W. B. Spatz

Superior olivary and extraolivary origin of centrifugal innervation of the cochlea in guinea pig. A horseradish peroxidase study

Abstract The superior olivary orgin of crossed and uncrossed centrifugal fibers to the cochlea which has recently been questioned was confirmed in the guinea pig by use of the retrograde axonal transport of horseradish peroxidase (HRP) administered to the cochlea. Beyond this, evidence is presented for the existence of crossed and uncrossed extraolivary centrifugal fibers which take their origin from neurons of the ventral nucleus of the lateral lemniscus (VLL) and terminate in the cochlea.

Electron microscopical identification of 3,3',5,5'-tetramethylbenzidine-reacted horseradish peroxidase after retrograde axoplasmic transport

Tetramethylbenzidine (TMB) histochemistry for retrogradely transported horseradish peroxidase (HRP) has been successfully applied in electron microscopical preparations in the guinea pig visual cortex. In ultrathin sections, the TMB--HRP reaction product appears as an accumulation of typical electron-dense crystals. These crystals were identified in the cytoplasm of labeled cells in the proximal portions of the dendrites, and in myelinated axons. It is demonstrated that the TMB--HRP method is well suitable to analyze the ultrastructure of labeled cells and their synaptology.

Origin of centrifugal fibers to the labyrinth in the frog (Rana esculenta) : a study with the fluorescent retrograde neuronal tracer Fast blue

After injecting a solution of a fluorescent retrograde neuronal tracer (Fast blue, Diamidino compound 253/50) into the perilymphatic space of the frog labyrinth (Rana esculenta), labeled cells were found in the ventral and dorsal nuclei of the VIIIth nerve and in the nucleus reticularis medius. We consider these labeled cells to be the origin of the efferent innervation of the frog labyrinth. No evidence was found for the existence of a direct cerebello-labyrinthine connection.

Area 17 of anthropoid primates does participate in visual callosal connections

Injections of retrograde tracers into the border region of areas 17 and 18 in Callithrix and Macaca labeled a small group of neurons in the border region of contralateral area 17, in addition to cells in contralateral area 18. It is concluded that area 17 of anthropoid primates sends (and receives) fibers through the corpus callosum.

Unipolar brush cells in the human cochlear nuclei identified by their expression of a metabotropic glutamate receptor (mGluR2/3)

Unipolar brush cells (UBCs) reside in the mammalian vestibulo-cerebellum and the ventral (VCN) and, particularly, dorsal cochlear nuclei (DCN). Human cerebellar UBCs are numerous too, but auditory UBCs have escaped detection. The human DCN, considered a degenerated structure, lost lamination and possibly neurons common in lower mammals, like UBCs. We searched for human auditory UBCs probing their immunoreactivity against the calcium-binding protein calretinin (CR-IR), and a metabotropic glutamate receptor (mGluR2/3-IR). We found: UBCs are constituents of the human DCN and VCN, though in small numbers. These auditory UBCs are not CR-IR, in contrast to human cerebellar UBCs and cerebellar and auditory UBCs in non-primate mammals, but display mGluR2/3-IR. The human DCN, thus, appears more complete than previously thought. This may be of interest regarding auditory brainstem electrode implantations in deaf patients.

Reduced fading of Fast Blue fluorescence in the brain of the guinea-pig by treatment with sodium-nitroprusside.

Fading of the emitted fluorescent light of the retrogradely transported neuronal tracer Fast Blue is reduced considerably by treating sections for 20 min with sodium-nitroprusside (0.4% in 0.1 M acetate buffer; pH 3.3) and mounting sections from acetate buffer. Mounting from phosphate buffer abolishes the antifading effect of sodium-nitroprusside.

Unipolar brush cells in the cochlear nuclei of a primate (Callithrix jacchus)

Unipolar brush cells (UBCs) have been recognized in the cerebella of many species including primates. They have also been identified in the cochlear nuclei (CN) of many mammals, however, not in any primate. Our immunohistochemical study in the marmoset demonstrates the presence of abundant calretinin immunoreactive (CR-ir) UBCs in the cerebellum, as in other mammals. In the marmoset CN, in contrast, CR-ir UBCs could hardly be identified. The reverse pattern was evident in sections immunostained for a metabotropic glutamate receptor (mGluR2/3-IR): beautifully stained UBCs were present in the CN, but the stained cerebellar structures were difficult to identify as UBCs. The present findings indicate that UBCs are present in the CN of primates, as in other mammals, but that cerebellar and CN UBCs might differ in their molecular equipment in primates.

Location of efferent neurons to the labyrinth of the green tree frog (Hyla cinerea)

ZusammenfassungDer Ursprung der labyrinthären Efferenz wurde beim amerikanischen Laubfrosch (Hyla cinerea) mit Hilfe von Meerrettich-Peroxidase, die an den Nervus octavus appliziert wurde, identifiziert. Markierte Zellen ließen sich lediglich im Nucleus reticularis medius ipsilateral zur Injektion nachweisen. Die primären Kerne des Nervus octavus waren durch anterograden Transport von Merrettich-Peroxidase markiert, enthielten jedoch keine Ursprungszellen.SummaryThe origin of centrifugal fibers to the labyrinth was determined by application of horseradish peroxidase to the severed octavus nerve of the green tree frog (Hyla cinerea). Labeled neurons were found exclusively in the nucleus reticularis medius of the reticular formation ipsilateral to the injection site. In particular, no retrogradely labeled neurons were found in the octavus nuclei.

A new heterotropic callosal projection of primary visual cortex in the monkey, Callithrix jacchus

A callosal projection of area 17 upon the dorsomedial visual area in the marmoset monkey was demonstrated by means of retrograde transport of neuronal tracers. The projection was restricted to those regions representing the vertical meridian in the two areas. This finding, and the data of other authors, indicate that the monkey area 17 projects transcallosally onto homotopic and several heterotopic targets.

Purkinje-like cells in the cochlear nucleus of the Common Tree Shrew (Tupaia glis) identified by calbindin immunohistochemistry

The dorsal cochlear nucleus (DCN) of Tree Shrews (Tupaia glis; n=2) was examined by calbindin (CB) immunohistochemistry for the presence of Purkinje-like cells (PLCs), detected previously in only four different mammals. We found up to eight CB-immunoreactive PLCs in the left and right DCN, and a few axons, likely of PLC origin, that appeared to leave the DCN. These findings suggest that PLCs may have a wider distribution through mammalian species, and may represent more than just misrouted cells.