Autoregulatory Properties of (+)-Thujopsene and Influence of Environmental Conditions on Its Production by <Emphasis Type="Italic">Penicillium decumbens</Emphasis>

A Penicillium decumbens strain was collected from a water-damaged building, and the production of microbial volatile organic compounds (MVOCs) was investigated by means of headspace solid-phase microextraction, followed by GC-MS analysis. The strain was characterized by a high production of (+)-thujopsene. The influence of various temperatures, relative humidity (RH) values, substrates, and inoculum concentrations on fungal growth and (+)-thujopsene production was studied. The optimal temperature and relative humidity for P. decumbens growth were 30°C and 100% RH, respectively. In general, the more favourable the incubation parameters were for growth, the faster maximum (+)-thujopsene production was reached. Moreover, the antifungal activity of thujopsene was tested against 16 fungal strains. The growth of five of these fungal strains was negatively affected both by thujopsene alone and when grown in contact with the MVOCs produced by P. decumbens. Following these results and since growth of P. decumbens itself was also inhibited by thujopsene, an autoregulatory function for this compound was proposed. Few data are present in the literature about chemical communication between fungi. The present research could, therefore, contribute to understanding fungal metabolism and behaviour in indoor environments.     

Evidence that Polymyxa species may infect Arabidopsis thaliana

Polymyxa spp. are obligate biotrophs belonging to the plasmodiophorid group, responsible for transmitting a large number of plant viruses to many crop species. Their obligate nature makes them difficult to study. Controlled environment experiments were used to investigate the potential of infection of Arabidopsis thaliana by Polymyxa spp. to provide a more tractable system. Two ecotypes of Arabidopsis, Columbia and Landsberg erecta, were grown in soils known to be infested with Polymyxa. At the end of a 2-month growth period, both ecotypes were found to harbour Polymyxa-like structures or spores. These findings were confirmed by Polymyxa-specific PCR tests and rDNA sequencing, which positively identified the presence of Polymyxa in the roots of both ecotypes of Arabidopsis. Both Polymyxa graminis and Polymyxa betae were identified. This is the first report of infection of Arabidopsis by Polymyxa spp. and shows the possibility of using this system for studies of infection biology and host-parasite interactions.     

Salmonid biomass and habitat relationships for small lakes

Lake morphometry and water chemistry were analyzed as predictors of brook trout and total salmonid biomass (brook trout, Atlantic salmon and Arctic char) in water bodies of Newfoundland. Lake morphometric variables included surface area, depth, perimeter and catchment area while water chemistry variables included conductivity/TDS and total Phosphorus. The broadly used Morpho-Edaphic Index was also assessed. Fish biomass/ha varied by an order of magnitude in the study lakes, despite similar water chemistry. Interactive stepwise multiple regression analysis suggested that Basin Permanence Index best explains brook trout biomass while surface area best explains the variance of total salmonid biomass in the relatively small, unproductive water bodies of Insular Newfoundland. In contrast, the Morphoedaphic Index performed poorly. The results suggest that biomass relationships with easily measured habitat variables such as surface area provide useful information, especially in management of water bodies under similar climate and nutrient regimes.     

The interaction between endothelin-1 and nitric oxide in the vasculature: new perspectives

Nitric oxide (NO) and endothelin-1 (ET-1) are natural counterparts in vascular function, and it is becoming increasingly clear that an imbalance between these two mediators is a characteristic of endothelial dysfunction and is important in the progression of vascular disease. Here, we review classical and more recent data that suggest that ET-1 should be regarded as an essential component of NO signaling. In particular, we review evidence of the role of ET-1 in models of acute and chronic NO synthase blockade. Furthermore, we discuss the possible mechanisms by which NO modulates ET-1 activity. On the basis of these studies, we suggest that NO tonically inhibits ET-1 function, and in conditions of diminished NO bioavailability, the deleterious effects of unmitigated ET-1 actions result in vasoconstriction and eventually lead to vascular remodeling and dysfunction.     

ACAP4 protein cooperates with Grb2 protein to orchestrate epidermal growth factor-stimulated integrin β1 recycling in cell migration

ARF6 GTPase is an important regulator of membrane trafficking and actin-based cytoskeleton dynamics active at the leading edge of migrating cells. The integrin family heterodimeric transmembrane proteins serve as major receptors for extracellular matrix proteins, which play essential roles in cell adhesion and migration. Our recent proteomic analyses of ARF6 effectors have identified a novel ARF6 GTPase-activating protein, ACAP4, essential for EGF-induced cell migration. However, molecular mechanisms underlying ACAP4-mediated cell migration have remained elusive. Here, we show that ACAP4 regulates integrin β1 dynamics during EGF-stimulated cell migration by interaction with Grb2. Our biochemical study shows that EGF stimulation induces phosphorylation of tyrosine 733, which enables ACAP4 to bind Grb2. This interaction of ACAP4 with Grb2 regulates integrin β1 recycling to the plasma membrane. Importantly, knockdown of ACAP4 by siRNA or overexpression of ACAP4 decreased recycling of integrin β1 to the plasma membrane and reduced integrin-mediated cell migration. Taken together, these results suggest a novel function for ACAP4 in the regulation of cell migration through controlling integrin β1 dynamics.     

Natural but not inducible regulatory T cells require TNF-alpha signaling for in vivo function

TNF-α has a multifunctional role in autoimmune diseases as reflected in the variable responses of different human diseases to anti-TNF-α therapy. Recent studies have suggested that TNF-α modulates autoimmunity partially via effects on regulatory T cells (Tregs) and that these effects are mediated through the type II TNFR (TNFR2). We have investigated the requirement for TNFR2-expression on murine natural Tregs (nTregs) and induced Tregs (iTregs) in mediating suppression of colitis. Surprisingly, we find that TNFR2-expression is required for both spleen- and thymus-derived nTreg-mediated suppression, but is not required for iTreg-mediated suppression. Abnormal TNFR2(-/-) nTreg function was not associated with an in vivo decrease in accumulation, stability, or expression of markers known to be relevant in Treg function. Because iTregs are generated in the presence of TGF-β, we investigated whether activation in the presence of TGF-β could overcome the functional defect in TNFR2(-/-) nTregs. Although preactivation alone did not restore suppressive function of nTregs, preactivation in the presence of TGF-β did. These results identify potentially critical differences in activation requirements for nTregs versus iTregs. Furthermore, our findings are consistent with reports suggesting that nTregs are activated in sites of inflammation while iTregs are activated in lymph nodes. Finally, by demonstrating that nTregs require TNF-α for optimal function whereas iTregs do not, our results suggest that the enigma of variable responses of different human diseases to anti-TNF-α therapy may relate to whether nTregs or iTregs have the predominant regulatory role in a given disease.     

The link between the PDL1 costimulatory pathway and Th17 in fetomaternal tolerance

Fetomaternal tolerance has been shown to depend both on regulatory T cells (Tregs) and negative signals from the PD1-PDL1 costimulatory pathway. More recently, IL-17-producing T cells (Th17) have been recognized as a barrier in inducing tolerance in transplantation. In this study, we investigate the mechanisms of PDL1-mediated regulation of fetomaternal tolerance using an alloantigen-specific CD4(+) TCR transgenic mouse model system (ABM-tg mouse). PDL1 blockade led to an increase in embryo resorption and a reduction in litter size. This was associated with a decrease in Tregs, leading to a lower Treg/effector T cell ratio. Moreover, PDL1 blockade inhibited Ag-specific alloreactive T cell apoptosis and induced apoptosis of Tregs and a shift toward higher frequency of Th17 cells, breaking fetomaternal tolerance. These Th17 cells arose predominantly from CD4(+)Foxp3(-) cells, rather than from conversion of Tregs. Locally in the placenta, similar decrease in regulatory and apoptotic markers was observed by real-time PCR. Neutralization of IL-17 abrogated the anti-PDL1 effect on fetal survival rate and restored Treg numbers. Finally, the adoptive transfer of Tregs was also able to improve fetal survival in the setting of PDL1 blockade. This is to our knowledge the first report using an alloantigen-specific model that establishes a link between PDL1, Th17 cells, and fetomaternal tolerance.     

Analysis of intrahost variation in Venezuelan equine encephalitis virus reveals repeated deletions in the 6-kilodalton protein gene

RNA viruses exist as a spectrum of mutants that is generated and maintained during replication within the host. Consensus sequencing overlooks minority genotypes present in the viral sample that may impact the population's phenotype. In-depth sequencing of an original field isolate of subtype IE Venezuelan equine encephalitis virus (VEEV) demonstrated the presence of multiple deletions within the 6,000-molecular-weight (6K) protein gene. Using in vitro and in vivo experiments, similar deletions were generated in an additional VEEV strain originating from an infectious cDNA clone. Time course experiments demonstrated that the deletions are produced during acute infection although not until 24 h postinfection. Molecular clones containing some of these deletions were generated, and although the larger deletions appear to be noninfectious, viruses with the smaller deletions were viable and formed small plaques. Serial passages provided no evidence that these deletion mutants function as defective interfering particles. Furthermore, since wild-type infections generally occur at a low multiplicity of infection, it is unlikely that these deletions are propagated in natural transmission cycles. However, they could affect pathogenesis at later stages of infection. Because they are ubiquitously generated both in vivo and in vitro, further investigation is warranted to understand the generation of these deletions and their significance for disease.     

An isotopic approach to measuring nitrogen balance in caribou

Nutritional restrictions in winter may reduce the availability of protein for reproduction and survival in northern ungulates. We refined a technique that uses recently voided excreta on snow to assess protein status in wild caribou (Rangifer tarandus) in late winter. Our study was the first application of this non-invasive, isotopic approach to assess protein status of wild caribou by determining dietary and endogenous contributions of nitrogen (N) to urinary urea. We used isotopic ratios of N (δ¹⁵N) in urine and fecal samples to estimate the proportion of urea N derived from body N (p-UN) in pregnant, adult females of the Chisana Herd, a small population that ranged across the Alaska-Yukon border. We took advantage of a predator-exclosure project to examine N status of penned caribou in April 2006. Lichens were the primary forage (>40%) consumed by caribou in the pen and δ¹⁵N of fiber tracked the major forages in their diets. The δ¹⁵N of urinary urea for females in the pen was depleted relative (−1.3 ± 1.0 parts per thousand [‰], ) to the δ¹⁵N of body N (2.7 ± 0.7‰). A similar proportion of animals in the exclosure lost core body mass (excluding estimates of fetal and uterine tissues; 55%) and body protein (estimated by isotope ratios; 54%). This non-invasive technique could be applied at various spatial and temporal scales to assess trends in protein status of free-ranging populations of northern ungulates. Intra- and inter-annual estimates of protein status could help managers monitor effects of foraging conditions on nutritional constraints in ungulates, increase the efficiency and efficacy of management actions, and help prepare stakeholders for potential changes in population trends. © 2010 The Wildlife Society.