Effects of Zn2+ and niflumic acid on photosynthesis in Glycine soja and Glycine max seedlings under NaCl stress

The effects of two anion/Cl^? channel inhibitors, Zn²⁺ and niflumic acid (NA), on seedling photosynthetic and fluorescent parameters of two Glycine soja populations (salt-tolerant BB52; salt-sensitive N23227) and Glycine max cultivar (salt-tolerant Lee68) were studied and compared under salt stress. Treatments with Zn²⁺ and NA only (10, 20 μmol L^?1) were also imposed for comparisons. Results showed that, there were non-toxic and non-nutritional effects of Zn²⁺ and NA treatments alone on seed germination and seedling growth of soybeans. Under 150 mmol L^?1 NaCl for 6 d, leaf chlorophyll and carotenoid contents, net photosynthetic rate (P_n), stomatal conductance (G_s), intercellular CO₂ concentration (C_i), transpiration rate (Tr), and the maximum photochemical efficiency of photosystem II (PS II) (F_v/F_m) except the stomatal limitation (Ls) significantly decreased in three kinds of soybean seedlings when compared with their control plants. The NaCl stress plus additional 20 μmol L^?1 Zn showed an obvious enhancement of leaf chlorophyll and carotenoid contents, P_n, G_s, C_i and Tr, especially for the G. max cultivar Lee68, but the supplementation of 20 μmol L^?1 NA showed the reverse effects.     

Environmental indicators for estimating the potential soil respiration rate in alpine zone

Soil respiration is the main form of carbon flux from soil to atmosphere in the global carbon cycle. The effect of temperature on soil respiration rate is important in evaluating the potential feedback of soil organic carbon to global warming. We incubated soils from the alpine meadow zone and upper rocky zone along an altitudinal gradient (4400–5500 m a.s.l.) on the Tibetan Plateau under various temperature and soil moisture conditions. We evaluated the potential effects of temperature and soil moisture on soil respiration and its variation across altitudes. Soil respiration rates increased as the temperature increased. At 60% of soil water content, they averaged 0.21–5.33 μmol g soil⁻¹ day⁻¹ in the alpine meadow zone and 0.11–0.50 μmol g soil⁻¹ day⁻¹ in the rocky zone over the experimental temperature range. Soil respiration rates in the rocky zone did not increase between 25 and 35 °C, probably because of heat stress. Rates of decomposition of organic matter were high in the rocky zone, where the CN ratio was smaller than in the middle altitudes. Soil respiration rates also increased with increasing soil water content from 10% to 80% at 15 °C, averaging 0.04–2.00 μmol g soil⁻¹ day⁻¹ in the alpine meadow zone and 0.03–0.35 μmol g soil⁻¹ day⁻¹ in the rocky zone. Maximum respiration rates were obtained in the middle part of the alpine slope in any case of experimental temperature and soil moisture. The change patterns in soil respiration rate along altitude showed similar change pattern in soil carbon content. Although the altitude is a variable including various environmental factors, it might be used as a surrogate parameter of soil carbon content in alpine zone. Results suggest that temperature, soil moisture and altitude are used as appropriate environmental indicators for estimating the spatial distribution of potential soil respiration in alpine zone.     

Determination of biogenic amines in beer with pre-column derivatization by high performance liquid chromatography

Eighteen samples of commercially available Chinese beer were analyzed in order to determine the content of biogenic amines. The method involves pre-column derivatization of the amines with 4-chloro-3,5-dinitrobenzotrifluoride (CNBF) and subsequent analysis by RP-HPLC (reversed phase-high performance liquid chromatography) with diode array detection. The labeled biogenic amines were separated on a Kromasil C18 column (250 mm × 4.6 mm, 5 μm) at room temperature and UV detection was applied at 254 nm. The separation of seven labeled biogenic amines was achieved within 22 min by elution acetonitrile and HAc–NaAc buffers. The method linearity, calculated for each biogenic amine, has a correlation coefficient higher than 0.9925, in concentrations ranging from 2.9 μmol L^?1 to 565 μmol L^?1. Detection limits of biogenic amines were 0.056–0.87 μmol L^?1, at a signal-to-noise ratio of 3. The proposed method has been applied to the quantitative determination of spermine, phenethylamine, spermidine, histamine, tyramine, tryptamine and putrescine in beer with recoveries of 91.9–103.1% and R.S.D. of 2.86–5.63%. Quantitation is relative to external standards. The results showed that each kind of beer examined contained at least three biogenic amines. Putrescine, histamine and tyramine were detected in all samples. Spermidine was detected in 89% of the beers. Spermine, tryptamine and phenylethylamine occurred in 78%, 61% and 44% of the beers examined, respectively. These levels were below the level that may elicit direct adverse reactions for most consumers.     

Effects of shade treatments on the photosynthetic capacity,chlorophyll fluorescence,and chlorophyll content of Tetrastigma hemsleyanum Diels et Gilg

Tetrastigma hemsleyanum Diels et Gilg was grown under full sunlight and moderate and high levels of shade for one month to evaluate its photosynthetic and chlorophyll fluorescence response to different light conditions. The results showed that T. hemsleyanum attained greatest leaf size and P_n when cultivated with 67% shade. Leaves of seedlings grown with 90% shade were the smallest. Leaf color of plants grown under full sunlight and 50% shade was yellowish-green. The P_n value increased rapidly as PPFD increased to 200 μmol m^?2 s^?1 and then increased slowly to a maximum, followed by a slow decrease as PPFD was increased to 1000 μmol m^?2 s^?1. P_n was highest for the 67% shade treatment and the LSP for this shade treatment was 600 μmol m^?2 s^?1. Full sunlight and 50% shade treatments resulted in significant reduction of ETR and qP and increased NPQ. Chl a, Chl b and total chlorophyll content increased and Chl a/b values decreased with increased shading. Results showed that light intensity greater than that of 50% shade depressed photosynthetic activity and T. hemsleyanum growth. Irradiance less than that of 75% shade limited carbon assimilation and led to decreased plant growth. Approximately 67% shade is suggested to be the optimum light irradiance condition for T. hemsleyanum cultivation.     

Urea loading from a spring storm—Knysna estuary,South Africa

Urea concentrations were tracked in the Knysna estuary, South Africa, following a strong initial storm of the austral summer rainy season in 2000. These post-storm urea concentrations are compared against a 1-year survey of these concentrations and demonstrate the initial and longer-term impacts of urea loading on a near-pristine estuary. Fifteen stations along the main channel of the estuary were sampled four times each, 2–4 weeks before the storm, providing and average urea concentration of 1.4 μmol N L⁻¹. When these same stations were sampled 12 h after the storm the average urea concentration had increased to 9.4 μmol N L⁻¹. The average urea concentration at these 15 stations remained high, averaging 10.2 μmol N L⁻¹ and 10.0 μmol N L⁻¹ 36 and 84 h post-storm, respectively. The urea concentrations in the rivers supplying fresh water to the Knysna estuary, one draining pasturelands and the other draining informal housing settlements that relied on pit toilets and open sewers are also compared before and after this storm. These data suggest that spring storms significantly influence nutrient availability, which in turn, may be related to the large dinoflagellates blooms witnessed in the Knysna estuary during the later portion of the wet summer season.     

Effect of light quality on Bacillus amyloliquefaciens JBC36 and its biocontrol efficacy

Light is one of the most important environmental signals regulating physiological processes of many microorganisms. However, very few studies have been reported on the qualitative or quantitative effects of light on control of postharvest spoilage using antagonistic bacteria. In this study, we investigated the effects of white, red, green, and blue light at photon flux densities of 40, 240, and 360 μmol m^?2 s^?1 on Bacillus amyloliquefaciens JBC36 (JBC36), which has been reported as a promising candidate for biocontrol of green and blue mold on mandarin fruit. With the exception of blue light at 240 and 360 μmol m^?2 s^?1, light generally stimulated growth of JBC36 compared to the controls grown in the dark. Red light increased swarming motility irrespective of intensity and significantly enhanced biofilm formation at 240 μmol m^?2 s^?1. Production of antifungal metabolites and antifungal activity on Penicillium digitatum was also affected by light quality. Interestingly, antifungal activity was significantly increased when JBC36 and P. digitatum was co-incubated under red and green light at an intensity of 240 μmol m^?2 s^?1. We also demonstrated that the quality of light resulted in changes in colonization of JBC36 on mandarin fruit and control of green mold. In particular, red light increased the population level on mandarin fruit and biocontrol efficacy against green mold. These results represent the first report on the effect of light quality on an antagonistic bacterium for the control of postharvest spoilage. We believe that an improved understanding of the JBC36 response to light quality may help in the development of strategies to increase biocontrol efficacy of postharvest spoilage.     

Phosphorus availability and rootstock affect copper-induced damage to the root ultra-structure of Citrus

The control of several citrus diseases requires continuous applications of fungicides containing copper (Cu) which favor to the accumulation of this metal in the soil. Therefore, the evaluation of how nutrient availability and rootstock interact with Cu toxicity in the citrus trees is required to maintain sustainability of fruit production in Cu-contaminated soils. Valencia orange trees on Sunki mandarin (SM) or Swingle citrumelo (SC) rootstock were grown in nutrient solutions combining adequate Cu (1.0 μmol L⁻¹), excess Cu (50.0 μmol L⁻¹), deficient phosphorus (P) (0.01 mmol L⁻¹) and sufficient P (0.5 mmol L⁻¹). The excess Cu reduced root and shoot growth, chlorophyll and relative water content in the leaves of the trees compared to those under adequate Cu supply. Furthermore, excess Cu caused severe damage to the root ultra-structure, characterized by the degeneration of the middle lamella and the presence of a thin and sinuous cell wall, as well as, starch accumulation in the plastids, disruption of the mitochondrial membranes and cellular plasmolysis. The damage caused by excess Cu in the cell wall and middle lamella on the root cells of SC was less severe than SM. Sufficient P supply improved the structure of the cell wall and middle lamella of trees subjected to excess Cu in comparison to P-deficient ones. Thus, the occurrence of more preserved cell wall and middle lamella supports the idea that sufficient P availability in the rooting medium and the use of SC rootstock might contribute to increase the ability of young citrus trees to cope with Cu toxicity.     

Performance of a composite membrane bioreactor treating toluene vapors: Inocula selection,reactor performance and behavior under transient conditions

In this study, a membrane biofilm reactor performance for toluene as a model pollutant is presented. A composite membrane consisting of a porous polyacrylonitrile (PAN) support layer coated with a very thin (0.3 μm) dense polydimethylsiloxane (PDMS) top layer was used. Batch experiments were performed to select an appropriate inocula (slaughterhouse wastewater treatment sludge with a specific toluene consumption rate of 118 ± 23 μg g^?1 VSS L^?1) among the three available sources of inoculums. The maximum elimination capacity gas-side reactor volume based (EC)_v and membrane based (EC)_{m, max} obtained were 609 g m^?3 h^?1 and 1.2 g m^?2 h^?1 respectively, which is much higher than other membrane bioreactors. Further experiments involved the study of the membrane biofilm reactor flexibility when operational parameters as temperature, loading rate etc. were modified. In all cases, the membrane biofilm reactor showed a rapid adaptation and new steady-states were obtained within hours. Overall, the results illustrate that membrane bioreactors can potentially be a good option for treatment of air pollutants such as toluene.     

Impact of in vitro CO2 enrichment and sugar deprivation on acclimatory responses of Phalaenopsis plantlets to ex vitro conditions

We assessed the effect of growth at either 400 μmol mol^?1 (ambient) or 1000 μmol mol^?1 (elevated) CO₂ and 0 g L^?1 (deprivation) or 30 g L^?1 (supplementation) sugar on morphological traits, photosynthetic attributes and intrinsic elements of the CAM pathway using the CAM orchid Phalaenopsis ‘Amaglade’. The growth of shoot (retarded) and root (induced) was differently affected by CO₂ enrichment and mixotrophic regime (+sugar). The Fv/Fm ratio was 14% more in CO₂-enriched treatment than at ambient level during in vitro growth. At elevated level of CO₂ and sugar treatment, the content of Chl(a + b), Chl a/b and Chl/Car was enhanced while carotenoid content remained unaltered. During in vitro growth, gas-exchange analysis indicated that increased uptake of CO₂ accorded with the increased rate of transpiration and unchanged stomatal conductance at elevated level of CO₂ under both photo- and mixotrophic growth condition. At elevated level of CO₂ and sugar deprivation, activities of Rubisco (26.4%) and PEPC (74.5%) was up-regulated. Among metabolites, the content of sucrose and starch was always higher under CO₂ enrichment during both in vitro and ex vitro growth. Our results indicate that plantlets grown under CO₂ enrichment developed completely viable photosynthetic apparatus ready to be efficiently transferred to ex vitro condition that has far-reaching implications in micropropagation of Phalaenopsis.     

Evaluation of the effects of light intensity on growth of the benthic dinoflagellate Ostreopsis sp. 1 using a newly developed photoirradiation-culture system and a novel regression analytical method

Benthic dinoflagellates of the genus Ostreopsis are found all over the world in temperate, subtropical, and tropical coastal regions. Our recent studies revealed that a putative “cryptic” species of Ostreopsis ovata is present widely along Japanese coasts. This organism, Ostreopsis sp. 1, possesses palytoxin analogs and thus its toxic blooms may be responsible for potential toxification of marine organisms. To evaluate the bloom dynamics of Ostreopsis sp. 1, the present study examined the growth responses of Ostreopsis sp. 1 strain s0716 to various light intensities (photon flux densities: μmol photons m⁻² s⁻¹) using a newly devised photoirradiation-culture system. This novel system has white light-emitting diodes (LEDs) capable of more closely simulating the wavelength spectrum of light entering the oceanic water column than do fluorescent tubes and halogen lamps. In this system, the light intensity of the white LEDs was reduced through two polarizing filters by varying the rotation angles of the filters. Thereby, the new system was capable of culturing microalgae under well-controlled light intensity conditions. Ostreopsis sp. 1 grew proportionally when light intensity was increased from 49.5 to 199 μmol photons m⁻² s⁻¹, but its growth appeared to be inhibited slightly at ≥263 μmol photons m⁻² s⁻¹. The relationship between observed growth rates and light intensity was calculated at R > 0.99 (P < 0.01) using a regression analysis with a modified equation of the photosynthesis-light intensity (P-L) model. The equation determined the critical light intensities for growth of Ostreopsis sp. 1 and the organism's growth potential as follows: (1) the threshold light intensity for growth: 29.8 μmol photons m⁻² s⁻¹; (2) the optimum light intensity (L_m) giving the maximum growth rate (μ_max = 0.659 divisions day⁻¹): 196 μmol photons m⁻² s⁻¹; (3) the optimum light intensity range (L_opt) giving ≥95% μ_max: 130–330 μmol photons m⁻² s⁻¹; (4) the semi-optimum range (L_sopt) giving ≥80% μ_max: 90 to over 460 μmol photons m⁻² s⁻¹. The L_sopt represents 4.5–23% ambient light intensity present in surface waters off of a temperate region of the Japanese coast, Tosa Bay; putatively, this semi-optimum range of light intensity appears at depth of 12.9–27.8 m. Considering these issues, our data indicate that Ostreopsis sp. 1 in coastal environments may form blooms at ca. ∼28 m depth in regions along Japanese coasts.     

Quantification of theobromine and caffeine in saliva,plasma and urine via liquid chromatography–tandem mass spectrometry: A single analytical protocol applicable to cocoa intervention studies

Targeted analyses of clinically relevant metabolites in human biofluids often require extensive sample preparation (e.g., desalting, protein removal and/or preconcentration) prior to quantitation. In this report, a single ultra-centrifugation based sample pretreatment combined with a designed liquid chromatography–tandem mass spectrometry (LC–MS/MS) protocol provides selective quantification of 3,7-dimethylxanthine (theobromine) and 1,3,7-trimethylxanthine (caffeine) in human saliva, plasma and urine samples. The optimized chromatography permitted elution of both analytes within 1.3 min of the applied gradient. Positive-mode electrospray ionization and a triple quadruple MS/MS instrument operated in multiple reaction mode were used for detection. ¹³C₃ isotopically labeled caffeine was included as an internal standard to improve accuracy and precision. Implementing a 20-fold dilution of the isolated low MW biofluid fraction prior to injection effectively minimized the deleterious contributions of all three matrices to quantitation. The assay was linear over a 160-fold concentration range from 2.5 to 400 μmol L^?1 for both theobromine (average R² 0.9968) and caffeine (average R² 0.9997) respectively. Analyte peak area variations for 2.5 μmol L^?1 caffeine and theobromine in saliva, plasma and urine ranged from 5 and 10% (intra-day, N = 10) to 9 and 13% (inter-day, N = 25) respectively. The intra- and inter-day precision of theobromine and caffeine elution times were 3 and <1% for all biofluids and concentrations tested. Recoveries for caffeine and theobromine ranged from 114 to 118% and 99 to 105% at concentration levels of 10 and 300 μmol L^?1. This validated protocol also permitted the relative saliva, plasma and urine distribution of both theobromine and caffeine to be quantified following a cocoa intervention.     

Long-term effects of exogenous silicon on cadmium translocation and toxicity in rice (Oryza sativa L.)

Most nutrient solution studies on the interactions between silicon (Si) and cadmium (Cd) are short term. Here we reported a long-term experiment in which rice (Oryza sativa L.) was cultured for 105 days and harvested at four different growth stages to measure biomass accumulation and Cd uptake and distribution in shoots and roots. Exogenous Si increased shoot biomass by 61–238% and root biomass by 48–173% when the culture solution was free of Cd. When 2 μmol L^?1 Cd was added, Si supply increased shoot and root biomass by 125–171% and by 100–106% compared to the zero-Si treatment. Increasing the Cd concentration to 4 μmol L^?1 decreased the beneficial effects of Si on root and shoot biomass. Silicon supply decreased shoot Cd concentrations by 30–50% and Cd distribution ratio in shoot by 25.3–46%, compared to the treatment without Si supply. Additionally, lower Si supply or more serious Cd stress would lead to roots with bigger biomass and higher Si concentration. Energy-dispersive X-ray microanalysis showed that both Si and Cd accumulated synchronously in the border and middle of phytoliths of the shoots. We conclude that Si enhances plant growth and decreases Cd accumulation in shoots and thereby helps to lower the potential risks of food contamination.     

Toward the production of flavone-7-O-β-d-glucopyranosides using Arabidopsis glycosyltransferase in Escherichia coli

Flavonoid glycosides are highly attractive targets due to their dominant roles in clinical, cosmetic production and in the food industry. In this research, an Escherichia coli strain bearing the reconstructed uridine-diphosphate glucose (UDP-glucose) pathway cassette and a putative glycosyltransferase from Arabidopsis thaliana, was developed as a host for the production of apigenin-7-O-β-d-glucoside (APG) and baicalein-7-O-β-d-glucoside (BCG) from exogenously supplied flavone aglycones (apigenin and baicalein, respectively). In order to improve the yield, genetic engineering of E. coli strains for optimization of intracellular UDP-glucose generation, as well as media optimization were carried out. The production was scaled up using a fed batch fermentation, and the maximal yield of products reached 90.88 μM (39.28 mg L^?1) and 76.82 μM (33.19 mg L^?1) of APG and BCG, respectively. And, the maximum bioconversion rate corresponded to 90.88% and 76.82% of apigenin and baicalein, respectively.     

Treatment of acidic wastewater arising from the refining of vegetable oil by crossflow microfiltration at very low transmembrane pressure

The refining process of vegetable oils generates acidic wastewater with the following characteristics: pH (1–1.5), COD (10–30 g O₂ L⁻¹), suspended solids (7–12 g L⁻¹) and fats (2–4 g L⁻¹). In order to reduce the effluent load and recover a fraction of the fats without using any additives, a microfiltration (0.2–1.4 μm) process involving ceramic membranes at very low transmembrane pressure values (0.1–1 bar) was assessed. Four batches of acidic wastewater from different manufacturing runs were tested. Trials with a constant volumetric reduction ratio of 30 were carried out for periods of more than 5 h. With a 0.5 μm membrane it was possible to maintain a permeate flux of 100 L h⁻¹ m⁻² for 24 h and achieve a 91% reduction in SS, a 96% reduction in fat and a COD reduction of more than 60%. In addition, the retentate thus extracted separated spontaneously into two phases, both of which could be exploited: the upper phase mainly consisting of fats as a by-product and the lower clarified phase which could be mixed into the permeate.     

Elevated CO2 and water-availability effect on gas exchange and nodule development in N2-fixing alfalfa plants

N₂-fixing alfalfa plants were grown in controlled conditions at different CO₂ levels (350 μmol mol^?1 versus 700 μmol mol^?1) and water-availability conditions (WW, watered at maximum pot water capacity versus WD, watered at 50% of control treatments) in order to determine the CO₂ effect (and applied at two water regimes) on plant growth and nodule activity in alfalfa plants. The CO₂ stimulatory effect (26% enhancement) on plant growth was limited to WW plants, whereas no CO₂ effect was observed in WD plants. Exposure to elevated CO₂ decreased Rubisco carboxylation capacity of plants, caused by a specific reduction in Rubisco (EC 4.1.1.39) concentration (11% in WW and 43% in WD) probably explained by an increase in the leaf carbohydrate levels. Plants grown at 700 μmol mol^?1 CO₂ maintained control photosynthetic rates (at growth conditions) by diminishing Rubisco content and by increasing nitrogen use efficiency. Interestingly, our data also suggest that reduction in shoot N demand (reflected by the TSP and especially Rubisco depletion) affected negatively nodule activity (malate dehydrogenase, EC 1.1.1.37, and glutamate-oxaloacetate transaminase, EC 2.6.1.1, activities) particularly in water-limited conditions. Furthermore, nodule DM and TSS data revealed that those nodules were not capable to overcome C sink strength limitations.     

The harmful alga Aureococcus anophagefferens utilizes 19′-butanoyloxyfucoxanthin as well as xanthophyll cycle carotenoids in acclimating to higher light intensities

Aureococcus anophagefferens is a picoplanktonic microalga that is very well adapted to growth at low nutrient and low light levels, causing devastating blooms (“brown tides”) in estuarine waters. To study the factors involved in long-term acclimation to different light intensities, cells were acclimated for a number of generations to growth under low light (20 μmol photons m^? 2 s^? 1), medium light (60 or 90 μmol photons m^? 2 s^? 1) and high light (200 μmol photons m^? 2 s^? 1), and were analyzed for their contents of xanthophyll cycle carotenoids (the D pool), fucoxanthin and its derivatives (the F pool), Chls c₂ and c₃, and fucoxanthin Chl a/c polypeptides (FCPs). Higher growth light intensities resulted in increased steady state levels of both diadinoxanthin and diatoxanthin. However, it also resulted in the conversion of a significant fraction of fucoxanthin to 19′-butanoyloxyfucoxanthin without a change in the total F pool. The increase in 19′-butanoyloxyfucoxanthin was paralleled by a decrease in the effective antenna size, determined from the slope of the change in F₀ as a function of increasing light intensity. Transfer of acclimated cultures to a higher light intensity showed that the conversion of fucoxanthin to its derivative was a relatively slow process (time-frame of hours). We suggest the replacement of fucoxanthin with the bulkier 19′-butanoyloxyfucoxanthin results in a decrease in the light-harvesting efficiency of the FCP antenna and is part of the long-term acclimative response to growth at higher light intensities.     

Refolding and purification of recombinant human granulocyte colony-stimulating factor using hydrophobic interaction chromatography at a large scale

High level expression of recombinant human granulocyte colony-stimulating factor (rhG-CSF) in Escherichia coli (E. coli) usually forms insoluble and inactive aggregates, i.e. inclusion bodies. In the present work, high performance hydrophobic interaction chromatography (HPHIC) was applied to the refolding of rhG-CSF, which was solubilized by 8.0 mol L^?1 urea from the inclusion bodies. First a laboratorial scale column (10 mm × 20 mm I.D.) was employed to study the refolding process. Several factors, including concentration of ammonium sulfate, pH of the mobile phase and flow rate, were investigated in details. The results indicated that the rhG-CSF produced by E. coli could be successfully refolded with simultaneous purification by using HPHIC. The refolding process was further scaled up by using a large column (50 mm × 200 mm I.D.). 200 mL of rhG-CSF solution solubilized by 8.0 mol L^?1 urea, with a total amount of protein around 1.6 g, could be loaded onto the large column at one time. Under these conditions, the obtained rhG-CSF had a specific activity of 2.3 × 10⁸ IU mg^?1 and a purity of 95.4%, the mass recovery during the purification was 36.9%. This work might have great impact on practical production of rhG-CSF, and it also shed a light on protein refolding using liquid chromatography at large scales.     

Serum selenium levels of the very low birth weight premature newborn infants with bronchopulmonary dysplasia

BackgroundThe selenium (Se) is an essential trace element that has a critical role in synthesis and activity of a number of selenoproteins with protective properties against free radical damage. This study was conducted to detect the serum Se concentration in very low birth weight (VLBW) preterm infants and its association with bronchopulmonary dysplasia (BPD).Materials and methodsCord blood Se concentration was determined in 54 neonates with gestation age 30 week or less. Another sample was obtained from these infants at day 28 of birth and serum Se levels were measured by atomic absorption spectrophotometer. All neonates were followed for oxygen dependency at 28 day after birth and 36 week postmenstrual age.ResultsThe mean cord blood Se concentration in studied neonates was 64.78 ± 20.73 μg L^?1. Serum Se concentration was 60.33 ± 26.62 μg L^?1 at age 28-day. No significant correlation was observed for serum Se concentration at birth and at one month after birth (r = ?0.04, p = 0.72). BPD was diagnosed in 25 neonates (46%). The mean serum Se concentration at one month was 57.16 ± 29.68 μg L^?1 in patients with BPD (25 cases) and 63.27 ± 23.6 μg L^?1 in 29 patients without BPD (p = 0.40).ConclusionIn our study, serum Se concentration at 28 day of birth was lower than cord blood levels in preterm neonates, but we have not found significant difference among patients who had BPD or not with respect to serum Se concentrations at this age.     

Direct in vivo interaction of the antibiotic primycin with the plasma membrane of Candida albicans: An EPR study

The direct interaction of the antibiotic primycin with the plasma membrane was investigated by employing the well-characterized ergosterol-producing, amphotericin B-sensitive parental Candida albicans strain 33erg⁺ and its ergosterol-less amphotericin B-resistant plasma membrane mutant erg-2. The growth inhibition concentration in shaken liquid medium was 64 μg ml^?1 for 33erg⁺ and 128 μg ml^?1 for erg-2, suggesting that the plasma membrane composition influences the mode of action of primycin. To determine the primycin-induced changes in the plasma membrane dynamic, electron paramagnetic resonance (EPR) spectroscopy methods were used, the spin-labeled fatty acid 5-(4,4-dimethyloxazolidine-N-oxyl)stearic acid) being applied for the in vivo measurements. The phase transition temperatures of untreated strain 33erg⁺ and its mutant erg-2 were 12.5 °C and 11 °C, respectively. After 128 μg ml^?1 primycin treatment, these values increased to 17.5 °C and 16 °C, revealing a significant reduction in the phospholipid flexibility. Saturation transfer EPR measurements demonstrated that, the rotational correlation times of the spin label molecule for the control samples of 33erg⁺ and erg-2 were 60 ns and 100 ns. These correlation times gradually decreased on the addition of increasing primycin concentrations, reaching 8 μs and 1 μs. The results indicate the plasma membrane “rigidizing” effect of primycin, a feature that may stem from its ability to undergo complex formation with membrane constituent fatty acid molecules, causing alterations in the structures of phospholipids in the hydrophobic surface near the fatty acid chain region.     

Continuous production of selenomethionine-enriched Chlorella sorokiniana biomass in a photobioreactor

This article describes the enrichment of the fresh-water green microalga Chlorella sorokiniana in selenomethionine (SeMet). The microalga was cultivated in a 2.2 L glass-vessel photobioreactor, in a culture medium supplemented with selenate (SeO₄^2?) concentrations ranging from 5 to 50 mg L^?1. Although selenate exposure lowered culture viability, C. sorokiniana grew well at all tested selenate concentrations, however cultures supplemented with 50 mg L^?1 selenate did not remain stable at steady state. A suitable selenate concentration in fresh culture medium for continuous operation was determined, which allowed stable long-term cultivation at steady state and maximal SeMet productivity. In order to do that, the effect of dilution rate on biomass productivity, viability and SeMet content of C. sorokiniana at several selenate concentrations were determined in the photobioreactor. A maximal SeMet productivity of 21 μg L^?1 day^?1 was obtained with 40 mg L^?1 selenate in the culture medium. Then a continuous cultivation process at several dilution rates was performed at 40 mg L^?1 selenate obtaining a maximum of 246 μg L^?1 day^?1 SeMet at a low dilution rate of 0.49 day^?1, calculated on total daily effluent volume. This paper describes for the first time an efficient long-term continuous cultivation of C. sorokiniana for the production of biomass enriched in the high value amino acid SeMet, at laboratory scale.