Saurav Paul

Wideband reflectance tympanometry in chinchillas and humans

Wideband reflectance tympanometry was performed on twelve chinchillas ears. The complex input impedance of the middle ear, multifrequency admittance tympanograms, reflectance patterns (reflectance versus frequency), and reflectance tympanograms (reflectance versus ear-canal air pressure) were analyzed and compared to human data. The complex impedance of the chinchilla ear has a lower stiffness reactance at low frequencies, a higher mass reactance at high frequencies, and a lower resistance compared to the human. Multifrequency admittance tympanograms from chinchillas follow the same sequence of patterns as humans for low frequencies ( 8 kHz). Reflectance tympanograms for the two species show a single, centrally located minimum at low frequencies (<2 kHz) and are substantially different at higher frequencies. Results are shown for two animals that underwent eustachian tube obstruction. Reflectance patterns obtained with different ear-canal air pressures are substantially different. Reflectance results at any single ear-canal pressure (including ambient pressure) do not completely characterize the effects of middle-ear pathology.

Cellular Changes of Reissner's Membrane in Meniere's Disease: Human Temporal Bone Study

Objective: To study the cellular characteristics of Relssners membrane (RM) in temporal bones (TBs) from patients with endolymphatic hydrops with symptoms of Menleres disease (EH/+MD) and TBs with endolymphatic hydrops without symptoms of Menieres disease (EH/-MD) in an effort to understand the role of endolymphatic hydrops in MD symptoms. Study Design: Comparative study of human TB histopathology. Methods and Materials: Epithelial and mesothelial cellularity of RM from control TBs, TBs from patients with EH/+MD, and TBs from patients with EH/-MD were compared. The cellularity of epithelial and mesothelial cell nuclel (defined as number of cells/ 100 μm width of RM) were counted along the width of RM. The width of RM was measured from the vestibular crest of the spiral ligament to the limbus spiralis. Results: The cellular densities of epithelial cells in the basal and middle turns of RM were significantly higher in the EH/+MD and EH/-MD groups compared with “controls.” There was no difference in epithelial cellularity between EH/+MD and EH/-MD. There was a decrease in the number of mesothelial cells of RM in the basal turn in EH/+MD and EH/-MD groups (statistically significant only in EH/+MD group) when compared with controls. The number of mesothelial cells of RM in the middle turn in EH/+MD and EH/-MD groups were significantly decreased compared with normals. Discussion: Similar findings in cellularity of RM in temporal bones with EH/+MD and EH/-MD suggest that pathophysiologic mechanisms other than hydrops may be responsible for symptoms in Menieres disease.

Suppression of the Vertical Vestibulo-ocular Reflex in Older Persons at Risk of Falling

A case-control design was used to assess eye-head-trunk coordination for community-dwelling elders performing a stand-walk task. Eighteen elders with a high risk of falling were matched to 18 subjects with low risk on the basis of age, living status (living alone or with someone) and category of residence (independent living or assisted living facility). Standard electro-oculography was used in conjunction with an electromagnetic tracking device to measure eye and head-trunk motion, respectively. For the low-risk group, the mean slope of gaze-head and gaze-trunk relationships was significantly greater than zero (0.91 and 0.64, respectively), whereas high-risk elders did not demonstrate slope magnitudes significantly different from zero (0.52 and 0.16, respectively) due to large inter-subject variations. While the majority of subjects showed some counter-rotation of the eyes with head pitch, a greater percentage of subjects in the high-risk group did not suppress this response and consequently gaze and gaze velocity overcompensated for head pitch. These findings suggest that the vertical vestibulo-ocular reflex is not adequately suppressed during the stand-walk task in elders who are at a high risk of falling. Possible mechanisms contributing to these findings are discussed.A case-control design was used to assess eye-head-trunk coordination for community-dwelling elders performing a stand-walk task. Eighteen elders with a high risk of falling were matched to 18 subjects with low risk on the basis of age, living status (living alone or with someone) and category of residence (independent living or assisted living facility). Standard electro-oculography was used in conjunction with an electromagnetic tracking device to measure eye and head-trunk motion, respectively. For the low-risk group, the mean slope of gaze-head and gaze-trunk relationships was significantly greater than zero (0.91 and 0.64, respectively), whereas high-risk elders did not demonstrate slope magnitudes significantly different from zero (0.52 and 0.16, respectively) due to large inter-subject variations. While the majority of subjects showed some counter-rotation of the eyes with head pitch, a greater percentage of subjects in the high-risk group did not suppress this response and consequently gaze and gaze velocity overcompensated for head pitch. These findings suggest that the vertical vestibulo-ocular reflex is not adequately suppressed during the stand-walk task in elders who are at a high risk of falling. Possible mechanisms contributing to these findings are discussed.

Augmentation of blood circulation to the fingers by warming distant body areas.

Abstract Future activities in space will require greater periods of time in extreme environments in which the body periphery will be vulnerable to chilling. Maintaining the hands and fingers in comfortable conditions enhances finger flexibility and dexterity, and thus effects better work performance. We have evaluated the efficacy of promoting heat transfer and release by the extremities by increasing the blood flow to the periphery from more distant parts of the body. The experimental garment paradigm developed by the investigators was used to manipulate the temperature of different body areas. Six subjects, two females and four males, were evaluated in a stage-1 baseline condition, with the inlet temperature of the circulating water in the liquid cooling/warming garment (LCWG) at 33 °C. At stage 2 the total LCWG water inlet temperature was cooled to 8 °C, and at stage 3 the inlet water temperature in specific segments of the LCWG was warmed (according to protocol) to 45 °C, while the inlet temperature in the rest of the LCWG was maintained at 8 °C. The following four body- area-warming conditions were studied in separate sessions: (1) head, (2) upper torso/arm, (3) upper torso/arm/head, and (4) legs/feet. Skin temperature, heat flux and blood perfusion of the fingers, and subjective perception of thermal sensations and overall physical comfort were assessed. Finger temperature (Tfing) analyses showed a statistically significant condition × stage interaction. Post-hoc comparisons (Tfing) indicated that at stage 3, the upper torso/arm/head warming condition was significantly different from the head, upper torso/arm and legs/feet conditions, showing an increase in Tfing. There was a significant increase in blood perfusion in the fingers at stage 3 in all conditions. Subjective perception of hand warmth, and overall physical comfort level significantly increased in the stage 3 upper torso/arm/head condition. The findings indicate that physiological methods to enhance heat transfer by the blood to the periphery within protective clothing provide an additional tool for increasing total and local human comfort in extreme environments.