[Effects of dihydroartemisinin on radiosensitivity of Raji cells].

OBJECTIVE: To study the effects of dihydroartemisinin (DHA) on radiation sensitivity of Raji cells, and explore its mechanisms. METHODS: CCK8 was used to determine the effect of DHA on cell viability of Raji cells; apoptosis, intracellular reactive oxygen speies(ROS) and mitochondrial membrane potential of Raji cells were detected by flow cytometry; and the protein expressions of protein kinase B(AKT), phospho-rylated-protein kinase B(p-AKT), Bcl-2 and Bax were determined by Western blot. RESULTS: The cells were randomly divided into four groups:control group, DHA(5µmol/L DHA), irradiation(IR, 4 Gy), IR+DHA group (4 Gy IR+5 µmol/L DHA). Compared with the other three groups, cells in DHA+IR group exhibited lower mitochondrial membrane potential (P<0.01). While the intracellular ROS content and apoptosis rate of Raji cells in DHA+IR group were increased significantly(P<0.01). In addition, compared with the other three groups, there was no significant difference in the expression of AKT, but the phosphorylation of AKT protein were significantly inhibited and the expression of Bcl-2 protein was markedly decreased. However, the expressions of Bax and Cleaved-Caspase-3 protein were markedly increased. CONCLUSIONS: DHA might activate the mitochondrial apoptotic signal via inhibiting phosphoinositide 3-kinase (PI3K/AKT) pathway and increase oxidative stress to enhance the radiosensitivity of Raji cells.

The retromer complex influences Wnt secretion by recycling wntless from endosomes to the trans-Golgi network.

Secreted Wnt proteins play essential roles in many biological processes during development and diseases. However, little is known about the mechanism(s) controlling Wnt secretion. Recent studies have identified Wntless (Wls) and the retromer complex as essential components involved in Wnt signaling. While Wls has been shown to be essential for Wnt secretion, the function(s) of the retromer complex in Wnt signaling is unknown. Here, we have examined a role of Vps35, an essential retromer subunit, in Wnt signaling in Drosophila and mammalian cells. We provide compelling evidence that the retromer complex is required for Wnt secretion. Importantly, Vps35 colocalizes in endosomes and interacts with Wls. Wls becomes unstable in the absence of retromer activity. Our findings link Wls and retromer functions in the same conserved Wnt secretion pathway. We propose that retromer influences Wnt secretion by recycling Wntless from endosomes to the trans-Golgi network (TGN).

Atomic force microscopic examination of chromosomes treated with trypsin or ethidium bromide.

Trypsin treatment is frequently used during chromosome preparation for removal of cellular contaminants, and ethidium bromide (EB) staining of bands is often used to facilitate high-resolution observations by optical microscopy. However, conventional optical microscopy is unable to visualize potential aberrations of chromosome structures caused by these physicochemical treatments. In this article, we use atomic force microscopy (AFM) in the tapping mode to obtain and analyze high-resolution images of chromosome surface structure damage associated with trypsinization and EB treatment. According to our results, the trypsin-based digestion effects became more severe as incubations increased across a range from 10 to 40 s; a digestion time of 10 to 20 s appeared to be most suitable for observation by AFM. In terms of chromosomal damage induced by EB treatment, addition of EB into the media of cultured human blood cells induced chromosomal breakage in a dose-dependent fashion, and the results indicate centromeric region damnifyed severer than arms. Together, these results indicate that EB staining and the standard chromosomal preparative techniques of trypsinization can induce chromosomal damage that may affect the observed results.

Atomic force microscope tracking observation of Chinese hamster ovary cell mitosis.

CHO cells possess easily identifiable karyotypes, and CHO cell chromosomes are large and few in number, making these cells ideal for mutational and drug toxicity studies and suitable for investigations of animal chromosome structure. Here, we used atomic force microscopy (AFM) in the tapping mode for detailed visualizations of Chinese hamster ovary (CHO) cell chromosomes during various mitotic phases, including typical prophase, prometaphase, metaphase, anaphase and telophase. Based on our detailed observations, we were able to divide metaphase and anaphase into sub-phases: metaphase I, II and III, and anaphase I and II. Furthermore, we used the AFM error-signal mode to visualize chromosomal ultrastructures and cytokinesis. While these visualizations were all successful, we found that the image quality was affected by cellular debris, contamination. Collectively, our results show that the AFM technique has great potential for the detailed study of chromosomes and chromosomal ultrastructures during all phases of the cell cycle, but that careful standards of sample preparation must be maintained.

Expression of Smad4 during rat ovarian development.

OBJECTIVE: To clarify the signal transduction pathway of transforming growth factor-betasuperfamily (TGF-betas) in the regulation of follicle growth by investigating the expressions of Smad4 protein and mRNA in rat ovaries in different developmental stages. METHODS: Rat ovaries of different developmental stages were obtained to determine the expression of Smad4 protein by immunohistochemistry and image analysis system, with Smad4 mRNA measured by semi-quantitative RT-PCR. Specific primers of Smad4 and GAPDH (internal control) were used for amplification by RT-PCR, and the ratios of their integrated optical densities were calculated to estimate the relative quantity of Smad4 mRNA expression. RESULTS: Smad4 protein was widely expressed in the ovary, mainly in the follicles, and the location and intensity of Smad4 expression varied with the degree of maturation of the ovary. In the early developmental stages, Smad4 protein expressed mainly in the primordial and preantral follicles, but little in the stromal cells, and its expression intensity in the stroma increased gradually in the course of ovarian maturation. After sexual maturity, Smad4 expression intensity varied only insignificantly among the granulosa cells, theca cells and stromal cells of the antral and mature follicles (P>0.05). The staining intensity of Smad4 in the follicles also underwent changes in relation with their development, being less intense in the oocytes of the antral and matured follicles as compared to the preantral follicles (P<0.05 and P<0.01, respectively) but markedly greater in the theca cells of the antral and matured follicles than in the preantral follicles (P<0.01). No significant difference in Smad4 expression was found in the granulosa cells of different developmental stages (P>0.05). RT-PCR demonstrated that Smad4 mRNA was expressed in all the developmental stages of the rat ovary; and from the 3rd week on, the integrated optical density of Smad4 and GAPDH was significantly higher than that in 1-day-old neonatal rats. CONCLUSION: The expression patterns of Smad4 protein and mRNA in rat ovary in the course of its development indicate that Smad signal transduction may play a role in the folliculogenesis.