Epidemiology of gastric cancer

The incidence and mortality of gastric cancer have fallen dramatically in US and elsewhere over the past several decades. Nonetheless, gastric cancer remains a major public health issue as the fourth most common cancer and the second leading cause of cancer death worldwide. Demographic trends differ by tumor location and histology. While there has been a marked decline in distal, intestinal type gastric cancers, the incidence of proximal, diffuse type adenocarcinomas of the gastric cardia has been increasing, particularly in the Western countries. Incidence by tumor sub-site also varies widely based on geographic location, race, and socioeconomic status. Distal gastric cancer predominates in developing countries, among blacks, and in lower socioeconomic groups, whereas proximal tumors are more common in developed countries, among whites, and in higher socio-economic classes. Diverging trends in the incidence of gastric cancer by tumor location suggest that they may represent two diseases with different etiologies. The main risk factors for distal gastric cancer include Helicobacter pylori （H pylori） infection and dietary factors, whereas gastroesophageal reflux disease and obesity play important roles in the development of proximal stomach cancer. The purpose of this review is to examine the epidemiology and risk factors of gastric cancer, and to discuss strategies for primary prevention.

苯唑西林敏感耐甲氧西林金黄色葡萄球菌(OS-MRSA)研究进展

金黄色葡萄球菌(Staphylococcus aureus,SA)是导致医院内感染及社区获得性感染的一种常见病原菌,可引起宿主不同部位的感染,感染类型多样。耐甲氧西林金黄色葡萄球菌(methicillin resistant Staphylococcus aureus,MRSA)呈现对多种类型抗菌药物的耐药特征,其在不同国家和地区的检出率和流行特征存在明显差异。随着对MRSA耐药性和耐药机制研究的不断深入,一种具有特殊耐药特征的MRSA亚群逐渐被报道,即苯唑西林敏感的耐甲氧西林金黄色葡萄球菌(oxacillin-susceptible methicillin-resistant Staphylococcus aureus,OS-MRSA)。OS-MRSA典型特征为携带抗药性基因mecA,但其对苯唑西林的MIC值较低(通常<4mg/L)。由于目前临床实验室主要采用苯唑西林和或头孢西丁药敏试验方法来区分MRSA及甲氧西林敏感金黄色葡萄球菌(MSSA),而很少应用基因检测方法(mecA基因)进行检测或确认,因此OS-MRSA常被错误报告为MSSA,临床依据药敏报告进行抗感染治疗,常导致治疗失败及患者病死率的增加。此外,OS-MRSA菌株在不同国家和地区人群分离率及其分子流行病学特征存在较大差异。因此,本文将从分子流行病学、实验室检测方法、耐药机制、毒力特征及临床治疗等5个方面对OSMRSA的最新研究进展进行综述。

HIV and HCV:from Co-infection to Epidemiology,Transmission,Pathogenesis,and Treatment

Human immunodeficiency virus (HIV) is the infectious agent causing acquired immu-nodeficiency syndrome (AIDS),a deadliest scourge of human society. Hepatitis C virus (HCV) is a major causative agent of chronic liver disease and infects an estimated 170 million people worldwide,resulting in a serious public health burden. Due to shared routes of transmission,co-infection with HIV and HCV has become common among individuals who had high risks of blood exposures. Among hemophiliacs the co-infection rate accounts for 85%; while among injection drug users (IDU) the rate can be as high as 90%. HIV can accelerate the progression of HCV-related liver disease,particularly when immunodeficiency has developed. Although the effect of HCV on HIV infection is controversial,most studies showed an increase in mortality due to liver disease. HCV may act as a direct cofactor to fasten the progression of AIDS and decrease the tolerance of highly active antiretroviral therapy (HARRT). Conversely,HAART-related hepatotoxicity may enhance the progression of liver fibrosis. Due to above complications,co-infection with HCV and HIV-1 has imposed a critical challenge in the management of these patients. In this review,we focus on the epidemiology and transmission of HIV and HCV,the impact of the two viruses on each other,and their treatment.

Prevalence of cholelithiasis in patients with chronic inflammatory bowel disease

AIM： To investigate the effect of chronic inflammatory bowel disease （CIBD） specific risk factors for cholecystolithiasis, as duration and involvement pattern of the disease and prior surgery in patients with Crohn＇s disease （CD） and ulcerative colitis （UC）. METHODS： A total of 222 patients with CD （135 females, 87 males, average age, 35.8±11.8 years; range 17-81 years） and 88 patients with UC （39 females, 49 males; average age, 37.2±13.6 years; range 16-81 years） underwent clinical and ultrasound examinations. Besides age, sex and degree of obesity, patients＇ CIBD specific parameters, including duration and extent of disease and prior operations were documented and evaluated statistically using logistic regression. RESLTLTS： The overall prevalence of gallbladder stone disease in patients with CD was 13% （n = 30）. Only age could be shown to be an independent risk factor （P = 0.014）. Compared to a collective representative for the general population in the same geographic region, the prevalence of cholecystolithiasis was higher in all corresponding age groups. Patients with UC showed an overall prevalence of gallbladder stone disease of only 4.6%. CONCLUSION：Only age but not disease-specific factors such as duration and extent of disease, and prior surgery are independent risk factors for the development of cholecystolithiasis in patients with CIBD.

Evidence of human papilloma virus infection and its epidemiology in esophageal squamous cell carcinoma

AIM： To look for the evidence of human papilloma virus （HPV） infection in esophageal squamous cell carcinomas （ESCC） and to investigate the potential role and epidemiology of HPV infection in the pathogenesis of esophageal carcinomas in Henan emigrants. METHODS： Papilloma virus （PV） and HPV were determined by UltrasensiveTM S-P immunohistochemistry （IHC） and in situ hybridization （ISH） in esophageal carcinoma tissues （82 cases） and the normal mucosa （40 cases）. RESULTS： IHC revealed that the positive rate of PV was 75.0%, 68.18% and 72.5% respectively while the HPV （16/18-E6） positive rate was 45.0%, 36.36%, 37.5%, respectively in esophageal carcinoma tissue specimens from Henan emigrants,the local citizens and patients in Hubei Cancer Hospital. The PV and HPV （16/18-E6） were negative in all normal esophageal mucosa specimens. No correlation was found between HPV in esophageal squamous cell carcinoma tissues and in grade 1-3 esophageal squamous cell carcinoma cells. In situ hybridization showed that the HPV （16/18） DNA positive rate was 30.0%, 31.8%, 25.0%, respectively in the 3 groups of samples. No positive hybridization signal was found in 40 normal esophageal mucosa specimens. The positive rate of HPV （16/18） DNA in the esophageal carcinoma specimens was significantly higher than that in normal mucosa specimens （P〈0.05）. The positive rate was not different among the 3 groups of esophageal carcinoma tissue specimens （P〉0.05）.CONCLUSION： HPV infection is high in esophageal carcinoma of Henan emigrants, local residents and patients in Hubei Cancer Hospital. HPV is closely related with esophageal squarnous cell carcinoma. HPV infection may play an important role in esophageal squarnous cell carcinoma.

Genetic Variation in Field Populations of Baculoviruses: Mechanisms for Generating Variation and Its Potential Role in Baculovirus Epizootiology

Baculoviridae is a family of insect-specific DNA viruses that have been used as biological control agents for insect pest control. In most cases these baculovirus control agents are natural field isolates that have been selected based on their infectivity and virulence. The advent of molecular tools such as restriction endonucleases, targeted polymerase chain reaction and new DNA sequencing strategies have allowed for efficient detection and characterization of genotypic variants within and among geographic and temporal isolates of baculovirus species. It has become evident that multiple genotypic variants occur even within individual infected larvae. Clonal strains of baculovirus species derived either by in vitro or in vivo approaches have been shown to vary with respect to infectivity and virulence. Many of the cell culture derived plague-purified strains have deletions that interrupt egt expression leading to virus strains that kill infected hosts more quickly. As well, in vitro clones often involve larger genomic deletions with the loss of pif gene function, resulting in strains deficient for oral infectivity. There are an increasing number of baculovirus species for which complete genome sequences are available for more than one strain or field isolate. Results of comparative analysis of these strains indicated that hr regions and bro genes often mark "hot spots" of genetic variability between strains and of potential recombination events. In addition, the degree of nucleotide polymorphisms between and within strains and their role in amino acid substitutions within ORFs and changes in promoter motifs is also beginning to be appreciated. In this short review the potential mechanisms that generate and maintain this genetic diversity within baculovirus populations is discussed, as is the potential role of genetic variation in host-pathogen interactions.

Gastroesophageal reflux disease at the turn of millennium

Gastroesophageal reflux disease (GERD) has been an area of active research in the Asia-Pacific region in the recent years. This article outlines some of the interesting research findings. It comprises three parts. The first part dealt with recent data on the changing epidemiology of GERD in Asia.The second part summarized published studies on the relationship between GERD and Helicobacter pylori, relevant to the Asia-Pacific region. The last part discussed some of the recent advances in the treatment of GERD.

Approaches to antiretroviral therapy in China

China has recognized the threat of HIV to its population and responded with a national antiretroviral treatment （ART） program. However, high ART failure rates and the spread of resistance within populations are important realities to consider when developing and managing ART programs in China and worldwide. Concepts which will define treatment success and local and national programmatic goals are 1） access to ART, 2） durability of ART at the patient level, 3） scalability of treatment modalities, and the 4） sustainability of the program at the community or national level. In the face of limited resources, China must also consider when to start ARV therapy, which agents to use, when to switch them, and how to treat highly experienced patients with drug resistance. The optimal ARV regimen to start with is changing frequently with the introduction of new agents and the presentation of new data. Currently, a regimen including tenofovir, emtricitabine or lamivudine and a nonnucleoside reverse transcriptase inhibitor appears to have optimal characteristics to treat HIV/AIDS in China. However, critical to all of these choices is the evaluation of programs implemented to insure wide scale success. China has wisely begun this process of evaluating the perlormance of local programs through systematic monitoring and evaluation of treatment outcomes. This will allow regimens and programs that work to be expanded, and programs with high failure rates to be eliminated. In the end,evidence based data supporting treatment strategies will allow China to successfully contront its AIDS epidemic early and prevent its tragic consequences

SARS病毒与严重的急性呼吸道综合症——香山科学会议第203次学术讨论会综述

面对突如其来的SARS危害,社会各界心急如焚。而在新出现的SARS病毒面前,我们都还是小学生,因为大家至今对它还知之不多。在这一特殊时刻要解决SARS这一特殊问题,多学科、跨部门的专家学者及时交流信息与加强合作研究,尤为重要且刻不容缓。