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P Chen

Publications and source records attributed to P Chen.

At least 109 records · Page 6Linked to original sources
PubMed2001

Amplified delivery of indium-111 to EGFR-positive human breast cancer cells.

A method is described to amplify the delivery of 111In to human breast cancer cells utilizing a novel human serum albumin-human EGF (HSA-hEGF) bioconjugate substituted preferentially in the HSA domain with multiple DTPA metal chelators for 111In. 111In-DTPA-HSA-hEGF exhibited a lower receptor-binding affinity than 111In-DTPA-hEGF but was rapidly and specifically bound, internalized and translocated to the nucleus in EGFR-positive MDA-MB-468 breast cancer cells. 111In-DTPA-HSA-hEGF was cytotoxic in vitro mainly through the emission of short-range Auger electrons and partially through the effects of the hEGF moiety to MDA-MB-468 cells overexpressing EGFR (1-2 x 10(6) receptors/cell) but not towards MCF-7 breast cancer cells with a 100-fold lower level of EGFR on their surface. The cytotoxicity in vitro against MDA-MB-468 cells of 111In-DTPA-HSA-hEGF substituted with nine DTPA chelators was enhanced 4-fold compared to 111In-DTPA-hEGF monosubstituted with DTPA. Studies are planned to further evaluate 111In-DTPA-HSA-hEGF in vivo as a new imaging and targeted radiotherapeutic agent for breast cancer.

Breast Neoplasms↗
PubMed2001

A photic visual cycle of rhodopsin regeneration is dependent on Rgr.

During visual excitation, rhodopsin undergoes photoactivation and bleaches to opsin and all-trans-retinal. To regenerate rhodopsin and maintain normal visual sensitivity, the all-trans isomer must be metabolized and reisomerized to produce the chromophore 11-cis-retinal in biochemical steps that constitute the visual cycle and involve the retinal pigment epithelium (RPE; refs. 3-8). A key step in the visual cycle is isomerization of an all-trans retinoid to 11-cis-retinol in the RPE (refs. 9-11). It could be that the retinochrome-like opsins, peropsin, or the retinal G protein-coupled receptor (RGR) opsin12-16 are isomerases in the RPE. In contrast to visual pigments, RGR is bound predominantly to endogenous all-trans-retinal, and irradiation of RGR in vitro results in stereospecific conversion of the bound all-trans isomer to 11-cis-retinal. Here we show that RGR is involved in the formation of 11-cis-retinal in mice and functions in a light-dependent pathway of the rod visual cycle. Mutations in the human gene encoding RGR are associated with retinitis pigmentosa.

Animals↗
PubMed2001

Allergenic proteins are fragmented in low concentrations of sodium hypochlorite.

BACKGROUND: To facilitate allergen removal from indoor environments, it would be helpful to have household cleaning products that modified allergenic activity. Because NaOCl dissolves proteins in high concentrations and is both capable of killing bacteria and viruses and inactivating viral antigens at somewhat lower concentrations, we explored its effects on Mus m 1 and other indoor allergens. OBJECTIVE: To examine the ability of NaOCl to reduce the allergenicity of Mus m 1 and other indoor allergens. METHODS: Using purified mouse urinary allergen, we examined the effect on protein measured by Coomassie protein assay and on Mus m 1 measured by ELISA. We also examined the effects using SDS/PAGE and Western blots probed with sheep anti-Mus m 1 and with allergic human serum. RESULTS: When NaOCl and Mus m 1 were combined in a molar ratio of 100 : 1, IgE binding to Mus m 1 on Western blot was significantly reduced. At higher NaOCl concentrations the protein appeared to fragment and eventually became undetectable. Fragmentation appeared to be random in that peptides of a wide range of apparent molecular weight were produced. The reaction was complete within 1-2 min at OCl : pr ratios of greater than 200 : 1 and was optimal at pH 7.4. Immunological activity of other allergens (Fel d 1, Bla g 1, Der p 1) was decreased in vitro and dried allergen extracts were removed from surfaces. Adding an extraneous protein, BSA, to NaOCl:Mus m 1 solutions decreased the effect of NaOCl on the allergen. CONCLUSIONS: We concluded that NaOCl at concentrations commonly used in household products is capable of dramatically affecting allergenic protein.

Allergens↗
PubMed2001

Technical challenges of hepatic venous outflow reconstruction in right lobe adult living donor liver transplantation.

A right lobe graft that is drained by the right hepatic vein (RHV) is obtained by transecting the liver on the right side of the middle hepatic vein (MHV). On occasion, a small RHV that only drains a portion of the right lobe, with the predominant outflow achieved by the MHV, is encountered. If such variation is not recognized while performing right lobe liver transplantation and the RHV only is used for reconstruction, venous outflow obstruction with subsequent graft congestion and eventual graft failure will occur. Additionally, preservation of the main MHV and its branch drainage of the left lobe is crucial to avoid outflow blockage to the remaining segment 4 in the donor. We report 4 cases showing a variant type of small RHV and large MHV branch that drain not only segments 5 and 8, but also segments 6 and 7. These variations were simultaneously associated with a large-caliber inferior RHV that also required reconstruction. The methods used to diagnose such anatomic variations and the techniques for reconstruction in the donor and recipient are described.

Adult↗
PubMed2001

Liver transplantation for cholangiocellular carcinoma: analysis of a single-center experience and review of the literature.

Cholangiocellular carcinoma (CCC) is a biliary malignancy that frequently presents in advanced unresectable stages. The role of liver transplantation (LT) as a surgical modality is unclear. The goal of this study is to evaluate outcomes of patients with CCC undergoing LT. A retrospective analysis of all patients undergoing LT was undertaken. Only those patients with the pathological diagnosis of CCC were included on the study. Patients were divided into two groups based on primary tumor location: extrahepatic (EH)-CCC and intrahepatic (IH)-CCC. The Kaplan-Meier method was used to calculate overall and recurrence-free survival. Log-rank analysis was used to determine the significance of prognostic variables. Twenty-five patients were identified: 9 patients with EH-CCC (5 patients, Klatskin-type; 2 patients, the middle third; and 2 patients, the distal third) and 16 patients with IH-CCC. Mean age was 47.1 +/- 10.6 years. There were 14 men and 11 women. Tumor stage was local (stages I and II; n = 9) or advanced (stages III and IV; n = 16). Overall and disease-free survival rates were 71% and 67% at 1 year and 35% and 32% at 3 years, respectively. Analysis of variables showed statistically significant improved outcomes (P < .05) for the absence of contiguous organ invasion at LT, small tumor size, and single tumor foci. This study indicates that early survival after LT for CCC is acceptable. Three-year disease-free survival is achieved in approximately 30% of patients. These outcomes can be improved by applying strict selection criteria based on prognostic variables identified in this study.

Adult↗
PubMed2001

Morphological and positional asymmetries of young children with functional unilateral posterior crossbite.

This prospective clinical study evaluated the morphological and positional mandibular asymmetry of young patients with functional unilateral posterior crossbite. The sample included 9 girls and 6 boys (8.8 +/- 1.0 years of age), evaluated at the initiation of treatment and approximately 6 months after the retention phase (1.1 +/- 0.2 years after initiation of treatment). Each patient had a complete unilateral posterior crossbite involving 3 or more posterior teeth, a functional shift from centric relation-intercuspal position, and no signs or symptoms of temporomandibular disorder. A bonded palatal expansion appliance was used to rapidly expand the maxilla (1 month) and retain the treatment changes (6 months). Zonograms were used to assess articular joint spaces, and submental vertex radiographs were used to assess morphological and positional asymmetry. The results showed that the mandible was significantly longer on the noncrossbite side than it was on the crossbite side. The asymmetry was most evident for the ramus and involved both the condylar and the coronoid processes. The posterior and superior joint spaces were larger on the noncrossbite side than they were on the crossbite side. After treatment and retention, the mandible showed no significant morphological asymmetries. Mandibular growth was greater on the crossbite side than it was on the noncrossbite side, and the mandible had been repositioned; the crossbite side had rotated forward and medially toward the noncrossbite side. We concluded that unilateral posterior crossbites produce morphological and positional asymmetries of the mandible in young children, and that these asymmetries can be largely eliminated with early expansion therapy.

Cephalometry↗
PubMed2001

The relationship between cAMP, Ca(2)+, and transport of CFTR to the plasma membrane.

The mechanism whereby cAMP stimulates Cl(-) flux through CFTR ion channels in secretory epithelia remains controversial. It is generally accepted that phosphorylation by cAMP-dependent protein kinase increases the open probability of the CFTR channel. A more controversial hypothesis is that cAMP triggers the translocation of CFTR from an intracellular pool to the cell surface. We have monitored membrane turnover in Calu-3 cells, a cell line derived from human airway submucosal glands that expresses high levels of CFTR using membrane capacitance and FM1-43 fluorescence measurements. Using a conventional capacitance measurement technique, we observe an apparent increase in membrane capacitance in most cells that exhibit an increase in Cl(-) current. However, after we carefully correct our recordings for changes in membrane conductance, the apparent changes in capacitance are eliminated. Measurements using the fluorescent membrane marker FM1-43 also indicate that no changes in membrane turnover accompany the activation of CFTR. Robust membrane insertion can be triggered with photorelease of caged Ca(2)+ in Calu-3 cells. However, no increase in Cl(-) current accompanies Ca(2)+-evoked membrane fusion. We conclude that neither increases in cAMP or Ca(2)+ lead to transport of CFTR to the plasma membrane in Calu-3 cells. In addition, we conclude that membrane capacitance measurements must be interpreted with caution when large changes in membrane conductance occur.

Biological Transport↗
PubMed2001

A 10-year experience of liver transplantation for hepatitis C: analysis of factors determining outcome in over 500 patients.

OBJECTIVE: To determine the factors affecting the outcome of orthotopic liver transplantation (OLT) for end-stage liver disease caused by hepatitis C virus (HCV) and to identify models that predict patient and graft survival. SUMMARY BACKGROUND DATA: The national epidemic of HCV infection has become the leading cause of hepatic failure that requires OLT. Rapidly increasing demands for OLT and depleted donor organ pools mandate appropriate selection of patients and donors. Such selection should be guided by a better understanding of the factors that influence the outcome of OLT. METHODS: The authors conducted a retrospective review of 510 patients who underwent OLT for HCV during the past decade. Seven donor, 10 recipient, and 2 operative variables that may affect outcome were dichotomized at the median for univariate screening. Factors that achieved a probability value less than 0.2 or that were thought to be relevant were entered into a stepdown Cox proportional hazard regression model. RESULTS: Overall patient and graft survival rates at 1, 5, and 10 years were 84%, 68%, and 60% and 73%, 56%, and 49%, respectively. Overall median time to HCV recurrence was 34 months after transplantation. Neither HCV recurrence nor HCV-positive donor status significantly decreased patient and graft survival rates by Kaplan-Meier analysis. However, use of HCV-positive donors reduced the median time of recurrence to 22.9 months compared with 35.7 months after transplantation of HCV-negative livers. Stratification of patients into five subgroups, based on time of recurrence, revealed that early HCV recurrence was associated with significantly increased rates of patient death and graft loss. Donor, recipient, and operative variables that may affect OLT outcome were analyzed. On univariate analysis, recipient age, serum creatinine, donor length of hospital stay, donor female gender, United Network for Organ Sharing (UNOS) status of recipient, and presence of hepatocellular cancer affected the outcome of OLT. Elevation of pretransplant HCV RNA was associated with an increased risk of graft loss. Of 15 variables considered by multivariate Cox regression analysis, recipient age, UNOS status, donor gender, and log creatinine were simultaneous significant predictors for patient survival. Simultaneously significant factors for graft failure included log creatinine, log alanine transaminase, log aspartate transaminase, UNOS status, donor gender, and warm ischemia time. These variables were therefore entered into prognostic models for patient and graft survival. CONCLUSION: The earlier the recurrence of HCV, the greater the impact on patient and graft survival. The use of HCV-positive donors may accelerate HCV recurrence, and they should be used judiciously. Patient survival at the time of transplantation is predicted by donor gender, UNOS status, serum creatinine, and recipient age. Graft survival is affected by donor gender, warm ischemia time, and pretransplant patient condition. The authors' current survival prognostic models require further multicenter validation.

Adult↗
PubMed2001

Emergence of reduced susceptibility and resistance to fluoroquinolones in Escherichia coli in Taiwan and contributions of distinct selective pressures.

A survey of 1,203 Escherichia coli isolates from 44 hospitals in Taiwan revealed that 136 (11.3%) isolates were resistant to fluoroquinolones and that another 261 (21.7%) isolates had reduced susceptibility. Resistance was more common in isolates responsible for hospital-acquired (mostly in intensive care units) infections (17.5%) than in other adult inpatient (11.4%; P = 0.08) and outpatient isolates (11.9%; P > 0.1). Similarly, reduced susceptibility was more common in isolates responsible for hospital-acquired infections (30.9%) than in other adult inpatient (21.0%; P = 0.04) and outpatient (21.4%; P = 0.06) isolates. Isolates from pediatric patients were less likely to be resistant (1.3 versus 12.0%; P < 0.01) but were nearly as likely to have reduced susceptibility (17.7 versus 21.9%; P > 0.1) as nonpediatric isolates. There was an inverse relationship in the proportion of isolates that were resistant versus the proportion that had reduced susceptibility among isolates from individual hospitals (R = 0.031; P < 0.05). In an analysis of isolates from two hospitals, all 9 resistant strains possessed double point mutations in gyrA and all 19 strains with reduced susceptibility strains had single point mutations; no mutations were found among fully susceptible strains. Risk factors for resistance included underlying cancer (odds ratio [OR], 83; 95% confidence interval [CI(95)], 7.3 to 2,241; P < 0.001), exposure to a quinolone (OR, undefined; P = 0.02), and exposure to a nonquinolone antibiotic (OR, 20; CI(95), 2.2 to 482; P < 0.001); underlying cancer was the only independent risk factor (OR, 83; CI(95), 8.6 to 807; P < 0.001). There were no significant associations between any of these factors and reduced susceptibility. Whereas acute and chronic quinolone use in cancer patients is a major selective pressure for resistance, other undetermined but distinct selective pressures appear to be more responsible for reduced susceptibility to fluoroquinolones in E. coli.

Adolescent↗
PubMed2001

The group I strain of Streptococcus mutans, UA140, produces both the lantibiotic mutacin I and a nonlantibiotic bacteriocin, mutacin IV.

Strains of Streptococcus mutans produce at least three mutacins, I, II, and III. Mutacin II is a member of subgroup AII in the lantibiotic family of bacteriocins, and mutacins I and III belong to subgroup AI in the lantibiotic family. In this report, we characterize two mutacins produced by UA140, a group I strain of S. mutans. One is identical to the lantibiotic mutacin I produced by strain CH43 (F. Qi et al., Appl. Environ. Microbiol. 66:3221-3229, 2000); the other is a nonlantibiotic bacteriocin, which we named mutacin IV. Mutacin IV belongs to the two-peptide, nonlantibiotic family of bacteriocins produced by gram-positive bacteria. Peptide A, encoded by gene nlmA, is 44 amino acids (aa) in size and has a molecular mass of 4,169 Da; peptide B, encoded by nlmB, is 49 aa in size and has a molecular mass of 4,826 Da. Both peptides derive from prepeptides with glycines at positions -2 and -1 relative to the processing site. Production of mutacins I and IV by UA140 appears to be regulated by different mechanisms under different physiological conditions. The significance of producing two mutacins by one strain under different conditions and the implication of this property in terms of the ecology of S. mutans in the oral cavity are discussed.

Actinomycetales↗
PubMed2001

MAT1-modulated CAK activity regulates cell cycle G(1) exit.

The cyclin-dependent kinase (CDK)-activating kinase (CAK) is involved in cell cycle control, transcription, and DNA repair (E. A. Nigg, Curr. Opin. Cell. Biol. 8:312-317, 1996). However, the mechanisms of how CAK is integrated into these signaling pathways remain unknown. We previously demonstrated that abrogation of MAT1 (ménage à trois 1), an assembly factor and targeting subunit of CAK, induces G(1) arrest (L. Wu, P. Chen, J. J. Hwang, L. W. Barsky, K. I. Weinberg, A. Jong, and V. A. Starnes, J. Biol. Chem. 274:5564-5572, 1999). This result led us to investigate how deregulation of CAK by MAT1 abrogation affects the cell cycle G(1) exit, a process that is regulated most closely by phosphorylation of retinoblastoma tumor suppressor protein (pRb). Using mammalian cellular models that undergo G(1) arrest evoked by antisense MAT1 abrogation, we found that deregulation of CAK inhibits pRb phosphorylation and cyclin E expression, CAK phosphorylation of pRb is MAT1 dose dependent but cyclin D1/CDK4 independent, and MAT1 interacts with pRb. These results suggest that CAK is involved in the regulation of cell cycle G(1) exit while MAT1-modulated CAK formation and CAK phosphorylation of pRb may determine the cell cycle specificity of CAK in G(1) progression.

Cell Division↗
PubMed2001

Chk2 activation dependence on Nbs1 after DNA damage.

The checkpoint kinase Chk2 has a key role in delaying cell cycle progression in response to DNA damage. Upon activation by low-dose ionizing radiation (IR), which occurs in an ataxia telangiectasia mutated (ATM)-dependent manner, Chk2 can phosphorylate the mitosis-inducing phosphatase Cdc25C on an inhibitory site, blocking entry into mitosis, and p53 on a regulatory site, causing G(1) arrest. Here we show that the ATM-dependent activation of Chk2 by gamma- radiation requires Nbs1, the gene product involved in the Nijmegen breakage syndrome (NBS), a disorder that shares with AT a variety of phenotypic defects including chromosome fragility, radiosensitivity, and radioresistant DNA synthesis. Thus, whereas in normal cells Chk2 undergoes a time-dependent increased phosphorylation and induction of catalytic activity against Cdc25C, in NBS cells null for Nbs1 protein, Chk2 phosphorylation and activation are both defective. Importantly, these defects in NBS cells can be complemented by reintroduction of wild-type Nbs1, but neither by a carboxy-terminal deletion mutant of Nbs1 at amino acid 590, unable to form a complex with and to transport Mre11 and Rad50 in the nucleus, nor by an Nbs1 mutated at Ser343 (S343A), the ATM phosphorylation site. Chk2 nuclear expression is unaffected in NBS cells, hence excluding a mislocalization as the cause of failed Chk2 activation in Nbs1-null cells. Interestingly, the impaired Chk2 function in NBS cells correlates with the inability, unlike normal cells, to stop entry into mitosis immediately after irradiation, a checkpoint abnormality that can be corrected by introduction of the wild-type but not the S343A mutant form of Nbs1. Altogether, these findings underscore the crucial role of a functional Nbs1 complex in Chk2 activation and suggest that checkpoint defects in NBS cells may result from the inability to activate Chk2.

Cell Cycle↗
PubMed2001

Distinct phenotypes distinguish the molecular classes of Angelman syndrome.

BACKGROUND: Angelman syndrome (AS) is a severe neurobehavioural disorder caused by defects in the maternally derived imprinted domain located on 15q11-q13. Most patients acquire AS by one of five mechanisms: (1) a large interstitial deletion of 15q11-q13; (2) paternal uniparental disomy (UPD) of chromosome 15; (3) an imprinting defect (ID); (4) a mutation in the E3 ubiquitin protein ligase gene (UBE3A); or (5) unidentified mechanism(s). All classical patients from these classes exhibit four cardinal features, including severe developmental delay and/or mental retardation, profound speech impairment, a movement and balance disorder, and AS specific behaviour typified by an easily excitable personality with an inappropriately happy affect. In addition, patients can display other characteristics, including microcephaly, hypopigmentation, and seizures. METHODS: We restricted the present study to 104 patients (93 families) with a classical AS phenotype. All of our patients were evaluated for 22 clinical variables including growth parameters, acquisition of motor skills, and history of seizures. In addition, molecular and cytogenetic analyses were used to assign a molecular class (I-V) to each patient for genotype-phenotype correlations. RESULTS: In our patient repository, 22% of our families had normal DNA methylation analyses along 15q11-q13. Of these, 44% of sporadic patients had mutations within UBE3A, the largest percentage found to date. Our data indicate that the five molecular classes can be divided into four phenotypic groups: deletions, UPD and ID patients, UBE3A mutation patients, and subjects with unknown aetiology. Deletion patients are the most severely affected, while UPD and ID patients are the least. Differences in body mass index, head circumference, and seizure activity are the most pronounced among the classes. CONCLUSIONS: Clinically, we were unable to distinguish between UPD and ID patients, suggesting that 15q11-q13 contains the only significant maternally expressed imprinted genes on chromosome 15.

Adult↗
PubMed2001

Pax genes in development and maturation of the vertebrate visual system: implications for optic nerve regeneration.

Pax genes play a pivotal role in development of the vertebrate visual system. Pax6 is the master control gene for eye development: ectopic expression of Pax6 in Xenopus laevis and Drosphila melanogaster leads to the formation of differentiated eyes on the legs or wings. Pax6 is involved in formation of ganglion cells of the retina, as well as cells of the lens, iris and cornea. In addition Pax6 may play a role in axon guidance in the visual system. Pax2 regulates differentiation of the optic disk through which retinal ganglion cell axons exit the eye. Furthermore, Pax2 plays a critical role in development of the optic chiasm and in the guidance of axons along the contralateral or ipsilateral tracts of the optic nerve to visual targets in the brain. During development Pax7 is expressed in neuronal cells of one of the major visual targets in the brain, the optic tectum/superior colliculus. Neurons expressing Pax7 migrate towards the pia and concentrate in the stratum griseum superficiale (SGFS), the target site for retinal axons. Together, expression of Pax2, 6 and 7 may guide axons during formation of functional retinotectal/collicular projections. Highly regulated Pax gene expression is also observed in mature animals. Moreover, evidence suggests that Pax genes are important for regeneration of the visual system. We are currently investigating Pax gene expression in species that display a range of outcomes of optic nerve regeneration. We predict that such information will provide valuable insights for the induction of successful regeneration of the optic nerve and of other regions of the central nervous system in mammals including man.

Animals↗
PubMed2001

Simultaneous determination of nitrate and nitrite in saliva and foodstuffs by non-suppressed ion chromatography with bulk acoustic wave detector.

In the present paper, nitrate and nitrite in foodstuffs and saliva were simultaneously determined using a non-suppressed ion chromatography (IC) method with a bulk acoustic wave sensor (BAW) as detector, and 1.5 mmol/L potassium hydrogenphthalate (KHP) as mobile phase. The IC-BAW method is simple, rapid and accurate. The determination limits for nitrite and nitrate are 0.20 and 0.30 mg/L, respectively. The IC-BAW is comparable and agrees with the conventional spectrophotometric method for nitrite and nitrate determination.

Chromatography, Ion Exchange↗
PubMed2001

Hepatitis C virus infection and morphologic study in B lymphocytes of patient with hepatitis C.

OBJECTIVE: To study hepatitis C virus (HCV) infection in B lymphocytes of patients with hepatitis C and to establish a B cell line with HCV infection and observe the hepatitis C virus like particles. METHODS: A B lymphoblastoid cell line was established by Epstein-Barr virus induced transformation directly from peripheral blood mononuclear cells of a patient with hepatitis C. The HCV antigen and HCV RNA were detected by immunohistochemical technique. Reverse transcription-polymerase chain reaction(RT-PCR) and in situ hybridization and HCV particle were detected by electron microscopy. RESULTS: Positive HCV RNA was found in supernatants of B cell line. HCV Ag and HCV RNA were also showed positive. Electron microscopy observed HCV spherical virus like particles with a diameter of approximately 65 nm and 110 nm and the "bud mutation" of HCV in the cytoplasmic vesicles of B lymphocytes. CONCLUSIONS: HCV could infect B lymphocytes and replicate in the cell line. HCV particles are formed by "bud mutation" of HCV in the cytoplasmic vesicles of B-lymphocytes.

B-Lymphocytes↗