Hydrogen peroxide formation and lipid peroxidation in rat uterus—effect of hormones and vitamin E

The effect of estradiol-17β and progesterone given separately as well as in combination on the rate of hydrogen peroxide formation and lipid peroxidation in the uteri of ovariectomized rats was studied. Estradiol in 3μg dose per day per animal elicited maximum stimulatory response and progesterone (100μg), on the other hand, was without any such effect. However, progesterone given along with estradiol completely prevented the effect due to the latter. In the same way, vitamin E, a well known antioxidant was found to be extremelv effective in protecting the uterus from the highly peroxidative action of estradiol-17β.     

Application of Deuterated A-Tocopherols to the Biokinetics and Bioavailability of Vitamin E

-Tocopherol, a superior chain-breaking, peroxyl radical-trapping antioxidant and the most active component of vitamin E, is elevated in liver tumor cells, contributing to their greater resistance towards lipid peroxidation compared to cells from normal tissues. Also, in regenerating rat liver the level of vitamin E has been found to fluctuate in phase with the rate of cell division. In order to study the biokinetcis and mechanisms of the distribution of vitamin E in organs and within tissues of animals, deuterated forms of -tocopherol have been synthesized and their uptake into blood and tissues has been measured by gas chromatography-mass spectrometry. Measurement of the competitive uptake from a mixture of the RRR-and SRR--tocopherol stereoisomers labelled with different amounts of deuterium shows that the liver exerts a strong preference for secretion of the natural (RRR) stereoisomer into the plasma. It is suggested that a tocopherol-binding protein plays a key role in this process.     

Purification and partial characterisation of and α-tocopherol-binding protein from rabbit heart cytosol

An -tocopherol-binding protein has been isolated and purified from rabbit heart cytosol. The purified protein had an apparent molecular mass of 14,200, as derived from SDS-PAGE. The content of the protein in rabbit heart was around 11.8 g per g of tissue. The binding of -tocopherol to the purified protein was rapid, reversible, and saturable. Neither nor tocopherol could displace the bound -tocopherol from the protein, suggesting a high specificity for -tocopherol. -Tocopherol-binding protein did not bind oleate. Transfer of -tocopherol from liposomes to mitochodria was stimulated 8-fold in the presence of the binding protein, suggesting that this protein may be involved in the intracellular transport of -tocopherol in the heart.     

Antioxidant and Pigment Composition during Autumnal Leaf Senescence in Woody Deciduous Species Differing in their Ecological Traits

Abstract: Photoprotection mechanisms have been studied during autumnal senescence in sun and shade leaves of woody plants with different ecological characteristics and senescence patterns. Three of them belonging to the same family, Betulaceae: the shade‐intolerant and early successional species (Betula alba L.), the shade‐tolerant and late successional species (Corylus avellana L.), and an N‐fixing tree with low N resorption efficiency (Alnus glutinosa L.). The other two species: a shade‐intolerant (Populus tremula L.) and a shade‐tolerant (Cornus sanguinea L.), were chosen because of their ability to accumulate anthocyanins during autumnal leaf senescence. The study of plants with different ecological strategies allowed us to establish general trends in photoprotection mechanisms during autumnal senescence, when nutrient remobilisation occurs, but also during whole leaf ontogeny. We have not found a clear relationship between shade tolerance and the level of photoprotection; the main difference between both groups of species being the presence of α‐carotene in shade leaves of shade‐tolerant species. Preceding autumn, nitrogen resorption started in mid‐summer and occurred in parallel with a slight and continuous ascorbate, chlorophyll and carotenoid degradation. However, the ascorbate pool remained highly reduced and lipid oxidation did not increase at this time. Contrasting with ascorbate, α‐tocopherol accumulated progressively in all species. Only during the last stages of senescence was chlorophyll preferentially degraded with respect to carotenoids, leading to the yellowing of leaves, except in A. glutinosa in which a large retention of chlorophyll and N took place. Senescing leaves were characterised, except in C. sanguinea, by a relative increase in the proportion of de‐epoxidised xanthophylls: zeaxanthin, antheraxanthin and lutein. The light‐induced accumulation of anthocyanins in C. sanguinea could play an additional protective role, compensating for the low retention of de‐epoxidised xanthophylls. These different strategies among deciduous species are consistent with a role for photoprotective compounds in enhancing nitrogen remobilization and storage for the next growing season.     

γ-Tocopherol biokinetics and transformation in humans

Background: The uptake and biotransformation of γ-tocopherol (γ-T) in humans is largely unknown. Using a stable isotope method we investigated these aspects of γ-T biology in healthy volunteers and their response to γ-T supplementation.

Methods: A single bolus of 100 mg of deuterium labeled γ-T acetate (d²-γ-TAC, 94% isotopic purity) was administered with a standard meal to 21 healthy subjects. Blood and urine (first morning void) were collected at baseline and a range of time points between 6 and 240 h post-supplemetation. The concentrations of d² and d⁰-γ-T in plasma and its major metabolite 2,7,8-trimethyl-2-(b-carboxyethyl)-6-hydroxychroman (-γ-CEHC) in plasma and urine were measured by GC-MS. In two subjects, the total urine volume was collected for 72 h post-supplementation. The effects of γ-T supplementation on α-T concentrations in plasma and α-T and γ-T metabolite formation were also assessed by HPLC or GC-MS analysis.

Results: At baseline, mean plasma α-T concentration was approximately 15 times higher than γ-T (28.3 vs. 1.9 µmol/l). In contrast, plasma γ-CEHC concentration (0.191 µmol/l) was 12 fold greater than α-CEHC (0.016 µmol/l) while in urine it was 3.5 fold lower (0.82 and 2.87 µmol, respectively) suggesting that the clearance of α-CEHC from plasma was more than 40 times that of γ-CEHC. After d²-γ-TAC administration, the d² forms of γ-T and γ-CEHC in plasma and urine increased, but with marked inter-individual variability, while the d⁰ species were hardly affected. Mean total concentrations of γ-T and γ-CEHC in plasma and urine peaked, respectively, between 0–9, 6–12 and 9–24 h post-supplementation with increases over baseline levels of 6–14 fold. All these parameters returned to baseline by 72 h. Following challenge, the total urinary excretion of d²-γ-T equivalents was approximately 7 mg. Baseline levels of γ-T correlated positively with the post-supplementation rise of (d⁰ + d²) – γ – T and γ-CEHC levels in plasma, but correlated negatively with urinary levels of (d⁰ + d²)-γ-CEHC. Supplementation with 100 mg γ-TAC had minimal influence on plasma concentrations of α-T and α-T-related metabolite formation and excretion.

Conclusions: Ingestion of 100mg of γ-TAC transiently increases plasma concentrations of γ-T as it undergoes sustained catabolism to CEHC without markedly influencing the pre-existing plasma pool of γ-T nor the concentration and metabolism of α-T. These pathways appear tightly regulated, most probably to keep high steady-state blood ratios α-T to γ-T and γ-CEHC to α-CEHC.     

Oxidative stress,growth factor production and budding in potato tubers during cold storage

In order to verify the role played by oxidation in the budding of potato tubers (Solanum tuberosum L. cv. Kennebec), the physiological events occurring below bud at 4°C have been studied for a period of 6 months. The low temperature storage induced an increase in the degree of unsaturation and a decrease in the ratio of saturated/unsaturated fatty acids of membrane polar lipids with a subsequent increase of lipid hydroperoxides (LOOH). Cold stress increased both enzymatic antioxidative activities (superoxide dismutase, SOD, E.C.1.15.1.1; catalase, CAT, E.C. 1.11.1.6), and α-tocopherol levels thus protecting membrane's polyunsaturated lipids. Between 0 and 15 days of storage SOD/CAT ratio, α-tocopherol, LOOH levels and the degree of lipid unsaturation showed strong variations. After 30 to 120/150 days the antioxidative system seemed to reach a homeostasis different from that of time 0, accompanied by a constant increase of indole-3-acetic acid (IAA) after 60 days. The antioxidative system, after 150 days, lost its efficiency while LOOH levels were maintained higher than time 0 and IAA concentration was sufficient to allow sprouting.     

Free Radical-Induced Liver Injury. I. Effects of Dietary Vitamin E Deficiency on Triacylglycerol Level and its Fatty Acid Profile in Rat Liver

Effects of dietary vitamin E deficiency on the fatty acid compositions of total lipids and phospholipids were studied in several tissues of rats fed a vitamin E-deficient diet for 4, 6, and 9 months. No significant differences were observed between the vitamin E deficiency and controls except in the fatty acid profiles of liver total lipids. Triacylglycerol (TAG) accumulation was found in the liver of rats fed a vitamin E-deficient diet. The levels of TAG-palmitate and -oleate increased particularly in the liver from such animals. The fatty acid compositions of hepatic phospholipids were not affected by the diet. Increased TAG observed in the liver of rats fed a vitamin E-deficient diet was restored to normal when the diet was supplemented with 20 mg α-tocopheryl acetate/kg diet. These findings indicate that dietary vitamin E deficiency causes TAG accumulation in the liver and that the antioxidant, vitamin E, is capable of preventing free radical-induced liver injury.     

Purification and Some Properties of Arthrobacter globiformis Exo-l,6-α-glucosidase

A gram-positive and pleomorphic bacterium (strain I-42) isolated from soil as a producer of exo-l,6-α-glucosidase [EC 3.2.1.70] was identified as Arthrobacter globiformis. This Arthrobacter enzyme, inducible by dextran extracellularly, was partially purified from a cell-free culture supernatant. It was found most active at pH around 6.0 and most stable at pH 6.0~6.5. The enzyme was proved, by several experiments, to attack dextran in the exo-wise fashion to release only glucose leaving a macromolecular limit dextrandextrin. Transglucosylation from dextran to accumulating or added glucose was not observed.     

Response to different sources of vitamin E orally injected and to various doses of vitamin E in calf starter on the plasma vitamin E level in calves around weaning

Calves often face a lower plasma vitamin E level than the recommended level (3 µg/ml for adult cows) after weaning, a level which has been related to a good immune response. Two experiments were performed to determine the most effective source and level of vitamin E to be included in a calf starter to maintain the plasma vitamin E level above the recommended level after weaning. Experiment 1 (Exp 1) and experiment 2 (Exp 2) included a total of 32 and 40 calves, respectively, from 2 weeks before weaning until 2 weeks after weaning. In Exp 1, calves were orally injected a daily dose of different vitamin E sources including, no α-tocopherol (0 dose; Control), 200 mg/d of RRR-α-tocopherol (ALC), 200 mg/d of RRR-α-tocopheryl acetate (ACT), or 200 mg/d of all-rac-α-tocopheryl acetate (SYN). In Exp 2, a dose response study was carried out with 0, 60, 120, and 200 mg/kg of ALC in a pelleted calf starter. Final BW (100 ± 16 and 86 ± 11 kg) and average daily gain (956 ± 303 and 839 ± 176 g/d in Exp 1 and 2, respectively; mean ± SD) were unaffected by either source or level of α-tocopherol. In Exp 1, the plasma RRR-α-tocopherol level was affected by α-tocopherol source (P < 0.001), week (P < 0.001), and interaction between them (P < 0.001). At weaning time, the plasma RRR-α-tocopherol was 2.7, 2.1, 1.1, and 0.8 μg/ml in ALC, ACT, SYN, and Control, respectively. In Exp 2, the plasma α-tocopherol level was affected by ALC dose (P = 0.04), week (P < 0.001), and a tendency for an interaction between them was observed (P = 0.06). At weaning, a 36, 31, and 28% reduction in plasma α-tocopherol level was observed compared to the beginning of the experiment with 0, 60, and 120 mg/kg of ALC, respectively; however, with 200 mg/kg of ALC, a 9% increase in the plasma α-tocopherol level was observed. In addition, 200 mg/kg of ALC was able to maintain plasma α-tocopherol after weaning higher than the recommended level. The results showed that the ALC was the most efficient source of α-tocopherol supplementation to be used in a calf starter. In addition, the 200 mg/kg of ALC in the calf starter was the only effective dose to maintain the postweaning plasma vitamin E concentration at the recommended level after weaning and α-tocopherol similar to that observed before weaning.     

The comparative study of the effects of Fe2O3 and TiO2 micro- and nanoparticles on oxidative states of lung and bone marrow tissues and colony stimulating factor secretion

Nowadays, increased use of nanomaterials in industry and biomedicine poses potential risks to human health and the environment. Studying their possible toxicological effects is therefore of great significance. The present investigation was designed to examine the status of oxidative stress induced by nanoparticles (NPs) of ferric oxide (Fe₂O ₃) and titanium oxide (TiO ₂) with their micro-sized counterpart on mouse lung and bone marrow–derived normal tissue cells. We assessed the induction of oxidative stress by measuring its indicators such as antioxidant scavenging activity of superoxide dismutase and catalase as well as malondialdehyde concentration. Moreover, colony formation of bone marrow cells was assayed following induction with colony stimulating factor (CSF) from lung cells. NPs had a more potent stimulatory effect on the oxidative stress status than their micron-sized counterparts. In addition, the highest level of oxidative stress derived from TiO ₂ NPs was observed in both tissue types. Cotreatment with NPs and the antioxidant α-tocopherol reduced antioxidant activities and membrane lipid peroxidation (LPO) in the lung cells, but increased CSF-induced colony formation activity of bone marrow cells, suggesting that oxidative stress may be the cause of the cytotoxic effects of NPs. It is concluded that free radicals generated following exposure to NPs resulted in significant oxidative stress in mouse cells, indicated by increased LPO and antioxidant enzyme activity and decreased colony formation.