Contribution of ion binding affinity to ion selectivity and permeation in KcsA, a model potassium channel.

Ion permeation and selectivity, key features in ion channel function, are believed to arise from a complex ensemble of energetic and kinetic variables. Here we evaluate the contribution of pore cation binding to ion permeation and selectivity features of KcsA, a model potassium channel. For this, we used E71A and M96V KcsA mutants in which the equilibrium between conductive and nonconductive conformations of the channel is differently shifted. E71A KcsA is a noninactivating channel mutant. Binding of K(+) to this mutant reveals a single set of low-affinity K(+) binding sites, similar to that seen in the binding of K(+) to wild-type KcsA that produces a conductive, low-affinity complex. This seems consistent with the observed K(+) permeation in E71A. Nonetheless, the E71A mutant retains K(+) selectivity, which cannot be explained on the basis of just its low affinity for this ion. At variance, M96V KcsA is a rapidly inactivating mutant that has lost selectivity for K(+) and also conducts Na(+). Here, low-affinity binding and high-affinity binding of both cations are detected, seemingly in agreement with both being permeating species in this mutant channel. In conclusion, binding of the ion to the channel protein seemingly explains certain gating, ion selectivity, and permeation properties. Ion binding stabilizes greatly the channel and, depending upon ion type and concentration, leads to different conformations and ion binding affinities. High-affinity states guarantee binding of specific ions and mediate ion selectivity but are nonconductive. Conversely, low-affinity states would not discriminate well among different ions but allow permeation to occur.

Introducción de los nuevos tamaños pediátricos de la mascarilla laríngea I-gel en la práctica clínica. Un estudio observacional prospectivo / Introduction of the new paediatric sizes of I-gel laryngeal mask airway

Antecedentes: La mascarilla I-gel es un dispositivo supraglótico relativamente nuevo que se utiliza en pacientes adultos con una seguridad y eficacias probadas. Hasta la fecha, este dispositivo sólo estaba disponible en tamaños de 3 a 5, por lo que su funcionamiento sólo había sido evaluado en pacientes de más de 30 kg. Recientemente se han introducido en el mercado los tamaños pediátricos del mismo para pacientes de menor peso. En este artículo presentamos nuestros primeros datos en el uso de este dispositivo en estos nuevos tamaños. Métodos: Setenta pacientes pediátricos consecutivos sometidos a procedimientos quirúrgicos fueron anestesiados y ventilados utilizando la mascarilla laríngea I-gel sin utilizar ningún agente paralizante. Se midieron la facilidad de inserción y el número de intentos necesarios para lograr una ventilación adecuada. La presión de fuga durante la ventilación mecánica, así como la presión pico y presión media de la vía aérea fueron registradas. También se buscó la aparición de complicaciones derivadas de la utilización del dispositivo de vía aérea. Resultados: La mascarilla laríngea I-gel fue colocada con éxito, consiguiendo una ventilación mecánica adecuada en todos los casos. Su inserción fue muy fácil en el 92,4% de los pacientes. La presión media de fuga fue 28,9 cm de H2O. Se lograron volúmenes corrientes adecuados con una presión media de la vía aérea durante la ventilación mecánica de 9 cm de H2O.Conclusión: En vista de los resultados favorables, la mascarilla laríngea I-gel en sus nuevos tamaños pediátricos parece ser un dispositivo seguro y eficaz para el manejo de la vía aérea pediátrica durante procedimientos quirúrgicos cortos (AU)

Background and Objectives: The I-gel is a relatively new supraglottic airway device that has been used in adult patients with proven safety and eficacy. Until now this device was only available in sizes 3 to 5, and had only been evaluated in patiets over 30 kg. We present the first publised data on the new paediatric sizes of this device. Patients and Methods: Seventy consecutive paediatric patients undergoing general surgical procedures were anaesthetized and I-gel laryngeal mask airway introduced without the use of a paralyzing agent. Ease of insertion and number of attempts needed to achieve adequate ventilation were recorded. Leak pressure during mechanical ventilation, as well as mean and peak airway pressure were also recorded. We also looked for any complications derived from the use of the airway device. Results: The I-gel laryngeal mask airway was successfully placed and used for mechanical ventilation in all cases. Insertion was found to be very easy in 92,4% of the patients. Leak pressure was 28,9 cm H2O. Adequate tidal volumes were achieved, with mean airway pressure during mechanical ventilation of 9 cm H2O.Conclusions: In view of the favourable results, the paediatric sizes of the I-gel laryngeal mask airway seem to be a safe and effective device for paediatric airway management during short surgical procedures (AU)

Monitoring adenovirus infections with on-line and off-line methods.

Several known process monitoring methods were tested for their efficacy in the detection of adenovirus infections. The methods that we explored include several indirect indications of viral infections, including metabolic rate analysis, secondary gauges of respiration, cell size measurement, cell number and cell viability determination, and changes in capacitance. Direct indications of the adenovirus infection were also applied, including total viral particle and infectious particle measurements, as well as a flow cytometry method for detecting infected cells. All of the methods tested in the study provide some positive indication of an adenovirus infection. Many of the methods require repeated sampling, which may limit their utility in a manufacturing process. All of the indirect measures of viral infection may be limited by the fact that they do not uniquely identify an infection. The simplest monitoring methods appear to be detection of changes in respiration or the capacitance of the culture, both of which seem to provide a clear indication of an infection. Further work will be required to demonstrate that these indications are characteristic of only a successful and productive adenovirus infection.

Thermal softening of tracheal tubes: an unrecognized hazard of the Bair Hugger active patient warming system.

The Bair Hugger system is a new and highly effective active patient warming system which produces a layer of warm air between the patient and the warming system. We report an instance of marked softening and distortion of a polyvinyl chloride tracheal tube caused by this layer. We also present laboratory data indicating that this is a likely problem under routine theatre conditions, with suggestions for prevention.

Utilidad del terciopelo sintetico en el aislamiento de dermatofitos. / Synthetical velvet square usefulness in isolation of dermatophytes

En 50 pacientes con diagnostico de dermatofitosis se intento el aislamiento de sus agentes con el metodo clasico y utilizando cuadros de terciopelo sintetico. Los resultados con ambas tecnicas son concordantes. Las ventajas con el uso del terciopelo son las siguientes: material barato,facil de encontrar en el comercio, de preparar, no hay necesidad de esterilizar y se puede transportar sin problema cuando se realizan encuestas epidemiologicas