bluuebunny/crossref_metadata_2025_split huggingface dataset:
Physiology of Insect Ecdysis
Authors: Truman James W. 
Published: April 2021

ABSTRACT
At the end of the last larval instar the mature silkworm larva stops feeding and spins a silken cocoon. In this chamber the animal subsequently pupates and in some cases overwinters in a dormant condition-termed diapause. Under the influence of the warmth and lengthening days of spring, the pupa terminates diapause and initiates adult development. Weeks later the mature moth sheds the pupal exuviae and escapes from the cocoon. In Cecropia (Hyalophora cecropia) and many other saturniids the larva has prepared for this eventuality by spinning into the cocoon an ‘escape-hatch’ or valve through which the moth emerges (Van der Kloot & Williams, 1953). Among the silkworms of the genus Antheraea the moth resorts to chemistry to escape from its stout-walled and valveless cocoon (Kafatos & Williams, 1964). A few days prior to emergence the moth secretes a crystalline enzyme, cocoonase, on to the surface of its maxillary galeae. Then, during the process of eclosion, buffer produced in the labial glands is also secreted on to the galeal surface. The resulting protease solution then digests the sericin ‘glue’ from around the silk fibres and thus provides an opening for the moth. After struggling free, the moth clings to the outside of the cocoon and spreads its wings.
Intracellular Studies On Pacemaker and Follower Neurones in the Cardiac Ganglion of Limulus
Authors: Lang Fred 
Published: April 2021

ABSTRACT
Intracellular studies on the cardiac ganglion cells of invertebrates have been confined mainly to the hearts of decapod and stomatopod crustaceans. The cardiac ganglia of these animals contain relatively few neurones, thought to be divisible into large follower cells and small pacemaker cells (for reviews see Hagiwara, 1961 ; Bullock & Horridge, 1965).
Studies on follower cells of crustacean cardiac ganglia are numerous but intracellular studies on pacemaker cells, with one exception (Bullock & Terzuolo, 1957) seem to be limited to the cardiac ganglion of the stomatopod, Squilla (Watanabe et al. 1967a; Watanabe, Obara & Akiyama, 1967b, 1968, 1969). In Squilla the most anterior-cells exhibit pacemaker potentials and fire in bursts with each heart beat. However, all neurones in the ganglion are electrically coupled (Irisawa & Hama, 1965; Watanabe et al. 1967a), and pacemaker activity may also be initiated in the posterior part of the ganglion (Irisawa & Irisawa, 1957; Shibuya, 1961; Brown, 1964). The one study on. pacemaker activity in a decapod heart was made on the two largest of the posterior cells of a crab heart (Bullock & Terzuolo, 1957). These workers found that the neurones fired a burst of overshooting spikes during each heart beat. No pacemaker potentials were present but Bullock & Terzuolo (1957) concluded that these two large cells were spontaneously active since there were no excitatory postsynaptic potentials (EPSP).
The Limulus cardiac ganglion is known to be composed of many hundreds of cells (Patten & Redenbaugh, 1899; Bursey & Pax, 1970). Electrical activity of ganglion cells was studied by Heinbecker (1933, 1936) and Prosser (1943). These workers recorded extracellularly from small pieces of the ganglion in an attempt to isolate single units. Prosser (1943) successfully recorded units firing once per burst and other units firing a train of spikes superimposed on a slow wave during each burst. Intracellular studies have been limited to one investigation of the activity of the largest cells in the ganglion, the large pigmented unipolars. These cells fire a train of attenuated spike potentials’)* superimposed on a slow depolarization, similar to that found in follower cells of crustacean cardiac ganglia (Palese, Becker & Pax, 1970).
In their exhaustive morphological study of the ganglion Bursey & Pax (1970) reported that there were five types of neurones present: large unipolars, bipolars and multipolars and small bipolars and multipolars. Only the large unipolars have been studied electrophysiologically and these have been shown to be follower cells (Palese et al. 1970). A study of the remaining morphological types of neurones has therefore been undertaken in an attempt to assess their role in ganglionic activity.
Bend Propagation by A Sliding Filament Model for Flagella
Authors: Brokaw C. J. 
Published: April 2021

ABSTRACT
If active sliding occurs between flagellar filaments, as suggested for the sliding filament mechanism for muscular contraction, it will generate positive bending in one direction along the flagellum and negative bending in the opposite direction. Bends will therefore be propagated automatically if the sliding process is activated by bending. The active bending moment required to match the viscous bending moments resulting from the uniform propagation of bending waves can be generated by a simple relationship between the curvature of the flagellum at any point and the magnitude of the moment per unit length generated by the active sliding process at that point. This propagation mechanism incorporates features of the two mechanisms proposed previously for flagellar-bend propagation. The major difficulties which arise when these propagation mechanisms are developed in terms of a ‘local-bending’ model for flagellar bending are avoided when a ‘sliding filament’ model is used. The elastic constants of the flagellum have a minor role in bend propagation, and without additional assumptions their magnitudes cannot be obtained from measurements of the parameters of flagellar bending-wave propagation.
Regulation of Water and Some Ions in Gammarids (Amphipoda)
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
Previous work on Gammarus duebeni from brackish and fresh waters established that a correlation exists between certain features of sodium regulation and the sodium concentration of the particular habitat occupied by a population. In populations from fresh water sodium losses in the urine are reduced and the transporting system at the body surface has a higher affinity for sodium ions (Sutcliffe, 1971). There is also some evidence to suggest that the sodium concentration in the blood tends to fall more rapidly in animals from brackish-water populations than in animals from freshwater populations when they are exposed to media containing less than 10 mM/1 sodium (Sutcliffe, 1967; Sutcliffe & Shaw, 1968). This investigation provides some further information on the regulation of sodium, chloride and potassium in the blood of animals acclimatized to low external concentrations. Chloride regulation at salinities above 2 % sea water was studied by Beadle & Cragg (1940 a), who also found that when G. duebeni was placed in distilled water the blood chloride concentration fell to a lower level in animals from a brackish-water locality compared with animals from a freshwater locality (Beadle & Cragg, 1940b).
Regulation of Water and Some Ions in Gammarids (Amphipoda)
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
The water content, and the concentrations of sodium potassium and chloride in the blood and body water were determined in Gammaruspulex acclimatized to external salinities ranging from 0·06 mM/l NaCl up to 50 % sea water. The mean body water content remained constant at 79·0–80·3 % body wet weight. The total body sodium and chloride concentrations were lowered in 0·06 mM/l NaCl and increased markedly at salinities above 10% sea water. The normal ratio of body sodium/chloride was 1·45–1· 70, decreasing to 1·0 at 50% sea water. The total body potassium concentration remained constant at 47·5–55·2 mM/kg body H2O. The rate of potassium loss across the body surface was relatively fast. Potassium balance was maintained at an external potassium concentration of 0·010–0·015 mM/l by starved animals, and at 0*005 by fed animals. The proportion of body water in the blood space was calculated from the concentrations of potassium and chloride in the blood and in the body water. The blood space contained 38–42% body H2O in animals from fresh water. The blood space decreased to 31 % body H2O in animals from 0*06 mM/l NaCl. The sodium space was equivalent to about 70 % body H2O. The mean intracellular concentrations of sodium, potassium and chloride were estimated and the results were compared with previous analyses made on the tissues of G. pulex and other crustaceans. It was concluded that in G. pulex from fresh water the distribution of potassium and chloride ions between the extracellular blood space and the intracellular space approximately conforms to a Donnan equilibrium. 30-40% of the body sodium is apparently located in the intracellular space.
An Electrophysiological Study of Parapodial Innervation Patterns in Aplysia Fasciata
Authors: Hughes George M. 
Published: April 2021

ABSTRACT
Studies have been made of the patterns of parapodial innervation in Aplysia fasciata and A. depilans using electrophysiological methods. Sensory fibres are chiefly found in the main parapodial nerves. The areas innervated by these nerves overlap somewhat and such overlapping extends to the branches of individual parapodial nerves. Responses to mechanical stimulation of the parapodial surface gives rise to varying sizes of spike, the smaller spikes being usually more slowly adapting, the larger being highly phasic. Although the general pattern of innervation is common to all specimens there are wide variations in detail. Electrical stimulation of parapodial nerves produces mechanical contractions which are associated with responses in some of the sensory fibres. Usually the afferent units which are stimulated in this way have sensory fields within overlapping areas supplied by the two branches. Such proprioceptive feedback responses usually declined with repetition.
Neural Activation of the Heart of the Lobster Homarus Americanus
Authors: Anderson Margaret , Cooke I. M. 
Published: April 2021

ABSTRACT
Glass microelectrodes were used to record intracellular activity from the striated muscle fibres of the heart of the lobster Homarus americanus. In spontaneously beating hearts bursts of impulses are generated at regular intervals by neurones in the cardiac ganglion. These bursts produce depolarizations of the muscle fibres. Each depolarization is associated with a contraction of the heart. The depolarizations consist of many depolarizing steps; each step is related in a one- to-one manner to a nerve impulse and is believed to be an excitatory junction potential (EJP). The depolarizations (400–700 ms duration in different preparations) exhibit a fast rise to a peak (35-40 mV) followed by a plateau (20–25 mV) which decays to the resting level (51·5 ± 3·2 mV, n = 148). Current-voltage curves indicate that the EJPs do not give rise to regenerative membrane responses. Small, spontaneously produced potentials were recorded in the presence of TTX. Autocovariance tests show that the potentials occur independently and are likely to be miniature junction potentials. Polyneuronal innervation of the muscle fibres was demonstrated by applying stimuli of gradually increasing intensity to the distal ends of cut nerves while recording the responses of a muscle fibre. When a train of stimuli is applied at an intensity to evoke activity from a single axon, the first response of a muscle fibre is usually greater than the second; facilitation of the second and subsequent responses takes place. The degree of facilitation developed depends on the frequency of stimulation. Facilitation decays exponentially with a time constant of a few seconds. In two-pulse experiments the second response was depressed when the interpulse intervals were ⩽ 0·5s. Examples of combined facilitation and depression are presented.
The Effect of Hypoxia and Anaemia on the Swimming Performance of Rainbow Trout (Salmo Gairdneri)
Authors: Jones David R. 
Published: April 2021

ABSTRACT
A series of increasing water-velocity tests in a water tunnel has been used to investigate the maximum swimming performance of two groups of rainbow trout, one acclimated to high temperature (21–23 °C) and the other to low temperature (8–10 °C). At temperatures close to their acclimation temperatures there was no significant difference between the maximum swimming speeds of the two groups of trout. .Exposure to an environmental oxygen tension of half the air-saturation value resulted in a 43 % reduction in maximum swimming performance at low temperature and a 30% reduction at high temperature compared with normal animals. Reduction in haematocrit to one-half or one-third normal resulted in a 34% reduction in maximum swimming speed at low temperature and a 40% reduction at high temperature compared with control animals (blank injected). The results are discussed in terms of whether fish can be assumed to be in a steady state at all velocities below the critical velocity and whether it is possible to attribute the differences in performance, during anaemia and hypoxia, to increased metabolic cost of the cardiac and branchial pumps.
Central Control of Auditory Input in the Goldfish: I. Effect of Shocks to the Midbrain
Authors: Piddington R. W. 
Published: April 2021

ABSTRACTShocks applied to three midbrain regions reversibly suppressed the click-evoked action potential at the medulla. Clicks in air did not activate lateral-line fibres. Only one midbrain region, the torus semicircularis, showed a distinct afferent auditory response; the other two regions (anterior optic tectum and midbrain below) were used to avoid unwanted antidromic activation of medullary afferents by shocks to the torus. Muscular action on the mechanical auditory pathway was excluded by showing that shocks had no effect on the saccular microphonie or receptor potential. The results are consistent with the action of a descending inhibitory pathway that suppresses auditory input either at the medulla or at the sacculus. One brief shock is effective, but the system is mainly dependent on temporal and spatial summation. The dependency on click intensity may be complex, both high-threshold and low-threshold fibres can be inhibited and occasionally a component of the compound spike shows facilitation instead. Shocks affect the two-click recovery cycle in a complex maimer. Recovery is enhanced if the clicks are presented less than 40 msec after the shocks but depressed at longer intervals, even beyond 500 msec.
Central Control of Auditory Input in the Goldfish: II. Evidence of Action in the Free-Swimming Animal
Authors: Piddington R. W. 
Published: April 2021

ABSTRACTIn the free-swimming electrode-implanted goldfish, the neural response in the medulla to a constant auditory stimulus may exhibit reversible fluctuations in amplitude which are abolished by anaesthesia. The results are consistent with the action of an auditory control system which can reduce or enhance the input following a click. Noise-masking effects and reflex muscular control were excluded by demonstrating the relative constancy of the rectified microphonic during simultaneous changes in the click-evoked action potential at the medulla. There are three kinds of response modification: habituation, rapid inhibitory feedback, and facilitation. Both feedback and habituation act predominantly on high-threshold auditory fibres. Low-threshold fibres do not become habituated, and dishabituation does not occur. As in the mammal, anaesthetic reduces the tendency of the system to become habituated by an amount which depends on the dosage. Auditory fibres with highest threshold have the greatest tendency to become habituated and are the least affected in this respect by anaesthetic. Simple conditioning experiments indicate that control influences exerted over the input can be biased by positive or negative reinforcement which follows the auditory stimulus. The control system may work in attention, in frequency analysis, or in suppressing input to self-made sounds. A new hypothesis is made on the biological significance of hearing in fish. A fish may be able to tell if other swimming fish are approaching, receding, or moving tangentially by analysing the proportions in time of the compressions and rarefactions present in the swimming sounds, which are proposed to be asymmetrical.
Studies on the Adaptation of the Toad Bufo Viridis to High Salinities: Oxygen Consumption, Plasma Concentration and Water Content of the Tissues*
Authors: Katz Uri 
Published: April 2021

ABSTRACT
The toad Bufo viridis was adapted to various salinities up to 800 mOsm NaCl solutions. The blood was always hypertonic to the external solutions and had a high urea concentration. Urea concentration in the plasma was higher in summer than in winter. Urine was hypotonic to the plasma in low salinities and became isotonic with the plasma at 400 mOsm and higher salinities. Water content of the whole body and the skeletal muscles decreased somewhat with salinity. Oxygen consumption was unaffected by salinity when animals were gradually adapted to high salinities. It increased, however, upon acute dehydration whether this was caused by immediate transfer to high salinity or by rapid evaporative dehydration in air.
Neurohormonal alteration of integrative properties of the cardiac ganglion of the lobster Homarus americanus
Authors: Cooke I. M. , Hartline D. K. 
Published: April 2021

ABSTRACT
The spontaneous burst discharges of isolated lobster (Homarus americanus) cardiac ganglia were recorded with a spaced array of electrodes. Small regions (&lt; 1 mm) of the ganglion were exposed to the cardioexcitor neurohormone in extracts of pericardial organs (XPO) or to 10−5M 5-hydroxytryptamine (5HT). All axons were excited (increased mean firing frequency,) by both substances, but only by applications in the region between the soma (but excluding it) and proximal site of impulse initiation. Units not so exposed changed their relatively little despite increases of as much as threefold in exposed units and changes in burst rate and overall length. Regularity and grouping of all impulse activity into bursts was never disturbed. 5HT increases burst rate at any point of application. The increases are larger if small cells are affected than if only large cells are exposed. Burst length decreases except when the pacemaker is affected. In contrast, XPO affects neither burst rate or length unless small cells are affected. Length is increased if nonpacemaker small cells are affected; both rate and length increase if the pacemaker is affected. The pacemaker usually exhibits an of intermediate value. Rate changes are not simply related to its . A small cell can ‘burst’ in the absence of impulses from any other cells. XPO may enhance endogenous ‘driver potentials,’ while 5HT may excite by depolarizing at limited sites.
Properties of A Symmetric Pair of Serotonin-Containing Neurones in the Cerebral Ganglia of Planorbis
Authors: Berry M. S. , Pentreath V. W. 
Published: April 2021

ABSTRACT
There is a bilaterally symmetric pair of large serotonin-containing neurones in the cerebral ganglia of Planorbis corneus. In some animals these neurones are connected by a non-rectifying electrotonic synapse, and fire in synchrony even at prolonged high frequency. In other animals the neurones are not coupled, and fire independently except when driven by common input. Occasionally the coupling is weak. Both coupled and non-coupled serotonin neurones have processes in the major nerve trunks of both buccal ganglia. Synapses are made with many neurones in the buccal ganglia. The serotonin neurones can initiate firing in several motoneurones and thus produce movements of the buccal mass. During spontaneous feeding cycles the input and firing pattern of the serotonin neurones do not bear any obvious relation to the movements of the buccal mass. The data suggest that the serotonin neurones are modulatory cells, altering the level of excitability of buccal ganglion neurones.
An Electrophysiological Study of Mechanisms Controlling Polyp Retraction in Colonies of the Scleractinian Coral Goniopora Lobata
Authors: Anderson Peter A. V. 
Published: April 2021

ABSTRACT
Electrical or mechanical stimulation of Goniopora lobata produces coordinated retraction of polyps in the colony. With repetitive stimulation, the response spreads in linear, radial increments which become successively smaller with each stimulus. Electrical activity recorded from these colonies is interpreted as originating in a conduction system responsible for effecting the colonial retraction response. The electrical activity spreads incrementally through the colony in a similar manner to the behavioural response. Various hypotheses have been proposed to account for such a spread of electrical activity. Of these, only interneural facilitation is of appreciable importance to Goniopora. Temporary termination of a pathway, by the passage of an impulse through it, was found and interpreted as being an additional and important property of the colonial conduction system.
Mechanical Stimulation of Starfish Sperm Flagella
Authors: Okuno Makoto , Hiramoto Yukio 
Published: April 2021

ABSTRACT
The responses of starfish sperm flagella to mechanical stimulation with a microneedle were analysed. Flagellar movement was recorded by high-speed microcinematography and by stroboscopic observation. The amplitude of the bending wave of a flagellum was restricted over its entire length when the microneedle was brought near to the flagellum at its proximal region. Beyond the restricted part, the amplitude of the wave, and the bend angle, became smaller than those of a normally beating flagellum, while the curvature was practically unchanged. When the tip of the microneedle was in contact with the flagellum, propagation of the bending wave beyond the microneedle was inhibited. The part of the flagellum between the base and the microneedle continued beating in some cases and stopped beating in other cases. The flagellum beyond the arrested part stopped beating and remained straight. When the microneedle was removed, the bending wave which existed in the part of the flagellum proximal to the microneedle, or the wave which was passively formed de novo at the time of the removal of the microneedle, propagated over the arrested part towards the tip. A flagellum amputated by a microneedle in a medium containing ATP continued beating with a small amplitude, small curvature, small bend angle and low frequency. When the amputated flagellum was passively bent by a microneedle at the region near the point of amputation, this bend propagated towards the tip with a constant bend angle. The beating frequency of the flagellum could be modulated by the application of a rhythmic external force generated by vibrating a microneedle near the flagellum. The beating was completely synchronized with vibration of the microneedle in the frequency range from 23 Hz to 43 Hz.
Temperature Regulation and Heat Dissipation During Flight in Birds
Authors: Torre-Bueno Jose R. 
Published: April 2021

ABSTRACT
Core and skin temperature were measured by radiotelemetry in starlings (Sturnus vulgaris) during 30 min flights in a wind tunnel. Core temperature was independent of ambient temperature from o to 28 °C. The temporal mean of the monitored core temperature during flight was 42·7 °C in one bird and 44·0 °C in another. These temperatures are 2–4 °C higher than the resting temperature in starlings, and are among the highest steady-state temperatures observed in any animal. Skin temperature on the breast was within a few degrees of core temperature. In some locations skin temperature was higher at low ambient temperatures than at intermediate ambient temperatures. An analysis of the data shows that a high core temperature does not function as an aid to heat dissipation. On the contrary, insulation is adjusted to maintain a high temperature, presumably because it is necessary for flight. The increase in skin temperature at low ambient temperatures is believed to be a result of a decrease in heat flow through the breast feathers brought about by feather adjustments, to compensate for an unavoidable increase in heat flow in unfeathered or poorly feathered parts of the body.