Changes in haemolymph ion concentrations of Astacus astacus L. and Pacifastacus leniusculus (Dana) after exposure to low pH and aluminium

During exposure to soft water, acidified to pH 4.0, the haemolymph concentrations of Na⁺, K⁺, and Cl^– decreased whereas the Ca²⁺ concentration fluctuated in Astacus astacus. The haemocyte content of K⁺ decreased from 9% to 2% of the total haemolymph K⁺ content after exposure to pH 3.7 for 3 days. Within 14 days, 250 µg Al³⁺ l^–1, as Al₂(SO₄)₃ at pH 5.0, reduced the haemolymph Na⁺ content in Astacus astacus and Pacifastacus leniusculus, however, the effects were less pronounced than earlier reported for fish. Disturbed ion regulation, mainly depending on low pH, is thought to contribute to the absence of these species in acid waters.     

Winter Host Plant Specialization in a Host-Alternating Aphid

The host alternating aphid, Rhopalosiphum padi (L.), feeds in summer on several different species of grasses but is monophagous on its winter host, Prunus padus L. The monophagy on P. padus could be a result of the restricted host range of the several different generations colonizing, or feeding, on this host during autumn–winter–spring. This study shows that the winter host plant specificity of R. padi is controlled mainly by the preference of the females remigrating (gynoparae) to the winter host, P. padus, in autumn. The other generations living on the winter host, i.e., sexual females, males, and spring generations, all accept a broader range of winter hosts. One alternative host plant, Prunus spinosa L., could be utilized by all generations associated with the winter host, except for the females remigrating at autumn.     

Quantifying Cancer Absolute Risk and Cancer Mortality in the Presence of Competing Events after a Myotonic Dystrophy Diagnosis

Recent studies show that patients with myotonic dystrophy (DM) have an increased risk of specific malignancies, but estimates of absolute cancer risk accounting for competing events are lacking. Using the Swedish Patient Registry, we identified 1,081 patients with an inpatient and/or outpatient diagnosis of DM between 1987 and 2007. Date and cause of death and date of cancer diagnosis were extracted from the Swedish Cause of Death and Cancer Registries. We calculated non-parametric estimates of absolute cancer risk and cancer mortality accounting for the high non-cancer competing mortality associated with DM. Absolute cancer risk after DM diagnosis was 1.6% (95% CI=0.4-4%), 5% (95% CI=3-9%) and 9% (95% CI=6-13%) at ages 40, 50 and 60 years, respectively. Females had a higher absolute risk of all cancers combined than males: 9% (95% CI=4-14), and 13% (95% CI=9-20) vs. 2% (95%CI= 0.7-6) and 4% (95%CI=2-8) by ages 50 and 60 years, respectively) and developed cancer at younger ages (median age =51 years, range=22-74 vs. 57, range=43-84, respectively, p=0.02). Cancer deaths accounted for 10% of all deaths, with an absolute cancer mortality risk of 2% (95%CI=1-4.5%), 4% (95%CI=2-6%), and 6% (95%CI=4-9%) by ages 50, 60, and 70 years, respectively. No gender difference in cancer-specific mortality was observed (p=0.6). In conclusion, cancer significantly contributes to morbidity and mortality in DM patients, even after accounting for high competing DM mortality from non-neoplastic causes. It is important to apply population-appropriate, validated cancer screening strategies in DM patients.     

A strategy for identification of protein tyrosine phosphorylation

To develop methods for studying phosphorylation of protein tyrosine residues is an important task since this protein modification regulates many cellular functions and often is involved in oncogenesis. An optimal protocol includes enrichment of tyrosine phosphorylated (pTyr) peptides or proteins, followed by a high resolving analytical method for identification of the enriched components. In this Methods paper, we describe a working strategy on how immunoaffinity enrichments, using anti-pTyr antibodies, combined with mass spectrometric (MS) analysis can be used to study the pTyr proteome. We describe in detail how our procedure was used to characterize the pTyr proteome of K562 leukemia cells. Important questions concerning the use of different anti-pTyr antibodies, enrichments performed at the peptide and/or the protein level, pooling of enrichments and requirements for the MS characterization are discussed.     

Killer toxin-like chitinases in filamentous fungi: Structure,regulation and potential roles in fungal biology

Fungal chitinases are hydrolytic enzymes responsible for degradation of chitin. Chitinases are involved in several aspects of fungal biology, including cell wall remodelling during hyphal growth, conidial germination, autolysis, mycoparasitism and nutrient acquisition. They are divided into three distinct phylogenetic groups; A, B and C. Chitinases from the C group show structural similarities with the killer toxin zymocin produced by the yeast Kluyveromyces lactis and it is speculated that they have a similar function in filamentous ascomycetes, by facilitating penetration of toxins into cells of competing individuals. Genome analyses show that certain fungal species with a mycoparasitic lifestyle contain high numbers of killer toxin-like chitinases, compared with specialized saprotrophs and plant pathogens. Recent developments within this research field have revealed considerable variation in the modular structure and regulation of killer toxin-like chitinases, suggesting more diverse roles than merely fungal-fungal interactions. In this review, we summarize the current knowledge about this intriguing class of chitinases, including their modular structure, evolution, gene regulation, and functional analyses in mycoparasitic as well as in saprotrophic species. We also propose important questions for future research.     

Identification of a novel calreticulin isoform (Crt2) in human and mouse

The human REIC gene is a recently found mortalization-related gene and a candidate tumor suppressor gene expression of which is largely attenuated in many immortalized and tumor-derived cell lines (Biochem. Biophys. Res. Commun. 268 (2000) 20-24). To gain insight into the mechanisms of the down-regulation, we investigated the genomic structure and promoter activity of the human REIC gene. The gene, identical with the DKK-3 gene, resides on chromosome 11p15.1, consists of nine exons, and has two promoters. Methylation in the main promoter region was detected in 11 out of 21 cell lines tested (52%) derived from a variety of human tumors, in which the expression of the REIC gene was decreased. In ten of these 11 cell lines the minor promoter was also methylated. Similarly, the REIC gene expression was decreased in 14 of 24 fresh non-small cell lung cancer specimens (58%) compared to that in corresponding non-cancerous tissue, though allelic loss and tumor-specific mutation were rare. Of these 14 tumors, at least five tumors exhibited heavy methylation of the REIC promoter region. These results indicate that the down-regulation of the REIC gene expression is ascribed to the aberrant promoter hyper-methylation at least in a subset of human tumors. The expression was restored upon treatment of SQ5 cells with 5-aza-deoxycytidine, confirming DNA methylation as the mode of downregulation. A notable single nucleotide polymorphism in the coding region (cSNP) with an amino acid substitution of glycine (GGG) to arginine (AGG) was found at codon 335 of the REIC gene. However, the distribution of the cSNP showed no significant difference between lung cancer patients and healthy population.     

Colorectal carcinomas have a characteristic ganglioside pattern

The gangliosides in six colorectal and two pancreatic carcinomas were examined. Their concentration in the primary tumour and the metastases was 5-10 fold higher than in normal colon mucosa. This increase involved the simple gangliosides, GM3 and GD3, as well as complex mono- and disialogangliosides. Some complex monosialogangliosides were detected in all the colorectal and pancreatic carcinomas but neither in normal colon mucosa and pancreas nor in kidney and lung carcinomas.     

Crystal structures of Trypanosoma brucei and Staphylococcus aureus mevalonate diphosphate decarboxylase inform on the determinants of specificity and reactivity

Mevalonate diphosphate decarboxylase (MDD) catalyzes the ATP-dependent decarboxylation of mevalonate 5-diphosphate (MDP) to form isopentenyl pyrophosphate, a ubiquitous precursor for isoprenoid biosynthesis. MDD is a poorly understood component of this important metabolic pathway. Complementation of a temperature-sensitive yeast mutant by the putative mdd genes of Trypanosoma brucei and Staphylococcus aureus provides proof-of-function. Crystal structures of MDD from T. brucei (TbMDD, at 1.8 A resolution) and S. aureus (SaMDD, in two distinct crystal forms, each diffracting to 2.3 A resolution) have been determined. Gel-filtration chromatography and analytical ultracentrifugation experiments indicate that TbMDD is predominantly monomeric in solution while SaMDD is dimeric. The new crystal structures and comparison with that of the yeast Saccharomyces cerevisiae enzyme (ScMDD) reveal the structural basis for this variance in quaternary structure. The presence of an ordered sulfate in the structure of TbMDD reveals for the first time details of a ligand binding in the MDD active site and, in conjunction with well-ordered water molecules, comparisons with the related enzyme mevalonate kinase, structural and biochemical data derived on ScMDD and SaMDD, allows us to model a ternary complex with MDP and ATP. This model facilitates discussion of the molecular determinants of substrate recognition and contributions made by specific residues to the enzyme mechanism.