bluuebunny/crossref_metadata_2025_split huggingface dataset:
Active and Electrogenic Absorption of Na+ and Cl− Across Posterior Gills of Eriocheir Sinensis: Influence of Short-Term Osmotic Variations
Authors: Onken Horst 
Published: April 2021

ABSTRACT
Split lamellae of posterior gills of Chinese crabs (Eriocheir sinensis) acclimated to fresh water were mounted in a modified Ussing-type chamber, and the transepithelial short-circuit current and conductance were measured. The epithelium shows independent active and electrogenic absorption mechanisms for Na+ and Cl− that can be measured as positive and negative short-circuit currents, respectively, in the absence of the counter ion. Increasing the osmolarity of the haemolymph-side saline by addition of sucrose resulted in a marked decrease in active uptake of both Na+ and Cl−. In contrast, increasing the internal osmolarity by addition of urea or moderately decreasing the haemolymph-side osmolarity resulted in a marked increase in Na+ as well as Cl− transport. Circuit analysis revealed that Na+ current changes are mostly due to alterations in the apical amiloride-sensitive Na+ conductance, while Cl− current changes are caused not only by alterations in the transcellular conductance but also by changes in the electromotive force for Cl− absorption. Osmotic perturbations in the external bath induced current changes in the same directions, but the magnitudes of the effects were smaller than those after internal osmotic variations, indicating that the external barrier has a lower water permeability than the internal barrier. Short-term osmotic perturbations did not significantly affect the leak conductance, which is not associated with active transport and which may mostly reflect the paracellular conductance.
Squid (Lolliguncula Brevis) Life in Shallow Waters: Oxygen Limitation of Metabolism and Swimming Performance
Authors: Finke E. , Pörtner H. O. , Lee P. G. , Webber D. M. 
Published: April 2021

ABSTRACT
Squid (Lolliguncula brevis) were exercised in a tunnel respirometer during a stepwise increase in water velocity in order to evaluate the anaerobic threshold, i.e. the critical swimming speed above which anaerobic metabolism contributes to energy production. The average anaerobic threshold was found at speeds of 1.5–2 mantle lengths s−1. Above this velocity, α-glycerophosphate, succinate and octopine started to accumulate in the mantle tissue. ATP levels fell and phospho-L-arginine was progressively depleted, while the levels of glucose 6-phosphate and inorganic phosphate rose. The finding of a simultaneous onset of anaerobic metabolism in the cytosol and the mitochondria indicates that a limited oxygen supply to the mitochondria elicits anaerobic energy production. This finding is opposite to the situation found in many other vertebrate and invertebrate species, in which energy requirements in excess of aerobic energy production are covered by anaerobic metabolism, with mitochondria remaining aerobic. In L. brevis, swimming at higher speeds is associated with a small factorial increase in metabolic rate based on a high resting rate of oxygen consumption. Pressure recordings in the mantle cavity support this finding, indicating a high basal level of spontaneous activity at rest and a small rise in mean pressure at higher swimming velocity. Bursts of higher pressures from the jet support elevated swimming speeds and may explain the early transition to anaerobic energy production which occurs when pressure amplitudes exceed 1.2–1.5 kPa or when mean pressure rises above 0.22–0.25 kPa.
The finding of mitochondrial hypoxia at a low critical speed in these squid is interpreted to be related to their life in shallow coastal and bay waters, which limits the necessity to maintain high swimming velocities. At increased swimming velocities, the animals oscillate between periods of high and low muscular activity. This behaviour is interpreted to reduce transport cost and to permit a longer-term net use of anaerobic resources when speed exceeds the critical value or when the squid dive into hypoxic waters. The simultaneous onset of anaerobic metabolism in the cytosol and the mitochondria emphasizes that squid generally make maximal use of available oxygen under resting conditions, when their energy requirements are the highest among marine invertebrates.
Pharmacological Properties of Voltage-Gated Na+ Currents in Motor Neurones from a Hydrozoan Jellyfish Polyorchis Penicillatus
Authors: Spafford J. David , Grigoriev Nikita G. , Spencer Andrew N. 
Published: April 2021

ABSTRACT
The Na+ current of ‘swimming motor neurones’ in the hydromedusan Polyorchis penicillatus was tetrodotoxin-insensitive. The local anaesthetics lidocaine and procainamide caused partial, non use-dependent blockade of the Na+ channel. Veratridine produced partial blockade of the Na+ channel without affecting inactivation. An order of blocking potency of di- and trivalent cations was established as: La3+ = Zn2+ = Cd2+ &gt; Ni2+ &gt; Mn2+ = Co2+ &gt; Ca2+ &gt; Ba2+ &gt; Mg2+. All these cations, except Ba2+, produced depolarizing shifts in the conductance–voltage curves. Even at relatively high concentrations, the dihydropyridines nicardipine, nitrendipine and (+)Bay K 8644 produced only weak blockade of the Na+ current; while nimodipine, nifedipine and (−)Bay K 8644 were ineffective. Diltiazem and verapamil weakly blocked the Na+ current in a dose-dependent manner with no evidence of use-dependence. The calmodulin inhibitors W7 and calmidazolium were ineffective blockers of Na+ currents. Crude Conus venoms and the Conus peptides, μ-conotoxin GIIA, μO-conotoxin MrVIA, w-conotoxin GVIA and ω-conotoxin MVIIC, were without effect. Capsaicin produced rapid, reversable blockade of Na+ current.
It has been suggested that ‘primitive’ Na+ channels could be expected to have pharmacological properties that are intermediate between those of Na+ and Ca2+ channels. If such channels exist, the Na+ channel described here is clearly not one of them.
Temporal and Spatial Distribution of V-ATPase and its mRNA in the Midgut of Moulting Manduca Sexta
Authors: Jäger Dieter , Novak Frans J. S. , Harvey William R. , Wieczorek Helmut , Klein Ulla 
Published: April 2021

ABSTRACT
The spatial and temporal distribution of the plasma membrane V-ATPase and its encoding mRNA in the midgut of Manduca sexta were investigated during the moult from the fourth to the fifth larval instar. Digoxigenin-labelled RNA probes were used for in situ hybridization of V-ATPase mRNA of both peripheral and integrated subunits; monoclonal antibodies to subunits of the peripheral sector of the purified plasma membrane V-ATPase were used for immunocytochemistry. Extensive mRNA labelling was found in both mature columnar and goblet cells of intermoult and moulting larvae. Hybridization screening in several tissues suggested that only cells with increased V-ATPase biosynthesis were labelled by our hybridization method. Mature goblet cells contain a large amount of V-ATPase in the apical plasma membrane and were therefore expected to contain V-ATPase mRNA. The intense mRNA signal found in mature columnar cells was unexpected. However, after refining the techniques of tissue preparation, immunolabelling in apical blebs of columnar cells was demonstrated. Since this immunoreactivity did not appear to be membrane-associated, it suggested a cytosolic localization of peripheral V1 subunits. The mRNA encoding subunit A of the peripheral V1 sector was distributed unevenly in columnar cells with a strong apical preference, whereas the mRNA for the proteolipid of the integral V0 sector was evenly distributed in the cytosol. This spatial pattern reflected the distribution of free ribosomes and rough endoplasmic reticulum in the cell, supporting the view that V1 subunits are synthesized at free ribosomes, whereas the V0 subunits are synthesized at the rough endoplasmic reticulum. All undifferentiated cells exhibited intense mRNA signals for V-ATPase subunits of both holoenzyme sectors from the start of proliferation and thus precursors of columnar and goblet cells could not be distinguished.
Stimulation Of Ciliary Beat Frequency By Serotonin Is Mediated By A Ca2+ Influx In Ciliated Cells Of Helisoma Trivolvis Embryos
Authors: Christopher Kimberley J. , Chang John P. , Goldberg Jeffrey I. 
Published: April 2021

ABSTRACT
Serotonin (5-HT) has been established as a regulator of ciliary beating in numerous systems. In early embryos of Helisoma trivolvis, a cilia-driven rotational movement is modulated by the release of endogenous serotonin from a pair of embryonic neurons, ENC1s, directly onto the ciliated epithelium. The present study was undertaken to examine the signal transduction mechanisms underlying serotonin-mediated cilio-excitation in Helisoma trivolvis embryos. Using time-lapse videomicroscopy, the ciliary beat frequency (CBF) of cultured embryonic ciliated cells was measured in response to various pharmacological manipulations. Serotonin increased CBF in a dose-dependent manner. Addition of 8-bromo-cyclic AMP, isobutylmethylxanthine (IBMX) or a combination of forskolin and IBMX, treatments that elevate the concentration of intracellular cyclic AMP, did not mimic the serotonin-induced increase in CBF. Thus, cyclic AMP does not appear to be involved in the regulation of CBF in this system. In contrast, depolarizing the cells with KCl or veratridine, and artificially raising the intracellular Ca2+ concentration with thapsigargin or A23187, caused a serotonin-like increase in CBF. Furthermore, the serotonin response was abolished in a Ca2+-depleted medium or in a medium containing the L-type Ca2+ channel blockers verapamil or nifedipine. These results suggest that serotonin-stimulated cilio-excitation in cultured Helisoma trivolvis cells involves an influx of Ca2+ to increase intracellular Ca2+ concentration. The link between serotonin–receptor binding and Ca2+ influx in these cells has yet to be determined.
The Metamorphosis of Feeding Kinematics in Salamandra Salamandra and the Evolution of Terrestrial Feeding Behavior
Authors: Reilly Stephen M. 
Published: April 2021

ABSTRACT
The striking similarity between aquatic feeding behaviors in fishes and tetrapods and terrestrial prey transports in tetrapods and their contrasts to terrestrial tongue projection kinematics have led to a general hypothesis that terrestrial prey capture evolved from terrestrial prey transport, which, in turn, evolved from aquatic feeding behavior. This hypothesis is examined in Salamandra salamandra by comparing the kinematics of prey capture and transport before and after metamorphosis in the same group of eight individuals. Kinematics of aquatic and terrestrial strikes and transports are used to describe the metamorphosis of feeding behavior in S. salamandra and provide the first kinematic description of both aquatic and terrestrial feeding behaviors in the family Salamandridae. On the basis of the shared characteristics among the four behaviors, the two aquatic behaviors are most similar, and these are more similar to terrestrial transports than to terrestrial strikes. Given the ontogenetic polarity of these behaviors in salamanders, I suggest, on the basis of the shared similarities and functional shifts, that terrestrial transport is an intermediate behavior between aquatic feeding and terrestrial tongue projection. These results support the hypothesis that a shift from aquatic feeding to terrestrial transport to terrestrial tongue projection represents an evolutionary transformation series in the evolution of terrestrial feeding in early tetrapods.
Elastic and Length–Force Characteristics of the Gastrocnemius of the Hopping Mouse (Notomys Alexis) and the Rat (Rattus Norvegicus)
Authors: Ettema G. J. C. 
Published: April 2021

ABSTRACT
The aim of this study was to compare the contractile and series elastic properties of terrestrial mammals that use bipedal versus quadrupedal gaits. The gastrocnemius muscle of the hopping mouse (body mass 30.2±2.4 g, mean ± S.D.) and the rat (313±10.7 g) were compared with data from the literature for the wallaby and the kangaroo rat to distinguish scaling effects and locomotion-related effects on muscle properties. Contractile length–force properties and series elastic stiffness were measured in situ during maximal tetanic contractions.
The rat had a larger muscle-fibre-to-tendon-length ratio. The rat and hopping mouse showed similar normalised length–force characteristics of the gastrocnemius. Normalised stiffness in the hopping mouse was higher. The hopping mouse showed a higher capacity to store elastic energy per unit of contractile work capacity, as well as per unit of body mass.
Accounting for body size differences, the rat had a smaller relative muscle mass and thus smaller work capacity than the three hopping animals considered. This is in agreement with a quadrupedal versus bipedal locomotion style.
The differences in contractile and elastic properties of the gastrocnemius of the rat and hopping mouse seem to be closely related to locomotion patterns. Small animals seem to be able to utilise the storage and release of elastic energy to a far lesser extent than larger animals. However, even in animals as small as hopping mice, the storage and utilisation of elastic energy during locomotion is of functional significance and probably depends on locomotor behaviour.
Thermal Avoidance During Flight in the Locust Locusta Migratoria
Authors: Robertson R. Meldrum , Kuhnert Christopher T. , Dawson Jeff W. 
Published: April 2021

ABSTRACT
In this paper, thermal avoidance in tethered flying locusts is described for the first time. Changes in body posture examined using high-speed cinematography revealed that the animals responded to a laterally positioned heat source with contralaterally directed abdomen and hindleg ruddering, behavioural patterns resembling manoeuvres observed in collision avoidance and in response to auditory signals. The analysis also showed that, during stimulation, left and right forewing depression became asymmetrical during the downstroke but remained symmetrical during the upstroke. Hindwing depression and elevation remained symmetrical during stimulus presentations. Electromyographic recordings from the left and right first basalar muscles (M97; forewing depressors) showed that contralateral depressor muscle activity was advanced by 10–12 ms relative to that on the stimulated side. There was also an increase in burst duration on the contralaterally stimulated side and an increase in wingbeat frequency of approximately 3 Hz. Ablation experiments showed that removal of the antennal flagella, which are the site of previously described thermoreceptors, did not abolish thermal avoidance manoeuvres. We conclude that thermal avoidance is triggered by an infrared sensitivity that is not mediated by the compound eyes, the ocelli or the antennal flagella.
Mapping Motor Neurone Activity to Overt Behaviour in the Leech: Internal Pressures Produced During Locomotion
Authors: Wilson R. J. A. , Skierczynski B. A. , Blackwood S. , Skalak R. , Kristan W. B. 
Published: April 2021

ABSTRACT
Several behaviour patterns have been studied in the leech at both the kinematic and neuronal levels. However, very little is known about how patterns of motor neurone activity map to actual movements. Internal pressure is an essential biomechanical property in this process, being responsible for producing the rigidity and posture that allow the directed delivery of forces produced by muscle contraction. To obtain a better understanding of the biomechanical processes involved in movement of the leech, we have measured the internal pressure of the animal by placing catheters through the body wall and into the gut of intact animals showing normal patterns of behaviour.
Each type of behaviour had a characteristic pressure waveform. The elongation phase of crawling produced a rapid increase in pressure that peaked when midbody segments were maximally elongated. The pressure produced during the contraction phase of crawling depended on the type of crawl, only inchworm crawling producing a second peak. Whole-body shortening in response to a head poke also produced a pressure peak, but it had a faster rise time. Swimming produced the largest pressure, which was marked by a large sustained increase that fluctuated phasically with undulations of the body. Dual pressure recordings using two catheters demonstrated that pressure was not uniform along the length of the leech, indicating that the body cavity is functionally compartmentalised.
Injecting fluid into the gut via a recording catheter allowed us to determine the effects of increasing internal volume on pressure. In line with previous predictions made using an abstract biomechanical model of the leech hydroskeleton, we found that an increase in the volume caused a reduction in the pressure. We are in the process of constructing a more realistic biomechanical model of the leech, based on actual data reported elsewhere. The results in this paper will provide key tests for refining these models.
The Variation of Resolution and of Ommatidial Dimensions in the Compound Eyes of the Fiddler Crab Uca Lactea Annulipes (Ocypodidae, Brachyura, Decapoda)
Authors: Zeil Jochen , Al-Mutairi Maha M. 
Published: April 2021

ABSTRACT
We studied variations in the optical properties of the compound eyes of Uca lactea annulipes using in vivo optical and histological techniques. The distribution of resolving power in the eyes of this fiddler crab species is typical for arthropods that inhabit flat environments: the eyes possess a panoramic equatorial acute zone for vertical resolution and a steep decrease of resolution away from the eye equator in the dorsal and ventral visual fields. The dimensions of the cellular components of the ommatidia vary accordingly: in the equatorial part of the eyes, facets are larger, and crystalline cones and rhabdoms are longer than in the dorsal and ventral parts of the eyes. Along the eye equator, horizontal resolution is low compared with vertical resolution and varies little throughout the visual field. The eyes of Uca lactea annulipes are unusual in that the gradient of vertical anatomical and optical resolution is steeper in the dorsal than in the ventral visual field. We interpret this difference as indicating that the information content of the world as seen by the crabs differs above and below the horizon line in specific and predictable ways.
Wingbeat Frequency of Birds in Steady Cruising Flight: New Data and Improved Predictions
Authors: Pennycuick C. J. 
Published: April 2021

ABSTRACT
Wingbeat frequencies of 15 species of birds, observed in the field in level, cruising flight were compared with predicted frequencies, calculated according to the formula derived from an earlier sample of 32 species. All of the data were collected by the author, using the same methods throughout. The new observations were predicted well for species with low wingbeat frequencies, but were underestimated at the higher frequencies. The following revised proportionality gave the best fit of the wingbeat frequency (f) to the combined data set of 47 species: ,where m is the body mass, g is the acceleration due to gravity, b is the wingspan, S is the wing area, I is the wing moment of inertia, and ρ is the air density. As measurements of I were not available for most species, its exponent was combined with those of m and b, by assuming that I∝mb2. The following equation was fitted to the data on this basis: These formulae are dimensionally correct, according to the rules derived in the earlier paper, and the equation is also numerically correct as it stands, without requiring a multiplication factor. For allometric comparisons between geometrically similar species, where body mass and wing measurements vary together (including wing moment of inertia), the expected relationship is f∝m−1/6. If the mass alone varies, owing to feeding or consumption of fuel, while the wing measurements and other variables remain unchanged, the expected relationship is f∝m1/2. These relationships apply to any dimensionally correct formula and are not affected by adjusting the coefficients within the dimensional constraints.
An Elastic Value of Protoplasm, with Further Observations on the Viscosity of Protoplasm
Authors: Seifriz William 
Published: April 2021

ABSTRACT
A technique for measuring the elastic value of living protoplasm is described. An elastic value of the cortical layer of the protoplasm of the Echinarachnius egg is given. The presence of an elastic property in protoplasm is incompatible with the emulsion hypothesis of protoplasmic structure.
The Nutrition of Mycorrhiza Plants: Calluna Vulgaris
Authors: Rayner M. C. 
Published: April 2021

ABSTRACT
An account is given of the formation and Seasonal development of mycorrhiza in Ling (Calluna vulgaris). Digestion of the intracellular complex of mycelium in the mycorrhiza cells is recorded for the first time and the cytology of the process is described. Knowledge of the distribution of the endophyte in the shoot tissues has been extended, and is confirmed by experimental work on cuttings struck in sterilised sand under controlled conditions. The endophyte has been recovered and identified from the shoot. The results thus obtained are compared with those described by Christoph, whose observations are interpreted in the light of the account now given of the formation of “suppressed mycorrhiza” in roots of cuttings, and also in those of seedlings and mature plants when certain conditions exist in the rooting medium. It is pointed out that the “obligate relation” in Calluna is associated with infection and seedling development and not with mycorrhiza formation and growth. The view is expressed that plants would probably grow quite well without mycorrhiza could seedlings be raised free from infection. In nature, the formation of mycorrhiza in all roots is the rule; the activities of the endophyte and its digestion products are presumably related to the nutrition of the plant and may be correlated with its growth in particular soils. The evidence for exchange of nutritive material is stated and examined. The view has been reached that such exchange exists, with a “balance of profit” on the side of the vascular plant. In view of its application to cases for which experimental data are not available, it is suggested that the term “symbiosis” as applied to mycorrhiza plants should be used in the older sense defined by de Bary.