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Biomedical subjects

M S Chen

Publications and source records attributed to M S Chen.

At least 73 records · Page 4Linked to original sources
PubMed1996

Characterization of an hsp70 related clone encoding a 33 kDa protein with homology to a protein which associates with polysomes.

Characterization of an hsp70 related Chinese hamster cDNA clone revealed that it encodes a 33 kDa protein with homology to a mouse ribosomal component p40 which associates with polysomes (Auth and Brawerman (1992) Proc. Natl. Acad. Sci. USA 89, 4368). The predicted amino acid sequence of this cDNA which differs by only two residues from p40, shares significant similarity with various members of the hsp70 family. Sequence analysis revealed a 29% identity between the N-terminal region (residues 1 to 120) of the 33 kDa protein and the ATP binding domain of the Chinese hamster hsc70, but no significant sequence similarity was found between the remaining C-terminal regions of the 33 kDa polypeptide and the hsc70 protein. The N-terminal region of the 33 kDa protein lacks the typical consensus motif for ATP binding, suggesting that the N-terminal domain of the 33 kDa protein may not be involved in ATP binding. In the light of the fact that this 33 kDa protein is a ribosomal component, we speculate that the N-terminal domain may interact with structures containing nucleotides such as RNA.

Amino Acid Sequence↗
PubMed1996

Kinetic analysis of the interaction of cidofovir diphosphate with human cytomegalovirus DNA polymerase.

Cidofovir [CDV,(S)-1-(3-hydroxy-2-phosphonylmethoxypropyl)cytosine, HPMPC] is an acyclic cytosine nucleoside phosphonate analog with potent in vitro and in vivo activity against a broad spectrum of herpesviruses. CDV diphosphate (CDVpp), the putative antiviral metabolite of CDV, is a competitive inhibitor of dCTP and an alternate substrate for human cytomegalovirus (HCMV) DNA polymerase. HCMV DNA polymerase used a synthetic DNA primer-template with a Km value of 90 +/- 8 nM and incorporated dCTP approximately 42 times more efficiently than CDVpp. HCMV DNA polymerase also utilized a synthetic DNA primer containing a single molecule of CDV at the 3'-terminus. The Km value for this DNA primer-template was 165 +/- 42 nM and incorporation of dCTP was approximately 17 times more efficient than that of CDVpp. The slower rate of incorporation of CDVpp was due mostly to the higher Km value of CDVpp toward the enzyme-primer-template complexes. These data demonstrate that incorporation of a single CDV into DNA by HCMV DNA polymerase does not lead to chain termination.

Animals↗
PubMed1996

Fabrication and selective surface modification of 3-dimensionally textured biomedical polymers from etched silicon substrates.

A new method is described for producing biomedically relevant polymers with precisely defined micron scale surface texture in the x, y, and z planes. Patterned Si templates were fabricated using photolithography to create a relief pattern in photoresist with lateral dimensions as small as 1 micron. Electroless Ni was selectively deposited in the trenches of the patterned substrate. The Ni served as a resilient mask for transferring the patterns onto the Si substrate to depths of up to 8.5 microns by anisotropic reactive ion etching with a fluorine-based plasma. The 3-dimensional (3-D) textured silicon substrates were used as robust, reusable molds for pattern transfer onto poly (dimethyl siloxane), low density poly (ethylene), poly (L-lactide), and poly (glycolide) by either casting or injection molding. The fidelity of the pattern transfer from the silicon substrates to the polymers was 90 to 95% in all three planes for all polymers for more than 60 transfers from a single wafer, as determined by scanning electron microscopy and atomic force microscopy. Further, the 3-D textured polymers were selectively modified to coat proteins either in the trenches or on the mesas by capillary modification or selective coating techniques. These selectively patterned 3-D polymer substrates may be useful for a variety of biomaterial applications.

Biocompatible Materials↗
PubMed1996

Oral health and quality of life in New Zealand: a social perspective.

This study addresses the social dimensions of oral health by relating oral quality of life (i.e. dental symptoms, perceived oral well-being and oral functioning) to oral health status. We propose a conceptual model which postulates that socioeconomic status, oral health behavior and oral health status each influence oral quality of life. Using data from the New Zealand National Oral Health Survey, we describe and analyze oral health status and oral quality of life among children aged 12-13 and adults aged 35-44 and 65-74. The study demonstrates the impact of oral health problems on the oral quality of life of children, middle-aged adults and older adults in New Zealand. The majority have experienced at least one dental symptom in the past year. Some of them perceive poor oral health and also dislike the way their teeth/dentures look. Various aspects of their social and physical functioning are adversely affected by oral health problems. The results of multiple regression analyses of oral quality of life demonstrate that perceived general health is a consistent predictor of quality of life. Furthermore, the adults' oral quality of life is positively related to asymptomatic dental visits and negatively related by symptomatic dental visits. Children's oral quality of life is positively related to more frequent brushing and flossing. Oral health status is closely associated with oral quality of life for both adults and children. Analyzing the New Zealand oral quality of life data and reviewing previous research findings using a conceptual model provide the possibility for a more comprehensive and integrated understanding of oral quality of life issues.

Adolescent↗
PubMed1996

alpha-Amylase inhibitors from wheat: amino acid sequences and patterns of inhibition of insect and human alpha-amylases.

Four alpha-amylase inhibitors, WRP24, WRP25, WRP26, and WRP27, were purified from wheat flour by preparative, reversed-phase high performance liquid chromatography. All have polypeptide molecular masses of about 14 kDa and are members of the cereal superfamily of protease and alpha-amylase inhibitors. Sedimentation velocity analysis indicated that WRP25 and WRP27 are monomeric proteins, whereas WRP24 is a dimer. WRP24 is identical in N-terminal amino acid sequence to the well characterized 0.19 dimeric inhibitor from wheat kernels. WRP25 and WRP26 differ in sequence from each other at only three positions and represent previously unseparated forms of the 0.28 wheat inhibitor. WRP27 is a previously uncharacterized inhibitor and is more similar in sequence to the 0.28 inhibitor than to the 0.19 inhibitor. WRP25 and WRP26 inhibited alpha-amylases from the rice weevil, red flour beetle, and the yellow meal worm, but did not inhibit human salivary alpha-amylase. WRP24 inhibited the human as well as the insect alpha-amylases, but inhibited one of the two rice weevil alpha-amylases much more strongly than the other. WRP27 was notable in that, of the enzymes tested, it strongly inhibited only the rice weevil alpha-amylases. We observed that the growth rate of red flour beetle larvae was slowed when purified WRP24 was included in the diet at a level of 10%. Addition of WRP24 to corn starch resulted in greater weight loss of red flour beetle adults than occurred on control diets. Our results support the hypothesis that these alpha-amylase inhibitors provide wheat seeds with a selective evolutionary advantage since the inhibitors can slow the growth of insect pests that attack cereal grains.

Amino Acid Sequence↗
PubMed1996

Inhibition of cell-induced vitreous contraction by synthetic peptide derived from the collagen receptor binding sequence.

Cell-mediated tractional retinal detachment (TRD) is the end result of various intraocular proliferative disorders. Interactions between cells and extracellular matrix via cellular surface receptors, integrins, play an important role. Anti-adhesion therapy has been suggested as a promising way to treat the integrin-dependent pathological events. We tested three synthetic peptides, Gly-Arg-Gly-Asp-Ser (GRGDS), derived from the fibronectin receptor binding domain; Try-Ile-Gly-Ser-Arg (YIGSR), from the laminin receptor binding domain, and Ala-Asp-Gly-Glu-Ala (ADGEA), from the collagen receptor binding domain, to evaluate their inhibitory effect on cell-mediated matrix attachment and vitreous contraction in vitro, and on cell-induced TRD in rabbit eyes in vivo. Indirect immunofluorescent stain demonstrated both bovine retinal pigment epithelial (RPE) cells and rabbit dermal fibroblasts expressed the alpha 2 beta 1, alpha 5 beta 1 and alpha 6 beta 1 integrins, the collagen, fibronectin, and laminin receptors, respectively. GRGDS exhibited a broad spectrum of inhibitory activity on RPE cell attachment to extracellular matrices. YIGSR specifically inhibited RPE cell attachment to laminin, whereas ADGEA inhibited RPE cell attachment to collagen type I and IV. ADGEA inhibited RPE cell-induced vitreous contraction in a dose-dependent manner, whereas GRGDS and YIGSR had no effect. ADGEA (1250 micrograms/mL) delayed the development of TRD but did not prevent it. ADGEA was nontoxic to cells and retina, as demonstrated by cytotoxicity tests and histological examination. The synthetic peptide, ADGEA, and its analogs may be potential candidates for the treatment of cell-mediated collagenous contraction in the ocular tissues.

Animals↗
PubMed1996

Comparative kinetic analyses of interaction of inhibitors with Rauscher murine leukemia virus and human immunodeficiency virus reverse transcriptases.

The inhibitory effects of several nucleoside triphosphate analogs on Rauscher murine leukemia virus (RMuLV) and human immunodeficiency virus (HIV) type 1 reverse transcriptases (RTs) were studied. With RNA as the template, the apparent K(m) and apparent K(i) values of HIV RT toward its substrates and inhibitors are 12 to 500 times lower than the corresponding values for RMuLV RT. However, the k(i)/k(m) ratios (inhibition efficiencies) for HIV and RMuLV RTs'are similar for AZTTP (zidovudine triphosphate), d4TTP [3'-deoxythymidine-2'-ene-(3'-deoxy-2',3'-didehydrothymidine) triphosphate], PMEADP [9-(2-phosphonylmethoxyethyl)adenine diphosphate], FIAUTP [1-(2-fluoro-2-deoxy-beta-D-arabinofuranosyl)-5-iodouracil triphosphate], and HPMPCDP [(S)-1-(3-hydroxy-2-phosphylmethoxypropyl) cytosine diphosphate]. With DNA as the template, the K(m) values are similar for HIV and RMuLV RTs. However, the K(i)/K(m) values of HIV and RMuLV RTs are significantly different for ddCTP, ddATP, and 3TCTP (2',3'-dideoxy-3'-thiacytidine). The RTs of RMuLV and HIV are sufficiently different from one another that the kinetic inhibition constants for a particular antiviral compounds should be determined to indicate whether anti-RMuLV activity is likely to be predictive for the anti-HIV activity of the compound. This information, in conjunction with species-specific drug metabolism differences and tissue culture antiviral activity, is important in determining the suitability of a particular animal model.

Adenine↗
PubMed1996

Novel mutation (K70E) in human immunodeficiency virus type 1 reverse transcriptase confers decreased susceptibility to 9-[2-(phosphonomethoxy)ethyl]adenine in vitro.

9-[2-(phosphonomethoxy)ethyl]adenine (PMEA), an acyclic nucleoside phosphonate analog, is active against several retroviruses and herpesviruses and has shown anti-human immunodeficiency virus (HIV) activity in clinical trials. Serial passage of HIV type 1 (strain IIIb, in MT2 cells in increasing concentrations of PMEA resulted in viruses with > 12-fold increases in their 50% inhibitory concentrations of PMEA compared with that for strain IIIb. Sequence analyses of these PMEA-selected viruses demonstrated the presence of a novel lysine-to-glutamic acid mutation at amino acid 70 (K70E) in HIV reverse transcriptase. A recombinant virus carrying the K70E mutation was constructed and showed a 10-fold increase in its 50% inhibitory concentrations of PMEA and 2',3'-dideoxy-3'-thiacytidine but showed wild-type susceptibility levels to 2',3'-dideoxycytosine, 2',3'-dideoxyinosine,2',3'-didehydro-2'3'-dideoxythymidine, 3'-azido-3'-deoxythymidine, foscarnet, and two additional phosphonates, 9-[(R)-2-(phosphonomethoxy)propyl]adenine and 9-[2,5-dihydro-5-(phosphonomethoxy)-2-furanyl]adenine. Additionally, the K70E recombinant showed a minor reduction in growth kinetics compared with those of the wild-type virus in vitro.

Adenine↗
PubMed1996

The blood-aqueous barrier in anisometropia and high myopia.

Functional disorder of the blood-ocular barrier has been suggested in cases of degenerative high myopia. Whether the blood-aqueous barrier among young high myopes with healthy vitreous suffers changes is worthy to be explored. Flare density was measured with the laser flare cell meter (Kowa) in highly myopic and anisometropic students. The mean flare density of highly myopic eyes in the myopic group (4.28 +/- 1.13 photon counts/ms) was similar to that of the emmetropic control group (4.24 +/- 1.79 photon counts/ms). Moreover, the difference in flare density between the two eyes of anisometropic patients was not statistically significant. Thus, the blood-aqueous barrier seems intact in young high myopes with healthy posterior vitreous and fundus.

Adolescent↗
PubMed1996

Amplification and altered expression of the hsc70/U14 snoRNA gene in a heat resistant Chinese hamster cell line.

We have recently demonstrated that the heat resistant phenotype of the HR-1 variant isolated from HA-1 Chinese hamster fibroblasts after a series of heat shocks is associated with the increased expression of Hsc70, the constitutive form of Hsp70 (Laszlo and Li 1985). Here, we report the cloning and characterization of the Chinese hamster hsc70 gene and its organization and expression in wild type HA-1 and permanently heat resistant HR-1 cells. DNA sequencing revealed that the structure and nucleotide sequence of the hamster hsc70 gene is highly homologous to the human and rat genes coding for Hsc70. Three of the eight introns of the hamster hsc70 gene encode U14 small nucleolar RNAs, as has been demonstrated in other species. Although putative transcriptional elements, including a TATA box, two inverted CAT boxes, and two sets of heat shock elements (HSEs) are completely conserved in the human and hamster hsc70 genes, the regulation of expression of the hamster hsc70 gene is different from that reported for its human counterpart in that the mRNA coding for Hsc70 increases at least 10-fold after a mild heat shock in Chinese hamster cells while no induction of Hsc70 by heat shock has been reported in human cell lines. In situ hybridization revealed a complex chromosomal rearrangement in HR-1 cells which results in the 4- to 5-fold amplification of the hsc70 gene as indicated by genomic Southern blots. In association with this amplification of the hsc70 gene, the levels of Hsc70 mRNA and U14 snoRNA are increased in the HR-1 cells under both normal growing conditions and after heat shock. Thus, the elevated expression of both Hsc70 and U14 snoRNA might play a role in the heat resistant phenotype of the HR-1 cells. This is the first report of the amplification of a heat shock gene and the possible induction of gene amplification by heat shock.

Amino Acid Sequence↗
PubMed1996

Inhibition of retinal pigment epithelial cell-induced tractional retinal detachment by disintegrins, a group of Arg-Gly-Asp-containing peptides from viper venom.

PURPOSE: Integrin-mediated extracellular matrix (ECM) attachment plays an important role in vitreous contraction of retinal pigment epithelial (RPE) cells. Disintegrins, a group of Arg-Gly-Asp (RGD)-containing peptides from viper venom, are potential anti-adhesion agents that interfere with integrin-ECM binding. This study was performed to determine whether disintegrins were effective in inhibiting RPE cell-induced matrix attachment in vitro and tractional retinal detachment in a rabbit model in vivo. METHODS: Two disintegrins, echistatin from viper Echis carinatus and flavoridin from Trimeresurus flavoviridis, were used. The expression of integrins on the surface of bovine and rabbit RPE cells was examined by indirect immunofluorescent stain with specific anti-integrin monoclonal antibodies. The inhibitory effect of disintegrins on RPE cell-mediated ECM attachment and vitreous contraction was evaluated with cell adhesion and vitreous contraction assays. In the in vivo model, rabbit eyes were injected intravitreously with either homologous rabbit RPE cells alone or together with disintegrins to induce tractional retinal detachment. The cytotoxic effect of disintegrins was examined with a cell proliferation assay using the alamar blue method. Retinal toxicity of disintegrins was evaluated with electroretinograms and histologic examination of the rabbit eyes. RESULTS: Bovine and rabbit RPE cells showed the positive staining for the integrins alpha 2 beta 1 and alpha 5 beta 1 on cell surface. Disintegrins, echistatin, and flavoridin inhibited RPE cell attachment to the ECM. The potency of disintegrins was 150 to 300 times higher than that of Gly-Arg-Gly-Asp-Ser (GRGDS) peptide. The disintegrins also inhibited RPE cell-induced vitreous contraction in a dose-dependent manner, whereas the GRGDS peptide had no effect. In the in vivo experiment, echistatin (50 microgram/ml) or flavoridin (80 microgram/ml) significantly inhibited RPE cell-induced tractional retinal detachment compared with the control group at week 2 (P< 0.05) and week 4 (P< 0.01) after surgery. Disintegrins were nontoxic to RPE cells and rabbit retina as evaluated by cytotoxicity tests, electroretinograms, and histologic examinations. CONCLUSIONS: The disintegrins were effective in inhibiting RPE cell attachment to the ECM and vitreous contraction in vitro. They also were effective in suppressing RPE cell-induced tractional retinal detachment in the rabbit eyes. They were nontoxic. Disintegrins and their analogs might be potential anti-adhesion therapeutic agents in the treatment of proliferative vitreoretinopathy.

Amino Acid Sequence↗
PubMed1996

Identification of enzymes catalyzing two-step phosphorylation of cidofovir and the effect of cytomegalovirus infection on their activities in host cells.

Cidofovir [CDV; (S)-1-(3-hydroxy-2-phosphonomethoxyethyl)cytosine] is an acyclic nucleotide analog with potent and selective in vitro and in vivo activities against a broad spectrum of herpesviruses and other DNA viruses. We studied the mechanism of enzymatic synthesis of CDV diphosphate, the putative antiviral metabolite of CDV. The phosphorylation is two-step process catalyzed by several enzymes. An enzymatic activity phosphorylating CDV to its monophosphate derivative was purified from human liver and identified as pyrimidine nucleoside monophosphate kinase (EC 2.7.4.14.). CDV (Km = 2.10 +/- 0.18 mM and Vmax = 1.10 +/- 0.05 micromol/min/mg) was found to be a substantially weaker substrate for purified enzyme than CMP, UMP, or dCMP. Pyrimidine nucleoside monophosphate kinase was used for preparative enzymatic synthesis of CDV monophosphate. Pyruvate kinase (EC 2.7.1.40), creatine kinase (EC 2.7.3.2), and nucleoside diphosphate kinase (EC 2.7.4.6) were found to catalyze CDV diphosphate synthesis from CDV monophosphate, whereas phosphoglycerate kinase (EC 2.7.2.3) and succinyl-CoA synthetase (EC 6.2.1.4) did not. Based on Vmax/Km (phosphorylation efficiency) values determined with enzymes purified from human sources, the most efficient phosphorylation of CDV monophosphate is catalyzed by pyruvate kinase. After infection of human lung fibroblasts with cytomegalovirus, the intracellular activities of pyrimidine nucleoside monophosphate kinase, pyruvate kinase, creatine kinase, and nucleoside diphosphate kinase increased 2-, 1.3-, 3-, and 5-fold, respectively. The metabolism of [3H]CDV in mock- and cytomegalovirus-infected cells was examined. The intracellular levels of CDV monophosphate and CDV diphosphate increased approximately 20- and 8-fold, respectively, in cytomegalovirus-infected cells, presumably due to the stimulation of CDV uptake and higher activities of phosphorylating enzymes.

Antiviral Agents↗
PubMed1995

Clinical application of modified Anyang type 2 esophageal intubation instrument--a new esophageal intubation method.

The preliminary experience in the clinical use of Anyang Type 2 esophageal intubation instrument, designed by ourselves, in 11 patients with severe esophageal obstruction due to advanced carcinoma of the esophageal was reported. The diagnosis of all 11 cases was confirmed by barium-meal roentgenography. After intubation, all the patients could take liquid or soft diet by mouth. There was no operative mortality and the patients survived 2 to 14 months (mean 5.7 months). All of them could take food by mouth before death. The clinical application proved that the intubation has been a safe and suitable management.

Adult↗
PubMed1995

Effect of pilocarpine on anterior chamber angles.

Pilocarpine is widely used in the treatment of glaucoma, especially for the acute form of angle-closure glaucoma. Previous studies have shown that pilocarpine decreases central anterior chamber depth. In the present study, a quantitative measurement method, applying Scheimpflug photography, was used to report whether pilocarpine also affected the anterior chamber angles. Twenty-nine normal Chinese subjects, 17 female and 12 male with an age range from 11 to 63 years old, were enrolled. One eye of each subject was treated with one drop of 2% pilocarpine. Photographs of each of four quadrants were taken prior to, and after, pilocarpine treatment in both eyes, using a rotating slit-lamp video camera based on the Scheimpflug principle. The slit beams were set at 0 degrees and 90 degrees. The eyes which did not receive pilocarpine treatment served as control. The angles of the four quadrants were calculated for both eyes both prior to, and after, pilocarpine treatment, and results were compared by Student's paired t-test. The comparison of angles between the eyes prior to, and after, pilocarpine treatment indicated that there is a significant narrowing of angles in all quadrants. The complex factors involved in the change of anterior chamber angle are reviewed in the light of muscarinic action of pilocarpine.

Adolescent↗
PubMed1995

Fronto-sternal traction: an adjunct to orthognathic surgery.

A case is reported in which an unexpected occlusal result arose following bimaxillary osteotomy for correction of a skeletal Class III discrepancy. In order to correct the occlusion, the mandible was protracted independently of the recently plated maxilla, by means of a fronto-sternal traction device.

Adult↗
PubMed1995

Incidence and progression of diabetic retinopathy among non-insulin-dependent diabetic subjects: a 4-year follow-up.

BACKGROUND: To assess the incidence and progression of diabetic retinopathy and explore risk factors associated with them among non-insulin-dependent diabetes mellitus (NIDDM) patients. METHODS: A total of 471 NIDDM subjects aged > or 40 were recruited from four primary health care centres of northern Taiwan in 1986 and followed up for 4 years. Their ocular fundi were clearly visible by ophthalmoscopy and the status of diabetic retinopathy could be graded. A structured questionnaire interview was conducted to collect basic data. Overnight fasting venous blood was collected every year to measure the levels of glucose, glycosylated haemoglobin (HbA1c), cholesterol and high density lipoprotein cholesterol. RESULTS: Among the 344 subjects who had no retinopathy initially, 66 subjects developed retinopathy 4 years later giving a 4-year cumulative incidence of 19.2%. Of the 120 subjects initially with background or preproliferative retinopathy, evidence of deterioration developed in 36 subjects. The cumulative incidence of progression was 30%. Seven subjects developed proliferative retinopathy giving a cumulative incidence of progression to proliferative retinopathy of 5.8%. The univariate analysis disclosed that the development of retinopathy was correlated with mean fasting blood glucose (MFBG) and HbA1c, diabetic duration, diabetic treatment and residential area. The progression of retinopathy correlated with MFBG and proteinuria, and the progression to proliferative retinopathy correlated with MFBG. Stepwise logistic regression analysis revealed that MFBG and HbA1c were the significant risk factors related to the development of retinopathy. CONCLUSIONS: Diabetic control assessed by MFBG or HbA1c was the significant risk factor correlated with the incidence and progression of retinopathy.

Adult↗