bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contributions of K+:Cl− cotransport and Na+/K+-ATPase to basolateral ion transport in malpighian tubules of Drosophila melanogaster
Authors: Linton Stuart M. , O’Donnell M. J. 
Published: April 2021

ABSTRACT
Mechanisms of Na+ and K+ transport across the basolateral membrane of isolated Malpighian tubules of Drosophila melanogaster were studied by examining the effects of ion substitution and putative inhibitors of specific ion transporters on fluid secretion rates, basolateral membrane potential and secreted fluid cation composition. Inhibition of fluid secretion by [(dihydroindenyl) oxy]alkanoic acid (DIOA) and bumetanide (10−4 mol l−1) suggested that a K+:Cl− cotransporter is the main route for K+ entry into the principal cells of the tubules. Differences in the effects of bumetanide on fluxes of K+ and Na+ are inconsistent with effects upon a basolateral Na+:K+:2Cl− cotransporter. Large differences in electrical potential across apical (&gt;100 mV, lumen positive) and basolateral (&lt;60 mV, cell negative) cell membranes suggest that a favourable electrochemical gradient for Cl− entry into the cell may be used to drive K+ into the cell against its electrochemical gradient, via a DIOA-sensitive K+:Cl− cotransporter. A Na+/K+-ATPase was also present in the basolateral membrane of the Malpighian tubules. Addition of 10−5 to 10−3 mol l−1 ouabain to unstimulated tubules depolarized the basolateral potential, increased the Na+ concentration of the secreted fluid by 50–73 % and increased the fluid secretion rate by 10–19 %, consistent with an increased availability of intracellular Na+. We suggest that an apical vacuolar-type H+-ATPase and a basolateral Na+/K+-ATPase are both stimulated by cyclic AMP. In cyclic-AMP-stimulated tubules, K+ entry is stimulated by the increase in the apical membrane potential, which drives K+:Cl− cotransport at a faster rate, and by the stimulation of the Na+/K+-ATPase. Fluid secretion by cyclic-AMP-stimulated tubules was reduced by 26 % in the presence of ouabain, suggesting that the Na+/K+-ATPase plays a minor role in K+ entry into the tubule cells. Malpighian tubules secreted a Na+-rich (150 mmol l−1) fluid at high rates when bathed in K+-free amino-acid-replete saline (AARS). Secretion in K+-free AARS was inhibited by amiloride and bafilomycin A1, but not by bumetanide or hydrochlorothiazide, which inhibit Na+:Cl− cotransport. There was no evidence for a Na+ conductance in the basolateral membrane of unstimulated or cyclic-AMP-stimulated tubules. Possible mechanisms of Na+ entry into the tubule cells include cotransport with organic solutes such as amino acids and glucose.
Sound emission and the acoustic far field of a singing acridid grasshopper (Omocestus viridulus L.)
Authors: Michelsen Axel , Elsner Norbert 
Published: April 2021

ABSTRACT
An array of eight microphones, all at a distance of 15 cm, was used to make simultaneous recordings of the sounds emitted by courting male acridid grasshoppers of the species Omocestus viridulus. In this species, the movement pattern for sound production differs in the two hindlegs, and in most cases the leg facing the female moves with the larger amplitude. The sonic sound intensity (the total sound in the one-third octave bands with centre frequencies from 5 to 20 kHz) is maximal ipsilateral to the leg stridulating with the larger amplitude (the dominant leg). A spontaneous switch of dominance to the other leg may cause a significant change in the emitted sound power. The sound intensities contralateral to the dominant leg and frontal to the animal are, on average, approximately half (−3 dB) of the ipsilateral value, whereas the mean sound intensities behind and above the singer are approximately one-fifth (−7 dB) of the ipsilateral value. In most singers, the patterns of sound radiation are close to these mean values, but in some singers the radiation patterns are radically different. The sound radiated in various directions differs not only in terms of sound intensity but also with respect to the frequency spectrum, which was studied up to the one-third octave band with a centre frequency of 31.5 kHz. In particular, the ratio between the ultrasonic and sonic components is much smaller in the forward direction than in other directions. This may allow the courted female to hear whether the courting male is oriented directly towards her.
Heat transfer from starlings Sturnus vulgaris during flight
Authors: Ward S. , Rayner J. M. V. , Möller U. , Jackson D. M. , Nachtigall W. , Speakman J. R. 
Published: April 2021

ABSTRACT
Infrared thermography was used to measure heat transfer by radiation and the surface temperature of starlings (Sturnus vulgaris) (N=4) flying in a wind tunnel at 6–14 m s−1 and at 15–25 °C. Heat transfer by forced convection was calculated from bird surface temperature and biophysical modelling of convective heat transfer coefficients. The legs, head and ventral brachial areas (under the wings) were the hottest parts of the bird (mean values 6.8, 6.0 and 5.3 °C, respectively, above air temperature). Thermal gradients between the bird surface and the air decreased at higher air temperatures or during slow flight. The legs were trailed in the air stream during slow flight and when air temperature was high; this could increase heat transfer from the legs from 1 to 12 % of heat transfer by convection, radiation and evaporation (overall heat loss). Overall heat loss at a flight speed of 10.2 m s−1 averaged 11.3 W, of which radiation accounted for 8 % and convection for 81 %. Convection from the ventral brachial areas was the most important route of heat transfer (19 % of overall heat loss). Of the overall heat loss, 55 % occurred by convection and radiation from the wings, although the primaries and secondaries were the coolest parts of the bird (2.2–2.5 °C above air temperature). Calculated heat transfer from flying starlings was most sensitive to accurate measurement of air temperature and convective heat transfer coefficients.
Boron is required for zebrafish embryogenesis
Authors: Rowe Ruby I. , Eckhert Curtis D. 
Published: April 2021

ABSTRACT
Boron is the only element known to be essential for plants, but only circumstantial evidence for essentiality exists in animals. We report here that boron is essential for the embryonic development of zebrafish (Danio rerio). Zebrafish were maintained in water with a boron concentration of 0.1 μmol l−1 or supplemented to a concentration of 45 μmol l−1 using ultrapure boric acid. Both groups were fed boron-depleted brine shrimp. This procedure depleted the boron content of the blastulas from low-boron parents to only 5 % of the boron content of the blastulas from boron-supplemented parents. Sperm from low-boron males successfully fertilized eggs from low-boron females, but 92 % of the embryos died within 10 days. The early cleavage stage of development was the most sensitive to boron deficiency. Of the fertilized embryos, 46% did not live to complete the blastula stage. Repletion of low-boron embryos during the first hour after fertilization rescued them from death. These observations provide strong evidence that boron is essential for zebrafish development.
Effects of anoxia on the extra- and intracellular acid–base status in the land snail Helix lucorum (L.): lack of evidence for a relationship between pyruvate kinase down-regulation and acid–base status
Authors: Michaelidis Basile , Pallidou Artemis , Vakouftsi Paraskevi 
Published: April 2021

ABSTRACT
The aims of the present study were to describe a possible correlation between the regulation of the key glycolytic enzyme pyruvate kinase and the acid–base status in the haemolymph and in several other tissues of land snails during anoxia. To illustrate whether such a relationship exists, we determined (i) the acid–base variables in the haemolymph and tissues of the land snail Helix lucorum, (ii) the kinetic properties of pyruvate kinase from several tissues and (iii) the levels of the anaerobic end-products D-lactate and succinate in the haemolymph and tissues of aerobic and anoxic Helix lucorum. The results showed that the pH of haemolymph (pHe) decreased significantly over the first 20 h of anoxia and then recovered slowly towards control values. A similar pattern was observed for intracellular pH (pHi), which decreased significantly over the first 16 h of anoxia and slowly returned towards control levels. The reduction and recovery of pHi and pHe seem to reflect the rate of anaerobic metabolism. The main anaerobic end-products, D-lactate and succinate, accumulated rapidly during the initial stages of anoxia and more slowly as anoxia progressed. The decrease in the rate of accumulation of anaerobic end-products during prolonged anoxia was due to the conversion of tissue pyruvate kinase to a less active form. The results demonstrate a correlation between pyruvate kinase down-regulation and the recovery of acid–base status in the haemolymph and the tissues of land snails during anoxia.
Experimental changes to limb muscles elicit contralateral reactions: the problem of controls
Authors: Lu Da-Xing , Käser Lorenzo , Müntener Markus 
Published: April 2021

ABSTRACT
The extensor digitorum longus muscle (EDL) or soleus muscle (SOL) in rats was mechanically overloaded on one side. The muscles were (i) untreated (normal) or (ii) self- or foreign-reinnervated (leading to persisting muscle fibres) or transplanted (leading to regenerating muscle fibres). The effects of the different procedures were studied in the treated and untreated muscles on the operated side and in the untreated muscles on the contralateral side. Overloading led to an absolute increase in mass (versus control values) in the normal muscles and to a relative increase in mass (versus the lower mass after reinnervation) in the treated muscles. The mechanism underlying this gain in mass was usually a compensatory hypertrophy. Overloading was followed by transformation of fibres from fast to slow in normal muscles. In the reinnervated muscles, the fibre distribution changed in response to the new nervous input and then remained constant. The majority of the experimental procedures elicited significant muscular changes in the contralateral muscles, including hyperplasia, fibre transformation and fibre hypertrophy or atrophy. The changes are interpreted as the consequence of a general compensatory neuromuscular activity designed to maintain a symmetrical posture during walking and running. These frequent and substantial muscular changes in the unoperated muscles clearly show that the muscles of the contralateral side cannot be used as normal controls.
‘Un chant d’appel amoureux’: acoustic communication in moths
Authors: Conner William E. 
Published: April 2021

ABSTRACT
Tympanal sound receptors in moths evolved in response to selective pressures provided by echolocating insectivorous bats. The presence of these ultrasound detectors also set the stage for the later evolution of ultrasonic courtship signals in the tympanate moth families. Male moths have repeatedly exploited the bat-detection mechanisms in females for the purpose of finding, identifying and obtaining mates. Ultrasonic courtship has been described in several members of the moth families Arctiidae, Noctuidae and Pyralidae, and ultrasound is predicted to play a significant role in the courtship of other tympanate moths including the Sphingidae, Lymantriidae, Notodontidae and Geometridae. Ultrasonic signals are involved in species recognition, in male–male competition for mates and in female mate-choice systems.
Pre-existing motor systems, including those involved in bat defence, have also been exploited for the purpose of generating high-frequency courtship signals. Sound production mechanisms in moths include thoracic tymbals, tegular tymbals, alar castanets and genital stridulatory organs. Thus, in both their sensory and motor aspects, the weapons of bat/moth warfare have frequently evolved into components of courtship systems.
Mechanical versus physiological determinants of swimming speeds in diving Brünnich’s guillemots
Authors: Lovvorn James R. , Croll Donald A. , Liggins Geoffrey A. 
Published: April 2021

ABSTRACT
For fast flapping flight of birds in air, the maximum power and efficiency of the muscles occur over a limited range of contraction speeds and loads. Thus, contraction frequency and work per stroke tend to stay constant for a given species. In birds such as auks (Alcidae) that fly both in air and under water, wingbeat frequencies in water are far lower than in air, and it is unclear to what extent contraction frequency and work per stroke are conserved. During descent, compression of air spaces dramatically lowers buoyant resistance, so that maintaining a constant contraction frequency and work per stroke should result in an increased swimming speed. However, increasing speed causes exponential increases in drag, thereby reducing mechanical versus muscle efficiency.
To investigate these competing factors, we have developed a biomechanical model of diving by guillemots (Uria spp.). The model predicted swimming speeds if stroke rate and work per stroke stay constant despite changing buoyancy. We compared predicted speeds with those of a free-ranging Brünnich’s guillemot (U. lomvia) fitted with a time/depth recorder. For descent, the model predicted that speed should gradually increase to an asymptote of 1.5–1.6 m s−1 at approximately 40 m depth. In contrast, the instrumented guillemot typically reached 1.5 m s−1 within 10 m of the water surface and maintained that speed throughout descent to 80 m. During ascent, the model predicted that guillemots should stroke steadily at 1.8 m s−1 below their depth of neutral buoyancy (62 m), should alternate stroking and gliding at low buoyancies from 62 to 15 m, and should ascend passively by buoyancy alone above 15 m depth. However, the instrumented guillemot typically ascended at 1.25 m s−1 when negatively buoyant, at approximately 1.5 m s−1 from 62 m to 25 m, and supplemented buoyancy with stroking above 25 m. Throughout direct descent, and during ascent at negative and low positive buoyancies (82–25 m), the guillemot maintained its speed within a narrow range that minimized the drag coefficient.
In films, guillemots descending against high buoyancy at shallow depths increased their stroke frequency over that of horizontal swimming, which had a substantial glide phase. Model simulations also indicated that stroke duration, relative thrust on the downstroke versus the upstroke, and the duration of gliding can be varied to regulate swimming speed with little change in contraction speed or work per stroke. These results, and the potential use of heat from inefficient muscles for thermoregulation, suggest that diving guillemots can optimize their mechanical efficiency (drag) with little change in net physiological efficiency.
Na+/Ca2+ exchange current in ventricular myocytes of fish heart: contribution to sarcolemmal Ca2+ influx
Authors: Vornanen Matti 
Published: April 2021

ABSTRACT
Influx of extracellular Ca2+ plays a major role in the activation of contraction in fish cardiac cells. The relative contributions of Na+/Ca2+ exchange and L-type Ca2+ channels to Ca2+ influx are, however, unknown. Using a physiological action potential as the command pulse in voltage-clamped heart cells, we examined sarcolemmal Ca2+ influx through Na+/Ca2+ exchange and L-type Ca2+ channels in crucian carp (Carassius carassius L.) ventricular myocytes. When other cation conductances were blocked, a Ni2+-sensitive current with the characteristic voltage- and time-dependent properties of the Na+/Ca2+ exchange current could be distinguished. At the maximum overshoot voltage of the ventricular action potential (+40 mV; [Na+]i=10 mmol l−1), the density of the Na+/Ca2+ exchange current was 2.99±0.27 pA pF−1 for warm-acclimated fish (23 °C) and 2.38±0.42 pA pF−1 for cold-acclimated fish (4 °C) (means ± S.E.M., N=5–6; not significantly different, P=0.26). The relative contributions of the Na+/Ca2+ exchanger and L-type Ca2+ channels to Ca2+ influx were estimated using two partly different methods. Integration of the Ni2+-sensitive Na+/Ca2+ exchange current and the verapamil- and Cd2+-sensitive L-type Ca2+ current suggests that, during the action potential, approximately one-third of the activating Ca2+ comes through Na+/Ca2+ exchange and approximately two-thirds through L-type Ca2+ channels. An alternative method of analysis, using the inward tail current as a measure of the total sarcolemmal Ca2+ flux from which the Ni2+-sensitive Na+/Ca2+ exchange current was subtracted to obtain the Ca2+ influx through the channels, suggests that L-type Ca2+ channels and Na+/Ca2+ exchange are almost equally important in the activation of contraction. Furthermore, the time course of cell shortening is not adequately explained by sarcolemmal Ca2+ influx through the channels alone, but is well approximated by the sum of Ca2+ influx through the channels and the exchanger. The present results indicate that reverse Na+/Ca2+ exchange in crucian carp ventricular myocytes has sufficient capacity to trigger contraction and suggest that the exchange current makes a significant contribution to contractile Ca2+ during the physiological action potential. The relative significance of channels and exchanger molecules in sarcolemmal Ca2+ entry into crucian carp ventricular myocytes was unaffected by thermal acclimation when determined at 22 °C.
Oscillatory dynamics and information processing in olfactory systems
Authors: Gelperin Alan 
Published: April 2021

ABSTRACT
Oscillatory dynamics is a universal design feature of olfactory information-processing systems. Recent results in honeybees and terrestrial slugs suggest that oscillations underlie temporal patterns of olfactory interneuron responses critical for odor discrimination. Additional general design features in olfactory information-processing systems include (1) the use of central processing areas receiving direct olfactory input for odor memory storage and (2) modulation of circuit dynamics and olfactory memory function by nitric oxide. Recent results in the procerebral lobe of the terrestrial slug Limax maximus, an olfactory analyzer with oscillatory dynamics and propagating activity waves, suggest that Lucifer Yellow can be used to reveal a band-shaped group of procerebral neurons involved in the storage of an odor memory. A model has been constructed to relate wave propagation and odor memory bands in the procerebral lobe of L. maximus and to relate these findings to glomerular odor representations in arthropods and vertebrates.
Spatio-Temporal Learning by the ant Ectatomma Ruidum
Authors: Schatz Bertrand , Lachaud Jean-Paul , Beugnon Guy 
Published: April 2021

ABSTRACT
We tested, under field and laboratory conditions, whether the neotropical ant Ectatomma ruidum Roger can learn several associations between temporal and spatial changes in the daily pattern of food availability. Honey was shuffled between two or three feeding sites following a fixed daily schedule. Foragers learnt to associate particular sites with the specific times at which food was available, individually marked ants being observed on the correct sites at the correct times. Some ants anticipated the time of food delivery by approximately 30 min, and it was not necessary for them to be rewarded at the first stage of the sequence of food collection to continue their search for honey according to the correct schedule of reward. Ants also followed the same schedule when no honey was supplied at each stage of the sequence, and they stayed at the expected unrewarded site for a period equivalent to the reward period of the corresponding training phase, indicating that they had learnt when and for how long the food was available. Thus, ants rely on their spatio-temporal memory rather than on local cues coming from the honey source to guide them.
Energy metabolism during embryonic development and larval growth of an Antarctic sea urchin
Authors: Marsh Adam G. , Leong Patrick K. K. , Manahan Donal T. 
Published: April 2021

ABSTRACT
Developmental energetics of an Antarctic sea urchin, Sterechinus neumayeri, were quantified to describe the physiological bases underlying ontogenetic changes in metabolic rate at extreme cold temperatures (−1.5 °C). Rates of development from a four-arm to a six-arm larval stage were not affected by food availability. The respiratory cost of development to the six-arm larval stage (day 60) was 14.0 mJ for fed larvae and 8.2 mJ for unfed larvae. We observed three phases of metabolic regulation during development. During embryogenesis (day 0–22), increasing metabolic rates were proportional to increases in cell numbers. During early larval development (day 22–47), the differences in respiratory rate between fed and unfed larvae were not accounted for by cell number, but by cell-specific metabolic rate (respiratory rate normalized to DNA content). Once an advanced larval stage had been reached (day 47–60), cell-specific respiratory rate and mitochondrial densities (citrate synthase activity normalized to DNA content) were more equivalent between fed and unfed larvae, suggesting that size-specific metabolic rates were determined at a level of physiological regulation that was independent of cell numbers or feeding history.
Na+/K+-ATPase activity during early development and growth of an antarctic sea urchin
Authors: Leong P. K. K. , Manahan D. T. 
Published: April 2021

ABSTRACT
In Antarctic environments, the physiological bases for long larval life spans under natural conditions of limited food availability are not understood. The Na+ pump is likely to be involved with hypometabolic regulation in such cold environments. Changes in the activity and metabolic importance of Na+/K+-ATPase were measured in embryos of the Antarctic sea urchin Sterechinus neumayeri and in larvae reared under different feeding conditions. The rate of increase of total Na+/K+-ATPase activity was 3.9 times faster in fed than in unfed larvae. During development and growth, there was an increase in the percentage of total, potential Na+/K+-ATPase activity that was physiologically utilized. In early (10-day-old) gastrulae, 17 % was utilized in vivo, increasing to 77 % in six-arm pluteus (48-day-old) larvae. The metabolic importance of in vivo Na+/K+-ATPase activity also increased during development, accounting for 12 % of metabolic rate at day 10 and 84 % at day 48. When compared at the same enzyme assay temperature (15 °C), the protein-specific total Na+/K+-ATPase activities for late embryonic (prism) and early larval (pluteus) stages of S. neumayeri were 2.6 times lower than those for comparable developmental stages of two temperate sea urchin species (Strongylocentrotus purpuratus and Lytechinus pictus).