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Biomedical subjects

R Mayo

Publications and source records attributed to R Mayo.

At least 19 recordsLinked to original sources
PubMed2003

Macrophage proteomic fingerprinting predicts HIV-1-associated cognitive impairment.

BACKGROUND: Specific proteins produced from monocytes may be linked to the pathogenesis and aid in the diagnosis of HIV-1-associated dementia (HAD). OBJECTIVE: The authors assessed whether a diagnostic phenomic protein profile could be obtained from monocyte-derived macrophages (MDM) from HIV-1-infected patients with cognitive impairment. METHODS: Twenty-one HIV-1-infected Hispanic women and 10 seronegative controls matched by age and sex were followed at the University of Puerto Rico Medical Sciences Campus, where neuropsychological, immune, and viral parameters were tested. Monocytes were recovered by Percoll gradient centrifugation from peripheral blood mononuclear cells. MDM lysates were prepared after 7 days of cultivation and protein profiles analyzed by surface enhanced laser desorption/ionization (SELDI)-time of flight (TOF) ProteinChip tests. Classification trees were prepared for statistical analyses. RESULTS: A total of 177 protein peaks from 2 to 80 kDa were evaluated in 31 patient MDM lysates by SELDI-TOF ProteinChip assays. Select protein peaks, at 5028 and 4320 Da, separated HIV-1-infected from HIV-1-seronegative subjects with a sensitivity of 100% and a specificity of 80%. Thirty-eight peaks were used to differentiate HIV-1-infected subjects with and without cognitive impairment. A 4348 Da protein separated the two groups with a sensitivity of 100% and a specificity of 75%. CONCLUSIONS: The identification of unique phenomic MDM profiles from cognitively impaired HIV-1-infected patients supports the hypothesis that changes in monocyte function parallel the development of HAD.

AIDS Dementia Complex↗
PubMed2001

Effects of vowel height and vocal intensity on anticipatory nasal airflow in individuals with normal speech.

The purpose of this study was to determine the effects of vowel height and vocal intensity on the magnitude of anticipatory nasal airflow in normal speakers when producing vowel-nasal-vowel (VNV) sequences. Measurements of nasal and oral airflow were obtained from 15 men and 12 women with normal speech during production of the VNV sequences /ini/ and /ana/ at low, medium, and high intensity levels. Ratios of nasal to oral-plus-nasal airflow were calculated for the initial vowel of both utterances at each of the intensity levels. Analysis of variance (ANOVA) procedures indicated a significant main effect of intensity level and a significant vowel-by-sex interaction effect (p < .05) on the airflow ratios. Overall, the airflow ratio was reduced at high as compared to low intensity levels, regardless of sex of the speaker or vowel type. Female speakers exhibited greater airflow ratios during production of /ini/ than during productions of /ana/. Their airflow ratios were also greater during production of /ini/ than were those of male speakers. The results suggest that vocal intensity may affect velopharyngeal (VP) function in an assimilative nasal phonetic context. The results further suggest that anticipatory nasal airflow may be determined by the configuration of the oral cavity to a greater extent in women than in men. Theoretical and clinical implications are discussed.

Adolescent↗
PubMed2001

The relationship between spectral characteristics and perceived hypernasality in children.

The purpose of this study was to quantify perceived hypernasality in children. One-third octave spectra of the isolated vowel [i] were obtained from 32 children with cleft palate and 5 children without cleft palate. Four experienced listeners rated the severity of hypernasality of the 37 speech samples using a 6-point equal-appearing interval scale. When the average 1/3-octave spectra from the hypernasal group and the normal resonance group were compared, spectral characteristics of hypernasality were identified as increased amplitudes between F1 and F2 and decreased amplitudes in the region of F2. Based on the findings of the children's speech, 36 speech samples with manipulated spectral characteristics were used to minimize the influences of voice source characteristics on perceived hypernasality. Multiple regression analysis revealed a high correlation (R = 0.84) between the amplitudes of 1/3-octave bands (1 k, 1.6 k, and 2.5 kHz) and the perceptual ratings. Increased amplitudes of bands between F1 and F2 (1 k, 1.6 kHz) and decreased amplitude of the band of F2 (2.5 kHz) was associated with an increasing perceived hypernasality. These results suggest that the amplitudes of the three 1/3-octave bands are appropriate acoustic parameters to quantify hypernasality in the isolated vowel [i].

Adolescent↗
PubMed2000

BP: developing excellence in the global enterprise.

World-class supply management organizations like Honda of America, John Deere, Chrysler, Hewlett Packard, and Motorola all understand the power of continuous improvement in the supply base. The best supplier management and development programs help suppliers--on a long-term basis--develop their own strength and expertise in suggestion systems, new product development, and high quality production results.

Benchmarking↗
PubMed1999

Respiratory responses to sudden pressure venting during stop consonant production.

Twenty healthy adults, age range 20-55 years, participated in a study to assess the responses of the upper airway to sudden, unanticipated pressure venting during speech production. A computer was used to open or close a valve in a random fashion during one of two productions of the word 'hamper'. The SAR System (Microtronics Corp., Chapel Hill, N.C., USA) was used to collect and monitor respiratory variables associated with speech production. Results indicated no significant changes in duration between vented and unvented conditions. Although intraoral pressure was reduced under vented conditions, the magnitude was sufficient for sound generation. Respiratory effort increased when the airway was suddenly vented, suggesting a compensatory response to experimental perturbation. However, the response contrasted somewhat from what has been observed in patients with velopharyngeal inadequacy, indicating that the strategy used may be different.

Adult↗
PubMed1998

Comparative study of the effects of clozapine and clothiapine in different preparations of guinea pig and rat isolated organs.

1. A study has been made to know the effects of clozapine and clothiapine on the responses of rat isolated vas deferens to norepinephrine, dopamine and potassium, those of the rat isolated uterus to serotonin and potassium, and that of guinea pig isolated ileum to histamine. 2. Clozapine was a noncompetitive antagonist to norepinephrine, dopamine, serotonin and histamine; it inhibited potassium-induced contraction in isolated rat uterus and vas deferens. 3. Clothiapine was a competitive antagonist to serotonin and a noncompetitive antagonist to norepinephrine, dopamine and histamine; it inhibited potassium-induced contractions in isolated rat uterus and vas deferens.

Animals↗
PubMed1998

Nasal coarticulation in normal speakers: a re-examination of the effects of gender.

The purpose of this study was to re-examine the influence of gender on nasal coarticulation in normal speakers. Twenty adult speakers (10 men, 10 women) produced the vowel-nasal-vowel (VNV) sequence /ini/ within a carrier phrase using two stress patterns: (1) with equal stress placed on both syllables, and (2) with contrastive stress placed on the second syllable. A partitioned, circumferentially vented pneumotachograph mask and microphone were used to determine nasal airflow, ratios of nasal to oral-plus-nasal airflow, and sound pressure levels (SPLs) at the midpoints of the first and second vowels of the syllables. Volume ratios of nasal to oral-plus-nasal airflow that reflected the entire duration of the vowels were also obtained. Results indicated that all speakers except 1 woman exhibited nasal airflow at the midpoint of the first vowel when /ini/ was produced with equal stress; all speakers exhibited carryover nasal airflow during the second vowel. During contrastive stress, all speakers except 1 woman and 1 additional man exhibited anticipatory nasal airflow; all speakers exhibited carryover nasal airflow. Analysis of variance (ANOVA) procedures with repeated measures indicated significant main effects of syllable stress (p < 0.001) relative to nasal airflow and ratios of nasal to oral-plus-nasal airflow. Regardless of the gender of the speakers, syllable stress resulted in reduced anticipatory and carryover nasal airflow during the first and second vowels of /ini/, respectively. The results suggest that (a) both men and women adhere to similar patterns of velar articulation, and (b) velopharyngeal closure during the vowel /i/ may be enhanced during stressed syllables. Implications relative to aspects of speech production and clinical practice are discussed.

Adult↗
PubMed1998

Intraoral pressure and velopharyngeal function.

OBJECTIVE: The objective of this study was to determine the influence of velopharyngeal (VP) inadequacy on respiratory speech compensations. DESIGN: The pressure-flow technique was used to measure pressure, airflow, and timing variables associated with VP closure during the production of the initial plosive consonant /p/ in a series of the utterance "papa." SETTING: The study was conducted in the speech and breathing laboratory of the UNC Craniofacial Center. PARTICIPANTS: Eighty-two subjects with cleft lip and/or palate were assessed. The subjects were divided into two groups, those with adequate VP closure (VP size <.010 cm2) and those with inadequate VP closure (VP size >0.10 cm2). The adequate group was comprised of 62 subjects, and 20 subjects were categorized as inadequate. RESULTS: Peak intraoral pressure decreased in the inadequate group, but the difference was not significant. Nasal airflow increased (p < .01), but duration of the pressure pulse was the same for both groups. The area under the pressure curve decreased for the inadequate group (p = .04). CONCLUSION: These data contrast with previously reported published data using /p/ in the utterance "hamper." This suggests that phonetic context influences the compensatory response to velopharyngeal inadequacy. Additionally, while the findings are somewhat similar to studies that involved noncleft subjects whose oral airway was suddenly vented during the production of /p/, there is enough difference to suggest that learning also affects the compensatory outcome.

Adolescent↗
PubMed1997

The response to sudden change in vocal tract resistance during stop consonant production.

The speech respiratory system is configured in ways that tend to maximize its ability to respond to changes in the airway environment. Intraoral pressures remain at levels sufficient to generate reliably recognized consonant sounds even in the presence of structural deficits such as velopharyngeal inadequacy. Similar respiratory compensations occur when bite blocks and bleed valves are used to vent airway pressures. The purpose of the present study was to determine the sensitivity of the monitoring system psychophysically and to assess its physiological response to sudden, unanticipated perturbations. Twenty adults were asked to produce the utterance/pa/, and a calibrated perturbator valve permitted air to escape from the oral cavity on randomly selected productions. Respiratory responses were recorded using PERCI-SARS instrumentation. The results indicated that sudden openings of 0.14 cm2 (SD = 0.04) were detected by speakers. Compensatory respiratory responses to suprathreshold pressure-venting occurred rapidly (i.e., 27 ms [SD = 8]) after valve opening. Although peak pressure and area under the pressure pulse fell with valve opening, the magnitude of pressure was nevertheless sufficient for sound generation. Measurements of the slope of the rise in intraoral pressure after subthreshold pressure-venting in 10 participants were compared to measurements obtained from an-elastic model of the upper airway. The data demonstrated a significant difference between vented and unvented conditions for the model, but not the participants. This suggests that elastic recoil is actively and unconsciously controlled in humans to compensate for losses in airway pressure during speech.

Adult↗
PubMed1996

Aerodynamic and temporal aspects of velopharyngeal function in normal speakers.

Aerodynamic and temporal characteristics of velopharyngeal function were determined for 42 adult male and female speakers. All subjects produced the word "hamper" at self-determined loudness levels and rates of speaking. Measurements of intraoral air pressure, nasal airflow, and estimates of velopharyngeal orifice size were obtained during production of the /m/ and /p/ segments. Volume measurements of nasal airflow were determined for the entire word, the /m/ segment, and the segments preceding /m/. Fifteen timing measures associated with the pressure-flow events of the nasal-plosive sequence were also determined. Results indicated that males generated significantly higher levels of peak intraoral air pressure than females during /p/. Male speakers also exhibited a significantly shorter interval in the rise of oral pressure associated with the /p/ segment. Male and female speakers, however, exhibited similar levels of anticipatory coarticulation as reflected by nasal air volume measurements. Finally, variability of selected measurements within speakers suggested that temporal aspects of velopharyngeal function were more constrained than aerodynamic aspects. The results are discussed relative to (a) sex differences in respiratory and velar function and (b) normative data for adult speakers.

Adolescent↗
PubMed1996

Microphone sensitivity as a source of variation in nasalance scores.

A two-part study was conducted to determine the sources of variation in nasalance scores derived from the Nasometer. In Study #1, a function generator was used as a signal source to calibrate and input sine and square waves directly into the Nasometer. Ten stimuli ranging from 105 to 330 Hz in 25 Hz increments were evaluated. In Study #2, the same signal source and an amplified loudspeaker were used to calibrate and present square waves to the nasometer via five different sets of microphones. The sound pressure level of all stimuli was maintained at 88 dB. Each microphone set was calibrated using the 105 Hz signals. Results from Study #1 indicated consistent nasalance scores across all frequencies (i.e., all scores were within 2% of calibration). Results from Study #2 demonstrated deviations greater than 2% from calibration as a function of frequency for all five sets of microphones. The smallest deviation was 5%, whereas the largest deviation was 14%. We suggest that the variation in nasalance as a function of stimulus frequency may be due to a mismatch in the sensitivity of microphones (i.e., different frequency response characteristics). It is further suggested (a) that individual investigators determine the response characteristics of their microphones and (b) that relatively small variations in nasalance scores (i.e., 5-14%) either within or across speakers be interpreted with caution.

Amplifiers, Electronic↗
PubMed1996

Nasalance and nasal area values: cross-racial study.

Nasometry and nasal cross-sectional area data were obtained from 80 normal male and female speakers (40 African-Americans and 40 white Americans) all of whom were over the age of 18 and spoke the Mid-Atlantic dialect of American English. The nasalance scores for readings of the Zoo Passage did not differ significantly between the groups. However, nasalance scores for readings of the Nasal Sentences were found to be significantly higher among the white speakers. The pressure-flow method was used to obtain nasal cross-sectional area values. There were no racial differences in nasal cross-sectional area. The Nasal Sentences scores were not highly correlated with nasal cross-sectional area. The clinical significance of these findings is discussed.

Adult↗
PubMed1996

Dyspnea following experimentally induced increased nasal airway resistance.

Nasal resistance (NRZ) values for healthy adults range from 1.0 to 3.5 cm H2O/L/sec. Some oral breathing tends to occur at values above 3.5. The purpose of the present study was to determine at what level of NRZ individuals sense that nasal breathing is difficult. A diaphragm was used to add four different resistance loads in random to 15 adult subjects. These loads were 5,8, and 15 cm H2O/L/sec and a value 40% above the individual's normal NRZ. Loads were added under four conditions: normal breathing, fixed flow rate, fixed breathing rate, and fixed flow and breathing rate. The pressure-flow technique was used to measure NRZ under all conditions. The study revealed that the sensation of breathing difficulty occurred at a median resistance of 5 cm H2O/L/sec and, as subjects were constrained to maintain fixed flow and breathing rates, the magnitude of RZ, at which the sensation of dyspnea was noted, decreased. The values observed in this study support previous findings suggesting that individuals switch to some oral breathing to maintain an adequate level of upper airway resistance at values between 3.5 and 4.5 cm H2O/L/sec. The findings also show that individuals attempt to minimize increases in airway resistance by modifying breathing behaviors.

Adaptation, Physiological↗
PubMed1996

Aerodynamic and acoustic characteristics of a speaker with turbulent nasal emission: a case report.

Aerodynamic and acoustic characteristics were determined from the speech of an adult female with mild mental retardation and severe velopharyngeal inadequacy. The speaker's productions of /s/ were characterized by consistent nasal grimacing and turbulent air emission. Aerodynamic assessment estimated the size of the velopharyngeal orifice to exceed 200 mm2 during plosive production. Nasal cross-sectional area was estimated to be 35 mm2 during quiet breathing. Nasometric evaluation indicated nasalance of 63% associated with the "Zoo" passage. Acoustic analysis of the separately recorded oral and nasal speech signals indicated spectral energies in the region of approximately 2.5 to 7.0 kHz associated with nasal emission during /s/ production. The occurrence of these frequencies suggested an acoustic/perceptual function of the nasal grimace. Pressure-flow evidence also suggested that the nasal grimace, perhaps with lingual assistance, functioned to enhance speech aerodynamics.

Adult↗
PubMed1996

The enteric neural network and three dimensional computer modelling of intestinal peristalsis.

A computer model of the enteric nervous system has been developed using MATLAB in order to determine the extent to which the nature of intestinal activity can be explained by our current understanding of the projections and connectivity of enteric neurons. The model is based on repeated, identical overlapping modules, each of which contains the same number of neurones and circular muscle. The connections between modules were derived from microanatomical data. This simple model explains some characteristic features of the generation of an intestinal motor pattern.

Animals↗
PubMed1995

The regulation of nerve growth factor synthesis and delivery to peripheral neurons.

Recent experiments have provided new insights into the way in which the synthesis of nerve growth factor (NGF) is regulated. In particular, a variety of agents have been found to influence the cellular concentration of mRNANGF and NGF both in vitro and in vivo. However, no clear mechanism has been found to indicate the existence of a feedback regulation of NGF synthesis by effector tissue innervation. We have argued in this review that some form of feedback control is likely to exist between the innervation and the cells producing the factor. One such possibility, the regulation of the availability of NGF by control of its secretion, is discussed.

Animals↗
PubMed1994

Hypernasality and velopharyngeal impairment.

Although the primary cause of hypernasality is impaired velopharyngeal (VP) function, a variety of other factors influence the outcome perceived by the listener. The purpose of the current study was to assess the relationship between oral-nasal resonance balance and (1) velopharyngeal orifice area; (2) nasal airflow rate; and (3) duration of nasal airflow. The pressure-flow technique was used to estimate VP area and measure nasal airflow rate and duration. Ratings of oral-nasal balance were made on a 6-point equal-appearing interval scale. Results indicated a moderate correlation between hypernasality rating and VP area (0.66), nasal airflow (0.61), and nasal airflow duration (0.53). Adults tended to be perceived as more hypernasal than children for a given degree of VP impairment. Finally, when the degree of VP opening was small, perceived oral-nasal resonance balance appeared to be related to duration of the opening-closing movements.

Adolescent↗