Mannitol Does Not Enhance Tobramycin Killing of Pseudomonas aeruginosa in a Cystic Fibrosis Model System of Biofilm Formation

Cystic Fibrosis (CF) is a human genetic disease that results in the accumulation of thick, sticky mucus in the airways, which results in chronic, life-long bacterial biofilm infections that are difficult to clear with antibiotics. Pseudomonas aeruginosa lung infection is correlated with worsening lung disease and P. aeruginosa transitions to an antibiotic tolerant state during chronic infections. Tobramycin is an aminoglycoside currently used to combat lung infections in individuals with CF. While tobramycin is effective at eradicating P. aeruginosa in the airways of young patients, it is unable to completely clear the chronic P. aeruginosa infections in older patients. A recent report showed that co-addition of tobramycin and mannitol enhanced killing of P. aeruginosa grown in vitro as a biofilm on an abiotic surface. Here we employed a model system of bacterial biofilms formed on the surface of CF-derived airway cells to determine if mannitol would enhance the antibacterial activity of tobramycin against P. aeruginosa grown on a more clinically relevant surface. Using this model system, which allows the growth of robust biofilms with high-level antibiotic tolerance analogous to in vivo biofilms, we were unable to find evidence for enhanced antibacterial activity of tobramycin with the addition of mannitol, supporting the observation that this type of co-treatment failed to reduce the P. aeruginosa bacterial load in a clinical setting.     

Tissue-Specific Contributions of Paternally Expressed Gene 3 in Lactation and Maternal Care of Mus musculus

Paternally Expressed Gene 3 (Peg3) is an imprinted gene that controls milk letdown and maternal-caring behaviors. In this study, a conditional knockout allele has been developed in Mus musculus to further characterize these known functions of Peg3 in a tissue-specific manner. The mutant line was first crossed with a germline Cre. The progeny of this cross displayed growth retardation phenotypes. This is consistent with those seen in the previous mutant lines of Peg3, confirming the usefulness of the new mutant allele. The mutant line was subsequently crossed individually with MMTV- and Nkx2.1-Cre lines to test Peg3’s roles in the mammary gland and hypothalamus, respectively. According to the results, the milk letdown process was impaired in the nursing females with the Peg3 mutation in the mammary gland, but not in the hypothalamus. This suggests that Peg3’s roles in the milk letdown process are more critical in the mammary gland than in the hypothalamus. In contrast, one of the maternal-caring behaviors, nest-building, was interrupted in the females with the mutation in both MMTV- and Nkx2.1-driven lines. Overall, this is the first study to introduce a conditional knockout allele of Peg3 and to further dissect its contribution to mammalian reproduction in a tissue-specific manner.     

Better to Be in Bad Company than to Be Alone? Aedes Vectors Respond Differently to Breeding Site Quality in the Presence of Others

This study focuses on two competing species, Aedes aegypti and Aedes albopictus (Diptera: Culicidae), both invasive mosquitoes of the New World. Context-specific competition between immature forms inside containers seems to be an important determinant of the coexistence or displacement of each species in different regions of the world. Here, competition experiments developed at low density (one, two or three larvae) and receiving four different resource food concentration, were designed to test whether Ae. albopictus and Ae. aegypti respond differently to competition, and whether competition can be attributed to a simple division of resources. Three phenotypic traits - larval development, adult survival under starvation and wing length - were used as indicators of performance. Larvae of neither species were limited by resource concentration when they were alone, unlike when they developed with competitors. The presence of conspecifics affected Ae. aegypti and Ae. albopictus, inducing slower development, reduced survival and wing length. The response to resource limitation was different when developing with heterospecifics: Ae. aegypti developing with one heterospecific showed faster development, producing smaller adults with shorter lives, while in the presence of two competitors, development increased and adults lived longer. Aedes albopictus demonstrated a better performance when developing with heterospecifics, with no loss in their development period and improved adult survival. Overall, our results suggest that response to competition can not simply be attributed to the division of resources, and that larvae of both species presented large phenotypic plasticity in their response to the presence or absence of heterospecifics and conspecifics.     

Effect of medicating ingredients and other additives on microflora present on swine and chicken feeds from a Manitoba mill

The occurrence of microfloral components on medicated and non-medicated swine and chicken feed pellets and crumbles, produced in a Manitoba feed mill between June 1991 and October 1992, was determined. Addition of medicates to feeds generally decreased bacterial incidence and increased that of Eurotium spp. fungi. The effect was less pronounced when copper sulphate was added to medicated swine feeds.Contribution No. 1662.     

IL-2 secretion is pertussis toxin sensitive in a T lymphocyte hybridoma

Interaction of specific ligands with TCR initiates a cascade of biochemical events which leads to expression of high affinity IL-2R and subsequent IL-2 secretion. Activation of phospholipase C (PL-C) is considered to be a key event in the initiation of this cascade. However, in addition to this PL-C-dependent pathway, PL-C-independent pathways have been hypothesized. Identification of the steps constituting these PL-C-independent pathways has been difficult because activation of PL-C and the subsequent cascade of events mask the effects of such pathways. Specific inhibitors for PL-C, or mutants defective in, the PL-C pathway would facilitate delineation of alternative activation pathways. We have identified a murine pork insulin/IAd-specific T cell hybridoma, B8P3.11, in which perturbation of the B8P3.11 TCR by either Ag in association with Ia, anti-CD3 antibodies, or a mitogenic lectin does not induce increases in myo-inositol 1,4,5-triphosphate production or cytosolic free calcium, yet it does lead to IL-2 secretion. Treatment of B8P3.11 with pertussis toxin, at concentrations which ADP-ribosylate GTP-binding proteins, inhibits IL-2 secretion. Thus, signal transduction resulting in IL-2 secretion by B8P3.11 likely involves a G protein. In contrast, TCR/ligand interaction activates the PL-C-dependent pathway in LBRM 331A5, a T cell lymphoma. Furthermore, pertussis toxin treatment, which blocks IL-2 secretion by B8P3.11, does not alter IL-2 secretion by LBRM 331A5. However, similar pertussis toxin substrates are present in both cells. Therefore, B8P3.11 T cells should help to elucidate PL-C-independent activation pathways.     

Genome-wide CRISPR Screens Reveal Host Factors Critical for SARS-CoV-2 Infection

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BET inhibition blocks inflammation-induced cardiac dysfunction and SARS-CoV-2 infection

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