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Biomedical subjects

N Chapuis

Publications and source records attributed to N Chapuis.

10 recordsLinked to original sources
PubMed1993

Estimation of passive horizontal linear whole-body displacement in humans.

1. Passive linear self-motion estimation along the X and Y axes was investigated in human subjects. 2. A target was viewed from a distance of 0.8 or 2.4 m from the starting point. Subjects were then blindfolded and transported toward the target on a distance of 3.2 m and back to the start. Acceleration was constant: +/- 0.2 or +/- 1 m/s2. The subjects pushed a button on both outward and return paths, when they passed the previously seen target. 3. The results showed anticipation of the target on the outward path, and not on the return. This was identical for both axes and both accelerations. 4. The data are in accord with a model of double integration of the otolith signal, suggesting that linear path integration is a basic sensory mechanism.

Acceleration↗
PubMed1993

[Flexible choledochoscopy: two years experience].

This study is a retrospective review of 258 procedures on the gallbladder and bile ducts (115 without and 143 with flexible choledochoscope). There were 14 bile duct explorations for stone removal without choledochoscopy and 16 with a flexible choledochoscope. Residual stones were found in 2/14 (14.2%) cases without and 1/16 (6.3%) case with choledochoscope. A review of the literature confirms that there are fewer residual bile duct stones following flexible choledochoscopy. There were no complications attributable to the procedure.

Cholelithiasis↗
PubMed1993

[Simultaneous proximal and distal revascularization for arterial obstruction of the leg at two sites. Indications, techniques and results].

In chronic aortoiliac occlusive disease, 50 to 75% of the patients have further femoropopliteal lesions. The surgical treatment of these multilevel obstructions is sometimes controversial: the distal reconstruction can be performed at the time of the proximal one or deferred to a later date. It can be difficult to determine the hemodynamic importance of an iliac stenosis. Angiography is not a perfect predictor of the iliac segment hemodynamics because as it underestimates the severity of aorto-iliac stenoses when single plane views are taken. Direct measurement of the femoral pressure at angiography disclosing a gradient between brachial and femoral arteries indicates significant iliac stenosis. Intraarterial papaverine administration can also be of importance to determine critical stenoses. Despite proximal reconstruction, distal ischemia can persist if peripheral resistance is high. Distal revascularization can relieve ischemic symptoms, providing an adequate outflow bed. However some patients do not benefit from this two-level procedure because of a steal phenomenon in the intermediate vascular bed.

Aged↗
PubMed1993

[In situ venous grafts. Indications, technique and results. Prospective study of 26 consecutive cases].

The in situ saphenous vein bypass has been introduced in our department since 1989. A total of 26 bypasses in 22 patients have been followed prospectively. Indications for revascularisation have been severe arterial insufficiency in 73% of the cases (stage III or IV). With the exception of one postoperative death (myocardial infarction), all the patients have recovered uneventfully, with a regression to stage I. No amputation has been necessary. Morbidity has been 30%, with mainly minor local complications. The primary patency rate is 83% at one year and 78% after 2 and 3 years, whereas the secondary patency rate is 91% at one year, and remains constant thereafter up to 3 years. Considering our results and those from the literature, we believe that the in situ technique is very valuable, especially for below-knee vascular reconstruction. Technical difficulties of the method are analysed.

Adult↗
PubMed1992

Effect of post-training unilateral labyrinthectomy in a spatial orientation task by guinea pigs.

The effects of unilateral labyrinthectomy in guinea pigs have been studied on an angular orientation task consisting, in an open field, of running to a hidden goal oriented at 45 degrees with respect to the cephalocaudal axis of the animal placed in a starting-box. The task was conducted in light but in an homogeneous environment, i.e. without visual, auditory or olfactory cues indicating the location of the goal. A second group of animals was submitted to a similar task running to a hidden goal but the place of the goal was indicated by a colored card. All the animals were trained before the lesion and tested in their respective task for 1 month after the lesion. In the task conducted without conspicuous cues, animals were dramatically disturbed. In contrast, animals pretrained in the visually guided task were not impaired after the lesion. These results point out the important role of vestibular information in performing spatial tasks based on angular estimation, since, even if proprioceptive and visuokinesthetic information remain available, subjects seemed not able to maintain a correct angular trajectory. The trajectories being not disturbed in the visually guided task, one can exclude the hypothesis that such deficit was due to a purely motor disturbance.

Animals↗
PubMed1991

Spatial problem-solving in a wheel-shaped maze: quantitative and qualitative analyses of the behavioural changes following damage to the hippocampus in the rat.

The behaviour of sham-operated rats and rats with damage to the dorsal hippocampus was compared in a complex spatial problem-solving task using a 'hub-spoke-rim' wheel type maze. Compared to the classical Olton 8-arm radial maze and Morris water maze, this apparatus presents the animal with a series of possible alternative routes both direct and indirect to the goal (food). The task included 3 main stages: exploration, feeding and testing, as do the classic problem-solving tasks. During exploration, hippocampal rats were found to be more active than sham rats. Nevertheless, they displayed habituation and a relatively efficient circumnavigation, though, in both cases, different from those of sham rats. During test trials, hippocampal rats were characterized as being less accurate, making more errors than sham rats. Nevertheless, both groups increased their accuracy of first choices over trials. The qualitative analyses of test trial performance indicated that hippocampal rats were less accurate in terms of the initial error's deviation from the goal, and less efficient in terms of corrective behaviour than sham rats which used either the periphery or the spokes to attain economically the goal. Surprisingly, hippocampal rats were not limited to a taxon type orientation but learned to use the periphery, a tendency which developed over time. Seemingly, for sham rats, the problem-solving process took the form of updating information during transit. For hippocampal rats, the use of periphery reflected both an ability to discriminate its usefulness in reaching the goal via a taxis type behaviour, and some sparing of ability to generalize the closeness and the location of the goal. These results, especially the strategic correction patterns, are discussed in the light of Sutherland and Rudy's 'configurational association theory'.

Animals↗