ATM and ATR:Sensing DNA damage

Cellular response to genotoxic stress is a very complex process, and it usually starts with the “sensing” or “detection” of the DNA damage,followed by a series of events that include signal transduction and activation of transcription factors.The activated transcription factors induce expressions of many genes which are involved in cellular functions such as DNA repair,cell cycle arrest,and cell death. There havebeen extensive studies from multiple disciplines exploring the mechanisms of cellular genotoxic responses, which have resulted in the identification of many cellular components involved in this process,including the mitogen-activated protein kinases (MAPKs) cascade. Although the initial activation of protein kinase cascade is not fully understood,human protein kinases ATM (ataxia-telangiectasia, mutated) and ATR (ATM and Rad3-related) are emerging as potential sensors of DNA damage. Current progresses in ATM/ATR research and related signaling pathways are discussed in this review, in an effort to facilitate a better understanding of genotoxic stress response.

Study of a Novel Antiosteoporosis Screening Model Targeted on Cathepsin K

Objective To establish an effective assay to access the effects of natural products on cathepsin K for screening antiosteoporosis drugs. Methods To obtain the purified cathepsin K, we cloned the target fragment from the mRNA of human osteosacoma cell line MG63 and demonstrated its correctness through DNA sequencing. Cathepsin K was expressed in a high amount in E.coli after IPTG induction, and was purified to near homogenetity through resolution and column purification. The specificity of the protein was shown by Western blotting experiment. The biological activity of the components in the fermentation broth was assayed by their inhibitory effects on cathepsin K and its analog papain. Results With the inhibition of papain activity as a screen index, the fermentation samples of one thousand strains of fungi were tested and 9 strains among them showed strong inhibitory effects. The crude products of the fermentation broth were tested for their specific inhibitory effects on the purified human cathepsin K, the product of fungi 2358 shows the highest specificity against cathepsin K. Conclusions The compounds isolated from fungi 2358 show the highest biological activity and are worth further structure elucidation and function characterization.

Response of human REV3gene to gastric cancer inducing carcinogen N-methyl-N'-nitro-N-nitrosoguanidine and its role in mutagenesis

AIM: To understand the response of human REV3gene to gastric cancer inducing carcinogen N-methyl-N'-nitro-Nnitrosoguanidine (MNNG) and its role in human mutagenesis.METHODS: The response of the human REV3 gene to MNNG was measured in human 293 cells and FL cells by RT-PCR. By using antisense technology, mutation analysis at HPRTlocus (on which lesion-targeted mutation usually occurs) was conducted in human transgenic cell line FLREV3- by 8-azaguanine screening, and mutation occurred on undamaged DNA template was detected by using a shuttle plasmid pZ189 as the probe in human transgenic cell lines 293-REV3- and FL-REV3-. The blockage effect of REV3 was measured by combination of reverse transcriptionpolymerase chain reaction to detect the expression of antisense REV3 RNA and Western blotting to detect the REV3protein level.RESULTS: The human REV3 gene was significantly activated by MNNG treatment, as indicated by the upregulation of REV3 gene expression at the transcriptional level in MNNG-treated human cells, with significant increase of REV3 expression level by 0.38 fold, 0.33 fold and 0.27fold respectively at 6 h, 12 h and 24 h in MNNG-treated 293 cells (P＜0.05); and to 0.77 fold and 0.65 fold at 12 h and 24 h respectively in MNNG-treated FL cells (P＜0.05).In transgenic cell line (in which REV3 was blocked by antisense REV3 RNA), high level of antisense REV3 RNA was detected, with a decreased level of REV3 protein.MNNG treatment significantly increased the mutation frequencies on undamaged DNA template (untargeted mutation), and also at HPRT locus (lesion-targeted mutation). However, when REV3 gene was blocked by antisense REV3 RNA, the MNNG-induced mutation frequency on undamaged DNA templates was significantly decreased by 3.8 fold (P＜0.05) and 5.8 fold (P＜0.01)respectively both in MNNG-pretreated transgenic 293 cells and FL cells in which REV3was blocked by antisense RNA,and almost recovered to their spontaneous mutation levels.The spontaneous HPRT mutation was disappeared in REV3disrupted cells, and induced mutation frequency at HPRT locus significantly decreased from 8.66×10-6 in FL cells to 0.14×10-6 in transgenic cells as well (P＜0.01).CONCLUSION: The expression of the human REV3 can be upregulated at the transcriptional level in response to MNNG. The human REV3 gene plays a role not only in lesion-targeted DNA mutagenesis, but also in mutagenesis on undamaged DNA templates that is called untargeted mutation.

Urinary nucleosides as biological markers for patients with colorectal cancer

AIM: Fourteen urinary nucleosides, primary degradation products of tRNA, were evaluated to know the potential as biological markers for patients with colorectal cancer.METHODS: The concentrations of 14 kinds of urinary nucleosides from 52 patients with colorectal cancer, 10patients with intestinal villous adenoma and 60 healthy adults were determined by column switching high performance liquid chromatography method.RESULTS: The mean levels of 12 kinds of urinary nucleosides (except uridine and guanosine) in the patients with colorectal cancer were significantly higher than those in patients with intestinal villous adenoma or the healthy adults. Using the levels of 14 kinds of urinary nucleosides as the data vectors for principal component analysis, 71% (37/52) patients with colorectal cancer were correctly classified from healthy adults, in which the identification rate was much higher than that of CEA method (29%).Only 10% (1/10) of patients with intestinal villous adenoma were indistinguishable from patients with colorectal cancer. The levels of m1G, Pseu and m1A were positively related with tumor size and Duke's stages of colorectal cancer. When monitoring the changes in urinary nucleoside concentrations of patients with colorectal cancer associated with surgery, it was found that the overall correlations with clinical assessment were 84% (27/32)and 91% (10/11) in response group and progressive group, respectively.CONCLUSION: These findings indicate that urinary nucleosides determined by column switching high performance liquid chromatography method may be useful as biological markers for colorectal cancer.

Cold Plasma Surface Modification of NiTi for Biomedical Applications

Surface-grafted poly(ethylene glycol) (PEG) molecules are known to prevent protein adsorption to the surface. Nitinol samples were coated under tetraglyme ECR cold plasma conditions to enhance its biocompatibility. The modified Nitinol surfaces were characterized by high resolution ESCA and contact angle, it was demonstrated that the deposited PEG-like coatings were built up mainly of-CH2-CH2-O- linkages in surfaces. The surface wettability of the modified Nitinol was increased compared with the control surface. Human plasma protein was adsorbed on Nitinol evaluated by SEM, the protein adsorption on modified surfaces decreased rapidly. Thus, the potential benefits of cold plasma technique will be of use to the biomedical industries improving the biocompatibility of metals.

Platelet Adhesion onto Nitinol Surfaces Modified by Microwave Cold-plasma

The macromolecular structures on nitinol surfaces were prepared by ECR microwave cold-plasma of tetraglyme conditions. The surface chemistry was characterized by high resolution ESCA. The results showed that the modified nitinol surfaces were built up mainly of -CH2-CH2-O- linkages and were particularly effective in preventing platelet adhesion.

BLOOD PRESSURE CHANGE WITH AGE IN SALT-SENSITIVE TEENAGERS

Objective To observe blood pressure change with age in salt-sensitive teenagers whose salt sensitivity were determined by repeated testing. Methods Salt sensitivity was determined through intravenous infusion of normal saline combined with volume-depletion by oral diuretic furosemide in 55 teenagers. After five years, salt sensitivity was re-examined and subject blood pressure was followed up. Blood pressure changes in salt-sensitive teenagers were compared to that of non-salt sensitive teenagers over five years. Results After 5 years, the repetition rate of salt sensitivity determined by intravenous saline loading is 92.7%. In teena-gers with salt sensitivity on the baseline, both the systolic blood pressure increments and increment rates were much higher than non-salt sensitive teenagers (12.7±12.1 mmHg vs. 2.8 ±5.2 mmHg, P< 0.01; 12.2% ±12.0% vs. 2.5% ±4.4%, P< 0.001, respectively). There was a similar trend for diastolic blood pressure (8.4 ±6.4 mmHg vs. 3.7 ±6.4 mmHg, P= 0.052; 13.2% ±10.6 % vs. 6.8% ±10.1%, P= 0.053, respectively). Conclusions Salt sensitivity determined by intravenous saline loading showed good reproducibility. Blood pressure increments with age were much higher in salt-sensitive teenagers than non-salt sensitive teenagers, especially in terms of systolic blood pressure.

Effects of heat treatment on structures and properties of high speed steel rolls

The effects of quenching temperature, cooling pattern, temper temperature andtemper times on the structure and properti-es of high speed steel (HSS) rolls have beeninvestigated. The results show that, when the quenching temperature is lower than 1050℃ thehardness of HSS increases with the quenching temperature increasing in oil cooling, but when thequenching temperature exceeds 1100℃ the hardness decreases. In the conditions of salt bath coolingand air cooling, the effect of quenching temperature on the hardness is similar to the above law,but the quenching temperature obtaining the highest hardness is higher than that in oil cooling.When the temper temperature below 350℃ the hardness of HSS has a little change, when above 475℃the hardness will increase with the temper temperature increasing, and the highest hardness isobtained at 525℃. When the temper temperature continues to increase, the hardness decreases. Twicetemper has little effect on the hardness, but three times temper decreases the hardness. HSS in aircooling has lower hardenability, oil cooling can easily produce crackle, and HSS quenching in saltbath has high harde-nability and excellent wear resistance.

Recent Progress on Selected Topics in Database Research-A Report by Nine Young Chinese Researchers Working in the United States

The study on database technologies, or more generally, the technologies ofdata and information management, is an important and active research field. Recently, many excitingresults have been reported. In this fast growing field, Chinese researchers play more and moreactive roles. Research papers from Chinese scholars, both in China and abroad, appear in prestigiousacademic forums. In this paper, we, nine young Chinese researchers working in the United States,present concise surveys and report our recent progress on the selected fields that we are workingon. Although the paper covers only a small number of topics and the selection of the topics is farfrom balanced, we hope that such an effort would attract more and more researchers, especially thosein China, to enter the frontiers of database research and promote collaborations. For the obviousreason, the authors are listed alphabetically, while the sections are arranged in the order of theauthor list.