bluuebunny/crossref_metadata_2025_split huggingface dataset:
Neuromodulation in invertebrate sensory systems: from biophysics to behavior
Authors: Birmingham John T. , Tauck David L. 
Published: September 2003

SUMMARYNeuromodulation may enhance the ability of sensory circuits to respond appropriately to widely variable environmental stimuli. The functional significance of neuromodulation will emerge from understanding the effects of modulators not just on single cells and synapses, but also on networks and the behavior of intact animals. With their relatively simple circuitry and large identifiable cells, invertebrate nervous systems offer insights into the complex roles of neuromodulators in modifying networks to meet the changing needs of the animal. Here we describe the role of neuromodulation in several invertebrate sensory systems that have been studied at a variety of levels,from the biophysical up to the behavioral.
Discontinuous gas exchange and the significance of respiratory water loss in scarabaeine beetles
Authors: Chown Steven L. , Davis Adrian L. V. 
Published: September 2003

SUMMARYRespiratory water loss in insects is a controversial topic. Whilst earlier studies considered respiratory transpiration a significant component of overall water loss, to the extent that it was thought to be responsible not only for the evolution of discontinuous gas exchange cycles (DGCs) but also for variation in DGC patterns, later work repeatedly questioned its importance. In particular, investigations of the proportional contribution of respiratory transpiration to total water loss in species showing DGCs suggested that respiratory transpiration was unlikely to be important in these species. In turn, these studies have been criticized on analytical grounds. In this study we investigated variation in cuticular and respiratory water loss rates in five Scarabaeus dung beetle species, all of which show discontinuous gas exchange cycles, to ascertain the significance of respiratory water loss using modern analytical techniques. In particular, we determined whether there is variation in water loss rates amongst these beetles, whether both respiratory and cuticular water loss rates contribute significantly to variation in the former, and whether metabolic rate variation and variation in the duration of the DGC periods contribute significantly to variation in respiratory water loss rate. Total water loss rate varied such that species from arid areas had the lowest rates of water loss, and both cuticular and spiracular transpiration contributed significantly to variation in overall water loss rate. Moreover, variation in metabolic rate and in the duration of the DGC periods contributed significantly to variation in respiratory water loss rate. By contrast, examination of proportional water loss revealed little other than that it varies between 6.5% and 21%, depending on the species and the temperature at which it was examined. Cuticular water loss scaled as mass0.721, but did not differ from that expected from geometric considerations alone. By contrast, respiratory water loss scaled as mass0.531, suggesting that gas exchange takes place by diffusion and convection. Our results provide direct evidence that respiratory water loss forms a significant component of water balance, and that changes in both metabolic rate and DGC characteristics contribute to modulation of respiratory water loss.
Lactate sequestration by osteoderms of the broad-nose caiman,Caiman latirostris, following capture and forced submergence
Authors: Jackson Donald C. , Andrade Denis V. , Abe Augusto S. 
Published: September 2003

SUMMARYLactate accumulation in osteoderms of the broad-nose caiman, Caiman latirostris, was determined following capture and surgery and after a period of forced submergence and related to concurrent values in blood. Control samples of bone and blood were taken after recovery from surgery and before submergence. In addition, samples of osteoderm were incubated in a lactate solution to determine equilibrium concentration, and additional samples were analyzed for elemental and CO2 concentrations. The composition of the osteoderms closely resembles that of typical vertebrate bone, with a high concentration of calcium and phosphate. Plasma and osteoderm lactate concentrations were both elevated following surgery and decreased significantly after 1 day of recovery. Submergence produced a typical lactate pattern in the plasma, with only a modest increase during the dive and then a sharp increase during recovery to a peak of 31.2±1.9 μmol ml-1 after 1 h. When caimans were anesthetized 2 h after submergence, osteoderm lactate in the same animals was significantly increased to 14.8 μmol g-1 wet mass. The ratio of the osteoderm:plasma lactate concentration after submergence was similar to the ratio observed in the incubated samples, suggesting that osteoderm lactate concentrations in vivo were equilibrated with circulating plasma levels. We conclude that caiman osteoderms sequester lactate during lactic acidosis and that the time course is fast enough to have benefit to these animals following normal anaerobic burst activity.
A comparison of the effects of environmental ammonia exposure on the Asian freshwater stingrayHimantura signiferand the Amazonian freshwater stingrayPotamotrygon motoro
Authors: Ip Yuen K. , Tam Wai L. , Wong Wai P. , Loong Ai M. , Hiong Kum C. , Ballantyne James S. , Chew Shit F. 
Published: September 2003

SUMMARYThe white-edge whip tail ray Himantura signifer inhabits a freshwater environment but has retained the capability to synthesize urea de novo through the arginine-ornithine-urea cycle (OUC). The present study aimed to elucidate whether the capacity of urea synthesis in H. signifer could be upregulated in response to environmental ammonia exposure. When H. signifer was exposed to environmental ammonia,fairly high concentrations of ammonia were accumulated in the plasma and other tissues. This would subsequently reduce the net influx of exogenous ammonia by reducing the NH3 partial pressure gradient across the branchial and body surfaces. There was also an increase in the OUC capacity in the liver. Since the ammonia produced endogenously could not be excreted effectively in the presence of environmental ammonia, it was detoxified into urea through the OUC. In comparison, the South American freshwater stingray Potamotrygon motoro, which has lost the capability to synthesize urea de novo, was unable to detoxify ammonia to urea during ammonia loading. No increase in glutamine was observed in the various tissues of H. signifer exposed to environmental ammonia despite a significant increase in the hepatic glutamine synthetase activity. These results indicate that the excess glutamine formed was channelled completely into urea formation through carbamoyl phosphate synthetase III. It has been reported elsewhere that both urea synthesis and urea retention were upregulated in H. signiferexposed to 20‰ water for osmoregulatory purposes. By contrast, for H. signifer exposed to environmental ammonia in freshwater, the excess urea formed was excreted to the external medium instead. This suggests that the effectiveness of urea synthesis de novo as a strategy to detoxify ammonia is determined not simply by an increase in the capacity of urea synthesis but, more importantly, by the ability of the animal to control the direction (i.e. absorption or excretion) and rate of urea transport. Our results suggest that such a strategy began to develop in those elasmobranchs,e.g. H. signifer, that migrate into a freshwater environment from the sea but not in those permanently adapted to a freshwater environment.
Morphological and enzymatic correlates of aerobic and burst performance in different populations of Trinidadian guppiesPoecilia reticulata
Authors: Odell Jason P. , Chappell Mark A. , Dickson Kathryn A. 
Published: September 2003

SUMMARYWe examined the mechanistic basis for two whole-animal performance traits,aerobic capacity and burst speed, in six laboratory-reared Trinidadian guppy populations from different native drainages with contrasting levels of predation. Using within- and between-population variation, we tested whether variation in organs and organ systems (heart, gill and swimming motor mass)and the activities of several enzymes that support locomotion (citrate synthetase, lactate dehydrogenase and myofibrillar ATPase) are correlated with aerobic performance (maximum rates of oxygen consumption, V̇O2max) or burst performance (maximum swim speed during escape responses). We also tested for associations between physiological traits and habitat type (different drainages and predation levels).Organ size and enzyme activities showed substantial size-independent variation, and both performance measures were strongly correlated to body size. After accounting for size effects, neither burst nor aerobic performance was strongly correlated to any organ size or enzymatic variable, or to each other. Two principal components (PCI, PC2) in both males and females accounted for most of the variance in the organ size and enzymatic variables. In both sexes, heart and gill mass tended to covary and were negatively associated with citrate synthetase and lactate dehydrogenase activity. In males (but not females), variation in aerobic performance was weakly but significantly correlated to variation in PC1, suggesting that heart and gill mass scale positively with V̇O2max. Neither of the component variables and no single morphological or enzymatic trait was correlated to burst speed in either sex.Evolutionary changes in important life history traits occur rapidly in guppy populations subjected to different predation intensities (high mortality in downstream sites inhabited by large predatory fish; low mortality in upstream sites lacking large predators). We found significant differences between stream drainages in all morphological variables and most enzymatic variables, but only the mass of the swimming motor and LDH activity were significantly affected by predation regime. Overall, our data show that microevolution has occurred in the physiological foundations of locomotor performance in guppies, but evolutionary changes in physiology do not closely correspond to the predation-induced changes in life history parameters.
Time-course of the effect of dietaryl-tryptophan on plasma cortisol levels in rainbow troutOncorhynchus mykiss
Authors: Lepage Olivier , Vílchez Inmaculada Molina , Pottinger Tom G. , Winberg Svante 
Published: September 2003

SUMMARYIsolated juvenile rainbow trout were fed a feed supplemented with l-tryptophan (TRP) for 3, 7 or 28 days, after which they were either sampled directly (undisturbed) or subjected to a standardised stressor prior to sampling. Controls (stressed and undisturbed) received the same feed but without any supplementary TRP. Stress resulted in a significant elevation of plasma [cortisol] in fish fed control feed and in fish fed TRP-supplemented feed for 3 and 28 days. However, fish fed TRP-supplemented feed for 7 days did not show any significant elevation of plasma [cortisol] in response to stress. Plasma levels of adrenocorticotropin followed the same general pattern as cortisol. Plasma and brain [TRP] were elevated in fish fed TRP-supplemented feed. The amino acid TRP is the precursor of the monoamine neurotransmitter serotonin (5-hydroxytryptamine, 5-HT) and the brain 5-HT system is known to be involved in the control of the hypothalamic-pituitary-interrenal (HPI) axis. Fish fed TRP-supplemented feed showed elevated levels of 5-hydroxyindoleacetic acid (5-HIAA, a major 5-HT metabolite) in the hypothalamus and optic tectum. However, TRP treatment did not appear to result in any effects on brain dopaminergic activity and the effects on brain norepinephric activity do not support a role of norepinephrine in mediating the effects of TRP on HPI axis reactivity in rainbow trout.
Characterization of the passive component of force enhancement following active stretching of skeletal muscle
Authors: Herzog W. , Schachar R. , Leonard T. R. 
Published: September 2003

SUMMARYThe mechanisms causing the steady-state force enhancement following active skeletal muscle stretching are not well understood. Recently, we found direct evidence that part of the force enhancement is associated with the engagement of a passive component. In this study, we reproduced the conditions that give consistent passive force enhancement and evaluated the mechanical properties of this passive force enhancement so as to gain insight into its source. The three primary results were that (1) the passive force enhancement is long lasting (&gt;25 s), (2) passive force enhancement was reduced in a dose-dependent manner by the amount of shortening preceding active muscle stretching, and (3) passive force enhancement could be abolished`instantaneously' by shortening-stretching the passive muscle by an amount equivalent to the active stretch magnitude. Together with the remaining results, we conclude that the source of the passive force enhancement must be arranged in parallel with the contractile force, it must consist of a viscoelastic molecular spring whose stiffness characteristic can be reset by shortening, and it must have a characteristic length that is governed by the length of the contractile components, possibly the sarcomeres. Based on these results, the molecular spring titin emerges as a possible candidate for the passive component of the steady-state force enhancement observed in this and previous studies.
The effect of side-restraint bearings on the performance of base-isolated buildings
Authors: Talbot J P , Hunt H E M 
Published: September 2003

Base-isolation of buildings is a common solution to the problem of ground-borne vibration from urban road and rail networks. Conventional designs incorporate vibration isolation bearings between a building and its foundation, aligned in the vertical direction so as to isolate the building from vertical motion of its foundation. In some cases, in order to accommodate horizontal loads, additional side-restraint bearings aligned in the horizontal direction are required. This paper describes a theoretical investigation into the effect of side-restraint bearings on the performance of base-isolated buildings. Three generic models, based on a modern concrete-framed building, are used to demonstrate that a building's flexibility, the nature of the vibration input and the presence of a flexible foundation are all important in determining isolation performance. It is also illustrated how the concept of isolation frequency, commonly used to indirectly specify the stiffness of base bearings, may not be generally extended to side-restraint bearings. The models indicate that, for maximum performance, the stiffness of any side-restraint bearings should be minimized.
Use of the inverse method to check the stress predictions in rough elastohydrodynamic lubrication contacts lubricated with a non-Newtonian fluid for a range of asperity geometries
Authors: Hooke C J , Li K Y 
Published: September 2003

The inverse method enables a check to be made on the pressures and stresses calculated in rough elastohydrodynamic lubrication (EHL) contacts. Essentially, a rough, soft surface is run against a smooth, hard counterface in a twin disc machine for a limited time. This tends to deform the asperities on the soft disc and, at the end of the run, the profile is measured and used as input to an EHL solver to determine the hydrodynamic pressures. From these the stresses are calculated. If the material has deformed and deformation has ceased, the maximum stress should be equal to the yield strength of the soft disc. This comparison provides a quantitative check on the accuracy of the EHL analysis and on the assumptions made about the fluid rheology. Allowance has, of course, to be made for the build-up of residual stress in the disc material. The method is applied here to surfaces in which defects with a range of sizes have been manufactured. A non-Newtonian fluid with reasonably well-established characteristics was used under conditions of moderate slip. Good agreement is found between the predicted stresses and the material strength for all defect geometries, suggesting that the fluid properties are sufficiently well defined for accurate predictions to be made of the pressures and stresses in EHL conjunctions.
Nucleation phenomena in a multi-stage low pressure steam turbine
Authors: Bohn D. E. , Sürken N , Kreitmeier F 
Published: September 2003

During the expansion of steam in the low pressure (LP) stages of steam turbines, the originating two-phase wet-steam mixture causes considerable thermodynamic losses as well as aerodynamic losses. The reduction of these loss mechanisms is the subject of research project at the Institute of Steam and Gas Turbines, Aachen University. A three-dimensional nucleating wet steam flow with homogeneous/heterogeneous nucleation in the three front stages of an industrial LP-steam turbine is investigated numerically. The steady, viscous, and compressible metastable steam flow calculations are performed with a Navier—Stokes flow solver incorporating the IAPWS-IF97 steam tables. A union numerical approach for both the homo- and heterogeneous nucleation occurring on soluble nuclei is employed to capture the effects related to the nucleation phenomenon. The model links the interfacial surface tension, the size of nuclei, the chemical characteristics of the substances forming the droplets, and the expansion rate with the nucleation rate. In order to take into account the additional viscous effects due to shrouded bladings, the open shroud cavities are modeled in detail. Droplet density spectra, radial droplet number, droplet diameter, and wetness fraction distributions at the exit of the third stage are calculated. It is shown that impurities can cause nucleation to appear at lower supersaturations with higher nucleation rates compared to homogeneous nucleation of pure steam. In this way, thermodynamic and kinematic relaxation losses are reduced. Owing to the dissipative viscous effects near the endwalls, the nucleation fronts exhibit convex shapes. They are locally bound within the region of high expansion rates in the second stage's nozzle guide vane. For both heterogeneous and homogenous nucleating flows the wetness is highly dispersed with narrow droplet density spectra behind the three front stages.
Hydrolysis of Diribonucleoside Monophosphate Diesters Assisted by a Manganese(II) Complex
Authors: Yashiro Morio , Higuchi Maiko , Komiyama Makoto , Ishii Youichi 
Published: September 2003

Abstract
An Mn2+ complex with 2,2′:6′,2″-terpyridine (terpy) was found to promote the hydrolysis of NpN (NpN = diribonucleoside monophosphate diester) efficiently at pH 7.0 and 50 °C under ambient conditions. The structure of the Mn2+ complex involving a phosphodiester molecule, [(terpy)(dpp)MnII(μ-dpp)2MnII(dpp)(terpy)], dpp = diphenyl phosphate anion, was established by X-ray crystallography, and the coordination mode of Mn2+ to a phosphodiester molecule was considered.
Convergent Total Syntheses of Oligosaccharides by One-Pot Sequential Stereoselective Glycosylations
Authors: Hashihayata Takashi , Ikegai Kazuhiro , Takeuchi Kazuya , Jona Hideki , Mukaiyama Teruaki 
Published: September 2003

Abstract
A convergent total synthesis of F1α antigen, a member of the tumor-associated O-linked mucin glycosyl amino acid, was tried by one-pot sequential glycosylation. Highly α-selective glycosylation of amino acid 7 with thioglycoside 6 was successfully carried out by combining trityl trifluoromethanesulfonate (TrOTf) and N-iodosuccimide (NIS) which gave glycosyl amino acid 21 in high yield (97%, α/β = 83⁄17). Next, the glycosylation of thioglycoside 4 with galactosyl phenyl carbonate 2 or fluoride 3 was tried by the promotion of trityl tetrakis(pentafluorophenyl)borate [TrB(C6F5)4] or trifluoromethanesulfonic acid (TfOH); protected F1α 25 was afforded in 80 or 89% overall yield, respectively, by the further addition of glycosyl amino acid 5 and NIS. The desired trisaccharide was obtained in high yield after removal of the protecting groups. Next, a convergent total synthesis of branched hepta-β-glucoside 30 having phytoalexin-elicitor activity was efficiently performed by way of two one-pot sequential glycosylation reactions: that is, trisaccharide 34 was synthesized in high yield by TfOH-catalyzed one-pot glycosylation using three given monosaccharides (31, 35, and 36) as shown in Scheme 12 and by subsequent selective deprotection of 6′-O-TBDPS group. The second one-pot glycosylation of trisaccharide 34 with three monosaccharides (31, 32, and 33d) also proceeded smoothly to afford heptaglucoside 43 stereoselectively in 48% total yield based on monosaccharide 32. Phytoalexin-elicitor active branched hepta-β-glucoside 30 was afforded by the sequential deprotection.
Efficient Synthesis of Heterocyclic 2-Deoxysteptamine Derivatives as RNA Binding Ligands
Authors: Ding Yili , Hofstadler Steven A , Swayze Eric E , Griffey Richard H 
Published: September 2003

Abstract
An efficient strategy for the synthesis of heterocyclic 2-deoxystreptamine derivatives is described. The resulting compounds showed good RNA binding affinities from ESI-MS RNA binding assay.
Synthesis and Properties of Carbazole–Terephthalate Cyclophane
Authors: Tani Keita , Matsumura Koh , Togo Eiichi , Hori Kazushige , Tohda Yasuo , Takemura Hiroyuki , Ohkita Hideo , Ito Shinzaburo , Yamamoto Masahide 
Published: September 2003

Abstract
As a first example of carbazole–acceptor cyclophane, carbazole–terephthalate cyclophane 1a was prepared. The structure of 1a was characterized by 1H NMR and X-ray analysis. Absorption spectrum of 1a showed the existence of transannular π–π electronic interaction and little charge transfer interaction. Fluorescence spectrum of 1a in THF exhibited intramolecular exciplex emission around 525 nm.
Synthesis of Stannole Anion by Alkylation of Stannole Dianion
Authors: Saito Masaichi , Haga Ryuta , Yoshioka Michikazu 
Published: September 2003

Abstract
Reaction of tert-butylchloride with the stannole dianion first and simply prepared by the reduction of 1,1,2,3,4,5-hexaphenylstannole with lithium in ether gave 1-tert-butylstannole anion which was characterized by 1H, 13C, 119Sn, and 7Li NMR spectra and whose reactivities were investigated.
Biphenylene Bridged Bifunctional Hybrid Mesoporous Silsesquioxanes with Sulfonic Acid Functionalities and Crystalline Pore Walls
Authors: Kapoor Mahendra P , Yang Qihua , Goto Yasutomo , Inagaki Shinji 
Published: September 2003

Abstract
The first synthesis of highly hydrophobic bifunctional biphenylene bridged hybrid mesoporous silsesquioxane with sulfonic acid functionalities and crystalline pore walls is reported.
Water-soluble Fluorescent Nanospheres as Fluorosensor for Detection of Cu2+
Authors: Xu Shiyi , Tu Guoli , Han Xiaozu 
Published: September 2003

Abstract
A novel water-soluble fluorescent nanosphere as fluorosensor was prepared by emulsifier-free emulsion copolymerization of styrene with naphthalimide derivative (A). The fluorosensor was high sensitive for detection of Cu2+. Comparied with other fluorosensors based on organic fluorophore, it has two advantages. First, there is no pollution to environment in the use of it. Second, it can be used repeatedly.
A Facile Method for Synthesis of Alkyl Phenyl Selenides. The Reaction of Diphenyl Diselenide with Oxygen-containing Compounds Using La/Me3SiCl/cat.I2/cat.CuI System
Authors: Nishino Toshiki , Nishiyama Yutaka , Sonoda Noboru 
Published: September 2003

Abstract
Alcohols, ethers, and esters were directly converted to the corresponding alkyl phenyl selenides by the reaction of diphenyl diselenide and the La/Me3SiCl/cat.I2/cat.CuI. It was suggested that alkyl phenyl selenides were formed by the SH2 type reaction of diphenyl diselenide with alkyl radicals generated from alcohols, ethers or esters.