Transport and hydrolysis of antibacterial peptide analogues in Escherichia coli: backbone-modified aminoxy peptides

Aminoxy analogues of di- and tripeptides in which the peptide linkage is replaced by -CO-NHO-, either as an L- or D-2-aminoxypropionic acid (L or D-OAla) residue, have been examined for antibacterial activity in vitro and for uptake into Escherichia coli. Isolation of analogue-resistant mutants and cross-resistance tests with peptide-transport mutants indicate that all three peptide permeases can transport these backbone-modified analogues. A number of mutants with defects in particular intracellular peptidases show decreased sensitivity to a range of these analogues, allowing identification of the enzymes responsible for their cleavage and confirming that hydrolysis is essential for their toxicity. Ala-OAla is a bacteriostatic agent that inhibits nucleic acid and protein synthesis within 1 min of being added to an exponentially growing culture. In crude extracts Ala-OAla inhibits transaminase activity but only after liberation of OAla by endogenous peptidases. These antibacterial agents illustrate an approach to drug targeting in which peptide carriers are used to promote uptake of essentially impermeant toxic moieties.     

Does sociality drive the evolution of communicative complexity? A comparative test with ground-dwelling sciurid alarm calls

While sociality has been hypothesized to drive the evolution of communicative complexity, the relationship remains to be formally tested. We derive a continuous measure of social complexity from demographic data and use this variable to explain variation in alarm repertoire size in ground-dwelling sciurid rodents (marmots, Marmota spp.; prairie dogs, Cynomys spp.; and ground squirrels, Spermophilus spp.). About 40% of the variation in alarm call repertoire size was explained by social complexity in the raw data set. To determine the degree to which this relationship may have been influenced by historical relationships between species, we used five different phylogenetic hypotheses to calculate phylogenetically independent contrasts. Less variation was significantly explained in contrast-based analyses, but a general positive relationship remained. Social complexity explained more variation in alarm call repertoire size in marmots, while sociality explained no variation in repertoire size in prairie dogs and no variation in phylogenetically based analyses of squirrels. In most cases, substantial variation remained unexplained by social complexity. We acknowledge that factors other than social complexity, per se, may contribute to the evolution of alarm call repertoire size in sciurid rodents, and we discuss alternative hypotheses. Our measure of social complexity could be used by other researchers to test explicit evolutionary hypotheses that involve social complexity.     

Population studies of pond zooplankton

Summary Quantitative plankton samples were collected from three small ponds weekly for fourteen weeks during the summer. Seven species of Cladocera and five species of Copepoda were collected. Nine of the species had significant affinities which were formed into one recurrent group and three associated species. The recurrent group of two cladocerans, one calanoid and three cyclopoids resembled the species composition of many small to medium lakes.The members of the recurrent group were sub-divided into filter-feeders and seizers. There were no constant numerical dominance (W) relations among the filter-feeders; W was highly significant for the seizers. There were significant differences in relative abundance for both sub-groups. The test for concordance was insignificant for both sub-groups.The population cycle of each species in each pond is described. Correlation analysis of population units of each species and several environmental factors is presented.Populations of each species found in more than one pond were compared. Population trends were compared by correlation analysis. Few significant correlations were found. Population levels were compared by analysis of variance. Many significant differences were found but the measured environmental data did not explain the differences.The diversity index did not differ significantly among weeks or among ponds. More significant correlations occurred among the species in the recurrent group; the second highest number occurred between associated species and recurrent group species. Few correlations occurred among associated species or among non-associated species or between non-associated species and any other species grouping. The significance of these patterns of diversity and correlations to the idea of a community is discussed.

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Résumé Des échantillons de plancton ont été recueillis chaque semaine de trois petits étangs pendant quatorze semaines de lété. Sept espèces de Cladocères et cinq espèces de Copepodes ont été recueillies. Neuf des espèces avaient des affinités importantes et étaient formées dans un groupe récurrent et trois espèces avaient une association avec le groupe récurrent. Le groupe récurrent, composé de deux Cladocères, un Calanoide, et trois Cyclopoides, ressemblait la composition des espèces trouvées dans des petits lacs ou dans des lacs moyens.Les members du groupe récurrent étaient subdivisés entre des filtreurs et des prédateurs. Entre les filtreurs on ne pouvait pas trouver une domination numérique (W) qui était constante; (W) était vraiment important dans les prédateurs. Il y avait des différences importantes dans l'abondance relative pour les deux sous-groupes. L'épeuve de concordance était significative pour les deux sous-groupes.Le cycle de population de chaque espèce trouvée dans chaque étang est décrit. Les éléments de population de chaque espèce et plusieurs facteurs d'environnement ont été analysés corrélativement et les résultats sont présentés ici. Les populations des espèces trouvées dans plusieurs étangs ont été comparées. Les tendances de population ont été comparées par des analyses de corrélations. Peu de corrélations importantes ont été trouvées. Les hauteurs de population ont été comparées par des analyses de variabilité. Beaucoup de différences significatives ont été trouvées, mais les données d'environnement mesurées n'ont pas expliqué les differences trouvées.L'indice de diversité n'était pas différent d'une manière significative entre les semaines ou entre les étangs. Les corrélations les plus significative ont été trouvées parmi les espèces dans le groupe récurrent; le deuxième nombre de corrélations significatives le plus haut se présentait entre les espèces ayant une affinité et les espèces du groupe récurrent. Peu de corrélations ont été trouvé parmi les espèces ayant une affinité ou parmi les espèces n'ayant aucune affinité ou entre les espèces n'ayant aucune affinité et d'autres groupes d'espèces. La signification de ces modèles de diversités et de la corrélation à l'idée d'une communauté est discutée.

     

Population dynamics of pond zooplankton,I. Diaptomus pallidus Herrick

The simultaneous and lag relationships between 27 environmental variables and seven population components of a perennial calanoid copepod were examined by simple and partial correlations and stepwise regression. The analyses consistently explained more than 70% of the variation of a population component. The multiple correlation coefficient (R) usually was highest in no lag or in 3-week or 4-week lag except for clutch size in which R was highest in 1-week lag. Population control, egg-bearing, and clutch size were affected primarily by environmental components categorized as weather; food apparently was relatively minor in affecting population control or reproduction.     

Repercussions of the COVID-19 pandemic on athletes: a cross-sectional study

The COVID-19 pandemic has presented significant challenges and implications for the sports community. Thus, this study aimed to describe the prevalence of COVID-19 in Brazilian athletes and identify the epidemiological, clinical, athletic, life and health factors associated with the disease in these individuals. A cross-sectional study was performed involving 414 athletes from 22 different sports using an online questionnaire from August to November 2020. The association between the athletes’ characteristics and COVID-19 was evaluated using a logistic regression model. The prevalence of COVID-19 was 8.5%, although only 40% of athletes reported having been tested. Being under 27 years of age (3-fold), having children (~5-fold), having a teammate test positive for COVID-19 (2.5-fold), and smoking (14-fold) were associated with a possible higher risk of disease. Almost 20% of athletes self-reported musculoskeletal injuries during the period of the pandemic that was studied. Athletes with a university education (P = 0.02), a profession other than sports (P < 0.001), those from a low-income family (P = 0.01), and public health system users (P = 0.04) were significantly less frequently tested for COVID-19, whereas international competitors, athletes who received a wage, and athletes who had a teammate who tested positive for COVID-19 were 2-, 3-, and 15-fold more likely to be tested for COVID-19, respectively. Approximately 26% of the athletes who tested negative or were untested reported more than three characteristic COVID-19 symptoms, and 11% of athletes who tested positive for COVID-19 were asymptomatic. The identification of modifiable (have children, smoking, and teammates positively tested) and non-modifiable (age under 27 years) factors related to COVID-19 in athletes can contribute to implementing surveillance programmes to decrease the incidence of COVID-19 in athletes and its negative impacts in sports.