Cationic bactericidal peptides are components of natural host defenses against infections. While the mode of antibacterial action of cationic peptides remains controversial, several targets, including the cytoplasmic membrane and macromolecular synthesis, have been identified for peptides acting at high concentrations. The present study identified peptide effects at lower, near-lethal inhibitory concentrations. An amidated hybrid of the flounder pleurocidin and the frog dermaseptin (P-Der), two other pleurocidin derivatives, and pleurocidin itself were studied. At 2 g/ml, the MIC, P-Der inhibited Escherichia coli growth in a broth dilution assay but did not cause bacterial death within 30 min, as estimated by viable count analysis. Consistent with this, P-Der demonstrated a weak ability to permeabilize membranes but was able to translocate across the lipid bilayer of unilamellar liposomes. Doses of 20 g/ml or more Short, positively charged, amphipathic peptides are being considered as a novel class of antimicrobials. Most of these are based on natural templates present in virtually all species of life. Indeed, hundreds of polycationic peptides with broad spectra of antimicrobial activity have been isolated from a multitude of organisms, and their roles in preventing the onset of infections have been recognized (2, 13).Pleurocidin, an ␣-helical cationic peptide, is derived from winter flounder (7), and its processing and expression pattern in flounder tissues have recently been described (6, 9). Several variants of the 25-amino-acid pleurocidin and its closest homologues, frog-derived dermaseptin (23) and insect-derived ceratotoxin (19), have been constructed and tested for their antimicrobial activities (15). Of those, pleurocidin amidated at its C terminus (P-CN) and a C-terminally amidated hybrid of pleurocidin and dermaseptin (P-Der) exhibited improved activity against Vibrio anguillarum in vitro (15). In addition, P-CN was shown to protect coho salmon from V. anguillarum infections (15). Also, the activity of pleurocidin against V. anguillarum and Aeromonas salmonicida was shown to be potentiated by salmon histone H1 peptides (26).The major purpose of modifying natural cationic antimicrobial peptides is to increase their antimicrobial effects and decrease their toxicities. To do that in a rational rather than an empirical manner, some understanding of the peptide mode of action and structure-function relationships is required. There are numerous hypotheses to explain the mode of action of these peptides. Cationic peptides are well suited to interaction with bacterial membranes, and many, including peptides like pleurocidin, only fold into their characteristic secondary structures upon insertion into these membranes. However, how this interaction with membranes leads to bacterial cell death is somewhat controversial and indeed may vary from peptide to peptide. Different investigators have proposed destruction of the cytoplasmic membrane permeability barrier, inhibition of cytoplasmic targets, and lysis as pos...

Recent research has identified endogenous cationic antimicrobial peptides as important factors in the innate immunity of many organisms, including fish. It is known that antimicrobial activity, as well as lysozyme activity, can be induced in coho salmon (Oncorhynchus kisutch) mucus after exposure of the fish to infectious agents. Since lysozyme alone does not have antimicrobial activity against Vibrio anguillarum and Aeromonas salmonicida, a four-step protein purification protocol was used to isolate and identify antibacterial fractions from bacterially challenged coho salmon mucus and blood. The purification consisted of extraction with hot acetic acid, extraction and concentration on a C 18 cartridge, gel filtration, and reverse-phase chromatography on a C 18 column. N-terminal amino acid sequence analyses revealed that both the blood and the mucus antimicrobial fractions demonstrated identity with the N terminus of trout H1 histone. Mass spectroscopic analysis indicated the presence of the entire histone, as well as fragments thereof, including a 26-amino-acid N-terminal segment. These fractions inhibited the growth of antibiotic-supersuscptible Salmonella enterica serovar Typhimurium, as well as A. salmonicida and V. anguillarum. Synthetic peptides identical to the N-terminally acetylated or C-terminally amidated 26-amino-acid fragment were inactive in antimicrobial assays, but they potentiated the antimicrobial activities of the flounder peptide pleurocidin, lysozyme, and crude lysozymecontaining extracts from coho salmon. The peptides bound specifically to anionic lipid monolayers. However, synergy with pleurocidin did not appear to occur at the cell membrane level. The synergistic activities of inducible histone peptides indicate that they play an important role in the first line of salmon defenses against infectious pathogens and that while some histone fragments may have direct antimicrobial effects, others improve existing defenses.

En el presente estudio, se propone estimar la probabilidad que tiene una persona en Bogotá de fallecer al contraer el virus SARS-COV-2. Esta probabilidad es estimada a partir de modelos econométricos probabilísticos, para este caso a partir del Modelo Logit. Se proponen diferentes variables sociales y económicas, que pueden incidir de manera directa en las personas que residen en las diferentes localidades de la ciudad. En el estudio se evidencia que la población más afectada y de mayor probabilidad de contagiarse es la de más escasos recursos y que vive en condiciones de vulnerabilidad.