Accumulation of arachidonic acid-rich triacylglycerols in the microalga Parietochloris incisa (Trebuxiophyceae,Chlorophyta)

The freshwater green microalga Parietochloris incisa is the richest known plant source of the polyunsaturated fatty acid (PUFA), arachidonic acid (20:4omega6, AA). While many microalgae accumulate triacylglycerols (TAG) in the stationary phase or under certain stress conditions, these TAG are generally made of saturated and monounsaturated fatty acids. In contrast, most cellular AA of P. incisa resides in TAG. Using various inhibitors, we have attempted to find out if the induction of the biosynthesis of AA and the accumulation of TAG are codependent. Salicylhydroxamic acid (SHAM) affected a growth reduction that was accompanied with an increase in the content of TAG from 3.0 to 6.2% of dry weight. The proportion of 18:1 increased sharply in all lipids while that of 18:2 and its down stream products, 18:3omega6, 20:3omega6 and AA, decreased, indicating an inhibition of the Delta12 desaturation of 18:1. Treatment with the herbicide SAN 9785 significantly reduced the proportion of TAG. However, the proportion of AA in TAG, as well as in the polar lipids, increased. These findings indicate that while there is a preference for AA as a building block of TAG, the latter can be produced using other fatty acids, when the production of AA is inhibited. On the other hand, inhibiting TAG construction did not affect the production of AA. In order to elucidate the possible role of AA in TAG we have labeled exponential cultures of P. incisa kept at 25 degrees C with [1-14C]arachidonic acid and cultivated the cultures for another 12 h at 25, 12 or 4 degrees C. At the lower temperatures, labeled AA was transferred from TAG to polar lipids, indicating that TAG of P. incisa may have a role as a depot of AA that can be incorporated into the membranes, enabling the organism to quickly respond to low temperature-induced stress.     

Addition of terpenoids to pear ester plus acetic acid increases catches of codling moth (Lepidoptera: Tortricidae)

Field studies were conducted to evaluate new kairomone blends in combination with pear ester (E,Z)‐2,4‐ethyl decadienoate (PE) and acetic acid (AA) for their attraction of male and female codling moth, Cydia pomonella (L.), in apple, Malus domestica Borkhausen. The addition of decanal to either AA or PE alone significantly increased total and female moth catches. However, the addition of decanal did not improve the attraction of PE + AA. The addition of either the pyranoid (PyrLOX) or furanoid (FurLOX) linalool oxide but not linalool (LOL) increased moth catches with PE but did not increase catches with PE + AA. Similarly, the addition of PyrLOX plus decanal did not improve PE + AA. The addition of (E)‐4,8‐dimethyl‐1,3,7‐nonatriene (DMNT) to either AA, PE + AA or PE + AA+decanal did not significantly increase moth catches. However, the addition of PyrLOX to traps with PE + AA and DMNT (4‐component lure) significantly increased moth catches compared with PE + AA alone or any of the ternary blends of these volatiles. Females accounted for 60%–80% of the total catch with this 4‐component lure. The 4‐component blend with PyrLOX was a more attractive lure than similar blends that substituted LOL, or a binary blend of LOL and FurLOX for PyrLOX. The 4‐component blend caught nearly fourfold more total and female moths than the purported attractant N‐butyl sulphide when it was used in combination with PE + AA. These results indicate that significant improvements in monitoring, mating disruption and mass trapping of codling moth are possible. Further studies are needed to assess the new attractive blend's effectiveness in combination with sex pheromone lures and to evaluate whether other host plant volatiles can be added or substitute for DMNT or LOX when used in combination with PE + AA.     

Reversible cross-linking and CO treatment as an approach in red cell stabilization

We explored the use of the reversible cross-linking reagent dimethyl 3,3-dithiobispropionimidate (DTBP) in combination with CO treatment as an approach to stabilizing erythrocyte structure and function. Erythrocytes were cross-linked with different concentrations of DTBP for different times. DTBP increased erythrocyte osmotic stability, blocked lysolecithin-induced echinocytosis, and decreased erythrocyte deformability in a concentration- and time-dependent manner. Reversal of the cross-linking with the reducing agent dithioerythritol (DTE) restored osmotic fragility and response to lysolecithin as well as deformability. Complete reversal, however, is a function of the DTBP concentration and the time of cross-linking. The effects of cross-linking with 5 mM DTBP for 1 h were completely reversible after treatment with 10 mM DTE for 20 min. Longer incubation times or higher concentrations of DTBP resulted in partial reversal by DTE of the effects produced by DTBP. Cross-linking and reversal only slightly reduced the ATP content. The hemoglobin contained in the cross-linked and reversed cells could still undergo reversible oxygenation and deoxygenation. Erythrocytes were pretreated with CO, cross-linked with 5 mM DTBP for 1 or 3 h, loaded with a solution containing 500 mM glucose for 24 h, and freeze-dried in a medium containing 15% (w/v) albumin. Rehydration followed in distilled water. Complete recovery, measured as the percentage of free hemoglobin, was achieved for cells cross-linked with 5 mM DTBP for 3 h and freeze-dried to a final water content of 10-15%. Non-cross-linked cells lysed 100% on rehydration in distilled water. No methemoglobin (MetHb) formation as a result of freeze-drying was detected in CO-treated cells. In non-CO-treated cells 20% of the Hb was converted to MetHb.     

Evidence suggesting that ghrelin O-acyl transferase inhibitor acts at the hypothalamus to inhibit hypothalamo-pituitary-adrenocortical axis function in the rat

Production of n-octanoyl-modified ghrelin (GHREL), an active form of the peptide requires prohormone processing protease and GHREL O-acyltransferase (GOAT), as well as n-octanoic acid. Recently a selective GOAT antagonist (GO-CoA-Tat) was invented and this tool was used to study the possible role of endogenous GHREL in regulating HPA axis function in the rat. Administration of GOAT inhibitor (GOATi) resulted in a notable decrease in plasma ACTH, aldosterone and corticosterone concentrations at min 60 of experiment. Octanoic acid (OA) administration had no effect on levels of studied hormones. Plasma levels of unacylated and acylated GHREL remained unchanged for 60min after either GOATi or OA administration. Under experimental conditions applied, no significant changes were observed in the levels of GOAT mRNA in hypothalamus, pituitary, adrenal and stomach fundus. After GOATi injection hypothalamic CRH mRNA levels were elevated at 30 min and pituitary POMC mRNA levels at 60 min. Both GOATi and OA lowered basal, but not K(+)-stimulated CRH release by hypothalamic explants and had no effect on basal or CRH-stimulated ACTH release by pituitary slices. Neither GOATi nor OA affected corticosterone secretion by freshly isolated or cultured rat adrenocortical cells. Thus, results of our study suggest that in the rat endogenous GHREL exerts tonic stimulating effect on hypothalamic CRH release. This effect could be demonstrated by administering rats with selected inhibitor of ghrelin O-acyltransferase, the enzyme responsible for GHREL acylation, a process which is absolutely required for both GHSR-1a binding and its central endocrine activities.     

Exchange of reduced sulfur gases between lichens and the atmosphere

Fourteen lichens, 10 green algal lichens and four cyanolichens, as well as a cyanobacterium emitted significant quantities of H₂S (0.01–0.04 pmol g dw^–1 s^–1) and DMS (0.005–0.025 pmol g dw^–1 s^–1) but were sinks for COS (0.015–0.14 pmol g dw^–1 s^–1). In contrast, exchange of CH₃SH and CS₂ were sporatic and inconsistent. Although some interspecific variation occurred for the first three gases, exchange rates were relatively uniform and were not influenced by irradiance conditions. In contrast to DMS and H₂S emission, COS uptake was strongly influenced by degree of thallus hydration. Because lichen dominated systems cover extensive terrestrial habitats, COS uptake is potentially important in the world's sulfur budget.     

Fibrillar seeds alleviate amyloid-β cytotoxicity by omitting formation of higher-molecular-weight oligomers

Amyloid-β (Aβ) peptides can exist in distinct forms including monomers, oligomers and fibrils, consisting of increased numbers of monomeric units. Among these, Aβ oligomers are implicated as the primary toxic species as pointed by multiple lines of evidence. It has been suggested that toxicity could be rendered by the soluble higher-molecular-weight (high-n) Aβ oligomers. Yet, the most culpable form in the pathogenesis of Alzheimer’s disease (AD) remains elusive. Moreover, the potential interaction among the insoluble fibrils that have been excluded from the responsible aggregates in AD development, Aβ monomers and high-n oligomers is undetermined. Here, we report that insoluble Aβ fibrillar seeds can interact with Aβ monomers at the stoichiometry of 1:2 (namely, each Aβ molecule of seed can bind to two Aβ monomers at a time) facilitating the fibrillization by omitting the otherwise mandatory formation of the toxic high-n oligomers during the fibril maturation. As a result, the addition of exogenous Aβ fibrillar seeds is seen to rescue neuronal cells from Aβ cytotoxicity presumably exerted by high-n oligomers, suggesting an unexpected protective role of Aβ fibrillar seeds.     

Methylglyoxal accumulation de-regulates HoxA5 expression,thereby impairing angiogenesis in glyoxalase 1 knock-down mouse aortic endothelial cells

Impaired angiogenesis leads to long-term complications and is a major contributor of the high morbidity in patients with Diabetes Mellitus (DM). Methylglyoxal (MGO) is a glycolysis byproduct that accumulates in DM and is detoxified by the Glyoxalase 1 (Glo1). Several studies suggest that MGO contributes to vascular complications through mechanisms that remain to be elucidated. In this study we have clarified for the first time the molecular mechanism involved in the impairment of angiogenesis induced by MGO accumulation.Angiogenesis was evaluated in mouse aortic endothelial cells isolated from Glo1-knockdown mice (Glo1KD MAECs) and their wild-type littermates (WT MAECs). Reduction in Glo1 expression led to an accumulation of MGO and MGO-modified proteins and impaired angiogenesis of Glo1KD MAECs. Both mRNA and protein levels of the anti-angiogenic HoxA5 gene were increased in Glo1KD MAECs and its silencing improved both their migration and invasion. Nuclear NF-?B-p65 was increased 2.5-fold in the Glo1KD as compared to WT MAECs. Interestingly, NF-?B-p65 binding to HoxA5 promoter was also 2-fold higher in Glo1KD MAECs and positively regulated HoxA5 expression in MAECs. Consistent with these data, both the exposure to a chemical inhibitor of Glo1 “SpBrBzGSHCp2” (GI) and to exogenous MGO led to the impairment of migration and the increase of HoxA5 mRNA and NF-?B-p65 protein levels in microvascular mouse coronary endothelial cells (MCECs).This study demonstrates, for the first time, that MGO accumulation increases the antiangiogenic factor HoxA5 via NF-?B-p65, thereby impairing the angiogenic ability of endothelial cells.     

Guava leaf volatiles and dimethyl disulphide inhibit response of Diaphorina citri Kuwayama to host plant volatiles

The Asian citrus psyllid, Diaphorina citri Kuwayama, vectors the causal pathogen of huanglongbing (HLB), which is likely the most important disease affecting worldwide citrus production. Interplanting citrus with guava, Psidium guajava L., was reported to reduce D. citri populations and incidence of HLB. We describe a series of investigations on the response of D. citri to citrus volatiles with and without guava leaf volatiles and to synthetic dimethyl disulphide (DMDS), in laboratory olfactometers and in the field. Volatiles from guava leaves significantly inhibited attraction of D. citri to normally attractive host‐plant (citrus) volatiles. A similar level of inhibition was recorded when synthetic DMDS was co‐released with volatiles from citrus leaves. In addition, the volatile mixture emanating from a combination of intact citrus and intact guava leaves induced a knock‐down effect on adult D. citri. Compounds similar to DMDS including dipropyl disulphide, ethyl‐1‐propyl disulphide, and diethyl disulphide did not affect the behavioural response of D. citri to attractive citrus host plant volatiles. Head‐space volatile analyses were conducted to compare sulphur volatile profiles of citrus and guava, used in our behavioural assays, with a gas chromatography‐pulsed flame photometric detector. DMDS, produced by wounded guava in our olfactometer assays, was not produced by similarly wounded citrus. The airborne concentration of DMDS that induced the behavioural effect in the 4‐choice olfactometer was 107 pg/ml. In a small plot field experiment, populations of D. citri were significantly reduced by deployment of synthetic DMDS from polyethylene vials compared with untreated control plots. Our results verify that guava leaf volatiles inhibit the response of D. citri to citrus host plant volatiles and suggest that the induced compound, DMDS, may be partially responsible for this effect. Also, we show that field deployment of DMDS reduces densities of D. citri and thus may have potential as a novel control strategy.     

Glyceraldehyde-3-phosphate dehydrogenase activity studied under physiological conditions with a linear assay.

An assay method for glyceraldehyde-3-phosphate dehydrogenase in which none of the primary products accumulate and which gives linear kinetics under physiological conditions has been developed. It is based on the use of the 1,3-diphosphoglycerate produced by the enzyme for the formation of NADPH, while the NADH produced is recycled with an auxiliary system. Revised Km values at pH 7.4 for the muscle (rabbit and rat) enzyme are: glyceraldehyde-3-P, 50 μM; NAD, 100 μM; Pi, 10 mM. The rat erythrocyte enzyme gave similar values except for glyceraldehyde-3-P which was 300 μM. Cooperativity for NAD⁺ tends to be positive but is a variable parameter.