Twilight activity patterns and angling vulnerability of yellowmouth barracuda (Sphyraena viridensis Cuvier, 1829), a range-expanding thermophilic fish

Among the thermophilic fishes that have become established in the north-western Mediterranean as a consequence of sea warming, the yellowmouth barracuda (Sphyraena viridensis Cuvier, 1829) appears to be one of the most successful and abundant in the coastal rocky environment, having increasingly become the object of recreational and commercial exploitation in the study area. Lure-fishing sessions were carried out from May 2016 to November 2018 in the Catalan Sea (NE Spain) at dawn and dusk, with the aim of providing new insight into the behavioural, spatial and feeding ecology and vulnerability to angling of this poorly known species. Generalized mixed-effects linear models showed that S. viridensis is a crepuscular inshore dweller, whose vulnerability to angling is significantly influenced by solar and lunar light intensities, being highest in the pre-spawn and spawning periods. Asymmetries between dawn and dusk activity patterns were detected, evidently related to a drop in aggressiveness at dusk following the spawning period. The simple study design adopted may be applied to other contexts, aiming to the recognition of several levels of fish vulnerability to angling.     

Annual cycle of stored spermatozoa within the ovaries of Helicolenus dactylopterus dactylopterus (Teleostei, Scorpaenidae)

The aim of this work was to analyse the ultrastructure of storage crypts and stored spermatozoa, and to describe changes during the annual reproductive cycle of the bluemouth Helicolenus dactylopterus dactylopterus , which has internal fertilization and a zygoparous mode of reproduction. Spermatozoa had elongated heads and long midpieces, two characteristics which are thought to be fairly advanced and correlated with internal fertilization, as is the case of the bluemouth. A remarkable spermatozoon feature was the retention of a significant quantity of cytoplasm around the head, a condition that appeared to be related to nourishment during the long storage period, up to 10 months in the intraovarian crystal structures of the female. Male sex cells' protection against the female immune system was ensured by junctional complexes between the crypt cells composed of tight junctions and desmosomes.     

Triterpene saponins from Cylicodiscus gabunensis.

Four new saponins were isolated from the alcoholic extract of the bark of Cylicodiscus gabunensis by means of flash chromatography. They were characterized on the basis of spectral and chemical data as 3-O-beta-[alpha-L-arabinopyranosyl (1----2),alpha-L-arabinopyranosyl(1----3),beta-D-glucopyranosyl(1- ---)] maslinic acid-28-[beta-D-glucopyranosyl(1----6),beta-D-glucopyranosyl(1----2),alp ha-L- rhamnopyranosyl(1----)] ester; 3-O-beta-[alpha-L-arabinopyranosyl(1----2),alpha-L-arabinopyran osyl (1----3),beta-D-glucopyranosyl(1----)]maslinic acid-28-[beta-D-glucopyranosyl(1----2),alpha-L-rhamnopyranosyl(1----)] ester, 3-O-beta-[alpha-L-arabinopyranosyl(1----2),alpha-L-arabinopyran osyl (1----3),beta-D-glucopyranosyl(1----)]maslinic acid and 3-O-beta(alpha-L-arabinopyranosyl(1----3),beta-D-glucopyranosyl (1----)] cylicodiscic acid.     

Silver and mercury probing of deoxyribonucleic acid structures in the filamentous viruses fd, If1, IKe, Xf, Pf1, and Pf3

Ag+ binding and Hg2+ binding to both double-stranded DNA (dsDNA) and single-stranded DNA (ssDNA) have been examined in some detail, and the results have been applied to study the structures of circular ssDNA in several filamentous viruses. It has been known for some time that Ag+ and Hg2+ bind to the bases of DNA producing characteristic large changes in absorbance and circular dichroism (CD) spectra, as well as changes in sedimentation rates. In the case of Ag+, it is known that there are three modes of binding to isolated dsDNA, referred to as types I, II, and III. Type III binding, by definition, occurs when Ag+ binds to Ag-dsDNA complexes having sites for binding types I and II extensively occupied, if not saturated. It produces CD spectra, assigned in this study, and absorbance spectra that are isosbestic with those of the Ag-dsDNA complexes present prior to its onset. In phosphate buffers binding is restricted to types I and II, whereas in borate buffers weaker type III binding can occur. Characteristics of types I, II, and III were observed for the DNAs in fd, If1, IKe, and Xf, but not for those in Pf1 and Pf3. Similarly, many of the spectral changes seen when Hg2+ binds to isolated double-stranded DNA are mimicked by Hg2+ binding to the DNAs within fd, IKe, If1, and Xf, but not for those in Pf1 and Pf3. The Ag+ and Hg2+ results indicate the presence of right-handed DNA helices in fd, If1, IKe, and Xf, with the two antiparallel strands of the covalently closed single-stranded DNAs having the bases directed toward the virion axes. For Pf1 and Pf3, Ag+ and Hg2+ binding cause large absorbance changes but only small CD changes. The very different results for Pf1 and Pf3 are consistent with the presence of inverted DNA structures (I-DNA) with the bases directed away from the structure axes, but the two structures differ from one another. Sedimentation velocity changes with Ag+ and Hg2+ binding strongly suggest structural linkages between the DNA and the surrounding protein sheath in each of the viruses.     

Decreased susceptibility of melanized Cryptococcus neoformans to UV light.

Melanized Cryptococcus neoformans cells were less susceptible than nonmelanized cells to the fungicidal effects of UV light. Phenoloxidase-catalyzed production of melanin-like pigments may serve to protect the fungus against ionizing radiation.     

Multimeric structure of the membrane erythropoietin receptor of murine erythroleukemia cells (Friend cells). Cross-linking of erythropoietin with the spleen focus-forming virus envelope protein.

In erythroleukemia cells infected with the polycythemia strain of the Friend virus complex, erythropoietin could be cross-linked mainly to a protein of 63 kDa when using disuccinimidyl suberate. In contrast, erythropoietin in other erythroleukemia cells cross-linked to two proteins of 85 and 100 kDa. When native erythropoietin receptor complexes were immunoprecipitated, the 63-kDa erythropoietin-cross-linked protein could be precipitated both by antibodies directed against the intracellular part of the cloned chain of the erythropoietin receptor and by antibodies directed against the envelope proteins of the Friend virus. However, after denaturation of the complexes, the 63-kDa protein was only precipitated by antibodies directed against the envelope proteins of the Friend virus. Enzymatic deglycosylation confirmed that erythropoietin was cross-linked with the envelope protein of the defective virus and bidimensional diagonal gel electrophoresis analyses showed that some of the erythropoietin cross-linked envelope proteins were dimerized by disulfide bonds. Thus, the main erythropoietin-receptor complex in the plasma membrane of these cells consisted of a molecule of the cloned chain of the erythropoietin receptor noncovalently associated with one or two disulfide-bonded molecule(s) of the envelope protein of the defective virus. Moreover, our results also showed that the viral envelope protein associated with the cloned chain of the erythropoietin receptor at a site distinct from the erythropoietin binding site.     

Erythropoietin induces the tyrosine phosphorylation of its own receptor in human erythropoietin-responsive cells.

Using the human erythropoietin-responsive hematopoietic cell line UT-7, we showed that erythropoietin (Epo) rapidly and specifically induced the tyrosine phosphorylation of its own receptor (M(r) 75,000) and increased the tyrosine phosphorylation of other proteins of M(r) 140,000, 120,000, 95,000, 60,000, 57,000, and 42,000. Neither granulocyte-macrophage colony-stimulating factor, interleukin 3, interleukin 6, nor the kit ligand induced the phosphorylation of the M(r) 75,000 receptor protein, although these growth factors induced the phosphorylation of other proteins. Cross-linking experiments using 125I-Epo indicated that the UT-7 cells expressed three Epo receptor subunits, of M(r) 100,000, 85,000, and 75,000, among which only the M(r) 75,000 subunit was tyrosine-phosphorylated following activation with Epo.     

Review: Pathogenesis of Helicobacter pylori infection

The original strategies developed by Helicobacter pylori to persistently colonise its host and to deregulate its cellular functions make this bacterium an outstanding model to study host‐pathogen interaction and the mechanisms responsible for bacterial‐induced carcinogenesis. During the last year, significant results were obtained on the role of bacterial factors essential for gastric colonisation such as spiral shape maintenance, orientation through chemotaxis and the formation of bacteria clonal population islands inside the gastric glands. Particularities of the H pylori cell surface, a structure important for immune escape, were demonstrated. New insights in the bacterial stress response revealed the importance of DNA methylation‐mediated regulation. Further findings were reported on H pylori components that mediate natural transformation and mechanisms of bacterial DNA horizontal transfer which maintain a high level of H pylori genetic variability. Within‐host evolution was found to be niche‐specific and probably associated with physiological differences between the antral and oxyntic gastric mucosa. In addition, with the progress of CryoEM, high‐resolution structures of the major virulence factors, VacA and CagT4SS, were obtained. The use of gastric organoid models fostered research revealing, preferential accumulation of bacteria at the site of injury during infection. Several studies further characterised the role of CagA in the oncogenic properties of H pylori, identifying the activation of novel CagA‐dependent pathways, leading to the promotion of genetic instabilities, epithelial‐to‐mesenchymal transition and finally carcinogenesis. Recent studies also highlight that microRNA‐mediated regulation and epigenetic modifications, through DNA methylation, are key events in the H pylori‐induced tumorigenesis process.     

Why Has the Number of Scientific Retractions Increased?

Background

The number of retracted scientific publications has risen sharply, but it is unclear whether this reflects an increase in publication of flawed articles or an increase in the rate at which flawed articles are withdrawn.

Methods and Findings

We examined the interval between publication and retraction for 2,047 retracted articles indexed in PubMed. Time-to-retraction (from publication of article to publication of retraction) averaged 32.91 months. Among 714 retracted articles published in or before 2002, retraction required 49.82 months; among 1,333 retracted articles published after 2002, retraction required 23.82 months (p<0.0001). This suggests that journals are retracting papers more quickly than in the past, although recent articles requiring retraction may not have been recognized yet. To test the hypothesis that time-to-retraction is shorter for articles that receive careful scrutiny, time-to-retraction was correlated with journal impact factor (IF). Time-to-retraction was significantly shorter for high-IF journals, but only ∼1% of the variance in time-to-retraction was explained by increased scrutiny. The first article retracted for plagiarism was published in 1979 and the first for duplicate publication in 1990, showing that articles are now retracted for reasons not cited in the past. The proportional impact of authors with multiple retractions was greater in 1972–1992 than in the current era (p<0.001). From 1972–1992, 46.0% of retracted papers were written by authors with a single retraction; from 1993 to 2012, 63.1% of retracted papers were written by single-retraction authors (p<0.001).

Conclusions

The increase in retracted articles appears to reflect changes in the behavior of both authors and institutions. Lower barriers to publication of flawed articles are seen in the increase in number and proportion of retractions by authors with a single retraction. Lower barriers to retraction are apparent in an increase in retraction for “new” offenses such as plagiarism and a decrease in the time-to-retraction of flawed work.