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Biomedical subjects

D Robert

Publications and source records attributed to D Robert.

At least 91 records · Page 5Linked to original sources
PubMed1996

Directional hearing by mechanical coupling in the parasitoid fly Ormia ochracea.

Sound localization is a basic processing task of the auditory system. The directional detection of an incident sound impinging on the ears relies on two acoustic cues: interaural amplitude and interaural time differences. In small animals, with short interaural distances both amplitude and time cues can become very small, challenging the directional sensitivity of the auditory system. The ears of a parasitoid fly Ormia ochracea, are unusual in that both acoustic sensors are separated by only 520 microns and are contained within an undivided air-filled chamber. This anatomy results in minuscule differences in interaural time cues (ca. 2 microseconds) and no measurable difference in interaural intensity cues generated from an incident sound wave. The tympana of both ears are anatomically coupled by a cuticular bridge. This bridge also mechanically couples the tympanana, providing a basis for directional sensitivity. Using laser vibrometry, it is shown that the mechanical response of the tympanal membranes has a pronounced directional sensitivity. Interaural time and intensity differences in the mechanical response of the ears are significantly larger than those available in the acoustic field. The tympanal membranes vibrate with amplitude differences of about 12 dB and time differences on the order of 50 microseconds to sounds at 90 degrees off the longitudinal body axis. The analysis of the deflection shapes of the tympanal vibrations shows that the interaural differences in the mechanical response are due to the dynamic properties of the tympanal system and reflect its intrinsic sensitivity to the direction of a sound source. Using probe microphones and extracellular recording techniques, we show that the primary auditory afferents encode sound direction with a time delay of about 300 microseconds. Our data point to a novel mechanism for directional hearing in O. ochracea based on intertympanal mechanical coupling, a process that amplifies small acoustic cues into interaural time and amplitude differences that can be reliably processed at the neural level. An intuitive description of the mechanism is proposed using a simple mechanical model in which the ears are coupled through a flexible lever.

Acoustics↗
PubMed1996

Tympanal hearing in tachinid flies (Diptera, Tachinidae, Ormiini): the comparative morphology of an innovation.

Tympanal hearing organs have been reported only recently for Diptera. All the cases documented so far relate to parasitoid tachinid flies of the ormiine tribe. In the ormiine flies, the presence of tympanal hearing is functionally linked to their reproductive behavior. Indeed, female ormiine flies detect and localize their host, typically singing orthopterans, by hearing their calling songs. The three ormiine fly species investigated here at the comparative level share the key morphological features associated with tympanal hearing. The extent of these structural modifications becomes evident in the light of comparison with the closely related atympanate tachinid Myiopharus doryphorae. We document a series of eight characters that constitute specialized modifications of the ventral prothorax: (1) an inflation of the probasisternum, providing a rigid frame to span the large tympanal membranes; (2) an increased surface area of the prosternal membranes that constitute very thin, corrugated tympanal membranes; (3) a forked, broad presternum with tympanal pits to which the sensory organs directly attach; (4) several modifications of the tracheal system comprising the enlargement of the prosternal air sac, a supplementary tracheal tube to the prosternal air sac accompanied by a subpartioning of the spiracular atrium, and larger mesothoracic spiracles; (5) the presence of two scolopophorous chordotonal organs in the unpartitioned prosternal air sac; (6) stiff cuticular apodemes linking the chordotonal organs to the presternum; (7) reduction in size of the cervical sclerites; and (8) several structural modifications of the prosternal apophyses, creating new attachment sites for neck muscles. This comparative approach brings out differences and similarities of the homologous cuticular structures found on the ventral prothorax of both tympanate and atympanate tachinids. It is proposed that, given the degree of similarity between the ormiine hearing organs, the ormiine tribe is monophyletic, whereby all members of this tribe evolved from a common ancestor, an acoustic parasitoid of a singing orthopteran insect.

Animals↗
PubMed1996

Tympanal hearing in insects.

Specialized hearing organs, known as tympanal organs, have evolved in at least seven different orders of insects. Tympanal organs are usually defined by the presence of a tympanal membrane (or eardrum). They are backed by an air-filled space or cavity and are innervated by a chordotonal sensory organ. In some insects, however, a recognizable tympanal membrane may not be easily identified by visual inspection, yet may possess tympanal hearing organs. In insects that possess them, tympanal hearing organs may mediate the detection of predators, prey, and potential mates and rivals. Unlike the ears of vertebrates, which are localized to cranial segments, the ears of insects may be found in a bewildering variety of locations on their bodies, depending on the species. The embryological and evolutionary origins of tympanal organs are related to ancestral states as proprioceptive chordotonal organs.

Journal Article↗
PubMed1996

Objective evaluation of dysphonia: preliminary results of a device allowing simultaneous acoustic and aerodynamic measurements.

Voice quality analysis was performed in 88 normal speakers and 157 dysphonic speakers using a device that allows simultaneous study of acoustic and aerodynamic parameters during pronunciation of a sustained /a/. We compared the results with those of voice quality grading by a jury. The Mann-Whitney test showed significant differences between the grades of dysphonia for all the parameters chosen. Comparison of results (using discriminant factorial analysis) with perceptual evaluation by a jury showed concordance in 66.1%. Based on these preliminary results, the authors conclude that their protocol overlooks some relevant voice parameters like middle-term variations. Further study will be undertaken to take into account this type of variations.

Adolescent↗
PubMed1996

[Preliminary study of acoustic and aerodynamic parameters after Tucker frontal anterior laryngectomy].

Currently, not objective method has been demonstrated to be reliable for the evaluation of vocal handicap after partial laryngectomy. Such a tool would allow objective assessment of the post-operative voice and its clinical course as well as a comparison of different surgical techniques in terms of voice quality. We used a EVA device to measure simultaneously acoustic and aerodynamic parameters. We included 23 normal subjects and 34 patients who had undergone a Tucker laryngectomy. All subjects were males. At sustained voice production, acoustic measures of vibration stability (jitter, coefficient of variation in the fundamental frequency, shimmer, coefficient of variation in intensity) and air leak from the glottis (buccal air flow over intensity). The quality of voice in operated patients was judged by a jury of listeners who assigned a global score to voice quality. Results were analyzed to verify the correlation between objective measurements and the jury's score, taken as the reference measurement. The pertinence of the objective measurements was demonstrated for the stability of the frequency and the glottal air leak. Multiple regression analysis demonstrated that total variance of the objective measurements accounted for 84.7% of the scores provided by the jury (R2 = 0.847, p < 0.0001). These satisfactory results emphasize the interest of multiparametric analysis including aerodynamic measurements. These preliminary results led to the hypothesis that objective and subjective measurements could be useful in techniques aimed at improving voice quality (temporal organization of vibratory instability, work on intralaryngeal pressures).

Acoustics↗
PubMed1995

[Behçet's disease and renal amyloidosis].

We report the case of an 29-year-old male Turkish patient suffering from generalized Behçet's disease. After an evolution of twelve years, he suddenly presented a nephrotic syndrome, a terminal renal insufficiency and thrombosis of the renal veins as well as the inferior vena cava. A percutaneous renal biopsy showed amyloidosis of the AA type, characteristic of secondary amyloidosis. Attempts to install an arterio venous shunt of the arm and to set up a peritoneal dialysis catheter were complicated by septic thrombosis. The patient died of renal failure. The association of renal amyloidosis and Behçet's disease is rare. It is, as far as we know, the first case reported in Switzerland.

Acute Kidney Injury↗
PubMed1995

The tympanal hearing organ of a fly: phylogenetic analysis of its morphological origins.

A key adaptation for any parasitoid insect is the sensory modality that it uses to locate its host insect. All members of the speciose family Tachinidae (Diptera) are parasitoids, but only flies of the tribe Ormiini use acoustic cues to find their hosts. Ormiine flies are parasitoids of various genera of crickets and katydids. Gravid females of one ormiine species, Ormia ochracea, hear the reproductive calling song of male field crickets and home in on those calls to locate their hosts. While many flies possess various kinds of "ears" to detect airborne sounds, only ormiine flies have been reported to possess true tympanal hearing organs. Such organs are well-known to occur in their cricket and katydid hosts. The ormiine ear is an evolutionary innovation within Diptera. Our objective was to trace the phylogenetic origins of the tympanal hearing organ among higher flies. Since the ormiine hearing organ is a complex organ within the prothorax, we examined possible precursor structures in the prothoraces of selected Diptera. We have uncovered a suite of characters that define the ormiine ear. These characters in the prothorax include a pair of prosternal tympanal membranes, a pair of chordotonal sensory organs, and modifications of the tracheal system. We have been able to identify and trace the presumptive homologs of these ormiine characters through selected species of related Diptera, using the method of outgroup comparison.

Animals↗
PubMed1995

Home parenteral nutrition and AIDS.

The evolution of AIDS in 25 patients enrolled in a home parenteral nutrition(HPN) programme was analysed retrospectively. All patients were grade 4C or 4D (CDC criteria). All suffered from major gastrointestinal symptoms, 13 had anorexia (< 700 kcal/day) and the overall mean weight loss was 21%. HPN involved administration of an all-in-one nutritional formula (caloric intake = 148% of MREE) which was infused at night through a Broviac type silastic catheter or a subcutaneous infusion port. It was continued until the patient's death or temporary recovery. 19 patients died during PN, 4 showed a temporary stabilisation. The average duration of PN was 180 days (54-358). Because of rehospitalizations for opportunistic infections or PN complications, the mean time spent at home was only 101 days (13-296), or 58.5% of the total duration of PN. 21 patients experienced weight gain and the Karnofsky activity index increased in half the patients. A temporary return to work was possible in only 3 patients. 15 PN related septicaemias were diagnosed for 4400 days of PN (0.34 for 100 days). On the whole, HPN seems to have been beneficial in 13 out of 25 patients, but the criteria for identifying patients who are likely to respond are not clearly established.

Journal Article↗
PubMed1995

Mechanically coupled ears for directional hearing in the parasitoid fly Ormia ochracea.

An analysis is presented of the mechanical response to a sound field of the ears of the parasitoid fly Ormia ochracea. This animal shows a remarkable ability to detect the direction of an incident sound stimulus even though its acoustic sensory organs are in very close proximity to each other. This close proximity causes the arrival times of the sound pressures at the two ears to be less than 1 to 2 microseconds depending on the direction of propagation of the sound wave. The small differences in these two pressures must be processed by the animal in order to determine the incident direction of the sound. In this fly, the ears are so close together that they are actually joined by a cuticular structure which couples their motion mechanically and subsequently magnifies interaural differences. The use of a cuticular structure as a means to couple the ears to achieve directional sensitivity is novel and has not been reported in previous studies of directional hearing. An analytical model of the mechanical response of the ear to a sound stimulus is proposed which supports the claim that mechanical interaural coupling is the key to this animal's ability to localize sound sources. Predicted results for sound fields having a range of incident directions are presented and are found to agree very well with measurements.

Animals↗
PubMed1995

Side effects of nasal continuous positive airway pressure in sleep apnea syndrome. Study of 193 patients in two French sleep centers.

Nasal continuous positive airway pressure (N-CPAP) is now the treatment of choice for patients with sleep apnea syndrome (SAS). Side effects and adverse reactions have been described with this device. We have therefore systematically studied side effects of N-CPAP in 193 patients recruited consecutively from two French sleep centers (Lyon and Grenoble). Patients were followed up with repeated polysomnography, clinical assessment, and a formal questionnaire about subjective benefits and side effects of treatment. The patients (mean age, 59 +/- 12 years) were obese (body mass index, 32 +/- 7 kg/m2) and had been using N-CPAP for 19 +/- 17 months for moderate to severe SAS (respiratory disturbance index [RDI] = 53 +/- 25/h). The clinical presentation was the same in the two sleep centers. Fifty percent of the patients complained of at least one side effect due to the nasal mask (allergy to the face, air leaks, abrasions of the ridge of the nose). Using individually molded masks, the patients exhibited fewer abrasions of the bridge of the nose (p < 0.01) and had red eyes every morning in only 9% of cases vs 24% for the patients using industrial silicone nasal masks (p < 0.025). Patients with silicone nasal masks also had more allergic reaction to the face (13% vs 5%), but this difference did not reach significance. Dry nose or mouth in the morning affected 65% of the patients. Sneezing and nasal drip were present in more than 35% of the subjects and nasal congestion in 25%. When the patients were separated in two groups, whether or not using a humidifier, no difference was found for any of the side effects described. The clinical presentation as to the clinical benefits obtained from N-CPAP were different when comparing mild vs moderate-to-severe SAS. However, no differences were shown in the two subgroups regarding the side effects due to the nasal mask. The discomfort of the N-CPAP apparatus in terms of noise was described more frequently in the subgroup with mild SAS. We did not observe any correlation between the side effects and the level of pressure used during N-CPAP. The rate of compliance remains high with a daily use of 6.5 +/- 3 h, with 88% of the patients using their device every night. This could be explained by the clinical benefit obtained: only 1% of the patients had no subjective benefit induced by their therapy.(ABSTRACT TRUNCATED AT 400 WORDS)

Female↗
PubMed1995

Sleep fragmentation in kyphoscoliotic individuals with alveolar hypoventilation treated by NIPPV.

Intermittent positive pressure ventilation (IPPV) delivered via nasal access can normalize alveolar ventilation for individuals with chronic alveolar hypoventilation (CAH) due to neuromuscular disease, spinal cord injury, or skeletal deformity. The purpose of this study was to evaluate the effect of nasal IPPV (NIPPV) air leakage-associated oxyhemoglobin desaturations (dSATs) on the sleep efficiency of kyphoscoliotic individuals with severe pretreatment nocturnal dSATs. Only individuals using nocturnal NIPPV without supplemental oxygen therapy were studied. Seven such individuals were able to maintain PaO2 greater than 60 mm Hg without supplemental oxygen therapy (five had been using oxygen therapy in the pretreatment period), had fewer hospitalizations, and had improvements in symptoms, arterial blood gas values, and nocturnal oxyhemoglobin saturation (SAT) by nocturnal NIPPV. This occurred despite polysomnographically observed sleep disruption and sleep stage changes associated with frequent transient dSATs and massive insufflation leakage. Arousals and dSATs were most frequent during rapid eye movement (REM) sleep with the latter occurring at a frequency of 10/h. The dSATs resulted in brief arousals or lightening of sleep stage 76% of the time. With or without arousal, central nervous system mediated reflex muscular activity occurred to diminish leak and normalize SAT. We conclude that the effectiveness of nocturnal NIPPV is dependent in part on central mediated muscular activity.

Adult↗
PubMed1995

[Objective vocal evaluation of dysphonia by simultaneous measurement of acoustic and aerodynamic parameters with the EVA device].

Authors present the analysis of the voice in 88 normal subjects and 159 dysphonic patients by simultaneously measurements of Jitter (acoustical short-term indicator of aperiodicity) and "Glottal Leakage" (aerodynamic parameter calculated by the ratio of Oral Airflow and Intensity). All the measurements were performed, with EVA apparatus, on the most stable part of a steady-state vowel /a/. The reference method was the rating by a jury along a global perceptual scale. Statistical tests confirm that Jitter and "Glottal Leakage" are relevant to evaluate the quality of the voice. Discriminant analysis allows to find out a fairly-good rate of discrimination of 63.1% (Randomly rating would have been 25%) The authors conclude on the interest of such a protocol and present suggestions to improve it by taking in count phénomena during the vocal attack and middle-term variations.

Acoustics↗
PubMed1995

[Reconstructive anterior frontal laryngectomy. Long-term results in T2 glottic cancers].

Between 1982 and 1992, we performed near total laryngectomy with epiglottic reconstruction in 142 patients with state T1 and T2 according to the 1987 Union Internationale contre le Cancer. In this paper, we report our experience with 61 T2 patient who were followed-up 5 years or until death. Actuarial survival was 83%. Actuarial tumor control was obtained in 91%. There were no post-operative mortalities and follow-up was usually simple. All patients underwent decanulation and were able to eat by normal track. The main drawback of this technique is speech disability. We use near total laryngectomy with epiglottic reconstruction in certain T2 patients selected according to local extension. This choice is justified by good functional results and an excellent local control. The contraindications are age over 75 years, poor patient cooperation, cardiac or pulmonary disease, fixation of the arytenoids, subglottic extension of more than 1 cm in front and 0.5 cm laterally, and extensive involvement of the ventricular folds or anterior commissure.

Adult↗
PubMed1995

Timing of tracheostomy in neuromuscular patients with chronic respiratory failure.

Noninvasive and invasive mechanical ventilation play a fundamental role in the treatment of neuromuscular patients with respiratory failure. At present no guidelines concerning timing of tracheostomy in neuromuscular patients are available. The authors summarize the factors to be considered in the decision-making process, as illustrated during an international meeting (Tradate, Italy; March 1994) held with the participation of a group of authorities on respiratory care of neuromuscular patients.

Humans↗