bluuebunny/crossref_metadata_2025_split huggingface dataset:
Remote Control of the Swimmeret Central Pattern Generator in Crayfish (Procambarus Clarkii and Pacifastacus Leniusculus): Effect of a Walking Leg Proprioceptor
Authors: Cattaert Daniel , Barthe Jean-Yves , Neil Douglas M. , Clarac Francois 
Published: April 2021

ABSTRACT
An isolated preparation of the crayfish nervous system, comprising both the thoracic and the abdominal ganglia together with their nerve roots, has been used to study the influence of a single leg proprioceptor, the coxo-basal chordotonal organ (CBCO), on the fictive swimmeret beating consistently expressed in this preparation. Both mechanical stimulation of the CBCO and electrical stimulation of its nerve were used. In preparations not displaying rhythmic activity, electrical or mechanical stimulations evoked excitatory postsynaptic potentials (EPSPs) in about 30% of the studied motor neurones with a fairly short and regular delay, suggesting an oligosynaptic pathway. Such stimulation could evoke rhythmic activity in swimmeret motor nerves. The evoked swimmeret rhythm often continued for several seconds after the stimulus period. When the swimmeret rhythm was well established, electrical and mechanical stimuli modified it in a number of ways. Limited mechanical or weak electrical stimuli produced a small increase in swimmeret beat frequency, while more extreme movements of the CBCO or strong electrical stimuli had a disruptive effect on the rhythm. The effect of low-intensity stimulation on existing swimmeret beating was phase-dependent: it shortened the beat cycle when applied during the powerstroke phase and lengthened it when applied during the retumstroke phase. Rhythmic mechanical stimulation of CBCO or electrical stimulation of the CBCO nerve entrained the swimmeret rhythm within a limited range in relative or absolute coordination. Electrical stimuli also produced systematic effects on the whole metachronal pattern of the swimmeret rhythm, perturbing the interganglionic coordination.
Posterior Lymph Heart Pressure and Rate and Lymph Flow in the Toad Bufo Marinus in Response to Hydrated and Dehydrated Conditions
Authors: Jones Judy M. , Wentzell Lee A. , Toews Daniel P. 
Published: April 2021

ABSTRACT
Posterior lymph heart pressure, rate and flow were measured in chronically cannulated Bufo marinus during normal hydrated and dehydrated conditions. A new surgical technique was developed which allowed direct and constant measurement of the functioning of the posterior lymph hearts with minimal disruption to normal lymph drainage. The mean intra-lymph-heart systolic pressure was 2.29±0.12kPa for hydrated animals at rest, decreasing to 1.01±0.10kPa after 24h of dehydration. Similarly, lymph heart rate, which was 48.2±1.7beats min−1 under hydrated conditions, decreased to 31.8±4.6beats min−1 after 18h of dehydration. Lymph flow decreased almost to zero during dehydration from a hydrated rate of 1.11±0.04mlh−1100g−1. This is the first study to measure directly and to correlate these variables in an amphibian and to show specifically that pressure, rate and lymph flow are significantly reduced during periods of dehydration.
The Stopping Response of Xenopus Laevis Embryos: Pharmacology and Intracellular Physiology of Rhythmic Spinal Neurones and Hindbrain Neurones
Authors: Boothby Kate M. , Roberts Alan 
Published: April 2021

ABSTRACT
Xenopus laevis embryos stop swimming in response to pressure on the cement gland. This behaviour and ‘fictive’ stopping are blocked by bicuculline (10μmoll−1), tubocurarine (110μmoll−1) and kynurenic acid (0.5 mmol l−1). Intracellular recordings from spinal neurones active during swimming have shown that pressure on the cement gland evokes compound, chloride-dependent inhibitory postsynaptic potentials (IPSPs). These are blocked by bicuculline, tubocurarine and kynurenic acid, but are unaffected by strychnine (2μmoll−1). When the cement gland is pressed, trigeminal ganglion activity precedes both the IPSPs and the termination of ‘fictive’ swimming activity recorded in rhythmic spinal neurones. The trigeminal discharge is unaffected by the antagonists bicuculline, tubocurarine, kynurenic acid and strychnine. Intracellular recordings from the hindbrain have revealed neurones that are normally silent, but rhythmically inhibited during ‘fictive’ swimming. In these neurones pressure on the cement gland evokes depolarising potentials, often with one or more spikes. We propose that the stopping response depends on the excitation of pressure-sensitive trigeminal receptors which innervate the cement gland. These release an excitatory amino acid to excite brainstem GABAergic reticulospinal neurones, which inhibit spinal neurones to turn off the central pattern generator for swimming. There may also be a less direct pathway.
Disk-Sphere Transformation in Mammalian Red Cells
Authors: Furchgott Robert F. , Ponder Eric 
Published: April 2021

ABSTRACT
The transformation of red cells from disks to spheres in a drop of a saline suspension between slide and coverglass (Ponder, 1929, 1934) has recently been shown by one of us (Furchgott, 1939) to be the result of two changes. The first is a rise in the pH of the suspension above 9·2 because of the alkaline nature of the glass surfaces. The second is an adsorption out of the suspension by the glass surfaces of a substance which, if present, prevents the formation of spheres at the pH attained between slide and coverglass. The determination of the chemical nature of this substance, termed the “anti-sphering factor”, and experimental attempts to gain an insight into the physical mechanism of the phenomena of shape changes are the subject of this paper.
The Effect of Deafferentation Upon the Locomotory Activity of Amphibian Limbs
Authors: Gray J. , Lissmann H. W. 
Published: April 2021

ABSTRACT
In 1912-13 Graham Brown and Sherrington showed, independently, that rhythmical activity could be maintained in a pair of deafferentated antagonistic mammalian muscles; since then it has been customary to regard locomotory rhythms as the expression of intrinsic activity within the nerve cord. On the other hand, a study of the responses of vertebrate limbs to suitable reflex stimulation makes it difficult to believe that impulses coming from peripheral sense organs do not play a very important role in the co-ordination of normal locomotory movements. The present paper constitutes an attempt to decide how far locomotion can occur in animals whose limbs have been completely desensitized by cutting the roots of their afferent nerves.
The Daily Rhythm of Activity of the Cockroach, Blatta Orientalis L
Authors: Mellanby Kenneth 
Published: April 2021

ABSTRACT
Trapping experiments were made to investigate the activity of cockroaches in a naturally infested animal room. Under normal conditions of illumination (light by day and dark by night), activity only occurred at night, and most activity occurred during the period just before midnight. There was little activity during the later hours of darkness. Artificial illumination of the order of 6 m.c. almost entirely prevented the cockroaches from appearing. Even lower intensities of light greatly reduced the number which appeared. Darkening the room during the day did not cause the cockroaches to appear, unless the room had been artifically illuminated during the previous night. Mechanical vibration and air movements appear to have little effect on the rhythmic activity of the cockroach. The rhythmic activity of the cockroach appears to be controlled by some internal mechanism which we do not yet understand. External factors like light can modify the rhythm and may temporarily abolish it, but under normal conditions it is readily re-established.
The Humidity Behaviour of the Mealworm Beetle, Tenebrio Molitor L
Authors: Pielou D. P. , Gunn D. L. 
Published: April 2021

ABSTRACT
Humidity is well known to be a factor of great importance in the lives of many insects and other terrestrial arthropods. Apart, however, from the pioneer work of Shelford (1913) and his school on the rather complex stimulus of “evaporating power of the air”, there has been, until recently, little detailed and exact study of the behaviour of animals towards humidity as a stimulus. The recently developed methods of Gunn & Kennedy (1936) now make such study possible. By means of these methods, humidity behaviour has been examined in the wood-louse, Porcellio scaber, by Gunn (1937); in the locust, Locusta migratoria, by Kennedy (1937); in the mosquitoes, Anopheles gambiae and A.funestus, by De Meillon (1937); in the mosquito, Culex fatigans, by Thomson (1938) and in the cockroach, Blatta orientalis, by Gunn & Cosway (1938). The work described below deals with the reactions of the adult mealworm beetle, Tenebrio molitor L., towards humidity. This beetle lives in flour, bran and similar products and is moderately resistant to desiccation. It loses about 4% of its weight per day in dry air at 25° C. and dies in 8–9 days. Its resistance to desiccation is therefore less than that of its. larva, which was investigated by Buxton (1930).
Physiological Effects of a Hypotonic Environment
Authors: Wells G. P. , Ledingham Isabel C. 
Published: April 2021

ABSTRACT
Numerous studies have been published on the extent to which aquatic animals can maintain internal environments differing in osmotic pressure from their surroundings. In the case of polychaete worms, it has been shown that some species, especially Nereis diversicolor, can maintain a considerable degree of hypertonicity, even in very dilute brackish water, while in others, such as Arenicola marina, the internal and external fluids are always isotonic (Schlieper, 1929; Beadle, 1937; Zenkewitch, 1938). These facts have been correlated with the extent to which the various species can invade brackish water. In one respect, however, our knowledge is at present very deficient. Remarkably little—in the case of polychaete worms, nothing—is known about the extent to which the tissues of animals can tolerate dilution of their bathing media. Information on this question is evidently necessary if the significance of the body-fluid data is to be properly understood.
Second-Order Olfactory and Visual Learning in the Optic Tectum of the Goldfish
Authors: Sanders F. K. 
Published: April 2021

ABSTRACT
The goldfish (Carassius auratus) learns to swim to concealed food when an illuminated disk is presented. The presentation of an olfactory stimulus at the same time as the optic stimulus, during reinforcement of this visual learning, results in the addition of the olfactory stimulus to the stimulus complex necessary to call forth the learned reaction. Five animals learned to react to a situation in which—after preliminary training with an optic stimulus with food as reward—amyl acetate was given as olfactory stimulus and the optic stimulus as reward. This effect is termed second-order learning. It is comparable to second-order conditioned reflexes. In four animals trained in this way operations involving removal of large areas of the optic tectum, or cuts made at its anterior border, caused disturbances in the second-order learning. There exists, therefore, in the Teleostean optic tectum a mechanism capable of second-order olfactory-optic learning. The connexion between the telencephalic primary olfactory centre and the tectum involved in this learning passes into the tectum at its anterior border, since cuts made in this region interfered with the learning while leaving a great deal of the tectum intact.
The Effect of Certain Environmental Factors on the Growth of Brown Trout (Salmo Trutta L.)
Authors: Wingfield C. A. 
Published: April 2021

ABSTRACT
The factors responsible for seasonal variations in the growth of brown trout in any one environment are examined. The probable basic importance of the water temperature is established. A critical temperature of 6° C. below which no growth takes place is deduced. It is shown that the seasonal variations in growth observed do not result in corresponding variations in the width of the scale rings: such variations appear to be the direct result of fluctuations in available food supply. Under natural conditions both water temperature and available food supply apparently act as limiting factors during the winter: during the summer, provided that the water temperature does not rise to a lethal level, only the available food supply is limiting. The possible importance of light intensity as a limiting factor is indicated. Differences in the growth rate of trout from different environments are also considered. The role of dissolved calcium is investigated. It appears unlikely that the amount of dissolved calcium is responsible for the differences in trout growth in “hard” and “soft” waters. It is suggested that such differences may be effected not by differences in the concentration of any one specific ion, but by departures from the optimum ionic balance brought about by variations in the relative concentration of any of the ions present.
Effects of Diet on Responses to Hypoxia in Sturgeon (Acipenser Naccarii)
Authors: Randall D. J. , McKenzie D. J. , Abrami G. , Bondiolotti G. P. , Natiello F. , Bronzi P. , Bolis L. , Agradi E. 
Published: April 2021

ABSTRACT
We investigated the effects of a diet enriched in omega-3 (ω3) polyunsaturated fatty acids (PUFA) and vitamin E on responses of sturgeon (Acipenser naccarii) to hypoxia. After 3 months of feeding, there were significant increases in ω3 PUFA in liver and muscle, and of vitamin E in muscle, of fish fed the enriched diet (ED) compared with fish on a standard diet (SD), indicating that tissue composition is influenced by diet. Acute exposure to hypoxia (10 min at 10.8 kPa water O2 tension, ) had no effect on oxygen consumption , increased gill ventilation frequency (fg) and reduced arterial blood O2 content in both dietary groups, but ED sturgeon exhibited a significantly smaller decrease in than did SD animals. Progressive hypoxic exposure ( decreasing gradually from 20.5 to 3.6kPa within 45–60min) led to a significant increase in at intermediate levels of in SD sturgeon that was not seen in ED animals. Furthermore, ED sturgeon showed no significant reduction in arterial plasma pH (pHa) and at levels that caused significant reductions in these variables in SD sturgeon. ED sturgeon exhibited a smaller increase in plasma lactate level than did SD fish. We suggest that PUFA and/or vitamin E contribute significantly to regulation of metabolism in hypoxia.
The Effect of Temperature on the Burst Swimming Performance of Fish Larvae
Authors: Batty R. S. , Blaxter J. H. S. 
Published: April 2021

ABSTRACT
Newly hatched herring and plaice larvae were stimulated by probes to make C-start escape responses at temperatures between 5 and 15°C. The responses and the subsequent burst-speed swimming were recorded and analysed using highspeed video at 400 frames s−1. The muscle contraction time of the initial C-start was temperature-dependent, ranging from 22–33 ms at 5°C to 17–21 ms at 15°C. Immediately following the C-start, tail-beat frequency ranged from 18s−1 at 5°C to 35 s−1 at 15°C. Tail-beat amplitude, equivalent to 0.4–0.6 of a body length (L), and stride length, about 0.5 L, were not temperature-dependent. The escape speed ranged from 8Ls−1 at 5°C to 15 Ls−1 at 15°C. These results and those of other workers can be described by the equation: where f is tail-beat frequency, t is temperature and L is length.
Electrophysiological Pharmacology of the Nicotinic and Muscarinic Cholinergic Responses of Isolated Neuronal Somata From Locust Thoracic Ganglia
Authors: Benson Jack A. 
Published: April 2021

ABSTRACT
Mechanically isolated neuronal somata from the thoracic ganglia of the locust Locusta migratoria remain electrophysiologically viable under current-or voltage-clamp in vitro for many hours. Nicotine and muscarine evoke different responses when pressure-microapplied to these somata. The response to acetylcholine is mainly nicotinic but contains a small muscarinic component. The nicotinic (AChl) response is a rapid depolarisation accompanied by a decrease in membrane resistance. In voltage-clamped somata, the current mediating the AChl response is inward over the membrane potential range −30 to − 110 mV, decreasing with depolarisation and with a projected reversal potential of about +20 mV. The muscarinic (ACh2) response is a slow depolarisation accompanied by a decrease in membrane resistance. In voltage-clamped somata, the current mediating the ACh2 response is inward, decreasing to zero at potentials of −80 to −90 mV. The AChl response is evoked by nicotine, anabasine, tetramethylammonium, DMPP and relatively high concentrations of the nitromethylene heterocycle insecticide, PMNI. Suberyldicholine or decamethonium evoke the response only when acetylcholine is present in the bathing saline. Nicotinic antagonists of the AChl response, in descending order of potency, are PMN1 &gt; α-bungarotoxin⩾lobeline⩾mecamylamine&gt;trimethaphan camsylate&gt;chlorisondamine⩾d-tubo-curarine⩾hexamethomium⩾gallamine triethiodide⩾tetracthylammonium. This response is also potently blocked by strychnine and more weakly blocked by δ-philanthotoxin, bicuculline and picrotoxin. The ACh2 response is evoked by muscarine, oxotremorine, arecoline, pilocarpine and, very weakly, by the Mj-selective agonist McN-A-343. Muscarinic antagonists of the ACh2 response, in descending order of potency, are QNB&gt; scopolamine&gt;atropine&gt;4-DAMP (M3) ⩾benactyzine⩾HHSiD (M1/M3) ⩾ pirenzepine (M1). QNX (M1), AF-DX116 (M2), gallamine triethiodide (M2) and methoctramine (M2) are almost or completely inactive. With the exception of pirenzepine and QNX, all of the muscarinic antagonists used in this study also block the nicotinic AChl response with EC50 values in the range 5 to 50μmol l−1, similar to those for δ-philanthotoxin, bicuculline and picrotoxin. Pirenzepine is inactive (10μmol l−1), but QNX is potently active, with an EC50 value of approximately 20 nmol l−1, similar to that of α-bungarotoxin. The extrasynaptic nicotinic and muscarinic receptors of Locusta migratoria neurones are pharmacologically distinct from the corresponding mammalian receptors studied so far.
Suppression of Ventilatory Reafference in the Elasmobranch Electrosensory System: Medullary Neuron Receptive Fields Support A Common Mode Rejection Mechanism
Authors: Bodznick David , Montgomery John C. 
Published: April 2021

ABSTRACT
Elasmobranch fishes have an electroreceptive system which they use for prey detection and orientation. Sensory inputs in this system are corrupted by a form of reafference generated by the animal’s own ventilation. However, we show here that in the carpet shark, Cephaloscylium Isabella, as in two previously studied batoid species, this ventilatory ‘noise’ is reduced by sensory processing within the medullary nucleus of the electrosensory system. It has been proposed that the noise cancellation is achieved by a common mode rejection mechanism. One prediction of this hypothesis is that secondary neurons within the medullary nucleus should have both excitatory and inhibitory components to their receptive fields. This prediction is experimentally verified here. Projection neurons of the medullary nucleus in the carpet shark typically have a focal excitatory, and a diffuse inhibitory, receptive field organization including a component of contralateral inhibition. This result provides strong support for the hypothesis that ventilatory suppression in the elasmobranch electrosensory system is achieved by a common mode mechanism.
Calcium and Potassium Currents in leg Motoneurons During Postembryonic Development in the Hawkmoth Manduca Sexta
Authors: Hayashi Jon H. , Levine Richard B. 
Published: April 2021

ABSTRACT
During insect metamorphosis the nervous system is reorganized to accommodate changes in behavior. In the hawkmoth, Manduca sexta, many identified larval motoneurons persist to innervate new adult muscles, while undergoing changes in dendritic morphology and synaptic connections. The thoracic leg motoneurons, for example, innervate different sets of muscles in the larva and adult and participate in distinct types of locomotor behavior in the two stages of life. To determine whether changes in the biophysical properties of these motoneurons accompany the structural and functional modifications that have been described, we used the whole-cell voltage-clamp technique to compare the Ca2+ and K+ currents expressed by leg motoneurons isolated from the larval, pupal and adult stages of Manduca. After 24h in culture, the somata of leg motoneurons isolated from all three stages expressed voltage-sensitive Ca2+ currents that could be blocked by Cd2+, Co2+ or Ni2+. The currents were larger with Ba2+ as the charge carrier. The Ca2+ current density was significantly lower in these motoneurons during the early pupal stage than in either the larva or adult. Similar experiments revealed both transient and sustained K+ currents in the leg motoneurons that could be blocked with Cs+. There was a significant decrease in the density of the transient, inactivating outward current in leg motoneurons isolated from the early pupal stage. Thus, the levels of some types of ionic currents are modulated during metamorphosis. These changes may be important for the developmental or behavioral changes that accompany metamorphosis.
Infrasound Sensitivity in the Plaice (Pleuronectes Platessa)
Authors: Karlsen Hans Erik 
Published: April 2021

ABSTRACT
The sensitivity of plaice (Pleuronectes platessa) to infrasound has been examined using a seawater-filled test chamber suspended by steel wires like a swing and driven by a vibrator. The sensitivity to low-frequency vibrations was determined using the cardiac conditioning technique. All plaice readily responded to infrasound down to 0.1 Hz, which was the lowest frequency tested, with threshold values of approximately 4×10−5ms−2 rms. This sensitivity is comparable to infrasound thresholds found in other fish species and it agrees with the acceleration thresholds for plaice in the frequency range 30–100 Hz. The water movements relative to the fish surface produced during stimulation were below lateral-line thresholds. The inner ear otolith organs are thus probably responsible for the observed responses to infrasound. The hearing capabilities of plaice may be explained by these organs functioning as slightly underdamped harmonic oscillators with a resonant frequency close to 100Hz.