Effects of Iodine upon the Structure and Function of Mitochondria

Abstract The influence of iodine in its positive and negative monovalent form upon the oxygen consumption in euthyroid and thyroidectomized rats and the oxidative phosphorylation in liver mitochondria isolated from both groups of animals, as well as the spontaneous swelling and total ATPase activity of mitochondria have been studied. It was established that the administration of ICI increased the oxygen consumption of normal and thyroidectomized rats while under the same conditions no effect was found with NaI .IBr stimulated the oxygen consumption in vitro in liver mitochondria isolated both from normal and thyroidectomized rats and decreased the P/O ratio while NaI had no effect. I2 and IBr increased the swelling and inhibited the ATPase activity of isolated rat liver mitochondria, while these effects were not observed when KI was used. The thyroidstatic 1-methyl-2-mercaptoimidazol decreased the stimulating effect of iodine upon the swelling of mitochondria and to a certain extent lowered its inhibiting effect upon the ATPase activity. It is concluded that iodine in its positive monovalent form has a thyroxine-like effect upon the structure and function of isolated rat liver mitochondria, as well as in vivo upon the respiration of euthyroid and thyroidectomized rats

(Tables 3-4, pages 112-115) Chemical composition of Fe-Mn micronodules from metalliferous sediments of the East Pacific Rise and the Mid-Atlantic Ridge TAG areas

A geochemical study of Fe-Mn micronodules associated with the metalliferous sediments at two spreading centres has shown that their composition depends on the site of micronodule formation. Close to the hydrothermal mounds they exhibit significant variation in elemental content related to the type of hydrothermal discharge (low- or high-temperature), the nature of primary hydrothermal matter (plume fall-out, oxidised sulfides), and the extent of diagenesis. In this environment three types of micronodules can be distinguished although not observed as pure end-members: (1) diagenetic micronodules; (2) micronodules formed generally from the plume fall-out of oxyhydroxide matter; and (3) micronodules grown on the oxidised sulfide grains supplied to the sediments by slumping or fall-out of nearby buoyant plume. Away from the active spreading centre, the hydrothermal signatures of primary precipitates are gradually masked and hydrogenous/diagenetic processes lead the micronodule formation. Composition of micronodules becomes less variable. Well-pronounced, deep rift valleys confine the hydrothermal plume, which brings the hydrothermal suspension into contact with restricted volumes of seawater and, consequently, weakens the hydrogenous influence on the primary hydrothermal matter. Shallow rift valleys do not confine hydrothermal plumes, which are scattered over hundreds of kilometres by bottom currents. This brings the hydrothermal suspended matter into contact with large volumes of seawater. Extensive scavenging occurs, which masks the hydrothermal signal away from the spreading axis and enhances the hydrogenous one. Thus, the ridge crest morphology, defined by the spreading rate, is supposed to play a certain role, though indirect, in the chemical composition of the primary precipitates and, consequently, in the composition of the micronodules formed

Cosmic spherules from metalliferous sediments: a long journey to the seafloor

The iron cosmic spherules found in the metalliferous sediments of two spreading centers (Mid-Atlantic Ridge and East Pacific Rise) represent different stages of the four-step model suggested by Bi et al. (1993). The occurrence of one spherule with a conic tail and the detailed study of the whole spherule set allow the development of the “Dong Bi” model. If an interplanetary body (iron or iron-rich stony meteorite) has hypervelocity and enters the Earth’s atmosphere under low incidence angle, the path of its derivates to the Earth’s surface will be long. This will provide possibilities for development of the next, fifth step of the “Dong Bi” model: iron oxide shell reversal and formation of a conic tail. If the flight of the iron oxide spherule continues after the first 4 stages (ablation, oxidation, core protrusion, and core detachment) it reverses with its light hollow part back. The surface layer of the front side of the spherule ablates. The removed liquid droplets, entrained in a trail after the flying spherule, crystallize in the antipodal zone of rarefaction capping the hollow with a conic tail

Sorosite (eta-Cu6Sn5)-bearing native tin and lead assemblage from the Mir zone (Mid-Atlantic Ridge, 26 degrees N)

A number of small, irregular-shaped and spherical shiny metallic particles have been found in the sediments from the Mir zone, Trans-Atlantic Geotraverse hydrothermal held (Mid-Atlantic Ridge, 26 degreesN). The phase variety of the particles examined is represented by metallic tin: tin-rich lead, and tin-copper phases. A detailed mineralogical study of these particles was carried out using optical microscopy, nuclear microscopy, scanning electron microscopy, electron microprobe, proton microprobe and X-ray diffraction analysis. Tin-lead grains have the typical eutectic microtexture of the metal components. Tin-copper grains are formed from single crystals of sorosite, eta -Cu6Sn5. The Sn-Pb-Cu complex grains are composed of fine stannoan lead (Pb0.74Sn0.26) and tin crystals as well as fine (or occasionally larger) sorosite (Cu6.1Sn4.9) idiomorphic crystals, in a tin-lead matrix forming eutectic microtexture. On the basis of data obtained, a natural origin is proposed for the examined Sn-Pb-Cu association, and its parent relations with the tectono-magmatic events in the rift zone. This association has probably been formed (1) during the hydrothermal seepings through the Trans-Atlantic Geotraverse sediment cover, or (2) during the evolution of ridge crest magmatic systems. Crystallisation sequence from an initial melt with falling temperature is: firstly sorosite (Cu6Sn5) (T less than or equal to 380 degreesC) --> crystallisation of tin crystals (T less than or equal to 227 degreesC) --> crystallisation of Sn-Pb eutectic mixture, composed of tin + stannoan lead (T less than or equal to 183 degreesC) --> limited tin exsolutions in stannoan lead (T < < 183 degreesC). Sn-Pb-Cu grains might be present as accessory minerals in the basic rocks of the east rift wall, which have undergone degradation, permitting their deposition into rift valley sediments.De petites particules métalliques brillantes de forme irrégulière et sphériques ont été trouvées dans les dépôts de la zone hydrothermale de Mir (dorsale, médio-Atlantique, 26 °N). Les particules examinées représentent lˈétain métallique, lˈétain riche en plomb et lˈétain riche en cuivre. Une étude minéralogique détaillée de ces particules a été effectuée en utilisant la microscopie optique, la microscopie nucléaire, le microscope électronique à balayage, la micro-sonde dˈélectrons, la micro-sonde de protons et la diffraction de rayons X. Les grains étain–plomb présentent une microtexture typique des composants métalliques. Des grains d’étain–cuivre sont formés de cristaux simples de sorosite η-Cu6Sn5. Les grains complexes de Sn–Pb–Cu se composent de cristaux fins d’étain–plomb (Pb0.74Sn0.26) et d’étain ; les cristaux idiomorphes du sorosite (Cu6.1Sn4.9) fin dans une matrice d’étain–plomb formant la microtexture eutectique. Une origine « normale » est proposée pour lˈassociation examinée de Sn–Pb–Cu, et ses relations de parenté avec les événements tectono–magmatiques dans la zone de rift. Cette association a été probablement formée (1) pendant une infiltration hydrothermale par la couverture de dépôt géotraverse trans-Atlantique, ou (2) pendant lˈévolution des systèmes magmatiques des dorsales. La succession de cristallisations à partir d’une fusion initiale avec la température en baisse est la suivante : le sorosite (Cu6Sn5) (T ≤ 380°C) → cristallisation des cristaux d’étain (T ≤ 227°C) → cristallisation du mélange eutectique de Sn–Pb, composé d’étain + étain–plomb (T ≤ 183°C) → exsolutions limités d’étain dans étain–plomb (T << 183°C). Les grains de Sn–Pb–Cu pourraient être présents comme des minéraux accessoires des roches basiques de la paroi est du rift qui ont subi la dégradation, permettant leur dépôt dans les sédiments de la vallée de rift

Mineralogy, geochemistry and microbiology insights into precipitation of stibnite and orpiment at the Daiyon-Yonaguni Knoll (Okinawa Trough) hydrothermal barite deposits

Samples of active chimneys, chimney flanges and massive sulfides from the Daiyon-Yonaguni Knoll hydrothermal field are composed of major barite and minor stibnite and orpiment. Barite is inferred to precipitate from focused-discharge fluids composed of &gt;40% hydrothermal end-member fluid at T = 100-240°C, whereas the stibnite and orpiment are later and lower temperature precipitates. The hydrothermal fluids from this field were subject of sub-seafloor boiling and phase separation and, consequently, are brine-rich depleted in volatile and enriched in non-volatile elements. Boiling and phase separation exerted major control on the rare earth elements (REE) partitioning in the vent fluids: high-chlorinity high-temperature fluids were enriched in light REE and low-chlorinity low-temperature fluids were enriched in heavy REE. Y/Ho molar ratio and Ce anomaly of the vent fluids suggest that the seawater has not completely reacted with the basement rocks and has not equilibrated with them. The trace element concentrations in the hydrothermal deposits suggest a complex interplay among hydrothermal, hydrogenetic and microbial processes. Sulfur isotope composition of the sulfides suggests that the sulfide S is a mixture of both basement rock and seawater S with a higher proportion of the basement rock S. The sulfate dissolved in the fluids was subjected to reduction during a slow mixing of hydrothermal fluid and seawater within the chimney walls of the Tiger and Abyss vents and this resulted in a heavy S-isotope composition of the vent fluid sulfate. Lead isotope composition of the hydrothermal deposits indicates mixing relationships suggesting that Pb and potentially other metals with similar geochemical behavior were derived from two or three sources. The Pb isotopes in the hydrothermal deposits imply that an enriched source, either sediments or extended continental lithosphere, and a depleted source, potentially back-arc mafic volcanics, are present in the area of Daiyon-Yonaguni Knoll. Filamentous orpiment found in the deposits is supposed to be either heavily mineralized fungal hyphae or pure abiogenic biomorphs. Presence of carbonaceous matter on and around the orpiment filaments suggests for microbial activity during filament formation. The filaments experienced temperature of 209.1±37.1°C which falls within the temperature range of the Daiyon-Yonaguni Knoll vent fluids. Stability phase diagrams modeling reveals that the stability of stibnite does not depend on the vent fluid chlorinity, but depends on the vent fluid temperature: the area of stibnite stability increases with decreasing vent fluid temperature and results in stibnite precipitation at low log10a of Sb2S42- and less reduced environment (Eh still &lt;0). Orpiment is stable in a wide range of log10a of H2AsO4-, in reduced conditions and at high S activity. Barite is stable in wide range of log10a of Ba2+ and precipitates in slightly reduced to slightly oxic conditions

Hydrothermal carbonate chimneys from a continental rift (Afar Rift): Mineralogy, geochemistry, and mode of formation

Carbonate chimney-like deposits up to 60 m high are scattered or arranged in rows at the shores of a desiccating hypersaline and alkaline lake from a continental rift setting (Lake Abhé, Afar Rift, Djibouti). The chimneys formed sub-aqueously in the lake water body at a higher water level than observed today. Alternating calcite and low-Mg calcite + silica concentric layers compose the chimney structures. Mineralogical and geochemical investigations of the chimneys, lake water, and hot spring (hydrothermal) fluids suggest that the chimneys are a result of rapid carbonate precipitation during the mixing of hydrothermal fluids with lake water. In contrast to the hot spring fluid, lake water is enriched in HREE and possesses a pronounced positive Ce anomaly, features that are preserved in the carbonate chimney layers. Mixing calculations based on Sr- isotope and concentration data indicate a hydrothermal fluid contribution of ~ 45 % in the chimney interior, which decreases to ~ 4 % in the external chimney layer. Sr in the hydrothermal fluids is predominantly leached from the underlying volcanic rocks, whereas the lake’s Sr budget is dominated by riverine input. Considering the fluid mixing ratios calculated by Sr-data, the measured C and O isotope compositions indicate that chimney carbonates precipitated at temperatures between 14 °C (internal part) and 22 °C (external part) with δ13C-carbonate mainly controlled by isotope equilibrium exchange of lake water with atmospheric CO2. The low-Mg calcite layers, including the outermost layer, have enhanced signals of lake water inheritance based on elevated concentrations of immobile elements, ΣREE, and Sr and Ca isotope compositions. Ca-isotope data reveal that internal chimney layers formed by non-equilibrium calcite precipitation with a predominantly hydrothermal Ca source. The external low-Mg calcite layer received Ca contributions from both hydrothermal fluid and lake water, with the latter being the dominant Ca source. Highly positive δ44/40Ca of lake water likely reflects non-equilibrium Ca-carbonate precipitation during lake water evaporation with resulting 44Ca enrichment of residual lake water. The strong degree of 44Ca enrichment may point towards multiple lake drying and Ca-reservoir depletion events. Coupled C-O-Ca-isotope data of the sampled carbonate chimney suggest late-stage (low-temperature) hydrothermal carbonate chimney formation during strongly evaporative lake conditions at the time of low-Mg calcite precipitation. U-Th age dating suggests the chimneys formed no earlier than 0.82 kyr BP (0.28 ± 0.54)