Research blogs and the discussion of scholarly information

The research blog has become a popular mechanism for the quick discussion of scholarly information. However, unlike peer-reviewed journals, the characteristics of this form of scientific discourse are not well understood, for example in terms of the spread of blogger levels of education, gender and institutional affiliations. In this paper we fill this gap by analyzing a sample of blog posts discussing science via an aggregator called ResearchBlogging.org (RB). ResearchBlogging.org aggregates posts based on peer-reviewed research and allows bloggers to cite their sources in a scholarly manner. We studied the bloggers, blog posts and referenced journals of bloggers who posted at least 20 items. We found that RB bloggers show a preference for papers from high-impact journals and blog mostly about research in the life and behavioral sciences. The most frequently referenced journal sources in the sample were: Science, Nature, PNAS and PLoS One. Most of the bloggers in our sample had active Twitter accounts connected with their blogs, and at least 90% of these accounts connect to at least one other RB-related Twitter account. The average RB blogger in our sample is male, either a graduate student or has been awarded a PhD and blogs under his own name.     

H5-type influenza virus hemagglutinin is functionally recognized by the natural killer-activating receptor NKp44

Antiviral immune defenses involve natural killer (NK) cells. We previously showed that the NK-activating receptor NKp44 is involved in the functional recognition of H1-type influenza virus strains by NK cells. In the present study, we investigated the interaction of NKp44 and the hemagglutinin of a primary influenza virus H5N1 isolate. Here we show that recombinant NKp44 recognizes H5-expressing cells and specifically interacts with soluble H5 hemagglutinin. H5-pseudotyped lentiviral particles bind to NK cells expressing NKp44. Following interaction with target cells expressing H5, pseudotyped lentiviral particles, or membrane-associated H5, NK cells show NKp44-mediated induced activity. These findings indicate that NKp44-H5 interactions induce functional NK activation.     

Binding and activation of thiamin diphosphate in acetohydroxyacid synthase

Acetohydroxyacid synthases (AHASs) are biosynthetic thiamin diphosphate- (ThDP) and FAD-dependent enzymes. They are homologous to pyruvate oxidase and other members of a family of ThDP-dependent enzymes which catalyze reactions in which the first step is decarboxylation of a 2-ketoacid. AHAS catalyzes the condensation of the 2-carbon moiety, derived from the decarboxylation of pyruvate, with a second 2-ketoacid, to form acetolactate or acetohydroxybutyrate. A structural model for AHAS isozyme II (AHAS II) from Escherichia coli has been constructed on the basis of its homology with pyruvate oxidase from Lactobacillus plantarum (LpPOX). We describe here experiments which further test the model, and test whether the binding and activation of ThDP in AHAS involve the same structural elements and mechanism identified for homologous enzymes. Interaction of a conserved glutamate with the N1' of the ThDP aminopyrimidine moiety is involved in activation of the cofactor for proton exchange in several ThDP-dependent enzymes. In accord with this, the analogue N3'-pyridyl thiamin diphosphate does not support AHAS activity. Mutagenesis of Glu47, the putative conserved glutamate, decreases the rate of proton exchange at C-2 of bound ThDP by nearly 2 orders of magnitude and decreases the turnover rate for the mutants by about 10-fold. Mutant E47A also has altered substrate specificity, pH dependence, and other changes in properties. Mutagenesis of Asp428, presumed on the basis of the model to be the crucial carboxylate ligand to Mg(2+) in the "ThDP motif", leads to a decrease in the affinity of AHAS II for Mg(2+). While mutant D428N shows ThDP affinity close to that of the wild-type on saturation with Mg(2+), D428E has a decreased affinity for ThDP. These mutations also lead to dependence of the enzyme on K(+). These experiments demonstrate that AHAS binds and activates ThDP in the same way as do pyruvate decarboxylase, transketolase, and other ThDP-dependent enzymes. The biosynthetic activity of AHAS also involves many other factors beyond the binding and deprotonation of ThDP; changes in the ligands to ThDP can have interesting and unexpected effects on the reaction.     

Tolerance induction in presensitized bone marrow recipients by veto CTLs: effective deletion of host anti-donor memory effector cells

Veto cells have been defined as cells capable of inducing apoptosis of effector CD8 cells recognizing their disparate MHC Ags. Tolerance induced by donor-type veto cells is desirable, because it is restricted to depletion of anti-donor clones without depletion of other immune specificities. It has been shown that anti-third party CTLs exhibit marked veto activity with reduced capacity to induce graft-vs-host disease, when tested on naive effector cells. However, presensitized T cells could play an important role in graft rejection, and therefore, their sensitivity to veto cells could be critical to the implementation of the latter cells in bone marrow transplantation. To address this question, we compared naive and presensitized TCR transgenic effector CD8 T cells, bearing a TCR against H-2(d). Both cell types exhibited similar predisposition to killing by veto CTLs in vitro, and this killing was dependent in both cell types on Fas-FasL signaling as shown by using Fas-deficient CD8 T cells from (lprx2c) F(1) mice. When tested in a stringent mouse model, in which bone marrow rejection is mediated by adoptively transferred host type T cells into lethally irradiated recipients, veto CTLs were equally effective in overcoming rejection of naive or presensitized host T cells.     

General water chemistry and quality in newly-created subtropical wetland lake

Sixty km2 of the southern Hula Valley (northern Israel) peat lands were flooded in 1994 as part of the Hula Valley Restoration Project. The small, shallow lake (110 ha, mean depth < 1 m) and network of ca. 90 km of canals created were designed to ameliorate problems (e.g., underground fires, soil subsidence, increased nutrient loading downstream to Lake Kinneret) resulting from drying the Lake Hula wetlands in the 1950s. This new wetland area now serves as the focus for developing eco-tourism in northern Israel. The initial development of this new ecosystem has been followed closely by a multi-disciplinary team of researchers, with an emphasis on water quality in the new lake and the potential impact of the project on Lake Kinneret. Here we report an overview of developments in general water chemistry of Lake Agmon during its first three years (1994–1996). Water quality in Agmon was within general expectations for a shallow lake situated on peat. The first year of Agmon was characterized by the heavy influence of stream and drainage inflows with high pH, alkalinity, turbidity and electrical conductivity and high concentrations of sulfate and total dissolved solids. By the third year, however, many in lake processes (e.g., nutrient cycling and algal and macrophytic production) were well-developed and thus strongly affected lake water quality. Excessive phosphorus and nitrogen concentrations in the lake have led to hypertrophy, characterized by low dissolved oxygen concentrations and prolific blooms of nuisance algae. The management of this new ecosystem in the near future will require persistent, and innovative measures.     

Membrane-associated heparan sulfate proteoglycans are involved in the recognition of cellular targets by NKp30 and NKp46

Lysis of virus-infected and tumor cells by NK cells is mediated via natural cytotoxicity receptors (NCRs). We have recently shown that the NKp44 and NKp46 NCRs, but not the NKp30, recognize viral hemagglutinins. In this study we explored the nature of the cellular ligands recognized by the NKp30 and NKp46 NCRs. We demonstrate that target cell surface heparan sulfate proteoglycans (HSPGs) are recognized by NKp30 and NKp46 and that 6-O-sulfation and N-acetylation state of the glucose building unit affect this recognition and lysis by NK cells. Tumor cells expressing cell surface heparanase, CHO cells lacking membranal heparan sulfate and glypican-1-suppressed pancreatic cancer cells manifest reduced recognition by NKp30 and NKp46 and are lysed to a lesser extent by NK cells. Our results are the first clue for the identity of the ligands for NKp30 and NKp46. Whether the ligands are particular HSPGs, unusual heparan sulfate epitopes, or a complex of HSPGs and either other protein or lipid moieties remains to be further explored.     

The management of Lake Agmon Wetlands (Hula Valley,Israel)

Hydrobiologia - Lake Hula and its surrounding swamps were drained in the 1950s. Forty years later a draw down of groundwater table and peat soils degradation resulted in damage to agricultural...     

Altered glycosylation of recombinant NKp30 hampers binding to heparan sulfate: a lesson for the use of recombinant immunoreceptors as an immunological tool

NKp30 is a natural cytotoxicity receptor expressed by human NK cells and involved in NK lytic activity. We previously published that membranal heparan sulfate serves as a coligand for human NKp30. In the present study, we complement our results by showing direct binding of recombinant NKp30 to immobilized heparin. The heparan sulfate epitope(s) on target tumor cells and the heparin epitope(s) recognized by NKp30 share similar characteristics. Warren and colleagues (Warren HS, Jones AL, Freeman C, Bettadapura J, Parish CR. 2005. Evidence that the cellular ligand for the human NK cell activation receptor NKp30 is not a heparan sulfate glycosaminoglycan. J Immunol. 175:207-212) published that NKp30 does not bind to membranal heparan sulfate on target cells and that heparan sulfate is not involved in NKp30-mediated lysis. In the current study, we examine the binding of six different recombinant NKp30s to membranal heparan sulfate and conclude that NKp30 does interact with membranal heparan sulfate. Yet, two of the six recombinant NKp30s, including the commercially available recombinant NKp30 (employed by Warren et al.) did not show heparan sulfate-dependent binding. We demonstrate that this is due to an altered glycosylation of these two recombinant NKp30s. Upon removal of its N-linked glycans, heparan sulfate-dependent binding to tumor cells and direct binding to heparin were restored. Overall, our results emphasize the importance of proper glycosylation for analysis of NKp30 binding to its ligand and that membranal heparan sulfate could serve as a coligand for NKp30. At the cellular level, soluble heparan sulfate enhanced the secretion of IFNgamma by NK-92 natural killer cells activated with anti-NKp30 monoclonal antibody. We discuss the involvement of heparan sulfate binding to NKp30 in NKp30-mediated activation of NK cells.     

In vivo and in vitro CO2 titration curves in the rabbit: adaptation to hypercapnic conditions

Arterial blood acid-base status of unanesthetized, unrestrained rabbits was studied during 6-12 hr of exposure to 7, 10 and 14.5% CO2. Most of the changes in blood acid-base status occurred during the first 20-60 min of exposure to hypercapnia and only minor changes occurred during the remaining exposure period (up to 12 hr). Blood buffer values obtained were not different from those reported for other terrestrial mammals. The whole body buffer values obtained here for the rabbit (0.58 nM H+/mmHg PCO2) is higher than that reported previously for man and dog. This relatively high whole body buffer value complies well with the high tolerance to CO2 reported for the rabbit.