Replicator dynamics with diffusion on multiplex networks.

In this study we present an extension of the dynamics of diffusion in multiplex graphs, which makes the equations compatible with the replicator equation with mutations. We derive an exact formula for the diffusion term, which shows that, while diffusion is linear for numbers of agents, it is necessary to account for nonlinear terms when working with fractions of individuals. We also derive the transition probabilities that give rise to such macroscopic behavior, completing the bottom-up description. Finally, it is shown that the usual assumption of constant population sizes induces a hidden selective pressure due to the diffusive dynamics, which favors the increase of fast diffusing strategies.

Scarcity may promote cooperation in populations of simple agents.

In the study of the evolution of cooperation, resource limitations are usually assumed just to provide a finite population size. Recently, however, it has been pointed out that resource limitation may also generate dynamical payoffs able to modify the original structure of the games. Here we study analytically a phase transition from a homogeneous population of defectors when resources are abundant to the survival of unconditional cooperators when resources reduce below a threshold. To this end, we introduce a model of simple agents, with no memory or ability of recognition, interacting in well-mixed populations. The result might shed light on the role played by resource constraints on the origin of multicellularity.

Analytical models for well-mixed populations of cooperators and defectors under limiting resources.

In the study of the evolution of cooperation, resource limitations are usually assumed just to provide a finite population size. Recently, however, agent-based models have pointed out that resource limitation may modify the original structure of the interactions and allow for the survival of unconditional cooperators in well-mixed populations. Here, we present analytical simplified versions of two types of agent-based models recently published: one in which the limiting resource constrains the ability of reproduction of individuals but not their survival, and a second one where the limiting resource is necessary for both reproduction and survival. One finds that the analytical models display, with a few differences, the same qualitative behavior of the more complex agent-based models. In addition, the analytical models allow us to expand the study and identify the dimensionless parameters governing the final fate of the system, such as coexistence of cooperators and defectors, or dominance of defectors or of cooperators. We provide a detailed analysis of the occurring phase transitions as these parameters are varied.

Coexistence of cooperators and defectors in well mixed populations mediated by limiting resources.

Traditionally, resource limitation in evolutionary game theory is assumed just to impose a constant population size. Here we show that resource limitations may generate dynamical payoffs able to alter an original prisoner's dilemma, and to allow for the stable coexistence between unconditional cooperators and defectors in well-mixed populations. This is a consequence of a self-organizing process that turns the interaction payoff matrix into evolutionary neutral, and represents a resource-based control mechanism preventing the spread of defectors. To our knowledge, this is the first example of coexistence in well-mixed populations with a game structure different from a snowdrift game.

Thiol redox proteomics identifies differential targets of cytosolic and mitochondrial glutaredoxin-2 isoforms in Saccharomyces cerevisiae. Reversible S-glutathionylation of DHBP synthase (RIB3).

Yeast Grx2 plays a role in the antioxidant glutathione linked defense acting on the redox status of protein cysteines, but the exact action or its specificity is not known. Moreover, it localizes in cytosol and mitochondria where it can exert different functions. To search for functions of Grx2 we determined the differential "Thiolic Redox Proteome" of control and peroxide-treated yeast mutant cells lacking the gene for Grx2 or expressing Grx2 exclusively in the mitochondria. Forty-two proteins have been identified that have alternative redox oxidation states as a consequence of Grx2 absence from the cell or expression in the mitochondria and absence from the cytosol. The precise cysteine residues affected have been mapped for each protein. One target protein, Rib3p, which has as yet an undefined function in respiration, was confirmed to have its Cys56 reversibly S-glutathionylated in vitro in a Grx2p dependent process. Grx2-dependent redox changes in key enzymes of glutamate consuming amino acid biosynthetic pathways could favor glutathione biosynthesis. Other target proteins are involved in membrane fusion, cell wall structure and ribosome assembly, but others are of unknown function. These results provide clues on the metabolic hot spots of redox regulatory mechanisms.

[Left ventricular diastolic dysfunction in young people with type 1 diabetes mellitus. Associated factors]. / Disfunción diastólica del ventrículo izquierdo en jóvenes con diabetes mellitus tipo 1. Factores asociados.

AIM: The aim of our study was to evaluate left ventricular function of diastolic in young (< 40 years) asymptomatic patients with type 1 diabetes mellitus free of cardiovascular disease symptoms and to analyze the associated factors to the left ventricular diastolic dysfunction (LVDD) in these patients. PATIENTS AND METHODS: Thirty-five type-1 diabetic patients (mean age 27.8+/-7.5 years) old and 54 healthy controls (mean age 26.1+/-4.1 years) were studied. Anamnesis, physical exploration, general analytical studies, microalbuminuric and Doppler-echocardiographic studies were performed. RESULTS: The LVDD was present in 13 (37.1%) of the diabetic patients and none of the control patients. The ratio of peak early to peak late (atrial) filling velocity was significantly decreased in diabetic compared with control subjects (1.1+/-0.3 versus 1.5+/-0.2; p<0.01). The isovolumetric relaxation time was increased in diabetic patients compared with control subjects (104+/-11 versus 79+/-11; p<0.01). Diabetics with LVDD were older aged, predominantly males, had worse glucemic control, more alteration of lipidic metabolism and higher levels of microalbuminuria, than diabetics without LVDD. CONCLUSIONS: The LVDD is frequent in young diabetics free of cardiovascular disease symptoms. These studies suggest that because this patients were of older age, of the masculine sex with, poor glucemic control, altered lipidic metabolism, and microalbuminuria they might be a group that is associated with LVDD which, in the absence of cardiovascular disease, might be an early preclinical alteration, potentially related to subsequent development of diabetic cardiomyopathy.

Growth hormone response to acute growth hormone releasing hormone administration in uraemic patients on haemodialysis.

To examine the response of growth hormone (GH) to growth hormone releasing factor (GHRF) in patients on haemodialysis, we performed the acute GHRF test (50 micrograms administered intravenously as a bolus) in 10 uraemic male patients on haemodialysis and eight normal controls. Each patient was tested before and after a haemodialysis session (at 08.30 and 12.30). Controls were tested on the same time schedule. At 08.30, patients had significantly greater basal and peak GH values (2.5 +/- 0.6 and 27.8 +/- 5.5 micrograms/l) than controls (0.68 +/- and 11.5 +/- 4 micrograms/l). After the haemodialysis session, basal and peak values declined significantly (P less than 0.01) in the uraemic group (0.5 +/- 0.03 and 3.1 +/- 1.1 micrograms/l), whereas the controls did not show such a change in the 12.30 test. Basal and intratest glycaemic values were comparable both before and after haemodialysis. After dialysis test results did not change either with the use of glucose-free dialysate or with bicarbonate buffer. Uraemic patients display a greater GH response to GHRF injection than normal subjects, and this response decreases after haemodialysis. The degree of reduction has no relationship with either glycaemia or the dialysate buffer. We suggest that other GH secretion regulating factors are altered by the haemodialysis procedure.

[Prolactin response to acute administration of growth hormone releasing hormone in patients with uremia]. / Respuesta de la prolactina a la administración aguda de la hormona liberadora de la hormona de crecimiento en pacientes urémicos.

The Growth Hormone Releasing Hormone (GH-RH) constitutes the most potent and specific stimulus for Growth Hormone secretion. Nevertheless, in some pathologic situations a Prolactin (PRL) response to GH-RH stimulus is also observed. In order to evaluate the possible effect of GH-RH over seric levels of PRL in uremic patients we carried out a study in a group of ten male patients on hemodialysis (HD), who were given an acute stimulus of GH-RH (an IV 50 mcg. bolus) immediately before and after the HD session, with blood extractions at times -15, 0, 15, 30, 45, 60, and 90 minutes for PRL determinations. The same procedure was carried out in 8 healthy controls. Basal PRL levels in the HD group (14 +/- 3.2 micrograms/L) were significantly greater (p less than 0.01) than control group (3.8 +/- 1.4 micrograms/L). There was no PRL response to GH-RH either in uremic patients before or after HD or in healthy controls. Our results show that there is a significant increase in PRL levels in uremic patients both before and after dialysis with a GH-RH response comparable to healthy subjects.