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Biomedical subjects

A T Chen

Publications and source records attributed to A T Chen.

At least 19 recordsLinked to original sources
PubMed2001

Lung vagal afferent activity in rats with bleomycin-induced lung fibrosis.

Bleomycin treatment in rats results in pulmonary fibrosis that is characterized by a rapid shallow breathing pattern, a decrease in quasi-static lung compliance and a blunting of the Hering-Breuer Inflation Reflex. We examined the impulse activity of pulmonary vagal afferents in anesthetized, mechanically ventilated rats with bleomycin-induced lung fibrosis during the ventilator cycle and static lung inflations/deflations and following the injection of capsaicin into the right atrium. Bleomycin enhanced volume sensitivity of slowly adapting stretch receptors (SARs), while it blunted the sensitivity of these receptors to increasing transpulmonary pressure. Bleomycin treatment increased the inspiratory activity, while it decreased the expiratory activity of rapidly adapting stretch receptors (RARs). Pulmonary C-fiber impulse activity did not appear to be affected by bleomycin treatment. We conclude that the fibrosis-related shift in discharge profile and enhanced volume sensitivity of SARs combined with the increased inspiratory activity of RARs contributes to the observed rapid shallow breathing of bleomycin-induced lung fibrosis.

Adaptation, Physiological↗
PubMed2000

Effects of vagal perineural capsaicin treatment on vagal efferent and airway neurogenic responses in anesthetized rats.

The acute effect of vagal perineural capsaicin treatment (VPCT) on parasympathetic bradycardia and tracheal neurogenic protein extravasation was examined. In nine anesthetized male Wistar rats the effect of VPCT on the bradycardia induced by electrical stimulation of the vagus was examined. In 24 anesthetized male Wistar rats the effect of VPCT on the tracheal protein extravasation induced by the inhalation of capsaicin aerosols was also studied. VPCT did not alter the bradycardia induced by vagal stimulation or the tracheal protein extravasation induced by the inhalation of capsaicin aerosol. The results of these studies further demonstrate the selectivity of perineural capsaicin treatment on vagal sensory nonmyelinated fibers in the rat and indicate that it is a useful tool for examining the role of sensory vagal C-fibers in pulmonary and cardiovascular reflexes and in isolating C-fiber-mediated reflex responses from those mediated by the release of neuropeptides.

Action Potentials↗
PubMed1999

Effect of diet-ingested pirfenidone on pulmonary function, cardiovasculature and blood gas measurements in rats.

Pirfenidone is an antifibrotic drug that we have shown attenuates the increase in collagen buildup in hamsters exposed to bleomycin, in turn reducing pulmonary function and blood gas decrements seen in this model of interstitial pulmonary fibrosis. The systemic effects of pirfenidone ingestion, however, are unknown. We examined the effect of diet-ingested pirfenidone on pulmonary function, systemic and pulmonary cardiovasculature and blood gas measurements, breathing pattern and lung hydroxyproline content in rats fed either a control diet or a diet containing 0.5% pirfenidone. Residual volume was higher and expiratory reserve volume lower in the pirfenidone group, with no change in functional residual capacity. Tidal volume was also lower in the pirfenidone group, with no change in the overall level of ventilation. There was a trend toward a reduced hydroxyproline content and an increased lung compliance in the pirfenidone group. There were no differences in systemic or pulmonary pressures, cardiac output, stroke volume, heart rate, pH or blood gases between the two groups. These data indicate that pirfenidone has few systemic side-effects but may have a mild effect on the basal level of lung collagen content with resulting clinical changes in some pulmonary function measurements and changes in breathing pattern.

Animals↗
PubMed1989

Increased chromosome fragility as a consequence of blood folate levels, smoking status, and coffee consumption.

Chromosome fragility in 96 h, low-folate cultures was found to be associated with smoking status, coffee consumption, and blood folate level. The higher proportion of cells with chromosome aberrations in cigarette smokers was attributable to lower red cell folate levels in smokers compared with nonsmokers. There was a positive linear relationship between the average cups of coffee consumed per day and the proportion of cells with aberrations. This association was independent of the effects of smoking and red cell folate level. These data suggest that smoking history, coffee consumption, and red cell folate level are important considerations for the design and interpretation of fragile site studies in cancer cytogenetics.

Chromosome Aberrations↗
PubMed1989

Complete culture medium is better than low folate medium for detecting increased chromosome aberrations in smokers in 48-h lymphocyte cultures.

We compared chromosome breakage in parallel, 48-h lymphocyte cultures established from smokers and nonsmokers using minimal essential medium (MEM) and MEM without folate (MEM-FA). There was a statistically significant, higher frequency of aberrations for smokers than for nonsmokers in cells cultured in MEM, but not in those cultured in MEM-FA. Thus, these data support the recommendation of the World Health Organization (1985) that population monitoring studies for exposure assessment should not use a low folate medium.

Adult↗
PubMed1988

Increased sister chromatid exchange associated with smoking and coffee consumption.

Sister chromatid exchange (SCE) is a very sensitive cytogenetic assay for detecting exposure to chemical mutagens and carcinogens. One application of SCE is the monitoring of populations believed to be exposed to such agents. We have, however, relatively little knowledge about common lifestyle factors that may influence SCE and therefore complicate any study designed to examine the effects of exposure to genotoxins. In this study, we assessed the effect of cigarette smoking and coffee consumption on SCE. Smoking was associated with an increase of approximately 2 SCEs per cell and a decrease in cell proliferation. A positive linear relationship between SCE and coffee consumption was also observed. This effect was similar for smokers and nonsmokers. Additionally, the folic acid content of cell culture medium seemed to affect neither SCE nor cell proliferation.

Adult↗
PubMed1988

Effects of folate in culture medium on common fragile sites in lymphocyte chromosomes from normal and leukemic children.

The expression of common fragile sites at 69 bands was evaluated in 20 normal children and in 15 children with newly diagnosed acute leukemia using medium with folate (FA+) and without folate (FA-). As expected, the FA- medium significantly increased expression of aberrations in all study groups but the differences were larger for normal children than leukemic children. The major effect of the FA- medium was a generalized increase in aberration frequency over all sites rather than site-specific increases. A tendency toward clumping of aberrations within cells was exhibited in both media. Aberrations were seen at 81% (FA+) and 83% (FA-) of the 69 bands, with 4 sites - 3p14, 6p21, 9q13, and 17q23 - recorded in most of the study individuals. In addition, 12 sites not previously recorded as common or rare sites had significant levels of expression in at least one study group.

Acute Disease↗
PubMed1986

Folic acid and chromosome breakage. III. Types and frequencies of spontaneous chromosome aberrations in proliferating lymphocytes.

The types and frequencies of spontaneous chromosome aberrations were studied in human lymphocytes cultured for 96 h in minimal essential medium (MEM) or MEM without folic acid (MEM-FA). In both media, the most frequent aberrations were chromatid gaps, isochromatid gaps and chromatid breaks. Chromosome (isochromatid) breaks and dicentrics were seen less frequently. Neither of these less frequent aberrations was seen in 4000 cells from MEM, but both were seen in 4000 cells from MEM-FA.

Cells, Cultured↗
PubMed1986

Folic acid and chromosome breakage. IV. Variance estimates from longitudinal studies of normal individuals and their implications for sample size and power to detect differences between populations.

The frequency of chromosome aberrations was studied in minimal essential medium (MEM) with and without folic acid (FA) in lymphocytes of 4 normal individuals, each sampled 12 times over a 1-year period. The cells cultured without FA had significantly more breaks and gaps. In both media about 75% of aberrations were classified as gaps. Calculations based on variance estimates suggest that the use of medium without FA could enhance the statistical power to distinguish differences in proportions of chromosome breakage between groups in the same study.

Analysis of Variance↗
PubMed1985

Transformed T lymphocytes infected by a novel isolate of human T cell leukemia virus type II.

Human T cell leukemia virus type II (HTLV-II) has been isolated from a patient (Mo) with features of leukemic reticuloendotheliosis (LRE) and from a patient with acquired immunodeficiency syndrome (AIDS). We have obtained another isolate of HTLV-II from a patient (CM) with severe hemophilia A, pancytopenia, and a 14-year history of staphylococcal and candidal infections but no evidence of T cell leukemia/lymphoma, AIDS, or LRE. Fresh mononuclear cells and cultured lymphocytes from CM express retroviral antigens indistinguishable by molecular criteria from HTLV-IIMo. Leukocyte cultures from CM yield hyperdiploid (48,XY, +2, +19) continuous lymphoid lines; human fetal cord blood lymphocytes (CBL) are transformed by cocultivation with these CM cell cultures but retain normal cytogenetic constitution. Electron microscopic examination of the CM cultures and transformed CBL reveals budding of extracellular viral particles, intracellular tubuloreticular structures, and viral particles contained within intracellular vesicles. CM cell cultures and the transformed CBL do not require exogenous interleukin 2, have T cell cytochemical features and mature T helper phenotypes, and exhibit minimal T helper and profound T suppressor activity on pokeweed mitogen-stimulated differentiation of normal B cells. These characteristics, which are similar to those observed with the first HTLV-II isolate, may represent properties of all HTLV-II-infected T cells.

Adult↗
PubMed1984

Cytogenetic findings in persons living near the Love Canal.

Cytogenetic analyses were performed on peripheral blood from 46 present or past residents of the area surrounding Love Canal, a former dump site for chemical wastes in Niagara Falls, NY. Participants included 17 persons in whom cytogenetic analyses had been performed in 1980 and 29 persons who had been living in 1978 in seven homes that directly adjoined the canal and in which environmental tests showed elevated levels of chemicals spreading from the canal. Frequencies of chromosomal aberrations and of sister chromatid exchange (SCE) did not differ significantly from control levels. For all participants, cigarette smoking was associated with an increase in sister chromatid exchange frequency.

Chromosome Aberrations↗
PubMed1983

Love canal.

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Chromosome Aberrations↗
PubMed1983

Folic acid and chromosome breakage. I. Implications for genotoxicity studies.

Chromosome breakage is significantly lower in culture medium containing folic acid than in medium that does not. This effect is similar to that observed in studies of chromosome fragile sites and suggests that fragile sites and some types of chromosome breakage may share a common mechanism. It also suggests that high non-physiological levels of folic acid in many commonly used culture media may artifactually decrease chromosome breakage.

Cells, Cultured↗
PubMed1982

Autosomal mosaicism in amniotic fluid cells from a twin pregnancy.

Amniocentesis was performed on a 39-year-old gravida 4 woman because of maternal age. Ultrasonography demonstrated a twin pregnancy, and two amniotic fluid specimens were obtained under direct ultrasound guidance. All cells analyzed from the first specimen were 46,XX. In the second specimen, one colony in each of two flasks had trisomy 9; the remaining 3 colonies analyzed were 46,XX. The total cell count in the second specimen was 14 (24%) of 58 cells which were trisomic for chromosome 9. The parents elected to continue the pregnancy, which resulted in two live-born infants, a male and a female, both chromosomally normal. The most likely explanation for the amniotic fluid finding is that fluid from one sac was sampled twice and that trisomic cells from the amnion were obtained during the second tap.

Adult↗