PIWI-interacting small RNAs: the vanguard of genome defence

PIWI-interacting RNAs (piRNAs) are a distinct class of small non-coding RNAs that form the piRNA-induced silencing complex (piRISC) in the germ line of many animal species. The piRISC protects the integrity of the genome from invasion by 'genomic parasites'--transposable elements--by silencing them. Owing to their limited expression in gonads and their sequence diversity, piRNAs have been the most mysterious class of small non-coding RNAs regulating RNA silencing. Now, much progress is being made into our understanding of their biogenesis and molecular functions, including the specific subcellular compartmentalization of the piRNA pathway in granular cytoplasmic bodies.     

Extent of height variability explained by known height-associated genetic variants in an isolated population of the Adriatic coast of Croatia

Background

Human height is a classical example of a polygenic quantitative trait. Recent large-scale genome-wide association studies (GWAS) have identified more than 200 height-associated loci, though these variants explain only 2∼10% of overall variability of normal height. The objective of this study was to investigate the variance explained by these loci in a relatively isolated population of European descent with limited admixture and homogeneous genetic background from the Adriatic coast of Croatia.

Methodology/Principal Findings

In a sample of 1304 individuals from the island population of Hvar, Croatia, we performed genome-wide SNP typing and assessed the variance explained by genetic scores constructed from different panels of height-associated SNPs extracted from five published studies. The combined information of the 180 SNPs reported by Lango Allen el al. explained 7.94% of phenotypic variation in our sample. Genetic scores based on 20∼50 SNPs reported by the remaining individual GWA studies explained 3∼5% of height variance. These percentages of variance explained were within ranges comparable to the original studies and heterogeneity tests did not detect significant differences in effect size estimates between our study and the original reports, if the estimates were obtained from populations of European descent.

Conclusions/Significance

We have evaluated the portability of height-associated loci and the overall fitting of estimated effect sizes reported in large cohorts to an isolated population. We found proportions of explained height variability were comparable to multiple reference GWAS in cohorts of European descent. These results indicate similar genetic architecture and comparable effect sizes of height loci among populations of European descent.     

Probabilistic kinetic model of slow oxidation of low-density lipoprotein: II. Experiments

Theoretical probabilistic kinetic model has been applied to describe the measurements of several oxidation markers as a function of time, during slow oxidation of low-density lipoprotein (LDL). It has been demonstrated that such a process could be described as tocopherol-mediated peroxidation (TMP), initiated and sustained by the action of copper ions, present in LDL in trace amounts. In that process concentration of alpha-tocopherol remains essentially unaltered. Tocopherol and copper ions act as catalysts, oscillating between the oxidized and reduced states. The fitting of the theoretical model to the experimental data resulted in determination of the numerical values for the kinetic parameters. It has been found that the parameter values used for the fitting of the data collected for a number of samples from various donors differ rather little. The kinetic chain length of 1.3 (in presence of co-antioxidants) and 2.9 (in the absence of co-antioxidants) is shorter than found by others. The difference probably comes from the much lower concentration of copper ions in our systems (about 0.1 ion per LDL particle).     

Distribution of Chlamydia trachomatis Serotypes in Clinical Urogenital Samples from North-Eastern Croatia

The purpose of this study was to determine prevalence of Chlamydia trachomatis (Ct) urogenital infection and its serotype distribution from clinical samples in north-eastern Croatia. During a 3-year period, 2,379 urogenital samples were analyzed by real-time polymerase chain reaction (A group), while 4,846 genital swabs were analyzed by direct fluorescent antibody test (B group). 132 Ct positive specimens were genotyped by omp1 gene sequencing. The prevalence rate of Ct was 3.2 % in A and 1 % in B group. The most prevalent chlamydial genotype was E (44 %), followed by F (33 %), K (11.5 %), G (8 %), J/UW (5.3 %), D-IC (4.4 %), D-B120 (1.8 %), and B/IU, J/IU, Ia/IU (0.9 % each) serotypes. Single-nucleotide polymorphisms (SNPs) of omp1 gene were detected in E, K, and G serotypes. Some of these SNPs (C/T at position 272 and G/A at position 813 in E strain; C/T at position 884 in D strain) might represent novel omp1 variants.     

Effectiveness of mowing for the flora diversity preservation: a case study of steppe-like grassland in Croatia (NATURA 2000 site)

Intensive human activities have resulted in a critical reduction of grasslands in Croatia, one of the richest Europian countries in terms of biodiversity. Sub-Pannonic steppic grasslands are very rare, only few occur in the continental part of Croatia and most of them are protected as NATURA 2000 sites. We studied vascular flora of the Sub-Pannonic stepic grassland with the aim to examine the changes in plant communities 15 years from the mowing application. Results showed that hand mowing once per year at the end of vegetation season increased the species diversity as well as the number of medium and low growth taxa. The critically endangered, nearly threatened and vulnerable species remained preserved. The occurrence of trees, shrubs and invasive species as a consequence of succession and anthropogenic influences could be important threat for steppe-like grassland flora. From a conservation point of view infrequent mowing regime could be an effective management tool, although it needs to be adapted to regional and local circumstances for maintaining high biodiversity of steppe-like grasslands and valuable plant species.     

Biochemical and biological properties of 5-bromotubercidin: differential effects on cellular DNA-directed and viral RNA-directed RNA synthesis

We have studied the biochemical and biological properties of 5-bromotubercidin (4-amino-5-bromo-7-beta-d-ribofuranosyl-pyrrolo [2,3-d]pyrimidine) (BrTu), a synthetic analogue of the highly cytotoxic pyrrolo[2,3-d]pyrimidine ribonucleoside antibiotic tubercidin (Tu) that interferes with numerous cellular processes, and has been shown to possess biological specificity and selectivity. Thus, BrTu entered the mammalian cell nucleotide pool by phosphorylation, was incorporated into RNA in an unmodified form and, as a consequence, reversibly inhibited (15 microM) mammalian cell growth and the synthesis of high-molecular-weight cellular RNA species (i.e., mRNA and rRNA). However, BrTu (300 microM) did not inhibit picornavirus RNA synthesis or multiplication, and thus discriminated between virus RNA-dependent and all forms of DNA-dependent RNA synthesis whether of cellular or viral origin; because of this BrTu should prove valuable as a metabolic probe for studying the cell-virus relationship. Furthermore, BrTu is a substrate for adenosine kinase (K(m)=24 microM), and is also its potent inhibitor (K(i)=0.93 microM); thus, low concentrations of BrTu (1.5 microM), which did not inhibit cell growth, blocked phosphorylation and the cellular uptake of other, highly cytotoxic pyrrolo-pyrimidine nucleoside analogues (e.g., tubercidin). This block in cellular uptake and incorporation of toxic analogues was associated with the protective effect of BrTu against cell killing by the analogues, providing a mechanism by which BrTu and these analogues can, as we reported elsewhere [J. Virol.1999, 73, 6444], be used for the selective inactivation of replicating picornaviruses.     

Comparative study of antioxidant capacity in organs of different Allium species

Cultivated and wild Allium species were investigated in order to compare the antioxidant capacity of their leaves and bulbs. Leaf and bulb anti-oxidative enzymes and scavenger activities, along with quantities of non-enzymic antioxidants, malonyl-dialdehyde and OH radicals were determined. Results obtained suggest that leaves possess higher anti-oxidant and scavenging activities than bulbs in the majority of cultivated and wild Allium species examined. Cultivation of some wild species such as A. flavum L., A. schoenoprasum L. and A. ursinum L. could be conducted in the future in order to produce Allium species with high antioxidant capacity in leaves and bulbs.     

Epilepsy in the elderly and depression

Epilepsy is one of the most common neurological problems affecting approximately 1% of the world's population with higher incidence among elderly individuals. Although depression is a common comorbid condition in patients with epilepsy, there is a paucity of information regarding depression in geriatric patients with epilepsy. This study analysed a group of 83 patients affected by different epilepsy phenotypes accompanied by mental disorders, especially depression. Antiepileptic and antipsychotic drug treatment has been evaluated, particularly a positive effect of the new antiepileptics (monotherapy and polytherapy) both on the reduction of seizures and mental disorders.     

The effects of the perinatal treatment with 5-hydroxytryptophan or tranylcypromine on the peripheral and central serotonin homeostasis in adult rats

Serotonin (5HT) is a biologically active amine present in mammals in the brain and the peripheral tissues. Autism is a neurodevelopmental disorder in which 5HT homeostasis is disturbed both centrally and peripherally, but the relationship between the 5HT disturbances in the two compartments is not understood. In an attempt to explore the relationship between the disturbed peripheral 5HT homeostasis and central 5HT functioning, we exposed the developing rat brain to increased 5HT concentrations, by treatment of rats with subcutaneous injections of the immediate 5HT precursor 5-hydroxy-l-tryptophan (5HTP, 25 mg/kg), or the non-selective MAO inhibitor tranylcypromine (TCP, 2 mg/kg), during the period of the most intensive development of 5HT neurons - from gestational day 13 to post-natal day 21. The effects of the mentioned treatments on peripheral and central 5HT levels were then studied in adult rats. Platelet and plasma 5HT concentrations (measured by ELISA), as well as cortical and midbrain 5HT, tryptophan and 5-hydroxyindoleacetic acid levels (measured by HPLC) were determined in twelve 5HTP treated and eight TCP treated rats, and compared with the values measured in 10 control, saline treated rats. Treatment with 5HTP significantly raised peripheral but not central 5HT concentrations. At adult age, peripheral 5HT homeostasis was re-established, while modest decrease in 5HT concentration was observed in frontal cortex, presumably due to hyperserotonemia-induced loss of 5HT terminals during brain development. Treatment with TCP induced significant 5HT elevations in both compartments. At adult age, permanent changes in 5HT homeostasis were observed, both peripherally (as hyperserotonemia) and centrally (as altered 5HT metabolism with decreased 5HT concentrations). Further studies are planned in order to explore the nature of the different disturbances of 5HT homeostasis induced by the two compounds, and their results are expected to shed some light on the role of hyperserotonemia in autism.