Motility fractionation of bacteria by centrifugation

Centrifugation is a widespread laboratory technique used to separate mixtures into fractions characterized by a specific size, weight or density. We demonstrate that centrifugation can be also used to separate swimming cells having different motility. To do this we study self-propelled bacteria under the influence of an external centrifugal field. Using dynamic image correlation spectroscopy we measure the spatially resolved motility of bacteria after centrifugation. A significant gradient in swimming-speeds is observed for increasing centrifugal speeds. Our results can be reproduced by a model that treats bacteria as "hot" colloidal particles having a diffusion coefficient that depends on the swimming speed.Comment: 7 pages, 5 figures (in press

The uptake and transmission of protein by the gut of the neonatal rat

The studies reported in this thesis deal with the in vivo transmission of homologous and heterologous IgG and other proteins across the proximal small intestine of the suckling rat. The uptake of these labelled macromolecules from the intestine was monitored, and the subsequent appearance of radioactive material in the serum, viscera and carcass was examined by ultrafiltration and ultracentrifugation techniques. The rate of transmission of intact IgG and IgG breakdown products across the intestinal barrier was measured with the intention of obtaining further information about the mechanisms of immunoglobulin transport. The significance of the digestive activity of the suckling rat gut to the process of antibody transmission was also assessed. This was done by gel filtration analysis of the radioactive material present in the gut wall and wash after the intraluminal injection of labelled rat IgG. The ability of trypsin inhibitor to stimulate the transmission of intact IgG was investigated, and the possibility that the IgG receptor on the surface of proximal enterocytes was trypsin sensitive was also examined. Attempts were made, using a variety of subcellular fractionation techniques, to isolate and identify the organelles involved in the receptor mediated transcellular transport of IgG

The uptake and transmission of protein by the gut of the neonatal rat

The studies reported in this thesis deal with the in vivo transmission of homologous and heterologous IgG and other proteins across the proximal small intestine of the suckling rat. The uptake of these labelled macromolecules from the intestine was monitored, and the subsequent appearance of radioactive material in the serum, viscera and carcass was examined by ultrafiltration and ultracentrifugation techniques. The rate of transmission of intact IgG and IgG breakdown products across the intestinal barrier was measured with the intention of obtaining further information about the mechanisms of immunoglobulin transport. The significance of the digestive activity of the suckling rat gut to the process of antibody transmission was also assessed. This was done by gel filtration analysis of the radioactive material present in the gut wall and wash after the intraluminal injection of labelled rat IgG. The ability of trypsin inhibitor to stimulate the transmission of intact IgG was investigated, and the possibility that the IgG receptor on the surface of proximal enterocytes was trypsin sensitive was also examined. Attempts were made, using a variety of subcellular fractionation techniques, to isolate and identify the organelles involved in the receptor mediated transcellular transport of IgG

Calidad de atención en los Consultorios de Medicina del Hospital Luis N. Sáenz 2018

El estudio fue cuantitativo y corresponde a un estudio descriptivo de tipo transversal, con el propósito evaluar la calidad sobre atención según el usuario de acuerdo a una calidad de atención que se espera, así como la recibida en el Hospital Luis N. Sáenz 2018 en consultorios. La metodología utilizada tuvo diseño descriptivo y correlacional, corte transversal, que valora la vinculación de dos variables. La población atendida fue de 1800 que acude a consultas externas de medicina del mencionado Hospital, la muestra fue de 400 usuarios, los cuales fueron seleccionados de manera aleatoria. El instrumento a utilizar en la satisfacción del usuario fue la encuesta SERVQUAL y tuvo como conclusiones de relación significativa entre atención calidad recibida y esperada. Además, la atención de calidad esperada en los usuarios fue medio y/o regular con un 45,6%. Del mismo modo la calidad de atención esperada según sus dimensiones en usuario de la consulta externa de medicina en el Hospital Luis N, esperan que la calidad sea media (expectativas), en la fiabilidad (53,9%), capacidad de respuesta (45,8%) y empatía (45,6%), sin embargo, sus expectativas son bajas con la seguridad (46,8%) y los aspectos tangibles (39, 9%). Finalmente, la atención de calidad recibida fue medio con un 55,2% en consulta externa de medicinaTesi

Additional diagnostic value of implantable loop recorder in patients with initial diagnosis of real or apparent transient loss of consciousness of uncertain origin

Aims Non-syncopal transient loss of consciousness (T-LOC) encompasses disorders that sometimes resemble syncope, and the differential diagnosis with true syncope may be challenging. The implantable loop recorder (ILR) is potentially useful, but has never been systematically assessed. The aim of the study is to evaluate the diagnostic value of ILR in distinguishing syncope from non-syncopal forms of T-LOC. Methods and results We implanted an ILR in 58 patients (mean age 71 ± 17 years, 25 males) who had had 4.6 ± 2.3 episodes of real or apparent T-LOC, in order to distinguishing epilepsy from syncope (#28), unexplained fall from syncope (#29), or functional pseudo-syncope from syncope (#1). During 20 ± 13 months of follow-up, 33 patients (57%) had a spontaneous event documented by ILR. A diagnosis of syncope was established by ILR documentation of an arrhythmia in 15 (26%) patients: an asystole of 6 s (IQR 4–10 s) duration was documented at the time of the spontaneous event in seven patients with initial suspicion of epilepsy and in five patients with unexplained fall; atrial tachyarrhythmia was documented at the time of the spontaneous event in 1 and 1 patient, respectively, and ventricular tachycardia in 1 patient with unexplained fall. Conversely, in another 18 patients, ILR monitoring documented no significant rhythm abnormalities at the time of T-LOC recurrence, thus excluding an arrhythmic syncope. Finally, ILR was unable to document any syncopal episode in 25 (43%) patients. Among the 15 patients with an established diagnosis of arrhythmic syncope, syncope recurred during follow-up in 2 of 11 patients who were on pacemaker therapy and in 3 of 4 patients who were on other therapies. Conclusion Implantable loop recorder monitoring provides additional diagnostic value in 'difficult' patients with an initial diagnosis of non-syncopal real or apparent T-LOC

A method for selective stimulation of leg chemoreceptors in whole crustaceans

The integration of sensory information with adequate motor outputs is critical for animal survival. Here, we present an innovative technique based on a non-invasive closed-circuit device consisting of a perfusion/stimulation chamber chronically applied on a single leg of the crayfish Procambarus clarkii. Using this technique, we focally stimulated the leg inside the chamber and studied the leg-dependent sensory-motor integration involving other sensory appendages, such as antennules and maxillipeds, which remain unstimulated outside the chamber. Results show that the stimulation of a single leg with chemicals, such as disaccharides, is sufficient to trigger a complex search behaviour involving locomotion coupled with the reflex activation of antennules and maxillipeds. This technique can be easily adapted to other decapods and/or other sensory appendages. Thus, it has opened possibilities for studying sensory-motor integration evoked by leg stimulation in whole aquatic animals under natural conditions to supplement, with a direct approach, current ablation/silencing techniques

Dynamics of solid growth under a gravitational field: Influence of the formation of a diffusive layer

We discuss the gravitational sedimentation of particles in terms of a stochastic model considering, in view of experimental evidence, that the aggregation to the growing surface (deposit) is mediated by the formation of a layer of suspended particles subject to gravitational forces, thermal agitation, as well as aggregation (contact) forces. The aggregation of such partially buoyant particles is ruled by the rates of occurrence of the different stochastic events: incorporation to the layer of suspended particles, sedimentation, and gravitationally biased diffusion. The model introduces bridges across different standard solid on solid deposition models which can be considered as limit cases of the present one. Analytical and numerical results show that for finite (realistic) deposits there are different regimes of aggregation including situations in which the deposit is grown completely during the transient time of the system.Instituto de Investigaciones Fisicoquímicas Teóricas y Aplicada

Chemosensitivity in the Sea Urchin Paracentrotus lividus (Echinodermata: Echinoidea) to Food-Related Compounds: An Innovative Behavioral Bioassay

Like other animals, echinoderms rely on chemical senses to detect and localize food resources. Here, we evaluate the chemical sensitivity of the sea urchin Paracentrotus lividus to a number of stimuli possibly related to food, such as a few sugars, compared to the blue-green algae Spirulina (Arthrospira platensis). To do this we developed a simple, innovative method based on the recording of “urchinograms” estimating the movements of spines, pedicellariae, tube feet, and eventually of the whole sea urchin, in response to chemicals, while keeping both the whole animal and the stimulus in their natural environment, underwater. Our results show that Spirulina is a highly stimulating compound for the sea urchin, by acting in a dose-dependent manner. The animals resulted also sensitive, even if to a lesser extent, to some sugars, such as the monosaccharide glucose, but not to its isomer fructose, while among disaccharides, they sensed cellobiose, but not sucrose or trehalose. From an applied point of view, any insight into the chemical sensitivity of sea urchins toward potential food-related compounds may lead to the discovery of key chemicals that would help improve the efficiency and reduce the costs of dietary substrates for optimization of intensive rearing strategies. Although this method has been developed for P. lividus, it will be suitable to evaluate the chemical sensitivity of other echinoderms and other marine invertebrates characterized by low mobility

Blue-Green Algae as Stimulating and Attractive Feeding Substrates for a Mediterranean Commercial Sea Urchin Species, Paracentrotus lividus

Sea urchins rely on chemical senses to localize suitable food resources, therefore representing model species for chemosensory studies. In the present study, we investigated the chemical sensitivity of the Mediterranean sea urchin Paracentrotus lividus to the blue-green alga Aphanizomenon flos-aquae, namely "Klamath", and to a few amino acids chosen from the biochemical composition of the same algae. To this end, we used the "urchinogram" method, which estimates the movement rate of the sea urchins in response to chemicals. Our results showed that Klamath represents a strong chemical stimulus for P. lividus as it elicits an overall movement of spines, pedicellariae, and tube feet coupled, in some cases, to a coordinated locomotion of the animals. Sea urchins also displayed a sensitivity, even if to a lesser extent, to leucine, threonine, arginine, and proline, thus implying that the amino acids contained in Klamath may account, at least in part, for the stimulating effects exerted by the whole algae. Additionally, our results show that Klamath, as well as spirulina, another blue-green alga with high nutritional value, is very attractive for this sea urchin species. These findings gain further importance considering the potential profit of echinoderms for commercial consumers and their growing role in aquaculture. Klamath and spirulina combine high nutritional profiles with attractive and stimulating abilities and may be considered potential valuable feed supplements in sea urchin aquaculture