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Biomedical subjects

R Chen

Publications and source records attributed to R Chen.

At least 379 records · Page 21Linked to original sources
PubMed1997

[The inhibitory effect of tissue plasminogen activator combined with 5-fluorouracil polyphase liposome on the scar formation in experimental filtration surgery].

OBJECTIVE: To study the effect of tissue plasminogen activator (t-PA) in combination with 5-fluorouracil (5-Fu) polyphase liposome on the prevention of scar formation in filtration surgery. METHODS: Bilateral trabeculectomy filtering procedures were performed on 16 New Zealand white rabbits. The rabbits were divided into 4 groups of four rabbits each. In a randomized fashion, the first group received intracameral normal saline (0.1 ml) immediately following surgery and subconjunctival injection of 0.2 ml polyphase liposome (no drug) every 4 days serving as the control. The second group received intracameral t-PA 25 micrograms (0.1 ml) immediately following surgery. The third group received subconjunctival 5-Fu polyphase liposome 5 mg immediately after the procedures of filtration surgery and then every four days for another three injections. The fourth group received both intracameral t-PA 25 micrograms and subconjunctival 5-Fu polyphase liposome as in the third group. All eyes of the four groups were enucleated two weeks after the operation. RESULTS: Two weeks after the surgery, the average intraocular pressure demonstrated a significant decrease in the third and fourth groups (P < 0.05), but did not show a significant decrease (P > 0.05) in the control and the second groups, as compared with the average preoperative intraocular pressure correspondingly. Morphometric analysis of the area of fibrosis from histopathological sections demonstrated a significant decrease of episcleral fibrosis in the three drug-treated groups as compared with the control group. Moreover, the area of fibrosis in the fourth group was the least among the three drug-treated groups. Analysis of variance of 2 x 2 factorial design showed that t-PA and 5-Fu polyphase liposome had synergetic effect on the inhibition in all of the drug-treated eyes. CONCLUSION: Postoperatively, the inhibitory effect of intracameral t-PA combined with subconjunctival 5-Fu polyphase liposome on the scar formation in filtration surgery is more prominent than that of t-PA or 5-Fu used alone. They had synergetic effect on the inhibition of scar formation in filtration surgery.

Animals↗
PubMed1997

Two novel mutations in phenylalanine hydroxylase gene and in vitro expression analysis on mutation Arg252Gln.

We report novel mutations in exon 7 of human phenylalanine hydroxylase (PAH) gene of phenylketonuria (PKU) in southern Chinese, analysed by using PCR-DGGE (denaturing gradient gel electrophoresis), solid phase DNA sequencing and in vitro expression. One of the 2 novel mutations, IVS6nt-1, is an intron-exon junctional mutation which results a splicing defect in mRNA. Arg252Gln is another novel mutation with residual PAH activity only 24% compared to wild type in in vitro mutagenesis and expression in Cos-1 cell. Other 3 known mutations and polymorphism including Arg241Cys, Arg243Gln and Val245Val (GTG to GTA) together with these novel mutations composed the mutational profile of exon 7 in the PAH gene of PKUs in this populations.

Exons↗
PubMed1997

Chinese dietary composition and intakes of elements and radionuclides by ingestion.

As update and complement of Chinese Total Diet Study in 1990, a renewing study was conducted during 1992-1993 according to regulated procedure. Contents of 32 elements, including 19 newly determined, in 12 categories of food from 12 provinces were analyzed by NAA or AAS technique and the daily intakes of Chinese adult man were estimated and hygienically evaluated. Meanwhile, a typical survey on dietary composition and intake for difference among 4 age groups and between Spring and Autumn was surveyed too. The results provide important basis for decision for further improvement of Chinese diet from hygienic view point and compilation of physiological characteristics of Chinese Reference Man. At the end of this article, the estimated nationwide average intakes for adult man are compared with those for current ICRP Reference Man.

Adolescent↗
PubMed1997

[An analysis of maicaodi by high performance liquid chromatography].

Maicaodi has recently been developed and produced by the pesticide plant of Nanjing Agricultural University. The quantitative analysis of the effective components--tribenuron methyl and R (-)napropamide in wettable powder of Maicaode, by a high performance liquid chromatographic method was carried out with a Lichrosorb Si-60 20cm x 0.46cm i.d. column, mobile phase of petroleum ether/isopropanol/methanol/acetonitrile/chloroform mixture solvent (80:5:5:5:5) and internal standard of diisooctyl phthalate. The sample was detected by ultraviolet absorption at 254 nm. The retention times of tribenuron methyl and R (-)napropamide were 10-11min and 6-7min respectively. The coefficient of variation of this analysis was 0.34% with a recovery of 99.51%-100.32%. The coefficient of linear correlation was 0.9999.

Chromatography, High Pressure Liquid↗
PubMed1997

[Luminescence properties and energy transfer between Ce3+ and Tb3+ ions in KA1F4: Ce, Tb].

Matrix KA1F4 was prepared through reaction of mixtures of solution K2CO3 upon certain solution of Al(OH)3 plus HF(40%),dehydrating at 100 degrees C and annealing for 48hr at 450 degrees C. A series of KA1F4 : Ce,Tb phosphors were synthesized by a solid reaction method. Their excitation and emission spectra have been investigated. It was observed that Ce3+ can effectively sensitize Tb3+ in KA1F4, so as to enhance the emission of Tb3+ significantly. KA1F4 :Ce,Tb might be a new high efficient green emitting phosphor.

English Abstract↗
PubMed1997

[Far FT-IR spectra of gallium hexafluoride ions].

Far FT-IR spectra of Rb3GaF6, alpha-Cs3GaF6 and high temperature form Cs3GaF6 and their XDS have been studied in this paper. The results indicated that Rb3GaF6 and high temperature form Cs3GaF6 are tetragonal, a = 0.632,c = 0. 886nm and a = 0.687,c = 0. 987nm respectively. alpha-Cs3GaF6 is orthorhombic, a = 1. 062,b = 0. 996,c = 0. 561nm

English Abstract↗
PubMed1997

Enantioselective determination of diprafenone in human plasma.

A sensitive (10.0 ng/ml) and stereoselective HPLC method for analysis of S(-)- and R(+)-diprafenone in human plasma has been developed. The assay is based on derivatization with homochiral R(-)-1-(1-naphthyl)ethyl isocyanate to give the diastereomeric derivates and their separation and quantitation using HPLC with UV-detection (220 nm). Details of this stereoselective assay procedure which has already been applied to the multisample analyses from a human pharmacokinetic study are described. The data obtained indicated that the stereoselective disposition of diprafenone enantiomers is quite different from their structural and pharmacological analog propafenone.

Administration, Oral↗
PubMed1997

Elevated hCG as an isolated finding during the second trimester biochemical screen: genetic, ultrasonic, and perinatal significance.

This study was undertaken in an attempt to determine the significance of elevated maternal serum human chorionic gonadotropin (MShCG), in the presence of an otherwise normal screen with respect to fetal malformations, chromosomal aberrations, and pregnancy outcome. Targeted ultrasound findings and perinatal outcome of 298 women in whom serum hCG was > or = 2.5 MOM and who were screen-negative for Down syndrome (the study group) were compared with a control group of 229 women in whom serum hCG as well as the other parameters were within the normal range. Genetic amniocentesis was performed in 125 women from the study group. Ultrasonically detected malformations were significantly more frequent among the study group (12 vs. 1, P = 0.01). Pregnancy complications were similar in the two groups, with the exception of pre-eclampsia-toxaemia, which was significantly more frequent in the study group (5 vs. 0, P = 0.02). There was one case of an abnormal karyotype (47,XXY). Although genetic amniocentesis does not appear warranted, isolated elevated MShCG levels during the second trimester screening was associated with an increased risk of fetal anomalies detected by ultrasound and of toxaemia of pregnancy.

Adult↗
PubMed1997

[Determination of plasma D-dimer in patients with pregnancy induced hypertension].

OBJECTIVE: To investigate the changes and the clinical significance of plasma D-dimer in normal pregnant women and patients with pregnancy induced hypertension (PIH). METHODS: Using ELISA method, we measured the level of plasma D-dimer in 160 cases, including 106 normal pregnant women and 25 patients with mild and moderate PIH, 18 patients with preeclampsia and 11 patients with eclampsia. RESULTS: The value (2.27 +/- 0.92 mg/L) of plasma D-dimer in mild and moderate PIH patients was markedly higher than that of normal third trimester pregnant women (1.45 +/- 0.38 mg/L, P < 0.01). The value (3.09 +/- 1.65 mg/L) of plasma D-dimer in preeclampsia patients was markedly higher than that of mild and moderate PIH patients (P < 0.01). The value (5.62 +/- 1.34 mg/L) of plasma D-dimer in eclampsia patients was markedly higher than that of preeclampsia patients. CONCLUSION: Determination of plasma D-dimer level in second and third trimester pregnant women was of great significance in diagnosing early PIH and predicting the prognosis of PIH.

Adult↗
PubMed1996

A flower-specific gene encoding an osmotin-like protein from Lycopersicon esculentum.

The flower-specific cDNA Tomf216 representing an mRNA encoding an osmotin-like protein was identified by the differential screening of a cDNA library produced from mRNA extracted from premeiotic tomato flowers (Lycopersicon esculentum). The cDNA is 894 nucleotides in length and encodes a protein of 252 amino acids. The deduced protein has a molecular mass of 27.2 kDa, an N-terminal region predicted to be a signal sequence, and a predicted molecular mass of 24.7 kDa for the mature protein. The protein contains 16 cysteine residues and has 30% to 32% amino acid sequence identity to pathogenesis-related osmotins. The gene is expressed in flowers and fruit with the highest levels of transcript accumulation in pistils from flowers at anthesis. No expression was detected in vegetative organs.

Amino Acid Sequence↗
PubMed1996

Redesigning secondary structure to invert coenzyme specificity in isopropylmalate dehydrogenase.

Rational engineering of enzymes involves introducing key amino acids guided by a knowledge of protein structure to effect a desirable change in function. To date, all successful attempts to change specificity have been limited to substituting individual amino acids within a protein fold. However, the infant field of protein engineering will only reach maturity when changes in function can be generated by rationally engineering secondary structures. Guided by x-ray crystal structures and molecular modeling, site-directed mutagenesis has been used to systematically invert the coenzyme specificity of Thermus thermophilus isopropylmalate dehydrogenase from a 100-fold preference for NAD to a 1000-fold preference for NADP. The engineered mutant, which is twice as active as wild type, contains four amino acid substitutions and an alpha-helix and loop that replaces the original beta-turn. These results demonstrate that rational engineering of secondary structures to produce enzymes with novel properties is feasible.

3-Isopropylmalate Dehydrogenase↗
PubMed1996

COOH-terminal processing of nascent polypeptides by the glycosylphosphatidylinositol transamidase in the presence of hydrazine is governed by the same parameters as glycosylphosphatidylinositol addition.

Proteins anchored to the cell membrane via a glycosylphosphatidylinositol (GPI) moiety are found in all eukaryotes. After NH2-terminal peptide cleavage of the nascent protein by the signal peptidase, a second COOH-terminal signal peptide is cleaved with the concomitant addition of the GPI unit. The proposed mechanism of the GPI transfer is a transamidation reaction that involves the formation of an activated carbonyl intermediate (enzyme-substrate complex) with the ethanolamine moiety of the preassembled GPI unit serving as a nucleophile. Other nucleophilic acceptors like hydrazine (HDZ) and hydroxylamine have been shown to be possible alternate substrates for GPI. Since GPI has yet to be purified, the use of readily available nucleophilic substitutes such as HDZ and hydroxylamine is a viable alternative to study COOH-terminal processing by the putative transamidase. As a first step in developing a soluble system to study this process, we have examined the amino acid requirements at the COOH terminus for the transamidation reaction using HDZ as the nucleophilic acceptor instead of GPI. The hydrazide-forming reaction shows identical amino acid requirement profiles to that of GPI anchor addition. Additionally, we have studied other parameters relating to the kinetics of the transamidation reaction in the context of rough microsomal membranes. The findings with HDZ provide further evidence for the transamidase nature of the enzyme and also provide a starting point for development of a soluble assay.

Acyltransferases↗
PubMed1996

Use of corticosteroids alone or combined with glucose to treat ketosis in dairy cows.

OBJECTIVE: To compare relative efficacy of dexamethasone and flumethasone alone or in combination with rapid IV infusion of glucose for treatment of ketosis in cattle. DESIGN: Clinical trial. ANIMALS: 127 cows with urine acetoacetate concentration > or = 60 mg/dl. PROCEDURE: Cows were treated with 500 ml of 50% glucose solution. IV, and 40 mg of dexamethasone, IM (group 1), 40 mg of dexamethasone, IM (group 2), 5 mg of flumethasone (group 3), or 500 ml of 50% glucose solution, IV, and 5 mg of flumethasone (group 4). Treatment success was defined as recovery after a single treatment without relapse during the same lactation. Uterine disease (retained placenta or metritis), parity, and pretreatment plasma glucose, serum beta-hydroxybutyric acid, and urine acetoacetate concentrations were evaluated as possible confounding factors affecting recovery. RESULTS: Only uterine disease was found to have a significant effect on recovery. Treatments 1 and 4 were significantly more efficacious than was treatment 2, but efficacy of treatment 2 was not significantly different from that of treatment 3. Regardless of treatment, cows with uterine disease were less likely to have a successful outcome than were cows without uterine disease. In all treatment groups, plasma glucose concentration increased and serum beta-hydroxybutyric acid and urine acetoacetate concentrations decreased following treatment. CLINICAL IMPLICATIONS: In this study, treatment of ketosis in dairy cattle with a corticosteriod alone was less efficacious than treatment with glucose and a corticosteroid.

3-Hydroxybutyric Acid↗
PubMed1996

Screening derivatized peptide libraries for tight binding inhibitors to carbonic anhydrase II by electrospray ionization-mass spectrometry.

This paper describes the use of electrospray ionization-mass spectrometry (ESI-MS) to screen two libraries of soluble compounds to search for tight binding inhibitors for carbonic anhydrase II (EC 4.2.1.1). The two libraries, H2NO2SC6H4C(O)NH-AA1-AA2-C(O)NHCH2CH2CO2H where AA1 and AA2 are L-amino acids (library size: 289 compounds) or D-amino acids (256 compounds), were constructed by attaching tripeptides to the carboxyl group of 4-carboxybenzenesulfonamide. Screening of both libraries yielded, as the tightest binding inhibitor, compound 1 (AA1 = AA2 = L-Leu; binding constant Kb = 1.4 x 10(8) M-1). The ability of ESI-MS to estimate simultaneously the relative binding affinities of a protein to soluble ligands in a library, if general, should be useful in drug development.

Amino Acid Sequence↗
PubMed1996

Determinants of cofactor specificity in isocitrate dehydrogenase: structure of an engineered NADP+ --> NAD+ specificity-reversal mutant.

The 7-fold mutation Cys201Met/Cys332Tyr/Lys344Asp/Tyr345Ile/Val35 1Ala/Tyr391Lys/Arg395Ser converts the cofactor specificity of Escherichia coli isocitrate dehydrogenase from a 7000-fold preference for NADP+ to a 200-fold preference for NAD+, with overall activity comparable to that of wild-type NAD+-dependent isocitrate dehydrogenases. The structure of the NAD+-dependent mutant has been determined and refined to a working R-factor of 0.186 at 1.9 A resolution. The structure shows that NADP+ affinity is destroyed by removing favorable interactions between the 2'-phosphate and Tyr345, Tyr391, and Arg395 and by adding a repulsive interaction with Asp344. NAD+ affinity is enhanced by adding hydrogen bonds between Asp344 and the free 2'-hydroxyl. The favorable Asp344-2'-OH interaction requires a change in the pucker of the ribose to C2' endo and a shift in the adenine ring. The ring shift is made possible by a series of changes in steric packing interactions. The linchpin for repacking in the adenosine binding site is residue 351. The side chain of this "second layer" residue dictates packing of the surrounding "first layer" residues which interact with the 2' moiety and, in turn, directly determine specificity.

Amino Acid Sequence↗
PubMed1996

Pulmonary function measures as predictors and correlates of cognitive functioning in later life.

The relation between pulmonary function and cognitive functioning was investigated in a cohort of 3,036 Japanese-American men living in Hawaii. Pulmonary function, as indicated by forced expiratory volume in 1 second (FEV1), was measured at the baseline examination from 1965 to 1968. Cognitive function was assessed by the Cognitive Abilities Screening Instrument (CASI) test at least 23 years later (1991-1993). Baseline FEV1 was significantly correlated with follow-up CASI score (r = 0.22, p = 0.0001). Although the strength of the association was reduced by controlling for the effects of other factors, stepwise multiple linear regression showed that FEV1 during middle age was a significant predictor of CASI in later life, after taking into account the effects of age, education, stroke, sedentary job activity, nonmanual occupation, height, generation, and Japanese speaking ability. The mean CASI value was significantly greater for men whose FEV1 exceeded 2.8 liter compared with those whose FEV1 levels were in the lowest (<2.5 liters) quartile. Furthermore, the test on the effect of interaction between FEV1 and age was statistically significant (p = 0.0024), with subjects less than 55 years of age at the baseline examination showing a stronger direct association of FEV1 with CASI than the men aged 55 or older. These findings suggest that pulmonary function impairment may be associated with cognitive function impairment in later life.

Aged↗