Gastric activity studies using a magnetic tracer

Peptide-modulated pH rhythms

Many drugs adjust and/or control the spatiotemporal dynamics of periodic processes such as heartbeat, neuronal signaling and metabolism, often by interacting with proteins or oligopeptides. Here we use a quasi-biocompatible, non-equilibrium pH oscillatory system as a biomimetic biological clock to study the effect of pH-responsive peptides on rhythm dynamics. The added peptides generate a feedback that can lengthen or shorten the oscillatory period during which the peptides alternate between random coil and coiled-coil conformations. This modulation of a chemical clock supports the notion that short peptide reagents may have utility as drugs to regulate human body clocks.

Superficial magnetic imaging by an xy-scanner of three magnetoresistive channels

A scanning system developed for planar magnetic surfaces composed of a moving line of three magnetoresistive ultrasensitive transducers, complemented by a signal conditioning circuit is presented. After the calibration of the sensors, it was used to determine magnetized surface images with different shapes to evaluate the sensitivity of the device, and the images are represented in gray levels on a scale from 0 to 255 intensities, to get a visual representation of the magnetic field strength. The device is shown to be sensitive enough to detect gradients homogeneities and discontinuities in the magnetic field maps and images of magnetic susceptibility.

Electrical bioimpedance and other techniques for gastric emptying and motility evaluation

The aim of this article is to identify non-invasive, inexpensive, highly sensitive and accurate techniques for evaluating and diagnosing gastric diseases. In the case of the stomach, there are highly sensitive and specific methods for assessing gastric motility and emptying (GME). However, these methods are invasive, expensive and/or not technically feasible for all clinicians and patients. We present a summary of the most relevant international information on non-invasive methods and techniques for clinically evaluating GME. We particularly emphasize the potential of gastric electrical bioimpedance (EBI). EBI was initially used mainly in gastric emptying studies and was essentially abandoned in favor of techniques such as electrogastrography and the gold standard, scintigraphy. The current research evaluating the utility of gastric EBI either combines this technique with other frequently used techniques or uses new methods for gastric EBI signal analysis. In this context, we discuss our results and those of other researchers who have worked with gastric EBI. In this review article, we present the following topics: (1) a description of the oldest methods and procedures for evaluating GME; (2) an explanation of the methods currently used to evaluate gastric activity; and (3) a perspective on the newest trends and techniques in clinical and research GME methods. We conclude that gastric EBI is a highly effective non-invasive, easy to use and inexpensive technique for assessing GME.

Encapsulation of Superparamagnetic Iron Oxide Nanoparticles by the Supercritical Antisolvent Process

The aim of the experiments in this research was to produce a coated superparamagnetic iron oxide nanoparticle (SPION) product that may be used as a contrasting agent for MRI. There are several methods that can be employed to coat SPIONs. However, many of the current methods employ toxic organic solvents which can be difficult to remove from the product solution. The encapsulation and characterization of SPIONs in Eudragit was done using a supercritical antisolvent system (SAS) with ethanol as the solvent and supercritical carbon dioxide (SC-CO2) as the antisolvent. Particles of diameters less than 200 nm were produced which had preserved superparamagnetic properties. An encapsulation efficiency of 70 % was achieved.

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.

Stress profile, coping style, anxiety, depression, and gastric emptying as predictors of functional dyspepsia: a case-control study

OBJECTIVE

To determine whether gastric emptying, stomach peristaltic frequencies, stress profile, depressive symptoms, anxiety, and salivary cortisol levels could predict functional dyspepsia (FD).

METHODS

Magnetogastrography (MGG) was used to measure gastric emptying time and the gastric peristaltic frequencies in 15 patients with FD diagnosis and in 17 healthy volunteers. In all the participants, stress profile, anxiety, and depressive symptoms were evaluated by means of standardized questionnaires, and morning salivary samples were collected for the measurement of cortisol levels. A univariate logistic regression model was used to examine the probability of the measured variables to predict the presence of FD.

RESULTS

The univariate logistic regression model showed that the half-time of gastric emptying (OR=1.16 P=.01); the subscale of stress items (OR=1.08, P=.003); negative appraisal of subscale coping strategies (OR=1.03, P=0.007); anxiety (OR=1.05, P=.01); and depression (OR=1.23, P=.02) had a significant predictive value for the presence of FD. However, by applying the stricter multiple comparison criteria, only stress, negative appraisal, and anxiety arose as predictors of FD. The FD patients compared with healthy volunteers showed significantly elevated half-time of gastric emptying (P<.0006), high scores in the subscales of stress (P<.000003), in behavior type "A" (P<.04), in coping styles (P<.008), in depression (P<.0004), and in anxiety (P<.0002).

CONCLUSIONS

These findings indicate that psychosocial stress, mood symptoms, and coping style are predictors of FD. The stress shows high sensibility and specificity in the patients with FD, indicating a contribution in the etiopathogenesis of dyspepsia.

Magnetogastrography (MGG) reproducibility assessments of gastric emptying on healthy subjects

The aim of this study was to evaluate the half-time gastric emptying reproducibility measured by magnetogastrography (MGG). Seven healthy subjects were subjected to a magnetic pulse of 32 mT for 17 ms, seven times in 90 min. The procedure was repeated one and two weeks later. Assessments of the gastric emptying were carried out for each one of the measurements and statistical analyses of ANOVA and Bland-Altman were performed for every group of data. A mean of 21.7 +/- 3.3 min was measured for the half-time of gastric emptying for yoghurt. Reproducibility estimation was above 85%. Therefore, magnetogastrography seems to be a reliable technique to be implemented in routine clinical trials.