Synthesis and biological activity of certain 4'-thio-D-arabinofuranosylpurine nucleosides

A series of 4'-thio-D-arabinofuranosylpurine nucleosides was prepared and evaluated as potential anticancer agents. The details of a convenient and high-yielding synthesis of the carbohydrate precursor 1-O-acetyl-2,3,5-tri-O-benzyl-4-thio-D-arabinofuranose (6) are presented. Proof of structure and configuration at all chiral centers of the nucleosides was obtained through an X-ray crystal structure of 9alpha as well as through NOE experiments on 9beta and 9alpha. All six target compounds were evaluated in a series of human cancer cell lines in culture. Two target compounds, beta anomers with diaminopurine (12) and guanine (16) as the bases, had significant cytotoxicity. One of these compounds (12) was selected for animal studies but was found to have no selectivity at the maximum tolerated dose in the murine colon 36 tumor model.

Verbal behaviors of preschool stutterers and conversational partners: observing reciprocal relationships

Standard counseling practices with the families of young stutterers include recommendations that listeners' negative verbal behaviors be modified in order to reduce the likelihood of stuttering. This study tested the hypothesis that stuttering and normal disfluencies in preschool stutterers are related to selected verbal behaviors in conversational partners. Twelve 2- to 6-year-old stutterers were video recorded while playing with their mother, father, and a familiar peer. The resulting videotapes were transcribed and two types of social communicative analyses (total number of words and utterances, verbal intent of the speaker) were undertaken. Results suggested that fathers used more words and utterances than mothers and peers. Parents provided more positive interactions with their stutterer offspring than did peers. Parents also asked significantly more negative and routine questions when talking to their stuttering child. Peer playmates were significantly more negative and generally commented more frequently when interacting with stutterers than did the parents. Stutterers were involved in significantly more positive interactions with their fathers. The frequency of fluency failures did not differ significantly when stutterers communicated with their mother, father, or peer partners. Implications regarding verbal styles of partners in relationship to the stuttering of preschool children are discussed.

Nonfluencies of preschool stutterers and conversational partners: observing reciprocal relationships

Nonfluencies produced by 12 stutterers (2-6 years old) interacting in three dyadic sessions were analyzed. A stutterer played with his own mother, own father, and a familiar peer for 10 min. Results indicated that the total frequencies and types of nonfluency observed were very similar in each of the play situations. Although stutterers exhibited more part-word repetitions and prolongations than any other type of nonfluency, they did not differ in the amount and type of nonfluency when talking to their three conversational partners. Because children have more breakdowns in fluency than adults, it was not surprising that peers were more nonfluent when talking to the stutterer than were the parents. Peers used significantly more part- and whole-word repetitions, tense pauses, and interjections than the parents did. The nonfluency levels of the parent partners were quite similar when talking to the stutterers.