80 research outputs found
Xenopus tropicalis allurin: Expression, purification, and characterization of a sperm chemoattractant that exhibits cross-species activity
AbstractPreviously we reported the identification of the first vertebrate sperm chemoattractant, allurin, in the frog Xenopus laevis (Xl) and demonstrated that it was a member of the CRISP family of proteins. Here we report identification, purification, and characterization of Xenopus tropicalis (Xt) allurin, a homologous protein in X. tropicalis. “Egg water” as well as purified allurin from both species exhibit efficient cross-species sperm chemoattractant activity. Western blots show that Xt egg water contains a single anti-allurin cross-reactive protein whose molecular weight (20,497 Da by MALDI MS) agrees well with the molecular weight of the hypothetical gene product for a newly recognized “Crisp A” gene in the X. tropicalis genome. A recombinant form of the protein, expressed in 3T3 cells, exhibits chemoattraction for both Xt and Xl sperm and cross reacts with anti-allurin antibodies. Examination of Crisp protein expression in the Xt oviduct using RT-PCR showed that of five documented Xt Crisp genes (Crisps 2, 3, LD1, LD2 and A) only Crisp A was expressed. In contrast, Crisp 2, Crisp 3, Crisp LD1, and Crisp LD2, but not Crisp A, were all found to be expressed in the Xt testes while subsets of Crisp proteins where expressed in the Xt ovary. These data suggest that Crisp proteins in amphibians may play multiple roles in sperm production, maturation and guidance just as they are thought to in mammals indicating that Crisp protein involvement in reproduction may not be limited to mammals
Evidence for the Role of B Cells and Immunoglobulins in the Pathogenesis of Multiple Sclerosis
The pathogenesis of multiple sclerosis (MS) remains elusive. Recent reports advocate greater involvement of B cells and immunoglobulins in the initiation and propagation of MS lesions at different stages of their ontogeny. The key role of B cells and immunoglobulins in pathogenesis was initially identified by studies in which patients whose fulminant attacks of demyelination did not respond to steroids experienced remarkable functional improvement following plasma exchange. The positive response to Rituximab in Phase II clinical trials of relapsing-remitting MS confirms the role of B cells. The critical question is how B cells contribute to MS. In this paper, we discuss both the deleterious and the beneficial roles of B cells and immunoglobulins in MS lesions. We provide alternative hypotheses to explain both damaging and protective antibody responses
Quantitative trait loci analysis reveals candidate genes implicated in regulating functional deficit and CNS vascular permeability in CD8 T cell-initiated blood–brain barrier disruption
Sustainable food security decision-making : an agent-based modelling approach.
Ensuring a consistent and regular availability of food is crucial for food security. Food markets, supplied through both domestic production and international trade, are governed by several risks emerging from unpredictable supply chain disruptions, volatility of commodity prices, along with other unforeseen circumstances such as natural disasters. To mitigate the challenges threatening the stability of food systems, decision-making within the food sector should be enhanced and robust to accommodate any changes that might cause food shortages. Dynamic models, that can predict the behavior of food systems in order to avoid potential future knock-on effects and deficits, are incumbent to ensure the sustainable performance of food systems. This study proposes a dynamic decision-making scheme that simulates strategies of the perishable food market under different circumstances. An agent-based model (ABM) is developed and implemented using python MESA library for a case study in Qatar, illustrating the potential performance of tomato under three different scenarios to be considered, namely: (a) baseline scenario - aiming to reflect current production and market conditions; (b) water resource efficiency scenario - basing decisions on crop water requirement (CWR) depending on weather conditions; and (c) economic risk scenario - applying the concept of forward contracts to hedge against future uncertainties in crop prices. The findings of this study demonstrate that under the baseline conditions, a tomato crop can be supplied through a combination of domestic production and imports depending on the available inventories and prices imposed by exporters. The results obtained for the CWR scenario suggest the need for total reliance on imports in order to meet domestic demand, as there is potentially high-water loss, which amounts to an average of 4.9 Billion m3 per year, if tomato is grown locally. In contrast, the results from the forward contract scenario recommend a 57% dependency on local production in order to mitigate the effects of volatility in global food prices, which contributes to a 63% reduction in environmental emissions. Findings of this research provide insight into the factors that influence strategic decision making by the food sector to enhance its economic and environmental performances under diverse circumstances
Sticky molecules in not-so-sticky cells
The assignment of specific roles to cell-surface proteins by standard methods can be a major problem. In the technique described below, Schneider-2 (S2) cells, an established Drosophila cell line, have been used in cell transfection and aggregation experiments. As such, they have proved to be a useful tool for the functional characterization of putative cell-adhesion molecules.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29592/1/0000681.pd
Antigenic relationships between Mojave toxin subunits, Mojave toxin and some crotalid venoms.
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