Ammonia fiber expansion (AFEX) treatment of eleven different forages: Improvements to fiber digestibility in vitro

With the increased attention to bioenergy and especially cellulosic ethanol, there are concerns regarding potential competition for available land between biofuels and feeds/foods. Ammonia fiber expansion (AFEX), a pretreatment process for cellulosic ethanol, may also be used to improve ruminant digestibility of feedstuffs not traditionally used as forages. Eleven forages – including traditional forages, agricultural residues, and dedicated energy crops – were AFEX treated and digested in vitro with rumen inoculum. AFEX treatment improved 48-h neutral detergent fiber (aNDFom) digestion for several moderately indigestible forages compared to untreated samples, but showed no improvement for highly digestible samples. Of particular interest are corn stover and late-harvest switchgrass, as AFEX treatment improved digestibility by 52% and 128% over untreated material, whereas the improvement was 74% and 70% over conventional ammonia treatment, respectively. The crude protein content of all treated samples increased to more than 100 g/kg dry forage. This research strongly suggests that AFEX-treated feedstuffs can be competitive with traditional forages, and thus offer expanded options for ruminant feeding.     

Uterine growth responses of the mature castrate rat to estradiol-17B

To examine estrogen-stimulated uterine growth we have monitored changes in uterine DNA synthesis, ornithine decarboxylase (ODC) activity and protein content as well as luminal epithelial (LE) cell mitotic index and ultrastructural changes. We have utilized this model to examine castrate mature rat uterine growth as a function of time between 18 and 40 hours following a single injection of 25.0 ug of estradiol-17B. LE cell mitotic index and protein content increases were maximally elevated as early as 18 hours postinjection while uterine ODC activity was maximal at 28 hours; uterine DNA synthesis increases continued throughout the experiment. In addition, the infusion of either 1 or 2 ug E2 plus progesterone over a 24 hour period, stimulated elevated ODC activity under both treatment regimens and LE cell mitotic index which was inversely related to E2 dose.     

Development of a Förster resonance energy transfer assay for monitoring bacterial collagenase triple-helical peptidase activity

Due to their efficiency in the hydrolysis of the collagen triple helix, Clostridium histolyticum collagenases are used for isolation of cells from various tissues, including isolation of the human pancreatic islets. However, the instability of clostridial collagenase I (Col G) results in a degraded Col G that has weak collagenolytic activity and an adverse effect on islet isolation and viability. A Förster resonance energy transfer triple-helical peptide substrate (fTHP) has been developed for selective evaluation of bacterial collagenase activity. The fTHP [sequence: Gly-mep-Flp-(Gly-Pro-Hyp)₄-Gly-Lys(Mca)-Thr-Gly-Pro-Leu-Gly-Pro-Pro-Gly-Lys(Dnp)-Ser-(Gly-Pro-Hyp)₄-NH₂] had a melting temperature (T_m) of 36.2 °C and was hydrolyzed efficiently by bacterial collagenase (k_cat/K_M = 25,000 s⁻¹ M⁻¹) but not by clostripain, trypsin, neutral protease, thermolysin, or elastase. The fTHP bacterial collagenase assay allows for rapid and specific assessment of enzyme activity toward triple helices and, thus, potential application for evaluating the efficiency of cell isolation by collagenases.     

Local environment and density-dependent feedbacks determine population growth in a forest herb

Linking spatial variation in environmental factors to variation in demographic rates is essential for a mechanistic understanding of the dynamics of populations. However, we still know relatively little about such links, partly because feedbacks via intraspecific density make them difficult to observe in natural populations. We conducted a detailed field study and investigated simultaneous effects of environmental factors and the intraspecific density of individuals on the demography of the herb Lathyrus vernus. In regression models of vital rates we identified effects associated with spring shade on survival and growth, while density was negatively correlated with these vital rates. Density was also negatively correlated with average individual size in the study plots, which is consistent with self-thinning. In addition, average plant sizes were larger than predicted by density in plots that were less shaded by the tree canopy, indicating an environmentally determined carrying capacity. A size-structured integral projection model based on the vital rate regressions revealed that the identified effects of shade and density were strong enough to produce differences in stable population sizes similar to those observed in the field. The results illustrate how the local environment can determine dynamics of populations and that intraspecific density may have to be more carefully considered in studies of plant demography and population viability analyses of threatened species. We conclude that demographic approaches incorporating information about both density and key environmental factors are powerful tools for understanding the processes that interact to determine population dynamics and abundances.     

Impaired neutrophil extracellular trap formation: a novel defect in the innate immune system of aged individuals

Neutrophil extracellular traps (NETs) are a recently discovered addition to the defensive armamentarium of neutrophils, assisting in the immune response against rapidly dividing bacteria. Although older adults are more susceptible to such infections, no study has examined whether aging in humans influences NET formation. We report that TNF‐α‐primed neutrophils generate significantly more NETs than unprimed neutrophils and that lipopolysaccharide (LPS)‐ and interleukin‐8 (IL‐8)‐induced NET formation exhibits a significant age‐related decline. NET formation requires generation of reactive oxygen species (ROS), and this was also reduced in neutrophils from older donors identifying a mechanism for reduced NET formation. Expression of IL‐8 receptors (CXCR1 and CXCR2) and the LPS receptor TLR4 was similar on neutrophils from young and old subjects, and neutrophils challenged with phorbol‐12‐myristate‐13‐acetate (PMA) showed no age‐associated differences in ROS or NET production. Taken together, these data suggest a defect in proximal signalling underlies the age‐related decline in NET and ROS generation. TNF‐α priming involves signalling through p38 MAP kinase, but activation kinetics were comparable in neutrophils from young and old donors. In a clinical setting, we assessed the capacity of neutrophils from young and older patients with chronic periodontitis to generate NETs in response to PMA and hypochlorous acid (HOCL). Neutrophil extracellular trap generation to HOCL, but not PMA, was lower in older periodontitis patients but not in comparison with age‐matched controls. Impaired NET formation is thus a novel defect of innate immunity in older adults but does not appear to contribute to the increased incidence of periodontitis in older adults.     

Temporal variability in nutrient use among Streptomyces suggests dynamic niche partitioning

Soil bacteria spend significant periods in dormant or semi-dormant states that are interrupted by resource pulses which can lead to periods of rapid growth and intense nutrient competition. Microbial populations have evolved diverse strategies to circumvent competitive interactions and facilitate coexistence. Here, we show that nutrient use of soilborne Streptomyces is temporally partitioned during experimental resource pulses, leading to reduced niche overlap, and potential coexistence. Streptomyces grew rapidly on the majority of distinct 95 carbon sources but varied in which individual resources were utilized in the first 24 h. Only a handful of carbon sources (19 out of 95) were consistently utilized (>95% of isolates) most rapidly in the first 24 h. These consistently utilized carbon sources also generated the majority of biomass accumulated by isolates. Our results shed new light on a novel mechanism microbes may employ to alleviate competitive interactions by temporally partitioning the consumption of carbon resources. As competitive interactions have been proposed to drive the suppression of disease-causing microbes in agronomic soils, our findings may hold widespread implications for soil management for plant health.     

Measuring Home-Range Changes Following Density Reduction of Australian Brushtail Possum

It is not clear whether animals consistently change their home ranges in response to density reduction. This is important to understand for better management of pest species where sustained control is required. Our objective was to measure whether home ranges of Australian brushtail possums (Trichosurus vulpecula) change following density reduction, using global positioning system (GPS) tracking. We experimentally reduced the densities of 2 populations (1 high-density at 7 possums/ha and 1 low-density at 1.5 possums/ha) and did not manipulate another population. We then monitored home ranges of individual possums. The high-density manipulated population had a significant increase in home-range size and overlap within 5 weeks following reduction, whereas the other 2 populations did not. This research suggests that changes in possum home ranges following control are likely influenced by the initial density of the pest population. © 2019 The Wildlife Society.     

Respiratory supercomplexes enhance electron transport by decreasing cytochrome c diffusion distance

Respiratory chains are crucial for cellular energy conversion and consist of multi‐subunit complexes that can assemble into supercomplexes. These structures have been intensively characterized in various organisms, but their physiological roles remain unclear. Here, we elucidate their function by leveraging a high‐resolution structural model of yeast respiratory supercomplexes that allowed us to inhibit supercomplex formation by mutation of key residues in the interaction interface. Analyses of a mutant defective in supercomplex formation, which still contains fully functional individual complexes, show that the lack of supercomplex assembly delays the diffusion of cytochrome c between the separated complexes, thus reducing electron transfer efficiency. Consequently, competitive cellular fitness is severely reduced in the absence of supercomplex formation and can be restored by overexpression of cytochrome c. In sum, our results establish how respiratory supercomplexes increase the efficiency of cellular energy conversion, thereby providing an evolutionary advantage for aerobic organisms.     

Avian IgY binds to a monocyte receptor with IgG-like kinetics despite an IgE-like structure

An ancestor of avian IgY was the evolutionary precursor of mammalian IgG and IgE, and present day chicken IgY performs the function of human IgG despite having the domain structure of human IgE. The kinetics of IgY binding to its receptor on a chicken monocyte cell line, MQ-NCSU, were measured, the first time that the binding of a non-mammalian antibody to a non-mammalian cell has been investigated (k(+1) = 1.14 +/- 0.46 x 10(5) mol(-1)sec(-1), k(-1) = 2.30 +/- 0.14 x 10(-3) s(-1), and K(a) = 4.95 x 10(7) m(-1)). This is a lower affinity than that recorded for mammalian IgE-high affinity receptor interactions (Ka approximately 10(10) m(-1)) but is within the range of mammalian IgG-high affinity receptor interactions (human: Ka approximately 10(8)-10(9) m(-1) mouse: Ka approximately 10(7)-10(8) m(-1). IgE has an extra pair of immunoglobulin domains when compared with IgG. Their presence reduces the dissociation rate of IgE from its receptor 20-fold, thus contributing to the high affinity of IgE. To assess the effect of the equivalent domains on the kinetics of IgY binding, IgY-Fc fragments with and without this domain were cloned and expressed in mammalian cells. In contrast to IgE, their presence in IgY has little effect on the association rate and no effect on dissociation. Whatever the function of this extra domain pair in avian IgY, it has persisted for at least 310 million years and has been co-opted in mammalian IgE to generate a uniquely slow dissociation rate and high affinity.     

Targeting of hFis1 to peroxisomes is mediated by Pex19p

The processes of peroxisome formation and proliferation are still a matter of debate. We have previously shown that peroxisomes share some components of their division machinery with mitochondria. hFis1, a tail-anchored membrane protein, regulates the membrane fission of both organelles by DLP1/Drp1 recruitment, but nothing is known about the mechanisms of the dual targeting of hFis1. Here we demonstrate for the first time that peroxisomal targeting of hFis1 depends on Pex19p, a peroxisomal membrane protein import factor. hFis1/Pex19p binding was demonstrated by expression and co-immunoprecipitation studies. Using mutated versions of hFis1 an essential binding region for Pex19p was located within the last 26 C-terminal amino acids of hFis1, which are required for proper targeting to both mitochondria and peroxisomes. The basic amino acids in the very C terminus are not essential for Pex19p binding and peroxisomal targeting, but are instead required for mitochondrial targeting. Silencing of Pex19p by small interference RNA reduced the targeting of hFis1 to peroxisomes, but not to mitochondria. In contrast, overexpression of Pex19p alone was not sufficient to shift the targeting of hFis1 to peroxisomes. Our findings indicate that targeting of hFis1 to peroxisomes and mitochondria are independent events and support a direct, Pex19p-dependent targeting of peroxisomal tail-anchored proteins.