Dario Cantino

Isolation of Renal Progenitor Cells from Adult Human Kidney

We describe here isolation and characterization of CD133+ cells derived from normal adult human kidney. These cells lacked the expression of hematopoietic markers and expressed PAX-2, an embryonic renal marker, suggesting their renal origin. Renal tissue-derived CD133+ cells and clones of individual cells were capable of expansion and limited self-renewal and differentiated in vitro into epithelial or endothelial cells. On subcutaneous implantation in SCID mice, the undifferentiated cells formed tubular structures expressing renal epithelial markers. At variance, when differentiated in endothelial cells, these cells formed functional vessels. On intravenous injection in SCID mice with glycerol-induced tubulonecrosis, the in vitro expanded renal-derived CD133+ cells homed into the injured kidney and integrated in tubules. We propose that CD133+ cells from kidney represent a multipotent adult resident stem cell population that may contribute to the repair of renal injury.

Localization of the clustering protein gephyrin at GABAergic synapses in the main olfactory bulb of the rat.

The tubulin‐binding protein gephyrin is essential for the formation of postsynaptic glycine‐receptor clusters in cultured spinal neurons. In addition, there is increasing evidence that gephyrin can also be present at nonglycinergic synapses. Here we analyzed immunocytochemically the subcellular localization of gephyrin in the main olfactory bulb of the rat and compared its distribution with that of γ‐aminobutyric acid (GABA) and of two major GABAA‐receptor subunits. Gephyrin was selectively localized to the postsynaptic side of symmetric synaptic junctions, where the presynaptic terminals contained GABA. Moreover, gephyrin colocalized extensively with the α1 and γ2 subunits of the GABAA receptor. In contrast, gephyrin was not detected at presumed glutamatergic synapses. These results indicate that gephyrin is not uniquely associated with glycine receptors, but can also be found at distinct GABAergic synapses. Thus, they raise the possibility that gephyrin is involved in anchoring certain GABAA‐receptor subtypes in the postsynaptic membrane. J. Comp. Neurol. 395:231–244, 1998.

Presynaptic co-localization of carnosine and glutamate in olfactory neurones.

OLFACTION plays a dominant role in modulating behaviour in most vertebrate species and the olfactory bulb is considered a model system for characterizing principles of neural computation. Nevertheless, although the physiology and neurochemistry of the olfactory circuits have been widely studied, the neurotransmitter released by olfactory receptor neurones remains unknown. We now describe the ultrastructural localization of the dipeptide carnosine and the excitatory amino acid glutamate in the glomerular layer of the mouse olfactory bulb. We demonstrate that both carnosine-like and glutamate-like immunoreactivities are selectively co-localized in the olfactory neurone boutons. These observations, taken with the recent findings of glutamate-receptor subunit expression in rodent olfactory bulb, argue compellingly for a role of glutamate in olfactory neurotransmission and suggest a modulatory effect of carnosine.

Cell death in the developing chick optic tectum

Abstract The degeneration and death of early developing neuroblasts in the optic tectum of chick embryo during normal development have been investigated by electron microscopy. The disappearance of part of the cell population in the tectum was observed between the 10th and 11th incubation day, i.e. shortly before the ultimate spatial arrangement of differentiating cells into a complex multilayered organization. The ultrastructural features of degenerative changes are described with special reference to previously reported observations on cell degeneration and death during morphogenesis. A comparison is also made with reported findings relating to cell degeneration and death in other nerve centers.

Cellular and subcellular localization of γ-aminobutyric acidB receptors in the rat olfactory bulb

Abstract Olfactory nerve axons terminate in rounded regions of the olfactory bulb, termed glomeruli, where they make excitatory synapses with the dendrites of second-order neurons. Neurotransmission from the olfactory nerve to the postsynaptic targets is negatively regulated by γ -aminobutyric acid (GABA), and there is evidence that inhibition of sensory input is mediated, at least in part, by GABA B receptors. Using an antiserum that recognizes two GABA B receptor splice variants (GBR1a and GBR1b), we show here that GABA B receptors are located on the axon terminals of the olfactory nerve, where they are concentrated at sites of axodendritic apposition. Taken with previous data, these results indicate that GABA B receptors act presynaptically to regulate the release of glutamate from olfactory nerve terminals.

Immunocytochemical localization of glutamate and gamma-aminobutyric acid in the accessory olfactory bulb of the rat.

The synaptic organization of the accessory olfactory bulb (AOB) was studied in the rat with antibodies against the excitatory neurotransmitter glutamate (Glu) and the inhibitory neurotransmitter γ‐aminobutyric acid (GABA). To a large extent, the immunoreactivity patterns produced by the two antibodies were complementary. Glu‐like immunoreactivity (‐LI) was observed in the glomerular neuropil, in the mitral cells, and in large neurons located in the periglomerular region. Immunogold electron microscopy revealed particularly high levels of Glu‐LI in the axon terminals of vomeronasal neurons. GABA‐LI was present in granule and periglomerular cells and in their processes. The dendritic spines of granule cells, which were presynaptic to mitral cells, were strongly labelled by the antiserum against GABA. Labelling of serial semithin sections showed that the GABA‐positive and Glu‐positive neurons of the periglomerular region are generally distinct, and colocalization of Glu and GABA occurred only in a few cells. These results are consistent with electrophysiological studies indicating that the synaptic organization of the AOB is similar to that of the main olfactory bulb. In both systems, Glu is the neurotransmitter used by primary afferents and output neurons, whereas GABA is involved in the circuits underlying lateral and feed‐back inhibition. J. Comp. Neurol. 408:61–72, 1999.

Postsynaptic colocalization of gephyrin and GABAA receptors.

Postsynaptic Colocalization of Gephyrin and GABAA Receptors MARCO SASSOÈ-POGNETTO, MAURIZIO GIUSTETTO, PATRIZIA PANZANELLI, DARIO CANTINO, JOACHIM KIRSCH, AND JEAN-MARC FRITSCHY Department of Anatomy, Pharmacology and Forensic Medicine, University of Turin, Corso Massimo d’Azeglio 52, I-10126 Turin, Italy Max-Planck-Institut für Hirnforschung, Frankfurt am Main, Germany Institute of Pharmacology, University of Zürich, Zürich, Switzerland

Co-localization of carnosine and glutamate in photoreceptors and bipolar cells of the frog retina

Immunocytochemical methods were used to visualize carnosine (beta-alanyl-L-histidine)-like immunoreactivity (-LI) in the frog retina and to compare its localization with that of glutamate. Carnosine-LI was conspicuous in photoreceptors and bipolar cells. The axon terminals of labelled bipolar cells formed five bands in the inner plexiform layer. A few presumed amacrine and ganglion cells, as well as Müller cell endfeet, were also labelled. Post-embedding immunocytochemistry revealed particularly high levels of glutamate-LI in the synaptic axon terminals of bipolar cells, with a mean gold particle density 5 x higher than that of amacrine cells. Photoreceptor terminals were also labelled, but with a labelling intensity about half that of bipolar cells. Labelling of serial semithin sections showed co-localization of carnosine and glutamate in photoreceptors and bipolar cells. These findings are consistent with the notion that glutamate is the neurotransmitter of neuronal elements that transfer information vertically through the retina. We propose that carnosine may modulate GABA and/or glutamate receptors by virtue of its ability to chelate Zn2+ and other ions.

Glutamate and carnosine in the vestibular system of the frog

We demonstrate that both glutamate-like and carnosine-like immunoreactivities are present in hair cells and in fibers of the vestibular organ of the frog inner ear. Comparison of the two immunoreactivity patterns indicates that glutamate and carnosine might be colocalized in some hair cells. The presence of glutamate-like immunoreactivity in hair cells is consistent with biochemical and pharmacological data indicating glutamate as the excitatory neurotransmitter in these sensory receptors. There is also evidence that carnosine might have a neuromodulatory function.

Carnosine-like immunoreactivity is associated with synaptic vesicles in photoreceptors of the frog retina

The distribution of carnosine-like immunoreactivity in photoreceptors of the frog retina was studied by post-embedding electron microscope immunocytochemistry. Different fixation and embedding procedures were applied and the best results were achieved on sections from tissue embedded in the hydrophilic resin LR White. All photoreceptor types present in the frog retina (red and green rods, single and double cones) were intensely reactive for the carnosine antiserum. The immunoreactivity was particularly prominent in the synaptic terminal, nucleus and myoid, but decreased in the ellipsoid and in the outer segment. Müller glial cells and horizontal and bipolar cell processes in the outer plexiform layer were completely unstained. At the level of the photoreceptor terminals, the presence of gold particles within the synaptic vesicles could be demonstrated. This study is the first to provide the anatomical evidence for the presence of carnosine in the synaptic vesicles of a nervous cell. The present data may be relevant to the understanding of the biological functions of carnosine (and related dipeptides) and offer an exploitable system in which to verify its proposed role as a neurotransmitter or neuromodulator in sensory systems.