Biomedical subjects

Di Wu

Publications and source records attributed to Di Wu.

116 records · Page 7Linked to original sources

PubMed2003

Genetic interactions between Pten and p53 in radiation-induced lymphoma development.

Genetic analysis of radiation-induced lymphomas from p53 heterozygous or null mice has revealed a high frequency of genetic alterations on mouse chromosome 19. Detailed microsatellite analysis of chromosome 19 deletions identified three independent regions of loss of heterozygosity, one of which was refined to a 0.3 Mb interval that contained the Pten tumor suppressor gene. More than 50% of radiation-induced tumors from p53+/- and p53-/- mice showed heterozygous loss of one Pten allele. In most cases, the remaining allele was wild type and expressed, suggesting that Pten is a haploinsufficient tumor suppressor gene for mouse lymphoma development. This conclusion was supported by the detection of specific intragenic deletions in Pten in tumors that retained one wild-type allele. Pten heterozygous mice were just as sensitive as p53+/- mice to induction of tumors by radiation, and surprisingly, the double p53+/-Pten+/-mice were equivalent to p53 null mice in radiation sensitivity. Despite the fact that Pten appears to be a haploinsufficient tumor suppressor gene, most tumors from both the single and double heterozygous mice had lost the remaining wild-type allele. The mechanism of loss in all cases involved the complete chromosome, suggesting that it is driven by other tumor suppressor genes on this chromosome. This sensitized screen therefore identified complementary roles for Pten and p53 pathways in suppression of tumor development induced by radiation exposure.

Animals↗

PubMed2003

The adsorption behavior of p-hydroxybenzoic acid on a silver-coated filter paper by surface enhanced Raman scattering.

On dried filter paper coated with silver nanoparticles, surface-enhanced Raman scattering (SERS) spectra of p-hydroxybenzoic acid (PHBA) were studied, and high-quality SERS spectra were obtained, indicating that the silver-coated filter paper is a highly SERS-active substrate. The analysis showed that the adsorption behavior of PHBA molecules on silver nanoparticles coated on filter paper was different from that in silver aqueous colloids. On the filter paper, it was found that the SERS spectra of PHBA changed with the proportion of PHBA molecules and silver nanoparticles, indicating that the adsorption behavior of PHBA molecules changed with the proportion. The probable reasons are given.

Journal Article↗

PubMed2003

Expression and purification of the h1 and h2 isoforms of calponin.

Three homologous calponin isoforms, named h1, h2, and acidic calponins, have been found in birds and mammals. Based primarily on studies of chicken gizzard smooth muscle (h1) calponin, calponin has been identified as a family of actin-associated proteins that inhibit actomyosin ATPase activity. Evolutionary divergence of the calponin isoforms suggests differentiated function. While the role of h1 calponin in smooth muscle contraction is under investigation, h2 calponin has been shown regulating the function of actin cytoskeleton. Using cloned cDNA, we expressed mammalian h1 and h2 calponins in Escherichia coli. We have developed effective methods to purify biologically active h1 and h2 calponin proteins from transformed bacterial culture. The purified calponin isoform proteins were used to generate monoclonal antibodies that reveal epitopic structure difference between h1 and h2 calponins. Together with their differential expression in tissues and during development, the structural diversity of h1 and h2 calponins suggests non-redundant physiological function. Nevertheless, h1 and h2 calponins bind F-actin with similar affinity, indicating a conserved mechanism for their role in regulating actin filaments in smooth muscle and non-muscle cells.

Actins↗

PubMed2003

The promoter targeting sequence facilitates and restricts a distant enhancer to a single promoter in the Drosophila embryo.

Transcriptional enhancers in large gene complexes activate promoters over huge distances, yet little is known about the mechanism of these long-range interactions. We report that the promoter targeting sequence (PTS) from the Abdominal-B locus of the Drosophila bithorax complex facilitates the activity of a distantly located enhancer in transgenic embryos and that it restricts the enhancer to a single promoter. These functions are heritable in all successive generations. We also show that the PTS functions only when itself and an insulator are located between the enhancer and the promoter. These findings suggest that the PTS may facilitate long-range enhancer-promoter interactions in the endogenous Abdominal-B locus. We propose that the PTS establishes a stable chromatin structure between an enhancer and a promoter, which facilitates yet restricts an enhancer to a single promoter.

Animals↗

PubMed2002

Novel compounds from Piper methysticum Forst (Kava Kava) roots and their effect on cyclooxygenase enzyme.

Milled Piper methysticum roots were extracted sequentially with hot water and methanol. Cyclooxygenase (COX) enzyme inhibitory assay directed purification of the methanol extract yielded bornyl esters of 3,4-methylenedioxy cinnamic acid (1) and cinnamic acid (2), pinostrobin (3), flavokawain B (4), and 5,7-dimethoxyflavanone (5). The structures of compounds 1-5 were accomplished by spectral experiments. The aqueous extract contained previously reported kava lactones, as confirmed by TLC analysis. Compounds 3 and 5 were isolated for the first time from kava kava roots. Compound 4 showed the highest COX-I inhibitory activity at 100 microg/mL. All the compounds tested gave good COX-I and moderate COX-II enzyme inhibitory activities at 100 microg/mL. This is the first report of COX-I and -II inhibitory activities for compounds 1-5.

Cinnamates↗

PubMed2002

[Pathological features of atrial isomerism and its diagnosis by computed tomography].

OBJECTIVE: To study the diagnostic significance of computed tomography (CT) in atrial isomerism. METHOD: In one of the 2 cases of left atrial isomerism, abdominal CT scan with and without contrast enhancement were both performed, the other had plain thoraco-abdominal CT scan, and another case of right atrial isomerism received thoraco-abdominal contrast enhanced scan and thin-slice scan of the trachea. The diagnoses of all the 3 cases were surgically and pathologically confirmed. RESULT: In the CT images of the 2 cases of left atrial isomerism, some typical features were identified including bilaterally symmetric bronchi, levoversion of the heart, horizontally positioned liver, absence of hepatic segment of the inferior vena cava and dilated azygos, short pancreas and double spleen, and mirror image isomerism of the major arteries and abdominal organs. The case of right atrial isomerism had bilateral upper lobe tracheal bronchus, mirror image isomerism of the heart and abdominal organs, short pancreas, translocation of the inferior vena cava to the left of the abdominal aorta, both of which were on the left of the spine. CONCLUSIONS: CT have distinct diagnostic value in revealing thoraco-abdominal organs and major vessels, which can be crucial in the diagnosis and surgical management of patients with atrial isomerism.

Adolescent↗

PubMed2002

[Positive and negative selection of thymocytes].

Maturation of T cells in thymus plays key roles in antigen-specific immune response. In maturation, thymocytes undergo positive and negative selection. The MHC restriction of T cell is determined in positive selection. The tolerance of T cells to autoantigen is acquired during negative selection. Quantitation (avidity) theory points out that difference of avidity between thymocytes and stroma cells leads to difference in the signals integrated inside cells. When the signal reaches a particular threshold, positive or negative selection takes place. In this article, the selection mechanism and the relationship between positive and negative selection are mini-reviewed.

Animals↗

PubMedDate not supplied

Sodium dicarboxylate cotransporter-1 expression in renal tissues and its role in rat experimental nephrolithiasis.

BACKGROUND: Nephrolithiasis is a common disease with a high recurrence rate; however, calcium stone pathogenesis remains unknown because of complex multiple factors. Hypocitraturia induced by citrate transport disturbance is known to be involved in nephrolithiasis development. Sodium dicarboxylate cotransporter (NaDC) mediates citrate uptake from the renal proximal tubule. However, the role of NaDC in nephrolithiasis is unclear. This study aimed to investigate NaDC-1 expression in rat renal proximal tubule epithelial cells and its relationship with experimental nephrolithiasis. METHODS: Male Wastar rats were divided into control, ethylene glycol (EG)-treated and potassium citrate-treated groups. Calcium oxalate (CaOx) crystal deposition and histological changes in the kidneys were examined with anatomical and light microscopes. The plasma and urinary biochemical parameters, such as citrate, oxalate etc, were analyzed by routine biochemical methods. NaDC-1 mRNA expression in kidneys was determined by northern blot analysis, the change in NaDC-1 protein abundance was detected by immunohistochemistry. RESULTS: It was found that NaDC-1 expression and its mRNA significantly increased in the EG group when compared with controls. Increased NaDC-1 expression was associated with a decline in urinary citrate excretion. Potassium citrate administration could significantly down-regulate NaDC-1 expression and its mRNA, and elevate urinary citrate content alleviate renal pathological changes and reduce nephrolithiasis occurrence. CONCLUSION: Increased NaDC-1 expression on the renal proximal tubule epithelial cells could play an important role in nephrolithiasis development, suggesting it could be a therapeutic target for the treatment of nephrolithiasis.

Animals↗