Biomedical subjects

Lei Wang

Publications and source records attributed to Lei Wang.

At least 253 records · Page 14Linked to original sources

PubMed2005

Characterization and expression of AmphiARF gene encoding a new member of ARF family from amphioxus Branchiostoma belcheri tsingtauense.

The cDNA AmphiARF, encoding a novel member of ARF family was for the first time identified from the gut cDNA library of amphioxus Branchiostoma becheri tsingtauense. The deduced amino acid sequence includes the motifs involved in GTP binding (DVGG, NKQD and SAK) and hydrolysis (GXDXXGK), and a glycine at position 2 for N-terminal myristoylation, which are all characteristic of ARFs. However, it has a 46 amino acid C-terminal extension (positions 183-227), which was not found in any ARF family previously described including ARF-like proteins. This suggests that AmphiARF is a new member of ARF family, which was also supported by the phylogenetic analysis. It is highly likely that the extended C-terminal of AmphiARF is a novel addition occurring after cephalochordate/vertebrate split. Northern blotting analysis revealed that AmphiARF transcript was present in all tissues examined, consistent with the involvement of ARFs in the fundamental role like vesicular trafficking of proteins.

ADP-Ribosylation Factors↗

PubMed2005

A molecular-capsular-type prediction system for 90 Streptococcus pneumoniae serotypes using partial cpsA-cpsB sequencing and wzy- or wzx-specific PCR.

In a previous study, a molecular capsular type (MCT) prediction system for 51 Streptococcus pneumoniae serotypes was developed based on a combination of partial cpsA-cpsB sequencing and serotype(s)/group(s)-specific PCR. In this study, another 169 S. pneumoniae isolates were added to the existing database of 427 isolates, including representatives of all 39 serotypes not previously studied. In addition to the authors' own limited sequence data for all 90 serotypes, cpsA-cpsB sequence data published by the S. pneumoniae capsular loci-sequencing group (http://www.sanger.ac.uk/Projects/S_pneumoniae/CPS/) at the Sanger Institute or available from GenBank were incorporated into the database. All serotypes, except 25A, were represented by at least two isolates. The number of sequence types identified was 138, of which 110 corresponded to single conventional serotypes (CSs); of these, 57 were represented by two or more isolates. Twenty-six sequence types were shared by between two and four CSs. To resolve these shared cpsA-cpsB sequence types and increase the discriminatory power of our system, the genes encoding the capsular polysaccharide flippase (wzx) and polymerase (wzy) were annotated and 24 new serotype(s)/group(s)-specific PCRs targeting wzy and two targeting wzx were designed. Using both cpsA-cpsB sequencing and wzx/wzy PCR, MCT correctly predicted the CSs of 516 (73 %) and the serogroup of an additional 155 (22 %) of the 708 isolates evaluated. For 5 % of isolates, MCT could not distinguish between members of five serotype pairs (37 isolates) containing members of different serogroups. Although further study of the relationship between MCT and CS is needed, this system now allows serotype or serogroup identification of 95 % of S. pneumoniae isolates.

Bacterial Capsules↗

PubMed2005

A programmable microsystem using system-on-chip for real-time biotelemetry.

A telemetry microsystem, including multiple sensors, integrated instrumentation and a wireless interface has been implemented. We have employed a methodology akin to that for System-on-Chip microelectronics to design an integrated circuit instrument containing several "intellectual property" blocks that will enable convenient reuse of modules in future projects. The present system was optimized for low-power and included mixed-signal sensor circuits, a programmable digital system, a feedback clock control loop and RF circuits integrated on a 5 mm x 5 mm silicon chip using a 0.6 microm, 3.3 V CMOS process. Undesirable signal coupling between circuit components has been investigated and current injection into sensitive instrumentation nodes was minimized by careful floor-planning. The chip, the sensors, a magnetic induction-based transmitter and two silver oxide cells were packaged into a 36 mm x 12 mm capsule format. A base station was built in order to retrieve the data from the microsystem in real-time. The base station was designed to be adaptive and timing tolerant since the microsystem design was simplified to reduce power consumption and size. The telemetry system was found to have a packet error rate of 10(-3) using an asynchronous simplex link. Trials in animal carcasses were carried out to show that the transmitter was as effective as a conventional RF device whilst consuming less power.

Computer Systems↗

PubMed2005

A criterion for optimizing kernel parameters in KBDA for image retrieval.

A criterion is proposed to optimize the kernel parameters in Kernel-based Biased Discriminant Analysis (KBDA) for image retrieval. Kernel parameter optimization is performed by optimizing the kernel space such that the positive images are well clustered while the negative ones are pushed far away from the positives. The proposed criterion measures the goodness of a kernel space, and the optimal kernel parameter set is obtained by maximizing this criterion. Retrieval experiments on two benchmark image databases demonstrate the effectiveness of proposed criterion for KBDA to achieve the best possible performance at the cost of a small fractional computational overhead.

Algorithms↗

PubMed2005

Crystal structures of apo wild-type M. jannaschii tyrosyl-tRNA synthetase (TyrRS) and an engineered TyrRS specific for O-methyl-L-tyrosine.

The Methanococcus jannaschii tRNA(Tyr)/TyrRS pair has been engineered to incorporate unnatural amino acids into proteins in E. coli. To reveal the structural basis for the altered specificity of mutant TyrRS for O-methyl-L-tyrosine (OMeTyr), the crystal structures for the apo wild-type and mutant M. jannaschii TyrRS were determined at 2.66 and 3.0 A, respectively, for comparison with the published structure of TyrRS complexed with tRNA(Tyr) and substrate tyrosine. A large conformational change was found for the anticodon recognition loop 257-263 of wild-type TyrRS upon tRNA binding in order to facilitate recognition of G34 of the anticodon loop through pi-stacking and hydrogen bonding interactions. Loop 133-143, which is close to the tRNA acceptor stem-binding site, also appears to be stabilized by interaction with the tRNA(Tyr). Binding of the substrate tyrosine results in subtle and cooperative movements of the side chains within the tyrosine-binding pocket. In the OMeTyr-specific mutant synthetase structure, the signature motif KMSKS loop and acceptor stem-binding loop 133-143 were surprisingly ordered in the absence of bound ATP and tRNA. The active-site mutations result in altered hydrogen bonding and steric interactions which favor binding of OMeTyr over L-tyrosine. The structure of the mutant and wild-type TyrRS now provide a basis for generating new active-site libraries to evolve synthetases specific for other unnatural amino acids.

Crystallography, X-Ray↗

PubMed2005

Contributions of protein structure and gene position to the compartmentalization of the regulatory proteins sigma(E) and SpoIIE in sporulating Bacillus subtilis.

At an early stage in endospore formation Bacillus subtilis partitions itself into two dissimilar compartments with unique developmental fates. Transcription appropriate to each compartment is initiated by the activation of compartment-specific RNA polymerase sigma subunits, sigma(E) in the mother cell and sigma(F) in the forespore. Among the possible factors contributing to the compartment specificity of sigma(E) and sigma(F) is the selective accumulation of the sigma(E) protein in the mother cell and that of SpoIIE, a regulatory phosphatase essential to the activation of sigma(F), in the forespore. In the current work, fluorescent microscopy is used to investigate the contributions of sigma(E) and SpoIIE's protein structures, expression and the genetic asymmetry that develops during chromosome translocation into the forespore on their abundance in each compartment. Time of entry of the spoIIE and sigE genes into the forespore was found to have a significant effect on the enrichment of their products in one or the other compartment. In contrast, the structures of the proteins themselves do not appear to promote their transfer to a particular compartment, but nonetheless contribute to compartmentalization by facilitating degradation in the compartment where each protein's activity would be inappropriate.

Bacillus subtilis↗

PubMed2005

Preclinical profiling and safety studies of ABT-769: a compound with potential for broad-spectrum antiepileptic activity.

PURPOSE: The objective of this study was to characterize the antiseizure and safety profiles of ABT-769 [(R)-N-(2 amino-2-oxoethyl)spiro[2,5]octane-1-carboxamide]. METHODS: ABT-769 was tested for protection against maximal electroshock and pentylenetetrazol-induced seizures in the mouse and for suppression of electrically kindled amygdala seizures and spontaneous absence-like seizures in the rat. The central nervous system safety profile was evaluated by using tests of motor coordination and inhibitory avoidance. The potential for liver toxicity was assessed in vitro by using a mitochondrial fatty acid beta-oxidation assay. Teratogenic potential was assessed in the mouse. RESULTS: ABT-769 blocked maximal electroshock, subcutaneous pentylenetetrazol and intravenous pentylenetetrazol-induced seizures with median effective dose (ED50) values of 0.25, 0.38, and 0.11 mmol/kg, p.o., respectively. No tolerance was evident in the intravenous pentylenetetrazol test after twice-daily dosing of ABT-769 (0.3 mmol/kg, p.o.) for 4 days. ABT-769 blocked absence-like spike-wave discharge (ED50, 0.15 mmol/kg, p.o.) and shortened the cortical and amygdala afterdischarge duration of kindled seizures (1 and 3 mmol/kg, p.o.). The protective indices (ED50 rotorod impairment/ED50 seizure protection) were 4.8, 3.2, and 10.9 in the maximal electroshock, subcutaneous pentylenetetrazol and intravenous pentylenetetrazol seizure tests, respectively. ABT-769 did not affect inhibitory avoidance performance (0.1-1 mmol/kg, p.o.). ABT-769 did not affect mitochondrial fatty acid beta-oxidation or induce neural tube defects. CONCLUSIONS: ABT-769 is an efficacious antiseizure agent in animal models of convulsive and nonconvulsive epilepsy and has a favorable safety profile. ABT-769 has a broad-spectrum profile like that of valproic acid. Its profile is clearly different from those of carbamazepine, phenytoin, lamotrigine, topiramate, vigabatrin, and tiagabine.

Abnormalities, Drug-Induced↗

PubMed2005

Structural and genetic characterization of enterohemorrhagic Escherichia coli O145 O antigen and development of an O145 serogroup-specific PCR assay.

Enterohemorrhagic Escherichia coli O145 strains are emerging as causes of hemorrhagic colitis and hemolytic uremic syndrome. In this study, we present the structure of the E. coli O145 O antigen and the sequence of its gene cluster. The O145 antigen has repeat units containing three monosaccharide residues: 2-acetamido-2-deoxy-D-glucose (GlcNAc), 2-acetamidoylamino-2,6-dideoxy-L-galactose, and N-acetylneuraminic acid. It is very closely related to Salmonella enterica serovar Touera and S. enterica subsp. arizonae O21 antigen. The E. coli O145 gene cluster is located between the JUMPStart sequence and the gnd gene and consists of 15 open reading frames. Putative genes for the synthesis of the O-antigen constituents, for sugar transferase, and for O-antigen processing were annotated based on sequence similarities and the presence of conserved regions. The putative genes located in the E. coli O145 O-antigen gene cluster accounted for all functions expected for synthesis of the structure. An E. coli O145 serogroup-specific PCR assay based on the genes wzx and wzy was also developed by screening E. coli and Shigella isolates of different serotypes.

Amino Sugars↗

PubMed2005

Structural and genetic characterization of the Shigella boydii type 10 and type 6 O antigens.

Comparison of the O antigens of Shigella boydii types 10 and 6 by chemical analysis and nuclear magnetic resonance spectroscopy showed that their structures are similar, with the only difference being the presence or absence of d-ribofuranose, which is the immunodominant sugar in S. boydii type 10. In S. boydii type 6, a residue previously reported as alpha-d-GlcpA, was shown to be beta-d-GlcpA as in S. boydii type 10. S. boydii types 10 and 6 are reported not to cross-react serologically, and the role of d-ribofuranose in the specificity of S. boydii was confirmed by making a mutant of type 10 that lacked d-ribofuranose. However, S. boydii type 11, which has a d-ribofuranose but with different linkage does show cross-reaction with type 10. The O-antigen gene loci of S. boydii types 10 and 6 were shown to be virtually identical except that orf8 (wbaM), which was confirmed as the ribofuranosyltransferase gene, is interrupted by IS629 in type 6. Therefore, it is proposed that the O-antigen gene cluster of S. boydii type 6 was derived from type 10 by an IS element insertion.

Amino Acid Sequence↗

PubMed2005

Development of PCR assays targeting the genes involved in synthesis and assembly of the new Escherichia coli O 174 and O 177 O antigens.

Escherichia coli O 174 and O 177 are newly described O serogroups which were reported as human pathogens. Identification of these strains by serotyping has been restricted, as the required sera are not commercially available. In this study, a collection of 13 E. coli O 174 strains and 12 E. coli O 177 strains was studied on the O:H serotypes and virulence markers. The O-antigen gene clusters of E. coli O 174 and O 177 were sequenced, and associated genes were assigned functions on the basis of homology. Two genes, each specific for E. coli O 174 and O 177, were identified. PCR assays based on the O-antigen-specific genes were developed and tested on 25 clinical and environmental isolates of those two serogroups as well as 26 isolates of other O serogroups. As little as 1 pg per mul of chromosomal DNA and as few as 0.1 CFU per g of pork and water samples were detected for either strain. The PCR assays established in this study were shown to be highly sensitive and reliable and could be the method of choice for detection of these two human pathogens from clinical, food, and other environmental samples.

Animals↗

PubMed2005

Sequence analysis of the Escherichia coli O15 antigen gene cluster and development of a PCR assay for rapid detection of intestinal and extraintestinal pathogenic E. coli O15 strains.

A collection of 33 Escherichia coli serogroup O15 strains was studied with regard to O:H serotypes and virulence markers and for detection of the O-antigen-specific genes wzx and wzy. The strains were from nine different countries, originated from healthy or diseased humans and animals and from food, and were isolated between 1941 and 2003. On the basis of virulence markers and clinical data the strains could be split into different pathogroups, such as uropathogenic E. coli, enteropathogenic E. coli, Shiga toxin-producing E. coli, and enteroaggregative E. coli. H serotyping and genotyping of the flagellin (fliC) gene revealed 11 different H types and a close association between certain H types, virulence markers, and pathogroups was found. Nucleotide sequence analysis of the O-antigen gene cluster revealed putative genes for biosynthesis of O15 antigen. PCR assays were developed for sensitive and specific detection of the O15-antigen-specific genes wzx and wzy. The high pathotype diversity found in the collection of 33 O15 strains contrasted with the high level of similarity found in the genes specific to the O15 antigen. This might indicate that the O15 determinant has been spread by horizontal gene transfer to a number of genetically unrelated strains of E. coli.

Escherichia coli↗

PubMed2005

MEKK1 transduces activin signals in keratinocytes to induce actin stress fiber formation and migration.

Activins and other members of the transforming growth factor beta family play a critical role in morphological changes of the epidermis that require epithelial cell movement. We investigated the molecular pathways in the transmission of activin signals that lead to actin reorganization and epithelial cell migration. We found that activins cause the activation of RhoA but not of Rac and CDC42, leading to MEKK1-dependent phosphorylation of JNK and transcription factor c-Jun. Through a RhoA-independent mechanism, the activins also induce p38 activity in keratinocytes from wild-type but not from MEKK1-deficient mice. Although neither pathway is dependent on Smad activation, the MEKK1-mediated JNK and p38 activities are both essential for activin-stimulated and transcription-dependent keratinocyte migration. Only JNK is involved in transcription-independent actin stress fiber formation, which needs also the activity of ROCK. Because ROCK is required for JNK activation by RhoA and its overexpression leads to MEKK1 activation, we propose a RhoA-ROCK-MEKK1-JNK pathway and a MEKK1-p38 pathway as Smad-independent mechanisms in the transmission of activin signals. Together, these pathways lead to the control of actin cytoskeleton reorganization and epithelial cell migration, contributing to the physiologic and pathological effects of activins on epithelial morphogenesis.

Actins↗

PubMed2005

Molecular analysis of Shigella boydii O1 O-antigen gene cluster and its PCR typing.

Shigella is an important human pathogen and is closely related to Escherichia coli. O-antigen is the most variable part of the lipopolysaccharide on the cell surface of Gram-negative bacteria and plays an important role in pathogenicity. The O-antigen gene cluster of S. boydii O1 was sequenced. The putative genes encoding enzymes for rhamnose synthesis, transferases, O-unit flippase, and O-unit polymerase were identified on the basis of homology. The O-antigen gene clusters of S. boydii O1 and E. coli O149, which share the same O-antigen form, were found to have the same genes and organization by adjacent gene PCR assay. Two genes specific for S. boydii O1 and E. coli O149 were identified by PCR screening against E. coli- and Shigella-type strains of the 186 known O-antigen forms and 39 E. coli clinical isolates. A PCR sensitivity of 103 to 104 CFU/mL overnight culture of S. boydii O1 and E. coli O149 was obtained. S. boydii O1 and E. coli O149 were differentiated by PCR using lacZ- and cadA-based primers.

Bacterial Typing Techniques↗

PubMed2005

Relationship between bone mineral density and syndrome types described in traditional chinese medicine in chronic obstructive pulmonary disease: a preliminary clinical observation.

Osteoporosis is a common finding following chronic obstructive pulmonary disease (COPD), but there are few reports on the relationship between bone mineral density (BMD) and the syndrome types described in traditional Chinese medicine (TCM) in patients with COPD. A cross-sectional medical survey was used in this study. Twenty-six male patients with COPD and 26 age-matched male healthy subjects were recruited. The symptom questionnaire survey of TCM was implemented, and thereafter the COPD patients were divided into two subgroups: type of deficiency of the lung and spleen (TDLS) and type of deficiency of the lung, spleen and kidney (TDLSK). BMD of lumbar spine (L2-4), non-dominant femoral neck (Neck), Ward's triangle (Ward's), and great trochanter (Troch) were measured by dual-energy x-ray absorptiometry. In addition, the other bone turnover markers were also examined. The results showed that BMD was much more decreased in TDLSK than that in TDLS patients (p < 0.05), and BMD in the patients of the TDLS subgroup without symptoms of kidney-vacuity has showed the decreased trend from healthy subjects to TDLS patients. Furthermore, there was a higher incidence of osteoporosis in patients with TDLSK compared with that in TDLS (p < 0.05, OR > 2.0). Therefore, the data suggest that: (1) BMD might be a marker more sensitive than the symptom for the diagnosis of kidney-vacuity in COPD patients; (2) the deficiency of kidney would be the key factor of bone mineral loss; and (3) that invigorating the kidney should be performed in the phase of TDLS in COPD patients in advance.

Absorptiometry, Photon↗

PubMed2005

Identification of differentially expressed genes in metastatic and non-metastatic nasopharyngeal carcinoma cells by suppression subtractive hybridization.

BACKGROUND & OBJECTIVE: Nasopharyngeal carcinoma (NPC) is an epithelial neoplasm with high occurrence rates in southern China. The disease often metastasizes to regional lymphnodes at a very early stage. Local recurrences and metastasis occur frequently in patients with NPC and are a leading cause of death, despite improvements on treatment modalities. The molecular mechanism underlying the metastasis of nasopharyngeal carcinoma remains poorly understood, however, and requires additional elucidation. The aim of this study was to explore possible NPC gene candidates that may play key roles in NPC metastasis. METHODS: Subtractive suppression hybridization (SSH) was performed to isolate differentially expressed clones between the metastatic 5-8F and non-metastatic 6-10B nasopharyngeal carcinoma cell lines. Differentially expressed clones were screened and confirmed by reverse Northern blotting. The sequences of cDNA fragments were subsequently analyzed and compared to known sequences in Genbank. RESULTS & DISCUSSION: The SSH library contained thousands of positive clones. Random analysis of 300 clones by PCR demonstrated that 269 clones contained inserted fragments. Reverse Northern blot confirmed that 20 out of 192 clones examined were significantly up-regulated in the 5-8F cell line. Among these 20 clones, 16 were previously identified genes (flotilin-2, ezrin, pim-3, fli-1, mel, neugrin, znf216, ASB1, raly, UBE2A, keratin6A, TMED7, EIF3S9, FTL, two ribosomal proteins RPL21 and RPL16), two were predicted genes (c9orf74 and MDS006), and two sequences shared no homology with known genes listed in GenBank and may represent novel genes. The proposed functions of the genes identified in this study include cell signal transduction, cell survival, transcription regulation, cell mobility, protein synthesis, and DNA damage repair. Flotillin-2, fli-1, pim-3 and ezrin have previously been reported to be associated with tumor metastasis and progression. The remaining up-regulated genes identified in this study have not been reported to be markers of metastasis and may represent new candidates of NPC metastasis-related genes. The results of this study may provide novel points of therapeutic intervention for NPC.

DNA, Complementary↗

PubMed2005

Interaction of 1-dodecyl-azacycloheptan-2-one with mouse stratum corneum.

The interactions of 1-dodecyl-azacycloheptan-2-one (Azone), a penetration enhancer, with mouse skin were analyzed by fluorescence microscopy, solid-state 13C-CP/MAS-NMR spectroscopy and Attenuated Total Reflectance Fourier-transform infrared (ATR-FT-IR) spectroscopy. Ferulic acid was employed as fluorescent probe to observe the delivery pathway in the stratum corneum (SC) after treatment with Azone. Results suggested that the interaction between Azone and the SC occurs in the lipid domains as well as the protein domains. FT-IR measurements show that treatment with Azone results in significant shifts toward larger wavenumbers at v(as)CH2 and v(s)CH2, indicating an increased gauche conformational isomer content of lipid CH2. Further, a decrease of (13C)T1 values and a shift of the SC protein amide-II band to a short wavenumber were found when the SC was pretreated with Azone. It is concluded that Azone can partially convert the SC protein from an alpha-helix conformation to a beta-sheet conformation and loosen the aggregating SC keratins at room temperature.

Adjuvants, Pharmaceutic↗

PubMed2005

Endocannabinoid activation at hepatic CB1 receptors stimulates fatty acid synthesis and contributes to diet-induced obesity.

Endogenous cannabinoids acting at CB(1) receptors stimulate appetite, and CB(1) antagonists show promise in the treatment of obesity. CB(1) (-/-) mice are resistant to diet-induced obesity even though their caloric intake is similar to that of wild-type mice, suggesting that endocannabinoids also regulate fat metabolism. Here, we investigated the possible role of endocannabinoids in the regulation of hepatic lipogenesis. Activation of CB(1) in mice increases the hepatic gene expression of the lipogenic transcription factor SREBP-1c and its targets acetyl-CoA carboxylase-1 and fatty acid synthase (FAS). Treatment with a CB(1) agonist also increases de novo fatty acid synthesis in the liver or in isolated hepatocytes, which express CB(1). High-fat diet increases hepatic levels of the endocannabinoid anandamide (arachidonoyl ethanolamide), CB(1) density, and basal rates of fatty acid synthesis, and the latter is reduced by CB(1) blockade. In the hypothalamus, where FAS inhibitors elicit anorexia, SREBP-1c and FAS expression are similarly affected by CB(1) ligands. We conclude that anandamide acting at hepatic CB(1) contributes to diet-induced obesity and that the FAS pathway may be a common molecular target for central appetitive and peripheral metabolic regulation.

Animals↗

PubMed2005

Dietary uridine-5'-monophosphate supplementation increases potassium-evoked dopamine release and promotes neurite outgrowth in aged rats.

Membrane phospholipids like phosphatidylcholine (PC) are required for cellular growth and repair, and specifically for synaptic function. PC synthesis is controlled by cellular levels of its precursor, cytidine-5'-diphosphate choline (CDP-choline), which is produced from cytidine triphosphate (CTP) and phosphocholine. In rat PC12 cells exogenous uridine was shown to elevate intracellular CDP-choline levels, by promoting the synthesis of uridine triphosphate (UTP), which was partly converted to CTP. In such cells uridine also enhanced the neurite outgrowth produced by nerve growth factor (NGF). The present study assessed the effect of dietary supplementation with uridine-5'-monophosphate disodium (UMP-2Na+, an additive in infant milk formulas) on striatal dopamine (DA) release in aged rats. Male Fischer 344 rats consumed either a control diet or one fortified with 2.5% UMP for 6 wk, ad libitum. In vivo microdialysis was then used to measure spontaneous and potassium (K+)-evoked DA release in the right striatum. Potassium (K+)-evoked DA release was significantly greater among UMP-treated rats, i.e., 341+/-21% of basal levels vs. 283+/-9% of basal levels in control rats (p<0.05); basal DA release was unchanged. In general, each animal's K+-evoked DA release correlated with its striatal DA content, measured postmortem. The levels of neurofilament-70 and neurofilament-M proteins, biomarkers of neurite outgrowth, increased to 182+/-25% (p<0.05) and 221+/-34% (p<0.01) of control values, respectively, with UMP consumption. Hence, UMP treatment not only enhances membrane phosphatide production but also can modulate two membrane-dependent processes, neurotransmitter release and neurite outgrowth, in vivo.

Aging↗