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Biomedical subjects

Xiang Liu

Publications and source records attributed to Xiang Liu.

At least 55 records · Page 3Linked to original sources
PubMed2005

[Quantitative analysis of dominating intestinal flora among groups of people with different body fat].

OBJECTIVE: To investigate the alteration of dominating intestinal floras among groups of people with different body fat and probe into the possible effect on lipid metabolism. METHODS: According to the BMI values, subjects were divided into 4 groups, including fleshless group, normal group, overweight group and obese group. Five dominating floras of all fresh stools were quantitated using selective culture method, and all data were analyzed statistically. RESULTS: With the increase of BMI values, there is a decreasing trend in the amount of Lactobacillus, Bifidobacterium and Enterobacillus, and the amounts of Bacteriodes obviously increased (P < 0.01). No obvious alternation of the amounts of Enterococcus and Clostridium was observed. CONCLUSION: Bacteriodes may exert an boosting effect on the pile of fat and development of obese, however Enterobacillus, Lactobacillus, and Bifidobacterium have a potential opposite effect.

Adipose Tissue↗
PubMed2004

Green fluorescent protein as a vital elimination marker to easily screen marker-free transgenic progeny derived from plants co-transformed with a double T-DNA binary vector system.

We investigated the potential of a novel double T-DNA vector for generating marker-free transgenic plants. Co-transformation methods using a double T-DNA vector or using mixture of two Agrobacterium tumefaciens strains were compared, and showed that the double T-DNA vector method could produce marker-free transgenic tobacco (Nicotiana tabacum L.) plants more efficiently. A dual marker double T-DNA vector was then constructed by assembling the green fluorescent protein (GFP) gene mgfp5 and the neomycin phosphotransferase gene nptII into the same T-DNA. The frequency of co-transformants produced by this vector was 56.3%. Co-expression of mgfp5 and nptII was found in 28 out of 29 T1 lines, and segregation of the reporter beta-glucuronidase gene, gusA, from mgfp5 to nptII was found in 12 out of 29 T1 lines. Therefore, GFP could be used as a vital marker to improve the transformation efficiency and to easily monitor the segregation of marker genes, thus facilitating screening of marker-free progeny.

Agrobacterium tumefaciens↗
PubMed2004

[Oropharyngeal measure in patients with obstructive sleep apnea-hypopnea syndrome before and after uvulopalatopharyngoplasty].

OBJECTIVE: To explore the relationship between the extent of enlarged oropharynx and efficiency through measuring the anterior-posterior and transverse diameter of oropharynx of patients with obstructive sleep apnea-hypopnea syndrome (OSAHS) before and after uvulopalatopharyngoplasty (UPPP). METHODS: Thirty eight patients with OSAHS were studied. The following indexes were measured before and after UPPP: width of uvula base, length of uvula, distance between uvula and posterior pharyngeal wall (DBUP), distance between anterior pillar (DBPP), apnea-hypopnea index (AHI), body mass index (BMI) and SaO2. RESULTS: The preoperative DBAP and DBPP were significantly less than those of normal adults (P < 0.05). DBUP, length of uvula and width of uvula base has no significant difference between preoperative patients and normal adults (P > 0.05). There was no significance difference in DBAP. DBPP and DBUP between postoperative patients and normal adults (P > 0.05). The preoperative AHI, IBM, minimal SaO2, mean SaO2, DBUP, DBPP, DBAP, length of uvula and width of uvula base has no significant difference between good responders and nonresponders (P > 0.1). CONCLUSIONS: Transverse diameter of OSAHS patients is shorter than that of normal adults but anterior-posterior diameter of OSAHS patients has no difference compared with normal adults. Transverse diameter could be enlarged by UPPP. Not only anatomical abnormality but also other factors will contribute to the effect of UPPP.

Adult↗
PubMed2004

[The influence on the biodegradation of phenanthrene by nonionic surfactant, Tween20].

The objective of this study was to quantify the bioavailability of phenanthrene solubilized in surfactants by a mixed phenanthrene-degrading culture isolated from the petroleum contaminated soils. An nonionic surfactant, Tween20, was used. The effects of Tween20 on the microbial degradation of phenanthrene were evaluated depending on the rotary flasks experiments. The results showed that the concentrations of Tween20 above the critical micelle concentration (CMC) could increase the solubility of phenanthrene on great extent and were not toxic to the phenanthrene-degrading bacteria, and that the presence of surfactant micelles did not inhibit the biodegradation of phenanthrene. Phenanthrene solubilized in the micelles of Tween20 in liquid media was bioavailable and degradable by the mixed culture of bacteria.

Biodegradation, Environmental↗
PubMed2004

[Endoscopic thyroid gland surgery without carbon dioxide neck insufflation].

OBJECTIVE: To evaluate endoscopic thyroid gland surgery without carbon dioxide neck insufflation. METHODS: Sixteen patients with thyroid gland benign tumor, aged from 23-62 years, were selected and treated with endoscopic surgery. Eight cases received whole thyroid lobectomy and the other eight cases received partial thyroid lobectomy, the procedure was through a wall method or a single 2.0-3.0 cm horizontal skin incision. Among the 16 cases, 6 were thyroid adenoma and 10 were nodular goiter. RESULTS: All patients received endoscopic surgery, 2 cases with sub-clavicle approach and 14 cases with a single 2.0-3.0 cm horizontal skin incision approach. The recurrent laryngeal nerve and parathyroid glands were easily identified and preserved during operation, the operating time lasted from 1.1 hours to 4.0 hours, no complication occurred, the postoperative cosmetic outcome was excellent. CONCLUSIONS: The results indicated that gasless technique is feasible and safe, so it suggested that the video-assisted thyroid surgery without carbon dioxide neck insufflation could be an alternative for thyroid gland surgery.

Adult↗
PubMed2004

[Diagnosis and treatment on osteoradionecrosis of skull base after radiotherapy for nasopharyngeal carcinoma].

OBJECTIVE: To investigate the diagnosis and management on osteoradionecrosis (ORN) of skull base in the patients with nasopharyngeal carcinoma (NPC) after radiotherapy. METHODS: All patients (n = 15) diagnosed as NPC and ORN of skull base were studied on the clinical data, diagnosis and therapy. RESULTS: All the patients were found with foul odor, headache, bleeding and exposed necrotic bone. 9 patients were treated by surgery, among them 2 patients died of temporal lobe radionecrosis, and the survival time of remaining 7 patients was 2 to 7 years. 5 patients with extensive ORN and 1 patient with local ORN were treated by conservative methods, among them 3 died of nasopharyngeal bleeding and 1 died of respiratory and heart failure, survival time of the remaining 2 patients was 3 to 5 years. CONCLUSIONS: ORN can be diagnosed by clinical characteristics, CT or MR, and endoscopic findings. Surgery is the best choice for ORN. The patients with extensive ORN or radiation-induced cranial neuropathy had poor prognosis. The most common causes of death were nasopharyngeal bleeding and exhaustion.

Adult↗
PubMed2003

Analysis of intrachannel four-wave mixing in differential phase-shift keying transmission with large dispersion.

Intrachannel four-wave mixing (IFWM) in highly dispersed differential phase-shift keying (DPSK) transmission systems is studied with a simple analytical model and numerical simulation. It is found that the IFWM effect in DPSK systems is smaller and less dependent on the bit pattern than in on-off-keying systems with the same average power. The reduced pulse energy in DPSK and correlation between the nonlinear phase shifts of two adjacent pulses contribute to the robustness of DPSK versus IFWM.

Journal Article↗
PubMed2003

Experimental test of dense wavelength-division multiplexing using novel, periodic-group-delay-complemented dispersion compensation and dispersion-managed solitons.

In an all-Raman amplified, recirculating loop containing 100-km spans, we have tested dense wavelength-division multiplexing at 10 Gbits/s per channel, using dispersion-managed solitons and a novel, periodic-group-delay-complemented dispersion-compensation scheme that greatly reduces the timing jitter from interchannel collisions. The achieved working distances are approximately 9000 and approximately 20,000 km for uncorrected bit error rates of <10(-8) and <10(-3), respectively, the latter corresponding to the use of "enhanced" forward error correction; significantly, these distances are very close to those achievable in single-channel transmission in the same system.

Journal Article↗
PubMed2003

In vitro and in vivo dimerization of human endonuclease III stimulates its activity.

Human endonuclease III (hNTH1), a DNA glycosylase with associated abasic lyase activity, repairs various mutagenic and toxic-oxidized DNA lesions, including thymine glycol. We demonstrate for the first time that the full-length hNTH1 positively cooperates in product formation as a function of enzyme concentration. The protein concentrations that caused cooperativity in turnover also exhibited dimerization, independent of DNA binding. Earlier we had found that the hNTH1 consists of two domains: a well conserved catalytic domain, and an inhibitory N-terminal tail. The N-terminal truncated proteins neither undergo dimerization, nor do they show cooperativity in turnover, indicating that the homodimerization of hNTH1 is specific and requires the N-terminal tail. Further kinetic analysis at transition states reveals that this homodimerization stimulates an 11-fold increase in the rate of release of the final product, an AP-site with a 3'-nick, and that it does not affect other intermediate reaction rates, including those of DNA N-glycosylase or AP lyase activities that are modulated by previously reported interacting proteins, YB-1, APE1, and XPG. Thus, the site of modulating action of the dimer on the hNTH1 reaction steps is unique. Moreover, the high intranuclear (2.3 microM) and cytosolic (0.65 microM) concentrations of hNTH1 determined here support the possibility of in vivo dimerization; indeed, in vivo protein cross-linking showed the presence of the dimer in the nucleus of HeLa cells. Therefore, it is likely that the dimerization of hNTH1 involving the N-terminal tail masks the inhibitory effect of this tail and plays a critical role in its catalytic turnover in the cell.

Aminopeptidases↗
PubMed2003

A metallothionein-like gene htMT2 strongly expressed in internodes and nodes of Helianthus tuberosus and effects of metal ion treatment on its expression.

A cDNA sequence encoding a type-2 metallothionein (MT)-like protein, designated htMT2, was isolated from a Helianthus tuberosus L. tuber cDNA library. The isolated cDNA is 509 bp, coding a 7.8-kDa polypeptide. Two partial genomic fragments covering the open reading frame of htMT2 were cloned by PCR. The fragments htMTG-1 (986 bp) and htMTG-2 (982 bp) contain three exons and two introns. The N- and C-terminal domains of the predicted polypeptide have eight and seven cysteine residues, separated by a central cysteine-free spacer. Sequence alignment revealed that the predicted protein was homologous to type-2 MTs of plants. Southern blot analysis indicated that htMT2 is encoded by a small multi-gene family in the H. tuberosus genome. Northern blot analysis showed that htMT2 transcripts were predominantly expressed in internodes and nodes, but were low in leaves, leafstalks, tubers and young roots, and none was detected in roots. Treatment with Cu(2+) reduced the expression of htMT2 in internodes, nodes, leaves and leafstalks. In addition, the expression levels in internodes and nodes share an inverse relationship with the concentrations of Cu(2+). In internodes and nodes, treatment with Zn(2+) at 10 and 100 microM reduced the expression levels of htMT2, and 1000 microM Zn(2+)reduced it to the lowest level, but 500 microM Zn(2+) had little effect. The expressions of htMT2 in different tissues were not appreciably affected by heat shock. It is suggested that HtMT2 might be involved in the transport or availability of Cu(2+) and Zn(2+) to some apo-metal enzymes or apo-metal proteins.

Amino Acid Sequence↗
PubMed2003

Collision-induced time shift of a dispersion-managed soliton and its minimization in wavelength-division-multiplexed transmission.

The formula for the time shift of a dispersion-managed soliton that results from its collision with other solitons in different channels consists of two terms, one related to the frequency shift during collision, and the other related to the residual frequency shift after collision. It is found that an optimal relative delay exists between pulses in adjacent channels after each dispersion-managed span that balances the contributions from the two terms and minimizes the overall time shift, leading to a substantial improvement in transmission performance.

Journal Article↗
PubMed2003

Reduction of collision-induced timing jitter in dense wavelength-division multiplexing by the use of periodic-group-delay dispersion compensators.

We show how replacement of a modest fraction of the usual fiber-based dispersion compensation with a periodic-group-delay dispersion-compensating module can result in a drastic reduction in collision-induced timing jitter in dense wavelength-division multiplexing with dispersion-managed solitons. The principal mechanism here is a correspondingly large reduction in the net path over which a pair of colliding pulses interact.

Journal Article↗
PubMed2003

Photonic analog-to-digital converter using soliton self-frequency shift and interleaving spectral filters.

We propose a novel ultrafast photonic analog-to-digital converter that uses the soliton self-frequency shift in an optical fiber as an optical power-to-frequency conversion mechanism and a set of interleaving spectral filters as the optical comparators. Our method does all the signal processing in the optical domain and requires binary receivers in only the electronic domain. In contrast to the usual exponential scaling, the simultaneous binary search architecture that we propose results in a flash analog-to-digital converter with remarkable linear scaling between the number of comparators and the number of bits resolved.

Journal Article↗
PubMed2003

Transformation of tobacco with genes encoding Helianthus tuberosus agglutinin (HTA) confers resistance to peach-potato aphid (Myzus persicae).

The effects of the hta gene encoding Helianthus tuberosus agglutinin (HTA) on an insect in the order Homoptera were investigated. Homologous cDNAs of hta-a, hta-b, hta-c and hta-d with CaMV35S as promoter were introduced into tobacco via Agrobacterium tumefaciens. Southern blot results showed that the exogenous hta gene was inserted into the genome of host plants, and northern blot analysis confirmed that hta was expressed in transgenic plants. A bioassay with peach-potato aphid (Myzus persicae) demonstrated that transgenic plants had deleterious effects on the insect. The average population of aphids fed on transgenic T0 plants during an 11-day assay decreased by 70%, compared controls. In transgenic plants of T1 generation, aphid fecundity inhibitions were 53.0% (hta-b) and 64.6% (hta-c), respectively. The development of aphids was notably retarded. We conclude that hta could be a novel and promising candidate for plant transgenic engineering against homopteran insect pests.

Agglutinins↗
PubMed2003

Systemic genetic transfer of p21WAF-1 and GM-CSF utilizing of a novel oligopeptide-based EGF receptor targeting polyplex.

Based on the fact that aberrant overexpression of some growth factor receptors was observed in a variety of human cancer cells, a novel nonviral gene delivery system GE7, which contains a 16-amino-acid ligand for identifying EGF receptor was constructed for tumor-targeted gene therapy. Intravenous administration of GE7 system revealed that it has the ability to target beta-galactosidase (beta-gal) reporter gene into murine hepatoma (Hepa) cells. Owing to the limited antitumor effects elicited by a single-gene transfer, recent efforts to treat malignancy using combined gene therapy have been accomplished with varying degrees of success. In this study, the human cyclin-dependent kinase inhibitor gene p21(WAF-1) and the murine cytokine gene granulocyte-macrophage colony-stimulating factor (GM-CSF) were used simultaneously for in vivo gene therapy through systemic injection of the EGF R targeted GE7/DNA complex into murine hepatoma-bearing mice. The results demonstrated that combined administration of p21(WAF-1) and GM-CSF could remarkably inhibit the growth of subcutaneously transplanted hepatoma Hepa cells, and significantly increase the survival rate of tumor-bearing mice. The activities of natural killer (NK) cells and specific cytotoxic T lymphocytes (CTL) were clearly enhanced after combined gene therapy. In vitro experiments showed that p21(WAF-1) gene transfer exhibited a suppressive function on the growth of Hepa cells and the expression of H-2K(b) and B7-1 molecules on Hepa cells increased significantly after combined genes delivery. All these results suggested that the GE7 system was able to target therapeutic genes efficiently to cancer cells, which showed high EGF R expression. The cotransfer of p21(WAF-1) and GM-CSF genes apparently inhibited the growth of tumors through (a) the arrest of tumor cell growth and (b) the enhancement of systemic antitumor immunity.

Amino Acid Sequence↗
PubMed2003

CT perfusion imaging and CT subtraction angiography in the diagnosis of ischemic cerebrovascular disease within 24 hours.

OBJECTIVE: To evaluate the value of the clinical use of CT perfusion imaging (CTPI) and CT subtraction angiography (CTSA) for diagnosing acute ischemic cerebrovascular disease (AICVD). METHODS: Twenty-four patients with AICVD onset within 24 hours were examined with regular CT, CTPI, and CTSA. Some cases received CTPI, magnetic resonance imaging (MRI), magnetic resonance angiography (MRA), digital subtraction angiography (DSA) or single photon emission computer tomography (SPECT) during follow-up examinations. RESULTS: Of the 24 cases, 11 had negative results from regular CT scans 3 - 6 hours after onset of stroke in 6 cases, 6 - 12 hours in 3 cases, and 12 - 24 hours in 2 cases. Ten of these cases were then confirmed by CTPI as having ischemic lesions, 2 with middle cerebral artery occlusion (MCAO), and 1 case with transient ischemic attack (TIA) with CTPI negative. Of the 24 cases, 13 had positive results from regular CT, 9 were diagnosed with ischemic lesions larger by using CTPI than regular CT, 1 case had MCAO and 1 had internal carotid artery occlusion (ICAO). There were 4 cases with ischemic lesions observed with regular CT having nearly the same range as that of lacunar infarctions using CTPI. Another 4 cases had more than 2 lesion areas. The peak time (PT), mean transit time (MTT) and relative flow (RF) of 24 cases were markedly different. The sides of ischemic lesions compared to each other and the core of the lesion compared to peripheral zones were also altered significantly (P < 0.01). CONCLUSIONS: Combined CTPI with CTSA can detect acute ischemic lesions at early and hyper-early stages and could distinguish between TIA, lacunar infarction and a larger area of infarction. Using semiquantitative blood perfusion analysis status, CTPI with CTSA could define position, area and range of the ischemic lesion and penumbra. These scans can also analyze the brain blood perfusion status. It is important to early diagnose the occlusion of the entire division of the internal carotid artery or middle cerebral artery and it is meaningful to assess prognosis and assignment of therapy.

Adult↗
PubMed2003

[Post-transcriptional gene silencing--a plant defense strategy to viruses invasion].

Gene silencing is a kind of epigenetic phenomenon discovered in transgenic plants in recent years. Gene silencing can be divided into two types: position effect and homology dependent gene silencing (HdGS). Homology-dependent gene silencing (HdGS), which is the generic term for transcriptional gene silencing (TGS), post-transcriptional gene silencing (PTGS) and RNA-mediated virus-resistance (RmVR) have been shown to frequently occur in transgenic plants. Post-transcriptional gene silencing (PTGS) is an antiviral defense system of plants, which has led to a new understanding of the relationship between viruses and plants. And it's a co-evolution result between plants and viruses. A few hypothesis models have been proposed to elucidate the mechanism of gene silencing, but they could not explain all the phenomena in gene silencing. In this paper, we reviewed the relationship between PTGS and the plants defense mechanism to virus, and proposed a model of gene silencing based on our experiments results.

Gene Silencing↗