Biomechanics. Turning the key on Drosophila audition.
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Acoustic Stimulation↗
Biomedical subjects
D Robert
Publications and source records attributed to D Robert.
Active auditory mechanics in mosquitoes.
In humans and other vertebrates, hearing is improved by active contractile properties of hair cells. Comparable active auditory mechanics is now demonstrated in insects. In mosquitoes, Johnston's organ transduces sound-induced vibrations of the antennal flagellum. A non-muscular 'motor' activity enhances the sensitivity and tuning of the flagellar mechanical response in physiologically intact animals. This motor is capable of driving the flagellum autonomously, amplifying sound-induced vibrations at specific frequencies and intensities. Motor-related electrical activity of Johnston's organ strongly suggests that mosquito hearing is improved by mechanoreceptor motility.
Animals↗
Comprehensive study on the chemical structure of dioxane lignin from plantation Eucalyptus globulus wood.
Results of a comprehensive study on the chemical structure of lignin from plantation Eucalyptus globulus Labill are presented. Lignin has been isolated by a modified mild acidolysis method and thoroughly characterized by functional group analysis, by a series of degradation techniques (nitrobenzene oxidation, permanganate oxidation, thioacidolysis, and Py-GC-MS), and (1)H and (13)C NMR spectroscopy. Plantation Eucalyptus globulus lignin was found to be of the S/G type with an extremely high proportion of syringyl (S) units (82-86%) and a minor proportion of p-hydrophenyl propane (H) units (roughly 2-3 mol %). Unknown C-6 substituted and 4-O-5' type syringyl substructures represent about 65% of lignin "condensed" structures. Eucalypt lignin showed high abundance of beta-O-4 (0.56/C(6)) structures and units linked by alpha-O-4 bonds (0.23/C(6)). The proportion of phenylcoumaran structures was relatively low (0.03/C(6)). Different kinds of beta-beta substructures (pino-/syringaresinol and isotaxiresinol types) in a total amount of 0.13/C(6) were detected. ESI-MS analysis revealed a wide molecular weight distribution of lignin with the center of gravity of mass distribution around 2500 u.
Dioxanes↗
Structure-toxicity relationships of polycyclic aromatic hydrocarbons using molecular quantum similarity.
The establishment of quantitative structure-activity relationship (QSAR) models for the toxicity of polycylic aromatic hydrocarbons (PAHs) is described. Two properties, in vitro percutaneous absorption in rat skin and discrete levels of carcinogenic activity, are examined using molecular quantum similarity measures (MQSM). The results show that MQSM produces comparable, or even better, results than other approaches using physicochemical, topological and quantum-chemical molecular descriptors. Furthermore, a careful analysis puts into evidence that most of the information characterized by the original descriptors is in fact contained in the molecular density functions, the basis of MQSM. The present paper, together with several other reported by our laboratory, proves that MQSM might be appropriate theoretical tools for QSAR and computer-aided drug design, comparable to other highly predictive QSAR methodologies.
Carcinogens↗
3D light scanning macrography.
The technique of 3D light scanning macrography permits the non-invasive surface scanning of small specimens at magnifications up to 200x. Obviating both the problem of limited depth of field inherent to conventional close-up macrophotography and the metallic coating required by scanning electron microscopy, 3D light scanning macrography provides three-dimensional digital images of intact specimens without the loss of colour, texture and transparency information. This newly developed technique offers a versatile, portable and cost-efficient method for the non-invasive digital and photographic documentation of small objects. Computer controlled device operation and digital image acquisition facilitate fast and accurate quantitative morphometric investigations, and the technique offers a broad field of research and educational applications in biological, medical and materials sciences.
Animals↗
A shot in the dark: the silent quest of a free-flying phonotactic fly.
To reproduce, females of the parasitoid fly Ormia ochracea detect and localise a calling male cricket upon which they deposit their endoparasitic larvae. Calling male crickets are therefore subject to both sexual and natural selection by simultaneously attracting mates and phonotactic parasitoids. The possible strategy of song interruption employed by the cricket host to reduce his attractiveness to acoustic parasitoids was tested in the laboratory by examining the fly's phonotactic quest in response to synthetic cricket songs. Phonotactic flight trajectories were recorded in three dimensions with a stereo infrared video tracking system while the sound stimulus was controlled on-line as a function of the fly's position in space. Within a single flight, three distinct phases could be observed: a take-off phase, a cruising phase, during which course and altitude were rather constant, and a landing phase characterised by a spiralling descent towards the sound source. The flies showed remarkable phonotactic accuracy in darkness; they landed at a mean distance of 8.2 cm from the centre of the loudspeaker after a flight distance of approximately 4 m. The present data illustrate the fly's surprising ability to gauge the direction and distance of a sound source in three dimensions and, subsequently, to find it in darkness and silence.
Acoustic Stimulation↗
Outcome of patients with idiopathic pulmonary fibrosis admitted to the ICU for respiratory failure.
STUDY OBJECTIVES: To analyze the outcome of acute respiratory failure (ARF) in patients with idiopathic pulmonary fibrosis (IPF), and to evaluate the benefits of invasive and noninvasive mechanical ventilation (MV). DESIGN: Retrospective study. SETTING: University hospital. PATIENTS: Fifteen consecutive patients with IPF referred to the ICU for ARF between January 1989 and June 1998. MEASUREMENTS AND RESULTS: Fifteen patients (mean +/- SD age, 64 +/- 10 years) were included. Eight patients had clinical, functional, and radiologic features of IPF, and the remaining seven patients also had biopsy specimen-proven IPF. The mean duration between diagnosis of IPF and admission to the ICU was 26.5 +/- 28 months. At the time of ICU admission, mean arterial blood gas levels were as follows: PaO(2)/fraction of inspired oxygen, 113 +/- 95; pH, 7.32 +/- 0.10; and PaCO(2), 55 +/- 21 mm Hg. All patients received MV; 12 patients required tracheal intubation, either at the time of ICU admission (n = 10) or after failure of noninvasive ventilation (NIV; n = 2); and 3 patients only received NIV. Three of the five patients receiving NIV died of respiratory failure. Eleven patients died in the ICU, either from hypoxemia (n = 8) or from septic shock (n = 3). Four patients were discharged alive from the ICU, and two of them died shortly thereafter. CONCLUSION: The outcome of patients with IPF referred to the ICU for ARF was very poor and not improved by MV. Without a clearly identified reversible cause of ARF, these patients should not benefit from admission to the ICU.
Acute Disease↗
Innovative biomechanics for directional hearing in small flies.
In humans and animals alike, the localization of sound constitutes a fundamental processing task of the auditory system. Directional hearing relies on acoustic cues such as the interaural amplitude and time differences and also, sometimes, the signal spectral composition. In small animals, such as insects, the auditory receptors are forcibly set close together, a design constraint imposing very short interaural distances. Due to the physics of sound propagation, the close proximity of the sound receivers results in vanishingly small amplitude and time cues. Yet, because of their directionality, small auditory systems embed original and innovative solutions that can be of inspirational value to some acute problems of technological miniaturization. Such ears are found in a parasitoid fly that acoustically locates its singing cricket host. Anatomically rather unconventional, the fly's auditory system is endowed with a directional sensitivity that is based on the mechanical coupling between its two hemilateral tympanal membranes. The functional principle permitting this directionality may be of particular relevance for technological applications necessitating sensors that are low cost, low weight, and low energy. Based on silicon-etching technology, early prototypes of sub-millimeter acoustic sensors provide evidence for directional mechanical responses. Further developments hold the promise of applications in hearing aid technology, vibration sensors, and miniature video-acoustic surveillance systems.
Animals↗
Tracking of flying insects using pan-tilt cameras.
Potent and affordable video and computer systems for automatic data acquisition are becoming increasingly important in behavioural neuroscience. It has remained challenging, however, to acquire data from small and fast-moving animals, such as insects in flight, due to the limited spatial and temporal resolution of the systems currently available. Our research on free-flying insects motivated the development of new methods in the context of two different experimental settings. First, the position and precise body axis direction of honey bees approaching a food source were automatically measured. Second, the flight trajectories of a phonotactic parasitoid fly homing in on its cricket host were recorded in 3D. We used pan-tilt cameras, i.e. cameras with moveable optics, to follow the animal's path with a close up image. Novel methods were developed for image acquisition and position measurement using pan-tilt cameras, as well as calibration and data evaluation in 3D world coordinates. The innovations of this system comprise: (1) Acquisition of images in high spatial detail over large observation areas. (2) Image acquisition at a field rate of 50 Hz PAL. (3) Free positioning of the cameras for 3D acquisition. (4) Computation of the flight path in 3D world coordinates. We illustrate the capabilities of the system with data obtained from a calibration object as well as from the behaviour of unrestricted, free-flying flies and bees. Potential applications in behavioural neuroscience and the psychophysics of sensory perception are briefly discussed.
Animals↗
Sleep disordered breathing: from pathophysiology to evidence-based-medicine.
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Cardiovascular Diseases↗
Principles of mandibular advancement device applied to the therapeutic of snoring and sleep apnea syndrome.
Mandibular advancement device (MAD) represents a therapeutic option for simple snoring to obstructive sleep apnea syndrome (OSAS). The different available studies report an improvement either on nocturnal respiratory events or on the quality of sleep. The decrease in the intensity of snoring is confirmed by the patient's partner and by objective studies. For the time being the effects of these mandibular advancement devices on the upper airway resistance syndrome has not yet been well documented. The significant clinical improvement is secondary to the decrease in apnea hypopnea index (AHI). A polysomnographically proved cure has been reported with AHI < 10/h. Sleep architecture is also improved with wearing MAD demonstrating a decrease in the time passed in stage 1 sleep and an increase in slow wave sleep and rapid eye movement sleep (REM). A decrease in microarousals index has been shown. Daytime vigilance disorders are subjectively and objectively less remarkable. Then MAD can be beneficial for mild to moderate SAOS.
Humans↗
Nocturnal hypoventilation in chronic respiratory failure (CRF) due to neuromuscular disease.
Decrease of respiratory muscle capacities in neuromuscular disease can lead to chronic respiratory failure with permanent alveolar hypoventilation. Respiratory centers elaborate a strategy of breathing dedicated to prevent overt respiratory muscles fatigue. This strategy may worsen chronic hypercapnia. During sleep, ventilation decreases because a lessening in respiratory centers function. During NREM sleep hypoventilation is only an exacerbation of what is seen during wakefulness. During REM sleep, atonia worsens much more hypoventilation particularly when diaphragmatic function is impaired. The effects of atonia are amplified by a very low reactivity of respiratory centers. Nocturnal mechanical ventilation improves nocturnal hypoventilation and daytime arterial blood gases (ABG). Mechanism of improvement in ABG and how nocturnal hypoventilation and diurnal hypoventilation interact, are still a matter of debate.
Arousal↗
Nanometre-range acoustic sensitivity in male and female mosquitoes.
Johnston's sensory organ at the base of the antenna serves as a movement sound detector in male mosquitoes, sensing antennal vibrations induced by the flight sounds of conspecific females. Simultaneous examination of acoustically elicited antennal vibrations and neural responses in the mosquito species Toxorhynchites brevipalpis has now demonstrated the exquisite acoustic and mechanical sensitivity of Johnston's organ in males and, surprisingly, also in females. The female Johnston's organ is less sensitive than that of males. Yet it responds to antennal deflections of +/- 0.0005 degrees induced by +/- 11 nm air particle displacements in the sound field, thereby surpassing the other insect movement sound detectors in sensitivity. These findings strongly suggest that the reception of sounds plays a crucial role in the sensory ecology of both mosquito sexes.
Animals↗
Free-flight phonotaxis in a parasitoid fly: behavioural thresholds, relative attraction and susceptibility to noise.
The phonotactic capacity of tachinid flies to acoustically detect and localize a sound source simulating their cricket host was investigated in a large flight room. Acoustic measurements were performed to estimate the actual stimulus delivered to the flies, revealing highly heterogeneous sound fields. When presented with a simulated cricket song in red or infrared light conditions, the flies readily flew to the sound source and landed on it. Behavioural phonotactic thresholds were established as a function of carrier frequency and were found to coincide well with the frequency of the host's natural song (4.5-5.2 kHz). Experiments revealed that the same range of frequencies is preferentially attractive to the free-flying flies, and that the reliability of signal detection in the presence of noise is best at behaviourally relevant frequencies.
Acoustic Stimulation↗
The histological architecture of the auditory organs in the parasitoid fly Ormia ochracea.
Gravid females of the parasitoid fly species Ormia ochracea (Diptera: Tachinidae) rely on their sense of hearing to detect and localize their hosts, field crickets of the genus Gryllus. As in any hearing insect species, the fly's auditory system consists of a rather complex cascade of mechanical and physiological mechanisms, starting with the conversion of the acoustic energy in the sound field into mechanical vibrations that, in turn, are sensed in the auditory sensory organs by multicellular mechanoreceptive units - the scolopidia. This article reports on the histological architecture of the sensory organs using conventional histological serial sections and their three-dimensional reconstructions, and confocal laser microscopy. The scolopidia's spatial distribution and the three-dimensional organization of the actin-containing attachment cells are described. Morphometric measurements show that individual scolopales vary in their size and shape. Pronounced intersexual differences have been previously shown to exist in auditory function, in particular with respect to frequency sensitivity, peripheral auditory anatomy, and notably behavior. The present results show that intersexual differences in the histoarchitecture of the sensory organs are small. Results are compared with some other insect auditory systems and are also discussed in terms of their significance for frequency sensitivity.
Actins↗
Use of electron-electron repulsion energy as a molecular descriptor in QSAR and QSPR studies.
Electron-electron repulsion energy ( ) is presented as a new molecular descriptor to be employed in QSAR and QSPR studies. Here it is shown that this electronic energy parameter is connected to molecular quantum similarity measures (MQSM), and as a consequence can be considered as a complement to steric and electronic parameters in description of molecular properties and biological responses of organic compounds. The present strategy considers the molecule as a whole, thus there is no need to employ contributions of isolated fragments as in many calculations of molecular descriptors, like log P or the Free-Wilson analysis. The procedure has been tested in a widespread set of molecules: alcohols, alkanamides, indole derivatives and 1-alkylimidazoles. Molecular properties, as well as toxicity, are correlated using as a parameter, and extensions to the method are given for handling difficult systems. In almost all studied cases, satisfactory linear relationships were finally obtained.
Computer-Aided Design↗
Hepatitis B exacerbation with a precore mutant virus following withdrawal of lamivudine in a human immunodeficiency virus-infected patient.
Chronic active hepatitis B exacerbations have been reported following development of resistance to or withdrawal of lamivudine in HIV-infected patients. A 38-year-old woman with HIV and chronic HBV infections was hospitalized because of acute hepatitis. The occurrence of cytolysis with replication of HBV 2 months after withdrawing lamivudine suggests that our patient experienced a severe reactivation of HBV infection due to the modification of her treatment. Sequencing of the HBV precore region showed the strain to be a mutant. We conclude that lamivudine should not be stopped in HIV- and HBV-infected patients, but could be continued at the dose of 100mg/day as used in isolated HBV infection.
Adult↗
Photometric observations of a polychromatic laser guide star.
We report the photometric observation of a polychromatic laser guide star (PLGS) using the AVLIS laser at the Lawrence Livermore National Laboratory (LLNL). The process aims at providing a measurement of the tilt of the incoming wave front at a telescope induced by atmospheric turbulence. It relies on the two-photon coherent excitation of the 4D5/2 energy level of sodium atoms in the mesosphere. We used two laser beams at 589 and 569 nm, with a maximum total average output power of approximately 350 W. For the purpose of photometric calibration, a natural star was observed simultaneously through the same instrument as the PLGS at the focus of the LLNL 50-cm telescope. Photometric measurements of the 330-nm return flux confirm our previous theoretical studies that the PLGS process should allow us at a later stage to correct for the tilt at wavelengths as short as approximately 1 microm at good astronomical sites. They show also that, at saturation of two-photon coherent absorption in the mesosphere, the backscattered flux increases by a factor of approximately 2 when the pulse repetition rate decreases by a factor of 3 at constant average power. This unexpected behavior is briefly discussed.
Journal Article↗