bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intra- and Extracellular Use and Evaluation of Ammonium-Selective Microelectrodes
Authors: Fresser F. , Moser H. , Mair N. 
Published: April 2021

ABSTRACT
An NH4+-selective membrane for microelectrodes (NH4ISMs) was tested under ‘biological conditions’ in normal Astacus saline (NAS), two simulated intracellular salines (SIS) and the sensory neurone of the crayfish stretch receptor. The effects of several physiological variables on intracellular NH4+ measurements were tested in vitro. Changes in the background K+ and Na+ concentrations, the ratio K+/Na+, pH, ionic strength, osmotic pressure and volume were examined. Phenomena specific for NH4ISMs, such as a positive potential shift, an undershoot and a difference between pre-and postcalibration curves are described and discussed. We propose to consider the values of intracellular NH4+ concentration as apparent. The detection limit of the NH4ISM is closely related to background K+ concentration. It is in the region of 0.1mmoll-1 NH4+ in NAS (at 5.4mmoll-1 K+) and about 5 mmol l-1 in SIS (at 194 mmol l-1 K+). When comparing levels of intracellular NH4+, either measured directly by NH4ISM or calculated, according to Boron and de Weer (J. gen. Physiol. 67, 91–112), from simultaneously recorded pHi, we found that [NH4+] i obtained by direct measurement differed quantitatively from that of the Boron and de Weer model, but that some of the qualitative and temporal aspects of the model agreed with our results. The quantitative difference in [NH4+]i determined by the two methods cannot be attributed to temporal and/or quantitative limitations of the NH4ISM.
An X-Ray Study of the Influence of Vasoactive Intestinal Polypeptide and Substance p on the Secretion of gas Into the Swimbladder of a Teleost Gadus Morhua
Authors: Lundin Kersti , Holmgren Susanne 
Published: April 2021

ABSTRACT
The rate of gas secretion into the swimbladder of the Atlantic cod Gadus tnorhua was studied with X-ray measurements of swimbladder size. A direct correlation was found between the area of the swimbladder in the X-ray photographs and the volume of the swimbladder. Removal of the swimbladder gas stimulates the fish to produce new gas, and the mean rate of refilling of the swimbladder in the cod was found to be 1.5 ml kg-1 h-1 during the first 24 h. The influence of drugs and of vagotomy on the rate of filling was measured. Gas secretion was completely inhibited by vagotomy and partly inhibited by injections of atropine or porcine vasoactive intestinal polypeptide (VIP). Substance P and VIP both increased the rate of secretion in atropinized fish, while 5-hydroxytryptamine (5-HT) and noradrenaline did not affect the rate of filling in either control or atropinized fish. Carbachol, VIP and substance P did not induce secretion in vagotomized fish, indicating that certain other fibres in the vagus might be necessary for gas secretion. It is concluded that a VIP-like and a substance-P-like peptide might be involved in the control of the secretion of gas in the cod swimbladder, VIP by a neuronal mechanism and substance P by a neuronal and/or humoral mechanism.
Adrenergic Inhibition of Carbon Dioxide Excretion by Trout Red Blood Cells In Vitro is Mediated by Activation of Na+/H+ Exchange
Authors: Perry S. F. , Wood C. M. , Thomas S. , Walsh P. J. 
Published: April 2021

ABSTRACT
We have used a sensitive new technique to assess the mechanism(s) of adrenergic inhibition of rainbow trout (Oncorhynchus mykiss) red blood cell (RBC) carbon dioxide excretion in vitro. The effect was only apparent using blood acidified to simulate metabolic acidosis. Red blood cell CO2 excretion was inhibited in a dose-dependent manner by physiologically relevant concentrations of noradrenaline (10– 1000 nmol l−1) or adrenaline (100– 1000 nmol l−1). The β -adrenoceptor antagonist propranolol abolished the inhibitory effect of noradrenaline, whereas the ir-adrenoceptor antagonist phentolamine was without effect. The action of noradrenaline on RBC CO2 excretion was mimicked by the β-adrenoceptor agonist isoproterenol, but not by the α-adrenoceptor agonist phenylephrine. Therefore, adrenergic inhibition of CO2 excretion is mediated by RBC β -adrenoceptors, presumably of the β1 subtype. The Na+/H+ exchange inhibitor amiloride effectively blocked adrenergic stimulation of Na+/H+ exchange (as indicated from measurements of pHe and RBC pHi) and entirely prevented the inhibition of CO2 excretion. Noradrenaline significantly reduced the rate of CO2 excretion even in the presence of the C1−/HCO3− exchange inhibitor SITS. Therefore, adrenergic inhibition of CO2 excretion is accomplished via activation of RBC Na+/H+ exchange rather than by a direct inhibition of CC/ HCO3− exchange. The observed relationship between CO2 excretion rates and the RBC transmembrane pH difference (pHe —pHi) and the occurrence of the inhibition only at low pHe provide further evidence of the linkage with RBC Na+/H+ exchange. We suggest that adrenergic activation of RBC Na+/H+ exchange impedes CO2 excretion by causing a rise in intracellular HCO3−levels concurrent with a reduction of intracellular . The net result is a reduced gradient for HCO3− entry into the RBC in conjunction with a diminution of the outwardly directed gradient. Thus, the rate of formation of CO2 from the dehydration of plasma HCO3− is reduced and, in turn, a portion of this CO2 is not excreted but recycled through the red blood cell.
Power Output of Fish Muscle Fibres Performing Oscillatory Work: Effects of Acute and Seasonal Temperature Change
Authors: Johnson Timothy P. , Johnston Ian A. 
Published: April 2021

ABSTRACT
Fast muscle fibres were isolated from the abdominal myotomes of the short-horned sculpin Myoxocephalus scorpius L. Sinusoidal length changes were imposed about resting muscle length and fibres were stimulated at a selected phase during the strain cycle. The work output per cycle was calculated from the area of the resulting force-position loops. The strain amplitude required for maximum work per cycle had a distinct optimum at ±5 % of resting length, which was independent of temperature. Maximum positive work loops were obtained by retarding the stimulus relative to the start of the length-change cycle by 30° (full cycle=360°). The maximum negative work output was obtained with a 210° stimulus phase shift. At intermediate stimulus phase shifts, work loops became complex with both positive (anticlockwise) and negative (clockwise) components. The number and timing of stimuli were adjusted, at constant strain amplitude (±5 % of resting muscle length), to optimize net positive work output over a range of cycle frequencies. The cycle frequency required for maximum power output (work per cycle times cycle frequency) increased from around 5-7 Hz at 4°C to 9-13 Hz at 15°C. The maximum tension generated per cycle at 15 °C was around two times higher at all cycle frequencies in summer-relative to winter-acclimatized fish. Fast muscle fibres from summer fish produced consistently higher tensions at 4°C, but the differences were only significant at 15 Hz. Acclimatization also modified the relationship between peak length and peak force at 4 °C and 15 °C. The maximum power output of muscle fibres showed little seasonal variation at 4°C and was in the range 20-25Wkg-1. In contrast, at 15°C, maximum muscle power output increased from 9 Wkg-1 in the winter-to 30 Wkg-1 in the summer-acclimatized fish.
Routes of Transpiratory Water Loss in a Dry-Habitat Tenebrionid Beetle
Authors: Zachariassen Karl Erik 
Published: April 2021

ABSTRACT
Routes of evaporative water loss in the tenebrionid beetle Phrynocolus petrosus Gerstaecker from dry savanna in East Africa were investigated. The humidity of the air surrounding the abdomen, the air surrounding the head and pronotum and the air inside the subelytral cavity was varied independently, and the effects on organismal rate of water loss were observed.
The rate of organismal water loss dropped when the humidity around the head and pronotum and inside the subelytral cavity increased. Saturation of these air compartments, which both exchange respiratory gases with the tracheae through the spiracles, reduced the organismal rate of water loss by more than 80 %, even when the large abdominal surface was surrounded by dry air. The results indicate that the transcuticular water loss makes up only about 20% of the total transpiratory water loss in these beetles, i.e. transcuticular water permeability is very low.
The results also indicate that the average air humidity inside the subelytral cavity of normal intact beetles is close to saturation. Water loss from the subelytral chamber is reduced accordingly, and appears to make up less than 10% of the total transpiratory water loss. The water loss over the pronotal spiracles amounts to about 70 %, and is thus the dominant component of transpiratory water loss in these beetles.
The Fate of Calcium in The Diet of Rhodnius Prolixus: Storage in Concretion Bodies in the Malpighian Tubules
Authors: Maddrell S. H. P. , Whittembury G. , Mooney R. L. , Harrison J. B. , Overton J. A. , Rodriguez B. 
Published: April 2021

ABSTRACT
We have investigated the fate of the large amounts of calcium ingested by Rhodnius prolixus in its meals of blood. 45Ca2+ injected into the haemolymph or fed to fifth-stage Rhodnius reared on rabbits is accumulated at high concentrations in the cells of the upper Malpighian tubules; very little is excreted from the body. This 45Ca2+ accumulation goes on continuously for at least 12 days and the rate of uptake is increased several-fold within 3–4 days of a meal. The extent of calcium accumulation in tubule cells is correlated with the presence of intracellular membrane-bound concretion bodies, which are therefore likely sites of calcium deposition. X-ray diffraction showed that the calcium deposits are non-crystalline. Tubules from rabbit-fed fifth-stage Rhodnius contain 410 mmol l −1 calcium; in those from chicken-fed insects the calcium concentration is over Imoll−1; and in those fed in vitro on heparinised low-K+ sheep blood the calcium concentration is only 21 mmol l−1. The concentration of calcium in the haemolymph in all these insects was 8 mmol I−1 and its activity determined by an ion-selective electrode was 2.5 mmol l−1. 45Ca2+ deposited in the tubules is readily exchangeable, but the efflux preferentially passes to the haemolymph side of the tubule epithelium. The ability to sequester calcium in the Malpighian tubules may prevent calcium from interfering with reabsorptive processes in the rectum.
Oxygen Supply and In Vitro Performance of the Systemic Heart of Octopus Vulgaris: Effects of Haemocyanin
Authors: Agnisola C. , Houlihan D. F. 
Published: April 2021

ABSTRACT
The effect of increasing oxygen supply on the perfused systemic heart of Octopus vulgaris (Lam.) by using oxygenated or haemocyanin-containing perfusates was investigated. Providing aerated blood or seawater solutions of haemocyanin that were comparable with blood in oxygen-carrying capacity improved the performance of the isolated heart compared with that of hearts perfused with aerated sea water. Aortic outputs were similar to in vivo values (44 ml min-1 g-1) at close to in vivo values of preload and afterload owing to an increase in both heart rate (from 24.0 to 38.4 beats min-1) and stroke volume (from 0.69 to 1.10ml g-1). Coronary flow fell in these conditions, becoming 2.5 % of the aortic output (against 24% with aerated sea water). A parallel increase in coronary resistance was found. Oxygenated sea water also improved the performance of the heart, mainly by improving the stroke volume. Both with haemocyanin solutions or blood and with oxygenated sea water, the isolated heart was able to do more work at lower preloads compared with the hearts perfused with aerated sea water. Power output was linearly related to total oxygen consumption and carbon dioxide production. The major site of oxygen consumption was the coronary bed. Haemocyanin released about 70 % of the bound oxygen as it passed through the ventricular wall.
Sulphide Silver Staining for Endogenous Heavy Metals Reveals Subsets of Dorsal Unpaired Median (Dum) Neurones In Insects
Authors: Siegler Melody V. S. , Manley Philip E. , Thompson Karen J. 
Published: April 2021

ABSTRACT
The central nervous systems of many insects contain segmentally arranged groups of unpaired midline neurones. These have been called DUM (dorsal unpaired median) neurones because of the position of their cell bodies. The larger DUM neurones, with bilaterally symmetrical peripheral axons, have been most extensively studied in grasshoppers and locusts. DUM cells in the metathoracic ganglion modulate tension of skeletal muscle, potentiate synaptic transmission at neuromuscular junctions and slow a myogenic rhythm (Evans and O’Shea, 1977, 1978; Whim and Evans, 1989), whereas those in the abdominal ganglia alter tension in visceral muscle (Lange and Orchard, 1984). In fireflies, DUM neurones of the terminal abdominal ganglia control flashing by activating the photocytes of the lantern (Christensen and Carlson, 1981). The effects are mediated by the biogenic amine octopamine (Carlson and Jalenak, 1986; Evans and O’Shea, 1977, 1978; Morton and Evans, 1984; Orchard and Lange, 1985), which is also implicated in other modulatory actions (see Ramirez and Orchard, 1990, for references). In grasshoppers, in addition to the octopamine-containing efferent DUM neurones, there are a substantial number of local and intersegmental DUM interneurones with small cell bodies (Thompson and Siegler, 1989, 1991).
The Influence of Hypoxia on the Preferred Temperature of Rainbow Trout Oncorhynchus Mykiss
Authors: Schurmann H. , Steffensen J. F. , Lomholt J. P. 
Published: April 2021

ABSTRACT
The behavioural thermoregulation of rainbow trout Oncorhynchus mykiss was investigated in a shuttlebox at normoxia and at three levels of hypoxia: 13.3, 9.3 and 5.3 kPa. The final preferred temperatures at normoxia, and at 13.3, 9.3 and 5.3 kPa, were 16.1, 14.9, 15.0 and 12.7°C, respectively. A decreased rate of metabolism and an increased blood oxygen-affinity are among the physiological advantages of selecting a lower temperature during hypoxia. It is suggested that catecholamines may play a part in controlling temperature selection during hypoxia. In natural environments, this behaviour may result in habitat shifts of fish living in heterothermal environments with changing oxygen tensions.
Sailing Downwind: Aerodynamic Performance of the Velella Sail
Authors: Francis Lisbeth 
Published: April 2021

ABSTRACT
Using a wind tunnel built over a shallow pool and methods devised for measuring the performance of yacht sails, I describe aerodynamic performance in situ for the sailor-by-the-wind, Velella velella. By contrast with designers of the modern yacht mainsail, natural selection has apparently favored stability and seaworthiness over performance to windward. The Velella sail is a low aspect ratio airfoil with an unusually flat polar plot. Primarily a drag-based locomotory structure, this thin, leaf-like sail generates maximum force when oriented at attack angles between 50° and 90°. In the wind tunnel, free-sailing animals spontaneously assumed stable orientations at attack angles ranging from 28° to 87° and sailed with their hulls approximately broadside to the apparent flow of oncoming water. At these angles, aerodynamic force on the sail is asymmetrical, with the center of pressure upwind of the sail midline. Since aerodynamic force on the sail is balanced at equilibrium by hydrodynamic force on the hull, this orientation must be caused by asymmetrical forces acting on surface and underwater parts as the wind drags the animal along the surface of the water.
Consequences of a Gait Change During Locomotion in Toads (Bufo Woodhousii Fowleri)
Authors: Anderson Bruce D. , Feder Martin E. , Full Robert J. 
Published: April 2021

ABSTRACT
Most animals cannot sustain speeds above that at which the rate of oxygen consumption reaches a maximum Fowler’s toad (Bufo woodhousii fowler), by contrast, has a maximum aerobic speed (MAS, the speed at ) of 0.27 km h−1 but can sustain speeds as high as 0.45 km h−1 without increasing the , above the . The present study investigates the discrepancy between MAS and the maximum sustainable speed (MSS). Toads switched from walking to hopping as their speed increased. The cost of a hop (4.1×10−4ml O2g−1 hop−1) was greater than the cost of a walking stride (2.5×10−4ml O2g−1 stride−1) and was independent of speed for both hopping and walking. However, individual hops were much longer than walking strides, which more than offset the greater cost of a hop. The calculated cost to traverse a given distance was approximately 1.9 times as much for walking as for hopping. During natural locomotion animals used combined walking and hopping. Individual toads that favored walking had higher locomotor costs than those that favored hopping. The estimated cost of exclusive hopping was less than the cost of natural locomotion at all but the highest speeds. This discrepancy may reflect the fact that the natural gait is a combinastion of both the less economical walking gait and the more economical hopping gait. To achieve speeds above the MAS toads walked less and used the more economical hopping gait more, and thus did not increase energy cost above that of . The speed at which the estimated cost of exclusive hopping exceeded the cost of a natural gait and approached the was close to the MSS. Creatine phosphate and lactate concentrations in the muscles of the thigh and calf did not change from resting levels at sustainable speeds greater than the MAS.
Insect-Like Characteristics of the Malpighian Tubules of a Non-Insect: Fluid Secretion in the Centipede Lithobius Forficatus (Myriapoda: Chilopoda)
Authors: Wenning Angela , Greisinger U. T. E. , Proux Jacques P. 
Published: April 2021

ABSTRACT
Fluid secretion by isolated upper and lower portions of Malpighian tubules in the centipede Lithobius forficatus L. was studied. Ion requirements, cellular and transepithelial potentials, dependence on external osmolality and the effects of an insect diuretic factor and transport-active drugs were investigated. Unlike many insects, L. forficatus exhibited strongly Na+-dependent, K+-independent urine formation. However, as in many insects, upper and lower tubule portions from L. forficatus produced a K+-enriched, hypertonic fluid, and the transepithelial potential was positive with respect to the haemolymph. Furthermore, furosemide (5×10−4mol l−1) reversibly inhibited urine formation. Ouabain, even at 10−3mol l−1, had little effect on urine flow rate in upper tubules but inhibited secretion in lower tubules, albeit not completely. Locust diuretic hormone (at 10−7mol l−1) enhanced fluid secretion in L. forficatus, but its action was not mimicked by dibutyryl cyclic AMP. The results suggest that some characteristics attributed exclusively to insects are common to non-insect arthropods.
Effects of Exercise, Hypoxia and Feeding on the Gastrointestinal Blood flow in the Atlantic Cod Gadus Morhua
Authors: Axelsson Michael , Fritsche Regina 
Published: April 2021

ABSTRACT
Cardiac output, ventral and dorsal aortic blood pressure, heart rate, and coeliac and mesenteric artery blood flow were recorded simultaneously in the Atlantic cod, Gadus morhua L., at rest, during exercise, during hypoxia and after feeding.
In the resting unfed animals, coeliac artery blood flow was 4.1±0.8mI min−1 kg−1 and mesenteric artery blood flow was 3.5±1.1 ml min−1 kg−1 (mean± S.E.M., N=10); together, these flows represent approximately 40% of the cardiac output.
Exercise or exposure to hypoxia resulted in increased visceral vascular resistance, leading to reductions in the coeliac and mesenteric artery blood flows.
Coeliac and mesenteric blood flows were increased 24 h after feeding and the coeliac and systemic vascular resistances decreased in comparison with the prefeeding values. Phentolamine did not affect the gastrointestinal artery blood flow, but produced a significant decrease in the mesenteric and systemic vascular resistance.
Treatment with bretylium and phentolamine revealed differences between the coeliac and the mesenteric vasculature regarding the control mechanisms during hypoxia and during exercise and feeding. During hypoxia, an adrenergic control of the gastrointestinal vasculature with both nervous and humoral components was found, whereas during exercise and after feeding an additional non-adrenergic mechanism controlling gut blood flow was demonstrated.
Moments of Inertia of Bat Wings and Body
Authors: Thollesson Mikael , Norberg Ulla M. 
Published: April 2021

ABSTRACT
The moments of inertia of the wings about the shoulder joint and about the roll axis were estimated in eight species of bats, using strip analysis. The moment of inertia of the bat’s trunk about the roll axis was estimated by assuming the body and head to be ellipsoids. The slopes of the regressions of moment of inertia of one wing about the shoulder joint (Jw) versus body mass (mtot), wing span (b) and wing area (S) were as expected for geometrically similar animals of different size. The exponent for Jwversus body mass in bats deviates from that found for birds, while the exponent for Jwversus wing span does not. A multiple regression was used to show that Jw may be estimated by:
The mean value of the moment of inertia originating from the trunk is 7% of the bat’s total moment of inertia (of wings and body combined) about the roll axis. The mass of one wing (mw) was plotted against body mass for the eight bat species, which gives:
The slope for our bats, 1.11, is similar to that obtained for birds, 1.10. Adaptations to reduce the moments of inertia may be more important for increasing a bat’s flight agility (roll acceleration) than for decreasing the total mechanical power required to fly. The influences of wing moment of inertia and wing shape on manoeuvrability and agility are discussed.
Swimming Energetics and Performance of Instrumented Adélie Penguins (Pygoscelis Adeliae)
Authors: Culik Boris , Wilson Rory P. 
Published: April 2021

ABSTRACT
The effects of implanted and of externally attached instruments (1.8% of body cross-sectional area) were studied on Adélie penguins (Pygoscelis adeliae) using a 21 m long canal in conjunction with respirometry at Esperanza Bay, Antarctica. Penguins in both groups covered the same mean distance (173 m in 5 min) as controls. Implanted birds preferred to swim at slower speeds (1.3–1.7 m s−1) than did the controls (1.9–2.1 m s−1), whereas penguins with external instruments had a bimodal speed distribution with maxima at 1.7–1.9 and 2.3-2.5ms−1. Power input during swimming averaged 20% less in implanted penguins (12.7 W kg−1) and 42% more in penguins fitted with external instruments (22.5Wkg−1) compared with controls (15.8 W kg− x). Similarly, cost of transport was 23% lower in implanted penguins (7.0 J kg−1 m−1) and 25% higher in externally instrumented birds (11.3 Jkg−1 m−1) compared with controls (9.0 Jkg−1m−1). Possible reasons for the effects caused by the devices are discussed and the advantages and disadvantages of implanted and externally fitted devices are compared.