bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ventilation and partitioning of oxygen uptake in the frog Rana pipiens: effects of hypoxia and activity
Authors: Pinder A. W. , Burggren W. W. 
Published: April 2021

ABSTRACT
Pulmonary and cutaneous oxygen uptake and lung ventilation were measured in frogs floating in water with access to air in respirometers, with and without ventilation of the skin provided by stirring. The frogs were exposed to hypoxia in both water and air, and were variably active.
In inactive frogs floating in unstirred respirometers at 25°C, 23% of total is through the skin. Activity of the animal increases total and also ventilates the skin, so that cutaneous increases with increasing total . When the respirometer is stirred, cutaneous increases to 35 % of total in resting animals. Activity no longer affects cutaneous .
Lung ventilation volume is directly proportional to lung ventilation rate in normoxia. Ventilation rate, and therefore ventilation volume, is proportional to pulmonary . Ventilation rate approximately doubles in hypoxia . The pattern of ventilation also changes in hypoxia, from a very irregular pattern in normoxia to one showing regular, large oscillations of lung volume over several ventilation movements.
Increased lung ventilation, enhancing pulmonary , is the primary adjustment to increased O2 demand. Partitioning of shifts towards the lung during both activity and hypoxia. In both cases, however, ventilation of the skin can supplement total by increasing absolute levels of cutaneous .
Thermal dependence of contractile properties of skeletal muscle from the lizard Sceloporus occidentalis with comments on methods for fitting and comparing force-velocity curves
Authors: Marsh R. L. , Bennett A. F. 
Published: April 2021

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°C intervals from 10 to 40°C. The mean isometric parameters at 35°C, the preferred body temperature of this species, were as follows: maximum isometric force (Po), 187 ± 8 (S.E.M.) kN m-2; ratio of twitch force to tetanic force (PTW/P0)&gt; 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%R), 8·2 ±0·3 ms. From 20 to 35°C P0 was almost constant (within 8% of the value at 35°C). At 10 and 15°C Po dropped to approximately 80 % of the value at 35°C. P0 was very unstable at 40°C. PTW/P0 was almost constant at all temperatures. The time-related isometric parameters were positively modified by temperature at all temperatures measured (Q10&gt; 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: To describe the curvature of this or any other force-velocity relationship, we propose the power ratio, Ẇmax/VmaxP0 (where Ẇmax 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 21·9L0s-1 at 35°C (where L0 is muscle length). This parameter was directly related to temperature between 10 and 35 °C with Q10&gt; 1·8. The shape of the force-velocity curve is not influenced by temperature (Ẇ max/ Vmax P0 = 0·11).
Single-Channel Studies of the Action of ( + )-Tubocurarine on Locust Muscle Glutamate Receptors
Authors: Kerry C. J. , Ramsey R. L. , Sansom M. S. P. , Usherwood P. N. R. , Washio H. 
Published: April 2021

ABSTRACT
The effects of ( + )-tubocurarine (TC) on single glutamate-activated channels in voltage-clamped locust muscle fibres have been examined using the patch-clamp technique. Glutamate alone produced a concentration-dependent increase in the probability of the channel being in the open state (po), but an increase in the concentration of glutamate (5× 10−5–5× 10−3 moll−1) in the presence of 5× 10−4 moll−1 TC left po essentially unchanged. TC (5× 10−6–5× 10−4moll−1) caused a concentration-dependent decrease in the mean open time and in po for channels opened by 10−4moll−1 glutamate. Correlations between successive openings and successive closings, which are characteristic of the kinetics of the muscle glutamate-receptorgated channel of locust muscle, were weakened in the presence of TC. There was little evidence of voltage sensitivity of TC action over the limited membrane potential (Vm) range —70 to —120 mV. The results are consistent with the idea that TC blocks the cation-selective channel gated by glutamate receptors in insect muscle and that the unblocking rate is low. They suggest also that block is at the level of the open channel, a conclusion supported by the wholly activation-induced depression of the neurally evoked twitch contraction of locust muscle by TC. Based upon a simple model for open channel block, TC is estimated to have a dissociation constant of 1·57μmoll−1 (Vm = — 100mV). The rate of association of blocker with channel is estimated to be 8·74×103ms−1 (moll−1)−1 (Vm= –100mV). The rate of dissociation, estimated indirectly from the single-channel data, is 1·53× 10−2ms−1, which gives a mean channel block time of 65·4 ms.
Internal Hypoxia-Hypercapnia in Tench Exposed to Aluminium in Acid Water: Effects on Blood Gas Transport, Acid-Base Status and Electrolyte Composition in Arterial Blood
Authors: Jensen Frank B. , Weber Roy E. 
Published: April 2021

ABSTRACT
Tench exposed for 6 days to acid (pH 5) hard water ([Caz+] = 3·5 mmol I−1) in the presence of aluminium (2 mg I−1) showed a rapid decrease (within 3 h) in dorsal aortic and a simultaneous rise in -Arterial oxygen content and haemoglobin oxygen (Hb-O2) saturation decreased sharply, as did red cell [Hb], whereas blood haematocrit (Het) and [Hb] increased. Red cell nucleoside triphosphate (NTP) content was reduced within 1 day through a selective reduction in guanosine triphosphate (GTP).
Although the rising caused an extracellular acidosis (to which lactic acid production and perhaps H+ influx at the gills contributed), red cell pH increased compared to control values, mainly as a result of the decrease in Hb-O2 saturation. Plasma [Cl−] declined, whereas [HCO3−], [K+] and [Ca2+] increased. Ionic disturbances, however, were small compared to the changes in blood O2 transport, which appeared to correlate with high ambient [Ca2+],
Tench exhibited a high tolerance to the acid-Al exposure and most of the above parameters showed partial recovery within 1–2 days. In some specimens, however, the exposure was lethal because of an obstruction of gill function, and arterial blood became almost completely deoxygenated and showed very low pH values and high lactate concentrations, attesting to deep internal hypoxia.
A possible role for protein dissociation in the functioning of embryonic haemoglobins
Authors: Brittain T. 
Published: April 2021

ABSTRACT
During early mammalian development the changing demands for oxygen in embryonic tissues are met, in part, by the synthesis of a series of embryonic haemoglobins. At the earliest stages of development three embryonic haemoglobins are synthesized in both humans and mice (Melderis, Steinheider & Ostertag, 1974; Shimizu & Watanabe, 1978; Brotherton, Chui, Gauldie & Patterson, 1979; Purdie, Wells & Brittain, 1983; Brittain & Wells, 1983). The proportions of each haemoglobin present in the mouse red blood cells vary significantly from the ninth day of gestation until parturition (Purdie et al. 1983). Although studies have been made on this developmental system of gene switching and haemoglobin composition (Brotherton et al. 1979) very few studies have been made on the functional characteristics of these embryonic haemoglobins, mainly because of the limited amount of material available (Bauer et al. 1975 ; Brittain & Wells, 1983 ; Purdie et al. 1983). The oxygen binding curves for whole blood from the earliest embryos show anomalous binding patterns (Wells & Brittain, 1981; Purdie et al. 1983; Brittain & Wells, 1983). The high oxygen affinity component present in the red blood cells of early embryonic mice has been correlated with the presence of embryonic haemoglobin El, which has a subunit structure χ2ϵ2 (Melderis et al. 1974). This haemoglobin species El shows very low cooperativity in both its equilibrium and kinetic functions (Purdie et al. 1983; Brittain, Sutherland & Greenwood, 1986). Recent investigations have indicated that the functioning of this haemoglobin is not related to any unusual redox balance within the embryonic red blood cell (Brittain & Tottle, 1986) and thus the occurrence of an essentially non-cooperative haemoglobin with a tetrameric subunit structure has posed something of a paradox. This study presents data on the dimerization of mouse embryonic haemoglobin El over a range of conditions and, together with numerical simulations of oxygen binding curves, illustrates how, within the early embryonic red blood cell, high oxygen affinity and sensitivity to pH may be obtained by protein dimerization.
Regulation of Tarsal Taste Threshold in the Blowfly, Phormia Regina
Authors: Edgecomb Robert S. , Murdock Larry L. , Smith André B. , Stephen Margaret D. 
Published: April 2021

ABSTRACT
The nutritional condition of adult blowflies (Phormia regina Meigen) affects their readiness to respond with proboscis extension when their tarsi contact food stimuli. Thresholds are high in sated flies (100–1000 mmol I−1 sucrose) and low in starved flies (1–10 mmol I−1 sucrose). Two feeding regimes employing aqueous sucrose were used to reveal factors regulating tarsal taste threshold in this insect: long-term feeding (ad libitum) and single meals administered to starved flies.
A positive logarithmic relationship was found between crop weight and tarsal taste threshold, expressed as mean acceptance threshold, in flies fed aqueous sucrose ad libitum for 4 days. Threshold changes after a single meal were positively correlated to both concentration and volume of the sugar solution fed. Thresholds observed in flies fed a single meal were not as high as those in ad libitum-fed flies having the same crop volume.
Nerve-transection experiments demonstrated that the median abdominal nerve plays no direct role in threshold regulation in either single-meal-fed or ad libitum-ied flies. Transection of the recurrent nerve (RN), however, significantly attenuated the post-feeding rise in tarsal threshold in starved flies fed a single meal and markedly reduced threshold in sated flies fed ad libitum. Thresholds for RN-transected flies subjected to either feeding regime were still significantly higher than thresholds for starved flies. Haemocoel-injected D-glucose did not significantly elevate threshold in starved flies.
These observations establish that the RN plays an important role in the regulation of tarsal taste threshold in blowflies. The effect of the RN on threshold depends largely on the prior feeding activity of the flies. It appears, however, that other factors, in addition to the recurrent nerve, affect taste threshold after feeding.
Studies of the cardiac-like action potential in crayfish giant axons induced by platinized tungsten metal electrodes
Authors: Orr L. A. , Lieberman E. M. 
Published: April 2021

ABSTRACT
A lightly platinized tungsten (Pt-W) wire electrode, axially inserted into a crayfish giant axon, causes the development of cardiac-like action potentials with durations of up to 4 s. The plateau in membrane potential typically occurs within 10 min of the start of action potential elongation. The effect occurs without passing current through the Pt-W electrode and is temporally related to a dramatic decrease in intracellular pH (pH,). Such an effect cannot be induced by a decrease in pH, produced by equilibrating the axon with HCO3−-CO2 solution (pH 6), an NH4C1 rebound or direct intracellular injection of PO43− buffer (pH 4 5). Action potential elongation is accompanied by a block of delayed rectification and the possibility that inward rectification also develops cannot be ruled out. Plateau generation requires Na+ and Caz+ inward currents as demonstrated by abolition of the plateau by [Na+]o or [Ca2+]o depletion or treatment with tetrodotoxin (TTX) or verapamil. The block of outward rectification by Pt-W requires external Na+ or Ca2+. Action potential elongation produced by 3,4-diaminopyridine is not sensitive to verapamil and the waveform is different from that produced by Pt-W. The data support the possibility that different classes of excitable membranes have similar channel populations and that the functional differences between them reside in the inhibitory or masking influences that are present in the microenvironments of the various membrane channels.
The Sulphide-Binding Protein in the Blood of the Vestimentiferan Tube-Worm, Riftia Pachyptila, is the Extracellular Haemoglobin
Authors: Arp Alissa J. , Childress James J. , Vetter Russell D. 
Published: April 2021

ABSTRACT
The sulphide-binding protein that occurs in high concentrations in the vascular blood and coelomic fluid of the hydrothermal vent tube-worm Riftia pachyptila Jones is the haemoglobin. Sulphide binding does not occur at the oxygen-binding sites of the haem, but may occur via thiol-disulphide exchange at the interchain disulphide bridges on the macromolecule. We have confirmed the report that vascular blood is heterogeneous for two haemoglobins (FI and FII) that are different in MT, but we conclude that the coelomic fluid is homogeneous for the lower Mr haemoglobin FII, in the intact, living animal. These two haemoglobins occur naturally in the living animals, and FII is not a dissociation product of the higher Mr FI. The sulphide-binding capacities of the two haemoglobin species differ by about a factor of two. Consequently, the vascular blood and the coelomic fluid also have different sulphide-binding capacities. These differences in sulphide-binding capacity may have important ramifications for the physiology of this unusual animal.
The effects of prolonged epinephrine infusion on the physiology of the rainbow trout, Salmo gairdneri: I. Blood respiratory, acid-base and ionic states
Authors: Perry S. F. , Vermette M. G. 
Published: April 2021

ABSTRACT
Rainbow trout were infused continuously for 24 h with epinephrine in order to elevate circulating levels of this hormone to those measured during periods of acute extracellular acidosis (approximately 5×l0−8moll−1). Concomitant effects on selected blood respiratory, acid–base and ionic variables were evaluated. Infusion of epinephrine caused a transient respiratory acidosis as a result of hypoventilation and/or inhibition of red blood cell (RBC) bicarbonate dehydration. The acidosis was regulated by gradual accumulation of plasma bicarbonate. Even though whole blood pH (pHe) was depressed by 0·16 units, RBC pH (pHi) remained constant, thereby causing the transmembrane pH gradient (pHe–pHi) to decrease. A similar effect of epinephrine on RBC pH was observed in vitro, although the response required a higher concentration of epinephrine (2·0× 10−7 mol I−1). We speculate that the release of epinephrine during periods of depressed blood pH is important for preventing excessive shifts in RBC pH and for initiating a series of responses leading to plasma HCO3− accumulation and eventual restoration of blood acid-base status.
The Effects of Aerial Exposure on the Distribution of Body Water and Ions in the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Taylor E. W. , Tyler-Jones R. , Wheatly M. G. 
Published: April 2021

ABSTRACT
Submerged crayfish had a total body water content of 76% body mass. Haemolymph volume was around 30% and was dependent on mass, the relationship being described by the regression equation y (volume) = 3·98+0·177x (mass). The inulin space was greater than the copper space in abdominal muscle, suggesting the existence of an interstitial component of the extracellular fluid into which haemo-cyanin does not penetrate. Crayfish exposed to water-saturated air (100% relative humidity, RH) did not lose mass and haemolymph levels of K+ and Na+ were unchanged from the submerged values. When exposed to air (70-80% RH) crayfish progressively dehydrated at the rate of 0·38 % body massh-1 (0·5 % body water h-1) and died after 72 h when 27 % of initial mass had been lost. After a 10 % reduction in mass, haemolymph volume was significantly reduced to about 75 % of its submerged value in 10-g animals and to 65 % in 60-g animals, the decrease in volume being approximately equivalent to the mass lost. After 48 h in air (19% reduction in mass) haemolymph volume was further reduced to 24% of the submerged volume. The total water content of the abdominal muscles showed a small but significant reduction when animals were dehydrated which could be accounted for by a reduction in the extracellular fluid volume, including the interstitial space. After 48 h dehydration in air the osmolarity of the haemolymph increased by 36%, [K+] by 47 % and [Cl-] by 57 % above the submerged levels whilst [Na+] showed an insignificant decrease of 10%. In the abdominal muscle [K+] increased by 15 %, [Na+] increased by 23 % and [Cl-] decreased by 27 %. [Caz+] levels in the haemolymph doubled after 24 h in air, an increase which was independent of the degree of dehydration. The increase is thus a result of emersion and not dehydration and may be due to a mobilization of CaCO3 from the exoskeleton to buffer a respiratory acidosis, as it corresponds to a doubling in [HCO3- + CO32-]. A substantial loss of ions from the haemolymph during dehydration cannot be fully accounted for by uptake into the tissues or by urinary losses, but a 500 mmol 1-1 increase in the Na+ concentration of the proventricular contents suggests that the foregut may play an important role in ionoregulation.
Intracellular Free Potassium, Sodium and Chloride Measured with Ion-Selective Microelectrodes from Salivary Gland Cells of the Snail Planorbis Corneus
Authors: Barber Andrew 
Published: April 2021

ABSTRACT
Double-barrelled, ion-selective microelectrodes (ISMEs) have been used to measure the intracellular free concentrations of K+ ([K+]1), Na+ ([Na+]1) and Cl- ([Cl-]1), together with membrane potentials (EM), from single salivary gland acinar cells of the pond snail Planorbis corneus. After adjustments had been made for the cross-sensitivities of the ion-exchangers to other intracellular ions, the mean concentrations were estimated to be: [K+]1, 42·9mmol1-1; [Na+]1, 2·4mmol1-1; and [Cl-]1, 10·3 mmol 1-1. The mean Nernstian equilibrium potentials for K+, Na+ and Cl- were calculated to be —88 mV, +74·4mV and —41 mV, respectively. The basolateral membrane of Planorbis salivary cells appears to be permeable to K+ and Na+ under resting conditions, because blocking the electrogenic Na+/K+ pump with K+-free saline or ouabain revealed the presence of a large passive efflux of K+ and an influx of Na+. Salivary gland cells also lose intracellular Cl- rapidly in CD-free saline (extracellular Cl- replaced by sulphate) which, along with other evidence, indicates a substantial resting permeability of the salivary cell membrane to Cl-. Stimulating gland cells with 10−4 mol 1-1 acetylcholine (ACh) led to a depolarization of EM1 a rise in [Na+]1 and a fall in [K+]1. This was followed by a transient hyperpolarization of EM and a recovery of [Na+]1 and [K+]1 to their original levels. There was no evidence that [Cl-]1 changes after stimulation with ACh. The mechanism of action of ACh on Planorbis salivary gland cells and its relevance for secretion are discussed.
Turning flight of bats
Authors: Aldridge H. D. 
Published: April 2021

ABSTRACT
The turning flight of six microchiropteran bat species is described. The bats’ abilities to turn tightly were determined by their abilities to fly slowly and to generate high lateral accelerations. Rhinolophus ferrumequinum developed high lateral accelerations by flapping its banked wings while flying at very low speed. Plecotus auritus turned at relatively low speed and at low lateral acceleration. The other species were all moving fast as they turned and generated lateral accelerations either by developing high bank angles or by flapping their wings with low bank angles. There was a significant correlation between wing loading and turning curvature, indicating that low wing loadings improve manoeuvrability.
Precision and Dynamics of Positioning by Canada Geese Flying in Formation
Authors: Hainsworth F. Reed 
Published: April 2021

ABSTRACT
A method is described for reconstructing perspective-distorted film images of geese flying in V formations to allow measurements of wing tip spacing (WTS, the distance between wing tips of adjacent birds perpendicular to the flight path) and depth (the distance along the flight path between birds). Measurements for eight formations are used to test for savings in induced power from wing placement in a vortex field generated by other wings, using the model of Lissaman & Schollenberger (1970) to estimate savings. The median WTS for 55 geese corresponded to an induced power saving of 36%, about half the maximum possible. There was considerable variation in WTS between and within formations. Some birds maintained WTS close to an optimum for saving energy; others maintained WTS with excessive gap. Birds at the apex and those at large depths achieved low energy savings. Savings were enhanced by periodic changes in flight direction in response to variations in the position of the bird ahead. Individuals in some formations adjusted WTS more rapidly when they were displaced a greater distance from the optimum, and some position adjustments appeared to reflect the distribution of savings predicted from vortex theory.
Role of glycolysis in adenylate depletion and repletion during work and recovery in teleost white muscle
Authors: Dobson G. P. , Hochachka P. W. 
Published: April 2021

ABSTRACT
Measurements of metabolite concentrations before and immediately after swimming of trout to exhaustion indicate that all three potential endogenous fuels of anaerobic metabolism [glycogen, phosphocreatine (PCr) and adenosine triphosphate (ATP)] are utilized during anaerobic white muscle work. Lactate, H+, creatine, Pi, NH4+ and inosine monophosphate (IMP) are formed in the process. Glycolysis is considered to be functionally (if loosely) coupled to adenylate depletion by setting up conditions favouring AMP-deaminase-catalysed formation of IMP and NH3. During recovery under these experimental conditions, glycolysis appears to outcompete oxidative metabolism as an ADP acceptor; therefore, in this kind of white muscle, glycolysis is also linked to IMP reconversion to AMP and thus to adenylate replenishment. The net process generates H+, which is why ATP replenishment must be completed before PCr concentrations can be returned to pre-exercise values.