Bioassay Technique Research Articles

Research of Spatial-Temporal Transformation of the Qualitative Composition of the River Salgir Waters

The main objective of the research is a complex assessment of the actual ecological status of Salgir River waters based on several methods: visual survey of the watercourse as well as studying spatial and temporal transformation of water quality and determining the degree of water pollution by means of an integral criterion –water pollution index (IES) and bioassay techniques carried on seeds of two test crops (cress salad and wheat), and also zoning a watercourse according to several criteria. The assessment found a tendency to increasing degradation of water quality due to the increase of the anthropogenic load (increase in water abstracted from the river). The typical pollutants in the Salgir river are petroleum products, phosphates, lead, copper, biological oxygen uptake (BOU5). Phosphate content is in the range of 5.5–27.5, lead – 3.06–6.67, copper –1.02–4.52 MPC. The most powerful source of pollution of the river is the treatment facilities of Simferopol. The results of this comprehensive study made it possible not only to reflect the real situation at the water facility, but also to highlight sections of the river where a set of measures aimed at reducing/preventing the consequences of anthropogenic impact should be carried out as a priority.

A proposed stepwise screening framework for the selection of polycyclic aromatic hydrocarbon (PAH)-degrading white rot fungi.

This study suggests a simple three-step screening protocol for the selection of white rot fungi (WRF) capable of degrading polycyclic aromatic hydrocarbons (PAHs), which combines easily applicable bioassay techniques, and verifies that protocol by evaluating the PAH degradation activity, ligninolytic enzyme secretion, and relevant gene expressions of the selected PAH-degraders. Using 120 fungal strains, a sequence of bioassay techniques was applied: Bavendamm's reaction (Step 1), remazol brilliant blueR (RBBR) decolorization (Step 2); assays for tolerance to four mixed PAHs-phenanthrene, anthracene, fluoranthene, and pyrene (Step 3). This stepwise protocol selected 14 PAH-degrading WRF, including Microporus vernicipes, Peniophora incarnata, Perenniporia subacida, Phanerochaete sordida, Phlebia acerina, and Phlebia radiata. Of these, P. incarnata exhibited the highest PAH degradative activity, ranging from 40 to > 90%, which was related to the time-variable secretions of three extracellular ligninolytic enzymes: laccase, manganese-dependent peroxidase (MnP) and lignin peroxidase (LiP). Laccase and MnP production by P. incarnata tended to be greater in the early stages of PAH degradation, whereas its LiP production became intensified with decreasing laccase and MnP production. Pilc1 and pimp1 genes encoding laccase and MnP were expressed, indicating the occurrence of extracellular enzyme-driven biodegradation of PAH by the fungal strains.

Experimental Toxoplasmosis in Pigeons (Columba livia)

The purpose of the present study was to establish experimental model of toxoplasmosis in pigeons, to investigate pathogenesis and compare tissue lesions by clinical, histopathological, serological and bioassay techniques. Total of 60 unknown aged pigeons (Columba livia), 21 males and 39 females were used. They were divided into groups as oral (Group I and II) and parenteral (Group III, IV, V and VI) infection groups (Table 1). While some pigeons in Group IV showed acute infection signs such as anorexia, weight loss, pale cockscomb, bend of head and neck and partial paralyze; chronic infection signs such as anorexia, weakness, weight loss, diarrhea, difficulties in breathing, and conjunctivitis were seen in Group IV, V, and VI. In necropsy, the pigeons in Group IV had hyperemia and focal hemorrhages in the meninges and brain; the pigeons in Groups V and VI had yellowish color of the liver, the pigeons in Group V had the pale chest muscles, pericardial thickening and opaqueness. There were no macroscopic findings in pigeons in Group I and III. Histopathological examination revealed nonsuppurative meningoencephalitis and tachyzoites and bradyzoite cysts formation of T. gondii in brain tissue, lymphoid cell infiltration and necrotic focal hepatitis and nephritis in Group IV. While pigeons in Group V had nonsuppurative focal myositis, myocarditis, hepatitis, gastritis, enteritis, pneumonitis, and necrotic pancreatitis, one of them had toxoplasma bradyzoite cyst in the sinusoid in the liver. In group VI, nonsuppurative focal hepatitis, myocarditis, nephritis and necrotic pancreatitis were detected in pigeons. Bioassay tests were performed with tissue samples taken from seropositive pigeons and parasitic tachyzoites were isolated from the peritoneal fluid of the mice. Seropositivity in the oral and parenteral groups was determined by Sabin-Feldman Dye Test (SFDT) and Indirect Hemagglutination Assay (IHA). As a result; in similar studies that will be performed investigating pathogenesis of Toxoplasmosis and subclinical cases that may be overlooked, serologic tests and bioassay applications should be used together for the diagnosis of toxoplasmosis.

Bioautography and GC-MS based identification of piperine and trichostachine as the active quorum quenching compounds in black pepper

In the search of new and safe antibacterial compounds, the quorum sensing system (QS) modulation by natural products has been studied. As a result, many plant-derived compounds have been identified as potent quorum sensing inhibitors. Piper nigrum L. (black pepper) ethanolic extract inhibits the QS in some Gram-negative bacteria but the active components have not been previously identified. Thus, the objective of this work was to identify the P. nigrum peppercorns main components that block the QS, applying bioassay and chromatographic techniques. Piperine and trichostachine were identified as the main components responsible for the quorum quenching (QQ) activity of P. nigrum peppercorns extract. Piperine at 30 mg/L, decreased the violacein production by Chromobacterium violaceum CV026 by 35%, without affecting bacterial growth. Piperine concentration of 40 mg/L decreases violacein production by C. violaceum CV026 by 70% and growth in only 4.34%. Trichostachine at 50 mg/L decreases violacein production by C. violaceum CV026 by 12%, without affecting bacterial growth. P. nigrum extract concentration of 0.5 g/L decreased violacein production in 40 % and no effects on growth were observed. Neither P. nigrum extract, piperine, nor trichostachine did affect QS of Pseudomonas aeruginosa PAO1. Data here described exhibit the potential of piperamides as modulators of QS, not previously reported.

Nondestructive quantification of single-cell nuclear and cytoplasmic mechanical properties based on large whole-cell deformation.

The mechanical properties of cell nuclei have been recognized to reflect and modulate important cell behaviors such as migration and cancer cell malignant tendency. However, these nuclear properties are difficult to characterize accurately using conventional measurement methods, which are often based on probing or deforming local sites over a nuclear region. The corresponding results are sensitive to the measurement position, and they are not decoupled from the cytoplasmic properties. Microfluidics is widely recognized as a promising technique for bioassay and phenotyping. In this report, we develop a simple and nondestructive approach for the single-cell quantification of nuclear elasticity based on microfluidics by considering different deformation levels of a live cell captured along a confining microchannel. We apply two inlet pressure levels to drive the flow of human nasopharyngeal epithelial cells (NP460) and human nasopharyngeal cancerous cells (NPC43) into the microchannels. A model considering the essential intracellular components (cytoplasm and nucleus) for describing the mechanics of a cell deforming along the confining microchannel is used to back-calculate the cytoplasmic and nuclear properties. On the other hand, we also apply a widely used chemical nucleus extraction technique to examine its possible effects (e.g., reduced nuclear modulus and reduced lamin A/C expression). To determine if the decoupled nuclear properties are representative of cancer-related attributes, we classify the NP460 and NPC43 cells using the decoupled physical properties as classification factors, resulting in an accuracy of 79.1% and a cell-type specificity exceeding 74%. It should be mentioned that the cells can be recollected at the device outlet after the nondestructive measurement. Hence, the reported cell elasticity measurement can be combined with downstream genetic and biochemical assays for general cell research and cancer diagnostic applications.

ИСПОЛЬЗОВАНИЕ КОМПЛЕКСНОГО АНАЛИЗА ДЛЯ ОЦЕНКИ СОВРЕМЕННОГО ЭКОЛОГИЧЕСКОГО СОСТОЯНИЯ РЕКИ БЕШТЕРЕК

Introduction. The problem of restoring and preserving the environmental state of watercourses with an increase in anthropogenic load has recently become more urgent, but the use of only one method or approach does not allow us to judge the current state of a river, so there is a need to combine various methods aimed at obtaining integrated information. The purpose of this study was to analyze the environmental state of the water bodies in the Beshterek River Basin (Republic of Crimea). Methods. The studies were carried out during 2018–2019 and included: visual observations of the watercourse state, water-protection zone, channel ponds; water flow measurement; sampling for the study of water chemistry; calculation of the water pollution index (WPI) and the integrated indicator of ecological condition (IIEC); study of water toxicity by means of bio-assay techniques using wheat and cress seeds; development of environmental measures. Results. The studies have found that the main pollutants in river water are sulfates, phosphates as well as heavy metals: Cd, Pb, Cu, Zn. The concentration of sulfates increased from 0.15–0.22 MAC (upper river) to 1.5–2.4 MAC (mouth of the river), which indicates the ingress of domestic wastewater into the watercourse. The content of phosphates in the middle reaches exceeded the standards by 1.9–11.1 times. The heavy metal content exceeding the MAC was recorded at all river stations: zinc (station No. 1 — 2.1 MAC), cadmium (station No. 3 — 1.24 MAC), lead (station No. 4 — 1.23 MAC) and copper (station No. 4 — 1.5–10 MAC). The water quality in terms of the WPI was II and III (“clean” and “moderately polluted”) in the river and II, III and IV (“polluted”) in the channel ponds. The bio-assay testing showed no toxic effect on the test cultures. Conclusion. Among the priorities, the following can be distinguished: the need to establish a permanent monitoring network for the observation of the qualitative and quantitative characteristics of the river flow, and develop a program for sewage handling in villages located in the river valley.

Toxicity of azoles towards the anaerobic ammonium oxidation (anammox) process

AbstractBACKGROUNDAzoles are an important class of compounds that are widely used as corrosion inhibitors in aircraft de‐icing agents, cooling towers, semiconductor manufacturing and household dishwashing detergents. They also are important moieties in pharmaceutical drugs and fungicides. Azoles are widespread emerging contaminants occurring frequently in water bodies. Azole compounds can potentially cause inhibition towards key biological processes in natural ecosystems and wastewater treatment processes. Of particular concern is the inhibition of azoles to the nitrification process (aerobic oxidation of ammonium). This study investigated the acute toxicity of azole compounds towards the anaerobic ammonia oxidation (anammox) process, which is an important environmental biotechnology gaining traction for nutrient‐nitrogen removal during wastewater treatment. In this study, using batch bioassay techniques, the anammox toxicity of eight commonly occurring azole compounds was evaluated.RESULTSThe results show that 1H‐benzotriazole and 5‐methyl‐1H‐benzotriazole had the highest inhibitory effect on the anammox process, causing 50% decrease in anammox activity (IC50) at concentrations of 19.6 and 17.8 mg L−1, respectively. 1H‐imidazole caused less severe toxicity with an IC50 of 79.4 mg L−1. The other azole compounds were either nontoxic (1H‐pyrazole, 1H‐1,2,4‐triazole and 1‐methyl‐pyrazole) or at best mildly toxic (1H‐benzotriazole‐5‐carboxylic acid and 3,5‐dimethyl‐1H‐pyrazole) towards the anammox bacteria at the concentrations tested.CONCLUSIONSThis study showed that most azole compounds tested displayed mild to low or no toxicity towards the anammox bacteria. The anammox bacteria were found to be far less sensitive to azoles compared to nitrifying bacteria. © 2019 Society of Chemical Industry

ASSESSING COSMECEUTICALS PROPERTIES OF SOME MACROFUNGI FOR IMPROVED SKINCARE

Objective: This study has investigated cosmeceutical properties namely, antibacterial, sun protection factor and total phenolics contents of some selected macrofungi. The studies were conducted on five reference cultures collected from Indian type culture collection center (IMTEC, Chandigarh, India) and five isolates collected from TERI-Deakin Nano Biotechnology Centre facility at TERI Gram, Gurugram, India.
 Methods: The cosmeceutical properties of the crude extracts from selected macrofungi were analyzed using standard bioassay techniques. Antibacterial activity was analyzed against Staphylococcus epidermidis, Escherichia coli, Micrococcus luteus, Bacillus megaterium, Pseudomonas aeruginosa, Staphylococcus aureus, and Acinetobacter baumannii using Agar well diffusion method. The sun protection factor was estimated and calculated using the Mansur equation. Free radical scavenging activity using DPPH was performed to assess the antioxidant activity of the extracts.
 Results: Ethyl acetate extracts of the broth from P. florida and TERI-G1 cultures showed a broad-spectrum antibacterial activity against S. epidermidis, E. coli, M. luteus and B. megaterium. Ethyl acetate extracts of the broth from TERI-G3 showed the highest SPF activity of 34.02 at 200 µg. ml-1 concentration. Ethyl acetate extract of the broth from F. velutipes, P. florida, P. ostreatus, and TERI-G1 showed comparable antioxidant activity of 66.86%, 79.51%, 82.02%, and 69.58% respectively when compared to ascorbic acid (85.83%) and quercetin (83.09%) taken as positive control in the study and their total phenolic contents were found to be 6.93, 43.68, 20.88 and 13.77 Gallic acid equivalent (GAE) per gram. The minimal inhibitory concentration of F. velutipes, P. florida, P. ostreatus, and TERI-G1 was found to be 3552.89 µg. ml-1, 1250 µg. ml-1, 2418.9 µg. ml-1 and 3219 µg. ml-1 respectively.
 Conclusion: The work is in progress to identify and characterize TERI-G1and TERI G3 cultures. Further studies on the anti-inflammatory, anti-tyrosinase, elastase inhibition properties of the cultures will be assessed to identify potential cosmeceutical active ingredients with promising applications in cosmeceutical products.

Nematode-Associated Bacteria: Production of Antimicrobial Agent as a Presumptive Nominee for Curing Endodontic Infections Caused by Enterococcus faecalis.

Xenorhabdus and/or Photorhabdus bacteria produce antibacterial metabolites to protect insect cadavers against food competitors allowing them to survive in nature with their nematode host. The effects of culture supernatant produced by Xenorhabdus and Photorhabdus spp. were investigated against the multidrug-resistant dental root canal pathogen Enterococcus faecalis. The efficacy of seven different cell-free supernatants of Xenorhabdus and Photorhabdus species against E. faecalis was assessed with overlay bioassay and serial dilution techniques. Additionally, time-dependent inactivation of supernatant was evaluated. Among the seven different bacterial species, X. cabanillasii produced the strongest antibacterial effects. Loss of bioactivity in a phosphopantetheinyl transferase-deficient mutant of X. cabanillasii indicated that this activity is likely based on non-ribosomal peptide synthetases (NRPSs) or polyketide synthases (PKSs). Subsequent in silico analysis revealed multiple possible biosynthetic gene clusters (BGCs) in the genome of X. cabanillasii including a BGC homologous to that of zeamine/fabclavine biosynthesis. Fabclavines are NRPS-derived hexapeptides, which are connected by PKS-derived malonate units to an unusual polyamine, also PKS-derived. Due to the known broad-spectrum bioactivity of the fabclavines, we generated a promoter exchange mutant in front of the fabclavine-like BGC. This leads to over-expression by induction or a knock-out by non-induction which resulted in a bioactive and non-bioactive mutant. Furthermore, MS and MS2 experiments confirmed that X. cabanillasii produces the same derivatives as X. budapestensis. The medicament potential of 10-fold concentrated supernatant of induced fcl promoter exchanged X. cabanillasii was also assessed in dental root canals. Calcium hydroxide paste, or chlorhexidine gel, or fabclavine-rich supernatant was applied to root canals. Fabclavine-rich supernatant exhibited the highest inactivation efficacy of ≥3 log10 steps CFU reduction, followed by calcium hydroxide paste (≤2 log10 step). The mean percentage of E. faecalis-free dental root canals after treatment was 63.6, 45.5, and 18.2% for fabclavine, calcium hydroxide, and chlorhexidine, respectively. Fabclavine in liquid form or preferably as a paste or gel formulation is a promising alternative intracanal medicament.

Trans-resveratrol, piceatannol and gallic acid: Potent polyphenols isolated from Mezoneuron benthamianum effective as anticaries, antioxidant and cytotoxic agents

Phytochemical investigation of the ethyl acetate extract of the root of Mezoneuron benthamianum, a shrub commonly used as chewing stick in the southwest of Nigeria, led to the isolation of three compounds characterised as trans-resveratrol, piceatannol and gallic acid by the use of spectroscopic techniques. The anticaries activity of the polyphenols was evaluated against four oral bacteria pathogens (Streptococcus mutans, Pseudomonas aeruginosa, Staphylococcus aureus and Escherichia coli), isolated from clinical samples presented by patients having dental caries, while their antioxidant and cytotoxic activities were determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and brine shrimp (artemia salina nauplii) bioassay techniques. The results showed that the isolated compounds exhibited very strong anticaries activity with minimum inhibitory concentration (MIC) ranging from 25 to 300 µg/ml, antioxidant activity with IC50 of 35.81, 30.35 and 11.73 µg/ml, when compared with ascorbic acid (IC50 = 38.20 µg/ml) and cytotoxic activity with LC50 of 7.15, 99.99 and 98.71 µg/ml for resveratrol, piceatannol and gallic acid respectively The isolated compounds demonstrated very strong anticaries, antioxidant and cytotoxic activities. This study further justifies the ethno-medicinal use of M. benthamianum as an effective tool in maintaining oral hygiene.

Allelopathic potential of 73 weed species in Pakistan

This study represents the comprehensive screening of allelopathic activity of weeds in Pakistan by applying sandwich and dish pack methods. The source for existing research of weed control towards classifying the potent organic compounds for controlling weeds in crops is the screening of large quantities of plants. Strong allelopathic weeds species have been acknowledged from analysis to provide direction for further research. Under laboratory conditions 73 weeds species were examined for their allelopathic potentials through latest bioassay activity evaluation techniques. The research information generated from the present work can be used as a benchmark for future research on the allelochemical identification and characterization. During the follow up work of present endeavor; methanolic leaf extracts of strongest allelopathic species shall be tested for antioxidant activities on crops pathogens and will also be recommended as allelopathic cover crop for biological control of weeds to support agro-environment conservation. In Pakistan, the allelopathic activity evaluation of plants through bioassay techniques is quite rare. There is a dire need to develop a complete data base of plants having strong allelopathic potential through application of these latest techniques.

Proximity to highways has limited influence on space use and physiology of terrestrial testudines

Transportation infrastructure is one of the mainstays of human modification of terrestrial landscapes. Turtle populations are highly affected by roads through direct mortality, contributing to population declines. However, sub-lethal effects, such as increased physiological stress, may indirectly affect turtle demographic rates, particularly in populations recently exposed to roads. We took advantage of a unique study system in southeast Ohio, where an intact forest was bisected by a four-lane highway in 2013, exposing eastern box turtles (Terrapene carolina carolina) to a new threat. The goal of this study was to evaluate ecological, physiological, and behavioral effects of exposure to a new road by comparing a roadside turtle population to a control population in a nearby roadless area, and guide mitigation on new and existing roadways. We used a unique combination of radio telemetry to assess space use, behavior, and habitat selection of turtle, and bioassay techniques to analyze chronic stress using corticosterone stored in nail keratin. We found no differences in home range sizes and habitat selection between the two sites, but roadside turtles showed strong highway avoidance, despite spending a significant amount of time in its immediate vicinity. All turtles selected for higher woody debris and understory vegetation cover, and males at both sites selected for higher canopy cover. Corticosterone concentrations from nails collected upon initial capture (2017) did not differ between the two sites, but males showed a wider range of variation. Corticosterone concentrations were significantly higher in 2018, with roadside animals showing the highest levels, but they were not correlated with home range size or proximity to highway. As such, further work is needed to evaluate indirect effects of multiple stressors on turtle endocrinology and their demographic implications, as well as the level of demographic compensation resulting from road avoidance.

Susceptibility of Caligus rogercresseyi collected from the native fish species Eleginops maclovinus (Cuvier) to antiparasitics applied by immersion.

A major challenge for Chilean salmon farming is infestation by the ectoparasite Caligus rogercresseyi. In addition, there is evidence that a loss of chemotherapeutic treatment efficacy against important fish pathogens is occurring in salmon farming, including antiparasitic efficacy. Currently, there are known techniques that allow the determination of the susceptibility profile of parasites to antiparasitic treatment. However, there is scarce information about both threshold values and categorization of antiparasitic susceptibility for C. rogercresseyi. Bioassay technique allowed the determination of both mean values and the natural variation of EC50%, which were contrasted with available susceptibility thresholds. Results allowed to determine that parasites from the native fish host, Eleginops maclovinus, are susceptible to azamethiphos, deltamethrin and cypermethrin treatments, showing a high susceptibility profile to antiparasitics.

Combination of Repurposed Drug Diosmin with Amoxicillin-Clavulanic acid Causes Synergistic Inhibition of Mycobacterial Growth

Effective therapeutic regimens for the treatment of tuberculosis (TB) are limited. They are comprised of multiple drugs that inhibit the essential cellular pathways in Mycobacterium tuberculosis (Mtb). The present study investigates an approach which enables a combination of Amoxicillin-Clavulanic acid (AMC) and a repurposed drug for its synergistic effect towards TB treatment. We identified Diosmin (DIO), by targeting the active site residues of L,D-transpeptidase (Ldt) enzymes involved in Mtb cell wall biosynthesis by using a structure-based drug design method. DIO is rapidly converted into aglycone form Diosmetin (DMT) after oral administration. Binding of DIO or DMT towards Ldt enzymes was studied using molecular docking and bioassay techniques. Combination of DIO (or DMT) and AMC exhibited higher mycobactericidal activity against Mycobacterium marinum as compared to individual drugs. Scanning electron microscopy study of M. marinum treated with AMC-DIO and AMC-DMT showed marked cellular leakage. M. marinum infected Drosophila melanogaster fly model showed an increased fly survival of ~60% upon treatment with a combination of AMC and DIO (or DMT). Finally, the enhanced in vitro antimicrobial activity of AMC-DIO was validated against Mtb H37Ra and a MDR clinical isolate. Our results demonstrate the potential for AMC and DIO (or DMT) as a synergistic combination for the treatment of TB.

Western corn rootworm pyrethroid resistance confirmed by aerial application simulations of commercial insecticides

The western corn rootworm (Diabrotica virgifera virgifera LeConte) (WCR) is a major insect pest of corn (Zea mays L.) in the United States (US) and is highly adaptable to multiple management tactics. A low level of WCR field-evolved resistance to pyrethroid insecticides has been confirmed in the US western Corn Belt by laboratory dose-response bioassays. Further investigation has identified detoxification enzymes as a potential part of the WCR resistance mechanism, which could affect the performance of insecticides that are structurally related to pyrethroids, such as organophosphates. Thus, the responses of pyrethroid-resistant and -susceptible WCR populations to the commonly used pyrethroid bifenthrin and organophosphate dimethoate were compared in active ingredient bioassays. Results revealed a relatively low level of WCR resistance to both active ingredients. Therefore, a simulated aerial application bioassay technique was developed to evaluate how the estimated resistance levels would affect performance of registered rates of formulated products. The simulated aerial application technique confirmed pyrethroid resistance to formulated rates of bifenthrin whereas formulated dimethoate provided optimal control. Results suggest that the relationship between levels of resistance observed in dose-response bioassays and actual efficacy of formulated product needs to be further explored to understand the practical implications of resistance.

Saflufenacil Dose-Response Curves Applied to Brazilian ‘Cerrado’ Soils

The objective of this study was to evaluate the phytotoxicity of saflufenacil in Brazilian Cerrado soils with contrasting properties. Experiments were performed in a factorial design. To quantify herbicide phytotoxicity, the bioassay technique was used and cucumber (Cucumis sativum) was selected as a test plant. A greater reduction of the dry mass was observed for bioindicator plants in comparison to others in the Typic Dystrophic Red Latosol. A rate of 11.76 g i.a. ha-1 was required to reach 50% reduction of the plant dry mass for this soil. Rates of 30.87; 44.10, and 119.56 g i.a. ha-1, respectively, are needed to achieve a 50% reduction of the plant dry mass in the Typic Acric Red Latosol, Typical Orthic Arenosols Quartzipsamment, and Washed Sand. The bioavailability of saflufenacil is affected by soil properties and therefore the soil type should be considered when deciding upon possible rates.

Shear Stress Analysis of Synthesis and Nitric Oxide Release from Huvecs Exposed to Supraphysiologic Glucose

The purpose of this study is to analyze the magnitude and duration of shear stress in normal endothelial cell (HUVECs) cultures and those exposed to supraphicological glucose which affected synthesis and release of NO detected by bioassay techniques. The results of this study concluded that large shear stress applied to endothelial cell culture for a long time (± 15 minutes) will increase the synthesis and release of NO. In normal endothelial cell culture a large shear stress exposure in a long time can increase NO synthesis and release very significantly compared to low shear stress (6 dyne/cm2 for 5 minutes). Likewise, endothelial cell culture which was exposed to 22 mM glucose for 7 days, giving a large amount of shear stress for a long time (15 minutes) could increase NO synthesis and release, although it was far compared to normal endothelial cell culture. It can be said that the synthesis and release of NO in endothelial dysfunction can be improved through exposure to large and long-standing shear stress.

Volumetric mass transfer coefficient for carbon monoxide in a dual impeller stirred tank reactor considering a perfluorocarbon–water mixture as liquid phase

Overall volumetric mass transfer coefficient (kLa) of carbon monoxide in a perfluorocarbon–distilled water mixture was evaluated in a dual impeller stirred tank bioreactor (Rushton-type and Smith-type). Two agitation speeds (300 and 500 rpm), three specific gas flow rates (2.0, 2.5 and 2.7 vvm), two working volumes (0.75 and 1 L) were tested, as well as four different liquid phase compositions: pure distilled water; distilled water and perfluorodecalin (PFC); distilled water and Tween® 80; and distilled water, PFC and Tween® 80. CO concentration in liquid phase was determined using a myoglobin bioassay technique and kLa and saturated CO concentration were determined using Maximum Likelihood Estimation (MLE) with a hybrid optimization strategy. A maximum kLa of 603.48 h−1 was obtained at 500 rpm, 2.7 vvm and distilled water, PFC and Tween® 80 as liquid phase. Tween® 80 was responsible for increasing mass transfer when mixing these three components comparing to a liquid phase composed of PFC and distilled water (7 time increase at 2.7 vvm and 500 rpm), and pure distilled water (2.9 time increase at 2.0 vvm and 1.6 times at 2.5 vvm). Moreover, MLE proved to be a valuable tool to critically analyse experimental uncertainty in parameter estimation.

Allelopathic Effects of Four Plant Species on Lettuce Seed Germination and Seedling Growth

Allelopathy is an inherent feature of a number of plant species. The aim of this study was to investigate the individual and relative allelopathic potential of four plant species: Parthenium (Parthenium hysterophorus L.), Tamarindus (Tamarindus indica), Litchi (Litchi chinensis) and Citharexylum (Citharexylum spinosum L ). The experiment was set up using the sandwich multi-well method, with Lettuce as the test species. The multi-well protocol is a standardized widespread and commonly used bioassay technique to study allelopathy. Leaf litter was used as plant material giving that the selected species contain or are supposed to contain allelochemicals on their leaves but also for comparison sake. This experiment will fill the gap of the current knowledge regarding the allelopathic potential of species investigated especially Litchi and Citharexylum, but will also provide a rating of the relative phytotoxicity of each of them. We might be able to determine which of the four plants exhibits the highest allelopathic potential. It is equally expected that each of these species displays some level of allelopathy.

The use of in vitro assays for the assessment of cytotoxicity on the example of MTT test

In recent years, biological tests have been developed based on cell cultures and successfully used to the hygienic assess of a variety of samples. In vitro assays become the complement of conventional chemical methods. They do not narrow the results only to the quantitative and qualitative information on toxic substances, but also increase knowledge on the direct impact on the organism. They are also an alternative for animal testing, which are currently given up for ethical reasons. At present, the market is steadily increasing in the number of tests and bio-assay techniques. Based on our own studies we conclude that the MTT test is perfect as a diagnostic method for evaluating the cytotoxicity of materials of different composition such as mycotoxins, pesticides, bacterial cultures, moulds isolates, food, feed, as well as a vast spectrum of other environmental samples.