Showing papers in "The Journal of Experimental Biology in 1986"
TL;DR: Strain levels recorded at the trot-gallop transition and top galloping speeds of the goat were similar to the values reported for the dog and horse, despite large differences in absolute speed.
Abstract: SUMMARY Principal strains were recorded in vivo from the radial and tibial midshafts of three goats as they increased speed and changed gait. These data were compared with strain data measured for the radius and tibia of the dog (Rubin & Lanyon, 1982) and the horse (Biewener, Thomason & Lanyon, 19836) in order to test the hypothesis that similar peak bone strains (stresses) occur at functionally equivalent points in the gaits of different species. Multiple recordings of in vivo strain along the caudal diaphyses of the radius and tibia of one goat were made to test the validity of this technique for measuring peak locomotor stress. Measured strains were extremely consistent over the animal's full range of speed (coefficient of variation for the radius 0-05-0-08, and for the tibia 0-06-0-11). The data from the three gauges, which were spaced 15 mm apart, demonstrated that maximal strains act at the midshaft, substantiating the use of this technique to measure peak locomotor bone strains. Strain levels recorded at the trot-gallop transition and top galloping speeds of the goat were similar to the values reported for the dog and horse, despite large differences in absolute speed (goat, 4-3ms~ 1 ; dog, 6-9ms~'; horse, 7'5ms"' at maximum gallop). The second moments of area of the tibia and radius (+ ulna) of the dog are 29 % and 113 % greater than for goats of equal size, explaining how similar strains are achieved in the dog at higher speeds than the goat. Furthermore, peak bone strains recorded at the fastest trotting speed were similar to those recorded at the fastest galloping speed for each species. Peak strains recorded for the goat at a maximum gallop correspond to stresses of +37-9 MPa (cranial) and — 47-7 MPa (caudal) in the radius and +36-3 MPa (cranial) and —50-3 MPa (caudal) in the tibia, representing a safety factor to yield failure of three.
282 citations
TL;DR: Exhaustive 'burst-type' exercise in the rainbow trout resulted in a severe acidosis in the white muscle, with pHi dropping from 7.21 to a low of 6.62, as measured by DMO distribution, suggesting that there was an uncoupling of ATP hydrolysis and glycolysis.
Abstract: Exhaustive ‘burst-type’ exercise in the rainbow trout resulted in a severe acidosis in the white muscle, with pHi dropping from 7.21 to a low of 6.62, as measured by DMO distribution. An accumulation of lactate and pyruvate, depletions of glycogen, ATP and CP stores, and a fluid shift from the extracellular fluid to the intracellular fluid of white muscle were associated with the acidosis. The proton load was in excess of the lactate load by an amount equivalent to the drop in ATP, suggesting that there was an uncoupling of ATP hydrolysis and glycolysis. Initially, lactate was cleared more quickly than protons from the muscle, a difference that was reflected in the blood. It is suggested that during the early period of recovery (0–4 h), the bulk of the lactate was oxidized in situ, restoring pHi to a point compatible with glyconeogenesis. At that time, lactate and H+ were used as substrates for in situ glyconeogenesis, which was complete by 24 h. During this time, lactate and H+ disappearance could account for about 75% of the glycogen resynthesized. The liver and heart showed an accumulation of lactate, and it is postulated that this occurred as a result of uptake from the blood. Associated with the lactate load in these tissues was a metabolic alkalosis. Except for an apparent acidosis immediately after exercise, the acid-base status of the brain was not appreciably affected. Despite the extracellular acidosis, red cell pHi remained nearly constant.
249 citations
TL;DR: Catecholamines play an important role in maintaining oxygen transport to aerobic muscles, following burst swimming and the associated acidotic conditions, and are concluded to be responsible for the increase in erythrocytic pH.
Abstract: Rainbow trout were subjected to burst swimming to exhaustion followed by 4 h aerobic swimming at 80% critical swimming velocity. Severe physiological disturbances, including a marked plasma acidosis caused by the burst swim, were corrected during the 4 h of subsequent aerobic exercise. Erythrocytic pH and arterial oxygen content increased, even though plasma pH was reduced. We suggest that the increase in erythrocytic pH was caused by the action of elevated adrenaline and noradrenaline levels in the blood acting on beta-adrenergic receptors on the trout red blood cell, causing the cell to swell and raising intracellular pH, offsetting any effect of a reduction of plasma pH on erythrocyte pH and haemoglobin-oxygen binding. Propranolol blocked the action of catecholamines on trout erythrocytes. We conclude that catecholamines play an important role in maintaining oxygen transport to aerobic muscles, following burst swimming and the associated acidotic conditions.
217 citations
TL;DR: The nature of data which have demonstrated multiple channel types are described, the literature suggesting that many cells have several kinds of Ca2+ channels is reviewed, and newer data regarding a neurotoxin that distinguishes among different Ca2+, channels are discussed.
Abstract: Ca2+ channels allow passage of Ca2+ ions into the cytoplasm through a selective pore which is opened in response to depolarization of the cell membrane (for reviews see Hagiwara & Byerly, 1981, 1983; Tsien, 1983; Reuter, 1983). The Ca2+ flux creates a net inward, depolarizing current and the resulting accumulation of Ca2+ in the cytoplasm can act as a chemical trigger for secretion of hormones and neurotransmitters, contraction of muscle and a variety of other Ca2+-sensitive events. Thus, upon sensing membrane potential changes, Ca2+ channels simultaneously generate an electrical signal while directly creating an intracellular chemical messenger. This dual ability is unique among the family of ion channels and allows the Ca2+ channel to play a variety of roles in excitation-secretion and excitation-contraction coupling. It has now become clear that versatility of function is reflected by diversity of the types of Ca2+ channels on the membrane of individual cells. This article describes the nature of data which have demonstrated multiple channel types, reviews the literature suggesting that many cells have several kinds of Ca2+ channels, and discusses newer data regarding a neurotoxin that distinguishes among different Ca2+ channels.
209 citations
TL;DR: Exhaustive exercise induced a severe short-lived respiratory, and longer-lived metabolic, acidosis in the extracellular fluid of the rainbow trout, and whole-body pHi was slower to recover than pHe, requiring up to 12 h, with no subsequent alkalosis.
Abstract: Exhaustive exercise induced a severe short-lived (0-1 h) respiratory, and longer-lived (0-4 h) metabolic, acidosis in the extracellular fluid of the rainbow trout. Blood 'lactate' load exceeded blood 'metabolic acid' load from 1-12 h after exercise. Over-compensation occurred, so that by 8-12 h, metabolic alkalosis prevailed, but by 24 h, resting acid-base status had been restored. Acid-base changes were similar, and lactate levels identical, in arterial and venous blood. However, at rest venous RBC pHi was significantly higher than arterial (7.42 versus 7.31). After exercise, arterial RBC pHi remained constant, whereas venous RBC pHi fell significantly (to 7.18) but was fully restored by 1 h. Resting mean whole-body pHi, measured by DMO distribution, averaged approx. 7.25 at a pHe of approx. 7.82 and fell after exercise to a low of 6.78 at a pHe of approx. 7.30. Whole-body pHi was slower to recover than pHe, requiring up to 12 h, with no subsequent alkalosis. Whole-body ECFV decreased by about 70 ml kg-1 due to a fluid shift into the ICF. Net H+ excretion to the water increased 1 h after exercise accompanied by an elevation in ammonia efflux. At 8-12 h, H+ excretion was reduced to resting levels and at 12-24 h, a net H+ uptake occurred. Lactate excretion amounted to approx. 1% of the net H+ excretion and only approx. 2% of the whole blood load. Only a small amount of the anaerobically produced H+ in the ICF appeared in the ECF and subsequently in the water. By 24 h, all the H+ excreted had been taken back up, thus correcting the extracellular alkalosis. The bulk of the H+ load remained intracellular, to be cleared by aerobic metabolism.
167 citations
TL;DR: It is argued that JH functions to control the time during the last larval instar when pupal commitment occurs by dictating when PTTH will undergo gated release.
Abstract: Pupal development is elicited early in the last larval instar of the tobacco hornworm, Manduca sexta (Johannson), by a precise temporal and quantitative increase in the haemolymph titre of 20-hydroxyecdysone. This increase in the titre is referred to as the pupal commitment peak, and it occurs once the titre of juvenile hormone (JH) has dropped. If the haemolymph titre of JH remains elevated at this time due to topical application of the hormone or of its analogue ZR512, commitment is delayed or inhibited in a dose-dependent manner. This delay or inhibition is due to the curtailment of the commitment peak in the ecdysteroid titre, which results from a failure of the prothoracic glands (PG) to increase the synthesis/secretion of the premoulting hormone, ecdysone. Since the PG from ZR512- and JH 1-treated larvae are capable of being activated in vitro by the prothoracicotropic hormone (PTTH), the effect of JH on the PG does not involve suppression of gland sensitivity to PTTH. The locus of the JH effect was determined to be the brain-retrocerebral complexes (Br-CC-CA), on the basis of experiments which tested the effect of implanted Br-CC-CA from pre-commitment larvae treated with JH on the occurrence of pupal commitment in head-ligated larval hosts. The implanted, JH-treated Br-CC-CA exhibited a delayed release of PTTH, and the effect was at concentrations of JH that were physiological. These results argue that JH functions to control the time during the last larval instar when pupal commitment occurs by dictating when PTTH will undergo gated release.
148 citations
TL;DR: The results argue that this high-conductance, Ca2+-activated K+ channel contains at least six Ca2-binding sites involved in the activation process.
Abstract: Ca2+-activated K+ channels from rat muscle transverse tubule membranes were inserted into planar phospholipid bilayers, and the activation of these channels by Ca2+ was studied. On the cytoplasmic side of the channel, calcium ions (in the range 10-100 mumol l-1) increase the opening probability of the channel in a graded way. This 'activation curve' is sigmoid, with an average Hill coefficient of about 2. Magnesium ions, in the range 1-10 mmol l-1, increase the apparent affinity of the channel for Ca2+ and greatly enhance the sigmoidicity of the Ca2+ activation curve. In the presence of 10 mmol l-1 Mg2+, the Hill coefficient for Ca2+ activation is about 4.5. This effect depends upon Mg2+ concentration but not upon applied voltage. Mg2+ is effective only when added to the cytoplasmic side of the channel. The results argue that this high-conductance, Ca2+-activated K+ channel contains at least six Ca2+-binding sites involved in the activation process.
146 citations
TL;DR: Two lectins have been identified that are expressed early in development in the superficial dorsal horn that may contribute to the development of sensory afferent projections in the spinal cord.
Abstract: Dorsal root ganglion (DRG) neurones transmit cutaneous sensory information from the periphery to the dorsal horn of the spinal cord. Subpopulations of DRG neurones that subserve distinct sensory modalities project to discrete regions in the dorsal horn. The formation of specific sensory connections during development may involve cell-surface interactions with spinal cord cells. Molecules that are expressed on the surface of functional subpopulations of DRG and dorsal horn neurones have therefore been identified. Distinct subsets of DRG neurones express globo- or lactoseries carbohydrate differentiation antigens. The expression of defined carbohydrate structures correlates with the embryonic lineage, peptide phenotype and the central termination site of DRG neurones. Similar or identical glycoconjugates have been implicated in cellular interactions that contribute to preimplantation embryonic development. Small-diameter DRG neurones that project to the superficial dorsal horn express N-acetyllactosamine backbone structures that are potential ligands for beta-galactoside-specific binding proteins (lectins). Two lectins have been identified that are expressed early in development in the superficial dorsal horn. These complementary molecules may contribute to the development of sensory afferent projections in the spinal cord.
144 citations
TL;DR: The intrinsic mechanical capabilities of the trout heart were greater than those observed previously in less active, benthic teleosts and the roles of catecholamines and extracellular calcium are discussed with respect to post-exercise cardiac performance in trout.
Abstract: A perfused rainbow trout heart was developed which generated its own intrinsic heart rate and a physiological power output. This preparation was used to examine the intrinsic mechanical properties of the trout heart, the dose-response effects of catecholamines and extracellular calcium on these properties, and the effects of catecholamines and extracellular calcium during exposure to acidotic conditions. The trout heart was relatively pressure-insensitive to a physiological range of ventral aortic pressures. Preload exerted an important control over cardiac output through the Starling response. Heart rate was independent of both these intrinsic mechanisms. The intrinsic mechanical capabilities of the trout heart were greater than those observed previously in less active, benthic teleosts. Physiological concentrations of catecholamines significantly improved cardiac contractility through positive inotropy and chronotropy. Adrenaline was more potent than noradrenaline, indicating that these effects were mediated by beta 2-adrenoceptors. Elevated extracellular calcium produced only a modest improvement of cardiac contractility compared to that produced by adrenaline. Positive inotropy and negative chronotropy were observed with elevated extracellular calcium. Extracellular acidosis always reduced cardiac contractility through negative chronotropy and inotropy. Extracellular calcium improved the inotropic state of the acidotic heart and restored contractility, but the overall improvement of cardiac performance was compromised by an accompanying negative chronotropy. Physiological levels of adrenaline improved cardiac performance during extracellular acidosis. The roles of catecholamines and extracellular calcium are discussed with respect to post-exercise cardiac performance in trout.
136 citations
TL;DR: The hypothesis that there is an increase in plasma catecholamines during exercise in fish and that they play an important role in the cardiovascular adjustments during exercise was investigated in the lesser spotted dogfish and rainbow trout.
Abstract: The hypothesis that there is an increase in plasma catecholamines during exercise in fish and that they play an important role in the cardiovascular adjustments during exercise was investigated in the lesser spotted dogfish and rainbow trout. In resting fish plasma catecholamines were at a concentration of 10(−9)-10(−8) mol l-1. During spontaneous swimming in the dogfish, adrenaline increased by 3.3 times to 1.9 X 10(−8) mol l-1 and noradrenaline increased by 2.3 times to 3.2 X 10(−8) mol l-1. In rainbow trout swimming at a steady 1 body length s-1 (Ls-1) in a water channel, the levels of both amines decreased to approximately 25% of the resting values. When swimming to apparent exhaustion at approximately 2 Ls-1, adrenaline was 10 times the resting value at 1.4 X 10(−8) mol l-1, whereas noradrenaline was 2.2 times the resting value at 2.3 X 10(−8) mol l-1. Only after repeated burst swimming for 2–3 min did the levels of plasma catecholamines increase substantially above the resting values. In the dogfish, both amines were at 10(−7) mol l-1, whereas in the rainbow trout, noradrenaline was at 8.5 X 10(−8) mol l-1 and adrenaline was at 2 X 10(−7) mol l-1. These levels were compared with the concentrations of catecholamines used by other workers to elicit changes in the branchial vasculature, gas exchange at the gills or gas transport to the tissues. In lesser spotted dogfish, the levels of adrenaline and noradrenaline present in the plasma during spontaneous swimming have 80% and 50% of maximum effect on gill blood vessels, respectively, whereas in rainbow trout the levels present when swimming to apparent exhaustion have approximately 20% of maximum effect on the branchial vasculature. The levels present in the trout after repeated burst swimming have 40% of maximum effect on blood vessels in the gills. The difference between the dogfish and the trout may be related to the lack of innervation of the gill blood vessels in the former. Enhancement of gas exchange across the gills of rainbow trout can be demonstrated by using adrenaline at the concentration found after repeated burst swimming. It is possible, however, that the concentration of adrenaline found in the plasma of trout after swimming to apparent exhaustion may cause an increase in the concentration of oxygen in arterial blood, thus enhancing oxygen delivery to the tissues.(ABSTRACT TRUNCATED AT 400 WORDS)
133 citations
TL;DR: Tilapia can increase the mobility of their hard tissue calcium during periods of low calcium stress, indicating that even in low-calcium water, tilapia absorb a significant amount of their calcium requirement directly from the water.
Abstract: Calcium fluxes and internal calcium pools were measured in fed, rapidly growing, male tilapia, Oreochromis mossambicus , acclimated to 0.8 mmol l −1 (FW) and 0.2mmoll −1 (LFW) Ca 2+ . Plasma calcium levels were slightly and significantly higher in the LFW tilapia, but muscle calcium concentrations were independent of ambient Ca 2+ . At the time of the experiments, the LFW fish were growing and accumulated calcium, although the calcium content of their hard tissues was reduced. The LFW fish had higher Ca 2+ influx and efflux rates than the FW fish. The increase in the influx of Ca 2+ in LFW fish was, however, substantially greater than the increase in the efflux of Ca 2+ , giving these fish a more than four-fold increase in net Ca 2+ influx from the water: for a 20-g tilapia net uptake rates of Ca 2+ from the water were 390 and 1620 nmol Ca 2+ h −1 for FW- and LFW-adapted fish, respectively. These values were calculated to represent at least 69% of the total calcium accumulated by these growing fish. This indicates that even in low-calcium water, tilapia absorb a significant amount of their calcium requirement directly from the water. The pool of readily exchangeable calcium in the bone of FW fish was estimated to be about 7 % of the total hard tissue calcium. In the fish acclimated to LFW, this percentage increased to about 15 % as total hard tissue mineralization decreased. This may indicate that tilapia can increase the mobility of their hard tissue calcium during periods of low calcium stress.
TL;DR: The hypothesis that fish may utilize information about the infrasound pattern in the sea for orientation during migration, probably in addition to an array of other sensory inputs, is put forward.
Abstract: Below about 50 kHz the level of ambient noise in the sea increases continuously towards lower frequencies. In the infrasound range the spectral slope is particularly steep. This low-frequency noise may propagate long distances with little attenuation, causing a directional pattern of infrasound in the sea. Using a standing-wave acoustic tube, we have studied the sensitivity of cod to infrasound down to 0.1 Hz by means of the cardiac conditioning technique. The threshold values, measured as particle acceleration, showed a steady decline towards lower frequencies below 10 Hz, reaching a value close to 10(−5)ms-2 at 0.1 Hz. The spectrum level at 0.1 Hz in the sea ranges between 120 and 180 dB (re 1 microPa), with corresponding particle accelerations from less than 10(−6) to more than 10(−4)ms-2. The sensitivity of cod is thus sufficient to detect the highest levels of ambient infrasound, and we put forward the hypothesis that fish may utilize information about the infrasound pattern in the sea for orientation during migration, probably in addition to an array of other sensory inputs.
TL;DR: A structural engineering approach to the pleated wings of Odonata has been developed during a functional study of wing morphology in the group, finding that the membrane significantly increases the rigidity of wing components.
Abstract: A structural engineering approach to the pleated wings of Odonata has been developed during a functional study of wing morphology in the group. The wing can be regarded as a folded plate structure within which each pleat-side acts as a deep plate-girder. Small cross-veins act as stiffeners within the girders, allowing the membrane to carry web shearing forces as pure tension, through a stressed-skin effect. Bending experiments confirm that the membrane significantly increases the rigidity of wing components. The properties of the membrane are unknown. It lacks birefringence, is very thin, and may be pure epicuticle. The advantages of stressedskin construction are discussed, and possible modes of structural failure considered. The wing seems adapted to yield reversibly to unpredictable heavy loads.
TL;DR: The exercise hypertension observed in cod depends on the effect of adrenergic vasomotor fibres maintaining the systemic vascular resistance, and also on the increase in cardiac output, which is likely to be non-adrenergic.
Abstract: Atlantic cod were subjected to 12-15 min swimming exercise at 2/3 body lengths s-1 in a Blazka-type swim tunnel. Pre- and postbranchial blood pressures, cardiac output (ventral aortic blood flow) and heart rate were continuously recorded, and blood samples for measurement of arterial and mixed venous oxygen tension were taken before and at the end of the exercise period. In a second group of fish, subjected to similar exercise regimes, blood samples were taken for analysis of the plasma concentrations of catecholamines. Pre- and postbranchial blood pressures and cardiac output increase during exercise, while the mixed venous oxygen tension decreases. The effect on cardiac output is due to an increase of both heart rate and stroke volume. There are no significant changes in either systemic or branchial vascular resistances, or in the plasma concentrations of catecholamines. Injection of the adrenergic neurone-blocking drug bretylium produces a decrease in postbranchial blood pressure in resting cod, due to a decrease in the systemic vascular resistance. Exercising cod treated with bretylium have a significantly lower pre- and postbranchial blood pressure than exercising control cod. This is due mainly to a dramatic reduction in the systemic vascular resistance. The alpha-adrenoceptor antagonist phentolamine does not further affect the blood pressure in cod treated with bretylium. It is concluded that the exercise hypertension observed in cod depends on the effect of adrenergic vasomotor fibres maintaining the systemic vascular resistance, and also on the increase in cardiac output. An adrenergic innervation of the heart may play some role in the control of cardiac performance both at rest and during exercise, but the main cardioregulatory mechanism is likely to be non-adrenergic, most probably including cardiac control via variation of the cholinergic vagal cardioinhibitory tonus.
Journal Article•
TL;DR: In this article, the wake of a jackdaw in slow forward flight is described and the three-dimensional velocity field is investigated qualitatively and quantitatively by analysis of multiple-flash stereophotographs of the motion of neutrally buoyant helium bubbles.
Abstract: The wake of a jackdaw in slow forward flight is described. The three-dimensional velocity field was investigated qualitatively and quantitatively by analysis of multiple-flash stereophotographs of the motion of neutrally buoyant helium bubbles. The best description of the wake structure appears to be a chain of planar, nearcircular, discrete, small-cored, vortex loops, each produced by vorticity shed during a single downstroke. However, the momentum measured in such a wake is approximately 35% of that required for weight support under these flight conditions. Some evidence is presented that this apparent wake momentum deficit may arise because the description of the real wake vorticity distribution is too simplistic. The implications of these results for theoretical models of bird flight are briefly discussed.
TL;DR: Insect skeletal muscles are frequently innervated by small numbers of motor neurones and present excellent model systems in which to study the basic principles of neuromuscular transmission and the modulation of these effects by biogenic amines and peptides.
Abstract: Insect skeletal muscles are frequently innervated by small numbers of motor neurones, all of which can be uniquely identified physiologically. They therefore present excellent model systems in which to study the basic principles of neuromuscular transmission and the modulation of these effects by biogenic amines and peptides. The extensor-tibiae muscle of the hind leg of the locust is a much studied, large muscle that is innervated by three identified motor neurones and one identified modulatory neurone. Much attention has recently been focused on the modulation of neuromuscular transmission and muscular contraction in this muscle by biogenic amines and peptides.
One proximal bundle of muscle fibres in the extensor-tibiae muscle exhibits a myogenic rhythm of contraction and relaxation. The rhythm is stimulated by a variety of peptides including proctolin, the AKH-related peptides M1 and M2, and by small cardioactive peptide (SCPB). In addition, it is activated by 5-hydroxytryptamine and by oneclass of adenosine analogues. The rhythm is inhibited by octopamine and by a second class of adenosine analogues. The actions of these various modulatory compounds will be discussed in terms of the likely numbers of pharmacologically distinct receptors in this preparation and their modes of action.
Neuromuscular transmission and muscular contraction in the extensor-tibiae muscle is modulated by the biogenic amine octopamine and by the peptides, proctolin and FMRFamide. The actions of these modulators are discussed in relation differences in the responsiveness of various regions of the muscle, to the frequency dependence of their effects on motor neurone activityand to their modes of action.
The cellular locations and mode of transmission to the muscle of some of these modulators will be considered. Octopamine and proctolin are contained within neurones which innervate the muscle, whilst FMRFamide- and SCPB-like peptides appear to be released into the locust haemolymph as neurohormones.
TL;DR: Rates of oxygen consumption during hover-feeding of wild, unrestrained, adult male Anna hummingbirds were measured with an artificial outdoor feeder converted into a respirometer mask, automatically detecting the presence of a hummingbird from a drop in the O2 concentration and photoelectrically timing the duration over which the feeder functioned as a mask.
Abstract: Rates of oxygen consumption during hover-feeding of wild, unrestrained, adult male Anna hummingbirds (Calypte anna) were measured with an artificial outdoor feeder converted into a respirometer mask. A computer sampled changes in O2 concentration in air drawn through the mask, automatically detecting the presence of a hummingbird from a drop in the O2 concentration, and photoelectrically timing the duration over which the feeder functioned as a mask. Birds coming to the feeder were weighed on a trapeze perch suspended from a force transducer. Feeding bouts consisted of sallies which carried the head in and out of the feeding mask about once a second. The volume of O2 consumed per feeding sally was linearly related to the length of the sally. The energy cost of hover-feeding in five hummingbirds, mean mass 4.6 g, was 41.5 +/− 6.3 ml O2 g-1 h-1.
TL;DR: The kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at a range of velocities are described, with changes in the wings' incidence angles suggesting thrust generation and weight support and negative thrust.
Abstract: The kinematics and aerodynamics of the greater horseshoe bat, Rhinolophus ferrumequinum, in horizontal flight at a range of velocities are described. As flight speed increases there is a gradual change in the bat's wingbeat kinematics, wingbeat frequency decreasing and wingbeat strokeplane angles increasing. Associated with these changes are changes in the wings' incidence angles, particularly during the upstroke. At low speeds these are large and negative, suggesting thrust generation, while at high speeds these are positive and large, indicating that weight support and negative thrust are being generated. The change from one kinematic pattern to the other occurred gradually. The possible energetic and aerodynamic reasons for these changes are discussed.
TL;DR: Catecholamines are released into the blood in proportion to the fall in blood pH but if the pH is maintained the circulating catecholamine levels return to their initial low levels if acidotic conditions are maintained.
Abstract: A fall in blood pH was generated either by infusion of HCl or by reducing gill ventilation and raising blood PCO2 in rainbow trout, Salmo gairdneri Richardson. The acute acidosis resulting from HCl infusion caused an increase in plasma adrenaline and noradrenaline concentrations, the adrenaline increase being proportional to the decrease in blood pH. Fish subjected to a prolonged respiratory acidosis, caused by a reduction in gill ventilation, showed no increase in catecholamines 24 h after the change in gill ventilation. We suggest that catecholamine levels increase in response to a pH decrease, but if acidotic conditions are maintained, circulating catecholamines return to low levels. There was a much smaller decrease in erythrocytic pH with a fall in plasma pH when catecholamine levels were high. This ameliorating effect of catecholamines on erythrocytic pH during a plasma acidosis maintains the oxygen-carrying capacity of the haemoglobin. If erythrocytic pH was decreased by increasing blood PCO2 in vitro, then there was a fall in haemoglobin oxygen-carrying capacity which was proportional to the reduction in pH. We conclude that catecholamines are released into the blood in proportion to the fall in blood pH but if the pH is maintained the circulating catecholamines return to their initial low levels. The elevated catecholamine concentrations in blood safeguard against any impairment of haemoglobin oxygen-carrying capacity by maintaining erythrocytic pH in the face of a plasma acidosis.
TL;DR: The male reproductive organ of rainbow trout and chum salmon consists of a pair of testes and sperm ducts, and testicular spermatozoa demembranated with Triton X-100 exhibited motility, although the motility was less than that of dememBRanated spermatoza from the sperm duct, suggesting that the acquisition of motility may correspond with the development of some function of the plasma membrane.
Abstract: The male reproductive organ of rainbow trout and chum salmon consists of a pair of testes and sperm ducts. Spermatozoa in the distal portion of the sperm ducts exhibit full motility in the K+-free medium. However, spermatozoa from the testis were almost immotile in this medium. This suggests that the spermatozoa acquire a capacity for movement during their passage from the testis along the sperm duct. In chum salmon migrating into a bay, the sperm duct was almost empty. However, after the fish have travelled upstream for 1 km to their spawning ground in the river, the spermatozoa have left the testis, moved into the sperm duct and are capable of becoming motile. Thus it is probable that the process of acquiring the ability to move occurs within a relatively short period in this simple reproductive organ. Additionally, testicular spermatozoa demembranated with Triton X-100 exhibited motility, although the motility was less than that of demembranated spermatozoa from the sperm duct, suggesting that the acquisition of motility may correspond with the development of some function of the plasma membrane.
TL;DR: The tubular components of the wall appear to reinforce against fracture along the weak plane and the entire wall organization provides the mechanical capability for limiting and controlling fracture in this tissue.
Abstract: An engineering fracture mechanics approach was applied to the analysis of the fracture resistance of equine hoof-wall. The relationship between fracture toughness and the morphological organization of the keratin hoof tissue was investigated. Fracture toughness was evaluated using the J-integral analysis method which employs the compact tension test geometry. Tensile tests were also conducted to evaluate the effect of the morphological organization on the stress-strain behaviour. Hoof-wall has greatest fracture resistance for cracks running proximally, parallel to the tubular component of the wall keratin. For fully hydrated material tested in this direction the mean critical J-integral value at failure was 1.19 X 10(4)J m-2. This was nearly three times greater than the value determined for the weakest orientation, in which the crack ran parallel to the material between the tubules. The lower fracture toughness of the intertubular material dominates the fracture behaviour of this tissue. The tubular components of the wall appear to reinforce against fracture along the weak plane and the entire wall organization provides the mechanical capability for limiting and controlling fracture in this tissue.
TL;DR: This result, with those in the accompanying paper, suggests that unlike the Retzius cell and similar to cell 204, cells 21 and 61 synaptically contact cells of the swim central pattern generator (CPG).
Abstract: Two pairs of serotonin-containing neurones, designated cells 21 and 61, were characterized physiologically and anatomically in the hirudinid leeches Macrobdella decora and Hirudo medicinalis. Both of these cells are bilaterally paired interneurones and each cell is weakly electrically coupled to the other serotonin-containing cells both intra- and interganglionically. Cells 21 and 61 are excited polysynaptically by individual identified mechano-sensory neurones. Segmental nerve shock sufficient to elicit an episode of swimming strongly excites cells 21 and 61, which then tend to generate bursts of impulses that are phase-locked to the swim motor pattern. Intracellular stimulation of either cell 21 or cell 61 often causes the initiation of swimming, acting in parallel with the nonserotonergic swim-initiator cell 204. Cells 61 and 204 are also weakly electrically coupled. The latency to swim onset by stimulating cell 21 or 61 is similar to that of cell 204 and different from that of the serotonergic Retzius cell. This result, with those in the accompanying paper (Nusbaum, 1986), suggests that unlike the Retzius cell and similar to cell 204, cells 21 and 61 synaptically contact cells of the swim central pattern generator (CPG).
TL;DR: In this paper, the pH of interlamellar water of trout (Salmo gairdneri ) was investigated by following changes in the downstream pH of expired water using a stopped-flow method.
Abstract: We investigated the pH of interlamellar water of trout ( Salmo gairdneri ) by following changes in the downstream pH of expired water using a stopped-flow method. As water flowed over the gills of control fish, there was a significant decrease in water pH. Acetazolamide added to the water increased the CO2 disequilibrium, while carbonic anhydrase (CA) eliminated the CO2 disequilibrium relative to control water. Mucus excreted by the fish was found to contain CA activity by the pH-stat technique. We conclude water acidification is due to the conversion of excreted CO2 to HCO3− and H+ at the gill surface.
Journal Article•
TL;DR: Kynurenate was a potent and selective inhibitor of the Ia EPSP, acting via a postsynaptic mechanism, which indicates that L-glutamate, or a glutamate-like compound, but not L-aspartate, is likely to be the predominant excitatory transmitter that mediates fast exciteatory post synapses at primary afferent synapses with both dorsal horn neurones and motoneurones.
Abstract: Intracellular recording techniques have been used to provide information on the identity of excitatory transmitters released at synapses formed between dorsal root ganglion (DRG) and spinal cord neurones in two in vitro preparations. Explants of embryonic rat DRG were added to dissociated cultures of embryonic dorsal horn neurones and synaptic potentials recorded intracellularly from dorsal horn neurones after DRG explant stimulation. More than 80% of dorsal horn neurones received at least one fast, DRG-evoked, monosynaptic input. In the presence of high divalent cation concentrations (5 mmol l-1 Ca2+, 3 mmol l-1 Mg2+) the acidic amino acid receptor agonists, L-glutamate, kainate (KA) and quisqualate (QUIS) excited all dorsal horn neurones which received a monosynaptic DRG neurone input, whereas L-aspartate and N-methyl-D-aspartate (NMDA) had little or no action. 2-Amino-5-phosphonovalerate (APV), a selective NMDA receptor antagonist, was relatively ineffective at antagonizing DRG-evoked synaptic potentials and L-glutamate-evoked responses. In contrast, kynurenate was found to be a potent antagonist of amino acid-evoked responses and of synaptic transmission at all DRG-dorsal horn synapses examined. The blockade of synaptic transmission by kynurenate appeared to result from a postsynaptic action on dorsal horn neurones. Intracellular recordings from motoneurones in new-born rat spinal cord were used to study the sensitivity of the Ia excitatory postsynaptic potential (EPSP) to antagonists of excitatory amino acids. Superfusion of the spinal cord with APV did not inhibit the Ia EPSP but did suppress later, polysynaptic components of the afferent-evoked response. Kynurenate was a potent and selective inhibitor of the Ia EPSP, acting via a postsynaptic mechanism. These findings indicate that L-glutamate, or a glutamate-like compound, but not L-aspartate, is likely to be the predominant excitatory transmitter that mediates fast excitatory postsynaptic potentials at primary afferent synapses with both dorsal horn neurones and motoneurones.
TL;DR: The observed increase in plasma bicarbonate concentration during 5% hypercapnic exposure was attributable to net gain of bICarbonate equivalent ions from (or release of H+-equivalent ions to) the environmental water, suggesting that acid-base relevant ions were transferred for compensation of the intracellular body compartments.
Abstract: To study both temporal and quantitative effects of hypercapnia on the extent of pH compensation in the arterial blood, specimens of carp (Cyprinus carpio) were exposed to a PCO2 of about 7.5 mmHg (1 mmHg = 133.3 Pa) (1% CO2) in the environmental water for several weeks, and a second group of animals was subjected to an environmental PCO2 of about 37 mmHg (5% CO2) for up to 96 h. A third series of experiments was designed to test the possibility that infusion of bicarbonate would increase the extent of plasma pH compensation. Dorsal aortic plasma pH, PCO2 and [HCO3-], as well as net transfer of HCO3- -equivalent ions, NH4+, Cl- and Na+, between fish and ambient water, were monitored throughout the experiments. Exposure to environmental PCO2 of 7.5 mmHg resulted in the expected respiratory acidosis with the associated drop in plasma pH, and subsequent compensatory plasma [HCO3-] increase. The compensatory increase of plasma bicarbonate during long-term hypercapnia continued during 19 days of exposure with plasma bicarbonate finally elevated from 13.0 mmoll-1 during control conditions to 25.9 mmoll-1 in hypercapnia, an increase equivalent to 80% plasma pH compensation. Exposure to 5% hypercapnia elicited much larger acid-base effects, which were compensated to a much lesser extent. Plasma pH recovered to only about 45% of the pH depression expected at constant bicarbonate concentration. At the end of the 96-h exposure period, plasma [HCO3-] was elevated by a factor of 2.5 to about 28.2 mmoll-1. The observed increase in plasma bicarbonate concentration during 5% hypercapnic exposure was attributable to net gain of bicarbonate equivalent ions from (or release of H+-equivalent ions to) the environmental water. Quantitatively, the gain of 15.6 mmol kg-1 was considerably larger than the amount required for compensation of the extracellular space, suggesting that acid-base relevant ions were transferred for compensation of the intracellular body compartments. The uptake of bicarbonate-equivalent ions from the water was accompanied by a net release of Cl-and, to a smaller extent, by a net uptake of Na+, suggesting a 75% contribution of the Cl-/HCO-3 exchange mechanism. Infusion of bicarbonate after 48 h of exposure to 7.5 mmHg PCo2 had only a transient effect on further pH compensation. The infused bicarbonate was lost to the ambient water, and pre-infusion levels of bicarbonate were reattained within 24 h. Repetition of the infusion did not result in a notable improvement of the acid-base status.(ABSTRACT TRUNCATED AT 400 WORDS)
TL;DR: The isometric and isotonic contractile properties of fast-twitch glycolytic fibres of the iliofibularis muscle in the lizard Sceloporus occidentalis were measured in vitro at 5 degrees C intervals form 10 to 40 degrees C and two alternative equations for fitting these data are presented.
Abstract: The isometric and isotonic contractile properties of fast-twitch glycolytic fibres of the iliofibularis muscle (FG-IF) in the lizard Sceloporus occidentalis were measured in vitro at 5 degrees C intervals form 10 to 40 degrees C. The mean isometric parameters at 35 degrees C, the preferred body temperature of this species, were as follows: maximum isometric force (Po), 187 +/- 8 (S.E.M.) kNm-2; ratio of twitch force to tetanic force (PTW/Po), 0.46 +/- 0.02; time to peak twitch tension (tPTW), 7.0 +/- 0.3 ms; and time from peak twitch force to 50% relaxation (t50% ), 8.2 +/- 0.3 ms. From 20 to 35 degrees C Po was almost constant (within 8% of the value at 35 degrees C). At 10 and 15 degrees C C. Po dropped to approximately 80% of the value at 35 degrees C. Po was very unstable at 40 degrees C. PTW/Po was almost constant at all temperatures. The time-related isometric parameters were positively modified by temperature at all temperatures measured (Q10 greater than 1.9). The force-velocity curves of the FG-IF deviated from the simple hyperbolic relation of A. V. Hill's characteristic equation. We present two alternative equations for fitting these data. These equations resulted in residual sums of squares from nonlinear least-squares analysis that were at least seven-fold lower than those from Hill's equation. The equation that best describes our data is a hyperbola modified by the addition of a linear component: V = B(1 - P/Po)/(A + P/Po) + C(1 - P/Po). To describe the curvature of this or any other force-velocity relationship, we propose the power ratio, Wmax/VmaxPo (where Wmax is the maximum power calculated from the force-velocity relationship and Vmax is the predicted maximum velocity of shortening at zero force). Vmax of the FG-IF was 21.9LoS-1 at 35 degrees C (where Lo is muscle length). This parameter was directly related to temperature between 10 and 35 degrees C with Q10 greater than 1.8. The shape of the force-velocity curve is not influenced by temperature (Wmax/VmaxPo = 0.11).
TL;DR: In this paper, a differential pressure transducer linked to an ultrasonic transmitter carrying average pressure data encoded on impulse frequency was designed to be carried inside the mantle cavity of a free-swimming squid.
Abstract: 1. 1. Measurements of oxygen consumption (Voo2, ml h−1) and mantle cavity pressure (P, kPa) of squid, Illex illecebrosus , of various masses (M, kg), swimming at various speeds (U, ms−1) in a tunnel respirometer yielded two relationships:
1. (a) Voo2 = 245M0.73 e1.59U
2. (b) Voo2 = 555M0.75 P0.77
2. 2. Both jet frequency and peak pressures increase with increasing speed. Patterns varied considerably between individuals, but total area under the pressure curve (P) was well correlated with oxygen consumption and speed.
3. 3. A differential pressure transducer linked to an ultrasonic transmitter carrying average pressure data encoded on impulse frequency was designed to be carried inside the mantle cavity. It was tested in both the swim-tunnel and in video-taped free-swimming animals.
4. 4. The relationships above held over a range of speeds from 0 to 1.4 ms−1, the maximum speed observed, indicating that such transducers could provide direct estimates of both the metabolic rates and activities of these pelagic carnivores in nature; their use to test hypotheses about several energy-saving strategies is discussed.
5. 5. Average thrusts, calculated from pressure data, are consistent with rigid body drag predictions and with overall locomotor efficiencies of 5 %, which are also consistent with the relative costs of transport and efficiency estimates for fish.
TL;DR: High-energy phosphate stores in the liver were greatly depleted, although there was no measurable decline in liver glycogen content and Glycolytic activation in the white muscle is argued to have a major impact on the hypoxia tolerance of trout.
Abstract: Rainbow trout were subjected to 1 and 3h of environmental hypoxia (20Torr, 4°C), after which samples of blood, heart, brain, liver, and red and white muscle were removed for metabolite determination. The heart, brain and white muscle all showed signs of glycolytic activation. High-energy phosphate stores in the liver were greatly depleted, although there was no measurable decline in liver glycogen content. Glycolytic activation in the white muscle is argued to have a major impact on the hypoxia tolerance of trout, as this tissue produces the bulk of the lactate. These responses of the trout are contrasted with those of the African lungfish, a fish which is relatively tolerant of hypoxia.
TL;DR: The endurance of three bats was so much greater near the middle of their speed ranges that the maximum flight distances ought to be achieved at these velocities, even though the cost of transport would be lower at higher speeds.
Abstract: Up to eight physiological parameters were measured on members of four species of fruit bats with a size range of 0.188-0.650 kg as they flew in a wind tunnel. Regression lines were calculated for the relationships between body masses of bats and their power inputs (P 1 ), heart and respiratory rates. These were compared to similar relationships for flying birds. Respiratory evaporation dissipated only 10% of the heat produced. At ambient temperatures (T a ) above 15°C, heat loss was facilitated by vasodilation of feet and wing membranes, but this mechanism became less effective at high T a when thermal differential between wings and air was reduced. Bats are apparently unable to increase greatly their respiratory evaporation, and overheated at T a of 25–30°C. At low T a ) the flight ability of two bats was reduced, suggesting that reduced coordination or even freezing of wings might be a general problem for bats flying at T a close to 0°C. The endurance of three bats was so much greater near the middle of their speed ranges that the maximum flight distances ought to be achieved at these velocities, even though the cost of transport would be lower at higher speeds. Endurance at an airspeed was proportional to the relative power input (P i /P i,min ) raised to the power of −7.45; flying at a speed that raised P i /P i,min by 10% reduced endurance by half.
TL;DR: Monitoring of diving behaviour and heart rate in tufted ducks under circumstances which simulated various environmental conditions such as feeding under ice in winter suggested that the ducks could gradually switch over to a 'classical' oxygen-conserving response during these prolonged voluntary dives.
Abstract: Diving behaviour and heart rate were monitored in tufted ducks diving under circumstances which simulated various environmental conditions such as feeding under ice in winter. When distance to food was increased on a covered outdoor pond, dive duration increased proportionately, but it was calculated that time available for feeding was reduced during the longer-distance ‘extended’ dives. There was a gradual reduction in heart rate to 77.3 +/− 13.8 beats min-1, which is significantly lower than the resting value of 121.1 +/− 14.1 beats min-1, during the course of extended dives, suggesting that the ducks could gradually switch over to a ‘classical’ oxygen-conserving response during these prolonged voluntary dives. The duration of the pre-dive preparatory period was positively correlated with dive distance. When the ducks were briefly unable to resurface during an otherwise normal feeding dive in an indoor tank, a situation which may occur if they become disoriented under ice, there was an immediate switch to a full bradycardia. Reduction in heart rate during these ‘enclosed’ dives occurred only when the ducks were apparently aware of the situation and the rate of onset of bradycardia was very similar to that previously observed during involuntary submersion of tufted ducks. Minimum heart rate was the same at 46 beats min-1 after 15 s of enclosed dives and after 30 s of involuntary submersions, despite the differences in levels of activity in the two situations.