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Biomedical subjects

Li Xu

Publications and source records attributed to Li Xu.

At least 145 records · Page 8Linked to original sources
PubMed2003

Expression of angiotensin II type 1 receptor in rat hepatic stellate cells and its effects on cell growth and collagen production.

OBJECTIVE: To investigate the contribution of angiotensin II towards the process of hepatic fibrosis that is largely due to hepatic stellate cell growth. METHODS: Adult rat hepatic stellate cells were cultured and checked for the expression of angiotensin II receptor 1a (AT(1a)) mRNA by RT-PCR and sequence analysis. The effects of angiotensin II were observed on stimulation of hepatic stellate cell growth detected by MTT assays, (3)H-thymidine incorporation and cell count, and collagen synthesis by (3)H-proline incorporation. RESULTS: We demonstrated that cultured adult rat hepatic stellate cells expressed AT(1a) mRNA, and angiotensin II in a concentration-dependent manner stimulated hepatic stellate cell growth at a concentration of 10(-7)-10(-9) mol/l and collagen synthesis at a concentration of 10(-6)-10(-10) mol/l. Also, AT(1a) receptor antagonist, in a concentration-dependent manner, blocked the cell growth from 10(-6) to 10(-8) mol/l and collagen synthesis from 10(-6) to 10(-9) mol/l. CONCLUSIONS: The results provided direct evidence that AT(1a) mRNA was expressed in rat hepatic stellate cells and angiotensin II could contribute towards the development of hepatic fibrosis via AT(1a) receptor.

Angiotensin II↗
PubMed2003

Human estrogen receptor beta 548 is not a common variant in three distinct populations.

Several isoforms of estrogen receptor (ER) beta (also known as NR3A2) have been reported, including variants with different N-terminal ends. In rodents, two in-frame initiation codons (ATGs) are used to produce proteins of 530 and 549 amino acids, respectively. In humans, the upstream ATG is out of frame in all clones reported, until recently, when human clones with an extra A-T base pair placing the upstream ATG in frame were reported. The authors suggested that this could represent a novel polymorphism in the ERbeta gene. Because human ERbeta548 (hERbeta548) and hERbeta530 display different functional characteristics in vitro, it is of interest to determine if this variant constitutes a polymorphism in human populations. We therefore determined the frequency of this novel isoform in several populations including African (n = 96), Caucasian (n = 100), and Asian (n = 128) subjects using denaturing HPLC. We did not detect any alleles that correspond to hERbeta548 in these samples or in additional samples of heterogeneous origin. It is concluded that hERbeta548 is not a common variant in Africans, Caucasians, or Asians.

Alleles↗
PubMed2003

Selection and identification of mimic epitopes for gastric cancer-associated antigen MG7 Ag.

Phage display technology is now well established as an important experimental approach in designing new reagents for diagnosis of diseases and development of novel vaccines. Aiming at identifying possible immunogenic mimotopes of gastric cancer-associated antigen, we used a monoclonal antibody against gastric cancer, named monoclonal antibody MG7, to screen two phage-displayed nanopeptide libraries. All selected phages were used to immunize BALB/c mice separately. By immunohistochemical staining the tissue sections with the immunized mice sera, we identified one phage that induced gastric cancer-specific antibody response. Consistent with our reported results before, we demonstrate that specific immunogenic epitopes can be isolated by screening phage-displayed library even when natural antigens are not readily available.

Animals↗
PubMed2003

[Study on the ex vivo expansion characteristics of umbilical cord blood CD34+ cells and mononuclear cells].

OBJECTIVE: To explore the ex vivo expansion characteristics of selected CD(34)(+) cells and mononuclear cells (MNC). METHODS: CD(34)(+) cells were isolated from umbilical cord blood MNC by MiniMACS system, expanded under the same conditions as that for MNC. The effects of re-isolation and the MNC supernatant (MNC-SN) on the selected CD(34)(+) cells were investigated. And the CD(34)(-) cells of MNC were cultured ex vivo. RESULTS: In the culture of selected CD(34)(+) cells, both the colony density and the proportion of the CD(34)(+) cells declined continuously with the culturing, although they presented a high proliferation potential. However, in the culture of the MNC, from day 0 to day 7, the colony density and the proportion of CD(34)(+) cells were increased from 412 +/- 167/10(5) cells and (1.12 +/- 0.42)% to 1 162 +/- 566/10(5) cells and (4.17 +/- 1.44)%, respectively. It was found that both the total cells and the CD(34)(+) cells restored expansion potential by re-isolating. CD(34)(-) cells of MNC had the ability to form colony and could transform to CD(34)(+) cells. MNC-SN can promote colony forming ability and lead to CD(34)(+) cells differentiation at the same time. CONCLUSIONS: In ex vivo culture, selected CD(34)(+) cells presented a high proliferation and differentiation potentials, and the CD(34)(-) cells produced during the cultivation had inhibition effect on CD(34)(+) cells expansion. CD(34)(-) cell population from cord blood MNC contained hematopoietic stem/progenitor cells and the cytokines secreted by CD(34)(-) cells could induce CD(34)(+) cells to more mature colony-forming cells.

Antigens, CD34↗
PubMed2003

[An eighteen-year study on phenylketonuria].

A study on phenylketonuria (PKU) has been carried out in China-Japan Friendship Hospital since 1984. The results revealed that: (1) Totally 603 patients with PKU were diagnosed and treated in the hospital from October 1984 to September 2002. Among which 136 cases were identified by neonatal screening and treated within 3 months. One hundred and ninety-five cases were treated when the children were 3-12 months of age. Another 272 PKU children were diagnosed when they were more than 1 year old. All of these late-treated cases had some signs and symptoms of PKU. Mental retardation was found in 467 cases and various patterns of seizures in 119 cases. After treatment with low-phenylalanine diet, the follow-up for early-treated patients revealed that their physical and mental developments were normal. In late-treated patients, abnormal behaviour was significantly improved and their developmental quotient were elevated. Prenatal gene diagnosis of PKU risk foetus in 22 PKU families was successfully performed. (2) Urinary pterins obtained from 369 HPA patients were measured by HPLC. Twenty two patients with BH4 deficiency have been recognized. Six single base mutations were detected in 18 unrelated northern Chinese BH4 deficiency families, and the mutations at nucleotides 259C-->T and 286G-->A were common mutations. Eighteen BH4 deficient patients were treated with BH4, L-dopa and 5-hydroxytryptophan, and the results were satisfactory. (3) The abnormal rate of EEG was high in untreated patients with PKU, mainly showing epileptiform discharges and partly showing background activity abnormality. The most frequent finding was patchy areas of increased signal intensity in white matter on MRI in the brain of PKU patients, while delayed myelination and brain agenesis were often detected. After dietary treatment, follow-ups with EEG and MRI revealed that the abnormalities were decreased significantly. (4) The relationship between genotype and intellectual phenotype was examined in 29 late-treated patients with classical PKU. It was found that the genotype of 22 patients were compatible with intellectual phenotype and not well matched in 7 cases. The result indicate that the genotype was well matched with intellectual phenotype in classical PKU patients.

Biopterins↗
PubMed2003

[The effects of smoking on gingival crevicular fluid volume and elastase before and after initial periodontal treatment].

OBJECTIVE: To investigate the relationship between smoking and gingival crevicular fluid volume (GCF), level of elastase (EA) in 37 severe periodontitis patients before and after 1 month periodontal initial treatment. METHODS: The GCF samples were collected from 122 sites in 22 heavy smokers (>or= 20 cigarettes/day) and 90 sites in 15 non-smokers before and after 1 month periodontal initial treatment. There is no difference (P > 0.05) on pocket depth between smoking sites (5.6 +/- 1.2) mm and non-smoking sites (5.4 +/- 1.2) mm at baseline. The volume of each GCF sample was measured by Periotron 6000 and the elastase in GCF were determined by substrate (meosuc-als-als-pro-val-NA) method. RESULTS: After non-surgical treatment both GCF volume and elastase level were significantly decreased (P < 0.001) in both smokers and non-smokers. But the decrease of GCF volume (91 sites, 74.6%) and elastase level (70 sites, 76.1%) in smokers were significant lower (P < 0.01) than non-smokers (GCF, 88 sites, 97.8%; EA, 56 sites, 93.3%). CONCLUSION: These findings suggest that smoking has effect on gingival crevicular fluid volume and elastase level of patients with periodontitis.

Adult↗
PubMed2003

[Cardioprotective effect and influence on NOS expression of Montelukast sodium in rats].

AIM: To determine the protective effect and influence on NOS expression of Montelukast sodium--a leukotriene antagonist on myocardial necrosis in rats. METHODS: Myocardial ischemia and necrosis were induced in rats by isoproterenol (2 mg.kg-1, s.c., qd for 2 d). Serum activity of LDH, CK, MDA, NO content in myocardium and scope of myocardial necrosis were measured. nNOS, iNOS and eNOS were investigated by immunohistochemical evaluation. RESULTS: Decreased serum level of LDH, CK, MDA and attenuated myocardial necrosis area were found in rats pretreated with Montelukast sodium 10 and 30 mg.kg-1. Montelukast sodium 30 mg.kg-1 also enhanced NO content in myocardium. Montelukast sodium activated the eNOS expression and reduced the iNOS expression. CONCLUSION: Montelukast sodium is cardioprotective during myocardial injury in rats by halting the leukotrienes-induced inflammatory response and upregulating the eNOS expression as well as downregulating the iNOS expression. This may represent an approach to the treatment of myocardial ischemia with leukotriene antagonists.

Acetates↗
PubMed2002

A chlorine isotope effect for enzyme-catalyzed chlorination.

Several chlorinated organic compounds (COCs) that have been detected in a wide range of human, animal, and environmental samples may be derived from natural or anthropogenic sources. To determine whether the Cl isotope ratios of these compounds could be used to differentiate sources, we investigated the chlorine isotope effect for enzyme-catalyzed chlorination. Two aromatic substrates, 1,3,5-trimethylbenzene (TMB) and 3,5-dimethylphenol (DMP), were treated with a chloroperoxidase isolated from the fungus Caldariomyces fumago. A kinetic isotope effect (KIE) (in terms of k35/k37) was calculated to be 1.012 for TMB and 1.011 for DMP. A similar reaction, but not catalyzed, with hypochlorite yielded a much smaller KIE. These results indicate that a substantial KIE exists for this process. Furthermore, natural COCs synthesized by this enzymatic pathway may have Cl isotope ratios that will be easily distinguished from anthropogenic COCs.

Chloride Peroxidase↗
PubMed2002

The West Falmouth oil spill after thirty years: the persistence of petroleum hydrocarbons in marsh sediments.

The long-term fate of petroleum hydrocarbons in marsh sediments (West Falmouth, MA) contaminated in 1969 by the spill of the barge Florida was investigated. A 36-cm-long sediment core was collected in August 2000, and sediment extracts were analyzed by gas chromatography (GC) and comprehensive two-dimensional gas chromatography (GC x GC). The latter technique is capable of separating 1 order of magnitude more compounds than the former and was used to observe whether any compositional changes in the unresolved complex mixture (UCM) occurred. No evidence of petroleum residues was detected in the top 6 cm (0-6 cm) and the lower 8 cm (28-36 cm) of the core. However, the central sections 16-28 cm) were dominated by a UCM in the boiling range of n-C13-n-C25 alkanes, consistent with a No. 2 fuel oil source. The 12-14- and 14-16-cm sections had the highest concentrations of UCM approximately 8 mg g(-1)). These values are similar to concentrations observed shortly after the spill. Initial GC x GC analysis revealed that only the n-alkanes were completely degraded, and contrary to previous studies, pristane and phytane as well as numerous other branched alkanes are still present in the sediments. These results suggestthatatthis site hydrocarbon contamination will persist indefinitely in the sedimentary record.

Accidents↗
PubMed2002

Minimal variation in T-20 binding domain of different HIV-1 subtypes from antiretroviral-naive and -experienced patients.

In-vitro differences in T-20 susceptibility among HIV-1 subtypes have been reported. We therefore studied the T-20 binding domain of a variety of virus subtypes from both antiretroviral-naive and -experienced patients. Minimal variation in the HR-1 region of gp41 was observed, especially within the region responsible for T-20 resistance. Any subtype differences in T-20 susceptibility do not appear to be related to HR-1 genetic variation.

Anti-HIV Agents↗
PubMed2002

Effects of stimulus level on speech perception with cochlear prostheses.

This study is one of a series that examines stimulus features important for cochlear implant function. Here, we examine effects of stimulus level. In subjects with cochlear implants, a number of psychophysical tests of temporal discrimination (pulse rate discrimination, gap detection, etc.) show marked improvement as a function of stimulus level through most or all of the dynamic range, while electrode-place discrimination can improve or degrade as a function of level. In this study, effects of these combined potential influences were studied by examining the effects of stimulus level on syllable identification. We tested two hypotheses: that syllable identification varies as a function of stimulus level and that level and electrode configuration interact in affecting syllable identification. We examined vowel and consonant identification as a function of stimulus level for bipolar and monopolar electrode configurations. We used experimental processor maps where upper and lower stimulation limits of each electrode pair were equated to eliminate confounding effects of dynamic range, which varies across subjects and electrodes. For each channel, stimulation amplitude was set to a fixed percentage of its dynamic range. Eight adult subjects with Nucleus CI24M implants were tested using the SPEAK processing strategy. With each electrode configuration, stimulus levels were tested from 0% to 90% of the dynamic range in nine steps. The effects on consonant and vowel identification were similar. Phoneme identification was usually better for monopolar than for bipolar stimulation. In the lower half of the dynamic range, syllable identification usually increased as a function of stimulus level. In the upper half of the dynamic range, syllable identification continued to increase as a function of level to 90% of the dynamic range for some subjects, while for others there was no appreciable change or a decrease as a function of level. Decreases in performance at high levels were more common with monopolar than bipolar stimulation. These results suggest that if speech processors are programmed to optimize level for each individual, speech perception performance could be improved.

Acoustic Stimulation↗
PubMed2002

Radiocarbon as a tool to apportion the sources of polycyclic aromatic hydrocarbons and black carbon in environmental samples.

To determine the relative inputs of polycyclic aromatic hydrocarbons (PAHs) and black carbon (BC) in environmental samples from the combustion of fossil fuels and biomass, we have developed two independent analytical methods for determining the 14C abundance of PAHs and BC. The 5730 yr half-life of 14C makes it an ideal tracer for identifying combustion products derived from fossil fuels (14C-free) versus those stemming from modern biomass (contemporary 14C). The 14C abundance of PAHs in several environmental Standard Reference Materials was measured by accelerator mass spectrometry after extraction and then purification by high-performance liquid chromatography and preparative capillary gas chromatography. This method yields pure compounds that allow for a high degree of confidence in the 14C results. The PAHs data were then used to compare and evaluate results from an operationally defined thermal oxidation method used to isolate a BC fraction. The 14C compositions of PAHs and BC were very similar and suggest that the thermal oxidation method employed for isolating BC is robust and free from interferences by non-BC components. In addition, these data indicate that both the PAHs and the BC species derive mostly from fossil fuels and/or their combustion products.

Biomass↗
PubMed2002

Prediction of survival in patients with head and neck cancer using the histoculture drug response assay.

BACKGROUND: Chemoresponse is a significant outcome predictor in patients with head and neck cancer, regardless of the treatment modality used. The histoculture drug response assay (HDRA) has been shown to be a reliable method for in vitro chemoresponse assessment. In this study, we have correlated the HDRA assessment with survival in patients with head and neck squamous cell carcinoma (HNSCC). METHOD: Tumor specimens from 41 of 42 patients undergoing treatment for HNSCC were successfully evaluated by the HDRA. Tumor tissue was histocultured on Gelfoam sponges gel in 24-well plates, followed by treatment with cisplatin (15 microg/mL) or 5-fluorouracil (40 microg/mL) in triplicate. A control group received no drug treatment. After completion of drug treatment, the relative cell survival in the tumors was determined using the MTT assay. The inhibition rate (IR) for each drug was calculated relative to the control for each case, and sensitivity was defined as a tumor IR of greater than 30%. Treatment was based on established protocols for the location and stage of the tumor and included surgery, radiation, and/or chemotherapy. Survival comparisons were performed using the generalized Wilcoxon test for the comparison of Kaplan-Meier survival curves. RESULTS: Resistance to 5-fluorouracil was present in 13 cases (32%), to cisplatinum in 13 cases (32%), and to both agents in 11 cases (27%). The 2-year cause-specific survival was significantly greater for patients sensitive to 5-fluorouracil (85% vs 64%; p =.04), cisplatinum (86% vs 64%; p =.05), or both agents (85% vs 63%; p =.01). The association between HDRA assessment of chemoresponse and clinical outcome remained significant even after controlling for the effects of TNM stage and the presence of recurrent cancer at presentation by multivariate analysis. CONCLUSIONS: Chemosensitivity determined by the HDRA seems to be a strong predictor of survival in patients with advanced HNSCC and should be considered further.

Antimetabolites, Antineoplastic↗
PubMed2002

Systematic analysis of E-, N- and P-cadherin expression in mouse eye development.

Cadherins are a family of Ca(2+)-dependent cell adhesion molecules. Through their homophilic binding interactions, cadherins play important roles in tissue formation and maintenance during development. Here the authors compare the expression patterns of the three classical cadherins, E-, N- and P-cadherin, during mouse eye development from embryonic day 9.5 (E9.5) to adult. It was found that: (1) The expression patterns of N- and P-cadherin are mutually exclusive in most ocular tissues during development. N-cadherin mRNA is detected specifically in the lens placode during lens induction at E9.5, and is absent in the rest of the surface ectodermal tissues. In contrast, P-cadherin is expressed in the surface ectoderm but not in the lens vesicle. N-cadherin is expressed continuously in the lens pit, lens vesicle, and in the epithelial cells and newly differentiating fiber cells of the mature lens. P-cadherin is expressed in the epithelial cells of the cornea, eyelids and Harderian gland. Reciprocal expression patterns of N-and P-cadherins are also seen during retinal development. N-cadherin is initially expressed in both the inner and outer layers of the optic cup at E9.5. N-cadherin expression persists in the inner layer as it develops into neural retina, but is turned off in the outer layer where the cells differentiate into retinal pigment epithelial (RPE) cells and express P-cadherin. Reciprocal patterns of expression are also seen in the ciliary epithelium. N-cadherin is expressed in the inner layer and P-cadherin in the outer layer of the ciliary epithelium. (2) E- and P-cadherins are epithelial cadherins. Their expression patterns in the eye are not identical. Both cadherins are found in the epithelia of the cornea, eyelid and Harderian gland. In contrast, lens epithelial cells express E- but not P-cadherin, and RPE cells express P- but not E-cadherin. (3) In addition to its high expression in surface ectoderm-derived tissues, E-cadherin mRNA was also detected in some of the retinal ganglion neurons at postnatal day 14 (P14). E-cadherin expression in the neural retina has not been reported before. This study shows that cell fate determination in the eye occurs in conjunction with distinct changes in the patterns of cadherin gene expression.

Animals↗
PubMed2002

Residue levels of HCHs, DDTs and PCBs in shellfish from coastal areas of east Xiamen Island and Minjiang Estuary, China.

Shellfish samples were collected from the coastal cultivating areas of east Xiamen Island and Minjing Estuary, China and analyzed for hexachlorocyclohexanes (HCHs), DDTs and polychlorinated biphenyls (PCBs) by GC. Concentration ranges of HCHs, DDTs and PCBs in the coastal area of east Xiamen Island were 0.18-345, 75.2-2143 and ND-23 ng g(-1) dry wt., respectively; those for Minjiang Estuary were ND-5.07, 21.5-2396 and ND-6.78 ng g(-1) dry wt., respectively. The results showed that the organochlorines were evidently accumulated in marine bivalve molluscs, particularly in oyster. The concentrations of organocholorine pollutants in shellfish samples varied with the sampling locations, the season of collection and organism species, but were generally higher than those in the sediments. The concentrations of DDTs in the shellfish were high as compared with HCHs and PCBs, so that DDTs can be considered as the typical organochlorines in the survey areas. The residue levels and compositions of HCHs, DDTs and PCBs are discussed.

Animals↗
PubMed2002

Radiocarbon content of synthetic and natural semi-volatile halogenated organic compounds.

Some halogenated organic compounds, such as polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and polybrominated diphenyl ethers (PBDEs), have been suggested to have natural sources but separating these compounds from their commercially synthesized counterparts is difficult. Molecular-level 14C analysis may be beneficial since most synthetic compounds are manufactured from petrochemicals (14C-free) and natural compounds should have "modern" or "contemporary" 14C levels. As a baseline study, we measured, for the first time, the 14C abundance in commercial PCB and PBDE mixtures, a number of organochlorine pesticides, as well as one natural product 2-(3',5'-dibromo-2'-methoxyphenoxy)-3,5-dibromoanisole. The latter compound was isolated from a marine sponge and is similar in structure to a PBDE. All of the synthetic compounds were 14C-free except for the pesticide toxaphene. which had a modern 14C abundance, as did the brominated natural compound. The result for toxaphene was not surprising since it was commercially synthesized by the chlorination of camphene derived from pine trees. These results suggest that measuring the 14C content of halogenated organic compounds may be quite useful in establishing whether organic compounds encountered in the environment have natural or synthetic origins (or both) provided that any synthetic counterparts derive from petrochemical feedstock.

Animals↗
PubMed2002

Bovine anti-Helicobacter pylori antibodies for oral immunotherapy.

BACKGROUND: Passive immunization with orally administered antibodies against specific pathogens has previously been successfully used therapeutically in both animal and human studies. We employed a similar strategy for experimental treatment of mice infected with the gastric pathogen Helicobacter pylori. METHODS: An anti-H. pylori bovine colostral hyperimmune immunoglobulin preparation (BIC) was generated and its efficacy was tested in different in vitro experiments, such as binding to the Lewis(b) blood group antigen, inhibition of adherence of H. pylori to human gastric mucosa tissue sections in situ and in a haemagglutination assay. The BIC preparation was also given in the drinking water to H. pylori-infected mice. RESULTS: An inhibition of 95% of the binding of H. pylori to Lewis(b) glycoconjugate was observed in vitro. Furthermore, a blocking activity of almost 90% was observed when the BIC was preincubated with H. pylori bacteria. Finally, the BIC preparation inhibited the haemagglutination of H. pylori and human red blood cells. Seven of 40 (17.5%) mice remained infected in the treatment group as compared with 25 of 45 (55.5%) in the control group. Hence, the cure rate was 66%, P = < 0.001. The mean number of colonies in the antibody-treated mice where eradication was not successful was also reduced (P < 0.05). In trials using FVB/N transgenic Lewis(b) expressing mice, a cure rate of 50%-66% was observed. CONCLUSION: Bovine colostral antibodies against H. pylori can be generated in high titres, inhibit binding in vitro and can eradicate or reduce the number of bacteria in infected mice.

Animals↗