Improved negative staining of microfilament arrangements in detergent-extracted Physarum amoeboflagellates

A motile, lamellipodium-like structure, the ridge, forms as amoeboflagellate cells of Physarum polycephalum release from a substratum and begin swimming in fluid. Actin microfilaments form a distinct laminar core within the ridge; they are seen as a sparse, disordered meshwork in cytoskeletons prepared by conventional methods using uranyl acetate negative staining [10]. Preservation and visualization of these filaments and their arrangements improved considerably when cytoskeletons were imaged with phosphotungstic acid buffered with ammonium hydroxide (PTA(NH4]. Microfilaments within ridge cytoskeletons were found to form loose bundles and criss-crossing, 'meshwork' arrays several layers deep. Differences could be detected in morphology and detailed arrangement of microfilaments within cytoskeletons prepared in the presence of phalloidin. PTA(NH4) may be useful for studies of cytoskeletal elements and their rearrangements in dynamic, motile regions of cells.     

Modelled population growth based on reproduction differs from life tables based on age determination in Danish raccoon dogs ( Nyctereutes procyonoides )

The population of raccoon dogs (Nyctereutes procyonoides) in Denmark has increased rapidly from 1995 when the first was recorded until today where 3291 raccoon dogs are trapped, shot by hunters or road killed. The aims of this study are to present the first data on reproduction and life tables of raccoon dogs in Denmark and to compare mortality from modelled life tables with game bag records and sampled raccoon dogs in different age groups. In this study, the uteri of 89 adult females (> 10 months) were examined for placental scars (PSC), and 561 individuals (289 males, 272 females) were aged using pulp cavity width and dental lines in canine teeth. The litter size of raccoon dogs in Denmark is to date the largest litter size recorded in the wild (mean ± SE) 10.8 ± 0.4, range 1–16 pubs and fecundity 8.4 ± 0.6 pubs. The percent-reproducing females are 78–83%, based on dark and all PSC, respectively. A significant difference was found between the proportion of individuals composing the different age groups based on age determination of individuals collected (Ntage) and the modelled number of individuals in age groups based on fecundity and different mortality rate (Ntmodel), X2 = 8, p < 0.05. The discrepancy between the relatively high reproduction and lifetables may be due to older and more experienced animals that avoid culling. A low population density in a newly founded Danish population of raccoon dogs, together with a milder climate where raccoon dogs can forage during the winter, may cause an exceptionally high reproduction in Danish raccoon dogs.     

RPA alleviates the inhibitory effect of vinylphosphonate internucleotide linkages on DNA unwinding by BLM and WRN helicases

Bloom (BLM) and Werner (WRN) syndrome proteins are members of the RecQ family of SF2 DNA helicases. In this paper, we show that restricting the rotational DNA backbone flexibility, by introducing vinylphosphonate internucleotide linkages in the translocating DNA strand, inhibits efficient duplex unwinding by these enzymes. The human single-stranded DNA binding protein replication protein A (RPA) fully restores the unwinding activity of BLM and WRN on vinylphosphonate-containing substrates while the heterologous single-stranded DNA binding protein from Escherichia coli (SSB) restores the activity only partially. Both RPA and SSB fail to restore the unwinding activity of the SF1 PcrA helicase on modified substrates, implying specific interactions of RPA with the BLM and WRN helicases. Our data highlight subtle differences between SF1 and SF2 helicases and suggest that although RecQ helicases belong to the SF2 family, they are mechanistically more similar to the SF1 PcrA helicase than to other SF2 helicases that are not affected by vinylphosphonate modifications.     

Construction of a Gammaretrovirus with a Novel Tropism and Wild-Type Replication Kinetics Capable of Using Human APJ as Entry Receptor

We have constructed a replication-competent gammaretrovirus (SL3-AP) capable of using the human G-protein-coupled receptor hAPJ as its entry receptor. The envelope protein of the virus was made by insertion of the 13-amino-acid peptide ligand for hAPJ, flanked by linker sequences, into one of the variable loops of the receptor binding domain of SL3-2, a murine leukemia virus (MLV) that uses the xenotropic-polytropic virus receptor Xpr1 and which has a host range limited to murine cells. This envelope protein can utilize hAPJ as well as murine Xpr1 for entry into host cells with equal efficiencies. In addition, the SL3-AP virus replicates in cells expressing either of its receptors, hAPJ and murine Xpr1, and causes resistance to superinfection and downregulation of hAPJ in infected cells. Thus, SL3-AP is the first example of a retargeted replication-competent retrovirus, with replication characteristics and receptor interference properties similar to those of natural isolates.     

A trypsin-like protease with apparent dual function in early Lepeophtheirus salmonis (Kr?yer) development

Background  

Trypsin-like serine proteases are involved in a large number of processes including digestive degradation, regulation of developmental processes, yolk degradation and yolk degradome activation. Trypsin like peptidases considered to be involved in digestion have been characterized in Lepeophtheirus salmonis. During these studies a trypsin-like peptidase which differed in a number of traits were identified.     

Trends from 2002 to 2010 in Daily Breakfast Consumption and its Socio-Demographic Correlates in Adolescents across 31 Countries Participating in the HBSC Study

Breakfast is often considered the most important meal of the day and children and adolescents can benefit from breakfast consumption in several ways. The purpose of the present study was to describe trends in daily breakfast consumption (DBC) among adolescents across 31 countries participating in the HBSC survey between 2002 to 2010 and to identify socio-demographic (gender, family affluence and family structure) correlates of DBC. Cross-sectional surveys including nationally representative samples of 11–15 year olds (n = 455,391). Multilevel logistic regression analyses modeled DBC over time after adjusting for family affluence, family structure and year of survey. In all countries, children in two-parent families were more likely to report DBC compared to single parent families. In most countries (n = 19), DBC was associated with family affluence. Six countries showed an increase in DBC (Canada, Netherland, Macedonia, Scotland, Wales, England) from 2002. A significant decrease in DBC from 2002 was found in 11 countries (Belgium Fr, France, Germany, Croatia, Spain, Poland, Russian Federation, Ukraine, Latvia, Lithuania and Norway), while in 5 countries (Portugal, Denmark, Finland, Ireland, Sweden) no significant changes were seen. Frequency of DBC among adolescents in European countries and North America showed a more uniform pattern in 2010 as compared to patterns in 2002. DBC increased significantly in only six out of 19 countries from 2002 to 2010. There is need for continued education and campaigns to motivate adolescents to consume DBC. Comparing patterns across HBSC countries can make an important contribution to understanding regional /global trends and to monitoring strategies and development of health promotion programs.     

Trends in Food Habits and Their Relation to Socioeconomic Status among Nordic Adolescents 2001/2002-2009/2010

Background

In the Nordic countries, substantial policy and intervention efforts have been made to increase adolescents'' consumption of fruit and vegetables and to reduce their intake of sweets and soft drinks. Some initiatives have been formulated in a Nordic collaboration and implemented at national level. In recent years, social inequalities in food habits have been attracted particular governmental interest and several initiatives addressing the socioeconomic gradient in food habits have been highlighted. However, few internationally published studies have evaluated how trends in adolescents'' food habits develop in the context of Nordic nutrition policy, or have compared differences between the Nordic countries.

Methods

The study was based on Danish, Finnish, Norwegian and Swedish cross-sectional data from the international Health Behaviour in School-Aged Children (HBSC) study, collected via three nationally representative and comparable questionnaire surveys in 2001/2002, 2005/2006 and 2009/2010. Food habits were identified by students'' consumption of fruit, vegetables, sweets and sugar sweetened soft drink. Socioeconomic status (SES) was measured with the Family Affluence Scale (FAS). Multilevel logistic regression was used to analyze the data.

Results

Trends in fruit consumption developed differently across countries, characterized by an increase in Denmark and Norway and more stable trends in Sweden and Finland. Vegetable consumption increased particularly in Denmark and to a lesser extent in Norway, whereas Sweden and Finland displayed stable trends. Decreased trends were observed for sweet and soft drink consumption and were similar in Norway, Sweden and Finland. Sweet consumption decreased across all survey years, whereas soft drink consumption decreased between 2001/2002–2005/2006 and was stable thereafter. Denmark displayed an increase between 2001/2002–2005/2006 followed by a similar decrease between 2005/2006–2009/2010 for both sweet and soft drink consumption. Socioeconomic inequalities in fruit and vegetable consumption were observed in all countries, with no cross-country differences, and no changes over time. Small but not significant cross-country variation was identified for SES inequalities in sweet consumption. Reduced SES inequalities were observed in Sweden between 2005/2006 and 2009/2010. SES was not associated with soft drink consumption in this study population, with the exception of Denmark for the survey year 2009/2010.

Conclusion

Different trends resulted in increased country differences in food habits during the time of observations. In survey year 2009/2010, Danish students reported a higher intake of fruit and vegetable consumption than their counterparts in the other Nordic countries. Finnish students reported the lowest frequency of sweets and soft drink consumption. Despite the positive dietary trends documented in the present study, the majority of Nordic adolescents are far from meeting national dietary recommendations. Our findings underline the need for more comprehensive initiatives targeting young people''s food habits as well as a more deliberate and focused action to close gaps in social inequalities that affect food choices.     

Monoclonal antibodies binding to the tail of Dictyostelium discoideum myosin: their effects on antiparallel and parallel assembly and actin- activated ATPase activity

Eight monoclonal antibodies that bind to specific sites on the tail of Dictyostelium discoideum myosin were tested for their effects on polymerization and ATPase activity. Two antibodies that bind close to the myosin heads inhibited actin activation of the ATPase either partially or completely, without having an effect on polymerization. Two other antibodies bind to sites within the distal portion of the tail that has been shown, by cleavage mapping, to be important for polymerization. One of these antibodies binds close to the sites of heavy chain phosphorylation which is known to regulate both myosin polymerization and actin-activated ATPase activity. Both antibodies showed strong inhibition of polymerization accompanied by complete inhibition of the actin-activated ATPase activity. A unique effect was obtained with an antibody that binds to the end of the myosin tail. This antibody prevented the formation of bipolar filaments. It caused myosin to assemble into unipolar filaments with heads at one end and the antibody molecules at the other. Only at concentrations higher than required for its effect on polymerization did this antibody show substantial inhibition of the actin-activated ATPase. These results indicate that, using a monoclonal antibody as a blocking agent, parallel assembly of myosin can be dissected out from antiparallel association, and that essentially normal actin-activated ATPase activity could be obtained after significant reductions in filament size.