Biomedical subjects

Gorm Danscher

Publications and source records attributed to Gorm Danscher.

At least 19 recordsLinked to original sources

PubMed2006

Localization of ZnT7 and zinc ions in mouse retina--immunohistochemistry and selenium autometallography.

Zinc transporter 7 (ZnT7, Slc30a7), a member of the Slc30 family, is involved in mobilizing zinc ions from the cytoplasm into the Golgi apparatus. In the present study, we examined the distribution and localization of ZnT7 and the labile zinc ions in the mouse retina using immunohistochemistry and in vivo zinc-selenium autometallography (ZnSe(AMG)). Our results showed that ZnT7 is abundantly expressed in the ganglion cells and pigment epithelial cells of the mouse retina. ZnT7 is also expressed in the amacrine cells and the layer of optic fibers of the mouse retina, but to a lesser extent. Weak staining of ZnT7 was detected in the inner plexiform layer, outer plexiform layer, and outer segment of the photoreceptors. However, ZnT7 was not detected in the outer nuclear layer and inner segment of the photoreceptors. A high level of labile zinc pool was detected in the pigment epithelial cells, the inner segment of the photoreceptors, and the marginal region of the inner nuclear layer. Less amount of labile zinc ions were detected in the ganglion cells of the retina. These observations strongly suggest that ZnT7 may play critical roles in retinal zinc homeostasis and that chelatable zinc pools may have multiple functions in the retina.

Amacrine Cells↗

PubMed2006

Silver enhancement of quantum dots resulting from (1) metabolism of toxic metals in animals and humans, (2) in vivo, in vitro and immersion created zinc-sulphur/zinc-selenium nanocrystals, (3) metal ions liberated from metal implants and particles.

Autometallographic (AMG) silver enhancement is a potent histochemical tool for tracing a variety of metal containing nanocrystals, e.g. pure gold and silver nanoclusters and quantum dots of silver, mercury, bismuth or zinc, with sulphur and/or selenium. These nanocrystals can be created in many different ways, e.g. (1) by manufacturing colloidal gold or silver particles, (2) by treating an organism in vivo with sulphide or selenide ions, (3) as the result of a metabolic decomposition of bismuth-, mercury- or silver-containing macromolecules in cell organelles, or (4) as the end product of histochemical processing of tissue sections. Such nano-sized AMG nanocrystals can then be silver-amplified several times of magnitude by being exposed to an AMG developer, i.e. a normal photographic developer enriched with silver ions. The present monograph attempts to provide a review of the autometallographic silver amplification techniques known today and their use in biology. After achieving a stronghold in histochemistry by Timm's introduction of the "silver-sulphide staining" in 1958, the AMG technique has evolved and expanded into several different areas of research, including immunocytochemistry, tracing of enzymes at LM and EM levels, blot staining, retrograde axonal tracing of zinc-enriched (ZEN) neurons, counterstaining of semithin sections, enhancement of histochemical reaction products, marking of phagocytotic cells, staining of myelin, tracing of gold ions released from gold implants, and visualization of capillaries. General technical comments, protocols for the current AMG methods and a summary of the most significant scientific results obtained by this wide variety of AMG histochemical approaches are included in the present article.

Animals↗

PubMed2006

Neurotoxic zinc translocation into hippocampal neurons is inhibited by hypothermia and is aggravated by hyperthermia after traumatic brain injury in rats.

Hypothermia reduces excitotoxic neuronal damage after seizures, cerebral ischemia and traumatic brain injury (TBI), while hyperthermia exacerbates damage from these insults. Presynaptic release of ionic zinc (Zn2+), translocation and accumulation of Zn2+ ions in postsynaptic neurons are important mechanisms of excitotoxic neuronal injury. We hypothesized that temperature-dependent modulation of excitotoxicity is mediated in part by temperature-dependent changes in the synaptic release and translocation of Zn2+. In the present studies, we used autometallographic (AMG) and fluorescent imaging of N-(6-methoxy-8-quinolyl)-para-toluenesulfonamide (TSQ) staining to quantify the influence of temperature on translocation of Zn2+ into hippocampal neurons in adult rats after weight drop-induced TBI. The central finding was that TBI-induced Zn2+ translocation is strongly influenced by brain temperature. Vesicular Zn2+ release was detected by AMG staining 1 h after TBI. At 30 degrees C, hippocampus showed almost no evidence of vesicular Zn2+ release from presynaptic terminals; at 36.5 degrees C, the hippocampus showed around 20% to 30% presynaptic vesicular Zn2+ release; and at 39 degrees C vesicular Zn2+ release was significantly greater (40% to 60%) than at 36.5 degrees C. At 6 h after TBI, intracellular Zn2+ accumulation was detected by the TSQ staining method, which showed that Zn2+ translocation also paralleled the vesicular Zn2+ release. Neuronal injury, assessed by counting eosinophilic neurons, also paralleled the translocation of Zn2+, being minimal at 30 degrees C and maximal at 39 degrees C. We conclude that pathological Zn2+ translocation in brain after TBI is temperature-dependent and that hypothermic neuronal protection might be mediated in part by reduced Zn2+ translocation.

Animals↗

PubMed2005

Abundant expression of zinc transporters in Bergman glia of mouse cerebellum.

Zinc transporters (ZnTs) are membrane proteins involved in zinc ion transportation in mammalian cells. Seven members of ZnT family, ZnT1-7, have been cloned and characterized. These transporter proteins have different cellular and sub-cellular locations, suggesting that they may play different roles in zinc homeostasis in normal and pathological conditions in different tissues. Cerebellum is one of the most zinc-enriched regions in the central nervous system, but little is known about zinc metabolism in the cerebellum. In the present study, we investigated the detailed distributions of four members (ZnT1, ZnT3, ZnT4 and ZnT6) of the ZnT family, in the mouse cerebellum. Immunostaining and confocal microscopic observations revealed a similar staining pattern of ZnTs in the molecular layer and the Purkinje cell layer. Double labeling with anti-S-100beta or anti-MAP2 and anti-ZnTs clearly showed that the Bergman glial cell bodies in the Purkinje cell layer and their radial processes in the molecular layer exhibited strong immunofluorescence of all the tested ZnTs. However, the somata of the Purkinje cells contained a moderate immunostaining for ZnT1, but virtually lack of other three ZnTs. In the granular layer, ZnTs appeared with different immunostaining patterns. ZnT1 was expressed in a small number of neuronal cell bodies and their primary dendrites, whereas ZnT3 and ZnT4 were present in nerve terminals but not in the neuronal somata. ZnT6 was undetectable in either the cell bodies or processes in the granular layer. The present results indicate that the Bergman glial cells may play an important role in zinc metabolism in the mouse cerebellar cortex.

Animals↗

PubMed2005

Adrenalectomy-induced ZnT3 downregulation in mouse hippocampus is followed by vesicular zinc depletion.

The effects of adrenalectomy (ADX) on the vesicular zinc content of zinc-enriched (ZEN) terminals in mouse hippocampus were investigated at light microscopic levels using zinc transporter-3 immunohistochemistry (ZnT3IHC) and zinc selenium autometallography (ZnSeAMG). ZnT3 resides in the synaptic vesicle membranes of ZEN neurons and is believed to move zinc ions into the vesicles. ZnT3IHC staining closely corresponds to the ZnSeAMG staining, but in the present study we present evidence of a delayed decrease of ZEN zinc, as compared to downregulation of the ZnT3 protein following ADX. Twenty-four hours after adrenalectomy the level of ZnT3IHC was visibly reduced while the ZnSeAMG staining intensity seemed unchanged. After 10 and 30 days, however, downregulation of ZnT3 was paralleled by a distinct reduction in ZnSeAMG staining. The total protein concentration of ZnT3 was reduced by about 53%, and the total zinc concentration in the hippocampus of the same mice was reduced by 43-64%, 30 days after the adrenalectomy. The present results support previous results suggesting that ZnT3 is responsible for transport of zinc ions into a pool of synaptic vesicles in ZEN terminals.

Adrenalectomy↗

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↗

PubMed2005

Zinc-specific autometallographic in vivo selenium methods: tracing of zinc-enriched (ZEN) terminals, ZEN pathways, and pools of zinc ions in a multitude of other ZEN cells.

In vivo-applied sodium selenide or sodium selenite causes the appearance of zinc-selenium nanocrystals in places where free or loosely bound zinc ions are present. These nanocrystals can in turn be silver enhanced by autometallographic (AMG) development. The selenium method was introduced in 1982 as a tool for zinc-ion tracing, e.g., in vesicular compartments such as synaptic vesicles of zinc-enriched (ZEN) terminals in the central nervous system, and for visualization of zinc ions in ZEN secretory vesicles of, e.g., somatotrophic cells in the pituitary, zymogene granules in pancreatic acinar cells, beta-cells of the islets of Langerhans, Paneth cells of the crypts of Lieberkühn, secretory cells of the tubuloacinar glands of prostate, epithelium of parts of ductus epididymidis, and osteoblasts. If sodium selenide/selenite is injected into brain, spinal cord, spinal nerves containing sympathetic axons, or intraperitoneally, retrograde axonal transport of zinc-selenium nanocrystals takes place in ZEN neurons, resulting in accumulation of zinc-selenium nanocrystals in lysosomes of the neuronal somata. The technique is, therefore, also a highly specific tool for tracing ZEN pathways. The present review includes an update of the 1982 paper and presents evidence that only zinc ions are traced with the AMG selenium techniques if the protocols are followed to the letter.

Animals↗

PubMed2004

Does selenium deficiency unmask mercury toxicity in motor neurons?

OBJECTIVE: Inorganic mercury enters in particular motor neurons and has been implicated in motor neuron diseases. One way that cells protect themselves from mercury toxicity is via selenium, so we sought to determine whether the motor neurons of mice on a low selenium diet would be more susceptible to mercury toxicity. METHODS: Recently weaned mouse pups were placed on diets containing either low, normal or high levels of selenium. Twenty days later, half were exposed to mercury vapor. Ninety days after exposure, their spinal motor neurons and phrenic motor axons were examined histologically. Mercury in the spinal cord was sought using autometallography. RESULTS: Neither low nor high selenium diets combined with mercury vapor had any clinical effect on the mice. Mercury was seen within the spinal motor neurons of all exposed mice. Spinal motor neurons and phrenic motor axons however appeared normal in morphology and size across the groups. CONCLUSION: Diets low or high in selenium did not damage motor neurons with or without mercury. This suggests that changes in the selenium environment are unlikely to precipitate mercury toxicity in motor neurons.

Animals↗

PubMed2004

Exchangeable zinc ions transiently accumulate in a vesicular compartment in the yeast Saccharomyces cerevisiae.

The baker's yeast Saccharomyces cerevisiae was used as a model to visualize intracellular labile zinc under conditions of nutritional zinc imbalance. Zinc-specific staining was performed in yeast cells using both Zinquin fluorescence and zinc-selenium autometallography. Both techniques resulted in specific labeling of an intracellular vesicular compartment that was present in wild type cells as well as in the vacuolar Zn transporter mutants Deltazrc1 and Deltacot1. This compartment, that closely resembles mammalian zincosomes, appeared rapidly under conditions of zinc availability and was independent of endocytosis. However, persistence of the zinc loaded vesicles in nutritional zinc deficiency was dependent on the presence of functional Zrc1 and Cot1 vacuolar transporters. Overall our findings indicate that labile zinc in yeast cells enters a dynamic vesicular compartment which could represent an extremely important defence to buffer both zinc excess and deficiency.

Cation Transport Proteins↗

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↗

PubMed2004

Immersion autometallography: histochemical in situ capturing of zinc ions in catalytic zinc-sulfur nanocrystals.

In the mid-1980s, two versions of Timm's original immersion sulfide silver method were published. The authors used immersion of tissue in a sulfide solution as opposed to Timm, who used immersion of tissue blocks in hydrogen sulfide-bubbled alcohol. The autometallography staining resulting from the "sulfide only immersion" was not particularly impressive, but the significance of this return to an old approach became obvious when Wenzel and co-workers presented their approach in connection with introduction by the Palmiter group of zinc transporter 3 (ZnT3). The Wenzel/Palmiter pictures are the first high-resolution, high-quality pictures taken from tissues in which free and loosely bound zinc ions have been captured in zinc-sulfur nanocrystals by immersion. The trick was to place formalin-fixed blocks of mouse brains in a solution containing 3% glutaraldehyde and 0.1% sodium sulfide, ingredients used for transcardial perfusion in the zinc-specific NeoTimm method. That the NeoTimm technique results in silver enhancement of zinc-sulfur nanocrystals has been proved by proton-induced X-ray multielement analyses (PIXE) and in vivo chelation with diethyldithiocarbamate (DEDTC). The aims of the present study were (a) to make the immersion-based capturing of zinc ions in zinc-sulfur nanocrystals work directly on sections and slices of fixed brain tissue, (b) to work out protocols that ensure zinc specificity and optimal quality of the staining, (c) to apply "immersion autometallography" (iZnSAMG) to other tissues that contain zinc-enriched (ZEN) cells, and (d) to make the immersion approach work on unfixed fresh tissue.

Animals↗

PubMed2003

Immunocytochemical localization of zinc transporter 3 in the ependyma of the mouse spinal cord.

We report, for the first time, the light microscopical and ultrastructural appearance of ZnT3-immunoreactivities in the ependymal cells of the central canal of the mouse spinal cord. Light microscopy revealed the presence of ZnT3-immunoreactive (Ir) ependymal cells in 1 microm thick epon sections stained by the ABC method. The ZnT3-Ir cells were observed at all levels of the spinal cord, but were a little more numerous in lumbosacral segments than in cervicothoracic segments. The ZnT3-Ir cells had large, ovoid nuclei with abundant cytoplasm, and protruded into the lumen of the central canal. Our ultrastructural findings suggest that the ZnT3-Ir ependymal cells possess secretory activity directed towards the central canal. We propose that they may play a role in the trans-ependymal mechanism responsible for zinc homeostasis between cerebrospinal fluid and the central area of the gray matter.

Animals↗

PubMed2003

Degenerative patterns following denervation of temporal structures in a rat model of mnemonic dysfunction.

The temporal region makes up an important substrate for mnemonic function in both humans and animals. Rats with transection of fibers connecting the temporal and entorhinal cortices display impaired visual memory. The use of hematoxylin and eosin (HE) or Nissl staining has proved insufficient for characterization of the degenerative events that take place after the lesions, and in the present study we therefore applied Fluoro-Jade dye, and zinc autometallography (AMG) in order to describe degenerative changes with AMG. We found that 14 days survival resulted in a much more severe degeneration of cell bodies in the temporal, perirhinal, entorhinal, and postrhinal cortices than was seen after 8 days survival. Corresponding degeneration of cell bodies was optimally observed 7 days following surgery with the Fluoro-Jade staining. HE staining did not reveal degenerative changes with survival times of 8 or 14 days. A substantial increase in AMG staining for zinc ions after lesion revealed an increase in zinc enriched neuronal terminals in the temporal areas and was interpreted as sprouting from local zinc enriched neuronal projections. The present data are related to the memory deficits observed in rats with similar denervations in previous studies.

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↗

PubMed2002

Bismuth-induced neuronal cell death in rat dorsal root ganglion: a stereological study.

The goal of the present study has been to quantify the morphological changes in myelinated nerve roots and dorsal root ganglion (DRG) cells in rats exposed to bismuth subnitrate. Male Wistar rats (n =30) were divided into three groups of ten animals. The ten animals in each group were given intraperitoneal injections of one of the following: (1) 500 mg/kg bismuth subnitrate, (2) 1,000 mg/kg bismuth subnitrate, or (3) saline. The mean total cell number of B-cells in the DRG was significantly smaller in the two treated groups, 18% (2P <0.001) and 23% (2P <0.001), respectively, than it was in the control group. In addition, there was an 11% reduction in the number of A-cells (2P =0.039) in rats exposed to the highest concentration of bismuth. Bismuth did not affect the total number or mean cross sectional area of axons and myelin sheaths of the myelinated nerve fibers in the ventral or dorsal nerve root of the DRG. This is the first study to investigate pathological changes of the peripheral nervous system after bismuth intoxication.

Animals↗

PubMed2002

Retrograde tracing of zinc-enriched (ZEN) neuronal somata projecting to the olfactory bulb.

Zinc ions seem to be important to several neurological functions and have been connected to the pathophysiology of epilepsy, neuronal cell death after seizure or stroke, and Alzheimer's disease. Both epilepsy and Alzheimer's disease are clinical conditions believed to involve the olfactory bulb. The mammalian olfactory bulb is densely innervated by zinc-enriched (ZEN) neurons, and the distribution of the ZEN terminals in the mouse olfactory bulb has previously been described. The aim of this study was to describe the origins of ZEN terminals projecting into the main olfactory bulb of the rat. Selective labeling of ZEN terminals was accomplished by intracerebral infusion of sodium selenide, whereby zinc selenium clusters are created in the ZEN terminals. Some of these clusters move by retrograde axonal transport to the somata where they can be silver-enhanced by autometallography (AMG). After infusion of sodium selenide into the main olfactory bulb, retrogradely labeled ZEN somata were found (1) ipsilaterally in all anterior olfactory nuclei, taenia tecta, piriform cortex and lateral entorhinal cortex, and (2) contralaterally in anterior olfactory nuclei except the external division. The ipsilateral anterior olfactory nucleus had the densest population of ZEN somata, and it was found that these somata originated mainly from pyramidal neurons in layers II and III of each area. The olfactory-related centrifugal afferents to the main olfactory bulb are discussed.

Afferent Pathways↗

PubMed2002

In vivo liberation of gold ions from gold implants. Autometallographic tracing of gold in cells adjacent to metallic gold.

For some years, the implantation of small pieces of gold has been used as an unauthorised remedy for osteoarthritis and pain. The aim of the present study was to evaluate whether gold ions are released from gold implants. Pieces of pure gold were placed in the connective tissue of skin, bone and brains of anaesthetised animals. Ten days to several months later the animals were anaesthetised and killed by transcardial perfusion. Tissue blocks containing the gold pieces were cut, and the sections were silver-enhanced by autometallography. It was found that gold ions are released from the implanted gold and diffuse out into the surrounding tissue. The gold-containing cells in connective tissues were macrophages, mast cells and fibroblasts. In the brain, gold accumulated in astrocytes and neurons. Proton-induced X-ray emission spectroscopy analysis of the tissue surrounding gold implants confirmed that gold ions are liberated. The findings suggest that the gold implant technique, on a local scale, mimics systemic treatment with a gold-containing drug.

Animals↗