We have analyzed the localization of the highly conserved telomeric sequence (TTAGGG)n in four salmonid species, two of the genus Salmo (Salmo trutta and Salmo salar) and two of the genus Oncorhynchus (Onchorhynchus mykiss and Onchorhynchus kisutch), by fluorescent in situ hybridization. As expected, the hybridization signal was mostly localized at the telomeres of all chromosomes in the four species. Two species evidenced special hybridization sites with the telomeric probe: (i) interstitial heterochromatic blocks in particular long chromosomes in S. salar; this observation supports tandem fusions as the karyotypic evolutionary mechanism leading to the formation of the long acrocentric and submetacentric chromosomes in the karyotype of S. salar; (ii) the whole NOR region in O mykiss; this observation suggests that the (TTAGGG)n sequence is scattered all along this chromosome region.
Azaspiracids (AZAs) are a group of shellfish toxins that were discovered in mussels from Irish waters in 1995. Because of the rare occurrence of poisoning incidents, the toxicity of the compounds is a continued matter of debate. Neither their mechanism of action nor their pharmacokinetic behavior has been elucidated, principally because of the lack of standards and reference tissues. Procedures to isolate AZAs from contaminated shellfish or to synthesize them have been developed; in particular, the procedures used for the preparative isolation of these toxins are currently being improved. The present paper describes the stability of AZAs in an array of pH and temperature conditions in methanolic solution, in shellfish tissue, and in aqueous mixtures of acids and shellfish tissues. Strong acids such as hydrochloric and formic acid led to rapid degradation of AZA1 at mM concentration, while the weaker acetic acid required harsher temperature conditions (70 degrees C) and greater concentrations to show similar effects. AZAs showed much greater stability in aqueous acidic mixtures with shellfish tissues, suggesting a significant protective effect of the matrix. A mechanism for the acid-catalyzed degradation is proposed, supported by mass spectral evidence from some of the degradation products. Strong bases (sodium hydroxide) also showed a detrimental effect on AZA1; however, weaker bases (ammonium hydroxide) did not lead to degradation over 24 h at room temperature. Finally, the toxic potential of acid degradation products of AZAs was found to be dramatically reduced compared to the parent compounds, as assessed through cytotoxicity.
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