bluuebunny/crossref_metadata_2025_split huggingface dataset:
Heavy metal detoxification in crustacean epithelial lysosomes: role of anions in the compartmentalization process
Authors: Sterling Kenneth M. , Mandal Prabir K. , Roggenbeck Barbara A. , Ahearn Sean E. , Gerencser George A. , Ahearn Gregory A. 
Published: September 2007

SUMMARYCrustacean hepatopancreatic lysosomes are organelles of heavy metal sequestration and detoxification. Previous studies have shown that zinc uptake by lysosomal membrane vesicles (LMV) occurred by a vanadate- and thapsigargin-sensitive ATPase that was stimulated by a transmembrane proton gradient established by a co-localized V-ATPase associated with this organelle. In the present study, hepatopancreatic LMV from the American lobster Homarus americanus were prepared by standard centrifugation methods and 65Zn2+, 36Cl–, 35SO42– and 14C-oxalate2– were used to characterize the interactions between the metal and anions during vesicular detoxification events. Vesicles loaded with SO42– or PO43– led to a threefold greater steady-state accumulation of Zn2+ than similar vesicles loaded with mannitol,Cl– or oxalate2–. The stimulation of 65Zn2+ uptake by intravesicular sulfate was SO42– concentration dependent with a maximal enhancement at 500 μmol l–1. Zinc uptake in the presence of ATP was proton-gradient enhanced and electrogenic, exhibiting an apparent exchange stoichiometry of 1Zn+/3H+. 35SO42– and 14C-oxalate2– uptakes were both enhanced in vesicles loaded with intravesicular Cl– compared to vesicles containing mannitol, suggesting the presence of anion countertransport. 35SO42– influx was a sigmoidal function of external [SO42–] with 25 mmol l–1 internal [Cl–], or with several intravesicular pH values (e.g. 7.0, 8.0 and 9.0). In all instances Hill coefficients of approximately 2.0 were obtained, suggesting that 2 sulfate ions exchange with single Cl– or OH– ions. 36Cl– influx was a sigmoidal function of external[Cl–] with intravesicular pH of 7.0 and 9.0. A Hill coefficient of 2.0 was also obtained, suggesting the exchange of 2 Cl– for 1 OH–. 14C-oxalate influx was a hyperbolic function of external [oxalate2–] with 25 mmol l–1 internal [Cl–], suggesting a 1:1 exchange of oxalate2– for Cl–. As a group,these experiments suggest the presence of an anion exchange mechanism exchanging monovalent for polyvalent anions. Polyvalent inorganic anions(SO42– and PO43–) are known to associate with metals inside vesicles and a detoxification model is presented that suggests how these anions may contribute to concretion formation through precipitation with metals at appropriate vesicular pH.
In vivored blood cell sickling and mechanism of recovery in whiting,Merlangius merlangus
Authors: Koldkjær Pia , Berenbrink Michael 
Published: September 2007

SUMMARYHaemoglobin concentrations in vertebrate red blood cells are so high that in human sickle cell disease a single surface amino acid mutation can result in formation of large insoluble haemoglobin aggregates at low oxygen levels,causing peculiar cell deformations or `sickling'. This may cause vascular occlusion and thereby severe pain, organ failure and death. Here, using light and transmission electron microscopy, we demonstrate extensive in vivo sickling of whiting red blood cells after capture stress without any apparent haemolysis and show its subsequent recovery. We show exceptionally high cooperative proton binding during the sickling process in vitroand identify the reduction of extracellular pH below resting values as the primary cause for in vivo sickling, although the response is modulated to a lesser extent also by oxygen tension. Using isotope tracer fluxes, we further show that β-adrenergic hormones, which are released under capture stress, activate a powerful endogenous Na/H exchanger in these fish red blood cells, which is known to elevate intracellular pH.β-adrenergic treatment further leads to a marked reduction of acid-induced in vitro sickling, which is impaired when Na/H exchange is inhibited by amiloride. We propose that this mechanism protects red blood cells of some fishes against the problem of haemoglobin aggregation and red blood cell sickling, except under most severe acidosis. This system offers a unique example of how, over evolutionary time, nature may have overcome what is still a deadly disease in humans.
Nitric oxide formation from nitrite in zebrafish
Authors: Jensen Frank B. 
Published: September 2007

SUMMARY
Nitrite is a potential nitric oxide (NO) donor and may have important biological functions at low concentrations. The present study tests the hypothesis that nitrite accumulation across the gills in fish will cause a massive NO production from nitrite. Zebrafish were exposed to three different nitrite levels for variable time periods, and changes in blood nitrosylhemoglobin (HbNO), methemoglobin (metHb), oxygenated hemoglobin(oxyHb) and deoxygenated hemoglobin (deoxyHb) were evaluated by spectral deconvolution. Blood HbNO (a biomarker of internal NO production) was low in controls, increased to a stable level around 3.7% of total Hb in fish exposed to 0.6 mmol l–1 nitrite, and to 12.1% (at day 2) in fish exposed to 2 mmol l–1 nitrite. The very high HbNO levels testify to an extensive conversion of nitrite to NO. With deoxyHb-mediated reduction of nitrite being a major NO-producing mechanism, the data reveal the significance of this mechanism, when hemoglobin cycles between full and intermediate oxygen saturations in the arterial–venous circulation. Fish exposed to 0.6 mmol l–1 nitrite for up to 5 days could be divided into responding (with elevated metHb) and non-responding individuals. Exposure to 2 mmol l–1 nitrite caused a time-dependent increase in metHb to 59% of total Hb within 2 days. Taking HbNO into account,the functional (potential O2 carrying) Hb was reduced to 29% at this stage. Total blood [Hb] was also significantly decreased. In spite of the reduced blood O2 capacitance, and the possibility that excess NO may inhibit mitochondrial respiration, whole animal routine oxygen consumption was not depressed.
FoxK1splice variants show developmental stage-specific plasticity of expression with temperature in the tiger pufferfish
Authors: Fernandes Jorge M. O. , MacKenzie Matthew G. , Kinghorn James R. , Johnston Ian A. 
Published: September 2007

SUMMARYFoxK1 is a member of the highly conserved forkhead/winged helix (Fox)family of transcription factors and it is known to play a key role in mammalian muscle development and myogenic stem cell function. The tiger pufferfish (Takifugu rubripes) orthologue of mammalian FoxK1(TFoxK1) has seven exons and is located in a region of conserved synteny between pufferfish and mouse. TFoxK1 is expressed as three alternative transcripts: TFoxK1-α, TFoxK1-γ and TFoxK1-δ. TFoxK1-α is the orthologue of mouse FoxK1-α, coding for a putative protein of 558 residues that contains the forkhead and forkhead-associated domains typical of Fox proteins and shares 53% global identity with its mammalian homologue. TFoxK1-γ and TFoxK1-δ arise from intron retention events and these transcripts translate into the same 344-amino acid protein with a truncated forkhead domain. Neither are orthologues of mouse FoxK1-β. In adult fish, the TFoxK1 splice variants were differentially expressed between fast and slow myotomal muscle, as well as other tissues, and the FoxK1-α protein was expressed in myogenic progenitor cells of fast myotomal muscle. During embryonic development, TFoxK1 was transiently expressed in the developing somites, heart,brain and eye. The relative expression of TFoxK1-α and the other two alternative transcripts varied with the incubation temperature regime for equivalent embryonic stages and the differences were particularly marked at later developmental stages. The developmental expression pattern of TFoxK1 and its localisation to mononuclear myogenic progenitor cells in adult fast muscle indicate that it may play an essential role in myogenesis in T. rubripes.
Putative Role of Hyaluronan and Its Related Genes,HAS2andRHAMM, in Human Early Preimplantation Embryogenesis and Embryonic Stem Cell Characterization
Authors: Choudhary Meenakshi , Zhang Xin , Stojković Petra , Hyslop Louise , Anyfantis George , Herbert Mary , Murdoch Alison P. , Stojković Miodrag , Lako Majlinda 
Published: September 2007

AbstractHuman embryonic stem cells (hESC) promise tremendous potential as a developmental and cell therapeutic tool. The combined effort of stimulatory and inhibitory signals regulating gene expression, which drives the tissue differentiation and morphogenetic processes during early embryogenesis, is still very poorly understood. With the scarcity of availability of human embryos for research, hESC can be used as an alternative source to study the early human embryogenesis. Hyaluronan (HA), a simple hydrating sugar, is present abundantly in the female reproductive tract during fertilization, embryo growth, and implantation and plays an important role in early development of the mammalian embryo. HA and its binding protein RHAMM regulate various cellular and hydrodynamic processes from cell migration, proliferation, and signaling to regulation of gene expression, cell differentiation, morphogenesis, and metastasis via both extracellular and intracellular pathways. In this study, we show for the first time that HA synthase gene HAS2 and its binding receptor RHAMM are differentially expressed during all stages of preimplantation human embryos and hESC. RHAMM expression is significantly downregulated during differentiation of hESC, in contrast to HAS2, which is significantly upregulated. Most importantly, RHAMM knockdown results in downregulation of several pluripotency markers in hESC, induction of early extraembryonic lineages, loss of cell viability, and changes in hESC cycle. These data therefore highlight an important role for RHAMM in maintenance of hESC pluripotency, viability, and cell cycle control. Interestingly, HAS2 knockdown results in suppression of hESC differentiation without affecting hESC pluripotency. This suggests an intrinsic role for HAS2 in hESC differentiation process. In accordance with this, addition of exogenous HA to the differentiation medium enhances hESC differentiation to mesodermal and cardiac lineages.Disclosure of potential conflicts of interest is found at the end of this article.
Functional Sarcoplasmic Reticulum for Calcium Handling of Human Embryonic Stem Cell-Derived Cardiomyocytes: Insights for Driven Maturation
Authors: Liu Jing , Fu Ji Dong , Siu Chung Wah , Li Ronald A. 
Published: September 2007

Abstract
Cardiomyocytes (CMs) are nonregenerative. Self-renewable pluripotent human embryonic stem cells (hESCs) can differentiate into CMs for cell-based therapies. In adult CMs, Ca2+-induced Ca2+ release from the sarcoplasmic reticulum (SR) via the ryanodine receptor (RyR) is key in excitation-contraction coupling. Therefore, proper Ca2+ handling properties of hESC-derived CMs are required for their successful functional integration with the recipient heart. Here, we performed a comprehensive analysis of CMs differentiated from the H1 (H1-CMs) and HES2 (HES2-CMs) hESC lines and human fetal (F) and adult (A) left ventricular (LV) CMs. Upon electrical stimulation, all of H1-, HES2-, and FLV-CMs generated similar Ca2+ transients. Caffeine induced Ca2+ release in 65% of FLV-CMs and ∼38% of H1- and HES2-CMs. Ryanodine significantly reduced the electrically evoked Ca2+ transient amplitudes of caffeine-responsive but not -insensitive HES2- and H1-CMs and slowed their upstroke; thapsigargin, which inhibits the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA) pump, reduced the amplitude of only caffeine-responsive HES2- and H1-CMs and slowed the decay. SERCA2a expression was highest in ALV-CMs but comparable among H1-, HES2-, and FLV-CMs. The Na+-Ca2+ exchanger was substantially expressed in both HES2- and H1-CMs relative to FLV- and ALV-CMs. RyR was expressed in HES2-, H1-, and FLV-CMs, but the organized pattern for ALV-CMs was not observed. The regulatory proteins junctin, triadin, and calsequestrin were expressed in ALV-CMs but not HES2- and H1-CMs. We conclude that functional SRs are indeed expressed in hESC-CMs, albeit immaturely. Our results may lead to driven maturation of Ca2+ handling properties of hESC-CMs for enhanced contractile functions.
Disclosure of potential conflicts of interest is found at the end of this article.
Ground improvement techniques beneath existing rail tracks
Authors: Adam D. , Vogel A. , Zimmermann A. 
Published: September 2007

Increased demand on rail tracks owing to decreased intervals, heavier and faster trains and the wearing of old railway lines often requires improvement of the ground and sub-ballast beneath conventional ballasted rail tracks. The rail traffic should not be restrained; thus methods are welcome, which allow a soil compaction or replacement of the soil while tracks and sleepers remain in place. In the current paper methods are presented, which allow a deep improvement of poor and soft soil beneath the rail track and a complete exchange of the near-surface rail track structure including the base layers, ballast, sleepers and tracks. L'augmentation de la demande en rails, due à la réduction des intervalles, à la circulation de trains plus lourds et plus rapides, et à l'état de voies ferrées usées nécessite souvent le renforcement du terrain et du sub-ballast des voies sur ballast traditionnelles. Étant donné qu'il est nécessaire de ne pas entraver la circulation ferroviaire, on recherche des méthodes permettant le tassement du terrain ou le remplacement du sol tout en laissant les rails et les traverses en place. Cette communication présente des méthodes permettant de renforcer des sols de mauvaise qualité et boulants sous la voie ferrée, ainsi que le remplacement intégral de la voie à proximité de la surface, y compris la base, le ballast, les traverses et les rails.
Heavy tamping integrated dynamic compaction control
Authors: Adam D. , Brandl H. , Kopf F. , Paulmichl I. 
Published: September 2007

Heavy tamping is a deep dynamic compaction technique and has been increasingly used since the beginning of the 1970s. The present paper reports on in situ measurements and theoretical investigations referring to the decay of free soil vibrations caused by the falling weight after each impact. This behaviour is significant for the respective soil—falling mass interaction and enables a site-specific optimisation of the heavy tamping technique. The field tests comprised acceleration measurements of the falling mass and the soil whereby the falling height was changed repeatedly. The decay of the amplitudes of free vibrations provided a damping coefficient and a damped natural frequency, which are used to determine the Poisson's ratio and the E-modulus of the ground after each impact from numerical calculations. The scope of the research project was to gain a reliable indicator for the degree of compaction of the soil immediately after each impact, and hence obtain a method for compaction control and documentation. Le pilonnage lourd est une technique de compactage dynamique en profondeur, utilisée de plus en plus depuis le début des années 1970. La présente communication rend compte de mesures in situ et de recherches théoriques portant sur la dégradation des vibrations propres dans le sol, causées par la retombée du poids après chaque impact. Ce comportement est significatif pour l'interaction entre le sol et la masse tombante, et permet d'optimiser la technique du pilonnage lourd spécifiquement pour chaque lieu d'utilisation. Les essais sur place comprenaient des mesures de l'accélération de la masse tombante et du sol, et comportait le changement répété de la hauteur de chute. Le décroissement de l'amplitude des vibrations libres permettait d'obtenir un coefficient d'amortissement et une fréquence amortie naturelle, qui sont utilisés pour déterminer le coefficient de Poisson et le module E du sol après chaque impact, au moyen de calculs numériques. L'objet de ce projet de recherche était d'obtenir une méthode pour le contrô le et la documentation du compactage.
Lethal and sublethal effects of ammonia to juvenileLampsilismussels (unionidae) in sediment and water-only exposures
Authors: Newton Teresa J. , Bartsch Michelle R. 
Published: September 2007

AbstractWe compared the sensitivity of two juvenile unionid mussels (Lampsilis cardium and Lampsilis higginsii) to ammonia in 96-h water-only and sediment tests by use of mortality and growth measurements. Twenty mussels were placed in chambers buried 2.5 cm into reference sediments to approximate pore-water exposure (sediment tests) or elevated above the bottom of the experimental units (water-only tests). In the sediment tests, a pH gradient existed between the overlying water (mean 8.0), sediment–water interface (mean 7.7), and 2.5 cm depth (mean 7.4). We assumed that mussels were exposed to ammonia in pore water and report effect concentrations in pore water, but if they were exposed to the higher pH water, more of the ammonia would be in the toxic un-ionized (NH3) form. The only differences in toxicity and growth between mussel species occurred in some of the water-only tests. In sediment tests, median lethal concentrations (LC50s) ranged from 124 to 125 μg NH3-N/L. In water-only tests, LC50s ranged from 157 to 372 μg NH3-N/L. In sediment tests, median effective concentrations (EC50s based on growth) ranged from 30 to 32 μg NH3-N/L. Juvenile mussels in the water-only tests grew poorly and did not exhibit a dose–response relation. These data demonstrate that growth is a sensitive and valuable endpoint for studies on ammonia toxicity with juvenile freshwater mussels and that growth should be measured via sediment tests.
Intra- and interlaboratory variability in acute toxicity tests with glochidia and juveniles of freshwater mussels (unionidae)
Authors: Wang Ning , Augspurger Tom , Barnhart M. Chris , Bidwell Joseph R. , Cope W. Gregory , Dwyer F. James , Geis Steve , Greer I. Eugene , Ingersoll Chris G. , Kane Cynthia M. , May Thomas W. , Neves Richard J. , Newton Teresa J. , Roberts Andy D. , Whites David W. 
Published: September 2007

Abstract
The present study evaluated the performance and variability in acute toxicity tests with glochidia and newly transformed juvenile mussels using the standard methods outlined in American Society for Testing and Materials (ASTM). Multiple 48-h toxicity tests with glochidia and 96-h tests with juvenile mussels were conducted within a single laboratory and among five laboratories. All tests met the test acceptability requirements (e.g., ≥90% control survival). Intralaboratory tests were conducted over two consecutive mussel-spawning seasons with mucket (Actinonaias ligamentina) or fatmucket (Lampsilis siliquoidea) using copper, ammonia, or chlorine as a toxicant. For the glochidia of both species, the variability of intralaboratory median effective concentrations (EC50s) for the three toxicants, expressed as the coefficient of variation (CV), ranged from 14 to 27% in 24-h exposures and from 13 to 36% in 48-h exposures. The intralaboratory CV of copper EC50s for juvenile fatmucket was 24% in 48-h exposures and 13% in 96-h exposures. Interlaboratory tests were conducted with fatmucket glochidia and juveniles by five laboratories using copper as a toxicant. The interlaboratory CV of copper EC50s for glochidia was 13% in 24-h exposures and 24% in 48-h exposures, and the interlaboratory CV for juveniles was 22% in 48-h exposures and 42% in 96-h exposures. The high completion success and the overall low variability in test results indicate that the test methods have acceptable precision and can be performed routinely.
Chronic toxicity of copper and ammonia to juvenile freshwater mussels (unionidae)
Authors: Wang Ning , Ingersoll Christopher G. , Greer I. Eugene , Hardesty Douglas K. , Ivey Christopher D. , Kunz James L. , Brumbaugh William G. , Dwyer F. James , Roberts Andy D. , Augspurger Tom , Kane Cynthia M. , Neves Richard J. , Barnhart M. Chris 
Published: September 2007

Abstract
The objectives of the present study were to develop methods for conducting chronic toxicity tests with juvenile mussels under flow-through conditions and to determine the chronic toxicity of copper and ammonia to juvenile mussels using these methods. In two feeding tests, two-month-old fatmucket (Lampsilis siliquoidea) and rainbow mussel (Villosa iris) were fed various live algae or nonviable algal mixture for 28 d. The algal mixture was the best food resulting in high survival (≥90%) and growth. Multiple copper and ammonia toxicity tests were conducted for 28 d starting with two-month-old mussels. Six toxicity tests using the algal mixture were successfully completed with a control survival of 88 to 100%. Among copper tests with rainbow mussel, fatmucket, and oyster mussel (Epioblasma capsaeformis), chronic value ([ChV], geometric mean of the no-observed-effect concentration and the lowest-observed-effect concentration) ranged from 8.5 to 9.8 μg Cu/L for survival and from 4.6 to 8.5 μg Cu/L for growth. Among ammonia tests with rainbow mussel, fatmucket, and wavy-rayed lampmussel (L. fasciola), the ChV ranged from 0.37 to 1.2 mg total ammonia N/L for survival and from 0.37 to 0.67 mg N/L for growth. These ChVs were below the U.S. Environmental Protection Agency 1996 chronic water quality criterion (WQC) for copper (15 μg/L; hardness 170 mg/L) and 1999 WQC for total ammonia (1.26 mg N/L; pH 8.2 and 20°C). Results indicate that toxicity tests with two-month-old mussels can be conducted for 28 d with &gt;80% control survival; growth was frequently a more sensitive endpoint compared to survival; and the 1996 chronic WQC for copper and the 1999 chronic WQC for total ammonia might not be adequately protective of the mussel species tested. However, a recently revised 2007 chronic WQC for copper based on the biotic ligand model may be more protective in the water tested.
Acute and chronic toxicity of pesticide formulations (atrazine, chlorpyrifos, and permethrin) to glochidia and juveniles ofLampsilis siliquoidea
Authors: Bringolf Robert B. , Cope W. Gregory , Barnhart M. Chris , Mosher Shad , Lazaro Peter R. , Shea Damian 
Published: September 2007

AbstractFreshwater mussels are among the most imperiled faunal groups in North America; approximately 67% of the nearly 300 native freshwater mussel species (family Unionidae) are listed as endangered, threatened, or of special concern. Despite evidence that glochidia and juvenile life stages are highly sensitive to some chemical contaminants, the effects of pesticides on early life stages of unionid mussels are largely unknown. In the United States, pesticide registration is based on toxicity data of the active ingredient, not formulations as they are sold and applied. Some pesticide formulations, however, are more toxic than their active ingredient (technical-grade pesticide) alone because of the presence of surfactants, adjuvants, or other ingredients in the formulation. The objective of the present study was to compare the toxicity of active ingredients of several current-use pesticides (atrazine, chlorpyrifos, and permethrin) to the toxicity of pesticide formulations to glochidia and juvenile life stages of a freshwater mussel (Lampsilis siliquoidea). The atrazine formulation (Aatrex) was more toxic than technical-grade atrazine in chronic tests with juvenile L. siliquoidea. For other pesticides, acute and chronic toxicity of technical-grade pesticides were similar to the toxicity of pesticide formulations. Median effective concentrations for chlorpyrifos were 0.43 mg/L for glochidia at 48 h, 0.25 mg/L for juveniles at 96 h, and 0.06 mg/L for juveniles at 21 d. Atrazine and permethrin as well as their formulations did not cause significant acute toxicity in glochidia or juveniles at exposure concentrations approaching water-solubility limits. Additional research is needed on other pesticides with different modes of action, on the role of different routes of exposure, and with other species of unionid mussels to evaluate similarities of toxic response.