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Biomedical subjects

C Wu

Publications and source records attributed to C Wu.

At least 487 records · Page 27Linked to original sources
PubMed1993

Chromosomal localization of a sequence with in vivo activity for initiation of DNA replication.

The genomic fragment containing the sequence of human cDNA clone 343, previously characterized as capable of autonomous replication upon transfection into mammalians cells and occupying a genomic region inclusive of an initiation zone for DNA replication, was mapped on human chromosome 6q22-qter by a combination of in situ hybridization and G-banding. Southern blot hybridization with a panel of human-hamster somatic cells confirmed the location of the 343 gene on chromosome 6. Fragile sites have been mapped to the region at 6q21 and 6q26. Several neoplastic disorders, including melanoma, acute nonlymphocytic leukemia, acute lymphocytic leukemia, and malignant lymphoma, have also exhibited translocations and deletions involving the region 6q21-6q27.

Animals↗
PubMed1993

Hepatitis C virus in pregnancy: seroprevalence and risk factors for infection.

OBJECTIVES: Our purpose was to define the prevalence of antibodies to hepatitis C virus among inner-city prenatal patients. We also sought to examine both the reliability of traditional hepatitis risk factors to predict evidence of infection among these women and the incidence of coinfection in this population with other blood-borne and sexually transmissible agents. STUDY DESIGN: An anonymous serosurvey was performed to define and compare anti-hepatitis C virus prevalences among women registering for prenatal care at both an inner-city, university hospital-based clinic and an academic private practice based at the same institution. RESULTS: Anti-hepatitis C virus antibodies were detected in 4.3% of 599 pregnant women screened. In comparison, 0.8% had positive antibody tests for human T-lymphotropic virus and 0.5% were positive for antibodies to human immunodeficiency virus. Evidence of chronic hepatitis B infection was seen in 0.8%. The relative risk of other coexisting infections was significantly higher among women with anti-hepatitis C virus antibodies than among those who were antibody negative. Substance abuse was the most commonly identified risk factor for anti-hepatitis C virus-positive status, although risk factor-targeted screening would have failed to detect half of the anti-hepatitis C virus-positive women in this study. CONCLUSIONS: Hepatitis C virus infection among inner-city pregnant women, with its potential for maternal-fetal transmission, represents a public health issue of sufficient magnitude to warrant more extensive study. More information is needed, given this documented reservoir of maternal seropositivity, regarding the vertical transmissibility of the virus and the effects of coinfections on neonatal disease.

Adult↗
PubMed1993

The stability in liver homogenates of indium-111 and yttrium-90 attached to antibody via two popular chelators.

To investigate the influence of chelator on the stability in liver homogenates of 111In and 90Y-labeled antibodies, the C110 antibody was conjugated with the cyclic anhydride of DTPA (cDTPA) and with isocyanatobenzyl-DTPA (SCN-Bz-DTPA) and labeled with both radionuclides. After incubation in fresh liver homogenates at 37 degrees C for 1-2 days, the soluble fraction was analyzed by filtration, HPLC and TLC to determine the nature and extent of transchelation of the label and catabolism of the antibody. The loss of activity from antibody, as shown by passage through a low molecular weight (10 kDa cut-off) filter, was 3-5 times more pronounced for 90Y (51 and 68% at 1 and 2 days) than 111In (11 and 29%, respectively). No significant difference was observed between chelators. Furthermore, analysis of these low molecular weight species showed that even at 1 day, 90Y in contrast to 111In was present as one or more weak complexes and therefore no longer chelated to either DTPA or Bz-DTPA. Little evidence was observed for instability in liver of the thiourea bond whereby SCN-Bz-DTPA is attached to the antibody. By contrast the identification of 111In-DTPA in the homogenates demonstrates the instability of the amide bond generated by cDTPA conjugation. In conclusion, as expected, 90Y was shown to form less stable chelates than 111In, however, in this investigation the greater denticity of Bz-DTPA over DTPA did not improve stability with either radiolabel.

Animals↗
PubMed1993

Biological functions of entactin.

Entactin is a sulfated multidomain glycoprotein component of basement membranes. The molecule consists of 1217 amino acids which are organized into two terminal globular domains linked by a rod-like structure largely composed of four EGF- and one thyroglobulin-like cysteine-rich homology repeats. Entactin binds to laminin, collagen IV, fibrinogen, and fibronectin. In the parietal endoderm M1536-B3 cell line, the laminin-entactin complex is formed intracellularly and transported in membrane enclosed vesicles to the extracellular compartment. Transfection of human choriocarcinoma JAR cells, which do not synthesize entactin, with entactin cDNA results in the synthesis and insertion of entactin into the extracellular matrix where it becomes associated with laminin and collagen IV. Indirect immunofluorescent staining also reveals that entactin co-localizes with fibronectin in the extracellular matrix of the embryonal carcinoma-derived 4CQ cell line. These observations suggest that entactin plays an important role in the assembly and properties of diverse extracellular matrices. In addition, entactin binds to immobilized fibrinogen, and more specifically, to the A alpha and B beta chains. The binding of radiolabeled entactin to immobilized fibrinogen is not dependent on metal ions, and is inhibited by antibodies against either fibrinogen or entactin, soluble fibrinogen, and unlabeled entactin. This interaction combined with the chemotactic and phagocytic promoting activities of entactin may be important in hemostasis and would healing.

Animals↗
PubMed1993

Activation of Drosophila heat shock factor: conformational change associated with a monomer-to-trimer transition.

The induction of heat shock genes in eukaryotic cells is regulated by the transcription factor heat shock factor (HSF). Activation of HSF occurs at two independent levels, DNA binding and the acquisition of transcriptional competence. The binding of HSF to DNA is accomplished by a stress-induced oligomeric switch of HSF protein. We have defined the oligomeric state of the latent and induced forms of HSF by measuring the sedimentation coefficient and the Stokes radius of the protein in Drosophila cell extracts. Calculation of the native molecular mass indicates that the two forms of Drosophila HSF are best described as a monomer and trimer, respectively, of the 77-kDa HSF polypeptide. The monomeric and trimeric states of HSF were verified by chemical cross-linking experiments. The finding of a monomeric composition for the latent form of HSF is incompatible with speculative models which suggest that molecular chaperones such as hsp70 feed back to inhibit trimerization of HSF by forming a stable heteromeric complex. We also found that both HSF monomers and HSF trimers exhibit unusually high frictional ratios, indicating that they have asymmetric shapes. The degree of asymmetry is significantly greater for the HSF trimer, suggesting that the monomer undergoes a conformational change to a more extended structure upon trimerization. These findings are consistent with a model for the inert HSF protein that is based on a monomer constrained by intramolecular coiled-coil interactions between amino- and carboxy-terminal domains.

Animals↗
PubMed1993

Repression of Drosophila pair-rule segmentation genes by ectopic expression of tramtrack.

The tramtrack (ttk) protein has been proposed as a maternally provided repressor of the fushi tarazu (ftz) gene in Drosophila embryos at the preblastoderm stage. Consistent with this hypothesis, we have detected by immunohistochemistry the presence of ttk protein in preblastoderm embryos. This is followed by a complete decay upon formation of the cellular blastoderm when ftz striped expression is at its peak. In addition, the highly complex pattern of zygotic ttk expression suggests specific functions for ttk late in development that are separate from the regulation of ftz. We have produced ttk protein ectopically in blastoderm-stage embryos transformed with a heat shock-ttk construct. Ectopic ttk caused complete or near-complete repression of the endogenous ftz gene, as well as significant repression of the pair-rule genes even skipped, odd skipped, hairy and runt. These findings suggest that specific repression by ttk (or by undiscovered repressors) may be more than an isolated phenomenon during the rapid cleavage divisions, a period when the need for genetic repression has not been generally anticipated.

Animals↗
PubMed1993

Enhanced attachment and growth of human endothelial cells derived from umbilical veins on ammonia plasma modified surfaces of PTFE and ePTFE synthetic vascular graft biomaterials.

Ammonia plasma generated by electrical discharge at low pressure was employed for the surface modification of PTFE and ePTFE. A new chemistry at the plasma treated surfaces is reported. X-ray photoelectron spectroscopy studies showed the incorporation of C-N, C-O, C = O etc functional groups on the plasma treated surfaces. Human endothelial cells derived from umbilical veins (HUEC) were used to seed the plasma treated PTFE and ePTFE surfaces to assess the attachment and growth. Enhanced attachment and growth of HUEC was observed on the plasma treated surfaces. In addition, the performance of these surfaces in this respect was found to be considerably superior to human collagen or human fibronectin or collagen-fibronectin coated PTFE. HUEC attachment and growth on these plasma treated surfaces was further enhanced by immobilizing collagen or fibronectin or collagen-fibronectin. Ammonia plasma treated and untreated ePTFE vascular graft samples were seeded with 3.6 X 10(4) cells/sample. At 24 hrs after seeding, HUEC cell attachment was studied. Although, HUEC attachment on collagen or fibronectin coated ePTFE was improved, but there was no significant difference between the number of cells attached to these surfaces when compared with those adhered to plasma treated ePTFE without collagen or fibronectin coating. Collagen or fibronectin coated plasma treated surfaces showed better performance over their respective controls.

Ammonia↗
PubMed1993

Neural networks for molecular sequence classification.

A neural network classification method has been developed as an alternative approach to the search/organization problem of large molecular databases. Two artificial neural systems have been implemented on a Cray supercomputer for rapid protein/nucleic acid sequence classifications. The neural networks used are three-layered, feed-forward networks that employ back-propagation learning algorithm. The molecular sequences are encoded into neural input vectors by applying an n-gram hashing method or a SVD (singular value decomposition) method. Once trained with known sequences in the molecular databases, the neural system becomes an associative memory capable of classifying unknown sequences based on the class information embedded in its neural interconnections. The protein system, which classifies proteins into PIR (Protein Identification Resource) superfamilies, showed a 82% to a close to 100% sensitivity at a speed that is about an order of magnitude faster than other search methods. The pilot nucleic acid system, which classifies ribosomal RNA sequences according to phylogenetic groups, has achieved a 100% classification accuracy. The system could be used to reduce the database search time and help organize the molecular sequence databases. The tool is generally applicable to any databases that are organized according to family relationships.

Base Sequence↗
PubMed1993

[Effects of the stimulating point and non-point on human cerebral evoked potential and spinal cord evoked potential].

The experiments were carried out on 36 normal subjects. Pain stimulation points are at Neiguan or Hegu and pain stimulation nonpoints are nearby Neiguan or Hegu. The Record locations are at cortex and cervical vertebrae. The feature of evoked cerebral potential (ECP) and spinal cord evoked potential (ESP) by pain stimulation the points or non-points were studied. The results have been obtained. 1. Pain stimulation point ECP generally consists of wave P1, N1, P2, N2, P3, N3, P4 and N4. There is a certain amplitude and latency of each wave. 2. The elements of pain stimulation non-point ECP are Similar to point ECP in the feature. Comparing Pain stimulation Point ECP with non-point ECP, the amplitude of wave P3-N3 of stimulation point ECP increases (P < 0.05). 3. Pain stimulation Point ESP and non-point ESP consist of wave P1, N1 and P2, N3. Comparing Pain stimulation point with non-point there are no significant changes in the amplitude and the latency of ESP.

Acupuncture Points↗
PubMed1993

[Unequal genetic contributions of parents to offsprings and their optimal control].

Due to the joint effects of natural and artificial selection, the proportions of genetic materials originating from different parents may vary in the gene pool of offsprings, and this creates a problem of unequal genetic contributions of parents to offsprings. It is shown that unequal genetic contribution substantially affects the genetic gain via realized selection differential and effective population size, and brings error to the empirical prediction formulae of selection response: R = i.sigma P.h2. The aim of breeding should be to select the genetically superior individuals and then to make more genetic contributions of better parents to offspring gene pool. However, the latter aspect has been ignored in theoretical study as well as in certain breeding practice. To deal with the problem, a method which takes maximizing genetic advance as general objective and considers some breeding restrictions, is suggested to control the percentage of genetic contributions. A numerical example from egg-type chicken breeding is used to demonstrate the effects of optimal control of unequal genetic contributions. The result indicates that at the same level of effective population size, the realized selection response for different traits under the optimal pattern of unequal genetic contributions could be 34.27-216.57% higher than that under the actual unequal pattern.

Animals↗
PubMed1993

Early diagnosis of typhoid fever using monoclonal antibody.

In our study, a reverse passive hemagglutination assay (RPHA) method was established using monoclonal antibody-IgM to detect the Salmonella typhi O9 antigen. This method has the advantages of sensitivity, specificity, rapidity, and simplicity, and helps make an early diagnosis of typhoid fever using only small amounts of blood.

Animals↗
PubMed1993

Human hepatic stimulator substance: a product of gene expression of human fetal liver tissue.

Cloning of human hepatic stimulator substance requires clarification of whether the substance is the product of gene expression of liver cells. In this article the translation experiment in Xenopus laevis oocytes indicates that poly (A)+ messenger RNA of human fetal liver cells could conduct the biosynthesis of human hepatic stimulator substance. The translated human hepatic stimulator substance is a heat-, acid- and alkaline-resistant, but specific hepatic-stimulating, protein with a molecular weight in the range of 10 to 30 kD and with secreting ability. The characteristics of the translated human hepatic stimulator substance are consistent with those of biochemically purified human hepatic stimulator substance from human fetal liver cells. These results demonstrate that human hepatic stimulator substance is a product of gene expression of human fetal liver cells and that the complementary DNA of human hepatic stimulator substance could be screened from the complementary DNA library of human fetal liver tissue.

Animals↗
PubMed1992

Rapid changes in ascorbate and dopamine release in rat nucleus accumbens after intracerebroventricular administration of NMDA.

In vivo voltammetry at electrochemically pretreated carbon fibre electrodes was used to investigate the effect of intracerebroventricular (i.c.v.) administration of N-methyl-D-aspartic acid (NMDA) on neuronal activity in rat nucleus accumbens. Infusion of a low dose of NMDA (1 nmol) was followed a few minutes later by rapid changes in both Peak 1 and Peak 2 heights indicating large but short-lived increases in the extracellular concentrations of ascorbate and catecholamines, respectively. These responses did not seem to be dependent on the dose infused since infusion of NMDA for a longer time period neither changed the amplitude nor the time-course of these effects. The increase in Peak 2 height was resistant to pargyline pretreatment indicating that this response mainly reflected the release of dopamine. The administration of NMDA was followed by behavioural activation in the animals but not convulsions. Co-administration of the competitive NMDA receptor antagonist, CPP (1 nmol), completely blocked these effects while the acetylcholine receptor antagonist, atropine (1.5 nmol), and the GABA receptor antagonist, picrotoxin (1 nmol), failed in this respect. The phenomenon spreading depression is discussed as a possible explanation of these results.

Animals↗
PubMed1992

IL-4 induces conformational change of CD20 antigen via a protein kinase C-independent pathway. Antagonistic effect of anti-CD40 monoclonal antibody.

The CD20 molecule is a unique phosphoprotein exclusively expressed on B cells during most stages of B cell ontogeny. We here report that rIL-4 down-regulates the expression of CD20 with anti-Leu-16 mAb (clone L27) on both unstimulated and anti-mu preactivated normal and leukemic B cells. None of the other recombinant lymphokines tested (IL-1, IL-2, IL-3, IL-6, IFN-alpha, and IFN-gamma, granulocyte/macrophage-CSF, transforming growth factor-beta, TNF-alpha, and lymphotoxin) decreased CD20 expression. Incubation of unstimulated or anti-mu preactivated B cells with IL-4 did not affect the steady state CD20 mRNA, suggesting that IL-4 exerted its effect mainly at a nontranscriptional level. Hence, IL-4 selectively down-regulates the CD20 epitope recognized by clone L27 without affecting seven other different epitopes, indicating that IL-4 acts by modifying the conformation of the CD20 molecule rather than by inhibiting its production or inducing its internalization. IL-4 most likely utilizes a protein kinase C-independent signal transduction pathway to modify CD20 molecule inasmuch as staurosporine, an inhibitor of protein kinase C, antagonizes phorbol esters (PMA) but not IL-4-induced CD20 down-regulation. In contrast, anti-CD40 mAb reverses the IL-4 but not the PMA inhibitory effect on CD20 expression. Given that CD20 may be part of a Ca2+ ion channel and plays a role in B cell activation and proliferation, it is proposed that the ability of anti-CD40 mAb to maintain the CD20 molecule in a given epitopic configuration on IL-4-stimulated B cells may be related to the long term proliferation of normal B cells that are strictly dependent on the presence of IL-4 and cross-linked anti-CD40 mAb for their continuous growth.

Antibodies, Monoclonal↗
PubMed1992

Protein classification artificial neural system.

A neural network classification method is developed as an alternative approach to the large database search/organization problem. The system, termed Protein Classification Artificial Neural System (ProCANS), has been implemented on a Cray supercomputer for rapid superfamily classification of unknown proteins based on the information content of the neural interconnections. The system employs an n-gram hashing function that is similar to the k-tuple method for sequence encoding. A collection of modular back-propagation networks is used to store the large amount of sequence patterns. The system has been trained and tested with the first 2,148 of the 8,309 entries of the annotated Protein Identification Resource protein sequence database (release 29). The entries included the electron transfer proteins and the six enzyme groups (oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases), with a total of 620 superfamilies. After a total training time of seven Cray central processing unit (CPU) hours, the system has reached a predictive accuracy of 90%. The classification is fast (i.e., 0.1 Cray CPU second per sequence), as it only involves a forward-feeding through the networks. The classification time on a full-scale system embedded with all known superfamilies is estimated to be within 1 CPU second. Although the training time will grow linearly with the number of entries, the classification time is expected to remain low even if there is a 10-100-fold increase of sequence entries. The neural database, which consists of a set of weight matrices of the networks, together with the ProCANS software, can be ported to other computers and made available to the genome community. The rapid and accurate superfamily classification would be valuable to the organization of protein sequence databases and to the gene recognition in large sequencing projects.

Computers, Mainframe↗