Biomedical subjects

C Cheng

Publications and source records attributed to C Cheng.

At least 37 records · Page 2Linked to original sources

PubMed2001

A novel human hydroxysteroid dehydrogenase like 1 gene (HSDL1) is highly expressed in reproductive tissues.

We report the cloning and characterization of a novel human hydroxysteroid dehydrogenase like gene (HSDL1) located on human chromosome 16q24.2. The HSDL1 cDNA is 3407 base pair in length, encoding a 309 amino acid polypeptide related to human 17beta-HSD3. Northern blot reveals that the HSDL1 is highly expressed in testis and ovary. In situ hybridization indicates that the expression of HSDL1 is predominantly increased in the prostate cancer tissue compared with the normal prostate tissue, which suggests that the gene expression is important to the arising of prostate cancer.

Amino Acid Sequence↗

PubMed2001

Assessing coping flexibility in real-life and laboratory settings: a multimethod approach.

This research sought to formulate a theoretically based conceptualization of coping flexibility and to adopt a multimethod approach in assessing this construct. A self-report daily measure and an experiment were designed geared to theoretical and empirical grounds. The new daily measure was used in Study 1 to examine coping flexibility in a life transition. Findings showed individual differences in patterns of coping flexibility across different real-life stressful events. In Study 2, coping flexibility was examined in both real-life and laboratory settings. Results replicated those of Study 1 and further revealed consistency between the self-report and the experiment data. Study 3 extended previous studies by adopting a longitudinal design over a 3-month time span. Participants' flexibility in coping with laboratory tasks was found to predict how flexible they would be in handling real-life stressful events.

Adaptation, Psychological↗

PubMed2001

A neural network to predict melting temperature (Tm) of RNA duplex.

A straightforward method to predict RNA duplex stability by neural network is described. The best network consists of three layers in which the input layer units are 12 (frequencies of 10 nearest-neighbors and 2 terminals), the hidden layer units are 3 and the output layer unit is 1 (measured Tm). This method to predict Tm has the advantage that the determinations of thermodynamic parameters is not needed.

Base Sequence↗

PubMed2001

Does diabetes target ganglion neurones? Progressive sensory neurone involvement in long-term experimental diabetes.

Targeting of dorsal root ganglia by diabetes could account for the selective sensory abnormalities that patients with early diabetic polyneuropathy develop. In this work, we addressed survival, phenotype and gene expression in sensory neurones in lumbar dorsal root ganglia in a long-term model of experimental streptozotocin-induced diabetes in rats, designed to reflect human disease. Motor and sensory conduction slowing developed early, by the 2-month time point. At 2 months, sensory neurones had no detectable alterations in their calibre or gene expression, assessed using quantitative in situ hybridization studies for mRNA markers that included alpha CGRP, beta CGRP, NFM, t alpha 1-tubulin, SP, VIP, B50 (GAP43), galanin, somatostatin, PACAP, HSP27, c-jun, SNAP 25, p75, TrkA, TrkB and TrkC. By 12 months, however, diabetics had developed neurone perikaryal and distal axon atrophy, accompanied by generalized downregulation of mRNA expression, particularly of CGRP transcripts, PACAP, SP, NFM, p75, trkA and trkC. With the exception of HSP-27, no elevation in mRNAs that increase after injury, such as VIP, galanin, CCK, PACAP, B50 and t alpha 1-tubulin, was observed and constitutive levels, when detectable, trended towards lower rather than increased levels. There was relative preservation of neurone numbers at 12 months; only a non-significant trend towards fewer diabetic neurones was detected using a rigorous and systematic physical dissector counting approach through the entire L5 ganglia. There was no change in the relative populations of CGRP- and SP-immunoreactive neurones. Our findings indicate that even long-term experimental diabetes is associated with relative preservation of sensory neurone populations, but the neurones are atrophic and their gene expression is altered. This pattern of change differs from that following axotomy, implies a degenerative rather than an injury phenotype and has important implications for how such neurones might be rescued.

Animals↗

PubMed2001

Discriminative facility and its role in the perceived quality of interactional experiences.

Discriminative facility refers to an individual's sensitivity to subtle cues about the psychological meaning of a situation. This research aimed at examining (a) the conceptual distinctiveness of discriminative facility, (b) the situation-appropriate aspect of this construct, and (c) the relationship between discriminative facility and interpersonal experiences. Discriminative facility was assessed by a new measure of situation-appropriate behaviors across a variety of novel stressful situations. Results from study 1 showed that discriminative facility had weak positive relationships with cognitive complexity and nonsignificant relationships with self-monitoring and social desirability, indicating that discriminative facility is a unique construct. Results from Study 2 revealed that higher levels of discriminative facility were associated with higher levels of perceived social support and a greater number of pleasant interpersonal events experienced, thus providing support for the theoretical proposition that discriminative facility is an aspect of social intelligence.

Adult↗

PubMed2001

Molecular cloning, structure and expression of a novel nuclear RNA-binding cyclophilin-like gene (PPIL4) from human fetal brain.

The cyclophilins are members of a highly conserved, ubiquitous family, and play an important role in protein folding, immunosuppression by cyclosporin A (CsA), and infection of HIV-1 virions. Here we report that a novel member of the cyclophilin family, PPIL4, was cloned and identified during the large-scale sequencing analysis from a human fetal brain cDNA library. The PPIL4 gene encodes a protein which shares 96% amino acid identity with a protein encoded by a putative gene recently cloned from several different early stages of mouse embryo, and its homologues are found in several other organisms. According to bioinformatics analysis, the PPIL4 gene was found to be located in chromosome 6q24-->q25. Besides the PPIase motif, PPIL4 also has an RNA recognition motif (RRM), a pair of bipartite nuclear targeting sequences, and a lysine rich domain. RT-PCR analysis indicated that PPIL4 gene expression is abundant in kidney but has a ubiquitously low expression pattern in other human adult tissues.

Amino Acid Motifs↗

PubMed2001

Feasibility of early catheter removal after radical retropubic prostatectomy.

PURPOSE: This study was conducted to determine if early (1 week) removal of the urethral catheter after radical prostatectomy is feasible. MATERIAL AND METHODS: Eighty patients underwent surgery from 1992 to 1999. Of the 78 patients with analyzable results, 22 (28%) had the catheter removed after 3 weeks (group 1) and 56 (72%) after 1 week (group 2). RESULTS: Median follow-up of 49 months revealed no mortality or major morbidity in the two groups of patients. Urinary functions were satisfactory and similar in both groups of patients. Group 2 patients had an improved continence rate of 92%, achieving full continence at 3 months, compared to 59% for group 1. The mean duration of hospitalization of 8.2 days for group 2 was better than the 12.1 days for group 1. CONCLUSIONS: Early removal of the catheter after radical prostatectomy was feasible, did not impose any short- or long-term morbidity, and may offer some benefits.

Aged↗

PubMed2000

Identification and purification of an intrinsic human muscle myogenic factor that enhances muscle repair and regeneration.

The limited ability of damaged muscle to regenerate after gross injuries is a major clinical problem. To date, there is no effective therapeutic treatment for muscle injuries. In the present study, we have examined the ability of crude and fractionated human skeletal muscle extracts to promote myogenic cell proliferation and differentiation. It was found that the crude muscle extract could significantly stimulate BrdU incorporation in C2C12 myogenic cell line. In addition, the extract also promoted myogenic cell alignment and fusion. Using electrophoresis techniques, in conjunction with in vitro refolding technique, a protein with molecular weight of approximately 40 kDa was identified that could produce the same effects as the crude muscle exdtract. We also tested the ability of semipurified (30-50 kDa) muscle extract to promote muscle repair in adult rats. Surgical intervention was used to induce muscle damage in the tibialis anterior. The semipurified muscle extract (fraction H) was injected subcutaneously over the tibialis anterior for a period of 5 days. It was found that the damaged muscle fibers were replaced by newly regenerated muscle fibers. These newly regenerated fibers originated from the fusion of differentiated satellite cells as revealed by BrdU-labeling analysis. In contrast, the injury site of muscles treated with BSA control protein contained mainly fibroblasts.

Adult↗

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

The mammalian sodium channel BNC1 is required for normal touch sensation.

Of the vertebrate senses, touch is the least understood at the molecular level The ion channels that form the core of the mechanosensory complex and confer touch sensitivity remain unknown. However, the similarity of the brain sodium channel 1 (BNC1) to nematode proteins involved in mechanotransduction indicated that it might be a part of such a mechanosensor. Here we show that disrupting the mouse BNC1 gene markedly reduces the sensitivity of a specific component of mechanosensation: low-threshold rapidly adapting mechanoreceptors. In rodent hairy skin these mechanoreceptors are excited by hair movement. Consistent with this function, we found BNC1 in the lanceolate nerve endings that lie adjacent to and surround the hair follicle. Although BNC1 has been proposed to have a role in pH sensing, the acid-evoked current in cultured sensory neurons and the response of acid-stimulated nociceptors were normal in BNC1 null mice. These data identify the BNC1 channel as essential for the normal detection of light touch and indicate that BNC1 may be a central component of a mechanosensory complex.

Animals↗

PubMed2000

Characterization of halotolerant rhizobia isolated from root nodules of Canavalia rosea from seaside areas.

Twelve nodule isolates from Canavalia rosea, an indigenous leguminous halophyte growing in the seaside areas of southern Taiwan, were effective symbionts for the original host and able to grow at NaCl concentrations up to 3-3.5% (w/v). The taxonomy of these isolates was investigated using a polyphasic approach, including phenotypic characteristics, banding patterns of total proteins from sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), genomic fingerprint patterns from random amplified polymorphic DNA (RAPD) analysis, pulsed-field gel electrophoresis (PFGE) analysis, amplified 16S rDNA restriction analysis (ARDRA), 16S rRNA gene sequencing, and nifH gene sequencing. Based on the SDS-PAGE, RAPD, PFGE and ARDRA results, the 12 isolates are highly diverse. The 16S rRNA and nifH gene sequences were determined for isolates with distinct ARDRA patterns and compared with other members of the rhizobial species. We propose these isolates should be classified into the genus Sinorhizobium and distinguished from the current species of this genus.

Journal Article↗

PubMed2000

Regulation of glycogen synthase. Identification of residues involved in regulation by the allosteric ligand glucose-6-P and by phosphorylation.

The major yeast glycogen synthase, Gsy2p, is inactivated by phosphorylation and activated by the allosteric ligand glucose-6-P. From studies of recombinant proteins, the control can be accommodated by a three-state model, in which unphosphorylated enzyme has intermediate activity (state II). Glucose-6-P increased V(max)/K(m) by about 2-fold (state III), whereas phosphorylation by the cyclin-dependent protein kinase Pcl10p/Pho85p decreased V(max)/K(m) by approximately 30-fold (state I). In the presence of glucose-6-P, state III is achieved regardless of phosphorylation state. The enzyme forms complexes in solution with the yeast glycogenin Glg2p, but this interaction appears not to affect control either by glucose-6-P binding or by phosphorylation. Scanning mutagenesis was applied to identify residues potentially involved in ligand binding. Of 22 mutant enzymes analyzed, seven were essentially inactive. Five mutant proteins were altered in their activation by glucose-6-P, and two were completely unaffected by the hexose phosphate. One of these, R586A/R588A/R591A (all three of the indicated Arg residues mutated to Ala), had wild-type activity and was normally inactivated by phosphorylation. A second mutant, R579A/R580A/R582A, had somewhat reduced V(max), but its activity was not greatly reduced by phosphorylation. The Arg residues in these two mutants are restricted to a highly conserved, 13-residue segment of Gsy2p that we propose to be important for glucose-6-P binding and/or the ability of the enzyme to undergo transitions between activity states.

Allosteric Regulation↗

PubMed2000

Vaccinia topoisomerase and Cre recombinase catalyze direct ligation of activated DNA substrates containing a 3'-para-nitrophenyl phosphate ester.

DNA topoisomerases and DNA site-specific recombinases are involved in a diverse set of cellular processes but both function by making transient breaks in DNA. Type IB topoisomerases and tyrosine recombinases cleave DNA by transesterification of an active site tyrosine to generate a DNA-3'-phosphotyrosyl-enzyme adduct and a free 5'-hydroxyl (5'-OH). Strand ligation results when the 5'-OH attacks the covalent complex and displaces the enzyme. We describe the synthesis of 3'-phospho-(para-nitrophenyl) oligonucleotides (3'-pNP DNAs), which mimic the natural 3'-phosphotyrosyl intermediate, and demonstrate that such pre-activated strands are substrates for DNA ligation by vaccinia topoisomerase and Cre recombinase. Ligation occurs by direct attack of a 5'-OH strand on the 3'-pNP DNA (i.e., without a covalent protein-DNA intermediate) and generates free para-nitrophenol as a product. The chromogenic DNA substrate allows ligation to be studied in real-time and in the absence of competing cleavage reactions and can be exploited for high-throughput screening of topoisomerase/recombinase inhibitors.

Arginine↗

PubMed2000

Resolution of a Holliday junction by vaccinia topoisomerase requires a spacer DNA segment 3' of the CCCTT/ cleavage sites.

Vaccinia virus DNA topoisomerase catalyzes resolution of synthetic Holliday junctions in vitro. The mechanism entails concerted transesterifications at two recognition sites, 5'-CCCTT/, that are opposed within a partially mobile four-way junction. Efficient resolution occurs on a junction with a 10 bp segment of branch mobility (5'-GCCCTTATCG) that extends 4 bp 3' of the scissile phosphate. Here we report that resolution is decreased when branch mobility is limited to an 8 bp segment extending 2 bp 3' of the cleavage site and then eliminated when branch mobility is confined to the 6 bp GCCCTT sequence 5' of the scissile phosphate. We surmise that a spacer region 3' of CCCTT is needed for simultaneous cleavage at two opposing sites at the junction. Branch mobility is not required for reaction chemistry at a junction, because topoisomerase cleaves a single CCCTT site in a non-mobile four-way junction where the scissile phosphate is at the crossover point. The junction resolvase activity of topo-isomerase may be involved in forming the hairpin telomeres of the vaccinia genome.

Base Sequence↗

PubMed2000

Peptide inhibitors of DNA cleavage by tyrosine recombinases and topoisomerases.

The study of biochemical pathways requires the isolation and characterization of each and every intermediate in the pathway. For the site-specific recombination reactions catalyzed by the bacteriophage lambda tyrosine recombinase integrase (Int), this has been difficult because of the high level of efficiency of the reaction, the highly reversible nature of certain reaction steps, and the lack of requirements for high-energy cofactors or metals. By screening synthetic peptide combinatorial libraries, we have identified two related hexapeptides, KWWCRW and KWWWRW, that block the strand-cleavage activity of Int but not the assembly of higher-order intermediates. Although the peptides bind DNA, their inhibitory activity appears to be more specifically targeted to the Int-substrate complex, insofar as inhibition is resistant to high levels of non-specific competitor DNA and the peptides have higher levels of affinity for the Int-DNA substrate complex than for DNA alone. The peptides inhibit the four pathways of Int-mediated recombination with different potencies, suggesting that the interactions of the Int enzyme with its DNA substrates differs among pathways. The KWWCRW and KWWWRW peptides also inhibit vaccinia virus topoisomerase, a type IB enzyme, which is mechanistically and structurally related to Int. The peptides differentially affect the forward and reverse DNA transesterification steps of the vaccinia topoisomerase. They block formation of the covalent vaccinia topoisomerase-DNA intermediate, but have no apparent effect on DNA religation by preformed covalent complexes. The peptides also inhibit Escherichia coli topoisomerase I, a type IA enzyme. Finally, the peptides inhibit the bacteriophage T4 type II topoisomerase and several restriction enzymes with 2000-fold lower potency than they inhibit integrase in the bent-L pathway.

Amino Acid Sequence↗

PubMed2000

Expression of glial cell line-derived neurotrophic factor family of growth factors in peripheral nerve injury in rats.

The glial cell line-derived neurotrophic factor (GDNF) family of growth factors may be involved in the regenerative support of neurons in the peripheral nervous system. In order to study the role of these growth factors and their receptors following rat peripheral nerve injury we examined the changes in their mRNA levels in the spinal cord, the dorsal root ganglia and the peripheral nerve trunk. Following transaction of the sciatic nerve GDNF mRNA was up-regulated rapidly in the denervated nerve distal to the cut along with the mRNA for one of its receptors, GFRalpha-1. GFRalpha-1 mRNA was also increased in the DRG ipsilateral to the nerve injury suggesting that GDNF may be involved in the trophic support of DRG sensory neurons. In contrast there were no analogous changes in the mRNA levels of neurturin, persephin and artemin following injury.

Animals↗

PubMed2000

DNA strand transfer catalyzed by vaccinia topoisomerase: ligation of DNAs containing a 3' mononucleotide overhang.

The specificity of vaccinia topoisomerase for transesterification to DNA at the sequence 5'-CCCTT and its versatility in strand transfer have illuminated the recombinogenic properties of type IB topoisomerases and spawned topoisomerase-based strategies for DNA cloning. Here we characterize a pathway of topoisomerase-mediated DNA ligation in which enzyme bound covalently to a CCCTT end with an unpaired +1T nucleotide rapidly and efficiently joins the CCCTT strand to a duplex DNA containing a 3' A overhang. The joining reaction occurs with high efficiency, albeit slowly, to duplex DNAs containing 3' G, T or C overhangs. Strand transfer can be restricted to the correctly paired 3' A overhang by including 0.5 M NaCl in the ligation reaction mixture. The effects of base mismatches and increased ionic strength on the rates of 3' overhang ligation provide a quantitative picture of the relative contributions of +1 T:A base pairing and electrostatic interactions downstream of the scissile phosphate to the productive binding of an unlinked acceptor DNA to the active site. The results clarify the biochemistry underlying topoisomerase-cloning of PCR products with non-templated 3' overhangs.

Adenosine Triphosphate↗

PubMed2000

An accessory DNA binding motif in the zinc finger protein Adr1 assists stable binding to DNA and can be replaced by a third finger.

The DNA binding domain of Adr1, the protein derived from alcohol dehydrogenase regulatory gene 1, is unusual for zinc finger proteins in that it consists of two classical Cys2His2 zinc fingers and an amino-terminal proximal accessory region termed PAR. PAR is unstructured in the free protein and becomes structured in the DNA-bound form. We investigated the role of PAR in DNA binding using molecular and biochemical approaches, and its importance for activation in vivo, using Adr1-dependent reporter genes. PAR was unimportant for DNA binding when a third finger was added to Adr1, and its importance was diminished but not eliminated by mutations in finger two that increased DNA binding affinity. The kinetic rate constants for three Adr1 proteins containing or lacking PAR were determined by surface plasmon resonance. PAR increased the on rate and decreased the off rate for specific DNA sites for Adr1 containing wild-type fingers one and two. Surprisingly, PAR had no significant effect on the kinetic rate constants when a third finger was present, or when single-stranded DNA was used as the substrate for DNA binding. A mutant form of Adr1-F1F2 in which finger 2 makes three base-specific contacts with DNA had a higher affinity for DNA than Adr1 containing three fingers, yet the mutant protein still depended on PAR for optimal binding affinity. The ability to activate transcription in vivo was correlated with a low dissociation rate, suggesting that stabilizing an activator at the promoter might be rate-limiting for transcription in vivo. PAR may have evolved to lend additional stability to DNA-Adr1 complexes encompassing short binding sites. In addition, PAR may have a role in transcription at a step after DNA binding since deletion of PAR from Adr1 with three fingers decreased activation in vivo but had no effect on DNA binding kinetics.

Alcohol Dehydrogenase↗