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961.
Ivan F.N. Hung Pierre Chan Sally Leung Fion S.Y. Chan Axel Hsu David But Wai Kay Seto Siu Yin Wong Chi Kuen Chan Qing Gu Teresa S.M. Tong Ting Kin Cheung Kent Man Chu Benjamin C.Y. Wong 《Helicobacter》2009,14(6):505-511
Background: Recent studies have suggested the eradication rate for Helicobacter pylori infection with standard amoxycillin–clarithromycin‐containing triple therapy as first‐line treatment have fallen below 80%. Levofloxacin‐containing triple therapy was proposed as an alternative. The aim of this study is to compare the efficacy and tolerability of the standard 7‐day clarithromycin‐containing triple therapy against the 7‐day levofloxacin‐containing triple therapy, and to assess whether the classical triple therapy is still valid as empirical first‐line treatment for H. pylori infection in Hong Kong. Methods: Three hundred consecutive H. pylori‐positive patients were randomized to receive either 1 week of EAL (esomeprazole 20 mg b.d., amoxycillin 1 g b.d., and levofloxacin 500 mg daily) or EAC (esomeprazole 20 mg b.d., amoxycillin 1 g b.d., and clarithromycin 500 mg b.d.). H. pylori status was rechecked by 13C‐urea breath test 6 weeks after treatment. Patients who failed either of the first‐line eradication therapy were invited to undergo H. pylori susceptibility testing. Results: H. pylori eradication was achieved in 128 of 150 (85.3%) patients in EAL and 139 of 150 (92.7%) patients in EAC groups, respectively (p = .043), for both intention‐to‐treat and per‐protocol analysis. More patients in the clarithromycin‐ than the levofloxacin‐containing therapy group developed side effects from the medication (21.3% vs 13.3%, p = .060). Nine patients (six from the EAL group and three from the EAC group) who failed their corresponding eradication therapy returned for susceptibility testing. All nine isolates were highly resistant to levofloxacin (minimum inhibitory concentration or MIC > 32 μg/mL), whereas only two of the six isolates from the EAL group were resistant to clarithromycin (MIC > 0.5 μg/mL). Conclusions: The standard 7‐day clarithromycin‐containing triple therapy is still valid as the most effective empirical first‐line eradication therapy for H. pylori infection in Hong Kong, as prevalence of primary resistance of H. pylori to amoxycillin and clarithromycin remains low. Patients who failed their empirical first‐line eradication therapy should undergo H. pylori susceptibility testing to guide further treatment. 相似文献
962.
Ana M. Mateus Nicole Gorfinkiel Alfonso Martinez Arias 《Seminars in cell & developmental biology》2009,20(7):877-884
Morphogenesis is the process whereby cells assemble into tissues and organs. Recent studies of this process have revealed heterogeneity of individual cell behaviours that contrasts with the deterministic activity of tissues as a whole. Here we review these observations and suggest that fluctuations and heterogeneities are a central substrate for morphogenesis and that there might exist mechanisms dedicated to the averaging of these fluctuations to ensure robust and reproducible behaviours at the tissue level. 相似文献
963.
Atanas V. Demirev Ji Seon Lee Bhishma R. Sedai Ivan G. Ivanov Doo Hyun Nam 《Journal of microbiology (Seoul, Korea)》2009,47(4):473-478
The gene locus for acetyl-CoA carboxylase (ACC) involved in the primary metabolism was identified from the genomic library
of Streptomyces toxytricini which produces a lipase inhibitor lipstatin. The 7.4 kb cloned gene was comprised of 5 ORFs including accD1, accA1, hmgL, fadST1, and stsF. In order to confirm the biochemical characteristics of AccA1, the gene was overexpressed in Escherichia coli cells, and the recombinant protein was purified through Ni2+ affinity chromatography. Because most of the expressed AccAl was biotinylated by host E. coli BirA in the presence of D-biotin, the non-biotinylated apo-AccA1 was purified after gene induction without D-biotin, followed by exclusion of holo-AccA1 using streptavidin beads. The separated apo-AccA1 was post-translationally biotinylated
by S. toxytricini biotin apo-protein ligase (BPL) in a time- and enzyme-dependent manner. This result supports that this gene cluster of S. toxytricini encodes the functional ACC enzyme subunits to be biotinylated. 相似文献
964.
Nathaly Lhermitte-Vallarino Michela Barbuto Kerstin Junker Renaud Boistel Ivan Ineich Samuel Wanji Odile Bain 《Parasitology international》2009,58(4):375-383
Rhabdias rhampholeonis n. sp. from Rhampholeon (Rh.) spectrum, Cameroon, and Rhabdias mariauxi n. sp. from Rieppeleon brevicaudatus, Tanzania, are the first lung worms from leaf chameleons. The new species are similar to the majority of species parasitic in chamaeleonids by having a long (≥10 mm) and thick body (≥500 µm), long oesophagus (≥800 µm), wide buccal capsule (≥40 µm) and low buccal ratio (<0.5). They most closely resemble Rhabdias chamaeleonis and Rhabdias cristati parasitic in Trioceros spp. from East Africa and Cameroon, respectively. Main distinctive characters are a buccal capsule composed of two segments and the head shape. The dorso-ventrally flattened buccal capsule of R. mariauxi n. sp. is unique in Rhabdias parasitising Chamaeleonidae. Sequences of the 12S rDNA and mitochondrial cytochrome c oxidase subunit 1 (coxI) genes were obtained and compared to those of Rhabdias okuensis, the only sequences published for chamaeleonid lung worms. The smallest nucleotide interspecific distances were found between R. mariauxi n. sp. and the former species of Trioceros from Cameroon. Hermaphroditism in females in the lungs, and R. mariauxi n. sp. free-living stages are like in other species from Chamaeleonidae, but the number of infective larvae produced per free-living female (one or two) was not fixed. 相似文献
965.
Oksana Breus Ganna Panasyuk Ivan T. Gout Valeriy Filonenko Ivan Nemazanyy 《Biochemical and biophysical research communications》2009,385(4):581-585
The complex interplay between cellular signaling and metabolism in eukaryotic cells just start to emerge. Coenzyme A (CoA) and its derivatives play a key role in cell metabolism and also participate in regulatory processes. CoA Synthase (CoASy) is a mitochondria-associated enzyme which mediates two final stages of de novo CoA biosynthesis. Here, we report that CoASy is involved in signaling events in the cell and forms a functional complex with p85αPI3K in vivo. Importantly, observed interaction of endogenous CoASy and p85αPI3K is regulated in a growth factor dependent manner. Surprisingly, both catalytic p110α and regulatory p85α subunits of PI3K were detected in mitochondrial fraction where mitochondria-localized p85αPI3K was found in complex with CoASy. Unexpectedly, significant changes of PI3K signaling pathway activity were observed in experiments with siRNA-mediated CoASy knockdown pointing on the role of CoA biosynthetic pathway in signal transduction. 相似文献
966.
Nasidze I Quinque D Rahmani M Alemohamad SA Asadova P Zhukova O Stoneking M 《American journal of physical anthropology》2009,138(1):82-89
The Northern Talysh from Azerbaijan and the Southern Talysh from Iran self‐identify as one ethnic group and speak a Northwestern Iranian language. However, the Northern and Southern Talysh dialects are so different that they may actually be separate languages. Does this linguistic differentiation reflect internal change due to isolation, or could contact‐induced change have played a role? We analyzed mtDNA HVI sequences, 11 Y‐chromosome bi‐allelic markers, and 9 Y‐STR loci in Northern and Southern Talysh and compared them with their neighboring groups. The mtDNA data show a close relatedness of both groups with each other and with neighboring groups, whereas the Northern Talysh Y‐chromosome variation differs from that of neighboring groups, probably as a result of genetic drift. This genetic drift most likely reflects a founder event in the male gene pool of Northern Talysh: either fewer males than females migrated to Azerbaijan, or there was a higher degree of relatedness among the male migrants. Since we find no evidence of substantial genetic contact between either Northern or Southern Talysh and neighboring groups, we conclude that internal change, rather than contact‐induced change, most likely explains the linguistic differentiation between Northern and Southern Talysh. Am J Phys Anthropol, 2009. © 2008 Wiley‐Liss, Inc. 相似文献
967.
Despite new information concerning functional morphology of spleen, there are still some inaccuracies mostly regarding the
spleen blood circulation. Billroth’s (splenic) cords are formed from three-dimensional network of fibroblastic reticular cells
located among branched sinuses. Results from our study using scanning electron microscopy confirm an intimate contact between
adjacent reticular cells and erythrocytes. Arterial terminals can be observed in the Billroth’s cords. The wall of sinuses
reminds a sieve and it is lined with a special type of endothelium. In electron microscope, endothelial cells look like rods
oriented parallel to the longitudinal axis of sinuses. Based on our observations fibroblastic reticular cells change to fixed
phagocytes under no circumstances, hence they do not participate in phagocytosis. They may have a recognition function for
cells circulating around them. According to our opinion, the open and the closed blood circulation are present in the human
spleen simultaneously. Blood flowing in the closed circulation can help “absorption” of extra-vascular liquid and the blood
elements into the vascular lumen. Due to sporadic occurrence of smooth muscle cells in the capsule and trabeculae, we assume
that human spleen is not a blood reservoir, unlike the spleen in some other animals. 相似文献
968.
The main goal of this study was to evaluate the dynamics of sarcomeres during isometric activation of skeletal muscle myofibrils. Rabbit psoas myofibrils (n=14) were attached between a pair of cantilevers for force measurements at one side and a rigid glass needle at the other side, and their images were used for measurements of individual sarcomere lengths (SL) during contractions. Myofibrils were set at average SL between 2.13 and 3.06 μm, and were activated and held isometric for 20–35 s during which SL and force were continuously measured. SL dispersion increased from the rest state to activation, but it remained mostly constant during the activation period. Even with the length non-uniformity developed during myofibril activation, most sarcomeres stabilized their length changes during the isometric contraction. As a result, sarcomeres contracted at different degrees of filament overlap while producing similar forces. When the myofibrils were separated in two groups that produced force at averaged short (≤2.5 μm) or long (≥2.5 μm) SL, the initial non-uniformity was greater in long lengths, but changes observed in sarcomeres during the activation period were similar, suggesting that sarcomere stability is not length-dependent. 相似文献
969.
Sabino Pacheco Isabel G��mez Ivan Arenas Gloria Saab-Rincon Claudia Rodr��guez-Almaz��n Sarjeet S. Gill Alejandra Bravo Mario Sober��n 《The Journal of biological chemistry》2009,284(47):32750-32757
Bacillus thuringiensis Cry toxins are used worldwide as insecticides in agriculture, in forestry, and in the control of disease transmission vectors. In the lepidopteran Manduca sexta, cadherin (Bt-R1) and aminopeptidase-N (APN) function as Cry1A toxin receptors. The interaction with Bt-R1 promotes cleavage of the amino-terminal end, including helix α-1 and formation of prepore oligomer that binds to APN, leading to membrane insertion and pore formation. Loops of domain II of Cry1Ab toxin are involved in receptor interaction. Here we show that Cry1Ab mutants located in domain II loop 3 are affected in binding to both receptors and toxicity against Manduca sexta larvae. Interaction with both receptors depends on the oligomeric state of the toxin. Monomers of loop 3 mutants were affected in binding to APN and to a cadherin fragment corresponding to cadherin repeat 12 but not with a fragment comprising cadherin repeats 7–12. In contrast, the oligomers of loop 3 mutants were affected in binding to both Bt-R1 fragments but not to APN. Toxicity assays showed that either monomeric or oligomeric structures of Cry1Ab loop 3 mutations were severely affected in insecticidal activity. These data suggest that loop 3 is differentially involved in the binding with both receptor molecules, depending on the oligomeric state of the toxin and also that possibly a “ping pong” binding mechanism with both receptors is involved in toxin action. 相似文献
970.
Adrien W. Schmid Diego Chiappe V��r��ne Pignat Valerie Grimminger Ivan Hang Marc Moniatte Hilal A. Lashuel 《The Journal of biological chemistry》2009,284(19):13128-13142
Tissue transglutaminase (tTG) has been implicated in the pathogenesis of
Parkinson disease (PD). However, exactly how tTG modulates the structural and
functional properties of α-synuclein (α-syn) and contributes to
the pathogenesis of PD remains unknown. Using site-directed mutagenesis
combined with detailed biophysical and mass spectrometry analyses, we sought
to identify the exact residues involved in tTG-catalyzed cross-linking of
wild-type α-syn and α-syn mutants associated with PD. To better
understand the structural consequences of each cross-linking reaction, we
determined the effect of tTG-catalyzed cross-linking on the oligomerization,
fibrillization, and membrane binding of α-syn in vitro. Our
findings show that tTG-catalyzed cross-linking of monomeric α-syn
involves multiple cross-links (specifically 2-3). We subjected tTG-catalyzed
cross-linked monomeric α-syn composed of either wild-type or Gln →
Asn mutants to sequential proteolysis by multiple enzymes and peptide mapping
by mass spectrometry. Using this approach, we identified the glutamine and
lysine residues involved in tTG-catalyzed intramolecular cross-linking of
α-syn. These studies demonstrate for the first time that
Gln79 and Gln109 serve as the primary tTG reactive
sites. Mutating both residues to asparagine abolishes tTG-catalyzed
cross-linking of α-syn and tTG-induced inhibition of α-syn
fibrillization in vitro. To further elucidate the sequence and
structural basis underlying these effects, we identified the lysine residues
that form isopeptide bonds with Gln79 and Gln109. This
study provides mechanistic insight into the sequence and structural basis of
the inhibitory effects of tTG on α-syn fibrillogenesis in vivo,
and it sheds light on the potential role of tTG cross-linking on modulating
the physiological and pathogenic properties of α-syn.Parkinson disease
(PD)2 is a progressive
movement disorder that is caused by the loss of dopaminergic neurons in the
substantia nigra, the part of the brain responsible for controlling movement.
Clinically, PD is manifested in symptoms that include tremors, rigidity, and
difficulty in initiating movement (bradykinesia). Pathologically, PD is
characterized by the presence of intraneuronal, cytoplasmic inclusions known
as Lewy bodies (LB), which are composed primarily of the protein
“α-synuclein” (α-syn)
(1) and are seen in the
post-mortem brains of PD patients with the sporadic or familial forms of the
disease (2). α-Syn is a
presynaptic protein of 140 residues with a “natively” unfolded
structure (3). Three missense
point mutations in α-syn (A30P, E46K, and A53T) are associated with the
early-onset, dominant, inherited form of PD
(4,
5). Moreover, duplication or
triplication of the α-syn gene has been linked to the familial
form of PD, suggesting that an increase in α-syn expression is
sufficient to cause PD. Together, these findings suggest that α-syn
plays a central role in the pathogenesis of PD.The molecular and cellular determinants that govern α-syn
oligomerization and fibrillogenesis in vivo remain poorly understood.
In vitro aggregation studies have shown that the mutations associated
with PD (A30P, E46K, and A53T) accelerate α-syn oligomerization, but
only E46K and A53T α-syn show higher propensity to fibrillize than
wild-type (WT) α-syn
(6-8).
This suggests that oligomerization, rather than fibrillization, is linked to
early-onset familial PD (9).
Our understanding of the molecular composition and biochemical state of
α-syn in LBs has provided important clues about protein-protein
interactions and post-translational modifications that may play a role in
modulating oligomerization, fibrillogenesis, and LB formation of the protein.
In addition to ubiquitination
(10), phosphorylation
(11,
12), nitration
(13,
14), and C-terminal truncation
(15,
16), analysis of post-mortem
brain tissues from PD and Lewy bodies in dementia patients has confirmed the
colocalization of tissue transglutaminase (tTG)-catalyzed cross-linked
α-syn monomers and higher molecular aggregates in LBs within
dopaminergic neurons (17,
18). Tissue transglutaminase
catalyzes a calcium-dependent transamidating reaction involving glutamine and
lysine residues, which results in the formation of a covalent cross-link via
ε-(γ-glutamyl) lysine bonds
(Fig. 2F). To date,
seven different isoforms of tTGs have been reported, of which only tTG2 seems
to be expressed in the human brain
(19), whereas tTG1 and tTG3
are more abundantly found in stratified squamous epithelia
(20). Subsequent
immuno-histochemical, colocalization, and immunoprecipitation studies have
shown that the levels of tTG and cross-linked α-syn species are
increased in the substantia nigra of PD brains
(17). These findings, combined
with the known role of tTG in cross-linking and stabilizing bimolecular
assemblies, led to the hypothesis that tTG plays an important role in the
initiation and propagation of α-syn fibril formation and that it
contributes to fibril stability in LBs. This hypothesis was initially
supported by in vitro studies demonstrating that tTG catalyzes the
polymerization of the α-syn-derived non-amyloid component (NAC) peptide
via intermolecular covalent cross-linking of residues Gln79 and
Lys80 (21) and by
other studies suggesting that tTG promotes the fibrillization of amyloidogenic
proteins implicated in the pathogenesis of other neurodegenerative diseases
such as Alzheimer disease, supranuclear palsy, Huntington disease, and other
polyglutamine diseases
(22-24).
However, recent in vitro studies with full-length α-syn have
shown that tTG catalyzes intramolecular cross-linking of monomeric α-syn
and inhibits, rather than promotes, its fibrillization in vitro
(25,
26). The structural basis of
this inhibitory effect and the exact residues involved in tTG-mediated
cross-linking of α-syn, as well as structural and functional
consequences of these modifications, remain poorly understood.Open in a separate windowFIGURE 2.tTG-catalyzed cross-linking of α-syn involves one to three
intramolecular cross-links. A-C, MALDI-TOF/TOF analysis of native
(—) and cross-linked (- - -) α-syn, showing that most
tTG-catalyzed cross-linking products of WT or disease-associated mutant forms
of α-syn are intramolecularly linked (predominant peak with two
cross-links), and up to three intramolecular cross-links can occur (left
shoulder). The abbreviations M and m/cl are
used to designate native and cross-linked α-synuclein, respectively.
D and E, kinetic analysis of α-syn (A30P)
cross-linking monitored by MALDI-TOF and SDS-PAGE. F, schematic
depiction of the tTG-catalyzed chemical reaction (isodipeptide formation)
between glutamine and lysine residues.In this study, we have identified the primary glutamine and lysine residues
involved in tTG-catalyzed, intramolecularly cross-linked monomeric α-syn
and investigated how cross-linking these residues affects the oligomerization,
fibrillization, and membrane binding of α-syn in vitro. Using
single-site mutagenesis and mass spectrometry applied to exhaustive
proteolytic digests of native and cross-linked monomeric α-syn, we
identified Gln109 and Gln79 as the major tTG substrates.
We demonstrate that the altered electrophoretic mobility of the
intramolecularly cross-linked α-syn in SDS-PAGE occurs as a result of
tTG-catalyzed cross-linking of Gln109 to lysine residues in the N
terminus of α-syn, which leads to the formation of more compact
monomers. Consistent with previous studies, we show that intramolecularly
cross-linked α-syn forms off-pathway oligomers that are distinct from
those formed by the wild-type protein and that do not convert to fibrils
within the time scale of our experiments (3-5 days). We also show that
membrane-bound α-syn is a substrate of tTG and that intramolecular
cross-linking does not interfere with the ability of monomeric α-syn to
adopt an α-helical conformation upon binding to synthetic membranes.
These studies provide novel mechanistic insight into the sequence and
structural basis of events that allow tTG to inhibit α-syn
fibrillogenesis, and they shed light on the potential role of tTG-catalyzed
cross-linking in modulating the physiological and pathogenic properties of
α-syn. 相似文献