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Biomedical subjects

L Yan

Publications and source records attributed to L Yan.

At least 271 records · Page 15Linked to original sources
PubMed1991

Effect of selenium compounds and thiols on human mammary tumor cells.

The effect on cell viability and growth rate of sodium selenite, selenocystine, sodium selenate, and selenomethionine at selenium concentrations of 6.25 and 12.5 uM was studied in vitro on cells of the human mammary tumor cell line HTB123/DU4475. Selenite and selenocystine affected both cell viability and growth rate of the tumor cells at these selenium concentrations. Selenite and selenocystine decreased intracellular glutathione concentrations, but did not affect tumor cell glutathione peroxidase activity. After six days of exposure to either selenate or selenomethionine, the viability of tumor cells remained stable, but cell growth, as measured by numbers of cells, was retarded. Neither selenate nor selenomethionine produced changes in concentrations of intracellular glutathione. The toxic effect of selenite on tumor cells was enhanced by addition of 0.25 mM glutathione to the growth medium. Preincubation of the tumor cells with 62.5 uM buthionine sulfoximine decreased cellular glutathione to 15% of controls at 24 h and enhanced the toxicity of selenite toward the tumor cells. Glutathione, 2-mercaptoethanol, and L-cysteine were all toxic to the tumor cells in a dose-dependent manner.

Aged↗
PubMed1991

Effect of dietary selenium and magnesium on human mammary tumor growth in athymic nude mice.

The effect of dietary selenium (Se) supplementation and low dietary magnesium (Mg) on growth of cells of the human mammary tumor cell line (HTB123/DU4475) and the tissue glutathione (GSH) content in female athymic nude mice was studied. Sixty three- to four-week-old female athymic nude mice were randomly divided into six dietary groups of 10 animals. The mice were fed a modified AIN-76A diet with two levels of Mg (100 and 665 mg/kg) and three levels of Se (0.04, 0.2, and 4.0 mg/kg). At the fourth week of dietary treatment, mice were subcutaneously inoculated with 2.5 x 10(6) viable tumor cells on the dorsal lumbar region and then fed their respective diets for another four weeks. Dietary Se supplementation had no significant effect on tumor growth or tissue GSH content. Low dietary Mg limited both tumor growth and tissue GSH synthesis but raised Mg and GSH levels in tumor tissues. The growth of mice fed the diet containing 100 mg/kg Mg and 4.0 mg/kg Se was significantly retarded. This study demonstrated that neither Se deficiency nor Se supplementation had any effect on mammary tumor growth or tissue GSH content in athymic nude mice. Low dietary Mg did retard tumor growth and inhibited GSH synthesis. Low dietary Mg also resulted in an apparent increase in Se toxicity in these animals.

Animals↗
PubMed1991

[An investigation of fluoride pollution caused by burning coal containing fluoride in Xiushan and Baojing].

This paper reports an investigation of contents of soluble fluoride in the environment and foods in Xiushan and Baojing. On the basis of measuring concentrations of soluble fluoride in drinking water, soil, coal, air, fly ash, maize, chilli, and other kinds of vegetables, it is first to expand the pathway of fluoride migrating from coal into human body is through pollution of air by fluoride contained in fly ash on burning of coal, and then via consumption of polluted maize by air. The significant correlation between both the concentrations of fluoride in maize and in fly ash is proved. It is suggested to select the concentration of fluoride in fly ash or in air as the quality index of indoor air and the control target to prevent fluorosis.

Air Pollutants↗
PubMed1990

[The role of hemorheologic changes in the pathogenesis of acute hemorrhagic necrotizing pancreatitis].

The hemorheologic alterations were studied in experimental acute hemorrhagic necrotizing pancreatitis (AHNP) which was induced by injection of 5% sodium taurocholate into the main pancreatic duct. The results showed that during the early stage of AHNP, all of hemorheologic parameters were significantly elevated, and continually increased at the rest intervals. The authors suggested that the blood viscosity and hematocrit increase, red blood cells tend to aggregate, and erythrocyte deformation decrease are the causation of pancreatic microcirculatory disturbances and promoting pancreatic progressive necrosis. After using low molecular dextran and Salvia miltiorrhizae, the hemorheologic alterations in AHNP were recovered, and the histologic observation improved. Our data indicate the hemorheologic disturbances is one of the key factors in the pathogenesis of AHNP.

Acute Disease↗
PubMed1990

[Epidemiological survey of endemic fluorosis in Xiou Shan and Bao Jing areas].

It may be affirmed that Mushan in Bao Jing county is a light fluorosis area and Yan Tian in Xiou Shan county is a middle fluorosis area with the help of following investigations: fluoride levels in inhalatable dust, food, drinking water, soil, coal, biological effects of fluoride on habitants and the burden of fluoride in the body of habitants. It is demonstrated that the cause of fluorosis is above areas is essentially the oral intake of excess fluoride through the foods, mainly maize, polluted by burning coal fly ash containing fluoride.

Air Pollution↗
PubMed1987

Improvement in sensitivity of fast atom bombardment mass spectrometry of amino acids by di-isopropylphosphorylation.

Positive ion fast atom bombardment mass spectrometric sensitivities of seven amino acids and the corresponding di-isopropylphosphorylated derivatives were carefully compared. Results showed that an improvement in sensitivity by factors of 4-29, mostly above 10, were achieved after the derivatization. The chemical noise derived from glycerol matrix was also greatly reduced by this derivatization.

Amino Acids↗
PubMed1987

An automated method for autoradiographic analysis of cultured Schwann cells.

A semi-automated analysis system based on video image analysis was developed to count labelled and unlabelled nuclei of Schwann cells which had been exposed to tritiated thymidine followed by processing for autoradiography. A Model 3000 Image Analysis system (Image Technology Corporation, Deer Park, NY) was used to acquire and process the images and provide quantitative measurements based on the distinctive size and shape of the Schwann cell nucleus. The maximum and minimum dimensions for the labelled and unlabelled nuclei were determined. These stored dimensional parameters were then compared with the dimensions of a given field of cell nuclei by the image analysis system. The counts from various fields were collected until a total of 1000 labelled and unlabelled nuclei had been analyzed. A labelling index (LI = ratio of labelled cells to total cells X 100) was then calculated and printed by the system. LIs of autoradiographs determined by automated analysis correlated well with those determined by visual cell counting. The principle of the image analysis program as described here is applicable to other systems for the measurement of LIs of a particular cell type in a mixed population. This automated process eliminates both the subjectivity and fatigue of visual counting and facilitates the rapid measurement of the LI of large numbers of autoradiographs with precision.

Animals↗
PubMedDate not supplied

Effect of selenite on cell surface fibronectin receptor.

Incubation of cells with selenite, under conditions in which there is no effect on cell viability, results in a decrease in the rate of their subsequent attachment to extracellular matrix proteins such as fibronectin (1). The attachment was inhibited by a pentapeptide containing the RGD sequence and by antibody against the cellular fibronectin receptor (alpha 5 beta 1 integrin), indicating that it is receptor-mediated. To investigate whether exposure to selenite has an effect on fibronectin receptors, we assayed for their presence on the cell surface by measuring the ability of cells to attach to a surface that had been coated with antibodies to the receptor. Brief exposure of cells to low concentrations of selenite resulted in a significant decrease in their ability to attach to monoclonal antibodies against the alpha 5 or beta 1 subunits of the fibronectin receptor, as well as to polyclonal antibodies against the complete receptor. This indicates that exposure to selenite results in a decrease in receptors that are present at the cell surface. Exposure of the cells to selenate, selenocystine or selenomethionine did not result in a significant decrease in cell surface receptors. Preincubation of the cells with selenite was required for the effect, indicating that selenite does not directly interfere with receptor structure or function.

Antibodies, Monoclonal↗
PubMedDate not supplied

Effects of air pollution on respiratory health of adults in three Chinese cities.

The authors examined potential associations between air-pollution exposures and respiratory symptoms and illnesses of 4,108 adults who resided in 4 districts of 3 large, distinct Chinese cities. Data on respiratory health outcomes and relevant risk factors for parents and children were obtained via standardized questionnaires in the winter of 1988. (The effects in children were described previously.) The yearly averages of ambient levels of total suspended particles in the 4 districts for the years 1985-1988 differed greatly. The authors constructed logistic-regression models to assess the respiratory health parameters of parents of the children. The results revealed significant and strong effects, by district, on prevalence rates of cough, phlegm, persistent cough and phlegm, and wheeze for both the mothers and the fathers. In addition, the odds ratios increased as ambient total suspended particle concentration increased across the 3 urban districts. Other local within-city risk factors, however, may have confounded the total suspended particles-effects association, especially for asthma prevalence. Findings for adults were similar to those found for their children. A strong adverse effect of active tobacco smoking on the fathers' respiratory health was observed. The children appeared to be more strongly affected by passive smoking exposure received in their homes than their mothers.

Adult↗
PubMedDate not supplied

Underdiagnosis of Chlamydia trachomatis infection. Diagnostic limitations in patients with low-level infection.

To determine limitations in commonly used methods for detection of Chlamydia trachomatis, 601 genitourinary specimens from patients in a sexually transmitted disease clinic were examined with quantitative cultures and by 2 different direct antigen tests, immunofluorescence (Micro Trak; Syva Company, Palo Alto, CA) and enzyme immunoassay (Chlamydiazyme; Abbott Laboratories, North Chicago, IL). Genital specimens were held no longer than 5 hours (at 4 degrees C) prior to inoculation for culture; 28% (168/601) were positive. To evaluate the effect of storage on culture efficacy, duplicate specimens were also stored at -70 degrees C and brought out subsequently for culture a second time. Only 32% (8/25) of specimens cultured within 5 hours and having less than 10 inclusions were positive on reculture, compared with 98% (49/50) positive for specimens with greater than or equal to 10 inclusions initially (P less than 0.001). Sensitivities of the two antigen tests were similar and taken together diminished significantly (P less than 0.001) as the number of organisms (inclusion forming units) in corresponding cultures decreased: 82% (51/62) sensitivity in cultures with greater than 100 inclusions; 50% (22/44) with 10-100 inclusions; and only 11% (6/53) with less than 10. Lack of urethral discharge in men with C. trachomatis infection (free of Neisseria gonorrhoeae) was associated with low numbers of inclusions (less than 10) and antigen tests failed in 68% (15/22) of these patients.

Antigens, Bacterial↗
PubMedDate not supplied

Phenotypic plasticity and terminal differentiation of the intercalated cell: the hensin pathway.

The intercalated cell of the collecting tubule exists in a spectrum of types. The alpha form secretes acid by an apical H(+) ATPase and a basolateral Cl:HCO(3) exchanger which is an alternatively spliced form of the red cell band 3 (kAE1), while the beta form secretes HCO(3) by having these transporters on the reverse membranes. In a clonal cell line of the beta form we found that seeding density causes this conversion. A new protein, termed hensin, was deposited in the extracellular matrix of high-density cells which on purification reversed the polarity of the transporters. Hensin also induced the expression of the microvillar protein, villin, and caused the appearance of the apical terminal web proteins, cytokeratin 19 and actin, all of which led to the development of an exuberant microvillar structure. In addition, hensin caused the beta cells to assume a columnar shape. All of these studies demonstrate that the conversion of polarity in the intercalated cell, at least in vitro, represents terminal differentiation and that hensin is the first protein in a new pathway that mediates this process. Hensin, DMBT1, CRP-ductin, and ebnerin are alternately spliced products from a single gene located on human chromosome 10q25-26, a region often deleted in several cancers, especially malignant gliomas. Hensin is expressed in many epithelial cell types, and it is possible that it plays a similarly important role in the differentiation of these epithelia as well.

Animals↗
PubMedDate not supplied

Epidemiological studies of nasopharyngeal cancer in the Guangzhou area, China. Preliminary report.

In the city of Guangzhou (Canton) and its surroundings nasopharyngeal cancer (NPC) constitutes about 32% of all cancer and is therefore the most common kind of cancer. Three types of etiological factors seem to be involved: 1) a hereditary factor, 2) Epstein-Barr virus, and 3) external factors in food and water. An epidemiological study has been started in the Guangzhou area with interviews of NPC cases, matching controls and mothers of the cases and controls concerning especially food and environmental factors and infections in childhood. The questions put to the controls and cases covered the last seven years and the age of ten, while those to the mothers covered the first three years of life and the age of ten for the controls and cases. Results are now available for 140 cases, 140 controls and the corresponding living mothers. They indicate that salted fish, particularly of Cantonese style, was consumed more by NPC cases than by controls and also had more frequently been given to weaning children in whom NPC later developed. Furthermore, salted vegetables and salted pork were consumed to a greater extent by NPC cases than by controls. Drinking of polluted water in childhood was more common among the NPC cases. Consumption of fresh fruit was more rare among the cases. Most of the NPC cases had a positive VCA-IgA titre.

China↗
PubMedDate not supplied

Fluorescence spectroscopic study of the interaction of saporin with phospholipid vesicles.

Saporin-S6 (SO-6) is a type-1 ribosome-inactivating protein purified from the seeds of Saponaria officinalis. The fluorescence characteristics of SO-6 were studied in the presence and absence of phospholipids. The interaction of SO-6 with DMPG or DMPC vesicles results in a decrease in the fluorescence emission intensity of tryptophan without any shift in the emission maximal wavelength. The results of fluorescence titration indicate that DMPG/SO-6 saturation molar ratio is 100: 1, but the binding of DMPC with SO-6 does not reach a saturating plot. A shielding of the tryptophan fluorescence from quenching by acrylamide on interaction with the phospholipids was observed, and this shielding was more pronounced in the presence of DMPG. The interaction of SO-6 with DMPG vesicles is stronger in the liquid-crystalline phase than in the gel phase. Extrinsic fluorescence studies indicated that the interaction of the protein with DMPG vesicles does not modify the phase transition temperature of the lipid, but decreases the amplitude of the change of fluorescence anisotropy associated with the co-operative melting of 1,6-diphenyl-1,3,5-hexatriene (DPH)-labelled vesicles. These results indicate that both electrostatic and hydrophobic components are involved in the SO-6-lipid vesicle interaction.

Acrylamide↗