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Biomedical subjects

D Li

Publications and source records attributed to D Li.

At least 613 records · Page 34Linked to original sources
PubMed1997

[A prospective study on respiratory symptoms and functions in new employees exposed to cotton dust].

Sixty new employees in a cotton textile mill were followed up for five years to study their occurrence of byssinosis and its natural history. Results showed that the workers complained more cough, expectoration and other respiratory irritation symptoms at their early exposure to cotton dust, and the frequency of chest tightness in them reached the peak one year after exposure and remained at higher level later. Stratified analysis showed that all the respiratory symptoms did not correlate with their smoking habits, specific body constitution, etc. Forced expiratory volume at one second (FEV1) after shift declined with length of exposure and appeared a tendency to exacerbate gradually, especially in workers with a positive skin test of cotton antigen. Smoking had no influence on it. It suggests that exposure to cotton dust and idiosyncracy of the workers play important roles in damage to lung function.

Adolescent↗
PubMed1997

[Polymorphism and pologenetic affinities of genotype in pathogenic yeast].

The classification of pathogenic yeast, which is one of the most common reasons of opportunistic infection in human body, will be useful for the epidemiological survey and clinical works. The genotypic polymorphism of intergenus, interspecies and intraspecies in 48 isolates, including Candida, Cryptococcus, Torulopsis, Trichosporon, Saccaromyces had been administered carefully with patterns amplified by RAPD (Randomly amplified polymorphic DNA) in 53 primers. The pologenetic affinities had been evaluated by similarity coefficients obtained from these profiles. The results indicated that there are significant difference among intergenus, interspecies and intraspecies in Candida and related yeast. The similarity coefficients among Candida and Crytococcus, Trichosporon were maintained about 80%. The similarity coefficients among interspecies of Candida ranged from 82%-87%, and ones of intraspecies of different Candida species were more than 90%. The genotypic typing of species except C. guilliermondii seems to be related to morphological classification.

Candida↗
PubMed1997

[Correlation between shape and direction of small articular surface in lower lumbar vertebrae and degeneration of intervertebral disc].

To assess the possible correlation between the shape and the direction of the small articular surface in the lower lumbar vertebrae and the degeneration of the intervertebral disc, we investigated with computed tomography (CT) and evaluated with statistics the small articular surface and the transverse interface-joint angle (TIFA) of the L4-5 and the L5-S1 in 152 cases who had normal or degenerative discs verified through CT, MRI or operation. The small articular surface was found arc in 69.1% of the L4-5 and in 23.0% of the L5-S1. The TIFA of the L4-5 was less than that of the L5-S1. There was no correlation between the ratio of degeneration of the intervertebral disc at the L4-5 and the TIFA of the L4-5 and the L5-S1, but the ratio of degeneration of the intervertebral disc at the L5-S1 had postive correlation with the TIFA of the L4-5, negative correlation with the TIFA of the L5-S1, and particular correlation with the TIFA of the L5-S1 and L4-5. These results suggest that the shape and direction of the lower lumbar facet joint are related to the lumbar degeneration of intervertebral disc and the causes of degeneration at the L4-5 disc differ from those at the L5-S1 disc in biomechanics.

Adolescent↗
PubMed1996

Cochlear integrity in rats with experimentally induced audiogenic seizure susceptibility.

While chronic susceptibility of rodents to audiogenic seizures (AGSs) is often accompanied by cochlear lesions, it has not been demonstrated whether cochlear hair cell losses are essential to pathogenesis in this epileptic disorder. An alternative possibility is that the neonatal timing of hearing losses is what unites various models of chronic AGS susceptibility. In the latter case, either transient or permanent hearing losses might induce susceptibility as long as they concur with a critical period of development. To address this issue, it was examined whether lesions were universally present in cochleas of adult rats after having been made susceptible to sound-triggered seizures by different types and severities of neonatal auditory trauma. Neonatal treatments included: (1) an 8 min exposure of rat pups to intense noise (125 dB SPL) on postnatal day (PND) 14; (2) injections of low doses of kanamycin (KM: 100 mg/kg) on PNDs 9-12; or (3) injections of high doses of KM (500 mg/kg) on PNDs 9-12. As adults, rats in all experimental groups, but not in sham-treated groups, exhibited sound-triggerable seizure responses. Nonetheless, this outcome did not depend on integrity of cochleas. Hair cells were rarely missing in the cochleas of noise-exposed, low-dosage KM-treated, or sham-treated rats. By contrast, all inner and outer hair cells were missing from the basal 75% of cochleas of adult rats which had been treated with high-dose KM on PNDs 9-12. Results indicate that cochlear lesions are not requisite for the induction or expression of AGS susceptibility. At the same time, however, significant hair cell losses do not necessarily preclude susceptibility. It appears that the neonatal timing rather than the permanence of hearing losses may be what engenders chronic AGS susceptibility.

Animals↗
PubMed1996

Factors influencing redox thermodynamics and electron self-exchange for the [Fe4S4] cluster in Chromatium vinosum high potential iron protein: the role of core aromatic residues in defining cluster redox chemistry.

The roles of aromatic core residues in regulating the reduction potential, the enthalpy and entropy of reduction, and the self-exchange rate constants for electron-transfer reactions for the prosthetic [Fe4S4]3+/2+ cluster of Chromatium vinosum high potential iron protein (HiPIP) have been addressed by a combination of site-directed mutagenesis, high field NMR (EXSY) experiments, and variable temperature spectrochemical redox titration measurements. Minimal changes are observed following nonconservative mutation of residues Tyr19, Phe48, and Phe66. Apparently these hydrophobic residues play only a minor role in defining the electronic properties of the cluster. These data support a model, first defined from results obtained on Tyr19 mutant HiPIP's [Agarwal, A., Li, D., & Cowan, J.A. (1995) Proc. Natl. Acad. Sci. U.S.A. 92, 9440-9444], in which the aromatic core restricts solvent accessibility and thereby stabilizes the oxidized [Fe4S4]3+ cluster.

Bacterial Proteins↗
PubMed1996

In vitro induction of benzo(a)pyrene diol epoxide-DNA adducts in peripheral lymphocytes as a susceptibility marker for human lung cancer.

Given the same exposure, DNA adduct profiles can be considered as a phenotypic marker for carcinogen metabolism and DNA repair, which may reflect individual susceptibility to chemical carcinogenesis. Based on this notion, we have established a straightforward assay that measures induced DNA adducts in peripheral lymphocytes exposed in vitro to a model carcinogen, benzo(a)pyrene diol epoxide (BPDE) by 32P-postlabeling. To test the hypothesis that the levels of induced DNA adducts are a predictor for cancer risk, we conducted a pilot study of 21 lung cancer patients and 41 healthy frequency-matched controls. We found that the peripheral lymphocytes of cancer patients tended to accumulate higher levels of BPDE-DNA adducts than controls did (mean +/- SE of relative adduct labeling x 10(7) value; 59.6 +/- 12.0 versus 39.4 +/- 6.1 for cases and controls, respectively; P = 0.09). Using the tertile relative adduct labeling value of controls (10 adducts/10(7) nucleotides) as the cutoff point, 18 of 21 cases and 23 of 41 controls distributed above this level (odds ratio, 4.7; 95% confidence interval, 1.2-18.5). In logistic regression analysis, the level of induced adduct was an independent risk factor (odds ratio, 6.4; 95% confidence interval, 1.3-29.4) after adjustment for the potential confounding factors, i.e., age, sex, ethnicity, and smoking. Stratified analyses showed that greater differences in DNA adduct levels induced by BPDE between cases and controls were observed in individuals younger than 65 years and in nonsmokers. Despite the small sample size, the significant association between the level of BPDE-induced DNA adducts and risk for lung cancer suggests that this assay is a promising method for further investigations.

7,8-Dihydro-7,8-dihydroxybenzo(a)pyrene 9,10-oxide↗
PubMed1996

The effects of alpha tocopherol supplementation on monocyte function. Decreased lipid oxidation, interleukin 1 beta secretion, and monocyte adhesion to endothelium.

Low levels of alpha tocopherol are related to a higher incidence of cardiovascular disease and increased intake appears to afford protection against cardiovascular disease. In addition to decreasing LDL oxidation, alpha tocopherol may exert intracellular effects on cells crucial in atherogenesis, such as monocytes. Hence, the aim of this study was to test the effect of alpha tocopherol supplementation on monocyte function relevant to atherogenesis. Monocyte function was assessed in 21 healthy subjects at baseline, after 8 wk of supplementation with d-alpha tocopherol (1,200 IU/d) and after a 6-wk washout phase. The release of reactive oxygen species (superoxide anion, hydrogen peroxide), lipid oxidation, release of the potentially atherogenic cytokine, interleukin 1 beta, and monocyte-endothelial adhesion were studied in the resting state and after activation of the monocytes with lipopolysaccharide at 0, 8, and 14 wk. There was a 2.5-fold increase in plasma lipid-standardized and monocyte alpha tocopherol levels in the supplemented phase. After alpha tocopherol supplementation, there were significant decreases in release of reactive oxygen species, lipid oxidation, IL-1 beta secretion, and monocyte-endothelial cell adhesion, both in resting and activated cells compared with baseline and washout phases. Studies with the protein kinase C inhibitor, Calphostin C, suggest that the inhibition of reactive oxygen species release and lipid oxidation is due to an inhibition of protein kinase C activity by alpha tocopherol. Thus, this study provides novel evidence for an intracellular effect of alpha tocopherol in monocytes that is antiatherogenic.

Adult↗
PubMed1996

The physical association of casein kinase 2 with nucleolin.

CK2 (formerly called casein kinase 2) is a ubiquitous messenger-independent serine/threonine protein kinase implicated in cell growth and proliferation. To investigate the regulation and functions of this enzyme, experiments were carried out to search for CK2-interacting proteins. The methods employed included an overlay technique, co-purification, co-immunoprecipitation, and the use of glutathione S-transferase (GST) CK2 fusion proteins. By the CK2 overlay technique, one protein of 110 kDa was found to bind to CK2 with very high affinity. The binding was inhibited by CK2 effectors such as heparin, polyarginine, and histone H1, but was not affected by the CK2 substrate, casein. Protein p110 was also detected by co-immunoprecipitation using anti-CK2 antiserum, suggesting an in vivo association of this protein with CK2. Co-purification of p110 with CK2 from Sf-9 cells that overexpressed CK2 was also observed through sequential chromatographic steps. Using GST fusion proteins of CK2, the CK2-p110 interaction was investigated further and was found to occur primarily through CK2 alpha or alpha' subunits, but not the beta subunit. Protein p110 was purified from 3T3 L1 mouse fibroblast cell lines using a GST-CK2 affinity resin. Amino acid sequence analysis of peptides obtained from the protein indicated that it is the nuclear protein, nucleolin. Furthermore, p110 was recognized by anti-nucleolin antiserum. At present, the physiological significance of the strong interaction between CK2 and nucleolin, an excellent substrate for the enzyme, is not clear. However, this association may be important for regulating rDNA transcription.

3T3 Cells↗
PubMed1996

Malignant conversion of chemically transformed normal human cells.

Two structurally unrelated chemicals, aflatoxin B1 and propane sultone, transformed human foreskin cells to a stage of anchorage-independent growth. Isolation from agar and repopulation in monolayer culture of these transformed cells was followed by transfection with a cDNA library, which resulted in cells that exhibited an altered epithelioid morphology. Chemically transformed/nontransfected cells and transfected normal cells did not undergo a significant morphological change. These epithelioid-appearing, transfected cells, when inoculated into nude mice, form progressively growing tumors. The tumors are histopathologically interpreted as carcinomas. All of the first generation tumors in the surrogate hosts exhibited characteristic rates of growth similar to those of transplants of spontaneous human tumors. In the second generation of tumor xenografts, the progressively growing tumors derived from the transfected cells exhibited a more rapid rate of growth. Southern analysis and reverse transcription PCR confirmed that a 1.3-kb genetic element was integrated into the genome and was actively being transcribed. Examination of the metaphase chromosomes in normal human cells revealed that the genetic element responsible for this conversion was located at site 31-32 of the q arm of chromosome 7. The DNA sequence of this 1.3-kb genetic element contains a coding region for 79 amino acids and a long 3'-untranslated region and appears to be identical to CATR1.3 isolated from tumors produced by methyl methanesulfonate-converted, nontransplantable human tumor cells.

Aflatoxin B1↗
PubMed1996

Combination gene therapy for oral cancer in a murine model.

Combination therapy involving adenovirus-mediated transfer of the genes for herpes thymidine kinase (tk) and murine interleukin 2 (mIL-2) was used to treat head and neck cancer in C3H/HeJ mice. Tumors were generated by transcutaneous injection of 5 X 10(5) murine squamous carcinoma cells into the floor of the mouth of these syngeneic mice. After 1 week, recombinant adenoviral vectors containing both therapeutic and control genes in various combinations were injected directly into the established tumors, and subsequently all mice were administered ganciclovir twice daily (25 mg/kg) for 6 days. Animals receiving either tk alone or tk + mIL-2 demonstrated significant tumor regression compared to mIL-2 alone or control vector-treated mice (P < 0.008). Mice receiving both tk + mIL-2, however, also demonstrated a significantly greater regression of tumors compared to those treated with tk alone (P<0.008), indicating a synergistic effect of the combination gene therapy. This synergism was confirmed in survival studies because tk + mIL-2 treated mice showed increased survivals (P=0.0002). Clinical and microscopic exam of regional surrounding tissues and distant organs showed no evidence of cytotoxicity for representative animals in each experimental group. These results suggest that combination tk and mIL-2 gene therapy may provide a powerful new modality for the treatment of head and neck cancer.

Adenoviridae↗
PubMed1996

The Ty1-copia group retrotransposons in Vicia species: copy number, sequence heterogeneity and chromosomal localisation.

We present an in-depth study of the Ty1-copia group of retrotransposons within the plant genus Vicia, which contains species with widely differing genome sizes. We have compared the numbers and sequence heterogeneities of these genetic elements in three diploid Vicia species chosen to represent large (V. faba, 1C = 13.3 pg), medium (V. melanops, 1C = 11.5 pg) and small (V. sativa, 1C = 2.3 pg) genomes within the genus. The copy numbers of the retrotransposons are all high but vary greatly, with V. faba containing approximately 10(6) copies, V. melanops about 1000 copies and V. sativa 5000 copies. The degree of sequence heterogeneity of Ty1-copia group elements correlates with their copy number within each genome, but neither heterogeneity nor copy number are related to the genome size of the host. In situ hybridization to metaphase chromosomes shows that the retrotransposons in V.faba are distributed throughout all chromosomes but are much less abundant in certain heterochromatic regions. These results are discussed in the context of plant retrotransposon evolution.

Amino Acid Sequence↗
PubMed1996

Aromatic DNA adducts in adjacent tissues of breast cancer patients: clues to breast cancer etiology.

The etiology of the majority of human breast cancers is unknown. Environmental factors have long been suspected to play a role, but no specific causative agent has been identified. If the hypothesis that environmental carcinogen exposure contributes to human breast cancer is true, carcinogen-DNA adducts would be expected to be present in human breast tissues. To address this possibility, aromatic DNA adducts were measured in 87 surgical specimens of normal human breast tissues from 87 breast cancer patients undergoing mastectomy using the nuclease P1-enhanced version of the 32P postlabeling assay. Breast tissue samples from 29 noncancer patients undergoing reduction mammoplasty served as controls. Whereas aromatic DNA adducts were detected in all tissue samples examined, the total adduct levels in cancer patients were significantly higher than that in noncancer controls [mean +/- SEM, 97.4 +/- 23.4/10(9) nucleotides (range, 3.8-1737.1) versus 18.1 +/- 11.6/10(9) nucleotides (range, 5.6-56.7), respectively; P < 0.01, t test and Mann-Whitney test]. This difference was not affected by the age distribution of the two groups. The typical smoking-related DNA adduct pattern (i.e., a diagonal radioactive zone) was observed in 29 of 87 tissues (17 of 17 current smokers, 5 of 8 former smokers, 4 of 52 nonsmokers, and 3 of 10 patients with unknown smoking status) and in 2 of 10 control tissues. It was of interest that a benzo(a)pyrene (BP)-like DNA adduct was observed in 36 normal adjacent breast tissues (41%), 27 of which were from nonsmokers. Levels of this BP-like adduct were extremely high (> 100/10(9) nucleotides) in 5 patients (4 nonsmokers and 1 smoker) and moderately high (> 10/10(9) nucleotides) in 13 other patients (8 nonsmokers and 5 smokers). One patient exhibited this adduct at a level of 1500/10(9) nucleotides, which is comparable to the highest level of total adducts reported in human tissues related to carcinogen exposure (e.g., cigarette smoking). In contrast, this adduct was absent (< 1/10(9) nucleotides) in all of the control tissues. Cochromatography and rechromatography analysis of DNA samples from human breast tissues and from MCF-7 cells treated with BP revealed that this adduct could be generated by BP exposure but is not the major BP 7,8-diol-9,10-epoxide-deoxyguanine adduct detected previously in animal tissues and human mammary epithelial cells. These findings support the hypothesis that environmental carcinogen exposure, in addition to cigarette smoking, may be associated with the etiology of human breast cancer.

Adult↗