Effects of environmental complexity on neurogenesis in the hippocampal dentate gyrus

Introduction. Postnatal neurogenesis in the hippocampal dentate gyrus, can be modulated by numerous determinants, such as hormones, transmitters and stress. Among the factors positively interfering with neurogenesis, the complexity of the environment appears to play a particularly striking role. Adult mice reared in an enriched environment produce more neurons and exhibit better performance in hippocampus-specific learning tasks. While the effects of complex environments on hippocampal neurogenesis are well documented, there is a lack of information on the effects of living under socio-sensory deprivation conditions. Due to the immaturity of rats and mice at birth, studies dealing with the effects of environmental enrichment on hippocampal neurogenesis were carried out in adult animals, i.e. during a period of relatively low rate of neurogenesis. The impact of environment is likely to be more dramatic during the first postnatal weeks, because at this time granule cell production is remarkably higher than at later phases of development. The aim of the present research was to clarify whether and to what extent isolated or enriched rearing conditions affect hippocampal neurogenesis during the early postnatal period, a time window characterized by a high rate of precursor proliferation and to elucidate the mechanisms underlying these effects. The experimental model chosen for this research was the guinea pig, a precocious rodent, which, at 4-5 days of age can be independent from maternal care. Experimental design. Animals were assigned to a standard (control), an isolated, or an enriched environment a few days after birth (P5-P6). On P14-P17 animals received one daily bromodeoxyuridine (BrdU) injection, to label dividing cells, and were sacrificed either on P18, to evaluate cell proliferation or on P45, to evaluate cell survival and differentiation. Methods. Brain sections were processed for BrdU immunhistochemistry, to quantify the new born and surviving cells. The phenotype of the surviving cells was examined by means of confocal microscopy and immunofluorescent double-labeling for BrdU and either a marker of neurons (NeuN) or a marker of astrocytes (GFAP). Apoptotic cell death was examined with the TUNEL method. Serial sections were processed for immunohistochemistry for i) vimentin, a marker of radial glial cells, ii) BDNF (brain-derived neurotrofic factor), a neurotrophin involved in neuron proliferation/survival, iii) PSA-NCAM (the polysialylated form of the neural cell adhesion molecule), a molecule associated with neuronal migration. Total granule cell number in the dentate gyrus was evaluated by stereological methods, in Nissl-stained sections. Results. Effects of isolation. In P18 isolated animals we found a reduced cell proliferation (-35%) compared to controls and a lower expression of BDNF. Though in absolute terms P45 isolated animals had less surviving cells than controls, they showed no differences in survival rate and phenotype percent distribution compared to controls. Evaluation of the absolute number of surviving cells of each phenotype showed that isolated animals had a reduced number of cells with neuronal phenotype than controls. Looking at the location of the new neurons, we found that while in control animals 76% of them had migrated to the granule cell layer, in isolated animals only 55% of the new neurons had reached this layer. Examination of radial glia cells of P18 and P45 animals by vimentin immunohistochemistry showed that in isolated animals radial glia cells were reduced in density and had less and shorter processes. Granule cell count revealed that isolated animals had less granule cells than controls (-32% at P18 and -42% at P45). Effects of enrichment. In P18 enriched animals there was an increase in cell proliferation (+26%) compared to controls and a higher expression of BDNF. Though in both groups there was a decline in the number of BrdU-positive cells by P45, enriched animals had more surviving cells (+63) and a higher survival rate than controls. No differences were found between control and enriched animals in phenotype percent distribution. Evaluation of the absolute number of cells of each phenotype showed that enriched animals had a larger number of cells of each phenotype than controls. Looking at the location of cells of each phenotype we found that enriched animals had more new neurons in the granule cell layer and more astrocytes and cells with undetermined phenotype in the hilus. Enriched animals had a higher expression of PSA-NCAM in the granule cell layer and hilus Vimentin immunohistochemistry showed that in enriched animals radial glia cells were more numerous and had more processes.. Granule cell count revealed that enriched animals had more granule cells than controls (+37% at P18 and +31% at P45). Discussion. Results show that isolation rearing reduces hippocampal cell proliferation but does not affect cell survival, while enriched rearing increases both cell proliferation and cell survival. Changes in the expression of BDNF are likely to contribute to he effects of environment on precursor cell proliferation. The reduction and increase in final number of granule neurons in isolated and enriched animals, respectively, are attributable to the effects of environment on cell proliferation and survival and not to changes in the differentiation program. As radial glia cells play a pivotal role in neuron guidance to the granule cell layer, the reduced number of radial glia cells in isolated animals and the increased number in enriched animals suggests that the size of radial glia population may change dynamically, in order to match changes in neuron production. The high PSA-NCAM expression in enriched animals may concur to favor the survival of the new neurons by facilitating their migration to the granule cell layer. Conclusions. By using a precocious rodent we could demonstrate that isolated/enriched rearing conditions, at a time window during which intense granule cell proliferation takes place, lead to a notable decrease/increase of total granule cell number. The time-course and magnitude of postnatal granule cell production in guinea pigs are more similar to the human and non-human primate condition than in rats and mice. Translation of current data to humans would imply that exposure of children to environments poor/rich of stimuli may have a notably large impact on dentate neurogenesis and, very likely, on hippocampus dependent memory functions.

Entrepreneurial opportunities, capability development and the performance of new firms

This study aims at providing a theoretical framework encompassing the two approaches towards entrepreneurial opportunity (opportunity discovery and opportunity creation) by outlining a trajectory from firm creation to capability development, to firm performance in the short term (firm survival) and the medium/long term (growth rate). A set of empirically testable hypotheses is proposed and tested by performing qualitative analyses on interviews on a small sample of entrepreneurs and event history analysis on a large sample of firms founded in the United States in 2004.

Development and performance assessment of a Plasma Focus electron beam generator for Intra-Operative Radiation Therapy

The Plasma Focus is a device designed to generate a plasma sheet between two coaxial electrodes by means of a high voltage difference. The plasma is then driven to collapse into a “pinch”, where thermonuclear conditions prevail. During the “pinch phase” charged particles are emitted, with two main components: an ion beam peaked forward and an electron beam directed backward. The electron beam emitted backward by Plasma Focus devices is being investigated as a radiation source for medical applications, using it to produce x-rays by interaction with appropriate targets (through bremsstrahlung and characteristic emission). A dedicated Plasma Focus device, named PFMA-3 (Plasma Focus for Medical Applications number 3), has been designed, put in operation and tested by the research groups of the Universities of Bologna and Ferrara. The very high dose rate (several gray per discharge, in less than 1 µs) is a peculiarity of this device that has to be investigated, as it might modify the relative biological effectiveness (RBE). Aim of this Ph.D. project was to investigate the main physical properties of the low-energy x-ray beams produced by a Plasma Focus device and their potential medical applications to IORT treatments. It was necessary to develop the optimal geometrical configuration; to evaluate the x-rays produced and their dose deposited; to estimate the energy electron spectrum produced in the “pinch phase”; to study an optimal target for the conversion of the x-rays; to conduct simulations to study the physics involved; and in order to evaluate the radio-biological features of the beam, cell holders had to be developed for both irradiations and cell growth conditions.

Ricerca di Escherichia coli produttori di verocitotossine e definizione di obiettivi di performance nella produzione primaria di alimenti di origine animale

La presenza di Escherichia coli produttori di verocitotossine (VTEC o STEC) rappresenta una tra le più importanti cause di malattia alimentare attualmente presenti in Europa. La sua presenza negli allevamenti di animali destinati alla produzione di alimenti rappresenta un importante rischio per la salute del consumatore. In conseguenza di comuni contaminazioni che si realizzano nel corso della macellazione, della mungitura i VTEC possono essere presenti nelle carni e nel latte e rappresentano un grave rischio se la preparazione per il consumo o i processi di lavorazione non comportano trattamenti in grado d’inattivarli (es. carni crude o poco cotte, latte non pastorizzato, formaggi freschi a latte crudo). La contaminazione dei campi coltivati conseguente alla dispersione di letame o attraverso acque contaminate può veicolare questi stipiti che sono normalmente albergati nell’intestino di ruminanti (domestici e selvatici) e anche prodotti vegetali consumati crudi, succhi e perfino sementi sono stati implicati in gravi episodi di malattia con gravi manifestazioni enteriche e complicazioni in grado di causare quadri patologici gravi e anche la morte. Stipiti di VTEC patogeni ingeriti con gli alimenti possono causare sintomi gastroenterici, con diarrea acquosa o emorragica (nel 50% dei casi), crampi addominali, febbre lieve e in una percentuale più bassa nausea e vomito. In alcuni casi (circa 5-10%) l’infezione gastroenterica si complica con manifestazioni tossiemiche caratterizzate da Sindrome Emolitico Uremica (SEU o HUS) con anemia emolitica, insufficienza renale grave e coinvolgimento neurologico o con una porpora trombotica trombocitopenica. Il tasso di mortalità dei pazienti che presentano l’infezione da E. coli è inferiore all’1%. I dati forniti dall’ECDC sulle infezioni alimentari nel periodo 2006-2010 hanno evidenziato un trend in leggero aumento del numero di infezioni a partire dal 2007. L’obiettivo degli studi condotti è quello di valutare la prevalenza ed il comportamento dei VTEC per una analisi del rischio più approfondita.

Analysis and modelling of the performance of technologies for flue gas treatment in Waste-to-Energy processes

Waste management represents an important issue in our society and Waste-to-Energy incineration plants have been playing a significant role in the last decades, showing an increased importance in Europe. One of the main issues posed by waste combustion is the generation of air contaminants. Particular concern is present about acid gases, mainly hydrogen chloride and sulfur oxides, due to their potential impact on the environment and on human health. Therefore, in the present study the main available technological options for flue gas treatment were analyzed, focusing on dry treatment systems, which are increasingly applied in Municipal Solid Wastes (MSW) incinerators. An operational model was proposed to describe and optimize acid gas removal process. It was applied to an existing MSW incineration plant, where acid gases are neutralized in a two-stage dry treatment system. This process is based on the injection of powdered calcium hydroxide and sodium bicarbonate in reactors followed by fabric filters. HCl and SO2 conversions were expressed as a function of reactants flow rates, calculating model parameters from literature and plant data. The implementation in a software for process simulation allowed the identification of optimal operating conditions, taking into account the reactant feed rates, the amount of solid products and the recycle of the sorbent. Alternative configurations of the reference plant were also assessed. The applicability of the operational model was extended developing also a fundamental approach to the issue. A predictive model was developed, describing mass transfer and kinetic phenomena governing the acid gas neutralization with solid sorbents. The rate controlling steps were identified through the reproduction of literature data, allowing the description of acid gas removal in the case study analyzed. A laboratory device was also designed and started up to assess the required model parameters.

Monitoring and Prediction of Thermal Emergencies in High Performance Computing Systems

Modern scientific discoveries are driven by an unsatisfiable demand for computational resources. High-Performance Computing (HPC) systems are an aggregation of computing power to deliver considerably higher performance than one typical desktop computer can provide, to solve large problems in science, engineering, or business. An HPC room in the datacenter is a complex controlled environment that hosts thousands of computing nodes that consume electrical power in the range of megawatts, which gets completely transformed into heat. Although a datacenter contains sophisticated cooling systems, our studies indicate quantitative evidence of thermal bottlenecks in real-life production workload, showing the presence of significant spatial and temporal thermal and power heterogeneity. Therefore minor thermal issues/anomalies can potentially start a chain of events that leads to an unbalance between the amount of heat generated by the computing nodes and the heat removed by the cooling system originating thermal hazards. Although thermal anomalies are rare events, anomaly detection/prediction in time is vital to avoid IT and facility equipment damage and outage of the datacenter, with severe societal and business losses. For this reason, automated approaches to detect thermal anomalies in datacenters have considerable potential. This thesis analyzed and characterized the power and thermal characteristics of a Tier0 datacenter (CINECA) during production and under abnormal thermal conditions. Then, a Deep Learning (DL)-powered thermal hazard prediction framework is proposed. The proposed models are validated against real thermal hazard events reported for the studied HPC cluster while in production. This thesis is the first empirical study of thermal anomaly detection and prediction techniques of a real large-scale HPC system to the best of my knowledge. For this thesis, I used a large-scale dataset, monitoring data of tens of thousands of sensors for around 24 months with a data collection rate of around 20 seconds.

Applicazioni tecnologiche e nuovi metodi di valutazione della performance negli sport acquatici

Nello sport di alto livello l’uso della tecnologia ha raggiunto un ruolo di notevole importanza per l’analisi e la valutazione della prestazione. Negli ultimi anni sono emerse nuove tecnologie e sono migliorate quelle pre-esistenti (i.e. accelerometri, giroscopi e software per l’analisi video) in termini di campionamento, acquisizione dati, dimensione dei sensori che ha permesso la loro “indossabilità” e l’inserimento degli stessi all’interno degli attrezzi sportivi. La tecnologia è sempre stata al servizio degli atleti come strumento di supporto per raggiungere l’apice dei risultati sportivi. Per questo motivo la valutazione funzionale dell’atleta associata all’uso di tecnologie si pone lo scopo di valutare i miglioramenti degli atleti misurando la condizione fisica e/o la competenza tecnica di una determinata disciplina sportiva. L’obiettivo di questa tesi è studiare l’utilizzo delle applicazioni tecnologiche e individuare nuovi metodi di valutazione della performance in alcuni sport acquatici. La prima parte (capitoli 1-5), si concentra sulla tecnologia prototipale chiamata E-kayak e le varie applicazioni nel kayak di velocità. In questi lavori è stata verificata l’attendibilità dei dati forniti dal sistema E-kayak con i sistemi presenti in letteratura. Inoltre, sono stati indagati nuovi parametri utili a comprendere il modello di prestazione del paddler. La seconda parte (capitolo 6), si riferisce all’analisi cinematica della spinta verticale del pallanuotista, attraverso l’utilizzo della video analisi 2D, per l’individuazione delle relazioni Forza-velocità e Potenza-velocità direttamente in acqua. Questo studio pilota, potrà fornire indicazioni utili al monitoraggio e condizionamento di forza e potenza da svolgere direttamente in acqua. Infine la terza parte (capitoli 7-8), si focalizza sull’individuazione della sequenza di Fibonacci (sequenza divina) nel nuoto a stile libero e a farfalla. I risultati di questi studi suggeriscono che il ritmo di nuotata tenuto durante le medie/lunghe distanze gioca un ruolo chiave. Inoltre, il livello di autosomiglianza (self-similarity) aumenta con la tecnica del nuoto.

Growth performance, gut health, and metabolism of broilers under thermoneutral and heat stress conditions: multidisciplinary studies on the effects of nutritional strategies and genotype

This PhD project aimed to (i) investigate the effects of three nutritional strategies (supplementation of a synbiotic, a muramidase, or arginine) on growth performance, gut health, and metabolism of broilers fed without antibiotics under thermoneutral and heat stress conditions and to (ii) explore the impacts of heat stress on hypothalamic regulation of feed intake in three broiler lines from diverse stages of genetic selection and in the red jungle fowl, the ancestor of domestic chickens. Synbiotic improved feed efficiency and footpad health, increased Firmicutes and reduced Bacteroidetes in the ceca of birds kept in thermoneutral conditions, while did not mitigate the impacts of heat stress on growth performance. Under optimal thermal conditions, muramidase increased final body weight and reduced cumulative feed intake and feed conversion ratio in a dose-dependent way. The highest dose reduced the risk of footpad lesions, cecal alpha diversity, the Firmicutes to Bacteroidetes ratio, and butyrate producers, increased Bacteroidaceae and Lactobacillaceae, plasmatic levels of bioenergetic metabolites, and reduced the levels of pro-oxidant metabolites. The same dose, however, failed to reduce the effects of heat stress on growth performance. Arginine supplementation improved growth rate, final body weight, and feed efficiency, increased plasmatic levels of arginine and creatine and hepatic levels of creatine and essential amino acids, reduced alpha diversity, Firmicutes, and Proteobacteria (especially Escherichia coli), and increased Bacteroidetes and Lactobacillus salivarius in the ceca of thermoneutral birds. No arginine-mediated attenuation of heat stress was found. Heat stress altered protein metabolism and caused the accumulation of antioxidant and protective molecules in oxidative stress-sensitive tissues. Arginine supplementation, however, may have partially counterbalanced the effects of heat stress on energy homeostasis. Stable gene expression of (an)orexigenic neuropeptides was found in the four chicken populations studied, but responses to hypoxia and heat stress appeared to be related to feed intake regulation.

Ship performance modelling for least-CO2 emission routes

Decarbonization of maritime transport requires immediate action. In the short term, ship weather routing can provide greenhouse gas emission reductions, even for existing ships and without retrofitting them. Weather routing is based on making optimal use of both envi- ronmental information and knowledge about vessel seakeeping and performance. Combining them at a state-of-the-art level and making use of path planning in realistic conditions can be challenging. To address these topics in an open-source framework, this thesis led to the development of a new module called bateau , and to its combination with the ship routing model VISIR. bateau includes both hull geometry and propulsion modelling for various vessel types. It has two objectives: to predict the sustained speed in a seaway and to estimate the CO2 emission rate during the voyage. Various semi-empirical approaches were used in bateau to predict the ship hydro- and aerodynamical resistance in both head and oblique seas. Assuming that the ship sails at a constant engine load, the involuntary speed loss due to waves was estimated. This thesis also attempted to clarify the role played by the actual representation of the sea state. In particular, the influence of the wave steepness parameter was assessed. For dealing with ships with a greater superstructure, the wind added resistance was also estimated. Numerical experiments via bateau were conducted for both a medium and a large-size container ships, a bulk-carrier, and a tanker. The simulations of optimal routes were carried out for a feeder containership during voyages in the North Indian Ocean and in the South China Sea. Least-CO2 routes were compared to the least-distance ones, assessing the relative CO2 savings. Analysis fields from the Copernicus Marine Service were used in the numerical experiments.