ABSTRACT
We applied four fractal dimension estimation algorithms on the temporal electrical impedance signal of normal MDCK type II cell cultures monitored by ECIS technique and showed that the fractal dimension due to micromotion allows discriminating processes not sensed by the spectral impedance of the culture. In this work we subjected cell cultures to electric current damage and drug exposure to analyze the changes in the fractal structure of the temporal signal. Among the changes presented and detected are the differentiation between a healthy monolayer and one exposed to a drug, as well as the distinction between a seeding process and a wound-healing process performed by electric current. The four algorithms used were validated by applying them on topological functions of known fractal dimension, a study that determined the necessary conditions for a correct estimation.
ABSTRACT
El artículo aborda la experiencia de implementación de un sistema de admisión a la nueva carrera de Medicina de la Universidad Nacional de Río Negro, Argentina, analizada desde los debates en torno a las formas de admisión e ingreso en los sistemas de educación superior. A partir de los relatos de quienes formaron parte del proceso, se describen las características del ingreso y los balances realizados. Se concluye sobre la importancia del acompañamiento docente en la implementación de cursos de ingresos con cupos.(AU)
This article describes the experience of implementing the admissions system for the new course in medicine offered by the Universidad Nacional de Río Negro , Argentina. The experience is analyzed drawing on the debate surrounding types of admissions processes and entrance into higher education systems. Based on the stories of people who have taken part in this process, we describe income characteristics of the admission and the balances made. It is concluded that it is important to provide pedagogical support for the implementation of admissions courses with quotas.(AU)
O artigo trata da experiência de implantação de um sistema de ingresso à nova carreira de Medicina na Universidad Nacional de Río Negro , Argentina, analisada a partir dos debates em torno das formas de admissão e ingresso nos sistemas de ensino superior. A partir das histórias de quem fez parte do processo, são descritas as características da renda e os saldos realizados. Conclui-se sobre a importância do apoio pedagógico na implantação de cursos vestibulares com cotas.(AU)
ABSTRACT
We apply the electric cell-substrate impedance sensing (ECIS) technique to monolayers of Madin-Darby canine kidney type II cells cultured on microelectrodes of different sizes. We analyze the effect of the microelectrode radius on the parameters provided by existing ECIS models. The cellular properties inferred from the models should be invariant to the change in the microelectrode radius used for the measurements, since these properties are inherent to the type of cells studied. The current standard model, the Giaever-Keese (GK) model, derived from electrical balances of a single cell extended to infinity by suitable boundary conditions, assumes an infinite microelectrode. The model is fitted to experimental data acquired with a large-radius microelectrode, which can be considered infinite for practical purposes. We compute the impedance of the other cell-covered microelectrodes from the parameters obtained with the GK model, resulting in values strongly discrepant with the experimental data for small microelectrodes. We repeat the process with the mean field (MF) model, an alternative model that depends on the microelectrode radius but not on the cell radius. In this paper we introduce the mesoscopic model, an analytical model that simultaneously includes the properties of an individual cell and the sizes of the microelectrode and the insulator (region between the microelectrode and the ground). The impedances calculated with the mesoscopic model are in excellent agreement with experimental data. Finally, the mesoscopic model reduces to the MF model when the insulator goes to infinity and to the GK model when it goes to zero.
ABSTRACT
In this work we present an assay to discriminate between normal and cancerous cells. The method is based on the measurement of electrical impedance spectra of in vitro cell cultures. We developed a protocol consisting on four consecutive measurement phases, each of them designed to obtain different information about the cell cultures. Through the analysis of the measured data, 26 characteristic features were obtained for both cell types. From the complete set of features, we selected the most relevant in terms of their discriminant capacity by means of conventional statistical tests. A linear discriminant analysis was then carried out on the selected features, allowing the classification of the samples in normal or cancerous with 4.5% of false positives and no false negatives.
Subject(s)
Cell Separation/methods , Dielectric Spectroscopy , Cell Line, Tumor , Cell Proliferation , HumansABSTRACT
La protección radiológica del paciente busca evitar dosis innecesarias, que aumentan el riesgo de cáncer en la población. Se apunta a justificar y optimizar las prácticas, proteger a los individuos más sensibles, prevenir accidentes, realizar los estudios con radiación sólo cuando son imprescindibles y obtener las mejores imágenes con la menor dosis posible.
Subject(s)
Humans , Diagnostic Imaging , Patients , Radiation ProtectionABSTRACT
We present a novel experimental technique to determine eye ulcers in animals using a spectral electrical impedance technique. We expect that this technique will be useful in dry eye syndrome. We used a sensor that is basically a platinum (Pt) microelectrode electrically insulated by glass from a cylindrical stainless steel counter-electrode. This sensor was applied to the naked eye of New Zealand rabbits (2.0-3.5 kg in weight). Whereas half of the eyes were normal (control), we applied to the remainder a few drops of 20% (v/v) alcohol to produce an ulcer in the eye. Using a multispectral electrical impedance system we measured ulcerated and control eyes and observed significant difference between normal and pathological samples. We also investigated the effects of different applied pressures and natural degradation of initially normal eyes as a function of time. We believe that this technique could be sufficiently sensitive and repetitive to help diagnose ocular surface diseases such as dry eye syndrome.
Subject(s)
Dielectric Spectroscopy/instrumentation , Electric Impedance , Eye Diseases/diagnosis , Ulcer/diagnosis , Animals , Pressure , RabbitsABSTRACT
BACKGROUND: The purpose of this study is to report the effect of different media osmolarity on a cell line monolayer of normal human conjunctival epithelia (IOBA-NHC) using Electric Cell-substrate Impedance Sensing (ECIS). METHODS: We built our own ECIS system. We fabricated biocompatible microelectrodes. We used a monolayer of IOBA-NHC cells with media at different osmolarities (315, 360, 446, and 617 mOsm/l). RESULTS: When there is an increase in hyperosmolarity, there is a slight decrease in the measured resistance of the naked microelectrode (without cells), whereas its capacitance remained practically unchanged. The evaluation of resistance and capacitance of a microelectrode covered by a monolayer of IOBA-NHC in relation to a naked microelectrode showed no difference in the standard media (315 mOsm/l), a small difference with 360 mOsm/l, and significant differences with hyperosmolarities of 446 mOsm/l and 610 mOsm/l. The resistance with a confluent cell monolayer is up to three times greater compared to the value of the resistance of the naked electrode with standard media. CONCLUSIONS: Both resistance and capacitance measurements for the cell monolayer were sensitive to changes in osmolarity.
