bluuebunny/crossref_metadata_2025 huggingface dataset:
Clone-specific expression, transcriptional regulation, and action of interleukin-6 in human colon carcinoma cells
Authors: Brozek Wolfgang , Bises Giovanna , Fabjani Gerhild , Cross Heide S , Peterlik Meinrad
Published: January 2008

Background

Many cancer cells produce interleukin-6 (IL-6), a cytokine that plays a role in growth stimulation, metastasis, and angiogenesis of secondary tumours in a variety of malignancies, including colorectal cancer. Effectiveness of IL-6 in this respect may depend on the quantity of basal and inducible IL-6 expressed as the tumour progresses through stages of malignancy. We therefore have evaluated the effect ofIL-6modulators, i.e. IL-1β, prostaglandin E2, 17β-estradiol, and 1,25-dihydroxyvitamin D3, on expression and synthesis of the cytokine at different stages of tumour progression.

Methods

We utilized cultures of the human colon carcinoma cell clones Caco-2/AQ, COGA-1A and COGA-13, all of which expressed differentiation and proliferation markers typical of distinct stages of tumour progression. IL-6 mRNA and protein levels were assayed by RT-PCR and ELISA, respectively. DNA sequencing was utilized to detect polymorphisms in theIL-6gene promoter.

Results

IL-6mRNA and protein concentrations were low in well and moderately differentiated Caco-2/AQ and COGA-1A cells, but were high in poorly differentiated COGA-13 cells. Addition of IL-1β (5 ng/ml) to a COGA-13 culture raised IL-6 production approximately thousandfold via a prostaglandin-independent mechanism. Addition of 17β-estradiol (10-7M) reduced basal IL-6 production by one-third, but IL-1β-inducible IL-6 was unaffected. Search for polymorphisms in theIL-6promoter revealed the presence of a single haplotype, i.e., -597A/-572G/-174C, in COGA-13 cells, which is associated with a high degree of transcriptional activity of theIL-6gene. IL-6 blocked differentiation only in Caco-2/AQ cells and stimulated mitosis through up-regulation of c-mycproto-oncogene expression. These effects were inhibited by 10-8M 1,25-dihydroxyvitamin D3.

Conclusion

In human colon carcinoma cells derived from well and moderately differentiated tumours, IL-6 expression is low and only marginally affected, if at all, by PGE2, 1,25-dihydroxyvitamin D3, and 17β-estradiol. However, IL-6 is highly abundant in undifferentiated tumour cells and is effectively stimulated by IL-1β. In case of overexpression of anIL-6gene variant with extreme sensitivity to IL-1β, massive release of the cytokine from undifferentiated tumour cells may accelerate progression towards malignancy by paracrine action on more differentiated tumour cells with a still functioning proliferative IL-6 signalling pathway.
Loss of Endocan tumorigenic properties after alternative splicing of exon 2
Authors: Depontieu Florence , Grigoriu Bogdan-Dragos , Scherpereel Arnaud , Adam Estelle , Delehedde Maryse , Gosset Philippe , Lassalle Philippe
Published: January 2008

Background

Endocan was originally described as a dermatan sulfate proteoglycan found freely circulating in the blood. Endocan expression confers tumorigenic properties to epithelial cell lines or accelerate the growth of already tumorigenic cells. This molecule is the product of a single gene composed of 3 exons. Previous data showed that endocan mRNA is subject to alternative splicing with possible generation of two protein products. In the present study we identified, and functionally characterized, the alternative spliced product of the endocan gene: the exon 2-deleted endocan, called endocanΔ2.

Methods

Stable, endocanΔ2-overexpressing cell lines were generated to investigate the biological activities of this new alternatively spliced product of endocan gene. Tumorigenesis was studied by inoculating endocan and endocanΔ2 expressing cell lines subcutaneously in SCID mice. Biochemical properties of endocan and endocanΔ2 were studied after production of recombinant proteins in various cell lines of human and murine origin.

Results

Our results showed that the exon 2 deletion impairs synthesis of the glycan chain, known to be involved in the pro-tumoral effect of endocan. EndocanΔ2 did not promote tumor formation by 293 cells implanted in the skin of severe combined immunodeficient (SCID) mice.

Conclusion

Our results emphasize the key role of the polypeptide sequence encoded by the exon 2 of endocan gene in tumorigenesis, and suggest that this sequence could be a target for future therapies against cancer.
Establishing a nationwide emergency department-based syndromic surveillance system for better public health responses in Taiwan
Authors: Wu Tsung-Shu Joseph , Shih Fuh-Yuan Frank , Yen Muh-Yong , Wu Jiunn-Shyan Julian , Lu Shiou-Wen , Chang Kevin Chi-Ming , Hsiung Chao , Chou Jr-How , Chu Yu-Tseng , Chang Hang , Chiu Chan-Hsien , Tsui Fu-Chiang Richard , Wagner Michael M , Su Ih-Jen , King Chwan-Chuen
Published: January 2008

Background

With international concern over emerging infectious diseases (EID) and bioterrorist attacks, public health is being required to have early outbreak detection systems. A disease surveillance team was organized to establish a hospital emergency department-based syndromic surveillance system (ED-SSS) capable of automatically transmitting patient data electronically from the hospitals responsible for emergency care throughout the country to the Centers for Disease Control in Taiwan (Taiwan-CDC) starting March, 2004. This report describes the challenges and steps involved in developing ED-SSS and the timely information it provides to improve in public health decision-making.

Methods

Between June 2003 and March 2004, after comparing various surveillance systems used around the world and consulting with ED physicians, pediatricians and internal medicine physicians involved in infectious disease control, the Syndromic Surveillance Research Team in Taiwan worked with the Real-time Outbreak and Disease Surveillance (RODS) Laboratory at the University of Pittsburgh to create Taiwan's ED-SSS. The system was evaluated by analyzing daily electronic ED data received in real-time from the 189 hospitals participating in this system between April 1, 2004 and March 31, 2005.

Results

Taiwan's ED-SSS identified winter and summer spikes in two syndrome groups: influenza-like illnesses and respiratory syndrome illnesses, while total numbers of ED visits were significantly higher on weekends, national holidays and the days of Chinese lunar new year than weekdays (p < 0.001). It also identified increases in the upper, lower, and total gastrointestinal (GI) syndrome groups starting in November 2004 and two clear spikes in enterovirus-like infections coinciding with the two school semesters. Using ED-SSS for surveillance of influenza-like illnesses and enteroviruses-related infections has improved Taiwan's pandemic flu preparedness and disease control capabilities.

Conclusion

Taiwan's ED-SSS represents the first nationwide real-time syndromic surveillance system ever established in Asia. The experiences reported herein can encourage other countries to develop their own surveillance systems. The system can be adapted to other cultural and language environments for better global surveillance of infectious diseases and international collaboration.
Biomolecular network querying: a promising approach in systems biology
Authors: Zhang Shihua , Zhang Xiang-Sun , Chen Luonan
Published: January 2008

The rapid accumulation of various network-related data from multiple species and conditions (e.g. disease versus normal) provides unprecedented opportunities to study the function and evolution of biological systems. Comparison of biomolecular networks between species or conditions is a promising approach to understanding the essential mechanisms used by living organisms. Computationally, the basic goal of this network comparison or 'querying' is to uncover identical or similar subnetworks by mapping the queried network (e.g. a pathway or functional module) to another network or network database. Such comparative analysis may reveal biologically or clinically important pathways or regulatory networks. In particular, we argue that user-friendly tools for network querying will greatly enhance our ability to study the fundamental properties of biomolecular networks at a system-wide level.
Inhibition of hyaluronan export reduces collagen degradation in interleukin-1 treated cartilage
Authors: Deiters Barthold , Prehm Peter
Published: January 2008

Background

Osteoarthrosis is characterized by cartilage erosion, proteolysis of aggrecan and collagen, and disturbed rates of synthesis of aggrecan and hyaluronan by chondrocytes, with hyaluronan over-production being an early reaction. We considered that inhibition of hyaluronan export might prevent subsequent proteoglycan loss and collagen degradation.

Methods

To test this hypothesis, we studied a tissue culture model using bovine cartilages explants activated with IL-1α to induce osteoarthritic reactions using the phosphodiesterase-5 inhibitors tadalafil, zaprinast and vardenafil.

Results

These drugs inhibited hyaluronan export, but they did not inhibit hyaluronan synthase activity. Simultaneously, they inhibited proteoglycan loss and collagen degradation, but not their synthesis. They also reduced the release of gelatinases into the culture media and diffusion of the indicator protein horseradish peroxidase through the cartilage explants. The mechanism of action of these compounds may be through inhibition of hyaluronan exporter multidrug resistance-associated protein 5 (MRP5), because the effective drug concentrations were much higher than required for phosphodiesterase-5 inhibition and intracellular cGMP accumulation.

Conclusion

Inhibition of hyaluronan over-production may be an appropriate target to attenuate IL-1-induced reactions in osteoarthritic cartilage.
Assessment of measurement errors for galvanic-resistivity electrodes of different composition
Authors: LaBrecque Douglas , Daily William
Published: January 2008

This research provides an empirical study of electrodes used to measure galvanic resistivity. The central element of this work is an estimation of errors in resistivity measurements that arise because of the type of electrode material used. Fourteen types of electrodes were tested including metal electrodes, metal-salt-compound (nonpolarizing) electrodes, and one nonmetal electrode, under conditions that are typical of those encountered during geophysical surveys. Measurement errors for resistance and chargeability were estimated using the reciprocity of data from an array of electrodes such as might be used for electric-resistance tomography. The same error analysis was applied to data from a network of high-precision resistors to separate instrument errors from electrode errors. Significant differences were observed in errors produced by different electrode materials. We conclude that the choice of electrode is very important for resistivity or chargeability surveys. Iron, steel (including rebar), lead, and phosphor bronze produced the smallest errors in resistance and chargeability. Aluminum, magnesium, titanium, copper, and zinc produced the largest errors. Stainless steel (alloy 316), tin, and brass performed reasonably well, as did carbon, which was the only nonmetal tested.
Simulating migrated and inverted seismic data by filtering a geologic model
Authors: Toxopeus Gerrit , Thorbecke Jan , Wapenaar Kees , Petersen Steen , Slob Evert , Fokkema Jacob
Published: January 2008

The simulation of migrated and inverted data is hampered by the high computational cost of generating 3D synthetic data, followed by processes of migration and inversion. For example, simulating the migrated seismic signature of subtle stratigraphic traps demands the expensive exercise of 3D forward modeling, followed by 3D migration of the synthetic seismograms. This computational cost can be overcome using a strategy for simulating migrated and inverted data by filtering a geologic model with 3D spatial-resolution and angle filters, respectively. A key property of the approach is this: The geologic model that describes a target zone is decoupled from the macrovelocity model used to compute the filters. The process enables a target-orientedapproach, by which a geologically detailed earth model describing a reservoir is adjusted without having to recalculate the filters. Because a spatial-resolution filter combines the results of the modeling and migration operators, the simulated images can be compared directly to a real migration image. We decompose the spatial-resolution filter into two parts and show that applying one of those parts produces output directly comparable to 1D inverted real data. Two-dimensional synthetic examples that include seismic uncertainties demonstrate the usefulness of the approach. Results from a real data example show that horizontal smearing, which is not simulated by the 1D convolution model result, is essential to understand the seismic expression of the deformation related to sulfate dissolution and karst collapse.
Hybrid Fourier finite-difference 3D depth migration for anisotropic media
Authors: Fei Tong W. , Liner Christopher L.
Published: January 2008

When a subsurface is anisotropic, migration based on the assumption of isotropy will not produce accurate migration images. We develop a hybrid wave-equation migration algorithm for vertical transversely isotropic (VTI) media based on a one-way acoustic wave equation, using a combination of Fourier finite-difference (FFD) and finite-difference (FD) approaches. The hybrid method can suppress an additional solution that exists in the VTI acoustic wave equation, and it offers speed and other advantages over conventional FFD or FD methods alone. The algorithm is tested on a synthetic model involving log data from onshore eastern Saudi Arabia, including estimates of both intrinsic and layer-induced VTI parameters. Results indicate that VTI imaging in this region offers some improvement over isotropic imaging, primarily with respect to subtle structure and stratigraphy and to image continuity. These benefits probably will be overshadowed by perennial land seismic data issues such as near-surface distortions and multiples.
Decimeter-resolution 3D seismic volume in shallow water: A case study in small-object detection
Authors: Vardy Mark E. , Dix Justin K. , Henstock Timothy J. , Bull Jonathan M. , Gutowski Martin
Published: January 2008

The 3D chirp subbottom profiler provides high-resolution imaging of coastal and inshore seabed and subseabed structure by combining the known, highly repeatable source waveform of chirp profilers with the coherent processing and interpretation afforded by true 3D seismic volumes. Comprising 60 hydrophone groups arranged around a Maltese cross of four chirp transducers, 3D chirp permits acquisition of a true 3D volume with a horizontal resolution of [Formula: see text], providing an excellent base for shallow-water engineering, archaeological, military, and geologic studies. Here, we present results from surveying an atidal basin on the southern coast of England to map bedrock protrusions and the size and distribution of buried objects. The study area of [Formula: see text] provided a series of unique challenges, including a large number of discrete objects ranging from tens of centimeters to several meters in size, buried in a thin veneer (0.5 to [Formula: see text]) of unconsolidated silt overlaying a flat bedrock surface that showed high acoustic contrast and short wavelength roughness. By comparing comprehensive postsurvey dredging of the entire site with a prestack time-migrated 3D volume, it is possible to confirm a 100% detection rate for all discrete buried objects larger than [Formula: see text] in an illuminated area, although one acoustic anomaly could not be accounted for in the dredging results.
A Role for Intestinal Endocrine Cell-Expressed G Protein-Coupled Receptor 119 in Glycemic Control by Enhancing Glucagon-Like Peptide-1 and Glucose-Dependent Insulinotropic Peptide Release
Authors: Chu Zhi-Liang , Carroll Chris , Alfonso Jean , Gutierrez Veronica , He Hongmei , Lucman Annette , Pedraza Melinda , Mondala Helen , Gao Hui , Bagnol Didier , Chen Ruoping , Jones Robert M. , Behan Dominic P. , Leonard James
Published: January 2008

We recently showed that activation of G protein-coupled receptor 119 (GPR119) (also termed glucose dependent insulinotropic receptor) improves glucose homeostasis via direct cAMP-mediated enhancement of glucose-dependent insulin release in pancreatic β-cells. Here we show that GPR119 also stimulates incretin hormone release and thus may regulate glucose homeostasis by this additional mechanism. GPR119 mRNA was found to be expressed at significant levels in intestinal subregions that produce glucose-dependent insulinotropic peptide and glucagon-like peptide (GLP)-1. Furthermore, in situ hybridization studies indicated that most GLP-1-producing cells coexpress GPR119 mRNA. In GLUTag cells, a well-established model of intestinal L-cell function, the potent GPR119 agonist AR231453 stimulated cAMP accumulation and GLP-1 release. When administered in mice, AR231453 increased active GLP-1 levels within 2 min after oral glucose delivery and substantially enhanced total glucose-dependent insulinotropic peptide levels. Blockade of GLP-1 receptor signaling with exendin(9–39) reduced the ability of AR231453 to improve glucose tolerance in mice. Conversely, combined administration of AR231453 and the DPP-4 inhibitor sitagliptin to wild-type mice significantly amplified both plasma GLP-1 levels and oral glucose tolerance, relative to either agent alone. In mice lacking GPR119, no such enhancement was seen. Thus, GPR119 regulates glucose tolerance by acting on intestinal endocrine cells as well as pancreatic β-cells. These data also suggest that combined stimulation of incretin hormone release and protection against incretin hormone degradation may be an effective antidiabetic strategy.
Minireview: Obesity and LipOdystrophy—Where Do the Circles Intersect?
Authors: Chehab Farid F.
Published: January 2008

Adipose tissue is unique in that it can undergo significant hypertrophy and atrophy, resulting in wide ranges of obesities and lipodystrophies. At the base of this elasticity is the lipid-filled adipocyte, which can either overfill by storing large amounts of triglycerides or shrink to a tiny cell by depleting its lipids and as such is remarkable in sustaining insults. As a major energy reservoir, the adipocyte may hold considerable calories necessary for survival and reproduction, two functions that are essential for the survival of the species. This review will summarize some of the recent studies that have advanced our understanding of the central and peripheral mechanisms that are initiated by adipocyte-secreted factors such as leptin, adiponectin, resistin, and retinol-binding protein 4. The intersection of obesity and lipodystrophy results in insulin resistance, which may be unlocked by elucidating the roles of these factors in pathways that control insulin sensitivity and glucose uptake.
Polyamines Are Essential in Embryo Implantation: Expression and Function of Polyamine-Related Genes in Mouse Uterus during Peri-Implantation Period
Authors: Zhao Yue-Chao , Chi Yu-Jing , Yu Yong-Sheng , Liu Ji-Long , Su Ren-Wei , Ma Xing-Hong , Shan Chun-Hua , Yang Zeng-Ming
Published: January 2008

Polyamines are key regulators in cell growth and differentiation. It has been shown that ornithine decarboxylase (Odc) was essential for post-implantation embryo development, and overexpression of spermidine/spermine N1-acetyltransferase will lead to ovarian hypofunction and hypoplastic uteri. However, the expression and function of polyamine-related genes in mouse uterus during early pregnancy are still unknown. In this study we investigated the expression, regulation, and function of polyamine-related genes in mouse uterus during the peri-implantation period. Odc expression was strongly detected at implantation sites and stimulated by estrogen treatment. The expression of Odc antizyme 1 and spermidine/spermine N1-acetyltransferase was also highly shown at implantation sites and regulated by Odc or polyamine level in uterine cells. Embryo implantation was significantly inhibited by α-difluoromethylornithine, an Odc inhibitor. Moreover, the reduction of Odc activity caused by α-difluoromethylornithine treatment was compensated by the up-regulation of S-adenosylmethionine decarboxylase gene expression. Collectively, our results indicated that the coordinated expression of uterine polyamine-related genes may be important for embryo implantation.
Minireview: Adenosine 5′-Monophosphate-Activated Protein Kinase Regulation of Fatty Acid Oxidation in Skeletal Muscle
Authors: Osler Megan E. , Zierath Juleen R.
Published: January 2008

AMP-activated protein kinase (AMPK) is master regulator of energy balance through suppression of ATP-consuming anabolic pathways and enhancement of ATP-producing catabolic pathways. AMPK is activated by external metabolic stresses and subsequently orchestrates a complex downstream signaling cascade that mobilizes the cell for efficient energy production. AMPK has emerged as a key kinase driving lipid oxidation in skeletal muscle, and this function has important implications for exercise adaptations as well as metabolic defects associated with obesity.
Regulation of SREBP1c Gene Expression in Skeletal Muscle: Role of Retinoid X Receptor/Liver X Receptor and Forkhead-O1 Transcription Factor
Authors: Kamei Yasutomi , Miura Shinji , Suganami Takayoshi , Akaike Fumiko , Kanai Sayaka , Sugita Satoshi , Katsumata Aki , Aburatani Hiroyuki , Unterman Terry G. , Ezaki Osamu , Ogawa Yoshihiro
Published: January 2008

Sterol regulatory element binding protein 1c (SREBP1c) is a master regulator of lipogenic gene expression in liver and adipose tissue, where its expression is regulated by a heterodimer of nuclear receptor-type transcription factors retinoid X receptor-α (RXRα) and liver X receptor-α (LXRα). Despite the potential importance of SREBP1c in skeletal muscle, little is known about the regulation of SREBP1c in that setting. Here we report that gene expression of RXRγ is markedly decreased by fasting and is restored by refeeding in mouse skeletal muscle, in parallel with changes in gene expression of SREBP1c. RXRγ or RXRα, together with LXRα, activate the SREBP1c promoter in vitro. Moreover, transgenic mice overexpressing RXRγ specifically in skeletal muscle showed increased gene expression of SREBP1c with increased triglyceride content in their skeletal muscles. In contrast, transgenic mice overexpressing the dominant-negative form of RXRγ showed decreased SREBP1c gene expression. The expression of Forkhead-O1 transcription factor (FOXO1), which can suppress the function of multiple nuclear receptors, is negatively correlated to that of SREBP1c in skeletal muscle during nutritional change. Moreover, transgenic mice overexpressing FOXO1 specifically in skeletal muscle exhibited decreased gene expression of both RXRγ and SREBP1c. In addition, FOXO1 suppressed RXRα/LXRα-mediated SREBP1c promoter activity in vitro. These findings provide in vivo and in vitro evidence that RXR/LXR up-regulates SREBP1c gene expression and that FOXO1 antagonizes this effect of RXR/LXR in skeletal muscle.
Retinoic acid counteracts developmental defects in the substantia nigra caused by Pitx3 deficiency
Authors: Jacobs Frank M. J. , Smits Simone M. , Noorlander Cornelle W. , von Oerthel Lars , van der Linden Annemarie J. A. , Burbach J. Peter H. , Smidt Marten P.
Published: January 2008

Selective neuronal loss in the substantia nigra (SNc), as described for Parkinson's disease (PD) in humans and for Pitx3 deficiency in mice,highlights the existence of neuronal subpopulations. As yet unknown subset-specific gene cascades might underlie the observed differences in neuronal vulnerability. We identified a developmental cascade in mice in which Ahd2 (Aldh1a1) is under the transcriptional control of Pitx3. Interestingly, Ahd2 distribution is restricted to a subpopulation of the meso-diencephalic dopaminergic (mdDA) neurons that is affected by Pitx3 deficiency. Ahd2 is involved in the synthesis of retinoic acid(RA), which has a crucial role in neuronal patterning, differentiation and survival in the brain. Most intriguingly, restoring RA signaling in the embryonic mdDA area counteracts the developmental defects caused by Pitx3 deficiency. The number of tyrosine hydroxylase-positive (TH+)neurons was significantly increased after RA treatment in the rostral mdDA region of Pitx3-/- embryos. This effect was specific for the rostral part of the developing mdDA area, and was observed exclusively in Pitx3-/- embryos. The effect of RA treatment during the critical phase was preserved until later in development, and our data suggest that RA is required for the establishment of proper mdDA neuronal identity. This positions Pitx3 centrally in a mdDA developmental cascade linked to RA signaling. Here, we propose a novel mechanism in which RA is involved in mdDA neuronal development and maintenance, providing new insights into subset-specific vulnerability in PD.
Identification of a silicatein(-related) protease in the giant spicules of the deep-sea hexactinellidMonorhaphis chuni
Authors: Müller Werner E. G. , Boreiko Alexandra , Schloßmacher Ute , Wang Xiaohong , Eckert Carsten , Kropf Klaus , Li Jinhe , Schröder Heinz C.
Published: January 2008

Silicateins, members of the cathepsin L family, are enzymes that have been shown to be involved in the biosynthesis/condensation of biosilica in spicules from Demospongiae (phylum Porifera), e.g. Tethya aurantium and Suberites domuncula. The class Hexactinellida also forms spicules from this inorganic material. This class of sponges includes species that form the largest biogenic silica structures on earth. The giant basal spicules from the hexactinellids Monorhaphis chuni and Monorhaphis intermedia can reach lengths of up to 3 m and diameters of 10 mm. The giant spicules as well as the tauactines consist of a biosilica shell that surrounds the axial canal, which harbours the axial filament, in regular concentric, lamellar layers, suggesting an appositional growth of the spicules. The lamellae contain 27 kDa proteins, which undergo post-translational modification (phosphorylation), while total spicule extracts contain additional 70 kDa proteins. The 27 kDa proteins cross-reacted with anti-silicatein antibodies. The extracts of spicules from the hexactinellid Monorhaphis displayed proteolytic activity like the silicateins from the demosponge S. domuncula. Since the proteolytic activity in spicule extracts from both classes of sponge could be sensitively inhibited by E-64 (a specific cysteine proteinase inhibitor), we used a labelled E-64 sample as a probe to identify the protein that bound to this inhibitor on a blot. The experiments revealed that the labelled E-64 selectively recognized the 27 kDa protein. Our data strongly suggest that silicatein(-related) molecules are also present in Hexactinellida. These new results are considered to also be of impact for applied biotechnological studies.
Fluid and osmolyte recovery in the common pond snailLymnaea stagnalisfollowing full-body withdrawal
Authors: Ebanks Sue C. , Grosell Martin
Published: January 2008

The common pond snail Lymnaea stagnalis sacrifices 40–60% of its extracellular fluid (ECF) including solutes to the surrounding environment to fully retract into its shell. Our objectives were to determine recovery time following such ECF loss and characterize mechanisms involved in recovering Na+, the primary cationic osmolyte in this snail. Pallial fluid was initially collected post-stimulation and again after a second stimulation on sub-groups of those snails 2 h to 10 weeks after initial sampling. Samples were analyzed for pH, osmotic pressure, and individual solute concentrations. Lost volume was recovered within 8 h with no significant changes in pH or total CO2. Significant decreases in osmotic pressure, [Na+] (43% loss), and [Cl–]recovered in 48 h as a result of enhanced uptake from the water. Copper and total extracellular proteins took 5 weeks to recover. Measurements of Na+ transport kinetics completed before and immediately after fluid loss revealed a near threefold increase in both affinity and capacity of the Na+ uptake system. Sodium uptake was independent of ambient Cl– and HCO3– in both control and fluid-depleted snails. Amiloride significantly reduced recovery-phase Na+ uptake rates but did not influence baseline Na+flux. Recovery uptake was significantly reduced by amiloride,ethylisopropylamiloride, bafilomycin and ethoxzolamide indicating dependency upon Na+/H+ exchange, H+ pump activity and H+ from carbonic anhydrase-catalyzed CO2 hydration. Thus enhanced uptake during recovery is likely via electrogenic Na+/H+ exchange and/or possibly a cation channel.
Hematological changes associated with egg production: estrogen dependence and repeatability
Authors: Wagner Emily C. , Prevolsek Jaime S. , Wynne-Edwards Katherine E. , Williams Tony D.
Published: January 2008

The `cost of reproduction' (i.e. the trade-off between current reproduction and future fecundity and/or survival) is a central concept in life history theory, yet we still know very little about the physiological mechanisms underlying such costs. Recently it has been recognized that reproduction itself or the regulatory (hormonal) mechanisms underlying reproduction might result in `costs' (cf. resource-allocation based mechanisms). As one example,it has been suggested that the decrease in hematocrit observed during egg production in birds might be due to antagonistic pleiotropic effects of estrogens. This could generate costs of reproduction by reducing oxygen-carrying capacity during subsequent aerobically demanding stages such as chick-provisioning. Here we show that the reduction in hematocrit during egg-laying is dependent on receptor-mediated actions of endogenous estrogens:blocking estrogen receptors using the anti-estrogen tamoxifen reduces the decrease in hematocrit during egg production in female zebra finches(Taeniopygia guttata) such that hematocrit at the 1-egg stage is not significantly different than pre-breeding, baseline values. We also show that both pre-breeding hematocrit and the decrease in hematocrit associated with egg production are repeatable, and that females with the highest pre-breeding hematocrit values tend to show the largest decreases in hematocrit during egg production. We suggest that hematological changes during egg production are a good candidate mechanism for a regulatory-network based trade-off involving antagonistic pleiotropic effects of estrogens, which otherwise have essential reproductive functions.
Gap junctions in Malpighian tubules ofAedes aegypti
Authors: Weng Xing-He , Piermarini Peter M. , Yamahiro Atsuko , Yu Ming-Jiun , Aneshansley Daniel J. , Beyenbach Klaus W.
Published: January 2008

We present electrical, physiological and molecular evidence for substantial electrical coupling of epithelial cells in Malpighian tubules via gap junctions. Current was injected into one principal cell of the isolated Malpighian tubule and membrane voltage deflections were measured in that cell and in two neighboring principal cells. By short-circuiting the transepithelial voltage with the diuretic peptide leucokinin-VIII we largely eliminated electrical coupling of principal cells through the tubule lumen,thereby allowing coupling through gap junctions to be analyzed. The analysis of an equivalent electrical circuit of the tubule yielded an average gap-junction resistance (Rgj) of 431 kΩ between two cells. This resistance would stem from 6190 open gap-junctional channels,assuming the high single gap-junction conductance of 375 pS found in vertebrate tissues. The addition of the calcium ionophore A23187 (2 μmol l–1) to the peritubular Ringer bath containing 1.7 mmol l–1 Ca2+ did not affect the gap-junction resistance, but metabolic inhibition of the tubule with dinitrophenol (0.5 mmol l–1) increased the gap-junction resistance 66-fold,suggesting the regulation of gap junctions by ATP. Lucifer Yellow injected into a principal cell did not appear in neighboring principal cells. Thus, gap junctions allow the passage of current but not Lucifer Yellow. Using RT-PCR we found evidence for the expression of innexins 1, 2, 3 and 7 (named after their homologues in Drosophila) in Malpighian tubules. The physiological demonstration of gap junctions and the molecular evidence for innexin in Malpighian tubules of Aedes aegypti call for the double cable model of the tubule, which will improve the measurement and the interpretation of electrophysiological data collected from Malpighian tubules.
Active control of free flight manoeuvres in a hawkmoth, Agrius convolvuli
Authors: Wang Hao , Ando Noriyasu , Kanzaki Ryohei
Published: January 2008

By combining optical triangulation with the comb-fringe technique and dual-channel telemetry, wing kinematics and body attitudes accompanying muscle activities of free-flying male hawkmoths were recorded synchronously when they performed flight manoeuvres elicited by a female sex pheromone. The results indicate that the wing leading edge angular position at the ventral stroke reversal, which can be decomposed by two orthogonal angular parameters (a flapping angle and a deviation angle), is well controllable. Two specific flight muscles, the dorsal-ventral muscle (DVM, indirect muscle, a wing elevator) and the third axillary muscle (3AXM, direct muscle, a wing retractor), can modulate the flapping angle and the deviation angle,respectively, by means of regulating the firing timing of muscle activities. The firing timing can be expressed by the firing latency absolutely, which is just before the timing of ventral stroke reversal. The results illustrate that lengthening the firing latency of the DVM and of the 3AXM can increase the flapping angle and the deviation angle, respectively, which both strengthen the downstroke at the ventral stroke reversal. The relationship of bilateral asymmetry shows that the bilateral differences in the firing latency of the DVM and of the 3AXM will cause bilateral differences in the wing position,which accompany the variations of yaw and roll angles in time course. This implies the contribution of the two muscles to active steering controls during turning or banking, though the DVM being an indirect muscle was generally treated as a power generator. Finally, the relationship between the pitch angle and the 3AXM latency, deduced from the relationships between the pitch angle and the deviation angle and between the deviation angle and the 3AXM latency, shows that lengthening the 3AXM latency can increase the pitch angle at the ventral stroke reversal by moving the wing tip far away from the centre of gravity of the body, which indicates a functional role of the 3AXM in active pitching control.
Neuromechanical response of musculo-skeletal structures in cockroaches during rapid running on rough terrain
Authors: Sponberg S. , Full R. J.
Published: January 2008

A musculo-skeletal structure can stabilize rapid locomotion using neural and/or mechanical feedback. Neural feedback results in an altered feedforward activation pattern, whereas mechanical feedback using visco-elastic structures does not require a change in the neural motor code. We selected musculo-skeletal structures in the cockroach (Blaberus discoidalis)because their single motor neuron innervation allows the simplest possible characterization of activation. We ran cockroaches over a track with randomized blocks of heights up to three times the animal's `hip' (1.5 cm),while recording muscle action potentials (MAPs) from a set of putative control musculo-skeletal structures (femoral extensors 178 and 179). Animals experienced significant perturbations in body pitch, roll and yaw, but reduced speed by less than 20%. Surprisingly, we discovered no significant difference in the distribution of the number of MAPs, the interspike interval, burst phase or interburst period between flat and rough terrain trials. During a few very large perturbations or when a single leg failed to make contact throughout stance, neural feedback was detectable as a phase shift of the central rhythm and alteration of MAP number. System level responses of appendages were consistent with a dominant role of mechanical feedback. Duty factors and gait phases did not change for cockroaches running on flat versus rough terrain. Cockroaches did not use a follow-the-leader gait requiring compensatory corrections on a step-by-step basis. Arthropods appear to simplify control on rough terrain by rapid running that uses kinetic energy to bridge gaps between footholds and distributed mechanical feedback to stabilize the body.
The lycaenid butterfly Polyommatus icarus uses a duplicated blue opsin to see green
Authors: Sison-Mangus Marilou P. , Briscoe Adriana D. , Zaccardi Guillermo , Knüttel Helge , Kelber Almut
Published: January 2008

The functional significance of gene duplication is rarely addressed at the level of animal behavior. Butterflies are excellent models in this regard because they can be trained and the use of their opsin-based visual pigments in color vision can be assessed. In the present study, we demonstrate that the lycaenid Polyommatus icarus uses its duplicate blue (B2) opsin, BRh2, in conjunction with its long-wavelength (LW) opsin, LWRh, to see color in the green part of the light spectrum extending up to 560 nm. This is in contrast to butterflies in the genus Papilio, which use duplicate LW opsins to discriminate colors in the long-wavelength range. We also found that P. icarus has a heterogeneously expressed red filtering pigment and red-reflecting ommatidia in the ventral eye region. In behavioural tests, the butterflies could not discriminate colors in the red range (570–640 nm). This finding is significant because we have previously found that the nymphalid butterfly Heliconius erato has filter-pigment mediated color vision in the long wavelength range. Our results suggest that lateral filtering pigments may not always influence color vision in insects.
Performance trade-offs in the flight initiation ofDrosophila
Authors: Card Gwyneth , Dickinson Michael
Published: January 2008

The fruit fly Drosophila melanogaster performs at least two distinct types of flight initiation. One kind is a stereotyped escape response to a visual stimulus that is mediated by the hard-wired giant fiber neural pathway, and the other is a more variable `voluntary' response that can be performed without giant fiber activation. Because the simpler escape take-offs are apparently successful, it is unclear why the fly has multiple pathways to coordinate flight initiation. In this study we use high-speed videography to observe flight initiation in unrestrained wild-type flies and assess the flight performance of each of the two types of take-off. Three-dimensional kinematic analysis of take-off sequences indicates that wing use during the jumping phase of flight initiation is essential for stabilizing flight. During voluntary take-offs, early wing elevation leads to a slower and more stable take-off. In contrast, during visually elicited escapes, the wings are pulled down close to the body during take-off, resulting in tumbling flights in which the fly translates faster but also rotates rapidly about all three of its body axes. Additionally, we find evidence that the power delivered by the legs is substantially greater during visually elicited escapes than during voluntary take-offs. Thus, we find that the two types of Drosophila flight initiation result in different flight performances once the fly is airborne,and that these performances are distinguished by a trade-off between speed and stability.
Shadow response in the blind cavefishAstyanaxreveals conservation of a functional pineal eye
Authors: Yoshizawa Masato , Jeffery William R.
Published: January 2008

The blind cavefish Astyanax mexicanus undergoes bilateral eye degeneration during embryonic development. Despite the absence of light in the cave environment, cavefish have retained a structurally intact pineal eye. We show here that contrary to visual degeneration in the bilateral eyes, the cavefish pineal eye has conserved the ability to detect light. Larvae of two different Astyanax cavefish populations and the con-specific sighted surface-dwelling form (surface fish) respond similarly to light dimming by shading the pineal eye. As a response to shading, cavefish larvae swim upward vertically. This behavior resembles that of amphibian tadpoles rather than other teleost larvae, which react to shadows by swimming downward. The shadow response is highest at 1.5-days post-fertilization (d.p.f.), gradually diminishes, and is virtually undetectable by 7.5 d.p.f. The shadow response was substantially reduced after surgical removal of the pineal gland from surface fish or cavefish larvae, indicating that it is based on pineal function. In contrast, removal of one or both bilateral eye primordia did not affect the shadow response. Consistent with its light detecting capacity,immunocytochemical studies indicate that surface fish and cavefish pineal eyes express a rhodopsin-like antigen, which is undetectable in the degenerating bilateral eyes of cavefish larvae. We conclude that light detection by the pineal eye has been conserved in cavefish despite a million or more years of evolution in complete darkness.
Scaling of metabolism inHelix aspersasnails: changes through ontogeny and response to selection for increased size
Authors: Czarnołęski Marcin , Kozłowski Jan , Dumiot Guillaume , Bonnet Jean-Claude , Mallard Jacques , Dupont-Nivet Mathilde
Published: January 2008

Though many are convinced otherwise, variability of the size-scaling of metabolism is widespread in nature, and the factors driving that remain unknown. Here we test a hypothesis that the increased expenditure associated with faster growth increases metabolic scaling. We compare metabolic scaling in the fast- and slow-growth phases of ontogeny of Helix aspersasnails artificially selected or not selected for increased adult size. The selected line evolved larger egg and adult sizes and a faster size-specific growth rate, without a change in the developmental rate. Both lines had comparable food consumption but the selected snails grew more efficiently and had lower metabolism early in ontogeny. Attainment of lower metabolism was accompanied by decreased shell production, indicating that the increased growth was fuelled partly at the expense of shell production. As predicted,the scaling of oxygen consumption with body mass was isometric or nearly isometric in the fast-growing (early) ontogenetic stage, and it became negatively allometric in the slow-growing (late) stage; metabolic scaling tended to be steeper in selected (fast-growing) than in control (slow-growing)snails; this difference disappeared later in ontogeny. Differences in metabolic scaling were not related to shifts in the scaling of metabolically inert shell. Our results support the view that changes in metabolic scaling through ontogeny and the variability of metabolic scaling between organisms can be affected by differential growth rates. We stress that future approaches to this phenomenon should consider the metabolic effects of cell size changes which underlie shifts in the growth pattern.
Dietary protein influences the rate of 15N incorporation in blood cells and plasma of Yellow-vented bulbuls (Pycnonotus xanthopygos)
Authors: Tsahar Ella , Wolf Nathan , Izhaki Ido , Arad Zeev , del Rio Carlos Martínez
Published: January 2008

The rate at which an animal's tissues incorporate the isotopic composition of food determines the time window during which ecologists can discern diet changes. We investigated the effect of protein content in the diet on the incorporation rate of 15N into the plasma proteins and blood cells of Yellow-vented bulbuls (Pycnonotus xanthopygos). Using model comparison analyses, we found that one-compartment models described incorporation data better than two-compartment models. Dietary protein content had a significant effect on the residence time of 15N in plasma proteins and blood cells. The diet with the highest protein content led to a 15N retention time of 21 and 5 days for cells and plasma,respectively. In contrast, average 15N retention time in the cells and plasma of birds fed on the diet with the lowest protein was 31 and 7 days,respectively. The isotopic discrimination factorΔ 15N=δ15Ntissues–δ15Ndietwas also dependent on dietary protein content, and was lowest in birds fed the diet with the highest protein content. Blood, plasma and excreta were enriched in 15N relative to diet. In contrast, ureteral urine was either significantly depleted of 15N in birds fed the diet with the lowest protein content or did not differ in δ15N from the diets with the intermediate and high protein content. Thus, isotopic incorporation rates and tissue-to-diet discrimination factors cannot be considered fixed, as they depend on diet composition.
How to identify dear enemies: the group signature in the complex song of the skylarkAlauda arvensis
Authors: Briefer Elodie , Aubin Thierry , Lehongre Katia , Rybak Fanny
Published: January 2008

Song geographic variation and Neighbour–Stranger (N–S)discrimination have been intensively but separately studied in bird species,especially in those with small- to medium-sized repertoires. Here, we establish a link between the two phenomena by showing that dialect features are used for N–S recognition in a territorial species with a large repertoire, the skylark Alauda arvensis. In this species, during the breeding season, many pairs settle in stable and adjoining territories gathered in locations spaced by a few kilometres. In a first step, songs produced by males established in different locations were recorded, analyzed and compared to identify possible microgeographic variation at the syntax level. Particular common sequences of syllables (phrases) were found in the songs of all males established in the same location (neighbours), whereas males of different locations (strangers) shared only few syllables and no sequences. In a second step, playback experiments were conducted and provided evidence for N–S discrimination consistent with the dear-enemy effect,i.e. reduced aggression from territorial birds towards neighbours than towards strangers. In addition, a similar response was observed when a `chimeric'signal (shared phrases of the location artificially inserted in the song of a stranger) and a neighbour song were broadcast, indicating that shared sequences were recognized and identified as markers of the group identity. We thus show experimentally that the shared phrases found in the songs of neighbouring birds constitute a group signature used by birds for N–S discrimination, and serve as a basis for the dear-enemy effect.
Swarm formation in the desert locustSchistocerca gregaria:isolation and NMR analysis of the primary maternal gregarizing agent
Authors: Miller Gabriel A. , Islam M. Saiful , Claridge Timothy D. W. , Dodgson Tim , Simpson Stephen J.
Published: January 2008

Depending on their rearing density, female desert locusts Schistocerca gregaria epigenetically endow their offspring with differing phenotypes. To identify the chemical basis for such maternal transmission, we compared solitarious and gregarious locust egg pod foam using high performance liquid chromatography (HPLC). We revealed causal relationships between foam chemistry and hatchling phenotype (phase state) by iteratively applying HPLC fractions from gregarious locust egg foam extracts to solitarious eggs and assessing resulting hatchlings with a behavioural bioassay involving logistic regression. Selection and application of increasingly specific HPLC fractions allowed us to isolate compounds with gregarizing properties. Hatchling gregarization was triggered only by certain fractions and was dose dependent. In a final series of experiments, we characterized the most specific gregarizing fraction by nuclear magnetic resonance (NMR) spectroscopy. Here we present tentative structural features of the primary locust maternal gregarizing agent, which appears to be an alkylated l-dopa analogue. In addition, we propose a mechanism for phase-dependent regulation of this compound's activity.