On a class of rational matrices and interpolating polynomials related to the discrete Laplace operator

Let \dlap be the discrete Laplace operator acting on functions (or rational matrices) $f:\mathbf{Q}_L\to\mathbb{Q}$, where $\mathbf{Q}_L$ is the two dimensional lattice of size $L$ embedded in $\mathbb{Z}_2$. Consider a rational $L\times L$ matrix $\mathcal{H}$, whose inner entries $\mathcal{H}_{ij}$ satisfy \dlap\mathcal{H}_{ij}=0. The matrix $\mathcal{H}$ is thus the classical finite difference five-points approximation of the Laplace operator in two variables. We give a constructive proof that $\mathcal{H}$ is the restriction to $\mathbf{Q}_L$ of a discrete harmonic polynomial in two variables for any $L>2$. This result proves a conjecture formulated in the context of deterministic fixed-energy sandpile models in statistical mechanics.Comment: 18 pag, submitted to "Note di Matematica

Heterogeneous Mean Field for neural networks with short term plasticity

We report about the main dynamical features of a model of leaky-integrate-and fire excitatory neurons with short term plasticity defined on random massive networks. We investigate the dynamics by a Heterogeneous Mean-Field formulation of the model, that is able to reproduce dynamical phases characterized by the presence of quasi-synchronous events. This formulation allows one to solve also the inverse problem of reconstructing the in-degree distribution for different network topologies from the knowledge of the global activity field. We study the robustness of this inversion procedure, by providing numerical evidence that the in-degree distribution can be recovered also in the presence of noise and disorder in the external currents. Finally, we discuss the validity of the heterogeneous mean-field approach for sparse networks, with a sufficiently large average in-degree

Average synaptic activity and neural networks topology: a global inverse problem

The dynamics of neural networks is often characterized by collective behavior and quasi-synchronous events, where a large fraction of neurons fire in short time intervals, separated by uncorrelated firing activity. These global temporal signals are crucial for brain functioning. They strongly depend on the topology of the network and on the fluctuations of the connectivity. We propose a heterogeneous mean--field approach to neural dynamics on random networks, that explicitly preserves the disorder in the topology at growing network sizes, and leads to a set of self-consistent equations. Within this approach, we provide an effective description of microscopic and large scale temporal signals in a leaky integrate-and-fire model with short term plasticity, where quasi-synchronous events arise. Our equations provide a clear analytical picture of the dynamics, evidencing the contributions of both periodic (locked) and aperiodic (unlocked) neurons to the measurable average signal. In particular, we formulate and solve a global inverse problem of reconstructing the in-degree distribution from the knowledge of the average activity field. Our method is very general and applies to a large class of dynamical models on dense random networks

On a class of rational matrices and interpolating polynomials related to the discrete Laplace operator

Let \dlap be the discrete Laplace operator acting on functions(or rational matrices) $f:\mathbf{Q}_L\rightarrow\mathbb{Q}$,where $\mathbf{Q}_L$ is the two dimensional lattice of size $L$embedded in $\mathbb{Z}_2$. Consider a rational $L\times L$ matrix $\mathcal{H}$, whose inner entries $\mathcal{H}_{ij}$ satisfy \dlap\mathcal{H}_{ij}=0. The matrix $\mathcal{H}$ is thus theclassical finite difference five-points approximation of theLaplace operator in two variables. We give a constructive proofthat $\mathcal{H}$ is the restriction to $\mathbf{Q}_L$ of adiscrete harmonic polynomial in two variables for any L>2. Thisresult proves a conjecture formulated in the context ofdeterministic fixed-energy sandpile models in statisticalmechanics

Survival of high grade glioma patients depends on their age at diagnosis.

Although the prognosis for malignant gliomas is normally dismal, it's not infrequent in neurooncologist's experience to find cases with unusually prolonged survival. In order to understand what factors influence survival of high grade glioma patients, a cohort of 196 high (III-IV) grade glioma patients was investigated for possible association between (1) survival and age at diagnosis; (2) survival and micronuclei in tumor tissue; (3) survival and gender; (4) micronuclei in tumor tissue and age at diagnosis.Patients diagnosed at an older age (64 years) had a significantly higher hazard as compared to younger patients (or=64 years), indicating that older patients survived shorter. On the contrary, no association was found between survival and micronuclei or gender.Survival analysis was performed by the Cox' proportional hazards regression model.Age at diagnosis, together with other established prognostic factors such as histologic characteristics, extent of surgery and Karnofsky Performance Score may to a certain extent predict survival of high grade glioma patients

Clinical Impact of COVID-19 Outbreak on Cancer Patients: A Retrospective Study

Background: Coronavirus disease (COVID-19), an acute respiratory syndrome caused by a novel severe acute respiratory syndrome coronavirus (SARS-CoV-2), has rapidly spread worldwide, significantly affecting the outcome of a highly vulnerable group such as cancer patients. The aim of the present study was to evaluate the clinical impact of COVID-19 infection on outcome and oncologic treatment of cancer patients. Patient and methods: We retrospectively enrolled cancer patients with laboratory and/or radiologic confirmed SARS-CoV-2 infection, admitted to our center from February to April 2020. Descriptive statistics were used to summarize the clinical data and univariate analyses were performed to investigate the impact of anticancer treatment modifications due to COVID-19 outbreak on the short-term overall survival (OS). Results: Among 61 patients enrolled, 49 (80%) were undergoing anticancer treatment and 41 (67%) had metastatic disease. Most patients were men; median age was 68 years. Median OS was 46.6 days (40% of deaths occurred within 20 days from COVID-19 diagnosis). Among 59 patients with available data on therapeutic course, 46 experienced consequences on their anticancer treatment schedule. Interruption or a starting failure of the oncologic therapy correlated with significant shorter OS. Anticancer treatment delays did not negatively affect the OS. Lymphocytopenia development after COVID was significantly associated with worst outcome. Conclusions: COVID-19 diagnosis in cancer patients may affect their short-term OS, especially in case of interruption/starting failure of cancer therapy. Maintaining/delaying cancer therapy seems not to influence the outcome in selected patients with recent COVID-19 diagnosis

Editing of HIV-1 RNA by the double-stranded RNA deaminase ADAR1 stimulates viral infection

Adenosine deaminases that act on dsRNA (ADARs) are enzymes that target double-stranded regions of RNA converting adenosines into inosines (A-to-I editing) thus contributing to genome complexity and fine regulation of gene expression. It has been described that a member of the ADAR family, ADAR1, can target viruses and affect their replication process. Here we report evidence showing that ADAR1 stimulates human immuno deficiency virus type 1 (HIV-1) replication by using both editing-dependent and editing-independent mechanisms. We show that over-expression of ADAR1 in HIV-1 producer cells increases viral protein accumulation in an editing-independent manner. Moreover, HIV-1 virions generated in the presence of over-expressed ADAR1 but not an editing-inactive ADAR1 mutant are released more efficiently and display enhanced infectivity, as demonstrated by challenge assays performed with T cell lines and primary CD4+ T lymphocytes. Finally, we report that ADAR1 associates with HIV-1 RNAs and edits adenosines in the 5′ untranslated region (UTR) and the Rev and Tat coding sequence. Overall these results suggest that HIV-1 has evolved mechanisms to take advantage of specific RNA editing activity of the host cell and disclose a stimulatory function of ADAR1 in the spread of HIV-1

Natriuretic peptides elevations after chronic exposure to cocaine

N/ACocaine is known to produce life-threatening cardiovascular complications. When cocaine abuse is suspected, the investigation of the causes of death may be challenging in forensic medicine. No exhaustive answer can be obtained in most cases, reinforcing the need of further investigational tools to be used in this field. The increasing knowledge in the available biomarkers of cardiac function together with the availability of high sensitive assays can provide new tools in the investigation of sudden cardiac death in chronic abuser. In this work, the assessment of cardiac dysfunction was assessed by measuring troponin I and natriuretic peptides as biomarkers, and considering other standard endpoints used in preclinical toxicology studies. All the procedures and endpoints considered were designed to allow an easy and complete translation from the laboratory animals to human beings. Lister Hooded rats were treated with cocaine in chronic (up to 12-18 weeks) self administration studies. Troponin I (cTnI) and Atrial Natriuretic Peptide (ANP) were evaluated at different timepoints and heart weight and histopathology was assessed at the end of the treatment period. Furthermore, cocaine and its main metabolites were measured in the rat fur, to assess rats\u2019 cocaine exposure. The results obtained showed that no morphological changes were present in the rat hearts, despite their chronic exposure to cocaine. Cardiac troponin I values in cocaine treated rats were normal, not different from control rats, further supporting the absence of morphological changes. On the contrary, ANP showed an increasing trend with time in all cocaine treated animals considered. The same approach was also adopted with a group of chronic health human cocaine abusers: 10 healthy cocaine abuser volunteers (with no cardiac pathologies) were considered, and troponin T, NT proBNP serum levels, cocaine and metabolites hair concentrations were measured. As in rats, no changes were observed in troponin serum levels, whereas the natriuretic peptides showed variations that suggest a parallelism with the minimal changes observed in rats. Similar changes are described in subjects considered at risk for hypertension. Natriuretic peptides are normally adopted as diagnostic/prognostic markers in the follow up of a number of cardiac or cardiovascular diseases; in this context, natriuretic peptides may represent a sensitive biomarker of heart dysfunction after cocaine chronic exposure

Allele and genotype frequencies of eight DNA polymorphisms in the Italian population

We report the allele and genotype frequencies in Italians of eight unlinked commonly utilized polymorphic loci: HUMTHO1, HUMFES/FPS, HLA-DQA1, LDLR, GYPA, HBGG, D7S8 and GC. Genomic DNA from at least 100 individuals was amplified by PCR and typed after electrophoresis (HUMTHO1, HUMFES/FPS), or reverse dot-blot (HLA-DQA1 and the other five loci). The allelic frequencies determined were compared with available population data. These results are useful for population and individual identification studies. \ua9 1995 Academic Press