Abundance Of Sulfate Research Articles

Keratocyte Phenotype Mediates Proteoglycan Structure: A ROLE FOR FIBROBLASTS IN CORNEAL FIBROSIS

In pathological corneas, accumulation of fibrotic extracellular matrix is characterized by proteoglycans with altered glycosaminoglycans that contribute to the reduced transparency of scarred tissue. During wound healing, keratocytes in the corneal stroma transdifferentiate into fibroblasts and myofibroblasts. In this study, molecular markers were developed to identify keratocyte, fibroblast, and myofibroblast phenotypes in primary cultures of corneal stromal cells and the structure of glycosaminoglycans secreted by these cells was characterized. Quiescent primary keratocytes expressed abundant protein and mRNA for keratocan and aldehyde dehydrogenase class 3 and secreted proteoglycans containing macromolecular keratan sulfate. Expression of these marker compounds was reduced in fibroblasts and also in transforming growth factor-beta-induced myofibroblasts, which expressed high levels of alpha-smooth muscle actin, biglycan, and the extra domain A (EDA or EIIIA) form of cellular fibronectin. Collagen types I and III mRNAs were elevated in both fibroblasts and in myofibroblasts. Expression of these molecular markers clearly distinguishes the phenotypic states of stromal cells in vitro. Glycosaminoglycans secreted by fibroblasts and myofibroblasts were qualitatively similar to and differed from those of keratocytes. Chondroitin/dermatan sulfate abundance, chain length, and sulfation were increased as keratocytes became fibroblasts and myofibroblasts. Fluorophore-assisted carbohydrate electrophoresis analysis demonstrated increased N-acetylgalactosamine sulfation at both 4- and 6-carbons. Hyaluronan, absent in keratocytes, was secreted by fibroblasts and myofibroblasts. Keratan sulfate biosynthesis, chain length, and sulfation were significantly reduced in both fibroblasts and myofibroblasts. The qualitatively similar expression of glycosaminoglycans shared by fibroblasts and myofibroblasts suggests a role for fibroblasts in deposition of non-transparent fibrotic tissue in pathological corneas.

The chemical weathering regime of Kärkevagge, arctic–alpine Sweden

Kärkevagge is a valley located in Swedish Lapland at approximately 68°N and represents an arctic–alpine landscape. It is a presently periglacial, glaciated trough incised into essentially horizontal metamorphic rocks, some of which are presumably pyrite-rich. A set of coordinated studies was undertaken to investigate the nature of chemical weathering and pedogenesis in the valley and upon the abutting ridges. August 1996 water quality measures reveal considerable spatial variation in solute totals with the highest Total Dissolved Solute abundances being correlated with high sulfate abundances. Ridge-crest soils exhibited poor horizonation, but more extensive development of secondary clay minerals developed in situ than was found in valley-flank and valley-bottom soils. Valley soils exhibited multiple thin horizons, many of which were buried, and are taken to reflect great paraglacial and periglacial instability. Favorable microenvironments in the valley permit significant development of Spodosols. Coarse debris along and across the valley bears both weathering rinds and rock coatings. Rock coatings in the valley include several types of iron films, sulfate crusts, carbonate skins, and heavy metal skins. Kärkevagge represents a mild arctic environment, which does not preclude substantial chemical weathering in locations where abundant pyrite-rich bedrock and water coincide. This weathering follows pathways which are eminently expectable given that weathering of the pyrite-rich rock permits generation of sulfuric acid which, in turn, weathers muscovite mica and calcite in local schists and marble, respectively. Zones of intense chemical weathering also generate clearly visible deposits of gypsum and iron sulfate deposits such as jarosite. Not all arctic and/or alpine environments are likely to be so active chemically, but the results from Kärkevagge clearly show that dismissal of chemical weathering in cold regions on the basis of presumed first principles is erroneous. Consequently, chemical weathering in such environments merits substantially more attention than it has hitherto received.

THE VALENCE AND SPECIATION OF SULFUR IN GLASSES BY X-RAY ABSORPTION SPECTROSCOPY

The geochemical behavior of sulfur in magmas depends strongly on the oxidation state of sulfur, but this is not easily determined by standard analytical methods. We have measured XANES absorption spectra at the sulfur K-edge and have found that such measurements are useful to characterize the oxidation state and speciation of sulfur in silicate glasses of geological rel evance. Measured spectra of a set of reference minerals show the effects of different oxidation states and coordination numbers of sulfur; there is a large shift in energy (~10‐12 eV) of the sulfur K-edge between S 2‐ and S 6+ . This large and easily detectable difference makes possible the measurement of the valence of sulfur in unknown samples by measuring the shift in energy of the absorption edge. This approach is applicable to both crystalline and glassy materials, and useful results have been obtained on samples with as little as 450 ppm S. We have used XANES measurements to characterize oxidation state and speciation of sulfur in a set of natural and synthetic sulfur-bearing glasses. The samples cover a range of composition from basaltic to almost rhyo litic, and some were synthesized over a range of pressure, temperature and oxygen fugacity; glass S content varies between 450 and 3000 ppm. XANES analyses, carried out in fluorescence mode at LURE, allowed determination of the sulfur oxidation state in all of the samples and clearly show that some samples contain a mixture of S 2‐ and S 6+ ; no other sulfur species were observed. Quantitative determination of the abundance of sulfide and sulfate shows good agreement with independent measurements based on electron-microprobe determination of the wavelength shift of sulfur K X-rays.

A fingerprinting method for chondroitin/dermatan sulfate and hyaluronan oligosaccharides

A previously published method for the analysis of glycosaminoglycan disaccharides by high pH anion exchange chromatography (Midura,R.J., Salustri,A., Calabro,A., Yanagishita,M. and Hascall,V.C. (1994), Glycobiology,4, 333-342) has been modified and calibrated for chondroitin and dermatan sulfate oligosaccharides up to hexasaccharide in size and hyaluronan oligosaccharides up to hexadecasaccharide. For hyaluronan oligosaccharides chain length controls elution position; however, for chondroitin and dermatan sulfate oligosaccharides elution times primarily depend upon the level of sulfation, although chain length and hence charge density plays a role. The sulfation position of GalNAc residues within an oligosaccharide is also important in determining its elution position. Compared to 4-sulfation a reducing terminal 6-sulfate retards elution; however, when present on an internal GalNAc residue it is the 4-sulfate containing oligosaccharide which elutes later. These effects allow discrimination between oligosaccharides differing only in the position of GalNAc sulfation. Using this simple methodology, a Dionex CarboPac PA-1 column with NaOH/NaCl eluents and detection by absorbance at 232 nm, a quantitative analytical fingerprint of a chondroitin/dermatan sulfate chain may be obtained, allowing a determination of the abundance of chondroitin sulfate, dermatan sulfate, and hyaluronan along with an analysis of structural features with a linear response to approximately 0.1 nmol. The method may readily be calibrated using either commercial disaccharides or the di- and tetrasaccharide products of a limit digest of commercial chondroitin sulfate by chondroitin ABC endolyase. Commercially available and freshly prepared shark, whale, bovine, and human cartilage chondroitin sulfates have been examined by this methodology and we have confirmed that freshly isolated shark cartilage CS contains significant amounts of the biologically important GlcA2Sbeta(1-3)GalNAc6S structure.

Determination of sodium, chloride and sulfate in dolomites: a new technique to constrain the composition of dolomitizing fluids

A new analytical procedure has been developed to determine sodium, chloride and sulfate concentrations in dolomite. Non-dolomite phases are removed during sample preparation, and 10 mg of at least 99% pure dolomite are dissolved in nitric acid. This solution is diluted, and sodium, chloride and sulfate are determined by standard DCP and IC methods. To evaluate the geochemical significance of sodium, chloride and sulfate abundances in dolomite, 108 samples from various locations were analyzed. Their depositional age and the composition of the dolomitizing fluid were previously determined on the basis of petrographic, geochemical and stratigraphic evidence. Dolomites that were interpreted to have formed from seawater-derived evaporitic brines, seawater/fresh-water mixtures and deep formation waters exhibit significant differences in sodium, chloride and sulfate content, and molar Na/Cl ratios. This new technique provides a valuable geochemical tool to constrain the composition of dolomitizing solutions, complementing field observations, petrographic evidence, isotope- and fluid inclusion data.

Sedimentary sulfur geochemistry of the Paleogene Green River Formation, western USA: Implications for interpreting depositional and diagenetic processes in saline alkaline lakes

The sulfur geochemistry of the lacustrine Paleogene Green River Formation (Colorado, Utah, and Wyoming, USA) is unlike that of most marine and other lacustrine rocks. Distinctive chemical, isotopic, and mineralogical characteristics of the formation are pyrrhotite and marcasite, high contents of iron mineral sulfides strikingly enriched in 34S, cyclical trends in sulfur abundance and δ 34S values, and long-term evolutionary trends in δ 34S values. Analyses that identified and quantified these characteristics include carbonate-free abundance of organic carbon (0.13–47 wt%), total iron (0.31–13 wt%), reactive iron (>70% of total iron), total sulfur (0.02–16 wt%), acid-volatile monosulfide (S Av), disulfide (S Di > 70% of total sulfur), sulfate (S SO 4) and organosulfur (S Org); isotopic composition of separated sulfur phases (δ 34S Di,Av up to +49‰); and mineralogy, morphology and paragenesis of sulfide minerals. Mineralogy, morphology, δ 34S Di,Av, and δ 34S Org have a distinctive relation, reflecting variable and unique depositional and early diagenetic conditions in the Green River lakes. When the lakes were brackish, dissimilatory sulfate-reducing bacteria in the sediment produced H 2S, which initially reacted with labile iron to form pyrite framboids and more gradually with organic matter to form organosulfur compounds. During a long-lived stage of saline lake water, the amount of sulfate supplied by inflow decreased and alkalinity and pH of lake waters increased substantially. Extensive bacterial sulfate reduction in the water column kept lake waters undersaturated with sulfate minerals. A very high H 2S:SO 4 ratio developed in stagnant bottom water aided by the high pH that kinetically inhibited iron sulfidization. Progressive removal of H 2S by coeval formation of iron sulfides and organosulfur compounds caused the isotopic composition of the entire dissolved sulfur reservoir to evolve to δ 34S values much greater than that of inflow sulfate, which is estimated to have been +20‰ A six-million-year interval within Lake Uinta cores records this evolution as well as smaller systematic changes in δ 34S, interpreted to reflect ~ 100,000-year lake-level cycles. When porewater was exceptionally reducing, unstable FeS phases eventually recrystallized to pyrrhotite during diagenesis. A much later reaction related to weathering altered pyrrhotite to marcasite.

A review of Archean volcanic-hosted massive sulfide and sulfate mineralization in Western Australia

Archean volcanic-hosted massive sulfide mineralization in Western Australia ranges in age from ca. 3.46 to 2.70 Ga. Barite-rich, Zn-Pb-Cu mineralization is hosted by relatively large ion lithophile element-rich calc-alkaline volcanic rocks in the ca. 3.46 Ga Warrawoona Group and ca. 3.3 Ga Gorge Creek Group in the eastern Pilbara craton. The high lead contents and 100 Zn/Zn + Pb ratios of between 60 and 80 are typical ofPhanerozoic mineralization hosted by silicic volcanic rocks, rather than of most Archean massive Cu-Zn sulfide deposits. The abundance of sulfate in these deposits, combined with evidence for evaporitic sulfates elsewhere in the Warrawoona Group, also suggests at least local oxidation of reduced suliur in the upper layer of the ocean at this time. Lead-rich, Zn-Pb-Cu mineralization also occurs in the ca. 2.99 Ga Whim Creek Group in the western Pilbara craton. This volcanic and sedimentary sequence formed in a rapidly subsiding basin within older continental crust, and the volcanic rocks are characterized by relatively high large ion lithophile element contents. In the east Yilgarn craton, Cu-Zn mineralization occurs in a bimodal assemblage of tholeiitic basalts and rhyolites at Teutonic Bore, in the Norseman-Wiluna belt. This deposit was mined during the 1980s. In the western Yilgarn block, Cu-Zn mineralization occurs in an assemblage of ca. 3.0 Ga. deep-water, calc-alkaline volcanic and sedimentary rocks in the Golden Grove belt. Mineralization in this belt is typically associated with magnetite and includes the Scuddles and Gossan Hill deposits. Alteration at these deposits is similar to that of Mattabi-type deposits in the Canadian Archcan and includes iron-rich chlorite and carbonates in poorly developed, or laterally extensive, feeder zones. The lead content of the host volcanic sequence and mineralization in this belt is typically much lower than that of the Pb-rich Pilbara mineralization. The Scuddles deposit with a mine recoverable reserve of about 10 million tons of 11 percent Zn, 0.8 percent Pb, and 1.2 percent Cu is currently being mined.

Volatile compounds in shergottite and nakhlite meteorites

Abstract— Vacuum pyrolysis and quadrupole mass spectrometry were used to measure evolved‐gas profiles and total concentrations of H2O, CO2, CO, SO2, S2, H2S, HCl, Cl, and hydrocarbons in both exterior and interior samples of shergottites (ALHA77005, EETA79001, and Shergotty), a nakhlite (Nakhla), and eucrites (ALHA81001, EETA79004, and Pasamonte). Eucrites were analyzed as control samples to monitor effects of terrestrial weathering and contamination, relative to properties sought for the shergottite‐nakhlite parent body. In contrast with eucrites, shergottites and Nakhla contain large proportions of their sulfur as oxidized sulfur compounds. Sulfate occurs in all shergottite and Nakhla samples and carbonate was confirmed in EETA79001 and Nakhla. Carbonate and sulfate abundances are inversely correlated but total chlorine abundance varies directly with fractional sulfate abundance. Most of the volatile compounds seem to be anhydrous, based on low bulk water contents in the meteorites (<0.1% H2O), although Nakhla might contain significant water that is chemically associated with chlorine. Traces of saturated and unsaturated hydrocarbons in some samples are most likely terrestrial contaminants. The indigenous volatile compounds indicate that the shergottite‐nakhlite parent body was highly oxidizing and supported aqueous geochemistry during at least part of its history.

Occurrence of tyrosine sulfate in proteins – a balance sheet

1. The abundance of tyrosine sulfate in membrane proteins was quantified in four different cell lines and compared to that in soluble cellular and secreted proteins. 2. Upon metabolic labelling of HepG2, Ltk-, AtT20 and PC12 cells with [35S]sulfate or [3H]tyrosine, a fraction enriched in integral membrane proteins was found to contain small, but significant, amounts of protein-bound tyrosine sulfate (up to 2.5% of the total cellular plus secreted protein-bound tyrosine sulfate). On the other hand, the frequency of sulfation of tyrosine residues of membrane proteins was within the same order of magnitude as that of secreted proteins, indicating that the low abundance of tyrosine sulfate in membrane proteins was largely a reflection of the low abundance of these proteins themselves. Consistent with this conclusion were the results of an analysis showing that 14 out of 32 selected membrane-spanning proteins contain potential tyrosine sulfation sites. 3. In HepG2 cells, three tyrosine-sulfated integral membrane glycoproteins of molecular mass 100, 125 and 150 kDa were identified. Characterization of the 150-kDa tyrosine-sulfated membrane protein revealed that it was protected from proteolysis in intact cells, suggesting a localization in an intracellular organelle. 4. Together with the results reported in the preceding paper in this journal, our data suggest that tyrosine sulfation occurs in various classes of trans-Golgi-derived proteins, soluble as well as membrane, and extracellularly exposed as well as intracellularly retained, proteins. This suggests that tyrosine sulfation may have a variety of physiological functions, depending on the individual tyrosine-sulfated protein or protein class.

Occurrence of tyrosine sulfate in proteins – a balance sheet

1. The abundance of tyrosine sulfate in secretory proteins and in various classes of cellular proteins has been quantified and compared to protein-bound carbohydrate sulfate. 2. HepG2 cells and fibroblasts, two cell types showing only the constitutive pathway of secretion, and PC12 cells, which show both the constitutive and the regulated pathway of secretion, were subjected to pulse-chase and/or long-term labelling with [35S]sulfate and [3H]tyrosine, followed by analysis of proteins in the cells and medium. Under both conditions of labelling, 65-92% of the protein-bound tyrosine sulfate and 44-84% of the protein-bound carbohydrate sulfate were found to be secretory. In HepG2 cells, the frequency of sulfation of tyrosine residues, which can be determined independently from protein abundance and the rate of protein synthesis, was 8-22 times higher in proteins secreted into the medium than in cellular proteins. 3. All cell lines studied contained significant amounts, not only of carbohydrate sulfate, but also of tyrosine sulfate in specific cellular proteins. As shown for fibroblasts, these tyrosine-sulfated proteins were retained within the cells for at least 100 min of chase following a pulse with [35S]sulfate and were almost completely recovered in a light membrane fraction after subcellular fractionation. 4. Lysosomes were found to contain small, but significant, amounts of protein-bound tyrosine sulfate in addition to protein-bound carbohydrate sulfate. Protein-bound tyrosine sulfate in lysosomes reached a peak at 20 min of chase and rapidly disappeared thereafter, whereas protein-bound carbohydrate sulfate accumulated after 20 min of chase. Examination of the known sequences of eleven lysosomal enzymes revealed the presence of potential tyrosine sulfation sites in five of them. 5. Our results show that secretory proteins are the most abundant, but not exclusive, in vivo substrates for tyrosine sulfation and suggest the presence of soluble tyrosine-sulfated proteins in lysosomes and other, as yet unidentified, organelles of the secretory pathway. In the following paper in this journal we describe the abundance of tyrosine sulfate in integral membrane proteins.

Hydrogeology of two Saskatchewan tills, II. Occurrence of sulfate and implications for soil salinity

The occurrence of sulfate salts in groundwater and solids was documented at two sites, named Dalmeny and Warman, where clayey tills overlie regional aquifers. At Dalmeny the till is thinner and approximately two orders of magnitude more permeable than at Warman. Samples for sulfur and sulfate determinations were collected to depths of approximately 14 m, and at horizontal spacings of a few tens of meters. Large numbers of indirect measurements of bulk salt content were obtained with a noncontacting earth conductivity meter. Results showed that the bulk sulfur and sulfate contents of solids could not in general be adequately characterized with point or “grab” samples from boreholes. At Dalmeny, measurements representing larger averaging volumes revealed a spatially-intricate pattern of sulfate abundance and depletion which extends vertically through the oxidized and unoxidized zones of the till to the underlying aquifer. Similar measurements at Warman suggest that sulfate variability there is limited to the oxidized zone. These findings, and the observed coincidence of sulfate patterns with the groundwater flow patterns documented in Part I 2, show that the bulk permeability of the till controls the manner in which the subsurface sulfate “reservoir” is affected by microtopographic focussing of surface water input. Conceptual analysis of the responses of these systems to various land management practices indicates that where tills are relatively permeable, these practices would primarily affect the quality of groundwater recharge to underlying aquifers. Where tills have low permeability, the same practices would have no effect on aquifer water quality, but they would affect the potential for surface and soil salinization.

Effects of El Chichón on stratospheric aerosols late 1982 to early 1984

Stratospheric aerosols collected over the western United States from late 1982 to early 1984 show the strong effects of El Chichón's eruption. Although mineral particles disappeared during this period, large (> 0.9‐μm diameter) acid droplets were still common. Because these have never been seen in prevolcanic, background‐level collections, they apparently result from increased droplet growth made possible by the unusual abundance of sulfate. Aerosol size distributions show a wide variety of multimodal curves due to mixing of air masses containing aerosols of various ages or histories. Toward the end of the study time there are fewer large aerosols because of gravitational settling and poleward transport. The result is a steady reduction in sulfate, as most aerosol mass is concentrated in a small number of large droplets. Even the later sulfate levels (0.3 μg m−3) are, however, 5 times typical prevolcanic background contents (about 0.06 μg m−3). Thus the influence of El Chichón on high‐altitude (15–21 km) air was still considerable 22 months after eruption.

The Johnson River Prospect, Alaska; gold-rich sea-floor mineralization from the Jurassic

The Johnson River prospect on the Alaskan peninsula is an unusually well preserved Jurassic example of gold-rich sea-floor mineralization accompanied by extensive anhydrite. The prospect is a gold-zinc-copper-lead deposit located within the dominantly dacitic middle portion of the lower Jurassic Talkeetna Formation, a complex succession of unmetamorphosed volcanic and volcaniclastic rocks. The mineralization at the Johnson prospect forms a discordant quartz-sulfide stockwork body in a series of subaqueous tuffs and debris flows.The mineralization and alteration can be divided into an early, pervasive nodular anhydrite-Mg chlorite-clay-sericite stage essentially barren of base metals and gold and a later quartz-sulfide gold stage associated with barite, Fe chlorite, sericite, and vein-type anhydrite. The abundance of sulfate far exceeds that of total sulfide at the Johnson River prospect. The anhydrite-bearing assemblages form a stratigraphically restricted zone in which anhydrite may constitute up to 80 percent of the rock. Textures indicating both replacement of fragments by anhydrite, and more commonly, open-space growth of anhydrite can probably be explained by anhydrite precipitation in highly porous unconsolidated tuffs. Early sulfide and oxide mineralization consists of jasper veins, sinuous pale sphalerite veins and chambers, and quartz-barite-sphalerite nodules accompanied by large volumes of chalcedonic quartz. Late sulfide mineralization includes chalcopyrite-rich veins and hydrothermal breccias accompanied by dark sphalerite, galena, pyrite, and native gold. High-grade gold is concentrated at the highest stratigraphic occurrences of significant copper mineralization.Whole-rock chemical analyses of anhydrite-chlorite rock shows that it is depleted in SiO 2 and enriched in MgO relative to stratigraphically equivalent unaltered tuff. The retrograde solubility of anhydrite, the prograde solubility of quartz, and the large Mg content of the chlorites suggest that this assemblage formed by heating of large volumes of cold seawater in a vigorous convection cell within the unconsolidated tuffs of the Talkeetna Formation. It is suggested that the convection cell was generated by the incursion of heated, metal-bearing fluids from below which eventually came to dominate the hydrothermal system with time as mineral precipitation gradually insulated the stockwork body from cold seawater.

Mineralogy and geochemistry of a sediment‐hosted hydrothermal sulfide deposit from the Southern Trough of Guaymas Basin, Gulf of California

Samples dredged from a 15‐m‐high hydrothermal mound atop the flat turbidite pond in the Southern Trough of Guaymas Basin consist of pyrrhotite‐rich massive sulfide, barite, barite + calcite, talc, and opaline silica as well as substrate material composed of fossiliferous, clay‐rich ooze. An 11‐m‐long sediment core taken near the dredge site shows increasing hydrothermal alteration with depth; anhydrite‐filled fractures near the base of the core appear to be channels for hydrothermal discharge. Oxidation of the sulfide‐rich samples to an assemblage of geothite, lepidocrocite, and amorphous Fe oxyhydroxide is ubiquitous. Compared to other massive sulfide deposits on sediment‐starved oceanic ridges, the hydrothermal deposit dredged in Guaymas Basin has a high pyrrhotite/pyrite ratio, a low Zn sulfide and combined ore metal (Cu + Zn + Pb + Ag + Cd) content, and a greater abundance of sulfate, carbonate, and silicate phases. Venting hydrothermal solutions are alkaline with moderately high pH; high Ca, Ba, and SiO2 content; low ƒS2 and ƒo2; and very low transition metal content. Disequilibrium assemblages of pyrrhotite and sulfate minerals form during rapid mixing of this evolved vent fluid with ambient bottom waters at the discharge site. Talc is formed at a temperature near 270°C by mixing or entrainment of Mg‐rich bottom water or pore fluid with upwelling hydrothermal fluid that is saturated with silica. Calcite may precipitate from the alkaline, Ca‐rich fluid during degassing of CO2. The minimum temperature range for sulfide and nonsulfide deposition is approximately 190°–326°C. The composition of hydrothermal deposits, vent solutions, and altered sediment requires that circulating fluids evolve during deep penetration into the basaltic basement complex, further interaction with the organic‐and carbonate‐rich sediment pile, and near‐surface mixing with ambient seawater. Although the stable assemblage albite‐epidote‐clinochlore present at depth in the sediment pile requires very low dissolved Mg and Fe in the altering fluid, the addition of Mg to deeply buried sediment indicates significant recharge of the system by Guaymas Basin bottom water.

Some constituents of the sea cucumber Cucumaria frondosa

Solvent extraction of Cucumaria frondosa, collected in Passamaquoddy Bay, has afforded a variety of natural products. Silica gel chromatography of the chloroform extract has provided an abundance of sterol glycosides, sterol sulfates and free sterols which have been examined by gas chromatography/mass spectrometry (GC/MS) and nuclear magnetic resonance spectroscopy ( 1H nmr). It appears that the free sterol and the sterol glycoside mixtures are composed mainly of Δ 7-sterols, whereas the sterol sulfate mixture is composed predominantly of cholesterol and cholestanol. By methanol extraction, a mixture of triterpenoid saponins has been obtained. Partial hydrolysis of this material has yielded several monosaccharides, aglycones and one aglycone with a xylose unit attached. A new triterpenoid lactone has been isolated and its structure is proposed on the basis of 1H nmr, infrared (IR), and MS data. From the light petroleum ether extract, a number of compounds have been obtained, including the known carotenoid canthaxanthin and a plastochromanol never previously reported from marine sources. Alkaline hydrolysis of the lipid fraction provided a mixture of sterols and the known compound batyl alcohol.

Comparison of proteoglycans extracted from high and low weight-bearing human articular cartilage, with particular reference to sialic acid content.

Proteoglycan subunits extracted in the presence of proteinase inhibitors from autologous knee and shoulder cartilage were examined in different donors of various ages, in order to determine the effect of weight bearing on the age-related changes in proteoglycan structure. At each age, high density proteoglycans from the two joints of the same individual were virtually identical with respect to chemical composition, hydrodynamic size, ability to aggregate with hyaluronic acid, and chondroitin sulfate chain length. The proteoglycan content of the cartilage decreased with age, as did the size of the proteoglycan subunits. In contrast, the proportions of keratan sulfate to chondroitin sulfate, protein to glycosaminoglycan, and chondroitin 6 sulfate to chondroitin 4-sulfate all increased with age. These changes occurred to the same extent in both knee and shoulder cartilage. There was no change in the ability of the proteoglycan to aggregate with hyaluronic acid. The sialic acid profile on Bio-Gel P-10 chromatography, following alkaline borohydride degradation, showed the presence of both keratan sulfate and oligosaccharide chains. The oligosaccharide content of the core protein of the proteoglycan appeared to decrease during the aging process, but it could not be ascertained whether this was related to the increased abundance of keratan sulfate.

Stability of brines on Mars

The detection of high chlorine and sulfate abundances and duricrusts on Mars strongly suggests the occasional presence of brines on the Martian surface. Ternary phase diagrams for the likely chloride and sulfate brines indicate that the minimum temperature at which a brine can be stable is near 210°K with a water concentration of approximately 70 wt% and a high concentration of calcium chloride. The dominance of sulfate over chlorine in the Martian regolith suggests precipitation of salts at temperatures higher than the minimum.

Criteria for Recognition of Diverse Dolostone Types from Host Rocks for Mississippi Valley-Type Ore Deposits: ABSTRACT

Dolostones are the favored host rocks for low-temperature lead and zinc ore deposits, probably because these dolostones formed in evaporitic environments. Sulfate concentration, providing a local sulfur source, probably enhanced the chances of ore formation. Reduction of sulfate by organic reducing agents, commonly gas or oil, is the most likely intermediate step. If this is so, the presence of the sulfide ores in apparently sulfate-free dolostones may indicate a former sulfate abundance. Orebodies are commonly associated with solution-collapse breccias, many of which are attributed to evaporite solution. The nearly complete, subsequent removal of the evaporites renders proof of the supposition difficult. In the big southeast Missouri breccia-hosted ore deposits, evidence in favor of former evaporitic conditions is conclusive. Most randomly selected dolostones have minute solid inclusions of gypsum or anhydrite that can be released by solution of the enclosing carbonate. Greatly enlarged and readily recognizable crystal aggregates can be cultured from the insoluble residues. In the Lockport Dolostone of southern Ontario, gypsiferous vugs are common. Chloride ions are so abundant in the Lockport that serious corrosion problems arise when structural steel is encased in concrete using crushed-stone aggregate derived from this source. Fluid inclusions within sphalerite in Mississippi Valley-type ore deposits typically indicate ore precipitation from strongly hypersaline and even saturated brines. Geologic evidence supports the growth of white sparry dolomite gangue contemporaneously with such sphalerite. We conclude that most ancient dolostones are formed in association with evaporitic facies and/or hypersaline brines. End_of_Article - Last_Page 416------------

The Oxygen Status of Lake Sediments

AbstractThe presence of oxygen in the surface layer of sediments greatly affects the abundance and availability of Fe, Mn, nitrates, phosphates, and sulfates. The concentration of O2 in the oxidized layer depends on the balance between the rate of O2 diffusion into the sediment and the rate of consumption by the sediment. Several mathematical diffusion models were developed to describe this relationship between diffusion and consumption. With these models the flux of O2 across the water‐mud interface and the thickness of the oxidized zone can be calculated. Experimental testing of the models showed that the steady state O2 consumption rates were proportional to the square root of the O2 concentration at the mud surface. The relative contribution of biological and chemical O2 consumption depended mainly on the organic matter content of the sediment, the biological consumption being highest in high‐organic matter soils. Determination of the Fe distribution near the sediment surface showed that Fe diffused upward from the reduced soil and accumulated in the oxidized zone. This freshly precipitated Fe could function as a phosphate sink, absorbing phosphates from the water and storing it in the sediment.