Fate of selectable marker DNA integrated into the genome of Nicotiana tabacum

To compare the effects of different transformation methods on the integration behavior and structural stability of integrated foreign genes in plant cells, tobacco protoplasts were transformed with Escherichia coli plasmid pLGV2103neo DNA using the Ca phosphate DNA coprecipitation technique. Parallel transformations were done by cocultivation with Agrobacterium tumefaciens harboring the Ti plasmid derivatives pGV3850::2103neo or pGV3850::1103neo. A comparison of the fine structure of the integrated donor DNA obtained by direct gene transfer and by cocultivation indicates that the donor DNA in cells transformed by the former technique undergoes structural changes and concatemerizations, while the DNA integrated by the latter procedure is often unaltered. The cotransformed nopaline synthase gene, which is present in the donor Ti plasmid DNA, was inactivated in two out of nine cases. Once integrated, the arrays of selectable marker DNA appear to be structurally stable under different cell culture and selection conditions, as well as after genetic transmission

Effects of context and word class on lexical retrieval in Chinese speakers with anomic aphasia

BACKGROUND: Differences in processing nouns and verbs have been investigated intensely in psycholinguistics and neuropsychology in past decades. However, the majority of studies examining retrieval of these word classes have involved tasks of single word stimuli or responses. While the results have provided rich information for addressing issues about grammatical class distinctions, it is unclear whether they have adequate ecological validity for understanding lexical retrieval in connected speech which characterizes daily verbal communication. Previous investigations comparing retrieval of nouns and verbs in single word production and connected speech have reported either discrepant performance between the two contexts with presence of word class dissociation in picture naming but absence in connected speech, or null effects of word class. In addition, word finding difficulties have been found to be less severe in connected speech than picture naming. However, these studies have failed to match target stimuli of the two word classes and between tasks on psycholinguistic variables known to affect performance in response latency and/or accuracy. AIMS: The present study compared lexical retrieval of nouns and verbs in picture naming and connected speech from picture description, procedural description, and story-telling among 19 Chinese speakers with anomic aphasia and their age, gender, and education matched healthy controls, to understand the influence of grammatical class on word production across speech contexts when target items were balanced for confounding variables between word classes and tasks. METHODS & PROCEDURES: Elicitation of responses followed the protocol of the AphasiaBank consortium (http://talkbank.org/AphasiaBank/). Target words for confrontation naming were based on well-established naming tests, while those for narrative were drawn from a large database of normal speakers. Selected nouns and verbs in the two contexts were matched for age-of-acquisition (AoA) and familiarity. Influence of imageability was removed through statistical control. OUTCOMES & RESULTS: When AoA and familiarity were balanced, nouns were retrieved better than verbs, and performance was higher in picture naming than connected speech. When imageability was further controlled for, only the effect of task remained significant. CONCLUSIONS: The absence of word class effects when confounding variables are controlled for is similar to many previous reports; however, the pattern of better word retrieval in naming is rare but compatible with the account that processing demands are higher in narrative than naming. The overall findings have strongly suggested the importance of including connected speech tasks in any language assessment and evaluation of language rehabilitation of individuals with aphasia

Interlaboratory precision study of a whole sediment toxicity test with the bioluminescent bacteriumVibrio fischeri

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A platform for genomics in South Africa

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