bluuebunny/crossref_metadata_2025_split huggingface dataset:
Regulation of Water and Some Ions in Gammarids (Amphipoda)
Authors: Sutcliffe D. W. 
Published: April 2021

ABSTRACT
A comparison was made of the body water contents and the concentrations of sodium, potassium and chloride in the blood and body water of Gammarus zaddachi, G. locusta and Marinogammarus finmarchicus. G. zaddachi had a slightly higher body water content than G. locusta and M. finmarchicus. In all three species the blood chloride concentration was lower than the external chloride concentration in 80–113 % sea water, but the blood sodium concentration was equal to or slightly above the sodium concentration in the external medium. The total body sodium concentration was always greater than the total body chloride concentration. In M. finmarchicus the ratio of body sodium/chloride increased rom 1·2 to 1·3 over the salinity range 100–20% sea water. In G. zaddachi the ratio of body sodium/chloride increased from 1·08 at 100% sea water to 1–87 in 0·25 mM/L NaCl. The total body potassium concentration remained constant. The potassium loss rate and the balance concentration were relatively high in G. zaddachi. The porportion of body water in the blood space was calculated from the assumption that a Donnan equilibrium exists between chloride and potassium ions in the extracellular blood space and the intracellular space. In G. zaddachi the blood space was equivalent to 60% body H2O at 100% sea water, and equivalent to 50% body H2O at 40% sea water down to 0·5 mM/l NaCl. In M. finmarchicus the blood space was equivalent to 38–44% body H2O at salinities of 20–100% sea water. The mean intracellular concentrations of sodium, potassium and chloride were also calculated. It was concluded that for each ion its intracellular concentration is much the same in the four euryhaline gammarids. The intracellular chloride concentration is roughly proportional to the blood chloride concentration. The intracellular sodium concentration is regulated in the face of large changes in the blood sodium concentration.
Oxygen Tension Distribution in Water and Blood at the Secondary Lamella of the Dogfish Gill
Authors: Hughes G. M. , Hills B. A. 
Published: April 2021

ABSTRACT
An analysis is given which makes it possible to trace out the changes in oxygen tensions in the blood and water during their passage along a secondary lamella of the dogfish gill. The analysis depends on a knowledge of the oxygen-dissociation curve of the blood, the shape of the secondary lamella and the oxygen tensions of the two media before and after their passage through the gills. It indicates the differences to be expected according to whether the flows are co-current or counter-current. The method, with modifications, could be applied to the gills of all fishes.
Water Relations in an Insect, Thermobia Domestica
Authors: Okasha A. Y. K. 
Published: April 2021

ABSTRACT
Water uptake is not inhibited by centrifugation, exposure to 45 °C, burning of the integument or by submergence in water for 1 h. Repeated desiccation followed by rehydration does not inhibit water uptake. This, however, results in insects with an extremely high water content. Starvation also results in insects with a very high water content, the latter depending on the length of starvation, and also results in the depletion of dry matter. Desiccation followed by rehydration does not result in any loss in dry matter additional to that caused by starvation. The ability to rehydrate of insects desiccated at various stages of the moulting cycle is described. It is concluded that at the later stages of the moulting cycle water uptake ceases. The results are discussed in the light of current theories of the uptake mechanism. It is suggested that the uptake mechanism is primarily concerned with volume regulation. It is also suggested that anal blockage, which is known to arrest uptake, results in a nervous inhibition bringing about such an effect, rather than the rectum being the site of uptake."
The Swimming Energetics of Trout
Authors: Webb P. W. 
Published: April 2021

ABSTRACT
The oxygen consumption of rainbow trout was measured at a variety of sub fatigue swimming speeds, at a temperature of 15 °C. Five groups of fish were used, a control group and four groups with extra drag loads attached to the body. The logarithm of oxygen consumption was linearly related to swimming speed in all five groups, the slope of the relationship increasing with the size of the extra drag load. The mean standard rate of oxygen consumption was 72·5 mg O2/kg wet weight/h. The active rate of oxygen consumption was highest for the control group(628 mg O2/kg/h) and fell with increasing size of the attached drag load. The active rate for the control group was high in comparison with other salmonid fish, and in comparison with the value expected for the fish. This was not a result of the extra drag loads in the other groups. No explanation for this high value can be found. The critical swimming speed for a 60 min test period was 58·1 cm/sec (2·0 body lengths/sec) for the control group. The values for the critical swimming speeds were slightly higher than those measured for the same species in a previous paper (Webb, 1971). The difference between the two sets of critical swimming speeds is attributed to seasonal changes in swimming performance. The aerobic efficiency was found to reach values of 14·5–15·5% based on the energy released by aerobic metabolism in comparison with the calculated required thrust. The anaerobic contribution to the total energy budget in increasing-velocity tests is considered to be small, and can be neglected. It is concluded that the efficiency of the muscle system in cruising will be approximately 17–20% over the upper 80% of the cruising-speed range, while the caudal propeller efficiency will increase from about 15–75 % over same range. Consideration of the efficiency values for the caudal propeller calculated here, and those predicted by Lighthill’s (1969) model of fish propulsion, suggest that the efficiency of the propeller system will reach an optimum value at the maximum cruising speeds of most fish, and will remain close to this value at spring speeds.
Electrical Activity in the Optic Tectum and Colour Change in the Minnow (Phoxinus Phoxinus L.) *
Authors: Gentle Michael J. 
Published: April 2021

ABSTRACT
The electrical activity of the optic tectum was recorded from the minnow under various conditions to investigate its relationship to colour change. The superficial E.E.G. was found to consist of two rhythms a 6–14 Hz (20–112 V) and a 18–24 Hz (6–18 μV). When the fish were deeply anaesthetized the E.E.G. was reduced virtually to nothing. Almost no activity was present in the optic tectum 30 min after bilateral blinding. There was an increase in activity after 5 h and this continued for 5 or more days but never returned to normal. In darkness the activity of the superficial E.E.G. first increased and then decreased, and when the eyes were re-exposed to light the activity increased again. The E.E.G. patterns were recorded and analysed from various depths and positions in the optic tectum during background reversal. In the stratum plexiforme et fibrosum externum, plexiforme internum and griseum internum no changes were observed. In the stratum fibrosum profundum and griseum periventriculare an increase in the high-frequency activity of approximately 10 Hz was observed on a black background.
The Neuronal Basis of A Sensory Analyser, The Acridid Movement Detector System. I. Effects of Simple Incremental and Decremental Stimuli in Light and Dark Adapted Animals
Authors: Rowell C. H. Fraser , O’shea Michael 
Published: April 2021

ABSTRACT
The response of the movement detector (MD) system to proportionally constant incremental and decremental stimuli has been studied at various degrees of light and dark adaptation. Action potentials in the descending contralateral movement detector neurone were taken as the indicator of response. Over a range of at least six log10 units of adapting luminance, the MD system behaves as an on/off unit, giving responses to both incremental and decremental changes in the illumination of a 5° target. With increasing amplitudes of stimuli, both the on and off responses saturate rapidly. Saturation is reached sooner at higher levels of light adaptation. At all levels of light adaptation, the off response is greater than the on. The ratio for saturating stimuli is approximately constant at around 3:2. At the brightest adapting luminances used (20000 cd/m2) the on response is reduced but not lost. At the lowest (0·004 cd/m2) the off response to a 5° disc fails, but can be regained by increasing the test area to 10°. From what is known of the retina of locusts and other insects, it is thought that light and dark adaptation in the MD system can be adequately explained by events at the retinula cell.
The Neuronal Basis of A Sensory Analyser, The Acridid Movement Detector System. II. Response Decrement, Convergence, and the Nature of the Excitatory Afferents to the Fan-Like Dendrites of the Lgmd
Authors: O’shea Michael , Rowell C. H. Fraser 
Published: April 2021

ABSTRACT
No dendritic spikes occur in the input fan of the lobular giant movement detector (LGMD) neurone. The action potentials are initiated at the point of thickening of the axon, which therefore represents the site of convergence of the retinotopic projection in the MD system. Previous work has shown that the site of decrement in response to repetitive visual stimulation is distal to this point. No change in spiking threshold in the LGMD could be demonstrated, and decrement in the number of LGMD action potentials is completely explained by the observed decrement of EPSPs recorded in the LGMD input dendritic fan. Possible postsynaptic mechanisms which might affect EPSP amplitude are excluded experimentally or shown to be improbable. Latency measurements during electrical stimulation in the second chiasma (which produces a decrementing EPSP in the fan) indicate that the pathway from the chiasma afferents to the LGMD fan is probably monosynaptic. By exclusion, the site of decrement appears to be located at the presynaptic terminal of that synapse. Generalization of habituation of the response to ON and OFF stimuli is demonstrated, showing that the presynaptic neurone at the labile synapse is an ON/OFF unit. The greater part of the previously described sensitivity gradient on the retina, relative to the MD response, appears to be explicable by the geometry of the LGMD fan and of the retinotopic projection. We conclude that the LGMD is fed by a homogeneous population of ON/OFF units running in the second optic chiasma, which form labile synapses on the input fan.
Active Transport of Calcium Across the Isolated Midgut of Hyalophora Cecropia
Authors: Wood John L. , Harvey William R. 
Published: April 2021

ABSTRACT
The net flux of 45Ca from lumen to blood side across the isolated and short-circuited Cecropia midgut was 1·9 ± 0·2 μequiv. cm−2 h−1 in 8 mm Ca and the flux ratio was as high as 56 to 1. The calcium influx was depressed by anoxia; 73 % after 30 min. The kinetics of Ca transport were anomalous; the apparent Km varied with Ca concentration from &lt; 0·2 to &gt; 5·6 mm Ca and the apparent Vmax varied from &lt; 1·3 to &gt; 3·3 μequiv. cm−2 h−1. The calcium influx showed a delay before the tracer steady state was attained, indicating the existence in the transport route of a calcium pool equivalent to 5·7 μequiv/g. wet weight of midgut tissue. High calcium (16 mm) depressed the short-circuit current and potassium transport from blood to lumen side across the midgut. Calcium depressed magnesium transport, from lumen to blood side across the midgut, and magnesium depressed the calcium transport. Ca transport by the midgut does not regulate the Ca level in the haemolymph in vivo; it merely aids the diffusion of calcium down its electrochemical gradient. However, Ca transport may assist the uptake of the nutrients from the midgut contents.
Importance of Air and Water Breathing in Relation to Size of the African Lungfish Protopterus Amphibius Peters*
Authors: Johansen K. , Lomholt J. P. , Maloiy G. M. O. 
Published: April 2021

ABSTRACT
Oxygen uptakes from air and water have been measured in relation to weight of the African lungfish Protopterus amphibius Peters. Combined O2 uptake from air and water ranged from 60 ml O2 kg−1 h−1 STPD, in a 3·7 g specimen, to 30 ml O2kg−1 h−1, in a 255 g specimen. While the combined O2 uptake changed by a factor of 2, within the weight range under study, the aquatic O2 uptake changed 8-fold within the same range. The smaller fish satisfy 70% of their O2 requirement by aquatic breathing compared to 10–15% in the grown specimens. The pattern of bimodal breathing in P. amphibius is discussed in relation to the natural habitat of the species.
Possible Involvement of Monoamines in the Release of Adipokinetic Hormone in the Locust Schistocerca Gregaria
Authors: Samaranayaka Manthri 
Published: April 2021

ABSTRACT
The adipokinetic hormone release, which can be induced by anticholinesterases, is reduced by depleting the content of monoamines in the nervous system. The participation of monoamines in the pathway of release of adipokinetic hormone is studied in vivo and in vitro. A possible mechanism for anticholinesterase-induced release of this hormone involving cholinergic and aminergic transmission is postulated.
Interactions of Membrane Potential and Cations in Regulation of Ciliary Activity in Paramecium
Authors: Machemer Hans 
Published: April 2021

ABSTRACT
Ciliary activity in Paramecium was investigated in different external solutions using techniques of voltage clamp and high frequency cinematography.
An increase in the external concentration of K, Ca or Mg ions decreased the resting potential. It had no effect on ciliary activity.
When the membrane potential was fixed, an increase in external Ca or Mg and, to a lesser extent, an increase in K concentration, raised the frequency of normal beating or decreased the frequency of reversed beating of the cilia. Similar effects resulted from membrane hyperpolarization with constant ionic conditions.
Increase in concentration of Ca, but not of Mg or K, enhanced hyperpolarization-induced augmentation of ciliary frequency. Increase in Ca concentration also specifically augmented the delayed increase in inward current during rapid hyperpolarizing clamp.
The results support the view that [Ca]i regulates the frequency and direction of ciliary beating. It is suggested that the insensitivity of the ciliary motor system to elevations of the external concentrations of ions results from compensation of their effects on [Ca]i. Depolarization itself appears to increase [Ca]i while elevation of the external ion concentrations at a fixed membrane potential appears to decrease [Ca]i.
Aerodynamics of Hovering Flight in the Long-Eared Bat Plecotus Auritus
Authors: Norberg U. M. 
Published: April 2021

ABSTRACT
Steady-state aerodynamic and momentum theories were used for calculations of the lift and drag coefficients of Plecotus auritus in hovering flight. The lift coefficient obtained varies between 3·1 and 6·4, and the drag coefficient between –5·0 and 10·5, for the possible assumptions regarding the effective angles of attack during the upstroke. This demonstrates that hovering flight in Plecotus auritus can not be explained by quasi-steadystate aerodynamics. Thus, non-steady-state aerodynamics must prevail.
Magnetic Fields and the Orientation of Homing Pigeons Under Sun
Authors: Walcott Charles 
Published: April 2021

ABSTRACT
Applying a magnetic field of 0.1 Gs (1 gauss = 10−4T) to the heads of pigeons homing from unfamiliar release sites significantly increased the scatter of the birds’ vanishing bearings. A magnetic field of 0-3 gauss caused no difference between the orientation of birds wearing coils with either their north or south pole up. But a field of 0.6 gauss (equal to that of the Earth) produced a small difference in the vanishing bearings of the two groups. Since an applied magnetic field has an effect on pigeon orientation under sun, it appears that pigeons do not simply switch between a magnetic and a sun compass, but that there is some interaction between the two systems.
Circadian Rhythm of Output From Neurones in the Eye of Aplysia
Authors: Benson Jack A. , Jacklet Jon W. 
Published: April 2021

ABSTRACT
The circadian rhythm of CAP frequency recorded from the optic nerve of isolated eyes at 15 °C was damped out by constant illumination (1100 lux) after several cycles of the rhythm. During illumination (LL) the rhythm was skewed with a rapid rising phase and slow falling phase, and the period was decreased by about 1 h. It is postulated that the circadian clock was stopped by LL at its lowest phase point, and that following cessation of LL, the rhythm was reinitiated from this phase point after a latency of 6-8 h. For light pulses of 80 lux and 1100 lux, the photoresponse of the dark-adapted eye to 20 min light pulses applied beginning at 2 h intervals was not influenced by the circadian clock. At 5 lux there was a periodicity in the magnitude of the photoresponse, in phase with the circadian rhythm of spontaneous CAP production. Small CAPs of non-circadian frequency were recorded together with normal CAPs in about 10% of records of output from isolated eyes. The cells producing the small CAPs had a different temperature sensitivity from those producing normal CAPs. The response of these cells to short light pulses consisted of a phasic burst of activity at light onset, followed by silence during the remainder of the short light pulse, and for 1 or 2 min following cessation of illumination. These small CAPs may be the activity either of H-type receptors or of secondary cells desynchronized from the major population.
Salt and Water Balance of the Spiny Lobster, Panulirus Argus: the Role of the Antennal Glands
Authors: Malley D. F. 
Published: April 2021

ABSTRACT
Panulirus argus in full sea water differs from most other marine isosmotic decapods by regulating Cl− levels in the haemolymph slightly below those in sea water and by having haemolymph K+ levels similar to those in sea water. The species is typical in regulating haemolymph Na+ and Ca2+ above, and Mg2+ and SO42− below, sea-water levels of these ions. Its haemolymph Mg24−and SO42− concentrations are amongst the lowest reported in marine decapods. The antennal glands contribute to this regulation of Mg24− SO42− and Cl− by producing urine with markedly, and approximately equally, elevated Mg24− and SO42− levels, and slightly elevated Cl−levels, compared with those in the haemolymph. The antennal glands show a small tendency to conserve water.
Saltatory Movements of Organelles in Intact Nerves of Rhodnius Prolixus Stål
Authors: Heslop J. P. , Howes E. A. 
Published: April 2021

ABSTRACT
Abdominal nerves of Rhodnius prolixus were studied with the light microscope under high-power Nomarski optics with a minimum of surgical interference. The preparation was perfused with bathing solutions which could be changed during time-lapse cinematography. The structure of the nerve trunks was studied by light and electron microscopy. The movements of intracellular organelles are described and discussed. Saltatory movements of organelles, probably mitochondria, were followed at different temperatures. Rate of saltation varied linearly with temperature. Axonal flow (bulk movement of cytoplasm) did not occur in healthy abdominal nerves.
Ionic Requirements For Non-Synaptic Electrogenesis in the Muscle Fibres of A Lepidopterous Insect
Authors: Yamamoto Daisuke , Fukami Jun-Ichi 
Published: April 2021

ABSTRACT
Study was made of the influence of external sodium, calcium and magnesium concentrations on the directly elicited response of the segmental muscle fibres of the larva of Galleria mellonella, as recorded with intracellular microelectrodes. The graded response caused by an outward current pulse was converted into an all-or-none spike in the presence of 10 mM tetraethylammonium. The amplitude of these spikes increased with increasing external Ca concentration but not with increasing Na or Mg concentration. The spikes were not influenced by tetrodotoxin (3 × 10−5 M) but were suppressed by Mn ions (20 mM). After replacement of TEA-containing saline with an isotonic CaCl2 solution, spikes were still produced in the latter. It appears that only calcium ions act as charge carriers of inward current at the non-synaptic membrane.
The Neuronal Control of Dragonfly Flight
Authors: Simmons Peter 
Published: April 2021

ABSTRACT

The neuronal control of flight in dragonflies has been investigated by making intracellular recordings from identified motor neurones, singly and in pairs, in tethered flying and non-flying animals.
It is concluded that, as in the locust, populations of interneurones generate the flight rhythm and drive motor neurones. The diversity of motor neurone activity in dragonflies is presumably related to their well-known aerial manoeuvres.
Asymmetric Waveforms in Echinoderm Sperm Flagella
Authors: Goldstein Stuart F. 
Published: April 2021

ABSTRACT
Dark-field, multiple-exposure photographs of live spermatozoa of a number of echinoderms were analysed. Bends develop at the base in pairs, as they do in flagella with symmetrical waveforms. However, the angles of these bends do not cancel, so that microtubular sliding – of up to over 50 % of that associated with bend propagation – is transferred distally. This sliding implies that (a) microtubules are not rigidly cross-linked within straight regions, and (b) bends can propagate normally in spite of appreciable extrinsic microtubular sliding. Both the sperm head and the asymmetry of the waveform appear to affect the swim path of a spermatozoon.
CO2-Inhibition of the Amplitude of Bending of Triton-Demembranated Sea Urchin Sperm Flagella
Authors: Brokaw C. J. 
Published: April 2021

ABSTRACT
Demembranated sea urchin spermatozoa were reactivated in solutions containing KHCO3 and observed in a covered well slide. Although KHCO3 itself causes a small inhibition of flagellar beat frequency, the results confirm previous observations of a direct inhibition of flagellar bend angle by CO2 with no effect of CO2 on frequency.
Observation of the effect of pH on the inhibition of bend angle in solutions containing KHCO3 indicates that a given concentration of OH− has a similar effect to the same concentration of HCO3−, as would be expected if CO2-inhibition results from reaction of CO2 with protein-NH3+ groups to form carbamates.
CO2 may interfere with a control mechanism which selectively suppresses dynein cross-bridge activity in order to generate rhythmic bending. This control mechanism may incorporate a feedback control involving a measure of flagellar amplitude, which fails to operate successfully when the amplitude is reduced below a critical level.