Journal of Gastroenterology and Hepatology (2005) 20, 126–134 DOI: 10.1111/j.1400-1746.2004.03493.x Blackwell Science, LtdOxford, UKJGHJournal of Gastroenterology and Hepatology0815-93192004 Blackwell Publishing Asia Pty Ltd201126134Original Article HOC analysis of liver regeneration indicesC Liatsos et al. Correspondence: Dr Leontios J Hadjileontiadis, Aristotle University of Thessaloniki, Department of Electrical and Computer Engineering, D Building, 6th Floor, Office #3, GR 54124 Thessaloniki, Greece. Email: leontios@auth.gr Accepted for publication 27 January 2004. HEPATOLOGY Using higher-order crossings to distinguish liver regeneration indices in hepatectomized diabetic and non-diabetic rats CHRISTOS LIATSOS,* ,† LEONTIOS J HADJILEONTIADIS, ‡ STAMOS THEOCHARIS,* EVANGELIA PETRIDOU,* ALEXANDRA MARGELI,* SPYRIDON SKALTSAS,* CHRISTOS MAVROGIANNIS † AND MICHAEL MYKONIATIS* *Department of Experimental Pharmacology, Medical School, † Gastroenterology and Liver Unit, Faculty of Nursing, University of Athens, Athens and ‡ Department of Electrical and Computer Engineering, Aristotle University of Thessaloniki, Thessaloniki, Greece Abstract Background and Aims: Diabetes mellitus is implicated in several liver diseases; hence, its potential affection to liver regenerative capacity is an open research question. So far, only sporadic studies have addressed this issue, mainly using basic statistical techniques. The current study evaluated the ability of a novel technique, namely higher-order crossings (HOC), based on liver DNA biosynthesis and thymi- dine kinase (TK) enzymatic activity data, to discriminate liver regeneration processes between hepate- ctomized diabetic and non-diabetic rats. Methods: We used 251 adult male rats, divided in two groups; diabetic by Alloxan injection and non- diabetic control, subjected to 70% partial hepatectomy and killed at different time intervals post-partial hepatectomy (PH) (0–240 h). The rate of tritiated thymidine ( 3 HTdR) incorporation into hepatic DNA and the enzymatic activity of liver TK were estimated and, after proper interpolation, were analyzed using HOC sequences. Changes of the latter were captured and used as a means for linear discrimination between the two groups. Results: Ninth-order HOC estimated for post-PH (24, 28, 40, 44, 72 and 84 h) exhibited linear dis- crimination for the rate of 3 HTdR incorporation, whereas second-order HOC estimated for (44–72 h) post-PH exhibited linear discrimination for the TK enzymatic activity data. Fuzzy logic-based c-means cluster analysis of HOC provided distinct areas of group categorization (100% accuracy) for diagnostic distinctions (P < 0.001). The data grouping pointed out by the HOC-based analysis revealed an onset delay in the liver regeneration process when Alloxan diabetes was present (P < 0.05). Conclusions: Our results suggest that HOC have the potential to linearly discriminate between exper- imentally induced diabetic and non-diabetic liver regeneration post-PH processes, based on two liver regeneration indices, capturing the delay seen in the liver regeneration process due to Alloxan diabetes, fostering their use as an efficient classification tool. In this way, HOC could be used as an advanced, eas- ily implemented and user-friendly method to thoroughly analyze liver regeneration processes. © 2004 Blackwell Publishing Asia Pty Ltd Key words: experimentally induced diabetes mellitus, higher-order crossings, liver DNA biosynthesis, liver regeneration, thymidine kinase enzymatic activity. INTRODUCTION Liver regeneration is a vital component of the reparative process following liver injury and/or surgical resection. 1 As diabetes mellitus is implicated in several liver diseases 2–5 it is expected to affect the regenerative capac- ity of the liver. However, the examination of the liver regeneration process in diabetic patients confronts seri- ous ethical issues. As a result, related experimental studies initially focused on animal experiments. The assessment of liver regeneration usually uses several tis- sue and serum-based methods, that is, thymidine and