bluuebunny/crossref_metadata_2025 huggingface dataset:
Macrophage migration inhibitory factor in cerebrospinal fluid from patients with central nervous system infection
Authors: Østergaard Christian , Benfield Thomas
Published: June 2009

Introduction

Macrophage migration inhibitory factor (MIF) plays an essential pathophysiological role in septic shock, but its role in central nervous system infection (CNS) remains to be defined.

Methods

We investigated cerebrospinal fluid (CSF) levels of MIF in 171 patients who were clinically suspected of having meningitis on admission. Of these, 31 were found to have purulent meningitis of known aetiology, 20 purulent meningitis of unknown aetiology, 59 lymphocytic meningitis and 11 encephalitis, whereas 50 were suspected of having but had no evidence of CNS infection.

Results

CSF MIF levels were significantly higher in patients with purulent meningitis of known aetiology (median [interquartile range]: 8,639 [3,344 to 20,600] ng/l) than in patients with purulent meningitis of unknown aetiology (2,209 [1,516 to 6,550] ng/l; Mann-Whitney test, P = 0.003), patients with lymphocytic meningitis (1,912 [1,302 to 4,105] ng/l; P < 0.001) and patients suspected of having but without evidence of CNS infection (1,472 [672 to 3,447] ng/l; P < 0.001). Also, patients with encephalitis (6,937 [3,961 to 8,353] ng/l) had higher CSF MIF than did patients without CNS infection (P < 0.01). Among patients with purulent meningitis, CSF MIF levels were significantly higher in patients infected with pneumococci than in those with meningococcal infection (11,569 [8,615 to 21,935] ng/l versus 5,006 [1,717 to 10,905] ng/l; P = 0.02), in patients who required versus those not requiring assisted ventilation (10,493 [5,961 to 22,725] ng/l versus 3,240 [1,563 to 9,302] ng/l; P = 0.003), and in patients with versus those without impaired consciousness (8,614 [3,344 to 20,935] ng/l versus 2,625 [1,561 to 7,530] ng/l; P = 0.02). CSF MIF levels correlated significantly with meningeal inflammation (P < 0.05) but not with systemic inflammatory response (P > 0.05) in patients with purulent meningitis of known aetiology, those with lymphocytic meningitis and those with encephalitis.

Conclusions

MIF was significantly increased in the CSF of patients with purulent meningitis and encephalitis, and was to some degree associated with severity of the infection. Our findings indicate that MIF may play an important role in CNS infection.
iBsu1103: a new genome-scale metabolic model of Bacillus subtilisbased on SEED annotations
Authors: Henry Christopher S , Zinner Jenifer F , Cohoon Matthew P , Stevens Rick L
Published: June 2009

Background

Bacillus subtilis is an organism of interest because of its extensive industrial applications, its similarity to pathogenic organisms, and its role as the model organism for Gram-positive, sporulating bacteria. In this work, we introduce a new genome-scale metabolic model of B. subtilis 168 called iBsu1103. This new model is based on the annotated B. subtilis 168 genome generated by the SEED, one of the most up-to-date and accurate annotations of B. subtilis 168 available.

Results

The iBsu1103 model includes 1,437 reactions associated with 1,103 genes, making it the most complete model of B. subtilis available. The model also includes Gibbs free energy change (Δ
r
G'°) values for 1,403 (97%) of the model reactions estimated by using the group contribution method. These data were used with an improved reaction reversibility prediction method to identify 653 (45%) irreversible reactions in the model. The model was validated against an experimental dataset consisting of 1,500 distinct conditions and was optimized by using an improved model optimization method to increase model accuracy from 89.7% to 93.1%.

Conclusions

Basing the iBsu1103 model on the annotations generated by the SEED significantly improved the model completeness and accuracy compared with the most recent previously published model. The enhanced accuracy of the iBsu1103 model also demonstrates the efficacy of the improved reaction directionality prediction method in accurately identifying irreversible reactions in the B. subtilis metabolism. The proposed improved model optimization methodology was also demonstrated to be effective in minimally adjusting model content to improve model accuracy.
An experimental study of the dilation factor
Authors: Bathija Arpita Pal , Batzle Michael Lee , Prasad Manika
Published: June 2009

Dilation factor [Formula: see text] is the ratio of relative change in velocity to relative change in deformation (strain). It has significant implications for 4D seismic studies where it can be used to infer reservoir or overburden thickness changes from seismic changes, but the effect of stress on [Formula: see text] and its components is not well understood. We conduct static strain and ultrasonic velocity measurements to study the effect of stress on [Formula: see text] and its components. Measured absolute [Formula: see text] values (6–91 in sandstones and 6–11 in shale) depend on the deformation mechanisms causing the strain. The dynamic (low-amplitude) Young’s modulus generally is higher than the static (high-amplitude) Young’s modulus. Hence, theoretical models that use the same mechanism to describe wave propagation and macroscopic deformation are invalid. The ratio of dynamic to static modulus depends on the direction of stress applied with respect to the density and placement of cracks. Values of [Formula: see text] differ for P- and S-waves, especially in the presence of fluids. The values also depend strongly on the stress states; hence, using a constant value of [Formula: see text] from the surface to reservoir depth should be avoided. Absolute [Formula: see text] values increase for sandstones and decrease for shales with decreasing confining pressure, which explains the low [Formula: see text] values from 4D seismic data. Our data offer insight into the behavior of [Formula: see text] values with different rock types, stress, and fluid, and they can be used to constrain model calculations.
Temporal geophysical signatures from contaminant-mass remediation
Authors: Che-Alota Vukenkeng , Atekwana Estella A. , Atekwana Eliot A. , Sauck William A. , Werkema D. Dale
Published: June 2009

We have previously documented changes in bulk electrical conductivity, self-potential (SP), and ground-penetrating-radar (GPR) reflections in a field setting caused by biogeochemical transformations of hydrocarbon-contaminated media. These transformations are associated with hydrocarbon biodegradation. The results of surface geophysical surveys acquired in 1996, 2003, and 2007 document changes in geophysical signatures associated with removing hydrocarbon mass in the contaminated zone. Initial investigations in 1996 showed that relative to background, the contaminated area was characterized by higher bulk electrical conductivity, positive SP anomaly, and attenuated GPR reflections. Repeated surveys in 2003 and 2007 over the contaminated area showed that in 2007, the bulk electrical conductivityhad reverted to near-background conditions, the positive SP anomaly became more negative, and the zone of attenuated GPR reflections showed increased signal strength. Removal of hydrocarbon mass in the vadose zone over the plume by a soil vapor-extraction system installed in 2001 was primarily responsible for the changing geophysical responses. Although chemical data from groundwater showed a [Formula: see text]-thick con-ductive plume in 2007, the plume was not imaged by elec-trical resistivity. Forward modeling suggests that apparent bulk electrical conductivity of the saturated zone plume has to be three to five times higher than background values to be imaged by electrical resistivity. We suggest that removing hydrocarbon-contaminant-mass reduction by natural or engineered bioremediation can be imaged effectively by temporal geophysical surveys.
Biochemical Factors Governing the Steady-State Estrone/Estradiol Ratios Catalyzed by Human 17β-Hydroxysteroid Dehydrogenases Types 1 and 2 in HEK-293 Cells
Authors: Sherbet Daniel P. , Guryev Oleg L. , Papari-Zareei Mahboubeh , Mizrachi Dario , Rambally Siayareh , Akbar Sharareh , Auchus Richard J.
Published: June 2009

Human 17β-hydroxysteroid dehydrogenase types 1 and 2 (17βHSD1 and 17βHSD2) regulate estrogen potency by catalyzing the interconversion of estrone (E1) and estradiol (E2) using nicotinamide adenine dinucleotide (phosphate) cofactors NAD(P)(H). In intact cells, 17βHSD1 and 17βHSD2 establish pseudo-equilibria favoring E1 reduction or E2 oxidation, respectively. The vulnerability of these equilibrium steroid distributions to mutations and to altered intracellular cofactor abundance and redox state, however, is not known. We demonstrate that the equilibrium E2/E1 ratio achieved by 17βHSD1 in intact HEK-293 cell lines is progressively reduced from 94:6 to 10:90 after mutagenesis of R38, which interacts with the 2′-phosphate of NADP(H), and by glucose deprivation, which lowers the NADPH/NADP+ ratio. The shift to E2 oxidation parallels changes in apparent Km values for purified 17βHSD1 proteins to favor NAD(H) over NADP(H). In contrast, mutagenesis of E116 (corresponding to R38 in 17βHSD1) and changes in intracellular cofactor ratios do not alter the greater than 90:10 E1/E2 ratio catalyzed by 17βHSD2, and these mutations lower the apparent Km of recombinant 17βHSD2 for NADP(H) only less than 3-fold. We conclude that the equilibrium E1/E2 ratio maintained by human 17βHSD1 in intact cells is governed by NADPH saturation, which is strongly dependent on both R38 and high intracellular NADPH/NADP+ ratios. In contrast, the preference of 17βHSD2 for E2 oxidation strongly resists alteration by genetic and metabolic manipulations. These findings suggest that additional structural features, beyond the lack of a specific arginine residue, disfavor NADPH binding and thus support E2 oxidation by 17βHSD2 in intact cells.
Chorionic Gonadotropin Regulates Prostaglandin E Synthase via a Phosphatidylinositol 3-Kinase-Extracellular Regulatory Kinase Pathway in a Human Endometrial Epithelial Cell Line: Implications for Endometrial Responses for Embryo Implantation
Authors: Banerjee Prajna , Sapru Kavita , Strakova Zuzana , Fazleabas Asgerally T.
Published: June 2009

Successful implantation necessitates modulation of the uterine environment by the embryo for a specific period of time during the menstrual cycle. Infusion of chorionic gonadotropin (CG) into the oviducts of baboons to mimic embryo transit induces a myriad of morphological, biochemical, and molecular changes in the endometrium. Endometrial epithelial cells from both baboons and humans when stimulated by CG in vitro, activates a cAMP-independent MAPK pathway leading to prostaglandin E2 (PGE2) synthesis. This study shows that in the human endometrial cell line, HES, CG, acting via its G-protein coupled receptor, phosphorylates protein kinase B, c-Raf, and ERK1/2 in a phosphatidylinositol 3-kinase (PI3K)-dependent manner. Furthermore, ERK1/2 phosphorylation is independent of the signaling paradigms of Gαs, GαI, and epidermal growth factor receptor (EGFR) transactivation, typical of gonadal cells, indicating an alternative signaling pattern in the endometrium. After phosphorylation by CG, ERK1/2 translocates to the nucleus in a time-dependent manner. Downstream of ERK1/2, CG activates the nuclear transcription factor, Elk1, also in a PI3K-MAPK-dependent manner. Lastly, we show that in HES cells, this pathway regulates the expression of the microsomal enzyme PGE2 synthase (mPTGES), a terminal prostanoid synthase responsible for PGE2 synthesis. CG regulates the mPTGES promoter and also induces mPTGES synthesis in HES cells via the PI3K-ERK1/2 pathway. We suggest that this alternative PI3K-ERK-Elk pathway activated by CG regulates prostaglandin production by the endometrial epithelium and serves as an early trigger to prepare the endometrium for implantation.
ASCOM Controls Farnesoid X Receptor Transactivation through Its Associated Histone H3 Lysine 4 Methyltransferase Activity
Authors: Kim Dae-Hwan , Lee Jeongkyung , Lee Bora , Lee Jae W.
Published: June 2009

Activating signal cointegrator-2 (ASC-2), a coactivator of multiple nuclear receptors and transcription factors, belongs to a steady-state complex named ASCOM (for ASC-2 complex), which contains histone H3 lysine 4 (H3K4) methyltransferase MLL3 or its paralog MLL4. ASC-2 binds to many nuclear receptors in a ligand-dependent manner through its two LxxLL motifs. Here we show that the first LxxLL motif of ASC-2 shows relatively weak but specific interaction with the nuclear receptor farnesoid X receptor (FXR) and that ASCOM plays crucial roles in FXR transactivation. Our results reveal that ASC-2, MLL3, and MLL4 are recruited to FXR target genes in a ligand-dependent manner. We further show that the recruitment of MLL3 requires ASC-2 and that FXR ligand induces not only expression of FXR-target genes but also their H3K4 trimethylation in a manner dependent on the presence of ASC-2, MLL3, and MLL4. In addition, MLL3 and MLL4 function redundantly with FXR transactivation. Correspondingly, expression of FXR target genes is partially impaired in mice expressing an enzymatically inactivated mutant form of MLL3, and these mice show disrupted bile acid homeostasis. Overall, these results suggest that ASCOM-MLL3 and ASCOM-MLL4 play redundant but essential roles in FXR transactivation via their H3K4 trimethylation activity.
Limiting factors to encapsulation: the combined effects of dissolved protein and oxygen availability on embryonic growth and survival of species with contrasting feeding strategies
Authors: Brante Antonio , Fernández Miriam , Viard Frédérique
Published: June 2009

Encapsulation is a common strategy among marine invertebrate species. It has been shown that oxygen and food availability independently constrain embryo development during intracapsular development. However, it is unclear how embryos of species with different feeding strategies perceive these two constraints when operating jointly. In the present study, we examined the relative importance of dissolved albumen, as a food source, oxygen condition and their interaction on embryonic growth and the survival of two calyptraeid species, Crepidula coquimbensis and Crepidula fornicata,exhibiting different embryo feeding behaviours (i.e. presence vsabsence of intracapsular cannibalism). Two oxygen condition treatments(normoxia and hypoxia) and three albumen concentrations (0, 1 and 2 mg l–1) were studied. In addition, albumen intake by embryos was observed using fluorescence microscopy. Our study shows that embryos of both species incorporated dissolved albumen but used a different set of embryonic organs. We observed that embryo growth rates in C. coquimbensis were negatively affected only by hypoxic conditions. Conversely, a combination of low albumen concentration and oxygen availability slowed embryo growth in C. fornicata. These findings suggest that oxygen availability is a limiting factor for the normal embryo development of encapsulated gastropod species, regardless of feeding behaviour or developmental mode. By contrast,the effect of dissolved albumen as an alternative food source on embryo performance may depend on the feeding strategy of the embryos.
Do cephalopods communicate using polarized light reflections from their skin?
Authors: Mäthger Lydia M. , Shashar Nadav , Hanlon Roger T.
Published: June 2009

Cephalopods (squid, cuttlefish and octopus) are probably best known for their ability to change color and pattern for camouflage and communication. This is made possible by their complex skin, which contains pigmented chromatophore organs and structural light reflectors (iridophores and leucophores). Iridophores create colorful and linearly polarized reflective patterns. Equally interesting, the photoreceptors of cephalopod eyes are arranged in a way to give these animals the ability to detect the linear polarization of incoming light. The capacity to detect polarized light may have a variety of functions, such as prey detection, navigation, orientation and contrast enhancement. Because the skin of cephalopods can produce polarized reflective patterns, it has been postulated that cephalopods could communicate intraspecifically through this visual system. The term `hidden' or`private' communication channel has been given to this concept because many cephalopod predators may not be able to see their polarized reflective patterns. We review the evidence for polarization vision as well as polarization signaling in some cephalopod species and provide examples that tend to support the notion – currently unproven – that some cephalopods communicate using polarized light signals.
A supracellular system of actin-lined canals controls biogenesis and release of virulence factors in parasitoid venom glands
Authors: Ferrarese Roberto , Morales Jorge , Fimiarz Daniel , Webb Bruce A. , Govind Shubha
Published: June 2009

Parasitoid wasps produce virulence factors that bear significant resemblance to viruses and have the ability to block host defense responses. The function of these virulence factors, produced predominantly in wasp venom glands, and the ways in which they interfere with host development and physiology remain mysterious. Here, we report the discovery of a specialized system of canals in venom glands of five parasitoid wasps that differ in their infection strategies. This supracellular canal system is made up of individual secretory units, one per secretory cell. Individual units merge into the canal lumen. The membrane surface of the proximal end of each canal within the secretory cell assumes brush border morphology, lined with bundles of F-actin. Systemic administration of cytochalasin D compromises the integrity of the secretory unit. We show a dynamic and continuous association of p40, a protein of virus-like particles from a Drosophila parasitoid, L. heterotoma, with the canal and venom gland lumen. Similar structures in three Leptopilina species and Ganaspis xanthopoda,parasitoids of Drosophila spp., and Campoletis sonorenesis,a parasitoid of Heliothis virescens, suggest that this novel supracellular canal system is likely to be a common trait of parasitoid venom glands that is essential for efficient biogenesis and delivery of virulence factors.
The behavioural, digestive and metabolic characteristics of fishes with different foraging strategies
Authors: Fu Shi-Jian , Zeng Ling-Qing , Li Xiu-Ming , Pang Xu , Cao Zhen-Dong , Peng Jiang-Lan , Wang Yu-Xiang
Published: June 2009

To test the hypothesis that digestion has a more notable physiological effect on ambush foragers than on active foragers, we investigated the behavioural, digestive and metabolic characteristics, as well as the postprandial locomotory capacity, of four species of juvenile fish distributed along the Yangtze River, China, with distinct foraging strategies. The ambush foraging southern catfish (Silurus meridionlis) had the fewest movements per minute (MPM), lowest per cent time spent moving (PTM), slowest critical swimming speed (Ucrit), lowest maintenance metabolism(V̇O2rest) and lowest maximum locomotory metabolism(V̇O2max). However, the southern catfish had the highest feeding level and maximum feeding metabolism(V̇O2peak) and the greatest decrease in Ucrit after consumption of a large meal. Thus, this fish is highly adapted to its ambush behavioural strategy and sedentary life style. In the herbivorous grass carp (Ctenopharyngodon idellus), a low digestive capacity led to little change in postprandial locomotory performance, which benefits its frequent grazing behaviour. In this species, the greater amount of energy spent on routine activity and avoiding predators versus Ucrit might be related to its herbivorous life style and high predation risk. The active foraging crucian carp(Carassius auratus) adopts a unique high energy cost strategy that allows for high capacity in both routine activity and digestion, and the great flexibility of its cardio-respiratory capacity (increased V̇O2max after feeding) guarantees a small decrease in Ucrit even after maximum feeding. Finally, the sluggish foraging darkbarbel catfish(Pelteobagrus vachelli) has low digestive and locomotory capacity,but its energy-efficient venomous defence strategy may be related to its abundance. These results show that the digestive, behavioural and metabolic strategies differ among these fish species. The locomotory capacity in the sedentary fishes decreased profoundly after feeding, whereas it decreased little or not at all in the active fishes. The maintenance of high locomotory capacity after eating in the active fishes is probably related to a large metabolic capacity, a lower digestive capacity or an improvement in cardio-respiratory capacity after feeding.
Function of the sexually dimorphic ear of the American bullfrog,Rana catesbeiana: brief review and new insight
Authors: Werner Y. L. , Pylka J. , Schneider H. , Seifan M. , Walkowiak W. , Werner-Reiss U.
Published: June 2009

The dimorphic ear of the bullfrog, Rana catesbeiana, has long been enigmatic. The male's tympanic membrane (TM) area approximates twice the area of the female's; however, similar size differences in the area of the columellar footplate were not observed between the sexes. Hence, the male's hearing is expected to be more sensitive than the female's but this is not the case. Asking what offsets the advantage of the large TM, we applied a series of experiments to the auditory system. Male and female audiograms based on stimulation with airborne sound and on both multi-unit responses from the brain and alternating cochlear potentials (`microphonics') showed equal sensitivity and a small difference in frequency response; at low frequencies the male was more sensitive than the female. Amputating the columella and stimulating the stump with mechanical vibration showed that for an equal microphonic response, the male's footplate vibrated with lower amplitude than the female's footplate. Mechanically stimulating the TM of the intact ear replicated this result, excluding the involvement of the mechanical lever. The TM of the male weighs five times the TM of the female, and artificial loading of the TM of either sex greatly reduced the ear's sensitivity. Hence, the male's excessive area ratio (TM to columellar footplate) is offset by the heavier cartilage cushion on the male's TM, damping the TM's response to sound. This is corroborated by experimentally artificially loading the TM. The product of area ratio and footplate vibration amplitude would result in similar stimulation of the inner ear in the two sexes.
A study of synchronisation between the flagella of bull spermatozoa, with related observations
Authors: Woolley David M. , Crockett Rachel F. , Groom William D. I. , Revell Stuart G.
Published: June 2009

Flagellar synchronisation has been observed between bull spermatozoa as they swam in a viscous medium, confined to a glass surface. This process is of interest in understanding the regulation of flagellar oscillation in general. Exact and persisting synchrony between bull spermatozoa occurred only when the spermatozoan heads were tightly coupled mechanically. For these cells, viscous coupling between the flagella was not by itself sufficient to establish synchronisation. Immediately on synchronisation, with the spermatozoan heads superposed, the paired spermatozoa showed rises in conjoint beat frequency,wave velocity and swimming velocity, i.e. in nearly all cases, the new conjoint values were greater than those shown by either of the two singleton spermatozoa. In our interpretation of these results, we put forward hydrodynamic arguments for seeing the primary change as a rise in wave velocity, via a decreased viscous resistance to bend propagation. Mechanistically, the rise in beat frequency is mysterious unless, as we suggest, it is consequential to the rise in wave velocity, and mediated by an as-yet-unknown mechanical feedback process. The rise in swimming velocity is not surprising given the rise in wave velocity but there is evidence for an additional influence due to a subtle re-orientation of the conjoint spermatozoan heads, such that they experienced less frictional drag.
Targets for TNFα-induced lipolysis in gilthead sea bream(Sparus aurata L.) adipocytes isolated from lean and fat juvenile fish
Authors: Cruz-Garcia Lourdes , Saera-Vila Alfonso , Navarro Isabel , Calduch-Giner Josep , Pérez-Sánchez Jaume
Published: June 2009

The present study aimed to analyze adiposity heterogeneity and the role of liver X receptor (LXRα) and peroxisome proliferator-activated receptors(PPARs) as targets of tumour necrosis factor-α (TNFα) in gilthead sea bream (Sparus aurata L.). The screening of 20 fish at the beginning of the warm season identified two major groups with fat and lean phenotypes. Fat fish showed increased liver and mesenteric fat depots. This increased adiposity was concurrent in the adipose tissue to enhanced expression of lipoprotein lipase (LPL) whereas mRNA levels of the hormone-sensitive lipase (HSL) remained almost unchanged. The resulting LPL/HSL ratio was thereby highest in fat fish, which suggests that this group of fish has not reached its peak fat storage capacity. This is not surprising given the increased expression of PPARγ in the absence of a counter-regulatory raise of TNFα. However, this lipolytic cytokine exerted dual effects in primary adipocyte cultures that differ within and between lean and fat fish. One set of fat fish did not respond to TNFαtreatment whereas a second set exhibited a lipolytic response (increased glycerol release) that was apparently mediated by the downregulated expression of PPARβ. In lean fish, TNFα exerted a strong and non-transcriptionally mediated lipolytic action. Alternatively, TNFαwould inhibit lipid deposition via the downregulated expression of adipogenic nuclear factors (PPARγ and LXRα). TNFα targets are therefore different in fish with lean and fat phenotypes, which is indicative of the complex network involved in the regulation of fish lipid metabolism.
African lungfish,Protopterus annectens, possess an arginine vasotocin receptor homologous to the tetrapod V2-type receptor
Authors: Konno Norifumi , Hyodo Susumu , Yamaguchi Yoko , Kaiya Hiroyuki , Miyazato Mikiya , Matsuda Kouhei , Uchiyama Minoru
Published: June 2009

In tetrapods, arginine vasopressin and its counterpart, arginine vasotocin(AVT), are involved in renal water conservation through vascular V1a-type and tubular V2-type receptors, and only the former has thus far been cloned in fish. We successfully cloned the V1a-type and V2-type AVT receptor from the kidney of the African lungfish, Protopterus annectens, and the deduced amino acid sequences exhibited high homology with amphibian V1a- and V2-type receptors, respectively. Functional analysis showed that AVT addition to CHO cells transfected with lungfish V1a-type receptor increased[Ca2+]i in a concentration-dependent manner, whereas CHO cells transfected with lungfish V2-type receptor responded with cAMP accumulation after AVT stimulation. Lungfish V2-type receptor mRNA was strongly expressed in the heart and kidney, while V1a-type receptor mRNA was ubiquitously expressed in all the tissues examined. In the kidney,immunohistochemistry using a specific antibody to lungfish V2-type receptor showed localization in the basolateral area of the cells in the late part of the distal tubules. Artificial estivation (EST) for 90 days significantly increased plasma osmolality and sodium and urea concentrations. There was no significant difference in the V2-type receptor mRNA and protein expression levels in the kidney between the freshwater and EST lungfish, while the AVT precursor mRNA level in the hypothalamus was remarkably higher in the EST lungfish. Our results indicate that African lungfish possess a functional V2-type receptor similar to that in tetrapods, suggesting that elevated plasma AVT during estivation exerts a renal tubular antidiuretic effect through the V2-type receptor expressed in the distal segments of lungfish kidney.
Hyperunstable matrix proteins in the byssus of Mytilus galloprovincialis
Authors: Sagert Jason , Waite J. Herbert
Published: June 2009

The marine mussel Mytilus galloprovincialis is tethered to rocks in the intertidal zone by a holdfast known as the byssus. Functioning as a shock absorber, the byssus is composed of threads, the primary molecular components of which are collagen-containing proteins (preCOLs) that largely dictate the higher order self-assembly and mechanical properties of byssal threads. The threads contain additional matrix components that separate and perhaps lubricate the collagenous microfibrils during deformation in tension. In this study, the thread matrix proteins (TMPs), a glycine-, tyrosine- and asparagine-rich protein family, were shown to possess unique repeated sequence motifs, significant transcriptional heterogeneity and were distributed throughout the byssal thread. Deamidation was shown to occur at a significant rate in a recombinant TMP and in the byssal thread as a function of time. Furthermore, charge heterogeneity presumably due to deamidation was observed in TMPs extracted from threads. The TMPs were localized to the preCOL-containing secretory granules in the collagen gland of the foot and are assumed to provide a viscoelastic matrix around the collagenous fibers in byssal threads.
Lift and drag performance of odontocete cetacean flippers
Authors: Weber Paul W. , Howle Laurens E. , Murray Mark M. , Fish Frank E.
Published: June 2009

Cetaceans (whales, dolphins and porpoises) have evolved flippers that aid in effective locomotion through their aquatic environments. Differing evolutionary pressures upon cetaceans, including hunting and feeding requirements, and other factors such as animal mass and size have resulted in flippers that are unique among each species. Cetacean flippers may be viewed as being analogous to modern engineered hydrofoils, which have hydrodynamic properties such as lift coefficient, drag coefficient and associated efficiency. Field observations and the collection of biological samples have resulted in flipper geometry being known for most cetacean species. However,the hydrodynamic properties of cetacean flippers have not been rigorously examined and thus their performance properties are unknown. By conducting water tunnel testing using scale models of cetacean flippers derived via computed tomography (CT) scans, as well as computational fluid dynamic (CFD) simulations, we present a baseline work to describe the hydrodynamic properties of several cetacean flippers. We found that flippers of similar planform shape had similar hydrodynamic performance properties. Furthermore, one group of flippers of planform shape similar to modern swept wings was found to have lift coefficients that increased with angle of attack nonlinearly, which was caused by the onset of vortex-dominated lift. Drag coefficient versus angle of attack curves were found to be less dependent on planform shape. Our work represents a step towards the understanding of the association between performance, ecology, morphology and fluid mechanics based on the three-dimensional geometry of cetacean flippers.
Naïve bats discriminate arctiid moth warning sounds but generalize their aposematic meaning
Authors: Barber Jesse R. , Chadwell Brad A. , Garrett Nick , Schmidt-French Barbara , Conner William E.
Published: June 2009

Naïve red (Lasiurus borealis Müller) and big brown(Eptesicus fuscus Beauvois) bats quickly learn to avoid noxious sound-producing tiger moths. After this experience with a model tiger moth,bats generalize the meaning of these prey-generated sounds to a second tiger moth species producing a different call. Here we describe the three-dimensional kinematic and bioacoustic details of this behaviour, first,as naïve bats learn to deal with an unpalatable model tiger moth and subsequently, as they avoid acoustic mimics. The tiger moths' first clicks influenced the bats' echolocation behaviour and the percentage of interactions that included terminal buzzes was associated with capture and investigatory behaviour. When the mimic was introduced, the bats decreased both their minimum distance to the tiger moth and the time at which they broke off their attack compared with their exposure to the model on the night before. These kinematic signatures closely match the bats' behaviour on their first night of experience with the model. Minimum distances and time of pursuit cessation increased again by the last night of the mimic's presentation. These kinematic and bioacoustic results show that although naïve bats generalize the meaning of aposematic tiger moth calls, they discriminate the prey-generated signals as different and investigate. Extrapolating to experienced bats, these results suggest that acoustic predators probably exert potent and fine-scaled selective forces on acoustic mimicry complexes.
The effect of short- and long-term fasting on digestive and metabolic flexibility in the Andean toad, Bufo spinulosus
Authors: Naya Daniel E. , Veloso Claudio , Sabat Pablo , Bozinovic Francisco
Published: June 2009

Hibernation in ectothermic animals was historically considered as a simple cold-induced torpor state resulting from the inability to maintain a high body temperature at low ambient temperatures. During the last decades this vision changed and nowadays there is a myriad of studies showing that hibernation implies different adjustments at the genetic, molecular, biochemical and cellular levels. However, studies oriented to evaluate changes of whole organism structure and physiology still are scarce, which is particularly true for amphibians that hibernate on land. Accordingly, in the Andean toad(Bufo spinulosus), we investigated the effect of short-term fasting and hibernation on the hydrolytic activity of digestive enzymes, histology of the small intestine, gross morphology of digestive and other internal organs and standard metabolic rate. Based on the pattern of size variation, internal organs may be grouped into those that were affected by both season and feeding condition (small intestine, stomach and liver), those that were only affected by season (fat bodies), those that were only affected by feeding condition(kidneys) and, finally, those that did not change between the three groups(large intestine, heart and lungs). Hydrolytic activity of maltase, trehalase and aminopeptidase-N followed the same pattern of variation(feeding>fasting>hibernating toads), although the change for the latter enzyme was less noticeable than for the disaccharidases. Enzymatic adjustments were correlated with changes in small intestine histology: villus and enterocyte height increased from hibernating to fasting and more markedly from fasting to feeding toads. Metabolic rate decreased during hibernation to 7.8%(at 5°C) and 13.6% (at 15°C) of summer values, which is one of the highest metabolic depressions reported for any ectothermic vertebrate. Our results suggest that amphibian persistence in highly seasonal environments is related to a large capacity of phenotypic flexibility at different organisational levels; an ability that may be related to the extensive ranges of temporal existence and geographic distribution of these vertebrates.
Visualization of the spatial and spectral signals of orb-weaving spiders, Nephila pilipes, through the eyes of a honeybee
Authors: Chiao Chuan-Chin , Wu Wen-Yen , Chen Sheng-Hui , Yang En-Cheng
Published: June 2009

It is well known that the honeybee has good color vision. However, the spectral range in which the bee can see is different from that of the human eye. To study how bees view their world of colors, one has to see through the eyes of the bee, not the eyes of a human. A conventional way to examine the color signals that animals can detect is to measure the surface reflectance spectra and compute the quantum catches of each photoreceptor type based on its known spectral sensitivity. Color signal and color contrast are then determined from the loci of these quantum catches in the color space. While the point-by-point measurements of the reflectance spectra using a standard spectrometer have yielded a significant amount of data for analyzing color signals, the lack of spatial information and low sampling efficiency constrain their applications. Using a special filter coating technique, a set of filters with transmission spectra that were closely matched to the bee's sensitivity spectra of three photoreceptor types (UV, blue, and green) was custom made. By placing these filters in front of a UV/VIS-sensitive CCD camera and acquiring images sequentially, we could collect images of a bee's receptor with only three shots. This allowed a direct visualization of how bees view their world in a pseudo-color RGB display. With this imaging system, spatial and spectral signals of the orb-weaving spider, Nephila pilipes, were recorded,and color contrast images corresponding to the bee's spatial resolution were constructed and analyzed. The result not only confirmed that the color markings of N. pilipes are of high chromatic contrast to the eyes of a bee, but it also indicated that the spatial arrangement of these markings resemble flower patterns which may attract bees to visit them. Thus, it is likely that the orb-weaving spider (N. pilipes) deploys a similar strategy to that of the Australian crab spider (Thomisus spectabilis)to exploit the bee's pre-existing preference for flowers with color patterning.
Rapid clearance of circulating protein by early chicken embryo blood cells
Authors: Wu Guojin , Li Zandong
Published: June 2009

It has been speculated that free amino acids digested from proteins in bird eggs are transported to the circulation for the nourishment of the embryo. In the present study, we found that early chicken embryo protein in the serum might be utilized efficiently as a nutrient. Proteins injected into the blood of embryonic day 3 (E3) embryos were partially degraded and rapidly cleared. The rapid clearance of the injected proteins might be the result of efficient pinocytosis by blood cells, which then efficiently digested the intracellular proteins. An evaluation of the fluorescence intensity of injected fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) indicated that about half was taken up by the blood cells 80 min after injection. About 4 h after injection, most of the FITC-BSA was digested and the products were released into the serum, which implies that circulating blood cells may serve as a digestive system in early chick embryos. However, the endocytic activity of blood cells decreased after E5, and BSA may reside in the circulation with a longer half-life after E5. These results imply that blood cells would serve as a digestive system only in early embryos. In summary, the mechanism revealed here gives the early embryo the ability to make use of protein as a nutrient without prior digestion outside the embryo.
The effect of leading-edge droop on the performance of cavitating hydrofoil in an oscillating environment
Authors: Park K , Sun H , Lee S
Published: June 2009

The hydrodynamics of cavitating hydrofoil in oscillating motion are important in the aspect of the performance and hydro-elasticity of the control surface of the ship. The effect of leading-edge droop is numerically studied in the oscillating hydrofoil with cavitation. A two-phase incompressible Navier—Stokes solver is used to compute the cavitation flow. The hydrodynamic performance of the baseline hydrofoil is compared with that of the fixed droop and the variable droop hydrofoil. The droop models delay the separation behind the sheet cavitation near the maximum angle of attack. When the pitch goes down, the drooped models suppress the collapse of the sheet cavitation. Therefore, they result in the improved hydrodynamic performance against the baseline model through the oscillation cycle. Among the three hydrofoils, the variable droop showed the smallest change of the lift-to-drag ratio.
Development of a single-shot linear actuator for a deep-sea sampling valve
Authors: Wu S-J , Yang C-J , Xie Y-Q , Yang L , Chen Y
Published: June 2009

In this article, a new kind of linear actuator for the deep-sea sampling valve has been described. Based on the working principle of the triggering ring, the actuator employs a preloaded spring to generate an output force and linear movement. The actuator is designed to be used 4000 m underwater and can produce a force of 510 N at the maximal output displacement of 3.5 mm, which can be easily modified by changing the preloaded spring and spring seats. The actuator has been successfully tested to actuate the sampling valve at an ambient pressure of 40 MPa.
A simple dynamic model and stability analysis of a steam boiler drum
Authors: Bracco S , Troilo M , Trucco A
Published: June 2009

This study is focused on the steam boilers dynamics modelling used as a powerful instrument to predict the response of boilers to external inputs and transient operating conditions.

The article describes a mathematical simulation model that has been developed to study the stability of a steam boiler drum subjected to different initial operating conditions. The phenomenological study has been based on several simulations that have been done considering steam boilers characterized by different nominal values of both pressure and steam mass flowrate; the attention has been given mainly to the effect of different pumping characteristics and thermal flux values on the boilers stability. The article shows the main results of the simulations and lists all the boilers’ possible operating conditions, both stable and unstable.
Prediction of fretting motion in a controllable pitch propeller during service
Authors: Godjevac M , van Beek T , Grimmelius H T , Tinga T , Stapersma D
Published: June 2009

This paper focuses on the forces acting in a controllable pitch propeller (CPP) mechanism and the manifestation of unwilling, small amplitude, vibrating motion (fretting) in a blade bearing caused by seaway. If this happens, fretting can result in fretting fatigue of components, fretting wear, and increase of friction in bearings. An attempt has been made to define the circumstances leading to fretting in a CPP and to describe the influence of sea state on fretting behaviour. Using hydrodynamic tools it is possible to determine the theoretical conditions for fretting. A combination of theoretical and experimental results provides a better understanding of the fretting phenomenon in a CPP. The first part of the paper gives an introduction to the working regimes and forces acting on a CPP. In the second part the presence of fretting is defined based on the calculation of forces and moments during one revolution of a blade in the non-actuating regime for the design condition of a specific propeller. The third part investigates self-propulsion tests in irregular seas and hydrodynamic forces acting on a CPP in those conditions. The results indicate a decrease of fretting in higher waves and higher speeds. It has been shown that it is not wise to look only at the load mean value as design criteria.
A novel coupled-mode theory with application to hydroelastic analysis of thick, non-uniform floating bodies over general bathymetry
Authors: Athanassoulis M A , Belibassakis K
Published: June 2009

A new coupled-mode system of horizontal equations is presented for the hydroelastic analysis of large floating bodies or ice sheets of general, finite thickness, lying over variable bathymetry regions. The present method is based on the theory of shear deformable plates (or beams), and is derived by an enhanced representation of the elastic displacement field, containing additional elastic vertical modes and permitting shear strain and stress to vanish on both the upper and lower boundaries of the thick floating plate. This model extends existing third-order plate theories to plates and beams of general shape. The presented coupled-mode system of horizontal differential equations is obtained by means of a variational principle composed of the one-field functional of the elastodynamics in the plate region, and a pressure functional in the water region. The wave potential in the water column is represented by means of a local-mode series expansion containing an additional mode providing the appropriate correction term on the bottom boundary, when the slope is not mild. In the above sense, the proposed method extends previous approaches concerning hydroelastic problems based on thin-plate theory. The focus of this work is on the scattering of linear, coupled, hydroelastic waves propagating through an inhomogeneous sea ice environment, containing ice sheets of variable thickness and a non-mildly-sloped interface. Numerical results are presented in the simple two-dimensional case, showing that the presented approach efficiently models the hydroelastic problem and is able to provide accurate results when only a few terms are used in the expansion. Ideas for extending the proposed method to three dimensions are also discussed.
The effect of a cooling field on exchange bias in a nanoparticle system
Authors: Hu Y , Liu Y , Du A
Published: June 2009

Interest in exchange bias in magnetic nanoparticles has increased in the past few years by virtue of its potential for applications in fields such as ultrahigh-density magnetic recording. A modified Monte Carlo Metropolis method is employed to simulate the effect of cooling field on exchange bias and coercivity of a granular system of ferromagnetic nanoparticles embedded in an antiferromagnetic matrix, based on the classical three-dimensional Heisenberg model. The results show that the exchange bias is constantly negative, and that its absolute value decreases to a metastable value initially, while the coercivity increases monotonically with increase in the cooling field, and they both level off as the cooling field gains sufficient strength. The phenomena can be attributed to the energy barriers arising from the high antiferromagnetic anisotropy and the frustrated core—matrix structure. However, the interfacial coupling may change the configuration of the antiferromagnetic matrix to influence the exchange bias.
Optimal Supply Diversification Under General Supply Risks
Authors: Federgruen Awi , Yang Nan
Published: June 2009

We analyze a planning model for a firm or public organization that needs to cover uncertain demand for a given item by procuring supplies from multiple sources. The necessity to employ multiple suppliers arises from the fact that when an order is placed with any of the suppliers, only a random fraction of the order size is usable. The model considers a single demand season with a given demand distribution, where all supplies need to be ordered simultaneously before the start of the season. The suppliers differ from one another in terms of their yield distributions, their procurement costs, and capacity levels.

The planning model determines which of the potential suppliers are to be retained and what size order is to be placed with each. We consider two versions of the planning model: in the first, the service constraint model (SCM), the orders must be such that the available supply of usable units covers the random demand during the season with (at least) a given probability. In the second version of the model, the total cost model (TCM), the orders are determined so as to minimize the aggregate of procurement costs and end-of-the-season inventory and shortage costs. In the classical inventory model with a single, fully reliable supplier, these two models are known to be equivalent, but the equivalency breaks down under multiple suppliers with unreliable yields.

For both the service constraint and total cost models, we develop a highly efficient procedure that generates the optimal set of suppliers as well as the optimal orders to be assigned to each. Most importantly, these procedures generate a variety of important qualitative insights, for example, regarding which sets of suppliers allow for a feasible solution, both when they have ample supply and when they are capacitated, and how various model parameters influence the selected set of suppliers, the aggregate order size, and the optimal cost values.