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Biomedical subjects

M Allard

Publications and source records attributed to M Allard.

At least 19 recordsLinked to original sources
PubMed2000

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.

Journal Article↗
PubMed2000

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.

Adult↗
PubMed2000

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.

Aged↗
PubMed2000

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.

Adult↗
PubMed2000

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.

Adult↗
PubMed2000

[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.

Adult↗
PubMed1999

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.

Adult↗
PubMed1999

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.

Animals↗
PubMed1999

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.

Animals↗
PubMed1999

[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.

Adult↗
PubMed1999

[Treatment of chronic ankle instability with the Chrisman-Snook's technique].

PURPOSE OF THE STUDY: We report our experience on lateral ankle instability treated by the Chrisman Snook procedure. We studied the objective and subjective results as well as the effect on peroneus brevis tendon function. MATERIAL AND METHODS: Among 110 patients treated for chronic lateral ankle instability between 1991 and 1997, 32 cases were treated with this technique. The average age was 25 years (16-37) and the average time to surgery from the initial trauma was 30 months. This was a retrospective study using the Karlson Peterson form while the laxity was measured with Telos device (120 N). Cybex testing was performed on 10 patients. Twenty-seven patients participated in sport. RESULTS: The follow-up ranged from 6 to 65 months (average 25 months). The average Karlson's score was 82.6 with 78 per cent excellent and good results. Lateral ligament laxity was reduced from 17 mm to 4 mm on Telos measurements and no osteoarthritis was noticed radiographically. The joint mobility consistently returned to the preoperative level. Twenty four patients returned to sport although half of the patients had some pain during sport activities or with fast walking. DISCUSSION: Males and patients participating in sporting activities had the best results and none of the patients had recurrent instability despite new sport injuries. The persistence of some pain may be associated with the long period of instability prior to reconstruction in this group of patients. CONCLUSION: The Chrisman Snook lateral ligament reconstruction is a technically easy and solid technique and we recommend it in patients with significant chronic lateral ligament instability.

Adolescent↗
PubMed1998

Evidence for a hypothalamic oxytocin-sensitive pattern-generating network governing oxytocin neurons in vitro.

During lactation and parturition, magnocellular oxytocin (OT) neurons display a characteristic bursting electrical activity responsible for pulsatile OT release. We investigated this activity using hypothalamic organotypic slice cultures enriched in magnocellular OT neurons. As shown here, the neurons are functional and actively secrete amidated OT into the cultures. Intracellular recordings were made from 23 spontaneously bursting and 28 slow irregular neurons, all identified as oxytocinergic with biocytin and immunocytochemistry. The bursting electrical activity was similar to that described in vivo and was characterized by bursts of action potentials (20.1 +/- 4.3 Hz) lasting approximately 6 sec, over an irregular background activity. OT (0.1-1 microM), added to the medium, increased burst frequency, reducing interburst intervals by 70%. The peptide also triggered bursting in 27% of nonbursting neurons. These effects were mimicked by the oxytocin receptor (OTR) agonist [Thr4, Gly7]-OT and inhibited by the OTR antagonist desGly-NH2d(CH2)5[D-Tyr2,Thr4]OVT. Burst rhythmicity was independent of membrane potential. Hyperpolarization of the cells unmasked volleys of afferent EPSPs underlying the bursts, which were blocked by CNQX, an AMPA/kainate receptor antagonist. Our results reveal that OT neurons are part of a hypothalamic rhythmic network in which a glutamatergic input governs burst generation. OT neurons, in turn, exert a positive feedback on their afferent drive through the release of OT.

Animals↗
PubMed1998

Regulated expression of the cell adhesion glycoprotein F3 in adult hypothalamic magnocellular neurons.

F3, a glycoprotein of the immunoglobulin superfamily implicated in axonal growth, occurs in oxytocin (OT)-secreting and vasopressin (AVP)-secreting neurons of the adult hypothalamo-neurohypophysial system (HNS) whose axons undergo morphological changes in response to stimulation. Immunocytochemistry and immunoblot analysis showed that during basal conditions of HNS secretion, there are higher levels of this glycosylphosphatidyl inositol-anchored protein in the neurohypophysis, where their axons terminate, than in the hypothalamic nuclei containing their somata. Physiological stimulation (lactation, osmotic challenge) reversed this pattern and resulted in upregulation of F3 expression, paralleling that of OT and AVP under these conditions. In situ hybridization revealed that F3 expression in the hypothalamus is restricted to its magnocellular neurons and demonstrated a more than threefold increase in F3 mRNA levels in response to stimulation. Confocal and electron microscopy localized F3 in secretory granules in all neuronal compartments, a localization confirmed by detection of F3 immunoreactivity in granule-enriched fractions obtained by sucrose density gradient fractionation of rat neurohypophyses. F3 was not visible on any cell surface in the magnocellular nuclei. In contrast, in the neurohypophysis, it was present not only in secretory granules but also on the surface of axon terminals and glia and in extracellular spaces. Taken together, our observations reveal that the cell adhesion glycoprotein F3 is colocalized with neurohypophysial peptides in secretory granules. It follows, therefore, the regulated pathway of secretion in HNS neurons to be released by exocytosis at their axon terminals in the neurohypophysis, where it may intervene in activity-dependent structural axonal plasticity.

Animals↗
PubMed1998

Periganglionic foraminal steroid injections performed under CT control.

PURPOSE: The purpose of our study was to evaluate the efficacy of direct intraforaminal steroid injections into the periganglionic space in the treatment of radicular pain. METHODS: Periganglionic infiltrations were performed in 41 patients with acute or chronic radicular pain. Neuroradiologic imaging in all patients showed foraminal stenosis due to degenerative disorders or herniated disk. All injections were performed under CT control. RESULTS: Seventy percent of patients had significant pain reduction, with the greatest success (90% of patients) in those whose foraminal stenosis was due to degenerative disorders; 45% of patients with foraminal herniated disks had pain relief. CONCLUSION: Intraforaminal steroid injection is useful in the treatment of radicular pain, particularly in cases of foraminal degenerative stenosis.

Adult↗
PubMed1997

Expression of high levels of the extracellular matrix glycoprotein, tenascin-C, in the normal adult hypothalamoneurohypophysial system.

Glia and neurons of the hypothalamoneurohypophysial system (HNS) undergo reversible morphological changes, which are concomitant with the remodelling of afferents onto the neurons, under different conditions of neurohormone secretion. Here, we show that the adult rat HNS contains high levels of tenascin-C (TN-C), which is an extracellular matrix glycoprotein whose expression is usually associated with neuronal-glial interactions in the developing and lesioned central nervous system (CNS). By using light and electron microscopic immunocytochemical procedures, we visualized TN-C immunoreactivity in the hypothalamic supraoptic (SON) and paraventricular nuclei, where somata of the neurons are localized; in the median eminence, where their axons transit; and in the neurohypophysis, where they terminate. Hypothalamic areas adjacent to the magnocellular nuclei were devoid of immunoreactivity. Electron microscopy of the neurohypophysis showed immunolabelling of perivascular spaces, glial (pituicyte) and axonal surfaces, a type of labelling that also characterized the median eminence. In the hypothalamic nuclei, there was labelling of extracellular spaces and astrocytic surfaces. In normal animals, we detected no cytoplasmic reaction in glia somata, neurons, or endothelial cells. However, in animals treated with the intracellular transport blocker colchicine, there was intracytoplasmic labelling of all HNS glial cells, indicating a glial source for TN-C. Immunoblot analysis revealed TN-C isoforms of apparent high molecular weight (225, 240, and 260 kD) in the SON and median eminence, whereas lower MW forms (190/200 kD) predominated in the neurohypophysis. By using immunocytochemistry and immunoblot analysis, we found no visible differences in TN-C expression in relation to age, sex, or differing neurohypophysial secretion, which suggests that the expression of TN-C is a permanent feature of the HNS.

Animals↗
PubMed1996

Cardiovascular effects induced by the stimulation of neuropeptide FF receptors in the dorsal vagal complex: an autoradiographic and pharmacological study in the rat.

Previous studies have suggested that central administration of neuropeptide FF-related peptides may modulate cardiovascular parameters in the rat. In the present study, we investigated the role of dorsal vagal complex neuropeptide FF receptors in the central regulation of cardiovascular parameters. The fate of neuropeptide FF receptors in normal and nodose ganglionectomized rats was investigated using an autoradiographic approach with 125I-[DTyr1, (NMe)Phe3]NPFF as ligand for these receptors. We showed that neuropeptide FF binding sites are preferentially located postsynaptically with respect to the vagal afferent fibers in the nucleus tractus solitarius. Thus, ganglionectomy reduced by only 30% and 17% the density of peptide binding sites in the rostral and caudal regions of this nucleus, respectively. Bilateral microinjection of neuropeptide FF (1 nmol) into the commissural nucleus tractus solitarius produced an increase in blood pressure (+13.8 +/- 0.8 mmHg, n = 6), bradycardia (-29.0 +/- 3.2 bpm) and a significant inhibition (-47.6 +/- 3.1%) of the cardiac component of the baroreceptor reflex. Further studies with doses below 1 nmol indicate that NTS microinjections of the neuropeptide produced a dose-dependent decrease in heart rate. Similar cardiovascular effects were observed after bilateral NTS microinjections of one analog neuropeptide FF receptor agonist, [DTyr1, (NMe)Phe3]NPFF (1 nmol). Pretreatment with prazosin (100 micrograms/kg), an alpha 1-adrenoreceptor antagonist, inhibited the neuropeptide FF-evoked blood pressure effect. In addition, the neuropeptide FF-induced heart rate decrease was abolished by pretreatment with atropine (30 micrograms/kg), a muscarinic receptor antagonist. Taken together, these anatomical and pharmacological data suggest that neuropeptide FF receptors within the nucleus tractus solitarius, preferentially located on the postsynaptic component, are involved in the central reflex regulation of cardiovascular parameters.

Animals↗