Latin America 2040 — Breaking Away from Complacency: An Agenda for Resurgence

Latin America

Field-induced delocalization and Zener breakdown in semiconductor superlattices

We investigate the energy spectrum and the electron dynamics of a band in a semiconductor superlattice as a function of the electric field. Linear optical spectroscopy shows that, for high fields, the well-known localization of the Bloch states is followed by a field-induced delocalization, associated with Zener breakdown. Using time-resolved measurements, we observe Bloch oscillations in a regime where they are damped by Zener breakdown

The LIM-only protein FHL2 attenuates lung inflammation during bleomycin-induces fibrosis

Fibrogenesis is usually initiated when regenerative processes have failed and/or chronic inflammation occurs. It is characterised by the activation of tissue fibroblasts and dysregulated synthesis of extracellular matrix proteins. FHL2 (four-and-a-half LIM domain protein 2) is a scaffolding protein that interacts with numerous cellular proteins, regulating signalling cascades and gene transcription. It is involved in tissue remodelling and tumour progression. Recent data suggest that FHL2 might support fibrogenesis by maintaining the transcriptional expression of alpha smooth muscle actin and the excessive synthesis and assembly of matrix proteins in activated fibroblasts. Here, we present evidence that FHL2 does not promote bleomycin-induced lung fibrosis, but rather suppresses this process by attenuating lung inflammation. Loss of FHL2 results in increased expression of the pro-inflammatory matrix protein tenascin C and downregulation of the macrophage activating C-type lectin receptor DC-SIGN. Consequently, FHL2 knockout mice developed a severe and long-lasting lung pathology following bleomycin administration due to enhanced expression of tenascin C and impaired activation of inflammation-resolving macrophages

Spontaneous tumor rejection by cbl-b–deficient CD8+ T cells

The concept of tumor surveillance implies that specific and nonspecific components of the immune system eliminate tumors in the early phase of malignancy. Understanding the biochemical mechanisms of tumor immunosurveillance is of paramount significance because it might allow one to specifically modulate spontaneous antitumor activity. We report that inactivation of the E3 ligase Casitas B cell lymphoma-b (Cbl-b) confers spontaneous in vivo rejection of tumor cells that express human papilloma virus antigens. Moreover, cbl-b−/− mice develop significantly fewer ultraviolet B (UVB)–induced skin malignancies and reject UVB-induced skin tumors. CD8+ T cells were identified as key players in the spontaneous tumor rejection response. Loss of Cbl-b not only enhances antitumor reactivity of CD8+ T cells but also occurs in the absence of CD4+ T cells. Mechanistically, cbl-b−/− CD8+ T cells are resistant to T regulatory cell–mediated suppression and exhibit enhanced activation and rapid tumor infiltration. Importantly, therapeutic transfer of naive cbl-b−/− CD8+ T cells is sufficient to mediate rejection of established tumors. Even up to 1 yr after the first encounter with the tumor cells, cbl-b−/− mice carry an “anticancer memory.” These data identify Cbl-b as a key signaling molecule that controls spontaneous antitumor activity of cytotoxic T cells in different cancer models. Inhibition of Cbl-b is a novel approach to stimulate long-lasting immunity against cancer

Benzotrithiophenes vs. Benzo/Naptha-dithiophenes: The Effect of Star-Shaped versus Linear Conjugation on Their Electronic Structures

Star-shaped complexes of π-conjugated chromophores are currently of great interest for use in optoelectronic devices.1 Recently, different planar central cores involving three thiophene rings fused to a benzenic ring (BTTs) have been described. In these systems, the coplanarity and extended π-conjugation of the BTT skeleton should promote intermolecular π-stacking, which would induce strong aggregation and enhanced packing in the solid state of BTT-containing molecules. We propose here the study of a BTT conjugated system with DPPT fragments, in which three DPP2T units are linked to a central rigid trithienobenzene core. Comparison with homologous linear systems, based on the benzodithiophene (BDT) unit and the naphtodithiophene (NDT) unit,2 will be carried out in order to elucidate the effect of star-shaped configuration versus linear conformation on the optical and electrical properties.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech

Antiferromagnetism and d-wave superconductivity in cuprates: a uster DMFT study

We present a new approach to investigate the coexistence of antiferromagnetism and d-wave superconductivity in the two dimensional extended Hubbard model within a numerically exact cluster dynamical mean-field approximation. Self-consistent solutions with two non-zero order parameters exists in the wide range of doping level and temperatures. A linearized equation for energy spectrum near the Fermi level have been solved. The resulting d-wave gap has the correct magnitude and k-dependence but some distortion compare to the pure d_{x^2-y^2} superconducting order parameter due to the presence of underlying antiferromagnetic ordering.Comment: 4 pages, 3 figure

There is no functional small-fibre neuropathy in prurigo nodularis despite neuroanatomical alterations

Prurigo nodularis (PN) is a pruritic condition with altered epidermal neuroanatomy as demonstrated previously. Here we elucidated neuroimmunological mechanisms by combining functional, morphological and gene expression experiments in twelve subjects with PN and eight healthy controls. Subjects with PN showed a reduced intra‐epidermal nerve fibre density (IENFD) in lesional skin. Quantitative sensory testing indicated maintenance of somatosensory function compared to controls. None of the tested molecular markers including the neuron‐distracting SEMA3A and neuron‐attracting NGF were altered in lesional vs non‐lesional skin in PN subjects. Accordingly, we speculate that scratching may contribute to reduced IENFD rather than an authentic endogenous neuropathy.FSW - Self-regulation models for health behavior and psychopathology - ou

Fecal pancreatic elastase-1 levels in older individuals without known gastrointestinal diseases or diabetes mellitus

Background - Structural changes occur in the pancreas as a part of the natural aging process. With aging, also the incidence of maldigestive symptoms and malnutrition increases, raising the possibility that these might be caused at least in part by inadequate pancreatic enzyme secretion due to degenerative processes and damage of the gland. Fecal elastase-1 is a good marker of pancreatic exocrine secretion. The aim of this study was to investigate the fecal elastase-1 levels among over 60 years old Finnish and Polish healthy individuals without any special diet, known gastrointestinal disease, surgery or diabetes mellitus. Methods - A total of 159 patients participated in this cross-sectional study. 106 older individuals (aged 60-92 years) were recruited from outpatient clinics and elderly homes. They were divided to three age groups: 60-69 years old (n = 31); 70-79 years old (n = 38) and over 80 years old (n = 37). 53 young subjects (20-28 years old) were investigated as controls. Inclusion criteria were age over 60 years, normal status and competence. Exclusion criteria were any special diet, diabetes mellitus, any known gastrointestinal disease or prior gastrointestinal surgery. Fecal elastase-1 concentration was measured from stool samples with an ELISA that uses two monoclonal antibodies against different epitopes of human elastase-1. Results - Fecal elastase-1 concentrations correlated negatively with age (Pearson r = -0,3531, P < 0.001) and were significantly lower among subjects over 70 years old compared to controls (controls vs. 70-79 years old and controls vs. over 80 years old, both P < 0.001). Among the over 60 years old subjects, the fecal elastase-1 concentrations were below the cut off level of 200 μg/g in 23 of 106 (21.7%) individuals [mean 112 (86-138) μg/g] indicating pancreatic exocrine insufficiency. Of those, 9 subjects had fecal elastase-1 level below 100 μg/g as a marker of severe pancreatic insufficiency. Conclusion - In our study one fifth of healthy older individuals without any gastrointestinal disorder, surgery or diabetes mellitus suffer from pancreatic exocrine insufficiency and might benefit from enzyme supplementation therapy.peerReviewe

The mechanisms by which polyamines accelerate tumor spread

Increased polyamine concentrations in the blood and urine of cancer patients reflect the enhanced levels of polyamine synthesis in cancer tissues arising from increased activity of enzymes responsible for polyamine synthesis. In addition to their de novo polyamine synthesis, cells can take up polyamines from extracellular sources, such as cancer tissues, food, and intestinal microbiota. Because polyamines are indispensable for cell growth, increased polyamine availability enhances cell growth. However, the malignant potential of cancer is determined by its capability to invade to surrounding tissues and metastasize to distant organs. The mechanisms by which increased polyamine levels enhance the malignant potential of cancer cells and decrease anti-tumor immunity are reviewed. Cancer cells with a greater capability to synthesize polyamines are associated with increased production of proteinases, such as serine proteinase, matrix metalloproteinases, cathepsins, and plasminogen activator, which can degrade surrounding tissues. Although cancer tissues produce vascular growth factors, their deregulated growth induces hypoxia, which in turn enhances polyamine uptake by cancer cells to further augment cell migration and suppress CD44 expression. Increased polyamine uptake by immune cells also results in reduced cytokine production needed for anti-tumor activities and decreases expression of adhesion molecules involved in anti-tumor immunity, such as CD11a and CD56. Immune cells in an environment with increased polyamine levels lose anti-tumor immune functions, such as lymphokine activated killer activities. Recent investigations revealed that increased polyamine availability enhances the capability of cancer cells to invade and metastasize to new tissues while diminishing immune cells' anti-tumor immune functions