Effects of Sulphur Dioxide on Sugar and Free Amino Acid Content of Pine Seedlings

Treatment of jack pine (Pinus banksiana Lamb.) seedlings with gaseous SO₂ resulted in a shift between the reducing and non-reducing sugars. Increasing concentrations of gaseous SO₂ caused an increase in reducing sugars and a decline in the non-reducing sugars, suggesting a conversion from the latter to the former at high SO₂ concentrations. The total amino acid content of the intact tissues also increased with increasing concentrations of gaseous SO₂. Gas-liquid chromatographic analyses of the amino acids indicated that SO₂ (1. 34 mg · m^-3 for 96 h) resulted in an increase in the content of alanine, valine, glycine, isoleucine, leucine, threonine, aspartic acid tyrosine, lysine, and arginine, and a decrease in the content of serine and glutamic acid. The enzymatic and other implications of such changes are discussed.     

Equilibrium and dynamic investigations of organic acids adsorption onto ion-exchange resins

The aim of the study was to determine properties of selected ion-exchange resins for citric and lactic acids recovery, to define sorption isotherms for these acids at different temperatures (in the range of 20–60°C) and to determine diffusion coefficients inside sorbent particles. A mathematical model of the ion-exchange process in the chromatographic column and its experimental verification is also presented. During investigations 18 types of ion-exchange resins were tested. It was found that weakly basic resins were more suitable for the recovery process than strongly basic ones. The best resin for the separation of citric acid was Amberlite IRA-67 and for lactic acid Amberlite IRA-92. As a result of transient-state sorption experiments diffusion coefficients of the citric acid inside the sorbent particle at different temperatures were obtained. It was found that D_p increased with the temperature by two times in the range of 20–60°C, and its value at 60°C was 7.2×10^–10 m²/s. The proposed mathematical model was applied to identify bed operation parameters in the column for the needs of the simulated moving bed chromatography method.List of symbols b Equilibrium constant in Langmuir equation, [dm³/g] - c Acid concentration in the liquid phase inside the particle pores, [g/dm³] - C Acid concentration in the liquid, [g/dm³] - D_L Axial dispersion coefficient, [m²/s] - D_p Intraparticle diffusion coefficient, [m²/s] - k_f Liquid film mass transfer coefficient, [m/s] - L Ion-exchanger bed height, [m] - q Acid concentration in the adsorbent phase, [g/dm³] - R_p Particle radius, [m] - U Volumetric flow rate of the feeding solution, [dm³/s] - V Volume of the solution, [dm³] - W Weight of the wet resin particles, [g] - The ion-exchanger bed porosity, [-] - _p Particle porosity, [-] - Linear liquid velocity, [m/s] - Apparent density of the wet resin, [g/dm³]     

Laser microdissection of conifer stem tissues: Isolation and analysis of high quality RNA,terpene synthase enzyme activity and terpenoid metabolites from resin ducts and cambial zone tissue of white spruce (<Emphasis Type="Italic">Picea glauca</Emphasis>)

Background  

Laser microdissection (LMD) has been established for isolation of individual tissue types from herbaceous plants. However, there are few reports of cell- and tissue-specific analysis in woody perennials. While microdissected tissues are commonly analyzed for gene expression, reports of protein, enzyme activity and metabolite analysis are limited due in part to an inability to amplify these molecules. Conifer stem tissues are organized in regular patterns with xylem, phloem and cortex development controlled by the activity of the cambial zone (CZ). Defense responses of conifer stems against insects and pathogens involve increased accumulation of terpenoids in cortical resin ducts (CRDs) and de novo formation of traumatic resin ducts from CZ initials. These tissues are difficult to isolate for tissue-specific molecular and biochemical characterization and are thus good targets for application of LMD.     

Metabolism of α-aminoisobutyric acid in mungbean hypocotyls in relation to metabolism of 1-aminocyclopropane-1-carboxylic acid

1-Aminocyclopropane-1-carboxylic acid (ACC) is known to be converted to ethylene and conjugated into N-malonyl-ACC in plant tissues. When -amino[1-¹⁴C]isobutyric acid (AIB), a structural analog of ACC, was administered to mungbean (Vigna radiata L.) hypocotyl segments, it was metabolized to ¹⁴CO₂ and conjugated to N-malonyl-AIB (MAIB). -Aminoisobutyric acid inhibited the conversion of ACC to ethylene and also inhibited, to a lesser extent, N-malonylation of ACC and d-amino acids. Although the malonylation of AIB was strongly inhibited by ACC as well as by d-amino acids, the metabolism of AIB to CO₂ was inhibited only by ACC but not by d-amino acids. Inhibitors of ACC conversion to ethylene such as anaerobiosis, 2,4-dinitrophenol and Co²⁺, similarly inhibited the conversion of AIB to CO₂. These results indicate that the malonyalation of AIB to MAIB is intimately related to the malonylation of ACC and d-amino acids, whereas oxidative decarboxylation of AIB is related to the oxidative degradation of ACC to ethylene.Abbreviations ACC 1-aminocyclopropane-1-carboxylic acid - AIB -aminoisobutyric acid - MACC 1-(malonylamino)-cyclopropane-1-carboxylic acid - MAIB -(malonylamino)-isobutyric acid - Mes 2-(N-morpholino)ethanesulfonic acid     

Mapping QTL controlling fatty acid composition in a doubled haploid rapeseed population segregating for oil content

Increasing oil content and improving the fatty acid composition in the seed oil are important breeding goals for rapeseed (Brassica napus L.). The objective of the study was to investigate a possible relationship between fatty acid composition and oil content in an oilseed rape doubled haploid (DH) population. The DH population was derived from a cross between the German cultivar Sollux and the Chinese cultivar Gaoyou, both having a high erucic acid and a very high oil content. In total, 282 DH lines were evaluated in replicated field experiments in four environments, two each in Germany and in China. Fatty acid composition of the seed oil was analyzed by gas liquid chromatography and oil content was determined by NIRS. Quantitative trait loci (QTL) for fatty acid contents were mapped and their additive main effects were determined by a mixed model approach using the program QTLMapper. For all fatty acids large and highly significant genetic variations among the genotypes were observed. High heritabilities were determined for oil content and for all fatty acids (h ² = 0.82 to 0.94), except for stearic acid content (h ²= 0.38). Significant correlations were found between the contents of all individual fatty acids and oil content. Closest genetic correlations were found between oil content and the sum of polyunsaturated fatty acids (18:2 + 18:3; r _G = −0.46), the sum of monounsaturated fatty acids (18:1 + 20:1 + 22:1; r _G = 0.46) and palmitic acid (16:0; r _G = −0.34), respectively. Between one and eight QTL for the contents of the different fatty acids were detected. Together, their additive main effects explained between 28% and 65% of the genetic variance for the individual fatty acids. Ten QTL for fatty acid contents mapped within a distance of 0 to 10 cM to QTL for oil content, which were previously identified in this DH population. QTL mapped within this distance to each other are likely to be identical. The results indicate a close interrelationship between fatty acid composition and oil content, which should be considered when breeding for increased oil content or improved oil composition in rapeseed.     

Absorption of short-chain fatty acids across ruminal epithelium of sheep

Investigations on the absorption of shortchain fatty acids across ruminal epithelium of sheep were performed both in vitro (Ussing chamber technique, using propionic acid representatively for shortchain fatty acids) and in vivo (washed, isolated reticulorumen). A pH-induced, nearly tenfold increase in the concentration of undissociated propionate led to an only twofold increase in mucosal-to-serosal flux of propionate (in vitro). Neither amiloride (1 mmol·l^-1, in vitro) nor theophylline (10 mmol·l^-1, in vivo), inhibitors of the ruminal Na⁺/H⁺ exchanger, exerted any significant influence on propionate fluxes or short-chain fatty acids absorption, respectively. Total replacement of luminal Na⁺ (by choline) did not alter short-chain fatty acids absorption (in vivo). Mucosal 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (0.1 mmol·l^-1) or mucosal nitrate (40 mmol·l^-1) markedly reduced propionate net flux (in vitro). Increasing mucosal Cl^- concentration brought about a significant drop in mucosal-to-serosal flux of propionate (in vitro) and in short-chain fatty acids net absorption (in vivo), respectively. The results obtained suggest that short-chain fatty acids are absorbed both as anions and as undissociated acids across ruminal epithelium of sheep. It is concluded that short-chain fatty acids anions either compete with Cl^- for binding sites at a common anion-exchange mechanism or that they are absorbed by an short-chain fatty acids anion/HCO ₃ ^- exchanger indirectly coupled to a Cl^-/HCO ₃ ^- exchanger via intracellular bicarbonate.Abbreviations DIDS 4,4-diisothiocyanatostilbene-2,2-disulfonic acid - DMSO dimethylsulfoxide - G _t tissue conductance - HSCFA protonated - SCFA i.e. undissociated form - J _ms mucosal-to-serosal flux - J _sm serosal-to-mucosal flux - J _net net flux - I _sc short-circuit current - MOPS (3-[N-morpholino]propanesulfonic acid) - mu mucosal - Prop Propionate - SCFA ^- SCFA anions, i.e. dissociated form - SCFA short-chain fatty acids - SEM standard error of mean     

Effects of excitatory neurotransmitter amino acids on swelling of rat brain cortical slices.

Abstract— With the single rat brain cortical slice serving as an in vitro bio-assay system, the effects of neurotransmitter amino acids (1 mm ) on brain swelling, water, sodium and potassium content, inulin space, and lactate production were studied. The putative dicarboxylic amino acid neurotransmitters, l -glutamic acid and l -aspartic acids, greatly increased intracellular brain swelling with increased intracellular Na⁺, water content and lactate production, and decreased inulin space and intracellular K⁺. Equimolar GABA, taurine, glycine, the putative inhibitory neurotransmitter amino acids, and equimolar α-amino-isobutyric acid had no effect. Brain swelling and intracellular Na⁺/K⁺ ratios were greatly increased by l -glutamate and l -aspartate at a concentration of 10 mm . However, l -aspartate at these concentrations greatly depleted the K⁺ content and lactate production as compared to l -glutamate. Further studies indicated that only the structural analogs and isomers of the dicarboxylic amino acids possessing two acidic groups and an α-amino group had a similar effect on the induction of brain swelling. Among the analogs of glutamic acid, dl -homocysteic acid and kainic acid had a greater effect on brain swelling, as observed from the total adenosine 5′-triphosphate (ATP) levels and the time-course and dose-response. A biphasic response in lactate production was induced by dl -homocysteic acid and kainic acid, suggesting that these analogs had a neurotoxic effect on cellular metabolism at higher concentrations.     

Responses of Neodiprion sertifer (Hym., Diprionidae) larvae to variation in needle resin acid concentration in Scots pine

Summary We have studied how differences in needle resin acid concentrations between two clones of Scots pine influenced larval survival, larval developmental time, and cocoon weight in Neodiprion sertifer. Larvae were reared under controlled conditions in the laboratory on needles showing a three-fold difference, in resin acid concentration. Larval developmental time was significantly longer for larvae fed needles high in resin acids. No significant differences were found in cocoon weight. Larvae fed needles high in resin acids suffered significantly higher mortality, most of which occurred, in the first two instars. Data on relative growth rate for last-instar larvae, based on a traditional growth efficiency experiment, did not show any negative effects of resin acids, indicating that a possible induction takes place during early instars. Observations on the feeding behaviour of last-instar larvae, the high consumption of bark tissue (with high concentrations of resin acids) by larvae fed needles low in resin acids and preference for needle tissues high in resin acids, indicate that these larvae might actively search for tissues rich in resin acids. We conclude that the physiology and behaviour of N. sertifer has been shaped, in part, by the conflict between the negative effects of resin acids, primarily in early instars (longer developmental time with a corresponding increase in exposure to natural enemies and an increase in direct mortality), and the positive effect of resin acids in later instars (a need for resin acids for use in its own predator defence secretion).     

Plasma free amino acid kinetics in rainbow trout (<Emphasis Type="Italic">Oncorhynchus mykiss</Emphasis>) using a bolus injection of <Superscript>15</Superscript>N-labeled amino acids

To gain insight into the metabolic design of the amino acid carrier systems in fish, we injected a bolus of ¹⁵N amino acids into the dorsal aorta in mature rainbow trout (Oncorhynchus mykiss). The plasma kinetic parameters including concentration, pool size, rate of disappearance (R _d), half-life and turnover rate were determined for 15 amino acids. When corrected for metabolic rate, the R _d values obtained for trout for most amino acids were largely comparable to human values, with the exception of glutamine (which was lower) and threonine (which was higher). R _d values ranged from 0.9 μmol 100 g⁻¹ h⁻¹ (lysine) to 22.1 μmol 100 g⁻¹ h⁻¹ (threonine) with most values falling between 2 and 6 μmol 100 g⁻¹ h⁻¹. There was a significant correlation between R _d and the molar proportion of amino acids in rainbow trout whole body protein hydrolysate. Other kinetic parameters did not correlate significantly with whole body amino acid composition. This indicates that an important design feature of the plasma-free amino acids system involves proportional delivery of amino acids to tissues for protein synthesis.     

Autotrophe Gewebekulturen von Ruta graveolens und deren 14CO2-Markierungsprodukte

Summary It is possible to obtain autotrophic callus cultures by inhibiting cell respiration. During a first passage of four weeks the cultures synthesized chlorophyll on an agar-medium with a minimum of organic substances such as sugar, amino acids and vitamins. In the second passage these cultures were kept on the same medium but were aerated with a mixture of 99% N₂ and 1% CO₂. In the third and last passage the medium contained only mineral substances and the same mixture of N₂ and CO₂ was used for aeration. This pure mineral medium was supplemented with the Hoagland's solution.These autotrophic callus cultures were grown for about two years under these conditions and showed a growth quotient of ten.Three different groups of tissues were taken for the ¹⁴CO₂-fixation. The first group was grown for four weeks on a heterotrophic medium and aerated with O₂. This is the socalled respirating group. The second and third group were both aerated with the mixture of N₂/CO₂ but they were grown on different mediums. One of these groups was grown on a heterotrophic medium for four weeks: these are heterotrophic photosynthesizing tissues. The third group was grown on a pure mineral medium, and these are the autotrophic photosynthesizing callus tissues.Respirating tissues are different from photosynthesizing cultures in respect to the quantity of light-induced CO₂-fixation.The thin-layer chromatograms reveal the difference between heterotrophic and autotrophic tissues. In the light dependent ¹⁴CO₂-incorporation the difference is in the amounts of the labelled amino acids glycine and serine. In the dark dependent incorporation the difference is found in the amount of the labelled amino acid aspartic acid. The more autotrophic these tissues are, the higher the level of the CO₂-fixation in these amino acids is.

---

---

Mit Hilfe der Deutschen Forschungsgemeinschaft.     

Solid-Phase synthesis of peptide nucleic acids

Peptide nucleic acids (PNA) were synthesized by a modified Merrifield method using several improvements. Activation by O-(benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate in combination with in situ neutralization of the resin allowed efficient coupling of all four Boc-protected PNA monomers within 30 min. HPLC analysis of the crude product obtained from a fully automated synthesis of the model PNA oligomer H-CGGACTAAGTCCATTGC-Gly-NH₂, indicated an average yield per synthetic cycle of 97.1%. N¹-benzyloxycarbonyl-N6³-methylimidazole triflate substantially outperformed acetic anhydride as a capping reagent. The resin-bound PNAs were successfully cleaved by the ‘low–high’ trifluoromethanesulphonic acid procedure.     

不同甜叶菊品种叶中绿原酸类成分的比较研究

该文以14个扦插培育的甜叶菊品种叶为材料,从8种不同型号的树脂中筛选出一种合适的大孔吸附树脂对甜叶菊叶中绿原酸类成分进行纯化前处理,采用HPLC法对不同甜叶菊品种叶中所含绿原酸类成分进行比较分析。结果表明:(1)在8种不同型号的树脂中,XAD^-16对甜叶菊叶中绿原酸类成分吸附-解析性能最佳。(2)经优化,上样液浓度1.20 mg·mL^-1、样品溶液pH 3、解析液乙醇体积分数70%时XAD^-16树脂对甜叶菊叶中绿原酸类成分具有较好的纯化效果。(3) HPLC检测分析表明,在14个品种中共检测出新绿原酸、绿原酸、隐绿原酸、异绿原酸B、异绿原酸A、异绿原酸C六种绿原酸类成分,其中主要成分均为异绿原酸A、绿原酸、异绿原酸C,而在品种3、5、13、14中没有检测出异绿原酸B。(4) 14个品种中6个绿原酸类成分的含量分别为异绿原酸A 20.55⁵4.3 mg·g^-1、绿原酸17.96³2.93 mg·g^-1、异绿原酸C 4.15^1<...     

Optimization of growth and fatty acid composition of a unicellular marine picoplankton,Nannochloropsis sp., with enriched carbon sources

A unicellular marine picoplankton, Nannochloropsis sp., was grown under CO₂-enriched photoautotrophic or/and acetate-added mixotrophic conditions. Photoautotrophic conditions with enriched CO₂ of 2800 l CO₂ l^–1 and aeration gave the highest biomass yield (634 mg dry wt l^–1), the highest total lipid content (9% of dry wt), total fatty acids (64 mg g^–1 dry wt), polyunsaturated fatty acids (35% total fatty acids) and eicosapentaenoic acid (EPA, 20:53) (16 mg g^–1 dry wt or 25% of total fatty acids). Mixotrophic cultures gave a greater protein content but less carbohydrates. Adding sodium acetate (2 mM) decreased the amounts of the total fatty acids and EPA. Elevation of CO₂ in photoautotrophic culture thus enhances growth and raises the production of EPA in Nannochloropsis sp.     

Proton conductance caused by long-chain fatty acids in phospholipid bilayer membranes

Summary Mechanisms of proton conductance (G _H) were investigated in phospholipid bilayer membranes containing long-chain fatty acids (lauric, myristic, palmitic, oleic or phytanic). Membranes were formed from diphytanoyl phosphatidylcholine in decane plus chlorodecane (usually 30% vol/vol). Fatty acids were added either to the aqueous phase or to the membrane-forming solution. Proton conductance was calculated from the steadystate total conductance and the H⁺ diffusion potential produced by a transmembrane pH gradient. Fatty acids causedG _H to increase in proportion to the first power of the fatty acid concentration. TheG _H induced by fatty acids was inhibited by phloretin, low pH and serum albumin.G _H was increased by chlorodecane, and the voltage dependence ofG _H was superlinear. The results suggest that fatty acids act as simple (A^– type) proton carriers. The membrane: water partition coefficient (K _p ) and adsorption coefficient () were estimated by finding the membrane and aqueous fatty acid concentrations which gave identical values ofG _H. For palmitic and oleic acidsK _p was about 10⁵ and was about 10^–2 cm. The A^– translocation or flip-flop rate (k _a ) was estimated from the value ofG _H and the fatty acid concentration in the membrane, assuming that A^– translocation was the rate limiting step in H⁺ transport. Thek _A 's were about 10^–4 sec^–1, slower than classical weak-acid uncouplers by a factor of 10⁵. Although long-chain fatty acids are relatively inefficient H⁺ carriers, they may cause significant biological H⁺ conductance when present in the membrane at high concentrations, e.g., in ischemia, hypoxia, hormonally induced lipolysis, or certain hereditary disorders, e.g., Refsum's (phytanic acid storage) disease.     

Bryophytes attenuate anthropogenic nitrogen inputs in boreal forests

Productivity in boreal ecosystems is primarily limited by available soil nitrogen (N), and there is substantial interest in understanding whether deposition of anthropogenically derived reactive nitrogen (N_r) results in greater N availability to woody vegetation, which could result in greater carbon (C) sequestration. One factor that may limit the acquisition of N_r by woody plants is the presence of bryophytes, which are a significant C and N pool, and a location where associative cyanobacterial N‐fixation occurs. Using a replicated stand‐scale N‐addition experiment (five levels: 0, 3, 6, 12, and 50 kg N ha^?1 yr^?1; n=6) in the boreal zone of northern Sweden, we tested the hypothesis that sequestration of N_r into bryophyte tissues, and downregulation of N‐fixation would attenuate N_r inputs, and thereby limit anthropogenic N_r acquisition by woody plants. Our data showed that N‐fixation per unit moss mass and per unit area sharply decreased with increasing N addition. Additionally, the tissue N concentrations of Pleuorzium schreberi increased and its biomass decreased with increasing N addition. This response to increasing N addition caused the P. schreberi N pool to be stable at all but the highest N addition rate, where it significantly decreased. The combined effects of changed N‐fixation and P. schreberi biomass N accounted for 56.7% of cumulative N_r additions at the lowest N_r addition rate, but only a minor fraction for all other treatments. This ‘bryophyte effect’ can in part explain why soil inorganic N availability and acquisition by woody plants (indicated by their δ¹⁵N signatures) remained unchanged up to N addition rates of 12 kg ha^?1 yr^?1 or greater. Finally, we demonstrate that approximately 71.8% of the boreal forest experiences N_r deposition rates at or below 3 kg ha^?1 yr^?1, suggesting that bryophytes likely limit woody plant acquisition of ambient anthropogenic N_r inputs throughout a majority of the boreal forest.     

Plant regeneration by somatic embryogenesis from cultured immature embryos of oak (Querem robur L.) and linden (Tilia cordata Mill.)

Embryogenic cultures and somatic embryos were obtained from immature zygotic embryos of oak (Quercus robur L.) cultured on a modified MS medium and WPM containing BAP (1 mg·l^–1) and GA₃ (1 mg·l^–1) or BAP and IBA. Germination and conversion of oak somatic embryos into plantlets was achieved on WPM containing a reduced concentration of cytokinin. Linden (Tilia cordata Mill.) somatic embryos developed in embryogenic tissues initiated from immature zygotic embryos cultured on a modified MS medium supplemented with 2,4-D (0.3-2.0 mg·l^–1). Germination of linden somatic embryos and plantlet formation occurred on MS medium containing a low concentration of IBA. Oak and linden plantlets produced from somatic embryos were successfully established in soil. Somatic embryos and plantlets were also regenerated from embryogenic cultures of Quercus petraea and Tilia platyphyllos.Abbreviations BAP 6-benzyIaminopurine - GA₃ gibberellic acid - IBA indole-3-butyric acid - 2,4-D 2,4-dichlorophenoxyacetic acid - MS Murashige and Skoog (1962) - WPM woody plant medium     

Phosphate accumulation of <Emphasis Type="Italic">Acetobacter xylinum</Emphasis>

The cells of Acetobacter xylinum decreased phosphate concentration in the medium from 5 to 2.5 or 0.3 mM during incubation in the presence of Mg²⁺ and glucose, or Mg²⁺ and casamino acids, respectively. The prevalence of orthophosphate or polyphosphate in the biomass of A. xylinum depends on the medium composition. Under phosphate uptake in the presence of glucose, the content of orthophosphate in the biomass changed little, while that of polyphosphate increased fourfold. At incubation with casamino acids, the content of orthophosphate increased 15 times, while that of polyphosphate increased only 2.5 times. Some part of orthophosphate in this case seems to be bound with the cell surface. The polyphosphate chain length in the cells of A. xylinim increases under phosphate uptake. This increase is more noticeable in the presence of glucose. Casamino acids can be replaced by α-ketoglutaric acid in combination with (NH₄)₂SO₄, or arginine, or glutamine, the catabolism of which results in formation of NH₄ ⁺ and α-ketoglutarate.     

Extremely high activities of phosphoenolpyruvate carboxylase in thermogenic tissues of Araceae

Phosphoenolpyruvate carboxylase activity in extracts of a wide range of thermogenic tissues of the Araceae was shown to be in the range 10–100 mol g^-1 fresh weight min^-1 (0.5–3.7 mol mg^-1 protein min^-1). Such high activities were not found in non-thermogenic tissues of the Araceae or in thermogenic tissues of Aristolochia brasiliensis Mart. and Zucc., Victoria amazonica Schomb. and Encephalartos barteri Carruth. During development and thermogenesis in the club of Arum maculatum L. the high activities of the carboxylase did not lead to any marked accumulation of citrate, isocitrate, 2-oxoglutarate, fumarate, malate and oxaloacetate. Clubs of Arum maculatum and of Arum italicum Miller readily fixed ¹⁴CO₂ in the dark, mostly into aspartate, malate, alanine and glutamate. Pulse and chase experiments showed that most of the fixed carbon was very rapidly metabolized to CO₂. The detailed distribution suggest that this occurred largely by decarboxylation of C-4 acids. It is suggested that thermogenic tissues of the Araceae are characterized by very high activities of phosphoenolpyruvate carboxylase, and that in vivo this leads to synthesis of C-4 acids which are promptly decarboxylated.     

Long-chain acyl CoA synthetase in microsomes from rat brain gray matter and white matter

Long-chain acyl coenzyme A (CoA) synthetase in homogenates and microsomes from rat brain gray and white matter was studied. The formation of the thioesters of CoA was studied upon addition of [1-¹⁴C]-labeled fatty acids. The maximal activities were seen with linoleic acid, followed by arachidonic, palmitic, and docosahexaenoic acids in both gray and white matter homogenates and microsomes. The specific activities in microsomes were 3–5 times higher than in homogenates. The presence of Triton X-100 in the assay system enhanced the activity of long-chain acyl CoA synthetase in homogenates. The effect was more pronounced in palmitic and docosahexaenoic acid activation. The apparentK _m values andV _max values for palmitic and docosahexaenoic acids were much lower than for linoleic and arachidonic acids. The presence of Triton X-100 in the medium caused a definite decrease in the apparentK _m and Vmax values for all the fatty acid except palmitic acid in which case the reverse was true. There were no significant differences observed in the kinetic measurements between gray and white matter microsomes. These findings are similar to those resulting from the known interference of Triton X-100 in the measurement of kinetic variables of long-chain acyl CoA synthetase of liver microsomes. In this work, no correlation was observed between the fatty acid composition of gray and white matter and the capacity of these tissues for the activation of different fatty acids.     

Metabolism of alpha-Ketoglutarate by Roots of Woody Plants

The uptake and metabolism of α-ketoglutarate-5-¹⁴C by peach, apple, and privet root tissues were studied over various time intervals. As much as 80% of the absorbed ¹⁴C appeared as ¹⁴CO₂ in 320 minutes in peach roots. Apple and privet roots were less effective in this conversion with the bulk of the ¹⁴C found in the organic acid fraction. This indicates differences in organic acid metabolism among species of woody plants.

The ¹⁴C accumulated in malate earlier and in larger quantities than in citrate. Both glutamate and aspartate were labeled in 10 minutes and glutamate was labeled as early as 3 minutes. The labeling pattern does not clearly distinguish between the synthesis of glutamate by glutamic dehydrogenase or by transamination with oxaloacetate.

The rapid metabolism of α-ketoglutarate to glutamate by the 3 species studied indicates the presence of enzyme systems important in amino acid synthesis in the roots of woody plants.