Biomedical subjects

Rong Shi

Publications and source records attributed to Rong Shi.

41 records · Page 3Linked to original sources

PubMed2002

Pseudo-symmetry of C19 steroids, alternative binding orientations, and multispecificity in human estrogenic 17beta-hydroxysteroid dehydrogenase.

Steroids are implicated in many physiological processes, such as reproduction, aging, metabolism, and cancer. To understand the molecular basis for steroid recognition and discrimination, we studied the human estrogenic 17beta-hydroxysteroid dehydrogenase (17beta-HSD1) responsible for the last step in the bioactivation of all estrogens. Here we report the first observation of the conversion of dihydrotestosterone (DHT) into 3beta,17beta-androstanediol (3beta-diol) by 17beta-HSD1, an estrogenic enzyme studied for more than half a century. Kinetic observations demonstrate that both the 3beta-reduction of DHT into 3beta-diol (kcat = 0.040 s(-1)1; Km = 32 +/- 9 microM) and the 17beta-oxidation of DHT into androstandione (A-dione) (kcat = 0.19 s(-1); Km = 26 +/-6 microM) are catalyzed by 17beta-HSD1 via alternative binding orientation of the steroid. The reduction of DHT was also observed in intact cells by using HEK-293 cells stably transformed with 17beta-HSD1. The high-resolution structure of a 17beta-HSD1-C19-steroid (testosterone) complex solved at 1.54 A demonstrates that the steroid is reversibly oriented in the active site, which strongly supports the existence of alternative binding mode. Such a phenomenon can be explained by the pseudo-symmetric structure of C19-steroids. Our results confirm the role of the Leu149 residue in C18/C19-steroid discrimination and suggest a possible mechanism of 17beta-HSD1 in the modulation of DHT levels in tissues, such as the breast, where both the enzyme and DHT are present.

17-Hydroxysteroid Dehydrogenases↗

PubMed2002

[Analysis with DNA chips of the changes of gene expressions in K562 cells in response to As2O3 treatment].

OBJECTIVE: To investigate differential gene expression in apoptotic cells induced by As(2)O(3), and identify novel apoptosis-related genes. METHOD: Apoptosis of K562 cells cultured in RPMI 1640 medium supplemented with 10 % calf serum was induced by As(2)O(3). Total RNA of the apoptotic and normal cells were then extracted, purified and subject to reverse transcription into first-strand cDNA, labeled with Cy3/Cy5. Placenta DNA microarrays containing 348 DNA fragments were used to analyze the changes in gene expressions in the cells treated with As(2)O(3). RESULT: Eleven differentially expressed genes were identified in the apoptotic cells in comparison with the normal cells, 3 of which were associated with apoptosis, while the others were related to cell growth and proliferation. CONCLUSION: The placenta DNA microarrays we constructed may well apply to the analysis of the differentially expressed genes.

Antineoplastic Agents↗

PubMed2002

[Effect of probe purification on the reutilization of gene chip].

OBJECTIVE: To investigate the effect of probe purity on the reutilization of gene chips. METHODS: Purified and unpurified probes were respectively hybridized with the gene chip and after being scanned with Scanarry lite, a laser scanning device, the gene chip was treated with stripping solution to wash off the probes. After another round of scanning under the same condition to obtain the images, the gene chip was recycled for another hybridization. RESULTS: Hybridization of unpurified probes resulted in high background noise and obscure positive signals, which were present even after wash with stripping solution for 4 times. Hybridization using purified probes, in contrast, presented low background noise that was completely eliminated after the gene chip was washed twice before it was used again. CONCLUSION: The purity of probes is of great importance to the recycling of the gene chips, and hybridization with unpurified probes renders the chips impossible for reutilization.

DNA, Complementary↗

PubMed2002

[Application of Agilent 2100 Bioanalyzer in the study of differential gene expression].

OBJECTIVE: To study the application of Agilent 2100 Bioanalyzer in the study of gene differential expression. METHODS: The total RNAs were extracted and purified from Saccharomyces cerevisiae to synthesize double-stranded cDNAs by reverse transcription. Restriction display-PCR was employed to obtain the cDNA fragments, which were examined by Agilent 2100 Bioanalyzer and agarose gel electrophoresis. RESULTS: The analysis showed that Agilent 2100 Bioanalyzer was more sensitive and faster to isolate and display the differentially expressed genes, providing at the same time accurate quantitative information for each fragment in the DNA sample. CONCLUSION: Agilent 2100 Bioanalyzer can be instrumental for the study of differential gene expression.

DNA, Complementary↗

PubMedDate not supplied

Measurement of trabecular bone mineral density in the thoracic spine using cardiac gated quantitative computed tomography.

OBJECTIVES: To develop a method and evaluate the performance of thoracic bone mineral density (BMD) measurement using cardiac gated quantitative computed tomography (QCT). METHODS: A total of 762 participants (57% female) with a mean age of 61 years had a CT examination of the heart using prospective cardiac gating. A subset of 443 participants had replicate CT examinations of the heart. Another, nonindependent subset of 464 participants had CT examination of the abdomen. A QCT calibration phantom was included in all scans. Trabecular BMD was measured in the thoracic (T6-T11) and lumbar (T11-L4) spine. Tests of calibration and refinement and simple correlations between replicate thoracic BMD measurements and between thoracic and lumbar BMD measurements were calculated. RESULTS: There was high correlation between replicated thoracic BMD measurements in men (r = 0.995, P < 0.0001) and in women (r = 0.995, P < 0.0001). There was high correlation between thoracic and lumbar BMD in men (r = 0.90, P < 0.0001) and in women (r = 0.94, P < 0.0001). The mean BMD was higher in the thoracic spine than the lumbar spine in men (137.58 mg/cm3 vs. 126.94 mg/cm3, P < 0.0001) and in women (152.07 mg/cm3 vs. 133.44 mg/cm3, P < 0.0001). In both genders, thoracic and lumbar BMD was inversely associated with age (all P < 0.05). CONCLUSIONS: Cardiac gated CT, primarily intended for measurement of coronary vascular calcium, can be used to measure thoracic BMD with high precision. Thoracic BMD measurements using this method are highly correlated with QCT measurements in the lumbar spine.

Adult↗