bluuebunny/crossref_metadata_2025_split huggingface dataset:
The ClpPX protease is required for radioresistance and regulates cell division after γ‐irradiation in Deinococcus radiodurans
Authors: Servant Pascale , Jolivet Edmond , Bentchikou Esma , Mennecier Samuel , Bailone Adriana , Sommer Suzanne 
Published: November 2007

SummaryProtein degradation in bacteria is involved in diverse cellular responses to environmental stimuli and in removing potentially toxic damaged proteins or protein aggregates. ATP‐dependent proteases play a key role in these processes. Here, we have individually inactivated all the ATP‐dependent proteases belonging to the Clp or Lon families in Deinococcus radiodurans. The mutants were tested for survival after γ‐irradiation and for sensitivity to the tRNA analogue puromycin in order to assess the impact of each disruption on radioresistance, as well as on proteolysis of misfolded proteins. We found that inactivation of the ClpPX protease significantly decreased cell survival at elevated γ‐irradiation doses, while inactivation of Lon1 and Lon2 proteases reduced resistance to puromycin, suggesting that they play a role in eliminating damaged proteins. Mutants devoid of ClpPX protease displayed altered kinetics of DNA double‐strand break repair and resumed cell division after an exceedingly long lag phase following completion of DNA repair. During this stasis period, most of the ΔclpPX irradiated cells showed decondensed nucleoids and abnormal septa and some cells were devoid of DNA. We propose that the ClpPX protease is involved in the control of proper chromosome segregation and cell division in cells recovering from DNA damage.
Campylobacter sialyltransferase gene polymorphism directs clinical features of Guillain–Barré syndrome
Authors: Yuki Nobuhiro 
Published: November 2007

AbstractProgress has been made in Guillain–Barré syndrome, a post‐infectious autoimmune neuropathy, especially on identifying Campylobacter jejuni genes responsible for the development and determinant of clinical features. C. jejuni strains carrying a sialyltransferase gene (cst‐II), which is essential for the biosynthesis of ganglioside‐like lipo‐oligosaccharides (LOSs), are associated with the development of Guillain–Barré syndrome. The C. jejuni sialyltransferase (Cst‐II) consists of 291 amino acids, and the 51st determines its enzymatic activity. Strains with cst‐II (Thr51) expressed GM1‐like and GD1a‐like LOS, whereas strains with cst‐II (Asn51) expressed GT1a‐like and GD1c‐like LOS. Patients infected with the cst‐II (Thr51) strains had anti‐GM1 or anti‐GD1a IgG antibodies, and showed limb weakness. Patients infected with the cst‐II (Asn51) strains had anti‐GQ1b IgG antibodies, and showed ophthalmoplegia and ataxia. The cst‐II gene is responsible for the development of Guillain–Barré and Fisher syndromes, and the polymorphism (Thr/Asn51) determines which syndrome develops after C. jejuni enteritis.
The function of sphingolipids in the nervous system: lessons learnt from mouse models of specific sphingolipid activator protein deficiencies
Authors: Matsuda Junko , Yoneshige Azusa , Suzuki Kunihiko 
Published: November 2007

AbstractWe have generated specific saposin A and D deficient mouse mutants by the gene targeting technology. Saposin A deficient mice showed the clinical, biochemical and pathological phenotype of a chronic form of globoid cell leukodystrophy (Krabbe disease) establishing that saposin A is essential for in vivo degradation of galactosylceramide. Saposin D deficient mice showed an accumulation of ceramides containing α‐hydroxy fatty acids (HFA/d18:1) in the brain and kidney and showed renal tubular degeneration and cerebellar Purkinje cell loss. Here we review the current information which we have learnt from these mouse models of specific sphingolipid activator protein deficiencies. Collectively, the information provides support for the potential importance of sphingolipids in the function of the nervous system.
Glycosignaling in neural stem cells: involvement of glycoconjugates in signal transduction modulating the neural stem cell fate
Authors: Yu Robert K. , Yanagisawa Makoto 
Published: November 2007

AbstractThe mammalian CNS is organized by a variety of cells, such as neurons and glia, which are generated from neural stem cells (NSCs), undifferentiated neural cells characterized by their high proliferative potential while retaining their capacity for self‐ renewal and multipotency. Various signals from the environment, such as the ‘niche,’ modulate the fate of NSCs in their ability for self‐renewal, proliferation, differentiation, and survival. There is increasing evidence that glycoconjugates, including proteoglycans, glycoproteins, and glycolipids, which are part of the plasma membrane glycocalyx network, are involved in mediation of these signals. In the present review, we discuss the roles of glycoconjugates in regulating the fate of NSCs and in supporting the underlying signal transduction mechanisms.
Experimental approaches to interfere with the polysialylation of the neural cell adhesion molecule in vitro and in vivo§
Authors: Bork Kaya , Gagiannis Daniel , Orthmann André , Weidemann Wenke , Kontou Maria , Reutter Werner , Horstkorte Rüdiger 
Published: November 2007

AbstractSialic acid (Sia) is expressed as terminal sugar in many glycoconjugates and plays an important role during development and regeneration. Addition of homopolymers of Sia (polysialic acid; polySia/PSA) is a unique and highly regulated post‐translational modification of the neural cell adhesion molecule (NCAM). The presence of polySia affects NCAM‐dependent cell adhesion and plays an important role during brain development, neural regeneration, and plastic processes including learning and memory. PolySia‐NCAM is expressed on several neuroendocrine tumors of high malignancy and correlates with poor prognosis. Two closely related enzymes, the polysialyltransferases ST8SiaII and ST8SiaIV, catalyze the biosynthesis of polySia. This review summarizes recent knowledge on Sia biosynthesis and the correlation between Sia biosynthesis and polysialylation of NCAM and report on approaches to modify the degree of polySia on NCAM in vitro and in vivo. First, we describe the inhibition of polysialylation of NCAM in ST8SiaII‐expressing cells using synthetic Sia precursors. Second, we demonstrate that the key enzyme of the Sia biosynthesis (UDP‐N‐acetylglucosamine 2‐epimerase/N‐acetylmannosamine kinase) regulates and limits the synthesis of polySia by controlling the cellular Sia concentration.
Modulation of cell functions by glycosphingolipid metabolic remodeling in the plasma membrane
Authors: Prinetti Alessandro , Chigorno Vanna , Mauri Laura , Loberto Nicoletta , Sonnino Sandro 
Published: November 2007

AbstractThe endoplasmic reticulum and the Golgi apparatus are the subcellular sites for glycosphingolipid neobiosynthesis. In addition to this very well‐established knowledge, it is now emerging that post‐Golgi changes in glycosphingolipid structures occurring at the plasma membrane are an important opportunity to modulate cell glycosphingolipid composition and to affect consequently a number of signaling processes. In fact, it is possible to modify very rapidly the membrane organization by the modulation of plasma membrane‐associated enzymes through external stimuli, thus affecting the membrane environment and the functional properties of plasma membrane proteins involved in cell signaling.The number of enzymes for glycosphingolipid metabolism that have been shown to be associated with the plasma membrane and the information on their features are growing very rapidly, and today some of these enzymes have been deeply characterized. In this review, we focus on the possible role and on the involvement of these plasma membrane‐associated enzymes in modulating cell functions.
The way we view cellular (glyco)sphingolipids
Authors: Hoetzl Sandra , Sprong Hein , Van Meer Gerrit 
Published: November 2007

AbstractMammalian cells synthesize ceramide in the endoplasmic reticulum (ER) and convert this to sphingomyelin and complex glycosphingolipids on the inner, non‐cytosolic surface of Golgi cisternae. From there, these lipids travel towards the outer, non‐cytosolic surface of the plasma membrane and all membranes of the endocytic system, where they are eventually degraded. At the basis of the selective, anterograde traffic out of the Golgi lies the propensity of the sphingolipids to self‐aggregate with cholesterol into microdomains termed ‘lipid rafts’. At the plasma membrane surface these rafts are thought to function as the scaffold for various types of (glyco) signaling domains of different protein and lipid composition that can co‐exist on one and the same cell. In the past decade, various unexpected findings on the sites where sphingolipid‐mediated events occur have thrown a new light on the localization and transport mechanisms of sphingolipids. These findings are largely based on biochemical experiments. Further progress in the field is hampered by a lack of morphological techniques to localize lipids with nanometer resolution. In the present paper, we critically evaluate the published data and discuss techniques and potential improvements.
Focused microarray analysis of glyco‐gene expression in human glioblastomas
Authors: Kroes Roger A. , Dawson Glyn , Moskal Joseph R. 
Published: November 2007

AbstractAltered glycosylation has been linked to cancer cell metastasis and invasivity. We have previously shown that expressing a specific sialyltransferase gene in gliomas inhibited tumor formation, in vivo. In order to identify other “glyco‐gene” targets with therapeutic potential, focused 45‐mer oligonucleotide microarrays were constructed containing all of the cloned human glyco‐genes. Gene expression profiles of normal human brain and malignant gliomas were compared and microarray datasets analyzed using significance analysis of microarrays algorithms. There were 11 genes more highly expressed in gliomas compared to normal brain and 25 genes more highly expressed in normal brain compared to gliomas. Among the most noteworthy were high levels of MAN2A2 and ST6GalNAcV in normal brain tissue and high levels of POFUT1 and CHI3L1 in the gliomas, all changes corroborated by qRT‐PCR. Historically, identification of changes in tumor‐associated glycoconjugate expression was obtained by measuring individual enzyme activities or structural changes of specific molecules. With microarray technology, it is possible to measure all of genes associated with glycoconjugate biosynthesis and degradation simultaneously. Our data demonstrate that there are many significant and novel differences in glyco‐gene expression that represent potential targets for the development of therapeutics for the treatment of brain tumors.
Hepatitis B Virus e Antigen Loss during Adefovir Dipivoxil Therapy Is Associated with Enhanced Virus-Specific CD4+T-Cell Reactivity
Authors: Cooksley Helen , Chokshi Shilpa , Maayan Yafit , Wedemeyer Heiner , Andreone Pietro , Gilson Richard , Warnes Thomas , Paganin Simona , Zoulim Fabien , Frederick David , Neumann Avidan U. , Brosgart Carol L. , Naoumov Nikolai V. 
Published: November 2007

ABSTRACTWeak T-cell reactivity to hepatitis B virus (HBV) is thought to be the dominant cause for chronic HBV infection. Treatment with adefovir dipivoxil (ADV) increases the rate of HBV e antigen (HBeAg) loss; however, the immune mechanisms associated with this treatment response are not understood. Serial analysis of HBV-specific CD4+T-cell reactivity was performed during 48 weeks of therapy with ADV and correlated with treatment outcome for 19 HBeAg-positive patients receiving ADV (n= 13) or the placebo (n= 6). We tested T-cell reactivity to HBV at seven protocol time points by proliferation, cytokine production, and enzyme-linked immunospot assays. A panel of serum cytokines was quantitated by cytokine bead array. ADV-treated patients showed increased CD4+T-cell responses to HBV and lower serum levels of cytokines compared to those of placebo-treated patients. Enhanced CD4+T-cell reactivity to HBV, which peaked at treatment week 16, was confined to a subgroup of ADV-treated patients who achieved greater viral suppression (5.3 ± 0.3 log10copies/ml [mean ± standard error of the mean {SEM}] serum HBV DNA reduction from baseline) and HBeAg loss, but not to ADV-treated patients with moderate (3.4 ± 0.2 log10copies/ml [mean ± SEM]) viremia reduction who remained HBeAg positive or to patients receiving the placebo. In conclusion, T-cell reactivity to HBV increases in a proportion of ADV-treated patients and is associated with greater suppression of HBV replication and HBeAg loss.
Exonuclease Removal of Dideoxycytidine (Zalcitabine) by the Human Mitochondrial DNA Polymerase
Authors: Hanes Jeremiah W. , Johnson Kenneth A. 
Published: November 2007

ABSTRACT
The toxicity of nucleoside analogs used for the treatment of human immunodeficiency virus infection is due primarily to the inhibition of replication of the mitochondrial genome by the human mitochondrial DNA polymerase (Pol γ). The severity of clinically observed toxicity correlates with the kinetics of incorporation versus excision of each analog as quantified by a toxicity index, spanning over six orders of magnitude. Here we show that the rate of excision of dideoxycytidine (zalcitabine; ddC) was reduced fourfold (giving a half-life of ∼2.4 h) by the addition of a physiological concentration of deoxynucleoside triphosphates (dNTPs) due to the formation of a tight ternary enzyme-DNA-dNTP complex at the polymerase site. In addition, we provide a more accurate measurement of the rate of excision and show that the low rate of removal of ddCMP results from both the unfavorable transfer of the primer strand from the polymerase to the exonuclease site and the inefficient binding and/or hydrolysis at the exonuclease site. The analogs ddC, stavudine, and ddATP (a metabolite of didanosine) each bind more tightly at the polymerase site during incorporation than normal nucleotides, and this tight binding contributes to slower excision by the proofreading exonuclease, leading to increased toxicity toward mitochondrial DNA.
The NleE/OspZ Family of Effector Proteins Is Required for Polymorphonuclear Transepithelial Migration, a Characteristic Shared by EnteropathogenicEscherichia coliandShigella flexneriInfections
Authors: Zurawski Daniel V. , Mumy Karen L. , Badea Luminita , Prentice Julia A. , Hartland Elizabeth L. , McCormick Beth A. , Maurelli Anthony T. 
Published: November 2007

ABSTRACTEnteropathogenicEscherichia coli(EPEC) andShigella flexneriare human host-specific pathogens that infect intestinal epithelial cells. However, each bacterial species employs a different infection strategy within this environmental niche. EPEC attaches to the apical surface of small intestine enterocytes, causing microvillus effacement and rearrangement of the host cell cytoskeleton beneath adherent bacteria. In contrast,S. flexneriinvades the large intestine epithelium at the basolateral membrane, replicates, and spreads cell to cell. Both EPEC andS. flexnerirely on type three secretion systems (T3SS) to secrete effectors into host cells, and both pathogens recruit polymorphonuclear leukocytes (PMNs) from the submucosa to the lumen of the intestine. In this report, we compared the virulence functions of the EPEC T3SS effector NleE and the homologousShigellaprotein Orf212. We discovered that Orf212 was secreted by theS. flexneriT3SS and renamed this protein OspZ. Infection of polarized T84 intestinal epithelial cells with anospZdeletion mutant ofS. flexneriresulted in reduced PMN transepithelial migration compared to infection by the wild type. AnnleEdeletion mutant of EPEC showed a similar reduction of PMN migration. The ability to induce PMN migration was restored in both mutants when eitherospZornleEwas expressed from a plasmid. An infection of T84 cells with the ΔospZmutant resulted in reduced extracellular signal-related kinase phosphorylation and NF-κB activation compared to infection with the wild type. Therefore, we conclude that OspZ and NleE have similar roles in the upstream induction of host signaling pathways required for PMN transepithelial migration inShigellaand EPEC infections.
Pneumocystis carinii
Exhibits a Conserved Meiotic Control Pathway
Authors: Burgess Joshua W. , Kottom Theodore J. , Limper Andrew H. 
Published: November 2007

ABSTRACT

Pneumocystis carinii
is an opportunistic fungus causing severe pneumonia in immune-compromised hosts. Recent evidence suggests that
Pneumocystis
exists as separate sex types, though definitive evidence is currently lacking. These studies were undertaken to determine whether
Pneumocystis
maintains functional meiotic control molecules, which are required for sexual life stages in eukaryotes. Using the
Pneumocystis carinii
Genome Project database, two partial sequences for meiotic control molecules were detected, namely, PC
Ran1
, a presumptive meiotic control kinase, and PC
Mei2
, a homologue to a primary activator of meiosis in
Schizosaccharomyces pombe
. Rapid amplification of cDNA ends was employed to obtain the full open reading frames and to further investigate the functions of these proteins. These presumptive meiotic control molecules were most homologous to molecules present in
S. pombe
(52% identical and 67% homologous for PC
Ran1
and 75% identical and 88% homologous for PC
Mei2
by BLAST analysis). Heterologous expression of these
Pneumocystis
meiotic genes in corresponding temperature-sensitive and knockout strains of
S. pombe
, respectively, further verified the functions of the PCRan1 and PCMei2 proteins. These proteins were further shown to control downstream components of the meiotic pathway in
S. pombe
. Lastly, in vitro kinase assays were used to determine that PCRan1p phosphorylates PCMei2p. These experiments represent the first characterization of any proteins in
P. carinii
involved in meiosis and indicate the presence of a conserved meiotic pathway in
Pneumocystis
. Elucidation of this pathway will be essential in gaining a greater understanding of this important opportunistic fungal pathogen.
Toll-Like Receptor 9-Dependent Macrophage Activation byEntamoeba histolyticaDNA
Authors: Ivory Catherine P. A. , Prystajecky Michael , Jobin Christian , Chadee Kris 
Published: November 2007

ABSTRACTActivation of the innate immune system by bacterial DNA and DNA of other invertebrates represents a pathogen recognition mechanism. In this study we investigated macrophage responses to DNA from the intestinal protozoan parasiteEntamoeba histolytica.E. histolyticagenomic DNA was purified from log-phase trophozoites and tested with the mouse macrophage cell line RAW 264.7. RAW cells treated withE. histolyticaDNA demonstrated an increase in levels of tumor necrosis factor alpha (TNF-α) mRNA and protein production. TNF-α production was blocked by pretreatment with chloroquine or monensin. In fact, an NF-κB luciferase reporter assay in HEK cells transfected with human TLR9 demonstrated thatE. histolyticaDNA signaled through Toll-like receptor 9 (TLR9) in a manner similar to that seen with CpG-ODN. Immunofluorescence assays confirmed NF-κB activation in RAW cells, as seen by nuclear translocation of the p65 subunit. Western blot analysis demonstrated mitogen-activated protein kinase activation byE. histolyticaDNA.E. histolyticaDNA effects were abolished in MYD88−/−mouse-derived macrophages. In the context of disease, immunization withE. histolyticaDNA protected gerbils from anE. histolyticachallenge infection. Taken together, these results demonstrate thatE. histolyticaDNA is recognized by TLR9 to activate macrophages and may provide an innate defense mechanism characterized by the induction of the inflammatory mediator TNF-α.
Glutamine protects against increases in blood ammonia in football players in an exercise intensity-dependent way
Authors: Bassini-Cameron A , Monteiro A , Gomes A , Werneck-de-Castro J P S , Cameron L 
Published: November 2007

Objective:High-intensity and prolonged exercise significantly enhances the levels of plasma ammonia, a metabolite with toxic effects on the central nervous system. The main purpose of the present study was to evaluate the metabolic response of athletes to glutamine (Gln) and alanine (Ala) supplementation, since these amino acids have a significant influence on both anaplerosis and gluconeogenesis.Methods:Professional football players were assigned to groups receiving either Gln or Ala supplementation (100 mg kg−1body weight); this supplementation was either short-term or long-term and was given immediately before exercise. The players were evaluated using two exercise protocols, one with intervals (n = 18) and the other with continuous intensity (n = 12).Results:Both types of exercises increased ammonia, urate, urea and creatinine in blood. Chronic Gln supplementation partially protected against hyperammonemia after a football match (intermittent exercise: Gln −140 (SEM 13)% vs Ala −240 (SEM 37)%) and after continuous exercise at 80% of the maximum heart rate (Gln −481 (SEM 44)% vs placebo −778 (SEM 99)%). Urate increased by 10−20% in all groups, independently of supplementation. Glutamine once a day supplementation induced a greater elevation in urate as compared to alanine at the end of the game; however, long-term supplementation provoked a lesser increment in urate. Exercise induced similar increases in creatinine as compared to their respective controls in either acute or chronic glutamine administration.Conclusions:Taken together, the results suggest that chronically supplemented Gln protects against exercise-induced hyperammonemia depending on exercise intensity and supplementation duration.
Ultrastructure of teliospores and promycelium and basidiospore formation in the four-spored form of Gymnoconia nitens, one of the causes of orange rust of Rubus
Authors: Mims Charles W. , Richardson Elizabeth A. , Taylor Josephine 
Published: November 2007

Orange rust of Rubus is an interesting disease because of the fact that it can be caused by three different rust fungi that produce virtually identical symptoms. One is Gymnoconia peckiana (Howe in Peck) Trotter, which is a demicyclic species, while the other two are endocyclic forms historically referred to as Gymnoconia nitens (Schwein.) Kern & H.W. Thurston. Although the spores produced on infected Rubus leaves by these latter two forms are morphologically identical to the aeciospores of G. peckiana, they actually function as teliospores. However, the teliospores of one of the forms gives rise to two-celled promycelia that bear only two basidiospores, while teliospores of the other produce four-celled promycelia bearing four basidiospores. Here, we examined the teliospores of the four-spored form along with the sequence of events that lead to basidiospore development. Developing and mature teliospores were binucleate, and we saw no evidence that karyogamy occurred in these spores. Upon germination, both spore nuclei migrated into the promycelium and underwent mitosis to form a total of four nuclei. Four transverse septa then developed, creating four uninucleate cells. A tapered sterigma arose from each cell and gave rise to a basidiospore. These findings indicate that the basidiospores of the four-spored form of G. nitens were formed in an asexual fashion.