bluuebunny/crossref_metadata_2025_split huggingface dataset:
Mass-Dependence of Anaerobic Metabolism and Acid-Base Disturbance During Activity in the Salt-Water Crocodile,Crocodylus Porosus
Authors: Bennett A. F. , Seymour R. S. , Bradford D. F. , Webb G. J. W. 
Published: April 2021

ABSTRACTLactate concentration ([lactate−]), pH, and bicarbonate concentration ([HCO3−]) were measured in the blood of salt-water crocodiles (Crocodylus porosus Schneider) exhausted during field capture. Body temperature after capture averaged 31·1 °C. All animals underwent high levels of anaerobic metabolism and metabolic acidosis. The largest animals attained the highest blood [lactate−] and lowest pH ever observed in any animal as a result of activity. Peak levels of [lactate−] increased with increasing body mass (slope = 9·72 mmol 1−1 logM−1; mass M in kg), indicating a greater anaerobic capacity in larger animals. Several large crocodiles had [lactate−] in excess of 50mmol 1−1. Blood pH decreased with mass (slope = 0·163 pH unitslogM−1) and reached 6·6 in the largest animals. One animal remained acidotic for several hours and had a minimal pH of 6·42. Blood increased significantly and [HCO3−] decreased significantly with increasing body mass. Struggling time before exhaustion was greater in larger animals, ranging from about 5min in small (&lt;1 kg) crocodiles to over 30min in animals over 100 kg. During recovery, mean blood [lactate−] decrement after 2h was 6·0 mmol 1−1 and was not significantly related to mass. Proton elimination from the blood, however, was more rapid in larger animals (slope = 0·0443 μmol 1 −1 log M −1 ). The positive mass-dependence of acid-base disturbance could be related to the greater susceptibility of large crocodiles (&gt;700 kg) to post-capture mortality.
Adrenalin-Induced Na+/H+ Exchange In Trout Erythrocytes and its Effects Upon Oxygen-Carrying Capacity
Authors: Cossins A. R. , Richardson P. A. 
Published: April 2021

ABSTRACT
Addition of adrenalin (10−4moll−1) to trout erythrocytes in an unbuffered saline resulted in a rapid acidification of the extracellular medium. This process was inhibited by amiloride (K1/2∼10−4moll−1) and by the removal of extracellular Na +. The rate of acidification was a saturable function of extracellular Na+ concentration.
When extracellular pH was maintained constant by continual titration with KOH, adrenalin induced a transient burst of H+ efflux. During this period the loss of cellular H+ equivalents was approximately equal to the net gain of Na+, providing evidence for a Na+/H+ exchange with a stoichiometry of 1. The steady state following stimulation with adrenalin could be disturbed by changes in extracellular pH. After the addition of adrenalin, intracellular pH (pHi) was increased by 0·2–0·3 units but did not exceed extracellular pH, as required if the Na+ and H+ concentration ratios came into equilibrium. The increase in pHi in stimulated compared with control cells was maintained approximately constant over a wide range of pH0, suggesting that pH equilibration by the Jacob-Stewart cycle was operating normally and that the activation of Na+ / H+ exchange provides an offset to the normal relationship between pHi and pHo. The steady state results from a balance of an increase Na+/H+ and CD/HCO3− exchange with an increased rate of Na+ pumping and next KC1 efflux.
In a buffered saline, adrenalin caused a 22–46 % increase in the oxygen-carrying capacity of trout erythrocytes. It is suggested that this was due to a Root effect of trout haemoglobin caused by cellular alkalinization when the Na+/H+ exchange mechanism was activiated. This observation suggests that many published values for oxygencarrying capacity of fish blood require re-evaluation.
Muscle Protein Synthesis Rates During Temperature Acclimation in a Eurythermal (Cyprinus Carpio) and a Stenothermal (Salmo Gairdneri) Species of Teleost
Authors: Loughna P. T. , Goldspink G. 
Published: April 2021

ABSTRACT
Rates of protein synthesis were measured in the white myotomal muscle of carp (Cyprinus carpio) and rainbow trout (Salmo gairdneri) at a number of environmental temperatures before and after they had spent an acclimatory period at these temperatures. For carp previously kept at a mid-range temperature of 15 °C the rates of muscle protein synthesis showed a Q10 of 3·07 over the range of 10–25 °C. Acclimation to low temperatures resulted in the rate of protein synthesis being elevated whilst acclimation to high temperatures resulted in the depression of protein synthesis rate. Rainbow trout also initially maintained at 15 °C showed an initial Q10 of 3·57 between 5 and 20 °C. In this species, however, there was no significant difference in protein synthesis rates after being kept for 1 month at any given temperature within this temperature range. In the carp where acclimatory changes were recorded, it was found that these changes occurred at a faster rate at 25 °C than at 10°C. The ability of the carp to modify its protein metabolism in this way is discussed as a strategy for reducing temperature effects upon growth and muscle function.
Ventilation and Oxygen Uptake byNautilus
Authors: Wells M. J. , Wells J. 
Published: April 2021

ABSTRACTThe shell of Nautilus prevents the mantle from playing any part in creating the ventilatory stream. This is generated instead by movements of the collar and funnel folds which fuse to form flaps (the ‘wings’), overlapping below and joined to the head above. The gills lie horizontally, dividing the space enclosed by the wings into three cavities, two lateral and prebranchial, on either side of the head, and a common ventral postbran-chial space. Water is drawn in above, behind the eyes, and expelled forward through the siphon of the funnel, which is used both for ventilation and jet propulsion. The pressures driving the ventilatory stream are small (of the order of 0·1 kPa), but the complex movement of the wings, described below, is such that there is (very nearly) always a pressure differential and a water flow across the gills, despite a pulsed intake and outward jet. Oxygen extraction is low by the standards of other cephalopods, only 5-10%, falling during jet propulsion and rising (exceptionally to 40 %) at rest after exercise. Ventilation frequency, 35 min−1 at 16°C, rises with temperature. Ventilation stroke volumes ranged from 5 to 22 ml for an animal of 395 g. At 17 °C Nautilus can regulate its oxygen uptake down to a of about 75 mmHg. Uptake at rest ranged from 0·22 to 0·46 ml kg−1 min−1 (exceptionally 0·75 ml kg−1 min−1 after feeding) for animals of 351-395 g. In terms of flesh weight, this yields an average of 0·50 ml kg−1 min−1, half to one-third of the uptake one would expect from coleoids of similar weights and at similar temperatures.
Nereistoxin: Actions on a Cns Acetylcholine Receptor/ion Channel in the CockroachPeriplaneta Americana
Authors: Sattelle D. B. , Harrow I. D. , David J. A. , Pelhate M. , Callec J. J. , Gepner J. I. , Hall L. M. 
Published: April 2021

ABSTRACTNereistoxin hydrogen oxalate (NTX), at low concentrations (in the range 2·0 × 10−8—1·0 × 10−6 mol 1−1), induced a dose-dependent partial block of transmission at cereal afferent, giant interneurone synapses in the terminal abdominal ganglion (A6) of the cockroach Periplaneta americana which was not accompanied by changes in either membrane potential or input resistance of the postsynaptic membrane. At a concentration of 1·0xl0−7moH−1, NTX suppressed, in a voltage-dependent manner, acetylcholine-induced currents recorded from voltage-clamped cell bodies of both giant interneurone 2 (GI 2) in A6, and the fast coxal depressor motoneurone of the metathoracic ganglion (T3). At higher concentrations (in the range 1·0 × 10−5—1·0 × 10−3moll−1) depolarization of the postsynaptic membrane was observed. Axonal depolarization was noted at concentrations above 1·0 × 10−4moll−1. Voltage-clamp experiments showed that the axonal actions of NTX included suppression of sodium and potassium currents and an increase in the membrane leak current. The concentrations of NTX (in the range 1·0 × 10−5-1·0 × 10−3 moll−1) which show the postsynaptic depolarizing effect are in the same range as the NTX concentrations (1·7 × 10−4 and 6·6 × 10−5moll−1) required for 50% inhibition of the binding of 125I-α-bungarotoxin to Periplaneta abdominal nerve cord extracts and Drosophila head extracts, respectively. Thus a potent, voltage-dependent, blocking action of NTX is detected at the CNS acetylcholine receptor/ion channel complex of the cockroach. This, possibly together with the synaptic and axonal depolarizing effects noted at much higher concentrations, may contribute to the mechanism of action of this natural invertebrate neurotoxin which is also the active form of the synthetic insecticide Cartap.
Body Hydration and Haemolymph Osmolality Affect Feeding and its Neural Correlate in the Terrestrial Gastropod,Limax Maximus
Authors: Phifer Curtis B. , Prior David J. 
Published: April 2021

ABSTRACTWhen terrestrial slugs (Limax maximus) are dehydrated to 65–70 % of their initial body weight (IBW) their feeding responsiveness is greatly decreased. There is a 90 % decrease in feeding responsiveness when slugs are injected with hyperosmotic mannitol solution that raises the haemolymph osmolality to that of slugs dehydrated to 65–70 % IBW (i.e. 200 mosmolkg−1 H2O). The duration of the Feeding Motor Programme (FMP) that can be recorded from an isolated CNS-lip preparation is reduced by increasing the osmolality of the saline bathing the preparation. The osmolality of the saline that can modify the FMP corresponds to that of the haemolymph of a slug dehydrated to 65–70 % IBW. The pattern of the motor programme is not affected. A gradual increase in saline osmolality which temporally mimics the progressive increase in haemolymph osmolality of a dehydrating slug also causes a decrease in the duration of the FMP. The neural network underlying the FMP appears to adapt to hyperosmotic saline since the duration of FMP bouts gradually returns to normal levels after long-term exposure (6–8 h).
Efferent Influences on the Afferent Activity From the Octopus Angular Acceleration Receptor System
Authors: Williamson R. 
Published: April 2021

ABSTRACT
Electrophysiological recordings were made from afferent units of the octopus angular acceleration receptor system during the electrical stimulation of efferent axons to this system. Of the afferent units examined, 93% changed their activity in response to stimulation of the efferent axons.
During efferent stimulation 77% of the afferent units decreased their activity. The magnitude of the inhibition and the time to maximum response were frequency dependent, with most units showing an increase in inhibition with increase in efferent stimulation frequency. The poststimulus recovery from inhibition was of two types: either a gradual increase in activity to the pre-stimulus resting level of activity (Fig. 3) or a rapid increase in activity to a level above the pre-stimulus level, i.e. a post-inhibitory rebound or facilitation, and then a gradual decline to the resting level of activity (Fig. 4). During long periods of efferent stimulation (&gt; 40 s) the inhibition was not maintained.
During stimulation of the efferent axons 16% of the afferent units increased their activity. The post-stimulus response consisted of either a gradual decrease in activity to the pre-stimulus level of resting activity or a rapid increase in activity followed by a gradual decrease to the resting level of activity (Fig. 6). During long periods of efferent stimulation the excitation increased to a plateau level which was maintained for the duration of the stimulus period (Fig. 7).
Sinusoidal oscillations of the statocyst evoked bursts of afferent activity in time with the movement. The magnitude of these bursts could be decreased or increased by stimulation of the efferent axons (Fig. 8).
It is proposed that two populations of efferents are present in the octopus statocyst, one inhibitory and the other excitatory, and that both types of efferent affect single afferent units.
Differences Between Upstroke and Downstroke in Swimming Dolphins
Authors: Videler John , Kamermans Pauline 
Published: April 2021

ABSTRACT
Steady swimming movements of dolphins were recorded in a search for direct evidence of asymmetry between upstrokes and downstrokes. Kinematic swimming and gliding data from frame-by-frame analysis of ciné pictures taken at constant frame rates with a camera in a fixed position are presented. We estimated the propulsive forces generated by the tail blade with a simple hydrodynamic model.
Dolphins accelerate during the downstroke and decelerate during the upstroke: the net hydrodynamic force in the animal is always positive during the downstroke and negative during the upstroke. Both parts of the stroke cycle are equally long. The propulsive forces of downstrokes are on average larger than the forces of the upstrokes. Occasionally the average forces within an upstroke are greater than within a downstroke of the same sequence. Our data suggest that the drag on the body during the upstroke exceeds the drag in the course of the downstroke. The specific swimming speed or stride length of dolphins swimming at low speeds is about 0·9 body lengths per tail beat.
Experimental Demonstration of Volterra’s Periodic Oscillations in the Numbers of Animals
Authors: Gause G. F. 
Published: April 2021

ABSTRACT
From purely theoretical considerations Lotka (1920) and Volterra (1926) concluded that a biological system consisting of two interdependent species (predator and prey) will exhibit regular periodic fluctuations in respect to the absolute and relative abundance of each species, even when random fluctuations due to external environmental factors have been eliminated. So far as is known this conclusion has not been investigated by direct experimental methods.
The Effect of Bacterial Products on Amoebic Growth
Authors: Cutler D. Ward , Crump Lettice M. 
Published: April 2021

ABSTRACT
The interrelationships that exist between various groups of Protozoa in nature and the bacteria which occur in the same environments are undoubtedly of more than academic interest. This is especially the case perhaps in soil, where both types of organisms are present in very large numbers, and where a marked degree of activity is evidenced by the continual fluctuation to which these numbers are subject. The food relationships of one member of the soil population, the amoeba Hartmanella hyalina, was described in a previous paper (2), where it was shown that certain kinds of bacteria afforded a more efficient food supply than others as judged by the reproductive rate of the amoeba. A priori this might have been due to the fact that the bacteria giving a high reproductive rate to the amoebae were of greater food value than the others ; or that the by-products formed by the less valuable bacterium in the course of growth were deleterious in their effects; but preliminary experiments indicated that for the species of bacteria concerned it was a true food value effect and not one caused by the presence of any by-products.
The Effect of Captivity Upon the Reproductive Cycle of the South African Clawed Toad (Xenopus Laevis)
Authors: Alexander S. S. , Bellerby C. W. 
Published: April 2021

ABSTRACT
The South African clawed toad (Xenopus laevis) can be maintained in captivity in a healthy condition provided that it is adequately fed. No atrophic changes are found to occur in the ovary as reported by Zwarenstein and Shapiro for animals kept in captivity in Cape Town. The developmental condition of the ovary depends directly upon the amount of food available. The normal periods of ovarian growth and retrogression which occur in the toad under natural conditions can be explained on the basis of fluctuation in food supply.
The Effects of Temperature and Humidity on the Cheese Skipper, Piophila Casei (L.)
Authors: Smart John 
Published: April 2021

ABSTRACT
The extraordinary resistance of all the developmental stages of Piophila casei (L.) to adverse conditions and their general tenacity to life has been noticed by several authors. Alessandrini (1909) reports the results of the treatment of the larvae with some seventy reagents; Krausse (1909) reports on a similar series of tests, and Simmons (1927) gives details of some rather more carefully controlled experiments together with a general summary of our knowledge of the fly at the time of the publication of his paper. The resistance of the fly in its various stages to conditions usually lethal for insects, suggested that it might prove of interest to examine some of the reactions of the Cheese Skipper to conditions of controlled temperature and humidity such as Buxton (1931 b) and Mellanby (1932,1934) have applied to various other insects. The present paper is the result of this investigation.
Blood Flow in Acute Hypoxia in A Cephalopod
Authors: Wells M. J. , Wells J. 
Published: April 2021

ABSTRACT
This paper reports a method of measuring blood flow in the dorsal aorta of Octopus vulgaris using fixed magnet flow meters. Blood flow, like blood pressure, falls progressively during acute hypoxia. Flow increases greatly as soon as the ambient rises, with values for a given external exceeding those found during the preceding development of hypoxia. On average, about 70 % of the total systemic blood flow runs down the aorta to the head and arms; the rest goes to the gonad, to the mantle, to the coronary circulation and to the guts. This pattern remains unchanged as the ambient falls.
A Potassium-Selective Channel in Isolated Lymnaea Stagnalis Heart Muscle Cells
Authors: Brezden B. L. , Gardner D. R. , Morris C. E. 
Published: April 2021

ABSTRACT
Lymnaea stagnalis heart ventricle muscle cells, isolated by enzymatic dispersion, are suitable for patch clamp recording. A channel has been identified which is primarily selective for potassium, although it also appears to conduct sodium. This channel is not blocked by 4-aminopyridine or tetraethylammonium but is sensitive to quinidine. The relationship between the membrane potential, the external potassium concentration and the channel currents, when compared with results obtained from whole cell recording, suggests that this channel could mediate a large part of the cell’s resting conductance.
The probability of this channel being open is increased by stretching the patched cell membrane. This has led to speculations about further possible functional roles for this channel.
Hydrostatic Pressures in Glomeruli and Renal Vasculature of the Hagfish, Eptatretus Stouti
Authors: Riegel J. A. 
Published: April 2021

ABSTRACT
Hydrostatic pressures in the renal vasculature of hagfish have been studied. Estimates of the blood colloid osmotic pressure (COP) have been made. In blood vessels supplying the renal corpuscles, the average hydrostatic pressure is about 1 kPa. The average hydrostatic pressure falls to a value of 0·04 kPa within the postcardinal vein efferent to the renal corpuscle. Within the glomerular capillaries the hydrostatic pressure averages 0·21 kPa. Since the blood COP averages about 1–4 kPa, it is clear that glomerular filtration in the hagfish is not underlain by the hydrostatic pressure of the arterial pulse.
In some blood vessels efferent to the renal corpuscles, hydrostatic pressure may be as high as in the afferent supply. Evidence is presented that the glomerular capillaries are shunted by this high pressure vascular pathway.
Blood Oxygen Transport In The Free-Swimming Hagfish, Eptatretus Cirrhatus
Authors: Wells R. M. G. , Forster M. E. , Davison W. , Taylor H. H. , Davie P. S. , Satchell G. H. 
Published: April 2021

ABSTRACT
Arterial and mixed venous blood were sampled through chronically implanted cannulae from rested and swimming hagfish. remained high when hagfish were swum for 15min at a velocity of 20cms-1. fell from 17-2mmHg at rest to 3’5 mmHg after swimming, and the arteriovenous pH difference increased from 0·15 to 0·25 pH units. Whole blood oxygen equilibrium curves were essentially hyperbolic (Hill’s n value = 1·38) and gave a half-saturation (P50) value of 12·3 mmHg at pH 7·8 and 16°C. A CO2-Bohr factor (ϕ = ΔlogP50/ΔpH) of –0·43 and a limited buffering capacity of the blood, amounting to approx. 4slykes, were observed. The role of the blood in transporting oxygen and carbon dioxide both at rest and after swimming is established by in vivo blood gas measurements and in vitro oxygen-binding data. The low internal at rest is close to the P50 measured under similar conditions and the hyperbolic equilibrium curve permits further oxygen unloading when falls during swimming.
The Relationship of Muscle Electrical Activity, Tremor And Heat Production To Shivering Thermogenesis In Japanese Quail
Authors: Hohtola Esa , Stevens E. Don 
Published: April 2021

ABSTRACT
We measured the electrical activity and the tremor of the pectoral muscle and total body heat production in control and cold-acclimated Japanese quail at +26°C, + 12°C and +2°C before and after 3 weeks of acclimation, using electromyography, accelerometer recordings, and indirect calorimetry. Japanese quail shiver in 0·2- to 3-s bursts that occur in groups. An increase in both the frequency and the duration of bursts and burst groups contributes to the increase in heat production by shivering at low temperatures. A compilation of shivering patterns in birds is given and its implications for the neural control and phylogeny of shivering are discussed. A rather non-specific increase in electromyographic (EMG) activity and heat production was observed after cold acclimation at all experimental temperatures, although many of the normal signs of cold acclimation (e.g. decrease in gonad mass, increase in heart mass and serum triiodothyronine) were seen. The increase in muscle electrical activity was greater than the increase in oxygen uptake, which resulted in a lower ratio. The amplitude distribution of muscle electrical activity remained normal, but a shift towards higher frequencies occurred in the EMG spectra of cold-acclimated birds. Despite the increase in muscle electrical activity, power spectra of accelerometer recordings indicated that the amplitude of the muscle tremor was lower in cold-acclimated birds. The increase in the high-frequency components of the EMG indicates that decreased synchronization of motor unit firing may account for the lower tremor amplitude. We suggest that this change is adaptive because it reduces heat loss and/or because more fatigue-resistant motor units are recruited. These results show that temperature acclimation modifies the neural control of shivering in skeletal muscle.
Mechanical Analysis of Spontaneous Breathing in the Semi-Aquatic Turtle, Pseudemys Scripta
Authors: Vitalis Timothy Z. , Milsom William K. 
Published: April 2021

ABSTRACT
The normal breathing pattern of Pseudemys scripta (Schoepff) consists of a continuous burst of breaths separated by a variable period of breath holding. Under normoxic conditions, tidal volume was 6·9 ml kg−1 and the number of breaths was 1·9 min−1. Increases in pulmonary ventilation upon stimulation by hypercapnia (3 % CO2) or hypoxia (4 % O2) are caused primarily by increases in the number of breaths per minute due to a shortening of the breath-hold period. Tidal volume and breath duration remain unchanged. The instantaneous breathing frequency (f′ = 60/Ttot) of 35 ± 2min−1 corresponds to continuous pump frequencies that minimize the rate of the mechanical work of breathing in anaesthetized turtles. This indicates that turtles breathe at a combination of tidal volume and f′ that minimizes the power required to ventilate the lungs. To increase ventilation, the breath hold is shortened and more breaths are taken at this optimal combination. Bilateral vagotomy drastically alters the breathing pattern, producing an elevation in tidal volume, a slowing of breathing frequency, and a prolongation of breath duration while total ventilation remains unchanged. These data suggest that periodic breathing in this species may represent an adaptive strategy which is under vagal control and which serves to minimize the cost of breathing.