bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of extracellular changes on spontaneous heart rate of normoxia-and anoxia-acclimated turtles (Trachemys scripta)
Authors: Stecyk Jonathan A. W. , Farrell Anthony P. 
Published: January 2007

SUMMARYHeart rate (fH) of the anoxia-tolerant freshwater turtle (Trachemys scripta) during prolonged anoxia exposure is 2.5-to 5-times lower than the normoxic rate, but whether alterations in blood composition that accompany prolonged anoxia contribute to this bradycardia is unknown. We examined how temperature acclimation, oxygen deprivation,acidosis, hyperkalemia, hypercalcemia and adrenaline affect chronotropy in the turtle myocardium. We monitored spontaneous contraction rates of right-atrial preparations obtained from 21°C- and 5°C-acclimated turtles that had been exposed to either normoxia or anoxia (6 h at 21°C; 2 weeks at 5°C). Sequential exposures to saline solutions were designed to mimic, in a step-wise manner, the shift from a normoxic to anoxic extracellular condition (for normoxia-acclimated preparations) or the reverse (for anoxia-acclimated preparations). Our results clearly show that prolonged anoxia exposure re-sets the intrinsic fH of turtles at both temperatures, with reductions in intrinsic fH in the range of 25%–53% compared with normoxia. This intrinsic change would contribute to the bradycardia observed with prolonged anoxia. Further, we found negative chronotropic effects of extracellular anoxia, acidosis and hyperkalemia, and positive chronotropic effects of hypercalcemia and adrenaline. The exact nature of these extracellular effects depended, however,on the acclimation temperature and the prior exposure of the animal to anoxia. With normoxia-acclimated preparations at 21°C, combined anoxia and acidosis (pH reduced from ∼7.8 to ∼7.2) significantly reduced spontaneous fH by 22% and subsequent exposure to hyperkalemia (3.5 mmol l–1K+) further decreased fH. These negative chronotropic effects were ameliorated by increasing the adrenaline concentration from the tonic level of 1 nmol l–1 to 60 nmol l–1. However, in anoxia-acclimated preparations at 21°C, anoxia alone inhibited fH (by ∼30%). This negative chronotropic effect was counteracted by both hypercalcemia (6 mmol l–1Ca2+) and adrenaline (60 nmol l–1). At 5°C,only the combination of anoxia, acidosis (pH reduced from ∼8.0 to∼7.5) and hyperkalemia (3.5 mmol l–1 K+)significantly reduced spontaneous fH (by 23%) with preparations from normoxia-acclimated turtles. This negative chronotropic effect was fully reversed by hypercalcemia (10 mmol l–1Ca2+). By contrast, spontaneous fH of anoxia-acclimated preparations at 5°C was not affected by any of the extracellular changes. We conclude that prior temperature and anoxia experiences are central to determining fH during prolonged anoxia in Trachemys scripta both as a result of the re-setting of pacemaker rhythm and through the potential influence of extracellular changes.
Spectral sensitivity of four species of fiddler crabs (Uca pugnax,Uca pugilator,Uca vomerisandUca tangeri) measured byin situmicrospectrophotometry
Authors: Jordão Joana M. , Cronin Thomas W. , Oliveira Rui F. 
Published: January 2007

SUMMARYFiddler crabs have compound eyes that are structurally fairly well understood. However, there has been much debate regarding their spectral sensitivity and capacity to enable colour discrimination. We examined the visual pigments of two North-American species (Uca pugnax and U. pugilator), one species from the Indo-West Pacific (U. vomeris)and the only Eastern-Atlantic species (U. tangeri) of fiddler crabs using in situ microspectrophotometry of frozen sections of dark-adapted eyes. Only one spectral class of visual receptor was found in the larger (R1–7) retinular cells of each species, with maximum absorption peaking between 508 nm and 530 nm (depending upon species). The R8 retinular cell, that might contain a short-wavelength sensitive photopigment and provide a basis for colour vision, was too small to analyze by these methods. Rhabdoms were lined with screening pigment which strongly influenced each species'spectral sensitivity, sharpening the peak and shifting the maximum towards longer wavelengths, on occasion to as far as the 600 nm region. We hypothesize that sensitivity to longer wavelengths enhances contrast between background(blue sky or tall vegetation) and the male major claw during the waving display.
Relationship between n-3 PUFA content and energy metabolism in the flight muscles of a migrating shorebird: evidence for natural doping
Authors: Maillet Dominique , Weber Jean-Michel 
Published: January 2007

SUMMARYDuring their fall migration from the Arctic to South America, semipalmated sandpipers Calidris pusilla stop in the Bay of Fundy (east coast of Canada) before flying non-stop for ∼4500 km across the ocean. Refueling birds double their body mass by feeding on Corophium volutator, an amphipod containing high amounts of n-3 polyunsaturated fatty acids (n-3 PUFA), particularly eicosapentaenoic (20:5) and docosahexaenoic acid (22:6). In mammals, high dietary intake of n-3 PUFA is known to increase capacity for oxidative metabolism. Therefore, we hypothesized that tissue incorporation of n-3 PUFA would be associated with increases in the activity of key muscle enzymes to upregulate energy metabolism for prolonged exercise.Birds were collected at various stages of fat loading to monitor changes in lipid composition and flight muscle enzymes simultaneously. Enzymes were measured to assess oxidative capacity [citrate synthase (CS)],β-oxidation [carnitine palmitoyl transferase (CPT) and 3-hydroxyacyl dehydrogenase (HOAD)] and glycolytic capacity [lactate dehydrogenase (LDH)]. Changes in the fatty acid composition of muscle membranes (phospholipids) and fuel reserves (neutral lipids) were measured separately to distinguish between membrane-related and systemic effects of n-3 PUFA. Results show that muscle CS and HOAD are stimulated during refueling and that their activities are correlated with n-3 PUFA content in phospholipids (22:6 for CS, 20:5 for HOAD)and in neutral lipids (20:5 for CS). This suggests that 20:5 and 22:6 have different effects on energy metabolism and that they act via changes in membrane structure and systemic mechanisms. CPT and LDH did not change during refueling, but LDH activity was significantly related to the n-3 PUFA content of fuel reserves. This study shows that oxidative capacity increases rapidly during refueling and supports the idea that dietary n-3 PUFA are used as molecular signals to prime flight muscles of some long-distance migrants for extreme exercise.
Predicting the energy cost of terrestrial locomotion: a test of the LiMb model in humans and quadrupeds
Authors: Pontzer Herman 
Published: January 2007

SUMMARYThe energy cost of terrestrial locomotion has been linked to the muscle forces generated to support body weight and swing the limbs. The LiMb model predicts these forces, and hence locomotor cost, as a function of limb length and basic kinematic variables. Here, I test this model in humans, goats and dogs in order to assess the performance of the LiMb model in predicting locomotor cost for bipeds and quadrupeds. Model predictions were compared to observed locomotor cost, measured via oxygen consumption, during treadmill trials performed over a range of speeds for both walking and running gaits. The LiMb model explained more of the variation in locomotor cost than other predictors, including contact time, Froude number and body mass. The LiMb model also accurately predicted the magnitude of vertical ground forces. Results suggest the LiMb model reliably links locomotor anatomy to force production and locomotor cost. Further, these data support the idea that limb length may underlie the scaling of locomotor cost for terrestrial animals.
Serotonin stimulates [Ca2+]i elevation in ciliary ectodermal cells of echinoplutei through a serotonin receptor cell network in the blastocoel
Authors: Katow Hideki , Yaguchi Shunsuke , Kyozuka Keiichiro 
Published: January 2007

SUMMARYA full-length serotonin receptor mRNA from the 5Hthpr gene was sequenced from larvae of the sea urchin, Hemicentrotus pulcherrimus.The DNA sequence was most similar to 5HT-1A of the sea urchin Strongylocentrotus purpuratus found by The Sea Urchin Genome Project,and the protein sequence predicted the presence of seven transmembrane domains. Immunohistochemistry with anti-5HThpr antibodies indicated that the protein was expressed on blastocoelar cells that comprised the major blastocoelar network (serotonin receptor cell network). These network cells inserted their processes into the ectoderm in various regions, including the ciliary band region. Serotonin injected into the blastocoel stimulated a transient elevation of cytoplasmic Ca2+ concentration([Ca2+]i) in the ectoderm, as detected by Oregon-Green dextran, injected earlier in development. The calcium transient propagated as a wave at about 175 μm s–1, but was not detectable in the serotonin receptor-positive cell network. In larvae treated with p-chlorophenylalanine, a potent and irreversible serotonin synthesis inhibitor, serotonin application did not stimulate[Ca2+]i, the serotonin receptor cell network did not develop properly, and the swimming behavior of the larvae was abnormal. However, formation of a different nervous system comprising synaptotagmin-possessed neurites was not affected by p-chlorophenylalanine treatment. These results imply that serotonin secreted from the apical ganglion into the blastocoel stimulates the elevation of [Ca2+]i in the larval ectodermal cells through the serotonin receptor cell network.
Running stability is enhanced by a proximo-distal gradient in joint neuromechanical control
Authors: Daley M. A. , Felix G. , Biewener A. A. 
Published: January 2007

SUMMARYWe currently know little about how animals achieve dynamic stability when running over uneven and unpredictable terrain, often characteristic of their natural environment. Here we investigate how limb and joint mechanics of an avian biped, the helmeted guinea fowl Numida meleagris, respond to an unexpected drop in terrain during running. In particular, we address how joint mechanics are coordinated to achieve whole limb dynamics. Based on muscle–tendon architecture and previous studies of steady and incline locomotion, we hypothesize a proximo-distal gradient in joint neuromechanical control. In this motor control strategy, (1) proximal muscles at the hip and knee joints are controlled primarily in a feedforward manner and exhibit load-insensitive mechanical performance, and (2) distal muscles at the ankle and tarsometatarso-phalangeal (TMP) joints are highly load-sensitive, due to intrinsic mechanical effects and rapid, higher gain proprioceptive feedback. Limb kinematics and kinetics during the unexpected perturbation reveal that limb retraction, controlled largely by the hip, remains similar to level running throughout the perturbed step, despite altered limb loading. Individual joints produce or absorb energy during both level and perturbed running steps, such that the net limb work depends on the balance of energy among the joints. The hip maintains the same mechanical role regardless of limb loading, whereas the ankle and TMP switch between spring-like or damping function depending on limb posture at ground contact. Initial knee angle sets limb posture and alters the balance of work among the joints, although the knee contributes little work itself. This distribution of joint function results in posture-dependent changes in work performance of the limb, which allow guinea fowl to rapidly produce or absorb energy in response to the perturbation. The results support the hypothesis that a proximo-distal gradient exists in limb neuromuscular performance and motor control. This control strategy allows limb cycling to remain constant, whereas limb posture,loading and energy performance are interdependent. We propose that this control strategy provides simple, rapid mechanisms for managing energy and controlling velocity when running over rough terrain.
Hair plate mechanoreceptors associated with body segments are not necessary for three-dimensional path integration in desert ants,Cataglyphis fortis
Authors: Wittlinger Matthias , Wolf Harald , Wehner Rüdiger 
Published: January 2007

SUMMARYIn formicine ants, the hair fields associated with the neck and the petiole(alitrunk–petiole and petiole–gaster joints) have long been established to function in graviception. Here, we examine a possible role of these hair receptors in three-dimensional (3-D) path integration of the(formicine) desert ant, Cataglyphis fortis. Cataglyphisjudge the ground distance when travelling over hills, allowing correct homing even in (unpredictably) uneven terrain. We eliminated the function of these hair sensors in graviception either by shaving the hairs or by immobilising the joints monitored by the hair plates. With that major component of their sense of graviception eliminated, one would expect the ants to disregard, or at least misgauge, the ascents and descents performed across hills during outbound journey. The ants should thus consider the (much longer) actual walking trajectory, instead of the base distance, when calculating their homing distance. Surprisingly, neither shaving nor immobilisation of the hair sensillae affected correct path integration, across both uneven terrain (3-D)and level surface. If anything, the ants underestimated homing distance, which may reflect a general, safety-oriented navigation strategy. Animals that had performed the outbound journey with their gaster fixed in a horizontal position underestimated their homing so dramatically that this latter explanation cannot hold.
The directional hearing abilities of two species of bamboo sharks
Authors: Casper Brandon M. , Mann David A. 
Published: January 2007

SUMMARYAuditory evoked potentials (AEPs) were used to measure the directional hearing thresholds of the white-spotted bamboo shark Chiloscyllium plagiosum and the brown-banded bamboo shark Chiloscyllium punctatum at four frequencies and seven directions, using a shaker table designed to mimic the particle motion component of sound. Over most directions and frequencies there were no significant differences in acceleration thresholds, suggesting that the sharks have omni-directional hearing abilities. Goldfish Carassius auratus were used as a baseline to compare a species with specialized hearing adaptations versus sharks with no known adaptations, and were found to have more sensitive directional responses than the sharks. Composite audiograms of the sharks were created from the average of all of the directions at each frequency and were compared with an audiogram obtained for C. plagiosum using a dipole stimulus. The dipole stimulus audiograms were significantly lower at 50 and 200 Hz compared to the shaker audiograms in terms of particle acceleration. This difference is hypothesized to be a result of the dipole stimulating the macula neglecta, which would not be stimulated by the shaker table.
The interaction of CO2 concentration and spatial location on O2 flux and mass transport in the freshwater macrophytes Vallisneria spiralis and V. americana
Authors: Nishihara Gregory N. , Ackerman Josef D. 
Published: January 2007

SUMMARY
The biology of aquatic organisms determines the maximum rates of physiological processes, but the mass transport of nutrients determines the nominal rates at which these processes occur. Maximum O2 flux(Pmax) at 17.1 mmol m–3 CO2was higher for the leaves of the freshwater macrophyte Vallisneria spiralis [Pmax=0.013±0.001 mmol m–2 s–1 (gchla+bm–2)–1 (mean ± s.e.m.)] than for the closely related species, Vallisneria americana[Pmax=0.008±0.001 mmol m–2s–1 (gchla+bm–2)–1]. The O2 flux saturated at freestream velocities &gt;4.5±1.2 cm s–1 and was spatially invariant for both species. However, a tenfold decrease in CO concentration to 1.71 mmol m–3 changed the nature of the relationship between O2 flux and spatial location along the leaf surface, and reduced the O2 flux of V. spiralis to values similar to V. americana. The O2 flux[Pmax=0.007±0.001 mmol m–2s–1 (gchla+bm–2)–1] saturated at the upstream location(i.e. 1 cm from the leading edge of the leaf) but was found to increase linearly with freestream velocity [slope=0.057±0.011 mmol m–2 s–1 (gchla+bm–2)–1 (m s–1)–1] at the downstream location (i.e. 7 cm from the leading edge) at freestream velocities &gt;1.8±0.9 cm s–1. Conversely, mass transfer rates did not vary with CO2 concentration, and were characteristic of a laminar concentration boundary layer at the upstream location and a turbulent concentration boundary layer at the downstream location. Rates of mass transfer measured directly from O2 profiles were not predicted by theoretical values based on hydrodynamic measurements. Moreover, the concentration boundary layer thickness (δCBL) values measured directly from O2 profiles were 48±2% and 21±1% of the predicted theoretical δCBL values at the upstream and downstream locations, respectively. It is evident that physiological processes involving mass transport are coupled and vary in space. Mass transport investigations of biological systems based solely on hydrodynamic measurements need to be interpreted with caution.
Cu2+ and acute thermal stress induce protective eventsviathe p38-MAPK signalling pathway in the perfusedRana ridibundaheart
Authors: Gaitanaki Catherine , Pliatska Maria , Stathopoulou Konstantina , Beis Isidoros 
Published: January 2007

SUMMARYIn the present study, we investigated the induction of the p38-MAPK signalling pathway by copper, as exemplified by CuCl2, in the isolated perfused heart of the amphibian Rana ridibunda. We found that p38-MAPK phosphorylation by CuCl2 occurs in a dose-dependent manner, with maximum activation (8.73±1.43-fold relative to control values) attained by perfusion with 500 μmol l–1CuCl2 for 15 min, while this activation sustained even after 60 min of reperfusion with normal bicarbonate buffer. CuCl2 also induced the phosphorylation of the small heat shock protein 27 (Hsp27) in a p38-MAPK dependent manner, as revealed by experiments using the p38-MAPK inhibitor SB203580. p38-MAPK and Hsp27 phosphorylations were also strongly induced by hyperthermia (42°C), while the simultaneous use of hyperthermia and CuCl2 had a synergistic effect on p38-MAPK activation. Furthermore,perfusions with the potent antioxidant L-ascorbic acid (100 μmol l–1), the antioxidant enzymes catalase (CAT) (150 U ml–1) or superoxide dismutase (SOD) (30 U ml–1) in the presence of 500 μmol l–1CuCl2 did not attenuate the CuCl2-induced p38-MAPK activation, implying that at least the reactive oxygen species (ROS) scavenged by these agents are not implicated in this kinase activation. The p38-MAPK phosphorylation induced by the combined action of CuCl2 and hyperthermia was partially inhibited by catalase, indicating that hyperthermia possibly activates the kinase through the production of H2O2. Caspase-3, an effector protease of apoptosis,remained inactive in hearts perfused at normal or hyperthermic conditions, in the absence or presence of 500 μmol l–1 CuCl2. All the above results suggest that, in the amphibian Rana ridibundaheart, p38-MAPK activation by copper has a possible protective role through the small Hsp27.
Trimethylamine oxide suppresses stress-induced alteration of organic anion transport in choroid plexus
Authors: Villalobos Alice R. A. , Renfro J. Larry 
Published: January 2007

SUMMARYThe effect of physicochemical stress on organic anion transport across the vertebrate blood–cerebrospinal fluid (CSF) barrier in the presence and absence of an endogenous cytoprotectant, trimethylamine oxide (TMAO), was investigated in isolated IVth choroid plexus (CP) of spiny dogfish shark(Squalus acanthias), an animal with naturally high levels of TMAO(∼70 mmol l–1). Active transepithelial absorption of the organic anion, 2,4-dichlorophenoxyacetic acid (2,4-D), by IVth CP mounted in Ussing chambers was measured after in vitro stress, and a marker for the cellular stress response, inducible heat shock protein 70 (Hsp70), was assayed by immunoblot analysis. Transient heat stress (a shift from the normal 13.5°C to 23.5°C for 1 h) decreased 2,4-D transport by ∼66%;however, the same stress minus TMAO (isosmotic replacement with urea) had no effect on transport rate. In the absence of TMAO, stress-induced Hsp70 accumulation was more than double that seen in the presence of TMAO. Likewise,exposure to 50 μmol l–1 Zn for 6 h induced a twofold greater Hsp70 accumulation in the absence of TMAO than in its presence, and the higher Hsp70 level was associated with a higher 2,4-D transport rate. Heat stress and 50 μmol l–1 Zn also induced more pronounced increases in Hsp70 mRNA in the absence of TMAO. Thus, the cellular stress response can significantly alter CP organic anion transport capacity, and an endogenous osmolyte can suppress that response.
Preparation of Mixed Oxide Nanotubes by Precursor-accumulation on Carbon Nanofiber Templates
Authors: Ogihara Hitoshi , Sadakane Masahiro , Nodasaka Yoshinobu , Ueda Wataru 
Published: January 2007

Abstract
Various mixed oxide nanotubes, such as perovskite-type compounds, ferrites, and silica-based mixed oxides, could be synthesized using carbon nanofibers as templates. Carbon nanofibers are effective templates for preparing mixed oxide nanotubes because they are easily coated with mixed oxide by the accumulation of precursors on their surface.
Synthesis and Photophysical Properties of [60]Fullerene Adducts Carrying Oligocarbazole Dendrons
Authors: Nakamura Yosuke , Konno Takashi , Watanabe Satoru , Suzuki Masato , Yoshihara Toshitada , Tobita Seiji , Nishimura Jun 
Published: January 2007

Abstract
[60]Fullerene adducts carrying oligocarbazole moieties were successfully prepared by the Bingel reactions. Their fluorescence spectra and transient absorption spectra suggested the intramolecular electron transfer from the oligocarbazole moiety to the fullerene moiety mainly via 1C60*.
Formation of Intrinsic Point Defects in Fluorine-doped Synthetic SiO2 Glass by 60Co γ-ray Irradiation
Authors: Kajihara Koichi , Hirano Masahiro , Skuja Linards , Hosono Hideo 
Published: January 2007

Abstract
Intrinsic point defect formation in a fluorine-doped synthetic silica (SiO2) glass by 60Co γ-ray irradiation was examined. The most abundantly formed defects are oxygen vacancies (Si–Si bonds). The concentrations of Si–Si bonds and interstitial oxygen molecules increase almost linearly with the γ-ray dose. These observations indicate that the primarily intrinsic defect process in SiO2 glass irradiated with 60Co γ-rays is the Frenkel pair formation, rather than a simple cleavage of an Si–O bond into a pair of silicon and oxygen dangling bonds.
Density Functional Study on the 1,4-Hydride Migration in the η5-Naphthalene Manganese Complex [(exo-R-η5-C10H8)Mn(CO)3]
Authors: Hwang Sungu , Jang Joonkyung , Chung Young Keun 
Published: January 2007

Abstract
The mechanism of 1,4-hydride migration in [(exo-R-η5-C10H8)Mn(CO)3] was investigated by density functional theoretical study. Diene hydride intermediate is located, and the Gibbs free energy of activation and the stability of the equilibrium mixture are in good agreement with the experimental results.
Peculiar Crystal Structure of a Thiophene/Phenylene Co-oligomer of 2,5-Bis(4′-methoxybiphenyl-4-yl)thiophene
Authors: Hotta Shu , Goto Midori , Azumi Reiko 
Published: January 2007

Abstract
The crystal structure of a thiophene/phenylene co-oligomer of 2,5-bis(4′-methoxybiphenyl-4-yl)thiophene has been investigated. The crystals are orthorhombic with space group Cmc21. The crystal structure is characterized by that the molecular long axis is rigorously perpendicular to the bottom crystal plane (the bc-plane).