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Biomedical subjects

F Zhang

Publications and source records attributed to F Zhang.

627 records · Page 35Linked to original sources
PubMed1983

The bioenergetics of Golgi apparatus function: evidence for an ATP-dependent proton pump.

The energy requirement for the processing of newly-synthesized proteins by the Golgi was examined. Rat liver Golgi preparations enriched more than 100-fold have high ATPase activity that co-purified with the Golgi marker enzyme galactosyl transferase. The ATPase activity was 80% inhibited by dicyclohexylcarbodiimide and may represent a proton pump. Evidence is presented for a functional role of the ATPase in Golgi. First, measurement of [14C]methylamine uptake demonstrated ATP-dependent acidification. Second, inhibition of the ATPase with dicyclohexylcarbodiimide resulted in a 3-fold accumulation of newly-synthesized protein in the Golgi.

Adenosine Triphosphatases↗
PubMedDate not supplied

Isolation, purification, and characterization of calcitonin gene-related peptide receptor.

Intact calcitonin gene-related peptide (CGRP) receptors were solubilized from porcine neural membranes using sodium cholate: potassium buffer. The solubilized receptors were purified sequentially by hydrophobic interaction and ion-exchange chromatography followed by specific affinity chromatography. Using these procedures, we have isolated 2 nmol of highly purified active CGRP receptor to a homogeneity (5 x 10(8)-fold purification). The isolated receptors retained their specificity and the capacity to bind to 125I-CGRP, and showed no cross-reactivity with a number of other peptides, except with amylin having 46% amino acid sequence homology to h-CGRP. The solubilized receptors were adsorbed by WGA-agarose and concanavalin-A, suggesting a glycoprotein nature. SDS-PAGE, size-exclusion HPLC, and autoradiography confirmed that CGRP receptor is a monomeric membrane protein with M(r) 66 kDa.

Animals↗
PubMedDate not supplied

Protein-protein interaction of the Ro-ribonucleoprotein particle using multiple antigenic peptides.

Protein protein interactions play a significant role in maintaining the structural and functional integrity of the cell. We used multiple antigen peptides (MAPs) to analyze such interactions within the Ro (or SSA) ribonucleoprotein complex. Our data showed that 60 kD Ro and La colocalize in the nucleus of the cell. Previous data have indicated that 60 kD Ro and La co-exist via interactions with the hYRNAs. We were interested to see whether 60 kD Ro and La interact with each other through protein protein interactions. MAPs were produced with sequences derived from the autoepitopes of 60 kD Ro. When used in agarose immunodiffusion certain MAPs formed precipitin lines specifically with Ro and La antigens. Used in affinity chromatography the Ro MAPs purified the Ro ribonucleoprotein particle from lymphocyte extract. Solid phase immunoassay and surface plasmon resonance (SPR) confirmed the observations obtained with agarose diffusion. Using SPR, kinetic analyses gave an apparent affinity constant of about 1 x 10(7) M(-1) for Ro-MAP-60 kD Ro interactions. The autoantigens Ro and La are specific targets in autoimmune diseases, particularly systemic lupus erythematosus (SLE) and Sjögren's syndrome, and are known to exist together as a complex with hYRNAs. The present data indicate that there are protein-protein interactions between Ro and La.

Amino Acid Sequence↗
PubMedDate not supplied

125I labelling of human serum albumin and fibrinogen and a study of protein adsorption properties on the surface of titanium oxide film.

In order to detect the surface concentration of proteins adsorbed on a solid surface for selecting blood compatible materials, a gentle iodination reagent, Iodogen, was used to label human serum albumin and fibrinogen, and has been applied to the study of protein adsorption properties on a plate of titanium oxide film. The yields of the labelled albumin and fibrinogen are 69.7% and 49.6%. The results of adsorption show that [125I]HSA and [125I]HFG are efficacious at the surface concentration detection and can be used to investigate the protein adsorption properties of a solid material.

Adsorption↗
PubMedDate not supplied

k-resonant benzenoid systems and k-cycle resonant graphs.

A benzenoid system (or hexagonal system) H is said to be k-resonant if, for 1 < or = t < or = k, any t disjoint hexagons of H are mutually resonant; that is, there is a Kekule structure (or perfect matching) K of H such that each of the k hexagons is an K-alternating hexagon. A connected graph G is said to be k-cycle resonant if, for 1 < or = t < or = k, any t disjoint cycles in G are mutually resonant. The concept of k-resonant benzenoid systems is closely related to Clar's aromatic sextet theory, and the concept of k-cycle resonant graphs is a natural generalization of k-resonant benzenoid systems. Some necessary and sufficient conditions for a benzenoid system (respectively a graph) to be k-resonant (respectively k-cycle resonant) have been established. In this paper, we will give a survey on investigations of k-resonant benzenoid systems and k-cycle resonant graphs.

Journal Article↗
PubMedDate not supplied

Ultrastructural changes of nucleoli in common wheat induced by actinomycin D.

Common wheat root tip meristematic cells were treated with low concentrations of actinomycin D (ActD), then stained whole by silver nitrate. We showed by transmission electron microscopy that the typical nucleolar structure did not form, but a granular and fibrillar network was exhibited in the nucleolar region. Our results support a correlation between nucleolar organization/assembly and the activation of RNA Polymerase I transcription. Furthermore, we speculate that the fibrillar network present in the nucleolar region of ActD treated cells may represent the basic skeletal structure required to support the nucleolus.

Cell Nucleolus↗
PubMedDate not supplied

Expression of matrix metalloproteinases 2 and 9 and tissue inhibitors of metalloproteinase 1 and 2 in inflammation-induced corneal neovascularization.

PURPOSE: Matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinase (TIMPs) have been linked to the angiogenic process in general. In order to understand the potential roles of MMP-2, MMP-9 and TIMPs in the corneal neovascularization process, we examined the expression and activities of MMP-2, MMP-9 and TIMPs during the course of cauterization-induced corneal neovascularization in a rat model. METHODS: Neovascularization of rat corneas was induced by silver nitrate cauterization. The expression of MMP-2, MMP-9, TIMP-1 and TIMP-2 was examined by immunohistochemistry and RT-PCR. The protein activities of MMPs and TIMPs were compared in pre- and postcauterization corneas by gelatin zymography and reverse zymography, respectively. RESULTS: MMP-2, TIMP-1 and TIMP-2 immunoreactivities were expressed in normal corneas, predominantly in the corneal epithelium. After injury, immunoreactivities of both MMPs and TIMPs were increased, notably in the healing corneal epithelium, infiltrating inflammatory cells, stromal fibroblasts and ingrowing vascular endothelial cells. The increase in gross MMP-2 enzymatic activity paralleled the maximal vascular ingrowth on day 4, while the gross MMP-9 enzymatic activity rose immediately on day 1, then decreased steadily, which paralleled the magnitude of inflammatory cell infiltration. The immunoreactivity of MMPs/TIMPs decreased significantly 2 weeks after cauterization. On day 35, MMP-2, TIMP-1 and TIMP-2 staining was seen only in corneal epithelium and vascular endothelial cells. Both the RT-PCR and reverse zymography results revealed a more constant expression of TIMP-2, while the TIMP-1 expression appeared to be more inducible. CONCLUSION: MMPs as well as TIMPs were upregulated in cauterization-induced corneal neovascularization, suggesting that both may participate in extracellular matrix remodeling in the corneal wound healing, inflammation and neovascularization processes.

Animals↗
PubMedDate not supplied

An embryonal carcinoma multiple phenotype locus maps to the proximal position of the mouse X chromosome.

A mutant embryonal carcinoma cell line, NR1-6, was established subsequent to retroviral insertion. The insertion was shown to be causative for a number of aberrant properties associated with the mutant cells. Analysis of >17 kb of the insertion site flanking region failed to reveal any homology between this locus and any reported sequence with the exception of one EST of unknown function and a few repetitive elements including B1 element and a CA dinucleotide repeat. CA repeats occur commonly in the mouse genome and usually show size variation. In this study, we mapped this multiphenotype locus using CA repeat polymorphism and Jackson Laboratory's interspecific backcross panels. The locus maps to the proximal end of the X chromosome between MGI offsets 1.5 and 4.5 and has been designated DXUalb1. There are several interesting candidate genes within this region. Analyses of their expression pattern may lead us to a better understanding of the molecular regulation of the variant mutant phenotypes.

Animals↗
PubMedDate not supplied

Ectopic expression of truncated Sp1 transcription factor prolongs the S phase and reduces the growth rate.

The role of the transcription factor Sp1 in cell growth and survival was investigated by induced expression of its DNA-binding C-terminal fragment. Transfection of a constitutively expressed Sp1-170C plasmid construct into HeLa cells failed to produce viable clones, suggesting that this peptide interferes with cell growth. However, transfection with the muristerone A-inducible vector system produced four clones with low levels of expression of Sp1-170C. Muristerone A transiently induced higher levels of Sp1-170C, and this was accompanied by a reduced growth rate and prolongation of the S phase of the cell cycle. This is the first report that a dominant negative Sp1 can affect the cell cycle.

Base Sequence↗
PubMedDate not supplied

Platelet-activating factor antagonists suppress the generation of tumor necrosis factor-alpha and superoxide induced by lipopolysaccharide or phorbol ester in rat liver macrophages.

Platelet-activating factor (PAF) has been shown to play an important role in the generation of tumor necrosis factor-alpha (TNF-alpha) and superoxide in guinea pig peritoneal macrophages. In this study, the effects of the PAF receptor antagonists, WEB 2170 and RP 59277, and of a PAF analogue, HAGPT, on TNF-alpha and superoxide production by rat Kupffer cells was investigated. The liver macrophages produced very little TNF-alpha and superoxide when exposed to PAF, but released substantial amounts of superoxide following treatment with zymosan or phorbol 12-myristate 13-acetate (PMA). WEB 2170 not only inhibited the generation of superoxide by PMA but also suppressed the LPS-induced TNF-alpha synthesis by Kupffer cells in a concentration-dependent manner. Northern blot analysis revealed that the expression of TNF-alpha mRNA induced by lipopolysaccharide (LPS) in Kupffer cells was partially abrogated by WEB 2170 or RP 59227. Furthermore, WEB 2170 reduced the PMA-induced leakage of lactate dehydrogenase (LDH) from Kupffer cells in a dose-dependent manner. These data suggest that TNF-alpha and superoxide syntheses in Kupffer cells are rather insensitive to exogenous PAF. On the other hand, the PAF antagonists used in this study interfere with the transduction of the signals induced by LPS, PMA or zymosan. It is questionable whether the PAF receptor of the plasma membrane is involved in the inflammatory response of rat Kupffer cells.

Animals↗
PubMedDate not supplied

IL-2 gene therapy of advanced lung cancer patients.

We report here Phase I clinical-trial studies of retroviral-mediated interleukin-2 (IL-2) gene transfer to tumor-infiltrating lymphocytes that are re-infused to advanced lung cancer patients with pleural effusions. Ten lung cancer patients with malignant pleural effusions for whom all conventional therapy had failed were included in this Phase I protocol. Tumor infiltrating lymphocytes (TIL) from the patients were exposed to the retroviral plasmid pL(IL-2)SN containing the human IL-2 gene. Approximately 1-6 x 10(10) TIL cells transfected with IL-2 were re-infused into the chest cavity of each patient. The toxicity of this treatment with TIL/IL-2 gene therapy in these patients was minimal with transient slight fever of approximately 37.5. Pleural effusions did not re-accumulate for at least 4 weeks in six of ten patients. One patient was observed to have not only the resolution of the pleural effusions, but in addition the size of the original tumor decreased as seen by CT. The clinical results indicate this method of cancer gene therapy is safe and possibly efficacious against pleural effusions due to advanced lung cancer.

Adenocarcinoma↗