bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence for Membrane-Bound Carbonic Anhydrase in the Air Bladder of bowfin (Amia Calva), a Primitive air-Breathing Fish
Authors: Gervais Matthieu R. , Tufts Bruce L. 
Published: April 2021

ABSTRACT
The purpose of this study was to examine the subcellular distribution and isoenzyme characteristics of carbonic anhydrase from the gills and respiratory air bladder of bowfin Amia calva, a primitive air-breathing fish. Separation of subcellular fractions by differential centrifugation revealed that the vast majority of carbonic anhydrase from the gills of bowfin originated from the cytoplasmic fraction. Washing of the gill microsomal pellet also indicated that the carbonic anhydrase originally associated with this pellet was largely due to contamination from the cytoplasmic fraction. Experiments with a carbonic anhydrase inhibitor, sulphanilamide, and the plasma carbonic anhydrase inhibitor from this species confirmed that the bowfin gill probably contains only one carbonic anhydrase isoenzyme which had properties resembling those of CA II. In contrast to the situation in the gills, a relatively large percentage (27 %) of the total air bladder carbonic anhydrase was associated with the microsomal fraction. Washing of the air bladder microsomal pellet removed little of the carbonic anhydrase activity, indicating that most of the carbonic anhydrase in the microsomal fraction was associated with the membranes. Like the mammalian pulmonary CA IV isoenzyme, microsomal carbonic anhydrase from the bowfin air bladder was less sensitive to the bowfin plasma carbonic anhydrase inhibitor, sodium dodecylsulphate (SDS) and sulphanilamide than was cytoplasmic carbonic anhydrase from the air bladder. Microsomal carbonic anhydrase from the bowfin air bladder also resembled CA IV in that it appears to be anchored to the membrane via a phosphatidylinositol–glycan linkage which could be cleaved by phosphatidylinositol-specific phospholipase C. Taken together, these results suggest that a membrane-bound carbonic anhydrase isoenzyme resembling mammalian CA IV in terms of inhibition characteristics and membrane attachment is present in the air-breathing organ of one of the most primitive air-breathing vertebrates.
Relationships Between Blood Pressure and Heart Rate in the Saltwater Crocodile Crocodylus Porosus
Authors: Altimiras Jordi , Franklin Craig E. , Axelsson Michael 
Published: April 2021

ABSTRACT
The cardiac limb of the baroreflex loop was studied in the saltwater crocodile Crocodylus porosus. The classical pharmacological methodology using phenylephrine and sodium nitroprusside was used to trigger blood pressure changes, and the resulting alterations in heart rate were analysed quantitatively using a logistic function. Interindividual differences in resting heart rates and blood pressures were observed, but all seven animals displayed clear baroreflex responses. Atropine and sotalol greatly attenuated the response. A maximal baroreflex gain of 7.2 beats min−1 kPa−1 was found at a mean aortic pressure of 6.1 kPa, indicating the active role of the baroreflex in a wide pressure range encompassing hypotensive and hypertensive states. At the lowest mean aortic pressures (5.0 kPa), the synergistic role of the pulmonary-to-systemic shunt in buffering the blood pressure drop also contributes to blood pressure regulation.
Pulse pressure showed a better correlation with heart rate and also a higher gain than mean aortic, systolic or diastolic pressures, and this is taken as an indicator of the existence of a differential control element working simultaneously with a linear proportional element.
Enhancement of Insect Antifreeze Protein Activity by Solutes of Low Molecular Mass
Authors: Li Ning , Andorfer Cathy A. , Duman John G. 
Published: April 2021

ABSTRACT
Antifreeze proteins (AFPs) lower the non-equilibrium freezing point of water (in the presence of ice) below the melting point, thereby producing a difference between the freezing and melting points that has been termed thermal hysteresis. In general, the magnitude of the thermal hysteresis depends upon the specific activity and concentration of the AFP. This study describes several low-molecular-mass solutes that enhance the thermal hysteresis activity of an AFP from overwintering larvae of the beetle Dendroides canadensis. The most active of these is citrate, which increases the thermal hysteresis nearly sixfold from 1.2 °C in its absence to 6.8 °C. Solutes which increase activity approximately fourfold are succinate, malate, aspartate, glutamate and ammonium sulfate. Glycerol, sorbitol, alanine and ammonium bicarbonate increased thermal hysteresis approximately threefold. Interestingly, 0.5 mol l−1 sodium sulfate eliminated activity. Solute concentrations between 0.25 and 1 mol l−1 were generally required to elicit optimal thermal hysteresis activity. Glycerol is the only one of these enhancing solutes that is known to be present at these concentrations in overwintering D. canadensis, and therefore the physiological significance of most of these enhancers is unknown. The mechanism(s) of this enhancement is also unknown.
The AFP used in this study (DAFP-4) is nearly identical to previously described D. canadensis AFPs. The mature protein consists of 71 amino acid residues arranged in six 12-or 13-mer repeats with a consensus sequence consisting of Cys-Thr-X3-Ser-X5-X6-Cys-X8-X9-Ala-X11-Thr-X13, where X3 and X11 tend to be charged residues, X5 tends to be Thr or Ser, X6 to be Asn or Asp, X9 to be Asn or Lys and X13 to be Ala in the 13-mers. DAFP-4 is shorter by one repeat than previously described D. canadensis AFPs.
Effects of Wheat Germ Agglutinin and Colchicine on Microtubules of the Mitochondria-Rich Cells and Ca2+ Uptake in Tilapia (Oreochromis Mossambicus) Larvae
Authors: Tsai Jong-Chang , Hwang Pung-Pung 
Published: April 2021

ABSTRACT
The organization of the microtubules and actin filaments in the gills of tilapia (Oreochromis mossambicus) larvae was revealed by confocal microscopy. The fluorescence intensity of the microtubules in the gills was increased by adding wheat germ agglutinin (WGA, 40 ng ml−1) to the ambient water for 30 min, but the staining pattern of the actin filaments was not changed. The fluorescence intensity of the microtubules in the gills was decreased by treatment with the microtubule-disrupting reagent colchicine at 0.2 mmol l−1 for 4 h. WGA treatment concurrently raised Ca2+ influx rates, and the increase was particularly large when the larvae were kept in water with extremely low Ca2+ levels ([Ca2+]=0.002 mmol l−1). Colchicine treatment, in contrast, reduced the Ca2+ influx rate. These results indicate that the microtubule network in tilapia gills, particularly in mitochondria-rich cells, could play a critical role in the uptake of Ca2+ in tilapia larvae.
The Rhodopsin Gene of the Cuttlefish Sepia Officinalis: Sequence and Spectral Tuning
Authors: Bellingham James , Morris Alex G. , Hunt David M. 
Published: April 2021

ABSTRACT
The cephalopod molluscs are a group of invertebrates that occupy a wide range of oceanic photic environments. They are an ideal group of animals, therefore, in which to study the evolution of rhodopsin. The cDNA sequence of the rhodopsin gene of the cuttlefish Sepia officinalis (L.) (Sub-class Coleoidea, Order Sepiida) is presented, together with an analysis of the structure of the gene. A proline-rich C terminus is present; this structure is characteristic of cephalopod rhodopsins. In common with all invertebrate opsins studied so far, the equivalent site to the counterion in vertebrate opsins is occupied by an aromatic amino acid. An intron is present that splits codon 107, in contrast to the intronless rhodopsin gene in two species of myopsid squid. A spectral tuning model involving substitutions at only three amino acid sites is proposed for the spectral shifts between the rhodopsins of Sepia officinalis, three species of squid and Paroctopus defleini.
Biosynthetic Activity of Corpora Allata, Growth of Sex Accessory Glands and Mating in the Male Moth Agrotis Ipsilon (Hufnagel)
Authors: Duportets Line , Dufour Marie-Cécile , Couillaud Franck , Gadenne Christophe 
Published: April 2021

ABSTRACT
The involvement of both juvenile hormone acid (JHA) and the sex accessory glands (SAGs) in the reproduction of the male moth Agrotis ipsilon was studied as a function of age and mating status. Total protein content analysis followed by gel electrophoresis of the SAGs, radiochemical assay for JHA biosynthesis and surgical and behavioural experiments were performed. Both the protein content of the SAGs and the biosynthetic activity of the corpora allata (CA) increased with age. Allatectomy and JHA/JH treatments showed that the protein content of the SAGs is linked with the activity of the CA. The protein content of the glands, but not the rate of JHA biosynthesis, decreased just after mating, and both increased sharply 24 h later. Injection of fluvastatin, an inhibitor of JH biosynthesis, in males immediately after mating prevented the increase in JHA synthesis and lowered the total protein content of the SAGs. Moreover, fluvastatin disrupted normal spermatophore transfer during the next mating of the injected males. Our results show that JHA controls the reproduction of A. ipsilon males by its separate actions on the sex accessory glands and on sexual behaviour.
Are there Distinct Subcellular Populations of Mitochondria in Rainbow Trout Red Muscle?
Authors: Battersby Brendan J. , Moyes Christopher D. 
Published: April 2021

ABSTRACT
Ultrastructural analysis typically shows vertebrate striated muscles to possess mitochondria residing primarily in two locations. One population is interlaced throughout the myofibrils and another occurs directly beneath the cell membrane. The two populations of mitochondria can be separated and studied in vitro. Subsarcolemmal mitochondria (SSmt) are released by mechanical shearing of the tissue, whereas protease treatment is required to release the intermyofibrillar population (IMFmt). These methods were applied to rainbow trout (Oncorhynchus mykiss) red muscle to investigate the possible existence of distinct populations in this tissue. The two populations were very similar in mitochondrial DNA content (mtDNA mg−1 mitochondrial protein) and enzymatically (activities of carnitine palmitoyl transferase, β-hydroxyacyl CoA dehydrogenase, complex I, citrate synthase, cytochrome c oxidase expressed per milligram of mitochondrial protein). Respiration rates were the same for pyruvate and succinate, but IMFmt oxidized palmitoyl carnitine 26 % faster than SSmt (P&lt;0.05). Apart from these minor differences in fatty acyl carnitine oxidation rates, no differences in biochemical or genetic properties were detected between populations. The lack of distinct subcellular populations in fish, in contrast to the situation in mammalian striated muscle, probably relates to the high mitochondrial volume density in fish red muscle.
Photoreception in the planktonic larvae of two species of pullosquilla, a lysiosquilloid stomatopod crustacean
Authors: Jutte Pamela A. , Cronin Thomas W. , Caldwell Roy L. 
Published: April 2021

ABSTRACT
Optical microscopy, electron microscopy and microspectrophotometry were used to characterize pigments in the eyes of planktonic larvae of two species of the lysiosquilloid stomatopod Pullosquilla, P. litoralis and P. thomassini, which live sympatrically in French Polynesia. In contrast to the adult retina, which contains a diverse assortment of visual pigments in the main rhabdoms, the principal photoreceptors throughout the larval eyes of both species were found to contain a single rhodopsin with an absorption maximum (λmax) close to 446 nm. The expression of this visual pigment may survive metamorphosis, since several adult rhodopsins occur at a similar spectral position. The retinas of these planktonic larvae also contain a novel yellow photostable pigment, which is arrayed in a regular pattern at the distal margin of the larval retina. The absorption spectrum of this pigment is well matched to the larval rhodopsin, suggesting that it acts to screen the rhabdoms from stray light. By replacing opaque, black screening pigment, the transparent yellow pigment may act together with a blue iridescent layer in the larval retina to reduce the visual contrast of the larval eye against downwelling and sidewelling light, while simultaneously acting as a retinal screen.
Functional geometry of ciliated tentacular arrays in active suspension feeders
Authors: Grünbaum Daniel , Eyre David , Fogelson Aaron 
Published: April 2021

ABSTRACT
Parallel tentacular structures with lateral cilia that produce suspension-feeding and respiratory flows occur repeatedly in many diverse taxonomic groups. We use a computational hydrodynamic model of flow through ciliated tentacles to simulate flow rates through ciliated tentacle arrays. We examine the functional relationship of one performance measure, flow rate per unit length of array, to geometrical variables, such as cilia length, cilia tip speed and the gap between adjacent tentacles, and to hydrodynamic operating conditions, such as adverse pressure drops across the array. We present a scaling and interpolation scheme to estimate flow rates for a wide range of geometries that span many taxa. Our estimates of flow rate can be coupled with the hydrodynamic characteristics of biological piping systems to understand design trade-offs between components of these systems. As a case study, we apply the model to the blue mussel Mytilus edulis by investigating the effect on performance of changes in the gap between neighboring tentacles. Our model suggests that the observed gaps between tentacles in M. edulis reflect flow-maximizing geometries. Even relatively weak adverse pressure drops have strong effects on flow-maximizing geometries and flow rates. One consequence is that an intermediate range of pressure drops may be unfavorable, suggesting that animals may specialize into high-pressure and low-pressure piping systems associated with differences in organism size and with their strategy for eliminating depleted water.
Air transmissivity of feathers
Authors: Müller Werner , Patone Giannino 
Published: April 2021

ABSTRACT
The flight feathers and their coverts of a European kestrel Falco tinnunculus have been tested for their air transmissivity. The transmissivity was measured in both directions, i.e. from ventral to dorsal and vice versa; the mean difference between the two directions was less than 10 %. However, the transmissivity of the inner versus outer vanes of the remiges and coverts differed significantly, with the outer vanes being more transmissive than the inner vanes. A functional interpretation of the different transmissivities of the inner and outer vanes is given, and we propose that its significance lies in the formation of a smooth, continuous wing surface. The individual feathers are pushed firmly towards one another as a result of the different transmissivities, which cause a pressure gradient to build up from the less-transmissive inner vane towards the overlying, more-transmissive outer vane of the adjacent feather. In another test series, the transmissivity of the flight and covert feathers of 27 species was measured; the differences found between species were small.
Underwater punting by an intertidal crab: a novel gait revealed by the kinematics of pedestrian locomotion in air versus water
Authors: Martinez Marlene M. , Full R. J. , Koehl M. A. R. 
Published: April 2021

ABSTRACT
As an animal moves from air to water, its effective weight is substantially reduced by buoyancy while the fluid-dynamic forces (e.g. lift and drag) are increased 800-fold. The changes in the magnitude of these forces are likely to have substantial consequences for locomotion as well as for resistance to being overturned. We began our investigation of aquatic pedestrian locomotion by quantifying the kinematics of crabs at slow speeds where buoyant forces are more important relative to fluid-dynamic forces. At these slow speeds, we used reduced-gravity models of terrestrial locomotion to predict trends in the kinematics of aquatic pedestrian locomotion. Using these models, we expected animals in water to use running gaits even at slow speeds. We hypothesized that aquatic pedestrians would (1) use lower duty factors and longer periods with no ground contact, (2) demonstrate more variable kinematics and (3) adopt wider stances for increased horizontal stability against fluid-dynamic forces than animals moving at the same speed on land. We tested these predictions by measuring the three-dimensional kinematics of intertidal rock crabs (Grapsus tenuicrustatus) locomoting through water and air at the same velocity (9 cm s−1) over a flat substratum. As predicted from reduced-gravity models of running, crabs moving under water showed decreased leg contact times and duty factors relative to locomotion on land. In water, the legs cycled intermittently, fewer legs were in contact with the substratum and leg kinematics were much more variable than on land. The width of the crab’s stance was 19 % greater in water than in air, thereby increasing stability against overturning by hydrodynamic forces. Rather than an alternating tetrapod or metachronal wave gait, crabs in water used a novel gait we termed ‘underwater punting’, characterized by alternating phases of generating thrust against the substratum and gliding through the water.
The myth of scorpion suicide: are scorpions insensitive to their own venom?
Authors: Legros Christian , Martin-Eauclaire Marie-France , Cattaert Daniel 
Published: April 2021

ABSTRACT
The resistance of the scorpion Androctonus australis to its own venom, as well as to the venom of other species, was investigated. A comparison of the electrical and pharmacological properties of muscle and nerve fibres from Androctonus australis with those from the crayfish Procambarus clarkii enabled us to understand the lack of effect of scorpion venom (110–180 μg ml−1) and purified toxins, which are active on voltage-gated Na+ and K+ channels, Ca2+-activated K+ channels, on scorpion tissues. Voltage-clamp experiments showed that peptide K+ channel blockers from scorpion and snake have no effect on currents in muscle and nerve fibres from either scorpions or crayfish. The scorpion toxin kaliotoxin (KTX), a specific blocker of Kv1.1 and Kv1.3 K+ channels, had no effect on muscle fibres of A. australis (2 μmol l−1) or P. clarkii (400 nmol l−1). Similarly, charybdotoxin (ChTX) had no effect on the muscle fibres of A. australis (10 μmol l−1) or P. clarkii (200 nmol l−1) and neither did the snake toxin dendrotoxin (DTX) at concentrations of 100 nmol l−1 in A. australis and 200 nmol l−1 in P. clarkii. These three toxins (KTX, ChTX and DTX) did not block K+ currents recorded from nerve fibres in P. clarkii. The pharmacology of the K+ channels in these two arthropods did not conform to that previously described for K+ channels in other species. Current-clamp experiments clearly indicated that the venom of A. australis (50 μg ml−1) had no effect on the shape of the action potential recorded from nerve cord axons from A. australis. At a concentration of 50 μg ml−1, A. australis venom greatly prolonged the action potential in the crayfish giant axon. The absence of any effect of the anti-mammal α-toxin AaH II (100 nmol l−1) and the anti-insect toxin AaH IT1 (100 nmol l−1) on scorpion nerve fibres revealed strong pharmacological differences between the voltage-gated Na+ channels of scorpion and crayfish. We conclude that the venom from A. australis is pharmacologically inactive on K+ channels and on voltage-sensitive Na+ channels from this scorpion.
Cyclic changes in the tension of the contractile vacuole complex membrane control its exocytotic cycle
Authors: Tominaga Takashi , Allen Richard D. , Naitoh Yutaka 
Published: April 2021

ABSTRACT
The freshwater protozoan Paramecium multimicronucleatum maintains a constant cytosolic osmolarity through the exocytotic activity of its contractile vacuole complex. The contractile vacuole (CV) expels the excess cytosolic water, acquired osmotically, to the exterior of the cell at fairly regular intervals. In a single exocytotic cycle, the CV swells as the cytosolic water enters the vacuole, rounds up, and then rapidly shrinks as the fluid is expelled through the pore of the CV. The exocytotic activity of the CV complex can sometimes be slowed and distorted by microelectrode impalement. Using a CV with exocytotic activity slowed in this way makes it possible to determine more precisely the time course of changes in the exocytotic-activity-related membrane capacitance and membrane potential of the organelle. We have clearly demonstrated that the radial arms of the CV were always severed after the CV had exhibited rounding. Microelectrode impalement sometimes caused a failure of the CV pore to open after rounding up, so that the CV entered the next fluid-filling phase without expelling its fluid. The radial arms remained severed from the CV during such prolonged rounding phases and then rejoined the CV at the start of the next fluid-filling phase. The rounding of the CV corresponds to an increase in the tension of the CV membrane. This suggested that the periodic development of increased tension in the CV membrane might be the primary event leading to periodic severing of the radial arms and the opening of the pore. We then observed that the CV and its radial arms sometimes became fragmented into vesicles when the cell had been mechanically ruptured in a salt solution. Many of the resulting in vitro vesicles showed periodic rounding and slackening which occurred at different times so that they were out of phase one with the other. This indicates that the membranes of the CV and the radial arms maintain their ability to develop a periodic increase in tension even after the cell has been ruptured. We propose the hypothesis that the CV membrane (together with its associated cytoskeletal structures) possesses a mechanism by which its tension is periodically increased. Such a periodic change in membrane tension may govern the exocytotic cycle of the contractile vacuole complex by increasing the tension to a point that the radial arms sever from the CV and the pore opens. Conversely, a decrease in the tension causes closure of the pore and rejoining of the radial arms to the CV. Transformation of the CV membrane into 40 nm tubules is assumed to be responsible for the development of tension in the planar CV membrane. The causes of this periodic tubulation must now be sought.
Differential air sac pressures in diving tufted ducks Aythya fuligula
Authors: Boggs Dona F. , Butler Patrick J. , Wallace Stacy E. 
Published: April 2021

ABSTRACT
The air in the respiratory system of diving birds contains a large proportion of the body oxygen stores, but it must be in the lungs for gas exchange with blood to occur. To test the hypothesis that locomotion induces mixing of air sac air with lung air during dives, we measured differential pressures between the interclavicular and posterior thoracic air sacs in five diving tufted ducks Aythya fuligula. The peak differential pressure between posterior thoracic and interclavicular air sacs, 0.49±0.13 kPa (mean ± S.D.), varied substantially during underwater paddling as indicated by gastrocnemius muscle activity. These data support the hypothesis that locomotion, perhaps through associated abdominal muscle activity, intermittently compresses the posterior air sacs more than the anterior ones. The result is differential pressure fluctuations that might induce the movement of air between air sacs and through the lungs during dives.