Three-dimensional quantitative structure-activity relationships from tuned molecular quantum similarity measures: prediction of the corticosteroid-binding globulin binding affinity for a steroid family

Predictive models based on tuned molecular quantum similarity measures and their application to obtain quantitative structure-activity relationships (QSAR) are described. In the present paper, the corticosteroid-binding globulin binding affinity of a 31 steroid family is studied by means of a multilinear regression using molecular descriptors derived from mixed steric-electrostatic quantum similarity matrixes as parameters, obtaining satisfactory predictions. A systematic procedure to treat outliers by using triple-density quantum similarity measures is also presented. This method depicts an alternative to the grid-based QSAR techniques, providing a consistent approach that avoids problematic result dependency on the grid parameters.

[Medialization of paralysed vocal cord by expansive polytetrafluoroethylene implant (Gore-Tex)]

We report a technique for medialization of a paralyzed vocal cord using a Gore-Tex (expanded polytetrafluoroethylene) implant inserted under local anesthesia via a cervical incision. Gore-Tex is an expanded form of Teflon. It is used in vascular surgery (vessel repair) and esthetic surgery (particularly to increase lip volume). In esthetic surgery, the development of inflammatory processes difficult to control have been observed with teflon and appear to be less frequent with Gore-Tex due to the absence of free particles in the expanded form. The minimally invasive technique is simple and reproducible and can be performed under local anesthesia. We report a series of 9 cases operated from October 1995 to October 1997. During this period, this technique predominated (two other patients had Teflon injections). Excepting one case of extrusion of the implant material, vocal results were very satisfactory, based on both subjective and objective analysis of vocal parameters. The contribution of this technique in comparison with the reference endoscopic techniques (Teflon, collagen) and surgical techniques (silicone, cartilage) is discussed. Early results would suggest that Gore-Tex implantation can be used in the more severe forms due to vocal cord paralysis in the lateral position.

Molecular quantum similarity measures tuned 3D QSAR: an antitumoral family validation study

In this work, a new methodology to construct a tuned QSAR model is presented, which is based on a convex set formalism. The present procedure continues previous 3D QSAR studies, performed using molecular quantum similarity measures (MQSM). With this new computational tool, the efficiency of MQSM applied to QSAR analysis is significantly improved. A reliable QSAR model is obtained using convex linear combinations of different kinds of MQSM, corresponding to different quantum-mechanical operators related to the quantum similarity integral. The active compounds studied here, as a case study, are a set of antitumor agents, the camptothecin molecule and analogues, and the property evaluated is the topoisomerase-I inhibition activity. Before performing a tuned QSAR analysis with this particular molecular set, a simple QSAR study for all the different possible types of MQSM is carried out. In addition, another application of MQSM is presented, to determine which method can be used to optimize molecular structures in order to reproduce experimental molecular geometries as well as possible.

Oxygen tolerance in patients with acute respiratory failure

OBJECTIVE

To search for a threshold of pulmonary oxygen toxicity in patients with acute respiratory failure.

DESIGN

Retrospective study over a 10-year period.

SETTING

Three intensive care units of two university hospitals.

PATIENTS AND PARTICIPANTS

Seventy-four patients with acute respiratory failure ventilated continuously with a FIO2 > or = 0.9 for at least 48 h were selected.

INTERVENTIONS

Information regarding status, scoring, diagnosis and therapeutic interventions upon admission and ICU course were extracted from the patients' charts.

MEASUREMENTS AND RESULTS

We found that total exposure [mean (standard error of the mean)] to a FIO2 of 0.9 (TE 90) or more was 5.6 (1.1) days in the 17 survivors (S) versus 5.9 (0.5) days in the 57 non-survivors (D) (NS). Total exposure time to a FIO2 more than 0.5 (TE 50) was 16.5 (2.6) days in S and 11.2 (1) days in D (p < 0.05). The PaO2/FIO2 ratio became significantly higher in S only 5 days after beginning FIO2 of 0.9 or more. Hypoxemia was not frequent at the time of death, whereas in 70% of the non-survivors there were at least three organ failures in the last 48 h. In univariate analysis, the duration of exposure to FIO2 of 0.9 or more was not different in survivors and non-survivors, and the average total duration of exposure to FIO2 of more than 0.5 was even longer in survivors. In multivariate analysis, exposure shorter than 10 days to FIO2 more than 0.5 and exposure longer than 4 days to a FIO2 of 0.9 or more were significantly associated with death. However, despite a larger exposure to a FIO2 of 0.9 or more during the last 5 years of the study, the trend moved towards a higher survival rate during this period compared with the first 5 years of the study.

CONCLUSIONS

Thus, our data provide circumstantial evidence that the lungs of patients with acute respiratory failure might exhibit some relative resistance to prolonged oxygen exposure. Therefore, it might be worthwhile carrying out a prospective study of different FIO2 strategies in such patients.

Forewing asymmetries during auditory avoidance in flying locusts

Flying locusts orient to sounds in their environment. Sounds similar to those produced by echolocating bats cause a flying locust to change its flight path. We used high-speed cinematography and videography to study changes in body posture and wing kinematics of tethered locusts in response to stimulation with bat-like sounds. Locusts showed both negative and positive phonotaxis to this stimulus. Within a few wingbeats of stimulus onset (between 126 and 226ms), locusts deflected their abdomens to one side, and the angle of the left and right forewings with respect to the dorsal&shy;ventral body axis became asymmetrical during the downstroke. This forewing asymmetry, in which the forewing on the inside of the turn became more depressed, ranged from 20 to 45&deg; (37&plusmn;9.7&deg;, mean &plusmn; s.d.) and was correlated with the direction and magnitude of abdomen deflection, a measure of steering in tethered, flying locusts. Hindwing stroke angle asymmetries were minimal or non-existent after stimulation. Coincident with changes in forewing asymmetry and abdomen deflection was a decrease in stroke amplitude (19&plusmn;6.5&deg;) of the forewing on the inside of the attempted turn. Motor patterns from forewing first basalar (M97) muscles showed an asymmetry in the timing of left and right depressor activation that ranged from 10.4 to 1.6ms (4.23&plusmn;2.85ms). The number of spikes per depressor burst increased to a maximum of three spikes in the muscle on the inside of the attempted turn, and depressor frequency (wingbeat frequency) increased by approximately 2Hz (2.17&plusmn;0.26Hz). We suggest that the asymmetry in forewing first basalar activity is causally related to the asymmetry in the timing of the initiation of the downstroke, resulting in an asymmetry in the ranges of the stroke angles of the forewings, which would impart a roll torque to the locust. This would augment the steering torques generated by concurrent changes in the angle of attack of the fore- and hindwings and changes in abdomen position to effect rapid avoidance manoeuvres.

Prone position in mechanically ventilated patients with severe acute respiratory failure

The purpose of this study was to characterize changes in oxygenation, expressed as PaO2/F(I)O2, when patients with severe acute respiratory failure (PaO2/F(I)O2 < 150), unrelated to left ventricular failure to atelectasis, were turned to and from a supine to prone position at 1- and 4-h intervals. Ventilator settings were unchanged. Thirty-two consecutive patients were studied 1 h before, 1 and 4 h during and 1 h after placing in a prone position with PaO2/F(I)O2 of 103 +/- 28, 158 +/- 62, 159 +/- 59, and 128 +/- 52, respectively (ANOVA, p < 0.001). After 1 h in a prone position, improvement of PaO2/F(I)O2 by 20 mm Hg or more was considered a positive response. Seven patients studied had no response (22%), hereafter referred to as nonresponders, and 25 had a positive response (78%), hereafter referred to as responders. Among the seven nonresponders, two did not tolerate the prone position and were returned supine before the end of the 4-h trial. With the remaining five, PaO2/F(I)O2 evolution was 83 +/- 29, 77 +/- 19, 83 +/- 33, and 81 +/- 47, respectively. For two of the 25 responders, measurements are missing after returning to the supine position. In 10 of the 23 responders (43%) who completed the 4 h prone trial, the PaO2/F(I)O2 returned to its starting value when patients were repositioned supine: 117 +/- 24, 164 +/- 44, 156 +/- 55, and 110 +/- 34, respectively (ANOVA, p < 0.01). In 13 of the 23 (57%) improvement persisted: 105 +/- 27, 187 +/- 58, 189 +/- 49, and 157 +/- 49, respectively (ANOVA, p < 0.001). Repeated improvements after turning to a prone position were frequently observed. Side effects in the 32 patients after a total of 294 periods in a prone position included minor skin injury and edema, two instances of apical atelectasis, one catheter removal, one catheter compression, one extubation, and one transient supraventricular tachycardia.

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.

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.

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.

Clinical determination of tissue optical properties by endoscopic spatially resolved reflectometry

A noninvasive method to measure the optical properties of a diffusing and absorbing medium is described. Based on the spatially resolved measurement of diffuse reflectance at the sample surface, this method is particularly suitable for investigating the in vivo optical properties of biological tissues endoscopically in a clinical context. The sensitivity of the measurement is discussed, and two optical probes for two different clinical applications are presented. Preliminary measurements are performed on a nonbiological medium, which illustrate the possibilities of the proposed method. Finally, we report on in vivo measurements of the optical properties of the human esophageal wall at 630 nm.

[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).

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.

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.