Biomedical subjects

N Stergiou

Publications and source records attributed to N Stergiou.

8 recordsLinked to original sources

PubMed2001

A dynamical systems investigation of lower extremity coordination during running over obstacles.

OBJECTIVE: To investigate intralimb coordination during running over a level surface and over obstacles of three different heights. DESIGN: The phasing relationships between the foot and leg motions in the frontal plane, and the shank and thigh motions in the sagittal plane were used to compare patterns of coordination. BACKGROUND: The coordinated actions of lower extremity segments are necessary to absorb the impact forces generated during running. The behavioral patterns of these segments can be studied under changing task demands using analysis techniques from the Dynamical Systems Theory. METHODS: Ten subjects ran at their self-selected pace under four conditions: over a level surface and over obstacles of different heights (5%, 10%, 15% of their standing height). A force platform was used to record impact forces during landing after obstacle clearance, while kinematics were collected using a two-camera system. RESULTS: The increases in obstacle height resulted in significant changes in impact forces (34% increase between the two extreme conditions) and more in-phase relationships between the segments during early stance. No changes were observed in the variability of the phasing relationships. CONCLUSIONS: The coordination changes observed might be compensatory strategies aimed to reduce forces and potential injury. However, since the impact forces still increased significantly, it is also possible that the observed changes might be at-risk movement patterns predisposing runners to injury.

Adult↗

PubMed2001

Intralimb coordination following obstacle clearance during running: the effect of obstacle height.

The purpose of this study was to investigate the different coordination strategies used following obstacle clearance during running. Ten subjects ran over a level surface and over obstacles of six different heights (10, 12.5, 15, 17.5, 20 and 22.5% of their standing height). Analysis based upon the dynamical systems theory (DST) was used and the phasing relationships between lower extremity segments were examined. The results demonstrated that the increasing obstacle height elicited behavioral changes. The foot and the leg became more independent in their actions, while the leg and the thigh strengthened their already stable relationship. The 15% obstacle height seems to be a critical height for the observed changes.

Adult↗

PubMed2001

Topical application of nitrates onto the papilla of Vater: manometric and clinical results.

BACKGROUND AND STUDY AIMS: Systemic administration of nitrates inhibits motility of the sphincter of Oddi (SO) but is hampered by a decrease of the arterial blood pressure. We evaluate whether topical application of glyceril trinitrate (GTN) onto the papilla can facilitate cannulation of the common bile duct during routine endoscopic retrograde cholangiopancreatography (ERCP) and compare the effect of topical GTN with that of isosorbide dinitrate (ISDN) on SO motility. PATIENTS AND METHODS: A total of 80 patients undergoing routine ERCP for suspected biliary obstruction received topical application of either saline (n = 40) or 10 mg of GTN (n = 40) onto the papilla of Vater in a randomized, double-blind fashion. Thereafter, selective bile-duct cannulation was attempted with a 0.035" hydrophilic guide wire. In another trial, 16 biliary type III patients underwent endoscopic SO-manometry and received in a randomized fashion either 10 mg of GTN (n = 8) or 10 mg of ISDN (n = 8) which was infused topically onto the papilla via the manometric catheter. Thereafter, the manometric recording was continued for a further 5 minutes. RESULTS: A spontaneous opening of the papilla with concurrent transpapillary bile flow was observed in 24/40 patients after topical GTN, and in only 8/40 patients after topical saline (P < 0.01). However, neither the number of cannulation attempts nor the time until successful cannulation differed significantly between the groups. In addition, the pre-cut rate was nearly identical in the two groups. Topical GTN showed no significant influence on the mean arterial blood pressure. The SO-baseline pressure was significantly lowered by topical GTN (28.2+/-12.9 mm Hg before ISDN vs. 22.5+/-13.7 mmHg after P<0.01). The phasic SO motility was also strongly inhibited by both drugs. However, the effect of GTN completely wanes after 3 minutes, whereas ISDN inhibited SO motility for > 5 minutes in all patients. CONCLUSIONS: Both topically administered GTN and ISDN evoked a profound inhibition of SO motility, but the effect of ISDN was longer lasting than that of GTN. However, locally administered GTN did not facilitate selective bile-duct access during routine ERCP.

Administration, Topical↗

PubMed2001

Correlation between sphincter of Oddi manometry and intraductal ultrasound morphology in patients with suspected sphincter of Oddi dysfunction.

BACKGROUND AND STUDY AIMS: Intraductal ultrasonography (IDUS) makes it possible to study sphincter of Oddi morphology during endoscopy. Two recent IDUS studies have described the sphincter of Oddi as a circumferential hypoechoic layer in the papilla, but there have as yet been few published data from patients with suspected sphincter of Oddi pathology. PATIENTS AND METHODS: Twenty-one consecutive patients with suspected biliary sphincter of Oddi dysfunction (seven men, 14 women; age 54 +/- 17 years) were enrolled in the study. Endoscopic sphincter of Oddi manometry was carried out using a 4-Fr electronic microtransducer device. After this, a wire-guided 6-Fr ultrasound catheter was placed in the common bile duct (CBD), and IDUS was carried out while the ultrasound catheter was being withdrawn from the CBD toward the duodenum. RESULTS: Sphincter of Oddi manometry and IDUS were carried out successfully in 18 of the 21 patients. Sphincter of Oddi manometry revealed sphincter of Oddi hypertension (baseline pressure > 35 mmHg) in eight patients. The mean sphincter of Oddi baseline pressure was 32 +/- 17 mmHg, and the mean phasic sphincter of Oddi pressure was 132 +/- 31 mmHg. During IDUS, a circumferential hypoechoic layer was clearly delineated in all patients. There was a significant correlation between the manometrically determined length of the sphincter of Oddi (8 +/- 2 mm) and the thickness of the hypoechoic layer (6 +/- 2 mm) as assessed by IDUS (r = 0.66, P < 0.001). However, no correlation was found between the baseline or phasic sphincter of Oddi pressures and the thickness of the hypoechoic layer. Accordingly, IDUS did not allow identification of patients with sphincter of Oddi hypertension. Mild pancreatitis was observed in one of the 18 patients (6 %). CONCLUSIONS: The circumferential hypoechoic layer of the papilla visualized by IDUS is the ultrasonographic correlate of the sphincter of Oddi. IDUS of the papilla is technically feasible and safe in patients with suspected sphincter of Oddi dysfunction. IDUS may provide additional information at the sphincter of Oddi level, but cannot be used as a substitute for sphincter of Oddi manometry.

Adult↗

PubMed2001

[Endoscopic mucosal resection of premalignant lesions of the upper gastrointestinal tract].

BACKGROUND: Surgical therapy of early malignancies of the upper gastrointestinal tract is associated with substantial morbidity and mortality, especially in elderly and co-morbid patients. In Japan endoscopic mucosal resection (EMR) has been proven to be safe and efficacious in this indication. PATIENTS AND METHODS: 22 patients (68 +/- 14 years, 9 females) with high-grade dysplasia of the esophagus (n = 5), early carcinoma of the esophagus (T1N0M0, n = 11) or early gastric cancer (T1N0M0, n = 6) proven by high-resolution videoendoscopy (plus chromoendoscopy in most cases), miniprobe-endosonography (12-20 MHz) and biopsy were enrolled. The lesion size ranged from 7-40 mm in diameter. EMR was performed using a monofile snare, in almost all cases after submucosal injection of an attenuated epinephrine-solution (1:20,000) to effect a lifting sign. "En bloc" resection was possible in 17/22 cases (77 %), but in 5 patients piecemeal-resection had to be performed due to a larger lesion size. RESULTS: Active bleeding occurred on 14 of 22 occasions (64 %), in another 5 patients secondary bleeding (within 24 h after EMR) were detected. All these events could be managed endoscopically (mainly by hemoclip application) and blood transfusion was not required. Other complications did not occur. A complete resection (R0) was achieved in 21/22 cases, however, one patient had to undergo a second EMR procedure because histology of the first resected specimen had revealed malignant infiltration of the resection margin (R1). After the second EMR procedure complete (R0)-resection was obtained. Compared to the histological findings after EMR the pre-procedural staging proved to be correct in all cases. The control examinations (clinical exam, lab data, endoscopy with multiple biopsies, endosonography and CT) after EMR revealed no local or systemic cancer recurrence in 21/22 patients (median follow-up 5 months, range 3-12 months). However, in one patient with adenocarcinoma and Barrett-esophagus another mucosal adenocarcinoma was detected 3 months after EMR (located in opposite to the initial carcinoma treated with EMR). CONCLUSION: EMR seems to be a safe and effective (regarding local tumor control) therapy for high-grade dyplasia and early malignancies in the upper gastrointestinal tract. However, long-term follow-up in these patients has to be awaited.

Adenocarcinoma↗

PubMed2000

Phase determination during normal running using kinematic data.

Algorithms to predict heelstrike and toe-off times during normal running at subject-selected speeds, using only kinematic data, are presented. To assess the accuracy of these algorithms, results are compared with synchronised force platform recordings from ten subjects performing ten trials each. Using a single 180 Hz camera, positioned in the sagittal plane, the average RMS error in predicting heelstrike times is 4.5 ms, whereas the average RMS error in predicting toe-off times is 6.9 ms. Average true errors (negative for an early prediction) are +2.4 ms for heelstrike and +2.8 ms for toe-off, indicating that systematic errors have not occurred. The average RMS error in predicting contact time is 7.5 ms, and the average true error in predicting contact time is 0.5 ms. Estimations of event times using these simple algorithms compare favourably with other techniques requiring specialised equipment. It is concluded that the proposed algorithms provide an easy and reliable method of determining event times during normal running at a subject selected pace using only kinematic data and can be implemented with any kinematic data-collection system.

Adult↗

PubMed1999

Asynchrony between subtalar and knee joint function during running.

PURPOSE: It has been suggested that during running proper coordination between subtalar joint pronation/supination and knee joint flexion/extension via tibial rotation is important to attenuate ground reaction impact forces (GRIF). Lack of coordination may produce over time a wide range of injuries. The goal of this study was to investigate the relationship between subtalar pronation/supination and knee flexion/extension with GRIF increases during distance running. METHODS: Eight subjects ran under different speeds (a self-selected pace, 10% faster, 10% slower, and 20% faster) and over different obstacle heights (5%, 10%, and 15% of their standing height) on their self-selected pace. Sagittal, rear-view kinematic, and GRIF data were collected. The biomechanical results were also compared with data from a clinical evaluation of the subjects. RESULTS: Speed changes and obstacle heights produced increases in GRIF and differences between rearfoot and knee angular velocities. The higher the obstacle and the faster the speed, the greater the GRIF and the greater the velocity differences. A change of the rearfoot angle curve from a unimodal (one minimum) to a bimodal (two minimums) parabolic configuration was also observed. The appearance of the second minimum was attributed to a lateral deviation of the tibia as a rebound effect due to the increased impact with the ground. The velocity differences between the actions of the subtalar and the knee joint, which in essence capture the antagonistic nature of their relationship, produced the highest correlation with the clinical evaluation. CONCLUSIONS: It was suggested that a possible mechanism responsible for various running injuries could be lack of coordination between subtalar and knee joint actions. This mechanism may have potential for predicting runners with susceptibility to injury.

Adult↗

PubMed1998

Effects of magnesium orotate on exercise tolerance in patients with coronary heart disease.

In a pilot study at 14 patients with coronary heart disease (CHD) and left-ventricular dysfunction (left ventricular enddiastolic volume [LVEDV] > or = 100 ml), who actively participated in an ambulatory cardiac sports group, left ventricular endsystolic volume (LVESV), LVEDV and duration of exercise were analyzed by echocardiographic and ergometric tests. An initial workup was followed by a 4 week double blind treatment phase, in which magnesium orotate 3 x 1 g or placebo was given additionally to medication taken prior to the study. At the end of this phase a concluding workup was performed. Magnesium orotate decreased significantly (p = 0.016) LVESV, increased significantly (p = 0.035) EF, decreased in tendency (p = 0.054) LVEDV and increased significantly (p = 0.011) exercise duration. The study gives references to favourable effects of oral magnesium orotate to left ventricular function and exercise tolerance in patients with CHD.

Coronary Disease↗