A multi-technique comparison of the electronic properties of pristine and nitrogen-doped polycrystalline SnO2.

Nitrogen doped tin(iv) oxide (SnO2) materials in the form of nanometric powders have been prepared by precipitation with ammonia. Their properties have been compared with those of undoped materials obtained in a similar way using various physical techniques such as photoelectron spectroscopies (XPS and UPS), UV-Vis-NIR spectroscopy and electron paramagnetic resonance (EPR). Nitrogen doping leads to the formation of various nitrogen containing species, the more relevant of which is a nitride-type ionic species, based on the substitution of a lattice oxygen atom with a nitrogen atom. This species exists in two forms, paramagnetic (hole centre, formally N(2-)) and diamagnetic (N(3-)). The mutual ratio of the two species varies according to the oxidation state of the material. The doped solid, like most of the semiconducting oxides, tends to lose oxygen forming oxygen vacancies upon annealing under vacuum and leaving an excess of electrons in the solid. The stoichiometry of the solid can thus be markedly changed depending on the external conditions. Excess electrons are present both as itinerant electrons in the conduction band and as Sn(ii) states lying close to the valence band maximum. The presence of nitride-type centres, which are low energy states located below the top of the valence band, decreases the energy cost for the formation of oxygen vacancies by O2 release from the lattice. This particular feature of the doped system represents a severe limit to the preparation of a p-type SnO2via nitrogen doping.

Dumbbell-shaped spinal solitary fibrous tumor: Combined approach and a review of the literature.

INTRODUCTION: Spinal solitary fibrous tumors are rare entities, particularly when considered in a dumbbell-shaped form. CASE DESCRIPTION: The authors report on a 23-year-old female patient with dorsalgia and a D11-D12 dumbbell-shaped lesion on MRI, and highly vascularized on angiography. After a biopsy-based diagnosis, an integrated approach was performed with a preoperative embolization of the feeding intercostal arteries and an en bloc resection. At 3 months postoperatively, the patient had no pain or other neurologic symptoms and a complete resection was performed and documented on MRI. CONCLUSION: To our knowledge, only 3 previous reports of dumbbell-shaped spinal solitary fibrous tumors were carried-out and this is the first case, to our knowledge, treated by pre-operatory embolization. Nevertheless, this tumor should be considered among other spinal dumbbell-shaped lesions with a differential diagnosis, i.e. meningioma and schwannoma.

Hydrophilic/hydrophobic features of TiO2 nanoparticles as a function of crystal phase, surface area and coating, in relation to their potential toxicity in peripheral nervous system.

The hydrophilic/hydrophobic properties of a variety of commercial TiO(2) nanoparticles (NP), to be employed as inorganic filters in sunscreen lotions, were investigated both as such (dry powders) and dispersed in aqueous media. Water uptake and the related interaction energy have been determined by means of adsorption microcalorimetry of H(2)O vapor, whereas dispersion features in aqueous solutions were investigated by dynamic light scattering and electrokinetic measurements (zeta potential). The optimized dispersions in cell culture medium were employed to assess the possible in vitro neuro-toxicological effect on dorsal root ganglion (DRG) cells upon exposure to TiO(2)-NP, as a function of crystal phase, surface area and coating. All investigated materials, with the only exception of the uncoated rutile, were found to induce apoptosis on DRG cells; the inorganic/organic surface coating was found not to protect against the TiO(2)-induced apoptosis. The risk profile for DRG cells, which varies for the uncoated samples in the same sequence as the photo-catalytic activity of the different polymorphs: anatase-rutile>anatase>>rutile, was found not to be correlated with the surface hydrophilicity of the uncoated/coated specimens. Aggregates/agglomerates hydrodynamic diameter was comprised in the ~200-400 nm range, compatible with the internalization within DRG cells.

The nitrogen-boron paramagnetic center in visible light sensitized N-B co-doped TiO(2). Experimental and theoretical characterization.

Nitrogen boron co-doped TiO(2) prepared via sol-gel synthesis and active under visible light, contains two types of paramagnetic extrinsic defects, both exhibiting a well resolved EPR spectrum. The first center is the well characterized [N(i)O]˙ species (i = interstitial) also present in N-doped TiO(2), while the second one involves both N and B. This latter center (labeled [NOB]˙) exhibits well resolved EPR spectra obtained using either (14)N or (15)N which show a high spin density in a N 2p orbital. The structure of the [NOB]˙ species is different from that previously proposed in the literature and is actually based on the presence of interstitial N and B atoms both bound to the same lattice oxygen ion. The interstitial B is also linked to two other lattice oxygen ions reproducing the trigonal planar structure typical of boron compounds. The energy level of the [NOB]˙ center lies near the edge of the valence band of TiO(2) and, as such, does not contribute to the visible light absorption. However, [NOB]˙ can easily trap one electron generating the [NOB](-) diamagnetic center which introduces a gap state at about 0.4 eV above the top of the valence band. This latter species can contribute to the visible light activity.

Severe polyneuropathy in a patient with Churg-Strauss syndrome.

We describe the clinicopathologic features of a 56-year-old woman affected with Churg-Strauss syndrome with major peripheral nerve involvement. The patient presented with a 1-month history of mainly distal upper-limb symmetrical paresthesias and hypostenia (bilateral "wrist drop"), palpable purpura and eosinophilia. Multiple pulmonary infiltrates and asthma had been present since the age of 52. Skin biopsy demonstrated an eosinophilic necrotizing vasculitis. During the hospitalization she was submitted to cardiac, bronchopulmonary, renal, and gastrointestinal evaluation and EMG. Peripheral nerve and skeletal muscle biopsies were performed. Sural nerve biopsy showed a marked degree of demyelination. A perivascular cellular infiltrate within the epineurium was immunoreactive for T lymphocytes and macrophages. Strong HLA-DR immunostaining was present in the endoneurium. IgM, IgE and fibrinogen deposition was found in some epi- and endoneurial vessels. Muscle biopsy showed neurogenic changes and 1 thrombosed vessel surrounded by mononuclear cells. Membrane attack complex (MAC) deposition was present in a few capillaries and major histocompatibility complex products I (MHCP I) was expressed at the subsarcolemmal level in a few isolated perivascular muscle fibers. After immunosuppressive therapy, the patient showed progressive improvement of both clinical symptoms and neurophysiological parameters.

Schwann cell undergoes apoptosis during experimental allergic neuritis (EAN).

Schwann cell apoptosis is not detectable in the normal mature mammalian peripheral nervous system (PNS). However, during PNS cell-mediated demyelination, apoptosis contributes to the elimination of endoneurial T-lymphocytes. We report here that approximately 10% of Schwann cells die by apoptosis during the early phases of recovery from experimental autoimmune neuritis (EAN) in the adult rat, a model for the Guillain-Barrè syndrome. Schwann cell apoptosis, follows endoneurial T-cell clearance, and is prominent in the nerve roots, the site of most severe segmental demyelination, but is rare in the more distal regions of the PNS, where Wallerian degeneration predominates. Further immunological analysis showed that the p75 neurotrophin receptor (p75NTR) is expressed in 2% of both apoptotic and non apoptotic Schwann cells, while Ki-67, a marker of cell proliferation, is expressed in 20% of apoptotic and in 1% of non apoptotic Schwann cells. Our new observations indicate that apoptosis during cell-mediated demyelination can be a phenomenon related either to the development or the recovery of autoimmune cell mediated inflammation.

p75 neurotrophin receptor induction and macrophage infiltration in peripheral nerve during experimental diabetic neuropathy: possible relevance on regeneration.

In this study we examined the expression of the neurotrophin receptor p75 (p75NTR) and the activation of macrophages in the sciatic nerve of rats at different time points after the induction of diabetes with streptozotocin (STZ). Northern blot and immunocytochemical analysis showed that p75NTR was not detectable in the sciatic nerve by Week 2 after STZ treatment. At this time, single nerve fiber immunostaining using ED1 monoclonal antibody revealed that active macrophages were infiltrating the endoneurium, which had a normal morphological aspect. By Weeks 5 and 15 p75NTR mRNA and protein were induced in the endoneurium of diabetic animals. Immunocytochemical analysis of teased single nerve fibers showed that p75NTR protein was distributed uniformly along isolated fibers with no pathological evidence of axonal degeneration or myelin disruption. At this time, cells of the phagocyte lineage had already disappeared from the nerve. These data show that during experimental diabetic neuropathy, the endoneurial induction of p75NTR is localized along isolated nerve fibers showing no morphological alterations, and in time, follows the recruitment of active macrophages in the nerve, suggesting that these cells, directly or through their products, can influence p75NTR induction. This process might play an important role in STZ diabetic neuropathy, as a response to decreased levels of neurotrophins such as NGF and promoting nerve regeneration in the early phases of the disease.

Induction of p75NGFR in human diabetic neuropathy.

In this immunohistochemical study we investigated the expression of low-affinity NGF receptor (p75NGFR) in peripheral nerves from 16 patients with type I or type II diabetes mellitus. Fourteen nerves from age- and sex-matched normal individuals and nine nerves from non-diabetic patients with ischemic neuropathy served as controls. All nerve samples were preliminarily examined by standard histology, fiber teasing and electron microscopy. Increased p75NGFR immunoreactivity was detectable within the endoneurium of cross-sections from ischemic and particularly from diabetic nerves. Immuno-teasing demonstrated that p75NGFR immunostaining was distributed along the entire length of isolated nerve fibers undergoing axonal degeneration. Quantitative assessment of p75NGFR immunoreactivity, performed by histospectrophotometry and expressed as percentage of adsorbance, was 21.20 +/- 3.50 in nerves from diabetic patients, 13.35 +/- 3.62 in nerves from non-diabetic patients with ischemic neuropathy and 9.02 +/- 2.75 in normal controls. The increased expression of p75NGFR in diabetic nerves is consistent with an axonopathic defect and further suggests involvement of NGF and other neurotrophins in the pathogenesis of human diabetic neuropathy.