Hepatic regeneration and growth factors

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Programma di ray-tracing nel magnetoplasma ionosferico

Il pacchetto applicativo “IONORT” per il calcolo del ray-tracing può essere utilizzato dagli utenti che impiegano il sistema operativo Windows. È un programma la cui interfaccia grafica con l’utente è realizzata in MATLAB. In realtà, il programma lancia un eseguibile che integra il sistema d’equazioni differenziali scritto in linguaggio Fortran e ne importa l’output nel programma MATLAB, il quale genera i grafici e altre informazioni sul raggio. A completamento di questa premessa va detto che questo pacchetto, nella sua parte computazionale, è figlio di un programma di Jones e Stephenson del 1975, dal titolo “A versatile three-dimensional ray-tracing computer program for radio waves in the ionosphere”, il quale a sua volta si rifaceva principalmente a un programma di ray-tracing di Dudziak (1961) e di altri ricercatori quali Croft and Gregory (1963), ecc.. Pertanto, come tutti i recenti programmi di ray- tracing, questo è un programma fatto di programmi e non si può non menzionare qui la prima applicazione numerica di ray-tracing di Haeselgrove (1955). Attualmente questi programmi sono stati ottimizzati e adattati alle applicazioni dei radar oltre l’orizzonte - Over The Horizon, OTH – [Coleman, 1998][Nickish, 2008] sfruttando le potenzialità di potenti computer e periferiche per la presentazione e l’utilizzo real-time nel problema delle coordinate registration CR. In ultimo, si precisa che tutti i parametri di input, output e le modalità d’uso del pacchetto applicativo sviluppato saranno forniti nel manuale utente allegato al CD

Cell proliferation and oncogene expression after bile duct ligation in the rat: Evidence of a specific growth effect on bile duct cells

The proliferative response of the rat liver was measured after temporary or permanent total biliary obstruction (BDO) and in different regions after selective ligation of the lobar ducts draining the right 60% of the hepatic mass. The results were compared with those after 70% partial hepatectomy (PH). Cell proliferation was assessed globally by measuring DNA synthesis and stratified to the separate cell populations with cytostaining techniques that allowed distinction of hepatocytes, duct cells, and nonparenchymal cells (NPCs). In selected experimental groups, gene expression was determined of transforming growth factor-β1 (TGFβ-1), prothrombin, c-erb-B2, transforming growth factor alpha (TGFα), human Cyclophilin (CyP), and 28S ribosomal RNA. The stimulation of a proliferative response to total BDO required obstruction for longer than 24 hours, but after this deligation did not switch off regeneration. In the first week after permanent BDO, there was progressive infiltration of NPCs, fibrous linkage of some portal areas, and a crescendo of DNA synthesis that was obvious at 24 hours, maximal at 48 hours, and back nearly to baseline at 6 days. At the 2-day mark, the bile duct cells had a 17-fold increase in proliferation, accompanied by a threefold to fourfold increase in hepatocyte renewal. Little or no increase in expression of TGFα or the hepatocyte-specific prothrombin gene was detectable in the first 48 hours, whereas levels of the oncogene c-erb-B2 that is associated with cholangiocarcinoma were expressed from 48 to 96 hours. Livers subjected to regional BDO with or without immunosuppressive treatment with FK 506 and cyclosporine had an inflammatory reaction only on the side with ligated ducts. DNA synthesis increased in both the obstructed and freely draining lobes to approximately half the level that occurred after total BDO. The proliferation of the obstructed side was similar to the mixed duct cell/hepatocyte response after total BDO, but this almost exclusively involved duct cells on the freely draining side. In contrast to the findings after BDO, livers after PH regenerated maximally at 24 hours rather than 48 hours, had a predominantly noninflammatory hepatocyte as opposed to duct cell response, and had marked expression of the prothrombin and TGFα genes but only weakly and late of c-erb-B2 messenger RNA. The results show that the liver responds as a whole and in a biologically intelligent way to the nature of the injury inflicted on any part of it. It further implies the presence of humoral communications and control networks that assure organ homeostasis and relate this to total body homeostasis. © 1995

A method to test HF ray tracing algorithm in the ionosphere by means of the virtual time delay

It is well known that a 3D ray tracing algorithm furnishes the ray’s coordinates, the three components of the wave vector and the calculated group time delay of the wave along the path. The latter quantity can be compared with the measured group time delay to check the performance of the algorithm. Simulating a perfect reflector at an altitude equal to the virtual height of reflection, the virtual time delay is assumed as a real time delay. For a monotonic electronic density profile we find a very small relative difference between the calculated and the virtual delay for both analytic and numerical 3D electronic density models

Effects of rapamycin on cultured hepatocyte proliferation and gene expression

Rapamycin, a potent immunosuppressive drug that disrupts normal signal‐transduction processes, inhibited hepatocyte proliferation without evidence of inherent cytotoxicity in rat hepatocytes cultured in conventional medium or in a medium enriched with epidermal growth factor. The antiproliferative effect was dose dependent, uninfluenced by the concentration of epidermal growth factor in the medium and long lasting after a brief exposure. The effect of rapamycin was unaltered by the concomitant presence of FK 506 in the medium, suggesting that different binding affinities of these two drugs or even a separate rapamycin binding site may exist. Hepatocytes harvested 12 and 24 hr after partial hepatectomy were progressively less responsive to the antiproliferative effect of rapamycin. The gene expression of transforming growth factor‐β was reduced under in vivo rapamycin treatment, but at the same time the gene expression of albumin and glyceraldehyde‐3‐phosphate dehydrogenase was unchanged or increased. The experiments confirm that rapamycin has inherent growth‐control qualities, and they strengthen the hypothesis that the recently defined immunophilin network is central to many aspects of cellular growth control. (HEPATOLOGY 1992;15:871–877). Copyright © 1992 American Association for the Study of Liver Disease