Biomedical subjects

David A Berry

Publications and source records attributed to David A Berry.

15 recordsLinked to original sources

PubMed2006

The influence of epilarynx area on vocal fold dynamics.

OBJECTIVE: This study investigated the influence of epilarynx area on an excised human vocal fold during phonation. STUDY DESIGN: A hemilarynx set-up using an excised human larynx was used. An artificial vocal tract with an epilarynx tube of variable cross-sectional area was attached. High-speed imaging was performed and standard phonatory variables were measured. RESULTS: Glottal airflow, fundamental frequency, and sound level increased as a function of subglottal pressure. A decrease in epilarynx area decreased phonation threshold pressure, glottal airflow, and vocal fold displacements and velocities. CONCLUSIONS: Preliminary experimental results confirm that narrowing the epilarynx area facilitates phonation by decreasing phonation threshold pressure, presumably through impedance matching of the glottal source and vocal tract. SIGNIFICANCE: As this phenomenon associated with epilarynx narrowing is further quantified and generalized, eventually new surgical alterations of the epilaryngeal structure may be suggested to facilitate phonation, in addition to standard phonosurgical procedures.

Aged↗

PubMed2006

The influence of subglottal acoustics on laboratory models of phonation.

Many previous laboratory investigations of phonation involving physical models, excised larynges, and in vivo canine larynges have failed to fully specify the subglottal system. Many of these same studies have reported a variety of nonlinear phenomena, including bifurcations (e.g., various classes of phonation onset and offset, register changes, frequency jumps), subharmonics, and chaos, and attributed such phenomena to the biomechanical properties of the larynx. However, such nonlinear phenomena may also be indicative of strong coupling between the voice source and the subglottal tract. Consequently, in such studies, it has not been clear whether the underlying mechanisms of such nonlinear phenomena were acoustical, biomechanical, or a coupling of the acoustical and biomechanical systems. Using a physical model of vocal fold vibration, and tracheal tube lengths which have been commonly reported in the literature, it is hypothesized and subsequently shown that such nonlinear phenomena may be replicated solely on the basis of laryngeal interactions with the acoustical resonances of the subglottal system. Recommendations are given for ruling out acoustical resonances as the source of nonlinear phenomena in future laboratory studies of phonation.

Humans↗

PubMed2006

Mechanisms of irregular vibration in a physical model of the vocal folds.

Previous investigations have shown that one mechanism of irregular vocal fold vibration may be a desynchronization of two or more vibratory modes of the vocal fold tissues. In the current investigation, mechanisms of irregular vibration were further examined using a self-oscillating, physical model of vocal fold vibration, a hemi-model methodology, and high-speed, stereoscopic, digital imaging. Using the method of empirical eigen-functions, a spatiotemporal analysis revealed mechanisms of irregular vibration in subharmonic phonation and biphonation, which were not disclosed in a standard acoustic spectrum.

Acoustics↗

PubMed2006

Aerodynamically and acoustically driven modes of vibration in a physical model of the vocal folds.

In a single-layered, isotropic, physical model of the vocal folds, distinct phonation types were identified based on the medial surface dynamics of the vocal fold. For acoustically driven phonation, a single, in-phase, x-10 like eigenmode captured the essential dynamics, and coupled with one of the acoustic resonances of the subglottal tract. Thus, the fundamental frequency appeared to be determined primarily by a subglottal acoustic resonance. In contrast, aerodynamically driven phonation did not naturally appear in the single-layered model, but was facilitated by the introduction of a vertical constraint. For this phonation type, fundamental frequency was relatively independent of the acoustic resonances, and two eigenmodes were required to capture the essential dynamics of the vocal fold, including an out-of-phase x-11 like eigenmode and an in-phase x-10 like eigenmode, as described in earlier theoretical work. The two eigenmodes entrained to the same frequency, and were decoupled from subglottal acoustic resonances. With this independence from the acoustic resonances, vocal fold dynamics appeared to be determined primarily by near-field, fluid-structure interactions.

Glottis↗

PubMed2005

Visualization and quantification of the medial surface dynamics of an excised human vocal fold during phonation.

SUMMARY: The purpose of this investigation was to investigate physical mechanisms of vocal fold vibration during normal phonation through quantification of the medial surface dynamics of the fold. An excised hemilarynx setup was used. The dynamics of 30 microsutures mounted on the medial surface of a human vocal fold were analyzed across 18 phonatory conditions. The vibrations were recorded with a digital high-speed camera at a frequency of 4,000 Hz. The positions of the sutures were extracted and converted to three-dimensional coordinates using a linear approximation technique. The data were reduced to principal eigenfuctions, which captured over 90% of the variance of the data, and suggested mechanisms of sustained vocal fold oscillation. The vibrations were imaged as the following phonatory conditions were manipulated: glottal airflow, an adductory force applied to the muscular process, and an elongation force applied to the thyroid cartilage. Over the range of variables studied, only the variation in glottal airflow yielded significant changes in subglottal pressure and fundamental frequency. All recordings showed high correlation for the distribution of the dynamics across the medial surface of the vocal fold. The distribution of the different displacement directions and velocities showed the highest variations around the superior region of the medial surface. Although the computed vibration patterns of the two largest empirical eigenfunctions were consistent with previous experimental observations, the relative prominence of the two eigenfunctions changed as a function of glottal airflow, impacting theories of vocal efficiency and vocal economy.

Aged↗

PubMed2005

Fluorous affinity purification of oligonucleotides.

[structure: see text] Nucleoside phosphoramidites bearing a fluorous dimethoxytrityl (FDMT) group were used to synthesize fluorous-tagged oligonucleotides, which were subjected to solid-phase extraction using a pH-stable fluorinated adsorbent. On-column detritylation afforded the purified oligonucleotides. The fluorous affinity purification method offers one-pass loading without ammonia removal, high selectivity for the removal of failure sequences, high recoveries (typically 70-100%), and the ability to purify long oligonucleotides (e.g., 50-100-mers).

Affinity Labels↗

PubMed2005

Tethered phytic acid as a probe for measuring phytase activity.

A novel approach for measuring phytase activity is presented. We have developed a new chromophoric substrate analog of phytic acid, 5-O-[6-(benzoylamino)hexyl]-d-myo-inositol-1,2,3,4,6-pentakisphosphate that permits direct measurement of the phosphate ester bond-cleavage reaction using HPLC. This compound, along with its dephosphorylated T-phosphatidylinositol intermediates, are quantified using reversed phase chromatography with UV detection.

Aspergillus niger↗

PubMed2005

Computation of the three-dimensional medial surface dynamics of the vocal folds.

To increase our understanding of pathological and healthy voice production, quantitative measurement of the medial surface dynamics of the vocal folds is significant, albeit rarely performed because of the inaccessibility of the vocal folds. Using an excised hemilarynx methodology, a new calibration technique, herein referred to as the linear approximate (LA) method, was introduced to compute the three-dimensional coordinates of fleshpoints along the entire medial surface of the vocal fold. The results were compared with results from the direct linear transform. An associated error estimation was presented, demonstrating the improved accuracy of the new method. A test on real data was reported including computation of quantitative measurements of vocal fold dynamics.

Algorithms↗

PubMed2005

Synthesis of 3-aminoimidazo[4,5-c]pyrazole nucleoside via the N-N bond formation strategy as a [5:5] fused analog of adenosine.

3-Amino-6-(beta-D-ribofuranosyl)imidazo[4,5-c]pyrazole (2) was synthesized via an N-N bond formation strategy by a mononuclear heterocyclic rearrangement (MHR). A series of 5-amino-1-(5-O-tert-butyldimethylsilysilyl-2,3-O-isopropylidene-beta-D-ribofuranosyl)-4-(1,2,4-oxadiazol-3-yl)imidazoles (6a-d), with different substituents at the 5-position of the 1,2,4-oxadiazole, were synthesized from 5-amino-1-(beta-D-ribofuranosyl)imidazole-4-carboxamide (AICA Ribose, 3). It was found that 5-amino-1-(5-O-tert-butyldimethylsilyl-2,3-O-isopropylidene-beta-D-ribofuranosyl)-4-(5-methyl-1,2,4-oxadiazol-3-yl)imidazole (6a) underwent the MHR with sodium hydride in DMF or DMSO to afford the corresponding 3-acetamidoimidazo[4,5-c]pyrazole nucleoside(s) (7b and/or 7a) in good yields. A direct removal of the acetyl group from 3-acetamidoimidazo[4,5-c]pyrazoles under numerous conditions was unsuccessful. Subsequent protecting group manipulations afforded the desired 3-amino-6-(beta-D-ribofuranosyl)imidazo[4,5-c]pyrazole (2) as a 5:5 fused analog of adenosine (1).

Adenosine↗

PubMed2005

A quantitative study of the medial surface dynamics of an in vivo canine vocal fold during phonation.

OBJECTIVES/HYPOTHESIS: The purpose of this study was to measure the medial surface dynamics of a canine vocal fold during phonation. In particular, displacements, velocities, accelerations, and relative phase velocities of vocal fold fleshpoints were reported across the entire medial surface. Although the medial surface dynamics have a profound influence on voice production, such data are rare because of the inaccessibility of the vocal folds. STUDY DESIGN: Medial surface dynamics were investigated during both normal and fry-like phonation as a function of innervation to the recurrent laryngeal nerve for conditions of constant glottal airflow. METHODS: An in vivo canine model was used. The larynx was dissected similar to methods described in previous excised hemilarynx experiments. Phonation was induced with artificial airflow and innervation to the recurrent laryngeal nerve. The recordings were obtained using a high-speed digital imaging system. Three dimensional coordinates were computed for fleshpoints along the entire medial surface. The trajectories of the fleshpoints were preprocessed using the method of Empirical Eigenfunctions. RESULTS: Although considerable variability existed within the data, in general, the medial-lateral displacements and vertical displacements of the vocal fold fleshpoints were large compared with anterior-posterior displacements. For both normal and fry-like phonation, the largest displacements and velocities were concentrated in the upper medial portion. During normal phonation, the mucosal wave propagated primarily in a vertical direction. Above a certain threshold of subglottal pressure (or stimulation to the recurrent laryngeal nerve), an abrupt transition from chest-like to fry-like phonation was observed. CONCLUSIONS: The study reports unique, quantitative data regarding the medial surface dynamics of an in vivo canine vocal fold during phonation, capturing both chest-like and fry-like vibration patterns. These data quantify a complex set of dynamics. The mathematical modeling of such complexity is still in its infancy and requires quantitative data of this nature for development, validation, and testing.

Animals↗

PubMed2005

Medial surface dynamics of an in vivo canine vocal fold during phonation.

Quantitative measurement of the medial surface dynamics of the vocal folds is important for understanding how sound is generated within the larynx. Building upon previous excised hemilarynx studies, the present study extended the hemilarynx methodology to the in vivo canine larynx. Through use of an in vivo model, the medial surface dynamics of the vocal fold were examined as a function of active thyroarytenoid muscle contraction. Data were collected using high-speed digital imaging at a sampling frequency of 2000 Hz, and a spatial resolution of 1024 x 1024 pixels. Chest-like and fry-like vibrations were observed, but could not be distinguished based on the input stimulation current to the recurrent laryngeal nerve. The subglottal pressure did distinguish the registers, as did an estimate of the thyroarytenoid muscle activity. Upon quantification of the three-dimensional motion, the method of Empirical Eigenfunctions was used to extract the underlying modes of vibration, and to investigate mechanisms of sustained oscillation. Results were compared with previous findings from excised larynx experiments and theoretical models.

Animals↗

PubMed2005

Influence of vocal fold scarring on phonation: predictions from a finite element model.

OBJECTIVES: A systematic study of the influence of vocal fold scarring on phonation was conducted. In particular, phonatory variables such as fundamental frequency, oral acoustic intensity, and phonation threshold pressure (PTP) were investigated as a function of the size and position of the laryngeal scar. METHODS: By means of a finite element model of vocal fold vibration, the viscoelastic properties of both normal and scarred vocal fold mucosae were simulated on the basis of recent rheological data obtained from rabbit and canine models. RESULTS: The study showed that an increase in the viscoelasticity of the scarred mucosa resulted in an increase in fundamental frequency, an increase in PTP, and a decrease in oral acoustic intensity. With regard to positioning of the scar, the PTP increased most significantly when the scar was within +/-2 mm of the superior-medial junction of the vocal folds. CONCLUSIONS: The systematic data obtained in this investigation agree with the general clinical experience. In the future, these findings may be further validated on human subjects as newly emerging technologies such as linear skin rheometry and optical coherence tomography allow the histologic and viscoelastic properties of the normal and scarred vocal fold mucosae to be measured in the clinic.

Animals↗

PubMed2003

An investigation of cricoarytenoid joint mechanics using simulated muscle forces.

Rotational and translational stiffnesses were calculated for arytenoid motion about the cricoarytenoid joint. These calculations were obtained from measurements on five excised human larynxes. For each larynx, known forces were applied to the arytenoid cartilage, and three markers were tracked as a function of applied forces. Assuming rigid body motion, arytenoid translations and rotations were computed for each applied force. Translational stiffnesses were obtained by plotting force versus displacement, and rotational stiffnesses were calculated by plotting torque versus angular rotation. A major finding was that the translational stiffness along the anterior-posterior direction was three times as great as the translational stiffnesses in the other two directions. This nonisotropic nature of the stiffnesses may be an important consideration for phonosurgeons who wish to avoid subluxation of the cricoarytenoid joint in patients. The computed rotational and translational stiffnesses currently are being implemented in 2D and 3D models. These stiffness parameters play a vital role in prephonatory glottal shaping, which in turn exerts a majorinfluence on all aspects of vocal fold vibration, including fundamental frequency, voice quality, voice register, and phonation threshold pressure.

Adult↗

PubMed2003

Laryngeal biomechanics and vocal communication in the squirrel monkey (Saimiri boliviensis).

The larynges of eight squirrel monkeys were harvested, dissected, mounted on a pseudotracheal tube, and phonated using compressed air. Patterns of vocal fold oscillation were compared with sound spectrograms of calls recorded from monkeys in our colony. Four different regimes of vocal fold activation were identified. Regime 1 resembled typical human vowel production, with regular vocal-fold vibration, a prominent fundamental frequency, and an accompanying series of harmonic overtones. This regime is likely to give rise to squirrel monkey "cackles," as well as a variety of other harmonically structured calls. In regime 2, the pattern of vibrations exhibited the presence of two or more unrelated frequencies (biphonation). This regime of glottal activity resembled the biphonation observed in many exemplars of "twitter" and "kecker" calls. The vocal folds oscillated continuously in regime 3, but produced glottal pulses whose amplitudes waxed and waned rhythmically. This phenomenon resulted in the percept of a series of discrete pulses, and may give rise to "errs," "churrs," and other calls composed of a rapid sequence of acoustic elements. In regime 4, the period of each oscillation was quasi-irregular. Shrieks and other broadband calls or call elements that lack an apparent fundamental frequency may be produced in this manner.

Animals↗

PubMed2003

Modeling measured glottal volume velocity waveforms.

The source-filter theory of speech production describes a glottal energy source (volume velocity waveform) that is filtered by the vocal tract and radiates from the mouth as phonation. The characteristics of the volume velocity waveform, the source that drives phonation, have been estimated, but never directly measured at the glottis. To accomplish this measurement, constant temperature anemometer probes were used in an in vivo canine constant pressure model of phonation. A 3-probe array was positioned supraglottically, and an endoscopic camera was positioned subglottically. Simultaneous recordings of airflow velocity (using anemometry) and glottal area (using stroboscopy) were made in 3 animals. Glottal airflow velocities and areas were combined to produce direct measurements of glottal volume velocity waveforms. The anterior and middle parts of the glottis contributed significantly to the volume velocity waveform, with less contribution from the posterior part of the glottis. The measured volume velocity waveforms were successfully fitted to a well-known laryngeal airflow model. A noninvasive measured volume velocity waveform holds promise for future clinical use.

Air Movements↗