Modelizzazione spazio-temporale delle dinamiche di uso del suolo ed analisi comparativa di differenti approcci predittivi. Uso integrato di SIG e telerilevamento nello studio dei processi di deforestazione nella regione La Joyanca in Peten, Guatemala

L’uso frequente dei modelli predittivi per l’analisi di sistemi complessi, naturali o artificiali, sta cambiando il tradizionale approccio alle problematiche ambientali e di rischio. Il continuo miglioramento delle capacità di elaborazione dei computer facilita l’utilizzo e la risoluzione di metodi numerici basati su una discretizzazione spazio-temporale che permette una modellizzazione predittiva di sistemi reali complessi, riproducendo l’evoluzione dei loro patterns spaziali ed calcolando il grado di precisione della simulazione. In questa tesi presentiamo una applicazione di differenti metodi predittivi (Geomatico, Reti Neurali, Land Cover Modeler e Dinamica EGO) in un’area test del Petén, Guatemala. Durante gli ultimi decenni questa regione, inclusa nella Riserva di Biosfera Maya, ha conosciuto una rapida crescita demografica ed un’incontrollata pressione sulle sue risorse naturali. L’area test puó essere suddivisa in sotto-regioni caratterizzate da differenti dinamiche di uso del suolo. Comprendere e quantificare queste differenze permette una migliore approssimazione del sistema reale; é inoltre necessario integrare tutti i parametri fisici e socio-economici, per una rappresentazione più completa della complessità dell’impatto antropico. Data l’assenza di informazioni dettagliate sull’area di studio, quasi tutti i dati sono stati ricavati dall’elaborazione di 11 immagini ETM+, TM e SPOT; abbiamo poi realizzato un’analisi multitemporale dei cambi uso del suolo passati e costruito l’input per alimentare i modelli predittivi. I dati del 1998 e 2000 sono stati usati per la fase di calibrazione per simulare i cambiamenti nella copertura terrestre del 2003, scelta come data di riferimento per la validazione dei risultati. Quest’ultima permette di evidenziare le qualità ed i limiti per ogni modello nelle differenti sub-regioni.

Sindrome di Down e fattori di rischio nel declino neurocognitivo

Down syndrome (DS) or Trisomy 21, occurring in 1/700 and 1/1000 livebirths, is the most common genetic disorder, characterized by a third copy of the human chromosome 21 (Hsa21). DS is associated with various defects, including congenital heart diseases, craniofacial abnormalities, immune system dysfunction, mental retardation (MR), learning and memory deficiency. The phenotypic features in DS are a direct consequence of overexpression of genes located within the triplicated region on Hsa21. In addition to developmental brain abnormalities and disabilities, people with DS by the age of 30-40 have a greatly increased risk of early-onset of Alzheimer’s disease (AD) and an apparent tendency toward premature aging. Many of the immunological anomalies in DS can be enclosed in the spectrum of multiple signs of early senescence. People with DS have an increased vulnerability to oxidative damage and many factors, including amyloid beta protein (Abeta), genotype ApoE4, oxidative stress, mutations in mitochondrial DNA (mtDNA), impairment of antioxidant enzymes, accelerated neuronal cell apoptosis, are related to neuronal degeneration and early aging in DS. SUBJECTS and METHODS: Since 2007 a population of 50 adolescents and adults with DS, 26 males and 24 females (sex-ratio: M/F = 1.08), has been evaluated for the presence of neurological features, biomarkers and genetic factors correlated with neuronal degeneration and premature aging. The control group was determined by the mother and the siblings of the patients. A neuropsychiatric evaluation was obtained from all patients. The levels of thyroid antibodies (antiTg and antiTPO) and of some biochemical markers of oxidative stress, including homocysteine (tHcy), uric acid, cobalamin, folate were measured. All patients, the mother and the siblings were genotyped for ApoE gene. RESULTS: 40% of patients, with a mild prevalence of females aged between 19 and 30 years, showed increased levels of antiTg and antiTPO. The levels of tHcy were normal in 52% patients and mildly increased in 40%; hyperomocysteinemia was associated with normal levels of thyroid antibodies in 75% of patients (p<0.005). The levels of uric acid were elevated in 26%. Our study showed a prevalence of severe MR in patients aged between 1-18 years and over 30 years. Only 3 patients, 2 females and one male, over 30 years of age, showed dementia. According to the literature, the rate of Down left-handers was high (25%) compared to the rest of population and the laterality was associated with increased levels of thyroid antibodies (70%). 21.5% of patients were ApoE4 positive (ApoE4+) with a mean/severe MR. CONCLUSIONS: Until now no biochemical evidence of oxidative damage and no deficiency or alteration of antioxidant function in our patients with DS were found. mtDNA sequencing could show some mutations age-related and associated with oxidative damage and neurocognitive decline in the early aging of DS. The final aim is found predictive markers of early-onset dementia and a target strategy for the prevention and the treatment of diseases caused by oxidative stress. REFERENCES: 1) Rachidi M, Lopes C: “Mental retardation and associated neurological dysfunctions in Down syndrome: a consequence of dysregulation in critical chromosome 21 genes and associated molecular pathways.” - Eur J Paediatr Neurol. May;12(3):168-82 (2008). 2) Lott IT, Head E: “Down syndrome and Alzheimer's disease: a link between development and aging.” - Ment Retard Dev Disabil Res Rev, 7(3):172-8 (2001). 3) Lee HC, Wei YH: “Oxidative Stress, Mitochondrial DNA Mutation, and Apoptosis in Aging.” - Exp Biol Med (Maywood), May;232(5):592-606 (2007).