bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electrophysiological and Endocrinological Correlates During the Metamorphic Degeneration of A Muscle Fibre in Galleria Mellonella (L.) (Lepidoptera)
Authors: Runion H. I. , Pipa R. L. 
Published: April 2021

ABSTRACT
Excitatory postsynaptic potentials (e.p.s.p.s), membrane resting potentials, and intensity of birefringence were measured from the two principal planta retractor muscles (PPRMs) of the first pair of prolegs during metamorphosis of Galleria mellonella. This was done to determine whether cessation of efferent nerve impulses to these single fibres signals their degeneration. E.p.s.p.s were elicited reflexively by brushing the insect’s last abdominal segment. Though they become attenuated, e.p.s.p.s can be recorded until 11-12 hr. after pupal ecdysis. By this time the membrane resting potential has dropped from c. 55 mV. to less than 18 mV., and the intensity of birefringence has become minimal. Continuous electromyographic records taken during the initial 18 hr. after pupal ecdysis suggest that the PPRMs are being excited regularly as they degenerate. No ‘sparing effect’ on the degeneration of the PPRMs could be detected when programmed, current-limited stimuli were administered to pupae via chronically implanted electrodes. Removing all acknowledged endocrines by transecting newly emerged pupae has negligible effect on the decrease of the PPRM birefringence, but greatly retards the degradation of the membrane resting potential and e.p.s.p.s. This retardation can be alleviated by injecting the steriod hormone 20-hydroxyecdysone.
Chloride Regulation at Low Salinities by Nereis Diversicolor (Annelida, Polychaeta)
Authors: Smith Ralph I. 
Published: April 2021

ABSTRACT
Evaluation of the chloride exchanges of Nereis diversicolor in the steady state has shown that this worm ‘cuts its losses’, i.e. reduces the fluxes, of chloride at very low salinities (Smith, 1970a), and that this reduction of chloride loss takes place mainly in the urinary component of the efflux, as has also been suggested by previous authors. Jorgensen & Dales (1957) measured the rates of osmotic gain or loss of water, and concluded that at low salinities N. diversicolor could reduce its permeability to water by over 60%. Assuming a comparable reduction in permeability to chloride, they calculated that the observed reduction of chloride efflux could be accounted for by reduction of urine volume, without the necessity of postulating the production of a urine rendered hypotonic to the body fluids by recovery of solutes by the nephridia. Potts & Parry (1964), on the other hand, in their review of the previous authors’ work, felt unable to accept the evidence for a reduction of permeability to water and, on the assumption of no permeability changes, drew up a balance sheet in support of the hypothesis that reduction of chloride loss was achieved in N. diversicolor by recovery of ions from a consequently hypotonic urine. These views are not mutually exclusive, and the problem is not to choose between them but to obtain evidence to indicate the extent to which each postulated mechanism may be operative. In the previous paper (Smith, 1970a), evidence was presented compatible with the concept that the urine of N. diversicolor may be hypotonic in chloride to the coelomic fluid at low salinities, although this evidence was indirect and not conclusive. In a subsequent paper (Smith, 1970b) direct evidence will be presented that the urine of N. diversicolor is hypo-osmotic. In order fully to evaluate the hypothesis of Jorgensen & Dales it would be necessary to measure both permeability to water and urine volume. So far, it has not been possible to measure urine volume, but data on permeability to water have been obtained, and an estimate of water fluxes attempted.
The Effects of Prolactin and Divalent Ions On the Permeability to Water of Fundulus Kansae
Authors: Potts W. T. W. , Fleming W. R. 
Published: April 2021

ABSTRACT
Measurements have been made of the rate of exchange of tritiated water in both intact and hypophysectomized Fundulus kansae in a variety of media. Hypophysectomy reduces the rate of exchange in fresh water. Low doses (30 mu) of ovine prolactin stimulate water turnover in hypophysectomized fish in fresh water. The rate of exchange declines in both intact and hypophysectomized animals with increasing salinity. Experiments with synthetic solutions show that the decline in the rate of exchange in sea water and in higher salinities is due mainly to the effects of calcium ions. Fishes maintained in synthetic sea water containing a low concentration of calcium have both a higher rate of exchange of tritiated water and a higher drinking rate than fish in normal sea water. Supported in part by National Science Foundation Grant GB 7200, and by Biomedical Support Grant Fr-07053 from the General Research Support Branch, Division of Research Resources, Bureau of Health Professional Education and Manpower Training, National Institutes of Health. Visiting Professor, Zoology Department, University of Missouri, Columbia. Professor Potts’s travel and research was supported by the Faculty Improvement Programme. Prolactin (NIH-P-S9) was generously supplied by the National Institute of Arthritis and Metabolic Diseases.
Responses of the Respiratory Pumps to Hypoxia in the Rainbow Trout (Salmo Gairdnert)
Authors: Hughes G. M. , Saunders R. L. 
Published: April 2021

ABSTRACT
Unanaesthetized rainbow trout, when subjected to a lowered Po2 of the inspired water, show an increase in amplitude of pressures recorded from the buccal and opercular cavities. Pressure amplitudes were commonly found to be 0·5 cm of water in resting trout and increased 4-or 5-fold as inspired Po2 was reduced. Differential pressures across the gills also increased with hypoxia. Typically the minute volume in a 400–600 g trout increased from about 0·2 to 0·6 1/kg/min when the inspired was lowered from 150 to 80 mm Hg, but rose to 1–5 1/kg/min at lower Po2. Increased minute volumes are mainly due to increases in stroke volume; respiratory frequency remains fairly constant at Po2’ s above about 80 mm Hg. The relation between differential pressure and minute volume is fairly linear over much of the range, but minute volume increases more rapidly than differentia] pressure. Oxygen consumption of the non-swimming fish increases during hypoxia and is related to the increased ventilation and differential pressure across the gills. Estimates of the oxygen cost of breathing were made from the increased oxygen consumption during hyperventilation. Comparison of these estimates with estimates of the work done, using the pressure and volume measurements, gave figures for the overall efficiency of the pumping mechanism of about 10%.
Fluorescence Localization of Monoamines in Crab Neurosecretory Structures
Authors: Cooke I. M. , Goldstone Martha W. 
Published: April 2021

ABSTRACT
The pericardial organs and anterior ramifications (both neurohaemal structures) of six species of crabs have been examined as whole mounts by the histochemical method for monoamines based on formaldehyde-induced fluorescence. A small number of specifically fluorescing axons (not more than six green and six yellow) innervate the pericardial organ; one of the green-fluorescent and one yellow-fluorescent axon branches and also innervates the anterior ramification. All of the fluorescing axons enter via segmental nerves 1, 2 and 3 from the ventral ganglion. One large, brilliant green-fluorescing axon, and the small green-fluorescing axon which branches to the AR, have been traced in Carcinus to cell bodies in the circumoesophageal connective ganglion. These cells may give rise to the entire population of green-fluorescing axons and terminals in the neurohaemal organs. Each axon, throughout its course in the pericardial organ, supplies a dense array of varicosities (blebs) at surfaces which are directly exposed to the haemolymph. The anterior ramifications are also supplied with blebs. Lack of fluorescence in controls not exposed to paraformaldehyde, reversible quenching of fluorescence by treatment with sodium borohydride, and depletion of the fluorescence by reserpinization of the crabs, all confirm that the fluorescence is specific and represents the intracellular localization of monoamines. With the aid of data available elsewhere we conclude that there are distributed, in parallel with peptide-secreting axons and terminals in the pericardial organs and anterior ramifications, a group of dopamine-containing and a group of 5-hydroxy-tryptamine-containing axons and terminals.
Release of A Neurosecretory Hormone as Peptide by Electrical Stimulation of Crab Pericardial Organs
Authors: Berlind A. , Cooke I. M. 
Published: April 2021

ABSTRACT
Saline which had bathed an isolated crab pericardial organ was chromatographed on a column of Sephadex G-25. The fractions were divided and assayed for cardioexcitor activity and for ninhydrin colour following hydrolysis. Fluid from pericardial organs which had been stimulated electrically to give a maximum propagated compound action potential showed both cardio-excitor activity and ninhydrin colour. These were always in the same fractions, which corresponded to the volume for elution of small peptides. Fluid from unstimulated preparations gave negative assays. The cardio-excitor activity of fluid from stimulated pericardial organs and of distilled-water homogenates of pericardial organs behaved identically in Sephadex G-25 chromatography. No evidence could be obtained of the cardio-excitor peptide binding to a protein. This work provides evidence that neural stimulation of crab pericardial organs results in release to the bathing fluid of cardio-excitor hormone as free peptide.
Axonal Localization of An Excitatory Post-Synaptic Potential in A Molluscan Neurone
Authors: Gorman A. L. F. , Mirolli M. 
Published: April 2021

ABSTRACT
Stimulation of the lateral nerve gives rise to an excitatory post-synaptic potential (EPSP) in the Anisodoris G cell. The amplitude of this EPSP is either unchanged or slightly reduced by moderate hyperpolarization of the soma membrane, whereas stronger hyperpolarization produces an increase. Two factors contribute to this paradoxical behaviour. First, the conductance of the G cell membrane increases when it is hyperpolarized. Second, the apparent changes in cell conductance associated with the EPSP are small relative to the input conductance of the G cell. There are two major regions of the G cell where presumed synaptic contacts can be demonstrated anatomically. The first is on branches of the stem process of the soma in the gastro-oesophageal ganglion neuropile, and the other is on the main trunk of the axon and on axonal branches in the gastro-oesophageal nerve. Presynaptic fibres from the lateral nerve are present in the latter region. No synaptic contacts are found on the soma surface. A comparison of the effects of axonal and somatic polarization on the behaviour of the lateral nerve EPSP indicates that the EPSP occurs on the axon or on axonal branches.
Circadian Rhythm of Locomotion and Its Temperature Dependence in Blattella Germanica
Authors: Dreisig Hans , Nielsen Erik Tetens 
Published: April 2021

ABSTRACT
The activity in Blattella germanica was investigated under standard conditions. Periods of latency and increment were recognized. The free-running rhythm in continuous darkness was determined at different temperatures and showed about the same period. The free-running rhythm in confinons light could not be determined unless the light intensity was extremely low. The period of activity was not released immediately after a change from light to darkness if this was advanced in relation to the normal time. The activity was then only slightly advanced. Delay of the onset of darkness caused the activity to diminish gradually after the usual time of change from light to dark. If the temperature was lowered some time before the expected time of activity in continuous darkness the activity was advanced much more than normally. If the temperature was raised the activity was delayed. Based upon these and other studies, a theory is advanced which explains the activity rhythms in insects as being the result of the interaction between a gradually increasing, temperature-dependent sensitization and different thresholds of release determined by light and temperature. A theory is propounded concerning the temperature-independence of the free-running rhythm in continuous darkness, assuming a temperature-dependent threshold of release.
Innervation of Coxal Depressor Muscles in the Cockroach, Periplaneta Americana
Authors: Pearson K. G. , Iles J. F. 
Published: April 2021

ABSTRACT
The innervation of the mesothoracic and metathoracic coxal depressor muscles has been investigated using intracellular microelectrodes. Five motor axons have been found to innervate the coxal depressor muscles; the largest is a fast axon, the second largest a slow axon and the three smallest are all inhibitory axons. The fast axon innervates the anterior and posterior coxal depressor muscles as well as parts of the coxal branches of the main leg depressor muscle. The slow innervates all fibres in the coxal branches of the main leg depressor muscle. The three inhibitory axons innervate only those parts of the coxal branches of the main leg depressor muscle which are not innervated by the fast axon. The three inhibitory axons were found to be branches of three different common inhibitory motoneurones.
Active Transport of Sodium by the Isolated Midgut of Hyalophora Cecropia
Authors: Harvey W. R. , Zerahn K. 
Published: April 2021

ABSTRACT
Sodium and lithium are actively transported by the isolated midgut of Hyalophora cecropia. The short-circuit current in 32 mM sodium solution is about half of that in 32 mm potassium solution. The sodium flux measured with 22Na from blood-side to lumen accounts for all of the short-circuit current and is 19 times the flux from lumen to blood-side. In a solution containing 16 mm potassium and 16 mm sodium there is no transport of sodium, although a large current remains. The sodium transport mechanism is not sensitive to ouabain.
The Central Nervous Control of Colour Change in the Minnow (Phoxinus Phoxinus L.)
Authors: Gentle Michael J. 
Published: April 2021

ABSTRACT
The colour of the minnow Phoxinus phoxinus L. and its ability to undergo colour change were studied after partial and complete blinding. The blinding was accomplished either by section of the optic nerve or by tectal ablation. Following bilateral section of the optic nerve the blinded minnows darken. After the initial darkening, half of the fish pale and the other half remain dark. The colour of the fish blinded by bilateral section of the optic nerve could not be affected by external conditions. Following complete removal of the optic tectum the fish at first paled, but after 24 h they darkened to very variable tints. Unilateral section of the optic nerve coupled with unilateral tectal removal on the same or opposite side did not affect the ability of the fish to change colour. The bilateral removal of the anterior tectum from a blinded darkened fish did not affect its colour. The bilateral removal of the posterior tectum of a darkened fish caused maximal pallor.. By a series of lesions an area in the dorsal posterior part of the optic tectum was found to cause darkening in the blinded fish because following its removal the fish paled. It is suggested that the fibres from the tectum may act by exciting or inhibiting the neurones of the paling centre in the anterior medulla
Rhythmic Activity in the Insect Nervous System
Authors: Miller P. L. 
Published: April 2021

ABSTRACT
Mechanical or electrical stimulation of widely separated parts of the body or appendages of Sphodromantis lineola produces a premature expiratory stroke with coupled spiracle movements when the ongoing frequency is low. The rhythm is then normally reset. Flashes of light directed at the eyes produce the same results. The responses may become phase-locked to repeated stimuli but usually soon habituate. Similar stimulation during CO2-evoked hyperventilation produces at most tonic effects. Electrical stimulation of thoracic or abdominal connectives with single shocks at up to 3 Hz can produce non-habituating phase-locked ventilation. Such stimulation also produces miniature bursts in spiracle 1 which follow shocks on a 1:1 basis sometimes at up to 45 Hz. It is suggested that they result from the stimulation of an interneurone which co-ordinates ventilatory activity in the insect.
Calcium Regulation in the Freshwater Mollusc Limnaea Stagnalis (L.) (Gastropoda: Pulmonata)
Authors: Greenaway Peter 
Published: April 2021

ABSTRACT
Three major calcium compartments have been identified in L. stagnalis: the shell, the blood and the fresh tissues. The distribution of 45Ca, absorbed from the medium, in the tissues of L. stagnalis has been studied. Absorbed calcium appears first in the blood and then in the shell and other tissues. 30% of the total fresh tissue calcium and about 20% of mantle calcium exchanges with blood calcium. A continual exchange between shell and blood calcium occurs. During net calcium loss from L. stagnalis a net movement of calcium from shell to blood occurs at a rate similar to the rate of net loss. During net calcium uptake, the reverse movement from blood to shell at a rate similar to the rate of net uptake occurs. A simple mechanism which might account for the control of blood calcium concentration has been proposed.
The Pharmacology of Efferent Synapses in the Lateral-Line System of Xenopus Laevis
Authors: Russell I. J. 
Published: April 2021

ABSTRACT
The nature of the transmitter substance released at the lateral-line efferent synapses was investigated by histochemical techniques in Xenopus and Acerina and by pharmacological methods in Xenopus. The bases of lateral-line hair-cells and fine fibres in the lateral-line nerves reacted positively for acetylcholinesterase in Acerina and to a lesser extent in Xenopus. Acetylcholine (10−6M, and acetyl-β-methyl choline (5×10−6M), which has a muscarinic action, caused strong reversible inhibition of afferent impulses when pipetted on to the undersides of lateral-line stitches. Carbachol (5 × 10−4 to 5 × 10−6M) caused a smaller reversible inhibition of spontaneous afferent impulses, but other nicotinic substances (propionylcholine and buterylcholine) had no effect. Physostigmine (5 × 10−8M) prolonged inhibition of afferent impulses by electrical stimulation of efferent fibres, but atropine (5 × 10−6M) blocked it. Calcium and magnesium interact at the efferent synapses in a way similar to that found at the amphibian neuromuscular junction. Arguments are put forward to support the hypothesis that acetylcholine is released at lateral-line efferent synapses.
Behavioural Physiology of the Colonial Hydroid Obelia
Authors: Morin James G. , Cooke Ian M. 
Published: April 2021

ABSTRACT
The bioluminescent system of Obelia responds to stimulation by producing a burst of excitatory potentials (luminescent potentials, LPs) with each stimulus except the first. These LPs initiate flashes from the coupled luminescent effectors. There is temporal facilitation between the applied stimulus and the LP-system ; the LP-system shows adaptation to stimulation by a rise in threshold as well as fatigue. There is facilitation within the LP-system that is temporal at a given point and spatial (in the distance of spread) between two or more points. The result is a limited spread of the first potentials and decreasing numbers of potentials with increasing distance but often a through-conduction of the final potentials. The conduction velocity of the LPs is about 22 cm/s at 12 ° C; the refractory period is about 60 ms at 20 ° C and 150 ms at 12 ° C; the latency from stimulation to the first LP in a stimulus train first decreases from 130 – 600 ms to 20 – 80 ms and then increases again to 150 – 600 ms at 20 ° C. The latency between LP and the flash is about 20 + 9 ms. The intervals between LPs in bursts evoked by stimuli applied at 1/s gradually increase from about 65 ms to about 135 ms at 20 ° C. The absolute LP intervals are temperature-dependent (the relative ratios are not) but independent of the stimulus frequency. The number of LPs in a burst is frequency dependent. The facilitation curve of the LP-system-luminescent effector junctions, as determined from flash intensity, shows a rapid rise between 60 and 80 ms, a fairly rapid decay between 80 and 200 ms, and a long residual decay which lasts for several hundred milliseconds.
Pharmacology of the Malpighian Tubules of Rhodnius and Carausius: The Structure-Activity Relationship of Tryptamine Analogues and the Role of Cyclic Amp
Authors: Maddrell S. H. P. , Pilcher D. E. M. , Gardiner B. O. C. 
Published: April 2021

ABSTRACT
5-Hydroxytryptamine (5-HT) and a few of its derivatives will cause an acceleration of secretion by the isolated Malpighian tubules of Rhodnius prolixus and Carausius morosus. Substitution in the terminal amino group of 5-HT causes little loss of effect, but changes in the indole ring and the hydroxy group in general abolish activity. Most derivatives of 5-HT which do not stimulate secretion, and many other related amines, act as inhibitors of secretion in Rhodnius. This inhibition is probably of the competitive type. Substances which stimulate secretion in Rhodnius are easily washed off the Malpighian tubules, although they will stimulate secretion at very low concentrations By contrast, competitive inhibitors wash away relatively slowly and inhibit only at much higher concentrations. It is suggested therefore that stimulation involves only momentary interactions between stimulant and receptor sites, but that competitive inhibitors spend considerably longer attached to the sites. Cyclic 3 ′,5 ′ -adenosine monophosphate (cyclic AMP) will stimulate secretion by tubules of both Rhodnius and Carausius. Tubules of both species are very sensitive to cyclic AMP, measurable effects being produced at concentrations of 4×10−5 M/ l in Rhodnius and 10−4 M/ l in Carausius. Aminophylline (theophylline ethylene diamine) at a concentration of 10−4 M/ l stimulates secretion by Carausius tubules. This compound and other inhibitors of phosphodiesterase have no stimulatory action on Rhodnius tubules, but any such effect may be masked by the adverse reaction of the tubules to the high concentrations necessary. Inhibitors of 5-HT action such as tryptamine and tyramine also inhibit secretion by Rhodnius Malpighian tubules induced by cyclic AMP. This may be due to a dependence of the action of cyclic AMP on the state of the diuretic hormone receptor site. The evidence is consistent with the idea that 5-HT, other stimulant molecules related to 5-HT and the diuretic hormones interact with Malpighian tubule cells of Rhodnius and Carausius at specific sites, probably on the cell membrane facing the haemolymph. As a result of this, secretion is induced, possibly through the action of intracellular cyclic AMP produced as a response.