bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pharmacological Studies on A Locust Neuromuscular Preparation
Authors: Clements A. N. , May T. E. 
Published: April 2021

ABSTRACT
The structure-activity relationships of agonists of the locust excitatory neuromuscular synapse have been reinvestigated, paying particular attention to the purity of compounds, and to the characteristics and repeatability of the muscle response. The concentrations of compounds required to stimulate contractions of the retractor unguis muscle equal in force to the neurally evoked contractions provided a measure of the relative potencies. Seven amino acids were capable of stimulating twitch contractions, glutamic acid being the most active, the others being analogues or derivatives of glutamic or aspartic acid. Aspartic acid itself had no excitatory activity. Excitatory activity requires possession of two acidic groups, separated by two or three carbon atoms, and an amino group α to a carboxyl. An L-configuration appears essential. The ω-acidic group may be a carboxyl, sulphinyl or sulphonyl group. Substitution of any of the functional groups generally causes total loss of excitatory activity, but an exception is found in kainic acid in which the nitrogen atom forms part of a ring. The investigation of a wide variety of compounds revealed neuromuscular blocking activity among isoxazoles, hydroxylamines, indolealkyl-amines, β-carbolines, phenazines and phenothiazines. No specific antagonist of the locust glutamate receptor was found, but synaptic blocking agents of moderately high activity are reported.
Control of Moulting and Metamorphosis in the Tobacco Hornworm, Manduca Sexta (L.): Growth of the Last-Instar Larva and the Decision to Pupate
Authors: Nijhout H. Frederik , Williams Carroll M. 
Published: April 2021

ABSTRACT
The dynamics of growth and the timing of release of the brain ‘s pro-thoracicotropic hormone (PTTH) in final instar larvae of Manduca sexta are consistent with the following hypothesis. When a 5th-stage larva reaches a critical weight of about 5 g an unidentified process is initiated which requires 24 h to be completed. At the completion of this process the brain is rendered competent to release PTTH. The actual release of PTTH is gated by the photoperiod and occurs when the gate opens during the very next photophase.
Nitrogen Metabolism in the American Cockroach: an Examination of Whole Body and Fat Body Regulation of Cations in Response to Nitrogen Balance
Authors: Mullins Donald E. , Cochran Donald G. 
Published: April 2021

ABSTRACT
The effects of nitrogen balance on uric acid/urate, K+ and Na+ storage or mobilization were examined in the American cockroach Periplaneta americana (L.). Cockroaches on a high nitrogen diet increased in whole body uric acid/urates, K+ and Na+. Those on a semi-starvation diet maintained fairly constant levels of uric acid/urates, K+ and Na+. However, those on a low nitrogen diet mobilized stored uric acid/urates and K+, but not Na+. Analyses for uric/urates K+, Na+, Ca2+ and Mg2+ in fat body tissue from insects maintained on 12 diets containing different concentrations and sources of dietary nitrogen showed that only K+ concentration could be correlated with fat body uric acid/urate storage. Whole body storage and mobilization of uric acid/urates, K+ and Na+ were reflected in the faecal/dietary ratios of K+ and Na+. A model for a uric acid/urate ion sink which might be associated with ionic and osmotic balances is proposed, and some evidence for its existence is discussed.
Interneurones in Crab Connectives (Carcinus Maenas (L.)): Giant Fibres
Authors: Fraser Peter J. 
Published: April 2021

ABSTRACT
Five interneurones with cell bodies and dendritic trees in the brain have axons 40–60μm diameter in one oesophageal connective. The fibres are phasic and multimodal, responding to visual and tactile stimuli. They have complex adaptation properties and two are suppressed completely during certain movements of the animal. The role of the fibres in overt behaviour has not been revealed by electrical stimulation or by examination of output in free walking animals. Several smaller intemeurones in the connective are briefly described anatomically and physiologically.
Effects of Acetylcholine on Resting and Action Potentials, and On Contractile Force in the Ventricle of Dolabella Auricularia
Authors: Hill Robert B. 
Published: April 2021

ABSTRACT
Acetylcholine (2 ×10−8 to 2 × 10−3 M) depolarized the isolated ventricle of Dolabella auricularia. The depolarization was accompanied by a negatively inotropic effect from 2 × 10−8 M to 2 × 10−4 M, and by a positively ionotropic effect from 2 ×10−4 M to 2 × 10−3 M. The interaction of acetylcholine and 5-hydroxytryptamine was studied by artificially prolonging the plateau of the cardiac action potential by treatment with 5-HT. Acetylcholine had the effect of shortening the plateau established by 5-hydroxytryptamine. Force was reduced correspondingly.
Water Uptake and Hatching in the Potato Cyst Nematode, Heterodera Rostochiensis, and the Root Knot Nematode, Meloidogyne Incognita
Authors: Ellenby C. 
Published: April 2021

ABSTRACT
The second-stage larva of the plant parasitic nematode Heterodera rostochiensis shows very little movement while confined to the egg; on the other hand, the larva of the closely related Meloidogyne incognita is very active Using interference microscopy, it is shown that the water content of the Heterodera larva increases immediately it is liberated from the egg while that of the Meloidogyne larva remains constant. It is suggested that the Heterodera larva is physically constricted by the egg shell and that this restricts both its movement and its water content. Measurement of larval and egg volume in both forms supports this hypothesis. The Meloidogyne larva has about 30% of free space inside the egg shell while the Heterodera larva fits it completely. It is suggested that these differences can be correlated with differences in the distribution and life-history of the two forms.
The Reduced Glucose Permeability of the Isolated Malpighian Tubules of the Blowfly Calliphora Vomitoria
Authors: Knowles G. 
Published: April 2021

ABSTRACT
The excretion of several sugars by the isolated Malpighian tubules of Calliphora vomitoria has been investigated. The isolated tubules do not excrete glucose or trehalose at rates similar to those of sugars of the same molecular weight. Trehalose can be hydrolysed to glucose as it traverses the tubule wall. It is proposed that glucose can be reabsorbed by the tubule. Evidence is presented to suggest that glucose reabsorption can be saturated. Phloridzin was found to increase the rate of glucose excretion by the isolated Malpighian tubule.
Motor patterns in the stomatogastric ganglion of the lobster Panulirus argus
Authors: Hartline Daniel K. , Maynard Donald M. 
Published: April 2021

ABSTRACT
Activity patterns arising from the thirty cells of the stomatogastric ganglion of Panulirus argus are described for both a semi-intact preparation and an isolated one. The thirty or so cells can be divided so far into two functional groupings: the gastric mill group, with at least ten motor elements, and the pyloric group with at least fourteen. There is some, but not extensive, interaction between groups. The main gastric mill activity is arranged in two sets of elements, each of which is composed of reciprocating elements innervating antagonistic muscles. Thus alternation in activity between the single LC and the two LG neurones results in alternate closing and opening of the lateral teeth; alternation between the four GM and single CP units results in alternate protraction and retraction of the medial tooth. The two sets are phased to each other in such a way that they cause gastric mill teeth to operate effectively to masticate food. The main pyloric activity is arranged in a three-part cycle with each of three sets of units active in sequence. Activity in two PD and one AB unit is followed by bursts in IC and LP units followed in turn by activity in up to seven PY units. Activity in a single VD neurone is locked to this cycle in a more complex pattern.
The Role of the ‘Walking Legs’ in Aquatic and Terrestrial Locomotion of the Crayfish Austropotamobius Pallipes (Lereboullet)
Authors: Pond Caroline M. 
Published: April 2021

ABSTRACT
The hydrodynamic drag acting on the crayfish Austropotamobius pallipes is measured and it is concluded that, in the range of velocities used in walking, the drag is independent of the posture of the limbs and the direction of motion of the body. At swimming velocities the streamlining caused by promotion of the legs reduces the drag losses to half that of a crayfish moving in the forwards walking posture at the same speed. The forwards walking of intact crayfish is compared with that of the same animal after amputation of one or more pairs of legs. It is concluded that the third and fourth pair of legs provide most of the propulsion under water and the second pair is not essential to locomotion under any of the conditions tried.
Activity and habituation in the brain of the polyclad flatworm Freemania litoricola
Authors: Koopowitz Harold 
Published: April 2021

ABSTRACT
A variety of spontaneously active units was measured in the brain of the polyclad flatworm Freemania litoricola. Following application of MgCl2 there was both a decrease in number of active units and a decrease in frequency of firing of those cells which persisted in their activity. Receptors which respond to vibration stimuli evoke potentials in the posterior part of the brain. Repetitive stimulation leads to habituation, the extent of which is dependent on both the number of times stimulated and the strength of the stimulus. Weaker stimuli habituate more rapidly than strong stimuli. Habituated responses can be dishabituated by tactile stimuli and also by stronger intensity stimuli of the same modality. The vibration-evoked potentials appear to occur in at least second-order cells, since vibration responses are abolished by the application of MgCl2. Tactile responses can also be elicited from the posterior portion of the brain when the stimulus is applied to the periphery of the animal. These responses are insensitive to MgCl2. Both vibration and tactile evoked responses are able to evoke further barrages of spike activity. The presence of a dual sensitizing and inhibitory system during habituation is discussed.
The Optokinetic Responses of the Mysid Shrimp Praunus Flexuosus
Authors: Neil D. M. 
Published: April 2021

ABSTRACT
The optokinetic responses of the mysid shrimp Praunus flexuosus in the horizontal and vertical-transverse planes have been studied. The horizontal optokinetic nystagmus is fragmented, and eyestalk following speed is a function of stimulus speed. The vertical optokinetic response is not a nystagmus, but involves maintained eyestalk, deviations. These deviations, and eyestalk following speed are both functions of stimulus speed. The velocity gain (eye speed/slip speed) of the responses in both dimensions has a constant value between drum speed z°/sec and 40°/sec, which suggests that they subserve a simple rheotactic function. The vertical optokinetic response is modulated by statocyst input, and possible mechanisms underlying this effect are discussed.
The cardioregulatory system of crayfish: The role of circumoesophageal interneurones
Authors: Field L. H. , Larimer J. L. 
Published: April 2021

ABSTRACT
Interneurones located in the circumoesophageal commissures were found to control the activity of the cardioinhibitor and cardioaccelerator regularity neurones. These interneurones (cardiac command fibres) fell into three classes: (1) strong inhibitors, which caused cardiac arrest, (2) weak inhibitors, which caused bradycardia, and (3) accelerators, which caused tachycardia. When the positions of interneurones were plotted collectively, they formed distinct clusters, suggesting that each cluster was represented by one command unit in an individual preparation. Twenty strong inhibitor units and 16 accelerator units were found. Weak inhibitors did not form clusters. Stimulus threshold characteristics were as low as 3·0 V and 3 Hz for the strong inhibitor units (mean range 4·7−7·1 and 14−V 30 Hz). Higher values were found for weak inhibitors and accelerators. The strong inhibitor command drives always showed a positive bias toward the contralateral cardioinhibitor neurone, relative to the ipsilateral cardioinhibitor. Plots of command neurone stimulating frequency versus evoked cardioinhibitor activity displayed steep positive slopes for strong inhibitor command units and shallow positive slopes for weak inhibitor units. Reciprocity between the cardioinhibitor and cardioaccelerator neurones occurred during both inhibitory and acceleratory command drives. This is not likely to be a property inherent in the command units themselves because reciprocity was earlier observed during chemical and tactile reflex inhibition of the heart. (Field & Larimer, 1974a).
Thermoregulation in Small Flies (Syrphus Sp.): Basking and Shivering
Authors: Heinrich Bernd , Pantle Curt 
Published: April 2021

ABSTRACT
Flies of the genus Syrphus aggregated at specific sites in the field (Tecks’). Flies at leeks were always capable of ‘instant’ take-of, even at ambient temperatures of 10 °C or less. The flies regulated their thoracic temperature by a combination of basking and shivering. During hovering flight in sunshine thoracic temperature rose 12−14 °C above the ambient temperature. The flies engaged in frequent brief chases while at the leeks. At an air temperature &gt; 18 °C the flies at the leek remained in hovering flight most of the time. The vibration frequencies of the thorax during shivering and flight ranged from about 100 to 200 Hz at 10−27 °C, though at a given temperature and spike frequency the vibration rate during warm-up was higher than the wing-beat frequency (assumed to be the same as thoracic vibration frequency) during flight. During shivering, but not in flight, there is a tendency for the indirect flight muscles to be activated in synchrony.
Stimulus-secretion coupling in an insect salivary gland: cell activation by elevated potassium concentrations
Authors: Berridge M. J. , Lindley B. D. , Prince W. T. 
Published: April 2021

ABSTRACT
Fluid secretion by isolated salivary glands was stimulated by elevating the external potassium concentration. The stimulatory effect of potassium was dependent on external calcium and was potentiated by a subthreshold dose of 5-hydroxytryptamine (5-HT). During the action of 120 mM potassium there was a large calcium dependent decrease in transepithelial resistance similar to that produced with 5-HT at normal potassium concentrations. These results on Calliphora salivary glands are compared with other cases where cells are activated by high potassium. In most cases, the effect of high potassium is dependent upon calcium, suggesting that the latter plays a primary role in cell activation.
Effects of viscosity and ATP concentration on the movement of reactivated sea-urchin sperm flagella
Authors: Brokaw C. J. 
Published: April 2021

ABSTRACT
Spermatozoa from the sea urchin, Lytechinus pictus, can be demem-branated with solutions containing Triton X-100 and 5 mM-CaCl2 and reactivated in ATP solutions containing low concentrations (10−9 M) of free Ca2+ ion to give symmetrical bending wave movements, even at very low ATP concentrations. At ATP concentrations of 0·01−0·02 mw the reactivated spermatozoa have beat frequencies near 1 Hz, nearly normal bend angles, and wave-lengths about 50% longer than normal. The effects of increased viscosity, obtained by addition of methyl cellulose to the reactivation solutions, on bend angle and beat frequency decrease with decreasing ATP concentration, and become almost undetectable at 0 ·01 mM ATP. On the other hand, the effect of increased viscosity on wavelength shows relatively little change with ATP concentration, although it is noticeably reduced at o-oi mM ATP. These observations suggest that the beat frequency at low ATP concentrations is determined by an intrinsic rate-limiting process, in contrast to the viscosity-limited behaviour at high beat frequencies. Quantitative agreement with the experimental results is obtained with a model in which ATP concentration and viscosity each determine the rates of one step in a two-step reaction cycle which determines the beat frequency. Two other models which can qualitatively explain the effects of ATP concentration and viscosity on flagellar beat frequency fail to show quantitative agreement with the experimental results. In one of these models, ATP concentration determines the maximum rate of shear between filaments. In the other, ATP concentration determines a time delay which is required to bring the active moment into phase with the elastic moments which would be expected to dominate the bending resistance at low beat frequencies.
Sodium activity of insect blood: physiological significance and relevance to the design of physiological saline
Authors: Treherne J. E. , Buchan P. B. , Bennett R. R. 
Published: April 2021

ABSTRACT
The apparent activity coefficients for sodium (γ ′Na) in the blood of six insect species have been calculated from measurements made with sodium-selective electrodes and a flame photometer. In every case γ’Na was significantly lower than that for this cation in free solution (γ Na). In Periplaneta americana γ ′Na varied considerably, during a period of 90 days, so that a relatively constant sodium activity (aNa) was maintained in the blood in the face of large variations in the total sodium content measured by flame photometry. Despite the relative constancy of aNa (of around 0·088M) appreciable fluctuations were observed in the sodium and potassium content of nervous connectives over a period of 140 days. The values of aNa and aK were used to devise a satisfactory cockroach saline for use in experiments with isolated nerve cords.
The Withdrawal Response of a Freshwater Snail (Lymnaea Stagnalis L.)
Authors: Cook Anthony 
Published: April 2021

ABSTRACT
Electrical stimulation of a variety of nerves towards the brain results in movements of the neck of the snail similar to those associated with the withdrawal response of the intact animal. The columellar and cervical nerves mediate most of the movements being measured. Repetition of the stimuli results in a decline in response amplitude which is complicated by a superimposed incremental process which is itself subject to a decremental process as stimuli are repeated. As stimuli are repeated the response latency increases. Consecutive stimulation of pairs of nerves indicates that the response decrement is specific to the nerve being stimulated. The involvement of the pleuro-pedal connectives in the response has been demonstrated both in a semi-intact preparation stimulated electrically and in a free-roaming animal treated surgically and stimulated visually. Visual stimuli associated with the withdrawal response are detected by photoreceptors on the head and in the mantle.
Central patterning and reflex control of antennular flicking in the hermit crab Pagurus alaskensis (Benedict)
Authors: Snow P. J. 
Published: April 2021

ABSTRACT
The effects of altering sensory input on the motoneuronal activity underlying antennular flicking have been tested. Removal of the short segments of the outer flagellum results in a reduction of the number of spikes/burst in the fast flexor motoneurones A31F and A32F. During a flick the delay between the burst in motoneurone A31F and the burst in motoneurone A32F is insensitive to alteration of sensory input. Sensory feedback from the flexion phase of a flick is necessary for the activation of either extensor motoneurone. Evidence is presented to suggest that this feedback is primarily from joint-movement receptors at the MS-DS and DS–OF joints. The results are incorporated into a model in which the patterns of flexor activity result from some specified properties of three components: a trigger system, a follower system, and the spike initiating zone of the flexor motoneurones. The trigger system determines when a flick will occur. The follower system determines the number of flexor spikes during a flick. Properties of the spike initiating zone determine the spike frequency and the timing between bursts in the flexor motoneurones. Extensor activity in the model is reflexively elicited by feedback from phasic, unidirectional receptors sensitive to joint flexion. The functional significance of reflex control of extensor activity is discussed in relation to the form and proposed function of antennular flicking. It is suggested that this form of control is adapted to the function of antennular flicking because flexion at the MS-DS joint is not always necessary for the fulfilment of the function of a flick.
Oxygen consumption, ventilatory frequency and heart rate of lampreys (Lampetra fluviatilis) during their spawning run
Authors: Claridge P. N. , Potter I. C. 
Published: April 2021

ABSTRACT
The standard rate of oxygen consumption, ventilatory frequency and heart rate of adult Lampetra fluviatilis were measured during the light phase of the photoperiod and at times corresponding to various stages in the upstream migration. All three parameters increased during the spawning run but only in mature individuals were significant differences found between the sexes. The regression coefficients for the logarithmic relationship between oxygen consumption and body weight of immature animals were 0·912 and 0·925 at 9·5 and 16 °C respectively. Both the standard rate of oxygen consumption and the amount of oxygen taken up during activity increased greatly during the hours of darkness. Oxygen consumption, ventilatory frequency and, to a lesser extent, heart rate increased significantly at 9·5 °C over the 100–20% range of saturation with air. Below 20 % saturation with air, lampreys no longer remained attached by their oral disc for prolonged periods and the ventilatory frequency rose even more rapidly to reach a maximum of 175 beats/min at 12·5 %. Exposure to 7·5 % resulted in death within 5–8 h.
A technique for repeated sampling of the blood of individual resting fish
Authors: Soivio A. , Nynolm K. , Westman K. 
Published: April 2021

ABSTRACT
A dorsal cannulation technique is described. It has been employed for repeated blood sampling in unanaesthetized rainbow trout (Salmo gairdneri) kept singly in special receptacles described in the paper. The level of the studied haematological parameters (Haematocrit, Hb, glucose, lactate, K+, Na+, Ca2+) differed between fish kept in receptacles for 1 week and free-swimming fish, most probably owing to differences in the motility of the fish. The receptacle seems to minimize visual and handling disturbances, and permits both the standardization of experimental conditions and quick and easy sampling via the dorsal aorta cannula. The general variation in the blood parameter values was very small compared with the previously reported variation in such values for rainbow trout.