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Biomedical subjects

D Prins

Publications and source records attributed to D Prins.

At least 19 recordsLinked to original sources
PubMed1999

Partial rescue of epithelial phenotype in integrin beta4 null mice by a keratin-5 promoter driven human integrin beta4 transgene.

Integrin beta4 null mice exhibit extensive epidermal detachment, reminiscent of the human skin blistering disease junctional epidermolysis bullosa associated with pyloric atresia. Hemidesmosomes, the stable adhesion structures of squamous epithelia, are not formed in the absence of alpha6beta4. Null mutant mice die shortly after birth, but apart from their striking epithelial phenotype, no obvious developmental defects have been observed. To elucidate the cause of death in these mice, we generated transgenic mice with a heterologous construct consisting of the squamous epithelial-specific keratin-5 promoter and a human integrin beta4 subunit cDNA. The transgene was not expressed in the presence of endogenous beta4, probably as a result of competition for a limited pool of alpha6 subunits. In a beta4 null background, however, the transgene was expressed, and its expression pattern followed that of squamous epithelial-specific keratins. These rescued pups appeared healthy and ultrastructural analysis revealed that the interspecies heterodimer alpha6(mouse)/beta4(human) was sufficient to trigger the assembly of hemidesmosomes. After a variable period of up to 48 hours after birth these animals began to exhibit haemorrhages at the plantar and palmar areas. We observed the formation of small blisters and found that the transgene was not detectably expressed in this region, which is devoid of hair follicles. The rescued neonates became increasingly cyanotic and died soon after the onset of this phenomenon. We performed a developmental study of the expression of beta4 in the complete respiratory tract, but we found no correlation between the spatiotemporal distribution of beta4 and the onset of the respiratory insufficiency. It became clear, however, that there was a gradual detachment of squamous epithelia in the oral and nasal cavities which led to obstruction of the respiratory tract, suggesting that in beta4 null and rescued mice, neonatal death was a direct consequence of decreased adhesion properties of hairless squamous epithelia, rather than a developmental defect of the lungs.

Animals↗
PubMed1997

Lexicalization in adults who stutter.

Three recent theories have implicated lexical processing failures as a possible source of fluency disruption in persons who stutter. Two experiments that bear upon these theories are reported. Both evaluate the effects on speech response latency of picture naming tasks designed to place selective demands on lexicalization: Experiment I, effects of one-word versus two-word responses; Experiment II, effects of a word's frequency of occurrence versus its number of syllables. Twelve adults who stutter and 12 with normally fluent speech participated in each experiment. In Experiment I, increases in naming latency for two-word (noun + verb) versus one-word (noun or verb) responses showed that demands for parallel processing did not differentiate the experimental groups. However, the between-group difference, showing longer latencies among those who stutter, was six times greater for the verb, than for the noun, task. Moreover, the group difference for verbs fully accounted for the size of the difference in the two-word task. Experiment II showed that the relative increase in naming latency associated with the word frequency effect versus the syllable latency effect was significantly greater in the stuttering than the nonstuttering group. Outcomes of the two experiments suggest that during lexicalization, as early as the L1 stage and first phase of L2, slow processing could serve to disrupt fluency in some persons who stutter. Under certain conditions, as specified in the three theories cited, such disruptions could set the occasion for stutter events.

Adult↗
PubMed1994

Word familiarity, syllabic stress pattern, and stuttering.

The correspondence of stuttering and linguistic characteristics of utterances has led to speculations that a source factor for stutter events is a speaker's inadequate formulation of the speech code. In this study, the effects of word frequency and syllabic stress pattern on stuttering frequency were evaluated using specially designed sentences read orally by 10 adult stutterers and 10 adult nonstutterers. Results revealed statistically significant differences in stuttering frequency between sentences with low and high frequency words, but not between sentences with regular and irregular syllabic stress patterns. The significant rank order correlation between stutterers' word recognition vocabulary scores and amount of stuttering on sentences with high versus low frequency words affirmed that word familiarity, not simply word prominence, is an important factor contributing to the word frequency effect. The outcomes are discussed in relation to current psycholinguistic theories of stuttering, proposing that word access and phonological encoding difficulties could be a source factor that underlies the occurrence of stutter events.

Adult↗
PubMed1992

Constancy of interstress intervals in the fluent speech of people who stutter during adaptation trials.

The constancy of interstress intervals (ISIs) was studied in the fluent speech of 2 people who stutter during five adaptation trials. Counter to prediction, ISI constancy did not improve as an accompaniment to the reduction of stuttering from Readings 1-5. Overall, the subjects' ISIs were substantially more variable in duration than those of 2 nonstutterers. This was accounted for by the subjects' unusually long ISIs in utterances that placed greater demands on speech motor control processes. Implications for impairment source factors in stuttering are discussed.

Adolescent↗
PubMed1991

Syllabic stress and the occurrence of stuttering.

The occurrence of stuttering on stress-peak and unstressed syllables in connected speech was studied in 10 young adult stutterers. Results showed a significant coincidence of stutter events and syllabic stress peaks, particularly in polysyllabic words. Stuttering on the first three words of principal clauses, however, appeared independent of syllabic stress. Similarities between the loci of stutter events and segmental errors of speech are considered in relation to explanations that regard stuttering as evidence of failure in normal speech production processes.

Adolescent↗
PubMed1990

Acoustical durations of speech segments during stuttering adaptation.

Acoustical durations of stutter- and disfluency-free speech segments from Readings #1 and #5 in an adaptation series were measured in 4 adapting, 4 nonadapting, and 4 nonstuttering subjects. The segment durations measured were intervocalic interval, stop-gap, voice onset time, and vowel duration. No clear trends in the change of acoustical durations from Reading #1 to Reading #5 distinguished the adapting, nonadapting, or nonstuttering subjects. Moreover, on the basis of speech naturalness judgements, listeners did not differentiate the Reading #1 and #5 phrase segments of subjects with high adaptation versus those with low adaptation scores. From these findings and related literature, adaptation of stuttering, as well as other fluency-inducing conditions, are viewed as circumstances that reduce demands upon central motor-linguistic processes.

Adaptation, Physiological↗
PubMed1988

Response contingent stimuli and stuttering: issues and implications.

The first papers concerning effects of response contingent stimuli (RCS) on stuttering and speech disfluency were published approximately 30 years ago. Research in this area fluorished until about 1980 after which relatively few studies have been reported. Reasons for the decline in interest are not altogether clear because crucial issues remain unresolved. This paper highlights and evaluates these issues and considers their implications for future research.

Behavior Therapy↗
PubMed1980

Principal and differential effects of haoperidol and placebo treatments upon speech disfuluencies in stutterers.

Fourteen stutterers completed a double-blind crossover study of the effects of Haloperidol and Placebo treatments upon their speech disfluencies. Although clearly not clinically effective, Haloperidol had a statistically significant effect upon reducing disfluency frequency and increasing speaking rate. For most subjects, drug-related reductions in disfluency severity resulted from a decrement in whole-word and phrase repetition, interjection, and revision-type disfluencies rather than from fewer part-word (elemental) repetitions and prolongations of sound or of silence. Neurotic personality profile correlated positively with an overall placebo effect, and there was a positive correlation between abnormal EEG and the drug effect. These findings are discussed in light of the nature of speech disfluency and stuttering and Haloperidol's biochemical and behavioral actions.

Adolescent↗
PubMed1980

Defense preference and stutterers' speech disfluencies: implications for the nature of the disorder.

Psychological defense mechanism preference was assessed in 16 adult stutterers. From this group, two subgroups of six subjects each were identified by their opposite extremes in defensive style: (1) expressive defenders; (2) avoidance defenders. Subsequently, these subgroups were found to be significantly different in measures of stuttering frequency and disfluency type. The expressive defenders showed higher frequency stuttering than the avoidance defenders (21.5% vs. 4.66%) while the avoidance subgroup showed preference for the use of accessory-type disfluencies; that is, interjections, phrase repetitions, and whole word repetitions. The possibility that the speech disfluencies of stutterers may vary as a function of defense preference is discussed in relation to: (1) definitions of stuttering phenomena and the disorder; (2) the developmental nature of stuttering as a problem and the role of learning; (3) different syndromes of stuttering; and (4) the contributions of etiologic versus pathogenic factors to the origins of the disorder.

Adult↗
PubMed1978

Neural response time of stutterers and nonstutterers in selected oral motor tasks.

Neural response time (NRT) was compared for 12 adult stutterers and 12 matched normal speakers on two verbal tasks (production of /pae/ and /bae/) and one oral, nonverbal task (lip closure) in response to visual and auditory stimulation. The auditory response stimulus was presented separately to the left and right ears, and the visual stimulus to both eyes. NRT was defined as the time interval between stimulus offset and the onset of electromyographic (EMG) activity from orbicularis oris superior muscle. Results show, in general, that stutterers are slower in NRT for all response tasks in both stimulus modes. Significant differences were found, however, for only the auditory mode. Analyses of the differences between and within groups for response tasks and stimulus modes are discussed in terms of recent research in and theory of timing disturbances in stuttering.

Acoustic Stimulation↗
PubMed1976

Stutterers' perceptions of therapy improvement and of posttherapy regression: effects of certain program modifications.

In an attempt to improve its effectiveness, a traditional, symptomatic stuttering therapy program for school-age children was modified to (1) focus more upon self-therapy activities while reducing group work emphasis; (2) specify more precisely the target responses used to replace stuttering; (3) establish clearly the criteria for client progress; and (4) provide well-defined activities for the transfer of speech change. Participants used a questionnaire to evaluate their improvement and post-therapy regression in various dimensions of stuttering severity, and results were compared with questionnaire findings from an earlier treatment program. Significantly greater improvement in speech fluency was perceived by the participants following the modified program, and follow-up videotape samples confirmed their perceptions as revealed on the questionnaire.

Adolescent↗