Biomedical subjects

Gang Ma

Publications and source records attributed to Gang Ma.

At least 19 recordsLinked to original sources

PubMed2007

Condensing effect of palmitic acid on DPPC in mixed Langmuir monolayers.

The interaction between deuterated dipalmitoylphosphatidylcholine (DPPC-d62) and palmitic acid (PA) in mixed Langmuir monolayers is studied using vibrational sum frequency generation (VSFG) spectroscopy. Palmitic acid is an additive in exogenous lung surfactant preparations such as Survanta and Surfaxin. The effect of PA on the chain conformation and orientation of DPPC in the liquid-expanded and condensed phases is explored. A condensing effect of PA on DPPC is observed with VSFG. At 12 mN/m, DPPC-d62 alone is in the liquid-expanded phase. Adding PA increases the conformational ordering of DPPC chains and causes DPPC to transition from the expanded phase into the condensed phase. At 42 mN/m, DPPC-d62 and PA form a mixed structure in the condensed phase. The presence of PA decreases the chain tilt angle of DPPC, increasing the orientational ordering of DPPC chains. At 42 mN/m, there is also evidence from the frequency red shift of the PO2- symmetric stretch that the carboxyl group of PA forms a hydrogen bond with the phosphate group of DPPC in the condensed phase. From this work the effect of PA on DPPC is 2-fold: (1) PA increases the chain ordering of DPPC and promotes the LE and TC phase separation and (2) due to the miscibility between DPPC and PA in the condensed phase, PA decreases the collapse pressure.

Journal Article↗

PubMed2006

Real-time investigation of lung surfactant respreading with surface vibrational spectroscopy.

The respreading of a lung surfactant monolayer at the air-water interface is investigated with broad bandwidth sum frequency generation (BBSFG) spectroscopy. The lung surfactant mixture contains chain perdeuterated dipalmitoylphosphatidylcholine (DPPC-d62), palmitoyloleoylphosphatidylglycerol (POPG), palmitic acid (PA), and KL4 (a 21-residue polypeptide analogue to the surfactant protein SP-B). DPPC-d62 serves as a probe molecule for the spectroscopic investigation. The BBSFG spectra of DPPC-d62 in the lung surfactant mixture are obtained in the C-D stretching region in real-time during film compression and expansion in a Langmuir trough. The BBSFG intensity of the CD3 stretch peak from DPPC-d62 terminal methyl groups is used as a measure of the interfacial density of DPPC-d62 after careful consideration of orientation effects. For the first time, the interfacial loss of DPPC in a complex lung surfactant mixture is quantified. Spectroscopic results reveal that there is an 18% DPPC-d62 interfacial loss during film respreading. However, the surface pressure-area isotherm measurements demonstrate that there is a rather large trough area reduction (37%) during film expansion. The relatively small interfacial loss of DPPC-d62 and the rather large trough area reduction indicate that the respreading of DPPC and non-DPPC components in the lung surfactant is not uniform and a surface refinement process exists during film compression and expansion. This refinement process results in a DPPC-enriched monolayer with a significant depletion of non-DPPC components after film respreading. Implication for replacement surfactant design from this work is discussed.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Functional variants in the promoter region of Chitinase 3-like 1 (CHI3L1) and susceptibility to schizophrenia.

The chitinase 3-like 1 gene (CHI3L1) is abnormally expressed in the hippocampus of subjects with schizophrenia and may be involved in the cellular response to various environmental events that are reported to increase the risk of schizophrenia. Here, we provide evidence that the functional variants at the CHI3L1 locus influence the genetic risk of schizophrenia. First, using case-control and transmission/disequilibrium-test (TDT) methodologies, we detected a significant association between schizophrenia and haplotypes within the promoter region of CHI3L1 in two independent cohorts of Chinese individuals. Second, the at-risk CCC haplotype (P=.00058 and .0018 in case-control and TDT studies, respectively) revealed lower transcriptional activity (P=2.2 x 10(-7)) and was associated with lower expression (P=3.1 x 10(-5)) compared with neutral and protective haplotypes. Third, we found that an allele of SNP4 (rs4950928), the tagging SNP of CCC, impaired the MYC/MAX-regulated transcriptional activation of CHI3L1 by altering the transcriptional-factor consensus sequences, and this may be responsible for the decreased expression of the CCC haplotype. In contrast, the protective TTG haplotype was associated with a high level of CHI3L1 expression. Our findings identify CHI3L1 as a potential schizophrenia-susceptibility gene and suggest that the genes involved in the biological response to adverse environmental conditions are likely to play roles in the predisposition to schizophrenia.

Adipokines↗

PubMed2006

DPPC Langmuir monolayer at the air-water interface: probing the tail and head groups by vibrational sum frequency generation spectroscopy.

Dipalmitoylphosphatidylcholine (DPPC) is the predominant lipid component in lung surfactant. In this study, the Langmuir monolayer of deuterated dipalmitoylphosphatidylcholine (DPPC-d62) in the liquid-expanded (LE) phase and the liquid-condensed (LC) phase has been investigated at the air-water interface with broad bandwidth sum frequency generation (BBSFG) spectroscopy combined with a Langmuir film balance. Four moieties of the DPPC molecule are probed by BBSFG: the terminal methyl (CD3) groups of the tails, the methylene (CD2) groups of the tails, the choline methyls (CH3) in the headgroup, and the phosphate in the headgroup. BBSFG spectra of the four DPPC moieties provide information about chain conformation, chain orientation, headgroup orientation, and headgroup hydration. These results provide a comprehensive picture of the DPPC phase behavior at the air-water interface. In the LE phase, the DPPC hydrocarbon chains are conformationally disordered with a significant number of gauche configurations. In the LC phase, the hydrocarbon chains are in an all-trans conformation and are tilted from the surface normal by 25 degrees. In addition, the orientations of the tail terminal methyl groups are found to remain nearly unchanged with the variation of surface area. Qualitative analysis of the BBSFG spectra of the choline methyl groups suggests that these methyl groups are tilted but lie somewhat parallel to the surface plane in both the LE and LC phases. The dehydration of the phosphate headgroup due to the LE-LC phase transition is observed through the frequency blue shift of the phosphate symmetric stretch in the fingerprint region. In addition, implications for lung surfactant function from this work are discussed.

1,2-Dipalmitoylphosphatidylcholine↗

PubMed2006

Cell-free immune reactions in insects.

Insects, like many other multicellular organisms, are able to recognise and inactivate potential pathogens and toxins in the absence of cells. Here we show that the recognition and inactivation of lipopolysaccharides (LPS) and bacteria is mediated by lipophorin particles, which are the lipid carrier in insects. In immune-induced insects sub-populations of lipophorin particles are associated with pattern recognition proteins and regulatory proteins that activate prophenoloxidase. Moreover, interactions with lectins result in the assembly of lipophorin particles into cage-like coagulation products, effectively protecting the surrounding tissues and cells from the potentially damaging effects of pathogens and phenoloxidase products. The existence of cell-free defence reactions implies that immune signals exist upstream of cell-bound receptors.

Animals↗

PubMed2006

Development and validation of pheochromocytoma of the adrenal gland scaled score for predicting malignant pheochromocytomas.

OBJECTIVES: To evaluate the diagnostic performances of the pheochromocytoma of the adrenal gland scaled score (PASS) proposed in a previous report and that of a logistic model developed in this investigation. METHODS: In all 130 patients with malignant or assumed benign pheochromocytomas, 15 predictive variables were observed. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic performance of PASS. The logistic model was developed using the 15 predictive variables. Its performance was evaluated by calculating the area under the ROC curve and comparing it with that of the PASS. RESULTS: The PASS had the area under the ROC curve of 0.899 (95% confidence interval 0.844 to 0.954). Of the 15 variables entered in the logistic regression analysis, 9 were retained in the model. The area under the ROC curve for the logistic model was 0.983 (95% confidence interval 0.967 to 0.998). CONCLUSIONS: ROC analysis indicated that the PASS could be used for the diagnosis of malignant pheochromocytomas. The logistic model was able to improve the diagnostic performance of the PASS using a different variable weighting method. We emphasize, however, that a clinical prospective evaluation is needed to confirm their actual value.

Adrenal Gland Neoplasms↗

PubMed2006

Epidermal growth factor promotes invasiveness of pancreatic cancer cells through NF-kappaB-mediated proteinase productions.

OBJECTIVES: Overexpression of epidermal growth factor (EGF) and EGF receptor has been associated with progression and invasive phenotype in pancreatic cancer. However, the underlying molecular mechanism by which EGF worked in pancreatic cancer cells has been poorly understood. In this study, we determined the effect of EGF on the invasiveness and the related regulatory mechanism in two pancreatic cancer cell lines NOR-P1 and KP4. METHODS: Invasion assay was performed to examine the invasiveness of tumor cells induced by EGF, and the expression of matrix metalloproteinase (MMP)-9, MMP-2, and plasminogen activator (uPA) was determined by reverse transcription-polymerase chain reaction and Western blot. Gelatin zymography was used to detect the activities of MMP-9 and MMP-2, and the nuclear factor-kappaB (NF-kappaB) binding activity was determined by electrophoretic mobility shift assay (EMSA). RESULTS: EGF significantly increased the invasiveness of both cell lines but did not affect cell proliferation or adhesion. Increased invasiveness was associated with the induction of MMP-9 and uPA at both mRNA and protein levels. Furthermore, EGF stimulated NF-kappaB binding activity. Moreover, pretreatment of cells with NF-kappaB inhibitors, pyrrolidine dithiocarbamate or ibuprofen, markedly attenuated EGF-induced NF-kappaB activation. Subsequently, the EGF-induced MMP-9 and uPA expression and MMP-9 activity, as well as cell invasiveness, were also inhibited by these NF-kappaB inhibitors. CONCLUSIONS: Our findings indicated that NF-kappaB-mediated MMP-9 and uPA induction was responsible for EGF-induced invasiveness in these pancreatic cancer cell lines and implicate that such anti-NF-kappaB therapy as the use of NF-kappaB inhibitors may contribute to the reduction of invasiveness of pancreatic cancer.

Cell Adhesion↗

PubMed2005

Recognition and inactivation of LPS by lipophorin particles.

Lipophorin is the major lipid carrier in insects, but various observations indicate that lipophorin is also involved in immune reactions. To examine a possible role of lipophorin in defence reactions, we mixed hemolymph plasma from Galleria mellonella with LPS and noticed that lipophorin forms detergent-insoluble aggregates, while most other plasma proteins are not affected. Lipophorin particles isolated by low-density gradient centrifugation retained LPS-induced aggregation properties, which suggested to us that these immune-reactive particles are able to recognise LPS and respond by forming insoluble aggregates. Antibodies against LPS-binding proteins, such as immulectin-2 and beta-1,3-glucan binding protein, cross-reacted with proteins associated with purified lipophorin particles. To examine whether LPS-mediated aggregates inactivate LPS, we added LPS-lipophorin mixtures to purified lipophorin particles and monitored aggregate formation. Under these conditions lipophorin did not form insoluble aggregates, which indicates that lipophorin particles sequester LPS into non-toxic aggregates.

Acute-Phase Proteins↗

PubMed2005

Clinicopathological significance of p53 and mdm2 protein expression in human pancreatic cancer.

AIM: To study the clinicopathological significance of p53 and mdm2 protein expression in human pancreatic cancer. METHODS: To investigate the expression of p53 and mdm2 in pancreatic cancer by immunohistochemistry, and the relationships between the p53 and mdm2 protein expression and clinicopathological parameters in pancreatic cancer. RESULTS: The positive expression of p53 protein was found in 40 of 59 patients (67.8%) and that of mdm2 protein in 17 of 59 patients (28.8%). No obvious relationships were found between p53 as well as mdm2 expression and sex, tumor site, TNM staging and histological differentiation. p53 expression was increased in patients younger than 65 years old, while mdm2 had no relationship with age. The survival time of the patients with the positive expression of p53 and mdm2 proteins was obviously shorter than the other groups. CONCLUSION: Both p53 and mdm2 presented relatively high expression in human pancreatic cancer. The overexpression of p53 and mdm2 might reflect the malignant proliferation of pancreatic cancer and their co-expression might be helpful to evaluate the prognosis of the patients with pancreatic cancer.

Adult↗

PubMed2005

Adsorption of 4-picoline and piperidine to the hydrated SiO2 surface: probing the surface acidity with vibrational sum frequency generation spectroscopy.

Vapor adsorption is an important process influencing the migration and the fate of many organic pollutants in the environment. In this study, vibrational sum frequency generation (SFG) spectroscopy was used to study the adsorption of two surface acidity probe molecules, 4-picoline (pKa = 5.94) and piperidine (pKa = 11.24), onto the amorphous SiO2 surface. The adsorption of 4-picoline onto the silica surface occurs by forming weak hydrogen bonds between the nitrogen atoms of 4-picoline molecules and the hydrogen atoms of surface silanol OH groups. Piperidine molecules are strongly chemisorbed onto the SiO2 surface through the protonation of piperidine molecules by surface silanol OH groups. The SFG results indicate that the surface acidity constant of silanol OH groups (pKa-(HOSi triple bond)) is in the range of 5.94-11.24 at the air/solid interface. Although this range of surface acidity constants is quite wide, it is possible to narrow it by choosing probe molecules with a smaller pKa range. Together with theoretical prediction methods, adsorption studies using vibrational SFG spectroscopy are capable of quantifying the surface acidity of mineral oxides by carefully choosing the acidity probe molecules.

Adsorption↗

PubMed2005

Is the mature endotoxin Cry1Ac from Bacillus thuringiensis inactivated by a coagulation reaction in the gut lumen of resistant Helicoverpa armigera larvae?

Bacillus thuringiensis endotoxins (Bt-toxins) are the most important biopesticides used in controlling insect pests and vectors of diseases. The emergence of widespread resistance to Bt in some insect species is a serious threat to agricultural production. Analysis of Bt-resistant and susceptible laboratory strains of Helicoverpa armigera revealed elevated immune responses involving increased melanization and the presence of a soluble toxin-binding glycoprotein in the hemolymph and gut lumen of the resistant strain. We propose a resistance mechanism against toxins based on a systemic immune-induction that can be transmitted to the next generation by a maternal effect.

Amino Acid Sequence↗

PubMed2005

Spectroscopic and computational studies of aqueous ethylene glycol solution surfaces.

The combination of Monte Carlo, ab initio, and DFT computational studies of ethylene glycol (EG) and EG-water hydrogen-bonding complexes indicate that experimental vibrational spectra of EG and EG-water solution surfaces have contributions from numerous conformations of both EG and EG-water. The computed spectra, derived from harmonic vibrational frequency calculations and a theoretical Boltzmann distribution, show similarity to the experimental surface vibrational spectra of EG taken by broad-bandwidth sum frequency generation (SFG) spectroscopy. This similarity suggests that, at the EG and aqueous EG surfaces, there are numerous coexisting conformations of stable EG and EG-water complexes. A blue shift of the CH2 symmetric stretch peak in the SFG spectra was observed with an increase in the water concentration. This change indicates that EG behaves as a hydrogen-bond acceptor when solvated by additional water molecules. This also suggests that, in aqueous solutions of EG, EG-EG aggregates are unlikely to exist. The experimental blue shift is consistent with the results from the computational studies.

Computer Simulation↗

PubMed2005

[Postoperative complications in lung cancer patients with moderate pulmonary hypofunction].

BACKGROUND & OBJECTIVE: With the development of surgery treatment for lung cancer, the importance of preoperative pulmonary function assessment evoked more and more attention. This research was set to analyze postoperative complications of lung cancer patients with moderate pulmonary hypofunction, and explore associated factors. METHODS: Statistic t test and Chi(2) test were used to compare postoperative complications of 31 patients with moderate pulmonary hypofunction and 62 patients with normal pulmonary function (control group), logistic regression was performed to find associated factors. RESULTS: In the 31 patients with moderate pulmonary hypofunction, hypoxemia (41.9%), arrhythmia or cardiac dysfunction (25.8%), pulmonary inflammation (25.8%) were common postoperative complications; incidence of severe complications, such as respiratory failure, and cardiac failure, was 9.2%; in-hospital mortality was 3.2%. In control group, the occurrence rates were 16.1%, 8.1%, 9.6%, and 3.2%, accordingly, no in-hospital death occurred. Regression analysis showed that age and resection range associated with the occurrence of postoperative complications. CONCLUSIONS: compared with control group, incidences of common postoperative complications in patients with moderate pulmonary hypofunction are remarkably increased, but severe complications and in-hospital mortality are not significantly high. Patients with older age and larger resection range have a high risk of develop complications.

Age Factors↗

PubMed2005

[Expression of programmed cell death 4 and its clinicopathological significance in human pancreatic cancer].

OBJECTIVE: To investigate the expression of programmed cell death 4 (PDCD4) protein and its clinicopathological significance in human pancreatic cancer. METHODS: Immunohistochemistry was used to examine the expression of PDCD4 protein in 69 specimens of pancreatic cancer and Western blot in 8 fresh specimens. RESULTS: The expression of PDCD4 protein was significantly lower in all 8 fresh pancreatic cancer tissues than that in non-cancerous tissues detected by Western blot. Compared with non-cancerous pancreatic tissue (> 80% of positive cells), low PDCD4 expression was shown in 69 pancreatic cancer tissues (< 30% of positive cells in 36 cases and 30%-80% of positive expression cells in 33 cases). In the 33 cases with 30% and 80% of positive expression cells, the expression rates of PDCD4 protein were 57.6%, 24.2%, and 18.2% in well, moderately, and poorly differentiated cancers, respectively. In the 36 cases less than 30% of positive expression cells, however, the expression rate of PDCD4 protein in well, moderately, and poorly differentiated cases were 19.4%, 41.7%, and 38.9%, respectively. 67.4% (15/23) of the moderately differentiated cases and 70% (14/20) of the poorly differentiated cases showed < 30% of positive expression cells. Only 26.9% (7/26) of the well differentiated cases, however, showed < 30% of positive expression cells, indicating that low PDCD4 expression was associated with histological grade (P < 0.01). There was no relationship between PDCD4 expression and other clinicopathological parameters including patients' sex, age, and TNM stage. CONCLUSIONS: Expression of PDCD4 protein is low in human pancreatic cancer and is correlated with the differentiation levels of human pancreatic cancer. PDCD4 may play an important role in the occurrence and development of pancreatic carcinomas.

Adult↗

PubMed2004

Piperidine adsorption on hydrated alpha-alumina (0001) surface studied by vibrational sum frequency generation spectroscopy.

The adsorption of piperidine vapor on the hydrated alumina (alpha-Al2O3, corundum) (0001) surface was investigated using vibrational broad bandwidth and scanning sum frequency generation (SFG) spectroscopy. The interfacial vibrational signature in the C-H stretching region of piperidine at the alumina (0001) surface is shown to be a sensitive spectroscopic probe revealing the adsorption mechanism. The neat piperidine surface, aqueous piperidine surface, and aqueous piperidium chloride surface were also investigated in the C-H stretching region by SFG to establish vibrational reference frequencies. After piperidine adsorption, piperidine vapor was removed and piperidine was found to be chemisorbed onto the alumina (0001) surface through protonation by surface hydroxyl groups. The O-H stretching region of the alumina surface before and after piperidine adsorption was also investigated, and the results revealed the decrease of the surface number density of alumina surface hydroxyl groups.

Journal Article↗

PubMed2004

Mechanism for transcriptional synergy between interferon regulatory factor (IRF)-3 and IRF-7 in activation of the interferon-beta gene promoter.

The interferon-beta promoter has been studied extensively as a model system for combinatorial transcriptional regulation. In virus-infected cells the transcription factors ATF-2, c-Jun, interferon regulatory factor (IRF)-3, IRF-7 and NF-kappaB, and the coactivators p300/CBP play critical roles in the activation of this and other promoters. It remains unclear, however, why most other combinations of AP-1, IRF and Rel proteins fail to activate the interferon-beta gene. Here we have explored how different IRFs may cooperate with other factors to activate transcription. First we showed in undifferentiated embryonic carcinoma cells that ectopic expression of either IRF-3 or IRF-7, but not IRF-1, was sufficient to allow virus-dependent activation of the interferon-beta promoter. Moreover, the activity of IRF-3 and IRF-7 was strongly affected by promoter context, with IRF-7 preferentially being recruited to the natural interferon-beta promoter. We fully reconstituted activation of this promoter in insect cells. Maximal synergy required IRF-3 and IRF-7 but not IRF-1, and was strongly dependent on the presence of p300/CBP, even when these coactivators only modestly affected the activity of each factor by itself. These results suggest that specificity in activation of the interferon-beta gene depends on a unique promoter context and on the role played by coactivators as architectural factors.

Animals↗

PubMed2003

Interferon regulatory factor-7 synergizes with other transcription factors through multiple interactions with p300/CBP coactivators.

Interferon regulatory factor (IRF)-7 is activated in response to virus infection and stimulates the transcription of a set of cellular genes involved in host antiviral defense. The mechanism by which IRF-7 is activated and cooperates with other transcription factors is not fully elucidated. Activation of IRF-7 results from a conformational change triggered by the virus-dependent phosphorylation of its C terminus. This conformational change leads to dimerization, nuclear accumulation, DNA-binding, and transcriptional transactivation. Here we show that activation of IRF-7, like that of IRF-3, is dependent on modifications of two distinct sets of Ser/Thr residues. Moreover, we show that different virus-inducible cis-acting elements display requirements for specific IRFs. In particular, the virus-responsive element of the ISG15 gene promoter can be activated by either IRF-3 or IRF-7 alone, whereas the P31 element of the interferon-beta gene is robustly activated only when IRF-3, IRF-7, and the p300/CBP coactivators are all present. Furthermore, we find that IRF-7 interacts with four distinct regions of p300/CBP. These interactions not only stimulate the intrinsic transcriptional activity of IRF-7, but they are also indispensable for its ability to strongly synergize with other transcription factors, including c-Jun and IRF-3.

Amino Acid Sequence↗

PubMed2002

Diffuse reflection broad bandwidth sum frequency generation from particle surfaces.

We report the first vibrational sum frequency generation (VSFG) spectroscopic study from particle surfaces of powdered solids using a modified SFG approach, diffuse reflection broad bandwidth sum frequency generation (DR-BBSFG). The DR-BBSFG spectrum of sodium dodecyl sulfate (SDS, C(12)H(25)SO(4)Na) powdered solids was obtained. Five peaks were resolved by calculated fits. Possible origins of the SFG response from SDS particle surfaces are discussed. Potential applications of DR-BBSFG spectroscopy are addressed.

Journal Article↗