bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular calcium translocation during the contraction–relaxation cycle in scorpionfish swimbladder muscle
Authors: Suzuki Suechika , Hino Naoki , Sugi Haruo 
Published: February 2004

SUMMARY
To examine intracellular Ca2+ translocation during the contraction–relaxation cycle in vertebrate striated muscle, electron probe X-ray microanalysis was performed on the swimbladder muscle (SBM) fibres of a scorpionfish Sebastiscus marmoratus. The SBM fibres were rapidly frozen at rest, during contraction and at various times after the onset of relaxation. Changes in calcium distribution in the components of the sarcoplasmic reticulum (SR) were examined on the SBM fibre cryosections. In resting fibres, the calcium concentration was highest around the boundary between the A and I bands (A–I boundary), where the terminal cisternae(TC) were located. In contracting fibres, the calcium concentration decreased around the A–I boundary, while it increased in all other regions of the sarcomere, indicating Ca2+ release from the TC into the myoplasm. During relaxation, the calcium concentration first increased around the regions, where the fenestrated collars (FC) and the longitudinal tubules (LT)were located, and then gradually returned to the levels seen in resting fibres. These results support the view that, after the onset of relaxation in the SBM fibres, Ca2+ in the myoplasm is first taken up by the FC and the LT, and then gradually returns to the TC.
Microspectrophotometry of visual pigments and oil droplets in a marine bird, the wedge-tailed shearwaterPuffinus pacificus: topographic variations in photoreceptor spectral characteristics
Authors: Hart Nathan S. 
Published: February 2004

SUMMARYMicrospectrophotometric examination of the retina of a procellariiform marine bird, the wedge-tailed shearwater Puffinus pacificus, revealed the presence of five different types of vitamin A1-based visual pigment in seven different types of photoreceptor. A single class of rod contained a medium-wavelength sensitive visual pigment with a wavelength of maximum absorbance (λmax) at 502 nm. Four different types of single cone contained visual pigments maximally sensitive in either the violet(VS, λmax 406 nm), short (SWS, λmax 450 nm), medium (MWS, λmax 503 nm) or long (LWS,λ max 566 nm) spectral ranges. In the peripheral retina, the SWS, MWS and LWS single cones contained pigmented oil droplets in their inner segments with cut-off wavelengths (λcut) at 445 (C-type),506 (Y-type) and 562 nm (R-type), respectively. The VS visual pigment was paired with a transparent (T-type) oil droplet that displayed no significant absorption above at least 370 nm. Both the principal and accessory members of the double cone pair contained the same 566 nm λmax visual pigment as the LWS single cones but only the principal member contained an oil droplet, which had a λcut at 413 nm. The retina had a horizontal band or `visual streak' of increased photoreceptor density running across the retina approximately 1.5 mm dorsal to the top of the pecten. Cones in the centre of the horizontal streak were smaller and had oil droplets that were either transparent/colourless or much less pigmented than at the periphery. It is proposed that the reduction in cone oil droplet pigmentation in retinal areas associated with high visual acuity is an adaptation to compensate for the reduced photon capture ability of the narrower photoreceptors found there. Measurements of the spectral transmittance of the ocular media reveal that wavelengths down to at least 300 nm would be transmitted to the retina.
Stimulation by cadmium of myohemerythrin-like cells in the gut of the annelidNereis diversicolor
Authors: Demuynck Sylvain , Bocquet-Muchembled Beatrice , Deloffre Laurence , Grumiaux Fabien , Leprêtre Alain 
Published: February 2004

SUMMARYIsolated guts of Nereis diversicolor revealed the existence of a cadmium-binding protein, the MPII, belonging to the group of hemerythrins and myohemerythrins. The presence of MPII in the cells of the intestine was demonstrated by immunocytochemistry, using anti-MPII, a monoclonal antibody. In addition, using in situ hybridization and northern blotting, it was shown that MPII-cells are the site of synthesis of this molecule. Exposure of the worms to cadmium led to the cellular activation process of MPII-cells(i.e. transformation of the nucleolus, development of the endoplasmic reticulum and the Golgi apparatus), although MPII mRNA transcript levels were unchanged. Enzyme-linked immunosorbent assay (ELISA) of gut extracts revealed that MPII levels were increased after exposure to Cd, so it appears that this protein is synthesized as a response to Cd exposure without any new synthesis of mRNA. This mechanism of regulation is quite similar to that reported in the case of mammalian ferritin and may be involved in the regulation of Cd levels in this worm.
The effect of molluscan glue proteins on gel mechanics
Authors: Pawlicki J. M. , Pease L. B. , Pierce C. M. , Startz T. P. , Zhang Y. , Smith A. M. 
Published: February 2004

SUMMARYSeveral molluscs have been shown to alternate between a non-adhesive trail mucus and a similar gel that forms a strong glue. The major structural difference between the two secretions is the presence of specific proteins in the adhesive mucus. The present study identifies similar proteins from the glue of the slug Arion subfuscus and the land snail Helix aspersa. To investigate the role played by these proteins in adhesion,the proteins were isolated from the adhesive mucus of different molluscs and added to commercial polymer solutions. The effect was observed qualitatively,and quantified using a dynamic rheometer. The isolated proteins triggered gelling or visible stiffening of agar, pectin and polygalacturonic acid. The effect was stronger on more negatively charged polymers. The effect of the proteins was concentration dependent with an optimal concentration of 1–1.5 mg ml–1, and was weakened when their structure changed. Other proteins and carbohydrates found in the adhesive mucus had no clear mechanical effect on gels. These findings show that the addition of these proteins to large, anionic polymers plays a central role in the formation of a glue from a mucus-like secretion. Such a mechanism may be common among invertebrates, and it may guide biomimetic approaches in the development of glues and gels.
Unsteady aerodynamic forces of a flapping wing
Authors: Wu Jiang Hao , Sun Mao 
Published: February 2004

SUMMARYThe unsteady aerodynamic forces of a model fruit fly wing in flapping motion were investigated by numerically solving the Navier–Stokes equations. The flapping motion consisted of translation and rotation [the translation velocity (ut) varied according to the simple harmonic function (SHF), and the rotation was confined to a short period around stroke reversal]. First, it was shown that for a wing of given geometry with ut varying as the SHF, the aerodynamic force coefficients depended only on five non-dimensional parameters, i.e. Reynolds number (Re), stroke amplitude (Φ), mid-stroke angle of attack(αm), non-dimensional duration of wing rotation(Δτr) and rotation timing [the mean translation velocity at radius of the second moment of wing area (U), the mean chord length (c) and c/U were used as reference velocity, length and time, respectively]. Next, the force coefficients were investigated for a case in which typical values of these parameters were used (Re=200;Φ=150°; αm=40°; Δτr was 20%of wingbeat period; rotation was symmetrical). Finally, the effects of varying these parameters on the force coefficients were investigated.In the Re range considered (20–1800), when Re was above ∼100, the lift(C̄L) and drag(C̄D) coefficients were large and varied only slightly with Re (in agreement with results previously published for revolving wings); the large force coefficients were mainly due to the delayed stall mechanism. However, when Re was below∼100, C̄L decreased and C̄D increased greatly. At such low Re, similar to the case of higher Re, the leading edge vortex existed and attached to the wing in the translatory phase of a half-stroke; but it was very weak and its vorticity rather diffused, resulting in the small C̄L and large C̄D. Comparison of the calculated results with available hovering flight data in eight species(Re ranging from 13 to 1500) showed that when Re was above∼100, lift equal to insect weight could be produced but when Rewas lower than ∼100, additional high-lift mechanisms were needed.In the range of Re above ∼100, Φ from 90° to 180°and Δτr from 17% to 32% of the stroke period (symmetrical rotation), the force coefficients varied only slightly with Re, Φand Δτr. This meant that the forces were approximately proportional to the square of Φn (n is the wingbeat frequency); thus, changing Φ and/or n could effectively control the magnitude of the total aerodynamic force.The time course of C̄L(or C̄D) in a half-stroke for ut varying according to the SHF resembled a half sine-wave. It was considerably different from that published previously for ut, varying according to a trapezoidal function (TF) with large accelerations at stroke reversal, which was characterized by large peaks at the beginning and near the end of the half-stroke. However, the mean force coefficients and the mechanical power were not so different between these two cases (e.g. the mean force coefficients for ut varying as the TF were approximately 10% smaller than those for utvarying as the SHF except when wing rotation is delayed).
Locomotor performance of closely relatedTropidurusspecies:relationships with physiological parameters and ecological divergence
Authors: Kohlsdorf Tiana , James Rob S. , Carvalho José E. , Wilson Robbie S. , Dal Pai-Silva Maeli , Navas Carlos A. 
Published: February 2004

SUMMARYTropidurid lizards have colonized a variety of Brazilian open environments without remarkable morphological variation, despite ecological and structural differences among habitats used. This study focuses on two Tropidurussister-species that, despite systematic proximity and similar morphology,exhibit great ecological divergence and a third ecologically generalist congeneric species providing an outgroup comparison. We quantified jumping capacity and sprint speed of each species on sand and rock to test whether ecological divergence was also accompanied by differences in locomotor performance. Relevant physiological traits possibly associated with locomotor performance – metabolic scopes and fiber type composition, power output and activity of the enzymes citrate synthase, pyruvate kinase and lactate dehydrogenase of the iliofibularis muscle – were also compared among the three Tropidurus species. We found that the two sister-species exhibited remarkable differences in jumping performance, while Tropidurus oreadicus, the more distantly related species, exhibited intermediate values. Tropidurus psamonastes, a species endemic to sand dunes,exhibited high absolute sprint speeds on sand, jumped rarely and possessed a high proportion of glycolytic fibers and low activity of citrate synthase. The sister-species Tropidurus itambere, endemic to rocky outcrops,performed a large number of jumps and achieved lower absolute sprint speed than T. psamonastes. This study provides evidence of rapid divergence of locomotor parameters between sister-species that use different substrates,which is only partially explained by variation in physiological parameters of the iliofibularis muscle.
The physiological consequences of exposure to chronic, sublethal waterborne nickel in rainbow trout (Oncorhynchus mykiss): exercisevsresting physiology
Authors: Pane Eric F. , Haque Aziz , Goss Greg G. , Wood Chris M. 
Published: February 2004

SUMMARYIn rainbow trout (Oncorhynchus mykiss), following chronic (42 day)exposure to both 384 μg Ni l–1 and 2034 μg Ni l–1, Ni accumulation was greatest in the gill, kidney and plasma, with the plasma as the main sink for Ni. Indeed, trapped plasma analysis revealed that extensive loading of Ni in the plasma accounted for substantial percentages of accumulated Ni in several tissues including the liver and heart. Accumulated Ni in the gill and kidney was less dependent on plasma Ni concentration, suggesting a more intracellular accumulation of Ni in these tissues.We present evidence for a clear, persistent cost of acclimation to chronic,sublethal Ni exposure. Chronic (40–99 day) exposure to sublethal waterborne Ni (243–394 μg Ni l–1; ∼1% of the 96 h LC50) impaired the exercise physiology, but not the resting physiology, of rainbow trout. Ni acted as a limiting stressor, decreasing maximal rates of oxygen consumption(\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \({\dot{M}}_{\mathrm{O}_{2},\mathrm{max}}\) \end{document})during strenuous exercise in trout exposed for 34 days to sublethal Ni. This drop in high-performance gas exchange was attributed mainly to a reduction in relative branchial diffusing capacity (Drel) caused by thickening of secondary lamellae. Morphometric analysis of the gills of chronically exposed fish revealed overall swelling of secondary lamellae, as well as hypertrophic respiratory epithelia within secondary lamellae. Additionally, contraction of the lamellar blood pillar system and narrowing of interlamellar water channels occurred, possibly contributing to decreased high-performance gas exchange. Decreased aerobic capacity persisted in fish previously exposed to nickel despite a clean-water exposure period of 38 days and an almost complete depuration of gill Ni, suggesting that extrabranchial mechanisms of chronic Ni toxicity may also be important.Chronic impairment of such a dynamically active and critical organ as the gill may depress the overall fitness of a fish by impairing predator avoidance, prey capture and migration success with obvious environmental implications.
Light-dependent magnetoreception in birds: analysis of the behaviour under red light after pre-exposure to red light
Authors: Wiltschko Wolfgang , Möller Andrea , Gesson Marcus , Noll Catrin , Wiltschko Roswitha 
Published: February 2004

SUMMARYIn previous experiments, migratory birds had been disoriented under 635 nm red light, apparently unable to use their magnetic compass. The present study with European robins, Erithacus rubecula, confirms these findings for red light at the levels of 6×1015 quanta s–1m–2 and 43×1015 quanta s–1m–2, suggesting that the disorientation under red light was not caused by the test light being below the threshold for magnetoreception. However, pre-exposure to red light for 1 h immediately before the critical tests under red light of 6–7×1015 quanta s–1 m–2 enabled robins to orient in their seasonally appropriate migratory direction in spring as well as in autumn. Pre-exposure to darkness, by contrast, failed to induce orientation under red light. Under green light of 7×1015 quanta s–1 m–2, the birds were oriented in their migratory orientation after both types of pre-exposure. These findings suggest that the newly gained ability to orient under red light might be based on learning to interpret a novel pattern of activation of the magnetoreceptors and hence may represent a parallel to the previously described enlargement of the functional window to new magnetic intensities. Mechanisms involving two types of spectral mechanisms with different absorbance maxima and their possible interactions are discussed.
Magnetic orientation in the mealworm beetle Tenebrio and the effect of light
Authors: Vácha Martin , Soukopová Helena 
Published: February 2004

SUMMARY
There is evidence for both light-dependent and light-independent mechanisms of magnetoreception of terrestrial animals. One example of a light-independent mechanism frequently cited is the magnetic compass of the mealworm beetle(Tenebrio molitor). We found that magnetoreception of the mealworm beetle per se is a replicable phenomenon but that, in contrast to earlier findings, Tenebrio only exhibited consistent magnetic compass orientation when light was present. The problem of whether the loss of orientation is due to a light-dependent magnetoreception mechanism or is instead an effect of motivation change is discussed.
Measurement of cell velocity distributions in populations of motile algae
Authors: Vladimirov V. A. , Wu M. S. C. , Pedley T. J. , Denissenko P. V. , Zakhidova S. G. 
Published: February 2004

SUMMARY
The self-propulsion of unicellular algae in still ambient fluid is studied using a previously reported laser-based tracking method, supplemented by new tracking software. A few hundred swimming cells are observed simultaneously and the average parameters of the cells' motility are calculated. The time-dependent, two-dimensional distribution of swimming velocities is measured and the three-dimensional distribution is recovered by assuming horizontal isotropy. The mean and variance of the cell turning angle are quantified, to estimate the reorientation time and rotational diffusivity of the bottom-heavy cell. The cells' phototactic and photokinetic responses to the laser light are evaluated. The results are generally consistent both with earlier assumptions about the nature of cell swimming and quantitative measurements, appropriately adjusted. The laser-based tracking method, which makes it possible to average over a large number of motile objects, is shown to be a powerful tool for the study of microorganism motility.
Charge Transport in a π-Stacked Poly(dibenzofulvene) Film
Authors: Nakano Tamaki , Yade Tohru , Yokoyama Masaaki , Nagayama Norio 
Published: February 2004

Abstract
Hole drift mobility of poly(dibenzofulvene) was found to be 2.7 × 10−4 cm2V−1s−1 at 299 K at a field strength of 7 × 105 Vcm−1 by the time-of-flight (TOF) measurement on a cast film containing 2,4,7-trinitrofluorenylidene-9-malononitrile as an electron acceptor. This value is higher than that of main-chain π-conjugating poly(π-phenylenevinylene) (1 × 10−5 cm2V−1s−1), is comparable to that of main-chain σ-conjugating poly(methylphenylsilane) (1 × 10−4 cm2V−1s−1), and is slightly lower than that of Se (10−4 cm2V−1s−1 order), an inorganic semiconductor.
Effects of K5SiW11O39Co on Mitogenic Activity of Basic Fibroblast Growth Factor
Authors: Sun Liwei , Wu Qiang , Liu Ning , Yang Cheng , Liu Liyan , Liu Zhiqiang , Zhao Daqing 
Published: February 2004

Abstract
The interaction between polyoxometalate (POM) of Keggin class (K5SiW11O39Co) and human basic fibroblast growth factor (bFGF) was studied by fluorescence and CD spectra. The results indicate that the binding of POM to bFGF causes conformational changes of bFGF. The cell proliferation assay showed that in lower molar ratios, POM stimulates mitogenic activity of bFGF; in higher molar ratios, POM inhibits the mitogenic activity of bFGF.
Monophosphate as Eminent Ligand to Bind Ce(IV)/EDTA Complex for Site-selective DNA Hydrolysis
Authors: Chen Wen , Igawa Tomoyuki , Sumaoka Jun , Komiyama Makoto 
Published: February 2004

Abstract
By the use of oligonucleotides bearing a terminal monophosphate, 10-base gap was formed in substrate DNA and the monophosphates were placed at the edge of gap. Upon the treatment of these systems with Ce(IV)/EDTA complex, the gap-site was selectively hydrolyzed. The monophosphates remarkably promoted both the selectivity and the efficiency of scission.
Carbon–Carbon Bond Formation in Glycolic Acid Generated Spontaneously from Dichloromethane in Hot Water
Authors: Wakai Chihiro , Morooka Saiko , Matubayasi Nobuyuki , Nakahara Masaru 
Published: February 2004

Abstract
Hydrothermal reaction of dichloromethane (CH2Cl2) at 1 mol/dm3 leads to the formation of glycolic acid without metal catalysts at temperatures of 200–250 °C. The reaction consists of three steps. First CH2Cl2 is converted into methanediol through hydrolysis. The disproportionation of methanediol then produces methanol and formic acid. Finally, glycolic acid is formed from methanediol and formic acid catalyzed by the acid (HCl) generated by the dechlorination of CH2Cl2. The yield of glycolic acid exceeds 50% at 225 and 250 °C.
Bi(OTf)3- and Bi(TFA)3-Catalyzed Ring Opening of Epoxides with Anilines under Microwave Irradiation
Authors: Khosropour Ahmad R , Khodaei Mohammad M , Ghozati Kazem 
Published: February 2004

Abstract
A facile and environmentally friendly methodology for ring opening of epoxides with anilines has been developed in the presence of catalytic amounts of bismuth (III) triflate or bismuth (III) trifluoroacetate using microwave-assisted heating. The ease of this procedure allowed preparation of the β-aminoalcohols quickly and efficiently.
Stereoselective Intercalation of Hexose for Layered Double Hydroxide by Calcination–Rehydration Reaction
Authors: Aisawa Sumio , Hirahara Hidetoshi , Takahashi Satoshi , Umetsu Yoshio , Narita Eiichi 
Published: February 2004

Abstract
The intercalation of four kinds of hexose for Mg–Al layered double hydroxide (LDH) by the calcination–rehydration reaction using the Mg–Al oxide precursor has been investigated. In spite of non-ionized organic guest, hexose was intercalated for the LDH, and the intercalation behavior of hexose was greatly influenced by the number of axial OH group. The intercalation driving force was thought to be based on hydrogen bond between axial OH group of the intercalated hexose and hydroxide basal layer.
First Example of a Heptacyclic Tetranuclear, Five- and Six-coordinate Titanium Complex, [{(iPrO)2Ti(μ3-O)TiCl(iPrO)((OC6H4)2PPh)}2]
Authors: Priya Srinivasan , Balakrishna Maravanji S , Mague Joel T 
Published: February 2004

Abstract
Novel heptacyclic tetranuclear titanium complex containing penta- and hexacoordinated titanium centers was synthesised by the reaction of bis(o-phenol)phenylphosphine with titanium tetrachloride.
The Sea Urchin-shaped CaCO3 via Template Mineralization on Surface-functionalized Vaterite Particles by Tiopronin-protected Gold Nanoparticles
Authors: Keum Dong-Ki , Naka Kensuke , Chujo Yoshiki 
Published: February 2004

Abstract
The sea urchin-shaped particles of CaCO3, i.e., spherical vaterite covered with needle-shaped aragonite, were formed by template mineralization of CaCO3 in the presence of the anionic gold nanoparticles modified spherical vaterite in water.
Iron(III) Chloride as a Water-Compatible Lewis Acid for Diastereoselective Aldol Reactions in Water in the Presence of a Surfactant
Authors: Aoyama Naohiro , Manabe Kei , Kobayashi Shu 
Published: February 2004

Abstract
Diastereoselective aldol reactions of various aldehydes with silicon enolates in water have been successfully carried out using iron(III) chloride and a surfactant. Contrary to previous understanding, iron(III) chloride has been shown to be a water-compatible Lewis acid. In this catalytic system, epimerization of the product was not observed, and this result indicates that the diastereoselectivity was controlled kinetically.
A Facile Synthesis of Various Fluorine-Containing Indole Derivatives via Palladium-Catalyzed Annulation of Internal Alkynes
Authors: Chae Jungha , Konno Tsutomu , Ishihara Takashi , Yamanaka Hiroki 
Published: February 2004

Abstract
The palladium-catalyzed annulation reaction of a variety of fluorine-containing internal alkynes with 2-iodoaniline derivatives took place smoothly to give the corresponding 2,3-disubstituted indole derivatives in good to excellent yields.
A Reaction Intermediate Involved in Oxygenation of Catecholatoiron(III) Complexes with Molecular Oxygen — Relevance to Catechol Dioxygenases
Authors: Hitomi Yutaka , Tase Yuichiro , Higuchi Masakazu , Tanaka Tsunehiro , Funabiki Takuzo 
Published: February 2004

Abstract
Formation of an intermediate in the step of O2 binding to a catecholatoiron(III) complex was first clearly shown by construction of a labile coordination site on the ferric center. In addition, spectral changes indicated reversible interconversion between the catecholatoiron(III) complex and the intermediate.