Diversity of 23S rRNA Genes within Individual Prokaryotic Genomes

The concept of ribosomal constraints on rRNA genes is deduced primarily based on the comparison of consensus rRNA sequences between closely related species, but recent advances in whole-genome sequencing allow evaluation of this concept within organisms with multiple rRNA operons. was the only species in which intragenomic diversity >3% was observed among 4 paralogous 23S rRNA genes.These findings indicate tight ribosomal constraints on individual 23S rRNA genes within a genome. Although classification using primary 23S rRNA sequences could be erroneous, significant diversity among paralogous 23S rRNA genes was observed only once in the 184 species analyzed, indicating little overall impact on the mainstream of 23S rRNA gene-based prokaryotic taxonomy

Decreased hippocampal volume, indirectly measured, is associated with depressive symptoms and consolidation deficits in multiple sclerosis

Item does not contain fulltextBackground: The human hippocampus plays a role in episodic memory and depression. Recently, it has been shown, using manual tracings, that the hippocampus is smaller in volume in MS patients compared with healthy controls, and that, at least for depression, hippocampal atrophy correlates with symptom severity. Methods: Because manual tracing of the hippocampus is time consuming, we used a semi-automatic procedure for temporal horn volumetry in 72 multiple sclerosis (MS) patients and 16 control subjects as an indirect measure of hippocampal volume. We analysed memory performance with the California Verbal Learning Test (using separate indices for encoding, consolidation and retrieval) and depressive mood with the Beck’s Depression Inventory (distinguishing between psychic and somatic aspects). Results: MS patients had significantly larger temporal horn volumes and volume correlated with psychic symptoms of depressive mood. Temporal horn volume was also associated with consolidation, in particular in the most impaired group. Conclusions: Temporal horn volume can be measured relatively easily and appears to correlate with two major clinical problems in MS patients: memory performance and depressive mood. The link between temporal horn volume, consolidation and depression may be hippocampal atrophy, as suggested by their adjacent neuroanatomical localization, and by the similarity in functional loss following impairment of these two structures.10 p