Free Edges in Epithelial Cell Sheets Stimulate Epidermal Growth Factor Receptor Signaling

The ability of epithelia to migrate and cover wounds is essential to maintaining their functions as physical barriers. Wounding induces many cues that may affect the transition to motility, including the immediate mechanical perturbation, release of material from broken cells, new interactions with adjacent extracellular matrix, and breakdown of physical separation of ligands from their receptors. Depending on the exact nature of wounds, some cues may be present only transiently or insignificantly. In many epithelia, activation of the epidermal growth factor receptor (EGFR) is a central event in induction of motility, and we find that its continuous activation is required for progression of healing of wounds in sheets of corneal epithelial cells. Here, we examine the hypothesis that edges, which are universally and continuously present in wounds, are a cue. Using a novel culture model we find that their presence is sufficient to cause activation of the EGFR and increased motility of cells in the absence of other cues. Edges that are bordered by agarose do not induce activation of the EGFR, indicating that activation is not due to loss of any specific type of cell–cell interaction but rather due to loss of physical constraints.     

Guidelines for the Control of Human Immunodeficiency Virus Infection in Adolescents

Although adolescents account for only 0.4% of reported cases of the acquired immunodeficiency syndrome (AIDS) in the United States, they are sexually active and, therefore, at risk of acquiring human immunodeficiency virus (HIV) infection. To address issues of HIV control in adolescents, we developed guidelines that emphasize education and medical care and deemphasize antibody testing. For adolescents known to be infected with HIV, we recommend no restrictions on access to educational or treatment programs except when their health providers recommend such restrictions to protect them from exposure to opportunistic infections. For adolescents of unknown antibody status with a possible previous exposure to HIV, we recommend that as long as the incidence of HIV infection and clinical AIDS remains low, there should be no restrictions on residential placements and no routine antibody testing.     

Partial purification and characterization of a new phosphoprotein kinase from cells infected with pseudorabies virus

Cytoplasmic fractions from normal baby hamster kidney fibroblasts and from fibroblasts infected with pseudorabies virus were fractionated by DEAE-cellulose chromatography and fractions assayed for protein kinase activity. In preparations from uninfected and infected cells protein kinase activities identified as casein kinase I and II, the two isoforms of the cyclic-AMP-dependent protein kinase, protein kinase C, and a presumed proteolytic fragment of protein kinase C were present in comparable amounts. However in infected cells a new protein kinase activity was detected, appearing about 4 h after infection and increasing during the following 6 h at least. This new protein kinase was purified 100-fold by high-performance gel-permeation and ion-exchange chromatography, and characterized. It has an apparent relative molecular mass of 68 000 on the basis of gel-permeation chromatography, and a sedimentation coefficient of 4.3 S. It catalysed the phosphorylation of serine residues of basic proteins in vitro, with protamine a better substrate than mixed histones; and used ATP (apparent Km = 60 microM), but not GTP, as phosphoryl donor. Molecules that can serve as effectors for other protein kinases (cyclic AMP, cyclic GMP, Ca2+ + calmodulin, Ca2+ + phospholipid, double-stranded RNA, and heparin) did not significantly alter the activity of this enzyme. A distinguishing characteristic of the protein kinase was a high KCl concentration optimum with the persistence of activity up to 800 mM KCl, at least.     

Root traits of perennial C4 grasses contribute to cultivar variations in soil chemistry and species patterns in particulate and mineral-associated carbon pool formation

Recent studies have indicated that the C₄ perennial bioenergy crops switchgrass (Panicum virgatum) and big bluestem (Andropogon gerardii) accumulate significant amounts of soil carbon (C) owing to their extensive root systems. Soil C accumulation is likely driven by inter- and intraspecific variability in plant traits, but the mechanisms that underpin this variability remain unresolved. In this study we evaluated how inter- and intraspecific variation in root traits of cultivars from switchgrass (Cave-in-Rock, Kanlow, Southlow) and big bluestem (Bonanza, Southlow, Suther) affected the associations of soil C accumulation across soil fractions using stable isotope techniques. Our experimental field site was established in June 2008 at Fermilab in Batavia, IL. In 2018, soil cores were collected (30 cm depth) from all cultivars. We measured root biomass, root diameter, specific root length, bulk soil C, C associated with coarse particulate organic matter (CPOM) and fine particulate organic matter plus silt- and clay-sized fractions, and characterized organic matter chemical class composition in soil using high-resolution Fourier-transform ion cyclotron resonance mass spectrometry. C₄ species were established on soils that supported C₃ grassland for 36 years before planting, which allowed us to use differences in the natural abundance of stable C isotopes to quantify C₄ plant-derived C. We found that big bluestem had 36.9% higher C₄ plant-derived C compared to switchgrass in the CPOM fraction in the 0–10 cm depth, while switchgrass had 60.7% higher C₄ plant-derived C compared to big bluestem in the clay fraction in the 10–20 cm depth. Our findings suggest that the large root system in big bluestem helps increase POM-C formation quickly, while switchgrass root structure and chemistry build a mineral-bound clay C pool through time. Thus, both species and cultivar selection can help improve bioenergy management to maximize soil carbon gains and lower CO₂ emissions.     

Inverted repetition in the chromosome of pseudorabies virus.

An electron microscope examination of pseudorabies virus DNA single strands after self-annealing shows a loop of single-stranded DNA at one end of the molecule contiguous to a double-strand region. The molecule then terminates in a further single-stranded region that does not form a loop. It is suggested that the DNA contains a sequence of 13.3 x 106 daltons at one end, which is repeated internally with opposite polarity. The segment of the genome separating the repeats has a double-strand molecular weight of 5.4 x 106. The whole native DNA has a molecular weight of 90 x 106 to 95 x 106.     

Utilization of Xylan by Two Species of Human Colonic Bacteroides

During growth of two strains of human colonic Bacteroides on xylan, several oligomers, the smallest of which was xylobiose, were released into the medium.     

Effects of Cortisol and Dexamethasone on Insulin Signalling Pathways in Skeletal Muscle of the Ovine Fetus during Late Gestation

Before birth, glucocorticoids retard growth, although the extent to which this is mediated by changes in insulin signalling pathways in the skeletal muscle of the fetus is unknown. The current study determined the effects of endogenous and synthetic glucocorticoid exposure on insulin signalling proteins in skeletal muscle of fetal sheep during late gestation. Experimental manipulation of fetal plasma glucocorticoid concentration was achieved by fetal cortisol infusion and maternal dexamethasone treatment. Cortisol infusion significantly increased muscle protein levels of Akt2 and phosphorylated Akt at Ser473, and decreased protein levels of phosphorylated forms of mTOR at Ser2448 and S6K at Thr389. Muscle GLUT4 protein expression was significantly higher in fetuses whose mothers were treated with dexamethasone compared to those treated with saline. There were no significant effects of glucocorticoid exposure on muscle protein abundance of IR-β, IGF-1R, PKCζ, Akt1, calpastatin or muscle glycogen content. The present study demonstrated that components of the insulin signalling pathway in skeletal muscle of the ovine fetus are influenced differentially by naturally occurring and synthetic glucocorticoids. These findings may provide a mechanism by which elevated concentrations of endogenous glucocorticoids retard fetal growth.