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C T Chen

Publications and source records attributed to C T Chen.

At least 37 records · Page 2Linked to original sources
PubMed2003

Ferromagnetism induced by clustered Co in Co-doped anatase TiO2 thin films.

We investigated ferromagnetism of a newly discovered ferromagnetic semiconductor Co-doped anatase TiO2 thin film, using the magnetic circular dichroism (MCD) at the Co L(2,3) absorption edges. The magnetic moment was observed to be approximately 0.1 micro(B)/Co in the measurements, but the MCD spectral line shape is nearly identical to that of Co metal, showing that the ferromagnetism is induced by a small amount of clustered Co. With thermal treatments at approximately 400 degrees C, the MCD signal increases, and the moment reaches up to approximately 1.55 micro(B)/Co, which is approximately 90% of the moment in Co metal. In the latter case, the cluster size was observed to be 20-60 nm.

Journal Article↗
PubMed2002

Sympathoinhibitory action of nociceptin in the rat spinal cord.

1. Whole-cell patch recordings were made from antidromically identified sympathetic preganglionic neurons (SPN) of immature rat spinal cord slices. Bath application of nociceptin (0.1-1 micromol/L) suppressed excitatory postsynaptic potentials (EPSP) and hyperpolarized a population of SPN; these effects were naloxone (1 micromol/L) insensitive. 2. Nociceptin suppressed the amplitude of EPSP without causing a concomitant change in glutamate-induced depolarizations, suggesting a presynaptic inhibitory action. 3. Analysis of current-voltage relationships showed that nociceptin hyperpolarized SPN by increasing an inwardly rectifying K+ current. 4. Intrathecal injection of nociceptin (3, 10 and 30 nmol) to urethane-anaesthetized rats dose-dependently reduced the mean arterial pressure and heart rate; these effects were not prevented by prior intravenous injection of naloxone (1 mg/kg). 5. Results from our in vitro and in vivo experiments suggest that nociceptin suppresses spinal sympathetic outflow either by attenuating excitatory synaptic responses or hyperpolarizing SPN.

Adrenergic Fibers↗
PubMed2002

Ginsenoside Rb1 enhances peripheral nerve regeneration across wide gaps in silicone rubber chambers.

Silicone rubber chambers filled with collagen containing ginsenoside Rb1 (GRb1) were used to repair lesioned rat sciatic nerves with 15-mm gaps between stumps. Six weeks after implantation, histology of the nerve regenerated in the chambers filled with GRb1 and collagen contained larger axons than those in the chambers with collagen only. This study showed that the GRb1 could exert a positive influence on nerve regeneration when using silicone rubber tubes.

Animals↗
PubMed2001

Mechanisms of orexin-induced depolarizations in rat dorsal motor nucleus of vagus neurones in vitro.

1. Whole-cell patch-clamp recordings were made from neurones of the dorsal motor nucleus of the vagus (DMNV), including Fluoro-gold-labelled parasympathetic preganglionic neurones (PPNs), in slices of the rat medulla. In the latter case, rats had received an I.P. injection of Fluoro-gold solution (10 microg) 2-3 days earlier. 2. Superfusion of orexin A or B (10-300 nM) caused a slow depolarization in approximately 30% of the DMNV neurones, including PPNs. Orexin-induced depolarizations, which persisted in TTX (0.5 microM)-containing Krebs solution, were reduced by 70% in a low-Na+ (26 mM) Krebs solution, indicating the involvement of Na+ ions. A significant change in orexin-induced depolarizations was not obtained in either a high-K+ (7 mM) or Cd2+ (100 microM) Krebs solution. 3. Inclusion of the hydrolysis-resistant guanine nucleotide GDP-beta-S in the patch solution significantly reduced the orexin A- or B-induced depolarizations. 4. Under whole-cell voltage-clamp conditions, the orexin-induced inward current declined with hyperpolarization, but did not reverse polarity in the potential range between -120 and 0 mV. In low-Na+ solution, the orexin-induced current was reduced, and the I-V curve reversed polarity at about -105 mV; the response was further reduced and the reversal potential shifted to -90 mV in a low-Na+, high-K+ Krebs solution. 5. It is concluded that the peptides orexin A and B, acting on orexin receptors, which are GTP-binding-protein coupled, are excitatory to DMNV neurones. In addition, more than one conductance, which may include a non-selective cation conductance and a K+ conductance, appears to be involved in the orexin-induced depolarization.

Animals↗
PubMed2001

Catalytic nucleophilic acyl substitution of anhydrides by amphoteric vanadyl triflate.

[reaction--see text] Among four vanadyl species examined, vanadyl triflate was the most efficient catalyst to facilitate nucleophilic acyl substitution of anhydrides with a myriad array of alcohols, amines, and thiols in high yields and high chemoselectivity. By using mixed-anhydride technique, one can achieve oleate and peptide syntheses. In marked contrast to common metal triflates, the amphoteric character of the V=O unit in vanadyl species was proven to be responsible for the catalytic profile in this process.

Journal Article↗
PubMed2001

Evidence of doping-dependent pairing symmetry in cuprate superconductors.

Scanning tunneling spectroscopy studies reveal long-range spatial homogeneity and predominantly d(x(2)-y(2))-pairing spectral characteristics in under- and optimally doped YBa2Cu 3O (7-delta) superconductors, whereas STS on YBa2(Cu 0.9934Zn 0.0026Mg (0.004))3O (6.9) exhibits microscopic spatial modulations and strong scattering near the Zn or Mg impurity sites, together with global suppression of the pairing potential. In contrast, in overdoped (Y 0.7Ca (0.3))Ba 2Cu 3O (7-delta), (d(x(2)-y(2))+s)-pairing symmetry is found, suggesting significant changes in the superconducting ground state at a critical doping value.

Journal Article↗
PubMed2001

Sequence-selective peptide detection by small synthetic chemosensors selected from an encoded combinatorial chemosensor library.

Synthetic chemosensors hold great potential in many diagnostic applications. In this study, we describe the design and preparation of the first encoded combinatorial library of chemosensors for tripeptides. Subsequent screening of the library resulted in the discovery of novel chemosensors able to distinguish between random tripeptides.

Combinatorial Chemistry Techniques↗
PubMed2001

Determinants of drug delivery and transport to solid tumors.

This presentation addresses the barriers and determinants and the importance of drug-induced apoptosis in drug transport and delivery to organs and solid tumors. In particular, we examined the roles of interstitial space, drug removal by capillaries, tissue structure and tissue composition on drug distribution. Drug transport in bladder tissues is described by the distributed model which combined monodimensional Fickian diffusion and first order removal of drug by the perfusing blood. Microscopic evaluation of the spatial drug distribution in bladder, prostate and tongue indicates heterogeneous drug distribution with large and erratic concentration gradient. In general, drug distribution favors interstitial space and vasculature, with little penetration in muscles. Drug penetration into 3-dimensional solid tumors is typically 5- to 10-fold slower than in monolayer cultures. The transport of highly protein-bound drugs such as paclitaxel and doxorubicin in a solid tumor is retarded by a high tumor cell density and enhanced by drug-induced apoptosis. Accordingly, the delivery of a highly protein-bound drug to cells in a solid tumor is affected by its apoptotic effects and is therefore determined by the drug concentration and the treatment duration, i.e. treatment schedule. Under in vitro and in vivo conditions, the delivery of highly protein-bound drugs to tumor can be enhanced by using a pretreatment that induces apoptosis and reduction in cell density, and by using treatment schedules designed to take advantage of these drug-induced changes in tumor tissue composition. In conclusion, in addition to the usual processes involved in drug transport such as distribution through vascular space, transport across microvessel walls, and diffusion through interstitial space in tumor tissue, other factors including tissue structure and composition and alteration by drug-induced apoptosis are important determinants of drug distribution in organs and solid tumors.

Animals↗
PubMed2001

Does hormonal therapy influence sexual function in men receiving 3D conformal radiation therapy for prostate cancer?

PURPOSE: We evaluated the effect of three-dimensional conformal radiation therapy (3D-CRT) with or without hormonal therapy (HT) on sexual function (SF) in prostate cancer patients whose SF was known before all treatment. METHODS AND MATERIALS: Between March 1996 and March 1999, 144 patients received 3D-CRT (median dose = 70.2 Gy, range 66.6-79.2 Gy) for prostate cancer and had pre- and post-therapy SF data. All SF data were obtained with the O'Leary Brief SF Inventory, a self-administered, multidimensional, validated instrument. We defined total sexual potency as erections firm enough for penetration during intercourse. Mean follow-up time was 21 months (SD +/- 11 months). The Wilcoxon signed-rank test was used to test for significance of the change from baseline. RESULTS: Before 3D-CRT, 87 (60%) of 144 men were totally potent as compared to only 47 (47%) of 101 at 1-year follow-up. Of the 60 men totally potent at baseline and followed for at least 1 year, 35 (58%) remained totally potent. These changes corresponded to a significant reduction in SF (p < 0.05). Patients who had 3D-CRT alone were more likely to be totally potent at 1 year than those receiving 3D-CRT with HT (56% vs. 31%, p = 0.012); however, they were also more likely to be potent at baseline (71% vs. 44%, p = 0.001). Although these two groups had a significant reduction in SF from baseline, their change was not significantly different from each other. CONCLUSION: These data indicate that 3D-CRT causes a significant reduction in total sexual potency as compared to pretreatment baseline. The addition of HT does not appear to increase the risk of sexual dysfunction.

Aged↗
PubMed2001

Catalytic asymmetric coupling of 2-naphthols by chiral tridentate oxovanadium (IV) complexes.

A series of chiral oxovanadium(IV) complexes derived from tridentate N-3,5-substituted and N-3,4-benzo- and N-5,6-benzo-salicylidene-alpha-amino acids can serve as efficient catalysts for the enantioselective oxidative couplings of various 3-, 6-, and 7-substituted 2-naphthols under O(2). The best scenario involves the use of a vanadyl complex arising from 2-hydroxy-1-naphthaldehyde and valine (or phenylalanine) in CCl(4), leading to BINOLs in good yields (75-100%) and with enantioselectivities of up to 68%.

Journal Article↗
PubMed2001

X-ray absorption spectroscopy investigations on oxidized Ni/Au contacts to p-GaN.

X-ray absorption spectroscopy was used to investigate the electronic structure of as-deposited and oxidized Ni/Au contacts to p-GaN and to elucidate the mechanism responsible for low impedance. X-ray absorption near edge spectra of Ni K- and L3,2-edges clearly indicate formation of NiO on the sample surface after annealing. The reason for low impedance may be attributed to increase in hole concentration and existence of p-NiO layer on the surface.

Journal Article↗
PubMed2001

Dosimetric analysis of urinary morbidity following prostate brachytherapy (125I vs. 103Pd) combined with external beam radiation therapy.

The purpose of this analysis was to correlate isotope selection with the urinary symptoms of patients who received a combination of external beam radiotherapy (EBRT) and a transperineal interstitial permanent prostate brachytherapy (TIPPB) boost with either a (103)palladium ((103)Pd) or a (125)iodine ((125)I) radioisotope. Postimplant dosimetry was performed to evaluate both urethral dose and implant quality. The American Urologic Association (AUA) scores in both the (125)I and (103)Pd groups were similar initially. However, at 1, 3, 6, and 12 months of follow-up, the mean AUA scores for the (125)I and (103)Pd patients were 18 +/- 6 vs. 11 +/- 9, 17 +/- 7 vs. 11 +/- 7, 10 +/- 3 vs. 9 +/- 4, and 14 +/- 8 vs. 7 +/- 5, respectively (P < 0.01). The only significant difference between the postimplant dose-volume histogram (DVH) of the (125)I and (103)Pd implants was the minimum dose that 90% of the urethra received (D(90)). The increased AUA score of the (125)I group was weakly correlated (R(2) = 0.20) with the D(90) dose but that of the (103)Pd patients was not (R(2) = 0.00). This suggests that the higher AUA score of the (125)I patients was not necessarily the result of the higher D(90) dose. Thus, patients who received (103)Pd experienced less urinary morbidity than those implanted with (125)I. We recommend further validating these findings in prospective studies in which the quality of the (125)I and (103)Pd implants can be evaluated.

Brachytherapy↗
PubMed2001

Inhibition of choroidal neovascularization by intravenous injection of adenoviral vectors expressing secretable endostatin.

Endostatin is a cleavage product of collagen XVIII that inhibits tumor angiogenesis and growth. Interferon alpha2a blocks tumor angiogenesis and causes regression of hemangiomas, but has no effect on choroidal neovascularization (CNV). Therefore, inhibitors of tumor angiogenesis do not necessarily inhibit ocular neovascularization. In this study, we used an intravenous injection of adenoviral vectors containing a sig-mEndo transgene consisting of murine immunoglobulin kappa-chain leader sequence coupled to sequence coding for murine endostatin to investigate the effect of high serum levels of endostatin on CNV in mice. Mice injected with a construct in which sig-mEndo expression was driven by the Rous sarcoma virus promoter had moderately high serum levels of endostatin and significantly smaller CNV lesions at sites of laser-induced rupture of Bruch's membrane than mice injected with null vector. Mice injected with a construct in which sig-mEndo was driven by the simian cytomegalovirus promoter had approximately 10-fold higher endostatin serum levels and had nearly complete prevention of CNV. There was a strong inverse correlation between endostatin serum level and area of CNV. This study provides proof of principle that gene therapy to increase levels of endostatin can prevent the development of CNV and may provide a new treatment for the leading cause of severe loss of vision in patients with age-related macular degeneration.

Adenoviridae↗
PubMed2001

Effect of addition of Rhodobacter sp. to activated-sludge reactors treating piggery wastewater.

Under aerobic conditions, the decay rates of purple nonsulfur bacteria (Rhodobacter sp.) in the light and dark follow first-order kinetics with rate constants of 0.22 and 0.32 day(-1), respectively. The performance of the conventional activated-sludge reactor (CASR) treating anaerobically pretreated piggery wastewater (656-1.110 mg chemical oxygen demand, COD/L) can be enhanced by the addition of Rhodobacter sp. By performing regressive and statistical analyses using the proposed model and experimental data, the kinetic constants k and Y(T), and the fraction of refractory organic materials (f) of the Rhodobacter sp.-supplemented activated-sludge reactor (RASR) are 40% larger, 21% less, and 34% less than those of the CASR, respectively. From parametric sensitivity analyses, the substrate removal efficiencies of the CASR and RASR are most sensitive to the parameters k and the food to microorganisms ratio (F/M) but least sensitive to the parameter f; the specific oxygen utilization rates of the CASR and RASR are most sensitive to the parameters a and k but least sensitive to the parameter b.

Animals↗
PubMed2001

Aeolian flux of metals in Taiwan in the past 2600 years.

To identify anthropogenic sources of pollution, it is useful to compare recent and historical data, yet unfortunately such data are lacking in Taiwan. Thus, we studied the sediments deposited in the remote anoxic, subalpine Great Ghost Lake over a time span of 2600 yrs. Not only could a baseline be established, but also natural variations could be identified. Aeolian Asian dust particles seem to have played a significant role in the flux of 26 elements (Al, As, Ba, Br, Ca, Cd, Ce, Cl, Cr, Cs, Cu, Fe, Ga, K, Mg, Mn, Na, Ni, Pb, Rb, Si, Sr, Ti, V, Zn and Zr) in Great Ghost Lake. The fluxes have generally been higher during dry periods, especially since 1350 AD. On the other hand, local pollution from lead seems to have gained importance since 1945 AD. Recent aeolian fluxes were also calculated based on sediment data, and those results agree with direct measurements obtained in the region.

Climate↗
PubMed2001

Chondrocyte necrosis and apoptosis in impact damaged articular cartilage.

A decrease in chondrocyte numbers is one characteristic of osteoarthritic cartilage. This decrease may be the result of apoptosis or other forms of cell death induced by mechanical damage. Furthermore, cell death may contribute to the structural and metabolic changes found in osteoarthritic cartilage. Therefore, we investigated cell viability and the mode of cell death in cartilage subjected to an increasing severity of impact loads expected to cause compositional damage and osteoarthritic-like metabolic alterations. Canine cartilage explants were subjected to cyclic indentation impacts of 5 megapascals at 0.3 Hz for 0, 2, 20, and 120 min and then kept in culture for 2, 4, 48, and 144 h. Cell death was assessed by the TUNEL assay and by uptake of propidium iodide. Viable cells were detected by the ability to metabolize fluorescein diacetate. Nuclear morphology and ultrastructure of the cell were examined using Hoechst 33342 fluorescent staining and transmission electron microscopy (TEM). As controls for necrosis and apoptosis, cartilage was, respectively, frozen and thawed or incubated with mitomycin-C, an apoptosis inducer. In cartilage that had been loaded for 2 h, 32% of the chondrocytes in the loaded core took up propidium iodide within 2 h after loading. Most of these were in the middle to superficial zones and reflected leaky cell membranes usually characteristic of necrosis. Less than 1% of these chondrocytes were positive in the TUNEL assay after 4 h. After additional culture for 2 days, however, the proportion of chondrocytes which were positive in the TUNEL assay reached 73%. A dose dependent response to duration of loading was detected with the TUNEL assay at this time. The TUNEL assay was not specific for apoptosis since 92% of chondrocytes in freeze/thawed cartilage were TUNEL positive. However, some cells with apoptotic bodies and chromatin condensation characteristic of apoptosis were found in the transition zone between necrotic and normal chondrocytes, but not in the superficial and upper zones, in impact damaged cartilage. We concluded that in this study, necrosis occurred first, followed by apoptosis.

Animals↗
PubMed2001

Inhibition of prostacyclin by indomethacin ameliorates the splanchnic hyposensitivity to glypressin in haemorrhage-transfused common bile duct-ligated rats.

Prostacyclin (PGI2) is an important contributor to the mediation of hyporeactivity to vasoconstrictors and the development of hyperdynamic circulation in portal hypertensive states. Inhibition of PGI2 synthesis in haemorrhage-transfused partially portal vein-ligated rats could ameliorate the splanchnic hyposensitivity to glypressin, a long-acting vasopressin analogue. This study investigated whether the hyposensitivity to glypressin also exists in rats with common bile duct ligation (BDL) and whether the inhibition of PGI2 synthesis by indomethacin could potentiate the portal-hypotensive effect of glypressin in bleeding BDL rats. Two series of BDL rats were used. Series 1 investigated the haemodynamic effects of low dose glypressin (0.07 mg kg-1) in BDL rats with or without bleeding by catheterization. In series 2, haemodynamic parameters were measured in stable or bleeding BDL rats that were receiving intravenously high dose glypressin (0.2 mg kg-1) or indomethacin (5 mg kg-1) followed by high dose glypressin. In rats with a hypotensive haemorrhage, 4.5 mL of blood was withdrawn and 50% of the withdrawn blood was reinfused before the administration of glypressin or indomethacin. Splanchnic hyposensitivity to glypressin was demonstrated in haemorrhage-transfused BDL rats receiving high, but not low, doses of glypressin. Indomethacin infusion did not cause significant systemic and portal haemodynamic changes in bleeding BDL rats (P > 0.05). The addition of indomethacin significantly enhanced the portal-hypotensive effects of glypressin (P < 0.05) and potentiated the increases in mean arterial pressure induced by glypressin infusion (P < 0.001) in bleeding BDL rats. Splanchnic hyposensitivity to glypressin observed in haemorrhage-transfused BDL rats could be ameliorated by the addition of indomethacin, suggesting a role of endogenous PGI2 in its pathophysiology.

Animals↗