Biomedical subjects
Publications and source records attributed to Xue Li.
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This report documents the feasibility and advantages of integrating hydrogen/deuterium exchange (HDX) methodology with cyanylation (CN)-based methodology to determine the conformation of cystinyl proteins and intermediates during refolding. The CN-based methodology can be used to trap, identify, and preserve the disulfide structure of a given cystinyl protein folding intermediate, while the HDX methodology can be used to assess other conformational features of the intermediate. Specifically, in this study, CN-based methodology was used to trap a 1-disulfide bond and a 2-disulfide intermediate of long Arg(3) insulin-like growth factor-I (LR(3)IGF-I), which was then exposed to HDX using D(2)O at pD 6.8 and subsequently digested with pepsin before analysis by matrix-assisted laser desorption/ionization mass spectrometry. The HDX results show an increasing degree of secondary and tertiary structure as a function of disulfide bond formation. In addition, the HDX results for two overlapping peptic fragments suggest that a segment of the polypeptide exists in two conformations, which can be distinguished by HDX and pepsin. These results from HDX mass spectrometry are in reasonably good agreement with those from nuclear magnetic resonance studies of native LR(3)IGF-I and IGF-I, in which approximately 5000 times more material was used than in our study. Indications are that the integrated use of HDX and CN-based methodologies will be effective in studying the refolding of cystinyl proteins at the subnanomole level.
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OBJECTIVE: To assess the long effect of atraumatic restorative treatment (ART) restorations in a school environment. METHODS: Five middle-level dentists placed 294 ART restorations in the permanent teeth of 197 children. Standard instruments and procedures for ART were used. The restorative material used was a high-strength glass-ionomer. The restorations were evaluated annually by the same examiner who was not involved in the placement of the restorations. Occlusal wear of the restoration was assessed using a standard rheinberger scale. At the 5th year examination an independent external examiner evaluated the restorations using USPHS criteria. RESULTS: The cumulative survival rates of small class I restorations in the sixth year it was 75%. The corresponding figures for large class I restorations were 61% (P < 0.05). The net wear rate for both the small and large class I restorations in the first year was about 48 microm, which was significantly higher than those of the later years, which were about 20 - 25 micro m (P < 0.05). In the fifth year 93% of the small restorations were assessed as being satisfactory for marginal integrity, as against 80% for the large ones by using USPHS criteria. CONCLUSIONS: The ART approach for treating tooth decay in school children was appropriate, effective and acceptable. The 6-year survival rates of the restorations are high but are related to the size and type of the restoration.
To assess the role of microsatellite instability(MSI) on chromosome 19 in the carcinogenesis of gastric cancer. 26 microsatellite markers on chromosome 19 were amplified by Fluorescence-Labelled Primers Multiplex PCR in 44 paired gastric cancer tissues for MSI. The amplified fragments ran in PAGE gel by ABI 377 sequencer and the gel images were analyzed by GeneScan and Genotyper. Meanwhile, MSI of four of all microsatellite sites were also analyzed using PCR-SSLP-silver stain method. MSI was observed in 22 of 26(84.62%) microsatellite sites. D19S402 showed the highest frequency(22.73%). The total frequency of MSI was 8.3%. In 44 gastric cancer samples, 34(77.27%) cases showed MSI at one or more than one site. MSI, as a possible mechanism of carcinogenesis, might play an important role in human primary gastric cancer. MSI detections will become an integral part of the routine classification of all gastrointestinal tumors in the very near future.
Resistance to the growth inhibitory effects of transforming growth factor-beta (TGF-beta) is a characteristic of many transformed cells. The purpose of this study was to determine the response of ovarian cancer cells to TGF-beta1 and to investigate the roles of components of the TGF-beta/Smads signaling pathway in carcinogenesis of ovarian cancer. Three ovarian cancer cell lines, HO-8910, HO-8910PM and SKOV3, were treated with TGF-beta1 and assayed for growth response by MTT assay. Furthermore, expression and subcellular localization of the components of TGF-beta/Smads signaling pathway in these cell lines in the absence or presence of TGF-beta1 were determined by RT-PCR and immunofluorescence analysis. We found that proliferation of SKOV3 cell was not significantly inhibited by TGF-beta1 while it expressed all components of the TGF-beta/Smads signaling pathway. After exposure to TGF-beta1, Smad7 protein in SKOV3 increased transiently and translocated to cytoplasm from nucleus while P-Smad2 translocated into nucleus from cytoplasm. Taken together, the results suggested that the TGF-beta/Smads signaling pathway remained functional in human ovarian cancer cells, HO-8910, HO-8910PM and SKOV3, and the abnormalities of the downstream effectors of Smads proteins might contribute to the resistance of SKOV3 cell to TGF-beta1.
The precise mechanistic relationship between gene activation and repression events is a central question in mammalian organogenesis, as exemplified by the evolutionarily conserved sine oculis (Six), eyes absent (Eya) and dachshund (Dach) network of genetically interacting proteins. Here, we report that Six1 is required for the development of murine kidney, muscle and inner ear, and that it exhibits synergistic genetic interactions with Eya factors. We demonstrate that the Eya family has a protein phosphatase function, and that its enzymatic activity is required for regulating genes encoding growth control and signalling molecules, modulating precursor cell proliferation. The phosphatase function of Eya switches the function of Six1-Dach from repression to activation, causing transcriptional activation through recruitment of co-activators. The gene-specific recruitment of a co-activator with intrinsic phosphatase activity provides a molecular mechanism for activation of specific gene targets, including those regulating precursor cell proliferation and survival in mammalian organogenesis.
Several studies have demonstrated that BK virus (BKV) and JC virus (JCV) establish latent infection in peripheral blood leukocytes (PBLs) of healthy individuals; however, the main populations studied are European. In this study, the prevalence of BKV and JCV DNA in PBLs from healthy adult individuals and umbilical cord blood from newborn children in China was detected by semi-nested polymerase chain reaction (snPCR) followed by restriction enzyme analysis. The results suggest that the healthy adult Chinese population harbors BKV and JCV DNA in peripheral leukocytes. Overall, the prevalence of BKV and JCV DNA in PBLs of healthy adult individuals was 42.1% and 7.8%, respectively. The overall prevalence of BKV DNA was significantly higher than that of JCV DNA. None of the umbilical cord blood samples from newborn children were positive for BKV and JCV DNA. To understand further the target tissues involved in establishment of BKV and JCV latency in healthy individuals, the presence of DNA from both viruses was detected in normal arterial wall samples from 20 young trauma victims by the same method used for leukocyte DNA. BKV DNA was detected alone in 20% of samples tested; JCV DNA was not detected alone in any of the samples. DNA from both viruses was found in 5% of samples. This is the first report to show that normal arterial walls of healthy individuals may be another target site of latency for BKV and JCV.
The abnormal proliferation of cardiac fibroblasts is involved in the pathophysiologic process of left ventricular hypertrophy (LHV) associated with essential hypertension. Arginine vasopressin (AVP) has been reported to contribute significantly to the pathogenesis of hypertension. In this study, the authors investigated the effects of AVP and its V1 receptor antagonist [d(CH2)5Tyr2(Me)]AVP on the growth of rat cardiac fibroblasts. Cardiac fibroblasts of neonatal Sprague-Dawley rats were isolated, and growth-arrested cardiac fibroblasts were stimulated with 2.5% fetal calf serum in the presence and absence of AVP (0.001, 0.01, 0.1, and 1 microM) and [d(CH2)5Tyr2(Me)]AVP (0.1 microM). DNA synthesis was measured by [3H]thymidine incorporation. Thiazolyl blue assay and flow cytometry techniques were adopted to measure cell numbers and analyze cell cycle, respectively. Arginine vasopressin (0.1 and 1 microM) significantly increased DNA synthesis in cardiac fibroblasts. Moreover, AVP (0.1 and 1 microM) significantly increased the number of cardiac fibroblasts. Analysis of cell cycle showed that AVP (0.1 microM) increased S-stage percentage and proliferation index (PI). The V1 receptor antagonist [d(CH2)5Tyr2(Me)]AVP (0.1 microM) significantly inhibited DNA synthesis in cardiac fibroblasts. The cell number, S-stage percentage, and PI induced by AVP (0.1 microM) were significantly decreased by [d(CH2)5Tyr2(Me)]AVP (0.1 microM). These findings suggest that AVP might promote the proliferation of rat cardiac fibroblasts, which seems to be mediated via the V1 receptor. Arginine vasopressin may be involved in the pathophysiologic process of LVH by promoting cardiac fibroblast proliferation.
A combined experimental and theoretical charge density study of the pentapeptide Boc-Gln-d-Iva-Hyp-Ala-Phol (Boc, butoxycarbonyl; Gln, glutamine; Iva, isovaline; Hyp, hydroxyproline; Ala, ethylalanine; Phol, phenylalaninol) is described. The experimental analysis, based on synchrotron x-ray data collected at 20 K, is combined with ab initio theoretical calculations. The topologies of the experimental and theoretical densities are analyzed in terms of the atoms in molecules quantum theory. Topological parameters, including atomic charges and higher moments integrated over the atomic basins, have been evaluated with the program topxd and are used to calculate the electrostatic interactions between the molecules in the crystal. The interaction energies obtained after adding dispersive and repulsive van der Waals contributions agree quite well with those based on M-B3LYP/6-31G** dimer calculations for two of the three dimers in the crystal, whereas for the third a larger stabilization is obtained than predicted by the calculation. The agreement with theory is significantly better than that obtained with multipole moments derived directly from the aspherical atom refinement. The convergence of the interaction as a function of addition of successively higher moments up to and including hexadecapoles (l = 4) is found to be within 2-3 kJ/mol. Although shortcomings of both the theoretical and experimental procedures are pointed out, the agreement obtained supports the potential of the experimental method for the evaluation of interactions in larger biologically relevant molecules.
Mammalian organogenesis requires the expansion of pluripotent precursor cells before the subsequent determination of specific cell types, but the tissue-specific molecular mechanisms that regulate the initial expansion of primordial cells remain poorly defined. We have genetically established that Six6 homeodomain factor, acting as a strong tissue-specific repressor, regulates early progenitor cell proliferation during mammalian retinogenesis and pituitary development. Six6, in association with Dach corepressors, regulates proliferation by directly repressing cyclin-dependent kinase inhibitors, including the p27Kip1 promoter. These data reveal a molecular mechanism by which a tissue-specific transcriptional repressor-corepressor complex can provide an organ-specific strategy for physiological expansion of precursor populations.
The preparation of fullerene complexes with metal tetraarylporphyrins in the presence of excess ferrocene (Cp(2)Fe) results in the formation of new solvent-free and multicomponent molecular crystals. New isomorphous complexes of C(60) with PyZnTPP (ZnTPP identical with zinc 5,10,15,20-tetraphenyl-21H,23H-porphyrinate) and PyCoTPP (CoTPP identical with cobalt(II) 5,10,15,20-tetraphenyl-21H,23H-porphyrinate) containing Cp(2)Fe and the isostructural C(70) complex with PyZnTPP have been prepared. The crystal structures of the new layered C(60) complexes CoTMPP x C(60) (obtained in the presence of Cp(2)Fe) and CoTMPP x 2C(60) x 3C(7)H(8) (obtained in the absence of Cp(2)Fe) have been described (CoTMPP identical with cobalt(II) 5,10,15,20-tetrakis(p-methoxyphenyl)-21H,23H-porphyrinate). Cobalt atoms of the PyCoTPP and CoTMPP molecules are weakly coordinated to C(60) with Co...C(C(60)) distances in the 2.64-2.82 A range, whereas zinc atoms of PyZnTPP, as well as cobalt atoms of the CoTMPP molecules in the solvent-free phase, form only van der Waals contacts with fullerenes. Different packing arrangements in the crystals of fullerene-porphyrin complexes have been discussed.
Dlx homeobox genes are mammalian homologs of the Drosophila Distal-less (Dll) gene. The Dlx/Dll gene family is of ancient origin and appears to play a role in appendage development in essentially all species in which it has been identified. In Drosophila, Dll is expressed in the distal portion of the developing appendages and is critical for the development of distal structures. In addition, human Dlx5 and Dlx6 homeobox genes have been identified as possible candidate genes for the autosomal dominant form of the split-hand/split-foot malformation (SHFM), a heterogeneous limb disorder characterized by missing central digits and claw-like distal extremities. Targeted inactivation of Dlx5 and Dlx6 genes in mice results in severe craniofacial, axial, and appendicular skeletal abnormalities, leading to perinatal lethality. For the first time, Dlx/Dll gene products are shown to be critical regulators of mammalian limb development, as combined loss-of-function mutations phenocopy SHFM. Furthermore, spatiotemporal-specific transgenic overexpression of Dlx5, in the apical ectodermal ridge of Dlx5/6 null mice can fully rescue Dlx/Dll function in limb outgrowth.
In this report, we identify myogenin as an important transcriptional target under the control of three intracellular signaling pathways, namely, the p38 mitogen-activated protein kinase- (MAPK), calcium-calmodulin-dependent protein kinase- (CaMK), and calcineurin-mediated pathways, during skeletal muscle differentiation. Three cis-elements (i.e., the E box, myocyte enhancer factor [MEF] 2, and MEF3 sites) in the proximal myogenin promoter in response to these three pathways are defined. MyoD, MEF2s, and Six proteins, the trans-activators bound to these cis-elements, are shown to be activated by these signaling pathways. Our data support a model in which all three signaling pathways act in parallel but nonredundantly to control myogenin expression. Inhibition of any one pathway will result in abolished or reduced myogenin expression and subsequent phenotypic differentiation. In addition, we demonstrate that CaMK and calcineurin fail to activate MEF2s in Rhabdomyosarcoma-derived RD cells. For CaMK, we show its activation in response to differentiation signals and its effect on the cytoplasmic translocation of histone deacetylases 5 are not compromised in RD cells, suggesting histone deacetylases 5 cytoplasmic translocation is necessary but not sufficient, and additional signal is required in conjunction with CaMK to activate MEF2 proteins.
OBJECTIVE: The aim of this survey was to obtain some information of the prevalence of dental caries in the youth aged 12, 15 and 18 years of Sichuan province. METHODS: Based on WHO and national oral health survey standards, dental caries prevalence and treatment needs were investigated randomly in selected young individuals of Sichuan province in 1995. RESULTS: The prevalent rates of caries of 12-, 15-, and 18-year-old adolescents were 28.47% and 36.40% and 39.54% respectively. The mean DMFT of 12-, 15- and 18-year-old were 0.52, 0.81, and 0.99. There are more pit and fissure caries than smooth caries in the young of 12-year-old than those of 15- and 18-year-old. CONCLUSION: Despite improvement can be seen in adolescents' oral health in Sichuan, there remains a proportion of active untreated decays. Some simple prevention programs are needed to stabilize the caries.
OBJECTIVE: The purpose of the study was to investigate the prevalence of oral malodor in a group of health cohorts in Chengdu, China by using different diagnostic methods. METHODS: Volatile sulfur compounds (VSCs) level was evaluated by using Halimeter. The organoleptic score and tongue coating index were also evaluated. A questionnaire interview was conducted at the same time. RESULTS: There were 21.61% subjects whose oral VSCs level were more than 300 ppb. No significant difference was found between male and female for the VSCs values. The subjects with malodor (score > or = 6) evaluated by organoleptic score were 28.91%, and the difference between the male and female was significant (P < 0.05). Further, a significant correlation could be detected between the VSCs level, organoleptic score and tongue coating index (P < 0.05). CONCLUSION: The study indicates that nearly one of fourth people suffer from oral malodor. Malodor has significant correlation with tongue coating, so cleaning of tongue dorsum is very important to reduce oral malodor.