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Biomedical subjects

H Wu

Publications and source records attributed to H Wu.

At least 721 records · Page 40Linked to original sources
PubMed1994

Cerebral morphometry and clozapine treatment in schizophrenia.

Studies of brain morphology in schizophrenia may be informative about basic pathophysiologic processes, provide clinically useful indicators of treatment response, and lead to the identification of markers for selective treatment effects. This paper reviews findings from magnetic resonance imaging studies of patients with schizophrenia conducted at Hillside Hospital, with special attention to (1) findings that have helped distinguish patients who respond well to typical neuroleptics from those who have gone on to trials of clozapine, (2) the capacity of morphological measures to predict clozapine treatment response, and (3) the possibility that selective hypertrophy of striatal structure may be caused by chronic treatment with typical neuroleptics, but not by clozapine.

Atrophy↗
PubMed1994

Mutations in the gyrB domain of eukaryotic topoisomerase II can lead to partially dominant resistance to etoposide and amsacrine.

Anti-topoisomerase II agents represent a major class of anticancer therapeutic agents. Resistance to this class of agents can be mediated by several possible mechanisms. One mechanism may involve mutations in the structural gene(s) for topoisomerases, altering the drug sensitivity of the enzymes. Several mutations have been described in mammalian cell lines that were selected for resistance to topoisomerase II-targeting drugs such as Adriamycin, etoposide, or amsacrine. The difficulty of performing genetic analysis in mammalian cell lines has complicated the determination of whether the observed mutations are responsible for drug resistance. We have reconstructed, in the yeast topoisomerase II gene, the arginine to glutamine mutation at position 450 of human topoisomerase II alpha that was originally identified by Bugg et al. [Proc. Natl. Acad. Sci. USA 88:7654-7658 (1991)]. Mutation of Lys439, the equivalent amino acid in the yeast protein, to either glutamine or glutamic acid confers resistance to etoposide and amsacrine. Interestingly, in diploid yeast cells the heterozygous mutation can still confer partial drug resistance, compared with a diploid strain that is homozygous for wild-type topoisomerase II. Because mutations in the topoisomerase II gene that can confer dominant resistance to anti-topoisomerase II agents are relatively rare, mutations in the gyrB region may be important in the development of clinical drug resistance.

Amino Acid Sequence↗
PubMed1994

Inhibitory effects of high molecular weight substances from CAPD dialysate on mouse bone marrow progenitor cells and lymphocyte transformation.

The isolation and purification of F A1 (MW 23-64 KD), F B1 (MW 24-54 KD), F A2 and F B2 (both MW 67 KD) of high molecular weight substances (HMS) from continuous ambulatory peritoneal dialysis (CAPD) dialysate of 2 end staged renal disease (ESRD) patients (A and B) were carried out by precipitation, desalting, gradient elution, chromatography and concentration. 0.1ml of tris-buffer, 0.2ml of uremic serum. 0.1ml of F A1, F B1, 0.2ml of F A2 were separately added to mouse bone marrow culture medium and lymphocyte culture medium, then colony-forming unit of erythroid (CFU-E), burst-forming unit of erythroid (BFU-E), colony-forming unit of granulocyte-macrophage (CFU-GM) and lymphocyte transformation (LT) were measured. We found that the uremic serum and F A1, F B1 could inhibit CFU-E, BFU-E very significantly (P < 0.001) compared to the tris-buffer control, but could not inhibit CFU-GM. The uremic serum and F A1 could inhibit LT significantly (P < 0.01) compared to the tris-buffer control, while F A2 could inhibit neither CFU-E nor BFU-E. If the dosage of erythropoietin (EPO) added to mouse bone marrow progenitor cell culture medium increased 3-6 times. F A1 could not express its inhibitory effect on CFU-E or BFU-E.(ABSTRACT TRUNCATED AT 250 WORDS)

Anemia↗
PubMed1993

Determination and refinement of the canine parvovirus empty-capsid structure.

The canine parvovirus (CPV) empty-capsid structure has been determined and refined to 3.0 A resolution in the tetragonal space group P4(3)2(1)2 with cell dimensions a = b = 254.5 and c = 795.0 A. The successful structure determination shows that reasonably good diffraction data were obtained in spite of the very long c axis. The structure was solved by molecular replacement using the electron density of CPV full particles in a monoclinic space group. The phases were refined by non-crystallographic symmetry averaging. The structure refinement was carried out by using the programs PROLSQ and X-PLOR. The final R factor for the structure that included 85 water molecules per icosahedral asymmetric unit was 21.1% for reflections between 6.0 and 3.0 A resolution with an r.m.s. deviation of bond lengths of 0.020 A from ideal values. The structure of CPV empty capsids showed conformational differences with respect to full capsids at a region where icosahedrally ordered DNA in full particles interacts with the capsid protein. It also confirmed the absence of density along the fivefold axis in the CPV empty-particle structure in contrast to the situation in CPV full particles.

Journal Article↗
PubMed1993

The canine parvovirus empty capsid structure.

The structure of empty canine parvovirus capsids shows that residues 37 to the carboxy-terminal residue 584 (VP2 numbering) are ordered in each of the 60 subunits. The central structural motif of each subunit is the eight-stranded antiparallel beta-barrel that has been found in many other virus structures. Five beta-hairpin turns form a beta-cylindrical structure at each icosahedral 5-fold axis. The N-terminal glycine-rich sequence can be accommodated within this cylinder without excessive steric hindrance, consistent with the electron density distribution. By far the largest conformational differences between the full and empty virus were found in the region where some ordered DNA has been observed to bind in canine parvovirus full particles. Extensive interactions among 3-fold related subunits indicate that a trimeric subunit might be a viral assembly intermediate.

Amino Acid Sequence↗
PubMed1993

Mutagenesis of ribosomal protein S8 from Escherichia coli: expression, stability, and RNA-binding properties of S8 mutants.

Protein S8, a 129 amino acid component of the Escherichia coli ribosome, plays an essential role in the assembly of the 30S ribosomal subunit and in the translational regulation of the spc operon by virtue of its capacity to bind specifically to rRNA and mRNA. To study structure-function relationships within the protein, we have constructed a vector for its high-level expression in vivo and developed efficient methods for its purification. Under our conditions, S8 accumulates to a level of 35% of the cellular protein and can be prepared at a purity of over 98% using either HPLC or a combination of ion-exchange and gel-filtration chromatography. The unique cysteine residue at position 126 was replaced by alanine or serine by oligonucleotide-directed mutagenesis, and the two mutant proteins, CA126 and CS126, were expressed and isolated. The effects of the mutations on the RNA-binding ability, secondary structure, and stability of S8 were assessed. CD spectra indicated that wild-type S8 and the two mutant proteins have very similar secondary structures at 25 degrees C. In addition, both mutants are metabolically stable in vivo as inferred from pulse-chase labeling and immunoprecipitation experiments. However, while CA126 exhibits the same affinity for RNA and the same susceptibility to urea and thermal denaturation as wild-type S8, CS126 is severely impaired in its ability to interact with RNA and displays a dramatic reduction in conformational stability. Our results suggest that Cys126 is unlikely to play a specific role in RNA recognition but that it is an integral part of the RNA-binding domain of protein S8.

Alanine↗
PubMed1993

Assignment of the chromogranin A (Chga) locus to homologous regions on mouse chromosome 12 and rat chromosome 6.

Chromogranin A is an acidic protein, stored and released with catecholamines, and is overexpressed in genetic hypertension. In the human genome, its locus has previously been positioned on the long arm of Chromosome 14 in the 14q32 region. As a first step toward evaluating its potential linkage with hereditary hypertension, we determined its chromosomal position in mouse and rat. Chromogranin A was present as a single-copy gene in both mouse and rat. Analysis of the allele distribution in an interspecific mouse backcross by single-strand conformation polymorphism positioned the chromogranin A locus on Chromosome 12, between Igh-C and D12Pas1. Evaluation of a rat/mouse somatic cell hybrid panel indicated that chromogranin A is on rat Chromosome 6. In each case (mouse, rat, and human), chromogranin A is in a conserved region with nearby markers including the immunoglobulin heavy chain locus.

Animals↗
PubMed1993

Induction of changes in the secondary structure of globular proteins by a hydrophobic surface.

Circular dichroism, ellipsometry and radiolabeling techniques were employed to study the induction of changes in the secondary structure of BSA, myoglobin and cytochrome C by a hydrophobic surface. The results showed that adsorbed protein molecules lose their ordered native structure in the initial stage of adsorption and the structure appears to be a random or disordered conformation. Protein molecules adsorbed in later stages adopt a more ordered secondary structure (alpha helix and beta structure). The changes of secondary structure of globular proteins induced by a hydrophobic surface can be explained by the steric interaction between adsorbed proteins as well as by hydrophobic interactions during the adsorption process. In addition, there is obviously an intermediate stage in which the protein molecules are mainly in the beta structure, indicating that for certain proteins, the beta structure may be a more stable secondary structure than alpha helix on the hydrophobic surface.

Adsorption↗
PubMed1993

Susceptibility of type I collagen containing mutated alpha 1(1) chains to cleavage by human neutrophil collagenase.

Two members of the matrix metalloproteinase family which can cleave native types I, II and III triple helical collagens are collagenases from fibroblasts and neutrophils. These enzymes are the products of different genes which share structural motifs but are only 57% identical. In this study, we determined the site of cleavage in the alpha 1(I) chains and showed that the neutrophil collagenase acted at the same site as the fibroblast collagenase. We also used collagens as substrates which were generated by site-directed mutagenesis of the murine Col1a1 gene and found that the pattern of susceptibility to cleavage by purified neutrophil collagenase was indistinguishable from that previously described for the fibroblast collagenase. Collagens containing substitutions of Pro for Ile-776 (P1) were not cleaved; whereas those containing substitutions of Met for Ile-776 were cleaved. Type I collagen which contained alpha 1(I) chains in which there were double substitutions of Pro for Gln-774 (P2) and Ala-777 (P2') were also not cleaved. These type I collagens contained wild type alpha 2(I) chains as well as mutant alpha 1(I) chains in the mixed helical trimers; the alpha 2(I) chain in the trimers containing the resistant alpha 1(I) chains were also not cleaved by the neutrophil collagenase.

Amino Acid Sequence↗
PubMed1993

Cortactin, an 80/85-kilodalton pp60src substrate, is a filamentous actin-binding protein enriched in the cell cortex.

Two related cellular proteins, p80 and p85 (cortactin), become phosphorylated on tyrosine in pp60src-transformed cells and in cells stimulated with certain growth factors. The amino-terminal half of cortactin is comprised of multiple copies of an internal, tandem 37-amino acid repeat. The carboxyl-terminal half contains a distal SH3 domain. We report that cortactin is an F-actin-binding protein. The binding to F-actin is specific and saturable. The amino-terminal repeat region appears to be both necessary and sufficient to mediate actin binding, whereas the SH3 domain had no apparent effect on the actin-binding activity. Cortactin, present in several different cell types, is enriched in cortical structures such as membrane ruffles and lamellipodia. The properties of cortactin indicate that it may be important for microfilament-membrane interactions as well as transducing signals from the cell surface to the cytoskeleton. We suggest the name cortactin, reflecting the cortical subcellular localization and its actin-binding activity.

Actins↗
PubMed1993

Fibronectin binding site in type I collagen regulates fibronectin fibril formation.

Mov13 fibroblasts, which do not express endogenous alpha 1(I) collagen chains due to a retroviral insertion, were used to study the role of type I collagen in the process of fibronectin fibrillogenesis. While Mov13 cells produced a sparse matrix containing short fibronectin fibrils, transfection with a wild type pro alpha 1(I) collagen gene resulted in the production of an extensive matrix containing fibronectin fibrils of normal length. To study the amino acids involved in the fibronectin-collagen interaction, mutations were introduced into the known fibronectin binding region of the pro alpha 1(I) collagen gene. Substitution of Gln and Ala at positions 774 and 777 of the alpha 1(I) chain for Pro resulted in the formation of short fibronectin fibrils similar to what was observed in untransfected Mov13 cells. Type I collagen carrying these substitutions bound weakly to fibronectin-sepharose and could be eluted off with 1 M urea. The effect of this mutation on fibronectin fibrillogenesis could be rescued by adding either type I collagen or a peptide fragment (CB.7) which contained the wild type fibronectin binding region of the alpha 1(I) chain to the cell culture. These results suggest that fibronectin fibrillogenesis in tissue culture is dependent on type I collagen synthesis, and define an important role for the fibronectin binding site in this process.

Amino Acid Sequence↗
PubMed1993

The tumor suppressor p53 regulates its own transcription.

The ability of p53 to suppress transformation correlates with its ability to activate transcription. To identify targets of p53 transactivation, we examined the p53 promoter itself. Northern (RNA) analysis and transient transfection experiments showed that p53 transcriptionally regulated itself. A functionally inactive mutant p53 could not regulate the p53 promoter. Deletion analysis of the p53 promoter delineated sequences between +22 and +67 as being critical for regulation. Electrophoretic mobility shift analysis and methylation interference pinpointed the p53 DNA responsive element. When oligomerized in front of a heterologous minimal promoter, this element was regulated by wild-type p53 and not by mutant p53. Point mutations in the DNA element that eliminated protein-DNA interactions also resulted in a nonresponsive p53 promoter. The DNA element in the p53 promoter responsive to p53 regulation is similar to the p53 consensus sequence. However, we have been unable to detect a direct interaction of p53 with its promoter.

3T3 Cells↗