Phytosociological analysis of the mesophilic forest of the San Pedro volcano (Guatemala).

From a standpoint of phytosociological research, little is known about the phytocoenosis found on the volcanoes of Central America. This paper analyses the distribution of the vegetation on the volcano of San Pedro in terms of its species-richness, composition, structure and abundance, and the possible relationships between these components and the changes in elevation and orientation that occur there. We divided the study area into three altitudinal belts between 2,400 and 3,020 m a.s.l. where carried out 36 inventories, each one in an area of 0.1 ha. We then applied multivariate analysis to classify and order the data in the matrix obtained from the frequency of the sampled plants. Our results lead us to propose two mixed cloud-forest associations within the class Alnetea acuminatae. The first, Saurauio oreophilae-Alnetum acuminatae ass. nova, is found on the more humid western side, while the second, Adianto andicolae-Quercetum peduncularis ass. nova, appears in sunnier and less shady sites, mainly on the east face. As part of this latter association, we also identified the new subassociation festucetosum amplissimae subass. nova. These syntaxa are part of the alliance Oreopanacion xalapensis all. nova, which we have created to embrace the mesophytic montane forests dominated by broad-leaved species.

Obesity as a Risk Factor for Dementia and Alzheimer's Disease: The Role of Leptin.

Obesity is a growing worldwide health problem, affecting many people due to excessive saturated fat consumption, lack of exercise, or a sedentary lifestyle. Leptin is an adipokine secreted by adipose tissue that increases in obesity and has central actions not only at the hypothalamic level but also in other regions and nuclei of the central nervous system (CNS) such as the cerebral cortex and hippocampus. These regions express the long form of leptin receptor LepRb, which is the unique leptin receptor capable of transmitting complete leptin signaling, and are the first regions to be affected by chronic neurocognitive deficits, such as mild cognitive impairment (MCI) and Alzheimer's Disease (AD). In this review, we discuss different leptin resistance mechanisms that could be implicated in increasing the risk of developing AD, as leptin resistance is frequently associated with obesity, which is a chronic low-grade inflammatory state, and obesity is considered a risk factor for AD. Key players of leptin resistance are SOCS3, PTP1B, and TCPTP whose signalling is related to inflammation and could be worsened in AD. However, some data are controversial, and it is necessary to further investigate the underlying mechanisms of the AD-causing pathological processes and how altered leptin signalling affects such processes.

Specific networks of plasma acute phase reactants are associated with the severity of chronic obstructive pulmonary disease: a case-control study.

Objectives. A detailed understanding of the intricate relationships between different acute phase reactants (APRs) in chronic obstructive pulmonary disease (COPD) can shed new light on its clinical course. In this case-control study, we sought to identify the interaction networks of a number of plasma APRs in COPD, with a special focus on their association with disease severity. Methods. COPD cases and healthy smoking controls (3:1 ratio) were recruited in our outpatient pulmonary clinic. Cardiopulmonary exercise testing was used to rule out the presence of ischemic heart disease. All subjects were males as per protocol. Multiple plasma APRs - including α-2-macroglobulin, C-reactive protein (CRP), ferritin, fibrinogen, haptoglobin, procalcitonin (PCT), serum amyloid A (SAA), serum amyloid P, and tissue plasminogen activator (tPA) - were measured using commercial Acute Phase Bio-Plex Pro Assays and analyzed on the Bio-Plex manager software. Correlations between different APRs were investigated using a heat map. Network visualization and analyses were performed with the Cytoscape software platform. Results. A total of 96 COPD cases and 33 controls were included in the study. Plasma A2M, CRP, and SAP levels were higher in COPD patients than in controls. Circulating concentrations of haptoglobin and tPA were found to increase in parallel with the severity of the disease. Increasing disease severity was associated with distinct intricate networks of APRs, which were especially evident in advanced stages. Conclusions. We identified different networks of APRs in COPD, which were significantly associated with disease severity.

An adaptive jitter mechanism for reactive route discovery in sensor networks.

This paper analyses the impact of jitter when applied to route discovery in reactive (on-demand) routing protocols. In multi-hop non-synchronized wireless networks, jitter--a small, random variation in the timing of message emission--is commonly employed, as a means to avoid collisions of simultaneous transmissions by adjacent routers over the same channel. In a reactive routing protocol for sensor and ad hoc networks, jitter is recommended during the route discovery process, specifically, during the network-wide flooding of route request messages, in order to avoid collisions. Commonly, a simple uniform jitter is recommended. Alas, this is not without drawbacks: when applying uniform jitter to the route discovery process, an effect called delay inversion is observed. This paper, first, studies and quantifies this delay inversion effect. Second, this paper proposes an adaptive jitter mechanism, designed to alleviate the delay inversion effect and thereby to reduce the route discovery overhead and (ultimately) allow the routing protocol to find more optimal paths, as compared to uniform jitter. This paper presents both analytical and simulation studies, showing that the proposed adaptive jitter can effectively decrease the cost of route discovery and increase the path quality.