Sang Mai Thanh - Academia.edu (original) (raw)

Papers by Sang Mai Thanh

Free Radical Biology and Medicine, 2010

Abnormal proliferation of vascular smooth muscle cells (VSMCs) contributes to intima formation af... more Abnormal proliferation of vascular smooth muscle cells (VSMCs) contributes to intima formation after stenting and balloon angioplasty. Pin1, a peptidyl prolyl isomerase recognizing phosphorylated Ser/Thr-Pro, isomerizes the peptide bond. Because Pin1 overexpression is associated with transformation and the uncontrolled cell growth of tumors, we hypothesized that Pin1 functions as a chronic stimulator of VSMC proliferation. Pin1-positive smooth muscle cells were seen in the neointimal region of the femoral artery after guidewire injury. Exposure of VSMCS to platelet-derived growth factor (PDGF) increased Pin1 expression in a concentration-dependent manner. Basal cell growth rate and cyclin D1 expression were enhanced in Pin1-overexpressing VSMCs (Pin1-VSMCs). Moreover, PDGF-induced production of reactive oxygen species (ROS) in Pin1-VSMCs was higher than in control VSMCs. In Pin1-VSMCs, heme oxygenase-1 (HO-1) induction in response to nitric oxide donor was suppressed compared to control VSMCs. Nuclear translocation of nuclear factor E2-related factor-2 (Nrf2) was also diminished in Pin1-VSMCs. In contrast, the activity of the inducible minimal antioxidant response element (ARE) was potentiated in Pin1-null mouse embryonic fibroblasts (MEFs), compared to Pin1-wild-type MEFs. Moreover, Nrf2 ubiquitination was stimulated by Pin1 overexpression. Intraperitoneal injection of juglone (a Pin1 inhibitor) for 3weeks (1mg/kg, two times a week) significantly suppressed neointimal formation induced by wire injury. In conclusion, Pin1 induction during neointimal formation may be associated with ROS-mediated VSMC proliferation via down-regulation of Nrf2/ARE-dependent HO-1 expression. Pin1 may be a novel therapeutic target for several vascular diseases including atherosclerosis and stenosis.

Process Biochemistry

The activation of mast cells by immunoglobulin E-mediated stimuli is considered as a central even... more The activation of mast cells by immunoglobulin E-mediated stimuli is considered as a central event in allergic responses. In this regard, chitosan oligosaccharides (COS) of two different molecular weight ranges (1-3 kDa and 3-5 kDa) were investigated for their capabilities against the activation of RBL-2H3 mast cell sensitized with dinitrophenyl-specific immunoglobulin E antibody and stimulated by antigen dinitrophenyl-bovine serum albumin. It was found that COS significantly inhibited RBL-2H3 cell degranulation via attenuating the releases of histamine and ␤-hexosaminidase. Moreover, the inhibitory activity of COS was accompanied by a reduction in intracellular Ca 2+ elevation. Notably, the expression of immunoglobulin Fc epsilon receptor I (FcRI) in RBL-2H3 cells was down-regulated by COS treatment in a dose-dependent manner. The suppressive effect of COS on RBL-2H3 cell activation suggested that COS may be potential candidates of novel inhibitors against allergic reactions.

Toxicology in Vitro, 2010

Retroviral gene transfer technology is frequently used to establish stable transgenic cell lines.... more Retroviral gene transfer technology is frequently used to establish stable transgenic cell lines. However, no studies to date have evaluated antioxidant defense systems in cells infected with retroviral particles. In the present study, we examined the effects of retroviral infection on antioxidant defense systems using H4IIE cells infected with a retrovirus that overexpresses green fluorescent protein (retro-H4IIE cells). Total oxyradical scavenging capacity and glutathione (GSH), malondialdehyde, and peroxide levels were not significantly altered in retro-H4IIE cells; however, retro-H4IIE cells showed a higher resistance against cytotoxicity, GSH depletion, and malondialdehyde elevation under H 2 O 2 -induced oxidative stress conditions. Immunoblot analysis showed that alpha-class GSH S-transferase (GST) was increased 2.5-fold in retro-H4IIE cells as compared with H4IIE cells; however, catalase, GSH peroxidase-1, peroxiredoxin-1, and thioredoxin-1 remained unaltered or slightly decreased. L-Buthionine-(S,R)-sulfoximine, a GSH synthesis inhibitor, and 1-chloro-2,4-dinitrobenzene, a GST substrate and competitive inhibitor, decreased the difference in H 2 O 2 responses between the two cell types. These results support the hypothesis that the resistance of retro-H4IIE cells to H 2 O 2 can be attributed to an increase in alpha-class GST expression, as levels of GSH and GSH peroxidase-1 were not altered. The present study suggests that antioxidant enzyme expression may change during the establishment of stable transformed cell lines using retroviral techniques.

Web user session clustering is very important in web usage mining for web personalization. This p... more Web user session clustering is very important in web usage mining for web personalization. This paper proposes a particle swarm optimization (PSO) based sequence clustering approach and presents an experimentally investigation of the PSO based sequence clustering methods, which use three original PSO variants and their corresponding variants of a hybrid PSO with real value mutation. The investigation was conducted in 45 test cases using five web user session datasets extracted from a real world web site. The experimental results of these methods are compared with the results obtained from the traditional k-means clustering method. Some interesting observations have been made. In the most of test cases under consideration, the PSO and PSO-RVM methods have better performance than the k-means method. Furthermore, the PSO-RVM methods show better performance than the corresponding PSO methods in the cases in which the similarity measure function is more complex.

Molecular Crystals and Liquid Crystals, 2009

A series of polyimide (PI) and copolyimide (Co-PI) films were prepared by two-step imidization pr... more A series of polyimide (PI) and copolyimide (Co-PI) films were prepared by two-step imidization processes from the poly (amicacid) precursors. The color and visible light transmission of the Co-PI films were much better than those of the general Kapton type PI ...

In this paper, we present the design and implementation of an Open Computing Language (OpenCL) fr... more In this paper, we present the design and implementation of an Open Computing Language (OpenCL) framework that targets heterogeneous accelerator multicore architectures with local memory. The architecture consists of a general-purpose processor core and multiple accelerator cores that typically do not have any cache. Each accelerator core, instead, has a small internal local memory. Our OpenCL runtime is based on software-managed caches and coherence protocols that guarantee OpenCL memory consistency to overcome the limited size of the local memory. To boost performance, the runtime relies on three source-code transformation techniques, work-item coalescing, web-based variable expansion and preload-poststore buffering, performed by our OpenCL C source-to-source translator. Work-item coalescing is a procedure to serialize multiple SPMD-like tasks that execute concurrently in the presence of barriers and to sequentially run them on a single accelerator core. It requires the webbased variable expansion technique to allocate local memory for private variables. Preload-poststore buffering is a buffering technique that eliminates the overhead of software cache accesses. Together with work-item coalescing, it has a synergistic effect on boosting performance. We show the effectiveness of our OpenCL framework, evaluating its performance with a system that consists of two Cell BE processors. The experimental result shows that our approach is promising.

Journal of Molecular Catalysis B-enzymatic, 2007

Ionic liquids (ILs) were used as additives to protect the inactivation of enzymes by released alc... more Ionic liquids (ILs) were used as additives to protect the inactivation of enzymes by released alcohol and shrinking of gel during the sol-gel process. The Candida rugosa lipases immobilized by using ILs in sol-gel process showed higher activity and stability than lipase immobilized without ILs. The hydrolytic and esterification activities of lipase coimmobilized with ILs were 5-fold and 16-fold greater than in silica gel without ILs. After 5 days incubation of lipase coimmobilized with 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide at 50 • C, residual activity of lipase was about 80% of initial activity, while the lipase immobilized without ILs was completely inactivated. ILs may act as a template during gelation and reduce shrinkage of gel by pore filling. They can also behave as a stabilizer to protect the enzyme from the inactivation.

From 2006 plans were implemented to create a deep-sea water port linked to an Economic Zone in th... more From 2006 plans were implemented to create a deep-sea water port linked to an Economic Zone in the coastal Province of Ha Tinh, located in north central Vietnam. The multi-purpose Zone entitled ‘Vung Ang’, was to attract foreign investors, while the port would provide a link to nearby Laos and Thailand. The project obviously had large implications for the administrations

A technique to optimize the Standard Additive Model (SAM) fuzzy system for nonlinear system appro... more A technique to optimize the Standard Additive Model (SAM) fuzzy system for nonlinear system approximation is presented. First, fuzzy rules are initialized more much than usual by employing Centroid Neural Network (CNN) and then the genetic algorithm-based optimization process used to exclude unnecessary and redundant rules; thereafter, the fuzzy rule parameters are tuned by the gradient descent method incorporated with momentum technique. Finally, we demonstrate with numerical experiments based on approximating some nonlinear functions and chaotic time series. From the results, we can see that the proposed method is more effective than normal approach in terms of accuracy and training time.

Lignin-based thermoplastic copolyester was synthesized for eco-friendly polymers and composite ap... more Lignin-based thermoplastic copolyester was synthesized for eco-friendly polymers and composite applications using lignin as a macromonomer to form a high molecular weight polymer. Kraft lignin was polymerized with sebacoyl chloride in the presence of triethylamine in N,N-dimethylacetamide (DMAc), and the molecular weight of the synthesized polymer was controlled by the polymerization temperatures and [COCl]/[OH] ratios providing up to 39 000 corresponding to 4–5 repeating units of lignin macromonomers. The glass transition temperature of the synthesized polymer was difficult to measure due to the random distribution of functional groups and irregular configurational or conformational arrangement of natural lignin. Therefore, the complex electric modulus (CEM) technique was used to determine the glass transition of the synthesized polymer to give around 70°C measured by the peak of the imaginary part of CEM. The synthesized lignin-copolyester exhibited good thermal stability up to 200°C in TGA analysis and, thus, it was possible to shape the synthesized polymer using the solvent casting or hot-melt processing techniques at 120°C–140°C without generating odor, fume or irritation. Although the molecular weight should further be increased in the future, the developed methodology may help to exploit new applications for eco-friendly sustainable materials in various fields.

Free Radical Biology and Medicine, 2010

Abnormal proliferation of vascular smooth muscle cells (VSMCs) contributes to intima formation af... more Abnormal proliferation of vascular smooth muscle cells (VSMCs) contributes to intima formation after stenting and balloon angioplasty. Pin1, a peptidyl prolyl isomerase recognizing phosphorylated Ser/Thr-Pro, isomerizes the peptide bond. Because Pin1 overexpression is associated with transformation and the uncontrolled cell growth of tumors, we hypothesized that Pin1 functions as a chronic stimulator of VSMC proliferation. Pin1-positive smooth muscle cells were seen in the neointimal region of the femoral artery after guidewire injury. Exposure of VSMCS to platelet-derived growth factor (PDGF) increased Pin1 expression in a concentration-dependent manner. Basal cell growth rate and cyclin D1 expression were enhanced in Pin1-overexpressing VSMCs (Pin1-VSMCs). Moreover, PDGF-induced production of reactive oxygen species (ROS) in Pin1-VSMCs was higher than in control VSMCs. In Pin1-VSMCs, heme oxygenase-1 (HO-1) induction in response to nitric oxide donor was suppressed compared to control VSMCs. Nuclear translocation of nuclear factor E2-related factor-2 (Nrf2) was also diminished in Pin1-VSMCs. In contrast, the activity of the inducible minimal antioxidant response element (ARE) was potentiated in Pin1-null mouse embryonic fibroblasts (MEFs), compared to Pin1-wild-type MEFs. Moreover, Nrf2 ubiquitination was stimulated by Pin1 overexpression. Intraperitoneal injection of juglone (a Pin1 inhibitor) for 3weeks (1mg/kg, two times a week) significantly suppressed neointimal formation induced by wire injury. In conclusion, Pin1 induction during neointimal formation may be associated with ROS-mediated VSMC proliferation via down-regulation of Nrf2/ARE-dependent HO-1 expression. Pin1 may be a novel therapeutic target for several vascular diseases including atherosclerosis and stenosis.

Process Biochemistry

The activation of mast cells by immunoglobulin E-mediated stimuli is considered as a central even... more The activation of mast cells by immunoglobulin E-mediated stimuli is considered as a central event in allergic responses. In this regard, chitosan oligosaccharides (COS) of two different molecular weight ranges (1-3 kDa and 3-5 kDa) were investigated for their capabilities against the activation of RBL-2H3 mast cell sensitized with dinitrophenyl-specific immunoglobulin E antibody and stimulated by antigen dinitrophenyl-bovine serum albumin. It was found that COS significantly inhibited RBL-2H3 cell degranulation via attenuating the releases of histamine and ␤-hexosaminidase. Moreover, the inhibitory activity of COS was accompanied by a reduction in intracellular Ca 2+ elevation. Notably, the expression of immunoglobulin Fc epsilon receptor I (FcRI) in RBL-2H3 cells was down-regulated by COS treatment in a dose-dependent manner. The suppressive effect of COS on RBL-2H3 cell activation suggested that COS may be potential candidates of novel inhibitors against allergic reactions.

Toxicology in Vitro, 2010

Retroviral gene transfer technology is frequently used to establish stable transgenic cell lines.... more Retroviral gene transfer technology is frequently used to establish stable transgenic cell lines. However, no studies to date have evaluated antioxidant defense systems in cells infected with retroviral particles. In the present study, we examined the effects of retroviral infection on antioxidant defense systems using H4IIE cells infected with a retrovirus that overexpresses green fluorescent protein (retro-H4IIE cells). Total oxyradical scavenging capacity and glutathione (GSH), malondialdehyde, and peroxide levels were not significantly altered in retro-H4IIE cells; however, retro-H4IIE cells showed a higher resistance against cytotoxicity, GSH depletion, and malondialdehyde elevation under H 2 O 2 -induced oxidative stress conditions. Immunoblot analysis showed that alpha-class GSH S-transferase (GST) was increased 2.5-fold in retro-H4IIE cells as compared with H4IIE cells; however, catalase, GSH peroxidase-1, peroxiredoxin-1, and thioredoxin-1 remained unaltered or slightly decreased. L-Buthionine-(S,R)-sulfoximine, a GSH synthesis inhibitor, and 1-chloro-2,4-dinitrobenzene, a GST substrate and competitive inhibitor, decreased the difference in H 2 O 2 responses between the two cell types. These results support the hypothesis that the resistance of retro-H4IIE cells to H 2 O 2 can be attributed to an increase in alpha-class GST expression, as levels of GSH and GSH peroxidase-1 were not altered. The present study suggests that antioxidant enzyme expression may change during the establishment of stable transformed cell lines using retroviral techniques.

Web user session clustering is very important in web usage mining for web personalization. This p... more Web user session clustering is very important in web usage mining for web personalization. This paper proposes a particle swarm optimization (PSO) based sequence clustering approach and presents an experimentally investigation of the PSO based sequence clustering methods, which use three original PSO variants and their corresponding variants of a hybrid PSO with real value mutation. The investigation was conducted in 45 test cases using five web user session datasets extracted from a real world web site. The experimental results of these methods are compared with the results obtained from the traditional k-means clustering method. Some interesting observations have been made. In the most of test cases under consideration, the PSO and PSO-RVM methods have better performance than the k-means method. Furthermore, the PSO-RVM methods show better performance than the corresponding PSO methods in the cases in which the similarity measure function is more complex.

Molecular Crystals and Liquid Crystals, 2009

A series of polyimide (PI) and copolyimide (Co-PI) films were prepared by two-step imidization pr... more A series of polyimide (PI) and copolyimide (Co-PI) films were prepared by two-step imidization processes from the poly (amicacid) precursors. The color and visible light transmission of the Co-PI films were much better than those of the general Kapton type PI ...

In this paper, we present the design and implementation of an Open Computing Language (OpenCL) fr... more In this paper, we present the design and implementation of an Open Computing Language (OpenCL) framework that targets heterogeneous accelerator multicore architectures with local memory. The architecture consists of a general-purpose processor core and multiple accelerator cores that typically do not have any cache. Each accelerator core, instead, has a small internal local memory. Our OpenCL runtime is based on software-managed caches and coherence protocols that guarantee OpenCL memory consistency to overcome the limited size of the local memory. To boost performance, the runtime relies on three source-code transformation techniques, work-item coalescing, web-based variable expansion and preload-poststore buffering, performed by our OpenCL C source-to-source translator. Work-item coalescing is a procedure to serialize multiple SPMD-like tasks that execute concurrently in the presence of barriers and to sequentially run them on a single accelerator core. It requires the webbased variable expansion technique to allocate local memory for private variables. Preload-poststore buffering is a buffering technique that eliminates the overhead of software cache accesses. Together with work-item coalescing, it has a synergistic effect on boosting performance. We show the effectiveness of our OpenCL framework, evaluating its performance with a system that consists of two Cell BE processors. The experimental result shows that our approach is promising.

Journal of Molecular Catalysis B-enzymatic, 2007

Ionic liquids (ILs) were used as additives to protect the inactivation of enzymes by released alc... more Ionic liquids (ILs) were used as additives to protect the inactivation of enzymes by released alcohol and shrinking of gel during the sol-gel process. The Candida rugosa lipases immobilized by using ILs in sol-gel process showed higher activity and stability than lipase immobilized without ILs. The hydrolytic and esterification activities of lipase coimmobilized with ILs were 5-fold and 16-fold greater than in silica gel without ILs. After 5 days incubation of lipase coimmobilized with 1-octyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]amide at 50 • C, residual activity of lipase was about 80% of initial activity, while the lipase immobilized without ILs was completely inactivated. ILs may act as a template during gelation and reduce shrinkage of gel by pore filling. They can also behave as a stabilizer to protect the enzyme from the inactivation.

From 2006 plans were implemented to create a deep-sea water port linked to an Economic Zone in th... more From 2006 plans were implemented to create a deep-sea water port linked to an Economic Zone in the coastal Province of Ha Tinh, located in north central Vietnam. The multi-purpose Zone entitled ‘Vung Ang’, was to attract foreign investors, while the port would provide a link to nearby Laos and Thailand. The project obviously had large implications for the administrations

A technique to optimize the Standard Additive Model (SAM) fuzzy system for nonlinear system appro... more A technique to optimize the Standard Additive Model (SAM) fuzzy system for nonlinear system approximation is presented. First, fuzzy rules are initialized more much than usual by employing Centroid Neural Network (CNN) and then the genetic algorithm-based optimization process used to exclude unnecessary and redundant rules; thereafter, the fuzzy rule parameters are tuned by the gradient descent method incorporated with momentum technique. Finally, we demonstrate with numerical experiments based on approximating some nonlinear functions and chaotic time series. From the results, we can see that the proposed method is more effective than normal approach in terms of accuracy and training time.

Lignin-based thermoplastic copolyester was synthesized for eco-friendly polymers and composite ap... more Lignin-based thermoplastic copolyester was synthesized for eco-friendly polymers and composite applications using lignin as a macromonomer to form a high molecular weight polymer. Kraft lignin was polymerized with sebacoyl chloride in the presence of triethylamine in N,N-dimethylacetamide (DMAc), and the molecular weight of the synthesized polymer was controlled by the polymerization temperatures and [COCl]/[OH] ratios providing up to 39 000 corresponding to 4–5 repeating units of lignin macromonomers. The glass transition temperature of the synthesized polymer was difficult to measure due to the random distribution of functional groups and irregular configurational or conformational arrangement of natural lignin. Therefore, the complex electric modulus (CEM) technique was used to determine the glass transition of the synthesized polymer to give around 70°C measured by the peak of the imaginary part of CEM. The synthesized lignin-copolyester exhibited good thermal stability up to 200°C in TGA analysis and, thus, it was possible to shape the synthesized polymer using the solvent casting or hot-melt processing techniques at 120°C–140°C without generating odor, fume or irritation. Although the molecular weight should further be increased in the future, the developed methodology may help to exploit new applications for eco-friendly sustainable materials in various fields.