Preoptic FMRF-amide-like immunoreactive projections to the retina in the lamprey (Lampetra fluviatilis).

A centrifugal visual system showing FMRF-amide-like immunoreactivity has been demonstrated in Lampetra fluviatilis by using immunocytochemical and hodological techniques. From 50 to 60 immunoreactive neurons, labelled after contralateral intraocular injection of rhodamine beta-isothiocyanate, form a small, clearly defined, nucleus in the lateral neural plate of the magnocellular preoptic nucleus. These cells give rise to immunoreactive axons which have been observed at the base of the nucleus, in the optic chiasma and in the optic nerve, to project into the intermediate plexiform layer of the retina, which separates the layer of internal horizontal cells from the layer of external horizontal cells. This FMRF-amide-like immunoreactive centrifugal visual system is compared to that described in Gnathostomes.

Synaptic circuitry in the retinorecipient layers of the optic tectum of the lamprey (Lampetra fluviatilis). A combined hodological, GABA and glutamate immunocytochemical study.

The ultrastructure of the retinorecipient layers of the lamprey optic tectum was analysed using tract tracing techniques combined with GABA and glutamate immunocytochemistry. Two types of neurons were identified; a population of large GABA-immunonegative cells, and a population of smaller, highly GABA-immunoreactive interneurons, some of whose dendrites contain synaptic vesicles (DCSV). Five types of axon terminals were identified and divided into two major categories. The first of these are GABA-immunonegative, highly glutamate-immunoreactive, contain round synaptic vesicles, make asymmetrical synaptic contacts, and can in turn be divided into AT1 and AT2 terminals. The AT1 terminals are those of the retinotectal projection. The origin of the nonretinal AT2 terminals could not be determined. AT1 and AT2 terminals establish synaptic contacts with DCSV, with dendrites of the retinopetal neurons (DRN), and with conventional dendritic (D) profiles. The terminals of the second category are GABA-immunoreactive and can similarly be divided into AT3 and AT4 terminals. The AT3 terminals contain pleiomorphic synaptic vesicles and make symmetrical synaptic contacts for the most part with glutamate-immunoreactive D profiles. The AT4 terminals contain rounded synaptic vesicles and make asymmetrical synaptic contacts with DRN, with DCSV, and with D profiles. A fifth, rarely observed category of terminals (AT5) contain both clear synaptic vesicles and a large number of dense-core vesicles. Synaptic triads involving AT1, AT2 or AT4 terminals are rare. Our findings are compared to these of previous studies of the fine structure and immunochemical properties of the retinorecipient layers of the optic tectum or superior colliculus of Gnathostomes.

Fine structure of the visual dorsolateral anterior thalamic nucleus of the pigeon (Columba livia): a hodological and GABA-immunocytochemical study.

The ultrastructure of the lateroventral subcomponent of the visual dorsolateral anterior thalamic nucleus of the pigeon (DLLv) was analyzed using hodological techniques and GABA-immunocytochemistry. Two types of GABA-immunonegative hyperpalliopetal neurons and a single type of strongly GABA-immunoreactive (-ir) interneuron were identified, the latter displaying long dendrites with some containing synaptic vesicles (DCSV). Ten types of axon terminal were identified and divided into two categories. The first, GABA-immunonegative and making asymmetrical synaptic contact, contain round (RT1, RT2, RT3) or pleiomorphic synaptic and many dense-core vesicles (DCT). RT1 terminals are retinothalamic and RT2 terminals hyperpalliothalamic; both mainly contact dendrites of projection neurons (72% and 78% respectively), less frequently dendrites of interneurons and sometimes DCSV; RT1 terminals are rarely involved in synaptic triads. The second category are consistently GABA-immunopositive. Four types (PT1-4), distinguished by their pleiomorphic synaptic vesicles, make symmetrical synaptic contact essentially with dendrites of projection neurons, more rarely on dendrites of interneurons (PT2). PT1 terminals are very probably those of interneurons, whereas the rare PT4 terminals are of retinal origin. A fifth type (RgT) contains round synaptic vesicles and makes asymmetrical synaptic contact with dendrites of projection neurons and interneurons. PT2 and RgT terminals occasionally contact DCSV of interneurons, which are sometimes involved in synaptic triads. Two final subcategories (DCgT1-2) contain many dense-core vesicles. Our findings are compared with those of previous studies concerning the fine structure and neurochemical properties of the GLd of reptiles and mammals, with special reference to the origin of the extraretinal and extracortical projections to this structure.

Distribution of ganglion cells in the pigeon retina labeled via retrograde transneuronal transport of the fluorescent dye rhodamine beta-isothiocyanate from the telencephalic visual Wulst.

The distribution of retinal ganglion cells (RGCs) providing input to the thalamofugal visual system in the pigeon was studied with an anatomical transneuronal transport technique using the fluorescent dye rhodamine beta-isothiocyanate (RITC). Unilateral injections of RITC made into the telencephalic visual Wulst resulted in the retrograde (1) first-order labeling (FOL) of dorsal thalamic (n. dorsolateralis anterior and n. superficialis parvocellularis: SPC) and brainstem somata as well as (2) second-order labeling of other cell populations within the brain and of retinal ganglion cells in both eyes obtained after transneuronal transfer of the tracer from neurons labeled directly via FOL. The mapping and counting of labeled RGCs in retinal flat-mounts showed that they were mainly distributed within the nasal portion of the retinal yellow field (YF) and that their total numbers were consistently higher (averaging 57%) in the eye contralateral to the tracer injection. Labeled RGCs in the retinal red field (RF) represented 13.4% and 12.0% of total labeled cells in the ipsilateral and contralateral eye, respectively. Moreover, the average densities of labeled cells/mm(2) in the RF and YF were respectively 8.4 and 42.8 (ipsilateral) and 17.9 and 54.0 (contralateral). The preferential distribution of labeled RGCs within the nasal YF supports the notion that the thalamofugal visual system in the lateral-eyed pigeon is mainly concerned with viewing in the lateral visual field. Conversely, the relatively low numbers of labeled RGCs observed within the specialized RF indicate that, unlike the case in frontal-eyed bird species and mammals, this system does not appear to be involved in binocular visual processing.

GnRH-immunoreactive centrifugal visual fibers in the Nile crocodile (Crocodylus niloticus).

Thin varicose centrifugal visual fibers, between 30-45 in number and displaying cGnRH-I immunoreactivity, were identified in Crocodylus niloticus. Approximately 80% of these fibers were also FMRF-amide-like immunoreactive. The cGnRH-I fibers extended from the preoptic region to the retina where they appeared to terminate in the external portion of the inner plexiform layer. The location of their neurons of origin could not be determined precisely following the intraocular injection of the retrograde axonal tracer RITC. Nevertheless, the presence of cGnRH-I-immunoreactive neurons exclusively within the complex comprising the terminal nerve and the septo-preoptic region, and of several retinopetal fibers labelled retrogradely with the axonal tracer at the septo-preoptic junction, indicates that the cGnRH-immunoreactive centrifugal visual system originates from within this complex.

Presumptive FMRF-amide-like immunoreactive retinopetal fibres in Crocodylus niloticus.

A small contingent of 30-50 of centrifugal visual fibres, showing FMRF-amide-like immunoreactivity, has been identified in C. niloticus; these fibres extend from the chiasmatic region into the retina. They do not take the marginal optic tract, but pass medially to the chiasmatic fascicles, from the preoptic region. The cells of origin of these fibres have not been identified. However, none of the retinopetal neurons of the brainstem [M. Medina, J. Reperant, R. Ward, D. Miceli, Centrifugal visual system of Crocodylus niloticus : a hodological, histochemical and immunocytochemical study, J. Comp. Neurol. 468 (2004) 65-85], labelled by retrograde transport of rhodamine beta-isothiocyanate after intraocular injection of this tracer, show FMRF-amide-like immunoreactivity; neither are any of the FMRF-amide-like immunopositive neurons in the crocodile brain, particularly those of the complex involving the terminal nerve and the septo-preoptic region, labelled by rhodamine after its intraocular injection.

Centrifugal visual system of Crocodylus niloticus: a hodological, histochemical, and immunocytochemical study.

The retinopetal neurons of Crocodylus niloticus were visualized by retrograde transport of rhodamine beta-isothiocyanate or Fast Blue administered by intraocular injection. Approximately 6,000 in number, these neurons are distributed in seven regions extending from the mesencephalic tegmentum to the rostral rhombencephalon, approximately 70% being located contralaterally to the injected eye. None of the centrifugal neurons projects to both retinae. The retinopetal neurons are located in rostrocaudal sequence in seven regions: the formatio reticularis lateralis mesencephali, the substantia nigra, the griseum centralis tectalis, the nucleus subcoeruleus dorsalis, the nucleus isthmi parvocellularis, the locus coeruleus, and the commissura nervi trochlearis. The greatest number of cells (approximately 93%) is found in the nucleus subcoeruleus dorsalis. The majority are multipolar or bipolar in shape and resemble the ectopic centrifugal visual neurons of birds, although a small number of monopolar neurons resembling those of the avian isthmo-optic nucleus may also be observed. A few retinopetal neurons in the griseum centralis tectalis were tyrosine hydroxylase (TH) immunoreactive. Moreover, in the nuclei subcoeruleus dorsalis and isthmi parvocellularis, both ipsilaterally and contralaterally, approximately one retinopetal neuron in three (35%) was immunoreactive to nitric oxide synthase (NOS), and a slightly higher proportion (38%) of retinopetal neurons were immunoreactive for choline acetyltransferase (ChAT). Some of them contained colocalized ChAT and NOS/reduced nicotinamide adenine dinucleotide phosphate-diaphorase. Fibers immunoreactive to TH, serotonin (5-HT), neuropeptide Y (NPY), or Phe-Met-Arg-Phe-amide (FMRF-amide) were frequently observed to make intimate contact with rhodamine-labeled retinopetal neurons. These findings are discussed in relation to previous results obtained in other reptilian species and in birds.

Serotonin immunoreactivity in the retinal projecting isthmo-optic nucleus and evidence of brainstem raphe connections in the pigeon.

Serotonin (5-HT) immunoreactive (-ir) profiles within the isthmo-optic nucleus (ION) of the centrifugal visual system (CVS) were studied in the pigeon using light microscopic immunohistofluorescent and electron microscopic immunocytochemical pre-embedding techniques. The brainstem origin of the 5-HT input upon the ION was determined by combining 5-HT immunohistofluorescence (FITC) and retrograde transneuronal tracing after intraocular injection of Rhodamine beta-isothiocyanate. The light microscopic results showed that 5-HT endings were mainly localised within the neuropillar zones of the ventral ION. The 5-HT-ir cell bodies, belonging to a lateral extension of the dorsal raphe system, were observed within the same region as the centrifugal ectopic neurons (EN) underlying the ION and some displayed dendritic processes which penetrated the nucleus. Double-labeled neurons, representing 5-HT-ir afferents to the ION, were identified only within the n. linearis caudalis region of the ventral raphe. The electron microscopic results confirmed the presence of 5-HT-ir dendritic processes within the ventral part of the nucleus and showed that they were contacted by axon terminals belonging to intrinsic interneurons. The functional organisation of the ION and the possible contribution of serotonergic raphe afferents and efferents are discussed in relation to present hypotheses linking the avian CVS to mechanisms of visual attention.

Radio-ulnar deviation of the primate carpus: an X-ray study.

The lack of contact between the ulna and first row of carpals characterizes the wrist morphology of hominoids as compared to other primates. This distinctive feature--generally interpreted as a significant synapomorphy between humans and other hominoids--was a priori considered to be an indication of an increased capacity for ulnar deviation, allowing a greater diversity of hand movements. This X-ray study aimed to test this hypothesis by comparing the shifting of the carpals throughout radioulnar deviation in eight extant genera endowed with ulno-carpal contact or lacking it. The results show that the amplitude of ulnar deviation is not directly correlated with the presence or absence of an ulno-carpal contact: most ulnar deviation takes place at the antebrachio-carpal joint in those primates that lack an ulno-carpal contact (hominoids), instead of at the mid-carpal joint in primates whose ulna articulates with the triquetral (cercopithecoids, platyrrhines, most strepsirrhines). Analysis of the X-ray suggests that the loss of ulno-carpal contact improved the ability to supinate at the radio-ulnar joints, with correlated unfitness for palmigrade/semidigitigrade walking. This evolutive change, associated with a considerable reduction of the share of body weight carried on the forelimbs, likely cleared the way for either knuckle walking or bipedalism and handiness.

Effects of fixation and preservation conditions on immunohistochemical profiles of the skeletal muscle fibers in Japanese macaques.

Effects of fixation and preservation conditions of muscle tissues on immunohistochemical profiles are investigated. Samples of the hind limb and epaxial muscles were removed from 4 adult female Japanese macaques (Macaca fuscata) fixated with 10% formalin and preserved in the same solution under different conditions for 6 months to 4 years and 6 months. Sections were stained with indirect immunofluorescence and avidin-biotin peroxidase complex methods using an antibody against fast myosin (Mouse Monoclonal Anti-skeletal Myosin-Fast, clone MY-32, Sigma) as a primary antibody. Clear responses to the antibody were demonstrated in the samples from the specimens fixated by injection or immersion with 10% formalin and preserved in the same solution for 6 months to 1 year and 6 months. Distribution patterns of the fibers reacting to the antibody coincided with that of the fast twitch fibers determined using enzyme-histochemical techniques in these samples. Clear responses to the antibody were not demonstrated in the samples from the specimen repeatedly rinsed in water for gross anatomical dissections during the preservation period. The results of this study warrant applications of immunohistochemical techniques to the study of fiber type composition in muscle samples from specimens fixated with formalin and preserved in the same solution for a long term.