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Biomedical subjects

B Wu

Publications and source records attributed to B Wu.

At least 91 records · Page 5Linked to original sources
PubMed2000

NMR structure of tissue inhibitor of metalloproteinases-1 implicates localized induced fit in recognition of matrix metalloproteinases.

A high quality solution structure of the matrix metalloproteinase inhibitory N-terminal domain of recombinant human tissue inhibitor of metalloproteinases-1 (N-TIMP-1) has been determined. For the rigidly packed residues, the average RMSD to the mean structure is 0. 57 A for the backbone atoms and 1.00 A for all heavy atoms. Comparison of the solution structure of free N-TIMP-1 with the crystal structure of TIMP-1 bound to the catalytic domain of MMP-3 ( Gomis-R]uth et al., 1997 ) shows that the structural core of the beta barrel flanked by helices is nearly unchanged by the association with MMP-3, evident from a backbone RMSD of 1.15 A. However, clear differences in the conformation of the MMP-binding ridge of free and MMP-bound TIMP-1 suggest induced fit throughout the ridge. The MMP-dependent conformational changes in the ridge include a dramatic bending of AB loop residues Glu28 through Leu34, moderate hinge bending of the CD-loop about residues Ala65 and Cys70, and modest bending of the Cys1 through Pro6 segment. A large number of interresidue Nuclear Overhauser enhancements (NOEs) augmented by stereospecific assignments, torsion restraints, and dipolar couplings (an average of 18 non-trivial restraints per residue) engender confidence in these structural inferences. A tight cluster of three lysine residues and one arginine residue atop beta-strands A and B, and identical among TIMP sequences, form the heart of a highly conserved electropositive patch that may interact with anionic components of the extracellular matrix.

Catalytic Domain↗
PubMed2000

Major T cell epitope-containing peptides can elicit strong antibody responses.

Peptides containing major T cell epitopes have the capacity to induce T cell anergy and have therefore been proposed for the treatment of allergic and autoimmune diseases. Such peptides should not be immunogenic, i. e. should not contain a B cell recognition site. We have evaluated in BALB/c mice the therapeutic potential of a 15-mer peptide (p21 - 35) derived from Der p2, a major allergen of the house dust mite Dermatophagoides pteronyssinus, which contains a dominant T cell epitope but is not recognized by antibodies to Der p2. Unexpectedly, p21 - 35 elicited strong immune responses, suggesting the presence of a cryptic B cell epitope. Similar results were obtained with mice of three additional MHC haplotypes. A core sequence of four amino acids (Ile-Ile-His-Arg) corresponding to residues 28 - 31 was shared by the B and T cell epitopes. Critical residues for B cell recognition were Arg31 and Lys33, while Ile28 was essential for T cell recognition. A Lys33Ala mutant of p21 - 35 still activated T cells but had much reduced immunogenic properties, making it a suitable alternative peptide for T cell anergy induction. Careful investigation of the immunogenic potential of peptides used to induce T cell anergy should be carried out prior to their clinical application.

Allergens↗
PubMed2000

Molecular mechanisms of lipopolysaccharide induced ICAM-1 expression in A549 cells.

OBJECTIVE AND DESIGN: Lung intercellular adhesion molecule-1 (ICAM-1) expression is increased by LPS or hyperoxia on type II cells in vivo. The goals of the present study were to determine the mechanisms of ICAM-1 expression in a lung alveolar epithelial cell line (A549) exposed to lipopolysaccharide (LPS). MATERIALS: A549 cells, a transformed human cell line with characteristics of alveolar epithelial cells, were used. TREATMENT: Cells were exposed to LPS, TNF-alpha, IL-1beta, or media alone for up to 12 h. METHODS: Northern blot analyses were done to determine mRNA expression of ICAM-1 after exposures. Protein binding to NF-kappaB sequences were determined by gel mobility shift assays and super-shift analysis. RESULTS: ICAM-1 mRNA expression was induced in A549 cells with exposure to LPS for 1 to 4 h, and was diminished to baseline at 8 h, and the inductions were independent of TNF-alpha and IL-1beta expression. Nuclear protein extracts from LPS-exposed cells bound to a NF-kappaB sequence and the timing of increased binding correlated closely with ICAM-1 mRNA induction. Super-shift studies indicated that p65 was involved in the binding to the NF-kappaB sequence and p50 was not. CONCLUSION: LPS inducibility of ICAM-1 mRNA in A549 cells is independent of TNF- and IL-1 in A549 cells, and the similar time course of mRNA induction and NF-kappaB activation suggest the induction of ICAM-1 is mediated, in part, by NF-kappaB.

Binding Sites↗
PubMed2000

Unique chromosome identification and sequence-specific structural analysis with short PNA oligomers.

We have extended our earlier work to show that individual 14-20mer peptide nucleic acid probes directed against interspersed alpha-satellite sequences can specifically identify chromosomes. Peptide nucleic acid (PNA) probes were used to detect chromosomal abnormalities and repeat structure in the human genome by fluorescence in situ hybridization (FISH). The hybridization of a single PNA probe species directed against a highly abundant alpha-satellite DNA repeat sequence was sufficient to absolutely identify a chromosome. Selection of highly repetitive or region-specific DNA repeats involved DNA database analysis. Distribution of a specific repeat sequence in human genome was estimated through two means: a computer program "whole genome" approach based on approximately 400 Mb (12%) human genomic sequence. The other method involved directed search for alpha satellite sequences. In total, approximately 240 unique DNA repeat candidates were found. Forty-two PNA probes were designed for screening chromosome-specific probes. Ten chromosome-specific PNA probes for human Chromosomes (Chrs) 1, 2, 7, 9, 11, 17, 18, X, and Y have been identified. Interphase and metaphase results demonstrate that chromosome-specific PNA probes are capable of detecting simple aneuploidies (trisomies) in human. Another set of PNA probes showed distinct banding-like patterns and could be used as sequence-specific stains for chromosome "bar coding". Potential application of PNA probes for investigating repeat structure and function is also discussed.

Base Sequence↗
PubMed2000

Conformational characterization of a helix-nucleated bicyclic GCN4 decapeptide by proton NMR.

A bicyclic decapeptide, GCN4brM1, which was designed to be a helix-locked analog of the DNA-binding basic region from the yeast transcription factor GCN4, was synthesized and characterized using circular dichroism (CD) spectropolarimetry and 1H-NMR. This peptide has two Lys(i), Asp(i+4) side chain lactam bridges incorporated into its structure in overlapping positions in the peptide chain, linking residues 3 and 7 and residues 4 and 8. CD spectra of GCN4brM1 in aqueous solution are consistent with the expected helical conformation, and indicate that this conformation is remarkably resistant to heat denaturation and is essentially unchanged by addition of 50% (v/v) trifluoroethanol (TFE) as cosolvent. NMR spectra measured in aqueous solution at -5 degrees C show long-range nuclear Overhauser effects (NOEs) that are consistent with an alpha-helical conformation throughout the peptide structure. The measured 3J(HN) coupling constants are also in agreement with an alpha-helical structure. Extremely slow proton-deuterium exchange rates measured for backbone amides in the middle of the peptide indicate that this helix is highly stabilized and rarely unfolds within the side chain bridged sequence. NOE-constrained molecular dynamics simulations gave rise to a single family of converged structures that are fully alpha-helical throughout the GCN4brM1 backbone, and show a single, well-defined conformation for the two side chain bridges. This study demonstrates that two overlapping Lys(i), Asp(i+4) lactam bridges, positioned in consecutive residue positions in a hexapeptide segment, form a rigid alpha-helical structure in aqueous solution that is propagated in both the N-terminal and C-terminal directions.

Amino Acid Sequence↗
PubMed2000

Job characteristics and leisure physical activity.

OBJECTIVES: This study employs a sample population of older workers to estimate an empirical model of leisure exercise activity. Alternative theories relating work and leisure attitudes relevant for understanding the exercise behavior of older workers are tested empirically. METHODS: Responses of 6,433 full-time older workers (51 to 61 years old) from the 1992 Health and Retirement Study (HRS) are grouped into two white-collar and blue-collar worker categories and are analyzed to test whether self-reported levels of regular physical activity are associated with the physical demands and stress associated with one's job. RESULTS: Although the white-collar workers, whose jobs involve more physical efforts, are more likely to do light physical activity, the blue-collar workers, whose jobs are more physically demanding, tend to engage in more vigorous exercise. DISCUSSION: The empirical results are most supportive of the generalization theory, and they also illustrate the complexity of relationships between work and leisure physical activity.

Demography↗
PubMed2000

[Study on the p53 gene mutation and microsatellite instability of gastric carcinoma].

OBJECTIVE: To observe the relationship between p53 gene mutation and microsatellite instability (MSI) of the preoperative staging of gastric carcinoma by endoscopic ultrasonography(EUS). METHODS: A total of 73 cases of gastric carcinoma were taken for the preoperative staging with EUS. Silver staining PCR-SSCP method was used to detect mutations in exons 5, 6, 7, 8 of p53 gene and MSI at 4 loci on chromosomes 2, 5, 17 in the 73 paraffin-embedded biopsy specimens, and the relationship between them was studied further. RESULTS: The overall mutated rate of p53 gene was 54.8%, with 6.8%, 15.1%, 19.2% and 13.7% in exons 5 to 8, respectively. Analysis of the relation of the mutation with the preoperative staging by EUS showed that it was significantly higher in T3(64.3%) and T4(67.9%) than in T1(0) or T2(25.0%)(P<0.05), and it was 67.6% in cases with lymph node metastasis, which was significantly higher than that without metastasis (41.7%)(P<0.05). The overall detective rate of MSI was 37.0%. The detective rate of MSI had no relation with the depth of invasion, which was 40.0%, 33.3%, 39.3% and 34.5% at T1 to T4 stages (P<0.05), respectively, but it was significantly higher in cases with lymph node metastasis(51.4%) than those without metastasis(22.2%)(P<0.05). Although the detective rate of MSI showed an increasing trend in the mutated cases of p53 gene as compared with the no mutation cases, there was no relationship between MSI and p53 gene mutation (P<0.05). CONCLUSION: These results suggest that the gene mutation of p53 and MSI may represent the different mechanisms of carcinogenesis. They can reflect the cytobiologic malignant behavior of gastric carcinoma in varying degrees, which may be of reference significance in analysing the prognosis of the patients in clinics.

Adult↗
PubMed2000

[Matching of brain sections based on fourier descriptors].

We developed an algorithm based on Fourier Descriptors(FD) to match brain sections and specially aimed to pool electro-physiological data from individual animals and composite the results on a single brain. To test this algorithm, curvilinear features were first extracted from each section image of the midbrain of the rat resulting in three closed boundaries. A set of boundaries of 38 consecutive sections was then taken as standard templates for matching with any other brain sections processed in a similar way. Each section was represented by Fourier descriptors of these boundaries. Matching was done by minimizing the similarity function between an experimental brain section and the set of standard templates. This algorithm has been successfully used for the study of functional organization of AM-sound sensitive auditory neurons in the midbrain.

Algorithms↗
PubMed2000

Investigation on interaction between Streptococcus sanguis and Porphyromonas gingivalis in specific pathogen-free rats.

OBJECTIVE: To examine whether endogenous Streptococcus can prevent or reduce the colonization of the virulent Porphyromonas gingivalis strain. METHODS: Successful implantation of the endogenous strain of S. sanguis and P. gingivalis 381 within 14 days was demonstrated in the study rats following administration of doxycycline for 7 days. Thirty specific pathogen-free (SPF) rats were divided into 6 groups. After administration of doxycycline for 7 days, groups A and B were inoculated orally once a day for 5 days with P. gingivalis. Group C and E were inoculated orally once a day for 5 days with S. sanguis. Then, group A was inoculated for 5 days with S. sanguis, and rats in group C and D were inoculated for 5 days with P. gingivalis. Group F served as a negative control. After inoculation, the levels of S. sanguis and P. gingivalis in the mouths of the rats were determined at 12 hours, 24 hours, 36 hours, 7 days, and 14 days. RESULTS: Both precolonization of S. sanguis and superinfection with S. sanguis reduced the level of P. gingivalis in experimental rats. However, the reduction was maintained for only 24 to 36 hours. The level of S. sanguis remained stable during the 14-days observation period. CONCLUSION: S. sanguis to function as the effector strain, the successful implantation of S. sanguis and the antagonistic action efficiently produced in vivo by S. sanguis is required.

Animals↗
PubMed2000

[High risk factors lead to noscomial pulmonary infections caused by MRSA].

OBJECTIVE: To investigate major risk factors leading to death by noscomial MRSA pulmonary infections. METHOD: The data of hospitalized patients diagnosed as noscomial MRSA pulmonary infections were sorted out and analyzed for recent three years. RESULTS: Case mortality of 64 patients with noscomial MRSA pulmonary infections were 44%. Of these, 18 cases complicated fungi, 11 Klebsiella pneumoniae, 9 Pseudomonas maltophilia and 7 Enterococcus. Case mortality of fungi and Pseudomonas maltophilia were 67% and 61%, respectively. 23 cases had fever, 18 died (case mortality 78%) and 41 had no fever, 10 died (case mortality 24%) (chi 2 = 15.253, P < 0.005). The case mortality with reduction, normal and increase of leukocyte were 80%, 24% and 45%, respectively. The comparison between three groups had obvious significance (chi 2 = 12.554, P < 0.005) and the case mortality of leukocytopenia was higher than that of other two groups (chi 2 = 8.626, P < 0.005). The case mortality of hypoproteinemia was higher than that of the control group (chi 2 = 6.914, P < 0.01). The patients who developed fulminant lesions in liver, kidneys and lungs showed higher mortality rate. CONCLUSIONS: Case mortality of noscomial pneumonia caused by MRSA is very high. In addition to common causes, underling diseases, leukocytopenia, malnutrition and complex infections are also risk factors of MRSA infection.

Adult↗
PubMed2000

[Detection and effect of telomerase activity in oral mucosal squamous cell carcinoma].

OBJECTIVE: To study telomerase activity in 20 oral squamous cell carcinoma(SCC), and 10 normal oral tissues and 9 oral SCC and 9 adjacent normal tissue. METHODS: A modified PCR-based telomeric repeat amplification protocal assay(TRAP) was used. RESULTS: The telomerase activity was significantly higher in SCC than that of normal mucosa, and than that of adjacent tissue as well. CONCLUSIONS: These findings indicated that telomerase activation might be a critical step in the formation and development of cancer.

Carcinoma, Squamous Cell↗
PubMed2000

[Effect of mouse p53 minigene on lung cancer cells with different 172 structures regulated by tetracycline].

OBJECTIVE: To investigate the effect of mouse 172 wild-type p53 (Arg), pseudo-wild-mutant-type p53 (Arg-->Leu) and mutant-type p53 (Arg-->His) induced by absence of tetracycline on the growth of PG cell line. METHODS: Three variant types of p53 minigene were sub-cloned by gene recombination into an expression vector which was controlled by tetracycline. Through LipofectAMINE, the vectors were transfected into p53 defective PG (248CGG-->CTT) cells, and the transfectants were screened in the selecting medium containing puromycin. Tumor suppressing effects were studied by MTT absorption, flow cytometry and Western blotting. RESULTS: Wild-type p53 and pseudo-wild-mutant-type p53 could lead cells to decrease their growth rates, arrest cell cycle and transactivation of p21(WAF1). Mutant-type p53 was defective in tumor suppression. CONCLUSION: Wild-type p53 and pseudo-wild-type p53 may inhibit cell growth and induce cell cycle arrest. Some p53 variants such as 172 Arg-->Leu can still retain the tumor suppression function of the wild-type.

Amino Acid Substitution↗
PubMed2000

[Inhibition of growth and metastasis of human giant cell carcinoma of the lung by transfection of antisense VEGF121 cDNA].

OBJECTIVE: To explore the effects of blocking the VEGF/VEGF receptor paracrine pathway on growth and metastasis of human lung carcinoma cell line PG and to evaluate its potential application in gene therapy of cancer. METHODS: The eukaryotic expression vectors bearing either sense-VEGF121 cDNA or antisense-VEGF121 cDNA was constructed and transfected into PG cells. In vitro and in vivo tests such as Northern blotting hybridization, Western blotting immunochemistry analysis, as well as xenografting in nude mice were used to analyze the effect of antisense-VEGF. RESULTS: The transfectants stably expressing antisense VEGF121 were observed to produce markedly reduced 3.3 kb VEGF mRNA and 45 KD, 41 KD, 32KD VEGF proteins. When xenografted s.c. into nude mice, growth and metastasis of the antisense-VEGF transfected cell lines were greatly inhibited when compared with control cells. CONCLUSION: Antisense VEGF gene significantly inhibited tumor growth and metastasis and may provide an experimental example for the development of antiangiogenic gene therapy.

Animals↗
PubMed2000

[An experimental study of antibiotic -- induced endotoxin release in Pseudomonas aeruginosa bacteremia inburned rats].

OBJECTIVE: To assess the intensity of endotoxin release in Pseudomonas aeruginosa challenged burned rats after the administration of various antibiotics. METHODS: Rats were inflicted with 30% TBSA burn, and they were challenged with Pseudomonas aeruginosa (PA103). After the administration of different beta lactam antibiotics, serum endotoxin level and blood bacterial count were determined. RESULTS: All the antibiotics used were effective in eradicating the bacteria with concomitant release of endotoxin in varying amounts. It was found that Imipenem released the least amount of endotoxin, followed in order by Cefoperazone, Ceftazidime, and Cefotxime. CONCLUSIONS: Different antibiotics possessed varying capacity of inducing endotoxin release from PA, and the amount released did not bear any relation with the bactericidal capability of the antibiotics.

Animals↗
PubMed2000

[Autologous bone marrow transplantation for patients with chronic myelogenous leukemia after in vitro purging of the graft with bcr/abl antisense oligodeoxynucleotides].

OBJECTIVE: To investigate the efficacy of autologous bone marrow transplantation (ABMT) for patients with chronic myelogenous leukemia (CML) after in vitro purging of the graft with bcr/abl antisense oligodeoxynucleotides (AS-ODN). METHODS: Five CML patients, 2 in chronic phase (CP), 1 in accelerated phase (AP) and 2 in blast crisis (BC), all confirmed the presence of b3a2 bcr/abl mRNA by RT-PCR (reverse transcriptase-polymerase chain reaction). Patients had received 2 courses of intensive chemotherapy for "in vivo purging" before bone marrow harvesting. The autologous bone marrow cells were concentrated by CS3000plus and then incubated with 18-mer phosphorothioate bcr/abl AS-ODN (40 - 60 microg/ml, for 48 - 60 h). Conditioning regimens were TBI + Cy (total body irradiation + cyclophosphamide) or MAC + CCNU. RESULTS: After intensive chemotherapy, ph(+) cells in bone marrow reduced to 34% (24% - 46%) and the numbers of bcr/abl mRNA (+) CFU-GM to 45.6% (33% - 58%). After bcr/abl AS-ODN in vitro purging, two patients were bcr/abl mRNA negative and three positive with the number of bcr/abl mRNA (+) CFU-GM markedly reduced. Delayed hematopoietic reconstitutions were observed in all patients after ABMT. During a more than 2 years follow-up period, three patients obtained major cytogenetic remission (MCR) and lasted for 9 - 12 months and the durations of CP after ABMT were longer than that before ABMT. One of this three in BC before ABMT being survived disease-freely for 37 months with bcr/abl mRNA (-) after ABMT. Another patient in BC had a short duration of MCR and relapsed at +7 months. One patient died from severe infection and bleeding at day +74 because of delayed reconstitution. CONCLUSION: ABMT with bcr/abl AS-ODN purged graft can result in quite long duration of MCR and prolonged CP in some patients with CML.

Adolescent↗
PubMed2000

[The construction of a recombined E. coli strain with stable and high production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)].

Plasmid pJMC2 was constructed by cloning the parDE fragment of RK2 into pTZ18U-PHB which harbored phaCAB from Alcaligenes eutrophus and was transferred into E. coli HMS174 and E. coli JM107 separately. It is very stable in its hosts cultured in medium without ampicillin. E. coli HMS 174(pTZ18U-PHB) and E. coli JM107(pTZ18U-PHB) produced P(3HB-co-3HB) in a low phosphate concentration medium(18 mmol/L). The proportion of 3-hydroxyvalerate(3HV) in the polymer was 5%-8%. A fed-batch culture of E. coli HMS174(pJMC2) was conduct in a 5 L automatically controlled fermentor, the final dry cell weight, P(3HB-co-3HV) content, and th 3HV proportion were 42.5 g/L, 70% and 4.9% respectively.

Culture Media↗