Thermoluminescence properties of Eu‐doped and Eu/Dy‐codoped Sr2Al2SiO7 phosphors

We report the thermoluminescence properties of Sr_1.96Al₂SiO₇:Eu_0.04 and Sr_1.92Al₂SiO₇:Eu_0.04Dy_0.04 phosphors. These phosphors were prepared by a high‐temperature solid‐state reaction method. The prepared phosphors were characterized by X‐ray diffraction. A 254 nm source was used for ultraviolet (UV) irradiation and a ⁶⁰Co source was used for γ‐irradiation. The effect of heating rate and UV‐exposure were examined. The thermoluminescence temperature shifts to higher values with increasing heating rate and thermoluminescence intensity increases with increasing UV exposure time. The trapping parameters such as activation energy (E), order of kinetics and frequency factor (s) were calculated by peak shape method. The effect of γ‐ and UV‐irradiation on thermoluminescence studies was also examined.     

Pyrazolo[4,3-e][1,2,4]triazine sulfonamides as carbonic anhydrase inhibitors with antitumor activity

A series of sildenafil analogues and aniline substituted pyrazolo[4,3-e][1,2,4]triazine sulfonamides were prepared and evaluated as carbonic anhydrase (CA, EC 4.2.1.1) inhibitors and for their anticancer activity against two human breast cancer cell lines (MCF-7, MDA-MB-231). The new compounds were ineffective as CA I inhibitors, poorly inhibited CA II, but were more effective against the tumor-associated isoforms CA IX and XII, with some compounds acting as low nanomolar inhibitors. Evaluation of the cytotoxicity by using an MTT assay, the inhibition of [³H]thymidine incorporation into DNA as well as collagen synthesis inhibition, demonstrated that these sulfonamides exhibit cytotoxic effects on breast cancer cell lines ex vivo.     

An ATP-Sensitive K+ Current that Regulates Progression Through Early G1 Phase of the Cell Cycle in MCF-7 Human Breast Cancer Cells

Whole-cell recordings were used to identify in MCF-7 human breast cancer cells the ion current(s) required for progression through G1 phase of the cell cycle. Macroscopic current-voltage curves were fitted by the sum of three currents, including linear hyperpolarized, linear depolarized and outwardly rectifying currents. Both linear currents, but not the outwardly rectifying current, were increased by 1 μm intracellular Ca²⁺ and blocked by 2 mm intracellular ATP. When tested at concentrations previously shown to inhibit proliferation by 50%, linogliride, glibenclamide and quinidine inhibited the linear hyperpolarized current, and quinidine and linogliride inhibited the linear depolarized current; none of these agents affected the outwardly rectifying current. In contrast, tetraethylammonium completely inhibited the outwardly rectifying current, but did not inhibit either linear current. Changing the bath solution to symmetric K⁺ shifted the reversal potential of the linear hyperpolarized current from near the K⁺ equilibrium potential (−84 mV) to −4 mV. Arrest of the cell cycle in early G1 by quinidine was associated with significantly smaller linear hyperpolarized currents, without a change in the linear depolarized or outwardly rectifying currents, but this reduction was not observed with arrest by lovastatin at a site ≈6 hr later in G1. The linear hyperpolarized current was significantly larger in ras-transformed than in untransformed cells. We conclude that the linear hyperpolarized current is an ATP-sensitive K⁺ current required for progression of MCF-7 cells through G1 phase. Received: 22 January 1999/Revised: 11 May 1999     

HPV18 E7致癌蛋白的高效表达、纯化和鉴定

目的为进一步研究人乳头状瘤病毒18（Human papillomavirus18，HPV18）E7蛋白的结构与功能。方法构建HPV18 E7的谷胱甘肽S-转移酶融合蛋白质粒pGEX-6P-1-GST-HPV18 E7，重组质粒转入大肠埃希菌BL21进行可溶性融合蛋白的高效表达。结果柱上切除法去除GST标签，表达产物经glutathione Sepharose 4B亲和层析纯化，获得了SDS-PAGE和HPLC-ESI-MS纯度的HPV18 E7均质蛋白，非变性PAGE和凝胶过滤表明HPV18 E7以稳定的单体形式存在于水溶液中。高压液相色谱-电喷雾质谱（HPLC-ESI-MS）分析得到HPV18 E7精确分子量为12865．0 Da，与其理论值吻合。纯化蛋白经HPLC-ESI-MS／MS鉴定为目的产物，鉴定出的9个匹配肽段覆盖率为HPV18 E7整个氨基酸序列的96．5％。结论本文所建立的技术可以有效地大量制备HPV18 E7，为进一步研究其结构与功能和致癌机制奠定了重要的物质基础。     

ShRNA knock‐down of CXCR7 inhibits tumour invasion and metastasis in hepatocellular carcinoma after transcatheter arterial chemoembolization

To investigate the effects of lentiviral vector‐mediated shRNA suppressing CXCR7 on tumour invasion and metastasis in hepatocellular carcinoma (HCC) after transcatheter arterial chemoembolization (TACE). HCCLM3 cell lines were cultured and assigned into the CXCR7‐shRNA, negative control (NC) and blank groups. The qRT‐PCR and Western blotting were applied to detect the mRNA and protein expressions of CXCR7, CXCR4 and MMP‐2 in HCCLM3 cells. Cell proliferation and invasion were evaluated by MTT and Transwell assays. A Buffalo rat model of HCC was established. Fifty model rats were divided into the CXCR7‐shRNA + TACE, CXCR7‐shRNA, TACE, NC and control groups. Immunohistochemistry was performed to detect the expressions of CXCR7, MMP‐2, vascular endothelial growth factor (VEGF) and intratumoral CD31‐positive vessel count in tumour tissues of mice. Compared with the blank and NC groups, the mRNA and protein expressions of CXCR7 and MMP‐2 were decreased in the CXCR7‐shRNA group. The cell proliferation and invasion rates of the CXCR7‐shRNA group were lower than the blank and NC groups. At the 4th week after TACE, tumour weight of the CXCR7‐shRNA + TACE group increased continuously. The CXCR7‐shRNA + TACE group showed longer survival time and smaller tumour sizes than other groups. Compared with other groups, the CXCR7‐shRNA + TACE and CXCR7‐shRNA groups had less number of lung metastatic nodules and lower expressions of CXCR7, MMP‐2, VEGF and CD31‐positive vessel count. CXCR7‐shRNA inhibits tumour invasion and metastasis to improve the efficacy of TACE in HCC by reducing the expressions of CXCR7, MMP‐2 and VEGF.     

RUNAWAY COEVOLUTION: ADAPTATION TO HERITABLE AND NONHERITABLE ENVIRONMENTS

Populations evolve in response to the external environment, whether abiotic (e.g., climate) or biotic (e.g., other conspecifics). We investigated how adaptation to biotic, heritable environments differs from adaptation to abiotic, nonheritable environments. We found that, for the same selection coefficients, the coadaptive process between genes and heritable environments is much faster than genetic adaptation to an abiotic nonheritable environment. The increased rate of adaptation results from the positive association generated by reciprocal selection between the heritable environment and the genes responding to it. These associations result in a runaway process of adaptive coevolution, even when the genes creating the heritable environment and genes responding to the heritable environment are unlinked. Although tightening the degree of linkage accelerates the coadaptive process, the acceleration caused by a comparable amount of inbreeding is greater, because inbreeding has a cumulative effect on reducing functional recombination over generations. Our results suggest that that adaptation to local abiotic environmental variation may result in the rapid diversification of populations and subsequent reproductive isolation not directly but rather via its effects on heritable environments and the genes responding to them.     

Differential susceptibility to hydrogen sulfide-induced apoptosis between PHLDA1-overexpressing oral cancer cell lines and oral keratinocytes: Role of PHLDA1 as an apoptosis suppressor

Hydrogen sulfide (H₂S) is a novel gasotransmitter that plays multiple biological roles in various body systems. In addition to its endogenous production, H₂S is produced by bacteria colonizing digestive organs, including the oral cavity. H₂S was previously shown to enhance pro-apoptotic effects in cancer cell lines, although the mechanisms involved remain unclear. To properly assess the anti-cancer effects of H₂S, however, investigations of apoptotic effects in normal cells are also necessary. The aims of this study were (1) to compare the susceptibility to H₂S-induced apoptosis between the oral cancer cell line Ca9-22 and oral keratinocytes that were derived from healthy gingiva, and (2) to identify candidate genes involved in the induction of apoptosis by H₂S. The susceptibility to H₂S-induced apoptosis in Ca9-22 cells was significantly higher than that in keratinocytes. H₂S exposure in Ca9-22 cells, but not keratinocytes, enhanced the expression of pleckstrin homology-like domain, family A, member 1 (PHLDA1), which was identified through a differential display method. In addition, PHLDA1 expression increased during actinomycin D-induced apoptosis in Ca9-22 cells. Knockdown of PHLDA1 expression by small interfering RNA in Ca9-22 cells led to expression of active caspase 3, thus indicating apoptosis induction. The tongue cancer cell line SCC-25, which expresses PHLDA1 at a high level, showed similar effects. Our data indicate that H₂S is an anti-cancer compound that may contribute to the low incidence of oral cancer. Furthermore, we demonstrated the role of PHLDA1 as an apoptosis suppressor.     

DNA replication stress: Causes,resolution and disease

DNA replication is a fundamental process of the cell that ensures accurate duplication of the genetic information and subsequent transfer to daughter cells. Various pertubations, originating from endogenous or exogenous sources, can interfere with proper progression and completion of the replication process, thus threatening genome integrity. Coordinated regulation of replication and the DNA damage response is therefore fundamental to counteract these challenges and ensure accurate synthesis of the genetic material under conditions of replication stress. In this review, we summarize the main sources of replication stress and the DNA damage signaling pathways that are activated in order to preserve genome integrity during DNA replication. We also discuss the association of replication stress and DNA damage in human disease and future perspectives in the field.     

Identification of functional PDZ domain binding sites in several human proteins

TIP-15 was previously identified as a cellular protein that can bind to the C-terminal end of the HTLV-1 Tax protein via its two PDZ domains. The sequence of the N-terminal part of TIP-15 is identical to that of the synaptic protein PSD-95. Both proteins are likely to be produced from the same gene by alternative splicing. Whereas expression of the PSD-95 mRNA was detected only with brain RNAs, that of TIP-15 was detected with RNAs from thymus, brain, skeletal muscle and Jurkat cells. The TIP-15 protein exhibits an apparent molecular weight of 40 kD and is weakly expressed in T cell lines. A two-hybrid screen performed with TIP-15 as bait revealed the presence of a PDZ binding site (PDZ-BS) in the following proteins: Lysyl tRNA synthetase, 6-phosphogluconolactonase (6-GPL), Stress-activated protein kinase 3 (SAPK3), NET-1, Diacylglycerol kinase zeta, MTMR1, MCM7, and hSec8. The sequence at the C-terminal ends of these proteins matches the X-S/T-X-V-COOH consensus previously defined for PDZ-BSs, with the exception of 6-GPL and SAPK3 which include a leucine as the C-terminal residue. For Lysyl tRNA synthetase, NET1, MTMR1 and hSec8, binding to TIP-15 was confirmed by co-immunoprecipitation experiments performed with the extracts of transfected COS7 cells. These results show the existence of functional PDZ-BSs in these proteins, but future studies will be necessary to establish whether or not TIP-15 represents a physiological partner. The significance of the presence of a PDZ-BS in these various proteins is discussed with respect to their function.     

Free radicals impair the anti-oxidative stress activity of DJ-1 through the formation of SDS-resistant dimer

DJ-1 is a causative gene for familial Parkinson’s disease (PD). Loss-of-function of DJ-1 protein is suggested to contribute to the onset of PD, but the causes of DJ-1 dysfunction remain insufficiently elucidated. In this study, we found that the SDS-resistant irreversible dimer of DJ-1 protein was formed in human dopaminergic neuroblastoma SH-SY5Y cells when the cells were exposed to massive superoxide inducers such as paraquat and diquat. The dimer was also formed in vitro by superoxide in PQ redox cycling system and hydroxyl radical produced in Fenton reaction. We, thus, found a novel phenomenon that free radicals directly affect DJ-1 to form SDS-resistant dimers. Moreover, the formation of the SDS-resistant dimer impaired anti-oxidative stress activity of DJ-1 both in cell viability assay and H₂O₂-elimination assay in vitro. Similar SDS-resistant dimers were steadily formed with several mutants of DJ-1 found in familial PD patients. These findings suggest that DJ-1 is impaired due to the formation of SDS-resistant dimer when the protein is directly attacked by free radicals yielded by external and internal stresses and that the DJ-1 impairment is one of the causes of sporadic PD.