Biomedical subjects

A Stuart

Publications and source records attributed to A Stuart.

At least 37 records · Page 2Linked to original sources

PubMed1997

Effect of speaking into a passive resonator on stuttering frequency.

The effect on stuttering frequency of speaking into a passive resonator was investigated. Eight participants who stuttered read aloud with and without the benefit of the resonator. A statistically significant reduction of approximately 30% in stuttering frequency was observed while the participants spoke with the resonator. These and similar commercially available devices may be employed with individuals who stutter, particularly children, as a means of enhancing fluency.

Adolescent↗

PubMed1997

Word recognition in continuous noise, interrupted noise, and in quiet by normal-hearing listeners at two sensation levels.

The effect of presentation level on word recognition performance-intensity functions in continuous and interrupted broadband noise and in quiet was explored. Normal-hearing participants were tested at 30 and 50 dB sensation levels (SLs). Performance-intensity functions in both noises were determined at signal-to-noise ratios (S/Ns) of 10, 5, 0, -5, -10, -15, and -20 dB. There was no effect of SL presentation on word recognition performance in quiet (p = 0.136). A significant main effect was observed for S/N in both continuous and interrupted broadband noise conditions (p < 0.0001). Performance increased with increases in S/N regardless of the competing noise condition. A significant main effect for SL presentation was only observed in the interrupted noise condition (p = 0.0019). That is, performance was higher for the 50 SL for the interrupted noise condition only. It is suggested that the observed difference in performance in interrupted noise at different SLs offers additional evidence for level-dependent, temporal masking phenomena.

Hearing↗

PubMed1997

Effect of frequency altered feedback and audience size on stuttering.

The effect of frequency altered feedback (FAF) and audience size on stuttering frequency was examined. Nine adults who stutter orally read to audiences of two, four and 15 people under conditions of FAF (one-half octave shift down) and non-altered auditory feedback (NAF). There was no statistically significant effect of audience size on stuttering frequency (p > 0.05). A statistically significant reduction in stuttering frequency was found under FAF relative to NAF (p < 0.5). Collapsed across audience conditions, stuttering frequency was reduced by 74%. These findings suggest that FAF may be useful as a treatment tool.

Adult↗

PubMed1997

Clinical pharmacology of filgrastim following high-dose chemotherapy and autologous bone marrow transplantation.

We evaluated the pharmacokinetics and pharmacodynamics of filgrastim during a Phase I study of this cytokine following high-dose chemotherapy and autologous bone marrow transplantation. Serum granulocyte colony-stimulating factor concentrations were determined by ELISA in 21 patients receiving 14-day continuous i.v. filgrastim infusions and 10 patients receiving daily 4-h infusions. Models were developed for filgrastim systemic clearance (Cls) by incorporation of receptor-binding theory. Mean plasma half-life (t1/2) in the 4-h infusion group was 197 min, and the volume of distribution approximated plasma volume. WBC counts transiently fell, then rebounded immediately postinfusion, which correlated with a delay in the disappearance of serum granulocyte colony-stimulating factor. The effect of WBC concentrations on filgrastim Cls was determined in patients receiving continuous infusions by segregation of study periods based on the presence of severe neutropenia. Clearance increased in all 14 patients receiving doses of 4-32 microgram/kg/day during WBC recovery. The effect of WBCs on Cls was described by a differential equation that included a static component and one component that varied with WBC concentration. These data suggest that currently used filgrastim dosing strategies following autologous bone marrow transplantation may be suboptimal.

Adult↗

PubMed1996

Fluency effect of frequency alterations of plus/minus one-half and one-quarter octave shifts in auditory feedback of people who stutter.

The effect of frequency alterations in auditory feedback of people who stutter on stuttering frequency was investigated. Twelve participants who stutter read aloud under nonaltered auditory feedback (NAF) and four conditions of frequency-altered feedback ([FAF], plus/minus one-half and one-quarter octaves) at normal and fast speech rates. Stuttering frequency was significantly higher while reading aloud with NAF relative to the four conditions of FAF (p < 0.05). There were no differences among participants' stuttering frequency between the four FAF conditions (p > 0.05). Reductions in stuttering frequency of approximately 50% to 60% were found with FAF relative to NAF. More disfluencies occurred with the fast versus the normal speech rate condition (p = .0007) irrespective of auditory feedback condition. These findings suggest that slight alterations in the frequency of auditory feedback of people who stutter are fluency-enhancing.

Adult↗

PubMed1996

Word recognition in continuous and interrupted broadband noise by young normal-hearing, older normal-hearing, and presbyacusic listeners.

OBJECTIVE: Word recognition performance in continuous and interrupted broadband noise was examined in young normal-hearing (YNH), older normal-hearing (ONH), and presbyacusic (older hearing-impaired [OHI]) listeners. DESIGN: Participants (N = 36) were presented with identical Northwestern University Auditory Test No. 6 stimuli at 30 dB sensation level re their respective speech reception thresholds. The speech stimuli were presented in quiet and in both competing noise conditions with signal to noise ratios (S/Ns) of 10, 5, 0, -5, -10, -15, and -20 dB. RESULTS: In general performance was superior in quiet, improved with increasing S/N, and was greater in the interrupted broadband noise than in the continuous broadband noise. Significant main effects of group and S/N were found in both competing noises (p < 0.0001). Post hoc pairwise comparisons revealed all groups performed differently, with superior performance being displayed by the YNH group followed by the ONH and OHI groups, respectively (p < 0.05). A significant group by S/N interaction was observed in only the interrupted noise condition (p = 0.019). The degree of change in word recognition performance as a function of S/N was greatest in the OHI group followed by the ONH group and the YNH group. CONCLUSIONS: Group effects observed in the interrupted noise would imply that the two older groups of listeners had an auditory temporal deficit relative to the YNH listeners. The paradigm reveals the patency of the temporal processes that are responsible for the perceptual advantage (i.e., a release from masking) a listener has in interrupted competing stimulus.

Adult↗

PubMed1996

Fluent speech, fast articulatory rate, and delayed auditory feedback: creating a crisis for a scientific revolution?

In 1970 Kuhn argued that science does not progress through a process of accretion. It is typified, rather, by the successive emergence of different paradigms which during their reign dictate the direction of normal science's puzzle-solving activity. Normal science inevitably exposes an anomaly which violates expectations predicted by the reigning paradigm. The "crisis" evoking anomaly may induce a destructive/constructive paradigm change. Transformations from one paradigm to another constitute a scientific revolution and dictate the growth and maturation of a field. This paper suggests the recent finding, that stutterers experience enhancement of fluency while speaking under delayed auditory feedback at a fast articulatory rate, be viewed as an anomaly. By challenging the notion that a slowed speech rate is necessary for amelioration of stuttering, the anomalous finding may be perceived as a crisis in the study of stuttering.

Attention↗

PubMed1996

Effect of instruction to sing on stuttering frequency at normal and fast rates.

Singing as a fluency-enhancing mechanism is well-established. The fluency derived by singing has been attributed to a reduced speech rate, memorized material, semantically reduced content, and an imposed rhythm. In this study, we attempted to address each of these explanations. 12 participants who stuttered were instructed to read or sing each of four different passages under the following conditions: reading at a normal rate, reading at a fast rate, singing at a normal rare, and singing at a fast rate. Participants exhibited a statistically significant increase in disfluencies while reading, i.e., participants displayed a 75% reduction in disfluency in the singing condition relative to the reading condition. There was no difference in stuttering frequency with rate conditions. Current findings suggest that stutterers are capable of internally generating fluent speech production by imposing idiosyncratic melodic structures or some derivation of melody when asked simply to sing. There is no claim that these participants were singing, as skills and capabilities varied tremendously, only that participants achieved dramatic enhancement of fluency after they were just asked to sing. Thus, the only intervening variable was the instruction to sing, which suggests the attempt to follow the instruction, no matter how futile, generated fluent speech. Since fluency was maintained in both the normal and fast rates of production, alternate central mechanisms must be held accountable for these findings.

Adolescent↗

PubMed1996

Stuttering amelioration at various auditory feedback delays and speech rates.

The primary purpose of this study was to determine if the finding of Kalinowski et al. (1993) of dramatic reductions in stuttering under delayed auditory feedback (DAF) at normal and fast speech rates could be replicated. The second purpose was to determine if stuttering frequency is differentially affected by various delays in an attempt to identify the optimal delay for fluency enhancement for both normal and fast speech rates. Fourteen adult stutterers read eight different passages at either a normal or fast speech rate under non-altered auditory feedback (NAF) and DAF with delays of 25, 50 and 75 ms. Results showed that significant fluency enhancement occurred under DAF at both normal and fast speech rates at all DAF settings (p < 0.05). This finding corroborates the notion that a slowed rate of speech is not a necessary antecedent for fluency improvement under conditions of altered auditory feedback. In addition, the results indicated that 50 ms appears to be the shortest delay producing the maximum reduction in stuttering frequency.

Adolescent↗

PubMed1995

Effect of single and combined altered auditory feedback on stuttering frequency at two speech rates.

The purpose of this study was to determine if combining delayed auditory feedback (DAF) and frequency altered feedback (FAF) would enhance fluency more than either DAF or FAF alone. Ten stutterers read at normal and fast speech rates under nonaltered auditory feedback (NAF), DAF (i.e., a 50 ms delay), FAF (i.e., a one half octave downward shift), and a combination of DAF and FAF [(COMBO), i.e., a 50 ms delay plus a one half octave downward shift]. Results indicated that stuttering frequency was significantly reduced under all altered auditory conditions at high speech rates relative to the NAF condition. There were, however, no significant differences between the altered auditory feedback conditions (i.e., DAF, FAF, and COMBO). It is suggested that further studies be undertaken to explore the combination of altered auditory feedback conditions, as it may be the case that a floor effect was demonstrated with the singular presentations of DAF and FAF and further improvements in fluency enhancement could not be exhibited in the combined condition. Finally, these findings support the notion that a slowed rate of speech is not necessary for fluency enhancement under conditions of altered auditory feedback.

Adult↗

PubMed1995

A randomized trial of an education and support program for HIV-infected individuals.

OBJECTIVES: To assess the effectiveness of an intervention for providing information and support to HIV-positive donors on changes in their sexual behavior, and to assess which donor characteristics are predictive of behavior change. DESIGN: Subjects were randomly assigned to a structured intervention or community referral group. Follow-up assessments were conducted every 6 months. SETTING: New York City, New York, USA. PARTICIPANTS: A cohort of 271 HIV-infected persons who donated blood to the New York Blood Center. INTERVENTION: Donors randomized to the structured intervention program met individually with a nurse for counseling and were offered a six-session support group. The program was designed to provide information, encourage safer sexual behavior and provide support. MAIN OUTCOME MEASURES: Sexual behavior, psychological distress and psychological help seeking, and immune function. RESULTS: In both groups there was a large decrease over time in reports of unsafe sexual activity. However, more than 30% of participants in both groups reported unsafe sexual activity at the 1-year follow-up visit. Donors randomized to the structured intervention program did not report significantly more behavior change at the 1-year follow-up. CONCLUSIONS: Better programs to promote behavior change in seropositive individuals are needed.

Adult↗

PubMed1995

Source localization for template implants with particular reference to stepping-source afterloaders.

Source localization from radiographs can be very difficult for template-guided implants if the needle images overlap. At UCSF several techniques to make this task easier have been developed. The techniques include selection of an optimum simulator gantry angle, use of different types of dummies, and differential dummy loading. In addition, several modifications have been made in our brachytherapy planning computer program to facilitate source entry. As a result of these improvements, source localization is now accomplished in much less time with improved accuracy.

Brachytherapy↗

PubMed1995

Protection against chemotherapy-induced alopecia by cyclosporin A in the newborn rat animal model.

BACKGROUND: We have previously shown that several agents will protect against chemotherapy-induced alopecia in the newborn rat animal model. Such protective agents render the hair follicle keratinocytes resistant to chemotherapy possibly by the expression of P-glycoprotein (Pgp). Cyclosporin A (CSA) is a potent inhibitor of Pgp. METHODS AND RESULTS: Efficacy of CSA was tested in its effects on chemotherapy-induced alopecia in the newborn rat animal model. CSA, when applied topically, protected rats from local alopecia induced by various agents. CONCLUSION: The mechanism of protection by CSA and its relationship to Pgp remain uncertain. The potential clinical applicability of this observation remains to be determined.

Administration, Cutaneous↗

PubMed1995

Hemispheric picture-naming hierarchies in stuttering subjects.

The present study was done to investigate the linguistic organization of the right hemisphere of stuttering subjects and the interhemispheric interactions that underlie verbal output in this population. Naming reaction times of 14 stuttering adults were measured to unilaterally presented pictures corresponding to vocabulary levels of < 5.5, 9.5-10.5, and > 18.0 years of age. An analysis of variance of latencies showed a significant main effect for picture vocabulary-age. Post hoc tests were interpreted as suggesting that the right hemisphere of stuttering subjects was capable of differential picture-encoding operations in a manner similar to the left hemisphere of normal speakers. Also, naming latencies favored left visual-field stimulations by 34 msec. Taken with significant and high correlations between visual fields for each level of picture vocabulary score, the right hemispheres of the stuttering subjects appeared responsible for picture-encoding operations. Left-hemispheric stimulus processing was not predicted, suggesting differences may exist in interhemispheric interactions underlying picture-naming functions in stuttering populations.

Adult↗

PubMed1995

Cytokines in proliferative diabetic retinopathy and proliferative vitreoretinopathy.

We determined whether interleukin-8, monocyte chemotactic protein-1, and macrophage-colony stimulating factor are present in the vitreous of patients with proliferative diabetic retinopathy (PDR) or proliferative vitreoretinopathy (PVR). The levels of these cytokines were measured by specific enzyme-linked immunoassays in vitreous from 30 patients with PDR, 13 patients with PVR, and 26 control individuals, including 10 cadaver eyes and 16 patients with idiopathic macular holes, idiopathic macular puckers, vitreous hemorrhages, or uncomplicated retinal detachments. Detectable levels of interleukin-8 were found in 90% of vitreous samples of patients with PDR, 85% with PVR, and 58% of control samples. IL-8 was significantly increased in PDR (mean +/- SEM; 25.0 +/- 5.3 ng/ml; p = 0.01), but not in PVR (11.9 +/- 3.9 ng/ml; p = 0.50) compared to control human vitreous (8.5 +/- 2.5 2.5 ng/ml). MCP-1 was detected in 90% of vitreous samples of patients with PDR, 92% with PVR, and 81% of control samples. MCP-1 was significantly increased in PDR (6.2 +/- 0.9 ng/ml, p = 0.001) and PVR (7.7 +/- 2.5 ng/ml, p = 0.001) over the levels in control vitreous (1.2 +/- 0.2 ng/ml). M-CSF was detected in 94% of vitreous samples of patients with PDR, 88% with PVR, and 92% from control vitreous. M-CSF was significantly elevated in PDR (32.3 +/- 8.3 ng/ml, p = 0.03), but not in PVR (23.6 +/- 12.8 ng/ml, p = 0.4) compared to control (10.7 +/- 3.5 ng/ml). Our results suggest that IL-8, MCP-1, and M-CSF participate in the pathogenesis of PDR and PVR.

Chemokine CCL2↗

PubMed1995

Word recognition performance in continuous and interrupted broad-band noise by normal-hearing and simulated hearing-impaired listeners.

Word recognition performance was investigated in 12 normal-hearing young adults in continuous and interrupted broad-band noise as a function of signal-to-noise ratio (S:N) with and without a simulated high frequency hearing loss (i.e., low-pass filtered at 2000 Hz). Subjects exhibited conventional sigmoid performance-intensity functions in continuous noise, for both unfiltered and filtered conditions. In contrast, subjects demonstrated shallower performance-intensity functions in the interrupted noise conditions with overall superior performance under adverse signal-to-noise ratios relative to the continuous noise conditions. Separate two-way analyses of variances investigating mean word recognition performance differences as a function of normal listening (unfiltered) versus the simulated hearing loss (filtered). Signal-to-noise ratio for both continuous and interrupted noise conditions revealed a significant main effects for S:N with both noise conditions (p < .05) and a significant main effect for the simulated hearing loss only in the interrupted noise condition (p < .05). It was hypothesized that subjects' diminished performance in the interrupted noise condition with the stimulated high frequency hearing loss reflected a reduced ability to temporally resolve auditory information between the gaps of noise.

Adult↗

PubMed1994

Applicability of standard irregular field calculations for high-energy photon beams.

Irregular-field calculations are usually based on a sector-summation technique. This technique typically involves separating the dose into primary and scatter components. While the conceptual basis for this procedure is valid at lower energies, it becomes suspect at higher energies. However, despite this limitation, a straightforward application of the technique yields good accuracy for 18 MV X-rays if certain limitations are observed. This work describes the calculational formalism used and the approximations made. Computed results are compared with measurements. The levels of uncertainty in both are discussed.

Humans↗

PubMed1994

Effect of high-pass filtering on the neonatal auditory brainstem response to air- and bone-conducted clicks.

The effect of standard high-pass analog filtering on the neonatal auditory brainstem response (ABR) to air- and bone-conducted clicks at low intensity screening levels was investigated. Simultaneous three channel recorded ABRs were obtained from 20 neonates with filter settings of 30-3000, 100-3000, and 150-3000 Hz at intensity levels of 20, 30, and 40 dB nHL. Statistically significant reductions in wave V amplitude and decreases in wave V latency were observed for both transducers across all three low level stimulus intensities with the progressive increase in the high-pass filter cutoff (p < .05). These data support the advocacy of less restrictive high-pass filtering (e.g., 30 Hz) for neonatal and infant ABR screening to air- and bone-conducted clicks.

Adult↗