The Search for Candidate Relevant Subsets of Variables in Complex Systems.

We describe a method to identify relevant subsets of variables, useful to understand the organization of a dynamical system. The variables belonging to a relevant subset should have a strong integration with the other variables of the same relevant subset, and a much weaker interaction with the other system variables. On this basis, extending previous work on neural networks, an information-theoretic measure, the dynamical cluster index, is introduced in order to identify good candidate relevant subsets. The method does not require any previous knowledge of the relationships among the system variables, but relies on observations of their values over time. We show its usefulness in several application domains, including: (i) random Boolean networks, where the whole network is made of different subnetworks with different topological relationships (independent or interacting subnetworks); (ii) leader-follower dynamics, subject to noise and fluctuations; (iii) catalytic reaction networks in a flow reactor; (iv) the MAPK signaling pathway in eukaryotes. The validity of the method has been tested in cases where the data are generated by a known dynamical model and the dynamical cluster index is applied in order to uncover significant aspects of its organization; however, it is important that it can also be applied to time series coming from field data without any reference to a model. Given that it is based on relative frequencies of sets of values, the method could be applied also to cases where the data are not ordered in time. Several indications to improve the scope and effectiveness of the dynamical cluster index to analyze the organization of complex systems are finally given.

Plasma and follicular fluid fatty acid profiles in dairy cows.

Composition of follicular fluid to which the preovulatory follicle is exposed may be one of the major factors determining subsequent fertility, as fatty acids are a precursor of hormones involved in dominance, ovulation and atresia mechanisms. The objective of this paper is to observe fatty acid profiles in various lipid classes according to estrogenic activity of follicles. For each of the 18 cows, we analysed plasma and follicular fluid fatty acid profiles of phospholipids, non-esterified fatty acid (NEFA), cholesteryl esters and triglycerides fractions. Follicles were classified as active (ratio oestrogen to progesterone E2/P4 > 1) and inactive (E2/P4 < 1). For seven cows, we get both types of follicles, six had only one active follicle and five cows had only one inactive follicle. The NEFA profile for palmitic acid, stearic acid, oleic acid, linoleic acid, C20:3n6, arachidonic acid and docosapentaenoic acid (DPA; p < 0.001) is different between inactive and active follicles and plasma. Compared with active follicular fluid and plasma, follicular fluid of inactive follicles showed lower stearic acid, higher oleic acid, arachidonic acid and DPA (p < 0.05) in phospholipids. No significant differences were observed in the cholesteryl ester fraction, which is composted mainly of linoleic acid. Triglyceride concentrations were too low to get reliable results. This study suggests that follicles have a specific fatty acid metabolism depending on oestrogen activity.

Brain natriuretic peptide variations are linked to volume status in hemodialysis patients.

AIMS: To evaluate the usefulness of monthly brain natriuretic peptide (BNP) dosage in assessing dry weight in hemodialysis patients. PATIENTS AND METHODS: Over a 2-year period, we performed in 46 hemodialysis patients monthly BNP level measurements, and adapted dry weight following the determination of variations in BNP concentrations for each month during the study period. Then we tested our approach by looking for a statistical relation between monthly alterations in BNP levels and monthly variations in the patients' weight, blood pressure, hemoglobinemia and albuminemia which are in themselves related to fluid status variations. RESULTS: Monthly BNP level variations were found to be positively correlated with monthly end-dialysis weight alterations (r = +0.24, p < 0.001), with monthly systolic and diastolic blood pressure variations before dialysis (r = +0.09, p < 0.001; r = +0.24, p < 0.001), and with systolic and diastolic blood pressure changes after dialysis (r = +0.09, p = 0.001; r = +0.25, p < 0.001). Moreover, monthly BNP level variations were negatively correlated with monthly hemoglobinemia changes (r = -0.17, p = 0.004) and with monthly albuminemia alterations (r = -0.14, p = 0.001). CONCLUSION: In a non-selected population of hemodialysis patients it was found that monthly BNP level variations were positively correlated with monthly volume status alterations as evaluated by clinical and biological criteria. BNP appears to be a useful tool for dry weight assessment despite the absence of a standardized cut-off point for BNP levels in hemodialysis patients.

Sufficient conditions for emergent synchronization in protocell models.

In this paper, we study general protocell models aiming to understand the synchronization phenomenon of genetic material and container productions, a necessary condition to ensure sustainable growth in protocells and eventually leading to Darwinian evolution when applied to a population of protocells. Synchronization has been proved to be an emergent property in many relevant protocell models in the class of the so-called surface reaction models, assuming both linear- and non-linear dynamics for the involved chemical reactions. We here extend this analysis by introducing and studying a new class of models where the relevant chemical reactions are assumed to occur inside the protocell, in contrast with the former model where the reaction site was the external surface. While in our previous studies, the replicators were assumed to compete for resources, without any direct interaction among them, we here improve both models by allowing linear interaction between replicators: catalysis and/or inhibition. Extending some techniques previously introduced, we are able to give a quite general analytical answer about the synchronization phenomenon in this more general context. We also report on results of numerical simulations to support the theory, where applicable, and allow the investigation of cases which are not amenable to analytical calculations.

Molecular adsorbents recirculating system treatment in acute-on-chronic hepatitis patients on the transplant waiting list improves model for end-stage liver disease scores.

BACKGROUND: The aim of our study was to show an improvement in Model for End-Stage Liver Disease (MELD) score after treatment with Molecular adsorbents recirculating system (MARS) in acute-on-chronic hepatitis (AoCHF) patients. MELD was adopted to determine the prognosis of patients with liver chronic desease. We evaluated the possibility to improve the MELD score of patients awaiting liver transplantation using a liver support device, namely, MARS. PATIENTS AND METHODS: From September 1999 to April 2006, we treated 80 patients whose diagnoses were hepatitis C, 41.25%; hepatitis B, 27.5%; alcholic, 17.5%; intoxication, 8.75%; primary biliary cirrhosis, 5%. The overall mean age was 45 years (23 to 62), the cohort included 56 men and 24 women. Inclusion criteria were bilirubin >15 mg/dL; MELD >20; encephalopathy >II; and International Normalized Ratio, >2.1. Other parameters evaluated included ammonia, creatinine, lactate, glutamic oxalic transminase, and guanosine 5'-triphosphate. All patients were treated with a mean of 6-hour cycles of MARS (range, 5 to 8 hours) for a minimum of three treatments and a maximum of 20 treatments over 3 months. Clinical conditions were evaluated by improved hemodynamic parameters, kidney function, liver function, coagulation, neurologic status using the SOFA score, Glasgow Coma Scale (GCS), and Acute Physiology and Chronic Health Evaluation II Criteria. RESULTS: The MELD score for all categories of living patients showed significant improvements at the end of treatment and at 3-months follow-up, but the small number of patients was a limitation to determine prediction of mortality. CONCLUSION: Our study shows that MARS treatment improved multiple organ functions-liver, renal, neurologic, and hemodynamic. The improved MELD score gave patients on the transplant waiting list longer survival, allowing them a greater opportunity for liver transplantation.

[An exceptional etiology of left ventricular aneurysm: type AA amyloidosis]. / Une cause exceptionnelle d'anévrisme du ventricule gauche: l'amylose de type AA.

Left ventricular aneurysms most often occur in the course of myocardial infarction. In rare cases they can be detected when the coronary network is devoid of any lesions. The aetiology is therefore multiple and dependent on the context. One aetiology seems less exceptional and concerns idiopathic aneurysms encountered in the African population, where the role of a "debilitating condition" such as tuberculosis has been evoked. We report the case history of a young patient from Zaire with a left ventricular aneurysm discovered in association with ganglionic tuberculosis complicated by AA amyloidosis. Histological analysis allowed the aetiological diagnosis to be established. Aneurysmal dilatation of the left ventricle was reported in the presence of amyloid deposits at the intra-myocardial arteriole level, whereas the context suggested a tubercular role. In spite of the difficulty of establishing a precise aetiological diagnosis, there seems to exist a consensus for surgical management.

[A class of models to discriminate ancient populations under the bio-demographic aspect. The link of the "Partecipanze"]. / Una classe di modelli per differenziare popolazioni antiche nell'aspetto bio-demografico. Il vincolo delle "Partecipanze".

"The paper is concerned with the problem of discriminating two ancient populations with respect to the presence of the 'Istituto delle Partecipanze', a sort of collective property of the land, beginning in 1253 in some areas of the Emilia region. A time series analysis on the marriages registered in the last four centuries has been performed and different classes of the ARIMA models have been fitted to the data. The results give evidence to the heterogeneous development that characterizes the two populations in some aspects of the their bio-demographic history." (SUMMARY IN ENG AND FRE)