scholarly journals Freshwater dissolved oxygen dynamics: changes due to glyphosate, 2,4-D and their mixture, both under clear and turbid-organic conditions.

2021 ◽  
Author(s):  
Veronica Laura Lozano ◽  
Cecilia Evelin Miranda ◽  
Vinocur Liliana Alicia ◽  
Carmen Alejandra Sabio y Garcia ◽  
Maria Solange Vera ◽  
...  
Keyword(s):  
Heterotrophic Bacteria ◽  
High Concentration ◽  
Eukaryotic Phytoplankton ◽  
Mesocosm Experiments ◽  
Herbicide Mixture ◽  
Single Input ◽  
Induced Changes ◽  
Oxygen Dynamics ◽  
Concentration Levels ◽  
Mixotrophic Algae

We performed two independent outdoor mesocosm experiments where we measured the variation of DO saturation (DO%) in freshwater after a single input of Roundup Max (G) (glyphosate-based formulation), AsiMax 50 (2,4-D) (2,4-D-based formulation) and their mixture (M). Two concentration levels were tested; 0.3 mg/L G and 0.135 mg/L 2,4-D (Low; L) and 3 mg/L G and 1.35 mg/L 2,4-D (High; H). We assayed consolidated microbial communities coming from a system in organic turbid eutrophic status and a system in clear mesotrophic status during 21 and 23 days, respectively. A sample of phytoplankton (micro+nano, pico-eukaryotes, pico-cyanobacteria), mixotrophic algae and heterotrophic bacteria was collected to determine abundances at each of four sampling dates. The clear and turbid systems showed similar, but not synchronized, patterns of daily DO% changes in relation to the controls (DO%v), after exposure to both single and combined formulations. Under glyphosate scenarios (GL, GH, ML and MH), the two types of systems showed similar DO%v but different microbial abundances, being associated to an increase in the micro+nano and pico-eukaryotic phytoplankton fractions for the clear system. In contrast, in the turbid system changes were associated with increased pico-cyanobacteria and decreased mixotrophic algae. Effects of 2,4-D were only observed in the turbid system, leading to decreased micro+nano phytoplankton abundances. Under the turbid scenario, the herbicide mixture at high concentration had a synergistic effect on DO%v and recovery was not detected by the end of the experiment. Our results revealed that herbicides inputs induced changes in phytoplankton abundances that leads to measurable DO variations.

Oscillating conditions for influencing the composition of mixed biological cultures

1998 ◽  
Vol 37 (4-5) ◽  
pp. 259-262 ◽  
Author(s):  
Bjarne R. Horntvedt ◽  
Morten Rambekk ◽  
Rune Bakke
Keyword(s):  
Growth Rate ◽  
Specific Growth ◽  
Heterotrophic Bacteria ◽  
Bacterial Species ◽  
Rate Reduction ◽  
Similar Strategy ◽  
Sinusoidal Oscillations ◽  
Specific Growth Rates ◽  
Rate Limiting ◽  
Concentration Levels

This paper presents a strategy in which mixed biological cultures are exposed to oscillating concentration levels, to improve the potential for coexistence of desired bacterial species. A mechanistic mathematical model is constructed to investigate and illustrate this strategy. This paper is focused on competition between nitrifying, denitrifying and aerobic heterotrophic bacteria in a CSTR with sludge recycle. For nitrifying and aerobic heterotrophic cultures, the effect of sinusoidal oscillations in DO levels with an amplitude of 1.0 mg/l is a 16% specific growth rate reduction compared to that at a constant DO level. The denitrifiers growth rate is increased by an average of 59%, compared to the constant DO level situation. A similar strategy has been tested in a pilot plant. It is concluded that the influence on specific growth rates is a function of the amplitude of the oscillations. The effects are greatest when concentrations fluctuate around the half saturation concentration of the rate limiting component(s).

Secondary biosynthesis of aflatoxin B1 in Aspergillus parasiticus

1970 ◽  
Vol 16 (10) ◽  
pp. 959-963 ◽  
Author(s):  
R. W. Detroy ◽  
C. W. Hesseltine
Keyword(s):  
Protein Synthesis ◽  
Aflatoxin B1 ◽  
Aspergillus Parasiticus ◽  
Synthetase Activity ◽  
Macromolecular Synthesis ◽  
High Concentration ◽  
Methyl Group ◽  
Aflatoxin B ◽  
Concentration Levels

The effect of two inhibitors on the formation of aflatoxin B1 synthetase activity in strain NRRL 2999 Aspergillus parasiticus has been studied. Aflatoxin B1 synthesizing activity was measured in vivo by incorporation of the 14C-methionine methyl group into aflatoxin B1. Cycloheximide at a concentration of 150 μg/ml blocks protein synthesis completely. If addition of cycloheximide is made before B1 synthetase appears, no activity accumulates; if added during accumulation, activity is frozen at the level reached at the time of addition. The cycloheximide effect is reversible since morphogenesis, total protein synthesis, and aflatoxin B1 synthetase activity all resume after removal of the inhibitor.DL-p-Fluorophenylalanine partially inhibits aflatoxin B1 synthesis in vivo; however, its effect upon macromolecular synthesis is incomplete even at high concentration levels. Once formed, the aflatoxin synthetase appears to maintain B1 synthesis when further protein synthesis is blocked; i.e., it is not rapidly degraded.

scholarly journals Nitrogen isotopic evidence for a shift from nitrate- to diazotroph-fueled export production in the VAHINE mesocosm experiments

2016 ◽  
Vol 13 (16) ◽  
pp. 4645-4657 ◽  
Author(s):  
Angela N. Knapp ◽  
Sarah E. Fawcett ◽  
Alfredo Martínez-Garcia ◽  
Nathalie Leblond ◽  
Thierry Moutin ◽  
...  
Keyword(s):  
N2 Fixation ◽  
Significant Fraction ◽  
Organic N ◽  
Total Biomass ◽  
Export Production ◽  
Dominant Source ◽  
Isotopic Evidence ◽  
Surface Ocean ◽  
Eukaryotic Phytoplankton ◽  
Mesocosm Experiments

Abstract. In a coastal lagoon with a shallow, 25 m water column off the southwest coast of New Caledonia, large-volume ( ∼  50 m3) mesocosm experiments were undertaken to track the fate of newly fixed nitrogen (N). The mesocosms were intentionally fertilized with 0.8 µM dissolved inorganic phosphorus to stimulate diazotrophy. N isotopic evidence indicates that the dominant source of N fueling export production shifted from subsurface nitrate (NO3−) assimilated prior to the start of the 23-day experiments to N2 fixation by the end of the experiments. While the δ15N of the sinking particulate N (PNsink) flux changed during the experiments, the δ15N of the suspended PN (PNsusp) and dissolved organic N (DON) pools did not. This is consistent with previous observations that the δ15N of surface ocean N pools is less responsive than that of PNsink to changes in the dominant source of new N to surface waters. In spite of the absence of detectable NO3− in the mesocosms, the δ15N of PNsink indicated that NO3− continued to fuel a significant fraction of export production (20 to 60 %) throughout the 23-day experiments, with N2 fixation dominating export after about 2 weeks. The low rates of organic N export during the first 14 days were largely supported by NO3−, and phytoplankton abundance data suggest that sinking material primarily comprised large diatoms. Concurrent molecular and taxonomic studies indicate that the diazotroph community was dominated by diatom–diazotroph assemblages (DDAs) at this time. However, these DDAs represented a minor fraction (< 5 %) of the total diatom community and contributed very little new N via N2 fixation; they were thus not important for driving export production, either directly or indirectly. The unicellular cyanobacterial diazotroph, a Cyanothece-like UCYN-C, proliferated during the last phase of the experiments when N2 fixation, primary production, and the flux of PNsink increased significantly, and δ15N budgets reflected a predominantly diazotrophic source of N fueling export. At this time, the export flux itself was likely dominated by the non-diazotrophic diatom, Cylindrotheca closterium, along with lesser contributions from other eukaryotic phytoplankton and aggregated UCYN-C cells, as well as fecal pellets from zooplankton. Despite comprising a small fraction of the total biomass, UCYN-C was largely responsible for driving export production during the last  ∼  10 days of the experiments both directly ( ∼  5 to 22 % of PNsink) and through the rapid transfer of its newly fixed N to other phytoplankton; we infer that this newly fixed N was transferred rapidly through the dissolved N (including DON) and PNsusp pools. This inference reconciles previous observations of invariant oligotrophic surface ocean DON concentrations and δ15N with incubation studies showing that diazotrophs can release a significant fraction of their newly fixed N as some form of DON.

Modelling the effect of atmospheric nitrogen deposition on marine phytoplankton in the Singapore Strait

2010 ◽  
Vol 61 (4) ◽  
pp. 859-867 ◽  
Author(s):  
P. Sundarambal ◽  
P. Tkalich ◽  
R. Balasubramanian
Keyword(s):  
Atmospheric Deposition ◽  
Nitrate Nitrogen ◽  
Relative Effect ◽  
Marine Phytoplankton ◽  
High Concentration ◽  
Relative Contribution ◽  
Temporal And Spatial Variability ◽  
Model Features ◽  
Oxygen Dynamics ◽  
Singapore Strait

Atmospheric deposition is an important source of nutrients to the ocean, potentially stimulating primary production, but its relative effect on coastal eutrophication remains largely unknown. This paper presents data generated by the 3-D modelling program NEUTRO to assess the proportion of atmospheric nutrient fluxes, allowing a quantification of the relative contribution of atmospheric and ocean fluxes in the Singapore Strait. This work included an assessment of the importance of high concentration episodic inputs of nitrate-nitrogen associated with transport of polluted air onto the surface water. The NEUTRO model features a nutrient-fuelled food web composed of nutrients, plankton, and dissolved oxygen dynamics. Model simulations show that atmospheric deposition fluxes alone might contribute nitrate-nitrogen mass up to 15% into the Singapore Strait. This amount might be a significant contributor toward regional eutrophication when the system is under nutrient-depleted conditions. Model calibrations for temporal and spatial variability of nutrients qualitatively and quantitatively agreed with available measurements.

Cephapirin in Acute Lung Diseases in Children

1974 ◽  
Vol 2 (2) ◽  
pp. 125-131 ◽  
Author(s):  
Hugo Trujillo ◽  
Rafael Manotas ◽  
Cecilia Salazar ◽  
Alfonso Rodriguez ◽  
Alvaro Uribe ◽  
...  
Keyword(s):  
Intravenous Administration ◽  
Plasma Levels ◽  
Lung Diseases ◽  
Peak Plasma ◽  
Parenteral Administration ◽  
Gram Negative Bacteria ◽  
High Concentration ◽  
Gram Negative ◽  
Intramuscular Injections ◽  
Concentration Levels

Parenteral administration, intravenous followed by intramuscular, or intramuscular alone, cured thirty children with pneumonia and empyema caused by S. aureus, D. pneumoniae, Klebsiella sp. and other gram-negative bacteria, within one to three weeks. Pathogens disappeared from pleural pus in all empyema cases within the first forty-eight hours of treatment. Following intravenous administration peak plasma levels ( 117 mcg/ml) were obtained in five minutes, and following intramuscular injections peak plasma levels ( 55 mcg/ml) were obtained in one hour. High concentration levels were observed in pleural pus ( 23-37 mcg/ml) in two hours. The drug was very well tolerated both locally and systemically.

Acquiring reproducible fluorescence spectra of dissolved organic matter at very low concentrations

2009 ◽  
Vol 60 (6) ◽  
pp. 1385-1392 ◽  
Author(s):  
B. R. H. Peiris ◽  
H. Budman ◽  
C. Moresoli ◽  
R. L. Legge
Keyword(s):  
Organic Matter ◽  
Dissolved Organic Matter ◽  
High Concentration ◽  
Low Concentration ◽  
Low Concentrations ◽  
Fibre Optic Probe ◽  
On Line ◽  
Optic Probe ◽  
Membrane Treatment ◽  
Concentration Levels

A method that would allow for fast and reliable measurements of dissolved organic matter (DOM), both at low and high concentration levels would be a valuable tool for online monitoring of DOM. This could have applications in a variety of areas including membrane treatment systems for drinking water applications which is of interest to our group. In this study, the feasibility of using fluorescence spectroscopy for monitoring DOM at very low concentration levels was demonstrated with an emphasis on optimizing the instrument parameters necessary to obtain reproducible fluorescence signals. Signals were acquired using a cuvette or a fibre optic probe assembly, the latter which may have applications for on-line or in-line monitoring. The instrument parameters such as photomultiplier tube (PMT) voltage, scanning rate and slit width were studied in detail to find the optimum parameter settings required. The results showed that larger excitation and emission slit widths were preferred, over larger PMT voltage or lower scanning rates, to obtain reproducible and rapid measurements when measuring very low concentration levels of DOM. However, this approach should be implemented with caution to avoid any reduction of the signal resolution.

Effects of a pharmaceutical mixture at environmentally relevant concentrations on the amphipod Gammarus fossarum

2010 ◽  
Vol 61 (2) ◽  
pp. 196 ◽  
Author(s):  
Sabine Dietrich ◽  
Shana Dammel ◽  
Florian Ploessl ◽  
Franz Bracher ◽  
Christian Laforsch
Keyword(s):  
Body Length ◽  
Aquatic Organisms ◽  
Freshwater Ecosystems ◽  
Control Treatment ◽  
High Concentration ◽  
Gammarus Fossarum ◽  
Drug Mixture ◽  
High Concentrations ◽  
Concentration Levels ◽  
Complex Drug

The continuous discharge of pharmaceuticals into the environment results in the chronic exposure of aquatic organisms to complex drug mixtures. We examined the influence of a mixture of pharmaceuticals (carbamazepine (CBZ), diclofenac (DIC), metoprolol (MET) and 17α-ethinylestradiol (EE2)) at environmentally relevant (‘env’) and artificially high (‘high’) concentrations on Gammarus fossarum. Different sublethal responses such as moulting, reproduction and the content of the energy-storage component glycogen were analysed. The drug mixture influenced the moulting behaviour of gammarids at both the ‘env’ and ‘high’ concentration levels, leading to a discontinuous increase of body length in successive moults, compared with the constant increase of body length in the control treatment. Moreover, the time between successive moults of animals exposed to the ‘env’ and ‘high’ pharmaceutical concentrations was decreased because of shortened intermoult periods. We observed no significant impact of the pharmaceuticals on reproduction. In addition, the content of glycogen was not significantly affected by the drug mixture. Permanent exposure of G. fossarum to a wider range of pharmaceuticals in natural aquatic systems may influence moulting behaviour and accompanied life-history parameters, followed by severe ecological consequences as gammarids play an important role in many freshwater ecosystems of the northern hemisphere.

scholarly journals HPLC profiling of selected phenolic acids and flavonoids in Salvia eigii, Salvia hierosolymitana and Salvia viridis growing wild in Jordan and their in vitro antioxidant activity

PeerJ ◽  
2020 ◽  
Vol 8 ◽  
pp. e9769
Author(s):  
Hala I. Al-Jaber ◽  
Ashok K. Shakya ◽  
Zaha A. Elagbar
Keyword(s):  
Antioxidant Activity ◽  
Phenolic Acids ◽  
Rosmarinic Acid ◽  
Salvianolic Acid B ◽  
Total Flavonoids ◽  
High Concentration ◽  
Total Flavonoids Content ◽  
Concentration Levels ◽  
In Vitro Antioxidant Activity

Background Salvia eigii., Salvia hierosolymitana and Salvia viridis are native to the Mediterranean region, and are used in traditional medicine for the treatment of many ailments. In the current investigation, the methanolic extracts obtained from the air dried aerial parts of S. eigii, S. hierosolymitana and S. viridis from Jordan were screened for their total phenolics content (TPC), total flavonoids content (TFC) and their in vitro antioxidant activity. Additionally, the presence of four bioactive phenolic acids including gallic acid, caffeic acid, rosmarinic acid and salvianolic acid B and other seven flavonoids including luteolin-7-O-glucoside, apigenin, apigenin-7-O-glucoside, rutin, nariginin, hesperidin and quercetin was determined using Liquid chromatography-Electron Spray Ionization-Tandom Mass Spectrometry (LC-ESI-MS/MS). Methods Antioxidant activity of the obtained three extracts were examined via the DPPH•, ABTS• + radical scavenging methods in addition to Ferrous Ion Chelating (FIC) effect. TFC and TPC of the extracts were measured using the aluminum chloride colorimetric method and the Folin-Ciocalteau method, respectively. The presence and concentration of the selected 11 compounds was further determined through LC-ESI-MS/MS. Results The results indicated that three Salvia species had high total flavonoids content expressed in mg quercetin/g dry extract (S. heirosolymitana: 770.85 ±  5.26; S. eigii: 520.60 ±  6.24, S. viridis: 311.36 ±  4.41). S. heirosolymitana had the highest DPPH• activity (0.184 ±  1.22 × 10−2 mg/ml) and FIC effect (0.354 ±  0.018 mg/ml). S. heirosolymitana had slightly higher ABTS• + scavenging activity than S. eigii (0.176 ±  1.16 × 10−2 mg/ml; 0.183 ±  0.031 mg/ml, respectively). All 11 compounds were detected in the extracts of the three Salvia species. Luteolin-7-O-glucoside was detected in high concentration levels in the three species (1756.73, 21651.36, and 26125.14 mg/kg dry plant; S. eigii, S. hierosolyimitana and S. viridis, respectively), yet rosmarinic acid had the highest contribution to both S. hierosolymitana (27124.93 mg/kg) and S. eigii (15783.33 mg/kg). Notably, S. hierosolymitana and S. viridis contained salvianolic acid B (896.11; 890.9 mg/kg). Conclusions The three Salvia species exhibited good antioxidant activity, especially S. heirosolymitana due to its high TPC, TFC, and the presence of high concentration levels of romarinic acid and other phenolic acids and flavonoids. This is the first phytochemical and antioxidant evaluation of S. eigii, S. hierosolymitana and S. viridis from Jordan. Prior to this investigation, no phytochemical investigation on S. eigii was reported.

scholarly journals Establishment of Tetranychid Mites in vitro

1998 ◽  
Vol 8 (2) ◽  
pp. 179-182
Author(s):  
Masood Z. Hadi ◽  
Mark P. Bridgen ◽  
John P. Sanderson
Keyword(s):  
Tetranychus Urticae ◽  
Sodium Hypochlorite ◽  
In Vitro Cultures ◽  
Tween 20 ◽  
Torenia Fournieri ◽  
High Concentration ◽  
Time Periods ◽  
Concentration Levels ◽  
Bean Leaves

Procedures were developed to determine if live, adult two-spotted spidermites (Tetranychus urticae Koch) could be surface disinfested before being introduced into in vitro cultures of torenia (Torenia fournieri L.). Three time periods (5, 10, and 15 minutes) and five levels of sodium hypochlorite (0.05% to 0.25%) were evaluated. Surface disinfestation was accomplished by agitating 2 × 3 cm pieces of infested bean leaves in sodium hypochlorite solutions and then drying in a mite drier apparatus. All sodium hypochlorite concentrations disinfested the mites completely, however high concentration levels were lethal to the mites. Exposure periods of 10 and 15 minutes also significantly increased mortality. For optimum disinfestation of two-spotted spidermites with minimum mortality, a concentration of 0.05% sodium hypochlorite and 0.05% Tween-20 for 5 minutes should be used.

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