Use of isotopic signatures to assess the food web in a tropical shallow marine ecosystem of Southeastern Brazil

A dual isotope approach was used to assess the relative importance of terrestrial vegetation detritus and other primary producers in the trophic web of Flamengo Sound (Ubatuba, SP), SE Brazil, surrounded by the Atlantic Rain Forest. Primary producers showed distinct C signatures and the observed values suggest that little terrestrial or bulk sediment organic matter enter the food web of the sound. Suspended particulate organic matter (POM, supports the bulk of the consumers, with some contribution by macroalgae . Consumers C values ranged from −17.4 to . At least three trophic levels were detectable in the food web. The N value of POM was , while that of sediment and detritus was . The N values of suspension feeding benthic invertebrates were 8.2–, deposit feeders 8.3–, and carnivores 10.7–. Values for fishes were for detritivore, 11.4– for benthic feeders, 12.4– for zooplanktivores, and for piscivores/benthic invertebrate feeders. Squid mean value was . There is a reasonable agreement between feeding habits information from the literature and N values from this study. In the sound, the first and second trophic steps seem to be about 1– higher than those of similar organisms studied in temperate waters and this may reflect an input of allochtonous anthropogenic nitrogen enriched in ¹⁵N from human activities.     

Potato in the age of biotechnology

Biotechnology-based tools are now widely used to enhance and expand the traditional remit of potato in food production. By modifying its functionality, the capacity of the potato to produce, for example, therapeutic or industrial compounds is now a reality, and its ability to resist disease can also be radically improved. Two developments have been crucial to expanding the role of potato: the recent advances in the fields of structural and functional potato genomics and the ability to integrate genes of interest into the potato genome. In this review we discuss how both developments have diversified the remit of this crop.     

A mechanistic model may explain the dissimilar biological efficiency of the fungal elicitors cerato-platanin and cerato-populin

Among their various functions, the members of the cerato-platanin family can stimulate plants' defense responses and induce resistance against microbial pathogens. Recent results suggest that conserved loops, also involved in chitin binding, might be a structural motif central for their eliciting activity. Here, we focus on cerato-platanin and its orthologous cerato-populin, searching for a rationale of their diverse efficiency to elicit plants' defense and to interact with oligosaccharides. A 3D model of cerato-populin has been generated by homology modeling using the NMR-derived cerato-platanin structure as template, and it has been validated by fitting with residual dipolar couplings. Loops β1-β2 and β2-β3 have been indicated as important for some CPPs members to express their biological function. When compared to cerato-platanin, in cerato-populin they present two mutations and an insertion that significantly modify their electrostatic surface. NMR relaxation experiments point to a reduced conformational plasticity of cerato-populin loops with respect to the ones of cerato-platanin. The different electrostatic surface of the loops combined with a distinct network of intra-molecular interactions are expected to be factors that, by leading to a diverse spatial organization and dissimilar collective motions, can regulate the eliciting efficacy of the two proteins and their affinity for oligosaccharides.     

Mitochondria-localized NAD biosynthesis by nicotinamide mononucleotide adenylyltransferase in Jerusalem artichoke (<Emphasis Type="Italic">Helianthus tuberosus</Emphasis> L.) heterotrophic tissues

Current studies in plants suggest that the content of the coenzyme NAD is variable and potentially important in determining cell fate. In cases that implicate NAD consumption, re-synthesis must occur to maintain dinucleotide pools. Despite information on the pathways involved in NAD synthesis in plants, the existence of a mitochondrial nicotinamide mononucleotide adenylyltransferase (NMNAT) activity which catalyses NAD synthesis from nicotinamide mononucleotide (NMN) and ATP has not been reported. To verify the latter assumed pathway, experiments with purified and bioenergetically active mitochondria prepared from tubers of Jerusalem artichoke (Helianthus tuberosus L.) were performed. To determine whether NAD biosynthesis might occur, NMN was added to Jerusalem artichoke mitochondria (JAM) and NAD biosynthesis was tested by means of HPLC and spectroscopically. Our results indicate that JAM contain a specific NMNAT inhibited by Na-pyrophosphate, AMP and ADP-ribose. The dependence of NAD synthesis rate on NMN concentration shows saturation kinetics with K _m and V _max values of 82 ± 1.05 μM and 4.20 ± 0.20 nmol min⁻¹ mg⁻¹ protein, respectively. The enzyme’s pH and temperature dependence were also investigated. Fractionation studies revealed that mitochondrial NMNAT activity was present in the soluble matrix fraction. The NAD pool needed constant replenishment that might be modulated by environmental inputs. Thus, the mitochondrion in heterotrophic plant tissues ensures NAD biosynthesis by NMNAT activity and helps to orchestrate NAD metabolic network in implementing the survival strategy of cells.     

Two separate pathways for d-lactate oxidation by Saccharomyces cerevisiae mitochondria which differ in energy production and carrier involvement

In this work we looked at whether and how mitochondria isolated from Saccharomyces cerevisiae (SCM) oxidize d-lactate. We found that: (1). externally added d-lactate causes oxygen uptake by SCM with P/O ratio equal to 1.5; in the presence of antimycin A (AA), P/O ratio was 1.8, differently in the presence of the non-penetrant alpha-cyanocinnamate (alpha-CCN-) no P/O ratio could be measured. Consistently, mitochondrial electrical membrane potential (deltapsi) generation was found, due to externally added d-lactate in the presence of antimycin A, but not of alpha-CCN-. (2). SCM oxidize d-lactate in two different manners: (i). via inner membrane d-lactate dehydrogenase which leads to d-lactate oxidation without driving deltapsi generation and ATP synthesis and (ii). via the matrix d-lactate dehydrogenase, which drives deltapsi generation and ATP synthesis by using taken up d-lactate. (3). Pyruvate newly synthesised in the mitochondrial matrix is exported via the novel d-lactate/pyruvate antiporter. d-Lactate/pyruvate antiport proved to regulate the rate of pyruvate efflux in vitro. (4). The existence of the d-lactate/H+ symporter is also proposed as shown by mitochondrial swelling. The d-lactate carriers and d-lactate dehydrogenases could account for the removal of the toxic methylglyoxal from cytosol, as well as for the d-lactate-dependent gluconeogenesis.     

Effects of in vivo exposure to GSM-modulated 900 MHz radiation on mouse peripheral lymphocytes

The aim of this study was to evaluate whether daily whole-body exposure to 900 MHz GSM-modulated radiation could affect spleen lymphocytes. C57BL/6 mice were exposed 2 h/day for 1, 2 or 4 weeks in a TEM cell to an SAR of 1 or 2 W/kg. Untreated and sham-exposed groups were also examined. At the end of the exposure, mice were killed humanely and spleen cells were collected. The number of spleen cells, the percentages of B and T cells, and the distribution of T-cell subpopulations (CD4 and CD8) were not altered by the exposure. T and B cells were also stimulated ex vivo using specific monoclonal antibodies or LPS to induce cell proliferation, cytokine production and expression of activation markers. The results did not show relevant differences in either T or B lymphocytes from mice exposed to an SAR of 1 or 2 W/kg and sham-exposed mice with few exceptions. After 1 week of exposure to 1 or 2 W/kg, an increase in IFN-gamma (Ifng) production was observed that was not evident when the exposure was prolonged to 2 or 4 weeks. This suggests that the immune system might have adapted to RF radiation as it does with other stressing agents. All together, our in vivo data indicate that the T- and B-cell compartments were not substantially affected by exposure to RF radiation and that a clinically relevant effect of RF radiation on the immune system is unlikely to occur.     

A nucleophilic catalysis step is involved in the hydrolysis of aryl phosphate monoesters by human CT acylphosphatase

Acylphosphatase, one of the smallest enzymes, is expressed in all organisms. It displays hydrolytic activity on acyl phosphates, nucleoside di- and triphosphates, aryl phosphate monoesters, and polynucleotides, with acyl phosphates being the most specific substrates in vitro. The mechanism of catalysis for human acylphosphatase (the organ-common type isoenzyme) was investigated using both aryl phosphate monoesters and acyl phosphates as substrates. The enzyme is able to catalyze phosphotransfer from p-nitrophenyl phosphate to glycerol (but not from benzoyl phosphate to glycerol), as well as the inorganic phosphate-H(2)18O oxygen exchange reaction in the absence of carboxylic acids or phenols. In short, our findings point to two different catalytic pathways for aryl phosphate monoesters and acyl phosphates. In particular, in the aryl phosphate monoester hydrolysis pathway, an enzyme-phosphate covalent intermediate is formed, whereas the hydrolysis of acyl phosphates seems a more simple process in which the Michaelis complex is attacked directly by a water molecule generating the reaction products. The formation of an enzyme-phosphate covalent complex is consistent with the experiments of isotope exchange and transphosphorylation from substrates to glycerol, as well as with the measurements of the Br?nsted free energy relationships using a panel of aryl phosphates with different structures. His-25 involvement in the formation of the enzyme-phosphate covalent complex during the hydrolysis of aryl phosphate monoesters finds significant confirmation in experiments performed with the H25Q mutated enzyme.     

The M-phase-promoting factor modulates the sensitivity of the Ca2+ stores to inositol 1,4,5-trisphosphate via the actin cytoskeleton

The resumption of the meiotic cycle (maturation) induced by 1-methyladenine in prophase-arrested starfish oocytes is indicated by the breakdown of the germinal vesicle and is characterized by the increased sensitivity of the Ca2+ stores to inositol 1,4,5-trisphosphate (InsP3) to InsP3 starting at the animal hemisphere (where the germinal vesicle was originally located) and propagating along the animal/vegetal axis of the oocyte. This initiates Ca2+ signals around the germinal vesicle before nuclear envelope breakdown. Previous studies have suggested that the final activation of the maturation-promoting factor (MPF), a cyclin-dependent kinase, which is the major element controlling the entry of eukaryotic cells into the M phase, occurs in the nucleus. MPF is then exported to the cytoplasm where its activity is autocatalytically amplified following a similar animal/vegetal spatial pattern. We have investigated whether activated MPF was involved in the increased sensitivity of the Ca2+ response to InsP3. We have found that the development of increased sensitivity of the Ca2+ stores to InsP3 receptors together with the Ca2+ signals in the perinuclear region was blocked in oocytes treated with the specific MPF inhibitor roscovitine. That the nuclear MPF activation is indeed required for changes of the InsP3 receptors sensitivity was shown by enucleating or by dissecting oocytes into vegetal and animal hemispheres prior to the addition of 1-MA. MPF activity 50 min after 1-methyladenine addition was much lower in the enucleated oocytes and in the vegetal hemisphere, which did not contain the germinal vesicle, as compared with the animal hemisphere, which did contain it. The Ca2+ increase induced by InsP3 under these experimental conditions correlated with the changes in actin cytoskeleton induced by MPF.     

Immunophenotypic properties and estrogen dependency of budding cell structures in the developing mouse mammary gland

Abstract. The initial phase of growth of the parenchymal component of the mouse mammary gland is ductal clongation, which is mainly accomplished by proliferating cells in a specialized structure termed end bud. End buds are composed of multiple layers of epithelial cells (so called body cells) which are capped by a single layer of morphologically unique cells termed cap cells.
We sought to examine the interrelationship between cap cells and other epithelial cell subclasses using a variety of antibodies to different keratin proteins and also antibodies to vimentin, actin and collagen IV. An extensive immunohistochemical characterization of the epithelial components of the developing and differentiating mammary gland demonstrated that cap cells were devoid of any immunohistochemically - detectable keratins but were positive for collagen IV. In contrast, the majority of cells in the end bud along with the luminal epithelial and myoepithelial cells were keratin positive. The body cells of the end bud were the only cells which were positive for antibody to keratin 6, a keratin which previously has been reported to be expressed in proliferating mammary epithelial cells. In addition, estrogen receptor was localized only to epithelial cells of ducts, alvcoli and body cells of end buds, but not to cap cells or myoepithelial cells. We interpret these results to suggest that cap cells are not totpotent stem cells but rather cells specialized in paving the way for ductal elongation as well as serving as precursors to myoepithelial cells.     

Ability of recombinant interferon γ in vitro to restore the defective polymorphonuclear-cell-but not lymphocyte-mediated cytotoxic activities in patients with myelodysplastic syndromes

Summary In this study we analysed the in vitro effect of recombinant interferon on cytotoxic activities mediated by both lymphoid and polymorphonuclear cells from 16 patients with myelodysplastic syndromes. Our results indicate the inability of interferon to restore the defective natural killer activity, natural killer cells and lectin-induced cytotoxicity. On the contrary we detected a boosting effect on the depressed polymorphonuclear cell cytotoxic activities. In our view, the ability of interferon to potentiate polymorphonuclear cell lytic efficiency could support an alternative defensive pathway against either neoplastic or infectious agents.