bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Influence of Body Mass on the Endurance to Restrained Submergence in the Pekin Duck
Authors: Hudson Dennis M. , Jones David R. 
Published: April 2021

ABSTRACT
Pekin ducks, ranging in mass from 0·05 to 3·5 kg, were force-dived to determine the maximum tolerance to diving asphyxia. The size of the respiratory and blood oxygen storage compartments and oxygen utilization during the dive were also measured. By the end of a maximum dive, less than 4% of the original O2 store remained in the blood, whereas almost 25% remained in the respiratory system. In contrast, the level of arterial glucose did not change significantly during diving.
The relationship of a number of measured variables to body mass was analysed using linear regression analysis on log10-transformed variables to generate power equations of the form Y = aXb (Y, any variable; X, body mass; a, mass coefficient; b, mass exponent). The mass exponent was 1·19 for the total oxygen stores and 0·64 for maximum diving duration. Using measurements of brain and heart mass and literature estimates of the scaling of O2 consumption, it was also possible to predict a mass exponent aerobic metabolism by these organs during a maximum dive. Allometric cancellation of mass exponents for O2 availability and predicted utilization resulted in a residual mass exponent almost identical to the measured value for maximum dive duration. Thus it is possible to predict the relationship of maximum underwater endurance to body mass in Pekin ducks from a knowledge of the oxygen consumption by, and availability to, the central aerobic organs.
Localization and Stimulation of Chromatophore Motoneurones in the Brain of the Squid, Lolliguncula Brevis
Authors: Dubas Francoise , Hanlon Roger T. , Ferguson Graham P. , Pinsker Harold M. 
Published: April 2021

ABSTRACT
The relatively simple chromatophore system of the squid, Lolliguncula brevis, was studied with combined behavioural, morphological and electrophysiological methods in order to understand how the chromatophore patterns in the skin are organized at the level of the posterior chromatophore lobes (PCL). There are nine simple chromatic components of patterning in L. brevis. Retrograde transport of horseradish-peroxidase from chromatophores in the mantle skin established that the chromatophore motoneurones are located in the PCL. Focal threshold stimulation of the PCL in perfused, semi-intact preparations showed that the motor fields of individual chromatophore motoneurones are compact, including 2-60 chromatophores, generally of the same colour. Adjacent motoneurones in the lobe do not necessarily have adjacent motor fields in the skin.
Two Types of Action Potentials in A Secretory Epithelium of A Clam Mantle
Authors: Beirão Paulo S. , Sorenson A. L. 
Published: April 2021

ABSTRACT
The secretory epithelium that faces the shell of the clam Anomalocardia brasiliana is electrically excitable. It was found that two types of action potentials could be elicited by electrical stimulation. In mantles showing signs of being in the phase of shell secretion, cardiac-like action potentials were observed. They had an overshoot of 48·4 ±8·8mV (±S.D.), a rate of rise of 54·7 ±5·6 Vs−1 and three phases of repolarization of 9·3 ± 4·8, 1·44 ± 0·70 and 4·7 ± 1·1 Vs−1. Their duration averaged 38·4 ± 13·3 ms. Mantles of clams resorbing the shell had spike-like action potentials with an overshoot of 38·7 ± 5·5 mV, a rate of rise of 52·7 ± 16·8 Vs−1, and a single phase of repolarization of 12·4 ± 2·5 Vs−1. Their duration was 11·1 ± l’4ms. It is suggested that the presence of a plateau may be related to shell secretion. Significant differences were also found in the resting potentials: −54·8±5·4mV in cells of mantles with cardiac-like responses and −62·5 ±4·9 mV in cells of mantles with spikes. In both types of mantles the action potentials were propagated throughout the epithelium and both exhibited a refractory period. Lowered Ca or increased frequency of stimulation reduced the plateau of cardiac-like action potentials without any marked alteration in the resting potential, rate of rise, or overshoot. The action potential was elicited by outward (depolarizing) current across the basolateral membrane, and not by similarly-directed current across the apical membrane, so we conclude that the basolateral membrane is the excitable one.
The Contribution of Nasal Receptors to the Cardiac Response to Diving in Restrained and Unrestrained Redhead Ducks (Aythya Americana)
Authors: Furilla R. A. , Jones David R. 
Published: April 2021

ABSTRACT
In restrained redhead ducks, forced submergence caused heart rate to fall from 100 ± 3 beats min−1 (mean± S.E.M., N = 12) to a stable underwater rate of 35 ± 4 beats min−1 (N = 12) within 5 s after submergence. Bradycardia was unaffected by breathing oxygen before a dive, but was virtually eliminated by local anaesthesia of the narial region. In contrast, in a dabbling duck (Anas platyrhynchos) bradycardia in short dives was eliminated by breathing oxygen before a dive. In unrestrained diving, on a man-made pond, heart rate in redheads diving voluntarily (y) was related to pre-dive heart rate (x) by the equation y = 76+0·29 ± 0·05× ± 17 (r2 = 0·71). Chasing, to induce submergence, had variable effects on this relationship. Local anaesthesia of the narial region inhibited voluntary diving but heart rates in chase-induced dives after nasal blockade were significantly higher, by 10–30%, than those obtained from untreated ducks in chase-induced dives. Breathing oxygen before voluntary dives had no apparent effect on heart rate after 2–5 s submergence. Voluntary head submersion by dabbling ducks caused no change in heart rate. We conclude that nasal receptors make only a minor contribution to cardiac responses in unrestrained dives, compared with forced dives, in diving ducks. Furthermore, these results show that little can be learned about cardiac responses in free diving ducks from studies of forced dives in dabblers or divers.
The Regulation of Haemocyanin Oxygen Affinity During Emersion of the Crayfish Austropotamobius Pallipes: I. An In Vitro Investigation of the Interactive Effects of Calcium and L-Lactate On Oxygen Affinity
Authors: Morris S. , Tyler-Jones R. , Taylor E. W. 
Published: April 2021

Abstract
The haemolymph of the crayfish Austropotamobius pallipes exhibits a high affinity for oxygen (P50 = 2·7 Torr at pH 7·9 and 15°C) and a modest Bohr effect (φ =−0·455). The affinity of haemolymph dialysed against a crayfish Ringer was lower with a P50 value of 6·4 Torr at the same temperature and pH. The oxygen affinity of the dialysed haemolymph can be increased markedly by increased concentrations of L-lactate and to a greater extent by elevated concentrations of calcium ions.
In the dialysed preparation, the potentiating effects of L-lactate and Ca2+ on haemocyanin oxygen affinity were found to be interdependent. Elevating the concentration of one of these two ions reduced the effect of the other.
The increase in the oxygen affinity of the haemocyanin brought about by elevated Ca2+ and L-lactate was insufficient to account for the difference in affinity between dialysed and nondialysed haemolymph. The mutually agonistic effects of Ca2+ and L-lactate are described both empirically and graphically.
Two Coupling Mechanisms Which Determine the Coordination of Ipsilateral Legs in the Walking Crayfish
Authors: Cruse Holk , Müller Uwe 
Published: April 2021

ABSTRACT
In a crayfish walking on a motor-driven belt at constant speed, the power stroke (stance phase) of an individual leg is experimentally prolonged for a short time; the ways the legs retain their normal coordination are then observed. The results are shown in a modified phase-response curve. Only ipsilateral coupling is considered in detail.
Two coordinating mechanisms are necessary and sufficient to describe the experimental results. (1) The forward-directed influence is only active when the controlling (posterior) leg performs a power stroke. If the controlled leg is in power stroke, this influence leads it to interrupt the power stroke and start a return stroke. If the leg is in return stroke, it is influenced to continue the return stroke, the duration of which is thereby prolonged. The speed of the return stroke is also decreased. (2) The backward-directed influence is active only during the last part of the power stroke and the first part of the return stroke of the controlling (forward) leg. If the controlled leg is in return stroke, it is influenced to interrupt the return stroke and start a power stroke. If it is at the end of its power stroke, it is influenced to continue this stroke.
For legs 3 and 4, each of which possesses both anterior and posterior neighbours, the influences exerted by these two coordinating mechanisms are assumed to be additive. A model calculation shows that the two mechanisms are sufficient to describe the behaviour observed. The results are compared with previous findings from the literature.
Intracellular Free Calcium Measured with Calcium-Selective Microelectrodes From Salivary Gland Cells of the Snail Planorbis Corneus
Authors: Barber Andrew 
Published: April 2021

ABSTRACT
Double-barrelled Ca2+-selective microelectrodes have been used to make simultaneous measurements of the intracellular concentration of free Ca2+ ([Ca2+]i) and membrane potential (EM) from single salivary gland acinar cells of the pond snail Planorbis corneus. The mean [Ca2+]i recorded from nine cells in unstimulated glands was l·24×10−7moll−1 (S.D. ± 0·84×10−7moll−1), while the mean EM was −67·1 ±4·1 mV. The equilibrium potential for Ca2+ in these cells was calculated to be +132mV. Stimulating the glands with 10−4moll−1 acetylcholine (ACh) produced a simultaneous depolarization of EM and an increase in [Ca2+]i by 2·9×10−7moll−1 (S.D. ± 10× 10−7moll−1, N= 12), followed by a transient hyperpolarization of EM and the restoration of [Ca2+]i to its original level. ACh-induced increases in [Ca2+]i were abolished, or much reduced in size, after the removal of extracellular Ca2+, though the EM response to ACh was unaffected in Ca2+-free saline. This finding indicates that the application of ACh leads to an influx of Ca2+ from the medium bathing the glands. Li+ caused an increase in the size of the ACh-induced elevation in the Ca2+ signal and inhibited the recovery of [Ca2+]i following stimulation. The implications of this observation are discussed.
Ion Absorption by the Distal Tubules of Onychophoran Nephridia
Authors: Campiglia S. S. , Maddrell S. H. P. 
Published: April 2021

Abstract
The distal tubules of the 4th and 5th pairs of nephridia of Peripatus acacioi (Onychophora) absorb ions from the fluid passing through them. Since water follows this movement only to a limited extent, the fluid in the lumen becomes hypo-osmotic.
Absorption of ions stops when sodium is replaced by choline in the perfusion fluid and is much reduced by treatment with ouabain, particularly when this is applied to the basolateral faces of the cells. These results suggest that ion absorption may be driven by an Na/K exchange pump.
Cyclic AMP at 10−2moll−1 increases the rate of salt uptake by about four times; it seems likely from this that the tubules are hormonally controlled.
Chemical and Tactile Inputs to the Lymnaea Feeding System: Effects on Behaviour and Neural Circuitry
Authors: Kemenes G. , Elliott C. J. H. , Benjamin P. R. 
Published: April 2021

ABSTRACT
Transfer of snails from distilled water to solutions of sucrose or maltose stimulated feeding behaviour. As the concentrations were increased from 10−5mol l−1 to 10−1mol l−1 the proportions of snails showing feeding movements and the median rate of feeding both increased until at 10−3 mol l−1 they reached a plateau. At higher concentrations (10−1 mol l−1), maltose, but not sucrose, reduced the proportion of feeding snails and median feeding rate to values occurring at 10−5 mol l−1. Increases in median feeding rate were due to an increase in the regularity of the feeding rhythm rather than increases in the maximum rates of feeding.
Sugars and tactile stimuli were applied to putative sensory structures (interior of the buccal mass, lips and tentacles) in two types of semi-intact preparation whilst intracellular recordings were made from feeding motoneurones (1, 3, 4, 5 and 7 cells) and higher-order interneurones (Cerebral Giant Cells, CGCs, and the Slow Oscillator, SO). Both types of sensory stimuli applied to the lip–tentacle preparation produced strong activation of the CGCs but only long latency weak excitation of motoneurones with no clear initiation of synaptic inputs from central pattern generating (CPG) interneurones. In a more complex lip–tentacle–buccal mass preparation the evoked responses to sugars were comparable to those in the intact snail. Initiation of motoneuronal activity or increased frequency of activity was observed. This was due to increased CPG synaptic inputs as well as activation of a modulatory interneurone, the SO. Multiple sensory pathways from the periphery, present only in the lip–tentacle–buccal mass preparation, were necessary for sensory initiation of the feeding rhythm. The results support the hypothesis that multimodal sensory inputs are likely to be involved in the initiation or modulation of feeding in Lymnaea and act at several levels in the system.
The Role of Catecholamines in Erythrocyte pH Regulation and Oxygen Transport in Rainbow Trout (Salmo Gairdneri) During Exercise
Authors: Primmett D. R. N. , Randall D. J. , Mazeaud M. , Boutilier R. G. 
Published: April 2021

ABSTRACT
Rainbow trout were subjected to burst swimming to exhaustion followed by 4 h aerobic swimming at 80% critical swimming velocity. Severe physiological disturbances, including a marked plasma acidosis caused by the burst swim, were corrected during the 4h of subsequent aerobic exercise. Erythrocytic pH and arterial oxygen content increased, even though plasma pH was reduced. We suggest that the increase in erythrocytic pH was caused by the action of elevated adrenaline and noradrenaline levels in the blood acting on β-adrenergic receptors on the trout red blood cell, causing the cell to swell and raising intracellular pH, offsetting any effect of a reduction of plasma pH on erythrocyte pH and haemoglobin-oxygen binding. Propranolol blocked the action of catecholamines on trout erythrocytes. We conclude that catecholamines play an important role in maintaining oxygen transport to aerobic muscles, following burst swimming and the associated acidotic conditions.
Sodium-Calcium Action Potential Associated With Contraction in the Heliozoan Actinocoryne Contractilis
Authors: Febvre-Chevalier Colette , Bilbaut André , Bone Quentin , Febvre Jean 
Published: April 2021

ABSTRACT
The electrophysiology of the contractile protozoan Actinocoryne contractilis was studied with conventional intracellular recording techniques.
Resting membrane potential (−78 mV, S.D. = 8, A =18) was dependent upon external K+. Rapid action potentials (overshoot up to 50 mV) were evoked either by mechanical stimulation or by current injection. Graded membrane depolarizations induced by graded mechanical stimuli correspond to receptor potentials.
The receptor potential was mainly Na+-dependent; the action potential was also mainly Na+-dependent, but involved a minor Ca2+-dependence. The two components of the action potential could be separated in Ca2+-free solution containing EGTA (1 mmol l−1), in low-Na+ solutions or by the addition of Co2+. The repolarizing phase of the action potential was sensitive to TEA ions and to 4-aminopyridine (4-AP).
Action potentials were followed in 10–20 ms by a rapid all-or-none contraction of the axopods and stalk. Contraction was blocked in Ca2+-free solution containing EGTA and by Co2+, which suggests a requirement of external Ca2+ for this event. Contraction was also abolished by 4-AP.
Properties and Roles of the Three Subclasses of Histamine Receptors in Brain
Authors: Schwartz Jean-Charles , Arrang Jean-Michel , Garbarg Monique , Korner Marie 
Published: April 2021

ABSTRACT
In brain, histamine (HA) is the transmitter of a neuronal system resembling other monoaminergic systems. It is also present in mast cells from which it may control vascular and inflammatory processes. Its various actions are mediated not only by the two well known H1 and H2-receptor subclasses but also by the recently discovered H1-receptors, with distinct localization and pharmacology. H1-receptors mediate a series of biochemical responses which have several features in common: they require intact cells to be observed and largely depend upon the availability of Ca2+.
H1 receptor-mediated responses include glycogenolysis, stimulation of cyclic GMP formation, potentiation of cyclic AMP formation. Recent studies indicate that H1-receptors are linked with phosphatidylinositol breakdown and generation of two intracellular signals which both contribute to the final response (e.g. in the cyclic AMP generation).
H2-receptors seem.to be directly linked with an adenylate cyclase and their stimulation results in enhanced electrophysiologically recorded responses to excitatory agents.
Finally whereas H1 and H2-receptors appear to be postsynaptically located, a novel subclass (H3) of HA receptors was recently revealed with a presynaptic localization. H3-receptors are autoreceptors mediating inhibition of HA release from and biosynthesis in histaminergic nerve terminals in the CNS.
The physiological and pharmacological implications of three distinct receptor subclasses for HA will be discussed.
Messenger-Mediated Control of Potassium Channels in Secretory Cells
Authors: Petersen O. H. , Findlay I. , Suzuki K. , Dunne M. J. 
Published: April 2021

ABSTRACT
In exocrine acinar cells (pancreas, salivary gland, lacrimal gland) stimulation with hormones or neurotransmitters evokes K+ loss due to opening of K+ channels in the plasma membrane whereas in the insulin-secreting pancreatic β-cells, stimulation with glucose or glyceraldehyde evokes membrane depolarization due to closure of K+ channels. By measuring directly the small K+ currents flowing through single channels, in electrically isolated patches of plasma membrane of intact cells, it can be shown that stimulants having no direct access to the small membrane area from which recording is made can influence the pattern of channel opening. In the case of hormonal activation of exocrine acinar cells, Ca2+ is the final messenger and the K+-selective channel involved in the response has a high unit conductance, is very voltage sensitive and can be blocked by external tetraethylammonium. In the case of the insulin-secreting cells, the K+ channel which is inhibited by metabolic stimulation is a voltage-insensitive, inward rectifier which can be blocked by quinine. In experiments on permeabilzed cells or cell-free excised, inside-out, membrane patches it can be shown that ATP evokes channel closure and ATP produced by glycolysis may therefore function as the internal messenger.
Inositol Lipid Metabolism and Signal Transduction in Clonal Pituitary Cells
Authors: Drummond Alan H. 
Published: April 2021

ABSTRACT
A number of clonal cell lines derived from a rat pituitary tumour, collectively termed GH cells, have retained a range of differentiated cell functions, including their ability to secrete the hormones prolactin and growth hormone in response to stimuli such as thyrotropin-releasing hormone (TRH). The mechanisms underlying this release process involve, at least in part, an increase in cytosolic free calcium levels, and the cells have proved useful as a model system in studies of receptor-controlled calcium mobilization. The initial response of the cells to the addition of TRH now appears to be the interaction of the occupied TRH receptor with a GTP-binding protein. A sophisticated signalling system is then activated which initially involves the phosphodiesteratic hydrolysis of phosphatidylinositol 4,5-bisphosphate to 1,2-diacylglycerol and inositol 1,4,5-trisphosphate. Both of these products are important intracellular messengers, and their formation leads to a plethora of biochemical and electrical changes which culminate in. the biphasic release of hormone from the cell. The changes in cytosolic free calcium that occur following TRH addition follow a complex temporal pattern. Within 1 s, the concentration starts to increase from a resting level, in the range 100–150 nmol l−1, to a peak value of around 1 μmol l−1 which is attained within 6–8 s. This ‘spike’ of calcium is almost exclusively derived from intracellular stores, probably the endoplasmic reticulum, in response to the formation of inositol 1,4,5-trisphosphate. With high concentrations of the peptide, the cytosolic free calcium concentration declines promptly, due to the activation of a protein kinase C-mediated extrusion and/or sequestration process. This inhibitory phase is less marked at low agonist concentrations but, in all cases, is superseded by a second increase in free calcium, which is due to the stimulated influx of the cation through dihydropyridine-sensitive calcium channels. These biphasic changes in calcium, in concert with the activation of protein kinase C, appear sufficient to regulate prolactin secretion.
Ionic Signalling by Growth Factor Receptors
Authors: Moolenaar W. H. , Defize L. H. K. , Laat S. W. DE 
Published: April 2021

ABSTRACT
The proliferation of cells in vivo and in culture is regulated by polypeptide growth factors, such as epidermal growth factor (EGF) and platelet-derived growth factor (PDGF). Growth factors initiate their action by binding to specific cell surface receptors. Receptor occupancy triggers a cascade of physiological changes in the target cell which ultimately lead to DNA synthesis and cell division. Immediate consequences of receptor activation include tyrosine-specific protein phosphorylations, a sustained increase in cytoplasmic pH (pH,) and a transient rise in free Ca2+. The rise in pH, has a permissive effect on DNA synthesis and is mediated by an otherwise quiescent Na+/H+ exchange mechanism in the plasma membrane, which is turned on by protein kinase C, the cellular receptor for phorbol esters. The rapid Ca2+ signal is due to either release from internal stores (PDGF) or net entry via a voltage-independent channel in the plasma membrane (EGF). Phorbol esters, acting via kinase C, inhibit the growth factor-induced Ca2+ signals without affecting resting Ca2+ levels.
Monoclonal antibodies against the human EGF receptor can act as partial agonists in that they activate the tyrosine-specific protein kinase without inducing any of the ionic signals. These antibodies fail to induce DNA synthesis when added to quiescent fibroblasts, indicating that the Ca2+ and pH, signals can be dissociated from tyrosine kinase activity and suggesting that these signals are indispensable for the stimulation of cell proliferation.
The Temperature and Humidity Relations of the Cockroach
Authors: Gunn Donald L. , Notley F. B. 
Published: April 2021

ABSTRACTThe thermal death-points of three species of cockroaches in dry and in moist air have been determined for 1-day and 1-hour exposures. Moist air is more favourable than dry in the longer exposures, because in dry air death occurs from desiccation when the temperature itself is not fatal. Dry air is more favourable than moist in the shorter exposures, owing to the fact that the evaporation of water lowers the body temperature. Bearing in mind the thermotactic behaviour of these animals, these observations would seem to have little ecological importance