Biomedical subjects
M Allard
Publications and source records attributed to M Allard.
Parkinsonism following anterior choroidal artery stroke.
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[Functional neuronavigation. Fusion of functional MRI data in a neuronavigation system].
Neuronavigation systems integrating functional magnetic resonance imaging data have been reported recently, but generally without many details about methodology. We propose an easy method to perform functional neuronavigation by integrating functional MRI data analyzed with the Statistical Parametric Mapping 99 reference software, in the Stealth Station which is the most common neuronavigation system. Users of this new and promising technique, which requires further validation, must be aware of its limitations. Functional MRI data seem to be the major source of imprecision. As a result we do not yet recommend the use of functional neuronavigation without the control of direct cortical stimulations.
[Computer-assisted surgery of the anterior cruciate ligament].
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[Supercentenarians: geography and epidemiology of longevity].
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Mobilization of the cell adhesion glycoprotein F3/contactin to axonal surfaces is activity dependent.
F3/contactin is a cell adhesion/recognition molecule of the immunoglobulin superfamily implicated in axonal growth. We examined its subcellular distribution and mobilization to the cell surface in oxytocin- (OT-) secreting neurons, which express it throughout life and the axons of which undergo activity-dependent remodelling. This was performed in hypothalamic organotypic slice cultures containing OT neurons with properties of adult neurosecretory cells. Immunocytochemistry and immunoblot analysis confirmed that OT neurons express high levels of F3/contactin in vitro. Light and confocal microscopy of cultures that underwent double immunofluorescence after fixation showed F3/contactin immunoreactivity throughout the cytoplasm of OT somata, dendrites and axons, and also in non-OT axons and in putative synaptic boutons which contacted OT neurons. By contrast, after treatment of live cultures with anti-F3/contactin antibodies followed by double immunofluorescence for the glycoprotein and OT, F3/contactin immunoreactivity was visible only on the surface of axons, whether or not OT-immunoreactivity was present. Because of its glycosylphosphatidyl-inositol (GPI) linkage, F3/contactin can occur in a membrane-bound or soluble form. As seen from immunocytochemistry of live cells and immunoblot analysis, treatment of cultures with a GPI-specific phospholipase C (GPI-PLC) resulted in loss of F3/contactin immunoreactivity from all cell surfaces. F3/contactin immunoreactivity reappeared on axonal surfaces within 5 h after enzyme washout. Such re-expression was accelerated by neuronal activity facilitation (by K+ depolarization or gamma-aminobutyric acid (GABA)-A receptor blockade with bicuculline) and inhibited by neuronal activity repression [by blockade of Ca2+ channels with Mn2+, Na+ channels with tetrodotoxin (TTX) or excitatory inputs with glutamate antagonists]. Our observations establish therefore that F3/contactin surface expression in hypothalamic neurons is polarized to the axons where it occurs mainly in a GPI-linked form. We also provide direct evidence that externalization of F3/contactin depends on Ca2+ entry and neuronal electrical activity. Taken together with our earlier finding that the glycoprotein is localized in neurosecretory granules, we demonstrate that F3/contactin is mobilized to the axonal surface via the activity-dependent regulated pathway, thus arriving at the correct place and time to intervene in activity-dependent remodelling of axons.
Extraoral removal of mandibular odontogenic dentigerous cysts: a report of 2 cases.
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Plasma fibronectin in French centenarians.
Plasma fibronectin was shown to increase with age, the difference between individuals (the SD of the mean) also increases with age. Fibronectin is highly sensitive to proteolytic degradation and several of the degradation products were shown to have noxious effects as proper proteolytic activity, activation of IL-1 and collagenase expression and also activation of fibronectin biosynthesis. It was therefore interesting to compare the plasma fibronectin values of centenarians in relatively good health with an elderly population in a geriatric hospital, somewhat younger (70-96 years) but with a variety of pathologies. A third population of men and women between 59 and 70 in good health (the EVA-epidemiological study) was also used for comparison. Plasma fibronectin was determined by a specific and highly sensitive Elisa assay. Fibronectin fragments were characterized by immunoblot. It could be shown that plasma fibronectin in centenarians had a lower distribution with lower average values than the geriatric population. Fibronectin fragments could be demonstrated in the plasma of a selection of geriatric patents but not in the plasma of centenarians. These results suggest a more moderate increase of plasma fibronectin in the relatively healthy centenarians as compared to a younger but pathological population. They also show that the plasma fibronectin of the investigated centenarians was better protected from proteolytic degradation than in the geriatric population. The above results also confirm the contention that epigenetic mechanisms such as an age-dependent increase of fibronectin synthesis and degradation and the potential noxious effects of degradation products may well play an important role in the age-dependent decline of physiological functions.
Influence of cognitive strategies on the pattern of cortical activation during mental subtraction. A functional imaging study in human subjects.
Functional magnetic resonance imaging (fMRI) at 1.5 T was used to investigate the influence of cognitive strategies on cortical activation during mental calculation. Twenty-nine right-handed subjects performed a serial subtraction of prime numbers. Even though a common corpus of brain areas was activated during this mental calculation, differences appeared between subjects in function of their spontaneous cognitive strategy. In subjects using a so called verbal strategy (n=15), the main activation was located in the whole left dorsolateral frontal cortex with a little activation of the inferior parietal cortex. In subjects using a so called visual strategy (n=14), a bilateral activation in the prefrontal cortex and a high activation in the left inferior parietal cortex were observed. These results demonstrate that numbers are processed through a distributed network of cortical areas, the lateralization of which is clearly influenced by subject strategy.
Outpatient CAPD catheter salvage for persistent exit-site/tunnel infection.
BACKGROUND: Partial replantation (i.e. replacement of the extraperitoneal portion of the catheter with creation of a new subcutaneous tunnel) has been suggested to avoid catheter removal in patients with persistent exit-site/tunnel infection (ESTI). However, published experience with this technique is limited. METHODS: Partial replantation was performed on an outpatient basis under local anesthesia for seven patients with persistent ESTI of >3 months duration. All patients resumed CAPD immediately following surgery. RESULTS: One patient had dialysate leakage less than 1 week after surgery that required catheter removal. The other patients had no complications and mean catheter survival following surgery was 7. 7 months (range 3.5-13 months). There was no recurrence of ESTI after surgery, although two patients presented with exit-site infection unrelated to the initial episode (i.e. different organism, long latency). Three other patients presented with episodes of peritonitis unrelated to surgery (i.e. delay >1 month) or ESTI (i.e. different organism). CONCLUSIONS: Partial replantation allows significant prolongation of catheter survival without major complications or interruption of CAPD. This novel procedure appears to be an appropriate alternative to catheter removal for the management of persistent ESTI. However, further studies are needed to prospectively compare partial replantation with catheter removal.
Role of the mode of sensory stimulation in presurgical brain mapping in which functional magnetic resonance imaging is used.
OBJECT: The aim of this study was to evaluate different types of sensory stimulation used to distinguish between microvasculature and venous drainage on functional magnetic resonance (fMR) images with blood oxygen level-dependent (BOLD) contrast. METHODS: Seven volunteers received three sensory stimulations. One consisted of small discontinuous automated pokes to the ventral aspect of the right thumbtip. The other two were delivered by the investigator, who vigorously brushed the ventral aspect of the right thumbtip either alone or in combination with the thenar region. Seven contiguous axial slices of the head were acquired using echoplanar fMR imaging during each mode of stimulation. Boxcar analysis and Student's t-test were performed. Cluster analysis was used to determine significant differences between rest and activation phases. The major findings were 1) that a discontinuous sensory stimulation involving a small skin area was able to evoke a limited activated area in the postcentral gyrus with a low activation index (AI [2%]); 2) that this limited activated area was included in the activated area elicited by the continuous sensory stimulations; and 3) that this also evoked multiple activated areas exhibiting AIs of either approximately 2% or greater than 5%. This indicated that the limited discontinuous tactile stimulation evoked a BOLD-contrast fMR image essentially of microvasculature, whereas the more extensive continuous stimulations evoked a BOLD-contrast fMR image in both microvasculature and venous drainage. CONCLUSIONS: Different sensory stimulations are necessary to differentiate primary sensory cortex from venous drainage for presurgical brain mapping.
Functional MR imaging analysis of pain-related brain activation after acute mechanical stimulation.
BACKGROUND AND PURPOSE: Most studies concerning imaging of pain processing have used thermal, chemical, or electrical nociceptive stimulation. The aim of the present study was to determine the cortical representation of mechanical pain. For this, using functional MR (fMR) imaging at 1.5 T, we compared activation patterns during painful and nonpainful tonic mechanical stimulation in healthy volunteers. METHODS: Eleven right-handed subjects ranging in age from 21 to 46 years underwent gradient-echo echo-planar fMR imaging while quantified tonic pressure was applied to the first metacarpophalangeal joint. Imaging parameters were 3,000/60 (TR/TE) with a 5-mm section thickness in a 7.30-minute sequence with 2 x 90 seconds of painful stimulation interleaved with 3 x 90 seconds of nonpainful stimulation. Functional images were processed using dedicated IDL software. RESULTS: Mechanical tonic nociceptive pressure was associated with activation of the primary somatosensory cortex contralateral to the hand stimulated and variable, often bilateral activation of the secondary somatosensory, temporal, anterior and posterior cingulate, insular, and prefrontal cortexes. Thalamic activation was inconsistent and always contralateral to stimulation. CONCLUSION: The interindividual variability found in this fMR imaging study calls for repetitive single-subject analysis or more extensive studies of large groups of patients. Either may be based on fMR imaging analysis of brain activation after tonic mechanically induced pain, which leads to deep pain sensation similar to patients' painful sensations most commonly encountered in clinical practice.
[Arthroscopic rotator cuff repair: a multicentric retrospective study of 87 cases with anatomical assessment].
PURPOSE OF THE STUDY: The aim of this study was to evaluate the anatomical and technical limits of endoscopic rotator cuff repair. Anatomical results were also compared with functional assessment of the shoulder. MATERIAL AND METHODS: A multicentric serie of 87 patients presenting a full thickness rotator cuff tear repaired endoscopically was retrospectively reviewed at 25.4 months (mean) post surgery. Limits of the surgical technique were studied in correlation with functional results and anatomic radiographic evaluation (arthroscans in 93 p. 100). RESULTS: Anatomical repair (normal thickness and no contrast in the subacromial space on arthroscan) was achieved in 83 p. 100 of the rotator cuffs with limited damage to the frontal part of the supra spinatus tendon. This percentage fell to 57.8 p. 100 in case of posterior extension of the tear to the supra spinatus tendon and further dropped to 40.8 p. 100 in case of retraction to the apex of the humeral head. Functional outcome evaluated with the Constant score was strongly related to the radiographic cuff condition (p <0.05). For distal and anterior tears of the supra spinatus tendon, the Constant score at revision was 89.8 points in cases with anatomic repair at revision. This score fell to 75 when the rotator cuff tear was evidenced radiographically (p <0.0001). For tears involving the entire supra spinatus tendon repaired by arthroscopy, the functional difference at revision was 8 points on the Constant scale. Objective and subjective analysis of the surgical procedure identified significant peroperative elements predictive of clinical and anatomical outcome (difficult reduction, p <0.05; subjective degree of solidity, p <0.0001; anatomical aspect of the repaired cuff, p <0.05). DISCUSSION: A comparison of our findings with data on equivalent lesions reported in the literature suggests that endoscopic surgery for rotator cuff tears offers both functional and anatomic results equivalent to those achieved with conventional open surgery. This assumes that the surgical procedure is carried out by surgeons experienced in shoulder arthroscopy who can precisely gauge the posterior/anterior extension of the tears and the limits of the surgical technique.
A functional magnetic resonance imaging study of mental subtraction in human subjects.
The neuronal network involved in a precise type of calculation procedure, mental subtraction, was investigated by means of functional magnetic resonance imaging. Two tasks were used requiring covert production of numbers: (1) with calculation; (2) without calculation. During the first task, activation was observed in the left dorsolateral prefrontal and premotor cortices, in Broca's area and bilaterally in the inferior parietal cortex. During the second task, activation was mainly observed in Broca's area and to a less extent in the left prefrontal and premotor cortices. Statistical comparison of data in the two situations revealed that the procedure of mental subtraction is mediated by a distributed system which includes predominantly the left dorsolateral prefrontal cortex and the inferior parietal cortex bilaterally.
Unilateral joint inflammation induces bilateral and time-dependent changes in neuropeptide FF binding in the superficial dorsal horn of the rat spinal cord: implication of supraspinal descending systems.
Using quantitative autoradiography, the effects of acute and chronic inflammation on specific 125I-1DMethyl-FLFQPQRFamide binding were investigated in the rat spinal cord dorsal horn superficial layers, at 6 and 24 h and 2, 4, 6 and 12 weeks after induction of monoarthritis produced by injection of killed Mycobacterium butyricum suspended in Freund adjuvant in one tibio-tarsal joint. Six hours after monoarthritis induction, no modification in specific 125I-1DMethyl-FLFQPQRFamide binding was observed, whereas a significant bilateral increase occurred after 24 h and 2 weeks in L4/L5 dorsal horns, with a return to control values at 4, 6 and 12 weeks. Specific 125I-1DMethyl-FLFQPQRFamide binding was also investigated 24 h after monoarthritis induction in rats submitted 4 days before the induction to spinal cord lesions at the thoracic level (T9-T10). Hemisection of the spinal cord contralateral to the affected ankle prevented the transient bilateral increase in specific 125I-1DMethyl-FLFQPQRFamide binding, whereas total spinal cord section induced a significant bilateral decrease. All of these modifications were restricted to the spinal segments receiving afferent input from the arthritic ankle (L4/L5); no modifications were found at the levels L1 or C6-C8. These data suggest that FLFQPQRFamide is involved in spinal nociceptive processing during sustained peripheral nociceptor activation. The effects of spinal cord lesions in monoarthritic rats indicate that the modifications seen in the FLFQPQRFamide system activity, during sustained peripheral inflammation, depend on afferent fiber activation as well as on supraspinal controls.
Evidence for neuropeptide FF (FLFQRFamide) in rat dorsal root ganglia.
By using specific antibodies and radioimmunological and immunohistochemical methods, we here show that neuropeptide FF (NPFF) occurs in cervical and lumbar dorsal root ganglia cells. Levels in the ganglia were low because they were detectable only after colchicine treatment or after unilateral dorsal rhizotomy. Similar high-performance liquid chromatography profiles were obtained from dorsal root ganglia and spinal cord extracts, indicating that the NPFF-immunoreactivity in the dorsal root ganglia represented similar molecular forms to that in the spinal cord. Immunocytochemistry localized NPFF-immunoreactivity in small- and medium-sized cells. These data suggest that low levels of NPFF present in fine diameter primary afferent fibers could be involved in the treatment of nociceptive information from fore- or hindlimb.
[Influence of individual strategies on brain activation patterns during cognitive tasks].
Functional magnetic resonance imaging (fMRI) at 1.5 T was used to investigate the influence of cognitive strategies on cortical activation during mental calculation. Twenty-nine right-handed subjects performed a serial subtraction of prime numbers. Data were analyzed taking into account whether the spontaneous strategy of subjects was verbal (n = 15) or visual (n = 14). Even thought a common corpus of brain areas was activated during this mental calculation task, i.e. the dorsolateral prefrontal, premotor and parietal cortices, and Broca's area, differences appeared between the two groups of subjects. In subjects using a verbal strategy, the main activation was located in the whole left dorsolateral frontal cortex with a little activation of the inferior parietal cortices. In subjects using a visual strategy, a bilateral activation in the prefrontal cortex and a high activation in the left inferior parietal cortex were observed. These results demonstrate that numbers are processed through a distributed network of cortical areas, the lateralization of which is clearly influenced by subject strategy. Taken together this data reveals a functional interaction between the left inferior parietal cortex and the right prefrontal cortex in the visuo-spatial sketchpad for number processing. This network could be involved in sustained selective attention to mental numerical images generated in the left inferior parietal cortex.