Trung Nguyen - Academia.edu (original) (raw)

Papers by Trung Nguyen

The European journal of neuroscience, 2005

AH neurons in the enteric nervous system play an essential role in initiating intestinal reflexes... more AH neurons in the enteric nervous system play an essential role in initiating intestinal reflexes and factors that control AH neuron excitability therefore influence the state of the digestive system. Prominent afterhyperpolarizations that follow action potentials in these neurons strongly affect their excitability. In the present work, we have investigated the regulation of the afterhyperpolarizing current (I AHP ) by protein kinase C (PKC). Electrophysiological responses and protein translocation were investigated in AH neurons of freshly dissected preparations of myenteric ganglia from the guinea-pig ileum. The activator of conventional and novel PKCs, phorbol dibutyrate, but not the activator of novel PKCs, ingenol, blocked the I AHP . Phorbol dibutyrate had no effect on the hyperpolarization-activated current (I h ) or on the A current (I A ). Stimulation of synaptic inputs to the neurons also reduced the I AHP , and had no effect on I h or I A . Phorbol dibutyrate also reduced a background outward current that was present after the I AHP current had been blocked by clotrimazole. Both phorbol dibutyrate and ingenol caused translocation of the novel PKC, PKCe, in these neurons. Only phorbol dibutyrate caused translocation of PKCc, a conventional PKC. The studies thus indicate that the activation of PKC by phorbol esters and by nerve stimulation affects AH neurons in a similar way, and that PKC activation targets both the I AHP and another background K + current. The I AHP is targeted by a conventional PKC, suggested to be PKCc, as this is the only conventional PKC that is prominent in AH neurons.

Critical care (London, England), 2006

New onset thrombocytopenia and multiple organ failure (

Haematologica, 2007

We studied the state of ultra-large von Willebrand factor (ULVWF) proteolysis in 21 pediatric pat... more We studied the state of ultra-large von Willebrand factor (ULVWF) proteolysis in 21 pediatric patients with severe sepsis and found that the overall group of patients had moderately reduced ADAMTS-13 activity, but 31% had severe enzymatic deficiency. The severe deficiency correlated with greater adhesion activity of von Willebrand factor, severity of thrombocytopenia and plasma levels of interleukin-6. It also correlated clinically with severity of illness and organ dysfunction. These results suggest that ULVWF proteolysis is insufficient in septic patients and severely deficient in a subgroup of patients. The deficiency may contribute to the development of thrombocytopenia and ischemic organ failure associated with sepsis.

Development, 2009

Oligodendrocytes in the central nervous system (CNS) produce myelin sheaths that insulate axons t... more Oligodendrocytes in the central nervous system (CNS) produce myelin sheaths that insulate axons to ensure fast propagation of action potentials. β1 integrins regulate the myelination of peripheral nerves, but their function during the myelination of axonal tracts in the CNS is unclear. Here we show that genetically modified mice lacking β1 integrins in the CNS present a deficit in myelination but no defects in the development of the oligodendroglial lineage. Instead, in vitro data show that β1 integrins regulate the outgrowth of myelin sheaths. Oligodendrocytes derived from mutant mice are unable to efficiently extend myelin sheets and fail to activate AKT (also known as AKT1), a kinase that is crucial for axonal ensheathment. The inhibition of PTEN, a negative regulator of AKT, or the expression of a constitutively active form of AKT restores myelin outgrowth in cultured β1deficient oligodendrocytes. Our data suggest that β1 integrins play an instructive role in CNS myelination by promoting myelin wrapping in a process that depends on AKT.

Clinical and Experimental Immunology, 2007

The role of basophils in an anaphylactic response is well recognized but is usually masked by mas... more The role of basophils in an anaphylactic response is well recognized but is usually masked by mast cells, which contain similar mediators for the induction of generalized vasodilatation and laryngeal constriction. The rapid onset of systemic anaphylactic symptoms, particularly in insect stings and ingested food, suggest that basophils, a circulating pool of cells containing histamine and other potent mediators such as leukotrienes, may be more involved in systemic anaphylaxis than originally thought. We wished to examine if secretory phospholipase A2, a systemic allergen found in honey bee venom (HBV-sPLA2) may activate basophils directly leading to rapid systemic mediator release. Basophils were isolated from human blood and stimulated with increasing concentrations of HBV-sPLA2. We found that physiological concentrations of HBV-sPLA2 induce rapid leukotriene C4 production from purified human basophils within 5 min, while interleukin (IL)-4 expression and production was induced at later time-points. Histamine release was not induced, signifying that HBV-sPLA2 did not induce generalized degranulation. Surface expression of CD63, CD69 and CD11b were up-regulated following HBV-sPLA2 treatment. Stimulation of basophils with anti-immunoglobulin E (IgE) following treatment with HBV-sPLA2 did not induce more leukotriene release. To investigate the mechanism of leukotriene production, 9–12 octadecadiynioc acid, a cyclooxygenase-1 (COX-1) and 15-lipoxygenase inhibitor, was used and this abrogated leukotriene production. These results indicate that HBV-sPLA2 can directly activate human basophils in vitro to induce leukotriene production.

International Journal of Pharmaceutics, 2008

The success of the chemotherapeutic treatment of hydatid disease is based upon the drug ability t... more The success of the chemotherapeutic treatment of hydatid disease is based upon the drug ability to operate on the germinal layer and on the protoscolices of the hydatid cyst interior at adequate concentrations for sufficient periods. The goal of this study was to evaluate the ability of the drug diffusion through the cyst membrane from sheep hydatid cysts and the increase of drug concentration in the cyst environment. In the first part of this work, the permeation behaviour through the hydatid cyst membrane was studied with five model molecules, having different molecular descriptors (log P, molecular weight, polar surface area …) onto static Franz glass diffusion cells. A good correlation has been observed between the permeation coefficient and the partition coefficient, log P (r = 0.951). In the second part, albendazole-loaded nanoparticles (about 300 nm) prepared by the emulsion solvent evaporation method have shown a sufficient entrapment efficiency (36.4 ± 6.4%) to raise the apparent solubility of albendazole. The diffusion of drug from the nanoparticles across the hydatid cyst membrane was also improved compare to albendazole suspension. These results have shown the interest of the albendazole-loaded nanoparticles for the treatment of hydatid cysts in the future.

Journal of clinical microbiology, 2004

Group A rotaviruses are the major cause of diarrhea in young children worldwide. From March 2001 ... more Group A rotaviruses are the major cause of diarrhea in young children worldwide. From March 2001 to April 2002, 836 children less than 5 years of age were investigated in Hanoi, Vietnam. This included 587 children with diarrhea and 249 age-matched controls. Group A rotavirus was identified in 46.7% of the children with diarrhea and 3.6% of the controls, which was a significant difference. Within the diarrhea group, the highest prevalence was seen in children from 13 to 24 months of age, and the prevalence was higher in males than in females. The symptoms of acute diarrhea caused by rotavirus were watery diarrhea, vomiting, fever, and dehydration. A higher prevalence of rotavirus detection was obtained for children who had all of these symptoms, followed by those who had diarrhea with vomiting-dehydration, fever-dehydration, and dehydration.

Journal of clinical microbiology, 2005

Diarrhea continues to be one of the most common causes of morbidity and mortality among infants a... more Diarrhea continues to be one of the most common causes of morbidity and mortality among infants and children in developing countries. Escherichia coli is an emerging agent among pathogens that cause diarrhea. The development of a highly applicable technique for the detection of different categories of diarrheagenic E. coli is important. We have used multiplex PCR by combining eight primer pairs specific for enteroaggregative E. coli (EAEC), enteroinvasive E. coli (EIEC), enterohemorrhagic E. coli, enteropathogenic E. coli (EPEC), and enterotoxigenic E. coli (ETEC). This facilitates the identification of five different categories of diarrheagenic E. coli from stool samples in a single reaction simultaneously. The prevalences of diarrheagenic E. coli were 22.5 and 12% in the diarrhea group and the control group, respectively. Among 587 fecal samples from Vietnamese children under 5 years of age with diarrhea, this technique identified 132 diarrheagenic E. coli strains. This included 68 samples (11.6%) with EAEC, 12 samples (2.0%) with EIEC, 39 samples (6.6%) with EPEC, and 13 samples (2.2%) with ETEC. Among the 249 age-matched controls, 30 samples were positive for diarrheagenic E. coli. The distribution was 18 samples (7.2%) with EAEC, 11 samples (4.4%) with EPEC, and 1 sample (0.4%) with ETEC.

Thrombosis Research, 2010

Introduction: Endothelial microparticles (EMP) have been described as markers of endothelial dysf... more Introduction: Endothelial microparticles (EMP) have been described as markers of endothelial dysfunction. As the end effect of anti-angiogenesis drugs is the inhibition of endothelial growth, we tested the hypothesis that the outcome of the treatment with these agents might be assessed by measuring changes in the plasma levels of EMP. Aim: To measure the levels of EMP in the blood of patients with metastatic renal cell carcinoma (mRCC) over the course of treatment with Sunitinib. Methods: In-vitro study: Cultured human umbilical vein endothelial cells (HUVECs) were activated using TNF-alpha to produce measurable levels of EMP in culture medium. In-vivo study: 11 patients with mRCC were recruited after the ethics approval. Each patient had four blood samples drawn in specific time-lines of their treatment. Eleven matching healthy volunteers were also recruited as controls. EMPs-levels were measured in the plasma. Flow cytometry analysis (FCM) was used in both studies to measure the levels of EMP using CD54 (ICAM-1), CD62e (E selectin), CD105 (Endoglin), and CD106 (VCAM-1) markers. The gate was identified using Megamix® beads. Results: Significant increases in the levels of EMPs were measured in the medium of HUVECs after activation with TNF-alpha. No differences were recorded in the plasma levels of EMPs between healthy volunteers and RCC patients, and no unified patterns of change were revealed in the plasma of RCC patient along the treatment course with Sunitinib. Conclusion: Although our experiments demonstrated no specific patterns of change in the plasma levels of normal (non-neoplastic) EMP during treatment with Sunitinib; this does not exclude possible changes in the levels of EMPs generated by neoplastic endothelium. Therefore we are testing cancer-vasculature-specific markers to measure the plasma levels of EMPs in these patients. We are also looking closely into the different patterns of changes in EMP-levels in correlation to cancer response or nonresponse to treatment.

Diabetes Care, 2007

OBJECTIVE -The sympathetic nervous system and thiazolidinediones control lipid metabolism and hav... more OBJECTIVE -The sympathetic nervous system and thiazolidinediones control lipid metabolism and have been implicated in body weight regulation. This study was conducted to determine whether the simultaneous activation of these two signaling systems might synergize to exert beneficial effects on the expression of key genes involved in lipid metabolism and mitochondrial biogenesis in subcutaneous fat in nondiabetic subjects.

Oral Surgery, 2008

Aim: To provide a classification system of mandibular prognathism (MP) as a guide for proper diag... more Aim: To provide a classification system of mandibular prognathism (MP) as a guide for proper diagnosis and treatment planning of the various forms of skeletal discrepancies seen in mandibular prognathism and to a communication tool among orthodontists and surgeons. Materials and Methods: Six different types of MP were presented. Recommended surgical procedures for each MP categories were presented. Twenty-three consecutive MP patients were evaluated by a panel of three orthodontists. The panel categorized each patient according to Cho's MP classification system. The recommended surgery by the MP classification system and actual surgery performed for each were compared. Result: The recommended surgical procedure(s) respective to the MP category of each individual corresponded to the actual surgery performed with exception of a few individuals. Conclusion: This MP classification system proved to be a good diagnostic tool and led to an appropriate orthodontic and surgical treatment plan.

Molecules (Basel, Switzerland), 2014

Pleurotus florida has been widely used for nutritional and medicinal purposes. The present study ... more Pleurotus florida has been widely used for nutritional and medicinal purposes. The present study was conducted to evaluate the antioxidant and anti-inflammatory effects of the fruiting bodies of P. florida extracted with acetone, methanol, and hot water. The antioxidant activities of the acetone and methanol extracts of P. florida showed stronger inhibition of β-carotene-linoleic acid compared to that of the hot water extract. The acetone extract (8 mg/mL) showed a high reducing power of 1.86. The acetone and methanol extracts showed more effective DPPH radical scavenging activities than the hot water extract. The chelating effect of the extracts at lower concentrations was significantly effective compared to that of the positive control. Thirteen phenolic compounds were detected from acetonitrile and hydrochloric acid solvent extracts. Nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression in lipolysaccahride (LPS) stimulated RAW 264.7 cells, a murine macrophage cell line, were inhibited significantly by the mushroom extracts in a concentration dependent manner. The anti-inflammatory activity on carrageenan-induced edema in the rat hind-paw reduced significantly by the mushroom extracts. Therefore, we have demonstrated that P. florida fruiting bodies possess antioxidant and anti-inflammatory activites related to their inhibitory activities on NO production, iNOS protein expression, and carrageenan-induced paw edema in rats. The results suggest that the fruiting bodies of P. florida are a good source of natural antioxidant and anti-inflammatory agents.

IEEE Transactions on Systems, Man, and Cybernetics, 2012

Particle swarm optimization (PSO) has been shown as an effective tool for solving global optimiza... more Particle swarm optimization (PSO) has been shown as an effective tool for solving global optimization problems. So far, most PSO algorithms use a single learning pattern for all particles, which means that all particles in a swarm use the same strategy. This monotonic learning pattern may cause the lack of intelligence for a particular particle, which makes it unable to deal with different complex situations. This paper presents a novel algorithm, called self-learning particle swarm optimizer (SLPSO), for global optimization problems. In SLPSO, each particle has a set of four strategies to cope with different situations in the search space. The cooperation of the four strategies is implemented by an adaptive learning framework at the individual level, which can enable a particle to choose the optimal strategy according to its own local fitness landscape. The experimental study on a set of 45 test functions and two real-world problems show that SLPSO has a superior performance in comparison with several other peer algorithms.

International Symposium on Communication Systems, Networks and Digital Signal Processing, 2008

Abstract Multipulse pulse-position modulation (MPPM) is a preferred signaling scheme for free-sp... more Abstract Multipulse pulse-position modulation (MPPM) is a preferred signaling scheme for free-space optical (FSO) communications under certain constraints. In order to enable the combination of MPPM with many types of error-correcting codes, it is desirable that the MPPM ...

IEEE Pacific Rim Conference on Communications, Computers and Signal Processing, 2007

In this paper, orthogonal frequency division multiplexing (OFDM) with space-time and space-freque... more In this paper, orthogonal frequency division multiplexing (OFDM) with space-time and space-frequency block codes (STBCs and SFBCs) for transmission with multiple antennas is considered. A peak-to-average power ratio (PAPR) reduction method applying the technique of partial transmit sequences (PTS), well established for single-antenna OFDM, together with efficient time-domain search is devised for both STBC-and SFBC-OFDM employing generalized orthogonal designs. Numerical results show that PTS compares well with methods that have previously been proposed for OFDM with STBCs and SFBCs.

Journal of medicinal chemistry, Jan 10, 2012

Substances with dual tyrosyl-DNA phosphodiesterase I -topoisomerase I inhibitory activity in one ... more Substances with dual tyrosyl-DNA phosphodiesterase I -topoisomerase I inhibitory activity in one low molecular weight compound would constitute a unique class of anticancer agents that could potentially have significant advantages over drugs that work against the individual enzymes. The present study demonstrates the successful synthesis and evaluation of the first dual Top1-Tdp1 inhibitors, which are based on the indenoisoquinoline chemotype. One bis(indenoisoquinoline) had significant activity against human Tdp1 (IC 50 = 1.52 ± 0.05 μM), and it was also equipotent to camptothecin as a Top1 inhibitor. Significant insights into enzyme-drug interactions were gained via structure-activity relationship studies of the series. The present results also document the failure of the previously reported sulfonyl ester pharmacophore to confer Tdp1 inhibition in this indenoisoquinoline class of inhibitors, even though it was demonstrated to work well for the steroid NSC 88915 (7). The current study will facilitate future efforts to optimize dual Top1-Tdp1 inhibitors.

Journal of neurophysiology, 2007

The late afterhyperpolarizing potential (AHP) that follows the action potential in intrinsic prim... more The late afterhyperpolarizing potential (AHP) that follows the action potential in intrinsic primary afferent neurons of the gastrointestinal tract has a profound influence on their firing patterns. There has been uncertainty about the identity of the channels that carry the late AHP current, especially in guinea pigs, where the majority of the physiological studies have been made. In the present work, the late AHP was recorded with intracellular microelectrodes from myenteric neurons in the guinea pig small intestine. mRNA was extracted from the ganglia to determine the identity of the guinea pig intermediate conductance potassium (I(K)) channel gene transcript. The late AHP was inhibited by two blockers of I(K) channels, TRAM34 (0.1-1 microM) and clotrimazole (10 microM), and was enhanced by the potentiator of the opening of these channels, DC-EBIO (100 nM). Action potential characteristics were unchanged by TRAM34 or DC-EBIO. The full sequence of the gene transcript and the deduced amino acid sequence were determined from extracts including myenteric ganglia and from bladder urothelium, which is a rich source of I(K) channel mRNA. This showed that the guinea pig sequence has a high degree of homology with other mammalian sequences but that the guinea pig channel lacks a phosphorylation site that was thought to be critical for channel regulation. It is concluded that the channels that carry the current of the late afterhyperpolarizing potential in guinea pig enteric neurons are I(K) channels.