Axonal Varicosity Density as an Index of Local Neuronal Interactions

Diffuse transmission is an important non-synaptic communication mode in the cerebral neocortex, in which neurotransmitters released from en passant varicosities interact with surrounding cells. In a previous study we have shown that the cholinergic axonal segments which were in the microproximity with dopaminergic fibers possessed a greater density of en passant varicosities compared to more distant segments, suggesting an activity-dependent level of en passant varicosities in the axonal zone of interaction. To further evaluate this plastic relationship, the density of cholinergic varicosities was quantified on fiber segments within the microproximity of activated or non-activated pyramidal cells of the prefrontal cortex (mPFC). Repetitive 14 days patterned visual stimulation paired with an electrical stimulation of the cholinergic fibers projecting to the mPFC from the HDB was performed to induce persistent axonal plastic changes. The c-Fos early gene immunoreactivity was used as a neuronal activity marker of layer V pyramidal cells, labelled with anti-glutamate transporter EAAC1. Cholinergic fibers were labeled with anti-ChAT (choline acetyltransferase) immunostaining. The density of ChAT+ varicosities on and the length of fiber segments within the 3 µm microproximity of c-Fos positive/negative pyramidal cells were evaluated on confocal images. More than 50% of the pyramidal cells in the mPFC were c-Fos immunoreactive. Density of ChAT+ varicosities was significantly increased within 3 µm vicinity of activated pyramidal cells (0.50±0.01 per µm of ChAT+ fiber length) compared to non-activated cells in this group (0.34±0.001; p≤0.05) or control rats (0.32±0.02; p≤0.05). Different types of stimulation (visual, HDB or visual/HDB) induced similar increase of the density of ChAT+ varicosities within microproximity of activated pyramidal cells. This study demonstrated at the subcellular level an activity-dependent enrichment of ChAT+ varicosities in the axonal zone of interaction with other neuronal elements

Microscopic structure of the polymer-induced liquid precursor for calcium carbonate

Many biomineral crystals form complex non-equilibrium shapes, often via transient amorphous precursors. Also in vitro crystals can be grown with non-equilibrium morphologies, such as thin films or nanorods. In many cases this involves charged polymeric additives that form a polymer-induced liquid precursor (PILP). Here, we investigate the CaCO3 based PILP process with a variety of techniques including cryoTEM and NMR. The initial products are 30–50 nm amorphous calcium carbonate (ACC) nanoparticles with ~2 nm nanoparticulate texture. We show the polymers strongly interact with ACC in the early stages, and become excluded during crystallization, with no liquid–liquid phase separation detected during the process. Our results suggest that “PILP” is actually a polymer-driven assembly of ACC clusters, and that its liquid-like behavior at the macroscopic level is due to the small size and surface properties of the assemblies. We propose that a similar biopolymer-stabilized nanogranular phase may be active in biomineralization

Heat Shock Proteins Expression in Canine Intracutaneous Cornifying Epithelioma and Squamous Cell Carcinoma

Heat shock proteins (HSPs) are strongly implicated in the control of cell growth, differentiation andbiological behaviour of many human cutaneous neoplasms. To our knowledge, no data have been published inthe veterinary literature concerning either normal or neoplastic skin. In this study, the immunohistochemicalexpression of Hsp27, Hsp72 and Hsp73 was evaluated in normal canine skin, 14 intracutaneous cornifying epitheliomas(ICE), 10 well-differentiated and 5 moderately differentiated squamous cell carcinomas (SCC). Expressionwas correlated with the histological degree of keratinocyte differentiation and proliferation, and investigatedas to its usefulness in the differential diagnosis of these canine tumours. In normal epidermis, Hsp27 exhibitedcytoplasmic labelling in the spinous and granular layers, whereas in neoplastic tissues it was detected particularlyin those areas showing squamous differentiation. Hsp72 immunoreactivity was more intense in ICE and welldifferentiatedSCC than in normal skin; however, reduced immunolabelling was observed in moderately differentiatedSCC. Unlike Hsp72, Hsp73 showed less intense labelling in ICE and well-differentiated SCC than in normalepithelium and an increased positivity in moderately differentiated SCC. These results indicate that HSPimmunoreactivity differs between normal and neoplastic canine skin. Hsp27 expression seems to correlatedirectly with cellular differentiation; by contrast, the involvement of Hsp72/73 in proliferation and differentiationof tumour cells remains controversial. The pattern and intensity of immunolabelling of each investigated HSPdid not show, however, significant differences between ICE and SCC; therefore, they do not seem to be useful inthe differential diagnosis of these two canine tumours.[...