bluuebunny/crossref_metadata_2025_split huggingface dataset:
Elasticity, unexpected contractility and the identification of actin and myosin in lobster arteries
Authors: Wilkens J. L. , Cavey M. J. , Shovkivska I. , Zhang M. L. , Keurs H. E. D. J. ter 
Published: February 2008

SUMMARYLobster arteries, which exhibit non-uniform elasticity when stretched, have a trilaminar organization. The inner layer is an elastic connective tissue and the outer layer is a collagenous connective tissue; the middle layer of an artery is an aggregation of cells containing microfilaments. Arterial cells possess actin, myosin and tropomyosin. Except for the dorsal abdominal artery,striated muscle cells are not evident in the walls of any of the vessels. The neurotransmitter glutamic acid and the neurohormone proctolin elicit slow circumferential contractions in all of the arteries leaving the lobster heart. Only the dorsal abdominal artery contracts when stimulated electrically. Longitudinal strips of the arteries do not respond to either drugs or electrical stimulation. Arterial contraction will have profound effects on resistance to blood flow and may be an important component of the control mechanisms regulating blood distribution.
Response properties of electrosensory units in the midbrain tectum of the paddlefish (Polyodon spathula Walbaum)
Authors: Hofmann M. H. , Jung S. N. , Siebenaller U. , Preißner M. , Chagnaud B. P. , Wilkens L. A. 
Published: February 2008

SUMMARY
Paddlefish use their peculiar rostrum to detect minute electric fields from their main prey, small water fleas. Electroreceptors over the rostrum and head sense these fields and send the information into a single hindbrain area, the dorsal octavolateral nucleus (DON). From there, information is sent to various midbrain structures, including the tectum. The response properties of primary afferent fibers and DON units has been well investigated, but nothing is known about electrosensory units in the midbrain. Here we recorded the responses of single units in the midbrain tectum and DON to uniform electric fields. Tectal units exhibited little spontaneous activity and responded to sine waves with a few, well phase-locked spikes. Phase locking was still significant at amplitudes one order of magnitude lower than in the DON. If stimulated with sinusoidal electric fields of different frequencies, phase locking in DON units decreased proportionally with frequency whereas the response of tectal units depended little on frequency. This is in agreement with behavioral studies showing that relevant frequencies range from DC to ca 20 Hz.
Feeding kinematics, suction and hydraulic jetting capabilities in bearded seals (Erignathus barbatus)
Authors: Marshall Christopher D. , Kovacs Kit M. , Lydersen Christian 
Published: February 2008

SUMMARYFeeding kinematics, suction and hydraulic jetting capabilities of bearded seals (Erignathus barbatus) were characterized during controlled feeding trials. Feeding trials were conducted both on land and in water, and allowed a choice between suction and biting, but food was also presented that could be ingested by suction alone. Four feeding phases, preparatory, jaw opening, hyoid depression and jaw closing were observed; the mean feeding cycle duration was 0.54±0.22 s, regardless of feeding mode(P&gt;0.05). Subjects feeding on land used biting and suction 89.3%and 10.7% of the time, respectively. Subjects feeding in water used suction and hydraulic jetting 96.3% and 3.7% of the time, respectively. No biting behavior was observed underwater. Suction feeding was characterized by a small gape (2.7±0.85 cm), small gape angle (24.4±8.13°), pursing of the rostral lips to form a circular aperture, and pursing of the lateral lips to occlude lateral gape. Biting was characterized by large gape(7.3±2.2 cm), large gape angle (41.7±15.2°), and lip curling to expose the teeth. An excavation behavior in which suction and hydraulic jetting were alternated was used to extract food from recessed wells. The maximum subambient and suprambient pressures recorded were 91.2 and 53.4 kPa,respectively. The inclusion of suction data for phocids broadens the principle that suction feeding kinematics is conserved among aquatic vertebrates. Furthermore, bearded seals support predictions that mouth size, fluid flow speed, and elusiveness of prey consumed are among a suite of traits that determine the specific nature of suction feeding among species.
Vision in the nocturnal wandering spider Leucorchestris arenicola (Araneae: Sparassidae)
Authors: Nørgaard Thomas , Nilsson Dan-Eric , Henschel Joh R. , Garm Anders , Wehner Rüdiger 
Published: February 2008

SUMMARY
At night the Namib Desert spider Leucorchestris arenicola performs long-distance homing across its sand dune habitat. By disabling all or pairs of the spiders' eight eyes we found that homing ability was severely reduced when vision was fully abolished. Vision, therefore, seems to play a key role in the nocturnal navigational performances of L. arenicola. After excluding two or three pairs of eyes, the spiders were found to be able to navigate successfully using only their lateral eyes or only their anterior median eyes. Measurement of the eyes' visual fields showed that the secondary eyes combined have a near full (panoramic) view of the surroundings. The visual fields of the principal eyes overlap almost completely with those of the anterior lateral eyes. Electroretinogram recordings indicate that each eye type contains a single photopigment with sensitivity peaking at ∼525 nm in the posterior and anteriomedian eyes, and at ∼540 nm in the anteriolateral eyes. Theoretical calculations of photon catches showed that the eyes are likely to employ a combination of spatial and temporal pooling in order to function at night. Under starlit conditions, the raw spatial and temporal resolution of the eyes is insufficient for detecting any visual information on structures in the landscape, and bright stars would be the only objects visible to the spiders. However, by summation in space and time, the spiders can rescue enough vision to detect coarse landscape structures. We show that L. arenicola spiders are likely to be using temporal summation to navigate at night.
Physiological characterization of stolon regression in a colonial hydroid
Authors: Vogt Kimberly S. Cherry , Geddes Gabrielle C. , Bross Lori S. , Blackstone Neil W. 
Published: February 2008

SUMMARYAs with many colonial animals, hydractiniid hydroids display a range of morphological variation. Sheet-like forms exhibit feeding polyps close together with short connecting stolons, whereas runner-like forms have more distant polyps and longer connecting stolons. These morphological patterns are thought to derive from rates of stolon growth and polyp formation. Here,stolon regression is identified and characterized as a potential process underlying this variation. Typically, regression can be observed in a few stolons of a normally growing colony. For detailed studies, many stolons of a colony can be induced to regress by pharmacological manipulations of reactive oxygen species (e.g. hydrogen peroxide) or reactive nitrogen species (e.g. nitric oxide). The regression process begins with a cessation of gastrovascular flow to the distal part of the stolon. High levels of endogenous H2O2 and NO then accumulate in the regressing stolon. Remarkably, exogenous treatments with either H2O2 or an NO donor equivalently trigger endogenous formation of both H2O2 and NO. Cell death during regression is suggested by both morphological features, detected by transmission electron microscopy, and DNA fragmentation, detected by TUNEL. Stolon regression may occur when colonies detect environmental signals that favor continued growth in the same location rather than outward growth.
Modulatory effects of adenosine and adenine nucleotides on different heart preparations of the American lobster,Homarus americanus
Authors: Maurer Gereon , Wilkens Jerrel L. , Grieshaber Manfred K. 
Published: February 2008

SUMMARYAs shown previously, adenosine and the adenine nucleotides cause a rapid increase in heart rate (fH) and haemolymph velocity(vHL) when infused into intact American lobster(Homarus americanus). Here we compare the effects of adenosine and adenine nucleotides on different heart preparations in order to gain insight into their sites of action. In the semi-isolated (in situ) heart preparation where the heart is uncoupled from neural and hormonal influence AMP, ADP and ATP, but not adenosine increased contractile force. None of the purines altered fH. Thus, the adenine nucleotides directly affect the myocardium and not the fH-setting cardiac ganglion.In cardioregulatory-denervated animals in which the cardiac ganglion only was severed from the central nervous system (CNS), purines caused a small and gradual increase in fH, indicating that in vivoan alteration of fH arises indirectly through the central nervous system which in turn sends the information to the heart viathe dorsal nerves. The gradual increase in fH of cardioregulatory-denervated animals may also result from neurohormones released into the circulatory system, although no significant changes in haemolymph concentration of dopamine, serotonin and octopamine were found during adenosine infusion.In semi-isolated (in situ) hearts adenine nucleotides also increased haemolymph flow, as a consequence of increased heart contractile force, but again adenosine had no effect. These data show that in vivo adenosine does not influence the myocardium, only the adenine nucleotides affect the myocardium directly. Obviously adenosine possesses an indirect effect, perhaps on cardio-arterial valves and arterial resistance,but other, as yet unidentified, modifying factors are also possible.
Pharmacology of ionotropic and metabotropic glutamate receptors on neurons involved in feeding behavior in the pond snail, Helisoma trivolvis
Authors: Scannell Elizabeth , Dell'Ova Carly A. , Quinlan Elizabeth M. , Murphy A. Don , Kleckner Nancy W. 
Published: February 2008

SUMMARY
Glutamate is a key regulatory neurotransmitter in the triphasic central pattern generator controlling feeding behavior in the pond snail, Helisoma trivolvis. It excites phase two motor neurons while inhibiting those in phases one and three. However, the receptors that mediate this regulation are only partially characterized. The purpose of these experiments was to further characterize the glutamate receptors on three buccal neurons modulated by glutamate. Intracellular recordings from B5, B19 and B27 neurons were taken during the perfusion of isolated buccal ganglia with agonists that are selective for different vertebrate glutamate receptors. The firing rate of all three neurons was inhibited in a dose-dependent manner by glutamate, including that of B27, a phase 2 motor neuron known to be excited by glutamate in vivo. Quisqualate also reduced the firing rate in all three neurons, and(1S,3R)-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), a relatively non-selective metabotropic glutamate receptor (mGluR) agonist,reduced the firing rate in B5 neurons, but not in B19 or B27 neurons. Agonists selective for vertebrate group I, II and III mGluRs did not affect the firing rate in any of the Helisoma buccal neurons tested, suggesting that mGluR agonist binding sites on these neurons do not closely resemble those on any vertebrate mGluR subtypes. An increase in frequency of action potentials was observed in all three cell types in the presence of 100 μmol l–1 kainate (KA), suggesting the presence of excitatory(S)-α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/KA-like receptors. However, electrotonic coupling between B19 and B27 neurons, and a lack of effect of KA on isolated B19 neurons suggest the excitatory effects of KA on this neuron are indirect. These findings suggest the presence of multiple glutamate receptor subtypes in molluscan neurons that do not always resemble vertebrate receptors pharmacologically.
The functional morphology of color changing in a spider: development of ommochrome pigment granules
Authors: Insausti Teresita C. , Casas Jérôme 
Published: February 2008

SUMMARYStudies on the formation of ommochrome pigment granules are very few,despite their generalized occurrence as screening pigments in insect eyes. This is particularly true for ommochrome granules responsible for epidermal coloration. The aims of this study were to characterize the localization of major body pigments in a color changing mimetic spider, Misumena vatia (Thomisidae), and to describe the formation and location of ommochrome pigment granules responsible for the spider's color change from white to yellow. The unpigmented cuticula of this spider is transparent. Both the guanine localized in guanine cells in the opisthosoma and the uric acid localized in epidermis cells in the prosoma are responsible for the white coloration. The bright yellow color is due to the combination of ommochrome pigment granules and the white reflectance from coincident guanine and/or uric acid. The formation of ommochrome pigment granules in epidermis cells proceeds via three distinctive steps. Translucent, UV fluorescent, progranules(type I) are produced by a dense network of endoplasmic reticulum associated with numerous mitochondria and glycogen rosettes. These progranules are present in white spiders only, and regularly distributed in the cytoplasm. The merging of several progranules of type I into a transient state(progranule type II) leads to the formation of granules (type III) characterized by their lack of fluorescence, their spherical sections and their osmophilic-electron-dense contents. They are found in yellow spiders and in the red stripes on the body sides. Their color varies from yellow to red. Thus, white spiders contain only type I granules,yellow tinted spiders contain type II and III granules and bright yellow spiders contain only type III granules. We present a synthetic view of the ontogeny of ommochrome granules. We discuss the physiology of color changing and the nature of the chemical compounds in the different types of granules. Extended studies on the ultrastructural modification and physiological processes associated with color change are required before any statement about the adaptiveness of the color change can be made.
Malvolio is a copper transporter inDrosophila melanogaster
Authors: Southon Adam , Farlow Ashley , Norgate Melanie , Burke Richard , Camakaris James 
Published: February 2008

SUMMARYDivalent metal ion transporter 1 (DMT1; also known as SLC11A2) can transport several metals including Fe and Cu in mammalian systems. We set out to determine whether Malvolio (Mvl), the Drosophila melanogasterorthologue of DMT1, can also transport Cu. Overexpression of Mvlcaused Cu accumulation in Drosophila S2 cultured cells and conversely dsRNAi knockdown of endogenous Mvl reduced cellular Cu levels. Cell viability under Cu limiting conditions was reduced following dsRNAi knockdown. A homozygous viable Mvl loss-of-function mutant(Mvl97f) was sensitive to excess Cu and female Mvl97f flies were also sensitive to Cu limitation. An MtnA-EYFP reporter was used as a proxy measure of Cu distribution within Mvl97f/+ larvae. Under basal conditions Cu levels were reduced in the anterior midgut and proventriculus relative to control larvae. These results demonstrate Mvl is a functional Cu transporter and that despite partial functional redundancy with the Ctr1 proteins, Cu uptake through this pathway is necessary for optimal viability at the cellular and organismal levels.
Oxygen profiles in egg masses predicted from a diffusion–reaction model
Authors: Woods H. Arthur , Moran Amy L. 
Published: February 2008

SUMMARYWe developed a novel diffusion–reaction model to describe spatial and temporal changes in oxygen concentrations in gelatinous egg masses containing live, respiring embryos. We used the model in two ways. First, we constructed artificial egg masses of known metabolic density using embryos of the Antarctic sea urchin Sterechnius neumayeri, measured radial oxygen profiles at two temperatures, and compared our measurements to simulated radial oxygen profiles generated by the model. We parameterized the model by measuring the radius of the artificial masses, metabolic densities (=embryo metabolic rate×embryo density) and oxygen diffusion coefficients at both ambient (–1.5°C) or slightly warmer (+1.5–2°C)temperatures. Simulated and measured radial oxygen profiles were similar,indicating that the model captured the major biological features determining oxygen distributions. Second, we used the model to analyze sources of error in step-change experiments for determining oxygen diffusion coefficients(D), and to determine the suitability of simpler, analytical equations for estimating D. Our analysis indicated that embryo metabolism can lead to large (several-fold) overestimates of D if the analytical equation is fitted to step-down-traces of central oxygen concentration (i.e. external oxygen concentration stepped from some high value to zero). However, good estimates of D were obtained from step-up-traces. We used these findings to estimate D in egg masses of three species of nudibranch molluscs: two Antarctic species (Tritonia challengeriana and Tritoniella belli; –1.5 and +2°C)and one temperate Pacific species (Tritonia diomedea; 12 and 22°C). D for all three species was approximately 8×10–6 cm2 s–1, and there was no detectable effect of temperature on estimated D. For the Antarctic species, D in egg masses was 70–90% of its value in seawater of similar temperature.
Temperature–oxygen interactions in Antarctic nudibranch egg masses
Authors: Woods H. Arthur , Moran Amy L. 
Published: February 2008

SUMMARYThe Southern Ocean is one of the coldest, most stable marine environments on Earth and represents a unique environment for investigating metabolic consequences of low temperature. Here we test predictions of a new diffusion–reaction model of O2 distributions in egg masses,using egg masses of the Antarctic nudibranch mollusk, Tritonia challengeriana. When warmed from –1.5° to +1.5°C, embryos of T. challengeriana showed large increases in O2consumption (Q10 values of 9.6–30.0). Oxygen electrode measurements in intact masses showed, however, that O2 levels were high throughout and virtually unaffected by temperature. The model suggested that both effects stemmed from very low metabolic densities in egg masses. Detailed morphological measurements of egg masses of T. challengeriana and a temperate congener, T. diomedea, revealed large differences in structure that may be related to O2availability. Egg masses of T. challengeriana were approximately twice as thick. However, the most dramatic effects were observed in embryos:embryos of T. challengeriana were &gt;32 times larger (by volume)than embryos of T. diomedea. Antarctic embryos also were contained singly in large egg capsules (∼500 μm diameter). Consequently,Antarctic embryos occurred at much lower densities, with very low metabolic densities.
A Polyaxial System for Testing of Jointed Rock Mass Models
Authors: Rao K. Seshagiri , Tiwari Rajendra P. 
Published: February 2008

Abstract
A polyaxial loading system was designed and developed at Indian Institute of Technology Delhi, India for laboratory testing of mechanical behavior of rock mass. The large-scale rock mass models of different joint geometry can be tested under polyaxial stress state simulating in situ stress conditions using this true-triaxial system. The system consists of a 1000 kN capacity vertical frame, a biaxial frame of 300 kN capacity fitted with two pairs of hydraulic jacks and platens, constant confining pressure unit for applying, monitoring, and maintaining horizontal stresses (σ2 and σ3) on specimen faces, eight-channel data acquisition system, and a personal computer to record all load and deformation data. Its working was verified by conducting true-triaxial testing on several models specimens of sand-lime blocks having three sets of orthogonal joints.
In Vitro Model of Bromodeoxyuridine or Iron Oxide Nanoparticle Uptake by Activated Macrophages from Labeled Stem Cells: Implications for Cellular Therapy
Authors: Pawelczyk Edyta , Arbab Ali S. , Chaudhry Aneeka , Balakumaran Arun , Robey Pamela G. , Frank Joseph A. 
Published: February 2008

Abstract
There is increasing interest in using exogenous labels such as bromodeoxyuridine (BrdU) or superparamagnetic iron oxide nanoparticles (SPION) to label cells to identify transplanted cells and monitor their migration by fluorescent microscopy or in vivo magnetic resonance imaging (MRI), respectively. Direct implantation of cells into target tissue can result in &gt;80% cell death due to trauma or apoptosis. Bystander uptake of labeled cells by activated macrophages (AM) can confound the interpretation of results. This study investigated the frequency of BrdU or SPION uptake by AM using the Boyden chamber model of inflammation. SPION/BrdU-labeled bone marrow stromal cells or HeLa cells, AM, and mouse fibroblasts (MF) or human fibroblasts (HF) were mixed in various ratios in Matrigel in the upper chamber and incubated for up to 96 hours. The AM were chemotactically induced to migrate to the lower chamber. Fluorescence-activated cell sorting analysis of AM from lower and upper chambers, in the presence of either MF or HF using anti-CD68, anti-BrdU, anti-dextran antibodies, revealed 10%–20% dextran-positive or 10% BrdU-positive AM after 96 hours of incubation. Transfer of iron to AM accounted for &lt;10% of the total iron in labeled cells. The uptake of BrdU and SPION was dependent on the ratio of labeled cells to inflammatory cells and microenvironmental conditions. Direct implantation of BrdU/SPION-labeled cells into target tissue can result in uptake of label by AM; therefore, care should be taken to validate by histology transplanted cells for bystander cell markers and correlation with MRI results.
Disclosure of potential conflicts of interest is found at the end of this article.
Thrombopoietin Inhibits Murine Mast Cell Differentiation
Authors: Martelli Fabrizio , Ghinassi Barbara , Lorenzini Rodolfo , Vannucchi Alessandro M. , Rana Rosa Alba , Nishikawa Mitsuo , Partamian Sandra , Migliaccio Giovanni , Migliaccio Anna Rita 
Published: February 2008

AbstractWe have recently shown that Mpl, the thrombopoietin receptor, is expressed on murine mast cells and on their precursors and that targeted deletion of the Mpl gene increases mast cell differentiation in mice. Here we report that treatment of mice with thrombopoietin or addition of this growth factor to bone marrow-derived mast cell cultures severely hampers the generation of mature cells from their precursors by inducing apoptosis. Analysis of the expression profiling of mast cells obtained in the presence of thrombopoietin suggests that thrombopoietin induces apoptosis of mast cells by reducing expression of the transcription factor Mitf and its target antiapoptotic gene Bcl2.Disclosure of potential conflicts of interest is found at the end of this article.