bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Mild Hypercapnia on the Effects of Environmental Acidification on Rainbow Trout (Salmo Gairdneri)
Authors: Neville C. M. 
Published: April 2021

ABSTRACT
The physiological consequences of lethal ambient acid levels in adult fish have been previously investigated (Lloyd & Jordan, 1964; Packer & Dunson, 1972; Lievestad & Muniz, 1976). Acidaemia associated with a loss of total carbonate and/ or electrolyte loss have been implicated as the cause of death but the sublethal physiological effects leading to one or both of these conditions have not been fully clarified. Neville (1979) has shown that the acidaemia of trout exposed to pH 4 under normocapnic conditions for 5 days is not due to build-up of lactic acid.
An Ocellar Dorsal Light Response in A Dragonfly
Authors: Stange Gert , Howard Jonathon 
Published: April 2021

ABSTRACT
One of the functional roles suggested for the insect ocelli is their involvement in flight behaviour such as the maintenance of stability by monitoring movements of the animal relative to the horizon (Hesse, 1908). In a recent study on second order ocellar neurones in locusts, Wilson (1978) concluded from physiological and anatomical considerations that this system is ideally suited ‘to detect rapid movements of the whole visual field which represent instability in flight’. In fact, indirect behavioural evidence for this concept was provided by Mittelstaedt (1950), who observed that dragonflies with occluded ocelli go through a sequence of unstable flight attitudes and stalls when released in the presence of a single light source of small angular dimensions. We report here simple experiments which give direct evidence that the ocelli do function as equilibrium organs during flight.
Circadian Rhythm from the Eye of Aplysia: Temperature Compensation of the Effects of Protein Synthesis Inhibitors
Authors: Jacklet Jon W. 
Published: April 2021

ABSTRACT
The circadian rhythm of compound action potentials (CAP) frequency recorded from the isolated eye of Aplysia in culture medium and darkness was subjected to step and pulse treatments with anisomycin, a protein synthesis inhibitor. The step application of anisomycin and its continued presence in the culture medium lengthened the period of the rhythm in a dose-dependent manner. At 10−8 M the period was increased from the normal 26·5 h to about 28 h and at io-7 M the period was lengthened to 31 h or longer. At 10−7 M the rhythm was suppressed but the CAP activity continued without the cyclic variations in CAP frequency. Six-hour pulses of anisomycin at 10−8 M caused phase-dependent phase-shifts of the rhythm. Maximum phase delays of 15 h were obtained at CT (circadian time) 2 and maximum phase advances of 4 h were obtained at CT 6. The phase response curves at 12, 15 and 17 °C were essentially identical. Anisomycin appears to act rather selectively on the circadian clock mechanism. It does not alter the CAP amplitude and duration and it does not alter the bursting pacemaker mechanism of the optic nerve CAP or central neurones. The results support the hypothesis that the synthesis of a protein or polypeptide on eucaryotic ribosomes is an essential part of the circadian clock timing mechanism. The sensitivity of the clock to anisomycin is the same at three different temperatures (12, 15 and 17 °C) within the physiological range of temperatures for Aplysia, as expected for a clock whose period length is temperature compensated (Q10 1·02) over that same range. At the critical phases of CT 1–4, anisomycin pulses often caused unusual perturbations of the rhythm. These effects are consistent with the hypothesis that the circadian rhythm is a multioscillator system.
Separable Phases of Light-Evoked Depolarizations in the Retina of Strombus
Authors: Quandt Frederick N. , Gillary Howard L. 
Published: April 2021

ABSTRACT
The waveforms of light-evoked depolarizations in Strombus retinal neurones can exhibit two sequential peaks or phases, the relative amplitudes of which vary with changes in stimulus intensity and interstimulus interval. Experiments employing either the passage of constant intracellular current or voltage clamp techniques indicate that both phases reverse polarity at intracellular potentials less negative than the resting potential. The potential at which the first phase reverses its polarity is considerably more positive than that of the second phase. The results indicate that the light-evoked depolarizations are generated by at least two different processes ; these appear to be separate conductance changes, neither of which is voltage dependent. Under certain conditions, the second phase was inhibited by high extracellular concentrations of Mg2+, indicating that it may arise as a result of chemically mediated synaptic transmission. The first phase did not show such inhibition and appears to be caused by the direct action of light on the cell.
Involvement of Cyclic Gmp in the Release of Stereotyped Behaviour Patterns in Moths by A Peptide Hormone
Authors: Truman James W. , Mumby Susanne M. , Welch Susan K. 
Published: April 2021

ABSTRACT
A peptide hormone, the eclosion hormone, triggers two behavioural patterns - the pre-eclosion and eclosion patterns - when injected into pharate silkmoths. Injection of cyclic nucleotides caused the same behavioural responses with cGMP being 10 to 100 times more potent than cAMP. Exogenous cGMP also acted directly on the isolated nervous system to evoke the characteristic motor programmes. Protection of endogenous cyclic nucleotides by pretreatment of moths with a phosphodiesterase inhibitor, theophylline, markedly enhanced the sensitivity of the moths to the hormone. Injection of partially purified hormone preparations was followed by an increase in nervous system cGMP but not cAMP. The increase preceded the behavioural response to the hormone. When various doses of hormone were tested, the behavioural effectiveness of each dose was correlated with its ability to cause a cGMP increase. It was concluded that the behavioural effects of the eclosion hormone are mediated through an increase in cGMP in the nervous system.
Neuroethological Studies of Freely Swimming Aplysia Brasiliana
Authors: Von Der Porten Kenneth , Redmann Greg , Rothman Barry , Pinsker Harold 
Published: April 2021

ABSTRACT
Recently developed neurophysiological and behavioural techniques were used to study swimming in the marine gastropod Aplysia brasiliana. Aplysia swim by bilateral parapodial flapping with an anterior to posterior metachronal wave. Parapodial oscillations are measured from video records. Population recordings from nerves innervating the parapodia during normal swimming in intact Aplysia reveal synchronous phasic activity in large efferent units associated with parapodial opening. Isolated brain studies and stimulation of central pathways in intact animals suggest a central pattern generator. We conclude that the output of the neuronal oscillator that controls parapodial flapping radiates synchronously from each pedal ganglion. The putative command to swim originates within the cerebral ganglia.
The effects of enforced activity on ventilation, circulation and blood acid-base balance in the semi-terrestrial anuran, Bufo Marinus
Authors: McDonald D. G. , Boutilier R. G. , Toews D. P. 
Published: April 2021

ABSTRACT
The ovulation hormone producing neuro-endocrine cells of Lymnaea stagnate, the caudo-dorsal cells (CDC), are comparable to the bag cells of Aplysia. Both cell types are capable of the production of a long-lasting activity (afterdischarge) during which an ovulation hormone is released. The CDC (30 cells in the left cerebral ganglion and 70 cells in the right) are usually electrically silent but an afterdischarge can be brought about in all cells of both groups by direct, repetitive electrical stimulation of single CDC. This is not possible in every preparation, indicating that the CDC can be in different states of excitability.
All cells participate in the afterdischarge and fire approximately synchronously. All CDC are electrotonically connected. Results of experiments in which neurones were injected with horseradish peroxidase suggest that the demonstrated electrotonic connexions between the two opposite groups of CDC are brought about by 10–12 special axons.
The Effects of Extracts From Neurosecretory Cells in the Anterior Vena Cava and Pharyngo-Ophthalmic Vein Upon the Hearts of Intact Free-Moving Octopuses
Authors: Wells M. J. , Mangold K. 
Published: April 2021

ABSTRACT
Recordings of pressure and frequency were made from the hearts of free-moving Octopus vulgaris. The effects of extracts from neurosecretory endings in the anterior vena cava (AVC) and the pharyngo-ophthalmic vein (POV), injected through fine cannulae into a branchial heart, efferent branchial vessel or the dorsal aorta, were studied and compared with the effects of acetylcholine, 5-hydroxytryptamine, adrenaline, histamine and tyramine. AVC and POV extracts each produce a different spectrum of effects, unlike those of any of the drugs tested. AVC extract is effective at doses of less than 2 % of the material extractable from a single vein per kg, increasing the force and amplitude of the heartbeats. With a natural release point just upstream of the branchial hearts the AVC material must be relevant to the normal performance of the hearts. POV extract is effective only at doses equivalent to several veins per kg, and is unlikely to have a role in cardiac regulation. Section of the visceral nerves did not affect the action of drugs or extracts, indicating that effects were not indirectly mediated via the CNA. Further experiments were made with hearts and the aorta in vitro with effects that did not always parallel those found in vivo. Reasons for these differences are discussed.
Functional Anatomy of Feeding in the Bluegill Sunfish, Lepomis Macrochirus: In Vivo Measurement of Bone Strain
Authors: Lauder G. V. , Lanyon L. E. 
Published: April 2021

ABSTRACT
The suction feeding mechanism of the bluegill sunfish, Lepomis macrochirus, was studied in unrestrained fishes by the simultaneous recording of cranial muscle electromyograms, opercular cavity pressures, and opercular bone strain patterns. The electromyographic profile was similar to that of other advanced teleosts and consisted of preparatory, expansive, and compressive phases. The pectoral girdle remained nearly stationary during the strike. Opercular cavity pressures showed peak negative values of 145 cm H2O followed by a positive afterpressure of up to 50 cm H2O as water flowed out of the opercular chamber. Characteristic ‘coughing’ patterns showed an initial positive phase, followed by a negative phase, and then a final positive pressure pulse. Bone strain on the operculum was measured with rosette and single element strain gauges. Peak principal compression during the strike was 1800 με and the peak strain rate was − 615 × 103με/s, more than ten times that previously recorded in vertebrate bone during normal activity. Opercular bone strain results from the rapid reduction of pressure in the opercular cavity which causes the operculum to deform medially and does not result from muscle activity. The observed strain pattern is consistent with a stress regime of bending and twisting moments applied to the operculum during feeding. Two prominent orthogonal bony struts on the medial opercular surface are hypothesized to resist these bending and twisting moments.
The Statistical Treatment of Hydrogen Ion Concentration and pH
Authors: Boutilier R. G. , Shelton G. 
Published: April 2021

ABSTRACT
A certain amount of confusion exists amongst respiratory physiologists about the statistical treatment of pH measurements taken from animals during replicated experiments. In some cases average pH (with standard deviations or standard errors as appropriate) is calculated directly whilst in others, pH determinations are converted to corresponding hydrogen ion concentrations before the statistical calculations are carried out. Values for pH may or may not then be recalculated but, if they are, the result of these manipulations is an asymmetry of standard deviations or errors about the mean which is neither useful nor acceptable to the statistician. Our interest in this subject was the result of a mild irritation on being told by a referee of one of our papers that we made the common error of taking simple pH averages. Further enquiry and thought led us to the present paper.
Ba2+ influx measures the duration of membrane excitation in Paramecium
Authors: Ling Kit-Yin , Kung Ching 
Published: April 2021

ABSTRACT
We have developed an assay for the duration of membrane excitation in Paramecium tetraurelia by tracing the influx of 133Ba2+. This assay is performed at physiological temperatures and in physiological solutions. Ba2+ enters the paramecia through the Ca channels, since mutants defective in Ca channels show no significant Ba2+ influx. Ba2+ enters only when the Ca channels are opened during excitation which can be triggered by Na+ or Ba2+ itself. The ionic species and relative concentrations determine the duration of the action potentials and hence the duration of spinning or backward swimming. The longer the average period of excitation, the larger the Ba2+ influx. In a Ba-Ca solution the cells spend 30% of their time in the excited state. The rate of Ba2+ entry into the paramecia in that state is 1·3 mM/min. Ba2+ influx occurs over a 50-fold range of Ba2+ concentration. There is very little Ba2+ efflux. The fate of the entered Ba2+, the consequences of the large and rapid influx, the advantages and drawbacks of the Ba2+ influx assay, and the possible use of the assay for Ca channel function in cell-free preparations are discussed.
Feeding Motor Programme in Limax. II. Modulation by Sensory Inputs in Intact Animals and Isolated Central Nervous Systems
Authors: Reingold Stephen C. , Gelperin Alan 
Published: April 2021

ABSTRACT
The sources of variability in feeding motor programme (FMP) of the terrestrial slug, Limax maximus, were examined in relation to: (1) changes in load on the feeding apparatus; (2) changes in concentration of attractive food stimuli; and (3) changes in satiety signalled by feedback from the gut. These sources of variability, which affect both timing of the central pattern generator for feeding and probability of occurrence of FMP, were compared in intact animals and in isolated brain preparations.
The load on feeding apparatus of intact animals is altered by varying the hardness of their food. An animal will show a higher ‘bite cycle’ frequency on soft food as compared with hard food. In physiological preparations, weights attached to buccal muscles similarly increase load. Cycle frequency of FMP triggered by food extracts is increased when buccal muscles are-unloaded compared with FMP when muscles are loaded.
Increasing the chemostimulant concentration of food results in greater numbers of intact animals feeding for longer periods. Increasing the food extract concentration used to trigger FMP in physiological preparations causes similar increases in feeding duration.
Intact animals use cues from gut distention to indicate satiation and terminate feeding. Inflation of the crop in physiological preparations causes an early termination of feeding activity, along with decreased FMP cycle frequency.
Wing Mechanics and Take-Off Preparation of Thrips (Thysanoptera)
Authors: Ellington C. P. 
Published: April 2021

ABSTRACT
All of the wing fringe cilia of Thrips physapus, except those along the hindwing leading edge, pivot in elongated sockets which lock them into two positions. The wings lie parallel over the abdomen when not in use, with the cilia locked in the closed position at an angle of 15-20° to the wing axis. The closing of the fringes prevents entanglement of the trailing edge cilia and lateral projection of the forewing leading edge cilia. During flight the cilia are locked in the open position, doubling the wing area. The locking force is stronger than the combined aerodynamic and inertial forces on the cilia. The fringes are opened by abdominal combing and closed by tibial combing. The same morphological features are found in other members of the sub-order Terebrantia. Parallel wings at rest are characteristic of this suborder, and the collapsible fringe system is viewed as an effective method for parking the wings. The fringes of the sub-order Tubulifera are not collapsible. The wings overlap on the abdomen at rest and a similar parking problem does not arise.
Synaptic Relationships of the Cerebral Giant Cells With Motoneurones in the Feeding System of Lymnaea Stagnalis
Authors: McCrohan C. R. , Benjamin P. R. 
Published: April 2021

ABSTRACT
The cerebral giant cells (CGCs) of Lymnaea have a tonic, modulatory effect on the intensity of output from feeding motoneurones in the buccal ganglia. Short latency, excitatory and probably monosynaptic connexions occur between the CGCs and three identified feeding motoneurones. Unitary excitatory postsynaptic potentials in these motoneurones, following CGC spikes, are of different sizes and durations, and hence have different summation properties. The CGCs make long latency, excitatory polysynaptic connexions with four other feeding motoneurone types. Bursts of spikes in the CGCs, resulting from phasic synaptic input, synchronous with the feeding cycle, amplify their modulatory effect on burst intensity in feeding motoneurones. The different latencies of the CGCs’ effects on different motoneurones are appropriate for reinforcing their cyclic burst activity.
Magnesium Transport by the Urinary Bladder of the Crab, Cancer Magister
Authors: Holliday Charles W. 
Published: April 2021

ABSTRACT
Anuric crabs, Cancer magister, in 100% sea water lose most of their ability to regulate serum magnesium levels below that of the external medium, indicating that the antennal gland is the site of most of the crab’s hypo-regulatory ability. In vitro measurement of unidirectional fluxes of 28Mg across tissue from the urinary bladder (the terminal element of the antennal gland) showed a significant, serosa-to-lumen (SL) net flux of 0.280 ± 0.059 µequiv cm-2h-1 which was greatly reduced by 5 mm ouabain. Based on the calculated surface area of the bladder in the crab, the net SL flux of magnesium in vitro is sufficient to account for the in vivo rate of magnesium excretion by the antennal gland. Bladder tissue from magnesium-depleted crabs which had stopped concentrating magnesium in the urine did not show a significant, net SL flux of MMg in vitro. It is speculated that magnesium enters the bladder cell by a sodium-coupled process at the serosal border and is actively transported into the urine at the luminal border. Eyestalk ablation caused no significant changes in urinary rate or magnesium levels in serum or urine ; thus neurosecretory centres in the eyestalk are apparently not involved in control of magnesium secretion by the antennal gland. Large, nearly equal, net effluxes of 22Na (1.33 ± 0.19 µequiv cm-2 h-1, ouabain-insensitive) and 36C1 (1.26 ± 0.34 µequiv cm-2 h-1) from the urine were measured in bladder preparations in vitro. It is speculated that this net efflux of salt may be the driving force for fluid reabsorption from the urine by the antennal gland.
Uses and Limitations of Inulin and Mannitol for Monitoring Gill Permeability Changes in the Rainbow Trout
Authors: Kirschner Leonard B. 
Published: April 2021

ABSTRACT
Inulin and mannitol are excreted at measurable rates across gills in freshwater and sea-water-adapted trout. Clearance behaviour suggests that the effluxes may reflect passive permeation, which might make such compounds suitable for monitoring permeability changes. Application of poly-L-lysine and elevation of environmental temperature made FW trout gills reversibly ‘leaky’ to Na+. Mannitol efflux paralleled that of Na+ in both experiments. However, Na+ efflux was reduced in SW trout gills, by increasing external Ca2+ and mannitol efflux was unchanged. The data suggest that these nonelectrolytes can be used to assess permeability changes that do not involve highly selective ionic channels.
The Use of A New Tilting Tunnel Respirometer to Investigate Some Aspects of Metabolism and Swimming Activity of the Plaice (Pleuronectes Platessa L.)
Authors: Priede I. G. , Holliday F. G. T. 
Published: April 2021

ABSTRACT
Plaice and other flatfish can be induced to swim down a slope of about 6o° against an upwelling water flow in a water tunnel. A tilting Brett-type tunnel respirometer based on the above principle enabled laboratory experiments on swimming plaice to be carried out. From trials at 5°, 10°, 15 °C, the relationship between specific swimming speed, V (body lengths s-1), oxygen consumption, R (mg-1, kg-1 h-1) and temperature, T is: log10 = 0·3318V+log10(2·4T + 26·52). If the fish is resting (i.e. V = 0), the oxygen consumption is lower than predicted by the above equation. At rest: The cost of swimming in plaice is very similar to that of typical round fish such as haddock but the resting metabolic rate is lower than for haddock. Before swimming, a negatively buoyant fish such as plaice must lift off the bottom. This cost of lift-off or posture effect makes it uneconomical for plaice to swim at speeds below 0·6V
Mechanisms of Body-Temperature Regulation in Honeybees, Apis Mellifera
Authors: Heinrich Bernd 
Published: April 2021

ABSTRACT
Honeybees when endothermically heated maintained an elevated head temperature (TH) During free flight at 17 °C TH was approximately 7 °C above ambient temperature (TA). However, during flight at TA near 46 °C, head temperature averaged 3 °C below TA. When tethered bees were heated on the head till TH reached 46 °C, they regurgitated nectar from their honeycrop, held it on their ‘tongue’, and initiated violent aortic pulsations in the head and in-out movements of the nectar droplet. Temperature changes in the head corresponded with heart pulsations. Head temperature was prevented from rising and was stabilized. The heart pulsations in the abdomen and aortic pulsations in the head (and abdominal ventilatory movements) were often synchronous, but during heating of the head they were often independent of each other in both frequency and amplitude. The fluid droplet was several degrees Centigrade below head, thoracic and ambient temperatures, and it remained in motion in and out of the body. It caused TH to be 4-8 °C lower, by the resulting evaporative cooling, than is possible without the droplet. It is concluded that at low TA the elevation and regulation of automatically results in the elevation of TTh. However, at low TH heat flows from the heated thorax to the head, not only by passive conduction but also by physiologically facilitated blood circulation.
Neural Interactions Controlling Timing of Flight Muscle Activity in Drosophila
Authors: Koenig J. H. , Ikeda Kazuo 
Published: April 2021

ABSTRACT
Simultaneous intracellular recordings were made from the six ipsilateral dorsal longitudinal muscle fibres of Drosophila in stationary flight. The influence of the firing of one motor unit upon the firing of another was analysed by observing the relationship between the interspike interval of a unit and the relative firing times of the other motor units within that interval. The analysis suggests that the influence is insignificant except when one unit would have fired soon after another. Then, a neural interaction occurs that can cause a unit to fire either earlier or later, depending on its firing relationship with the other units. Thus, the observation that no DLM fibre fires soon after another is the result of both a delaying effect and an effect which causes a cell to fire earlier than it normally would have fired.