bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Craft of Ruling in Plato's Euthydemus and Republic
Authors: Parry Richard 
Published: March 2003

AbstractWe will investigate the relation between the notion of the craft of ruling in the Euthydemus and in the Republic. In the Euthydemus, Socrates' search for an account of wisdom leads to his identifying it as the craft of ruling in the city. In the Republic, the craft of ruling in the city is the virtue of wisdom in the city and the analogue of wisdom in the soul. Still, the craft of ruling leads to aporia in the former dialogue while in the latter it is a central feature of Socrates' account of justice - both in the city and in the soul. Some commentators hold that the aporia at the end of the second protreptic interlude of the Euthydemus shows that Socrates' account of wisdom is fatally flawed and must be rejected. However, the difficulty for this position is that the craft of ruling from the Euthydemus is a hardy notion that plays an extremely important role in the Republic. Indeed, reflecting this fact, other commentators hold that the aporia is solved in the Republic. Still, what is so far missing is an analysis that clearly shows the way to this solution in the Republic. In what follows, we will analyze the two protreptic interludes in the Euthydemus in order to see how the aporia arises. As we shall see, Socrates presents the aporia as a labyrinth. Indeed, it is a labyrinth with a little noticed step that - once it is noticed - shows the way out. The result will be that the aporia of the Euthydemus points to a solution in which ruling in the soul implies a command of one's appetites and emotions.
Du vin pour le Collège de veille? Mise en lumière d'un lien occulté entre le Choeur de Dionysos et le νυκτερινος συλλογος dans les Lois de Platon
Authors: Larivée Annie 
Published: March 2003

AbstractCe texte cherche à montrer que plusieurs allusions textuelles indiquent l'existence d'un lien significatif entre le Choeur de Dionysos et le νυκτερινος συλλογος dans les Lois de Platon. Cette hypothèse inédite se trouve confirmée par un examen attentif des diverses correspondances entre les deux instances, examen qui permet en outre de préciser la nature de leur lien. Il semble d'abord que le Choeur de Dionysos ait pour rôle d'apporter un complément pédagogique de «musique appliquée» à l'élite politique et scientifique de la cité. Plus important encore, le Choeur Dionysien paraît être l'organe idéologique privilégié par lequel les gouvernants du Collège de veille peuvent donner une forme persuasive à leur science et exercer une influence civique puissante sur l'ensemble de la population.
Direct evidence for the role of pigment cells in the brain of ascidian larvae by laser ablation
Authors: Tsuda Motoyuki , Sakurai Daisuke , Goda Muneki 
Published: March 2003

SUMMARYThe anterior sensory vesicle of ascidian larvae contains a single large vesicle in which lie two distinct types of pigment cells, anterior and posterior. The ultrastructure of these pigment cells suggests that the anterior pigment cell is an otolith, presumably used for gravity detection,and the posterior pigment cell is an ocellus, used for photoreception. However, there is no direct experimental evidence for this assignment of function. Upward swimming behaviour occurring during the initial period of larval life was examined before and after laser ablation of the anterior pigment and posterior pigment cells. Posterior pigment cell-ablated larvae retained the upward swimming behaviour, but anterior pigment cell-ablated larvae lost it. These results suggest that the anterior pigment acts as a gravity sensor. The negatively phototactic swimming during the latter part of larval life was also examined before and after laser ablation of the anterior pigment or posterior pigment cells. Anterior pigment cell-ablated larvae retained the phototactic response, but posterior pigment cell-ablated larvae lost it. These results suggest that the posterior pigment of the sensory vesicle is involved in the negatively phototactic, downward swimming behavior. The effect of pressure on swimming behaviour was studied, and a putative pressure-detection organ was found not to be involved in the larval swimming behaviour. These are the first published experimental results that permit a functional role in ascidian larval behavior to be assigned to the sensory organs.
Honeybee navigation: properties of the visually driven `odometer'
Authors: Si Aung , Srinivasan Mandyam V. , Zhang Shaowu 
Published: March 2003

SUMMARY
Recent work has revealed that honeybees determine distance flown by gauging the extent to which the image of the environment moves in the eye as they fly toward their destination. Here we examine the properties of this visually driven `odometer', by training bees to fly to a feeder in a tunnel lined with a range of different visual patterns, and analysing their dances when they return to the hive. We find that the odometric signal is relatively unaffected by variations in the contrast and spatial frequency content of the patterns. Furthermore, a strong signal is generated even when the walls or the floor of the tunnel provide only weak optic-flow cues. Thus, distance flown is measured by a visually driven odometer that is surprisingly robust to variations in the texture or sparseness of the visual environment through which the bee flies.
Non-invasive imaging of blood cell concentration and blood distribution in zebrafishDanio rerioincubated in hypoxic conditionsin vivo
Authors: Schwerte Thorsten , Überbacher Dietmar , Pelster Bernd 
Published: March 2003

SUMMARYThis is the first study to use a combination of digital imaging techniques and vital video microscopy to study hypoxia-induced changes in blood cell concentration, angiogenesis and blood redistribution in entire animals. Zebrafish Danio rerio, which are known to be independent of convective oxygen transport until about 2 weeks post-fertilization, were raised under chronic hypoxia (PO2=8.7 kPa)starting at 1 day after fertilization (d.p.f.) until 15 d.p.f. In control animals, the concentration of red cells (i.e. the number of red cells per nl blood) remained constant until 7 d.p.f., and than decreased by approximately 70% until 15 d.p.f. In hypoxic animals, however, the concentration of red cells remained significantly elevated compared to control animals at 12 and 15 d.p.f. Assuming that the hemoglobin content of the red cells is similar,hypoxic animals have a higher oxygen carrying capacity in their blood. Red cell distribution within the various parts of the circulatory system, taken as an indicator for blood distribution, revealed a significant modification in the number of blood cells perfusing the organs in hypoxic animals. At 12 d.p.f., gut perfusion was reduced by almost 50% in hypoxic animals, while perfusion of the segmental muscle tissue was increased to 350% of control values. No significant changes in brain perfusion were observed under these conditions. At 15 d.p.f., the reduction in gut perfusion was abolished,although muscle perfusion was still significantly elevated. At this time,growth of hypoxic animals was less compared to control animals, revealing that hypoxia had become deleterious for further development. The vascular bed of various organs was not obviously different in hypoxic animals compared to normoxic animals.
The role of the subelytral spiracles in respiration in the flightless dung beetle Circellium bacchus
Authors: Byrne Marcus J. , Duncan Frances D. 
Published: March 2003

SUMMARY
The role of the subelytral cavity in flightless beetle species as an adaptation to water saving in arid habitats is still in dispute. We found that relatively little CO2 was released from the subelytral cavity of a large apterous beetle Circellium bacchus during simultaneous measurements of CO2 emission from the anterior mesothoracic spiracles and posterior body, which included the subelytral spiracles. However, when we sampled air directly from inside the subelytral cavity, we discovered that this pattern was reversed. A discontinuous gas exchange cycle(DGC) was recorded from the posterior body half, revealing a flutter phase that had been absent from the anterior mesothoracic DGC. The anterior mesothoracic and posterior subelytral spiracles act in synchrony to maintain high CO2 and water vapour levels inside the subelytral cavity. In addition, the O2 concentration of the air within the subelytral cavity is lower than the air around the elytral case, irrespective of the time of sampling. These findings lead us to conclude that the subelytral spiracles work in a coordinated fashion with the anterior spiracles to create a DGC,which allows us to extend the hypothesis of the function of the subelytral cavity as a respiratory water-saving device.
Serotonin modulates the electric waveform of the gymnotiform electric fishBrachyhypopomus pinnicaudatus
Authors: Stoddard Philip K. , Markham Michael R. , Salazar Vielka L. 
Published: March 2003

SUMMARYThe gymnotiform electric fish Brachyhypopomus pinnicaudatuscommunicates with a sexually dimorphic electric waveform, the electric organ discharge (EOD). Males display pronounced circadian rhythms in the amplitude and duration of their EODs. Changes in the social environment influence the magnitudes of these circadian rhythms and also produce more transient responses in the EOD waveforms. Here we show that injections of serotonin produce quick, transient, dose-dependent enhancements of the male EOD characters similar to those induced by encounters with another male. The response to serotonin administered peripherally begins 5-10 min post injection and lasts approximately 3 h. The magnitude of the response to serotonin is tightly associated with the magnitude of the day-to-night swing of the circadian rhythm prior to injection. Taken together these findings suggest that the male's social environment influences his response to serotonin by altering the function of some part of the downstream chain between the serotonin receptors and the ion channels involved in control of the EOD waveform. Although chronic activation of serotonin circuitry is widely known to elicit subordinate behavior, we find that 5-HT initially increases a dominance signal in these fish. These findings are consistent with the emerging view that serotonin facilitates different adaptive responses to acute and chronic social challenge and stress.
Minimal shortening in a high-frequency muscle
Authors: Moon Brad R. , Conley Kevin E. , Lindstedt Stan L. , Urquhart Michael R. 
Published: March 2003

SUMMARYReducing the cost of high-frequency muscle contractions can be accomplished by minimizing cross-bridge cycling or by recycling elastic strain energy. Energy saving by contractile minimization has very different implications for muscle strain and activation patterns than by elastic recoil. Minimal cross-bridge cycling will be reflected in minimal contractile strains and highly reduced force, work and power output, whereas elastic energy storage requires a period of active lengthening that increases mechanical output. In this study, we used sonomicrometry and electromyography to test the relative contributions of energy reduction and energy recycling strategies in the tailshaker muscles of western diamondback rattlesnakes (Crotalus atrox). We found that tailshaker muscle contractions produce a mean strain of 3%, which is among the lowest strains ever recorded in vertebrate muscle during movement. The relative shortening velocities(V/Vmax) of 0.2-0.3 were in the optimal range for maximum power generation, indicating that the low power output reported previously for tailshaker muscle is due mainly to contractile minimization rather than to suboptimal V/Vmax. In addition, the brief contractions(8-18 ms) had only limited periods of active lengthening (0.2-0.5 ms and 0.002-0.035%), indicating little potential for elastic energy storage and recoil. These features indicate that high-frequency muscles primarily reduce metabolic energy input rather than recycle mechanical energy output.
The effect of gait and digital flexor muscle activation on limb compliance in the forelimb of the horseEquus caballus
Authors: McGuigan M. Polly , Wilson Alan M. 
Published: March 2003

SUMMARYA horse's legs are compressed during the stance phase, storing and then returning elastic strain energy in spring-like muscle-tendon units. The arrangement of the muscle-tendon units around the lever-like joints means that as the leg shortens the muscle-tendon units are stretched. The forelimb anatomy means that the leg can be conceptually divided into two springs: the proximal spring, from the scapula to the elbow, and the distal spring, from the elbow to the foot. In this paper we report the results of a series of experiments testing the hypothesis that there is minimal scope for muscle contraction in either spring to adjust limb compliance. Firstly, we demonstrate that the distal, passive leg spring changes length by 127 mm(range 106-128 mm) at gallop and the proximal spring by 12 mm (9-15 mm). Secondly, we demonstrate that there is a linear relationship between limb force and metacarpo-phalangeal (MCP) joint angle that is minimally influenced by digital flexor muscle activation in vitro or as a function of gait in vivo. Finally, we determined the relationship between MCP joint angle and vertical ground-reaction force at trot and then predicted the forelimb peak vertical ground-reaction force during a 12 m s-1gallop on a treadmill. These were 12.79 N kg-1 body mass (BM)(range 12.07-13.73 N kg-1 BM) for the lead forelimb and 15.23 N kg-1 BM (13.51-17.10 N kg-1 BM) for the non-lead forelimb.
Conservation of ecdysis-triggering hormone signalling in insects
Authors: Žitňan D. , Žitňanová I. , Spalovská I. , Takáč P. , Park Y. , Adams M. E. 
Published: March 2003

SUMMARYPre-ecdysis- and ecdysis-triggering hormones (PETH and ETH) from endocrine Inka cells initiate ecdysis in moths and Drosophila through direct actions on the central nervous system (CNS). Using immunohistochemistry, we found Inka cells in representatives of all major insect orders. In most insects, Inka cells are numerous, small and scattered throughout the tracheal system. Only some higher holometabolous insects exhibit 8-9 pairs of large Inka cells attached to tracheae in each prothoracic and abdominal segment. The number and morphology of Inka cells can be very variable even in the same individuals or related insects, but all produce peptide hormones that are completely released at each ecdysis. Injection of tracheal extracts prepared from representatives of several insect orders induces pre-ecdysis and ecdysis behaviours in pharate larvae of Bombyx, indicating functional similarity of these peptides. We isolated several PETH-immunoreactive peptides from tracheal extracts of the cockroach Nauphoeta cinerea and the bug Pyrrhocoris apterus and identified the gene encoding two putative ETHs in the mosquito Anopheles gambiae. Inka cells also are stained with antisera to myomodulin, FMRFamide and other peptides sharing RXamide carboxyl termini. However, our enzyme immunoassays show that these antisera cross-react with PETH and ETH. Our results suggest that Inka cells of different insects produce only peptide hormones closely related to PETH and ETH, which are essential endocrine factors required for activation of the ecdysis behavioural sequence.
Freshwater environment affects growth rate and muscle fibre recruitment in seawater stages of Atlantic salmon (Salmo salarL.)
Authors: Johnston Ian A. , Manthri Sujatha , Alderson Richard , Smart Alistair , Campbell Patrick , Nickell David , Robertson Billy , Paxton Charles G. M. , Burt M. Louise 
Published: March 2003

SUMMARYThe influence of freshwater environment on muscle growth in seawater was investigated in an inbred population of farmed Atlantic salmon (Salmo salar L.). The offspring from a minimum of 64 families per group were incubated at either ambient temperature (ambient treatment) or in heated water(heated treatment). Growth was investigated using a mixed-effect statistical model with repeated measures, which included terms for treatment effect and random fish effects for individual growth rate (α) and the instantaneous growth rate per unit change in temperature (γ). Prior to seawater transfer, fish were heavier in the heated (61.6±1.0 g; N=298)than in the ambient (34.1±0.4 g; N=206) treatments, reflecting their greater growth opportunity: 4872 degree-days and 4281 degree-days,respectively. However, the subsequent growth rate of the heated group was lower, such that treatments had a similar body mass (3.7-3.9 kg) after approximately 450 days in seawater. The total cross-sectional area of fast muscle and the number (FN) and size distribution of the fibres was determined in a subset of the fish. We tested the hypothesis that freshwater temperature regime affected the rate of recruitment and hypertrophy of muscle fibres. There were differences in FN between treatments and a significant age×treatment interaction but no significant cage effect(ANOVA). Cessation of fibre recruitment was identified by the absence of fibres of &lt;10 μm diameter. The maximum fibre number was 22.4% more in the ambient (9.3×105±2.0×104 than in the heated (7.6×105±1.5×104)treatments (N=44 and 40 fish, respectively; P&lt;0.001). For fish that had completed fibre recruitment, there was a significant correlation between FN and individual growth rate, explaining 35% of the total variation. The density of myogenic progenitor cells was quantified using an antibody to c-met and was approximately 2-fold higher in the ambient than in the heated group, equivalent to 2-3% of the total muscle nuclei. The number of myonuclei in isolated fibre segments showed a linear relationship with fibre diameter. On average, there were 20.6% more myonuclei in 200-μm-diameter fibres isolated from the ambient (3734 myonuclei cm-1) than from the heated (3097 myonuclei cm-1) treatments. The maximum fibre diameter was greater in heated than in ambient groups, whereas the age×treatment interaction was not significantly different (ANCOVA). There were also no consistent differences in the rate of hypertrophy of muscle fibres between treatments. It was concluded that freshwater temperature regime affected fibre number and the nuclear content of fast muscle in seawater but not the rate of fibre hypertrophy. The mechanisms and life history consequences of developmental plasticity in fibre number are discussed.
Comparative equilibrium mechanical properties of bovine and lamprey cartilaginous tissues
Authors: Courtland Hayden-William , Wright Glenda M. , Root Robert G. , DeMont M. Edwin 
Published: March 2003

SUMMARYIn contrast to all other vertebrate cartilages, the major extracellular matrix protein of lamprey cartilages is not collagen. Instead, there exists a unique family of noncollagenous structural proteins, the significance of which is not completely understood. A custom-built uniaxial testing apparatus was used to quantify and compare equilibrium stress-relaxation behavior(equilibrium moduli, stress decay behavior, recovery times and relaxation times) of (1) lamprey pericardial cartilages with perichondria tested in tension (young adult and aged), (2) annular cartilages without perichondria tested in compression (young adult and aged) and (3) bovine auricular cartilage samples without perichondria tested in both tension and compression. Results of this study demonstrated that all cartilages were highly viscoelastic but with varying relaxation times; approximately 120 min for annular and pericardial cartilages and 30 min for bovine auricular cartilages. For mean equilibrium moduli, young adult lamprey annular cartilages (0.71 MPa)and pericardial cartilages (2.87 MPa) were found to be statistically different. The mean moduli of all bovine auricular cartilages were statistically identical to lamprey cartilages except in the case of aged adult pericardial cartilages, which were statistically larger than all other cartilages at 4.85 MPa. Taken together, the results of this study suggest that lamprey cartilages are able to exhibit mechanical properties largely similar to those of mammalian cartilages despite unique structural proteins and differences in extracellular matrix organization.
Prolactin increases open-channel density of epithelial Na+channel in adult frog skin
Authors: Takada Makoto , Kasai Miyoko 
Published: March 2003

SUMMARYThe short-term effect of prolactin on the skin of the adult tree frog Hyla arborea japonica was investigated using current-fluctuation analysis. Basolateral application of ovine prolactin (10 μg ml-1) (1) increased the amiloride-blockable short-circuit current(SCC) across the skin 2.6±0.4-fold and (2) increased the open-channel density (M) of the epithelial Na+ channel 6.1±1.2-fold but decreased the single-channel current i to 0.4±0.1 times the control value (N=9). The increase in SCC induced by prolactin was thus due to an increase in M, not i. Apparently, in amphibians prolactin has not only a counteracting effect on metamorphosis but also a stimulatory effect on the development of adult-type features, such as this amiloride-blockable SCC.
Whole-body mechanics and gaits in the gray short-tailed opossumMonodelphis domestica: integrating patterns of locomotion in a semi-erect mammal
Authors: Parchman Andrew J. , Reilly Stephen M. , Biknevicius Audrone R. 
Published: March 2003

SUMMARYGaits (footfall patterns) and external mechanical energy patterns of the center of mass were quantified in a generalized, semi-erect mammal in order to address three general questions. First, do semi-erect mammals exhibit the walk/run gait transitions that have been proposed as the primitive condition for tetrapods? Second, do small, semi-erect mammals employ the energy-saving pendular and spring-based mechanics used by erect mammals? Third, how well do mechanical locomotor patterns of the center of mass correlate with gaits?Monodelphis domestica utilizes only fast walking and running trot gaits over a fivefold increase in speed, over which we could illicit constant velocity steps, although running trots were their preferred gait. In sustained level locomotion the opossums did not use other walking gaits presumed to be primitive for tetrapods. Across the full range of speeds their trotting gaits exhibited force patterns and in-phase mechanical energy fluctuations that are characteristic of spring-mass mechanics. Thus, opossums appear to prefer trotting gaits with bouncing mechanics for sustained locomotion. Integration of center-of-mass versus footfall perspectives reveals that spring-mass mechanics is associated with both walking trot and running trot gaits. Furthermore, the onset of an aerial phase was not clearly associated with either the walk/run gait transition (50% duty factor) or a change in center-of-mass mechanics. The assumption that energy-saving mechanisms are ubiquitous among mammals is tenuous because small non-cursorial mammals do not appear to use pendular-based mechanics for sustained locomotion and, although they prefer spring-based mechanics, they probably lack clear musculoskeletal spring elements that could store energy during running. Thus, it appears that simply paying for locomotion with muscular work may be the primitive condition for mammals.