bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Beat Frequency on the Velocity of Microtubule Sliding in Reactivated Sea Urchin Sperm Flagella Under Imposed Head Vibration
Authors: Shingyoji Chikako , Yoshimura Kenjiro , Eshel Dan , Takahashi Keiichi , Gibbons Ian R. 
Published: April 2021

ABSTRACT
The heads of demembranated spermatozoa of the sea urchin Tripneustes gratilla, reactivated at different concentrations of ATP, were held by suction in the tip of a micropipette and vibrated laterally with respect to the head axis. This imposed vibration resulted in a stable rhythmic beating of the reactivated flagella that was synchronized to the frequency of the micropipette. The reactivated flagella, which in the absence of imposed vibration had an average beat frequency of 39 Hz at 2 mmol l−1 ATP, showed stable beating synchronized to the pipette vibration over a range of 20–70 Hz. Vibration frequencies above 70 Hz caused irregular, asymmetrical beating, while those below 20 Hz induced instability of the beat plane. At ATP concentrations of 10–100 µmol l−1, the range of vibration frequency capable of maintaining stable beating was diminished; an increase in ATP concentration above 2 mmol l−1 had no effect on the range of stable beating. In flagella reactivated at ATP concentrations above 100 µmol l−1, the apparent time-averaged sliding velocity of axonemal microtubules decreased when the imposed frequency was below the undriven flagellar beat frequency, but at higher imposed frequencies it remained constant, with the higher frequency being accompanied by a decrease in bend angle. This maximal sliding velocity at 2 mmol l−1 ATP was close to the sliding velocity in the distal region of live spermatozoa, possibly indicating that it represents an inherent limit in the velocity of active sliding. The results are consistent with the view that the sliding velocity of axonemal microtubules does not depend solely upon the local concentration of ATP, but is also dependent upon the oscillatory mechanism associated with initiation of new flagellar bends.
Heart Mitochondrial Properties and Aerobic Capacity are Similarly Related in a Mammal and a Reptile
Authors: Conley Kevin E. , Christian Keith A. , Hoppeler Hans , Weibel Ewald R. 
Published: April 2021

ABSTRACT
The heart mitochondrial properties and the aerobic capacity of the rat (Sprague-Dawley breed) and the Cuban iguana (Cyclura nubila) were used to evaluate the relationship between the oxidative capacity of the heart and the maximum oxygen delivery rate. Both species are active at body temperatures of 37–39 °C, have similar heart mitochondrial volumes [Vmt; 0.43±0.02 ml (S.E.M.) in the rat and 0.48±0.02 ml in the iguana] and differ less than twofold in (29.2±1.6 and 16.9±0.6 ml min−1, respectively). We found that Vmt was closely correlated with in the rat (r2=0.77, P&lt;0.005) and the iguana (r2=0.82; P&lt;0.001). Furthermore, the inner mitochondrial membrane (cristae) area (Sim) per unit did not differ between the rat and the iguana (0.60±0.02 and 0.71±0.02 m2 min ml−1 O2, respectively). This correspondence of indicates that the rat and the iguana have the same cardiac oxidative capacity at the maximum oxygen delivery rate. These results suggest that, despite the differences between the cardiovascular systems of these species, the cardiac cost of delivering oxygen at the aerobic capacity is similar in this mammal and this reptile.
A V-ATPase DRIVES ACTIVE, ELECTROGENIC AND Na+-INDEPENDENT Cl−ABSORPTION ACROSS THE GILLS OF ERIOCHEIR SINENSIS
Authors: Onken Horst , Putzenlechner Max 
Published: April 2021

ABSTRACT
Using biochemical and electrophysiological techniques, we have examined the proposal that an H+-ATPase is involved in Cl- uptake across the gills of the Chinese crab Eriocheir sinensis. Bafilomycin A1 (1 µ,mol l-1), a specific inhibitor of V-ATPases, was used to investigate the importance of this H+-translocating enzyme in Cl- transport across the gill. In homogenates of ion-transporting posterior gills, we found the activity of a bafilomycin-sensitive V-ATPase to be markedly higher than in the anterior gills, which are not involved in ion transport. A similar distribution was found for the Na+/K+-and the mitochondrial F1Fo-ATPase. After differential and density centrifugation, the specific activity of the V-ATPase was enriched by a factor of 5. Neither Na+/K+-and F1Fo-ATPase activities nor acid phosphatase activity copurified with the bafilomycin-sensitive ATPase activity, indicating that at least the major portion of V-ATPase activity is not of basolateral, mitochondrial or lysosomal origin. In fluorescence studies, using Acridine Orange or Oxonol V as dyes, membrane vesicles displayed ATP-dependent proton transport and membrane potential generation, which were markedly reduced in the presence of bafilomycin. In addition to these biochemical studies, we mounted split lamellae of posterior gills in an Ussing-type chamber and measured the negative short-circuit current (Isc), which was shown to reflect active, electrogenic, Na+-independent and ouabain-insensitive Cl- absorption. After the addition of 1 µ,mol l-1 bafilomycin to the external bath, this Isc was reduced to about 50–60 % of its original value. Concomitantly, the conductance of the preparation decreased by about 13 %. From these results, we conclude that an apical V-ATPase drives electrogenic Cl- uptake across the posterior gills of the Chinese crab.
Evidence for the Hormonal Function of a Crf-Related Diuretic Peptide (Locusta-Dp) in Locusta Migratoria
Authors: Patel Manju , Hayes Timothy K. , Coast Geoffrey M. 
Published: April 2021

ABSTRACT
Locusta-DP is a corticotropin-releasing factor (CRF)-related diuretic peptide isolated from the migratory locust Locusta migratoria. At nanomolar concentrations, synthetic Locusta-DP stimulated fluid secretion and cyclic AMP production by Malpighian tubules isolated in vitro and increased the rate of amaranth clearance in starved locusts to levels comparable with those observed during post-feeding diuresis. The peptide also caused a marked (approximately 10 %), but short-lived, reduction in the haemolymph volume of starved locusts.
A polyclonal antiserum raised against Locusta-DP(29-46) was shown to block peptidergic signal transfer in vitro and in vivo. Pre-treatment of Locusta-DP (5 nmol l-1) with antiserum diluted 1:100 resulted in a rapid reduction in the free peptide concentration to less than 1 nmol l-1, the threshold for a measurable effect on cyclic AMP production by isolated tubules. In intact insects, passive immunization with Locusta-DP antiserum blocked increases in the rate of amaranth clearance in response to exogenous diuretic peptide or in response to feeding. The latter was due specifically to the binding of Locusta-DP, because when the relevant antibodies were preadsorbed with Locusta-DP(29-46), the antiserum had no effect on amaranth clearance by recently fed insects. This provides unequivocal evidence of a hormonal function for Locusta-DP in the control of primary urine production.
Are Muscle Fibers Within Fish Myotomes Activated Synchronously? Patterns of Recruitment Within Deep Myomeric Musculature During Swimming in Largemouth Bass
Authors: Jayne Bruce C. , Lauder George V. 
Published: April 2021

ABSTRACT
The myomeric axial musculature of fish has a complex three-dimensional morphology, yet within-myomere motor patterns have not been examined to determine whether all portions of each myomere are activated synchronously during locomotion. To gain insight into recruitment patterns in the deep myomeric musculature of fish, we implanted a series of fine-wire electrodes arranged in a vertical row of six electrodes and a longitudinal row of three electrodes on both the left and right sides of each of five largemouth bass (Micropterus salmoides). After recording electromyograms (EMGs) during the burst-and-glide swimming of each fish, post-mortem dissections and X-rays determined the location of electrodes with respect to (1) the longitudinal position (by counting the underlying vertebrae), (2) the position of the myomere containing the electrode, and (3) the portion within each myomere containing an electrode. Because of the convoluted overlapping shape of the myomeres, electrodes within the vertical row of sites could be located in any one of six different myomeres. Thus, we compared muscle activity for locations with a constant longitudinal position and differing myomeric position (vertical row) and among sites with both variable longitudinal and myomeric positions. We detected significant heterogeneity in EMG onset times for sites within the vertical row of electrodes; however, the durations of the EMGs from different sites were similar. EMG onset times at more posterior longitudinal positions preceded those of more anterior longitudinal positions when electrodes of the latter site were within a more posterior myomere. Thus, the timing of EMGs was consistent with the posterior propagation of muscle activity via the sequential activation of myomeres rather than the simultaneous activation of all contractile tissue within the longitudinal span of a single vertebra. In addition, extreme epaxial and hypaxial portions of myomeres showed distinct activity patterns which did not necessarily correlate with activity in the central myomeric fibers nearer the horizontal septum.
Nitric Oxide Synthesis in Locust Olfactory Interneurones
Authors: Elphick Maurice R. , Rayne Richard C. , Riveros-Moreno Valentina , Moncada Salvador , O’Shea Michael 
Published: April 2021

ABSTRACT
The brain of the locust Schistocerca gregaria contains a nitric oxide synthase (NOS) that has similar properties to mammalian neuronal NOS. It catalyses the production of equimolar quantities of nitric oxide (NO) and citrulline from L-arginine in a Ca2+/calmodulin-and NADPH-dependent manner and is inhibited by the Nw-nitro and Nw-monomethyl analogues of L-arginine. In Western blots, an antiserum to the 160 kDa rat cerebellar NOS subunit recognises a locust brain protein with a molecular mass of approximately 135 kDa. NOS is located in several parts of the locust brain, including the mushroom bodies, but it is particularly abundant in the olfactory processing centres, the antennal lobes. Here it is present in two groups of local interneurones (a pair and a cluster of about 50) that project into the neuropile of the antennal lobes. The processes of these neurones terminate in numerous glomerulus-like structures where the synapses between primary olfactory receptor neurones and central interneurones are formed. NOS-containing local interneurones have also been identified in the mammalian olfactory bulb, suggesting that NO performs analogous functions in locust and mammalian olfactory systems. As yet, nothing is known about the role of NO in olfaction, but it seems likely that it is involved in the processing of chemosensory input to the brain. The locust antennal lobe may be an ideal ‘simple’ system in which this aspect of NO function can be examined.
Fatigue Rupture of Wallaby Tail Tendons
Authors: Wang Xiao Tong , Ker Robert F. , Alexander R. Mcneill 
Published: April 2021

ABSTRACT
Wallaby tail tendons fail after repeated application of stresses much lower than would be needed to break them in a single pull. We show that this is a fatigue phenomenon, distinct from the creep rupture that occurs after prolonged application of a constant stress. The two phenomena are distinguished by experiments in which tensile stress is cycled at different frequencies, ranging from 1 to 50 Hz.
Hindleg Muscle Energy and Substrate Balances In Cold-Exposed Rats
Authors: Adán C. , Ardévol A. , Remesar X. , Alemany M. , Fernández-López J. A. 
Published: April 2021

ABSTRACT
Rats chronically cannulated in the carotid artery and the muscular branch of the femoral vein were subjected to a cold (4 °C) environment for up to 2 h. The changes in blood flow (measured with 46Sc microspheres) and arterio-venous differences in the concentrations of glucose, lactate, triacylglycerols and amino acids allowed the estimation of substrate (and energy) balances across the hindleg. Mean glucose uptake was 0.28 μmol min-1, mean lactate release was 0.33 μmol min-1 and the free fatty acid basal release of 0.31 μmol min-1 was practically zero upon exposure to the cold; the initial uptake of triacylglycerols gave place to a massive release following exposure. The measurement of and pH also allowed the estimation of oxygen, CO2 and bicarbonate balances and respiratory quotient changes across the hindleg. The contribution of amino acids to the energy balance of the hindleg was assumed to be low.
These data were used to determine the sources of energy used to maintain muscle shivering with time. Three distinct phases were observed in hindleg substrate utilization. (1) The onset of shivering, with the use of glucose/glycogen and an increase in lactate efflux. Lipid oxidation was practically zero (respiratory quotient near 1), but the uptake of triacylglycerols from the blood remained unchanged. (2) A substrate-energy shift, with drastically decreased use of glucose/glycogen, and of lactate efflux; utilization of triacylglycerol as practically the sole source of energy (respiratory quotient approximately 0.7); decreasing uptake of triacylglycerol and increased tissue lipid mobilization. (3) The onset of a new heat-homeostasis setting for prolonged cold-exposure, with maintenance of muscle energy and heat production based on triacylglycerol utilization and efflux from the hindleg (muscle plus skin and subcutaneous adipose masses) contributing energy to help sustain heat production by the core organs and surrounding brown adipose tissue.
Adipokinetic Hormone Stimulates Neurones in the Insect Central Nervous System
Authors: Milde Jürgen J. , Ziegler Rolf , Wallstein Markus 
Published: April 2021

ABSTRACT
A simple preparation designed to screen and compare the central action of putative neuroactive agents in the moth Manduca sexta is described. This approach combines microinjections into the central nervous system with myograms recorded from a pair of spontaneously active mesothoracic muscles. Pressure injection of either octopamine or Manduca adipokinetic hormone (M-AKH) into the mesothoracic neuropile increases the monitored motor activity. Under the conditions used, the excitatory effects of M-AKH exceed those of the potent neuromodulator octopamine. This suggests that M-AKH plays a role in the central nervous system in addition to its known metabolic functions and supports recent evidence that neuropeptides in insects can be multifunctional.
Adaptive Changes in Locust Kicking and Jumping Behaviour During Development
Authors: Norman Alex P. 
Published: April 2021

ABSTRACT
The hind, or metathoracic, leg of a locust is specialised, enabling it to store energy that is used to extend the tibia rapidly during kicking and jumping; behaviours which share a common motor pattern. This study describes developmental changes in kicking and jumping behaviour and relates these changes to the development of the exoskeleton and jumping performance. In mature adults and intermoult larvae, the exoskeleton is strong and kicks can readily be elicited. Before and after the adult moult, when the exoskeleton is weak, kicks can be elicited less frequently, thus avoiding skeletal damage. At these times, animals do not generate the adult motor pattern for kicking, so that extension of the tibia is powered by direct muscle contraction, rather than through the release of stored energy. The muscles of all newly moulted animals are capable of generating sufficient force to damage the leg, but 14 days later the muscles can rarely generate sufficient force to damage the leg.
To mimic the forces generated during the preparation for a kick, when the flexor and extensor tibiae muscles co-contract, the extensor muscle was stimulated electrically at a range of frequencies and the nature and occurrence of the resulting mechanical damage to components of the skeleton were assessed over a 14 day period following the adult moult. In newly moulted animals, the proximal femur partially collapses and thus protects the leg from damage before the muscles generate sufficient force to damage chronically other components of the leg. This partial collapse of the femur is reversible when the extensor muscle is activated at low frequency, but high frequencies cause permanent damage. The muscles of all animals 1 day after the moult are also capable of generating sufficient force to damage the leg, but the proximal tibia breaks most commonly in the region where the extensor muscle apodeme attaches. 5 days after the moult, the muscles in only 50 % of animals can damage the leg and most commonly the extensor muscle apodeme breaks. In mature animals, the only structure that fails is the extensor muscle apodeme, which fractures close to its point of attachment to the tibia. Damaging a metathoracic leg can significantly decrease the ability of a locust to jump and to compete for mates. Changes in the likelihood of damage to a metathoracic leg occur at predictable stages of development. Locust behaviour is modified during development, avoiding such damage.
Physiological Properties of Wind-Sensitive and Tactile Trichoid Sensilla on the Ovipositor and Their Role During Oviposition in the Locust
Authors: Kalogianni Eleni 
Published: April 2021

ABSTRACT
The physiological properties of the ovipositor hair sensilla of the desert locust and their responses to wind and to direct mechanical displacement are described. The hairs on the external surfaces of the ventral and dorsal ovipositor valves respond to wind stimulation, whereas the hairs on the inner surfaces of the dorsal valves are not wind-sensitive. All ovipositor hairs, however, respond to tactile displacement. Imposed tactile stimulation reveals two physiologically distinct types of ovipositor tactile hairs: the hairs on the inner surface of the dorsal valves are high-threshold hairs (threshold angular deflection of 26–67 ° at 1 Hz) that respond phasically, whereas the hairs on the lateral and ventral areas of the ventral valves and the lateral areas of the dorsal valves are low-threshold hairs (threshold angular deflection of 6–20 ° at 1 Hz) that respond phasotonically. There is no apparent difference in the length of the two physiologically distinct types of hairs.
Both high- and low-threshold hairs are directionally sensitive, with maximal responses to proximal deflection, towards the abdomen, and are also velocity-sensitive. High-threshold hairs have velocity thresholds of 40–50 ° s-1 for some hairs and 110–140 ° s-1 for others for a deflection angle of 35 °, whereas low-threshold hairs have lower velocity thresholds of less than 5 ° s-1 for the same deflection. High-threshold hairs adapt rapidly to repetitive stimulation after as few as four cycles of stimulation at
0.5 Hz. Low-threshold hairs continue to respond after 40 cycles of stimulation at 0.5 Hz and show little adaptation to repetitive stimulation at frequencies ranging from 0.1 to 5 Hz. Low-threshold hairs respond with bursts of spikes at frequencies that reflect both the velocity and the duration of the stimulus. Furthermore, low-threshold hairs show little adaptation after 30 min of stimulation that simulates oviposition digging. It is suggested (a) that low- and high-threshold ovipositor hairs detect phasic wind and/or tactile stimuli in non-ovipositing locusts and (b) that low-threshold hairs can also signal rhythmic tactile inputs during oviposition digging.
‘Deep-Sea Spiders’ That Walk Through the Water
Authors: Marshall N. Justin , Diebel Carol 
Published: April 2021

ABSTRACT
Deep-sea isopods of the family Munnopsidae exhibit four modes of swimming: forward striding, slow backward pedalling, fast backward pedalling and escape, the first two of which use asymmetric phases of leg movement. Instead of moving the left and right limbs (pereopods, P2–P7) of a segment in-phase (e.g. RP2LP2, RP3LP3, RP4LP4), as do most aquatic insects, leg movement is more like that of fast-walking insects, where closest synchrony occurs between diagonal limbs (e.g. RP2LP3, RP3LP4, RP4LP2). This is similar to the alternating tripod gait used by many animals on land to prevent them from toppling over. It therefore seems likely that this group of isopods learned to walk before they could swim.
Evidence for Protein Damage at Environmental Temperatures: Seasonal Changes in Levels of Ubiquitin Conjugates and Hsp70 in the Intertidal Mussel Mytilus Trossulus
Authors: Hofmann Gretchen E. , Somero George N. 
Published: April 2021

ABSTRACT
We examined the seasonal variation in environmentally induced protein damage in natural populations of the intertidal mussel Mytilus trossulus. In order to compare the state of protein pools during seasonal variations in environmental temperature, we used solid-phase immunochemical analysis to quantify ubiquitin conjugate concentrations and relative levels of the stress protein hsp70. The two biochemical indices were selected for their cellular roles in irreversible and reversible protein denaturation, respectively. Proteins that are ubiquitinated are irreversibly damaged and are degraded by intracellular proteases; stress proteins act as molecular chaperones to re-fold thermally denatured proteins and, thus, indicate degrees of reversible protein damage. Comparisons involved mussels collected in February and August from two study sites: an intertidal site which subjected animals to a wide range of body temperatures (from approximately 10 to 35 °C in summer), and a subtidal site where animals remained submerged throughout the tidal cycle. Our results show that quantities of ubiquitin conjugates and hsp70 were greater in gill tissue from summer-collected mussels than in gills of winter-collected specimens. Ubiquitin conjugate and hsp70 levels were also greater in mussels collected from an intertidal location than in mussels from a submerged population. Our results show that the high summer temperatures normally experienced in the field are sufficient to cause increased denaturation of cellular proteins. Despite increases in the concentrations of heat shock proteins in summer-acclimatized mussels, elevated levels of irreversibly denatured, i.e. ubiquitinated, proteins were still observed, which indicates that the heat shock response may not be able to rescue all heat-damaged proteins. The energy costs associated with replacing heat-damaged proteins and with maintaining the concentrations and activities of heat shock proteins may contribute substantially to cellular energy demands. These increased energy demands may have an impact on the ecological energetic relationships of species, e.g. in the allocations of energy for growth and reproduction, and, as a consequence, may contribute to determining their distribution limits.