Biomedical subjects

Q Li

Publications and source records attributed to Q Li.

At least 469 records · Page 26Linked to original sources

PubMed1999

[A study on the treatment of congenital velopharyngeal insufficiency].

OBJECTIVE: To evaluate the effectiveness of speech therapy after pharyngoplasty in patients with congenital velopharyngeal insufficiency (CVPI). METHODS: Seven patients with CVPI had received pharyngoplasty and speech therapy. The blowing test and the Chinese articulation clear degree test were measured before and after speech therapy. RESULTS: The treatment results of seven patients appeared to be reasonably satisfactory after speech therapy. Both the index of blowing test and the Chinese articulation clear degree test increased significantly after speech therapy. CONCLUSION: Pharyngoplasty combined with speech therapy is effective in the treatment of patients with CVPI.

Child↗

PubMed1999

[Induction of osteointegration of rabbit mandibular central fissure with guided tissue regeneration]

OBJECTIVE:To observe the effect of guided tissue regeneration (GTR) on induction of ostegenesis in developmental bone clefts,and provide a basis for the use of GTR to repair bony clefts in cleft lip and palate patients.METHODS:The e-PTFE membrane was placed on the labial and lingual sides of the rabbit mandibular central fissure.A radiological and pathological study was performed to determine the healing of the fissure integration.RESULTS:The results showed that the bony cleft was completely integrated 4 weeks after placement of the barrier membrane.CONCLUSION:GTR is an effective approach to reconstruct bony cleft,and is likely to be used in repair of alveolar cleft and cleft palate.

Journal Article↗

PubMed1999

[Study on laser flash spectroscopy of processes of photoionization of tyrosine: pH effects].

The processes of photoionization of tyrosine on three different pH value solutions were investigated by 248 nm laser flash photolysis. The results showed that the processes of photoionization of tyrosine were affected by pH value of the solution. With pH value increasing, the molecule number of photoionization increases via a monophotonic process, and decreases via a biphotonic process. Furthermore, the pH effect of photoionization of tyrosine resulting from deprotonation of phenolic hydroxyl group in alkaline solution was demonstrated.

Hydrogen-Ion Concentration↗

PubMed1999

Daily injections of fluoxetine induce dose-dependent desensitization of hypothalamic 5-HT1A receptors: reductions in neuroendocrine responses to 8-OH-DPAT and in levels of Gz and Gi proteins.

The present studies examined the dose-response relationship of fluoxetine-induced desensitization of hypothalamic postsynaptic 5-HT1A receptors, as measured from the reduced neuroendocrine responses to a 5-HT1A agonist. Because hypothalamic Gz proteins mediate the ACTH and oxytocin responses to 5-HT1A receptor activation, we also determined the effect of fluoxetine on the levels of Gz proteins in the hypothalamus. Rats were injected daily for 14 days with saline or with fluoxetine doses of 0.3, 1, 3, 5, 7. 5, or 10 mg/kg/day. Fluoxetine produced a dose-dependent reduction in the oxytocin, ACTH, and corticosterone responses to the 5-HT1A agonist 8-hydroxy-2-(dipropylamino)tetralin (8-OH-DPAT, 50 micrograms/kg, s.c.). The lowest fluoxetine dose that significantly, although incompletely, reduced the neuroendocrine responses to 8-OH-DPAT was 5 mg/kg/day. The 10 mg/kg/day dose of fluoxetine maximally inhibited all neuroendocrine responses to 8-OH-DPAT. Hypothalamic levels of Gz protein were reduced by both the 7.5 and 10 mg/kg/day doses of fluoxetine, whereas Gi1 protein levels were reduced only after the highest dose (10 mg/kg/day) of fluoxetine. Gi2, Gi3, and Go levels were not reduced by any fluoxetine dose. Cytosolic levels of Gi1 and Gz proteins were unaltered, indicating that reductions in Gz and Gi1 proteins are not caused by a redistribution of the proteins from the membrane into the cytosol. The results from the present study indicate that fluoxetine-induced desensitization of hypothalamic postsynaptic 5-HT1A receptor systems is dose-dependent and may be caused in part by reductions in the hypothalamic levels of Gz proteins.

8-Hydroxy-2-(di-n-propylamino)tetralin↗

PubMed1998

Recombinant adenovirus expressing Von Hippel-Lindau-mediated cell cycle arrest is associated with the induction of cyclin-dependent kinase inhibitor p27Kip1.

A recombinant adenovirus containing the Von Hippel-Lindau (VHL) cDNA was constructed (AdVHL) and used to investigate the function of this tumor suppressor gene. Exposure of renal and breast cancer cell lines to AdVHL resulted in high levels of VHL mRNA and protein. AdVHL infection resulted in G1 cell cycle arrest and growth inhibition of renal and breast cancer cell lines. AdVHL-mediated cell cycle arrest was associated with induction of the cyclin-dependent kinase inhibitor (CDKI) p27Kip1 and inhibition of CDK2 and cyclinB1-dependent cdc2 activities. Nuclear run-on analyses and actinomycin D inhibition studies indicate that the induction of p27Kip1 RNA by VHL is mediated at least in part through an increase in p27Kip1 mRNA synthesis. Furthermore, [35S]methionine pulse-chase studies indicate that the increase in p27Kip expression is also regulated through posttranscriptional control mechanisms. These studies support a novel concept that the tumor suppressor gene VHL controls cell cycle progression by regulation of p27Kip1 at both the mRNA and protein levels.

Adenoviridae↗

PubMed1998

Human papillomavirus-induced carcinogenesis with p53 deficiency in mouse: novel lymphomagenesis in HPV16E6E7 transgenic mice mimicking p53 defect.

To investigate the transforming activity of human papillomavirus (HPV) E6 and E7 genes in vivo, we previously established transgenic mouse lines containing HPV16E6E7, in which male mice develop a Leydig cell tumors with a very high incidence. Because HPV-induced carcinogenesis is highly related to p53, we changed the dose of p53 gene in the transgenic lines by the mice crossing with p53-disrupted mice. The transgenic mice with homozygous wild-type p53 alleles developed only the testicular tumor, whereas novel T cell lymphomagenesis occurred in the heterozygous p53-disrupted E6E7 (p53+/-E6E7) transgenic mice. In this tumor and even in the normal spleen, the absence of p53 protein was observed, whereas the p53 mRNA was expressed with a normal size, suggesting the degradation of p53 protein in these tissues. These results suggest that HPV16E6 could stimulate p53 protein degradation in mouse cells and induced the lymphomagenesis in a manner indistinguishable from p53 deficiency.

Animals↗

PubMed1998

Aging and DNA methylation in colorectal mucosa and cancer.

DNA methylation of promoter-associated CpG islands may function as an alternate mechanism of silencing tumor suppressor genes in multiple neoplasias including colorectal cancer. De novo methylation of genes appears to be an early and frequent event in most neoplasias. For the ER and IGF2 genes, we have previously shown that methylation actually begins in the normal colon mucosa as an age-related event and progresses to hypermethylation in cancer. In this study, we have determined the frequency of age-related methylation in normal colonic mucosa among the genes hypermethylated in colorectal cancer. We studied six genes, including N33, MYOD, p16, HIC-1, THBS1, and CALCA. The N33 gene showed partial methylation in normal colon mucosa, which was age-related (r = 0.7; P = 0.003 using regression analysis). Adenomas and cancers showed further hypermethylation at this locus. Similarly, the MYOD gene showed age-related methylation in normal colon mucosa (r = 0.7; P < 0.00001 using regression analysis) and hypermethylation in cancers. Age-related methylation seems to be gene specific, because p16, THBS1, HIC-1, and CALCA were not affected. Furthermore, this process may also be modulated by tissue-specific factors. Our study suggests that aging is a major contributing factor to hypermethylation in cancer.

Aged↗

PubMed1998

Participation of upstream stimulator factor (USF) in cadmium-induction of the mouse metallothionein-I gene.

The roles of the bHLH-Zip protein, upstream stimulatory factor (USF), in mouse metallothionein-I (MT-I) gene expression were examined. The promoter contains a putative USF binding site which overlaps an antioxidant response element (ARE) located at -101 bp relative to the transcription start point. The USF/ARE composite element increases basal expression of the mouse MT-I gene, and partly mediates response to oxidative stress. However, other functions of this composite element and the in vivo roles for USF in MT-I promoter functions have not been examined. We report studies which indicate that USF participates via the USF/ARE element in cadmium responsiveness of the mouse MT-I promoter. During the course of these studies a second, higher affinity USF binding site at -223 bp was identified. Stable and transient transfection assays in mouse hepatoma cells, using the USF/ARE in the context of a minimal promoter and site-directed and truncation mutants of the MT-I promoter, revealed that the USF and the ARE sites contribute to cadmium (2-30 microM) but not zinc responsiveness, and to basal promoter activity. Overexpression of dominant-negative (dn)USF in co-transfection assays significantly attenuated cadmium induction of the USF/ARE in the context of a minimal promoter, and attenuated cadmium, but not zinc, induction of the intact MT-I promoter. A consensus E-box (CACATG) at -223 bp in the MT-I promoter was also found to bind USF in vitro , and to be constitutively footprinted in vivo . The interaction of USF with E-box1 was apparently 10-fold stronger than that with the USF/ARE. However, in contrast, E-box1 was not a strong basal promoter element nor was it metal ions responsive in mouse Hepa cells. In conclusion, these studies demonstrate a role for USF in cadmium-specific induction of the mouse MT-I gene, but bring into question an obligate role for USF in regulating basal activity of this gene. The data further suggest that USF interacts with ARE-binding proteins to influence MT-I gene expression.

Animals↗

PubMed1998

AF4 encodes a ubiquitous protein that in both native and MLL-AF4 fusion types localizes to subnuclear compartments.

Acute leukemia with t(4;11)(q21,q23) translocation results from the in-frame fusion of the MLL to the AF4/FEL gene. In previous studies, we and others demonstrated that AF4 transcripts are present in a variety of hematopoietic and nonhematopoietic human cells. To further study the wild-type and leukemia fusion AF4, we used glutathione S-transferase (GST)-fusion proteins as immunogens to produce rabbit polyclonal antibodies that were specific for normal and chimeric AF4 proteins. Using Western blotting analysis, we demonstrated that the AF4 gene encodes proteins with apparent molecular weight of 125 and 145 kD. A 45-kD protein coprecipitated with AF4 protein in immunoprecipitation. Also, the anticipated MLL-AF4-encoded 240-kD protein was detected in all cell lines with t(4;11) translocations; fusion proteins were present in lesser quantity than the wild-type AF4. The proteins recognized by the antibodies are of the predicted sizes of the AF4 and MLL-AF4-encoded proteins based on previous DNA sequencing analysis. The MLL-AF4 fusion protein had a similar subcellular distribution as AF4. Both t(4;11) and non-t(4;11) leukemic cells showed a similar pattern of punctate nuclear staining in all cell lines tested using confocal immunofluorescence microscopy. AF4 antibodies should be useful for further elucidation of the function of AF4 in normal cellular physiology, as well as the function of MLL-AF4 in leukemogenesis. The antibodies should also be helpful for the diagnosis of the MLL-AF4 fusion proteins in t(4;11) leukemias.

Acute Disease↗

PubMed1998

Xenopus NF-Y pre-sets chromatin to potentiate p300 and acetylation-responsive transcription from the Xenopus hsp70 promoter in vivo.

We identify Xenopus NF-Y as a key regulator of acetylation responsiveness for the Xenopus hsp70 promoter within chromatin assembled in Xenopus oocyte nuclei. Y-box sequences are required for the assembly of DNase I-hypersensitive sites in the hsp70 promoter, and for transcriptional activation both by inhibitors of histone deacetylase and by the p300 acetyltransferase. The viral oncoprotein E1A interferes with both of these activation steps. We clone Xenopus NF-YA, NF-YB and NF-YC and establish that NF-Y is the predominant Y-box-binding protein in Xenopus oocyte nuclei. NF-Y interacts with p300 in vivo and is itself a target for acetylation by p300. Transcription from the hsp70 promoter in chromatin can be enhanced further by heat shock factor. We suggest two steps in chromatin modification at the Xenopus hsp70 promoter: first the binding of NF-Y to the Y-boxes to pre-set chromatin and second the recruitment of p300 to modulate transcriptional activity.

Acetylation↗

PubMed1998

Comparison of expression of human globin genes transferred into mouse erythroleukemia cells and in transgenic mice.

To examine whether transfer of gamma globin genes into mouse erythroleukemia cells can be used for the analysis of regulatory elements of gamma globin gene promoter, Agamma gene constructs carrying promoter truncations that have been previously analyzed in transgenic mice were used for production of stably transfected mouse erythroleukemia (MEL) cell clones and pools. We found that constructs, which contain a microlocus control region (microLCR) that efficiently protects globin gene expression from the effects of the position of integration in transgenic mice, display position-dependent globin gene expression in MEL cell clones. Agamma globin gene expression among MEL cell clones carrying the muLCR(-201)Agamma and muLCR(-382)Agamma gene constructs ranged 15.5-fold and 17.6-fold, respectively, and there was no correlation between the Agamma mRNA levels and the copies of the transgene (r = .28, P = .18). There was significant variation in per copy Agamma globin gene expression among MEL cell pools composed of 10 clones, but not among pools composed of 50 clones, indicating that position effects are averaged in pools composed by large numbers of clones. The overall pattern of Agamma globin gene expression in MEL cell pools resembled that observed in transgenic mice indicating that MEL cell transfections can be used in the study of cis elements controlling gamma globin gene expression. MEL cell transfections, however, are not appropriate for investigation of cis elements, which either sensitize or protect the globin transgenes from position effects.

Animals↗

PubMed1998

A convenient method of aligning large DNA molecules on bare mica surfaces for atomic force microscopy.

Large DNA molecules remain difficult to be imaged by atomic force microscopy (AFM) because of the tendency of aggregation. A method is described to align long DNA fibers in a single direction on unmodified mica to facilitate AFM studies. The clear background, minimal overstretching, high reproducibility and convenience of this aligning procedure make it useful for physical mapping of genome regions and the studies of DNA-protein complexes.

Aluminum Silicates↗

PubMed1998

Gene therapy with extracellular superoxide dismutase attenuates myocardial stunning in conscious rabbits.

BACKGROUND: Administration of Cu/Zn superoxide dismutase (SOD) without catalase fails to alleviate myocardial stunning, but extracellular SOD (Ec-SOD) may be more effective because it binds to heparan sulfate proteoglycans on the cellular glycocalyx. We therefore used in vivo gene transfer to increase systemic levels of Ec-SOD and determined whether this gene therapy protects against myocardial stunning. METHODS AND RESULTS: The cDNA for human Ec-SOD was cloned behind the cytomegalovirus (CMV) promoter and incorporated into a replication-deficient adenovirus (Ad5/CMV/Ec-SOD). Injection of this virus (2x10(8) pfu/kg IV) produced high levels of Ec-SOD in the liver, which could be redistributed to the heart and other organs by injection of heparin. Conscious rabbits underwent a sequence of six 4-minute coronary occlusion/4-minute reperfusion cycles for 3 consecutive days starting 3 days after intravenous injection of Ad5/CMV/Ec-SOD or Ad5/CMV/nls/LacZ (negative control). Both groups were given heparin (2000 U/kg IV) 2 hours before the first sequence of occlusions. The severity of myocardial stunning was measured as the total deficit of LV wall thickening after the last reperfusion. On day 1, the total deficit of wall thickening was markedly decreased in Ad5/CMV/Ec-SOD rabbits versus controls and similar to that seen on days 2 and 3 in controls. CONCLUSIONS: The results demonstrate that in vivo gene transfer of the cDNA encoding Ec-SOD provides the heart with substantial protection against myocardial stunning without the need for concomitant administration of catalase. The present observations provide the basis for controlling gene therapy at the posttranslational level and for simultaneously protecting multiple organs from oxidant stress.

Adenoviruses, Human↗

PubMed1998

Quantification of infarct size on focal cerebral ischemia model of rats using a simple and economical method.

Quantification of infarct size is a very useful index to assess models of focal cerebral ischemia and effects of new therapies. Currently-used image analysis systems to carry out this task usually involve dedicated and expensive equipment. We present a low-cost and simple method to perform the image acquisition and analysis. Twelve Wistar rats were subject to focal cerebral ischemia and scarified 24 h after the insult. 2,3,5-triphenyl tetrazolium chloride (TTC) stain was used as a conventional method to differentiate ischemic damage from healthy brain tissue. Digital images were captured from the stained coronal sections using a flatbed color scanner and analyzed with a commercial image processing software. To evaluate the accuracy and reproducibility of this method, the data obtained with the current procedure was correlated with those from a dedicated standard image analysis system and intra-observor correlation coefficient was estimated. Also the sensitivity of this method in quantification of infarct volume was tested in two different experimental settings. There was close correlation in the outcome of infarct size measurement between the current method and the standard system (r = 0.93, p < 0.001). A high agreement of measurement of the percentage of infarct volume between two different examiners with the same source of samples (r = 0.98, p < 0.001). We demonstrated that this method was sensitive in detection of difference of infarct sizes when placebo-treated animals (n = 6) were compared to the group treated with a neuroprotective agent (n = 6). Our data demonstrated that ischemic lesion of focal cerebral ischemia in rat can be accurately and reproducibly quantified using this method. The low-cost and simplicity of this method may facilitate the application in determination of ischemic damage.

Animals↗

PubMed1998

The 77-kDa echinoderm microtubule-associated protein (EMAP) shares epitopes with the mammalian brain MAPs, MAP-2 and tau.

Previous work has shown that the echinoderm microtubule-associated protein (EMAP) was a unique MAP with little sequence similarity with the brain MAPs. The purpose of this study was to determine whether there were any small domains within EMAP that were shared by the mammalian brain MAPs, MAP-2, and tau. It is reported here that EMAP and the heat-stable MAP-2 and tau share antigenic determinants. A polyclonal antisera, raised against SDS-PAGE denatured EMAP, reacted strongly with both MAP-2 and tau on Western blots. In addition, a detailed sequence comparison, using a window of 5 amino acids at a time, revealed several short domains with approximately 20 residues that shared sequence similarity. The regions of sequence similarity were all located in regions implicated in microtubule binding, suggesting that EMAP and the mammalian brain MAPs may share short structural and functional domains.

Amino Acid Sequence↗

PubMed1998

AP-2 may contribute to IGF-II overexpression in rhabdomyosarcoma.

The human insulin-like growth factor II gene is regulated in a development-dependent manner and is not expressed in most adult tissues. However, high levels of insulin-like growth factor II mRNA are detected in many human tumors including rhabdomyosarcoma, an embryonal tumor of skeletal muscle origin. In this study, we demonstrate that the developmentally regulated transcription factor AP-2 is expressed at higher levels in human fetal skeletal muscle and rhabdomyosarcoma cells compared to human adult skeletal muscle. Endogenous insulin-like growth factor II mRNA derived from the P3 as well as transfected P3 promoter activity were modestly and consistently increased to the same extent following treatment of the rhabdomyosarcoma cell line RD with forskolin, a compound implicated in AP-2 transactivation. This effect of AP-2 on increased transcriptional activity was confirmed by nuclear run-on assays. Expression of AP-2B, a dominant-negative inhibitor of AP-2, suppressed the P3 promoter activity in AP-2 expressing RD cells. Furthermore, five AP-2 protected regions corresponding to six AP-2 specific binding sites were detected in the insulin-like growth factor II P3 promoter. These data together suggest that AP-2 may contribute to the high expression of IGF-II in rhabdomyosarcoma cells.

Binding Sites↗

PubMed1998

Neuroprotection by delayed administration of topiramate in a rat model of middle cerebral artery embolization.

Because topiramate (TPM) suppresses voltage-sensitive Na+ channels and non-N-methyl-D-aspartate (NMDA) receptors and enhances gamma-aminobutyric acid (GABA)-mediated inhibition, we tested whether it would protect against cerebral ischemia. The right middle cerebral artery (MCA) was embolized by an intra-arterial injection of autogenous thrombus. Two hours after thrombus injection, animals received intra-peritoneal injections (i.p.) of normal saline as control (n=6) or alternatively, a low- (20 mg/kg, i.p., n=6) or high-dose (40 mg/kg, i.p., n=6) of TPM. Neurological deficit was scored at 2 h and 24 h following the ischemic insult. The animals were sacrificed 24 h after ischemia and the coronal brain sections were stained with 2% 2,3,5-triphenyltetrazolium chloride (TTC) for determination of the percentage of infarct volume. Administration of TPM significantly improved the 24-h neurological deficit scores (low dose, 1.75+/-0.5; high dose, 1.17+/-0.41; p<0.05 for both doses). A reduction in the percentage of infarct volume (low dose, 22.9+/-8.9%, p=0.002; high dose 7.6+/-3.4%, p<0.001) was seen when compared to the controls (infarct size, 54.2+/-9.0%; neurobehavior score, 2. 67+/-0.52). Treatment with TPM at the higher dose induced more neuroprotection than that at the lower dose (p<0.05). Thus, treatment with TPM resulted in a dose- and use-dependent neuroprotective effect, when used 2 h after MCA embolization in a rat model of focal ischemia.

Animals↗

PubMed1998

Cisplatin induction of ERCC-1 mRNA expression in A2780/CP70 human ovarian cancer cells.

ERCC-1 is a critical gene within the nucleotide excision repair pathway, and cells without a functional ERCC-1 do not perform cisplatin-DNA adduct repair. We therefore investigated the cisplatin effect on ERCC-1 mRNA expression in vitro. In response to a 1-h cisplatin exposure, A2780/CP70 human ovarian cancer cells showed a 6-fold increase in steady-state level of ERCC-1 mRNA. This rise was attributable to increased transcription as measured by nuclear run-on assays and a 60% increase in ERCC-1 mRNA half-life. The increase in ERCC-1 mRNA was preceded by a 4-5-fold rise in mRNA expressions of c-fos and c-jun, a 14-fold increase in c-Jun protein phosphorylation, and an increase in in vitro nuclear extract binding activity to the AP-1-like site of ERCC-1. These data suggest that the induction of ERCC-1 expression in A2780/CP70 cells exposed to cisplatin results from two major factors: (a) an increase in the expression of transactivating factors that bind the AP-1-like site in the 5'-flanking region of ERCC-1 and (b) an increase in the level of c-Jun phosphorylation that enhances its transactivation property.

Amanitins↗