Mannitol metabolism in Eimeria tenella.

, and 1992. Mannitol metabolism in Eimeria tenella. International Journal for Parasitology 22: 1157–1163. Unsporulated oocysts of Eimeria tenella contain large quantities of carbohydrates, namely amylopectin, mannitol and glucose. Analysis of the carbohydrate content of sporulating oocysts revealed that mannitol content increased markedly during early stages of sporogony (first 4–6 h) but slowly diminished during the next 40 h of sporulation. Accumulation of mannitol was accompanied by a rapid decrease in amylopectin and free glucose, suggesting that mannitol might be synthesized from glucose released from amylopectin. Mannitol was also detected in sporozoite and merozoite extracts. All four mannitol cycle enzymes were detected in oocysts. Sporozoites excysted in vitro had lower activities of all four enzymes. Mannitol-1 -phosphatase and mannitol dehydrogenase activity was also detected in merozoites obtained from the second stage schizonts. Sporozoites incubated with ¹⁴C-glucose accumulated radioactively labelled precursor continuously for over 12 h and some of the ¹⁴C-glucose was converted into ¹⁴C-mannitol. These results indicate that mannitol plays an important role in the metabolism and development of the intracellular stages of the parasite.     

Uptake of 13C-glucose by cell suspensions of carrot (Daucus carota) measured by in vivo NMR: Cycling of triose-, pentose- and hexose-phosphates

After a lag phase of 2 days, batch-grown cells of carrot ( Daucus carota L.) cv. Flakkese entered the exponential growth phase and started to accumulate sucrose and hexoses. Short-term feeding ¹³C-glucose in this period resulted in only minor labelling of sucrose or fructose. CO₂ production from [1-¹³C]- and [6-¹³C]-glucose revealed, that at least 40% of the added glucose passed through the oxidative pentose phosphate pathway (OPPP), up to 40% through glycolysis leaving only minor ¹³C-glucose for incorporation in various cell components in the exponential growth phase. After about 11 days of culture, the medium sugars were exhausted, cells entered the stationary growth phase and consumed stored sugar. Both neutral and acid invertase (EC 3.2.1.26) and sucrose synthase (EC 2.4.1.13) increased 50% from day 0 to days 11–13; thereafter their levels decreased again. Labelling with ¹³C-glucose resulted in the accumulation of labelled sucrose and fructose during the stationary growth phase. Sucrose labelling was transient, i.e. after 6 h its level started to decrease again. Labelled fructose, however, evolved slower and increased even after 8 h. In sucrose and fructose up to 20% of the ¹³C-label was exchanged from C-1 to C-6 carbons, indicating intensive cycling of at least 40% of the carbon between hexoses and triose phosphates. In the stationary phase only 10% of the labelled glucose passed through the OPPP and about 30% passed through the respiratory pathway; the remaining 60% was incorporated in cell constituents and sugars. Comparing the various cycles revealed that the regulation of the OPPP operated relatively independently from the cytosolic cycling of hexose phosphates through sucrose and from the cycling between hexose phosphates and triose phosphates.     

Mechanism of chain initiation by dextransucrase: Absence of terminal ‘sucrose’ linkage in newly synthesized dextran chains

Dextran was synthesized using dextransucrase from Streptococus sanguis 10558 and (F)-[¹⁴C]sucrose as substrate to test the possibility that sucrose may be the initial acceptor for glucose. If sucrose is the initial acceptor, then dextran chains should have [¹⁴C] fructose in a terminal ‘sucrose’ linkage which can be cleaved under mild conditions. Although incorporation of [¹⁴C]fructose into dextran was observed, the label was not released by mild hydrolysis, indicating that sucrose is not the initiator for dextran synthesis. Incorporation of [¹⁴C]fructose into dextran might represent its ability to act as an acceptor, as suggested by the isolation of leucrose as a by-product in the reaction.     

Sucrose accumulation in developing peach fruit

Uptake of ¹⁴C-sugars and activities of sucrose metabolizing enzymes were determined in order to study the mechanism(s) of sucrose accumulation in developing peach fruit. Mesocarp of young peach fruit contained glucose and fructose but little sucrose. Starting 88 days after anthesis (DAA) the sucrose concentration increased greatly. The mechanism of sucrose accumulation was studied by measuring ¹⁴C-sucrose and ¹⁴C-glucose uptake rates at three different stages of fruit development, and by assaying weekly the activity of enzymes involved in the hydrolysis and/or synthesis of the soluble sugars. Uptake of 0.5–100 m M ¹⁴C-sucrose and ¹⁴C-glucose by mesocarp tissue slices showed a complex pattern at the first stage of fruit development (62 DAA). During the subsequent growth stages the pattern of sugar uptake changed and was approximately monophasic at the third stage of fruit development.
At 10 m M , glucose was taken up more rapidly than sucrose at the first and second stage of fruit development. Uptake was partially inhibited by the uncoupler carbonylcyanide m -chlorophenylhydrazone (CCCP) at 25 μ M. These results, together with the presence of a putative extracellular invertase, suggest an apoplastic route for sucrose uptake which is dependent, at least in part, on energy supply.
Activities of sucrose hydrolyzing enzymes (insoluble acid invertase, soluble acid invertase, neutral invertase, sucrose synthase) were high in young fruits and declined sharply with fruit development concomitantly with accumulation of sucrose. The storage of the sugar was not accompanied by a rise in synthetic activities (sucrose synthase, sucrose phosphate synthase), suggesting that sucrose could, at least in part enter the carbohydrate pool directly.     

Identification of [I]endothelin binding sites in human coronary tissue

In vitro receptor autoradiography has been used to study the distribution of [¹²⁵I]endothelin binding sites in human coronary tissue from patients undergoing cardiac transplantation. Dense binding of [¹²⁵I]endothelin was associated with the smooth muscle of epicardial coronary arteries as well as to perivascular regions of these vessels. Binding was also associated with the ventricular myocardium. There was an increased binding of [¹²⁵I]endothelin to atheromatous tissue, both coronary arteries and vein graft.

The [¹²⁵I]endothelin binding sites identified using in vitro autoradiography are likely to be functionally relevant since endothelin causes a concentration-dependent contraction of segments of human epicardial coronary arteries in vitro and also has positive inotropic activity on isolated human cardiomyocytes.

The presence of specific binding sites for [¹²⁵I]endothelin on coronary tissue and the increased binding in atheromatous tissue suggest that endothelin is a peptide which may play a role in the maintenance of vascular tone and/or the pathogenesis of ischaemic heart disease.     

Sugar Transport in Immature Internodal Tissue of Sugarcane: II. Mechanism of Sucrose Transport

The mechanism by which sucrose is transported into the inner spaces of immature internodal parenchyma tissue of sugarcane (Saccharum officinarum L. var. H 49-5) was studied in short term experiments (15 to 300 seconds). Transport of sucrose, glucose, and fructose was each characterized by a V_max of 1.3 μmoles/gram fresh weight·2 hours, and each of these three sugars mutually and competitively inhibited transport of the other two. When ¹⁴C-glucose was supplied exogenously, ¹⁴C-glucose 6-phosphate and ¹⁴C-glucose were the first labeled compounds to appear in the tissue; no ¹⁴C-sucrose was detected until after 60-second incubation. After 15-second incubation in ¹⁴C-sucrose, all intracellular radioactivity was in glucose, fructose, glucose 6-phosphate, and fructose 6-phosphate; trace amounts of ¹⁴C-sucrose were found after 30 seconds and after 5 minutes, 71% of the intracellular radioactivity was in sucrose. Although it was possible that sucrose was transported intact into the inner space and then immediately hydrolyzed, it was shown that the rate of hydrolysis under these conditions was too low to account for the rate of hexose accumulation. Pretreatment of the tissue with rabbit anti-invertase antiserum eliminated sucrose transport, but had no effect on glucose transport. Since the antibodies did not penetrate the plasmalemma, it was concluded that sucrose was hydrolyzed by an invertase in the free space prior to transport. The glucose and fructose moieties, or their phosphorylated derivatives, were then transported into the inner space and sucrose was resynthesized. No evidence for the involvement of sucrose phosphate in transport was found in these experiments.     

Dopamine receptor elevation by cholecystokinin

High concentrations of cholecystokinin (CCK) in the striatum and limbic areas of the brain suggest that this peptide may influence dopaminergic transmission. Thus, the effect of CCK on dopamine D₂ receptors in the striatum and nucleus accumbens of the rat brain both in vitro and in vivo (central and peripheral administration) was studied by determining the binding of ³H-spiperone. The density (B_max) of D₂ receptors was elevated (a) by 20% in the accumbens upon in vitro co-incubation with 10⁻⁶ M CCK. (A non-significant drop of 10% occurred in the striatum); (b) by about 40% in the accumbens and 25% in the striatum after continuous intraventricular infusion of CCK for 24 hr. The increase in receptor density in the accumbens was maintained for 14 days and in both tissues was specific to CCK (neurotensin infusion did not alter ³H-spiperone binding); (c) by 20% in the accumbens and 15% in the striatum 3 hr after a single IP injection of 50 μg/kg CCK or caerulein, and maintained up to 14 days later. These results suggest that CCK elevates dopamine D₂ receptors in the accumbens and striatum and may be a physiological modulator of the dopaminergic system.     

A review of the use of isotopic and nuclear techniques in animal production

Isotopic and nuclear techniques play an important role in food and agriculture, health and industry. This paper discusses the use of these techniques and highlights potential for their use in the area of Animal Production. These techniques are discussed in two parts: (1) Isotopic methods and (2) non-isotopic nuclear methods. The isotopic techniques discussed are: stable- (¹⁵N) and radio-isotope (³⁵S or ³²P) incorporation methods for measuring microbial mass in vitro and in vivo; ¹²⁵I-labelled bovine serum albumin and ¹⁴C-labelled polyethylene glycol assays for measuring tannin in feeds; a method based on the feeding of isotope-labelled protein (¹⁵N or ¹²⁵I) complexed with tannin for ranking different tannins for their abilities to release protein for digestion in vivo; ¹⁴C-uric acid and ¹⁴C-allantoin infusion methods for development of models describing excretion of purine derivatives in urine and microbial protein supply to ruminants, which permit assessment of nutritional status of animals and determination of nutritional quality of feed resources; a ¹⁵N isotope dilution technique using ¹⁵N-leucine to distinguish feed and endogenous secretions at the ileum, for determination of true digestibility of protein-rich tree leaves and aquatic plants in pigs; progesterone radioimmunoassay (RIA) for enhancing reproductive efficiency of ruminants, and RIA based leptin and insulin like growth factor assays for assessing the nutritional status of animals; feeding of ¹⁵N enriched plant material to generate ¹⁵N-labelled excreta for research on the fate of excreta N in the environment; ¹⁵N, ¹³C and ³⁴S isotopic methods for nutrient budgeting and for following the nutrient pathways in the soil–plant–animal continuum; ³²P- or ³³P-labelled fertilizers for estimating the efficiency of P utilization in legume leaf production used for livestock feeding; double labelled water (¹⁸O and ²H labelled) method for estimating energy expenditures of grazing animals, body composition, basal metabolic rate, and milk output in cows with calves; NaH¹³CO₃/NaH¹⁴CO₃ infusion for estimation of the carbon dioxide production, which in turn is used to estimate energy expenditure in free-ranging animals; ³H- or ¹⁴C-labelled methane and ¹⁴C-labelled volatile fatty acids dilution technique for direct and indirect (using stoichiometry of carbohydrate fermentation) for determination of methane emission from livestock; ¹⁵N dilution technique requiring labeling the soil with ¹⁵N fertilizer (¹⁵N-ammonium sulphate or ¹⁵N-urea) for estimation of nitrogen fixation by leguminous trees and pastures.

The non-isotopic nuclear techniques that have been used or have the potential for use are: dual energy X-ray absorptionmetry and computer tomography for body composition determination; nuclear magnetic resonance techniques, fast atom bombardment mass spectroscopy, and mass ionisation spectroscopy for identification and structure determination of bioactive moieties of plant origin having potential for rumen manipulation or controlling internal parasites; gamma irradiation for inactivating antinutrients such as protease inhibitors, lectin, phytic acid, non-starch polysaccharides and oligosaccharides in feeds; induced mutations with gamma radiation, electron beam and fast neutrons for producing useful mutants of forage plants with improved yield, nutrient profiles and uptake.     

In vitro steroid metabolic studies in human testes II: Metabolism of cholesterol, pregnenolone, progesterone, androstenedione and testosterone by testes of an estrogen-treated man

The effect of long-term in vivo estrogen treatment on in vitro steroidogenesis by the testes of a young man was investigated. In vitro incubation of testicular tissue of this man with ³H-pregnenolone, ³H-progesterone, ³H-androstenedione and ³H-testosterone demonstrated suppression of 17-hydroxylase activity, with little or no effect of the treatment on Δ⁵-3β-hydroxysteroid oxidoreductase, 5a-reductase and aromatase. Increased 20-hydroxysteroid oxidoreductase activity was observed. Determination of intratesticular steroid concentrations led to similar conclusions.     

Characteristics of microbial fermentation and potential digestibility of fiber in the hindgut of dugongs (Dugong dugon)

The number of microorganisms in the hindgut of dugongs (Dugong dugon) were estimated and their in vitro volatile fatty acid (VFA) production and degradation of eelgrass measured. Scanning electron microscopy showed that some rod bacteria attached to the surface of plant tissue degraded and eroded the cell walls. Number of starch-, lactate-, cellobiose-, pectin-, xylan- and cellulose-utilizing bacteria, sulfate-reducing bacteria and methane-producing bacteria were estimated at 10⁹ ∼ 10¹⁰ colony forming units g^-1. Microorganisms degraded the cellulose and noncellulolytic components of the eelgrass, and about 47.3% of dry matter was degraded after 36 h in vitro incubation. The total VFA concentration was 10.5 mmol dL^-1 at 36 h incubation, which included 55.7 mol% acetate, 18.0 mol% n-butyrate and 15.1 mol% propionate. The gas composition of in vitro fermentation was 68.4% carbon dioxide, 22.2% methane and 9.4% hydrogen.     

Regulatory effects of ammonia on carbon metabolism in photosynthesizing Chlorella pyrenoidosa

Addition of ammonia to Chlorella pyrenoidosa, photosynthesizing under steady-state conditions, causes changes in the metabolism which are due not only to the increased availability of NH₄⁺ for reductive amination but also to regulation of controlled enzymes. One such effect is an increased rate of the reaction which converts phosphoenolpyruvate to pyruvate in vivo. This regulatory effect was revealed by kinetic tracer studies with ¹⁴CO₂, paper chromatography and radioautographic analysis, which showed that upon addition of NH₄⁺ (1) the levels of both 3-phosphoglycerate and phosphoenolpyruvate drop, with the ratio of 3-phosphoglycerate/phosphoenolpyruvate increasing, (2) the level of labeled pyruvic acid increases and the rate of formation of alanine increases rapidly, while the rate of formation of serine is unaffected, (3) the rate of flow of carbon into the tricarboxylic acid cycle acids, malate and citrate, increases along with the increased rates of formation of glutamate, glutamine and aspartate and (4) the rate of labeling of lipids increases. The increased flow of carbon into amino acids is mostly at the expense of sucrose synthesis; starch synthesis decreases only slightly. The interruption of sucrose synthesis apparently is due to stopping the reaction between UDP-glucose and fructose 6-phosphate. The rate of conversion of fructose 1,6-diphosphate to fructose 6-phosphate is also decreased upon NH₄⁺ addition.     

Silverleaf whitefly stress impairs sugar export from cotton source leaves

Silverleaf whitefly (SLW), Bemisia argentifolii Bellows and Perring, is one of the most noxious pests of numerous field and vegetable crops, causing billions of dollars worth of damage throughout the world. SLW is a phloem feeder whose feeding is likely to interfere with phloem transport. The aim of this study was to test the hypothesis that SLW infestation impairs carbohydrate export from source leaves, and consequently increases their carbohydrate content. The youngest fully expanded leaves of cotton ( Gossypium hirsutum L., cv. Siv'on), grown under SLW-infested and noninfested conditions, were characterized for their diurnal changes in carbohydrate content and photoassimilate export. SLW infestation induced a considerable reduction in net photosynthetic rate (P_n), coupled with increased sucrose, glucose and fructose and decreased starch concentrations. Export rate was determined after 14 CO₂ pulse-labeling both by in situ monitoring of leaf radioactivity and by analyzing the content and radioactivity of the major carbon metabolites. Radioactive counting indicated a lower rate of 14 C efflux for the infested plants. A similar trend was found for the specific activities of sucrose and the three soluble sugars combined (sucrose, glucose and fructose). A single exponential decay function with asymptote was fitted to the above efflux curves. All the calculated exponential coefficients demonstrated lower export rates after SLW injury. These results indicate that SLW impairs photoassimilate export, suggesting possible down-regulation of P_n due to increased foliar soluble sugar contents.     

Living on a high sugar diet: the fate of sucrose ingested by a phloem-feeding insect,the pea aphid Acyrthosiphon pisum

The natural diet of aphids, plant phloem sap, generally contains high concentrations of sucrose. When pea aphids (Acyrthosiphon pisum) were fed on chemically defined diets containing sucrose radiolabelled in the glucose or fructose moiety, 2 to 12-fold and 87 to 110-fold more radioactivity was recovered from the tissues and honeydew, respectively, of aphids that ingested [U-(14)C-glucose]-sucrose than from those ingesting [U-(14)C-fructose]-sucrose. The total radioactivity recovered was 70% of the ingested [U-(14)C-glucose]-sucrose and <5% of ingested [U-(14)C-fructose]-sucrose. The dominant honeydew sugars produced by aphids feeding on 0.75 M sucrose diets were oligosaccharides comprising glucose. In vitro the guts of pea aphids had high sucrase activity, 1-5 U mg(-1) protein, generating equimolar glucose and fructose except at high sucrose concentrations where glucose production was inhibited (K(si)=0.1 M). These data suggest that the fructose moiety of ingested sucrose is assimilated very efficiently and may be preferentially respired by the aphid, and that the glucose moiety of sucrose is incorporated into oligosaccharides by the transglucosidase activity of the gut sucrase at high sucrose concentrations. These differences in the fate of sucrose-derived glucose and fructose are important elements in both the carbon nutrition and osmoregulation of aphids.     

Activity of dehydroabietic acid derivatives against wood contaminant fungi

The antifungal activity of 10 dehydroabietic acid derivatives with different configuration in A and B rings (cis/trans A/B junction) and different substituents and/or functionalities was evaluated in bioassays in vitro and in situ (pine wood blocks).

The test compounds dissolved in acetone were assayed at several concentrations w/w (test compound/culture medium) against the fungi. The Relative Inhibition (RI) was determined by measuring the radial growth of colonies of the fungi treated with the test compounds by comparison with those of control cultures; the results are expressed as EC₅₀.

The results of bioassays in vitro have shown that hydroxyl and aldehyde functions are required for antifungal activity in this group of compounds and deisopropylation can increase the activity. Our assay of antifungal activity in situ (in pine wood blocks) provides a means to investigate the preservative activities of these antifungal compounds under actual conditions of use.

The dehydroabietic acid derivative cis-deisopropyldehydroabietanol (10) inhibited the growth of several of the fungi tested, in vitro and in situ.

The results obtained in situ with the test compound (10) at 6% and 8% were not significantly different from the reference products and a good level of protection of the wood against the organisms tested was achieved.

The results in wood bioassays present new possibilities in the search for natural new compounds in the wood protection, as an alternative to conventional fungicides.     

Effects of nutrients on germination of Verticillium lecanii (=Lecanicillium sp.) conidia and infection of greenhouse whitefly, (Trialeurodes vaporariorum)

Laboratory experiments were conducted to assess effects of nutrients on germination of Verticillium lecanii (=Lecanicillium sp.) conidia and infection of the greenhouse whitefly, Trialeurodes vaporariorum. Suspensions of V. lecanii conidia were prepared in four nutrient solutions: 2% glucose, 2% sucrose, 2% maltose, and 2% peptone. Suspensions in de-mineralized water served as the control. At 23°C the germination rate was highest in the 2% glucose solution, followed by sucrose, maltose, demineralized water, and peptone, respectively. Germ tube growth was greatest at 23°C in the 2% glucose solution after 10 h incubation. Results of the bioassays indicated that the nutrients influenced whitefly infection. Infection levels were highest for conidial suspensions (1×10⁶ conidia/mL) prepared in 2% glucose, and were significantly greater than for peptone, demineralized water and maltose. Infection levels at 1×10⁸ conidia/mL were not significantly different from each other for all materials tested. The potential use of nutrients in a spray formulation as a means of enhancing field efficacy are discussed.     

Studies on the metabolism of testosterone trans-4-n-butylcyclohexanoic acid in the cynomolgus monkey, Macaca fascicularis

Metabolism of intravenously administered testosterone trans-4-n-butylcyclohexanoate (T bucyclate), a potent, long-acting androgen, was studied in cynomolgus monkeys (Macaca fascicularis). About 5% of the radioactivity of a dose of doubly labeled ester (¹⁴C, ³H) was excreted via the gastrointestinal tract. Most of the administered radioactivity was excreted in the urine within 120 h. No intact T bucyclate was recovered from either compartment. Tritium attributed to bucyclic acid and its metabolites was excreted rapidly (peak excretion was at 6 h after injection), while ¹⁴C excretion, attributed to testosterone and its metabolites, extended over 4 days. Testosterone metabolites were excreted predominantly as sulfate esters. Analysis of urinary products derived from the bucyclic acid moiety of T bucyclate showed no products susceptible to glucuronidase treatment, and showed a mixture of unidentified solvolyzable and unconjugated products. No unmetabolized trans-4-n-butylcyclohexanoic acid was detected in urine or feces. It is concluded that metabolism of testosterone bucyclate is initiated in vivo in cynomolgus monkeys by hydrolysis of ester to testosterone and bucyclic acid. The bucyclate side chain is rapidly cleared, and the testosterone is retained in the circulation.     

过表达MtVP1对马铃薯表型及糖代谢的影响

I型H⁺-PPase参与糖异生和蔗糖分解代谢,利用不同的糖(蔗糖、葡萄糖和果糖)饲喂拟南芥(Arabidopsis thaliana)Ⅰ型H⁺-PPase基因不同类型的突变体,产生的表型不一致,因此,推测Ⅰ型H⁺-PPase可能存在其它影响糖代谢的机制。为进一步明确该酶对糖代谢的影响,以过表达MtVP1的马铃薯(Solanum tuberosum)渭薯4号为研究对象,观察不同培养条件下的表型,监测糖含量变化,并利用转录组测序分析转录谱。结果表明,过表达MtVP1马铃薯表现出红色茎、紫色花和表皮毛更发达,单株块茎数减少,块茎变大,块茎皱缩速度加快;转基因马铃薯块茎中淀粉、葡萄糖和果糖含量显著下降,芽中葡萄糖和果糖含量也显著下降。果糖饲喂导致转基因马铃薯花青素含量显著降低;转基因马铃薯体内果糖-1,6-二磷酸酶和果糖-2,6-二磷酸酶基因表达上调3–7倍。研究结果为进一步从糖代谢角度探究Ⅰ型H⁺-PPase的生理功能提供参考。     

Phycomyces blakesleeanus car B mutants: Their use in assays of phytoene desaturase

Strains of car B (phytoene-accumulating) mutants of Phycomyces blakesleeanus have been characterized with respect to their carotene contents, in vitro formation of isoprenoids from [2-¹⁴C] mevalonic acid and their ability to produce [¹⁴C]phytoene in situ for use in coupled assays of phytoene desaturase activity. All strains produced predominantly (15-Z)-phytoene both in vivo and in vitro. Other isoprenoids were produced by cell extracts including squalene, sterols, prenyl diphosphates and prenyl alcohols. The addition of 1% Tween 60 to crude cell extracts of the mutants partially restored wild type carotenogenic activity and also altered the proportions of other isoprenoids formed. However, in a cytosolic fraction of the car B mutant, the addition of 1% Tween 60 did not result in the production of any carotenoid from phytoene. This fraction was the most effective source of [¹⁴C] phytoene for use in coupled assays of phytoene desaturase activity.     

Occurrence of singlet oxygen oxygenation of oleic acid and linoleic acid in the skin of live mice

To assess the contribution of singlet molecular oxygen [O₂ (¹Δ_g)] to lipid peroxidation in vivo, this study combined gas chromatography-mass spectrometry with thin layer chromatography to analyse peroxidized lipids in the skin of hairless mice. Hydroxyoctadecenoate isomers and unconjugated hydroxyoctadecadienoate isomers derived from peroxidized oleic acid and linoleic acid, respectively, which are specific to O₂ (¹Δ_g)-dependent oxygenation, were detected in the skin of live mice under ordinary feeding conditions. Short-term ultraviolet A (UVA)-irradiation of the skin in vivo elevated levels of the unconjugated hydroxyoctadecadienoate isomers significantly, whereas the irradiation of skin homogenate in vitro increased levels of all isomers derived from both O₂ (¹Δ_g) and free radical-dependent oxygenation to a much greater extent. This is the first report to demonstrate the occurrence of O₂ (¹Δ_g)-specific oxygenation of unsaturated fatty acids in living animals.