Mechanism of activation of 1,2-dehydro-N-acetyldopamine for cuticular sclerotization

The mechanism of oxidation of 1,2-dehydro-N-acetyldopamine (dehydro NADA) was examined to resolve the controversy between our group and Andersen's group regarding the reactive species involved in β-sclerotization. While Andersen has indicated that dehydro NADA quinone is the β-sclerotizing agent [Andersen, 1989], we have proposed quinone methides as the reactive species for this process [Sugumaran, 1987; Sugumaran, 1988]. Since dehydro NADA quinone has not been isolated or identified till to date, we studied the enzymatic oxidation of dehydro NADA in the presence of quinone traps to characterize this intermediate. Accordingly, both N-acetylcysteine and o-phenylenediamine readily trapped the transiently formed dehydro NADA quinone as quinone adducts. Interestingly, when the enzymatic oxidation was performed in the presence of o-aminophenol or different catechols, adduct formation between the dehydro NADA side chain and the additives had occurred. The structure of the adducts is in conformity with the generation and reactions of dehydro NADA quinone methide (or its radical). This, coupled with the fact that 4-hydroxyl or amino-substituted quinones instantly transformed into p-quinonoid structure, indicates that dehydro NADA quinone is only a transient intermediate and that it is the dehydro NADA quinone methide that is the thermodynamically stable product. However, since this compound is chemically more reactive due to the presence of both quinone methide and acylimine structure on it, the two side chain carbon atoms are “activated.” Based on these considerations, it is suggested that the quinone methide derived from dehydro NADA is the reactive species responsible for cross-link formation between dehydro NADA and cuticular components during β-sclerotization.     

On the mechanism of formation of N-acetyldopamine quinone methide in insect cuticle

The mechanism of formation of quinone methide from the sclerotizing precursor N-acetyldopamine (NADA) was studied using three different cuticular enzyme systems viz. Sarcophaga bullata larval cuticle, Manduca sexta pharate pupae, and Periplaneta americana presclerotized adult cuticle. All three cuticular samples readily oxidized NADA. During the enzyme-catalyzed oxidation, the majority of NADA oxidized became bound covalently to the cuticle through the side chain with the retention of o-diphenolic function, while a minor amount was recovered as N-acetylnorepinephrine (NANE). Cuticle treated with NADA readily released 2-hydroxy-3′,4′-dihydroxyacetophenone on mild acid hydrolysis confirming the operation of quinone methide sclerotization. Attempts to demonstrate the direct formation of NADA-quinone methide by trapping experiments with N-acetylcysteine surprisingly yielded NADA-quinone-N-acetylcysteine adduct rather than the expected NADA-quinone methide-N-acetylcysteine adduct. These results are indicative of NADA oxidation to NADA-quinone and its subsequent isomerization to NADA-quinone methide. Accordingly, all three cuticular samples exhibited the presence of an isomerase, which catalyzed the conversion of NADA-quinone to NADA-quinone methide as evidenced by the formation of NANE—the water adduct of quinone methide. Thus, in association with phenoloxidase, newly discovered quinone methide isomerase seems to generate quinone methides and provide them for quinone methide sclerotization.     

Isolation and cDNA cloning of an Em-like protein from mung bean (Vigna radiata) axes

Until now no 'early-methionine-labelled' (Em) proteins have been reported in the Fabaceae. To check whether a previously isolated low-molecular mass albumin from dry mung bean embryonic axes possibly corresponded to an Em-like protein, the protein was purified, sequenced and its cDNA clone isolated and characterized. N-terminal sequencing of cyanogen bromide cleavage products of the protein revealed homology with previously described Em-like proteins from other species. Analysis of cDNA clones encoding the mung bean Em protein revealed the presence of two classes of Em proteins and confirmed their homology to the previously characterized Em-like proteins. In vivo labelling and northern blot analysis further demonstrated that the mung bean protein is synthesized during early germination of the axes and that abscisic acid (ABA) extends its synthesis. It appears, therefore, that legumes also contain maturation-specific, ABA-responsive Em-like proteins.     

Cyst hatching in Anostraca accelerated by retinoic acid,amplified by Calcium Ionophore A23187, and inhibited by Calcium-channel blockers

Cyst hatching, under standardized conditions, of the Anostracan species Thamnocephalus platyurus and Streptocephalus dichotomus was significantly accelerated but not increased by applying the morphogen retinoic acid (RA). Cyst hatching was enhanced but not accelerated by artificially increasing the inflow of Ca²⁺ to the embryonic cells, using Calcium Ionophore A 23 187. Cyst hatching was accelerated and amplified, to a level in excess of the summed effects of each treatment, by a combined application of RA and ionophore. It was inhibited almost quantitatively by the Calcium-channel blockers Nifedipin and Verapamil. The significance of these findings is discussed.     

Draft genome sequencing and functional annotation and characterization of biofilm-producing bacterium Bacillus novalis PD1 isolated from rhizospheric soil

Antonie van Leeuwenhoek - Biofilm forming bacterium Bacillus novalis PD1 was isolated from the rhizospheric soil of a paddy field. B. novalis PD1 is a Gram-positive, facultatively anaerobic,...     

Dietary Administration of Probiotic Aeromonas veronii V03 on the Modulation of Innate Immunity,Expression of Immune-Related Genes and Disease Resistance Against Aeromonas hydrophila Infection in Common Carp (Cyprinus carpio)

This study investigates the effects of dietary Aeromonas veronii V03 supplementation on growth performances, innate immunity, and expression of immune-related genes in lymphoid organs of Cyprinus carpio and resistance to Aeromonas hydrophila infection. Fish were fed for 4 weeks with basal diet (BD; without probiotic), and experiment diet containing different doses of A. veronii V03 at 3.2 × 10⁷ (DI) and 3.5 × 10⁹ (DII) CFU g⁻¹ of diet. At the end of the probiotic feeding trial, fish were challenged with A. hydrophila, and the percentage of survival rates was recorded over 7 days. Results revealed that fish fed with A. veronii V03 demonstrated a significant improvement in growth and enhancement of innate immunity, including respiratory burst, myeloperoxidase, and lysozyme activities, and total immunoglobulin level compared with BD fed to fish. Relatively, expression of cytokines (MyD88, IL-1β1, IL-8, and IL-10) and c- and g-type lysozymes were significantly up- and downregulated in lymphoid organs of fish. Moreover, dietary supplementation of A. veronii V03 exhibited significantly (p < 0.001) higher survival rates of DI (90%) and DII (96.66%) compared with BD (53.33%) fed fish against A. hydrophila infection. These findings help to understand the effects of probiotic A. veronii V03 administrated feed influences on growth and ailment resistance to A. hydrophila infection by regulating innate and systemic immunity in common carp fish.

     

Phytochemical screening and anti-oxidant activity of Sargassum wightii enhances the anti-bacterial activity against Pseudomonas aeruginosa

In this study, the phytochemical, phenolic, flavonoid and bioactive compounds were successfully screened from crude extract of Sargassum wightii by LC-MS analysis after NIST interpretation. Bacterial growth inhibition study result was shown with 24 mm zone inhibition at 200 µg/mL concentration against P. aeruginosa. The increased phenolic content was much closed to gallic acid and the range was observed at 250 μg/mL concentration. In addition, flavonoid contents of the algae extract was indicated more significant with rutin at 200 μg/mL. In result, both the phenolic and flavonoid contents of the extract were more correlated with gallic acid and rutin. Further, the total anti-oxidant and DPPH radical scavenging activities were shown increased activity at 200 μg/mL concentrations. Furthermore, the excellent anti-bacterial alteration result was observed at 200 μg/mL concentration by minimum inhibition concentration. Therefore, the result was revealed that the marine algae Sargassum wightii has excellent phytochemical and anti-oxidant activities, and it has improved anti-bacterial activity against P. aeruginosa.     

Beta-Adrenergic Blockers as a Potential Treatment for COVID-19 Patients

More than 15 million people have been affected by coronavirus disease 2019 (COVID-19) and it has caused 640 016 deaths as of July 26, 2020. Currently, no effective treatment option is available for COVID-19 patients. Though many drugs have been proposed, none of them has shown particular efficacy in clinical trials. In this article, the relationship between the Adrenergic system and the renin-angiotensin-aldosterone system (RAAS) is focused in COVID-19 and a vicious circle consisting of the Adrenergic system-RAAS-Angiotensin converting enzyme 2 (ACE2)-severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) (which is referred to as the “ARAS loop”) is proposed. Hyperactivation of the ARAS loop may be the underlying pathophysiological mechanism in COVID-19, and beta-adrenergic blockers are proposed as a potential treatment option. Beta-adrenergic blockers may decrease the SARS-CoV-2 cellular entry by decreasing ACE2 receptors expression and cluster of differentiation 147 (CD147) in various cells in the body. Beta-adrenergic blockers may decrease the morbidity and mortality in COVID-19 patients by preventing or reducing acute respiratory distress syndrome (ARDS) and other complications. Retrospective and prospective clinical trials should be conducted to check the validity of the hypothesis. Also see the video abstract here https://youtu.be/uLoy7do5ROo .     

An Appended Domain Results in an Unusual Architecture for Malaria Parasite Tryptophanyl-tRNA Synthetase

Specific activation of amino acids by aminoacyl-tRNA synthetases (aaRSs) is essential for maintaining fidelity during protein translation. Here, we present crystal structure of malaria parasite Plasmodium falciparum tryptophanyl-tRNA synthetase (Pf-WRS) catalytic domain (AAD) at 2.6 Å resolution in complex with L-tryptophan. Confocal microscopy-based localization data suggest cytoplasmic residency of this protein. Pf-WRS has an unusual N-terminal extension of AlaX-like domain (AXD) along with linker regions which together seem vital for enzymatic activity and tRNA binding. Pf-WRS is not proteolytically processed in the parasites and therefore AXD likely provides tRNA binding capability rather than editing activity. The N-terminal domain containing AXD and linker region is monomeric and would result in an unusual overall architecture for Pf-WRS where the dimeric catalytic domains have monomeric AXDs on either side. Our PDB-wide comparative analyses of 47 WRS crystal structures also provide new mechanistic insights into this enzyme family in context conserved KMSKS loop conformations.