bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slow ATP loss and the defense of ion homeostasis in the anoxic frog brain
Authors: Knickerbocker Debra L. , Lutz Peter L. 
Published: April 2021

SUMMARY
For most vertebrates, cutting off the oxygen supply to the brain results in a rapid (within minutes) loss of ATP, the failure of ATP-dependent ion-transport process, subsequent anoxic depolarization of neuronal membrane potential and consequential neuronal death. The few species that survive brain anoxia for days or months, such as the freshwater turtle Trachemys scripta, avoid anoxic depolarization and maintain brain ATP levels through a coordinated downregulation of brain energy demand processes. The frog Rana pipiens represents an intermediate in anoxia-tolerance, being able to survive brain anoxia for hours. However, the anoxic frog brain does not defend its energy stores. Instead, anoxia-tolerance appears to be related to a retarded rate of ATP depletion. To investigate the relationship between this slow ATP depletion and the loss of ionic homeostasis, cerebral extracellular K+ concentrations were monitored and ATP levels measured during anoxia, during the initial phase of anoxic depolarization and during complete anoxic depolarization. Extracellular K+ levels were maintained at normoxic levels for at least 3 h of anoxia, while ATP content decreased by 35 %. When ATP levels reached 0.33±0.06 mmol l–1 (mean ± s.e.m., N=5), extracellular K+ levels slowly started to increase. This value is thought to represent a critical ATP concentration for the maintenance of ion homeostasis. When extracellular [K+] reached an inflection value of 4.77±0.84 mmol l–1 (mean ± s.e.m., N=5), approximately 1 h later, the brain quickly depolarized. Part of the reduction in ATP demand was attributable to an approximately 50 % decrease in the rate of K+ efflux from the anoxic frog brain, which would also contribute to the retarded rate of increase in extracellular [K+] during the initial phase of anoxic depolarization. However, unlike the anoxia-tolerant turtle brain, adenosine did not appear to be involved in the downregulation of K+ leakage in the frog brain. The increased anoxia-tolerance of the frog brain is thought to be a matter more of slow death than of enhanced protective mechanisms.
The influence of locomotion on air-sac pressures in little penguins
Authors: Boggs D. F. , Baudinette R. V. , Frappell P. B. , Butler P. J. 
Published: April 2021

SUMMARYAir-sac pressures have been reported to oscillate with wing beat in flying magpies and with foot paddling in diving ducks. We sought to determine the impact on air-sac pressure of wing beats during swimming and of the step cycle during walking in little penguins (Eudyptula minor). Fluctuations averaged 0.16±0.06 kPa in the interclavicular air sacs, but only 0.06±0.04 kPa in the posterior thoracic sac, generating a small differential pressure between sacs of 0.06±0.02 kPa (means ± s.e.m., N=4). These fluctuations occurred at approximately 3 Hz and corresponded to wing beats during swimming, indicated by electromyograms from the pectoralis and supracoracoideus muscles. There was no abdominal muscle activity associated with swimming or exhalation, but the abdominal muscles were active with the step cycle in walking penguins, and oscillations in posterior air-sac pressure (0.08±0.038 kPa) occurred with steps. We conclude that high-frequency oscillations in differential air-sac pressure enhance access to and utilization of the O2 stores in the air sacs during a dive.
Characterization of theDrosophila melanogasteralkali-metal/proton exchanger (NHE) gene family
Authors: Giannakou Maria E. , Dow Julian A. T. 
Published: April 2021

SUMMARYThe NHE family of Na+/H+ exchangers is believed to play an essential role in animals, but may play an additional, specialised epithelial role in insects. The pharmacological sensitivity of the Drosophila melanogaster Malpighian tubule to a range of amiloride derivatives was shown to be consistent with an effect on an exchanger, rather than a Na+ channel. Consistent with this, no degenerin/epithelial Na+ channel (ENaC) genes could be detected in Malpighian tubules by reverse transcriptase/polymerase chain reaction (RT-PCR). Using a low-stringency homology searching, three members of the NHE family were identified in the genomic sequence of Drosophila melanogaster, although only two genes were represented as expressed sequence tags. All three genes (DmNHE1 at cytological position 21B1, DmNHE2 at 39B1 and DmNHE3 at 27A1) were found by RT-PCR to be widely expressed, and one (DmNHE2) was shown to have multiple transcripts. The putative translations of the three genes mark them as distantly related members of the family, inviting the possibility that they may serve distinct roles in insects.
Intestinal iron uptake in the European flounder (Platichthys flesus)
Authors: Bury N. R. , Grosell M. , Wood C. M. , Hogstrand C. , Wilson R. W. , Rankin J. C. , Busk M. , Lecklin T. , Jensen F. B. 
Published: April 2021

SUMMARY
Iron is an essential element because it is a key constituent of the metalloproteins involved in cellular respiration and oxygen transport. There is no known regulated excretory mechanism for iron, and homeostasis is tightly controlled via its uptake from the diet. This study assessed in vivo intestinal iron uptake and in vitro iron absorption in a marine teleost, the European flounder Platichthys flesus. Ferric iron, in the form 59FeCl3, was reduced to Fe2+ by ascorbate, and the bioavailability of Fe3+ and Fe2+ were compared. In vivo Fe2+ uptake was significantly greater than Fe3+ uptake and was reduced by the iron chelator desferrioxamine. Fe2+ was also more bioavailable than Fe3+ in in vitro studies that assessed the temporal pattern and concentration-dependency of iron absorption. The posterior region, when compared with the anterior and mid regions of the intestine, was the preferential site for Fe2+ uptake in vivo. In vitro iron absorption was upregulated in the posterior intestine in response to prior haemoglobin depletion of the fish, and the transport showed a Q10 value of 1.94. Iron absorption in the other segments of the intestine did not correlate with haematocrit, and Q10 values were lower. Manipulation of the luminal pH had no effect on in vitro iron absorption. The present study demonstrates that a marine teleost absorbs Fe2+ preferentially in the posterior intestine. This occurs in spite of extremely high luminal bicarbonate concentrations recorded in vivo, which may be expected to reduce the bioavailability of divalent cations as a result of the precipitation as carbonates (e.g. FeCO3).
Nitric oxide induces centrally generated motor patterns in the locust suboesophageal ganglion
Authors: Rast Georg F. 
Published: April 2021

SUMMARYThe stimulatory effects of nitric oxide (NO) on central motor pattern generation in isolated locust suboesophageal ganglia (SOGs) were studied using extracellular recordings from motor nerves. Different NO donor molecules and a specific inhibitor of soluble guanylyl cyclases were used to confirm that the observed motor pattern occurred in response to activation of the NO/cyclic GMP signalling pathway. Experiments with muscarinic agonists and antagonists showed that the NO-induced motor pattern is generated independently from the motor pattern induced by muscarinic agonists described previously. Staining for NADPH-diaphorase and an antiserum directed against cyclic GMP were used to identify neurones representing potential sources of NO and their target cells within the SOG. Using intracellular dye injection and backfilling of peripheral nerves in combination with anti-cGMP immunohistochemistry, it was shown that identified efferent neurones involved in the mandibular motor pattern are potential target cells of NO.
Platelet-activating-factor-hydrolyzing phospholipase C in the salivary glands and saliva of the mosquitoCulex quinquefasciatus
Authors: Ribeiro José M. C. , Francischetti Ivo M. B. 
Published: April 2021

SUMMARYA phospholipase C activity specific for platelet-activating factor (PAF), named PAF phosphorylcholine hydrolase, was found in the salivary glands and saliva of the human-feeding mosquito Culex quinquefasciatus. The enzymatic activity was demonstrated by inhibition of PAF-induced platelet aggregation, and by identification of substrate consumption and production of diacyl glyceride by electrospray-ionisation mass spectrometry. The activity has a neutral optimal pH and an apparent molecular mass of 40–50 kDa. Two anthropophilic mosquito species, Aedes aegypti and Anopheles gambiae, do not have this salivary activity. The results are interpreted within the evolutionary context of the genera Culex, Aedes and Anopheles.
Swimming speeds and buoyancy compensation of migrating adult chum salmon Oncorhynchus keta revealed by speed/depth/acceleration data logger
Authors: Tanaka Hideji , Takagi Yasuaki , Naito Yasuhiko 
Published: April 2021

SUMMARY
Although the homing migration of Pacific salmon is well documented, the swimming behaviour of the returning salmon has been poorly described, principally as a result of the difficulties encountered in monitoring salmon behaviour in the sea. The present study describes the use of a recently developed electronic data logger to obtain simultaneous recordings of the swimming speed, depth, fin-beating activity and body angle of free-ranging chum salmon Oncorhynchus keta during their homing migration in coastal waters. Chum salmon migrated horizontally at speeds of 1.5–3.0 km h–1. The gross horizontal distance salmon moved during total recording periods were 1.24- to 19.0-fold greater than the net distance from the release site to the retrieval points. It is suggested that homing salmon did not drift passively but swam actively to the spawning grounds. Salmon preferred the surface water, but also made frequent vertical migrations. The travelled depth of each salmon ranged from 0.36 to 0.64 km per hour. Salmon descended at faster rates and steeper angles than they ascended. Both tailbeat frequency and tail thrust were higher during the ascent than the descent phase. These results suggest that chum salmon spent more energy during the ascent than the descent phase. Profiles of descent rate assumed an arched shape with respect to a change in hydrostatic pressure, while ascent rate increased with decreasing depth. High tailbeat frequencies were found during the course of ascent, which suggests that the salmon did not regulate the volume of air in the swim bladder during short-term vertical migrations.
Swimbladder gas gland cells cultured on permeable supports regain their characteristic polarity
Authors: Prem Caroline , Pelster Bernd 
Published: April 2021

SUMMARYA cell culture system has been developed in which swimbladder gas gland cells from the European eel (Anguilla anguilla) were cultured on a permeable support. Cells seeded on Anodisc 13 (Whatman) or Costar Transwell 13 mm membranes form a confluent cell layer within the first 2 or 3 days of culture but, on the basis of measurements of transepithelial resistance, it is a ‘leaky’ cell layer. In a superfusion system, the apical and basal sides of the cells were superfused asymmetrically, with saline on the apical side and a glucose-containing cell culture medium on the basal side. Under these conditions, the cells continuously produced lactic acid, and approximately 60–70 % of this lactate was released at the basal side. To mimic the in vivo situation, the saline solution supplied to the apical side was replaced by humidified air in an additional series of experiments. Cells cultured in an air/liquid system produced even more lactate, and this lactate was only released to the basal side; there was no leakage of fluid to the apical side. After 4 or 5 days in the superfusion system, the cells were fixed for histological examination. The cells were columnar, similar to gas gland cells in vivo, and showed a clear polarity, with some small microvilli at the apical membrane and extensive membrane foldings at lateral and basal membranes. Immunohistochemical localization of Na+/K+-ATPase revealed that this ATPase was present mainly in the lateral membranes; it was never found in the apical membranes. Cells cultured in the air/liquid system showed a similar structure and polarity.
Postnatal development and control of the pulmonary surfactant system in the tammar wallaby Macropus eugenii
Authors: Miller Natalie J. , Orgeig Sandra , Daniels Christopher B. , Baudinette Russell V. 
Published: April 2021

SUMMARY
Marsupials are born at an early stage of development and are adapted for future development inside the pouch. Whether the pulmonary surfactant system is fully established at this altricial stage is unknown. This study correlates the presence of surfactant proteins (SP-A, SP-B and SP-D), using immunohistochemistry, with the ex-utero development of the lung in the tammar wallaby Macropus eugenii and also investigates the control of phosphatidylcholine (PC) secretion from developing alveolar type II cells. All three surfactant proteins were found at the site of gas exchange in the lungs of joeys at all ages, even at birth when the lungs are in the early stages of the terminal air-sac phase. Co-cultures of alveolar type II cells and fibroblasts were isolated from the lungs of 30- and 70-day-old joeys and incubated with the hormones dexamethasone (10 μmol l–1), prolactin (1 μmol l–1) or triiodothyronine (100 μmol l–1) or with the autonomic secretagogues isoproterenol (100 μmol l–1) or carbamylcholine chloride (100 μmol l–1). Basal secretion of PC was greater at 30 days of age than at 70 days. Co-cultures responded to all five agonists at 30 days of age, but only the autonomic secretagogues caused a significant increase in PC secretion at 70 days of age. This demonstrates that, as the cells mature, their activity and responsiveness are reduced. The presence of the surfactant proteins at the site of gas exchange at birth suggests that the system is fully functional. It appears that surfactant development is coupled with the terminal air-sac phase of lung development rather than with birth, the length of gestation or the onset of air-breathing.
Maneuvering in an arboreal habitat: the effects of turning angle on the locomotion of three sympatric ecomorphs ofAnolislizards
Authors: Higham Timothy E. , Davenport Matthew S. , Jayne Bruce C. 
Published: April 2021

SUMMARYAlthough the maximal speeds of straight-ahead running are well-documented for many species of Anolis and other lizards, no previous study has experimentally determined the effects of turning on the locomotor performance of a lizard. Anolis lizards are a diverse group of arboreal species, and the discrete paths created by networks of perches in arboreal environments often force animals to turn in their natural habitats. For three species of Anolis with similar overall body size but different shape, we quantified the escape locomotor performance for arboreal locomotion on 4.8 cm diameter perches that were straight (0°) or had turning angles of 30° and 90°. The turning angle had widespread significant effects that were often species-dependent. This was shown by measuring the average gross velocity (including the times while the lizards paused) of the three species covering the middle 30 cm of a racetrack with either 30° or 90° turns. The results were expressed as a percentage of the gross velocity over the same distance on a straight racetrack. The values obtained for A. grahami (99 % for 30° turns and 79 % for 90° turns) showed a smaller effect of turning angle than for A. lineatopus (79 % for 30° turns and 50 % for 90° turns) and A. valencienni (74 % for 30° turns and 48 % for 90° turns). Consequently, the rank order of species based on speed depended on the angle of the turn. Some of the magnitudes of decreased locomotor speed associated with turning exceeded those reported previously for the effects of decreasing perch diameter for these species. For all species, more pausing occurred with increased turning angle, with the twig ecomorph (A. valencienni) pausing the most. Approximately half the individuals of each species jumped to traverse the 90° turn, but some of the potential benefits of jumping for increasing speed were offset by pauses associated with preparing to jump or recovering balance immediately after a jump. The tail of Anolis lizards may facilitate the substantial rotation (&gt;60°) of the body that often occurred in the airborne phase of the jumps.
A snake venom phospholipase A2 blocks malaria parasite development in the mosquito midgut by inhibiting ookinete association with the midgut surface
Authors: Zieler Helge , Keister David B. , Dvorak James A. , Ribeiro José M. C. 
Published: April 2021

SUMMARYOocyst formation is a critical stage in the development of the malaria parasite in the mosquito. We have discovered that the phospholipase A2 (PLA2) from the venom of the eastern diamondback rattlesnake (Crotalus adamanteus) inhibits oocyst formation when added to infected chicken blood and fed to mosquitoes. A similar transmission-blocking activity was demonstrated for PLA2s from the venom of other snakes and from the honeybee. This effect is seen both with the avian malaria parasite Plasmodium gallinaceum and with the human parasite Plasmodium falciparum developing in their respective mosquito hosts. The inhibition occurs even in the presence of an irreversible inhibitor of the active site of PLA2, indicating that the hydrolytic activity of the enzyme is not required for the antiparasitic effect. Inhibition is also seen when the enzyme is fed to mosquitoes together with ookinetes, suggesting that the inhibition occurs after ookinete maturation. PLA2 has no direct effect on the parasite. However, pretreatment of midguts with PLA2 (catalytically active or inactive) dramatically lowers the level of ookinete/midgut association in vitro. It appears, therefore, that PLA2 is acting by associating with the midgut surface and preventing ookinete attachment to this surface. Thus, PLA2 is an excellent candidate for expression in transgenic mosquitoes as a means of inhibiting the transmission of malaria.
Egocentric information helps desert ants to navigate around familiar obstacles
Authors: Bisch-Knaden Sonja , Wehner Rüdiger 
Published: April 2021

SUMMARY
Homing ants have been shown to associate directional information with familiar landmarks. The sight of these local cues might either directly guide the path of the ant or it might activate a landmark-based vector that points towards the goal position. In either case, the ants define their courses within allocentric systems of reference. Here, we show that desert ants, Cataglyphis fortis, forced to run along a devious path can use egocentric information as well. The ants were trained to deviate from their straight homebound course by a wide inconspicuous barrier that was placed between the feeding and nesting sites. At a distant test area, the ants were confronted with an identical barrier rotated through 45°. After passing the edge of the obstacle, the ants did not proceed in the trained direction, defined by the skylight compass, but rotated their courses to match the rotation of the barrier. Visual guidance could be excluded because, as soon as the ants turned around the end of the barrier, the visual cue it provided vanished from their field of view. Instead, the ants must have maintained a constant angle relative to their previous walking trajectory along the obstacle and, hence, must have determined their new vector course in an egocentric way.
Variations in respiratory muscle activity during echolocation when stationary in three species of bat (Microchiroptera: Vespertilionidae)
Authors: Lancaster Winston C. , Speakman J. R. 
Published: April 2021

SUMMARY
Echolocating bats use respiratory muscles to power the production of biosonar vocalisations. The physical characteristics of these calls vary among species of bat, and variations also exist in the timing and patterns of respiratory muscle recruitment during echolocation. We recorded electromyograms from the respiratory muscles of three species of bat (Family Vespertilionidae) while the animals vocalised from stationary positions. Activity was recorded consistently from the lateral abdominal muscles (internal abdominal oblique and transversus abdominis) from all calling bats, but we found much variation within and among species. Bats in the family Vespertilionidae devoted longer periods of expiratory muscle activity to each call than did the mormoopid bat Pteronotus parnellii. These differences correlate negatively with the duration of calls. We suggest that morphological adaptations in some bats may facilitate the economic production of echolocation calls at rest.
Geographic variation in thermal sensitivity of jumping performance in the frog Limnodynastes peronii
Authors: Wilson Robbie S. 
Published: April 2021

SUMMARY
I compared the thermal sensitivity of jumping performance of five populations of the striped marsh frog (Limnodynastes peronii) over a wide geographic range extending from the cool-temperate south to the tropical north of Australia. Maximum jumping performance of adult L. peronii was assessed for each population at eight temperatures between 5°C and 32°C using a custom-designed force platform. From force recordings for each individual jump, maximum jumping force (Fmax) and acceleration (Amax) and maximum power output (Pmax), take-off velocity (Umax), jump distance (DJ) and contact time on the platform (TC) were calculated. The body mass of adult L. peronii varied over their geographic range, from approximately 5 g for the lowland tropical population to more than 22 g for the cool-temperate populations. The thermal sensitivity of jumping performance varied over their geographic range, with the populations from the cooler climates generally performing better than those from the warmer climate populations at the cooler temperatures, and vice versa at the higher temperatures. However, not all parameters of jumping performance underwent parallel changes in thermal sensitivity amongst the populations of L. peronii. Only minor differences in the shape of the thermal sensitivity curves for Fmax and Amax were detected amongst the populations, while the thermal sensitivities of Umax, DJ and Pmax all displayed considerable variation amongst the populations. The optimal temperatures for Umax, DJ and Pmax were generally lower in the cool-temperate populations than in the tropical populations of L. peronii. To determine whether this geographic variation was due to genetic variation, or merely reflected phenotypic plasticity, I also compared the thermal sensitivity of jumping performance between metamorph L. peronii from two different populations raised under identical conditions in the laboratory. The maximum jumping distance of the metamorph L. peronii was assessed at seven temperatures between 8°C and 35°C for the two latitudinally extreme populations (i.e. lowland tropical Proserpine and cool-temperate Gippsland populations). Like adult L. peronii, the metamorphs from the cool-temperate population jumped further than those from the lowland tropical population at the lower temperatures, although no differences were detected at the higher temperatures. Thus, geographic variation in thermal sensitivity of jumping performance in L. peronii probably has a genetic component, and the different populations appear to have undergone genetic adaptation of their thermal sensitivity to the varied thermal environments.