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Biomedical subjects

Zheng Liu

Publications and source records attributed to Zheng Liu.

At least 37 records · Page 2Linked to original sources
PubMed2006

Promoter hypermethylation of DNA repair gene MGMT in laryngeal squamous cell carcinoma.

The relationship between hypermethylation of CpG islands in the promoter regions of O6-methylguanine DNA methyltransferase (MGMT) genes and laryngeal squamous cell carcinoma was explored. Methylation-specific PCR and semi-quantitative RT-PCR were used to study the promoter methylation and mRNA expression of the MGMT gene in laryngeal carcinoma tissues, tissues adjacent to the tumor and normal laryngeal tissues. Hypermethylation of MGMT gene was detected in 16 samples of 46 (34.8%) laryngeal squamous cell carcinoma samples. However, the MGMT hypermethylation was not detected in all tissues adjacent to the tumors and normal tissues. No significant difference in MGMT gene hypermethylation was found in samples with different histological grades (chi2 = 3.130, P = 0.077) or in samples from patients with different TNM status (chi2 = 3.957, P = 0.138). No expression of MGMT mRNA was detected in all hypermethylated laryngeal carcinoma tissues. The expression of MGMT mRNA was detected in all unmethylated laryngeal carcinoma tissues, tissues adjacent to the tumors and normal tissues. It suggests that MGMT gene promoter hypermethylation is associated with MGMT gene transcription loss in laryngeal carcinoma tissues and possibly plays an important role in carcinogenesis of laryngeal tissues.

Carcinoma, Squamous Cell↗
PubMed2006

Effect of methylation-associated silencing of the death-associated protein kinase gene on nasopharyngeal carcinoma.

Death-associated protein kinase (DAPK) is a Ca/calmodulin-regulated serine/threonine kinase and a positive mediator of apoptosis. Loss of expression of the DAPK gene by aberrant promoter methylation may play an important role in cancer development and progression. The aim of this study was to investigate the frequency of gene promoter methylation of DAPK in nasopharyngeal carcinoma (NPC) and the effect of 5-Aza-2'-deoxycytidine (5-Aza-CdR), a demethylating agent, on CNE cells, a human nasopharyngeal carcinoma cell line, and on xenografts of CNE cells. Methylation-specific PCR and RT-PCR were used to determine the promoter methylation status and mRNA expression of the DAPK gene in NPC. Furthermore, CNE cells were treated in vitro and in vivo with 5-Aza-CdR to explore the effect of demethylating agents on DAPK mRNA expression and tumor growth. Hypermethylation of the DAPK gene promoter was found in 35 (76.1%) of 46 NPC samples. There was no significant difference in the promoter hypermethylation rate among samples from patients with different TNM stages. No promoter hypermethylation of the DAPK gene was found in all six chronic inflammatory nasopharyngeal tissue specimens. DAPK mRNA expression was not detected in NPC tumor specimens with promoter hypermethylation. However, DAPK mRNA expression was observed in unmethylated NPC tumors and in the chronic inflammatory nasopharyngeal tissue specimens. Promoter hypermethylation of the DAPK gene was found and no DAPK mRNA expression was detected in CNE cells. DAPK mRNA expression in CNE cells and xenografts could be restored by treatment with 5-Aza-CdR. The CNE cell xenografts of nude mice treated with 5-Aza-CdR were obviously smaller in tumor volume than those of nude mice treated with PBS. These results demonstrate that loss of DAPK expression could be associated with promoter region methylation in NPC. 5-Aza-CdR may slow the growth of CNE cells in vitro and in vivo by reactivating the DAPK gene silenced by de novo methylation.

Adult↗
PubMed2006

Effect of resveratrol on L-type calcium current in rat ventricular myocytes.

AIM: To study the effect of resveratrol on L-type calcium current (I(Ca-L)) in isolated rat ventricular myocytes and the mechanisms underlying these effects. METHODS: I(Ca-L) was examined in isolated single rat ventricular myocytes by using the whole cell patch-clamp recording technique. RESULTS: Resveratrol (10-40 micromol/L) reduced the peak amplitude of I(Ca-L) and shifted the current-voltage (I-V) curve upwards in a concentration-dependent manner. Resveratrol (10, 20, 40 micromol/L) decreased the peak amplitude of I(Ca-L) from -14.2+/-1.5 pA/pF to -10.5+/-1.5 pA/pF (P<0.05), -7.5+/-2.4 pA/pF (P<0.01), and -5.2+/-1.2 pA/pF (P<0.01), respectively. Resveratrol (40 micromol/L) shifted the steady-state activation curve of I(Ca-L) to the right and changed the half-activation potential (V0.5) from -19.4+/-0.4 mV to -15.4+/-1.9 mV (P<0.05). Resveratrol at a concentration of 40 micromol/L did not affect the steady-state inactivation curve of I(Ca-L), but did markedly shift the time-dependent recovery curve of I(Ca-L) to the right, and slow down the recovery of I(Ca-L) from inactivation. Sodium orthovanadate (Na(3)VO(4); 1 mmol/L), a potent inhibitor of tyrosine phosphatase, significantly inhibited the effects of resveratrol (P<0.01). CONCLUSION: Resveratrol inhibited I(Ca-L) mainly by inhibiting the activation of L-type calcium channels and slowing down the recovery of L-type calcium channels from inactivation. This inhibitory effect of resveratrol was mediated by the inhibition of protein tyrosine kinase in rat ventricular myocytes.

Animals↗
PubMed2006

In vitro and in vivo evaluation of a novel oral insulin formulation.

AIM: To develop a stable self-emulsifying formulation for oral delivery of insulin. METHODS: Caco-2 cell line and diabetic beagles were used as in vitro and in vivo models to study the absorption mechanism and the hypoglycemic efficacy of the formulation. In addition, various physicochemical parameters of the formulation such as droplet size, insulin encapsulation efficiency and stability were evaluated. RESULTS: This formulation enabled changes in barrier properties of Caco-2 monolayers, as referred by transepithelial electrical resistance (TEER) and apparent permeability coefficients (P(app)) of the paracellular marker ranitidine (20-fold greater than control) but not transcellular marker propranolol, suggesting that the opening of tight junctions was involved. In diabetic beagle dogs, the bioavailability of this formulation was up to 15.2% at a dose of 2.5 IU/kg in comparison with the hypoglycemic effect of native insulin (0.5 IU/kg) delivered by subcutaneous injection. CONCLUSION: This formulation, recently approved by the China State Food and Drug Administration to enter clinical trials, was stable, degradation-protected and absorption-enhanced, and provided a promising formulation for oral insulin delivery.

Administration, Oral↗
PubMed2006

[Construction of Streptococcus mutans luxS gene allelic exchange plasmid].

OBJECTIVE: It is reported that Streptococcus mutans luxS gene may have an important role in the interspecies quorum sensing system. To construct the S. mutans luxS gene knockout mutant, this research aim to construct the luxS gene allelic exchange plasmid. METHODS: The upstream and downstream flank DNA fragments of S. mutans luxS gene (Xup, Xdn)and the E. coli kanamycin resistance gene (Kana) were enriched by pfu DNA polymerase with "nest PCR" methods. These fragments were ligated into pBluescript SK (+) Phagemids vector with double endonuclease reaction sequentially. RESULTS: With endonuclease reaction and DNA sequencing, it was proved that the objective plasmid, Xukd-pbsk, was constructed correctively and the kanamycin resistance gene could be expressed in vitro. CONCLUSION: The S. mutans luxS gene allelic exchange plasmid is constructed correctively in this research and can be used in the future research of S. mutans luxS gene knockout mutant.

Bacterial Proteins↗
PubMed2006

[Susceptibility of Streptococcus mutans biofilm to antimicrobial agents].

OBJECTIVE: To investigate the susceptibility of Streptococcus mutans (S. mutans) biofilms to antimicrobial agent by confocal laser scanning microscopy (CLSM). METHODS: S. mutans biofilms formed in vitro on glass slice were acted on with penicillin of different concentrations for 3 h. Then these biofilms were stained by fluorescence and were observed by CLSM. The bacterial density and viability of biofilms were recorded. RESULTS: When S. mutans biofilms were exposed to penicillin of 2 500 mg/L for 3 h, it was not completely killed. The higher the concentration of penicillin was, the weaker the biofilms against penicillin. CONCLUSIONS: Compared with planktonic S. mutans, S. mutans biofilms produced stronger resistance to penicillin. It suggests that we should find new strategies to control the infection caused by biofilm in clinic.

Anti-Infective Agents↗
PubMed2006

[Identification of P. gingivalis P. intermedia P. nigrescens by 16S rDNA and membrane microarray chip].

PURPOSE: The aim of this study is to identify three kinds of black-pigmented periodontal pathogens P. gingivalis Pg, P. intermedia Pi, P. nigrescens Pn by 16S rDNA and microarray. METHODS: A pair of universal primers which can amplify a section of conservative domain of bacterial 16S rDNA based on the sequences of 16S rDNA in Genebank were designed. Then the specific oligonucleotide probes for Pg Pi Pn based on the sequences of the conservative domain were constructed. Standard bacterial genomic DNAs were amplified using the designed universal primers by PCR, and labeled by digoxigenin at the same time, the products of PCR were hybridized with the microarray in which the specific probes were added. The results of hybridization were analysed. RESULTS: The results of hybridization showed that the specific probes of Pg Pi Pn on microarray reacted only with corresponding PCR products of Pg Pi Pn, not reacted with others. CONCLUSION: The method of 16S rDNA and membrane microarray could be useful to identify Pg Pi Pn, and had high specificity. It will be developed into a kind of clinical bacterial detective system.

Comparative Genomic Hybridization↗
PubMed2006

[Effects of chitosans with different molecular weights on Streptococcus sanguis biofilm].

PURPOSE: To investigate the effects of chitosan on Streptococcus sanguis biofilm. METHODS: Streptococcus sanguis biofilm was formed on saliva-coated glass (SCG) in a flow culture system, then exposed to 2% chitosans with different molecular weights (5 cps, 80 cps, 600 cps) for 3, 10, 30 minutes. Confocal laser scanning microscope and Vital/Dead fluorescent staining technique (vital stained green, dead stained red) were combined to observe the biofilm thickness, bacterial density. Analysis of variance was used for comparison. RESULTS: The biofilm thickness and bacterial density reduced significantly after treatment by 2% chitosan. Of all the treatment groups, 5 cps (low molecular weight) chitosan is most effective (P<0.01). CONCLUSIONS: 5 cps (low molecular weight) chitosan seems to be most effective in detaching biofilm.

Biofilms↗
PubMed2006

[Treacher Collins syndrome: case report and literature review].

OBJECTIVE: To study the genetic background, clinical features, diagnosis, management, and prenatal testing and counseling of Treacher Collins syndrome (TCS). METHOD: The clinical data of a patient and his mother suffering from TCS was reported and the relevant literatures were also reviewed. RESULT: TCS is an autosomal dominant disorder characterized by craniofacial mal-development, including antimongoloid slant of the eyes, micrognathia, microtia and other deformity of the ears. TCS results from the mutation in TCOF1 gene (Treacher Collins-Franceschetti Syndrome gene), located in 5q32-q33.1. Diagnosis of TCS is made through clinical evaluation, radiographic examination, and molecular genetic analysis. Treatment is tailored to the specific needs of each individual by a multidisciplinary craniofacial management team. The choosing of optimal operation time and method is very important. Prenatal testing and genetic counseling for risky pregnancy is necessary. CONCLUSION: The stepwise regimen of treatment is craniofacial reconstruction, orthognathic procedures, orthodontic alignment of the teeth, nasal reconstruction, external ear reconstruction and external auditory canal and middle ear reconstruction.

Female↗
PubMed2006

Corticosteroids induce chemotherapy resistance in the majority of tumour cells from bone, brain, breast, cervix, melanoma and neuroblastoma.

Glucocorticoids (GCs) such as dexamethasone (DEX) have been widely used as co-medication in cancer therapy because they have potent proapoptotic properties in lymphoid cells, can reduce nausea, and alleviate acute toxic effects in healthy tissue. However, GCs are used in a supportive-care role, even though no prospective clinical studies have assessed the effect of these steroids on the growth of solid tumours. Data from preclinical and, to some extent, clinical studies, suggest that GCs induce treatment resistance in some solid tumours. Since it is unknown whether GC-induced resistance occurs only occasionally or is a more common phenomenon, we performed a screening study using several established cell lines from bone, brain, breast and cervix carcinoma as well as melanoma and neuroblastoma together with fresh surgical resections from patients with breast cancer. We found that DEX inhibits cisplatin and 5-fluorouracil-induced apoptosis and promotes the growth of the majority of examined malignant cells. In contrast, and as expected, DEX acted pro-apoptotically and promoted the cytotoxic effect of chemotherapy in established and primary lymphoid cells. Thus, these data demonstrate the need for detailed molecular studies to clarify the mechanism of differential glucocorticoid signaling as well as controlled, prospective clinical studies.

Antineoplastic Agents, Hormonal↗
PubMed2006

[The expression of transforming growth factor beta1, interleukin-6, 11 and 17 in nasal mucosa of allergic rhinitis patients].

OBJECTIVE: To explore the protein expression of transforming growth factor (TGF)-beta1, interleukin (IL)-6, 11, and 17 in the nasal mucosa of allergic rhinitis patients. METHOD: The protein expression of TGF-beta1, IL-6, 11, and 17 in the inferior turbinate tissues from 19 allergic rhinitis patients and from 21 non-allergic patients underwent nasal septum operation was detected by enzyme-linked immunosorbent assay. RESULT: (1) Compared with tissues from non-allergic patients, the expression of TGF-beta1 protein was significant increased in the tissues from allergic rhinitis patients (P < 0.01); (2) As to the protein expression of IL-6, 11 and 17, there was no significant difference between allergic rhinitis patients and non-allergic patients (P > 0.05); (3) The expression of TGF-beta1, IL-6, 11, and 17 was similar between the allergic rhinitis patients with and without asthma (P > 0.05). CONCLUSION: TGF-beta1 , while not IL-6, 11 and 17, may play a role in the tissue remodeling processes in allergic rhinitis. This expression profile may contribute to the difference in the tissue remodeling between allergic rhinitis and asthma.

Adolescent↗
PubMed2006

[Expression of transforming growth factor beta receptor I and II in chronic rhinosinusitis, nasal polyps and normal nasal mucosa tissues].

OBJECTIVE: To explore the expression of transforming growth factor beta receptor(TGFpR) I, II in the chronic rhinosinusitis, nasal polyps and normal nasal mucosa tissues. METHOD: The protein expression of the TGFbetaR I and TGFbetaR II were determined by means of immunohistochemistry in chronic rhinosinusitis tissues from 25 patients, nasal polyps tissues from 21 patients and inferior turbinate mucosa tissues from 17 patients with deviation of nasal septum. RESULT: (1) In chronic rhinosinusitis and nasal polyps tissues, compared with controls, the expression of TGFbetaR I and TGFbetaR II protein was increased significantly (P < 0.01). (2) The expression of TGFbetaR I and TGFbetaR II protein in nasal polyps tissues was significant increased than that in chronic rhinosinusitis tissues (P < 0.01). CONCLUSION: The different expression level and pattern of TGFbetaR I and TGFbetaR II in chronic rhinosinusitis and nasal polyps tissues indicates TGFbetaR may play a different role in the pathogenesis chronic rhinosinusitis and nasal polyps.

Adolescent↗
PubMed2005

Identification of gene expression signatures in autoimmune disease without the influence of familial resemblance.

Even though autoimmune diseases are heterogeneous, believed to result from the interaction between genetic and environmental components, patients with these disorders exhibit reproducible patterns of gene expression in their peripheral blood mononuclear cells. A portion of this gene expression profile is a property of familial resemblance rather than autoimmune disease. Here, we wanted to identify the portion of this gene expression profile that is independent of familial resemblance and determine whether it is a product of disease duration, disease onset or other factors. By employing supervised clustering algorithms, we identified 100 genes whose expression profiles are shared in individuals with various autoimmune diseases but are not shared by unaffected family members of individuals with autoimmune disease or by controls. Individuals with early disease (1 year after onset) and established disease (10 years after onset) exhibit a near-identical expression pattern, suggesting that this unique profile is a product of disease onset rather than disease duration.

Algorithms↗
PubMed2005

Determination of optical isomers for left-handed or right-handed chiral double-wall carbon nanotubes.

The handedness relationship between adjacent layers in nested double-wall carbon nanotubes (DWNTs) has been investigated for the first time. Our high-resolution electron microscopy analysis on a series of specimen tilts can successfully tell the handedness of each constituent nanotube in a DWNT, and therefore the chiral indices (n, m) including their optical isomers [(n, m) or (m, n)] of inner and outer nanotubes can be uniquely determined. It is shown that right-handed and left-handed nanotubes are equally distributed for both the inner and outer nanotubes in the examined specimens and a preferable handedness relationship between the adjacent layers in DWNT may exist.

Journal Article↗
PubMed2005

Resveratrol reduces intracellular free calcium concentration in rat ventricular myocytes.

Resveratrol (trans-3, 4', 5-trihydroxy stilbene), a phytoalexin found in grape skins and red wine, has been reported to have a wide range of biological and pharmacological properties. It has been speculated that resveratrol may have cardioprotective activity. The objective of our study was to investigate the effects of resveratrol on intracellular calcium concentration ([Ca(2+)](i)) in rat ventricular myocytes. [Ca(2+)](i) was detected by laser scanning confocal microscopy. The results showed that resveratrol (15~60 mumol/L) reduced [Ca(2+)](i) in normal and Ca(2+)-free Tyrode's solution in a concentration-dependent manner. The effects of resveratrol on [Ca(2+)](i) in normal Tyrode's solution was partially inhibited by pretreatment with sodium orthovanadate (Na3VO4, 1.0 mmol/L, P<0.01), an inhibitor of protein tyrosine phosphatase, or L-type Ca(2+) channel agonist Bay K8644 (10 mumol/L, P<0.05), but could not be antagonized by NO synthase inhibitor L-NAME (1.0 mmol/L). Resveratrol also markedly inhibited the ryanodine-induced [Ca(2+)](i) increase in Ca(2+)-free Tyrode's solution (P<0.01). When Ca(2+) waves were produced by increasing extracellular Ca(2+) concentration from 1 to 10 mmol/L, resveratrol (60 mumol/L) could reduce the velocity and duration of propagating waves, and block the propagating waves of elevated [Ca(2+)](i). These results suggest that resveratrol may reduce the [Ca(2+)](i) in isolated rat ventricular myocytes. The inhibition of voltage-dependent Ca(2+) channel and tyrosine kinase, and alleviation of Ca(2+) release from sarcoplasmic reticulum (SR) are possibly involved in the effects of resveratrol on rat ventricular myocytes. These findings could help explain the protective activity of resveratrol against cardiovascular disease.

Animals↗
PubMed2005

Self-assembly of designed oligomeric siloxanes with alkyl chains into silica-based hybrid mesostructures.

A novel self-assembly route to ordered silica-organic hybrids using well-defined siloxane oligomers with alkoxy functionality and covalently attached alkyl chains has been investigated. Various hybrid mesostructures were obtained by hydrolysis and polycondensation without the use of any structure-directing agents. The oligomers 1(Cn), having an alkylsilane core and three branched trimethoxysilyl groups, formed highly ordered lamellar phases when n = 14-18, while those with shorter alkyl chains formed cylindrical assemblies, slightly distorted two-dimensional (2D) hexagonal structures (n = 6-10), and a novel 2D monoclinic structure (n = 12). Furthermore, the mixtures of 1(Cn) with different chain lengths yielded well-ordered 2D hexagonal phases, possibly due to the better packing of the precursors. The hybrids consisting of cylindrical assemblies were converted to ordered porous silica with tunable pore sizes upon calcination to remove organic groups. The liquid-state 29Si NMR analysis of the hydrolysis and polycondensation processes of 1(Cn) revealed a unique intramolecular reaction yielding primarily the oligomer with a tetrasiloxane ring which is a new class of amphiphilic molecule having both self-assembling ability and high cross-linking ability. We also found that the mesostructure (lamellar or 2D hexagonal) was strictly controlled by varying the number of siloxane units per alkyl chain. These results provide a deeper understanding of the present self-assembly process that is strongly governed by the molecular packing of oligosiloxane precursors.

Magnetic Resonance Spectroscopy↗
PubMed2005

Molecular simulation of polymer assisted protein refolding.

Protein refolding in vitro, the formation of the tertiary structure that enables the protein to display its biological function, can be significantly enhanced by adding a polymer of an appropriate hydrophobicity and concentration into the refolding buffer. A molecular simulation of the refolding of a two-dimensional simple lattice protein was presented. A protein folding map recording the occurrence frequency of specified conformations was derived, from which the refolding thermodynamics and kinetics were interpreted. It is shown that, in the absence of polymer, the protein falls into the "energy trapped" conformations characterized by a high intramolecular hydrophobic interaction, denoted as HH contact, and a high magnitude of the structure overlap function, chi. This makes it difficult for the protein to fold to the native state. The polymer with a suitable chain length, concentration, and hydrophobicity has formed complex with partially folded protein and created diversified intermediates with low chi. This gives more pathways for the protein to fold to the native state. At a given hydrophobicity, the short chain polymer has a broader concentration range where it assists protein folding than those of long chains. The above simulation agrees well with the experimental results reported elsewhere [Cleland et al., J. Biol. Chem. 267, 13327 (1992); ibid., Bio/Technology 10, 1013 (1992); Chen et al., Enzyme Microb. Technol. 32, 120 (2003); Lu et al., Biochem. Eng. J. 24, 55 (2005); ibid., J. Chem. Phys. 122, 134902 (2005); ibid., Biochem. Eng. J. (to be published)] and is of fundamental importance for the design and application of polymers for protein refolding.

Computer Simulation↗