Characterization of antioxidant systems, oxidation status and lipids in brain of wild-caught size-class distributed Aristeus antennatus (Risso, 1816) Crustacea, Decapoda

The objectives of the study were to characterize the enzymic antioxidant system (free radical scavenging enzymes such as catalase, superoxide dismutase, glutathione peroxidases, glutathione transferase and glutathione reductase), dietary antioxidants (vitamin E), the oxidation status (malondialdehyde (MDA) levels and the fluorescence intensity of lipid-soluble fluorescent products (LSFP)) and lipid composition (lipid classes and polyunsaturated fatty acids (PUFA) as pro-oxidants) in neural tissues from males and females of wild-caught size-class distributed blue and red marine shrimp Aristeus antennatus (Risso, 1816), trawled off the south coast of Spain. Moreover, the mechanisms that may result in the deposition of age-pigments in relation to the physiological age of this species in its natural environment were investigated. Three different size classes were defined for males and four for females, and differences were observed for the different variables measured between sexes. The proportion of polar lipids (primarily phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine) predominated over that of neutral lipids, increasing significantly in males but decreasing in females. However, cerebrosides increased significantly from size–age class I to III in males but no significant differences were observed in females. The fatty acid composition showed increases in monounsaturated fatty acids (particularly 18:1 and 24:1 isomers) and dimethyl acetals, but decreases in PUFA (primarily 22:6(n-3)) with increasing size–age in both sexes. The concentration of MDA (nmol g⁻¹ brain) did not present any marked trend with size–age in both sexes. In contrast, fluorescence intensity showed increasing trends in both sexes with increasing size–age, when expressed as % fluorescence brain⁻¹ (λ_ex/em 350–445 nm and λ_ex/em 400–455). However, when expressed as % fluorescence mg⁻¹ brain total lipid, only males presented an upward trend with size–age (λ_ex/em 400–455). The concentration of vitamin E (ng mg⁻¹ brain) did not show significant differences between different size–age classes within the same sex and showed a molar ratio of one molecule of vitamin E per approximately 200 molecules of PUFA in brain membranes. The antioxidant enzyme activities showed clearer patterns with increasing size–age in males than in females, with catalase and glutathione transferase presenting downward trends and superoxide dismutase and total glutathione peroxidase showing upward trends. The fluorescence analysis of brain LSFP was not a useful tool to separate the population into different size–age classes, although the different patterns encountered between sexes for the variables measured points to males as better subjects for this type of study.     

Effect of Vitamin E and Its Analogues Having Various Molecular Structures on the Growth and Lipid Composition of Pythium debaryanum

The effect of exogenously added vitamin E and its synthetic analogues (the hydrophilic form of vitamin E and chromans C₁₃and C₁) at a concentration of 9.86 × 10^–5M on the growth, lipogenic activity, and the fatty acid composition of the eicosapolyenoic acid–synthesizing oomycete Pythium debaryanumwas studied. The effect was found to depend on the molecular structure of particular compounds. For instance, vitamin E and chroman C₁₃stimulated fungal growth, whereas chroman C₁inhibited it. The hydrophilic form of vitamin E enhanced the lipogenic activity of the oomycete. The studied compounds, which possess antioxidant activity, did not exert any noticeable effect on the content of eicosapolyenoic acids and the degree of the unsaturation of fungal lipids.     

Effects of Ca2+ and vitamin E on posttranslational regulation of acetylcholine receptor expression in the somata of identified molluscan neurons

The effects of Ca²⁺ and vitamin E (-tocopherol) on acetylcholine (Ach)-induced Cl^– currents in LP11 and RBc4 neurons of the snail Helix pomatia have been studied. Injection of Ca²⁺ into the cells and application of vitamin E (10^–5 mole/liter) induced the appearance of potentiation of Ach-induced currents in membrane parts more remote from the axon than the Ach-sensitive regions in the control. The Hill coefficient (n) for such Ach receptors was equal to 0.8, unlike 1.8 for Ach receptors active in the control. Arachidonic acid (10^–5 mole/liter) and phorbol ester TPA (10^–6 mole/liter) inhibited Ach responses, while oleoylacetyglycerol (10^–6 mole/liter) produced no effect. Calmidazolium (10^–6 mole/liter) decreased the effects of Ca²⁺ and vitamin E on Ach responses, while nordihydroquiaretic acid (5 · 10^–6 mole/liter) enhanced the modulating effect of vitamin E and weakened that of arachidonic acid. It is suggested that the expression of Ach receptors activated by Ca²⁺ and vitamin E is mediated through posttranslational mechanisms, since cycloheximide and actinomycin D, inhibitors of protein synthesis, did not influence the effects of C²⁺ and vitamin E. The mechanisms responsible for the stimulating effects of Ca²⁺ and vitamin E are discussed.Translated from Neirofiziologiya, Vol. 25, No. 1, pp. 31–39, January–February, 1993.     

Estradiol protects cultured articular chondrocytes from oxygen-radical-induced damage

Osteoarthritis (OA) is aggravated in menopausal women possibly because of changed serum estrogen levels. Estradiol has been postulated to affect oxidative stress induced by reactive oxygen species (ROS) in articular chondrocytes. We generated ROS in cultured bovine articular chondrocytes by incubating them with combined Fe₂SO₄, vitamin C, and hydrogen peroxide. The release of thiobarbituric-acid-reactive substances (TBARS, lipid peroxidation) and lactate dehydrogenase (LDH, membrane damage) was measured photometrically. Various estradiol doses and vitamin E, serving as control with an established anti-oxidative capacity, were applied either upon each exchange of medium and during radical production (strategy 1) or only during radical production (strategy 2). In chondrocytes incubated according to strategy 1, the production of TBARS and LDH release were significantly suppressed by 10^–10–10^–4 M estradiol or by vitamin E. Under strategy 2, the production of TBARS was significantly suppressed at estradiol concentrations higher than 10^–6 M, whereas LDH release was inhibited at concentrations of 10^–6–10^–4 M. Vitamin E showed no significant effects. As repeated application of estradiol and vitamin E produced the best results, estradiol, like vitamin E, was speculated to accumulate in the plasma membrane and to decrease membrane fluidity resulting in protection against lipid peroxidation (non-genomic effect). Thus, in contrast to the neuroprotective effect of 17-estradiol in supraphysiological doses reported recently, the anti-oxidative potential of estradiol appears to protect articular chondrocytes from ROS-induced damage when the hormone is given repeatedly in a physiological range. Decreased estradiol levels may therefore contribute to menopausal OA in the long term.     

The GABAA receptor family in the mammalian brain

The GABA_A-benzodiazepine receptor protein from bovine brain was purified by affinity chromatography and the subunit composition examined by gel electrophoresis in sodium dodecyl sulfate. Protein staining revealed a doublet at 51–53 kDa, a band at 55 kDa, and a broad band at 57–59 kDa. The 51 and 53 kDa bands co-migrated with the ₁ and ₂ gene products identified by Western blotting with subtype-specific antibodies. These two bands were also photoaffinity labeled by [³H]flunitrazepam, as was a breakdown product at 44 kDa. Partial sequencing of proteolytic fragments of these polypeptides yielded sequences found in all clones, and identified the benzodiazepine binding site within residues 8–297 and probably between 106–297 of ₁; the 44 kDa and 31 kDa bands yielded fragments containing ₃ sequence. The native ₃ polypeptide was identified with subtype-specific antibody at 57 kDa overlapping with the two major bands photolabeled with [³H]muscimol at 55 and 58 kDa. Antisera to a -selective peptide recognized four bands at 60, 58, 57 and 55 kDa. Thus, one can identify 6–8 distinct polypeptides with the possibility of another 4–6 in purified GABA_A receptor proteins, depending on brain region, consistent with the family of gene products suggested by molecular cloning.Special issues dedicated to Dr. Eugene Roberts     

Characteristics of specific intermediate filament proteins in human brain tumors

The content of glial fibrillary acidic protein (GFAP) was measured in human brain tumours with different histological structure, origin and rate of malignancy. The polypeptide composition of CFAP was established in human brain and tumours by SDS polyacrylamide gel electrophoresis followed by immunoblotting. In tumours with an astrocyte type of differentiation, GFAP was revealed as a set of immunologically related and partially degraded polypeptides with a molecular weight of around and below 37 kD. It was assumed that the appearance of intact GFAP polypeptides (49 kD) in some tumours may be considered as a result of penetration of reactive astrocytes into tumour tissue.     

On the functional significance of the polypeptide PsbY for photosynthetic water oxidation in the cyanobacterium<Emphasis Type="Italic"> Synechocystis</Emphasis> sp. strain PCC 6803

Recent investigations have revealed that the cyanobacterial photosystem II complex contains more than 26 polypeptides. The functions of most of the low-molecular-mass polypeptides, including PsbY, have remained elusive. Here we present a comparative characterization of the wild-type Synechocystis sp. strain PCC 6803 and a PsbY-free mutant derived from it. The results show that growth of the PsbY-free mutant was comparable to that of the wild-type when cells were cultivated in complete BG11 medium or under initial manganese or chloride limitation, and when illuminated at 20 or 200 E m^–2 s^–1. However, while growth rates of both the wild-type and the PsbY-free mutant were reduced when cells were cultivated in BG11 medium in the absence of calcium, the reduction was significantly greater in the case of the PsbY-free mutant. This differential effect on growth of the mutant relative to the wild-type in CaCl₂ deficient medium was detected when the cells were illuminated with high-intensity light (200 E m^–2 s^–1) but not when light levels were lower (20 E m^–2 s^–1). The differential effect on growth was associated with lower O₂ evolving activity in the mutant compared to wild-type cells. The mutant was also found to be more sensitive to photoinhibition, and showed an altered pattern of fluorescence emission at 77 K. In addition, mass spectrometric analysis revealed that PsbY-free cells cultivated in CaCl₂ sufficient medium (in which no growth reduction was observed) had a significantly higher O₂ evolution from hydrogen peroxide and a lower O₂ evolution from water under flash light illumination than wild-type cells. These results imply that photosystem II is slightly impaired in the PsbY-free mutant, and that the mutant is less capable of coping with low levels of Ca²⁺ than the wild-type.Communicated by R. G. Herrmann     

Growth,vitamin B12, and photopigment formations of Rhodopseudomonas sphaeroides S growing on propionate media under dark and light conditions

Summary The effects of light illumination and dissolved oxygen concentration (DO) on the growth characteristics of Rhodopseudomonas sphaeroides S and intracellular accumulations of vitamin B₁₂ and photopigments were studied in continuous cultures of aerobic-dark (S-1, DO>5 mg l^–1), aerobic-light (S-2, DO>5 mg l^–1, 4.5 klux), microaerobic-light (S-3, DO0,4.5 klux) and anaerobic-light (S-4, 4.5 klux) conditions using propionate media. Growth yields from propionic acid determined in S-3 and 4 were 1.5 to twofold greater than in S-1 and 2. Carbon dioxide evolution observed in S-3 and 4 was 0.05 to 0.1 times that in S-1 and 2. Overall carboxylase activity was maximal in S-4. Intracellular accumulations of bacteriochlorophyll and carotenoid were maximal in S-4, followed by S-3 and almost nil in S-1 and 2. The high growth yields observed in S-3 and 4 could be accounted for the high level of activity of carbon dioxide fixation and by the additional or effective utilization of light energy.Intracellular accumulation of vitamin B₁₂ in S-2, 3 and 4 was 1.5 to 1.8 times that in S-1. The maximum content of the vitamin was 74 g-B₁₂ g-cell^–1. The maximum productivity of vitamin B₁₂, g-B₁₂ l^–1 h^–1, was 6.6 in S-3 since specific growth rate, growth yield and the vitamin content of the cells were maximal in S-3.     

Impact of aluminium,fluoride and fluoroaluminate complex on ATPase activity ofNostoc linckia andChlorella vulgaris

This study demonstrates a pH-dependent inhibition of Mg²⁺- and Ca²⁺- ATPase activities ofNostoc linckia andChlorella vulgaris exposed to AlCl₃, AlF₃, NaF and AlCl₃ + NaF together. AlF₃ and the combination of AlCl₃ + NaF were more inhibitory to both the enzymes as compared with AlCl₃ and NaF. Toxicity of the test compounds increased with increasing acidity. Interaction of AlCl₃ + NaF was additive onN. linckia andC. vulgaris, respectively, at pH 7.5 and 6.8, and synergistic at pH 6.0 and 4.5. In the presence of 60 and 100 m PO₄ ^3- an increased NaF concentration (in the AlCl₃ + NaF combination) was required to produce the same degree of inhibition in ATP synthesis and ATPase activity. Toxicity of fluoroaluminate was reduced in the presence of EDTA and citrate. Except for beryllium to some extent, combinations of cadmium, cobalt, iron, manganese, tin and zinc with fluoride were not as effective as aluminium in inhibiting the ATPase activity. The presence of a 100 kDa protein band in SDS-PAGE of both control as well as AlCl₃ + NaF-treated samples suggested that AlF₄ ^– inhibits the ATPase activity by acting as a functional barrier without affecting the structure of the enzyme.     

Effects of Ionizing Radiation and Aluminum Chloride on Protein of Glial Intermediate Filaments in the Rat Brain

We studied the effects of irradiation with X-rays (the total dose of 0.0129 C/kg was attained over 7, 14, or 21 days), increased entry of Al³⁺ into the organism (0.2% AlCl₃ in drinking water), and the combined influence of these factors for 21 days on the contents of the soluble and filamentous forms of glial fibrillary acidic protein (GFAP) in the tissues of the hippocampus, cerebellum, and neocortex of albino rats. After irradiation for 7 days, a clear trend toward drops in the GFAP contents in the structures under study was observed, while irradiation in the same dose, but for 14 or 21 days, resulted in increases in the contents of both GFAP forms (within a range of 13-29%, as compared with the control). Entry of aluminum chloride with water also resulted in an increase in the GFAP contents in all studied structures; changes in the filamentous form were more intensive. The combined influence of irradiation and Al³⁺ resulted in more intensive shifts in the GFAP levels; the content of its filamentous form increased in all structures by about 50%, while shifts of the soluble form were somewhat smaller.     

Decrease of polypeptides in the PS I antenna complex with increasing growth irradiance in the red alga Porphyridium cruentum

Thylakoids isolated from cells of the red alga Porphyridium cruentum exhibit an increased PS I activity on a chlorophyll basis with increasing growth irradiance, even though the stoichiometry of Photosystems I and II in such cells shows little change (Cunningham et al. (1989) Plant Physiol 91: 1179–1187). PS I activity was 26% greater in thylakoids of cells acclimated at 280 mol photons · m^–2 · s^–1 (VHL) than in cells acclimated at 10 mol photons · m^–2 · s^–1 (LL), indicating a change in the light absorbance capacity of PS I. Upon isolating PS I holocomplexes from VHL cells it was found that they contained 132±9 Chl/P700 while those obtained from LL cells had 165±4 Chl/P700. Examination of the polypeptide composition of PS I holocomplexes on SDS-PAGE showed a notable decrease of three polypeptides (19.5, 21.0 and 22 kDa) in VHL-complexes relative to LL-complexes. These polypeptides belong to a novel LHC I complex, recently discovered in red algae (Wolfe et al. (1994a) Nature 367: 566–568), that lacks Chl b and includes at least six different polypeptides. We suggest that the decrease in PS I Chl antenna size observed with increasing irradiance is attributable to changes occurring in the LHC I-antenna complex. Evidence for a Chl-binding antenna complex associated with PS II core complexes is lacking at this point. LHC II-type polypeptides were not observed in functionally active PS II preparations (Wolfe et al. (1994b) Biochimica Biophysica Acta 1188: 357–366), nor did we detect polypeptides that showed immunocross-reactivity with LHC II specific antisera (made to Chlamydomonas and Euglena LHC II).Abbreviations Bis-Tris bis(2-hydroxyethyl)imino-tris(hydroxymethyl)methane - DCPIP 2,6-dichlorophenol indophenol - -dm dodecyl--d-maltoside - HL high light of 150 mol photons · m^–2 · s^–1 - LGB lower green band - LHC I light-harvesting complex of PS I - LHC II light-harvesting complex of PS II - LL low light of 10 mol photons · m^–2 · s^–1 - ML medium light of 50 mol photons · m^–2 · s^–1 - MES 2-(N-morpholino) ethanesulfonic acid - P700 reaction center of PS I - PFD photon flux density - Trizma tris(hydroxymethyl)aminomethane - UGB upper green band - VHL very high light of 280 mol photons · m^–2 · s^–1     

Methods for measuring the properties of the turbulence in bubble flow

Summary A constant temperature hot film anemometer has been used to evaluate mean liquid flow velocity, bubble frequency, turbulence scale and intensity, and the rate of energy dissipation by liquid phase bubble flow.Symbols M mass - L lenght - T time - a gas/liquid interfacial area L² - a=a/V_L specific gas/liquid interfacial area with regard to the volume of the liquid L^–1 - d bubble diameter L - d mean bubble diameter L - d_e dynamic equilibrium (maximum stable) bubble size L - d_p primary bubble diameter L - d_s Sauter bubble diameter L - E specific energy dissipation rate with regard to the volume of the liquid ML^–1T^–3 - E V_L energy dissipation rate ML²T^–3 - E=E/ since =1 g cm^–3, E has the same numerical value as E. Therefore, the symbol E is used everywhere in the present paper for E and called energy dissipation rate (S. s^–2=Stokes. s^–2) L²T^–3 - E_G or _G local relative gas hold up L²T^–3 - f() autocorrelation function [Eq. (10)] L²T^–3 - f(r) cross correlation function [Eq. (11)] L²T^–3 - g acceleration of gravity LT^–2 - k constant LT^–2 - k_L mass transfer coefficient LT^–1 - k_La volumetric mass transfer coefficient with regard to the volume of the liquid T^–1 - N₀ number of crossings of u and T^–1 - n_B bubble frequency T^–1 - r distance between two points 1 and 2 of the cross correlation function L - t time T - u momentaneous liquid velocity LT^–1 - mean liquid velocity LT^–1 - mean square fluctuation velocity L²T^–2 - intensity of turbulence LT^–1 - x position coordinate L - V volume of the bubbling layer in the column L³ - V_L volume of the bubble free layer in the column L³ - V electrical voltage (in Fig. 2) L³ - v velocity scale [Eq. (6)] LT^–1 - We_crit critical Weber number [Eq. (4)] LT^–1 - w_SG superficial gas velocity LT^–1 - w_SL superficial liquid velocity LT^–1 - _G or E_G local relative gas hold up LT^–1 - smallest scale [Eq. (6)] L - time delay in the autocorrelation function [Eq. (10)] T - energy dissipation scale [E. (15)] L - _f: Taylor's vorticity scale [E. (14)] L - kinematic viscosity of the liquid L²T^–1 - density of the liquid ML^–3 - surface tension MT^–2 - dynamic pressure of the turbulence [Eq. (8)] ML^–1T^–2 - p primary (at the aerator) - e equilibrium (far from the aerator)     

The influence of flow rate and the composition of supplied CO2/air mixtures on discontinuous growth of Tetraselmis sp.

Summary This paper studies the influence of the flow rate of gaseous mixtures on the kinetics of growth and the fatty acid composition of Tetraselmis sp. at CO₂/air ratios of 3 × 10^–4 and 2 × 10^–5. The specific growth rate rises with increased flow rate up to values of approximately 0.086 h^–1 and 0.063 h^–1 at CO₂/air ratios of 3 × 10^–4 and 2 × 10^–5 respectively, when the flow rate is approximately 3 v/v per minute. At higher flow rates, the specific growth rate decreases. The polyunsaturated fatty acid content decreases slightly as the gaseous mixture flow rate increases, whereby the ratio 3/6 remains between 2 and 3, indicating good nutritional values. Offprint requests to: E. Molina     

Al NMR relaxation studies of molten salts containing ethylaluminum dichloride

The microdynamics of room temperature molten salts containing EtAlCl₂ are examined by ²⁷Al NMR relaxation methods as a function of melt composition and temperature. The melts examined include neat EtAlCl₂ and mixtures of EtAlCl₂, 1-ethyl-3-methylimidazolium chloride (MEICl) and AlCl₃. Information obtained from this study indicates interactions between EtAlCl₂ containing species (EtAlCl₃⁻ and EtAlCl₂ dimers) and MEICl or AlCl₃. Quadrupole coupling constants obtained for ²⁷Al using the extreme narrowing condition compare favorably with those obtained previously by the dual spin probe (DSP) method.     

Synthesis of polypeptides by microwave heating II. Function of polypeptides synthesized during repeated hydration-dehydration cycles

Summary Polypeptides, synthesized from a mixture of amino acid amides by microwave heating during repeated hydration-dehydration cycles, showed hydrolase- and oxidoreductase-like catalytic activities. Poly(GAVDH), polypeptides synthesized from an equimolar mixture (each 0.1 M) of glycinamide,l-alaninamide,l-valinamide,l-aspartic acid -amide, andl-histidinamide, catalyzed the hydrolysis of PNPAc. The hydrolytic rate of PNPAc with poly(GAVDH) was the quadruple of that ofl-histidine alone. Though the k_cat values of different resulting polypeptides were 10³–10⁶ times less than those of native hydrolases, the K_m value of the polypeptides further containing phenylalanine residues was nearly equal to that of the esterase. This result indicates the presence of hydrophobic interaction between a substrate and the polypeptides. Resulting polypeptides also showed catalytic activity for the reduction of ferricyanide ion [Fe(CN)^3–] with NADH. The polypeptides seemed to have a strong affinity for adenine nucleotides, because the reaction was inhibited by adenine derivatives such as NAD⁺ and AppA. A hypothesis for the emergence of primitive protein enzymes is discussed.     

Optimization of a Propionibacterium acidipropionici continuous culture utilizing sucrose

To produce propionic acid and vitamin B₁₂ from sucrose, the strain Propionibacterium acidipropionici NRRL B3569 was selected by screening a number of Propionibacterium strains. The nutrient composition and the fermentation conditions for this strain were optimized in continuous culture. The investigations show that within a concentration range of 30–170 g l^–1 of sucrose in the fermentation medium, no significant substrate inhibition occurred. For the production of propionic acid and vitamin B₁₂, concentrations of 1.5 mg FeSO₄·7H₂O g^–1 dry biomass, 0.75 mg cobalt ions g^–1 dry biomass, 0.3 mg 5,6-dimethylbenzimidazole g^–1 dry biomass, and 12 g yeast extract 1^–1 were necessary additions to the sources of nitrogen, phosphate, and magnesium ions. The extra addition of up to 2.8 g betaine g^–1 dry biomass significantly increases the production of vitamin B₁₂. In the optimization of the pH value, temperature, and aeration, it was established that the conditions for propionic acid production and vitamin B₁₂ production are different. Whereas the optimal production of propionic acid took place under completely anaerobic conditions with a pH value of 6.5 and a temperature of 37°C, optimal vitamin B₁₂ production required a temperature of 40°C and aerobic conditions (0.5 vvm aeration at 100 rpm) with a pH value of 6.5.     

Environmental effects on growth and biochemical composition ofNitzschia inconspicua Grunow

The effects of nitrate and silicate levels, and carbon source on growth, biochemical composition and fatty acid composition ofNitzschia inconspicua were investigated using batch cultures. Within the range of silicate levels supplied (8.8–176 M), no marked variations in growth trend, biochemical composition or fatty acid composition were shown. Biomass at stationary phase, ranging from 64–66 mg ash-free dry weight (AFDW) L^–1, and specific growth rate () based on chlorophylla (0.41–0.50 d^–1) of the cultures grown within 0.3–3.0 mM NaNO₃ were not significantly different. Cultures supplemented with glucose (0.1 % w/v), acetate (0.1 % w/v) or 5% CO₂ attained higher biomass (85, 85, 97 mg AFDW L^–1) than the control which was grown in synthetic seawater and agitated by magnetic stirring. Cells grown at <3.0 mM NaNO₃ contained higher carbohydrate contents (14.8–21.5% AFDW) than those grown at 3.0 mM (4.0% AFDW). Lipid content increased at the expense of proteins in cells aerated with 5% CO₂. The dominant fatty acids, 16:0 and 16:1, ranged from 35.7–45.0% and 36.4–45.4% total fatty acids (TFA), respectively, while the relative proportions of 20:4 (n-6) and 20:5 (n-3) ranged from 1.7–5.4% and 3.4–5.9% TFA respectively. Cultures aerated with 5% CO₂ attained the highest biomass (97 mg AFDW L^–1) and yield of 20:5 (n-3) (0.34 mg L^–1).     

Effects of aluminum,iron, oxygen and nitrate additions on phosphorus release from the sediment of a Danish softwater lake

The effects of oxygen, aluminum, iron and nitrate additions on phosphate release from the sediment were evaluated in the softwater Lake Vedsted, Denmark, by a 34-day experiment with undisturbed sediment cores. Six treatments were applied: (1) Control - O₂ (0–20% saturation), (2) O₂ (100% saturation) (3) Al³⁺ – O₂, (4) Fe³⁺ + O₂, (5) Fe³⁺ – O₂, and (6) NO₃ ^– – O₂. Al₂(SO₄)₃*18 H₂O and FeCl₃*4H₂O were added in amounts that theoretically should immobilize the exchangeable P-pool in the top 5 cm of the sediment, while sodium nitrate concentrations were increased to 5 mg N l^–1. The four treatments with metals or NO₃ ^– reduced the P efflux from the sediment significantly as compared to the suboxic control treatment. Mean accumulated P-release rates for suboxic treatments with Al³⁺, Fe³⁺, and NO₃ ^– were: –0.27 mmol m^–2 (st. dev = 0.02 mmol m^–2, N = 5), 0.58 mmol m^–2 (st. dev = 0.30 mmol m^–2, N = 5) and 1.40 mmol m^–2 (st. dev = 0.14 mmol m^–2, N = 5), respectively. The oxic treatment with Fe³⁺ had a P efflux of 0.36 mmol m^–2 (st. dev = 0.08 mmol m^–2, N = 5). The two highest P-release rates were observed in the control treatment and the treatment with O₂ (14.50 mmol m^–2 (st. dev = 3.90 mmol m^–2, N = 5) and 2.31 mmol m^–2 (st. dev = 0.80 mmol m^–2, N = 5), respectively). In order to identify changes in the P and Fe binding sites in the sediment as caused by the treatments, a sequential P extraction procedure was applied on the sediment before and after the efflux experiment. Addition of O₂, Fe³⁺ and NO₃ ^– to the sediment increased the amounts of oxidized Fe³⁺ and P_BD. Al³⁺ addition resulted in a lower fraction of P_BD but a correspondingly higher fraction of Al-bound P. Addition of Al³⁺ decreased the Fe-efflux from the suboxic sediment as well as the amount of oxidized Fe³⁺ in the sediment. This questions the use of Al compounds that contain sulfate because of the possible formation of FeS, which will restrict upward migration of Fe²⁺ and the formation of new Fe-oxides in the surface sediment. Instead, we suggest the use of AlCl₃ for lake restoration purposes.     

Characterisation of the Role of Calcium in AlF4-Induced Long-Term Potentiation in Area CA1 of Rat Hippocampus

We investigated calcium influx in the long lasting potentiation induced in area CA1 of rat hippocampus by brief bath application of the G-protein activator AlF₄ ^–(NaF/AlCl₃). Brief (10 min) bath application of AlF₄ ^– in standard saline (with 2mM Ca²⁺) consistently induced a long lasting potentiation which was not observed if AlF₄ ^– was bath-applied in nominally calcium free saline. Increasing the potential calcium influx, either by raising extracellular calcium concentration to 3.5 mM or by addition of the voltage operated calcium channel (VOCC) agonist BayK8644. failed to increase the number of slices exhibiting potentiation or the mean level of potentiation. Bath application of AlF₄ ^– in the presence of the VOCC antagonist failed to block the potentiation and AlF₄ ^– readily induced a long lasting potentiation under voltage clamp conditions, strongly suggesting that the calcium influx required for AlF₄-induced potentiation is not through NMDA receptors or VOCC channels. It is suggested that the calcium required may be provided by an ongoing recharging and emptying of IP3 sensitive intracellular Ca²⁺ stores.     

Changes in n-6 and n-3 polyunsaturated fatty acids during lipid-peroxidation of mitochondria obtained from rat liver and several brain regions: effect of α-tocopherol

The effect of intraperitoneal administration of α-tocopherol (100 mg/kg weight/24 h) on ascorbate (0–0.4 mM) induced lipid peroxidation of mitochondria isolated from rat liver, cerebral hemispheres, brain stem and cerebellum was examined. The ascorbate induced light emission in hepatic mitochondria was nearly completely inhibited by α-tocopherol (control-group: 114.32±14.4; vitamin E-group: 17.45±2.84, c.p.m.×10⁻⁴). In brain mitochondria, 0.2 mM ascorbate produced the maximal chemiluminescence and significant differences among both groups were not observed. No significant differences in the chemiluminescence values between control and vitamin E treated groups were observed when the three brain regions were compared. The light emission produced by mitochondrial preparations was much higher in cerebral hemispheres than in brain stem and cerebellum. In liver and brain mitochondria from control group, the level of arachidonic acid (C20:4n6) and docosahexaenoic acid (C22:6n3) was profoundly affected. Docosahexaenoic in liver mitochondria from vitamin E group decreased by 30% upon treatment with ascorbic acid when compared with mitochondria lacking ascorbic acid. As a consequence of vitamin E treatment, a significant increase of C22:6n3 was detected in rat liver mitochondria (control-group: 6.42 ±0.12; vitamin E-group: 10.52 ±0.46). Ratios of the α-tocopherol concentrations in mitochondria from rats receiving vitamin E to those of control rats were as follows: liver, 7.79; cerebral hemispheres, 0.81; brain stem, 0.95; cerebellum, 1.05. In liver mitochondria, vitamin E shows a protector effect on oxidative damage. In addition, vitamin E concentration can be increased in hepatic but not in brain mitochondria. Lipid peroxidation mainly affected, arachidonic (C20:4n6) and docosahexaenoic (C22:6n3) acids.