Search PubMed⌕ Search

Biomedical subjects

A Angelucci

Publications and source records attributed to A Angelucci.

26 records · Page 2Linked to original sources
PubMed1995

Layer-specific programs of development in neocortical projection neurons.

How are long-range axonal projections from the cerebral cortex orchestrated during development? By using both passively and actively transported axonal tracers in fetal and postnatal ferrets, we have analyzed the development of projections from the cortex to a number of thalamic nuclei. We report that the projections of a cortical area to its corresponding thalamic nuclei follow highly cell-specific programs of development. Axons from cells in the deepest layers of the cerebral cortex (layer 6 and superficial subplate neurons) appear to grow very slowly and be delayed for several weeks in the cerebral white matter, reaching the thalamus over a protracted period. Neurons of layer 5, on the other hand, develop their projections much faster; despite being born after the neurons of deeper layers, layer 5 neurons are the first to extend their axons out of the cortical hemisphere and innervate the thalamus. Layer 5 projections are massive in the first postnatal weeks but may become partly eliminated later in development, being overtaken in number by layer 6 cells that constitute the major corticothalamic projection by adulthood. Layer 5 projections are area-specific from the outset and arise as collateral branches of axons directed to the brainstem and spinal cord. Our findings show that the early development of corticofugal connections is determined not by the sequence of cortical neurogenesis but by developmental programs specific for each type of projection neuron. In addition, they demonstrate that in most thalamic nuclei, layer 5 neurons (and not subplate or layer 6 neurons) establish the first descending projections from the cerebral cortex.

Animals↗
PubMed1989

Segregation and overlap of callosal and association neurons in frontal and parietal cortices of primates: a spectral and coherency analysis.

The spatial relations between selected classes of association and callosal neurons were studied in the frontal and parietal lobes of the macaque monkey using retrogradely transported fluorescent dyes. Fast blue and nuclear yellow were injected in the left frontal (areas 4 and 6) and right posterior parietal (area 5) cortices, respectively. These injections led to the retrograde labeling, in the right frontal cortex, of callosal neurons projecting homotopically and association neurons projecting to ipsilateral area 5; in the left superior parietal lobule, of callosal neurons projecting to contralateral area 5 and association neurons projecting to the ipsilateral frontal lobe. In both frontal and parietal cortices, callosal and association neurons were located in layers III and V-VI; a few neurons were also found in layer II. The contribution of layers V-VI to the callosum was significantly higher in areas 4 and 6 than in area 5. Only a small number of neurons (less than 1%) were double labeled. Spectral analyses were used to characterize the spatial periodicities of the distributions of callosal and association neurons. In areas 4, 6, and 5, both association and callosal spectra were dominated by a strong elevation in the range of low spatial frequencies, corresponding to periodicities in cell density with a peak-to-peak distance of about 8 mm. This indicated an arrangement of these corticocortical cells in the form of bands. The latter displayed various shapes and orientations and were composed of more discrete assemblies of cell clusters of about 400-1000 microns width. Their presence was revealed in the power spectra by a small elevation in the range of high spatial frequencies. The coherency analysis assessed the degree of linear relationships for each spatial frequency, and therefore the degree of similarity, between callosal and association cell distributions, together with their phase relations. Little coherency was found in areas 4 and 6 between bands of callosal and association neurons, which suggests that the 2 cell populations are differently and independently distributed in the tangential domain, with no simple phase relations. The overall mean coherency was higher in area 5 than in the frontal cortex: callosal and association bands were more similar in shape, with more extensive zones of overlap. These data indicate that callosal and association neurons share common principles of spatial organization despite the great regional variability of their interrelations in the tangential cortical domain.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMedDate not supplied

Culture conditions modulate cell phenotype and cause selection of subpopulations in PC3 prostate cancer cell line.

PC3 cell line contains different cell variants. A first variant grows as spherical multicellular aggregates and shows anchorage-independent growth. A second variant grows as single small rounds and shows anchorage-dependent growth without cell spreading. A third variant, representing the most abundant population, grows as adherent cells. These populations differ in alpha 2 beta 1 and alpha 3 beta 1 integrin expression with low levels in the suspended (S) cells, intermediate in partially adherent (R) cells and high in adherent cells (A). TPA, which up-regulates the expression of beta 1 integrins, increases invasiveness of cells. In addition, PC3 variants differ in MMP9 and uPA secretion and activity. High levels of TIMP1 and PAI1 present in S variant reduce MMP9 and uPA activities, respectively. In conclusion, PC3 cell line shows variants with strong phenotypic heterogeneity reflecting also the in vitro culture condition. Our observations may explain some of the contradictions in the literature. Therefore, the data obtained with this line should be evaluated more carefully, considering morphological and functional characteristics of the possible variants in the cell population. However, this heterogeneity may represent a good model in the study of tumor progression.

Antigens, CD↗