bluuebunny/crossref_metadata_2025_split huggingface dataset:
A novel inwardly rectifying K+ channel, Kir2.5, is upregulated under chronic cold stress in fish cardiac myocytes
Authors: Hassinen Minna , Paajanen Vesa , Vornanen Matti 
Published: June 2008

SUMMARYA new member of the inward-rectifier K+ channel subfamily Kir2 was isolated and characterised from the crucian carp (Carassius carassius) heart. When expressed in COS-1 cells this 422 amino acid protein produced an inward-rectifying channel with distinct single-channel conductance, mean open time and open probability. Phylogenetic sequence comparisons indicate that it is not homologous to any known vertebrate Kir channel, yet belongs to the Kir2 subfamily. This novel crucian carp channel increases the number of vertebrate Kir2 channels to five, and has therefore been designated as ccKir2.5 (cc for Carassius carassius). In addition to the ccKir2.5 channel, the ccKir2.2 and ccKir2.1 channels were expressed in the crucian carp heart, ccKir2.1 being present only in trace amounts (&lt;0.8%of all Kir2 transcripts). Whole-cell patch clamp in COS-1 cells demonstrated that ccKir2.5 is a stronger rectifier than ccKir2.2 or ccKir2.1, and therefore passes weakly outward current. Single-channel conductance, mean open time and open probability of ccKir2.5 were, respectively, 1.6, 4.96 and 4.17 times as large as that of ccKir2.2. ccKir2.5 was abundantly expressed in atrium and ventricle of the heart and in skeletal muscle, but was a minor component of Kir2 in brain, liver, gill and kidney. Noticeably, ccKir2.5 was strongly responsive to chronic cold exposure. In fish reared at 4°C for 4 weeks,ccKir2.5 mRNA formed 59.1±2.1% and 65.6±3.2% of all ccKir2 transcripts in atrium and ventricle, respectively, while in fish maintained at 18°C the corresponding transcript levels were only 16.2±1.7% and 23.3±1.7%. The increased expression of ccKir2.5 at 4°C occurred at the expense of ccKir2.2, which was the main Kir2 isoform in 18°C acclimated fish. A cold-induced increase in the slope conductance of the ventricular IK1 from 707±49 to 1001±59 pS pF–1 (P&lt;0.05) was thus associated with an isoform shift from ccKir2.2 towards ccKir2.5, suggesting that ccKir2.5 is a cold-adapted and ccKir2.2 a warm-adapted isoform of the inward-rectifying K+ channel.
The morphology and mechanical sensitivity of lateral line receptors in zebrafish larvae (Danio rerio)
Authors: Van Trump William J. , McHenry Matthew J. 
Published: June 2008

SUMMARYThe lateral line system of fish and amphibians detects water flow with receptors on the surface of the body. Although differences in the shape of these receptors, called neuromasts, are known to influence their mechanics, it is unclear how neuromast morphology affects the sensitivity of the lateral line system. We examined the functional consequences of morphological variation by measuring the dimensions of superficial neuromasts in zebrafish larvae (Danio rerio) and mathematically modeling their mechanics. These measurements used a novel morphometric technique that recorded landmarks in three dimensions at a microscopic scale. The mathematical model predicted mechanical sensitivity as the ratio of neuromast deflection to flow velocity for a range of stimulus frequencies. These predictions suggest that variation in morphology within this species generates a greater than 30-fold range in the amplitude of sensitivity and more than a 200-fold range of variation in cut-off frequency. Most of this variation was generated by differences in neuromast height that do not correlate with body position. Our results suggest that natural variation in cupular height within a species is capable of generating large differences in their mechanical filtering and dynamic range.
Propulsion performance of a skeleton-strengthened fin
Authors: Zhu Qiang , Shoele Kourosh 
Published: June 2008

SUMMARYWe examine numerically the performance of a thin foil reinforced by embedded rays resembling the caudal fins of many fishes. In our study, the supporting rays are depicted as nonlinear Euler–Bernoulli beams with three-dimensional deformability. This structural model is then incorporated into a boundary-element hydrodynamic model to achieve coupled fluid–structure interaction simulation. Kinematically, we incorporate both a homocercal mode with dorso-ventral symmetry and a heterocercal mode with dorso-ventral asymmetry. Using the homocercal mode, our results demonstrate that the anisotropic deformability of the ray-reinforced fin significantly increases its capacity of force generation. This performance enhancement manifests as increased propulsion efficiency, reduced transverse force and reduced sensitivity to kinematic parameters. Further reduction in transverse force is observed by using the heterocercal mode. In the heterocercal model, the fin also generates a small lifting force, which may be important in vertical maneuvers. Via three-dimensional flow visualization, a chain of vortex rings is observed in the wake. Detailed features of the wake, e.g. the orientation of the vortex rings in the heterocercal mode, agree with predictions based upon particle image velocimetry (PIV) measurements of flow around live fish.
Expression of myogenic regulatory factors in the muscle-derived electric organ ofSternopygus macrurus
Authors: Kim Jung A. , Laney Christine , Curry Jeanne , Unguez Graciela A. 
Published: June 2008

SUMMARYIn most groups of electric fish, the current-producing cells of electric organs (EOs) derive from striated muscle fibers but retain some phenotypic characteristics of their precursor muscle cells. Given the role of the MyoD family of myogenic regulatory factors (MRFs) in the transcriptional activation of the muscle program in vertebrates, we examined their expression in the electrocytes of the gymnotiform Sternopygus macrurus. We estimated the number of MRF genes in the S. macrurus genome and our Southern blot analyses revealed a single MyoD, myogenin, myf5 and MRF4 gene. Quantitative RT-PCR showed that muscle and EO transcribe all MRF genes. With the exception of MyoD, the endogenous levels of myogenin, myf5 and MRF4 transcripts in electrocytes were greater than those detected in muscle fibers. These data indicate that MRF expression levels are not sufficient to predict the level to which the muscle program is manifested. Qualitative expression analysis of MRF co-regulators MEF2C, Id1 and Id2 also revealed these genes not to be unique to either muscle or EO, and detected similar expression patterns in the two tissues. Therefore, the partial muscle program of the EO is not associated with a partial expression of MRFs or with apparent distinct levels of some MRF co-factors. In addition, electrical inactivation by spinal cord transection(ST) resulted in the up-regulation of some muscle proteins in electrocytes without an accompanying increase in MRF transcript levels or notable changes in the co-factors MEF2C, Id1 and Id2. These findings suggest that the neural regulation of the skeletal muscle program via MRFs in S. macrurus might differ from that of their mammalian counterparts. Together, these data further our understanding of the molecular processes involved in the plasticity of the vertebrate skeletal muscle program that brings about the muscle-like phenotype of the non-contractile electrogenic cells in S. macrurus.
Vocal fold elasticity of the Rocky Mountain elk (Cervus elaphus nelsoni) – producing high fundamental frequency vocalization with a very long vocal fold
Authors: Riede Tobias , Titze Ingo R. 
Published: June 2008

SUMMARY
The vocal folds of male Rocky Mountain elk (Cervus elaphus nelsoni) are about 3 cm long. If fundamental frequency were to be predicted by a simple vibrating string formula, as is often done for the human larynx, such long vocal folds would bear enormous stress to produce the species-specific mating call with an average fundamental frequency of 1 kHz. Predictions would be closer to 50 Hz. Vocal fold histology revealed the presence of a large vocal ligament between the vocal fold epithelium and the thyroarytenoid muscle. In tensile tests, the stress–strain response of vocal fold epithelium and the vocal ligament were determined. Elasticity of both tissue structures reached quantitative values similar to human tissue. It seems unlikely that the longitudinal stress in elk vocal folds can exceed that in human vocal folds by an order of magnitude to overcome the drop in fundamental frequency due to a 3:1 increase in vocal fold length. Alternative hypotheses of how the elk produces high fundamental frequency utterances,despite its very long vocal fold, include a reduced effective vocal fold length in vibration, either due to bending properties along the vocal fold, or by actively moving the boundary point with muscle stiffening. The relationships between an individual's average fundamental frequency, vocal fold length and body size are discussed.
Scallops visually respond to the size and speed of virtual particles
Authors: Speiser Daniel I. , Johnsen Sönke 
Published: June 2008

SUMMARYThe unique eyes of scallops are abundant along the right and left valve mantle margins. These eyes form images by reflection off a concave spherical mirror, and give scallops an angular resolution of around 2°, far better than the 13–40° angular resolution provided by the eyes of other bivalves. It has been argued that bivalve mantle eyes primarily act as predator detectors, but behavioral studies have suggested that vision may serve additional purposes in scallops. By placing specimens of the bay scallop Argopecten irradians (Lamarck 1819) in a tank with 5–10 cm s–1 flow, showing them simulated images of moving particles,and recording their behavior, we tested whether visual cues may influence feeding behavior in these animals. We found that scallops opened their anterior mantle gapes significantly more often when they were shown 1.5×1.5 mm virtual particles (with angular sizes of 3.4°) than when they were shown 0.6×0.6 mm particles (1.4°; P&lt;0.001) or no particles at all (P&lt;0.05). We also found that scallops opened their anterior mantle gapes significantly more often when they were shown virtual particles moving at 2.5 cm s–1 (P&lt;0.01)or 5 cm s–1 (P&lt;0.05) than when they were shown particles moving at 10 cm s–1. Because scallops must open their anterior mantle gapes to feed, our findings suggest that these animals may visually detect the size and speed of moving particles and use this information to help identify favorable feeding conditions.
Cell-mediated immune activation rapidly decreases plasma carotenoids but does not affect oxidative stress in red-legged partridges (Alectoris rufa)
Authors: Perez-Rodriguez Lorenzo , Mougeot François , Alonso-Alvarez Carlos , Blas Julio , Viñuela Javier , Bortolotti Gary R. 
Published: June 2008

SUMMARY
In animals yellow-orange-red sexual traits pigmented by carotenoids have been suggested to act as signals of current health. Because carotenoids have important physiological functions, individuals might trade-off allocating these pigments to self-maintenance versus coloration. Carotenoids may act as scavengers of free radicals that are released during an immune response. Here, we experimentally assessed whether a local cell-mediated immune response affects circulating carotenoids, antioxidant status, oxidative damage and the expression of a carotenoid-based trait. Male red-legged partridges (Alectoris rufa) were subcutaneously injected with phytohaemagglutinin (PHA) or with phosphate buffer solution (controls). The effect of the treatment on circulating carotenoids, total plasma antioxidant status (TAS), lipid oxidative damage in erythrocytes (TBARS) and ornamentation was assessed. Immune challenge induced a 13% decrease in circulating carotenoids within 24 h. However, this treatment did not affect TAS, TBARS or coloration. Coloration, circulating carotenoids and cell-mediated immune response were positively correlated, but these were not related to TAS or TBARS. Carotenoids were only weakly related to TAS after controlling for the effect of uric acid levels. These results suggest that carotenoid-based ornaments may honestly indicate immunocompetence but probably not antioxidant capacity in this species, and that carotenoids might be relatively weak antioxidants in the plasma. Furthermore, even a relatively harmless and locally elicited immune challenge had important effects on circulating carotenoids, but this effect did not appear to be associated with oxidative stress. Alternative mechanisms linking carotenoids to immunity (not necessarily relying on the use of these pigments as antioxidants) should be considered in future studies on birds.
Multimodal signaling in fowl,Gallus gallus
Authors: Smith Carolynn L. , Evans Christopher S. 
Published: June 2008

SUMMARYMany social birds produce food-associated calls. In galliforms, these vocalizations are typically accompanied by a distinctive visual display,creating a multimodal signal known as tidbitting. This system is ideal for experimental analysis of the way in which signal components interact to determine overall efficacy. We used high-definition video playback to explore perception of male tidbitting by female fowl, Gallus gallus. Hens experienced four treatments consisting of multimodal tidbitting, visual tidbitting without sound, audible tidbitting without a male present, and a silent empty cage control. Hens took longer to begin food search when the display was silent, but the overall rate of this response did not differ among the multimodal, visual only or audio only playback treatments. These results suggest that the visual and vocal components of tidbitting are redundant, but they also highlight the importance of a temporal dimension for any categorization scheme. Visual displays also evoked inspection behavior,characterized by close binocular fixation on the head of the playback male,which is known to facilitate individual recognition. This may also allow hens to assess male quality. Such social responses reveal that tidbitting probably has multiple functions and provide a new insight into the selective factors responsible for the evolution of this complex multimodal signal.
Why go bipedal? Locomotion and morphology in Australian agamid lizards
Authors: Clemente Christofer J. , Withers Philip C. , Thompson Graham , Lloyd David 
Published: June 2008

SUMMARYBipedal locomotion by lizards has previously been considered to provide a locomotory advantage. We examined this premise for a group of quadrupedal Australian agamid lizards, which vary in the extent to which they will become bipedal. The percentage of strides that each species ran bipedally, recorded using high speed video cameras, was positively related to body size and the proximity of the body centre of mass to the hip, and negatively related to running endurance. Speed was not higher for bipedal strides, compared with quadrupedal strides, in any of the four species, but acceleration during bipedal strides was significantly higher in three of four species. Furthermore, a distinct threshold between quadrupedal and bipedal strides, was more evident for acceleration than speed, with a threshold in acceleration above which strides became bipedal. We calculated these thresholds using probit analysis, and compared these to the predicted threshold based on the model of Aerts et al. Although there was a general agreement in order, the acceleration thresholds for lizards were often lower than that predicted by the model. We suggest that bipedalism, in Australian agamid lizards, may have evolved as a simple consequence of acceleration, and does not confer any locomotory advantage for increasing speed or endurance. However, both behavioural and threshold data suggest that some lizards actively attempt to run bipedally, implying some unknown advantage to bipedal locomotion.
Front leg movements and tibial motoneurons underlying auditory steering in the cricket (Gryllus bimaculatusdeGeer)
Authors: Baden T. , Hedwig B. 
Published: June 2008

SUMMARYFront leg movements in the cricket (Gryllus bimaculatus) were measured during phonotactic steering on a trackball together with electromyogram recordings of the tibial extensor and flexor muscles. Up–down leg movements clearly indicated the step cycle and were independent of auditory stimulation. By contrast, left–right movements of the front leg were dependent on sound direction, with crickets performing rapid steering leg movements towards the active speaker. Steering movements were dependent on the phase of sound relative to the step cycle, and were greatest for sounds occurring during the swing phase. During phonotaxis the slow extensor tibiae motoneuron responded to ipsilateral sounds with a latency of 35–40 ms, whereas the fast flexor tibiae motoneurons were excited by contralateral sound. We made intracellular recordings of two tibial extensor and at least eight flexor motoneurons. The fast extensor tibiae, the slow extensor tibiae and one fast flexor tibiae motoneurons were individually identifiable, but a group of at least four fast flexor tibiae as well as at least three slow flexor tibiae motoneurons of highly similar morphology could not be distinguished. Motoneurons received descending inputs from cephalic ganglia and from local prothoracic networks. There was no overlap between the dendritic fields of the tibial motoneurons and the auditory neuropile. They did not respond to auditory stimulation at rest. Neither extracellular stimulation of descending pathways nor pharmacological activation of prothoracic motor networks changed the auditory responsiveness. Therefore, any auditory input to tibial motoneurons is likely to be indirect, possibly via the brain.
Cold rearing improves cold-flight performance inDrosophila viachanges in wing morphology
Authors: Frazier Melanie R. , Harrison Jon F. , Kirkton Scott D. , Roberts Stephen P. 
Published: June 2008

SUMMARYWe use a factorial experimental design to test whether rearing at colder temperatures shifts the lower thermal envelope for flight of Drosophila melanogaster Meigen to colder temperatures. D. melanogaster that developed in colder temperatures (15°C) had a significant flight advantage in cold air compared to flies that developed in warmer temperatures(28°C). At 14°C, cold-reared flies failed to perform a take-off flight∼47% of the time whereas warm-reared flies failed ∼94% of the time. At 18°C, cold- and warm-reared flies performed equally well. We also compared several traits in cold- and warm-developing flies to determine if cold-developing flies had better flight performance at cold temperatures due to changes in body mass, wing length, wing loading, relative flight muscle mass or wing-beat frequency. The improved ability to fly at low temperatures was associated with a dramatic increase in wing area and an increase in wing length (after controlling for wing area). Flies that developed at 15°C had∼25% more wing area than similarly sized flies that developed at 28°C. Cold-reared flies had slower wing-beat frequencies than similarly sized flies from warmer developmental environments, whereas other traits did not vary with developmental temperature. These results demonstrate that developmental plasticity in wing dimensions contributes to the improved flight performance of D. melanogaster at cold temperatures, and ultimately, may help D. melanogaster live in a wide range of thermal environments.
Impact of ER gene polymorphisms on overweight and obesity in Down Syndrome
Authors: Ferrara Mara , Capozzi Laura , Russo Rosa 
Published: June 2008

Abstract
The impact of ER XbaI and PvuII α gene polymorphisms on overweight and obesity were studied in 77 subjects with Down Syndrome (DS), of which 32 were children (18 boys, 14 girls), mean age 8.7 ± 2.3 years, and 45 adolescents (28 boys, 17 girls) mean age 14 ± 2.5 years. Their lifestyle was compared to 40 healthy age-matched controls. DS subjects had significant lesser physical activity than controls (p<0.05) and a lower caloric intake than the recommended requirements, which was significantly lesser than controls (p<0.05). Body Mass Index (BMI), Arm Circumference (AC) and Triceps Skinfold Thickness (TST) were significantly higher in DS subjects than controls (p<0.05), while metabolic and cardiovascular parameters were not significantly different between the groups (p>0.05). The frequency of ER genotypes in DS subjects was compared with the healthy controls, finding that there was a high prevalence of XXER genotype in DS subjects. Children and adolescents with DS, lacking ER XbaI site, showed significantly higher BMI and body fat distribution than other XbaI genotypes. The lack of ER XbaI site can indicate added risk of obesity in DS. No differences in metabolic and cardiovascular parameters were observed among ER genotypes. However, childhood obesity is associated with increased cardiovascular risk.
The influence of LTS-4, a saponoside from Lysimachia thyrsiflora L., on human skin fibroblasts and human melanoma cells
Authors: Galanty Agnieszka , Michalik Marta , Sędek Łukasz , Podolak Irma 
Published: June 2008

AbstractWe investigated the effect of a triterpene saponoside from Lysimachia thyrsiflora L. upon the viability, proliferation, morphology and cell motility of human melanoma HTB-140 cells and human skin fibroblasts (HSFs). The compound, denoted LTS-4, decreased the viability and rate of cell growth of both cell types in a time-and dose-dependent manner, and proved cytotoxic against cancer cells at significantly lower concentrations than for fibroblasts. LTS-4 also affected the morphology of the examined cells, causing vacuolisation and actin cytoskeleton disintegration, and had an inhibitory effect on the tumour cell motility.
Defects in quantum dots of IIB–VI semiconductors
Authors: Babentsov V. , Sizov F. 
Published: June 2008

AbstractThis review discusses the properties of structural defects in quantum dots of IIB–VI semiconductors. A great part of this knowledge has been developed in the last years and combined with the improvement in passivation technologies has contributed significantly to the nanotechnology.In this review we introduced the main characterization methods which are used for the study of defects in the nanoform of semiconductors, presented a short description of how native defects can influence the emission spectra, underlined the restrictions which the Auger and deep-level defect recombination imposes on the excitonic emission. We also highlighted the importance of the defect passivation associated with efficiency and photostability of devices.
Systems of sets with multiplicative asymptotic density
Authors: Jahoda Pavel , Pěluchová Monika 
Published: June 2008

Abstract
The authors define a notion of system of sets with multiplicative asymptotic density in this paper. A criterion and one necessary condition for a given system {A
i}i=1∞ to be a system with multiplicative asymptotic density is given. Properties of certain special types of systems of sets with multiplicative asymptotic density are treated.
On automorphisms of finite Abelian p-groups
Authors: Golasiński Marek , Gonçalves Daciberg 
Published: June 2008

Abstract
Let A be a finitely generated abelian group. We describe the automorphism group Aut(A) using the rank of A and its torsion part p-part A
p.
For a finite abelian p-group A of type (k
1, ..., k
n), simple necessary and sufficient conditions for an n × n-matrix over integers to be associated with an automorphism of A are presented. Then, the automorphism group Aut(A) for a finite p-group A of type (k
1, k
2) is analyzed.