Dynamics of the level of randomness in gastric electrical activity.

This study was undertaken to investigate the dynamics of the level of randomness in gastric electrical signals. Combined recordings of internal gastric electrical activity (GEA) and electrogastrograms (EGG) were obtained from 16 unconscious dogs and two postoperative patients. The signals were amplified using specially designed amplifiers with flexible frequency range and were digitized with 10-Hz sampling frequency. The 4.27-min portions of the digital signals were subjected to a previously described turning point test for randomness. The distributions of the number of turning points (NTP) in successive time intervals calculated from all GEA signals were compared to the estimated NTP distribution of a random signal. NTP dynamics of internal GEA signals was also correlated to the NTP dynamics of cutaneous EGG. In five of 16 recordings from the dogs and in two of the 14 recordings from the patients, NTP values calculated from some internal GEA channels exceeded the 1% probability level for entering the normal NTP distribution of a random signal (P > 0.01). In all measurements the distributions of the NTP values recorded from cutaneous EGG channels were significantly different (P < 0.01) from the NTP distribution of a random signal. There was significant correlation (P < 0.01) between the NTP dynamics of internal GEA and EGG. The level of randomness in internal GEA recorded with the short-distance bipolar technique is substantially higher than that in cutaneous EGG, probably due to the occurrence of spike activity. Although the level of randomness in EGG is affected by many external factors, its dynamics correlated significantly with the level of randomness in internal GEA.

Reliability of percent distribution of power of the electrogastrogram in recognizing gastric electrical uncoupling.

The aim of this study was to examine the reliability of percent distribution of electrogastrographic (EGG) power in recognizing gastric electrical uncoupling. Sixteen anaesthetized dogs underwent laparotomy and implantation of six pairs of stainless-steel wire electrodes. Distal stomach was measured and three sections with approximately equal lengths were defined. Two pairs of electrodes were implanted in each section. Eight-channel EGG was also recorded. Three separate half-hour recordings were made: in the basal state; after a full circumferential separation of the distal antral section from the rest; after a second circumferential cut completely separating the middle from the proximal sections. EGG digital power spectra were split into three frequency ranges and dynamics of percent distribution of power was statistically examined. After the first cut, changes in the percent distribution of EGG power in the normal range were not significant (p = 0.2). Significant changes in the low range were noted (p < 0.05) and changes in the high range were borderline nonsignificant (p = 0.056). After the second cut, changes in percent distribution in the normal and the high range became significant (p < 0.01) while changes in the low range were insignificant (p = 0.075). Severe uncoupling was reflected in EGG by significant changes in the high-frequency range without internal tachygastria necessarily being present.

Comparative assessment of power dynamics of gastric electrical activity.

This study was undertaken to investigate the correlation between power dynamics of gastric electrical activity (GEA) assessed with different recording techniques. A total of seven eight-channel 1-hr combined recordings were obtained from three subjects in five consecutive postoperative days. Four channels were recorded from bipolar electrodes implanted into the gastric antral wall, and four channels were electrogastrographic (EGG). Six pairs of bipolar electrodes were inserted into the antral wall (three anterior; three posterior) of 16 anaesthetized dogs. Fourteen-channel (six internal GEA and eight EGG) 1/2-hr recordings were obtained from each dog. Sets of power values calculated from channel pairs (internal, EGG or mixed) were cross-correlated and the significance of the obtained correlation coefficients was examined (P < 0.05). The majority of power correlations of internal GEA channel pairs, and those of mixed (internal GEA-EGG) channel pairs were insignificant. These findings question the claims that EGG power dynamics mirrors the power dynamics of internal GEA.

[Position changes of mandibular condyle in Herbst treatment. Radiographic study]. / Lageveränderungen des Condylus Mandibulae bei der Herbst-Behandlung. Eine röntgenkephalometrische Untersuchung.

The study aimed to analyse the short- und long-term changes in condyle position in Class II/1 malocclusions treated with the Herbst appliance. Cephalometric reoentgenograms from a Herbst group (n = 30, mean age 12.1 years) were compared to those of a Control group (n = 12, mean age 11.0 years). The total observation period was 3 1/2 years. Centric occlusion and mouth open profile roentgenograms (to visualize the condyle) were analysed at four occasions. Mandibular tracings from the mouth open headfilms were superimposed on the centric occlusion headfilms using the Nasion-Sella-Line (NSL) for reference. NSL and its perpendicle NSLP through Sella (S) were used as a reference grid for linear measurements. When starting Herbst treatment the condyle was displaced 6 mm anteriorly and caudally. After 7 months of treatment the condyle was located 0.8 mm caudally to the pre-treatment position. No difference existed, however, between the Herbst and Control group. During the total observation period of 3 1/2 years the condyle in both examination groups moved caudally and posteriorly. This was thought to be a result of normal growth changes. It was concluded that Herbst treatment did not have an adverse effect on the position of the condyle.