Biomedical subjects

Na Liu

Publications and source records attributed to Na Liu.

63 records · Page 4Linked to original sources

PubMed2004

[Studies on in vitro capacitation of goat spermatozoa by heparin treatment].

Systematical studies are lacking on the influencing factors and mechanisms of the heparin enhanced sperm capacitation, although many studies have shown that heparin enhanced sperm capacitation. The effect of heparin concentration and exposure time, incubation temperature and co-culture with oviductal epithelial cells or cumulus cells on goat sperm capacitation were investigated in this study. The motility, membrane and acrosome integrity and capacitated percentage of goat spermatozoa were assessed after different heparin treatments, and rates of fertilization and embryo cleavage were compared after in vitro insemination of oocytes with spermatozoa capacitated by different heparin treatments. The major results are summarized as follows: 1) When spermatozoa were capacitated with heparin at 5, 10, 25, 50 and 100 microg/mL for 45 min, 50 and 100 microg/mL heparin treatments produced the highest capacitated percentages of 55% and 56%, respectively, but the percentage of spermatozoa with intact acrosomes in the 100 microg/mL heparin treatment decreased significantly (P < 0.05) in comparison with that in the control group, indicating that the optimal heparin concentration for goat sperm capacitation would be 50 microg/mL. 2) Capacitated percentage of spermatozoa increased with extension of treatment time when goat sperm were treated with 50 microg/mL heparin for 0, 10, 20, 30, 45, 60 or 120 min. Although heparin treatments for 45 to 120 min did not differ significantly (P > 0.05) in capacitated sperm percentages, sperm motility and membrane integrity decreased significantly when treated with heparin for 120 min. This suggested that the optimal exposure time of heparin at 50 microg/mL for goat sperm capacitation would be 45 to 60 min. 3) Significantly higher capacitated percentages of spermatozoa were obtained when goat sperm were treated at 42 and 38.5 degrees C than at 15 and 37 degrees C, but sperm motility and acrosome integrity were significantly lower when spermatozoa were treated at 42 degrees C than they were treated at other temperatures. Temperature of 38.5 degrees C would, therefore, be the optimal temperature for goat sperm capacitation. 4) The capacitated percentage of spermatozoa was significantly higher when goat sperm were co-cultured with oviductal epithelial cells than when treated with heparin alone or co-cultured with cumulus cells, but sperm motility and membrane and acrosome integrity did not differ significantly among the three treatments. Rates of fertilization (91.3%) and cleavage (72.2%) were significantly higher in the oviductal epithelial cell co-culture group than those in the heparin alone group. This indicated that co-culture with oviductal epithelial cells significantly enhanced goat sperm capacitation by heparin treatment.

Acrosome Reaction↗

PubMed2003

Suppression of the dual-specificity phosphatase MKP-1 enhances HIF-1 trans-activation and increases expression of EPO.

Hypoxia-inducible factor 1 (HIF-1) is a phosphorylated protein and its phosphorylation is involved in HIF-1alpha subunit stabilization as well as in the regulation of HIF-1 transcriptional activity. In a variety of cell lines, the phosphorylation of HIF-1alpha is dependent on ERK or p38, two members of the mitogen-activated protein kinase (MAPK) superfamily. In addition, active MAPK could be inactivated through dephosphorylation by mitogen-activated protein kinase phosphatase-1 (MKP-1). MKP-1 has been identified as a hypoxia responsive gene, but its role in the response of cells to hypoxia is poorly understood. Here we found that hypoxia induces MKP-1 expression in human hepatoma cells HepG2 in a time-dependent manner. Inhibition of MKP-1 expression using siRNA technique could enhance HIF-1alpha phosphorylation, accompanied by an increase in transcriptionally active HIF-1 as well as a rise in the levels of HIF-1-induced erythropoietin expression.

Carcinoma, Hepatocellular↗

PubMed2003

Small interfering RNA: a new tool for gene therapy.

The use of anti-gene agents to disrupt the expression of disease-related genes could potentially be of utility in the treatment of a large number of illnesses, including most neoplasms. Traditional anti-gene agents include antisense oligonucleotides and ribozymes. Recent observations have provided evidence for another promising anti-gene technology-RNA interference (RNAi), in which the introduced double-stranded RNA (dsRNA), after a complicated series of processing steps, disrupts the expression of the targeted cellular gene. Further studies have indicated that small interfering RNAs (siRNAs) of generally 21 ~ 23 nucleotides, which resemble the processing products of long dsRNA, can induce RNAi directly in mammalian cells. Because of their high specificity and efficiency, siRNAs might be a new class of anti-gene medicines for gene therapy applications.

Genetic Therapy↗

PubMed2003

Development of an oral DNA vaccine against MG7-Ag of gastric cancer using attenuated salmonella typhimurium as carrier.

AIM: To develop an oral DNA vaccine against gastric cancer and evaluate its efficacy in mice. METHODS: The genes of the MG7-Ag mimotope and a universal Th epitope (Pan-DR epitope, PADRE) were included in the PCR primers. By PCR, the fusion gene of the two epitopes was amplified. The fusion gene was confirmed by sequencing and was then cloned into pcDNA3.1(+) plasmid. The pcDNA3.1 (+)-MG7/PADRE was used to transfect an attenuated Salmonella typhimurium. C57BL/6 mice were orally immunized with 1X10(8) cfu Salmonella transfectants. Salmonella harboring the empty pcDNA3.1(+) plasmid and phosphate buffer saline (PBS) were used as negative controls. At the 6th week, serum titer of MG7-Ag specific antibody was detected by ELISA. At the 8th week cellular immunity was detected by an unprimed proliferation test of the spleenocytes by using a ((3)H)-thymidine incorporation assay. Ehrlich ascites carcinoma cells expressing MG7-Ag were used as a model in tumor challenge assay to evaluate the protective effect of the vaccine. RESULTS: Serum titer of antibody against MG7-Ag was significantly higher in mice immunized with the vaccine than that in control groups (0.841 vs 0.347, P<0.01; 0.841 vs 0.298, P<0.01), while in vitro unprimed proliferation assay of the spleenocytes showed no statistical difference between those three groups. Two weeks after tumor challenge, 2 in 7 immunized mice were tumor free, while all the mice in the control groups showed tumor formation. CONCLUSION: Oral DNA vaccine against the MG7-Ag momitope of gastric cancer is immunogenic. It can induce significant humoral immunity against tumor in mice, and the vaccine has partially protective effects.

Administration, Oral↗

PubMed2003

[Rac subfamily expression and activity in gastrointestinal cancer cell lines].

OBJECTIVE: To investigate the significance of Rac subfamily members in the gastrointestinal carcinogenesis and progression. METHODS: The mRNA expression of Rac1, Rac2 and Rac3 in 12 kinds of gastrointestinal cancer cell lines was examined by semi-quantitative RT-PCR. The activities of Rac1 protein in 5 kinds of gastric cancer cell lines were tested by pull-down assay. RESULTS: Compared with the normal gastric mucosa and intestinal epithelial cell line, the mRNA expression of Rac1 and Rac3 was up-regulated in most of gastrointestinal cancer cell lines. The activities of Rac1 protein increased markedly in gastric cancer cell lines. CONCLUSION: The increased mRNA expression of Rac1 and Rac3 in gastrointestinal cancer cell lines and the abnormal activation of Rac1 protein in gastric cancer cell lines might be correlated with the carcinogenesis of gastrointestinal cancer.

Cell Line, Tumor↗

PubMed2003

[Protective effect of selective cyclooxygenase-2 inhibitor on alcohol-induced liver injury in rats].

OBJECTIVES: To investigate the effect of selective cyclooxygenase-2 (COX-2) inhibitor on alcohol-induced liver injury in rats. METHODS: 58 male Wistar rats were randomly divided into three groups: control group treated with dextrose and corn oil, model group with ethanol and corn oil, treatment group with corn oil and ethanol plus a selective COX-2 inhibitor celecoxib. All treatments were injected into stomach through intragastric tubes. Liver samples were analyzed for histopathology with light microscope (LM) and transmission electron microscope (TEM), and the expression of COX-2 with western blotting. Levels of aspartate aminotransferase (AST) and alanine aminotransferase (ALT) in serum, levels of 6-Keto-prostaglandin F1 alpha (6-k-PGF1a) and thromboxane B2 (TXB2) in liver, and activity of glutathione s-transferase (GST) both in liver tissue and in plasma were measured. RESULTS: LM and TEM indicated hepatocytes were injured obviously in the model group and slightly in the treatment group. The levels of AST and ALT in serum, TXB2 in liver and the activity of GST in plasma increased significantly in the model group (t> or =2.294, P<0.05), but the activity of GST in liver decreased significantly (t=8.856, P<0.01) compared with those in the control group. To compare with the model group, the levels of AST and TXB2 decreased significantly (t=4.305, P<0.01; t=2.799, P<0.01), meanwhile the activity of GST increased significantly (t=10.134, P<0.01) in the treatment group. COX-2 expression in liver by western blotting increased significantly in the model group, compared with the control group (t=4.067, P<0.01) and the treatment group (t=2.251, P<0.05). Exceptionally, the level of 6-k-PGF1a decreased significantly (t=2.284, P<0.05) in the model group. CONCLUSION: COX-2 has involved in the alcohol-induced liver injury, and its inhibitor can diminish alcohol-induced liver injury in rats through decreasing TXB2 level

Animals↗

PubMed2003

[Study on a new IL-12 inducing gene NAP2].

AIM: To study the function of newly cloned NF-kappaB-activating gene (NAP2) and its mechanism. METHEDS: Activation of NF-kappaB and IL-12 promoters as well as modulation of IL-12 synthesis by NAP2 in macrophages were observed by NF-kappaB and IL-12 luciferase reporter assay and intracellular IL-12 staining. RESULTS: NAP2 could activate NF-kappaB and IL-12 promoter. But IkappaBalphaDN could inhibit their activation. In addition, NAP2 could induce IL-12 expression in macrophage cell line J774. CONCLUSION: NAP2 as a newly cloned NF-kappaB activating gene can activate IL-12 promoter and induce IL-12 expression in macrophages. The data suggest that NAP2 regulates the expression of IL-12 most likely through its modulation of NF-kappaB transcription factor.

Cell Line↗

PubMed2002

The peroxisome proliferator phenylbutyric acid (PBA) protects astrocytes from ts1 MoMuLV-induced oxidative cell death.

Oxidative stress is involved in the pathogenesis of several neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, and HIV neuroAIDS. In this study, we have investigated an agent, phenylbutyric acid, that ameliorates cell death in murine astrocytes infected with ts1 MoMuLV (ts1). Phenylbutyric acid, an aromatic short chain fatty acid, was shown to prevent the loss of catalase that occurs in ts1 infected astrocytes, and to prevent ts1-mediated cell death. Cell cotransfection studies demonstrated that phenylbutyric acid activates peroxisome proliferator receptors (PPARs) in astrocytes, and binds to the peroxisome proliferator-activated receptors alpha and gamma. This observation suggests that the effects of PBA may be mediated by PPARs in astrocytes. Phenylbutyric acid also maintained catalase protein levels in brain of ts1-infected mice, and delayed the hindlimb paralysis caused by ts1 infection. Because PBA activates peroxisome proliferator-activated receptors and prevents loss of catalase, we suggest that ts1-induced oxidative stress in infected astrocytes that is alleviated by PBA is mediated via PPARalpha and/or PPARgamma.

Animals↗

PubMed2002

[Development of oral DNA vaccine based on MG(7)-Ag mimotope of gastric cancer].

OBJECTIVE: To develop an oral DNA vaccine based on MG(7)-Ag mimotope of gastric cancer using attenuated Salmonella typhimurium and evaluate its efficacy and protective effect. METHODS: The eukaryotic expression vector including the MG(7)-Ag mimotope and a Th epitope was constructed, and then transduced into an attenuated Salmonella typhimurium to get the oral DNA vaccine. C57BL/6 J mice were orally immunized with 1 x 10(8) cfu Salmonella transfectants, with Salmonella harboring empty plasmid, with phophate buffered saline (PBS) as control. At the 6th week, serum titer of MG(7) antibody was detected by ELISA. In the 8th week, a [(3)H]-thymidine incorporation assay was performed to test the proliferation of murine spleen cells to the stimulant of MG(7)-Ag mimicry peptide. At the same time, Ehrlich ascites carcinoma cells expressing MG(7)-Ag were used in tumor challenge assay to evaluate the protective effect of the immunization. RESULTS: The oral DNA vaccine induced MG(7) antibody in mice, while in vivo unprimed proliferation assay of the spleenocytes showed no difference among the three groups. Two weeks after tumor challenge, 2 in 7 immunized mice were tumor free, while none in the control group was protected. CONCLUSION: Oral DNA vaccine based on the MG(7)-Ag momitope is immunogenic. It is able to induce specific immunity response against tumor in mice, and the vaccine is partially protective.

Administration, Oral↗