Soils under seal carcasses with varying degrees of decomposition: oasis of nutrients and vegetation in Antarctica.

Areas of high concentration of seal carcasses have been observed in localized areas of James Ross Island, Antarctica. Such carcasses show an unusual vegetation development, in a semi-arid area with bare soils under intense winds, high salinity and sandy texture. We investigated carcasses of seals around a lake in James Ross Island, with four different stages of decomposition, with three replicates: Seal (S01), with recently mummified carcasses; S02, with partially degraded carcasses; S03, with broken carcasses with partially degraded exposed bones, and S04, with completely broken, scattered skeletons. The vegetation showed a maximum degree of development in carcasses at stages S02 and S03, with the environment between the skin and the skeleton as the preferred place for vegetation establishment. The chemical alteration was greater with increasing carcass decomposition but reduced with the spreading and final decomposition of the bones, with anomalous values observed only in the vicinity of the carcasses. It is concluded that the presence of carcasses of seals, concentrated in wet places, even in a semi-desert climate, represent important oases of nutrients, with a combination of physical and chemical effects throughout the decomposition process that favor plant establishment and succession.

Who takes the lead in the development of ulcerative colitis-associated colorectal cancers: mutator, suppressor, or methylator pathway?

Although several genetic alterations have been identified in patients with ulcerative colitis (UC), it remains unclear whether these changes indicate an increased risk for malignancy. This paper analyzes the involvement of suppressor, mutator, and methylator pathways in malignant transformation associated with UC. A total of 60 colonic samples (47 affected non-neoplastic mucosa, 7 dysplasia, and 6 carcinoma) from 51 UC patients were analyzed for 22 microsatellite markers. p53 gene exons 5-8 were analyzed by single-strand conformational polymorphism, and APC gene by denaturing gradient gel electrophoresis (exons 1-14) and protein truncation test (exon 15). Methylation studies for MLH1 and CSPG2 genes were also performed. Microsatellite instability was absent in all samples whereas allelic imbalance (AI) and loss of heterozygosity (LOH) were detected mainly in samples with neoplastic transformation (P<0.0001). AI and/or LOH at loci located on chromosomes 5, 9, and 18 were significantly more frequent in neoplastic samples (P<0.01), as were TP53 gene mutations (P<0.007). A single mutation was detected for APC gene in a cancer sample. MLH1 gene methylation was absent in all analyzed samples, whereas CSPG2 gene methylation was detected in a single non-neoplastic sample. Our results suggest that the suppressor pathway plays the main role in UC associated tumorigenic progression. LOH at specific loci located on chromosomes 5, 9, and 18 appears to be specifically associated with malignancy risk.

Association of colonic and endometrial carcinomas in Portuguese families with hereditary nonpolyposis colorectal carcinoma significantly increases the probability of detecting a pathogenic mutation in mismatch repair genes, primarily the MSH2 gene.

BACKGROUND: Hereditary nonpolyposis colorectal carcinoma (HNPCC) significantly raises the risk of developing colorectal carcinoma (CRC) and other extracolonic tumors. It is defined by the Amsterdam Criteria and is associated with germline mutations in mismatch repair genes, primarily MLH1 and MSH2. The objectives of the current study were to evaluate the presence of CRC (Type I) and other extracolonic tumors (Type II) in families with HNPCC and to analyze the findings for correlations with germline mutations in the MLH1 and MSH2 genes. METHODS: Seventy families with an HNPCC diagnosis were analyzed. Denaturing gradient gel electrophoresis and direct sequencing were used for germline mutation analysis in the MLH1 and MSH2 genes. RESULTS: Forty-three of 70 families (61%) presented with HNPCC Type II. In 21 of 30 families that had a complete genetic diagnosis, 16 pathogenic germline mutations (7 MLH1 mutations and 9 MSH2 mutations) and 5 mutations of unknown pathogenecity (all MLH1 mutations) were found. In the remaining nine families, no mutations were detected. Unequivocally pathogenic mutations were far more common in families with HNPCC Type II compared with families that had CRC only (P = 0.01). Families with endometrial carcinoma presented with the greatest probability of mutational detection (P = 0.005). MLH1 was only gene affected in families with HNPCC Type I, whereas mutations in both MLH1 and MSH2 were found in families with HNPCC Type II (P = 0.04). However, the MSH2 gene was more frequently involved in families with HNPCC in which endometrial carcinoma was present (P = 0.005). CONCLUSIONS: CRC and endometrial carcinoma were associated with a greater probability of detecting pathogenic mutations in mismatch repair genes, with MSH2 involvement predominating. The results support specific mutational screening strategies, based on observed phenotypes, for families with HNPCC.