Guillermo Ayala

Loss of endocytic clathrin-coated pits upon acute depletion of phosphatidylinositol 4,5-bisphosphate

Phosphatidylinositol 4,5-bisphosphate [PI(4,5)P2], a phosphoinositide concentrated predominantly in the plasma membrane, binds endocytic clathrin adaptors, many of their accessory factors, and a variety of actin-regulatory proteins. Here we have used fluorescent fusion proteins and total internal reflection fluorescence microscopy to investigate the effect of acute PI(4,5)P2 breakdown on the dynamics of endocytic clathrin-coated pit components and of the actin regulatory complex, Arp2/3. PI(4,5)P2 breakdown was achieved by the inducible recruitment to the plasma membrane of an inositol 5-phosphatase module through the rapamycin/FRB/FKBP system or by treatment with ionomycin. PI(4,5)P2 depletion resulted in a dramatic loss of clathrin puncta, which correlated with a massive dissociation of endocytic adaptors from the plasma membrane. Remaining clathrin spots at the cell surface had only weak fluorescence and were static over time. Dynamin and the p20 subunit of the Arp2/3 actin regulatory complex, which were concentrated at late-stage clathrin-coated pits and in lamellipodia, also dissociated from the plasma membrane, and these changes correlated with an arrest of motility at the cell edge. These findings demonstrate the critical importance of PI(4,5)P2 in clathrin coat dynamics and Arp2/3-dependent actin regulation.

Applying logistic regression to relevance feedback in image retrieval systems

This paper deals with the problem of image retrieval from large image databases. A particularly interesting problem is the retrieval of all images which are similar to one in the users mind, taking into account his/her feedback which is expressed as positive or negative preferences for the images that the system progressively shows during the search. Here we present a novel algorithm for the incorporation of user preferences in an image retrieval system based exclusively on the visual content of the image, which is stored as a vector of low-level features. The algorithm considers the probability of an image belonging to the set of those sought by the user, and models the logit of this probability as the output of a generalized linear model whose inputs are the low-level image features. The image database is ranked by the output of the model and shown to the user, who selects a few positive and negative samples, repeating the process in an iterative way until he/she is satisfied. The problem of the small sample size with respect to the number of features is solved by adjusting several partial generalized linear models and combining their relevance probabilities by means of an ordered averaged weighted operator. Experiments were made with 40 users and they exhibited good performance in finding a target image (4 iterations on average) in a database of about 4700 images. The mean number of positive and negative examples is of 4 and 6 per iteration. A clustering of users into sets also shows consistent patterns of behavior.

Spatial size distributions: applications to shape and texture analysis

This paper proposes new descriptors for binary and gray-scale images based on newly defined spatial size distributions (SSD). The main idea consists of combining a granulometric analysis of the image with a comparison between the geometric covariograms for binary images or the auto-correlation function for gray-scale images of the original image and its granulometric transformation; the usual granulometric size distribution then arises as a particular case of this formulation. Examples are given to show that in those cases in which a finer description of the image is required, the more complex descriptors generated from the SSD could be advantageously used. It is also shown that the new descriptors are probability distributions so their intuitive interpretation and properties can be appropriately studied from the probabilistic point of view. The usefulness of these descriptors in shape analysis is illustrated by some synthetic examples and their use in texture analysis is studied. Various cases of SSD and several former methods for texture classification are compared.

Suction catheter guided insertion of the ProSeal™ laryngeal mask airway is superior to the digital technique

Objectif Tester ľhypothese voulant que ľinsertion digitale du masque larynge ProSeal™ (ML ProSeal™) soit mieux reussie avec une sonde ďaspiration (SA) comme guide.PurposeWe tested the hypothesis that digital insertion of the ProSeal™ laryngeal mask airway (ProSeal™ LMA) is more successful when using a suction catheter (SC) as a guide.MethodsTwo hundred and forty-three patients (ASA physical status I–III; aged 18–84 yr) were randomly allocated for the digital or SC-guided technique. The digital technique was performed according to the manufacturer’s instructions. The SC technique involved priming the drain tube with the SC so that it protruded by 15 cm, blindly inserting the SC into the pharynx to a depth of 15 cm, followed by the digital technique. Failed insertion was defined by any of the following criteria: 1) failed passage into the pharynx; 2) malposition; and 3) ineffective ventilation. Any airway trauma, and visible or occult blood was noted. Sore throat, dysphonia and dysphagia were assessed 16 to 24 hr postoperatively.ResultsFewer insertion attempts were required with the SC-guided technique (P = 0.02), but first attempt and overall success were similar. The time taken to provide an effective airway was shorter for the SC-guided technique (36 ± 24 secvs 44 ± 28 sec,P = 0.02). A lateral approach was required less frequently with the SC-guided technique (0%vs 4%,P = 0.0004). There were no adverse events. Mouth trauma was more frequent with the digital technique (P = 0.04), but overall trauma was similar. There were no differences in the frequency of visible or occult blood. There were no differences in postoperative airway morbidity.ConclusionsThe SC-guided technique is more frequently successful than the digital technique and is associated with less mouth trauma during insertion of the ProSeal™ LMA. We suggest that the SC technique may be a useful alternative when the digital technique fails.RésuméObjectifTester ľhypothèse voulant que ľinsertion digitale du masque laryngé ProSeal™ (ML ProSeal™) soit mieux réussie avec une sonde ďaspiration (SA) comme guide.MéthodeĽinsertion digitale ou guidée par une SA ont été aléatoirement appliquées chez 243 patients ďétat physique ASA I–III, de 18 à 84 ans. La technique digitale a été réalisée selon les instructions du fabricant. La technique SA comprenait ľamorçage du drain avec la SA pour qu’il sorte de 15 cm, ľinsertion à ľaveugle de la SA dans le pharynx jusqu’ à une profondeur de 15 cm, puis la technique digitale. Ľéchec de ľinsertion était défini par n’importe lequel de ces critères : 1) passage manqué dans le pharynx ; 2) malposition et 3) ventilation inefficace. Tout trauma aux voies aériennes et la présence de sang visible ou occulte étaient notés. Le mal de gorge, la dysphonie et la dysphagie ont été évalués de 16 à 24 h après ľopération.RésultatsLa technique guidée par SA a requis moins ďessai (P= 0,02), mais la réussite du premier essai et le succès global étaient similaires. Avec la technique guidée par SA, le temps nécessaire au contrôle des voies aériennes a été plus court (36 ± 24 s vs 44 ± 28 s, P = 0,02) et une approche latérale a été moins souvent nécessaire (0 % vs 4 %, P = 0,0004). Il n’y a pas eu ďévénements indésirables. Les lésions buccales ont été plus fréquentes avec la technique digitale (P = 0,04), mais globalement, les traumas ont été similaires. Il n’y a pas eu de différence pour la fréquence de sang visible ou occulte ni pour la morbidité postopératoire des voies aériennes.ConclusionLa technique guidée par SA est plus souvent réussie que la technique digitale et est associée à moins de lésion buccale pendant ľinsertion du Ml ProSeal™. La technique SA peut donc remplacer la technique digitale en cas ďéchec.

A novel Bayesian framework for relevance feedback in image content-based retrieval systems

This paper presents a new algorithm for image retrieval in content-based image retrieval systems. The objective of these systems is to get the images which are as similar as possible to a user query from those contained in the global image database without using textual annotations attached to the images. The main problem in obtaining a robust and effective retrieval is the gap between the low level descriptors that can be automatically extracted from the images and the user intention. The algorithm proposed here to address this problem is based on the modeling of user preferences as a probability distribution on the image space. Following a Bayesian methodology, this distribution is the prior distribution and its parameters are modified based on the information provided by the user. This yields the a posteriori from which the predictive distribution is calculated and used to show to the user a new set of images until he/she is satisfied or the target image has been found. Experimental results are shown to evaluate the method on a large image database in terms of precision and recall.

Granulometric moments and corneal endothelium status

Abstract Specular microscopy is a common practice in Ophthalmology. The corneal endothelium status is usually evaluated by means of the density, the hexagonality, the mean, the standard deviation and the coefficient of variation of cell areas. We propose to replace the cell area moments by the corresponding moments of a different probability distribution, the granulometric size distribution associated to a disc. All cells touching the frame are ignored by the area moments but used by the granulometric moments. Twenty images have been analyzed. When the size of the focused region is reduced, the area moments show a greater variation than the corresponding granulometric moments.

Biofilm development by potentially pathogenic non-pigmented rapidly growing mycobacteria

BackgroundA study to evaluate the biofilm-development ability in three different media (Middlebrook 7H9, sterile tap water and PBS-5% glucose) was performed with 19 collection strains from 15 different species on non-pigmented rapidly growing mycobacteria (NPRGM). A microtiter plate assay was developed to evaluate the percentage of covered surface of the microtiter plate wells in different days from day 1 to day 69.ResultsAll strains were able to develop biofilm in all the tested media. Middlebrook 7H9 showed the fastest growth, followed by sterile tap water and PBS-5% glucose. A sigmoid growth curve was detected in all the strains both in Middlebrook 7H9 and in sterile tap water. A difference could be detected for Mycobacterium abscessus in tap water, where it showed faster growth than all the other strains.ConclusionBiofilm development seems to be a property of all the species of NPRGM and it depends on the nutrients present in the medium. The microtiter plate assay described here is a useful tool to evaluate differences in biofilm development among the different species of rapidly growing mycobacteria.

[Ľinsertion du masque laryngé ProSeal™, guidée par une sonde ďaspiration, est supérieure à la technique digitale]

Objectif Tester ľhypothese voulant que ľinsertion digitale du masque larynge ProSeal™ (ML ProSeal™) soit mieux reussie avec une sonde ďaspiration (SA) comme guide.PurposeWe tested the hypothesis that digital insertion of the ProSeal™ laryngeal mask airway (ProSeal™ LMA) is more successful when using a suction catheter (SC) as a guide.MethodsTwo hundred and forty-three patients (ASA physical status I–III; aged 18–84 yr) were randomly allocated for the digital or SC-guided technique. The digital technique was performed according to the manufacturer’s instructions. The SC technique involved priming the drain tube with the SC so that it protruded by 15 cm, blindly inserting the SC into the pharynx to a depth of 15 cm, followed by the digital technique. Failed insertion was defined by any of the following criteria: 1) failed passage into the pharynx; 2) malposition; and 3) ineffective ventilation. Any airway trauma, and visible or occult blood was noted. Sore throat, dysphonia and dysphagia were assessed 16 to 24 hr postoperatively.ResultsFewer insertion attempts were required with the SC-guided technique (P = 0.02), but first attempt and overall success were similar. The time taken to provide an effective airway was shorter for the SC-guided technique (36 ± 24 secvs 44 ± 28 sec,P = 0.02). A lateral approach was required less frequently with the SC-guided technique (0%vs 4%,P = 0.0004). There were no adverse events. Mouth trauma was more frequent with the digital technique (P = 0.04), but overall trauma was similar. There were no differences in the frequency of visible or occult blood. There were no differences in postoperative airway morbidity.ConclusionsThe SC-guided technique is more frequently successful than the digital technique and is associated with less mouth trauma during insertion of the ProSeal™ LMA. We suggest that the SC technique may be a useful alternative when the digital technique fails.RésuméObjectifTester ľhypothèse voulant que ľinsertion digitale du masque laryngé ProSeal™ (ML ProSeal™) soit mieux réussie avec une sonde ďaspiration (SA) comme guide.MéthodeĽinsertion digitale ou guidée par une SA ont été aléatoirement appliquées chez 243 patients ďétat physique ASA I–III, de 18 à 84 ans. La technique digitale a été réalisée selon les instructions du fabricant. La technique SA comprenait ľamorçage du drain avec la SA pour qu’il sorte de 15 cm, ľinsertion à ľaveugle de la SA dans le pharynx jusqu’ à une profondeur de 15 cm, puis la technique digitale. Ľéchec de ľinsertion était défini par n’importe lequel de ces critères : 1) passage manqué dans le pharynx ; 2) malposition et 3) ventilation inefficace. Tout trauma aux voies aériennes et la présence de sang visible ou occulte étaient notés. Le mal de gorge, la dysphonie et la dysphagie ont été évalués de 16 à 24 h après ľopération.RésultatsLa technique guidée par SA a requis moins ďessai (P= 0,02), mais la réussite du premier essai et le succès global étaient similaires. Avec la technique guidée par SA, le temps nécessaire au contrôle des voies aériennes a été plus court (36 ± 24 s vs 44 ± 28 s, P = 0,02) et une approche latérale a été moins souvent nécessaire (0 % vs 4 %, P = 0,0004). Il n’y a pas eu ďévénements indésirables. Les lésions buccales ont été plus fréquentes avec la technique digitale (P = 0,04), mais globalement, les traumas ont été similaires. Il n’y a pas eu de différence pour la fréquence de sang visible ou occulte ni pour la morbidité postopératoire des voies aériennes.ConclusionLa technique guidée par SA est plus souvent réussie que la technique digitale et est associée à moins de lésion buccale pendant ľinsertion du Ml ProSeal™. La technique SA peut donc remplacer la technique digitale en cas ďéchec.

A random set view of texture classification

Texture classification of an image or subimage is an important problem in texture analysis. Many procedures have been proposed. A global framework for texture classification based on random closed set theory is proposed in this paper. In this approach, a binary texture is considered as an outcome of a random closed set. Some distributional descriptors of this stochastic model are used as texture features in order to classify the binary texture, in particular spherical and linear contact distributions and K-functions. If a grayscale texture has to be classified, then the original texture is reduced to a multivariate random closed set where each component (a different random set) corresponds with those pixels verifying a local property. Again, some functional descriptors of the multivariate random closed set defined from the texture can be used as texture features to describe and classify the grayscale texture. Marginal and cross spherical and linear contact distributions and K-functions have been used. Experimental validation is provided by using Brodatzs database and another standard texture database.

Spatio-Temporal Analysis of Constitutive Exocytosis in Epithelial Cells

Exocytosis is an essential cellular trafficking process integral to the proper distribution and function of a plethora of molecules, including transporters, receptors, and enzymes. Moreover, incorrect protein targeting can lead to pathological conditions. Recently, the application of evanescent wave microscopy has allowed us to image the final steps of exocytosis. However, spatio-temporal analysis of fusion of constitutive vesicular traffic with the plasma membrane has not been systematically performed. Also, the spatial sites and times of vesicle fusion have not yet been analyzed together. In addition, more formal tests are required in testing biological hypotheses, rather than visual inspection combined with statistical descriptives. Ripley K-functions are used to examine the joint and marginal behavior of locations and fusion times. Semiautomatic detection and mapping of constitutive fusion sites reveals spatial and temporal clustering, but no dependency between the locations and times of fusion events. Our novel approach could be translated to other studies of membrane trafficking in health and diseases such as diabetes