Search PubMed⌕ Search

Biomedical subjects

O Bousquet

Publications and source records attributed to O Bousquet.

At least 19 recordsLinked to original sources
PubMed1998

Is the hippocampus a Kalman filter?

Based on a large body of neurophysiological, neuroanatomical, and behavioral data, it has been suggested that the hippocampal formation serves as a spatial learning and localization system. This spatial representation is metric in nature and arises as a result of associations between sensory inputs and dead-reckoning information generated by the animal. However, despite the fact that these two information streams provide uncertain information (e.g., recognition errors, dead-reckoning drifts, etc.), the hippocampal computational models suggested to date have not explicitly addressed information fusion from erroneous sources. In this paper we develop a computational model of hippocampal spatial learning and relate its functioning to a probabilistic tool used for uncertain sensory fusion in robots: the Kalman filter. This parallel allows us to derive statistically optimal update expressions for the localization performed by our computational model.

Animals↗
PubMed1996

Cytoskeleton: missing links found?

The quest for the function of BPAG1, a major hemidesmosomal protein of skin keratinocytes, has led to the discovery of a group of protein isoforms derived from the same genomic locus that are involved in organizing and integrating cytoskeletal networks in sensory neurons.

Animals↗
PubMed1996

Aggregation of a subpopulation of vimentin filaments in cultured human skin fibroblasts derived from patients with giant axonal neuropathy.

Giant axonal neuropathy (GAN) is a generalized disorder of intermediate filament networks which results in the formation of an ovoid aggregate in a large variety of cell types. We investigated the cytoskeletal organization of cultured skin fibroblasts derived from three GAN patients by indirect immunofluorescence, confocal, and electron microscopy. Whereas the organization of microfilaments seemed normal, the microtubule network appeared disorganized and tangled. The organization of the intermediate filament network, composed of vimentin, was probed with three antibodies directed against different epitopes: two vimentin-specific antibodies, a monoclonal antibody (mAb V9) and a polyclonal antibody, and a serum specific for all type III IFPs (PI serum). These experiments showed that 20% of cultured skin fibroblasts from GAN patients have a vimentin aggregate composed of densely packed filaments which coexists with a well-organized vimentin network. After depolymerization of microtubules with nocodazole, all fibroblasts from GAN patients contained a vimentin aggregate which seemed to arise from a subpopulation of vimentin filaments normally integrated in the vimentin network. Such aggregates were never observed in any condition in control fibroblasts. Moreover, the ultrastructural analysis of GAN cells revealed the presence of swollen mitochondria. We suggest that GAN may be due to a defect in a factor which stabilizes cytoplasmic intermediate filament networks, and we speculate on its identification and properties.

Actin Cytoskeleton↗
PubMed1996

[Neuronal intermediate filament proteins].

The characteristics of the seven intermediate filament proteins expressed during the development of neurons are reviewed. The most extensively studied have been neurofilament proteins (NFP) and peripherin. The relative plasticity of the peripherin network can account for its possible role during development when the axons of the neurons in which this protein is expressed have to find their targets crossing a non-neural environment probably in answer to signals from this environment and from their respective targets. Peripherin may assume a similar role when axons regenerate. NFP are considered as maintaining the axonal caliber, thus ensuring a normal axonal transport. Their network is highly disrupted in several diseases, particularly in motor neuron diseases. Mice transgenic for human NFP or in which mouse NFP are overexpressed have been obtained and are considered as animal models for these diseases.

Animals↗
PubMed1993

Peripherin and neurofilaments: expression and role during neural development.

This review focuses attention on the expression of peripherin and the low-molecular mass neurofilament protein during development, as well as on recent results concerning the roles of these neuronal proteins. Peripherin is the only type III intermediate filament that has been shown to be expressed in neurons but exclusively in motor, sensory and sympathetic neurons; moreover, it is co-expressed with neurofilament proteins (NFP). Clearly, peripherin is expressed concomitantly with axonal growth during development, and its synthesis appears necessary to axonal regeneration in the adult. As to NFP, they are presumed to maintain the axonal diameter and thereby ensure a normal conduction velocity. In many neuropathies, either occurring in man or provoked by different means in animals, the neurofilament network is disrupted thus giving rise to bundles of filaments in perikarya or along axons; consequently, the axonal transport is impaired. The possible significance of the overexpression of NFP is discussed.

Animals↗
PubMed1992

[Portal hypertension: a rare cause of hematuria].

A patient with undiagnosed cirrhosis presented with massive haematuria 16 years after augmentation colonoplasty. Portal hypertension (PHT) was responsible for a portocaval collateral circulation with vesical varices detected by low pressure endoscopy performed between episodes of haematuria. A very similar case was published in 1991. Surgical haemostatis with partial or total resection of the colonoplasty was only temporarily effective in our patient, who subsequently underwent liver transplantation due to repeated episodes of hepatic encephalopathy. No recurrence of haematuria was observed six years after the diversion. This rare cause of haematuria must be considered in view of the widespread use of intestinal conduits in urology: a dozen cases have been reported after transileal cutaneous ureterostomy, occurring an average of 3 years after the operation. Direct treatment of the varices, either by surgical devascularisation or resection or be endoscopic laser sclerosis or coagulation, is only temporarily effective. Treatment of the PHT appears to be the most effective measure in the long term: beta-blockers administered in the absence of episodes of haematuria or portal by-pass surgery in the case of failure.

Hematuria↗
PubMed1990

[Listeria monocytogenes liver abscess. In a diabetic patient].

Most liver abscesses are caused by Enterobacteriaceae, sometimes associated with anaerobes. Listeriosis is an exceptional cause of liver abscess, usually in a context of disseminated infections. We report the case of a diabetic woman who had liver abscess due to Listeria monocytogenes. The organism was isolated after guided needle aspiration, and there was no other site of infection. The course of the disease gradually moved towards recovery under an antibiotic therapy that was based on sensitivity tests. A search for immunodeficiency proved negative. A review of the literature showed that the rare cases of listerial liver abscess share a common factor, diabetes mellitus, the importance of which has not yet been noticed.

Diabetes Mellitus, Type 2↗
PubMed1990

[Interferon alpha-2a treatment of 26 patients with chronic non-A non-B hepatitis. Predictive factors of response].

The type and predicting factors of response to alpha interferon therapy have been studied in 26 patients with chronic non-A non-B hepatitis. Interferon was administered three times weekly during 6 months at a dose of 3 millions units/day. Eleven patients (42 percent) had serum alanine aminotransferase levels below 1.5 times the upper limit of normal range at the end of treatment. Only eight (31 percent) patients had persistent normalization of seric alanine aminotransferase value, 6 months after the end of the interferon treatment. The main factors involved in the response to therapy were age, apparent duration of the disease, and mode of contamination: patients who responded to interferon were younger, had a shorter duration of hepatitis and a parenterally transmitted disease.

Adolescent↗
PubMed1988

[Spontaneous esophageal perforation. Radiological diagnosis].

Esophageal perforations are rare and usually occur after instrumentation. We relate here a case unsuspected spontaneous esophageal perforation. Computed chest tomography firstly showed signs of mediastinal abscess. Secondary barium meal confirmed the diagnosis.

Esophageal Perforation↗
PubMed1982

[A case of VIP and somatostatin-secreting phaeochromocytoma (author's transl)].

A man with watery diarrhoea was found to have adrenal tumour. Pre-operative examinations located the tumour in the right adrenal gland and revealed that it secreted an excess of vasoactive intestinal peptide (VIP). All symptoms disappeared after excision of the phaeochromocytoma; they have not recurred after a 3 years' follow-up period. Histological examination of the tumour confirmed that it was the site of a triple hormonal secretion (VIP somatostatin and catecholamines).

Adrenal Gland Neoplasms↗