Sex chromosome composition revealed in Characidium fishes (Characiformes: Crenuchidae) by molecular cytogenetic methods

The W chromosome of the fishes Characidium cf. fasciatum, Characidium sp. and Characidium cf. gomesi is heterochromatic, as is usually seen in most Characidium species. Samples of W-chromatin were collected by mechanical microdissection and amplified by DOP-PCR (degenerate oligonucleotide-primed polymerase chain reaction), to be used as painting probes (DCg and CgW) and for sequence analysis. FISH (fluorescence in situ hybridization) with DCg probe painted the whole W chromosome, the pericentromeric region of Z chromosomes and the terminal region of B chromosomes. DOP-PCR-generated fragments were cloned, sequenced and tested by in situ hybridization, but only CgW4 produced positive hybridization signals. Clone sequence analysis recovered seven distinct sequences, of which six did not reveal any similarity to other known sequences in the GenBank or GIRI databases. Only CgW9 clone sequence was recognized as probably derived from a Helitron-transposon similar to that found in the genome of the zebrafish Danio rerio. Our results show that the composition of Characidium’s W chromosome does seem rich in repetitive sequences as well as other W chromosomes found in several species with a ZW sex-determining mechanism.     

The crystal structure of a TIR domain from Arabidopsis thaliana reveals a conserved helical region unique to plants

Plants use a highly evolved immune system to exhibit defense response against microbial infections. The plant TIR domain, together with the nucleotide‐binding (NB) domain and/or a LRR region, forms a type of molecule, named resistance (R) proteins, that interact with microbial effector proteins and elicit hypersensitive responses against infection. Here, we report the first crystal structure of a plant TIR domain from Arabidopsis thaliana (AtTIR) solved at a resolution of 2.0 Å. The structure consists of five β‐strands forming a parallel β‐sheet at the core of the protein. The β‐strands are connected by a series of α‐helices and the overall fold mimics closely that of other mammalian and bacterial TIR domains. However, the region of the αD‐helix reveals significant differences when compared with other TIR structures, especially the αD3‐helix that corresponds to an insertion only present in plant TIR domains. Available mutagenesis data suggest that several conserved and exposed residues in this region are involved in the plant TIR signaling function.     

Forensic identification of the guitarfish species Rhinobatos horkelli, R. percellens and Zapteryx brevirostris using multiplex-PCR

Rhinobatos percellens, Rhinobatos horkelli and Zapteryx brevirostris, known as guitarfish, are commonly found inshore and caught by trawl nets. Recently, these species have been suffering sharp population declines. One of the main impediments to the development of conservation plans is the lack of information related to each species catch. Gathering this information is made more difficult by the fishermen's practice of removing parts of the animals before landing, as well as the morphological similarities among the three species. To address these issues, this work presents multiplex-PCR protocols that were developed to distinguish among these species using their genetic characteristics.     

Isolation of an <Emphasis Type="Italic">Escherichia coli</Emphasis> K4 <Emphasis Type="Italic">kfoC</Emphasis> mutant over-producing capsular chondroitin

Background  

Chondroitin sulphate is a complex polysaccharide having important structural and protective functions in animal tissues. Extracted from animals, this compound is used as a human anti-inflammatory drug. Among bacteria, Escherichia coli K4 produces a capsule containing a non-sulphate chondroitin and its development may provide an efficient and cheap fermentative production of the polysaccharide.     

Endocytosis optimizes the dynamic localization of membrane proteins that regulate cortical polarity

Diverse cell types require the ability to maintain dynamically polarized membrane-protein distributions through balancing transport and diffusion. However, design principles underlying dynamically maintained cortical polarity are not well understood. Here we constructed a mathematical model for characterizing the morphology of dynamically polarized protein distributions. We developed analytical approaches for measuring all model parameters from single-cell experiments. We applied our methods to a well-characterized system for studying polarized membrane proteins: budding yeast cells expressing activated Cdc42. We found that a balance of diffusion, directed transport, and endocytosis was sufficient for accurately describing polarization morphologies. Surprisingly, the model predicts that polarized regions are defined with a precision that is nearly optimal for measured endocytosis rates and that polarity can be dynamically stabilized through positive feedback with directed transport. Our approach provides a step toward understanding how biological systems shape spatially precise, unambiguous cortical polarity domains using dynamic processes.     

Community structure and physiological characterization of microbial mats in Byers Peninsula, Livingston Island (South Shetland Islands, Antarctica)

The community structure and physiological characteristics of three microbial mat communities in Byers Peninsula (Livingston Island, South Shetland Islands, Antarctica) were compared. One of the mats was located at the edge of a stream and was dominated by diatoms (with a thin basal layer of oscillatorian cyanobacteria), whereas the other two mats, located over moist soil and the bottom of a pond, respectively, were dominated by cyanobacteria throughout their vertical profiles. The predominant xanthophyll was fucoxanthin in the stream mat and myxoxanthophyll in the cyanobacteria-dominated mats. The sheath pigment scytonemin was absent in the stream mat but present in the soil and pond mats. The stream mat showed significantly lower delta13C and higher delta15N values than the other two mats. Consistent with the delta15N values, N2 fixation was negligible in the stream mat. The soil mat was the physiologically most active community. It showed rates of photosynthesis three times higher than in the other mats, and had the highest rates of ammonium uptake, nitrate uptake and N2 fixation. These observations underscore the taxonomic and physiological diversity of microbial mat communities in the maritime Antarctic region.     

GSTM1, GSTT1 and CYP1A1 detoxification gene polymorphisms and susceptibility to smoking-related coronary artery disease: a case-only study

Cigarette smoking is a powerful risk factor for coronary artery disease (CAD), leading to the formation of DNA alterations within blood vessels and heart. However, the degree of smoking-related atherosclerosis varies from individual to individual. Genetic polymorphisms of relevant xenobiotic metabolising enzymes may determine the susceptibility of an individual response to environmental toxicants. The purpose of this study was to test the hypothesis that the inheritance of polymorphic genes encoding cytochrome P450 1A1 (CYP1A1 MspI) and glutathione S-transferases (GSTM1(null) and GSTT1(null)) may be causally associated with the presence and severity of smoking-induced CAD. In a case-only design, 222 (179 male, 57.8+/-10.3 years) consecutive smoker patients who had undergone elective and diagnostic coronary angiography were recruited. We found a group (n=169) of smoker patients with significant CAD, defined as>50% reduction in diameter of at least one major vessel, and a group without obstructive CAD (n=53). No significant differences were observed in CYP1A1 genotypes frequencies between CAD and non-CAD smokers (p=0.1). Homozygous deletion of GSTM1 had a frequency of 58.6% among patients with CAD and 45.3% among those without CAD (p=0.08). The frequency of the GSTT1(null) genotype was 43.8% among the patients with CAD and 24.5% among CAD-free subjects (p=0.01). After adjustment for traditional risk factors, the presence of combined GSTM1(null)GSTT1(null) genotypes was significantly associated with an increased risk of CAD (OR=3.9; 95% CI: 1.3-11.4, p=0.01). Moreover, smokers with combined GSTM1(null)GSTT1(null) genotypes had significantly higher number of stenosed vessels than those with the positive genotype (2.3+/-0.9 versus 1.7+/-0.8, p=0.03). Our findings showed that smokers carrying GST deleted genotypes have an increased susceptibility to the smoking related coronary artery disease. Exploring gene-smoking effect provides an excellent model in order to understand gene-environment toxicants interaction and its implications to cardiovascular disease.     

Cardiac imaging: the biological effects of diagnostic cardiac ultrasound

Diagnostic cardiac ultrasounds are an environment-friendly and non-ionising imaging technology. However, ultrasounds are not biologically inert, and their use might have profound clinical impact. This paper summarizes the known effects of cardiac ultrasound—compared to other major imaging techniques—to exposed patients and to clinically exposed physicians practising ultrasound imaging. Furthermore, this review also provides an overview of the evidences on the biological effects of diagnostic ultrasound—which suggest that ultrasound with frequency, intensity and duration fully in the diagnostic range have significant molecular, cellular and organ effects.

A better understanding of these effects may improve our understanding of the complex interactions between ultrasound and biological tissues and may open new avenues to therapeutic applications based on the ultrasound-modulated cell functions, such as membrane transduction, apoptosis, cell permeability and thrombolysis.     

A novel plant gene essential for meiosis is related to the human CtIP and the yeast COM1/SAE2 gene

Obligatory homologous recombination (HR) is required for chiasma formation and chromosome segregation in meiosis I. Meiotic HR is initiated by DNA double-strand breaks (DSBs), generated by Spo11, a homologue of the archaebacterial topoisomerase subunit Top6A. In Saccharomyces cerevisiae, Rad50, Mre11 and Com1/Sae2 are essential to process an intermediate of the cleavage reaction consisting of Spo11 covalently linked to the 5' termini of DNA. While Rad50 and Mre11 also confer genome stability to vegetative cells and are well conserved in evolution, Com1/Sae2 was believed to be fungal-specific. Here, we identify COM1/SAE2 homologues in all eukaryotic kingdoms. Arabidopsis thaliana Com1/Sae2 mutants are sterile, accumulate AtSPO11-1 during meiotic prophase and fail to form AtRAd51 foci despite the presence of unrepaired DSBs. Furthermore, DNA fragmentation in AtCom1 is suppressed by eliminating AtSPO11-1. In addition, AtCOM1 is specifically required for mitomycin C resistance. Interestingly, we identified CtIP, an essential protein interacting with the DNA repair machinery, as the mammalian homologue of Com1/Sae2, with important implications for the molecular role of CtIP.     

Kinetic mechanism of the Zn-dependent aryl-phosphatase activity of myo-inositol-1-phosphatase

Myo-inositol-1-phosphatase (EC 3.1.3.25) is able to hydrolyze myo-inositol-1-phosphate in the presence of Mg(2+) ions at neutral pH, and also p-nitrophenyl phosphate in the presence of Zn(2+)-ions at acidic pH. This enzyme plays a role in phosphatidylinositol cell signalling and is a putative target of lithium therapy in manic depression. We elucidate here the kinetic mechanism of the Zn-dependent activity of myo-inositol-1-phosphatase. As part of this analysis it was necessary to determine the basicity constants of p-nitrophenyl phosphate and the stability constant of its metal-complex in the presence of zinc chloride. We find that the Zn-dependent reaction may be described either by a rapid-equilibrium random mechanism or an ordered steady-state mechanism in which the substrate binds to the free enzyme prior to the metal ion. In both models the Zn-substrate complex acts as a high affinity inhibitor, yielding a dead-end species through its binding to the enzyme-Zn-substrate in rapid-equilibrium or to the enzyme-phosphate complexes in a steady-state model. Phosphate is a competitive inhibitor of the enzyme with respect to the substrate and an uncompetitive inhibitor with respect to zinc ions.