Heterotrophic production potential of omega-3 polyunsaturated fatty acids by microalgae and algae-like microorganisms

Twenty microbial strains were screened for their potential of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) production using heterotrophic flask cultures on two different carbon sources, glucose (5 g L-1) and acetate (1 g L-1). Of the 20 microalgae tested, 19 strains showed growth on glucose, whereas only 12 of them could grow on acetate. Glucose was the preferred carbon source for growth, and EPA and DHA production. There was a complete absence or a marked decrease in EPA and DHA contents in all the microalgae except in Amphidinium sp. CS-259 while acetate was used as the sole carbon and energy source. The EPA yields of Amphidinium carterae Hullburt UTEX LB 1002 (8.3 mg L-1) and Schizochytrium aggregatum Goldstein et Belsky ATCC 28209 (9.3 mg L-1) on glucose were higher than those produced by all the other microalgae when grown on acetate or glucose. Amphidinium sp. CS-259 while grown on acetate had the highest EPA proportion (20.7% of total fatty acids) which was higher than those produced by all the other microalgae when grown on acetate or glucose. Crypthecodinium cohnii (Seligo) Chatton UTEX L1649, the heterotrophic dinoflagellate grown on glucose had the highest DHA yield (15.0 mg L-1) due to its significantly high biomass concentrations (1.9 g L-1).link_to_subscribed_fulltex

Turnover analysis of N-methyl-D-aspartate receptor subunit NR1 protein in PC12 cells

The post-translational fate of N-methyl-D-aspartate receptor (NMDAR) subunit NR1 was characterized in PC12 cells using pulse-chase labeling, block of protein synthesis by cyclohexamide and deglycosylation by endoglycosidase H. Metabolic labeling of NR1 protein indicated a biphasic degradation of NR1 protein with half-lives of 1.6 and 16.1 h for a rapidly (78\%) and a slowly (22\%) degrading population. Immunoprecipitation of NR1 following the block of protein synthesis by cyclohexamide revealed that the rapidly and slowly degrading pools mainly consisted of the NR1 splice variants NR1-4a and NR1-2a. Sensitivity of NR1 protein to deglycosylation by endoglycosidase H indicated the presence of an immature form of NR1 that was retained in the endoplasmic reticulum. PC12 cells serve as a useful model for the elucidation of translational and post-translational mechanisms of NMDAR expression. (C) 2002 Published by Elsevier Science Ireland Ltd

Eicosapentaenoic acid and docosahexaenoic acid production potential of microalgae and their heterotrophic growth

Twenty microalgal strains were investigated in photoautotrophic flask cultures for their potential for eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) production. The highest EPA proportion (% of total fatty acids) was produced by Monodus subterraneus UTEX 151 (34.2%), followed by Chlorella minutissima UTEX 2341 (31.3%) and Phaeodactylum tricornutum UTEX 642 (21.4%). The highest DHA proportion (% of total fatty acids) was obtained in Crypthecodinium cohnii UTEX L1649 (19.9%), followed by Amphidinium carterae UTEX LB 1002 (17.0%) and Thraustochytrium aureum ATCC 28211 (16.1%). Among the 20 strains screened, the EPA yield was high in M. subterraneus UTEX 151 (96.3 mg/L), P. tricornutum UTEX 642 (43.4 mg/L), Chl. minutissima UTEX 2341 (36.7 mg/L), and Por. cruentum UTEX 161 (17.9 mg/L) owing to their relatively high biomass concentrations. The DHA yield was high in C. cohnii UTEX L1649 (19.5 mg/L) and A. carterae UTEX LB 1002 (8.6 mg/L). Heterotrophic growth of these 20 microalgae was also tested on two different carbon sources, acetate and glucose. All microalgae except Nannochloropsis oculata UTEX LB 2164 showed growth on glucose (5 g/L) under heterotrophic conditions. Twelve of them could grow heterotrophically when acetate (1 g/L) was used as their sole carbon and energy source.link_to_subscribed_fulltex

Translational regulation of the N-methyl-D-aspartate receptor subunit NR1

Formation of functional N-methyl-D-aspartate ( NMDA) receptor channels requires the essential NMDA receptor subunit NR1 and one or more of the modulatory subunits NR2A-D and in some cases an additional subunit NR3A or NR3B. Recent studies indicate that NR1 expression is regulated at translation under both physiological and pathological conditions. The rat pheochromocytoma cell line (PC12) has been used as a model system for NR1 gene expression studies. Characterization of the posttranscriptional regulatory mechanisms suggested the posttranslational degradation and translational regulation of NR1 protein in PC12 cells. In addition a recent study on the translational regulation of NR1 mRNA in intact brain identified two translationally distinct pools of NR1 mRNA. In this review we summarize the evidence for translational regulation of NR1 expression in PC12 cells and the brain. Copyright (C) 2004 S. Karger AG, Basel

Translational activity of N-methyl-D-aspartate receptor subunit NR1 mRNA in PC12 cells

PC12 cells contain NR1 mRNA but lack significant expression of NR1 protein suggesting translational or post-translational regulation. Translational activity of NR1 mRNA in PC12 cells was examined by sucrose gradient fractionation and by heterologous luciferase NR1 gene expression studies. The cosedimentation and association of NR1 mRNA with large polyribosomes (polysomes) confirmed the translatability of NR1 message in PC12 cells. Possible initiation and/or elongation defects during the translation of NR1 mRNAs were investigated by cyclohexamide treatment. The marked decline in the number of ribosomes associated with NR1 mRNA after prolonged exposure to cyclohexamide suggested that initiation was limiting translation of NR1 mRNA in PC12 cells. Consequently, the effect of the 5' and 3' untranslated regions (UTRs) on translation was examined using fusion constructs consisting of the luciferase coding region fused to either or both the 5' UTR and 3' UTR of NR1. The transfection of PC12 cells with the luciferase NR1-UTR fusion constructs revealed that the 3' UTR of NR1 had a significant inhibitory effect on luciferase expression. In contrast, the 5' UTR of NR1 had no inhibitory effect on mRNA translation in PC12 cells. The results from this study indicate that the translation of NR1 mRNA in PC12 cells may be impeded at initiation and this inhibition may be regulated at least in part through the 3' UTR of NR1. Copyright (C) 2003 S. Karger AG, Basel

The impact of assimilation of MODIS data for the prediction of a tropical low-pressure system over India using a mesoscale model

Copyright 2009 Elsevier B.V., All rights reserved.A low-pressure system formed over the Bay of Bengal, India on 15 October 2003 and crossed the east coast of India during the late hours of 17 October 2003. The system, which provided copious rainfall over the Bay of Bengal and stations on the east coast, is investigated in this study using the fifth Generation Mesoscale Model (MM5). Three sets of numerical experiments are designed in this study. While the first set utilizes National Center for Environmental Prediction - Aviation (NCEP-AVN) analysis (for the initial conditions and lateral boundary conditions) only in the MM5 simulation, the second set utilizes the vertical profiles of temperature and humidity obtained from Moderate Resolution Imaging Spectroradiometer (MODIS) (as well as a few radiosonde station data) to provide an improved analysis. The third set used the vertical profiles of temperature and humidity from MODIS alone to provide an improved analysis. The results of the three sets of simulation are compared with one another as well as with the analysis and observations. It is found that the predicted sea level pressure of the MM5 simulation which utilized the improved analysis: reproduces the large-scale structure of the low-pressure system as manifested in the NCEP-AVN analysis; provides a stronger and deeper low-pressure system as seen from the sea level pressure field; and shows a larger northward extent of the associated precipitation pattern as compared with the simulation with just the analysis. The results of the third experiment (impact of vertical profiles of temperature and humidity using MODIS alone) compare well with the results of the second experiment except that in the former, the associated cyclonic circulation in the lower troposphere appears weaker. The results of this study, although restricted to a single case study, demonstrate that inclusion of MODIS derived vertical temperature and humidity profiles together with radiosonde data caused a favourable impact on the simulated structure of the low-pressure system.Peer reviewe