bluuebunny/crossref_metadata_2025_split huggingface dataset:
Copepod feeding currents: flow patterns, filtration rates and energetics
Authors: van Duren Luca A. , Stamhuis Eize J. , Videler John J. 
Published: December 2002

SUMMARY
Particle image velocimetry was used to construct a quasi 3-dimensional image of the flow generated by the feeding appendages of the calanoid copepod Temora longicornis. By scanning layers of flow, detailed information was obtained on flow velocity and velocity gradients.
The flow around feeding T. longicornis was laminar, and was symmetrical viewed dorsally, but highly asymmetrical viewed laterally, with high levels of vorticity on the ventral side. The flow rate through the feeding appendages varied between 77 and 220 ml day-1 per individual. The morphology of the flow field ensured that water was entrained over the full length of the first antennae. These were kept out of areas with high velocity gradients that could interfere with distant mechano- or chemoreception.
The volume of influence, i.e. the volume of water around the foraging copepod, where shear rates were significantly higher than background levels,was calculated. Implications for encounter probability and mechanoreception are discussed. The average rate of energy dissipation within the copepod's volume of influence is several times higher than the levels of turbulent energy dissipation these animals are likely to encounter in their environment. Even in highly turbulent environments, adult T. longicornis will not experience very significant effects of turbulence.
Within the volume of influence of the copepods the energy dissipation due to viscous friction varied between 6.6×10-11 and 2.3×10-10W. Taking mechanical efficiency and muscle efficiency into account, this results in a total energetic cost of the feeding current of 1.6×10-9W per copepod. This value represents only a small percentage of the total energy budget of small calanoid copepods.
Escape from viscosity: the kinematics and hydrodynamics of copepod foraging and escape swimming
Authors: van Duren Luca A. , Videler John J. 
Published: December 2002

SUMMARY
Feeding and escape swimming in adult females of the calanoid copepod Temora longicornis Müller were investigated and compared. Swimming velocities were calculated using a 3-D filming setup. Foraging velocities ranged between 2 and 6 mm s-1, while maximum velocities of up to 80 mm s-1 were reached during escape responses. Foraging took place at Reynolds numbers between 2 and 6, indicating that viscous forces are considerable during this swimming mode. Inertial forces are much more important during escape responses, when Reynolds numbers of more than 100 are reached.
High-speed film recordings at 500 frames s-1 of the motion pattern of the feeding appendages and the escape movement of the swimming legs revealed that the two swimming modes are essentially very different. While foraging, the first three mouth appendages (antennae, mandibular palps and maxillules) create a backwards motion of water with a metachronal beating pattern. During escape movements the mouth appendages stop moving and the swimming legs beat in a very fast metachronal rhythm, accelerating a jet of water backwards. The large antennules are folded backwards, resulting in a streamlined body shape.
Particle image velocimetry analysis of the flow around foraging and escaping copepods revealed that during foraging an asymmetrical vortex system is created on the ventral side of the animal. The feeding motion is steady over a long period of time. The rate of energy dissipation due to viscous friction relates directly to the energetic cost of the feeding current. During escape responses a vortex ring appears behind the animal, which dissipates over time. Several seconds after cessation of swimming leg movements, energy dissipation can still be measured. During escape responses the rate of energy dissipation due to viscous friction increases by up to two orders of magnitude compared to the rate when foraging.
Visualization of modulatory effects of serotonin in the silkmoth antennal lobe
Authors: Hill Evan S. , Okada Koutaroh , Kanzaki Ryohei 
Published: December 2002

SUMMARY
A unique serotonin-immunoreactive neuron innervates every glomerulus of the contralateral antennal lobe (AL), the primary olfactory center, of the male silkmoth Bombyx mori. In order to examine the possible modulatory effects of serotonin in the AL, we utilized high-speed optical imaging with a voltage-sensitive dye combined with bath application of serotonin. We found that serotonin at 10-4moll-1 caused significant and reversible increases in the optical responses in both the macroglomerular complex (MGC) and the ordinary glomeruli (Gs) evoked by electrical stimulation of the antennal nerve. Optical responses in both the MGC and Gs were also significantly longer lasting following serotonin application. Serotonin exerted a significantly greater enhancing effect in the toroid glomerulus of the MGC than in the cumulus, and the effects of serotonin were also non-homogenously distributed in the Gs. Our results are evidence that serotonin acts in both the MGC and Gs to modulate the responses of neuronal populations.
Endothermic heat production in honeybee winter clusters
Authors: Stabentheiner Anton , Pressl Helga , Papst Thomas , Hrassnigg Norbert , Crailsheim Karl 
Published: December 2002

SUMMARYIn order to survive cold northern winters, honeybees crowd tightly together in a winter cluster. Present models of winter cluster thermoregulation consider the insulation by the tightly packed mantle bees as the decisive factor for survival at low temperatures, mostly ignoring the possibility of endothermic heat production. We provide here direct evidence of endothermic heat production by `shivering' thermogenesis. The abundance of endothermic bees is highest in the core and decreases towards the surface. This shows that core bees play an active role in thermal control of winter clusters. We conclude that regulation of both the insulation by the mantle bees and endothermic heat production by the inner bees is necessary to achieve thermal stability in a winter cluster.
Freezing survival and cryoprotective dehydration as cold tolerance mechanisms in the Antarctic nematode Panagrolaimus davidi
Authors: Wharton David A. , Goodall Gordon , Marshall Craig J. 
Published: December 2002

SUMMARY
The relative importance of freezing tolerance and cryoprotective dehydration in the Antarctic nematode Panagrolaimus davidi has been investigated. If nucleation of the medium is initiated at a high subzero temperature (-1°C), the nematodes do not freeze but dehydrate. This effect occurs in deionised water, indicating that the loss of water is driven by the difference in vapour pressure of ice and supercooled water at the same temperature. If the nematodes are held above their nucleation temperature for a sufficient time, or are cooled slowly, enough water is lost to prevent freezing (cryoprotective dehydration). However, if the medium is nucleated at lower temperatures or if the sample is cooled at a faster cooling rate, the nematodes freeze and can survive intracellular ice formation. P. davidi thus has a variety of mechanisms that ensure its survival in its harsh terrestrial Antarctic habitat.
Adaptive color vision in Pullosquilla litoralis (Stomatopoda,Lysiosquilloidea) associated with spectral and intensity changes in light environment
Authors: Cheroske Alexander G. , Cronin Thomas W. , Caldwell Roy L. 
Published: December 2002

SUMMARY
Some stomatopod crustacean species that inhabit a range of habitat depths have color vision systems that adapt to changes in ambient light conditions. To date, this change in retinal function has been demonstrated in species within the superfamily Gonodactyloidea in response to varying the spectral range of light. Intrarhabdomal filters in certain ommatidia within the specialized midband of the eye change spectrally, modifying the sensitivity of underlying photoreceptors to match the spectrum of available light. In the present study, we utilized Pullosquilla litoralis, a member of the superfamily Lysiosquilloidea that also has a wide depth range. Individuals were placed within one of three light treatments: (1) full-spectrum,high-intensity `white' light, (2) narrow-spectrum `blue' light and (3)full-spectrum, reduced-intensity `gray' light. After 3 months, the intrarhabdomal filters in Row 3 ommatidia of the midband in blue- and gray-light-treated animals were short-wavelength shifted by 10-20 nm compared with homologous filters in animals in white-light treatments. These spectral changes increase the relative sensitivity of associated photoreceptors in animals that inhabit environments where light spectral range or intensity is reduced. The adaptable color vision system of stomatopods may allow animals to make the best use of the ambient light occurring at their habitat regardless of depth. The major controlling element of the plasticity in lysiosquilloid stomatopod color vision appears to be light intensity rather than spectral distribution.
Auditory encoding during the last moment of a moth's life
Authors: Fullard James H. , Dawson Jeff W. , Jacobs David S. 
Published: December 2002

SUMMARYThe simple auditory system of noctuoid moths has long been a model for anti-predator studies in neuroethology, although these ears have rarely been experimentally stimulated by the sounds they would encounter from naturally attacking bats. We exposed the ears of five noctuoid moth species to the pre-recorded echolocation calls of an attacking bat (Eptesicus fuscus) to observe the acoustic encoding of the receptors at this critical time in their defensive behaviour. The B cell is a non-tympanal receptor common to all moths that has been suggested to respond to sound, but we found no evidence of this and suggest that its acoustic responsiveness is an artifact arising from its proprioceptive function. The A1 cell, the most sensitive tympanal receptor in noctuid and arctiid moths and the only auditory receptor in notodontid moths, encodes the attack calls with a bursting firing pattern to a point approximately 150 ms from when the bat would have captured the moth. At this point, the firing of the A1 cell reduces to a non-bursting pattern with longer inter-spike periods, suggesting that the moth may no longer express the erratic flight used to escape very close bats. This may be simply due to the absence of selection pressure on moths for auditory tracking of bat echolocation calls beyond this point. Alternatively, the reduced firing may be due to the acoustic characteristics of attack calls in the terminal phase and an acoustic maneuver used by the bat to facilitate its capture of the moth. Although the role of less sensitive A2 cell remains uncertain in the evasive flight responses of moths it may act as a trigger in eliciting sound production, a close-range anti-bat behaviour in the tiger moth, Cycnia tenera.
Mussel MAP, a major gonad-duct esterase-like protein, is released into sea water as a dual constituent of the seminal fluid and the spermatozoon
Authors: Torrado Mario , Paz María , Korochkin Leonid I. , Mikhailov Alexander T. 
Published: December 2002

SUMMARYOur interest in the comparative analysis of male reproductive-tract esterases in different animal groups has led us to undertake a detailed study of the Mytilus galloprovincialis male-associated polypeptide (MAP)throughout the mussel gonad-duct tract and at spawning. The results of this work indicate that MAP is a major protein in M. galloprovincialissemen, with dual presence in both sperm cells and cell-free seminal fluid. Shortly after spawning, the released sperm mass is subdivided in diffused cloudy-like and thread-shaped `clots', in which a soluble-phase MAP may persist as long as the clots keep their compact form. Additional experiments involving the incubation of spawned spermatozoa at increasing Triton X-100 concentrations demonstrated that MAP is also strongly associated with sperm cells. These results were further validated by immunofluorescent staining,which revealed that MAP is localized in the mid-piece region of spawned spermatozoa. This unexpected finding raises the possibility that MAP may play a role in sperm fertility in bivalves. Using whole-mount histology and micromanipulation techniques, we studied the structural patterning of the mantle gonad-duct network and assessed the sampling of luminal contents from the ducts. Of particular interest is the observation that MAP content in the luminal fluid increases from the lumen of the spermatogenic tubules to that of the collecting gonad ducts, where MAP is detected at a very high concentration. These high levels may lead to a significant presence of MAP in semen and consequently to a prolonged survival of sperm spawned at sea. In addition, data related to the potential structural similarity between mussel MAP and esterase S of the Drosophila virilis ejaculatory bulb are presented and discussed. Finally, we show that the 64kDa protein of human semen reveals positive cross-reactivity with antibodies directed against Mytilus MAP and Drosophila esterase S. Taken together, the results reveal mussel MAP as the only esterase-like protein described so far whose distribution in the gonad and semen can be specifically associated with maturation, transport, emission and survival of spermatozoa outside.
Muscle fine structure may maintain the function of oxidative fibres in haemoglobinless Antarctic fishes
Authors: O'Brien K. M. , Skilbeck C. , Sidell B. D. , Egginton S. 
Published: December 2002

SUMMARYMuscle fine structure and metabolism were examined in four species of Antarctic fishes that vary in their expression of haemoglobin (Hb). To determine how locomotory pectoral muscles maintain function, metabolic capacity, capillary supply and fibre ultrastructure were examined in two nototheniid species that express Hb (Notothenia coriiceps and Gobionotothen gibberifrons) and two species of channichthyid icefish that lack Hb (Chaenocephalus aceratus and Chionodraco rastrospinosus). Surprisingly, icefish have higher densities of mitochondria than red-blooded species (C. aceratus, 53±3% of cell volume; C. rastrospinosus, 39±3%; N. coriiceps,29±3%; G. gibberifrons, 25±1%). Despite higher mitochondrial densities the aerobic metabolic capacities per g wet mass,estimated from measurements of maximal activities of key metabolic enzymes,are lower in icefish compared to red-blooded species. This apparent incongruity can be explained by the significantly lower mitochondrial cristae surface area per unit mitochondrion volume in icefishes (C. aceratus,20.8±1.6 μm-1; C. rastrospinosus,25.5±1.8 μm-1) compared to red-blooded species (N. coriiceps, 33.6±3.0 μm-1; G. gibberifrons,37.7±3.6 μm-1). Consequently, the cristae surface area per unit muscle mass is conserved at approximately 9 m2g-1. Although high mitochondrial densities in icefish muscle do not enhance aerobic metabolic capacity, they may facilitate intracellular oxygen movement because oxygen is more soluble in lipid,including the hydrocarbon core of intracellular membrane systems, than in aqueous cytoplasm. This may be particularly vital in icefish, which have larger oxidative muscle fibres compared to red-blooded nototheniods (C. aceratus, 2932±428 μm2; C. rastrospinosus,9352±318 μm2; N. coriiceps, 1843±312μm2; G. gibberifrons, 2103±194μm2). These large fibres contribute to a relatively low capillary density, which is partially compensated for in icefish by a high index of tortuosity in the capillary bed (C. aceratus=1.4, N. coriiceps=1.1).
Serotonin regulates repolarization of theC. eleganspharyngeal muscle
Authors: Niacaris Timothy , Avery Leon 
Published: December 2002

SUMMARYCaenorhabditis elegans feeds by rhythmically contracting its pharynx to ingest bacteria. The rate of pharyngeal contraction is increased by serotonin and suppressed by octopamine. Using an electrophysiological assay,we show that serotonin and octopamine regulate two additional aspects of pharyngeal behavior. Serotonin decreases the duration of the pharyngeal action potential and enhances activity of the pharyngeal M3 motor neurons. Gramine, a competitive serotonin antagonist, and octopamine have effects opposite to those of serotonin: gramine and octopamine increase action potential duration and suppress M3 activity. The effects of serotonin, gramine and octopamine on action potential duration are dependent on the pharyngeal motor neurons MC and M3. When the MC and M3 motor neurons are functionally defective, serotonin and octopamine do not regulate the action potential. Our data suggest that serotonin alters pharyngeal physiology to allow for rapid contraction—relaxation cycles. Reciprocal regulation of pharyngeal behavior by serotonin and octopamine provides a mechanism for adapting to the presence and absence of food, respectively.
Quantitative changes in yolk protein and other components in the ovary and testis of the sea urchin Pseudocentrotus depressus
Authors: Unuma T. , Yamamoto T. , Akiyama T. , Shiraishi M. , Ohta H. 
Published: December 2002

SUMMARY
Both male and female sea urchins accumulate the major yolk protein (MYP;the most abundant yolk granule protein in sea urchin eggs) in the nutritive phagocytes of immature gonads before gametogenesis. In this study,quantitative changes in MYP as well as in other biochemical components in the ovary and testis were examined in the course of gametogenesis in Pseudocentrotus depressus. Before gametogenesis, both the ovary and testis contained large quantities of proteins, lipids and polysaccharides. MYP reached about 80% of total protein in both sexes. In the testis, MYP decreased rapidly as spermatogenesis proceeded, and the fully mature testis contained little MYP; the levels of lipids and polysaccharides also decreased. In contrast, the levels of nucleic acids and proteins other than MYP increased markedly. In the ovary, MYP decreased gradually as oogenesis proceeded, and the fully mature ovary contained less than half of the initial amount of MYP. Polysaccharides also decreased, whereas proteins other than MYP increased. These results, taken together with those from other studies, suggest that MYP serves as a protein reserve that accumulates before gametogenesis and is used as material for synthesizing new substances constituting gametes in both male and female sea urchins.
Tissue-specific expression of inducible and constitutive Hsp70 isoforms in the western painted turtle
Authors: Scott Michelle Anne , Locke Marius , Buck Leslie Thomas 
Published: December 2002

SUMMARYExpression of Hsp73 and Hsp72 in four tissues of the naturally anoxia-tolerant western painted turtle (Chrysemys picta) was investigated in response to a 24 h forced dive and following 1 h recovery. Of the tissues examined, brain and liver displayed approximately threefold and sevenfold higher basal Hsp73 expression than heart and skeletal muscle. Basal Hsp72 expression was relatively low in all tissues examined. After the 24 h forced dive and 1 h recovery, Hsp73 expression did not differ significantly from basal expression with the exception of liver, where expression decreased significantly after 1 h recovery. Hsp72 expression was unchanged in liver following a 24 h dive; however, it increased twofold in brain and threefold in heart and skeletal muscle. Dive-induced Hsp72 expression was found to correlate inversely with basal Hsp73 expression. Following 1 h recovery, Hsp72 expression was significantly elevated in all tissues above levels in dived animals. These data indicate a tissue-specific pattern of Hsp73 and Hsp72 expression in the western painted turtle during both unstressed and stressed conditions.
Preferred temperature of juvenile Atlantic codGadus morhuawith different haemoglobin genotypes at normoxia and moderate hypoxia
Authors: Petersen Maria Faldborg , Steffensen John Fleng 
Published: December 2002

SUMMARYAtlantic cod Gadus morhua has polymorphic haemoglobin, which can be separated into two homozygous types, HbI-1 and HbI-2, and one heterozygous type HbI-1/2. The geographical distribution of Atlantic cod with the different haemoglobin types varies, with the HbI2 allele occurring at high frequency in northern regions, and the HbI1 allele dominant in warmer areas. To determine if temperature is a selective parameter in the distribution of the haemoglobin types, the preferred temperature of the homozygous genotypes HbI-1 and HbI-2 was measured. We found that HbI-2 cod preferred a temperature of 8.2±1.5°C while HbI-1 cod preferred 15.4±1.1°C, and this preference was significant. The effect of hypoxia (35% oxygen saturation) on the preferred temperature was also measured. Previous studies showed that the preferred temperature of fish decreases during hypoxia, and this was the case for HbI-1 cod, which preferred 9.8±1.8°C during hypoxia, whereas HbI-2 cod did not show this effect. The results indicate that environmental temperature changes will lead to a distributional change in the different haemoglobin types of Atlantic cod,global warming providing an advantage for HbI-1 cod. However, since HbI-1 cod prefer a low temperature under hypoxic conditions, a combination of increased water temperature and hypoxia could be unfavourable for Atlantic cod stocks.
Site-Selective Activation of RNA Leading to Sequence-Selective RNA Cutters
Authors: Komiyama Makoto , Kuzuya Akinori , Mizoguchi Ryo 
Published: December 2002

Abstract
New types of RNA cutters for site-selective scission are prepared by combining metal ions with oligonucleotides bearing an acridine. Both lanthanide(III) ions and various divalent metal ions (e.g., Zn(II), Mn(II), and Mg(II)) are used without being bound to any sequence-recognizing moiety. The modified oligonucleotide forms a hetero-duplex with the RNA, and activates the phosphodiester linkages in front of the acridine. As a result, these linkages are preferentially hydrolyzed over the others, even though the metal ions are not fixed anywhere. The scission is efficient under physiological conditions, irrespective of the sequence at the target site. Site-selective RNA scission is also accomplished by combining an oligonucleotide bearing an acridine at its terminus, another unmodified oligonucleotide, and a metal ion. In the proposed mechanism, the acridine pushes the unpaired ribonucleotide out of the hetero-duplex and changes the conformation of RNA at the target site for the sequence-selective activation.
Ab Initio Direct Molecular Dynamics Simulations and QM/MM Computations in Search of Organic Reaction Mechanisms
Authors: Yamataka Hiroshi , Aida Misako 
Published: December 2002

Abstract
Ab initio direct-MD simulations and combined QM/MM computations are the theoretical methods that are expected to play an important role in the study of organic reaction mechanisms in the near future. This account reviews recent achievements with these methods in mechanistic studies of organic reactions. In particular the focus is placed on proton transfer, SN1, SN2, and SN2/ET borderline reactions as illustrative examples. The direct-MD simulations revealed the importance of dynamics in controlling the reaction path, which can often be different from the minimum energy path on the potential energy surface. It was also demonstrated that the QM/MM computations could be a promising method to analyze reactions in solution.
Synthesis, Structure, and Photochemistry of 2,3,5,6-Tetrasilyl-1,4-benzoquinones and Related Compounds
Authors: Tsutsui Shinobu , Sakamoto Kenkichi , Ebata Keisuke , Kabuto Chizuko , Sakurai Hideki 
Published: December 2002

Abstract
2,3,5,6-Tetrasilyl- and 2,3,5,6-tetragermyl-1,4-benzoquinones were obtained by oxidation of the corresponding 1,4-dimetaloxybenzene derivatives with pyridinium chlorochromate. X-ray crystallographic analysis revealed that the quinone ring of 2,3,5,6-tetrakis(trimethylsilyl)-1,4-benzoquinone (1a) was distorted into a chair form. The deformed quinone ring allowed a σ(Cquinone-Si)–π* electronic transition in 1a. Photolysis of 1a resulted in an isomerization, creating a ketene derivative, 4-carbonyl-2,3,5,5-tetrakis(trimethylsilyl)-2-cyclopenten-1-one.