Search PubMed⌕ Search

Biomedical subjects

X Liang

Publications and source records attributed to X Liang.

At least 55 records · Page 3Linked to original sources
PubMed2001

Use of long-range repetitive element polymorphism-PCR to differentiate Bacillus anthracis strains.

The genome of Bacillus anthracis is extremely monomorphic, and thus individual strains have often proven to be recalcitrant to differentiation at the molecular level. Long-range repetitive element polymorphism-PCR (LR REP-PCR) was used to differentiate various B. anthracis strains. A single PCR primer derived from a repetitive DNA element was able to amplify variable segments of a bacterial genome as large as 10 kb. We were able to characterize five genetically distinct groups by examining 105 B. anthracis strains of diverse geographical origins. All B. anthracis strains produced fingerprints comprising seven to eight bands, referred to as "skeleton" bands, while one to three "diagnostic" bands differentiated between B. anthracis strains. LR REP-PCR fingerprints of B. anthracis strains showed very little in common with those of other closely related species such as B. cereus, B. thuringiensis, and B. mycoides, suggesting relative heterogeneity among the non-B. anthracis strains. Fingerprints from transitional non-B. anthracis strains, which possessed the B. anthracis chromosomal marker Ba813, scarcely resembled those observed for any of the five distinct B. anthracis groups that we have identified. The LR REP-PCR method described in this report provides a simple means of differentiating B. anthracis strains.

Bacillus anthracis↗
PubMed2001

Utilization of the rpoB gene as a specific chromosomal marker for real-time PCR detection of Bacillus anthracis.

The potential use of Bacillus anthracis as a weapon of mass destruction poses a threat to humans, domesticated animals, and wildlife and necessitates the need for a rapid and highly specific detection assay. We have developed a real-time PCR-based assay for the specific detection of B. anthracis by taking advantage of the unique nucleotide sequence of the B. anthracis rpoB gene. Variable region 1 of the rpoB gene was sequenced from 36 Bacillus strains, including 16 B. anthracis strains and 20 other related bacilli, and four nucleotides specific for B. anthracis were identified. PCR primers were selected so that two B. anthracis-specific nucleotides were at their 3' ends, whereas the remaining bases were specific to the probe region. This format permitted the PCR reactions to be performed on a LightCycler via fluorescence resonance energy transfer (FRET). The assay was found to be specific for 144 B. anthracis strains from different geographical locations and did not cross-react with other related bacilli (175 strains), with the exception of one strain. The PCR assay can be performed on isolated DNA as well as crude vegetative cell lysates in less than 1 h. Therefore, the rpoB-FRET assay could be used as a new chromosomal marker for rapid detection of B. anthracis.

Animals↗
PubMed2001

Identification of a genomic island present in the majority of pathogenic isolates of Pseudomonas aeruginosa.

Pseudomonas aeruginosa, a ubiquitous gram-negative bacterium, is capable of colonizing a wide range of environmental niches and can also cause serious infections in humans. In order to understand the genetic makeup of pathogenic P. aeruginosa strains, a method of differential hybridization of arrayed libraries of cloned DNA fragments was developed. An M13 library of DNA from strain X24509, isolated from a patient with a urinary tract infection, was screened using a DNA probe from P. aeruginosa strain PAO1. The genome of PAO1 has been recently sequenced and can be used as a reference for comparisons of genetic organization in different strains. M13 clones that did not react with a DNA probe from PAO1 carried X24509-specific inserts. When a similar array hybridization analysis with DNA probes from different strains was used, a set of M13 clones which carried sequences present in the majority of human P. aeruginosa isolates from a wide range of clinical sources was identified. The inserts of these clones were used to identify cosmids encompassing a contiguous 48.9-kb region of the X24509 chromosome called PAGI-1 (for "P. aeruginosa genomic island 1"). PAGI-1 is incorporated in the X24509 chromosome at a locus that shows a deletion of a 6,729-bp region present in strain PAO1. Survey of the incidence of PAGI-1 revealed that this island is present in 85% of the strains from clinical sources. Approximately half of the PAGI-1-carrying strains show the same deletion as X24509, while the remaining strains contain both the PAGI-1 sequences and the 6,729-bp PAO1 segment. Sequence analysis of PAGI-1 revealed that it contains 51 predicted open reading frames. Several of these genes encoded products with predictable function based on their sequence similarities to known genes, including insertion sequences, determinants of regulatory proteins, a number of dehydrogenase gene homologs, and two for proteins of implicated in detoxification of reactive oxygen species. It is very likely that PAGI-1 was acquired by a large number of P. aeruginosa isolates through horizontal gene transfer. The selection for its maintenance may be the consequence of expression of any one of the genes of unknown function or the genes which allow P. aeruginosa to survive under the conditions that generate reactive oxygen species. Alternatively, one or both of the transcriptional regulators encoded in PAGI-1 may control the expression of genes in the P. aeruginosa chromosome, which provides a selective advantage for strains that have acquired this genomic island.

Cloning, Molecular↗
PubMed2001

Effects of long-term enalapril and losartan therapy of hypertension on cardiovascular aldosterone.

BACKGROUND: Plasma aldosterone escape is found during long-term angiotensin-converting enzyme inhibitor therapy. Evidence for aldosterone production in cardiovascular tissues raised the question of whether or not aldosterone escape occurs in these tissues. METHOD: Spontaneously hypertensive rats were treated with enalapril (20 mg/kg/day) and losartan (50 mg/kg/day) for 20 weeks; untreated spontaneously hypertensive and Wistar rats were used as positive and normal controls, respectively. Ex vivo mesenteric artery and heart perfusion, high-performance liquid chromatography, and radioimmunoassay for aldosterone were performed. RESULTS: The results showed that enalapril failed to significantly inhibit aldosterone production in mesenteric artery, myocardium and plasma. Losartan significantly inhibited aldosterone production to that of Wistar rats in the mesenteric artery, myocardium and plasma. CONCLUSION: This study provides the first evidence that long-term angiotensin-converting enzyme inhibition therapy induces aldosterone escape in hypertensive cardiovascular tissues, and angiotensin II subtype 1 receptor antagonist does not induce aldosterone escape in mesenteric artery, myocardium and plasma of spontaneously hypertensive rats.

Aldosterone↗
PubMed2001

Composition, characteristic and activity of rare earth element-bound polysaccharide from tea.

The compositions and structural characteristics of rare earth elements-bound polysaccharides from tea (REE-TPS) were studied with the methods of Inductively Coupled Plasma Mass Spectrometry (ICP-MS), Gas Chromatography (GC) and Extended X-ray Absorption Fine Structure (EXAFS) spectroscopy. The results show that polysaccharide from tea (TPS) was a sort of glycoprotein and coordinated with Rare Earth Elements (REE) closely. The sugar fraction was composed of Rha, Ara, Xyl, Fuc, Glc, and Gal. There existed almost all natural amino acids with Glx, Asx, and Hyp as the major parts in the protein fraction. The REEs in REE-TPS were mainly composed of La, Ce, and Nd, especially, more than 75% of them was La. The coordination atom of the first coordination shell of La in REE-TPS was oxygen, the coordination number of which was 6, and the average distance between the atoms was 2.52 A. The second shell was formed from sulfur atoms, the coordination number and the average distance were 3 and 2.91 A, respectively. The bio-experiments show that REE-TPS could decrease the content of blood glucose in mice significantly.

Animals↗
PubMed2001

Antagonism of the osteoclast vitronectin receptor with an orally active nonpeptide inhibitor prevents cancellous bone loss in the ovariectomized rat.

An orally active, nonpeptide Arg-Gly-Asp (RGD) mimetic alpha(v)beta3 antagonist, (S)-3-Oxo-8-[2-[6-(methylamino)-pyridin-2-yl]-1-ethoxy]-2-(2,2,2-trifluoroethyl)-2,3,4,5-tetrahydro-1H-2-benzazepine-4-acetic acid (compound 1), has been generated, which prevented net bone loss and inhibited cancellous bone turnover in vivo. The compound binds alpha(v)beta3 and the closely related integrin alpha(v)beta5 with low nanomolar affinity but binds only weakly to the related integrins alpha(IIb)beta3, and alpha5beta1. Compound 1 inhibited alpha(v)beta3-mediated cell adhesion with an IC50 = 3 nM. More importantly, the compound inhibited human osteoclast-mediated bone resorption in vitro with an IC50 = 11 nM. In vivo, compound 1 inhibited bone resorption in a dose-dependent fashion, in the acute thyroparathyroidectomized (TPTX) rat model of bone resorption with a circulating EC50 approximately 20 microM. When dosed orally at 30 mg/kg twice a day (b.i.d.) in the chronic ovariectomy (OVX)-induced rat model of osteopenia, compound 1 also prevented bone loss. At doses ranging from 3 to 30 mg/kg b.i.d., compound 1 partially prevented the OVX-induced increase in urinary deoxypyridinoline. In addition, the compound prevented the OVX-induced reduction in cancellous bone volume (BV), trabecular number (Tb.N), and trabecular thickness (Tb.Th), as assessed by quantitative microcomputerized tomography (microCT) and static histomorphometry. Furthermore, both the 10-mg/kg and 30-mg/kg doses of compound prevented the OVX-induced increase in bone turnover, as measured by percent osteoid perimeter (%O.Pm). Together, these data indicate that the alpha(v)beta3 antagonist compound 1 inhibits OVX-induced bone loss. Mechanistically, compound 1 prevents bone loss in vivo by inhibiting osteoclast-mediated bone resorption, ultimately preventing cancellous bone turnover.

Animals↗
PubMed2001

[Using fluorescence PCR analysis for early diagnosis and carriers detection of Chinese Wilson's disease].

OBJECTIVE: To diagnose the pre-symptomatic cases of Chinese Wilson's disease(WD) and detect the potential carriers by using fluorescence PCR technique. METHODS: Screening the high frequency spot Arg778Leu of WD gene mutation in 66 Chinese WD patients, 55 healthy family members and 30 controls, and selecting 3 random samples (2 from WD patients, 1 from controls) for DNA sequencing to testify the accuracy of fluorescence PCR. RESULTS: Among 66 Chinese WD cases, 5 were found homozygous for mutation of Arg778Leu and 21 were compound heterozygous; the gene mutation rate was totally 39.4%. Out of 55 healthy family members, 12 were found heterozygous, and it was confirmed that 11 of these 12 individuals were WD gene carriers but not pre-symptomatic patients. The results of direct DNA sequencing consisted with those results detected by fluorescence PCR. CONCLUSION: The Arg778Leu mutation in exon 8 is the high frequency spot of Chinese Wilson's disease gene. Fluorescence PCR analysis is a rapid, accurate gene diagnostic method and demonstrates a high detecting rate.

Adolescent↗
PubMed2001

[The construction of rapid amplification of cDNA ends cDNA libraries from human fetal bone and joint].

OBJECTIVE: To construct rapid amplification cDNA ends(RACE) cDNA libraries from human fetal bone and joint and provide resources for isolation of bone- and joint-specific development-related genes. METHODS: Total RNA of bone and joint were extracted with the modified single-step method of RNA isolation by acid guanidinium thiocyanate-phenol-chloroform extraction. The double-stranded end-blunted cDNA were synthesized using TaKaRa's cDNA synthesis kit and ligated to cassette adaptors. All of the cDNA molecules were amplified by a pair of common primers. RESULTS: A protocol for RACE cDNA library construction from bone and joint was established and two RACE cDNA libraries from human fetal bone and joint were successfully constructed. CONCLUSION: The protocol of RACE cDNA library construction from limited materials proved to be simple and efficient and the library was suitable for RACE to isolate tissue-specific genes.

Bone and Bones↗
PubMed2001

[A study of gene products encoded by Wilson disease gene].

OBJECTIVE: To investigate the pathogenesis of Wilson disease (WD) by detecting its gene products encoded by WD gene (ATP7B). METHODS: Patients diagnosed as WD were analyzed by SDS-PAGE in conjunction with Western blot. Two antibodies were used, which are specially against the sixth copper binding domain (Anti-CuBD) and ATP binding domain (Anti-ABD) of WD protein. RESULTS: The WD proteins were not expressed in two patients when using anti-CuBD, and poorly expressed when using anti-ABD. CONCLUSIONS: WD is highly heterogeneous in clinical manifestations and inheritance pattern. Two WD patients might simultaneously have exon 5 mutations and exon 8 mutations. The study of WD gene products would probe into the pathogenesis of WD.

Adenosine Triphosphatases↗
PubMed2001

[A study of Wilson's disease gene encoded products and gene mutations].

OBJECTIVE: To investigate the pathogenesis of Wilson's disease(WD). METHODS: Hepatocytes were isolated from WD patients' bioptic hepatic samples and cultured in vitro; WD proteins, the gene putative encoded products, were detected by SDS-PAGE in conjunction with Western blotting in liver samples of three patients and two controls. Their genomic DNAs were analyzed by means of direct DNA sequencing of WD gene (ATP7B) on exon 8. RESULTS: The WD proteins lanes from two WD patients were found to be much weaker than that from the control, from which one WD patient was proven as heterozygote of 778 position CGG-->CTG(Arg778Leu) and 770 position CTC-->CTG change of ATP7B. CONCLUSION: WD is highly heterogeneous in clinical manifestations and inheritance pattern. Abnormally expressed putative WD proteins in WD patients might be the results of ATP7B mutations, and the study of ATP7B products would help to probe into the pathogenesis of WD.

Adenosine Triphosphatases↗
PubMed2001

[A study on antigen presentation of eosinophils in vivo and in vitro].

OBJECTIVE: To elucidate the process and characteristics of antigen presentation of eosinophils in vitro and in vivo. METHODS: BALB/c mice were sensitized and challenged by ovalbumin to recruit the aggregated eosinophil in the airways. The isolated airway eosinophils were co-cultured with sensitized T lymphocytes. Meanwhile, purified eosinophils were instilled into the trachea of sensitized mice, and then T cells from the draining lymph nodes were collected. The proliferation responses of T cells both in vitro and in vivo were observed. RESULTS: In the absence of eosinophils in in vitro experiments, T cells did not proliferate even when incubated with exogenous antigen. The addition of ovalbumin sensitized eosinophils (in vivo) yielded significant eosinophil dose-dependent increases in T-cell proliferation. In sensitized mice that received airway instillation of antigen-exposed eosinophils, T-cell proliferation in the paratracheal lymph nodes developed within 1 day, reaching peak at day 3, and declined over 1 week. The in vivo T-cell proliferative responses increased with increasing numbers of eosinophils instilled into the tracheas. In both in vitro and in vivo experiments, antigen-exposed could only present antigen to T cells sensitized with the same antigen. CONCLUSIONS: Eosinophils can uptake and process antigen both in vitro and in vivo, and then present processed antigen to sensitized T cells and thus induce T-cell proliferation. Moreover, eosinophil-induced T-cell proliferation is antigen specific.

Animals↗
PubMed2001

[Relationship between the expression of Bax and apoptosis induced by hyperthermia in BcaCD885 cells].

OBJECTIVE: This study aimed to investigate the role of Bax gene in apoptosis induced by hyperthermia in BcaCD885 cells. METHODS: After inducing apoptosis through hyperthermia, the expression of Bax protein and mRNA were examined with FCM antibody analysis and RT-PCR technique respectively. RESULTS: Up regulation of Bax protein was noted after hyperthermia. The correlation coefficient r between the apoptotic rate and the expression Bax protein was 0.9240. The expression of Bax mRNA was also raised after hyperthermia. CONCLUSION: Hyperthermia acting as an external signal may up-regulates expression of Bax gene and then induces apoptosis in BcaCD885 cells.

Apoptosis↗
PubMed2001

[Effects of olive oil and fish oil on serum lipids and lipid peroxidation in rats].

The effects of olive oil and fish oil on serum lipids and lipid peroxidation were studied in rats. The rats were divided into four groups: negative control, high fat control, fish oil (high fat diet and tube feeding with fish oil 4 ml.kg-1.d-1) and olive oil (high fat diet and tube feeding with olive oil 4 ml.kg-1.d-1) groups. The results showed that the total serum cholesterol and the triglyceride decreased significantly both in fish oil group and olive oil group, and there was a significant increase of serum high-density-lipoprotein (HDL) cholesterol in fish oil group. Both fish oil and olive oil increased superoxide dismutase (SOD) in erythrocyte and decreased serum MDA.

Animals↗
PubMed2001

[A dietary intervention study on the hypertensive high risk population in a northern rural area of Beijing].

To investigate the relationship between optimal living mode, healthy dietary pattern and the incidence of primary hypertension, a dietary intervention study on hte hypertensive high risk population was carried out in Fangshan district of Beijing during 1997-1999. The subjects were divided into two groups: control group and intervention group. A 3-day-dietary-recall combined with weighing method and a healthy diet education program were used in the study. The results indicated that the dietary pattern was not reasonable in the hypertensive high risk population. After two-year-intervention, the dietary pattern of people in the intervention group has changed distinctively. Compared with the results in 1997, the dietary risk factors decreased obviously in the intervention group, but increased in control group, such as high energy, fat, oil and cholesterol which can promote hypertension. Furthermore, in the past two years, the number of over weight + obese people increased by 24.6% in control group, but was no change in the intervention group. The intervention group subjects experienced an average decline of 3.7 and 5.1 mmHg of systolic blood pressure(SBP) and diastolic blood pressure(DBP) respectively, and new cases of hypertension observed in the intervention group were significantly lower than in control group. Thus it can be considered that the dietary intervention may be effective for the high risk population and play a very important role in the prevention of hypertension.

Adult↗
PubMed2001

Management of post-traumatic aniridia with retinal detachment.

PURPOSE: To reconstruct the anatomic and functional impairment in patients with post-traumatic aniridia, aphakia, and retinal detachment. METHODS: Four patients with unilateral aniridia and aphakia as well as retinal detachment as results of severe eye injuries underwent scleral buckling, vitrectomy, membrane peeling, endolaser photocoagulation, silicone oil or gas temponade, combined with iris diaphragm-IOL implantation. RESULTS: All four patients achieved successfully anatomic and functional reconstruction after surgery. During five to 22 months postoperative follow-up, all retinas remained attached. The final visual acuity increased from finger counting to 0.1-0.3. CONCLUSIONS: The combination of vitreoretinal surgery and iris diaphrgm-IOL implantation is an effective method for post-traumatic aniridia, aphakia and traumatic retinal detachment. It could ameliorate photophobia and improve the biocular vision. Furthermore, artificial iris diaphragm implantation could prevent silicone oil-endothelia contact and salvage silicone keratopathy.

Adult↗
PubMed2001

[Biological assessment of sintered titanium alloy for dental crown and bridge by means of slip casting].

OBJECTIVE: To evaluate the biological safety of sintered titanium alloy for dental crown and bridge, and provide a sound scientific basis for dental clinical practice. METHODS: A series of tests, including acute toxicity test, cytotoxity test (agar overlay), sensitization test, oral mucous membrane irritation test, haemolysis test and micronucleus test were conducted to examine the dental crown/bridge-used titanium alloy which is processed with vacuum-sintered powder metallurgy. RESULTS: The haemolysis rate of this material was 2.21% (less than 5%), an index of good blood compatibility. Cytotoxic effect was not observed in cell culture, nor was toxic effect observed in mouse toxicity test. Local mucous membrane irritation reaction was not found. No potential mutagenicity of this material was noted. CONCLUSION: Dental crown/bridge-used titanium alloy material is of reliable was noted biological safety in dental clinical application.

Animals↗