Biosynthesis of collagen

During the biosynthesis and assembly of collagen structures, disulfide links can serve several functions. During biosynthesis they successively stabilize intra-peptide folding and associations of three chains into one molecule. Studies on the refolding and reassociation of reduced and denatured carboxyl propeptides of procollagen I showed that successive interactions of folding and assembly are successively weaker. Disulfide bridges were reestablished within correctly refolded carboxyl propeptides. Rearrangements of disulfide bridges may occur during the processing of type V procollagen molecules as these collagens become incorporated into extracellular matrix. The basement membrane procollagen IV molecules become disulfide linked at each end into networks, and there are indications that further rearrangements of disulfide links may allow additional modulation.     

Genetic Polymorphisms in Vitamin D Metabolism and Signaling Genes and Risk of Breast Cancer: A Nested Case-Control Study

Genetic polymorphisms in vitamin D metabolism and signaling genes have been inconsistently associated with risk of breast cancer, though few studies have examined SNPs in vitamin D-related genes other than the vitamin D receptor (VDR) gene and particularly have not examined the association with the retinoid X receptor alpha (RXRA) gene which may be a key vitamin D pathway gene. We conducted a nested case-control study of 734 cases and 1435 individually matched controls from a population-based prospective cohort study, the Northern Sweden Mammary Screening Cohort. Tag and functional SNPs were genotyped for the VDR, cytochrome p450 24A1 (CYP24A1), and RXRA genes. We also genotyped specific SNPs in four other genes related to vitamin D metabolism and signaling (GC/VDBP, CYP2R1, DHCR7, and CYP27B1). SNPs in the CYP2R1, DHCR7, and VDBP gene regions that were associated with circulating 25(OH)D concentration in GWAS were also associated with plasma 25(OH)D in our study (p-trend <0.005). After taking into account the false discovery rate, these SNPs were not significantly associated with breast cancer risk, nor were any of the other SNPs or haplotypes in VDR, RXRA, and CYP24A1. We observed no statistically significant associations between polymorphisms or haplotypes in key vitamin D-related genes and risk of breast cancer. These results, combined with the observation in this cohort and most other prospective studies of no association of circulating 25(OH)D with breast cancer risk, do not support an association between vitamin D and breast cancer risk.     

Stability of the Associations between Early Life Risk Indicators and Adolescent Overweight over the Evolving Obesity Epidemic

Background

Pre- and perinatal factors and preschool body size may help identify children developing overweight, but these factors might have changed during the development of the obesity epidemic.

Objective

We aimed to assess the associations between early life risk indicators and overweight at the age of 9 and 15 years at different stages of the obesity epidemic.

Methods

We used two population-based Northern Finland Birth Cohorts including 4111 children born in 1966 (NFBC1966) and 5414 children born in 1985–1986 (NFBC1986). In both cohorts, we used the same a priori defined prenatal factors, maternal body mass index (BMI), birth weight, infant weight (age 5 months and 1 year), and preschool BMI (age 2–5 years). We used internal references in early childhood to define percentiles of body size (<50, 50–75, 75–90 and >90) and generalized linear models to study the association with overweight, according to the International Obesity Taskforce (IOTF) definitions, at the ages of 9 and 15 years.

Results

The prevalence of overweight at the age of 15 was 9% for children born in 1966 and 16% for children born in 1986. However, medians of infant weight and preschool BMI changed little between the cohorts, and we found similar associations between maternal BMI, infant weight, preschool BMI, and later overweight in the two cohorts. At 5 years, children above the 90^th percentile had approximately a 12 times higher risk of being overweight at the age of 15 years compared to children below the 50^th percentile in both cohorts.

Conclusions

The associations between early body size and adolescent overweight showed remarkable stability, despite the increase in prevalence of overweight over the 20 years between the cohorts. Using consequently defined internal percentiles may be a valuable tool in clinical practice.     

Lep d 2 polymorphisms in wild and cultured Lepidoglyphus destructor mites.

We have previously cloned, expressed and characterized two variants of the major allergen Lep d 2 from cultured Lepidoglyphus destructor mites. These variants, Lep d 2.0101 and Lep d 2.0201, differ at 13 amino acid positions. In this study we investigated Lep d 2 sequence diversity between wild and cultured mites. PCR, Southern blot and DNA sequence analysis revealed the presence of two different Lep d 2 genes, one with and one without an intron. In addition, two new variants of Lep d 2, Lep d 2.0102 and Lep d 2.0202, were found at different frequencies in wild and cultured mites. When we expressed the Lep d 2 variants and compared their IgE binding properties by ELISA inhibition, we found that Lep d 2.0102 was a more potent inhibitor than Lep d 2.0101, and to a lesser extent Lep d 2.0202 was more potent than Lep d 2.0201. Long-term cultures of peripheral blood mononuclear cells were used to assess the ability of the expressed Lep d 2 variants to induce cytokine release. Although cells from different individuals released different amounts of interferon-gamma and interleukin-5, no consistent cytokine release pattern could be linked to any specific Lep d 2 variant. In conclusion, we show that both cultured and wild Lepidoglyphus destructor mites contain the same pattern of polymorphism. Furthermore, this Lep d 2 sequence diversity seems not to have any significant impact on the allergens IgE binding or its ability to induce T cell cytokine release.     

Visco-elastic membrane tethers extracted from Escherichia coli by optical tweezers

Tethers were created between a living Escherichia coli bacterium and a bead by unspecifically attaching the bead to the outer membrane and pulling it away using optical tweezers. Upon release, the bead returned to the bacterium, thus showing the existence of an elastic tether between the bead and the bacterium. These tethers can be tens of microns long, several times the bacterial length. Using mutants expressing different parts of the outer membrane structure, we have shown that an intact core lipopolysaccharide is a necessary condition for tether formation, regardless of whether the beads were uncoated polystyrene or beads coated with lectin. A physical characterization of the tethers has been performed yielding visco-elastic tether force-extension relationships: for first pull tethers, a spring constant of 10-12 pN/μm describes the tether visco-elasticity, for subsequent pulls the spring constant decreases to 6-7 pN/μm, and typical relaxation timescales of hundreds of seconds are observed. Studies of tether stability in the presence of proteases, lipases, and amylases lead us to propose that the extracted tether is primarily composed of the asymmetric lipopolysaccharide containing bilayer of the outer membrane. This unspecific tethered attachment mechanism could be important in the initiation of bacterial adhesion.     

Positron Emission Tomography and Magnetic Resonance Imaging of the Brain in Fabry Disease: A Nationwide,Long-Time,Prospective Follow-Up

Background

Fabry disease is a rare metabolic glycosphingolipid storage disease caused by deficiency of the lysosomal enzyme α-galactosidase A—leading to cellular accumulation of globotriasylceramide in different organs, vessels, tissues, and nerves. The disease is associated with an increased risk of cerebrovascular disease at a young age in addition to heart and kidney failure.

Objective

The objective of this study was to assess brain function and structure in the Danish cohort of patients with Fabry disease in a prospective way using 18-fluoro-deoxyglucose (F-18 FDG) positron emission tomography (PET) and magnetic resonance imaging (MRI).

Patients

Forty patients with Fabry disease (14 males, 26 females, age at inclusion: 10–66 years, median: 39 years) underwent a brain F-18-FDG-PET-scan at inclusion, and 31 patients were followed with FDG-PET biannually for up to seven years. All patients (except one) had a brain MRI-scan at inclusion, and 34 patients were followed with MRI biannually for up to nine years.

Image Analysis

The FDG-PET-images were inspected visually and analysed using a quantitative 3-dimensional stereotactic surface projection analysis (Neurostat). MRI images were also inspected visually and severity of white matter lesions (WMLs) was graded using a visual rating scale.

Results

In 28 patients brain-FDG-PET was normal; in 23 of these 28 patients brain MRI was normal—of the remaining five patients in this group, four patients had WMLs and one patient never had an MRI-scan. In 10 patients hypometabolic areas were observed on brain-FDG-PET; all of these patients had cerebral infarcts/hemorrhages visualized on MRI corresponding to the main hypometabolic areas. In two patients brain-FDG-PET was ambiguous, while MRI was normal in one and abnormal in the other.

Conclusion

Our data indicated that, in patients with Fabry disease, MRI is the preferable clinical modality—if applicable—when monitoring cerebral status, as no additional major brain-pathology was detected with FDG-PET.     

Science in drug control: the alkaloid content of afghan opium

Opium samples from Afghanistan were analyzed by HPLC for their content of morphine and three further alkaloids (codeine, thebaine, and papaverine). To our knowledge, this is the largest set of authentic opium samples analyzed in one study until now. The purpose was to assess possible correlations between samples and selected external factors, such as region of origin within Afghanistan, year of harvest, or intra-batch variation. In the investigated samples, a trend towards higher morphine concentrations in opium from the North-Eastern parts of Afghanistan was observed in the period from 2003 to 2005. More than 75% of the samples contained above 10% of morphine, the overall average was 14.4%.