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Biomedical subjects

L Cao

Publications and source records attributed to L Cao.

At least 91 records · Page 5Linked to original sources
PubMed2000

LMP1 of Epstein-Barr virus induces proliferation of primary mouse embryonic fibroblasts and cooperatively transforms the cells with a p16-insensitive CDK4 oncogene.

The latent membrane protein LMP1 of Epstein-Barr virus (EBV) is often present in EBV-associated malignancies including nasopharyngeal carcinoma and Hodgkin's lymphoma. Previous work demonstrates that the LMP1 gene of EBV is sufficient to transform certain established rodent fibroblast cell lines and to induce the tumorigenicity of some human epithelial cell lines. In addition, LMP1 plays pleiotropic roles in cell growth arrest, differentiation, and apoptosis, depending on the background of the target cells. To examine the roles of LMP1 in cell proliferation and growth regulation in primary culture cells, we constructed a recombinant retrovirus containing an LMP1 gene. With this retrovirus, LMP1 was shown to stimulate the proliferation of primary mouse embryonic fibroblasts (MEF cells). It has a mitogenic activity for MEF cells, as demonstrated by an immediate induction of cell doubling time. In addition, it significantly extends the passage number of MEF cells to more than 30 after retroviral infection, compared with less than 5 for uninfected MEF cells. Furthermore, LMP1 cooperates with a p16-insensitive CDK4(R24C) oncogene in transforming MEF cells. Our results provide the first evidence of the abilities of the LMP1 gene, acting alone, to effectively induce the proliferation of primary MEF cells and of its cooperativity with another cellular oncogene in transforming primary cells.

Animals↗
PubMed2000

High-titer, wild-type free recombinant adeno-associated virus vector production using intron-containing helper plasmids.

Recombinant adeno-associated virus (rAAV) is capable of directing long-term, high-level transgene expression without destructive cell-mediated immune responses. However, traditional packaging methods for rAAV vectors are generally inefficient and contaminated with replication-competent AAV (rcAAV) particles. Although wild-type AAV is not associated with any known human diseases, contaminating rcAAV particles may affect rAAV gene expression and are an uncontrolled variable in many AAV gene transfer studies. In the current study, a novel strategy was designed to both optimize AAV rep gene expression and increase vector yield, as well as simultaneously to diminish the potential of generating rcAAV particles from the helper plasmid. The strategy is based on the insertion of an additional intron in the AAV genome. In the AAV infectious clone, the intron insertion had no effects on the properties of Rep proteins expressed. Normal levels of both Rep and Cap proteins were expressed, and the replication of the AAV genome was not impaired. However, the generation of infectious rcAAV particles using intronized AAV helper was greatly diminished, which was due to the oversized AAV genome caused by the insertion of the artificial introns. Moreover, the rAAV packaging was significantly improved with the appropriate choice of intron and insertion position. The intron is another element that can regulate the rep and cap gene expression from the helper plasmid. This study provides for a novel AAV packaging system which is highly versatile and efficient. It can not only be combined with other AAV packaging systems, including rep-containing cell lines and herpes simplex virus hybrid packaging methods, but also be used in other vector systems as well.

Dependovirus↗
PubMed2000

Enhanced T cell responsiveness to citrulline-containing myelin basic protein in multiple sclerosis patients.

Myelin basic protein (MBP), a candidate autoantigen in multiple sclerosis (MS), exists in different isoforms and charge isomers generated by differential splicing of exons and by a combination of posttranslational modifications, respectively. These various isoforms and charge isomers of MBP vary in abundance and most likely serve different functions during myelinogenesis and remyelination. The least cationic among the charge isomers of MBP is citrullinated and is referred to as MBP-C8. MBP-C8 is relatively increased in the population of MBP isomers in more developmentally immature myelin and in MS brain tissue. In a previous study, we found that MBP-C8-reactive T cells could be detected in CD4+ T cell lines (TCL) generated with MBP from both MS patients and normal controls. Here, we examined the frequency and peptide specificity of MBP-C8-specific TCL generated with MBP-C8 in MS patients and controls. Ten subjects grouped in five sets, each an MS patient and a control, were studied. In all cases, the MS patient had either a higher overall number of MBP-C8-responding lines, responded with greater sensitivity to the MBP-C8 antigen or both. Few lines responded to the MBP-C8 peptides but, if they did, they appeared to be specific to the carboxyl-half of the MBP-C8 molecule. Given the large amounts of citrullinated MBP in MS brain tissue, a preferential T cell response to MBP-C8 may be involved in the induction and perpetuation of this disease. Multiple Sclerosis (2000) 6 220 - 225

Adult↗
PubMed2000

Purification and reconstitution of an integral membrane protein, the photoreaction center of Rhodobacter sphaeroides, using synthetic sugar esters.

Detergents are indispensable reagents for the extraction and solubilization of integral membrane proteins, but their removal from a reconstituted phospholipid-protein complex is usually desirable. In this paper, we describe a novel method in which the synthetic sugar esters 6-O-octanoyl-beta-D-glucose (OG) or 6-O-octanoyl-beta-D-mannose (OM) are used as detergents for both the isolation and the rapid reconstitution of the photosynthetic reaction center protein of Rhodobacter sphaeroides. Following solubilization of the reaction center with OG or OM and reconstitution of this protein in liposomes, a convenient removal of these detergents was achieved within less than two hours by hydrolytic cleavage of the sugar esters using immobilized lipases. Best results were achieved with lipase from Bacillus sp. immobilized on silica gel.

Detergents↗
PubMed2000

Epidermal growth factor induces cell cycle arrest and apoptosis of squamous carcinoma cells through reduction of cell adhesion.

Most squamous epithelial cells are strictly anchorage-dependent cell types. We observed that epidermal growth factor (EGF) promoted the growth of A431 squamous carcinoma cells in suspension cultures but suppressed cell growth and induced apoptosis in monolayer cultures, suggesting that loss of adhesion is responsible for the effects observed in monolayer culture, before cell death. Consistent with this finding, we demonstrated that EGF reduced cell attachment, cell-cell interaction, and cell spreading. Treatment with EGF increased cell adhesion-regulated expression of p21 but suppressed expressions of cyclin A, D1, cdk2, and retinoblastoma protein (pRb), leading to cell cycle arrest and adhesion-regulated programmed cell death. To test directly whether promoting cell adhesion could reduce the effects of EGF, we grew cultures on plates coated with type II collagen. On these plates, cell adhesion was enhanced and EGF treatment had little effect on cell adhesion and apoptosis when cells were attached to the collagen. The collagen effects were dose dependent, and cell cycle and cell cycle-associated proteins were altered accordingly. Finally, when cultures were plated on bacterial Petri dishes, which completely disrupted cell attachment to substratum, the level of apoptosis was greatly higher and cell cycle was arrested as compared with monolayer cultures. Taken together, our results strongly suggest that the EGF-induced cell cycle arrest and apoptosis in monolayer cultures was the result of a decline in cell adhesion.

Apoptosis↗
PubMed2000

[Molecular cloning of a novel gene located on chromosome 3p25.3 and an analysis of its expression in nasopharyngeal carcinoma].

OBJECTIVE: To obtain the novel genes associated with human nasopharyngeal carcinoma(NPC) on chromosome 3p24-26. METHODS: Twenty epithelial-derived expressed sequence tags(EST) were selected from chromosome 3p24-26 where loss of heterozygosity(LOH) frequently occurs in NPC tissues. Primers were designed based on the sequences of these ESTs. RT-PCR was used to amply their corresponding cDNA fragments from NPC cell line HNE1 and primary cultures of normal nasopharyngeal epithelial cells. The differential expression of two ESTs, T93093 and R41598, was confirmed by Northern blot. Then, expression of EST T93093 was further detected in 7 normal nasopharyngeal and 19 NPC biopsies. cDNA library screening was used to get its full cDNA sequence and the sequence of this novel gene was analyzed by bioinformatics. RESULTS: Thirteen ESTs(T62511, N39155, N68660, R61275, T95314, R06143, H52697, H66521, AA128685, AA284537, N52379, AA054180, and H98090) showed the similar expression level and 5 ESTs(R00732, R07573, R98052, H91759, H17566) showed no expression in both types of cells. EST T93093 was down-expressed, whereas EST R41598 up-expressed in NPC HNE1 cells. The EST T93093 was also found to be down-expressed in 26.3%(5/19) of NPC biopsies. The full length cDNA of this gene was obtained and named NAG-7, which is located at chromosome 3p25.3. Its 1677 bp full length cDNA has a potential open reading frame(ORF) predicting a 94 amino acid protein with a molecular weight of 11023.87 Dalton. Bioinformatics analysis of the NAG-7 gene shows that it is a transmembrane protein containing a protein kinase C(PKC) phosphorylation site and a myristyl site. It has no significant homology to any reported genes in database of GenBank(AF086709). CONCLUSION: NAG-7 is a novel gene down-expressed in NPC, which may be involved in the development of NPC.

Chromosome Mapping↗
PubMed2000

Low dose gossypol for male contraception.

AIM: To ascertain whether the side effects of gossypol, hypokalemia and irreversibility, could be avoided on dose reduction. METHODS: Seventy-seven male volunteers were divided into 3 groups: control (22 cases), 10 mg gossypol (29 cases) and 12.5 mg (26 cases). Serum levels of testosterone, FSH and LH were measured by RIA and potassium by flame photometry. Sperm counts and motility were examined before and regularly after treatment for the evaluation of contraceptive efficacy. RESULTS: The average sperm density and motility started to decrease significantly by the end of month 2 of medication and gradually reached the infertility levels (< 4 million/mL) in both treated groups. After that the 10 mg group was asked to take the same dose every other day for up to a total observation period of 16-18 months for the maintenance of infertility. Subjects in the 12.5 mg group did not take gossypol any more so as to observe the length of the loading dose required, but in a few, a maintenance dose of 12.5 mg every other day was instituted for a few more months. In both treated groups, none of the spouses was pregnant during the maintenance dose period. Serum levels of potassium, FSH, LH and testosterone were not significantly changed and not a single volunteer complained of myoasthenia. After cessation of drug administration, the semen data returned to pretreatment levels. CONCLUSION: A regimen with 10 or 12.5 mg of gossypol as the daily loading dose and 35 or 43.75 mg as the weekly maintenance dose could induce infertility in male volunteers without developing hypokalemia or irreversibility.

Contraceptive Agents, Male↗
PubMed2000

[The effect of tetrahydropalmatine on ouabain-induced delayed after depolarization and triggered ventricular arrhythmia].

OBJECTIVE: To study the effect and mechanism of tetrahydropalmatine (THP) ouabain-induced on delayed after depolarization (DAD) and anti-triggered ventricular arrhythmia in in-vivo rabbit heart. METHODS: 14 rabbits were divided into two groups at random, control group and THP group. The monophasic action potential (MAP) of right ventricule and the surface lead II electrocardiogram (ECG) were simultaneously recorded. The changes of MAP and ECG in the THP group were compared with those in the control group after administration of ouabain 150-170 ug/kg and before using the drug. RESULTS: The incidence and couple interval of DAD in the two groups had no apparent difference (P > 0.05) after administration of ouabain, but the amplitude of DAD and the incidence of triggered ventricular arrhythmia in the THP group were significantly lower than those in the control group (P < 0.05). CONCLUSION: THP had the effect of decreasing the amplitude of DAD of rabbit heart induced by ouabain thus reducing the chance of triggered ventricular arrhythmia induced by DAD.

Action Potentials↗
PubMed2000

Fractionated radioimmunotherapy using low doses of iodine-131 labeled anti-CEA monoclonal antibody after tumor volume reduction.

OBJECTIVE: To assess the efficacy of fractionated administration of radiolabeled monoclonal antibody in the treatment of metastases after tumor volume reduction surgery, various experimental therapies were studied comparatively. METHODS: A total of 200 inbred mice received tumor implantation from a murine adenocarcinoma cell line. The mice were randomly grouped to give saline, Arc-a, 131I-C50 in single or fractionated doses, cold C50, or non-specific 131I-IgG with or without surgical removal of the implanted tumor xenograft. RESULTS: In comparison to controls, animals receiving Arc-a and radioactive agents had longer survival, smaller tumor, better clinical condition, and less metastases foci. The best therapeutic response was noted after fractionated doses of 131I-C50, which showed better results in every aspect than those treated with other modalities. The favorable outcome was even more pronounced after tumor volume reduction. CONCLUSIONS: Fractionated dosing may improve the deposition of radiolabeled monoclonal antibody (McAb) and provide the best therapeutic effect on implanted tumor and metastases. Thus fractionated radioimmunotherapy (RIT) after tumor volume reduction might be a practical method with promising therapeutic results.

Animals↗
PubMed2000

A cDNA located on chromosome 7q32 shows loss of expression in epithelial cell line of nasopharyngeal carcinoma.

OBJECTIVE: To isolate and clone the tumor suppressor gene on chromosomal region 7q32 correlated with the carcinogenesis of human nasopharyngeal carcinoma (NPC). METHODS: The genotypes of polymorphic microsatellite markers on 7q32 in DNA from 24 biopsies of nasopharyngeal carcinoma and matched normal blood cells were identified. The expression levels of 20 expressed sequence tags (ESTs) on 7q32 between human nasopharyngeal carcinoma epithelial 1 (HNE1) and primary cultures of normal nasopharyngeal epithelial (PNNE) cells were compared using differential RT-PCR and Northern hybridization. The quantity of AA070437 DNA and mRNA was detected by differential PCR and differential RT-PCR, respectively. RESULTS: Loss of heterozygosity (LOH) was found in 25%-46% of NPC biopsies. AA070437 EST expression was down-regulated in HNE1 cell compared to PNNE cells. The down-regulation of AA070437 was found in 30.7% of NPC biopsies and allelic loss of AA070437 was observed in 29.1% of NPC biopsies. CONCLUSION: Our results show that AA070437 EST is negatively related with the occurrence of human NPC and may represent a candidate tumor suppressor gene of NPC on 7q32.

Chromosomes, Human, Pair 7↗
PubMed2000

c-myc gene inactivation during induction of nasopharyngeal carcinoma cells with retinoic acid.

OBJECTIVE: To investigate the effects of retinoic acid (RA) on the growth, morphology, oncogene expression and regulation of nasopharyngeal carcinoma cells. METHODS: Nasopharyngeal carcinoma cell line (HNE1) was induced by RA. The RA-treated and control cells were established and cellular morphology and growth patterns were defined. Oncogene expression and regulation were detected by Northern hybridization and DNase-I hypersensitive site analysis. RESULTS: RA markedly inhibited cell growth. The growth of HNE1 cells was reduced to 50% of the control level on the 4th day of RA (10(-4) mol/L) treatment. After 4 days of treatment, the rapidly growing polygonal cells were reversed into a slow growing phenotype, with flattened morphology similar to fibroblast-like cells. Northern hybridization showed that c-myc and c-Ha-ras expression was high in HNE1 cells and undetectable in normal blood cells. c-myc was down-regulated at 48 h of RA treatment. In contrast, the c-Ha-ras was not affected. DNase I hypersensitive site analysis detected changes in the regulatory elements of c-myc and c-Ha-ras genes. 5 hypersensitive sites were found in the c-myc of HNE1 cells, while 3 hypersensitive sites disappeared upon HNE1 induction. However, only 1 hypersensitive site was found in c-Ha-ras of RA treated cells and controls. In normal peripheral white blood cells, no DNase I hypersensitive sites were found in the inactive c-myc and c-Ha-ras gene. CONCLUSION: RA can induce differentiation in a nasopharyngeal carcinoma cell line at high concentration of RA; HNE1 shows some similar patterns of DNase I hypersensitive sites with the common one in other types of cells expressing c-myc. The repression of c-myc expression with induction is accompanied by the loss of 3 DNase-I hypersensitive sites; c-myc has more than one inactive conformation.

Antineoplastic Agents↗
PubMed2000

[Study on apoptosis and its related genes in pregnancy induced hypertension].

OBJECTIVE: To investigate apoptosis and its related genes expression in serious pregnancy induced hypertension (SPIH). METHODS: 40 cases of normal term pregnancy(NTP) and 40 cases of SPIH were enrolled in this study. Apoptosis was detected using DNA in situ terminal deoxynucleotidyl transferas (TDT)-mediated deoxyuridine triphosphate (dUTP)-biotin nick ending labeling (TUNEL); bax and bcl-2 were detected by immunohistochemical staining (SP). RESULTS: In NTP group apoptosis index(AI) of cytotrophoblasts(CT) and syncytiophoblasts(ST) in placenta was (1.1 +/- 0.9)% and (41.8 +/- 1.5)%; bax positive rate was (1.0 +/- 0.9)% and (28.9 +/- 9.7)%; bcl-2 was (2.2 +/- 0.8)% and (22.9 +/- 0.7)% respectively; bax/bcl-2 was 0.7-1.7. In SPIH group, AI was (4.3 +/- 1.2)% and (45.3% +/- 1.4)%; bax was (2.2 +/- 0.8)% and (42.5 +/- 11.7)%; bcl-2 was (3.2 +/- 0.8)% and (23.3 +/- 7.8)%; bax/bcl-2 was 1.0-3.2. The difference between SPIH and NTP was significant respectively (P < 0.01); bax/bcl-2 was balance in NTP, while the balance was broken in SPIH. CONCLUSIONS: Apoptosis and its related genes expression are simultaneous. The balance and imbalance of apoptosis and bax/bcl-2 affect the structure and the function of placenta, and then may further affect the outcome of pregnancy.

Adult↗
PubMed2000

[Flow cytometric 3-color analysis of circulating activated platelets and its clinical significance in ischemic cerebrovascular diseases].

OBJECTIVE: To explore the flow cytometric 3-color analysis of circulating activated platelets (CAP) and its clinical significance in ischemic cerebrovascular diseases. METHODS: The fibrinogen receptor (FIB-R) and P-selectin (CD62P) were used for molecular marker of CAP, which were analyzed by flow cytometric 3-color immunofluorescence. RESULTS: Expression of FIB-R and CD62P on the resting platelet membrane surface was very lower in normal individuals, the median of FIB-R and CD62P positive percent was 1.40% and 0.70% respectively. Platelet can be obviously activated by 0.1 micromol/L ADP, and 10.0 micromol/L ADP leaded to the peak expression of FIB-R and CD62P on the activated platelet membrane surface, FIB-R and CD62P positive percent of 87.8% and 81.34% respectively. That monoclonal antibody of the FIB-R combined with ADP activating platelets was inhibited by synthetic peptide (RGDS). The quantity of CAP with FIB-R expression was markedly higher (P < 0.01) and the amount of CAP with CD62P expression was not significantly higher (P > 0.05) in blood of 112 patients with thrombotic tendency and 120 patients with ischemic cerebrovascular diseases than in healthy individuals. The expression of CAP with FIB-R of in front and behind treatment of acute cerebral infarction continuously decreased (P < 0.05), and the quantity of CAP with FIB-R expression was related negatively to Europe stroke score (ESS) of patients with acute cerebral infarction. CONCLUSION: The FIB-R may be regarded as sensitive and specific molecular marker in detection of CAP. The level of platelet activation in vivo can be reflected accurately by flow cytometric 3-color analysis of CAP, which has an important clinical significance for the study of pathogenesis, estimation of prognosis and supervision of curative effect in ischemic cerebrovascular diseases.

Adenosine Diphosphate↗
PubMed2000

[Effects of hypoxia alone or exercise combined on capillarization of rat gastrocnemius muscle and its mechanism].

OBJECTIVE: To study the effects of hypoxia and hypoxia-combined-exercise on capillary density and vascular endothelial growth factor (VEGF) and its receptor KDR of skeletal muscle in rats. METHODS: Myosin-ATPase histochemistry was used to assay the size and capillary density of skeletal muscle. VEGF and its receptor KDR were studied by immunohistochemistry. RESULTS: Five-week hypoxia (simulated 5,000 m altitude) resulted in a decrease in cross-sectional area of skeletal muscle fiber and an increase in capillary density (CD), but the capillary/fiber ratio (C/F) remained unchanged. After 5-week-exercise at high altitude (1 h/d, 6 d/w), the muscle fibers did not undergo atrophy. At the same time, CD and C/F were increased. VEGF protein was found primarily in the matrix between muscle fibers; VEGF receptor-KDR was shown mainly in endothelial cells of capillary. VEGF was more strongly stained in the skeletal muscle of hypoxia-combined-exercise rats than the other two groups. CONCLUSION: Hypoxia itself can not induce neovascularization, while hypoxia-combined-exercise rats show capillary proliferation in skeletal muscle. VEGF and its receptor might play roles in this process.

Animals↗
PubMed2000

[Analysis of the factors related to the change of energy expenditure in burned patients].

OBJECTIVE: To analyze the factors related to the change of energy expenditure in burned patients. METHODS: Indirect calorimetry was employed to detect energy expenditure (EE) dynamically in 45 cases of burned patients and to analyze their change. RESULTS: EE increased immediately postburn and reached top level in about one week (11, 443.78 plus minus 3, 295.32) kJ/d. EE value was positively correlated to the size of burn area. EE was also correlated to the development of the disease. The EE variation happened in the early postburn stage. The degree of variation was positively correlated to the size of burn area. The EE value in patients with medium size burn and inhalation injury was higher than that without inhalation injury. Postoperative EE decreased obviously in patients with major burn who had undergone escharectomy. EE in male patients was higher than that in female. CONCLUSION: Postburn EE varied with some regularity, but was affected by burn depth and size, postburn time, inhalation injury, escharectomy, sex and individual difference.

Adolescent↗
PubMed2000

[Protective effect of exogenous glial cell line derived neurotrophic factor on neurons after sciatic nerve injury in rats].

The aim of the study was to investigate the effect of exogenous glial cell line derived neurotrophic factor (GDNF) on spinal cord neurons after sciatic nerve axotomy. Upon silicone tubulization of transected sciatic nerve in the adult rat, either 0.9% saline or GDNF solution was injected into the silicone chamber. It was observed by Nissl and enzyme histochemistry staining that exogenous GDNF decreased lesion induced motor neuron death in lateral nucleus of spinal anterior horn and the changes in activity of cholinesterase and acid phosphatase in spinal cord and sensory ganglions. These results suggest that exogenous GDNF is capable of protecting motor neurons from death induced by peripheral nerve injury.

Animals↗
PubMed2000

[Analysis of Amomun villosum species and some adulterants of zingiberaceae by RAPD].

Different Amomum villosum Lour. species and some their adulterants of Zingiberaceae were researched using RAPD. The PCR indicates favourable differentiation of the reaction. The Amomum villosum Lour. species have the similar DNA fingerprints while it is obviously differ from adulterants. There are 12.17 percent of primers which appear polymorphism. We can identify different species according to these dissimilarity. We also construct the tree of the molecular evolution through NJ software, the hereditary distance of the graph shows different relationships between Amomum villosum Lour. species and their adulterants. The result created by software is analogous the traditional methods.

Amomum↗