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Ezio Venturino

Publications and source records attributed to Ezio Venturino.

7 recordsLinked to original sources
PubMed2006

The role of transmissible diseases in the Holling-Tanner predator-prey model.

Transmissible diseases are known to induce remarkable major behavioral changes in predator-prey systems. However, little attention has been paid to model such situations. The latter would allow to predict useful applications in both dynamics and control. Here the Holling-Tanner model is revisited to account for the influence of a transmissible disease, under the assumption that it spreads among the prey species only. We have found the equilibria and analyzed the behavior of the system around each one of them. A threshold result determining when the disease dies out has been identified. We also investigated the parametric space under which the system enters into Hopf and transcritical bifurcations, around the disease free equilibrium. The system is shown to experience neither saddle-node nor pitch-fork bifurcation. Global stability results are obtained by constructing suitable Lyapunov functions.

Animals↗
PubMed2006

How diseases affect symbiotic communities.

Examples of species living in symbiotic communities are well known among biologists. In this study we extend our previous analysis of predator-prey or competing models subject to a disease spreading among one of the species to populations mutually benefiting from interactions. We assume that one of the species is subject to a disease which cannot cross the species barrier and investigate the behavior of such a community. Our findings indicate that there are parameter ranges for which an interesting phenomenon occurs. Namely, the equilibrium shifts to a higher value. That is, the disease seems to have a positive effect on the environment as also field experiments show.

Algorithms↗
PubMed2006

Population screening for coeliac disease in a low prevalence area in Italy.

OBJECTIVE: A screening program was proposed for the village of Carcare (population 5700), located in a region of Italy with an apparently low prevalence of coeliac disease (CD): only 1 patient diagnosed out of 2557 inhabitants. The study group comprised 1002 individuals (568 F, 434 M, age range 13-90 years) recruited from blood donors, secondary school pupils and people referred to the local outpatient facilities for routine blood chemistry. MATERIAL AND METHODS: Total IgA, IgA anti-tissue transglutaminase (tTG) (ELISA, recombinant human antigen) and IgA antiendomysium (EMA) (IFI, umbilical cord substrate) antibodies were measured in the serum of all participants. All patients with IgA deficiency were investigated for IgG tTG antibodies, and in the case of disagreement between tTG and EMA, they were typed for HLA DQ2-DQ8 haplotypes. RESULTS: Thirteen subjects were positive and 988 negative for autoantibodies (3/988 had IgA deficiency). One serum sample was positive for tTG antibodies but negative for EMA. Ten out of 13 positive subjects consented to undergo duodenal biopsy, which invariably produced evidence of CD despite the absence of clinical signs/symptoms. A post-diagnostic clinical investigation provided evidence showing mild iron deficiency (4 subjects) and osteoporosis (2 subjects). After counselling, all subjects accepted a gluten-free diet. CONCLUSIONS: The prevalence of CD in the study group was 1:100 (1.0%; 95% CI: 0.5-1.8%): this indicates that CD is largely underdiagnosed in Carcare. Our results suggest that the low prevalence of CD observed in some regions is likely to be due to underdiagnosis.

Adolescent↗
PubMed2002

Epidemics in predator-prey models: disease in the predators.

The author has recently proposed and investigated models for the study of interacting species subject to an additional factor, a disease spreading among one of them, that somehow affects the other one. The inadequacy of such a model comes from the basic assumption on the interacting species. It is well known that the cycles found in the Lotka-Volterra system exhibit a neutral stability, and this phenomenon is carried over to the proposed model. Here we would like to extend the study to account for population dynamics leading to carrying capacities, i.e. logistic behaviour. This corresponds to the so-called quadratic predator-prey models found in the literature. We are able to show that in some cases the trajectories are bounded, and also analyse the local stability of some equilibria.

Animals↗
PubMedDate not supplied

Management of patients with gastrointestinal stromal tumors: experience from an Italian hospital.

Gastrointestinal stromal tumors are malignancies originating from stromal/mesenchymal tissues, most commonly in the stomach and small intestine, although they can be located everywhere in the gastrointestinal tract. Diagnosis is based on histological and immunohistochemical examination, and these rare tumors are characterized by c-kit (CD117) staining. Complete removal of the tumor is often curative in localized gastrointestinal stromal tumors and is always recommended. Clinically, their behavior is difficult to predict, and mitotic count and tumor size seem to be the most effective prognostic factors. We performed a retrospective analysis of clinical presentation and course, surgical management and pathological features of patients with gastrointestinal stromal tumors treated in our institution from 1995 to 2003. Twenty-two patients were enrolled in the study, and all of them underwent surgery. There were two perioperative deaths, and global morbidity was about 13%. Nineteen patients were followed (mean, 31 months): 4 patients had disease progression/recurrence and died, and one patient experienced a local recurrence and was reoperated with a curative intent; 14 patients were disease free. Our experience shows that histological and immunohistochemical examinations are fundamental for a definitive diagnosis and to assess the risk of aggressive behavior. Moreover, our results confirm that in stromal tumors complete surgical resection remains the mainstay of treatment in localized gastrointestinal stromal tumors, although the recurrence rate is relatively high. It is conceivable that treatment and prognosis of metastatic and non-resectable gastrointestinal stromal tumors, as well as the adjuvant treatment of high-risk, radically excised gastrointestinal stromal tumors will be strongly impacted by the c-kit target therapy.

Aged↗
PubMedDate not supplied

Chaos and order in plankton dynamics. Complex behavior of a simple model.

The role of the diffusive interaction between fish-populated and fish-free habitats in a patchy environment in plankton pattern formation is studied by means of a minimal reaction-diffusion model of the nutrient-plankton-fish food chain. It is shown that such interaction can give rise to spatio-temporal plankton patterns. The fractal dimension of the patterns is shown dependent on the fish predation rate. The spatially averaged plankton dynamics depending on both fish predation rate and distance between fish-populated habitats can exhibit chaotic and regular behavior. The chaotic plankton dynamics is characteristic of a wide parameter range.

Animals↗