , Wenstrup Jeffrey J. 
Published: April 2021

ABSTRACT
We examined aspects of hearing in the red bat (Lasiurus borealis) related to its use of biosonar. Evoked potential audiograms, obtained from volume-conducted auditory brainstem responses, were obtained in two bats, and the sound pressure transformation of the pinna was measured in three specimens. Field-recorded echolocation signals were analysed for comparison. The fundamental sonar search calls sweep from 45 to 30 kHz (peak energy at 35 kHz), approach-phase calls sweep from 65 to 35 kHz (peak 40 kHz) and terminal calls sweep from 70 to 30 kHz (peak 45 kHz). The most sensitive region of the audiogram extended from 10 kHz to 45–55 kHz, with maximum sensitivity as low as 20 dB SPL occurring between 25 and 30 kHz. A relative threshold minimum occurred between 40 and 50 kHz. With increasing frequency, the acoustic axis of the pinna moves upwards and medially. The sound pressure transformation was noteworthy near 40–45 kHz; the acoustic axis was closest to the midline, the −3 dB acceptance angles showed local minima, and the pinna gain and interaural intensity difference were maximal. These results are related to the known echolocation and foraging behavior of this species and match the spectral components of approach- and final-phase calls. We conclude that co-evolution with hearing prey has put a higher selective pressure on optimizing localization and tracking of prey than on improving detection performance.
Alterations of Ionic Membrane Permeabilities in Multidrug-Resistant Neuroblastoma × Glioma Hybrid Cells
Authors: Gérard Valerie , Rouzaire-Dubois Beatrice , Dilda Pierre , Dubois Jean-Marc 
Published: April 2021

ABSTRACT
A population of NG108-15 neuroblastoma cells resistant to doxorubicin (NG/DOXR) was established. The cells exhibited a multidrug resistance phenotype with cross-resistance to vinblastin and colchicine, overexpression of a 170 kDa membrane protein identified as P-glycoprotein and reversal of resistance by verapamil and quinine. Compared with NG108-15 cells, NG/DOXR cells showed an increase in Na+ current density and a decrease in cyclic-AMP-activated Cl− current density with no change in K+- and volume-sensitive Cl− current densities. As previously observed in NG108-15 cells, the vacuolar-type H+-ATPase inhibitors bafilomycin A1 and nitrate induced membrane depolarizations in NG/DOXR cells. The resting potentials of sensitive and resistant cells were not significantly different, but the depolarizations evoked by these agents were significantly larger in NG/DOXR than in NG108-15 cells. The resting membrane potential of NG/DOXR cells, but not that of NG108-15 cells, was depolarized by verapamil, and this effect was abolished by bafilomycin. The volume-sensitive Cl− currents of drug-sensitive and drug-resistant cells were inhibited by a decrease in intracellular pH from 7.3 to 6.8. Whereas bafilomycin prevents activation of Cl− currents in both drug-sensitive and drug-resistant cells, verapamil inhibited the Cl− current only in NG/DOXR cells. The results are discussed in terms of the roles of cytoplasmic pH and membrane potential in multidrug resistance.
Muscle Power Output Limits Fast-Start Performance in Fish
Authors: Wakeling James M. , Johnston Ian A. 
Published: April 2021

ABSTRACT
Fast-starts associated with escape responses were filmed at the median habitat temperatures of six teleost fish: Notothenia coriiceps and Notothenia rossii (Antarctica), Myoxocephalus scorpius (North Sea), Scorpaena notata and Serranus cabrilla (Mediterranean) and Paracirrhites forsteri (Indo-West-Pacific Ocean). Methods are presented for estimating the spine positions for silhouettes of swimming fish. These methods were used to validate techniques for calculating kinematics and muscle dynamics during fast-starts. The starts from all species show common patterns, with waves of body curvature travelling from head to tail and increasing in amplitude. Cross-validation with sonomicrometry studies allowed gearing ratios between the red and white muscle to be calculated. Gearing ratios must decrease towards the tail with a corresponding change in muscle geometry, resulting in similar white muscle fibre strains in all the myotomes during the start. A work-loop technique was used to measure mean muscle power output at similar strain and shortening durations to those found in vivo. The fast Sc. notata myotomal fibres produced a mean muscle-mass-specific power of 142.7 W kg−1 at 20 °C. Velocity, acceleration and hydrodynamic power output increased both with the travelling rate of the wave of body curvature and with the habitat temperature. At all temperatures, the predicted mean muscle-mass-specific power outputs, as calculated from swimming sequences, were similar to the muscle power outputs measured from work-loop experiments.
Morphometric and Biochemical Characteristics of Ventricular Hypertrophy in Male Rainbow Trout (Oncorhynchus Mykiss)
Authors: Clark Raymond J. , Rodnick Kenneth J. 
Published: April 2021

ABSTRACT
We examined the morphometric and biochemical effects of ventricular hypertrophy in male rainbow trout (Oncorhynchus mykiss) during sexual maturation. Our investigation focused on characterizing the growth of ventricular layers, on cardiomyocyte dimensions (length, cross-sectional area and cell volume) and on the activities of enzymes involved in intermediary metabolism.
Relative ventricle mass (100×ventricle mass/body mass) increased by as much as 2.4-fold during sexual maturation [as defined by an increasing gonadosomatic index (100×gonad mass/body mass)], and this resulted in an increased proportion of epicardium relative to endocardium. Ventricular enlargement was associated with increased length (+31 %) and transverse cross-sectional area (+83 %) of cardiomyocytes, which resulted in an expansion of up to 2.2-fold in mean myocyte volume (from 1233 to 2751 μm3). These results indicate that sexual maturation induces ventricular enlargement through myocyte hypertrophy. Cell length and cross-sectional area were similar in both myocardial layers, and myocytes were elliptical rather than circular in transverse cross section. Ventricular hypertrophy did not alter transverse cell shape, perhaps reflecting the maintenance of short diffusion distances for small molecules as cells hypertrophy. Myocyte hypertrophy could not account entirely for the sevenfold range of ventricle masses from different-sized fish, indicating that myocyte hyperplasia contributes substantially to ventricular growth as trout grow.
Measurements of the maximal activities of metabolic enzymes demonstrated that ventricular hypertrophy was associated with (1) higher epicardial but not endocardial activities of citrate synthase (by 23 %) and β-hydroxyacyl-CoA dehydrogenase (by 20 %); (2) lower activities of hexokinase (by 50 %) in both layers, and (3) no change in lactate dehydrogenase or pyruvate kinase activities, which were also similar between layers. These results suggest that the energetic needs of the hypertrophied trout ventricle may be met through increased reliance on fatty acid oxidation, particularly by the endocardium, but decreased reliance on glucose as a metabolic fuel in both layers.
Ontogenetic Scaling Of Hydrostatic Skeletons: Geometric, Static Stress And Dynamic Stress Scaling Of The Earthworm Lumbricus Terrestris
Authors: Quillin Kim J. 
Published: April 2021

ABSTRACT
Soft-bodied organisms with hydrostatic skeletons range enormously in body size, both during the growth of individuals and in the comparison of species. Therefore, body size is an important consideration in an examination of the mechanical function of hydrostatic skeletons. The scaling of hydrostatic skeletons cannot be inferred from existing studies of the lever-like skeletons of vertebrates and arthropods because the two skeleton types function by different mechanisms. Hydrostats are constructed of an extensible body wall in tension surrounding a fluid or deformable tissue under compression. It is the pressurized internal fluid (rather than the rigid levers of vertebrates and arthropods) that enables the maintenance of posture, antagonism of muscles and transfer of muscle forces to the environment. The objectives of the present study were (1) to define the geometric, static stress and dynamic stress similarity scaling hypotheses for hydrostatic skeletons on the basis of their generalized form and function, and (2) to apply these similarity hypotheses in a study of the ontogenetic scaling of earthworms, Lumbricus terrestris, to determine which parameters of skeletal function are conserved or changed as a function of body mass during growth (from 0.01 to 8 g). Morphometric measurements on anesthetized earthworms revealed that the earthworms grew isometrically; the external proportions and number of segments were constant as a function of body size. Calculations of static stresses (forces per cross-sectional area in the body wall) during rest and dynamic stresses during peristaltic crawling (calculated from measurements of internal pressure and body wall geometry) revealed that the earthworms also maintained static and dynamic stress similarity, despite a slight increase in body wall thickness in segment 50 (but not in segment 15). In summary, the hydrostatic skeletons of earthworms differ fundamentally from the rigid, lever-like skeletons of their terrestrial counterparts in their ability to grow isometrically while maintaining similarity in both static and dynamic stresses.
Long-Lasting Depolarization Of Leech Neurons Mediated By Receptors With A Nicotinic Binding Site
Authors: Szczupak Lidia , Edgar Julia , Peralta Maria Luisa , Kristan William B. 
Published: April 2021

ABSTRACT
The serotonergic Retzius neurons of the leech midbody ganglia respond in a complex manner to pressure pulses of acetylcholine (ACh) applied onto their soma with a fast depolarization followed by a slower hyperpolarization and an additional delayed long-lasting depolarization. The delayed depolarization is the subject of the present study. The delayed depolarization could be elicited by long (&gt;1 s) ACh pressure pulses or by short pulses (10 ms) of carbachol, nicotine and DMPP, but not by muscarinic agonists. It was inhibited by bath application of nicotine (10–100 μmol l−1), strychnine (100 μmol l−1) and atropine (10–100 μmol l−1). Nicotinic antagonists that blocked the fast depolarization and the slow hyperpolarization (100 μmol l−1 mecamylamine and d-tubocurarine) did not affect the delayed depolarization induced by carbachol. Partial replacement of the extracellular Na+ by glucamine caused a decrease in the amplitude of the response and a shift of its reversal potential to more negative values. Carbachol pulses applied to Retzius neurons of the ganglia innervating the reproductive segments elicited delayed depolarizations of much smaller amplitude than the ones recorded in Retzius neurons from standard segments. The delayed depolarization could be elicited by the application of short agonist pulses onto different loci over the surface of the ganglion, at a distance from the soma. Isolated cultured Retzius neurons did not exhibit the delayed depolarization although they readily expressed the earlier phases of the complex cholinergic response. Carbachol pulses applied to the soma of other neurons in the leech ganglion produced a variety of specific responses.
The results suggest that the delayed depolarization was produced by the activation of a cationic conductance mediated by receptors with a pharmacological profile similar to that of the α9 nicotinic receptors and was not a byproduct of the early phases of the cholinergic response. The response seemed to be initiated in the extensive neuropilar processes of the Retzius cell, enabling a persistent excitatory signal.
Basal Acetylcholine Release In Leech Ganglia Depolarizes Neurons Through Receptors With A Nicotinic Binding Site
Authors: Burgin Antonia Marín , Szczupak Lidia 
Published: April 2021

ABSTRACT
The response of Retzius neurons, the main neuronal source of serotonin in the leech nervous system, to cholinergic agonists has been extensively investigated. In this study, we analyzed the effects of inhibiting the acetylcholinesterase (AChE) activity in the leech midbody ganglion on the electrophysiological activity of the Retzius neurons. Bath application of neostigmine and physostigmine (0.1–100 μmol l−1) produced, after a delay, a strong depolarization of the Retzius neurons with a dose-dependent amplitude and latency. The amplitude of this depolarization increased as the extracellular level of Ca2+ increased and decreased as the extracellular level of Ca2+ decreased. The response to neostigmine and physostigmine was inhibited by curare (100 μmol l−1), nicotine (10 μmol l−1), atropine (100 μmol l−1) and strychnine (100 μmol l−1), but was not affected by mecamylamine (100 μmol l−1) or hexamethonium (100 μmol l−1). Superfusion with solutions containing 100 μmol l−1 strychnine or atropine produced a progressive hyperpolarization of the Retzius neurons, while superfusion with 100 μmol l−1 curare did not. The hyperpolarization induced by atropine was inhibited in the presence of curare. Other neurons in the ganglion showed distinctive responses to the AChE inhibitors that were coincident with their responses to cholinergic agonists.
The results suggest the existence of a basal level of acetylcholine (ACh) release in the leech ganglion that is powerfully counteracted by endogenous AChE activity. Under control conditions, this basal release appears to be sufficient to generate an ACh tonus that regulates the membrane potential of Retzius neurons. Since these neurons can support a sustained firing rate, which is dependent on the membrane potential, the results presented in this report suggest that the basal ACh tonus regulates the output of these neuromodulatory serotonergic neurons.
Regulation of Ion Transport Across Lamprey (Lampetra Fluviatilis) Erythrocyte Membrane by Oxygen Tension
Authors: Virkki Leila V. , Salama Annika , Nikinmaa Mikko 
Published: April 2021

ABSTRACT
We have measured the effects of oxygen tension on the transport of Na+, K+ and Cl− across the erythrocyte membrane of the lamprey Lampetra fluviatilis. The transport of each ion was affected by the oxygen tension of the medium. Hypoxic conditions (2 kPa) caused an increase in the acidification-induced influx of Na+via Na+/H+ exchange. The influx of K+ was only slightly affected by the oxygenation of the medium. In contrast, the basal K+ efflux, measured using the radioactive isotope 43K, was markedly reduced by decreasing the oxygen tension of the medium, whereas the K+ flux in hypotonic medium was not affected. Only minor effects of hypoxic conditions on the influx of Cl−were observed in either isotonic or hypotonic conditions (there was a tendency for the isotonic influx to increase) or on the efflux in isotonic conditions. However, deoxygenation caused a marked reduction in the Cl− efflux in hypotonic conditions. The results show that oxygen tension has a marked effect on the pH and volume regulatory transport pathways of lamprey erythrocytes. For K+ and Cl−, the regulation appears to be asymmetric, i.e. influx and efflux are affected differently.
An Analysis of the Relationship Between the Response Characteristics and Topography of Directional- and Non-Directional Auditory Neurons in the Torus Semicircularis of the Rainbow Trout
Authors: Wubbels R. J. , Schellart N. A. M. 
Published: April 2021

ABSTRACT
The response characteristics of auditory neurons in the multimodal midbrain torus semicircularis of rainbow trout were analyzed to examine their topography and functional differences. This analysis included the localization of recording sites, the measurement of spontaneous activity, the ratio of transient/sustained activity, and the synchronization, latency, preferred direction and directional range of the response. On average, units with a directionally selective (DS) response are positioned 60 μm more dorsally than other auditory units. Directionally selective units usually have a higher response rate, a higher transient/sustained activity ratio and are better synchronized. Auditory units encountered within the same electrode track tend to be either all DS or all non-DS. Within a track, there is no uniformity of the response characteristics observed except that the preferred direction of DS units appears to be the same. The anatomical stratification of the torus, containing 66 000 somata (5–10 μm in diameter), does not match the electrophysiologically observed vertical distribution of functionally distinct units. On the basis of the topographical distribution of response characteristics, two types of well-synchronized DS units can be distinguished, hypothetically representing separate channels for the processing of acoustic motion and (mainly) pressure information. A third type of DS unit which receives input from both these channels and actually encodes the source direction uniquely for all directions is postulated.
Neural Modulation Of Salt Secretion In Teleost Opercular Epithelium By α2-Adrenergic Receptors And Inositol 1,4,5-Trisphosphate
Authors: Marshall W. S. , Duquesnay R. M. , Gillis J. M. , Bryson S. E. , Liedtke C. M. 
Published: April 2021

ABSTRACT
Opercular epithelia from seawater-adapted killifish (Fundulus heteroclitus) were dissected with the nerve intact, mounted in Ussing-style membrane chambers and bathed in symmetrical saline solutions. Nerve stimulation rapidly inhibited transepithelial current (a measure of Cl− secretion rate) by 27.3±3.3 % (N=22), and the effect could be sustained for more than 10 min using intermittent pulse trains at 10 Hz. The effect was blocked in a dose-dependent manner by yohimbine, but not by propranolol, atropine or tubocurarine, indicating mediation by α2-adrenergic receptors. The effect was also present, but significantly diminished, in opercular membranes from animals that had been transferred to sea water for 48 h (18±8.6 % inhibition, N=14). The resting current and the effect were absent in membranes from freshwater-adapted animals. The addition of clonidine (1.0 μmol l−1 serosal side) started to inhibit Cl− current after 40–60 s; immediately before this, at 30 s, there was a significant rise (P&lt;0.05, N=14) in tissue inositol 1,4,5,-trisphosphate (InsP3) level, but no change at later times, compared with LiCl-treated control membranes and measured by radiolabeled receptor assay. The results indicate that seawater-adapted killifish can decrease their Cl− secretion rate through the action of the sympathetic nervous system, a response appropriate for the entry of estuarine fish to fresh water, and that the effect is mediated by α2-adrenoceptors via InsP3. The results imply that euryhaline fish entering fresh water can undergo an autonomic reflex reduction in salt secretion that does not require a stress response.
Hearing In Mole Crickets (Orthoptera: Gryllotalpidae) At Sonic And Ultrasonic Frequencies
Authors: Mason Andrew C. , Forrest Timothy G. , Hoy Ron R. 
Published: April 2021

ABSTRACT
We have studied auditory responses in two species of mole cricket (Scapteriscus borellii and S. abbreviatus) to determine (1) whether they show sensitivity to ultrasound, (2) whether their hearing (at both low and high frequencies) is based on the same neural circuitry as that of true crickets, and (3) whether ultrasound sensitivity in different mole cricket species varies with their ability to fly. S. borellii are sensitive to ultrasonic frequencies. There is evidence of a segregation of frequency bands in prothoracic auditory neurons. There are two pairs of omega neurons (ONs) with similar morphology to ON1 of true crickets. The two pairs of ONs differ in tuning. One pair has two sensitivity peaks: at the frequency of the calling song of this species (3 kHz), and in the ultrasonic range (25 kHz). The other pair lacks the high-frequency sensitivity and responds exclusively to frequencies in the range of the species song. These two types are not morphologically distinguishable. In S. abbreviatus, only one class of ON was found. S. abbreviatus ONs are narrowly tuned to the frequency of the species’ calls. A T-neuron had the best ultrasonic frequency sensitivity in S. borellii. This cell showed a broad tuning to ultrasonic frequencies and was inhibited by low-frequency stimuli. A morphologically similar neuron was also recorded in S. abbreviatus, but lacked the high-frequency sensitivity peak of that in S. borellii.
We also assessed the responses of flying S. borellii to ultrasound using field playbacks to free-flying animals. The attractiveness of broadcast calling song was diminished by the addition of an ultrasound signal, indicating that S. borellii avoid high-frequency sound.
The results indicate that mole crickets process low-frequency auditory stimuli using mechanisms similar to those of true crickets. They show a negative behavioural response to high-frequency stimuli, as do true crickets, but the organization of ultrasound-sensitive auditory circuitry in mole crickets differs from that of true crickets.