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Biomedical subjects

L Wang

Publications and source records attributed to L Wang.

At least 1,297 records · Page 72Linked to original sources
PubMed1998

Escherichia coli clone Sonnei (Shigella sonnei) had a chromosomal O-antigen gene cluster prior to gaining its current plasmid-borne O-antigen genes.

O antigen is part of the lipopolysaccharide present in the outer membrane of gram-negative bacteria. The surface-exposed O antigen is subject to selection by the host immune system, which may account for the maintenance of many different O-antigen forms. Characteristically, all genes specific to O-antigen synthesis are clustered in a region close to the his and gnd genes on the chromosome of Escherichia coli and related species. Shigella sonnei, essentially a clone of E. coli (E. coli clone Sonnei), is an important human pathogen and is unusual in that its O-antigen gene cluster is located on a plasmid. Our results suggest that it once had a normal chromosomal O-antigen gene cluster which has been largely deleted. We suggest that the O antigen encoded by the plasmid-borne genes offered a selective advantage in adapting to a new environment and that the chromosomal O-antigen genes were eventually inactivated. We also identified, by PCR and sequencing, a potential ancestor of E. coli Sonnei among the 166 known E. coli serotype strains.

Bacterial Proteins↗
PubMed1998

Multiple in vivo roles for the -12-region elements of sigma 54 promoters.

Alignment of sigma 54-dependent promoters indicates conservation of two sequence elements. Six nucleotides in the downstream -12 element were mutated individually to each nonconsensus nucleotide. mRNA levels were measured in vivo for each promoter under strongly activating conditions. The results showed that the consensus sequence was not the strongest promoter. Instead, the -12 consensus element consists of two subregions that behave differently when mutated. Single changes in the upstream TTT consensus subregion can lead to increases in transcription, whereas single changes in the downstream GC(A/T) can lead to decreases in transcription. Selected double mutations with changes in both subregions were constructed and studied in vivo. No double mutation increased promoter strength, and some decreased it. Mutant promoters were also assayed under nonactivating conditions in vivo. No mRNA was detected in 23 of the 24 promoters tested. However, one double mutant showed substantial levels of transcript, indicating that the -12 sequence was capable of specifying basal transcription under nonactivating conditions. Overall, the results show that the -12 region has multiple roles in transcription in vivo, including modulating both basal and induced RNA levels.

Consensus Sequence↗
PubMed1998

Identification of the fucose synthetase gene in the colanic acid gene cluster of Escherichia coli K-12.

GDP-L-fucose, the substrate for fucosyltransferases for addition of fucose to polysaccharides or glycoproteins in both procaryotes and eucaryotes, is made from GDP-D-mannose. L-Fucose is a component of bacterial surface antigens, including the extracellular polysaccharide colanic acid produced by most Escherichia coli strains. We previously sequenced the E. coli colanic acid gene cluster and identified one of the GDP-L-fucose biosynthetic pathway genes, gmd. We report here the identification of the gene (fcl), located downstream of gmd, encoding the fucose synthetase.

Amino Acid Sequence↗
PubMed1998

Sequencing of Escherichia coli O111 O-antigen gene cluster and identification of O111-specific genes.

Shiga toxin (Stx)-producing Escherichia coli strains of serogroup O111 are the most frequently isolated non-O157 strains causing outbreaks of gastroenteritis with hemolytic-uremic syndrome. The O111 O-antigen gene cluster had been cloned and about half of it has been sequenced; we have now sequenced the remainder of the gene cluster, which is 12.5 kb in length and which comprises 11 genes. On the basis of sequence similarity, we have identified all the O-antigen genes expected, including five sugar biosynthetic pathway genes, three transferase genes, the O-unit flippase gene, and the O-antigen polymerase gene. By PCR testing with E. coli strains representing all 166 O-antigen forms, some randomly selected gram-negative bacteria, and Salmonella enterica serovar Adelaide, we showed that four O-antigen genes are highly specific to O111. This work provides the basis for a sensitive test for the rapid detection of E. coli O111. This is important both for decisions related to patient care, because early treatment may reduce the risk of life-threatening complications, and for the detection of sources of contamination.

Antigens, Bacterial↗
PubMed1998

Herpes simplex virus type 1 glycoprotein gC mediates immune evasion in vivo.

Many microorganisms encode proteins that interact with molecules involved in host immunity; however, few of these molecules have been proven to promote immune evasion in vivo. Herpes simplex virus type 1 (HSV-1) glycoprotein C (gC) binds complement component C3 and inhibits complement-mediated virus neutralization and lysis of infected cells in vitro. To investigate the importance of the interaction between gC and C3 in vivo, we studied the virulence of a gC-null strain in complement-intact and C3-deficient animals. Using a vaginal infection model in complement-intact guinea pigs, we showed that gC-null virus grows to lower titers and produces less severe vaginitis than wild-type or gC rescued virus, indicating a role for gC in virulence. To determine the importance of complement, studies were performed with C3-deficient guinea pigs; the results demonstrated significant increases in vaginal titers of gC-null virus, while wild-type and gC rescued viruses showed nonsignificant changes in titers. Similar findings were observed for mice where gC null virus produced significantly less disease than gC rescued virus at the skin inoculation site. Proof that C3 is important was provided by studies of C3 knockout mice, where disease scores of gC-null virus were significantly higher than in complement-intact mice. The results indicate that gC-null virus is approximately 100-fold (2 log10) less virulent that wild-type virus in animals and that gC-C3 interactions are involved in pathogenesis.

Animals↗
PubMed1998

In vivo immune evasion mediated by the herpes simplex virus type 1 immunoglobulin G Fc receptor.

Herpes simplex virus (HSV) glycoproteins gE and gI form an immunoglobulin G (IgG) Fc receptor (FcgammaR) that binds the Fc domain of human anti-HSV IgG and inhibits Fc-mediated immune functions in vitro. gE or gI deletion mutant viruses are avirulent, probably because gE and gI are also involved in cell-to-cell spread. In an effort to modify FcgammaR activity without affecting other gE functions, we constructed a mutant virus, NS-gE339, that has four amino acids inserted into gE within the domain homologous to mammalian IgG FcgammaRs. NS-gE339 expresses gE and gI, is FcgammaR-, and does not participate in antibody bipolar bridging since it does not block activities mediated by the Fc domain of anti-HSV IgG. In vivo studies were performed with mice because the HSV-1 FcgammaR does not bind murine IgG; therefore, the absence of an FcgammaR should not affect virulence in mice. NS-gE339 causes disease at the skin inoculation site comparably to wild-type and rescued viruses, indicating that the FcgammaR- mutant virus is pathogenic in animals. Mice were passively immunized with human anti-HSV IgG and then infected with mutant or wild-type virus. We postulated that the HSV-1 FcgammaR should protect wild-type virus from antibody attack. Human anti-HSV IgG greatly reduced viral titers and disease severity in NS-gE339-infected animals while having little effect on wild-type or rescued virus. We conclude that the HSV-1 FcgammaR enables the virus to evade antibody attack in vivo, which likely explains why antibodies are relatively ineffective against HSV infection.

Animals↗
PubMed1998

Association of petrochemical exposure with spontaneous abortion.

OBJECTIVES: To assess the association between petrochemical exposure and spontaneous abortion, a retrospective epidemiological study in a large petrochemical complex in Beijing, China was conducted. METHODS: Plant employment records identified 3105 women who were married, were 20-44 years of age, and had never smoked. Of those, 3070 women (98.8%) reported at least one pregnancy. From this group, 2853 (93%) of the women participated in the study. According to their plant employment record, about 57% of these women workers reported occupational exposure to petrochemicals during the first trimester of their pregnancy. Trained interviewers administered a standardised questionnaire to this group of women and their husbands, collecting information on reproductive history, pregnancy outcomes, employment history, occupational exposure, smoking habits, alcohol consumption, indoor air pollution, and demographic variables. The results from the womens' first pregnancies were analysed. RESULTS: There was a significantly increased risk of spontaneous abortion for women working in all of the production plants with frequent exposure to petrochemicals (8.8%; range of 5.8%-9.8%) compared with those working in nonchemical plants (2.2%; range of 0.0%-7.1%). Also, when a comparison was made between exposed and non-exposed groups within each plant, exposure to petrochemicals was consistently associated with an increased risk of spontaneous abortion. The overall odds ratio (OR) was 2.7 (95% confidence interval (95% CI) 1.8 to 3.9) after adjusting for potential confounders. When the analysis was performed with the exposure information obtained from the women' interview responses for (self reported) exposures, the estimated OR for spontaneous abortions was 2.9 (95% CI 2.0 to 4.0). The analysis was repeated by excluding those 452 women who provided inconsistent reports between recalled exposure and work history, and a comparable risk of spontaneous abortion (OR 2.9; 95% CI 2.0 to 4.4) was found. In analyses for exposure to specific chemicals, an increased risk of spontaneous abortion was found with exposure to most chemicals, and the results for benzene (OR 2.5; 95% CI 1.7 to 3.7), gasoline (OR 1.8; 95% CI 1.1 to 2.9), and hydrogen sulphide (OR 2.3; 95% CI 1.2 to 4.4) were significant. CONCLUSION: An increased risk of spontaneous abortion was found associated with the exposure to petrochemicals, including benzene, gasoline, and hydrogen sulphide.

Abortion, Spontaneous↗
PubMed1998

Choledocholithiasis: evaluation of MR cholangiography for diagnosis.

PURPOSE: To evaluate the test performance of magnetic resonance (MR) cholangiography for help in diagnosing choledocholithiasis. MATERIALS AND METHODS: Fast spin-echo MR cholangiography was performed by using a torso multicoil array in 110 patients suspected of having bile duct obstruction. Axial and coronal images were reviewed by two observers who were blinded to results of direct cholangiography and final diagnoses. The final diagnosis was established by using direct cholangiographic (n = 103) or surgical (n = 7) findings. RESULTS: Of the 110 patients, 30 (27%) had choledocholithiasis, and 80 (73%) did not. Reviewer 1 used MR cholangiograms to achieve a sensitivity of 90%, specificity of 100%, positive predictive value of 100%, negative predictive value of 96%, and overall accuracy of 97%. Reviewer 2 achieved a sensitivity of 90%, specificity of 93%, positive predictive value of 82%, negative predictive value of 96%, and overall accuracy of 92%. Interobserver agreement for MR cholangiograms was 93% (kappa = 0.82). CONCLUSION: MR cholangiography exhibited excellent test performance and resulted in excellent interobserver agreement for the diagnosis of choledocholithiasis.

Cholangiography↗
PubMed1998

Regulation of c-Jun NH2-terminal kinases in isolated canine gastric parietal cells.

c-Jun NH2-terminal kinases (JNKs) are protein kinases that are activated by a wide variety of extracellular signals. This study investigated the expression and regulation of JNKs in isolated gastric canine parietal cells. Western blot analysis of cell lysates from highly purified (>95%) parietal cells with an antibody recognizing JNK1 and to a lesser degree JNK2 revealed the presence of two bands of 46 and 54 kDa, respectively. JNK1 activity was quantitated by immunoprecipitation and in-gel kinase assays. Of the different agents tested, carbachol was the most potent inducer of JNK1 activity, whereas histamine and epidermal growth factor induced weaker responses. The proinflammatory cytokine tumor necrosis factor-alpha stimulated JNK1 but had no effect on extracellular signal-regulated kinase (ERK2) induction, suggesting that activation of JNK1 might represent an important event in mediation of the inflammatory response in the stomach. The action of carbachol was dose (0.1-100 microM) and time dependent, with a maximal stimulatory effect (fourfold) detected after 30 min of incubation and sustained for 2 h. Addition of the specific protein kinase C (PKC) inhibitor GF109203X did not affect the stimulatory action of carbachol. The intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N', N'-tetraacetic acid-AM inhibited carbachol induction of JNK1 activity by 60%. Thapsigargin (1 microM), an intracellular Ca2+-rising agent, induced JNK1 activity more than threefold. Carbachol activation of JNK1 resulted in induction of c-Jun (protein) transcriptional activity and in stimulation of parietal cell mRNA content of c-jun. In conclusion, our data indicate that carbachol induces JNK activity in gastric parietal cells via intracellular Ca2+-dependent, PKC-independent pathways, leading to induction of c-jun gene expression via phosphorylation and transcriptional activation of c-Jun.

Animals↗
PubMed1998

Sepsis in mice stimulates muscle proteolysis in the absence of IL-6.

We tested the role of interleukin-6 (IL-6) in sepsis-induced muscle proteolysis by determining ubiquitin mRNA levels and protein breakdown rates in incubated extensor digitorum longus muscles from septic and sham-operated IL-6 knockout and wild-type mice. In addition, the effect of treatment of mice with human recombinant IL-6 on muscle protein breakdown rates was determined. Finally, protein breakdown rates were measured in myotubes treated for up to 48 h with different concentrations of IL-6. Sepsis in wild-type mice resulted in an approximately ninefold increase in plasma IL-6 levels, whereas IL-6 was not detectable in plasma of sham-operated or septic IL-6 knockout mice. Total and myofibrillar muscle protein breakdown rates were increased by approximately 30% and threefold, respectively, in septic IL-6 wild-type mice with an almost identical response noted in septic IL-6 knockout mice. Ubiquitin mRNA levels determined by dot blot analysis were increased during sepsis in muscles from both IL-6 knockout and wild-type mice, although the increase was less pronounced in IL-6 knockout than in wild-type mice. Treatment of normal mice or of cultured L6 myotubes with IL-6 did not influence protein breakdown rates. The present results suggest that IL-6 does not regulate muscle proteolysis during sepsis.

Animals↗
PubMed1998

NO does not mediate inhibitory neural responses in sheep airway and bronchial vascular smooth muscle.

Endogenous nitric oxide (NO) influences acetylcholine-induced bronchovascular dilation in sheep and is a mediator of the airway smooth muscle inhibitory nonadrenergic, noncholinergic neural response in several species. This study was designed to determine the importance of NO as a neurally derived modulator of ovine airway and bronchial vascular smooth muscle. We measured the response of pulmonary resistance (RL) and bronchial blood flow (Qbr) to vagal stimulation in 14 anesthetized, ventilated, open-chest sheep during the following conditions: 1) control; 2) infusion of the alpha-agonist phenylephrine to reduce baseline Qbr by the same amount as would be produced by infusion of Nomega-nitro-L-arginine (L-NNA), a NO synthase inhibitor; 3) infusion of L-NNA (10(-2) M); and 4) after administration of atropine (1.5 mg/kg). The results showed that vagal stimulation produced an increase in RL and Qbr in periods 1, 2, and 3 (P < 0.01) that was not affected by L-NNA. After atropine was administered, there was no increase in Qbr or RL. In vitro experiments on trachealis smooth muscle contracted with carbachol showed no effect of L-NNA on neural relaxation but showed a complete blockade with propranolol (P < 0.01). In conclusion, the vagally induced airway smooth muscle contraction and bronchial vascular dilation are not influenced by NO, and the sheep's trachealis muscle, unlike that in several other species, does not have inhibitory nonadrenergic, noncholinergic innervation.

Airway Resistance↗
PubMed1998

T1 hypointense lesion load in secondary progressive multiple sclerosis: a comparison of pre versus post contrast loads and of manual versus semi automated threshold techniques for lesion segmentation.

Magnetic resonance imaging (MRI) is increasingly being used as a monitoring tool for disease activity in therapeutic trials in multiple sclerosis. There is, however, only a limited relationship between MRI findings and clinical outcome measurements. It has been suggested that hypointense lesion load on T1 weighted imaging has a better correlation with disability than the more conventional T2 hyper intense lesion load. This study was undertaken to (i) evaluate different measurement techniques used to quantify T1 hypointense lesion load, and (ii) to compare lesion load as measured using different parameters and disability. Twenty-five patients with secondary progressive multiple sclerosis, mean age of 40 years (23-57), mean EDSS 5.7 (4-7) were analysed. T2 lesion load on FSE correlated well with both the hypointense lesion load on T1 pre-gadolinium (r = 0.8, P < 0.0001) and T1 post-gadolinium (r = 0.8, P < 0.0001) but less so with the enhancing lesion load (r = 0.4, P < 0.05). There was a very strong correlation with T1 hypo-intense lesion volume pre and post gadolinium (r = 0.96, P < 0.001). However, the EDSS was not correlated with the T2 lesion load (r = -0.27, P = 0.2), T1 pre-gadolinium load (r = -0.3, P = 0.1), T1 post gadolinium load (r = -0.4, P = 0.7) and enhancing lesion load (r = -0.28, P = 0.2), or with the degree of hypointensity of T1 weighted images determined using the threshold technique. There is a strong correlation between T1 hypointense lesion volume both pre and post gadolinium and also between T1 and T2 lesion volumes.

Adult↗
PubMed1998

Insulin-like growth factor I modulates induction of apoptotic signaling in H9C2 cardiac muscle cells.

Insulin-like growth factor I (IGF-I) is an important survival growth factor that has been shown to inhibit apoptosis, but the effects of IGF-I on apoptotic signaling remain largely unknown. To investigate IGF-I actions on apoptosis of H9C2 cardiac muscle cells, we have defined the effects of IGF-I on Bcl-2, Bax, caspase 3, DNA fragmentation, and cell survival. The abundance of Bcl-2 and Bax was determined with immunoblotting, and the activities of caspase 3 were assayed with the labeled substrate DEVD-p-nitroanilide. The occurrence of apoptosis was determined by electrophoresis of labeled DNA fragments and by in situ terminal deoxynucleotidyl transferase UTP nick end labeling assay. We found that apoptosis of H9C2 cells, induced by serum withdrawal and doxorubicin, was associated with the induction of Bax and the activation of caspase 3. IGF-I partially inhibited Bax induction, caspase 3 activation, DNA fragmentation, and enhanced cell survival. Interestingly, there is a compensatory rise in the abundance of Bcl-2 upon serum withdrawal and doxorubicin treatment, and IGF-I stimulation resulted in decreased induction of Bcl-2. These results suggest that serum withdrawal- and doxorubicin-induced apoptosis of H9C2 cells probably in part resulted from induction of Bax and caspase 3, and IGF-I inhibited apoptosis by attenuating Bax induction and caspase 3 activation.

Apoptosis↗
PubMed1998

A directed search for quantitative trait loci on chromosomes 4 and 7 in pigs.

Improvements in the porcine genetic map and availability of resource families to study performance traits in pigs have made it possible to re-examine previous findings that linked certain traits to genes or chromosomal regions. Previous studies suggested that chromosomes 4 and 7 may be associated with growth and performance traits. To confirm these previous results, an interval mapping-regression approach was used to determine whether quantitative trait loci (QTL) exist in the Iowa State University reference/resource families. Traits measured were birth weight; body weight at 21 d; weaning weight (weight at 42 d); average daily gain; backfat at the first, 10th, lumbar, and last ribs and average backfat thickness; loin eye area; meat color; marbling; and firmness. The total number of F2 pigs used ranged from 241 to 330 and came from five Chinese x American resource families. Five markers (S0001, SW871, S0175, S0214, and SW445) were genotyped and mapped on chromosome 4, and so were 10 markers (S0064, tumor necrosis factor alpha [TNFalpha], S0102, S0078, S0158, S0066, SW304, SW1083, S0101, and S0212) on chromosome 7. Data were analyzed for each family (breed cross) separately and were also pooled. Experiment-wise thresholds were used to determine significance. Suggestive evidence of QTL on chromosomes 4 and 7 was observed for several traits in pooled and individual family analyses. Suggestive evidence of a QTL with a relatively large effect for average daily gain was detected on chromosome 4 in the pooled analysis. Significant (P < .05) evidence for QTL was seen on chromosome 7 for 10th-rib, last-rib, and average backfat thickness in the pooled data set in a region of the chromosome that was near TNFalpha. These results verify in part that chromosomes 4 and 7 contain QTL for growth and carcass traits.

Animals↗
PubMed1998

Combined effect of chemopreventive agent N-(4-hydroxyphenyl) retinamide (4-HPR) and gamma-radiation on bladder cancer cell lines.

The incidence of bladder cancer has increased in the United States during the past 50 years, consistent with increased exposure to bladder carcinogens in the environment and tobacco use. Although N-(4-hydroxyphenyl) retinamide (4-HPR), a retinoid derivative, has been used as a chemopreventive agent of bladder cancer in clinical trials, little is known about its mechanisms of action against bladder cancer cells. Previous studies suggest this chemopreventive agent may inhibit tumor growth by inducing apoptosis. To further investigate this putative effect, we examined the effect of 4-HPR and gamma-radiation and their combined effects in three selected bladder cancer cell lines. Indeed, 4-HPR induced apoptosis in these cell lines in a dose-dependent manner. A 2.5 microM dose of 4-HPR and 50 rad of gamma-irradiation induced about 10% increase in apoptotic cells, respectively. However, this low dose 4-HPR combined with low dose gamma-irradiation had a synergistic effect on apoptosis, in which apoptotic cells increased by more than 30%. The findings have potential clinical implications and warrant further investigations both in vitro and in vivo in bladder cancer.

Antineoplastic Agents↗
PubMed1998

Over-expression of c-fos mRNA in the hippocampal neurons in Alzheimer's disease.

OBJECTIVE: To analyze the relationship between the proto-oncogene c-fos change and neuronal degeneration in the hippocampus of the patients with Alzheimer's disease. METHODS: The post mortem human hippocampal tissues were divided into three groups, namely, the aged, the young and Alzheimer's disease (AD) groups. Each group consisted of 10 patients. The diagnosis of AD was made by clinical manifestation and argentatine (Bodían) staining. Patients of both the young and the aged groups had no neurological disorders. The proto-oncogene c-fos mRNA was investigated in the hippocampal neurons using the method of in situ hybridization. RESULTS: The optical density of stained area and the integral within proto-oncogene c-fos mRNA revealed a significant increase in the hippocampal neurons in cases of Alzheimer's disease as compared with the controls. CONCLUSIONS: The over-expression of the proto-oncogene c-fos might play a role in the pathological process of Alzheimer's disease. These changes might result from a suffering stage of the hippocampal neurons or from a compensatory mechanism in the surviving neurons which are not yet affected-by the pathological process.

Adult↗
PubMed1998

[Study on the characteristics of brucellosis on the Baicaopo Pasture].

To study the current situation and characteristics of brucellosis on Baicaopo Pasture, a sero-epidemiological survey was conducted among local people, animals together with nearby county livestocks from Breed-improvement Stations, Bingdi township and Rekejue township which are far away from the pasture. The results showed that the infection rates of brucellosis in humans and yaks on the Baieaopo Pasture were 31.03% and 47.19% respectively, apparent higher than those in other places. There were more infected cases among local veterinarians and herdsmen than among other jobs. Young adults seemed to be at most risk.

Adolescent↗