Biomedical subjects

S C Wu

Publications and source records attributed to S C Wu.

At least 37 records · Page 2Linked to original sources

PubMed2001

Complete nucleotide sequence and cell-line multiplication pattern of the attenuated variant CH2195LA of Japanese encephalitis virus.

Strain-specific determinant of Japanese encephalitis virus (JEV) can be different among each virulence phenotype. We reported previously that the attenuated variant CH2195LA compared with the non-attenuated variant CH2195SA had four amino acid differences in E protein (E-85, E-306, E-331, and E-387) (Wu, S.-C., Lian, W.-C., Hsu, L.-C., Liau, M., 1997. Japanese encephalitis virus antigenic variants with characteristic differences in neutralization resistance and mouse virulence. Virus Res. 51, 173-181). Our present study determined the complete nucleotide sequences of these two variants and found another five amino acid changes in the nonstructural gene regions, including NS2A-215, NS3-350, NS4B-196, NS4B-197, and NS4B-198. The complete nucleotide sequences of the attenuated variant CH2195LA were compared with the non-attenuated variant CH2195SA and other 13 JEV strains. CH2195LA was mostly close to CH2195SA and JaOArS982, and phylogenetically distant to SA14-14-2, SA14-2-8, and RP-2ms of the attenuated JEV strains. The multiplication patterns for CH2195LA compared with CH2195SA in other seven cell lines were different from Vero cells. Relative fitness vector analysis based on a mixture of both variants during cell passage indicated the attenuated variant CH2195LA showed increased viral fitness in Vero cell adaptation. These results revealed that the attenuated variant CH2195LA was unique to culture in Vero cells.

Amino Acid Substitution↗

PubMed2001

Neutralizing peptide ligands selected from phage-displayed libraries mimic the conformational epitope on domain III of the Japanese encephalitis virus envelope protein.

The envelope (E) protein of Japanese encephalitis virus (JEV) contains 500 amino acids with six "conserved" disulfide bonds to maintain its conformational structure. Neutralizing epitopes located on the E protein are mostly conformational dependent. In this study, we used phage-displayed 12-residue combinatorial peptide libraries to select high-affinity peptide ligands bound to monoclonal antibody E3.3. The specific peptide ligands presented on ten high-affinity phage clones displayed six different amino acid sequences, all showing a novel cis-proline turn structure. After being superimposed onto the best fit of the three-dimensional structure of JEV E protein, these peptide structures were mapped to a conformational region constituted by three continuous polypeptide segments (E307-E309, E327-E333, E386-E390) in domain III. Synthetic peptide ligands based on one peptide sequence (E18) were further investigated using alanine scanning within the cis-proline turn structure to demonstrate its unique molecular characteristics. Our results showed that three residues forming the novel cis-proline turn structure were all important in eliciting JEV-specific neutralizing antibodies in mice.

Animals↗

PubMed2001

Stepwise logistic regression analysis of tumor contour features for breast ultrasound diagnosis.

To assist the ultrasound (US) differential diagnosis of solid breast tumors by using stepwise logistic regression (SLR) analysis of tumor contour features, we retrospectively reviewed 111 medical records of digitized US images of breast pathologies. They were pathologically proved benign breast tumors from 40 patients (i.e., 40 fibroadenomas) and malignant breast tumors from 71 patients (i.e., 71 infiltrative ductal carcinomas). Radiologists, before analysis by the computer-aided diagnosis (CAD) system, segmented the tumors manually. The contour features were calculated by measuring the radial length of tumor boundaries. The features selection process was accomplished using a stepwise analysis procedure. Then, an SLR model with contour features was used to classify tumors as benign or malignant. In this experiment, cases were sampled with "leave-one-out" test methods to evaluate the SLR performance using a receiver operating characteristic (ROC) curve. The accuracy of our SLR model with contour features for classifying malignancies was 91.0% (101 of 111 tumors), the sensitivity was 97.2% (69 of 71), the specificity was 80.0% (32 of 40), the positive predictive value was 89.6% (69 of 77), and the negative predictive value was 94.1% (32 of 34). The CAD system using SLR can differentiate solid breast nodules with relatively high accuracy and its high negative predictive value could potentially help inexperienced operators to avoid misdiagnoses. Because the SLR model is trainable, it could be optimized if a larger set of tumor images were supplied.

Adolescent↗

PubMed2001

Assessment of the effect of azo dye RP2B on the growth of a nitrogen fixing cyanobacterium--Anabaena sp.

Certain nitrogen fixing cyanobacteria are diazotrophic, which profoundly impacts the aquatic ecosystem chemically and biologically. Although certain types are banned due to their carcinogenicity, azo dyes are commonly used in the dyeing or textile industry. This work investigates the effect of azo dye on the growth of cyanobacteria. Anabaena sp. isolated from the Da Jia Brook is an odor producing, nitrogen fixing cyanobacterium. The growth rates of Anabaena sp. in the media with or without nitrogen source were 3.56 x 10(-2) mg/ml day and 2.44 x 10(-2) mg/ml day, respectively. Anabaena sp. could not use azo dye RP2B as the nitrogen source. Experimental results indicated that the growth of Anabaena sp. was inhibited in the medium containing RP2B. The degree of inhibition increased from 50% to 81% with an increasing concentration of RP2B (0-50 mg/l). The IC-50 (inhibitory concentration) of RP2B on the growth of Anabaena sp. was 5 mg/l (as based on dry weight) or 7 mg/l (as measured by chlorophyll a).

Anabaena↗

PubMed2001

Relationship between fetal nuchal translucency and crown-rump length in an Asian population.

OBJECTIVES: To investigate the relationship between the nuchal translucency (NT) thickness and crown-rump length (CRL) in normal Asian fetuses during the first trimester. DESIGN: A prospective observational study was conducted. Ultrasound measurement of NT and CRL was offered in 879 consecutive Taiwanese fetuses between 9 weeks and 14 weeks of gestation. Regression analysis was used to analyze the relationship between the NT thickness and CRL. Fetal sex was also considered in the analysis. The distribution of multiple of median (MoM) values of the NT measurements with CRL in 10-mm intervals and the 95th centile of MoM were also calculated. RESULTS: The present study shows that NT measurements increase with increasing CRL. A fixed cut-off point through the first trimester is not appropriate. The NT thickness has no relationship with fetal sex. Expressing the NT thickness by MoM values provides a simple method for clinical practice. CONCLUSIONS: The present study offers normative data of the fetal NT thickness in an Asian population, which may improve the performance of NT measurement during the first-trimester as a screening tool for chromosomal aberrations or other congenital abnormalities in the first trimester.

Adult↗

PubMed2001

Influence of erythropoietin treatment on gonadotropic hormone levels and sexual function in male uremic patients.

OBJECTIVE: The purpose of this study was to evaluate whether levels of sex hormones and sexual function differ in renal failure patients with and without uremia and the effect of treatment with recombinant human erythropoietin (rhuEPO). MATERIAL AND METHODS: Fifteen males with chronic renal failure who were not receiving hemodialysis and 25 male renal failure patients with uremia who were undergoing hemodialysis were enrolled before and after rhuEPO therapy. Fifteen male volunteers matched for age and weight were also studied. Levels of various blood biochemicals were measured in all patients before and 1 week after rhuEPO treatment. Sexual function was also studied in all patients before and 6 months after rhuEPO treatment. RESULTS: The control group had significantly higher levels of testosterone (6.21 +/- 1.21 ng/ml) and hematocrit (Hct) (43.2 +/- 2.1%) and significantly lower levels of prolactin (5.27 +/- 1.21 ng/ml), follicular-stimulating hormone (FSH) (7.51 +/- 2.36 mIU/ml) and leutinizing hormone (LH) (4.23 +/- 2.10 mIU/ml) than the two patient groups (p < 0.05 for all comparisons). Patients with renal failure only had significantly lower levels of testosterone and Hct (2.54 +/- 0.53 ng/ml and 21.4 +/- 1.4%, respectively) than those with uremia (3.65 +/- 0.52 ng/ml and 24.3 +/- 2.5%, respectively; p < 0.001 for both comparisons). After rhuEPO therapy, the testosterone and Hct levels of the two patient groups did not reach the level of the control subjects (p < 0.05 for both comparisons). Similarly, the levels of prolactin, FSH and LH were significantly higher in both patient groups than those of control subjects after rhuEPO therapy (p < 0.001 for both comparisons). However, after rhuEPO therapy, significant increases in testosterone and Hct levels were found in both patient groups (p < 0.001 for both comparisons). Sexual function was also markedly improved in the hemodialysis patient group. While 20/25 (80%) male hemodialysis patients reported improved sexual function after rhuEPO treatment, only 3/15 (20%) chronic renal failure patients reported improvement. CONCLUSIONS: In patients with advanced uremia, rhuEPO therapy may result in improved gonadotropic hormone levels and sexual function. Good dialysis quality may contribute to the increase in the incidence of patients with better sexual function.

Erythropoietin↗

PubMed2001

Age, period, and cohort effects on the attitude toward supporting parents in Taiwan.

PURPOSE: Using the perspectives of age, period, and cohort (APC) effects, this study explored the changes in attitudes toward supporting parents in Taiwan. DESIGN AND METHODS: Population-representative cross-sectional data taken at 1984, 1990, and 1995 from the Social Change Survey in Taiwan were synthesized. Cohort tables and multi-nominal logistic regression were used to analyze the APC effects. RESULTS: Period and age effects were found in the change in attitudes toward supporting parents. Agreement on living with sons or children has slowly decreased. Younger persons agree more than older ones in attitudes toward parents living with their married son or children. There was a reduction in the differences among cohorts across periods. There was no demonstration of cohort effect in this study. IMPLICATIONS: The results indicate that for married children, living with parents is no longer popular in Taiwan society. Social policy should address the unmet needs of elderly people in assistance with daily living.

Adult↗

PubMed2001

A prospective study of p53 expression and its correlation with clinical response of radiotherapy in nasopharyngeal carcinoma.

OBJECTIVES/HYPOTHESIS: Nasopharyngeal carcinoma (NPC) is a common malignant neoplasm of the head and neck that occurs in people in the southeastern Asian area, including Taiwan. The significant association of p53 expression in NPC suggested that p53 overexpression seemed to occur at an early stage in the development of NPC. Alterations of p53 status were probably the most commonly encountered in head and neck carcinomas, and there was extensive evidence that p53 status might determine tumor response to therapy. Ionizing radiation was studied extensively for the relationship between its damaging effect and p53 status in human cancer cells. STUDY DESIGN: This study was carried out to investigate whether there was any correlation between overexpression of p53 protein and locoregional tumor response in patients with NPC treated with 7000 cGy of radiotherapy. METHODS: Sixty-eight patients (50 males, 18 females) with NPC who were diagnosed and treated with radiotherapy were studied prospectively. Before they had received a radiation dose of 7000 cGy in 35 fractions, five fractions a week, p53 status from a nasopharyngeal biopsy was studied using immunohistochemical staining (IHC). RESULTS: The locoregional response rate of primary tumor was analyzed statistically. Forty-seven patients (69.1%) showed positive p53 staining in their tumors. There were 5 positive stains in 6 squamous cell carcinomas (SCC; 83.3%), 34 positive in 53 non-keratinizing carcinomas (NKC; 64.2%), and 8 positive in 9 undifferentiated carcinomas (UC; 88.9%). The mean ages for patients with three different histopathologies were 48.5, 46.1, and 61.1 years. There were 8 patients (7 positive stains, 1 negative stain) with residual tumor after radiotherapy and all were NKC (6 males, 2 females). Therefore, the clinical response rate of primary tumor was 85.1% in positive p53 immunostaining (40 of 47 cases), 95.2% in those with no immunostaining (20 of 21 cases); the former was poorer in locoregional tumor response than the latter, but there was no significant difference (P > .05, chi2 test). CONCLUSIONS: We conclude that there is no statistically significant correlation in locoregional response of primary tumor between p53 overexpression and radiotherapy in patients with NPC (P > .05, Fisher exact test).

Adolescent↗

PubMed2001

Mutagenicity and identification of mutagenic compounds of fumes obtained from heating peanut oil.

Since the fume of cooking oil has been reported to increase the risk of lung cancer, the objectives of this study were to evaluate the mutagenicity and to find the mutagens in the fumes of peanut oil heated to the smoke point. Peanut oil prepared from roasted peanut kernel showed a lower smoke point, less unsaturated fatty acids, more fume formation, and stronger mutagenicity than that from unroasted kernel. Further investigation of mutagenic compounds was performed by the Ames test and gas chromatography/mass spectrometry analysis. Among the 12 compounds identified from the neutral fraction of methanol extract, four compounds at a dose of 10 microg per plate were mutagenic to Salmonella Typhimurium TA98 and TA100 in the order of trans-trans-2,4-decadienal > trans-trans-2,4-nonadienal > trans-2-decenal > trans-2-undecenal. Results report the enal compounds formed as the mutagens in the fumes of peanut oil and indicate that inhaling cooking fumes might cause carcinogenic risk.

Gas Chromatography-Mass Spectrometry↗

PubMed2001

First-trimester Down's syndrome screening by fetal nuchal translucency measurement in Taiwan.

BACKGROUND: Fetal nuchal translucency (NT) measurement is now widely used in many Western countries as a screening tool for Down's syndrome during the first trimester. However, at present there is no data on its use in Taiwan. The purpose of the present study was to evaluate the efficacy of NT measurement in first-trimester Down's syndrome screening in Taiwan. METHODS: We conducted a prospective study from October 1997 to May 1999. Sonographic measurement of fetal NT was performed in 1,249 fetuses at 9-14 weeks of gestation. Transabdominal ultrasound scanning was performed to obtain a sagittal section of the fetus for measuring the crown-rump length (CRL) and the maximum thickness of the subcutaneous translucency between the skin and the soft tissue overlying the cervical spine. Two different cut-off points were used for screening: a fixed cut-off point of at least 2.5 mm and a CRL-related cut-off point. In the latter method, fetuses with an NT measurement in the 95th percentile were considered at high risk for Down's syndrome. RESULTS: Three fetuses had Down's syndrome, with NT measurements of 2.1 mm, 2.7 mm, and 4.0 mm. The false positive rates for the fixed cut-off point and CRL-related cut-off point were 6.3% and 4.6%, respectively. Both methods had a sensitivity of 66.7%. However, the screening program using the CRL-related cut-off point had two advantages: a higher specificity (95.5% vs 93.8%) and a more reasonable distribution pattern for screening. CONCLUSION: This study showed that NT measurement is a potential screening tool for Down's syndrome during the first trimester in Taiwan. Using CRL-related cut-off points for screening is more reasonable than using a fixed cut-off point.

Adult↗

PubMed2001

Expression of transforming growth factor-beta 1 and alpha-smooth muscle actin of myofibroblast in the pathogenesis of nasal polyps.

The pathophysiology of nasal polyps remains unclear, but recent work suggests that many cytokines are produced in nasal polyps (NPs) and that they may play various important roles in the pathogenesis of NPs. Transforming growth factor-beta 1 (TGF-beta 1), secreted by many inflammatory cells, is a potent inducer of myofibroblasts. Myofibroblasts express alpha-smooth muscle actin (alpha-SMA) and a source of extracellular matrix (ECM). In this study, we investigated a potential link between inflammation and the growth process in human NPs. Sixteen patients who were affected by NPs and who had undergone functional endoscopic sinus surgery were included in this study. Nasal mucosa of inferior turbinate (NM) of 10 patients who had received rhinoplasty or turbinectomy for other disease was used as the control. alpha-SMA and TGF-beta 1 were detected using immunohistochemistry and the number of labeled cells were counted (alpha-SMA and TGF-beta 1 indices). The expression of alpha-SMA and TGF-beta 1 indices found in NPs and NM was compared using Student's t-test. In our study, alpha-SMA and TGF-beta 1 indices were found to be significantly higher in nasal polyps than in nasal mucosa. TGF-beta 1 produced by inflammatory cells can influence the development of myofibroblasts which in turn can induce extracellular matrix accumulation and, therefore, TGF-beta 1 plays a important role in the formation of nasal polyps.

Actins↗

PubMed2001

[Factors related to post-treatment marital adjustment in women with breast cancer].

The purpose of this study was to explore post-treatment marital adjustment and related factors in women with breast cancer. The variables include characteristics of illness, pre- and post-treatment marital adjustment, as well as depression. Subjects were recruited by convenience sampling from two medical centers and one community hospital in the Taipei metropolitan area. A total of 119 married women who had received surgery for breast cancer were interviewed with structured questionnaires in a private space. The results showed no difference between marital adjustment pre- and post-treatment. A significant decrease in physical aspects of marriage satisfaction and a significant increase in both psychological and social aspects of marriage satisfaction post-treatment were demonstrated. However, stepwise regression analyses found that the most important predictor of post-treatment marital adjustment is pre-treatment adjustment. Such variables as post-morbid duration, stage of cancer, and different treatment modalities could also predict post-treatment marital adjustment. The results suggest that medical staff should encourage breast cancer patients to face their post-treatment marital status positively. The impact on physical aspects of marriage satisfaction of the breast cancer treatment should not be overlooked. Moreover, an assessment of ovarian function, sexual function, depression, and marital adjustment should be emphasized in women with breast cancer.

Adaptation, Psychological↗

PubMed2001

Ocular ischemic syndrome.

BACKGROUND: The purpose of this study was to investigate the clinical features and management of ocular ischemic syndrome (OIS) and factors influencing its development. METHODS: Ten patients (12 eyes) with OIS underwent detailed medical and ocular histories, complete ophthalmic evaluation including fluorescein angiography, internal carotid artery evaluation by duplex ultrasonography, and management. The following outcome measures were considered: visual acuity, anterior segment neovascularization, lens status, retinal and choroidal changes, and carotid artery stenosis or occlusion. RESULTS: The mean age of the patients was 63 +/- 8 years. Presenting visual symptoms included gradual (82.5%) or sudden (17.5%) onset of vision loss. At initial visit, eyes with OIS had visual acuity less than or equal to counting fingers in 50%, iris neovascularization in 58%, and neovascular glaucoma in 42%. Initially associated systemic diseases in these patients included arterial hypertension (60%), diabetes mellitus (40%), coronary artery disease (20%), previous stroke (30%) and hemodialysis (10%). Complete occlusion or severe occlusion (70-99%) of the internal carotid artery was seen in 75% on the side of OIS. Panretinal photocoagulation did not prevent OIS from progressing but vitreous hemorrhage and rubeosis iris regressed. Carotid endarterectomy had some benefit in stabilizing or improving vision in patients with OIS. CONCLUSION: OIS has a poor visual prognosis. It is imperative that the clinician be aware of the signs and symptoms of carotid disease in order to facilitate prompt diagnosis and appropriate referral, because OIS may be the presenting sign of serious ischemic cerebrovascular and ischemic heart disease.

Adult↗

PubMed2001

Measurement of serum vitamin E isomers in fullterm and preterm infants.

BACKGROUND: This study was conducted with the following aims: (1) to construct a methodology by high-performance liquid chromatography (HPLC) to measure vitamin E levels in our neonatal units; (2) to establish a reference range of serum vitamin E levels in fullterm neonates and their mothers; and (3) to compare these to levels in the preterm group. METHODS: During a 6-month period from September 1996 to February 1997, cord blood of 34 uneventful fullterm neonates (gestational age 38-42 weeks, birth weight 2840-3530 g) and venous blood of their healthy mothers were collected. Venous blood of 35 preterm neonates (gestational age 28-34 weeks, birth weight 940-1980 g) was collected at the same time. Serum vitamin E levels were measured by HPLC. The serum vitamin E/total lipids ratio was also examined. RESULTS: Serum levels of alpha-tocopherol in 34 fullterm neonates and their mothers were 0.212+/-0.127 and 1.160+/-0.513 mg/dl, and of gamma-tocopherol were 0.029+/-0.019 and 0.214+/-0.122 mg/dl, respectively. All fullterm neonates except 2 had serum levels less than 0.5 mg/dl. There was a positive relationship between serum E levels and total lipids. In addition, the correlation between neonatal vitamin E/total lipids ratios and maternal vitamin E/total lipids ratio was statistically significant. The serum level of alpha-tocopherol in 35 preterm infants was 0.170+/-0.090 mg/dl and that of gamma-tocopherol was 0.020+/-0.015 mg/dl; both levels were much lower than those of their fullterm counterparts. But the vitamin E/total lipids ratios did not significantly differ. CONCLUSIONS: We conclude that (1) measurement of serum vitamin E levels by the HPLC method is practical, and is useful in evaluating deficiencies in preterm infants and possibly useful in monitoring the adequacy after supplementation in future study, and (2) preterm infants had a much lower level of serum tocopherol, but no difference was seen in vitamin E/total lipids ratio.

Chromatography, High Pressure Liquid↗

PubMed2000

Study the mechanisms of U-50,488 to prevent the development of morphine tolerance in guinea pigs.

Previously we have shown that low dose of [trans-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl]-benzeneacetamide hydrochloride] (U-50,488) could prevent the development of morphine tolerance in guinea pigs. In the present study we tried to investigate the role of glutamate and nitric oxide in this process. Male Hartley guinea pigs (200-300 g) were chronically treated s.c. with either saline or morphine (15 mg/kg) or morphine + U-50,488 (0.003 mg/kg) twice a day for 7 days. Antinociceptive activity was assessed by hot-plate test on the first, fourth and seventh day. Spinal cord slices (450 microm) were prepared 30 min after drug treatment on eighth day and [3H] glutamate and nitric oxide (NO) released were determined. We found that coadministration of U-50,488 (0.003 mg/kg) suppressed the development of morphine tolerance to antinociceptive effect as we reported before. The percentage of in vitro spinal release of [3H] glutamate by 100 microM morphine was significantly higher in the chronic morphine group than the control group. On the other hand, coadministration of U-50,488 with morphine for 7 days blocked this effect significantly. The basal NO level released from the spinal cord slices was significantly higher in chronic morphine group but not in chronic (morphine + U-50,488) group. In vitro morphine (100 microM) increased the NO level in control group and chronic (morphine + U-50,488) group and also further increased NO in chronic morphine group. From the NMDA-displaced [3H] glutamate binding in guinea pig spinal cord, we found that the Bmax decreased in chronic morphine group but not in the chronic (morphine + U-50,488) group. In conclusion, chronic morphine treatment may activate the NMDA receptors by increasing the release of glutamate which causes the increase of synthesis and release of NO and following uncertain mechanisms to induce the development of morphine tolerance. And the mechanisms of U-50,488 to prevent the development of morphine tolerance may involve the inhibition of glutamate released by chronic morphine and also the decrease of NO induced by chronic morphine.

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

PubMed2000

Synthesis of 60- and 72 kDa heat shock proteins in early porcine embryogenesis.

Proteins of selected embryonic stages were metabolically labeled with [(35)S]-methionine and analyzed by two-dimensional SDS-polyacrylamide gel electrophoresis (2-D PAGE) to study protein expression from 4- to 8-cell to blastocyst stage of porcine embryos. Two proteins with molecular weights of 60 and 72kDa were de novo synthesized during the 4- to 8-cell stage were the earliest that were detected. They were identified as HSP60 and HSP72 according to their locations on 2-D autoradiography and the immunoblotting result of anti-HSP 60 and HSP 72 antibodies of 1-cell stage of porcine embryos. In protein translation in early pig embryogenesis the timing of their synthesis suggests that HSP60 and HSP72 play significant roles as chaperones.

Animals↗

PubMed2000

Analysis of the enzymatic racemization of D-aspartic acid to L-aspartic acid by the on-line coupling of a solid-phase extraction column and a ligand-exchange high-performance liquid chromatography column.

D-Aspartic acid can be enzymatically biotransformed with D-amino acid oxidase and aminotransferase to L-aspartic acid. The reaction was surveyed at three temperatures and a period of 3 days, however, L-aspartic acid can be produced only at the reaction temperature 90 degrees C. However, the separation of D-aspartic acid and L-aspartic acid by ligand-exchange chromatography showed matrix interference. Therefore, the column-switching technique by coupling a solid-phase extraction (SPE) column to the analytical ligand-exchange HPLC column was used to eliminate the matrix effect. The pretreatment of reaction samples with the SPE column was considered as a combination of size-exclusion chromatography and ion-pair chromatography. The ion-pair reagent was 0.005 M sodium 1-octanesulfonate aqueous solution adjusted to pH 2.2. Part of the first eluted peak from the SPE column was then switched through the ligand-exchange column and analyzed with a 0.25 mM Cu2+ aqueous mobile phase of pH 3.6. The quantitative analysis of D- and L-aspartic acids was performed by the standard addition method. Overall, the separation and analysis of D- and L-aspartic acids in the enzymic solution was convenient, fast, and successful with the developed on-line LC-LC column-coupling and column-switching system.

Aspartic Acid↗

PubMed2000

Purification and characterization of beta-adrenergic receptor mRNA-binding proteins.

Beta-adrenergic receptors (beta-ARs), like other G-protein-coupled receptors, can undergo post-transciptional regulation at the level of mRNA stability. In particular, the human beta(1)- and beta(2)-ARs and the hamster beta(2)-AR mRNA undergo beta-agonist-mediated destabilization. By UV cross-linking, we have previously described an approximately M(r) 36,000 mRNA-binding protein, betaARB, that binds to A/C+U-rich nucleotide regions within 3'-untranslated regions. Further, we have demonstrated previously that betaARB is immunologically distinct from AUF1/heterogeneous nuclear ribonucleoprotein (hnRNP) D, another mRNA-binding protein associated with destabilization of A+U-rich mRNAs (Pende, A., Tremmel, K. D., DeMaria, C. T., Blaxall, B. C., Minobe, W., Sherman, J. A., Bisognano, J., Bristow, M. R., Brewer, G., and Port, J. D. (1996) J. Biol. Chem. 271, 8493-8501). In this report, we describe the peptide composition of betaARB. Mass spectrometric analysis of an approximately M(r) 36,000 band isolated from ribosomal salt wash proteins revealed the presence of two mRNA-binding proteins, hnRNP A1, and the elav-like protein, HuR, both of which are known to bind to A+U-rich nucleotide regions. By immunoprecipitation, HuR appears to be the biologically dominant RNA binding component of betaARB. Although hnRNP A1 and HuR can both be immunoprecipitated from ribosomal salt wash proteins, the composition of betaARB (HuR alone versus HuR and hnRNP A1) appears to be dependent on the mRNA probe used. The exact role of HuR and hnRNP A1 in the regulation of beta-AR mRNA stability remains to be determined.

Amino Acid Sequence↗