bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical versus Biological Explanations
Authors: SCHUMMER JOACHIM
Published: July 2009

Abstract: This paper analyzes four controversies in the 19th century life sciences: the nature of fermentation, the nature of infectious diseases, the generation of life from inanimate matter, and vitalism. All these controversies appear to concern chemical versus biological explanations, suggesting that reduction of biology to chemistry was the common underlying issue. My analysis rejects such interpretations, including the labels for explanation, and instead points out sophisticated forms of interdisciplinarity between chemistry, medicine, and biology in the first three debates. I argue that the philosophically favored perspective on reductionism, historically induced by a few physicians in the fourth debate, leads us astray from understanding interdisciplinary research.
Social Background of the Discovery and the Reception of the Periodic Law of the Elements
Authors: KAJI MASANORI
Published: July 2009

Abstract: The favorable and relatively rapid reception of Mendeleev's periodic table of the elements can be attributed, in part at least, to his social connections. These connections were evident in the recently organized Russian Chemical Society. In addition, Mendeleev enjoyed the support of the editorial board of the journal of the German Chemical Society.
An Organic Framework for a Philosophical Appreciation of Chemical Phenomena
Authors: KHURI RICHARD K.
Published: July 2009

Abstract: The aim of this paper is to show how chemistry gives rise to philosophical reflection. Initially, some general remarks on philosophy and science are offered in the light of recent reductive controversy surrounding them both. An appeal is made for a broader and deeper outlook. The philosophical outlook favored is one of openness towards the phenomena: rather than confine them to some ‘‐ism’ or other. The phenomena are seen as at least potentially ‘bathed’ in more encompassing levels of being. The term ‘ontological suppleness’ is later introduced in this spirit, to express how something at a given level, say electronegativity in chemistry, has significance at far higher levels of being—in this case, the emergence of life, and our planet's ecology as a whole. Similar consideration is given to the conversion of a carcinogen (benzene) into a ‘miracle drug’ (aspirin). These illustrations are intended to highlight how science in general, including chemistry in particular, offers seamless transitions to what lies beyond the scope of science. What remains for us is to find a language adequate to deal with such transitions.
Chemistry Beyond Positivism
Authors: BRANDT WERNER W.
Published: July 2009

Abstract:Chemistry is often thought to be quite factual, and therefore might be considered close to the ‘positivist’ ideal of a value‐free science. A closer look, however, reveals that the field is coupled to the invisible realm of values, meanings, and purpose in various ways, and chemists interact with that realm loosely and unevenly. Tacit knowledge is one important locus of such interactions. We are concerned in this essay with two questions. What is the nature of the knowledge when we are in the early stages of discovery? and In what ways does the hidden reality we are seeking affect our search for an understanding of it? The first question is partly answered by Polanyi's theory of tacit knowledge, while the second one leads us to realize the limitations of our language when discussing ‘reality’—or certain chemical experimental results. A strictly positivist approach is of little use, but so is the opposite, the complete disregard of facts. The contrast between positivism and non‐formulable aspects of scientific reasoning amounts to a paradox that needs to be analyzed and can lead to a ‘connected’ chemistry. This in turn resembles networks described by Schweber and is more concerned than the chemistry ‘as it is’ with aspects such as the image of chemistry, the challenges chemists face as citizens, and chemistry in liberal education.
The National Science Foundation and the Philosophy of Chemistry
Authors: SEELY BRUCE E.
Published: July 2009

Abstract: Since its founding in 1950, the National Science Foundation has provided support for a variety of studies in history, philosophy, and social studies of science. The fact that a relatively small number of projects dealing with the philosophy of chemistry have received NSF support is due to the small number of such proposals that have been submitted. The NSF Science and Technology Studies Program (STS) welcomes proposals dealing with philosophy of chemistry.
Transmission of E1‐E2 Structural Changes in Response to Na+ or K+ Binding in Na,K‐ATPase
Authors: JORGENSEN PETER L.
Published: July 2009

Abstract: The extensive E1‐E2 conformational changes in response to Na+ or K+ binding in the absence of other ligands must be driven by motion of the side chains contributing to cation coordination, but the differences in structure of Na+ and K+ sites have not been resolved. The recent high resolution structure model of the E2 conformation of Ca‐ATPase offers the first opportunity to examine and model the changes accompanying the adjustment of the cation sites from an E1 form with specificity for Na+ to an E2 form with specificity for K+. The model of the E2 form provides a remarkable fit to the data of direct Tl+ or K+ binding after site‐directed mutagenesis of residues Asp804 and Asp808 in M6, Glu 779, Gln776, and Ser775 in M5, and Glu327 in M4. Cytoplasmic domain movements during E1↔ E2 conformational transition can be monitored by proteolytic cleavage. Protection of the chymotrypsin‐sensitive bond at Leu266 in L2/3 and rotation of the A domain is more complete in the E2Mg‐vanadate‐ouabain complex than in the E2[2K] form.
Investigating the Energy Transduction Mechanism of P‐type ATPases with Fe2+‐Catalyzed Oxidative Cleavage
Authors: KARLISH STEVEN J. D.
Published: July 2009

Abstract: This paper discusses specific oxidative cleavage of renal Na+,K+‐ATPase and gastric H+,K+‐ATPase, catalyzed by bound Fe2+ or the complex ATP‐Fe2+, and its implication for the energy transduction mechanism of P‐type ATPases. The cleavage technique provides information on the spatial organization of the proteins in different conformations and, since ATP‐Fe2+ substitutes for ATP‐Mg2+ in activating ATPase activity, on Mg2+‐ligating residues in different conformations. The experiments predict the existence of large movements of N, P, and A cytoplasmic domains accompanying E1‐E2 and E1 P‐E2P conformational transitions—open in E1 conformations and closed in E2 conformations. These features fit well with the Ca2+‐ATPase crystal structures in E1 or E2 conformations and also provide evidence on ATP and Mg2+ binding sites that is not available from the structures. By combining information from cleavage experiments with molecular modeling, based on the Ca2+‐ATPase structure, features such as an N to P domain interaction in an E1. ATP‐Mg2+ conformation can be inferred. The organization of the N, P, and A domains and the ATP and Mg2+ binding sites in the different conformational states appears to be essentially similar for Na+,K+‐ATPase, H+,K+‐ATPase, and Ca2+‐ATPase. The oxidative cleavage technique may be a valuable tool to investigate long‐range interactions that transduce the free energy of hydrolysis of ATP to active cation movements in P‐type ATPases.
Proteolytic Studies on the Transduction Mechanism of Sarcoplasmic Reticulum Ca2+‐ATPase
Authors: MØLLER JESPER V. , LENOIR GUILLAUME , LE MAIRE MARC , JUUL BIRTE STÆHR , CHAMPEIL PHILIPPE
Published: July 2009

Abstract: After proteinase K‐induced excision of five amino acid residues in the semiconserved polypeptide chain linking the end of the A domain with the S3/M3 transmembrane segment we find that Ca2+ transport is blocked while partial reactions like Ca2+ binding, ATP phosphorylation, and Ca2+‐occlusion are left intact. However, formation of the so‐called E2P state (either from the phosphorylated species formed in the presence of ATP and Ca2+ or from the Ca2+‐depleted unphosphorylated species) is blocked. We conclude that the proteinase K‐treated ATPase, while maintaining many of the partial reactions, is incapable of energy transduction because of the absence of an E2P state with Ca2+ binding sites exposed to the intravesicular space. Sequence comparisons and mutagenesis data point to an important role in energy transduction of P‐type ATPases of a conserved motif located at the end of the A domain.
Involvement of the Cytoplasmic Loop L6‐7 in the Entry Mechanism for Transport of Ca2+ through the Sarcoplasmic Reticulum Ca2+‐ATPase
Authors: CORRE F. , JAXEL C. , FUENTES J. , MENGUY T. , FALSON P. , LEVINE B. A. , MØLLER J. V. , LE MAIRE M.
Published: July 2009

Abstract: We have found that despite a markedly low calcium affinity the D813A/D818A mutant is capable, after complexation with Cr.ATP, of occluding Ca2+ to the same extent (1‐2 Ca2+ per ATPase monomer) as wild‐ type ATPase. The inherent ability of the synthetic L6‐7 loop peptide to bind Ca2+ was demonstrated with murexide and mass spectrometry. NMR analysis indicated the formation of specific 1:1 cation complexes of the peptide with calcium and lanthanum with coordination by all three aspartate residues D813/D815/D818 that resulted in an altered conformation of the peptide chain. Overall our observations suggest that, in addition to mediating contact between the intramembranous Ca2+ binding sites and the cytosolic phosphorylation site as previously suggested, the L6‐7 loop, in a preceding step, participates in the formation of an entrance port important for lodging Ca2+ at a high‐affinity binding site inside the membrane.
Molecular Modeling of SCH28080 Binding to the Gastric H,K‐ATPase and MgATP Interactions with SERCA‐ and Na,K‐ATPases
Authors: MUNSON KEITH , VAGIN OLGA , SACHS GEORGE , KARLISH STEVE
Published: July 2009

Abstract: We have used homology molecular modeling based on the srCaATPase E2 conformation, pdb1kju, to predict side chains involved in docking the K+ competitive inhibitor, SCH28080, to the H,K‐ATPase. A model for SCH28080 binding between residues L809 and A335 in the same space utilized by omeprazole is proposed. We also describe modeling MgATP binding to the E1 structure of the srATPase, pdb1eul, as a paradigm for the Na,K‐ and H,K‐ATPases. The resulting model, E1·MgATP, visualizes a conformation not yet available by crystallization and successfully predicts a range of published results, including backbone cleavages near V440 (N domain) and V712 (P domain) mediated by FeATP in the Na,K‐ATPase. A separate model for MgATP docked to E2 (pdb1kju) shows that access of the γ phosphate to D351 is blocked by the A domain. The E2· MgATP model explains FeATP‐mediated cleavages of the Na,K‐ATPase near V440 and E214 (A domain) and homologous results in the H,K‐ATPase.
Inhibition Kinetics of the Gastric H,K‐ATPase by K‐Competitive Inhibitor SCH28080 as a Tool for Investigating the Luminal Ion Pathway
Authors: VAGIN OLGA , MUNSON KEITH , DENEVICH SVETLANA , SACHS GEORGE
Published: July 2009

Abstract: The gastric H,K‐ATPase and the Na,K‐ATPase both are stimulated by luminal K+, but differ in sensitivity to K+‐competitive inhibitors (ouabain and SCH28080), which implies a difference in structure near the luminal ion pathways in these two pumps. Knowledge of the amino acids in the H,K‐ATPase that affect the mode of inhibition by SCH28080 and inhibitor affinity should provide insight into the regions of the membrane domain influencing the inhibitor selectivity and the luminal route to the ion transport site. Mutational scans in M4, 5, 6, and 8 have shown that amino acid residues affecting ion affinity (E343, K791, E795, E820, D824, E936) with either no or a lesser effect on the inhibitor affinity are located in the middle of the membrane domain. The residues significantly reducing inhibitor affinity, but not ion affinity (L809, P810, L811, T813, I816, Y925, T929), are located in the exoplasmic 5–6 loop and the luminal ends of M6 and M8. This suggests that the binding domain for SCH28080 contains the surface between L809 in the 5–6 loop and C813 at the luminal end of M6, ∼two helical turns out from the ion binding region, where it blocks an ion access pathway. The mutations that change inhibitor kinetics are on the opposing faces of M6 and M8 and apparently modify the normal ion pathway or, perhaps, create an alternate ion pathway.
Ion Occlusion/Deocclusion Partial Reactions in Individual Palytoxin‐Modified Na/K Pumps
Authors: ARTIGAS PABLO , GADSBY DAVID C.
Published: July 2009

Abstract:In P‐type ion‐motive ATPases, transported ions approach their binding sites from one membrane surface, become buried deep within ‘occluded’ conformations in which the sites are inaccessible from either membrane side, and are then deoccluded and released to the opposite membrane surface. This describes an alternating‐gate transport mechanism, in which the pump acts like an ion channel with two gates that open and close alternately. The occluded states ensure that one gate closes before the other can open, thus preventing the large electrodiffusive ion fluxes that would otherwise quickly undo the pump's electrochemical work. High‐resolution crystal structures of two conformations of the SERCA (sarcoplasmic and endoplasmic reticulum Ca2+) P‐type ATPase, together with mutagenesis results and analyses of structural models based on homology, have begun to provide a picture of the ion coordination sites in related P‐type ATPases, including the Na/K pump. However, in no P‐type ATPase are the structures and mechanisms of the gates known. The marine toxin, palytoxin (PTX), is known to bind to the Na/K pump and elicit a nonselective cation leak pathway, possibly by disrupting the strict coupling between the pump's inner and outer gates, allowing them to both be open. We recently found that ion flow through PTX‐modified Na/K pump‐channels appears to be modulated by two gates that can be regulated by the pump's physiological ligands in a manner suggesting that gating reflects underlying ion occlusion/deocclusion partial reactions. We review that work here and provide evidence that the pore of the PTX‐induced pump‐channel has a diameter > 6 Å.
Binding of 1 Rb+ Accelerates Dephosphorylation of the Na+,K+‐ATPase without Leading to Rb+ Occlusion
Authors: KAUFMAN SERGIO B. , GONZÁLEZ‐LEBRERO RODOLFO M. , GARRAHAN PATRICIO J. , ROSSI ROLANDO C.
Published: July 2009

Abstract: In steady‐state conditions and for concentrations of the K+‐congener Rb+ less than 2.5 mM, Rb+‐dependent ATPase activity is significantly higher than the steady‐state rate of breakdown of Rb+‐occluded states, a discrepancy that disappears at sufficiently high [Rb+]. Direct experimental evidence is provided that supports the explanation that the binding of a single Rb+ to the phosphoenzyme conformer E2P accelerates dephosphorylation without leading to the occlusion of the cation.
The E1/E2‐Preference of Gastric H,K‐ATPase Mutants
Authors: DE PONT JAN JOEP H. H. M. , SWARTS HERMAN G. P. , WILLEMS PETER H. G. M. , KOENDERINK JAN B.
Published: July 2009

Abstract:Gastric H,K‐ATPase has, in the absence of ATP and added ions, a preference for the E2conformation. Mutations in the cation‐binding pocket often result in a preference for the E1‐conformation. This can be paralleled by the occurrence of K+‐independentATPase activity. These two phenomena could be separated by combined mutagenesis of several residues in and around the cation‐binding pocket. Models of the three‐dimensional structure of H,K‐ATPase visualize the relationship between the E1/E2preference and the structure.
Functional Roles of the α Isoforms of the Na,K‐ATPase
Authors: LINGREL JERRY , MOSELEY AMY , DOSTANIC IVA , COUGNON MARC , HE SUIWEN , JAMES PAUL , WOO ALISON , O'CONNOR KYLE , NEUMANN JONATHAN
Published: July 2009

Abstract: The Na,K‐ATPase is composed of two subunits, α and β, and each subunit consists of multiple isoforms. In the case of α, four isoforms, α1, α2, α3, and α4 are present in mammalian cells. The distribution of these isoforms is tissue‐ and developmental‐specific, suggesting that they may play specific roles, either during development or coupled to specific physiological processes. In order to understand the functional properties of each of these isoforms, we are using gene targeting, where animals are produced lacking either one copy or both copies of the corresponding gene or have a modified gene. To date, we have produced animals lacking the α1 and α2 isoform genes. Animals lacking both copies of the α1 isoform gene are not viable, while animals lacking both copies of the α2 isoform gene make it to birth, but are either born dead or die very soon after. In the case of animals lacking one copy of the α1 or α2 isoform gene, the animals survive and appear healthy. Heart and EDL muscle from animals lacking one copy of the α2 isoform exhibit an increase in force of contraction, while there is reduced force of contraction in both muscles from animals lacking one copy of the α1 isoform gene. These studies indicate that the α1 and α2 isoforms carry out different physiological roles. The α2 isoform appears to be involved in regulating Ca2+ transients involved in muscle contraction, while the α1 isoform probably plays a more generalized role. While we have not yet knocked out the α3 or α4 isoform genes, studies to date indicate that the α4 isoform is necessary to maintain sperm motility. It is thus possible that the α2, α3, and α4 isoforms are involved in specialized functions of various tissues, helping to explain their tissue‐ and developmental‐specific regulation.
Ion Pump‐Interacting Proteins: Promising New Partners
Authors: PAGEL PHILIPP , ZATTI ALESSANDRA , KIMURA TOHRU , DUFFIELD AMY , CHAUVET VERONIQUE , RAJENDRAN VANATHY , CAPLAN MICHAEL J.
Published: July 2009

Abstract: The sorting and regulation of the Na,K and H,K‐ATPases requires that the pump proteins must associate, at least transiently, with kinases, phosphatases, scaffolding molecules, and components of the cellular trafficking machinery. The identities of these interacting proteins and the nature of their associations with the pump polypeptides have yet to be elucidated. We have begun a series of yeast two‐hybrid screens employing structurally defined segments of pump polypeptides as baits in order to gain insight into the nature and function of these interacting proteins.
Differential Degradation of the Na+/K+‐ATPase Subunits in the Plasma Membrane
Authors: YOSHIMURA SHIGE H. , TAKEYASU KUNIO
Published: July 2009

Abstract: The cell‐surface expression of the Na+/K+‐ATPase is tightly regulated at the ER/Golgi transit level. The assembly of the α‐ and β‐subunits is a prerequisite for the maturation of the enzyme and its exit from the ER. At present, the fate of the functional ATPase, once it reaches the plasma membrane, is obscure, although endocytosis, recycling, and degradation in the lysosome are known to be involved. In this study, we shall demonstrate the differential degradation of the Na+/K+‐ATPase subunits in the plasma membrane: that is, lysosomal degradation of α‐subunits and proteasomal degradation of β‐subunits, and propose the possibility of the subunit dissociation in the plasma membrane.
FXYD Proteins as Regulators of the Na,K‐ATPase in the Kidney
Authors: SWEADNER KATHLEEN J. , ARYSTARKHOVA ELENA , DONNET CLAUDIA , WETZEL RANDALL K.
Published: July 2009

Abstract: The FXYD gene family has seven members in mammals and others in fish. Five of these (FXYD1, FXYD2, FXYD4, FXYD7, and PLMS from shark) have been shown to alter the activity of the Na,K‐ATPase, as described by other papers in this volume. The gene structure of FXYD family members suggests assembly from protein domain modules and gene duplication. The γ subunit is unique in the family for having alternative splice variants in the coding region and can be posttranslationally modified with different final consequences for enzyme properties. The nonoverlapping distribution of γ and CHIF (FXYD4) in kidney helps to explain physiological differences in Na+ affinity among nephron segments. We also detected phospholemman (FXYD1) in kidney. By immunofluorescence, it was found in extraglomerular mesangial cells (EM cells) of the juxtaglomerular apparatus and in the afferent arteriole. Contrary to many reports that only α1 and β1 are expressed in the kidney, we found that α2 and β2 are present, although not in any nephron segment. Both were detected in arterioles, and β2 was found in the EM cells. In contrast, α1, β1, and γ were found in adjacent macula densa. Phospholemman, α2, and β2 are proposed to have distinct roles in regulating the sodium pump in structures involved in tubuloglomerular feedback.
Cell‐Specific Expression of Three Members of the FXYD Family along the Renal Tubule
Authors: FARMAN NICOLETTE , FAY MICHEL , CLUZEAUD FRANÇOISE
Published: July 2009

Abstract: The gamma subunit of Na/K/ATPase is a small membrane protein that shares homologies with other members of the FXYD family, like phospholemman and CHIF (corticosteroid hormone‐induced factor). Both the gamma subunit and CHIF modulate sodium pump properties. The gamma subunit increases the apparent affinity of the pump for ATP and reduces its apparent affinity for sodium. CHIF, in contrast, augments its apparent affinity for sodium. Gamma subunit expression is essentially restricted to the kidney, with two main splice variants, γa and γb, which differ only at their extracellular N‐termini. We have investigated in detail the cell‐specific expression of the two splice variants of gamma within the kidney and compared it to that of CHIF. While both gamma variants affect catalytic properties of the pump (without detectable difference between a and b forms), their localization along the nephron is partially distinct. Both variants are coexpressed in the proximal tubule and in the medullary part of the thick ascending limb of Henle's loop (TAL). In contrast, their expression differs in the downstream tubular segments. Within the renal cortex, the sole gamma a variant was found in macula densa cells and in principal cells of the initial parts of the collecting duct. Gamma b is in the cortical part of the TAL. Outer and inner medullary collecting ducts lack detectable gamma expression. These latter nephron segments express CHIF, and no overlap between gamma and CHIF expression along the nephron was observed. Such distinct cell‐specific expression argues for complementary roles to modulate Na/K/ATPase activity.
Dominant Isolated Renal Magnesium Loss Is Caused by Misrouting of the Na+,K+‐ATPase γ‐Subunit
Authors: MEIJ IWAN C. , KOENDERINK JAN B. , DE JONG JOKE C. , DE PONT JAN JOEP H. H. M. , MONNENS LEO A. H. , VAN DEN HEUVEL LAMBERT P. W. J. , KNOERS NINE V. A. M.
Published: July 2009

Abstract: Hereditary primary hypomagnesemia comprises a clinically and genetically heterogeneous group of disorders in which hypomagnesemia is due to either renal or intestinal Mg2+ wasting. These disorders share the general symptoms of hypomagnesemia, tetany and epileptiformic convulsions, and often include secondary or associated disturbances in calcium excretion. In a large Dutch family with autosomal dominant renal hypomagnesemia, associated with hypocalciuria, we mapped the disease locus to a 5.6‐cM region on chromosome 11q23. After candidate screening, we identified a heterozygous mutation in the FXYD2 gene, encoding the Na+,K+‐ATPase γ‐subunit, cosegregating with the patients of this family, which was not found in 132 control chromosomes. The mutation leads to a G41R substitution, introducing a charged amino acid residue in the predicted transmembrane region of the γ‐subunit protein. Expression studies in insect Sf9 and COS‐1 cells showed that the mutant γ‐subunit protein was incorrectly routed and accumulated in perinuclear structures. In addition to disturbed routing of the G41R mutant, Western blot analysis of Xenopus oocytes expressing wild‐type or mutant γ‐subunit showed mutant γ‐subunit lacking a posttranslational modification. Finally, we investigated two individuals lacking one copy of the FXYD2 gene and found their serum Mg2+ levels to be within the normal range. We conclude that the arrest of mutant γ‐subunit in distinct intracellular structures is associated with aberrant posttranslational processing and that the G41R mutation causes dominant renal hypomagnesemia associated with hypocalciuria through a dominant negative mechanism.
FXYD7, the First Brain‐ and Isoform‐Specific Regulator of Na,K‐ATPase
Authors: CRAMBERT GILLES , BÉGUIN PASCAL , ULDRY MARC , MONNET‐TSCHUDI FLORIANNE , HORISBERGER JEAN‐DANIEL , GARTY HAIM , GEERING KÄTHI
Published: July 2009

Abstract: The FXYD protein family has recently been defined as a result of the search for homologues of the Na,K‐ATPase γ subunit, CHIF, and phospholemman in EST and gene data banks. FXYD7 has been seen to have a role as a brain‐ and isozyme‐specific regulator of Na/K‐ATPase. In this study, the biosynthesis, membrane topology, nature, and role of the processing of FXYD7 are investigated.
The Regulation of SERCA‐Type Pumps by Phospholamban and Sarcolipin
Authors: MacLENNAN DAVID H. , ASAHI MICHIO , TUPLING A. RUSSELL
Published: July 2009

Abstract: Both sarcolipin (SLN) and phospholamban (PLN) lower the apparent affinity of either SERCA1a or SERCA2a for Ca2+. Since SLN and PLN are coexpressed in the heart, interactions among these three proteins were investigated. When SERCA1a or SERCA2a were coexpressed in HEK‐293 cells with both SLN and PLN, superinhibition resulted. The ability of SLN to elevate the content of PLN monomers accounts, at least in part, for the superinhibitory effects of SLN in the presence of PLN. To evaluate the role of SLN in skeletal muscle, SLN cDNA was injected directly into rat soleus muscle and force characteristics were analyzed. Overexpression of SLN resulted in significant reductions in both twitch and tetanic peak force amplitude and maximal rates of contraction and relaxation and increased fatigability with repeated electrical stimulation. Ca2+ uptake in muscle homogenates was impaired, suggesting that overexpression of SLN may reduce the sarcoplasmic reticulum Ca2+ store. SLN and PLN appear to bind to the same regulatory site in SERCA. However, in a ternary complex, PLN occupies the regulatory site and SLN binds to the exposed side of PLN and to SERCA.
Mechanism of Control of Na,K‐ATPase in Principal Cells of the Mammalian Collecting Duct
Authors: FÉRAILLE ERIC , MORDASINI DAVID , GONIN SANDRINE , DESCHÊNES GEORGES , VINCIGUERRA MANLIO , DOUCET ALAIN , VANDEWALLE ALAIN , SUMMA VANESSA , VERREY FRANÇOIS , MARTIN PIERRE‐YVES
Published: July 2009

Abstract: The collecting duct is the site of final Na reabsorption according to Na balance requirements. Using isolated rat cortical collecting ducts (CCD) and mpkCCDcl4 cells, a mouse cortical collecting duct cell line, we have studied the physiological control of Na,K‐ATPase, the key enzyme that energizes Na reabsorption. Aldosterone, a major regulator of Na transport by the collecting duct, stimulates Na,K‐ATPase activity through both recruitment of intracellular pumps and increased total amounts of Na pump subunits. This effect is observed after a lag time of 1 hour and is independent of Na entry through ENaC, but requires de novo transcription and translation. Vasopressin and cAMP, its second messenger, stimulate Na,K‐ATPase activity within minutes through translocation of Na pumps from a brefeldin A‐sensitive intracellular pool to the plasma membrane. Dysregulation of collecting duct Na,K‐ATPase activity is at least in part responsible of the Na retention observed in nephritic syndrome. In this setting, Na,K‐ATPase activity and subunit synthesis are specifically increased in CCD. In conclusion, aldosterone, vasopressin, and intracellular Na control the cell surface expression of Na,K‐ATPase and translocation from intracellular stores is a major mechanism of regulation of Na,K‐ATPase activity in collecting duct principal cells.
Antihypertensive Compounds That Modulate the Na‐K Pump
Authors: FERRARI P. , FERRANDI M. , TORIELLI L. , BARASSI P. , TRIPODI G. , MINOTTI E. , MOLINARI I. , MELLONI P. , BIANCHI G.
Published: July 2009

Abstract:A primary impairment of the kidney sodium excretion has been documented both in hypertensive patients (EH) and genetic animal models (Milan hypertensive rat [MHS]) carrying mutations of the cytoskeletal protein adducin and/or increased plasma levels of endogenous ouabain (EO). Ouabain (OU) itself induces hypertension in rats and both OU and mutated adducin activate the renal Na/K‐ATPase function bothin vivoand in cultured renal cells (NRK). A new antihypertensive agent, PST 2238, able to selectively interact with these alterations has been developed. PST lowers blood pressure (BP) by normalizing the expression and activity of the renal Na‐K pump selectively in those rat models carrying the adducin mutation (MHS) and/or increased EO levels (OS) at oral doses of 0.1‐10 μg/kg. In NRK cells either transfected with mutated adducin or incubated with 10−9M OU, PST normalizes the Na‐K pump activity. Recently, an association between EO and cardiac complications has been observed in both EH and rat models consistent with a prohypertrophic activity of OU. OS rats showed a 10% increase of left ventricle and kidney weights as compared with controls, and PST 2238 (1 μg/kg OS) prevented both ventricle and renal hypertrophy. This effect was associated with the ability of PST to antagonize the OU‐dependent activation of growth‐related genes, in the membrane subdomains of caveolae. In conclusion, PST is a new antihypertensive agent that may prevent cardiovascular complications associated with hypertension through the selective modulation of the Na‐K pump function.
National Surveillance for the Human Ehrlichioses in the United States, 1997–2001, and Proposed Methods for Evaluation of Data Quality
Authors: GARDNER STACY L. , HOLMAN ROBERT C. , KREBS JOHN W. , BERKELMAN RUTH , CHILDS JAMES E.
Published: July 2009

Abstract: This report describes the data accumulated during the first 5 years of national surveillance for the human ehrlichioses in the United States and territories, from its initiation in 1997 through 2001. Reported cases of human monocytic and granulocytic ehrlichiosis (HME and HGE) and cases of ‘other ehrlichiosis’ (OE), where the agent was unspecified, originated from 30 states. As anticipated, most HME cases were from the south‐central and southeastern United States, while HGE was most commonly reported from the northeastern and upper‐Midwestern region. State‐level incident reports of 487 HME, 1,091 HGE, and 11 OE cases were evaluated. The average annual incidences of HME, HGE, and OE per million persons residing in states reporting disease were 0.7, 1.6, and 0.2, respectively. The median ages of HME (53 yr) and HGE cases (51 yr) were consistent with published patient series. Most (> 57%) ehrlichiosis patients were male. The results suggest that national surveillance for the ehrlichioses, although imperfect in coverage, will help define endemic regions and may be useful for monitoring long‐term trends. Although the data appear representative of the demographic profiles established for HME and HGE, rigorous evaluation of the system is required. Methods are proposed for evaluating the quality and representativeness of HME and HGE surveillance data, using well‐established surveillance systems for Rocky Mountain spotted fever and Lyme disease.
Detection of Astrakhan Fever Rickettsia from Ticks in Kosovo
Authors: FOURNIER PIERRE‐EDOUARD , DURAND JEAN‐PAUL , ROLAIN JEAN‐MARC , CAMICAS JEAN‐LOUIS , TOLOU HERVÉ , RAOULT DIDIER
Published: July 2009

Abstract: Astrakhan fever is a summer spotted fever resembling Mediterranean spotted fever, endemic in Astrakhan, a region of Russia located by the Caspian sea. Its agent is a spotted fever group rickettsia, member of the Rickettsia conorii complex, transmitted to humans by Rhipicephalus sanguineus and Rhipicephalus pumilio ticks. In Summer 2001, French United Nations troops in Kosovo collected 2 ticks on asymptomatic soldiers (1 R. sanguineus and 1 Hyalomma marginatum) and 10 ticks on dogs (7 R. sanguineus, 2 Ixodes ricinus, and 1 H. marginatum) in the Morina region. By PCR amplification of both the gltA and ompA genes, we detected a rickettsia in 4 R. sanguineus, i.e., 3 of those collected on dogs and those taken from military personnel. As ticks were preserved in alcohol, culture was not possible. The sequences obtained from these PCR products identified, with a 100% homology, Astrakhan fever rickettsia. None of the other collected tick species was positive. The patient with the positive tick remained asymptomatic. Our study demonstrates, for the first time, the presence of Astrakhan fever rickettsia in ticks outside Russia. We suspect that the area of distribution of this rickettsia could be wider than initially suspected. Moreover, as R. sanguineus ticks bite humans, Astrakhan fever might be a cause of spotted fever in Kosovo.
Prevalence of Rickettsia spp. in Dermacentor marginatus Ticks Removed from Game Pigs (Sus scrofa) in Southern France
Authors: SANOGO Y. O. , DAVOUST B. , PAROLA P. , CAMICAS J. L. , BROUQUI P. , RAOULT D.
Published: July 2009

Abstract: During the months of October and November 2000 a total of 70 Dermacentor marginatus ticks were removed from different game pigs Sus scrofa in southern France and investigated by PCR using primers derived from the citrate synthase (gltA) and the outer membrane protein (OmpB) genes of rickettsiae. Based on sequence analysis of 1,150 bp fragment of gltA, Rickettsia slovaca was identified in 11 ticks (15.7%). These results confirm that Rickettsia slovaca, an emerging pathogen is highly prevalent in Dermacentor marginatus ticks in France. Moreover, a new Rickettsia genotype was detected in one specimen (1.4%). The pathogenic role of this new rickettsia has yet to be demonstrated.
Characterization of Orientia tsutsugamushi Isolated from Wild‐Caught Rodents and Chiggers in Northern Thailand
Authors: KHUNTIRAT B. , LERDTHUSNEE K. , LEEPITAKRAT W. , KENGLUECHA A. , WONGKALASIN K. , MONKANNA T. , MUNGVIRIYA S. , JONES J. W. , COLEMAN R. E.
Published: July 2009

Abstract: We previously reported Orientia tsutsugamushi detection from tissue samples (kidney, liver, spleen, and whole blood) of 12 wild‐caught rodents from Chiangrai Province, northern Thailand. Of the 30 chiggers individually removed from scrub typhus‐infected rodents, 2 were found positive for O. tsutsugamushi. We further characterized the O. tsutsugamushi detected from these rodents and chiggers by RFLP using three different enzyme digestions. All 14 O. tsutsugamushi samples (12 from tissue samples and 2 from chiggers) showed different digestion patterns when compared to those of reference strains (Karp, Kato, and Gilliam). Interestingly, nine RFLP profiles were observed from these 14 samples suggesting the presence of high genetic diversity of O. tsutsugamushi in this area. Furthermore, one sample displayed the same RFLP pattern as that of O. tsutsugamushi mild resistant strain previously isolated from scrub typhus patient in Chiangrai. Of the two samples from positive chiggers, only one was found to have a similar RFLP pattern to that of its host rodent. DNA sequencing of the entire 56 kDa genome of these O. tsutsugamushi samples is in progress.
Q Fever in Human and Livestock Populations in Oman
Authors: SCRIMGEOUR E. M. , AL‐ISMAILY S. I.N. , ROLAIN J. M. , AL‐DHAHRY S. H.S. , EL‐KHATIM H. S. , RAOULT D.
Published: July 2009

Abstract: In 2000, Q fever was documented for the first time in the Sultanate of Oman in two patients, one with chronic pericarditis and the other with acute pneumonia. In 2001, a study of a randomly selected group of 102 adult patients from different provinces in northern Oman, presenting to the University Hospital in Muscat with unrelated conditions (e.g., diabetes mellitus, ischemic heart disease), revealed that 10 (9.8%) were seropositive for previous Coxiella burnetii infection. Examination of sera from a randomly selected group of 54 healthy goats from eight different herds from three different provinces of Oman, obtained by the Veterinary Research Center in Muscat, revealed that 28 (52%) had been infected, and 5 sheep, each from one of four herds, were seropositive for C. burnetii. We suspect that Q fever is widely prevalent in human populations in Oman, and that infection is widespread in goat, and probably sheep and other livestock populations, throughout the country.
Prevalence and Sequence Analyses of Neorickettsia risticii
Authors: CHAE JOON‐SEOK , KIM EUN‐HA , KIM MIN‐SEOK , KIM MIN‐JU , CHO YOON‐HEE , PARK BAE‐KUEN
Published: July 2009

Abstract: The presence of Neorickettsia (Ehrlichia) risticii DNA was confirmed by PCR amplification and sequence analysis from cercaria in snails collected from stream water in Chungcheong and Jeonra provinces. A total of 3,219 snails were tested for trematode cercariae and N. risticii infection. N. risticii 16S rRNA gene fragment was amplified in cercariae from Semisulcospira libertina and Radix auricularia coreana snails by nested PCR. More than four genus cercariae (Schistosomatidae, Microphallidae, Furcocercus, and Xiphidiocercaria) as well as unidentified cercariae were found from Semisulcospira libertina snails. Three species of cercariae (E. cinetorichis, E. hortense, and Fasciola sp.) were found from Radix auricularia coreana snails. The cercariae were present in 429 (13.3%) snails of 3,216 collected at the Chungcheong and Jeonra provinces. The prevalence of N. risticii in these 429 cercariae was 17.9% (77 of 429 cercariae‐infected snails). The amplicons of N. risticii 16S rRNA gene fragment (527 bp) from cercariae DNA had two genotypes (NR‐JA1 and NR‐JA2) with an identity of 96.4% between their nucleotide sequences. However, when compared to the sequence of N. risticii Shasta strain these sequences showed a 94.3% and 96.4% homology, respectively. The comparison of N. risticii 51 kDa major antigen gene sequences (572 bp) from NR‐JA1 and NR‐JA2 were 100% identical to the sequence of the isolates from Juga sp., Caddisfly larvae, Shasta, Juga yrekaensis, and trematode of California. This study reports for the first time the detection of N. risticii from cercariae found in Radix auricularia coreana snail. These data also indicate that N. risticii could be widespread in Korea.
Human Granulocytic Ehrlichiosis in Slovenia
Authors: LOTRIČ‐FURLAN STANKA , PETROVEC MIROSLAV , AVŠIČ‐ŽUPANC TATJANA , STRLE FRANC
Published: July 2009

Abstract: Several reports indicate the presence of infection with Anaplasma phagocytophila in Europe. The first case with confirmed human granulocytic ehrlichiosis was reported from Slovenia in 1997. By 2002, 13 patients have been discovered in a prospective study on the etiology of febrile illnesses occurring within six weeks following a tick bite, conducted at the Department of Infectious Diseases, University Medical Centre, Ljubljana, Slovenia. The diagnosis was established by molecular identification of ehrlichial organisms and/or by seroconversion to A. phagocytophila. None of the patients had detectable morulae on blood smear examination. Clinical characteristics and laboratory findings were similar to those reported from the United States. The severity of the illness was mild to moderately severe. All patients recovered rapidly and without sequelae. HGE should be included in the differential diagnosis of febrile illnesses occurring after a tick bite in Slovenia.
Mediterranean Spotted Fever in Portugal
Authors: DE SOUSA RITA , NÓBREGA SÓNIA DÓRIA , BACELLAR FÁTIMA , TORGAL JORGE
Published: July 2009

Abstract: Mediterranean spotted fever (MSF) is the most important tick‐borne disease in Portugal. It is a notifiable disease and during 1989–2000 the annual incidence rate in Portugal was 9.8/105 inhabitants. Although recognized as a benign acute disease and treated mainly with ambulatory procedures, some cases are severe and fatalities have increased in the last few years. In 1997, MSF mortality became more evident in Beja, a Portuguese southern district, with a case fatality rate of 32.3% in hospitalized patients. Analysis of 55 variables regarding epidemiologic, clinical, laboratory, and therapeutic data of fatal and nonfatal MSF cases were compared to identify risk factors in 105 patients hospitalized in Beja District Hospital, between 1994 and 1998. It was statistically significant that the patients dying in 1997 were younger than those in other years. The risk of dying is statistically significant in those who presented with diabetes, vomiting, dehydration, and uremia. The interval between the onset of symptoms to administration of anti‐rickettsial therapy was the same for all patients. Therapy delay, reported by some authors to be associated with mortality of MSF, was not a risk factor in our study. The patients who died in 1997 died faster than those in other years. The variables studied could not explain the higher mortality rates observed in our study. Although one may speculate that the pathogenic strain of Israeli tick typhus, isolated in 1997, could be responsible for this increase of fatality rate, inherited patient factors might also be strongly associated with mortality.
Serological Hint Suggesting That Parachlamydiaceae Are Agents of Pneumonia in Polytraumatized Intensive Care Patients
Authors: GREUB GILBERT , BOYADJIEV IOANNA , LA SCOLA BERNARD , RAOULT DIDIER , MARTIN CLAUDE
Published: July 2009

Abstract: Parachlamydiaceae are potential emerging pathogens that naturally infect free‐living amoebae. Intensive‐care patients are highly exposed to aerosols and, consequently, exposed to free‐living amoebae and to their intracellular hosts. Thus, we tested intensive‐care patients for antibodies to Parachlamydia and determined if serum reactivity was associated with pneumonia. Patients who underwent intubation and were hospitalized in our intensive‐care unit were eligible. Clinical data and serum were recorded prospectively. Seventy‐three sera taken from 37 intensive‐care patients and 100 sera from healthy blood donors were tested for reactivity against Parachlamydia by immunofluorescence. We detected an antibody titer greater than or equal to 1:100 in 5 out of 37 intensive‐care unit patients (13.5%), including three seroconversions (8.1%). By contrast, no blood donors were reactive against Parachlamydia (P < 0.001). All patients with serological evidence of a recent exposure to Parachlamydia were trauma patients with head injury and aspiration pneumonia. Moreover, both patients with serological evidence of previous exposure to Parachlamydia were admitted for a cerebral hemorrhage. This serological study suggests that Parachlamydiaceae are associated with aspiration pneumonia in trauma patients admitted to intensive‐care units.
An Improved Method for the Purification and Refolding of r56‐kDa Proteins from Gilliam and Kato strains of Orientia tsutsugamushi
Authors: YANG QING , CHING WEI‐MEI , JIANG J.U. , LOUSTEAU LESLIE , RICHARDS ALLEN L.
Published: July 2009

Abstract: The immunodominant 56kDa outer membrane antigens from Orientia tsutsugamushi Kato and Gilliam strains were expressed as inclusion bodies (IBs) in E. coli. The IBs were purified and properly refolded with modifications of a previous procedure used for the production of Karp strain r56 antigen. A mixture of these three r56 proteins exhibited both high sensitivity and specificity for detection of O. tsutsugamushi antibodies by ELISA.
Mechanisms of Humoral Immunity during Ehrlichia chaffeensis Infection
Authors: WINSLOW GARY M. , YAGER ERIC , LI JULIA SHU‐YI
Published: July 2009

Abstract: Our laboratory has been investigating the mechanisms of host defense during Ehrlichia chaffeensis infection in the mouse. Although major roles are clearly played by T cells, we found that antibodies could also control infection in both normal and immunocompromised SCID mice, and could protect the latter from lethal infection. Antibodies are not generally effective during such intracellular infections, so we would like to understand exactly how antibodies can mediate immunity in this model. We have found that much of the humoral immune response is directed at the bacterial outer membrane proteins (OMPs), and that highly effective OMP antibodies (mostly IgG2a) exhibited picomolar affinities and very long binding half‐lives. These antibodies, which could mediate bacterial clearance from tissues as early as 24 hours after administration, require host Fc receptors for their function(s). In contrast, we have failed to find any role for complement or reactive nitrogen intermediates, or for neutrophils, or for NK cells. One possible mechanism is that antibodies or immune complexes trigger microbiocidal activities in infected macrophages that lead to the elimination of bacteria residing inside host macrophages. Alternatively, it is proposed that antibodies opsonize bacteria exposed during intercellular transfer. This notion is supported by studies that have demonstrated the presence of bacteria in the extracellular milieu during infection, and suggests that our understanding of the behavior of the bacterium in the host may be key to our understanding of its susceptibility to antibody‐mediated host defenses.
Differences in Cytokine mRNA Profiles between Naïve and in Vivo‐Primed Ovine PBMC after Exposure to Heat‐Inactivated Coxiella burnetii
Authors: TYCZKA JUDITH , MAASS WIEBKE , JÄGER CORNELIE , MENGE CHRISTIAN , BALJER GEORG
Published: July 2009

Abstract: During human Coxiella burnetii (C. burnetii) infections, high IL‐10 levels favor replication of C. burnetii in monocytes and development of chronic Q fever, whereas IFN‐γ promotes intracellular killing. Sheep are a common source for human C. burnetii infections, but in contrast to man become transiently infected only. In a first approach to unravel the role of cytokines during ovine C. burnetii infections, we investigated by semiquantitative RT‐PCR whether heat‐inactivated C. burnetii affects the transcription of genes coding for IL‐2, IL‐4, IL‐10, and INF‐γin vitro in PBMC from sheep seropositive or seronegative for C. burnetii. By computer‐assisted evaluation of band intensities the transcription rate of the cytokine genes was quantified in relation to transcription in Concanavalin A‐stimulated and nonstimulated controls. Transcription rates in PBMC from seropositive animals after incubation with C. burnetii for 4 hours strongly resembled those found in PBMC from seronegative sheep. However, upon prolonged incubation (24 h) C. burnetii induced an increased IL‐10 transcription in PBMC from 2 of 5 seronegative, but in PBMC from 5 of 5 seropositive animals. The data suggest that natural C. burnetii infections prime the ovine immune system towards a TH2‐like pattern and this action thereby represents the first clue for the involvement of ovine immune cells in the response to C. burnetii infections.
Early Induction and Late Abrogation of Respiratory Burst in A. phagocytophilum‐Infected Neutrophils
Authors: CHOI KYOUNG‐SEONG , DUMLER J. STEPHEN
Published: July 2009

Abstract: Human granulocytic ehrlichiosis is an emerging tick‐borne disease caused by the obligate intracellular pathogen, Anaplasma phagocytophilum. This organism is unique because it survives and propagates in neutrophil vacuoles. During phagocytosis professional phagocytes increase oxygen consumption (respiratory burst) through the activity of NADPH‐oxidase, which generates superoxide anion (O2−) and hydrogen peroxide (H2O2). We assayed the ability of A. phagocytophilum‐infected neutrophils to generate O2− in response to early infection (0, 3, and 5 hours) by using 2′,7′‐dichlorodihydrofluorescein diacetate (DCFH‐DA), a fluorogenic probe commonly used to detect cellular production of reactive oxygen species (ROS). Our flow cytometric analyses showed that cell‐free A. phagocytophilum induced respiratory burst 6.9‐fold greater than that of LPS, an effect still evident to a lesser degree after 3 h, but absent by 5h. A. phagocytophilum initially induces and then represses respiratory burst in neutrophils. The long‐term reduction in respiratory burst activity may be important for survival of A. phagocytophilum and other infectious agents in neutrophils. The effect of this may be to generate a limited functional equivalent of chronic granulomatous disease that predisposes to infections by opportunistic pathogens.