Cyanobacteria and seasonal death: A new taphonomic model for the Eocene Messel lake

Two new observations lead us to reconsider the taphonomy of Messel. First, several horses as well as turtles indicate death at a specific season although they come from different horizons. Second, specific structures in the Sediments are very similar to those found in Neumark-Nord. There they could be related to Cyanobacteria. Blooms of Cyanobacteria may poison die surface water. From actual observations it is known that animals drinking such poison water collapse immediately and die mostly near or within the water soon. This model might explain why birds and bats are so frequent throughout the entire profile of Messel. Both drink from the water surface during flight. In contrast to volcanic exhalations, assumed so far, such algae blooms occur repeatedly and always during early summer and autumn. An erratum to this article is available at .     

Endocranial morphology of Palaeocene Plesiadapis tricuspidens and evolution of the early primate brain

Expansion of the brain is a key feature of primate evolution. The fossil record, although incomplete, allows a partial reconstruction of changes in primate brain size and morphology through time. Palaeogene plesiadapoids, closest relatives of Euprimates (or crown-group primates), are crucial for understanding early evolution of the primate brain. However, brain morphology of this group remains poorly documented, and major questions remain regarding the initial phase of euprimate brain evolution. Micro-CT investigation of the endocranial morphology of Plesiadapis tricuspidens from the Late Palaeocene of Europe—the most complete plesiadapoid cranium known—shows that plesiadapoids retained a very small and simple brain. Plesiadapis has midbrain exposure, and minimal encephalization and neocorticalization, making it comparable with that of stem rodents and lagomorphs. However, Plesiadapis shares a domed neocortex and downwardly shifted olfactory-bulb axis with Euprimates. If accepted phylogenetic relationships are correct, then this implies that the euprimate brain underwent drastic reorganization during the Palaeocene, and some changes in brain structure preceded brain size increase and neocortex expansion during evolution of the primate brain.     

Decay of vertebrate characters in hagfish and lamprey (Cyclostomata) and the implications for the vertebrate fossil record

The timing and sequence of events underlying the origin and early evolution of vertebrates remains poorly understood. The palaeontological evidence should shed light on these issues, but difficulties in interpretation of the non-biomineralized fossil record make this problematic. Here we present an experimental analysis of decay of vertebrate characters based on the extant jawless vertebrates (Lampetra and Myxine). This provides a framework for the interpretation of the anatomy of soft-bodied fossil vertebrates and putative cyclostomes, and a context for reading the fossil record of non-biomineralized vertebrate characters. Decay results in transformation and non-random loss of characters. In both lamprey and hagfish, different types of cartilage decay at different rates, resulting in taphonomic bias towards loss of 'soft' cartilages containing vertebrate-specific Col2α1 extracellular matrix proteins; phylogenetically informative soft-tissue characters decay before more plesiomorphic characters. As such, synapomorphic decay bias, previously recognized in early chordates, is more pervasive, and needs to be taken into account when interpreting the anatomy of any non-biomineralized fossil vertebrate, such as Haikouichthys, Mayomyzon and Hardistiella.     

Interpreting the origin of mammals: new approaches to the history of palaeontology

New sociological techniques in the history of science are described. Their value is illustrated by reinterpreting the diagnostic disputes which occurred following the first discovery of the Stonesfield mammals. It is concluded that contextual explanations are more sympathetic to early savants and more conducive to the integration of science and social history.     

Preservation and Paleoenvironmental Significance of a Footprinted Surface on the Sandai Plain,Lake Bogoria,Kenya Rift Valley

An exhumed late Pleistocene land surface on the deltaic Sandai Plain north of Lake Bogoria, Kenya, preserves traces of bovids, suids, birds, and at least one hominid. The host sediments (Loboi Silts) are reddish brown, poorly bedded siltstones, mudstones and silty sandstones that were probably deposited in a shallow closed-basin lake. Most of the prints were impressed on exposed, moist lake-marginal mudflats. Print distribution is patchy due to a complex interaction between biogenic and sedimentological factors. The preservation of a single hominid track provides a fortuitous addition to the sparse hominid track record in East Africa. Field, petrographic, and mineralogical analyses of the fossil substrate were undertaken to determine how the footprinted surface was preserved. Comparison with modern lake-marginal processes suggests that the prints were initially stabilized by desiccation, soil-crusting, and organic films, followed by cementation of the surface sediments by calcite and analcime, with minor authigenic clay minerals and Fe-Mn-oxihydroxides. The zeolites formed by reaction of detrital silicates with saline, alkaline groundwater; calcite was precipitated from dilute runoff and fresher groundwaters. Cementation likely occurred during a prolonged period of relatively low, stable lake level. Following cementation, the surface was buried by Holocene lake sediments, then recently exhumed.     

A dynamic history of gene duplications and losses characterizes the evolution of the SPARC family in eumetazoans

The vertebrates share the ability to produce a skeleton made of mineralized extracellular matrix. However, our understanding of the molecular changes that accompanied their emergence remains scarce. Here, we describe the evolutionary history of the SPARC (secreted protein acidic and rich in cysteine) family, because its vertebrate orthologues are expressed in cartilage, bones and teeth where they have been proposed to bind calcium and act as extracellular collagen chaperones, and because further duplications of specific SPARC members produced the small calcium-binding phosphoproteins (SCPP) family that is crucial for skeletal mineralization to occur. Both phylogeny and synteny conservation analyses reveal that, in the eumetazoan ancestor, a unique ancestral gene duplicated to give rise to SPARC and SPARCB described here for the first time. Independent losses have eliminated one of the two paralogues in cnidarians, protostomes and tetrapods. Hence, only non-tetrapod deuterostomes have conserved both genes. Remarkably, SPARC and SPARCB paralogues are still linked in the amphioxus genome. To shed light on the evolution of the SPARC family members in chordates, we performed a comprehensive analysis of their embryonic expression patterns in amphioxus, tunicates, teleosts, amphibians and mammals. Our results show that in the chordate lineage SPARC and SPARCB family members were recurrently recruited in a variety of unrelated tissues expressing collagen genes. We propose that one of the earliest steps of skeletal evolution involved the co-expression of SPARC paralogues with collagenous proteins.     

Environmental stress and diagenetic modifications in inoceramids and belemnites from the Upper Cretaceous James Ross Basin, Antarctica

Summary New petrographic and isotopic data from inoceramid bivalve shells and belemnite rostra from the lower Campanian and belemnite rostra from the mid-upper Maastrichtian of the Marambio Group, James Ross Basin, Antarctica are presented. Most of the inoceramid data were processed from shell fragments of the large formAntarcticeramus rabotensis (Crame and Luther) at the stratigraphic level marking the extinction of the inoceramids in the James Ross Basin (uppermost early Campanian-basal late Campanian). Standard transmitted light microscopy and cathodoluminescence (CL) studies in thin sections ofA. rabotensis show clear evidence of environmental stress, which is reflected as marked growth breaks in the shell banding of this large inoceramid bivalve. At Redonda Point, CL and the mean oxygen isotopic value (δ¹⁸O=-3.11‰ 3 (PDB); n=11; t°=25.4°C) indicate a varied degree of diagenetic modification, but without any evidence of neomorphism along the prismatic microstructures. Early Campanian belemnite rostra are much less diagenetically modified (at the Brandy Bay section; and the Santa Marta section; δ¹⁸O=-0.50‰ (PDB); n=5; t°=14.0°C and 3 δ¹⁸O=-0.94‰ (PDB); n=21; t°=15.8°C) and are non luminescent 3 except for localized, organic-rich bands. The mean oxygen isotopic value for mid-late Maastrichtian belemnite rostra (at the Seymour Island section; δ¹⁸O=-0.11‰ 3 (PDB); n=5; t°=12.5°C) indicates a substantial drop in the sea-water paleotemperature, suggesting a causal relationship between the early extinction of the inoceramid bivalves in high latitudes of the Southern Hemisphere and the falling sea-water temperature.     

A theoretical experimental method to determine the locus of desensitization

Consider a ligand-gated channel with n agonist binding sites which can undergo desensitization. We present a theoretical experimental procedure for pinpointing the principal receptor state from which there is a transition to the desensitized state. The method is based on the observation that the dependence of the slope of the time constant of desensitization vs agonist concentration, at low concentrations, represents the state from which desensitization occurs. In those receptors where desensitization occurs from the open state (or the one immediately preceding it), the method also enables us to determine the number of binding sites.     

A simple method to determine the enantiomeric ratio in enantioselective biocatalysis

The enantiomeric ratio (E) is commonly used to characterize the enantioselectivity in enzyme-catalyzed kinetic resolution. In this paper this parameter is directly derived from the enantiomeric excess of substrate and product. This is formally more correct than using Chen's equation after calculating the degree of conversion from both ee values using the relation of Sih and Wu. New expressions and useful graphs have been generated for reversible and irreversible uni-uni reactions. The theoretical predictions have been verified experimentally for various reactions. Values for E and the thermodynamic equilibrium constant,K_EQ, were obtained for a ( -dehalogenase-catalyzed dehalogenation, a hydrolysis reaction by porcine pancreatic lipase, and for C. Cylindracea lipase-catalyzed esterification and transesterification. In view of the current developments in the field of chiral analysis, this method is an easily available tool in the quantitative treatment of enzyme-catalyzed resolution of enantiomers.     

A method to determine protein of bacteria grown in agar

A method is described to determine the amount of protein of bacteria grown in agar. Amino acid contents of hydrolysates of agar cultures are compared with the amino acids in hydrolysates of the same bacteria grown in a liquid medium. In the latter medium also the amount of bacterial protein is determined. From these data the protein content of bacteria grown in agar can be calculated.     

An application of beam theory to determine the stress and deformation of long bones

We present a generalized beam theory in which deformation and load are determined simultaneously, in order to analyze statically indeterminant problems involving long bones. We regard a long bone as a beam curved in three dimensions for which the cross-sectional properties vary continuously along its length. The theory is used to determine the force, moment, deflection and twist along the fifth metatarsal when it is subjected to both a pointwise and a distributed load.     

A simple method to determine released acetylcholine in the presence of choline

In experiments where the release of labeled acetylcholine is to be determined, the addition of choline oxidase to the incubation medium prevents any reuptake of choline. In addition, since betaine, the oxidation product of choline is not extractable into tetraphenylboron - butyronitrile, no further procedure to eliminate choline is required.     

The occurrence and preservation of ammonites in the Blue Lias Formation (lower Jurassic) of Devon and Dorset, England and their palaeoecological, sedimentological and diagenetic significance

More than two thirds of beds in the lowest Jurassic, Blue Lias Formation lack ammonites, which are commonly preserved in irregular or planar-bedded, bioturbated limestones, very rarely in laminated limestones and almost never in laminated black shales. Ammonites are preserved in 3D in nodular and planar-bedded limestones and at any orientation to bedding. Co-occurrence with macrobenthos and absence from beds without benthos suggest that Blue Lias ammonites were nektobenthonic. Scour structures and imbrication of ammonites in the Best Bed imply presence of traction currents. Lack of epifauna on large cephalopod shells (and other fossils) implies rapid deposition in event beds. Blue Lias deposition was episodic, not slow and continuous as the fine grain size implies. Undistorted trace fossils, uncrushed ammonites and stable isotope values all suggest early cementation of limestone beds from pore waters of a similar composition to contemporary Jurassic sea water. A clear diagenetic trend exists, with limestones having least, and laminated black shales most, modified stable isotope values. Contrast between trace fossil fills and host sediment demonstrates that Blue Lias rhythms are primary, but limestone beds have been diagenetically cemented.     

A method to determine rates and patterns of variability in ecological communities

It is well known that ecological communities are spatially and temporally dynamic. Quantifying temporal variability in ecological communities is challenging, however, especially for time-series data sets of less than 40 measurement intervals. In this paper, we describe a method to quantify temporal variability in multispecies communities over time frames of 10–40 measurement intervals. Our approach is a community-level extension of autocorrelation analysis, but we use Euclidean distance to measure similarity of community samples at increasing time lags rather than the correlation coefficient. Regressing Euclidean distances versus increasing time lags yields a measure of the rate and nature of community change over time. We demonstrate the method with empirical data sets from shortgrass steppe, old-field succession and zooplankton dynamics in lakes, and we investigate properties of the analysis using simulation models. Results indicate that time-lag analysis provides a useful quantitative measurement of the rate and pattern of temporal dynamics in communities over time frames that are too short for more traditional autocorrelation approaches.     

A method to determine the relative cAMP permeability of connexin channels

Here we present a method by which gap junction-mediated intercellular diffusion of adenosine 3',5'-cyclic monophosphate (cAMP) molecules can be monitored in "real-time" and the cAMP permeability of different gap junction channels can be compared. Intercellular cAMP diffusion was investigated throughout this study in human HeLa cells coexpressing murine connexin45 and cyclic nucleotide-gated (CNG) ion channels. The CNG channels were used as cAMP sensors, since CNG channel activation led to an increase of the cytosolic Ca2+ concentration, which was monitored by Ca2+ imaging. A cAMP gradient was generated between two contacting cells by restricting the photolysis of caged cAMP to only one cell. The intercellular diffusion of cAMP was measured by the increase in Ca2+ concentration in the neighboring cell. We developed a standardization procedure for the Ca2+ signal which allowed estimation of the amount of cAMP that diffused from cell to cell. The number of gap junction channels between each cell pair investigated was determined by double whole-cell patch-clamp measurements. On the basis of these data we calculated how many gap junction channels contributed to the diffusion of a certain amount of cAMP. The new method can be used to compare the selective permeabilities of different gap junction channels for cAMP and for cGMP which also activates the CNG channel.     

A NMR method to determine the anomeric specificity of glucose phosphorylation

A NMR method related to 2D CH correlation with an additional double quantum filter for ³¹P spin coupling was employed to follow the reaction kinetics of the two anomers of glucose during phosphorylation catalyzed by the enzyme yeast hexokinase. The kinetic parameters according to Michaelis–Menten for these reactions have been determined and it is shown that the β-anomer of glucose is phosphorylated faster by a factor of 1.4 versus the α-anomer. Use of human liver glucokinase as an enzyme yields more complex kinetics.     

A simple and rapid method to determine the zygosity of uPA-transgenic SCID mice

Successful transplantation of xenogeneic hepatocytes into uPA-transgenic SCID mice depends on the zygosity of the recipient mice. Normally, the difference between homozygous and heterozygous animals is determined via a quantitative Southern blot. We sequenced a part of the mouse genome that is eliminated upon integration of the transgene in the genome. Based on that sequence we developed a multiplex PCR that allows the unambiguous discrimination of negative, heterozygous, and homozygous uPA-transgenic SCID mice in a single day procedure. The speed of the procedure is an essential quality because transplantation of xenogeneic hepatocytes into uPA-SCID mice should be done as soon as possible after birth.