Population biology of the intertidal kelp, Alaria marginata Postels and Ruprecht: A non-fugitive annual

Persistence of annual plant populations requires sufficient seeds and suitable habitat for development and growth each year. Competition with perennials may prevent within site persistence and result in “fugitive” annual populations. Comparisons have been made between the population biology of annual macroalgae and terrestrial plants, but demographic information necessary to make strong comparisons is lacking for most of these algae, and life history differences may make such comparisons questionable. We studied population dynamics of the kelp Alaria marginata to determine if it was an annual and, if so, how populations persisted. This kelp is the dominant macroalga on exposed mid to low rocky intertidal shores along the Big Sur coast of California. Experimental clearings at two sites were used to assess recruitment timing and survivorship. Sporophytes were collected monthly to determine growth and fecundity. Recruitment occurred in late winter to early spring, primarily on geniculate corallines and residual A. marginata holdfasts. Thinning was inversely related to density, and occurred during the February through July growing season as larger thalli rapidly increased in length (up to 1.4 m month^− 1) and formed a thick canopy. Sorus development was positively related to size, began as early as March, peaked in late August-October, and decreased as adults were removed by winter surf. Spore release was generally highest (10⁸-10⁹ spores individual^− 11 h^− 1) between October and January and associated with high water motion. Survivorship of sporophytes beyond one year was < 1%, showing the populations were annual.Field observations and experiments on effects of canopy clearing, season of clearing, and influence of substrate type on recruitment were done to assess how these annual populations persist. Massive spore production at the onset of fall storms, survival of microscopic stages for 3-4 months facilitated by microhabitat refuges, rapid growth, large size and rapid maturation of sporophytes contributed to persistence. Furthermore, the dense stands with thick canopies may suppress potential competitors via shading and abrasion. Rather than being a fugitive, this combination of growth and life history features enables A. marginata and perhaps other large, annual kelps to maintain perennial populations.     

Inflammatory cytokines induce protein tyrosine nitration in rat astrocytes

Protein tyrosine nitration may be relevant for the pathogenesis of hepatic encephalopathy (HE). Infections, sepsis, and trauma precipitate HE episodes. Recently, serum levels of tumor necrosis factor (TNF)-alpha were shown to correlate with severity of HE in chronic liver failure. Here the effects of inflammatory cytokines on protein tyrosine nitration in cultured rat astrocytes and rat brain in vivo were studied. In cultured rat astrocytes TNF-alpha (50 pg/ml-10 ng/ml) within 6h increased protein tyrosine nitration. TNF-alpha-induced tyrosine nitration was related to an increased formation of reactive oxygen and nitrogen intermediates, which was downstream from a NMDA-receptor-dependent increase of intracellular [Ca(2+)](i) and nNOS-catalyzed NO production. Astroglial tyrosine nitration was also elevated in brains of rats receiving a non-lethal injection of lipopolysaccharide, as indicated by colocalization of nitrotyrosine immunoreactivity with glial fibrillary acidic protein and glutamine synthetase, and by identification of the glutamine synthetase among the tyrosine-nitrated proteins. It is concluded that reactive oxygen and nitrogen intermediates as well as protein tyrosine nitration by inflammatory cytokines may alter astrocyte function in an NMDA-receptor-, Ca(2+)-, and NOS-dependent fashion. This may be relevant for the pathogenesis of HE and other conditions involving cytokine exposure the brain.     

Guidelines: From artificial evolution to computational evolution: a research agenda

Computational scientists have developed algorithms inspired by natural evolution for at least 50 years. These algorithms solve optimization and design problems by building solutions that are 'more fit' relative to desired properties. However, the basic assumptions of this approach are outdated. We propose a research programme to develop a new field: computational evolution. This approach will produce algorithms that are based on current understanding of molecular and evolutionary biology and could solve previously unimaginable or intractable computational and biological problems.     

The effects of topical application of various fatty acids on pheromone and glandular lipid biosynthesis in the moth Heliothis virescens

Binary mixtures of deuterium-labeled palmitic acid and an excess of different fatty acids were applied to the sex pheromone gland of female Heliothis virescens and the effects on the terminal steps of pheromone biosynthesis, including incorporation of fatty acids into the glandular lipids, observed. Relative to labeled palmitic acid applied alone, application of all the binary mixtures resulted in decreased levels of the labeled pheromone component, (Z)-11-hexadecenyl acetate (Z11-16:OAc), but there was generally no decrease in the amounts of labeled pheromone precursor, (Z)-11-hexadecenoate, nor labeled palmitate in the glandular lipids. These data suggest that the excess of fatty acid in the gland inhibits Delta11-desaturation. However, in the case of excess myristoleic acid, the amount of labeled (Z)-11-hexadecenoate increased significantly, suggesting that this acid inhibited fatty acid reduction. Dose-response tests with certain of the fatty acids were consistent with the above interpretations and further indicated that the gland had a high capacity for rapidly activating and incorporating excess fatty acids into the glandular lipids. Finally, application of the various fatty acids resulted in increased levels of these acids in the gland and, in the cases of myristoleic, palmitoleic and myristic acids, it also resulted in increased levels of the corresponding aldehydes, which had previously been detected in the gland of female H. virescens. This suggests that the fatty acid reductase in H. virescens is not highly specific for the major component, and that the final ratio of pheromone components is determined in part by the availability of their corresponding fatty acids in the gland.     

Photoacoustically‐guided photothermal killing of mosquitoes targeted by nanoparticles

In biomedical applications, nanoparticles have demonstrated the potential to eradicate abnormal cells in small localized pathological zones associated with cancer or infections. Here, we introduce a method for nanotechnology‐based photothermal (PT) killing of whole organisms considered harmful to humans or the environment. We demonstrate that laser‐induced thermal, and accompanying nano‐ and microbubble phenomena, can injure or kill C. elegans and mosquitoes fed carbon nanotubes, gold nanospheres, gold nanoshells, or magnetic nanoparticles at laser energies that are safe for humans. In addition, a photoacoustic (PA) effect was used to control nanoparticle delivery. Through the integration of this technique with molecular targeting, nanoparticle clustering, magnetic capturing and spectral sharpening of PA and PT plasmonic resonances, our laser‐based PA‐PT nano‐theranostic platform can be applied to detection and the physical destruction of small organisms and carriers of pathogens, such as malaria vectors, spiders, bed bugs, fleas, ants, locusts, grasshoppers, phytophagous mites, or other arthropod pests, irrespective of their resistance to conventional treatments. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Allometric shape change and heterochrony in the freeliving coral Trachyphyllia bilobata (Duncan)

Regression analysis has been used to study the relationship between age, size, shape, and surface area in two ancestral-descendant populations of the Neogene Caribbean coral Trachyphyllia bilobata. Analyses of the relationship between size and age show that the relationship is isometric and that little difference occurs between populations in mean corallite length or height and in their rates of growth. Onset of columella growth is significantly earlier, however, in the descendant population. Studies of the relationship between size and shape show that growth is allometric, with shape change occurring in both corallum elongation and pinching of the corallite wall during ontogeny. In the descendant population, pinching and elongation initiate earlier in the ontogeny of the coral. These results suggest that the evolutionary development of the meandroid form in freeliving corals has been accomplished by heterochrony, involving a complex set of disassociated peramorphic changes in ontogeny accompanied by paedomorphic changes in astogeny. Further analyses show that the observed heterochronic changes serve to decrease corallum surface area which may in turn enhance sediment removal and nutrition in unstable habitats.     

Leukotrienes do not regulate interleukin 1 production by activated macrophages

The objective of this work was to investigate the role of leukotrienes in the production of IL-1 by activated human peripheral blood monocytes and mouse peritoneal macrophages. Using overnight adherent macrophages, stimulation with lipopolysaccharide or zymosan caused a time-dependent increase in IL-1 production. LTC4 was detected and preceded IL-1 production only in zymosan-treated macrophages. Lipopolysaccharide did not stimulate macrophages to produce LTC4. Zymosan-stimulated LTC4 production was inhibited by the lipoxygenase inhibitors, ICI207968 (3.20 microM), nordihydroguaiaretic acid (0.22 microM), phenidone (4.60 microM), REV5901 (0.20 microM), and the Merck 5-lipoxygenase "translocation inhibitor" MK886 (0.02 microM) with IC50 values as shown in parenthesis. However, none of these inhibitors reduced IL-1 production at concentrations which completely inhibited leukotriene synthesis. Taken together, these results do not support a role for leukotrienes in the production of IL-1 by zymosan-activated macrophages.     

Heating of tissues by microwaves: A model analysis

We consider the thermal response times for heating of tissue subject to nonionizing (microwave or infrared) radiation. The analysis is based on a dimensionless form of the bioheat equation. The thermal response is governed by two time constants: one(τ₁) pertains to heat convection by blood flow, and is of the order of 20–30 min for physiologically normal perfusion rates; the second (τ₂) characterizes heat conduction and varies as the square of a distance that characterizes the spatial extent of the heating. Two idealized cases are examined. The first is a tissue block with an insulated surface, subject to irradiation with an exponentially decreasing specific absorption rate, which models a large surface area of tissue exposed to microwaves. The second is a hemispherical region of tissue exposed at a spatially uniform specific absorption rate, which models localized exposure. In both cases, the steady-state temperature increase can be written as the product of the incident power density and an effective time constant τ_eff, which is defined for each geometry as an appropriate function of τ₁ and τ₂. In appropriate limits of the ratio of these time constants, the local temperature rise is dominated by conductive or convective heat transport. Predictions of the block model agree well with recent data for the thresholds for perception of warmth or pain from exposure to microwave energy. Using these concepts, we developed a thermal averaging time that might be used in standards for human exposure to microwave radiation, to limit the temperature rise in tissue from radiation by pulsed sources. We compare the ANSI exposure standards for microwaves and infrared laser radiation with respect to the maximal increase in tissue temperature that would be allowed at the maximal permissible exposures. A historical appendix presents the origin of the 6-min averaging time used in the microwave standard. Bioelectromagnetics 19:420–428, 1998. © 1998 Wiley-Liss, Inc.     

5-Azacytidine increases the total cellular copper content and basal level metallothionein mRNA accumulation of human Hep G2 cells.

In this study we have demonstrated the ability of 5-azacytidine to elevate the basal level expression of the metallothionein (MT)-IF and MT-IG genes and increase the basal level expression of the MT-IIA gene in Hep G2 cells, a cell line which exhibits heavy metal inducible MT gene expression. Atomic absorption analysis of 5-azacytidine treated Hep G2 cells detected a 2-fold increase in the total cellular copper content. Pretreatment of 5-azacytidine exposed cells with hydroxyurea and cycloheximide indicated that the increase in total cellular copper content was a direct response to 5-azacytidine treatment. S1 nuclease analysis illustrated that pretreatment of Hep G2 cells with KCN, a copper specific chelator and uptake inhibitor, suppressed 5-azacytidine- and copper-inducible MT-IG gene expression. Thus, the increase in MT gene expression in response to 5-azacytidine treatment can be correlated to an increase in the total cellular copper content. Possible mechanisms on how 5-azacytidine could alter the influx/efflux of copper in Hep G2 cells are discussed.     

Activity and quantity of ribulose bisphosphate carboxylase-and phosphoenolpyruvate carboxylase-protein in two Crassulacean acid metabolism plants in relation to leaf age,nitrogen nutrition,and point in time during a day/night cycle

Activity of ribulose 1,5-bisphosphate (RuBP) carboxylase in leaf extracts of the constitutive Crassulacean acid metabolism (CAM) plant Kalanchoe pinnata (Lam.) Pers. decreased with increasing leaf age, whereas the activity of phosphoenolpyruvate (PEP) carboxylase increased. Changes in enzyme activities were associated with changes in the amount of enzyme proteins as determined by immunochemical analysis, sucrose density gradient centrifugation, and SDS gel electrophoresis of leaf extracts. Young developing leaves of plants which received high amounts of NO ₃ ^- during growth contained about 30% of the total soluble protein in the form of RuBP carboxylase; this value declined to about 17% in mature leaves. The level of PEP carboxylase in young leaves of plants at high NO ₃ ^- was an estimated 1% of the total soluble protein and increased to approximately 10% in mature leaves, which showed maximum capacity for dark CO₂ fixation. The growth of plants at low levels of NO ₃ ^- decreased the content of soluble protein per unit leaf area as well as the extractable activity and the percentage contribution of both RUBP carboxylase and PEP carboxylase to total soluble leaf protein. There was no definite change in the ratio of RuBP carboxylase to PEP carboxylase activity with a varying supply of NO ₃ ^- during growth. It has been suggested (e.g., Planta 144, 143–151, 1978) that a rhythmic pattern of synthesis and degradation of PEP carboxylase protein is involved in the regulation of -carboxylation during a day/night cycle in CAM. No such changes in the quantity of PEP carboxylase protein were observed in the leaves of Kalanchoe pinnata (Lam.) Pers. or in the leaves of the inducible CAM plant Mesembryanthemum crystallinum L.Abbreviations CAM Crassulacean acid metabolism - RuBP ribulose 1,5-bisphosphate - PEP phosphoenolpyruvate - G-6-P glucose-6-phosphate