Life history, climate and biogeography interactively affect worldwide genetic diversity of plant and animal populations.

Understanding how biological and environmental factors interactively shape the global distribution of plant and animal genetic diversity is fundamental to biodiversity conservation. Genetic diversity measured in local populations (GDP) is correspondingly assumed representative for population fitness and eco-evolutionary dynamics. For 8356 populations across the globe, we report that plants systematically display much lower GDP than animals, and that life history traits shape GDP patterns both directly (animal longevity and size), and indirectly by mediating core-periphery patterns (animal fecundity and plant dispersal). Particularly in some plant groups, peripheral populations can sustain similar GDP as core populations, emphasizing their potential conservation value. We further find surprisingly weak support for general latitudinal GDP trends. Finally, contemporary rather than past climate contributes to the spatial distribution of GDP, suggesting that contemporary environmental changes affect global patterns of GDP. Our findings generate new perspectives for the conservation of genetic resources at worldwide and taxonomic-wide scales

Loss of heterozygosity at 18q21 region in gastric cancer involves a number of cancer-related genes and correlates with stage and histology, but lacks independent prognostic value

Several studies support a role of 18q21 LOH, involving the DCC locus, in colorectal cancer progression; however, its contribution to the natural history of gastric cancer is less clear. Recently, a number of cancer-related genes have been mapped in the 18q21 region, either centromeric or telomeric to DCC. This study searched for 18q21 LOH in 161 gastric cancers representative of all tumour stages and main histological types. To this purpose, seven highly polymorphic markers were used flanking the 18q21 band and spanning the entire region. Thirty-four out of 147 (23.1%) informative cases showed LOH. In 27 of 34 cases (79%), LOH involved all the informative loci. The remaining seven cases showed LOH at more telomeric sites and retained heterozygosity at more centromeric markers, mostly those proximal to the DCC gene. A strong correlation between 18q21 LOH and level of gastric wall invasion, lymph node metastases, or stage was found in cohesive (glandular+solid) and mixed tumours, but not in diffuse cancers. Cox univariate and multivariate analysis showed that invasion level, lymph node metastases, distant metastases, TNM stage, and histology were effective predictors of survival, whereas 18q21 LOH did not show predictive power. The simultaneous deletion of a variety of cancer-related genes with different and even opposite roles might explain why, apparently, 18q21 LOH does not per se contribute significantly to the natural history of gastric cancer, despite strong correlation with stage

Intracellular, Intercellular, and Stromal Invasion of Gastric Mucosa, Preneoplastic Lesions, and Cancer by Helicobacter pylori

BACKGROUND AND AIMS: It is not clear how Helicobacter pylori, an apparently extracellular pathogen colonizing the luminal side of the gastric epithelium, invariably causes an immune-inflammatory response on the stromal side of the mucosa. Penetration of H pylori into epithelial cell lines and its interaction with immune-inflammatory cells have been documented in vitro. Several investigations also showed in vivo bacterial penetration into the epithelium up to the lamina propria; however, the identification as H pylori of the bacteria-like bodies observed in unchanged, metaplastic, or neoplastic mucosa remained sometimes questionable. METHODS: To search for bacteria-like organisms, we used transmission electron microscopy on endoscopic biopsy specimens from 20 dyspeptic subjects and surgical specimens of neoplastic and nonneoplastic mucosa from 20 cancerous stomachs. To ascertain the H pylori nature of the organisms found, we used 6 different antibodies directed against bacterial lysates, purified vacuolating cytotoxin A, or purified cytotoxin-associated antigen A in immunogold tests. The results were compared with those of H pylori strains cultivated in vitro. RESULTS: In nonmetaplastic gastric epithelium, cytochemically proven H pylori were detected, in the majority of cases, inside cytoplasm of epithelial cells, in intraepithelial intercellular spaces, and in underlying lamina propria, often in direct contact with immune-inflammatory cells and sometimes inside small blood vessels. Cytochemically proven H pylori were also observed inside 6 of 8 intestinal metaplasias and 9 of 20 cancers. CONCLUSIONS: H pylori penetrates normal, metaplastic, and neoplastic gastric epithelium in vivo, intracellularly, or interstitially to cause a strong immune-inflammatory response and promote gastric carcinogenesis