bluuebunny/crossref_metadata_2025_split huggingface dataset:
Motor Neurone Coordination and Sensory Modulation in the Feeding System of the Mollusc Pleurobranchaea Californica
Authors: Siegler Melody V. S. 
Published: April 2021

ABSTRACT
This study on the marine mollusc, Pleurobranchaea californica, examined the electrophysiological basis of coordinated motor neurone activity associated with the intrinsic feeding rhythm of the buccal ganglion, and the sensory modulation of this rhythm.
Paired intracellular microelectrode recordings from antagonist motor neurones showed that each received alternating barrages of EPSPs and IPSPs; as one of the pair was depolarized, its antagonist was hyperpolarized. PSPs of opposite polarity in antagonists were one-for-one with each other, suggesting that common presynaptic interneurones were responsible. There was no evidence for direct synaptic interaction between antagonist motor neurones. Paired recordings from synergist motor neurones showed that they received similar barrages of PSPs which alternately depolarized and hyperpolarized them. Underlying these parallel changes in potential were one-to-one PSPs of the same polarity, again suggesting driving by common presynaptic interneurones.
The feeding rhythm that was recorded from the buccal ganglion with the buccal mass attached was compared quantitatively with that recorded from the same ganglion after deafferentation. There were significant differences in parameters of the rhythm measured under the two conditions. Rhythmic afferent activity was recorded from the distal stumps of buccal roots, during rhythmic feeding movements of the buccal mass. The spiking of different units was associated with different phases of the movement cycle. Sensory cells with central somata were stimulated individually in the isolated ganglion, and two effects were recorded. Some sensory neurones excited withdrawal motor neurones and inhibited eversion motor neurones; others inhibited withdrawal motor neurones.
Effect of Dehydration and Rehydration on the Water Content and Na+ and K+ Balance in Adult Male Periplaneta Americana
Authors: Tucker Lois E. 
Published: April 2021

ABSTRACT
Changes in live weight and in the water, Na+ and K+ content of the tissues and faeces have been examined in adult male Periplaneta americana in various states of hydration. During dehydration the haemolymph volume decreases markedly, but the Na+ and K+ concentrations rise only slightly. Less than 25 % of the Na+ removed from the haemolymph during dehydration was found to be excreted, but the K+ excreted during dehydration was in excess of that removed from the haemolymph alone. It seems likely that the major tissue for regulating the haemolymph Na+ during dehydration and rehydration is the fat body, in which dehydration causes an increase, and rehydration a decrease, in the Na:K ratio. The Na+ and K+ content of the fat body was found to be variable in both hydrated and dehydrated animals and absolute changes in the ion content of the tissue could not be estimated because of unknown changes in the amount of food reserves and excretory products.
Measurement of Electrogenic-Pump Current in Aplysia Neurones with Constant-current and Constant-Voltage Techniques
Authors: Junge D. , Ortiz C. L. 
Published: April 2021

ABSTRACT
The responses of the abdominal and pleural giant cells to warming and cooling were studied using constant-current and constant-voltage techniques. The potential change upon warming from about 7 °C to 22 °C was reversed by application of maintained inward current. The reversal potential was − 77 ± 12 mV. The membrane conductance increased with warming, but was not affected by pump-blocking agents. The electrogenic-pump current was found to be about 16 nA for a model in which the pump acted across the membrane ionic conductance. This model could explain the reversal of the warming response with hyperpolarization. In voltage-clamped cells, the response to warming was converted from an outward to an inward current by hyperpolarization. The reversal potential for the current response was 31 ± 7 mV more negative than resting, or about − 80 mV. The pump currents measured under voltage-clamp conditions were the same as those calculated for the hyperpolarizing responses in unclamped cells.
The Pattern of Carbon Dioxide Excretion in the Rainbow Trout Salmo Gairdneri
Authors: Haswell M. S. , Randall D. J. 
Published: April 2021

ABSTRACT
Patterns of carbon dioxide excretion were investigated in rainbow trout (Salmo gairdneri). The loss of erythrocytic carbonic anhydrase caused by severe anaemia does not affect acid/base regulation or the ability of fish to excrete CO2. Bicarbonate excretion across the saline-perfused gills of trout is significant even though residence time for the saline in the gills is only 1− 3 s. CO2 excretion across these saline-perfused gills is blocked by the carbonic anhydrase inhibitor, diamox. The excretion of CO2 in fish is via the movement of plasma bicarbonate into the gill epithelium where branchial carbonic anhydrase catalyses the production of CO2. Fish can adjust pH by regulating bicarbonate movement across the gills. The erythrocytic carbonic anhydrase is not necessary for CO2 excretion in the gills but is involved in facilitating Bohr and Root shifts to augment O2 delivery in the tissues.
Induction of Sulphate Transport and Hormonal Control of Fluid Secretion by Malpighian Tubules of Larvae of the Mosquito Aedes Taeniorhynchus
Authors: Maddrell S. H. P. , Phillips J. E. 
Published: April 2021

ABSTRACT
4th stage larvae of A. taeniorhynchus reared in sulphate-enriched sea water drink the medium at the same rate that they do when reared in sulphate-free sea water. They absorb into the haemolymph most of the water and nearly all of the sulphate from the ingested fluid. Larvae are able to keep the concentration of sulphate in the haemolymph at levels well below that of the medium, even when this contains as much as 89 mm sulphate. The Malpighian tubules of larvae reared in sulphate-containing waters soon develop an ability to transport sulphate. The rate of sulphate transport induced varies directly with the sulphate content of the water in which they are reared. This ability is not retained into the adult stage. The rate of fluid secretion by isolated Malpighian tubules is increased by up to 20 times when they are exposed to saline containing 1·5 mm cyclic AMP or concentrations of 5-hydroxytryptamine higher than 10−6M. Tubules isolated from unfed insects into stimulant-free saline secrete fluid only slowly, but similarly treated tubules from feeding insects initially secrete fluid very much faster. Extracts of the brain and of the thoracic ganglia stimulate Malpighian tubules to secrete fluid at a high rate. The brain is about four times as rich a source of stimulant as is the chain of thoracic ganglia. Treatment of the surface of the structures in the head with K-rich saline leads to the release of a factor which stimulates fluid secretion by the Malpighian tubules. The results suggest that the Malpighian tubules in larvae of A. taeniorhynchus are under the control of a diuretic hormone which is elaborated in the brain and possibly also in the thoracic ganglia and which reaches high levels in the circulating haemolymph of feeding animals. The rate of sulphate transport by isolated Malpighian tubules is strongly affected by the rate of fluid secretion. This behaviour is compatible with a passive leak of transported sulphate from the lumen back into the haemolymph through the permeable wall of the tubule.
Dependence of Prolonged Water Absorption by in Vitro Locust Rectum On Ion Transport
Authors: Goh S. , Phillips J. E. 
Published: April 2021

ABSTRACT
An in vitro preparation of the locust rectum, consisting of an everted cannulated sac, is described. After the first hour, the rates of ion and water transport, the electropotential difference and tissue volume do not change significantly over the next 4 h, i.e. a steady-state situation is approximated. The activities and properties of these rectal sacs are reasonably similar to those in vivo; they produce hyposmotic absorbate, exhibit rectification of osmotic flow, and absorb water from pure sucrose solution for 1 h. Inhibition of absorption by KCN + IAA and also ouabain indicates metabolic dependence. Analysis of absorbate shows that tissue ions are secreted to the haemocoel side when water is absorbed over the first hour from pure sucrose solutions. Prolonged transport of water (i.e. from second to fifth hour) requires the presence of ions on the lumen but not the haemocoel side. This is the first direct evidence that water absorption in the insect rectum is coupled to ion transport as previously postulated. The location of the proposed ion recycling suggested by these observations is discussed.
Mechanical Properties of Primary Feathers from the Pigeon
Authors: Purslow P. P. , Vincent J. F. V. 
Published: April 2021

ABSTRACT
The morphology of the primary feather shaft from the pigeon wing has been examined and its salient features noted. The cortex (outer wall) of the shaft appeared to be the most significant feature in relation to bending behaviour and was analysed quantitatively. A model that simulated bending of the shaft was made using this analysis and upon comparison of simulated results with observed bending behaviour it is shown that the shape and size of the cortex does indeed account for the majority of bending behaviour. The model does not include torsional effects and the effects of the pithy medulla and the transverse septa, but the magnitude of these effects is considered to be small in comparison with that of the cortex considered in simple bending. Differences in the shape of the cortex in the outermost primary and those proximal to it are shown to account for different mechanical properties and possible reasons for this are given. The shape and size of the cortex, as measured by its second moment of area, is shown to have some relation to the body weight of the bird.
Control of the Salivary Glands of Helisoma by Identified Neurones
Authors: Kater S. B. , Murphy A. D. , Rued J. R. 
Published: April 2021

ABSTRACT
The neural regulation of an exocrine gland was investigated at the level of identified effector neurones. The salivary gland neuroeffector system of Helisoma consists of a pair of acinous glands innervated by two symmetrically located, identified buccal ganglion neurones (4R and 4L). Neurones 4R and 4L usually are electrically coupled and display synchronous activity. Action potentials in these neurones elicit EPSPs and action potentials in epithelial cells of the salivary glands. Spontaneous miniature potentials similar to those seen at neuromuscular junctions can be recorded from many of the glandular cells. Neurones 4R and 4L, and thus also salivary gland cells, can display bursts of action potentials phase-locked with those seen in buccal mass motoneurones during feeding.
The Distribution of Bumps in the Tail of the Locust Photoreceptor Afterpotential
Authors: Horridge G. A. , Tsukahara Y. 
Published: April 2021

ABSTRACT
An extended tail or prolonged depolarizing afterpotential (PDA) follows the receptor potential of a locust retinula cell when the stimulating light is in the intensity range that saturates the receptor potential. The amplitude and duration of this afterpotential depend on the intensity and duration of the stimulus. As the afterpotential decays, apparently exponentially, it becomes resolved into bumps, which we call light-induced dark bumps (LID bumps).
The intervals between light-induced dark bumps are distributed in a way that is indistinguishable from a random (Poisson) distribution. As previously demonstrated, LID bumps are indistinguishable from bumps directly induced by low intensity light in light-adapted cells, which in turn grade into the slightly larger bumps produced, each by a single photon, in dark-adapted cells.
The light-induced dark bumps continue for up to an hour in darkness, slowly becoming like dark-adapted bumps in amplitude and shape. To account for the random occurrence and discrete features of bumps after so long a latency, we propose that intense light generates a significant amount of an intermediate molecule or packet which decays slowly to start the same process that normally generates bumps with a short delay.
Unusual Step Patterns in the Free Walking Grasshopper Neoconocephalus Robustus
Authors: Graham D. 
Published: April 2021

ABSTRACT
The free walking behaviour of the tettigonid Neoconocephalus robustus provides a unique quantitative description of the interactions that can occur between a rear and middle leg on the same side of the body in an insect. The rear legs step at approximately half the frequency of the anterior legs, and right and left sides of the body can function almost independently. Relative co-ordination produces a slow drift in the timing of the rear and middle leg protractions so that all the possible values of inter-leg phase may be observed.
A statistical examination of this behaviour shows that the duration of the middle leg step cycle is increased by the presence of a rear leg protraction, only when it occurs in the last half of the retraction stroke of the middle leg. If it occurs in the earlier part of the cycle there is no corresponding contraction of the middle leg step period. This and several other features of the walk exclude a ‘magnet effect’ or an ‘excitatory’ interaction between homologous points in the leg cycle and provide a verification of the ascending ‘inhibitory’ interaction proposed by Wilson (1966).
Co-ordinated walking in this insect appears to be a discrete process in which the performance of a protraction stroke activates a co-ordinating influence and, in conjunction with a frequency hierarchy, maintains the required time relationship between the legs.
Factors Affecting Glomerular Function in the Pacific Hagfish Eptatretus Stouti (Lockington)
Authors: Riegel J. A. 
Published: April 2021

ABSTRACT
Single glomerulus filtration rate in Eptatretus stouti averaged 20·3 + 2·13 (S.E.M.) nl min−1. Single glomerulus glomerular filtration rate (GFR) could be correlated with arterial pressure when arterial pressure exceeded about 4 cm H2O. Glomerular filtration was affected by postglomerular resistance brought about by alteration of the volume of urinary spaces. Filtration undoubtedly plays a role in glomerular function. However, average colloid osmotic pressure (COP) of the plasma is almost double the average hydrostatic pressure in the segmental arteries serving the glomeruli. The COP of glomerular fluid is essentially nil, therefore it is difficult to see how pressure filtration alone can account for primary urine formation.
When single glomeruli were perfused with colloid-containing Ringer at pressures within the normal range of blood pressures, GFR was within the normal range. GFR was related inversely to the colloid osmotic pressure of the perfusion Ringer. Colloid entered the urine during perfusion. However, in only a few instances did this result in conditions favourable to pressure filtration.
To assess the role of active processes in glomerular filtration, chemical inhibitors were added to the perfusion Ringer. Amiloride, acetazolamide, cyanide, 2-deoxy-D-glucose, iodoacetate and ethacrynic acid were without marked effect on glomerular filtration. Ouabain and dinitrophenol markedly reduced GFR; inhibition was probably not due to indirect effects upon the renal vasculature.
Short Communication A Note on ‘Clap And Fling’ Aerodynamics
Authors: Lighthill M. J. 
Published: April 2021

ABSTRACT
Weis-Fogh (1973) analysed the ‘Clap and Fling’ mode of hovering flight in the small chalcid wasp Encarsia formosa. He argued that the difficulty of generating wing lift sufficient to support the insect’s weight at the very low Reynolds numbers involved (about Re = 20) is overcome by a substantial enhancement of lift associated with this special mode of flight. Recently, the ‘Clap and Fling’ mechanism has been studied in model experiments by Bennett (1977) at Re = 83000.
On The Respiration of Torpedo Marmorata
Authors: Hughes G. M. 
Published: April 2021

ABSTRACT
The oxygen consumption of resting Torpedo marmorata was measured using three different methods. The results indicate that this species has a much lower oxygen consumption than other elasmobranchs of comparable size. The gills are ventilated by a mechanism similar to that of other rays, but a relatively small spiracular opening seems to be associated with a more important role of the oro-branchial pump. During hypoxia there is a marked increase in both frequency and amplitude of the ventilatory movements. The frequency of the heart beat is low and shows little change during hypoxia, except under extreme conditions when bradycardia occurs. In some individuals, coupling between cardiac and ventilatory pumps is relatively low but seems to increase at lower ventilatory frequencies and when the ratio between the ventilatory and cardiac frequencies is a whole number. Extreme hypoxia can be withstood for many hours but eventually the ventilatory rhythm ceases; it does not recommence immediately following a rise in ambient oxygen tension. The blood has a low oxygen-carrying capacity and a high affinity. The surface area of the gills is smaller than that of other species that have been investigated, but the quantity of oxygen transferred/unit surface area is similar to that known for other species. It is concluded that Torpedo is a sluggish fish adapted to conditions of low oxygen, but the conditions under which this occurs remain to be determined.
Influence of Water Temperature on the Electric Organ Discharge (Eod) of the Weakly Electric Fish Marcusenius Cyprinoides (Mormyridae)
Authors: Toerring M. J. , Serrier J. 
Published: April 2021

ABSTRACT
The influence of different water temperatures on the electric organ discharge (EOD) of a mormyrid fish Marcusenius cyprinoides was studied. The range of the water temperatures was fixed according to the seasonal temperature variations of the rivers in Central Africa, the natural habitat of this species. The EOD activity was characterized using the following parameters: mean EOD rate, EOD pattern in the form of Interpulse Interval Histograms (IIH), IIH range, and shortest pulse interval. These parameters remained constant during control experiments at constant temperature (27 °C) for 4 days. The mean EOD rate increases with increasing water temperatures. The lowest mean EOD rate is always found at 17 °C, the highest between 26 and 33 °C. The characteristics of the IIH are modified by stepwise temperature increases. These IIH show during high temperatures (26−33 °C similar patterns to those previously observed during high level motor activity and excitement. The IIH range diminishes with stepwise temperature increases. The shortest pulse interval has a negative, linear correlation with water temperature. The possible role of water temperature in the reproduction of the mormyrids is discussed. The high discharge rate of M. cyprinoïdes produced by high water temperatures during the rainy season could serve to improve the resolution of the electroreceptors during this period.
Effects of Epinephrine on Branchial Non-Electrolyte Permeability in Rainbow Trout
Authors: Isaia Jacques , Maetz Jean , Haywood Geoffrey P. 
Published: April 2021

ABSTRACT
Using isolated heads perfused at constant pressure, at rates close to those occurring in vivo, the permeability of the gills of the trout Salmo gairdneri to a range of solutes was measured. Under epinephrine-free conditions, butanol and water showed similar high branchial permeability coefficients. Urea, inulin and dextrans (mol. wt 3000 and 20000) were 7−12 times less permeant, and mannitol 60−70 times less permeant than water or butanol. Epinephrine, at 10−6 M, greatly increased the permeability of the gills to the small hydrophilic molecules, water and urea, and to the lipophilic substance, butanol, but did not affect the penetration of the large hydrophilic solutes, mannitol, inulin and dextrans.
In the presence of 10−6 M propanolol, a β-blocker, epinephrine had no effect on the permeation of any of the test substances except that the permeability to urea decreased somewhat.
The results suggest that epinephrine increases the permeability of the membranes of the branchial cells but does not affect the permeation of substances that cross the gill walls by paracellular routes or via an intracellular ‘bulk-transport’mechanism. Such an action would be expected to increase the branchial transfer of oxygen.
Spectral Sensitivities of the Anterior Median Eyes of the Orb Web Spiders, Argiope Bruennichii and A. Amoena
Authors: Yamashita Shigeki , Tateda Hideki 
Published: April 2021

ABSTRACT
Spectral sensitivities of the anterior median eyes of the orb web spiders, Argiope bruennichii and A. amoena have been studied by recording extracellular ERGs and intracellular receptor potentials. The anterior median eyes have three types of visual cells, with maximum sensitivities at about 360 nm (u.v. cell), 480–500 nm (blue cell) and 540 nm (green cell). The blue cells are the most sensitive and have a circadian oscillation of sensitivity. The green cells show a hypersensitivity, i.e. the sensitivity is greater for about 90 s after the cessation of illumination than during dark adaptation. Respiration is necessary for the maintenance of hypersensitivity.
Auditory Masking Patterns in the Goldfish (Carassius Auratus): Psychophysical Tuning Curves1
Authors: Fay Richard R. , Ahroon William A. , Orawski Arthur A. 
Published: April 2021

ABSTRACT
The masking effects of tones on the detection auditory signals were studied in goldfish using the psychophysical tuning-curve paradigm. For signals below 350 Hz, masking is an inverse function of the frequency separation between masker and signal; a finding consistent with previous masking studies on fishes, birds and mammals. For signals above 350 Hz, masking peaks occur both in the 350 Hz region and at the frequency of the signal. Quantitative comparisons with recent neural tuning curves for goldfish saccular neurones suggest that the filtering observed may be determined by mechanical frequency selectivity below 350 Hz, but by a neural analysis of temporal patterns above this range.