bluuebunny/crossref_metadata_2025_split huggingface dataset:
Proctolin and an Endogenous Proctolin-Like Peptide Enhance the Contractility of the Limulus Heart
Authors: Watson W. H. , Augustine G. J. , Benson J. A. , Sullivan R. E. 
Published: April 2021

ABSTRACT
Synthetic proctolin increases the force but not the rate of heart contractions of Limulus in a time- and dose-dependent manner. The threshold of this effect is 3 X 10−10M and the EDS0 is approximately 10−10M. At concentrations up to 10−7 M, proctolin has no effect on the rhythmic electrical activity of the isolated cardiac ganglion, and it does not change the simple and compound postsynaptic potentials recorded at the cardiac neuromuscular junction. Proctolin acts directly on the cardiac muscle fibres. Electrically stimulated myocardia show a proctolin-induced increase in contraction amplitude with the same concentration dependence as the intact heart. A compound with an apparent molecular weight of 700–800 occurs in the Limulus nervous system, particularly in the cardiac ganglion. This compound resembles proctolin in being heat-stable, resistant to trypsin and chymotrypsin cleavage, and losing activity in a time-dependent manner in response to treatment with leucine aminopeptidase or pronase. This peptide induces spontaneous contractions and a contracture of the cockroach hindgut in a manner similar to proctolin. Moreover, the Limulus inotropic peptide, like proctolin, increases the force of contraction of the Limulus heart without affecting beat frequency. It is concluded that an endogenous, proctolin-like peptide is an inotropic modulator of the Limulus heart, acting directly on the muscle fibres and not affecting cardiac ganglion activity.
Luminescence of Isolated Photocytes from Porichthys Photophores: Adrenergic Stimulation
Authors: Christophe B. , Baguet F. 
Published: April 2021

ABSTRACT
A fast transient peak of light, followed by a slow luminescence, was produced by isolated photophores of Porichthys notatus when exposed to 1 mm-epinephrine, norepinephrine or phenylephrine, an α-adrenergic agonist. Only a slow luminescence was induced by 1 mm-isoproterenol, the β-adrenergic agonist. After removal of the reflector and surrounding tissues, the isolated photogenic cells, i.e. the photocytes, responded to norepinephrine and phenylephrine by producing a fast transient peak of light, and to isoproterenol by a slow luminescence. Epinephrine evoked both types of luminescence. The emission latency time, the amplitude and the total duration of the light responses were significantly less than those of the photophore. The results suggest that both epinephrine and norepinephrine combine with sympathetic α or β receptors upon the photocytes to trigger light production.
Nerve Net Pacemakers And Phases of Behaviour in the Sea Anemone Calliactis Parasitica
Authors: Mcfarlane Ian D. 
Published: April 2021

ABSTRACT
Bursts of through-conducting nerve net (TCNN) pulses, 20–45 min apart, were recorded from Calliactis attached to shells. Within 15–25 min of the anemones being detached the TCNN bursts suddenly became more frequent (only 4–11 min apart). Such bursts continued for several hours if re-attachment was prevented. In an attached anemone simultaneous electrical stimulation of the TCNN and ectodermal slow system (SSI) with 20–30 shocks at one every 5 s also led to more frequent TCNN bursts, whether or not detachment took place. If, however, the anemone remained attached, the intervals between bursts returned to the normal resting duration after about 90 min. In all cases the decay of the 4–11 min interval TCNN bursts involved a reduction in pulse number, not an increase in burst interval. Partial activation of the TCNN pacemakers followed stimulation of the SS1 alone. It is suggested that in sea anemones the change from one behavioural phase to another is associated with a change in the patterned output of nerve net pacemakers.
Potassium Metabolism in Seawater Teleosts: II. Evidence for Active Potassium Extrusion Across the Gill
Authors: Sanders Martin J. , Kirschner Leonard B. 
Published: April 2021

ABSTRACT
Unidirectional K-fluxes were estimated in unanaesthetized trout and sculpin and in anaesthetized sculpin from observed 86Rb movement (JK = 1·3 JRb). In all three groups efflux exceeded influx; Jo/Jin was 2–3. The values predicted by the flux ratio equation were 0·5 for trout and 1·0 for sculpin, so active K-extrusion is indicated. The results also show that more than one half of the total influx must be ingested with food rather than passing across the gills. Flux data show that the gills are more permeable to K+ than to Na+, PK/PNa was 5·4 in trout and 2·6 in sculpin.
Changes in K-concentration in the external medium did not appear to affect efflux; there was no exchange component in the total fluxes. When both Na+ and K+ were omitted from the bathing solution, efflux decreased to about 15 % of the normal seawater value. This is more than would be expected if the flux were purely diffusive and supports the conclusion that extrusion contains an active component. Repletion of the ion-deficient medium with K+ (alone) increased K-efflux. However, it also repolarized the gill and increased plasma [K+], and the flux change could be accounted for by the augmented driving force; i.e. it was diffusive.
The additional plasma K came from the intracellular compartment, rather than an augmented influx from the medium.
The Role of Urinary Precipitates in the Excretion of Electrolytes and Urate in the Domestic Fowl
Authors: Long S. , Skadhauge E. 
Published: April 2021

ABSTRACT
In order to quantify losses of Na and K associated with precipitate fractions in semi-solid avian urines, Na, K, uric acid and urates (UA + U) and inulin were measured in plasma, in whole ureteral urine, and in urinary precipitates of hens. Ten animals were used, five fed a control commercial poultry meal (Diet A) and five maintained on a high protein, low-Na feed (Diet B). In ureteral urines from hens on Diet A, dried precipitate accounted for 5·6% of the total whole urine weight, on the average. UA + U constituted about two-thirds of the precipitates’ weight and 80 % of the total excreted UA + U load of 97-4 mm. The average molar fractions, [Na]/[UA + U] and [K]/[UA + U], in precipitates were in the range 0·1–0·2; and the Na and K lost in these fractions were 12·8 mequiv and 9·6 mequiv, respectively, per 1 whole urine. These losses represent 9 % and 23 % of total Na and K excretion. Diet B was used to accentuate potential cation loss in precipitates if obligatory binding of K and especially Na were to occur in precipitates. Urinary [UA + U] in whole urine rose to 146 mm of which 95 % was found in precipitates. The average molar fraction [Na]/[UA+ U], however, fell to 0·06 and that of [K]/[UA + U] to 0-08. Renal loss of Na was 8·5 mequiv and of K was 11·5 mequiv per 1 whole urine. These experiments reveal that significant but minor fractions of excreted Na and K are associated with precipitates of avian urine, although the loss is insignificant compared to that reported in starlings (Braun, 1978). They further indicate that the Na/inulin clearance ratio, based on measurements in whole urine and plasma, adequately reflects fractional excretion which, on Diet A, was 1·8% of the filtered load and, on the Na-poor Diet B, less than 0·1 %.
These values place the Na-reabsorbing abilities of these birds easily within the range reported for ureotelic vertebrates and suggest that uricotelism does not impose a major renal salt loss in birds.
Renal Acid Excretion In The Domestic Fowl
Authors: Long S. , Skadhauge E. 
Published: April 2021

ABSTRACT
In order to assess the role of uricotelism in net renal acid excretion, blood and ureteral urine samples were collected from five hens fed a commercial poultry feed (Diet A) and five hens fed a protein-rich, Na-poor feed (Diet B). All samples were analysed for pH, , ammonium, phosphate, uric acid and urates (UA + U) and inulin. On Diet A, average pH in venous blood was 7·42, while urinary pH (pHu) ranged from 4·74 to 7·25. At average pHu (6·10), uric acid accounted for 52 % of total acid excreted, H2PO4 for 20 % and NH4 for 28 %. Net acid excretion in ureteral urine was 345 μequiv h−1 kg body weight−1, or 5–10 times that observed in ureotelic vertebrates (amphibians and mammals). The relative contributions of these urinary buffers to net renal acid excretion changed with pHu. Significant negative correlations exist between pHu and both total phosphate and ammonium excretion rates (P&lt; 0·001). Excretion rates of (UA + U) showed a positive correlation (P&lt; 0·05) with pHu. Feeding on Diet B revealed the homeostatic power of the avian kidney. Blood pH and were not changed relative to values in hens fed the control diet while striking increases in excretion rates of all urinary buffers (except HCO3) were observed. Average pHu fell to 5·12, and the average net renal acid excretion rate doubled.
Utilization of the Ethanol Pathway in Carp Following Exposure to Anoxia
Authors: Johnston Ian A. , Bernard Lynne M. 
Published: April 2021

ABSTRACT
Crucian carp (Carassius carassius L.) and Common carp (Cyprinus carpió L.) were subjected to 2h progressive hypoxia followed by up to 6 h anoxia in closed respirometers at 15 °C. The concentrations of glycogen, glucose, phosphoryl creatine, alanine, succinate, lactate, ethanol and ammonia were determined in whole Crucian carp following exposure to both hypoxia and anoxia. Ethanol and lactate were the main anaerobic end products. Glycogen utilization during anoxia amounted to 2 mmol glucose equivalents-kg wet weight−1 h−1. Around 85% of the ethanol produced (2·8 mmol kg−1 h−1) was excreted. Lactate accumulation (0·7 mmol kg−1 h−1) was only sufficient to account for 18-5 % of the glycogen stores utilized. Ammonia production (0·2 mmol-kg body wt−1 h−1) was independent of the environmental oxygen availability. Ethanol concentrations (μmol-gwet wt−1) were 7 in red myotomal muscle, 4 in white myotomal muscle, and 2 in liver after 6h anoxia. In contrast to Crucian carp, Common carp (Cyprinus carpio L.) did not produce ethanol at 15 °C even after near lethal exposure to anoxia (5–6 h).
Responses to Acute Aquatic Hypoxia In Larvae of the Frog Rana Berlandieri
Authors: Feder Martin E. 
Published: April 2021

ABSTRACT
The oxygen consumption of larvae of the trog Rana berlandieri Baird was reduced during exposure to aquatic hypoxia at 25 °C, and under severe hypoxia the larvae lost oxygen to the water. The larvae responded to aquatic hypoxia by increasing aerial oxygen consumption and lung ventilatory frequency, and also by altering their heart rate and gill ventilation frequency. Under severe or prolonged aquatic hypoxia without access to air, Rana larvae accumulated lactate. When prevented from breathing air, the larvae were unable to compensate fully by increasing their aquatic oxygen consumption. Body size or the interaction of body size and oxygen partial pressure significantly affected the aerial oxygen consumption, the total oxygen consumption and gill ventilation frequency, but did not affect other aspects of larval gas exchange. Anuran larvae resemble air-breathing fishes in some responses to aquatic hypoxia (e.g. increased dependence upon aerial oxygen uptake and changes in ventilatory frequencies), but are unusual in some ways (e.g. oxygen loss to the water). The interactions of body size and hypoxia are not sufficient to explain why so many anuran larvae without lungs are small.
Patterns of Circular And Radial Mantle Muscle Activity in Respiration and Jetting of the Squid Loligo Opalescens
Authors: Gosline John M. , Steeves John D. , Harman Anthony D. , Demont M. Edwin 
Published: April 2021

ABSTRACT
By simultaneously recording the electromyographic (EMG) activity of squid mantle muscles, changes in mantle cavity pressure and changes in mantle diameter, we have been able to distinguish the pattern of radial muscle activity from circular muscle activity, and in so doing were able to determine the functional role of these muscle groups in motor behaviours. Three distinguishable phases of activity appear during escape jets : (i), hyper-inflation brought about by the contraction of the radial muscles; (ii), the jet powered by the contraction of circular muscles; and (iii), refilling powered largely by the elastic recoil of the mantle wall, but with a small contribution from the radial muscles. Two distinctly different patterns of muscular activity were seen in respiratory movements. One pattern (pattern I) is powered by the radial muscles alone, while the other (pattern II) is powered by the circular muscles alone. In both modes of respiration, the muscles are apparently antagonized by tissue elasticity. Thus, the storage of elastic energy in the connective tissue fibre-lattice of the mantle wall plays a very important role in both modes of squid movement.
The Effects of Aquatic Oxygen Concentration, Body Size and Respiratory Behaviour on the stamina of Obligate Aquatic (bufo americanus) and facultative air-breathing (Xenopus Laevis and Rana Berlandieri) Anuran Larvae
Authors: Wassersug Richard J. , Feder Martin E. 
Published: April 2021

ABSTRACT
Larvae of the anurans Rana berlandieri and Xenopus laevis have lungs and can breathe air as well as irrigate buccal and pharyngeal surfaces for aquatic respiration. Larvae of Bufo americanus lack lungs until just before metamorphosis and are obligately aquatic. We examined the relationship between the locomotor stamina (time to fatigue), aquatic oxygen concentration, body size, and respiratory behaviour of swimming larvae of these species, with the following results:
Stamina is size-dependent in all three species. Aquatic hypoxia reduces stamina in larvae of all three species, but most conspicuously in Bufo. Breathing air increases stamina in Rana larvae, especially in large animals and under aquatic hypoxia. In contrast to Rana larvae, Xenopus larvae swimming in normoxic water undergo a reduction in stamina when allowed to breathe air. In hypoxic water, aerial respiration moderates the reduction in stamina seen in Xenopus larvae. Branchial irrigation is associated with increased stamina in Xenopus, and is increased under hypoxia and at high swimming velocities. Respiratory demand, buoyancy and the drag associated with branchial irrigation all affect respiratory behaviour in Xenopus larvae.
The great amount of interspecific variation in the relationship between respiratory behaviour and stamina reveals the importance of measuring performance directly when attempting to interpret the functional significance of respiratory structures and behaviour.
Anatomy of Motor Axons to Direct Flight Muscles in Drosophila
Authors: King David G. , Tanouye Mark A. 
Published: April 2021

ABSTRACT
The direct flight muscles of Drosophila melanogaster are innervated by the anterior dorsal mesothoracic (ADM) nerve and the mesothoracic accessory (MAC) nerve. Each of the four conspicuously large axons in the ADM nerve serves one of the muscles designated pal, pa3, pa4 and pa5. Muscle pa4 is additionally innervated by a very small neurosecretory axon. Muscle pa6, also innervated by the ADM nerve, receives at least one small nerve fibre but no large axon. Musclepa2 is innervated by a large axon from the MAC nerve. Large motor axons, identified by serial section tracing from their respective muscles, are consistent among different individuals in both relative positions and relative diameters within the ADM nerve.
Temperature Sensitivity in the Prothoracic Ganglion of the Cockroach, Periplaneta Americana, and its Relationship to Thermoregulation
Authors: Murphy Bernard F. , Heath James E. 
Published: April 2021

ABSTRACT
Activity of neurones in the prothoracic ganglion of the cockroach, Periplaneta americana, recorded extracellularly, showed a wide range of temperature sensitivity. These responses were categorized by linear regression. The regression lines with the greatest slopes are proposed to characterize central temperature receptors; warm units with lower slopes may be the result of nonspecific Q10 responses of ordinary neurones. An overlap of regression lines from cells with high slopes occurs near the acclimation temperature of the animals; the regression lines of most of the warm-sensitive units reach zero firing rate near the mean chill-coma temperature (10·5 °C) for this species. The temperature selection by the whole animal in a temperature gradient shuttlebox was found to require central temperature receptors as well as the peripheral temperature receptors on either the antennae or tarsi. Both neural and behavioural data indicate a greater sensitivity to heat than cold in cockroach thermoregulatory behaviour.
Acetylcholine Receptors on the Cell Body Membrane of Giant Interneurone 2 in the Cockroach, Periplaneta Americana
Authors: Harrow I. D. , Sattelle D. B. 
Published: April 2021

ABSTRACT
lonophoresis of acetylcholine (ACh) onto the cell body membrane of an identified giant interneurone (GI2) in the central nervous system of the cockroach Periplaneta americana induced a depolarizing response at resting potential which was attributed to a population of extrasynaptic ACh receptors. The sensitivity of the cell body membrane of GI 2 to ionophoresis of ACh was determined. Perfusion of 1·0 × 10−6M neostigmine, an inhibitor of acetylcholine esterase, potentiated the ACh sensitivity of the cell body membrane of GI 2. This indicated that a high acetylcholinesterase activity was present in the periphery of the sixth abdominal ganglion (A6). The nicotinic antagonist, a-bungarotoxin (at a concentration of 1·0 × 10−7M) was found to block the ACh response of the cell body membrane of GI 2. By contrast, the muscarinic antagonist, quinuclidinyl benzilate, (at concentrations up to 1·0 × 10−5 M) had no detectable effect on the ACh response. It is suggested that an extrasynaptic nicotinic type of ACh receptor is present on the cell body membrane of GI 2.
Renal Function in Unanaesthetized River Lampreys (Lampetra Fluviatilis L.): Effects of Anaesthesia, Temperature and Environmental Salinity
Authors: Mcvicar A. J. , Rankin J. C. 
Published: April 2021

ABSTRACT
Improved estimates of urine flow rates of lampreys in various salinities were obtained by the collection of urine for periods of up to 48 h from minimally-stressed, unanaesthetized fish, following catheterization of the urinogenital papilla. The mean urine flow rate of freshwater lampreys was 200·7 ± 14·3 ml kg−1 day−1. Urine flow in freshwater lampreys was correlated with spontaneous changes in gill ventilation rate. MS222 anaesthesia reduced both ventilation and urine flow rates, but pronounced effects were only observed at concentrations greater than those needed to induce light anaesthesia (50–55 mgl−T). Urine flow rate in unanaesthetized fish was extremely sensitive to rapid (6°Ch−1) changes in temperature and Q10 (6–16°C) was approximately 5. Urine flow rate decreased rapidly as the osmotic difference between the body fluids and environment approached zero, and the rate of flow in 30% seawater lampreys was only 7·6% that of freshwater fish. There was no evidence for an effect of environmental calcium concentration on branchial osmotic permeability. Extensive tubular reabsorption of ions occurred in freshwater lampreys. The total daily excretion rate of sodium ions generally decreased in salinities hyperosmotic to the plasma, indicating enhanced reabsorption, but secretion of magnesium and sulphate ions was greatly increased. Urine osmolarity was significantly increased in lampreys in hyperosmotic salinities. Present data compare favourably with data obtained previously from anaesthetized animals, indicating that renal function in lampreys is not significantly impaired by light MS222 anaesthesia.
The Kinetics of Active K Transport by the Midgut of Lepidopteran Larvae: Effects of Divalent Ions
Authors: Moffett David F. , Koch Alan R. 
Published: April 2021

ABSTRACT
The isolated midgut of lepidopteran larvae actively transports K from haemolymph to lumen, providing a model for K transport in insect secretory and excretory tissues (reviewed by Harvey, 1980). The dependence of this transport on extracellular K has been studied by several investigators. Recently, Zerahn (1982) estimated a value of 10 mM for Km in Hyalophora cecropia from his data and also from previous observations (Harvey & Zerahn, 1972), and obtained a value of 40 mM from data for Manduca sexta (Moffett, 1979). In the studies upon H. cecropia, the only cation present in the bathing solution was K; in the study upon M. sexta, 5 mM-Ca and 5 mM-Mg were also present as well as sufficient NaCl to maintain constant osmolarity. Although there may be slight innate differences in the transport kinetics of the two species, we show here that the reported differences can be accounted for by the presence or absence of divalent cations.
The pCa-Tension Characteristics of Single Skinned Fibres Isolated from the Anterior and Posterior Latissimus Dorsi Muscles of the Chicken
Authors: Moore G. , Johnston I. A. , Goldspink G. 
Published: April 2021

ABSTRACT
The anterior latissimus dorsi (ALD) muscles of the chicken are mostly composed of multiply innervated slow fibres, and the posterior latissimus dorsi (PLD) muscles consist mostly of focally innervated fast fibres (Ginsborg, 1960). The rate of development of isometric tension is 8–10 times higher in the PLD than in the ALD, and the unloaded speed of shortening is 4–5 times higher (Canfield, 1971). On tetanic stimulation ALD fibres are able to maintain a steady isometric tension for more than 2 min, whereas the PLD begins to fatigue after only 1 s (Canfield, 1971). The fatigue resistance and economy (Goldspink, Larson & Davies, 1970) of the ALD when contracting isometrically are probably related to its postural role in holding the wings against the body. The rate of relaxation of PLD fibres following short tetani is eight times faster than for the ALD (Canfield, 1971). This difference is attributable in part to the less highly developed sarcoplasmic reticulum in the ALD (Page, 1969). The present study investigates the pCa-tension relationship of these fibres.