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N Nguyen

Publications and source records attributed to N Nguyen.

At least 37 records · Page 2Linked to original sources
PubMed2001

Stability-indicating HPLC assay and solution stability of a new diaziridinyl benzoquinone.

RH1, 3-methyl-6-hydroxymethyl-2,5-diaziridinyl-1,4-benzoquinone, is a NQO1 (NAD(P)H quinone oxidoreductase) directed anti-tumor agent. It is designed as a water soluble analog of MeDZQ (3,6-dimethyl-2,5-diaziridinyl-1,4-benzoquinone) and is a drug candidate for clinical evaluation. A HPLC assay has been developed for its analysis. The assay is sensitive (ldl<0.2 ng), precise (rsd<1%), linear (r(2)=0.9997), accurate (error<0.6%), and stability-indicating. Using the developed assay, aqueous stability of RH1 has been evaluated. Both aziridine rings in MeDZQ are known to be easily hydrolyzable in aqueous solutions, however, hydrolysis of the second aziridine ring in RH1 appears inhibited.

Aziridines↗
PubMed2001

Dynamic visualization of local protein synthesis in hippocampal neurons.

Using pharmacological approaches, several recent studies suggest that local protein synthesis is required for synaptic plasticity. Convincing demonstrations of bona fide dendritic protein synthesis in mammalian neurons are rare, however. We developed a protein synthesis reporter in which the coding sequence of green fluorescent protein is flanked by the 5' and 3' untranslated regions from CAMKII-alpha, conferring both dendritic mRNA localization and translational regulation. In cultured hippocampal neurons, we show that BDNF, a growth factor involved in synaptic plasticity, stimulates protein synthesis of the reporter in intact, mechanically, or "optically" isolated dendrites. The stimulation of protein synthesis is blocked by anisomycin and not observed in untreated neurons. In addition, dendrites appear to possess translational hot spots, regions near synapses where protein synthesis consistently occurs over time.

3' Untranslated Regions↗
PubMed2001

Cloning and expression of human sialic acid pathway genes to generate CMP-sialic acids in insect cells.

The addition of sialic acid residues to glycoproteins can affect important protein properties including biological activity and in vivo circulatory half-life. For sialylation to occur, the donor sugar nucleotide cytidine monophospho-sialic acid (CMP-SA) must be generated and enzymatically transferred to an acceptor oligosaccharide. However, examination of insect cells grown in serum-free medium revealed negligible native levels of the most common sialic acid nucleotide, CMP-N-acetylneuraminic acid (CMP-Neu5Ac). To increase substrate levels, the enzymes of the metabolic pathway for CMP-SA synthesis have been engineered into insect cells using the baculovirus expression system. In this study, a human CMP-sialic acid synthase cDNA was identified and found to encode a protein with 94% identity to the murine homologue. The human CMP-sialic acid synthase (Cmp-Sas) is ubiquitously expressed in human cells from multiple tissues. When expressed in insect cells using the baculovirus vector, the encoded protein is functional and localizes to the nucleus as in mammalian cells. In addition, co-expression of Cmp-Sas with the recently cloned sialic acid phosphate synthase with N-acetylmannosamine feeding yields intracellular CMP-Neu5Ac levels 30 times higher than those observed in unsupplemented CHO cells. The absence of any one of these three components abolishes CMP-Neu5Ac production in vivo. However, when N-acetylmannosamine feeding is omitted, the sugar nucleotide form of deaminated Neu5Ac, CMP-2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (CMP-KDN), is produced instead, indicating that alternative sialic acid glycoforms may eventually be possible in insect cells. The human CMP-SAS enzyme is also capable of CMP-N-glycolylneuraminic acid (CMP-Neu5Gc) synthesis when provided with the proper substrate. Engineering the CMP-SA metabolic pathway may be beneficial in various cell lines in which CMP-Neu5Ac production limits sialylation of glycoproteins or other glycans.

Amino Acid Sequence↗
PubMed2001

The contribution of UDP-glucuronosyltransferase 1A9 on CYP1A2-mediated genotoxicity by aromatic and heterocyclic amines.

The importance of environmental and dietary arylamines, and heterocyclic amines in the etiology of human cancer is of growing interest. These pre-carcinogens are known to undergo bioactivation by cytochrome P450 (CYP)-directed oxidation, which then become substrates for the UDP-glucuronosyltransferases (UGTs). Thus, glucuronidation may contribute to the elimination of CYP-mediated reactive intermediate metabolites, preventing a toxic event. In this study, human UGTs were analyzed for their ability to modulate the mutagenic actions of N-hydroxy-arylamines formed by CYP1A2. Studies with recombinant human UGT1A1, UGT1A3, UGT1A4, UGT1A6, UGT1A7, UGT1A8, UGT1A9, UGT1A10, UGT2B4, UGT2B7 and UGT2B15 expressed in heterologous cell culture confirmed that UGT1A9 glucuronidated the mutagenic arylamines N-hydroxy-2-acetylaminofluorene (N-hydroxy-2AAF) and 2-hydroxyamino-1-methyl-6-phenylimidazo(4,5-b)pyridine (N-hydroxy-PhIP). To examine the mutagenic potential of these agents, a genotoxicity assay was employed using Salmonella typhimurium NM2009, a bacterial strain expressing the umuC SOS response gene fused to a beta-galactosidase reporter lacZ gene. DNA modification results in the induction of the umuC gene and subsequent enhancement of beta-galactosidase activity. Both N-hydroxy-2AAF and N-hydroxy-PhIP stimulated a dose-dependent increase in bacterial beta-galactosidase activity. In addition, the procarcinogens 2AAF and PhIP were efficiently bioactivated to bacterial mutagens when incubated with Escherichia coli membranes expressing CYP1A2 and NADPH reductase. CYP1A2 generated 2AAF- and PhIP-mediated DNA damage, but only the action of N-hydroxy-2AAF was blocked by expressed UGT1A9. These results indicate that UGT1A9 can control the outcome of a genotoxic response. The results also indicate that while a potential toxicant such as N-hydroxy-PhIP can serve as substrate for glucuronidation, its biological actions can exceed the capacity of the detoxification pathway to prevent the mutagenic episode.

2-Acetylaminofluorene↗
PubMed2001

Requirement of cysteines and length of the human respiratory syncytial virus M2-1 protein for protein function and virus viability.

The M2-1 protein of human respiratory syncytial virus (hRSV) promotes processive RNA synthesis and readthrough at RSV gene junctions. It contains four highly conserved cysteines, three of which are located in the Cys(3)-His(1) motif at the N terminus of M2-1. Each of the four cysteines, at positions 7, 15, 21, and 96, in the M2-1 protein of hRSV A2 strain was individually replaced by glycines. When tested in an RSV minigenome replicon system using beta-galactosidase as a reporter gene, C7G, C15G, and C21G located in the Cys(3)-His(1) motif showed a significant reduction in processive RNA synthesis compared to wild-type (wt) M2-1. C96G, which lies outside the Cys(3)-His(1) motif, was fully functional in supporting processive RNA synthesis in vitro. Each of these cysteine substitutions was introduced into an infectious antigenomic cDNA clone derived from hRSV A2 strain. Except for C96G, which resulted in a viable virus, no viruses were recovered with mutations in the Cys(3)-His(1) motif. This indicates that the Cys(3)-His(1) motif is critical for M2-1 function and for RSV replication. The functional requirement of the C terminus of the M2-1 protein was examined by engineering premature stop codons that caused truncations of 17, 46, or 67 amino acids from the C terminus. A deletion of 46 or 67 amino acids abolished the synthesis of full-length beta-galactosidase mRNA and did not result in the recovery of viable viruses. However, a deletion of 17 amino acids from the C terminus of M2-1 reduced processive RNA synthesis in vitro and was well tolerated by RSV. Relocation of the M2-1 termination codon upstream of the M2-2 initiation codons did not significantly affect the expression of the M2-2 protein. Both rA2-Tr17 and rA2-C96G did not replicate as efficiently as wt rA2 in HEp-2 cells and was restricted in replication in the respiratory tracts of cotton rats.

Amino Acid Sequence↗
PubMed2001

Vietnamese diabetic patients and their physicians: what ethnography can teach us.

OBJECTIVES: To describe the cultural context of type 2 diabetes mellitus among Vietnamese immigrants in the United States, including people's ideas about cause and proper treatment; and to suggest ways in which better control of the disease can be achieved in this population. DESIGN: The method was ethnographic. A native speaker used a structured interview guide to talk with 38 Vietnamese patients, and family members of 2 other patients, being treated for type 2 diabetes. In addition, 8 Vietnamese health providers--5 physicians, 2 nurses, and an herbalist--were interviewed. SETTING: A low-income area of southern California populated by a large number of Vietnamese. PARTICIPANTS: Forty patients being treated for type 2 diabetes and 8 health practitioners. RESULTS: Three quarters of the patients had not achieved good control of their diabetes. Ideas about the cause and proper treatment of the disease were culturally shaped. Many patients used eastern (herbal) medicine and described a strong aversion to insulin injections. Patients stopped taking their oral medications when using eastern medicine, and a quarter lowered their dose whenever they felt "out of balance." Almost two thirds had used traditional home remedies for diabetes. Two had received nonstandard medical care from neighborhood physicians trained in Viet Nam; 1 of these patients died during the study. CONCLUSION: The Vietnamese community and physicians serving that community need culturally appropriate education about type 2 diabetes and modern therapy for the disease.

Aged↗
PubMed2001

Impact of sociodemographic characteristics on the identification rates of minority students as having mental retardation.

Ethnic disproportionality among students with mental retardation and relationships between disproportionality and sociodemographic factors were investigated. Using national data, we examined the effects of gender, ethnicity, and sociodemographic factors on the proportion of students identified as having mental retardation. Results indicate a clear association among ethnicity, gender, and mental retardation. Sociodemographic variables were also strongly associated with the proportion of students identified. A logistic regression model that included sociodemographic predictors was significantly better than models with gender and race alone. Findings indicate that both individual student characteristics and district sociodemographic characteristics were important in determining the likelihood of identification of mental retardation and that the impact of the sociodemographic characteristics is different for each gender/ethnicity group. Recommendations for future research are provided.

Child↗
PubMed2001

Acute profound thrombocytopenia without bleeding complications after re-administration of abciximab.

Abciximab (c7E3) is the Fab fragment of the chimeric (murine/human) monoclonal antibody directed against the platelet glycoprotein IIb/IIIa receptor, which is the final common pathway for platelet aggregation. Abciximab has been widely used for patients undergoing angioplasty who are at high risk for ischemic complications. Severe thrombocytopenia (defined as platelet count < 50,000 platelet/mm3) has been observed in both first-time administration and re-administration of abciximab. Platelet transfusion as treatment for the reversal of thrombocytopenia is ubiquitously accepted. Intravenous corticosteroid as an adjunctive therapy is being explored. We previously reported our experience with platelet transfusion combined with corticosteroid treatment for acute thrombocytopenia following first-time abciximab administration. We now report a case of acute profound thrombocytopenia following re-administration of abciximab successfully treated with a combination of platelet transfusion and intravenous corticosteroid.

Abciximab↗
PubMed2001

Management of cardiac arrhythmias in acute coronary syndromes.

A variety of atrial and ventricular arrhythmias are encountered in patients with acute coronary syndromes. These include both brady and tachyarrhythmias of supraventricular and ventricular origin. Sinus bradycardia and atrial fibrillation are the most common of supraventricular origin. Ventricular arrhythmias that merit consideration include premature ventricular complexes, accelerated idioventricular rhythm, ventricular tachycardia, and ventricular fibrillation. Intraventricular and atrioventricular conduction blocks associated with acute coronary syndromes include bundle branch blocks, fascicular blocks, and various degrees of atrioventricular block. A review of management of these arrhythmias is presented.

Angina, Unstable↗
PubMed2001

Management of unstable angina and non-ST-segment elevation myocardial infarction.

Most of the patients with acute coronary syndromes present with unstable angina or non-ST-segment elevation myocardial infarction. Recent advances in the diagnosis and treatment of these conditions have changed the management guidelines, allowing for better patient care. The purpose of this review is to summarize the current knowledge and present both established and new or evolving strategies used in the treatment of patients with unstable angina and non-ST-segment elevation myocardial infarction. Use of aspirin, nitrates, beta-blockers, calcium channel blockers, and anticoagulation with unfractionated heparin has been a common practice in these patients. While still effective and recommended, the emergence of new anticoagulants (low molecular weight heparins) and antiplatelet agents (ADP inhibitors and glycoprotein IIb/IIIa blockers) has added significant benefit to the treatment options and has resulted in a better prognosis for the patients. It also appears that, in view of recent trials, an early invasive approach is becoming the standard of care, especially for high-risk patients.

Angina, Unstable↗
PubMed2000

A mechanism for IL-10-mediated diabetes in the nonobese diabetic (NOD) mouse: ICAM-1 deficiency blocks accelerated diabetes.

Neonatal islet-specific expression of IL-10 in nonobese diabetic (NOD) mice accelerates the onset of diabetes, whereas systemic treatment of young NOD mice with IL-10 prevents diabetes. The mechanism for acceleration of diabetes in IL-10-NOD mice is not known. Here we show, by adoptive transfers, that prediabetic or diabetic NOD splenocytes upon encountering IL-10 in the pancreatic islets readily promoted diabetes. This outcome suggests that the compartment of exposure, not the timing, confers proinflammatory effects on this molecule. Moreover, injection of IL-10-deficient NOD splenocytes into transgenic IL-10-NOD.scid/scid mice elicited accelerated disease, demonstrating that pancreatic IL-10 but not endogenous IL-10 is sufficient for the acceleration of diabetes. Immunohistochemical analysis revealed hyperexpression of ICAM-1 on the vascular endothelium of IL-10-NOD mice. The finding suggests that IL-10 may promote diabetes via an ICAM-1-dependent pathway. We found that introduction of ICAM-1 deficiency into IL-10-NOD mice as well as into NOD mice prevented accelerated insulitis and diabetes. Failure to develop insulitis and diabetes was preceded by the absence of GAD65-specific T cell responses. The data suggest that ICAM-1 plays a role in the formation of the "immunological synapse", thereby affecting the generation and/or expansion of islet-specific T cells. In addition, ICAM-1 also played a role in the effector phase of autoimmune diabetes because adoptive transfer of diabetogenic BDC2.5 T cells failed to elicit clinical disease in ICAM-1-deficient IL-10-NOD and NOD mice. These findings provide evidence that pancreatic IL-10 is sufficient to drive pathogenic autoimmune responses and accelerates diabetes via an ICAM-1-dependent pathway.

Adoptive Transfer↗
PubMed2000

Uptake of radiolabeled 2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyluracil in cardiac cells after adenoviral transfer of the herpesvirus thymidine kinase gene: the cellular basis for cardiac gene imaging.

BACKGROUND: Gene therapy is a promising approach for the treatment of cardiac diseases. Coexpression of therapeutic genes with a suitable marker gene would allow for the noninvasive imaging of successful gene transfer and expression via radiolabeled marker substrates. In the present study, such an approach was first applied to cardiac tissue. METHODS AND RESULTS: The combination of the herpesvirus thymidine kinase reporter gene (HSV1-tk) and radiolabeled 2'-fluoro-2'-deoxy-5-iodo-1-beta-D-arabinofuranosyluracil (FIAU) was evaluated. H9c2 rat cardiomyoblasts were infected in vitro with a replication-defective HSV1-tk-containing adenovirus and a negative control virus. The intracellular uptake of [(14)C]FIAU increased with increasing multiplicity of infection and with time after infection. Uptake in negative controls remained <15% of positive controls. Additionally, vectors were applied intramyocardially in Wistar rats. The marker substrate [(125)I]FIAU was injected intravenously 3 days later, and animals were killed after 24 hours. Autoradiographically, regional transgene expression was clearly identified in animals receiving the adenovirus containing HSV1-tk (3. 4+/-2.2-fold increase of radioactivity at vector administration site compared with remote myocardium), whereas nonspecific uptake in negative controls was low (<10% of positive controls). CONCLUSIONS: Using an adenoviral vector, HSV1-tk can be successfully expressed in cardiac cells in vitro and in vivo, yielding high uptake of radiolabeled FIAU. The results suggest that imaging transgene expression in the heart is feasible and may be used to monitor gene therapy noninvasively.

Adenoviridae↗
PubMed2000

Identification of a novel chemokine (CCL28), which binds CCR10 (GPR2).

We report the identification and characterization of a novel CC chemokine designated CCL28 and its receptor CCR10, known previously as orphan G-protein-coupled receptor GPR2. Human and mouse CCL28 share 83% identity at the amino acid and 76% at the nucleic acid levels. We also identified the mouse homologues of CCL28 and of CCR10, which map to mouse chromosomes 13 and 11, respectively. CCL28 is expressed in a variety of human and mouse tissues, and it appears to be predominantly produced by epithelial cells. Both human and mouse CCL28 induce calcium mobilization in human and mouse CCR10-expressing transfectants. CCL28 desensitized the calcium mobilization induced in CCR10 transfectants by CCL27, indicating that these chemokines share this new chemokine receptor. In vitro, recombinant human CCL28 displays chemotactic activity for resting CD4 or CD8 T cells.

Amino Acid Sequence↗
PubMed2000

Recombinant respiratory syncytial viruses with deletions in the NS1, NS2, SH, and M2-2 genes are attenuated in vitro and in vivo.

Respiratory syncytial virus (RSV) encodes several proteins that lack well-defined functions; these include NS1, NS2, SH, and M2-2. Previous work has demonstrated that NS2, SH, and M2-2 can each be deleted from RSV genome and thus are considered as accessory proteins. To determine whether RSV can replicate efficiently when two or more transcriptional units are deleted, we removed NS1, NS2, SH, and M2-2 genes individually and in different combinations from an infectious cDNA clone derived from human RSV A2 strain. The following six mutants with two or more genes deleted were obtained: DeltaNS1NS2, DeltaM2-2SH, DeltaM2-2NS2, DeltaSHNS1, DeltaSHNS2, and DeltaSHNS1NS2. Deletion of M2-2 together with NS1 was detrimental to RSV replication. It was not possible to obtain a recombinant RSV when all four genes were deleted. All of the double and triple deletion mutants exhibited reduced replication and small plaque morphology in vitro. Replication of these deletion mutants was more reduced in HEp-2 cells than in Vero cells. Among the 10 single and multiple gene deletion mutants obtained, DeltaM2-2NS2 was most attenuated. DeltaM2-2NS2 formed barely visible plaques in HEp-2 cells and had a reduction of titer of 3 log(10) compared with the wild-type recombinant RSV in infected HEp-2 cells. When inoculated intranasally into cotton rats, all of the deletion mutants were attenuated in the respiratory tract. Our data indicated that the NS1, NS2, SH, and M2-2 proteins, although dispensable for virus replication in vitro, provide auxiliary functions for efficient RSV replication.

Animals↗
PubMed2000

Cloning and expression of the human N-acetylneuraminic acid phosphate synthase gene with 2-keto-3-deoxy-D-glycero- D-galacto-nononic acid biosynthetic ability.

Sialic acids participate in many important biological recognition events, yet eukaryotic sialic acid biosynthetic genes are not well characterized. In this study, we have identified a novel human gene based on homology to the Escherichia coli sialic acid synthase gene (neuB). The human gene is ubiquitously expressed and encodes a 40-kDa enzyme. The gene partially restores sialic acid synthase activity in a neuB-negative mutant of E. coli and results in N-acetylneuraminic acid (Neu5Ac) and 2-keto-3-deoxy-D-glycero-D-galacto-nononic acid (KDN) production in insect cells upon recombinant baculovirus infection. In vitro the human enzyme uses N-acetylmannosamine 6-phosphate and mannose 6-phosphate as substrates to generate phosphorylated forms of Neu5Ac and KDN, respectively, but exhibits much higher activity toward the Neu5Ac phosphate product.

Amino Acid Sequence↗
PubMed2000

Stability-indicating high-performance liquid chromatographic assay and analysis of decomposition products of 2-[4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy]propanoic acid.

A stability-indicating HPLC assay has been developed for 2-[4-[(7-chloro-2-quinoxalinyl)oxy]phenoxy]propanoic acid (XK469). XK-469 is the 7-chloro analog of herbicide Quizalofop and is currently under development as an antineoplastic agent. HPLC separation of XK469 is achieved with an ODS column using isocratic elution of an aqueous MeOH mobile phase. The assay is reproducible (RSD=0.9%), linear (r2=0.999), accurate (error=1.2%) and sensitive (LDL=1.2 ng). The HPLC separates XK469 from its forced decomposition products. Identities of the decomposition products have been elucidated.

Chromatography, High Pressure Liquid↗
PubMed2000

Kinetic Comparison of Trifluoroacetic Acid Cleavage Reactions of Resin-Bound Carbamates, Ureas, Secondary Amides, and Sulfonamides from Benzyl-, Benzhydryl-, and Indole-Based Linkers.

The kinetics of cleavage reactions of 16 resin-bound carbamates, ureas, secondary amides, and sulfonamides from four different acid labile linkers including benzyl, benzhydryl, and indole linkers has been investigated. The optimized cleavage conditions are generally milder than those commonly used and reported (e.g., 0.5% TFA as opposed to 5%). Among various linkers studied in this work, the indole linker has been found to be the most acid labile followed by the Rink linker. The rate of cleavage of compounds linked to the resin via various functional groups can be summarized as follows: sulfonamide >carbamate approximately urea > amide. This study shows that cleavages of 16 compounds from four different acid labile linkers have been optimized to much milder conditions in terms of TFA concentration and the reaction time. It also demonstrates that single bead FTIR is an effective tool for optimizing cleavage conditions.

Journal Article↗