The geometrical nature of optical resonances : from a sphere to fused dimer nanoparticles

We study the electromagnetic response of smooth gold nanoparticles with shapes varying from a single sphere to two ellipsoids joined smoothly at their vertices. We show that the plasmonic resonance visible in the extinction and absorption cross sections shifts to longer wavelengths and eventually disappears as the mid-plane waist of the composite particle becomes narrower. This process corresponds to an increase of the numbers of internal and scattering modes that are mainly confined to the surface and coupled to the incident field. These modes strongly affect the near field, and therefore are of great importance in surface spectroscopy, but are almost undetectable in the far field

Gender effects on plasma PGRN levels in patients with Alzheimer's disease : a preliminary study

Plasma progranulin (PGRN) levels constitute a potentially invaluable biomarker for neurodegenerative diseases including frontotemporal lobar degeneration (FTLD) and, perhaps, Alzheimer's disease (AD). We assessed plasma PGRN levels in 107 AD patients, 36 FTLD patients, and 107 controls. We found that, in female AD patients, there is a positive correlation between PGRN levels and age. Although no significant differences were found between patients and controls, we observed higher levels in females compared to males; in AD patients, a positive correlation between PGRN levels and age was observed in females. In conclusion, our data suggest that PGRN may not be a good biomarker for AD; moreover, gender may influence the plasma PGRN levels of AD patients. \ua9 2013 - IOS Press and the authors. All rights reserved

Deep Sequencing of the Nicastrin Gene in Pooled DNA, the Identification of Genetic Variants That Affect Risk of Alzheimer's Disease

Nicastrin is an obligatory component of the γ-secretase; the enzyme complex that leads to the production of Aβ fragments critically central to the pathogenesis of Alzheimer's disease (AD). Analyses of the effects of common variation in this gene on risk for late onset AD have been inconclusive. We investigated the effect of rare variation in the coding regions of the Nicastrin gene in a cohort of AD patients and matched controls using an innovative pooling approach and next generation sequencing. Five SNPs were identified and validated by individual genotyping from 311 cases and 360 controls. Association analysis identified a non-synonymous rare SNP (N417Y) with a statistically higher frequency in cases compared to controls in the Greek population (OR 3.994, CI 1.105–14.439, p = 0.035). This finding warrants further investigation in a larger cohort and adds weight to the hypothesis that rare variation explains some of genetic heritability still to be identified in Alzheimer's disease

The Coupling of Alternative Splicing and Nonsense-Mediated mRNA Decay

Most human genes exhibit alternative splicing, but not all alternatively spliced transcripts produce functional proteins. Computational and experimental results indicate that a substantial fraction of alternative splicing events in humans result in mRNA isoforms that harbor a premature termination codon (PTC). These transcripts are predicted to be degraded by the nonsense-mediated mRNA decay (NMD) pathway. One explanation for the abundance of PTC-containing isoforms is that they represent splicing errors that are identified and degraded by the NMD pathway. Another potential explanation for this startling observation is that cells may link alternative splicing and NMD to regulate the abundance of mRNA transcripts. This mechanism, which we call "Regulated Unproductive Splicing and Translation" (RUST), has been experimentally shown to regulate expression of a wide variety of genes in many organisms from yeast to human. It is frequently employed for autoregulation of proteins that affect the splicing process itself. Thus, alternative splicing and NMD act together to play an important role in regulating gene expression

Promising Therapies for Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD) is the most frequent progressive neurodegenerative disease. Cholinergic dysfunction is one of the major pathological alteration, although depletion of cholinergic neurons is caused by the well-established toxicity of the beta-amyloid plaques and neurofibrillary tangles. Cholinergic dysfunctions are consequences of the decrease in acetylcholine synthesis and release, and altered function of muscarinic and nicotinic cholinergic receptors. In addition, a direct correlation between cholinergic alteration, amyloidbeta production and tau phosphorylation, two main AD-pathology hallmarks, has been identified. METHODS: In the present review we focused our discussion on the identification of new allosteric or bitopic ligands able to modulate the cholinergic receptor activity. Moreover drug delivery methodology (nanoparticeles, liposomes, etc.) that might contribute to drive the drug in the brain, reducing their toxicity and potential side effects have been also discussed. RESULTS: Many drugs are currently in use for AD (e.g. donepezil, rivastigmine etc.) and several of those in development such as muscarininc and nicotinic agonists, target specifically the cholinergic system; the main mechanism aims to rescue the cholinergic dysfunction, to reduce neurotoxic protein accumulation and improve the cholinergic impairments responsible of the cognitive deficits. Promising approaches aim to either improve drug delivery into the brain or develope new compounds targeting known or new molecular pathways. Nanoparticles and liposomes are also described as new nanotechnology tools that overcome traditional routes of administration, with a particular focus on their employment for compounddelivery that targets the cholinergic system. Ultimately, a new fields of research is emerging as the use of induced pluripotent stem cells, a technology that allows to obtain cells directly from the patients that can be propagated indefinetely and differentiated into the susceptible neuronal subtypes. This may significantly contribute to improve the understanding of AD pathological processes and enhance current AD pharmacology beyond the cholinergic dysfunction. CONCLUSION: From the topics discussed in the present review, emerges that the combination between pharmacological studies and nanotechnological approaches for drug delivery and the identification of new specific models may largely enhance and improve the therapeutic strategies for different neurological disease including AD

Circulating miRNAs as Biomarkers for Neurodegenerative Disorders

Neurodegenerative disorders, such as Alzheimer’s disease (AD), Parkinson’s disease (PD) and frontotemporal dementias (FTD), are considered distinct entities, however, there is increasing evidence of an overlap from the clinical, pathological and genetic points of view. All neurodegenerative diseases are characterized by neuronal loss and death in specific areas of the brain, for example, hippocampus and cortex for AD, midbrain for PD, frontal and temporal lobes for FTD. Loss of neurons is a relatively late event in the progression of neurodegenerative diseases that is typically preceded by other events such as metabolic changes, synaptic dysfunction and loss, neurite retraction, and the appearance of other abnormalities, such as axonal transport defects. The brain’s ability to compensate for these dysfunctions occurs over a long period of time and results in late clinical manifestation of symptoms, when successful pharmacological intervention is no longer feasible. Currently, diagnosis of AD, PD and different forms of dementia is based primarily on analysis of the patient’s cognitive function. It is therefore important to find non-invasive diagnostic methods useful to detect neurodegenerative diseases during early, preferably asymptomatic stages, when a pharmacological intervention is still possible. Altered expression of microRNAs (miRNAs) in many disease states, including neurodegeneration, and increasing relevance of miRNAs in biofluids in different pathologies has prompted the study of their possible application as neurodegenerative diseases biomarkers in order to identify new therapeutic targets. Here, we review what is known about the role of miRNAs in the pathogenesis of neurodegeneration and the possibilities and challenges of using these small RNA molecules as a signature for neurodegenerative conditions

γ-secretase is differentially modulated by alterations of Homocysteine cycle in neuroblastoma and glioblastoma cells.

Multiple aspects of homocysteine metabolism were studied to understand the mechanism responsible for hyperhomocysteinemia toxicity in Alzheimer disease. Besides oxidative stress and vascular damage, homocysteine has also a great importance in regulating DNA methylation through S-adenosylmethionine, the main methyl donor in eukaryotes. Alterations of S-adenosylmethionine and methylation were evidenced in Alzheimer disease and in elderly. In order to clarify whether DNA methylation can provide the basis for amyloid-β overproduction, we used human SK-N-BE neuroblastoma and A172 glioblastoma cell lines. We tested the effects of folate, B12 and B6 deprivation and S-adenosylmethionine addition on methylation metabolism. Our results indicate that homocysteine accumulation induced through vitamin B deprivation could impair the "Methylation Potential" with consequent presenilin 1, BACE and amyloid-β upregulation. Moreover, we found that homocysteine alterations had an effect on neuroblastoma but not on glioblastoma cells; this suggests a possible differential role of the two cell types in Alzheimer disease. © 2007 - IOS Press and the authors. All rights reserved

Gene expression profiles of APP and BACE1 in Tg SOD1G93A cortical cells

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease defined by motor neuron loss. Transgenic mouse model (Tg SOD1G93A) shows pathological features that closely mimic those seen in ALS patients. An hypothetic link between AD and ALS was suggested by finding an higher amount of amyloid precursor protein (APP) in the spinal cord anterior horn neurons, and of A beta peptides in ALS patients skin. In this work, we have investigated the expression of some genes involved in Alzheimer's disease, as APP, beta- and gamma-secretase, in an animal model of ALS, to understand some possible common molecular mechanisms between these two pathologies. For gene expression analysis, we carried out a quantitative RT-PCR in ALS mice and in transgenic mice over-expressing human wild-type SOD1 (Tg hSOD1). We found that APP and BACE1 mRNA levels were increased 1.5-fold in cortical cells of Tg SOD1G93A mice respect to Tg hSOD1, whereas the expression of gamma-secretase genes, as PSEN1, PSEN2, Nicastrin, and APH1a, showed no statistical differences between wild-type and ALS mice. Biochemical analysis carried out by immunostaining and western blotting, did not show any significant modulation of the protein expression compared to the genes, suggesting the existence of post-translational mechanisms that modify protein levels