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T Wu

Publications and source records attributed to T Wu.

At least 19 recordsLinked to original sources
PubMed2001

In vivo persistence of retrovirally transduced murine long-term repopulating cells is not limited by expression of foreign gene products in the fully or minimally myeloablated setting.

Many nonmalignant hematologic disorders could potentially be treated by genetic correction of as few as 5-10% of target lineage cells. However, immune system clearance of cells expressing gene products perceived as foreign could be limiting. There is evidence that tolerance to foreign proteins can result when myeloablative conditioning is used, but this limits the overall applicability of such techniques. Therefore, we sought to evaluate the engraftment of hematopoietic stem cells carrying a foreign transgene after low-dose irradiation by comparing in vivo survival of murine long-term repopulating cells (LTRC) transduced with either a retroviral vector expressing the bacterial neomycin phosphotransferase gene (neo) or a vector containing neo gene sequences but modified to prevent protein expression (nonexpression). First, marrow cells from congenic donors were transduced with either vector and transplanted into recipients treated with standard dose irradiation of 800 rads. High-level engraftment and gene marking resulted, without differences in the marking levels or pattern of persistence of the cells between cells transduced with either vector. Low-dose irradiation at 100 rads was tested using higher cell doses. Marking levels as high as 10% overall were obtained, again with no differences between mice receiving cells transduced with the neo versus the nonexpression vectors. To investigate a potentially more immunogenic protein, marrow cells were transduced with a vector containing the green fluorescent protein (GFP) gene, and their persistence was studied in recipient mice receiving 100 rads. Stable GFP expression in 5-10% of circulating cells was observed long term. We conclude that even with very low dose conditioning, engraftment by genetically modified LTRC cells at clinically significant levels can be achieved without evidence for clearance of cells known to be expressing immunogenic proteins.

Animals↗
PubMed2001

A novel photosensitizer, 2-butylamino-2-demethoxy-hypocrellin B (2-BA-2-DMHB) - its photodynamic effects on HeLa cells: efficacy and apoptosis.

A novel hypocrellin congener, 2-butylamino-2-demethoxy-hypocrellin B (2-BA-2-DMHB) was found to be an effective photosensitizer. Compared with its parent compound hypocrellin B (HB), its absorption bands extended toward longer wavelength and the extinction coefficients raised to some degree (lambda(max) (nm) (log(epsilon)): 463 (4.06), 583 (4.09), 621 (4.10) for 2-BA-2-DMHB and 466 (4.06), 548 (3.70), 580 (3.52) for HB). And it also had a much higher photopotentiation factor than HB (i.e., more than 250 versus 10 at a dose of 24 J cm(-2) of red light on HeLa cells). This might be correlated to the higher ability of superoxide anion generation and the higher cellular uptake of 2-BA-2-DMHB. Meanwhile, the examinations of Hoechst 33342-labeled nuclei, DNA fragmentation on agarose gel and flow cytometry showed that 2-BA-2-DMHB induces apoptosis in photosensitized HeLa cells more quickly than HB, which might be correlated to the higher cellular uptake of 2-BA-2-DMHB and the difference of their cellular localization. The study suggested that 2-BA-2-DMHB was a well-suited candidate for a new generation of photodynamic therapy photosensitizer.

Apoptosis↗
PubMed2001

Electroresistance and electronic phase separation in mixed-valent manganites.

The sensitivity of transport in colossal magnetoresistance (CMR) manganites to external electric and magnetic fields is examined using field effect configurations with La(0.7)Ca(0.3)MnO(3) (LCMO), Na(0.7)Sr(0.3)MnO(3), La(0.7)Ba(0.3)MnO(3), and La(0.5)Ca(0.5)MnO(3) (0.5-doped LCMO) channels, and ferroelectric PbZr(0.2)Ti(0.8)O(3) (PZT) or dielectric (SrTiO(3)) gates. A large electroresistance (ER) of approximately 76% at 4 x 10(5) V/cm is found in LCMO with PZT-ferroelectric gate, but the magnitude of the effect is much smaller (a few percent) in the other three channels. The ER and CMR effects are remarkably complimentary. The size and systematics of the effect strongly favor a percolative phase separation picture.

Journal Article↗
PubMed2001

Immunotherapy with nondepleting anti-CD4 monoclonal antibodies but not CD28 antagonists protects islet graft in spontaneously diabetic nod mice from autoimmune destruction and allogeneic and xenogeneic graft rejection.

BACKGROUND: T-cell activation and the subsequent induction of effector functions require not only the recognition of antigen peptides bound to MHC molecules by T-cell receptor (TCR) for antigen but also a costimulatory signal provided by antigen presenting cells. CD4 T-cell activation and function require the CD4 molecule as a coreceptor of TCR. The CD28/B7 pathway is a major costimulatory signal for T-cell activation and differentiation. METHODS: The effect of targeting CD4 by nondepleting anti-CD4 monoclonal antibodies (mAbs) versus blocking CD28/B7 by CTLA4Ig, anti-CD80 mAbs, and anti-CD86 mAbs on the prevention of recurrence of autoimmune diabetes after MHC-matched nonobese diabetes-resistant (NOR) islet transplantation in nonobese diabetic (NOD) mice were compared. Whether nondepleting anti-CD4 mAbs prolong allogeneic islet graft survival and xenogeneic pig islet graft survival in diabetic NOD mice were studied. Furthermore, the effect of nondepleting anti-CD4 mAbs combined with CTLA4Ig on allogeneic islet graft survival in NOD mice was investigated. RESULTS: Recurrence of autoimmune diabetes can be prevented by nondepleting anti-CD4 mAbs. Blocking the CD28/B7 costimulatory pathway by CTLA4Ig or by anti-CD80 mAbs and anti-CD86 mAbs cannot prevent recurrence of autoimmune diabetes after islet transplantation. Short-term treatment with nondepleting anti-CD4 mAbs significantly prolongs allogeneic islet graft survival and xenogeneic pig islet graft survival in diabetic NOD mice. But nondepleting anti-CD4 mAbs combined with CTLA4Ig decreased allogeneic islet graft survival. CONCLUSIONS: Nondepleting anti-CD4 mAbs but not CD28 antagonists protect islet grafts in diabetic NOD mice from autoimmune destruction and allogeneic and xenogeneic graft rejection. The efficacy of nondepleting anti-CD4 mAbs is compromised when it combines with CTLA4Ig.

Abatacept↗
PubMed2001

Need for alternative trial designs and evaluation strategies for therapeutic studies of invasive mycoses.

Studies of invasive fungal infections have been and remain difficult to implement. Randomized clinical trials of fungal infections are especially slow and expensive to perform because it is difficult to identify eligible patients in a timely fashion, to prove the presence of the fungal infection in an unequivocal fashion, and to evaluate outcome in a convincing fashion. Because of these challenges, licensing decisions for antifungal agents have to date depended heavily on historical control comparisons and secondary advantages of the new agent. Although the availability of newer and potentially more effective agents makes these approaches less desirable, the fundamental difficulties of trials of invasive fungal infections have not changed. Therefore, there is a need for alternative trial designs and evaluation strategies for therapeutic studies of invasive mycoses, and this article summarizes the possible strategies in this area.

Antifungal Agents↗
PubMed2001

Application of furanyl carbamate cycloadditions toward the synthesis of hexahydroindolinone alkaloids.

A convenient synthesis of various substituted hexahydroindolinones has been achieved by an intramolecular Diels--Alder cycloaddition reaction (IMDAF) of furanyl carbamates bearing tethered alkenyl groups. The initially formed [4 + 2]-cycloadduct undergoes nitrogen-assisted ring opening followed by deprotonation of the resulting zwitterion to give the rearranged ketone. The stereochemical outcome of the IMDAF cycloaddition has the sidearm of the tethered alkenyl group oriented syn with respect to the oxygen bridge. A synthetic route to (+/-)-mesembrane and (+/-)-crinane was accomplished using this methodology. It was possible to carry out a stereoselective reduction of the initially formed hexahydroindolinone ring to produce the cis-3a-aryl-hydroindole skeleton. A related [4 + 2]-cycloaddition/rearrangement sequence was also used for a formal synthesis of the Chinese ornamental orchid (+/-)-dendrobine. The tricyclic alkaloid core was formed stereoselectivity from the thermolysis of N-[(2-methyl-2-cyclopentenyl)methyl]-N-(4-isopropyl-furan-2-yl)carbamic acid tert-butyl ester. Kende's advanced intermediate 33 was prepared in seven additional steps by standard transformations, thereby completing a formal synthesis of (+/-)-dendrobine.

Alkaloids↗
PubMed2001

Confocal microscopic study of glial-vascular relationships in the retinas of pigmented rats.

Astroglia are interposed between the cerebral vasculature and neurons, where they may mediate the transfer of substances from the circulation to neurons and couple changes in neuronal activity to changes in cerebral blood flow. The retina is a particularly advantageous model system for studying glial-vascular interactions in situ. Confocal microscopy and three-dimensional image reconstruction were used to study the anatomical relationships between glia and the surface vasculature in retinas acutely isolated from adult pigmented rats. Retinas were immunostained using antibodies directed against the basal lamina surrounding the vasculature as well as antibodies directed against glial fibrillary acidic protein. Surface vessels of all calibers were contacted by the processes of astrocytes. The vitreal surfaces of the large retinal vessels were covered by a meshwork of immunoreactive astrocyte processes of a variety of shapes, whereas the scleral surfaces of the vessels were supported by thick bundles of astrocyte processes. In addition, glial cells were filled intracellularly with the gap junction-permeable tracers Lucifer yellow and Neurobiotin. Intracellular fills clearly demonstrated the presence of astrocytes with somata that were closely apposed to the large retinal vessels. Tracer-filled astrocytes displayed a variety and complexity of shapes that was not apparent in immunostained material. Gap junctional coupling was stronger between astrocytes adjacent to the same artery than between periarterial astrocytes and astrocytes located away from arteries. Significantly fewer Müller cells were labeled when Neurobiotin was injected into astrocytes associated with arteries than when Neurobiotin was injected into astrocytes that were distant from arteries.

Animals↗
PubMed2001

Assessment of thermal tissue ablation with MR elastography.

An important part of thermal ablation therapy is the assessment of the spatial extent of tissue coagulation. In this work, the mechanical properties of thermally-ablated tissue were quantitatively evaluated using magnetic resonance elastography (MRE). This study shows that the mechanical properties of focused ultrasound ablated tissue are significantly different from normal tissue, and the difference can be imaged and measured using MRE. Repeated experiments revealed a reproducible pattern of tissue mechanical property change during thermal ablation in ex vivo bovine muscle. This pattern may reflect changes in intrinsic tissue structure and could be used to evaluate tissue coagulation during thermal ablation therapy. Magn Reson Med 45:80-87, 2001.

Animals↗
PubMed2001

Determination of traces of 237Np in environmental samples by ICP-MS after separation using TOA extraction chromatography.

A simple, rapid, cost-efficient, and robust method for separation of 237Np with an extraction chromatographic column (TOA: tri-n-octylamine on Teflon powder) is outlined in detail and further improved for direct ICP-MS analysis. The column efficiently retained 237Np in 2 mol L(-1) HNO3 medium and all of the 237Np was easily eluted with 0.02 mol L(-1) oxalic acid in 0.16 mol L(-1) HNO3 at 95 degrees C. The separated solutions were free from most matrix elements and were aspirated into the ICP-MS directly. The decontamination factor for 238U is more than 10(4). The instrumental detection limit for 237Np was 0.46 pg mL(-1), which corresponds to 1.2 x 10(-5) Bq mL(-1). The method is more rapid than traditional radiometric techniques. It is also considered to be more suitable for environmental monitoring than existing methods based on TOA.

Journal Article↗
PubMed2001

Merozoite surface protein 8 of Plasmodium falciparum contains two epidermal growth factor-like domains.

By motif searching of the unfinished sequences in the Malaria Genome Sequencing Project databases we have identified a novel EGF-like domain-containing protein of Plasmodium falciparum. The sequence lies within a single open reading frame of 1791 bp and is predicted to encode a polypeptide of 597 amino acids. There are hydrophobic regions at the extreme N- and C-termini, which could represent secretory signal peptide and GPI attachment sites, respectively. Similar to MSP1, there are two EGF-like domains located near the C-terminus. RT-PCR analysis of the novel gene shows that it is transcribed in asexual stages of the malaria parasite. We have expressed portions of the protein as recombinant GST fusions in Escherichia coli and raised antisera in rabbits. Antibodies to the EGF-like domains of the novel protein are highly specific and do not cross-react with the EGF-like domains of MSP1, MSP4 or MSP5 expressed as GST fusion proteins. Antiserum raised to the most C-terminal region of the protein reacts with four bands of 98, 50, 25 and 19 kDa in P. falciparum parasite lysates whereas antisera to the N-terminal fusion proteins recognise the 98 and 50 kDa bands, suggesting that the novel protein may undergo processing in a similar way to MSP1. Immunoblot analysis of stage-specific parasite samples reveals that the protein is present throughout the parasite asexual life cycle and in isolated merozoites, with the smaller fragments present in ring stage parasites. The protein partitions in the detergent-enriched phase after Triton X-114 fractionation and is localized to the surfaces of trophozoites, schizonts and free merozoites by indirect immunofluorescence. Antisera to the C-terminus stain the surface of rings, whereas antisera to the N-terminus do not, suggesting that a fragment of the protein is carried into the developing ring stage parasite. Based on the accepted nomenclature in the field we designate this protein MSP8. We have shown that the MSP8 fusion proteins are in a conformation that can be recognised by human immune sera and that there is very limited diversity in the MSP8 gene sequences from various P. falciparum laboratory isolates. MSP8 shows significant similarity to the recently reported sequence of the protective P. yoelii merozoite surface protein pypAg-2 [Burns JM, Belk CC, Dunn PD. Infect Immun 2000;68:6189-95.] suggesting that the two proteins are homologues. Taken together, these findings suggest that MSP8/pypAg-2 may play an important role in the process of red cell invasion and is a potential malaria vaccine candidate.

Amino Acid Sequence↗
PubMed2001

The effects of SCF/G-CSF prestimulation on radiation sensitivity and engraftment in nonmyeloablated murine hosts.

OBJECTIVE: Previous studies have shown improved engraftment in a murine model when granulocyte colony-stimulating factor (G-CSF) and stem cell factor (SCF) were administered for 5 days prior to irradiation, with significant levels of engraftment in the growth factor-preconditioned group even at very low radiation doses. We sought to explore the mechanisms behind this effect. METHODS: The radiation sensitivity of mice with or without 5 days of prestimulation with G-CSF (200 microg/kg/d) and SCF (50 microg/kg/d) was compared. To further evaluate whether growth factor prestimulation enhances engraftment by mobilization of hematopoietic progenitors into peripheral blood, thus creating less endogenous competition within the marrow compartment, female mice were pretreated with 5 days of G-CSF/SCF or control diluent. Engraftment of 40 x 10(6) peripheral blood stem cells (PBSCs) harvested from G-CSF/SCF-mobilized male mice was compared in the two recipient groups. RESULTS: There was no difference in survival between the pretreated and control mice at the radiation doses tested. Additionally, there was no significant difference in the recovery of blood counts, bone marrow cellularity, colony-forming unit (CFU) content, or stem cell numbers assessed 4 months later in a competitive repopulation model. Engraftment levels of male cells did not differ between G-CSF/SCF-pretreated and control recipients, and could be detected in 30% of recipients at 20-24 weeks (4/12 in each group) at overall levels of 0.1-1%. CONCLUSIONS: The enhanced engraftment in cytokine pretreated recipients is unlikely to be due to increased endogenous stem-cell killing or to the creation of endogenous marrow "space" by egress of endogenous stem cells after cytokine prestimulation.

Animals↗
PubMed2001

Efficacy of intracoronary or intravenous VEGF165 in a pig model of chronic myocardial ischemia.

OBJECTIVES: We sought to optimize vascular endothelial growth factor (VEGF) treatment for therapeutic angiogenesis in myocardial ischemia, we explored the efficacy of five different regimens. BACKGROUND: Although VEGF165 is one of the most potent pro-angiogenic growth factors, VEGF165 treatment for myocardial ischemia has been hampered by low efficacy and dose-limiting hypotension after systemic or intracoronary delivery. METHODS: This study evaluated the effect of intravenous or intracoronary rhVEGF165 in the presence or absence of nitric oxide (NO) synthase inhibition in a porcine model of chronic myocardial ischemia. Forty-two Yorkshire pigs with chronically occluded left circumflex coronary arteries were randomly assigned to receive 10 microg/kg of VEGF165: 1) rapid (40 min) intravenous VEGF165 0.25 microg/kg/min, 2) slow (200 min) intravenous VEGF165 0.05 microg/kg/min, 3) rapid intracoronary VEGF165 0.25 microg/kg/min, 4) rapid intracoronary VEGF165 0.25 microg/kg/min + nitro-L-arginine methyl ester hydrochloride (L-NAME) or 5) rapid vehicle infusion. RESULTS: Intracoronary and intravenous VEGF165 induced hypotension. Intracoronary VEGF-induced hypotension was blocked by L-NAME. Coronary angiography three weeks after treatment showed improvement in collateral index in both intracoronary groups but not the intravenous VEGF165 groups. Likewise, myocardial blood flow and microvascular function in the ischemic territory improved in both intracoronary groups but not in the intravenous groups. Global and regional myocardial function showed no significant improvements in any groups. CONCLUSIONS: Intracoronary infusion of VEGF165 significantly improves blood flow to the ischemic myocardium. Concomitant administration of L-NAME inhibits VEGF-induced hypotension while most likely preserving VEGF-induced angiogenesis. Intravenous infusion of VEGF165 was not effective in augmenting either myocardial flow or function in this model.

Animals↗
PubMed2001

Smoking and alcohol in the etiology of oral cancer: gender-specific risk profiles in the south of Greece.

Oral and pharyngeal cancer (OC) mortality is very low in Greece, especially among men, compared to other European countries. We conducted a case-control study of OC in Athens, and obtained information on tobacco, alcohol use and other potential risk factors and confounding variables for 110 incident cases and 115 hospital-based controls. We used multivariate logistic regression to estimate odds ratios (ORs) and 95% confidence intervals (CIs). Tobacco smoking (pack years, P(trend)=0.01) and alcohol use (drinks/week, P(trend)=0.07) were independent risk factors, with a multiplicative effect for combined exposures (OR, 8.3; 95% CI, 2.4-29.1, for >28 alcohol drinks/week and >50 pack years of cigarette smoking). The type of alcoholic beverage also seemed important: drinking ouzo and tsipouro (liquors of high ethanol concentration) was associated with greater increased OC risk than drinking comparable amounts of wine, beer or dark spirits. While alcohol drinking is more common for male cases versus controls, few men reported regularly consuming large quantities of ethanol associated with highest risk of OC in other studies. This may partially explain the low rates of male OC mortality in Greece. Among the 38% of our cases who were women, however, neither smoking nor alcohol drinking frequencies were significantly elevated compared to controls, and so the etiology of OC risk in females requires further investigation.

Adult↗
PubMed2001

Identification of methylated CpG motifs as inhibitors of the immune stimulatory CpG motifs.

The unmethylated CpG motifs within E. coli DNA (EC) cause immune stimulation. In contrast, mammalian DNA such as calf thymus (CT) DNA had been thought to be immunologically inert. In this article, we demonstrate that CT DNA unexpectedly specifically inhibits the immune activation by EC but not that by endotoxin. This inhibitory effect was mediated in the signaling pathway activated by EC since CT DNA markedly inhibited the CpG-induced nuclear translocation of the transcription factors, NF-kappaB and AP-1. In addition, CT DNA significantly inhibited the synergistic immune activation by EC and endotoxin. The mechanism of the inhibition by CT DNA probably did not involve the inhibition of the cellular uptake of EC. Using a CpG-depleted plasmid, we demonstrated that CpG methylation played an important role in the inhibition by CT DNA. Compared with unmethylated plasmid DNA, CpG-methylated DNA inhibited the immune activation by EC to the same extent as did CT DNA. Importantly, the inhibitory effect of CT DNA was also observed in vivo. Our results suggest that methylated DNA may be applied to alleviate the unwanted immune stimulation and inflammation in systemic inflammatory response syndrome and in gene therapy with plasmid DNA.

Animals↗
PubMed2001

Interaction of morin-cetyltrimethylammonium bromide with nucleic acids and determination of nucleic acids at nanograms per milliliter levels based on the enhancement of preresonance light scattering.

A new preresonance light scattering (PRLS) assay of nucleic acids is presented. At pH 7.30, the weak PRLS of morin-cetyltrimethylammonium bromide (CTMAB) can be greatly enhanced by the addition of nucleic acids, owing to the interaction between the nucleic acid and morin-CTMAB. After the addition of morin and CTMAB to DNA, the zeta potential of DNA decreases and changes from negative to positive, which is due to the formation of an associate, the aggregation of morin on nucleic acids and the electric neutralization between DNA and the cationic surfactant CTMAB. Mechanism studies showed that the enhanced PRLS comes from the aggregation of morin in the presence of nucleic acids and CTMAB. The enhanced intensity of PRLS is in proportion to the concentration of nucleic acids in the range 7.5 x 10(-9)-1.0 x 10(-5) g ml(-1) for calf thymus DNA, 7.5 x 10(-9)-1.0 x 10(-6) g ml(-1) for salmon sperm DNA and 1.0 x 10(-8)-1.0 x 10(-6) g ml(-1) for yeast RNA. The detection limits are 3.4, 6.2 and 4.1 ng ml(-1) for calf thymus DNA, salmon sperm DNA and yeast RNA, respectively. Synthetic samples were analyzed satisfactorily.

Animals↗
PubMed2001

Clinical intestinal transplantation: a decade of experience at a single center.

OBJECTIVE: To assess the long-term efficacy of intestinal transplantation under tacrolimus-based immunosuppression and the therapeutic benefit of newly developed adjunct immunosuppressants and management strategies. SUMMARY BACKGROUND DATA: With the advent of tacrolimus in 1990, transplantation of the intestine began to emerge as therapy for intestinal failure. However, a high risk of rejection, with the consequent need for acute and chronic high-dose immunosuppression, has inhibited its widespread application. METHODS: During an 11-year period, divided into two segments by a 1-year moratorium in 1994, 155 patients received 165 intestinal allografts under immunosuppression based on tacrolimus and prednisone: 65 intestine alone, 75 liver and intestine, and 25 multivisceral. For the transplantations since the moratorium (n = 99), an adjunct immunosuppressant (cyclophosphamide or daclizumab) was used for 74 transplantations, adjunct donor bone marrow was given in 39, and the intestine of 11 allografts was irradiated with a single dose of 750 cGy. RESULTS: The actuarial survival rate for the total population was 75% at 1 year, 54% at 5 years, and 42% at 10 years. Recipients of liver plus intestine had the best long-term prognosis and the lowest risk of graft loss from rejection (P =.001). Since 1994, survival rates have improved. Techniques for early detection of Epstein-Barr and cytomegaloviral infections, bone marrow augmentation, the adjunct use of the interleukin-2 antagonist daclizumab, and most recently allograft irradiation may have contributed to the better results. CONCLUSION: The survival rates after intestinal transplantation have cumulatively improved during the past decade. With the management strategies currently under evaluation, intestinal transplant procedures have the potential to become the standard of care for patients with end-stage intestinal failure.

Adult↗