Biomedical subjects
Publications and source records attributed to Yan Xu.
Whole cells of Candida rugosa catalyzed the conversion of (R)-2-octanol from the corresponding racemate with the optical purity of 97% e.e. and yield of 92% in 10 h. The product was formed through a stereoinversion involving enantioselective oxidation and asymmetric reduction with 2-octanone as the intermediate.
Metastasis is a vital target for cancer treatment, since the majority of cancer patients die from metastatic, rather than the primary disease. KiSS1 has been identified as a metastasis suppressor gene in melanoma and breast carcinomas. We show here that KiSS1 is also a metastasis suppressor in human ovarian cancer. Overexpression of KiSS1 in ovarian cancer cells inhibits cell migration induced by serum or lysophosphatidic acid (LPA), and colonization in soft agar, but not cell proliferation, representing the characteristics of a metastasis suppressor gene. Furthermore, using an experimental metastatic mouse model, we show that expression of KiSS1 in SKOV3 ovarian cancer cells suppresses >50% metastatic colonization in mice (P < 0.0001). We find that activating protein kinase C (PKC) reverses about 80% of the inhibited cell migration induced by KiSS1, while down-regulation of PKCalpha with shRNA restores KiSS1 effect, providing evidence that inhibiting PKCalpha may be an important mechanism of the effect of KiSS1. These results suggest that KiSS1 is a metastasis suppressor of ovarian cancer and may be a potential molecular target for the treatment.
BACKGROUND & AIMS: Patients with inflammatory bowel disease (IBD) are at increased risk of developing colorectal cancer (CRC). We sought to determine the frequency of high-level microsatellite instability (MSI-H) and the mutational and methylation profile of MSI-H IBD-related neoplasms (IBDNs). METHODS: A total of 124 IBDNs (81 cancers, 43 dysplasias) from 78 patients were studied for the frequency of MSI-H and hypermethylation of 3 target genes: MLH1 , HPP1 , and RAB-32 . Fifteen MSI-H IBDNs were characterized according to their profile of frameshift mutations in 28 mononucleotide repeats and compared with 46 sporadic MSI-H CRCs. RESULTS: Nineteen of 124 IBDNs were MSI-H. The frequency of frameshift mutations in coding mononucleotide repeats was significantly lower in MSI-H IBDNs than in sporadic MSI-H CRCs for TGFBR2 (7 of 14 vs 34 of 43 samples; P = .047) and ACVR2 (3 of 14 vs 25 of 43 samples; P = .029). In contrast, ICA1 was mutated in 3 of 9 MSI-H IBDNs vs 2 of 54 sporadic MSI-H CRCs ( P = .028). HPP1 and RAB32 methylation was independent of MSI status and was observed in 4 of 59 and 0 of 64 nondysplastic mucosae, 20 of 38 and 1 of 25 dysplasias, and 28 of 61 and 20 of 60 carcinomas, respectively. CONCLUSIONS: The profiles of coding microsatellite mutations (instabilotypes) differ significantly between MSI-H IBDNs and MSI-H sporadic CRCs. Specifically, TGFBR2 and ACVR2 mutations are significantly rarer in MSI-H IBDNs than in MSI-H sporadic CRCs. Furthermore, HPP1 methylation occurs early, in 7% of nondysplastic and approximately half of dysplastic mucosae, whereas RAB32 methylation occurs at the transition to invasive growth, being rarer in dysplasias.
The use of exogenous cytokines is part of translational immune-antiretroviral approaches to induce immune reconstitution and possibly eliminate the persistence of human immunodeficiency virus type 1 (HIV-1) in virally suppressed infected individuals on highly active antiretroviral therapy (HAART). Recently, our laboratories demonstrated that interleukin-7 (IL-7) has significant efficiency in stimulating HIV-1 replication from proviral latency in CD4+ T lymphocytes of infected patients. The authors now investigated the possible role of IL-7 in HIV-1-associated dementia (HAD). The authors demonstrated that the IL-7 receptor is expressed on both human neurons (i.e., differentiated NT2 cells) and human astrocytes, with relatively higher mRNA levels in neurons. The translational protein levels of IL-7 receptor alpha were not proportional to those of the mRNA levels in these central nervous system (CNS)-based cell types. Exogenous IL-7 was observed to only slightly down-regulate IL-7 receptor alpha expression on both neurons and astrocytes, as assayed by Western blotting. Instead of promoting survival, surprisingly, exogenous IL-7 induced neuronal apoptosis, as detected by TUNEL assays. Furthermore, IL-7 augmented neuronal apoptosis induced by HIV-1 gp120. Human apoptosis genomic microarray analyses of IL-7-treated human neurons showed up-regulated expression of proapoptotic genes: protein kinases, caspase-10, FAST kinase, tumor necrosis factor (TNF) receptor, and BCL2-antagonist of cell death. These data suggest that IL-7 leads to neuronal apoptosis by a molecular mechanism(s) that occurs via Fas-mediated activation-induced cell death. These studies may therefore not only be key in evaluating the potential use of IL-7 in vivo as a therapeutic modality, but also suggest that IL-7, which is increased endogenously in HIV-1-infected individuals late in disease, may be involved in the neuronal apoptosis demonstrated during HAD.
Highly active antiretroviral therapy (HAART) does not lead to viral eradication, due to HIV-1 residual disease. We investigated whether the cervicovaginal tract serves as a viral reservoir. Seven out of eight cervicovaginal fluids were positive for cell-free HIV-1, by supersensitive reverse transcriptase-polymerase chain reactions (RT-PCR), with a detection limit of 1 copy/ml. No viral outgrowth, intracellular proviral DNA, or viral RNA was detected from cervicovaginal lavage and ecto- and endocervical cells. The cervicovaginal tract of patients on HAART is likely not a major solid tissue reservoir for HIV-1. Nonetheless, the presence of even low cell-free HIV-1 RNA in cervicovaginal secretions continues to suggest the importance of practicing protected sex, even in the era of HAART.
Despite dramatic reduction of the levels of human immunodeficiency virus type I (HIV-1) virions in blood and seminal plasma of infected patients, highly active antiretroviral therapy (HAART) does not eradicate HIV-1. Three patients, with less than 50 copies/ml of plasma viral RNA, were enrolled in this eradication protocol. Didanosine (DDI) and hydroxyurea (HU) were added to their baseline HAART and after a month of therapy, low dose OKT3, followed by a 2-week course of interleukin 2 (IL-2), was administrated. All antiretroviral therapy was then interrupted and the three patients developed viral rebound in the peripheral blood. The V3 loop region of the HIV-1 gp120 from cell-free viral RNA and proviral DNA in blood and seminal compartments was sequenced in one patient. The two major viral isolates in semen cells were macrophage- tropic (R5) and dual-tropic (R5X4), and these isolates were also present in the PBMCs. Six months after the viral rebound, we demonstrated a shift toward dual tropism in semen cell-associated HIV-1 proviral DNA, with the first appearance of a T-lymphotropic (X4) provirus solely in this compartment. The virus responsible for the blood plasma viral rebound was never found in the semen microenvironment. This study suggests viral compartmentalization of the semen microenvironment after an intensification and stimulatory HIV-1 eradication protocol, with evidence of viral evolution.
The thermal stability of a G-quartet formed by incorporation of 8-methylguanine (m8G) in the DNA sequence at the 5' terminus of the Rb gene was examined by CD melting experiments. Substitutions of m8G at positions that show syn conformations in antiparallel G-quartets stabilize the structure. Formation of the G-quartet structure in the Rb gene acts as a barrier in DNA synthesis, as determined using a rapid and simple polymerase arrest assay. It was found that the C-rich complementary strand could form an i-motif structure at lower pH values.
DNA C1' radicals formed by hydrogen atom abstraction from the C1' position of the sugar backbone lead to the production of 2'-deoxyribonolactone as a DNA damage lesion. Although DNA C1' radicals may be involved in a variety of DNA damage processes, there is very little information on the molecular basis of DNA structure dependence in the reactions of C1' radicals. Here, we describe a detailed study of the reactivity of 2'-deoxyuridin-1'-yl radicals in single- and double-stranded B-form DNA and G-quartets in the formation of 2'-deoxyribonolactone, using the unnatural precursor 1'-pivaloyl-2'-deoxyuridine (1).
Platelet-derived growth factor receptor alpha (PDGFRalpha) is a type III receptor tyrosine kinase that is expressed on a variety of tumor types. A neutralizing monoclonal antibody to human PDGFRalpha, which did not cross-react with the beta form of the receptor, was generated. The fully human antibody, termed 3G3, has a Kd of 40 pmol/L and blocks both PDGF-AA and PDGF-BB ligands from binding to PDGFRalpha. In addition to blocking ligand-induced cell mitogenesis and receptor autophosphorylation, 3G3 inhibited phosphorylation of the downstream signaling molecules Akt and mitogen-activated protein kinase. This inhibition was seen in both transfected and tumor cell lines expressing PDGFRalpha. The in vivo antitumor activity of 3G3 was tested in human glioblastoma (U118) and leiomyosarcoma (SKLMS-1) xenograft tumor models in athymic nude mice. Antibody 3G3 significantly inhibited the growth of U118 (P=0.0004) and SKLMS-1 (P <0.0001) tumors relative to control. These data suggest that 3G3 may be useful for the treatment of tumors that express PDGFRalpha.
The persistence of HIV-1 in virally suppressed infected individuals on highly active antiretroviral therapy (HAART) remains a major therapeutic problem. The use of cytokines has been envisioned as an additional therapeutic strategy to stimulate latent proviruses in these individuals. Immune activation therapy using IL-2 has shown some promise. In the present study, we found that IL-7 was significantly more effective at enhancing HIV-1 proviral reactivation than either IL-2 alone or IL-2 combined with phytohemagglutinin (PHA) in CD8-depleted PBMCs. IL-7 also showed a positive trend for inducing proviral reactivation from resting CD4(+) T lymphocytes from HIV-1-infected patients on suppressive HAART. Moreover, the phylogenetic analyses of viral envelope gp120 genes from induced viruses indicated that distinct proviral quasispecies had been activated by IL-7, as compared with those activated by the PHA/IL-2 treatment. These studies thus demonstrate that different activators of proviral latency may perturb and potentially deplete only selected, specific portions of the proviral archive in virally suppressed individuals. The known immunomodulatory effects of IL-7 could be combined with its ability to stimulate HIV-1 replication from resting CD4(+) T lymphocytes, in addition to other moieties, to potentially deplete HIV-1 reservoirs and lead to the rational design of immune-antiretroviral approaches.
Crude enzyme extracted from soybean was used to convert isoeugenol into vanillin. The effects of several factors on the bioconversion were studied. Conversion was affected by the amount of substrate and was also improved by the addition of absorbents, among which powdered activated carbon was the best. The effect of H2O2 concentration on the conversion was also studied. The optimum concentration of H2O2 was 1% (v/v). With 10 g/L of powdered activated carbon and 0.1% H2O2 added, vanillin reached a maximum concentration of 2.46 g/L after 36 h, corresponding to a molar yield of 13.3%.
OBJECTIVE: To investigate the therapeutic effect of cisapride on gastric injury following hemorrhagic shock resuscitation. METHODS: 108 Wistar rats weighing (200 g+/-30 g) were randomly divided into a sham shock (SS) group (n=36), a hemorrhagic shock resuscitation (HS) group (n=36) and a hemorrhagic shock cisapride treated (HSC) group (n=36). Sampling at 1, 2 and 4 hours after resuscitation was done and 6 samples for each observation item were taken. The gastric blood flow volume was measured by isotope label biological microglobulin. Gastric pHi, gastric emptying, MDA and Na+-K+-ATPase of gastric mucosa were measured. RESULTS: In the HSC group, the relative residual rate of gastric pigment decreased significantly, the gastric blood flow volume elevated; gastric pHi increased significantly at 2 hours; the level of mucosal MDA decreased at 4 hours, the activity of Na+-K+-ATPase increased and the lactic acid level in the portal vein decreased significantly compared to the HS group. CONCLUSIONS: After hemorrhagic shock resuscitation, cisapride contained the following functions, 1) promoting gastric emptying, 2) increasing the blood flow of gastric blood flow volume and gastric pHi, 3) depressing the lactic acid concentration of the portal vein and improving MDA volume and Na+-K+-ATPase activity of gastric mucosa. It suggests that after complementing effective circulating blood volume for hemorrhagic shock resuscitation, early use of cisapride for gastric motility is helpful for an improvement of lasting ischemia and hypoxia in stomach.
STK15 (Serine/Threonine protein kinase 15) is a serine/threonine kinase encoding gene, whose overexpression in mammalian cells leads to centrosome amplification, chromosomal instability, and oncogenic transformation. 91A-->T, a single nucleotide polymorphism (SNP) in exon 3 of STK15, has recently been shown to be associated with human cancer susceptibility. Within exon 3 of STK15, there are three nonsynonymous SNPs: 91 A-->T, 169G-->A and 311C-->T. We have determined STK15 genotypes and haplotypes composed of 91A-->T and 169G-->A by PCR-RFLP in a randomly sampled cohort of 193 normal individuals from Northeast China. DNA samples from all individuals were subjected to first round of PCR using a pair of specific primers. For the subsequent nested PCR,a mismatch forward primer, which could introduce an EcoR I restriction site to the 91A allele, was included. The nested PCR products were digested with the restriction endonucleases EcoRI and AccII. The double restriction digests were separated by polyacrylamide gel electrophoresis. Three haplotypes,91A-169G, 91T-169A and 91T-169G, were detected and their frequencies were 68.65%, 10.88% and 20.47%, respectively. Six genotypes composed of the above three haplotypes were found,and their frequencies were 91A-169G/91 A-169G (46.11%), 91A-169G/91 T-169A (14.51%), 91A-169G/91T-169G (30.57%), 91T-169G/91T-169G (3.11%), 91T-169G/91T-169A (4.15%), 91T-169A/91T-169A (1.55%). Whereas no 91A-169A haplotype was detected in all individuals examined in the current study, linkage disequilibrium (LD) between the two SNPs was found.
OBJECTIVE: To study the change of nucleic acid sequence and the germicidal effect of an E. coli bacteriophage with broad host range isolated from hospital sewage as well as to study the mechanism of phage host specificity and the effect of killed bacteria by phage-disinfectant to the samples from sewage water. METHODS: To extract the nucleic acid from phage f(2) and phage with broad host range using anti-serum-carbamidine hydrochloride assay. Purity with agarose gel electrophoresis was then evaluated. Differences of nucleic acid sequence between phage f(2) and phage with broad host range with reverse transcription-polymerase chain reaction (RT-PCR) and random amplified polymorphic DNA (RAPD)-PCR were also comparing and analysed. Through observing the germicidal test of phage f(2) and phage with broad host range to samples from environment, different sterilization effects between the two phages were compared. RESULTS: Analystic test for nucleic acid revealed that the two phages both belonged to 6000 bp, single-stranded RNA bacteriophage. Significant differences in their specificity of RAPD-PCR and RT-PCR were found during the changed of host range; with 26 RAPD-cDNA differential fragments found that in two phages RAPD-PCR products. The RT-PCR product of phage f(2) was 450 bp cDNA fragment, but the phage with broad host range did not show PCR product. Treating the sewage water with phage under broad host range, the germicidal test showed that the cleaning rate of E. coli bacteria and phage f(2) in water samples from environment could reach 36.75% - 56.28%, 30.84% - 47.96%, 19.19% - 35.06% and 13.05% - 27.85%, respectively. CONCLUSION: The cleaning rates to E. coli and bacteria by phage with broad host range were obviously higher than phage f(2) (P = 0.000). Analytic test for nucleic acid indicated that host-specific lytic effect of phage with broad host range had been changed at genetic level.
OBJECTIVE: Human soluble tumor necrosis factor receptor (sTNFR) can interfere with the biological functions of interleukin-1, which may be appropriate to the treatment of periodontitis. The eukaryote expression vector of the human sTNFR gene must be constructed prior to conducting transgene therapy of periodontitis. METHODS: Both sTNFR gene and plasmid pcDNA 3.1 (+) DNA were digested with Kpn I and Xho I. After purification, the two fragments were ligated by TakaRa DNA Ligation Kit (Ver 2.0). This recombinant DNA was then transformed into E. Coli Competent Cells JM109 and positive clones were selected on the LB agarose plate containing ampicillin (80 microg/ul). RESULTS: Six single clones were indentified by double digestion with kpn I and xho I and two fragments with the size of 5.4 kb and 1.0 kb were produced as expected. CONCLUSION: The sTNFR gene was successfully inserted into the eukaryote expression vector plasmid pcDNA 3.1 (+) by recombination technology in vitro.
OBJECTIVE: To explore the mechanism of protective effect of oral L-arginine (L-Arg) on the intestine after scald injury in rats. METHODS: Sixty-six Sprague-Dawley (SD) rats were randomly divided into three groups: i.e. normal control (N, n = 6, without treatment), oral L-arginine group (A, n = 30, with 1 ml 70 g/L of L-Arg per os 2 times a day from 2 post scald hour (PSH)) on with normal enteral feeding and group B (n = 30, with oral feeding of cold boiled water after scald). The changes in the content of superoxide dismutase (SOD), malondialdehyde (MDA), nitric oxide (NO), endothelin (ET), ET/NO ratio in the intestine and the level of plasma endotoxin (LPS) in portal vein were assessed at 6, 12, 24, 48, 72 PSH. Ileum tissue samples were harvested for pathological examination. RESULTS: The ET content in the intestinal tissue in A group at 6, 12 and 24 PSH (0.80 +/- 0.26 ng/g, 0.75 +/- 0.30 ng/g, 0.63 +/- 0.22 ng/g) was obviously lower than that in B group (1.26 +/- 0.38 ng/g, 1.34 +/- 0.37 ng/g, 0.97 +/- 0.19 ng/g, P < 0.05), but the NO contents in the intestine in A group at the same time points were significantly higher than that in B group (P < 0.01). The ET/NO ratio and the level of plasma endotoxin in A group were significantly lower than those in B group at each time point (P < 0.05 or 0.01). Pathological examination showed that the intestinal mucosal injury in the A group was obviously milder than that in the B group. CONCLUSION: Oral L-arginine was shown to have the effects to ameliorate ischemia reperfusion injury of the intestine and to protect the barrier function of the intestinal mucosa. This might be related to an increase in the NO level in intestinal mucosa resulting in maintenance of a stable ET/NO ratio.
The study on the soil physical properties, nutrient contents, microbial amounts and enzyme activities of clear cutting and controlled burning Chinese fir stands showed that in comparing with the control, soil non-capillary porosity of clear cutting stand increased by 23%, whereas soil natural water capacity and capillary moisture capacity decreased by 25%. In controlled burning stand, soil bulk density increased by 10%, while soil non-capillary porosity, natural water capacity and capillary moisture capacity decreased by 61%, 48% and 26%, respectively. The contents of soil organic matter, total N, total P and total K in clear cutting stand decreased by 14%, 14%, 35% and 22%, and in controlled burning stand, they decreased by 37%, 37%, 47% and 7%, respectively. Soil alkalized N and available K in clear cutting stand increased by 24% and 31%, respectively, but soil available P decreased by 15%. The contents of soil alkalized N, available P and available K in controlled burning stand decreased by 25%, 43% and 40%, respectively. In clear cutting stand, the amounts of soil bacteria, fungi and actinomyces increased by 1.4, 11.3 and 0.8 times, respectively, but in controlled burning stand, the amounts of soil bacteria decreased by 24%, while those of soil fungi and actinomyces increased by 5.0 and 0.5 times, respectively. The activities of soil urease, catalase and cellulase in clear cutting stand increased by 1.9, 1.6 and 2.1 times, and in controlled burning land, they were 35%, 90% and 106% of the control, respectively. Damp soil had higher contents of organic matter, total N and total P, whereas porous soil was favorable for the accumulation of alkalized N, available P and available K and for the increase of soil urease activity. The amount of soil fungi decreased with increasing soil capillary porosity. Aerated soil was favorable for the increase of soil catalase activity.
The purpose of this study was to evaluate the clinical effect of using composite resin to fill dental attrition on occlusal surface. Whether the dental attrition had enough space to the material was determined first. Sometimes grinding the sharp and steep cusps or ridges of the opposite teeth was needed. Then the dental attrition was cleaned thoroughly, and finally filled with CLEARFIL bond and composite resin without preparing cavity. The follow-up period was 1 year. Out of 70 teeth from 25 patients, 52 were successful, 16 were curative, and 2 were failed. The curative rate was 97.14%. The method avoids endangering the dental pulp. It was easily accepted by the patients and operated by dentists, and can be widely applied in clinical cases.