bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hair Cell Mechanoreception in the Jellyfish Aglantha Digitale
Authors: Arkett S. A. , Mackie G. O. , Meech R. W. 
Published: April 2021

ABSTRACT
The jellyfish Aglantha digitale is equipped with clusters of hair cells on the velum and on the tentacle bases. The cells have a central non-motile cilium surrounded by a collar of microvilli. The microvilli are graded in length, from long on one side to short on the other, giving the collar a marked polarity. The hair cells are set in specific orientations in all regions where they occur, as shown by this polarity. Small mechanical displacements of the velum or tentacles in the vicinity of the hair cells evoke bursts of potentials which can be recorded extracellularly from the outer nerve ring. Intracellular recordings from the ring giant axon, which is implicated in escape locomotion, show patterns of facilitating EPSPs correlated with these potentials. Hair cell input may be important in feeding as well as in locomotory behaviour. Three classes of hair cells were studied : those of the tentacle bases (T cells) and those of the velum (C cells and F cells). Direct stimulation of the tentacle bases shows that the T cells respond to slight mechanical displacements. To distinguish the functions of the C cells and F cells, which lie close together, a laser was used to ablate selectively one or other kind. It was found that the C cells respond to small mechanical displacements of the velum but no response could be assigned to the F cells.
Serotonergic Modulation of Patterned Motor Output in Lymnaea Stagnalis
Authors: Tuersley M. D. , McCROHAN C. R. 
Published: April 2021

ABSTRACT
Rhythmic feeding motor output from the buccal ganglia of Lymnaea stagnalis was evoked by tonic depolarization of the pattern-initiating interneurone SO in the isolated central nervous system.
Perfusion with 10–4moll–1 serotonin (5-HT) led to a reduction in frequency of the SO-driven rhythm, and in some cases rhythmic activity was completely blocked. The frequency reduction was predominantly due to an increase in duration of the ‘inactive’ phase of the rhythm. In a number of preparations, the normal buccal rhythm was replaced by an ‘atypical’ pattern of bursting in buccal motoneurones in the presence of 5-HT. This was characterized by the absence of one phase (N2) of interneuronal activity in the feeding pattern generator.
Stimulation of the serotonergic giant cerebral interneurones (CGCs), to increase the mean spike frequency from 10 to 2-5 Hz, mimicked some of the effects of 5-HT perfusion. However, the timing of onset of CGC stimulation in relation to depolarization of SO was critical; prolonged activation of a CGC led to an apparent decrease in its effectiveness in suppressing the buccal rhythm.
Correlation Between Damping Coefficients and Externally Injected Currents in Oscillations Produced by Lithium ions in Frog Skin
Authors: Baptista Carlos Alberto , Ramos Margarida Perestrello , De Jesus Carlos Henriques 
Published: April 2021

ABSTRACT
Oscillations in the electrical parameters elicited by Li+ added to the mucosal side of frog skin in vitro were studied under different experimental conditions.
The correlation between the damping coefficient and the size of the externally injected current was ascertained. The size of the overall epithelial resistance in NaCl-Ringer seems to be a good indicator of the qualitative behaviour of the skin in the presence of Li+: the higher the resistance the less probable the occurrence of oscillations.
Addition of amiloride allowed the calculation of the electromotive force in Na+-and Li+-Ringer.
Calculations of the ‘total equivalent inductance’ and ‘total equivalent capacitance’ of an oscillating skin were made using resistance values (R), damping coefficients (σ) and frequency of oscillation (ω).
Parallel Antiport Mechanisms for Na+ and Cl– Transport in Herbivorous Teleost Intestine
Authors: Howard James N. , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
Transport mechanisms for NaCl in intestinal brush border membrane vesicles (BBMV) of herbivorous, seawater-adapted tilapia, Oreochromis mossambicus, were investigated with a rapid filtration technique using 22Na+ and 36C1− as tracers. Evidence to support the existence of cotransport mechanisms (Na+/Cl– or Na+/K+/2Cr) in tilapia intestinal BBMV was not found. An inwardly directed Cl gradient or KCl gradient did not stimulate the uptake of Na+ into tilapia intestinal BBMV. Furthermore, the uptake of Na+ under these conditions was not significantly affected by furosemide. Evidence was found to indicate the existence of Na+/H+ and C1−/HCO3– antiport mechanisms for NaCl transport in tilapia intestinal BBMV. An outwardly directed proton gradient (pH 6·0 in, pH 7·5 out) stimulated the uptake of Na+ above that of the control (pH 7·5 in, pH 7·5 out). Exogenous amiloride (1 mmol 1−1) significantly reduced Na+ uptake in the presence of an outwardly directed proton gradient. Apparent influxes of 1 mmol 1−1 Na+ were (nmol mg protein–1 15 s–1± 1 S.E.) : control, 1·46 ± 0·09; pH gradient, 3·36 ± 0·14; pH gradient plus amiloride, 1·55±0·05. The uptake of Cl– was stimulated by outwardly directed HCO3– and Cl– gradients in comparison with an outwardly directed gluconate gradient. Apparent influxes of 10 mmol 1−’Cl– were (nmol mg protein–1 15s–1 ± 1 s.E.): gluconate, 12·90±0·19; HCO3–, 15·83±0·34; Cl–, 14·62 ± 0·42. These results suggest that, in contrast to the cotransport mechanisms for NaCl that have been reported for other fish intestine, the herbivorous marine teleost, Oreochromis mossambicus, possesses dual antiport mechanisms for the transport of NaCl across its intestinal brush border membrane.
Short-Chain Fatty Acid Transport in the Intestine of A Herbivorous Teleost
Authors: Titus Eric , Ahearn Gregory A. 
Published: April 2021

ABSTRACT
Short-chain fatty acid (SCFA) concentrations of intestinal contents from the herbivorous tilapia, Oreochromis mossambicus, were analysed by gas and high-performance liquid chromatography. Concentrations of acetate ranging from 3 to 18 mmol I−1 were found along the full length of the intestinal tract, as were trace amounts of propionate. Characteristics of [3H]acetate transport by the intestinal brush-border membrane were analysed in isolated brush-border membrane vesicles (BBMV). Influx of [3H]acetate into BBMV occurred by apparent anion exchange and was not enhanced by inwardly directed gradients of sodium or potassium, indicating the lack of sodium-dependent coupling for acetate transport. Competition and stimulation studies with various organic and inorganic anions revealed the likelihood of a transport system in which [3H] acetate is exchanged specifically for intracellular bicarbonate or other SCFA. Other anions tested had only limited or negligible effects on [3H]acetate uptake. Kinetic analysis over a concentration range of external acetate from 0·1 to 35 mmol I−1 yielded a carrier transport Km of 6·4mmoll−1 and a Jmax of 5·3 nmol mg protein−1 10s−1. Transport of [3H]acetate was not significantly affected by inhibitory drugs specific for anion exchangers. This study suggests that there is a specific antiport system for anions that is shared by bicarbonate and short-chain volatile fatty acids in the intestinal brush-border membrane of this herbivorous teleost.
Effects of Ions on Nematocysts Isolated From Acontia of the Sea Anemone Caluactis Tricolor by Different Methods
Authors: Hidaka Michio , Mariscal Richard N. 
Published: April 2021

ABSTRACT
Differences in nematocyst isolating procedures significantly affected the discharge characteristics of the acontial nematocysts isolated from Calliactis tricolor. Most of the nematocysts isolated in artificial sea water (ASW) discharged instantaneously in 5 mmol 1-1 EGTA and to a lesser degree in distilled water (DW), but they did not discharge in Ca2+-free ASW or 50 mmol 1-1 CaCl2. Most of the nematocysts isolated in lmoll-1 sodium citrate discharged instantaneously when treated with any of the above solutions. Nematocysts isolated in DW or 1 mol 1-1 sucrose exhibited a modest degree of discharge in 5mmoll-1 EGTA after a considerable latent period. Some of the present results appear to be inconsistent with the hypothesis that removal of Ca2+ from the intracapsular fluid causes nematocyst discharge.
Branchial Na+/K+-Atpase and Osmoregulation in the Isopod, Idotea Wosnesenskii
Authors: Holliday Charles W. 
Published: April 2021

ABSTRACT
Pleopod Na+/K+-ATPase enzyme specific activity (ESA) and osmoregulatory performance were measured in isopods acclimated for 12-14 days in 100 %, 75 %, 50 % and 25 % sea water (SW). The animal was 63-65 mosmol kg–1 hyperosmotic to the medium in 100 % and 75 % SW, 214 mosmol kg–1 hyperosmotic in 50 % SW and 239 mosmol kg–1 hyperosmotic in 25% SW. The five pairs of pleopods are biramous but are not similar. The two anterior pairs do not stain with silver, have low and unchanging ESA, are smaller and more rigid than the three posterior pairs and are used for swimming. The posterior three pairs are thinner and more flexible; their endopodites stain with silver and have fivefold higher ESA than their exopodites or the front two pleopods. Only the endopodites of the posterior three pleopods showed large (twofold) increases in ESA in animals acclimated in dilute media. The time course of acclimation from 100% to 50% SW was measured: osmotic equilibrium occurred after 1 day; posterior endopodite ESA was elevated after 1 day and was fully activated after 3 days. Ablation of the endopodites of the posterior three pleopods eliminated the animal’s ability to hyperosmoregulate in 50% SW; ablation of the exopodites of the same append-ages or of both rami of the first two pairs of pleopods had no significant effect on osmoregulation. Thus, the endopodites of the posterior three pleopods of /. wosnesenskii are the sites of inward ion transport in dilute media.
The Aerobic Cost of Saltatory Locomotion in the Fowler’s Toad (Bufo Woodhousei Fowleri)
Authors: Walton Michael , Anderson Bruce D. 
Published: April 2021

ABSTRACT
Studies of kangaroos suggest that hopping provides energy savings during locomotion at high speeds, although studies of small mammals suggest that hopping is no more economical than running. To obtain comparative data on anurans, we exercised Fowler’s toads (Bufo woodhousei fowleri, 25·8 g) on treadmills at speeds ranging from 0·09 to 0·63 km h−1 while measuring oxygen consumption , endurance or hop kinematics. The toads walked at slow speeds and hopped at fast speeds. Steady-state increased linearly with speed to a maximum of 1·17mlO2g−1h−1 at 0·27kmh−1 and was nine times the average pre-exercise . The maximum rate of oxygen consumption during treadmill exercise was comparable to previously reported for less natural exercise regimes. At speeds ⩾0·27 kmh−1, was independent of speed. At speeds ⩽0·36 kmh−1, toads moved for over 1h, but endurance decreased sharply at higher speeds. Hop rate, hop length, hop height and angle of take-off increased with speed. Hopping in B. w. fowleri was not less costly than running in other animals of similar body size and was inefficient at converting metabolic to mechanical energy. The present study suggests that hopping in toads, as in small mammals, is not economical during sustained locomotion and is most important during short bursts of high-intensity activity.
Effects of External Acidification on the Blood Acid-Base Status and Ion Concentrations of Lamprey
Authors: Mattsoff Leona , Nikinmaa Mikko 
Published: April 2021

ABSTRACT
We studied the effects of acute external acidification on the acid-base status and plasma and red cell ion concentrations of lampreys. Mortality was observed within 24 h at pH5 and especially at pH4. The main reason for the high sensitivity of lampreys to acid water appears to be the large drop in blood pH: 0·6 and 0·8 units after 24 h at pH5 and pH4, respectively. The drop of plasma pH is much larger than in teleost fishes exposed to similar pH values. The difference in the plasma pH response between lampreys and teleosts probably results from the low buffering capacity of lamprey blood, since red cells cannot participate in buffering extracellular acid loads. Acidification also caused a decrease in both Na+ and Cl− concentrations and an elevation in K+ concentration of plasma. The drop in plasma Na+ concentration occurred faster than the drop in plasma Cl− concentration which, in turn, coincided with the decrease in total CO2 concentration of the blood.
Functional Characterization of A Voltage-Gated Anion Channel from Teleost Fish Intestinal Epithelium
Authors: Loretz Christopher A. , Fourtner Charles R. 
Published: April 2021

ABSTRACT
An anion channel was isolated, using patch-clamp technique, from the basolateral membrane of goby intestinal epithelial cells. Single-channel conductance varied over a range from 20 to 90 pS. The channel was voltage-gated over the physiological range of cell membrane potential with depolarization increasing the proportion of time in the open state. There was no Ca2+ sensitivity. The selectivity sequence was SO42− &gt; Cl− &gt; Mes−.
The channel may function in vivo as one of several avenues of basolateral membrane Cl− exit with the voltage-gating property serving to match basolateral Cl−exit to apical entry.
Control of Cercal Position During Flight in the Cockroach: A Mechanism for Regulating Sensory Feedback
Authors: Libersat Frederic , Camhi Jeffrey M. 
Published: April 2021

ABSTRACT
In a flying cockroach, the response of cereal wind receptors to standard wind stimuli was reduced by 40 % compared with when the animal was at rest. While flying, rhythmic bursts of action potentials, phase-locked to the wingbeat rhythm, descended the nerve cord. These bursts appeared responsible for a phase-locked rhythmic discharge of cereal motor neurones. This, in turn, evoked a cereal displacement, maintained throughout flight. It is suggested that this displacement causes a pressure block of the sensory nerve, since it has recently been shown that experimental displacement of the cercus in a non-flying cockroach causes a similar degree of sensory reduction (40%) by means of such a mechanism (Libersat, Goldstein & Camhi, 1987). The functional significance of this means of sensory reduction is discussed.
The Effect of Breathing Oxygen and Air on Diving Bradycardia in Cormorants (Phalacrocorax Auritus)
Authors: Jones David R. , Larigakis S. 
Published: April 2021

ABSTRACT
Cardiovascular chemoreceptors are crucial for the development of forced diving responses in dabbling ducks such as the mallard (Anas platyrhynchos). Denervation of the peripheral chemoreceptors or allowing the duck to breath 100 % oxygen before a forced dive eliminates or considerably delays the onset of noticeable bradycardia (Jones & Purves, 1970; Mangalam & Jones, 1984). These procedures have no effect on the level of bradycardia established after 10 s or so underwater in diving ducks or cormorants in forced dives (Butler & Woakes, 1982; Mangalam & Jones, 1984; Furilla & Jones, 1986). The afferent neural pathway for the dive response is unclear in cormorants, but in diving ducks it is the stimulation of nasal receptors with water that causes dive bradycardia (Furilla & Jones, 1986). When forced dives are prolonged, then peripheral chemoreceptors appear to affect heart rate in diving ducks. Heart rate is elevated in ducks (Aythya fuligula) in which the carotid body has been denervated, compared with intact ducks, after 50 s or so of forced submergence (Butler & Woakes, 1982). The purpose of the present study was to investigate whether chemoreflexes also influence heart rate in cormorants in forced dives of up to 120s duration.
Radular Kinetics During Grazing in Helisoma Trivolvis (Gastropoda: Pulmonata)
Authors: Smith David A. 
Published: April 2021

ABSTRACT
Three models for radular feeding in gastropod molluscs have been proposed: (1) odontophoral licking, where the radula is fixed to, and is directed by, a dynamic cartilage; (2) rope-and-pulley rasping, where the radula is dynamic and slides over a static cartilage; and (3) moving-conveyor-belt rasping, which involves independent though concurrent movements both of the radula and of the underlying cartilage. The implications of these alternative mechanical processes with regard to machine efficiency and to feeding optimality are considered. During radular feeding, individual Helisoma trivolvis (Say) employ the model which affords optimality both of food excavation and of food transport. Results showed that the radula of this species slides over the underlying cartilage while the cartilage independently accelerates across the substrate during each effective feeding stroke. Relative velocities (of the ribbon and of the odontophoral cartilage, VR: VO) ranged from 0·67:1 to 0·92:1 and these values were positively correlated with food availability.
Electrical Properties and Anion Permeability of Doubly Rectifying Junctions in the Leech Central Nervous System
Authors: Acklin Susan E. 
Published: April 2021

ABSTRACT
A study has been made of the electrical connections between touch sensory (T) neurones in the leech central nervous system (CNS) which display remarkable double rectification: depolarization spreads in both directions although hyperpolarization spreads poorly. Tests were made to determine whether this double rectification was a property of the junctions themselves or whether it resulted from changes in the length constants of processes intervening between the cell body and the junctions. Following trains of action potentials, T cells and their fine processes within the neuropile became hyperpolarized through the activity of an electrogenic sodium pump. When any T cell was hyperpolarized by 25 mV by repetitive stimulation, hyperpolarization failed to spread to the T cells to which it was electrically coupled. Further evidence for double rectification of junctions linking T cells was provided by experiments in which Cl− was injected electrophoretically. Cl− injection into one T cell caused inhibitory potentials recorded in it to become reversed. After a delay, Cl− spread to reverse IPSPs in the coupled T cell. Movement of Cl−, like current flow, was dependent on membrane potential. When the T cell into which Cl− was injected was kept hyperpolarized, Cl− failed to move into the adjacent T cell. Upon release of the hyperpolarization in the injected T cell, Cl− moved and reversed IPSPs in the coupled T cell. Together these results indicate that the gating properties of channels linking T cells are voltage-dependent, such that depolarization of either cell allows channels to open whereas hyperpolarization causes them to close.
Involvement of the Terminal Abdominal Ganglion in Neuroendocrine Regulation of Integumentary Water Loss in the Cockroach Periplaneta Americana L
Authors: Noble-Nesbitt John , Al-Shukur Marwan 
Published: April 2021

ABSTRACT
Neuroendocrine secretions from the terminal abdominal ganglion (TAG) augment the cephalic neuroendocrine regulation of integumentary water loss in the cockroach. As with the cephalic system, the TAG produces both promoting (TAGP) and restricting (TAGR) secretions which, respectively, lead to an increase or a decrease in the rate of integumentary water loss. The promoting factor (TAGP) requires priming by the cephalic promoting factor (BHP) before it is activated, and it probably acts by stimulating release of more BHP which in turn increases water loss through the integument. The restricting factor (TAGR) is autoactive and exerts its effects even in the absence of the cephalic neuroendocrine system or its secretions. It provides additional, independent restriction of integumentary water loss in adverse (desiccating) ambient conditions. Its action accounts for the longer-term decrease in water loss found in decapitated cockroaches.
These effects parallel closely the effects of the diuretic and antidiuretic hormones produced by the TAG. Measurement of faecal product demonstrates that the changes in overall water loss are not primarily due to changes in excretory loss but are due to regulation of integumentary permeability.
Barium and Calcium Block Bacillus Thuringiensis Subspecies Kurstaki δ-Endotoxin Inhibition of Potassium Current Across Isolated Midgut of Larval Manduca Sexta
Authors: Crawford Dwight N. , Harvey William R. 
Published: April 2021

ABSTRACT
Ba2+ and Ca2+ prevent and reverse the Btk δ-endotoxin inhibition of the short-circuit current in isolated lepidopteran midgut. These findings support the K+ pump–leak steady-state model for midgut K+ homeostasis and the K+ channel mechanism of Bt toxin action. They provide a new tool with which to study the interactions between Bt toxin and midgut cell membranes.
The Importance of Nervous and Humoral Mechanisms in the Control of Cardiac Performance in the Atlantic Cod Gadus Morhua at Rest and During Non-Exhaustive Exercise
Authors: Axelsson Michael 
Published: April 2021

ABSTRACT
The nervous regulation of heart rate and stroke volume in the Atlantic cod Gadus morhua was investigated both in vivo, during rest and exercise, and in vitro. The cholinergic and adrenergic influences on the heart were estimated in experiments with injections of atropine and sotalol. At rest the cholinergic and adrenergic tonus on the heart were 38% and 21%, respectively (ratio 1·81:1). At the end of an exercise period, the cholinergic tonus had decreased to 15% but the adrenergic tonus had increased to 28% (ratio 0·54:1). The results suggest that variation of the cholinergic tonus on the heart is a major factor in the regulation of the heart rate.
In one group of fish, cardiac output was also measured, allowing calculation of stroke volume. Cardiac output increased significantly during exercise, and this effect persisted in the presence of both atropine and sotalol, although the increase in heart rate was reduced or abolished. The persisting increase in cardiac output during exercise is due to an increase in stroke volume, reflecting a Starling relationship.
In the presence of the adrenergic neurone-blocking agent bretylium, a positive inotropic effect on isolated, paced atrial and ventricular strips was observed. In the atrial preparations the effect persisted after 24 h. The effect was prevented by pretreatment with sotalol or cocaine, but potentiated by phentolamine pretreatment. This shows that bretylium exerts its neurone-blocking action after being taken up into the adrenergic nerves, and suggests that the positive inotropic effect of bretylium observed in vivo is due to release of endogenous catecholamines.
The concentration-response curves for adrenaline on isolated spontaneously beating atrial preparations showed that the concentrations of catecholamines necessary to produce appreciable effects on the heart are higher than the concentrations found in cod plasma during ‘stress’ situations (handling and exhaustive swimming).