Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.     

Age-Specific Mortality During the 1918 Influenza Pandemic: Unravelling the Mystery of High Young Adult Mortality

The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.

“The war is over – and I must go” Egon Schiele, 1890–1918.

     

Persistence of Swidden Cultivation in the Face of Globalization: A Case Study from Communities in Calakmul, Mexico

Over the last decades, political, economic and environmental pressures have encouraged changes from swidden to more intensive agricultural practices, resulting in the hypothesis that swidden cultivation systems are disappearing. In Calakmul, southeastern Mexico, communities decreased the area under milpa, the traditional maize swidden system, but a collapse did not occur. To document and explain the persistence of swidden we employ a variety of data: (1) 59 standardized household surveys from 2003 and 2010 in five villages, (2) in-depth interviews in one village, and (3) coupled human–environmental timelines in this same village. Droughts, hurricanes, and remittances were important drivers of decreases in milpa cultivation. Market crop profitability and conservation programs were also reported to affect the area under milpa. Off-farm employment and governmental transfers have tended to stabilize household economies and decrease dependency on agricultural production, but have also allowed households to maintain their milpas for subsistence and cultural reproduction. Findings in Calakmul point to the need to consider swidden as an evolving and active response to changing policy, economic, and environmental conditions.     

The cover of living and dead corals from airborne remote sensing

Trends in coral cover are widely used to indicate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m² pixels and 6 spectral bands with 0.25-m² pixels. First, we show that an instrument with 10 spectral bands possesses adequate spectral resolution to distinguish living Porites, living Pocillopora spp., partially dead Porites, recently dead Porites (total colony mortality within 6 months), old dead (>6 months) Porites, Halimeda spp., and coralline red algae when there is no water column to confuse spectra. All substrata were distinguished using fourth-order spectral derivatives around 538 nm and 562 nm. Then, at a shallow site (Tivaru) at Rangiroa Atoll, Tuamotu Archipelago (French Polynesia), we show that live and dead coral can be distinguished from the air to a depth of at least 4 m using first- and fourth-order spectral derivatives between 562–580 nm. However, partially dead and recently dead Porites colonies could not be distinguished from an airborne platform. Spectral differences among substrata are then exploited to predict the cover of reef substrata in ten 25-m² plots at nearby Motu Nuhi (max depth 8 m). The actual cover in these plots was determined in situ using quadrats with a 0.01-m² grid. Considerable disparity occurred between field and image-based measures of substrate cover within individual 25-m² quadrats. At this small scale, disparity, measured as the absolute difference in cover between field and remote-sensing methods, reached 25% in some substrata but was always less than 10% for living coral (99% of which consisted of Porites spp.). At the scale of the reef (all ten 25-m² quadrats), however, disparities in percent cover between imagery and field data were less than 10% for all substrata and extremely low for some classes (e.g. <3% for living Porites, recently dead Porites and Halimeda). The least accurately estimated substrata were sand and coralline red algae, which were overestimated by absolute values 7.9% and 6.6%, respectively. The precision of sampling was similar for field and remote-sensing methods: field methods required 19 plots to detect a 10% difference in coral cover among three reefs with a statistical power of 95%. Remote-sensing methods required 21 plots. However, it took 1 h to acquire imagery over 92,500 m² of reef, which represents 3,700 plots of 25 m² each, compared with 3 days to survey 10 such plots underwater. There were no significant differences in accuracy between 1-m² and 0.25-m² image resolutions, suggesting that the advantage of using smaller pixels is offset by reduced spectral information and an increase in noise (noise was observed to be 1.6–1.8 times greater in 0.25-m² pixels). We show that airborne remote sensing can be used to monitor coral and algal cover over large areas, providing that water is shallow and clear, and that brown fleshy macroalgae are scarce, that depth is known independently (e.g. from sonar survey).     

Development of protegrins for the treatment and prevention of oral mucositis: structure-activity relationships of synthetic protegrin analogues

Protegrin antimicrobial peptides possess activity against gram-positive and gram-negative bacteria and yeasts. An extensive structure-activity relationship (SAR) study was conducted on several hundred protegrin analogues to gain understanding of the relationship between the primary and secondary structure of the protegrins and their antimicrobial activities, and to identify a protegrin analogue for clinical development. Native sequence protegrins are cationic, amphiphilic peptides that are characterized by the presence of a beta-sheet structure that is maintained by two disulfide bridges. The presence of the beta-sheet is key to the stability of the protegrin structure; linearized analogues or analogues that have amino acid substitutions that eliminate hydrogen bonding across the beta-sheet have reduced activity, especially in the presence of physiological concentrations of NaCl. Also, maintaining amphiphilicity of the beta-sheet is key; analogues with substitutions of polar amino acids in the hydrophobic face have reduced activity. Analogues with reduced positive charge tend to be less active, an observation that is more marked for gram-negative than gram-positive bacteria, and may implicate binding to lipopolysaccharide as a key mechanistic step in the killing of gram-negative bacteria. A very large number of amino acid substitutions are tolerated by the protegrin structure, implying that overall structural features such as amphiphilicity, charge, and shape are more important to activity than the presence of specific amino acids. This lack of importance of specific stereochemistry is supported by the fact that completely D-amino acid substituted protegrins are fully potent. Based on the SAR studies, and on the microbiological data from an animal model, one protegrin analogue, IB-367, was selected for clinical development as a topical agent to prevent the oral mucositis associated with cancer therapy.     

Gene transfer to pre-hematopoietic and committed hematopoietic precursors in the early mouse Yolk Sac: a comparative study between <Emphasis Type="Italic">in situ</Emphasis> electroporation and retroviral transduction

Background  

Hematopoietic development in vertebrate embryos results from the sequential contribution of two pools of precursors independently generated. While intra-embryonic precursors harbour the features of hematopoietic stem cells (HSC), precursors formed earlier in the yolk sac (YS) display limited differentiation and self-renewal potentials. The mechanisms leading to the generation of the precursors in both sites are still largely unknown, as are the molecular basis underlying their different potential. A possible approach to assess the role of candidate genes is to transfer or modulate their expression/activity in both sites. We thus designed and compared transduction protocols to target either native extra-embryonic precursors, or hematopoietic precursors.     

European society of intensive care medicine study of therapeutic hypothermia (32-35°C) for intracranial pressure reduction after traumatic brain injury (the Eurotherm3235Trial)

Background

Severe malaria remains a major cause of global morbidity and mortality. Despite the use of potent anti-parasitic agents, the mortality rate in severe malaria remains high. Adjunctive therapies that target the underlying pathophysiology of severe malaria may further reduce morbidity and mortality. Endothelial activation plays a central role in the pathogenesis of severe malaria, of which angiopoietin-2 (Ang-2) has recently been shown to function as a key regulator. Nitric oxide (NO) is a major inhibitor of Ang-2 release from endothelium and has been shown to decrease endothelial inflammation and reduce the adhesion of parasitized erythrocytes. Low-flow inhaled nitric oxide (iNO) gas is a US FDA-approved treatment for hypoxic respiratory failure in neonates.

Methods/Design

This prospective, parallel arm, randomized, placebo-controlled, blinded clinical trial compares adjunctive continuous inhaled nitric oxide at 80 ppm to placebo (both arms receiving standard anti-malarial therapy), among Ugandan children aged 1-10 years of age with severe malaria. The primary endpoint is the longitudinal change in Ang-2, an objective and quantitative biomarker of malaria severity, which will be analysed using a mixed-effects linear model. Secondary endpoints include mortality, recovery time, parasite clearance and neurocognitive sequelae.

Discussion

Noteworthy aspects of this trial design include its efficient sample size supported by a computer simulation study to evaluate statistical power, meticulous attention to complex ethical issues in a cross-cultural setting, and innovative strategies for safety monitoring and blinding to treatment allocation in a resource-constrained setting in sub-Saharan Africa.

Trial Registration

ClinicalTrials.gov Identifier: NCT01255215     

Integrin mechanotransduction stimulates caveolin-1 phosphorylation and recruitment of Csk to mediate actin reorganization

To identify the role of caveolin-1 in integrin mechanotransduction, we exposed bovine aortic endothelial cells to 10 dyn/cm2 of laminar shear stress. Caveolin-1 was acutely and transiently phosphorylated with shear, occurring downstream of beta1-integrin activation as the beta1-integrin blocking antibody JB1A was inhibitory. In manipulating Src family kinase (SFK) activity with knockdown of Csk or type 1 protein phosphatase (PP1) treatment, we observed coordinate increase and decrease in shear-induced caveolin-1 phosphorylation, respectively. Hence, shear-stimulated caveolin-1 phosphorylation is regulated by SFKs. Shear-induced recruitment and phosphorylation of caveolin-1 occurred at beta1-integrin sites in a beta1-integrin- and SFK-dependent manner. Csk, described to interact with pY14-caveolin-1 and integrins, bound to an increased pool of phosphorylated caveolin-1 after shear corresponding with elevated Csk at beta1-integrin sites. Like caveolin-1, treatment with JB1A and PP1 attenuated shear-induced Csk association with beta1-integrins. Csk function was assayed with transfection of a caveolin-1 phosphorylation domain peptide. The peptide attenuated shear-induced association of Csk at beta1-integrin sites, as well as colocalization of Csk with paxillin and phosphorylated caveolin-1. Because integrin and Csk activity regulate cytoskeletal reorganization, we evaluated the role of this mechanism in shear-induced myosin light chain (MLC) phosphorylation. Knockdown of Csk expression was sufficient to reduce MLC diphosphorylation due to shear. Disruption of Csk-integrin association by peptide treatment was also inhibitory of the MLC diphosphorylation response. Together these data indicate that integrin activation with shear stress results in SFK-regulated caveolin-1 phosphorylation that, in turn, mediates Csk association at integrin sites, where it plays a role in downstream, shear-stimulated MLC diphosphorylation.     

Untangling a Decline in Tropical Forest Resilience: Constraints on the Sustainability of Shifting Cultivation Across the Globe

Shifting cultivators depend on forest biomass inputs to nourish their crops. For them, forest resilience has an immediate impact: it affects crop productivity. A decline in the rate of recovery following shifting cultivation would ultimately affect local, regional and global carbon budgets, with feedbacks to climate. Yet the long-term impacts of shifting cultivation have been quantified in only six locations. In this study, we reanalyze data from these locations to determine whether the rate of biomass recovery is the same from cycle to cycle. Further, using case studies in Southern Yucatan, Mexico and West Kalimantan, Indonesia, we investigate the ecological and socioeconomic factors that affect forest resilience and thus determine whether or not shifting cultivation is sustainable. The reanalysis links aboveground biomass recovery following shifting cultivation to site productivity, forest age, fallow length, history of cultivation, and soil texture. Across locations, biomass accumulation rate declines by 9.3 percent with each cycle of shifting cultivation. Per cycle change in biomass accumulation rate is significantly more negative in younger forests and forests that experience a shorter fallow period. However, more detailed analyses for two case studies suggest that a purely ecological framework is of limited effectiveness in explaining variability in the effect of repeated shifting cultivation. Rather, socioeconomic factors such as migration, subsidies, roads, and settlement history can alter the outcome of shifting cultivation by limiting the accumulation and use of local knowledge.