bluuebunny/crossref_metadata_2025_split huggingface dataset:
Jumping performance of hylid frogs measured with high-speed cine film
Authors: Marsh Richard L. , John-Alder Henry B. 
Published: April 2021

ABSTRACT
Jumping performance at 20 °C was assessed in five species of hylid frogs using high-speed cine film. Mean takeoff velocities (Vt) varied from 1.5 to 2.4 m s−1 among the species. Peak Vt varied from 1.9 to 2.9 m s−1. Body-mass-specific power output averaged over the entire takeoff period varied from 29 to 91 W kg−1 during the jumps with the highest takeoff velocities. These values are similar to those predicted from jumping distance. As the mass of muscles available to power the jump probably amounts to no more than 17 % of the body mass, average muscle-mass-specific power can be over 500 W kg−1. The performance during jumping is even more impressive in view of the fact that the peak power during takeoff is about twice the average power. These frogs must use elastic storage to redistribute power during takeoff to produce the peak power required and may use pre-storage of elastic energy to boost the average power available.
Role of urea and methylamines in buoyancy of elasmobranchs
Authors: Withers Philip C. , Morrison Garrick , Hefter Glenn T. , Pang Tek-Siong 
Published: April 2021

ABSTRACT
The possible role of urea and trimethylamine oxide (TMAO) in providing positive buoyancy has been examined for elasmobranch fishes. TMAO has a considerably lower density than an equimolar solution of urea, and solutions of both TMAO and urea are considerably less dense than equimolar solutions of most other body fluid solutes. The body fluid composition of three elasmobranchs, the whiskery shark Furgaleus ventralis, the black whaler shark Carcharhinus obscurus and the shovelnosed ray Aptychotremata vincentiana, is typical for marine elasmobranchs, with plasma concentrations of about 260 mmol l−1 Na+, 250 mmol l−1 Cl−, 340 mmol l−1 urea and 70 mmol l−1 trimethylamine oxide. A plasma density of 1.015 was calculated for the whaler shark (from the concentrations, relative molecular masses and absolute molal volumes of plasma solutes), which would contribute a positive lift of 8.45 g l−1. There is a large positive contribution to buoyancy by urea (3.7 g l−1), trimethylamine oxide (1.8 g l−1) and Cl− (4.0 g l−1), whereas slight negative buoyancy is conferred by Na+ (−0.8g l−1). Divalent cations (Ca2+, Mg2+) contribute minimal negative buoyancy (about −0.1 g l−1 each) despite their rather negative partial molal volumes, because of their low concentrations. Muscle fluids contain about 40 mmol l−1 Cl−, 365 mmol l−1 urea, 160 mmol l−1 trimethylamine oxide, 16 mmol l−1 betaine and 69 mmol l−1 sarcosine. The organic solutes contribute about 12.1 g l−1 lift. Although urea and TMAO act as balancing osmolytes, and TMAO as a counteracting solute, a positive buoyancy role must be considered as a further adaptive function of urea and TMAO accumulation in chondrichthyean fishes.
An investigation of the midgut K+ pump of the tobacco hornworm (manduca Sexta) using specific inhibitors and amphotericin B
Authors: Schirmanns K. , Zeiske W. 
Published: April 2021

ABSTRACT
Active K+ secretion in isolated posterior midguts of Manduca sexta was studied by measuring the short-circuit current. One aim of this study was to verify the postulate from biochemical reports that the cooperative apical arrangement of a vacuolar-type H+-ATPase (V-ATPase) and a K+/H+ antiporter drive the short-circuit current. Hence, we tested several specific inhibitors of the V-ATPase on the in vitro midgut preparation. Nitrate, bafilomycin A1, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD-Cl) and amiloride all reduced the short-circuit current. This suggests that the H+-ATPase is involved in transepithelial K+ secretion. However, even at relatively high doses of these inhibitors, the block of the short-circuit current was not complete. Two other agents, thallium ions (Tl+, at millimolar concentrations) and trimethyltin chloride (TMT, 50 μmol l−1), did abolish the short-circuit current.
Apical, but not basal, use of the ionophore amphotericin B largely eliminated the short-circuit current. This supports the view that the current-generating source resides in the apical membranes. An apical (and probably intracellular) site of action for NO3−, Tl+ and TMT is suggested by the observation that basal amphotericin B is needed for blockage by NO3− but does not, however, influence the effect of Tl+ and TMT. Likely sites of action are the V-ATPase (for nitrate and TMT) and the K+/H+ antiporter (for Tl+).
The effects of muscle fatigue on bone strain
Authors: Yoshikawa Tomoaki , Mori Satoshi , Santiesteban A. J. , Sun T. C. , Hafstad Else , Chen Jie , Burr David B. 
Published: April 2021

ABSTRACT
There is anecdotal evidence that bone strains may increase to the point that bone becomes susceptible to rapid failure when muscles become fatigued. To determine whether neuromuscular response could be a factor in accelerating bone failure, we tested the hypothesis that muscle fatigue causes a significant increase in peak principal and shear strains in bone. Ten adult foxhounds were subjected to rigorous exercise that caused muscular fatigue while myoelectrical activity of the quadriceps and hamstrings and strain on the distal tibia were monitored simultaneously. Ground reaction forces on the dog hindlimbs were measured before and after strain gauges had been applied to the tibia. The data show a significant shift to lower median myoelectrical frequencies in the quadriceps, indicating muscular fatigue, following the 20 min exercise period. In conjunction with this shift, peak principal and shear strains increased on both compressive and tensile cortices of the tibia and shear strain on the tensile cortex increased significantly (P=0.02). The largest changes were along the anterior and antero-lateral surfaces of the tibia, where peak principal strain increased by an average of 26–35 % following muscular fatigue. The cross-sectional strain distribution was calculated at the gauge site at peak strain at the beginning of the exercise period and at peak strain after 20 min of exercise. These data show a change in strain distribution when muscle becomes fatigued. Strains on the posterior cortex of the bone showed the greatest change. Correlation analysis demonstrated a significant inverse association between median myoelectrical frequency and bone strain after 20 min of exercise (Spearman r2=1.00; P=0.05). These data show that muscle fatigue may be associated with increased bone strain.
Architecture and composition of the muscles that drive stomatopod eye movements
Authors: Jones Jeremy 
Published: April 2021

ABSTRACT
The peculiar structure of the stomatopod eye requires it to make complicated movements. These include slow ‘scans’, which relate to the animal’s colour vision system, as well as faster ‘saccades’. The myology of the eyecup is investigated and shown to consist of eight individual muscles which are divided, on kinematic grounds, into six functional groups. These groups form three pairs of dominant prime movers, with each having primary control over one of the eye movement axes (longitude, latitude and bearing). This is important as it allows each rotational axis to move independently of the other two. Histochemical typing reveals at least four distinct classes of fibre within each muscle. The relationship between the number of types of fibre and classes of eye movement is discussed, as are the implications of coordinate prime movers for neuromuscular control.
Motor neurones of the crayfish walking system possess tea+-Revealed regenerative electrical properties
Authors: Cattaert Daniel , Araque Alfonso , Buno Washington , Clarac François 
Published: April 2021

ABSTRACT
In crustaceans, some motor neurones (MNs) have been shown to be part of the central pattern generator in the stomatogastric system (Harris-Warrick et al. 1992; Moulins, 1990), the swimmeret system (Heitler, 1978) or the walking system (Chrachri and Clarac, 1990). These MNs induce changes in the central rhythm when depolarized and are conditional oscillators in the stomatogastric ganglion. Moreover, in the walking system, rhythmic activity can be triggered by muscarinic cholinergic agonists (Chrachri and Clarac, 1987). We have recently analyzed the role of muscarinic receptors in crayfish walking leg MNs (D. Cattaert and A. Araque, in preparation) and demonstrated that oxotremorine, a muscarinic agonist, evoked long-lasting depolarizing responses associated with an increased input resistance. The outward current blocked by oxotremorine is likely to be carried by K+, as is the case for the M current (IM) in vertebrates (Brown and Adams, 1980). In most neurones, K+ conductances play a principal role in maintaining the membrane potential at rest: for example, IM is active at the resting membrane potential, thus contributing to its maintenance, and the ‘delayed-rectifier’ (IK) assists the fast repolarization after an action potential. Some K+ conductances are Ca2+-dependent (IK,Ca) and are activated by an increase in internal Ca2+ concentration. In such cases, Ca2+ currents may result in hyperpolarization of the neurone through activation of IK,Ca. In opposition to these K+ currents, the direct effect of Na+ and Ca2+ conductances is to depolarize the neurone. For example, the persistant Na+ current (INap) that is responsible for the slow subthreshold depolarization termed slow pre-potentials (Gestrelius et al. 1983; Leung and Yim, 1991) participates in the formation of pacemaker depolarization (Barrio et al. 1991) and generates plateau-type responses in control conditions (Barrio et al. 1991; Llinas and Sugimori, 1980). Similarly Ca2+ or non-specific (Na+/Ca2+) conductances generate such events in Aplysia californica burster neurones (Adams and Benson, 1985), crustacean cardiac ganglion (Tazaki and Cooke, 1990), insect neurones (Hancox and Pitman, 1991) and crustacean stomatogastric ganglion (Kiehn and Harris-Warrick, 1992). Since crustacean MNs can participate in rhythm production, such depolarizing conductances may exist in most of them and may contribute to the long-lasting MN depolarizations and spike bursts present during locomotion.
Gas transport in the haemolymph of arachnids: II. Carbon dioxide transport and acid–Base balance
Authors: Paul R. J. , Pfeffer-Seidl A. , Efinger R. , Pörtner H. O. , Storz H. 
Published: April 2021

ABSTRACT
The relationships between and pH were determined in cell-free undiluted haemolymph of the arachnids Eurypelma californicum, Pandinus imperator and Cupiennius salei. The pH/bicarbonate diagrams and the CO2 equilibrium curves were calculated, using the Henderson–Hasselbalch equation, for haemolymph sampled at rest and during recovery from exercise. The calculations of solubility and dissociation constant (pK‴) were based on additional ion concentration measurements. Blood gas analyses corroborate these results: after locomotor activity, there is a metabolic acidosis linked to the accumulation of lactate in the haemolymph. The concentration of bicarbonate in the haemolymph of resting individuals is quite different in the three species and is related to the extent of post-exercise bicarbonate depletion. During early recovery, buffering in the haemolymph strongly depends upon CO2 release. Potassium and magnesium concentrations in the haemolymph increase after exercise. During cold-acclimation (to 10 °C), there is a metabolic acidosis in the tarantula’s haemolymph that is linked to the accumulation of acetate.
Adrenergic control of swimbladder perfusion in the european eel Anguilla anguilla
Authors: Pelster Bernd 
Published: April 2021

ABSTRACT
Adrenergic control of swimbladder blood flow was analysed in blood-perfused preparations of the European eel as well as in situ by recording the changes in swimbladder blood flow and blood pressure following an injection of catecholamine into the dorsal artery.
In blood-perfused swimbladder preparations, injection of the a-adrenergic agonist phenylephrine into the perfusion loop caused a marked dose-dependent increase in perfusion pressure at constant flow, while injection of the β-agonist isoproterenol slightly decreased perfusion pressure. The β-effect was not as pronounced as the a-adrenergic vasoconstriction and was observed only during the first application of catecholamine in each preparation.
In situ injection of adrenaline (final concentration 10−8-10−9 mol kg−1 body mass) into the dorsal aorta caused a dose-dependent transient increase in dorsal aortic blood pressure and in cardiac output which, after 5–10 min, returned to resting levels. Swimbladder perfusion also increased initially after an injection of adrenaline, but after about 1–2 min suddenly decreased and then slowly recovered to preinjection levels. Following the injection of adrenaline into the dorsal aorta, blood pressure changes in vessels at the swimbladder pole of the rete mirabile revealed a similar biphasic pattern with an initial increase, a subsequent decrease and a slow return to preinjection levels, while pressure in the arterial influx vessel of the rete resembled dorsal aortic pressure.
After injection of the β-blocker propranolol, adrenaline evoked a smaller initial increase in blood flow, but the subsequent reduction in flow was even more pronounced. Injection, in addition, of the a-adrenergic blocker phentolamine abolished the sharp adrenaline-induced decrease in swimbladder perfusion.
It is concluded that a- and β-adrenergically controlled resistance vessels are located close to the rete mirabile, probably at the arterial entrance into the rete. These vessels control perfusion of the rete mirabile and of the swimbladder and are thus involved in the control of gas deposition into the swimbladder.
Energy savings in formation flight of pink-footed geese
Authors: Cutts C. J. , Speakman J. R. 
Published: April 2021

ABSTRACT
Fifty-four skeins of pink-footed geese (Anser brachyrhynchus) were photographed from directly underneath to eliminate the effects of perspective distortion, and the wing-tip spacings (the distance between adjacent birds’ wing tips perpendicular to the flight path at maximum wingspan) and depths (the distance between adjacent birds’ body centres parallel to the flight path) were measured at the same time as local wind speeds. The photographs were used to test for savings in induced power from wing positioning relative to the predicted positions of vortices generated by other wings, using a theoretical model. The mean wing-tip spacing corresponded to a saving in induced power of 14 %, less than one-third of the maximum possible. The saving in total power might be as low as 2.4 %. The high variation in wing-tip spacing suggests that pink-footed geese found difficulty maintaining position and thus adopted a strategy of flying outboard of the optimal position that maximises savings. This may minimise the risk of straying into a zone where savings are negative. There was a significant correlation between depth and wing-tip spacing, supporting an alternative communication hypothesis, whereby the birds position themselves to obtain maximum information on their neighbour’s position. In high winds, there was little change in wing-tip spacing variation but a decrease in depth variation, suggesting a shift towards more regularly spaced skeins.
Determination of protein synthesis in rainbow trout, Oncorhynchus mykiss, using a stable isotope
Authors: Carter C. G. , Owen S. F. , He Z.-Y. , Watt P. W. , Scrimgeour C. , Houlihan D. F. , Rennie M. J. 
Published: April 2021

ABSTRACT
It has been suggested (Houlihan, 1991) that the consumption of 1 g of protein in a variety of species of fish stimulates the synthesis of, approximately, an equal amount of protein. Although synthesis of protein may account for as much as 40 % of the whole-animal oxygen consumption (Lyndon et al. 1992), only about 30 % of the synthesized proteins are retained as growth (Houlihan et al. 1988; Carter et al. 1993a,b). Thus, one focus of attention is the potential advantage gained by fish in allocating a considerable proportion of assimilated energy to protein turnover in contrast to relatively low-cost, low-turnover protein growth (Houlihan et al. 1993). Rates of protein synthesis in several species of fish have been measured using radioactively labelled amino acids, frequently given as a flooding dose (reviewed by Fauconneau, 1985; Houlihan, 1991). These measurements cannot be made for longer than a few hours because of the decline in specific radioactivity in the amino acid free pool. However, as protein synthesis rates vary during the course of a day as a result of the post-prandial stimulation, and since radiolabelled amino acid methodology is invasive, short-term and terminal, it has been difficult to be certain of the relationship between protein growth measured in the long term and protein synthesis rates measured in the short term. This paper addresses these problems by developing a method using 15N in orally administered protein to measure protein synthesis rates in fish over relatively long periods, the aim being to use procedures that are as non-invasive and repeatable as possible. The use of stable isotopes to measure protein metabolism is well established in terrestrial mammals (see Rennie et al. 1991; Wolfe, 1992), but to our knowledge the only published data for aquatic ectotherms are on the blue mussel (Mytilus edulis L.) (Hawkins, 1985). In the present study, rates of protein synthesis of individual rainbow trout [Oncorhynchus mykiss (Walbaum)] were calculated from the enrichment of excreted ammonia with 15N over the 48 h following the feeding of a single meal (dose) containing protein uniformly labelled with 15N by use of an end-point stochastic model (Waterlow et al. 1978; Wolfe, 1992). Application of this type of modelling would appear to be ideal for measuring ammonotelic fish nitrogen metabolism since, unlike the situation in mammals, the catabolic flux of amino acids through urea is very small. Further, ammonia is excreted directly into the surrounding water via the gills and is not stored for any length of time, in contrast to the situation in mammals, so the rate of tracer appearance is easily measurable.
Implications of hyperglycemia for post-exercise resynthesis of glycogen in trout skeletal muscle
Authors: West Timothy G. , Schulte Patricia M. , Hochachka Peter W. 
Published: April 2021

ABSTRACT
Rates of whole-body glucose turnover and muscle-specific glucose utilization were determined in rainbow trout (Oncorhynchus mykiss) at rest and at intervals during recovery from burst swimming. Plasma glucose level was high in the experimental animals (range 6–38 mmol l−1), but hyperglycemia was not related specifically to exercise. Estimated glucose turnover, 19.3±2.6 (rest) and 15.8±3.9 μmol min−1 kg−1 (recovery), was also highly variable, but was linearly associated with plasma glucose concentration (turnover=0.97[glucose]+0.57, r=0.93) in both resting and recovering fish. While utilization of glucose in the whole animal was clearly responsive to plasma glucose availability, estimated total skeletal muscle disposal of glucose accounted for less than 15 % of glucose turnover, indicating that glucose was utilized largely by tissues other than locomotory muscle. Rates of glucose utilization in white muscle (range 0.5–4 nmol min−1 g−1) provide direct evidence that glucose, regardless of plasma concentration, accounted for less than 10 % of glycogen repletion during exercise recovery. In red muscle, glucose uptake was influenced by plasma glucose level below 10–12 mmol l−1 (utilization range 1–15 nmol min−1 g−1), but was independent of glucose concentration above about 12 mmol l−1 (utilization plateaued at 15–20 nmol min−1 g−1). Trout red muscle is similar to mammalian white muscle in the sense that glucose is estimated to account incompletely for glycogen restoration (25–60 %), suggesting dependence on both glycogenesis and glyconeogenesis during recovery. It is concluded that hyperglycemia may be important to the pattern of substrate incorporation into red muscle glycogen and to the rate of repletion observed, but glucose availability has, as predicted from earlier indirect studies, little relevance to white muscle glycogen restoration. The regulatory mechanisms that govern apparently very high glucose turnover rates during extreme hyperglycemia, concomitant with low disposal rates in skeletal muscle, require further investigation.
Immunolocalization of an antigen associated with the invertebrate electrogenic 2Na+/1H+ antiporter
Authors: Kimura Claudine , Ahearn Gregory A. , Busquets-Turner Liz , Haley S. R. , Nagao Cherie , Couet H. Gert De 
Published: April 2021

ABSTRACT
Epithelial plasma membranes from crustacean gut, kidney and gills have been shown recently to display an electrogenic 2Na+/1H+ antiporter that differs considerably in its physiological properties from the vertebrate electroneutral 1Na+/1H+ exchange paradigm. In this study, we describe the histological and cytological localization of an antigen associated with invertebrate electrogenic 2Na+/1H+ antiport in lobster (Homarus americanus) tissues using a monoclonal antibody (MAb 11) raised in mice against purified brush border membranes of the hepatopancreatic epithelium. Previous work showed that MAb 11 inhibited electrogenic 2Na+/1H+ and Ca2+/H+ exchange by hepatopancreatic brush border membrane vesicles, but was without effect on Na+-dependent D-glucose transport, suggesting a restricted inhibitory specificity to the cation exchanger. MAb 11 binding occurred at hepatopancreatic epithelial R-cell brush border membranes, at plasma membranes of the antennal gland and gill podocytes, and at vacuolar membranes of hepatopancreatic B-and R-cells, gill nephrocytes and epithelial cells of the antennal gland labyrinth and gill lamellae, as assessed by FITC-labelled secondary antibodies. Control FITC-labelled antibodies raised in mice against vertebrate keratin proteins displayed only weak non-specific binding to the tissues and cells responding intensely to MAb 11, supporting the specific nature of MAb 11 binding to its cognate antigen. The broad histological and cytological distribution of MAb 11 binding to plasma membranes and vacuolar membranes from several lobster organ systems suggests that the physiological activities regulated by its antigen, possibly an element of the invertebrate electrogenic cation exchanger, may be diverse.
Studies on Nitrogen Fixation by Blue-Green Algae
Authors: Fogg G. E. 
Published: April 2021

ABSTRACT
Recent work, particularly that of De (1939), has shown that some blue-green algae are capable of utilizing the free nitrogen of the atmosphere in the synthesis of cell material. Much further work will be necessary, however, before the importance of nitrogen fixation by these organisms in nature can be estimated, our knowledge both of the distribution of the property within the group of the Myxophyceae and of the physiology of the process being very vague.
The Effects of Some Oestrogenic Substances and Cyclic Hydrocarbons On the Rate of Growth of Cells
Authors: Calcutt G. 
Published: April 2021

ABSTRACT
Oestrone in dilutions of 10− 5 to 10− 7 was found to stimulate the growth of Colpidium sp. over periods of about 24 hr. ; with longer exposures retardation and death occurred. Higher concentrations of the oestrone were found to be lethal; whilst lower ones had no detectable effect. Owing to the impossibility of obtaining suitable solutions of oestradiol benzoate and stilboestrol anomalous results were obtained.