Margot Martiny Christensen

Influence of mercuric chloride on resistance to generalized infection with herpes simplex virus type 2 in mice

The effect of mercuric chloride on resistance to generalized infection with herpes simplex virus type 2 (HSV-2) in mice was studied. The severity of the infection was evaluated by the amount of infectious virus in the liver. Mercury at a single dose of 20 micrograms aggravated the infection, and neither increasing the single dose to 80 micrograms nor giving repeated doses of 20 micrograms further intensified the infection. Examination of the course of infection after mercury exposure revealed an increased virus replication and dissemination during the first days of the infection, indicating that the early, nonspecific defence mechanisms were affected. Virus clearance and elimination, which is mediated by specific immunity, seemed not to be influenced. Examination of cells from the peritoneal cavity and of livers from virus-infected mice showed that mercury detectable by autometallography was exclusively found in mature peritoneal macrophages and in Kupffer cells of the liver. Inflammatory cells, recruited to the peritoneal cavity or infiltrating the infectious foci of the liver, did not show any mercury deposits. Attempts to demonstrate an effect in vivo of mercury on potential antiviral macrophage functions like interferon-alpha/beta (IFN-alpha/beta) and tumour necrosis factor-alpha (TNF-alpha) secretion and oxidative burst capacity were not successful, possibly because recruited, inflammatory cells, which have not been exposed to the high mercury concentrations at the site of injection, take over these functions of intoxicated macrophages.

Effect of mercuric chloride on macrophage-mediated resistance mechanisms against infection with herpes simplex virus type 2

Macrophages play an important role in the early, nonspecific resistance to infection with herpes simplex virus. Mercuric chloride (HgCl2) accumulates in macrophages and has in certain concentrations a marked influence on the functional capacity of these cells. Therefore the influence of HgCl2 on resistance to generalized infection with herpes simplex virus type 2 (HSV-2) in mice and its effect on the HSV-2-induced activation of macrophages in vitro was examined. Mice injected intraperitoneally with HgCl2 24 h before infection with HSV-2 had more than 100 times higher virus titres in the liver 4 days after infection than mice not receiving any mercury. HgCl2 exerted a toxic effect on macrophages in vitro, which was especially pronounced during their adherence. Macrophages infected with HSV-2 were activated for an enhanced respiratory burst. This activation was abolished by treatment of the cells for 24 h with relatively low concentrations of HgCl2, resulting in macrophages with a potential to react with a respiratory burst comparable to that of uninfected cells. The HSV-2-induced activation of macrophages is mediated through the production and synergistic interaction of interferon-alpha/beta and tumour necrosis factor-alpha in an autocrine manner. The ability of these cytokines to activate macrophages and to interact synergistically was not affected by mercury. However the production by macrophages of both cytokines during the HSV-2 infection, but especially interferon-alpha/beta, which is essential for the activation, was reduced at low concentrations of HgCl2. Collectively these data indicate that mercury, by interfering with the early macrophage-production of cytokines, disables the early control of virus replication, leading to an enhanced infection.

Toxicity and ultrastructural localization of mercuric chloride in cultured murine macrophages

The effects of mercuric chloride on cell survival, phagocytosis and cell migration were examined in cultured mouse peritoneal macrophages, and the accumulation of mercuric chloride in the cells was visualized by autometallography and evaluated by light and electron microscopy. Macrophages exposed to mercury concentrations from 1.25 μM to 10 μM mercuric chloride showed a concentration- and time-dependent increase in mercuric chloride accumulation, while cells exposed to 20 μM and 40 μM mercury showed an inverse relationship between mercury concentration and the accumulation of mercury. Mercury concentrations above these levels caused cell necrosis. Electron microscopy revealed that mercury was located primarily within lysosomes but also in the nucleus and cytoplasm. Mercury increased the death rate of macrophages in a concentration-dependent manner when cells were treated with mercury concentrations not causing cell necrosis. Further, we found that mercury clearly impaired macrophage random migration and possibly the capability for phagocytosis.

Histochemical tracing of bismuth in testis from rats exposed intraperitoneally to bismuth subnitrate

The histochemical silver amplification technique autometallography (AMG), was used to trace bismuth in the testis of Wistar rats injected intraperitoneally with bismuth subnitrate. In the seminiferous tubules, bismuth was located in lysosomes of Sertoli cells closely associated with heads of spermatids in the late stages of the spermatogenesis, i.e. shortly before the release of Step 19 spermatids in Stage XIII. No bismuth-specific AMG silver grains were detected in the spermatogenic cell line. However, tails of free sperm cells located in the tubular lumen showed autometallographic grains in close contact to the nine outer microtubule doublets in the axonema. Leydig cells concentrated huge amounts of AMG-bismuth in their lysosomes. Furthermore, parallel exposure to selenium significantly increased the amount of histochemically traceable bismuth in the rat testis.

Comparison of the interaction of methyl mercury and mercuric chloride with murine macrophages

The toxicity of organic methyl mercury was studied on murine macrophages in cell culture and compared to that of inorganic mercuric chloride. Long-term treatment of macrophage cultures with methyl mercury resulted in decreased cell viability in a concentration-dependent fashion. Experiments showed that 20 μM methyl mercury was highly toxic, causing cell death within a few days, while cultures exposed to lower levels were less severely affected. Comparison of the toxicity of organic and inorganic mercury by cell viability showed no difference between equimolar concentrations of methyl mercury and mercuric chloride. Furthermore, protein synthesis (interferon-α/ß) was reduced in a concentration dependent manner and had the same reduced magnitude in cells treated with either methyl mercury or mercuric chloride. However, impairment of random migration and phagocytosis of macrophages appeared at lower concentrations in cells exposed to methyl mercury than in cells exposed to mercuric chloride. Electron microscopy of cells exposed to methyl mercury revealed mercury deposits in lysosomes and dispersed in the cytoplasm and nuclei. The present study shows that methyl mercury and mercuric chloride impair cell viability and protein production in cell cultures at equimolar concentrations, while methyl mercury inhibits macrophage functions such as migration and phagocytosis at lower concentrations than mercuric chloride.

Methyl Mercury, Mercuric Chloride, and Silver Lactate Decrease Superoxide Anion Formation and Chemotaxis in Human Polymorphonuclear Leucocytes

Cytotoxic effects of mercuric chloride, methyl mercury, and silver lactate on polymorphonuclear leucocytes have been examined by assaying superoxide anion formation capability and chemotaxis of metal-exposed cells. Both superoxide anion formation and chemotaxis were negatively affected by all three metal compounds. Both bacteriotoxic functions were affected in a dose-dependent fashion, the functional deficits were seen at doses not affecting cell viability. Dose-response curves were remarkably similar for all three compounds. The bacteriotoxic capacity of polymorphonuclear leucocytes may be hampered by mercury and silver.

Effects of selenium on toxicity and ultrastructural localization of mercury in cultured murine macrophages

The effects of selenium on cellular toxicity and histochemical distribution of mercury were examined in a cell culture system of mouse peritoneal macrophages. Selenium protected against the toxicity of mercury in cultures exposed to 4 microM of mercuric chloride. Selenomethionine caused a significant increase in cell survival throughout the experiments, while sodium selenite delayed the toxicity of mercury for a while, after which selenite itself had a toxic effect. The amount of mercury visualized by autometallography was increased in macrophage cultures pre-exposed to sodium selenite or selenomethionine. The additional mercury made visible by this histochemical demonstration was located in the cytoplasm as well as in the lysosomes.

Histochemical localization of autometallographically detectable mercury in tissues of the immune system from mice exposed to mercuric chloride

SummaryThe distribution of mercury in the spleen, liver, lymph nodes, thymus and bone marrow was studied by autometallography in mice exposed to mercuric chloride intraperitoneally. Application of immunofluorescence histochemistry and an autometallographic silver amplification method was employed to the same tissue section. Mercury was not only detected in macrophages marked by the antibody M1/70 but also in macrophage-like cells, which were either autofluorescent or devoid of fluorescent signals. These two cell types were identified as macrophages at the electron microscopical level. Autometallographically stained macrophages were observed in the spleen, lymph nodes, thymus and in Kupffer cells of the liver. Furthermore, mercury was observed in endothelial cells. No obvious pathological disturbances were observed at light and electron microscopical level. At the subcellular level mercury was localized in lysosomes of macrophages and endothelial cells.

Differentiation of silver-enhanced mercury and gold in tissue sections of rat dorsal root ganglia.

SummaryAutometallography was used in conjunction with light and electron microscopy to detect traces of gold and mercury in the dorsal root ganglia of rats treated with sodium aurothiomalate and mercuric chloride. In order to differentiate between gold and mercury in tissue sections, the gold accumulations were removed by potassium cyanide, leaving mercury sulphides/selenides as the only possible catalysts for autometallographic development. With this technique, it is now possible to differentiate between all tissue metals capable of initiating the autometallographic process, i.e. gold, vesicular zinc, and sulphides and selenides of mercury and silver.

Autometallography used as a histochemical indicator of lysosome function in cultured cells

SummaryThe present paper suggests the autometallographic demonstration of intralysosomal silver as a sensitive tool for the detection of subtile toxic effects in cell cultures, the method is suggested to primarily detect lysosomal damage.