Early sponges and toxic protists: possible sources of cryostane, an age diagnostic biomarker antedating Sturtian Snowball Earth.

The period 800-717 million years (Ma) ago, in the lead-up to the Sturtian Snowball glaciation, saw an increase in the diversity of eukaryotic microfossils. To afford an independent and complementary view of this evolutionary period, this study presents the distribution of eukaryotic biomarkers from three pre-Sturtian successions across the supercontinent Rodinia: the ca. 780 Ma Kanpa Formation of the Western Australian Officer Basin, the ca. 800-740 Ma Visingsö Group of Sweden, and the 740 Ma Chuar Group in Arizona, USA. The distribution of eukaryotic steranes is remarkably similar in the three successions but distinct from all other known younger and older sterane assemblages. Cholestane was the only conventional structure, while indigenous steranes alkylated in position C-24, such as ergostane, stigmastane, dinosterane and isopropylcholestane, and n-propylcholestane, were not observed. This sterane distribution appears to be age diagnostic for the pre-Sturtian Neoproterozoic. It attests to the distinct evolutionary state of pre-Snowball eukaryotes, pointing to a taxonomic disparity that was still lower than in the Ediacaran (635-541 Ma). All three basins also show the presence of a new C28 sterane that was tentatively identified as 26-methylcholestane, here named cryostane. The only known extant organisms that can methylate sterols in the 26-position are demosponges. This assignment is plausible as molecular clocks place the appearance of the earliest animals into the pre-Sturtian Neoproterozoic. The unusual 26-methylsterol may have protected sponges, but also other eukaryotes, against their own membranolytic toxins. Some protists release lytic toxins to deter predators and kill eukaryotic prey. As conventional membrane sterols can be the site of attack for these toxins, sterols with unusual side-chain modification protect the cell. This interpretation of cryostane supports fossil evidence of predation in the Chuar Group and promotes hypotheses about the proliferation of eukaryophagy in the lead-up to the Cryogenian.

Evolutionary stasis of sporopollenin biochemistry revealed by unaltered Pennsylvanian spores.

The biopolymer sporopollenin present in the spore/pollen walls of all land plants is regarded as one of the most recalcitrant biomacromolecules (biopolymers), providing protection against a range of abiotic stresses. This long-term stability is demonstrated by the near-ubiquitous presence of pollen and spores in the fossil record with spores providing the first evidence for the colonization of the land. Here, we report for the first time chemical analyses of geologically unaltered sporopollenin from Pennsylvanian (c. 310 million yr before present (MyBP)) cave deposits. Our data show that Pennsylvanian Lycophyta megaspore sporopollenin has a strong chemical resemblance to extant relatives and indicates that a co-polymer model of sporopollenin formation is the most likely configuration. Broader comparison indicates that extant sporopollenin structure is similar across widely spaced phylogenetic groups and suggests land plant sporopollenin structure has remained stable since embryophytes invaded land.

[ALA fluorescent diagnosis of bladder cancer]. / ALA--fliuorestsentnaia diagnostika raka mochevogo puzyria.

Application of 5-aminolauvulin acid (ALA) fluorescence allows to detect not only exophytic tumors of the bladder but also flat, small tumors-satellites and preneoplastic changes of the bladder. 175 biopsies were performed in 53 patients with suspected superficial tumor of the bladder. 3 hours before surgery all the patients were intravesically instilled 50 ml 3% ALA solution. Cystoscopy employed white and blue light. Visual registration of exophytic masses and red fluorescence of the suspected sites was registered and consequently compared to the histological findings. 96 of 100 sites with malignancy/dysplasia showed red fluorescence. In 13% patients cancer and mucosal dysplasia were detected only under the blue light and were missed by standard cystoscopy. Residual red fluorescence of the resection margins was observed in 41% patients after TUR. Sensitivity of ALA-fluorescent detection reached 96%, specificity 52%. ALA-induced fluorescent diagnosis is more effective than standard cystoscopy. It is most effective in diagnosis of dysplasias, carcinoma in situ, flat, small, multiple superficial tumors of the bladder during primary TUR.

Molecular indicators for palaeoenvironmental change in a Messinian evaporitic sequence (Vena del Gesso, Italy). II: High-resolution variations in abundances and 13C contents of free and sulphur-bound carbon skeletons in a single marl bed.

The extractable organic matter of 10 immature samples from a marl bed of one evaporitic cycle of the Vena del Gesso sediments (Gessoso-solfifera Fm., Messinian, Italy) was analyzed quantitatively for free hydrocarbons and organic sulphur compounds. Nickel boride was used as a desulphurizing agent to recover sulphur-bound lipids from the polar and asphaltene fractions. Carbon isotopic compositions (delta vs PDB) of free hydrocarbons and of S-bound hydrocarbons were also measured. Relationships between these carbon skeletons, precursor biolipids, and the organisms producing them could then be examined. Concentrations of S-bound lipids and free hydrocarbons and their delta values were plotted vs depth in the marl bed and the profiles were interpreted in terms of variations in source organisms, 13 C contents of the carbon source, and environmentally induced changes in isotopic fractionation. The overall range of delta values measured was 24.7%, from -11.6% for a component derived from green sulphur bacteria (Chlorobiaceae) to -36.3% for a lipid derived from purple sulphur bacteria (Chromatiaceae). Deconvolution of mixtures of components deriving from multiple sources (green and purple sulphur bacteria, coccolithophorids, microalgae and higher plants) was sometimes possible because both quantitative and isotopic data were available and because either the free or S-bound pool sometimes appeared to contain material from a single source. Several free n-alkanes and S-bound lipids appeared to be specific products of upper-water-column primary producers (i.e. algae and cyanobacteria). Others derived from anaerobic photoautotrophs and from heterotrophic protozoa (ciliates), which apparently fed partly on Chlorobiaceae. Four groups of n-alkanes produced by algae or cyanobacteria were also recognized based on systematic variations of abundance and isotopic composition with depth. For hydrocarbons probably derived from microalgae, isotopic variations are well correlated with those of total organic carbon. A resistant aliphatic biomacromolecule produced by microalgae is, therefore, probably an important component of the kerogen. These variations reflect changes in the depositional environment and early diagenetic transformations. Changes in the concentrations of S-bound lipids induced by variations in conditions favourable for sulphurization were discriminated from those related to variations in primary producer assemblages. The water column of the lagoonal basin was stratified and photic zone anoxia occurred during the early and middle stages of marl deposition. During the last stage of the marl deposition the stratification collapsed due to a significant shallowing of the water column. Contributions from anaerobic photoautotrophs were apparently associated with variations in depth of the chemocline.

Evidence for gammacerane as an indicator of water column stratification.

A new route for the formation of gammacerane from tetrahymanol is proposed; in addition to dehydration and hydrogenation, sulphurisation and early C-S cleavage are shown to be important in the pathway of formation, especially in marine sediments. Evidence is twofold. First, relatively large amounts of the gammacerane skeleton are sequestered in S-rich macromolecular aggregates formed by natural sulphurisation of functionalised lipids. Selective cleavage of polysulphide linkages with MeLi/MeI led to formation of 3-methylthiogammacerane, indicating that the gammacerane skeleton is primarily bound via sulphur at position 3, consistent with the idea that tetrahymanol (or the corresponding ketone) is the precursor for gammacerane. Second, upon mild artificial maturation of two sediments using hydrous pyrolysis, gammacerane is released from S-rich macromolecular aggregates by cleavage of the relatively weak C-S bonds. The stable carbon isotopic compositions of gammacerane and lipids derived from primary producers and green sulphur bacteria in both the Miocene Gessoso-solfifera and Upper Jurassic Allgau Formations indicate that gammacerane is derived from bacterivorous ciliates which were partially feeding on green sulphur bacteria. This demonstrates that anaerobic ciliates living at or below the chemocline are important sources for gammacerane, consistent with the fact that ciliates only biosynthesize tetrahymanol if their diet is deprived of sterols. This leads to the conclusion that gammacerane is an indicator for water column stratification, which solves two current enigmas in gammacerane geochemistry. Firstly, it explains why gammacerane is often found in sediments deposited under hypersaline conditions but is not necessarily restricted to this type of deposits. Secondly, it explains why lacustrine deposits may contain abundant gammacerane since most lakes in the temperate climatic zones are stratified during summer.

Isotopic biogeochemistry of the Oxford Clay Formation (Jurassic), UK.

A total of 165 samples was obtained from the Oxford Clay Formation at seven different sites. Nearly all were from the Peterborough Member (Lower Oxford Clay), but seven were from the Stewartby and Weymouth Members (Middle and Upper Oxford Clay respectively). Five samples from the underlying Kellaways Formation were also examined. Stratigraphic relationships were estimated on the basis of ammonite subzones and results from all locations can be placed along a single stratigraphic scale. The following were determined for all samples: abundance and isotopic composition of organic carbon, abundances of carbonate carbon and total sulphur, and the Rock-Eval pyrolysis parameters hydrogen index, oxygen index and Tmax. For a subset of eight samples selected to be representative of geochemical and apparent palaeoenvironmental variations, soluble organic compounds were extracted and the isotopic composition of pristane, phytane, and long-chain n-alkanes determined by isotope-ratio-monitoring gas chromatograph mass spectrometry. Concentrations of organic carbon in samples from the Peterborough Member ranged from 0.5 to 16.6 % and delta values of total organic carbon (TOC) ranged from -27.7 to -23.1% v. PDB. Shales dominated by epifaunal bivalve assemblages have high concentrations of TOC and values of H index approaching 800, indicating preservation of hydrogen-rich organic material. Conversely, shell beds and calcareous and silty clay beds have lower abundances of TOC and values of H index dropping below 100, indicating extensive oxidation of the organic matter. Isotopic composition of pristane and phytane in the Peterborough and Stewartby Members average -31.7%, those in the Weymouth Member average -29.8. Values of delta for long-chain n-alkanes average -28%. Together these results indicate delta values for primary inputs as follows: terrestrial vascular plants, -23.5%; Peterborough Member algae, -28.2; Stewartby Member algae, -29.1%; Weymouth Member algae, -26.6% Comparison of primary delta values to those of TOC indicates that in some cases secondary processes enriched TOC relative to primary inputs by as much as 4%. Paleontological evidence in these same beds indicates development of extensive food-webs and supports attribution of this isotopic enrichment to heterotrophic reworking.

Molecular palaeontological evidence for food-web relationships.

NASA: The authors present evidence of organic compounds derived from insect waxes from sediments of the lagoonal and sabkha sedimentary systems of the coast of Abu Dhabi.^ieng