bluuebunny/crossref_metadata_2025_split huggingface dataset:
Exposure of brown troutSalmo truttato a sublethal concentration of copper in soft acidic water: effects upon gas exchange and ammonia accumulation
Authors: Beaumont M. W. , Butler P. J. , Taylor E. W. 
Published: December 2002

SUMMARYThe present study was undertaken to answer two questions relating to the exposure of brown trout Salmo trutta to sublethal concentrations of copper and low pH (CLP) for 96h. (1) What is the effect of these pollutants on the rate of oxygen consumption (ṀO2) at different levels of exercise and (2) why does ammonia accumulate within these fish, when the low external pH should favour the diffusion of NH3 across the gills? Mean ṀO2 of fish in CLP and control (normal pH and no added copper) conditions were not significantly different from each other at any level of exercise. This suggests that exposure to CLP was not a `loading' factor at any level of activity. However, both maximum ṀO2 and critical swimming speed (Ucrit) were significantly lower in the CLP trout (5.5±1.6 mmol O2 kg-1 h-1 and 1.12±0.06 BL s-1, respectively) than in control fish (18.5±2.3 mmol O2 kg-1 h-1 and 2.04±0.11 BL s-1, respectively). There was no evidence from cardiovascular variables, such as heart rate and cardiac output, to suggest any changes in the oxygen transport system to compensate for any possible reduction in branchial gas exchange. Thus, it is suggested that oxygen exchange and transport do not limit the swimming performance of CLP trout, but that exposure to CLP reduces the maximum demand for O2, i.e. it is a limiting factor.The accumulation of ammonia in the plasma and white muscles during exposure to CLP has already been implicated in reducing the swimming performance of brown trout. Inhibition of cortisol synthesis abolished a large proportion of the increases in both the accumulation and excretion of ammonia that occurred during the second 48 h of the exposure to CLP, but did not inhibit ammonia accumulation completely. It is suggested that CLP not only causes an increase in the rate of production of ammonia, which is enhanced when the level of cortisol starts to increase after 48 h, but that it also inhibits an excretory mechanism (most probably Na+/NH4+ exchange) that is non-obligatory under `normal' conditions (when passive diffusion is sufficient), but is required in order to respond to unusually high ammonia loads.
Forgetting and the extension of memory inLymnaea
Authors: Sangha Susan , McComb Chloe , Lukowiak Ken 
Published: December 2002

SUMMARYAerial respiratory behaviour in Lymnaea stagnalis was operantly conditioned using a procedure that results in long-term memory (LTM) persisting for 1 but not 3 days. By manipulating the snails' post-training environment, i.e. preventing Lymnaea from performing aerial respiratory behaviour, memory persistence was significantly extended. Memory retention, however, is only extended if snails are prevented from performing aerial respiration in the same context in which they were trained. Snails trained in the `standard' context but prevented from performing aerial respiration in the `carrot-odor' context (and vice versa) did not extend their memory. These data are consistent with the hypothesis that forgetting is due to interfering events, that occur following learning and memory consolidation.
Fine-scale patterns of odor encounter by the antennules of mantis shrimp tracking turbulent plumes in wave-affected and unidirectional flow
Authors: Mead Kristina S. , Wiley Megan B. , Koehl M. A. R. , Koseff Jeffrey R. 
Published: December 2002

SUMMARYMany marine animals track odor plumes to their source. Although studies of plume-tracking behavior have been performed in unidirectional flow, benthic animals such as crustaceans live in coastal habitats characterized by waves. We compared signal encounters by odor-plume-tracking stomatopods (mantis shrimp) in wave-affected and unidirectional flow in a flume. Stomatopods are small enough that we can study their natural behavior in a flume. They sample odors by flicking their antennules. A thin sheet of laser light illuminating an odor plume labeled with dye [planar laser induced fluorescence (PLIF) technique] permitted us to measure the instantaneous odor concentration encountered by the animal's chemosensory organs (antennules) while it tracked the plume. We simultaneously measured behavior and the high-resolution odor signal at the spatial and temporal scale of the animal. We found that the navigating animal encountered odor filaments more often in wave-affected flow than in unidirectional flow. Odor filaments along the animals' antennules were significantly wider and of higher concentration in waves than in unidirectional flow.
K+ amino acid transporter KAAT1 mutant Y147F has increased transport activity and altered substrate selectivity
Authors: Liu Zhilin , Stevens Bruce R. , Feldman Daniel H. , Hediger Matthias A. , Harvey William R. 
Published: December 2002

SUMMARYKAAT1, a K+-coupled, neutral amino acid transporter from larval insect midgut, differs from other members of the Na+:neurotransmitter transporter family (SNF) in two important ways: (1) it transports nutrient L-, α-amino acids, rather than neurotransmitters such as γ-aminobutyric acid (GABA), and (2) it accepts K+ as well as Na+ as a co-substrate. To determine whether the restoration of KAAT1 residues to their GABA transporter GAT1 cation-binding equivalents might abolish its K+ but not its Na+ recognition site, we constructed a multiple mutant in which nine divergent KAAT1 residues were mutated back to the conserved form of the superfamily. To investigate the amino-acid-binding site, we constructed several single mutants that had been identified in GAT1. Wild-type (WT) or mutant cRNA was injected into Xenopus oocytes and the effects of external amino acids and ions upon labeled leucine uptake and substrate-induced currents were examined.The multiple mutant exhibited no amino-acid-induced currents, indicating that one or more of the mutated residues are crucial for function. W75L and R76E mutations in the first transmembrane helix of KAAT1 led to results equivalent to those observed in the corresponding mutants of GAT1; namely,substrate (leucine) uptake and substrate-evoked net inward current were severely curtailed. The KAAT1 A523S mutant, which corresponds to a serotonin transporter mutant that is thought to render Li+ equivalent to Na+ as a co-transported ion, functioned no differently to WT.The effects of mutation Y147F in the third transmembrane helix of KAAT1 were dramatically different from the equivalent mutation, Y140F, in GAT1. Although kinetic characteristics, expression levels and plasma membrane localization were all similar in Y147F and WT, the Y147F mutant exhibited a sevenfold increase in labeled leucine uptake by Xenopus oocytes in Na+ buffer. This increase is in sharp contrast to the complete loss of uptake activity in the GAT1 Y140F mutant. KAAT1 Y147F also differed from WT in cation selectivity and substrate spectrum, as revealed by amino-acid-induced net inward currents that were measured with a two-electrode voltage clamp.Amino-acid-independent currents induced by Li+ and Na+ chloride salts were observed in both WT and the Y147F mutant. The Li+-induced current was 30% higher in Y147F than in WT, whereas no substrate-independent K+-induced currents above control levels were detected either in WT or Y147F. These results suggest that transport of K+, the physiological co-substrate in insect midgut, is tightly coupled to that of amino acids in KAAT1, in contrast to the independence of cation and amino acid transport in the closely related cation amino acid transporter channel, CAATCH1.
The dependence of electrical transport pathways in Malpighian tubules on ATP
Authors: Wu Daniel S. , Beyenbach Klaus W. 
Published: December 2002

SUMMARYThe relationship between the intracellular ATP concentration[ATP]i and the electrical properties of principal cells was investigated in Malpighian tubules of the yellow fever mosquito, Aedes aegypti. Under control conditions, [ATP]i was 0.91 mmol l-1, the input resistance of the principal cell(Rpc) was 334.1 kΩ, and the basolateral membrane was marked by a large K+-conductance and a membrane voltage(Vbl) of -75.8 mV. Peritubular cyanide (CN, 0.3 mmol l-1) reduced [ATP]i to 0.08 mmol l-1 in less than 2 min; however, Vbl dropped to -8 mV and Rpc increased to 3150.8 kΩ in 8 min, while the K+-conductance of the basolateral membrane disappeared. Upon washout of CN, Vbl and Rpc returned to control values within 2 min, and the basolateral membrane recovered its K+-conductance. The recovery of normal [ATP]i took 15 min. Dose-dependence and EC50 values for the CN-inhibition of Vbl and the increase in Rpc were strikingly similar (184.0 μmol l-1 and 164.4 μmol l-1). Similar effects of metabolic inhibition were observed with dinitrophenol (DNP), but the EC50 values were 50.3 μmol l-1 and 71.7 μmol l-1 for the effects on Vbl and Rpc, respectively. Barium, a blocker of K+-channels, significantly hyperpolarized Vbl to -89.1 mV and increased Rpc to 769.4 kΩ under control conditions, but had no effects during metabolic inhibition. These results illustrate a temporal relationship between[ATP]i and electrogenic and conductive transport pathways in principal cells that is consistent with the role of ATP as an integrator of transport steps at apical and basolateral membranes of the cell. When[ATP]i drops to levels that are 10% of control, the V-type H+-ATPase is inhibited, preventing the extrusion of K+to the tubule lumen. At the same time, basolateral membrane K+-channels close, preventing the entry of K+ from the hemolymph. Intracellular K+ homeostasis is thus protected during metabolic inhibition, allowing the cell to re-establish K+transport when ATP is synthesized again.
The myoglobin gene of the Antarctic icefish, Chaenocephalus aceratus, contains a duplicated TATAAAA sequence that interferes with transcription
Authors: Small Deena J. , Moylan Thomas , Vayda Michael E. , Sidell Bruce D. 
Published: December 2002

SUMMARY
Six of the 16 known species of Antarctic icefish (family Channichthyidae) have lost the ability to express cardiac myoglobin (Mb) via at least four independent events during radiation of these species. We report here that the lesion in Chaenocephalus aceratus Mb is a duplicated TATAAAA element that blocks transcription. This lesion is distinct from those of other icefish species that do not express cardiac Mb. The C. aceratus Mb gene is nearly identical to that of Chionodraco rastrospinosus, a closely related Mb-expressing icefish species, with one exception. A 15-bp segment is present in C. aceratus but absent from C. rastrospinosus; this insertion is located 648 bp upstream from the reference transcription start site of C. rastrospinosus and includes the sequence TATAAAA, which bound HeLa cell transcription factor IID (TFIID) and icefish nuclear proteins in gel-retardation assays. Reporter constructs containing the `full-length' C. aceratus Mb promoter were not expressed in transient expression assays in oxidative skeletal muscle of live icefish. By contrast, constructs employing the nearly identical `full-length' C. rastrospinosus Mb promoter were efficiently expressed in parallel assays in the same tissue. Truncated constructs of C. aceratus Mb that did not contain the 15-bp duplication were expressed at very low levels. These data confirm a third independent mechanism of Mb loss among channichthyid species, indicate that C. aceratus aerobic muscle is capable of expressing functional Mb genes and demonstrate that duplication of the muscle-specific TATAAAA sequence in an inappropriate context can result in loss of a gene's expression, resulting in significant physiological consequences.
Nutritive metal uptake in teleost fish
Authors: Bury Nicolas R. , Walker Paul A. , Glover Chris N. 
Published: December 2002

SUMMARYTransition metals are essential for health, forming integral components of proteins involved in all aspects of biological function. However, in excess these metals are potentially toxic, and to maintain metal homeostasis organisms must tightly coordinate metal acquisition and excretion. The diet is the main source for essential metals, but in aquatic organisms an alternative uptake route is available from the water. This review will assess physiological, pharmacological and recent molecular evidence to outline possible uptake pathways in the gills and intestine of teleost fish involved in the acquisition of three of the most abundant transition metals necessary for life; iron, copper, and zinc.
The hydrodynamics of locomotion at intermediate Reynolds numbers:undulatory swimming in ascidian larvae (Botrylloidessp.)
Authors: McHenry Matthew J. , Azizi Emanuel , Strother James A. 
Published: December 2002

SUMMARYUnderstanding how the shape and motion of an aquatic animal affects the performance of swimming requires knowledge of the fluid forces that generate thrust and drag. These forces are poorly understood for the large diversity of animals that swim at Reynolds numbers (Re) between 100 and 102. We experimentally tested quasi-steady and unsteady blade-element models of the hydrodynamics of undulatory swimming in the larvae of the ascidian Botrylloides sp. by comparing the forces predicted by these models with measured forces generated by tethered larvae and by comparing the swimming speeds predicted with measurements of the speed of freely swimming larvae. Although both models predicted mean forces that were statistically indistinguishable from measurements, the quasi-steady model predicted the timing of force production and mean swimming speed more accurately than the unsteady model. This suggests that unsteady force (i.e. the acceleration reaction) does not play a role in the dynamics of steady undulatory swimming at Re≈102. We explored the relative contribution of viscous and inertial force to the generation of thrust and drag at 100&lt;Re&lt;102 by running a series of mathematical simulations with the quasi-steady model. These simulations predicted that thrust and drag are dominated by viscous force (i.e. skin friction) at Re≈100 and that inertial force (i.e. form force) generates a greater proportion of thrust and drag at higher Rethan at lower Re. However, thrust was predicted to be generated primarily by inertial force, while drag was predicted to be generated more by viscous than inertial force at Re≈102. Unlike swimming at high (&gt;102) and low (&lt;100) Re, the fluid forces that generate thrust cannot be assumed to be the same as those that generate drag at intermediate Re.
What determines the tuning of hearing organs and the frequency of calls? A comparative study in the katydid genusNeoconocephalus(Orthoptera, Tettigoniidae)
Authors: Schul Johannes , Patterson Adam C. 
Published: December 2002

SUMMARYThe calls of five syntopic species of Neoconocephalus varied significantly in their spectral composition. The center-frequency of the narrow-band low-frequency component varied from 7kHz to 15kHz among the five species. Hearing thresholds, as determined from whole nerve recordings, did not vary accordingly among the five species but were lowest in the range from 16kHz to 18kHz in all five species. Iso-intensity response functions were flat for stimulus intensities up to 27dB above threshold, indicating an even distribution of the best frequencies of individual receptor cells. At higher stimulus intensities, the intensity/response functions were steeper at frequencies above 35kHz than at lower frequencies. This suggests the presence of a second receptor cell population for such high frequencies, with 25-30dB higher thresholds. This receptor cell population is interpreted as an adaptation for bat avoidance. The transmission properties of the Neoconocephalus habitat (grassland) had low-pass characteristics for pure tones. Frequencies below 10kHz passed almost unaffected, while attenuation in excess of spherical attenuation increased at higher frequencies. Considering these transmission properties and the tuning of female hearing sensitivity, call frequencies of approximately 9-10kHz should be most effective as communication signals in this group of insects. It is discussed that the frequency of male calls is strongly influenced by bat predation and by the transmission properties of the habitat but is not strongly influenced by the tuning of the female hearing system.
Sex differences in razorbill Alca torda parent—offspring vocal recognition
Authors: Insley Stephen J. , Paredes Rosana , Jones Ian L. 
Published: December 2002

SUMMARY
We investigated differences in parent—offspring vocal recognition between males and females in a natural population of razorbills Alca torda, a long-lived and highly social species of auk (Family: Alcidae). Razorbills provide biparental care to their chicks while at the nest site, after which the male is the sole caregiver for an additional period at sea. Parent—offspring recognition in razorbills is most challenging once the chick becomes mobile, leaves the nest site and goes to sea with the male parent. It is during this period when selection pressure acting on recognition behaviour is expected to be strongest. As a result, we predicted that parent—offspring recognition would be better developed in the male parent, that is, show a paternal bias. To test this prediction we used vocal playback experiments conducted on breeding razorbills at the Gannet Islands, Labrador, Canada. We found (1) most positive responses to playbacks (vocal and phonotactic) occurred close to fledging, (2) males responded more to calls from their chicks than to calls from strange chicks, (3) females responded indifferently to calls from their own or strange chicks and (4) chicks responded more to calls from their male parent than to calls from other adult males. The results provide clear evidence of mutual vocal recognition between the male parent and the chick but not between the female parent and the chick, supporting the prediction that parent—offspring recognition is male biased in this species. Such a bias could have important social implications for a variety of behavioural and basic life history traits such as cooperation and sex-biased dispersal.
Escape manoeuvres in damsel-fly larvae: kinematics and dynamics
Authors: Brackenbury John 
Published: December 2002

SUMMARYThe kinematics and hydrodynamics of rapid escape manoeuvres executed by final-stage larvae of Enallagma cyathigerum were investigated using videography combined with a simple wake-visualisation technique. Two kinds of escape manoeuvres were identified: first, a `rapid flex', comparable with the rapid C-start of fish, and, second, a `rapid twist' that involves a helical contraction of the body inducing motion in the yaw, pitch and roll planes. In both cases, the initial flexion phase is concerned with re-orientating the body, the extensional phase with acceleration of the body in the new direction. The behaviour of the caudal fin during twist indicates considerable independence of movement and aspect control within the three constituent lobes. Dye deposited beneath the resting larvae showed a thrust jet shed into the wake at the end of the extension phase. The estimated momentum of the ring vortex containing the jet was similar to that imparted to the body at the start of the translational phase. Similarities between the swimming dynamics of damsel-fly larvae and fish are discussed, as well as the wider implications of these findings to other aquatic invertebrates whose normal, steady swimming appears to be based on unsteady manoeuvres.
Expression and localization of carbonic anhydrase and ATPases in the symbiotic tubewormRiftia pachyptila
Authors: De Cian Marie-Cécile , Andersen Ann C. , Bailly Xavier , Lallier François H. 
Published: December 2002

SUMMARYThe symbiotic tubeworm Riftia pachyptila needs to fuel its chemoautotrophic symbiotic bacteria with inorganic carbon. CO2 is transported from the surrounding water to the bacteriocytes located in the trophosome, through the branchial plume and the body fluids. Previous studies have demonstrated the implication of carbonic anhydrase (CA) and proton pumps(ATPases) at various steps of CO2 transport. The present study describes the expression pattern of cytosolic CA using an RNA probe and its histochemical and immunocytochemical localization in the trophosome and branchial plume of Riftia. Immunolocalization of V-H+ATPase and Na+K+-ATPase were also performed and related to CA localization. In the branchial plume, CA is expressed and localized in the most apical region of the branchial epithelium,close to the surrounding water. V-H+ATPase is mostly colocalized with CA and both enzymes probably allow CO2 entry against the concentration gradient while regulating intracellular pH. Na+K+-ATPase is mostly restricted to the basal part of epithelial cells and probably participates in CO2 transport to the body fluids. In the trophosome lobules, cytosolic CA is expressed and found in bacteriocytes and peritoneal cells. Hypotheses on the role of CA in bicarbonate and CO2 interconversion to fuel the symbiotic bacteria are discussed.
A comparison of visual and haltere-mediated equilibrium reflexes in the fruit flyDrosophila melanogaster
Authors: Sherman Alana , Dickinson Michael H. 
Published: December 2002

SUMMARYFlies exhibit extraordinary maneuverability, relying on feedback from multiple sensory organs to control flight. Both the compound eyes and the mechanosensory halteres encode angular motion as the fly rotates about the three body axes during flight. Since these two sensory modalities differ in their mechanisms of transduction, they are likely to differ in their temporal responses. We recorded changes in stroke kinematics in response to mechanical and visual rotations delivered within a flight simulator. Our results show that the visual system is tuned to relatively slow rotation whereas the haltere-mediated response to mechanical rotation increases with rising angular velocity. The integration of feedback from these two modalities may enhance aerodynamic performance by enabling the fly to sense a wide range of angular velocities during flight.
Identification of magnetically responsive neurons in the marine molluscTritonia diomedea
Authors: Wang John H. , Cain Shaun D. , Lohmann Kenneth J. 
Published: December 2002

SUMMARYBehavioral experiments have demonstrated that the marine mollusc Tritonia diomedea can use the Earth's magnetic field as an orientation cue. Little is known, however, about the neural mechanisms that underlie magnetic orientation behavior in this or any other animal. In previous studies, two neurons in the brain of Tritonia, known as LPd5 and RPd5, were shown to respond with enhanced electrical activity to changes in earth-strength magnetic fields. We report evidence that two additional neurons, known as LPd6 and RPd6, also respond with increases in electrical activity when the magnetic field around the animal is altered.Anatomical analyses revealed that prominent neurites from the Pd6 cells are located within two ipsilateral nerves, pedal nerves 1 and 2. These nerves extend to the periphery of the animal and innervate tissues of the anterior ipsilateral foot and body wall. Electrophysiological recordings demonstrated that action potentials generated by the Pd6 cells propagate from the central ganglia toward the periphery. These results imply that the Pd6 cells play an efferent role in the magnetic orientation circuitry. Given that these cells contain cilio-excitatory peptides and that Tritonia crawls using ciliary locomotion, the Pd6 neurons may control or modulate cilia used in crawling, turning, or both.