bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on Freshwater Osmoregulation in the Ammocoete Larva of Lampetra planeri (Bloch)
Authors: Morris R. , Bull J. M. 
Published: April 2021

ABSTRACT
An investigation has been made of the factors which cause sodium loss from ammocoetes when they are immersed in de-ionized water at 1° and 10° C. Sodium influx ceases when animals are first immersed in de-ionized water, but can recommence when the animal loses sufficient sodium to the environment. The concentration of sodium required for influx to take place decreases with succeeding periods of immersion in de-ionized water at 10° C. and reaches minimum equilibrium concentrations as low as 0·005 mM-Na/l. Low temperature inhibits sodium influx and thus promotes net loss of sodium to de-ionized water. Low temperature also decreases the initial loss of sodium to de-ionized water and probably lowers the permeability of the external surfaces of the animal to ions. This effect is small compared with the inhibition of ion uptake so that the combined result is to increase the net loss of sodium from the animal. Since animals lose calcium to de-ionized water and show a decreased rate of sodium loss when calcium salts are added, it is believed that the high rates of sodium loss in de-ionized water are attributable to the effect of calcium on permeability. Lack of calcium may also explain why animals which have been depleted of sodium by low-temperature treatment take up sodium much faster at higher temperatures from dilute Ringer solutions than from pure sodium chloride solutions. When animals lose ions to de-ionized water at low temperature, sodium and chloride are lost from the extracellular space, whilst the muscle cells lose potassium. These ions are recovered into the extracellular space when animals are allowed to take up ions at 10° C. from diluted Ringer solution later.
An Application of the Constant-Field Theory to the Behaviour of Giant Neurones of the Snail,Helix aspersa
Authors: Moreton R. B. 
Published: April 2021

ABSTRACTThe resting potentials of giant neurones in the abdominal ganglia of the snail, Helix aspersa, have been measured, and their dependence on the extracellular concentration of potassium ions has been investigated. The behaviour of the resting potentials differs considerably from that of a potassium electrode, as given by the Nemst equation. A modification of the equation derived from the ‘constant-field’ theory is described, which transforms the equation for the resting potential into a linear relationship ; it is found that the experimental results can be fitted quite well by this equation, for potassium concentrations up to 12 mM. This is taken as evidence that the relative permeabilities of the cell membrane to potassium and sodium ions are independent of the external potassium concentration over the range of concentrations used. By fitting ‘best straight lines’ to the experimental data, estimates can be obtained from the ‘constant-field’ equation of the intracellular potassium concentration, and the ratio of permeabilities of the cell membrane to sodium and potassium ions, PNa/PK-The average results from experiments on fifty-seven neurones are : the error in each case being one standard deviation, calculated from the spread of the results. The average intracellular potassium concentrations of snail neurones show a distinct seasonal variation, being highest in the spring and lowest in the autumn. These changes are accompanied by changes in the selectivity of the cell membranes, as characterized by the ratio of permeabilities to sodium and potassium ions, so that the resting potentials of the cells are comparatively little affected. The changes could be connected with changes in the pattern of activity of the animals.
The Control of Water Loss in Locusta Migratoria Migratorioides R. & F
Authors: Loveridge J. P. 
Published: April 2021

ABSTRACT
The rate of water loss from the cuticle of Locusta is proportional to weight. The rate of water loss from the cuticle at 30° C., 0% R.H. is 5·63 ±0·67 mg./ locust/hr., giving a permeability of 0·022 mg./cm.2/mm. Hg/hr. The transition temperature at 46–48° C. is similar to that of Schistocerca (Beament, 1959) and probably indicates the existence of an oriented lipid monolayer in the epicuticle. At relative humidities of 0–50% the rate of water loss from whole locusts decreases with time. This phenomenon, which does not occur at 75% R.H., is partly due to the loss of adsorbed hydroscopic water during the initial period. A continuing apparent decrease in transpiration is shown to be a true permeability change. The relationship between saturation deficit and rate of water loss at 30° C. is curvilinear, falling away at high saturation deficits. This results in a saving of water amounting to 1·5–2·5 mg./locust/hr. at 25% R.H. and 2·7–4·0 mg./locust/hr. at 0% R.H. and will be biologically significant if not an artifact. The anomalous relationship between saturation deficit and rate of water loss is caused by the permeability change occurring at low R.H. Three theories which may account for these phenomena are discussed.
The Control of Water Loss in Locusta Migratoria Migratorioides R. & F
Authors: Loveridge J. P. 
Published: April 2021

ABSTRACT
The rate of total transpiratory water loss from Locusta is proportional to weight and is not affected by activity within the limits possible in an enclosed box. A trend for proportionately less water to be lost at low humidity than at high humidity probably involves active measures to control water loss from the tracheal system. The saving of water is 5 mg./locust/hr. at 0% R.H., 30° C. Experiments involving exposure of locusts to CO2 of different concentrations show that little control over water loss is exerted by the spiracles except in so far as they may influence the type of ventilation. Hyperventilation, predominantly of the tidal type, doubles normal water loss. Between 42 and 45° C. the ventilatory rate increases enormously with concomitantly greater water loss. Locusts pre-treated in dry air show a 23% reduction in abdominal ventilatory rate and a 25% reduction in water loss over locusts pre-treated in moist air. Ventilatory movements of locusts under conditions of progressive desiccation show decreased rate and amplitude and an increased incidence of discontinuities, which will conserve water. Ventilation and water loss are closely interdependent. The fact that ventilation can be controlled according to water reserves and the humidity of the air is important in water conservation.
Further Observations On the Physiology of Salinity Adaptation in the Crab-Eating Frog (Rana Cancrivora)
Authors: Gordon Malcolm S. , Tucker Vance A. 
Published: April 2021

ABSTRACT
Total rates of urea loss from adult euryhaline crab-eating frogs (Rana cancrivora) adapted to various environmental salinities between fresh water and 80% sea water increase as salinity increases above 40% sea water. Oxygen consumption is constant in rate in all salinities studied. The presence of urea in the Ringer solution bathing isolated pieces of skin of frogs adapted to 60% sea water increases both the electrical potential and the inwardly directed short-circuit current across the skin. In skeletal muscle cells addition of intracellular solutes maintains tissue hydration in the face of large increases in plasma osmotic concentration in high-salinity media. Changes in the intracellular urea and free amino acid concentrations are primarily responsible for increases in intracellular osmotic concentration. Some implications of these observations are discussed and comparisons made with the euryhaline green toad, Bufo viridis.
Tonic and Phasic Systems in Parallel in the Eyecup Responses of the Crab Carcinus
Authors: Horridge G. A. , Burrows M. 
Published: April 2021

ABSTRACT
Static positions of the eyecup are maintained by control of the frequency of impulses to tonic muscle fibres. In addition, phasic muscle fibres are excited when an optokinetic stimulus containing frequency components faster than about 0·1 Hz. exceeds about 0·1° in amplitude. Within the above limit, components of the stimulus of greater frequency or amplitude excite the phasic system, which adapts in a few seconds. Normally the tonic and phasic systems act in parallel. With oscillatory movements of a striped drum the tonic and phasic units do not have the same phase relation to the stimulus. The numerous components in parallel are so varied and interact at all stages, so that they cannot be related quantitatively to an analysis of the overall response. Although changes in frequency at each movement are large in one muscle and small in another, there is no question of coarse and fine control because none are separately controlled or dependent on the eyecup position.
Eyecup Withdrawal in the Crab, Carcinus, and Its Interaction With the Optokinetic Response
Authors: Burrows M. , Horridge G. A. 
Published: April 2021

ABSTRACT
Protective withdrawal of the eyecup is caused by a burst of impulses in two axons of the optic tract, one to muscles 19 a, 19 b and 20 a, the other to muscles 18, 20b, 21 and 22. At a reflex eyecup withdrawal other concurrent activity is mechanically overridden; the tonic activity in only one muscle is inhibited centrally. At a ‘spontaneous’ withdrawal, however, all motor activity to that eyecup is inhibited. The largest muscle, 19 a, inactive in other eyecup movements, is the prime mover in withdrawal, and some tonic fibres of this muscle hold the eyecup withdrawn. Two muscles which move the eyecup toward the mid line on optokinetic responses are excited during a withdrawal. It is therefore possible for one muscle to contribute to movements in opposite directions. Repeated reflex withdrawal of an eyecup moving towards the mid line inhibits the optokinetic response of the other eye. Weak stimulation of an eyecup region by a variety of means, including withdrawal, improves the optokinetic response of that eyecup and sometimes of the other eyecup
Observations On the Intake of Water and Electrolytes by the Duck (Anas Platyrhynchos) Maintained On Fresh Water and On Hypertonic Saline*
Authors: Fletcher G. L. , Holmes W. N. 
Published: April 2021

ABSTRACT
Intake of food, water and electrolyte by ducks maintained on fresh water and on hypertonic saline were measured over periods up to several months. Transfer to saline approximately equivalent to 60% sea water was followed during the first 24 hr. by a sharp rise and fall in the plasma concentrations of sodium and chloride, which thereafter remained similar to the concentrations found in the freshwater-maintained birds. Transfer to saline equivalent to 100% sea water resulted in a rise in these concentrations during the first 10 hr., which continued for a period up to 14 days, after which the birds either died or became unhealthy. Upon transfer to saline drinking water (284 mM/1. Na+, 6·0 mM/1. K+) there was a gradual loss of body weight accompanied by a reduction in the food and water intake. Body weights tended to become stable after about 3 weeks, but some individuals continued to lose weight while others regained what they had lost. When the concentration of sodium chloride in the drinking water exceeded 143 mM/1. the amount of sodium chloride ingested remained constant. Thus there was progressive decline in the volume of water drunk as the concentration increased. It would appear therefore that the saline-adapted duck possessed some mechanism whereby the daily intake of sodium chloride was regulated. The cloacal output from saline-adapted ducks over a 24 hr. period showed that only 10% of the ingested sodium was excreted via this pathway as compared with over 70% of the ingested potassium. Most of the sodium appeared to be excreted via the nasal glands. The possible interactions between the renal and extra-renal excretory pathways in the maintenance of homeostasis during adaptation to diets including hypertonic saline or seawater are discussed.
Pharmacological Properties of Excitatory Neuromuscular Synapses in the Locust
Authors: Usherwood P. N. R. , Machili P. 
Published: April 2021

ABSTRACT
The effects of a wide range of amino acids and related compounds on retractor unguis nerve-muscle preparations from the locust, grasshopper and cockroach have been investigated. L-glutamate is the most active excitatory substance. The presence of two acidic groups and one amino group is essential for excitatory activity while the position of the amino group is of some importance in determining the level of activity. When L-glutamate is applied iontophoretically to the muscle fibres, ‘glutamate’ depolarizations are recorded only at the synaptic sites. Other evidence that the action of glutamate is restricted to the synaptic sites is presented. Perfusion of isolated locust retractor unguis nerve-muscle preparations with locust haemolymph does not markedly affect the neurally evoked mechanical responses. It appears that locust haemolymph contains little ‘free’ L-glutamate. Four acidic amino aids have been identified in the perfusate from isolated retractor unguis preparations namely, glycine, alanine, aspartate and L-glutamate. However, only L-glutamate increases in concentration during stimulation of the retractor unguis nerve.
Electrical Activity in the Hydroid Cordylophora
Authors: Mackie G. O. 
Published: April 2021

ABSTRACT
Cordylophora has two major hydranth pacemaker systems, one producing slow,, biphasic pulses at 2·0–4·0 sec. intervals (slow pulse or SP system) and one exhibiting sharp, predominantly negative potentials singly or in bursts with a normal interval of 1·5−2·0sec. between pulses (fast pulses, FPs). Both SPs and FPs are recorded throughout the hydranth, but do not spread to and are not co-ordinated in adjacent hydranths. SPs could not consistently be evoked artificially and showed no clear behavioural correlates. FPs occur during feeding and following electrical stimulation, where they may accompany a muscle response. FPs appear superimposed on SPs when both systems are active. Such a composite event advances the SP rhythm by an amount close to the normal FP inter-pulse time, but compensatory adjustment of the SP rhythm then occurs. Treatment with 10−5g./ml. tetrodotoxin has no apparent effect on Cordylophora.
Changes in Textural Preferences in Octopus After Lesions
Authors: Wells M. J. , Young J. Z. 
Published: April 2021

ABSTRACT
Octopuses repeatedly tested at alternate trials with rough and smooth spheres presented without reward take more of the smooth than the rough spheres. The individuals that take most often show the greatest preference. The overall tendency to take decreases within each session of sixteen trials and recovers by the next session some hours later. There is a slight decrease in mean takes over the first few sessions but the level then remains at about 36% over ten sessions of sixteen trials. Animals without vertical lobes tested in the same way without rewards take more often (at 60% of all trials). As with the normals there is a decline in take within each session: Extinction is therefore not exclusively the result of changes in the vertical lobe. The preference for smooth is less marked in animals without the vertical lobes than in normals. Animals with the supraoesophageal lobes split by a vertical cut (‘half-brain animals ‘) and animals with the supraoesophageal lobes removed except for the buccal and ventral subfrontal take fewer objects than normal octopuses. The same animals show reduction or reversal of the smooth preference manifest in normal octopuses. Removal of the whole of the inferior frontal system produced animals that take more often than normal, at 63% of all trials. These octopuses showed a marked preference for smooth. The system for release of objects is defective in these animals and this may act to give the appearance of excesss of takes of smooth. The fact that blind but otherwise normal octopuses prefer smooth objects was confirmed in a discrimination training experiment. Normal animals trained with a smooth sphere as positive performed better initially than those trained in the other direction, though the asymptote reached was the same for both. Animals without vertical lobes showed in training about the same preference for smooth as normals but were variable. They learned more slowly than normals. Half-brain animals showed a strong preference for rough in training. The animals trained with smooth positive learned very slowly and had not reached the level of those trained with rough positive after 160 trials.
Respiration in the African Lungfish Protopterus Aethiopicus
Authors: Johansen Kjell , Lenfant Claude 
Published: April 2021

ABSTRACT
Factors controlling aerial and aquatic breathing have been studied in the intact, free-swimming African lungfish, Protopterus aethiopicus. Frequencies of aerial and branchial breathing were correlated with gas tensions in the lung and in blood from pulmonary and systemic arteries and veins. Studies were made, on fish resting in aerated water, during exposure to air and during hypoxic and hypercarbic conditions in the environment. Both branchial and pulmonary breathing were irregular during rest in aerated water. The rate of branchial breathing normally exceeded that of air breathing. An increased rate and vigour of branchial breathing commonly preceded an air breath. There was no indication that a new air breath was related to the values of arterial Po2 Air exposure elicited a marked and immediate increase in the rate of air breathing. Hypoxic water never evoked any compensatory breathing responses while breathing from a hypoxic gas mixture quickly increased the rate of air breathing. Bubbling 5% CO2 in air into the aquarium caused a reduction in branchial breathing while the rate of air breathing increased. Nicotine injected intravenously or in the water close to the gills elicited an increase in both aerial and branchial breathing. Respiratory and circulatory events were correlated during undisturbed breathing and during artificial lung inflation. Increased cardiac output and a shift in regional blood flow to a higher pulmonary flow occurred with air breaths.
A Wind-Tunnel Study of Gliding Flight in the Pigeon Columba Livia
Authors: Pennycuick C. J. 
Published: April 2021

ABSTRACT
A technique for training pigeons to fly in a tilting wind tunnel is described, and a method of determining lift and drag in gliding flight is explained. Drag measurements were made on wingless bodies and preserved feet in supplementary experiments. The results were used to analyse the measured total drag of live pigeons into (a) body drag, (b) foot drag, (c) induced drag, and (d) wing profile drag. As speed is increased, gliding pigeons drastically reduce their wing span, wing area and aspect ratio. The increased induced drag resulting from this is more than offset by a very large reduction in wing profile drag. Although the lift:drag ratio is at best 5·5-6·0, changes of wing area and shape keep it near its maximum, up to speeds at least twice the minimum gliding speed.
Power Requirements for Horizontal Flight in the Pigeon Columba Livia
Authors: Pennycuick C. J. 
Published: April 2021

ABSTRACT
Certain measurements made on pigeons flying horizontally in a wind-tunnel are described. A method, based on helicopter theory, for calculating the power required to fly at any given speed is explained. Induced, profile and parasite power are calculated separately. It is concluded that the pigeon can fly horizontally without incurring an oxygen debt at speeds from 3 to 16 m./sec. The minimum power speed is 8 – 9 m./sec. The maximum continuous power output is estimated to be 10·5 W., and the corresponding oxygen consumption about 170 ml./min. The maximum (sprint) power is estimated to be 20·4 W., from observations of vertical climb after take-off. The estimated best lift: drag ratio in horizontal flight is 5·9, giving a range of 11·8 km./g. of fat oxidized for a 400 g. pigeon. It is argued from considerations of structural strength that the early part of the downstroke is used mainly to impart angular velocity to the wing, and that air loads are only developed after most of the angular acceleration has taken place. The tension in the pectoralis insertion may exceed 60% of the breaking tension in fast horizontal flight. The power calculation was repeated for the ruby-throated hummingbird, using published data. Estimated best range is about 900 km./g. of fat oxidized, achieved at 9 m./sec. The corresponding effective lift: drag ratio is 4 ·1. The variation of power required and power available with size is considered, and the effect on hovering and take-off performance of different birds deduced. Performance estimates for the pigeon and ruby-throated hummingbird are very poor by engineering standards, but consistent with these birds’ known abilities, and are in general agreement with estimates of effective lift: drag ratio derived from published data on other species.
Some Features of the Central Co-Ordination of A Fast Movement in the Crayfish*
Authors: Roberts Alan 
Published: April 2021

ABSTRACT
The nervous and muscular activity pattern produced in an abdominal segment by a single giant-fibre impulse when all peripheral reflexes are abolished is described. This description depends on criteria for the identification of efferent neurones to the tail muscles. These are discussed and the identification of the inhibitor to the fast flexor muscles is established by anatomical homology. The pattern of response to a giant-fibre impulse is summarized in Fig. 4. Inhibition of the fast flexors, the lack of an extension command, the slow flexor contraction, the accessory neurone discharge and central nervous inhibition during the escape movement are among the features discussed.
The Energy-Sources in Ontogenesis
Authors: Needham Joseph 
Published: April 2021

ABSTRACTThe percentage growth-rate curves for carbohydrate and protein in the chick enbryo have been determined and compared with those already in the literature for the percentage growth-rates of the whole embryo, the dry substance, the fat, and the calorific value. The composition of the embryo in gm. per cent, of dry weight has been calculated and an ontogenetic succession of carbohydrate, protein, and fat, has been brought to fight. These three cell-constituents are at their highest levels in the embryo at 4, 11 and 20 days of incubation respectively. This may be correlated with the succession of maximum intensities of combustion, which have the same order (about 5,8· 5 and about 18 days). By comparing the curves for absorption-intensity with those representing the constitution of the embryo, it has been possible to trace the passage of building-materials from the yolk and white into the embryo and to analyse still further the movements of the fat and carbohydrate fractions. The concentration of the carbohydrate and protein in the water of the embryonic body has been calculated and compared with a curve already in existence for fat. The curve for intensity of absorption of total foodstuff has been calculated from the results of chemical analyses. It agrees as well as can be expected at present with that calculated from the oxygen consumption and the increase of dry substance in the embryo. The ratio Carbohydrate : Protein decreases during development, thus falling into line with the ratios Water : Solid, Inorganic Substance : Organic Substance, and Protein : Fat. Certain speculations arising out of these facts are discussed. There is a relation of simultaneity between the combustion of carbohydrate, protein, and fat, and the part these types of molecule play in the constitution of the whole embryo.