No abstract

Escherichia coli W3110 was found to be 50 times more sensitive to cephamycin C than to cephalosporin C, and also markedly more sensitive to 7a-methoxycephalosporin C than to 7ct-hydroxycephalospofin C. Accordingly, this organism could be used to establish a bioassay of cephalosporin C 7a-methoxylation by a Streptomyces clavuli~lerus cell-free extract. The bioassay results were complemented by HPLC analysis. Modification of the mobile phase from 100mM NaH2PO4, p H 4.2, to 200 raM, pH 4.0, improved HPLC resolution such that an unidentified peak could be separated from the 7a-hydroxycephalosporin C peak, and the formation of this intermediate as well as the product, 7a-methoxycephalosporin C, could be directly measured in the cell-free reaction system.

No abstract

Models of attention demonstrated the existence of top-down, bottom-up, and history-driven attentional mechanisms, controlled by partially segregated networks of brain areas. However, few studies have examined the specific deficits in those attentional mechanisms in intellectual disability within the same experimental setting. The aim of the current study was to specify the attentional deficits in intellectual disability in top-down, bottom-up, and history-driven processing of multisensory stimuli, and gain insight into effective attentional cues that could be utilized in cognitive training programs for intellectual disability. The performance of adults with mild to moderate intellectual disability (n = 20) was compared with that of typically developing controls (n = 20) in a virtual reality visual search task. The type of a spatial cue that could aid search performance was manipulated to be either endogenous or exogenous in different sensory modalities (visual, auditory, tactile). The results identified that attentional deficits in intellectual disability are overall more pronounced in top-down rather than in bottom-up processing, but with different magnitudes across cue types: The auditory or tactile endogenous cues were much less effective than the visual endogenous cue in the intellectual disability group. Moreover, the history-driven processing in intellectual disability was altered, such that a reversed priming effect was observed for immediate repetitions of the same cue type. These results suggest that the impact of intellectual disability on attentional processing is specific to attentional mechanisms and cue types, which has theoretical as well as practical implications for developing effective cognitive training programs for the target population.