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F Scalia

Publications and source records attributed to F Scalia.

At least 37 records · Page 2Linked to original sources
PubMed1985

The morphology of growth cones of regenerating optic nerve axons.

The morphology of growth cones of regenerating optic nerve axons was examined by light and electron microscopy in adult frogs (Rana pipiens), using a horseradish peroxidase (HRP) fiber-filling method, during early and later phases of regeneration. Optic nerve regeneration was initiated unilaterally by crushing the optic nerve in mid-orbit. Fiber filling was accomplished by severing the affected nerve closer to the eye 24-48 hrs. prior to sacrifice and applying HRP to the central stump. Regenerating axons and their growth cones were observed in the optic nerves, chiasma, tract, pretectal neuropil, and optic tectum. Growth cones of normal-appearing axons varied in shape and size. Flattened, foliate growth cones similar to those commonly described in vitro were observed in the pretectal neuropil and optic tectum. Other growth cones having vermiform, lanceolate, spatulate, and bulbous forms were observed throughout the optic pathway at all stages examined, although the longer (up to 70 micrograms) wormlike structures appeared only in the optic tract during the early period of outgrowth. Nearly complete serial-section reconstructions were obtained for two growth cones in the contralateral optic tectum at 8 wks. regeneration time. One was thinly flattened (to 30-50 nm in places) and extended broadly (8 micrograms in diameter) in contact with a neuronal perikaryon. The other formed a hood over the blind end of a severed, nonregenerating myelinated axon, which was normal-appearing except at its end within the confines of the growth cone. Morphological variation among the growth cones is discussed in relation to other descriptive in vivo studies and views concerning growth cone motility.

Animals↗
PubMed1983

The anti-retinotopic organization of the frog's optic nerve.

In Rana pipiens, axons marked by the intraretinal application of horseradish peroxidase (HRP) were traced within the optic nerve and tract. Axons arising from dorsal regions of the peripheral retina collect at the dorsal end of the elongate optic disc and form a compact group on the dorsal side of the nerve. Correspondingly, ventral axons locate on the ventral side of the nerve. However, nasal and temporal peripheral axons share passage on both the nasal and temporal sides of the nerve, segregating only upon reaching the brain. The ultimate sorting of nasal and temporal axons in the brain, following their intermingling in the optic nerve, supports the operation of a chemoaffinity mechanism, rather than passive mechanical guidance.

Afferent Pathways↗
PubMed1981

Long-term survival of centrally projecting axons in the optic nerve of the frog following destruction of the retina.

A significant number of unmyelinated axons and their synaptic endings in the frog, Rana pipiens, were found to retain a normal morphology long after separation from their cell bodies. At the end of various survival periods following unilateral removal of the retina, horseradish peroxidase (HRP) was administered to the optic nerve stump by a fiber-filling method. In frogs maintained at 20 degrees C, unmyelinated optic nerve axons conducted HRP from the site of application in the orbit to layers A, C, and E of the contralateral optic tectum, even though their retinas had been removed up to 69 days earlier. Such fiber-filling was absent beyond 19 days in other frogs surviving at 35 degrees C. No labeled fibers were continuous with any intracerebral neurons. The HRP was always localized intraaxonally, and the marked axons and terminals were ultrastructurally normal. Counts of surviving axons from electron micrographs of the optic nerves showed that, at 20 degrees C, more than half of the normal complement of unmyelinated axons disappeared in the first 10 days. All the myelinated axons degenerated during the first 6 weeks survival. However, approximately 55,000 normal-appearing unmyelinated axons (12% of the unmyelinated fiber population) persisted in the optic nerve at 10 weeks following removal of the retina. The survival rate was lower at 35 degrees C. In other frogs, one eye was injected with 3H-leucine to initiate axonal transport into the retinal ganglion cell axons. That eye was removed 48 hours later. Autoradiographic analysis of brain sections of frog surviving an additional 31 to 61 days at 20 degrees C showed strong labeling of the optic tract and layers A, C, and E of the contralateral optic tectum. The absence of displaced ganglion cells that might exist within the optic nerve was verified by other observations. It is hypothesized that the potential shown by frog optic axons for long-term survival in the absence of the cell-body expresses a general property of vertebrate (and invertebrate) axons, rather than a special property of the frog optic nerve.

Animals↗
PubMed1979

Topographic organization of the projections of the retina to the pretectal region in the rat.

The pattern of projection of the retina to the pretectal region and its retinotopic organization were investigated in the rat by autoradiographic and silver impregnation techniques for axonal pathways. The endings of retinal axons form three terminal fields in the pretectum in: 1, olivary pretectal nucleus (PO), bilaterally; 2, posterior pretectal nucleus (PP), bilaterally; and 3, nucleus of the optic tract (NTO), contralaterally. The following retinotopic pattern was observed in rats surviving peripheral retinal lesions and injections of 3H-proline in the same eye, when the positions occupied by terminal degeneration in Fink-Heimer stained sections were matched with the corresponding areas deficient in radiolabel in adjacent autoradiographic sections showing the surviving parts of the terminal fields. The nasal periphery of the retina maps along the adjoining edges of PO and PP, both of which extend obliquely, in a posterolateral direction, through the entire extent of the pretectum. Both nuclei map the line of representation of the anterior midline (in the temporal retina) along their opposite edges (anterolaterally, in PO; posteromedially, in PP). This mirror-image symmetry is completed by the representation of the ventral peripheral retina separately in the rostral poles and the dorsal peripheral retina separately in the caudal poles of both nuclei. The map in NTO is vertically oriented, with the temporal retina, dorsally, the nasal retina, ventrally, the ventral retina, rostrally, and the dorsal retina caudally represented. The binocular area of the terminal field in PO is subdivided by a terminal-free zone into two parts that may process separately events in the central and lateral visual field.

Animals↗
PubMed1975

The differential projections of the olfactory bulb and accessory olfactory bulb in mammals.

Three species were studied, the rabbit, opossum and rat. Lesions of the main olfactory bulb caused terminal degeneration, assayed by the Fink-Heimer method, to occur in the ipsilateral olfactory tubercle, prepyriform cortex (including its periamygdaloid part), ventrolateral entorhinal area, and in anterior and posterolateral divisions of the cortical amygdaloid nucleus. The various parts of the ipsilateral anterior olfactory nucleus and the rostroventral end of the anterior continuation of the hippocampus (hippocampal rudiment) also received this projection. Lesions of the accessory olfactory bulb, which receives its sensory input from the vomeronasal (Jacobson's) organ, caused terminal degeneration to occur in the medial amygdaloid nucleus and in a posteromedial part of the cortical amygdaloid nucleus. This projection was conveyed by an accessory olfactory tract, which is accompanied in part of its course by a small nucleus, the bed nucleus of the accessory olfactory tract. The accessory olfactory tract is initially a part of the lateral olfactory tract but becomes increasingly indivuated at more posterior levels. It parts company with the lateral olfactory tract at the rostral end of the amygdaloid region, and, in addition to distributing to the medio-cortical amygdaloid region, it enters the stria terminalis to terminate in the bed nucleus of the stria terminalis in a small region bearing cytoarchitectonic resemblance to the medial amygdaloid nucleus. The topographic segregation of the areas of termination of the olfactory and accessory olfactory (vomeronasal) projections is suggestive of a functional dichotomy in the organization of the olfactory system...

Amygdala↗
PubMed1970

Amygdaloid nucleus: new afferent input from the vomeronasal organ.

Terminal degeneration stained by the Fink-Heimer technique was found in the medial and cortical amygdaloid nuclei in a discrete zone after lesions were inflicted in the accessory olfactory bulb but not after lesions were made in the main olfactory bulb in the rabbit. Since the accessory olfactory bulb receives the endings of the vomeronasal nerve, the mediocortical complex of the amygdala is the central projection area for the vomeronasal sensory organ. The vomeronasal organ is seen as having new potential significance in sexual and feeding behavior because the cortical amygdaloid nucleus projects to the anterior, medial hypothalamus and the ventromedial nucleus.

Amygdala↗