Inhibition by puromycin of transneuronal transport in the mouse accessory olfactory bulb

Biogenesis of presynaptic terminal proteins

The delivery of proteins to the presynaptic terminals of guinea pig retinal ganglion cells by two of the major components of axonal transport, and the subsequent persistence and turnover of those proteins were examined in this study. Ganglion cell proteins were radiolabeled by intravitreal injection of radiolabeled amino acids and radioactive axonally transported proteins were analyzed in synaptosomes prepared from the superior colliculi. This procedure allowed examination of presynaptic components of ganglion cell synapses without having to compensate for postsynaptic or other unidentified contaminants. Each of the two major axonal transport components supplies a large number of proteins to the presynaptic terminal, in relative quantities similar although not identical to those seen in the axon. Proteins conveyed by the fast component of axonal transport reached the terminals by 3 h after intraocular injection, peaked by 24 h, and were largely undetectable by 15 days. Slow component b proteins reached the terminals by 12 days, peaked around 21 days, and persisted up to 63 days in the terminals. Proteins in both components demonstrated differential turnover relative to cotransported proteins once they reached the terminals. Differential turnover may account for change in relative concentration of a particular protein required to meet new functional demands on that protein once it enters the terminal.

A comparative radioautographic study of the bidirectional axonal and transcellular transport of different amino acids and sugars in the lamprey visual system

Following recent radioautographic evidence for the bidirectional axonal transport of [3H]proline from the eye of Lampetra fluviatilis, the present study examined the anterograde and/or retrograde labeling properties of 11 other amino acids and two sugars after intraocular injections of these tritiated substances in the lamprey. The intraocular injections of aspartic acid, glutamic acid, gamma-aminobutyric acid, arginine, phenylalanine, fucose and acetyl glucosamine resulted in a weak labeling of the primary visual centers: there was no evidence of either the transcellular transport of these tracers or the retrograde labeling of the retinopetal neurons. The primary visual system was found to be heavily labeled 24 h after eye injections of alanine, leucine, glycine, lysine, serine and valine. Among the latter only glycine produced a retrograde somatic labeling of retinopetal neurons. With a longer survival period (7 days), a specific transneuronal labeling was also noted after glycine injections. The significance of the differential uptake and transport of these different tracers in the lamprey visual system and possible mechanisms involved in the axonal retrograde transport of [3H]glycine and [3H]proline in the centrifugal pathways are discussed.

Experimental studies on the olfactory marker protein. I. Presence of the olfactory marker protein in tufted and mitral cells

Partial, unilateral olfactory nerve section was performed in mice, and the behavior of the olfactory marker protein (OMP) studied, after this experimental manipulation, with the peroxidase--antiperoxidase method. The protein, which in normal mice is present only in mature olfactory sensory neurons, after unilateral lesion of the fila olfactoria was observed in mitral and tufted cells of both olfactory bulbs. Positive elements, present at 5 days postoperative, increased in number up to 30 days and some could still be detected at 60 days. The functional implications of this finding are briefly discussed.

Electron microscope autoradiographic evidence for specific transneuronal transport in the mouse accessory olfactory bulb

The distribution of radioactive material was examined autoradiographically 8 h after application of [3H] proline to the vomeronasal organ in mice. Labelled material was transported along the axons of the vomeronasal nerves to their terminals in the glomerular layer of the accessory olfactory bulb (AOB). A lesser but consistent amount of radioactivity was found in the external plexiform layer (EPL) of the AOB. Electron microscopic autoradiography was used to determine which of the components of the EPL contained this labelled material. The method of proportional grain counts showed that the highest concentration of silver grains lay over the mitral cell dendrites, which are the elements immediately postsynaptic to the vomeronasal nerve axons. However, a fairly high proportion of grains also lay over the peripheral processes of granule cells. By application of a method of 'crossfire analysis' (which is explained in detail) it was possible to show that the observed grain distribution is best explained by the assumption that the radioactive material is confined to mitral cells, and the labelling over granule cell processes is due to crossfire from these sources. Im one animal at 5 days after [3H]proline administration label was found to have extended from mitral cells to granule cells, suggesting that the transsynaptically transported radioactive material, which was confined to the mitral cells at 8 h, may have become further redistributed at longer survivals. In a control experiment, [3H]proline was applied directly to the surface of the AOB. This gave rise to a completely different distribution of radioactivity in the EPL: radioactive material was present in all tissue components.