8-oxoguanine in a quadruplex of the human telomere DNA sequence

8-Oxoguanine is a ubiquitous oxidative base lesion. We report here on the effect of this lesion on the structure and stability of quadruplexes formed by the human telomeric DNA sequence 5'-dG(3)(TTAG(3))(3) in NaCl and KCl. CD, PAGE and absorption-based thermodynamic stability data showed that replacement of any of the tetrad-forming guanines by 8-oxoguanine did not hinder the formation of monomolecular, antiparallel quadruplexes in NaCl. The modified quadruplexes were, however, destabilized in both salts, the extent of this depending on the position of the lesion. These results and the results of previous studies on guanine-to-adenine exchanges and guanine abasic lesions in the same quadruplex show a noticeable trend: it is not the type of the lesion but the position of the modification that determines the effect on the conformation and stability of the quadruplex. The type of lesion only governs the extent of changes, such as of destabilization. Most sensitive sites were found in the middle tetrad of the three-tetrad quadruplex, and the smallest alterations were observed if guanines of the terminal tetrad with the diagonal TTA loop were substituted, although even these substitutions brought about unfavorable enthalpic changes. Interestingly, the majority of these base-modified quadruplexes did not adopt the rearranged folding induced in the unmodified dG(3)(TTAG(3))(3) by potassium ions, an observation that could imply biological relevance of the results.     

Antimicrobial peptides from marine invertebrates: challenges and perspectives in marine antimicrobial peptide discovery

The emergence of pathogenic bacteria resistance to conventional antibiotics calls for an increased focus on the purification and characterization of antimicrobials with new mechanisms of actions. Antimicrobial peptides are promising candidates, because their initial interaction with microbes is through binding to lipids. The interference with such a fundamental cell structure is assumed to hamper resistance development. In the present review we discuss antimicrobial peptides isolated from marine invertebrates, emphasizing the isolation and activity of these natural antibiotics. The marine environment is relatively poorly explored in terms of potential pharmaceuticals, and it contains a tremendous species diversity which evolved in close proximity to microorganisms. As invertebrates rely purely on innate immunity, including antimicrobial peptides, to combat infectious agents, it is believed that immune effectors from these animals are efficient and rapid inhibitors of microbial growth.     

Hawthorn special extract WS? 1442 increases red blood cell NO-formation without altering red blood cell deformability

WS(?) 1442 is a special extract of hawthorn leaves with flowers used for the treatment of mild cardiac failure. The activation of endothelial nitric oxide synthase (eNOS) has been shown to contribute to its vasodilating properties. Quite recently it has been demonstrated that red blood cells (RBCs) express a functional NO-synthase (rbcNOS) and rbcNOS activation has been associated with increased RBC deformability. The aim of the present study was to determine whether WS(?) 1442 is able to activate rbcNOS, to induce NO-formation in RBC and to alter RBC-deformability. Blood from healthy volunteers was incubated with WS(?) 1442 (25-100 μg/ml) for up to 30 min. RbcNOS activation was detected by immunohistochemical staining of phosphorylated rbcNOS and NO-formation was examined by diaminofluorescein (DAF) fluorescence. RBC deformability was measured by a laser assisted optical rotational cell analyzer. Serine 1177 of RbcNOS (rbcNOS Ser(1177)) was time- and concentration-dependently phosphorylated by WS(?) 1442. Rates of rbcNOS Ser(1177) phosphorylation were up to 149% higher in RBCs treated with WS(?) 1442 in comparison to control (DMSO 0.05%). WS(?) 1442 induced a time-dependent increase in NO-formation in RBCs which reached its maximum after 5 min. An increase in shear stress (0.3-50 Pa) caused an increase in RBC deformability. WS(?) 1442 did not change either basal or maximal RBC-deformability or shear stress sensitivity of RBC at normoxia. CONCLUSION: WS(?) 1442 activates rbcNOS and causes NO-formation in RBCs. WS(?) 1442-dependent NO-formation however does not affect RBC-deformability at normoxia.     

Immunohistochemical expression analysis of Cx43, Cx26, c-KIT and PlAP in contralateral testis biopsies of patients with non-seminomatous testicular germ cell tumor

Non seminomatous testicular germ cell tumors (NSTGCTs) express fetal stem cell markers and display dysregulation of connexin 43 expression. Persistence of fetal spermatogonial characteristics was implicated in the emergence of testicular germ cell tumors. The objective of this study was to analyze the tubular architecture in contralateral testes of patients with NSTGCT. We studied morphologic alterations, expression patterns of markers for the integrity of the germinal epithelium (gap junction proteins connexin 43 and 26), as well as of the embryonic markers c-KIT and placental alkaline phosphatase (PlAP), both established markers to detect carcinoma in situ (CIS). In all samples, tubules showing maturation of germ cells up to spermatozoa were observed. In addition, tubules with alterations in tubular architecture and with impaired spermatogenesis occurred. In tubules showing aberrant spermatogenesis, connexin 43 (Cx43) signal was down-regulated and a shift of signal from gap junctions to the cytoplasm occurred. Concomitantly, Cx26 was found highly up-regulated in tubules with incomplete and aberrant germ cell maturation. All testes exhibited single spermatogonia with positive reaction for c-KIT and a significant positive correlation was found between the mean number of c-KIT positive spermatogonia per tubule and the percentage of tubules presenting severely impaired spermatogenesis. Our data show alterations of the normal architecture of the germinal epithelium and disturbances of spermatogenesis in the contralateral testes of patients with NSTGCT in all cases evaluated. The concomitant occurrence of c-KIT positive spermatogonia and defects in tubular architecture is in line with the hypothesis that patients with NSTGCT suffer from disturbed germ cell development.     

Statistical epistasis and functional brain imaging support a role of voltage-gated potassium channels in human memory

Despite the current progress in high-throughput, dense genome scans, a major portion of complex traits' heritability still remains unexplained, a phenomenon commonly termed "missing heritability." The negligence of analytical approaches accounting for gene-gene interaction effects, such as statistical epistasis, is probably central to this phenomenon. Here we performed a comprehensive two-way SNP interaction analysis of human episodic memory, which is a heritable complex trait, and focused on 120 genes known to show differential, memory-related expression patterns in rat hippocampus. Functional magnetic resonance imaging was also used to capture genotype-dependent differences in memory-related brain activity. A significant, episodic memory-related interaction between two markers located in potassium channel genes (KCNB2 and KCNH5) was observed (P(nominal combined)=0.000001). The epistatic interaction was robust, as it was significant in a screening (P(nominal)=0.0000012) and in a replication sample (P(nominal)=0.01). Finally, we found genotype-dependent activity differences in the parahippocampal gyrus (P(nominal)=0.001) supporting the behavioral genetics finding. Our results demonstrate the importance of analytical approaches that go beyond single marker statistics of complex traits.     

Dissecting the within-Africa ancestry of populations of African descent in the Americas

Background

The ancestry of African-descended Americans is known to be drawn from three distinct populations: African, European, and Native American. While many studies consider this continental admixture, few account for the genetically distinct sources of ancestry within Africa – the continent with the highest genetic variation. Here, we dissect the within-Africa genetic ancestry of various populations of the Americas self-identified as having primarily African ancestry using uniparentally inherited mitochondrial DNA.

Methods and Principal Findings

We first confirmed that our results obtained using uniparentally-derived group admixture estimates are correlated with the average autosomal-derived individual admixture estimates (hence are relevant to genomic ancestry) by assessing continental admixture using both types of markers (mtDNA and Y-chromosome vs. ancestry informative markers). We then focused on the within-Africa maternal ancestry, mining our comprehensive database of published mtDNA variation (∼5800 individuals from 143 African populations) that helped us thoroughly dissect the African mtDNA pool. Using this well-defined African mtDNA variation, we quantified the relative contributions of maternal genetic ancestry from multiple W/WC/SW/SE (West to South East) African populations to the different pools of today''s African-descended Americans of North and South America and the Caribbean.

Conclusions

Our analysis revealed that both continental admixture and within-Africa admixture may be critical to achieving an adequate understanding of the ancestry of African-descended Americans. While continental ancestry reflects gender-specific admixture processes influenced by different socio-historical practices in the Americas, the within-Africa maternal ancestry reflects the diverse colonial histories of the slave trade. We have confirmed that there is a genetic thread connecting Africa and the Americas, where each colonial system supplied their colonies in the Americas with slaves from African colonies they controlled or that were available for them at the time. This historical connection is reflected in different relative contributions from populations of W/WC/SW/SE Africa to geographically distinct Africa-derived populations of the Americas, adding to the complexity of genomic ancestry in groups ostensibly united by the same demographic label.     

The influence of resistance training on patients with metabolic syndrome--significance of changes in muscle fiber size and muscle fiber distribution

People who are afflicted with "metabolic syndrome" exhibit multiple coronary disease risk factors such as insulin resistance, hypertension, hyperlipidemia, or obesity. Twenty-six volunteers (13 women and 13 men) with such disease risk factors (56 ± 5 years) participated in a 14-week resistance training program. Given the fact that resistance training may improve cardiometabolic parameters, the fasting total cholesterol, low-density lipoprotein (LDL), high-density lipoprotein (HDL), triglycerides, insulin, glucose value, homeostatic model assessment (HOMA) index, and blood pressure and body mass index (BMI) were measured before and after the training intervention. In addition, muscle biopsies from the vastus lateralis muscle of 11 of the men and 5 of the women were analyzed to determine whether changes in the muscle morphology influence the cardiometabolic parameters. Resistance training resulted in a significant increase in fasting HDL for the entire group (from 44.35 ± 9.43 to 48.57 ± 10.96 mg·dl(-1), p = 0.016). No other blood parameter changed significantly. No change was observed in the HOMA index, blood pressure, or BMI. The muscle fiber type distribution did not change, but a significant hypertrophy of muscle fibers was evident (an increase of the ellipse minor axis of 67.3 ± 16.6 to 72.1 ± 12.3 μm, p = 0.004). Moderate intensity resistance training, as was performed in our study, induces hypertrophic impulses but does not seem to have a clear positive influence on cardiometabolic risk factors. However, 2 sessions of moderate intensity resistance training per week can enhance the fasting HDL cholesterol in middle-aged subjects.