Cytogeography of the Phleum pratense group (Poaceae) in the Carpathians and Pannonia

Cytogeographical variability within the Phleum pratense group in the Carpathians and adjacent part of Pannonian lowland, based on 132 populations analysed by flow cytometry, is described. Only diploid and hexaploid plants were detected among 635 samples from the studied area. Diploids were found to be less frequent (127 plants, 20%) than hexaploids (508, 80%). With the exception of the single pure diploid population, diploids always co-occured with hexaploids (30 localities, 22.7%). The majority of populations (101, 76.5%) consisted of hexaploid plants. Most mixed populations occur in the Western Carpathians (26). In the Eastern Carpathians, mixed populations are much rarer, with three populations in Ukraine and one in Romania. In the Southern Carpathians, only hexaploids occur. The conventional taxonomic concept of the two species, diploid P. bertolonii and hexaploid P. pratense , was followed in spite of their sympatric occurence. Distribution maps based on chromosome number data from previous studies and on ploidy level estimates are given for both species in the studied area. The pattern of different distribution of the two taxa within the Carpathians is discussed.  © 2008 The Linnean Society of London, Botanical Journal of the Linnean Society , 2008, 157 , 475–485.     

Cytoplasmic Structures Associated with an Arbovirus Infection: Loci of Viral Ribonucleic Acid Synthesis

Unique cytoplasmic structures, herein designated as type I cytopathic vacuoles (CPV-I), are found in chick embryo cells early in the logarithmic phase of Semliki Forest virus replication. High resolution autoradiography demonstrated that the CPV-I are loci of (3)H-uridine incorporation. This evidence correlates well with previous biochemical data and electron microscopy of the subcellular fractions active in Semliki Forest virus ribonucleic acid synthesis. Origin of the CPV-I within host cell cytoplasm is confirmed by the distribution of electron-dense tracer particles and sequential ultrastructural observations.     

Effect of Bcl-2 on oxidant-induced cell death and intracellular Ca2+ mobilization

The mechanism by which Bcl-2 inhibits cell death is unknown. Ithas been suggested that Bcl-2 functions as an antioxidant. BecauseBcl-2 is localized mainly to the membranes of the endoplasmic reticulum(ER) and the mitochondria, which represent the main intracellularstorage sites for Ca²⁺, wehypothesized that Bcl-2 might protect cells against oxidant injury byaltering intracellular Ca²⁺homeostasis. To test this hypothesis, we examined the effect of oxidanttreatment on viability in normal rat kidney (NRK) cells and in NRKcells stably transfected with Bcl-2 in the presence or absence ofintracellular Ca²⁺, and wecompared the effect of Bcl-2 expression on oxidant-induced intracellular Ca²⁺ mobilizationand on ER and mitochondrial Ca²⁺pools. NRK cells transfected with Bcl-2 (NRK-Bcl-2) were significantly more resistant toH₂O₂-inducedcytotoxicity than control cells. EGTA-AM, an intracellularCa²⁺ chelator, as well as theabsence of Ca²⁺ in the medium,reducedH₂O₂-inducedcytotoxicity in both cell lines. Compared with controls, cellsoverexpressing Bcl-2 showed a delayed rise in intracellularCa²⁺ concentration([Ca²⁺]_i)afterH₂O₂treatment. After treatment with theCa²⁺ ionophore ionomycin,Bcl-2-transfected cells showed a much quicker decrease after themaximal rise than control cells, suggesting stronger intracellularCa²⁺ buffering, whereas treatmentwith thapsigargin, an inhibitor of the ERCa²⁺-ATPases, transientlyincreased[Ca²⁺]_iin control and in Bcl-2-transfected cells. Estimates of mitochondrial Ca²⁺ stores using an uncoupler ofoxidative phosphorylation show that NRK-Bcl-2 cells have a highercapacity for mitochondrial Ca²⁺storage than control cells. In conclusion, Bcl-2 may prevent oxidant-induced cell death, in part, by increasing the capacity ofmitochondria to store Ca²⁺.

     

Crosstalk between autophagy and DNA repair systems

Autophagy and DNA repair are two essential biological mechanisms that maintain cellular homeostasis. Impairment of these mechanisms was associated with several pathologies such as premature aging, neurodegenerative diseases, and cancer. Intrinsic or extrinsic stress stimuli (e.g., reactive oxygen species or ionizing radiation) cause DNA damage. As a biological stress response, autophagy is activated following insults that threaten DNA integrity. Hence, in collaboration with DNA damage repair and response mechanisms, autophagy contributes to the maintenance of genomic stability and integrity. Yet, connections and interactions between these two systems are not fully understood. In this review article, current status of the associations and crosstalk between autophagy and DNA repair systems is documented and discussed.     

Identifying specific matrix metalloproteinase-2-inhibiting peptides through phage display-based subtractive screening

Gelatinases A and B, which are members of the matrix metalloproteinase (MMP) family, play essential roles in cancer development and metastasis, as they can break down basal membranes. Therefore, the determination and inhibition of gelatinases is essential for cancer treatment. Peptides that can specifically block each gelatinase may, therefore, be useful for cancer treatment. In this study, subtractive panning was carried out using a 12-mer peptide library to identify peptides that block gelatinase A activity (MMP-2), which is a key pharmacological target. Using this method, 17 unique peptide sequences were determined. MMP-2 inhibition by these peptides was evaluated through zymogram analyses, which revealed that four peptides inhibited MMP-2 activity by at least 65%. These four peptides were synthesized and used for in vitro wound healing using human umbilical vein endothelial cells, and two peptides, AOMP12 and AOMP29, were found to inhibit wound healing by 40%. These peptides are, thus, potential candidates for MMP-2 inhibition for cancer treatment. Furthermore, our findings suggest that our substractive biopanning screening method is a suitable strategy for identifying peptides that selectively inhibit MMP-2.     

The properties of bioengineered chondrocyte sheets for cartilage regeneration

Background  

Although the clinical results of autologous chondrocyte implantation for articular cartilage defects have recently improved as a result of advanced techniques based on tissue engineering procedures, problems with cell handling and scaffold imperfections remain to be solved. A new cell-sheet technique has been developed, and is potentially able to overcome these obstacles. Chondrocyte sheets applicable to cartilage regeneration can be prepared with this cell-sheet technique using temperature-responsive culture dishes. However, for clinical application, it is necessary to evaluate the characteristics of the cells in these sheets and to identify their similarities to naive cartilage.     

Reproductive isolating barriers between colour‐differentiated populations of an African annual killifish,Nothobranchius korthausae (Cyprinodontiformes)

Allopatric populations separated by vicariance events are expected to evolve reproductive isolating mechanisms as a result of disparate selection pressures and genetic drift. The appearance of reproductive isolating mechanisms may vary across taxa with differences in the opportunity for mate choice, and may be asymmetrical. In addition, premating barriers may be affected by individual mating experience. We used choice and no‐choice experiments to investigate reproductive isolation between two allopatric (island and mainland) and colour‐differentiated populations of an African annual fish, Nothobranchius korthausae. Assortative mating under experimental conditions was limited and asymmetrical. Preference for sympatric males was only expressed in nonvirgin females from one population. Virgin fish from both populations mated indiscriminately. No difference in the number of eggs laid, fertilization rate and hatching success was detected in no‐choice experiments. All mating combinations produced viable offspring and no postmating barriers were detected in terms of the performance and fertility of F1 hybrids. Overall, we found little evidence for significant reproductive isolation, which is in contrast with the related killifish taxa in which assortative mating can be strong, even among allopatric populations with no colour differentiation. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 100 , 62–72.     

Effect of the lipophilic/hydrophilic character of cationic triarylmethane dyes on their selective phototoxicity toward tumor cells

The observation that enhanced mitochondrial transmembrane potential is a prevalent tumor cell phenotype has provided the conceptual basis for the development of mitochondrial targeting as a novel therapeutic strategy for both chemo- and photochemotherapy of neoplastic diseases. Because the plasma transmembrane potential is negative on the inner side of the cell and the mitochondrial transmembrane potential is negative on the inner side of this organelle, extensively conjugated cationic molecules (dyes) displaying appropriate structural features are driven electrophoretically through these membranes and tend to accumulate inside energized mitochondria. As a result of the higher mitochondrial transmembrane potential typical of tumor cells, a number of cationic dyes preferentially accrue and are retained for longer periods in the mitochondria of these cells compared to normal cells. This differential in both drug loading and retention brings about the opportunity to attack and destroy tumor cells with a high degree of selectivity. Only a small subset of the cationic dyes known to accumulate in energized mitochondria mediate the destruction of tumor cells with a high degree of selectivity, and the lack of a reliable model to describe the structural determinants of this tumor specificity has prevented mitochondrial targeting from becoming a more reliable therapeutic strategy. We describe here a systematic study of how the molecular structure of closely related cationic triarylmethanes affects the selectivity with which these dyes mediate the photochemical destruction of tumor cells. Based on our observations of how the lipophilic/hydrophilic character of these dyes affects tumor selectivity, we propose a simple model to assist in the design of new drugs tailored specifically for imaging and selective destruction of neoplastic tissue via mitochondrial targeting.