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Biomedical subjects

J J Powell

Publications and source records attributed to J J Powell.

At least 37 records · Page 2Linked to original sources
PubMed2001

Avoidance responses to aluminium in the freshwater bivalve Anodonta cygnea.

This study examined the effect of aluminium (Al) on the filtering behaviour (shell opening or gape) of the freshwater bivalve Anodonta cygnea L in neutral fresh water. Parallel measurements of Al concentration in the soft tissues were made to examine the relationship between changes in behaviour and accumulation of Al. The number of lysosomal granules in the gill, kidney and digestive gland were counted, as lysosomes are known to be involved in the excretion and detoxification of trace metals. The bivalves were exposed to two environmentally relevant concentrations of added Al i.e. 250 and 500 microg l(-1) (9.25 and 18.5 microM l(-1)) at neutral pH for 15 days and shell movement monitored continuously. Aluminium affected the mussels' filtering activity, producing an avoidance reaction whose magnitude was concentration-dependent; 250 microg l(-1) added Al produced no detectable change, while 500 microg l(-1) Al reduced mean duration of shell opening by 50%. This effect was irreversible over a 15 day recovery period. Tissue levels of Al after 15 days exposure were an order of magnitude higher in animals exposed to 250 microg l(-1) added Al than in those exposed to 500 microg l(-1). This was consistent with the inhibition of filtering activity due to valve closure at the higher concentration, which may have prevented uptake of Al. In addition, probable different chemical speciation of Al in the water column (soluble for 250 and colloidal for 500 microg l(-1)) may lead to marked differences in tissue uptake. The kidney and digestive gland were the main sites of accumulation of Al and concentrations remained significantly elevated 15 days after transfer of animals to clean water. It is suggested that mucus plays a role in the exclusion of Al as elevated concentrations were measured in the pseudofaeces of animals during and after exposure. Lysosomal granules may be involved in the intracellular handling and detoxification of Al as numbers increased significantly in all organs during exposure and continued to increase after the animals were transferred to clean water. The present study provides evidence for the bioavailability and toxicity of Al to mussels at neutral pH and at concentrations which are known to enter neutral freshwaters when mobilised by natural or anthropogenic acidity. The changes in behaviour and uptake of Al in the mussel observed in this investigation are, therefore, likely to be reflected in the natural environment and the degree to which Al affects the 'fitness' of the mussel populations and the transfer of Al through the food chain merit investigation.

Aluminum↗
PubMed2001

Rapid non-equilibrium aluminium-ligand interactions: studies on the precipitation of aluminium by laser light scattering, ultrafiltration and centrifugation.

The study aimed to develop simple assays to study aluminium-ligand interactions in natural/biological systems where equilibrium is rarely reached and thus where the initial seconds or hours of interactions are important. The immediate and non-equilibrium precipitation of aluminium hydroxide, in aqueous solution at neutral pH, was therefore studied by laser light scattering (diffraction), ultrafiltration and centrifugation. The interaction of weak ligands, present in the gastrointestinal lumen, on the precipitation of aluminium hydroxide was also investigated. The initial kinetics and particle sizes of precipitated aluminium hydroxide were sensitive to a number of external factors, including the presence of weak ligand (bicarbonate), sheer force (stirring), electrolyte concentration and initial (i.e. added) aluminium concentration. However, after a few seconds (no weak ligand), or several hundred seconds (with weak ligand), the subsequent observed changes to the solid phase were of small magnitude and occurred slowly. Thus, a 25-min window, within 5 and 30 min of pH adjustment, can be used to study the interactions of aluminium-ligand. This may approximate better to most natural systems where unperturbed aluminium-ligand equilibrium must rarely exist.

Aluminum↗
PubMed2001

Is eradication of Helicobacter pylori with colloidal bismuth subcitrate quadruple therapy safe?

BACKGROUND: When standard triple therapy fails to eradicate Helicobacter pylori, quadruple 'rescue' therapy is often used which, in Europe, generally comprises colloidal bismuth subcitrate (CBS) based triple therapy and a proton pump inhibitor. Since hypochlorhydria could greatly increase absorption of the toxic bismuth ion from CBS, we investigated the bismuth status of patients receiving anti-H. pylori quadruple therapy. MATERIALS AND METHODS: In a prospective open label study 34 patients with nonulcer dyspepsia or peptic ulcer disease, who had failed to eradicate H. pylori with standard triple therapy, were subsequently treated with CBS, omeprazole, amoxycillin and metronidazole (BOAM). A further 35 patients received triple therapy for the eradication of H. pylori: CBS, amoxycillin and metronidazole (BAM) (n = 18); placebo bismuth, amoxycillin and metronidazole (AM) (n = 9); or omeprazole, amoxycillin and metronidazole (OAM) (n = 8). Whole blood bismuth levels were determined before and within 24 hours of completing treatment. Analysis of bismuth was by inductively coupled plasma mass spectrometry, and concentrations were compared between groups and with the Hillemand 'alarm level' for blood bismuth (50-100 microg/l). RESULTS: BOAM gave higher blood bismuth levels than BAM (difference in means 13.1, CI 6.0-20.2, p <.001); three (8.8%) patients taking BOAM had concentrations within the Hillemand alarm level at 54.2, 64.7 and 91.8 microg/l. OAM and AM did not alter baseline blood bismuth levels. CONCLUSIONS: Caution should be observed in prescribing CBS with gastric acid suppression, and alternative bismuth preparations should be considered.

Adult↗
PubMed2001

Evidence against a role for polymorphisms at tumor necrosis factor, interleukin-1 and interleukin-1 receptor antagonist gene loci in the regulation of disease severity in acute pancreatitis.

BACKGROUND: Cytokines such as tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) and their endogenous antagonists such as IL-1 receptor antagonist (IL-1RA) are important mediators of disease severity in acute pancreatitis. Because the level of secretion of these cytokines is determined in part by genetic factors, the aim of this study was to examine the influence of genetically determined cytokine secretion upon disease severity in acute pancreatitis. METHODS: TNF (TNF-308, TNFB), IL-1beta, and IL-1 receptor antagonist (IL-1RA) genotypes were determined for 190 patients with acute pancreatitis and 102 healthy volunteers. To further assess the influence of genetic factors, the cytokine phenotype for TNF-alpha, IL-1beta, and IL-1RA was determined by using a whole blood culture technique in 51 patients after recovery. RESULTS: The distributions of TNF-308, TNFB, IL-1beta, and IL-1RA gene polymorphisms were similar in patients with mild or severe acute pancreatitis. Further, no difference in gene polymorphism frequencies was observed between patients with acute pancreatitis and healthy controls. With respect to phenotype, the secretion of TNF-alpha was similar in patients with previous mild and severe acute pancreatitis; however, the IL-1beta: IL-1RA ratio was significantly lower in patients with previous severe acute pancreatitis than in those with mild disease. CONCLUSIONS: Our observations suggest that genetic factors are not important in determining TNF-alpha secretion in patients with acute pancreatitis. However, a predetermined imbalance between IL-1beta and its antagonist IL-1RA would appear to exist in patients with severe acute pancreatitis, although the genetic basis for this altered relationship could not be determined.

Acute Disease↗
PubMed2001

Endothelial-derived selectins in the development of organ dysfunction in acute pancreatitis.

OBJECTIVE: The development of organ dysfunction is the principal determinant of outcome in acute pancreatitis and is mediated through a systemic inflammatory response characterized by leukocyte and endothelial cell activation. Up-regulation of the endothelial cell adhesion molecules, E-selectin and P-selectin, is important for endothelial/leukocyte interactions. Levels of serum-soluble E-selectin and P-selectin have been suggested as markers of endothelial activation. This study examines the kinetics of serum-soluble selectins in patients with acute pancreatitis complicated by organ dysfunction. DESIGN: Prospective observational study. SETTING: University teaching hospital with a specialist hepato-pancreatico-biliary service. PATIENTS: Eighteen patients with acute pancreatitis were studied, nine of whom had organ dysfunction. MEASUREMENTS AND MAIN RESULTS: Serial venous blood samples were collected on the first 3 days after admission for measurement of soluble E-selectin and P-selectin by enzyme-linked immunosorbent assay. In all patients, soluble P-selectin concentrations decreased significantly during the study period. Nonsurvivors had significantly higher levels of soluble P-selectin than survivors. In contrast, soluble E-selectin increased significantly during the study period in patients with organ dysfunction, whereas it remained constant in patients without evidence of organ dysfunction. CONCLUSIONS: These results suggest a role for endothelial-derived selectins in the development of organ dysfunction in patients with acute pancreatitis. The observed temporal differences in serum selectin concentrations is in keeping with in vitro observations of endothelial selectin expression.

APACHE↗
PubMed2001

Efficacy and tolerability of a low microparticle diet in a double blind, randomized, pilot study in Crohn's disease.

BACKGROUND: Ultrafine and fine particles are potent adjuvants in antigen-mediated immune responses, and cause inflammation in susceptible individuals. Following recent findings that microparticles accumulate in the phagocytes of intestinal lymphoid aggregates, this study is the first investigation of whether their reduction in the diet improves the symptoms of Crohn's disease. METHODS: In a double blind study, 20 patients with active corticosteroid-treated ileal or ileo-colonic Crohn's disease randomly received either a low microparticle diet (trial group; n = 10) or a control diet (n = 10) for 4 months. Crohn's disease activity index (CDAI) and corticosteroid requirements were compared. RESULTS: One patient in each group was withdrawn. In the trial group there was a progressive decrease in CDAI from entry (392 +/- 25) to month 4 (145 +/- 47) (P = 0.002 vs control group) and seven patients were in remission (CDAI <150). In contrast, the control group had returned to baseline levels (302 +/- 28 on entry and 295 +/- 25 at month 4), with none in remission. Corticosteroid intake was reduced more in the trial group although this did not reach significance. CONCLUSIONS: A low microparticle diet may be effective in the management of ileal Crohn's disease and could explain the efficacy of elemental diets, which similarly are low in microparticles.

Adult↗
PubMed2000

Aluminum toxicity in a molluscan neuron: effects of counterions.

Previous studies using the freshwater snail Lymnaea stagnalis have indicated significant accumulation of aluminum (Al) from simple salts (chloride or nitrate) or Al lactate [Al(lactate)3 preparations, but not from the Al maltol complex [Al(maltol)3]. This is in contrast to findings in mammalian systems, where uptake and neurotoxicity are greatest for the soluble and lipophilic Al(maltol)3 complex. This study was undertaken to investigate the direct effects of extracellular Al (100 microM) from three Al preparations [AlCl3, Al(lactate)3 and Al(maltol)3] on electrophysiological parameters of an identified neuron, the right parietal dorsal 1 (RPD1) neuron, of L. stagnalis in vitro. The effects of the corresponding counterion/ligand on the solubility and availability of Al in solution were also examined. Significant effects of Al on electrical properties, including membrane depolarization, increased firing activity, and abnormal firing patterns, were seen in the presence of AlCl3 and Al(lactate)3, which formed polyhydroxy and labile Al species in aqueous solution, but not with Al(maltol)3, which remained as the soluble monomeric complex. Qualitative differences were also observed between the response to AlCl3 and Al(lactate)3, despite their similar chemistry. The extent of action potential broadening was greater with Al(lactate)3, suggesting some interaction between Al and lactate in their cellular uptake and/or toxicity. It is suggested that polyhydroxy Al species are toxic to molluscan neurons, possibly via disruption of intracellular Ca2+ homeostasis.

Aluminum↗
PubMed2000

Immune potentiation of ultrafine dietary particles in normal subjects and patients with inflammatory bowel disease.

Various specific and non-specific environmental factors have been associated with the induction and/or exacerbation of disease activity in patients with Crohn's disease and ulcerative colitis. One such factor is the potential role of ingested ultrafine particles. In fact, based on a Western diet, recent data suggest that more than 10(12)ultrafine particles are ingested per person every day. These microparticles have been considered inert although they adsorb endogenous constituents of the intestinal lumen and are taken up by human intestinal lymphoid aggregates. Based on these observations, we determined whether one such dietary microparticle, titanium dioxide (TiO(2)), alters intestinal cell responsiveness to lipopolysaccharide (LPS) using colonic biopsy specimens from 28 patients with ulcerative colitis, 21 with Crohn's disease, and 36 healthy controls. These samples, as well as peripheral blood mononuclear cells when available, were incubated alone (control), or with either (a) LPS (1-2,000 ng/ml), (b) TiO(2)(5 microg/ml) or (c) LPS (1 ng/ml) adsorbed to TiO(2)(5 microg/ml). In each case, the levels of interleukin 1 (IL-1) produced in these assays were quantitated by bioassay and by ELISA. Interestingly, there was dramatic stimulation of peripheral blood mononuclear cells using the TiO(2)-LPS conjugate, with values 30-60-fold above controls and only minor stimulation with LPS or TiO(2)alone. In intestinal organ cultures there was no increase in IL-1 secretion when challenged with TiO(2)alone or with up to 2,000 ng/ml LPS. However, the TiO(2)-LPS conjugate produced a two-to-three-fold, significant increase in the intestinal secretion of IL-1. Our data demonstrate that ultrafine dietary particles are not immunologically inert and may be important adjuncts in overcoming normal gut cell hyporesponsiveness to endogenous luminal molecules. This may be particularly relevant to patients with inflammatory bowel disease where there is abnormal intestinal permeability.

Adjuvants, Immunologic↗
PubMed2000

Determination of titanium dioxide in foods using inductively coupled plasma optical emission spectrometry.

Titanium dioxide is a common food additive of increasing interest in dietary intake studies and dietary exclusion studies. Food labelling for titanium dioxide is imprecise so a method was developed for its rapid determination in foods using acid digestion and inductively coupled plasma optical emission spectrometry (ICPOES). Twenty-five foods thought to contain titanium dioxide were obtained. Based on preliminary digestion studies, samples (500 mg) were digested in 18 mol l-1 H2SO4 at 250 degrees C for 1 h and then diluted to 5.9 mol l-1 H2SO4 before determination of titanium by ICPOES at 336.121 nm. Emission intensity was suppressed by H2SO4 so standards were matched for acid concentration. Titanium dioxide embedded in gelatine was used to assess accuracy. A standard reference material of known titanium concentration and six foods of known titanium dioxide content were used as external reference materials. Limits of detection were 2-7.5 ppb, depending on spectral integration times, and the signal was linear up to 5 ppm. Results for all control samples were in good agreement with the expected values. Twelve of the foods contained detectable titanium, ranging from 0.001 to 0.782% by weight, but only eight indicated this on their labels, four being exempt under food labelling regulations. Based on food portion sizes, an individual's daily intake of titanium dioxide could exceed 200 mg from just one of these products. This method may facilitate future studies on titanium dioxide intake, given the present limitations of food labelling.

Food Additives↗
PubMed2000

Randomized controlled trial of the effect of early enteral nutrition on markers of the inflammatory response in predicted severe acute pancreatitis.

BACKGROUND: Recent evidence suggests that intestinal dysfunction has a role in sustaining the systemic inflammatory response in acute pancreatitis and may be ameliorated by the introduction of enteral nutrition. This study therefore assessed the effect of early enteral nutrition on the systemic inflammatory response in patients with prognostically severe acute pancreatitis. METHODS: Patients with prognostically severe acute pancreatitis within 72 h of disease onset were randomized to receive either enteral nutrition or conventional therapy consisting of a nil-by-mouth regimen. Serum interleukin (IL) 6, soluble tumour necrosis factor receptor I (sTNFRI) and C-reactive protein (CRP) were used as markers of the inflammatory response. Intestinal function was assessed using a differential sugar permeability technique. RESULTS: Of 27 patients, 13 received enteral nutrition. A median of 21 (range 0-100) per cent of calorific requirements was delivered over the first 4 days by enteral nutrition. There were no significant complications of enteral nutrition. The introduction of enteral nutrition did not affect the serum concentrations of IL-6 (P = 0.28), sTNFRI (P = 0.53) or CRP (P = 0.62) over the first 4 days of the study. Although there were no significant differences in intestinal permeability between the two patient groups at admission (chi2 = 2.33, d.f. = 1, P = 0.13), by day 4 abnormal intestinal permeability occurred more frequently in patients receiving enteral nutrition (chi2 = 4.94, d.f. = 1, P = 0.03) CONCLUSION: Early enteral nutrition did not ameliorate the inflammatory response in patients with prognostically severe acute pancreatitis. Furthermore, it did not have a beneficial effect on intestinal permeability. Presented in part to the Pancreatic Society of Great Britain and Ireland in Leeds, UK, November 1998 and at Digestive Disease Week in Orlando, Florida, USA, May 1999

Acute Disease↗
PubMed2000

Double-blind comparison of absorbable colloidal bismuth subcitrate and nonabsorbable bismuth subnitrate in the eradication of Helicobacter pylori and the relief of nonulcer dyspepsia.

BACKGROUND: Bismuth is widely used for the eradication of H. pylori, especially in developing countries, although there are concerns over its neurotoxicity. Whether bismuth has to be absorbed in humans to act against H. pylori is not known. In this study, we compared "absorbable" (colloidal bismuth subcitrate) and "nonabsorbable" (bismuth subnitrate) bismuth as part of triple therapy in the eradication of H. pylori. MATERIALS AND METHODS: A double-blind, randomized, placebo-controlled trial was carried out with 120 H. pylori-positive patients with nonulcer dyspepsia. Group CBS + Ab (n = 35) received colloidal bismuth subcitrate (one tablet qds), amoxicillin (500 mg qds), and metronidazole (400 mg tds). Group BSN + Ab (n = 35) received bismuth subnitrate (two tablets tds) and the same antibiotics. Group Ab (n = 35) received placebo bismuth (two tablets tds) and the antibiotics. Group BSN (n = 15) received bismuth subnitrate (two tablets tds) and placebo antibiotics. Bismuth was taken for 4 weeks and the antibiotics for the first 2 weeks. H. pylori eradication, side effects, compliance, pre- and post-treatment symptom scores, and bismuth absorption were assessed. RESULTS: H. pylori eradication was 69%, 83%, 31%, and 0% in CBS + Ab, BSN + Ab, Ab, and BSN, respectively. Side effects, compliance, and symptom relief were similar in all groups, but blood bismuth levels were significantly greater in CBS + Ab than the other three groups. CONCLUSION: The efficacy of bismuth-based therapies as part of triple therapy in the eradication of H. pylori is unrelated to absorption. Hence, the use of effective but poorly absorbed bismuth preparations should be encouraged for bismuth-based eradication therapies.

Adolescent↗
PubMed2000

Solubility, absorption, and anti-Helicobacter pylori activity of bismuth subnitrate and colloidal bismuth subcitrate: In vitro data Do not predict In vivo efficacy.

OBJECTIVES: The aim of this study was to compare the dissolution, bioavailability, and anti-Helicobacter pylori activity of bismuth subnitrate and colloidal bismuth subcitrate. This could, first, provide insights into the mechanism of action of bismuth and, second, help to develop optimal therapeutic strategies. METHODS: Solubility and aquated size of bismuth species were determined in human gastric juice, while absorption into blood and urinary excretion of bismuth was determined in volunteers. Activity against H. pylori was determined in vitro in the presence and absence of antibiotics, while H. pylori eradication was compared in vivo. RESULTS: Bismuth from colloidal bismuth subcitrate was at least 10% soluble and ultrafilterable and was absorbed in volunteers (>0.5%), whereas that from bismuth subnitrate was insoluble and not absorbed (<0.01%). Colloidal bismuth subcitrate was active against H. pylori (mean inhibitory concentration, </=12.5 microg/ml), while bismuth subnitrate was inactive (>400 microg/ml); neither was synergistic with antibiotics. With in vivo triple therapy, bismuth subnitrate was as effective as colloidal bismuth subcitrate in eradicating H. pylori (74% and 70% eradicated, respectively). CONCLUSIONS: Colloidal bismuth subcitrate, unlike bismuth subnitrate, is partially soluble, absorbed in humans, and directly toxic to H. pylori in vitro. Surprisingly, however, these preparations had similar efficacy in vivo against H. pylori within triple therapy, suggesting that bismuth compounds may also exhibit indirect antimicrobial effects. We propose that this is an effect on the gastric mucus layer. Nonabsorbable bismuth compounds should be preferentially considered in bismuth-based therapies against H. pylori, as they would minimize toxicity while maintaining efficacy.

Anti-Bacterial Agents↗
PubMed2000

A polymorphism of the interleukin-1 beta gene influences survival in pancreatic cancer.

Pro-inflammatory cytokines contribute to the cachexia associated with pancreatic cancer and stimulate the acute phase response which has been associated with shortened survival in such patients. Polymorphisms of cytokine genes may influence their production. The present study examined the effect of a polymorphism of the interleukin (IL)-1b gene upon the inflammatory state and survival in pancreatic cancer. Genomic DNA was obtained from 64 patients with pancreatic cancer and 101 healthy controls. Using the polymerase chain reaction and subsequent TaqI restriction enzyme digestion the subject's genotype for a diallelic polymorphism of the interleukin-1b gene was established. IL-1b production by peripheral blood mononuclear cells and serum C-reactive protein (CRP) levels from patients were also examined and survival noted. Patients homozygous for allele 2 of the IL-1b gene had significantly shorter survival than other groups (P = 0.0001). These patients also exhibited higher IL-1b production (P = 0.022). Possession of allele 2 was also associated with significantly shorter survival (median 144 vs 256 days, P = 0.034) and significantly higher CRP level (P = 0.0003). The possession of a genotype resulting in increased IL-1b production was associated with shortened survival and increased serum CRP level. This may reflect the role of IL-1b in inducing an acute phase protein response and cachexia in cancer or may be related to changes in tumour phenotype.

Adult↗
PubMed2000

Localization and fate of aluminium in the digestive gland of the freshwater snail Lymnaea stagnalis.

The digestive gland of the freshwater snail Lymnaea stagnalis, exposed to water containing an elevated concentration of aluminium at neutral pH for up to 30 days, followed by a 20 day recovery period, was examined by light and electron microscopy and X-ray microanalysis. Aluminium was localized in the yellow granules present in the digestive and excretory cells and in the green and small granules present in the digestive cells. More aluminium, silicon, phosphorus and sulphur were present in all three granule types from aluminium exposed snails. The number of yellow and green granules from the digestive gland of aluminium exposed snails showed a progressive increase over the experimental period compared to controls. The number and aluminium content of the granules is likely to reflect the role of the digestive gland as a 'sink' for accumulated aluminium. We propose that intracellular monomeric silica is involved in the detoxification of aqueous aluminium which at neutral pH is largely in the form of an insoluble polyhydroxide. The increased amounts of sulphur and phosphorus in the granules are likely to be part of a broad response to metal loading but probably do not play a significant role in the storage and detoxification of aluminium.

Aluminum↗
PubMed2000

Oligomeric but not monomeric silica prevents aluminum absorption in humans.

BACKGROUND: Soluble silica, a ubiquitous component of the diet, may be the natural ligand for dietary aluminum and may prevent its accumulation and toxicity in animals. However, previous studies on the inhibition of aluminum absorption and toxicity by soluble silica have produced conflicting results. We recently identified a soluble silica polymer, oligomeric silica, that has a much higher affinity for aluminum than does monomeric silica and that may be involved in the sequestration of aluminum. OBJECTIVE: By using (26)Al as a tracer, we investigated the effects of oligomeric and monomeric silica on the bioavailability of aluminum (study 1) and compared the availability of silicon from oligomeric and monomeric silica in the human gastrointestinal tract (study 2). DESIGN: In study 1, three healthy volunteers each ingested aluminum alone (control), aluminum with oligomeric silica (17 mg), and aluminum with monomeric silica (17 mg). In study 2, five healthy volunteers ingested both the oligomeric and monomeric forms of silica (34 mg). Serum and urine samples were analyzed for aluminum and silicon. RESULTS: Oligomeric silica reduced the availability of aluminum by 67% (P = 0.01) compared with the control, whereas monomeric silica had no effect (P = 0.40). Monomeric silica was readily taken up from the gastrointestinal tract and then excreted in urine (53%), whereas oligomeric silica was not detectably absorbed or excreted. CONCLUSIONS: The oligomeric, high-aluminum-affinity form of soluble silica reduces aluminum availability from the human gastrointestinal tract. Its potential role in the amelioration of aluminum toxicity in other biological systems requires attention.

Adult↗
PubMed2000

Assessment of iron absorption from ferric trimaltol.

Therapeutic iron compounds have limited absorption and often have side-effects, which limits patient compliance. Iron trimaltol is a novel, stable complex, formed between ferric iron (Fe3+) and maltol (3-hydroxy-2-methyl-4-pyrone), and is effective in the treatment of iron deficiency anaemia with few side-effects. However, the kinetics of iron absorption from ferric trimaltol and the reliability of normal colorimetric analysis in detecting iron absorbed from this complex have not been established. We measured increases in serum iron levels in 12 volunteers following oral challenge with four different pharmaceutical formulations of ferric trimaltol in a double-blind, cross-over, randomized study. The conventional colorimetric method for detecting serum iron was compared with thermal analyses after trichloroacetic acid (TCA) treatment of serum. Measurements of serum iron levels by TCA treatment and thermal analysis closely agreed with measurements by colorimetry. For all formulations, serum iron levels peaked at 90 min with a plateau of at least 5 h [mean (standard deviation) peak absorption 8.3% (6.3%) of ingested dose, n=48]. Absorption of iron, based on peak serum values or area under the serum curve, was not different for the four formulations (n=12 each) and correlated with the individual's iron status, as assessed by serum ferritin values (r = -0.6; P < 0.001). Normal colorimetry is suitable for analysis of serum iron levels following ingestion of ferric trimaltol. There is rapid and sustained absorption of iron from ferric trimaltol and, as with ferrous iron, uptake appears to be controlled through normal mechanisms of iron acquisition that depend upon body iron stores.

Adult↗
PubMed2000

Bioaccumulation and toxicity of aluminium in the pond snail at neutral pH.

The low solubility of aluminium (Al) at neutral pH means that it largely exists as colloidal particulates in aquatic systems. However, the pond snail Lymnaea stagnalis accumulates significant amounts of Al following exposure to water containing added Al (up to 500 microg l(-1)) at pH 7. This is accompanied by depression of behavioural activity (locomotion, feeding) which subsequently recovers, suggesting tolerance to the metal. The presence of silica ameliorates behavioural toxicity of Al, but does not prevent uptake of the metal. In vitro studies using the isolated central nervous system demonstrate toxicity at the cellular level. Extracellular application of Al (100 microM) led to membrane depolarisation, bursts of action potentials and action potential broadening. The chemical form in which Al is applied influences the extent of bioaccumulation and toxicity. Detailed knowledge of its solution chemistry is therefore essential.

Action Potentials↗