bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of Calcium on Flagellar Movement in the Trypanosome Crithidia Oncopelti
Authors: Holwill M. E. J. , Mcgregor J. L. 
Published: April 2021

ABSTRACT
The effects of calcium on the motility of different preparations of flagella from Crithidia oncopelti were studied using stroboscopic and high-speed cine photographic techniques. By varying the concentration of calcium in suspensions of chemically treated samples of the organism it was found that changes occurred in bend shape, wave direction and frequency. Waves on the flagellum of the organism in vivo possess the unusual ability to propagate from tip to base, but reverse in direction during an avoiding response. In chemically extracted and reactivated preparations tip to base propagation was observed only at low concentrations ( &lt; 10−4 mol m−3) of calcium ion; at high concentrations base to tip propagation only was seen. In cells treated with ionophores known to carry divalent ions across membranes, tip to base propagation was seen only in the presence of EGTA ; when calcium was added the majority of organisms propagated waves from base to tip. At certain values (ca. 10−3 mol m−3) of the calcium concentration the wave shape had meander-like characteristics, whereas at higher and lower concentrations it was more sinusoidal. At high calcium concentrations only one wave appeared on the flagellum whereas at low values two or three were observed. A reduction in frequency at high calcium concentrations was probably due to competitive inhibition of magnesium ions. The results suggest that wave reversal in living Crithidia is induced by the release of calcium ions within the flagellum following stimulation of the membrane. In terms of the sliding filament model of flagellar activity the effects of calcium suggest that the ion is effective in modifying the interaction between the spoke head and central sheath and may control the relative direction of microtubular sliding.
Role of Proprioceptive Feedback From Nonspiking Mechanosensory Cells in the Sand Crab, Emerita Analoga
Authors: Paul Dorothy Hayman 
Published: April 2021

ABSTRACT
The two programmes underlying uropod beating in Emerita (‘swimming’ and ‘treading water’) are distinguished by a difference in timing of the power stroke within the interval between return strokes (cycle). While ‘swimming’ (cycles approx. 80–400 ms) the phase and while ‘treading water’ (cycles approx. 100–700 ms) the latency of the power stroke are relatively invariant. Analyses of electromyograms of unrestrained Emerita, before and after bilateral surgical ablation of the four nonspiking mechano- receptive cells associated with each uropod, established that power strokes in ‘treading water’ are dependent upon proprioceptive feedback from the nonspiking cells. As cycle duration increases from 80 to 700 ms, the function of the reafference changes from reinforcement of the centrally generated ‘swimming’ pattern to production of the ‘treading water’ pattern.
Physiology of An Atp Receptor in Labellar Sensilla of the Tsetse Fly Glossina Morsitans Morsitans Westw. (Diptera: Glossinidae)
Authors: Mitchell B. K. 
Published: April 2021

ABSTRACT
Electrophysiological recordings have been made from cells in the eight large, labellar sensilla of G. morsitans. One of these cells in each sensillum was shown to respond to ATP over a concentration range of 10−6–10−3 M. It was also sensitive to several other adenosine phosphates, but much less sensitive to CTP, GTP and ITP. The activity of the receptor was depressed below pH 7, and sometimes considerably increased above pH 9. These aspects of the receptor’s physiology support the results of behavioural studies. It is concluded that the eight receptors mediate the flies’ behavioural response to ATP.
Stretch-Sensitive Neural Units in the Body Wall of the Earthworm, Lumbricus Terrestris L
Authors: Drewes C. D. , Fourtner C. R. 
Published: April 2021

ABSTRACT
Sensory neural units responding to sinusoidal longitudinal stretching of the body wall were studied in the earthworm, Lumbricus terrestris L. A phasic stretch-sensitive unit found in segmental nerve I responded optimally to stretching at frequencies of 4–6/min. The number of spikes per stretch and the spike frequency in the unit were directly related to the amplitude of the applied stretch within a range of 0·2–0·7 mm stretch/segment. The ranges of amplitude and frequency sensitivity for the unit in isolated preparations corresponded closely to stretch parameters seen during peristaltic locomotion in intact animals. Stretch-sensitive responses in segmental nerve II—III were more variable; some units responded to longitudinal stretch while others responded to relaxation.
Nervous Control of Light Responses in the Sea Anemone, Calamactis Praelongus
Authors: Marks Philip S. 
Published: April 2021

ABSTRACT
The burrowing sea anemone, Calamactis praelongus, responds to light with local, non-nervous contractions of the column. There are also more extensive responses of the column and retractor muscles co-ordinated by nerve net pulses (NNP’s) under pacemaker control. NNP’s occur in at least two types of bursts and in sequences which sometimes indicate a rotating site of pulse initiation. Light-evoked NNP sequences can be tape recorded and used later to drive a stimulator to reproduce the original sequences in the same or different anemones, evoking muscular responses which approximate the originals. This technique separates the pacemaker-directed component of the light response from the local effects of light stimulation. Isolated circular and parietal muscles contract slowly when stimulated by light or excited indirectly by NNP’s. Retractor muscles are insensitive to light but produce rapid contractions when excited by closely spaced light-evoked NNP’s. A model for light responses is proposed which incorporates the characteristics of isolated muscles and intact anemones.
Synaptic Transmission in the Sixth Ganglion of the Cockroach: Action Of 4-Aminopyridine
Authors: Hue B. , Pelhate M. , Callec J. J. , Chanelet J. 
Published: April 2021

ABSTRACT
Study was made of the action of 4-aminopyridine (5× 10−5M) on synaptic transmission in the last abdominal ganglion of Periplaneta americana. The ‘oil-gap’ technique was used to record postsynaptic events in a single giant axon. 4-AP quickly increased the ‘background’ of postsynaptic activity, which consisted of ‘spontaneous’ unitary EPSPs and IPSPs. Postsynaptic spikes were also propagated. Both evoked EPSPs (stimulation of cereal nerve XI) and evoked IPSPs (stimulation of cereal nerve X) were greatly increased in amplitude although their duration (half-time) was unaltered. 4-AP triggered presynaptic action potentials in the cereal nerves (recorded with external electrodes). These ‘antidromic’ potentials appeared singly or sometimes repetitively, especially after electrical stimulation of the cereal nerves. They were often in monosynaptic correlation with unitary EPSPs. Neither the resting potential nor the postsynaptic membrane resistance was modified. There were no changes in the equilibrium potentials of the ions involved in postsynaptic events. The results may be essentially explained by an increase in transmitter release after 4-AP treatment, which may be partly the result of a rise in presynaptic terminal excitability, and partly the result of a lengthening of the presynaptic action potentials.
The Hormonal Control of Diuresis in the Cabbage White Butterfly Pieris Brassicae
Authors: Nicolson Susan W. 
Published: April 2021

ABSTRACT
The diuresis which follows the pupal-adult ecdysis of Pieris brassicae is hormonally controlled. Use of the isolated Malpighian tubules as a bioassay shows the presence of substantial diuretic activity in homogenates of the brain and corpus cardiacum-corpus allatum complex. The hormone is probably produced in the brain and released from a storage site in the corpora cardiaca. The tubules of the butterfly are maximally responsive to the diuretic hormone at the time of eclosion.
Primitive Nervous Systems: Electrophysiology of the Pharynx of the Polyclad Flatworm, Enchiridium Punctatum
Authors: Stone George , Koopowitz Harold 
Published: April 2021

ABSTRACT
Electrical activity accompanying motor activity can be recorded from the excised pharynx of Enchiridium punctatum. Multiple stimuli elicit behaviour which consists of an initial aperture closure followed by extension and then peristalsis. If the stimulus parameters are increased the preparation bends from side to side instead of proceeding through the behavioural sequence. Bending appears to inhibit other movements differentially. The conduction involved with peristalsis is polarized and proceeds in a proximal direction. With stimulus intensities greater than those needed to produce the behavioural response an initial muscle potential (IMP) is evoked. The IMP is frequency sensitive. Maximum facilitation occurs within 100 ms and drops to 50 % of maximum within 250 ms. Conduction velocities of the IMP range from 0·05 m s−1 to 1·9 m s−1. Conduction velocities appear to increase with facilitation.
Evidence for Calcium Inactivation During Hormone Release in the Rat Neurohypophysis
Authors: Nordmann J. J. 
Published: April 2021

ABSTRACT
A study has been made of the relationship between 45Ca uptake into and hormone release from isolated rat neurohypophyses incubated in vitro. Hormone secretion is triggered by high-K (56 mm) but long exposure to the stimulus does not generate a maintained release of hormone. When hormone release began to wane, addition of Ba or La increased hormone output which suggests that the decline in output did not result from depletion of the neurosecretory granules at the nerve terminals. 45Ca uptake is enhanced in the presence of high-K concentration, but the initial high rate declines during long exposure to the potassium stimulus with a time constant similar to that of the decline in hormone release. After a period of incubation in a K-rich, calcium-free medium, addition of calcium to the medium induced hormone release. The magnitude of this release was dependent on the time of exposure to excess potassium. After inactivation of secretion, mobilization of internal calcium by means of a calcium ionophore increased hormone release.
Heart Action of the Freshwater Bivalve Anodonta Anatina During Activity
Authors: Brand A. R. 
Published: April 2021

ABSTRACT
Heart action of Anodonta anatina (L.) was investigated by recording the electrocardiogram (ECG), heart impedance, and ventricular and pericardial cavity pressure during different aspects of the normal behaviour. The contribution of mechanical and nervous mechanisms in controlling changes in heart action is discussed. Pressure recordings were generally more reliable than the other methods and it is suggested that pericardial pressure pulses indicate the stroke volume output of the ventricle. During spontaneous periods of prolonged shell closure there was an initial small increase in heart activity followed by a large reduction in both heart rate and systolic pressure, indicating that total heart output was considerably reduced. When the shell reopened, heart rate increased very rapidly with an initial overshoot of the normal level; systolic pressure increased more slowly with no overshoot. These major changes in heart activity appear to be associated with respiratory changes and are controlled largely by the nervous regulatory system, but some minor rhythmic variations in the amplitude of heart beat are probably caused by mechanical factors. Characteristic patterns of change in heart action were recorded during burrowing. These appear to result from haemodynamic changes associated with the muscular movements of the digging cycle. Control of the heart by the nervous regulatory system is apparently of much greater importance in relation to respiratory control than in relation to the haemodynamic functioning of the fluid-muscle system in locomotion.
Modulation of Hydra Attenuata Rhythmic Activity: Phase Response Curve
Authors: Taddei-Ferretti Cloe , Cordella Luigi 
Published: April 2021

ABSTRACT
We investigated the effect of photic stimulation on the frequency of Hydra attenuata column contractions. We used positive or negative abrupt light transitions, single or repetitive light or darkness pulses, and alternation of light and darkness periods.
The main results are: (a) The frequency of the contraction pulse trains (CPTs) varies transiently in response to an abrupt variation of the light intensity. (b) CPTs in progress can be inhibited by different types of photic stimuli, (c) The response time to a single photic stimulus varies during the inter-CPT interval and depends also on the polarity of the stimulus, (d) The CPTs are entrainable with repetitive light stimulation of various frequencies, (e) Long-lasting variations of the frequency of CPTs occur after the end of a repetitive light stimulation.
We suggest that the mechanism responsible for the rhythm of column contractions is quite similar to that on which other biological rhythmic phenomena are based.
Quantitative studies of the reactions to horizontal angular accelerations in axolotls
Authors: Brändle Kurt 
Published: April 2021

ABSTRACT
Artificially metamorphosed axolotls were exposed to both brief (impulse) and long-lasting horizontal angular accelerations on a turn-table. The animals responded with a head-turning reaction. The general course of the reaction to impulse acceleration was independent of stimulus intensity. The velocity of the head movement first increased to a maximum exponentially and then decreased in a negative exponential manner. Stimulus intensity had a linear relationship to the mean maximum velocity and mean total angle covered by head-turning. The average velocity-time curves at various stimulus intensities differed only by a velocity factor. During long-lasting constant accelerations the velocity of the head-turning increased to a maximum velocity in a sigmoid time-course and then decreased, first to a constant velocity, and then further. Mean values of the maximum velocity were correlated linearly with the stimulus intensity. It was concluded that the head-turning reflexes in axolotls do not agree with the accepted movements of the vertebrate cupula and therefore are not a simple ‘copy’ of the afferent input. It is also suggested that the reaction threshold differs from that for the labyrinthine input.
Quantitative studies of the reactions to horizontal angular accelerations in axolotls : II. head-turning reflexes in animals with a supernumerary pair of labyrinths
Authors: Brändle Kurt 
Published: April 2021

ABSTRACT
In axolotls (Ambystoma mexicanum) the labyrinths and the associated parts of the medulla were doubled artificially. In these so-called tandem-heads the vestibular afferent fibres from both labyrinths on one side united within the medulla to form common bundles.
The head-turning reflexes following impulse acceleration and during long-lasting acceleration were measured quantitatively and compared with those for normal animals. The form and the time-course of the reactions were almost identical in both groups. Tandem-heads showed a linear relationship between stimulus intensity and reaction strength, parallel to that in normal animals but with a greater reaction for a given stimulus. Consequent to this shift in the relationship, there was a significant decrease in the reaction threshold. The removal of one horizontal semicircular canal in tandem-heads proved that both pairs of labyrinths were functionally connected with the brain. It was suggested that during ontogenesis there exists a kind of specificity in the connexion of vestibular fibres. From the parallel shift of the intensity functions it was concluded that the input from both pairs of labyrinths in tandem-heads is not simply accumulated but compared with a reference parameter, which is also double in tandem-heads.
The locust jump. II. Neural circuits of the motor programme
Authors: Heitler W. J. , Burrows M. 
Published: April 2021

ABSTRACT
Neural circuits which co-ordinate the motorneurones of the metathoracic tibiae of the locust in jumping and kicking have been investigated. The fast extensor motorneurone is reflexly excited by the subgenual organ, by a network of cuticle strain receptors, and by Brunner’s organ. The subgenual organ and the cuticle strain receptors are excited by tension in the extensor muscle and mediate a positive feedback which could help to produce the burst of fast extensor spikes which precedes a jump or kick. Brunner’s organ is stimulated by pressure from the flexed tibia, and will be excited by the initial flexion and throughout the co-contraction phase of a kick. A central excitatory, connexion from the fast extensor to the slow extensor ensures that extensor muscle tension is as great as possible early in the co-contraction phase of a kick. A central excitatory connexion from the fast extensor to flexor motorneurones is confirmed. This ensures that flexor muscle tension is great enough to keep the tibia flexed when the extensor muscle tension starts to develop before a jump or kick. Reflex excitation of flexor motorneurones occurs in response to an extensor muscle twitch when the tibia is flexed. This helps to maintain the frequency of flexor spikes after habituation of the central fast extensor to flexor connexion. A receptor, the ‘lump receptor’, which is stimulated by flexor muscle tension only when the tibia is flexed, can inhibit the flexor motorneurones and may activate the trigger system which allows the extension of the tibia in a jump or kick. Receptors in the suspensory ligaments of the joint inhibit the fast extensor when the tibia extends.
Prothoracicotropic hormone in Manduca sexta: localization by a larval assay
Authors: Gibbs Daniel , Riddiford Lynn M. 
Published: April 2021

ABSTRACT
A new method for the assay of insect prothoracicotropic hormone (PTTH) is described, using fourth instar larvae of Manduca sexta. Larvae neck-ligated at a critical time to prevent release of PTTH from the head fail to undergo the next larval moult. Such ligated larvae moult to fifth instar larvae or larval-pupal intermediates after injection of brain homogenates from Manduca larvae, pupae or pharate adults. The degree of response is proportional to the concentration of brain homogenate injected. The source of PTTH in the pupal brain is the dorsal region of the protocerebrum containing the lateral neurosecretory cells. Microhomogen-nates of single pieces of brain showed activity with this method. PTTH activity in partially purified extracts is water soluble, stable to boiling for 10 min, and is destroyed by Pronase or trypsin.
The effect of the spacing of background elements upon optomotor memory responses in the crab: the influence of adding or deleting features during darkness
Authors: Hirsh Richard , Wiersma C. A. G. 
Published: April 2021

ABSTRACT
Study was made of the effect of separation between stripes in the visual field upon responses which indicate memory of those stripes. The amount of separation between white stripes had very little effect, whereas response strength and the amount of separation between black stripes were directly proportional. The presence of extra, non-displaced black stripes prior to or following displacement reduced the size of the memory responses. The effects of the amount of separation in the two cases were comparable. In both situations the separation affected only the responses to displacement of the stripe borders nearest to the extra stripe. The effect of extra stripes present prior to displacement was in turn affected by the duration of the dark period, whilst the effect of those present during the post-displacement period was not. This accounts for the larger effect of extra stripes present during the post-displacement period. By expanding stripe width during darkness it was possible to distinguish between the effects of distance between stripes and the amount of white space separating them. Reducing white space while distance remains constant causes reductions in response strength, whereas reducing the distance between a memory zone and the white space between it and the neighbouring stripe increased the size of the memory response.
The Effect of Salinity on Cadmium Uptake by the Tissues of the Shore Crab Carcinus Maenas
Authors: Wright D. A. 
Published: April 2021

ABSTRACT
Cadmium accumulation by the haemolymph, gills and carapace of the shore crab Carcinus maenas (L.) was significantly higher in dilute sea water. This was reflected in the whole-body cadmium concentrations. There was no salinity effect with the hepatopancreas or muscle cadmium concentration.
Over a 68-day period, cadmium was steadily accumulated by the carapace, with the salinity effect becoming increasingly apparent. In 50 % sea water the gill cadmium concentration apparently reached a maximum level after about 2 weeks of uptake. This was eventually overtaken by the tissue cadmium concentration in the gills of 100 % s.w. animals. After about 48 days the salinity effect had disappeared and the gill cadmium concentration of both 50% and 100% s.w. animals (in 20 μ-mol Cd l− 1 = 2· 3 mg I− 1) remained at approximately 0·3 μ-mol Cd g− 1 ( = 33·7 mg kg− 1) wet weight of tissue. The hepatopancreas cadmium also levelled off at about this concentration although no salinity effect was apparent.
When animals loaded with cadmium for a 37-day period were returned to clean sea water, their whole body cadmium concentration fell by about 50 % after 11 days. Losses from carapace and gills were important components of this reduction in cadmium concentration.
Asymmetrical Permeability of the Integument of Tree Frogs (Hylidae)
Authors: Yorio T. , Bentley P. J. 
Published: April 2021

ABSTRACT
The skin from four species of North American tree frogs (Hylidae) was found in vitro, to be remarkably permeable to water in the presence or absence of the neurohypophysial hormone vasotocin. This property was, however, only seen in preparations from the ventral integument; osmotic water movement across the dorsal skin was negligible. The ionic permeability, reflected by the electrical resistance, was also much greater in the ventral skin. Unidirectional fluxes of 22Na, 36C1, 14C-urea and tritiated water were measured in vitro in a single species, Agalychnis dacnicolor Cope. The ventral skin was 10−20 times more permeable to these molecules than the dorsal skin. The short-circuit current (usually reflecting active transmural Na transport) across the ventral skin was increased by aldosterone and vasotocin but these responses were absent on the dorsal side. The lipid content of the dorsal skin was four times greater than that on the ventral surface.
Ionic Basis of Axonal Excitability in An Extreme Euryhaline Osmoconformer, The Serpulid Worm Mercierella Enigmatica (Fauvel)
Authors: Carlson A. D. , Treherne J. E. 
Published: April 2021

ABSTRACT
Despite the extreme fluctuations in blood concentration experienced by this marine osmoconformer, essentially ‘conventional’ ionic mechanisms are involved in conduction by the giant axons in isosmotic conditions. The resting axonal membrane approximates to an ideal potassium electrode, with a 58·8 mV slope for decade change in [K+]0 above 10 mm. The action potential overshoot shows a 55·8 mV decline with decade reduction in [Na+]0 and the action potentials are blocked by tetrodotoxin at around 10−7 M.
The rising phase and overshoot of the action potential remain constant at potassium concentrations up to the relatively high level of 30 mm found in the blood, indicating an unusual absence of sodium inactivation over a wide range of resting potentials. Relatively rapid, symmetrical movement of potassium ions between the bathing medium and the axon surface is deduced from the potential changes induced by alterations in [K+]0. Outward movement of sodium ions (t0·5 = 33·5s) occurs at a similar rate to that of potassium, but inward movement of Na+ is relatively slow and complex. It is concluded that the ability of axons to function in dilute media must involve specific adaptations to osmotic and ionic stress.