Enhanced mutagenic response of MNU by post-treatment with methylmercury,caffeine or thymidine in V79 Chinese hamster cells

Post-treatment with a non-toxic dose of thymidine, caffeine or methylmercury-hydroxide enhanced the mutagenic response from MNU at high doses, whereas no enhancement was observed with low doses of MNU. No mutagenic effects were found with thymidine, caffeine or methylmercury alone at the doses used. Quantitatively, the modifying effects observed were similar for the 3 agents which indicates the possibility of a similar way of action.     

A new versatile and compact lentiviral vector

During the past decade, lentiviral vectors based on the HIV-1 genome have been developed to become highly useful tools for efficient and stable delivery of transgenes to dividing and nondividing cells in a variety of experimental protocols. The vector system has been progressively and substantially improved, mainly to meet growing concerns over safety issues. However, the actual design and size of the lentiviral transfer vector often makes transgene cloning and DNA preparation a troublesome task. In this study, the pHR transfer vector used for lentivirus production in many laboratories was modified to contain a more versatile polylinker than the one present in the original pHR vector. In addition, the vector was significantly reduced in size from 12 to 7 kb, by replacing the original vector backbone with sequence from the multipurpose pUC18 vector. These modifications allowed for easier cloning and higher DNA yields without compromising the fundamental ability of this vector system to transduce cells in vitro and in vivo. Finally, the trimmed vector sequence was fully characterized by sequencing the vector in its entirety. In both cultured cells and directly into the rat striatum, transduction with this lentivirus, based on the modified pHsCXW vector, was as efficient and durable as with the pHR vector-based virus. In conclusion, the modified lentiviral transfer vector pHsCXW holds promise as a new valuable tool for the research community in the field of gene transfer.     

CTLA4 polymorphisms are associated with vitiligo, in patients with concomitant autoimmune diseases

The cytotoxic T lymphocyte antigen4 (CTLA4) gene plays a critical role in the control of T cell activation. The gene encodes a surface molecule with inhibitory effects on activated T cells. Several studies have disclosed an association between the previously known variants of the CTLA4 gene and autoimmune disorders, but no study has as yet found any definite association between vitiligo and the CTLA4 polymorphisms. A recent study identified new candidate susceptibility polymorphisms in this region, associated with differential gene splicing and thereby the relative abundance of soluble CTLA4. To assess these new polymorphisms in patients with vitiligo, we genotyped 100 vitiligo patients and 140 healthy controls from the UK, for these novel polymorphisms. No association was found in patients with isolated vitiligo, but a significant association was seen in patients with vitiligo and other autoimmune diseases. The results indicate that the polymorphisms in the CTLA4 gene region confer susceptibility to vitiligo when occurring together with other autoimmune diseases, but not in patients with isolated vitiligo. This raises the possibility that there are two distinct forms of vitiligo where only a subgroup of patients may have a disease caused by the autoimmune destruction of melanocytes.     

Isomerisation of aldoses in pyridine in the presence of aluminium oxide

Addition of aluminium oxide to boiling pyridine solutions of D-xylose, L-arabinose, D-mannose and D-glucose strongly increased the reaction rate of the aldose-ketose transformation. The maximum content of 2-ketose was reached after less than 2h for the aldopentoses and 3h for the aldohexoses. D-Threo-2-pentulose (xylulose) was prepared from D-xylose, and isolated as its O-isopropylidene derivative, the yield was nearly twice that compared to that usually obtained in the classical Lobry de Bruyn-Alberda van Ekenstein transformation in pyridine.     

Mutagenicity and DNA repair of glycidamide-induced adducts in mammalian cells

Glycidamide (GA)-induced mutagenesis in mammalian cells is not very well understood. Here, we investigated mutagenicity and DNA repair of GA-induced adducts utilizing Chinese hamster cell lines deficient in base excision repair (BER), nucleotide excision repair (NER) or homologous recombination (HR) in comparison to parent wild-type cells. We used the DRAG assay in order to map pathways involved in the repair of GA-induced DNA lesions. This assay utilizes the principle that a DNA repair deficient cell line is expected to be affected in growth and/or survival more than a repair proficient cell. A significant induction of mutations by GA was detected in the hprt locus of wild-type cells but not in BER deficient cells. Cells deficient in HR or BER were three or five times, respectively, more sensitive to GA in terms of growth inhibition than were wild-type cells. The results obtained on the rate of incisions in BER and NER suggest that lesions induced by GA are repaired by short patch BER rather than long patch BER or NER. Furthermore, a large proportion of the GA-induced lesions gave rise to strand breaks that are repaired by a mechanism not involving PARP. It is suggested that these strand breaks, which might be the results from alkylation of the backbone phosphate, are misrepaired by HR during replication thereby leading to a clastogenic rather than a mutagenic pathway. The type of lesion responsible for the mutagenic effect of GA cannot be concluded from the results presented in this study.     

Metabolic stoichiometry and the fate of excess carbon and nutrients in consumers

Animals encountering nutritionally imbalanced foods should release elements in excess of requirements in order to maintain overall homeostasis. Quantifying these excesses and predicting their fate is, however, problematic. A new model of the stoichiometry of consumers is formulated that incorporates the separate terms in the metabolic budget, namely, assimilation of ingested substrates and associated costs, protein turnover, other basal costs, such as osmoregulation, and the use of remaining substrates for production. The model indicates that release of excess C and nonlimiting nutrients may often be a significant fraction of the total metabolic budget of animals consuming the nutrient-deficient forages that are common in terrestrial and aquatic systems. The cost of maintenance, in terms of not just C but also N and P, is considerable, such that food quality is important even when intake is low. Many generalist consumers experience short-term and unpredictable fluctuations in their diets. Comparison of model output with data for one such consumer, Daphnia, indicates that mechanisms operating postabsorption in the gut are likely the primary means of regulating excess C, N, and P in these organisms, notably respiration decoupled from biochemical or mechanical work and excretion of carbon and nutrients. This stoichiometrically regulated release may often be in organic rather than inorganic form, with important consequences for the balance of autotrophic and heterotrophic processes in ecosystems.     

The O-acetylation patterns in the O-antigens of Hafnia alvei strains PCM 1200 and 1203, serologically closely related to PCM 1205

Serological tests revealed immunochemical similarities between the lipopolysaccharides of Hafnia alvei strains PCM 1200, 1203 and 1205. Immunoblotting and ELISA showed cross-reactions between the strains. NMR spectroscopy showed that the O-deacetylated O-specific polysaccharides isolated from lipopolysaccharides of H. alvei strains PCM 1200 and 1203 possessed the same composition and sequence as the O-deacetylated O-specific polysaccharide of H. alvei strain PCM 1205, that is a glycerol teichoic-acid-like polymer with a repeating unit of the following structure: [carbohydrate structure: see text] NMR spectroscopic studies of the polysaccharides concluded that O-3 of the side chain beta-D-GlcpNAc is partially O-acetylated (50-80%) in both investigated strains. In strain PCM 1203 an additional O-acetyl group (50-80%) is linked to O-6 of the chain -->3)-alpha-D-GlcpNAc-(1--> residue. The structural features of the isolated O-specific polysaccharides were also the same as those of the O-specific polysaccharides on the bacterial cells directly observed by the HR-MAS NMR technique.     

Calanoid copepods from South Georgia,with special reference to size dimorphism within the genus Pseudoboeckella

Summary Three species of calanoid copepods, Boeckella michaelseni, Parabroteas sarsii and Pseudoboeckella poppei were recorded from 6 freshwater localities in the Husvik area, South Georgia. Of the latter species two distinct size morphs occurred, with no overlap in size even in closely situated populations. The large morph was recorded in lakes, the small was found in ponds. The small morph did not coexist with the large predatory P. sarsii, and we suggest predation pressure from this species as the major cause for the observed distribution of these morphs. The pronounced size segregation as well as small morphological dissimilarities suggest that these morphs are reproductively isolated. While the large morphotype corresponds to that of P. poppei, the taxonomic affinities of the small morph are uncertain.     

Premature Adult Death in Individuals Born Preterm: A Sibling Comparison in a Prospective Nationwide Follow-Up Study

BackgroundClose to one in ten individuals worldwide is born preterm, and it is important to understand patterns of long-term health and mortality in this group. This study assesses the relationship between gestational age at birth and early adult mortality both in a nationwide population and within sibships. The study adds to existing knowledge by addressing selected causes of death and by assessing the role of genetic and environmental factors shared by siblings.MethodsStudy population was all Norwegian men and women born from 1967 to 1997 followed using nation-wide registry linkage for mortality through 2011 when they were between 15 and 45 years of age. Analyses were performed within maternal sibships to reduce variation in unobserved genetic and environmental factors shared by siblings. Specific outcomes were all-cause mortality and mortality from cardiovascular diseases, cancer and external causes including accidents, suicides and drug abuse/overdoses.ResultsCompared with a sibling born in week 37–41, preterm siblings born before 34 weeks gestation had 50% increased mortality from all causes (adjusted Hazard Ratio (aHR) 1.54, 95% confidence interval (CI) 1.17, 2.03). The corresponding estimate for the entire population was 1.27 (95% CI 1.09, 1.47). The majority of deaths (65%) were from external causes and the corresponding risk estimates for these deaths were 1.52 (95% CI 1.08, 2.14) in the sibships and 1.20 (95% CI 1.01, 1.43) in the population.ConclusionPreterm birth before week 34 was associated with increased mortality between 15 and 45 years of age. The results suggest that increased premature adult mortality in this group is related to external causes of death and that the increased risks are unlikely to be explained by factors shared by siblings.     

Calcium content of crustacean zooplankton and its potential role in species distribution

SUMMARY 1. The occurrence and species composition of crustacean zooplankton in Norwegian lakes was related to ambient Ca concentrations, pH, total phosphorus and chlorophyll a , and to the presence/absence of other zooplankters and a planktivorous fish (roach: Rutilus rutilus ).
2. Ambient Ca concentrations appeared to influence the distribution of Daphnia species: Daphnia longispina often occurred in Ca-rich lakes with low fish-predation pressure while the smaller Daphnia cristata often occurred in opposite conditions.
3. Body Ca contents were measured in zooplankters from a wide range of localities, to examine Ca requirements and thus the potential for Ca-limitation of common species.
4. All Daphnia species had relatively high specific Ca contents [ranging from 0.8 to 4.4% Ca dry weight (DW)⁻¹] compared with other cladocerans and also copepods (ranging from 0.1 to 0.4% Ca DW⁻¹). Within the Daphnia genus, the specific Ca content increased with increasing body size of the species, and thus the large-bodied species had especially high Ca demands.
5. Because of their high Ca demands, species of Daphnia could be competitively disadvantaged in softwater lakes relative to less Ca-demanding species.