Background. The authors have previously demonstrated in different experimental models that sustained processes of cellular growth are characterized by alterations of cholesterol metabolism not only in the proliferating tissues but also in the plasma compartment. Methods. To evaluate whether alterations of cholesterol metabolism similar to those observed in experimental models are also associated with human cancer, in the present study cholesterol distribution in tumor tissues and lipid composition in the plasma compartment were determined in patients with different types of gastrointestinal cancer. Results. The results showed that tumor tissues contain increased amounts of cholesterol when compared with the corresponding normal tissues. Intracellular alterations of cholesterol were accompanied by specific changes of cholesterol in the plasma compartment: high‐density lipoprotein (HDL) cholesterol was markedly reduced in the serum of patients with gastrointestinal cancer and the lipoprotein profiles showed a decrease in HDL3 fraction, the main HDL subfraction in human serum. The decrease of HDL cholesterol was negatively associated with the clinical stage of the disease. No changes in either total or low‐density lipoprotein cholesterol levels were observed. Conclusions. A major function attributed to HDL is to maintain normal cell cholesterol homeostasis by removing excess of cholesterol from intracellular pools. Because the use and storage of cholesterol are increased within the tumor tissues during growth, it is possible to hypothesize that low HDL levels observed in patients with gastrointestinal cancer are associated with the increased cholesterol metabolism in proliferating tissues.

Summary The metabolism of cholesterol has been investigated in tumour cells, ascitic fluid and blood serum during the growth of an ascites hepatoma Alterations of cholesterol metabolism have been consistently observed in a variety of experimental tumour models (Coleman & Lavietes, 1981;Van Blitterswijk et al., 1985;Clayman et al., 1986; Erickson et al., 1988) as well as in human neoplasias (Gebhard et al., 1987). These alterations include an increase in cholesterol content, associated with enhanced rates of de novo cholesterol synthesis and deregulation at the level of hydroxy-methyl-glutarylcoenzyme A reductase (HMGR), the rate limiting enzyme in sterol synthesis. It has been suggested that such changes could be related to an increased requirement of cholesterol for new membrane biogenesis that accompany cell growth (Coleman & Lavietes, 1981). More recently, however, the possibility that an increased production of mevalonate and its nonsterol isoprenoid products is needed in the initiating phases of DNA replication has been also proposed (Habenicht et al., 1980;Siperstein, 1984). Similar patterns of intracellular cholesterol metabolism were found in the hepatic hyperplasia induced by a potent mitogen, lead nitrate (Dessi et al., 1984), and in regenerating liver after partial surgical hepatectomy (Dessi et al., 1986). These similarities indicate that the above changes in cholesterol metabolism are related to cell proliferation per se, rather than to tumour growth in particular. Hepatic hyperplasia was characterised by peculiar alterations of cholesterol distribution also in the plasma compartment, namely a decrease in HDL cholesterol as well as in the HDL2/HDL3 ratio (Dessi et al., 1986;.Cholesterol metabolism in the body is regulated through a complex series of transport and biosynthetic mechanisms, which rely on the continuous exchange of cholesterol between tissues and blood. It is thus conceivable that any substantial alteration in the metabolism of cholesterol at the cellular level (e.g. during cell proliferation) may entail changes in the plasmatic pools of cholesterol.In the present study, cholesterol metabolism was investigated in tumour cells and in the blood compartment in rats during the growth of a highly deviated fast growing ascites hepatoma (Yoshida AH-130).The study was made at different time intervals after tumour transplantation in order to evaluate the alterations occurring in the malignant cells and whether these were associated with changes in the cholesterol distribution in the plasma of the host animal, as already observed in different models of cell proliferation (Dessi et al., 1986;

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The aim of this study was to evaluate the antimicrobial activity of selected essential oils (Laurus nobilis, Eucalyptus globulus and Salvia officinalis), both alone and in combination, in cosmetic preparations characterized by an increasing risk of microbial contamination, i.e. an O/W skin cream, a hydrogel and a non-alcoholic hydrolyte. Their potential synergistic effect in combination with the usual cosmetic preservatives at low concentrations (up to 200-fold less than usual) was also investigated.

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Hair breakage during combing was evaluated by combing tresses and examining photographs of snags of hair fibers in combs. The

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