Biomedical subjects

L Tran

Publications and source records attributed to L Tran.

At least 19 recordsLinked to original sources

PubMed2001

Hepatocyte targeting with Gd-EOB-DTPA: potential application for gene therapy.

RATIONALE AND OBJECTIVES: To evaluate the suitability of the liver-specific MRI contrast agent Gd-EOB-DTPA as a nonviral vector for gene therapy of hepatocellular carcinoma. METHODS: Specific uptake of Gd-EOB-DTPA was quantified by relaxometry in rat cultured hepatocytes and the hepatoma cells HepG2 and Huh7. Nonviral vectors for gene transfer were synthesized by coupling Gd-EOB-DTPA to polyethyleneimine or polylysine as DNA condensing agents, and their efficiency was studied using beta-galactosidase (lacZ) as the reporter gene. RESULTS: Gd-EOB-DTPA was specifically taken up by rat cultured hepatocytes (4.32 vs. 1.08 mmol/L in nonhepatocyte control cells) but not by the hepatoma cells; this uptake was concentration-dependently inhibited by Bromsulphtalein. Polycation linkages were achieved with yields of 0.9 Gd-EOB-DTPA molecule per polyethyleneimine molecule and 10 Gd-EOB-DTPA molecules per polylysine molecule. Incubating the cells with plasmids containing lacZ reporter gene and polyethyleneimine-Gd-EOB-DTPA resulted in a few blue (transfected) cells, whereas no blue cells were observed on incubation with polylysine-Gd-EOB-DTPA. CONCLUSIONS: Gd-EOB-DTPA is taken up by normal hepatocytes but not by HepG2 and Huh7 cells, probably because of the lack of the organic anion transporter in these hepatoma cells. The Gd-EOB-DTPA polycation conjugates, such as polyethyleneimine-Gd-EOB-DTPA, could serve as transfer vectors of interest for gene targeting imagery at the early stage of hepatocarcinogenesis. However, the transfer efficiency of such conjugates is low and requires improvement.

Animals↗

PubMed2001

Strain differences in the expression of corticotropin-releasing hormone immunoreactivity in nerves that supply the spleen and thymus.

The existence of nerve fibers containing corticotropin-releasing hormone (CRH) immunoreactivity in primary and secondary lymphoid organs from three strains of young adult male rats was examined. Spleens and thymuses from Fischer 344 (F344), Sprague-Dawley (SD) and Lewis (LEW) rats were prepared for immunocytochemistry using antisera directed against CRH. In F344 and SD rats, we were unable to demonstrate CRH-immunoreactive nerves in either the thymus or the spleen. Despite the lack of CRH-containing nerves, CRH immunoreactivity was present in pleotropic cells in the septum, cortex and medulla of the thymus, and in the red and white pulp of spleens from F344 and SD rats. In contrast, CRH+ nerves were found in thymuses and spleens from LEW rats. CRH+ nerves coursed in the interlobular septa, capsule, cortex and medulla of the LEW rat thymus. Large CRH-immunoreactive nerve bundles were present in the hilar region of the LEW rat spleen, and individual CRH+ fibers coursed in the capsule, trabeculae, red pulp, venous sinuses and marginal zone of the white pulp of the spleen. These findings indicate strain differences in neurotransmitter-specific nerves that innervate the rat spleen and thymus under basal conditions.

Animals↗

PubMed2000

Erratum

Explore the source record for details and available documents.

Journal Article↗

PubMed2000

Model-free sib-pair linkage analysis: combining full-sib and half-sib pairs.

When sampling full-sibs for linkage studies, half-sibs are often available. Not only are half-sibs convenient to sample, but they can sometimes offer greater power than full-sibs. We propose a method to combine the information from full-sibs and half-sibs into a single test for linkage. This method is based on the Haseman and Elston [1972] method of regressing the squared trait-difference for a pair of sibs (either full- or half-sibs) on the estimated proportion of alleles shared identical by descent. To approximate the distribution of the test statistic, we propose a correction factor that considers the correlation among sibs, and demonstrate by simulations that this approximation works well in many situations, although there are some conditions for which the statistic can have an inflated Type-I error rate. The main appeal of our proposed method is the speed at which it can be computed, offering a rapid way to perform genome-wide linkage screens.

Alleles↗

PubMed2000

Accuracy and clinical impact of mediastinal lymph node staging with FDG-PET imaging in potentially resectable lung cancer.

To determine the sensitivity, specificity, and accuracy of staging mediastinal nodal disease in potentially resectable lung cancer using fluorodeoxyglucose-positron emission tomography (FDG-PET), computed tomography (CT), or both and compare these results to surgical staging. We also assessed whether PET scanning results changed clinical management. From 1992 to 1997, 50 patients underwent CT, and PET scanning before or close to the time of surgical staging. Sensitivity, specificity, accuracy, and predictive values were then calculated based on pathology results. A retrospective review of the records was performed to determine how PET results affected clinical treatment decisions. Forty-seven of 50 patients had non-small-cell lung cancer. The prevalence of pathologically confirmed mediastinal and hilar involvement was 38%. The sensitivity, specificity, and accuracy of mediastinal disease staging were as follows: CT alone = 73%, 77%, 76%; PET alone = 73%, 94%, 87%; PET + CT = 82%, 96%, 91%, respectively. PET was more specific and accurate than CT (p = 0.025). The results of PET changed management decisions in 12 of 50 cases (24%). Using FDG-PET in conjunction with CT scanning provides the most accurate staging of mediastinal disease in lung cancer by contributing complementary information. Furthermore, PET can affect clinical decision-making and allow some patients considered unresectable a chance for resection.

Adult↗

PubMed1999

Childhood-onset schizophrenia: progressive brain changes during adolescence.

BACKGROUND: Previous NIMH childhood onset schizophrenia (COS) anatomic brain MRI studies found progression of ventricular volume and other structural brain anomalies at 2-year follow up across mean ages 14 to 16 years. However, studies in adult patients generally do not show progression of ventricular volume or correlation of ventricular volume with duration of illness. To address issues of progression of brain anomalies in schizophrenia, this report extends previous studies to include a third longitudinal scan, uses a larger sample size, and includes measures of the amygdala and hippocampus. METHODS: Volumes of the total cerebrum, lateral ventricles, hippocampus, and amygdala were quantified on 208 brain magnetic resonance imaging scans from 42 adolescents with COS (23 with one or more repeat scan) and 74 age- and gender-matched controls (36 with one or more repeat scan). A statistical technique permitting combined use of cross-sectional and longitudinal data was used to assess age-related changes, linearity, and diagnostic group differences. RESULTS: Differential nonlinear progression of brain anomalies was seen during adolescence with the total cerebrum and hippocampus decreasing and lateral ventricles increasing in the COS group. The developmental curves for these structures reached an asymptote by early adulthood for the COS group and did not significantly change with age in the control group. CONCLUSIONS: These findings reconcile less striking progression of anatomic brain images usually seen for adult schizophrenia and complement other data consistent with time-limited, diagnostic-specific decreases in brain tissue. Adolescence appears to be a unique period of differential brain development in schizophrenia.

Adolescent↗

PubMed1999

A comparison of mixed effects logistic regression models for binary response data with two nested levels of clustering.

We compare mixed effects logistic regression models for binary response data with two nested levels of clustering. The comparison of these models occurs in the context of developmental toxicity data sets, for which multiple types of outcomes (first level) are measured on each rat pup (second level) nested within a litter (third level). Because the nested nature of such data is occasionally accommodated by ignoring one level of clustering, we consider three models: (i) a three-level model adjusting for clustering due to both pup and litter (M1); (ii) a two-level model adjusting for just pup (M2); and (iii) another two-level model adjusting for just litter (M3). The three types of effects of interest are: (i) differences among malformation types (first-level effects); (ii) differences among groups of pups (for example, sex of pup, second-level effects); and (iii) differences among groups of litters (for example, dose, third-level effects). Simulations and data analyses suggest that the M3 model leads to more bias than the M1 or M2 models for all three types of effects. In terms of coverage of confidence intervals for fixed effects log odds ratio parameters, the M1 model achieves nominal coverage, whereas the M2 model reduces coverage for the third-level effects and the M3 model obtains poor coverage for both first- and second-level effects. These reductions in coverage for certain model-parameter combinations worsen as baseline risk increases. The data analyses support these simulation-based conclusions to some extent.

Animals↗

PubMed1999

Filgrastim (r-metHuG-CSF) and its potential use in the reduction of radiation-induced oropharyngeal mucositis: an interim look at a randomized, double-blind, placebo-controlled trial.

We wished to determine if filgrastim administration to chemotherapy/radiation therapy-naive patients receiving external-beam irradiation for head-and-neck malignancies would reduce the incidence and severity of oral/oropharyngeal mucositis. Patients were randomized to receive subcutaneous injections of either filgrastim or placebo beginning on day 1 of radiation and continuing daily throughout treatment. Study medication was titrated to keep the neutrophil count between 10 x 10(9) and 30 x 10(9)/l. The left and right buccal mucosa, hard palate, and posterior pharyngeal wall were scored weekly, by a blinded evaluator using two different scales, and the most severe score per week was used in data analysis. Fourteen of a planned 54 patients were randomized (8 filgrastim, 6 placebo), and were evaluable for a planned interim analysis. No statistically significant between-group differences were seen in mean worst scores across time using repeated measures analysis of variance (Hickey, p = 0.231; WHO, p= 0.288). At almost all timepoints, however, the worst mean scores were lower in patients treated with filgrastim compared with those in patients treated with placebo, and the number of severe (i.e., grade 3) mucositis scores was significantly lower in the filgrastim-treated group. Filgrastim may decrease the severity of radiation-induced oral/oropharyngeal mucositis.

Adolescent↗

PubMed1998

Hepatitis C virus infection in acquired aplastic anemia.

Hepatitis-associated aplastic anemia (HAAA) is an uncommon disorder that usually is not due to hepatitis A or B virus infection. Hepatitis C virus (HCV) seropositivity is infrequently observed in aplastic anemia (AA) patients who have not been extensively transfused. However, HCV seropositivity may not be detected until several weeks or months after viral infection and AA patients may exhibit defective humoral immunity. Therefore, we evaluated sera from AA patients for the presence of HCV viremia using a reverse transcriptase polymerase chain reaction (RT-PCR) based assay and several serologic assays for HCV antibodies. Serum samples from 90 AA patients who presented to the UCLA Medical Center between March 1984 and February 1990 were analyzed. Overall, 17 patients were found to have HCV viremia by RT-PCR assay, of whom 14 had a positive second-generation HCV enzyme immunoassay (EIA-2) and only 6 were EIA-1 reactive. The frequency of HCV viremia increased with the duration of time between diagnosis and sample procurement, and the number of blood products transfused prior to sampling (P = 0.026). No patient who received fewer than 20 U of blood products or who was sampled less than 20 days after diagnosis had a positive HCV RT-PCR result. Of four patients with hepatitis-associated AA (HAAA), one who was sampled 23 days after diagnosis had hepatitis C viremia and a reactive EIA-2 assay. Therefore, the high frequency of HCV viremia in this patient population is most likely due to transfusion with contaminated blood products prior to the introduction of routine blood donor screening for HCV.

Anemia, Aplastic↗

PubMed1998

Interferon-alpha and granulocyte-macrophage colony-stimulating factor differentiate peripheral blood monocytes into potent antigen-presenting cells.

The diverse roles of interferon-alpha (IFN-alpha) in regulating the immune response to infectious agents suggested that it might affect dendritic cell (DC) development. Peripheral blood mononuclear cells cultured with IFN-alpha and granulocyte-macrophage colony-stimulating factor (GM-CSF) developed a dendritic morphology and expressed high levels of the class I and II human leukocyte antigens (HLA), B7 co-stimulatory molecules, adhesion proteins, and CD40. Elevated DC expression of B7-2 and HLA-DR was observed with increasing IFN-alpha concentrations up to 5000 U/mL. The effects of IFN-alpha on DC immunophenotype were not reversed by adding neutralizing antibodies against interleukin-4 (IL-4) or tumor necrosis factor alpha to the cell cultures or by eliminating lymphocytes from the cultures. The addition of IFN-alpha to cultures containing optimal concentrations of IL-4 and GM-CSF significantly increased the B7-2 and HLA-DR levels above those present on DCs grown in two cytokines. The DCs generated with IFN-alpha and GM-CSF were potent antigen-presenting cells in allogeneic mixed leukocyte reactions. They also were capable of taking up, processing, and presenting tetanus toxin to autologous T lymphocytes. These results demonstrate an important role for IFN-alpha in the generation of DCs with potent antigen-presenting capabilities from peripheral blood monocytes.

Cell Differentiation↗

PubMed1998

Thrombotic microangiopathy following allogeneic bone marrow transplantation is associated with intensive graft-versus-host disease prophylaxis.

Thrombotic microangiopathy (TM), manifesting clinically as thrombotic thrombocytopenic purpura or hemolytic uremic syndrome, is an uncommon complication after bone marrow transplantation (BMT). A retrospective analysis of potential risk factors for TM following allogeneic BMT was performed. Clinical data were analyzed from seven patients diagnosed with severe TM and 409 patients who underwent BMT during the same time period and who survived for at least 100 days afterwards. Six of the seven patients with TM received intensive GVHD prophylaxis consisting of cyclosporine, methotrexate and glucocorticoids, whereas only 66 of the 409 patients without TM received this regimen (P < 0.001, Fisher's exact test). This regimen was administered to patients older than 40 years, or recipients of a mismatched or unrelated allograft. Univariate analysis also revealed an increased risk of TM associated with the use of an unrelated bone marrow donor (P = 0.02), but no significant association with patient age or gender, diagnosis, amount of prior chemotherapy, transplant conditioning regimen or severity of GVHD. A multivariate exact logistic regression analysis revealed that only the type of GVHD prophylaxis had a significant impact on the risk for TM. The combined use of cyclosporine, methotrexate and glucocorticoids as GVHD prophylaxis may predispose to the development of TM following BMT.

Adult↗

PubMed1998

Ex vivo expansion and differentiation of unselected peripheral blood progenitor cells in serum-free media.

The ability to expand and differentiate unselected PBPC was investigated. Cells were grown in serum-free media containing stem cell factor, GCSF and megakaryocyte growth and development factor (pegylated PEG-rHuMGDF) with or without supplemental serum. Optimal proliferation occurred when PBPC were cultured without prior Ficoll-Paque separation in serum-free media. Cell yields after 17 days of culture were proportional to the percentage of CD34+ cells in the starting population and were 1170+/-302-fold higher than the starting numbers of CD34+ cells. Granulocyte-macrophage colony-forming units increased over 12 days of culture, whereas the numbers of erythroid colony-forming cells peaked between 4 and 7 days. Elimination of PEG-rHuMGDF from cell cultures resulted in significantly lower yields of myeloid and erythroid colony-forming cells and total cell numbers. Cell differentiation into neutrophils was indicated by progressive increases in CD11b, CD15, and CD66b expression. Expanded neutrophils phagocytosed and killed bacteria as efficiently as neutrophils from normal donors. Large-scale expansion studies yielded similar proliferation and differentiation results as parallel small-scale cultures. Therefore, unselected PBPC can be efficiently expanded and differentiated into large numbers of functional mature neutrophils.

Antigens, CD↗

PubMed1998

Evidence for selective degradation of platelet GP IIb/IIIa complex after prolonged in vitro ventricular assist.

BACKGROUND: Left ventricular assist devices (VAD) have improved survival in patients with end-stage heart failure. Past studies have shown that interactions between blood and synthetic surfaces promote initial bleeding and later thromboembolism. The exact mechanism of blood activation during VAD circulation remains unclear. The purpose of this study was to test the hypothesis that platelet glycoprotein (GP) IIb/IIIa receptor degradation occurs during clinical use of ventricular assist devices. METHODS: Five in vitro nonpulsatile centrifugal VAD circuits were simulated for 4 days using 450 mL of fresh human whole blood. Temperature, activated clotting time, pH, pCO2, pO2, Ca++, and glucose were maintained at physiologic values. Flow was maintained at a constant 2.0 L/min/m2. We examined whole blood platelet aggregation induced by ristocetin, collagen, and adenosine diphosphate (ATP). We also examined whole blood platelet degranulation induced by collagen and ADP. RESULTS: Platelet aggregation in response to ristocetin, collagen, and ADP irreversibly and progressively declined with prolonged circulation in the VAD. While ADP-induced aggregation declined within the first hour, ristocetin and collagen-induced aggregation declined after 10 hours. Collagen-induced platelet degranulation decreased similar to aggregation, whereas ADP-induced degranulation continued and was preserved throughout the experiment. CONCLUSIONS: These results suggest prolonged circulation of human blood in a VAD circuit irreversibly impair platelet aggregation. The response of circulating platelets to individual agonists suggests that this platelet degradation is partially receptor specific. In our VAD system, ADP-stimulated platelet aggregation is more rapidly degraded with circulation. These results offer preliminary evidence that circulation of human blood in a VAD circuit leads to early degradation of the platelet GP IIb/IIIa complex. GP IIb/IIIa complex degradation is likely to be the mechanism of early VAD associated bleeding.

Blood Platelets↗

PubMed1997

Thrombin causes a marked delay in skeletal myogenesis that correlates with the delayed expression of myogenin and p21CIP1/WAF1.

Thrombin is a multifunctional serine protease whose activity is regulated in the extravasculature by an extracellular inhibitor, protease nexin-1. Because protease nexin-1 expression has been shown to be regulated during skeletal muscle cell differentiation, we reasoned that thrombin inactivation may be an important requirement for this developmental process. To test this hypothesis, we examined the effects of thrombin on differentiating C2C12 myoblasts. We report here that myogenesis, as scored by myotube formation, is considerably delayed by thrombin. This regulation correlated with delayed expression of myogenin and p21(CIP1/WAF1), both considered critical components of the skeletal muscle cell differentiation program. Regulation occurred at the RNA level, indicating that the effect of thrombin is either transcriptional or post-transcriptional. Furthermore, we present evidence suggesting that this regulation is mediated by the thrombin receptor. Although thrombin is mitogenic for certain cell types, we found that delay of myogenesis in C2C12 cells did not involve a mitogenic signal. Taken together, these results imply that inhibition of the serine protease thrombin may be required for proper progression through the myogenic differentiation program. The data point to potentially important roles that thrombin and protease nexin-1 may play during skeletal muscle development.

Animals↗

PubMed1997

Preparation and ESR spectroscopic characterization of the zinc(II) and cadmium(II) complexes of streptonigrin semiquinone.

Semiquinone metal complexes derived from the antitumor antibiotic streptonigrin have been prepared for the first time. They were obtained by reduction of the zinc(II) and cadmium(II) complexes of the parent aminoquinone ligand with sodium borohydride, followed by air oxidation of the intermediate dihydroquinones. Alternatively, N-benzyldihydronicotinamide reduction was used to produce the same Cd(II) complex of the p-semiquinone free radical. Electron spin resonance spectroscopic studies showed that metal binding significantly changes the spin densities of the unpaired electron which is confined to the quinolinesemiquinone moiety of the complexed antibiotic. Complexation with both Cd(II) and Zn(II) perturbs the coupling constants of all atoms involved in delocalization of the unpaired electron, shifting its distribution toward the pyridine ring. The coupling constant of the pyridine ring-proton adjacent to the semiquinone ring increases from 0.31 to 0.43 G in the Cd(II) complex in methanol, while the proton meta to the pyridine nitrogen increases from 1.76 to 1.96 G. Furthermore, the coupling constant of the heterocyclic nitrogen increases from 0.46 to 0.61 G. A similar trend is noted for the Zn(II) complex as well, including the observed decrease in splitting constant of the amino nitrogen from 1.34 to 1.08 G, and perturbation of the previously equivalent amino protons from 0.89 and 0.89 to 1.09 and 0.95 G. The spectral parameters have been confirmed by deuteration. Complexation studies using isotopically enriched 113Cd(II) revealed hyperfine coupling of the unpaired electron of the p-semiquinone and the nuclear spin of 113Cd(II), indicating direct coordination between the metal and the complexing ligand. Although the metal complexes could readily be prepared in a series of different solvent systems, they appear to have substantially shorter half lives than the non complexed p-semiquinone radical (5 to 15 min vs. 2 to 3 wk in sealed ampoules). Formation of tight-binding p-semiquinone metal complexes as here described should provide useful leads for the design of related systems to study p-quinone-metal interactions for mechanistic elucidation of metal ion catalyzed quinone-dependent electron transfer reactions in biological oxidations.

Cadmium↗

PubMed1997

Age-related changes in trabecular cells in vitro.

The changes in the morphology and the amounts of selected extracellular matrix proteins in serially passaged porcine trabecular cells cultured from young animals (age range, 4-6 months) were investigated. After 4 weeks incubation, trabecular cells in primary confluent cultures had a flattened elongated profile, whereas the cells in secondary or tertiary cultures, after an additional 4 to 8 weeks incubation, respectively, were epithelioid in shape. Time-lapse micrography of the passaged cells revealed membrane ruffling at the cell periphery, but sparse cell movement. No mitotic events took place in either the secondary or tertiary cultures for 24 hr prior to harvesting the cells. No remarkable differences were observed in the total polypeptide profile of primary, secondary or tertiary cells analysed by SDS gel electrophoresis and silver staining. However, laser densitometry of immunoblots treated with antibodies against type VI collagen, thrombospondin, fibronectin, and laminin demonstrated that, compared to primary cultures of trabecular cells, the amount of type VI collagen was elevated 20.5-fold in tertiary cultures, thrombospondin 6-fold, and fibronectin 5-fold, but laminin was not detectable. Because aging trabecular cells in vitro exhibit specific biochemical characteristics that are comparable to those known to occur in the human trabecular meshwork in vivo, the present method provides a model for the investigation of age-related changes in this tissue at the cellular level under defined and controlled conditions.

Aging↗

PubMed1997

Synthesis and cleavage of oligodeoxynucleotides containing a 5-hydroxyuracil residue at a defined site.

Oxidation and hydrolysis of a cytosine residue can lead to the formation of 5-hydroxyuracil in DNA. The biological consequences of this modification are not fully understood. To facilitate biochemical and biophysical studies aimed at elucidating the effects of this modification in DNA, we have developed a solid-phase synthetic method for the placement of 5-hydroxyuracil residues at defined sites in oligodeoxynucleotides. This method is based upon the enhanced acidity of the 5-hydroxyl proton which allows selective aqueous acetylation. Under standard aqueous ammonia deprotection conditions, however, we observed that 5-hydroxyuracil residues are lost substantially from synthetic oligonucleotides. Substitution of aqueous ammonia with methanolic potassium carbonate and the use of phosphoramidite derivatives with alternatively protected amino groups allow synthesis of oligonucleotides containing 5-hydroxyuracil and all normal bases in high yield. The composition of the oligodeoxynucleotides prepared by this method has been verified by enzymatic digestion followed by high-performance liquid chromatography (HPLC) analysis as well as acid hydrolysis followed by GC/MS analysis. The location of the 5-hydroxyuracil residue is demonstrated by selective permanganate oxidation of the 5-hydroxyuracil residue followed by beta-elimination. We have also probed a synthetic oligonucleotide containing a unique 5-hydroxyuracil residue with uracil DNA N-glycosylase, previously reported to remove this lesion from DNA.

Antineoplastic Agents↗

PubMed1996

Urethrography and ischial intertuberosity line in radiation therapy planning for prostate carcinoma.

We analyzed our urethrography procedure regarding the validity of using the ischial tuberosity line (ITL) as the caudal margin of treatment portals for prostate carcinoma. The distances of the external urethral sphincter and the lowest margin of the opacified urinary bladder were analyzed in one hundred fifteen consecutive urethrograms. None showed the urethral sphincter to be caudal to the ITL. Ten percent of the sphincters were located less than 1.0 cm cephalad to the ITL, yielding inadequate treatment coverage if the ITL was relied on. Arbitrarily considering 2.0 cm or more of the urethral irradiation to be excessive, the use of the ITL would then have resulted in unnecessary normal tissue irradiation of 42.5%. The ITL should not be used as the caudal margin for prostate treatment portals. Variation in sphincter position, as also seen on lateral projections, reveal a need for urethrography as a necessary supplement to computed tomography to plan radiation portals for prostate cancer.

Contrast Media↗