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P Mercier

Publications and source records attributed to P Mercier.

At least 37 records · Page 2Linked to original sources
PubMed2001

Ideal intraspinal implantation site for the repair of ventral root avulsion after brachial plexus injury in humans. A preliminary anatomical study.

The advances made to date in root reimplantation for avulsion of the brachial plexus are modest considering that there are only reports from ten patients in the literature. However, the results are promising and should be applauded. The problem with reimplantation, in addition to the difficult surgical exposure, is to determine the ideal intraspinal implantation site for the graft. Given the non-permissive substrate properties of the CNS white matter, the outcome of grafts elsewhere in the spinal cord need to be evaluated. An inappropriate implantation site might explain the still modest recovery in this challenging group of patients. Consequently the microscopic anatomy of the cervical spinal cord segments C5 to T1 was studied. The aims were to 1--determine the relationships between the ventral gray horn and the ventrolateral sulcus of the spinal cord, and 2--analyse the location and course of the motoneuron fibres passing through the white matter to reach the ventral root. On the basis of the present findings it is proposed that reimplantation of nerve grafts or rootlets should be performed directly through the ventral root exit zone in contact with the ventromedial region of the ventral gray horn at a depth of 2 mm, rather than into the white matter of the lateral aspect of the cord. Initially we used a posterior approach with total facetectomies. An anterior approach is now evaluated for current use.

Brachial Plexus↗
PubMed2001

Surgical anatomy of the infratemporal fossa using the transmaxillary approach.

In this study we evaluated the ability of the transmaxillary route to expose the elements of the infratemporal fossa (ITF). Five adult cadaver heads were dissected on both sides, after making a paralateronasal incision. The maxillary branch of the trigeminal nerve served as a superior landmark to progress into the retroantral space and pterygopalatine fossa. The maxillary artery, lateral pterygoid muscle, pterygoid venous plexus, foramen rotundum and foramen ovale were identified. Distances between those elements and angle of approaches of the foramen ovale and foramen rotundum were measured in the horizontal plane. In all cases, the anterior loop of the maxillary artery and the sphenopalatine artery were located in the proximal retroantral fatty space and could be ligated without optic magnification. The maxillary nerve could be followed up to the foramen rotundum at a 44 mm mean distance from the opening. The mean angle of vision to the foramen rotundum was 31 degrees. Under the greater sphenoid wing and lateral to the pterygoid process, desinsertion and partial resection of the lateral pterygoid muscle were required to identify the pterygoid venous plexus and foramen ovale. The pterygoid venous plexus was organized as a compact network of channels between and superior to the muscle fibers; it was in close relation with the foramen ovale. Access to the foramen ovale was deep (mean 56 mm) and narrow (20 degrees). Our results indicate that the transmaxillary approach is a minimally invasive procedure that gives an appropriate window to the structures of the retroantral space and to the pterygomaxillary fissure and pterygopalatine fossa. Monitoring of the retropterygoid portion of the infratemporal fossa by this route is inadequate.

Adult↗
PubMed2001

Double hepatomesenteric artery: a rare anatomical variant.

A case of a "double hepatomesenteric artery", i.e. two persisting hepatic arteries arising from the superior mesenteric artery, is reported. Also observed was a lack of systematisation of the pancreaticoduodenal arteries. The variant, which does not appear to have been previously reported in the literature, was observed when dissecting the vessels of the duodenal bulb in a preserved male cadaver injected with neoprene latex. Its embryological origin, as well as the clinical, radiological (diagnostic or interventional) and surgical implications, are discussed.

Cadaver↗
PubMed2001

Pseudotumoral demyelination: a diagnosis pitfall (report of three cases).

Rare forms of demyelinating disease such as Balò's concentric sclerosis or Schilder's disease may simulate brain tumors, both clinically and on the computed tomography (CT) and magnetic resonance imaging (MRI). Even the histopathological diagnosis after a biopsy is not entirely reliable. We report three cases of pseudotumoral demyelinating disorders having required a stereotaxic biopsy, one of which was erroneously diagnosed as a malignant astrocytoma. We describe MRI especially the intense contrast enhancement with ill-defined margins, and the mild mass effect. We then detail the histopathological processes upon which differential diagnosis with a tumor can be based.

Adult↗
PubMed2001

DRB1 alleles in polymyalgia rheumatica and rheumatoid arthritis in southern France.

To investigate the association of HLA-DRB1 alleles with polymyalgia rheumatica (PMR) and rheumatoid arthritis (RA), 55 patients with PMR without giant cell arteritis, 203 patients with RA and 230 controls, all from the European population of Marseille, were HLA-DRB1 genotyped by PCR-SSO. HLA-DRB1*01 was significantly increased in both the PMR and RA groups compared to controls (35% versus 17%, P(c) < 0.05, and 41% versus 17%, P(c) < 0.001, respectively). HLA-DRB1*04 was significantly increased in the RA group compared to controls (48% versus 23%, P(c) < 0.001) but not in the PMR group. HLA-DRB1*04 subtype frequencies were significantly different between PMR patients and RA patients. Shared epitope-positive HLA-DRB1*04 alleles (DRB1*0401, 0404, 0405, 0408) were significantly overrepresented in RA patients compared to PMR patients and shared epitope-negative HLA-DRB1*04 alleles were overrepresented in PMR patients compared to RA patients. In conclusion, in the Mediterranean population studied, HLA-DRB1*01 is associated with RA and PMR whereas HLA-DRB1*04 is associated with RA only.

Aged↗
PubMed2001

The origin of the azygos venous system, as deduced from an anatomical and radiological study employing a corrosion technique.

The aim of this study is not only to describe the origin of the human azygos venous system by performing a 3-D reconstruction of a CT scan but also to evaluate the value of the techniques employed in investigating the topographical anatomy of a venous system in the body. Following perfusion with saline to wash away the blood, we injected an ALTUFIX/MINIUM mixture into the azygos vein of a cadaver. The head and trunk were subsequently corroded with hydrochloric acid (HCl). A CT scan of the trunk was obtained both before and after corrosion. According to the spatial resolution of the CT scan, the thinnest identifiable detail was measurable as 0.5 mm. The vertebral lumbar venous system was described, specifying the nomenclature of the lumbar veins (the lumbar veins being designated according to the vertebral body along which they run). On the right side, the lumbar veins at L2 and at L3 formed the lateral root of the azygos vein. On the left side, the vein at L2 formed the reno-azygo-lumbar arch (of Lejars). The lumbar veins, and the origin of the azygos system, were described and compared with previous studies. The 3-D reconstruction showed the importance of veins associated with the posterior paravertebral muscles. This description poses the problem of the metamerisation of the veins, but further evidence is required. Comparisons of the CT scans, 3-D reconstructions, and the ALTUFIX models of the veins obtained from the corrosion technique allowed verification of the 3-D reconstruction and correction of the errors inherent in a computer reconstruction. It is concluded that the description, and understanding, of such a complex system as the vertebral venous system is more valid when the results obtained using different techniques are compared.

Aged↗
PubMed2001

Influence of centrality and distinctiveness of actions on script sorting and ordering in patients with frontal lobe lesions.

In order to further investigate script knowledge in patients with frontal lobe lesions (FP), 30 participants with frontal brain damage, 14 controls with posterior brain damage (PC) and 30 normal controls (NC) were asked to sort script actions with various degrees of centrality and distinctiveness according to the script to which they belonged and their order of execution. Actions were given in 3 conditions: scripts with headers (SH), scripts without headers (SwH) and scripts with distractor header (SDH). Results confirmed the dual dissociation we observed in a previous study (Allain, Le Gall, Etcharry-Bouyx, Aubin, & Emile, 1999). Twelve FP made numerous errors in sequencing actions regardless of the conditions, but rejected the irrelevant title. Fourteen FP made few sequencing errors but used the irrelevant title. The last 4 FP performed as well as the PC and NC in every condition. Sorting errors made by the FP mainly concerned actions with low levels of centrality and distinctiveness. These data are consistent with the view that frontal lobe lesions selectively impair the syntactic component of script representation without affecting its semantic component.

Adult↗
PubMed2001

Anatomic relations between the cephalic vein and the sensory branches of the radial nerve: How can nerve lesions during vein puncture be prevented?

UNLABELLED: The cephalic vein of the forearm is often used for IV catheters because of its ease of access for peripheral venous cannulation. But its close relation to the sensory branch of the radial nerve sometimes causes it to be damaged when the vein is cannulated. Our anatomic study conducted on 33 specimens confirmed the risk of nerve lesion. However, it is impossible to define a safe zone, because of the randomly located nerve and vein crossing zones, where the iatrogenic risk of damaging the radial nerve is maximum. We suggest that to avoid incidents, the cephalic vein should be punctured above the emergence of the sensory branch of the radial nerve, e.g., at least 12 cm above the level of the styloid process of the radius. IMPLICATIONS: We attempted to determine the relationship between the cephalic vein and the sensory branch of the radial nerve at the wrist to help prevent lesions of the radial nerve when the cephalic vein is cannulated. We examined the anatomy of 33 postmortem specimens and suggest that puncture of the cephalic vein 12 cm or more proximal to the styloid process can prevent radial nerve lesions.

Catheterization↗
PubMed2001

c-myc Internal ribosome entry site activity is developmentally controlled and subjected to a strong translational repression in adult transgenic mice.

The expression of c-myc proto-oncogene, a key regulator of cell proliferation and apoptosis, is controlled at different transcriptional and posttranscriptional levels. In particular, the c-myc mRNA contains an internal ribosome entry site (IRES) able to promote translation initiation independently from the classical cap-dependent mechanism. We analyzed the variations of c-myc IRES activity ex vivo in different proliferating cell types, and in vivo in transgenic mice expressing a bicistronic dual luciferase construct. c-myc IRES efficiency was compared to that of encephalomyocarditis virus (EMCV) IRES under the same conditions. The c-myc IRES was active but with variable efficiency in all transiently transfected cell types; it was also active in the 11-day- old (E11) embryo and in some tissues of the E16 embryo. Strikingly, its activity was undetected or very low in all adult organs tested. In contrast, EMCV IRES was very active in most cell types ex vivo, as well as in embryonic and adult tissues. These data suggest a crucial role of IRES in the control of c-myc gene expression throughout development, either during embryogenesis where its activity might participate in cell proliferation or later on, where its silencing could contribute to the downregulation of c-myc expression, whose deregulation leads to tumor formation.

3T3 Cells↗
PubMed2001

Lateral interscalenic multilevel oblique corpectomies to repair ventral root avulsions after brachial plexus injury in humans: anatomical study and first clinical experience.

OBJECT: Because central nervous system white matter exerts a powerful inhibitory effect on axonal growth, implantation of nerve grafts or rootlets into the cervical spinal cord following ventral root avulsion injury should, ideally, be performed directly through the ventral root exit zone (VRExZ), which is located near the anteromedial aspect of the anterior horn; the grafts/rootlets should not be implanted into the white matter of the lateral cord. This is not possible when using a conservative posterior approach. Therefore, the authors have studied the anatomy encountered when using the anterolateral approach and evaluated the technique in the particular case of avulsed ventral nerve roots. They also present a case illustration of the procedure, which is used currently in their department. METHODS: Anterior access to the rootlets is obtained using a lateral interscalenic approach; the vertebral artery is exposed and mobilized, and oblique drilling of the vertebral bodies (VBs) is performed. Because the articular processes and half of the VBs are preserved, fusion is not required. The approach allows the surgeon to expose the anterior aspect of the cervical dura and the entire length of the emerging spinal nerves. The anterior aspect of the dura is opened at the desired levels for VRExZ exposure. and the position is ideal for implantation of the graft/rootlets. The interscalenic dissection is mandatory so that the lesions of the supraclavicular plexus can be evaluated and repaired. If necessary, the anterior approach allows for exploration of the infraclavicular plexus during the same procedure. CONCLUSIONS: The use of a true anterior approach to the ventral rootlets appears to be a valuable and appropriate approach that avoids extensive laminectomy/facetectomy while reimplantation is performed through the anterolateral sulcus itself. In this approach, however, reimplantation of dorsal roots into the spinal cord remains impossible.

Adult↗
PubMed2001

[Dermal sinus and dermoid cyst revealed by abscess formation in posterior fossa. Report of 2 pediatric cases and review of the litterature].

Cranial dermal sinus, usually associated with dermoid cyst, is the persistance of an abnormal embryonal communication between the skin and the central nervous system. It may be the source of intracranial infection, most often a meningitis and rarely an abscess formation. Two cases of little girls (18 months and 2 years) having dermal sinus with dermoid cyst revealed by cerebellar abscess formations are reported. In the first case there were multiple cerebellar abscesses with hydrocephalus leading to a raised intracranial pressure. In the second case there was an abscess formation adjacent to the dermoid cyst. CT scan showed cysts and abscesses but MRI, achieved in the second case, was useful in demonstrating the sinus tract as well as the associated cyst and abscess. The two patients underwent a posterior fossa surgery with antibiotic therapy. In the first case abscess drainage and ventricular external drainage were necessary before sinus and cyst excision. Two months after surgery the two patients were neurologically intact and developping well. Surgery with total excision of dermal sinus and dermoid cyst, even sometimes difficult, must be preferred to the simple abscess drainage and antibiotic therapy.

Abscess↗
PubMed2001

[A case of intramedullary primary melanocytic tumor: meningeal melanocytoma or malignant melanoma?].

We report a case of an intramedullary thoracic primary melanocytic tumor of the leptomeninges in a 38-year-old woman. According to the WHO classification, the lesion showed the histological features of a meningeal melanocytoma. Two local recurrences were successively operated on, two and three years after the first surgery respectively. The patient died of a subarachnoidian dissemination after a four year course. This case emphasized the therapeutic problems we have to deal with when facing an isolated black tumor of the central nervous system. The features and the differential diagnosis of the meningeal melanocytoma are detailed.

Adult↗
PubMed2000

Fibroblast growth factor 2 internal ribosome entry site (IRES) activity ex vivo and in transgenic mice reveals a stringent tissue-specific regulation.

Fibroblast growth factor 2 (FGF-2) is a powerful mitogen involved in proliferation, differentiation, and survival of various cells including neurons. FGF-2 expression is translationally regulated; in particular, the FGF-2 mRNA contains an internal ribosome entry site (IRES) allowing cap-independent translation. Here, we have analyzed FGF-2 IRES tissue specificity ex vivo and in vivo by using a dual luciferase bicistronic vector. This IRES was active in most transiently transfected human and nonhuman cell types, with a higher activity in p53 -/- osteosarcoma and neuroblastoma cell lines. Transgenic mice were generated using bicistronic transgenes with FGF-2 IRES or encephalomyocarditis virus (EMCV) IRES. Measurements of luciferase activity revealed high FGF-2 IRES activity in 11-d-old embryos (E11) but not in the placenta; activity was high in the heart and brain of E16. FGF-2 IRES activity was low in most organs of the adult, but exceptionally high in the brain. Such spatiotemporal variations were not observed with the EMCV IRES. These data, demonstrating the strong tissue specificity of a mammalian IRES in vivo, suggest a pivotal role of translational IRES- dependent activation of FGF-2 expression during embryogenesis and in adult brain. FGF-2 IRES could constitute, thus, a powerful tool for gene transfer in the central nervous system.

Animals↗
PubMed2000

Role of the structural domain of troponin C in muscle regulation: NMR studies of Ca2+ binding and subsequent interactions with regions 1-40 and 96-115 of troponin I.

The interaction between the calcium binding and inhibitory components of troponin is central to the regulation of muscle contraction. In this work, two-dimensional heteronuclear single-quantum coherence nuclear magnetic resonance (2D-¿1H,15N¿-HSQC NMR) spectroscopy was used to determine the stoichiometry, affinity, and mechanisms for binding of Ca2+ and two synthetic TnI peptides [TnI1-40 (or Rp40) and TnI96-115] to the isolated C-domain of skeletal troponin C (CTnC). The Ca2+ titration revealed that 2 equiv of Ca2+ binds to sites III and IV of CTnC with strong positive cooperativity and high affinity [dissociation constant (KD) </= 0.1 microM]. In this process, CTnC folds from a largely unstructured state to a compact domain capable of interacting with TnI. Titration of CTnC x 2Ca2+ with Rp40 occurs with a 1:1 stoichiometry and a KD of 2 +/- 1 microM. Titration of CTnC x 2Ca2+ with a peptide corresponding to the inhibitory region of TnI (TnI96-115) also reveals a 1:1 ratio, but weaker affinity (KD = 47 +/- 7 microM). Both Rp40- and TnI96-115-induced backbone amide chemical shift changes of CTnC x 2Ca2+ are similarly distributed along the sequence, indicating that these two regions of TnI may compete for the same binding site on CTnC x 2Ca2+. The changes induced by Rp40 are much larger, however, and define the interaction sites on TnC and regions where the flexibility of hinge and terminal residues is altered. To investigate the possibility of direct competition, TnI(96-115) was titrated into the CTnC x 2Ca(2+) x Rp40 complex, whereas Rp40 was titrated into the CTnC x 2Ca2+. TnI96-115 complex. The results show that Rp40 can displace TnI96-115 completely, while TnI96-115 has no effect on CTnC x 2Ca2+ x Rp40. Recent proposals for the mechanism of muscle regulation [Tripet, B. P., Van Eyk, J. E., and Hodges, R. S. (1997) J. Mol. Biol. 271, 728-750] suggest that the N-terminal and inhibitory regions of TnI competitively bind the structural domain of TnC. The findings presented here indicate that additional factors, such as interactions between the N-domain of TnC with the C-domain of TnI or the C-domain of TnT, are required, if the inhibitory region is going to successfully compete for the structural domain of TnC.

Amino Acid Sequence↗
PubMed2000

Modeling the HLA component in rheumatoid arthritis: sensitivity to DRB1 allele frequencies.

Rheumatoid arthritis is an inflammatory disease for which positive associations have been described with some HLA-DRB1 alleles. The associated alleles share a similar amino acid sequence in the third hypervariable region, the shared epitope, but differ at position 71 and 86. It has been suggested that HLA susceptibility to rheumatoid arthritis could be due not only to the shared epitope but could also be influenced by specific amino acids at positions 71 and 86. In this study, we investigated the role of these amino acids in rheumatoid arthritis on 203 unrelated patients. An involvement of amino acid 71 was detected but no conclusion was possible regarding amino acid 86. A study of the sensitivity of the conclusions to marker allele frequencies was performed. We showed that the results obtained for amino acid 71 are not very sensitive to allele frequencies but those obtained at position 86 are highly sensitive. This emphasizes the importance of studying the robustness of results to variations in allele frequencies before conclusions are drawn.

Amino Acid Sequence↗
PubMed2000

A limited anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for ventral brainstem tumor removal.

BACKGROUND: The present study describes the use of a limited subtemporal extradural anterior petrosectomy with preoperative embolization of the inferior petrosal sinus for the management of tumors located behind the clivus and ventral to the brainstem. Details of the procedure and its application in five cases are presented. METHODS: This procedure consists of using the extradural route to approach the upper side of the petrosal pyramid so that it can be drilled medially, and to resect the apex to come out into the posterior fossa. This route gives a petrosectomy just medial to the horizontal segment of the petrous carotid artery in front of the cochlea. It goes around the labyrinthine mass and the internal auditory canal from above to expose the posterior fossa dura between the two petrosal sinuses. The dural opening exposes the ventral aspect of the pons from the trigeminal nerve to the origin of the abducens nerve, ventral to the facial nerve. Preoperative embolization of the inferior petrosal sinus allows its intraoperative section for a wider exposure along the lower clivus. This approach can easily be combined with an intradural approach to provide additional exposure above the trigeminal nerve. Patients who underwent this procedure had prepontine cisternal chordoma or epidermoid cyst of the petroclival region. RESULTS: One patient experienced a cranial nerve deficit as a direct result of the surgical procedure (VIth nerve palsy requiring surgery) but no other patient has had permanent neuromuscular compromise. Complications consisted of a wound infection in one case. Tumor removal was total in three cases and partial in two cases. CONCLUSION: Quite easy to master, the anterior petrosectomy with preoperative embolization of the inferior petrosal sinus is a time-conserving approach giving one of the best routes to reach the ventral brainstem while working in front of the cranial nerves and preserving hearing.

Abducens Nerve Diseases↗
PubMed2000

HLA-DRB1 and DQB1 polymorphisms in southern France and genetic relationships with other Mediterranean populations.

This study presents the results of HLA-DRB1 and DQB1 sequence-specific oligonucleotide probe (SSOP) typing for a population sample of 181 individuals originating from southern France. On the basis of allele and haplotype frequencies, we compared our population with others from the Mediterranean area. Allele frequencies are comparable to those found in other western European populations (France, Portugal, Spain) and indicate neighboring exchanges. The haplotype frequencies showed relationships with North Africans and Jewish populations, as well as the common origin of Moroccan and Lebanese Jews. Therefore, allele frequencies seem to be more able to show recent exchanges while haplotype frequencies might show ancestral relationships. These results may serve as references for future studies of HLA and disease in southern France.

Alleles↗