Prenatal exposure to medicines and the risk of childhood brain tumor

Background: Childhood brain tumors are associated with high mortality and morbidity but little is known about its causes. About half of women use medicines when pregnant and some of the medicines commonly used might be carcinogenic. Objective: The aim with this population-based case–control study was to analyze associations between specific groups of medicines taken during pregnancy and the risk of brain tumor in the offspring. Methods: All children, up to 15 years of age, born in Sweden between 1975 and 1984 were eligible for the study. Cases (N = 512) were children diagnosed with brain tumor and controls (N = 525) were randomly selected from the Medical Birth Register. Exposure data on medicines was extracted blindly from antenatal medical records and grouped according to Anatomical Therapeutic Chemical (ATC) code. Information on maternal reproductive history was received from the Medical Birth Register. We used logistic regression to estimate associations between fetal exposure to medicines and childhood brain tumor. Results: No significant changes in risk were noted after exposure to iron supplementation, antiemetics, analgesics, antibiotics or any other main ATC group. A tendency of protective effect was seen for prenatal exposure to folic acid (adjusted OR 0.6, 95% CI 0.3–1.1). Ten children with a diagnosis of brain tumor had been exposed to β-blocking agents in fetal life as compared to two children without brain tumor (adjusted OR 5.3, 95% CI 1.2–24.8). Conclusions: In this case–control study, an increased risk of brain tumor was seen in children exposed to β-blocking agents during fetal life. However, due to the low number of exposed the interpretation of this finding should be made with caution.     

New method for toxicity assessment in marine and brackish environments using the macroalga Gracilaria tenuistipitata (Gracilariales,Rhodophyta)

A growth inhibition test method was developed using the macroalga Gracilaria tenuistipitata as the test organism. This alga was chosen because of its high laboratory growth rates, commonly 30–40% d^–1, which are reached in salinities between 5 and 40, and its epiphyte resistance. The toxicity of a number of substances, including heavy metals, herbicides and complex wastewaters towards the alga was assayed. Anti-fouling paints were tested with a modification of the method. EC50 values for heavy metals varied between 0.05 and 17 mg l^–1 and for herbicides between 0.002 and 0.02 mg l^–l. The sensitivity to the toxicant was generally higher at low salinity. Omitting nitrogen and phosphorus additions to the test medium increased the sensitivity and a semi-static performance was possible with maintained or increased sensitivity. Preliminary tests done with a computerised photosynthesis inhibition method produced promising results.In conclusion, this is a simple, sensitive and reproducible test method for assessing the toxicity of substances, wastewaters and anti-fouling paints in brackish and marine environments.     

Comparative proteomics of industrial lager yeast reveals differential expression of the cerevisiae and non-cerevisiae parts of their genomes

The proteomes of three industrial lager beer strains, CMBS33, OG2252 and A15, were analysed under standardised laboratory growth conditions. Protein spots in the 2-DE pattern of the lager strains were subjected to MS/MS to identify protein variants. We found the protein composition of the three lager strains to be qualitatively rather similar, while being substantially different from the Saccharomyces cerevisiae strain BY4742. Database searches using several fully sequenced genomes from the Saccharomyces genera indicated that the non-cerevisiae proteins in the 2-D pattern of lager strains were most closely related to S. bayanus. For many proteins the regulation of the bayanus-like protein and its cerevisiae counterpart varied in a strain-dependent manner, e.g. the bayanus-like form of Tdh3p was roughly eight-fold more abundant than the cerevisiae form in the OG2252 strain. We also found differential regulation of cerevisiae- and bayanus-like proteins during various stress conditions like low temperature growth, and adaptation to high temperatures or high salinity, e.g. for Arg1p, Sti1p and Pdc1p. Our data on the differential regulation of the two genomes in these hybrid strains may have important industrial implications for strain improvement and strain protection.     

Crystal structure and enzymatic properties of a bacterial family 19 chitinase reveal differences from plant enzymes

We describe the cloning, overexpression, purification, characterization and crystal structure of chitinase G, a single-domain family 19 chitinase from the Gram-positive bacterium Streptomyces coelicolor A3(2). Although chitinase G was not capable of releasing 4-methylumbelliferyl from artificial chitooligosaccharide substrates, it was capable of degrading longer chitooligosaccharides at rates similar to those observed for other chitinases. The enzyme was also capable of degrading a colored colloidal chitin substrate (carboxymethyl-chitin-remazol-brilliant violet) and a small, presumably amorphous, subfraction of alpha-chitin and beta-chitin, but was not capable of degrading crystalline chitin completely. The crystal structures of chitinase G and a related Streptomyces chitinase, chitinase C [Kezuka Y, Ohishi M, Itoh Y, Watanabe J, Mitsutomi M, Watanabe T & Nonaka T (2006) J Mol Biol358, 472-484], showed that these bacterial family 19 chitinases lack several loops that extend the substrate-binding grooves in family 19 chitinases from plants. In accordance with these structural features, detailed analysis of the degradation of chitooligosaccharides by chitinase G showed that the enzyme has only four subsites (- 2 to + 2), as opposed to six (- 3 to + 3) for plant enzymes. The most prominent structural difference leading to reduced size of the substrate-binding groove is the deletion of a 13-residue loop between the two putatively catalytic glutamates. The importance of these two residues for catalysis was confirmed by a site-directed mutagenesis study.     

Suppressors of T-cell receptor signaling Sts-1 and Sts-2 bind to Cbl and inhibit endocytosis of receptor tyrosine kinases

The ubiquitin (Ub) ligase Cbl plays a critical role in attenuation of receptor tyrosine kinase (RTK) signaling by inducing ubiquitination of RTKs and promoting their sorting for endosomal degradation. Herein, we describe the identification of two novel Cbl-interacting proteins, p70 and Clip4 (recently assigned the names Sts-1 and Sts-2, respectively), that inhibit endocytosis of epidermal growth factor receptor (EGFR) and platelet-derived growth factor receptor. Sts-1 and Sts-2 contain SH3 domains that interacted with Cbl, Ub-associated domains, which bound directly to mono-Ub or to the EGFR/Ub chimera as well as phosphoglycerate mutase domains that mediated oligomerization of Sts-1/2. Ligand-induced recruitment of Sts-1/Sts-2 into activated EGFR complexes led to inhibition of receptor internalization, reduction in the number of EGFR-containing endocytic vesicles, and subsequent block of receptor degradation followed by prolonged activation of mitogenic signaling pathways. On the other hand, interference with Sts-1/Sts-2 functions diminished ligand-induced receptor degradation, cell proliferation, and oncogenic transformation in cultured fibroblasts. We suggest that Sts-1 and Sts-2 represent a novel class of Ub-binding proteins that regulate RTK endocytosis and control growth factor-induced cellular functions.     

Distinct monoubiquitin signals in receptor endocytosis

Numerous cellular proteins are post-translationally modified by the addition of the small modifier protein ubiquitin (Ub). The functional consequences of the type of ubiquitination vary, such that polyubiquitinated proteins are targeted for degradation by the proteasome, whereas monoubiquitination is implicated in other cellular functions, including endocytic trafficking and DNA repair. The monoubiquitination of trafficking cargoes, such as receptors and associated proteins, as well as of endocytic accessory Ub-binding proteins, raises the question of the precise function of monoubiquitin signals in the endocytic route. Recent biochemical and genetic evidence shows that multiple monoubiquitination of epidermal growth factor and platelet-derived growth factor receptors provides trafficking and sorting tags that ensure receptor endocytosis and degradation, whereas monoubiquitination of accessory proteins might play a role in regulating their function as Ub-receptors in the endosome.     

Tick-Borne Encephalitis Virus Sequenced Directly from Questing and Blood-Feeding Ticks Reveals Quasispecies Variance

The increased distribution of the tick-borne encephalitis virus (TBEV) in Scandinavia highlights the importance of characterizing novel sequences within the natural foci. In this study, two TBEV strains: the Norwegian Mandal 2009 (questing nymphs pool) and the Swedish Saringe 2009 (blood-fed nymph) were sequenced and phylogenetically characterized. Interestingly, the sequence of Mandal 2009 revealed the shorter form of the TBEV genome, similar to the highly virulent Hypr strain, within the 3′ non-coding region (3′NCR). A different genomic structure was found in the 3′NCR of Saringe 2009, as in-depth analysis demonstrated TBEV variants with different lengths within the poly(A) tract. This shows that TBEV quasispecies exists in nature and indicates a putative shift in the quasispecies pool when the virus switches between invertebrate and vertebrate environments. This prompted us to further sequence and analyze the 3′NCRs of additional Scandinavian TBEV strains and control strains, Hypr and Neudoerfl. Toro 2003 and Habo 2011 contained mainly a short (A)3C(A)6 poly(A) tract. A similar pattern was observed for the human TBEV isolates 1993/783 and 1991/4944; however, one clone of 1991/4944 contained an (A)3C(A)11 poly(A) sequence, demonstrating that quasispecies with longer poly(A) could be present in human isolates. Neudoerfl has previously been reported to contain a poly(A) region, but to our surprise the re-sequenced genome contained two major quasispecies variants, both lacking the poly(A) tract. We speculate that the observed differences are important factors for the understanding of virulence, spread, and control of the TBEV.