Biomedical subjects

H M Yang

Publications and source records attributed to H M Yang.

96 records · Page 6Linked to original sources

PubMedDate not supplied

Effect of silica inhalation on the pulmonary clearance of a bacterial pathogen in Fischer 344 rats.

Silica inhalation predisposes workers to bacterial infection and impairments in pulmonary defense function. In this study, we evaluated the effect of pre-exposure to silica on lung defense mechanisms by use of a rat pulmonary Listeria monocytogenes infection model. Male Fischer 344 rats were exposed by inhalation to filtered air or silica (15 mg/m3 x 6 h/day x 5 days/wk). After 21 or 59 days of silica exposure, the rats were inoculated intratracheally with 5 x 10(3) L. monocytogenes. At 0 (noninfected controls), 3, and 7 days after infection, the left lungs were removed, homogenized, and the number of viable L. monocytogenes was counted after an overnight culture at 37 degrees C. Bronchoalveolar lavage (BAL) was performed on the right lungs. Alveolar macrophages (AM) were collected, and the AM production of chemiluminescence (CL), an index of reactive oxygen species generation, was measured. The number of lavagable neutrophils (PMNs) and acellular BAL lactate dehydrogenase (LDH) activity were determined as indices of inflammation and injury, respectively. Pre-exposure to silica for 59 days caused substantial increases in PMN number and LDH activity compared with the air controls, whereas silica inhalation for both 21 and 59 days significantly enhanced the pulmonary clearance of L. monocytogenes compared with air controls. Dramatic elevations were also observed in zymosan- and phorbol myristate acetate (PMA)-stimulated CL production by lung phagocytes recovered from rats pre-exposed to silica for 59 days. These results demonstrate that short-term exposure to inhaled silica particles activates lung phagocytes, as evidenced by increases in reactive oxygen species. This up-regulation in the production of antimicrobial oxidants is likely responsible for the enhancement in pulmonary clearance of L. monocytogenes observed with short-term silica inhalation.

Administration, Inhalation↗

PubMedDate not supplied

Computer-assisted rheological evaluation of microsamples of mucus.

Dynamic viscoelasticity measurements are required in many studies on biological fluids and they can be performed by determining the corresponding strain when a sinusoidal shear stress is applied to a sample. In several circumstances the amount of fluid that can be obtained for analysis in physiological conditions does not exceed microliters. In this context, the microrheometer technique is a useful approach to determine the dynamic rheological profile of the samples. However, the manual calculation of the desired parameters is tedious and time-consuming. This paper describes a menu-oriented program in order to facilitate its use by non-experts. The comparison between manual and computer-aided calculations demonstrated that the program reduced the time of measurement, and reduced intra- and interobserver variations. The program was developed on an IBM compatible PC in Microsoft C 5.1, and tested in a blind study to check the advantages in terms of time and reproducibility of the system verified by the concordance of two independent observers (interobserver influence) in two different occasions (intraobserver influence).

Bronchi↗

PubMedDate not supplied

Esterified estrogen therapy in postmenopausal women. Relationships of bone marker changes and plasma estradiol to BMD changes: a two-year study.

OBJECTIVE: To determine the relationships among bone mineral density changes, bone marker changes, and plasma estrogens in postmenopausal women receiving estrogen replacement therapy. DESIGN: A total of 406 postmenopausal women received 1,000 mg calcium and continuous esterified estrogens (0.3 mg, 0.625 mg, or 1.25 mg) or placebo daily for up to 24 months. Bone mineral density and bone marker measurements were determined at 6-month intervals; plasma estrogens were measured in a subset after 12, 18, and 24 months. RESULTS: Esterified estrogens produced significant increases in bone mineral density (lumbar spine, hip) compared with baseline and placebo at 6, 12, 18, and 24 months. Bone markers decreased from baseline with all esterified estrogen doses relative to placebo. Bone marker changes at 6 months correlated negatively with bone mineral density changes at 24 months (correlation coefficient range = -0.122 to -0.439). The strongest correlation was noted for spine bone mineral density changes and serum osteocalcin. Mean plasma estrogen levels increased with esterified estrogen dose, and bone mineral density changes correlated positively with plasma estrogen levels. Positive bone mineral density changes were noted in treatment groups with plasma estradiol levels at and above 25 pg/mL. CONCLUSIONS: Esterified estrogens, at doses from 0.3 mg to 1.25 mg/day, unopposed by progestin, increase bone mineral density of the spine and hip in postmenopausal women. These bone mineral density changes correlated significantly with bone marker changes at 6 months and with plasma estrogens at 12, 18, or 24 months. Data variability minimizes the predictive value of the bone marker changes in monitoring individual therapy.

Absorptiometry, Photon↗

PubMedDate not supplied

Effects of diesel exhaust particles on the release of interleukin-1 and tumor necrosis factor-alpha from rat alveolar macrophages.

The effects of diesel exhaust particles (DEP) and their components (washed dust and methanol extracts) on the release of proinflammatory cytokines, interleukin-I (IL-1), and tumor necrosis factor-alpha (TNF-alpha) by alveolar macrophages (AM) were investigated. Rat AM were incubated with 0, 5, 10, 20, 50, or 100 micrograms/10(6) AM/mL of DEP, methanol-washed DEP, or equivalent concentrations of DEP methanol extracts at 37 degrees C for 24 h. AM-conditioned supernatants were collected and assayed for the activities of IL-1 and TNF-alpha. At high concentrations both DEP and DEP methanol extracts were shown to increase IL-I-like activity secreted by AM, whereas methanol-washed DEP had no effect. Neither DEP, methanol-washed DEP, nor DEP methanol extracts was found to stimulate the secretion of TNF-alpha. The effects of DEP on the release of IL-I and TNF-alpha by lipopolysaccharide (LPS)- or interferon-gamma (IFN-gamma)-primed AM were also studied. AM were preincubated with various concentrations of DEP for 2 h, then challenged with either 0.1 microgram/mL of LPS or 5 units/mL of IFN-gamma. DEP inhibited LPS-stimulated production of H-I and TNF-alpha. These inhibitory effects were attributed to the organic extracts of DEP. In contrast, stimulation of AM production of TNF-alpha by IFN-gamma was not affected by DEP exposure. In summary, evidence that DEP enhanced the production of IL-1 by AM in vitro suggests that this proinflammatory cytokine may play a role in the pulmonary response to DEP inhalation. The suppressive response of DEP-pretreated AM to LPS stimulation may be a contributing factor to the impairment of pulmonary defense system after prolonged DEP exposure.

Animals↗

PubMedDate not supplied

Abnormal transcripts of FHIT gene in Chinese brain tumors.

FHIT located at chromosome 3p14.2 was discovered and proposed as a candidate tumor suppressor gene in several cancers. To determine whether the FHIT gene at 3p14.2 is altered in Chinese brain tumors, we examined 13 brain tumors for deletions within FHIT locus. Evaluation of the FHIT gene in the panel of brain tumors led to a comprehensive mutation analysis. The complete sequence of the FHIT gene was determined and deletions between exon 5-8 were found in all 13 cases. In addition, single point mutation of amino acid from two glioblastoma and one atypical meningioma cases and multiple amino acid mutations from one pituitary tumor were observed. Our results support the hypothesis that FHIT gene alteration is involved in tumorigenic development of human neoplasms.

Acid Anhydride Hydrolases↗

PubMedDate not supplied

Abnormal transcripts of FHIT gene in thyroid cancer.

Abnormalities of the FHIT gene were found in many carcinoma cell lines and human tumors as reported which suggest an etiological function in tumorigenesis. To investigate whether the FHIT gene is a target of thyroid tumor specific 3p alterations, we screened the FHIT gene for alteration in thyroid tumors and found that the tumors exhibited aberrant FHIT gene expression. The complete sequence of the FHIT gene in seven cases was determined and deletions between exon 2-9 in different regions were found. Goiter samples as control had normal FHIT transcripts while both normal and aberrant transcripts of FHIT were found not only in the tumor samples but also in the adjacent non-tumorous portion of the thyroid tumor. Our results support the hypothesis that FHIT gene alteration is involved in tumorigenetic development of human neoplasms in thyroid glands.

Acid Anhydride Hydrolases↗