Biomedical subjects

X Pang

Publications and source records attributed to X Pang.

At least 19 recordsLinked to original sources

PubMed2004

Elicitation of both CD4 and CD8 T-cell-mediated specific immune responses to HCA587 protein by autologous dendritic cells.

We recently cloned a new member of cancer/testis antigen named HCA587, which was highly expressed in human hepatocellular carcinoma (HCC) tissues. To investigate it as a potential tumour-specific target for immunotherapy, the immunogenicity of this protein, especially the ability to induce specific cellular immune responses, was evaluated in the present study. As dendritic cells (DC) are the most potent antigen-presenting cells, DC-based vaccination has recently shown marked promise for the treatment of human malignancies by immunological intervention. Here, we demonstrate that autologous DC loaded with HCA587 protein could induce specific T-cell responses in healthy individuals by in vitro stimulations. Enzyme-linked immunospot analysis for interferon-gamma (IFN-gamma) secretion demonstrated HCA587-specific CD8(+) T cells in the antigen-stimulated peripheral blood lymphocytes, and the analysis of CD4(+) T cells by proliferation assay also showed antigen-specific reactivities in normal donors. Two-colour flow cytometric analysis of surface markers and intracellular cytokine expression demonstrated that HCA587-specific cytotoxic T lymphocytes exhibited a heterogeneous CD8(+)/CD56(+) expression, and a striking T-helper 1 cytokine bias (IFN-gamma(high)/IL-4(low)) was observed for both CD4(+) and CD8(+) HCA587-specific lymphocyte populations. We conclude that HCA587 is a potent immunogen that can induce CD4(+) and CD8(+) T-cell-mediated specific immune responses, and these findings propose HCA587 as a good candidate for the development of a therapeutic protein-based DC tumour vaccine for the treatment of HCC patients.

Antigens, Neoplasm↗

PubMed2002

Effect of La3+ on the activities of antioxidant enzymes in wheat seedlings under lead stress in solution culture.

In order to improve the plant ability to resist lead stress, effect of 0.05 mg/l La(NO3)3 on the activities of catalase (CAT), superoxide dismutase (SOD), the level of malondialdehyde (MDA) in wheat seedlings under lead stress was studied. The effect of La3+ on plant growth, chlorophyll content in wheat seedlings after adding 0, 50, 100 mg/l Pb(NO3)3 to the nutrient solution for 12 days was observed. The plants were grown in nutrient solution in a strictly controlled climate growth room. Effects of La3+ (with La treatment) compared with check groups was evidently observed. The activities of SOD and CAT in root were enhanced 0.45-1.69 times and 33.20-77.77% respectively and MDA content was reduced 11.05-27.49% in root after treatments from the second day till the end of the experiment. The activities of SOD and CAT was found to be increased slightly (P < 0.05) and MDA content decreased in shoot and root of wheat seedlings by La3+ under lead stress within five days after treatments compared with Pbl and Pb2 groups. It was assumed that antioxidant enzymes was found to be increased by La(NO3)3, the antioxidant potential of the wheat seedlings to resist lead stress enhanced. It is suggested that La3+ could be used to resist lead stress at the beginning under stress while the stress was not so serious.

Catalase↗

PubMed2001

Development of dengue virus replicons expressing HIV-1 gp120 and other heterologous genes: a potential future tool for dual vaccination against dengue virus and HIV.

BACKGROUND: Toward the goals of providing an additional vector to add to the armamentarium available to HIV vaccinologists and of creating a bivalent vaccine effective against dengue virus and HIV, we have attempted to create vectors which express dengue virus non-structural proteins and HIV immunogens. Previously we reported the successful construction of dengue virus replicons which lack structural genes necessary for virion release and spreading infection in culture but which can replicate intracellularly and abundantly produce dengue non-structural proteins. Here we attempted to express heterologous genetic material from these replicons. RESULTS: We cloned into a Deltapre-M/E dengue virus replicon genes for either green fluorescent protein (GFP), HIV gp160 or HIV gp120 and tested the ability of these constructs to express dengue virus proteins as well as the heterologous proteins in tissue culture after transfection of replicon RNA. CONCLUSIONS: Heterologous proteins were readily expressed from these constructs. GFP and gp120 demonstrated minimal or no toxicity. Gp160 expressing replicons were found to express proteins abundantly at 36 hours post transfection, but after 50 hrs of transfection, few replicon positive cells could be found despite the presence of cellular debris positive for replicon proteins. This suggested that gp160 expressed from dengue virus replicons is considerably more toxic than either GFP or gp120. The successful expression of heterologous proteins, including HIV gp120 for long periods in culture suggests this vector system may be useful as a vaccine vector, given appropriate delivery methods.

Dengue↗

PubMed2001

[Application of the IFN-gamma ELISPOT assay for monitoring CD8(+) T cell response to specific antigen from hepatocellular carcinoma patients].

OBJECTIVE: To study the specific CD8(+) T cell response to HLA-A2 binding peptide Flu p58-66 from HLA-A2-positive hepatocellular carcinoma patients and healthy donors. METHODS: The CD8(+) T cells were separated with immunobeads from PBMC of HCC patients and healthy donors, respectively. The irradiated autologous CD8(-) PBMC or isolated dendritic cells were loaded with influenza matrix peptide as APC. After 7 days' culture, the frequency of effector cells to secrete IFN-gamma in response to Flu p58-66 was detected in ELISPOT assay. RESULTS: With CD8(-) PBMC as APC, the frequency of effector cells to secrete IFN-gamma in response to Flu peptide was 22 +/- 9/well in HCC patients (n = 8) and 59 +/- 27/well in healthy donors (n = 12) when the effector cells were 5 x 10(4)/well (P < 0.01). To compare the antigen-presenting capacity of APC derived from 5 healthy donors, DC was better than CD8(-) PBMC. CONCLUSION: Although the frequency of specific effector CTL to secrete IFN-gamma in response to Flu p58 - 66 was lower in HCC patients than in healthy individuals, the majority of HCC patients have the cellular immunity specific to antigen peptides.

Animals↗

PubMed2001

Development of Dengue virus type 2 replicons capable of prolonged expression in host cells.

BACKGROUND: As part of a program to develop a Dengue virus vaccine which avoids the deleterious effects of antibody dependent enhancement (ADE) of infection mediated by antibodies to Dengue virus structural proteins, we have begun to investigate the possibility of designing Dengue vaccines based on non-structural proteins. RESULTS: Dengue constructs which lack major structural proteins replicate intracellularly in tissue culture. These replicons are capable of prolonged expression of Dengue virus non-structural proteins for at least seven days in culture. CONCLUSIONS: Dengue virus genomes lacking major structural proteins can, like other flaviviruses, replicate intracellularly and express virus non-structural proteins with minimal toxicity to host cells. These findings pave the way for the development of dengue virus replicons as a form of live, attenuated virus vaccine.

Animals↗

PubMed2001

Acute stress increases permeability of the blood-brain-barrier through activation of brain mast cells.

Disruption of the blood-brain-barrier (BBB) is important in the pathophysiology of various inflammatory conditions of the central nervous system (CNS), such as multiple sclerosis (MS), in which breakdown of the BBB precedes any clinical or pathological findings. There is some evidence that relapsing-remitting MS attacks may be correlated with certain types of acute stressful episodes. Stress typically activates the hypothalamic-pituitary-adrenal (HPA) axis through the release of corticotropin releasing hormone (CRH), leading to production of glucocorticoids that down regulate immune responses. However, acute stress also has pro-inflammatory effects that appear to be mediated through activation of mast cells. Here we show that acute stress by immobilization increased permeability of rat BBB to intravenous 99Technetium gluceptate (99Tc). This effect was statistically significant in the diencephalon and the cerebellum, while it was absent in the cerebral cortex where there are not mast cells. Immobilization stress also induced activation of mast cells in diencephalon, the site where most mast cells are found in the rat brain. Both BBB permeability and mast cell activation were inhibited by the 'mast cell stabilizer' disodium cromoglycate (cromolyn). These results expand the pathophysiology of mast cells and implicate them in CNS disorders, that may possibly be induced or exacerbated by stress.

Acute Disease↗

PubMed2001

[Effect of lead stress on the activity of antioxidant enzymes in wheat seedling].

The changes of the antioxidant enzyme activity, such as superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were researched through nutrient solution culture. The results showed that the activity of SOD in shoot and root were significantly enhanced under lead stress. The activity of CAT in root was also improved, but the degree was not bigger than that of SOD activity. However, the MDA content in shoot and root was significantly higher than that of check group, it suggested that the membrane system were damaged by lead stress. The experiments also revealed that the shoot of wheat seedling was influenced by lead stress greatly stronger than that of root.

Catalase↗

PubMed2001

[Detection of DNA crosslinks with comet assay].

A simple and rapid method for the detection of DNA cross-links was explored. DNA cross-links was induced by formaldehyde (FA) in TK6 cells. Hydrogen peroxide was used as a standard DNA breakage agent. Two protocols on detecting DNA cross-links with comet assay were tested and compared. The results showed that with increasing FA, the length of DNA migration caused by H2O2 was decreased. When the level of FA was 1000 mumol/L, no any tailed cell could be observed, the migration of DNA was inhibited completely even H2O2 was used. The detection of DNA cross-link could be tested by both protocols. However, when the DNA cross-link agent (FA) was added to the cells before the treatment with DNA breakage agent (H2O2), the result of the scheme was much better than that in the opposite order. The former scheme was much easy to be manipulated, with no influence from DNA repair and had better dose-response relationship in the detection of DNA cross-links. The comet assay is indeed a sensitive, convenient and rapid method for the detection of DNA cross-link.

Comet Assay↗

PubMed2000

A sensitive HPLC technique for the quantitation of dauricine.

To establish the determination method of dauricine (Dau) concentration in rats' blood and other biological samples, a reverse-phase HPLC method was adopted. Under the given condition, dauricine could be well separated. The retention time (tR) of Dau and its internal standard, daurisoline were 9.2 and 6.1 respectively. The detection limit was 10(-2) mg/ml. The absolute recoveries of all kinds of samples were above 70%, and the relative ones were over 85%. A good liner relationship has been obtained over the entire range of 0.030 to 3.000 mg/L in blood samples and 0.050 to 5.000 mg/L in other tissue samples. The intraday and interday coefficients of variation were below 10%. The results showed that the method can be used for detecting Dau in all kinds of biological samples.

Alkaloids↗

PubMed2000

Hydroxyzine inhibits experimental allergic encephalomyelitis (EAE) and associated brain mast cell activation.

Experimental allergic encephalomyelitis (EAE) has been used as an animal model for the human demyelinating disease multiple sclerosis (MS). In acute MS or EAE, early disruption in the integrity of the blood-brain-barrier (BBB) precedes brain infiltration by inflammatory cells or any clinical evidence of disease. BBB permeability could be affected by vasoactive mediators and cytokines released from perivascular brain mast cells. We investigated the number and degree of activation of brain mast cells in EAE and the effect of the heterocyclic histamine-1 receptor antagonist hydroxyzine, a piperazine compound known to also block mast cells. Acute EAE was induced in Lewis rats by immunization with whole guinea pig spinal cord homogenate and complete Freund's adjuvant (CFA). A second group of animals were treated orally with hydroxyzine for one day before immunization and then continuously for 14 days. Control rats were treated with CFA or hydroxyzine alone. The clinical progression of EAE was assessed on days 10, 12 and 14 after immunization. The number of metachromatic mast cells and the degree of degranulation was assessed in the thalamus with light microscopy. At day 14, there was a three-fold increase in the number of brain mast cells with EAE, as compared to controls. These cells were positive for the immunoglobulin E binding protein (FcepsilonRI), while those from control rats were not. Over 40% of all thalamic mast cells studied in EAE showed partial staining or extruded secretory granule indicative of secretion. Hydroxyzine treatment inhibited (p<0.05) the progression and severity of EAE by 50% and the extent of mast cell degranulation by 70% (p<0.05). These findings indicate that brain mast cells are associated with EAE development and that inhibition of their activation correlates positively with the clinical outcome.

Animals↗

PubMed2000

Cloning and cellular localization of the rat mast cell 78-kDa protein phosphorylated in response to the mast cell "stabilizer" cromolyn.

Disodium cromoglycate (cromolyn) inhibits mast cell secretion, but its mechanism has not been elucidated. One possibility is the phosphorylation of a 78-kDa mast cell protein, two fragments of which are homologous to moesin, a member of the ezrin, radixin, moesin family. These proteins appear to be involved in signal transduction by regulating functional associations between the cell surface and the cytoskeleton. Moesin cDNA was cloned from rat basophil leukemia cells, which are similar to mucosal mast cells, and polyclonal antiserum was prepared against recombinant moesin expressed in Escherichia coli. Moesin phosphorylated in mast cells treated with cromolyn shifted from the soluble to the precipitable fraction and associated with Sepharose-linked beta-actin. Recombinant moesin also associated with Sepharose-linked beta-actin, and so did purified RBL moesin, but only if the latter was first denatured. Moesin thus appears to have actin binding sites that are not exposed under normal conditions but may become available by in vivo phosphorylation or by denaturation. Immunocytochemistry using confocal microscopy showed moesin to be primarily localized on the inner aspect of the plasma membrane and around secretory granules. Double immunocytochemistry for moesin and actin colocalized them in most areas. Ultracryoimmunoelectron microscopy to preserve the antigenicity of moesin identified the protein close to the plasma and secretory granule membranes. Cromolyn appeared to induce clustering of moesin around secretory granules. It is hypothesized that conformational changes of moesin, regulated by phosphorylation/dephosphorylation, may lead to positional rearrangements with respect to the membrane/cytoskeleton that could possibly regulate mast cell secretion.

Actins↗

PubMed2000

[Evaluation of plant protectants against pest insects].

An interference index of population control (IIPC) was constructed for investigating the complex effects of plant protectants, including the effects of repelling insect pests away from the plant, deterring the egg laying of adults and the continuation of feeding, and causing death by toxicity. At the same time, indicated by IIPC, the alcohol extracts of some common plants, such as Eucalytus rubusta, Wedelia chinensis etc. and the neem oil gave very good results to protect the plant against Plutella xylostella. The D-C-Tron NR Petroleum Spray Oil (CALTEX) also gave an excellent effect to protect citrus against red mite. All the experiments show the important role of the repellent effect on the pests.

Animals↗

PubMed2000

[Arthropod diversity in leafy vegetable field and sampling technology].

Two sampling units (plant and quadrat) and two sampling methods (random and fixed) were adopted to compare the variation degree of the diversity of arthropod communities in different chinese cabbage fields. The results show that a lower variation degree was found when the random sampling method was adopted with quadrat (0.11 m2) as sampling unit at seedling stage and with plant as sampling unit from growing to mature stage. The community diversity was relatively steady, when the critical number of samples was more than 12 quatrats (0.11 m2) at seedling stage, 30 plants in growing period, and 20 plants at mature stage. The optimum sampling unit, sampling method and sampling number of arthropod diversity in leafy vegetable field were also determined.

Animals↗

PubMed2000

[Lifetable of cotton bollworm under different control condition].

The lifetables of 3rd and 4th generation of cotton bollworm Helicoverpa armigera Hubner were established by action factors under four different control conditions. The results showed that under natural control, the egg parasitic rates of 3rd and 4th cotton bollworm were 4.39% and 1.19%, the predatory rates were 21.11% and 15.80%, and the larvae parasitic rates were 19.34% and 16.20% respectively. The indexes of population trend were only 0.0032 and 0.0014 respectively, after using selective pesticides IKI and Bt to control cotton bollworm. Though the index of population trend decreased to 48.66% and 61.67% after contantly praying chemical pesticides, the number of predators also decreased to 23.48% and 41.26% respectively. Transgenic Bt cotton could inhibit the population increase of cotton bollworm, but had no effect on predators. The parasitic rates of 3rd and 4th cotton bollworm on Transgenic Bt cotton were 51.14% and 0% respectively, as compared to control.

Animals↗

PubMed2000

Expression of the MAGE-1 gene in human hepatocellular carcinomas.

OBJECTIVE: To further investigate the expression of MAGE-1 gene in hepatocellular carcinoma (HCC). METHODS: The tumors and adjacent liver tissue from 45 HCC patients and liver tissue from 28 non-HCC patients (16 with liver cirrhosis and 12 with normal liver) were characterized by RT-PCR. A 421 bp PCR product from a cDNA fragment spanning exons 1, 2 and 3 was sequenced. The HLA type was assayed by standard ELISA in 43 HCC patients. RESULTS: Thirty-two of 45 tumor tissues from HCC patients expressed MAGE-1 mRNA (71.1%). In contrast, MAGE-1 mRNA was not detected in adjacent tissues. Three were found to have point mutations at 3 identical sites resulting in the substitution of two amino acid residues. The most frequent HLA types in 43 HCC patients were: HLA-A2, 53.5%; A11, 25.6%; A24, 20.9%; A33, 20.9%; HLA-B13, 28.3% and B35, 23.2%. Expression of HLA-A33 (20.9%) was higher in HCC patients than that predicted in the normal Chinese population (8.8%). There was no discemable correlation between MAGE-1 expression and alpha-FP level, tumor size and hepatitis B or C virus infection. The identification of peptides which are restricted by haploptypes other than A1 should increase the opportunity for peptide based immunotherapy. CONCLUSIONS: This study shows that MAGE-1 mRNA is highly expressed in HCC tumor tissue in Chinese patients. Previously unreported point mutations in the MAGE-1 gene are described and may also provide additional opportunities for immunotherapy.

Amino Acid Sequence↗

PubMed2000

[Dynamic analysis of junctional sequences of T cell receptor (TCR) delta and gamma gene rearrangement in childhood with acute lymphoblastic leukemia].

OBJECTIVE: To explore the junctional sequence difference of T cell receptor delta and gamma gene rearrangement in childhood acute lymphoblastic leukemia (ALL) at diagnosis, complete remission (CR) and relapse. METHODS: By using the T-vector molecular cloning and sequencing and polymerase chain reaction, the junctional sequences of TCRdeltaV-D and TCRgammaV-J were dynamically analyzed in 34 bone marrow samples of ALL. RESULTS: The junctional sequence of TCR delta, gamma gene showed significant difference and regularity before and after remission and during relapsed periods. The sequence of TCRdeltaV-D were analyzed in 24 samples from ALL. Among them, the intact Vdelta2 and 5'Ddelta3 sequences were observed in 10 samples at diagnosis, of which 7 samples had T-->C mutation in Ddelta3 nonamer sequence. The deletions of rearranged Vdelta2, 5'Ddelta3 and Ddelta3 haptamer sequences were found in 11 complete remission (CR) samples with ALL, but none had T-->C mutation in Ddelta3 nonamer sequence. The deletion rate of Vdelta2 or Ddelta3 sequences and the T-->C mutation in Ddelta3 nonamer sequence were extremely differed between samples at diagnosis and in remission (calculate exact probabilities P = 0.001). The junctional rearrangement sequence of 5'Ddelta3 sequences tended to remain intact in 3 relapsed samples. The findings of TCRgammaV-J sequences were similar to that of TCRdeltaV-D in 10 ALL patients. CONCLUSION: The difference of TCRdeltaV-D and TCRgammaV-J junctional sequences were related to the development, therapeutic effectiveness and outcome in ALL.

Child↗

PubMed1999

Morphological and functional demonstration of rat dura mater mast cell-neuron interactions in vitro and in vivo.

Mast cells derive from a distinct bone marrow precursor and mature in tissues under the influence of stem cell factor, nerve growth factor (NGF) and certain interleukins. Intracranial mast cells first appear in the meninges and are located perivascularly close to neurons. They can be activated by antidromic stimulation of the trigeminal nerve, as well as by acute immobilization stress. Substance P (SP) and corticotropin-releasing hormone (CRH) are particularly potent in stimulating mast cell release of vasoactive, inflammatory and nociceptive molecules. These findings have suggested that mast cells may be involved in neuroinflammatory conditions, such as migraines. In this study, dura mast cells were shown to have characteristics of connective tissue mast cells (CTMC) as they contained histamine, heparin and rat mast cell protease I (RMCP-I). Mast cells were localized close to SP-positive neurons immunocytochemically and mast cell-neuron contacts were also documented using scanning electron microscopy. Dura stimulated by SP and carbachol in situ released histamine. Preincubation of dura with estradiol slightly augmented histamine release by SP, an effect possibly mediated through estrogen receptors identified on dura mast cells. Acute stress by immobilization led to dura mast cell degranulation which was prevented by pretreatment with a neutralizing antibody to CRH or a CRH receptor antagonist. The present results further clarify the biology of intracranial mast cells and support their involvement in the pathophysiology of migraines which are precipitated or worsened by stress.

Animals↗

PubMed1999

Acute immobilization stress triggers skin mast cell degranulation via corticotropin releasing hormone, neurotensin, and substance P: A link to neurogenic skin disorders.

Many skin disorders, such as atopic dermatitis and psoriasis, worsen during stress and are associated with increased numbers and activation of mast cells which release vasoactive, nociceptive, and proinflammatory mediators. Nontraumatic acute psychological stress by immobilization has been shown to induce mast cell degranulation in the rat dura and colon. Moreover, intradermal injection of corticotropin-releasing hormone (CRH) or its analogue urocortin (10(-5)-10(-7) M) induced skin mast cell degranulation and increased vascular permeability. Here, we investigated the effect of acute immobilization stress on skin mast cell degranulation by light microscopy and electron microscopy. Immobilization for 30 min resulted (P < 0.05) in degranulation of 40.7 +/- 9.1% of skin mast cells compared to 22.2 +/- 7.3% in controls killed by CO(2) or 17.8 +/- 2.4% in controls killed by pentobarbital. Pretreatment intraperitoneally (ip) with antiserum to CRH for 60 min prior to stress reduced (P < 0.05) skin mast cell degranulation to 21.0 +/- 3. 3%. Pretreatment with the neurotensin (NT) receptor antagonist SR48692 reduced (P < 0.05) mast cell degranulation to 12.5 +/- 3.4%, which was significantly (P < 0.05) below control levels. In animals treated neonatally with capsaicin to deplete their sensory neurons of their neuropeptides, such as substance P (SP), mast cell degranulation due to immobilization stress was reduced to about 15%. This is the first time that stress has been shown to trigger skin mast cell degranulation, an action not only dependent on CRH, but apparently also involving NT and SP. These findings may have implications for the pathophysiology and possible therapy of neuroinflammatory skin disorders such as atopic dermatitis, neurogenic pruritus, or psoriasis, which are induced or exacerbated by stress.

Acute Disease↗