Biomedical subjects

X Teng

Publications and source records attributed to X Teng.

11 recordsLinked to original sources

PubMed2006

RNA polymerase II transcription is required for human papillomavirus type 16 E7- and hydroxyurea-induced centriole overduplication.

Aberrant centrosome numbers are detected in virtually all human cancers where they can contribute to chromosomal instability by promoting mitotic spindle abnormalities. Despite their widespread occurrence, the molecular mechanisms that underlie centrosome amplification are only beginning to emerge. Here, we present evidence for a novel regulatory circuit involved in centrosome overduplication that centers on RNA polymerase II (pol II). We found that human papillomavirus type 16 E7 (HPV-16 E7)- and hydroxyurea (HU)-induced centriole overduplication are abrogated by alpha-amanitin, a potent and specific RNA pol II inhibitor. In contrast, normal centriole duplication proceeded undisturbed in alpha-amanitin-treated cells. Centriole overduplication was significantly reduced by siRNA-mediated knock down of CREB-binding protein (CBP), a transcriptional co-activator. We identified cyclin A2 as a key transcriptional target of RNA pol II during HU-induced centriole overduplication. Collectively, our results show that ongoing RNA pol II transcription is required for centriole overduplication whereas it may be dispensable for normal centriole duplication. Given that many chemotherapeutic agents function through inhibition of transcription, our results may help to develop strategies to target centrosome-mediated chromosomal instability for cancer therapy and prevention.

Amanitins↗

PubMed2001

An allyltitanium derived from acrolein 1,2-dicyclohexylethylene acetal and (eta(2)-propene)Ti(O-i-Pr)(2) as a chiral propionaldehyde homoenolate equivalent that reacts with imines with excellent stereoselectivity. An efficient and practical access to optically active gamma-amino carbonyl compounds.

A chiral allyltitanium compound 2, prepared in situ by the reaction of optically active acrolein 1,2-dicyclohexylethylene acetal (3) with (eta(2)-propene)Ti(O-i-Pr)(2) (1), reacts with a variety of acyclic and cyclic imines 4 in a regiospecific way to afford alpha-addition products 5 as a mixture of the E- and Z-isomers in good combined yield, where the former is predominant in a ratio of 92:8 to >95:5. The mixture of (E)- and (Z)-5 and pure (E)-5 which could be isolated in several cases were respectively converted to the corresponding beta-amino ester 6 to confirm the absolute configuration and enantiomeric purity. The ee of the newly formed asymmetric center of 5 is more than 78% for the mixture of (E)- and (Z)-5 and more than 96% for pure (E)-5. By taking advantage of the versatility of the vinyl ether moiety in 5, optically active gamma-amino aldehydes 8, gamma-amino aldehyde acetals 7 and 10, gamma-amino acids 9, beta-amino esters 6, and pyrrolidinoisoquinolines 12 were readily prepared. In the reaction of 2 with optically active alpha-silyloxyimine 4n, remarkable double stereodifferentiation was observed; thus, the reaction of 2 derived from (S,S)- or (R,R)-3 provided syn- and anti-5n in a ratio of 55:45 or 0:100, respectively. Meanwhile, the stereochemistry of the product in the reaction of 2 with beta-silyloxyimine 4o was controlled mainly by 2. Thus, the reaction of beta-silyloxyimine 14 with 2 derived from 1 and (R,R)-3 afforded gamma-silyloxyimine 15 with 92% diastereoselectivity, from which 4-amino-6-hydroxypentadecanal dimethyl acetal (13), a key intermediate for the synthesis of batzelladine D, was synthesized.

Journal Article↗

PubMed2001

Quantitative assay of telomerase activity in head and neck squamous cell carcinoma and other tissues.

OBJECTIVES: To confirm the applicability and use of a new technique to detect and quantify telomerase activity of specimens from head and neck malignant neoplasms and to explore whether the levels of telomerase activity can be a useful marker for cancer risk assessment in head and neck malignant neoplasms. DESIGN: Ninety-six specimens from 39 patients with head and neck malignant neoplasms were obtained. The specimens included 39 from patients with primary tumors (25 with head and neck squamous cell carcinoma and 14 with others), 10 from patients with neck metastases, 10 from patients with dysplasias, and 37 from patients with normal tissue. HeLa cell lines were used as positive control samples. MAIN OUTCOME MEASURE: The levels of telomerase activity were determined using a liquid scintillation counter. RESULTS: The new method has a high rate of outcome reproducibility. The intrabatch and extrabatch variations were 15.6% and 16.4%, respectively. The linear relationship was good between the telomerase activity and the value within 700 radioactive cpm (rcpm) to approximately 7000 rcpm. The levels of telomerase activity determined by radioactive count were more than 1000 rcpm in 42 of the 49 malignant specimens and much more than that in the normal tissues, with the exception of 3 specimens. The levels of telomerase activity in normal tissues were less than 1000 rcpm in every sample and less than that in the malignant neoplasm samples, with the exception of 1 specimen (P < .000). Higher levels of telomerase activity in 2 of 10 tissues from patients who had dysplasias were detected (2 specimens from patients who had severe dysplasia). The differences in the levels of telomerase activity between the head and neck squamous cell carcinomas and the other tumors were not statistically significant (P > .05). CONCLUSIONS: Detection of telomerase activity in head and neck malignant neoplasms can be a useful marker for the assessment of cancer. Telomerase reactivation may play an important role in tumorigenesis in head and neck squamous cell carcinoma. The quantification of telomerase activity may have clinical diagnostic value for head and neck malignant neoplasms.

Adult↗

PubMed2001

[Mutations of mitochondrial 12S rRNA gene in type 2 diabetes].

OBJECTIVE: To investigate mutations at points 1310, 1438 and 1442 of mitochondrial 12S rRNA gene in Chinese type 2 diabetes and screen for new mutations associated with type 2 diabetes in this area. METHODS: The mitochondrial DNAs (mtDNAs) of 86 patients with type 2 diabetes and those of 70 normal controls were analyzed using PCR-SSCP and PCR product direct sequencing technique. RESULTS: One patient was found with the mitochondrial DNA G --> A mutation at point 1438, and one with the G two head right arrow A mutation at point 1442, whereas none of the normal controls was found to have mutation at these two points. No C --> T mutation at nucleotide pair 1310 of the mitochondrial 12S rRNA gene was identified. CONCLUSION: The G --> A mutation at points 1438 and 1442 is likely to be associated with the development of type 2 diabetes; the occurrence of the C -->T mutation at point 1310 is probably rare in the blood cells, and the development of type 2 diabetes may be related to heterogeneity in mitochondrial genetic changes.

Adult↗

PubMed2000

A reverse nuclear factor-kappaB element in the rat type II nitric oxide synthase promoter mediates the induction by interleukin-1beta and interferon-gamma in rat aortic smooth muscle cells.

The rat type II nitric oxide synthase (iNOS) promoter contains two nuclear factor-kappaB (NF-kappaB)-binding sites, one upstream (-965 to -956 bp) and one downstream (-107 to -98 bp), which are important for iNOS induction. We have identified a third NF-kappaB site located at -901 to -892 bp whose sequence is identical to that of the upstream site but with the opposite orientation ("the reverse NF-kappaB site"). We hypothesized that the reverse NF-kappaB site, like the other two sites, is important for iNOS induction. With the use of a rat iNOS promoter fragment of -906 to -887 bp as probe, electrophoretic mobility shift assays were performed on nuclear proteins extracted from rat aortic smooth muscle cells (RASMCs) treated with interleukin-1beta (IL-1beta, 100 U/ml) +/- interferon-gamma (IFN-gamma, 250 U/ml) for 30 min. IL-1beta, but not IFN-gamma, induced a DNA-protein complex that was supershifted by either anti-NF-kappaB p50 or anti-NF-kappaB p65 antibody. The functionality of the reverse NF-kappaB site was evaluated by mutation experiments and transfection assays. The wild-type and mutated -1.4 kb rat iNOS promoter-luciferase constructs were transfected into RASMCs. Compared with the wild type, reverse-NF-kappaB site (-901 to -892 bp) deletion, substitution of T for C at -894 bp, and substitution TTT for CCC at -896 to -894 bp decreased the IL-1beta-induced promoter activity by 67% (p < 0.001), 45% (p < 0.001), and 56% (p < 0.001), respectively. These deletion/substitutions also decreased the IL-1beta- and IFN-gamma-induced promoter activity by 74% (p < 0.001), 53%(p < 0. 001), and 63% (p < 0.001), respectively. In conclusion, a p50 and p65 NF-kappaB heterodimer binds to a reverse-NF-kappaB site on the rat iNOS promoter and contributes to iNOS induction by IL-1beta and IFN-gamma in RASMCs.

Animals↗

PubMed2000

Non-NF-kappaB elements are required for full induction of the rat type II nitric oxide synthase in vascular smooth muscle cells.

We have investigated the role of the NF-kappaB binding sites and other promoter elements beyond NF-kappaB in iNOS induction in rat vascular smooth muscle cells (SMC). Rat aortic SMC transfected with iNOS promoter constructs with either mutation or deletion of the downstream NF-kappaB site exhibited about 50% reduction in promoter activity in response to a cytokine mixture, whereas either mutation or deletion of the upstream NF-kappaB site reduced promoter activity by 90%, suggesting that the latter site is the most important, and that co-existence of two NF-kappaB sites is necessary for iNOS induction. Nuclear NF-kappaB activity was robustly induced by TNF-alpha. However, TNF-alpha alone did not induce iNOS promoter activity, protein expression, or nitrite production, indicating that NF-kappaB activation alone is not sufficient for iNOS induction. The construct up to -890 bp, containing the downstream NF-kappaB site, exhibited little response to cytokines. The construct up to -1.0 kb, containing the two NF-kappaB sites exhibited only 22% of full promoter activity. The regions -1001 to -1368 bp and -2 to -2.5 kb contributed an additional 43 and 22% promoter activity, respectively. Internal deletion or reversal of the orientation of -1001 to -1368 bp in the full promoter resulted in 40% reduction in promoter activity. These data suggest that the co-existence of two NF-kappaB sites is essential for core promoter activity, but that full induction of the rat SMC iNOS gene requires other elements located between -1.0 to -1.37 and -2.0 to -2.5 kb of the promoter.

Animals↗

PubMed1999

[Effect of testosterone on spermatogenesis: dynamics of testosterone secretion in adult rat testis].

OBJECTIVE: To study the effect of testosterone on spermatogenesis. METHODS: Testosterone concentrations were measured in testicular interstitial fluid (IF), and serum sample from the testicular artery, testicular veins on the surface of the testis, and the peripheral venous, inferior vena cave and proximal spermatic veins in adult SD rats. The left and bilateral veins at the proximal end of the spermatic cord were ligated respectively. Testosterone concentrations and weight of the testis were measured, and the changes of the testicular morphology were studied 3 days and 21 days after ligation respectively. RESULTS: The testosterone concentrations were highest in IF. The serum testosterone concentrations were highest in the testicular veins on the surface of the testis. The serum testosterone concentrations in the proximal spermatic veins, the testicular artery, the peripheral venous and inferior vena cave were (42.503 +/- 12.749), (42.503 +/- 12.749), (5.598 +/- 3.649), (2.533 +/- 1.719) and (2.418 +/- 1.495) mg/L respectively. Three days after the proximal spermatic veins were ligated bilaterally, the weights of the testis and the serum testosterone concentrations declined markedly. The epithelium of the seminiferous tubules degenerated slightly and part of the structure was indistinct. Three days after the left proximal spermatic veins were ligated, the weights of the left testis, the testosterone concentrations in the left IF and in the serum of the left testicular artery declined distinctly except the serum testosterone concentration of the peripheral venous, inferior vena cave and those of the right testis. The epithelium of the seminiferous tubules in the left testis degenerated slightly and part of the structure was indistinct. It was restored 21 days after ligation. CONCLUSIONS: A "small circulation" (testis-the testicular veins-the spermatic veins-the spermatic artery-the testicular artery-testis) may exist. The results indicate that after ligation of the proximal spermatic veins, the reduction of the testosterone concentrations and changes of testicular morphology is temporary and may be recovered.

Animals↗

PubMed1998

Molecular cloning and analysis of the rat inducible nitric oxide synthase gene promoter in aortic smooth muscle cells.

We have cloned five DNA fragments (-0.32, -0.48, -1.7, -3.2, and -5.1 kb) of the 5'-flanking region of the rat inducible nitric oxide synthase (iNOS) gene from rat genomic DNA. The functional importance of the 5'-flanking region was determined by transient expression of iNOS promoter-luciferase constructs in cultures of rat aortic smooth muscle cells. The -0.48 kb construct, containing one nuclear factor kappaB (NF-kappaB) binding site, expressed basal promoter activity but showed only a 1.5- and 1.7-fold increase in luciferase activity in response to lipopolysaccharide (LPS) or a cytokine mixture, respectively. However, the -3.2 kb construct (containing a second NF-kappaB binding site) showed full promoter activity with a 24-fold increase in response to LPS or cytokine mixture. The -5.1 kb construct showed no further increase in luciferase activity, suggesting that the 1.9 kb upstream of -3.2 kb may not be important in rat iNOS regulation. Rat iNOS promoter induction did not appear to be transcriptionally regulated by NO since NOS inhibitors did not affect induction. These data are in marked contrast to the mouse iNOS promoter in which a DNA sequence as short as a -85 bp, containing one NF-kappaB site, confers 10-fold inducibility by LPS. The present findings demonstrate that the rat iNOS gene is transcriptionally regulated by cytokines and LPS, but, unlike the mouse gene, the downstream NF-kappaB site does not appear to be a key region in responses to cytokines and LPS. These data suggest that the regulation of the rat gene may require the coexistence of at least two NF-kappaB sites or other elements upstream of -0.48 kb of the 5'-flanking region.

Animals↗

PubMed1998

Characterization of the P25 silk gene and associated insertion elements in Galleria mellonella.

Insect silk genes attract attention by their precise territorial and developmental regulations and extremely high expression rates. Our present investigations demonstrated that the P25 silk gene of Galleria mellonella is down-regulated by ecdysteroid hormones. The gene was identified within 5217 nucleotides (nt) of two genomic clones. In contrast to other silk genes, Galleria P25 lacks the canonical TATA box. Transcription is initiated within a region of three nucleotides that lie at the end of a capsite initiator sequence ACAGT and about 90 nt downstream from a CAAT box. A stretch of 32 nt with a core sequence CTTTT was detected in the 5' region of Galleria P25 as well as in the presumptive regulatory regions of all other silk genes that are expressed in the posterior silk gland. However, consensus sequences reported for the regulatory regions of Bombyx silk genes are not obvious in Galleria P25. The coding sequence of this gene included 654 nt, is interrupted by 4 introns, and ends in position +3369; a potential polyadenylation signal starts at +4382. The gene contains 3 copies of a short interspersed nuclear element (SINE), which are located in the upstream region (-833 to -579) and in the first (+542 to +840) and second (+2259 to +2556) introns. The repeat, which was named Gm1, occurs in some other Galleria genes and exhibits homology to Bm1 SINE of the silkworm and to a similar element of a spider. Another insertion of at least 150 nt and with loosely defined borders is present in the 3' untranslated region (UTR) of Galleria P25. It includes a box (+3453 to +3552) of 99 nt that is tentatively called Lep1 because it was disclosed also in some other Lepidoptera. Lep1 seems to represent the core region of insertion elements that occur in the genomes of lepidopteran insects in various species specific and region specific modifications.

Amino Acid Sequence↗

PubMed1998

[The fluorescence properties of DaYaWan soil humic acid].

The fluorescence properties of humic acid derived from DaYaWan soil were analyzed using the conventional fluorescence and synchronous scan fluorescence spectroscopy. The results show that synchronous technique applied to the study of humic acid can reduce the fluorescence spectrum of a compound to a single sharp peak, and decrease the signal overlapping. In addition, the effects of various deltalambda, concentration and pH values on synchronous fluorescence spectroscopy were investigated in detail.

China↗

PubMed1997

A methodology for specifying PET VOI's using multimodality techniques.

Volume-of-interest (VOI) extraction for radionuclide and anatomical measurements requires correct identification and delineation of the anatomical feature being studied. We have developed a toolset for specifying three-dimensional (3-D) VOI's on a multislice positron emission tomography (PET) dataset. The software is particularly suited for specifying cerebral cortex VOI's which represent a particular gyrus or deep brain structure. A registered 3-D magnetic resonance image (MRI) dataset is used to provide high-resolution anatomical information, both as oblique two-dimensional (2-D) sections and as volume renderings of a segmented cortical surface. VOI's are specified indirectly in two dimensions by drawing a stack of 2-D regions on the MRI data. The regions are tiled together to form closed triangular mesh surface models, which are subsequently transformed into the observation space of the PET scanner. Quantification by this method allows calculation of radionuclide activity in the VOI's, as well as their statistical uncertainties and correlations. The methodology for this type of analysis and validation results are presented.

Brain↗