bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pulsatile Pressures in the Cranial Fluids of Heterodontus Portusjacksoni
Authors: Satchell G. H. , Rossiter G. T. 
Published: April 2021

ABSTRACT
It has been shown in mammals (Hamilton, Woodbury & Harper, 1936, 1944) that dilation of the craniospinal blood vessels by the pressure pulses caused by straining and coughing is largely prevented by the direct communication of the raised intra-thoracic pressure to the cerebrospinal fluid (CSF). The pathways through which pressure is communicated include the loose areolar tissue around the spinal nerves, and the venous blood in the paravertebral plexuses which communicate with the large veins at the back of the thorax and abdomen. McIntosh, Estes & Warren (1956) have shown by means of myelograms that as the intrathoracic pressure rises, the spinal nerves move medially and the subarachnoid space narrows.
The Port Jackson shark, Heterodontus portusjacksoni exhibits spontaneous, rhythmic, and evoked coughing during which the pharynx is contracted and water is forced from the mouth and gill slits (Satchell & Maddalena, 1972). During an evoked cough water pressure in the pharynx may exceed 70 cm H2O ; this is more than thirty times that of normal respiration. Some preliminary observations indicated that here too the rise of pressure in the pharynx is communicated via the dorsal aorta to the craniospinal vessels, and, by some more direct route to the fluid surrounding the brain. The totally different anatomy of the respiratory system of a fish compared with that of a mammal suggested that the phenomenon required investigation.
Statocyst-Induced Eye Movements in the CrabScylla Serrata
Authors: Sandeman D. C. , Okajima A. 
Published: April 2021

ABSTRACTIrrigation of the statocysts of the crab Scylla serrata will activate the oculomotor neurones associated with eye movements. An investigation of the central mechanism of statocyst-induced nystagmus has been started with the description of the statocyst canals and a characterization of the sensory input from the hair receptors in the canals. The canals are shaped like two toroids joined at approximately right angles to one another. Direct observation of isolated statoliths and glass models of them shows that when they are rotated, fluid moves around the circumference of the statocyst canals and displaces the hair receptors protruding into them. The direction of displacement of the different groups of receptors in both statocysts is related to the axes of rotation and provides a unique output for rotation about each axis. Electrical recordings from the three types of receptor hairs show that the thread hairs are most probably the receptors responsible for detection of rotation about the vertical axis. The free hook hairs are sensitive enough to detect rotation about the horizontal axes. The statolith hairs are sensitive to maintained changes of position.
Osmotic and Ionic Regulation in A Terrestrial Snail, Pomatias Elegans (Gastropoda, Prosobranchia) With A Note on Some Tropical Pomatiasidae
Authors: Rumsey T. J. 
Published: April 2021

ABSTRACT
The mechanisms of ionic regulation in terrestrial snails of the subclass Pulmonata have stimulated interest for some time (Duval, 1930; Fischer, 1931; Arvanitaki & Cardot, 1932; Pusswald, 1948; Vorwohl, 1961; Burton, 1966, 1968a, b, 1971); but relatively little work has been done on the terrestrial Prosobranchia. The latter have colonized land either via fresh water (Fam. Cyclophoridae) or by migration from the intertidal zone (Fam. Pomatiasidae). This study involves the latter group, concentrating on the British species Pomatias elegans (Müller).
The Pomatiasidae are restricted to calcareous soils (Kilian, 1951; Avens, 1964; C. Little, personal communication) and P. elegans is only found in damp environments (Kilian, 1951), never being active below a R.H. of 95 % (Meyer, 1925). From the restricted distribution of pomatiasids (Kerney, 1968; Rumsey, 1971) it would be expected that adaptation to the terrestrial habitat is minimal, and that this will be partly reflected in their homeostatic mechanisms.
Properties of the Optokinetic Motor Fibres in the Rock Lobster: Build-Up, Flipback, Afterdischarge and Memory, Shown by Their Firing Patterns
Authors: York B. , Wiersma C. A. G. , Yanagisawa K. 
Published: April 2021

ABSTRACT
The properties of sets of motor fibres responding to both clockwise and anticlockwise rotation have been studied in the oculomotor nerve of the rock lobster. There are probably three, but perhaps four, units in each set. None of these fibres has statocyst input, but there is weak input onto the tonio fibres from the antennal joints such that the eye turns in the direction toward which e antenna points. Many preparations show bilateral visual input onto all fibres but the degree of coupling between the eyes is very variable, and at times can be nearly totally absent. Depending on the speed of rotation the fibres show a gradual build-up in frequency, during rotation in the preferred direction, interrupted by flipbacks. During the fast stage of the resulting nystagmic movements all agonistic fibres can be completely inhibited and all antagonistic ones can be activated, usually for a period of about 0·5 sec. Fibre activity is demonstrated which appears to underlie an ‘optokinetic memory’ of contrasting target position in the visual field. It consists of (a) very prolonged afterdischarges for a stationary striped pattern (b) resumption of discharges at an appropriate frequency after dark periods up to 2 min, and (c) adjustment of such frequencies to changes in stripe position during the dark period. The fibres show habituation to repeated stripe movement but the response can be dishabituated by passive rotation of the animal. The largest visual responses were obtained to intermediate speeds of stripe rotation (about 2°/sec).
The Ionic Basis of Axonal Conduction in the Central Nervous System of Viviparus Contectus (Millet) (Gastropoda: Prosobranchia)
Authors: Sattelle D. B. 
Published: April 2021

ABSTRACT
The compound action potential recorded from the pleural-supraintestinal connective of Viviparus contectus consists of a large, slow component with an average conduction velocity of about 0·02 m/sec (at 23 °C) and a faster component with a conduction velocity of 0·10 m/sec (at 23 °C) for the fastest fibres. Both fast and slow action potentials are rapidly abolished by the substitution of tris chloride and choline chloride for the sodium salts of normal Ringer. Tetrodotoxin, applied at 10−5 M rapidly abolishes action potentials in all fibres. It is, therefore, concluded that a largely sodium-dependent mechanism of spike generation operates in all axons of the connective. Lithium ions effectively substitute for sodium ions in maintaining the fast action potentials for extended periods, whereas tetraethylammonium ions do not. When the calcium chloride of normal Ringer is replaced by sucrose, magnesium chloride or barium chloride, conduction of fast action potentials is maintained. A small increase in the sensitivity of all axons to tetrodotoxin is observed in calcium-free Ringer ; a slight reduction in the spike amplitude of fast action potentials follows the application of manganous ions at 5 mM/1 in normal Ringer. It is concluded that any possible contribution of calcium to the generation of the action current of the fast action potential is very small compared to that of sodium. All axons of the connective function for extended periods in sodium-free (dextran) Ringer. Under these conditions, tetrodotoxin blocks conduction in all fibres at concentrations of 10−6 M, suggesting that function in dextran Ringer is maintained by a sodium-dependent mechanism.
The Osmoregulatory System of the Amoeba, Acanthamoeba Castellanii
Authors: Pal R. A. 
Published: April 2021

ABSTRACT
It is estimated that Acanthamoeba castellanii eliminates a volume of water equal to its body volume in about 15–30 min. About 7% of the vacuolar discharge enters the body by means other than osmosis through the surface membrane. Food vacuoles fusing with the contractile vacuole do not significantly affect the rate of output. Vacuolar output declines with the age of culture so that during the stationary phase of growth it is about half of that during early log phase of growth. The rate of output of the contractile vacuole decreases with an increase of concentration of a non-penetrating solute in the external medium and shows a rectilinear relationship up to 0·07 M concentration. A low residual output after 0·07 M may be due to food vacuoles and pinocytic vacuoles. On the basis of vacuolar output the excess internal osmotic pressure and permeability constant of water has been estimated as 0·07 M non-electrolyte and 0·04 μm min−1 atm. −1 respectively. On the basis of vacuolar behaviour it is concluded that the relative permeabilities of the plasma membrane to different solutes follows this order: methyl alcohol &gt; ethylene glycol &gt; urea &gt; glycerol. On certain assumptions the permeability of the plasma membrane to ethylene glycol has been estimated provisionally as 0·107 × 10−16 mol/sec//im2/mol/l. Vacuolar behaviour suggests that sodium chloride, sodium nitrate, sodium sulphate and potassium chloride, but not magnesium chloride and calcium chloride, pass into the cell freely. Growth of populations of A. castellanii is almost normal in polyethylene glycol 600 up to 0·07 M concentration but in higher concentrations it is low. There are some indications of an increase in volume of A. castellanii in cultures of polyethylene glycol 600 up to 0·07 M concentration, but not in higher concentrations. For amoebae cultured in media containing polyethylene glycol 600 the rate of output of the contractile vacuole declines sharply with an increase of polyethylene glycol 600 up to 0·07 M concentration and then more gradually.
Inhibition of Spontaneous Lateral-Line Activity by Efferent Nerve Stimulation
Authors: Russell I. J. , Roberts B. L. 
Published: April 2021

ABSTRACT
Efferent nerve fibres innervating the lateral-line sense organs of the dogfish Scyliorhinus were stimulated with trains of stimuli while spontaneous afferent activity was monitored. Significant changes in spontaneous impulse frequency could be produced when the efferent nerves were stimulated by trains of pulses at frequencies between 20–100 sec−1; lower stimulus frequencies had no visible effect. The impulse frequency decreased or was totally inhibited during the stimulus period and for 150–200 msec following it. The inhibitory effect was very variable and declined with repetitive stimulation. Stimulation of the efferent nerves to inactive afferent units was followed after 500 msec by a brief low-frequency discharge.
The Locomotor Activity Rhythm of Talitrus Saltator (Montagu) (Crustacea, Amphipoda)
Authors: Bregazzi P. K. , Naylor E. 
Published: April 2021

ABSTRACT
Talitrus saltator possesses a clear-cut locomotor activity rhythm, largely under the control of a persistent endogenous timing mechanism of circadian frequency. In dim red illumination the period of the rhythm is somewhat greater than 24 b; in continuous white fight it is less than 24 h, provided that the animals are unable to avoid the light by burrowing. The rhythm is synchronized by light/dark fluctuations, and the animal is active during the dark period. The timing mechanism is temporarily advanced by increases in temperature, but otherwise it possesses a large measure of temperature independence within the normal environmental range. There is some evidence that, in groups, the animals influence one another and so reduce the rate of drift of the activity rhythm in constant conditions. The adaptive significance of the endogenous timing mechanism of Talitrus is discussed.
The Relationship between Cardiac and Respiratory Rhythms in the Dogfish, Scyliorhinus Canicula L
Authors: Hughes G. M. 
Published: April 2021

ABSTRACT
Recordings were made over long periods of the ECG and pressure changes in the orobranchial (OB) cavity of unanaesthetized dogfish, kept in a closed circulation of aerated and temperature controlled sea water. Variations in cardiac frequency (11–64/min) and in ventilatory frequency (22–80/min) were observed between individuals of similar body size. Similar variations were observed in non-experimental fish kept in holding tanks. Analysis of tape-recordings using a Biomac computer was made for interval histograms and showed a greater variability of the ECG interval than of the OB pressure, but not at all times. The relationship between the two rhythms was further investigated using event correlograms showing the position of the ECG in an averaged ventilation cycle, which was divided into ten equal phases. In many fish the heart tended to beat in a particular phase, at least for short periods, but in some cases this was never observed. Given individuals also varied in the preferred phase. Complete synchrony was rarely observed, most fish showing evidence of varying degress of coupling between the rhythms. Analysis of this incomplete synchrony was carried out using polar co-ordinates which showed that in 60% of the recordings analysed there was some significant (1 % level) coupling between the rhythms. The phase angle varied considerably and was most commonly between o° and i8o°, i.e. during the first half of the cycle following the maximum positive OB pressure. It is concluded that further understanding of the relationship between these rhythms requires more detailed knowledge of flow patterns of blood and water across the secondary lamellae.
Cuticular Water Content and the Rate of Evaporation in the Terrestrial Isopod Porcellio Scaber Latr
Authors: Salminen Inga , Lindqvist Ossi V. 
Published: April 2021

ABSTRACT
The free-water content of the cuticle of the isopod Porcellio scaber Latr. was measured after treatments which are known to affect the total rates of water loss from the animal. The animals were desiccated for various periods of time in dry air, after which the cuticular samples were taken. After antennectomy, which is known to reduce the evaporation rate in dry air, the water content of the cuticle remains steady but at a higher level than that of normal animals. The mean cuticular water contents 24 h after operation were 54·0 ± 0·80% and 50·6 ±0·88% (P &lt; 0·01) respectively for desiccated animals. The water content of the cuticle of non-desiccated animals was not altered by this treatment; the differences show up only after desiccation. Both hydration and removal of a pair of legs can result in an increased rate of evaporation; during desiccation the cuticular water content decreases with increasing desiccation. The slope of the regression curve for both hydrated and leg-amputated animals differs significantly from both the zero slope as well as from the control curve. A tentative model for the water permeability characteristics of the cuticle of Porcellio is presented to explain the above data.
Electrophysiology of the Heart of An Isopod Crustacean: Porcellio Dilatatus
Authors: Delaleu J. C. , Blondeau A. , Holley A. 
Published: April 2021

ABSTRACT
The effects of various ions and chemicals were tested on the resting or active membrane of the heart of the wood-louse Porcellio dilatatus. The curve relating the resting membrane potential to log [K+]0 was found to correspond with the theoretical curve expected from the Nernst equation at higher concentrations only. Excess K+ decreased both amplitude and rate of rise of the response while the rate of decline was increased. In K+-deficient solutions the duration of the plateau phase was at first increased, then depressed. The addition of K+ to a bathing medium deprived for several minutes of this ion caused a large increase in the membrane potential and in the response height. The way in which the membrane was seen to react was tentatively attributed to an electrogenic active pumping mechanism. In Na+-deficient solutions, the rate of rise and the height of the response were reduced while the resting membrane potential was decreased. Ca2+-deficient solutions depolarized the membrane and decreased both amplitude and duration of the response. Cessation of activity occurred in Ca2+-free solution. In excess calcium the membrane was hyperpolarized. The rhythm and the rate of rising were decreased and the plateau phase depressed. TTX blocked the heart activity, probably by acting upon the heart ganglion. Mn2+ depressed especially the humped plateau (when present) of the spontaneous responses. TEA, caffeine and procaine transformed spontaneous activity of weak amplitude into large and complex overshooting responses. In TEA solutions, several stable levels of polarization were observed. Contrary to what occurred in the normal solution, depolarizing current pulses could trigger large all-or-none action potentials when TEA was present. The TEA-induced regenerative response was analysed with the help of an intracellular stimulating current when [Na+]0 and [Ca2+]0 were varied. Additional data were obtained by applying TTX, Mn2+ or GABA. From the results, both Ca2+ and Na+ were thought to be involved in the ionic currents underlying spiketype activity. The spike-generating effect of TEA has been attributed to its property of increasing the membrane resistance and of allowing the ionic conductances which generate the weakly active component of the normal response, the plateau, but not the initial upstroke, to be amplified regeneratively. The large spikes elicited by TEA were found relatively less effective than weak sustained depolarization in inducing strong contractions. The functional significance of the data was tentatively interpreted by comparison with the properties of the heart of Limulus, Crustacea and vertebrates.
Photosensitive Neurones in the Marine Pulmonate Mollusc Onchidium Verruculatum
Authors: Hisano Nozomu , Tateda Hideki , Kuwabara Masutaro 
Published: April 2021

ABSTRACT
Giant photosensitive neurones were found in the sub-and supra-oesophageal ganglia of the marine pulmonate mollusc Onchidium verruculatum. Some were photo-excitative neurones; spikes appeared or their frequency increased in response to light stimuli. The others were photo-inhibitive neurones in which disappearance of spikes or decrease in their frequency was noted in response to light. Photosensitive neurones were distinguished according to whether or not they were ‘primary’ neurones, i.e. responded directly to a minute light spot. Three primary neurones and three secondary neurones were detected among the photo-excitative neurones. There were four primary photo-inhibitive neurones. It was not determined whether a neurone was primary or not. An inverse effect of light on one of the primary photo-excitative neurones, ES-I, occasionally occurred after illumination of long duration. A light stimulus which had previously excited the neurone, inhibited subsequent spontaneous discharge. The inhibitory effect of light on one of the primary photo-inhibitive neurones was overcome by some excitatory process during illumination of long duration or after repeated light stimuli.
The Effect of Increased Ambient CO2 On Arterial CO2 Tension, CO2 Content and pH in Rainbow Trout
Authors: Cameron James N. , Randall David J. 
Published: April 2021

ABSTRACT
The effect of exposure of rainbow trout to high and low levels of environmental (water) CO2 tension on blood CO2 and pH was studied. An increase in environmental CO2 caused a rise in the arterial CO2 tension , but the blood-to-water gradient (P1-Pa) remained about the same. Changes in arterial pH were small - about one-third of what would be predicted from the change in if plasma bicarbonate remained constant. There was a corresponding increase in the total CO2 content of the blood which involved an upward shift of the CO2 dissociation curve, and readjustment of the buffering to maintain pH. The results are consistent with the hypothesis that blood CO2 and pH levels are regulated via a chloride-bicarbonate exchange mechanism, rather than by ventilation and diffusive washout of gaseous CO2.
Changes in Chemoreceptor Sensilla on the Maxillary Palps of Locusta Migratoria in Relation to Feeding
Authors: Bernays E. A. , Blaney W. M. , Chapman R. F. 
Published: April 2021

ABSTRACT
The electrical resistance across the tips of the maxillary palps of Locusta migratoria is high immediately after a feed, but falls to a steady level in about 2 h after feeding. Only a small proportion of the individual sensilla on the domes of the palps respond to chemical stimulation immediately after feeding, but this proportion increases with the period of food deprivation. Gentle manipulation of the tips of non-responsive sensilla causes them to respond. It is suggested that the terminal pores of the sensilla can open and close and that the resistance across the tips of the palps varies inversely with the number of open sensilla. The possible significance of the changes is discussed.
On the Interactions Between Suctorial Adhesion, Gill Ventilation and Opercular Spine Erection In Xenocara Occidentalis*
Authors: Gradwell Norman 
Published: April 2021

ABSTRACT
Except for brief swimming from one site of adhesion to another, the oral sucker of Xenocara is constantly used to anchor the fish to the substratum. During adhesion oral inhalation is by rhythmic water flow through special grooves in the sucker wall. Coarse particles entering with the respiratory water elicit a cough-like response which is associated with large positive pressures in the bucco-pharynx and opercular cavities, and with enhancement of suctorial adhesion. Stronger adhesion occurs when the fish responds to tactile stimulation, during which large negative pressures are developed throughout the respiratory system and the opercular spines are thrust outward. In all responses separation of suctorial and respiratory function is facilitated by the action of a muscular oral valve. Precise co-ordination between the inlet valves of the maxillary barbels and the oral and opercular valves is important for efficiency of the suction and force pumps before the gills and the opercular suction pump behind them.
Physiology of Insect Rhythms
Authors: Truman J. W. 
Published: April 2021

ABSTRACT
In insects the development of a rigid exoskeleton requires that for growth and metamorphosis to occur a new cuticle must be periodically formed and the old one cast off. This process (the moult) is initiated with the release of the prothoracicotropic hormone (PTTH) from the brain. Then follows the secretion of a second hormone, ecdysone, by the prothoracic glands, the apolysis of the epidermis from the cuticle, the secretion of a new cuticle, and, finally, the shedding or ecdysis of the old cuticle. The type of cuticle formed is regulated by a third hormone, the juvenile hormone (JH), produced by the corpora allata (see Wigglesworth (1971) and Wyatt (1972) for current reviews of the hormonal control of moulting). Recently, a study of the eclosion of adult silkmoths revealed that the last step in the moulting process is also under endocrine control (Truman & Riddiford, 1970). In this case a neurosecretory hormone from the brain acts on the nervous system to trigger the behaviour involved in emergence (Truman, 1971 ; Truman & Sokolove, 1972).