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The relationship between cell proliferation and inositol lipid turnover has been studied by comparing the steady state of inositol derivative metabolism in quiescent and regenerating rat hepatocytes isolated at 4 h (G1 phase of first cell cycle) and 24 h (onset of M phase) after partial hepatectomy. The effect of two hormones able to regulate hepatic regeneration, insulin and vasopressin, has been considered, and the results can be summarized as follows: (i) at 4 h after partial hepatectomy, the precursor incorporation into inositol polyphosphates and the particulate phospholipase C activity increase with respect to quiescent hepatocytes, whereas the content of 11, 4, 5P3 does not change, suggesting an increased turnover of this molecule in this step of cell cycle priming; (ii) 24 h after partial hepatectomy, the radioactivity linked to IP3 and IP4, as well as soluble and particulate phospholipase C activity, and IP3 content increase, suggesting the presence, at the onset of M phase, of second messenger accumulation; (iii) only 24 h after partial hepatectomy, the inositol derivative metabolism is affected by vasopressin; and (iv) insulin exerts a modulatory role on inositol polyphosphate production without involving membrane-bound PLC activity or phosphoinositide hydrolysis. These data suggest that inositol-derived signal molecules are associated with hepatic regeneration; moreover, the metabolic pathway of such compounds seems to be regulated so that only specific inositol phosphates are present in each step of the cell cycle.

The composition of films deposited by dissociating pure tetramethyltin (TMT) or TMT/0 2 mixtures at 193 nm, was monitored by "in situ" Auger spectroscopy. The presence of C contamination, which was considerable in films obtained from the pure organometallic, was greatly reduced by the occurrence of oxidation and carbon-free films were achieved when the gas phase concentration of TMT was sufficiently small. The dependence of the OISn Auger electron spectroscopy peak-to-peak height ratio on the p(02)lp(TMT) ratio in the precursor mixture showed a saturation for large concentration of oxygen. The surface properties of the tin oxide films were investigated by synchrotron radiation ultraviolet photoemission spectroscopy (UPS). To this aim samples were transferred to a synchrotron radiation facility, without any exposure to air and kept in dynamical high vacuum. The UPS demonstrated that the films were essentially made of Sn02: in fact the valence band exhibited the typical features of Sn02 and the analysis of the 4dSn core levels demonstrated that all metal atoms were oxidized, since no contribution to the peak shape due to metallic tin was found. A weak emission from the band gap region indicated the presence of oxygen vacancies.

The binding and uptake of cholesterol enriched lipoproteins by isolated hepatocytes was decreased at 16 hours after partial hepatectomy, with a tendency to return to control values as the regeneration proceeds. The number of lipoprotein binding sites of total cellular membranes remained similar to control at 16 and 24 hours. The plasma lipoprotein pattern, determined by electrophoretic analysis, showed a lower per cent of very low density lipoproteins (VLDL) and a higher per cent of low density lipoproteins (LDL) at 16 and 24 hours post-partial hepatectomy. At these times, plasma lecithin: cholesterol acyltransferase (LCAT) activity was decreased. It is intriguing to suggest that the regenerating liver could regulate the blood lipoprotein pattern and the uptake of lipoproteins by modulating the surface expression of the receptors.