Bacterial communities associated with a mineral weathering profile at a sulphidic mine tailings dump in arid Western Australia.

We investigated bacterial community assemblages and functions down a hill slope contaminated by tailings from a volcanogenic massive sulphide mine in arid Western Australia. Weathering of waste rock, high in S and Fe, had resulted in a varying elemental dispersal down a face of the tailings hill. Bacterial community assemblage, characterised by PCR-DGGE fingerprinting, was significantly associated with electrical conductivity (E.C.) (ρ = 0.664; P < 0.01). Analysis of mobile salts showed that E.C. values were driven by ionic S, Zn, Cl and Al. The bacterial community assemblage was directly characterised across an E.C. gradient using an oligonucleotide microarray (PhyloChip). The dominant taxa at the site were Proteobacteria, Actinobacteria and Firmicutes; however, 37 phyla were detected. The most responsive taxa to variation in E.C. was Acidobacteria (negative correlation). Patterns of heterotrophic processes (BioLog analysis) were also best explained by variation in E.C. (ρ = 0.53; P < 0.01), showing a link between primary mineral weathering by lithotrophic bacteria and abiotic processes, and secondary biogeochemical processes by heterotrophic taxa. These data significantly broaden our knowledge of the bacteria present in metallomorphic ecosystems, establish that mobile phase elements are key drivers of community structure, and that primary biogeochemical cycling is directly influencing other geochemical interactions in the samples.

Enrichment and exposure assessment of As, Cr and Pb of the soils in the vicinity of Stawell, Victoria, Australia.

Stawell Gold Mine in NW Victoria, Australia, mines ores that contain large concentrations of As and significant quantities of the metals Pb and Cr. The aim of this research was to understand the dispersion, enrichment and probable exposure of these potentially hazardous elements around the mine site. Fifty-five surface soil samples were collected near the mine (<15 km) and analysed by ICP-MS/OES following bioavailable and four-acid extractions. Soils near the mine show greater concentrations of As, Cr and Pb than those near a regionally determined background. This is attributed to the combination of a natural geochemical halo around mineralization and anthropogenic dispersion due to mining and urbanization. Total As concentrations were between 16 and 946 mg kg(-1) near the mine in a regional background of 1-16 mg kg(-1). Total Cr concentrations were between 18 and 740 mg kg(-1) near the mine in a regional background of 26-143 mg kg(-1). Total Pb concentrations were between 12 and 430 mg kg(-1) near the mine in a regional background of 9-23 mg kg(-1). Dispersion of contaminant elements from the present ore processing is <500 m. The most enriched soils occur close to the town and are unrelated to present mining practices. The bioavailable As, Cr and Pb, soil ingestion rates and Risk Reference Doses were used to estimate health risks. An average toddler (12 kg) would need to consume at least 1.5 g, and most likely 12 g, of soil per day to show some symptoms of As toxicity. The maximum measured bioavailable As would pose a risk at average ingestion rates of 200 mg per day. Individuals with soil-eating disorders would exceed the safe daily consumption limits for As, and potentially Cr and Pb. Small children are not typically exposed to soil everyday, very few have soil eating disorders, and, therefore, the health risk from the soils around the mine is minimal.

Plant protection by the recombinant, root-colonizing Pseudomonas fluorescens F113rifPCB strain expressing arsenic resistance: improving rhizoremediation.

AIMS: The present study was designed to evaluate the stable insertion and expression of an arsenic resistance operon in the rhizosphere competent, PCB degrading strain Pseudomonas fluorescens F113rifPCB (F113rifPCB) and to investigate its ability to protect plants from arsenic. METHODS AND RESULTS: Introduction of the clone pUM3 (arsRDABC) into F113rifPCB was carried out by triparental conjugation. The resultant arsenic resistant strain was screened through a number of phenotypic tests including ability to grow on biphenyl, its rhizosphere competence and plant protection potential. CONCLUSIONS: Insertion and expression of arsenic resistant operon arsRDABC (from plasmid R773) into F113rifPCB strain has allowed this strain to grow, colonize the root and degrade biphenyl (100 mmol l(-1)) in the presence of sodium arsenate concentrations of up to 11.5 mmol l(-1). The strain retains its ability to colonize the rhizosphere of plants and appears to provide seed germination protection to arsenic which is not seen by the wild type. SIGNIFICANCE AND IMPACT OF THE STUDY: Owing to the significantly improved growth characteristics of both this rhizobacterium and plant species, the use of F113rifPCB-ars endowed with arsenic resistance capabilities may be a promising strategy to remediate mixed organic metal-contaminated sites. These types of strain could be used in the inoculation of metal accumulation plants for phytoremediation.

Enteric locus of action of prokinetics: ABT-229, motilin, and erythromycin.

We investigated the in vivo and in vitro locus of actions of prokinetics: motilin, erythromycin, and ABT-229. The test substances were infused close intra-arterially in short segments of the jejunum in the intact conscious state. Each prokinetic acted on a presynaptic neuron and utilized at least one nicotinic synapse to stimulate circular muscle contractions. The final neurotransmitter at the neuroeffector junction was ACh. Motilin and erythromycin, but not ABT-229, also released nitric oxide. Each prokinetic utilized somewhat different subtypes of muscarinic, serotonergic, tachykininergic, and histaminergic receptors, except for the M(3) receptor, which was common to all of them. In contrast, none of the prokinetics stimulated contractions in mucosa-free or mucosa-attached muscle strips, or rings, even though methacholine or electrical field stimulation induced phasic contractions in all of them. The prokinetics also did not release ACh in longitudinal muscle-myenteric plexus preparations. Each prokinetic, however, decreased the length of enzymatically dispersed single cells. In conclusion, each prokinetic may act on a different subset of presynaptic neurons that converge on the postsynaptic cholinergic and nonadrenergic noncholinergic motoneurons. The presynaptic neurons may be impaired in the muscle bath environment.

Interaction between blood flow and motility in normal and inflamed ileum.

The alterations in local and superior mesenteric blood flow during ileal inflammation and their correlations with motility in the normal and the inflamed ileum were investigated in the conscious state. Ileal inflammation decreased the local mesenteric blood flow but had no significant effect on the superior mesenteric blood flow. A significant reduction or an increase in local mesenteric blood flow in the normal or the inflamed ileum had no effect on local contractile activity. The vascular reactivity to vaso-dilators and vaso-constrictors was significantly reduced during inflammation. Local mesenteric blood flow increased significantly in the descending segment ahead of a caudal propagating giant migrating contraction. The local mesenteric blood flow oscillated during a migrating motor complex (MMC) cycle. We conclude that a several-fold increase or decrease in local mesenteric blood flow lasting for several minutes does not affect contractility. Ileal inflammation decreases local mesenteric blood flow but does not affect the total blood flow to the small intestine.

Immunocytes and abnormal gastrointestinal motor activity during ileitis in dogs.

Infiltration of specific immunocytes and stimulation of abnormal gastrointestinal motor activity during ileal inflammation induced by mucosal exposure to ethanol and acetic acid were investigated in 17 dogs. Ileal inflammation significantly increased the frequency of giant migrating contractions (GMCs) and decreased the frequency of migrating motor complexes (MMCs). The frequency of retrograde giant contractions (RGCs) increased only on the day of ethanol and acetic acid treatment. Diarrhea, urgency of defecation, and apparent abdominal discomfort were related to the increased frequency of GMCs. Ileal inflammation also prolonged the duration of postprandial MMC disruption. Histological and immunohistochemical findings indicated transmural inflammation with marked increase in polymorphonuclear cells in the lamina propria and muscularis externa layers. Myeloperoxidase activity increased severalfold in both layers. Cells containing interleukin-2 receptor (IL-2R) increased in the lamina propria. Other immunocytes, such as B and T lymphocytes, dendritic cells, and human leukocyte antigen DR-1 (HLADR)-positive cells, did not exhibit a significant increase in the inflamed ileum compared with the normal proximal jejunum. We conclude that stimulation of GMCs may be the major motility marker of intestinal inflammation.

Nitric oxide regulates migrating motor complex cycling and its postprandial disruption.

We investigated the role of nitric oxide (NO) in the regulation of migrating motor complex (MMC) cycling during the fasting state and its postprandial disruption. Intravenous infusion of N omega-nitro-L-arginine methyl ester (L-NAME) first produced a premature MMC and then disrupted MMC cycling for the rest of the day. The cycle length of the MMCs was significantly shorter than the control on the 2nd, 3rd, and 4th day after L-NAME infusion. The gastric cyclic motor activity (CMA) did not usually exhibit a premature cycle on the day of L-NAME infusion but was disrupted by L-NAME infusion; the duration of CMA disruption in the stomach was significantly longer than that of MMC disruption in the small intestine. Infusion of N omega-nitro-L-arginine (L-NNA) exhibited similar effects. The intravenous infusion of L-NAME also significantly shortened the duration of MMC disruption by a meal. L-Arginine alone had no significant effect on gastrointestinal motor activity during the fasting or the fed state, but when infused with L-NAME, it blocked the effects of NO synthase inhibition. Angiotensin II increased the mean arterial pressure to a level similar to that produced by L-NAME but had no significant effect on the fasting or the fed pattern of gastrointestinal motor activity. We conclude that NO containing nonadrenergic noncholinergic (NANC) neurons play a significant role in regulating MMC and CMA cycling during the fasting state and their disruption by a meal. However, NO may not be the only NANC neurotransmitter to inhibit contractions in the gut; phase I activity in the small intestine persisted during NO synthase inhibition by L-NAME or L-NNA.

Gastrointestinal motor effects of erythromycin in humans.

The effects of an antibacterially effective IV dose of erythromycin on gastrointestinal motor activity were investigated in eight normal healthy human volunteers in the fasted state and the fed state. Motor activity was recorded by a multilumen manometric tube. Data were analyzed visually and by a computer method. Blood samples were obtained for erythromycin and motilin assays. In the gastric antrum, erythromycin significantly increased the total duration, amplitude, and area under contractions from 0 to 60 minutes and frequency of contractions from 0 to 30 minutes from the start of its infusion in the fasted state. A similar response in the fed state occurred mostly from 0 to 30 minutes after the start of erythromycin infusion. By contrast, erythromycin inhibited the frequency and decreased the duration of small intestinal contractions in the fed state but had no effect in the fasted state. The gastric motor response was related to the plasma concentration of erythromycin, but not to plasma motilin. Erythromycin significantly shortened the duration of migrating motor complex disruption by a meal. Erythromycin also induced symptoms of upper abdominal pain, bloating, and nausea. Abdominal pain was related to strong antral contractions in both fasted and fed states; bloating occurred only in the fed state. Nausea occurred in both fasted and fed states, but it was not related to any specific pattern of motor activity. It is concluded that the strong antral contractions induced by erythromycin may accelerate the rate of gastric emptying, but they may also be responsible for causing the sensations of upper abdominal pain and bloating. The motor response to erythromycin is less during the fed than during the fasted state. The strong antral contractions induced by erythromycin are not mediated by the release of motilin.

Spatial and temporal patterns of human jejunal contractions.

We recorded human jejunal motor activity by a 12-lumen manometric tube with recording sites 2 cm apart. The contractile activity in the fasted and the fed state was analyzed by computer to define the spatial and temporal patterns of contractions. Mean duration and area of single contractions during phase III activity were not different from those during phase II activity. By contrast, the frequency and amplitude of contractions, their propagation distance, and the percentage of contractions that propagated for greater than or equal to 2 cm were significantly greater during phase III than during phase II activity. The mean frequency and percentage of propagated contractions in the fed state were intermediate between those during phase II and phase III activity. Mean propagation distance of postprandial contractions was not different from that of phase II contractions. Most contractions in the fed state were uncoordinated at adjacent recording sites. Occasionally, large-amplitude and long-duration contractions, called individual migrating contractions, propagated over long distances and frequently over the entire 22-cm study segment. We conclude that there are some significant differences between the spatial and temporal patterns of contractions between the fed state and phase II and phase III activity. The largely disorganized phasic contractions in the fed state may cause mostly mixing of the ingested meal and its slow distal propagation, whereas the infrequent individual migrating contractions may rapidly propel intestinal contents over longer distances.

Decreased ligand binding to the hepatic glucocorticoid and epidermal growth factor receptors after 2,3,4,7,8-pentachlorodibenzofuran and 1,2,3,4,7,8-hexachlorodibenzofuran treatment of pregnant mice.

2,3,4,7,8-Pentachlorodibenzofuran (PeCDF) and 1,2,3,4,7,8-hexachlorodibenzofuran (HCDF) are environmental contaminants which mimic many of the toxic effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Like TCDD, these polychlorinated dibenzofurans (PCDFs) induce hepatic benzo[a]pyrene hydroxylase activity (BPH) and possess high affinity for the Ah receptor. Another similarity of these PCDFs to TCDD is their ability to induce teratogenic effects such as cleft palate and hydronephrosis in mice. Recent studies have shown that TCDD modifies the equilibrium binding kinetics of the rat liver cytosolic glucocorticoid receptor (GRc) and the hepatic plasma membrane epidermal growth factor (EGF) receptor. To gain a better understanding of the action of halogenated hydrocarbons on these cytosolic and membrane-bound receptor systems during pregnancy, we investigated the biochemical effects of PeCDF and HCDF on the binding kinetics of maternal mouse liver GRc and EGF receptors and the induction of BPH activities. Pregnant C57BL/6N mice were treated once daily on gestation Days 10 through 13 with PeCDF (0-30 micrograms/kg) or HCDF (0-300 micrograms/kg). Hepatic [3H]dexamethasone and [125I]EGF equilibrium binding studies indicated that all doses of PeCDF tested (10, 20, and 30 micrograms/kg) significantly reduced the GRc and EGF receptor maximum binding capacities but did not affect the binding affinities of these receptors when compared to corn oil-treated control pregnant mice. Similar effects were observed for doses of HCDF greater than or equal to 100 micrograms/kg. These data suggest that the dibenzofuran-mediated decreases in GRc and EGF receptor binding capacities are similar to those caused by TCDD. Although the mechanism of action is not yet clear, our results indicate that halogenated aromatic compounds in addition to TCDD have profound effects on both steroid and growth factor receptor systems.

Cyproheptadine antagonism of p-chloroamphetamine hypothermia in mice.

Serotonin and 5-hydroxyindoleacetic acid levels were measured in the brains of mice following intraperitoneal administration of 10 mg/kg p-chloramphetamine (PCA). Indolyl levels were decreased at the 60 min interval, but were unchanged 30 min following PCA injection. PCA-induced hypothermia was found to be dependent upon dose and ambient temperature. Hypothermia was attenuated by cyproheptadine and slightly enhanced in the presence of fluoxetine. Mechanisms other than intraneuronal release and serotonin depletion appear to mediate PCA-induced hypothermia.

p-Chloroamphetamine antagonism of cobaltous chloride-induced hypothermia in mice.

Serotonin levels were measured in the brains of mice at 2 h and 10 days following the administration of a single dose of 10 mg/kg, i.p. of p-chloroamphetamine HCl (PCA). A 44% reduction in the concentration of brain serotonin was noted 2 h after PCA injection. No significant change in brain serotonin was observed 10 days following PCA administration. The time course of the body temperature response to cobaltous chloride (25 mg/kg, i.p.) was recorded 60 min following pretreatment with PCA (10 mg/kg, i.p.). PCA reduced the hypothermic response by approximately 60%, presumably through the depletion of central 5-hydroxytryptamine.