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Biomedical subjects

W Dai

Publications and source records attributed to W Dai.

At least 73 records · Page 4Linked to original sources
PubMed1998

Nuclease overexpression mutants of Serratia marcescens.

A family of mutants overexpressing the Serratia marcescens extracellular nuclease has been known for decades. A number of these alleles are characterized here at the molecular level, and the mutant genes are identified, yielding a likely model for their phenotype. The known mutations exert their effect indirectly on nucA expression by elevating the basal SOS response of the cell. Mutations have been found in xerC and uvrD, both of which result in partial SOS induction. A classic nucsu allele, that of strain W1050, is also likely to be in xerC.

Adenosine Triphosphatases↗
PubMed1998

[Retrospective analysis of 18 cases with agranulocytosis induced by antithyroid drugs].

OBJECTIVE: To analyse the routine WBC count's effect on predicting antithyroid drugs-induced agranulocytosis developing and risk factors of antithyroid drugs-induced agranulocytosis. METHODS: Retrospective analysis of 18 Graves' cases with agranulocytosis induced by antithyroid drugs during 1984-1995. RESULTS AND CONCLUSIONS: Most of antithyroid drugs-induced agranulocytosis happens 2-12 weeks after the administration of antithyroid drug, and are related with the drug's doses. Some agranulocytosis happens abruptly, routine WBC and granulocyte count can not predict some agranulocytosis developing. Fever and throat sore are the intitial symptoms of agranulocytosis, if it happens, the WBC and granulocyte count must be checked immediately. The treatment of granulocyte-macrophage colony stimulating factor is effective, the corticosteroid therapy seems not to be useful for the recovery of granulocyte count.

Adult↗
PubMed1998

[Human trabecular cell culture in vitro].

OBJECTIVE: To search the method of human trabecular cell (HTC) cultured in vitro, which could provide the necessary condition of experimental study on primary open angle glaucoma. METHOD: Organ and tissue culture were taken to get the different passages of human trabecular cells. In the meantime, human scleral fibrous cells were also cultured to contrast with HTC in morphology. RESULTS: (1) It took rather shorter time to get HTC by using organ culture method than simple tissue culture. (2) The 3rd to 5th passage of HTC was the most stable growth period, at that time they could be used in experiment. CONCLUSION: Stable growth shape and characteristic HTC could be obtained by HTC culture in vitro.

Cells, Cultured↗
PubMed1998

[An experimental study of human trabecular cell growth on a filter and hydraulic conductivity].

OBJECTIVE: To search a method of culturing human trabecular meshwork cells (HTC) on a filter support and provide a model to study the hydraulic conductivity of HTC in vitro. METHODS: The 3rd passage of HTC was cultured on a nylon filter, after that we measured the rate of different irrigation through the filter with HTC [Lp, microl/(min x mmHg x cm(2))]. RESULTS: HTC could continuously grow on the filter. The normal Lp was 10.45 microl/(min x mmHg x cm(2)). When the model was irrigated respectively by the solution containing epinephrine (EPI) and dexamethasone (DEX), the Lp value of HTC cultured in the same period was significantly higher than that of the normal group. However, after HTC exposed to DEX for a few days, Lp was significantly decreased. CONCLUSIONS: (1) Better information of hydraulic conductivity and the effects of medicine on HTC can be obtained from the dynamic filter model; (2) EPI can improve the conductivity of HTC, and DEX can do the same in early period.

Animals↗
PubMed1998

Human Bub1: a putative spindle checkpoint kinase closely linked to cell proliferation.

Eukaryotic cells have evolved a mechanism that delays the onset of anaphase until chromosomes are properly positioned on the spindle. To understand the molecular basis of such surveillance mechanism in human cells, we have cloned a full-length cDNA encoding a putative mitotic checkpoint kinase termed hBub1. Sequence comparison reveals that hBub1 is a structurally conserved protein, sharing 23% amino acid residue identity with BUB1 of budding yeast. In addition, the NH2-terminal portion (161 amino acids) of hBub1 shows a significant homology to yeast MAD3, a protein also known to be involved in the mitotic checkpoint response pathway. Northern blot analyses show that the hBub1 mRNA level is abundantly expressed in tissues or cells with a high mitotic index. When Dami cells undergo terminal differentiation after treatment with phorbol ester, hBub1 expression in this cell line is down-regulated rapidly. The hBub1 protein level is low in G1 and remains relatively constant in S, G2, and M phases. Immunofluorescence analysis shows that hBub1 protein colocalizes with a centromere-kinetochore antigen CREST in interphase, mitotic prophase, and nocodazole-treated cells. Antibody electroporation experiments show that hBub1 is an important component of the spindle checkpoint pathway. Furthermore, fluorescence in situ hybridization analysis maps the hBub1 gene to chromosome 2q12-13. Our studies suggest that hBub1 expression is restricted to proliferating cells and appears to be involved in regulating cell cycle progression. The molecular cloning of hBub1 cDNA will facilitate the study of its role in spindle checkpoint control as well as its potential role in certain genetic disorders.

Amino Acid Sequence↗
PubMed1997

Human Prk is a conserved protein serine/threonine kinase involved in regulating M phase functions.

Human prk encodes a novel protein serine/threonine kinase capable of strongly phosphorylating casein but not histone H1 in vitro. prk expression is tightly regulated at various levels during different stages of the cell cycle in lung fibroblasts. The Prk kinase activity is relatively low during mitosis, G1, and G1/S, and peaks during late S and G2 stages of the cell cycle. Recombinant human Prk expressed through the baculoviral vector system is capable of phosphorylating Cdc25C, a positive regulator for the G2/M transition. Human prk shares significant sequence homology with Saccharomyces cerevisiae CDC5 and Drosophila melanogaster polo, both of which are essential for mitosis and meiosis. Full-length prk transcripts greatly potentiate progesterone-induced meiotic maturation of Xenopus laevis oocytes. On the other hand, antisense prk transcripts significantly delay and reduce the rate of oocyte maturation. When expressed in a CDC5 mutant strain of S. cerevisiae, human Prk, but not a deletional mutant protein, fully rescues the temperature-sensitive phenotype of the budding yeast. Taken together, prk may represent a new protein kinase, playing an important role in regulating the onset and/or progression of mitosis in mammalian cells.

Amino Acid Sequence↗
PubMed1997

Dexamethasone potently enhances phorbol ester-induced IL-1beta gene expression and nuclear factor NF-kappaB activation.

The synthetic glucocorticoid dexamethasone, an immunosuppressive and anti-inflammatory agent, was investigated for its effect on PMA-mediated expression of the inflammatory cytokine IL-1beta in the human monocytic leukemic cell line THP-1. PMA alone induced the production of low levels of IL-1beta in THP-1 cells, whereas dexamethasone alone had no effect. However, dexamethasone potently enhanced PMA-mediated IL-1beta production. Using a selective and potent inhibitor of protein kinase C, we found that synergistic interaction between PMA and dexamethasone requires protein kinase C activation. PMA has been known to activate nuclear factor NF-kappaB in THP-1 cells. Using an oligonucleotide probe corresponding to an NF-kappaB DNA-binding motif of the IL-1beta gene promoter in gel electrophoresis mobility shift assays, we demonstrated that PMA-induced NF-kappaB activation was greatly potentiated by dexamethasone. Our results indicate that glucocorticoids can be positive regulators of inflammatory cytokine gene expression during monocytic cell differentiation.

Anti-Inflammatory Agents↗
PubMed1997

[Further clinical analysis on the prognosis of chronic lymphocytic thyroiditis].

OBJECTIVE AND METHODS: There have been many reports on the incidence of hypothyroidism and thyroid carcinoma in chronic lymphocytic thyroiditis patients, however, the incidence of thyroid carcinoma had been a widely debated issue. Therefore 300 cases of chronic lymphocytic thyroiditis from 1964 to 1995 were reviewed. There were 37 males and 263 females, and 52 had a pathological diagnosis of chronic lymphocytic thyroiditis. RESULTS: Among 300 patients, 2 had coexistent thyroid papillary carcinoma. The original symptom in 64.3% patients was hypothyroidism, and the total incidence of hypothyroidism was 76%. It was also indicated in this study that the occurrence of hypothyroidism in chronic lymphocytic thyroiditis patient was associated with the elevated level of antithyroglobulin antibody, enlargement and tenderness of thyroid gland. CONCLUSION: In our study, as the low incidence of coexisted thyroid carcinoma, with the high incidence of hypothyroidism it seemed to be that the elevated antithyroglobulin antibody could be a more effective factor in the development of hypothyroidism in chronic lymphocytic thyroiditis.

Adolescent↗
PubMed1997

[Application of proliferating cell nuclear antigen in the study of human trabecular cell proliferation].

OBJECTIVE: To evaluate the application of proliferating cell nuclear antigen (PCNA) in the study of human trabecular cell proliferation. METHODS: Immunohistochemical technique was used to observe the PCNA expressive level in the fourth passage of human trabecular meshwork, the effects of different concentrations of epinephrine, dexamethasone and epidermal growth factor on the level were also investigated, the results were compared with that of the normal cells cultured at the same time, and analyzed by a graphic device operation system in a computer. RESULTS: A stable proliferating curve was obtained according to the normal cell PCNA level, by which we could choose the best opportunity of drug application. Epinephrine and dexamethasone were found to significantly inhibit cell proliferation, while epidermal growth factor (EGF) could promote the proliferation. CONCLUSION: PCNA is considered to be a useful agent to observe the process of cell proliferation. The above mentioned methods are beneficial to the investigations of biochemical characteristics of trabecular meshwork cells and the pathogenic mechanisms of open-angle glaucoma.

Cell Division↗
PubMed1997

Spectrochemical investigations of fluorescence quenching agents. Part 5. Effect of surfactants of the ability of nitromethane to selectively quench fluorescence emission of alternant PAHs.

Applicability of the nitromethane selective quenching rule for discriminating between alternant vs. nonalternant polycyclic aromatic hydrocarbons (PAHs) is examined for 18 representative PAH solutes dissolved in micellar cetyltrimethylammonium chloride (CTACl), micellar dodecyltrimethylammonium bromide (DTAB), micellar Brij-35 and micellar sodium octanoate (SO) solvent media. Experimental results show that nitromethane quenched fluorescence emission of only the 10 alternant PAHs in the two cationic (CTACl and DTAB) and nonionic Brij-35 surfactant solvent media as expected. Emission intensities of nonalternant PAHs, except for the few exceptions noted previously, were unaffected by nitromethane addition. Unexpected quenching behavior was observed, however, in the case of nonalternant PAHs dissolved in micellar sodium octanoate solvent media. Nitromethane quenched fluorescence emission of all nonalternant PAHs studied in the SO solvent media, which is contrary to the selective quenching rule.

Fluorescent Dyes↗
PubMed1997

[A new subtype of potato class I patatin gene].

Potato class I and class II patatin gene belong to a multigene family with different tissuespecific expression patterns. A class I patatin gene was isolated from a genomic library of Chinese potato cultivar "Dongnong 303" (Solanum tuberosum) by using class II patatin promoter as probe. A 1.8kp DNA sequence was determined, including 1407bp of patatin gene 5' flanking sequence and 363bp of patatin structure gene. Its 5' flanking sequence showed that it is a class I patatin gene. Compared with six reported subtypes of class I patatin genes, there are a large fragment of deletion and insertion in its 5' flanking sequence. Therefore, it might be a new subtype of class I patatin gene.

Base Sequence↗
PubMed1996

Production of granulocyte colony-stimulating factor by THP-1 cells in response to retinoic acid and phorbol ester is mediated through the autocrine production of interleukin-1.

The human monocytic leukemic cell line, THP-1, which differentiates toward macrophages in response to phorbol 12-myristate 13-acetate (PMA) was investigated for its ability to produce granulocyte colony-stimulating factor (G-CSF). G-CSF protein was neither produced during PMA-induced differentiation nor in response to retinoic acid (RA) alone. However, when combined, PMA and RA synergistically stimulated G-CSF production with optimal effect observed at 10(-7)M for both PMA and RA. The synergistic interaction between PMA and RA on G-CSF production appeared to be mediated primarily through production of interleukin-1 beta (IL-1 beta) since neutralization of IL-1 beta activity inhibited about 80% of G-CSF production. It has been previously reported that IL-1 potently synergizes with RA to stimulate G-CSF production by THP-1 cells pretreated with PMA Using synthetic ligands to RA receptors (RAR) and retinoid X receptors (RXR) that selectively bind and activate RAR-RXR and RXR-RXR dimers respectively, we showed that the ability of RA to synergize with IL-1 was signaled through RAR-RXR heterodimer pathway. Finally, we demonstrated that RA can also enhance IL-1-induced G-CSF production in primary monocytes of human peripheral blood.

Drug Synergism↗
PubMed1996

Prk, a cytokine-inducible human protein serine/threonine kinase whose expression appears to be down-regulated in lung carcinomas.

We have cloned and characterized a putative protein serine/threonine kinase termed prk through a combination of polymerase chain reaction and conventional cDNA library screening approaches. There are apparently two distinct domains within prk protein deduced from its nucleotide sequences. The amino-terminal portion has the feature of the catalytic domain of a serine/threonine kinase and shows strong homology to mouse fnk and other polo family kinases including mouse snk, human and murine plk, Drosophila polo, and yeast Cdc5. The carboxyl-terminal portion, presumably the regulatory domain, shares extensive homology to mouse fnk. Northern blotting analyses reveal that prk expression is restricted to a very limited number of tissues with placenta, ovaries, and lung containing detectable amounts of prk mRNA. prk mRNA expression is also detected at a low level in the megakaryocytic cell line Dami, MO7e, and three brain glioma cell lines. In addition, refeeding of serum-deprived MO7e, Dami, and K562 cells of hematopoietic origin and GMOO637D of lung fibroblasts rapidly activates prk mRNA expression with its peak induction around 2 h after serum addition. prk gene activation by the serum requires no new protein synthesis. The recombinant cytokines such as interleukin-3 and thrombopoietin also activate prk mRNA expression in MO7e cells. Furthermore, a survey of RNAs isolated from the tumor and the uninvolved tissues from 18 lung cancer patients reveals that prk mRNA expression is significantly down-regulated in tumor tissues. Southern blotting analysis indicates that the prk gene is present in a single copy in the genome of tumors and normal cells. Taken together, these results suggest that prk expression may be restricted to proliferating cells and involved in the regulation of cell cycle progression. The molecular cloning of prk cDNA will facilitate the study of its biological role as well as its potential role in tumorigenesis.

Amino Acid Sequence↗
PubMed1996

Determination of the gene sequence and the three-dimensional structure at 2.4 angstroms resolution of methanol dehydrogenase from Methylophilus W3A1.

The DNA sequences for the genes encoding the heavy and light subunits of methanol dehydrogenase from Methylophilus methylotrophus W3A1 have been determined. The deduced amino acid sequence has enabled the structure of the enzyme to be refined at 2.4 angstrom resolution against X-ray data collected on a Hamlin area detector. The structure was refined using the programs PROFFT and X-PLOR with several model building step interspersed. The final model contains two heavy chains (571 amino acids), two light chains (69 amino acids), two molecules of pyrroloquinoline quinone, two Ca2+ and 521 solvent molecules. Each half molecule contains four disulfide linkages and four cis peptides. One of the disulfides is formed from two adjacent cysteine residues linked by a trans peptide which creates a novel eight-membered ring. The heavy subunit is an 8-fold beta-propeller, each "blade" of which is a four-stranded antiparallel twisted beta-sheet. The light chain is an elongated subunit stretching across the surface of the heavy subunit, with residues 1 to 32 containing four beta-turns and residues 33 to 62 forming a helix; however, it neither interacts with the active site, nor the other HL dimer and its functional role is obscure. Around the 8-fold beta-propeller there is a repeating pattern of tryptophan residues located in the outer strand of seven of the eight beta-leaflets, each packed between adjacent leaflets. Each of these tryptophan residues is centered in the beta-strand and participates in the main chain hydrogen bonding of the sheet. Five of the seven tryptophan residues have closely similar interactions with the adjacent beta-leaflet including stacking of the tryptophan indole rings against a peptide plane and formation of a hydrogen bond from NE1 of the indole ring to a main-chain carbonyl. This repeating pattern is conserved over a number of MEDH sequences. The PQQ is located on the pseudo 8-fold rotation axis of the heavy subunit, in a funnel-shaped internal cavity, sandwiched between the indole ring of Trp237 and the two sulfur atoms of the Cys103-Cys104 vicinal disulfide. A hexacoordinate Ca2+ is bound in the active site by one nitrogen and five oxygen ligands, three from the PQQ and the others from two protein side-chains. In the active site an isolated solvent molecule is bound to the O5 of PQQ and to a nearby aspartate side-chain; its position may be the binding site for methanol. The aspartate might than serve as a general base for proton abstraction from the substrate hydroxyl. The C5 atom of PQQ could be activated by electrophilic catalysis by a nearby argenine side-chain or by the calcium ion bound to PQQ.

Alcohol Oxidoreductases↗
PubMed1996

Haloenol lactones as inactivators and substrates of aldehyde dehydrogenase.

Human aldehyde dehydrogenase (EC 1.2.1.3) isozymes E1 and E2 were irreversibly inactivated by stoichiometric concentrations of the haloenol lactones 3-isopropyl-6(E)-bromomethylene tetrahydro-pyran-2-one and 3-phenyl-6(E)-bromomethylene tetrahydropyran-2-one. No inactivation occurred with the corresponding nonhalogenated enol lactones. Both the dehydrogenase and esterase activities were abolished. Activity was not regained on dialysis or treatment with 2-mercaptoethanol. The inactivation was subject to substrate protection: NAD afforded protection which increased in the presence of the aldehyde-substrate competitive inhibitor chloral. Saturation kinetics gave positive gamma-axis intercepts, allowing the determination of binding constants. Inactivation stiochiometry determined with 14C-labeled 3-(1-naphthyl)-6(E)-iodomethylene tetrahydropyran-2-one was found to correspond to the active-site number. The nonhalogenated lactone, 3-(1-naphthyl)-6(E)-methylene tetrahydropyran-1-one was shown to be a substrate for aldehyde dehydrogenase via its esterase function. Inactivation and enzymatic hydrolysis occurred within a similar time frame. Opening of the lactone ring to form enzyme-acyl intermediate with active site cysteine appears to be a necessary prerequisite to inactivation, since halogen in the lactone ring is nonreactive. Thus, the inactivation of aldehyde dehydrogenase by haloenol lactones is mechanism-based. Inactivation by haloenol lactones occurs in a manner analogous to that of chymotrypsin with which aldehyde dehydrogenase shares esterase activity and binding of haloenol lactones at the active site.

Aldehyde Dehydrogenase↗
PubMed1996

Expression of receptor protein tyrosine kinase tif is regulated during leukemia cell differentiation.

tif is a recently cloned and characterized cDNA predicting a transmembrane protein with a putative tyrosine kinase structure in its cytoplasmic domain. By analysis of the purified tif cytoplasmic domain expressed in Escherichia coli, we have demonstrated that tif is an active protein tyrosine kinase capable of autophosphorylation on tyrosine residues and this phosphorylation is inhibited by a tyrosine-specific inhibitor genistein. Northern blot analyses of various leukemia cell lines have revealed that tif mRNA expression is primarily confined to those bearing erythroid and megakaryocytic phenotypes. Megakaryocytic differentiation of K562 and HEL cells induced by phorbol 12-myristate 13-acetate is accompanied by down-regulation of tif mRNA expression. In addition, treatment of K562 and HEL with hexamethylene bis-acetamide, but not with hemin, decreases the steady-state level of tif mRNA. These combined results suggest that the receptor tyrosine kinase tif is involved in hematopoietic development.

Acetamides↗