Search PubMed⌕ Search

Biomedical subjects

L Zheng

Publications and source records attributed to L Zheng.

At least 73 records · Page 4Linked to original sources
PubMed2001

Microsatellite analysis of medfly bioinfestations in California.

The Mediterranean fruit fly, Ceratitis capitata, is a destructive agricultural pest with a long history of invasion success. This pest has been affecting different regions of the United States for the past 30 years, but a number of studies of medfly bioinfestations has focused on the situation in California. Although some progress has been made in terms of establishing the origin of infestations, the overall status of this pest in this area remains controversial. Specifically, do flies captured over the years represent independent infestations or the persistence of a resident population? We present an effort to answer this question based on the use of multilocus genotyping. Ten microsatellite loci were used to analyse 109 medflies captured in several infestations within California between 1992 and 1998. Using these same markers, 242 medflies from regions of the world having 'established' populations of this pest including Hawaii, Guatemala, El Salvador, Ecuador, Brazil, Argentina and Peru, were also analysed. Although phylogenetic analysis, amova analysis, the IMMANC assignment test and geneclass exclusion test analysis suggest that some of the medflies captured in California are derived from independent invasion events, analysis of specimens from the Los Angeles basin provides support for the hypothesis that an endemic population, probably derived from Guatemala, has been established.

Agriculture↗
PubMed2001

Tumour necrosis factor-alpha potentiates CR3-induced respiratory burst by activating p38 MAP kinase in human neutrophils.

CR3 and Fc gamma Rs are the main receptors involved in the phagocytic process leading to engulfment and killing of microbes by production of reactive oxygen intermediates (ROI) and degranulation. Various inflammatory mediators, such as tumour necrosis factor-alpha (TNF-alpha) and lipopolysaccharide (LPS), are known to prime neutrophils leading to increased bactericidal responses, but the underlying mechanism of priming has only been partially elucidated. The purpose of this study was to investigate how TNF-alpha primes neutrophils for subsequent stimuli via either CR3 or Fc gamma R. The receptors were specifically activated with pansorbins (protein-A-positive Staphylococcus aureus) coated with anti-CR3, anti-Fc gamma RIIa, or anti-Fc gamma RIIIb monoclonal antibody. Activation of neutrophils with these particles resulted in ROI production as measured by chemiluminescence. Anti-CR3 pansorbins induced the most prominent ROI production in neutrophils. TNF-alpha potentiated the CR3-mediated respiratory burst but had little effect on that mediated by Fc gamma Rs. The priming effect of TNF-alpha on CR3-mediated ROI production is associated with an increased activation of p38 MAPK as well as tyrosine phosphorylation of p72(syk). Pretreatment of neutrophils with the inhibitors for p38 MAPK and p72(syk) markedly suppressed the respiratory burst induced by CR3. Furthermore, TNF-alpha induced about a three-fold increase in the expression of CR3 in neutrophils, an effect which is blocked by the p38 MAPK inhibitor. Taken together, these results showed that TNF-alpha potentiates the CR3-mediated respiratory burst in neutrophils not only by triggering a p38 MAPK-dependent up-regulation of CD11b/CD18 but also by modulating the signalling pathways.

CD18 Antigens↗
PubMed2001

Macrophages, neutrophils and tumour necrosis factor-alpha expression in bronchiectatic airways in vivo.

Bronchiectasis is increasingly being recognized as an inflammatory condition of the airways in which pathological permanent dilation occurs. We have obtained endobronchial biopsies in 14 patients with stable bronchiectasis and 15 control subjects. Airway neutrophils, macrophages and tumour necrosis factor-alpha (TNFalpha)-positive cells were stained with monoclonal antibodies and the densities of positive cells in the lamina propria were determined by using a computer image analyser. There was significantly higher neutrophil, macrophage and TNFalpha-positive cell densities in the lamina propria of bronchiectatic than control airways (P < 0.001, P < 0.001 and P=0.0002, respectively). Airway neutrophil density in bronchiectasis but not in controls, correlated with TNFalpha-positive cell density (r=0.71, P=0.004). A significant correlation between airway macrophage and TNFalpha-positive cell densities was demonstrated in both control and bronchiectatic airways (r=0.63, P=0.016 and r=0.60, P=0.02 respectively). Neutrophil density negatively correlated with per cent forced vital capacity (FVC%) predicted among patients with bronchiectasis (r=-0.53, P=0.04). Bronchiectasis patients who were regular sputum producers had a significantly higher macrophage, but not neutrophil density than their counterparts (P=0.02 and P=0.48 respectively). Our original findings suggest that airway macrophages could contribute to neutrophil influx into airway walls through their production of TNFalpha and therefore play an important role in the pathogenesis of bronchiectasis.

Aged↗
PubMed2001

Aggression in toddlers: associations with parenting and marital relations.

This study examined the relation among parenting factors, marital relations, and toddler aggression. A structured questionnaire was administered to both parents of 254 2-year-olds. The authors used correlation and hierarchical multiple regression analyses to assess the extent to which certain personality traits, drug use, parenting style, and marital conflicts were related to the toddlers' aggressive behavior. Results showed that the maternal child-rearing and parental aggression domains had a direct effect on toddler aggression. The domain of maternal child rearing also served as a mediator for the domains of marital relations, paternal child rearing, parental aggression, and parental drug use. The findings indicated that maternal child-rearing practices, personality attributes, and drug use were more important than paternal attributes in relation to toddler aggression. Implications for prevention among families at risk are discussed.

Aggression↗
PubMed2001

An artificial intelligent algorithm for tumor detection in screening mammogram.

Cancerous tumor mass is one of the major types of breast cancer. When cancerous masses are embedded in and camouflaged by varying densities of parenchymal tissue structures, they are very difficult to be visually detected on mammograms. This paper presents an algorithm that combines several artificial intelligent techniques with the discrete wavelet transform (DWT) for detection of masses in mammograms. The AI techniques include fractal dimension analysis, multiresolution markov random field, dogs-and-rabbits algorithm, and others. The fractal dimension analysis serves as a preprocessor to determine the approximate locations of the regions suspicious for cancer in the mammogram. The dogs-and-rabbits clustering algorithm is used to initiate the segmentation at the LL subband of a three-level DWT decomposition of the mammogram. A tree-type classification strategy is applied at the end to determine whether a given region is suspicious for cancer. We have verified the algorithm with 322 mammograms in the Mammographic Image Analysis Society Database. The verification results show that the proposed algorithm has a sensitivity of 97.3% and the number of false positive per image is 3.92.

Algorithms↗
PubMed2001

Differentiation of two bovine lentiviruses by a monoclonal antibody on the basis of epitope specificity.

Bovine immunodeficiency virus (BIV) and Jembrana disease virus (JDV) are bovine lentiviruses that are closely related genetically. A recombinant fusion protein containing the capsid protein of BIV expressed in Escherichia coli was used to immunize mice and produce monoclonal antibodies. Six hybridomas specific for BIV capsid protein were identified, and one antibody, designated 10H1, was characterized further. Competitive binding assays were performed to analyze the topography of antigenic determinants by enzyme-linked immunosorbent assay and demonstrated the existence of at least three distinct antigenic determinants on capsid protein. The monoclonal antibody reacted specifically with both BIV capsid and the recombinant fusion protein in Western immunoblot analyses. However, it did not react with the recombinant capsid fusion protein of JDV, indicating that BIV contains at least one unique epitope in the capsid protein that is absent in JDV. Further mapping of the epitope by chemical cleavage analysis identified that the epitope is located at the 6.4-kDa N terminus of the 29-kDa capsid protein. This monoclonal antibody assay will be valuable for distinguishing the two closely related lentiviruses by Western blotting.

Animals↗
PubMed2001

WdChs2p, a class I chitin synthase, together with WdChs3p (class III) contributes to virulence in Wangiella (Exophiala) dermatitidis.

The chitin synthase structural gene WdCHS2 was isolated by screening a subgenomic DNA library of Wangiella dermatitidis by using a 0.6-kb PCR product of the gene as a probe. The nucleotide sequence revealed a 2,784-bp open reading frame, which encoded 928 amino acids, with a 59-bp intron near its 5' end. Derived protein sequences showed highest amino acid identities with those derived from the CiCHS1 gene of Coccidioides immitis and the AnCHSC gene of Aspergillus nidulans. The derived sequence also indicated that WdChs2p is an orthologous enzyme of Chs1p of Saccharomyces cerevisiae, which defines the class I chitin synthases. Disruptions of WdCHS2 produced strains that showed no obvious morphological defects in yeast vegetative growth or in ability to carry out polymorphic transitions from yeast cells to hyphae or to isotropic forms. However, assays showed that membranes of wdchs2Delta mutants were drastically reduced in chitin synthase activity. Other assays of membranes from a wdchs1Deltawdchs3Deltawdchs4Delta triple mutant showed that their residual chitin synthase activity was extremely sensitive to trypsin activation and was responsible for the majority of zymogenic activity. Although no loss of virulence was detected when wdchs2Delta strains were tested in a mouse model of acute infection, wdchs2Deltawdchs3Delta disruptants were considerably less virulent in the same model, even though wdchs3Delta strains also had previously shown no loss of virulence. This virulence attenuation in the wdchs2Deltawdchs3Delta mutants was similarly documented in a limited fashion in more-sensitive cyclophosphamide-induced immunocompromised mice. The importance of WdChs2p and WdChs3p to the virulence of W. dermatitidis was then confirmed by reconstituting virulence in the double mutant by the reintroduction of either WdCHS2 or WdCHS3 into the wdchs2Deltawdchs3Delta mutant background.

Amino Acid Sequence↗
PubMed2001

The effect of aging on nasal mucociliary clearance, beat frequency, and ultrastructure of respiratory cilia.

The increased susceptibility of the elderly to lower respiratory tract infection cannot be fully explained. Although mucociliary clearance, which is affected by ciliary beating and ultrastructure, plays a crucial role in the defense of the airways against inhaled microbes, little is known of the effects of aging on these parameters. We studied the nasal mucociliary clearance (NMCC) time, ciliary beat frequency, and ultrastructure of respiratory cilia in a cohort of healthy volunteers (age range 11 to 90 yr). Ciliary beat frequency of ciliated nasal epithelial cells was obtained via an established photometric method, and NMCC time was measured with the saccharine test. There was a correlation of ciliary beat frequency (r = -0.48, p = 0.0001) and NMCC time r = 0.64, p < 0.001) with increasing age. Transmission electron microscopy revealed an increase in the percent of subjects exhibiting microtubular disarrangement and single central microtubules with aging (p = 0.002 and p = 0.005, respectively). Subjects older than 40 yr of age had significantly slower ciliary beat frequency, higher percent of ciliary cross-sections displaying single tubules, and longer NMCC time than their younger counterparts (p < 0.05). These findings may help explain the frequent occurrence of respiratory infection in the elderly.

Adolescent↗
PubMed2001

Microsatellite polymorphism in tsetse flies (Diptera: Glossinidae).

In sub-Saharan Africa, tsetse flies are the vectors of trypanosomes, the causative agents of sleeping sickness in humans and nagana in animals. Certain wild populations of the palpalis group exhibit intraspecific variation and are suspect of manifest differences in vectorial capacity. The current study reports the identification of 13 polymorphic microsatellite loci from Glossina palpalis palpalis Robinean-Desvoidy. The majority of these markers amplify corresponding loci from the related species C. p. gambiensis Vanderplank, G. f. fuscipes Newstead, and G. tachinoides Westwood. Only seven of 13 loci were amplified from G. austeni Newstead. Genetic variability was estimated in one field population of G. p. gambiensis. These results confirmed that microsatellite markers may be used to examine the subpopulation structure of tsetse flies.

Alleles↗
PubMed2001

Calprotectin expression and mononuclear phagocyte subpopulations in peripheral blood and bronchoalveolar lavage.

BACKGROUND AND AIM OF THE WORK: The phenotype of human alveolar macrophages (AM) can be affected by the process of maturation/differentiation and by multiple factors from the local environment. The aim of our study was to assess the expression of selected phenotypic markers characteristic for subsets of mononuclear phagocytes in bronchoalveolar lavage fluid (BAL) and peripheral blood with special attention to calprotectin (27E10), a marker of acute inflammatory macrophages. METHODS: The expression of calprotectin and 13 other phenotypic markers was evaluated by an immunoperoxidase slide assay and computer image analysis. RESULTS: We consider calprotectin (27E10 antigen) to be a marker of freshly recruited, monocyte-like, mononuclear phagocytes, being expressed in 84 +/- 13% PBM and only 10 +/- 11% of AM, p < 0.001. Computer image analysis confirmed that calprotectin-positive mononuclear cells in peripheral blood and BAL are morphologically very similar in contrast to the much larger calprotectin-negative AM. On the other hand, 25F9 antigen, the transferrin receptor (CD71), KiM8 (CD68), RFD1 (marker of dendritic cells), RFD7 (marker of mature macrophages), RFD9 (marker of epithelioid cells and macrophages of germinal centers), and RM3/1 (macrophages of late phase inflammation) were restricted preferentially to mature AM. CONCLUSIONS: Our study demonstrates phenotypic differences between mononuclear phagocytes derived from BAL and their peripheral blood precursors, and indicates markers useful for assessing the stages of maturation/differentiation of these cells. The percentage of calprotectin (27E10) positive AM might represent a parameter for assessing mononuclear phagocyte influx from peripheral blood to the lung in the very early stage of inflammatory reactions.

Adult↗
PubMed2001

[Study on frequencies of aneuploidy in mouse oocyte and female pronucleus of one cell zygote induced by benzene].

OBJECTIVE: To study the effect of benzene on aneupoidy of oocytes and female pronucleus of one cell zygotes. METHOD: The NIH adult female mice were treated with varies doses of benzene (942, 1,881 and 3,762 mg/kg respectively) via single gavage and (706, 1,922 and 4,864 mg/m3, respectively) multiple inhalation. After gavage, the mice were pair-matched (1:1) with males overnight. The ovulated oocytes and the one cell zygotes were collected for cytogenetic analysis and the frequencies of aneuploidy were detected. RESULTS: The frequencies of aneuploid in M II oocytes significantly increased in the three groups treated with inhalation (7.06%, 7.50% and 7.76%, respectively, control group 0.00%, P < 0.05) of benzene, as compared with those in the control group (1.30%), with a dose-dependent response. Meiotic delay of M I oocytes was observed, with the frequency of M I oocytes of 1.16%, 3.61% and 5.75%, respectively, P < 0.05, in a dose-dependent response, too. In gavage treatment group, increase in frequency of M II oocyte aneuploidy was only observed in the high-dose group, and aneupliody frequency of female pronucleus in one cell zygotes was not induced. CONCLUSION: Exposure to high-dose benzene via gavage or inhalation was able to induce increase in aneuploidy frequency of M II oocytes in mice.

Aneuploidy↗
PubMed2001

[The effects of dexamethasone on biological characteristics of bone marrow stromal cells].

OBJECTIVE: To investigate the effects of dexamethasone on the proliferation and differentiation of bone marrow stromal cells(MSC). METHODS: MSC were isolated and cultured in vitro. After treatment with different concentrations of dexamethasone (0, 10(-10), 10(-9), 10(-8), 10(-7) and 10(-6) mol/L), the proliferation and alkaline phosphatase (ALP) activity of MSC were measured to evaluate the effect of dexamethasone on the biological characteristics of MSC. RESULTS: Dexamethasone inhibited cell proliferation. With the increase of concentration of dexamethasone, the effect was enhanced, which was more significant when the concentration of dexamethasone was over 10(-8) mol/L. At the same time, dexamethasone promoted the activity of ALP. This effect was enhanced with the increase of concentration of dexamethasone, but the alteration was small when the concentration of dexamethasone was over 10(-8) mol/L. The effects increased with the time. The activity of ALP was enhanced 2 to 4 times with the dexamethasone for 6 days. CONCLUSION: Dexamethasone inhabit the proliferation of MSC, while induce them to differentiate into osteoblasts. The appropriate concentration of dexamethasone was 10(-8) mol/L.

Animals↗
PubMed2001

[The current situation and future of extracellular matrix materials for bone tissue engineering].

The requirements of ideal extracellular matrix materials for bone tissue engineering were stated, and the advantages and disadvantages of bioceramics, biodegradable synthetic polymers and natural polymers were analyzed. Based on these, we highlight a point that the ideal extracellular matrix materials for bone tissue engineering should be made up of bioceramics materials, synthetic polymers or natural polymers. These materials should possess a morphological structure of three-dimensional foam and have a self-mediated drug delivery system of bone growth factors. The design and manufacture of such compound extracellular matrix materials for bone tissue engineering is a very important and urgent challenge.

Biocompatible Materials↗
PubMed2001

[Laparoscopic surgery in the treatment of early uterine malignancies: a report of 8 cases].

OBJECTIVE: To explore the feasibility of laparoscopic operation as treatment for early malignant uterine tumors. METHOD: Six patients with endometrial carcinoma underwent laparoscopic extensive total hysterectomy and bilateral adnexectomy, and 2 with cervical cancer underwent additional pelvic lymphadenectomy. RESULTS: The mean operating time of the 6 laparoscopic extensive total hysterectomy and bilateral adnexectomy was 220 min, and mean blood loss was 200 ml. The mean operating time of 2 cases underwent additional pelvic lymphadenectomy was 240 min. No organ trauma occurred, and the average post-operative hospital stay was 8 days. CONCLUSION: These results suggest that laparoscopic operation is safe and feasible in treating early stage malignant uterine tumors.

Aged↗
PubMed2001

A novel serine protease SNC19 associated with human colorectal cancer.

OBJECTIVE: To study the structure and function of a novel serine protease gene associated with human colorectal cancer SNC19. METHODS: The cDNA sequence was determined by both manual and automatic sequencing techniques. The full length cDNA sequence was obtained by the 5'-Rapid Amplification of cDNA Ends technique and web-based analysis. Open reading frame analysis and protein function prediction were also performed. Northern blot was used to detect the expression of SNC19 in various human normal tissues and tumor cell lines. Fluorescent in situ hybridization combined with fluorescent R-banding technique was employed to map the SNC19 gene on human chromosome. RESULTS: Full length SNC19 cDNA, size 3152 bp, encodes a protein highly homologous to a mouse serine protease epithin. In normal human tissues, high SNC19 expression levels were observed in the kidney, pancreas, prostate, small intestine and colon; moderate SNC19 expression levels were observed in the placenta, lung, liver, spleen thymus, testis and peripheral blood lymphocytes; and extremely low expression levels were observed in the heart, brain, skeletal muscle and ovary. In tumor cell lines, colorectal cancer cells SW480, SW620, SW1116 and Colo205, breast cancer cell Bcap37 and gastric cancer cells MKN28 and SGC7901 showed high levels of SNC19 expression; cervical cancer cell HeLa-S3, lung cancer PAA, oral epithelial cancer cell KB and lymphoma cell Raji showed moderate levels of SNC19 expression; and tongue squamous cancer cell Tca8113, leukemia cells HL-60, K562, MOLT-4, lung cancer cell A549 and melanoma cell G361 showed very low levels of SNC19 expression. SNC19 was mapped to human chromosome 11q24-25. CONCLUSION: SNC19 encodes a novel human serine protease with 855 amino acid residues. As a novel serine protease associated with human colorectal cancer, the expression of SNC19 in various tissues and cell lines may have very important impact on their phenotypes and biological behaviors.

Amino Acid Sequence↗
PubMed2001

Apoptosis inducing effects of arsenic trioxide on human bladder cancer cell line BIU-87.

OBJECTIVE: To explore the apoptosis inducing effects of arsenic trioxide (As2O3) on human bladder cancer cells and elucidate possible mechanisms. METHODS: After treatment with As2O3, the growth inhibition rates of human bladder cancer cell line BIU-87 were studied by MTT and cell counts methods. DNA synthesis rates were detected by 3H-TdR assay. The morphological changes of cancer cells were observed by light and electronic microscopy and cell apoptosis rates were detected by TdT-mediated dUTP nick end labeling (TUNEL). bcl-2 gene expression of BIU-87 cells was observed by strept avidin-biotin complex (SABC) immunohistochemical method. RESULTS: As2O3 could effectively inhibit the growth of BIU-87 (P < 0.05), which were time and concentration dependent. The inhibition rate of 4.0 mumol/L As2O3 for DNA synthesis of cancer cells was 55.64% (P < 0.01). Partial cancer cells presented the characteristic morphological changes of apoptosis which depended on the time of exposure to drug (P < 0.05). bcl-2 expression of BIU-87 cells was decreased significantly (P < 0.05). CONCLUSION: As2O3 can significantly induce apoptosis in bladder cancer cells by down-regulating the expression of the bcl-2 gene and inhibiting DNA synthesis. This provides a potentially effective method for prevention and cure of human bladder cancer.

Antineoplastic Agents↗
PubMed2001

Change on the horizontal and vertical meridians of the cornea after cataract surgery.

PURPOSE: To compare the course and magnitude of change on the horizontal and vertical meridians of the cornea after 5 different incisions for cataract: extracapsular cataract extraction (ECCE), 6 mm superior scleral tunnel (6Sup), 3 mm superior scleral tunnel (3Sup), 3 mm temporal scleral tunnel (3Temp), and 3 mm temporal corneal incision (3Cor). METHODS: Retrospective chart review of 665 cases of preoperative regular astigmatism. The preoperative keratometry (K) reading was subtracted from the postoperative K reading to determine mean net change on each meridian at 1 day, 1 week, 2 weeks, 1 month, 1.5 months, 2 months, 4 months, 6 months and 12 months and at 6 month intervals thereafter. After the superior incisions, the temporal changes on each meridian are well described by an analytic model with an initial and final plateau. The changes after the temporal incisions are described by a linear equation. RESULTS: After each superior incision, the steepness and length of the transition from the initial to final plateau for each meridian depend on incision length. Considering the uncertainty of measuring K, the corneal meridians stabilized 4.5 months after ECCE, 1.2 months after 6Sup, and 0.3 months after 3Sup. No significant change was detected on the horizontal and vertical meridians after 3Temp and 3Cor. CONCLUSION: The magnitude and the duration of changes on the horizontal and vertical meridians of the cornea after cataract surgery depend on both incision length and location. Small temporal incisions induce less change than superior incisions.

Adult↗