An examination of semantic impairment in amnestic MCI and AD : What can we learn from verbal fluency?

Introduction The Verbal Fluency Test (VF) is commonly used in neuropsychology. Some studies have demonstrated a marked impairment of semantic VF compared to phonemic VF in Alzheimer’s disease (AD). Since amnestic Mild Cognitive Impairment (aMCI) is associated with increased risk of conversion to incident AD, it is relevant to examine whether a similar impairment is observed in this population. The objective of the present empirical study is to compare VF performance of aMCI patients to those of AD and elderly controls matched one-to-one for age and education. Method Ninety-six participants divided into three equal groups (N = 32: AD, aMCI and Controls) were included in this study. Participants in each group were, on average, 76 years of age and had 13 years of education. A repeated measures ANOVA with the Group (AD, aMCI, NC) as between-subject factor and the Fluency condition (“P” and “animals”) as within-subject factor was performed. T-tests and simple ANOVAs were also conducted to examine the interaction. Results There was a significant interaction between the groups and the verbal fluency condition. In AD, significantly fewer words were produced in both conditions. In contrast, participants with aMCI demonstrated a pattern similar to controls in the phonemic condition, but generated significantly fewer words in the semantic condition. Conclusion These results indicate a semantic memory impairment in aMCI revealed by a simple, commonly-used neuropsychological test. Future studies are needed to investigate if semantic fluency deficits can help predict future conversion to AD

Billiard algebra, integrable line congruences, and double reflection nets

The billiard systems within quadrics, playing the role of discrete analogues of geodesics on ellipsoids, are incorporated into the theory of integrable quad-graphs. An initial observation is that the Six-pointed star theorem, as the operational consistency for the billiard algebra, is equivalent to an integrabilty condition of a line congruence. A new notion of the double-reflection nets as a subclass of dual Darboux nets associated with pencils of quadrics is introduced, basic properies and several examples are presented. Corresponding Yang-Baxter maps, associated with pencils of quadrics are defined and discussed.Comment: 18 pages, 8 figure

Learning and vulnerability to phonological and semantic interference in normal aging : an experimental study

This study compares semantic and phonological interference vulnerability across the full range of learning processes. Method: 43 controls aged 61–88 underwent a neuropsychological examination, French adaptation of the LASSI-L, and an experimental phonological test, the TIP-A. Paired sample t-tests, factorial ANOVA and hierarchical regressions were conducted, psychometric properties were calculated. Results: TIP-A efficiently generated phonological interference between concurrent word lists and was associated with short-term memory, unlike LASSI-L. On LASSI-L, proactive interference was higher than retroactive interference; the opposite pattern was found on TIP-A. Memory performance was better explained by age in the semantic than in the phonological task. Age was not associated with interference vulnerability. Intrusions and false recognition were associated with cognitive functioning regardless of age, particularly in the semantic context. Conclusion: To our knowledge, this is the first study to assess phonological and semantic interference using homologous concurrent word list tasks, and not a working memory build-up or DRM paradigm. The pattern obtained illustrates the weak initial memory trace in a phonological context and results are discussed according to depth-of-processing and dual-process theories. Similar paradigms could be studied among various pathologies for a better understanding of generalised interference vulnerability vs. specific semantic or phonological impairment

Overlapping reading frames at the LYS5 locus in the yeast Yarrowia lipolytica.

Mutants affected at the LYS5 locus of Yarrowia lipolytica lack detectable dehydrogenase (SDH) activity. The LYS5 gene has previously been cloned, and we present here the sequence of the 2.5-kilobase-pair (kb) DNA fragment complementing the lys5 mutation. Two large antiparallel open reading frames (ORF1 and ORF2) were observed, flanked by potential transcription signals. Both ORFs appear to be transcribed, but several lines of evidence suggest that only ORF2 is translated and encodes SDH. (i) The global amino acid compositions of Saccharomyces cerevisiae SDH and of the putative ORF2 product are similar and that of ORF1 is dissimilar. (ii) An in-frame translational fusion of ORF2 with the Escherichia coli lacZ gene was introduced into yeast cells and resulted in a beta-galactosidase activity regulated similarly to SDH; no beta-galactosidase activity was obtained with an in-frame fusion of ORF1 with lacZ. (iii) The introduction of a stop codon at the beginning of ORF2 prevented SDH expression in yeast cells, whereas no phenotypic effect was observed when ORF1 translation was blocked

An origin of replication and a centromere are both needed to establish a replicative plasmid in the yeast Yarrowia lipolytica.

Two DNA fragments displaying ARS activity on plasmids in the yeast Yarrowia lipolytica have previously been cloned and shown to harbor centromeric sequences (P. Fournier, A. Abbas, M. Chasles, B. Kudla, D. M. Ogrydziak, D. Yaver, J.-W. Xuan, A. Peito, A.-M. Ribet, C. Feynerol, F. He, and C. Gaillardin, Proc. Natl. Acad. Sci. USA 90:4912-4916, 1993; and P. Fournier, L. Guyaneux, M. Chasles, and C. Gaillardin, Yeast 7:25-36, 1991). We have used the integration properties of centromeric sequences to show that all Y. lipolytica ARS elements so far isolated are composed of both a replication origin and a centromere. The sequence and the distance between the origin and centromere do not seem to play a critical role, and many origins can function in association with one given centromere. A centromeric plasmid can therefore be used to clone putative chromosomal origins coming from several genomic locations, which confer the replicative property on the plasmid. The DNA sequences responsible for initiation in plasmids are short (several hundred base pairs) stretches which map close to or at replication initiation sites in the chromosome. Their chromosomal deletion abolishes initiation, but changing their chromosomal environment does not