Biomedical subjects

H Zhou

Publications and source records attributed to H Zhou.

At least 127 records · Page 7Linked to original sources

PubMed2001

Chimeric subgroup A respiratory syncytial virus with the glycoproteins substituted by those of subgroup B and RSV without the M2-2 gene are attenuated in African green monkeys.

Using the existing reverse genetics system developed for the subgroup A respiratory syncytial virus (RSV), a chimeric virus (designated rA-G(B)F(B)) that expresses subgroup B-specific antigens was constructed by replacing the G and F genes of the A2 strain with those of the 9320 strain of subgroup B RSV. rA-G(B)F(B) grew well in tissue culture, but it was attenuated in the respiratory tracts of cotton rats and African green monkeys. To further attenuate this chimeric RSV, the M2-2 open reading frame was removed from rA-G(B)F(B). rA-G(B)F(B)DeltaM2-2 was highly attenuated in replication in the respiratory tracts of the infected monkeys, but it provided complete protection against wild-type subgroup B RSV challenge following two doses of infection. In this study, rA2DeltaM2-2 (a recombinant A2 RSV that lacks the M2-2 gene) was also evaluated in African green monkeys. The replication of rA2DeltaM2-2 was highly restricted in both the upper and lower respiratory tracts of the infected monkeys and it induced titers of serum anti-RSV neutralizing antibody that were slightly lower than those induced by wild-type rA2. When rA2DeltaM2-2-infected monkeys were challenged with wild-type A2 virus, the replication of the challenge virus was reduced by approximately 100-fold in the upper respiratory tract and 45,000-fold in the lower respiratory tracts. rA2DeltaM2-2 and rA-G(B)F(B)DeltaM2-2 could represent a bivalent RSV vaccine composition for protection against multiple strains from the two RSV subgroups.

Animals↗

PubMed2001

Dichelobacter nodosus serotype M fimbrial subunit gene: implications for serological classification.

Dichelobacter nodosus fimbrial subunit gene (fimA) from a serotype M strain (M-SPAHL) was investigated in this study. A primer set targeting the relatively conserved fimA regions and based on the published sequence from Nepalese serogroup M isolates (Nepalese M), failed to amplify the fimA of M-SPAHL. However, when the downstream primer was substituted with a primer that is specific for other serogroups of D. nodosus, the fimA was successfully amplified. Cloning followed by DNA sequencing, revealed that the M-SPAHL fimA was different to the Nepalese M fimA. The predicted amino acid sequence of the M-SPAHL fimA did not show homology to any known serogroups or serotypes. The most similar sequence was from serotype F1, and not Nepalese M. The consequences of serological relatedness and sequence dissimilarity are discussed.

Amino Acid Sequence↗

PubMed2001

Effect of the interaction of parathyroid hormone and cyclosporine a on bone mineral metabolism in the rat.

Cyclosporine A (CsA) induces high turnover osteopenia in the rat and there is evidence for this in humans. Recent studies suggest that increases in parathyroid hormone (PTH) may be involved in posttransplantation bone loss. However, human studies are difficult to interpret since transplant patients usually receive a cocktail of immunosuppressants and have underlying disease. Our aim was to try to resolve the influence of the absence or presence of PTH on CsA-induced bone disease. Male Sprague Dawley rats aged 7-9 months, either sham operated or parathyroidectomized (PTX), were randomly divided into vehicle and CsA groups. All PTX rats were given oral calcium supplementation ad libitum. The rats were divided into groups: basal, sham/vehicle, sham/CsA, PTX/vehicle, and PTX/CsA. Serial biochemistry was performed 0, 14, and 28 days after the start of the experimental period; bone histomorphometry was performed 28 days after the start of the experimental period. Statistical analysis consisted of group comparisons and factorial analyses. The results showed that CsA alone produced a high turnover osteopenia consistent with previous studies. In the PTX animals there was an increase in bone mass. PTX also decreased osteoblast activity and recruitment, and serum 1,25OH2D levels. Serum levels of osteocalcin (BGP) were unaffected by PTX. The combination group (PTX/CsA) did not differ statistically from the controls in most of the histomorphometric parameters measured, with the exception of reduced mineral apposition and bone formation rates, reflecting the effects of PTX. Serum BGP and 1,25OH2D levels did not differ, but PTH was reduced from the control. Explanations for these results are (1) CsA and PTX exert their effects via separate mechanisms, negating each other; (2) in the absence of PTH, CsA managed to cause bone loss, and thus PTH may not be essential for CsA-induced bone loss; or (3) the profound accelerated bone loss produced by CsA in normal rats requires PTH. These findings may help explain the discrepancies found in clinical studies where bone loss occurs with either elevated or normal PTH levels.

Animals↗

PubMed2001

Bisphosphonates regulate cell growth and gene expression in the UMR 106-01 clonal rat osteosarcoma cell line.

Local growth of osteosarcoma involves destruction of host bone by proteolytic mechanisms and/or host osteoclast activation. Osteoclast formation and activity are regulated by osteoblast-derived factors such as the osteoclast differentiating factor, receptor activator of NF-kappaB ligand (RANKL) and the inhibitor osteoprotegerin (OPG). We have investigated the in vitro effects of bisphosphonates on a clonal rat osteosarcoma cell line. The aminobisphosphonate pamidronate was added to UMR 106-01 cell cultures (10(-8)M to 10(-4)M up to 5 days). The non-aminobisphosphonate clodronate was administered for the same time periods (10(-6)M to 10(-2)M). Cell proliferation, apoptosis and mRNA expression was assessed. Both agents inhibited cell proliferation in a time- and dose-dependent manner. ELISA analysis demonstrated an increase in DNA fragmentation although there was no significant dose-related difference between the doses studied. Bisphosphonate-treated cultures had a greater subpopulation of cells exhibiting morphological changes of apoptosis. Expression of mRNA for osteopontin and RANKL was down-regulated by both agents, while the expression of mRNA for alkaline phosphatase, pro-alpha1(I) collagen and OPG was not altered. Out in vitro work suggests the bisphosphonates not only have direct effects on osteosarcoma cell growth and apoptosis, but also, by altering the relative expression of osteoclast-regulating factors, they may inhibit the activity of osteoclasts and their recruitment.

Animals↗

PubMed2001

Identification of 10 novel snoRNA gene clusters from Arabidopsis thaliana.

Ten novel small nucleolar RNA (snoRNA) gene clusters, consisting of two or three snoRNA genes, respectively, were identified from Arabidopsis thaliana. Twelve of the 25 snoRNA genes in these clusters are homologous to those of yeast and mammals according to the conserved antisense sequences that guide 2'-O-ribose methylation of rRNA. The remaining 13 snoRNA genes, including two 5.8S rRNA methylation guides, are new genes identified from A.thaliana. Interestingly, seven methylated nucleotides, predicted by novel snoRNAs Z41a-Z46, are methylated neither in yeast nor in vertebrates. Using primer extension at low dNTP concentration the six methylation sites were determined as expected. These snoRNAs were recognized as specific guides for 2'-O:-ribose methylation of plant rRNAs. Z42, however, did not guide the expected methylation of 25S rRNA in our assay. Thus, its function remains to be elucidated. The intergenic spacers of the gene clusters are rich in uridine (up to 40%) and most of them range in size from 35 to 100 nt. Lack of a conserved promoter element in each spacer and the determination of polycistronic transcription from a cluster by RT-PCR assay suggest that the snoRNAs encoded in the clusters are transcribed as a polycistron under an upstream promoter, and individual snoRNAs are released after processing of the precursor. Numerous snoRNA gene clusters identified from A.thaliana and other organisms suggest that the snoRNA gene cluster is an ancient gene organization existing abundantly in plants.

Arabidopsis↗

PubMed2001

Identification of a novel high affinity copper transport complex in the fission yeast Schizosaccharomyces pombe.

Copper is an essential nutrient that serves as a co-factor for enzymes involved in critical cellular processes including energy generation, peptide hormone maturation, oxidative stress protection, and iron homeostasis. Although genes have been identified from yeast and mammals encoding a homologous subunit of a plasma membrane high affinity copper transporter, the presence of additional subunits that function as part of a copper transport complex has not been reported. We observed that ctr4(+), a previously identified copper transport protein from the fission yeast Schizosaccharomyces pombe, fails to complement bakers' yeast cells defective in high affinity copper transport and fails to be targeted to the plasma membrane. However, selection for S. pombe genes, which, when co-expressed with Ctr4, confer high affinity copper transport to S. cerevisiae cells resulted in the identification of ctr5(+). Both Ctr4 and Ctr5 are integral membrane proteins, are co-regulated by copper levels and the copper-sensing transcription factor Cuf1, physically associate in vivo, are interdependent for secretion to the plasma membrane, and are each essential for high affinity copper transport. These studies in S. pombe identify Ctr4 and Ctr5 as components of a novel eukaryotic heteromeric plasma membrane complex that is essential for high affinity copper transport.

Amino Acid Sequence↗

PubMed2001

An hsRPB4/7-dependent yeast assay for trans-activation by the EWS oncogene.

Chromosomal fusions of the N-terminal region of the Ewings Sarcoma Oncogene (EWS-Activation-Domain, EAD) to the DNA-binding domains of a variety of cellular transcription factors, produce oncogenic proteins (EWS-fusion proteins (EFPs)) that cause a variety of malignancies. The EAD can act as a potent transcriptional activation domain and is required for the oncogenic activity of EFPs. Previous studies demonstrating a physical interaction between the EAD and the human RNA Polymerase II subunit hsRPB7 suggest a crucial role for RPB7 and its partner, RPB4, in EAD function. Homologues of hsRPB4/7 exist in S. cerevisiae, and here we describe an RPB4/7-dependent yeast assay for EAD-mediated trans-activation. Conditional yeast strains lacking RPB4 are defective for trans-activation by a Gal4/EAD fusion protein at the permissive temperature. Introduction of hsRPB4 alone is unable to rescue trans-activation, while a combination of hsRPB4 and hsRPB7 significantly rescues activity. These findings provide the first functional evidence for a direct role of the RPB4/7 complex in EAD-mediated trans-activation. In addition, the yeast assay provides a tractable system for further molecular analysis of EAD and RPB4/7 action.

Genetic Techniques↗

PubMed2001

NRG1 is required for glucose repression of the SUC2 and GAL genes of Saccharomyces cerevisiae.

BACKGROUND: Glucose repression of transcription in the yeast, Saccharomyces cerevisiae, has been shown to be controlled by several factors, including two repressors called Mig1 and Mig2. Past results suggest that other repressors may be involved in glucose repression. RESULTS: By a screen for factors that control transcription of the glucose-repressible SUC2 gene of S. cerevisiae, the NRG1 gene was identified. Analysis of an nrg1Delta mutant has demonstrated that mRNA levels are elevated at both the SUC2 and of the GAL genes of S. cerevisiae when cells are grown under normally glucose-repressing conditions. In addition, genetic interactions have been detected between nrg1Delta and other factors that control SUC2 transcription. CONCLUSIONS: The analysis of nrg1Delta demonstrates that Nrg1 plays a role in glucose repression of the SUC2 and GAL genes of S. cerevisiae. Thus, three repressors, Nrg1, Mig1, and Mig2, are involved as the downstream targets of the glucose signaling in S. cerevisiae.

Adenosine Triphosphatases↗

PubMed2001

Imaging localized horseradish peroxidase on a glass surface with scanning electrochemical/ chemiluminescence microscopy.

Scanning electrochemical/chemiluminescence microscopy (SECM/SCLM) was developed for simultaneous imaging of chemiluminescence and topography of immobilized horseradish peroxidase (HRP) on a glass substrate. When the SECM tip for electrochemical generation of H2O2 scanned over the immobilized spot in an aqueous luminol solution, the immobilized enzymes catalyzed the oxidation of luminol to emit chemiluminescence, which was detected by a photon counter. The photon-counting intensity was plotted against the position of the tip to give a two-dimensional image, indicating the activity of immobilized enzymes. Since the current was sensitive to the topography of substrate, the topography image was also obtained by mapping the oxygen reduction current.

Electrochemistry↗

PubMed2001

Synthesis of 2-amino-3-fluoroacrylic acid containing peptides.

[reaction: see text] Peptides containing (E)- and (Z)-3-fluorodehydroalanine have been prepared from serine via a fluoro-Pummerer rearrangement. The resulting electrophilic moieties may be useful affinity labels for the identification of the targets of dehydroamino acid containing natural products that act by covalent mechanisms.

Acrylates↗

PubMed2001

Conformation and rigidity of DNA microcircles containing waf1 response element for p53 regulatory protein.

The tumor-suppressor activity of p53 is closely related to its DNA-binding properties. It binds a number of DNA response-elements and it is likely that these share a common structural feature. Here, we present a new, general method to determine the absolute twist of flexible DNA promoter sequences based on direct imaging of the topology of microcircles containing the sequences. We have used magnetically driven dynamic force microscopy ("MacMode" AFM) to observe, in solution, the conformation of 168 base-pair DNA microcircles, each containing four equally spaced copies of the waf1/cip1/p21 p53 response-element. Analysis of the images showed that the microcircles are markedly puckered with a small excess of negatively writhed molecules. The average measured values of writhe are 0.109+/-0.013 (for 60 positively writhed molecules) and -0.098+/-0.011 (for 65 negatively writhed molecules). These values lead directly to a difference in linking number for the positively and negatively writhed molecules prior to ligation, from which we derive a twist mismatch of 178 degrees (overtwist). This is 44.5 degrees for each 42-mer precursor containing a single waf1/cip1/p21 p53 response-element, in good agreement with the range of values deduced by indirect biochemical techniques. The two values of writhe may also be used to determine the ratio of the bending (B) to twisting (C) rigidity, yielding B/C=0.23. This is about one-third of the value for long, random-sequence DNA, suggesting that the waf1/cip1/p21 p53 response-element is extremely flexible, a result that is also consistent with indirect biochemical experiments. These results support the idea, proposed by us earlier, that torsional stress may play a role in the regulation of p53 binding through modulation of twist at the binding site.

Aluminum Silicates↗

PubMed2001

A novel osteoblast-derived C-type lectin that inhibits osteoclast formation.

We have cloned and expressed murine osteoclast inhibitory lectin (mOCIL), a 207-amino acid type II transmembrane C-type lectin. In osteoclast formation assays of primary murine calvarial osteoblasts with bone marrow cells, antisense oligonucleotides for mOCIL increased tartrate-resistant acid phosphatase-positive mononucleate cell formation by 3-5-fold, whereas control oligonucleotides had no effect. The extracellular domain of mOCIL, expressed as a recombinant protein in Escherichia coli, dose-dependently inhibited multinucleate osteoclast formation in murine osteoblast and spleen cell co-cultures as well as in spleen cell cultures treated with RANKL and macrophage colony-stimulating factor. Furthermore, mOCIL acted directly on macrophage/monocyte cells as evidenced by its inhibitory action on adherent spleen cell cultures, which were depleted of stromal and lymphocytic cells. mOCIL completely inhibited osteoclast formation during the proliferative phase of osteoclast formation and resulted in 70% inhibition during the differentiation phase. Osteoblast OCIL mRNA expression was enhanced by parathyroid hormone, calcitriol, interleukin-1alpha and -11, and retinoic acid. In rodent tissues, Northern blotting, in situ hybridization, and immunohistochemistry demonstrated OCIL expression in osteoblasts and chondrocytes as well as in a variety of extraskeletal tissues. The overlapping tissue distribution of OCIL mRNA and protein with that of RANKL strongly suggests an interaction between these molecules in the skeleton and in extraskeletal tissues.

Amino Acid Sequence↗

PubMed2001

Tyrosine kinase inhibitors. 18. 6-Substituted 4-anilinoquinazolines and 4-anilinopyrido[3,4-d]pyrimidines as soluble, irreversible inhibitors of the epidermal growth factor receptor.

4-Anilinoquinazoline- and 4-anilinopyrido[3,4-d]pyrimidine-6-acrylamides are potent pan-erbB tyrosine kinase inactivators, and one example (CI-1033) is in clinical trial. A series of analogues with a variety of Michael acceptor units at the 6-position were prepared to define the structural requirements for irreversible inhibition. A particular goal was to determine whether additional functions to increase solubility could be appended to the Michael acceptor. Substituted acrylamides were prepared by direct acylation of the corresponding 6-amines with the requisite acid or acid chloride. Vinylsulfonamide derivatives were obtained by acylation of the amines with chloroethylsulfonyl chloride followed by base-promoted elimination. Vinylsulfone and vinylsulfine derivatives were prepared by oxidation and base elimination of a hydroxyethylthio intermediate. The compounds were evaluated for their inhibition of phosphorylation of the isolated EGFR enzyme and for inhibition of EGF-stimulated autophosphorylation of EGFR in A431 cells and of heregulin-stimulated autophosphorylation of erbB2 in MDA-MB 453 cells. Substitution at the nitrogen of the acrylamide was tolerated only with a methyl group; larger substituents were dystherapeutic, and no substitution at all was tolerated at the acrylamide alpha-carbon. In contrast, while electron-donating groups at the acrylamide beta-carbon were not useful, even quite large electron-withdrawing groups (which increase its electrophilicity) were tolerated. A series of derivatives with solubility-enhancing substituents linked to the acrylamide beta-carbon via amides were potent irreversible inhibitors of isolated EGFR (IC50s = 0.4-1.1 nM), with weakly basic morpholine and imidazole derivatives being the best. Vinylsulfonamides were also potent and irreversible inhibitors, but vinylsulfones and vinylsulfines were reversible and only poorly active. Two compounds were evaluated against A431, H125, and MCF-7 xenografts in nude mice but were inferior in these assays to the clinical trial compound CI-1033.

Animals↗

PubMed2001

Helper-dependent adenoviral vector-mediated gene transfer in aged rat brain.

Transfer of the neurotrophin gene into brain can attenuate age-related deficits such as neuronal atrophy and memory loss, but a suitable vector for this procedure has been lacking. The toxicity and immunogenicity of first-generation adenoviral vectors with E1 deletion (fgAdv) prohibit the application of gene transfer in the majority of central nervous system disorders. Here, we report less toxic and persistent gene expression mediated by helper-dependent adenovirus (hdAdv) in aged rat brain. After intrahippocampal or intraventricular inoculation of the vector, transgene expression was monitored by X-Gal staining and compared with fgAdv-mediated expression. Host inflammatory and immune responses against these vectors were evaluated by immunohistochemical detection of microglia, astrocytes, and infiltrating macrophages, as well as by enzyme-linked immunosorbent assay of cytokines TNF-alpha and IL-1beta. Transgene expression mediated by hdAdv persisted for more than 183 days regardless of inoculation site, as compared with 33 and 66 days for fgAdv-mediated expression after intraventricular and intrahippocampal inoculation, respectively. Inoculation with hdAdv was also associated with reduced numbers of activated microglial cells, astrocytes, and infiltrating macrophages in brain tissue. Secretion of the proinflammatory cytokines TNF-alpha and IL-1beta was minimal after hdAdv but not after fgAdv inoculation. These findings indicate that hdAdv would provide a safe and effective means to transfer therapeutic genes into aged brain.

Adenoviridae↗

PubMed2001

Stretch-induced hairpin-coil transitions in designed polynucleotide chains.

The structural property of a poly( dG-dC) or poly( dA-dT) nucleotide is investigated. At low force and room temperatures, the polymer takes on compact hairpin structures. An abrupt transition from hairpin to random coil occurs at certain critical forces, its high cooperativity is related to the unfavorable formation of hairpin and other kinds of looped structures. It is hence necessary to consider the enthalpic effects of single-stranded loops in realistic models of RNA folding. A possible new way to obtain the statistical weights of elementary nucleotide arrangements is by single-macromolecular mechanical measurements on specifically designed polynucleotides.

Base Pairing↗

PubMed2001

Effects of leaf litter addition on meiofaunal colonization of azoic sediments in a subtropical mangrove in Hong Kong.

The responses of major meiofaunal taxa and nematode species assemblage to the decaying leaf litter of the mangrove Kandelia candel were investigated through a field colonization experiment in subtropical Hong Kong. Sixty-four replicate azoic and organic-free sediment cores were treated with leaf litter additions of 0x, 0.5x, 1x and 2x natural sediment organic concentration, respectively, and retrieved 1, 10, 30 and 60 days post-placement. Replicate cores of ambient sediment were also taken at each sampling date to provide baseline information. Results of ANOVAs suggested that either different meiofaunal taxa responded to the leaf litter in different ways or the response of the same taxon changed over decomposition time. Multivariate ordination performed on nematodes revealed an alteration in community structure after 10, 30 and 60 days between controls and treatments. This alteration was attributed to some deposit feeding nematodes, particularly a bacterivorous species, Diplolaimella sp., which bloomed in all the cores treated with leaf litter, testifying to the important role such meiofauna plays in the process of detritus decomposition.

Journal Article↗

PubMed2001

Analysis of genetic alterations in primary nasopharyngeal carcinoma by comparative genomic hybridization.

To identify genetic alterations associated with the development and progression of human nasopharyngeal carcinoma (NPC), 57 tumors were analyzed by comparative genomic hybridization (CGH). In 47 cases, chromosomal imbalances were found. Several recurrent chromosomal abnormalities were identified in the present study. The most frequently detected chromosomal gains involved chromosome arms 12q (24 cases, 51%), 4q (17 cases, 36%), 3q (16 cases, 34%), 1q (15 cases, 32%), and 18q (15 cases, 32%). Common regions of gain involved 12q13--q15, 4q12--q21, and 3q21--q26. High-copy-number increases of chromosomal materials were detected in four chromosomal regions, 3q21--q26.2, 4p12--q21, 8p, and 12q14--q15. The most frequently detected loss of chromosomal materials involved chromosome arms 16q (26 cases, 55%), 14q (21 cases, 45%), 1p (20 cases, 43%), 3p (20 cases, 43%), 16p (19 cases, 40%), 11q (17 cases, 36%), and 19p (16 cases, 34%). The most common regions of loss involved 14q24--qter, 1pter--p36.1, 3p22--p21.3, 11q21--qter, and the distal region of 19p. Genomic alterations detected by CGH were compared and found to be largely consistent with those identified in banding analysis and loss of heterozygosity studies. However, several previously unrecognized recurrent alterations were also identified in the present study, including gain of 4q and 18q, and loss of 16q, 14q, and 19p. In addition, gain of 1q, 8q, 18q, and loss of 9q showed a statistically significant association with advanced clinical stages (P < 0.05). Identification of recurrent sites of chromosomal gain and loss identify regions of the genome that may contain oncogenes or tumor suppressor genes, respectively, which may be involved in the tumorigenesis of NPC. Published 2000 Wiley-Liss, Inc.

Adult↗

PubMed2001

Type I interferons and IL-12: convergence and cross-regulation among mediators of cellular immunity.

Therapeutic use of type I IFN (IFN-alpha/beta) has become common. Many of the diverse diseases targeted are marked by pathogenetic abnormalities in cell-mediated immunity (CMI), these cellular immune responses either causing injury to the host, lacking sufficient vigor for virus or tumor clearance, or both. In general, therapeutic efficacy is limited. It is thus notable that the pleiotropic effects of type I IFN on CMI remain poorly understood. We characterized the effects of type I IFN on the production of IL-12, the central immunoregulatory cytokine of the CD4(+) T cell arm of CMI. We show that type I IFN are potent inhibitors of IL-12 production by human monocytes/macrophages. The underlying mechanism involves transcriptional inhibition of the IL-12p40 gene, marked by down-regulation of PU.1 binding activity at the upstream Ets site of the IL-12p40 promoter. Type I IFN have previously been shown to be able to substitute for IL-12 in driving IFN-gamma production from T and NK cells. The ability of IFN-alpha/beta to suppress IL-12 production while up-regulating IFN-gamma production suggests a possible mechanistic basis for the difficulties of employing these cytokines in diseases involving abnormalities of CMI.

Cells, Cultured↗