The rag locus of Porphyromonas gingivalis: a novel pathogenicity island

Previous studies in our laboratories of the serum IgG antibody response of periodontal patients have demonstrated the presence of an immunodominant surface antigen (Mr 55 kDa) in the outer membrane of Porphyromonas gingivalis W50. Genetic analysis of this antigen revealed that the corresponding gene forms part of a small operon which may have arisen via horizontal gene transfer into the genome of this strain. On the basis of sequence homology, the 55 kDa antigen (RagB) and the product of a cotranscribed gene (RagA) may act in concert at the surface of the bacterium to facilitate active transport, mediated through the periplasmic spanning protein, TonB, or form part of a signal transduction system in this organism. The rag locus is present in only a proportion of P. gingivalis laboratory strains and clinical isolates. Analysis of the distribution of ragB in subgingival samples by PCR demonstrated that rag+ P. gingivalis are more frequently detected in deep periodontal pockets than shallow sites in periodontal patients. These findings indicate that the rag genes may influence the virulence potential of P. gingivalis strains which harbour this locus and may thus be considered a novel pathogenicity island. Furthermore, horizontal gene transfer between organisms in subgingival plaque may represent a significant force in the evolution of these bacteria with ramifications for both diagnosis and targeted treatment of periodontal disease.     

基因组CpG岛甲基化检测技术研究进展

启动子CpG岛甲基化所致的抑癌基因失活和肿瘤发生密切相关，因而了解抑癌基因CpG岛甲基化情况具有重要意义。目前CpG岛甲基化的检测方法众多，其原理分别基于甲基化敏感的限制性内切酶切割和亚硫酸氢钠修饰，用于全基因组大量CpG岛甲基化检测和基因特异性CpG岛的一个或多个CpG位点甲基化检测。     

不同部位大鼠胰岛同种移植实验研究

探讨大鼠同种胰岛移植的适宜部位。方法 :将同种胰岛分别移植于大鼠脾髓内、肝实质内和经门静脉注入肝内 ,通过观察比较移植后大鼠空腹血糖、血清胰岛素的变化、术后肝功能、排斥反应发生时间以及组织学检查来评定三个移植部位的效果。结果 :肝实质内移植组其移植物存活期为 5 .83± 2 .48天 ,短于门静脉内移植组 9.2 5± 3.0 6天和脾髓内移植组 10 .2 2± 2 .95天 (P <0 .0 5 ) ,肝功能损害重 ,移植效果差。门静脉内移植组 ,胰岛对外周血糖变化敏感 ,移植物存活时间长 ;而脾髓内移植组 ,不但移植效果良好 ,且对受体无不良影响。结论 :脾脏是大鼠同种胰岛移植的适宜部位。     

经门脉肝内移植胰岛细胞治疗糖尿病鼠的实验研究

为了探讨胰岛移植部位对移植效果的影响，本实验利用四氢嘧啶诱发的糖尿病鼠，以肝脏为胰岛细胞移植部位，经门脉肝内移植用胶原酶消化提取的乳鼠胰岛细胞。结果，实验组治愈率８０％，与对照组差异有显著性，且无明显并发症，认为，肝脏具有特殊解剖、生理功能，是胰岛移植的理想部位。     

Methylation status of the retinoblastoma gene (RB1) in osteosarcoma: no evidence for hypermethylation

Alterations of the retinoblastoma (RB1) tumor suppressor gene are not only associated with retinoblastoma but also with several other malignancies including osteosarcoma. Besides direct sequence alterations, hypermethylation of a CpG island in the promoter region can cause inactivation of the RB1 gene as it has been shown in retinoblastomas. We examined the methylation status of the RB1 gene in 25 osteosarcoma specimens by using the methylation-sensitive restriction enzymes SacII and SmaI. The restriction fragments were hybridized with clone p123, which is a 1.8-kb genomic subclone that spans the RB1 CpG island including the promoter region and exon 1. Whereas we reconfirmed hypermethylation of the RB1 gene in a sporadic retinoblastoma, no hypermethylation could be detected in the 25 osteosarcoma specimens, suggesting that hypermethylation of the RB1 promoter is not of major importance during osteosarcoma genesis.     

DNA methylation of multiple promoter-associated CpG islands in meningiomas: relationship with the allelic status at 1p and 22q

The purpose of this research was to examine the DNA methylation profile of meningiomas. Accordingly, we examined the DNA methylation status of ten tumor-related genes (RB1, p16^INK4a, p73, MGMT, ER, DAPK, TIMP-3, p14^ARF, THBS1, and Caspase-8) in 98 meningiomas (68 grade I; 27 grade II; and 3 grade III samples) using methylation-specific PCR and sequencing. The most frequently methylated genes were THBS1 (30%), TIMP-3 (24%), p16^INK4a (17%), MGMT (16%), p73 (15%), ER (15%), and p14^ARF (13%), whereas methylation was relatively rare in the other genes (<10%). Methylation occurred in at least one gene in 77.5% of the cases and in three or more genes in 25.5%. Methylation was tumor specific since it was absent in the controls: two non-neoplastic meningeal samples and two non-neoplastic brain samples. The frequency of aberrant gene methylation in grade I versus grade II–III tumors showed some differences for TIMP-3, THBS1, MGMT, p16^INK4a and p73; these differences reached statistical significance for TIMP-3: 18% in grade I versus 40% in grade II–III (P<0.02). Our previous loss of heterozygosity studies provided the allelic constitution at 1p and 22q for 60 of the 98 meningiomas included in this report. The level of aberrant promoter methylation increased in tumors (30 samples) displaying 1p loss (either isolated or as concurrent deletion at 1p/22q; P=0.014). These meningiomas primarily accumulated the epigenetic changes of THBS1 (14/30; 47%; P<0.005), TIMP-3 (12/30; 40%; P<0.05), p73 (10/30; 26%; P<0.02) and p14^ARF/p16^INK4a (7/30 each one; 23%; not significant). Our findings indicate that aberrant DNA methylation of promoter-associated CpG islands in meningiomas contributes to the development of these tumors.     

Evidence for an extensive collagen type III/VI proximal domain in the rat femur. I. Diminution with ovariectomy

Collagenous proteins other than Type I have received little attention in hypogonadal bone loss. Using femora from 25 young (2.5 months) and older (11 months) control and ovariectomized adult rats killed 1–4 months postoperation, cancellous atrophy was histologically confirmed, and the immunolocalization of collagen Type III was examined. This occurred as numerous immunofluorescent Sharpey-like fibers, 5–25 μm thick, regularly associated with collagen Type VI, which ramified the femoral cortex. Sequential transverse cryosections enabled the mapping of the fibers in three-dimensions, demonstrating that they constituted an extensive subperiosteal domain which may be a lasting legacy of early skeletal development. Fiber density was greatest in the trochanters and femoral neck. The domain tapered distally and was apparently anchored into the mid-shaft by intracortical cartilaginous islands, staining for collagen Type VI (as well as Type II and fibronectin). Ovariectomy caused disconnection of the fibers and reduced the proximal domain of both young and older animals, previously positive areas of the cortex becoming negative. It is concluded that collagen Type III/VI occupies a substantial, discrete domain in the rat proximal femur as a complex extension of the periosteum. Diminution of this cortical domain with trabecular atrophy suggests that it has a proactive or reactive role in determining bone mass and strength by facilitating musculoskeletal exchange in a form that is disengaged by ovariectomy.     

Scrub typhus reemergence in the Maldives

In summer 2002, an outbreak of febrile illness began in the Maldives in the Indian Ocean. Through April 2003, officials recorded 168 cases with 10 deaths. The Armed Forces Research Institute of Medical Sciences in Bangkok confirmed Orientia tsutsugamushi and conducted a joint investigation with the Ministry of Health, Maldives. These cases of scrub typhus were the first in the Maldives since World War II.