Phagocytic function in cyclists: correlation with catecholamines and cortisol.

Flow cytometer measurements were made of the basal variations in peripheral blood functional monocytes and granulocytes over the course of a training season (January to November) of a cycling team. Parallel determinations were made of plasma concentration of catecholamines (chromatography) and cortisol (RIA) in a search for neuroendocrine markers. The results showed the greatest phagocytic capacity to occur in the central months (March, May, and July), coinciding with the greatest number and highest level of competitive events with good correlation with a peak in epinephrine during these months (r(2) = 0.998 for monocytes and r(2) = 0.674 for granulocytes). No good correlations were found between phagocytosis and norepinephrine or cortisol. The highest values for phagocytosis and epinephrine concentration were found in May. These results suggest that blood epinephrine concentration could be a good neuroendocrine marker of sportspeople's phagocytic response.     

Use of nuclear morphometry characteristics to distinguish between normal and abnormal cervical glandular histologies.

This is a methodological study exploring the use of quantitative histopathology applied to the cervix to discriminate between normal and cancerous (consisting of adenocarcinoma and adenocarcinoma in situ) tissue samples. The goal is classifying tissue samples, which are populations of cells, from measurements on the cells. Our method uses one particular feature, the IODs-Index, to create a tissue level feature. The specific goal of this study is to find a threshold for the IODs-Index that is used to create the tissue level feature. The main statistical tool is Receiver Operating Characteristic (ROC) curve analysis. When applied to the data, our method achieved promising results with good estimated sensitivity and specificity for our data set. The optimal threshold for the IODs-Index was found to be 2.12.     

Contribution of Mutation and RNA Recombination to the Evolution of a Plant Pathogenic RNA

The nucleotide sequence of 17 variants of the satellite RNA of cucumber mosaic virus (CMV-satRNA) isolated from field-infected tomato plants in the springs of 1989, 1990, and 1991 was determined. The sequence of each of the 17 satRNAs was unique and was between 334 and 340 nucleotides in length; 57 positions were polymorphic. There was much genetic divergence, ranging from 0.006 to 0.141 nucleotide substitutions per site for pairwise comparisons, and averaging 0.074 for any pair. When the polymorphic positions were analyzed relative to a secondary structure model proposed for CMV-satRNAs, it was found that there were significantly different numbers of changes in base-paired and non–base-paired positions, and that mutations that did not disrupt base pairing were preferred at the putatively paired sites. This supports the concept that the need to maintain a functional structure may limit genetic divergence of CMV-satRNA. Phylogenetic analyses showed that the 17 CMV-satRNA variants clustered into two subgroups, I and II, and evolutionary lines proceeding by the sequential accumulation of mutations were apparent. Three satRNA variants were outliers for these two phylogenetic groups. They were shown to be recombinants of subgroup I and II satRNAs by calculating phylogenies for different molecular regions and by using Sawyer's test for gene conversion. At least two recombination events were required to produce these three recombinant satRNAs. Thus, recombinants were found to be frequent (∼17%) in natural populations of CMV-satRNA, and recombination may make an important contribution to the generation of new variants. To our knowledge this is the first report of data allowing the frequency of recombinant isolates in natural populations of an RNA replicon to be estimated. Received: 14 May 1996 / Accepted: 17 July 1996     

Formation of micro‐spherulitic barite in association with organic matter within sulfidized stromatolites of the 3.48 billion‐year‐old Dresser Formation,Pilbara Craton

The shallow marine and subaerial sedimentary and hydrothermal rocks of the ~3.48 billion‐year‐old Dresser Formation are host to some of Earth's oldest stromatolites and microbial remains. This study reports on texturally distinctive, spherulitic barite micro‐mineralization that occur in association with primary, autochthonous organic matter within exceptionally preserved, strongly sulfidized stromatolite samples obtained from drill cores. Spherulitic barite micro‐mineralization within the sulfidized stromatolites generally forms submicron‐scale aggregates that show gradations from hollow to densely crystallized, irregular to partially radiating crystalline interiors. Several barite micro‐spherulites show thin outer shells. Within stromatolites, barite micro‐spherulites are intimately associated with petrographically earliest dolomite and nano‐porous pyrite enriched in organic matter, the latter of which is a possible biosignature assemblage that hosts microbial remains. Barite spherulites are also observed within layered barite in proximity to stromatolite layers, where they are overgrown by compositionally distinct (Sr‐rich), coarsely crystalline barite that may have been sourced from hydrothermal veins at depth. Micro‐spherulitic barite, such as reported here, is not known from hydrothermal systems that exceed the upper temperature limit for life. Rather, barite with near‐identical morphology and micro‐texture is known from zones of high bio‐productivity under low‐temperature conditions in the modern oceans, where microbial activity and/or organic matter of degrading biomass controls the formation of spherulitic aggregates. Hence, the presence of micro‐spherulitic barite in the organic matter‐bearing Dresser Formation sulfidized stromatolites lend further support for a biogenic origin of these unusual, exceptionally well‐preserved, and very ancient microbialites.     

Variation and evolution of plant virus populations

Over the last 15 years, interest in plant virus evolution has re-emerged, as shown by the increasing number of papers published on this subject. In recent times, research in plant virus evolution has been viewed from a molecular, rather than populational, standpoint, and there is a need for work aimed at understanding the processes involved in plant virus evolution. However, accumulated data from analyses of experimental and natural populations of plant viruses are beginning to delineate some trends that often run contrary to accepted opinion: (1) high mutation rates are not necessarily adaptive, as a large fraction of the mutations are deleterious or lethal; (2) in spite of high potential for genetic variation, populations of plant viruses are not highly variable, and genetic stability is the rule rather than the exception; (3) the degree of constriction of genetic variation in virus-encoded proteins is similar to that in their eukaryotic hosts and vectors; and (4) in spite of huge census sizes of plant virus populations, selection is not the sole factor that shapes their evolution, and genetic drift may be important. Here, we review recent advances in understanding plant virus evolution, and describe the experimental and analytical methods most suited to this purpose.     

Biological activity of hamster interferon-gamma is modulated by the carboxyl-terminal tail

The Syrian golden hamster (Mesocricetus auratus) is highly susceptible to a number of intracellular pathogens. Interferon-gamma (IFN-γ), the primary macrophage-activating cytokine, plays a key role in the host defense against intracellular pathogens. The hamster IFN-γ cDNA encodes a 174 amino acid protein that has an additional 17 amino acids at the carboxyl-terminus compared to IFN-γ of mice and rats. A homologous C-terminal tail is also found in other non-murine rodents. The biological activity of hamster IFN-γ had not been investigated previously so we first demonstrated the activity of native IFN-γ in assays of IFN-γ-induced receptor signaling and antiviral activity against vesicular stomatitis virus. We then tested the hypothesis that the C-terminal tail of hamster IFN-γ could influence its biological activity. A truncated hamster IFN-γ, in which the C-terminal 17 aa were removed by insertion of a stop codon at the position corresponding to the stop codon in the mouse sequence, had approximately 10-fold greater activity than the full length protein when measured in the two bioassays. Polyclonal and monoclonal anti-hamster IFN-γ antibodies specifically inhibited this biological activity. Collectively, these data indicate that this unique structural feature influences the biological activity of hamster IFN-γ.     

The Role of eIF1 in Translation Initiation Codon Selection in Caenorhabditis elegans

The selection of a proper AUG start codon requires the base-pairing interactions between the codon on the mRNA and the anticodon of the initiator tRNA. This selection process occurs in a pre-initiation complex that includes multiple translation initiation factors and the small ribosomal subunit. To study how these initiation factors are involved in start codon recognition in multicellular organisms, we isolated mutants that allow the expression of a GFP reporter containing a non-AUG start codon. Here we describe the characterization of mutations in eif-1, which encodes the Caenorhabditis elegans translation initiation factor 1 (eIF1). Two mutations were identified, both of which are substitutions of amino acid residues that are identical in all eukaryotic eIF1 proteins. These residues are located in a structural region where the amino acid residues affected by the Saccharomyces cerevisiae eIF1 mutations are also localized. Both C. elegans mutations are dominant in conferring a non-AUG translation initiation phenotype and lead to growth arrest defects in homozygous animals. By assaying reporter constructs that have base changes at the AUG start codon, these mutants are found to allow expression from most reporters that carry single base changes within the AUG codon. This trend of non-AUG mediated initiation was also observed previously for C. elegans eIF2β mutants, indicating that these two factors play a similar role. These results support that eIF1 functions in ensuring the fidelity of AUG start codon recognition in a multicellular organism.TRANSLATION initiation is thought to be one of the most complex cellular processes in eukaryotes. It involves at least 12 translation initiation factors (eIFs) comprising over 30 polypeptides (Pestova et al. 2007). These factors bring together an initiator methionyl tRNA (Met-tRNAi), the small ribosomal subunit, and a mRNA to form a 48S initiation complex. An important role performed by this complex is to select an AUG codon to initiate translation of the mRNA. Since the first AUG at the 5′ end of most mRNAs is selected as the start site, it is believed that the initiation complex scans for an AUG start codon as it moves from the 5′-capped end of the mRNA toward the 3′ end, as proposed in the ribosomal scanning model (Kozak 1978; Kozak 1989). The recognition of the AUG start codon is mediated by the anticodon of the Met-tRNAi, and the matching base-pairing interactions between the codon of the mRNA and the anticodon determine the site of initiation (Cigan et al. 1988). These base-pairing interactions are essential, but are likely not the only components required for accurately selecting the correct AUG start codon. Numerous initiation factors along with base-pairing interactions have been shown to aid in the AUG recognition process (Pestova et al. 2007).Translation initiation factors involved in start codon selection fidelity were first identified through genetic studies performed in the yeast Saccharomyces cerevisiae. Mutant strains with a modified His4 gene that had an AUU instead of an AUG at the native start site were selected for the ability to survive on media lacking histidine (Donahue et al. 1988; Castilho-Valavicius et al. 1990). These mutants were found to be able to produce the His4 protein by using a downstream inframe UUG codon (the third codon within the His4 coding region) as the translation start site. Further analyses determined that non-AUG initiation occurred mostly from a UUG codon and not significantly from other codons (Huang et al. 1997). These mutants defined five genetic loci and were named sui1-sui5 (suppressor of initiation codon) on the basis of their ability to initiate translation at a non-AUG codon.The sui1 suppressors were found to have missense mutations in eIF1. These missense mutations showed semidominant or codominant properties in non-AUG translation initiation while deletion of the eIF1 gene led to lethality in yeast (Yoon and Donahue 1992). eIF1 is a highly conserved protein with a size of approximately 12 kDa that plays a vital role in multiple translation initiation steps. eIF1 is incorporated into a multifactor complex that includes eIF1A, eIF3, and eIF5 and stimulates the recruiting of the ternary complex (consisting of eIF2 · GTP and the charged Met-tRNAi) to the small ribosomal subunit to form the 43S pre-initiation complex (Singh et al. 2004). eIF1 acts synergistically with eIF1A to promote continuous ribosomal scanning for AUG codons by stabilizing an open conformation that allows mRNA to pass through the complex (Maag et al. 2005; Cheung et al. 2007; Passmore et al. 2007). It also mediates the assembly of the ribosomal initiation complex at the AUG start codon (Pestova et al. 1998). eIF1 dissociates from the complex upon recognition of the AUG codon and this dissociation is necessary to trigger a series of conformational changes leading to the translation elongation phase (Algire et al. 2005). Consistent with these roles, sui1 mutations reduce the affinity of eIF1 for the ribosome and cause premature release of eIF1 at non-AUG codons (Cheung et al. 2007). Other sui mutations support the involvement of four additional genes in translation initiation fidelity in yeast. Mutations have been isolated in the heterotrimeric eIF2 as SUI2 (α-subunit) (Cigan et al. 1989), SUI3 (β-subunit) (Donahue et al. 1988), and SUI4 (γ-subunit) (Huang et al. 1997), and a mutation in eIF5 corresponds to the SUI5 mutant (Huang et al. 1997).However, the genetic studies that identified these translation fidelity mutants were conducted only in yeast. It is not known if there are similar mechanisms regulating translation initiation fidelity in multicellular organisms. To address this question, we designed a genetic system to isolate C. elegans mutants that have reduced fidelity in AUG start codon selection (Zhang and Maduzia 2010). Mutants were selected on the basis of their ability to express a GFP reporter that contains a GUG codon in place of its native translation start site. Here we report the characterization of two mutants that have mutations in eIF1. Unlike yeast sui1 mutants, which preferred the UUG codon, these mutants are capable of using a subset of non-AUG codons for translation initiation. Our results are consistent with eIF1 playing a role in the fidelity of AUG codon selection, perhaps by discriminating base-pairing interactions between the codon and anticodon during start-site selection.