Biomedical subjects

X Ding

Publications and source records attributed to X Ding.

At least 73 records · Page 4Linked to original sources

PubMed2000

[Reducing incidence and mortality from rectal cancer by polypectomy: a prospective cohort study].

OBJECTIVE: To address the hypothesis that colorectal cancers often arise from precursor lesion(s), either adenomas or non-adenomatous polyps. METHODS: A population-based mass screening for rectal cancer using 15cm rigid endoscopy was conducted in Haining County, Zhejiang province, from 1977 to 1980. Of over 230,000 participants, 4,076 of them were diagnosed with precursor lesions, either adenomas or non-adenomatous polyps, which were then removed. All individuals with precursor lesions were followed and re-examined by endoscopy every two to five years through 1998. RESULTS: After the initial screening, 952 metachronous adenomas and 417 non-adenomatous polyps were detected and removed from the cohort. Furthermore, 27 cases of colorectal cancer were detected and treated. Log-rank tests showed that the years of survival significantly increased among those cancer patients who had undergone mass screening compared to other rectal cancer patients (P < 0.001). According to the population-based cancer registry in Haining County, both age-adjusted incidence and mortality rates from rectal cancer decreased from 1977 to 1996. Observed accumulative incidence and mortality rates decreased to 68.6% and 82.4% comparing with expected numbers during the last 20 years. CONCLUSION: Mass rectal cancer screening in the general population followed by routine endoscopy for high-risk patients could decrease both rectal cancer incidence and mortality rates.

Adenoma↗

PubMed2000

[Drinking water types, microcystins and colorectal cancer].

OBJECTIVE: To assess the relationship between microcystins (a blue-green algal toxin) in drinking water and colorectal cancer. METHODS: Eight townships were randomly selected as study sites in Haining city of Zhejiang province, China. Four hundred and eight colon and rectum carcinoma cases diagnosed from 1977 to 1996 were identified from cancer registry in the study sites. A retrospective survey on types of drinking water of all 408 cases was conducted. Population data and drinking water sources data were provided by local household registration and local health institution, respectively. Water samples from different sources (well, tap-water, river and pond) were collected and microcystins concentrations were measured by an indirect competitive ELISA method. RESULTS: The incidence rates of colorectal cancer were significantly higher among people drinking river or pond water than those who drank well water or tap-water in both males and females. And comparing with other sources to well water, the relative risks (RR) were much higher for people using river water (7.94) and pond water (7.70). The positive detection rates (> 50 pg/ml) of microcystin in well, tap-water, river and pond water were 0.00%, 0.00%, 36.23% and 17.14% respectively. The highest concentrations of microcystins were 1 083.43 pg/ml (river) and 1 937.94 pg/ml (pond) in the positive samples. Microcystins concentrations in river and pond were significantly higher than the concentrations in well and tap water (P < 0.01). The Spearman rank correlation analysis showed that in the study sites, the microcystins concentrations of river and pond water were positively correlated with the incidence of colorectal cancer (r = 0.881, P < 0.01). CONCLUSION: Drinking surface water (river or pond) is one of the risk factors for colorectal cancer. Microcystins may be associated with incidence of colorectal cancer. It is suggested that further study should be carried out to clarify the relationship between colorectal cancer and microcystin in drinking water.

Bacterial Toxins↗

PubMed2000

[Distribution of minimal residual leukemia in Brown Norway rats express LacZ gene].

OBJECTIVE: To investigate the distribution of minimal residual leukemia (MRL) in vivo. METHODS: The MRL model in BN rat was established by using LT12nl leukemia cell line carrying LacZ gene. The marker gene (LacZ) was detected by using reverse transcriptase polymerase chain reaction (RT-PCR) and nested PCR, X-gal staining, and cytomorphological and pathological examination. RESULTS: PCR assays showed positive result in humerus at day 4, femur at day 6, and spleen at day 9 after CTX treatment. The peak positive signal in humerus was stronger at day 9. X-gal staining showed negative in spleen at day 9. PCR showed negative results in peripheral blood and liver. CONCLUSION: PCR can be used as an effective tool to investigate the distribution pattern in experimental MRL.

Animals↗

PubMed2000

[Study on physical properties of titanium alloy sample fabricated with vacuum-sintered powder metallurgy].

OBJECTIVE: To investigate the physical properties of titanium alloy fabricated with vacuum-sintered powder metallurgy. METHODS: The titanium powders of three different particle sizes(-160mesh, -200 - +300mesh, -300mesh) were selected, and mixed with copper and aluminum powder in different proportions. Two other groups were made up of titanium powder(-200 - +300mesh) plated with copper and tin. The build-up and, condensation method and a double-direction press with a metal mold were used. The green compacts were sintered at 1000 degrees C for 15 minutes in a vacuum furnace at 0.025 Pa. In the double-direction press, the specimens were compacted at the pressure of 100 MPa, 200 MPa and 300 MPa respectively. Then the linear shrinkage ratio and the opening porosity of the sintered compacts were evaluated respectively. RESULTS: 1. The linear shrinkage ratio of specimens decreased with the increased compacted pressure(P < 0.05). There was no significant difference among the linear shrinkage ratios of three different titanium powders at the same compacted pressure(P > 0.05), but that of titanium powder plated with copper and tin was higher than those of other specimens without plating(P < 0.05). 2. The opening porosity of specimens decreased with the increased compacted pressure(P < 0.05). Three different sized particle of titanium powder did not affect the opening porosity at the same compacted pressure(P > 0.05). CONCLUSION: The composition of titanium-based metal powder mixtures and the compacted pressures affect the physical properties of sintered compacts. Titanium powder plated with copper and tin is compacted and sintered easily, and the physical properties of sintered compacts are greatly improved.

Dental Alloys↗

PubMed2000

Quantitative study of basic fibroblast growth factor in vitreous with proliferative vitreoretinopathy.

OBJECTIVE: To quantitatively study basic fibroblast growth factor (bFGF) in the vitreous of proliferative vitreoretinopathy (PVR) in order to understand the role of bFGF in the development of PVR. METHOD: High sensitive sandwich enzyme immunoassay technique (ELISA) was used to measure bFGF level in vitreous of normal eyes, the eyes of PVR-C or PVR-D grade, eyes of vitreous hemorrhage and the serum levels of bFGF in PVR-D patients. RESULTS: The levels of bFGF in the vitreous were: median 5.20 ng/L, quartile 15.47 ng/L in 20 normal eyes; median 3.12 ng/L, quartile 10.48 ng/L in 35 PVR-C eyes; median 46.56 ng/L, quartile 113.96 ng/L in 26 PVR-D eyes; median 1.40 ng/L, quartile 6.25 ng/L in 25 vitreous hemorrhage eyes. The vitreous bFGF level in PVR-D group was significantly higher than that in the normal group, PVR-C group and vitreous hemorrhage group (P < 0.01). The mean of serum-bFGF level was 18.33 +/- 3.39 ng/L. The vitreous bFGF level of PVR-D group was significantly higher than serum-bFGF level (P < 0.01). And the vitreous-bFGF level in PVR-D group was significantly higher in larger retinal tear subgroup. CONCLUSION: The results suggested that bFGF is involved in the development of PVR.

Adult↗

PubMed2000

[Spectral study of the microenviroment change of aromatic amino-acid residues in BSA induced by pH].

The microenvironment change of aromatic amino-acid residues in BSA at various pH were studied by fluorescence spectra and ultraviolet absorption spectra. It suggested that the change of protein surface and surface hydrophobicity from result. Compared to neutral pH, the Trp microenvironment seemed to be more hydrophobic at lower pH indicating less local surface hydrophobicity of BSA. At higher pH, the protein undergo conformational changes and unhold, the more buried Phe exposed to solvents consistent with stronger surface hydrophobicity of BSA.

Amino Acids, Aromatic↗

PubMed2000

[The electroluminescence of organic and polymer thin film materials].

In recent years, researches on electroluminescence (EL) of organic and polymer thin film materials have been made with an outstanding progress, and have attracted much interest because of its large-area, full color, high luminance displays which can be driven with low dc voltage. In this paper, the history of the development on electroluminescence, the devices and the selection of luminescent materials and the electroluminescence principle are introduced briefly.

English Abstract↗

PubMed1999

Cytochrome P450 and steroid hydroxylase activity in mouse olfactory and vomeronasal mucosa.

The aims of this study are to identify the sex steroid-metabolizing cytochrome P450 enzymes of the vomeronasal organ (VNO) and to determine the activities of VNO microsomes to metabolize estradiol, progesterone, and testosterone. Several P450 isoforms, including CYP1A2, CYP2A, CYP2B, CYP2C, CYP2G1, and CYP3A, NADPH P450-reductase, and microsomal epoxide hydrolase were detected in mouse VNO, although their expression levels were much lower than those in the main olfactory epithelium. VNO microsomes were active toward the three steroid hormones, producing metabolite profiles similar to those seen with olfactory mucosal microsomes. Thus, the mammalian VNO, a steroid hormone target tissue, contains multiple steroid-metabolizing P450 isoforms and is capable of metabolic disposition of the three major sex steroid hormones. These findings support the proposed roles of olfactory mucosal and VNO microsomal P450 enzymes in maintaining cellular hormonal homeostasis and other perireceptor processes associated with olfactory chemosensory function.

Animals↗

PubMed1999

Corticotropin releasing factor and substance P mediate the nucleus amygdaloideus centralis-nucleus ventromedialis-nucleus dorsomedialis pressor system.

Prolonged emotional stress is an important factor in the development of neurogenic hypertension, but its mechanism is still unclear. The purpose of the present study is to analyze the possible neural basis of hypertension induced by prolonged emotional stress. In the brain many nuclei are involved in emotional reaction, stress or defense response; among them the nucleus amygdaloideus centralis (AC) is the most important one which widely connects with other nuclei controlling emotion and stress, such as nucleus ventromedialis (NVM), nucleus dorsomedialis (NDM), nucleus paraventricularis (NPV) etc. These nuclei contain corticotropin releasing factor (CRF)- and substance P (SP)-immunoreactive cell bodies, nerve terminals and corresponding receptors. Our previous and present studies showed that microinjection of CRF or SP into these nuclei induced pressor responses. These data imply that excitation of the AC can activate many nuclei controlling emotion and stress via CRF and SP, and excessive activities of these nuclei may be the neural basis of hypertension induced by prolonged emotional stress. The present study revealed that (1) the AC pressor response to glutamate (Glu) could be reduced by preinjection of CRF antagonist (alpha-Helical CRF[9-41] or SP antagonist ([D-Pro(2), D-Phe(7), D-Trp(9)]-substance P) into bilateral NVM, (2) the NVM pressor response to Glu were decreased by pretreatment of the NDM with CRF- or SP-antagonist, (3) the AC-, NVM- or NDM-pressor responses were all attenuated by preinjection of CRF- or SP-antagonist into bilateral NPV or rostral ventrolateral medulla (RVL). The results indicate that excitation of the AC can indirectly activate the NPV and RVL to evoke pressor response via the NVM-NDM, CRF and SP are transmitters in each connection of this pathway; this is one component of the mechanism underlying the AC pressor response. Taken together with the findings of our previous studies, it provides neurophysiological basis for the above-mentioned implications.

Amygdala↗

PubMed1999

Escherichia coli genes regulated by cell-to-cell signaling.

Utilizing the bicistronic reporter transposon mini-Tn5 lacZ-tet/1, we have identified lacZ fusions to four Escherichia coli genes/operons that are strongly activated by the accumulation of self-produced extracellular signals. These fusions were designated cma9, cma48, cma113, and cma114 for conditioned medium activated. Each of the cma fusions was expressed in a growth phase-dependent manner, and the presence of conditioned medium from a stationary phase E. coli culture resulted in the premature activation of these fusions in cells at early to mid-logarithmic phase. The cma48 and cma114 fusions were dependent on RpoS for growth phase expression and response to extracellular factors. The extracellular factors that activated the cma9, cma48, and cma114 fusions were produced in both rich complex and defined minimal media. The cma fusions were shown to be within the cysK (cma9), astD (cma48), tnaB (cma113), and gabT (cma114) genes. These genes function in the uptake, synthesis, or degradation of amino acids that yield pyruvate and succinate.

DNA Transposable Elements↗

PubMed1999

Prenatal fragile X detection using cytoplasmic and nuclear-specific monoclonal antibodies.

We have been carrying out studies aimed at improving prenatal detection of the fragile X chromosome/mutation. Our current protocol requires a turnaround time (TAT) of several days. In an attempt to reduce the TAT, we have turned to the use of monoclonal antibodies (mAbs). Monoclonal antibody 1A1 (provided by Dr. Mandel of INSERM) immunostaining was performed according to a modified three-step immunocytochemical procedure. We found that cytoplasmic staining intensities, using mAb 1A1/avidin biotinylated complex/diaminobenzidine, varied from light to heavy within each sample, with controls exhibiting a majority of heavily stained cells in both chorionic villus (CV) sample and amniotic fluid cultured cells. Using mAb 1A1 and a new nuclear-specific antibody, mAb 3F11, we found that CV cultured cells harboring the FMR1 full mutation could be distinguished from controls as early as 10 weeks of gestation in both male and female specimens. Western blot analysis showed that the antibodies have similar staining patterns but that mAb 3F11 has fewer background/nonspecific bands. Our results demonstrate that it is feasible to detect fragile X full mutations within one day after obtaining cells from CV specimens taken as early as 10 weeks of gestation.

Amino Acid Sequence↗

PubMed1999

Accelerated prenatal diagnosis of fragile X syndrome by polymerase chain reaction restriction fragment detection.

Prenatal diagnosis of fragile X syndrome requires detection of the full FMR1 mutation in chorionic villus or amniotic fluid cell samples. Although analysis of genomic DNA restriction fragment pattern is a highly reliable technique for identification of the full FMR1 mutation, standard Southern blot determination of this pattern requires significantly more genomic DNA than is initially available from a prenatal sample. To overcome this limitation we developed a method that determines the diagnostic pattern of genomic restriction fragments from a fraction of a prenatal specimen. The prenatal DNA sample is first digested with EcoRI and EagI, and after agarose gel electrophoresis, the 2- to 10-kb region of the gel is serially sectioned and amplified by polymerase chain reaction. Analysis of prenatal samples from an unaffected male and from a full mutation male showed that this approach generated a diagnostic pattern comparable with a Southern blot of 100-fold more material. This innovation enables laboratories to prenatally diagnose the full FMR1 mutation sooner than standard techniques.

Blotting, Southern↗

PubMed1999

A new genotype of TT virus (TTV) infection among Colombian native Indians.

Serum TTV DNA was assayed in 140 native Indians and 40 members of the general population in Colombia to determine the prevalence of TT virus (TTV) infection among Colombian native Indians. Of the 140 native Indians, 23 (16.4%) were positive for TTV DNA, compared to 4 (10.0%) of 40 from the general population (P = not significant). The prevalence of TTV DNA among native Indians was much higher than that of HBsAg and anti-HCV. Comparison of subjects with and without TTV DNA revealed no significant differences in all characteristics between the two groups. A phylogenetic tree, using the open reading frame 1 sequence (222 bp), indicated that the virus could be classified into four different genotypes, including three previously reported ones. The results show that TTV infection is common in Colombian native Indians without liver disease and also indicate the existence of a novel genotype of TTV.

Adolescent↗

PubMed1999

Occupational health survey on workers exposed to 2-bromopropane at low concentrations.

BACKGROUND: Recent case studies in Korea and animal studies revealed the reproductive and hematopoietic toxicity of 2-bromopropane introduced into workplaces as an alternative to ozone-layer depleting chlorofluorocarbons. We aimed to clarify the dose-effect relationship of 2-bromopropane in workers. METHOD: The exposure concentration of 2-bromopropane and hematological indices, hormonal levels, menstruation status, and sperm indices were examined in 25 workers (11 males, 14 females) at a 2-bromopropane factory. Regression analyses of the examined indices against time-weighted average (TWA) of exposure concentration were conducted. RESULTS: Amenorrhea or polymenorrhea was observed only in older females. Hematological indices had a significant relation with TWA of exposure concentration in females with normal menstruation. However, no other indices showed any significant relation with TWA of 2-bromopropane. CONCLUSIONS: No severe cases of reproductive or hematopoietic disorders were found at less than 10 ppm (TWA), but a possible adverse effect of 2-bromopropane on hematopoiesis could not be disproved.

Adult↗

PubMed1999

N-Nitrosobenzylmethylamine hydroxylation and coumarin 7-hydroxylation: catalysis by rat esophageal microsomes and cytochrome P450 2A3 and 2A6 enzymes.

N-Nitrosobenzylmethylamine (NBzMA) is a potent and selective esophageal carcinogen in the rat and may be a causative agent for human esophageal cancer. This nitrosamine, like most, must be metabolically activated to exert its carcinogenic potential. NBzMA may be metabolized by P450-catalyzed methyl or methylene hydroxylation; the latter is believed to be the activation pathway. The sensitivity of the esophagus to NBzMA-induced tumorigenesis is believed to be due, at least in part, to the presence of efficient P450 catalysts in this tissue. However, while it was reported almost 20 years ago that the rat esophagus catalyzes the methylene hydroxylation of NBzMA, the P450 that catalyzes this reaction has yet to be identified. We report here that human P450 2A6 and the closely related extrahepatic rat enzyme P450 2A3 both efficiently catalyze NBzMA methylene hydroxylation, characterized as benzaldehyde formation. The catalytic efficiency of P450 2A3 in this reaction was 3-fold greater than that of P450 2A6, 7.6 (K(m) = 0.63 +/- 0.18 microM and the V(max) = 4.8 nmol min(-)(1) nmol of P450(-)(1)) versus 2.3 (K(m) = 6.7 +/- 2.9 microM and the V(max) = 15.7 nmol min(-)(1) nmol of P450(-)(1)), respectively. Both enzymes catalyzed methylene hydroxylation at least 4-fold more efficiently than methyl hydroxylation. In addition, P450 2A6, but not P450 2A3, catalyzed benzyl ring hydroxylation, generating N-(p-hydroxybenzyl)methylamine. The identity of this metabolite was confirmed by synthesis of a standard and LC/MS and LC/MS/MS analysis. P450 2A6 is an efficient coumarin 7-hydroxylase, and we report here that P450 2A3 is an equally good catalyst of this reaction (K(m) = 1. 7 +/- 0.41 microM and V(max) = 1.7 +/- 0.08 nmol min(-)(1) nmol of P450(-)(1)). Rat esophageal microsomes (REM), like P450 2A3, were efficient catalysts of NBzMA methylene hydroxylation. However, in contrast to P450 2A3, the major product of this reaction was the product of benzaldehyde oxidation, benzoic acid. Antibody to the closely related mouse P450, 2A5, did not inhibit REM-catalyzed NBzMA metabolism, and most importantly, REM did not catalyze the 7-hydroxylation of coumarin. Therefore, P450 2A3 does not appear to be the P450 in the rat esophagus responsible for catalyzing the methylene hydroxylation of NBzMA.

Animals↗

PubMed1999

Prevalence of TT virus and GBV-C infections among patients with liver diseases and the general population in Shanghai, China.

To determine the prevalence of TT virus (TTV) and GB virus C/hepatitis G virus (GBV-C) infections among patients with liver disease and the general population in Shanghai, China, we studied 90 patients with liver diseases (acute hepatitis, 28; chronic hepatitis, 27; liver cirrhosis, 20; hepatocellular carcinoma, 15) and 90 age, sex matched healthy blood donors as controls. There were no significant differences in the clinical and demographic characteristics between the two groups, except for liver function test values. There was a statistical difference between the patient group and the control group with regard to the prevalence of TTV DNA (23.5% in patient group, 11.1% in control group, P < 0.05), although no differences in clinical features could be found between TTV DNA-positive and negative subjects. Also, no differences in TTV DNA prevalence among various categories of liver diseases were noted (P = NS). The prevalence of HBsAg was significantly different between the patient group (36.7%) and the control group (3.3%) (P0.01), whereas the prevalence of anti-HCV and GBV-C RNA were not significantly different between the two groups. The nucleotide sequences were determined in the TTV DNA-positive samples and evaluated using phylogenetic analysis which suggested that they could be divided into two main genotypes designated as genotype 1 and 2. There were five samples clustered into 3 hitherto unknown subtypes of genotype 2. We concluded that (1) although TTV infection is widespread among both groups and there is a statistical difference of TTV infection between them, no hepatic damaging evidence and correlation with certain liver disease could be found in this study, suggest that TTV may not be major cause of liver disease, (2) GBV-C infection is frequent, but the virus is not the cause of liver diseases, and (3) new subtypes of TTV may exist in Shanghai, China.

Adult↗

PubMed1999

The anti-desmoglein 1 autoantibodies in pemphigus vulgaris sera are pathogenic.

Pemphigus vulgaris and pemphigus foliaceus are two closely related, but clinically and histologically distinct, autoimmune skin diseases. The autoantigens for pemphigus vulgaris and pemphigus foliaceus are desmoglein 3 and desmoglein 1, respectively. The anti-desmoglein 1 antibodies in pemphigus foliaceus and anti-desmoglein 3 antibodies in pemphigus vulgaris are pathogenic as determined by immunoglobulin G passive transfer animal models. More than 50% of pemphigus vulgaris sera also contain anti-desmoglein 1 autoantibodies; however, the pathogenicity of the anti-desmoglein 1 autoantibodies in pemphigus vulgaris remains unknown. In this study, we used soluble recombinant extracellular domains of desmoglein 1 and desmoglein 3 to obtain affinity-purified anti-desmoglein 1 and anti-desmoglein 3 autoantibodies from pemphigus vulgaris sera and examined the pathogenicity of each fraction separately using the passive transfer mouse model. By immunoprecipitation, the purified anti-desmoglein 1 and anti-desmoglein 3 showed no cross-reactivity. The anti-desmoglein 1 autoantibodies in pemphigus vulgaris induced typical pemphigus foliaceus lesions in neonatal mice, whereas the anti-desmoglein 3 fraction induced pemphigus vulgaris-like lesions. In addition, the pathogenic anti-desmoglein 1 and anti-desmoglein 3 autoantibodies in pemphigus vulgaris had predominant IgG4 subclass specificity. These findings suggest that the anti-desmoglein 1 antibodies in pemphigus vulgaris are pathogenic.

Acantholysis↗

PubMed1999

TT virus infection among IVDUs in south western China.

To elucidate the prevalence and clinical implications of infection with the newly described TT virus (TTV) among intravenous drug users (IVDUs) in Yunnan, southwest China, serum samples from 158 IVDUs (129 M, 29 F; mean age 26.1 +/- 5.5 years) were examined for TTV DNA by semi-nested polymerase chain reaction (PCR) using primers derived from the open reading frame (ORFI) of TTV DNA. The seroprevalence of viral markers of HIV, HBV, HCV and GB virus C/hepatitis G virus (GBV-C) infection was also examined. A molecular evolutionary analysis was performed. Thirty one (20%) of the IVDUs were positive for TTV DNA, and 34 (22%), 6 (4%), 98 (62%), 76 (48%), 136 (86%) and 65 (41%) were positive for anti-HIV, HBsAg, anti-HBs, anti-HBc, anti-HCV and GBV-C RNA, respectively. When all the subjects were classified according to TTV DNA positivity, no significant differences were observed in demographic, biochemical or virological characteristics between the 2 groups. TTV infection was in all cases associated with co-infection with 1 or more of the other aforementioned viruses. There were no significant differences in the various combinations of co-infection between TTV positive and negative groups. Phylogenetic analysis revealed that the TTV isolates obtained in the study could be grouped mainly into TTV genotype 1, and that some of the isolates belonged to subgroups other than those previously described. These results indicate that: 1) TTV infection is prevalent among IVDUs in China; 2) TTV probably has minor liver pathogenicity; and 3) new subgroups of genotype 1 and 2 exist in China.

Adult↗