Studies on lipid oxidation in fish phospholipid liposomes

Fish phospholipid liposomes were prepared and used as an artificial membrane system to study factors influencing-lipid oxidation. The extent of lipid oxidation was indexed by measuring the amount of thiobarbituric acid reactive substances (TBARS) produced. Fe²⁺, Fe³⁺, and Cu²⁺ were potent prooxidants in catalysing lipid oxidation. These metal ions induced lipid oxidation in a dose dependent manner. However, Zn²⁺, Ni²⁺, and Mn²⁺ did not significantly (p>0.05) affect lipid oxidation at all the concentrations (1, 10, or 100 μM) studied. Morin, luteolin (flavonoids), butein (chalcone), tannic acid, ellagic acid (polyphenols), butylated hydroxyanisole (BHA), and butylated hydroxytoluene (BHT) (synthetic antioxidants) were potent antioxidants (producing <50% TBARS compared to control) of Fe²⁺-catalyzed lipid oxidation. Morin, luteolin, and butein possess two hydroxyl substituents, a C₄ ketone structure and a 2–3 double bond, all of which contributed to their antioxidative potential. Fe²⁺ caused some losses of polyunsaturated fatty acids (PUFA), whereas tannic acid protected the oxidation of several of the PUFA including C 16∶1 (Palmitoleic acid), C 18∶3 (Linolenic acid), C 20∶4 (Arachidonic acid), C 20∶5 (Eicosapentaenoic acid), and C 22∶6 (Docosahexaenoic acid).     

Chemolithoautotrophy and mixotrophy in the thiophene-2-carboxylic acid-utilizing Xanthobacter tagetidis

Xanthobacter tagetidis grew as a chemolithotrophic autotroph on thiosulfate and other inorganic sulfur compounds, as a heterotroph on thiophene-2-carboxylic acid, acetic acid and α-ketoglutaric acid, and as a mixotroph on thiosulfate in combination with thiophene-2-carboxylic acid and/or acetic acid. Autotrophic growth on one-carbon organosulfur compounds, and intermediates in their oxidation are also reported. Thiosulfate enhanced the growth yields in mixotrophic cultures, presumably by acting as a supplementary energy source, since ribulose bisphosphate carboxylase was only active in thiosulfate-grown cells and was not detected in mixotrophic cultures using thiosulfate with thiophene-2-carboxylic acid. Bacteria grown on thiophene-2-carboxylic acid also oxidized sulfide, thiosulfate and tetrathionate, indicating these as possible sulfur intermediates in thiophene-2-carboxylic acid degradation. Thiosulfate and tetrathionate were oxidized completely to sulfate and, consequently, did not accumulate as products of thiophene-2-carboxylic acid oxidation in growing cultures. K _m and V _max values for the oxidation of thiosulfate, tetrathionate or sulfide were 13 μM and 83 nmol O₂ min^–1 (mg dry wt.)^–1, respectively; thiosulfate and tetrathionate became autoinhibitory at concentrations above 100 μM. The true growth yield (Y_max) on thiophene-2-carboxylic acid was estimated from chemostat cultures (at dilution rates of 0.034–0.094 h^–1) to be 112.2 g mol^–1, with a maintenance coefficient (m) of 0.3 mmol thiophene-2-carboxylic acid (g dry wt.)^–1 h^–1, and the maximum specific growth rate (μ_max) was 0.116 h^–1. Growth in chemostat culture at a dilution rate of 0.041 h^–1 indicated growth yields [g dry wt. (mol substrate)^–1] of 8.1 g (mol thiosulfate)^–1, 60.9 g (mol thiophene-2-carboxylic acid)^–1, and 17.5 g (mol acetic acid)^–1, with additive yields for growth on mixtures of these substrates. At a dilution rate of 0.034 h^–1, yields of 57.8 g (mol α-ketoglutaric acid)^–1 and 60.7 g (mol thiophene-2-carboxylic acid)^–1 indicated some additional energy conservation from oxidation of the thiophene-sulfur. SDS-PAGE of cell-free preparations indicated a polypeptide (M _r, 21.0 kDa) specific to growth on thiophene-2-carboxylic acid for which no function can yet be ascribed: no metabolism of thiophene-2-carboxylic acid by cell-free extracts was detected. It was shown that X. tagetidis exhibits a remarkable degree of metabolic versatility and is representative of facultatively methylotrophic and chemolithotrophic autotrophs that contribute significantly to the turnover of simple inorganic and organic sulfur compounds (including substituted thiophenes) in the natural environment. Received: 1 July 1997 / Accepted: 3 November 1997     

Effects of flavonoid on calcium content in femoral tissue culture and parathyroid hormone-stimulated osteoclastogenesis in bone marrow culture in vitro

The effect of various flavonoids, which are present in food and plants, on bone calcium content and osteoclastogenesis were investigated to compare action of flavonoid on bone formation and bone resorption in vitro. Rat femoral-diaphyseal (cortical bone) and -metaphyseal (trabecular bone) tissues were cultured for 48 h in Dulbecco’s modified Eagle’s medium (high glucose) supplemented with antibiotics and bovine serum albumin. Amoung quercetin, myricetin, kaempferol, isorhamnetin, curcumin, hesperidin, or astaxanthin in the range of 10⁻⁷–10⁻⁵ M, culture with quercetin (10⁻⁶ or 10⁻⁵ M) caused a significant increase in diaphyseal calcium content. Such an effect was not seen in other compounds. Mouse bone marrow cells were cultured for 7 days in the presence of parathyroid hormone (PTH; 10⁻⁷ M), a bone-resorbing factor, in vitro. Culture with PTH caused a significant increase in osteoclast-like cell formation. This increase was significantly inhibited in the presence of quercetin, myricetin, kaempferol, isorhamnetin, or curcumin in the range of 10⁻⁸–10⁻⁶ M. Such an effect was not seen in the case of hesperidin or astaxanthin. In addition, culture with PTH (10⁻⁷ M) caused a significant decrease in diaphyseal calcium content. This decrease was completely prevented in the presence of quercetin, myricetin, kaempferal, or isorhamnetin of 10⁻⁶ M. This study demonstrates that various flavonoids have a potent inhibitory effect on osteoclastogenesis and bone resorption rather than bone formation in vitro. Among various flavonoids, quercetin had a stimulatory effect on bone formation and an inhibitory effect on bone resorption in vitro.     

Deficiency of the cystine-transporter gene, xCT, does not exacerbate the deleterious phenotypic consequences of SOD1 knockout in mice

Both α-lipoic acid (LA) and ascorbic acid (vitamin C) have been shown to improve endothelial dysfunction, a precursor of atherosclerosis. Since oxidant stress can cause endothelial dysfunction, we tested the interaction and efficacy of these antioxidants in preventing oxidant damage to lipids due to both intra- and extracellular oxidant stresses in EA.hy926 endothelial cells. LA spared intracellular ascorbate in culture and in response to an intracellular oxidant stress induced by the redox cycling agent menadione. Extracellular oxidant stress generated by incubating cells for 2 h in with 0.2 mg/ml LDL and 5 μM Cu²⁺ caused a time-dependent increase of the lipid peroxidation product malondialdehyde in both cells and LDL, preceded by rapid disappearance of` α-tocopherol in LDL. α-Lipoic acid at concentrations of 40–80 μM blunted these effects. Similarly, intracellular ascorbate concentrations of 1–2 mM also prevented Cu²⁺-induced lipid peroxidation in LDL and cells. Cu²⁺-dependent oxidation of LDL in the presence of ascorbate-loaded cells decreased intracellular ascorbate by 20%, but this decrease was not reversed by LA. Both LA and ascorbate protect endothelial cells and LDL from either intra- or extracellular oxidant stress, but that LA does not spare ascorbate in oxidatively stressed cells.     

Effect of Cu2+, Mn2+ and aromatic compounds on the production of laccase isoforms by Coprinus comatus

Six different extracellular laccase isoforms were identified in submerged cultures of the commercially important edible mushroom, Coprinus comatus. Although laccase activity (~55 IU/L) was readily detectable in unsupplemented control cultures containing 1.6 μM Cu²⁺ after 22-day incubation, mean enzyme levels (~150–185 IU/L) were 2.7–3.4-fold higher in cultures supplemented with 0.5–3.0 mM Cu²⁺. Laccase production was also stimulated by Mn supplementation over the range 0.05–0.8 mM Mn²⁺, and the peak value of ~225 IU/L recorded after 22 days in cultures containing 0.8 mM added Mn²⁺ was 4.5-fold higher compared with unsupplemented controls. Of 12 aromatic compounds tested for their effect on laccase isozyme production by C. comatus, highest laccase levels (~188 IU/L), equivalent to a 4.4-fold increase compared with unsupplemented controls (~43 IU/L), were recorded after 22 days in cultures supplemented with 3.0 mM caffeic acid. Other aromatic compounds tested all stimulated laccase production, with peak enzyme levels 1.3–3.3-fold higher compared with unsupplemented controls. Extracellular laccase levels in cultures supplemented with optimal concentrations of Mn²⁺ and caffeic acid together were 38% and 15% lower, respectively, compared with cultures containing the separate supplements. Lac1 was the most abundant laccase isoform produced under all the conditions tested, but marked differences were observed in the production patterns of Lac2–Lac6.     

Role of Quercetin on PCBs (Aroclor-1254) Induced Impairment of Dopaminergic Receptor mRNA Expression in Cerebral Cortex of Adult Male Rats

The present study is aimed to evaluate the putative neuroprotective effect of quercetin on PCB induced impairment of dopaminergic receptor mRNA expression in cerebral cortex of adult male Wistar rats. Group I (control) received only vehicle (corn oil; 0.1 ml/kg bwt) intraperitoneally (i.p); Group II Aroclor 1254 at a dose of 2 mg/kg bwt/day (i.p); Group III (Aroclor 1254—exposed (i.p), quercetin treated gavage (50 mg/kg bwt/day); Group IV received quercetin alone (gavage). 24 h after the 30th day treatment rats were euthanized. From each rat cerebral cortex tissues was collected and analyzed for mean activities of creatine kinase, acetylcholine esterase, Na⁺/K⁺, Ca²⁺ and Mg²⁺ATPases, Hydrogen peroxide generation, protein carbonyl content and lipid peroxidation levels. The fates of the mRNA expression of dopaminergic receptors, Cacna1d on all the groups were studied by RT–PCR. Results evidenced that significant reduction of neurodegeneration in PCBs exposed rats treated with quercetin was ascertained suggesting, quercetin treatment precludes against PCB induced oxidative stress and protects dopaminergic receptor dysfunction in rat cerebral cortex.     

Chemiluminescent in vitro estimation of the inhibitory constants of antioxidants ascorbic and uric acids in Fenton’s reaction in urine

The goal of this research was to measure in vitro the inhibitory constants of the antioxidants ascorbic and uric acid in urine, with lucigenin enhanced chemiluminescence (CL) in Fenton’s system. Maximum CL emission is registered in urine containing H₂O₂ (5·10⁻⁴ M), Fe²⁺ (5·10⁻⁵ M), EDTA (5·10⁻⁵ M), and chemical enhancer lucigenin (10⁻⁴ M) at pH 5.5 and 36°C. Ascorbic acid exhibits up to 4-fold stronger antioxidant effect than uric acid. The constants of antioxidant inhibition in urine were measured at concentrations 10⁻³ and 10⁻⁴ M: for ascorbic acid, 5.92 ± 0.04 and 24.05 ± 1.82 μmol·sec⁻¹; for uric acid, 1.60 ± 0.02 and 21.45 ± 0.97 μmol·sec⁻¹, respectively. Three phases of CL kinetics of urine are well observed: spontaneous CL (0–10 sec), fast flash of CL (10–50 sec), and latent period (50–300 sec). The antioxidant efficiency of ascorbic and uric acids in the final stage of catabolic processes in the body is discussed. Published in Russian in Biokhimiya, 2006, Vol. 71, No. 8, pp. 1062–1065.     

Effect of nutrition on fatty acid profiles of riverine, lacustrine, and aquaculture-raised salmonids of pre-alpine habitats

We examined trophic positions and fatty acid concentrations of riverine, lacustrine, and aquaculture diet and fish in Austrian pre-alpine aquatic ecosystems. It was hypothesized that dietary fatty acid (FA) profiles largely influence the FA composition of the salmonids Salvelinus alpinus, Salmo trutta, and Oncorhynchus mykiss. We analyzed trophic positions using stable isotopes (δ¹⁵N) and tested for correlations with polyunsaturated fatty acid (PUFA) concentrations. Gut content analysis revealed benthos (rivers), pellets (aquaculture), and zooplankton (lakes) as the predominant diet source. Results of dorsal muscle tissues analysis showed that the omega-3 PUFA, docosahexaenoic acid (DHA; 22:6n − 3), was the mostly retained PUFA in all fish of all ecosystems, yet with the highest concentrations in S. alpinus from aquaculture (mean: 20 mg DHA/g dry weight). Moreover, we found that eicosapentaenoic acid (EPA; 20:5n − 3) in fish of natural habitats (rivers, lakes) was the second most abundant PUFA (3–5 mg/g DW), whereas aquaculture-raised fish had higher concentrations of the omega-6 linoleic acid (18:2n – 6; 9–11 mg/g DW) than EPA. In addition, PUFA patterns showed that higher omega-3/-6 ratios in aquacultures than in both riverine and lacustrine fish. Data of this pilot field study suggest that salmonids did not seem to directly adjust their PUFA to dietary PUFA profiles in either natural habitats or aquaculture and that some alterations of PUFA are plausible. Finally, we suggest that trophic positions of these freshwater salmonids do not predict PUFA concentrations in their dorsal muscle tissues.     

The effect of some micronutrients and heavy metals on phosphate absorption by maize root cortex segments

The effect of salts (nitrates, chlorides, and sulfates) of microelements, Cd²⁺, Ni²⁺, and Co²⁺ and the effect of boric acid and ammonium molybdate on phosphate uptake by maize root cortex segments were tested. Higher concentration (0.1 mM) of Cu²⁺ salts caused enhancement of phosphate efflux to the extent that efflux was higher than influx. Inhibitory action on phosphate uptake by maize root cortex segments was exerted by following salts: 0.01 mM Cu²⁺ salts (20–30% inhibition), 0.5 mM ZnSO₄ (9.7%), 0.5 and 0.05 mM ZnCl₂ (34.3% and 20.8%), 0.1 mM salts of Cd²⁺, Ni²⁺, Co²⁺ (35–78%). 1 mM FeS_O4 had significant stimulatory effect (92%) on phosphate uptake. Much weaker stimulatory effect was exerted by 1 mM FeCl₃ (14%), 0.05 mM ZnS_O4 (9.6%), 0.005 mM ZnCla and ZnS_O4 (8.4 and 18.5%) and 0.001 mM CdCl2 and CdS_O4 (20.8 and 12.4%). All other tested salts-salts of Mn²⁺ (0.1 and 0.01 mM), 0.01 and 0.001 mM salts of Co²⁺ and Ni²⁺, 0.001 mM salts of Cu²⁺, 0.001–10 mM boric acid, and 0.001–0.1 mM ammonium molybdate left phosphate uptake unaffected.     

Boric acid inhibits stored Ca<Superscript>2+</Superscript> release in DU-145 prostate cancer cells

Boron (B) is a developmental and reproductive toxin. It is also essential for some organisms. Plants use uptake and efflux transport proteins to maintain homeostasis, and in humans, boron has been reported to reduce prostate cancer. Ca²⁺ signaling is one of the primary mechanisms used by cells to respond to their environment. In this paper, we report that boric acid (BA) inhibits NAD⁺ and NADP⁺ as well as mechanically induced release of stored Ca²⁺ in growing DU-145 prostate cancer cells. Cell proliferation was inhibited by 30% at 100μM, 60% at 250μM, and 97% at 1,000μM BA. NAD⁺-induced Ca²⁺ transients were partly inhibited at 250μM BA and completely at 1,000μM BA, whereas both NADP⁺ and mechanically induced transients were inhibited by 1,000μM BA. Expression of CD38 protein increased in proportion to BA exposure (0–1,000μM). In vitro mass spectrometry analysis showed that BA formed adducts with the CD38 products and Ca²⁺ channel agonists cyclic adenosine diphosphate ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). Vesicles positive for the Ca²⁺ fluorophore fluo-3 acetoxymethyl ester accumulated in cells exposed to 250 and 1,000μM BA. The BA analog, methylboronic acid (MBA; 250 and 1,000μM), did not inhibit cell proliferation or NAD⁺, NADP⁺, or mechanically stimulated Ca²⁺ store release. Nor did MBA increase CD38 expression or cause the formation of intracellular vesicles. Thus, mammalian cells can distinguish between BA and its synthetic analog MBA and exhibit graded concentration-dependent responses. Based on these observations, we hypothesize that toxicity of BA stems from the ability of high concentrations to impair Ca²⁺ signaling.     

Influence of some metal ions on the lipid content and arachidonic acid production byMortierella sp.

The influence of Ca²⁺, Mg²⁺, Mn²⁺, and Fe²⁺ ions on lipid accumulation, fatty acid composition and arachidonic acid (ARA) production byMortierella sp. S-17 was investigated. A beneficial effect of Mn²⁺ in the concentration range of 2–500 mg/L on lipogenesis was observed. The other elements at about 1 g/L repressed lipid accumulation and ARA yield. The highest yield of ARA (723 mg per liter or 148 mg per gram of dry mycelium) after incubation of the fungus in a glucose medium in the presence of 2 mg Mn²⁺ per liter was obtained. A strong inhibitory effect of Fe²⁺ (above 40 mg/L) on ARA formation was observed.     

Fifteen-year Change in Forest Floor Organic and Element Content and Cycling at the Turkey Lakes Watershed

To assess the long-term effects of atmospheric deposition on forest floor chemical composition, we took quantitative samplings of L-(Oi), F-(Oe), and H-(Oa) layers at an old-growth sugar maple–yellow birch stand on a till soil at the Turkey Lakes Watershed near Lake Superior, Ontario, Canada, in 1981 and 1996. We then assessed these samples for contents of organic matter (OM), total N, K, Ca, Mg, S, and Na, and exchangeable NH₄ ⁺, NO₃ ⁻, K⁺, Ca²⁺, Mg²⁺, SO₄ ²⁻, and Na⁺. Over the 15-year period, total OM and element contents remained unchanged, with the exception of N, which increased significantly from 61.3 kmol/ha in 1981 to 78.4 kmol/ha in 1996. On an area basis, there were significant increases in exchangeable Ca²⁺ (from 3.8 to 4.6 kmol/ha) and Na⁺ (from 0.05 to 0.08 kmol/ha) and decreases in exchangeable NH₄ ⁺-N (from 1.41 to 0.95 kmol/ha) and SO₄ ²⁻-S (from 1.29 to 0.96 kmol/ha). There were no significant differences in average annual litterfall OM, N, Ca, Mg, S or Na inputs between 1980 and 1985 and between 1992 and 1997. Average annual wet-only SO₄ ²⁻-S deposition during 1981–86 was 0.30; during 1992–97, it was 0.21 kmol/ha. Annual wet-only NO₃ ⁻-N averaged 0.33 kmol/ha during 1981–86 and was similar during 1992–97. Throughfall was less rich in SO₄ ²⁻ and Ca²⁺, Mg²⁺, and Na⁺ during 1992–97 than earlier. Throughfall NH₄ ⁺ and NO₃ ⁻ fluxes were unchanged. Efflux of cations from the forest floor reflected reduced throughput of SO₄ ²⁻. Overall, the results suggest that in spite of atmospheric inputs, active biological processes—including litter input, fine-root turnover, and tree uptake—serve to impart stability to the mineral composition of mature sugar maple forest floor. Received 5 October 1999; accepted 25 October 2000.     

Effects of quercetin and enhanced UV-B radiation on the soybean (Glycine max) leaves

The possible ameliorative effects of quercetin on soybean [Glycine max (L.) Merr.] leaves exposed to UV-B radiation were conducted in greenhouse. The symmetrical leaves supplied with quercetin solution (0.2%, 1%) were exposed to UV-B radiation (0, 3.5, 6.5 kJ m⁻² d⁻¹). 0.2% quercetin ameliorated leaf photosynthesis, improved leaf water content (LWC), and decreased lipid oxidation. The unfavorable effect on photosynthetic parameter was displayed in 1% quercetin treatment. The effect of quercetin on phenylalanine ammonia lyase (PAL) activity varied with the quercetin concentration, UV-B radiation intensity and leaf development. In the later development polyphenol oxidase (PPO) activity was increased significantly by quercetin treatments. We suggested that quercetin with suitable concentration could serve as UV-B protective agent partly due to its antioxidant capacity.     

Induction of a non-specific permeability transition in mitochondria from Yarrowia lipolytica and Dipodascus (Endomyces) magnusii yeasts

In this study we used tightly-coupled mitochondria from Yarrowia lipolytica and Dipodascus (Endomyces) magnusii yeasts, possessing a respiratory chain with the usual three points of energy conservation. High-amplitude swelling and collapse of the membrane potential were used as parameters for demonstrating induction of the mitochondrial permeability transition due to opening of a pore (mPTP). Mitochondria from Y. lipolytica, lacking a natural mitochondrial Ca²⁺ uptake pathway, and from D. magnusii, harboring a high-capacitive, regulated mitochondrial Ca²⁺ transport system (Bazhenova et al. J Biol Chem 273:4372–4377, 1998a; Bazhenova et al. Biochim Biophys Acta 1371:96–100, 1998b; Deryabina and Zvyagilskaya Biochemistry (Moscow) 65:1352–1356, 2000; Deryabina et al. J Biol Chem 276:47801–47806, 2001) were very resistant to Ca²⁺ overload. However, exposure of yeast mitochondria to 50–100 μM Ca²⁺ in the presence of the Ca²⁺ ionophore ETH129 induced collapse of the membrane potential, possibly due to activation of the fatty acid-dependent Ca²⁺/nH⁺-antiporter, with no classical mPTP induction. The absence of response in yeast mitochondria was not simply due to structural limitations, since large-amplitude swelling occurred in the presence of alamethicin, a hydrophobic, helical peptide, forming voltage-sensitive ion channels in lipid membranes. Ca²⁺- ETH129-induced activation of the Ca²⁺/H⁺-antiport system was inhibited and prevented by bovine serum albumin, and partially by inorganic phosphate and ATP. We subjected yeast mitochondria to other conditions known to induce the permeability transition in animal mitochondria, i.e., Ca²⁺ overload (in the presence of ETH129) combined with palmitic acid (Mironova et al. J Bioenerg Biomembr 33:319–331, 2001; Sultan and Sokolove Arch Biochem Biophys 386:37–51, 2001), SH-reagents, carboxyatractyloside (an inhibitor of the ADP/ATP translocator), depletion of intramitochondrial adenine nucleotide pools, deenergization of mitochondria, and shifting to acidic pH values in the presence of high phosphate concentrations. None of the above-mentioned substances or conditions induced a mPTP-like pore. It is thus evident that the permeability transition in yeast mitochondria is not coupled with Ca²⁺ uptake and is differently regulated compared to the mPTP of animal mitochondria.     

Purification and characterization of two cold-adapted extracellular tannin acyl hydrolases from an Antarctic strain <Emphasis Type="Italic">Verticillium</Emphasis> sp. P9

Two extracellular tannin acyl hydrolases (TAH I and TAH II) produced by an Antarctic filamentous fungus Verticillium sp. P9 were purified to homogeneity (7.9- and 10.5-fold with a yield of 1.6 and 0.9%, respectively) and characterized. TAH I and TAH II are multimeric (each consisting of approximately 40 and 46 kDa sub-units) glycoproteins containing 11 and 26% carbohydrates, respectively, and their molecular mass is approximately 155 kDa. TAH I and TAH II are optimally active at pH of 5.5 and 25 and 20°C, respectively. Both the enzymes were activated by Mg²⁺and Br⁻ ions and 0.5–2.0 M urea and inhibited by other metal ions (Zn²⁺, Cu²⁺, K⁺, Cd²⁺, Ag⁺, Fe³⁺, Mn²⁺, Co²⁺, Hg²⁺, Pb²⁺ and Sn²⁺), anions, Tween 20, Tween 60, Tween 80, Triton X-100, sodium dodecyl sulphate, β-mercaptoethanol, α-glutathione and 4-chloromercuribenzoate. Both tannases more efficiently hydrolyzed tannic acid than methyl gallate. E _a of these reactions and temperature dependence (at 0–30°C) of k _cat, k _cat/K _m, ΔG*, ΔH* and ΔS* for both the enzymes and substrates were determined. The k _cat and k _cat/K _m values (for both the substrates) were considerably higher for the combined preparation of TAH I and TAH II.     

Stability of metal ion complexes formed with methyl phosphate and hydrogen phosphate

 The acidity constants of methyl phosphoric acid, CH₃OPO(OH)₂, and orthophosphoric acid, HOPO(OH)₂, and the stability constants of the 1 : 1 complexes formed between Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, or Cd²⁺ and methyl phosphate, CH₃OPO₃ ^2–, or hydrogen phosphate, HOPO₃ ^2–, were determined by potentiometric pH titration in aqueous solution (25  °C;I = 0.1 M, NaNO₃). On the basis of previously established log K versus pK _a straight-line plots for the complexes of simple phosphate monoesters and phosphonate derivatives, R-PO₃ ^2–, where R is a noncoordinating residue, it is shown that the stability of the M(CH₃OPO₃) complexes is solely determined (as one might expect) by the basicity of the –PO₃ ^2– residue. It is emphasized that the mentioned reference lines may also be used to reveal increased complex stabilities, for example, for certain complexes formed with 8-quinolyl phosphate the occurrence of 7-membered chelates can be proven in this way; the same procedure is also applicable to complexes of nucleotides, etc. The M(HOPO₃) complexes are slightly more stable (on average by 0.08 log unit) than it is expected from the basicity of HPO₄ ^2–; this observation is attributed to a more effective solvation, including hydrogen bonding, than is possible with CH₃OPO₃ ^2– species. Received: 9 November 1995 / Accepted: 5 February 1996     

Atmospheric Deposition to the Turkey Lakes Watershed: Temporal Variations and Characteristics

We investigated the atmospheric concentrations and deposition fluxes of major ions to the Turkey Lakes Watershed (TLW) between 1980 and 1996. During that time, daily SO₄ ²⁻ concentrations in precipitation decreased markedly, while NO₃ ⁻, NH₄ ⁺, and H⁺ concentrations remained roughly constant. It appears that precipitation acidity did not decrease in spite of declining SO₄ ²⁻ concentrations due to a concurrent and counterbalancing decrease in the concentrations of Ca²⁺, Mg²⁺, and K⁺ in precipitation. The reasons for the decline in base cations are unknown, but this decline is probably related to decreasing emissions of soil-derived particles from agricultural, industrial, and road sources. A similar situation was seen during the same period in other parts of Canada, the eastern United States, and Europe. Wet, dry, and total (wet + dry) deposition fluxes of sulphur (S) and nitrogen (N) were estimated annually for the years 1980–96. The 17-year mean annual total (wet + dry) deposition of S to the watershed was estimated at 38.5 mmol m⁻² y⁻¹ (range 24.3–50.3). Total S deposition decreased by 35% from the early 1980s (1982–84) to the mid-1990s (1994–96), a decline consistent with the 23% decline in annual SO₂ emissions in eastern North America during the same period. In contrast, the annual total (wet + dry) deposition of oxidized N ranged from 39.8 to 60.4 mmol m⁻² y⁻¹, with a 15-year mean of 50.1 mmol m⁻² y⁻¹ and a net increase of 10% between the early 1980s (1983–85) and the mid-1990s (1994–96). This is in keeping with a 10% increase in NO_x emissions in eastern North America during the same period. For both S and N (oxidized), wet deposition dominated over dry deposition as the major mechanism for atmospheric input to the watershed. Annually, wet deposition accounted for approximately two-thirds of the total atmospheric deposition of both S and N. Dry S deposition was due more to gaseous SO₂ deposition (two-thirds of dry S deposition) than to particulate SO₄ ²⁻ deposition (one-third of dry S deposition). Dry deposition of oxidized N, however, was dominated (95%) by gaseous HNO₃ deposition, with minimal input from particulate NO₃ ⁻ deposition. Compared to several selected watershed/forest sites in Canada, the United States, and Europe, the estimated total deposition of S and N at the TLW was relatively high during the measurement period. Received 5 October 1999; accepted 1 March 2001.     

Lipids of the notothenioid fishes Trematomus spp. and Pagothenia borchgrevinki from East Antarctica

The notothenioid fishes Trematomus pennellii, T. newnesi, and T. bernacchii had 5–15% skeletal lipid, as percent dry weight, and this comprised 6–8% of the total body lipid. Trematomus hansoni and Pagothenia borchgrevinki had 2–4% skeletal lipid, which comprised 1% of total body lipid. Triacylglycerol was the major lipid class present in all tissues of all fish analyzed (up to 89% of total lipid), with minor components including sterol, phospholipid and wax esters. Monounsaturated fatty acids comprised 38.3–58.0% of the total fatty acids, and included primarily oleic [18 : 1(n-9)] and palmitoleic [16 : 1(n-7)] acids. Polyunsaturated fatty acids comprised 19.1–40.0% of the total fatty acids and included primarily eicosapentaenoic acid [20 : 5(n-3)] and docosahexaenoic acid [22 : 6(n-3)]. These five notothenioid fishes, which include benthic, benthopelagic, and cryopelagic species, are lower in lipid than other important Southern Ocean fishes (such as the Patagonian toothfish) and are estimated to be negatively buoyant. These data will be of use to research groups presently using signature lipid methodology. Accepted: 5 April 1999     

Effect of molecular weight on the antioxidant property of low molecular weight alginate from Laminaria japonica

In this study, three alginate fractions with different molecular weights and ratios of mannuronic acid (M) to guluronic acid (G) were prepared by enzymatic hydrolysis and ultrafiltration to assess the antioxidant property of alginates from Laminaria japonica with molecular weight below 10 kDa. The antioxidant properties of different molecular weight alginates were evaluated by determining the scavenging abilities on superoxide, hydroxyl, and hypochlorous acid and inhibitory effect on Fe²⁺-induced lipid peroxidation in yolk homogenate. The results showed that low molecular weight alginates exhibited high scavenging capacities on superoxide, hydroxyl, and hypochlorous acid radicals and good inhibition of Fe²⁺-induced lipid peroxidation in yolk. By comparison, alginate A1 with molecular weight below 1 kDa and M/G of 1.84 had better scavenging activity on superoxide, hydroxyl, and hypochlorous acid radicals in vitro than A2 (1–6 kDa), A3 (6–10 kDa), ascorbic acid, and carnosine. With similar M/G ratio, A2 exhibited better antioxidant activity on superoxide and hypochlorous acid radicals than A3. However, fraction A3 with molecular weight of 6–10 kDa exhibited higher inhibitory ability on lipid peroxidation in yolk in vitro than A1 and A2. The results indicated that molecular weight played a more important role than M/G ratio on alginate to determine the antioxidant ability. By comparison, low molecular weight alginates composed of guluronic acid and mannuronic acid exhibited better antioxidant ability on oxygen free radicals than sulfated polysaccharides from L. japonica in our previous study and represent a good source of marine polysaccharide with potential application as natural antioxidant.     

Antioxidant properties of <Emphasis Type="Italic">Galium verum</Emphasis> L. (Rubiaceae) extracts

The antioxidant properties of methanol extracts of Lady’s Bedstraw (Galium verum L., Rubiaceae) herb from two different localities in Serbia were evaluated. Antioxidant activity was assessed in four different model systems. Free radical scavenging capacity (RSC) was examined by measuring the scavenging activity of extracts on 2,2-diphenyl-1-pycrylhydrazil (DPPH) and hydroxyl radical (OH), as well as on hydrogen peroxide. In addition, the protective effects of lipid peroxidation (LP) in corn oil were evaluated by the TBA-assay using the Fe²⁺/ascorbate system of induction. The amount of dried extract, the content of total phenolics, flavonoids and chlorophylls was also determined. Extracts from both locations expressed very strong scavenger activity, reducing the DPPH^⊙ (IC₅₀=3.10 μg/mland 8.04 μg/ml) and OH radical formation (IC₅₀=0.05 μg/ml and 0.54 μg/ml) and neutralising H₂O₂ (IC₅₀=4.98 μg/ml and 3.80 μg/ml), in a dose dependant manner. Also, examined extracts showed notable inhibition of LP (IC₅₀=11.69 μg/ml and 19.47 μg/ml). The observed differences in antioxidant activity could be partially explained by the levels of phenolics (2.44–4.65 mg and 4.57–5.16 mg gallic acid equivalents/g dry extract), flavonoids (6.38–10.70 μg and 15.56–17.96 μg quercetin equivalents/g dry extract) and chlorophylls in the investigated Lady’s Bedstraw extracts.