Foto del docente

Maurizio Lazzari

Assistant professor

Department of Biological, Geological, and Environmental Sciences

Academic discipline: BIO/06 Comparative Anatomy and Cytology

Research

Keywords: Olfactory receptors Glial cells Brain microvessels Immunohistochemistry Histochemistry Morphology

  • Ultrastructural, histochemical and immunohistochemical studies of microvessels in the central nervous system of vertebrates.
  • Ultrastructural and immunohistochemical studies of vertebrate glial cells.
  • Ultrastructural, histochemical and immunohistochemical studies of the olfactory system of vertebrates.
  • Effects of toxicants and pollutants on acoustic and olfactory sensory epithelia of vertebrates.



The researches of Maurizio Lazzari are in the field of the comparative neurobiology of the vertebrates.
  • Ultrastructural, cytochemical and immunocytochemical studies have been done on the microvessels of amphibian and reptile central nervous system (CNS). In amphibians, ultrastructural observations showed that an endothelial type blood-brain barrier (BBB) is present. Histochemical and immunohistochemical techniques revealed that various vessel-associated enzymes ( phosphatases and Glut1 glucose transporter) have an asymmetrical distribution between the luminal and abluminal surfaces of the endothelial cells. These enzymes are likely involved in the functions of the BBB. In amphibians and reptiles the CNS angioarchitectural pattern was studied by scanning electron microscopic observations of resin microvascular casts. The three-dimensional network of single vessels appeared the prevailing pattern. A few species showed only hairpin-shaped paired vessels arising from the meningeal vasculature. Only in very few species, both single and paired vessels were found, but the single vessel network was prevailing. Moreover, vascular permeability was studied by intravascular injection of tracers, such as horseradish peroxidase and ionic lanthanum, in amphibians which received hyperosmolar mannitol solutions in vein. Interendothelial junctions, which in normal animals prevent the free diffusion of tracers into the extracellular spaces of the nervous parenchyma, were disrupted by hypertonic solutions.
  • Other studies focused on the vertebrate olfactory system in which the olfactory neuroepithelium possesses rather unique neurogenetic properties and is a useful model in investigating nervous cell differentiation. The olfactory receptor neurons, directly exposed to environmental factors, undergo a continuous cycle of cell proliferation and death both during development and in adult animals. Precursor cells present in the basal portion of the olfactory neuroepithelium, divide and give rise to immature neurons. These cells migrate to upper layers of the neuroepithelium and establish new connections both to the surface of the epithelium by their dendritic zone and to the olfactory bulb by synapses of their axons on the glomerular layer of the bulb. Superficial glycoconjugates of the olfactory receptors are considered to play a basic role  in olfaction as well as in cell recognition and fasciculation. Lectins, proteins or glicoproteins that bind with high specificity to terminal sugars of complex carbohydrates, were used as molecular probes to discriminate the primary olfactory neurons and their terminals in the olfactory bulbs on the basis of the composition of their surface glycoproteins. These studies were performed on various species representative of the different vertebrate classes with the exception of birds. This research shows that the vertebrate olfactory system is quite conservative in both the stuctural organization and the carbohydrate composition of the primary receptor neurons.
  • Other studies considered the presence and distribution of glial fibrillary acidic protein (GFAP) and vimentin which are molecular markers of glial cell intermediate filaments. This research was at first made in the African lungfish and in urodels. Throughout the CNS, the African lung fish and urodels show only one type of astroglial element: ependymal radial glia. Radial glial cells possess pear- or spindle-shaped cell bodies located in the ependymal or periependymal layer where they constitute the ependymal or periependymal radial glia, respectively. Their cell bodies give rise to long radially oriented cytoplasmic processes that terminate with laminar or bulbous endfeet apposed to the wascular wall as well as to the submeningeal surface. In the lungfish and Ambystoma, these cells are GFAP-immunopositive and vimentin immunonegative, on the contrary, in Triturus they express only vimentin. GFAP and vimentin were then studied in some reptile species. The vimentin immunopositivity is very reduced in reptiles, whereas GFAP positivity is clear even if its staining intensity is different in the same cell type. GFAP immunocytochemistry showed that in reptiles radial glial elements coexist with star-shaped astrocytes. The condition of reptiles appears morphologically more primitive than that found in birds and mammals. These results strongly support that the glial pattern of reptiles is transitional between anamniotes and other amniotes and that reptiles are an important step in the evolution of vertebrate glia.

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