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Biomedical subjects

T Liu

Publications and source records attributed to T Liu.

At least 181 records · Page 10Linked to original sources
PubMed2000

[Evaluation of cariogenic potential of Streptococcus mutans isolated from caries-free and -active persons: adherence properties to saliva-coated hydroxyapatite].

OBJECTIVE: In this study, authors used saliva-coated hydroxyapatite to simulate tooth surface in oral cavity to evaluate adherence of different Streptococcus mutans isolated from caries-free and -active persons to saliva-coated hydroxyapatite. METHODS: Streptococcus mutans isolated from people with different carious experiences were divided into two groups: the caried-free group (DMFS = 0) including 19 persons and the caries-active group (DMFS > or = 6) including 40 persons. Totally 105 genotype Streptococcus mutans strains were obtains, including 22 strains from the caries-free group, and 83 strains from the caries-active group. The adhering properties of Streptococcus mutans (serotype c) strains were investigated, and different adhering properties were compared between the caries-free group and the caries-active group in order to find the correlationship between carious experiences and adhering properties of Streptococcus mutans. Saliva-coated hydroxyapatite was used to simulated tooth surface in oral cavity. Streptococci mutans were cultured in TPY liquid medium containing 3H-TDR in the same radioactive concentration. After being cultured in an anaerobic incubator for 18 hours, Streptococci mutans were radiolabelled by 3H-TDR. Saliva-coated hydroxyapatite and bacterial liquid(BSA = 0.52) were mixed for 90 minutes. Samples were assayed by using liquid scintillation counter, and binding abilities of strains were evaluated by the count per minute(cpm). RESULTS: Binding abilities of strains were significantly different in two groups, Caries-active people harbored more Streptococci mutans with high binding abilities(cpm > 2000) than caries-free people did(P < 0.05). The binding abilities to saliva-coated hydroxyapatite were different between strains of differing genotypes isolated from the same person. Each person always harbored one or two strains with high binding abilities(cpm > 2000) in the caries-active group. CONCLUSION: 1. Different genotypes have different adhering properties. 2. In caries-active group, different genotype strains have synergic effects, and adhesion of high binding ability strains cause caries susceptibility. 3. The differences in binding properties of isolates might relate to differences in carious experiences.

Bacterial Adhesion↗
PubMed2000

[Evaluation of cariogenic potential of Streptococcus mutans isolated from caries-free and -active persons: abilities to synthesize water-soluble and -insoluble glucans].

OBJECTIVE: In this study, authors investigated abilities of Streptococcus mutans (serotype c) strains to synthesize water-soluble and water-insoluble glucans. METHODS: Streptococcus mutans strains were isolated from people with different carious experiences, which were divided into two groups: caries-free (DMFS = 0) group including 19 persons and caries-active group(DMFS > or = 6) including 40 persons. Totally 105 genotypes of Streptococcus mutans strains were obtained, including 22 strains from the caries-free group and 83 strains from the caries-active group. The differences of abilities to synthesize water-soluble and water-insoluble glucans between these two groups were compared in order to find the correlationship between the synthesis of glucans and caries experience. Then, Streptococcus mutans were cultured in TPY liquid medium containing 1% sucrose in an anaerobic incubator at 37 degrees C for 24 hours. Glucans synthesized by Streptococcus mutans was qualified by using infrared spectrophotometry. The amounts of water-soluble and water-insoluble glucans were measured by using the anthron method. RESULTS: According to the same absorption tops position analysed by infrared spectrophotometry, glucans samples were certified. The amounts of glucans synthesized by Streptococcus mutans strains were different between strains of different genotypes even isolated from the same person. Mostly, the amount of water-insoluble glucans was higher than that of water-soluble glucans between different genotype Streptococcus mutans strains. The oral environments of patients in the caries-active group harbored more Streptococcus mutans strains with higher water-soluble glucans producing ability than those of the caries-free group did (P < 0.05), and patients of the caries-active group also harbored more Streptococcus mutans strains with higher water-insoluble glucans producing ability than those of the caries-free group did(P < 0.01). CONCLUSION: 1. Glucosyltranferases of different genotype strains are different in glucans production, and different genotype strains relate to different cariogenic abilities. 2. Glucans was one of cariogenic factors, and water-insoluble glucans was more important than water-soluble glucans in cariogenic ability of Streptococcus mutans. 3. The differences in glucans production of isolated strains might relate to differences in carious experiences.

Dental Caries↗
PubMed2000

[The effects of tea polyphenols on the adherence of cariogenic bacterium to the salivary acquired pellicle in vitro].

OBJECTIVE: It has been proved that tea polyphenols (TP) can inhibit the sucrose-dependent adherence of oral cariogenic bacterium to the tooth surface. This study is carried on to investigate the effects of tea polyphenols on the preliminary adherence of main cariogenic bacterium to salivary acquired pellicle and reveal the anticarious mechanisms of tea polyphenols further. METHODS: The hydroxyapatites were coated by saliva to form S-HA, an in-vitro model of experimental pellicle. Streptococcus mutans 3a3 and Actinomyces viscosus ATCC 19246 were chosen as the main cariogenic bacterium, and the microorganisms were radiolabelled by growing them in TPY culture medium supplemented with 3H-thymidine. Tea polyphenols solution was prepared, the concentrations of which were 0.5, 1.0, 2.0 and 4.0 mg/ml respectively. Two parts of inhibited adherence tests were done with TP-treated S-HA or TP-treated bacterium. In the first one, S-HA was immerged into the TP solution of different concentrations for 1 h before the attachment of bacterium. In the other, the bacterium were mixed with the TP solution for 1 h and then centrifuged and washed before bound to S-HA. The whole process was carried on in KCl buffer solution. The number of 3H-thymidine-labelled bacterium which attached to S-HA were determined by scintillation counting. RESULTS: In both the two parts of this study, tea polyphenols solution, the concentrations of which were changed from 1.0 to 4.0 mg/ml, could decrease the number of S. mutans 3a3 and A. viscosus ATCC 19246, and the inhibition rates rose with the increase of the concentrations of TP solution. But the inhibitory effects of 0.5 mg/ml TP solution were inconsistent in different tests. The results showed that 1.0-4.0 mg/ml TP solution could inhibit the attachments of S. mutans and A. viscosus to S-HA effectively. The inhibitory functions of tea polyphenols were so obvious that in some experiments, while the concentrations of TP solution were changed from 2.0 to 4.0 mg/ml, the number of 3H-thymidine-labelled bacterium which attached to S-HA was even less than that of the same bacterium which attached to naked HA. CONCLUSION: Tea polyphenols can inhibit the preliminary adherence of Streptococcus mutans and Actinomyces viscosus to S-HA effectively. TP may prevent enamel from caries by decreasing the adherence of main cariogenic bacterium to salivary acquired pellicle.

Actinomyces viscosus↗
PubMed2000

[The effects of tea polyphenols on the adherence of cariogenic bacterium to the collagen in vitro].

OBJECTIVE: In the first phase of our study, it has been proved that tea polyphenols (TP) can inhibit the preliminary adherence of oral cariogenic bacterium to salivary acquired pellicle. This study is carried on to investigate the effects of tea polyphenols on the preliminary adherence of main cariogenic bacterium to collagen I and reveal the anticarious mechanisms of tea polyphenols further. METHODS: Tea polyphenols solution was prepared firstly, the concentrations of which were 0.5, 1.0, 2.0 and 4.0 mg/ml. An in-vitro model of experimental pellicle(C-HA) was formed by immerging the hydroxyapatites in 250 micrograms/ml collagen I solution for 1 h. Streptococcus mutans 3a3, Actinomyces viscosus ATCC 19246 and Lactobacillus ATCC 4546 were chosen as the main cariogenic bacterium and radiolabelled by growing them in TPY culture medium supplemented with 3H-thymidine. Two parts of inhibited adherence tests were done with TP-treated C-HA or TP-treated bacterium respectively. In the first one, C-HA was immerged into the TP solution of different concentrations for 1 h before the attachment of bacterium. In the other, the bacterium were mixed with the TP solution for 1 h and then centrifuged and washed before bound to C-HA. KCl buffer solution provided a steady condition to the whole process. Finally, the number of 3H-thymidine-labelled bacterium which attached to C-HA were determined by scintillation counting. RESULTS: In both the two parts of this study, tea polyphenols solution, the concentrations of which were changed from 1.0 to 4.0 mg/ml could inhibit the attachments of S. mutans 3a3, A. viscosus ATCC 19246 and Lactobacillus ATCC 4546 to C-HA effectively, and the inhibition rates rose with the increase of the concentrations of TP solution. But the inhibitory effects of 0.5 mg/ml TP solution were inconsistent in different tests. The inhibitory functions of tea polyphenols were so prominent that in some experiments, while the concentrations of TP solution were higher than 2.0 mg/ml, the number of 3H-thymidine-labelled bacterium which attached to C-HA was even less than that of the same bacterium which attached to naked HA. These results showed that TP had the remarkable inhibitory efficiency on the attachments of S. mutans, A. viscosus and Lactobacillus to C-HA. CONCLUSION: Tea polyphenols can inhibit the preliminary adherence of Streptococcus mutans, Actinomyces viscosus and Lactobacillus to C-HA effectively. TP may prevent dentine from caries by decreasing the adherence of main cariogenic bacterium to collagen.

Actinomyces viscosus↗
PubMed2000

[The application of liquid chromatography in genetic engineering].

The recent development of the molecular conformation, renaturation and intermediates on therapeutic proteins produced in biotechnology is reviewed. It also includs the quality control and in preparation of the therapeutic proteins in large scale by liquid chromatography in down-stream technology. This review includes 42 references.

Chromatography, High Pressure Liquid↗
PubMed2000

[Affection of exogenous gibberellic acid (GA3) on endogenus hormones of Panax quinquefolium seed during its morphological after ripening period].

According to the determination of endogenus hormones variation of Panax quinquefolium seed during its morphological afterripenging period, and the affection of exo-GA3 on the endogenus hormones dynamics, it suggested that exo-GA3 couldn't be used for accelerate the growth of Panax quinquefolium embryo, but was helpful in relieving seed dormancy during physiological afterripening period.

Abscisic Acid↗
PubMed2000

[Study on chemical constituents of essential oil of Biota orientalis by GC-MS].

The essential oil was extracted from Biota orientalis (L) Endl by using steam distillery, analyzed with SE-54(30 m x 0.25 mm I.d) fused silica capillary column. The optimum separate and analytical conditions were researched. The amount of the components from the essential oil was determinated by monoliration method. The separated components were identified by GC-MS. There are 33 components which are make up 80% of the total essential oil were separated and identified.

Alkenes↗
PubMed2000

[The secretion of chemokine RANTES in epithelial cells of nasal polyps and its significance].

OBJECTIVE: To investigate the effect of RANTES(regulated upon activation, normal T cell expressed and secreted) on chemotaxis, migration and accumulation of eosinophils in nasal polyps during epithelial immune responses. METHODS: The epithelial cells were obtained from nasal polyps and inferior turbinates in patients with snoring, and cultured for 24 and 48 hours with IL-1 beta(25 micrograms/L, 50 micrograms/L). RANTES was measured in the culture supernatant by ELISA. RESULTS: 1. On incubation with IL-1 beta, the epithelial cells from inferior turbinate and nasal polyps released 1.5-10 fold and 10-20 fold greater amounts of RANTES respectively than unstimulated samples. Significant increase in levels of RANTES was found in both groups(P < 0.001); 2. There was no difference between nasal polyp and inferior turbinate before incubation with IL-1 beta(P > 0.05) in the level of RANTES. After IL-1 beta stimulation, the concentration of RANTES was higher in polyp than in inferior turbinate (P < 0.001); 3. The expression of RANTES in both groups was dose-dependent and time-dependent upon stimulation of IL-1 beta. CONCLUSION: The epithelial cells of nasal mucosa are active end-organs, capable of releasing chemokine RANTES. In nasal polyps, RANTES has chemotactic activity for eosinophils and other inflammatory cells. It could affect the chemotaxis and eosinophil function and may play an important role in polyp formation.

Adult↗
PubMed2000

[Survival motor neuron gene and neuronal apoptosis inhibitory protein gene deletion in patients with spinal muscular atrophy].

OBJECTIVE: To investigate the frequencies of gene deletion survival motor neuron telomere (SMNTel) exon 7 and neuronal apoptosis inhibitory protein gene (NAIP) exon 5 in 55 Chinese spinal muscular atrophy (SMA) patients, and compare the relationship between these two candidate genes and the disease. METHODS: PCR-SSCP method was used to detect the deletion of SMNTel exon 7, direct visualization of PCR products by agarose electrophoresis was used to detect the deletion of NAIP exon 5 in 55 SMA patients with type I and type II. 40 normal individuals were involved in the study as controls. RESULTS: Homozygous deletion of the SMNTel exon 7 was identified in 92% (23/25) of SMA type I patients and 90% (27/30) of SMA type II patients. The same deletion was found in two mothers and one father of SMA patients. There was no homozygous deletion found in normal controls. None of the homozygous deletion of NAIP exon 5 was found in 55 SMA patients and normal controls. Only two patients were found to have the heterozygous deletion. CONCLUSIONS: The frequency of homozygous deletion of SMNTel exon 7 was 90.1%. Our data support that SMN gene is strongly associated with SMA.

Adult↗
PubMed2000

[Changes of p16 gene, cyclin D1 gene, and pRb protein in human pancreatic adenocarcinoma cell lines].

OBJECTIVE: To investigate the abnormalities of the relative factors of pRb-p16 cell regulatory pathway in pancreatic adenocarcinoma. METHODS: Five strains of human pancreatic adenocarcinoma cell lines were analysed by PCR and single-strand conformation polymorphism (SSCP) for homozygous deletion and mutation of the p16 gene, respectively. The gene amplification of cyclin D1 was detected by Southern blot analysis and the protein expression of pRb gene was examined by Western blot analysis. RESULTS: Homozygous deletion of exon 1 were found in two cell lines and no mutation was found within exon 1 and exon 2 in five cell lines. Cyclin D1 gene amplification was observed in one cell line and all of the five cell lines showed hyper-phosphorylated pRb protein. CONCLUSION: These findings have demonstrated that there are abnormalities of pRb-p16 regulatory pathway in pancreatic adenocarcinoma cell lines, revealing the alteration of the p16 and cyclin D1 genes.

Adenocarcinoma↗
PubMed2000

[Cytosine diaminase/5-flurocytosine mediated inhibiting effect on the growth of human pancreatic carcinoma cells].

OBJECTIVE: To study the inhibition effect of E. coli cytosine diaminase (CD)/5-flurocytosine (5-FC) system on the growth of human pancreatic carcinoma cell line cells. METHODS: Recombinant retroviral vector expressing CD genes was transduced into pancreatic carcinoma cell line cells. In vitro and in vivo prodrug sensitivity assays were carried out, including: (1) detection of growth and colony forming inhibition rate of transduced cells in the presence of 5-FC; (2) observation of bystander effect by MTT method; (3) observation of the growth inhibition effect of 5-FC on transduced cell xenografts in nude mice. RESULTS: The growth and colony forming inhibition rate of the transduced cells in the presence of 5-FC were 80.0% and 79.0%, which were obviously higher than 4.8% and 5.0% (P < 0.01) of nontransduced cells. Mixed cells containing only 10% of transduced cells showed 50.7% reduction of proliferation (bystander effect). The growth of transduced cells xenografts could be totally regressed by 5-FC. CONCLUSIONS: CD/5-FC system is a potential gene therapy strategy for pancreatic carcinoma.

Animals↗
PubMed1999

Activation of a frizzled-2/beta-adrenergic receptor chimera promotes Wnt signaling and differentiation of mouse F9 teratocarcinoma cells via Galphao and Galphat.

The frizzled gene family of putative Wnt receptors encodes proteins that have a seven-transmembrane-spanning motif characteristic of G protein-linked receptors, though no loss-of-function studies have demonstrated a requirement for G proteins for Frizzled signaling. We engineered a Frizzled-2 chimera responsive to beta-adrenergic agonist by using the ligand-binding domains of the beta(2)-adrenergic receptor. The expectation was that the chimera would be sensitive both to drug-mediated activation and blockade, thereby circumventing the problem of purifying soluble and active Wnt ligand to activate Frizzled. Expression of the chimera in zebrafish embryos demonstrated isoproterenol (ISO)-stimulated, propranolol-sensitive calcium transients, thereby confirming the beta-adrenergic nature of Wnt signaling by the chimeric receptor. Because F9 embryonic teratocarcinoma cells form primitive endoderm after stable transfection of Frizzled-2 chimera and stimulation with ISO, they were subject to depletion of G protein subunits. ISO stimulation of endoderm formation of F9 stem cells expressing the chimeric receptor was blocked by pertussis toxin and by oligodeoxynucleotide antisense to Galphao, Galphat2, and Gbeta2. Our results demonstrate the requirement of two pertussis toxin-sensitive G proteins, Galphao and Galphat, for signaling by the Frizzled-2 receptor.

Amino Acid Sequence↗
PubMed1999

Activation of rat frizzled-1 promotes Wnt signaling and differentiation of mouse F9 teratocarcinoma cells via pathways that require Galpha(q) and Galpha(o) function.

The frizzled gene family of putative Wnt receptors encodes proteins that have a seven transmembrane-spanning motif characteristic of G-protein-linked receptors, although no loss-of-function studies have demonstrated a requirement for G-proteins for Wnt signaling by the gene product of frizzled-1. Medium conditioned by mouse F9 teratocarcinoma stem cells stably transfected to express either Xenopus Wnt-5a or Wnt-8 was used to test primitive endoderm formation of F9 stem cells. F9 stem cells expressing the rat Frizzled-1 receptors demonstrated endoderm formation in response to conditioned medium containing Wnt-8 but not to medium containing Wnt-5a. Primitive endoderm formation stimulated by Wnt-8 acting on the rat Frizzled-1 receptor was blocked by treatment with pertussis toxin by depletion of either Galpha(o) or Galpha(q) via antisense oligodeoxynucleotides, as well as by inhibitors of protein kinase C (bisindoylmaleimide) and of mitogen-activated protein kinase kinase (PD98059). Our results demonstrate the requirement for G-protein subunits Galpha(o) (a pertussis toxin substrate) and Galpha(q) for signaling by Frizzled-1, and an obligate role for the protein kinase C (likely mediated through stimulation of Galpha(q)) and mitogen-activated protein kinase network at the level of mitogen-activated protein kinase kinase.

3',5'-Cyclic-GMP Phosphodiesterases↗
PubMed1999

Asthma self-management: do patient education programs always have an impact?

BACKGROUND: During the past 15 years, programs to improve self-management practices in adults with asthma have reported improvement in functional status and reduction of inappropriate use of health care services. However, these programs usually represent an ideal approach, applying multiple patient education methods. Consequently, when these programs are found to be efficacious, it is important to replicate the programs as well as to evaluate less complex methods that may be more appropriate for nonacademic health care settings. METHODS: We compared the following 3 standardized self-management treatments in a randomized, controlled trial: (1) a replication of the self-management program developed at a university medical center that was previously shown to be efficacious; (2) a modified version of this program including only the core elements; and (3) a usual-care program. Outcome measures included medication and inhaler regimen adherence, asthma symptoms, respiratory illness, functional status, and use of health care resources. RESULTS: All 3 groups improved on measures of respiratory illnesses, use of health care services, and functional status. Patients in both education groups did no better than the usual-care group. CONCLUSIONS: The results are inconsistent with the results of the first asthma self-management study at this institution and with those of efficacy studies of similar programs. Two factors, selection of the patient population and historical changes in asthma treatment, most likely contributed to the lack of impact of the self-management programs. As a result of the improved standards for usual care due to both factors, the opportunity to effect patient outcomes was substantially reduced.

Administration, Inhalation↗
PubMed1999

Three-state unfolding and self-association of maspin, a tumor-suppressing serpin.

Maspin is a tumor suppressor protein expressed by normal human mammary epithelium but not by many breast tumor cell lines. Recombinant human maspin (rMaspin) inhibits tumor cell motility, invasion, and metastasis and thus has potential value as an anti-cancer therapeutic. Maspin is a member of the serpin family and, although the molecular mechanism by which maspin acts is unknown, recent work suggests that tissue plasminogen activator is a potential target. A puzzling observation in previous cell culture studies was loss of rMaspin activity at higher protein concentrations. One hypothesis to explain these results is self-association of rMaspin at the higher concentrations, which would be consistent with the tendency of serpins to form noncovalent polymers. This hypothesis is addressed by examining the relationship between rMaspin stability and self-association. Urea denaturation of rMaspin at pH 7 and 25 degrees C and at protein concentrations ranging from 0.01 to 0.2 mg/ml has been monitored by circular dichroism and intrinsic tryptophan fluorescence. Denaturation profiles show a protein concentration dependence and indicate the presence of at least one unfolding intermediate. The results suggest that destabilization of native monomeric rMaspin leads to partial unfolding and formation of an intermediate which can self-associate.

Circular Dichroism↗
PubMed1999

Analysis of recombinant and modified proteins by capillary zone electrophoresis coupled with electrospray ionization tandem mass spectrometry.

A method for rapid characterization of recombinant and modified proteins with known sequences is described. The analytical system consists of a capillary zone electrophoresis (CZE) instrument coupled to an electrospray ionization ion trap tandem mass spectrometer via a sheath-flow interface. Following the procedure consists of proteolytic fragmentation, CZE peptide separation, tandem mass spectrometry (MS-MS) analysis of separated peptides, sequence database search and monitoring of the specific peptides, C 125 S mutated interleukin 2 (S-125-IL2) and bovine beta-casein were characterized as a model of recombinant protein and naturally modified protein, respectively. A tryptic peptide mixture derived from the synthetic salmon calcitonin (s-CT) was also analyzed to test the performance of the system. Although a conventional sheath-flow interface with much higher flow-rate compared to the microspray interface and nanospray interface was used, the proteins were identified at the low picomole level.

Amino Acid Sequence↗
PubMed1999

Zinc alleviates thermal hyperalgesia due to partial nerve injury.

Zinc has recently been shown to alleviate inflammatory hyperalgesia. In the present study, we showed that intrathecal, intraplantar or systemic injection of zinc chloride significantly relieved thermal hyperalgesia in rats with sciatic nerve injury. Alleviation of thermal hyperalgesia was dose dependent in each case, although higher doses were required for i.p. injections (ED50 = 13.6 nmole) than for intrathecal (ED50 = 0.05 nmole) or intraplantar injections (ED50 = 0.3 nmole). Neither intrathecal nor intraplantar zinc chloride influenced thermal nociception in normal rats without nerve injury. The results provide the first evidence that zinc alleviates neuropathic hyperalgesia.

Animals↗