Dielectric study of the adhesion of mesenchymal stem cells from human umbilical cord on a sugarcane biopolymer.

It is of current interest the identification of appropriate matrices for growing mesenchymal stem cells (MSC). These cells are able not only to regenerate themselves but also to differentiate into other type of functional cells, and so they have been extensively used in tissue engineering. In this work, we have evaluated the use of electric impedance spectroscopy (EIS) to follow the adhesion of MSC from Wharton's jelly of the human umbilical cord (hWJMSC) on sugarcane biopolymers (SCB). Impedance spectra of the systems were obtained in the frequency range of 10(2)-10(5) Hz. An EIS investigation showed that when deposited on a metallic electrode SCB films prevent the passage of electrons between the solution and the metallic interface. The impedance spectra of hWJMSCs adhered on SCB revealed that there is a significant increase in the magnitude of the impedance when compared to that of pure SCB. The corresponding resistance (real part of the impedance) was even higher for the SCB-hWJMSC system than for SCB without cells on their surface, in an indication of an increased blockage to the electron transfers. The resistance charge transfer is extracted by curve-fitting the impedance spectra to an equivalent circuit model. Also, a shift of the phase angle to higher frequencies was obtained for SCB-hWJMSC system as a result from hWJMSC adhesion. Our study demonstrates that EIS is an appropriate method to evaluate the adhesion of MSC. SCB can be considered as a promising biomaterial for tissue engineering.

Electrical impedance spectroscopy investigation of surfactant-magnetite-polypyrrole particles.

We report an electrical impedance spectroscopy (EIS) characterization of composite systems formed by emulsion polymerization of polypyrrole (PPY) in concentrated aqueous solutions of sodium dodecyl sulfate (SDS) containing dispersed magnetite particles. SDS-(Fe3O4)-(conducting polymer) microaggregates with different iron contents were prepared by varying in a reciprocal manner the relative amounts of the metal oxide and PPY. We have measured the zeta-potential and the average size of the corresponding dispersed particles and examined their relative composition through energy dispersive X-ray (EDX) microanalysis and Fourier transform infrared (FTIR) spectroscopy. Important aspects of the charge transport in these composite particles can be identified by mapping the real and imaginary parts of their complex impedance as a function of the frequency of the applied external electric field. For instance, for binary composites SDS-(Fe3O4) polarization effects are dominant at the low-frequency regime, with a well-defined dielectric relaxation easily identifiable. On the other hand, when the relative amount of PPY is progressively increased in the ternary SDS-(Fe3O4)-PPY composites, a transition between different charge transport mechanisms is observed at higher frequencies. The EIS results suggest that in these ternary aggregates the PPY chains envelop the metal oxide clusters and effectively shield them from the external field, and that only in binary samples that do not contain PPY is that the surfactant molecules can directly enclose the magnetite particles. These results are consistent with the fact that the average size of the aggregates in the ternary composites is in general larger than those of either SDS-PPY or SDS-magnetite binary particles.

Aggregation of methyl orange probed by electrical impedance spectroscopy.

We present results of an electrical impedance spectroscopy investigation of the evolution of the aggregation of methyl orange (MO) in pure aqueous solutions as the concentration of the dye is varied. By applying the constant phase element (CPE) approximation to model the electrical response of the MO solutions, we have verified that the formation of dimers and oligomers can be recognized by specific signatures in the loss and capacitive components of the dielectric response of the system. We interpret these well-defined changes in the dielectric properties of the solutions as a result of molecular rearrangements caused by the aggregation process that alter the current circulation pathways and the electric dipole distribution. The fact that these specific changes in the dielectric behavior coincide with critical concentrations where dimer and oligomer formation in pure aqueous MO solutions are known to occur suggests that electrical impedance spectroscopy can be a competitive technique for the investigation of aggregation behavior in dyes and surfactants.

Theoretical and experimental investigation of the second hyperpolarizabilities of methyl orange.

We describe experimental and theoretical studies of the third-order nonlinear optical coefficients of methyl orange solutions under different pH conditions. A combination of semiempirical and ab initio methods was adopted to investigate the most stable geometrical structures possible for this molecule. The experimental data obtained using the Z-scan technique for the third-order nonlinear optical properties of this compound has allowed the determination of the nonlinear refractive index and nonlinear absorption coefficient under picosecond excitation in the visible (532 nm) spectral region. From those experimental results, the second hyperpolarizability of methyl orange was inferred both for acidic and alkaline solutions. Comparison of these values to the results predicted by semiempirical methods suggests that even at low pH, when the probability of cis-trans isomerization is increased, the trans conformation of the methyl orange molecule should dominate the nonlinear spectra of this compound. The theoretical results were used as an auxiliary tool to identify possible trends on the nonlinear properties changes as a function of the distinct molecular conformations adopted by the methyl orange molecule under different pH conditions.

Lossy compression techniques, medical images, and the clinician.

There has been increasing interest in the storage and retrieval of medical images in hospitals and clinics here in Brazil and elsewhere. At the Heart Institute of São Paulo, with thousands of image-based procedures performed each month, the pursuit of optimal transmission and storage methods for digital images is a major concern. The use of data-compression techniques can reduce the enormous amount of imaging data to be stored or transmitted across a computer network, so that the efficiency of the computing system is preserved. The techniques for image compression can be categorized as "lossless" or "lossy," with "lossy" techniques being those in which some, supposedly irrelevant information is lost. Lossy techniques are much more efficient than lossless ones, achieving data-compression ratios as high as 100:1.

Hypermedia patient data retrieval and presentation through WWW.

WWW can be a helpful tool for PACS and HIS data retrieval and presentation. The use of gateways to access both text and hypermedia databases (images and video) enables fetched data to be presented in virtually any computer system. WWW browsers provide a very friendly interface and require little training to operate. This paper presents a prototype that uses a SQL gateway for accessing relational patient databases. The dataset used here include text data from reports of diagnostic procedures as well as pointers to the corresponding images. Images can be displayed by the browsers' viewers.

Lossy compression in nuclear medicine images.

The goal of image compression is to reduce the amount of data needed to represent images. In medical applications, it is not desirable to lose any information and thus lossless compression methods are often used. However, medical imaging systems have intrinsic noise associated to it. The application of a lossy technique, which acts as a low pass filter, reduces the amount of data at a higher rate without any noticeable loss in the information contained in the images. We have compressed images of nuclear medicine using the discrete cosine transform algorithm. The decompressed images were considered reliable for visual inspection. Furthermore, a parameter was computed from these images and no discernible change was found from the results obtained using the original uncompressed images.

Integrating Hospital Information Systems. The challenges and advantages of (re-)starting now.

With the new technologies available today, more complex and useful Hospital Information Systems (HIS) can be designed and implemented. These new technologies have allowed that information from different sources and nature such as documents, images and signals be integrated within a single environment. Open standards, reliable networks, powerful hardware and software and lower prices are among the issues that make all this possible. One of the main issues is what to do with old systems that do not adhere to this new HIS concept. At the Heart Institute (InCor), a decision was made towards starting developing a new system called I3S. This paper gives a brief description of that system.

Human leukocyte A and B antigen, gene and haplotype frequencies in the population of the city of São Paulo in Brazil.

1. Antigen, gene and haplotype frequencies are important data for population analysis, paternity exclusion testing, genetic studies, and for organ transplantation selection. 2. We have studied the Class I histocompatibility antigens of 617 unrelated individuals from the city of São Paulo, Brazil, to determine antigen and gene frequencies of 16 HLA-A and 28 HLA-B antigens. Estimated haplotype frequencies were also determined, as well as the genetic distances of this population from European Caucasian and Negro populations. 3. A previously unknown linkage disequilibrium was detected for A23-B49 and a clear trend towards antigen frequencies intermediate between Caucasoid and Negro populations was observed.

Human leukocyte a and B antigen, gene and haplotype frequencies in the population of the city of Säo Paulo in Brazil

Antigen, gene and haplotype frequencies are imnportant data for population analysis, poaternity exclusion testing, genetic studies, and for organ transplantation selection. We have studied the class I histocompatibility antigens of 617 unrelated individuals from the city of Säo Paulo, Brazil, to determine antigen and gene frequencies of HLA-A and 28 HLA-B antigens. Estimated haplotype frequencies were also determined, as well as the genetic distances of this population from European Caucasian and Negro populations. A previously unknown linkage disequilibrium was detected for A23-B49 and a clear trend towards antigen frequencies intermediate between Caucasoid and Negro populations was observed