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Biomedical subjects

C Wu

Publications and source records attributed to C Wu.

At least 451 records · Page 25Linked to original sources
PubMed1995

[Studies on theory and models of systemic conservation of animal and poultry genetic resources. II. Simulation experiment of systemic conservation of animal and poultry genetic resources].

Tribolium castaneum simulation and computer simulation proved the feasibility and rationality of Systemic Conservation of Animal and Poultry Genetic Resources (SCAPGR) theory and the biological meaning of the SCAPGR mathematical models. It also demonstrated that the right effective population size should be maintained and gene flow among populations should be controlled and adequate selecting method and mating system should determined according to population genetic characters of gene conserved in the SCAPGR population.

Animals↗
PubMed1995

[Studies on theory and models of systemic conservation of animal and poultry genetic resources. I. Theory analysis of systemic conservation of animal and poultry genetic resources].

The concept and fundamentals of Systemic Conservation of Animal and Poultry Genetics Resources (SCAPGR) and mathematical models of genetic structure with conservation population were proposed. The SCAPGR regarded all genes of a given species in definite time and space as conservation object and live animal preservation combining with modern biotechnology as basic method. The SCAPGR might systematically conserve genes controlling the characters of a given species as well as regional varieties. In a no overlapping generation population with selection, mutation migration and random drift under consideration, two mathematical models presented in this paper might describe change of frequencies of multiple alleles at a locus and population mean of metrical characters resp.

Animals↗
PubMed1994

Identification of chloroplast envelope proteins in close physical proximity to a partially translocated chimeric precursor protein.

Translocation intermediates of the chimeric protein precursor Oee1-Dhfr were generated and used to identify envelope components in close proximity to the arrested precursor. The translocation of Oee1-Dhfr across the chloroplast envelope can be arrested at low ATP levels or by prebinding the fusion precursor with anti-Dhfr IgGs. The arrested Oee1-Dhfr precursor appears to span both the outer and inner envelope membranes. Translocational arrest of Oee1-Dhfr by low ATP levels was reversible, and import was restored upon resupplementation with higher ATP levels. Chemical cross-linking and co-immunoprecipitation with monospecific antibodies indicate that two outer envelope membrane proteins (Com44 and Com70) and at least one inner envelope protein (Cim44 and Cim97) were found to be in close proximity to Oee1-Dhfr during translocation. The Com70 protein was further studied and additional evidence for its role in chloroplast protein import is presented.

Algal Proteins↗
PubMed1994

Back-propagation and counter-propagation neural networks for phylogenetic classification of ribosomal RNA sequences.

A neural network system has been developed for rapid and accurate classification of ribosomal RNA sequences according to phylogenetic relationship. The molecular sequences are encoded into neural input vectors using an n-gram hashing method. A SVD (singular value decomposition) method is used to compress and reduce the size of long and sparse n-gram input vectors. The neural networks used are three-layered, feed-forward networks that employ supervised learning paradigms, including the back-propagation algorithm and a modified counter-propagation algorithm. A pedagogical pattern selection strategy is used to reduce the training time. After trained with ribosomal RNA sequences of the RDP (Ribosomal Database Project) database, the system can classify query sequences into more than one hundred phylogenetic classes with a 100% accuracy at a rate of less than 0.3 CPU second per sequence on a workstation. When compared to other sequence similarity search methods, including Similarity Rank, Blast and Fasta, the neural network method has a higher classification accuracy at a speed of about an order of magnitude faster. The software tool will be made available to the biology community, and the system may be extended into a gene identification system for classifying indiscriminately sequenced DNA fragments.

Algorithms↗
PubMed1994

Stereospecific synthesis of peptidyl alpha-keto amides as inhibitors of calpain.

Peptidyl alpha-keto amides have been synthesized and tested as inhibitors of the cysteine protease calpain. A stereospecific synthesis was devised in which Cbz-dipeptidyl-alpha-hydroxy amides were oxidized with TEMPO/hypochlorite to the corresponding alpha-keto amides. This oxidation was accomplished in good yields and without epimerization of the chiral center adjacent to the ketone. The potent inhibition of porcine calpain I by the L,L diastereomers, combined with the poor inhibition by the L,D diastereomers, established the requirement for the all-L stereochemistry of the active inhibitor. The early lead inhibitors were very hydrophobic and, therefore, poorly soluble in aqueous solutions. Using the stereospecific route, new compounds were prepared with polar groups at the C- and N-termini. These modifications resulted in more soluble inhibitors that were still potent inhibitors of calpain. Studies of the stability of these alpha-keto amides showed that absolute stereochemistry can be maintained in acidic and unbuffered environments but general base-catalyzed epimerization of the chiral center adjacent to the ketone occurred rapidly. The alpha-hydroxy precursors were inactive as inhibitors of calpain, which supports the hypothesis that the alpha-keto compounds reversibly form an enzyme-bound tetrahedral species that results from the nucleophilic addition of the catalytic thiol of calpain to the electrophilic ketone of the inhibitor.

Amides↗
PubMed1994

Radioimmunotherapy of nude mice bearing a human interleukin 2 receptor alpha-expressing lymphoma utilizing the alpha-emitting radionuclide-conjugated monoclonal antibody 212Bi-anti-Tac.

The efficacy, specificity, and toxicity of bismuth (212Bi) alpha particle-mediated radioimmunotherapy was evaluated in nude mice bearing a murine lymphoma transfected with the human CD25 [human Tac; interleukin 2 receptor alpha (IL-2R alpha)] gene. The therapeutic agent used was the tumor-specific humanized monoclonal antibody anti-Tac conjugated to 212Bi. The human IL-2R alpha-expressing cell line was produced by transfecting the gene encoding human Tac into the murine plasmacytoma cell line SP2/0. The resulting cell line, SP2/Tac, expressed approximately 18,000 human IL-2R alpha molecules/cell. Following s.c. or i.p. injection of 2 x 10(6) SP2/Tac cells into nude mice, rapidly growing tumors developed in all animals after a mean of 10 and 13 days, respectively. The bifunctional chelate cyclohexyldiethylenetriaminepentaacetic acid was used to couple 212Bi to the humanized anti-Tac monoclonal antibody. This immunoconjugate was shown to be stable in vivo. Specifically, in pharmacokinetic studies in nude mice, the blood clearance patterns of i.v. administered 205/206Bi-anti-Tac and coinjected 125I-anti-Tac were comparable. The toxicity and therapeutic efficacy of 212Bi-anti-Tac were evaluated in nude mouse ascites or solid tumor models wherein SP2/Tac cells were administered either i.p. or s.c., respectively. The i.p. administration of 212Bi-anti-Tac, 3 days following i.p. tumor inoculation, led to a dose-dependent, significant prolongation of tumor-free survival. Doses of 150 or 200 microCi prevented tumor occurrence in 75% (95% confidence interval, 41-93%) of the animals. In the second model, i.v. treatment with 212Bi-anti-Tac 3 days following s.c. tumor inoculation also resulted in a prolongation of the period before tumor development. However, prevention of tumor occurrence decreased to 30% (95% confidence interval, 11-60%). In both the i.p. and s.c. tumor trials, 212Bi-anti-Tac was significantly more effective for i.p. (P2 = 0.0128 50/100 microCi 212Bi-anti-Tac versus 50/100 microCi Mik beta; P2 = 0.0142 150/200 microCi anti-Tac versus 150/200 microCi Mik beta) and for s.c. tumors (P2 = 0.0018 100 microCi anti-Tac versus 100 microCi Mik beta; P2 = 0.0042 200 microCi anti-Tac versus 200 microCi Mik beta 1) than the control antibody Mik beta 1 coupled to 212Bi at comparable dose levels. In contrast to the efficacy observed in the adjuvant setting, therapy of large, established s.c. SP-2/Tac-expressing tumors with i.v. administered 212Bi-anti-Tac (at doses up to 200 microCi/animal) failed to induce tumor regression.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

A miniature gamma camera.

We have described a mobile miniature-gamma-camera system for use in electrical trauma units and have presented images and imaging characteristics of a prototype system. The system has as its principal component a miniature gamma camera based on a PSPMT. The camera is 92 mm x 92 mm x 190 mm in size, weighs 5 kg, has a 48 mm x 48 mm field of view, and has an intrinsic resolution of approximately 3 mm FWHM and 6 mm FWTM. It is expected that devices of this type will be useful as imaging tools in electrical trauma units and laboratories where imaging studies regarding uptake mechanisms of radiopharmaceuticals for assessing tissue viability are carried out.

Electric Injuries↗
PubMed1994

Possible role of glutamatergic neurotransmission in regulating ethanol-evoked brain ascorbate release.

It was found that systemic application of ethanol induced brain ascorbate (AA) release. In order to study the mechanism of ethanol-evoked AA release, the role of brain glutamatergic neurotransmission was investigated using in vivo voltammetry in the striatum of freely moving rats. Pretreatment with L-trans-pyrrolidine-2,4-dicarboxylate (PDC, 10 nmol, i.c.v.), a glutamate (Glu) uptake blocker, potentiated ethanol (1 g/kg, intraperitoneal injection, i.p.)-evoked release of brain AA. N-methyl-D-aspartate (NMDA, 1 nmol, i.c.v.) produced a fast transient increase in extracellular AA, whereas alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA, 1 nmol, i.c.v.) produced a decrease in extracellular AA (75.8 +/- 3% of control). Kainate (KA, 1 nmol, i.c.v.) produced an initial decrease (48.7 +/- 11.7% of control) then an increase (250 +/- 68.5% of control) in extracellular AA. These results suggest that systemic administration of ethanol may affect the release or uptake of brain glutamatergic neurotransmitters which appear to regulate brain AA release. The NMDA, but not the non-NMDA, type of Glu receptor may be responsible for this regulation.

Animals↗
PubMed1994

The binding of fibronectin to entactin is mediated through the 29 kDa amino terminal fragment of fibronectin and the G2 domain of entactin.

Previous work has shown that fibronectin and entactin, an ubiquitous basement membrane glycoprotein, co-localize in the extracellular matrix of the embryonal carcinoma-derived 4CQ cell. Glutathione-S-transferase (GST) fusion proteins containing different domains of entactin have been obtained in the pGEX3X expression vector. These fusion proteins, GST-G1, GST-G2, GST-E and GST-G3, were purified with a glutathione affinity column. By using a solid phase binding assay, it was shown that the 125I-labeled 29 kDa amino terminal fragment of bovine fibronectin bound specifically to the immobilized GST-G2 fusion protein but not to GST-G1, GST-E, and GST-G3. Half saturation for binding of the 29 kDa fibronectin fragment to the immobilized GST-G2 fusion protein was obtained at a concentration of approximately 5 nM. It is suggested that the strong association between GST-G2, which contains the second globular domain of entactin, and the 29 kDa amino terminal fragment of fibronectin may be involved in the assembly of certain types of extracellular matrices.

Animals↗
PubMed1994

ATP-dependent nucleosome disruption at a heat-shock promoter mediated by binding of GAGA transcription factor.

Genetic control elements are usually situated in local regions of chromatin that are hypersensitive to structural probes such as DNase I. We have reconstructed the chromatin structure of the hsp70 promoter using an in vitro nucleosome assembly system. Binding of the GAGA transcription factor on existing nucleosomes leads to nucleosome disruption, DNase I hypersensitivity at the TATA box and heat-shock elements, and rearrangement of adjacent nucleosomes. ATP hydrolysis facilitates this process, suggesting that an energy-dependent pathway is involved in chromatin remodelling.

Adenosine Triphosphate↗
PubMed1994

NMR evidence for similarities between the DNA-binding regions of Drosophila melanogaster heat shock factor and the helix-turn-helix and HNF-3/forkhead families of transcription factors.

Heteronuclear multidimensional NMR experiments of residues 33-163 of the DNA-binding domain of Drosophila heat shock factor, dHSF(33-163), were recorded, using only 3 mg of uniformly 15N-labeled or 2 mg of uniformly 15N/13C-labeled protein. The polypeptide consists of a structured part comprising three helices, a three-stranded antiparallel beta-sheet, with the first two strands connected by a four-residue type I tight turn. The second helix is disrupted at its C-terminal end by a proline residue and is followed by an extended turn, leading to the third helix. The dHSF(33-163) protein is unstructured at its N- and C-termini, and a third unstructured region is found from Thr113 to Arg124. Exchange broadening of the 15N-1H correlations upon titration of 15N labeled HSF with a 13-base-pair DNA duplex suggests a DNA-binding motif in which the third helix acts as the recognition helix. Both the secondary structure and DNA-binding pattern of dHSF(33-163) suggest that the overall topology resembles that the helix-turn-helix bacterial activator CAP [Weber, I. T., & Steitz, T. A. (1987) J. Mol. Biol. 198, 311-326] and the liver-specific transcription factor HNF-3 gamma, the prototype of the HNF-3/forkhead protein family [Clark, K. L., Halay, E. D., Lai, E., & Burley, S. K. (1993) Nature 364, 412-420].

Amino Acid Sequence↗
PubMed1994

Interaction of the DNA-binding domain of Drosophila heat shock factor with its cognate DNA site: a thermodynamic analysis using analytical ultracentrifugation.

Heat shock transcription factor (HSF) mediates the activation of heat shock genes by binding to its cognate sites with high affinity and specificity. The high-affinity binding of HSF is dependent on the formation of an HSF homotrimer, which interacts specifically with the heat shock response element (HSE), comprised of 3 inverted repeats of the 5-bp sequence NGAAN. In order to investigate the thermodynamic basis of the interaction between HSF and HSE, we have overexpressed and purified a polypeptide (dHSF(33-163)) encompassing only the DNA-binding domain of HSF from Drosophila and analyzed its binding to DNA by equilibrium analytical ultracentrifugation using a multiwavelength scan technique. We demonstrate that dHSF(33-163) can bind as a monomer with 1:1 stoichiometry to a synthetic 13-bp DNA containing a single NGAAN sequence. The values of the thermodynamic parameters obtained from the temperature dependence of the equilibrium binding constants indicate that the changes of free energy for the binding of dHSF(33-163) to the wild-type site and a mutant DNA site are predominantly characterized by substantial negative changes of enthalpy. Binding to the wild-type DNA is characterized by a significant positive change of entropy, whereas binding to the mutant DNA is distinguished by a negative change of entropy of comparable magnitude. The binding to the mutant DNA was also highly sensitive to increasing salt concentrations, indicating a dominance of ionic interactions. The sequence-specific, 1:1 binding of dHSF(33-163) to the NGAAN sequence provides a basis for the analysis of higher order interactions between HSF trimers and the HSE.

Animals↗
PubMed1994

Comparative biodistribution of indium- and yttrium-labeled B3 monoclonal antibody conjugated to either 2-(p-SCN-Bz)-6-methyl-DTPA (1B4M-DTPA) or 2-(p-SCN-Bz)-1,4,7,10-tetraazacyclododecane tetraacetic acid (2B-DOTA).

The biodistribution of indium-111/yttrium-88-labeled B3 monoclonal antibody, a murine IgG1k, was evaluated in non-tumor-bearing mice. B3 was conjugated to either 2-(p-SCN-Bz)-6-methyl-DTPA (1B4M) or 2-(p-SCN-Bz)-1,4,7,10 tetraazacyclododecane tetra-acetic acid (2B-DOTA) and labeled with 111In at 1.4-2.4 mCi/mg and 88Y at 0.1-0.3 mCi/mg. Non-tumor-bearing nude mice were co-injected i.v. with 5-10 microCi/4-10 micrograms of 111In/88Y-labeled B3 conjugates and sacrificed at 6 h and daily up to 168 h post-injection. Mice injected with 111In/88Y-(1B4M)-B3 showed a similar biodistribution of the two radiolabels in all tissues except the bones, where significantly higher accretion of 88Y than 111In was observed, with 2.8% +/- 0.2% vs 1.3% +/- 0.16% ID/g in the femur at 168 h, respectively (P < 0.0001). In contrast, mice receiving the 111In/88Y-(DOTA)-B3 conjugate showed significantly higher accumulation of 111In than 88Y in most tissues, including the bones, with 2.0% +/- 0.1% vs 1.2% +/- 0.09% ID/g in the femur at 168 h, respectively (P < 0.0001). Whereas the ratios of the areas underneath the curve (%ID x h/g) in the blood, liver, kidney and bone were 0.96, 1.12, 1.13, and 0.74 for 111In/88Y-(1B4M)-B3 and 0.84, 1.23, 1.56, and 1.31 for 111In/88Y-(DOTA)-B3, respectively, ratios approximately 1 were observed between 111In-(1B4M)-B3 and 88Y-(DOTA)-B3. In summary, while neither 1B4M nor DOTA was equally stable for 111In and 88Y, the fate of 88Y-(DOTA)-B3 could be closely traced by that of 111In-(1B4M)-B3.

Animals↗
PubMed1994

Expression of type I and type II interleukin-1 receptors in mouse brain.

Although binding sites for IL-1 have been identified in the mouse brain, it is still unknown whether these binding sites correspond to the type I or type II IL-1 receptor. Quantitative autoradiography was used to confirm the presence of specific binding sites for radiolabelled recombinant human IL-1 alpha (125I-HuIL-1 alpha) in the brain of DBA/2 mice. IL-1 binding was highest in the dentate gyrus, consisting of a single class of high affinity binding sites with a Kd of 0.1 nM and a Bmax of 57 fmol/mg protein. A similar Kd of 0.2 nM was obtained using isolated membranes from the whole hippocampus, although the number of binding sites was lower (2 fmol/mg protein). Affinity cross-linking of 125I-Hu-IL-1 alpha to hippocampal membranes revealed the existence of two types of IL-1 receptor proteins, consistent with the sizes of the type I (85 kD) and type II (60 kD) IL-1 receptor. Oligonucleotide probes were then synthesized and used in RT-PCR followed by Southern blotting to show that the whole brain expresses transcripts for both the type I and type II IL-1 receptors. The murine neuroblastoma cell line, C1300, expresses type I rather than type II IL-1 receptor mRNA. The type I receptor protein can be identified by flow cytometry on the membrane of the C1300 neuronal cell line using indirect immunofluorescence with a rat anti-mouse type I IL-1 receptor MoAb. These data show that mouse brain expresses both type I and type II IL-1 receptor mRNA and proteins and offer further support to the idea that type I IL-1 receptors are synthesized and expressed by neurons.

Animals↗
PubMed1994

Pure-tone masking profiles for human auditory brainstem and middle latency responses to 500-Hz tones.

A simultaneous masking paradigm was used to determine the frequency selectivity of human auditory brainstem (ABR) and middle latency (MLR) responses to 60 dB pe SPL 500-Hz probe tones in 12 normal adults. Masking profiles for simultaneous recordings of the ABR and MLR were obtained in the presence of pure-tone maskers presented at 60- and 70-dB SPL. Results show sharp amplitude profiles with maximum reduction in amplitude seen using the 500-Hz maskers. There were no significant differences in the masking profiles for the ABR and MLR waves to the 500-Hz probe tones. An additional measure of frequency selectivity, bandwidth at 50% reduction in amplitude (W50), also demonstrated no significant difference between the ABR and MLR waves. In summary, the results of this study and those of an earlier study (Mackersie et al., 1993) suggest no significant difference in the frequency selectivity of the ABR and MLR to low-intensity (60 dB pe SPL) 500- and 2000-Hz tones.

Acoustic Stimulation↗
PubMed1994

Interferon-stimulated response element and NF kappa B sites cooperate to regulate double-stranded RNA-induced transcription of the IP-10 gene.

To understand the mechanisms involved in dsRNA-induced gene expression, we analyzed the poly(I/C)-induced transcription of the IFN-inducible chemokine gene IP-10 using the GRE cell line in which type I IFN genes have been deleted. Accumulation of IP-10 mRNA in GRE cells was more strongly stimulated by treatment with dsRNA than by IFN-alpha or IFN-gamma and was independent of protein synthesis. This same pattern of response was produced when GRE cells were transiently transfected with a plasmid containing 243 bases of sequence from the promoter of the murine IP-10 gene linked to the chloramphenicol acetyltransferase reporter gene. Deletion- and site-specific mutagenesis of the 243 base pair fragment indicated that an ISRE located between residues -204 and -228 was a primary target site for the action of dsRNA on this promoter. This was confirmed by results showing that two copies of this ISRE tandemly arrayed in front of the thymidine kinase promoter were able to mediate reporter gene transcription in dsRNA-stimulated cells. At least one of the two NF kappa B binding sites present in the 243 base pair IP-10 promoter is also necessary for response to dsRNA; mutation of both sites eliminates promoter activity. Thus the ISRE and one NF kappa B site cooperate to produce transcriptional response to dsRNA.

Base Sequence↗
PubMed1994

Epitope mapping of Escherichia coli cell division protein FtsZ with monoclonal antibodies.

A fusion between lacZ and ftsZ of Escherichia coli was constructed to obtain a beta-galactosidase-FtsZ fusion protein. This fusion protein was used to raise antibodies against cell division protein FtsZ. Six monoclonal antibodies were obtained, and they reacted with FtsZ from cytoplasm and membrane fractions. The epitopes in FtsZ were localized by studying the reactions of the monoclonal antibodies with fusion proteins truncated at the carboxy terminus and with fragments that were obtained by CNBr cleavage of purified FtsZ. Five different epitopes were defined. Epitopes I and III reacted with the same monoclonal antibody, without showing apparent amino acid homology. Epitope II was defined by monoclonal antibodies that cross-reacted with an unknown cytoplasmic 50-kDa protein not related to FtsZ. Epitopes IV and V were recognized by different monoclonal antibodies. All monoclonal antibodies reacted strongly under native conditions, so it is likely that the five epitopes are situated on the surface of native FtsZ. By using these data and computer analysis, a provisional model of FtsZ is proposed. The FtsZ protein is considered to be globular, with a hydrophobic pocket containing GTP-binding elements. Epitopes I and II are situated on each side of the hydrophobic pocket. Because the carboxy terminus contains epitope V, the carboxy terminus of FtsZ is likely oriented toward the protein's surface.

Animals↗