Cell-cell interaction and diversity of emergent behaviours

Despite myriads of possible gene expression profiles, cells tend to be found in a confined number of expression patterns. The dynamics of Boolean models of gene regulatory networks has proven to be a likely candidate for the description of such self-organisation phenomena. Because cells do not live in isolation, but they constantly shape their functions to adapt to signals from other cells, this raises the question of whether the cooperation among cells entails an expansion or a reduction of their possible steady states. Multi random Boolean networks are introduced here as a model for interaction among cells that might be suitable for the investigation of some generic properties regarding the influence of communication on the diversity of cell behaviours. In spite of its simplicity, the model exhibits a non-obvious phenomenon according to which a moderate exchange of products among adjacent cells fosters the variety of their possible behaviours, which on the other hand are more similar to one another. On the contrary, a more invasive coupling would lead cells towards homogeneity.

A dynamical model of genetic networks for cell differentiation

A mathematical model is proposed which is able to describe the most important features of cell differentiation, without requiring specific detailed assumptions concerning the interactions which drive the phenomenon. On the contrary, cell differentiation is described here as an emergent property of a generic model of the underlying gene regulatory network, and it can therefore be applied to a variety of different organisms. The model points to a peculiar role of cellular noise in differentiation and leads to non trivial predictions which could be subject to experimental testing. Moreover, a single model proves able to describe several different phenomena observed in various differentiation processes.

A comparative stereological study of the term placenta in the donkey, pony and Thoroughbred

The aim of the study was to compare horse and donkey placentae using stereological techniques. Term placentae were collected at spontaneous foaling from seven Thoroughbred mares, seven pony mares, and six jenny donkeys. Maternal and foal weights were recorded and the mass, volume, and gross area of each allantochorion was also recorded. Ten random biopsies were recovered and processed for light microscopy from which the surface density of the microcotyledons (S(v)) and the total microscopic area of fetomaternal contact were calculated stereologically. Gestation length was longer in the donkeys than the other two groups (median values: 371 vs. 327 and 341 days, P < 0.05). There were significant correlations between foal birthweight and gross area (rho = 0.89; n = 20; P < 0.05), mass (rho = 0.84; n = 20; P < 0.05) and volume (rho = 0.89; n = 20; P < 0.05) of the allantochorion. S(v) was higher in the donkey placenta than the other groups (median values: 0.05 vs. 0.03 and 0.04 microm(-1), P < 0.05) although placental efficiency was lower in the donkeys (median values: 0.87 vs. 1.33 and 1.32 kg/m2, P < 0.01). The results of the study confirmed that, although strong morphological similarities exist between the allantochorion of the horse and donkey, that of the donkey develops more complex microcotyledons, as judged stereologically, and exhibits a lower placental efficiency. These differences may be related to maternal genotype and/or the longer gestation length shown by the donkey compared to the horse, but a negative correlation (rho = -0.92, P < 0.01) was also found between age and placental efficiency in donkeys.

Oxytocin, vasopressin, prostaglandin F(2alpha), luteinizing hormone, testosterone, estrone sulfate, and cortisol plasma concentrations after sexual stimulation in stallions

This experiment was designed to determine the effects of sexual stimulation on plasma concentrations of oxytocin (OT), vasopressin (VP), 15-ketodihydro-PGF(2alpha) (PG-metabolite), luteinizing hormone (LH), testosterone (T), estrone sulfate (ES), and cortisol (C) in stallions. Semen samples were collected from 14 light horse stallions (Equus caballus) of proven fertility using a Missouri model artificial vagina. Blood samples were collected at 15, 12, 9, 6, and 3 min before estrous mare exposure, at erection, at ejaculation, and at 3, 6, and 9 min after ejaculation. Afterwards, blood sampling was performed every 10 min for the following 60 min. Sexual activity determined an increase in plasma concentrations of OT, VP, C, PG-metabolite, and ES and caused no changes in LH and T concentrations. The finding of a negative correlation between C and VP at erection, and between C and T before erection and at the time of erection, could be explained by a possible inhibitory role exerted by C in the mechanism of sexual arousal described for men.

Concentrations of 15-ketodihydro-PGF2alpha, cortisol, and progesterone in the plasma of healthy and pathologic newborn foals

Information regarding the plasma hormone profiles of prostaglandins (PGs), cortisol (C), and progesterone (P4) during pathologic processes in newborn foals is scarce. The aim of this study was to determine the plasma concentrations of these hormones in diseased foals (n=40) and healthy at-term foals (n=24) (Equus caballus) during the first 2 weeks of life. Blood samples were collected daily, before any treatment with nonsteroidal drugs in diseased foals, and plasma was analyzed by radioimmunoassay. 15-Ketodihydro-PGF(2alpha) (PGM) was consistently higher in diseased foals than in healthy foals, probably related to roles of PGs in completing organ maturation and/or the presence of oxidative stress or inflammation. Similar trends were observed for C and P4. In diseased newborns, only PGM was significantly higher in nonsurviving foals, although C showed a similar profile. When specific diseases were considered, the levels of PGM and C were lower in premature foals at 12h of life, whereas the concentration of P4 was higher than in controls. The results of this study demonstrate the differences in plasma hormone levels between healthy and pathologic newborn foals, particularly during the first 2 d of life, probably reflecting the inability of diseased foals to cope with the transition between fetal and neonatal life.

Outcome of acute type A aortic dissection: single-center experience from 1998 to 2007

INTRODUCTION

Acute aortic dissection (AAD) is a serious disease of the aorta with high mortality and morbidity, which requires emergency surgical treatment in order to close the site of the dissection and direct blood flow into the true lumen. Improvements in surgical technique have led to better management of patients with reduced operative mortality, although it still remains high. The aim of this study is to evaluate early and late outcomes of the surgical treatment of acute type A aortic dissection at the hospital of Lecce between 1998 and 2007. We also aim to establish a correlation between these outcomes and pre-operative conditions, surgical procedures and location of the site of the tear.

METHODS

From 1998 to 2007, 100 patients (69 males and 31 females, average age 62.2 +/- 12.3 years, range 22-85 years) underwent surgery for acute AAD at the center. Surgical techniques included replacement of the ascending aorta (Asc Ao) with or without valve replacement (including five patients who underwent the Bentall/De Bono procedure) and replacement of the Asc Ao with or without arch or hemiarch replacement.

RESULTS

In-hospital mortality was 22%, with different results between surgery for replacement of the aorta and for aorta with valve replacement (respectively, 16% and 23%). Different mortality rates were found between the distal surgical treatments, with rates of 20.8% and 18.2% respectively between replacements of the Asc Ao and of Asc Ao with arch/hemiarch, although they were not statistically significant. A different mortality rate that was subject to the patient's preoperative condition has also been found (33.3% of mortality in patients in unstable or high-risk condition vs 13.8% in patients in stable condition). The peak reached 43.5% mortality in patients taken to the operating room while in shock or cardiac tamponade. The location of the site of the tear is another factor that distinguishes mortality rates, which are 17.8% if localized at the proximal ascending aorta and 22.2% in the aortic arch. Assessment of the outcome (10 years after surgery), has shown that four patients died several years later but for reasons unrelated to the surgery.

CONCLUSIONS

The surgery of dissection is still an intervention with a relatively high in-hospital mortality risk, and whose outcome, which has been steady in the last 20 years, can be predicted according to the preoperative condition of the patient. This underlines the need to reduce the time of diagnosis indicating immediate surgical treatment.

Lung function predicts lung cancer risk in smokers: a tool for targeting screening programmes

The relationship between smoking, lung cancer and airflow obstruction is recognised but it is unclear whether the presence of minimal lung function damage constitutes an independent risk factor for the development of lung cancer. In order to identify those individuals at higher risk of lung cancer on the basis of functional impairment, we evaluated baseline pulmonary function tests of 3,806 heavy smokers undergoing annual chest computed tomography screening, and compared the forced expiratory volume in 1 s (FEV(1)) % predicted of 57 lung cancer cases and that of 3,749 subjects without cancer. We obtained odds ratios (ORs) of lung cancer and the corresponding 95% confidence intervals (CIs) using unconditional logistic regression, adjusting for age, sex, study and smoking variables. Compared with subjects with FEV(1) >or=90% pred, the OR of lung cancer was 2.45 (95% CI 1.39-4.33) for subjects with FEV(1) <90% pred and 2.90 (95% CI 1.34-6.27) for subjects with FEV(1) <70% pred. These data show that even a relatively small reduction in FEV(1) % pred is a significant predictor of increased lung cancer risk. Test screening for lung cancer using airflow obstruction with FEV(1) <90% is a strategy worth future consideration.

Cardiopulmonary response to exercise in patients with different degrees of lung toxicity after radio-chemotherapy for Hodgkin's disease

The combination of mediastinal radiotherapy (RT) and polychemotherapy (CT) regimens can produce late toxic pulmonary and cardiac effects which often remain at the subclinical level. The aim of the present study was to investigate the cardiopulmonary response to exercise in this kind of patient. Therefore, 126 patients suffering from Hodgkin's disease were investigated after a follow-up of at least 5 years from the completion of the combined treatment. Sixty-two patients had been submitted to ABVD (doxorubicin, bleomycin, vinblastine, dacarbazine)-RT, 40 to ABVD-MOPP (mechloretamine, vincristine, procarbazine, prednisone)-RT and 24 to VEBEP (vincristine, epidoxorubicin, bleomycin, cyclophosphamide, etoposide, prednisone)-RT. The patients were divided into three groups on the basis of respiratory function: group 1 (67 patients), normal spirometry and lung transfer function for carbon monoxide (DLCO); group 2 (52 patients), normal spirometry and DLCO less than 80% of predicted; and group 3 (7 patients), total lung capacity and DLCO less than 80% of predicted. The patients were submitted to respiratory function evaluation and 2D-echocardiography before exercise, and to the determination of cardiac output by the acetylene rebreathing method before and during symptom-limited exercise on a cycloergometer using an incremental protocol. The patients of group 3 and to a lesser extent the patients of group 2 showed, in comparison to patients of group 1, a lower tolerance to exercise, a lower oxygen consumption, a higher respiratory rate, a lower O2 pulse and a lower cardiac output per oxygen uptake. These data indicated an abnormal exercise physiology in the patients with persistent pulmonary impairment, especially when the reduction of DLCO was associated with a decrease of total lung capacity. The lower exercise capacity seems to be due to a combination of decreased cardiac performance and an impairment of gas diffusion capacity.

Why a simple model of genetic regulatory networks describes the distribution of avalanches in gene expression data

In a previous study it was shown that a simple random Boolean network model, with two input connections per node, can describe with a good approximation (with the exception of the smallest avalanches) the distribution of perturbations in gene expression levels induced by the knock-out of single genes in Saccharomyces cerevisiae. Here we address the reason why such a simple model actually works: we present a theoretical study of the distribution of avalanches and show that, in the case of a Poissonian distribution of outgoing links, their distribution is determined by the value of the Derrida exponent. This explains why the simulations based on the simple model have been effective, in spite of the unrealistic hypothesis about the number of input connections per node. Moreover, we consider here the problem of the choice of an optimal threshold for binarizing continuous data, and we show that tuning its value provides an even better agreement between model and data, valuable also in the important case of the smallest avalanches. Finally, we also discuss the choice of an optimal value of the Derrida parameter in order to match the experimental distributions: our results indicate a value slightly below the critical value 1.