Dehydrogenase Activity Test Research Articles

Re-evaluation and modification of dehydrogenase activity tests in assessing microbial activity for wastewater treatment plant operation

Reliable and cost-effective methods for monitoring microbial activity are critical for process control in wastewater treatment plants. The dehydrogenase activity (DHA) test has been recognized as an efficient measure of biological activity due to its simplicity and broad applicability. Nevertheless, the existing DHA test methods suffer from imperfections and are difficult to implement as routine monitoring techniques. In this work, an accurate and cost-effective modified DHA approach was developed and the procedure for the DHA test was critically evaluated with respect to the standard construction, sample pretreatment, incubation and extraction conditions. The feasibility of the modified DHA test was demonstrated by comparison with the oxygen uptake rate and adenosine triphosphate in a sequencing batch reactor. The sensitivities of the two typical tetrazolium salts to toxicant inhibition by heavy metals and antibiotics were compared, revealing that 2,3,5-triphenyltetrazolium chloride (TTC) exhibited a higher sensitivity. Furthermore, the sensitivity mechanism of the two DHA tests was elucidated through electrochemical experiments, theoretical analysis and molecular simulations. Both tetrazolium salts were found to be effective artificial electron acceptors due to their low redox potentials. Molecular docking simulations revealed that TTC could outperform other tetrazolium salts in accepting electrons and hydrogens from dehydrogenase. Overall, the modified DHA approach presents an accurate and cost-effective way to measure microbial activity, making it a practical tool for wastewater treatment plants.

CHARACTERIZATION AND BACTERIAL TOXICITY OF TITANIUM DIOXIDE NANOPARTICLES

India is a second highest populated developing country of the world. Environmental pollution is a big problem in India and the waste disposal laws are not as stringent as in the developed countries. Among the various nanoparticles, TiO NPs are receiving increasing attention for a large variety of 2 applications. Certainly, with the development of applications and production of the TiO NPs, there is a major concern on the toxic effects due to 2 their small size, large surface area and potential to produce ROS. TiO NPs are highly mobile and reach the environment by numerous routes and get 2 further degraded or modied into different forms by environmental factors. India carries a rich microbial diversity, producing industrial compounds like enzymes, antibiotic and biofertilizers. These massive number of nanoparticles continuously being released may lead to loss of our microbial diversity or effect their different physiological activities. In the present study, we showed how the structural differences in the cell walls of different bacteria play a very important role in the TiO NPs toxicity which was be assessed by traditional methods like growth inhibition assay as 2 well as rapid dehydrogenase activity tests

Enhancing inhibition of disinfection byproducts formation and opportunistic pathogens growth during drinking water distribution by Fe2O3/Coconut shell activated carbon.

The effects of biological activated carbon treatment using Fe2O3 modified coconut shell-based activated carbon (Fe/CAC) were investigated on the occurrence of opportunistic pathogens (OPs) and formation of disinfection by-products (DBPs) in simulated drinking water distribution systems (DWDSs) with unmodified CAC as a reference. In the effluent of annular reactor (AR) with Fe/CAC, the OPs growth and DBPs formation were inhibited greatly. Based on the differential pulse voltammetry and dehydrogenase activity tests, it was verified that extracellular electron transfer was enhanced in the attached biofilms of Fe/CAC, hence improving the microbial metabolic activity and biological removal of organic matter especially DBPs precursors. Meanwhile, the extracellular polymeric substances (EPS) on the surface of Fe/CAC exhibited stronger viscosity, higher flocculating efficiency and better mechanical stability, avoiding bacteria or small-scale biofilms falling off into the water. Consequently, the microbial biomass and EPS substances amount decreased markedly in the effluent of Fe/CAC filter. More importantly, Fe/CAC did significantly enhance the shaping role on microbial community of downstream DWDSs, continuously excluding OPs advantage and inhibiting EPS production. The weakening of EPS in DWDSs resulted in decrease of microbial chlorine-resistance ability and EPS-derived DBPs precursors supply. Therefore, the deterioration of water quality in DWDSs was inhibited greatly, sustainably maintaining the safety of tap water. Our findings indicated that optimizing biological activated carbon treatment by interface modification is a promising method for improving water quality in DWDSs.

Acetate kinase activity test - a new approach to biogas production monitoring in the presence of chlorophenols

The proper functioning of processes related to the use of alternative energy sources is one of the key aspects in the field of biotechnology. Therefore, there is a need to develop new techniques allowing the adequate monitoring of the biogas production, especially in the presence of potentially inhibiting substances. The negative impact of chlorophenols on methane fermentation proces was confirmed in numerous studies. The inhibition effect is usually monitored based on chemical and microbiological assessment. However, the results of the tests sometimes do not reflect adequately the actual process. In this research the acetate kinase activity test was proposed as a sensitive control parameter for the monitoring of biogas production in the presence of 2,4-dichlorophenol. Acetate kinase can be considered a key enzyme in methanogenesis. The determination of its activity is simpler and less time consuming compared to other monitoring methods. The amount of the iron acetyl hydroxyamine complex measured in the proposed assay corresponds to the amount of acetyl phosphate formed during the methane fermentation. It was revealed that the acetate kinase activity can better reflect the changes in biogas yield and in methane concentration compared with chemical and microbiological analyses as well as the total dehydrogenase activity tests. Keywords: 2,4-dichlorophenol; Methane fermentation; Biogas production monitoring; Acetate kinase

Comparison of biodegradation of lubricant wastes by Scenedesmus vacuolatus vs a microalgal consortium

Locally, the petroleum, aluminum and steel milling industries have expressed considerable interest in the utilization of bioremediation as a means for reducing their lubricant waste. Since hydrocarbons accumulate within microalgae, the aim of this study was to determine the efficiency of Scenedesmus vacuolatus vs a microalgal consortium (Chlamydomonas pitschmannii, Trebouxia australis and Pectinodesmus pectinatus) in the biodegradation lubricant waste products; from which these indigenous microalgae were originally isolated. To determine the biodegradation capability of these microalgae, dehydrogenase activity tests were carried out and indicated by % TPF values. Samples that tested positive for dehydrogenase activity, were analyzed using gas chromatography/mass spectrometry, to track the biotransformation of hydrocarbons intracellularly and extracellularly. Results were analyzed statistically with SPSS, p < 0.05. Dehydrogenase activity for both the coolant rolling oil (0.058 ± 0.001 mg/mL), and the spent rolling emulsion (0.047 ± 0.002) was higher for the microbial consortium compared to S. vacuolatus, 0.046 ± 0.001 mg/mL. Weekly, gas chromatography/mass spectrometry biotransformations, indicated no hydrocarbons present after five weeks, confirming 100% biodegradation. Irrespective of the use of either a single isolate or a microalgal consortium; complete biodegradation after just five weeks, makes the use of microalgae for bioremediation a viable strategy.

Cetuximab and epirubicin HCl-combined application as a possibility to treat both parental and epirubicin HCl-resistant liver cancer cells.

Targeted chemotherapeutics such as cetuximab can cause many side effects such as skin toxicity when used in high concentrations. In addition, cancer cells can develop resistance to some of the anticancer agents during treatment. The lack of the desired success in chemotherapy and the development of resistance to chemotherapeutics, such as epirubicin HCl, suggest that there is a need for combined therapies. The combination of targeted chemotherapeutics and conventional chemotherapy drugs may lead to the emergence of new strategies in the treatment of cancer. In this study, cytotoxic, antiproliferative, cell cycle inhibitive, oxidative stress generation, and apoptotic effects and effect mechanisms of cetuximab alone and together with epirubicin HCl on parental liver cancer cells (P-Hep G2) and epirubicin HCl-resistant liver cancer cells (R-Hep G2) were investigated. Cytotoxic effects of cetuximab alone and with epirubicin-HCl on cells were determined by Cell Titer-Blue® Cell Viability and Lactate Dehydrogenase Activity tests. Cell cycle distributions and apoptosis were detected by reverse transcription polymerase chain reaction (RT-PCR). Cetuximab with epirubicin HCl treatment increased the cytotoxic effect on both cells. Caspase-3/7 activity increased 3 and 1.5 times in comparison with control group in P-Hep G2 and R-Hep G2 cells, respectively, after treating with cetuximab alone, whereas the increase was found to be approximately 4.7 and 2.5 times when cetuximab was treated with epirubicin HCl in P-Hep G2 and R-Hep G2 cells, respectively. Both cetuximab alone and together with epirubicin HCl treatments caused increases in Bax/Bcl-2 ratio in both cells. Treatment of cetuximab with epirubicin HCl to P-Hep G2 and R-Hep G2 cells was found to be more effective in cytotoxic effect and inducing apoptosis comparison to cetuximab alone treatment. In addition, combination treatment showed different effects on pro-apoptotic/anti-apoptotic genes expression according to cells drug resistance properties.

Enhanced anticancer effect of cetuximab combined with stabilized silver ion solution in EGFR-positive lung cancer cells

Abstract Background Cytotoxic, antiproliferative, cell cycle inhibitive, oxidative and apoptotic effects of cetuximab [antibody for epidermal growth factor receptor (EGFR)] alone and together with stabilized silver ion solution (St-Ag) on P-H1299, R-H1299, A-431 and A-549 cells were investigated. Materials and methods Cytotoxic effects of cetuximab alone and together with St-Ag on cells were determined by Cell Titer-Blue® Cell Viability and Lactate Dehydrogenase Activity tests. Cell cycle distributions and apoptosis were detected by reverse transcription polymerase chain reaction (RT-PCR). Results St-Ag enhanced cetuximab cytotoxic effect on all cells. LDH activity, as a result of cell death, was found the highest level at treatment of cetuximab with St-Ag in all cells. Both treatment increased caspase-3/7 activity which is apoptotic enzyme was found higher in A-549 cells than other cells. Also, treatment of cetuximab with St-Ag caused increasing Bax/Bcl-2 ratio in all cells. Cetuximab with St-Ag treatment increased glutathione peroxidase activity in all cells generating oxidative stress. Proliferating Cell Nuclear Antigen (PCNA), topoisomerase II-alpha (except R-H1299), cyclin D1 and D2 genes expression were decreased in all cells which explain the cell cycle inhibition effect. Conclusion These findings suggest that treatment of cetuximab combined with St-Ag exhibit more carcinogenesis reducing potential than cetuximab alone.

Promoting deep-sowing germinability of corn (Zea mays) by seed soaking with gibberellic acid

ABSTRACTThe effects of seed soaking with gibberellic acid (GA3) on germinability of conventional corn variety ‘Nongda 108’ and super sweet corn variety ‘Chaotian 3’ were investigated under deep-sowing condition. GA3 soaking significantly improved seed germination and mesocotyl elongation of both varieties under 10 or 6 cm sowing depth. The most significant promotion occurred at 0.175 g L−1 GA3 in ‘Nongda 108’ and 0.035 g L−1 GA3 in ‘Chaotian 3’. To further illustrate the physiological explanations, seed respiration was estimated from dehydrogenase activity test and oxygen-sensing test. Dehydrogenase activities of both varieties were dramatically promoted after GA3 soaking. Compared with water soaking, the dehydrogenase activity in 0.175 g L−1 GA3-soaked seeds of ‘Nongda 108’ and 0.035 g L−1 GA3-soaked ones of ‘Chaotian 3’ was increased by 15.4% and 78.8%, respectively. Oxygen-sensing test showed that increased metabolism time (IMT) critical oxygen pressure (COP) and relative germination time (RGT) were decreased while oxygen metabolism rate (OMR) and relative germination rate (RGR) were increased in GA3-soaked seeds, suggesting that exogenous GA-accelerated seed respiration. Our results suggested that seed soaking with exogenous GA3 was a simple and practicable method to improve deep-sowing tolerance during corn seed germination, and the significant promotions were attributed to vigorous respiratory metabolism.

The effect of the melatonin on cryopreserved mouse testicular cells

After improvements in various cancer treatments, life expectancy has been raised, but success in treatment causes loss of fertility in many of the survived young men. Cryopreservation of immature testicular tissues or cells introduced as the only way to preserve fertility. However, freezing has some harmful effects. Melatonin, a pineal gland hormone, has receptors in reproductive systems of different species. It is assumed that melatonin has free radical scavenger properties. The aim of this study was to evaluate the effects of melatonin on the cryopreserved testicular cells in mouse. Cells from 7- 10 days old NMRI mice testes were isolated using two step enzymatic digestion. The testicular cells were divided into two groups randomly and cryopreserved in two different freezing media with and without the addition of 100 µm melatonin. Finally, apoptosis of the cells was assayed by flow cytometry. Also, lactate dehydrogenase activity test was performed to assess the cytotoxicity. The results of lactate dehydrogenase showed the nearly cytotoxic effect of melatonin. The results of flow cytometry showed increase in apoptosis in the cryopreserved cells in the media containing melatonin compared to the control group. The present study shows that melatonin has an apoptotic effect on cryopreserved mouse testicular cells.

Using the dehydrogenase activity for alert of activated sludge system under different copper concentrations

The aim of this study is to evaluate the effectiveness of dehydrogenase activities as an early warning indicator in wastewater treatment process under the impact of Cu(II). The substrate removals in sequencing batch reactors (SBR) on different Cu(II) concentrations (0, 5, 10, and 20 mg L−1) were investigated during long-term operation. Meanwhile, the dehydrogenase activities of activated sludge taken from SBR were observed in short-term bioassays. The results indicate that the inhibitory rates of Cu(II) on substrate removal efficiencies increased along with an increment of Cu(II) concentration. The dehydrogenase activities demonstrated similar trend. Logarithmic curves were used to describe the inhibitory effect of Cu(II) on dehydrogenase activities. Positive correlations were then obtained between the substrate removal efficiencies during long-term operation and dehydrogenase activities in short-term bioassays. Thus, 2-(p-iod-phenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride (INT)-dehydrogenase activity test can be applied as an effective method to alert the activated sludge system performance under the impact of heavy metal. In addition, median inhibitory concentration (IC50) by INT-dehydrogenase test after 1-h and 24-h Cu(II) exposure (5.93 mg L−1 for 1 h exposure and 5.45 mg L−1 for 24 h exposure) were obtained. These results showed that IC50 after 24 h of Cu(II) exposure appeared more sensitive to copper than that after 1 h. Therefore, INT-dehydrogenase test after 24 h Cu(II) exposure could be better fit for the early warning of wastewater treatment performance.

Seed viability and vigour in naturally aged seeds of coriander (Coriandrum sativum)

In the present investigation, three seed lots of eight varieties/genotypes, viz. DH 224, DH 226, DH 242, DH 259, DH 294, DH 296 (advance genotypes) and DH 228 (Hisar Bhoomit) and Hisar Anand (released varieties) of coriander were subjected to study the effect of natural ageing on different seed quality parameters. All the seed lots were analyzed for standard germination test (%), root length (cm), shoot length (cm), seedling dry weight (mg), seedling vigour index-I, seedling vigour index-II, accelerated ageing test (%), electrical conductivity (mS/cm/seed) of seed leachates, seed density (g/cc), dehydrogenase activity test (OD/g/mL), field emergence index and field establishment (%). Results revealed that all the varieties/genotypes showed the germination percentage above the Minimum Seed Certification Standards (60%) in Lot-A (½ year old seed) and Lot-B (1½ years old seed). Standard germination (%), seedling length (cm), seedling dry weight (mg), seedling vigour index-I &amp;II, accelerated ageing test (%), dehydrogenase activity test (OD/g/mL), field emergence index and field establishment (%) decreased significantly and progressively as the ageing period increased. The electrical conductivity was negatively and significantly correlated with all seed viability and vigour parameters. Results also revealed that viability and vigour of seeds declined with faster rate in Lot-C (2½ years old seed). Among all the varieties/genotypes, genotypes DH 224 and DH 228 were found most promising for various parameters of viability and vigour.

Controlled deterioration and paper-piercing tests predict seedling emergence potential in okra seed lots

The present study was conducted to evaluate some of the available seed vigour tests to predict field emergence in okra (Abelmoschus esculentus L. Moench) seed lots. Twenty-one commercial seed lots of okra were evaluated by the following laboratory vigour tests: germination, speed of germination, vigour index, brick gravel test, paper-piercing test, accelerated ageing, controlled deterioration, dehydrogenase activity and electrical conductivity. The vigour tests were able to assess vigour differences among the seed lots. The seedling emergence percentage in the field ranged from 35% to 63% for these seed lots. The correlation coefficient of following laboratory vigour tests viz., standard germination, speed of germination, brick gravel test, paper-piercing test and controlled deterioration were significantly and positively correlated with field emergence. The vigour index I, vigour index II and dehydrogenase activity test were not significant with field emergence. Determination coefficient of seed lots for standard germination, speed of germination, brick gravel test, paper-piercing test and controlled deterioration were found significant and explains 49%, 50%, 52%, 83% and 87% of variation in field emergence, respectively. The regression analysis result for vigour indices (I and II), dehydrogenase activity test and cold test explains 4%, 9%, 2% and 7% of the variation in field emergence, respectively. The correlation coefficient and determination coefficient of controlled deterioration test and paper-piercing test were found highly significant among all other vigour tests in predicting seedling emergence of okra seed lots.The results suggest that controlled deterioration and paper-piercing test can be successfully used to predict seedling emergence in okra seed lots.

Biodegradability evaluation of pollutants in acrylonitrile wastewaters based on particle size distribution

Acrylonitrile wastewaters (ANWs) treatment is a big trouble for chemical fiber industry in China, and there was not yet an effective biological treatment technology for ANWs due to the lack of detailed analysis on the biodegradability of pollutants. In this work, two typical point-source ANWs, acrylonitrile synthesis wastewater (ANSW), and acrylonitrile polymerization wastewater (ANPW) were fractionated by gradient membrane separation method based on the pollutants particle size distribution (PSD). Moreover, biochemical oxygen demand/chemical oxygen demand (COD) ratios, oxygen uptake respirometric tests, dehydrogenase activity tests, and simulated aeration tests were integrated to evaluate the biodegradability of PSD-based pollutants in ANWs. The results showed that most COD were from dissolved fractions in both of ANSW and ANPW. For ANSW, the soluble fractions had greater biodegradation potential than particulate and colloidal fractions. Colloidal fractions are easier to be biodegraded than particulate and soluble fractions in ANPW. The simulated aerobic tests showed that, only 54.72 and 21.62% of COD was removed from ANSW and ANPW, respectively. It indicated that activated sludge treatment process was inadequate to ANWs. The correlations between PSD-based pollutants and their biodegradability of ANWs can be used to guide the development of ANWs treatment technologies.

Evaluation of cytotoxicity of 10 dentin desensitizers

Dentin desensitizer is being widely used to treat hypersensitivity of teeth in dental clinics, and a variety of dentin desensitizers are commercially available. Because dentin desensitizers are applied close to oral tissues including gingiva and pulp, it is necessary to evaluate cytotoxicity of 10 desensitizers to secure the biological safety of the materials. In this study, we investigated cytotoxicity of dentin desensitizers by two different evaluation methods, mitochondrial dehydrogenase activity test with WST-8 and agar diffusion assay with neutral red. In the test with WST-8, Gluma Desensitizer, MicroPrime G, HurriSeal and Cervial Cement showed high cytotoxicity, followed by Zarosen, UltraEZ and Systemp desensitizer. In agar diffusion assay, Gluma Desensitizer, MicroPrime G and HurriSeal exhibited severe cytotoxicity, while other desensitizers showed moderate or mild cytotoxicity. Cervical Cement which exhibited relatively high toxicity in WST-8 assay showed mild cytotoxicity in the agar diffusion assay, of which difference was likely due to the difference of evaluation mechanism between WST-8 and neutral red. The highly cytotoxic Gluma Desensitizer, MicroPrime G, HurriSeal contain both or either of glutaraldehyde and 2-hydroxylethyl methacrylate (HEMA), suggesting that glutaraldehyde and HEMA induced strong cytotoxicity of the desensitizers.

A Dehydrogenase Activity Test for Monitoring the Growth of Streptomyces Venezuelae in a Nutrient Rich Medium

Jadomycin is a novel antibiotic that has shown activities against bacteria, yeasts and fungi as well as cytotoxic properties to cancer cells. Because of the wide range of its inhibitory actions, jadomycin shows promise as a novel antibiotic and cancer treatment drug. Streptomyces venezuelae are aerobic bacteria that are capable of producing jadomycin when shocked by alcohol in a nutrient deprived amino acid rich medium. The size of the bacterial population that is transferred from the growth medium to the production medium can significantly affect the jadomycin yield. Therefore, the number of transferred bacteria must be accurately measured. In this study, a dehydrogenase activity measurement test was developed for S. venezuelae using triphenyl tetrazolium chloride (TTC) to measure the cell growth and activity in maltose-yeast extract-malt extract (MYM) broth. The dehydrogenase activity was determined by measuring the visible color changes of the TTC to triphenyl formazan (TF). The test conditions which included extraction solvent, number of extractions, incubation time, incubation temperature and medium pH were evaluated. The results showed that the triphenyl formazan was related to the number of cells. Methanol was better able to permeate the cells and extract higher amount of TF than ethanol. The amount of TF increased with the number of extractions for both solvents. A lower medium pH and/or lower temperature produced the highest amount of TF. The best test conditions that produced the highest TF yield were three extractions using methanol after an incubation time of 1 hour at a temperature of 30oC and a medium pH of 6.

Experimental impact of aspirin exposure on rat intestinal bacteria, epithelial cells and cell line

Aspirin, a commonly used therapeutic non-steroidal anti-inflammatory drug (NSAID) is known to cause gastric mucosal damage. Intestinal bacteria having a regulatory effect on intestinal homeostasis play significant role in NSAID-induced intestinal injury. Bacteria and specific cell lines are considered to be suitable for toxicity screening and testing of chemicals. Therefore, to evaluate and compare in vitro toxicity, cultures of rat intestinal epithelial cells (IEC), isolated bacteria and IEC-6 cell line were assessed for viability, morphometric analysis, membrane transport enzymes and structural constituents for membrane damage, dehydrogenase activity test for respiratory and energy producing processes and esterase activity test for intra- and extra-cellular degradation, following the post exposure to aspirin (0-50 µg mL(- 1)). Similar pattern of dose-dependent changes in these parameters were observed in three types of cells. Similar in situ effects on IEC validated the in vitro findings. These findings indicate that higher aspirin concentrations may alter cellular functions of IEC and gut bacteria. Furthermore, results suggest that gut bacteria and IEC-6 cell line can be used for the initial screening of gastrointestinal cellular toxicity caused by NSAIDs.

Comprehensive study on dynamics of microbial community in Anaerobic-Oxic-Oxic process using PCR-DGGE, gas chromatography analysis, and dehydrogenase activity assays

This study was conducted to evaluate the relationship between the function of microbes and the change in their communities during the treatment of coking wastewater using a bio-fluidized bed Anaerobic-Oxic-Oxic (A/O/O) process. Polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE), Gas Chromatography (GC) analysis, and the triphenyl-tetrazolium chloride (TTC) dehydrogenase activity test (TTC test) were simultaneously conducted to analyze the dynamics of microbe communities during the process of coking wastewater treatment. The study suggests that combined approaches of PCR-DGGE, GC, and TTC provided a simple and accurate method to evaluate the changes in microbial activity, microbial structure, and population size with the shifting of contaminants in different treatment processes. It demonstrates that the structure and components of a microbial community are influenced by selecting pressure during the wastewater treatment process, which in turn determines the overall functionality of the system.

Experimental exposure of arsenic in cultured rat intestinal epithelial cells and cell line: Toxicological consequences

Arsenic is a naturally occurring metalloid and the drinking water contamination by inorganic arsenic remains a major public health problem. The trivalent arsenic (arsenite) is more toxic than the pentavalent form (arsenate), and is known to cause gastrointestinal toxicity. Specific immortal cell lines are considered to be suitable for toxicity screening and testing of chemicals as they are easy to handle and possess most of the biochemical pathways present in the corresponding cells present in vivo. The present study was designed to evaluate and compare the in vitro toxicity of arsenite on rat intestinal epithelial cell line (IEC-6) and primary cultures of rat intestinal epithelial cells (IEC). To evaluate in vitro toxicity, cultures of IEC and IEC-6 cells were assessed for viability, morphometric analysis, membrane transport enzymes and structural constituents for membrane damage, dehydrogenase activity test for respiratory and energy producing processes and esterase activity test for intra and extra cellular degradation, following the post exposures to arsenite (0–20 ppm). Significantly similar concentration-dependent changes in these toxicity-screening parameters in IEC and IEC-6 were observed. Highest tested concentration of arsenite (20 ppm) was found to be detrimental in both IEC and IEC-6. Furthermore, to evaluate arsenite toxicity in epithelial cells of rat intestine, intestinal loops were filled with arsenite solutions and incubated for 30 min in situ. In situ studies also showed a significant arsenite concentration-dependent decline in epithelial cell membrane transport enzyme activities and total hexose and sialic acid contents. Concomitant release of membrane enzymes, hexose and sialic acid in the intestinal luminal fluid following higher arsenite exposures further indicated partial membrane damage. Similar morphological changes in IEC and IEC-6 were also evident. These findings also suggest that IEC-6 cell lines are suitable for initial screening of gastrointestinal cellular toxicity caused by arsenite.

Studies on seed quality parameters in deteriorating seeds in Brassica (Brassica campestris)

Seeds of two promising varieties viz; Sangam and TH 68 of Brassica campestris were stored for 4 years under ambient conditions. Both these varieties with their four seed lots each were studied for various seed quality parameters. Results revealed that the germination percent of both these varieties remained above the prescribed Minimum Seed Certification Standard (85.00%) limit in 1 and 2 years old seeds. Germination percent, seedling length (cm), seedling dry weight (mg), speed of germination, seedling vigor index-1, seedling establishment (%), speed of emergence, seed yield (q/ha.), seed viability (%), dehydrogenase activity test, respiration rate (μlO 2 / seedling/h), oil content (%), pH of the seed leachates, total protein (mg/g) and peroxidase enzymes (unit g -1 Fr. wt.min -1 ) decreased significantly as the age of the seed increased. However, this decline was more rapid in 3 and 4 years old seeds in both these varieties. Electrical conductivity (μmhos/cm/seed) and total soluble carbohydrates (mg/g) increased significantly with increase in the age of the seed. Germination percent, seedling length (cm), seedling dry weight (mg), speed of germination, seedling vigor index-1, seed viability (%), respiration rate (μlO 2 /seedling/h), oil content (%), pH of the seed leachates, total protein (mg/g) and peroxidase enzymes (unit g -1 Fr. wt.min -1 ) are significantly correlated with speed of emergence, seedling establishment (%) and seed yield (q/ha.). Electrical conductivity (μmhos/cm/seed) and total soluble carbohydrates (mg) were negatively and significantly correlated with speed of emergence, seedling establishment (%) and seed yield (q/ha.).

INT–dehydrogenase activity test for assessing anaerobic biodegradability of organic compounds

This study assessed anaerobic biodegradability of organic compounds from microorganism activity. Dehydrogenase activity can be a good parameter characterizing the microorganism activity. A modified method of 2-(p-iodophenyl-3-(p-nitrophenyl)-5-pheny tetrazolium chloride-dehydrogenase activity determination was proposed in anaerobic biodegradability assessment. Cubic spline curves were adopted to link the data points. This curve was integrated twice to calculate areas. The microorganism activity index in anaerobic biodegradability assessment was calculated by standardizing the integral. According to the results of the activity index, 14 kinds of organic compounds were classified into readily, partially, and poorly biodegradable under anaerobic conditions, respectively. As a result, some conclusions for anaerobic biodegradability of organic compounds were reached, based on the activity index value.