The toxic effects of anticholinesterases on muscle

It has been shown that acute administration of ecothiopate iodine in vivo caused an approximate 80% depression of acetylcholinesterase activity in the diaphragms of mice. Inhibition of acetylcholinesterase was accompanied by an influx of calcium at the junctional region of the diaphragm, which continued during subsequent progressive development of a severe myopathy located in the same region. Myopathy was accompanied by loss of creatine kinase from the muscle and was represented, at the light microscope level, by hypercontraction, Procion Yellow staining and loss of cross striations within the muscle fibres. It appeared to reach a point of maximum severity approximately 3-6 hours after ecothiopate administration and then, by means of some repair/regeneration process, regained an apparently normal morphology within 72 hours of the intoxication. At the ultrastructural level, ecothiopate-induced myopathy was recognised by loss of Z-lines, swelling and vacuolation of mitochondria and sarcoplasmic reticulum, dissarray of myofilaments, crystal formation, and sometimes, by the complete obliteration of sarcomeric structure. The development of myopathy in vitro was shown to be nerve-mediated and to require a functional acetylcholine receptor for its development It was successfully treated therapeutically in vivo by pyridine-2-aldoxime methiodide and prophylactically by pyridostigmine bromide. However, the use of a range of membrane-on channel blockers, and of leupeptin, an inhibitor of calcium-activated-neutral-protease, have been unsuccessful in the prevention of ecothiopate-induced myopathy.

Nematode absolute densities and genus counts from four stations near the Antarctic Peninsula, collected with a multicorer device during POLARSTERN cruise ANT-XXIX/3 in January-March 2013

Marine free-living nematode communities were studied at similar depths (~500m) at two sides of the Antarctic Peninsula, characterised by different environmental and oceanographic conditions. At the Weddell Sea side, benthic communities are influenced by cold deep-water formation and seasonal sea-ice conditions, whereas the Drake Passage side experiences milder oceanic conditions and strong dynamics of the Antarctic Circumpolar Current. Surface primary productivity contrasted with observed benthic pigment patterns and varied according to the area studied: chlorophyll a concentrations (as a proxy for primary production) were high in the Weddell Sea sediments, but low in the surface waters above; this pattern was reversed in the Drake Passage. Differences between areas were largely mirrored by the nematode communities: nematode densities peaked in Weddell stations and showed deeper vertical occurrence in the sediment, associated with deeper penetration of chlorophyll a. Generic composition did not differ markedly between both areas, but rather showed distinct community shifts with depth in the sediment.

Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates - Collection of source datasets - Contribution to the MAREDAT World Ocean Atlas of Plankton Functional Types

The MAREDAT atlas covers 11 types of plankton, ranging in size from bacteria to jellyfish. Together, these plankton groups determine the health and productivity of the global ocean and play a vital role in the global carbon cycle. Working within a uniform and consistent spatial and depth grid (map) of the global ocean, the researchers compiled thousands and tens of thousands of data points to identify regions of plankton abundance and scarcity as well as areas of data abundance and scarcity. At many of the grid points, the MAREDAT team accomplished the difficult conversion from abundance (numbers of organisms) to biomass (carbon mass of organisms). The MAREDAT atlas provides an unprecedented global data set for ecological and biochemical analysis and modeling as well as a clear mandate for compiling additional existing data and for focusing future data gathering efforts on key groups in key areas of the ocean. The present collection presents the original data sets used to compile Global distributions of diazotrophs abundance, biomass and nitrogen fixation rates

(Appendix) Total organic carbon, pyrolysis characteristics, and organic matter types at DSDP Holes 77-535 and 77-540

Lower to middle Cretaceous sediments in the eastern Gulf of Mexico are richer in organic matter and have a more marine organic facies than their counterparts in the nearby western North Atlantic, suggesting that the Gulf was the more productive of the two areas. As in the western North Atlantic, the rate of supply of terrestrial organic matter was high when the rate of supply of noncarbonate clastic materials was high (at times of low sea level) and diminished as sea level rose. The rate of supply of marine organic matter was lower in the Early Cretaceous than in the Cenomanian, perhaps in response to the global rise in sea level over this period. Where they are thermally mature, the organic matterrich units drilled at Sites 535 and 540 should be excellent sources for liquid hydrocarbons. The Pleistocene sediments of the eastern Gulf are dominated by terrestrial organic matter representing Mississippi River effluent.

(Figure 2) Stratigraphic distribution of Schizosphaerella in DSDP Hole 79-547B

The Jurassic (hemi)pelagic continental margin deposits drilled at Hole 547B, off the Moroccan coast, reveal striking Tethyan affinity. Analogies concern not only types and gross vertical evolution of facies, but also composition and textures of the fine sediment and the pattern of diagenetic alteration. In this context, the occurrence of the nanno-organism Schizosphaerella Deflandre and Dangeard (sometimes as a conspicuous portion of the fine-grained carbonate fraction) is of particular interest. Schizosphaerella, an incertae sedis taxon, has been widely recorded as a sediment contributor from Tethyan Jurassic deeper-water carbonate facies exposed on land. Because of its extremely long range (Hettangian to early Kimmeridgian), the genus Schizosphaerella (two species currently described, S. punctulata Deflandre and Dangeard and S. astrea Moshkovitz) is obviously not of great biostratigraphic interest. However, it is of interest in sedimentology and petrology. Specifically, Schizosphaerella was often the only component of the initial fine-grained fraction of a sediment that was able to resist diagenetic obliteration. However, alteration of the original skeletal structure did occur to various degrees. Crystal habit and mineralogy of the fundamental skeletal elements, as well as their mode of mutual arrangement in the test wall with the implied high initial porosity of the skeleton (60-70%), appear to be responsible for this outstanding resistance. Moreover, the ability to concentrate within and, in the case of the species S. punctulata, around the skeleton, large amounts of diagenetic calcite also contributed to the resistance. In both species of Schizosphaerella, occlusion of the original skeletal void space during diagenesis appears to have proceeded in an analogous manner, with an initial slight uniform syntaxial enlargement of the basic lamellar skeletal crystallites followed, upon mutual impingement, by uneven accretion of overgrowth cement in the remaining skeletal voids. However, distinctive fabrics are evident according to the different primary test wall architecture. In S. punctulata, intraskeletal cementation is usually followed by the growth of a radially structured crust of bladed to fibrous calcite around the valves. These crusts are interpreted as a product of aggrading neomorphism, associated with mineralogic stabilization of the original, presumably polyphase, sediment. Data from Hole 547B, along with inferences, drawn from the fabric relationships, suggest that the crusts formed and (inferentially) mineralogic stabilization occurred at a relatively early time in the diagenetic history in the shallow burial realm. An enhanced rate of lithification at relatively shallow burial depths and thus the chance for neomorphism to significantly influence the textural evolution of the buried sediment may be related to a lower Mg/Ca concentration ratio in the oceanic system and, hence, in marine pore waters in pre-Late Jurassic times.

Sediment and ice characteristics at a buried ice-wedge system at Barrow

Barrow, the northernmost point in Alaska, is one of the most intensively studied areas in the Arctic. However, paleoenvironmental evidence is limited for northern Alaska for the Lateglacial-Holocene transition. For a regional paleoenvironmental reconstruction, we investigated a permafrost ice-wedge tunnel near Barrow, Alaska. The studied site was first excavated in the early 1960s and intercepts a buried ice-wedge system at 3-6 m depth below the surface. A multi-methodological approach was applied to this buried ice-wedge system and the enclosing sediments, which in their combination, give new insight into the Late Quaternary environmental and climate history. Results of geochronological, sedimentological, cryolithological, paleoecological, isotope geochemical and microbiological studies reflect different stages of mid to late Wisconsin (MW to LW), Allerod (AD), Younger Dryas (YD), Preboreal (PB), and Late Holocene paleoenvironmental evolution. The LW age of the site is indicated by AMS dates in the surrounding sediments of 21.7 kyr BP at the lateral contact of the ice-wedge system as well as 39.5 kyr BP below the ice-wedge system. It is only recently that in this region, stable isotope techniques have been employed, i.e. to characterize different types of ground ice. The stable isotope record (oxygen: d18O; hydrogen: dD) of two intersecting ice wedges suggests different phases of the northern Alaskan climate history from AD to PB, with radiocarbon dates from 12.4 to 9.9 kyr BP (ranging from 14.8 to 10.6 kyr cal BP). Stable isotope geochemistry of ice wedges reveals winter temperature variations of the Lateglacial-Holocene transition including a prominent YD cold period, clearly separated from the warmer AD and PB phases. YD is only weakly developed in summer temperature indicators (such as pollen) for the northern Alaska area, and by consequence, the YD cold stadial was here especially related to the winter season. This highlights that the combination of winter and summer indicators comprehensively describes the seasonality of climate-relevant processes in discrete time intervals. The stable isotope record for the Barrow buried ice-wedge system documents for the first time winter climate change at the Lateglacial-Holocene transition continuously and at relatively high (likely centennial) resolution.

(Table 1) Distribution of upper Campanian-lower Maestrichtian calcareous nannofossils at DSDP Hole 71-511

Calcareous nannofossils from upper Campanian-lower Maestrichtian Deep Sea Drilling Project Leg 71 Cores 511-23 and 511-24 are described and correlated with assemblages of similar age from piston and drill cores on the Falkland Plateau, South Atlantic Ocean. The Leg 71 cores partially fill a drilling gap of at least 20 meters left within a thick (50 m) carbonate section first drilled by DSDP Leg 36 at Site 327. Cores 511-23 and 511-24 both fall within the upper portion of the Biscutum coronum Zone of Wind and demonstrate an overlap in the range of Monomarginatus quaternarius with the ranges of M. pectinatus, Misceomarginatus pleniporus, and Biscutum coronum across the Campanian/ Maestrichtian boundary. Resolution of the sequence of highest occurrence datums for the latter species must await the recovery of a more complete section. Comparison of the Site 511 assemblages with those from Mas Orcadas Core 07-75-44 to the north confirms earlier speculation that the Falkland Plateau served as an important boundary between major water masses during the Late Cretaceous.

Reconsidering the Origins of Forsbergh Birefringence Patterns

In 1949, P. W. Forsbergh Jr. reported spontaneous spatial ordering in the birefringence patterns seen in flux-grown BaTiO3 crystals [1], under the transmission polarized light microscope [2]. Stunningly regular square-net arrays were often only found within a finite temperature window and could be induced on both heating and cooling, suggesting genuine thermodynamic stability. At the time, Forsbergh rationalized the patterns to have resulted from the impingement of ferroelastic domains, creating a complex tessellation of variously shaped domain packets. However, evidence for the intricate microstructural arrangement proposed by Forsbergh has never been found. Moreover, no robust thermodynamic argument has been presented to explain the region of thermal stability, its occurrence just below the Curie Temperature and the apparent increase in entropy associated with the loss of the Forsbergh pattern on cooling. As a result, despite decades of research on ferroelectrics, this ordering phenomenon and its thermodynamic origin have remained a mystery. In this paper, we re-examine the microstructure of flux-grown BaTiO3 crystals, which show Forsbergh birefringence patterns. Given an absence of any obvious arrays of domain polyhedra, or even regular shapes of domain packets, we suggest an alternative origin for the Forsbergh pattern, in which sheets of orthogonally oriented ferroelastic stripe domains simply overlay one another. We show explicitly that the Forsbergh birefringence pattern occurs if the periodicity of the stripe domains is above a critical value. Moreover, by considering well-established semiempirical models, we show that the significant domain coarsening needed to generate the Forsbergh birefringence is fully expected in a finite window below the Curie Temperature. We hence present a much more straightforward rationalization of the Forsbergh pattern than that originally proposed, in which exotic thermodynamic arguments are unnecessary.