‘Floc and Sink’ Technique Removes Cyanobacteria and Microcystins from Tropical Reservoir Water

Combining coagulants with ballast (natural soil or modified clay) to remove cyanobacteria from the water column is a promising tool to mitigate nuisance blooms. Nevertheless, the possible effects of this technique on different toxin-producing cyanobacteria species have not been thoroughly investigated. This laboratory study evaluated the potential effects of the “Floc and Sink” technique on releasing microcystins (MC) from the precipitated biomass. A combined treatment of polyaluminium chloride (PAC) with lanthanum modified bentonite (LMB) and/or local red soil (LRS) was applied to the bloom material (mainly Dolichospermum circinalis and Microcystis aeruginosa) of a tropical reservoir. Intra and extracellular MC and biomass removal were evaluated. PAC alone was not efficient to remove the biomass, while PAC + LMB + LRS was the most efficient and removed 4.3–7.5 times more biomass than other treatments. Intracellular MC concentrations ranged between 12 and 2.180 µg L⁻¹ independent from the biomass. PAC treatment increased extracellular MC concentrations from 3.5 to 6 times. However, when combined with ballast, extracellular MC was up to 4.2 times lower in the top of the test tubes. Nevertheless, PAC + LRS and PAC + LMB + LRS treatments showed extracellular MC concentration eight times higher than controls in the bottom. Our results showed that Floc and Sink appears to be more promising in removing cyanobacteria and extracellular MC from the water column than a sole coagulant (PAC).     

Effects of Polystyrene Microplastics on Growth and Toxin Production of Alexandrium pacificum

Microplastics (MP) widely distributed in aquatic environments have adverse effects on aquatic organisms. Currently, the impact of MP on toxigenic red tide microalgae is poorly understood. In this study, the strain of Alexandrium pacificum ATHK, typically producing paralytic shellfish toxins (PST), was selected as the target. Effects of 1 and 0.1 μm polystyrene MP with three concentration gradients (5 mg L⁻¹, 25 mg L⁻¹ and 100 mg L⁻¹) on the growth, chlorophyll a (Chl a), photosynthetic activity (F_v/F_m) and PST production of ATHK were explored. Results showed that the high concentration (100 mg L⁻¹) of 1 μm and 0.1 μm MP significantly inhibited the growth of ATHK, and the inhibition depended on the size and concentration of MP. Contents of Chl a showed an increase with various degrees after MP exposure in all cases. The photosynthesis indicator F_v/F_m of ATHK was significantly inhibited in the first 11 days, then gradually returned to the level of control group at day 13, and finally was gradually inhibited in the 1 μm MP treatments, and promotion or inhibition to some degree also occurred at different periods after exposure to 0.1 μm MP. Overall, both particle sizes of MP at 5 and 25 mg L⁻¹ had no significant effect on cell toxin quota, and the high concentration 100 mg L⁻¹ significantly promoted the PST biosynthesis on the day 7, 11 and 15. No significant difference occurred in the cell toxin quota and the total toxin content in all treatments at the end of the experiment (day 21). All MP treatments did not change the toxin profiles of ATHK, nor did the relative molar percentage of main PST components. The growth of ATHK, Chl a content, F_v/F_m and toxin production were not affected by MP shading. This is the first report on the effects of MP on the PST-producing microalgae, which will improve the understanding of the adverse impact of MP on the growth and toxin production of A. pacificum.     

The effects of Microcystis aeruginosa cells lysate containing microcystins on physiological and molecular responses in the nematode Caenorhabditis elegans

Microcystins (MCs) are potent toxins produced by environmental cyanobacterial blooms. The present study evaluated the effects of a Microcystis aeruginosa cyanobacterial lysate containing 0.1, 1, and 10 μg L^?1 MC‐LR equivalent in the C. elegans Bristol N2 wild‐type and the effects caused by equivalent concentrations of a MC‐LR standard. The lysate was prepared from a culture of toxic strain (RST9501) originated from the Patos Lagoon Estuary (RS, Brazil). The minimal concentration necessary to cause significant effects in C. elegans under exposure to M. aeruginosa lysate or to MC‐LR standard were, respectively, 10 and 0.1 μg L^?1 MC‐LR equivalent for growth and 10 and 1 μg L^?1 MC‐LR equivalent for fertility. Reproduction (ie, brood size) was only affected by the exposure to 10 μg L^?1 MC‐LR standard and was not affected by the lysate. The nematodes that were exposed to lysate containing 1 μg L^?1 MC‐LR equivalent or MC‐LR were also analyzed for pharyngeal pumping and gene expression using RT‐qPCR. The worms’ rhythmic contractions of the pharynx were similarly affected by the lysate containing 1 μg L^?1 of MC‐LR equivalent and the MC‐LR standard. The MC‐LR standard caused down‐regulation of genes related to growth (daf‐16), fertility (spe‐10), and biotransformation (gst‐2). This is the first study to evaluate the effects of a toxic cyanobacterial lysate using the C. elegans model. This study suggests the organism as a potential biotest to evaluate toxicity of natural waters containing M. aeruginosa cells and to environmental risk assessment associated to cyanobacterial bloom events.     

Protective Role of Native Rhizospheric Soil Microbiota Against the Exposure to Microcystins Introduced into Soil-Plant System via Contaminated Irrigation Water and Health Risk Assessment

Microcystins (MCs) produced in eutrophic waters may decrease crop yield, enter food chains and threaten human and animal health. The main objective of this research was to highlight the role of rhizospheric soil microbiota to protect faba bean plants from MCs toxicity after chronic exposure. Faba bean seedlings were grown in pots containing agricultural soil, during 1 month under natural environmental conditions of Marrakech city in Morocco (March–April 2018) and exposed to cyanobacterial extracts containing up to 2.5 mg·L⁻¹ of total MCs. Three independent exposure experiments were performed (a) agricultural soil was maintained intact “exposure experiment 1”; (b) agricultural soil was sterilized “exposure experiment 2”; (c) agricultural soil was sterilized and inoculated with the rhizobia strain Rhizobium leguminosarum RhOF34 “exposure experiment 3”. Overall, data showed evidence of an increased sensitivity of faba bean plants, grown in sterilized soil, to MCs in comparison to those grown in intact and inoculated soils. The study revealed the growth inhibition of plant shoots in both exposure experiments 2 and 3 when treated with 2.5 mg·L⁻¹ of MCs. The results also showed that the estimated daily intake (EDI) of MCs, in sterilized soil, exceeded 2.18 and 1.16 times the reference concentrations (0.04 and 0.45 µg of microcysin-leucine arginine (MC-LR). Kg⁻¹ DW) established for humans and cattle respectively, which raises concerns about human food chain contamination.     

A rapid and sensitive spectrophotometric method for the determination of benzoyl peroxide in wheat flour samples

A simple, rapid, and sensitive spectrophotometric method for the determination of benzoyl peroxide (BPO) in wheat flour samples was developed. The detection principle is based on BPO reacted with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) to obtain a blue-green colored product that was detected at 415 nm by spectrophotometry. The effect of factors influencing the color reaction was investigated. Under the selected conditions, the linear range for quantification of BPO was observed between 0.2–1.0 mg L⁻¹ with r² = 0.998. The limit of detection (LOD) was 0.025 mg L⁻¹. The developed method obtained superior precision (relative standard deviation < 2%) using 11 repeatability at 0.2 mg L⁻¹, 0.6 mg L⁻¹, and 0.8 mg L⁻¹. The proposed methodology was successfully applied to determine BPO in wheat flour samples.     

Chitosan as a Coagulant to Remove Cyanobacteria Can Cause Microcystin Release

Chitosan has been tested as a coagulant to remove cyanobacterial nuisance. While its coagulation efficiency is well studied, little is known about its effect on the viability of the cyanobacterial cells. This study aimed to test eight strains of the most frequent bloom-forming cyanobacterium, Microcystis aeruginosa, exposed to a realistic concentration range of chitosan used in lake restoration management (0 to 8 mg chitosan L⁻¹). We found that after 1 h of contact with chitosan, in seven of the eight strains tested, photosystem II efficiency was decreased, and after 24 h, all the strains tested were affected. EC₅₀ values varied from 0.47 to > 8 mg chitosan L^-1 between the strains, which might be related to the amount of extracellular polymeric substances. Nucleic acid staining (Sytox-Green^®) illustrated the loss of membrane integrity in all the strains tested, and subsequent leakage of pigments was observed, as well as the release of intracellular microcystin. Our results indicate that strain variability hampers generalization about species response to chitosan exposure. Hence, when used as a coagulant to manage cyanobacterial nuisance, chitosan should be first tested on the natural site-specific biota on cyanobacteria removal efficiency, as well as on cell integrity aspects.     

Myrtucommulone,a natural acylphloroglucinol,inhibits microsomal prostaglandin E2 synthase-1

Background and purpose:

The selective inhibition of prostaglandin (PG)E₂ formation via interference with microsomal PGE₂ synthase (mPGES)-1 could have advantages in the treatment of PGE₂-associated diseases, such as inflammation, fever and pain, compared with a general suppression of all PG biosynthesis, provided by inhibition of cyclooxygenase (COX)-1 and 2. Here, we addressed whether the naturally occurring acylphloroglucinol myrtucommulone (MC) from Myrtus communis L. (myrtle) affected mPGES-1.

Experimental approach:

The effect of MC on PGE₂ formation was investigated in a cell-free assay by using microsomal preparations of interleukin-1β-stimulated A549 cells as the source of mPGES-1, in intact A549 cells, and in lipopolysaccharide-stimulated human whole blood. Inhibition of COX-1 and COX-2 activity in cellular and cell-free assays was assessed by measuring 12(S)-hydroxy-5-cis-8,10-trans-heptadecatrienoic acid and 6-oxo PGF_1α formation.

Key results:

MC concentration-dependently inhibited cell-free mPGES-1-mediated conversion of PGH₂ to PGE₂ (IC₅₀ = 1 µmol·L⁻¹). PGE₂ formation was also diminished in intact A549 cells as well as in human whole blood at low micromolar concentrations. Neither COX-2 activity in A549 cells nor isolated human recombinant COX-2 was significantly affected by MC up to 30 µmol·L⁻¹, and only moderate inhibition of cellular or cell-free COX-1 was evident (IC₅₀ > 15 µmol·L⁻¹).

Conclusions and implications:

MC is the first natural product to inhibit mPGES-1 that efficiently suppresses PGE₂ formation without significant inhibition of the COX enzymes. This provides an interesting pharmacological profile suitable for interventions in inflammatory disorders, without the typical side effects of coxibs and non-steroidal anti-inflammatory drugs.     

A Summer of Cyanobacterial Blooms in Belgian Waterbodies: Microcystin Quantification and Molecular Characterizations

In the context of increasing occurrences of toxic cyanobacterial blooms worldwide, their monitoring in Belgium is currently performed by regional environmental agencies (in two of three regions) using different protocols and is restricted to some selected recreational ponds and lakes. Therefore, a global assessment based on the comparison of existing datasets is not possible. For this study, 79 water samples from a monitoring of five lakes in Wallonia and occasional blooms in Flanders and Brussels, including a canal, were analyzed. A Liquid Chromatography with tandem mass spectrometry (LC-MS/MS) method allowed to detect and quantify eight microcystin congeners. The mcyE gene was detected using PCR, while dominant cyanobacterial species were identified using 16S RNA amplification and direct sequencing. The cyanobacterial diversity for two water samples was characterized with amplicon sequencing. Microcystins were detected above limit of quantification (LOQ) in 68 water samples, and the World Health Organization (WHO) recommended guideline value for microcystins in recreational water (24 µg L⁻¹) was surpassed in 18 samples. The microcystin concentrations ranged from 0.11 µg L⁻¹ to 2798.81 µg L⁻¹ total microcystin. For 45 samples, the dominance of the genera Microcystis sp., Dolichospermum sp., Aphanizomenon sp., Cyanobium/Synechococcus sp., Planktothrix sp., Romeria sp., Cyanodictyon sp., and Phormidium sp. was shown. Moreover, the mcyE gene was detected in 75.71% of all the water samples.     

Sedimentation Patterns of Toxin-Producing Microcystis Morphospecies in Freshwater Reservoirs

Understanding the annual cycle of Microcystis is essential for managing the blooms of this toxic cyanobacterium. The current work investigated the sedimentation of microcystin-producing Microcystis spp. in three reservoirs from Central Spain during the summer and autumn of 2006 and 2007. We confirmed remarkable settling fluxes during and after blooms ranging 10⁶–10⁹ cells m⁻² d⁻¹, which might represent 0.1%–7.6% of the organic matter settled. A comprehensive analysis of the Valmayor reservoir showed average Microcystis settling rates (0.04 d⁻¹) and velocities (0.7 m d⁻¹) that resembled toxin settling in the same reservoir and were above most reported elsewhere. M. aeruginosa settling rate was significantly higher than that of M. novacekii and M. flos-aquae. Despite the fact that colony sizes did not differ significantly in their average settling rates, we observed extremely high and low rates in large colonies (>5000 cells) and a greater influence of a drop in temperature on small colonies (<1000 cells). We found a 4–14 fold decrease in microcystin cell quota in settling Microcystis of the Cogotas and Valmayor reservoirs compared with pelagic populations, and the hypothetical causes of this are discussed. Our study provides novel data on Microcystis settling patterns in Mediterranean Europe and highlights the need for including morphological, chemotypical and physiological criteria to address the sedimentation of complex Microcystis populations.     

In vitro and in vivo pharmacological role of TLQP-21, a VGF-derived peptide,in the regulation of rat gastric motor functions

Background and purpose:

Vgf gene expression has been detected in various endocrine and neuronal cells in the gastrointestinal tract. In this study we investigated the pharmacological activity of different VGF-derived peptides. Among these, TLQP-21, corresponding to the 556–576 fragment of the protein was the unique active peptide, and its pharmacological profile was further studied.

Experimental approach:

The effects of TLQP-21 were examined in vitro by smooth muscle contraction in isolated preparations from the rat gastrointestinal tract and, in vivo, by assessing gastric emptying in rats. Rat stomach tissues were also processed for immunohistochemical and biochemical characterization.

Key results:

In rat longitudinal forestomach strips, TLQP-21 (100 nmol·L⁻¹–10 µmol·L⁻¹) concentration-dependently induced muscle contraction (in female rats, EC₅₀ = 0.47 µmol·L⁻¹, E_max: 85.7 ± 7.9 and in male rats, 0.87 µmol·L⁻¹, E_max: 33.4 ± 5.3; n = 8), by release of prostaglandin (PG)E₂ and PGF_2a from the mucosal layer. This effect was significantly antagonized by indomethacin and selective inhibitors of either cyclooxygenase-1 (S560) or cyclooxygenase-2 (NS398). Immunostaining and biochemical studies confirmed the presence of VGF in the gastric neuronal cells. TLQP-21, injected i.c.v. (2–32 nmol per rat), significantly decreased gastric emptying by about 40%. This effect was significantly (P < 0.05) blocked by i.c.v. injection of indomethacin, suggesting that, also in vivo, this peptide acts in the brain stimulating PG release.

Conclusions and implications:

The present results demonstrate that this VGF-derived peptide plays a central and local role in the regulation of rat gastric motor functions.     

Antinociceptive and Anti-Inflammatory Effects of Recombinant Crotamine in Mouse Models of Pain

Crotamine, a toxin found in the venom of the South American rattlesnake Crotalus durissus terrificus, has been reported to have antinociceptive effects. We purified recombinant crotamine expressed in Escherichia coli and investigated its antinociceptive and anti-inflammatory effects using the hot-plate test, acetic-acid-induced writhing method, and formalin test in mice. Recombinant crotamine was administered intraperitoneally (0.04–1.2 mg kg⁻¹) or intraplantarly (0.9–7.5 μg 10 μL⁻¹) before the tests. The paw volume was measured with a plethysmometer. To evaluate the antagonistic and anti-inflammatory effects of naloxone, subcutaneous naloxone (4 mg kg⁻¹) or intraplantar naloxone (5 μg 10 μL⁻¹) was administered before recombinant crotamine. For tumor necrosis factor (TNF)-α assays, blood was drawn 3 h after formalin injection and measured using enzyme-linked immunosorbent assay. Intraperitoneal and intraplantar recombinant crotamine had antinociceptive and anti-inflammatory effects, neither of which were affected by pre-treatment with naloxone. The mean serum TNF-α levels were significantly lower in the intraperitoneal recombinant crotamine (0.4 and 1.2 mg kg⁻¹) or intraplantar (2.5 and 7.5 μg 10 μL⁻¹) recombinant crotamine groups than in the saline group and were not affected by naloxone pre-treatment. In conclusion, recombinant crotamine possesses significant antinociceptive and anti-inflammatory effects that do not appear to be related to the opioid receptor. The antinociceptive and anti-inflammatory effects of intraperitoneal or intraplantar recombinant crotamine are related to TNF-α.     

Fates of Microcystis aeruginosa Cells and Associated Microcystins in Sediment and the Effect of Coagulation Process on Them

During toxic Microcystis aeruginosa blooms, large amounts of cells can enter sediment through natural settlement, and coagulation treatment used to control water blooms can enhance the accumulation of cells. However, the current understanding of the fates of these cells and associated microcystins (MCs), as well as the effect of coagulation treatment on these factors, is limited. The results of the present study show that Microcystis aeruginosa cells in sediment were steadily decomposed under experimental conditions, and that they completely disappeared within 28 days. The major MCs released from settled cells were immediately degraded in sediment, and microbial degradation may be the main mechanism involved in this process. Coagulation treatment with PAC (polyaluminium chloride) + sepiolite can efficiently remove Microcystis aeruginosa cells from the water column and prevent their re-invasion. Furthermore, coagulation treatment with PAC + sepiolite had no significant effect on the release and decomposition of MCs and, thus, will not enhance the MCs pollution. However, coagulation treatment can accelerate the nutrient cycle by enhancing the settlement of cells. More attention should be paid to the effect on nutrient cycle when coagulation treatment is used for restoration of aquatic ecosystems.     

Montelukast inhibits neutrophil pro-inflammatory activity by a cyclic AMP-dependent mechanism

Background and purpose

The objective of this study was to characterize the effects of the cysteinyl leukotriene receptor antagonist, montelukast (0.1–2 µmol·L⁻¹), on Ca²⁺-dependent pro-inflammatory activities, cytosolic Ca²⁺ fluxes and intracellular cAMP in isolated human neutrophils activated with the chemoattractants, N-formyl-L-methionyl-L-leucyl-L-phenylalanine (1 µmol·L⁻¹) and platelet-activating factor (200 nmol·L⁻¹).

Experimental approach

Generation of reactive oxygen species was measured by lucigenin- and luminol-enhanced chemiluminescence, elastase release by a colourimetric assay, leukotriene B₄ and cAMP by competitive binding ELISA procedures, and Ca²⁺ fluxes by fura-2/AM-based spectrofluorimetric and radiometric (⁴⁵Ca²⁺) procedures.

Key results

Pre-incubation of neutrophils with montelukast resulted in dose-related inhibition of the generation of reactive oxygen species and leukotriene B₄ by chemoattractant-activated neutrophils, as well as release of elastase, all of which were maximal at 2 µmol·L⁻¹ (mean percentages of the control values of 30 ± 1, 12 ± 3 and 21 ± 3 respectively; P < 0.05). From a mechanistic perspective, treatment of chemoattractant-activated neutrophils with montelukast resulted in significant reductions in both post-peak cytosolic Ca²⁺ concentrations and store-operated Ca²⁺ influx. These montelukast-mediated alterations in Ca²⁺ handling by the cells were associated with a significant elevation in basal cAMP levels, which resulted from inhibition of cyclic nucleotide phosphodiesterases.

Conclusions and implications

Montelukast, primarily a cysteinyl leukotriene (CysLT₁) receptor antagonist, exhibited previously undocumented, secondary, neutrophil-directed anti-inflammatory properties, which appeared to be cAMP-dependent.     

Response of normoxic pulmonary arteries of the rat in the resting and contracted state to NO synthase blockade

1. The pulmonary vasculature is normally in a low resting state of tone. It has been hypothesized that this basal tone is actively maintained by the continuous release of a vasodilator in the resting state. However, evidence for basal release of nitric oxide (NO) is inconclusive.
2. We studied the release of NO in arteries from the pulmonary circulation of male Wistar-Kyoto rats by examining the effects of the L-arginine analogue N^G-nitro-L-arginine methyl ester (L-NAME) on resting pulmonary arteries and on vessels pre-contracted with prostaglandin F_2α (PGF_2α).
3. Rats (n=21) were killed by an overdose with pentobarbitone. Pulmonary arteries were dissected (mean internal diameter 459±11 μm) and mounted in a small vessel wire myograph. Resting tensions were set to simulate transmural pressures of 17.5 mmHg.
4. L-NAME (100 μM) was found to produce a contraction of 0.64±0.09 mN mm⁻¹ in resting pulmonary arteries when added alone to the myograph bath. This contraction was not produced following removal of the endothelium. Vessel contraction to PGF_2α (100 μM) was found to be significantly greater when carried out in the presence of L-NAME (100 μM)–1.37±0.15 mN mm⁻¹ compared with 1.96±0.17 mN mm⁻¹. Dilatation following acetylcholine (ACh) (1 μM) was abolished in the presence of L-NAME (100 μM).
5. Rat pulmonary artery contraction in response to the addition of L-NAME and the absence of contraction upon removal of the endothelium provides supportive evidence of the active release of nitric oxide for the maintenance of resting tone.

     

Inhibition of colonic motility and defecation by RS-127445 suggests an involvement of the 5-HT2B receptor in rodent large bowel physiology

Background:

5-HT_2B receptors are localized within the myenteric nervous system, but their functions on motor/sensory neurons are unclear. To explore the role of these receptors, we further characterized the 5-HT_2B receptor antagonist RS-127445 and studied its effects on peristalsis and defecation.

Experimental approach:

Although reported as a selective 5-HT_2B receptor antagonist, any interactions of RS-127445 with 5-HT₄ receptors are unknown; this was examined using the recombinant receptor and Biomolecular Interaction Detection technology. Mouse isolated colon was mounted in tissue baths for isometric recording of neuronal contractions evoked by electrical field stimulation (EFS), or under an intraluminal pressure gradient to induce peristalsis; the effects of RS-127445 on EFS-induced and on peristaltic contractions were measured. Faecal output of rats in grid-bottom cages was measured over 3 h following i.p. RS-127445 and separately, validation of the effective doses was achieved by determining the free, unbound fraction of RS-127445 in blood and brain.

Key results:

RS-127445 (up to 1 µmol·L⁻¹) did not interact with the 5-HT₄ receptor. RS-127445 (0.001–1 µmol·L⁻¹) did not affect EFS-induced contractions of the colon, although at 10 µmol·L⁻¹ the contractions were reduced (to 36 ± 8% of control, n= 4). RS-127445 (0.1–10 µmol·L⁻¹) concentration-dependently reduced peristaltic frequency (n= 4). RS-127445 (1–30 mg·kg⁻¹), dose-dependently reduced faecal output, reaching significance at 10 and 30 mg·kg⁻¹ (n= 6–11). In blood and brain, >98% of RS-127445 was protein-bound.

Conclusions and implications:

High-protein binding of RS-127445 indicates that relatively high doses are required for efficacy. The results suggest that 5-HT_2B receptors tonically regulate colonic motility.     

Effects of microcystins on broccoli and mustard, and analysis of accumulated toxin by liquid chromatography-mass spectrometry

Microcystins (MCs) are cyclic heptapeptides and protein phosphatase inhibitors produced by many species of cyanobacteria. MCs have been shown to cause adverse effects on animals as well as plants and therefore methods are needed for analysing MCs in different matrices. We assessed the effects of MC exposure on broccoli (Brassica oleracea var. italica) and mustard (Sinapis alba) by watering the seedlings with water containing 0, 1 or 10 μg MCs L⁻¹ (concentrations typically found in natural waters). Morphological characteristics, chlorophyll concentrations and chlorophyll fluorescence were investigated, but the only distinct difference compared to control plants was a slight (<10%) growth inhibition seen in broccoli. Afterwards the MC concentration of selected plant samples was quantitated using liquid chromatography-mass spectrometry. Among the four MC variants present in the exposure mixture, only MC-LR was clearly detectable, and the toxin was found only in the roots of broccoli and mustard. The detected MC-LR concentrations ranged from 0.9 to 2.6 ng (g fresh weight)⁻¹.     

Phormidium autumnale Growth and Anatoxin-a Production under Iron and Copper Stress

Studies on planktonic cyanobacteria have shown variability in cyanotoxin production, in response to changes in growth phase and environmental factors. Few studies have investigated cyanotoxin regulation in benthic mat-forming species, despite increasing reports on poisoning events caused by ingestion of these organisms. In this study, a method was developed to investigate changes in cyanotoxin quota in liquid cultures of benthic mat-forming cyanobacteria. Iron and copper are important in cellular processes and are well known to affect growth and selected metabolite production in cyanobacteria and algae. The effect of iron (40–4000 μg L⁻¹) and copper (2.5–250 μg L⁻¹) on growth and anatoxin-a quota in Phormidium autumnale was investigated in batch culture. These concentrations were chosen to span those found in freshwater, as well as those previously reported to be toxic to cyanobacteria. Anatoxin-a concentrations varied throughout the growth curve, with a maximum quota of between 0.49 and 0.55 pg cell⁻¹ measured within the first two weeks of growth. Growth rates were significantly affected by copper and iron concentrations (P < 0.0001); however, no statistically significant difference between anatoxin-a quota maxima was observed. When the iron concentrations were 800 and 4000 μg L⁻¹, the P. autumnale cultures did not firmly attach to the substratum. At 250 μg L⁻¹ copper or either 40 or 4000 μg L⁻¹ iron, growth was suppressed.     

Nanophyto-gel against multi-drug resistant Pseudomonas aeruginosa burn wound infection

Burn wound is usually associated by antibiotic-resistant Pseudomonas aeruginosa infection that worsens and complicates its management. An effective approach is to use natural antibiotics such as cinnamon oil as a powerful alternative. This study aims to investigate topical nanostructured lipid carrier (NLC) gel loaded cinnamon oil for Pseudomonas aeruginosa wound infection. A 2⁴ full factorial design was performed to optimize the formulation with particle size 108.48 ± 6.35 nm, zeta potential −37.36 ± 4.01 mV, and EE% 95.39 ± 0.82%. FTIR analysis revealed no excipient interaction. Poloxamer 407 in a concentration 20% w/w NLC gel was prepared for topical application. Drug release exhibited an initial burst release in the first five hours, followed by a slow, sustained release of up to five days. NLC-cinnamon gel has a significant ability to control the drug release with the lowest minimum inhibitory concentration again P. aeruginosa compared to other formulations (p < .05). In vivo study also showed NLC-cinnamon gel effectively healed the infected burned wound after a six-day treatment course with better antibacterial efficacy in burned animal models. Histological examination ensured the tolerability of NLC-cinnamon gel. The results suggest that nanoparticle-based cinnamon oil gel is a promising natural product against antibiotic-resistant strains of P. aeruginosa in wound infection.     

Evidence for a dilator function of 8-iso prostaglandin F2α in rat pulmonary artery

1. 8-Iso prostaglandin F_2α (8-iso PGF_2α) is one of a series of prostanoids formed independently of the cyclo-oxygenase pathway. It has been shown to be upregulated in many conditions of oxidant stress where its formation is induced by free radical-catalysed actions on arachidonic acid. As 8-iso PGF_2α is formed in vivo in diseases in which oxidant stress is high such as septic shock, we have assessed the relative potency and efficacy of this compound in pulmonary arteries from control and lipopolysaccharide (LPS)-treated rats.
2. Several studies have characterized the contractile actions of 8-iso PGF_2α on various smooth muscle preparations, but its potential dilator actions have not been addressed. Thus these studies examined both the contractile and dilator actions of 8-iso PGF_2α in rat pulmonary artery rings. The thromboxane mimetic U46619, PGE₂ sodium nitroprusside (SNP) and acetyl choline (ACh) were used for comparison. Each prostanoid had to be dissolved in ethanol to a maximum concentration of 1×10⁻² M. At high concentrations, ethanol directly contracted pulmonary vessels. We were therefore limited by the actions of the vehicle such that we were unable to add prostanoids at concentrations higher than 1×10⁻⁴ M. In some cases this meant that maximum responses were not achieved and in these cases the E_max and pD₂ values are apparent estimates.
3. The following rank order of potency was obtained from contractile studies; U46619>8-iso PGF_2α>PGE₂, each prostanoid producing concentration-dependent contractions (10⁻¹⁰3×10⁻⁴ M, 10⁻⁹10⁻⁴ M, 10⁻⁸10⁻⁴ M, respectively). As has been shown previously for other smooth muscle preparations, the thromboxane receptor (TP) antagonist ICI 192605, (1×10⁻⁶, 1×10⁻⁵ and 1×10⁻⁴ M), inhibited the contractions of 8-iso PGF_2α in a concentration-dependent fashion.
4. The nitric oxide synthase inhibitor, N^G-nitro-L-arginine methyl ester (L-NAME; 1×10⁻⁴ M), enhanced the contractile function of both 8-iso PGF_2α and PGE₂, but had no effect on that caused by U46619. Similarly, L-NAME inhibited the dilator function of all agents tested except the exogenous nitric oxide (NO) donor SNP, indicating that PGE₂ and 8-iso PGF_2α like ACh, act through the release of NO. The specificity of the effects of L-NAME were confirmed in studies with the inactive enantiomer D-NAME (1×10⁻⁴ M), which did not affect the contractile or the dilator actions of 8-iso PGF_2α. Furthermore, ICI 192605 enhanced the dilator actions of 8-iso PGF_2α, suggesting that the dilator component of 8-iso PGF_2α was achieved via activation of a non-TP receptor.
5. Isoprostanes may modulate vascular tone by a direct action on TP receptors to cause contraction and via a distinct receptor leading to the release of NO to cause dilatation.