Morphological analysis of micropyrite populations from the Toarcian of Bulgaria

Morphological analysis of micropyrite populations of argillaceous inner shelf deposits from the Toarcian of Bulgaria was carried out in order to evaluate their stratigraphic distribution and their potential as recorders for redox conditions. Four types of micropyrites were documented: 1) euxinic framboids; 2) oxic/dysoxic framboids; 3) polyframboids; and 4) non-framboidal diagenetic pyrites. Resedimented sulphides were also observed. Micropyrite morphologies denoted upper- to lower dysoxic depositional settings within the sampled successions. Anoxic conditions seem also possible to exist but at very narrow intervals.

Download Full-text

Ordovician Jeleniów Claystone Formation of the Holy Cross Mountains, Poland – Reconstruction of redox conditions using pyrite framboid study

Contemporary Trends in Geoscience ◽

10.2478/ctg-2014-0023 ◽

2014 ◽

Vol 3 (1) ◽

pp. 60-68 ◽

Cited By ~ 1

Author(s):

Justyna Smolarek ◽

Leszek Marynowski ◽

Wiesław Trela

Keyword(s):

Standard Deviation ◽

Water Column ◽

Redox Conditions ◽

Diameter Distribution ◽

Mean Values ◽

Anoxic Conditions ◽

Pyrite Framboids ◽

Holy Cross Mountains ◽

Two Samples ◽

Insight Into

Abstract The aim of this research is to reconstruct palaeoredox conditions during sedimentation of the Jeleniów Claystone Formation deposits, using framboid pyrite diameter measurements. Analysis of pyrite framboids diameter distribution is an effective method in the palaeoenvironmental interpretation which allow for a more detailed insight into the redox conditions, and thus the distinction between euxinic, dysoxic and anoxic conditions. Most of the samples is characterized by framboid indicators typical for anoxic/euxinic conditions in the water column, with average (mean) values ranging from 5.29 to 6.02 μm and quite low standard deviation (SD) values ranging from 1.49 to 3.0. The remaining samples have shown slightly higher values of framboid diameter typical for upper dysoxic conditions, with average values (6.37 to 7.20 μm) and low standard deviation (SD) values (1.88 to 2.88). From the depth of 75.5 m till the shallowest part of the Jeleniów Claystone Formation, two samples have been examined and no framboids has been detected. Because secondary weathering should be excluded, the lack of framboids possibly indicates oxic conditions in the water column. Oxic conditions continue within the Wólka Formation based on the lack of framboids in the ZB 51.6 sample

Download Full-text

Structural and Chemical Studies of Pathological Fibers in Human Neurofibrillary Degeneration

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s042482010012031x ◽

1985 ◽

Vol 43 ◽

pp. 726-729

Author(s):

K.S. Kosik ◽

L.K. Duffy ◽

S. Bakalis ◽

C. Abraham ◽

D.J. Selkoe

Keyword(s):

Monoclonal Antibodies ◽

Alzheimer Disease ◽

Human Brain ◽

Neurofibrillary Tangles ◽

Morphological Analysis ◽

High Specificity ◽

Cytoskeletal Proteins ◽

Neuritic Plaque ◽

Protein Chemistry ◽

Chemical Studies

The major structural lesions of the human brain during aging and in Alzheimer disease (AD) are the neurofibrillary tangles (NFT) and the senile (neuritic) plaque. Although these fibrous alterations have been recognized by light microscopists for almost a century, detailed biochemical and morphological analysis of the lesions has been undertaken only recently. Because the intraneuronal deposits in the NFT and the plaque neurites and the extraneuronal amyloid cores of the plaques have a filamentous ultrastructure, the neuronal cytoskeleton has played a prominent role in most pathogenetic hypotheses.The approach of our laboratory toward elucidating the origin of plaques and tangles in AD has been two-fold: the use of analytical protein chemistry to purify and then characterize the pathological fibers comprising the tangles and plaques, and the use of certain monoclonal antibodies to neuronal cytoskeletal proteins that, despite high specificity, cross-react with NFT and thus implicate epitopes of these proteins as constituents of the tangles.

Download Full-text