PubMed Health⌕ Search

Biomedical subjects

S Joubert

Publications and source records attributed to S Joubert.

9 recordsLinked to original sources
PubMed2004

Progressive prosopagnosia: clinical and neuroimaging results.

The authors report the longitudinal case study of a patient with the right temporal variant of frontotemporal lobar degeneration. His deficit, initially limited to visuoperceptual disturbances, progressed 2 years later to a severe semantic breakdown. Neuroimaging data indicate that the underlying degenerative process, initially confined to unimodal visual associative cortices, progressed along the ventral pathways to multimodal areas in charge of integrating knowledge from various modalities (the anterior temporal lobes).

Aged↗
PubMed2004

Evaluation of visual recognition memory in MCI patients.

BACKGROUND: Neurofibrillary tangles seen early in Alzheimer disease (AD) initially appear in a subregion of the perirhinal cortex. In the monkey, damage to the perirhinal cortex impairs performance on visual recognition memory tasks. The authors evaluated impairment of visual recognition memory as a potential early diagnostic marker of AD. METHODS: The authors developed a visual delayed matching-to-sample task (DMS48) designed to assess visual recognition memory in humans. Twenty-three patients fulfilling the criteria of amnestic mild cognitive impairment (MCI) (mean Mini-Mental State Examination [MMSE]: 26.6, SD = 1.6) were recruited. All underwent a full neuropsychological evaluation, which included the Free and Cued Selective Reminding (FCSR) test. Their performance was compared with that of 10 patients with mild AD, 20 patients with moderate AD, 20 patients with Parkinson disease (PD), and 40 age-matched controls. RESULTS: Control subjects and patients with PD performed close to ceiling. Patients with mild AD had very low scores, while patients with moderate AD answered at random. MCI patients obtained scores that were between those of control subjects and patients with mild AD (78%, SD = 16%). MCI patients who failed on the DMS48 had lower scores on free recall (p < 0.05) and received less benefit from cueing (p < 0.01) on the FCSR than the other MCI, suggesting a profile of genuine memory impairment related to medial temporal lobe lesions. CONCLUSION: The DMS48, a test of visual recognition memory, is impaired early in the course of patients with MCI. Further studies are necessary to determine whether the evaluation of visual recognition memory may contribute to the identification of patients with AD.

Aged↗
PubMed2004

[The human perirhinal cortex].

The perirhinal cortex is a structure that lies within the medial temporal lobe. In the present paper, we review current knowledge of the anatomical boundaries and functional correlates of this structure. In the past decade, numerous animal studies have attempted to understand the contribution of the perirhinal cortex to memory. Taken together, they suggest that the perirhinal cortex is crucially involved in recognition memory. This function appears to be independent from those assumed to be subserved by the hippocampus. In humans, data are scarce but tend to corroborate results found in the animal literature. The perirhinal cortex appears to support context-free (non-episodic) knowledge, such as general knowledge about the world and "item-specific" memories. Models of declarative memory that take into account the specific contribution of the perirhinal cortex are discussed, along with their potential application to early cortical neurodegenerative disorders.

Animals↗
PubMed2001

Reduced activity of the NPR-A kinase triggers dephosphorylation and homologous desensitization of the receptor.

NPR-A, the receptor for the atrial natriuretic peptide (ANP), is a 130-kDa protein presenting an extracellular ANP-binding domain, a single transmembrane domain, an intracellular regulatory kinase homology domain (KHD), and a guanylyl cyclase catalytic domain. Upon stimulation, NPR-A receptors are activated to produce cyclic guanosine monophosphate (cGMP) and are subsequently desensitized through dephosphorylation of residues at their KHD. We used wild-type rat (r) NPR-A (WT) and a disulfide-bridged mutant (C423S) expressed in human embryonic kidney (HEK) 293 cells to study receptor phosphorylation. We have previously characterized the C423S receptor as constitutively active and desensitized. At basal state, 32P incorporation in the rNPR-A(C423S) covalent dimer is about 24 times less efficient than incorporation in the WT rNPR-A. When membranes from WT and rNPR-A(C423S) are incubated with [35S]ATPgammaS, the mutant dimer receptor displays 3.5% of the thiophosphate incorporation found for WT rNPR-A. Since the rNPR-A(C423S) dimer is already extensively dephosphorylated, we then used the WT rNPR-A to study dephosphorylation. As previously documented, adding ANP globally induces time-dependent dephosphorylation of the receptor. However, in pulse-chase experiments with the WT rNPR-A, adding ANP during the chase does not lead to a significant effect on receptor dephosphorylation. On the other hand, thiophosphorylation of the WT rNPR-A previously desensitized with ANP is reduced to 8.3% of the incorporation for untreated receptor, similar to results found with the rNPR-A(C423S) at basal state. These results demonstrate that ANP-induced rNPR-A desensitization is modulated by a significant reduction in the activity or affinity of the rNPR-A kinase that contributes to the low phosphorylation level after induction. Moreover, we further document a close relationship between tight dimerization, dephosphorylation, and desensitization.

Amiloride↗
PubMed1997

Femorodistal bypass using cryopreserved venous allografts for limb salvage.

Critical ischemia due to extensive femoropopliteal occlusive disease often leads to amputation in patients in whom an autologous vein is unavailable for reconstruction. The purpose of this nonrandomized prospective study is to evaluate the usefulness of cryopreserved venous allografts (CPVA) as an arterial substitute in these cases. Between October 1990 and March 1993, long bypass to a tibial or a foot artery using a CPVA was performed in 25 consecutive patients with ulcerations or gangrene. There were 19 women and six men with a mean age of 72 years (range: 51-90). The indication for allograft reconstruction was absence (17 cases) or unsuitability (eight cases) of an autologous vein graft. Greater saphenous vein allografts were harvested from multiple organ donors and frozen at -80 degrees C with 12% dimethylsulfoxide (DMSO). Sixteen patients had undergone one or more previous unsuccessful limb salvage attempts. The plantar arch was absent or incomplete in 16 patients (64%). Patients were followed up prospectively for a mean of 21 months (range: 3-32). One patient died early (32 days) and three patients died late with patent bypasses. Cumulative survival rate was 77% at 1 year and 72% at 2 years. Cumulative secondary patency rate (Kaplan-Meier) was 88% at 1 months, 72% at 6 months, and 52% at 1 year. The cumulative limb salvage rate was 78% at 2 years. When an autologous vein is unavailable, long bypass using a CPVA is a simple, quick, minimally traumatic, economical, and effective method to achieve limb salvage in patients with severe distal arterial occlusive disease. However, CPVA causes immunoreaction and there is a risk of proximal postanastomotic stenosis. Doppler ultrasound surveillance of a subcutaneous graft allows accurate assessment and repair of the abnormalities with no increase in mortality or morbidity.

Aged↗
PubMed1982

The clinical presentation and biochemical diagnosis of acromegaly and gigantism.

Over a 5-year period 14 patients with acromegaly and gigantism were seen at the endocrine clinic of King Edward VIII Hospital: 9 were Blacks and 5 Indians; 8 of the patients were women. The mean age of the patients was 46 years. Surprisingly, only 2 patients complained of acral overgrowth. Symptomatology was varied and not characteristic of the condition. On examination all patients had unequivocal signs of soft-tissue and bony overgrowth, 64% had visual abnormalities and 50% hypertension. Radiologically, 88% showed an enlarged pituitary fossa. On biochemical investigation, the fasting levels of growth hormone (GH) were increased in 12 patients and during oral glucose tolerance tests, the GH levels in these 12 patients were not suppressed. One patient in whom the fasting GH level was not increased had progressed to the stage of panhypopituitarism, in the remaining patient challenge with thyrotrophin-releasing hormone (TRH) led to increased GH levels and L-dopa challenge resulted in a paradoxical decrease in GH levels. Seven patients with increased GH levels who were challenged with L-dopa showed the typical decrease in GH levels found in this condition; in 5 of these patients, challenged with TRH, GH levels increased. The findings emphasize that despite the ease of clinical diagnosis, appropriate biochemical investigations are necessary to confirm the exact status of the disease, which is rare in the population studied.

Acromegaly↗
PubMedDate not supplied

The role of nasals in reading: a normative study in French.

Dual-route models of reading assume that reading can be done in two ways. A most common lexical route, on the one hand, allows regular and irregular words to be read while a second sublexical route allows nonwords and novel words to be read. A graphemic processing stage in sublexical reading is assumed to assemble the individual letters of a word or a nonword into multiletter graphemes prior to grapheme-phoneme conversion. The purpose of this study was to determine whether vowel/nasal clusters required as much time to be processed asvowel/vowel and consonant/consonant clusters in sublexical nonword reading in French. Results indicate that nonwords that contain vowel/nasal clusters are read significantly faster than nonwords comprising vowel/vowel and consonant/consonant clusters. Furthermore, nonwords that contain single-letter graphemes are read significantly faster than nonwords comprising vowel/nasal clusters and nonwords comprising vowel/vowel and consonant/consonant clusters. These results taken as a whole support the idea that nasals act as diacritic marks rather than being processed by means of a graphemic parsing procedure.

Humans↗
PubMedDate not supplied

Grapheme-phoneme processing of single words.

Often used in cognitive studies measuring reaction times and in functional imaging studies, the subtraction paradigm is based on the comparison of performance on tasks presupposed to refer to different cognitive levels of processing. Within the framework of the study of phonological processing of words, manipulating the grapheme-phoneme transparency of stimuli can represent a means of counteracting the methodological drawbacks inherent to the subtraction paradigm. Thus, the purpose of this study was to determine the effect of the level of difficulty of grapheme-phoneme matching on the processing of transparent and nontransparent words. Grapheme-phoneme matching was carried out both on the final syllable of words and on sublexical segments within the word. The results indicate that processing is faster for the transparent than for the nontransparent stimuli. This task will now have to be reintroduced in brain imaging studies aiming to look at different levels of difficulty for grapheme-phoneme matching.

Adult↗