bluuebunny/crossref_metadata_2025_split huggingface dataset:
Patterns and bilateral coordination of scaphognathite rhythms in the lobster Homarus americanus
Authors: Wilkens J. L. , Young R. E. 
Published: April 2021

ABSTRACT
The bilateral patterns of forward and reversed scaphognathite (SG) pumping are described for the American lobster. During forward pumping the two SGs usually function synchronously, but may also function independently. The nine muscles of one SG are arranged into four functional groups which are sequentially active during forward pumping. During reversed beats, motor neurones to one group of muscles are inactive while bursts to another are either delayed or missing. Reversal beats do not appear to alter the phasing of thec entral oscillators that generate the basic SG rhythm.
Phase analysis of bilateral SG beating demonstrates two types of relationship : phase coupling or phase drifting with a tendency to couple. An animal may remain in one state for long periods of time or may alternate between states. Coupling can occur at more than one phase indicating phase multistability. The coupled state may remain constant at markedly different frequencies of beating, indicating phase rather than latency coupling between SGs. During the drifting state each SG tends to assume its ‘intrinsic’ rate of oscillation. The drift state reflects the inherent asymmetry of the two SG systems. The influence of several parameters of sensory stimulation on phase and frequency of SG beating are analyzed.
Micropuncture study of the renal responses of the urodele amphibian Necturus maculosus to injections of arginine vasotocin and an anti-aldosterone compound
Authors: Garland H. O. , Henderson I. W. , Brown J. A. 
Published: April 2021

ABSTRACT
Necturus maculosus kidney function has been examined using standard clearance techniques and renal tubular micropuncture methodology. Throughout, cyanocobalamin (vitamin B12) has been used to monitor glomerular filtration rate (GFR) and tubular water movements. It was established that this substance was handled by the Necturus kidney in a similar manner to inulin. It can be readily analysed, together with renal electrolytes, by electron microprobe techniques. Profiles of transtubular gradients (TF:P ratios) along the nephron were established for osmolarity, sodium, potassium, calcium and cobalt (of cyanocobalamin). Ureteral urine is always hyposmotic with respect to plasma and the site of dilution of the plasma ultrafiltrate is within the distal segment. Up to 30 % of the filtrate is isosmotically reabsorbed along the proximal tubule ; the tubular fluid : plasma ratio for osmolarity and sodium is around 1, and the TF : P for cobalt of cyanocobalamin is about 1·4 by the end of this segment. The renal effects of the neurohypophysial hormone arginine vasotocin (AVT) and an aldosterone antagonist (SC14266; Soldactone) have been examined. AVT was consistently antidiuretic causing both a decreased GFR and an enhanced distal tubular reabsorption of water. SC14266 also increased distal tubular reabsorption of water. Such an effect differs from that found in higher vertebrates, and may indicate a ‘glucocorticoid-type’ of renal action for aldosterone in amphibians.
Potassium exchange between bathing solution and midgut of Hyalophora cecropia and time delay for potassium flux through the midgut
Authors: Zerahn K. 
Published: April 2021

ABSTRACT
Exchange between potassium of the isolated midgut of the American silkworm Hyatophora cecropia and the bathing solutions has been determined by different authors, but with contradictory results. Therefore the experiments were repeated with another technique and the exchange determined for varying time intervals. It was found that the exchange was fast -half of the midgut K was exchanged in 2–3 minutes, which confirms the earlier findings by Harvey & Zerahn (1969).
Electrophysiological analysis of potassium and sodium movements in crustacean nervous system
Authors: Abbott N. J. , Moreton R. B. , Pichon Y. 
Published: April 2021

ABSTRACT
An electrophysiological method was used to estimate the half-times for sodium and potassium entry to, and efflux from, the extra-axonal space in peripheral nerve and central nervous connectives of two species of crustacean. Results from crab (marine) and crayfish (fresh water) were qualitatively similar. Peripheral nerve showed no evidence for diffusion barriers, potassium entry and efflux being rapid, and proceeding at comparable rates. In connective, potassium entry was extremely slow, with a half-time greater than 100 min, while potassium efflux was relatively rapid . Sodium movements were less restricted, but sodium entry was more rapid than sodium efflux. The potassium experiments were compared with the behaviour of a theoretical model system. Evidence is presented for diffusional restriction to potassium at the connective perineurial layer. The mechanism of restriction may involve changes in permeability or activation of an ion pump in the perineurial layer. The physiological significance of these findings is discussed.
Active transport of potassium by the Cecropia midgut; tracer kinetic theory and transport pool size
Authors: Wood J. L. , Harvey W. R. 
Published: April 2021

ABSTRACT
Tracer influx kinetics have been analysed theoretically to determine the size of the transport pool with no assumptions regarding the transport pathway. For a calculation of the size of the transport pool to be made, the following six conditions are required by the theory: tracer steady state attained, tissue steady state attained, Isc measures net flux, small magnitude and constant time-course of efflux, and correction for decay in pumping rate. The size of the pool, S1 is given by the steady state influx, J∞, divided by the mixing-time constant, α. Some experimental results are analysed by three different graphical methods, and it is shown that these three methods are equivalent. Specifically, a is equal to the reciprocal of the 75 % mixing time, divided by In 4 and is equal to the reciprocal of the lag time, X. The tracer kinetic theory is applied to active potassium transport across the isolated short-circuited midgut: the transport meets the six conditions required by the theory. The size of the transport pool of potassium in one midgut is calculated to be 80·5 μequiv./g wet weight under high-K steady-state conditions. A value as high as this suggests that the pool is intracellular.
Active transport of magnesium across the isolated midgut of Hyalophora cecropia
Authors: Wood J. L. , Jungreis A. M. , Harvey W. R. 
Published: April 2021

ABSTRACT
The 28Mg-measured net flux of magnesium from lumen-side to haemolymph-side of the isolated and short-circuited midgut was 1.97 + 0.28 µ-equiv cm−2 h−1 in 8 mM-Mg2+. The magnesium-influx shows a delay before the tracer steady-state is attained, indicating the existence of a magnesium-transport pool equivalent to 6.7 µ-equiv/g wet weight of midgut tissue. Magnesium depresses the short-circuit current produced the midgut but not the potassium transport, the depression being equal to the rate of magnesium transport. Magnesium transport yields a linear Lineweaver-Burk plot with an apparent Km of 34 mM-Mg2+ and an apparent Vmax of 14.9 µ-equiv cm−1 h−1. Magnesium is actively transported across the midgut and contributes to the regulation of the haemolymph magnesium concentration in vivo.
Cation distributions across the larval and pupal midgut of the lepidopteran, Hyalophora cecropia, in vivo
Authors: Harvey W. R. , Wood J. L. , Quatrale R. P. , Jungreis A. M. 
Published: April 2021

ABSTRACT
The levels of potassium, sodium, magnesium and calcium in leaves, midgut contents, midgut tissue, and blood were analysed in seven developmental stages between feeding, fourth-instar larvae and new pupae of the Cecropia silkworm. Three dramatic changes in cation levels were found: the K level in the contents drops from 284 ±51 mEquiv./l tissue water in the fifth-instar larva to 51 ± 6 mEquiv./l in the new pupa ; the Mg level in the midgut tissue increases from 28 ± 3 mEquiv./l at the time of gut evacuation to 1093 ± 104 mEquiv./l in the new pupa; and the Ca level in the contents drops temporarily from 56 ± 12 mEquiv./l in the feeding fourth instar larva to 17 ± 5 mEquiv./l in the new fifth instar larva. The Na level was never higher than 2·8 ± 0·5 mEquiv./l. The relative levels of the four cations were different for each tissue studied, but each tissue maintained the same relative levels during the developmental stages studied. The sequences are: leaf, Ca &gt; K &gt; Mg &gt; Na; midgut contents, K ⪢ Ca &gt; Mg &gt; Na; midgut tissue, K ⪢&gt; Mg &gt; Ca &gt; Na; and blood, Mg ⪢ K &gt; Ca &gt; Na. There were three large concentration gradients across the midgut ; the K level in the midgut contents is approximately 10 times the level in blood; the Mg level in contents is one-half to one-sixth the level in blood; and the Ca level in contents is 3—4 times the level in blood. The K gradient and the Ca gradient are opposed and the Mg gradient is favoured by the electrical gradient across the larval midgut, the contents being 100 mV positive with respect to the blood. The K gradient and the electrical gradient are not present across the pupal midgut while the Mg gradient and the Ca gradient persist. The K gradient is presumably maintained by the midgut K pump, the Mg gradient is aided by the midgut Mg pump, and the Ca gradient suggests that the midgut may possess a Ca pump.
A quantitative analysis of ventilation tachycardia and its control in two chelonians, Pseudemys scripta and Testudo graeca
Authors: Burggren W. W. 
Published: April 2021

SUMMARY
In both the turtle, Pseudemys scripta, and the tortoise, Testudo graeca, lung ventilation is closely accompanied by a tachycardia of predictable magnitude and duration. Efferent vagal activity progressively decreases as heart rate increases with the onset of lung ventilation. Atropine increases heart rate during apnoea to those levels observed during prolonged breathing series when vagal tone is negligible, β-adrenergic blockade of the heart does not affect the development, duration or magnitude of ventilation tachycardia. It is thus concluded that heart rate change during chelonian lung ventilation is mediated solely by alterations in vagal tone. Peripheral sensory reflexes involving pulmonary stretch receptors, arterial chemoreceptors and baroreceptors, and receptors stimulated by water immersion do not affect heart rate during breathing. It is suggested that ventilation tachycardia in these chelonians is the result of the spread of activity between the respiratory and cardiac centres of the medulla.
Diuresis in the tsetse fly Glossina austeni
Authors: Gee J. D. 
Published: April 2021

ABSTRACT
After taking a blood meal, the tsetse fly Glossina austeni excretes the excess water and salts of the meal in approximately 30 min. During this period a volume of fluid equivalent to 80% of the unfed weight of the fly passes through the haemolymph, whose composition nevertheless remains almost constant. The fluid excreted has a higher sodium and lower potassium concentration than the haemolymph, indicating that sodium may be the prime mover in urine formation in Glossina.
The Permeability to Ions of the Neural Lamella and the Extracellular Spaces in the C.N.S. of Anodonta Cygnea
Authors: Sattelle D. B. , Howes E. A. 
Published: April 2021

ABSTRACT
Rapid axonal depolarization follows the elevation of [K+]o in the Ringer bathing the surfaces of the connectives of both intact and desheathed cerebro-visceral connectives of Anodonta cygnea. Potassium movements between the blood or medium bathing the surface of the connectives and the axonal membranes can be accounted for in terms of a first-order diffusion process. No visible structural barriers to prevent free movements of materials through the neural lamella and the extracellular spaces can be detected in electron micrographs of the cerebro-visceral connectives. In desheathed preparations fast action potentials are conducted in sodium-free (dextran) Ringer. Mechanisms of axonal function and ionic regulation in this and other inverte-brate central nervous tissues are discussed in the light of these observations.
Extrinsic modulation of crayfish escape behaviour
Authors: Krasne F. B. , Wine J. J. 
Published: April 2021

ABSTRACT
Extrinsic systems were shown to control the excitability of the neurones which mediate tail-flip escape in the crayfish. Restraint suppresses the escape mediated by giant fibres and some, but not all, categories of non-giant mediated escape; autotomy of claws increases the excitability of non-giant mediated escape without affecting the lateral giant reflex.
The effects of restraint on the lateral giant reflex result from inhibition rather than reduced facilitation. The inhibition descends from thoracic and higher levels, and the lateral giant escape command neurone appears to be its primary target. Inhibition may serve to shift the control of escape behaviour from short latency ‘reflex’ systems to more flexible ‘voluntary’ ones which can produce responses at times most opportune for successful escape.
Effects of helium and other inert gases on Echinosphaerium nucleofilum (protozoa, heliozoa)
Authors: Miller J. B. , Aidley J. S. , Kitching J. A. 
Published: April 2021

ABSTRACT
The effects of helium, nitrogen, argon and krypton on Echinosphaerium nucleofilum (Heliozoa) have been studied at partial pressures of 10–130 atm. Additional experiments have been carried out with hydrostatic pressure alone. Helium causes shortening of the axopods over the whole range of pressures, and damage to the cell body at pressures of 60–90 atm, both with a maximum at 80 atm. These effects cannot be explained in terms of hydrostatic pressure alone; a ‘pressure reversal’ effect may be operating, causing the peak at 80 atm. Nitrogen also causes both cell damage and axopod shortening, the severity increasing with increasing pressure. Argon and krypton cause cell damage but no shortening. The order of potency for cell damage is krypton &gt; argon &gt; nitrogen &gt; helium. It is suggested that there may be tuo sites of action, possibly the microtubules (for axopod shortening) and the cell membrane (for cell damage). In appropriate mixtures of helium and argon, both the cell damage usually caused by argon, and the axopod shortening usually caused by helium, are prevented. Possible mechanisms include the effects of hydrostatic pressure on gas solubility coefficients, reversal of the effects of the gases by the increase in total pressure, and competition for sites of action.
Physical and adrenergic factors affecting systemic vascular resistance in the rainbow trout: a comparison with branchial vascular resistance
Authors: Wood C. M. , Shelton G. 
Published: April 2021

ABSTRACT
The passive distensibility and adrenergic reactivity of the systemic vascular resistance (Rs) in Salmogairdneri have been studied using perfused trunk pre-parations, and the data compared with previous results on the branchial resistance (Rg). At normal levels of efferent blood pressure, Rs is relatively more distensible than Rg in response to afferent pressure increases, but this difference may not be important in vivo, α-adrenergic constrictory receptors predominate in Rs, in contrast to β-adrenergic dilatory receptors in Rg; a significant a-adrenergic tone in Rs is lost during perfusion. Rs is far less sensitive than Rg to circulatory catecholamine levels. It is suggested that the sympathetic nervous system, rather than plasma catecholamines, provides the effective adrenergic control of Rs in vivo.
An electrophysiological analysis of chemoreception in the sea anemone Tealia felina
Authors: Dawn I. D. 
Published: April 2021

ABSTRACT
Electrophysiological techniques have been employed to examine the nature of the response observed in the ectodermal slow-conduction system (SS1) when dissolved food substances contact the column of Tealia felina. The response seems to consist entirely of sensory activity which may continue for periods of many minutes, provided that the stimulatory chemicals remain contacting the column. The interval between each evoked pulse gradually increases as the sensory response progresses. This does not result from fatigue in the conduction system but involves a genuine process of sensory adaptation. This may occur over a period of several minutes, which is much longer than comparable adaptation in higher animals. Physiological evidence suggests that the chemoreceptors involved are dispersed throughout the column ectoderm and are absent from the pedal disc, oral disc, tentacles and pharynx. The basic role of the SS1 in coordinating behavioural activity in sea anemones is reviewed. It is concluded that it functions primarily as a single, diffuse-conducting unit responsible for transmitting frequency-coded sensory information from ectodermal chemoreceptors to ectodermal (and perhaps endodermal) effectors.
Control of Mouth Opening and Pharynx Protrusion During Feeding in the Sea Anemone Calliactis Parasitica
Authors: McFARLANE I. D. 
Published: April 2021

ABSTRACT
Activity in all three known conducting systems (the nerve net, SS1, and SS2) may accompany feeding in Calliactis. The most marked response is an increase in pulse frequency in the SS2 (the endodermal slow conducting system) during mouth opening and pharynx protrusion. Electrical stimulation of the SS2 at a frequency of one shock every 5 s elicits mouth opening and pharynx protrusion in the absence of food. A rise in SS2 pulse frequency is also evoked by food extracts, some amino acids, and in particular by the tripeptide reduced glutathione, which produces a response at a concentration of 10−5 M. Although the SS2 is an endodermal system, the receptors involved in the response to food appear to be ectodermal. The epithelium that lines the pharynx conducts SSi pulses, but there is some evidence for polarization of conduction.
The significance of palpation by the maxillary palps of Locusta migratoria (L): an electrophysiological and behavioural study
Authors: Blaney W. M. , Duckett A. M. 
Published: April 2021

ABSTRACT
Palpation increases the amount of sensory input reaching the central nervous system compared with that obtained from sustained contact but that increase is not essential to allow discrimination.
During a meal on favoured food, phagostimulatory input from the palps is not needed to drive feeding. When less favoured food is taken, phagostimulatory input from the palps may enhance feeding. Even with favoured food, the palps are important in registering inhibitory substances.
Induction of transport of organic anions in Malpighian tubules of Rhodnius
Authors: Maddrell S. H. , Gardiner B. O. 
Published: April 2021

ABSTRACT
The ability of Rhodnius Malpighian tubules to transport organic anions such as p-aminohippuric acid (PAH) and amaranth depends on the physiological state of the insect. Unfed insects progressively lose this ability, but the transport mechanisms rapidly become activated after a blood meal. This induction occurs in adults as well as larval instars and is not prevented by decapitation. No increase in rates of excretion of organic anions follows a meal of Ringer’s solution or a single injection of 0·1 μmoles of PAH into the haemolymph. Accelerated PAH excretion is induced in insects fed (a) blood plasma alone or a suspension of red blood cells in saline, (b) solutions of serum albumin or casein, and (c) whole or diluted milk. These results show that the ingestion of a protein-rich meal is sufficient to induce an accelerated transport of organic anions such as PAH and they suggest that this induction is not controlled by a hormone released in response to abdominal distension but depends instead on the continued presence in the haemolymph of some product of digestion of the meal.
Form of developing bends in reactivated sperm flagella
Authors: Goldstein S. F. 
Published: April 2021

ABSTRACT
Dark-field, multiple-exposure photographs of reactivated tritonated sea urchin sperm flagella swimming under a variety of conditions were analysed. The length, radius and subtended angle of bends increased during bend development. The pattern of development was essentially the same under all conditions observed. The angles of the two bends nearest the base tend to increase at the same rate, cancelling one another, so that the development of new bends causes little if any net microtubular sliding. The direction of microtubular sliding within a bend is initially in the same direction as that within the preceding bend, and reverses as the bend develops.
Contribution of an electrogenic pump to the resting membrane polarization in a crustacean heart
Authors: Delaleu J. C. , Holley A. 
Published: April 2021

ABSTRACT
In the neurogenic heart of the isopod crustacean Porcellio dilatatus, external K+ removal depolarized the membrane (K0 effect) whereas subsequent restoration of K+ resulted in a rapid hyperpolarization (K1 effect). The amplitude of the K1 effect depended on the duration of the prior K+ deprivation and on the subsequent K+ concentration. The membrane resistance slightly increased during the K0 effect; during the K1 effect, it only returned to its control value. Ouabain, cooling and replacement of external Na+ by Li+ also produced depolarization. The Kj effect was suppressed by ouabain and markedly depressed by lowering the temperature to 4–6 °C. It was abolished if Li+ replaced Na+ during the prior privation of K+; moreover Li+ was unable to act as a substitute for external K+ in generating the K1 effect if used at equivalent concentration, but enhanced the effect at high concentration. The findings are consistent with the presence of an electrogenic sodium pump in the myocardium of Porcellio contributing to the resting membrane potential. Changes in the spontaneous rhythm observed during K0 and K1 are further suggestive of the presence of an electrogenic Na+ pump in the pacemaker neurons of the cardiac ganglion. Another explanation is also proposed. The magnitude of the spontaneous contractions of the heart was increased during the K0 effect and markedly decreased during the K1 effect. An indirect effect of the changes in internal Na+ concentration on the contractile processes is suggested.
Physiological properties of eel haemoglobin: hypoxic acclimation, phosphate effects and multiplicity
Authors: Weber R. E. , Lykkeboe G. , Johansen K. 
Published: April 2021

ABSTRACT
Unlike the whole blood oxygen affinity, which adapts readily to environmental oxygen tensions, haemoglobins prepared from normoxic-and hypoxic-acclimated eels (Anguilla anguilla) show no adaptive changes in oxygenation properties or in multiplicity. Hypoxic acclimation is, however, accompanied by a strong decrease in red cell nucleoside triphosphates, particularly guanosine triphosphate (GTP), which depresses oxygen affinity of the composite and component haemoglobins more strongly than does the concurring ATP. The effects of pH, temperature and salts on the oxygenation properties of the (isolated) haemoglobins are reported, discussed in relation to the varying environmental conditions encountered by eels, and compared with data on American and Japanese eels (A. rostrata and A. japonica, respectively).