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Biomedical subjects

P Tran

Publications and source records attributed to P Tran.

At least 19 recordsLinked to original sources
PubMed2001

Interleukin 15-mediated induction of cytotoxic effector cells capable of eliminating Epstein-Barr virus-transformed/immortalized lymphocytes in culture.

BACKGROUND: Interleukin 15 (IL-15) activates cytotoxic lymphocytes and drives the expansion of memory T cells. Its role in immune control of virus-transformed cells and other tumor cells remains to be elucidated. We investigated the role of IL-15 in controlling Epstein-Barr virus (EBV)-transformed/immortalized lymphocytes in culture. EBV is a highly potent lymphocyte-transforming and opportunistic oncogenic herpesvirus associated with several human tumors. METHODS: Peripheral blood mononuclear cells (PBMCs) from healthy donors were infected with EBV and cultured with either IL-15 or IL-15 plus anti-IL-15 antibodies for 3-4 weeks. We monitored EBV-induced transformation by assessing the clearly visible cell clusters by microscopy and analyzing the expression of EBV-encoded latent membrane oncoprotein-1 (LMP-1) and the EBV nuclear antigen (EBNA) complex by immunoblotting and immunofluorescence techniques, respectively. We depleted EBV-infected cultures of PBMCs of specific effector cell populations to investigate the effector cells involved in mediating IL-15 effect. RESULTS: The presence of IL-15 resulted in the complete elimination of EBV-transformed cells in PBMC cultures. Western blot and immunofluorescence analyses performed 3-4 weeks after infection showed no detectable levels of LMP-1 and EBNA in IL-15-treated EBV-infected cultures, whereas IL-15-untreated EBV-infected cultures and IL-15/anti-IL-15-treated cultures expressed both proteins. IL-15 mediated its anti-EBV effect through early and late response mechanisms, i.e., by first activating natural killer (NK) cells and subsequently inducing cytolytic NK-T cells. The presence of anti-IL-15 neutralizing antibodies abrogated IL-15's effect on both mechanisms. CONCLUSION: In vitro, IL-15 mediated complete elimination of EBV-infected/transformed lymphocytes via successive activation of NK and NK-T cytotoxic effectors. If these in vitro findings reflect in vivo mechanisms, then IL-15 might be considered for cytokine-based immunotherapy in patients with EBV-associated lymphoproliferative disorders/malignancies.

B-Lymphocytes↗
PubMed2001

Anthraquinone-peptides as inhibitors of AP-1 transcription factor.

Peptide-1-[N-[2-succinamidylethyl]amino]anthraquinones containing five seven amino acid residues including the KCR motif important in AP-1 protein binding to DNA have been synthesised as potential transcription factor inhibitors. These anthraquinone-peptides showed DNA intercalative binding and inhibition of AP-1 protein binding to its DNA consensus sequence.

Amino Acid Motifs↗
PubMed2001

A double-blind, randomized comparison of the efficacy and safety of intramuscular injections of olanzapine, lorazepam, or placebo in treating acutely agitated patients diagnosed with bipolar mania.

There are no rapid-acting intramuscular formulations of atypical antipsychotics available for quickly calming an agitated patient with bipolar disorder. In this study, 201 agitated patients with bipolar mania were randomly assigned to receive one to three injections of the atypical antipsychotic olanzapine (10 mg, first two injections; 5 mg, third injection), the benzodiazepine lorazepam (2 mg, first two injections; 1 mg, third injection), or placebo (placebo, first two injections; olanzapine, 10 mg, third injection) within a 24-hour period. Agitation was measured at baseline, every 30 minutes for the first 2 hours, and at 24 hours after the first injection using the Positive and Negative Syndrome Scale-Excited Component subscale and two additional agitation scales. At 2 hours after the first injection, patients treated with olanzapine showed a significantly greater reduction in scores on all agitation scales compared with patients treated with either placebo or lorazepam. At 24 hours after the first injection, olanzapine remained statistically superior to placebo in reducing agitation in patients with acute mania, whereas patients treated with lorazepam were not significantly different from those treated with placebo or olanzapine. Furthermore, no significant differences among the three treatment groups were observed in safety measures, including treatment-emergent extrapyramidal symptoms, the incidence of acute dystonia, or QTc interval changes. These findings suggest that intramuscular olanzapine is a safe and effective treatment for reducing acute agitation in patients with bipolar mania.

Adult↗
PubMed2001

Methanol solvent may cause increased apparent metabolic instability in in vitro assays.

Methanol was widely used as a substrate-delivering solvent in in vitro metabolic stability screenings. Its interaction with enzyme activities, particularly those of cytochrome P450s, has been investigated extensively in the past. Little was known about the interaction of methanol, whether direct or indirect, with substrates. The present study provided data for the first time to show that use of methanol may result in the formation of artifacts, which could mislead the metabolic stability information. The disappearance of LAQ094, metaraminol, and (-)-isoproterenol following 1-h incubation with human liver microsomes was 73, 85, and 66%, respectively, in the presence of 1% methanol, but was only 3, 15, and 24%, respectively, in the absence of organic solvent. The dramatically increased instability in the presence of methanol of these three compounds, each with 1,2-diamino or 1,2-amino hydroxy functional groups, was due to the formation of [M + 12] products resulting from condensation reaction of the substrates with formaldehyde. Formaldehyde was formed from methanol by human liver microsomal enzymes with an apparent K(m) of 35 mM and a V(max) of 7.9 nmol/min/mg of protein. The concentration of formaldehyde reached as high as 600 microM following a 60-min incubation. The [M + 12] products were characterized as five-membered heterocycles by liquid chromatography and tandem mass spectrometry analysis. Inclusion of 10 mM glutathione prevented the formation of such artifacts and is therefore suggested for future in vitro screenings. Our study also documented the novel finding of enzyme-dependent conversion of NADPH to nicotinamide in microsomal incubations.

Cytochrome P-450 Enzyme System↗
PubMed2001

Modulation of expression of the MHC class I-binding natural killer cell receptors, and NK activity in relation to viral load in HIV-infected/AIDS patients.

The natural killer (NK) cells play an important role in viral infections via their spontaneous cytolytic activity against virus-infected cells as well as via secreting a variety of soluble mediators. The MHC class I-binding NK receptors of these cells have emerged as the most important regulators of the effector activities of cytolytic cells (both NK and CTL). We have studied the modulation of NK activity and the expression of NK receptors in HIV-infected/AIDS patients and report here that the NK activities of the patients with the lowest plasma HIV load were minimal and vice versa, suggesting a decrease in this activity following suppression of HIV replication. Interestingly, the NK activity correlated negatively with the peripheral blood CD4+ T-cell counts of these patients. Furthermore, these patients showed decreased percentages of CD56+ cells expressing NK receptors of the immunoglobulin superfamily, whereas the percentages of CD8+ cells expressing these receptors were increased. Moreover, the expression of C-type lectin-like NK receptor-associated invariant molecule CD94 was increased on CD8+ cells in these patients as compared with HIV-seronegative controls. These changes in the expression of NK receptors were also evident within groups of these patients having different viral loads. These results show, for the first time, decreased innate immunity and changes in the expression of NK receptors on cytolytic cells in relation to viral burden in HIV-infected/AIDS patient.

Adult↗
PubMed2000

Charge transport along the lambda-DNA double helix.

We have measured the conductivity sigma along the lambda phage DNA (lambda-DNA) double helix at microwave frequencies using lyophilized DNA in and also without a buffer. The conductivity is strongly temperature dependent around room temperature with a crossover to a weakly temperature dependent conductivity at low temperatures. Removal of the water mantle around the double helix leads to reduced conductivity.

Bacteriophage lambda↗
PubMed2000

Trained nurses can provide safe and effective sedation for MRI in pediatric patients.

PURPOSE: To determine the success rate, safety and complications using a standard protocol and trained nurses to provide sedation for MRI under the supervision of a radiologist. MATERIALS AND METHODS: Nurses were trained to provide sedation via a standard protocol for pediatric patients undergoing diagnostic MRI. Oral chloral hydrate (80-100 mg x kg(-1)) was used for children less than 18 mo of age. Older children received either 1-6 mg x kg(-1) pentobarbital i.v., with or without 1-2 microg x kg x hr(-1) fentanyl, or 25 mg x kg(-1) thiopental pr. Sedation was defined as successful if it allowed completion of the MRI without image distorting patient movement. The records of 572 MRIs performed on 488 pediatric patients (mean age 5+/-4 yr; age 2 mo-14 yr) from 1991 to July 1995 were reviewed to determine the success rate and complications using the sedation program. RESULTS: Most, 91.8% (525/572), of the MRIs were successfully completed in 445 patients. The reasons for failure were inadequate sedation (45, 95.7%) and coughing (2, 4.2%). The failure rate was much higher before 1994 (38/272, 14%) than after (9/300, 3%; P<0.0001). Failure was more common if rectal thiopental was used (23/172, 14%) than intravenous pentobarbital (19/256, 7.4%; P<0.05). The failure rate was also high in patients with a history of a behavioural disorder (10/59, 17%). There were no deaths or unexpected admissions as a result of the sedation program. CONCLUSION: A high success rate can be achieved as experience is gained using a standard protocol and trained nurses to sedate children for MRI.

Administration, Rectal↗
PubMed2000

Hunger in legal immigrants in California, Texas, and Illinois.

OBJECTIVES: This study determined the prevalence of food insecurity and hunger in low-income legal immigrants. METHODS: We conducted a cross-sectional survey of Latino and Asian legal immigrants attending urban clinics and community centers in California, Texas, and Illinois with a food security questionnaire. RESULTS: Among 630 respondents, 40% of the households were food insecure without hunger and 41% were food insecure with hunger. Independent predictors of hunger were income below federal poverty level (odds ratio [OR] = 2.72, 95% confidence interval [CI] = 1.72, 4.30), receipt of food stamps (OR = 2.53, 95% CI = 1.57, 4.09), Latino ethnicity (OR = 2.39, 95% CI = 1.49, 3.82), and poor English (OR = 1.76, 95% CI = 1.10, 2.82). CONCLUSIONS: The prevalence of hunger among low-income legal immigrants is unacceptably high. Access to food assistance programs is important for the health and well-being of this population.

Adult↗
PubMed1999

Genetic polymorphisms in methylenetetrahydrofolate reductase and methionine synthase, folate levels in red blood cells, and risk of neural tube defects.

Folic acid administration to women in the periconceptional period reduces the occurrence of neural tube defects (NTDs) in their offspring. A polymorphism in the gene encoding methylenetetrahydrofolate reductase (MTHFR), 677C-->T, is the first genetic risk factor for NTDs in man identified at the molecular level. The gene encoding another folate-dependent enzyme, methionine synthase (MTR), has recently been cloned and a common variant, 2756A-->G, has been identified. We assessed genotypes and folate status in 56 patients with spina bifida, 62 mothers of patients, 97 children without NTDs (controls), and 90 mothers of controls, to determine the impact of these factors on NTD risk. Twenty percent of cases and 18% of case mothers were homozygous for the MTHFR polymorphism, compared to 11% of controls and 11% of control mothers, indicating that the mutant genotype conferred an increased risk for NTDs. The risk was further increased if both mother and child had this genotype. The MTR polymorphism was associated with a decreased O.R. (O.R.); none of the cases and only 10% of controls were homozygous for this variant. Red blood cell (RBC) folate was lower in cases and in case mothers, compared to their respective controls. Having a RBC folate in the lowest quartile of the control distribution was associated with an O.R. of 2.56 (95% CI 1.28-5.13) for being a case and of 3.05 (95% CI 1.54-6.03) for being a case mother. The combination of homozygous mutant MTHFR genotype and RBC folate in the lowest quartile conferred an O.R. for being a NTD case of 13.43 (CI 2.49-72.33) and an O.R. for having a child with NTD of 3.28 (CI 0.84-12.85). We propose that the genetic-nutrient interaction--MTHFR polymorphism and low folate status--is associated with a greater risk for NTDs than either variable alone.

5-Methyltetrahydrofolate-Homocysteine S-Methyltran↗
PubMed1999

Somatosensory stimulus entrains spindle oscillations in the thalamic VPL nucleus in barbiturate anesthetized rats.

This study reports the effect of external stimuli on spindle oscillations in the somatosensory thalamus of barbiturate anesthetized rats. Multi-unit responses to somatosensory stimuli were measured from the contralateral thalamic ventral posterior lateral (VPL) nucleus at different stimulus strengths and periods. Spindle oscillations could be entrained by the somatosensory stimuli at periods between 2 and 5 s. A resonance phenomenon described as a quiescent pre-stimulus period followed by entrained post-stimulus oscillations, was observed for somatosensory stimuli above the threshold for eliciting cortical evoked potentials and a stimulus period between 2 and 5 s. This study demonstrates an ascending pathway for localized modulation of spindle oscillations.

Anesthesia↗
PubMed1999

Total pancreatectomy with islet cell autotransplantation: anesthetic implications.

STUDY OBJECTIVE: To make recommendations for the perioperative management of patients undergoing total pancreatectomy with islet cell autotransplantation. DESIGN: Retrospective review. SETTING: University hospital. PATIENTS: 41 patients undergoing total pancreatectomy with autologous islet cell transplantation for chronic pancreatitis from 1977 to 1996. INTERVENTIONS: The charts and anesthetic records were reviewed, specifically investigating the changes in portal venous pressure, blood pressure (BP), and central venous pressure with islet cell injection. The records also were examined for blood glucose levels, type of fluids administered, blood loss, and postoperative complications. MEASUREMENTS AND MAIN RESULTS: Injection of islet cells into the portal vein caused a significant increase in portal venous pressures (8.5 +/- 4.8 to 27 +/- 16 cm/H2O; p < 0.001), which remained elevated at the end of injection (23 +/- 12 cm/H2O; p < 0.001). Central venous pressures also increased a small amount (9.3 +/- 4.3 to 10.6 +/- 5.8 mmHg; p < 0.05). In contrast, systolic blood pressures (SBPs) fell with administration of the islet cells (110 +/- 15 to 103 +/- 17 mmHg; p < 0.01), but SBP recovered in most patients at the end of injection (106 +/- 16 mmHg; p = NS). However, 6 patients (14.6%) required vasopressors to maintain adequate BPs. Blood glucose levels were significantly higher immediately prior to islet cell infusion in patients who had received dextrose-containing solutions than those who did not (246 +/- 80 vs. 176 +/- 43 gm/dl; p = 0.002). Median blood loss was 2000 ml (range 350 to 12,000 ml), and most patients (95.1%) required blood transfusions. CONCLUSION: Although total pancreatectomy with islet cell autotransplantation is a difficult operation, with significant blood loss, most patients tolerate surgery and injection of islet cells into their portal system without hemodynamic instability. Glucose-containing solutions should not be administered to patients prior to islet cell infusion because hyperglycemia, which can damage islet cells, may result.

Adolescent↗
PubMed1999

The structure and properties of methylenetetrahydrofolate reductase from Escherichia coli suggest how folate ameliorates human hyperhomocysteinemia.

Elevated plasma homocysteine levels are associated with increased risk for cardiovascular disease and neural tube defects in humans. Folate treatment decreases homocysteine levels and dramatically reduces the incidence of neural tube defects. The flavoprotein methylenetetrahydrofolate reductase (MTHFR) is a likely target for these actions of folate. The most common genetic cause of mildly elevated plasma homocysteine in humans is the MTHFR polymorphism A222V (base change C677-->T). The X-ray analysis of E. coli MTHFR, reported here, provides a model for the catalytic domain that is shared by all MTHFRs. This domain is a beta8alpha8 barrel that binds FAD in a novel fashion. Ala 177, corresponding to Ala 222 in human MTHFR, is near the bottom of the barrel and distant from the FAD. The mutation A177V does not affect Km or k(cat) but instead increases the propensity for bacterial MTHFR to lose its essential flavin cofactor. Folate derivatives protect wild-type and mutant E. coli enzymes against flavin loss, and protect human MTHFR and the A222V mutant against thermal inactivation, suggesting a mechanism by which folate treatment reduces homocysteine levels.

Amino Acid Sequence↗
PubMed1999

Four amino acid changes are associated with the Aldh3a1 locus polymorphism in mice which may be responsible for corneal sensitivity to ultraviolet light.

We studied the phenotype and the nucleotide sequence for the cDNAs of the Aldh3a1a and Aldh3a1c allelic forms of the dioxin-inducible cytosolic aldehyde dehydrogenase (ALDH3A1) present in inbred mouse strains. This gene is constitutively expressed in cornea, stomach, skin, urinary bladder and lungs. The Aldh3a1a allele is found in most inbred mouse strains and codes for a 'high-activity' corneal enzyme compared to the 'low-activity' encoded by the Aldh3a1c allele in SWR/J strain. The 'low-activity' variant is associated with extensive corneal clouding after a single exposure to ultraviolet light. The ALDH3A1 phenotype was examined in tissues from inbred mouse strains carrying the Aldh3a1a allele including, SJL/J, C57BL/6 J/Ibg, DBA/2 J/Ibg, C3H/Ibg and the Aldh3a1c allele (SWR/J). Only trace levels of ALDH3A1 activity were found in all SWR/J tissues. All other strains had significant levels of ALDH3A1 activity in eye, stomach, skin, less in urinary bladder and lungs and only trace amounts in liver. However, no differences were found in corneal and stomach ALDH3A1 mRNA levels between the 'low-' and 'high-activity' variants. A 1556-bp ALDH3A1 cDNA fragment, containing the entire coding region plus 5' and 3' untranslated regions, was amplified by reverse transcriptase-polymerase chain reaction from SWR/J and DBA/2 J/Ibg mouse strains. Sequence analysis revealed 13 nucleotide changes in the Aldh3a1c allele. Four of these changes result in G88R, I154N, H305R and I352V substitutions, whereas nine changes are silent. The I154N disrupts a potential alpha helix, which belongs to the Rossmann fold. Replacement of Arg with the more ionizable His at position 305 of a beta strand might directly affect catalytic activity of the enzyme. It is likely that structural changes associated with these amino acid changes are responsible for the loss of ALDH3A1 enzymatic activity in SWR/J mice.

Aldehyde Dehydrogenase↗
PubMed1998

A second genetic polymorphism in methylenetetrahydrofolate reductase (MTHFR) associated with decreased enzyme activity.

A common mutation in methylenetetrahydrofolate reductase (MTHFR), C677T, results in a thermolabile variant with reduced activity. Homozygous mutant individuals (approximately 10% of North Americans) are predisposed to mild hyperhomocysteinemia, when their folate status is low. This genetic-nutrient interactive effect is believed to increase the risk for neural tube defects and vascular disease. In this communication, we characterize a second common variant in MTHFR (A1298C), an E to A substitution. Homozygosity was observed in approximately 10% of Canadian individuals. This polymorphism was associated with decreased enzyme activity; homozygotes had approximately 60% of control activity in lymphocytes. Heterozygotes for both the C677T and the A1298C mutation, approximately 15% of individuals, had 50-60% of control activity, a value that was lower than that seen in single heterozygotes for the C677T variant. No individuals were homozygous for both mutations. Additional studies of the A1298C mutation, in the absence and presence of the C677T mutation, are warranted, to adequately address the role of this new genetic variant in complex traits. A silent genetic variant, T1317C, was identified in the same exon. It was relatively infrequent (allele frequency 5%) in our study group, but was quite common in a small sample of African individuals (allele frequency 39%).

Adult↗
PubMed1998

Gene structure of human and mouse methylenetetrahydrofolate reductase (MTHFR)

Methylenetetrahydrofolate reductase (MTHFR) catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine. A human cDNA for MTHFR, 2.2 kb in length, has been expressed and shown to result in a catalytically active enzyme of approximately 70 kDa. Fifteen mutations have been identified in the MTHFR gene: 14 rare mutations associated with severe enzymatic deficiency and 1 common variant associated with a milder deficiency. The common polymorphism has been implicated in three multifactorial diseases: occlusive vascular disease, neural tube defects, and colon cancer. The human gene has been mapped to chromosomal region 1p36.3 while the mouse gene has been localized to distal Chromosome (Chr) 4. Here we report the isolation and characterization of the human and mouse genes for MTHFR. A human genomic clone (17 kb) was found to contain the entire cDNA sequence of 2.2 kb; there were 11 exons ranging in size from 102 bp to 432 bp. Intron sizes ranged from 250 bp to 1.5 kb with one exception of 4.2 kb. The mouse genomic clones (19 kb) start 7 kb 5' exon 1 and extend to the end of the coding sequence. The mouse amino acid sequence is approximately 90% identical to the corresponding human sequence. The exon sizes, locations of intronic boundaries, and intron sizes are also quite similar between the two species. The availability of human genomic clones has been useful in designing primers for exon amplification and mutation detection. The mouse genomic clones will be helpful in designing constructs for gene targeting and generation of mouse models for MTHFR deficiency.

Amino Acid Sequence↗
PubMed1997

Identification of DNA methylation markers for human breast carcinomas using the methylation-sensitive restriction fingerprinting technique.

We have developed a PCR-based method, called methylation-sensitive restriction fingerprinting (MSRF), to screen changes in DNA methylation in breast carcinomas. Two hypermethylation-containing fragments, HBC-1 (for "hypermethylation in breast cancer") and HBC-2, were identified in the amplified breast tumor DNA relative to the amplified normal breast DNA of a patient. Nucleotide sequence analysis revealed no significant matches between the sequence of HBC-1 and the known sequences in the GenBank database, whereas the sequence of HBC-2 matched the upstream region of an antisense WT1 (Wilms' tumor suppressor gene) promoter. The methylation status in the breast tumor DNA from this patient was confirmed by Southern hybridization using HBC-1 and HBC-2 as probes, respectively. Further analysis showed that HBC-1 was methylated aberrantly in 90% (17 of 19 patients) of the primary breast carcinomas examined. This study demonstrates that MSRF provides a useful means for screening aberrant changes in DNA methylation during tumorigenesis. The commonly methylated fragments identified by MSRF could potentially supplement pathological markers currently used for cancers and additionally lead to the discovery of novel methylated tumor suppressor genes.

Base Sequence↗
PubMed1997

Polarized light microscopy and digital image processing identify a multilaminar structure of the hamster zona pellucida.

The zona pellucida (zona) is a glycoprotein coat that envelopes the oocyte and embryo, binds sperm during fertilization and facilitates transfer of the embryo through the Fallopian tube. Before implantation can occur, the blastocyst must hatch from the zona. Several lines of evidence suggest that the zona is multilaminar. We hypothesized that the multilaminar structure of the zona filaments could be imaged non-destructively with the polarized light microscope. A recent modification of the polarized light microscope (pol-scope), which combines innovations in polarization optics with novel image processing software, allows measurement of birefringence at all points of the image. Hamster metaphase II oocytes were placed on glass coverslips which replaced the bottom of culture dishes, imaged under differential interference contrast (DIC) and pol-scope optics, then digitized and processed to measure birefringence magnitude and orientation. The pol-scope revealed the zona to be divided into outer and inner layers separated by a zone of low retardance. This finding is consistent with filaments in the outer layer oriented tangentially and in the inner layer oriented radially. The multilaminar structure of the mammalian zona suggested by differential lectin binding and by scanning electron microscopy could be imaged non-destructively with the pol-scope. Because the pol-scope provides a non-destructive method to identify macro-molecular organization of the zona, it may prove useful in developmental studies of hatching and to direct resection of the zona.

Animals↗