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H Thoenen

Publications and source records attributed to H Thoenen.

At least 19 recordsLinked to original sources
PubMed1979

Nerve growth factor (NGF) in the rat CNS: absence of specific retrograde axonal transport and tyrosine hydroxylase induction in locus coeruleus and substantia nigra.

Selective, highly efficient uptake of [125I]NGF by nerve terminals followed by retrograde axonal transport, and specific induction of tyrosine hydroxylase by NGF are well known phenomena in peripheral adrenergic neurons of adult rats. In the present study these parameters were used in order to detect possible interactions of NGF with central catecholaminergic neurons. No selective retrograde transport of [125I]NGF could be detected by light microscopic autoradiography from the caudate nucleus to the dopaminergic neurons in the substantia nigra or from the hippocampus to the noradrenergic nerve cells of the locus coeruleus. Biochemically, no change in tyrosine hydroxylase activity could be observed for up to 3 days after injection of either NGF, anti-NGF antibodies, or control proteins close to the nerve cell bodies in the substantia nigra or the locus coeruleus. These data suggest a fundamental difference between central and peripheral adrenergic neurons with regard to their responsiveness of NGF.

Adrenergic Fibers↗
PubMed1979

Retrograde axonal transport of specific macromolecules as a tool for characterizing nerve terminal membranes.

The uptake of macromolecules by nerve terminals which is followed by retrograde axonal transport seems to occur by two different mechanisms, a specific and a nonspecific one. The nonspecific uptake depends on the presence of macromolecules (e.g., horseradish peroxidase) in the vicinity of the nerve terminals at very high concentrations and is enhanced by neuronal activity. In contrast, the specific uptake and subsequent retrograde axonal transport becomes apparent at much lower concentrations of the appropriate macromolecules, depends on the affinity of these ligands for specific binding sites on the surface of the neuronal membrane, and is independent of neuronal activity. The fact that lectins and some bacterial toxins bind to specific membrane glycoproteins or glycolipids allows conclusions to be drawn regarding qualitative and even quantitative aspects of the composition of the plasma membrane of the nerve terminals. 125I-labelled nerve growth factor (NGF), tetanus toxin, cholera toxin, wheat germ agglutinin (WGA), ricin II, phytohemagglutinin (PHA), and concanavalin A (ConA) were injected into the anterior eye chamber of rats where they were taken up by adrenergic nerve terminals and transported retrogradely to the superior cervical ganglion. The saturation of the uptake-transport found for NGF, WGA, choleragenoid and an atoxic binding-fragment of tetanus toxin indicates that limited numbers of binding sites, which showed also different affinities, are present for each ligand on the membrane of the nerve terminals. Competition experiments showed that the binding sites for the ligands investigated are largely independent. Two different classes of binding sites (high affinity--low capacity and intermediate affinity--intermediate capacity) seem to be involved in the saturable retrograde axonal transport of NGF. In contrast, WGA seems to have only a single class of binding-uptake sites with high capacity and relatively low affinity. Strong evidence for positive cooperativity was obtained for the uptake and subsequent transport of the tetanus toxin fragment.

Animals↗
PubMed1979

Selective retrograde transsynaptic transfer of a protein, tetanus toxin, subsequent to its retrograde axonal transport.

The fate of tetanus toxin (mol wt 150,000) subsequent to its retrograde axonal transport in peripheral sympathetic neurons of the rat was studied by both electron microscope autoradiography and cytochemistry using toxin-horseradish peroxidase (HRP) coupling products, and compared to that of nerve growth factor (NGF), cholera toxin, and the lectins wheat germ agglutinin (WGA), phytohaemagglutinin (PHA), and ricin. All these macromolecules are taken up by adrenergic nerve terminals and transported retrogradely in a selective, highly efficient manner. This selective uptake and transport is a consequence of the binding of these macromolecules to specific receptive sites on the nerve terminal membrane. All these ligands are transported in the axons within smooth vesicles, cisternae, and tubules. In the cell bodies these membrane compartments fuse and most of the transported macromolecules are finally incorporated into lysosomes. The cell nuclei, the parallel golgi cisternae, and the extracellular space always remain unlabeled. In case the tetanus toxin, however, a substantial fraction of the labeled material appears in presynaptic cholinergic nerve terminals which innervate the labeled ganglion cells. In these terminals tetanus toxin-HRP is localized in 500-1,000 A diam vesicles. In contrast, such a retrograde transsynaptic transfer is not at all or only very rarely detectable after retrograde transport of cholera toxin, NGF, WGA, PHA, or ricin. An atoxic fragment of the tetanus toxin, which contains the ganglioside-binding site, behaves like intact toxin. With all these macromolecules, the extracellular space and the glial cells in the ganglion remain unlabeled. We conclude that the selectivity of this transsynaptic transfer of tetanus toxin is due to a selective release of the toxin from the postsynaptic dendrites. This release is immediately followed by an uptake into the presynaptic terminals.

Adrenergic Fibers↗
PubMed1978

Nerve growth factor-mediated induction of tyrosine hydroxylase in rat superior cervical ganglia in vitro.

Exposure of rat sympathetic ganglia to 3 microgram/ml of 2.5 S nerve growth factor (NGF) resulted in a 100% increase in tyrosine hydroxylase activity within 48 h. Pulselabeling of proteins with [3H]leucine, followed by immunoprecipitation with antibodies to tyrosine hydorxylase and isolation of the precipitated enzyme by gel electrophoresis, demonstrated that the increase in tyrosine hydroxylase activity was due to enhanced de novo synthesis. The incorporation of [3H]leucine into tyrosine hydroxylase was increased by 150% compared to a 17% increase in total protein synthesis, which was not statistically significant. The fact that the half-life of pulse-labeled tyrosine hydroxylase was the same for NGF-treated and control organ cultures of superior cervical ganglia excludes the possibility that enhanced tyrosine hydroxylase labeling by NGF is due to decreased degradation. We conclude that, without modulatory factors which play a role in vivo, NGF can enhance the synthesis of tyrosine hydroxylase in sympathetic ganglia in vitro, provided organ culture conditions which permit optimal survival of adrenergic neurons are selected.

Animals↗
PubMed1978

Nerve growth factor-induced fiber outgrowth from isolated rat adrenal chromaffin cells: impairment by glucocorticoids.

Addition of nerve growth factor to cultures of dissociated rat adrenal medullary cells caused fiber outgrowth from chromaffin cells. These fibers exhibited all the characteristics of neurites, particularly the formation of typical growth cones exhibiting intense catecholamine-specific fluorescence. Because this nerve growth factor-mediated neurite outgrowth could be abolished by physiological concentrations of glucocorticoids, it is concluded that the high glucocorticoid concentrations normally present in the adrenal medulla prevent the fiber outgrowth from medullary chromaffin cells in vivo. In dissociated sympathetic neurons the same concentrations of glucocorticoids markedly reduce but do not completely abolish neuronal fiber outgrowth.

Adrenal Medulla↗