Chemical characteristics of dehydro-L-ascorbic acid

Dehydro-L-ascorbic acid (DAA) exists mainly in its C2 hydrated bicyclic form (5) in an aqueous solution, and monocyclic DAA (3), which is the expected reaction product immediately after the oxidation of AA, has not been observed by NMR spectroscopy. The formation mechanism for 5 from 3 and the stability of 5 were examined by the semi-empirical molecular orbital method (MOPAC). It was indicated that the protonation reaction was the key step in the formation of 5, therefore, the formation of 5 is thought to be more difficult under physiological conditions which mostly involve in the neutral or slightly alkaline state. However, by NMR, it was confirmed that, even in a neutral or slightly alkaline state very close to physiological conditions, the predominant form of DAA existing in an aqueous solution immediately after the enzymatic oxidation of AA was confirmed to be 5, although the possible existence of other forms of DAA at very low concentrations could not be completely excluded.     

The Mode of Binding of Carbohydrate in Ricin D

Dehydro-L-ascorbic acid (DAA) exists mainly in its C2 hydrated bicyclic form (5) in an aqueous solution, and monocyclic DAA (3), which is the expected reaction product immediately after the oxidation of AA, has not been observed by NMR spectroscopy. The formation mechanism for 5 from 3 and the stability of 5 were examined by the semi-empirical molecular orbital method (MOPAC). It was indicated that the protonation reaction was the key step in the formation of 5, therefore, the formation of 5 is thought to be more difficult under physiological conditions which mostly involve in the neutral or slightly alkaline state. However, by NMR, it was confirmed that, even in a neutral or slightly alkaline state very close to physiological conditions, the predominant form of DAA existing in an aqueous solution immediately after the enzymatic oxidation of AA was confirmed to be 5, although the possible existence of other forms of DAA at very low concentrations could not be completely excluded.     

The regulation of formation of prostaglandins and arachidonoyl-CoA from arachidonic acid in rabbit kidney medulla microsomes by linoleic acid hydroperoxide

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). In the present study, we investigated the effects of linoleic acid (LA) and 13-hydroperoxyoctadecadienoic acid (13-HPODE) on the PG and AA-CoA formation from high and low concentrations of AA (60 and 5 microM) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 microM [(14)C]-AA in 0.1M Tris-HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl(2) and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. LA (10-50 microM) reduced only PG formation from both 60 and 5 microM AA. 13-HPODE (10-50 microM) also reduced PG formation from 60 and 5 microM AA, but the inhibitory potency was much stronger than that by LA. Furthermore, 13-HPODE had the potential to increase the AA-CoA formation with a decrease in the PG formation from 5 microM AA. These results suggest that 13-HPODE, but not LA, may shift AA away from COX pathway into ACS pathway under low substrate concentration (near physiological concentration of AA).     

Oxidative stress-mediated antitumor activity of erythorbic acid in high doses

Intravenous (iv) infusion of high-dose ascorbic acid (AA) has been used as a treatment for cancer patients. The tumoricidal action of AA occurs due to its prooxidant effect. Erythorbic acid (EA), one of the AA epimers, has reduced vitamin C activity, while the antioxidant activity of EA is similar to that of AA. Currently, other physiological and pharmacological functions of EA are not well known. We examined the cytotoxicity of EA to murine colon carcinoma (colon-26) cells and the antitumor activity of EA in tumor-bearing mice. Cytotoxic activity of EA to colon-26 cells was evaluated by using the calcein-AM assay. EA showed the same cytotoxic activity to colon-26 cells as that of AA. The cytotoxicity of EA was shown to be caused by oxidative stress. Next, colon-26 tumor-bearing mice were iv administered EA and AA on alternate days for 4 times, and tumor growth rates were measured. Tumor growth was significantly inhibited by administration of high-dose EA in vivo as well as AA. Finally, the in vivo biodistribution and clearance of EA and AA were investigated in tumor-bearing mice. Endogenous AA in the tumor was consumed to resist oxidative stress caused by reactive oxygen species that was generated by administered EA. These results indicated that the oxidative stress-mediated antitumor activity is one of the pharmacological functions of high-dose iv EA.     

15-Hydroperoxyeicosapentaenoic acid, but not eicosapentaenoic acid, shifts arachidonic acid away from cyclooxygenase pathway into acyl-CoA synthetase pathway in rabbit kidney medulla microsomes

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). In the present study, we investigated the effects of eicosapentaenoic acid (EPA) and 15-hydroperoxyeicosapentaenoic acid (15-HPEPE) on the PG and AA-CoA formations from high and low concentrations of AA (60 and 5 microM) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 microM [(14)C]-AA in 0.1M Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl(2) and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. EPA reduced the PG and AA-CoA formations from both 60 and 5 microM AA. In contrast, 15-HPEPE decreased the PG formation without affecting the AA-CoA formation from 60 microM AA, and increased the AA-CoA formation at the expense of PG formation when 5 microM AA was used as substrate concentration. The experiments utilizing Fe(2+) and an electron spin resonance (ESR) revealed that 15-HPEPE elicits these effects in the form of hydroperoxy adduct. These results suggest that 15-HPEPE, but not EPA, has the potential to shift AA away from COX pathway into ACS pathway at low substrate concentration (close to the physiological concentration of AA).     

Microbial degradation of aspergillic acid by Trichoderma koningii M 102

A microorganism, strain M 102, capable of degrading aspergillic acid (AA), was first isolated from a soil sample in a drainage ditch and was identified as Trichoderma koningii Oudemans. This fungus degraded AA, but not hydroxyaspergillic acid (HAA) or deoxyaspergillic acid (DAA). The AA-degrading ability of M 102 was induced by incubation with AA but not with HAA or DAA. AA-degradation activity was found in a crude enzyme prepared from the mycelia induced by AA; this AA degradation reaction required NAD(P)H and oxygen.     

Media optimization of Parietochloris incisa for arachidonic acid accumulation in an outdoor vertical tubular photobioreactor

The green alga Parietochloris incisa contains a significant amount of the nutritionally valuable polyunsaturated fatty acid and arachidonic acid (AA) and is being considered for mass cultivation for commercial AA production. This study was primarily aimed to define a practical medium formulation that can be used in commercial mass cultivation that will contribute to a substantial increase in the AA productivity of P. incisa with concomitant reduction of nutritional cost. The effect of nutrient limitation on growth and AA content of this microalga was explored in a batch culture in outdoor conditions using a vertical tubular photobioreactor. The study was conducted in two parts: the first was primarily focused on the effect of different nitrogen concentration on growth and AA content and the second part compares nitrogen deprivation, combination of nitrogen and phosphorus deprivation, and combined overall nutrient limitations at different levels of deprivation under low and high population densities. Since complete nitrogen deprivation hampers lipid and AA accumulation of P. incisa, thus, a critical value of nitrogen supply that will activate AA accumulation must be elucidated under specific growth conditions. Under the present experimental conditions, 0.5?g(-1) sodium nitrate obtained a higher AA productivity and volumetric yield relative to the nitrogen-deprived culture corresponding to 36.32?mg?L(-1)?day(-1) and 523.19?mg?L(-1). The combined nitrogen and phosphorus limitation seemed to enhance AA productivity better than nitrogen deprivation alone. The effect of overall nutrient limitation indicates that acute nutrient deficiency can trigger rapid lipid and AA syntheses. The effect of light as a consequence of culture cell density was also discussed. This study therefore shows that the nutrient cost can be greatly reduced by adjusting the nutrient levels and culture density to induce AA accumulation in P. incisa.     

Influence of OKY-1581 on responses to arachidonic acid in the feline pulmonary vascular bed

The effects of OKY-1581, a thromboxane synthesis inhibitor, on pulmonary vascular responses to arachidonic acid (AA) were investigated under baseline and elevated tone conditions in the intact chest cat. Under conditions of controlled blood flow at baseline tone, intralobar injections of AA increased lobar arterial pressure in a dose-related manner. These pressor responses were reduced by OKY-1581, and a small vasodilator response was unmasked. The administration of indomethacin to these same animals abolished all responses to AA. When baseline tone in the pulmonary vascular bed was elevated by infusion of U46619, intralobar injections of AA caused a biphasic change in lobar arterial pressure characterized by an initial increase followed by a secondary fall in pressure. Treatment with OKY-1581 attenuated the pressor component of the response and enhanced the depressor component of the response. All responses to AA at elevated tone were also blocked by indomethacin. Pressor responses to intralobar injections of U46619 were not altered by OKY-1581 or indomethacin and were similar under baseline and high pulmonary vascular tone conditions. The results of this study suggest that the pulmonary pressor response to AA in the cat is dependent in large part on the formation of TXA2 and also suggest that TXA2, PGI2, and vasoconstrictor prostaglandins (PGF2 alpha, PGD2, PGE2) are formed from AA in the cat lung.     

Identification of 3,4-dihydroxy-2-oxo-butanal (L-threosone) as an intermediate compound in oxidative degradation of dehydro-L-ascorbic acid and 2,3-diketo-L-gulonic acid in a deuterium oxide phosphate buffer

Dehydro-L-ascorbic acid (DAA), an oxidation product of L-ascorbic acid (vitamin C), is unstable in the neutral and basic pH regions. When DAA was incubated in a phosphate buffer with deuterium oxide (pH 7.4), it was degraded to form the main degradation compound, which was identified as 3,4-dihydroxy-2-oxobutanal (L-threosone). This compound was also formed from diketo-L-gulonic acid (DKG) in a phosphate buffer with deuterium oxide. L-threosone had reducing activity, probably due to its enolization, and is likely to have been involved in the formation of the reducing activity that was observed in aqueous DAA and DKG solutions. As a reactive dicarbonyl compound, L-threosone might also take some role in the cross-linking of tissue proteins that are formed in vivo in the Maillard reaction.     

Reduction of dehydroascorbic acid by homocysteine

To determine the reductive process of extracellular dehydroascorbic acid (DHA), molecules (homocysteine, homocysteine thiolactone, methionine, cysteine, and homoserine) were tested to identify those with the potential to reduce DHA to ascorbic acid (AA). Homocysteine (Hcy) was the most potent of the molecules tested. The efficacy of Hcy was compared with that of other molecules able to reduce DHA (reduced glutathione (GSH) and cysteine (Cy)). Although all three molecules were able to reduce DHA, GSH and Cy were not to reduce DHA to AA at concentrations lower than 100 micromol/l, and only less than 5% DHA was reduced to AA at concentrations of 200-300 micromol/l. In contrast, Hcy reduced DHA to AA stoichiometrically at concentrations as low as 10 micromol/l. In Jurkat and U937 cells, the increasing concentrations of extracellular Hcy suppressed intracellular dehydroascorbic acid uptake, indicating that extracellular reduction of DHA by Hcy leads to decreasing extracellular DHA available for its intracellular uptake. Simultaneous oxidation and reduction of Hcy and DHA were accelerated extracellularly in the presence of quercetin, an inhibitor of DHA uptake, suggesting that extracellular ascorbic acid concentration increased via blocking DHA uptake by quercetin and reducing extracellular DHA by Hcy. The effect of homocysteine on DHA reduction and uptake was confirmed with human umbilical vein endothelial cells. The oxidation of Hcy also prevented the decrease in DNA synthesis in human umbilical vein endothelial cells, which would occur following exposure to Hcy.     

The effects of fatty acyl CoA esters on the formation of prostaglandin and arachidonoyl-CoA formed from arachidonic acid in rabbit kidney medulla microsomes

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). We have previously shown that palmitoyl-CoA (PA-CoA) shifts AA away from the COX pathway into the ACS pathway in rabbit kidney medulla at a low concentration of AA (5 microM, close to the physiological concentration of substrate). In the present study, we investigated the effects of stearoyl (SA)-, oleoyl (OA)- and linoleoyl (LA)- CoAs on the formation of PG and AA-CoA from 5microM AA in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 5microM [(14)C]-AA in 0.1 M-Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl(2)and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. SA- and OA-CoAs increased AA-CoA formation with a reduction of PG formation, as well as PA-CoA. On the other hand, LA-CoA decreased formation of both PG and AA-CoA. These results suggest that fatty acyl CoA esters can be regulators of PG and AA-CoA formation in kidney medulla under physiological conditions.     

Determination of ascorbic acid and its related compounds in foods and beverages by hydrophilic interaction liquid chromatography

A new hydrophilic interaction liquid chromatography method for the simultaneous determination of ascorbic acid (AA), erythorbic acid (EA), 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) and 2-O-beta-D-glucopyranosyl-L-ascorbic acid (AA-2betaG) was developed using a diol column with an isocratic solution of acetonitrile-66.7 mM ammonium acetate solution (85:15, v/v) at a detection wavelength of 260 nm. The calibration curves were found to be linear in the range of 1-50 microg/ml for AA and EA and in the range of 2.5-100 microg/ml for AA-2G and AA-2betaG. Detection limits of AA, EA, AA-2G and AA-2betaG were 0.3, 0.3, 0.03 and 0.03 microg/ml, respectively. This method was satisfactorily applied to the determination of AA, EA, AA-2G and AA-2betaG in a fruit, a food and beverages. The results show that the procedure is simple and sensitive and that it can be employed for the simultaneous determination of AA and its related compounds in foods and beverages.     

The role of ascorbic acid in the control of flowering time and the onset of senescence

Ascorbic acid (AA) is not only an important antioxidant, it also appears to link flowering time, developmental senescence, programmed cell death, and responses to pathogens through a complex signal transduction network. The biological activity of AA is defined by its oxidation and subsequent regeneration into the reduced form. Some studies suggest that the total endogenous level of AA influences induction of flowering and senescence. Both processes require the co-ordinated regulation of gene expression, which is mediated by various phytohormones. For example, gibberellins and salicylic acid are known to promote flowering, but inhibit or retard senescence in Arabidopsis. Ethylene and abscisic acid accelerate senescence. Ascorbic acid serves as an important co-factor for the synthesis of some of these hormones. Therefore, it is assumed that AA affects phytohormone-mediated signalling processes during the transition from the vegetative to the reproductive phase and the final stage of development, senescence. This review summarizes recent reports that investigate the effect of AA on flowering time and the onset of senescence. An attempt was made to bring these findings in context with previously characterized flowering and senescence pathways and a model is proposed that may explain how AA influences flowering and senescence both under long- and short-day conditions in Arabidopsis.     

Effects of endocrine disruptors on the formation of prostaglandin and arachidonoyl-CoA formed from arachidonic acid in rabbit kidney medulla microsomes

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). To explore the possible actions of endocrine disruptors on the metabolic fate of free AA into these two pathways, we investigated the effects of nonylphenol (NP), bisphenol A (BPA), di-n-butyl phthalate (DBP), benzyl-n-butyl phthalate (BBP) and di-2-ethylhexyl phthalate (DEHP) on the formation of PG and AA-CoA from 5 microM AA (close to the physiological concentration of the substrate) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 5 microM [(14)C]-AA in 0.1 M Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl(2) and CoA). After incubation, PG (as total PGs) and AA-CoA were separated by selective extraction using petroleum ether and ethyl acetate. NP (1-200 microM) strongly enhanced the AA-CoA formation with a coincident decrease in the PG formation. BPA, DBP, BBP and DEHP failed to show any effect on the PG and AA-CoA formation up to 200 microM. Experiments utilizing 60 microM AA as the substrate concentration indicated that, under a low concentration of AA, NP decreases PG formation by inhibiting the COX activity, and reduces the AA flow into the COX pathway through inhibition on the COX activity, increasing availability of the substrate for the ACS and leading to enhanced AA-CoA formation. These results firstly show that NP has the potential to disturb the balance of PG and AA-CoA formations under normal physiological conditions.     

The regulation of prostaglandin and arachidonoyl-CoA formation from arachidonic acid in rabbit kidney medulla microsomes by palmitoyl-CoA

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). In the present study, we investigated the effects of palmitic acid (PA) and palmitoyl-CoA (PA-CoA) on the PG and AA-CoA formation from high and low concentrations of AA (60 and 5 microM) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 microM [14C]-AA in 0.1 M-Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced glutathione and hydroquinone) and cofactors of ACS (ATP, MgCl2 and CoA). After incubation, PG (as total PGs), AA-CoA and residual AA were separated by selective extraction using petroleum ether and ethyl acetate. PA (10-100 microM) had no effect on the PG and AA-CoA formation from either 60 or 5 microM AA. PA-CoA (10-100 microM) was without effect on the PG and AA-CoA formation from 60 microM AA, whereas it markedly decreased the PG formation (6-40%) and increased the AA-CoA formation (1.1-2.3-fold) from 5 microM AA, showing that the effects of PA-CoA on the PG and AA-CoA formation change depending on the AA concentration. These results suggest that PA-CoA, but not PA, may regulate the PG and AA-CoA formation at low substrate concentrations (close to the physiological concentration of AA), and that this in-vitro method using 5 microM AA may be useful for clarifying the homeostatic control of the metabolic fate of AA into these two enzymatic pathways.     

Severe water deficit-induced ethylene production decreases photosynthesis and photochemical efficiency in flag leaves of wheat

Wheat (Triticum aestivum L.) cv. Jimai22 was used to evaluate the effect of ethylene evolution rate (EER) and 1-aminocyclopropane-1-carboxylic acid (ACC) and their relations with photosynthesis and photochemical efficiency in plants well-watered (WW) and under a severe water deficit (SWD). SWD caused a noticeable reduction in the grain mass. The marked increases in both EER and the ACC concentration were observed under SWD; it was reversed effectively by exogenous spermidine (Spd) or amino-ethoxyvinylglycine (AVG). Thermal images indicated that SWD increased obviously the temperature of flag leaves, mainly due to the decrease in transpiration rate under SWD. Exogenous Spd or AVG decreased to some extent the temperature of the flag leaves. The strong decline in photosynthetic rate (P _N) and stomatal conductance as well as the photodamage of PSII were also observed under SWD after 14 and 21 days after anthesis (DAA). Intercellular CO₂ concentration was reduced at 7 DAA, but slightly increased at 14 and 21 DAA under SWD, indicating that the decreased P _N at 7 DAA might result from stomatal limitations, while the decline after 14 and 21 DAA might be attributed to nonstomatal limitations. Correlation analysis suggested that EER and ACC showed negative relations to photosynthesis and photochemical efficiency. Data obtained suggested that the effects of SWD were mediated predominantly by the increase in EER and ACC concentration, which greatly decreased the leaf photosynthesis and photochemical efficiency, and, therefore, reduced the grain mass. Application of Spd or AVG reduced the EER and ACC, and thus positively influenced photosynthesis and photochemical efficiency under SWD.     

The effects of nitric oxide and peroxynitrite on the formation of prostaglandin and arachidonoyl-CoA formed from arachidonic acid in rabbit kidney medulla microsomes

Under physiological conditions, small amounts of free arachidonic acid (AA) are released from membrane phospholipids, and cyclooxygenase (COX) and acyl-CoA synthetase (ACS) competitively act on this fatty acid to form prostaglandins (PGs) and arachidonoyl-CoA (AA-CoA). To clarify factors deciding the metabolic fate of free AA into these two pathways, we investigated the effects of a nitric oxide (NO) donor 1-hydroxyl-2-oxo-3-(N-methyl-3-aminopropyl)-3-methyl-1-triazene (NOC7), and peroxynitrite (ONOO(-)) on the formation of PG and AA-CoA from high and low concentrations of AA (60 and 5 micro M) in rabbit kidney medulla microsomes. The kidney medulla microsomes were incubated with 60 or 5 micro M [14C]-AA in 0.1M Tris/HCl buffer (pH 8.0) containing cofactors of COX (reduced GSH and hydroquinone) and cofactors of ACS (ATP, MgCl(2) and CoA). After incubation, PG (as total PGs) and AA-CoA were separated by selective extraction using petroleum ether and ethyl acetate. When 60 micro M AA was used as the substrate concentration, NOC7 stimulated the PG formation at 0.5 micro M, and inhibited it at 50 and 100 micro M, without affecting the AA-CoA formation. When 5 micro M AA was used as the substrate concentration, NOC7 showed no effect on the PG and AA-CoA formation up to 10 micro M or below, but enhanced the AA-CoA formation with a coincident decrease in the PG formation at 50 micro M or over. Experiments utilizing a NO antidote, carboxy-2-phenyl-4,4,5,5-tetramethylimidazoline-1-oxyl 3-oxide, revealed that the observed effects of NOC7 using 60 and 5 micro M AA are caused by NO. On the other hand, ONOO(-) stimulated the PG formation from 60 micro M AA, with no alteration in the AA-CoA formation at a concentration of 100 micro M, but when 5 micro M AA was used as the substrate concentration, it was without effect on the PG and AA-CoA formation. These findings indicate that actions of NO and ONOO(-) on the PG and AA-CoA formation by the kidney medulla microsomes may change depending on the substrate concentration. The effects of NO using 5 micro M AA were reversed by the addition of the superoxide generating system (xanthine-xanthine oxidase plus catalase), indicating that superoxide is a vital modulator of the action of NO. These results suggest that NO, but not ONOO(-), can be a regulator of the PG and AA-CoA formation at low substrate concentrations (close to the physiological concentration of AA), and that superoxide may play an important role in the action of NO.     

Regulation of uterine and umbilical amino acid uptakes by maternal amino acid concentrations

We tested the hypothesis that decreased fetal amino acid (AA) supply, produced by maternal hypoaminoacidemia (low AA) during hyperglycemia (HG), is reversible with maternal AA infusion and regulates fetal insulin concentration ([I]). We measured net uterine and umbilical AA uptakes during maternal HG/low AA concentration ([AA]) and after maternal intravenous infusion of a mixed AA solution. After 5 days HG, all maternal [AA] except glycine were decreased >50%, particularly essential [AA] (P < 0.00005). Most fetal [AA] also were decreased, especially branched-chain AA (P < 0.001). Maternal AA infusion increased net uterine uptakes of Val, Leu, Ile, Met, and Ser and net umbilical uptakes of Val, Leu, Ile, Met, Phe, and Arg but did not change net uteroplacental uptake of any AA. Fetal [I] increased 55 +/- 14%, P < 0.001, with correction of fetal [AA], despite the lack of change in fetal glucose concentration. Thus generalized maternal hypoaminoacidemia decreases uterine and umbilical uptakes of primarily the essential AA and decreases fetal branched-chain [AA]. These changes are reversed with correction of maternal [AA], which also increases fetal [I].     

Production of the polyunsaturated fatty acids arachidonic acid and eicosapentaenoic acid by the fungus Pythium ultimum

Several strains of species of the fungal genus Pythium, and of Phytophthora cinnamomi, were screened for content of the polyunsaturated fatty acids (PUFAs) arachidonic acid (AA) and eicosapentaenoic acid (EPA). The aim of the investigation was to establish alternative sources of these PUFAs, which are of importance in human nutrition. As a relatively prolific producer of EPA and AA, P. ultimum strain #144 was selected for a study of conditions that enhance their production over baseline levels that are present in the fungus when cultured for 6 d at 25 degrees C with rotary shaking (120 r.p.m.) in Vogel's medium containing sucrose as the carbon substrate. The levels of AA and EPA under these conditions were 133 +/- 27 and 138 +/- 25 mg l-1 (n = 5), respectively. Maximal production of these fatty acids was accomplished by the following sequence of steps. (1) Incubate the cultures for 6 d after inoculation under the conditions described above. Then (2) add glucose to the cultures (2%, w/v, final concentration) and incubate for a further 6 d at 13 degrees C. Under these conditions, the AA content of the mycelium was 205% higher than baseline levels and the EPA content was 198% higher. (3) Allow the cultures to remain stationary for 10 d which increases the AA content to 253% above baseline levels and the EPA content by 236%. Using such a procedure, 322 mg AA l-1 and 383 mg EPA 1-1 were produced.