Identification of the role of a cysteine-rich region of PC6B by determining the enzymatic characteristics of its mutants

In the proprotein convertases family, mouse PC6B (mPC6B) has a very large cysteine-rich region (CRR), consisting of 22 tandem cysteine-rich (Cys-rich) repeated segments. The role of this region remains elusive. In this report, to get insight on the possible role of the CRR, we constructed four truncated mPC6B mutant genes with 0, 5, 11, and 22 Cys-rich repeated segments remaining; using the baculovirus-expression system and a simple purification method, we obtained four enzyme mutants of mPC6B. By determining their optimal pH and calcium ion concentration for enzymatic activity and their thermal stability, we found that CRR did not affect pH optimum and Ca²⁺ optimum compared with the p-domain. However, CRR acted as a stabilizing domain in addition to the p-domain. By kinetic analyses of four mutants, we found that the long Cys-rich repeats in the native form of mPC6B reduced its V _max. These facts suggest that CRR acts as an important part of functional domain.     

Expression of connexin 43 mRNA in microisolated murine osteoclasts and regulation of bone resorption in vitro by gap junction inhibitors

Several studies have demonstrated that connexin 43 (Cx43) mediates signals important for osteoblast function and osteogenesis. The role of gap junctional communication in bone resorption is less clear. We have investigated the expression of Cx43 mRNA in osteoclasts and bone resorption cultures and furthermore, the functional importance of gap junctional communication in bone resorption. RT-PCR analysis demonstrated Cx43 mRNA expression in mouse bone marrow cultures and in osteoclasts microisolated from the marrow cultures. Cx43 mRNA was also expressed in bone resorption cultures with osteoclasts and osteoblasts/stromal cells incubated for 48h on devitalized bone slices. An up-regulation of Cx43 mRNA was detected in parathyroid (PTH)-stimulated (0.1 nM) bone resorption. Two inhibitors of gap junction communication, 18alpha-glycyrrhetinic acid (30 microM) and oleamide (100 microM), significantly inhibited PTH- and 1,25-(OH)(2)D(3)-stimulated osteoclastic pit formation. In conclusion, our data indicate a functional role for gap junction communication in bone resorption.     

Coeliac disease patients carry conserved HLA-DR3-DQ2 haplotypes revealed by association of TNF alleles

Certain HLA-DQ alleles are known to contribute to predisposition to coeliac disease (CD). The existence of additional independent risk-modifying loci in the HLA complex is still being debated. The DR3-DQ2 haplotype has been studied most, but the evidence is conflicting. The discrepancies may stem from the absence of such an effect, insufficient statistical power to detect an effect (i.e. small studies) and/or incomplete control of linkage disequilibrium (LD) to the neighbouring DQ-loci, known to elicit a strong effect. In the present study, we aimed to undertake a statistically high-powered family-based analysis, fully controlling effects of LD between the major DQ-risk haplotypes and neighbouring candidate loci. We investigated five markers on DR3-DQ2, DR5-DQ7 and DR7-DQ2 haplotypes in 327 Norwegian and Swedish families. Our primary finding was that TNF-308A (TNF2) was significantly associated on the DR3-DQ2 haplotype [stratum specific odds ratio (OR)=2.40 (1.25–4.48), Pc=0.009, where P_c=Pn and n=number of tests performed]. Furthermore, we confirmed earlier indications that LD between TNF2 and DQA1*05-DQB1*02 on the DR3 haplotype is more strongly maintained in family-based cases than family-based controls. In conclusion, we confirmed in this study, the largest of its kind, that additional CD risk factors independent of DQ2 alleles do exist on the DR3 haplotype.     

Application and interpretation of transmission/disequilibrium tests: transmission of HLA-DQ haplotypes to unaffected siblings in 526 families with type 1 diabetes

It is widely believed that, if a genetic marker shows a transmission distortion in patients by the transmission/disequilibrium test (TDT), then a transmission distortion in healthy siblings would be seen in the opposite direction. This is also the case in a complex disease. Furthermore, it has been suggested that replacing the McNemar statistics of the TDT with a test of heterogeneity between transmissions to affected and unaffected children could increase the power to detect disease association. To test these two hypotheses empirically, we analyzed the transmission of HLA-DQA1-DQB1 haplotypes in 526 Norwegian families with type 1 diabetic children and healthy siblings, since some DQA1-DQB1 haplotypes represent major genetic risk factors for type 1 diabetes. Despite the strong positive and negative disease associations with particular DQ haplotypes, we observed no significant deviation from 50% for transmission to healthy siblings. This could be explained by the low penetrance of susceptibility alleles, together with the fact that IDDM loci also harbor strongly protective alleles that can override the risk contributed by other loci. Our results suggest that, in genetically complex diseases, detectable distortion in transmission to healthy siblings should not be expected. Furthermore, the original TDT seems more powerful than a heterogeneity test.     

The Mediating Role of Resilience in the Relationship between Big Five Personality and Anxiety among Chinese Medical Students: A Cross-Sectional Study

Backgrounds

The psychological distress of medical students is a major concern of public health worldwide. However, few studies have been conducted to evaluate anxiety symptoms of medical students in China. The purpose of this study was to investigate the anxiety symptoms among Chinese medical students, to examine the relationships between big five personality traits and anxiety symptoms among medical students, and to explore the mediating role of resilience in these relationships.

Methods

This multicenter cross-sectional study was conducted in June 2014. Self-reported questionnaires consisting of the Zung Self-Rating Anxiety Scale (SAS), Big Five Inventory (BFI), Wagnild and Young Resilience Scale (RS-14) and demographic section were distributed to the subjects. A stratified random cluster sampling method was used to select 2925 medical students (effective response rate: 83.57%) at four medical colleges and universities in Liaoning province, China. Asymptotic and resampling strategies were used to explore the mediating role of resilience.

Results

The prevalence of anxiety symptoms was 47.3% (SAS index score≥50) among Chinese medical students. After adjusting for the demographic factors, the traits of agreeableness, conscientiousness and openness were all negatively associated with anxiety whereas neuroticism was positively associated with it. Resilience functioned as a mediator in the relationships between agreeableness/conscientiousness/openness and anxiety symptoms.

Conclusions

Among Chinese medical students, the prevalence of anxiety symptoms was high and resilience mediated the relationships between big five personality traits and anxiety symptoms. Identifying at-risk individuals and undertaking appropriate intervention strategies that focus on both personality traits and resilience might be more effective to prevent and reduce anxiety symptoms.