bluuebunny/crossref_metadata_2025_split huggingface dataset:
L-Glutamate in Arthropod Blood Plasma: Physiological Implications
Authors: Murdock Larry L. , Chapman Grace Y. 
Published: April 2021

ABSTRACT
The L-glutamate concentration in blood plasma of the crayfish, Astacus lepto-dactylus and A. astacus, was found to be about 1·5 ×10−6M, as measured by a specific enzymatic method. Even 10 times this concentration of L-glutamate in saline failed to significantly affect neuromuscular transmission in the dactyl abductor muscle, although higher concentrations caused depression. L-Glutamate in the blood plasma of the spider, Dugesiella hentzii, amounted to 7 × 10−6M. As in the crayfish, even 10 times this concentration of L-glutamate in saline failed to affect neuromuscular transmission in the promotor tibiae muscle, while higher concentrations caused depression. The concentration of L-glutamate in Locusta migratoria blood plasma, ca. 7 ×10−6M, would appear to be sufficient to cause depression of neuromuscular transmission in vivo. Perfusion of the extensor tibiae preparation with 15 ×10−6ML-gluta-mate caused marked depolarization and decreases in the size of e.j.p.s. It appears that in the tarantula and the crayfish, blood plasma L-glutamate does not pose difficulties for neuromuscular transmission. In the locust, additional protective mechanisms which are not able to function in the saline-perfused in vitro preparation must be at work in the living animal.
The Physiology of the Tettigoniid Ear
Authors: Lewis D. B. 
Published: April 2021

ABSTRACT
The acoustic opening of the large, double prothoracic spiracle gives rise to a vesicula and a trachea which descends into the leg and divides to form the anterior and posterior tympanal air spaces, their apposed walls forming the secondary tympanal membrane. This trachea is independent of the respiratory system. The trachea is exponential or catenoidal in form in the Tettigoniids investigated, and the physics of horns is discussed in relation to the tracheal system. Bilateral recordings from the tympanal nerves have shown that blocking the spiracular opening eliminates the response to a sound signal at an intensity of 45 dB. Unilateral recordings during the blocking and reopening of both the spiracle and the tympanal slits has shown that at a sound intensity of 47·5 dB a response is obtained from the tympanal organ only when the sound is directed at an open spiracle; blocking the spiracle eliminates the response. Threshold curves for the ‘spiracle’ and for the ‘tympanal slits’ show a sensitivity difference of between 2 dB and 25 dB, the difference varying with frequency. The implications of this finding are discussed.
GAS EXCHANGES AND BLOOD GAS CONCENTRATIONS IN THE FORG RANA RIDIBUNDA
Authors: Emílio M. G. 
Published: April 2021

ABSTRACT
The respiratory exchanges through the lungs and skin of frogs and the time courses of blood gas concentrations were studied during emergence and diving periods. Most of the total oxygen uptake is carried out through the lungs. The partial pressure of oxygen in arterial blood falls to very low levels a few minutes after diving, showing that the cutaneous respiratory surface cannot compensate for the lack of lung respiration. Most of the metabolic carbon dioxide is disposed of through the skin. Although the skin output is maintained through diving periods, there is an important rise in the partial pressure of carbon dioxide in blood following submergence. However, the total concentration of CO2 in the blood decreases, as does the blood pH value. This phenomenon is probably the result of a metabolic acidosis due to the switching on of anaerobic processes during diving periods.
Directional Differences in the Colour Sensitivity of Daphnia Magna
Authors: Young Stephen 
Published: April 2021

ABSTRACT
The Daphnia compound eye movements can be driven by a flashing light. The action spectrum for the threshold light intensity required to evoke this response depends on the orientation of the stimulus light beam with respect to the animal. If the light falls on the eye through the top of the animal’s head the action spectrum peaks at the low wavelength end of the spectrum, while if it falls on the eye through the side of the head the peak is in the yellow-green. Eye movements cannot be evoked by illuminating any part of the animal except the compound eye so neither of these action spectra is due to a light receptor other than the compound eye. Some anomalous action spectra in the literature on the behaviour of free-swimming Daphnia are accounted for.
Calcium Balance at the Postmoult Stage of the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Greenaway Peter 
Published: April 2021

ABSTRACT
Net uptake of calcium by Austropotamobius begins 15–30 min after the moult and rapidly reaches a maximum level (2 μmoles/g/h at 10°C) which is maintained throughout stages A and B. At stage C1 the rate of net uptake falls sharply to a lower level which is gradually reduced until equilibrium is reached at C4. The uptake mechanism is near-saturated at 0·4 mm-Ca/l and half-saturated at 0·13 mm-Ca/1. In the absence of external HCO3− net uptake is reduced. Calcium uptake is against an electrochemical gradient. The concentration of ionised calcium in the haemolymph remains unchanged during the intermoult cycle.
Functional Aspects of Anuran Middle Ear Structures
Authors: Lombard R. Eric , Straughan Ian R. 
Published: April 2021

ABSTRACT
The opercular complex of amphibians functions to enhance perception of airborne environmental sounds below 1 KHz. The columella and tympanum of frogs function in the perception of acoustic information above 1 KHz. The opercular complex and amphibian papilla comprise the general hearing mechanism in amphibians. The tympanum, columella and basilar papilla, present in totality only in frogs, are concerned with reproductive communication. Interaction of the two systems in frogs provides a mechanism for enhancing input signal to noise ratio during chorusing. Experimental determinations of acoustic perception in amphibians must be controlled for anaesthesia and forelimb disposition. The presence of anaesthesia or unnatural limb position can affect the animal’s ability to perceive low frequency sounds by preventing normal opercularis function.
An Electrolytic, Digital Recording, Multichannel Micro-Respirometer
Authors: Turner B. D. , Stevenson R. A. 
Published: April 2021

ABSTRACT
A 20-channel micro-respirometer is described which replaces oxygen consumed by the respiring organism by that generated by the electrolysis of saturated copper sulphate solution. Electronic circuitry checks each respirometer once every second and provides a square-wave pulse 0·1 sec long and 1·0 mA in amplitude if oxygen is required. A single pulse produces 5·7 nl of oxygen at S.T.P. Electromechanical counters record when a pulse is required for oxygen generation. Total errors introduced by the electronics amount to less than 0·1%.
Muscular Activity of the Mantle of Sepia and Loligo (Cephalopoda) During Respiratory Movements and Jetting, and Its Physiological Interpretation
Authors: Packard A. , Trueman E. R. 
Published: April 2021

ABSTRACT
The action of the mantle of Sepia and Loligo has been monitored under nearly natural conditions. Respiratory movements are confined to the anterior mantle whilst during jet cycles the circular muscles contract powerfully throughout the mantle. Contraction of circular muscle results in thickening of the mantle and expulsion of water from the mantle cavity. Activity of radial muscles causes the mantle to become thinner and to expand in surface area so as to inhale water. During such movements these two groups of muscles antagonize each other directly without the participation of a discrete skeleton.
Free Amino Acids in the Haemocytes and Plasma of the Larva of Calliphora Vicina
Authors: Evans P. D. , Crossley A. C. 
Published: April 2021

ABSTRACT
Free amino acid concentrations have been measured in haemolymph samples taken from 3rd instar larvae of the blowfly, Calliphora vicina, at various stages prior to pupariation. The amino acids found in the haemocyte fraction only accounted for 6% of the total free amino acid concentration of the haemolymph. However, a high percentage of the dicarboxylic amino acids, glutamate and aspartate, 62% and 69% respectively, appeared to be sequestered in the haemocyte fraction at 72 h prior to pupariation. The percentage of the other individual amino acids found in the haemocyte fraction represented less than 10% of their amount in whole haemolymph. It is proposed that these results, together with the increase in the haemocyte levels of glutamate observed after injecting larvae with saline containing glutamate, are one of the first indications of a homeostatic function of insect haemocytes with respect to haemolypmh amino acids.
Control of Moulting and Metamorphosis in the Tobacco Hornworm, Manduca Sexta (L.): Cessation of Juvenile Hormone Secretion as A Trigger for Pupation
Authors: Nijhout H. Frederik , Williams Carroll M. 
Published: April 2021

ABSTRACT
During the final larval instar of the tobacco hornworm the presence of juvenile hormone (JH) inhibits the secretion of the brain ‘s prothoracicotropic hormone (PTTH). The corpora allata cease to secrete JH when the larvae attain a weight of approximately 5 g. The JH is cleared from the haemolymph in about 24 h. This process in itself renders the brain competent to release PTTH. The actual release of PTTH occurs at the very first photoperiodic gate after the JH has disappeared from the haemolymph. A functional failure of this normal mechanism is apparently responsible for the developmental standstill of Lepidoptera which diapause as mature larvae.
Effects of 5-Hydroxytryptamine On Action Potentials and On Contractile Force in the Ventricle of Dolabella Auricularia
Authors: Hill Robert B. 
Published: April 2021

ABSTRACT
Concentrations of 5-hydroxytryptamine from 10−8 10−5 M had the effect of starting quiescent ventricles, with a slow slight depolarization followed by the onset of beating, with hyperpolarization between beats. Concentrations of 5-hydroxytryptamine from 10−7 to 10−3 M had the effect of prolonging the cardiac action potential and increasing force. Over the entire range, an increase in concentration led to an increase in the duration and amplitude of the plateau phase of the action potential, and an increase in force of contraction.
Diffusion and Permeation of Water in the Frog Egg: the Effect of Tension and Tonicity
Authors: Mild Kjell Hansson , Løvtrup Søren 
Published: April 2021

ABSTRACT
The isotopic water permeability coefficient, P, of the plasma membrane of frog body cavity eggs has been determined as a function of the incubation time in media of different tonicity. It was found that the permeability decreases with the incubation time in hypotonic solutions. The observed changes may be correlated with an increase of the tension in the vitelline membrane. In the evaluation of the experimental results the diffusion of water in the external medium (‘unstirred layers’) is taken into account.
Sodium Regulation and Adaptation to Fresh Water in the Isopod Genus Asellus
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
The principal features of the sodium regulatory mechanism are compared in Asellus communis Say, A. aquaticus (L.) and A. meridianas Rae. Water content and total concentrations of sodium and chloride are similar in the three species, but they differ with respect to values for Kmax, Km, the loss rate, and the minimum sodium balance concentration. It is suggested that A. meridianas, A. aquaticus and A. communis represent a natural series of increasing adaptation to fresh water. A. communis from North America is completely adapted to fresh water. It has the lowest loss rate, the lowest maximum saturation level (Kmax) for sodium influx, and the highest affinity (low Km value) for sodium ions in the transporting system at the body surface. In many respects A. meridianus resembles freshwater populations of Mesidotea entomon and Gammarus duebeni, and may therefore have had a relatively short history in fresh water.
Some Factors Regulating Water Intake by the Eel, Anguilla Japonica
Authors: Hirano Tetsuya 
Published: April 2021

ABSTRACT
Internal as well as external factors affecting water ingestion in the eel were analysed using oesophagus-cannulated eels. Acute withdrawal of the blood induced an immediate drinking response in the freshwater eel, whereas infusion of a large amount of hypertonic saline interrupted the copious drinking observed in the seawater eel. The freshwater eel responded to slow infusion of hypertonic NaCl solution by constant drinking. Inhibition of drinking was observed in the seawater eel by distension of the stomach or intestine with isotonic mannitol solution. The freshwater eel started drinking immediately after transfer to sea water, and stopped drinking immediately after return to fresh water. Application of various salt solutions revealed that chloride ions are responsible for the induction of drinking in sea water. Stimulation of drinking by chloride ions and inhibition by fresh water may be an anticipatory drinking behaviour, which facilitates adaptation of eels to both sea water and fresh water.
Active Transport of Magnesium by the Malpighian Tubules of the Larvae of the Mosquito, Aedes Campestris
Authors: Phillips J. E. , Maddrell S. H. P. 
Published: April 2021

ABSTRACT
Larvae of Aedes campestris can survive in water containing up to 100 MM Mg even though they ingest and absorb into the haemolymph considerable amounts of magnesium-rich fluid. Isolated Malpighian tubules, unlike those of Rhodnius and Carausius secreted fluid containing elevated concentrations of magnesium. This transport displayed saturation kinetics, the half-maximal rate hieing at approximately 2·5 mm Mg. Active transport of magnesium was demonstrated by the secretion of this cation against a tenfold concentration gradient and an electrical potential difference of 15 mV. Magnesium ions are not required for fluid transport, which proceeds independently of magnesium transport. As a result fluid which is secreted slowly contains higher concentrations of magnesium than that which is secreted more rapidly. Magnesium is transported by isolated Malpighian tubules fast enough to account for the observed excretion of magnesium in living mosquito larvae.
The effect of temperature on the outward currents in the soma of molluscan neurones in voltage-clamp conditions
Authors: Magura I. S. , Valeyev A. E. , Zamekhovsky I. Z. 
Published: April 2021

ABSTRACT
The delayed outward current in snail neurones was separated into two components with different temperature sensitivity: (i) a persistent component and (ii) a transient (inactivating) component. The effect of cooling on the value of the transient current is strongly dependent upon the value of the conditioning potential. It was supposed that cooling causes a decrease in the negative surface potential in the vicinity of the potassium pathways and removes their inactivaton. Simultaneously cooling depresses the potassium conductance. The effect on surface potential is more distinct with conditioning potentials at which a significant fraction of the transient outward current is inactivated. The effect of cooling on the transient component of the fast outward current was similar to that on the transient component of the delayed outward current.
Peripheral control of acoustic signals in the auditory system of echolocating bats
Authors: Suga N. , Jen P. H. 
Published: April 2021

ABSTRACT
Many species of echolocating bats emit intense orientation sounds. If such intense sounds directly stimulated their ears, detection of faint echoes would be impaired. Therefore, possible mechanisms for the attenuation of self-stimulation were studied with Myotis lucifugus. The acoustic middle-ear-muscle reflex could perfectly and transiently regulate the amplitude of an incoming signal only at its beginning. However, its shortest latency in terms of electromyograms and of the attenuation of the cochlear microphonie was 3·4 and 4·8 msec, respectively, so that these muscles failed to attenuate orientation signals by the reflex. The muscles, however, received a message from the vocalization system when the bat vocalized, and contracted synchronously with vocalization. The duration of the contraction-relaxation was so short that the self-stimulation was attenuated, but the echoes were not. The tetanus-fusion frequency of the stapedius muscle ranged between 260 and 320/sec. Unlike the efferent fibres in the lateral-line and vestibular systems, the olivo-cochlear bundle showed no sign of attenuation of self-stimulation.
Electrophysiology of the peripheral nerve net in the polyclad flatworm Freemania litoricola
Authors: Koopowitz H. 
Published: April 2021

ABSTRACT
A diffuse-conducting system close to the dorsal epithelium of the polyclad flatworm Freemania litoricola is described. Tactile stimuli elicit small action potentials which can be conducted around lesions through the body wall. The potentials can occur in bursts or barrages. This conducting system appears to be insensitive to Mg2+ ions. Conduction velocities (0·26–71 m/sec) vary over the animal. Conduction spread in the anterior half of the animal appears to be greater than that in the posterior portion. Response decrement to repeated stimulation can be recorded in the peripheral system but it is not clear if this is due to habituation or fatigue. Conduction from the peripheral net to the brain occurs. Some central units appear to pick up information only, or mainly, through the anterior nerves, while other units can respond to information conducted through the network to nerves of the contralateral side. Different possibilities to account for this system are discussed, and it is suggested that the animals either possess a unique Mg2+ insensitive synaptic nerve-net or else the network is electrically coupled.
The Control of Eyestalk Movements in the Mysid Shrimp Praunus Flexuosus
Authors: Neil D. M. 
Published: April 2021

ABSTRACT
The compensatory eyestalk movements of intact and statocystless mysid shrimps Praunus flexuosus have been measured under a variety of light conditions. The results indicate that the statocyst organs in the urppods are the major gravity receptors, and that they are both necessary and sufficient to produce sinusoidal compensatory eyestalk movements. The addition of visual cues (vertical light beam, optokinetic stimuli) modifies the eyestalk response to some extent, but does not alter its general form. When the statocysts are removed, however, light stimuli become important orientational cues, and the eyestalks perform a tracking response which is considered to be the experimental counterpart of the dorsal light reaction of the free-swimming animal.
Nervous control of respiration: oxygen-sensitive elements in the prosoma of Limulus polyphemus
Authors: Thompson C. , Page C. H. 
Published: April 2021

ABSTRACT
Responses of oxygen-sensitive units in the prosomal haemal nerve of Limulus polyphemus were examined while varying the oxygen content of sea water bathmg the intercoxal cuticle. When exposed to high oxygen levels these units maintained a continuous background discharge of spikes. Unit activity was inhibited when oxygen content decreased. Upon réintroduction of oxygen tonic spike discharge resumed. Mechanosensitive units with receptive fields on the prosomal shield or intercoxal cuticle were also present in the haemal nerve. Neither the mechanosensitivity nor the background discharge of these units was affected by changes in oxygen content. It is proposed that the oxygen-sensitive respiratory reflexes of Limulus are an adaptation to existence in the intertidal zone. Published observations of the respiratory stress responses of many intertidal animals support this hypothesis.
Behavioural and electrophysiological studies of taste discrimination by the maxillary palps of larvae of Locusta Migratoria (L.)
Authors: Blaney W. M. 
Published: April 2021

ABSTRACT
Behavioural studies show that larvae of Locusta migratoria (L.) can discriminate between certain simple chemicals and between chemicals obtained from plant sources. Electrophysiological tests show that within each sensillum the same neurones respond to different chemicals. The frequency of occurrence of sensilla with enhanced specificity to certain chemicals is investigated. Statistical tests confirm that, despite the variability of response, across-fibre analysis could allow discrimination between chemicals pro-vided an adequate number of sensilla are used. The conclusions are discussed in relation to current theories of chemo-receptor functioning.
Colonial conduction systems in the Anthozoa: Octocorallia
Authors: Shelton G. A. B. 
Published: April 2021

ABSTRACT
The octocorals Alcyonium digitatum, Pennatula phosphorea and Virgularía mirabilis each have a through-conducting nerve net. The nerve net demonstrated electrophysiologically may well be the same as that previously shown by the use of histological techniques. It exhibits both facilitation and defacilitation in the rate of conduction of pulses. The distance of spread of nerve net activity is not limited by the number of stimuli applied. The nerve net controls fast muscle contractions; the frequency of pulses is important in determining which muscles contract and in which sequence. The nerve net is ‘spontaneously’ active. A previously undescribed slow system has been identified in Pennatula. It has many of the properties of slow systems in sea anemones and may well be ectodermal. It is suggested that multiple conduction systems are of common occurrence in the Anthozoa.
Respiratory and Circulatory Responses to Hypoxia in the Lobster Homarus Americanus
Authors: McMahon B. R. , Wilkens J. L. 
Published: April 2021

ABSTRACT
Contrary to previous reports, oxygen consumption is maintained over a wide range of external oxygen tensions in the lobster Homarus americanus. In animals acclimated to the experimental conditions this response is mediated by increased branchial pumping, increased effectiveness of oxygen uptake by the gills and an increased contribution by the respiratory pigment to the oxygen delivered to the tissues. Circulatory blood oxygen levels are generally high in lobsters resting in well-aerated water. Mechanisms for detection of hypoxia and possible control mechanisms are discussed.
Reversible Arrest of Uptake of Water from Subsaturated Atmospheres by the Firebrat, Thermobia Domestica (Packard)
Authors: Noble-Nesbitt J. 
Published: April 2021

ABSTRACT
A novel experimental technique incorporating a double-chambered array, which allows the independent and reversible exposure of head and tail ends of the insect to the surrounding atmosphere, without otherwise altering the constraints on the insect, is described. Using this technique, it has been possible to demonstrate that rapid uptake of water from subsaturated atmospheres occurs in Thermobia only when the tail-end is exposed. This effect is immediately and completely reversed when the tail-end is shielded from the atmosphere, and can be restored again on re-exposure of the tail-end, as shown repeatedly during electrobalance recordings. The relative humidity within the closed head-end chamber slowly rises, but within the closed tail-end chamber it falls, to approximately 50 % (the critical equilibrium humidity) with the desiccated insects and to 60-65% with hydrated insects, whilst the anal valves show movements indicating the operation of the rectal uptake mechanism. These findings are compatible with the anus being the avenue for the passage of water into the insect from the atmosphere.