Optimising models for prediction of tropospheric scintillation on satellite links

A phenomenon that also causes impairment in the received signal strength of the RF signal in satellite links operating at frequencies above 10 GHz, especially in those systems that operate at higher frequencies with small fade margins, is the tropospheric scintillation that occurs in the lower layer of the troposphere. In order to estimate the intensity, i.e. the variance between the scintillation amplitude fluctuations, there are several models in the literature, whose accuracy depends on the locality in which the models are implemented. In this Letter, new models are developed for the prediction of tropospheric scintillation that adjusts to localities in Spain, specifically Madrid city, based on measurements of the aforementioned phenomenon reported from Spain and the bios-inspired technique Cuckoo Search (CS). The results obtained, evaluated in terms of the root mean square error, were totally satisfactory, being the most outstanding cases the improved versions of the Ortgies-T, Statistical Temperature and Humidity 2 and Statistical Temperature and Refractivity 2 models

Polyglutamine Expansion Accelerates the Dynamics of Ataxin-1 and Does Not Result in Aggregate Formation

Polyglutamine expansion disorders are caused by an expansion of the polyglutamine (polyQ) tract in the disease related protein, leading to severe neurodegeneration. All polyQ disorders are hallmarked by the presence of intracellular aggregates containing the expanded protein in affected neurons. The polyQ disorder SpinoCerebellar Ataxia 1 (SCA1) is caused by a polyQ-expansion in the ataxin-1 protein, which is thought to lead to nuclear aggregates.Using advanced live cell fluorescence microscopy and a filter retardation assay we show that nuclear accumulations formed by polyQ-expanded ataxin-1 do not resemble aggregates of other polyQ-expanded proteins. Instead of being static, insoluble aggregates, nuclear accumulations formed by the polyQ-expanded ataxin-1 showed enhanced intracellular kinetics as compared to wild-type ataxin-1. During mitosis, ataxin-1 accumulations redistributed equally among daughter cells, in contrast to polyQ aggregates. Interestingly, polyQ expansion did not affect the nuclear-cytoplasmic shuttling of ataxin-1 as proposed before.These results indicate that polyQ expansion does not necessarily lead to aggregate formation, and that the enhanced kinetics may affect the nuclear function of ataxin-1. The unexpected findings for a polyQ-expanded protein and their consequences for ongoing SCA1 research are discussed

Accumulation of Endogenous LITAF in Aggresomes

LITAF is a 161 amino acid cellular protein which includes a proline rich N-terminus and a conserved C-terminal domain known as the simple-like domain. Mutations in LITAF have been identified in Charcot-Marie tooth disease, a disease characterized by protein aggregates. Cells transfected with cellular LITAF reveal that LITAF is localized to late endosomes/lysosomes. Here we investigated the intracellular localization of endogenous LITAF. We demonstrated that endogenous LITAF accumulates at a discrete cytoplasmic site in BGMK cells that we identify as the aggresome. To determine the domain within LITAF that is responsible for the localization of LITAF to aggresomes, we created a construct that contained the C-terminal simple-like domain of LITAF and found that this construct also localizes to aggresomes. These data suggest the simple-like domain is responsible for targeting endogenous LITAF to the aggresome

Lateral adhesion drives reintegration of misplaced cells into epithelial monolayers.

Cells in simple epithelia orient their mitotic spindles in the plane of the epithelium so that both daughter cells are born within the epithelial sheet. This is assumed to be important to maintain epithelial integrity and prevent hyperplasia, because misaligned divisions give rise to cells outside the epithelium. Here we test this assumption in three types of Drosophila epithelium; the cuboidal follicle epithelium, the columnar early embryonic ectoderm, and the pseudostratified neuroepithelium. Ectopic expression of Inscuteable in these tissues reorients mitotic spindles, resulting in one daughter cell being born outside the epithelial layer. Live imaging reveals that these misplaced cells reintegrate into the tissue. Reducing the levels of the lateral homophilic adhesion molecules Neuroglian or Fasciclin 2 disrupts reintegration, giving rise to extra-epithelial cells, whereas disruption of adherens junctions has no effect. Thus, the reinsertion of misplaced cells seems to be driven by lateral adhesion, which pulls cells born outside the epithelial layer back into it. Our findings reveal a robust mechanism that protects epithelia against the consequences of misoriented divisions.The authors are grateful to R. Nieuwburg, the St Johnston group, and other Gurdon Institute members for suggestions. We thank the Bloomington Stock Center, J. Knoblich, and the TRiP at Harvard Medical School (NIH/NIGMS R01-GM084947) for fly stocks. We thank N. Lowe for technical assistance. This work was supported by a Wellcome Trust Principal Fellowship to D.St.J. (080007), and by core support from the Wellcome Trust (092096) and Cancer Research UK (A14492). D.T.B. was supported by a Marie Curie Fellowship and the Wellcome Trust. H.E.L. was supported by a Herchel Smith Studentship.This is the author accepted manuscript. The final version is available from NPG via http://dx.doi.org/10.1038/ncb324

Modulation of polyglutamine inclusion formation by the Hsp70 chaperone machine

Components of the Hsp70 chaperone machine have been implied in protection against polyglutamine (poly-Q) pathologies. Yet, little is known about specific mechanisms and the rate-limiting components that account for this protective effect. Here, we examined the effects of an Hsp70 chaperone family member (HspA1A) and its cofactors Hsp4O (DnaJB1), Bag-1 and CHIP on poly-Q protein inclusion formation and SDS-insolubilization. Overexpression of HspA1A alone did not suppress inclusion formation, while overexpression of DnaJB1 reduced poly-Q inclusion formation and insolubilization. The reducing effect of DnaJB1 on inclusion formation was enhanced by coexpressing HspA1A, and was dependent on the interaction of DnaJB1 with Hsp70/Hsc70 chaperones. Additionally, two factors connecting Hsp70 activity with protein degradation by the ubiquitin-proteasome system Bag-1 and CHIP slightly decreased the levels of soluble poly-Q protein, but the amount of aggregated protein and fraction of cells with inclusions remained unaltered. our data suggest that the HspA1A chaperone machine can modulate poly-Q inclusion formation depending on the ratio of its components and that DnaJB1 is the rate-limiting step. (c) 2007 Elsevier Inc. All rights reserved

Modeling organic transformations by microorganisms of soils in six contrasting ecosystems: Validation of the MOMOS model

CDCHTULA (project C-765-95-01-B) and FONACIT (F-2002000424). We would like to thank Zulay Mendez for her technical assistance in the laboratory and Yann Martineau (SETEC International, F-13127 Vitrolles, France) and Klaas Metselaar (Soil Physics, Wageningen University, Netherlands) for the orientation in the modeling process. Amer geophysical union WashingtonInternational audienceThe Modeling Organic Transformations by Microorganisms of Soils (MOMOS) model simulates the growth, respiration, and mortality of soil microorganisms as main drivers of the mineralization and humification processes of organic substrates. Originally built and calibrated using data from two high-altitude sites, the model is now validated with data from a (14)C experiment carried out in six contrasting tropical ecosystems covering a large gradient of temperature, rainfall, vegetation, and soil types from 65 to 3968 m asl. MOMOS enabled prediction of a greater number of variables using a lower number of parameter values than for predictions previously published on this experiment. The measured (14)C mineralization and transfer into microbial biomass (MB) and humified compartments were accurately modeled using (1) temperature and moisture response functions to daily adjust the model responses to weather conditions and (2) optimization of only one parameter, the respiration rate k(resp) of soil microorganisms at optimal temperature and moisture. This validates the parameterization and hypotheses of the previous calibration experiment. Climate and microbial respiratory activity, related to soil properties, appear as the main factors that regulate the C cycle. The k(resp) rate was found to be negatively related to the fine textural fraction of soil and positively related to soil pH, allowing the proposition of two transfer functions that can be helpful to generalize MOMOS application at regional or global scale

Levels of DNAJB family members (HSP40) correlate with disease onset in patients with spinocerebellar ataxia type 3

In polyglutamine disorders, the length of the expanded CAG repeat shows a strong inverse correlation with the age at disease onset, yet up to 50% of the variation in age of onset is determined by other additional factors. Here, we investigated whether variations in the expression of heat shock proteins (HSP) are related to differences in the age of onset in patients with spinocerebellar ataxia (SCA)3. Hereto, we analysed the protein expression levels of HSPA1A (HSP70), HSPA8 (HSC70), DNAJB (HSP40) and HSPB1 (HSP27) in fibroblasts from patients and healthy controls. HSPB1 levels were significantly upregulated in fibroblasts from patients with SCA3, but without relation to age of onset. Exclusively for expression of DNAJB family members, a correlation was found with the age of onset independent of the length of the CAG repeat expansion. This indicates that DNAJB members might be contributors to the variation in age of onset and underlines the possible use of DNAJB proteins as therapeutic targets

Dynamic JUNQ inclusion bodies are asymmetrically inherited in mammalian cell lines through the asymmetric partitioning of vimentin

Aging is associated with the accumulation of several types of damage: in particular, damage to the proteome. Recent work points to a conserved replicative rejuvenation mechanism that works by preventing the inheritance of damaged and misfolded proteins by specific cells during division. Asymmetric inheritance of misfolded and aggregated proteins has been shown in bacteria and yeast, but relatively little evidence exists for a similar mechanism in mammalian cells. Here, we demonstrate, using long-term 4D imaging, that the vimentin intermediate filament establishes mitotic polarity in mammalian cell lines and mediates the asymmetric partitioning of damaged proteins. We show that mammalian JUNQ inclusion bodies containing soluble misfolded proteins are inherited asymmetrically, similarly to JUNQ quality-control inclusions observed in yeast. Mammalian IPOD-like inclusion bodies, meanwhile, are not always inherited by the same cell as the JUNQ. Our study suggests that the mammalian cytoskeleton and intermediate filaments provide the physical scaffold for asymmetric inheritance of dynamic quality-control JUNQ inclusions. Mammalian IPOD inclusions containing amyloidogenic proteins are not partitioned as effectively during mitosis as their counterparts in yeast. These findings provide a valuable mechanistic basis for studying the process of asymmetric inheritance in mammalian cells, including cells potentially undergoing polar divisions, such as differentiating stem cells and cancer cells