Dr. Quoc  Nguyen  Od image

Dr. Quoc Nguyen Od

9727 Spring Green Blvd Suite 300
Katy TX 77494
281 693-3931
Medical School: Other - Unknown
Accepts Medicare: No
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Participates In PQRS: No
Participates In EHR: No
License #: 8422T
NPI: 1083023881
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68Ga-PSMA has high detection rate of prostate cancer recurrence outside the prostatic fossa in patients being considered for salvage radiation treatment. - BJU international
To examine the detection rates of (68) Ga-PSMA-PET/CT in patients with biochemical recurrence (BCR) after radical prostatectomy (RP), and also the impact on their management.300 consecutive PC patients who underwent (68) Ga-PSMA-PET/CT between February and July 2015 were prospectively included in the ProCan-I Database. For this analysis, men were included with BCR (PSA ≥0.05ng/ml) after RP, PSA <1.0ng/ml, being considered for salvage radiation treatment (RT) according to FROGG guidelines. Two readers assessed each (68) Ga-PSMA-PET/CT, and all positive lesions were assigned to an anatomical location. For each patient, the clinical and pathological features were recorded, their association with pathological (68) Ga-PSMA uptake was investigated, and detection rates were determined according to PSA level.70 patients were included, 53 positive (68) Ga-PSMA lesions were detected in 38 (54%) positive patients. For PSA (ng/ml) 0.05-0.09, 8% were definitely positive; for 0.1-0.19, 23%; for 0.2-0.29, 58%; for 0.3-0.49, 36%; and for 0.5-0.99, 57%, respectively. Eighteen of 70 patients (27%) had pathological (68) Ga-PSMA uptake in the prostatic fossa, 11 (14.3%) in the pelvic nodes, and 5 (4.3%) in both the fossa and pelvic lymph nodes. Finally, there was uptake outside the pelvis with or without a lesion in the fossa or pelvic lymph nodes in 4 cases (8.6%). There was a major management impact in 20 (28.6%) men, all were attributable to the (68) Ga-PSMA findings.(68) Ga-PSMA appears useful for re-staging of PC in patients with rising PSA being considered for salvage RT even at PSA levels below 0.5 ng/ml. These results underline the need for further prospective trials to evaluate the changes in RT volume or management attributable to (68) Ga-PSMA findings. This article is protected by copyright. All rights reserved.This article is protected by copyright. All rights reserved.
Transport properties of track-etched membranes having variable effective pore-lengths. - Nanotechnology
The transport rate of molecules through polymeric membranes is normally limited because of their micrometer-scale thickness which restricts their suitability for more practical application. To study the effect of effective pore length on the transport behavior, polymer membranes containing cylindrical and asymmetric-shaped nanopores were prepared through a two-step ion track-etching technique. Permeation experiments were performed separately to investigate the transport properties (molecular flux and selectivity) of these track-etched membranes. The permeation data shows that the molecular flux across membranes containing asymmetric nanopores is higher compared to those having cylindrical pores. On the other hand, the cylindrical pore membranes exhibit higher selectivity than asymmetric pores for the permeation of charged molecules across the membrane. Current-voltage (I-V) measurements of single-pore membranes further verify that asymmetric pores exhibit lower resistance for the flow of ions and therefore show higher currents than cylindrical pores. Moreover, unmodified and polyethyleneimine (PEI) modified asymmetric-shaped pore membranes were successfully used for the separation of cationic and anionic analyte molecules from their mixture, respectively. In this study, two distinct effects (pore geometry and pore density, i.e. number of pores cm(-2)), which mainly influence membrane selectivity and molecular transport rates, were thoroughly investigated in order to optimize the membrane performance. In this context, we believe that membranes with high molecular transport rates could readily find their application in molecular separation and controlled drug delivery processes.
Synthesis and antibacterial and antifungal activities of N-(tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones. - Chemistry Central journal
Sydnone is a heterocycle that exhibits remarkable pharmacological activities, including antimicrobial, anti-inflammatory, analgesic, antipyretic and antioxidant activities. Thiosemicarbazones are of compounds that contain the -NHCSNHN=C< linkage group and are considerable interest because they exhibit important chemical properties and potentially beneficial biological activities. Similarly, thiosemicarbazones having carbohydrate moieties also exhibit various significant biological activities.The compounds of 3-formyl-4-phenylsydnones were obtained by Vilsmeyer-Haack's formylation reaction and were transformed into thiosemicarbazones by condensation reaction with N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazide. Reaction were performed in the presence glacial acetic acid as catalyst using microwave-assisted heating method. Reaction yields were 43‒85 %. The antimicrobial activities of these thiosemicarbazones were screened in vitro by using agar well diffusion and MIC methods. Among these thiosemicarbazones, compounds 4k, 4l, 4m and 4n were more active against all tested bacterial strains, especially against S. epidermidis, B. subtilis and E. coli. The MIC values in these cases are 0.156, 0.156 and 0.313 μg/mL, respectively. All compounds showed weak to moderate antifungal activity against C. albicans and A. niger than nystatin (MIC = 0.156‒0.625 μg/mL vs. MIC = 0.078 μg/mL of nystatin), and thiosemicarbazones 4l, 4m and 4n exhibited significant activity with MIC = 0.156 μg/mL. These compounds also had good antifungal activity against F. oxysporum similarly to nystatin (MIC = 0.156 μg/mL). Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against three strains of fungal organisms.In summary, we have developed a clean and efficient methodology for the synthesis of novel thiosemicarbazone derivatives bearing sydnone ring and d-glucose moiety; the heterocyclic and monosaccharide system being connected via ‒NH‒C(=S)NH‒N=C< linker using molecular modification approach. The methodology could be further extended and used for the synthesis of other thiosemicarbazones of biological importance. 4-Formyl-3-arylsydnone N-(2,3,4,6-tetra-O-acetyl-β-d-glucopyranosyl)thiosemicarbazones have been synthesized under microwave-assisted heating conditions. Almost all obtained compounds showed remarkable activities against the tested microorganisms. Among the tested compounds having halogen group 4k, 4l, 4m and 4n showed highest activity against all tested strains of bacterial and fungal organisms. Graphical abstract:Synthesis and antibacterial and antifungal activities of N-(tetra-O-acetyl-β-D-glucopyranosyl)thiosemicarbazones of substituted 4-formylsydnones.
Impact of a methadone maintenance therapy pilot in Vietnam and its role in a scaled-up response. - Harm reduction journal
As a dual response to the HIV epidemic and the high level of injecting drug use in Vietnam, the Ministry of Health (MOH) initiated a pilot methadone maintenance therapy (MMT) program in Hai Phong and Ho Chi Minh City (HCMC) in early 2009. The objectives of the pilot were to provide evidence on whether MMT could be successfully implemented in Vietnam and scaled up to other localities.A prospective study was conducted among 965 opiate drug users admitted to the pilot. Data on demographic characteristics, sexual behaviors, substance use behaviors (including heroin use), and blood-borne virus infection (HIV, hepatitis B, and hepatitis C) were collected at treatment initiation and then again at 3-, 6-, 9-, 12-, 18-, and 24-month intervals thereafter.Twenty-four months after treatment initiation, heroin use as measured by urine test or self-report had reduced from 100 % of participants at both sites to 14.6 % in Hai Phong and 22.9 % in HCMC. When adjusted for multiple factors in Generalized Estimating Equations (GEE) logistic regression modeling, independent predictors of continued heroin use after 24 months of MMT in HCMC were the following: poor methadone adherence (adjusted odds ratio (AOR) = 3.7, 95 % confidence interval (CI) 1.8-7.8); currently on antiretroviral treatment (ART) (AOR = 1.8, 95 % CI 1.4-2.4); currently on TB treatment (AOR = 2.2, 95 % CI 1.4-3.4); currently experiencing family conflict (AOR = 1.6, 95 % CI 1.1-2.4); and currently employed (AOR = 0.8, 95 % CI 0.6-1.0). For Hai Phong participants, predictors were the following: currently on ART (AOR = 2.0, 95 % CI = 1.4-3.0); currently experiencing family conflict (AOR = 2.0, 95 % CI = 1.0-3.9); and moderate adherence to methadone (AOR = 2.1, 95 % CI = 1.2-1.9). In Hai Phong, the percentage of participants who were employed had also increased by end of study from 35.0 to 52.8 %, while in HCMC the level remained relatively unchanged, between 52.2 and 55.1 %.Study findings were used in multiple fora to convince policymakers and the public on the significant and vital role MMT can play in reducing heroin use and improving quality of life for individuals and families. Four years after this study was completed, Vietnam had expanded MMT to 162 clinics in 44 provinces serving 32,000 patients.
Correlates of HIV infection among street-based and venue-based sex workers in Vietnam. - International journal of STD & AIDS
SummaryCommercial sex work is one of the driving forces of the HIV epidemic across the world. In Vietnam, although female sex workers carry a disproportionate burden of HIV, little is known about the risk profile and associated factors for HIV infection among this population. There is a need for large-scale research to obtain reliable and representative estimates of the measures of association. This study involved secondary data analysis of the 'HIV/STI Integrated Biological and Behavioral Surveillance' study in Vietnam in 2009-2010 to examine the correlates of HIV among female sex workers. Data collected from 5298 female sex workers, including 2530 street-based sex workers and 2768 venue-based sex workers from 10 provinces in Vietnam, were analyzed using descriptive statistics, bivariate and multivariate logistic regression analyses. HIV prevalence among the overall FSW population was 8.6% (n = 453). However, when stratified by female sex worker subpopulations, HIV prevalence was 10.6% (n = 267) for street-based sex workers and 6.7% (n = 186) for venue-based sex workers. Factors independently associated with HIV infection in multivariate analysis, regardless of sex work types, injecting drug use, high self-perceived HIV risk, and age ≥ 25 years. Additional factors independently associated with HIV risk within each female sex worker subpopulation included having ever been married among street-based sex workers and inconsistent condom use with clients and having sex partners who injected drugs among venue-based sex workers. Apart from strategies addressing modifiable risk behaviours among all female sex workers, targeted strategies to address specific risk behaviours within each female sex worker subpopulation should be adopted.© The Author(s) 2015.
Molecular dynamics studies of aqueous silica nanoparticle dispersions: salt effects on the double layer formation. - Journal of physics. Condensed matter : an Institute of Physics journal
The ion distribution around hydroxylated silica nanoparticles (NP-H) dispersed in brine was investigated by fully atomistic molecular dynamics. The NP-H dispersions in aqueous electrolyte media are simulated in solutions of varying salinity (NaCl, CaCl2, and MgCl2), salt concentration (0.06  ×  10(-3) to 3.00  ×  10(-3) mole fraction [Formula: see text]), and temperature (300 and 350 K) at 1 atm. The NP-H models reproduce the observed experimental concentration of silanol and geminal surface sites, which are responsible for local charge variations on the nanoparticles' surface. Interestingly, under certain salt concentration conditions, the formation of an electrical double layer (DL) around the overall neutral NP-H occurs. The resulting DLs are attenuated with increasing temperature for all evaluated salts. With increasing salt concentration, a sign inversion of the effective charge at the first ion layer is observed, which modifies the electrostatic environment around the nanoparticle. The minimum salt concentration that leads to a DL formation at 300 K is 1.05  ×  10(-3), 0.37  ×  10(-3), and 0.06  ×  10(-3) χs for NaCl, CaCl2, and MgCl2, respectively. The width of the DL decreases sequentially in ionic strength from NaCl to CaCl2 to MgCl2, which is similar to that found for highly charged surfaces. These results are in line with our previous experimental data for negative charged NP-H. All together, these observations suggest an interplay mechanism between the formation and narrowing of electric double layers on the stability of NP dispersions in both neutral and negatively charged NP-H.
Temperature dependent structural variations of OH(-)(H2O)n, n = 4-7: effects on vibrational and photoelectron spectra. - Physical chemistry chemical physics : PCCP
In this work, we identified a large number of structurally distinct isomers of midsized deprotonated water clusters, OH(-)(H2O)n=4-7, using first-principles methods. The temperature dependence of the structural variation in the solvation shell of OH(-) for these clusters was examined under the harmonic superposition approximation. We simulated the vibrational and photoelectron spectra based on these thermodynamic calculations. We found that the isomers with 3-coordinated hydroxide dominate the population in these midsized clusters. Furthermore, an increase in temperature causes a topological change from compact isomers with many intermolecular hydrogen bonds to open isomers with fewer but more directional intermolecular hydrogen bonds. We showed that this evolution in structure can be observed through the change in the vibrational spectra at 3200-3400 cm(-1). In addition, the increase in directional hydrogen bonded isomers, which have outer hydration shell with OH bonds pointing to the hydroxide, causes the vertical detachment energy to increase at higher temperatures. Lastly, we also performed studies to understand the variation in the aforementioned spectral quantities with the variation in the coordination number of the hydroxide.
Nuclear receptor Nurr1 agonists enhance its dual functions and improve behavioral deficits in an animal model of Parkinson's disease. - Proceedings of the National Academy of Sciences of the United States of America
Parkinson's disease (PD), primarily caused by selective degeneration of midbrain dopamine (mDA) neurons, is the most prevalent movement disorder, affecting 1-2% of the global population over the age of 65. Currently available pharmacological treatments are largely symptomatic and lose their efficacy over time with accompanying severe side effects such as dyskinesia. Thus, there is an unmet clinical need to develop mechanism-based and/or disease-modifying treatments. Based on the unique dual role of the nuclear orphan receptor Nurr1 for development and maintenance of mDA neurons and their protection from inflammation-induced death, we hypothesize that Nurr1 can be a molecular target for neuroprotective therapeutic development for PD. Here we show successful identification of Nurr1 agonists sharing an identical chemical scaffold, 4-amino-7-chloroquinoline, suggesting a critical structure-activity relationship. In particular, we found that two antimalarial drugs, amodiaquine and chloroquine stimulate the transcriptional function of Nurr1 through physical interaction with its ligand binding domain (LBD). Remarkably, these compounds were able to enhance the contrasting dual functions of Nurr1 by further increasing transcriptional activation of mDA-specific genes and further enhancing transrepression of neurotoxic proinflammatory gene expression in microglia. Importantly, these compounds significantly improved behavioral deficits in 6-hydroxydopamine lesioned rat model of PD without any detectable signs of dyskinesia-like behavior. These findings offer proof of principle that small molecules targeting the Nurr1 LBD can be used as a mechanism-based and neuroprotective strategy for PD.
Prospective Comparison of 18F-Fluoromethylcholine Versus 68Ga-PSMA PET/CT in Prostate Cancer Patients Who Have Rising PSA After Curative Treatment and Are Being Considered for Targeted Therapy. - Journal of nuclear medicine : official publication, Society of Nuclear Medicine
In prostate cancer with biochemical failure after therapy, current imaging techniques have a low detection rate at the prostate-specific antigen (PSA) levels at which targeted salvage therapy is effective. (11)C-choline and (18)F-fluoromethylcholine, though widely used, have poor sensitivity at low PSA levels. (68)Ga-PSMA (Glu-NH-CO-NH-Lys-(Ahx)-[(68)Ga-N,N'-bis[2-hydroxy-5-(carboxyethyl)benzyl]ethylenediamine-N,N'-diacetic acid]) has shown promising results in retrospective trials. Our aim was to prospectively compare the detection rates of (68)Ga-PSMA versus (18)F-fluoromethylcholine PET/CT in men who were initially managed with radical prostatectomy, radiation treatment, or both and were being considered for targeted therapy.A sample of men with a rising PSA level after treatment, eligible for targeted treatment, was prospectively included. Patients on systemic treatment were excluded. (68)Ga-PSMA, (18)F-fluoromethylcholine PET/CT, and diagnostic CT were performed sequentially on all patients between January and April 2015, and the images were assessed by masked, experienced interpreters. The findings and their impact on management were documented, together with the results of histologic follow-up when feasible.In total, 38 patients were enrolled. Of these, 34 (89%) had undergone radical prostatectomy and 4 (11%) had undergone radiation treatment. Twelve (32%) had undergone salvage radiation treatment after primary radical prostatectomy. The mean PSA level was 1.74 ± 2.54 ng/mL. The scan results were positive in 26 patients (68%) and negative with both tracers in 12 patients (32%). Of the 26 positive scans, 14 (54%) were positive with (68)Ga-PSMA alone, 11 (42%) with both (18)F-fluoromethylcholine and (68)Ga-PSMA, and only 1 (4%) with (18)F-fluoromethylcholine alone. When PSA was below 0.5 ng/mL, the detection rate was 50% for (68)Ga-PSMA versus 12.5% for (18)F-fluoromethylcholine. When PSA was 0.5-2.0 ng/mL, the detection rate was 69% for (68)Ga-PSMA versus 31% for (18)F-fluoromethylcholine, and when PSA was above 2.0, the detection rate was 86% for (68)Ga-PSMA versus 57% for (18)F-fluoromethylcholine. On lesion-based analysis, (68)Ga-PSMA detected more lesions than (18)F-fluoromethylcholine (59 vs. 29, P < 0.001). The tumor-to-background ratio in positive scans was higher for (68)Ga-PSMA than for (18)F-fluoromethylcholine (28.6 for (68)Ga-PSMA vs. 9.4 for (18)F-fluoromethylcholine, P < 0.001). There was a 63% (24/38 patients) management impact, with 54% (13/24 patients) being due to (68)Ga-PSMA imaging alone. Histologic follow-up was available for 9 of 38 patients (24%), and 9 of 9 (68)Ga-PSMA-positive lesions were consistent with prostate cancer ((68)Ga-PSMA was true-positive). The lesion positive on (18)F-fluoromethylcholine imaging and negative on (68)Ga-PSMA imaging was shown at biopsy to be a false-positive (18)F-fluoromethylcholine finding ((68)Ga-PSMA was true-negative).In patients with biochemical failure and a low PSA level, (68)Ga-PSMA demonstrated a significantly higher detection rate than (18)F-fluoromethylcholine and a high overall impact on management.© 2015 by the Society of Nuclear Medicine and Molecular Imaging, Inc.
Structural transition in Bcl-xL and its potential association with mitochondrial calcium ion transport. - Scientific reports
Bcl-2 family proteins are key regulators for cellular homeostasis in response to apoptotic stimuli. Bcl-xL, an antiapoptotic Bcl-2 family member, undergoes conformational transitions, which leads to two conformational states: the cytoplasmic and membrane-bound. Here we present the crystal and small-angle X-ray scattering (SAXS) structures of Bcl-xL treated with the mild detergent n-Octyl β-D-Maltoside (OM). The detergent-treated Bcl-xL forms a dimer through three-dimensional domain swapping (3DDS) by swapping helices α6-α8 between two monomers. Unlike Bax, a proapoptotic member of the Bcl-2 family, Bcl-xL is not converted to 3DDS homodimer upon binding BH3 peptides and ABT-737, a BH3 mimetic drug. We also designed Bcl-xL mutants which cannot dimerize and show that these mutants reduced mitochondrial calcium uptake in MEF cells. This illustrates the structural plasticity in Bcl-xL providing hints toward the probable molecular mechanism for Bcl-xL to play a regulatory role in mitochondrial calcium ion transport.

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