Thanh Truc - Academia.edu (original) (raw)
Papers by Thanh Truc
Reviews in Endocrine & Metabolic Disorders, 2001
This study examined whether the high sensitivity of plasma free metanephrines for diagnosis of ph... more This study examined whether the high sensitivity of plasma free metanephrines for diagnosis of pheochromocytoma may result from production of free metanephrines within tumors. Presence in pheochromocytomas of catechol-O-methyltransferase (COMT), the enzyme responsible for conversion of catecholamines to metanephrines, was confirmed by Western blot analysis, enzyme assay, and immunohistochemistry. Western blot analysis and enzyme assay indicated that membrane-bound and not soluble COMT was the predominant form of the enzyme in pheochromocytoma. Immunohistochemistry revealed colocalization of COMT in the same chromaffin cells where catecholamines are translocated into storage vesicles by the vesicular monoamine transporter. Levels of free metanephrines in pheochromocytoma over 10,000 times higher than plasma concentrations in the same patients before removal of tumors indicated production of
Neurochemical Research, 1999
Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOP... more Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOPA) and catecholamines were examined as markers of sympathetic innervation and catecholamine synthesis in peripheral tissues of sympathectomized and intact rats. Chemical sympathectomy with 6-hydroxydopamine (6-OHDA) markedly decreased norepinephrine and to a generally lesser extent TH activities and dopamine in most peripheral tissues (stomach, lung, testis, duodenum, pancreas, salivary gland, spleen, heart, kidney, thymus). Superior cervical ganglia, adrenals and descending aorta were unaffected and vas deferens showed a large 92% decrease in norepinephrine, but only a small 38% decrease in TH activity after 6-OHDA. Presence of chromaffin cells or neuronal cell bodies in these latter tissues, indicated by consistent expression of TH mRNA, explained the relative resistance of these tissues to 6-OHDA. Stomach also showed consistent expression of TH mRNA before, but not after 6-OHDA, suggesting that catecholamine synthesizing cells in gastric tissue are sensitive to the toxic effects of 6-OHDA. Tissue concentrations of DOPA were mainly unaffected by 6-OHDA, indicating that much of the DOPA in peripheral tissues is synthesized independently of local TH or sympathetic innervation. The differential effects of chemical sympathectomy on tissue catecholamines, DOPA, TH mRNA and TH activity demonstrate that these variables are not simple markers of sympathetic innervation or catecholamine synthesis. Other factors, including presence of neuronal cell bodies, parenchymal chromaffin cells, non-neuronal sites of catecholamine synthesis and alternative sources of tissue DOPA, must also be considered when tissue catecholamines, DOPA and TH are examined as markers of sympathetic innervation and local catecholamine synthesis.
Clinical & Experimental Metastasis, 2009
Pheochromocytomas are chromaffin cell-derived neuroendocrine tumors. There is presently no cure f... more Pheochromocytomas are chromaffin cell-derived neuroendocrine tumors. There is presently no cure for metastatic pheochromocytoma and no reliable way to distinguish malignant from benign tumors before the development of metastases. In order to successfully manage pheochromocytoma, it is necessary to better understand the biological determinants of tumor behavior. For this purpose, we have recently established a mouse model of metastatic pheochromocytoma using tail vein injection of mouse pheochromocytoma (MPC) cells. We optimized this model modifying the number of cells injected, length of trypsin pre-treatment, and incubation temperature and duration for the MPC cells before injection, and by serial passage and re-selection of tumors exhibiting the metastatic phenotype. We evaluated the effect of these modifications on tumor growth using serial in vivo Magnetic Resonance Imaging studies. These results show that number of cells injected, the pre-injection incubation temperature, and duration of trypsin treatment are important factors to produce faster growing, more aggressive tumors that yielded secondary metastatic lesions. Serial harvest, culture and re-selection of metastatic liver lesions produced even more aggressive pheochromocytoma cells that retained their biochemical phenotype. Microarray gene expression comparison and quantitative real-time PCR of these more aggressive cells to the MPC-parental cell line identified genes that may be important for the metastatic process.
Clinical Pharmacokinetics, 2009
The pharmacokinetic disposition of ciclosporin shows great intra-and interpatient variability, an... more The pharmacokinetic disposition of ciclosporin shows great intra-and interpatient variability, and that combined with a narrow therapeutic window makes therapeutic drug monitoring of ciclosporin necessary. The nonlinear mixed-effects population pharmacokinetic program NONMEM Ò predicts individual pharmacokinetic parameters based not only on individual patient observations but also on population characteristics and the patient's covariates. The aim of this model development is to potentially use it in the clinical setting to optimize ciclosporin dosing in renal transplant recipients. Methods: A population pharmacokinetic model of ciclosporin has been developed with NONMEM Ò using full 12-hour pharmacokinetic profiles from 29 renal transplant recipients, 3 months of daily follow-up data from an additional 11 recipients, and both 3 months of follow-up data and full 12-hour pharmacokinetic profiles from nine patients. The internal validation of the model was based on data splitting and jack-knife methods. In addition, the model was validated for its clinical applicability on standard trough and 2-hour post-dose concentration data from 12 additional patients with 3 months of follow-up. Results: The model that best described the ciclosporin data was a two-compartment model with first-order absorption process with lagged time. The population pharmacokinetic parameters were oral clearance (CL F) = 26.9 L h; central volume of distribution after oral administration (V 1 F) = 24.4 L; absorption rate constant (k a ) = 0.544 h -1 ; lag time = 0.460 h; peripheral volume of distribution = 1119 L and intercompartmental clearance after oral administration (Q F) = 19.6 L h. Three covariates had significant effect on a total of six pharmacokinetic parameters. These were bodyweight on V 1 F and k a , time after transplantation on k a , and age on CL F, k a and V 1 F. Cytochrome P450 3A5 genotype was also a significant covariate but was not included in the final model since such information is not available in clinical practice. The external validation showed that the model was able to predict ciclosporin concentrations in the 12 new patients with an average predictive error of 17.4 -14% when the standard sample concentrations from the previous week were given. Conclusion: A NONMEM Ò pharmacokinetic model for ciclosporin in renal transplant recipients was successfully developed and validated for the first 3 months post-transplantation. The model showed good predictability in a new patient cohort. After further clinical validation, the model may be applicable as a clinical tool for optimizing ciclosporin dosing in renal transplant recipients in the early post-transplant period.
Applied Organometallic Chemistry, 2000
The effects of triorganotins on the 4th instar stage of Aedes aegypti larvae were evaluated. The ... more The effects of triorganotins on the 4th instar stage of Aedes aegypti larvae were evaluated. The most effective of the 15 triorganotins used in the study was tributyltin chloride with an LC 50 value of 0.57 ± 0.07 mg dm −3 . The low LC 50 values obtained indicated that this class of ...
This paper presents an electronic tongue system with blind source separation (BSS) and wireless s... more This paper presents an electronic tongue system with blind source separation (BSS) and wireless sensor network (WSN) for remote multi-ion sensing applications. Electrochemical sensors, such as ion-sensitive field-effect transistor (ISFET) and extended-gate field-effect transistor (EGFET), only provide the combined concentrations of all ions in aqueous solutions. Mixed hydrogen and sodium ions in chemical solutions are observed by means of H+ ISFET and H+ EGFET sensor array. The BSS extracts the concentration of individual ions using independent component analysis (ICA). The parameters of ISFET and EGFET sensors serve as a priori knowledge that helps solve the BSS problem. Using wireless transceivers, the ISFET/EGFET modules are realized as wireless sensor nodes. The integration of WSN technology into our electronic tongue system with BSS capability makes distant multi-ion measurement viable for environment and water quality monitoring.
This study examined the mechanisms linking different biochemical and clinical phenotypes of pheoc... more This study examined the mechanisms linking different biochemical and clinical phenotypes of pheochromocytoma in multiple endocrine neoplasia type 2 (MEN 2) and von Hippel-Lindau (VHL) syndrome to underlying differences in the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis, and of phenylethanolamine N-methyltransferase (PNMT), the enzyme that converts norepinephrine to epinephrine. Signs and symptoms of pheochromocytoma, plasma catecholamines and metanephrines, and tumor cell neurochemistry and expression of TH and PNMT were examined in 19 MEN 2 patients and 30 VHL patients with adrenal pheochromocytomas. MEN 2 patients were more symptomatic and had a higher incidence of hypertension (mainly paroxysmal) and higher plasma concentrations of metanephrines, but paradoxically
The purpose of this paper is to describe the development of a technological innovation designed t... more The purpose of this paper is to describe the development of a technological innovation designed to assist teachers of the Foundational Approaches in Science Teaching program, or FAST. An electronic resource, or FASTeR, is a multimedia resource designed to provide support to teachers in implementing the FAST program by showing events of actual student investigations and teacher preparation. However, the effectiveness of multimedia in learner outcomes has been a continual debate since the days of Clark and Kozma. Proponents of the positive influences of multimedia maintain that learners process information in a myriad of different ways and that multimedia assists those learners. Opposition maintains that there is little empirical evidence as to how multimedia positively adds to learner outcomes. As the debate continues, the authors of this paper recognize that computer multimedia and its impact in education is a relatively new field of study and that additional empirical evidence will emerge as further research questions are advanced.
The purpose of this study was to conduct a mixed-methods study, including a phenomenological comp... more The purpose of this study was to conduct a mixed-methods study, including a phenomenological component, to understand the perceived roles of technology coordinators and library media specialists in Hawaii public schools. The purpose of this ...
Conservation Genetics Resources, 2010
Thirteen polymorphic microsatellite loci from topmouth culter (Culter alburnus) were isolated usi... more Thirteen polymorphic microsatellite loci from topmouth culter (Culter alburnus) were isolated using the fast isolation by AFLP of sequences containing repeats (FIASCO) protocol. These loci were characterized by genotyping 40 individuals. The observed number of alleles ranged from 7 to 15 with an average of 10.7 of each loci. The expected and observed heterozygosities ranged from 0.7047 to 0.9193 and from 0.4500 to 0.8250, respectively. Among these polymorphic microsatellite loci, three of the loci (TC04, TC07 and TC12) significantly deviated from (P
Reviews in Endocrine & Metabolic Disorders, 2001
This study examined whether the high sensitivity of plasma free metanephrines for diagnosis of ph... more This study examined whether the high sensitivity of plasma free metanephrines for diagnosis of pheochromocytoma may result from production of free metanephrines within tumors. Presence in pheochromocytomas of catechol-O-methyltransferase (COMT), the enzyme responsible for conversion of catecholamines to metanephrines, was confirmed by Western blot analysis, enzyme assay, and immunohistochemistry. Western blot analysis and enzyme assay indicated that membrane-bound and not soluble COMT was the predominant form of the enzyme in pheochromocytoma. Immunohistochemistry revealed colocalization of COMT in the same chromaffin cells where catecholamines are translocated into storage vesicles by the vesicular monoamine transporter. Levels of free metanephrines in pheochromocytoma over 10,000 times higher than plasma concentrations in the same patients before removal of tumors indicated production of
Neurochemical Research, 1999
Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOP... more Tyrosine hydroxylase (TH) mRNA and activity and concentrations of 3,4-dihydroxyphenylalanine (DOPA) and catecholamines were examined as markers of sympathetic innervation and catecholamine synthesis in peripheral tissues of sympathectomized and intact rats. Chemical sympathectomy with 6-hydroxydopamine (6-OHDA) markedly decreased norepinephrine and to a generally lesser extent TH activities and dopamine in most peripheral tissues (stomach, lung, testis, duodenum, pancreas, salivary gland, spleen, heart, kidney, thymus). Superior cervical ganglia, adrenals and descending aorta were unaffected and vas deferens showed a large 92% decrease in norepinephrine, but only a small 38% decrease in TH activity after 6-OHDA. Presence of chromaffin cells or neuronal cell bodies in these latter tissues, indicated by consistent expression of TH mRNA, explained the relative resistance of these tissues to 6-OHDA. Stomach also showed consistent expression of TH mRNA before, but not after 6-OHDA, suggesting that catecholamine synthesizing cells in gastric tissue are sensitive to the toxic effects of 6-OHDA. Tissue concentrations of DOPA were mainly unaffected by 6-OHDA, indicating that much of the DOPA in peripheral tissues is synthesized independently of local TH or sympathetic innervation. The differential effects of chemical sympathectomy on tissue catecholamines, DOPA, TH mRNA and TH activity demonstrate that these variables are not simple markers of sympathetic innervation or catecholamine synthesis. Other factors, including presence of neuronal cell bodies, parenchymal chromaffin cells, non-neuronal sites of catecholamine synthesis and alternative sources of tissue DOPA, must also be considered when tissue catecholamines, DOPA and TH are examined as markers of sympathetic innervation and local catecholamine synthesis.
Clinical & Experimental Metastasis, 2009
Pheochromocytomas are chromaffin cell-derived neuroendocrine tumors. There is presently no cure f... more Pheochromocytomas are chromaffin cell-derived neuroendocrine tumors. There is presently no cure for metastatic pheochromocytoma and no reliable way to distinguish malignant from benign tumors before the development of metastases. In order to successfully manage pheochromocytoma, it is necessary to better understand the biological determinants of tumor behavior. For this purpose, we have recently established a mouse model of metastatic pheochromocytoma using tail vein injection of mouse pheochromocytoma (MPC) cells. We optimized this model modifying the number of cells injected, length of trypsin pre-treatment, and incubation temperature and duration for the MPC cells before injection, and by serial passage and re-selection of tumors exhibiting the metastatic phenotype. We evaluated the effect of these modifications on tumor growth using serial in vivo Magnetic Resonance Imaging studies. These results show that number of cells injected, the pre-injection incubation temperature, and duration of trypsin treatment are important factors to produce faster growing, more aggressive tumors that yielded secondary metastatic lesions. Serial harvest, culture and re-selection of metastatic liver lesions produced even more aggressive pheochromocytoma cells that retained their biochemical phenotype. Microarray gene expression comparison and quantitative real-time PCR of these more aggressive cells to the MPC-parental cell line identified genes that may be important for the metastatic process.
Clinical Pharmacokinetics, 2009
The pharmacokinetic disposition of ciclosporin shows great intra-and interpatient variability, an... more The pharmacokinetic disposition of ciclosporin shows great intra-and interpatient variability, and that combined with a narrow therapeutic window makes therapeutic drug monitoring of ciclosporin necessary. The nonlinear mixed-effects population pharmacokinetic program NONMEM Ò predicts individual pharmacokinetic parameters based not only on individual patient observations but also on population characteristics and the patient's covariates. The aim of this model development is to potentially use it in the clinical setting to optimize ciclosporin dosing in renal transplant recipients. Methods: A population pharmacokinetic model of ciclosporin has been developed with NONMEM Ò using full 12-hour pharmacokinetic profiles from 29 renal transplant recipients, 3 months of daily follow-up data from an additional 11 recipients, and both 3 months of follow-up data and full 12-hour pharmacokinetic profiles from nine patients. The internal validation of the model was based on data splitting and jack-knife methods. In addition, the model was validated for its clinical applicability on standard trough and 2-hour post-dose concentration data from 12 additional patients with 3 months of follow-up. Results: The model that best described the ciclosporin data was a two-compartment model with first-order absorption process with lagged time. The population pharmacokinetic parameters were oral clearance (CL F) = 26.9 L h; central volume of distribution after oral administration (V 1 F) = 24.4 L; absorption rate constant (k a ) = 0.544 h -1 ; lag time = 0.460 h; peripheral volume of distribution = 1119 L and intercompartmental clearance after oral administration (Q F) = 19.6 L h. Three covariates had significant effect on a total of six pharmacokinetic parameters. These were bodyweight on V 1 F and k a , time after transplantation on k a , and age on CL F, k a and V 1 F. Cytochrome P450 3A5 genotype was also a significant covariate but was not included in the final model since such information is not available in clinical practice. The external validation showed that the model was able to predict ciclosporin concentrations in the 12 new patients with an average predictive error of 17.4 -14% when the standard sample concentrations from the previous week were given. Conclusion: A NONMEM Ò pharmacokinetic model for ciclosporin in renal transplant recipients was successfully developed and validated for the first 3 months post-transplantation. The model showed good predictability in a new patient cohort. After further clinical validation, the model may be applicable as a clinical tool for optimizing ciclosporin dosing in renal transplant recipients in the early post-transplant period.
Applied Organometallic Chemistry, 2000
The effects of triorganotins on the 4th instar stage of Aedes aegypti larvae were evaluated. The ... more The effects of triorganotins on the 4th instar stage of Aedes aegypti larvae were evaluated. The most effective of the 15 triorganotins used in the study was tributyltin chloride with an LC 50 value of 0.57 ± 0.07 mg dm −3 . The low LC 50 values obtained indicated that this class of ...
This paper presents an electronic tongue system with blind source separation (BSS) and wireless s... more This paper presents an electronic tongue system with blind source separation (BSS) and wireless sensor network (WSN) for remote multi-ion sensing applications. Electrochemical sensors, such as ion-sensitive field-effect transistor (ISFET) and extended-gate field-effect transistor (EGFET), only provide the combined concentrations of all ions in aqueous solutions. Mixed hydrogen and sodium ions in chemical solutions are observed by means of H+ ISFET and H+ EGFET sensor array. The BSS extracts the concentration of individual ions using independent component analysis (ICA). The parameters of ISFET and EGFET sensors serve as a priori knowledge that helps solve the BSS problem. Using wireless transceivers, the ISFET/EGFET modules are realized as wireless sensor nodes. The integration of WSN technology into our electronic tongue system with BSS capability makes distant multi-ion measurement viable for environment and water quality monitoring.
This study examined the mechanisms linking different biochemical and clinical phenotypes of pheoc... more This study examined the mechanisms linking different biochemical and clinical phenotypes of pheochromocytoma in multiple endocrine neoplasia type 2 (MEN 2) and von Hippel-Lindau (VHL) syndrome to underlying differences in the expression of tyrosine hydroxylase (TH), the rate-limiting enzyme in catecholamine synthesis, and of phenylethanolamine N-methyltransferase (PNMT), the enzyme that converts norepinephrine to epinephrine. Signs and symptoms of pheochromocytoma, plasma catecholamines and metanephrines, and tumor cell neurochemistry and expression of TH and PNMT were examined in 19 MEN 2 patients and 30 VHL patients with adrenal pheochromocytomas. MEN 2 patients were more symptomatic and had a higher incidence of hypertension (mainly paroxysmal) and higher plasma concentrations of metanephrines, but paradoxically
The purpose of this paper is to describe the development of a technological innovation designed t... more The purpose of this paper is to describe the development of a technological innovation designed to assist teachers of the Foundational Approaches in Science Teaching program, or FAST. An electronic resource, or FASTeR, is a multimedia resource designed to provide support to teachers in implementing the FAST program by showing events of actual student investigations and teacher preparation. However, the effectiveness of multimedia in learner outcomes has been a continual debate since the days of Clark and Kozma. Proponents of the positive influences of multimedia maintain that learners process information in a myriad of different ways and that multimedia assists those learners. Opposition maintains that there is little empirical evidence as to how multimedia positively adds to learner outcomes. As the debate continues, the authors of this paper recognize that computer multimedia and its impact in education is a relatively new field of study and that additional empirical evidence will emerge as further research questions are advanced.
The purpose of this study was to conduct a mixed-methods study, including a phenomenological comp... more The purpose of this study was to conduct a mixed-methods study, including a phenomenological component, to understand the perceived roles of technology coordinators and library media specialists in Hawaii public schools. The purpose of this ...
Conservation Genetics Resources, 2010
Thirteen polymorphic microsatellite loci from topmouth culter (Culter alburnus) were isolated usi... more Thirteen polymorphic microsatellite loci from topmouth culter (Culter alburnus) were isolated using the fast isolation by AFLP of sequences containing repeats (FIASCO) protocol. These loci were characterized by genotyping 40 individuals. The observed number of alleles ranged from 7 to 15 with an average of 10.7 of each loci. The expected and observed heterozygosities ranged from 0.7047 to 0.9193 and from 0.4500 to 0.8250, respectively. Among these polymorphic microsatellite loci, three of the loci (TC04, TC07 and TC12) significantly deviated from (P