Teodoro Cordova-Fraga

Understanding the magnetic susceptibility measurements by using an analytical scale

A description of the measurement procedure, related theory and experimental data analysis of the magnetic susceptibility of materials is given. A short review of previous papers in the line of this subject is presented. This work covers the whole experimental process, in detail, and presents a pragmatic approach for pedagogical sake.

Gastric activity studies using a magnetic tracer

A magnetic pulse generator has been set up in order to study gastric activity. Two coils 1.05 m in diameter, arranged in a Helmholtz configuration, were used. The system generated magnetic field pulses higher than 15 mT, of duration 17.3+/-1.2 ms. Measurements were performed in 11 male volunteers, with average age 29.3+/-6.4 years and body mass index 26.0+/-4.8 kg m(-2). Magnetite (Fe3O4) particles with diameters from 75 to 125 microm were used as magnetic tracers, which were mixed in 250 ml of yogurt in concentrations from 2 to 5 g. Signals were registered by using a high speed 3 axis fluxgate digital magnetometer and processed to determine the relaxation of the magnetic tracers by fitting a first-order exponential function to the data, a mean relaxation constant K = 116+/-40 s(-1) was obtained. Also, an average gastric peristaltic frequency was measured; a value of 3.2+/-0.3 cpm was determined.

Cr Localization and Speciation in Roots of Chromate Fed Helianthus annuus L. Seedlings Using Synchrotron Techniques

In order to gain knowledge on the potential use of Helianthus annuus L. for the remediation of Cr(VI) polluted waters, hydroponics experiments were set up to determine Cr uptake and tolerance in different Cr(VI)-sulfate conditions, and Cr biotransformations. Results indicated that Cr(VI) promoted seed germination, and plant tolerance was higher at younger plant stages. Cr uptake was dependent on sulfate concentrations. The highest Cr levels in roots and shoots (13,700 and 2,500 mg kg–1dry weight (DW), respectively) were obtained in 1 mM sulfate. The lowest Cr uptake in roots (10,600 mg kg–1DW) was observed in seedlings treated with no sulfate. In shoots, Cr concentration was of 1,500 mg kg–1DW for the 1 mM sulfate treatment, indicating a different level of interaction between chromate and sulfate in both tissues. For the first time, using micro X-ray florescence (μXRF), we demonstrated Cr reaches the root stele and is located in the walls of xylem vessels. Bulk and micro X-ray Absorption Near-Edge Structure (μXANES) results showed that Cr in the roots is mostly in the form of Cr(III) phosphate (80%), with the remainder complexed to organic acids. Our results suggest this plant species may serve for Cr(VI) rhizofiltration purposes.

Biomagnetic techniques for evaluating gastric emptying, peristaltic contraction and transit time

Biomagnetic techniques were used to measure motility in various parts of the gastrointestinal (GI) tract, particularly a new technique for detecting magnetic markers and tracers. A coil was used to enhance the signal from a magnetic tracer in the GI tract and the signal was detected using a fluxgate magnetometer or a magnetoresistor in an unshielded room. Estimates of esophageal transit time were affected by the position of the subject. The reproducibility of estimates derived using the new biomagnetic technique was greater than 85% and it yielded estimates similar to those obtained using scintigraphy. This technique is suitable for studying the effect of emotional state on GI physiology and for measuring GI transit time. The biomagnetic technique can be used to evaluate digesta transit time in the esophagus, stomach and colon, peristaltic frequency and gastric emptying and is easy to use in the hospital setting.

Mammalian cells exposed to ionizing radiation: Structural and biochemical aspects.

Acute or chronic exposure to ionizing radiation is a factor that may be hazardous to health. It has been reported that exposure to low doses of radiation (less than 50 mSv/year) and subsequently exposure to high doses produces greater effects in people. It has been reported that people who have been exposed to low doses of radiation (less than 50 mSv/year) and subsequently are exposed to high doses, have greater effects. However, at a molecular and biochemical level, it is an unknown alteration. This study, analyzes the susceptibility of a biological system (HeLa ATCC CCL-2 human cervix cancer cell line) to ionizing radiation (6 and 60 mSv/90 s). Our research considers multiple variables such as: total protein profile, mitochondrial metabolic activity (XTT assay), cell viability (Trypan blue exclusion assay), cytoskeleton (actin microfilaments), nuclei (DAPI), and genomic DNA. The results indicate, that cells exposed to ionizing radiation show structural alterations in nuclear phenotype and aneuploidy, further disruption in the tight junctions and consequently on the distribution of actin microfilaments. Similar alterations were observed in cells treated with a genotoxic agent (200 μM H2O2/1h). In conclusion, this multi-criteria assessment enables precise comparisons of the effects of radiation between various line cells. However, it is necessary to determine stress markers for integration of the effects of ionizing radiation.

Registration of Intravascular Pressure Curves: Magneto‐Mechanical Evaluation

In this work, graphs of the intravascular blood pressures at both the left primitive carotid artery and the left jugular vein are presented, by using a “magneto‐mechanical” technique with pulse‐pressure gauge, a device designed especially to register the magnetic flux variability of a magnetic marker placed superficially on the skin over a blood vessel. It is presented the implementation of a device used for registration of the magnetic induction generated by the periodical movements of a magnetic marker (MM) by using a magnetoresistive transductor, which is placed superficially on the skin (non‐invasive) over a blood vessel, at the cervical level in the path of the left carotid, identified by the amplitude of the arterial pulse.

Solid Test Meal to Measure the Gastric Emptying with Magnetogastrography

The gastric emptying is the time of evacuating the food ingested from the stomach to the duodenum in a controlled rate. Diverse studies express the results of the gastric emptying in form of half‐time (t1/2). The Magnetogastrography (MGG) is a biomagnetic technique that has the advantage of not being invasive, radiation free and does not interfere with the privacy of the subject. The objective was to analyze the magnetic signal of magnetic tracers mixed in a solid food to measure gastric emptying using Magnetogastrography. The ingested test meal displayed a magnetic signal, which served to obtain the signal registered by the fluxgate and the peristaltic contractions could be calculated while the stomach was emptying. The solid food product developed results to work satisfactorily in magnetogastrography.

Skin absorption studied by photoacoustic techniques

In this work we propose for the particular problem of penetration of substance into skin, a setup which is based on the conventional photoacoustic cell. In order to avoid some problems, intrinsic to the material under study and the sensibility of the technique, we use the thermal effusivity of the skin-substance system to monitor this phenomenon, in vivo and in situ. We measure the changes of thermal effusivity due to the absorption of some topical medicaments. These values are compared with those from an adjacent sample of clean skin (without medicament, natural fats or transpiration). This experiment was performed on a volunteer in different parts of the human skin. We use stainless steel (250 mm thickness) as the thermally thin light absorbance surface. The values for this parameter are in agreement with some reported in the literature. Besides the measurements described above.

Coronary artery segmentation in X-ray angiograms using gabor filters and differential evolution

Segmentation of coronary arteries in X-ray angiograms represents an essential task for computer-aided diagnosis, since it can help cardiologists in diagnosing and monitoring vascular abnormalities. Due to the main disadvantages of the X-ray angiograms are the nonuniform illumination, and the weak contrast between blood vessels and image background, different vessel enhancement methods have been introduced. In this paper, a novel method for blood vessel enhancement based on Gabor filters tuned using the optimization strategy of Differential evolution (DE) is proposed. Because the Gabor filters are governed by three different parameters, the optimal selection of those parameters is highly desirable in order to maximize the vessel detection rate while reducing the computational cost of the training stage. To obtain the optimal set of parameters for the Gabor filters, the area (Az) under the receiver operating characteristics curve is used as objective function. In the experimental results, the proposed method achieves an Az=0.9388 in a training set of 40 images, and for a test set of 40 images it obtains the highest performance with an Az=0.9538 compared with six state-of-the-art vessel detection methods. Finally, the proposed method achieves an accuracy of 0.9423 for vessel segmentation using the test set. In addition, the experimental results have also shown that the proposed method can be highly suitable for clinical decision support in terms of computational time and vessel segmentation performance.

PEMF on Neuroblastoma Cells Previously Exposed to Antidepressants

Interaction between magnetic field and living systems is inevitable; in fact, we are immersed in an ocean of magnetic field due to the magnetic field of the earth and the technology developments. Interaction between magnetic field and living systems is inevitable; in fact, we are immersed in an ocean of magnetic field due to the magnetic field of the earth and the technology developments, this one already have medical applications, currently, the pulsed electromagneticmagnetic fields (PEMF) are an alternative option for the treatment of some mental illness as the depression or schizophrenia. In order to have estimation of the side effects from PMF and drugs used for treat this kind of disorders. In this work, it is presented a comparison of the effects of imipramine, a drug for the treatment of depression, and the effects of PMF on cells from the line SHSY5Y, which provide us a representative model of neuronal tissue. The assays were done in both ways, the separately effects and the jointly effects. The imipramine at high dosage for a short period (120 mg/mL, for 20 min) shows cell damage on both, the morphology and the metabolism. Meanwhile, the PMF (50 Hz, 7 mT for 8 h) shows a cell proliferation and a decrease of their metabolism. The jointly assay indicates that the PMF balances the morphological negative effects from imipramine. In the long term these results can impact a therapy that may be more efficient. However, more research is needed in this area