1,721,089 research outputs found
La distribuzione di Poisson nel laboratorio biomedico
No full textLa moderna ricerca biomedica è prevalentemente concentrata sugli aspetti molecolari che presiedono al funzionamento delle cellule dei nostri tessuti. Questo è dovuto soprattutto all'enorme e rapido - e per certi versi strabiliante - progresso delle biotecnologie e della bioinformatica, che nell'ultimo decennio hanno permesso con relativa facilità di raccogliere ed interpretare moltissime informazioni sulla struttura ed espressione dell'informazione genetica, sugli aspetti metabolici e biochimici e in generale sulle reti molecolari che agiscono per regolare la vita cellulare. Difetti nel funzionamento anche di una sola molecola possono propagarsi all'intero sistema molecolare determinando patologie talvolta molto gravi. Grandi sforzi vengono oggi compiuti in tutto il mondo dai ricercatori biomedici per cercare di definire la carta d'identità molecolare delle malattie e, da un punto di vista tecnologico, per cercare di dominare l'estrema complessità delle reti molecolari delle cellule. Ma nonostante la sua grande potenzialità questo approccio presenta due limiti importanti: è un approccio essenzialmente descrittivo, poiché è estremamente difficile - se non impossibile - determinare la variazione delle quantità di tutte le molecole che partecipano alle numerose reazioni biochimiche in una cellula; l'approccio molecolare non dice nulla sulle interazioni dinamiche tra le diverse popolazioni cellulari in un tessuto, e tuttavia sono proprio queste interazioni a determinare processi fisiologici e patologici importanti come ad esempio la risposta immunitaria e i tumori.
Per quantificare la frequenza delle cellule che presiedono ad una certa funzione, sia da sole sia in interazione con altri tipi cellulari, è possibile ricorrere a metodi statistici che fanno largo uso della distribuzione di Poisson. Questi metodi sono noti fin dalla seconda metà del 1900 [B.1] e, cosa molto importante, rappresentano un esempio di come dovrebbe essere sempre la statistica a determinare e a guidare la sperimentazione biomedica, anche nei suoi aspetti meramente tecnologici ed operativi. Un fatto spesso trascurato dai moderni ricercatori biomedici
Estimating the growth kinetics of experimental tumours from as few as two determinations of tumour size: implications for clinical oncology
No full textClinical information on tumor growth is often limited to a few determinations of the size of the tumor burden taken at variable time. As a consequence, fitting of growth equations to clin- ical data is hampered by the small number of available data. On the other hand, characterising the tumor growth kinetics in terms of clinically relevant parameters, such as the doubling time of the tumors, is increasingly required to optimize and personalise treat- ments. A computational method is presented which can estimate the growth kinetics of tumors from as few as two determinations of its size taken at two successive time points, provided the size at which tumor growth saturates is known. The method is studied by using experimental data obtained in vitro with multicell tumor spheroids and in vivo with tumors grown in mice, and its outputs are compared to those obtained by fitting of experimental data with the Gompertz growth equation. Under certain assumptions and limitations the method provides comparable estimates of the doubling time of tumors with respect to the classical nonlinear fit- ting approach. The method is then tested against simulated tumor growth trajectories spanning the range of tumor sizes observed in the clinics. The simulations show that a relative classification of tu- mors on the basis of their growth kinetics can be obtained even if the size at which tumor growth saturates is not known. This re- sult opens the possibility to classify patients bearing fast or slow growing tumors and, hence, to adapt therapeutic regimens under a more rationale basis
Physical and computational issues in a simulation of multicellular tumor spheroids
No full textWe have developed a computer program which simulates the growth and development of multicellular tumor spheroids. The program implements a basic description of the metabolism, growth and proliferation of single cells, a full 3-dimensional geometry, and handles the complex problem of diffusion and transport of nutrients and metabolites into and out of cells, and in their surrounding environment. Here we discuss some of the challenging computational problems that arise in the implementation of this biophysical model
Tumor microenvironment in a real-life model of tumor spheroids
No full textTumors are complex bio-systems and cell growth is coupled to the chemical modifications of the extracellular microenvironment. Tumor cells and their microenvironment, therefore, constitute an evolving cellular ecosystem and a detailed understanding of the underlying dynamics might provide insights into tumor development and resistance to therapy. Here we present a real-life computer program for the simulation of multicell tumor spheroids. Simulation results compare quite well with experimental data and yields unique view of tumor microenvironment
Microplate spectrophotometry for the high-throughput screening of cytotoxic molecules
No full textObjectives: High-throughput chemical and biochemi- cal technologies are now exploited by modern phar- macology and toxicology to synthesize a multitude of new molecules with bioactive potential, or to isolate them from living matter. Testing molecules in cell sys- tems on a large scale, however, is a rate-limiting step in drug discovery or in toxicity assessment. In this study, we developed a low-cost high-throughput method for first-level screening of cytotoxic molecules.
Materials and methods: We used microplate spectro- photometry to measure growth kinetics of human tumour cells that grow in suspension (Molt3) or adherent to the plastic surface of culture wells (HeLa) in standard RPMI medium. Cells were trea- ted with colchicin, idarubicin or paclitaxel under var- ious treatment schedules. The effects were quantified and compared with those measured by optical microscopy using the trypan blue dye exclusion method to reveal dead cells.
Results: Proliferation kinetics of tumour cells can be quantified by measuring variations in optical densi- ties of cell samples at 410 and 560 nm wavelengths. For cells that grow in suspension, one single reading at 730 nm may be sufficient to reconstruct growth curves that parallel those obtained by direct cell counting. Effects of the cytotoxic treatments could also be quantified and results compared very favour- ably with those obtained using standard techniques. Conclusions: Microplate spectrophotometry is a robust and sensitive method to monitor growth of animal cell populations both in the absence and in
the presence of cytotoxic drugs. This method imple- ments existing technologies and can be fully auto- mated
Basalt intrusions in paleokarst caves in the Central Lessini mountains (Venetian Prealps, Italy)
Full text linkThe Lessini Mountains carbonate plateau (Venetian Prealps, It- aly) is one of the most important karst areas in Italy. Along with alpine-type caves and well-developed karst landscapes, palae- okarst features are also common. In most cases, palaeokarst is represented by caves and ssures lled by limonitic-haematitic palaeosols (ochres) in which fossiliferous arenite layers are sometimes embedded. ese features developed and fossilised during a late Eocene-middle Miocene phase of emersion. Be- tween the Palaeocene and the Oligocene, over a time span par- tially overlapping the development of palaeokarst, basaltic vol- canism took place in the Lessini Mountains. Along with ochre lls, cave passages that were intruded by basalt provide further evidence that a well as developed karst network existed in the Lessini Mountains area in the middle-late Palaeogene. More- over, basalt intrusions provide the only available data for the dating of palaeokarst in the central Lessini Mountains, where fossiliferous layers in ochre beds have not been found. We have started a new survey on palaeokarst in the Lessini pla- teau, with the aim of identifying ancient features on the basis of unusual lls (namely, ochre and basalt) and morphologies. New instances of basalt intrusions in three caves, Spigola di Canova, Covoli di Velo, and Covolo della Croce, have been recognised; evidence of pre-existing karst features lled by basalt in a pre- viously studied cave (Grotta A Veja) has been identi ed, and an unusual basalt outcrop that might relate to palaeokarst has also been observed. is paper aims to document the new ndings and to discuss previous ones. At the same time, we would like to point out some cautionary observations to prevent a “basalt = palaeokarst” misunderstanding
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