bluuebunny/crossref_metadata_2025 huggingface dataset:
The Corpus Allatum and Oogenesis in Rhodnius Prolixus (Stål.)
Authors: Pratt G. E. , Davey K. G.
Published: April 2021

Mated females lay more eggs than virgin females. They also oviposit earlier in the cycle, and at a higher rate, than virgins. Mated females produce, slightly more than two oocytes per ovariole. Virgin females produce a little more than one oocyte per ovariole. The first wave of oogenesis proceeds at the same rate in mated and virgin females, whereas the second wave is inhibited in virgins. The concentration of yolk protein in the haemolymph remains high for longer in virgins than in mated females. The inhibition of egg production during the second wave of oogenesis in virgins is thus not a consequence of a previous decline in yolk protein titre. Virgin females digest their blood meal more slowly than mated females. The follicular epithelium of an oocyte in the second wave of oogenesis in a virgin shows sparsely scattered intercellular spaces, whereas that of an oocyte from the first wave exhibits the abundant spaces characteristic of a follicle from a mated female. During the time when vitellogenesis is inhibited in virgins there is an accumulation of oocytes in the size range below that of activation. The corpora allata of both mated and virgin females undergo a cycle of increase in size associated with the cycle of oogenesis. There are no differences which can be correlated with the differences in the activities of the ovaries of mated and virgin females. Topical application of farnesyl methyl ether (FME) to decapitated mated females brings about egg development equivalent to that of virgin females. Topical application of FME to virgin females results in the production of the number of eggs characteristic of mated females, but very high doses are necessary to achieve this. These dose levels also result in an increase in rate of oviposition. These effects of high doses of FME are abolished if the virgin females lack their neurosecretory cells. It is concluded that the virgin inhibition of oogenesis results not from a deficiency of allatum hormone, but from the presence of an antigonadotropin released from ovaries which contain mature eggs.
Active Chloride Transport by the Gills of Rainbow Trout (Salmo Gairdneri)
Authors: Kerstetter Theodore H. , Kirschner Leonard B.
Published: April 2021

The kinetics of chloride transport by the irrigated trout gill have been studied. The transport system is saturable, and the half-saturation value is about 0·25 mM. Chloride uptake occurs equally well from solutions of non-penetrating cations and from NaCl solutions. The presence of potassium in the irrigating solution, however, significantly inhibits chloride uptake. The trout gill is permeable to potassium, and there appears to be an active component to potassium influx. Chloride transport is stimulated by injections of NaHCO3 and (NH4)HCO3. The carbonic anhydrase inhibitor, acetazolamide, has no apparent effect on chloride influx, and it is suggested that if a exchange exists in the trout gill, sufficient can be supplied by the blood. The mean intracellular potential (relative to the irrigating solution) of five gill filament cells was − 32 mV. This indicates the presence of an energy barrier to chloride uptake at the outer membrane of the epithelium, and therefore it is postulated that an active step for chloride transport is located on this membrane.
Function of the Neural Sheath in Marine and Freshwater Molluscs. Evidence for Restriction of Sodium Loss in Freshwater Species
Authors: Twarog Betty M. , Hidaka T.
Published: April 2021

Action potentials were observed in cerebrovisceral connectives of a marine bivalve, Mytilus edulis L., and two species of freshwater bivalve, Anodonta cataracta and Elliptio complanata. In Mytilus nerve, responses to stimulation in both the intact and the de-sheathed nerve were blocked after two minutes in a sodium-free saline. Restoration of normal sodium levels reversed the block within 5 min. In nerves of the freshwater species, Anodonta and Elliptio, the action potential of the sheathed nerve altered very slightly after one hour of stimulation in a sodium-free solution. The completely de-sheathed nerve, however, was blocked within one minute in sodium-free saline. The block was rapidly reversible. It is concluded, contrary to conclusions of previous investigators, that the neural sheath in freshwater clams is just as vital to restriction of sodium loss as it is in amphibia and insects, and it would seem logical to seek out a common denominator of sheath function. Several possible mechanisms are put forth and discussed.
Effects of Temperature on Branchial Sodium-Exchange and Extrusion Mechanisms in the Seawater-Adapted Flounder Platichthys Flesus L
Authors: Maetz J. , Evans D. H.
Published: April 2021

The effect of temperature on osmoregulation of teleosts has been investigated in several laboratories. In fresh water acclimatization to low temperature is accompanied by a decline in plasma levels of sodium and chloride, while in sea water, on the contrary, low temperature causes an increase in the concentrations of the major electrolytes (Umminger, 1969, 1970; see review by Pickford, Grant & Umminger, 1969).
Branchial Sodium Exchange and Ammonia Excretion in the Goldfish Carassius Auratus. Effects of Ammonia-Loading and Temperature Changes
Authors: Maetz J.
Published: April 2021

Krogh (1939) first suggested that in freshwater animals branchial or cutaneous excretion of ammonia may be related to sodium absorption. In both freshwater Crustacea (Astacus pallipes) and teleosts (Carassius auratus) independent active transport of Na+ and Cl− from the outside medium have been definitely established (Shaw, 1960a–c; Garcia Romeu & Maetz, 1964). Sodium in particular may be absorbed at very high rates without an accompanying anion. The maintenance of the electroneutrality of the external and internal media necessitates an exchange with an endogenous ion during sodium movement. The possibility that ammonium ions may fulfil this role is suggested by the fact that the gill is the main site of ammonia excretion (Smith, 1929,1953) and indirect experimental evidence has supported this hypothesis. Addition of ammonia to the outside medium, a procedure which inhibits ammonia excretion, interferes with the sodium uptake (Shaw, 1960a; Maetz & Garcia Romeu, 1964). Injection of ammonium ions, a procedure which increases ammonia excretion by the gill, produces an increase of sodium uptake in the goldfish (Maetz & Garcia Romeu, 1964) and in the eel (Garcia Romeu & Motais, 1966). No stoichiometric relationship between ammonia excretion rate and sodium net uptake in relation to experimental external salinity changes is, however, observed in the crayfish (Shaw, 1960b). Thus the exchange cannot be obligatory. In particular when ammonia excretion falls short of sodium uptake, a second exchange process, Na+ against H+, is thought to be operative, or when sodium uptake is blocked at low external sodium concentration, ammonium is thought to be accompanied by endogenous bicarbonate ions excreted by the gill (Shaw, 1960b).
A Regenerative Calcium Response in Paramecium
Authors: Naitoh Yutaka , Eckert Roger , Friedman Kenneth
Published: April 2021

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

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

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

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

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

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

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

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

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>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

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

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

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 > 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

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

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

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

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

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.
The Nature of Cellular Volume Regulation in Marine Bivalves*
Authors: Pierce Sidney K. , Greenberg Michael J.
Published: April 2021

Regulation of cell volume utilizing intracellular free amino acids has been studied in isolated ventricles from marine bivalves of the genus Modiolus. As in the intact animal, ventricles taken from Modiolus acclimated to various salinities show only a slight change in tissue hydration. This control over cell volume is accomplished by isosmotic intracellular regulation of taurine, alanine, glycine and proline concentrations. When stressed with decreased external salinities the isolated spontaneously beating ventricle becomes quiescent for a period, and then resumes activity. During the period of quiescence ninhydrin-positive substances (NPS) are released. The duration of quiscence and the amount of NPS released increase with increasing dilution of the external medium. The salinity-induced NPS efflux is composed of taurine, alanine, glycine and proline. In molluscs, the amino acids utilized for volume regulation are released from the cells unchanged and are not degraded into keto-acids and ammonia as they are in the crustaceans.
Kinetics of Water and Chloride Exchanges During Adaptation of the European Eel to Sea Water
Authors: Kirsch R. , Mayer-Gostan N.
Published: April 2021

Since Smith (1930) and Keys (1933) studied water and electrolyte exchanges in the eel much work has been done on osmoregulatory problems in teleosts, and the fundamental principles of osmoregulation in this group have now been established. The freshwater teleost drinks little and urinates abundantly to compensate for osmotic water uptake through the gill; the marine teleost drinks abundantly (‘drinks like a fish’ in fact) to make good water loss through the gill. The eel, euryhaline and migratory in varying salinities during its life-cycle, is an excellent choice for the study of osmoregulatory problems.

Transferring an eel from fresh water to sea water results in an increase of plasmatic electrolytes (Oide & Utida, 1968 ; Mayer & Nibelle, 1970; Kirsch, 1972). This increase could be caused by all or any of three factors – factors which it is difficult to dissociate experimentally or to estimate quantitatively. They are: (a) dehydration due to the reversal of the osmotic gradient between internal and external media; (b) an influx of electrolytes temporarily higher than the outflux ; (c) a considerable uptake of water from the digestive tract.

The present work is concerned with the last of these phenomena, with regard to which previous data are contradictory. Oide & Utida (1968) report a gradually increasing ingestion of sea water in vivo with a maximum on the 5th day after transfer, followed by a reduction and stabilization. Kirsch (1972b) isolated the head region of the eel and observed a considerable ingestion of water at the moment of osmotic shock. We have therefore undertaken complete and detailed study of the kinetics of the drinking rate during sea-water adaptation, with a parallel study of the little-known chloride exchanges. Dehydration was also followed indirectly by measurements of body weight.
Water Uptake and Loss in Relation to the Salinity of The Medium in the Amphipod Crustacean Gammarus Duebeni
Authors: Lockwood A. P. M. , Inman C. B. E.
Published: April 2021

The water fluxes across the body surface and the rate of urine production have been studied in the euryhaline amphipod Gammarus duebeni. Urine flow rates (fPOs) have been determined from measurements of loss of [131I]sodium diatrizoate from the body, and the expected urine flow (fPdiff) has been calculated from determinations of the osmotic gradient between blood and medium and the flux of tritiated water. For animals in 2% and 40% sea water the ratio of fPos/fPdiff are 1 ·16 and 1 ·44 respectively, and thus approximate fairly closely to unity. This implies that in these media the water subsequently excreted as urine enters the body by osmosis and that there is little interference with the free diffusion of water at the body surface due to passage through long pores or across unstirred layers. In sea water the ratio fPos/fPdiff is normally (assuming an osmotic gradient of 10 m-oamoles) almost twice unity but urine production is approximately halved when the animals are exposed to sea water saturated with an inhibitor of active sodium uptake (thionine). It is suggested that there is a prima facie case for assuming that part of the fluid subsequently excreted by this species, when in sea water, is taken into the body initially by a process dependent upon active ion transport.
Localization of Ion-Transport in the Intestine of the Migrating River Lamprey, Lampetra Fluviatilis L
Authors: Pickering Alan D. , Morris R.
Published: April 2021

Isolated intestinal preparations from migrating Lampetra fluviatilis re-adapted to 50 % sea water were used to localize ion transport. A large, active, monovalent-ion flux was found in the anterior intestine and its magnitude decreased towards the posterior end of the intestine. The monovalent-ion flux is responsible for a net water flux from mucosa to serosa in the anterior intestine. It is tentatively suggested that both sodium and chloride are actively transported by the mucosa. The divalent ions may be carried along with the monovalent ions to a limited extent. Studies at the light- and electron-microscope levels indicate that columnar cells of the anterior intestine are responsible for ion transport, and there is evidence that the same cells produce mucus.
The Control of Walking in Orthoptera
Authors: Burns M. D.
Published: April 2021

The patterns of leg movements during normal straight-line walking of the locust Schistocerca gregaria and the grasshopper Romalea microptera were recorded and analysed. The ratio of protraction to retraction increased with walking speed except in the prothoracic legs. At any one speed both protraction and retraction durations were variable but the variation was greatest for protraction. The locust employed an alternating tripod gait at all walking speeds recorded (2–8 steps/sec.) It displayed a high level of variability in its leg movements which appeared to be held in check by stabilising mechanisms operating on the first and last leg pairs. The movements of individual legs of the grasshopper were very similar to those of the locust but the gait used was not alternating tripod. Comparisons were made with other insects and it was suggested that the specialization of the metathoracic legs in the locust gave rise to most of the variability in leg movements and that the relative independence of the prothoracic legs reflects an exploratory role in walking.
Central Response to Infra-Red Stimulation of the Pit Receptors in A Crotaline Snake, Trimeresurus Flavoviridis
Authors: Goris Richard C. , Terashima Shin-Ichi
Published: April 2021

Both action potentials and evoked potentials were recorded from the tectum opticum of a crotaline snake, Trimeresurus flavoviridis, in response to infra-red stimulation of the facial pit organs. Action potentials from single units were recorded throughout the tectum. Most units responded to contralateral stimulation, while some responded to both ipsi- and contralateral stimulation. Firing patterns were tonic, phasic, or phasic-tonic, depending on the position of the stimulus and the type of unit being recorded. Sensitivity to stimulus movement was observed. All potentials differed from peripheral potentials in firing patterns. Firing frequency was directly proportional to stimulus intensity. Measurements were made of the vertical and horizontal response fields of single units. Background discharge was noted in all units and its nature discussed. The integrative function of the tectum in regard to infra-red perception was also discussed, as well as the possibility of stereoscopic perception.
Water Relations in An Insect, Thermobia Domestica
Authors: Okasha A. Y. K.
Published: April 2021

The concentrations of Na+ and K+ in the haemolymph remain relatively constant during the moulting cycle. Desiccation, desiccation followed by rehydration and starvation exert little or no effect on the concentrations of Na+ and K+ in the haemolymph. The volume of haemolymph decreases during desiccation and increases after rehydration. More Na+ is voided in the excreta during desiccation. Repeated desiccation and rehydration causes the loss of both Na+ and K+ from the body. The effects of desiccation and rehydration on the concentrations of chlorides and free amino acids in the haemolymph are described.
The Extracellular Space of A Simple Molluscan Nervous System and Its Permeability to Potassium
Authors: Mirolli M. , Gorman A. L. F.
Published: April 2021

The movement of ions through the extracellular space in the tissues surrounding the giant neuron (G cell) of the nudibranch mollusc, Anisodoris nobilis, was studied with anatomical and physiological techniques. The diffusion pathways in the gastro-oesophageal ganglion and nerve were identified anatomically in electron micrographs obtained from preparations which were first incubated in sea water containing lanthanum chloride and subsequently fixed in a basic solution of glutaraldehyde. A lanthanum precipitate was found extracellularly in the connective sheath, in the extracellular clefts between the glial cells and in the space between the glia and the G cell. The rate of diffusion of potassium was estimated from the rate of change of the G cell membrane potential following a change in the potassium concentration of the artificial sea water bathing the preparation. The average half-time for diffusion corresponds to an equivalent diffusion pathway of about 200 μ m. This value is sufficiently close to the average length (70–95 μ m) of the pathways identified with lanthanum to suggest that the restriction to diffusion is minor. The permeability of the extracellular space to potassium is high (5· 7× 10−1 cm/sec), and our calculations show that a difference larger than 2 mM, between the potassium concentration of the external solution and that of the fluid layer adjacent to the G cell membrane, cannot be maintained under most conditions.
Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni
Authors: Kaufman W. R. , Phillips J. E.
Published: April 2021

Of the total meal imbibed by female Dermacentor andersoni during the normal adult feeding cycle, about 80% is excreted. Of the total water excreted by the tick, 75 % is removed by salivation, less than 3 % is evaporated from the integument and spiracles, and the remainder is lost via the anus. Of the total excreted sodium and potassium, 4 and 82 % respectively are lost via the anus. The remainder in each case is presumed excreted via the salivary glands. The ionic and osmotic concentrations of the haemolymph and saliva stabilize at constant values by the third or fourth day of feeding. The volume of extracellular fluid is constantly maintained at 23 % of the body weight, even though the total body weight increases 75 times over the unfed weight, and the volume of excreted fluid passing through the haemolymph is about ten times the haemolymph volume at repletion.
Ion and Water Balance in the Ixodid Tick Dermacentor Andersoni
Authors: Kaufman W. R. , Phillips J. E.
Published: April 2021

The salivary gland of the ixodid tick, Dermacentor andersoni, can be induced to secrete fluid for at least 6 h when bathed in an artificial medium in vitro. Fluid secretion appears to be a consequence of active Cl secretion since (a) it is inhibited by 95 % when nitrate and by 100% when acetate replaces Cl in the bathing medium ; however, bromide can support secretion as well as Cl, (b) the rates of fluid and Cl secretion are linearly related to the concentration of Cl in the medium; and (c) the S/H ratio for Cl is greater than unity at all concentrations despite a transacinar P.D. of 35 mV (lumen negative). Although (in the presence of Na) a low concentration of K in the bathing medium stimulates the rate of fluid secretion fivefold, higher concentrations of K inhibit fluid secretion. The latter is largely due to a direct effect of K ion and not simply to increased osmotic pressure or reduced Na concentration. Fluid secretion is completely inhibited by 10−6 M ouabain. On the basis of these observations we propose that fluid secretion may be dependent on a Na-K activated ‘pump ATPase ‘, which is somehow involved in cation secretion. The S/H ratios of Na and K are greater than unity at all medium concentrations. The saliva secreted in vitro is slightly hypo-osmotic to the bathing medium over a wide range of medium concentration (300–920 mOsm/1). We postulate that the primary saliva is iso- or hyper-osmotic to the bathing medium; the final elaborated saliva is probably rendered hypo-osmotic by a process of solute reabsorption somewhere between the acini and the orifice of the main salivary duct.
Motor Control of Tail Spine Rotation of the Horseshoe Crab, Limulus Polyphemus
Authors: Silvey Gerald E.
Published: April 2021

Limulus polyphemus (L.), the horseshoe crab, rotates its tail spine in order to right tself and to keep itself balanced. Eight muscles, discrete bundles of muscle fibres, move the tail spine. Fibres of the muscles contract in sequence and thereby pull consecutively on the several tendons of each muscle in order to rotate the tail spine in either a clockwise or counterclockwise direction. Motoneurones in nerves to different muscles, fibres within a muscle and units in a nerve to a single muscle fire in different sequences during clockwise and counterclockwise rotation of the tail spine. The firing pattern consists of a major burst of small to large neurons which fire in clusters, and a minor burst of small neurones which appear to fire randomly. Motoneurones in both bursts are excitatory. The major burst develops tension, the minor burst acts during extension of the muscle and presumably impedes relaxation in order to produce stable deflexion and smooth rotation of the tail spine. Muscle fibres respond to motor output with small excitatory junctional potentials of < 5 mV. E.j.p.s sum and show facilitation, and in some cases develop spike-like potentials of 10–20 mV. Both spiking and the greatest increase in tension occur during the clustered firings in major bursts. Muscle fibres have sarcomere lengths of 6·5 ± 0·8 –m and diameters of 10–60 –m. Nerve fibres range from less than 3 to 32 μm in diameter in large nerve branches which contain between 50 and 100 fibres. These findings indicate that two different motor programs evoke contraction of muscle fibres in opposite sequences. Sequential contraction of fibres within a muscle means that muscle fibres which are activated together, rather than whole muscles, are the functional contractile entities.
Sodium Extrusion by A Fish Acclimated to Sea Water: Physiological and Biochemical Description OF A Na-For-K Exchange System
Authors: Evans David H. , Mallery Charles H. , Kravitz Larry
Published: April 2021

The effect of external potassium ions on the extrusion of sodium ions by the seawater-acclimated fat sleeper, Dormitator maculatus, was investigated. Removal of external potassium ions reduced the efflux of sodium from the fish by 22% while addition of io-4 M ouabain reduced the efflux of sodium ions by 14%. Addition of potassium ions to distilled-water baths into which fish were rapidly transferred stimulated sodium extrusion in a manner which could be described by the Michaelis-Menten equation. The Km of this potassium-stimulated sodium efflux was approximately 2 mm-K/1. The calculated rate of sodium extrusion was 10 times the oral ingestion of sodium ions. Biochemical assays of the levels of the enzyme Na-K-activated ATPase extracted from gill tissue determined that seawater-acclimated fish had 3 times the enzymic activity that fish acclimated to freshwater had. In vitro potassium stimulation of the extracted Na-K-activated ATPase showed Michaelis-Menten kinetics with a Km of approximately 2 mm-K/1. It is concluded that the extrusion of sodium ions by Dormitator maculatus acclimated to sea water is coupled with potassium uptake and is mediated by the enzyme Na-K-activated ATPase.