Biomedical subjects

W Peng

Publications and source records attributed to W Peng.

At least 19 recordsLinked to original sources

PubMed2006

Recent insights into the epidemiology and genetics of Ascaris in China using molecular tools.

Ascaris is a large parasitic roundworm (nematode) of the small intestine of humans and pigs, which causes the socio-economically important disease, ascariasis. To better understand the relationship of Ascaris between the 2 host species, recent studies in China have focused on investigating the genetics and epidemiology of Ascaris from humans and pigs using a mutation scanning-based approach. Findings provided support for a low level of gene flow between the human and porcine Ascaris populations. Extending the studies of genotypic variability within Ascaris from humans and pigs, experimental infections of mice and pigs with selected genotypes of Ascaris were carried out. Initial results indicate that there is a significant difference in the ability of Ascaris eggs of genotype G1 (derived from human) and G3 (derived from pig) to infect and establish as adults in pigs, supporting the difference in the frequencies of these genotypes in natural Ascaris populations between pigs and humans in China. Taken together, current information supports that there is limited cross-infection of Ascaris between humans and pigs in endemic regions and that pigs are not a significant reservoir of human infection with the adult nematode in such areas.

Animals↗

PubMed2006

Experimental infections of pigs and mice with selected genotypes of Ascaris.

Extending a previous investigation of the genotypic variability within Ascaris from humans and pigs, experimental infections of mice and pigs with selected genotypes of Ascaris were performed in the present study to explore possible host affiliation. Initial findings indicate that there is a significant difference in the ability of Ascaris eggs of genotype G1 (derived from human) and G3 (derived from pig) to infect and establish as larvae in mice and as adults in pigs, supporting the difference in the frequencies of the genotypes reported previously in natural Ascaris populations in pigs and humans in areas in China endemic for ascariasis.

Animals↗

PubMed2006

Expression mapping of 5-HT1 serotonin receptor subtypes during fetal and early postnatal mouse forebrain development.

Serotonin (5-HT) is implicated in several aspects of brain development, yet the ontogenetic expression patterns of 5-HT receptors responsible for transducing specific effects have largely not been characterized. Fifteen different 5-HT receptor genes have been cloned; therefore any spatial and/or temporal combination of their developmental expression could mediate a wide array of 5-HT effects. We undertook a detailed analysis of expression mapping of the Gi/o-coupled 5-HT1 (5-HT1A, 1B, 1D and 1F) receptor subtypes in the fetal and early postnatal mouse forebrain. Using receptor subtype-specific riboprobes and in situ hybridization, we observed that all 5-HT1 receptor subtypes are expressed as early as embryonic day (E) 14.5 in the forebrain, typically in gradients within specific structures. Among 5-HT1 receptors, the 5-HT1A receptor transcript is expressed densely in E14.5-16.5 thalamus, in hippocampus, and in a medial to lateral gradient in cortex, whereas the 5-HT1B receptor mRNA is expressed in more lateral parts of the dorsal thalamus and in the striatum at these ages. The 5-HT1D receptor transcript, which also is expressed heavily in E14.5-E16.5 thalamus, appears to be down-regulated at birth. The 5-HT1F receptor transcript is present in proliferative regions such as the cortical ventricular zone, ganglionic eminences, and medial aspects of the thalamus at E14.5-16.5, and otherwise presents similarities to the expression patterns of 5-HT1B and 1D receptor transcripts. Overall, the 5-HT1 subfamily of Gi/o-coupled 5-HT receptors displays specific and dynamic expression patterns during embryonic forebrain development. Moreover, all members of the 5-HT1 receptor class are strongly and transiently expressed in the embryonic dorsal thalamus, which suggests a potential role for serotonin in early thalamic development.

Age Factors↗

PubMed2005

Design, synthesis and in vitro and in vivo antitumor activities of novel beta-carboline derivatives.

To further our SAR study on the chemistry and antitumor activity/neurotoxicity of beta-carboline alkaloids, several series of beta-carboline derivatives with various substituents were designed and synthesized from the starting material l-tryptophan on the basis of harmine chemical structure. Cytotoxic activities of these compounds were investigated in vitro. The results showed that some beta-carboline derivatives had significant cytotoxic activities against human tumor cell lines. Among all the synthesized beta-carboline derivatives, the compounds 27, 28 and 32, having a benzyl substituent at both position-2 and 9, respectively, were found to be the most potent compounds with IC50 value lower than 50 microM against all human tumor cell lines examined. Acute toxicities and antitumor activities of the selected beta-carboline derivatives in mice were also evaluated. The results demonstrated that a benzyl substituent at position-2 increased the antitumor activity as well as acute toxicity significantly. However an (ethoxycarbonyl)amino substituent at position-3 reduced the acute toxicity as well as antitumor activity remarkedly. These data suggested that (1) the antitumor potencies of beta-carboline derivatives were enhanced by the introduction of benzyl substituent into the position-2; (2) the acute toxicity of beta-carboline derivatives reduced dramatically by the introduction of an appropriate substituent into the position-3 and 9; (3) the beta-carboline structure might be an important basis for the design and synthesis of new antitumor drugs with significant antitumor activity and low toxicity.

Animals↗

PubMed2005

Tightly-regulated suicide gene expression kills PSA-expressing prostate tumor cells.

We have previously shown that a dual system for controlling gene expression that relies both on transcriptional regulation and DNA recombination mediated by the site-directed recombinase, Flp, effectively controls the expression of a gene encoding diphtheria toxin (DT-A). In this study, we investigated the use of a chimeric modified enhancer/promoter sequence of the human prostate-specific antigen (PSA) gene to regulate DT-A expression in human prostate cancer cells in culture, in xenografts derived from these cells, and in autochthonous tumors in TRAMP mice. Following adenoviral delivery of DNA encoding PSA promoter-driven Flp recombinase and DT-A, we demonstrate that this transcriptional/DNA recombination control strategy effectively activates DT-A expression in a manner that correlates with the amount of PSA and androgen in cells. Significantly, the size of xenografts was reduced by 50%, and tumor cells in TRAMP mice died following intratumoral injection of DT-A viruses. Direct injection of virally-delivered DT-A into normal mouse prostates resulted in a dramatic reduction in the size of the gland. Our results suggest that the PSA promoter-driven Flp recombinase regulatory system will allow for targeted death of PSA-expressing cells. When combined with newly developed strategies for targeted gene delivery, this approach holds promise as an effective systemically-administered therapy for metastatic prostate cancer.

Adenoviridae↗

PubMed2005

Mutation of hydrophobic residues in the factor Va C1 and C2 domains blocks membrane-dependent prothrombin activation.

The binding of factor (FVa) to phosphatidylserine (PS) membranes regulates assembly of the prothrombinase complex. Two pairs of solvent-exposed amino acids, Tyr(1956)/Leu(1957) in the C1 domain and Trp(2063)/Trp(2064) in the C2 domain, each make significant contributions to the affinity of FVa for PS membranes, but individually neither pair of amino acids is required for prothrombinase assembly on 25% PS membranes. In this study we characterize a FVa mutant with alanine substitutions in both the C1 and C2 domains: (Y1956,L1957,W2063,W2064)A. We conclude that: (i) prothrombinase assembly on PS membranes requires Trp(2063)/Trp(2064) and/or Tyr(1956)/Leu(1957); (ii) combined mutation of Trp(2063)/Trp(2064) and Tyr(1956)/Leu(1957) results in only a modest 4-fold decrease in the rate of thrombin generation in the absence of membranes; (iii) the present data provide experimental support for the joint participation of the C1 and C2 domains in the binding of FVa to phospholipid membranes as suggested by the recently solved structure for FVai (A1/A3-C1-C2).

Cell Membrane↗

PubMed2004

Random-hole optical fiber evanescent-wave gas sensing.

Research on development of optical gas sensors based on evanescent-wave absorption in random-hole optical fibers is described. A process to produce random-hole optical fibers was recently developed that uses a novel in situ bubble formation technique. Gas molecules that exhibit characteristic vibrational absorption lines in the near-IR region that correspond to the transmission window for silica optical fiber have been detected through the evanescent field of the guided mode in the pore region. The presence of the gas molecules in the holes of the fiber appears as a loss at wavelengths that are characteristic of the particular gas species present in the holes. An experimental setup was constructed with these holey fibers for detection of acetylene gas. The results clearly demonstrate the characteristic absorptions in the optical spectra that correspond to the narrow-line absorptions of the acetylene gas, and this represents what is to our knowledge the first report of random-hole fiber gas sensing in the literature.

Journal Article↗

PubMed2004

Determinants of perioperative morbidity and mortality after pneumonectomy.

BACKGROUND: Pneumonectomy remains a relatively high-risk procedure. However, the underlying mechanism is still unknown. Thus, the effort to find out predisposing factors for surgical risks continues. We investigated the effect of both water-load control and sampling lymphadenectomy technique on perioperative morbidity and mortality after pneumonectomy. MATERIAL AND METHODS: A hundred and three consecutive patients undergoing simple pneumonectomy were included in the prospective study. Pneumonectomy was performed for lung cancer in 92 patients and for benign diseases in 11 cases; 81 patients were male and 22 female, and the mean age was 53.4 +/- 11.4 years. Both sampling and completion lymphadenectomy techniques were used randomly. Water-load was carefully limited to values as low as possible, depending on stable hemodynamics during and after operation. RESULTS: There were no deaths, and none of the patients needed postoperative mechanical ventilation. Major complications included dyspnea in 9 patients and supraventricular arrhythmias in 13 patients. Completion lymphadenectomy increased morbidity in both right and left pneumonectomy. CONCLUSIONS: Both water-load limitation and sampling lymphadenectomy technique may decrease morbidity and mortality after pneumonectomy.

Adult↗

PubMed2004

Mapping herpes simplex virus type 1 latency-associated transcript sequences that protect from apoptosis mediated by a plasmid expressing caspase-8.

LAT (latency-associated transcript) is the only herpes simplex virus type 1 (HSV-1) transcript abundantly expressed during neuronal latency. LAT expression is required for the high reactivation phenotype of HSV-1 and this phenotype correlates with LAT's anti-apoptosis properties. LAT nucleotides 1 to 1499 inhibit caspase-8 (death receptor apoptotic pathway), but not caspase-9 (mitochondrial apoptotic pathway), -induced apoptosis as efficiently as larger LAT fragments. LAT sequences important for inhibiting caspase-8-induced apoptosis were also localized. The ability of LAT nucleotides 1 to 1499 to efficiently inhibit caspase-8-induced apoptosis correlates with the high reactivation phenotype of a mutant virus expressing just the first 1.5 kb of LAT (nucleotides 1 to 1499).

Animals↗

PubMed2003

Ascaris egg profiles in human faeces: biological and epidemiological implications.

Since 2 morphological forms (fertilized and unfertilized) of egg can be produced by Ascaris, infected humans can release in their faeces fertilized eggs only (FEO), unfertilized eggs only (UEO) or both fertilized and unfertilized eggs (FUE) (designated herein as the 3 different egg profiles). Epidemiologically, fertilized eggs are of significance as they enable effective transmission of the parasite. This study, for the first time, characterizes the Ascaris egg profiles in human faeces in an endemic region of China, explores possible host- and parasite-factors related to these profiles, and discusses the biological and epidemiological implications of the findings. The 3 egg profiles were recorded throughout the study period of 2 years, and the overall percentages of people with FEO, FUE and UEO profiles were approximately 41-47%, 32-42% and 17-21%, respectively. The overall number of unfertilized eggs for the entire population accounted for approximately 6-9% of all eggs excreted. The different Ascaris egg profiles showed no correlation to host gender, but they did relate to age and worm burden of the host and to the sex ratio and developmental status of the parasite. While an annual universal anthelmintic treatment resulted in some fluctuation in the values of individual egg profiles, the general features of these profiles remained similar throughout the study period. The findings of this study should have significant implications for understanding transmission patterns of Ascaris and for the implementation of control measures against ascariasis in endemic regions.

Adolescent↗

PubMed2002

Molecular mechanisms of nickel carcinogenesis.

Humans are exposed to carcinogenic nickel (Ni) compounds both occupationally and environmentally. In this paper, molecular mechanisms of nickel carcinogenesis are considered from the point-of-view of the uptake of nickel sulfide particles in cells, their dissolution and their effects on heterochromatin. Molecular mechanisms by which nickel induces gene silencing, DNA hypermethylation and inhibition of histone acetylation, will be discussed.

Acetylation↗

PubMed2002

Comparison of the structures of natural and re-established populations of Ascaris in humans in a rural community of Jiangxi, China.

To compare the structures of natural and re-established populations of Ascaris in humans, universal (mass) chemotherapy was carried out at the beginning and the end of the study year using pyrantel pamoate. Worms expelled within 48 h of treatment were collected, their sex determined, and measurements made of length, width and weight. Length was used as the criterion for estimating the developmental stage of the worms. In comparison with the natural population, the reestablished population displayed similar sex ratio as well as distribution patterns among individuals and age groups of the host. However, the mean worm burden of the re-established population was significantly decreased, with a reduction of burdens in children aged 5-9 years. Also, the re-established population showed significant changes in population structure and worm measurements in that it comprised more immature and less fertile males, less fertile and more senile females, smaller and lighter males, larger (but not heavier) females than the natural population. The results suggested that the reestablished Ascaris population did not restore to its original status in relation to mean density, composition and fecundity. Therefore, universal treatment once a year should decrease the transmission of Ascaris in humans. Combined with previous results for the same study sites, the present findings also indicated that caution is warranted to avoid misleading conclusions when using prevalence and faecal egg counts as parameters for evaluating the success of control programmes.

Adolescent↗

PubMed2001

Connecting the vulcanization transition to percolation.

The vulcanization transition is addressed via a minimal replica-field-theoretic model. The appropriate long-wavelength behavior of the two- and three-point vertex functions is considered diagrammatically, to all orders in perturbation theory, and identified with the corresponding quantities in the Houghton-Reeve-Wallace field-theoretic approach to the percolation critical phenomenon. Hence, it is shown that percolation theory correctly captures the critical phenomenology of the vulcanization transition associated with the liquid and critical states.

Journal Article↗

PubMed2001

The histone deacetylase inhibitor trichostatin A reduces nickel-induced gene silencing in yeast and mammalian cells.

We have previously reported that nickel (Ni)-silenced expression of the URA3 gene in yeast (Saccharomyces cerevisiae) and gpt transgene in G12 Chinese hamster cells. In both cases, close proximity to a heterochromatic region was required for gene silencing. Yeast exposed to Ni exhibited reduced acetylation of the lysine residues in the N-terminal tail of histone H4. Ni-induced silencing of the gpt gene in mammalian cells involved hypermethylation of promoter region DNA. Yeast do not employ DNA methylation to silence gene expression. To determine if histone deacetylation participates in Ni-induced silencing of the URA3 and gpt genes, we exposed yeast and G12 hamster cells to the histone deacetylase inhibitor trichostatin A (TSA) prior to and concurrently with Ni. Treatment of yeast cells with 0.2-0.6mM NiCl(2) resulted in reduced expression of the URA3 gene as assessed by increased resistance to 1g/l 5-fluorotic acid (5-FOA). This effect was lessened when yeast were pre-treated with 50 microg TSA/ml. Similarly, treatment of G12 cells with 5 ng/ml TSA during and after exposure to 0.3 microg Ni(3)S(2)/cm(2) reduced silencing of the gpt gene as gauged by resistance to 10 microg/ml 6-thioguanine (6-TG). The ability of TSA alone and in combination with the DNA-demethylating agent (5-AzaC) to reactivate the gpt gene in Ni-silenced variants was also assessed. Although treatment with 100 ng/ml TSA for 48 h was partially effective in reactivating the gpt gene, treatment with 5 microM 5-AzaC was more efficacious. The greatest gpt gene reversion frequencies were observed following a sequential 5-AzaC/TSA treatment. Taken all together, our data from mammalian cells suggests that both DNA methylation and histone deacetylation participate in Ni-induced silencing of the gpt gene with DNA hypermethylation playing the more dominant role in maintaining the silenced state.

Acetylation↗

PubMed2001

An Arabidopsis mutant cex1 exhibits constant accumulation of jasmonate-regulated AtVSP, Thi2.1 and PDF1.2.

Jasmonates (JA) act as a regulator in plant growth as well as a signal in plant defense. The Arabidopsis vegetative storage protein (AtVSP) and plant defense-related proteins thionin (Thi2.1) and defensin (PDF1.2) have previously been shown to accumulate in response to JA induction. In this report, we isolated and characterized a novel recessive mutant, cex1, conferring constitutive JA-responsive phenotypes including JA-inhibitory growth and constitutive expression of JA-regulated AtVSP, Thi2.1 and PDF1.2. The plant morphology and the gene expression pattern of the cex1 mutant could be phenocopied by treatment of wild-type plants with exogenous JA, indicating that CEX1 might be a negative regulator of the JA response pathway.

Adenosine Triphosphatases↗

PubMed2001

Plasticity in serotonin uptake in primary neuronal cultures of serotonin transporter knockout mice.

The cross talk between dopaminergic and serotonergic systems in the brain has multiple neurophysiological and behavioral implications. Primary neuronal cultures of embryonic wild type (+/+) and serotonin transporter knockout (-/-) mice were used as a model to elucidate the possibility of plasticity at the level of serotonin uptake. Serotonergic neurons were identified in midbrain-hindbrain cultures of both wild type and knockout mice, using polyclonal anti-serotonin antibodies. Adding serotonin (10 microM) to wild type midbrain-hindbrain cultures increased the intensity of serotonin immunostaining, but did not change the number of serotonergic neurons. This increased intensity of serotonin staining was blocked by the serotonin transporter inhibitors fluoxetine and imipramine, but not with the dopamine transporter inhibitor nomifensine. In serotonin transporter knockout cultures, however, serotonin increased both the intensity of serotonin immunostaining and the number of serotonin positive neurons, and nomifensine decreased the number of serotonin-labeled neurons. Uptake of [3H]serotonin to wild type midbrain-hindbrain cultures was completely blocked by 1 microM fluoxetine, whereas nomifensine had a very small effect. In contrast, [3H]serotonin uptake to serotonin transporter knockout cultures, although very weak, was better inhibited by nomifensine than fluoxetine. The results imply that midbrain-hindbrain neuronal cultures of knockout mice, that do not express serotonin transporters, acquire the capacity to take up serotonin, apparently via dopamine transporters.

Adrenergic Uptake Inhibitors↗

PubMed2001

Apoptosis occurs in implantation site of the rhesus monkey during early stage of pregnancy.

The exact role of apoptosis that occurs in human placenta during the early stage of pregnancy remains unknown because of the difficulty in obtaining the intact implantation site. In this study, we used rhesus monkey as an animal model to examine apoptosis occurring in the implantation site at various stages of early pregnancy. It was shown that Fas and FasL mRNA and protein were localized in both the chorionic villi and glandular epithelium from day 15 to day 30 of pregnancy. Fas and FasL protein were also expressed in the epithelial plaque on day 15 of pregnancy. In situ 3'-end-labeling results showed that glandular epithelial cells underwent extensive apoptosis with obvious morphological degradation during the early stage of pregnancy. It was found that the cells that were 3'-end-labeled in the chorionic villi and anchoring villi were mainly localized in cytotrophoblast and cytotrophoblast column. It is therefore suggested that in primates apoptosis, which may be involved in the regulation of proliferation of trophoblast villi and degradation of epithelial plaque, as well as remodeling of the glands in the maternal decidua, may play an important role during the early stage of implantation and placentation.

Animals↗

PubMed2001

Pyrolytic characteristics of microalgae as renewable energy source determined by thermogravimetric analysis.

Two kinds of autotrophic microalgae, Spirulina platensis (SP) and Chlorella protothecoides (CP) were pyrolyzed at the heating rates of 15, 40, 60 and 80 degrees C/min up to 800 degrees C in a thermogravimetric analyzer to investigate their pyrolytic characteristics. Three stages (dehydration, devolatilization and solid decomposition) appeared in the pyrolysis process. SP and CP mainly devolatilized at 190-560 degrees C and 150-540 degrees C, respectively. A total volatile yield of about 71% was achieved from each microalga. As the heating rate increased, a lateral shift to higher temperatures was observed in their thermograms, and the instantaneous maximum and average reaction rates in the devolatilization stage were increased while the activation energy was decreased. The value of activation energy for CP pyrolysis was 4.22-5.25 x 10(4), lower than that of SP (7.62-9.70 x 10(4)), and the char in final residue of CP was 14.00-15.14%, less than that of SP by 2-3%. This indicated that CP is preferable for pyrolysis over SP. The experimental results may provide useful data for the design of pyrolytic processing systems using planktonic microalgae as feedstock.

Bioelectric Energy Sources↗