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Biomedical subjects

L C Chen

Publications and source records attributed to L C Chen.

At least 163 records · Page 9Linked to original sources
PubMed1990

Effect of dietary vitamin E on the development of altered hepatic foci and hepatic tumors induced by the peroxisome proliferator ciprofibrate.

The purpose of this study was to determine the effect of the dietary antioxidant vitamin E on hepatocarcinogenesis by peroxisome proliferators which, it is hypothesized, induce tumors by increased production of hydrogen peroxide or other oxygen radicals. Rats were fed diets containing the peroxisome proliferator ciprofibrate and one of three concentrations (10, 50, or 500 ppm) of alpha-tocopheryl acetate for 6 months or 21 months. The incidence of hepatic tumors and the number and volume of gamma-glutamyl-transpeptidase-positive, ATPase-negative, glucose-6-phosphatase-negative, and glucose-6-phosphatase-positive foci were quantified. No tumors or altered hepatic foci were seen at 6 months, but at 21 months the incidence of hepatic tumors and the number and volume of altered hepatic foci were increased in rats fed higher levels of vitamin E. Indices of oxidative damage--concentrations of malonaldehyde, conjugated dienes, and lipid-soluble fluorescence products--were not affected or were lower in rats fed higher amounts of vitamin E; the enhancing effect of vitamin E on the development of altered hepatic foci and hepatic tumors, therefore, was not related to the induction of cellular oxidative damage. Hepatic peroxisomal fatty acid beta-oxidation and vitamin C concentrations were not affected by vitamin E, whereas the glutathione concentration was decreased in rats fed higher amounts of vitamin E. This study shows that increasing the vitamin E content of the diet enhances ciprofibrate-induced hepatocarcinogenesis, but the mechanism of this effect is unclear.

Adenosine Triphosphatases↗
PubMed1990

Effect of the peroxisome proliferator perfluorodecanoic acid on growth and lipid metabolism in Sprague Dawley rats fed three dietary levels of selenium.

The possible interrelationships between the effects of dietary selenium and perfluorodecanoic acid (PFDA) on growth and lipid metabolism were studied in the male Sprague Dawley rat. Rats were divided into groups and placed on diets containing three levels of selenium (0.04, 0.2, and 1.0 ppm as sodium selenite). Two weeks later, half the rats in each group received a single 35 mg/kg IP injection of PFDA in corn oil, while their pair-fed companion received only vehicle. Rats injected with PFDA stopped gaining weight, and weighed less than pair-fed controls, despite equal food intakes. Two weeks following PFDA administration the rats were killed and plasma cholesterol and triglycerides, and liver peroxisomal enzyme activities were quantified. In contrast to other peroxisome proliferators, PFDA increased plasma triglycerides while decreasing plasma cholesterol. The rate of peroxisomal fatty acid beta-oxidation was decreased, even though the activity of fatty acyl-CoA oxidase, the first enzyme in the peroxisomal fatty acid beta-oxidation pathway, was increased. Dietary selenium, other than increasing the liver to body weight ratio, did not alter growth or lipid metabolism. This study demonstrates, for the first time, the existence of a "non-hypotriglyceridemic" peroxisome proliferator - PFDA.

Animals↗
PubMed1990

Comparative potency of inhaled acidic sulfates: speciation and the role of hydrogen ion.

Inhaled acidic sulfate aerosols affect various aspects of lung function, presumably by delivery of hydrogen ion (H+) to target sites. Recent evidence suggests that the relationship between response and H+ content of the exposure atmosphere may depend upon the specific sulfate species with which the H+ is associated. This study examined comparatively the effects of exposure to the two main ambient acidic sulfates, sulfuric acid (H2SO4) and ammonium bisulfate (NH4HSO4), using the phagocytic activity of alveolar macrophages as the endpoint. Rabbits were exposed to 250-2000 micrograms/m3 H2SO4 (as SO4(-2)) and 500-4000 micrograms/m3 NH4HSO4 (as SO4(-2)) for 1 hr/day for 5 days; bronchopulmonary lavage was then performed for recovery of free lung cells. Phagocytosis, measured by uptake of opsonized latex spheres in vitro, was altered by exposure to H2SO4 at concentrations greater than or equal to 500 micrograms/m3 and to NH4HSO4 at greater than or equal to 2000 micrograms/m3. Assessment of results in terms of the calculated hydrogen ion concentration in the exposure atmosphere showed that identical levels of H+ produced different degrees of response depending upon whether exposure was to H2SO4 or NH4HSO4. On the other hand, macrophages incubated in acidic environments in vitro responded similarly regardless of whether H2SO4 or NH4HSO4 was used to adjust the pH. Possible reasons for the difference in response observed in vivo and in vitro are discussed. Speciation of ambient acidic sulfate aerosols may be needed in atmospheric monitoring so as to assess the presence of H+ posing the greatest biologic hazard following inhalation exposure.

Aerosols↗
PubMed1990

Pulmonary effects of ultrafine coal fly ash inhaled by guinea pigs.

Guinea pigs were exposed to ultrafine coal fly ash produced in a laboratory furnace. The average mass median aerodynamic diameter and the average mass concentration of Illinois no. 6 fly ash produced in all exposure conditions were 0.21 microns and 5.8 mg/m3, respectively. In guinea pigs exposed to Illinois no. 6 fly ash, total lung capacity (TLC), vital capacity (VC), and diffusing capacity for carbon monoxide (DLco) were significantly reduced below the control values immediately, 2 h, and 8 h postexposure. The diffusing capacity was still 10% below the control 96 h after exposure. The total sulfate in the Illinois no. 6 fly ash as determined using ion chromatography is 1105 +/- 120 micrograms/m3. Animals exposed to the Montana lignite fly ash at comparable concentration and particle size did not show alteration in diffusing capacity. The data suggest that part of the sulfate present in the fly ash of Illinois no. 6 could be in the form of sulfuric acid and is responsible for the adverse effects observed in the exposed animals. The sulfuric acid in the fly ash of Montana lignite is neutralized by its high alkali content and produces no change in lung functions.

Administration, Inhalation↗
PubMed1990

Modulation of selenium-dependent glutathione peroxidase by perfluorodecanoic acid in rats: effect of dietary selenium.

Forty-eight male Sprague-Dawley rats fed a diet containing 0.4, 0.2 or 1.0 mg of selenium (Se)/kg of diet were injected with a single dose (35 mg/kg) of perfluorodecanoic acid (PFDA) in corn oil and killed 2 wk later. Control animals were pair-fed and treated with an equal volume of vehicle. PFDA treatment significantly increased Se-dependent glutathione peroxidase (Se-GSHPx) activity in liver cytosol of rats fed the 0.04 mg of Se/kg of diet but not in rats fed the other diets. The increase in liver cytosolic Se-GSHPx activity in rats fed 0.04 mg of Se/kg of diet paralleled increases in Se content and serum Se-GSHPx activity. Determination of Se-GSHPx by an enzyme-linked immunosorbent assay showed that PFDA caused a decrease in Se-GSHPx protein in rats fed 0.2 or 1.0 mg of Se/kg of diet but not in rats fed 0.04 mg of Se/kg of diet. Further analysis revealed that the ratio of Se-GSHPx activity to antibody-reactive protein was increased by PFDA in all three groups. The in vitro addition of PFDA directly to the assay mixture for Se-GSHPx activity did not produce any effect. Reduced glutathione was significantly increased by PFDA treatment in all three groups. These data show that PFDA affects the Se content, Se-GSHPx activity and Se-GSHPx protein in rat liver and that the effect is dependent on the dietary/hepatic Se level.

Animals↗
PubMed1990

Defining undernutrition for public health purposes in the United States.

Lack of consistency among definitions of undernutrition used for different public health purposes in the United States hinders an effective diagnosis of the problem and the design of interventions to prevent and treat undernutrition. No single-case definition of undernutrition is appropriate for all purposes. These purposes include surveillance of the prevalence of undernutrition in the population, epidemiological research on risk factors and consequences of undernutrition within population subgroups and communities, and screening, monitoring and evaluation of nutritional programs. We recommend that a cut-off of -2.0 SD (2.3 percentile) for weight-for-age, height-for-age, and weight-for-height on National Center for Health Statistics (NCHS) reference growth charts be used to estimate and monitor the prevalence of undernutrition in the United States, in accordance with guidelines of the World Health Organization. Epidemiological research on population-based risk factors for undernutrition and its functional consequences is required to identify the appropriate nutritional indicator and cut-off for screening and monitoring and evaluation of interventions.

Anthropometry↗
PubMed1990

Selenium and glutathione peroxidase levels in sickle cell anemia.

Levels of plasma selenium (Se) and glutathione peroxidase were measured in 20 sickle cell anemia (SCA) patients not in crisis and in 14 nonanemic control subjects. The results show that the levels of Se and glutathione peroxidase were significantly (p less than 0.005) lower than those of controls in both plasma and whole blood. These data are consistent with the previous reports that there is increased oxidative stress in SCA. Low blood Se levels and glutathione peroxidase activity observed in this research suggest that a weakened antioxidant potential may be associated with SCA patients. The low Se status in SCA patients may also affect the phenotypic expression of these patients.

Adult↗
PubMed1990

[The correlating factors affecting nursing personnel resignation in an university hospital].

Demographic characteristics of 1080 university hospital nursing personnel were studied from January 1979 to December 1987. These characteristics included age, marital status, number of children and educational background. Among them, 457 nurses have resigned, while others remain in service. We evaluated the correlations between resignation and various demographic characteristics and the reasons for resignation. This would provide valuable references for nursing recruitment and hospital administration. Our analysis revealed that the reasons for resignation are in the following order: Transfer to governmental hospital, advanced study, marriage, change of occupation, transfer to teaching, personal problems, medical corps to Saudi-Arabia, family responsibilities, and relocation to other cities. Regarding to demographic characteristics, both educational background and marital status affected the reasons for resignation. The average length of service time for nurses who resigned was 30.0 +/- 29.59 months. There are significant differences among the age, marital status, number of children and educational background. The nurses between the age of 21 and 30 years old, (79%) had the highest rate of resignation (45.64%). Those below the age of 20 had the shortest service time, while those above 30 years old had the longest service time. The married nurses also had a longer service time than the single ones. Those who had children had a longer service time compared to those without children. In view of their educational background, those with a bachelor degree had the shortest service time (16.8 +/- 10.3 months) and the highest rate of resignation (71.1%). Our analysis indicates that professional license and location of residence also affected the reasons for resignation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Loss of heterozygosity on chromosome 1q in human breast cancer.

Cytogenetic markers involving the long arm of chromosome 1 are the most frequently observed karyotypic changes seen in breast cancer. Based on cytogenetic data, we have used polymorphic DNA markers to search for allelic losses at this chromosome region among 48 breast carcinomas. For SPTA1, allelic losses were seen in 6 of 26 (23%) informative carcinomas, while 3 of 13 (23%) and 5 of 19 (26%) informative patients showed losses at AT3 and D1S53, respectively. The background frequency of allelic loss was obtained from data using 3 other loci on the 1q arm and 2 on the p arm of chromosome 1. With these markers, only 6 of 62 informative patients (8%) showed an allelic loss, with the range being 0-13%. The allelic losses seen on 1q, which were found in 9 carcinomas, comprised an overlapping set; the common region deleted was approximately 26 centimorgans on the q arm of chromosome 1 (bands q23-32 between AT3 and D1S53). These results suggest that inactivation of a gene(s) located on 1q23-32 might contribute to the genesis of breast cancer.

Alleles↗
PubMed1989

Effects of sulfur oxides on eicosanoids.

Ultrafine metal oxides and SO2 react during coal combustion or smelting operations to form primary emissions coated with an acidic SOx layer. Ongoing work in this laboratory has examined the effects of sulfur oxides on pulmonary functions of guinea pigs. We have previously reported that 20 micrograms/m3 acidic sulfur oxide as a surface layer on ultrafine ZnO particles decreases lung volumes, decreases carbon monoxide diffusing capacity, and causes lung inflammation in guinea pigs after 4 daily 3-h exposures. It also produces bronchial hypersensitivity following a single 1-h exposure. The importance of this surface layer is demonstrated by our observation that 200 micrograms/m3 of sulfuric acid droplets of equivalent size are needed to produce the same degree of hypersensitivity. This study characterized the concentration-dependent effects of in vivo exposures to sulfur oxides on arachidonic acid metabolism in the guinea pig lung, and investigated the time course and the relation between eicosanoid composition and pulmonary functions. We focused specifically on four cyclooxygenase metabolites of arachidonic acid, that is, prostaglandins (PG) E1, F2 alpha, 6-keto prostaglandin F1 alpha, and thromboxane (Tx) B2, and two groups of sulfidopeptide leukotrienes (C4, D4, E4, and F4). Guinea pigs were exposed to ultrafine ZnO aerosol (count median diameter = 0.05 microns, sigma g = 1.80) with a layer of acidic sulfur oxide on the surface of the particles. Lung lavage was collected after exposures, and the levels of arachidonic acid metabolites were determined using radioimmunoassay (RIA). Concentration-dependent promotion of PGF2 alpha and concentration-dependent suppression of LtB4 were observed. The increased PGF2 alpha was associated with depressed vital capacity and diffusing capacity of the lungs measured in guinea pigs exposed to the same atmosphere described in a previous study. There is no causal relationship between the levels of other arachidonic acid metabolites and the pulmonary functional changes after exposures to these aerosols.

Animals↗
PubMed1989

Furnace-generated acid aerosols: speciation and pulmonary effects.

Guinea pigs were exposed to ultrafine aerosols (less than 0.1 micron) of zinc oxide with a surface layer of sulfuric acid. These acid-coated aerosols are typical of primary emissions from smelters and coal combustors. Repeated daily 3-hr exposures for 5 days produce decrements in lung volumes and pulmonary diffusing capacity and elevations of lung weight/body weight ratio, protein, and number of neutrophils in pulmonary lavage fluid at concentrations of 20 micrograms/m3. A single 1-hr exposure to 20 micrograms/m3 causes increased bronchial reactivity. Higher concentrations of conventionally generated sulfuric acid mist are required to produce responses of similar magnitude.

Acid Rain↗
PubMed1989

Enteric group 17 in clinical isolates.

The Enteric Group 17, a new group of Enterobacteriaceae, has been classified (by the Centers for Disease Control, Atlanta, Georgia, U.S.A.) based on its positive methyl-red test as well as its negative response to Voges-Proskauer, motility, rhamnose and melibiose fermentation tests. The isolation rate of Enteric Group 17 among 500 clinical isolates of Enterobacteriaceae in Taiwan is 1.8% (9/500). This finding recommends that Taiwan's hospital laboratories should pay particular attention to the possible presence of this bacteria when an isolate has reactions similar to that of Enterobacter cloacae or other members of the Enterobacter species.

Azo Compounds↗
PubMed1988

Copper oxide aerosol: generation and characterization.

Effluent gases from high temperature systems such as fossil fuel combustion and pyrometallurgical processes contain inorganic material which has the potential to interact with sulfur dioxide (SO2) on the surface of particles to form an irritant aerosol. The submicron fraction of this inorganic material is especially important as the fine particles may penetrate deep into the lung and cause serious health effects. A laboratory furnace was designed to produce a submicrometer copper oxide aerosol to stimulate emissions from copper smelters and other pyrometallurgical operations. The ultimate aim of this research is to investigate the interaction of SO2 and the copper oxide aerosol at different temperatures and humidities in order to determine the reaction products and their potential health effects upon inhalation. The initial work, as presented in this paper, was to reproducibly generate a submicrometer copper oxide aerosol and to characterize it in terms of size, morphology and composition. Two experimental regimes were set up. One admitted filtered air, without water vapor, into the furnace, and the other admitted filtered air and water vapor. The size and morphology of the aerosols were determined using an electrical aerosol analyzer and transmission electron microscopy. The particles appear as chain aggregates with a count median diameter of 0.026 micron when no water vapor was added and 0.031 micron when water vapor was added into the furnace. Composition of the aerosol was determined using x-ray photoelectron spectroscopy. The aerosol, with or without water in the furnace, consists of a mixture of copper(I) oxide and copper(II) hydroxide.

Aerosols↗
PubMed1988

Pulmonary function of guinea pigs exposed to freshly generated ultrafine zinc oxide with and without spike concentrations.

Exposure of guinea pigs 3 hr/day for 5 consecutive days to freshly formed ultrafine zinc oxide (ZnO) (count median diameter: 0.05 micron; geometric standard deviation: 2.0) at a concentration of 7 mg/m3 produced a gradual decrease in total lung capacity and vital capacity over the course of the exposure period. The carbon monoxide (CO) diffusing capacity (DLCO) was not affected until the fourth day, when it dropped abruptly to 30% below control levels. Wet-lung weight/body weight ratios and wet-lung/dry-lung weight ratios increased, indicating the presence of edema. Exposures to 2.7 mg/m3 ZnO, using the same 3 hr/day, 5 day time frame, did not alter any parameters measured. In 2 experiments a single high peak of ZnO (25-34 mg/m3) occurred. In one experiment exposure was stopped, but pulmonary function measurements were made as scheduled; in the other case, exposures to ZnO were continued. In both, lung volumes were decreased abruptly and to a greater extent than when peaks were absent. Continued exposure caused greater decrements in total lung capacity (TLC) and vital capacity (VC) as well as decrements in functional residual capacity (FRC) and residual volume (RV) than were observed when exposure was stopped. Peak exposures reduced DLCO to 45%-60% below control. These values rose to 25%-30% below control with or without continued exposure. Airway resistance increased and compliance decreased following peak exposures. When exposure was stopped, these changes were reversible; with continued exposure they still were different from control levels on the fifth day.(ABSTRACT TRUNCATED AT 250 WORDS)

Airway Resistance↗
PubMed1988

Seasonal recurrence of transient hypothyroidism in a patient with autoimmune thyroiditis.

Two postpartum and 7 spontaneous episodes of transient hypothyroidism developed during 5 years of observation in a florist with autoimmune thyroiditis and seasonal allergic rhinitis. The spontaneous episodes recurred twice a year regularly in spring and in autumn, the seasons of her allergic rhinitis. In most of these episodes as well as in the postpartum ones, hypothyroidism was preceded by transient thyrotoxicosis. In addition to the similarity in the clinical course, the changes in antimicrosomal antibody titers in pregnancy-unrelated episodes were almost identical to those in postpartum episodes. Throughout the observation periods, she had supranormal serum total immunoglobulin (Ig) E concentrations and high antigen-specific Ig E levels for various pollen extracts such as cedar and ragweed. However, we failed to demonstrate a correlation between thyroid function and total or any antigen-specific Ig E level. The present findings suggest that the pregnancy-unrelated thyroid dysfunction in our patient developed as a result of silent thyroiditis and through similar immunological mechanisms to those in postpartum thyroiditis. And it is suspected, though unproved, that the seasonal recurrence of pregnancy-unrelated thyroiditis has some causal relation to her allergic disease.

Adult↗