bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Regenerative Calcium Response in Paramecium
Authors: Naitoh Yutaka , Eckert Roger , Friedman Kenneth 
Published: April 2021

ABSTRACT
Standard intracellular current-passing and recording techniques were used to investigate the electrical properties of the membrane of Paramecium caudatum. The surface membrane produces regenerative depolarizations graded in amplitude and rate of rise with the intensity of applied outward current pulses. In a solution of 1 mM-CaCl2, 1 mM-KCl and 1 mM Tris-HCl at pH 7·2 and 18 °C the overshoot reaches a maximum amplitude of +5 to +15 mV, and shows a maximum rate of rise of about 7 V/sec. The overshoot is insensitive to Li+, Na+, Cl−, TTX and procaine, but increases slightly (up to 10 mV/10-fold rise in ion concentration) in the presence of K+, Rb+, Cs+,, Mg2+ and tetraethylammonium. The overshoot increases 22–25 mV for each 10-fold increase in external [Ca]. Ba2+ and Sr2+ convert the graded response to one that is all-or-none. Repolarization following the peak of the response is more rapid than expected from the time constant of the resting membrane, suggesting delayed rectification. A conditioning depolarization causes inactivation of the regenerative response, and hyperpolarization depresses the response to a given stimulus current. Refractoriness persists for up to 200 msec after each response. The regenerative response of the membrane is consistent with a transient increase in conductance to Ca2+ (Ba2+, Sr2+) with a consequent inwardly directed calcium current. This agrees with recent evidence that ciliary reversal (which accompanies depolarization) is produced by an influx of Ca2+.
Sensory Mechanisms in Paramecium
Authors: Eckert R. , Naitoh Y. , Friedman K. 
Published: April 2021

ABSTRACT
Specimens of Paramecium caudatum were stimulated mechanically with a piezoelectrically driven microstylus. Membrane potentials were monitored and intracellular polarizing currents were passed with glass microelectrodes. Mechanical stimulation of the anterior 15% of the cell ‘s length produced depolarizing transients in membrane potential. This ‘anterior response’ was amplitude-graded up to a maximum with stimuli of increasing intensities, and was accompanied by a drop in membrane resistance. The anterior response consists of two components, a receptor potential in direct response to stimulus transduction, and a secondarily evoked regenerative component. Both are graded. With hyperpolarization of the cell membrane the regenerative component was suppressed and the receptor potential alone was seen. With hyperpolarization the size of the receptor potential was increased. The regenerative component is identical with the ‘calcium response’ which is elicited by direct stimulation with injected depolarizing current. This conclusion is supported by similar sensitivity of the overshoot to extracellular concentrations of calcium, similar refractory periods, similar inactivation by depolarization and suppression by hyperpolarization, and similar prolongation of the time course by TEA. It is concluded that local inflow of receptor current through the stimulated membrane of the anterior end depolarizes the cell membrane by electrotonic spread, activating the electrically excited calcium conductance of the membrane, and thereby eliciting the regenerative calcium response.
Conduction Processes in the Nerve Cord of the Moth Manduca Sexta in Relation to its Ultrastructure and Haemolymph Ionic Composition
Authors: Pichon Y. , Sattelle D. B. , Lane N. J. 
Published: April 2021

ABSTRACT
Connectives of the ventral nerve cord of Manduca sexta consist of glia-ensheathed axons surrounded by a perineurium and an acellular neural lamella, which is greatly expanded on the dorsal surface. The glial cells are linked to one another by desmosomes and tight junctions; the latter also occur between adjacent perineurial cells. There no continuous circum-neural fat-body sheath. A ten-fold change in the external potassium concentration results in a 43 mV change in the resting potential of de-sheathed connectives. Action potentials of such exposed axons are rapidly blocked in low-sodium or sodium-free saline and under these conditions neither calcium nor magnesium is able to maintain conduction. Spikes from de-sheathed preparations are rapidly abolished on exposure to 10−6 M tetrodotoxin. These findings indicate a conventional ionic basis of excitation for the axonal membrane of this insect. Analyses of the haemolymph reveal a mean sodium concentration of 25·4(s.E. ± 0·98) mm/1 and a mean potassium concentration of 25-1(s.E. ± 1·74) HIM/1. Action potentials recorded from sheathed connectives are maintained for extended periods in sodium-free saline. 5. Exposure of most sheathed connectives to elevated potassium concentrations results in a two-stage depolarization. A rapid, single-stage, apparently extraneuronal potential change is, however, observed in some preparations. These results on sheathed connectives indicate the presence of some peripheral barrier to the movements of sodium and potassium; the tight junctions between adjacent perineurial cells are considered to be possible sites of this restriction.
Body Weight and the Energetics of Temperature Regulation: A Re-Examination
Authors: Calder William A. , King James R. 
Published: April 2021

ABSTRACT
Investigations in the past two decades have shown the utility of the Newtonian model of heat loss from homoiotherms which was established in the biological literature by Scholander et al. (1950 a, b,c). The stimulative effect of those papers is seen in a proliferation of thermoregulatory studies (for reviews see Bartholomew, 1968; Dawson & Hudson, 1970). Sufficient data'have been generated from a wide range in body sizes to permit recognition of allometric generalizations that are useful for predictive purposes and for inter-class and intra-class comparisons (e.g. Herreid & Kessel, 1967; Lasiewski, Weathers & Bernstein, 1967; Kendeigh, 1969).
Some Aspects of Gas Exchange in Tuna*
Authors: Stevens E. D. 
Published: April 2021

ABSTRACT
Some aspects of gas exchange in restrained skipjack tuna were analysed. The average rate at which water flowed over the gills was 2·8 1/min.kg. The concentration of oxygen in water entering and leaving the gills was measured and used to calculate oxygen uptake (692 mg/h.kg) and utilization (0·71). The drop in hydrostatic pressure as water flowed over the gills was 1·9 cm water and agrees favourably with theoretical predictions. The partial pressure of oxygen was measured in blood afferent and efferent to the gills and used to calculate effectiveness of oxygen removal from the water (90%) and the transfer factor for oxygen (0·12 ml/min.kg.mmHg). The average utilization measured in free-swimming tuna was 0·56. The extraordinary ability of tuna to efficiently extract oxygen from the water at high gill water flow rates is discussed.
An Electromyographic Study of the Adductor Mandibulae Complex of A Free-Swimming Carp (Cyprinus Carpio L.) During Feeding
Authors: Ballintijn C. M. , Van Den Burg A. , Egberink B. P. 
Published: April 2021

ABSTRACT
The anatomy of the upper and lower jaws of the carp, together with the associated maxillaris and mandibularis muscles of the adductor mandibulae complex, is described. From the electromyograms of the adductor mandibulae muscles, recorded simultaneously with a 16 mm film of the mouth movements in a free-swimming carp, the muscle coordination of the diverse mouth movements during feeding has been studied. The interpretation of the results has been verified by electrical stimulation of the muscles, in different combinations, in a fish in which spontaneous movements were abolished by heavy anaesthesia.
Water Relations in an Insect, Thermobia Domestica: II. Relationships Between Water Content, Water Uptake from Subsaturated Atmospheres and Water Loss
Authors: Okasha A. Y. K. 
Published: April 2021

ABSTRACT
The percentage water content of Thermobia can be increased by starvation. After desiccation (3 days in dry air) the water content of starved insects is still above normal; yet such insects will take up water from a subsaturated atmosphere (83% R.H.). The rate of water loss into dry air from starved insects is not dependent upon water content. Both water content and rate of water loss remain constant throughout the moulting cycle. In general terms the uptake mechanism is not dependent upon water content. Severe starvation before desiccation seems to impair or inhibit the uptake mechanism.
The Circadian Rhythm of Flight Activity of The Mosquito Anopheles Gambiae: the Light-Response Rhythm
Authors: Jones M. D. R. , Cubbin C. M. , Marsh D. 
Published: April 2021

ABSTRACT
In sugar-fed A. gambiae females, light may affect flight activity directly or by changing the phase of the circadian rhythm; both responses depend on the phase of the rhythm. The phase-response curve (1 h, 70 lux, signals given in the first cycle in DD following LD 12:12) shows a sharp swing, at about 3 h after normal light-off, from a maximum phase-delay to a maximum phase-advance, each of about 2 h. When signals are given at this time, phase re-setting is very variable; cyclical activity continues but the individuals are out of phase. Phase shifting appears to be a function of the energy of the signal. A 5 min, 70 lux signal has no apparent effect. The effect of a 1 h signal increases with intensity, up to at least 500 lux, but does not appear to be significant below 10 lux. Light normally inhibits flight activity, but there is a burst of activity at light-on (light-on response) if it occurs during the active half of the cycle following the initial activity peak. A vigorous light-on response occurs even at the lowest intensity used (0·3 lux).
Comparative Effects of Temperature on the Sodium and Water Permeabilities of the Gills of a Stenohaline Freshwater Fish (Carassius Auratus) and a Stenohaline Marine Fish (Serranus Scriba, Serranus Cabrilla)
Authors: Isaia J. 
Published: April 2021

ABSTRACT
Comparative effects of temperature on the permeability of the gill to water and to sodium were studied in the marine sea perch Serranus and the freshwater goldfish Carassius. The acclimation Q10 for the water fluxes is higher in the freshwater fish than in the marine fish. In the goldfish the osmotic permeability (Pos) is greater than the diffusional permeability (Pdlf) at all acclimation temperatures, suggesting the presence of ‘water-filled channels’ in the branchial membrane. In the sea perch, on the other hand, Pos/Pdif, is approximately 1, indicating that water movements probably occur by simple diffusion. The permeabilities to water and to sodium are similar in the sea perch but very different in the goldfish. Considering these results together with those from a similar study on an elasmobranch, it would seem that the more perfect the semipermeability of the gill membrane and the weaker the transepithelial osmotic gradient, the greater is the branchial porosity. Assuming that temperature changes do not cause modification of the branchial surface or relative permeabilities to water and to sodium the independence of the temperature-coefficient variations for water and for sodium indicates a certain dissociation between the movements of salt and of water, in the sea perch.
In the goldfish, assuming a constant branchial surface and in view of the fact that Pos&gt;Pdif, the high temperature coefficients for the water fluxes suggest that the water in the ‘water-filled channels’ is in a highly organized state.
Evidence for an Effect of Ouabain on the Branchial Sodium-Excreting Pump of Marine Teleosts: Interaction Between the Inhibitor and External Na and K
Authors: Motais R. , Isaia J. 
Published: April 2021

ABSTRACT
In all marine fish, both stenohaline and euryhaline, the net sodium excretion by the gill, compensating for intestinal absorption, is the result of a Naint-Kext exchange. In a euryhaline fish, such as the eel, in which a sodium exchange diffusion (linkage of sodium influx and outflux) also occurs, the two kinds of exchange (Na-Na and Na-K) can be regarded as alternative modes of behaviour of the same transport system. In normal sea water both exchanges take place at the same time; in K-free sea water the system exchanges Na for Na exclusively and in Na-free solution containing K the system exchanges Na for K exclusively. The transport system is located on the external membrane since it is inhibited by ouabain added in the external medium. The Na-K process is ouabain-sensitive but K can antagonize the inhibitory action of the glycoside. The Na-Na process on the other hand is not ouabain-sensitive.
The Effects of Low Temperature upon the Locomotor Activity Rhythm of Talitrus Saltator (Montagu) (Crustacea: Amphipoda)
Authors: Bregazzi P. K. 
Published: April 2021

ABSTRACT
Chilling Talitrus causes a complete cessation of locomotor activity and a delay in the appearance of successive activity peaks following return to normal temperatures. Maximum delay occurs if chilling begins during inactivity and is about equal to the duration of the chill. At other times the delay is less than the duration of the chill. It is postulated that an inhibitory factor is concerned in the control of the locomotor rhythm of Talitrus, and a model is proposed to describe its possible mode of action.
The in Vitro Respiratory Properties of Blood of the Primitive Fish Polypterus Senegalus
Authors: Vokac Z. , Ahmed Nasr El Din , Magid A. M. Abdel 
Published: April 2021

ABSTRACT
Respiratory properties of blood of Polypterus senegalus were studied in vitro at 30 °C The following values were found in species which did not suffer from an apparent anaemia: erythrocyte count 0·7–1·15 x 108/mm3, haemoglobin concentration 10–14 g/100 ml, haematocrit 33–43 vol. %, mean erythrocyte volume 300–480/4ms, and mean erythrocyte size 18×10 μm. Subtracting the calculated volume of the nucleus, the ‘true’ mean corpuscular haemoglobin concentration in the erythrocyte cytoplasm was found to be 34 g/100 ml, which corresponds to the haemoglobin concentration in the non-nucleated mammalian erythrocytes. Transport of oxygen : The oxygen affinity of haemoglobin was found to be moderate, P50 being 23·5 mmHg at , 6 mmHg and pH 7·7. The O2 dissociation curve had a typical sigmoid shape. The oxygen capacity of the investigated samples was 13·5–18·5 ml/100ml, showing a binding capacity of approximately 1·34 ml O2 per 1 g Hb at pH &gt; 7·3. A slight Root effect was observed at pH lower than 7·2. The coefficients of the Bohr effect (A log P 50/A pH) and of the temperature shift of the oxygen dissociation curve (Δ log P50/ΔT) were −0·43 and 0·022, respectively. Transport of carbon dioxide: the CO2 combining power in oxygenated blood was 12·5 mM/1 at 30 mmHg and pH 7·3 and the CO2 dissociation curve showed the typical steep initial portion. The buffering capacity of blood was moderate, the coefficient being −15·4. The Haldane effect was also found to be moderate, cap. being–0.10. The dissociation constant of plasma carbonic acid (pK′) was assessed to be 0-03 higher than that of human plasma at corresponding pH and temperature 30 °C. The position of the absorption maxima of Polypterus oxyhaemoglobin and cyanmethaemoglobin solutions was the same as that of human haemoglobin solutions. The results are compared with the respiratory properties of lungfish and human blood.
Calcium Regulation in the Freshwater Crayfish Austropotamobius Pallipes (Lereboullet) I. Calcium Balance in the Intermoult Animal
Authors: Greenaway Peter 
Published: April 2021

ABSTRACT
Calcium regulation in normal and in calcium-depleted specimens of Austro-potamobius pallipes in the intermoult condition has been investigated. Calcium turnover was very low and the normal calcium balance was negative for much of the winter intermoult stage. Calcium uptake was against a small electrochemical gradient, at least part of the influx occurring by active transport. Most of the calcium loss occurred across the gills, and the urine contribution was small. Calcium-depleted animals showed only a small fall in haemolymph calcium concentration and calcium uptake was not significantly increased by depletion.
The Kinetics of Peripheral Exchanges of Water and Electrolytes in the Silver Eel (Anguilla Anguilla L.) in Fresh Water and in Sea Water
Authors: Kirsch R. 
Published: April 2021

ABSTRACT
New experimental techniques are described for the investigation of water and electrolyte fluxes in the eel by studying the internal medium, the urine and the external medium. An experimental tank made up of two compartments isolates the water containing the head from the water containing the trunk and tail of the animal. The two water circuits are separated by remote control. Measurement can thus be made without handling the eel previously adapted to experimental conditions. The freshwater eel shows low branchial exchanges and low chloride urinary losses. A positive correlation between urinary excretion of water and sodium has been shown. The silver eel’s skin is impermeable to water and chlorides. The eel reacts to FW-SW transfer by immediately drinking water. The drinking reflex is therefore not triggered by dehydration due to the osmotic gradient. During SW adaptation the eel presents a transitory hyperactivity phase of the branchial outflux corresponding to plasma hypermineralization. The eel which has been adapted to sea water for 3 weeks shows the lowest chloride exchanges ever recorded among marine teleosts.
Electrical and Mechanical Properties of the Red and White Muscles in the Silver Carp
Authors: Yamamoto T. 
Published: April 2021

ABSTRACT
Electrical and mechanical properties of the red muscle (M. levator pinnae pectoralis) and white muscle (M. levator pinnae lateralis abdominis) in the silver carp (Carasstus auratus Linné) were investigated by using caffeine and thymol. A complete tetanus could be produced in the red muscle. But in the white muscle no tetanus was produced and there was a gradual decrease in tension during continuous stimulation, even at a frequency of 1 c/s or less. Caffeine (0·5–1 mM) and thymol (0·25–0·5 mM) potentiated the twitch tension in both muscles without an increase in the resting tension; they produced a contracture in both muscles when the concentration was increased further. The falling phase of the active state of contraction was nearly the same in both muscles and was prolonged by caffeine (0·5 mM) and by thymol (0·25 mM). The resting membrane potential of the red muscle was scarcely affected by caffeine (0·5–5 HIM), whereas in the white muscles a depolarization of 10 mV was observed with caffeine of more than 2 mM. The resting potential of both muscles was little changed by 0·25 mM thymol. However, at a concentration of more than 0·5 mM thymol depolarized the membrane in both muscles to the same extent. In caffeine (2–3 mM) solution the mean specific membrane resistance was reduced from 8-8Ω cm2 to 6·0 kΩ cm2 in the red muscle, and from 5·0 kΩ cm2 to 2·7 kΩ cm2 in the white muscle. In thymol (0·5–1 mM) solution it was reduced from 11·2 kΩ cm2 to 6·5 kΩcm2 in the red muscle, and from 5·4 kΩ cm2 to 3·1 kΩ cm2 in the white muscle. The specific membrane capacitance, calculated from the time constant and the membrane resistance, remained more or less the same in both muscles after a treatment with these agents. Electrical properties of the muscles and the effects of caffeine and thymol on mechanical responses suggest that there are no fundamental differences between red and white muscles except for the excitation-contraction coupling. A lack of summation of twitch, a successive decline of twitch, and inability to produce potassium contracture in the white muscle may be due to the fact that the Ca-releasing mechanism is easily inactivated by depolarization of the membrane.
Electrophysiology of the Heart of An Isopod Crustacean: Porcellio Dilatatus
Authors: Holley A. , Delaleu J. C. 
Published: April 2021

ABSTRACT
The electrical properties (recorded with intracellular microelectrodes) and the mechanical properties of the myocardium of the wood-louse Porcellio dilatatus (Brandt), a terrestrial isopod crustacean, have been investigated. The diastolic membrane potential varied from – 50 to – 70 mV. Several types of spontaneous electrical responses have been recorded. Their amplitude was usually between 30 and 45 mV and their duration varied from 150 to 400 msec. Except for very rare cases, overshoot did not occur. The phase of depolarization began slowly; it became faster but the maximum rate of rise never exceeded 1– 2 V/sec. The rising phase, devoid of steps, was followed by a partial repolarization leading to a more or less sustained smooth plateau. Superimposed changes of potential occurred very rarely. A jagged appearance of the plateau, as seen in numerous neurogenic hearts and interpreted as junction potentials, could not be observed. During spontaneous activity intracellularly applied currents modified the frequency, the time course and the amplitude of the responses. The junctional nature of the rising phase is suggested. At rest the myocardial membrane displayed a ‘normal’ rectifying property and a weak delayed rectification; in addition, some preparations showed an active graded response of the membrane. A complete regenerative activity was never triggered. A tentative explanation of the electrical response is proposed : the rising phase could chiefly correspond to a junctional potential, the plateau might be a response of the membrane to the synaptic depolarization. The value of the membrane space constant (about 1 mm) suggests that the small muscle fibres, as observed under optical microscope, are interconnected electrically. The impulses delivered by the heart ganglion would activate the whole myocardium almost simultaneously, resulting in a high apparent conduction velocity and a good synchronization from one end to the other. The degree of tension or of relaxation of the fibres closely depended on the value of the membrane voltage. The magnitude of the contraction depended on the absolute level of the potential and the length of time during which the depolarization was maintained. The functional importance of the plateau phase is considered. Intracellular depolarizing pulses led to a contraction of the heart; conversely, hyperpolarizing pulses led to its relaxation. GABA (10− 6 g/ml) inhibited the functioning of the heart and reduced the membrane resistance. Picrotoxin (10−4 g/ml) acted as an antagonist to GABA, L-Glutamic acid (10− 4 g/ml) strongly depolarized the membrane, leading to the cessation of the activity.
An Electrophysiological Study of the Photo-Excitative Neurones of Onchidium Verruculatum in Situ
Authors: Hisano Nozomu , Tateda Hideki , Kuwabara Masutaro 
Published: April 2021

ABSTRACT
The distribution of the axons of the photo-excitative neurones in Onchidium verruculatum has been traced by intracellular stimulation of the soma and extracellular stimulation of the axon. They send axon branches mainly into the pleuro-parietal and abdominal nerves in both sides. In the whole-animal preparation, photo-excitative spikes could be recorded from neither the soma nor the nerves of inherently photo-excitative neurones during light stimulation. ‘On’ and ‘off’ spikes were initiated only immediately after the beginning and the cessation of illumination of a whole animal. ‘Off’ spikes originated from dorsal eyes and stalk eyes to which shadow stimuli were applied. Those spikes were not the direct response of photo-excitative neurones to light. The excitation of the inherently photo-excitative neurones in situ was suppressed by inhibitory inputs coming through the right and left pleuro-parietal nerves. Cutting one (or some) of the pleuro-parietal nerves was the only condition that diminished the inhibitory inputs to the photo-excitative neurones in the present work. Adequate electrical stimulation of the pleuro-parietal nerves inhibited spikes of photo-excitative neurones due to photo-excitator or spontaneous discharge.