Biomedical subjects

Agnete Larsen

Publications and source records attributed to Agnete Larsen.

7 recordsLinked to original sources

PubMed2005

Gene expression changes induced by bismuth in a macrophage cell line.

We have investigated the effect of bismuth by autometallography, cell viability, TUNEL assay and microarray analysis of a macrophage cell line. The cells accumulate bismuth in their lysosomes in a time- and dose-dependent manner. Cell viability assays show a significant decrease in the number of viable cells related to both bismuth concentrations and exposure time. TUNEL assays after 12 h and 24 h at a bismuth-citrate concentration of 50 microM revealed the presence of 30% and 70% TUNEL-positive cells, respectively, compared with 8% in the controls. We have analysed gene expression profiles for cells exposed to 50 microM bismuth-citrate and for untreated controls at 12 h and 24 h by microarray analysis, which confirmed that bismuth is a powerful metallothionein inducer. A number of glycolytic enzymes are induced by bismuth, suggesting that bismuth is able to induce "hypoxia-like" stress. BCL2/adenovirus E1B 19-kDa-interacting protein 3 (Bnip3) has been suggested as a regulator of hypoxia-induced cell death independent of caspase-3 activation and cytochrome c release. Bnip3 is up-regulated indicating the involvement of Bnip3 as a possible mechanism for bismuth-induced cell death. Differences have been noticed in cell viability and in the modification of the mRNA expression levels at 12 and 24 h. Only 13 genes are modified at both these times, suggesting a time-dependent molecular cascade in which bismuth-exposed cells enter a dormant stage with mRNA down-regulation being followed by cell death of susceptible cells.

Animals↗

PubMed2005

In vivo distribution of bismuth in the mouse brain: influence of long-term survival and intracranial placement on the uptake and transport of bismuth in neuronal tissue.

Bismuth is used for a multitude of industrial purposes and has partly replaced toxic heavy metals such as lead and mercury in e.g. lubricants and shotgun pellets. In medicine, bismuth-compounds have long been used to remedy gastrointestinal disorders; lately in combination with antibiotics to treat Helicobacter pylori associated peptic ulcers. An epidemic episode of bismuth-induced encephalopathy in France in the 1970s revealed the neurotoxic potential of bismuth. This incidence, involving almost 1000 patients, remains unexplained and the contribution of other factors besides bismuth has been postulated. Recently an autometallographic technique made it possible to detect bismuth in morphologically intact tissue. In the present study, autometallographicly detectable bismuth was seen throughout the brain following intraperitoneal and intracranial exposure. The neuronal staining pattern seems highly organized with some areas heavily stained and others with low or no staining. Long-term (8 months) intraperitoneal exposure led to higher bismuth uptake than short-term (2 weeks) exposure. Following both intraperitoneal and intracranial exposure, high amounts of bismuth were found in the reticular and hypothalamic nuclei, in the oculomotor and hypoglossal nuclei and in Purkinje cells. Within the central nervous system (CNS) retrograde axonal transport was seen after intracranial bismuth exposure. Axonal transport seems to influence the distribution of bismuth as the highest uptake of bismuth after intraperitoneal exposure was seen in the facial and the trigeminal motor nuclei, i.e. neurones with processes outside the blood-brain barrier, whereas these nuclei contained no bismuth following ic exposure. Ultrastructurally, accumulation of bismuth was seen in lysosomes.

Animals↗

PubMed2004

Dynamic zinc pools in mouse choroid plexus.

We examined the presence of Zn-transporters (ZnT1, ZnT3, ZnT4, and ZnT6) proteins and zinc ions in rat choroid epithelium with immunohistochemistry and zinc selenide autometallography (ZnSe(AMG)). The four ZnT proteins were all expressed in the choroid epithelial cells. ZnT3 immunostaining was found in vesicle membranes in the apical part of the cells, associated to the microvillus membrane. Correspondingly, the ZnSe(AMG) technique revealed zinc ions in small vesicles, in microvilli, and multivesicular bodies in the epithelial cells. Traceable zinc ions were also found in lysosome-like organelles of fenestrated endothelial cells, but here no corresponding ZnT3 immunostaining was seen. The observations suggests that the choroid plexus is instrumental to regulation of the level of zinc ions in the cerebrospinal fluid.

Animals↗

PubMed2004

Abundance of zinc ions in synaptic terminals of mocha mutant mice: zinc transporter 3 immunohistochemistry and zinc sulphide autometallography.

The mocha mouse is an autosomal recessive pigment mutant on mouse chromosome 10 caused by a deletion in the gene for the delta subunit of the adaptor-like complex AP-3. Based on zinc transporter 3 (ZnT3) immunohistochemistry, zinc TSQ fluorescence and a modified Timm method, previous studies found a lack of histochemically-detectable zinc and a substantial reduction in the ZnT3 immunoreactivity. It has, therefore, been suggested that the mocha mouse could serve as a model for studies of the significance of zinc ions in zinc-enriched (ZEN) neurons. We have chosen the mocha-zinc-model in a study of the significance of ZEN neurons in hypoxia-caused damage in mouse brain. In order to establish that the model was either void of zinc ions or had a significantly decreased level of zinc ions in their ZEN terminals, we repeated the studies that had lead to the above assumption, the only methodology difference being that we used the zinc specific Neo-Timm method instead of the Timm method applied in the original study. We found that, although the ZnS autometallography (AMG) technique revealed a reduction in staining intensity as compared to the littermate controls, there were still plenty of zinc ions in the ZEN terminals, in particular visible in telencephalic structures like neocortex and hippocampus. At ultrastructural levels the zinc ions were found in a pool of vesicles of the ZEN terminals as in the control animals, but additionally zinc ions could be traced in ZEN neuronal somata in the neocortex and hippocampus. The mossy fibres in the hippocampus of mocha mice also bind with TSQ, though less than in the controls. We found ZnS AMG grains in ZEN neuronal somata, which were also immunoreactive for ZnT3. Our study confirmed the decreased ZnT3 immunoreactivity in ZEN terminals of the mocha mouse found in the original study. Based on these findings, we suggest that the mocha mouse may not be an ideal model for studies of the histochemically-detectable zinc ion pool of the central nervous system.

Animals↗

PubMed2003

Autometallographic tracing of mercury in pilot whale tissues in the Faroe Islands.

OBJECTIVES: Autometallography (AMG) was applied for tracing mercury in long-finned pilot whales (Globicephala melas) harvested in the Faroe Islands. RESULTS: Ample mercury accumulation was found in kidney tubules, in contrast to the largely unstained glomeruli. Hepatocytes, as well as liver macrophages, exhibited high mercury uptake. The muscle tissue accumulated only scant amounts of mercury, primarily around the nuclei of the striated muscle cells. At the ultrastructural level, mercury was found to accumulate intracellularly in lysosomes, and extracellularly in the basement membranes of vessels. The results were verified by proton induced X-ray emission (PIXE) analysis, and it was established that the tissue contained no other AMG traceable metals. CONCLUSION: The use of AMG analysis on autopsies and biopsies is suggested as a tool for evaluating mercury pollution.

Animals↗

PubMed2003

Gastrointestinal and systemic uptake of bismuth in mice after oral exposure.

Bismuth compounds have been used in medicine for more than 200 years. In recent years, bismuth has gained renewed interest as a remedy for eradication of gastrointestinal pathogens, especially Helicobacter pylori. In this study we describe the anatomical distribution of bismuth in the gastrointestinal tract and other organs after oral exposure in a mouse model. After exposure of the experimental animals to ranitidine bismuth citrate or bismuth citrate, we used the autometallographic silver enhancement technique to demonstrate the presence of bismuth in tissue samples from the gastrointestinal tract, liver, spleen, thymus, kidney and lymph nodes. We exposed cultured murine peritoneal macrophages to bismuth citrate and examined the bismuth accumulation over time. We found that in the mouse bismuth is absorbed systemically after a single dose of either compound, ranitidine bismuth more easily than bismuth citrate. Uptake could be shown in the stomach, duodenum, ileum and kidney for hours after exposure. Weeks after the exposure, deposits of bismuth were found in lymph nodes, liver, spleen and kidney as well as in macrophages in the gastrointestinal lamina propria. At the subcellular level, bismuth was found exclusively in lysosomes, primarily in macrophages and dendritic cells. Subsequent analyses of macrophage cultures showed lysosomal accumulations to be time and dose dependent.

Absorption↗

PubMedDate not supplied

Influence of bismuth on the number of neurons in cerebellum and hippocampus of normal and hypoxia-exposed mouse brain: a stereological study.

The industrial use of bismuth is increasing. In medicine, bismuth compounds have long been used in the treatment of gastrointestinal disorders, recently in combination with antibiotics for the treatment of Helicobacter pylori-associated peptic ulcers. Bismuth-induced encephalopathy is a known side-effect. One of the symptoms of bismuth encephalopathy is ataxia, suggesting possible cerebellar involvement. The introduction of autometallography (AMG) for tracing BiS/BiSe nanocrystals has provided histochemical evidence supporting the cerebellum being involved in bismuth encephalopathy, but the effect of bismuth on the neuron number in the cerebellum has never been evaluated. In vitro studies have indicated that CA1 neurons may be targets for bismuth intoxication, but results have been conflicting. Recently, the loss of dorsal root ganglion cells was reported after moderate bismuth exposure. This raises the question whether the use of another neurotoxic stimulus, such as hypoxia, amplifies the toxic effects of bismuth. Despite AMG-detectable bismuth accumulations, stereological examinations revealed no statistically significant decrease in the number of Purkinje, CA1 or CA3 neurons or in the volume of the cerebellar granule layer. Surprisingly, intermittent hypoxia led to a statistically significant loss of Purkinje cells without affecting the hippocampus. Bismuth neither ameliorated nor exacerbated the hypoxic effects on the cerebellum.

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