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Y Chen

Publications and source records attributed to Y Chen.

At least 163 records · Page 9Linked to original sources
PubMed2004

Trans-diaryl epoxides: asymmetric synthesis, ring-opening, and absolute configuration.

Anthryl-phenyl, phenanthryl-phenyl, and naphthyl-phenyl trans-epoxides (1, 2, and 3, respectively) having enantiomeric purities of 95%, 99%, and 96% were synthesized from a diastereo and enantiopure sulfonium salt derived from Eliel's oxathiane. The determination of their (1R,2R) absolute configurations was achieved by application of the CD exciton chirality method using a Zn-porphyrin tweezer on the corresponding alcohols obtained after opening of these epoxides with LiAlH(4). The R-configuration at C2 of these epoxides, (-)-1, (+)-2, and (-)-3, is consistent with our previous results concerning asymmetric synthesis of monoaryl epoxides, cyclopropanes, and aziridines. The (1S,2R)-configuration of the cis isomer (when present) was also confirmed. Moreover, the agreement between the negative exciton chirality for conjugates of (S)-configuration predicted by molecular modeling and the observed CD spectra helps to clarify the relative steric size of phenyl and CH(2)-aryl (phenanthryl or anthryl), which is critical when the tweezer method is applied for absolute configurational assignment (phenyl = medium group; anthacenyl CH(2) and phenanthryl CH(2) = large group).

Amino Alcohols↗
PubMed2004

Characterization of chicken Nf2/merlin indicates regulatory roles in cell proliferation and migration.

The neurofibromatosis 2 (NF2) tumor suppressor protein merlin, or schwannomin, functions as a negative growth regulator such that inactivating mutations in Nf2 predispose humans to tumors. In addition, merlin has a critical role during embryonic development. Nf2-deficient mice die early during embryogenesis, with defects in gastrulation and extraembryonic tissues. To investigate the function of Nf2/merlin during embryonic development, we first identified the homologous Nf2 gene in chicken (cNf2) and examined the distribution of chicken merlin (c-merlin) during myogenesis. cNf2 encoded a full-length mRNA of 1,770 nucleotides and a protein of 589 residues. C-merlin shared high sequence homology and common protein motifs with vertebrate and Drosophila merlins. In addition, cNF2 functions as a negative growth regulator similar to human and Drosophila merlin in vitro. In vivo, c-merlin was expressed diffusely in the forming dermomyotome but down-regulated in migratory muscle precursors in the forelimb. As muscle formed in the limb, c-merlin expression was up-regulated. As an initial examination of c-merlin function during myogenesis, c-merlin was ectopically expressed in muscle precursors and the effects on muscle development were examined. We show that ectopic merlin expression reduces the proliferation of muscle precursors as well as their ability to migrate effectively in limb mesoderm. Collectively, these results demonstrate that c-merlin is developmentally regulated in migrating and differentiating myogenic cells, where it functions as a negative regulator of both muscle growth and motility.

Amino Acid Motifs↗
PubMed2004

Expression of different isoforms of protein kinase C in the rat hippocampus after pilocarpine-induced status epilepticus with special reference to CA1 area and the dentate gyrus.

At 4 h during pilocarpine-induced status epilepticus (DPISE) in rat, protein kinase C (PKC)beta1, PKCbeta2, and PKCgamma were induced at the border between the stratum oriens and alveus (O/A border) of CA1 in the hippocampus. Induced PKCgamma was colocalized with metabotropic glutamate receptor alpha (mGluR alpha). By intracerebroventricular injection of mGluR1alpha antagonists, (RS)-1-aminoindan-1,5-dicarboxylic acid (AIDA), PKCbeta1, PKCbeta2, and PKCgamma immunoreactive products decreased dramatically; however, intracerebroventricular injection of saline did not change the expression of PKCbeta1, PKCbeta2, and PKCgamma, suggesting that these three PKC isoforms might be involved in mGluR1alpha-related excitoneurotoxicity. One day after pilocarpine-induced status epilepticus (APISE), PKCdelta was induced in microglial cells. At this time point, both PKCgamma and PKCepsilon immunopositive products decreased in the inner molecular layer of upper blade of the stratum granulosum. At 7-31 days APISE, induced PKCbeta1, PKCdelta, PKCeta, and PKCzeta positive astrocytes were demonstrated in all parts of hippocampus, suggesting that they may be involved in gliosis. By this time, both PKCgamma and PKCepsilon immunopositive products in the inner molecular layer had almost disappeared, suggesting that they may be involved in the inhibition of granule cells by controlling neurotransmitter release presynaptically in the dentate gyrus of normal rats.

Animals↗
PubMed2004

Energy-based analysis of milling alpha-lactose monohydrate.

Some observations on the milling of alpha-lactose monohydrate with a Retsch single-ball mill are reported. The effects of mill loading and frequency of the mill motion were investigated. At a given frequency, a lower mill loading showed a higher milling efficiency. For a given mill loading, size reduction rate increased exponentially with frequency. The milling behavior was analyzed with three energy-based models; namely, Rittinger's, Kick's, and Bond's models. The results suggest that Rittinger's model best describes the milling behavior for low mill loadings at high frequencies, whereas the data for high loading milling at low frequencies fit Kick's model better. The results also indicate that attrition and/or chipping is the dominant mechanism for milling at low frequencies with high loadings because of the shear action of the milling ball rolling on the powder bed. Also, as a result of impact of the milling ball on the two ends of the milling jar, fragmentation is responsible for size reduction at high frequencies with low loadings.

Algorithms↗
PubMed2004

Characterization and nuclear localization of the fiber protein encoded by the late region 7 of bovine adenovirus type 3.

To identify the protein encoded by the L7 region of bovine adenovirus-3 (BAdV-3), specific antisera were raised by immunizing rabbits with bacterial fusion proteins encoding the N-terminus or C-terminus of the BAdV-3 fiber protein. Immunoprecipitation and Western blot analysis confirmed that the fiber is expressed as a 102 kDa glycoprotein, which is localized to the nucleus of infected cells. To identify the nuclear localization signals (NLS), BAdV-3 fiber deletion mutants and GFP/beta-galactosidase fusion proteins were expressed in transfected cells, and subcellular localization was visualized by immunofluorescence microscopy. Analysis of deletion mutants localized the NLS to the N-terminal 41 amino acids. Analysis of the N-terminal 41 amino acids identified a cluster of basic residues between amino acid 14 and 20. Substitution of the basic residues (16KAKR19) with acidic residues (16EAEE19) resulted in the accumulation of fiber in the cytoplasm. However, 16KAKR19 or 12VYPYKAKRPNI22 were not sufficient for efficient transport of a cytoplasmic protein GFP/beta-galactosidase to the nucleus. The recombinant BAdV-3 expressing mutant fiber containing 16EAEE19 instead of 16KAKR19 was unable to replicate efficiently in Madin-Darby bovine kidney cells, suggesting that the NLS of fiber carries out important in vivo functions.

Amino Acid Substitution↗
PubMed2004

An experimental study on biomass air-steam gasification in a fluidized bed.

The characteristics of biomass air-steam gasification in a fluidized bed are studied in this paper. A series of experiments have been performed to investigate the effects of reactor temperature, steam to biomass ratio (S/B), equivalence ratio (ER) and biomass particle size on gas composition, gas yield, steam decomposition, low heating value (LHV) and carbon conversion efficiency. Over the ranges of the experimental conditions used, the fuel gas yield varied between 1.43 and 2.57 Nm3/kg biomass and the LHV of the fuel gas was between 6741 and 9143 kJ/Nm3. The results showed that higher temperature contributed to more hydrogen production, but too high a temperature lowered gas heating value. The LHV of fuel gas decreased with ER. Compared with biomass air gasification, the introduction of steam improved gas quality. However, excessive steam would lower gasification temperature and so degrade fuel gas quality. It was also shown that a smaller particle was more favorable for higher gas LHV and yield.

Biomass↗
PubMed2004

Multiple primary tumours of the parotid gland.

The authors reviewed the clinical and histopathological records of 69 cases of multiple primary tumours (MPT) of the parotid gland treated at Peking University School of Stomatology. It accounted for 3.4% of all parotid tumours (2055 patients). Fifty-nine patients were male and 10 were female. The median age was 58 (range 24-80) years. The average time interval between the diagnosis of bilateral parotid tumours was 5 years (range 5 months-15 years). Three clinical types were classified as bilateral parotid tumours (31 cases), unilateral multifocal parotid tumours (29 cases), and the combination of bilateral parotid tumours with unilateral multifocal parotid tumours (9 cases). Histologically, Warthin's tumour was the most common type (60 patients), followed by pleomorphic adenoma (8 cases). Three cases were malignant including adenoid cystic carcinoma, squamous cell carcinoma and mucoepidermoid carcinoma. The histopathologies of tumours were of the same type in 63 patients, and distinctly different in six patients. The tumours were found and diagnosed synchronously in 48 patients, and metachronously in 21 patients. Since some parotid tumours are MPTs, careful preoperative diagnosis is necessary. B-mode ultrasound is the technique of choice for the screening of MPT. Meticulous intraoperative inspection and palpation of the glandular tissues and periglandular lymph nodes are necessary.

Adenolymphoma↗
PubMed2004

DT-MRI denoising and neuronal fiber tracking.

Diffusion tensor imaging can provide the fundamental information required for viewing structural connectivity. However, robust and accurate acquisition and processing algorithms are needed to accurately map the nerve connectivity. In this paper, we present a novel algorithm for extracting and visualizing the fiber tracts in the CNS, specifically in the brain. The automatic fiber tract mapping problem will be solved in two phases, namely a data smoothing phase and a fiber tract mapping phase. In the former, smoothing of the diffusion-weighted data (prior to tensor calculation) is achieved via a weighted TV-norm minimization, which strives to smooth while retaining all relevant detail. For the fiber tract mapping, a smooth 3D vector field indicating the dominant anisotropic direction at each spatial location is computed from the smoothed data. Neuronal fibers are then traced by calculating the integral curves of this vector field. Results are expressed using three modes of visualization: (1) Line integral convolution produces an oriented texture which shows fiber pathways in a planar slice of the data. (2) A streamtube map is generated to present a 3D view of fiber tracts. Additional information, such as degree of anisotropy, can be encoded in the tube radius, or by using color. (3) A particle system form of visualization is also presented. This mode of display allows for interactive exploration of fiber connectivity with no additional preprocessing.

Algorithms↗
PubMed2004

Hippocampal corticotropin releasing hormone: pre- and postsynaptic location and release by stress.

Neuropeptides modulate neuronal function in hippocampus, but the organization of hippocampal sites of peptide release and actions is not fully understood. The stress-associated neuropeptide corticotropin releasing hormone (CRH) is expressed in inhibitory interneurons of rodent hippocampus, yet physiological and pharmacological data indicate that it excites pyramidal cells. Here we aimed to delineate the structural elements underlying the actions of CRH, and determine whether stress influenced hippocampal principal cells also via actions of this endogenous peptide. In hippocampal pyramidal cell layers, CRH was located exclusively in a subset of GABAergic somata, axons and boutons, whereas the principal receptor mediating the peptide's actions, CRH receptor 1 (CRF1), resided mainly on dendritic spines of pyramidal cells. Acute 'psychological' stress led to activation of principal neurons that expressed CRH receptors, as measured by rapid phosphorylation of the transcription factor cyclic AMP responsive element binding protein. This neuronal activation was abolished by selectively blocking the CRF1 receptor, suggesting that stress-evoked endogenous CRH release was involved in the activation of hippocampal principal cells.

Animals↗
PubMed2004

Clinical experience of mycophenolate mofetil in the treatment of chronic allograft nephropathy in kidney transplantation: three-year follow-up.

BACKGROUND: Mycophenolate mofetil (MMF) in conjunction with calcineura antagonists has been shown to prevent acute rejection in renal allograft recipients. Its role in treatment of chronic rejection or allograft nephropathy is still controversial. We initiated the study to investigate the effect of adding MMF to a cyclosporine plus prednisolone regimen in renal recipients with chronic allograft nephropathy. MATERIALS AND METHODS: We retrospectively studied 36 patients with chronic allograft nephropathy, defined clinically as increased of serum creatinine, proteinuria, and hypertension. Renal function, cyclosporine level, renal biopsy, and renal scan were regularly done as indicated. MMF was added to 20 recipients after initial treatment with cyclosporine and prednisolone. The other 16 recipients were managed without adding MMF. Serum creatinine was monitored for 3 years. RESULTS: The demographic characteristics of the patients in the two groups were comparable. The average dose of prednisolone was unchanged throughout the study and the trough level of cyclosporine was maintained in the range of 100 to 150 ng/mL. The serum creatinine decreased initially in the group on MMF, but renal function deteriorated progressively after 6 months. There was a difference in serum creatinine between the two groups but this did not reach statistical significance. CONCLUSION: MMF therapy tender to improve renal function initially but did not attenuate significantly the impairment in chronic allograft nephropathy.

Creatinine↗
PubMed2004

De novo cancer occurrence after renal transplantation: a medical center experience in Taiwan.

INTRODUCTION: Renal transplantation has been advocated as the treatment of choice for end-stage renal disease. Organ transplantation increases the incidence of cancer through unclear mechanisms. A literature review showed that the most common neoplasms are of skin origin, which are uncommon in Eastern people. We reviewed cancer patterns in our renal transplant series. MATERIALS AND METHODS: From July 1981 to December 2002, among 560 renal transplantations performed in this hospital, we retrospectively surveyed cancer incidence, types, and usage of immunosuppressants. RESULTS: Twenty nine cancer cases 5.18% (incidence) included hepatocellular carcinoma (HCC) as the highest mortality rate (9 of 13 cases). Eight of these 13 cases were hepatitis B carriers. All four hepatitis C carriers expired three of them with unresectable multinodular tumors at diagnosis in Posttransplantation lymphoproliferative disorder (PTLD) was the second most common cancer (seven cases); all but one survived with reduced doses of or changes in immunosuppressants. No skin cancer other than four Kaposi's sarcomas with skin manifestations was detected in our series. DISCUSSIONS: HCC was the main cancer in our series. Accepting hepatitis B carriers as candidates for renal recipients and donors may be one of the causes. PTLD was the second most common cancer, while there were no skin cancers.

Adult↗
PubMed2004

Outcome of renal transplantation in children with pericardiopleural effusion.

INTRODUCTION: Children with end-stage renal disease may present with pericardiopleural effusion secondary to volume overload and overhydration. The present study was designed to investigate the efficacy and safety of renal transplantation in these pediatric patients. METHODS: From 1981 to 2001, six of 20 patients (30%) under 18 years old who received renal transplants showed pericardiopleural effusion after serial pretransplant imaging studies. These patients also displayed associated diseases, such as congestive heart failure (n = 3), ascites (n = 2), and splenomegaly (n = 2). The recipients included five boys and one girl of mean age of 12.7 years (range, 8 to 17 years), all of whom had undergone hemodialysis before transplantation. The waiting time for grafts ranged from 1.3 to 6 years (mean = 2.6 years). Episodes of acute pulmonary edema had been observed in three patients pretransplant. RESULTS: One recipient died with a functioning graft due to heart failure with acute pulmonary edema at 4 months after transplantation. Acute rejection episodes were observed in three, and chronic rejection in two children. The median follow-up was 11 years (range = 6 to 16 years) in the other five recipients, all of whom presently survive with functioning grafts. The posttransplant mean serum creatinine levels at 1 year, 3 years, and 5 years were 1.54 +/- 0.44, 1.74 +/- 0.56, and 1.92 +/- 0.56 mg/dL, respectively. CONCLUSION: Renal transplantation in children displaying pericardiopleural effusion was associated with a high success rate. However, these patients must be followed closely with regular cardiopulmonary evaluation since their condition may deteriorate.

Adolescent↗
PubMed2004

Does mycophenolate mofetil increase the incidence of infections in stable renal transplant recipients initially treated with a two-drug regimen?

BACKGROUND: A drug regimen including a calcineurin inhibitor (cyclosporine or tacrolimus) and prednisone has been the mainstay of maintenance immunosuppression in our renal transplant recipients for more than 10 years. After the introduction of mycophenolate mofetil (MMF), a new, potent immunosuppressant that may reduce the incidence of late rejection in renal transplant recipients, the immunosuppressive protocol in some recipients was changed to an MMF-based regimen. We sought to ascertain whether the addition of MMF lead to greater susceptibility to infectious complications. PATIENTS AND METHODS: Between May 1991 and November 2002, all renal transplant recipients who received a two-drug regimen initially for more than 6 months were changed to an MMF-based regimen. The study includes patients with functional grafts for more than 6 months thereafter. Differences in the incidence, etiology, and outcome of infections were compared during the non-MMF versus the MMF periods. RESULTS: Eighty patients of mean age of 38.6 years (range 13 to 69) included 43 men and 37 women. The mean daily MMF dose was 663 mg/patient (range 250 to 1500 mg). The mean follow-up time of non-MMF period and MMF periods were 3.4 and 2.1 years, respectively. The overall incidence of infections in the two periods was similar (0.2 infections/patient in the non-MMF period and 0.25 infections/patient in the MMF period, P = .57). No mortality was associated with these infectious complications. In conclusion, addition of MMF, a more potent immunosuppressive protocol, did not increase the incidence of infections in stable renal transplant recipients initially treated with a two-drug regimen.

Bacterial Infections↗
PubMed2004

Risks and quality-of-life changes in living kidney donors.

INTRODUCTION: Although the benefits of living donor organs for recipients are well documented, the risks and quality-of-life changes in living kidney donors are seldom reported. METHODS: From July 1992 to June 2002, all living kidney donors underwent regular follow-up at our hospital. The MOS 36-item short-form health survey (SF-36), a standardized questionnaire to measure quality of life, was used in this study. Furthermore, donor renal function and associate complications were assessed. RESULTS: Seventeen donors answered the questionnaire, including eight men and nine women of mean age of 41 years (range = 25 to 56). No perioperative mortality was noted. No proteinuria or hematuria was found during long-term follow-up. The mean serum creatinine level was 0.95 +/- 0.22 mg/dL before the operation. The postoperative mean serum creatinine levels at 6 months, 1 year, and 3 years were 1.22 +/- 0.34, 1.19 +/- 0.20, and 1.29 +/- 0.21 mg/dL, respectively. Two cases underwent scar revision and one complained long-term wound pain for more than 1 year. One donor became depressed because of graft failure in her son. The SF-36 scores were 84.4 +/- 4.4 (physical function), 84.0 +/- 4.7 (role-physical), 78.4 +/- 8.0 (body pain), 81.5 +/- 5.9 (general health), 83.2 +/- 3.7 (vitality), 83.9 +/- 5.9 (social functioning), 79.9 +/- 4.1 (role-emotional), and 78.6 +/- 2.3 (mental health), respectively. CONCLUSION: The quality-of-life changes and risks after donation are low; most donors are concerned about cosmetic problems and pain-related scar formation.

Adult↗
PubMed2004

Sirolimus (rapamycin) reduces the incidence of acute rejection episodes in renal transplantation: an initial experience in Taiwan.

BACKGROUND: Acute rejection is the major cause of graft loss in renal transplantation. Sirolimus (rapamycin) inhibits the effects of cytokines on T and B cells; therefore, it provides prophylaxis against acute renal rejection. This open-label trial assessed the incidence of biopsy-confirmed acute rejection episodes, variation in renal function, as well as graft and patient survival rates up to 12 months posttransplantation when using sirolimus in combination with cyclosporine and prednisolone as immunosuppressants. METHODS: Ten kidney transplant recipients received sirolimus 2 mg daily after a 6-mg loading dose. Doses were then adjusted to keep the whole-blood trough level between 5 and 20 mg/mL. All patients received sirolimus in combination with cyclosporine and prednisolone. RESULTS: At 12 months after renal transplantation, the graft and patient survival rates were 90% and 90%, respectively. One patient died at 2 months due to sepsis with a functioning graft. The mean serum creatinine levels at 1, 3, and 6 months were 1.59 mg/dL, 1.71 mg/dL, and 1.65 ml/dL, respectively. There was no biopsy-confirmed acute rejection episode within 12 months. CONCLUSIONS: Sirolimus in combination with cyclosporine and prednisolone significantly protected kidney transplant recipients from acute rejection for up to 1 year of follow-up.

Acute Disease↗
PubMed2004

Is sirolimus a safe alternative to reduce or eliminate calcineurin inhibitors in chronic allograft nephropathy in kidney transplantation?

PURPOSE: We evaluate whether cyclosporine (CsA) or tacrolimus (FK) could be reduced or eliminated after sirolimus was added in chronic allograft nephropathy (CAN). By reducing doses of CsA or FK, we expected that renal function would improve. METHOD AND MATERIAL: Twenty-one patients with CAN had sirolimus added as an immunosuppressive agent. We evaluated the creatinine (Cr) level 3 months after addition. The doses of CsA and FK were decreased gradually and then eliminated over a course of 4 to 6 weeks. If the Cr level rose rapidly or other prominent signs of rejection occurred; low-dose CsA or FK would be added per protocol. We evaluated the duration of engraftment before sirolimus and the Cr level when it was added. RESULTS: Renal function improved in 13 of 21 cases. The improvement in Cr ranged from 12.5% maximally to 1.84% minimally. Seven of 13 cases still required low-dose CsA. The average duration of engraftment before sirolimus was 13.66 +/- 10.80 months. The average Cr level before sirolimus was 1.65 +/- 0.56 mg/dL. In the other eight cases, the Cr level kept rising from 5.1% to 20.4%. The average duration of engraftment was 88.38 +/- 42.21 months. The average Cr level before sirolimus was 2.85 +/- 0.54 mg/dL. Hyperuricemia was noted in 31.3% and hyperlipidemia in 68.8%. CONCLUSION: Sirolimus is a safe alternative to reduce or eliminate CsA or FK in CAN. In cases with a long duration of engraftment and high Cr level, sirolimus might have some effect as a substitute for CNI and thus prevent further nephrotoxicity.

Chronic Disease↗