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Biomedical subjects

L Wu

Publications and source records attributed to L Wu.

At least 415 records · Page 23Linked to original sources
PubMed1998

[Expression of P27 protein in odontogenic tumors].

The expression of P27 protein was investigated in 40 cases of odontogenic tumors by immunohistochemical S-P assay. The results showed that P27 expression varied in different types of odontogenic tumors. Positive signals were present in 17/20 (85.0%) of the malignant odontogenic tumors, but in 6/20 (30.3%) of the benign ones (P < 0.005). It was suggested that P27 protein had certain practical value in the differentiation diagnosis of odontogenic tumors.

Ameloblastoma↗
PubMed1998

[Electrophoretic analysis of soluble antigens of a pathogenic isolate of Trichomonas vaginalis].

AIM: To analyze the parasite soluble antigens of a pathogenic isolate of Trichomonas vaginalis. METHODS: The soluble antigens of a pathogenic isolate of T. vaginalis isolated from a patient suffered from trichomonad vaginitis was studied by means of SDS-PAGE followed by densitometric analysis and immunoblotting. RESULTS: A total of 14 distinct protein bands was demonstrated using a 10% resolution gel concentration. Densitometrogram indicated that the soluble antigens with MWs of equal to and below 72 kDa accounted for 89.5% of the total volume with the dominant fractions of 48-51 kDa which accounted for 19.2%. Having MWs over 100 kDa accounted only for 7.4%, while the lowest M. W. fraction demonstrated was found to be at the site of 13 kDa. By immunoblotting, the specific anti-T. vaginalis antibodies raised in mice recognized a broad spectrum of molecular size range of these antigenic fraction. However, no immunological reaction was seen at the 86 kDa site. CONCLUSION: The proteins of MWs 48-51 kDa possess a larger protein content and a higher immunological reactivity.

Animals↗
PubMed1998

[Retinal light damage: I. The influences of light intensity and exposure duration at moderate and low intensities of cyclic light].

PURPOSE: To study the influences of moderate- and low intensity of cyclic light exposure on the light damage of rat retina and its relationship with light intensity and exposure duration. METHODS: Twenty five 8-10 weeks old of female Sprague-Dawley rats were divided into 5 groups randomly. One group were as controls reared in dark-room, others were exposured to 12 hour light: 12 hour dark cyclic white xenon light from 3 to 28 days. The light intensities were 90-115 Lux(100 Lux), 400-650 Lux(500 Lux), 800-1,150 Lux(1,000 Lux), 1,400-1,650 Lux(1,500 Lux) separately. After various duration of exposure, the retina were evaluated with light microscopy, electron microscopy and morphometric study. RESULTS: Except for the intensity of 100Lux group, all of the other exposure intensities can induce the light damage of rat retina. The photoreceptor cells were affected most early. The higher of light intensity and the longer of exposure duration, the severer of the photoreceptor cell loss. In the severely damaged eye, RPE were also damaged. CONCLUSIONS: For the light damage of rat retina which is induced by moderate- or low intensity of cyclic light, the damage degree was both affected by light intensity and exposure duration.

Animals↗
PubMed1998

The multi-channel VEP topographies in patients with late-stage glaucoma.

PURPOSE: To study the clinical application of multi-channel VEP topographies in patients with late-stage glaucoma. METHODS: The multi-channel checkerboard reversal VEP waves of 25 normal persons and 15 patients with late-stage glaucoma were recorded and analyzed, All patients were examined using Humphrey Field Analyzer. The VEP topographies of multi-channel VEP waves were shown by computer processing system. RESULTS: In normal subjects, the topographies showed symmetric distribution to full-field pattern stimulation. In all patients with late-stage glaucoma, even whose visual field was severely damaged, multi-channel VEP could be recorded, All channels showed simple 'NPN' wave form, N1, N2 waves were not conspicuous, even both were lost, all channels showed the reduced amplitudes of P1 waves, and longer latency. The multi-channel VEP topographies showed irregular distribution, Some showed amplitude asymmetry, other limited or widespread, lateralized. CONCLUSIONS: Despite the severely damaged visual field, the patients with late-stage glaucoma showed special multi-channel VEPs topographies, Multi-channel VEP topographies should be useful in following up patients suffering from late-stage glaucoma and studying visual processing in human brain.

Adolescent↗
PubMed1998

The study of local electrophysiology in macular diseases.

PURPOSES: To observe the features and clinical utility values of local electroretinogram (LERG) and local visual evoked potentials (LVEP) in macular diseases. METHODS: The spot stimuli were obtained by changing the shutters with different sizes of hole at the posterior of Ganzfeld ball. The recording electrode for LERG was made with the filament of platinum as blepharophthalmostat like. The LERG and LVEP were simultaneously recorded in macular diseases. RESULTS: The exudative AMD, Stargardt's disease, central serous chorioretinopathy and idiopathic macular hole had seriously decreased amplitudes of LERG and higher abnormal rates, comparing with atrophic AMD and idiopathic preretinal membranes in the region of 2.5 degrees and 5 degrees at macula. The abnormal rates in these diseases were higher for LERG than for LVEP. CONCLUSION: The LERG can objectively measure the variation of macular function in maculopathies. The sensitivities of LVEP are lower than those of LERG for macular diseases.

Adult↗
PubMed1998

Imaging of adenoviral-directed herpes simplex virus type 1 thymidine kinase reporter gene expression in mice with radiolabeled ganciclovir.

UNLABELLED: We are developing procedures to repeatedly and noninvasively image the expression of transplanted reporter genes in living animals and in patients, using PET. We have investigated the use of the Herpes Simplex Virus type 1 thymidine kinase gene (HSV1-tk) as a reporter gene and [8-14C]-ganciclovir as a reporter probe. HSV1-tk, when expressed, leads to phosphorylation of [8-14C]-ganciclovir. As a result, specific accumulation of phosphorylated [8-14C]-ganciclovir should occur almost exclusively in tissues expressing the HSV1-tk gene. METHODS: An adenoviral vector was constructed carrying the HSV1-tk gene along with a control vector. C6 rat glioma cells were infected with either viral vector and uptake of [8-3H]-ganciclovir was determined. In addition, 12 mice were injected with varying levels of either viral vector. Adenovirus administration in mice leads primarily to liver infection. Forty-eight hours later the mice were injected with [8-14C]-ganciclovir, and 1 hr later the mice were sacrificed and biodistribution studies performed. Digital whole-body autoradiography also was performed on separate animals. HSV1-tk expression was assayed, using both normalized HSV1-tk mRNA levels and relative HSV1-TK enzyme levels, in both the cell culture and murine studies. RESULTS: Cell culture, murine tissue biodistribution and murine in vivo digital whole-body autoradiography all demonstrate the feasibility of HSV1-tk as a reporter gene and [8-14C]-ganciclovir as an imaging reporter probe. A good correlation (r2 = 0.86) between the [8-14C]-ganciclovir percent injected dose per gram tissue from HSV1-tk positive tissues and HSV1-TK enzyme levels in vivo was found. An initial study in mice with [8-18F]-fluoroganciclovir and microPET imaging supports further investigation of [8-18F]-fluoroganciclovir as a PET reporter probe for imaging HSV1-tk gene expression. CONCLUSION: These results demonstrate the feasibility of using [8-14C]-ganciclovir as a reporter probe for the HSV1-tk reporter gene, using an in vivo adenoviral mediated gene delivery system in a murine model. The results form the foundation for further investigation of [8-18F]-fluoroganciclovir for noninvasive and repeated imaging of gene expression with PET.

Adenoviridae↗
PubMed1997

Detailed deletion mapping at chromosome 9p21 in non-small cell lung cancer by microsatellite analysis and fluorescence in situ hybridization.

We examined 82 cases of primary non-small cell lung cancer (NSCLC) for loss of heterozygosity (LOH) at the chromosome 9p21-24 region using 16 microsatellite markers. A total of 52 tumors (63%) displayed LOH, and 25 of these cases displayed LOH for all markers. Two cases had small hemizygous losses confined to the p16 gene and more distal markers, whereas 3 cases had loss proximal to p16 and extended through marker D9S126. This latter region has recently been described as another minimal region of loss at 9p21 in lung cancer. However, homozygous deletion of the p16 gene was observed in 18 of 85 cases, with only 5 cases having large deletions extended into the D9S126 region. Furthermore, we did not observe homozygous deletion at the 9p21 region that excluded the p16 gene. Fluorescence in situ hybridization (FISH) analysis using genomic probes spanning either the p16 or Hel-N1 (located at D9S126) gene was performed in 14 tumors. The results from FISH correlated with the chromosomal mapping data, suggesting that the p16 region is the major target of deletion at chromosome 9p21 in primary NSCLC.

Carcinoma, Non-Small-Cell Lung↗
PubMed1997

Induction of the cholesterol metabolic pathway regulates the farnesylation of RAS in embryonic chick heart cells: a new role for ras in regulating the expression of muscarinic receptors and G proteins.

We propose a novel mechanism for the regulation of the processing of Ras and demonstrate a new function for Ras in regulating the expression of cardiac autonomic receptors and their associated G proteins. We have demonstrated previously that induction of endogenous cholesterol synthesis in cultured cardiac myocytes resulted in a coordinated increase in expression of muscarinic receptors, the G protein alpha-subunit, G-alphai2, and the inward rectifying K+ channel, GIRK1. These changes in gene expression were associated with a marked increase in the response of heart cells to parasympathetic stimulation. In this study, we demonstrate that the induction of the cholesterol metabolic pathway regulates Ras processing and that Ras regulates expression of G-alphai2. We show that in primary cultured myocytes most of the RAS is localized to the cytoplasm in an unfarnesylated form. Induction of the cholesterol metabolic pathway results in increased farnesylation and membrane association of RAS. Studies of Ras mutants expressed in cultured heart cells demonstrate that activation of Ras by induction of the cholesterol metabolic pathway results in increased expression of G-alphai2 mRNA. Hence farnesylation of Ras is a regulatable process that plays a novel role in the control of second messenger pathways.

Animals↗
PubMed1997

Targeting retroviral vectors to vascular lesions by genetic engineering of the MoMLV gp70 envelope protein.

Targeted gene delivery to vascular lesions is a major challenge in the development of gene therapy protocols for cardiovascular diseases. One approach would be to enable retroviral vectors to accumulate at sites of vascular injury and enhance local vector concentration. An early step in wound repair is the adhesion of platelets to collagen exposed from damaged vasculature. Hence, the Moloney murine leukemia virus (MoMLV) envelope (env) protein was engineered to incorporate a high-affinity collagen-binding domain derived from von Willebrand clotting factor, and expressed in Escherichia coli and in mammalian cells. The chimeric env protein bound tightly to collagen, and virions bearing this collagen-binding env protein exhibited viral titers approaching those of virions expressing wild-type (WT) env protein. The chimeric virions were concentrated on collagen matrices, and they retained their infectivity under conditions in which virions bearing WT env protein were washed away. Targeted delivery of the chimeric env protein to injured mouse aorta and selective binding of the collagen-targeted virions to injured rabbit artery were observed. In comparative studies, vascular smooth muscle cell transduction was demonstrated in catheter-injured carotid arteries following infusion of collagen-targeted virions but not of virions bearing WT env protein. Taken together, these observations demonstrate the ability of collagen-targeted virions to localize gene delivery to sites of vascular injury.

3T3 Cells↗
PubMed1997

Genomic organization and mutation analysis of Hel-N1 in lung cancers with chromosome 9p21 deletions.

Allelic loss of chromosome 9p21 is common in small cell lung cancer (SCLC), but inactivation of the tumor suppressor gene CDKN2a is rare, implying the existence of another target gene at 9p21. A recent deletion mapping study of chromosome 9p has also identified a site of deletion in non-small cell lung cancer (NSCLC) centered around D9S126. The Hel-N1 (human elav-like neuronal protein 1) gene encodes a neural-specific RNA binding protein that is expressed in SCLC. We have mapped this potentially important gene in lung tumorigenesis to within 100 kb of the D9S126 marker at chromosome band 9p21 by using homozygously deleted tumor cell lines and fluorescence in situ hybridization to normal metaphase spreads. Hel-N1 is, therefore, a candidate target suppressor gene in both SCLC and NSCLC. We have determined the genomic organization and intron/exon boundaries of Hel-N1 and have screened the entire coding region for mutations by sequencing 14 primary SCLCs and cell lines and 21 primary NSCLCs preselected for localized 9p21 deletion or monosomy of chromosome 9. A homozygous deletion including Hel-N1 and CDKN2a was found in a SCLC cell line, and a single-base polymorphism in exon 2 of Hel-N1 was observed in eight tumors. No somatic mutations of Hel-N1 were found in this panel of lung tumors. Hel-N1 does not appear to be a primary inactivation target of 9p21 deletion in lung cancer.

Base Sequence↗
PubMed1997

Evidence that Snf-Swi controls chromatin structure over both the TATA and UAS regions of the SUC2 promoter in Saccharomyces cerevisiae.

The Snf-Swi complex of the yeast Saccharomyces cerevisiae has been shown to control gene expression by controlling chromatin structure. We have analyzed the promoter of the SUC2 gene, a gene strongly controlled by Snf-Swi, by a high resolution analysis of micrococcal nuclease digests. This analysis suggests that there are at least four nucleosomes positioned over the SUC2 TATA and UAS regions under conditions repressing SUC2 transcription. Under derepressing conditions this entire promoter region is much more sensitive to MNase digestion. Analysis of an snf2 Delta mutant demonstrates that even under derepressing conditions the SUC2 promoter is resistant to MNase digestion. Thus, the Snf-Swi complex appears to control chromatin structure over both the SUC2 TATA and UAS regions. The presence of nucleosomes over both promoter regions may explain the strong requirement of SUC2 for Snf-Swi function.

Adenosine Triphosphatases↗
PubMed1997

Interaction of chemokine receptor CCR5 with its ligands: multiple domains for HIV-1 gp120 binding and a single domain for chemokine binding.

CCR5 is a chemokine receptor expressed by T cells and macrophages, which also functions as the principal coreceptor for macrophage (M)-tropic strains of HIV-1. To understand the molecular basis of the binding of chemokines and HIV-1 to CCR5, we developed a number of mAbs that inhibit the various interactions of CCR5, and mapped the binding sites of these mAbs using a panel of CCR5/CCR2b chimeras. One mAb termed 2D7 completely blocked the binding and chemotaxis of the three natural chemokine ligands of CCR5, RANTES (regulated on activation normal T cell expressed and secreted), macrophage inflammatory protein (MIP)-1alpha, and MIP-1beta, to CCR5 transfectants. This mAb was a genuine antagonist of CCR5, since it failed to stimulate an increase in intracellular calcium concentration in the CCR5 transfectants, but blocked calcium responses elicited by RANTES, MIP-1alpha, or MIP-1beta. This mAb inhibited most of the RANTES and MIP-1alpha chemotactic responses of activated T cells, but not of monocytes, suggesting differential usage of chemokine receptors by these two cell types. The 2D7 binding site mapped to the second extracellular loop of CCR5, whereas a group of mAbs that failed to block chemokine binding all mapped to the NH2-terminal region of CCR5. Efficient inhibition of an M-tropic HIV-1-derived envelope glycoprotein gp120 binding to CCR5 could be achieved with mAbs recognizing either the second extracellular loop or the NH2-terminal region, although the former showed superior inhibition. Additionally, 2D7 efficiently blocked the infectivity of several M-tropic and dual-tropic HIV-1 strains in vitro. These results suggest a complicated pattern of HIV-1 gp120 binding to different regions of CCR5, but a relatively simple pattern for chemokine binding. We conclude that the second extracellular loop of CCR5 is an ideal target site for the development of inhibitors of either chemokine or HIV-1 binding to CCR5.

Animals↗
PubMed1997

DNA binding specificity of the CCAAT-binding factor CBF/NF-Y.

CBF is a heterotrimeric protein that binds to DNA containing CCAAT motifs. Here we have analyzed interactions of recombinant CBF with DNA using hydroxyl radical footprinting and methylation interference assays. In the CBF-DNA complex, three separate DNA regions are protected from hydroxyl radical cleavage, one located over and immediately adjacent to the CCAAT motif itself and the other two located on both sides of the CCAAT motif. The methylation interference assay showed, however, that only in the CCAAT motif region methylation of bases was able to interfere with the formation of a CBF-DNA complex, suggesting that CBF makes sequence-specific contacts only in the CCAAT motif region. To further determine the specific DNA sequences necessary for CBF binding, we employed a polymerase chain reaction-mediated random binding site selection method. This analysis showed that CBF binding to DNA requires the CCAAT sequence and other specific sequences immediately flanking both ends of the CCAAT motif. We also showed that the nature of the flanking nucleotide sequences affects the affinity of CBF for DNA. Interestingly, most of the CCAAT motifs present in various higher eukaryotic promoters correspond to the CBF binding sites that were selected, consistent with the hypothesis that these motifs are binding sites for CBF and, hence, that CBF could regulate transcription of numerous eukaryotic genes.

Base Sequence↗
PubMed1997

Recognition of nonconserved bases in the P22 operator by P22 repressor requires specific interactions between repressor and conserved bases.

The ability of P22 repressor protein to distinguish between the six naturally occurring operator binding sites is critically important in determining whether the bacteriophage chooses to grow lytically or lysogenically. We have shown that changes in the highly conserved bases at P22 operator positions 3, 5, 6, and 7 prevent specific binding of P22 repressor. Moreover, studies of mutant proteins identified the three repressor amino acids that directly contact these conserved bases. The pattern of operator sequence conservation permits these direct amino acid-base pair interactions to occur in all except one of the 12 operator half-sites in the phage chromosome. Therefore, repressor differential affinity for these sites cannot be due to these highly conserved base pair-amino acid interactions. Our binding studies show that the nonconserved bases at positions 2 and 4 also play an important role in determining the relative affinity of the naturally occurring P22 operators for P22 repressor. Our data indicate that the direct contacts between the three solvent-exposed amino acids and the conserved bases in the binding site lock these amino acids in place, forming a scaffold allowing the rest of the amino acids side chains to form weaker interactions with the nonconserved bases in the binding site.

Amino Acid Sequence↗
PubMed1997

Downregulation of cyclin G1 expression by retrovirus-mediated antisense gene transfer inhibits vascular smooth muscle cell proliferation and neointima formation.

BACKGROUND: The contemporary treatment of coronary athero-occlusive disease by percutaneous transluminal coronary angioplasty is hampered by maladaptive wound healing, resulting in significant failure rates. Morbid sequelae include smooth muscle cell (SMC) hyperplasia and restenosis due to vascular neointima formation. METHODS AND RESULTS: In this study, we examined the inhibitory effects of a concentrated retroviral vector bearing an antisense cyclin G1 gene on aortic SMC proliferation in vitro and on neointima formation in vivo in a rat carotid injury model of restenosis. Retroviral vectors bearing an antisense cyclin G1 construct inhibited the proliferation of transduced aortic SMCs in 2- to 6-day cultures, concomitant with down-regulation of cyclin G1 protein expression and decreased [3H]thymidine incorporation into DNA. Morphological examination showed evidence of cytolysis, giant syncytia formation, and apoptotic changes evidenced by overt cell shrinkage, nuclear fragmentation, and specific immunostaining of nascent 3'-OH DNA ends generated by endonuclease-mediated DNA fragmentation. Pronounced "bystander effects" including neighboring cells were noted in aortic SMCs transduced with the antisense cyclin G1 vector, as determined by quantitative assays and fluorescent labeling of nontransduced cells. In an in vitro tissue injury model, the proliferation and migration of antisense cyclin G1 vector-transduced aortic SMCs were inhibited. Moreover, in vivo delivery of high-titer antisense cyclin G1 vector supernatant to the balloon-injured rat carotid artery in vivo resulted in a significant reduction in neointima formation. CONCLUSIONS: These findings represent the first demonstration of the inhibitory effects of an antisense cyclin G1 retroviral vector on nonneoplastic cell proliferation. Taken together, these data affirm the potential utility of antisense cyclin G1 constructs in the development of novel gene therapy approaches to vascular restenosis.

Animals↗
PubMed1997

Examination of the transition state of the low-molecular mass small tyrosine phosphatase 1. Comparisons with other protein phosphatases.

The reactions of p-nitrophenyl phosphate (pNPP) with the low-molecular mass tyrosine phosphatase Stp1 and with the mutants D128N, D128A, D128E, and S18A have been studied by measurement of heavy-atom isotope effects in the substrate. The isotope effects were measured at the nonbridging oxygen atoms [18(V/K)nonbridge], at the bridging oxygen atom (the site of bond cleavage) [18(V/K)bridge], and at the nitrogen atom in the nitrophenol leaving group [15(V/K)]. The results with native Stp1 were 1.0160 +/- 0.0005 for 18(V/K)bridge, 1.0007 +/- 0.0001 for 15(V/K), and 1.0018 +/- 0.0003 for 18(V/K)nonbridge. The values for 18(V/K)nonbridge and 15(V/K) differ from those previously measured with other protein-tyrosine phosphatases and from those of the aqueous hydrolysis reaction of pNPP. The values indicate that in the transition state of the native Stp1 reaction the leaving group bears a partial negative charge, and there is nucleophilic interaction between the Cys nucleophile, and the phosphoryl group, causing some decrease in the nonbridge P-O bond order. The transition state remains highly dissociative with respect to the degree of bond cleavage to the leaving group. Mutation of the general acid from aspartic acid to glutamic acid slows catalysis but causes no change in the isotope effects and thus does not alter the degree of proton transfer to the leaving group in the transition state. Mutations of this residue to asparagine or alanine give values for 18(V/K)bridge of about 1.029, for 15(V/K) of about 1.003, and for 18(V/K)nonbridge of 1.0010 (D128A) to 1.0024 (D128N). These data indicate a dissociative transition state with the leaving group departing as the nitrophenolate anion and indicate more nucleophilic participation than in the aqueous hydrolysis of the pNPP dianion, just as in the native enzyme. The isotope effects with the S18A mutant, in which a hydrogen bonding stabilization of the anionic Cys nucleophile has been removed, were within experimental error of those with the native enzyme, indicating that this alteration has no effect on the transition state for phosphoryl transfer from pNPP.

Hydrogen-Ion Concentration↗
PubMed1997

Regulation of Schizosaccharomyces pombe Wee1 tyrosine kinase.

Wee1 tyrosine kinase regulates mitosis by carrying out the inhibitory tyrosine 15 phosphorylation of Cdc2 M-phase inducing kinase. Schizosaccharomyces pombe Wee1 is a large protein, consisting of a C-terminal catalytic domain of approximately 350 amino acids preceded by a N-terminal domain of approximately 550 residues. The functional properties of the Wee1 N-terminal domain were investigated by expressing truncated forms of Wee1 in S. pombe. Both positive and negative regulatory domains were identified. Sequences important for Wee1 function were mapped to a central region (residues 363-408). This region is not required for kinase activity or nuclear localization, suggesting it may be involved in substrate recognition. The negative regulatory domain resides in the N-terminal third of Wee1, Wee1 constructs lacking this domain are more effective at delaying mitosis than wild-type Wee1. The negative regulatory domain contains clusters of potential Cdc2 phosphorylation sites. Investigations to monitor the abundance of Wee1 mRNA and protein during the cell cycle were also carried out.

Base Sequence↗