Presence of plicidentine in the oral teeth of the coelacanth Latimeria chalumnae Smith 1939 (Sarcopterygii; Actinistia).

The extant coelacanth Latimeria is a sarcopterygian predatory fish with caniniform teeth on its upper and lower jaws. The teeth are constituted of a cone of dentine with an apical cap of enamel, and they are fixed to the osseous component of the jaws by an attachment bone. Internal walls of the tooth base show folds that have been firstly interpreted in the past as radial vascular canals. Three-dimensional visualisation of these foldings using X-ray tomographic techniques and new histological interpretation lead to reconsider these structures as true plicidentine. The folds of the dentine do not invade the whole pulp cavity of the tooth contrary to the plicated condition of most fossil sarcopterygian fishes (e.g., Eusthenopteron, Porolepis, Megalichthys) certain fossil marine reptiles (ichthyosaurs) and extant varanids; in Latimeria they are limited to the lower third to the half of the pulp cavity. The presence of plicidentine in Latimeria's teeth is proposed to be a plesiomorphic character for sarcopterygians.

First steps in adaptation of an evidential network for data fusion in the framework of medical remote monitoring.

This paper presents a medical remote monitoring application which aims at detecting falls. The detection system is based on three modalities: a wearable sensor, infrared sensors and a sound analysis module. The sound analysis is presented briefly. The multimodal fusion is made using the Dempster Schaffer theory through Evidential Network. A first evaluation of the use of data mining techniques in order to extract blindly data representatives is proposed. These representatives are used to continuously increase the system performances. The system is evaluated on a local recorded data base.

Limb preference in the gallop of dogs and the half-bound of pikas on flat ground.

During fast locomotion--gallop, half-bound, bound--of quadruped mammals, the ground contact of the limbs in each pair does not alternate symmetrically. Animals using such asymmetrical gait thus choose whether the left or the right limb will contact the ground first, and this gives rise to limb preference. Here, we report that dogs (Mammalia, Carnivora) and pikas (Mammalia, Lagomorpha) prefer one forelimb as trailing limb and use it as such almost twice as often as the other. We also show that this choice depends on the individual and is not a characteristic of the species, and that the strength of the preference was not dependent on the animal's running speed.

Anatomical sparing in the superior colliculus of hemispherectomized monkeys.

Using the monkey as a model for human hemispherectomy, the effects of early removal of a whole cerebral hemisphere on the cytoarchitecture and cytochrome oxidase histochemistry of the superior colliculus (SC) were evaluated. Results show that the SC ipsilateral to the cortical lesion suffers a 29.9% average volume reduction and a 32.7% total loss of neurons compared to the contralateral SC. Neuronal densities and metabolic activity are similar in normal and hemispherectomized monkeys. Furthermore, the ipsi- and contralesional SC receive retinal inputs as revealed with intraocular injections of tritiated proline. These data suggest that the superior colliculus retains functional capabilities following hemispherectomy in monkey.

[Skeletal configurations of cervical column during rest to motion transition: generalization that underlie the motor repertoire in rodents]. / Géométrie du squelette cervical durant la transition repos-locomotion: généralisation aux caractéristiques du répertoire moteur des rongeurs.

During forward locomotion, guinea pigs adopted a posture which, although different, was as stereotyped as at rest. The whole extent of the vertebral column was extended, parallel to the earth-horizontal plane. This result supports the hypothesis that, in mammals, gaze and postural control by the central nervous system would be simplified by the adoption of a limited number of skeletal configurations. They would be optimized for energy saving, biomechanical efficacy and limitation of the number of degrees of freedom of the skeletal apparatus. Transition between rest and forward locomotion displayed two prominent characteristics: the head was stabilized versus space throughout the whole transition and the modifications of the skeletal geometry were confined to the median plane and to two major articular regions. Such an organization revealed a fourth characteristic of the guinea pig postural control: the skeletal configurations retained by evolution would ensure that smooth transitions take place between rest and the various activities of its motor repertoire. Finally, our purely descriptive data shed new light on the architecture of the neuronal network which underlies the vestibular control of gaze and posture.

Postnatal development of thalamocortical projections upon striate and extrastriate visual cortical areas in the cat.

The development of visual thalamocortical projections was analyzed quantitatively by comparing, in cresyl violet-stained brain sections of early postnatal (10-17 days) and adult cats, the cell body dimensions and total cell packing density (CPD) of neuronal populations in different laminae (A, A1 and C) of the dorsal lateral geniculate (dLGN), medial interlaminar nucleus (MIN), and in lateral (LPl), intermediate (LPi) and medial (LPm) subdivisions of the lateral posterior complex. Following injections of different fluorescent tracers (FB, NY, EB, RITC) into cortical visual areas 17/18, posterior medial (PMLS) and posterior lateral (PLLS) lateral suprasylvian and anterior ectosylvian (AEV), the thalamic distribution and densities of retrogradely labeled neurons were analyzed. Projection CPDs and ratios of projection/total CPDs were determined and compared within the different thalamic components in the kitten and adult cat. A significant decrease in total cell packing density was observed in the various thalamic components of the adult cat, varying between 43% and 65%, and a marked increase in mean cell body diameter in the A, A1 and C laminae and MIN from kitten to adult (8.4+/-1.8 and 11.8+/-2.8 microm respectively) compared to the LP subnuclei (9.0+/-1.3 and 9.1+/-1.5 microm). The ratios of projection/total CPDs decreased significantly for projections upon areas 17/18 stemming from layers A and A1 (20 and 25%, respectively) and from LPi upon both PMLS (34%) and AEV (16%). Thalamocortical projections observed in the kitten from LPi upon areas 17/18 and from the A-laminae upon PMLS were absent in the adult cat. The data indicate that, in comparison to the lateral posterior nucleus, the maturation of neurons within the dLGN and MIN is incomplete with respect to cell body size during the early postnatal period. In addition, the developmental changes observed involve both reductions in the total number of thalamic neurons and a differential loss of cortical projections. The selective elimination of early cortical connections stemming from dorsal lateral geniculate laminae A and A1 and from the intermediate division of the lateral posterior nucleus may occur through a process of axon collateral withdrawal from the expanded cortical sites, thereby giving rise to the adult pattern.

Retinogeniculate projections following early cerebral hemispherectomy in the vervet monkey.

The effects of early, unilateral cerebral hemispherectomy on retinogeniculate projections were studied in the vervet monkey (Cercopithecus aethiops sabeus). Hemispherectomy eliminates all geniculocortical pathways and thus removes cortical factors involved in the survival of retinogeniculate projections. Complete removal of the left cerebral cortex was performed in two monkeys at 6 months and 8 months of age. After a post-surgical survival period of 50 months (SHG3) and 45 months (SHG4), both animals and a normal adult monkey received intraocular injections of [3H]proline (5 mCi) in the left eye and WGA-HRP (100 microliters, 5%) in the right eye. The dorsal lateral geniculate nucleuseuron (LGNd) ipsilateral to the hemispherectomy was on average 73% smaller than the contralateral LGNd. The magno- and parvocellular layers ipsilateral to the cortical ablation in both hemispherectomized subjects received a layered, eye-specific pattern of retinal input. This suggests that retinogeniculate projections could be sustained in the absence of geniculate relay cells.

Stereological evaluation of substantia nigra cell number in normal and hemispherectomized monkeys.

The assessment of the anatomical consequences of cortical lesions on subcortical visual relays is necessary to further understand residual visual capacities. Unbiased stereological techniques were used to evaluate cell numbers in the substantia nigra (SN), a structure involved in the control of saccadic eye movements. Cell numbers were very similar in the ipsi- and contralateral SN of the hemispherectomized animal (329,926 vs. 310,248). These numbers are close to what was observed in the normal monkey (300,130 and 320, 859). In one case, part of the striatum was lesioned in addition to the cerebral hemisphere. Noticeable effects were observed in the SN ipsilateral to the cortical lesion: volume was reduced by 30.5% while the number of neurons, compared to the contralateral side, dropped by 43.2% (186,644 vs. 328,757). These results suggest that due to its anatomical sparing following hemispherectomy the SN, in addition to other subcortical structures, is in a prime position to modulate the spared saccadic behaviors seen after massive cortical injuries.

Transneuronal degeneration of retinal ganglion cells in early hemispherectomized monkeys.

Transneuronal retrograde cell changes in the retina of the primate have been well documented after lesions to striate cortex, but little is known about the effects of hemispherectomy, a surgical procedure used in humans for the treatment of intractable epilepsy. In order to follow the time course of this degenerative process, we examined the retinae of six monkeys who underwent a total hemispherectomy at various postnatal ages with a survival period of 4 years. We demonstrate that transneuronal retrograde degeneration in the retina following hemispherectomy is inversely correlated with age at the time of the lesion. This degeneration is maximal when the lesion is induced within the first 4-6 months of life and less pronounced from 8 months to adulthood.

Retinal and cortical afferents to the dorsal lateral geniculate nucleus of the turtle, Emys orbicularis: a combined axonal tracing, glutamate, and GABA immunocytochemical electron microscopic study.

The dorsal lateral geniculate nucleus (GLd) of the turtle Emys orbicularis has been analyzed with axonal tracing methods and immunocytochemical techniques for glutamate (GLU) and gamma-aminobutyric acid (GABA), in combination with a quantitative study of the morphologic characteristics, distribution, and synaptology of the retinofugal and corticofugal terminals. Ultrastructural observations show that the vast majority of retinal terminals (Rtr) have clear, rounded synaptic vesicles and account for 16% of all profiles containing synaptic vesicles (PCSV). Their synaptic index (0.5) is low, and they make three times more contacts with the dendrites of projection cells than with those of interneurons. A low proportion of retinal terminals of a second category contain pleomorphic synaptic vesicles and are highly GABA immunoreactive. Axon terminals, unlabeled after intraocular injection of the tracer (SR), smaller in size and with more rounded clear synaptic vesicles, longer synaptic differentiations, and higher synaptic index than Rtr terminals, account for 19.7% of all PCSV and make asymmetric synaptic contacts with large dendrites of projection cells and less with the dendrites of interneurons. Some SR have been unambiguously identified as corticofugal terminals (Cg), either after cortical injection of the tracer (16%) or cortical lesion (37%). Retinal and Cg/SR terminals are spatially segregated within the GLd. Both are highly GLU immunoreactive, with the highest density of labeling over synaptic vesicles, suggesting that these terminals may use GLU as neurotransmitter. The level of GLU immunoreactivity of GABA-positive profiles is half that of Rtr and Cg/SR terminals and is greatest over mitochondria, possibly reflecting the 'metabolic' pool of GLU that serves as a precursor in the formation of GABA.

Size and distribution of retinal ganglion cells in the St. Kitts green monkey (Cercopithecus aethiops sabeus).

The topographical distribution of density and the soma size of retinal ganglion cells (RGCs) were studied in the St. Kitts green monkey (Cercopithecus aethiops sabeus). The total number of RGCs, estimated from light microscopic analysis of wholemounted and of transversely sectioned retinae, ranged between 1,183,721 and 1,273,715 (mean 1,228,646). These estimates are comparable to the number of optic nerve fibres (1,220,000) estimated from semithin sections. The topographic distribution of RGCs shows a strong centroperipheral gradient. The soma size distribution of RGCs in Nissl-stained flatmounts falls within a range of between 5.7 microm and 22.9 microm and is comparable to other primate species. Somata of RGCs were found to be generally smaller within the fovea than in peripheral regions. Ganglion cells, as reported for other diurnal primates, are nonuniformly distributed with a slight nasotemporal elongation of isodensity contours, and they exhibit nasotemporal asymmetry in the frequency distribution of soma size. The topography of the RGC distribution of this semiarboreal, ground-dwelling monkey is similar to what has been found in other diurnal Old World species.

Transneuronal retrograde degeneration of retinal ganglion cells following cerebral hemispherectomy in cats.

We have assessed the extent of transneuronal retrograde degeneration of retinal ganglion cells (RGCs) following the removal of a whole cerebral hemisphere at postnatal age 16 and 25 days. In the P16 animal, the nasal retina contralateral to the lesion suffered a 41% cell loss, whereas cell loss in the temporal retina ipsilateral to the lesion was 33%. Cell loss was greater in nasal retina and mainly included medium sized cells (200-600 microns2). In the P25 animal overall there was no evidence for ganglion cell loss.

Distribution of serotonin-immunoreactivity in the brain of the pigeon (Columba livia).

The distribution of serotonin (5-HT)-containing perikarya, fibers and terminals in the brain of the pigeon (Columba livia) was investigated, using immunohistochemical and immunofluorescence methods combined with retrograde axonal transport. Twenty-one different groups of 5-HT immunoreactive (IR) cells were identified, 2 of which were localized at the hypothalamic level (periventricular organ, infundibular recess) and 19 at the tegmental-mesencephalic and rhombencephalic levels. Ten of the cell groups were situated within the region of the midline from the isthmic to the posterior rhombencephalic level and constituted the raphe system (nucleus annularis, decussatio brachium conjunctivum, area ventralis, external border of the nucleus interpeduncularis, zona peri-nervus oculomotorius, zona perifasciculus longitudinalis medialis, zona inter-flm, nucleus linearis caudalis, nucleus raphe superior pars ventralis, nucleus raphe inferior). The 9 other cell populations belonged to the lateral group and extended from the posterior mesencephalic tegmentum to the caudal rhombencephalon [formatio reticularis mesencephali, nucleus ventrolateralis tegmenti, ectopic area (Ec) of the nucleus isthmo-opticus (NIO), nucleus subceruleus, nucleus ceruleus, nucleus reticularis pontis caudalis, nucleus vestibularis medialis, nucleus reticularis parvocellularis and nucleus reticularis magnocellularis]. Combining the retrograde axonal transport of rhodamine beta-isothiocyanate (RITC) after intraocular injection and immunohistofluorescence (fluoresceine isothiocyanate: FITC/5-HT) showed the centrifugal neurons (NIO, Ec) to be immunonegative. Serotonin-IR fibers and terminals were found to be very broadly distributed within the brain and were particularly prominent in several structures of the telencephalon (archistriatum pars dorsalis, nucleus taeniae, area parahippocampalis, septum), diencephalon (nuclei preopticus medianus, magnocellularis, nucleus geniculatus lateralis pars ventralis, nucleus triangularis, nucleus pretectalis), mesencephalon-rhombencephalon (superficial layers of the optic tectum, nucleus ectomamillaris, nucleus isthmo-opticus and in most of the cranial nerve nuclei). Comparing the present results with those of previous studies in birds suggests some major serotonin-containing pathways in the avian brain and clarifies the possible origin of the serotonin innervation of some parts of the brain. Moreover, comparing our results in birds with those obtained in other vertebrate species shows that the organization of the serotoninergic system in many regions of the avian brain is much like that found in reptiles and mammals.

Neural bases of residual vision in hemicorticectomized monkeys.

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.

A quantitative study of the effects of microphthalmia on the organisation of the primary visual system of the mouse.

The retinal projections of C57BL/Orl mice homozygous for the mutation microphthalmic-white (Miwh) were investigated by autoradiographic and HRP tracing techniques, and compared to those of heterozygous and normal mice of the same inbred strain; the anatomy of the eyes and optic nerves of the three genotypes were also examined. The eye of homozygous mutant mice is considerably reduced in size; the optic nerve shows a decrease in the number of myelinated fibres which is partially compensated by an increase in the proportion of unmyelinated axons. All primary visual centres that are labelled in normal mice receive retinal projections in mutant mice, although these centres are reduced in size in mutants. The reduction is most evident for those centres forming the thalamic relays of the retino-telencephalic pathway, to a lesser extent for the retino-collicular pathway and least of all for the retino-hypothalamic projections. These findings are compared to those obtained in naturally microphthalmic rodent species, and also to the effects of another mutation at the mi locus, maintained on a different background.

Fine structure of the dorsal lateral geniculate nucleus of the turtle, Emys orbicularis: a Golgi, combined HRP tracing and GABA immunocytochemical study.

The afferent and efferent cortical projections of the dorsal lateral geniculate nucleus (GLD) of adult specimens of the turtle Emys orbicularis were investigated after intraocular or intracortical injections of horseradish peroxidase (HRP), and the distribution of gamma aminobutyric acid (GABA) immunoreactivity in the nucleus was carried out by immunocytochemical techniques, both techniques being combined with light and electron microscopy. In addition, some specimens were prepared for double-labeling of HRP and GABA immunoreactivity, and additional samples impregnated by a rapid Golgi technique. On purely morphological grounds, four types of neurons can be distinguished by light microscopy: two types of large cells in the cell plate which project to the cortex, and two types of smaller cells in the neuropil and optic tract which do not. The small cells are consistently GABA-immunoreactive, while the former are, with extremely rare exceptions, immunonegative for GABA. The supposition that the small neurons of the neuropil are interneurons is supported by electron microscopic observations; these strongly GABA-immunoreactive cells have large plicated nuclei surrounded by a thin layer of cytoplasm poorly endowed with organelles. The dendrites of these cells may contain pleomorphic synaptic vesicles (DCSVs) and appear to be presynaptic to other dendritic profiles. These DCSVs are occasionally contacted by GABA-immunoreactive axon terminals, and more frequently by retinal terminals consistently immunonegative for GABA. The latter, frequently organized in glomeruli, also make synaptic contacts with immunonegative dendrites arising from corticopetal neurons of the cell plate. Two major categories of GABA-immunoreactive axon terminals can be distinguished, and we are led to the conclusion that one of these represents an intrinsic GABAergic innervation of the GLD, while the second is tentatively interpreted as an extrinsic source of GABA to the nucleus, possibly from ventral thalamic structures. The fine structure of the dorsal lateral geniculate nucleus of Emys orbicularis thus shows many similarities with that of mammals.

Ultrastructural study of the optic nerve in blind mole-rats (Spalacidae, Spalax).

The optic nerve in two species of subterranean mole-rats (Spalacidae) has been examined at the ultrastructural level. The axial length of the eye and the diameter of the optic nerve are 1.9 mm and 52.5 microns in Spalax leucodon, and 0.7 mm and 80.8 microns in Spalax ehrenbergi, respectively. An anti-glial fibrillary acidic protein postembedding procedure was used to distinguish glial cell processes from axons. In both species, the optic nerve is composed exclusively of unmyelinated axons and a spatial distribution gradient according to the size or the density of fibers is lacking. The optic nerve of S. leucodon contains 1790 fibers ranging in diameter from 0.07-2.30 microns (mean = 0.57 microns), whereas in S. ehrenbergi, only 928 fibers, with diameters of 0.04-1.77 microns (mean = 0.53 microns) are observed. In S. ehrenbergi, a higher proportion of glial tissue is present and the fascicular organization of optic fibers is less obvious. Distribution gradients according to size frequency or density of fibers in the optic nerve are absent in both species. Comparison with other mammals suggests that although ocular regression in microphthalmic species is correlated with a significant decrease in the total number of optic fibers and the relative proportion of myelinated fibers, no difference in the absolute size range of unmyelinated axons is observed. The total absence of myelinated fibers in Spalax may be related to the subcutaneous location of the eyes.(ABSTRACT TRUNCATED AT 250 WORDS)

Distribution of GABA immunoreactivity in the retino-recipient layer of the viper optic tectum. A light and electron microscope quantitative study.

The distribution of GABA-immunoreactivity was investigated in the principal retino-recipient layer of the optic tectum in the snake Vipera aspis. This layer, the stratum griseum et fibrosum superficiale, contained an important proportion (approximately 50%) of small GABA-immunoreactive interneurons, characterized by a voluminous invaginated nucleus surrounded by a thin rim of cytoplasm poor in organelles and occasionally showing pleiomorphic synaptic vesicles, which could also be observed in some of the dendrites that contained synaptic vesicles. In the neuropile, the GABA-immunoreactive profiles containing synaptic vesicles could be subdivided into dendrites containing synaptic vesicles and axon terminals with pleiomorphic synaptic vesicles. The dendrites containing synaptic vesicles (23.4% of all profiles containing synaptic vesicles) were postsynaptic either to optic terminals (39.2%), GABA-immunoreactive axon terminals with pleiomorphic synaptic vesicles (48.2%) or to immunonegative (S1) boutons with round synaptic vesicles (12.6%). These dendrites were presynaptic to GABA-immunoreactive (18%) neurons or immunonegative (82%) neurons. The axon terminals with pleiomorphic synaptic vesicles, which represented 47.4% of all profiles, were predominantly (99%) GABA-immunoreactive and four types could be distinguished according to cytological criteria. These axon terminals made synaptic contacts for the most part (78%) with immunonegative profiles, and more rarely (22%) with immunoreactive neurons. These data are compared to those previously obtained in the homologous structure of other vertebrate species, birds and mammals in particular.

Photic induction of Fos immunoreactivity in the suprachiasmatic nuclei of the blind mole rat (Spalax ehrenbergi).

Exposure to light during the dark phase entrains c-fos expression in cells of the suprachiasmatic nuclei in the blind mole rat (Spalax ehrenbergi). Labeled cells are mainly located in the ventral region of the nucleus where retinal afferents terminate. Despite severe atrophy of the eye and regression of thalamic and tectal structures, the retinal pathways and central mechanisms involved in photoperiodic perception and circadian regulation appear to be similar to those in other rodents.

Visual system of the fossorial mole-lemmings, Ellobius talpinus and Ellobius lutescens.

Ocular regression in subterranean species has been shown to be associated with a number of alterations in the retina and in retinal pathways. In order to examine the consequences of eye reduction, the visual system was studied in two species of the murine genus, Ellobius, a specialized fossorial rodent. The axial length of the eye is only 2.2 mm in E. lutescens and 2.9 mm in E. talpinus. The mean soma size of ganglion cells in Nissl-stained flatmounts is approximately 10 microns in E. lutescens and 12 microns in E. talpinus. The soma size distribution in both species appears unimodal and falls within a range of 6-17 microns in diameter. The topographic distribution of ganglion cells shows a weak centroperipheral gradient, and an area centralis cannot be distinguished. The total number of neurons in the ganglion cell layer in Nissl-stained flat mounts is 12,000 in E. lutescens and 28,500 in E. talpinus and, following injection of retrograde tracers in the superior colliculus, is, respectively, 3,600 and 20,000. Based on the axial length and maximum ganglion cell density, the calculated retinal magnification factor (20-26 microns/degree) and spatial resolution (0.4-0.9 cycles/degree) of these minute eyes are extremely reduced. Retinofugal projections, demonstrated by autoradiography and horseradish peroxidase histochemistry, are similar to those in other rodents. The superior colliculus is well developed and receives a predominantly contralateral projection. Ganglion cells projecting to the contralateral colliculus are distributed over the entire retina, while cells that project ipsilaterally are restricted to the ventrotemporal region. The dorsal lateral geniculate nucleus has clearly defined binocular and monocular segments, including a partial segregation of regions receiving ipsilateral or contralateral retinal innervation. In addition, a localized region of label is observed medial to the geniculate nucleus. The retina also sends a bilateral projection to the suprachiasmatic nucleus; the intergeniculate leaflet; the pretectum; and the medial, lateral, and dorsal terminal nuclei of the accessory optic system. Sparse retinal projections were also seen in the bed nucleus of the stria terminalis, the anterior thalamus, and the inferior colliculus. A substantial retinal projection is observed in the basal telencephalon, including the cortical amygdaloid region, the diagonal band of Broca, the olfactory tubercle, and the piriform cortex. The results suggest that the morphological constraints of reduced eye size are reflected in the retina by a generally homogeneous organization but that central visual projections are not substantially modified as in some more specialized, strictly subterranean rodents.