Transmission des voies olfactives aux cellules réticulospinales de la lamproie

Les informations olfactives sont connues pour leur capacité à induire des comportements moteurs spécifiques. En dépit de nombreuses observations comportementales chez les vertébrés, on ne connaît toujours pas les mécanismes et les voies nerveuses qui sous-tendent ces phénomènes de transformation olfacto-locomotrices. Chez la lamproie, des travaux récents ont permis de décrire cette voie, et les mécanismes responsables de la transformation des entrées olfactives en activité locomotrice (Derjean et al., 2010). Cette voie prend origine dans la partie médiane du bulbe olfactif, et envoie des projections vers le tubercule postérieur, une région qui se trouve dans le diencéphale. De là, les neurones projettent directement vers la Région Locomotrice Mésencéphalique, connue pour envoyer des connexions vers les neurones réticulospinaux, et activer la locomotion. L’objectif de cette étude était d’établir si l’ensemble des neurones réticulospinaux répond aux stimulations olfactives. Pour ce faire, nous avons utilisé sur une préparation de cerveau isolé de lamproie des techniques d’électrophysiologie et d’imagerie calcique. La stimulation électrique des nerfs olfactifs, de la région médiane du bulbe olfactif ou du tubercule postérieur a provoqué une activation de toutes les cellules réticulospinales qui se retrouvent dans les quatre noyaux réticulaires (ARRN : Noyau Réticulaire Rhombencéphalique Antérieur; MRN : Noyau Réticulaire Mésencéphalique; MRRN : Noyau Réticulaire Rhombencéphalique Moyen; PRRN : Noyau Réticulaire Rhombencéphalique Postérieur). Seule la partie médiane du bulbe olfactif est impliquée dans le passage de l’information olfactive vers les neurones réticulospinaux. Nous avons aussi découvert que le blocage des récepteurs GABAergiques dans la partie médiane du bulbe olfactif augmentait les réponses olfactives de façon considérable dans les cellules réticulospinales. Nous avons montré ainsi qu’il existe un tonus inhibiteur impliqué dans la dépression modulatrice de la voie olfacto-locomotrice. Ce travail a permis de montrer que la stimulation des afférences sensorielles olfactives active simultanément l’ensemble des populations de neurones réticulospinaux qui commandent la locomotion. De plus, il existerait un tonus inhibiteur GABAergique, au niveau de la partie médiane du bulbe olfactif, responsable d’une dépression modulatrice dans la voie olfacto-locomotrice.

Projections anatomiques des bulbes olfactifs chez la lamproie

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Étude comparative des projections des neurones dopaminergiques chez deux espèces animales.

Une des voies les plus étudiées dans le contrôle locomoteur est la voie dopaminergique ascendante, vu son importance dans les maladies qui touchent la locomotion, comme la maladie du Parkinson. La substance noire pars compacta (A9; SNc) et l’aire tegmentaire ventrale (A10; VTA) envoient des projections dopaminergiques (DA+) vers les ganglions de la base (GB) qui à leur tour projettent vers la région locomotrice mésencéphalique (RLM), une région de tronc cérébral qui contrôle la locomotion chez les vertébrés. Des terminaisons DA+ au niveau de la RLM ont récemment été découvertes chez le singe. Donc, il semblait intéressant de savoir d’où provenaient ces projections DA+ et si elles étaient maintenues de manière équivalente dans l’évolution des espèces animales. Nous nous sommes donc penchés sur deux espèces animales en particulier, la lamproie et le triton. Dans ce travail, nous avons observé une voie DA+ descendante du tubercule postérieur (PT; homologue à la substance noire pars compacta et à l’aire tegmentaire ventrale chez les mammifères) directement vers la RLM, sans passer par l’intermédiaire des GB. Cette voie DA+ descendante a été observée autant chez la lamproie que chez le triton, à la suite d’injections de marqueurs rétrogrades et de détection immunohistochimique de la tyrosine hydroxylase (TH) ou de la dopamine (DA). La voie DA+ descendante semble donc conservée au cours de l’évolution des espèces vertébrés, bien que l’importance relative de la voie ascendante DA+ semble augmenter au cours de l’évolution.

Determining the zone of reflection for posterior corneal surface comparison phakometry

Although comparison phakometry has been used by a number of studies to measure posterior corneal shape, these studies have not calculated the size of the posterior corneal zones of reflection they assessed. This paper develops paraxial equations for calculating posterior corneal zones of reflection, based on standard keratometry equations and equivalent mirror theory. For targets used in previous studies, posterior corneal reflection zone sizes were calculated using paraxial equations and using exact ray tracing, assuming spherical and aspheric corneal surfaces. Paraxial methods and exact ray tracing methods give similar estimates for reflection zone sizes less than 2 mm, but for larger zone sizes ray tracing methods should be used.

Is flapless implant surgery a viable option in posterior maxilla? : a review

This article reviews the literature on the outcome of flapless surgery for dental implants in the posterior maxilla. The literature search was carried out in using the keywords: flapless, dental implants and maxilla. A hand search and Medline search were carried out on studies published between 1971 and 2011. The authors included research involving a minimum of 15 dental implants with a followup period of 1 year, an outcome measurement of implant survival, but excluded studies involving multiple simultaneous interventions, and studies with missing data. The Cochrane approach for cohort studies and Oxford Centre for Evidence- Based Medicine were applied. Of the 56 published papers selected, 14 papers on the flapless technique showed high overall implant survival rates. The prospective studies yielded 97.01% (95% CI: 90.72–99.0) while retrospective studies or case series illustrated 95.08% (95% CI: 91.0–97.93) survival. The average of intraoperative complications was 6.55% using the flapless procedure. The limited data obtained showed that flapless surgery in posterior maxilla areas could be a viable and predictable treatment method for implant placement. Flapless surgery tends to be more applicable in this area of the mouth. Further long-term clinical controlled studies are needed.

Comparative effects of posterior eye cup tissues from Myopic and Hyperopic chick eyes on cultured scleral fibroblasts

The role of individual ocular tissues in mediating changes to the sclera during myopia development is unclear. The aim of this study was to examine the effects of retina, RPE and choroidal tissues from myopic and hyperopic chick eyes on the DNA and glycosaminoglycan (GAG) content in cultures of chick scleral fibroblasts. Primary cultures of fibroblastic cells expressing vimentin and -smooth muscle actin were established in serum-supplemented growth medium from 8-day-old normal chick sclera. The fibroblasts were subsequently co-cultured with posterior eye cup tissue (full thickness containing retina, RPE and choroid) obtained from untreated eyes and eyes wearing translucent diffusers (form-deprivation myopia, FDM) or -15D lenses (lens-induced myopia, LIM) for 3 days (post hatch day 5 to 8) (n=6 per treatment group). The effect of tissues (full thickness and individual retina, RPE, and choroid layers) from -15D (LIM) versus +15D (lens-induced hyperopia, LIH) treated eyes was also determined. Refraction changes in the direction predicted by the visual treatments were confirmed by retinoscopy prior to tissue collection. Glycosaminoglycan (GAG) and DNA content of the scleral fibroblast cultures were measured using GAG and PicoGreen assays. There was no significant difference in the effect of full thickness tissue from either FDM or LIM treated eyes on DNA and GAG content of scleral fibroblasts (DNA 8.9±2.6 µg and 8.4±1.1 µg, p=0.12; GAG 11.2±0.6 µg and 10.1±1.0 µg, p=0.34). Retina from LIM eyes did not alter fibroblast DNA or GAG content compared to retina from LIH eyes (DNA 27.2±1.7 µg versus 23.2±1.5 µg, p=0.21; GAG 28.1±1.7 µg versus. 28.7±1.2 µg, p=0.46). Similarly, the choroid from LIH and LIM eyes did not produce a differential effect on DNA content (DNA, LIM 46.9±6.4 versus LIH 51.5±4.7 µg, p=0.31), whereas GAG content was higher for cells in co-culture with choroid from LIH eyes (GAG 32.5±0.7 µg versus 18.9±1.2 µg, F1,6=9.210, p=0.0002). In contrast, fibroblast DNA was greater in co-culture with RPE from LIM eyes than the empty basket and DNA content less for co-culture with RPE from LIH eyes (LIM: 72.4±6.3 µg versus Empty basket: 46.03±1.0 µg; F1,6=69.99, p=0.0005 and LIH: 27.9±2.3 µg versus empty basket: 46.03±1.0 µg; p=0.0004). GAG content was higher with RPE from LIH eyes (LIH: 33.7±1.9 µg versus empty basket: 29.5±0.8 µg, F1,6=13.99, p=0.010) and lower with RPE from LIM eyes (LIM: 27.7±0.9 µg versus empty basket: 29.5±0.8 µg, p=0.021). GAG content of cells in co-culture with choroid from LIH eyes was higher compared to co-culture with choroid from LIM eyes (32.5±0.7 µg versus 18.9±1.2 µg respectively, F1,6=9.210, p=0.0002). In conclusion, these experiments provide evidence for a directional growth signal that is present (and remains) in the ex-vivo RPE, but that does not remain in the ex-vivo retina. The identity of this factor(s) that can modify scleral cell DNA and GAG content requires further research.

Chemotherapy induced reversible posterior leukoencephalopathy syndrome

The reversible posterior leukoencephalopathy syndrome (RPLES) is a condition characterised by reversible neurological and radiological findings that has been associated with use of immunosuppressive, chemotherapeutic and more recently novel targeted therapies. We describe the case of a 50-year-old woman with advanced non-small cell lung cancer who developed status epilepticus shortly after receiving cisplatin and gemcitabine chemotherapy. The clinical, radiological and EEG findings during and post event are presented and are in keeping with a diagnosis of RPLES. Early recognition of this rare syndrome, supportive management and withdrawal of the offending agent appear to result in a reversal of the manifestations described. © 2007 Elsevier Ireland Ltd. All rights reserved.

An evaluation of clinical procedures used in dental implant treatment in posterior maxilla using flapless technique

This study was a measure forward in cultivating the scientific basis for an approach to examine clinical procedure in Flapless dental implant surgery. The thesis is based on: the systematic review, retrospective study of flapless implants, and in vivo study on the osseo-integration in osteoporotic rats. Dr Doan investigated "clinical procedures used in dental implant treatment in posterior maxilla using flapless technique". The work has yielded significant contributions to the area of implant flapless surgery and its effects on osteoporotic patients having implants in the posterior maxilla.

The role of the posterior superior temporal sulcus in audiovisual processing

In this study we investigate previous claims that a region in the left posterior superior temporal sulcus (pSTS) is more activated by audiovisual than unimodal processing. First, we compare audiovisual to visual-visual and auditory-auditory conceptual matching using auditory or visual object names that are paired with pictures of objects or their environmental sounds. Second, we compare congruent and incongruent audiovisual trials when presentation is simultaneous or sequential. Third, we compare audiovisual stimuli that are either verbal (auditory and visual words) or nonverbal (pictures of objects and their associated sounds). The results demonstrate that, when task, attention, and stimuli are controlled, pSTS activation for audiovisual conceptual matching is 1) identical to that observed for intramodal conceptual matching, 2) greater for incongruent than congruent trials when auditory and visual stimuli are simultaneously presented, and 3) identical for verbal and nonverbal stimuli. These results are not consistent with previous claims that pSTS activation reflects the active formation of an integrated audiovisual representation. After a discussion of the stimulus and task factors that modulate activation, we conclude that, when stimulus input, task, and attention are controlled, pSTS is part of a distributed set of regions involved in conceptual matching, irrespective of whether the stimuli are audiovisual, auditory-auditory or visual-visual.

Long-term follow-up of flexor digitorum longus transfer and calcaneal osteotomy for stage II posterior tibial tendon dysfunction

Flexor digitorum longus transfer and medial displacement alcaneal osteotomy is a wellrecognised form of treatment or stage II posterior tibial tendon dysfunction. Although excellent short- and medium-term results have been reported, the long-term outcome is unknown. We reviewed the clinical outcome of 31 patients with a symptomatic flexible flatfoot deformity who underwent this procedure between 1994 and 1996. There were 21 women and ten men with a mean age of 54.3 years (42 to 70). The mean follow-up was 15.2 years (11.4 to 16.5). All scores improved significantly (p < 0.001). The mean American Orthopedic Foot and Ankle Society (AOFAS) score improved from 48.4 pre-operatively to 90.3 (54 to 100) at the final follow-up. The mean pain component improved from 12.3 to 35.2 (20 to 40). The mean function score improved from 35.2 to 45.6 (30 to 50). The mean visual analogue score for pain improved from 7.3 to 1.3 (0 to 6). The mean Short Form-36 physical component score was 40.6 (SD 8.9), and this showed a significant correlation with the mean AOFAS score (r = 0.68, p = 0.005). A total of 27 patients (87%) were pain free and functioning well at the final follow-up. We believe that flexor digitorum longus transfer and calcaneal osteotomy provides long-term pain relief and satisfactory function in the treatment of stage II posterior tibial tendon dysfunction.