Metal(loid) speciation and transformation by aerobic methanotrophs

Manufacturing and resource industries are the key drivers for economic growth with a huge environmental cost (e.g. discharge of industrial effluents and post-mining substrates). Pollutants from waste streams, either organic or inorganic (e.g. heavy metals), are prone to interact with their physical environment that not only affects the ecosystem health but also the livelihood of local communities. Unlike organic pollutants, heavy metals or trace metals (e.g. chromium, mercury) are non-biodegradable, bioaccumulate through food-web interactions and are likely to have a long-term impact on ecosystem health. Microorganisms provide varied ecosystem services including climate regulation, purification of groundwater, rehabilitation of contaminated sites by detoxifying pollutants. Recent studies have highlighted the potential of methanotrophs, a group of bacteria that can use methane as a sole carbon and energy source, to transform toxic metal (loids) such as chromium, mercury and selenium. In this review, we synthesise recent advances in the role of essential metals (e.g. copper) for methanotroph activity, uptake mechanisms alongside their potential to transform toxic heavy metal (loids). Case studies are presented on chromium, selenium and mercury pollution from the tanneries, coal burning and artisanal gold mining, respectively, which are particular problems in the developing economy that we propose may be suitable for remediation by methanotrophs. Video Abstract.

Urinary excretion of arsenic following rice consumption

Patterns of arsenic excretion were followed in a cohort (n = 6) eating a defined rice diet, 300 g per day d.wt. where arsenic speciation was characterized in cooked rice, following a period of abstinence from rice, and other high arsenic containing foods. A control group who did not consume rice were also monitored. The rice consumed in the study contained inorganic arsenic and dimethylarsinic acid (DMA) at a ratio of 1:1, yet the urine speciation was dominated by DMA (90%). At steady state (rice consumption/urinary excretion) ∼40% of rice derived arsenic was excreted via urine. By monitoring of each urine pass throughout the day it was observed that there was considerable variation (up to 13-fold) for an individual's total arsenic urine content, and that there was a time dependent variation in urinary total arsenic content. This calls into question the robustness of routinely used first pass/spot check urine sampling for arsenic analysis.

Temporal pattern and effect of sex on lipopolysaccharide-induced stress hormone and cytokine response in pigs

The temporal pattern and sex effect of immune and stress hormone responses to a lipopolysaccharide (LPS) challenge were assessed using a pig model. Secretion of the pro-inflammatory cytokines tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, and IL-6 increased in a time-dependent manner following LPS infusion. There was also a time-dependent increase in secretion of the stress-related hormones cortisol, epinephrine (E), and norepinephrine (NE) following LPS, with peak concentrations attained within 30 min. The magnitude of the TNF-alpha and IL-1beta responses were both positively associated (P < 0.05) with the magnitude of cortisol response following LPS, whereas serum IL-1beta and IL-6 were positively correlated with the magnitude of E and NE responses following LPS. Acute-phase protein production was also time-dependently increased following LPS. The concentration of immune cells in circulation was decreased (P < 0.05) at 5.5h post-LPS and negatively correlated with pro-inflammatory cytokine production. By 24h post-LPS, immune cell counts increased (P < 0.05) and were positively associated with both pro-inflammatory cytokine and stress hormone production. The amplitude of pro-inflammatory cytokine response following LPS was affected (P < 0.05) by sex classification; however, the magnitude of elevated cytokine concentrations was not. The magnitude of the NE response, but not of the E and cortisol responses, to LPS was influenced by sex (P < 0.05). Similar to the pro-inflammatory cytokines, the magnitude of exposure to the stress hormones following LPS was not influenced by sex. The production of serum amyloid A (SAA) was influenced by sex, with barrows producing more SAA than gilts at 24h post-LPS (P < 0.05). Collectively, these results demonstrate sex-specific, concomitant temporal changes in innate immune- and stress-related hormones.

Baseline soil variation is a major factor in arsenic accumulation in Bengal Delta paddy rice

Factors responsible for paddy soil arsenic accumulation in the tubewell irrigated systems of the Bengal Delta were investigated. Baseline (i.e., nonirrigated) and paddy soils were collected from 30 field systems across Bangladesh. For each field, soil sampled at dry season (Boro) harvest i.e., the crop cycle irrigated with tubewell water, was collected along a 90 m transect away from the tubewell irrigation source. Baseline soil arsenic levels ranged from 0.8 to 21. mg/kg, with lower values found on the Pliestocene Terrace around Gazipur (average, 1.6 +/- 0.2 mg/kg), and higher levels found in Holecene sediment tracts of Jessore and Faridpur (average, 6.6 +/- 1.0 mg/kg). Two independent approaches were used to assess the extent of arsenic build-up in irrigated paddy soils. First, arsenic build-up in paddy soil at the end of dry season production (irrigated - baseline soil arsenic) was regressed against number of years irrigated and tubewell arsenic concentration. Years of irrigation was not significant (P = 0.711), indicating no year-on-year arsenic build-up, whereas tubewell As concentration was significant (P = 0.008). The second approach was analysis of irrigated soils for 20 fields over 2 successive years. For nine of the fields there was a significant (P < 0.05) decrease in soil arsenic from year 1 to 2, one field had a significant increase, whereas there was no change for the remaining 10. Over the dry season irrigation cycle, soil arsenic built-up in soils at a rate dependent on irrigation tubewell water, 35* (tubewell water concentration in mg/kg, triple bond mg/L). Grain arsenic rises steeply at low soil/shoot arsenic levels, plateauing out at concentratations. Baseline soil arsenic at Faridpur sites corresponded to grain arsenic levels at the start of this saturation phase. Therefore, variation in baseline levels of soil arsenic leads to a large range in grain arsenic. Where sites have high baseline soil arsenic, further additional arsenic from irrigation water only leads to a gradual increase in grain arsenic concentration.

High percentage inorganic arsenic content of mining impacted and nonimpacted Chinese rice

Two approaches were undertaken to characterize the arsenic (As) content of Chinese rice. First, a national market basket survey (n = 240) was conducted in provincial capitals, sourcing grain from China's premier rice production areas. Second, to reflect rural diets, paddy rice (n = 195) directly from farmers fields were collected from three regions in Hunan, a key rice producing province located in southern China. Two of the sites were within mining and smeltery districts, and the third was devoid of large-scale metal processing industries. Arsenic levels were determined in all the samples while a subset (n = 33) were characterized for As species, using a new simple and rapid extraction method suitable for use with Hamilton PRP-X100 anion exchange columns and HPLC-ICP-MS. The vast majority (85%) of the market rice grains possessed total As levels < 150 ng g(-1). The rice collected from mine-impacted regions, however, were found to be highly enriched in As, reaching concentrations of up to 624 ng g(-1). Inorganic As (As(i)) was the predominant species detected in all of the speciated grain, with As(i) levels in some samples exceeding 300 ng g(-1). The As(i) concentration in polished and unpolished Chinese rice was successfully predicted from total As levels. The mean baseline concentrations for As(i) in Chinese market rice based on this survey were estimated to be 96 ng g(-1) while levels in mine-impacted areas were higher with ca. 50% of the rice in one region predicted to fail the national standard.

Market basket survey shows elevated levels of As in South Central U.S. processed rice compared to California: consequences for human dietary exposure

We report the largest market basket survey of arsenic (As) in U.S. rice to date. Our findings show differences in transitional-metal levels between polished and unpolished rice and geographical variation in As and selenium (Se) between rice processed in California and the South Central U.S. The mean and median As grain levels for the South Central U.S. were 0.30 and 0.27 mimcrog As g(-1), respectively, for 107 samples. Levels for California were 41% lower than the South Central U.S., with a mean of 0.17 microg As g(-1) and a median of 0.16 microg As g(-1) for 27 samples. The mean and median Se grain levels for the South Central U.S. were 0.19 microg Se g(-1). Californian rice levels were lower, averaging only 0.08 and 0.06 microg Se g(-1) for mean and median values, respectively. The difference between the two regions was found to be significant for As and Se (General Linear Model (GLM): As p < 0.001; Se p < 0.001). No statistically significant differences were observed in As or Se levels between polished and unpolished rice (GLM: As p= 0.213; Se p= 0.113). No significant differences in grain levels of manganese (Mn), cobalt (Co), copper (Cu), or zinc (Zn) were observed between California and the South Central U.S. Modeling arsenic intake for the U.S. population based on this survey shows that for certain groups (namely Hispanics, Asians, sufferers of Celiac disease, and infants) dietary exposure to inorganic As from elevated levels in rice potentially exceeds the maximum intake of As from drinking water (based on consumption of 1 L of 0.01 mg L(-1) In. As) and Californian state exposure limits. Further studies on the transformation of As in soil, grain As bioavailability in the human gastrointestinal tract, and grain elemental speciation trends are critical.

The potential for kelp manufacture to lead to arsenic pollution of remote Scottish islands

Burning seaweed to produce kelp, valued for its high potash and soda content, was formerly a significant industry in remote coastal areas of Scotland and elsewhere. Given the high concentrations of arsenic in seaweeds, up to 100 mg kg(-1), this study investigates the possibility that the kelp industry caused arsenic contamination of these pristine environments. A series of laboratory-scale seaweed burning experiments was conducted, and analysis of the products using HPLC ICP-MS shows that at least 40% of the arsenic originally in the seaweed could have been released into the fumes. The hypothesis that the burning process transforms arsenic from low toxicity arsenosugars in the original seaweeds (Fucus vesiculosus and Laminaria digitata) to highly toxic inorganic forms, predominantly arsenate, is consistent with As speciation analysis results. A field study conducted on Westray, Orkney, once a major centre for kelp production, shows that elevated arsenic levels (10.7+/-3.0 mg kg(-1), compared to background levels of 1.7+/-0.2 mg kg(-1)) persist in soils in the immediate vicinity of the kelp burning pits. A model combining results from the burning experiments with data from historical records demonstrates the potential for arsenic deposition of 47 g ha(-1) year(-1) on land adjacent to the main kelp burning location on Westray, and for arsenic concentrations exceeding current UK soil guideline values during the 50 year period of peak kelp production.

Arsenic sequestration in iron plaque, its accumulation and speciation in mature rice plants (Oryza sativa L.)

A compartmented soil-glass bead culture system was used to investigate characteristics of iron plaque and arsenic accumulation and speciation in mature rice plants with different capacities of forming iron plaque on their roots. X-ray absorption near-edge structure spectra and extended X-ray absorption fine structure were utilized to identify the mineralogical characteristics of iron plaque and arsenic sequestration in plaque on the rice roots. Iron plaque was dominated by (oxyhydr)oxides, which were composed of ferrihydrite (81-100%), with a minor amount of goethite (19%) fitted in one of the samples. Sequential extraction and XANES data showed that arsenic in iron plaque was sequestered mainly with amorphous and crystalline iron (oxyhydr)oxides, and that arsenate was the predominant species. There was significant variation in iron plaque formation between genotypes, and the distribution of arsenic in different components of mature rice plants followed the following order: iron plaque > root > straw > husk > grain for all genotypes. Arsenic accumulation in grain differed significantly among genotypes. Inorganic arsenic and dimethylarsinic acid (DMA) were the main arsenic species in rice grain for six genotypes, and there were large genotypic differences in levels of DMA and inorganic arsenic in grain.

Arsenic sequestration in iron plaque, its accumulation and speciation in mature rice plants (Oryza sativa L.)

A compartmented soil-glass bead culture system was used to investigate characteristics of iron plaque and arsenic accumulation and speciation in mature rice plants with different capacities of forming iron plaque on their roots. X-ray absorption near-edge structure spectra and extended X-ray absorption fine structure were utilized to identify the mineralogical characteristics of iron plaque and arsenic sequestration in plaque on the rice roots. Iron plaque was dominated by (oxyhydr)oxides, which were composed of ferrihydrite (81-100%), with a minor amount of goethite (19%) fitted in one of the samples. Sequential extraction and XANES data showed that arsenic in iron plaque was sequestered mainly with amorphous and crystalline iron (oxyhydr)oxides, and that arsenate was the predominant species. There was significant variation in iron plaque formation between genotypes, and the distribution of arsenic in different components of mature rice plants followed the following order: iron plaque > root > straw > husk > grain for all genotypes. Arsenic accumulation in grain differed significantly among genotypes. Inorganic arsenic and dimethylarsinic acid (DMA) were the main arsenic species in rice grain for six genotypes, and there were large genotypic differences in levels of DMA and inorganic arsenic in grain.

Increase in rice grain arsenic for regions of Bangladesh irrigating paddies with elevated arsenic in groundwaters

Concern has been raised by Bangladeshi and international scientists about elevated levels of arsenic in Bengali food, particularly in rice grain. This is the first inclusive food market-basket survey from Bangladesh, which addresses the speciation and concentration of arsenic in rice, vegetables, pulses, and spices. Three hundred thirty aman and boro rice, 94 vegetables, and 50 pulse and spice samples were analyzed for total arsenic, using inductivity coupled plasma mass spectrometry (ICP-MS). The districts with the highest mean arsenic rice grain levels were all from southwestern Bangladesh: Faridpur (boro) 0.51 > Satkhira (boro) 0.38 > Satkhira (aman) 0.36 > Chuadanga (boro) 0.32 > Meherpur (boro) 0.29 microg As g(-1). The vast majority of food ingested arsenic in Bangladesh diets was found to be inorganic; with the predominant species detected in Bangladesh rice being arsenite (AsIII) or arsenate (AsV) with dimethyl arsinic acid (DMAV) being a minor component. Vegetables, pulses, and spices are less important to total arsenic intake than water and rice. Predicted inorganic arsenic intake from rice is modeled with the equivalent intake from drinking water for a typical Bangladesh diet. Daily consumption of rice with a total arsenic level of 0.08 microg As g(-1) would be equivalent to a drinking water arsenic level of 10 microg L(-1).

Variation in arsenic speciation and concentration in paddy rice related to dietary exposure

Ingestion of drinking water is not the only elevated source of arsenic to the diet in the Bengal Delta. Even at background levels, the arsenic in rice contributes considerably to arsenic ingestion in subsistence rice diets. We set out to survey As speciation in different rice varieties from different parts of the globe to understand the contribution of rice to arsenic exposure. Pot experiments were utilized to ascertain whether growing rice on As contaminated soil affected speciation and whether genetic variation accounted for uptake and speciation. USA long grain rice had the highest mean arsenic level in the grain at 0.26 microg As g(-1) (n = 7), and the highest grain arsenic value of the survey at 0.40 microg As g(-1). The mean arsenic level of Bangladeshi rice was 0.13 microg As g(-1) (n = 15). The main As species detected in the rice extract were AsIII, DMAV, and AsV. In European, Bangladeshi, and Indian rice 64 +/- 1% (n = 7), 80 +/- 3% (n = 11), and 81 +/- 4% (n = 15), respectively, of the recovered arsenic was found to be inorganic. In contrast, DMAV was the predominant species in rice from the USA, with only 42 +/- 5% (n = 12) of the arsenic being inorganic. Pot experiments show that the proportions of DMAV in the grain are significantly dependent on rice cultivar (p = 0.026) and that plant nutrient status is effected by arsenic exposure.

Transfer of research-based HIV prevention interventions to community service providers: fidelity and adaptation

HIV prevention research interventions usually follow protocols with specific procedures. If a community-delivered intervention uses the same procedures with the same populations as those in the original research, the behavior change effects should be similar. However, community-based providers may not replicate an intervention exactly as it was conducted in the effectiveness study. Adaptation may be needed to better meet the needs of the clients, community, or organization. We propose that interventions can be defined in terms of core elements likely to be responsible for effectiveness. These core elements cannot be changed without fundamentally changing the intervention, whereas other characteristics may be modified without altering effectiveness. HIV prevention researchers and service providers can collaborate to develop interventions that not only are effective but can also be successfully implemented by service organizations. If researchers actively involve service providers and community members in intervention planning, technology transfer goals can be better achieved.

Validation of a liquid chromatographic tandem mass spectrometric method for the determination of sumatriptan in human biological fluids

A liquid chromatographic tandem mass spectrometric method for the quantitative determination of sumatriptan base in human plasma and urine has been developed and validated over the concentration range 0.2-20 ng base ml-1. Sumatriptan is a 5-HT1 receptor agonist which has found widespread use in the treatment of migraine. Sumatriptan and its internal standard (D3-sumatriptan) were extracted from human matrices using C2 solid phase cartridges. The extracts were chromatographed on a C18 column, ionised using a heated nebuliser assisted atmospheric pressure ionisation (API) interface and detected by MS/MS in the multiple reaction monitoring mode. The completed validation demonstrated the method to be robust, accurate, precise and specific for the direct quantification of sumatriptan in human fluids. The method was used on a routine basis to determine the levels of sumatriptan in human volunteers following the oral administration of a 25 mg dose of sumatriptan succinate.

A prospective study in high risk subjects of electrocardiographic changes with ivermectin

Thirty-two elderly Liberian men, mean age 61 years, were treated with ivermectin and serial electrocardiograms (EKG's) were performed. Twenty of the 32 (62.5%) had baseline EKG abnormalities including poor R wave progression, 1 degrees AV block, non-specific intraventricular conduction abnormalities, left anterior hemiblock, supraventricular premature beats, left axis deviation, and early repolarization. Twelve lead EKG's were done twice daily, pretreatment and on five occasions post-treatment. No significant changes and no new abnormalities were observed. This study fails to demonstrate any significant cardiac effect of ivermectin.

Effect of mass treatment of a human population with ivermectin on transmission of Onchocerca volvulus by Simulium yahense in Liberia, West Africa

The impact of mass treatment with ivermectin on the intensity of Onchocerca volvulus transmission by the black fly (Simulium yahense) was evaluated on the Liberian Agricultural Company rubber plantation in Liberia, West Africa. The adult pre-treatment prevalence of onchocerciasis was greater than 80%, and the average intensity of infection was 5.35 mf/mg of skin. The drug was administered at 2 annual intervals, reaching 58-60% of the approximately 14,000 people living in 73 camps. Landing/biting catches of black flies made in central and peripheral plantation zones indicated similar fly activity before and after ivermectin treatment (man hr index of 2.1 and 2.4 within the plantation, and 10 and 10.9 outside the plantation, respectively). The number of infected flies with developing larvae (L1, L2, L3 stages) of O. volvulus in treated areas was reduced by 93.4-95%; the number of infective flies with L3 larvae was reduced by 81.7-89.3%. Parasite loads of infected (L1, L2) and infective flies (L3 stages only) outside the plantation also decreased by 86.8% and 80%, respectively. Monthly transmission potential (MTP) showed a similar decrease: from 22.9 to 5.8 (74.6% reduction) in the treated area, and from 210 to 158.8 (24.4% reduction) in untreated areas. Mass treatment with ivermectin efficiently controlled, and at least temporarily interrupted, transmission of Onchocerca volvulus by black fly vectors.

Community-based treatment of onchocerciasis with ivermectin: acceptability and early adverse reactions

A study of community-based treatment of onchocerciasis with ivermectin was undertaken in a rain forest area of Liberia to investigate the possible occurrence of serious adverse effects. The total population was 13,704, the microfilarial load was 5.35 mf/mg skin, and the prevalence of Onchocerca volvulus infection was 50% at 9 years of age and over 80% among those aged 15 years and older. Certain groups (like pregnant women and young children) were excluded from treatment. Out of the 7956 people eligible for treatment, 7699 (97%) accepted the ivermectin. Data on possible adverse reactions were collected by four different methods, including systematic house-by-house follow-up visits three days after treatment, biweekly population surveillance, and monitoring of both mobile clinic records and hospital records. No severe adverse reactions were noted, and no deaths could be related to ivermectin treatment; only 1.3% of the persons treated had a moderate adverse reaction of the Mazzotti type, presumably related to the killing of microfilariae. The study showed good acceptance by the population, and that mass treatment campaigns with ivermectin are feasible.

Effect of single-dose ivermectin therapy on human Onchocerca volvulus infection with onchocercal ocular involvement

Ivermectin has shown promise as a potentially safe and effective microfilaricidal drug for the treatment of onchocerciasis. Several limited studies have shown it to have fewer side effects, especially ocular complications, than the currently available drug, diethylcarbamazine. The detailed ocular findings in 200 moderately to heavily infected Liberians who were enrolled in a safety and dose-finding study are presented. They received either 0, 100, 150, or 200 micrograms/kg of ivermectin and were followed up for 12 months. In clinical studies so far carried out ivermectin in a dose of 100, 150, or 200 micrograms/kg has not been associated with any major adverse reactions nor were there any sight-threatening effects even in the presence of severe ocular disease. Each of these doses significantly reduced the ocular microfilaria load for at least 12 months when compared with either the placebo (p less than 0.05) or pretreatment values (p less than 0.001). However, the 100 and 150 micrograms/kg doses caused fewer minor side effects than the higher dose. These results confirm that ivermectin in a single oral dose may be a safe and effective microfilaricidal drug for the treatment of onchocerciasis and that it appears to be free of major ocular side effects.

Controlled trial and dose-finding study of ivermectin for treatment of onchocerciasis

Ivermectin, given as a single oral dose, has shown considerable promise as a new treatment for onchocerciasis. We assessed the safety and efficacy of ivermectin and tried to determine the optimal dose. Two hundred Liberians received 100, 150, or 200 micrograms of ivermectin/kg or placebo and were followed up for 12 months. Therapy was associated with only minimal systemic and ocular side effects. A 200-micrograms/kg dose was associated with greater systemic reaction than was a 100-micrograms/kg dose. Each treatment group had significant reduction in skin microfilaria counts by day 3 and a decrease of approximately 95% at three months. At three months the proportion of persons with no microfilariae in a specimen of skin was significantly less in the 100-micrograms/kg group than in the 150-micrograms/kg or 200-micrograms/kg groups. At 12 months, the level of microfilariae in skin was still reduced approximately 80%. Significant reduction in ocular involvement was seen in all groups. These results confirm that single-dose ivermectin is effective and well-tolerated and suggest that 150 micrograms of ivermectin/kg may be the optimal dose for initial therapy.

A DNA sequence specific for forest form Onchocerca volvulus

Onchocerciasis, or river blindness, is caused by infection with Onchocerca volvulus, a filarial parasite which infects about 40 million people in Africa and Latin America. Epidemiological, clinical, entomological and serological studies of African onchocerciasis led to the hypothesis that Onchocerca volvulus exists in different forms in the forest and savannah. It is uncertain if these differences are due to genetic differences within O. volvulus itself, or to epigenetic factors, such as differences in the host populations. To date no basic biochemical differences between the forest and savannah populations of O. volvulus has been found, although isoenzyme studies have shown that differences in allele frequency between forest and savannah populations exist. Here we describe the isolation of a DNA sequence that seems to be specific for the forest form of O. volvulus, the first indication of a basic genetic difference between the savannah and forest forms.

Ivermectin effect on microfilariae of Onchocerca volvulus after a single oral dose in humans

Ivermectin is a broad spectrum anti-helminthic agent which is currently being tested for use in human onchocerciasis. Its activity is believed to result from its effect on GABA-mediated neurotransmission. We examined the effects of ivermectin on motility of microfilariae of O. volvulus following administration to humans. When ivermectin was given in dosages of 100, 150 and 200 mcg/kg on day 1 there was a clear reduction in motility of microfilariae obtained on day 3 when compared to microfilariae from the placebo group. The mean motility scores in microfilariae from ivermectin recipients were 3.1, 2.3, and 2.2 at 0, 12, and 24 hours of incubation compared to 3.3, 2.9, and 2.5, respectively, in microfilariae from placebo recipients (p less than 0.003, p less than 0.005, and p less than 0.012, respectively). Examination of the effect according to dose suggested a dose-response relationship. Microfilariae in the anterior chamber of the eye 2 days after a single oral dose of ivermectin showed abnormal and reduced winding and coiling. Microfilariae in 50% of ivermectin recipients showed abnormal motility compared to no such effects in subjects examined concurrently who received oral DEC, DEC lotion or placebo. These observations indicate that ivermectin has an effect on motility of microfilariae of O. volvulus following administration to humans.

A double blind controlled trial of Bencard house dust mite (Migen) hyposensitisation in Zambian asthmatics

A double blind controlled trial of Bencard HDM (Migen) for the prophylaxis of asthma in a group of Zambian asthmatics failed to show any benefit. The trial results suggest that asthmatics can benefit from regular supervision and the position of prophylactic and therapeutic medication.