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.

Renal function and urinary excretion of electrolytes in patients receiving cyclic parenteral nutrition

BACKGROUND

Long-term parenteral nutrition (LTPN) has been shown to induce renal impairment and bone demineralization. However, the mechanism of both injuries has not been clarified.

METHODS

This prospective study was performed in 16 patients with short bowel syndrome, aged 28 to 63 years, who had received LTPN for 31 +/- 7 months. Urinary excretion of electrolytes were measured before (diurnal, 12 hours) and during (nocturnal, 12 hours) parenteral nutrition. Glomerular filtration rate (GFR) and effective renal plasma flow (ERPF) were measured in the morning after the nutritional bag supply.

RESULTS

Mean GFR was 86 +/- 7 mL/min/1.73 m2 and ERPF was 412 +/- 31 mL/min/1.73 m2. Decreased GFR was present in 9 patients. There was no relation between renal function and age or the duration of LTPN. Urine volume and excretion of urea, creatinine, sodium, magnesium, and phosphate but not potassium increased significantly in nocturnal urine compared with diurnal urine. On the basis on 24-hour calciuria, 7 patients were normocalciuric (NCa) whereas 9 were hypercalciuric (HCa). Both had excessive nocturnal calciuria, but only the HCa group had diurnal hypercalciuria, the calcium supply being identical. Bone mineral density (BMD) was slightly, although not significantly, higher in NCa group, but in all patients BMD correlated significantly with calciuria. Serum parathyroid hormone and vitamin D were not different in the two groups.

CONCLUSIONS

In patients receiving LTPN, renal function is frequently impaired, by a mechanism which remains unclear. In nocturnal cyclic mode of nutrition, urinary volume and electrolyte excretion occurred predominantly during the infusion, but some patients have diurnal hypercalciuria. In these patients a defect in renal calcium reabsorption or more likely the inability of bone to retain the infused calcium may be responsible for bone demineralization.

Use of electron-electron repulsion energy as a molecular descriptor in QSAR and QSPR studies

Electron-electron repulsion energy (<Vee>) 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 <Vee> 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.

Light dosimetry for photodynamic therapy in the esophagus

BACKGROUND AND OBJECTIVE

Photodynamic therapy (PDT) is an efficient technique to treat superficial early cancers in the pharynx, esophagus, and tracheo-bronchial tree. However, the lack of selectivity of some of the clinically used photosensitizers can result in significant damage to the healthy tissue during the treatment. In the esophagus, this may lead to medical complications such as stenosis and fistula. Insufficient selectivity may be compensated to some extent by accurate light dosimetry. Here, we present an approach to safer and more efficient PDT by improved light dosimetry in the esophagus.

STUDY DESIGN/MATERIALS AND METHODS

This includes the utilization of a suitable light distributor, the estimation of the radiant energy density in the tissue, and the knowledge of the esophagus morphology. The light distributor presently used in the clinic is described and several techniques to study light propagation in the esophageal wall have been investigated and are discussed. Thickness of different histological layers of the esophageal wall have been measured ex vivo and are presented.

RESULTS

Under these conditions and based on a simple model of the light distribution in the tissue, some basic and clinically useful notions of light dosimetry can be drawn. These notions, associated with measured value of tissue optical properties at the wavelengths of interest with the presently used photosensitizers, are discussed regarding the particular morphology of the esophageal wall. In particular, the importance of the illumination wavelength from the safety point of view is shown.

CONCLUSION

The proposed approach allows for improved safety and efficacy of PDT in the esophagus, particularly in the clinical tests of new photosensitizers.

Three-dimensional optical phantom and its application in photodynamic therapy

BACKGROUND AND OBJECTIVE

A technique to manufacture a stable, reproducible three-dimensional optical phantom is presented. This phantom reproduces the tissue's optical properties as well as the geometry and, to some extent, the mechanical properties of the organ concerned. Easy to make and to handle, this phantom is a useful tool for numerous medical applications involving light interaction with biological tissues.

STUDY DESIGN/MATERIALS AND METHODS

The phantom is based on a transparent two-component silicone, which is molded into the desired shape and cured at room temperature. Specific optical properties are obtained by adding scatterers (Al2O3 particles or polystyrene microspheres) and absorbers (dyes or pigments). A method to measure the radiant energy fluence rate in the phantom is described. This method is based on a small isotropic optical detector.

RESULTS

A three-dimensional phantom of the bronchial tree is presented. This phantom is used for testing new light distributors designed for photodynamic therapy of the bronchi.

CONCLUSION

The proposed technique allows one to produce a stable three-dimensional phantom with accurately predictable optical properties.

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.

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.

[Mandibular advancement orthoses used in the treatment of obstructive sleep apnea syndrome]

Mandibular advancement devices represent a therapeutic option for obstructive sleep apnea syndrome (OSAS). Clinical improvement has been proven in the different available studies, mainly on nocturnal respiratory events and quality of sleep. Less snoring have been noted by bed partners and objective studies have demonstrated decrease in snoring frequency and intensity. The effect of these ortheses on upper airways resistance syndrome is not yet well documented. The significant clinical improvement is secondary to the decrease in the occurrence of apneas and hypopneas. Polysomnographic improvement criteria with an apnea hypopnea index less than 10 per hour has been noted in certain cases. Although no improvement or even worsening was noted in other cases. Sleep architecture has also changed in these patients, with a decrease in the time spent in stages 1 and 2, and an increase in the time spent in stages 3 and 4 and rapid eye movement sleep. Micro-arousals are also decreased in number certainly with the decrease in the occurrence of respiratory events. Somnolence and loss of attention are improved; these have been evaluated subjectively or by a well known and approved somnolence scale. In some cases a test for vigilance was done.

Quantification of the influence of single-point mutations on haloalkane dehalogenase activity: a molecular quantum similarity study

Controlled modifications in certain protein amino acid residues can lead to changes in their function and stability. Amino acid structural features and their relation to these changes were examined by using quantum molecular similarity techniques. The effect of deliberate mutations in position 172 of the haloalkane dehalogenase enzyme, yielding to variations on the dehalogenation of 1,2-dibromoethane, was studied qualitatively and quantitatively using molecular quantum similarity techniques. A valuable classification of the residues according to their effect on activity was obtained by representing the optimal two-dimensional classical scaling solution. In addition, satisfactory quantitative relationships were found, comparable to those attained by previous studies on this same data set using other techniques. Molecular quantum similarity analysis provides a consistent, unbiased, and homogeneous set of molecular descriptors and is a feasible alternative to the use of physicochemical properties.

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.

Quantitative voice analysis in the assessment of bulbar involvement in amyotrophic lateral sclerosis

Bulbar and pseudobulbar symptoms are diagnostic criteria of amyotrophic lateral sclerosis (ALS). One of the earliest symptoms of bulbar involvement is voice deterioration. Until now voice assessment in ALS patients has been done mainly by perceptual analysis. The objective parameters, including acoustic measures, one aerodynamic measure and the maximal phonation time, have been measured only in a few small series of patients. The first purpose of this prospective study was to determine which vocal parameters discriminate ALS patients with bulbar involvement from control patients. The second was to identify sensitive parameters for early detection of voice deterioration due to bulbar involvement in pre-symptomatic ALS patients. The voices of 63 female ALS patients, including 40 with bulbar symptoms (sALS patients) and 23 without bulbar symptoms (aALS patients), were studied using an objective voice analysis system that allows simultaneous analysis of acoustic and aerodynamic parameters. Measurements were compared with those obtained in 40 normal female subjects (control patients). Five of eight acoustic parameters were significantly different among the three groups: jitter, coefficient of variation for frequency, shimmer, number of harmonics, and maximum phonatory frequency range. Three aerodynamic parameters, phonatory airflow, cycle-to-cycle variation for phonatory airflow, and coefficient of variation for phonatory airflow were significantly different between sALS patients and control patients. No aerodynamic parameter allowed discrimination between aALS patients and control patients. This study shows that acoustic parameters are more sensitive than aerodynamic parameters for early detection of bulbar involvement. Nevertheless, the measurements used can predict bulbar involvement in 73% of those in the sALS group, but only in 52% of those in the aALS group.

Facet diagrams for quantum similarity data

The objective of this work is to demonstrate that an appropriate treatment of quantum similarity matrices can reveal hidden data grouping related to relevant structural features and even to biological properties of interest. Classical scaling is used here to extract the information contained in the similarity relationships between the elements of a molecular set. Facet theory is invoked to relate, in a qualitative way, the spatial regions to structural characteristics as well as to properties of interest. Two application examples are discussed: the Cramer steroid set and a benzene, toluene and xylene derivatives set.

Effects of prone position on alveolar recruitment and oxygenation in acute lung injury

OBJECTIVE

To investigate the effects of prone position (PP) on alveolar recruitment and oxygenation in acute respiratory failure.

DESIGN

Prospective physiologic study.

SETTING

Medical ICU two in a university hospital.

PATIENTS

Twelve adult patients intubated and mechanically ventilated with medical primary acute lung injury/adult respiratory distress syndrome (ALI/ARDS) in whom PP was indicated.

MEASUREMENTS AND RESULTS

We constructed the static inflation volume-pressure curves (V-P) of the respiratory system in the 12 patients and differentiated between lung and chest wall in ten of them. We determined the difference between end-expiratory lung volume on positive end-expiratory pressure (PEEP) and relaxation volume of the respiratory system on zero PEEP (delta FRC). The recruited alveolar volume was computed as the delta FRC times the ratio of static elastance of the respiratory system to the lung. These measurements together with arterial blood gases determination were made in supine position (SP1), after 1 h of PP and after 1 h of supine repositioning (SP2) at the same level of PEEP. The PaO2/FIO2 ratio improved from SP1 to PP (136 +/- 17 vs 204 +/- 24 mm Hg; p < 0.01). An PP-induced alveolar recruitment was found in five patients. The change in oxygenation correlated to the recruited volume. The static elastance of the chest wall decreased from 4.62 +/- 0.99 cmH2O/l in SP1 to 6.26 +/- 0.54 cmH2O/l in PP (p < 0.05) without any correlation to the change in oxygenation.

CONCLUSIONS

Alveolar recruitment may be a mechanism of oxygenation improvement in some patients with acute hypoxemic respiratory failure. No correlation was found between change in oxygenation and chest wall elastic properties.

Mosquito hearing: sound-induced antennal vibrations in male and female Aedes aegypti

Male mosquitoes are attracted by the flight sounds of conspecific females. In males only, the antennal flagellum bears a large number of long hairs and is therefore said to be plumose. As early as 1855, it was proposed that this remarkable antennal anatomy served as a sound-receiving structure. In the present study, the sound-induced vibrations of the antennal flagellum in male and female Aedes aegypti were compared, and the functional significance of the flagellar hairs for audition was examined. In both males and females, the antennae are resonantly tuned mechanical systems that move as simple forced damped harmonic oscillators when acoustically stimulated. The best frequency of the female antenna is around 230 Hz; that of the male is around 380 Hz, which corresponds approximately to the fundamental frequency of female flight sounds. The antennal hairs of males are resonantly tuned to frequencies between approximately 2600 and 3100 Hz and are therefore stiffly coupled to, and move together with, the flagellar shaft when stimulated at biologically relevant frequencies around 380 Hz. Because of this stiff coupling, forces acting on the hairs can be transmitted to the shaft and thus to the auditory sensory organ at the base of the flagellum, a process that is proposed to improve acoustic sensitivity. Indeed, the mechanical sensitivity of the male antenna not only exceeds the sensitivity of the female antenna but also those of all other arthropod movement receivers studied so far.

[Mandibular advancement orthotic for treatment of obstructive sleep apnea]

Mandibular advancement devices represent a therapeutic option for obstructive sleep apnea syndrome (OSAS). Clinical improvement has been proved in the different available studies, mainly on nocturnal respiratory events and quality of sleep. Less snoring have been noted by bed partners and objective studies have demonstrated decrease in snoring frequency and intensity. The effect of these ortheses on upper airways resistance syndrome is not yet well documented. The significant clinical improvement is secondary to the decrease in the occurrence of apneas and hypopneas. Polysomnographic improvement criteria with an apnea hypopnea index less than 10 per hour has been noted in certain cases. Although no improvement or even worsening was noted in other cases. Sleep architecture has also changed in these patients, with a decrease in the time spent in stages 1 and 2, and an increase in the time spent in stages 3 and 4 and rapid eye movement sleep. Microarousals are also decreased in number certainly with the decrease in the occurrence of respiratory events. Somnolence and loss of attention are improved; these have been evaluated subjectively or by a well known and approved somnolence scale. In some cases a test for vigilance was done.

Inhomogeneous Lineshape Profiles of C(2)H(2) Perturbed by Xe

Several infrared transitions of the nu(5) band of C(2)H(2) perturbed by Xe near 700 cm(-1) have been recorded using a tunable diode-laser spectrometer, equipped with a thermostatically regulated cell. The pressure and temperature regimes covered during the experiments are respectively ranging between 20 and 200 mbar and 170 and 350 K. The experimental profiles are accurately studied with a recently proposed lineshape model accounting for the collisional confinement narrowing of the Doppler spectral contribution, the inhomogeneous collisional broadening and shifting, and the exchange between the various speed classes of the Maxwell-Boltzmann distribution. The speed dependence of the collisional broadening is either ab initio calculated from a semiempirical potential or deduced from the experimental temperature dependence of the line broadening. It is shown that, for the considered range of temperature, this speed dependence does not significantly modify the lineshape, so that the usual hard and soft models conveniently account for most of the observed effects. Copyright 1999 Academic Press.

Tympanal hearing in the sarcophagid parasitoid fly Emblemasoma sp.: the biomechanics of directional hearing

In Diptera, tympanal hearing has evolved at least twice in flies that belong to two different families, the tachinids and the sarcophagids. Common to these flies is their parasitoid reproductive strategy, both relying on the acoustic detection and localization of their hosts, singing insects, by means of tympanal hearing organs. In the present study, the external anatomy of the unusual hearing organs of the sarcophagid fly Emblemasoma sp. is described. The sarcophagid ears bear numerous anatomical similarities with those of ormiine tachinids: they are located on the ventral prosternum and possess a pair of scolopidial mechanoreceptive sense organs. A striking difference, however, resides in the lack of a well-defined presternum in the sarcophagid tympanal system. Instead, a deep longitudinal fold, the tympanal fold, spans both hemilateral tympanal membranes across the midline of the animal. Measured using laser Doppler vibrometry, the tympanal mechanical response in the sound field reveals asymmetrical deflection shapes that differ from those of tachinids. Lacking a central fulcrum, the sarcophagid tympanal complex presents different vibrational modes that also result in interaural coupling. The evolutionarily convergent, yet distinct, solutions used by these two small auditory systems to extract directional cues from the sound field and the role of tympanal coupling in this process are discussed.