7. DISSOLUTION AND PRESERVATION OF DIATOMS IN THE SEA OF JAPAN AND THE EFFECT ON SEDIMENT THANATOCOENOSIS 1

ABSTRACT Sediments of Pliocene age from the Sea of Japan as well as the North Pacific frequently contain abundant remains of the centric diatom, Coscinodiscus marginatus, a species which is neither abundant in surface waters nor in surface sediments of those regions. To test whether these occurrences are a product of opaline silica dissolution, we selected several sediment samples from the Quaternary record of Hole 798A which had opaline silica concentrations ranging from less than 5% to approximately 16%. Laboratory-timed dissolution experiments using an alkaline solution (40 mL of 2 M Na 2 CO 3 ) were carried out at 80° C on the three bulk samples. At the end of each time interval the samples were centrifuged and the supernatant prepared for microscopic examination. The two samples with less than 5% opaline silica contained no diatoms or highly fragmented forms after the first 5 min of the experiment had elapsed. The third sample (with 16% opaline silica), however, showed an increase in percent C. marginatus as dissolution progressed (from less than 5% to more than 35%). These data suggest that high abundances of C. marginatus in sediments may be due to silica dissolution rather than to any unique paleoceanographic signal

Iron Behaving Badly: Inappropriate Iron Chelation as a Major Contributor to the Aetiology of Vascular and Other Progressive Inflammatory and Degenerative Diseases

The production of peroxide and superoxide is an inevitable consequence of aerobic metabolism, and while these particular "reactive oxygen species" (ROSs) can exhibit a number of biological effects, they are not of themselves excessively reactive and thus they are not especially damaging at physiological concentrations. However, their reactions with poorly liganded iron species can lead to the catalytic production of the very reactive and dangerous hydroxyl radical, which is exceptionally damaging, and a major cause of chronic inflammation. We review the considerable and wide-ranging evidence for the involvement of this combination of (su)peroxide and poorly liganded iron in a large number of physiological and indeed pathological processes and inflammatory disorders, especially those involving the progressive degradation of cellular and organismal performance. These diseases share a great many similarities and thus might be considered to have a common cause (i.e. iron-catalysed free radical and especially hydroxyl radical generation). The studies reviewed include those focused on a series of cardiovascular, metabolic and neurological diseases, where iron can be found at the sites of plaques and lesions, as well as studies showing the significance of iron to aging and longevity. The effective chelation of iron by natural or synthetic ligands is thus of major physiological (and potentially therapeutic) importance. As systems properties, we need to recognise that physiological observables have multiple molecular causes, and studying them in isolation leads to inconsistent patterns of apparent causality when it is the simultaneous combination of multiple factors that is responsible. This explains, for instance, the decidedly mixed effects of antioxidants that have been observed, etc...Comment: 159 pages, including 9 Figs and 2184 reference

43. MÖSSBAUER CHARACTERIZATION OF SEDIMENTS FROM SITES 798 AND 799, JAPAN SEA

ABSTRACT 57 Fe Mössbauer spectra for 26 sediment and 6 carbonate concretion samples from Sites 798 and 799 were recorded at 293 K. Most spectra were deconvolved to two quadrupole doublets without magnetic hyperfine structure. Typical Mössbauer parameters were: isomer shift (I.S.) = 0.34 mm/s and quadrupole splitting (Q.S.) = 0.64 mm/s for the paramagnetic Fe 3+ component (partly, pyrite); I.S. = 1.13 mm/s and Q.S. = 2.64 mm/s for the high-spin Fe 2+ component derived from iron-bearing aluminosilicates. A few spectra included other high-spin Fe 2+ components ascribed to iron-bearing carbonate minerals (e.g., ferroan magnesite), according to the Mössbauer parameters for Fe 2+ in the carbonate concretions. We present the distribution of iron among different chemical forms as a function of depth. These data might indicate changes of depositional and diagenetic conditions