Helicobacter pylori Chronic Infection Selects for Effective Colonizers of Metaplastic Glands.

Chronic gastric infection with Helicobacter pylori can lead to progressive tissue changes that culminate in cancer, but how H. pylori adapts to the changing tissue environment during disease development is not fully understood. In a transgenic mouse gastric metaplasia model, we found that strains from unrelated individuals differed in their ability to infect the stomach, to colonize metaplastic glands, and to alter the expression of the metaplasia-associated protein TFF3. H. pylori isolates from different stages of disease from a single individual had differential ability to colonize healthy and metaplastic gastric glands. Exposure to the metaplastic environment selected for high gastric colonization by one of these strains. Complete genome sequencing revealed a unique alteration in the frequency of a variant allele of the putative adhesin sabB, arising from a recombination event with the related sialic acid binding adhesin (SabA) gene. Mutation of sabB in multiple H. pylori strain backgrounds strongly reduced adherence to both normal and metaplastic gastric tissue, and highly attenuated stomach colonization in mice. Thus, the changing gastric environment during disease development promotes bacterial adhesin gene variation associated with enhanced gastric colonization. IMPORTANCE Chronic infection with Helicobacter pylori is the primary risk factor for developing stomach cancer. As disease progresses H. pylori must adapt to a changing host tissue environment that includes induction of new cell fates in the cells that line the stomach. We tested representative H. pylori isolates collected from the same patient during early and later stages of disease in a mouse model where we can rapidly induce disease-associated tissue changes. Only the later-stage H. pylori strains could robustly colonize the diseased stomach environment. We also found that the ability to colonize the diseased stomach was associated with genetic variation in a putative cell surface adhesin gene called sabB. Additional experiments revealed that SabB promotes binding to stomach tissue and is critical for stomach colonization by the late-stage strains. Thus, H. pylori diversifies its genome during disease progression and these genomic changes highlight critical factors for bacterial persistence.

The psychosocial impact of orthognathic surgery: a systematic review.

The aim of this study was to review the reported psychosocial benefits of orthognathic surgery. A systematic review of the literature was conducted using MEDLINE (1966 to December 2000), Web of Science (1981 to December 2000), and reference sections of identified articles. We also hand searched key orthodontic, oral surgery, and psychology journals. No language limitations were imposed. Randomized controlled trials, other controlled clinical trials, prospective studies (with or without controls), and retrospective studies (with or without controls) were considered for inclusion. Two reviewers extracted the data and independently assessed the quality of the studies. In all, 29 studies, including a number of prospective and retrospective studies, were identified as relevant. The results of the review indicated that orthognathic patients experience psychosocial benefits as a result of orthognathic surgery, including improved self-confidence, body and facial image, and social adjustment. However, there were wide variations in the study designs and a lack of uniformity in measuring the psychosocial constructs. This made it difficult to quantify the extent and the duration of the psychosocial benefits.

Reinnervation of developing rat molars.

The ability of regenerating inferior alveolar nerve (IAN) fibres to reinnervate dentine of developing rat first molar teeth was investigated. At intervals of 5, 15, 30 and 50 days after intramandibular transection of the IAN at the age of 20 days, the percentage of innervated dentinal tubules was estimated and compared with results from a series of control specimens. In addition, the myelinated axon populations of the root canal pulps were examined by light microscopy. Degeneration of almost all pulpal myelinated axons and dentinal unmyelinated axons occurred within 5 days of surgery. By 15 days after transection there was evidence of some pulpal reinnervation by myelinated axons but less than 2% of dentinal tubules showed reinnervation (control, 31.8%). At 30 days after surgery the figure for dentinal reinnervation was approximately 17.7% (control, 44.9%), and by 50 days after transection (70 days of age) mean innervation was about 70% of the level observed in control 70 days teeth, though the difference between control and experimental specimens was not significant at the 5% level of probability. The results indicate that reinnervation of dentine does occur in developing teeth after nerve transection. It is argued that the results suggest a faster and probably more complete reinnervation in young animals; and that reinnervation may be attributable more to an active than to a passive mechanism, and this may also apply to dentinal innervation during development.

Toxicologic and carcinogenic evaluation of Fenvalerate in the B6C3F1 mouse.

Groups of 50 male and 50 female B6C3F1 mice were fed dietary concentrations of 10, 50, 250 or 1250 ppm Fenvalerate for 2 years. Two groups of control mice, 50 per sex per group, received basal diet only. Mortality was increased and body weight was significantly decreased in male and female mice in the 1250 ppm treatment group. Mean body weight of female mice in the 250 ppm group was also generally lower than controls after the 60th week of feeding. Decreased albumin and increased glutamic oxaloacetic transaminase levels in mice fed 1250 ppm Fenvalerate were the only effects observed in the hematology and serum chemistry parameters examined. The only treatment related non-neoplastic pathologic effect observed in the study was multifocal microgranulomata in lymph nodes, liver and spleen of 1250 ppm male mice and 250 and 1250 ppm female mice. Less severe microgranulomatous changes were present in mesenteric lymph nodes of 50 and 250 ppm male mice. No statistically significant differences were observed in either the number or type of neoplasms in mice fed Fenvalerate diets when compared to concurrent controls. Thus, Fenvalerate was found not to be carcinogenic in B6C3F1 mice under the conditions of the test.