Development and validation of a competitive immunoassay for urinary S-phenylmercapturic acid and its application in benzene biological monitoring

An immunoassay that quantifies urinary S-phenylmercapturic acid (PMA), a benzene-specific biomarker, has been developed and its potential usefulness as a screening tool for monitoring occupational exposure to benzene has been demonstrated. Analytical reliability has been confirmed by correlation of results with gas chromatography-mass spectrometry (GC/MS) data (R = 0.92). The assay has been configured as a competitive enzyme-linked immunosorbent assay (ELISA) to facilitate rapid throughput of samples. The ELISA has a working range of 40-1200 nmol l^-1 urinary PMA and appears to be unaffected by the presence of structurally related urinary metabolites. Background levels of 0-1.9μmol PMA/mol creatinine (mean 0.9 μmol mol^-1, n = 32) were measured in non-smoking control subjects. Recent exposures to benzene (8 h time-weighted averages-TWA), during diverse industrial processes, over the range 0-4.8ppm were identified by application of the assay in biological monitoring programmes.     

Estimation of urinary cotinine cut-off points distinguishing non-smokers,passive and active smokers

Abstract

An objective assessment of exposure to tobacco smoke may be accomplished by means of examining particular biomarkers in body fluids. The most common biomarker of tobacco smoke exposure is urinary, or serum, cotinine. In order to distinguish non-smokers from passive smokers and passive smokers from active smokers, it is necessary to estimate cotinine cut-off points. The objective of this article was to apply statistical distribution of urinary cotinine concentration to estimate cut-off points distinguishing the three above-mentioned groups. The examined group consisted of 327 volunteers (187 women and 140 men) who were ethnically homogenous inhabitants of the same urban agglomeration (Sosnowiec, Poland). The values which enabled differentiation of the examined population into groups and subgroups were as follows: 50 µg l^?1 (differentiation of non-smokers from passive smokers), 170 µg l^?1 (to divide the group of passive smokers into two subgroups: minimally and highly exposed to environmental tobacco smoke), 550 µg l^?1 (differentiation of passive smokers from active smokers), and 2100 µg l^?1 (to divide group of active smokers into two subgroups: minimally and highly exposed to tobacco smoke). The results suggest that statistical distribution of urinary cotinine concentration is useful for estimating urinary cotinine cut-off points and for assessing the smoking status of persons exposed to tobacco smoke.     

Simultaneous determination of urinary 1- and 2-naphthols, 3- and 9-phenanthrols,and 1-pyrenol in coke oven workers

A method was developed for simultaneous quantification of urinary 1- and 2-naphthols, 3- and 9-phenanthrols and 1-pyrenol using gas chromatography with mass spectrometry (GC-MS). This method was applied to urine samples from coke oven workers (n =28) and controls (n =22) from Northern China. Geometric mean levels of urinary 1-naphthol (58.8 μg l^?1), 2-naphthol (34.1 μg l^?1), 3-phenanthrol (7.35 μg l^?1), 9-phenanthrol (1.28 μg l^?1) and 1-pyrenol (25.4 μg l^?1) were significantly higher among coke oven workers than controls. All the substances tested were highest among top-of-oven workers, who had 15-fold higher 1-naphthol, eight-fold higher 2-naphthol and 20-fold higher 1-pyrenol levels compared with controls. Using multiple linear regression models, 72.5% of the variation in 1- and 2-naphthol and 82.8% of the variation in 1-pyrenol were explained by the concentration of naphthalene or pyrene in the urine, the work category and the smoking intensity. Cigarette consumption significantly contributed to levels of urinary 1-pyrenol and naphthols, particularly 2-naphthol. A negative relationship between work category and the ratio of naphthols/1-pyrenol was observed among smokers. Our results suggest that urinary naphthols and phenanthrols reflect polycyclic aromatic hydrocarbon (PAH) exposure as well as the widely used 1-pyrenol, and that interactions between cigarette smoking and PAH exposure result in different patterns of metabolism for individual PAHs.     

Determination of free and total S-phenylmercapturic acid by HPLC/MS/MS in the biological monitoring of benzene exposure

Abstract

Urinary S-phenylmercapturic acid (SPMA) is a biomarker suggested by the American Conference of Governmental Industrial Hygienists (ACGIH) for assessing occupational exposure to benzene. A possible cause of the miscorrelation between environmental monitoring and biological monitoring for benzene exposure, which many authors complain about, is the existence of a urinary metabolite that turns into SPMA by acid hydrolysis. Forty urine samples were tested to determine which concentration value would correspond to the ACGIH Biological Exposure Index (BEI) of 25 µg g^?1 creatinine if exposure assessment was based on the determination of SPMA after quantitative hydrolysis of its precursor. An aliquot of each sample was hydrolysed with 9 M H₂SO₄, a second one was brought to pH 2 and a third one was used as it was (free SPMA). SPMA was determined by high-performance liquid chromatography/tandem mass spectrometric technique (HPLC/MS/MS) using an internal standard. The analytical method was validated in the range 0.5–50 µg l^?1. The average SPMA in pH 2 samples is 45–60% of the total, while free SPMA varies from 1% to 66%. The hydrolysis of pre-SPMA reduces the likelihood of variability in the results by reducing pH differences in urine samples and increasing the amount of measured SPMA. The BEI limit value would be about 50 µg g^?1 creatinine.     

Calcium‐dependent behavioural responses to acute copper exposure in Oncorhynchus mykiss

Using rainbow trout Oncorhynchus mykiss, the present study demonstrated that: (1) calcium (Ca) increased the range of copper (Cu) concentrations that O. mykiss avoided; (2) Ca conserved the maintenance of pre‐exposure swimming activity during inescapable acute (10 min) Cu exposure. Data showed that when presented with a choice of Cu‐contaminated water (ranging from 0 to 454 µg Cu l^?1) and uncontaminated water in a choice tank, O. mykiss acclimated and tested at low Ca concentration (3 mg Ca l^?1) avoided the 10 µg Cu l^?1 only. By contrast, O. mykiss acclimated and tested at high Ca concentration (158 mg Ca l^?1) avoided all the Cu concentrations ≥37 µg l^?1. The Cu avoidance was connected with increased spontaneous swimming speed in the Cu‐contaminated water. When subjected to inescapable Cu exposure (35 µg Cu l^?1), O. mykiss acclimated and tested at low Ca concentration reduced their spontaneous swimming speed, whereas no response was observed in O. mykiss acclimated and tested at high Ca concentration. Collectively, the data support the conclusion that in O. mykiss the behavioural responses to acute Cu exposure are Ca‐dependent.     

Physicochemical and elemental contamination assessment in groundwater samples of Khairpur Mir's,Pakistan

Drinking water contaminated with arsenic poses serious threat to the human health. The present study was aimed for quality assessment of the groundwater of Khairpur Mir's in respect with arsenic and other elemental contamination like Fe, Cu, Co, and Ni. The presence of the trace elements in groundwater from different sources in the study area was measured by using atomic absorption spectroscopy. For arsenic analysis hydride generation technique (MHS-15) was used with detection limit of 0.02 µg l^?1. Elevated level of arsenic was observed in most of the samples as compared to recommended value of World Health Organization (WHO) guidelines (10 µg l^?1). However, levels of Fe, Cu, Co, and Ni in hand pump (HP) water samples was found in the range of 4–1610 µg l^?1, 0–556 µg l^?1, 0–230 µg l^?1, and 0–700 µg l^?1, respectively. Whereas in tube well (TW) water samples the observed values are 5–1620 µg l^?1, 0–50 µg l^?1, 4–110 µg l^?1, and 0–360 µg l^?1 for Fe, Cu, Co, and Ni, respectively. Significant difference was observed between TW and HP water samples. It was concluded that the level of arsenic found was very high up to 13 fold more than the WHO recommended limit in study area. While the levels of other elements was noted within the safe limit.     

Exhaled breath condensate as matrix for toluene detection: A preliminary study

Abstract

The study was designed to investigate whether exhaled breath condensate, obtained by cooling exhaled air in spontaneous breathing, could be a suitable matrix for toluene quantitative analyses. Nine healthy subjects were exposed for a short period (20 min) to a known concentration of toluene. Exhaled breath condensate samples were collected before and at the end of the exposure, while the environmental concentration of toluene was continuously monitored. Toluene was analysed by head-space gas-chromatography mass spectrometry, and assay repeatability was also estimated in vitro. Baseline and post-exposure measurement of hippuric acid, the urinary toluene metabolite, was performed to assess current toluene exposure. Before the exposure toluene concentrations in the exhaled breath condensate were lower than the detectable limit in all subjects, while after the exposure toluene was detectable with a median value 0.35 µg l^?1 (range 0.15–0.55 µg l^?1) in all the exhaled breath condensate samples. As compared with the standard calibration in distilled water, the curves obtained by exhaled breath condensate were linear and comparable with the range examined in vivo for toluene. A significant correlation was found between the environmental toluene levels and toluene in the exhaled breath condensate at the end of exposure. Furthermore, a significant relationship between increased exhaled breath condensate toluene levels and urinary hippuric acid after the exposure was found. In conclusion, exhaled breath condensate is a promising matrix for toluene assessment, although its application in humans requires further investigations.     

An integrated approach to biomonitoring exposure to styrene and styrene-(7,8)-oxide using a repeated measurements sampling design

Abstract

The aim of this work was to investigate urinary analytes and haemoglobin and albumin adducts as biomarkers of exposure to airborne styrene (Sty) and styrene-(7,8)-oxide (StyOX) and to evaluate the influence of smoking habit and genetic polymorphism of metabolic enzymes GSTM1 and GSTT1 on these biomarkers. We obtained three or four air and urine samples from each exposed worker (eight reinforced plastics workers and 13 varnish workers), one air and urine samples from 22 control workers (automobile mechanics) and one blood sample from all subjects. Median levels of exposure to Sty and StyOX, respectively, were 18.2 mg m^?3 and 133 µg m^?3 for reinforced plastics workers, 3.4 mg m^?3 and 12 µg m^?3 for varnish workers, and <0.3 mg m^?3 and <5 µg m^?3 for controls. Urinary levels of styrene, mandelic acid, phenylglyoxylic acid, phenylglycine (PHG), 4-vinylphenol (VP) and mercapturic acids (M1+M2), as well as cysteinyl adducts of serum albumin (but not those of haemoglobin) were significantly associated with exposure status (controls相似文献   

Low concentrations of glyphosate‐based herbicide cause complete loss of sperm motility of yellowtail tetra fish Astyanax lacustris

Environmental relevant concentrations of glyphosate‐based herbicide as 50 µg l^?1, 300 µg l^?1 and 1800 µg l^?1 can affect sperm quality of yellowtail tetra fish Astyanax lacustris . Viability of sperm cells was impaired at 300 µg l^?1, a concentration that is within legal limits in U.S.A. waterbodies, while motility was impaired at 50 µg l^?1, which is the more stringent limit set in Brazilian law. Therefore, environment protection agencies must review regulations of glyphosate‐based herbicides on water bodies.     

Temporal dynamics of epidermal responses of guppies Poecilia reticulata to a sublethal range of waterborne zinc concentrations

This study assessed the histological changes in the epidermis of guppies Poecilia reticulata induced by waterborne zinc (Zn). Laboratory‐reared P. reticulata fry were maintained individually in separate vessels containing artificial water (8 µg l^?1 Zn) to which 0, 15, 30, 60 or 120 µg l^?1 Zn was added. Their epidermal response to Zn was monitored regularly over 4 weeks. Compared with controls, mucus was rapidly released and mucous cell numbers decreased at all concentrations. Thereafter mucous release, epidermal thickness, numbers and size of mucous cells fluctuated at a rate that varied with Zn concentration, but fluctuations declined after day 18. Results clearly highlight the dynamic nature of the epidermal response to sublethal concentrations of waterborne Zn. In general, low concentrations of Zn induced a rapid response with reduced numbers and size of mucous cells and shift in mucin composition, and a subsequent thickening of the epidermis. Epidermal thickness and mucous cell area fluctuated over time but were normal after a month of exposure to low Zn concentrations. The number of mucous cells, however, remained low. Virtually all mucous cells from fish maintained in 15 and 60 µg l^?1 Zn contained acidic mucins throughout the month, whereas fish maintained at 30 µg l^?1 Zn responded by production of neutral mucins during the first 12 days followed by a mixture of neutral and acidic mucins. At 120 µg l^?1 Zn, the most dramatic effects were the gradual but sustained decrease in numbers and area of mucous cells, and the shift to acidic mucins in these cells. Thus, as concentration of Zn increased, the epidermal responses indicated a disturbed host response (dramatic decline in mucous cell numbers, with mixed composition of mucins), which may have been less effective in preventing Zn uptake across the epithelium.     

Microcystin-LR equivalent concentrations in fish tissue during a postbloom Microcystis exposure in Loskop Dam,South Africa

The effects of a decomposing cyanobacteria bloom on water quality and the accumulation of microcystin-LR equivalent toxin in fish at Loskop Dam were studied in May 2012. Enzyme-linked immunosorbent assay [ELISA] was used to confirm the presence of microcystin-LR equivalent in the water and to determine the microcystin (MCYST) concentration in the liver and muscle of fish. The lowest concentration of extracellular MCYST-LR equivalent was recorded in the lacustrine zone, where no cyanobacterial cells were observed, while the highest concentration (3.25 µg l^?1), 3.25 higher than World Health Organization standard, was observed in the riverine zone. Extremely high MCYST-LR equivalent concentrations of 1.72 µg MCYST-LReq kg^?1 in the liver and 0.19 µg kg^?1 in muscles of Labeo rosae, and 2.14 µg MCYST-LReq kg^?1 in the liver and 0.17 µg kg^?1 in muscles of Oreochromis mossambicus, indicate that the consumption of sufficient fish biomass might cause severe adverse effects in humans. Microscopic analyses of the stomach content of both fish species revealed low numbers of cyanobacterial Microcystis aeruginosa cells in comparison to other phytoplankton. The extracellular MCYST-LR equivalent of the decomposing bloom may have played a major role in the high levels observed in the livers of the two fish species. These findings are important for all downstream water users.     

Determination of enalapril maleate and atenolol in their pharmaceutical products and in biological fluids by flow‐injection chemiluminescence

A chemiluminescent method using flow injection (FI) was investigated for rapid and sensitive determination of enalapril maleate and atenolol, which are used in the treatment of hypertension. The method is based on the sensitizing effect of these drugs on the Ce(IV)–sulfite reaction. The different experimental parameters affecting the chemiluminescence (CL) intensity were carefully studied and incorporated into the procedure. The method permitted the determination of 0.01–3.0 µg mL^?1 of enalapril maleate in bulk form with correlation coefficient r = 0.99993, lower limit of detection (LOD) 0.0025 µg mL^?1 (S/N = 2) and lower limit of quantitation (LOQ) 0.01 µg mL^?1. The linearity range of atenolol in bulk form was 0.01–2.0 µg mL^?1 (r = 0.99989) with LOD of 0.0003 µg mL^?1 (S/N = 2) and LOQ of 0.01 µg mL^?1. In biological fluids the linearity range of enalapril maleate was 0.1–2.0 µg mL^?1 in both urine and serum, and for atenolol the linearity range was 0.1–1.0 µg mL^?1 in both urine and serum. The method was also applied to the determination of the drugs in their pharmaceutical preparations. Copyright © 2009 John Wiley & Sons, Ltd.     

Pilot-scale culture of somatic embryos of Eleutherococcus senticosus in airlift bioreactors for the production of eleutherosides

Purpose of work

To establish pilot scale bioreactor cultures of somatic embryos of Siberian ginseng for the production of biomass and eleutherosides. Somatic embryos of Eleutherococcus senticosus were cultured in airlift bioreactors using Murashige and Skoog medium with 30 g sucrose l^?1 for the production of biomass and eleutherosides. Various parameters including the type of bioreactor, aeration volume, and inoculum density were optimized for 3 l capacity bioreactors. Balloon-type airlift bioreactors, utilizing a variable aeration volume of 0.1–0.3 vvm and an inoculum of 5 g l^?1, were suitable for biomass and eleutheroside production. In 500 l balloon-type airlift bioreactors, 11.3 g dry biomass l^?1, 220 µg eleutheroside B l^?1, 413 µg eleutheroside E l^?1, and 262 µg eleutheroside E1 l^?1 were produced.     

Environmental Risk Assessment of Trifluoroacetic Acid

The Montreal Protocol was developed in 1987 in response to concerns that the chlorofluorocarbons (CFCs) were releasing chlorine into the stratosphere and that this chlorine was causing a depletion of stratospheric ozone over Antarctica. This international agreement called for a phase out of these CFCs. Industry initiated a major effort to find replacements that are safe when properly used and safe to the environment. The toxicology and environmental fate of these first generation replacements has been studied extensively. It was determined that the new substances break down in the environment to give predominantly carbon dioxide, water and inorganic salts of chlorine and fluorine. The only exception is that some substances also break down to yield trifluoroacetic acid (HTFA), a substance resistant to further degradation. Recognizing this, industry embarked on a research and assessment program to study the potential effects of trifluoroacetate (TFA) on the environment and to investigate possible degradation pathways. The results of these recently completed studies are summarized below and described in further detail in this paper. Trifluoroacetic acid is a strong organic acid with a pKa of 0.23. It is miscible with water and its low octanol/water partition coefficient (log P_ow=?2.1) indicates no potential to bioaccumulate. Industrial use is limited and environmental releases are very low. Some additional TFA will be formed from the breakdown of a few halogenated hydrocarbons, most notably HFC-134a (CF₃CH₂F), HCFC-124 (CF₃CHFCl), and HCFC-123 (CF₃CHCl₂). As these substances have only been produced in limited commercial quantities, their contribution to environmental levels has been minimal. Surprisingly, environmental measurements in many of diverse locations show existing levels of 100 to 300?ng·l^?1 in water with one site (Dead Sea) having a level of 6400?ng·l^?1. These levels cannot be accounted for based on current atmospheric sources and imply a long-term, possibly pre-industrial source. Generally, soil retention of TFA is poor although soils with high levels of organic matter have been shown to have a greater affinity for TFA when contrasted to soils with low levels of organic matter. This appears to be an adsorption phenomenon, not irreversible binding. Therefore, TFA will not be retained in soil, but will ultimately enter the aqueous compartment. Modeling of emission rates and subsequent conversion rates for precursors has led to estimates of maximum levels of TFA in rain water in the region of 0.1?µ·^?1 in the year 2020. TFA is resistant to both oxidative and reductive degradation. While there had been speculation regarding the possibility of TFA being degraded into monofluoroacetic acid (MFA), the rate of breakdown of MFA is so much higher than for TFA that any MFA formed would rapidly degrade. Therefore, there would be no buildup of MFA regardless of the levels of TFA present in the environment. Although highly resistant to microbial degradation, there have been two reports of TFA degradation under anaerobic conditions. In the first study, natural sediments reduced TFA. However, even though this work was done in replicate, the investigators and others were unable to reproduce it in subsequent studies. In the second study, radiolabeled TFA was removed from a mixed anaerobic in vitro microcosm. Limited evidence of decarboxylation has also been reported for two strains of bacteria grown under highly specific conditions. TFA was not biodegraded in a semi-continuous activated sludge test even with prolonged incubation (up to 84 days). TFA does not accumulate significantly in lower aquatic life forms such as bacteria, small invertebrates, oligochaete worms and some aquatic plants including Lemna gibba (duckweed). Some bioaccumulation was observed in terrestrial higher plants, such as sunflower and wheat. This result appeared to be related to uptake with water and then concentration due to transpiration water loss. When transferred to clean hydroponic media, some elimination of TFA was seen. Also, more than 80% of the TFA in leaves was found to be water ex-tractable, suggesting that no significant metabolism of TFA had occurred. At an exposure level of 1200?mg·l^?1 of sodium trifluoroacetate (NaTFA) — corresponding to 1000?mg·l^?1 HTFA — no effects were seen on either Brachy-danio rerio (a fish) or Daphnia magna (a water flea). With duckweed, mild effects were seen on frond increase and weight increase at the same exposure level. At a concentration of 300?mg·l^?1 no effects were observed. Toxicity tests were conducted with 11 species of algae. For ten of these species the EC50 was greater than 100?mg·l^?1. In Selenastrum capricornutum the no-effect level was 0.12?mg·l^?1. At higher levels the effect was reversible. The reason for the unique sensitivity of this strain is unknown, but a recovery of the growth rate was seen when citric acid was added. This could imply a competitive inhibition of the citric acid cycle. The effect of TFA on seed germination and plant growth has been evaluated with a wide variety of plants. Application of NaTFA at 1000?mg·l^?1 to seeds of sunflower, cabbage, lettuce, tomato, mung bean, soy bean, wheat, corn, oats and rice did not affect germination. Foliar application of a solution of 100?mg·l^?1 of NaTFA to field grown plants did not affect growth of sunflower, soya, wheat, maize, oilseed rape, rice and plantain. When plantain, wheat (varieties Katepwa and Hanno) and soya were grown in hydroponic systems containing NaTFA, no effects were seen on plantain at 32?mg·l^?1, on wheat (Katepwa) and soya at 1?mg·l^?1, or on wheat (Hanno) at 10?mg·l^?1; some effects on growth were seen at, respectively, 100?mg·l^?1, 5?mg·l^?1, 5?mg·l^?1, and 10?mg·l^?1 and above. TFA is not metabolized in mammalian systems to any great extent. It is the major final metabolite of halothane, HCFC-123 and HCFC-124. The half-life of TFA in humans is 16 hours. As expected, the acute oral toxicity of the free acid is higher than the one of the sodium salt. The inhalation LC₅₀ (2 hour exposure) for mice was 13.5?mg·l^?1 (2900?ppm) and for rats it was 10?mg·l^?1 (2140?ppm). Thus, TFA is considered to have low inhalation toxicity. The irritation threshold for humans was 54?ppm. As one would expect of a strong acid, it is a severe irritant to the skin and eye. When conjugated with protein, it has been shown to elicit an immunolog-ical reaction; however, it is unlikely that TFA itself would elicit a sensitization response. Repeat administration of aqueous solutions have shown that TFA can cause increased liver weight and induction of peroxisomes. Relative to the doses (0.5% in diet or 150?mg·kg^?1·day^?1 gavage) the effects are mild. In a series of Ames assays, TFA was reported to be non-mutagenic. Its carcinogenic potential has not been evaluated. Although TFA was shown to accumulate in amniotic fluid following exposure of pregnant animals to high levels of halothane (1200?ppm), no fetal effects were seen. Likewise, a reproduction study that involved exposure of animals to halothane at levels up to 4000?ppm for 4 hours per day, 7 days per week, resulted in no adverse effects. Given the high levels of halothane exposure, it is unlikely that environmental TFA is a reproductive or developmental hazard. Overall the toxicity of TFA has been evaluated in stream mesocosms, algae, higher plants, fish, animals and humans. It has been found to be of very low toxicity in all of these systems. The lowest threshold for any effects was the reversible effect on growth of one strain of algae, Selenastrum capricornutum, which was seen at 0.12?mg·l^?1. There is a 1000-fold difference between the no-effect concentration and the projected environmental levels of TFA from HFCs and HCFCs (0.0001?mg·l^?1). Based on available data, one can conclude that environmental levels of TFA resulting from the breakdown of alternative fluorocarbons do not pose a threat to the environment.     

Effects of copper enrichment on survival,growth and photosynthetic pigment of seedlings and young plants of the eelgrass Zostera marina

Copper (Cu²⁺) is an essential nutrient for plants but toxic at high concentrations. We subjected seedlings and young plants of eelgrass Zostera marina to different seawater Cu concentrations (3, 4, 5, 10, 30 and 50?µg?l^?1) for over 30 days under controlled laboratory conditions. Natural seawater without added Cu (3?µg?l^?1) was used as reference seawater. We measured plant response in terms of survivorship, morphology, growth, productivity and leaf pigment concentration. Survival analysis combined with morphological, dynamic and productive assessment suggested that the optimum seawater Cu concentration for the establishment of Z. marina seedlings and young plants is 4?μg?l^?1. The photosynthetic response of young plants to copper enrichment, including an increase in chlorophyll content under low Cu concentration treatment but significant decrease when treated with high concentrations of Cu, is similar to those reported for other seagrass species. NOEC (no observed effect concentration), LOEC (lowest observed effect concentration) and LC₅₀ (lethal concentration that caused an increase in mortality to 50% of that of the control) values of seedlings were significantly lower than those of young plants, implying a reduced Cu tolerance to high concentrations (>10?μg?l^?1). This study provides data that could prove helpful in the development of successful eelgrass restoration and conservation.     

Immunological and cytotoxicological responses of the Asian clam,Corbicula fluminea (M.), experimentally exposed to cadmium

Abstract

Bivalve molluscs, as filter-feeding organisms, are known to accumulate metals that can produce deleterious effects on organisms. The phagocytic activity of haemocytes and lysosomal alterations in the digestive gland cells were measured in the freshwater Asian clam exposed to cadmium, in order to assess the possible use of immunocompetence and lysosomal responses as biomarkers of freshwater quality. Clams were exposed in the laboratory to nominal concentrations of 3, 10, 21.4, 46.5 and 100 µg l^?1 of cadmium and sampled after 7, 15 and 30 days of exposure. The results show a decrease of phagocytic activity after only 7 days of exposure to 10 µg l^?1 of cadmium. This response was also observed as the exposure time was increased. Lysosomes in the digestive cells increased in size and number after 7 days of exposure as cadmium concentration increased. After 30 days of exposure, a decrease in size and number indicated a change in the response to the metal from concentrations of 46.5 µg l^?1 of cadmium. A dose and time response both in phagocytic activity of haemocytes and lysosomal structure demonstrated a possible use of these biomarkers in freshwater biomonitoring.     

Occurrence and distribution of organochlorine pesticide residue levels in water,sediment and aquatic weeds in the Nyando River catchment,Lake Victoria,Kenya

Samples of water, sediments and aquatic weeds were collected from 26 sites in the Nyando River catchment of the Lake Victoria basin in 2005–2006. The objective was to investigate levels of organochlorine pesticides that have either been banned or are restricted for use in Kenya. The pesticides investigated were lindane, aldrin, endosulfan, endrin, dieldrin, DDT, heptachlor and methoxychlor. These pesticides had previously found wide applications in public health and agriculture in Kenya for control of disease vectors and crop pests respectively. Results showed that mean concentrations were highest for methoxychlor (8.817 ± 0.020?µg l^?1) in water, sediments (92.893 ± 3.039 µg kg^?1), and weeds (39.641 ± 3.045?µg kg^?1), the weeds also tended to accumulate aldrin (15.519 ± 3.756?µg kg^?1). The results show that the pesticides are still in use and are detected in the catchment. Stringent management and public awareness measures are required to enforce the ban on the organochlorine pesticides in order to safeguard the environment and ecosystems of Lake Victoria.     

Synthesis and biological evaluation of some thiazole derivatives as new cholinesterase inhibitors

In the present study, some thiazole derivatives were synthesized via the ring closure reaction of 1-[2-(2-oxobenzo[d]thiazol-3(2H)-yl)acetyl]thiosemicarbazide with various phenacyl bromides. The chemical structures of the compounds were elucidated by ¹H NMR, ¹³C NMR and mass spectral data and elemental analyses. Each derivative was evaluated for its ability to inhibit acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) using a modification of Ellman’s spectrophotometric method. The compounds were also investigated for their cytotoxic properties using MTT assay. The most potent AChE inhibitor was found as compound 4e (IC₅₀?=?25.5?±?2.12 µg/mL) followed by compounds 4i (IC₅₀?=?38.50?±?2.12 µg/mL), 4c (IC₅₀?=?58.42?±?3.14 µg/mL) and 4g (IC₅₀?=?68?±?2.12 µg/mL) when compared with eserine (IC₅₀?=?0.025?±?0.01 µg/mL). Effective compounds on AChE exhibited weak inhibition on BuChE (IC₅₀ > 80 µg/mL). MTT assay indicated that the cytotoxic dose (IC₅₀?=?71.67?±?7.63 µg/mL) of compound 4e was higher than its effective dose.     

Induction of non-protein thiols and phytochelatins by cadmium in Eichhornia crassipes

Abstract

Impact of root Cd concentration on production of cysteine, non-protein thiols (NP-SH), glutathione (GSH), reduced glutathione (GSSG), and phytochelatins (PCs) in Eichhornia crassipes exposed to different dilutions of brass and electroplating industry effluent (25%, 50%, and 75%), and synthetic metal solutions of Cd alone (1, 2.5, and 3.5?ppm) and with Cr (1?ppm Cd + 1?ppm Cr, 2.5?ppm Cd + 3?ppm Cr, and 3.5?ppm Cd + 4?ppm Cr) was assessed in a 45?days study. Different treatments were used to understand and compare differential antioxidant defense response of plant under practical drainage (effluent) and experimental synthetic solutions. The production of NP-SH and cysteine was maximum under 2.5?ppm Cd + 3?ppm Cr treatments i.e., 1.78?µmol/g fw and 288?nmol/g fw, respectively. The content of GSH declined whereas that of GSSG increased progressively with exposure duration in all treatments. HPLC chromatograms revealed that the concentrations of PC2, PC3, and PC4 (248, 250, and 288?nmol-SH equiv.g^?1 fw, respectively) were maximum under 1?ppm Cd, 1?ppm Cd + 1?ppm Cr, and 2.5?ppm Cd + 3?ppm Cr treatments, respectively. PC2, PC3, and PC4 concentrations increased with Cd accumulation in the range 812–1354?µg/g dry wt, 1354–2032?µg/g dry wt and 2032–3200?µg/g dry wt, respectively. Thus, the study establishes a direct proportionality relationship between concentration/length of phytochelatins and root Cd concentrations, upto threshold limits, in E. crassipes.     

Development of a colorimetric colony‐screening assay for detection of defluorination by micro‐organisms

Aims: To develop a colorimetric colony‐screening assay to facilitate the isolation of micro‐organisms capable of defluorination. Methods and Results: A metal‐dye chelate, zirconium‐xylenol orange was used to detect fluoride ions released from a fluorinated substrate through microbial metabolism. Depolymerised zirconium reagent gave the greatest visual contrast for the presence of fluoride compared to more polymerised forms of zirconium reagent. The sensitivity of the assay was greatest when the molar ratio of depolymerised zirconium to xylenol orange was 1 : 2. Using depolymerised zirconium and xylenol orange (150 and 300 nmol l^?1 respectively), the assay could detect a fluoride application spot (5 mmol l^?1) containing 50 nmoles of fluoride ions. Most media constituents were well tolerated by the assay, although phosphate ions needed to be restricted to 0·1 g l^?1 and some proteins digest to between 1 and 5 g l^?1. A microbial enrichment culture growing on solidified medium containing 20 mmol l^?1 fluoroacetate was screened using the assay, and defluorinating bacteria belonging to the genus Burkholderia isolated. Conclusions: A method was developed that is sensitive, rapid and reliable for detecting defluorination by micro‐organisms growing on solidified medium. Significance and Impact of the Study: This method can be used to facilitate the isolation of micro‐organisms capable of defluorination.