Biomedical subjects

Jun Yu

Publications and source records attributed to Jun Yu.

At least 163 records · Page 9Linked to original sources

PubMed2003

Evolution and variation of the SARS-CoV genome.

Knowledge of the evolution of pathogens is of great medical and biological significance to the prevention, diagnosis, and therapy of infectious diseases. In order to understand the origin and evolution of the SARS-CoV (severe acute respiratory syndrome-associated coronavirus), we collected complete genome sequences of all viruses available in GenBank, and made comparative analyses with the SARS-CoV. Genomic signature analysis demonstrates that the coronaviruses all take the TGTT as their richest tetranucleotide except the SARS-CoV. A detailed analysis of the forty-two complete SARS-CoV genome sequences revealed the existence of two distinct genotypes, and showed that these isolates could be classified into four groups. Our manual analysis of the BLASTN results demonstrates that the HE (hemagglutinin-esterase) gene exists in the SARS-CoV, and many mutations made it unfamiliar to us.

Amino Acid Motifs↗

PubMed2003

Genome organization of the SARS-CoV.

Annotation of the genome sequence of the SARS-CoV (severe acute respiratory syndrome-associated coronavirus) is indispensable to understand its evolution and pathogenesis. We have performed a full annotation of the SARS-CoV genome sequences by using annotation programs publicly available or developed by ourselves. Totally, 21 open reading frames (ORFs) of genes or putative uncharacterized proteins (PUPs) were predicted. Seven PUPs had not been reported previously, and two of them were predicted to contain transmembrane regions. Eight ORFs partially overlapped with or embedded into those of known genes, revealing that the SARS-CoV genome is a small and compact one with overlapped coding regions. The most striking discovery is that an ORF locates on the minus strand. We have also annotated non-coding regions and identified the transcription regulating sequences (TRS) in the intergenic regions. The analysis of TRS supports the minus strand extending transcription mechanism of coronavirus. The SNP analysis of different isolates reveals that mutations of the sequences do not affect the prediction results of ORFs.

Amino Acid Substitution↗

PubMed2003

Vertebrate gene predictions and the problem of large genes.

To find unknown protein-coding genes, annotation pipelines use a combination of ab initio gene prediction and similarity to experimentally confirmed genes or proteins. Here, we show that although the ab initio predictions have an intrinsically high false-positive rate, they also have a consistently low false-negative rate. The incorporation of similarity information is meant to reduce the false-positive rate, but in doing so it increases the false-negative rate. The crucial variable is gene size (including introns)--genes of the most extreme sizes, especially very large genes, are most likely to be incorrectly predicted.

Animals↗

PubMed2003

Organ-specific models of Streptococcus pneumoniae disease.

The variability of the course of infection by Streptococcus pneumoniae is well known but poorly understood. Most animal models of pneumonia, sepsis or meningitis have been forced to use site-specific bacterial inoculation to mimic localized human infection. This study examined the differences in the progression of disease-causing strains D39 (serotype 2), A66.1 (serotype 3) and TIGR4 (serotype 4) using isolates transformed with the Gram-positive lux transposon cassette, Tn4001 luxABCDE Km(r). Expression of the lux operon results in bioluminescence, permitting the detection of the bacteria within a living animal while using a CCD camera. Mice infected intranasally with A66.1 developed only pneumonia, those challenged with D39 experienced high-grade sepsis, while TIGR4 infection resulted in low-grade pneumonia and bacteremia ultimately progressing to meningitis. Quantitative analysis of bacterial titers confirmed these patterns, which were consistent across different lineages of mice. Mice anesthetized with ketamine and xylazine developed more severe forms of the disease compared with isoflurane. These studies unambiguously characterize 3 distinct models of the natural course of pneumococcal infection. Mapping these models provides a framework for detailed molecular modeling of pneumococcal virulence determinants at specific stages of disease.

Animals↗

PubMed2003

A population threshold for functional polymorphisms.

We sequenced 114 genes (for DNA repair, cell cycle arrest, apoptosis, and detoxification)in a mixed human population and observed a sudden increase in the number of functional polymorphisms below a minor allele frequency of approximately 6%. Functionality is assessed by considering the ratio in the number of nonsynonymous single nucletide polymorphisms (SNPs)to the number of synonymous or intron SNPs. This ratio is steady from below 1% in frequency-that regime traditionally associated with rare Mendelian diseases-all the way up to about 6% in frequency, after which it falls precipitously. We consider possible explanations for this threshold effect. There are four candidates as follows: (1). deleterious variants that have yet to be purified from the population, (2). balancing selection, in which a selective advantage accrues to the heterozygotes, (3). population-specific functional polymorphisms, and (4). adaptive variants that are accumulating in the population as a response to the dramatic environmental changes of the last 7000 approximately 17000 years.

Animals↗

PubMed2003

Immunization with attenuated Salmonella typhimurium producing catalase in protection against gastric Helicobacter pylori infection in mice.

AIM: To evaluate the protective effect of live attenuated Salmonella typhimurium expressing catalase against gastric Helicobacter pylori infection in mice, and to explore the underlying mechanisms of the protective immune reaction. MATERIALS AND METHODS: The H. pylori catalase gene was introduced into attenuated S. typhimurium strain SL3261. C57BL/6 mice were orally immunized with the SL3261 vaccine strain expressing catalase or with SL3261 alone or phosphate-buffered saline (PBS). Mice were sacrificed 4 weeks after immunization and 5 weeks after H. pylori challenge, respectively. RESULTS: All PBS control mice were infected. Eight of 13 (61.5%) mice immunized with the SL3261 vaccine strain and three of 14 (21%) mice immunized with SL3261 alone showed protection against H. pylori infection. Serum anti-H. pylori IgG2a levels of S. typhimurium-immunized mice were higher than those of PBS controls, both before and after H. pylori challenge, while there were no differences for IgG1 and IgA. Similarly, mRNA expression of interleukin (IL)-2, IL-12 and interferon-gamma in the gastric mucosa of S. typhimurium-immunized mice was significantly higher than that of PBS controls both before and after challenge. Moreover, S. typhimurium-immunized mice were characterized by marked infiltration of lymphocyte and mononuclear cells in the gastric mucosa after challenge. IL-4 and IL-10 were not detected in any of the three groups. IL-6 expression was increased in the PBS group compared with the S. typhimurium-immunized groups after challenge. CONCLUSIONS: This study demonstrates that oral immunization of mice with catalase delivered by an attenuated S. typhimurium strain offers protection against H. pylori infection. This protective immunity was mediated through a predominantly Th1-type response and was associated with post-immunization gastritis.

Animals↗

PubMed2003

Rapid direct method for monitoring antibiotics in a mouse model of bacterial biofilm infection.

We have developed a rapid, continuous method for monitoring the effectiveness of several antibacterial agents in real time, noninvasively, by using a recently described mouse model of chronic biofilm infection (J. L. Kadurugamuwa et al., Infect. Immun. 71:882-890, 2003), which relies on biophotonic imaging of bioluminescent bacteria. To facilitate real-time monitoring of infection, we used a Staphylococcus aureus isolate that was made bioluminescent by inserting a modified lux operon into the bacterial chromosome. This bioluminescent reporter bacterium was used to study the antimicrobial effects of several antibiotics belonging to different molecular families. Treatment with rifampin, tobramycin, and ciprofloxacin was started 7 days after subcutaneous implantation of catheters precolonized with 10(4) CFU of S. aureus. Three different doses of antibiotics were administered twice a day for 4 consecutive days. The number of metabolically active bacteria in untreated mice and the tobramycin- and ciprofloxacin-treated groups remained relatively unchanged over the 4-week observation period, indicating poor efficacies for tobramycin and ciprofloxacin. A rapid dose-dependent decline in metabolic activity in rifampin-treated groups was observed, with almost a 90% reduction after two doses and nearly undetectable levels after three doses. The disappearance of light emission correlated with colony counts. After the final treatment, cell numbers rebounded as a function of concentration in a time-dependent manner. The staphylococci isolated from the catheters of mice treated with rifampin were uniformly resistant to rifampin but retained their in vitro susceptibilities to tobramycin and ciprofloxacin. Since the metabolic activities of viable cells and a postantibiotic effect could be detected directly on the support matrix nondestructively and noninvasively, the methodology is specifically appealing for investigating the effects of antibiotics on biofilms in vivo. Moreover, our study points to the possible use of biophotonic imaging for the detection of the development of resistance to therapeutic agents during treatment of chronic infections in vivo.

Animals↗

PubMed2003

Real-time monitoring of bacterial infection in vivo: development of bioluminescent staphylococcal foreign-body and deep-thigh-wound mouse infection models.

Staphylococcal infections associated with catheter and prosthetic implants are difficult to eradicate and often lead to chronic infections. Development of novel antibacterial therapies requires simple, reliable, and relevant models for infection. Using bioluminescent Staphylococcus aureus, we have adapted the existing foreign-body and deep-wound mouse models of staphylococcal infection to allow real-time monitoring of the bacterial colonization of catheters or tissues. This approach also enables kinetic measurements of bacterial growth and clearance in each infected animal. Persistence of infection was observed throughout the course of the study until termination of the experiment at day 16 in a deep-wound model and day 21 in the foreign-body model, providing sufficient time to test the effects of antibacterial compounds. The usefulness of both animal models was assessed by using linezolid as a test compound and comparing bioluminescent measurements to bacterial counts. In the foreign-body model, a three-dose antibiotic regimen (2, 5, and 24 h after infection) resulted in a decrease in both luminescence and bacterial counts recovered from the implant compared to those of the mock-treated infected mice. In addition, linezolid treatment prevented the formation of subcutaneous abscesses, although it did not completely resolve the infection. In the thigh model, the same treatment regimen resulted in complete resolution of the luminescent signal, which correlated with clearance of the bacteria from the thighs.

Abscess↗

PubMed2003

Direct continuous method for monitoring biofilm infection in a mouse model.

We have developed a rapid, continuous method for real-time monitoring of biofilms, both in vitro and in a mouse infection model, through noninvasive imaging of bioluminescent bacteria colonized on Teflon catheters. Two important biofilm-forming bacterial pathogens, Staphylococcus aureus and Pseudomonas aeruginosa, were made bioluminescent by insertion of a complete lux operon. These bacteria produced significant bioluminescent signals for both in vitro studies and the development of an in vivo model, allowing effective real-time assessment of the physiological state of the biofilms. In vitro viable counts and light output were parallel and highly correlated (S. aureus r = 0.98; P. aeruginosa r = 0.99) and could be maintained for 10 days or longer, provided that growth medium was replenished every 12 h. In the murine model, subcutaneous implantation of the catheters (precolonized or postimplant infected) was well tolerated. An infecting dose of 10 (3) to 10 (5) CFU/catheter for S. aureus and P. aeruginosa resulted in a reproducible, localized infection surrounding the catheter that persisted until the termination of the experiment on day 20. Recovery of the bacteria from the catheters of infected animals showed that the bioluminescent signal corresponded to the CFU and that the lux constructs were highly stable even after many days in vivo. Since the metabolic activity of viable cells could be detected directly on the support matrix, nondestructively, and noninvasively, this method is especially appealing for the study of chronic biofilm infections and drug efficacy studies in vivo.

Animals↗

PubMed2003

Assessment of immunoreactive synthetic peptides from the structural proteins of severe acute respiratory syndrome coronavirus.

BACKGROUND: The widespread threat of severe acute respiratory syndrome (SARS) to human life has spawned challenges to develop fast and accurate analytical methods for its early diagnosis and to create a safe antiviral vaccine for preventive use. Consequently, we thoroughly investigated the immunoreactivities with patient sera of a series of synthesized peptides from SARS-coronavirus structural proteins. METHODS: We synthesized 41 peptides ranging in size from 16 to 25 amino acid residues of relatively high hydrophilicity. The immunoreactivities of the peptides with SARS patient sera were determined by ELISA. RESULTS: Four epitopic sites, S599, M137, N66, and N371-404, located in the SARS-coronavirus S, M, and N proteins, respectively, were detected by screening synthesized peptides. Notably, N371 and N385, located at the COOH terminus of the N protein, inhibited binding of antibodies to SARS-coronavirus lysate and bound to antibodies in >94% of samples from SARS study patients. N385 had the highest affinity for forming peptide-antibody complexes with SARS serum. CONCLUSIONS: Five peptides from SARS structural proteins, especially two from the COOH terminus of the N protein, appear to be highly immunogenic and may be useful for serologic assays. The identification of these antigenic peptides contributes to the understanding of the immunogenicity and persistence of SARS coronavirus.

Animals↗

PubMed2003

Effects of cholesterol on the phenotype of rabbit bile duct fibroblasts.

AIM: To investigate how cholesterol (Ch) can affect the phenotype of bile duct fibroblasts of New Zealand rabbits. METHODS: 16 rabbits were divided randomly into two groups: the control group and the experiment group. The rabbits in experiment group were fed with hypercholesterol diet for 8 weeks. Bile duct was dissociated from rabbits and prepared for transmission electron microscopy. The purified bile duct fibroblasts were cultured and divided randomly into three groups: control group, Ch middle concentration group (0.6 g/L), Ch high concentration group (1.2 g/L). After incubated for 72 h, the fibroblasts were made into specimens for transmission electron microscopy. The expression of alpha-actin in bile duct fibroblasts was measured by means of laser scanning confocal microscopy. RESULTS: With the transmission electron microscopy, the normal bile duct fibroblasts were shuttle-shaped, and there were abundant rough endoplasmic reticulums (RER), but few mitochondria or microfilaments in cytoplasm. This is the typical phenotype of fibroblasts. Bile duct fibroblasts of hypercholesterolemic rabbits were observed. by the transmission electron microscopy Rough endoplasmic reticulums were significantly reduced, with a lot of microfilament bundles or stress fibers appeared in cytoplasm, especially under plasma membrane. Dense bodies were scattered within these bundles. Macula densas and discontinuous sarcolemma were found under plasma membrane. It suggested that the bile duct fibroblasts of hypercholesterolemic rabbits presented the phenotype of smooth muscle cell. The cultured bile duct fibroblasts also had typical phenotype of fibroblasts. After stimulated by middle concentration cholesterol (0.6 g/L) for 72 h, there appeared lots of microfilaments in cytoplasm, but without dense body, macula densa and discontinuous sarcolemma. Observed with confocal microscopy, there were many regular bundles of microfilaments in fibroblasts treated with middle concentration ch (0.6 g/L) and the expression of alpha-actin was significantly increased. The average fluorescence value of middle concentration group was 1 628+/-189 (P<0.01 vs control group). Microfilaments and the expression of alpha-actin were greatly decreased in fibroblasts of high concentration group (1.2 g/L). The average fluorescence value of high concentration group was 1 427+/-153 (P<0.05 vs middle concentration group). There were a lower expression of alpha-actin and few microfilaments in bile duct fibroblasts of control group with an average fluorescence value of 1 224+/-138. CONCLUSION: Cholesterol can make bile duct fibroblasts have the phenotypic characteristics of smooth muscle cell both in vitro and in vivo and this effect is more significant in vivo. The effect is probably associated with some other factors besides cholesterol.

Animals↗

PubMed2003

Application of modified two-cuff technique and multiglycosides tripterygium wilfordii in hamster-to-rat liver xenotransplant model.

AIM: To modify the hamster-to-rat liver xenotransplant technique to prevent postoperative complications, and to study the inhibiting effect of multiglycosides tripterygium wilfordii (T(II)) on immune rejection. METHODS: Female golden hamsters and inbred male Wistar rats were used as donors and recipients, respectively. One hundred and twelve orthotopic liver xenotransplants were performed by Kamada's cuff technique with modifications. Over 72 hour survival of the animal after operation was considered as a successful operation. When the established surgical model became stable, 30 of the latest 42 cases were divided into untreated control group (n=15) and T(II) group (n=15) at random. Survival of recipients was observed. Liver specimens were collected at 2 and 72 h from the operated animals and postmortem, respectively, for histological study. RESULTS: The successfully operative rate of the 30 operations was 80 %, and the survival of the control and T(II) group was 7.1+/-0.35 was days and 7.2+/-0.52 days, respectively (t=0.087,P=0.931). The rate of conjunctival hyperemia in control group (100 %) differed significantly from that (31 %) in T(II) group (P=0.001). Rejection did not occur in both groups within 2 h postoperatively, but became obvious in control group at 72 h after surgery and mild in T(II) group. Although rejections were obvious in both groups at death of recipients, it was less severe in T(II) group than in control group. CONCLUSION: This modified Kamada's technique can be used to establish a stable hamster-to-rat liver xenotransplant model. Monotherapy with multiglycosides tripteryguiumwilfordii (30 mg x kg(-1) x d(-1)) suppresses the rejection mildly, but fails to prolong survival of recipients.

Animals↗

PubMed2003

Promoter hypermethylation of cyclooxygenase-2 in gastric carcinoma.

Overexpression of cyclooxygenase-2 (COX-2) is associated with loss of apoptosis, enhancement of proliferation and tumorigenesis. The role of promoter methylation in the transcriptional silencing of cox-2 gene in human gastric cancer is less determined. We investigated 5 gastric cancer cell lines and 58 primary gastric carcinomas for the presence of promoter hypermethylation in cox-2 gene. Combined methylation-specific polymerase chain reaction analysis and bisulfite sequencing analysis revealed that the cox-2 promoter was methylated in 2 of the gastric cancer cell lines. Treatment with 5-aza-2'-deoxycytidine, a DNA methyltransferase inhibitor, induced COX-2 expression in the methylated gastric cancer cell line. Among the 58 primary gastric cancers, hypermethylation was detected in 25 (43.1%) cases. However, none of the normal gastric tissues showed methylation in cox-2. Promoter hypermethylation was associated with loss of protein expression as determined by immunostaining (p=0.005). Our results indicate that hypermethylation of the CpG island in the cox-2 gene is a major mechanism that mediates transcriptional silencing in a subset of gastric cancers. Thus, gastric cancers with methylation in cox-2 may not be good candidates for treatment with specific COX-2 inhibitors.

Adenocarcinoma↗

PubMed2003

Tibetan patients with essential hypertension caused by underlying oxidative metabolism dysfunction and depressed nitric oxide synthesis.

OBJECTIVE: To assess the role of oxidative metabolism and nitric oxide synthesis for elucidating their pathophysiological mechanisms in a Tibetan patient with essential hypertension. METHODS: The serum levels of total superoxide dismutase (T-SOD), malondialdehyde (MDA), total antioxidant capacity (T-AOC), nitric oxide (NO) and nitric oxide synthase (NOS) were assayed in sixty native Tibetans (thirty hypertensive patients and thirty healthy volunteers as control). RESULTS: The levels of T-SOD, T-AOC, NO and NOS were significantly lower in the patient group than in the control group (P < 0.01); MDA was significantly higher in the patient group than in the control group (P < 0.01). The level of MDA had a strong negative correlation with T-SOD, T-AOC, NO and NOS (r = -0.82, -0.76, -0.79, -0.73, respectively, P < 0.001 for all). CONCLUSION: Tibetan patients with essential hypertension (EH) may have underlying oxidative metabolism dysfunction and depressed NO synthesis, both responsible for the hypertensive process.

Adult↗

PubMed2003

Highly efficient expression, purification of recombinant LTB protein and its activity against mucosal immunoadjuvant by nasal immunization.

OBJECTIVE: To develop an efficient expression, purification system of recombinant Escherichia coli heat-labile enterotoxin B subunit (rLTB) and study its activity against mucosal immunoadjuvant by nasal immunization. METHODS: A recombinant, pMMB68-LTB was generated by cloning the LTB cDNA fragment into an expression vector (pMMB68) and transformed it into the host strain marine vibrio VSP60. The relevant target protein was identified using SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot. Sephacryl S-100 gel filtration chromatography was carried out for purification of rLTB in engineering bacteria VSP60. BALB/c mice received hen egg lysozyme (HEL) alone or combined with rLTB by nasal administration. After three times immunization, IgG and IgA antibody levels in serum or small intestine wash samples were determined using ELISA. RESULTS: rLTB protein was highly expressed in VSP60. After gel filtration with Sephacryl S-100, the purity of rLTB reached 98.1%, the yield rate was about 52%. After immunization, IgG and IgA antibody responses specific to HEL in system and mucosa of HEL + rLTB groups were significantly increased, compared with the HEL alone group (P < 0.001). CONCLUSIONS: A set of protocols for large-scale rLTB preparation has been established, which is simple, efficient and applicable. The rLTB protein we prepared was proved to be a powerful mucocal adjuvant, which could greatly enhance systemic and mucosal immune responses to nasally co-administered antigen.

Adjuvants, Immunologic↗

PubMed2003

[Early diagnosis of pancreatic cancer is essential to improving the effect of treatment].

OBJECTIVES: To explore the relation between tumor TNM of pancreatic cancer and treatment, and to summarize the experience in diagnosis and treatment of pancreatic cancer. METHODS: The data on 321 patients with pancreatic cancer treated at our hospital between January 1990 and December 2000 were reviewed retrospectively. Radical resection and survival for various TNM stages were analyzed. RESULTS: The rates of radical resection for stage I, stage II, stage III, stage IVA, and stage IVB were 100%, 100%, 82.6%, 12.3% and 2.1% respectively. The 1-, 3- and 5-year survivals of stage I, II were 73.3%, 40.0% and 30.0% respectively, and higher than those of other groups. CONCLUSIONS: The patients with pancreatic cancer diagnosed early can undergo radical resection. The elevation of early diagnosis rate is significant for the improvement of survival.

Adolescent↗

PubMed2003

[Somatostatin mRNA expression in hippocampus of diabetic rats model].

OBJECTIVE: To investigate the relationship between diabetes and somatostatin (SOM). METHODS: We established a streptozocin-induced diabetic rats model and studied the changes of SOM mRNA in hippocampi of diabetic and normal rats by using in situ hybridication and computer image analysis. We studied the mechanism of chronic diabetes encephalopathy by observing the changes of somatostatin mRNA in the hippocampus of diabetic rats was studied. RESULT: The number, light density and average area of positive cells in dentate gyrus area of hippocampus in diabetes model were reduced significantly as compared with normal rats (P < 0.01). CONCLUSION: A decline in SOM mRNA expression may play a role in chronic diabetes encephalopathy because of SOM effect in brain.

Animals↗

PubMed2003

[Changes of plasma fibrinolysis system and the effect of captopril in high altitude pulmonary edema].

OBJECTIVE: To investigate the changes of plasma fibrinolysis system and the effect of captopril in patients with high altitude pulmonary edema. METHODS: The plasma levels of tissue plasminogen activator (tPA) and plasminogen activator inhibitor-1 (PAI-1) were measured before and after treatment in the captopril-group (group A, 35 cases) and the routine-group (group B, 37 cases) of patients with HAPE, while 20 healthy volunteers served as the control (group C). RESULTS: The plasma level of tPA was (0.40 +/- 0.14) x 10(3) IU/L in group A vs (0.39 +/- 0.19) x 10(3) IU/L in group B before treatment, and (0.58 +/- 0.13) x 10(3) IU/L vs (0.49 +/- 0.16) x 10(3) IU/L after treatment, and (0.59 +/- 0.17) x 10(3) IU/L in group C. The differences were significant both before and after treatment between group A and group B (P < 0.01, P < 0.05). While PAI-1 was (6.6 +/- 1.8) x 10(3) AU/L in group A vs (6.6 +/- 1.6) x 10(3) AU/L in group B before treatment, and (4.9 +/- 1.5) x 10(3) AU/L vs (5.8 +/- 1.7) x 10(3) AU/L after treatment, and (4.9 +/- 1.3) x 10(3) AU/L in group C. The differences were significant both before and after treatment between group A and group B (P < 0.01, P < 0.05). CONCLUSION: Patients with HAPE may present a disturbance of the fibrinolysis system, which could be reversed by captopril.

Adolescent↗