Transcriptome analysis of lipid metabolism in response to cerium stress in the oleaginous microalga Nannochloropsis oculata

Nannochloropsis oculata can accumulate large amounts of lipids under rare earth element (REE) conditions. However, the lipid accumulation mechanism responsible for REE stress has not been elucidated. In this study, the effects of cerium (the most abundant REE) on the growth and lipid accumulation of N. oculata were investigated. The de novo transcriptome data of N. oculata under cerium conditions were subsequently collected and analyzed. The results showed that N. oculata exhibited good cerium-resistance ability, showed slightly decrease in biomass but significantly increase in lipid content (55.8 % dry cell weight) under 6.0 mg/L cerium condition. Meanwhile, about 83.4 % cerium was biological fixated. Through transcriptome analysis, we found that the inhibited photosynthesis and carbon fixation pathways coupled with the stress-sensitive expression of ribosome biogenesis genes acclimatized the cells to REE stress. The active glycolysis pathway accelerated carbon flux to pyruvate and acetyl-CoA, and the upregulation of glycerol kinase and phosphatidate cytidylyltransferase genes further induced lipid accumulation. In addition, cerium downregulated the acyl-CoA oxidase and triacylglycerol lipase genes, which inhibited the degradation of lipids. Therefore, different responses to cerium demonstrate how N. oculata cells adapt to REE stress, and this knowledge may be used to extend our understanding of triacylglycerol (TAG) and the synthesis of other important metabolites.

Screening of two freshwater green microalgae in pulp and paper mill wastewater effluents in Nova Scotia, Canada

In recent years, the use of microalgae as feedstock for many marketable products, such as animal/aqua feeds, bioplastics and fertilizers, has gained renewed interest due to their fast growth potential coupled with relatively high lipid, carbohydrate and nutrient content. An algal biorefinery at an industrial site has the potential to sustainably and profitably convert carbon dioxide emissions into microalgal biomass and concomitantly reduce nitrogen and phosphorus from wastewaters. Industrial wastewaters are a potential alternative to traditional media used for large-scale microalgal cultivation. Pulp and paper mills are major consumers of water resources and discharge a huge amount of water to nearby lakes or rivers. This study investigated whether pulp and paper mill waste water is suitable for microalgal cultivation with the aim of achieving significant biomass production. Six different process waters from one Canadian pulp and paper mill were tested with two freshwater green microalgae. All of these waters were unable to support growth of microalgae due to inadequate nutrient concentrations, colour, turbidity and possible toxicity issues.

Nitric Oxide Mediates Nitrite-Sensing and Acclimation and Triggers a Remodeling of Lipids

Nitric oxide (NO) is an intermediate of the nitrogen cycle, an industrial pollutant, and a marker of climate change. NO also acts as a gaseous transmitter in a variety of biological processes. The impact of environmental NO needs to be addressed. In diatoms, a dominant phylum in phytoplankton, NO was reported to mediate programmed cell death in response to diatom-derived polyunsaturated aldehydes. Here, using the Phaeodactylum Pt1 strain, 2E,4E-decadienal supplied in the micromolar concentration range led to a nonspecific cell toxicity. We reexamined NO biosynthesis and response in Phaeodactylum NO inhibits cell growth and triggers triacylglycerol (TAG) accumulation. Feeding experiments indicate that NO is not produced from Arg but via conversion of nitrite by the nitrate reductase. Genome-wide transcriptional analysis shows that NO up-regulates the expression of the plastid nitrite reductase and genes involved in the subsequent incorporation of ammonium into amino acids, via both Gln synthesis and Orn-urea pathway. The phosphoenolpyruvate dehydrogenase complex is also up-regulated, leading to the production of acetyl-CoA, which can feed TAG accumulation upon exposure to NO. Transcriptional reprogramming leading to higher TAG content is balanced with a decrease of monogalactosyldiacylglycerol (MGDG) in the plastid via posttranslational inhibition of MGDG synthase enzymatic activity by NO. Intracellular and transient NO emission acts therefore at the basis of a nitrite-sensing and acclimating system, whereas a long exposure to NO can additionally induce a redirection of carbon to neutral lipids and a stress response.

Beta-adrenergic stimulation enhances the heat-shock response in fish

We have taken advantage of the unique properties of nucleated rainbow trout (Oncorhynchus mykiss) red blood cells (rbcs) to demonstrate that beta-adrenergic stimulation with the agonist, isoproterenol, significantly enhanced the heat-induced induction of heat-shock proteins (Hsps) in trout rbcs without affecting hsp expression on its own. Furthermore, this beta-adrenergic potentiation of hsp expression occurred only at physiologically relevant concentrations of adrenergic stimulation. In further experiments, we found that adrenaline increased 100-fold and noradrenaline increased 50-fold in trout after a 1-h heat shock at 25 degrees C, approximately 12 degrees C above acclimation temperature. This is the first time the adrenergic heat-shock response has been described for a temperate fish species. We conclude that beta-adrenergic stimulation enhances hsp expression in trout rbcs following heat stress, indicating physiological regulation of the cellular stress response in fish.

Improved mechanical properties of acrylic bone cement with short titanium fiber reinforcement

Acrylic bone cements are widely used in total joint arthroplasties to grout the prosthesis to bone. The changes in the tensile properties and fracture toughness of polymethylmethacrylate (PMMA) bone cements obtained by the addition of control and heat treated short titanium fibers are studied. Heat treatment of titanium fibers is conducted to precipitate titania particles on the fiber surface to improve the biocompatibility of the metal. Control and heat treated short titanium fibers (250 micro long and 20 micro diameter) were used as reinforcements at 3 volume %. X-ray diffraction indicated the presence of a rutile form of titania due to the heat treatments. The tensile and fracture properties were improved by the addition of fibers. Bone cements reinforced with titanium fibers heated at 550 degrees C for 1 h followed by 800 degrees C for 30 minutes show the largest increase in fracture toughness along with the smallest changes in elastic modulus and needs to be further investigated.

Improved mechanical properties of acrylic bone cement with short titanium fiber reinforcement

Acrylic bone cements are widely used in total joint arthroplasties to grout the prosthesis to bone. The changes in the tensile properties and fracture toughness of polymethylmethacrylate (PMMA) bone cements obtained by the addition of control and heat treated short titanium fibers are studied. Heat treatment of titanium fibers is conducted to precipitate titania particles on the fiber surface, which may improve the biocompatibility of the metal. Control (non-heat treated) and heat treated short titanium fibers (250 microm long and 20microm diameter) were used as reinforcements at 3 volume %. X-ray diffraction indicated the presence of a rutile form of titania due to the heat treatments. Results indicate that the tensile and fracture properties of unfilled bone cement were improved by the addition of control and heat-treated fibers. The fracture properties of bone cements reinforced with control titanium fibers were at least 10% higher than those reinforced with heat treated titanium fibers. Therefore, we recommend further studies on the use of non-heat treated titanium fibers to reinforce acrylic bone cement.

Pseudomonas sepsis does not cause more severe cardiovascular dysfunction in patients than non-Pseudomonas sepsis

To evaluate the clinical relevance of the experimental findings of a more severe cardiac depression in Pseudomonas (P.) than in non-P. sepsis, we retrospectively compared the hemodynamic data in 26 patients with P. sepsis (20 cases, single pathogen; six cases, more positive cultures with P. than with non-P. species), and 102 with non-P. sepsis. As in other studies, the left ventricular stroke work index (LVSWI) was used to assess cardiac performance. The two groups (all numbers are means) had a similar disease and sepsis severity profile (P. vs. non-P: septic shock, 81% vs. 87%; APACHE II scores, 29.1 vs. 29.2; Elebute sepsis scores, 18.1 vs. 18.1; mortality, 58% vs. 62%). Preload (pulmonary capillary wedge pressure 15.0 vs. 16.3 mm Hg) and systemic vascular resistance (588 vs 572 dyn.cm-5.sec) were comparable. Cardiac performance displayed no significant difference (LVSWI, 42.8 vs. 38.3 g.m/m2), a result reproduced in the subgroups with culture-proven bacteremia, with or without preexisting cardiovascular disease or septic shock. Thus, our data suggest that there is no difference in the degree of cardiovascular dysfunction in patients with Pseudomonas compared to non-Pseudomonas sepsis of otherwise equivalent disease severity.

Male territoriality and mating success in Nannothemis bella (Uhler) (Odonata: Libellulidae)

Observations of territorial behaviour of male Nannothemis bella indicated that females only laid eggs on males' territories after copulating with the territory holder. Results of daily censuses of marked individuals on a study area suggested that a distinct subpopulation within the male population never retained a territory for more than 1 day on the study area. Such males tend to die or emigrate sooner than do males that hold a territory on the study area for more than 1 day at some time in their lives. Further observations of territorial behaviour showed that males holding territories for less than 1 day achieved copulations at significantly lower overall rates while on those territories than did males that retained territories for more than 1 day. We infer that all males attempt to hold territories for as long as possible, but under conditions of high population density a male must have a relatively high intrinsic "territory-holding ability" in order to hold a territory for more than 1 day. Census data indicated that males emerging late in the season were less likely to retain a territory for more than 1 day than males emerging earlier.

Perturbational actions of barbiturate analogues on erythrocyte and synaptosomal membranes

The membrane perturbational actions of pentobarbital, methohexital, and phenobarbital were analyzed in terms of their effects on the incorporation of group-specific chemical probes into protein and phospholipid structural components and on the activity of various functionally distinct ATPases in erythrocyte and brain synaptosomal membranes. When compared at concentrations producing similar degrees of antihemolysis in red cells, the three analogues differed most markedly in the nature and degree of the structural and functional alterations induced in membrane proteins, with the most highly lipophilic agent, methohexital, being frequently, although not invariably, the most potent. Comparison of the effects of pentobarbital on characteristics of trinitrobenzenesulfonic acid and 5,5'-dithiobis-(2-nitrobenzoic acid) incorporation into erythrocyte membranes with results previously obtained using other anaesthetics at concentrations producing 50% antihemolysis showed that pentobarbital behaves similarly to neutral general anaesthetics but differently from cationic local anaesthetics. Our findings suggest that the membrane perturbational characteristics of barbiturates may contribute to their diverse and complex actions on excitable tissues.