Telomere shortening in human fibroblasts is not dependent on the size of the telomeric-3'-overhang

Telomeres shorten in human somatic cells with each round of DNA replication, and this shortening is thought to ultimately trigger replicative senescence. Telomere shortening is caused partly by the inability of semiconservative DNA replication to copy a linear strand of DNA to its very end. Post-replicative processing of telomeric ends, producing single-stranded G-rich 3' overhangs, has also been suggested to contribute to telomere shortening. This suggestion implies that a positive correlation should exist between the length of 3' overhangs and the rate of telomere shortening. We confirmed shortening of overhangs as human lung (MRC5) and foreskin (BJ) fibroblasts approach senescence by measuring overhang length using in-gel hybridization. However, a large study of fibroblast strains from 21 donors maintained under conditions which lead to two orders of magnitude of variation in telomere shortening rate failed to show any correlation between telomere overhang length and shortening rate, suggesting that overhang length is neither a cause nor a correlate of telomere shortening.     

In vitro Antifungal Activity of Essential oils and Major Components against Fungi Plant Pathogens

The indiscriminate use of synthetic fungicides has caused several problems to the environment, which place human and animal health at risk. Due to this fact, the search for natural alternatives to control phytopathogenic fungi growth has increased. This study aims to evaluate the antifungal activity of two essential oils (EOs) and three major components of EOs on the radial growth and spore germination of Fusarium verticillioides and Alternaria tenuissima. Minimum and half‐maximal inhibitory concentrations (CMI and CI₅₀) at 96 h for each treatment were calculated. Lemongrass EO and citral caused the highest inhibition for A. tenuissima (CMI of 1000 μl/l and CI₅₀ of 10 μl/l). For F. verticillioides, the most effective component was geraniol (CMI and CI₅₀ of 1000 and 250 μl/l, respectively). Spore germination rate was delayed by the EOs and major components tested. The use of EOs was effective to control these two fungal species in their different grow stages.     

Apoptosis, autophagy and cell cycle arrest following photodamage to mitochondrial interior

Cell death induced by oxidative insult targeted to mitochondrial interior of A431 cells was investigated. For stimulated production of ROS in the inner space of mitochondria, safranin-mediated photodynamic treatment (PDT) was employed. Another photosensitizer, mTHPC, which diffusely localizes to cellular membranes, was used for comparison. Cell response to the oxidative insult in mitochondrial interior was different from the response to the photodamage produced in cellular membranes. Autophagy and apoptotic features of cell death in response to mTHPC-PDT was observed in a wide range of PDT doses. Cell response to the oxidative stress in mitochondrial interior was dose-dependent. Damage up to CD50 did not reveal hallmarks of dead cells. At intermediate damage (CD50), cells manifested enhanced autophagy and reduced population of S-phase, but not apoptosis. Severe damage (beyond CD70) induced apoptosis following release of cytochrome c and caspase activation, in addition to autophagy and cell cycle arrest.     

Partitioning to uncover conditions for permutation tests to control multiple testing error rates

This article discusses specific assumptions necessary for permutation multiple tests to control the Familywise Error Rate (FWER). At issue is that, in comparing parameters of the marginal distributions of two sets of multivariate observations, validity of permutation testing is affected by all the parameters in the joint distributions of the observations. We show the surprising fact that, in the case of a linear model with i.i.d. errors such as in the analysis of Quantitative Trait Loci (QTL), this issue has no impact on control of FWER, if the test statistic is of a particular form. On the other hand, in the analysis of gene expression levels or multiple safety endpoints, unless some assumption connecting the marginal distributions of the observations to their joint distributions is made, permutation multiple tests may not control FWER.     

Focus: The Aging Brain: Neural stem/progenitor cells in Alzheimer’s disease

Alzheimer’s disease (AD) is the most prevalent neurodegenerative disease and a worldwide health challenge. Different therapeutic approaches are being developed to reverse or slow the loss of affected neurons. Another plausible therapeutic way that may complement the studies is to increase the survival of existing neurons by mobilizing the existing neural stem/progenitor cells (NSPCs) — i.e. “induce their plasticity” — to regenerate lost neurons despite the existing pathology and unfavorable environment. However, there is controversy about how NSPCs are affected by the unfavorable toxic environment during AD. In this review, we will discuss the use of stem cells in neurodegenerative diseases and in particular how NSPCs affect the AD pathology and how neurodegeneration affects NSPCs. In the end of this review, we will discuss how zebrafish as a useful model organism with extensive regenerative ability in the brain might help to address the molecular programs needed for NSPCs to respond to neurodegeneration by enhanced neurogenesis.     

Burkholderia species in human infections in Mexico: Identification of B. cepacia,B. contaminans,B. multivorans,B. vietnamiensis,B. pseudomallei and a new Burkholderia species

BackgroundBurkholderia sensu stricto is comprised mainly of opportunistic pathogens. This group is widely distributed in the environment but is especially important in clinical settings. In Mexico, few species have been correctly identified among patients, most often B. cepacia is described.Methodology/Principal findingsIn this study, approximately 90 strains identified as B. cepacia with the VITEK2 system were isolated from two medical centers in Mexico City and analyzed by MLSA, BOX-PCR and genome analysis. The initial identification of B. cepacia was confirmed for many strains, but B. contaminans, B. multivorans and B. vietnamiensis were also identified among clinical strains for the first time in hospitals in Mexico. Additionally, the presence of B. pseudomallei was confirmed, and a novel species within the B. cepacia complex was documented. Several strains misidentified as B. cepacia actually belong to the genera Pseudomonas, Stenotrophomonas and Providencia.Conclusions/SignificanceThe presence of different Burkholderia species in Mexico was confirmed. Correct identification of Burkholderia species is important to provide accurate treatment for immunosuppressed patients.     

Transition metal complexes with pyrazole based ligands, part 18: new binuclear Cu(I), Cu(II) and Co(II) complexes with 3,5-dimethyl-1-thiocarboxamide pyrazole: synthesis, structural and magnetic studies

Three new binuclear metal complexes of the formulas (L = 3,5-dimethyl-1-thiocarboxamide pyrazole) have been synthesized and characterized by chemical analysis, FT-IR spectroscopy, solution conductivity, solid state magnetic measurements and X-ray single crystal and variable temperature powder diffraction. Complex 1 forms doubly chloro-bridged dimers, with Cu(II) in distorted trigonal bipyramidal coordination with the apical positions occupied by chlorine atoms. Magnetic measurements indicate an antiferromagnetic interaction between the Cu(II) centres in the dimer, with the singlet-triplet exchange parameter of J = −19.40 cm⁻¹. Complex 2 forms doubly sulfur-bridged dimers, with Cu(I) in distorted tetrahedral coordination with apical positions occupied by bromine atoms. Complex 3 is a cobalt analogue of 1. It contains dinuclear units formed by five-coordinate high-spin Co(II) in a distorted trigonal bipyramidal environment. The magnetisation of 3 shows no significant departure from Curie-Weiss behaviour between room temperature and 5 K. All crystal structures are stabilized by two-dimensional hydrogen bonding networks between the carboxamide nitrogen donors and the terminal halide acceptors.     

Phosphorylation protects sperm‐specific histones H1 and H2B from proteolysis after fertilization

At intermediate stages of male pronucleus formation, sperm‐derived chromatin is composed of hybrid nucleoprotein particles formed by sperm H1 (SpH1), dimers of sperm H2A‐H2B (SpH2A‐SpH2B), and a subset of maternal cleavage stage (CS) histone variants. At this stage in vivo, the CS histone variants are poly(ADP‐ribosylated), while SpH2B and SpH1 are phosphorylated. We have postulated previously that the final steps of sperm chromatin remodeling involve a cysteine‐protease (SpH‐protease) that degrades sperm histones in a specific manner, leaving the maternal CS histone variants unaffected. More recently we have reported that the protection of CS histones from degradation is determined by the poly(ADP‐ribose) moiety of these proteins. Because of the selectivity displayed by the SpH‐protease, the coexistence of a subset of SpH together with CS histone variants at intermediate stages of male pronucleus remodeling remains intriguing. Consequently, we have investigated the phosphorylation state of SpH1 and SpH2B in relation to the possible protection of these proteins from proteolytic degradation. Histones H1 and H2B were purified from sperm, phosphorylated in vitro using the recombinant α‐subunit of casein kinase 2, and then used as substrates in the standard assay of the SpH‐protease. The phosphorylated forms of SpH1 and SpH2B were found to remain unaltered, while the nonphosphorylated forms were degraded. On the basis of this result, we postulate a novel role for the phosphorylation of SpH1 and SpH2B that occurs in vivo after fertilization, namely to protect these histones against degradation at intermediate stages of male chromatin remodeling. J. Cell. Biochem. 76:173–180, 1999. © 1999 Wiley‐Liss, Inc.     

Identification and Regulation of fusA,the Polyketide Synthase Gene Responsible for Fusarin Production in Fusarium fujikuroi

Fusarins are a class of mycotoxins of the polyketide family produced by different Fusarium species, including the gibberellin-producing fungus Fusarium fujikuroi. Based on sequence comparisons between polyketide synthase (PKS) enzymes for fusarin production in other Fusarium strains, we have identified the F. fujikuroi orthologue, called fusA. The participation of fusA in fusarin biosynthesis was demonstrated by targeted mutagenesis. Fusarin production is transiently stimulated by nitrogen availability in this fungus, a regulation paralleled by the fusA mRNA levels in the cell. Illumination of the cultures results in a reduction of the fusarin content, an effect partially explained by a high sensitivity of these compounds to light. Mutants of the fusA gene exhibit no external phenotypic alterations, including morphology and conidiation, except for a lack of the characteristic yellow and/or orange pigmentation of fusarins. Moreover, the fusA mutants are less efficient than the wild type at degrading cellophane on agar cultures, a trait associated with pathogenesis functions in Fusarium oxysporum. The fusA mutants, however, are not affected in their capacities to grow on plant tissues.