[Effects of organic fertilizer application on crop yield and soil properties in rice-wheat rotation system: A meta-analysis]. / 稻麦轮作体系下有机肥施用对作物产量和土壤性质影响的整合分析.

To clarify the effects of organic fertilizer application on crop yield and soil properties in rice-wheat rotation system in China, we carried out a meta-analysis to quantitatively evaluate the effects of organic fertilizer types (ordinary organic fertilizer, biochar, and straw), fertilization regimes (organic fertilizer alone, organic fertilizer + partial chemical fertilizer, and organic fertilizer + full amount of chemical fertilizer), and experiment duration (short term, medium term, and long term) on soil properties and the yield of rice and wheat, as well as their responses to soil conditions (acid, neutral, basic). Results showed that the application of organic fertilizer had similar yield-increase effect on rice yield (3.1%) and wheat yield (3.0%) compared to chemical fertilizer application alone. The effect of organic fertilizer application on soil quality was more obvious, significantly reducing soil bulk density by 5.7%, and increasing the concentrations of soil organic matter, total nitrogen, total phosphorus, alkali-hydrolyzable nitrogen, available phosphorus, available potassium, microbial biomass carbon, and microbial biomass nitrogen by 11.7%-38.4%. Among different types of organic fertilizer, the effects of ordinary organic fertilizer and biochar on soil properties improvement were better than straw. Compared to the organic fertilizer application alone, the effects of organic fertilizer combined with chemical fertilizer on crop yield was better, but poorer on soil property improvement. With the increasing duration of organic fertilizer application, crop yield and soil fertility gradually increased. Under the condition of acid soil, the effect of organic fertilizer application on crop yield was the best. The annual yield of rice and wheat showed significant negative correlation with soil bulk density, but a significant positive correlation with the concentrations of soil total nitrogen, available phosphorus, available potassium, and microbial biomass nitrogen.

[Nano-silicon Dioxide Affects Apoptosis of Alveolar Macrophages via PI3K/AKt Signaling Pathway].

OBJECTIVE: To investigate the effect of phosphatidyl inositol 3-kinase/protein kinase B (PI3K/AKt) signaling pathway on the apoptosis of alveolar macrophages (AM) induced by nano-silica (NS) dust. METHODS: After exposure to different concentrations of NS suspension, CCK-8 assay was used to detect the AM viability; the cellular morphology of apoptotic AM was observed under fluorescence microscopy; the apoptosis rate and mitochondrial transmembrane potential of cells were detected by flow cytometry before and after pretreatment with phosphatidyl inositol 3-kinase (PI3K) inhibitor LY294002; Western blot was used to detect the expression of apoptosis-related proteins Bax, Bcl-2, p-PI3K and p-AKt. RESLUTS: The survival rate of AM was decreased in a time-dose relationship after NS exposure. With LY294002 pretreatment, the mitochondrial transmembrane potential level and the expressions of p-PI3K, p-AKt and Bcl-2 were decreased, the expression of Bax and the apoptosis rate were increased. CONCLUSION: Our data suggested that the activation of PI3K/AKt signaling pathway played an important role in NS-induced apoptosis in alveolar macrophages.

Inhibition of AIM2 inflammasome activation by a novel transcript isoform of IFI16.

Mouse p202 is a disease locus for lupus and a dominant-negative inhibitor of AIM2 inflammasome activation. A human homolog of p202 has not been identified so far. Here, we report a novel transcript isoform of human IFI16-designated IFI16-ß, which has a domain architecture similar to that of mouse p202. Like p202, IFI16-ß contains two HIN domains, but lacks the pyrin domain. IFI16-ß is ubiquitously expressed in various human tissues and cells. Its mRNA levels are also elevated in leukocytes of patients with lupus, virus-infected cells, and cells treated with interferon-ß or phorbol ester. IFI16-ß co-localizes with AIM2 in the cytoplasm, whereas IFI16-α is predominantly found in the nucleus. IFI16-ß interacts with AIM2 to impede the formation of a functional AIM2-ASC complex. In addition, IFI16-ß sequesters cytoplasmic dsDNA and renders it unavailable for AIM2 sensing. Enforced expression of IFI16-ß inhibits the activation of AIM2 inflammasome, whereas knockdown of IFI16-ß augments interleukin-1ß secretion triggered by dsDNA but not dsRNA Thus, cytoplasm-localized IFI16-ß is functionally equivalent to mouse p202 that exerts an inhibitory effect on AIM2 inflammasome.

A novel transcript isoform of STING that sequesters cGAMP and dominantly inhibits innate nucleic acid sensing.

STING is a core adaptor in innate nucleic acid sensing in mammalian cells, on which different sensing pathways converge to induce type I interferon (IFN) production. Particularly, STING is activated by 2'3'-cGAMP, a cyclic dinucleotide containing mixed phosphodiester linkages and produced by cytoplasmic DNA sensor cGAS. Here, we reported on a novel transcript isoform of STING designated STING-ß that dominantly inhibits innate nucleic acid sensing. STING-ß without transmembrane domains was widely expressed at low levels in various human tissues and viral induction of STING-ß correlated inversely with IFN-ß production. The expression of STING-ß declined in patients with lupus, in which type I IFNs are commonly overproduced. STING-ß suppressed the induction of IFNs, IFN-stimulated genes and other cytokines by various immunostimulatory agents including cyclic dinucleotides, DNA, RNA and viruses, whereas depletion of STING-ß showed the opposite effect. STING-ß interacted with STING-α and antagonized its antiviral function. STING-ß also interacted with TBK1 and prevented it from binding with STING-α, TRIF or other transducers. In addition, STING-ß bound to 2'3'-cGAMP and impeded its binding with and activation of STING-α, leading to suppression of IFN-ß production. Taken together, STING-ß sequesters 2'3'-cGAMP second messenger and other transducer molecules to inhibit innate nucleic acid sensing dominantly.

Interplay between SIRT1 and hepatitis B virus X protein in the activation of viral transcription.

Hepatitis B virus (HBV) genome is organized into a minichromosome known as covalently closed circular DNA (cccDNA), which serves as the template for all viral transcripts. SIRT1 is an NAD+-dependent protein deacetylase which activates HBV transcription by promoting the activity of cellular transcription factors and coactivators. How SIRT1 and viral transactivator X protein (HBx) might affect each other remains to be clarified. In this study we show synergy and mutual dependence between SIRT1 and HBx in the activation of HBV transcription. All human sirtuins SIRT1 through SIRT7 activated HBV gene expression. The steady-state levels of SIRT1 protein were elevated in HBV-infected liver tissues and HBV-replicating hepatoma cells. SIRT1 interacted with HBx and potentiated HBx transcriptional activity on precore promoter and covalently closed circular DNA (cccDNA) likely through a deacetylase-independent mechanism, leading to more robust production of cccDNA, pregenomic RNA and surface antigen. SIRT1 and HBx proteins were more abundant when both were expressed. SIRT1 promoted the recruitment of HBx as well as cellular transcriptional factors and coactivators such as PGC-1α and FXRα to cccDNA. Depletion of SIRT1 suppressed HBx recruitment. On the other hand, SIRT1 recruitment to cccDNA was compromised when HBx was deficient. Whereas pharmaceutical agonists of SIRT1 such as resveratrol activated HBV transcription, small-molecule inhibitors of SIRT1 including sirtinol and Ex527 exhibited anti-HBV activity. Taken together, our findings revealed not only the interplay between SIRT1 and HBx in the activation of HBV transcription but also new strategies and compounds for developing antivirals against HBV.

ß-TrCP-mediated ubiquitination and degradation of liver-enriched transcription factor CREB-H.

CREB-H is an endoplasmic reticulum-resident bZIP transcription factor which critically regulates lipid homeostasis and gluconeogenesis in the liver. CREB-H is proteolytically activated by regulated intramembrane proteolysis to generate a C-terminally truncated form known as CREB-H-ΔTC, which translocates to the nucleus to activate target gene expression. CREB-H-ΔTC is a fast turnover protein but the mechanism governing its destruction was not well understood. In this study, we report on ß-TrCP-dependent ubiquitination and proteasomal degradation of CREB-H-ΔTC. The degradation of CREB-H-ΔTC was mediated by lysine 48-linked polyubiquitination and could be inhibited by proteasome inhibitor. CREB-H-ΔTC physically interacted with ß-TrCP, a substrate recognition subunit of the SCF(ß-TrCP) E3 ubiquitin ligase. Forced expression of ß-TrCP increased the polyubiquitination and decreased the stability of CREB-H-ΔTC, whereas knockdown of ß-TrCP had the opposite effect. An evolutionarily conserved sequence, SDSGIS, was identified in CREB-H-ΔTC, which functioned as the ß-TrCP-binding motif. CREB-H-ΔTC lacking this motif was stabilized and resistant to ß-TrCP-induced polyubiquitination. This motif was a phosphodegron and its phosphorylation was required for ß-TrCP recognition. Furthermore, two inhibitory phosphorylation sites close to the phosphodegron were identified. Taken together, our work revealed a new intracellular signaling pathway that controls ubiquitination and degradation of the active form of CREB-H transcription factor.

[Comparation of Toxic Effect of Silicious Mineral Dusts on Lung Epithelial A549 Cells].

Considering the high contents of minerals and the potential health risk of mineral dusts to human and the environment, this paper was aimed to figure out the toxic effect and mechanism of four common mineral particles (quartz, albite, sericite, and montmorillonite). Cytotoxicity assays for cell viability (MTT assay), membrane integrity (LDH assay), oxidative stress (H2O2 assay) and inflammatory cytokines (TNF-α and IL-6 assay) were applied. The results showed the influence of these mineral particles on A549 cell viability followed the order of momtmorillonite > cericite≥quartz > albite. There was no obvious relation between cell viability and the content of SiO2, however, good linear correlation with the content of iron, and the cytotoxicity of mineral dusts was strengthened with increasing iron content. Mineral dusts generated H2O2 in cell or cell-free systems. In particular, H2O2 exhibited a linear correlation with the iron content, which meant that iron in the mineral dusts played an important role in the generation of reactive radical. Among those samples, oxidative stress induced by montmorillonite was distinctly stronger, while there was negligible influence induced by quartz and albite. Besides, all the tested samples induced damage to A549 cell membrane, and triggered the release of TNF-α or IL-6, but differed by the kinds of mineral dusts. In conclusion, composition and structure directly affected, but were not the only factors that contributed to the biological activity of mineral dusts, the evaluation of cell viability, membrane damage, free radicals and inflammatory reaction induced by mineral dusts should take the external morphology, surface active groups, solubility, adsorption and ion exchange properties into consideration.

Diagnosing x-ray power and energy of tungsten wire array z-pinch with a flat spectral response x-ray diode.

Fast z-pinch is a very efficient way of converting electromagnetic energy to radiation. With an 8-10 MA current on primary test stand facility, about 1 MJ electromagnetic energy is delivered to vacuum chamber, which heats z-pinch plasma to radiate soft x-ray. To develop a pulsed high power x-ray source, we studied the applicability of diagnosing x-ray power from tungsten wire array z-pinch with a flat spectral response x-ray diode (FSR-XRD). The detector was originally developed to diagnose radiation of a hohlraum in SG-III prototype laser facility. It utilized a gold cathode XRD and a specially configured compound gold filter to yield a nearly flat spectral response in photon energy range of 0.1-4 keV. In practice, it was critical to avoid surface contamination of gold cathode. It is illustrated that an exposure of an XRD to multiple shots caused a significant change of response. Thus, in diagnosing x-ray power and energy, we used each XRD in only one shot after calibration. In a shot serial, output of FSR-XRD was compared with output of a nickel bolometer. In these shots, the outputs agreed with each other within their uncertainties which were about 12% for FSR-XRD and about 15% for bolometer. Moreover, the ratios between the FSR-XRD and the bolometer among different shots were explored. In 8 shots, the standard deviation of the ratio was 6%. It is comparable to XRD response change of 7%.

SIRT1 Suppresses Human T-Cell Leukemia Virus Type 1 Transcription.

UNLABELLED: Human T-cell leukemia virus type 1 (HTLV-1)-associated diseases are poorly treatable, and HTLV-1 vaccines are not available. High proviral load is one major risk factor for disease development. HTLV-1 encodes Tax oncoprotein, which activates transcription from viral long terminal repeats (LTR) and various types of cellular promoters. Counteracting Tax function might have prophylactic and therapeutic benefits. In this work, we report on the suppression of Tax activation of HTLV-1 LTR by SIRT1 deacetylase. The transcriptional activity of Tax on the LTR was largely ablated when SIRT1 was overexpressed, but Tax activation of NF-κB was unaffected. On the contrary, the activation of the LTR by Tax was boosted when SIRT1 was depleted. Treatment of cells with resveratrol shunted Tax activity in a SIRT1-dependent manner. The activation of SIRT1 in HTLV-1-transformed T cells by resveratrol potently inhibited HTLV-1 proviral transcription and Tax expression, whereas compromising SIRT1 by specific inhibitors augmented HTLV-1 mRNA expression. The administration of resveratrol also decreased the production of cell-free HTLV-1 virions from MT2 cells and the transmission of HTLV-1 from MT2 cells to uninfected Jurkat cells in coculture. SIRT1 associated with Tax in HTLV-1-transformed T cells. Treatment with resveratrol prevented the interaction of Tax with CREB and the recruitment of CREB, CRTC1, and p300 to Tax-responsive elements in the LTR. Our work demonstrates the negative regulatory function of SIRT1 in Tax activation of HTLV-1 transcription. Small-molecule activators of SIRT1 such as resveratrol might be considered new prophylactic and therapeutic agents in HTLV-1-associated diseases. IMPORTANCE: Human T-cell leukemia virus type 1 (HTLV-1) causes a highly lethal blood cancer or a chronic debilitating disease of the spinal cord. Treatments are unsatisfactory, and vaccines are not available. Disease progression is associated with robust expression of HTLV-1 genes. Suppressing HTLV-1 gene expression might have preventive and therapeutic benefits. It is therefore critical that host factors controlling HTLV-1 gene expression be identified and characterized. This work reveals a new host factor that suppresses HTLV-1 gene expression and a natural compound that activates this suppression. Our findings not only provide new knowledge of the host control of HTLV-1 gene expression but also suggest a new strategy of using natural compounds for prevention and treatment of HTLV-1-associated diseases.

[4-amino-1,8-naphthalimide on the Sensitive effect of arsenic trioxide in hepatocellular carcinoma cells].

OBJECTIVE: To study the effect and mechanism of 4-amino-1, 8-naphthalimide (4-AN) on the sensitive effect of arsenic trioxide (ATO) in hepatocellular carcinoma cells. METHODS: Hepatocellular carcinoma HepG2 cells were divided into two groups according to whether they were treated with 4-AN or not. Cell viability was evaluated by MTT assay, population doubling experiment and colony formation assay; genic mechanism was explored by 8-OH-dG assay, single cell gel electrophoresis (comet assay) and microriucleus test. RESULTS: At 2-10 micromol/L concentration of ATO, the cell viability and colony formation efficiency of the combinatio group (4-AN+ATO) were significantly lower than that of the ATO group (P<0.05); moreover, the tail-length (L-Tail) and olive tail moment (OTM) in comet assay were notablely higher than that of the ATO group (P<0.05). At 2-20 micromol/L concentration of ATO, the population doubling time and 8-OH-dG in combination group were significantly higher than that of ATO group (P<0.05). Results from DNA damage repair assay showed that the efficiency of DNA damage repair in combination group was remarkably lower than that of ATO group (P<0.05). At 5-20 micromol/L concentration of ATO, the frequency of micronucleated cells in combination group was significantly higher than that of ATO group (P<0.05). CONCLUSION: 4-AN can significantly increase the sensitivity of ATO in treatment with hepatocellular carcinoma cells and prevent DNA damage repair may be a primary mechanism for this effect.

[Epidemiological study on nasal carriage in hospitalized children infected with Staphylococcus aureus].

OBJECTIVE: To study the relationship between nasal carriage and Staphylococcus aureus (S. aureus) infection in hospitalized children. METHODS: Fifty-six hospitalized children infected with S. aureus were recruited in this study. Nasal swabs were collected and cultured, and the nasal carriage rate of S. aureus was examined. PVL virulence gene and mecA resistance gene were both detected in clinical strains and nasal carriage strains by PCR. RESULTS: Twenty-two (39%) of the 56 children had nasal carriage of S. aureus, and most of them (18 cases) were younger than one year. Among these 22 children, 11 (50%) had previous hospitalization over the past year. In the infected strains, the rate of methicillin-resistant S. aureus (MRSA) was 29% (16/56), while it was 32% (7/22) in carriage strains. The mecA positive results in clinical strains were consistent with the results in nasal carriage strains. Among 5 PVL-positive nasal carriage strains, 4 (90%) could be matched with their clinical strains, all of which were MRSA. CONCLUSIONS: Nasal carriage is a potential risk factor for S. aureus infection. Nosocomial transmission may lead to nasal carriage, which can cause S. aureus infection. The isolation rate of MRSA is high in hospitalized children infected with S. aureus, which implies that more attention is needed for this situation. The isolates from noses may be clonally identical to the isolates from clinical secretions, and the homology between them needs to be confirmed by multi-locus sequence typing.

Selective extraction of catecholamines by packed fiber solid-phase using composite nanofibers composing of polymeric crown ether with polystyrene.

For the first time, electrospun composite nanofibers comprising polymeric crown ether with polystyrene (PCE-PS) have been used for the selective extraction of catecholamines - dopamine (DA), norepinephrine (NE) and epinephrine (E) - prior to their analysis by high-performance liquid chromatography-electrochemical detection. Using a minicartridge packed with PCE-PS composite nanofibers, the target compounds were extracted effectively from urine samples to which diphenylborinic acid 2-aminoethyl ester was added as a complexing reagent. The extracted catecholamines could be liberated from the fiber by the addition of acetic acid. A good linearity was observed for catecholamines in the range of 2.0-200 ng mL(-1) (NE, E and DA). The detection limits of catecholamines (signal-to-noise ratio = 3) were 0.5 ng mL(-1) (NE), 0.2 ng mL(-1) (E) and 0.2 ng mL(-1) (DA), respectively. Under the optimized conditions, the absolute recoveries of the above three catecholamines were 90.6% (NE), 88.5% (E) and 94.5% (DA). The repeatability of extraction performance was from 5.4 to 9.2% (expressed as relative standard deviation). Our results indicate that the proposed method could be used for the determination of NE, E and DA in urine.

Requirement of CRTC1 coactivator for hepatitis B virus transcription.

Transcription of hepatitis B virus (HBV) from the covalently closed circular DNA (cccDNA) template is essential for its replication. Suppressing the level and transcriptional activity of cccDNA might have anti-HBV effect. Although cellular transcription factors, such as CREB, which mediate HBV transcription, have been well described, transcriptional coactivators that facilitate this process are incompletely understood. In this study we showed that CREB-regulated transcriptional coactivator 1 (CRTC1) is required for HBV transcription and replication. The steady-state levels of CRTC1 protein were elevated in HBV-positive hepatoma cells and liver tissues. Ectopic expression of CRTC1 or its homolog CRTC2 or CRTC3 in hepatoma cells stimulated the activity of the preS2/S promoter of HBV, whereas overexpression of a dominant inactive form of CRTC1 inhibited HBV transcription. CRTC1 interacts with CREB and they are mutually required for the recruitment to the preS2/S promoter on cccDNA and for the activation of HBV transcription. Accumulation of pregenomic RNA (pgRNA) and cccDNA was observed when CRTC1 or its homologs were overexpressed, whereas the levels of pgRNA, cccDNA and secreted HBsAg were diminished when CRTC1 was compromised. In addition, HBV transactivator protein HBx stabilized CRTC1 and promoted its activity on HBV transcription. Our work reveals an essential role of CRTC1 coactivator in facilitating and supporting HBV transcription and replication.

[A comparative study of the gene chip technology and acid-fast staining or mycobacterial culture to diagnose].

OBJECTIVE: To investigate the clinical value of mycobacterial DNA microarray technology for diagnosis of childhood tuberculosis. METHODS: 120 clinical specimens were collected from hospitalized child patients. Acid-fast staining, mycobacterial culture and DNA microarray assays were performed using these clinical specimens. The results of DNA microarray assays were compared with the results of acid-fast staining and mycobacterial culture. RESULTS: The sensitivity of DNA microarray assays for specimens from children with tuberculosis was 24.3% (17/70), of acid-fast staining 17.1% (12/70), of mycobacterial culture 20.0% (14/70), and the specificity of the three methods was all 100.0% (50/50). The difference between results of DNA microarray assays and that of acid-fast staining or mycobacterial culture was not significant. CONCLUSION: DNA microarray assay has reference value for the diagnosis of childhood tuberculosis. It provides a new way for the diagnosis of childhood tuberculosis.

[Clinical distribution and drug resistance of Staphylococcus aureus isolated from hospitalized children].

OBJECTIVE: To learn about the clinical distribution and drug resistance of Staphylococcus aureus (S. aureus) isolated from inpatients and provide evidence for clinically reasonable use of antibiotics. METHODS: Data including clinical features and drug sensitivity of S. aureus isolated from hospitalized patients in the last two years were analyzed. RESULTS: 248 S. aureus strains were isolated from inpatients of our hospital in the last 2 years. The most common disease caused by S. aureus was pneumonia with a total of 163 patients. The second was skin and soft tissue infection with 21 patients in total. Sepsis occurred in 11 patients. The most commonly used antibiotics included oxacillin, nafcillin, cefathiamidine and vancomycin. The average course of antibiotic was 12.48 days. Treatment course of pneumonia and sepsis was 13.71 and 15.11 respectively. 96.31% (235/244) of S. aureus were resistant to penicillin. Vancomycin-resistant S. aureus has not been isolated. CONCLUSION: S. aureus pneumonia is the leading cause of hospitalization of children with S. aureus infection. S. aureus is highly resistant to commonly used antibiotics and related infections need longer therapy. Clinicians should pay more attention to S. aureus infection.

[Nasal carriage of community-acquired Staphylococcus aureus and drug sensitivity tests in healthy children in Chengdu].

OBJECTIVE: To investigate nasal carriage of community-acquired Staphylococcus aureus and its drug sensitivities in healthy children in Chengdu. METHODS: Nasal swabs were collected from healthy children from primary schools and kindergartens in Chengdu in two stages (2005-2007 and 2008-2010). All specimens were cultivated. Once S. aureus was identified, drug susceptibility tests (disk diffusion method) were performed with penicillin, erythromycin, clindamycin, ceftazidime and vancomycin. RESULTS: 430 S. aureus were identified from 2373 specimens, with a positive rate of 18.12%. Resistant to penicillin was found in 90% of tests. The isolated S. aureus was also resistant (6.28%) to methicillin-resistant Staphylococcus aureus (MRSA). The first stage identified higher rate of MRSA than the second stage (4.28% versus 9.25%, P = 0.037). Isolates from children living in cities were more likely to be resistant to cefoxitin than isolates from children living in countryside (14.74% versus 2.56%, P = 0.006) in the second stage. We did not find vancomycin-resistant S. aureus. CONCLUSION: Nasal carriage of S. aureus among healthy children in Chengdu is common and the nasal carried S. aureus is highly resistant to commonly used antibiotics.

[Factors influencing short-term prognosis of tuberculous meningitis in children].

OBJECTIVE: To study the factors influencing short-term prognosis of tuberculous meningitis (TBM) in children. METHODS: The clinical data of 137 hospitalized children with TBM between January 2007 and February 2011 were retrospectively reviewed. A total of 30 potential factors influencing short-term prognosis of TBM were evaluated by univariate analysis and multivariate logistic regression analysis. RESULTS: Clinical staging showed that of the 137 children 21 cases (15.3%) were in the early stage, 67 cases (48.9%) in the medium stage and 49 cases (35.8%) in the late stage of TBM. The univariate analysis revealed 8 factors associated with a poor short-term prognosis: clinical stage of TBM (late), coma, positive Babinski signs, cranial nerve involvements, paralysis, seizures, obvious abnormalities in brain computed tomography (CT) or magnetic resonance imaging (MRI) and elevated protein concentrations in cerebrospinal fluid (CSF). Factors associated with a favourable short-term prognosis for TBM included glucocorticoid steroids therapy, positive reaction of PPD skin test and an increased length of stay in hospital. Multivariate logistic analysis revealed two independent risk factors for a poor short-term prognosis: clinical stage of TBM (late) (OR: 11.168, 95%CI: 3.521-35.426) and positive signs of meningeal irritation (OR: 4.275, 95%CI: 1.043-17.521). An increased length of stay in hospital was shown as a favorable factor (OR: 0.893, 95%CI: 0.825-0.968). CONCLUSIONS: Late-stage TBM and positive signs of meningeal irritation suggest a poor prognosis, while an appropriately longer length of stay in hospital may contribute to a favorable short-term prognosis for children with TBM.

[Nasal carriage of community-acquired methicillin-resistant Staphylococcus aureus in healthy children from Chengdu].

OBJECTIVE: To evaluate the prevalence of nasal carriage of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) in healthy children from Chengdu. METHODS: Strains of Staphylococcus aureus were isolated from nasal swabs of healthy children from five kindergartens in Chengdu from September, 2005 to December, 2005 and questionnaires were obtained. Antibiotic susceptibility test was performed with agar disk diffusion and Bauer-Kirby on Mueller-Hinton medium method to determine CA-MRSA. mecA and PVL genes were detected with PCR in all of the CA-MRSA isolates. RESULTS: A total of 801 children were enrolled. Overall 147 children (18.4%) were carried with Staphylococcus aureus and 9 (1.1%) were carried with CA-MRSA. All CA-MRSA isolates were positive for mecA gene, and 5 CA-MRSA isolates were positive for PVL gene. Of the 9 CA-MRSA isolates, 6 were multiresistant. CONCLUSIONS: CA-MRSA nasal colonization is present among Chengdu healthy children. The CA-MRSA isolates are multiresistant and parts of CA-MRSA isolates carry PVL gene. The nasal carriage of CA-MRSA in healthy children should be a concerned issue.

[Comparative study of the cytotoxicity induced by chrysotile asbestos, rock wool and substitute fibers in vitro].

OBJECTIVE: To study the cytotoxicity induced by chrysotile asbestos (CA), rock wool (RW) and wollastonite (WS). METHODS: V79 cells were divided into 4 groups. i.e. CA group, WS group, RW group and control group (200 microl PBS). The exposure concentration of dusts was 100 mg/L, The cell viability was detected by MTT and lactate dehydrogenase (LDH) activity assays. The technique of scanning electron microscopy was used to examine the change of V79 cells. RESULTS: SiO2 was main constituent for 3 kinds of dusts. In MTT assay, the cell viability of RW and WS groups was 64.8% and 65.7%, respectively, which were significantly higher than that (54.5%) of CA group (P < 0.01). In LDH assay, the LDH activity of RW and WS groups [(15.7 +/- 50.9), (12.3 +/- 3.7) U/L, respectively] was significantly lower than that [(20.2 +/- 0.9) U/L] of CA group (P < 0.05). In scanning electron microscopy examination, it was found that the two ends of V79 cells in CA group contained a great deal of fibers remaining bodies, but the V79 cell appearance in RW and WS groups was normal. CONCLUSION: The cytotoxicity induced by RW and WS is significantly lower than that induced by CA for V79 cell.