Acoustic microscopy of cultured cells. Distribution of forces and cytoskeletal elements.

The scanning acoustic microscope (SAM) allows one to measure mechanical parameters of living cells with high lateral resolution. By analyzing single acoustic images' sound attenuation and sound velocity, the latter corresponding to stiffness (elasticity) of the cortical cytoplasm can be determined. In this study, measurements of stiffness distribution in XTH-2 cells were compared with the organization of F-actin and microtubules. Single XTH-2 cells exhibit relatively high stiffness at the free margins; toward the cell center this value decreases and reaches a sudden minimum where the slope of the surface topography enlargens at the margin of the dome-shaped cell center. The steepness of the increase in slope is linearly related to the decrease in sound velocity at this site. Thus, a significant determinant of cell shape is paralleled by an alteration of stiffness. In the most central parts, no interferences could be distinguished, therefore, this region had to be excluded from the calculations. Stiffness distribution roughly coincided with the distribution of F-actin, but no correlation to microtubule arrangement was found. Following the treatment of XTH-2 cells with ionomycin in the presence of calcium (in the culture medium), the cell cortex first contracted as indicated by shape changes and by a marked increase in stiffness (deduced from sound velocity). This contraction phase was followed by a phase of microtubule and F-actin disassembly. Concomittantly, sound velocity decreased considerably, indicating the loss of elasticity in the cell cortex. No structural equivalent to sound attenuation has been identified.     

Population structure and dynamics of wood mouse Apodemus sylvaticus in Iceland

Five-year-studies of two wood mouse populations (Apodemus sylvaticus L.) were carried out outside the village Vík. S. Iceland, and in a birch forest close to the lake Mývatn, N. Iceland. The population at Vík was studied on a 1.10 ha grid on a slope covered with Angelica archangelica L., the seeds of which constituted a major food resource for the mice. Altogether 948 individuals were caught, marked and followed during 1973–1978. No other free-living small mammals occur in Iceland, and predator pressure is low and considered non-existent on the Angelica slope. The population density was extremely high; highest autumn density recorded was 150 ind ha^?1. Like other Apodemus populations, the one at Vík showed a typical seasonal pattern in numbers: a winter decrease, relatively stable numbers in late summer, and an autumn peak. Breeding started in late April or early May and ended in late September; no winter breeding was observed. Three or four litters were produced, and the last litter(s) of the season greatly contributed to the autumn increase. The output of young per reproductive female throughout the year was negatively correlated with spring density, and autumn peak density with the number of females in August. Also overwinter success and weight changes appeared to be associated with population density (and weather). Survival rates did not vary much between years and seasons and were consistently rather high. Autumn survival of juveniles was positively correlated with mean minimum temperatures. Juvenile survival was, at least at times, negatively affected by the presence of adult males. Trapping outside the main grid did not indicate any marked dispersal, though some immigration to the grid must have occurred, especially in spring and early summer. Among the factors governing the population density and dynamics of wood mouse at Vík we emphasize the absence of interspecific competition and predation, the rich and dependable food resources (mainly Angelica seeds), the mild (though moist and windy) climate, the shelter of dense Angelica stands, the abundance of crevices (e.g. nest-sites), and the social interactions. The birch forest in northern Iceland was low productive and the wood mouse population differed from the Vík population by exhibiting low density, short breeding season, and high vagility; characteristics we consider to be representative for most Apodemus populations in Iceland.     

Prediction of reversible IgG1 aggregation occurring in a size exclusion chromatography column is enabled through a model based approach

One important aspect of antibody separation being studied today is aggregation, as this not only leads to a loss in yield, but aggregates can also be hazardous if injected into the body. The aim of this study was to determine whether the methodology applied in the previous study could be used to predict the aggregation of a different batch of IgG1, and to model the aggregation occurring in a SEC column. Aggregation was found to be reversible. The equilibrium parameter was found to be 272 M^‐1 and the reaction kinetic parameter 1.33 × 10^‐5 s^‐1, both within the 95% confidence interval of the results obtained in the previous work. The effective diffusivities were estimated to be 1.45 × 10^‐13 and 1.90 10^‐14 m²/s for the monomers and dimers, respectively. Good agreement was found between the new model and the chromatograms obtained in the SEC experiments. The model was also able to predict the decrease of dimers due to the dilution and separation in the SEC column during long retention times.     

Polymorphisms in ABC Transporter Genes and Concentrations of Mercury in Newborns – Evidence from Two Mediterranean Birth Cohorts

Background

The genetic background may influence methylmercury (MeHg) metabolism and neurotoxicity. ATP binding cassette (ABC) transporters actively transport various xenobiotics across biological membranes.

Objective

To investigate the role of ABC polymorphisms as modifiers of prenatal exposure to MeHg.

Methods

The study population consisted of participants (n = 1651) in two birth cohorts, one in Italy and Greece (PHIME) and the other in Spain (INMA). Women were recruited during pregnancy in Italy and Spain, and during the perinatal period in Greece. Total mercury concentrations were measured in cord blood samples by atomic absorption spectrometry. Maternal fish intake during pregnancy was determined from questionnaires. Polymorphisms (n = 5) in the ABC genes ABCA1, ABCB1, ABCC1 and ABCC2 were analysed in both cohorts.

Results

ABCB1 rs2032582, ABCC1 rs11075290, and ABCC2 rs2273697 modified the associations between maternal fish intake and cord blood mercury concentrations. The overall interaction coefficient between rs2032582 and log2-transformed fish intake was negative for carriers of GT (β = −0.29, 95%CI −0.47, −0.12) and TT (β = −0.49, 95%CI −0.71, −0.26) versus GG, meaning that for a doubling in fish intake of the mothers, children with the rs2032582 GG genotype accumulated 35% more mercury than children with TT. For rs11075290, the interaction coefficient was negative for carriers of TC (β = −0.12, 95%CI −0.33, 0.09), and TT (β = −0.28, 95%CI −0.51, −0.06) versus CC. For rs2273697, the interaction coefficient was positive when combining GA+AA (β = 0.16, 95%CI 0.01, 0.32) versus GG.

Conclusion

The ABC transporters appear to play a role in accumulation of MeHg during early development.     

Influence of sexual intercourse on genital tract microbiota in infertile couples

Several studies have suggested the association of disturbed genital tract microbiota with infertility. Our aim was to clarify the influence of sexual intercourse on partner’s genital tract microbiota in infertile couples. Seventeen couples were studied, and in 5 men inflammatory prostatitis (IP) was diagnosed. Semen samples were collected during menstruation of the female counterpart, two self-collected vaginal samples were taken 3–5 days later – before intercourse and 8–12 h after intercourse. Ureaplasma parvum was found in 59% of women, its prevalence was higher in women whose partner had IP, as well as in half of their male partners. Sexual intercourse caused significant shifts in vaginal microbiota – increase of Nugent score and shifts in cultured microbiota (emergence and disappearance of several species). These changes were less expressed in the presence of normal vaginal microbiota but more prominent in the partners of IP men. These changes may interfere with fertilization.