Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests: Psychology, Locomotion, Medicine, Physical Medicine and Rehabilitation, Proprioception, and 15 moreGait, Mice, Kinematics, Female, Animals, Regression Analysis, High Speed, Surface Properties, Stride Length, Equipment Design, Environment, Biomechanical Phenomena, Psychology and Cognitive Sciences, Medical and Health Sciences, and STRIDE
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Retinal projections and visual thalamo-cortical connections were studied in the subterranean mole rat, belonging to the superspecies Spalax ehrenbergi, by anterograde and retrograde tracing techniques. Quantitative image analysis was used... more
Retinal projections and visual thalamo-cortical connections were studied in the subterranean mole rat, belonging to the superspecies Spalax ehrenbergi, by anterograde and retrograde tracing techniques. Quantitative image analysis was used to estimate the relative density and distribution of retinal input to different primary visual nuclei. The visual system of Spalax presents a mosaic of both regressive and progressive morphological features. Following intraocular injections of horseradish peroxidase conjugates, the retina was found to project bilaterally to all visual structures described as receiving retinal afferents in non-fossorial rodents. Structures involved in form analysis and visually guided behaviors are reduced in size by more than 90%, receive a sparse retinal innervation, and are cytoarchitecturally poorly differentiated. The dorsal lateral geniculate nucleus, as defined by cyto- and myelo-architecture, cytochrome oxidase, and acetylcholinesterase distribution as well as by afferent and efferent connections, consists of a narrow sheet 3-5 neurons thick, in the dorsal thalamus. Connections with visual cortex are topographically organized but multiple cortical injections result in widespread and overlapping distributions of geniculate neurons, thus indicating that the cortical map of visual space is imprecise. The superficial layers of the superior colliculus are collapsed to a single layer, and the diffuse ipsilateral distribution of retinal afferents also suggests a lack of precise retinotopic relations. In the pretectum, both the olivary pretectal nucleus and the nucleus of the optic tract could be identified as receiving ipsilateral and contralateral retinal projections. The ventral lateral geniculate nucleus is also bilaterally innervated, but distinct subdivisions of this nucleus or the intergeniculate leaflet could not be distinguished. The retina sends a sparse projection to the dorsal and lateral terminal nuclei of the accessory optic system. The medial terminal nucleus is not present. In contrast to the above, structures of the "non-image forming" visual pathway involved in photoperiodic perception are well developed in Spalax. The suprachiasmatic nucleus receives a bilateral projection from the retina and the absolute size, cytoarchitecture, density, and distribution of retinal afferents in Spalax are comparable with those of other rodents. A relatively hypertrophied retinal projection is observed in the bed nucleus of the stria terminalis. Other regions which receive sparse visual input include the lateral and anterior hypothalamic areas, the retrochiasmatic region, the sub-paraventricular zone, the paraventricular hypothalamic nucleus, the anteroventral and anterodorsal nuclei, the lateral habenula, the mediodorsal nucleus, and the basal telencephalon.(ABSTRACT TRUNCATED AT 400 WORDS)
Research Interests:
This review deals with recent studies on the lungs of fossil and extant coelacanths with classical techniques (dissections, photonic histology) and modern techniques (SEM, X-ray tomography). This recent knowledge allows to attest the... more
This review deals with recent studies on the lungs of fossil and extant coelacanths with classical techniques (dissections, photonic histology) and modern techniques (SEM, X-ray tomography). This recent knowledge allows to attest the homology between: i) the large bony plates of the calcified organ of extinct coelacanths and the small plates that surround the lung of the extant coelacanth Latimeria; ii) the (supposed functional) lung covered with bony plates of extinct coelacanths and the vestigial (non-functional) lung of the extant coelacanth Latimeria. These results point the fatty organ of Latimeria as probably a mesenteric specialization, questioning its previous attribution to its pulmonary origin.
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Research Interests:
In this series of studies, we have attempted to characterize anatomically the organization of the retinofugal pathways in monkeys that underwent the surgical removal in infancy of the entire left cerebral hemisphere. Hemidecordication in... more
In this series of studies, we have attempted to characterize anatomically the organization of the retinofugal pathways in monkeys that underwent the surgical removal in infancy of the entire left cerebral hemisphere. Hemidecordication in baby monkeys produced a transneuronal retrograde degeneration of the retinal ganglion cells (RGCs) that affected mainly the foveal rim. Although the density of RGCs in this region was drastically diminished, the soma sizes of the surviving cells remained normal. The lateral geniculate nucleus (dLGN) ipsilateral to the removed cortex was dramatically reduced in size although it still showed normal layering. There was a marked reduction in the number of neurons in both the parvocellular and magnocellular layers and a heavy gliosis. By contrast, the superior colliculus ipsilateral to the lesion was remarkably well preserved: although slightly reduced in volume, it showed little gliosis and a metabolic activity, as revealed by cytochrome oxidase histochemistry, similar to the superior colliculus contralateral to the lesion. Behavioral perimetry indicated a partial sparing of vision up to 45 degrees in the 'blind' hemifield. We argue that the preservation of the retino-tectal pathway mediates most of the residual visual functions found in the 'blind field' of hemispherectomized human subjects.
Research Interests:
The extant coelacanth was discovered in 1938;1 its biology and ecology remain poorly known due to the low number of specimens collected. Only two previous studies1,2 have attempted to determine its age and growth. They suggested a maximum... more
The extant coelacanth was discovered in 1938;1 its biology and ecology remain poorly known due to the low number of specimens collected. Only two previous studies1,2 have attempted to determine its age and growth. They suggested a maximum lifespan of 20 years, placing the coelacanth among the fastest growing marine fish. These findings are at odds with the coelacanth's other known biological features including low oxygen-extraction capacity, slow metabolism, ovoviviparity, and low fecundity, typical of fish with slow life histories and slow growth. In this study, we use polarized light microscopy to study growth on scales based on a large sample of 27 specimens. Our results demonstrate for the first time nearly imperceptible annual calcified structures (circuli) on the scales and show that maximal age of the coelacanth was underestimated by a factor of 5. Our validation method suggests that circuli are indeed annual, thus supporting that the coelacanth is among the longest-living fish species, its lifespan being probably around 100 years. Like deep-sea sharks with a reduced metabolism, the coelacanth has among the slowest growth for its size. Further reappraisals of age at first sexual maturity (in the range 40 to 69 years old) and gestation duration (of around 5 years) show that the living coelacanth has one of the slowest life histories of all marine fish and possibly the longest gestation. As long-lived species with slow life histories are extremely vulnerable to natural and anthropogenic perturbations, our results suggest that coelacanths may be more threatened than previously considered.
Research Interests:
Over the centuries, the composition of jar sealants in natural history museum fluid collections has changed but has not been the subject of extensive documentation. Consequently, it is of paramount interest to increase our knowledge of... more
Over the centuries, the composition of jar sealants in natural history museum fluid collections has changed but has not been the subject of extensive documentation. Consequently, it is of paramount interest to increase our knowledge of sealant composition as well as to correlate this information with the date of manufacture and type of preparation. As an initial step towards achieving this goal, an analytical protocol was developed to characterize the composition of sealants encountered in fluid collections of the Muséum national d'Histoire naturelle (MNHN) in Paris. Fourier transform-infrared (FT-IR) spectroscopy and pyrolysis-gas chromatography/mass spectrometry (GC/MS) were used to investigate the nature of selected jar sealants, and these techniques proved to be efficient for the identification and characterization of waxes and resin additives in sealing samples. First results are very promising; similar examinations should be continued on a large scale for an exhaustive ana...
Research Interests:
Research Interests:
Research Interests:
Research Interests:
Magnetic Resonance Imaging Scan of the Brain of a Slow Loris (<i>Nycticebus</i>) from http://braincatalogue.org/Slow_loris
Research Interests: Uncategorized and Zenodo
Magnetic Resonance Imaging Scan of the Brain of a Orangutan (<i>Pongo pygmaeus</i>) from http://braincatalogue.org/Orangutan
Research Interests:
Magnetic Resonance Imaging Scan of the Brain of a Nile Crocodile (<i>Crocodylus niloticus</i>) from http://braincatalogue.org/Nile_crocodile
Research Interests: Uncategorized and Zenodo
Triangular Mesh of a Black Rhinoceros Brain (Diceros Bicornis) from http://braincatalogue.org/Black_rhinoceros.
BrainScapes: The possible landscape of primate brain shapes. The accompanying website of the project lives here, with videos across the landscape of primate brain shapes, and evolutionary trajectories for the species back to the brain of... more
BrainScapes: The possible landscape of primate brain shapes. The accompanying website of the project lives here, with videos across the landscape of primate brain shapes, and evolutionary trajectories for the species back to the brain of the common ancestor. The shape of primate brains varies widely from small smooth to profusely folded large brains. Studying morphological diversity across phylogeny allows us to better understand how primate brains adapt, and in particular the evolutionary context of the human brain. Recent advances in generative machine learning models have led to algorithms capable of learning shape embeddings and to generate realistic new instances. We explored an autoencoder deep neural network to generate shapes of primate brains including 34 different species. Our network successfully learnt a landscape of changes in shape. Interestingly, species with brains of comparable volume were close in the learnt space, despite having been size-normalised for the traini...
Magnetic Resonance Imaging Scan of a Black Rhinoceros (Diceros Bicornis) from http://braincatalogue.org/Black_rhinoceros
Research Interests:
Magnetic Resonance Imaging Scan of a Bottlenose Dolphin Brain (<em>Tursiops truncatus</em>) from http://braincatalogue.org/Bottlenose_dolphin
Research Interests:
Research Interests:
Research Interests:
Significance Aryl hydrocarbon receptor (AHR) is well known to mediate xenobiotic metabolism in vertebrates. Growing evidence reveals that AHR seems to have endogenous roles in the development and functioning of different organs. In our... more
Significance Aryl hydrocarbon receptor (AHR) is well known to mediate xenobiotic metabolism in vertebrates. Growing evidence reveals that AHR seems to have endogenous roles in the development and functioning of different organs. In our current study, we describe a role of AHR in peripheral myelination and in nerve sheath tumors. We show that the AHR pathway is dysregulated in human biopsies of nerve tumors. The blockade of AHR provokes cell death in nerve tumors, suggesting a therapeutic avenue in the treatment of this invasive cancer. Furthermore, the inhibition of Ahr in mice provokes locomotor defects and alteration of myelin structure. This work unravels an endogenous role of Ahr in peripheral myelination and a potential treatment of nerve tumours.
Research Interests:
Research Interests:
As a sarcopterygian fish, the extant coelacanth Latimeria has muscular paired fins, different in their skeletal and muscular anatomy from the paired fins of actinopterygians. Although the muscular anatomy of the pectoral and pelvic fins... more
As a sarcopterygian fish, the extant coelacanth Latimeria has muscular paired fins, different in their skeletal and muscular anatomy from the paired fins of actinopterygians. Although the muscular anatomy of the pectoral and pelvic fins of Latimeria has been described by several studies, a detailed functional description of the muscles and their architecture has never been performed. Our detailed functional description of the muscles of the paired fins shows a more complex organization than previously described. The pectoral and pelvic fins have a different organization of their muscular anatomy, and the pelvic fin shows a more plesiomorphic configuration of the muscles since most of them are poly-articular and run from the pelvic girdle to the fin rays, an organization typical of actinopterygians. We found that the pectoral fins are stronger than the pelvic fins which is likely to be associated with the greater contribution of the pectoral fins to locomotion and manoeuvring. Finall...
Research Interests:
The use of specific preservative solutions by museum professionals to maintain fluid-preserved specimens has fluctuated over the years with advances in chemistry. The determining factors for the original choice of solution closely... more
The use of specific preservative solutions by museum professionals to maintain fluid-preserved specimens has fluctuated over the years with advances in chemistry. The determining factors for the original choice of solution closely correlate with the historical parameters and original usage of the collections. Consequently, for any given collection, changes and substitutions over time in the types of preservative fluids used have likely occurred. The present comparative analysis of the state of brain preservation, carried out at macroscopic, microscopic, and molecular levels, allowed us to evaluate the effect of the different treatments applied over time to fluid-preserved collections. Our results confirm that the duration of formaldehyde exposure of the tissues clearly has an effect on their long-term preservation. Despite the controversies associated with the quality or use of some historic fixatives, modern analytical methods such as medical imagery reveal the preservation quality...
Research Interests:
The presence of a pulmonary organ that is entirely covered by true bone tissue and fills most of the abdominal cavity is hitherto unique to fossil actinistians. Although small hard plates have been recently reported in the lung of the... more
The presence of a pulmonary organ that is entirely covered by true bone tissue and fills most of the abdominal cavity is hitherto unique to fossil actinistians. Although small hard plates have been recently reported in the lung of the extant coelacanth Latimeria chalumnae, the homology between these hard structures in fossil and extant forms remained to be demonstrated. Here, we resolve this question by reporting the presence of a similar histological pattern-true cellular bone with star-shaped osteocytes, and a globular mineralisation with radiating arrangement-in the lung plates of two fossil coelacanths (Swenzia latimerae and Axelrodichthys araripensis) and the plates that surround the lung of the most extensively studied extant coelacanth species, L. chalumnae. The point-for-point structural similarity of the plates in extant and fossil coelacanths supports their probable homology and, consequently, that of the organ they surround. Thus, this evidence questions the previous inte...
Research Interests:
Wet collections are rich in information to study the evolution of species or ancient pathologies. However, they are sometimes neglected, poorly documented and difficult to preserve. To keep these archives for future generations, we have... more
Wet collections are rich in information to study the evolution of species or ancient pathologies. However, they are sometimes neglected, poorly documented and difficult to preserve. To keep these archives for future generations, we have inventoried in detail the degradations observed in the collections and undertaken research on the hermeticity of the jars. To top up the jars appropriately, the fluids is first identified without opening the jar and the impact of a change of fluid from the macroscopic to the microscopic scale was studied. The results of this research are shared through publications and exchanges with collection managers.