Modeling of subglacial hydrological development following rapid supraglacial lake drainage.

The rapid drainage of supraglacial lakes injects substantial volumes of water to the bed of the Greenland ice sheet over short timescales. The effect of these water pulses on the development of basal hydrological systems is largely unknown. To address this, we develop a lake drainage model incorporating both (1) a subglacial radial flux element driven by elastic hydraulic jacking and (2) downstream drainage through a linked channelized and distributed system. Here we present the model and examine whether substantial, efficient subglacial channels can form during or following lake drainage events and their effect on the water pressure in the surrounding distributed system. We force the model with field data from a lake drainage site, 70 km from the terminus of Russell Glacier in West Greenland. The model outputs suggest that efficient subglacial channels do not readily form in the vicinity of the lake during rapid drainage and instead water is evacuated primarily by a transient turbulent sheet and the distributed system. Following lake drainage, channels grow but are not large enough to reduce the water pressure in the surrounding distributed system, unless preexisting channels are present throughout the domain. Our results have implications for the analysis of subglacial hydrological systems in regions where rapid lake drainage provides the primary mechanism for surface-to-bed connections. KEY POINTS: Model for subglacial hydrological analysis of rapid lake drainage eventsLimited subglacial channel growth during and following rapid lake drainagePersistence of distributed drainage in inland areas where channel growth is limited.

Early introduction of fish decreases the risk of eczema in infants.

BACKGROUND: Atopic eczema in infants has increased in western societies. Environmental factors and the introduction of food may affect the risk of eczema. AIMS: To investigate the prevalence of eczema among infants in western Sweden, describe patterns of food introduction and assess risk factors for eczema at 1 year of age. METHODS: Data were obtained from a prospective, longitudinal cohort study of infants born in western Sweden in 2003; 8176 families were randomly selected and, 6 months after the infant's birth, were invited to participate and received questionnaires. A second questionnaire was sent out when the infants were 12 months old. Both questionnaires were completed and medical birth register data were obtained for 4921 infants (60.2% of the selected population). RESULTS: At 1 year of age, 20.9% of the infants had previous or current eczema. Median age at onset was 4 months. In multivariable analysis, familial occurrence of eczema, especially in siblings (OR 1.87; 95% confidence interval (CI) 1.50 to 2.33) or the mother (OR 1.54; 95% CI 1.30 to 1.84), remained an independent risk factor. Introducing fish before 9 months of age (OR 0.76; 95% CI 0.62 to 0.94) and having a bird in the home (OR 0.35; 95% CI 0.17 to 0.75) were beneficial. CONCLUSIONS: One in five infants suffer from eczema during the first year of life. Familial eczema increased the risk, while early fish introduction and bird keeping decreased it. Breast feeding and time of milk and egg introduction did not affect the risk.

The glycogen synthase kinase (GSK) 3beta represses RNA polymerase I transcription.

Several oncogenic proteins and tumour suppressors target the RNA polymerase I and interfere with rRNA synthesis. Here, we show that the glycogen synthase kinase (GSK) 3beta, which phosphorylates the tumour suppressor PTEN (phosphatase and tensin homologue deleted on chromosome 10), is selectively enriched in nucleoli of RAS-transformed cells. Immunoprecipitation and chromatin immunoprecipitation assays performed on epithelial and endothelial cells transformed with oncogenic RAS show that GSK3beta and PTEN are part of the same complex and associate with promoter and coding region of the rDNA. An active GSK3beta mutant abolished nucleolar BrUTP incorporation and associated with the member of the selectivity factor 1 complex TAF(I)110. Finally, GSK3beta inhibition upregulated 45S, 18S and 28S rRNA synthesis in RAS-transformed epithelial cells as revealed by semiquantitative real-time PCR and promoted cellular proliferation. Our results underscore a repressive function for GSK3beta in rRNA biogenesis supporting its role as a tumour supressor.

Insights into bunyavirus architecture from electron cryotomography of Uukuniemi virus.

Bunyaviridae is a large family of viruses that have gained attention as "emerging viruses" because many members cause serious disease in humans, with an increasing number of outbreaks. These negative-strand RNA viruses possess a membrane envelope covered by glycoproteins. The virions are pleiomorphic and thus have not been amenable to structural characterization using common techniques that involve averaging of electron microscopic images. Here, we determined the three-dimensional structure of a member of the Bunyaviridae family by using electron cryotomography. The genome, incorporated as a complex with the nucleoprotein inside the virions, was seen as a thread-like structure partially interacting with the viral membrane. Although no ordered nucleocapsid was observed, lateral interactions between the two membrane glycoproteins determine the structure of the viral particles. In the most regular particles, the glycoprotein protrusions, or "spikes," were seen to be arranged on an icosahedral lattice, with T = 12 triangulation. This arrangement has not yet been proven for a virus. Two distinctly different spike conformations were observed, which were shown to depend on pH. This finding is reminiscent of the fusion proteins of alpha-, flavi-, and influenza viruses, in which conformational changes occur in the low pH of the endosome to facilitate fusion of the viral and host membrane during viral entry.

Responses of parasitoids to saproxylic hosts and habitat: a multi-scale study using experimental logs.

Species belonging to higher trophic levels are particularly vulnerable to habitat loss and consequential host population declines, but detection of effects depends on observation scale. We investigated the effects of habitat and host availability at multiple scales on parasitoids of early successional saproxylic beetles in middle boreal Sweden, where forestry has led to habitat fragmentation and coarse woody debris (CWD) loss. Parasitoid wasps and beetle hosts were collected from nine locations, each containing three spruce-dominated stand types (clear-cut, mature managed and unmanaged stands), using emergence traps on experimental CWD. We measured local CWD volumes and determined the availability of forests of a suitable age within the landscape. We tested parasitoid responses to stand type, CWD volume, abundance of known and probable hosts and longitude. Additionally, we tested whether parasitoids responded to the area of habitat of a suitable age within radii from 0.2 to 10 km. Stand type appeared in best-fit models for all common species, suggesting that wasps respond strongly to habitat at local scales. Longitude (largely climate) featured commonly, but CWD volume was never significant. Host abundance appeared in best-fit models for three of five common species, proving significant only for Bracon obscurator, the abundance of which correlated with that of Orthotomicus laricis at both trap and site levels. Rhimphoctona spp. also correlated significantly with its known host Tetropium castaneum at the trap level. B. obscurator responded to habitat area at scales of 0.6-1 km and Cosmophorus regius responded at radii greater than 7 km, while the larger species did not respond strongly to habitat area. The role of habitat area at greater scales thus varied greatly amongst species, but our data suggest that dispersal of these common early successional species may not be strongly restricted at the current scale of fragmentation of their boreal habitats.

Endostatin inhibits endochondral ossification.

BACKGROUND: Angiogenesis is essential for the replacement of cartilage by bone during skeletal growth and regeneration. Vascular endothelial growth factor-A (VEGF-A) is a key regulator of angiogenesis whereas endostatin, a potent inhibitor of endothelial cell proliferation and migration, is a natural antagonist of VEGF-A. The regulatory role of these peptides in angiogenesis and bone formation was investigated using adenoviral gene delivery of VEGF-A and endostatin in a mouse ectopic ossification model. METHODS: Bone formation was induced in the hamstring muscles of adult mice with native bone morphogenetic protein (BMP) extract implemented in gelatine gel together with VEGF-A and endostatin recombinant adenoviral vectors. The mice were sacrificed 1, 2, and 3 weeks after the operation and ectopic bone formation was followed radiographically and histologically. RESULTS: Significant bone formation was induced by BMP extract in all treatment groups. VEGF-A stimulated and endostatin prevented the formation of FVIII-related antigen-positive vessels as well as the number of cartilage-resorbing chondroclasts/osteoclasts. Endostatin alone or in conjugation with VEGF-A reduced bone formation. Excess of VEGF-A stimulated and endostatin reduced bone formation, respectively, at the 3-week time point. CONCLUSIONS: Our findings indicate that endostatin retards the cartilage phase in endochondral ossification which subsequently reduces bone formation in our experimental model. We conclude that bone growth and healing, which share features with ectopic bone formation, may be regulated by endostatin.

SIDS risk factors and factors associated with prone sleeping in Sweden.

OBJECTIVE: To compare the current prevalence of risk factors for sudden infant death syndrome (SIDS) in Sweden with a decade earlier, and assess factors associated with prone sleeping. METHODS: The results of a cohort study (Infants of Western Sweden) and a population based case-control study (Nordic Epidemiological SIDS Study) were examined. Subjects were 5600 healthy 6 month old infants born in 2003 in the Western Sweden region and 430 healthy Swedish infants born between 1991 and 1995. RESULTS: Prone sleeping decreased from 31.8% to 5.6% and supine sleeping increased from 35.3% to 47.3%. Side or side/supine sleeping increased from 25.2% to 43.8%. Maternal smoking during pregnancy decreased from 23.5% to 9.5%. The risk for prone sleeping increased if the mother was unemployed (OR 2.4, 95% CI 1.5 to 4.0), if she was a heavy smoker in the third trimester (OR 44.1, 95% CI 1.6 to 1199.6), and if the child was irritable (OR 2.5, 95% CI 1.3 to 5.1), shared a bedroom with siblings (OR 2.6, 95% CI 1.0 to 6.6), or never used a dummy (OR 3.2, 95% CI 1.9 to 5.4). CONCLUSIONS: Parents have complied with advice to prevent SIDS given at infant welfare centres for the last 10 years. A change in the preferred sleeping position from side variants to exclusively supine, and reducing the number of pregnant women smoking may be beneficial. Use of a prone sleeping position was associated with maternal employment status, maternal smoking, temperament of the child, dummy use, and sharing a bedroom with siblings.

The coxsackie-adenovirus receptor--a new receptor in the immunoglobulin family involved in cell adhesion.

The physiological and cell biological aspects of the Coxsackie-Adenovirus Receptor (CAR) is discussed in this review. The receptor obviously recognizes the group C adenoviruses in vivo, but also fibers from other groups except group B in vitro. The latter viruses seem to utilize a different receptor. The receptor accumulates at, or close to, the tight junction in polarized epithelial cells and probably functions as a cell-cell adhesion molecule. The cytoplasmic tail of the receptor is not required for virus attachment and uptake. Although there is a correlation between CAR and uptake of adenoviruses in several human tumor cells, evidence of an absolute requirement for integrins has not been forthcoming. The implication of these findings for adenovirus gene therapy is discussed.

Copper in drinking water: not a strong risk factor for diarrhoea among young children. A population-based study from Sweden.

AIM: To assess whether mean daily intake of copper or maximal concentration of copper in drinking water is related to the incidence of diarrhoea and vomiting among young children. METHODS: Mean daily intake of copper from drinking water was estimated prior to episodes of diarrhoea among 430 children aged 9 to 21 mo. A total of 4703 samples of tap water were collected in the homes of the children. The mean daily intake of copper and the maximal concentration of copper in samples of consumed water were used as measures of exposure. The cumulative incidence of acute diarrhoea and vomiting was studied during 12 wk of follow-up. Cases of diarrhoea caused by viral and bacterial infections were identified. RESULTS: The median copper level of the mean value for each child was 0.61 mg/L with 10th and 90th percentiles of 0.04 and 1.57 mg/L. Among the 430 children, 43 had episodes of acute diarrhoea, of which 23 had no identified viral or bacterial origin, and vomiting was reported in 95 children. No significant associations were found between daily intake of copper or maximal concentration of copper in drinking water and the risk of diarrhoea or vomiting. CONCLUSION: There is unlikely to be a strong association between daily intake of copper or maximal concentration of copper in drinking water and the risk of diarrhoea or vomiting within the range of copper intakes/concentrations studied.

Distinct differences in association of MHC class I with endoplasmic reticulum proteins in wild-type, and beta 2-microglobulin- and TAP-deficient cell lines.

In this study we have compared the interaction of human MHC class I molecules with IgG heavy chain (HC) binding protein (BiP), calnexin, calreticulin, tapasin and TAP in beta(2)-microglobulin (beta(2)m)- or TAP-deficient cells, as well as in wild-type B-LCL cells. Distinct differences between the association of HC and these endoplasmic reticulum (ER) proteins were found in the three cell lines. In the absence of beta(2)m (Daudi cells), HC associated with both BiP and calnexin. A prominent portion of HC was complexed simultaneously to both chaperones, as indicated by co-precipitation with either anti-calnexin or anti-class I antisera. In the presence of beta(2)m, but absence of TAP (T2 cells), HC could be co-precipitated with calnexin, whereas no detectable interaction with BiP could be demonstrated. This suggests that calnexin interacts with HC at a later stage than BiP. In B-LCL cells, HC-beta(2)m associated with calreticulin and tapasin, whereas no interaction with calnexin and BiP was observed. In the absence of beta(2)m, HC were rapidly degraded in the ER, while the ER retained HC were stabilized in the presence of beta(2)m, even in the absence of TAP. The dissociation of class I molecules from TAP in B-LCL cells correlated with the kinetics of appearance of class I molecules on the cell surface, suggesting that TAP retains peptide-free class I molecules in the ER. Taken together, our results suggest the model that BiP and calnexin sequentially control the folding of MHC class I, before MHC class I molecules associate with the loading complex.

Children's nutrient intake at preschool and at home.

UNLABELLED: A preschool-based dietary survey, using 7-d records, was carried out in a suburb of Stockholm. The aim was to assess the intake of food and the quality of the diet of preschool children aged 3-5 y at preschool and at home, and to compare the dietary intake with the Swedish dietary recommendations for preschool children. The respective mean intakes of protein, fat, carbohydrates and sucrose, expressed as a percentage of total energy intake were 14, 38, 50 and 9 at preschool, and at home 14, 36, 52 and 12 on weekdays, 14, 34, 55 and 16 on weekend days. The mean intakes of seven vitamins and minerals were low only for selenium as compared with the recommended level. No differences were found in nutrient density between diet at preschool and diet at home, with the exception of dietary fibre (higher at preschool). On weekdays there was a significantly higher nutrient density for calcium, zinc, selenium, vitamin A, riboflavin, vitamin C and dietary fibre compared with weekend days. CONCLUSION: The average intakes of energy and nutrients per meal at preschool compared with the recommended levels for children aged 4-6 y were low for all meals (breakfast, lunch and afternoon snack). This, however, was compensated for by home meals.

Reverse genetics system for Uukuniemi virus (Bunyaviridae): RNA polymerase I-catalyzed expression of chimeric viral RNAs.

We describe here the development of a reverse genetics system for the phlebovirus Uukuniemi virus, a member of the Bunyaviridae family, by using RNA polymerase I (pol I)-mediated transcription. Complementary DNAs containing the coding sequence for either chloramphenicol acetyltransferase (CAT) or green fluorescent protein (GFP) (both in antisense orientation) were flanked by the 5'- and 3'-terminal untranslated regions of the Uukuniemi virus sense or complementary RNA derived from the medium-sized (M) RNA segment. This chimeric cDNA (pol I expression cassette) was cloned between the murine pol I promoter and terminator and the plasmid transfected into BHK-21 cells. When such cells were either superinfected with Uukuniemi virus or cotransfected with expression plasmids encoding the L (RNA polymerase), N (nucleoprotein), and NSs (nonstructural protein) viral proteins, strong CAT activity or GFP expression was observed. CAT activity was consistently stronger in cells expressing L plus N than following superinfection. No activity was seen without superinfection, nor was activity detected when either the L or N expression plasmid was omitted. Omitting NSs expression had no effect on CAT activity or GFP expression, indicating that this protein is not needed for viral RNA replication or transcription. CAT activity could be serially passaged to fresh cultures by transferring medium from CAT-expressing cells, indicating that recombinant virus containing the reporter construct had been produced. In summary, we demonstrate that the RNA pol I system, originally developed for influenza virus, which replicates in the nucleus, has strong potential for the development of an efficient reverse genetics system also for Bunyaviridae members, which replicate in the cytoplasm.

Adenovirus-mediated overexpression of p15INK4B inhibits human glioma cell growth, induces replicative senescence, and inhibits telomerase activity similarly to p16INK4A.

The genes encoding the cyclin-dependent kinase inhibitors p16INK4A (CDKN2A) and p15INK4B (CDKN2B) are frequently homozygously deleted in a variety of tumor cell lines and primary tumors, including glioblastomas in which 40-50% of primary tumors display homozygous deletions of these two loci. Although the role of p16 as a tumor suppressor has been well documented, it has remained less well studied whether p15 plays a similar growth-suppressing role. Here, we have used replication-defective recombinant adenoviruses to compare the effects of expressing wild-type p16 and p15 in glioma cell lines. After infection, high levels of p16 and p15 were observed in two human glioma cell lines (U251 MG and U373 MG). Both inhibitors were found in complex with CDK4 and CDK6. Expression of p16 and p15 had indistinguishable effects on U251 MG, which has homozygous deletion of CDKN2A and CDKN2B, but a wild-type retinoblastoma (RB) gene. Cells were growth-arrested, showed no increased apoptosis, and displayed a markedly altered cellular morphology and repression of telomerase activity. Transduced cells became enlarged and flattened and expressed senescence-associated beta-galactosidase, thus fulfilling criteria for replicative senescence. In contrast, the growth and morphology of U373 MG, which expresses p16 and p15 endogenously, but undetectable levels of RB protein, were not affected by exogenous overexpression of either inhibitor. Thus, we conclude that overexpression of p15 has a similar ability to inhibit cell proliferation, to cause replicative senescence, and to inhibit telomerase activity as p16 in glioma cells with an intact RB protein pathway.

A controlled trial of self-help treatment of recurrent headache conducted via the Internet.

The Internet can reach a large number of people at a low cost and offers the opportunity for 2-way communication. The present study was designed to evaluate the effects of applied relaxation and problem solving in the treatment of recurrent headache when implemented via the Internet and E-mail. A group of 102 headache sufferers were randomized to 2 conditions: a 6-week treatment condition or a waiting-list control. The dropout was proportionately large (56%), and at the end of the study there were 20 participants in the treatment condition and 25 participants in the control condition. Results showed statistically significant reductions in headache for the treated participants. In 50% of these, the reduction was clinically significant. The Internet has the potential to serve as a complement in the treatment of recurrent headache and deserves further study.

Translation of p15.5INK4B, an N-terminally extended and fully active form of p15INK4B, is initiated from an upstream GUG codon.

The expression of the cyclin-dependent kinase inhibitor p15INK4B in normal cells after induction with TGF-beta1, or following overexpression from an adenovirus-encoded cDNA, appears on an SDS-polyacrylamide gel as a doublet. Here, the underlying mechanism behind the synthesis of the two species has been studied. By expressing cDNAs truncated at their 5' end, we found that the synthesis of the more slowly migrating form, called p15.5INK4B, is dependent on a sequence upstream of the first AUG codon thought to initiate translation of p15INK4B. Two potential, in frame, alternative upstream initiation codons, ACG and GUG, were individually changed to GCA encoding alanine. Analysis by in vitro translation, or immunoblotting of lysates from transfected 293 cells, showed that translation of p15.5INK4B is initiated at the GUG located 13 codons upstream of the first AUG. When this AUG was mutated, p15INK4B was no longer made. Instead, a shorter form, initiated at an in frame AUG located seven codons downstream, was synthesized. Finally, when both these AUGs were mutated, only p15.5INK4B was generated. Both p15INK4B and p15.5INK4B bound to CDK4 and CDK6, inhibited DNA synthesis, and caused replicative senescence of a human glioma cell line. We thus conclude that p15INK4B and p15.5INK4B, encoded by the CDKN2B gene, are functionally indistinguishable as based on these assays.

Characterization of fibroblast growth factor 1 binding heparan sulfate domain.

Fibroblast growth factors FGF-1 and FGF-2 mediate their biological effects via heparan sulfate-dependent interactions with cell surface FGF receptors. While the specific heparan sulfate domain binding to FGF-2 has been elucidated in some detail, limited information has been available concerning heparan sulfate structures involved in the recognition of FGF-1. In the current study we present evidence that the minimal FGF-1 binding heparan sulfate sequence comprises 5-7 monosaccharide units and contains a critical trisulfated IdoA(2-OSO3)-GlcNSO3(6-OSO3) disaccharide unit. N-Sulfated heparan sulfate decasaccharides depleted of FGF-1 binding domains showed dose-dependent and saturable binding to FGF-2. These data indicate that the FGF-1 binding domain is distinct from the minimal FGF-2 binding site, previously shown to contain an IdoA(2-OSO3) residue but no 6-O-sulfate groups. We further show that the FGF-1 binding heparan sulfate domain is expressed in human aorta heparan sulfate in an age-related manner in contrast to the constitutively expressed FGF-2 binding domain. Reduction of heparan sulfate O-sulfation by chlorate treatment of cells selectively impedes binding to FGF-1. The present data implicate the 6-O-sulfation of IdoA(2-OSO3)-GlcNSO3 units in cellular heparan sulfate in the control of the biological activity of FGF-1.