Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff,Latvia

Luk?evi?s, E., Ahlberg, P.E., Stinkulis, ?., Vasi?kova, J. & Zupi??, I. 2011: Frasnian vertebrate taphonomy and sedimentology of macrofossil concentrations from the Langsēde Cliff, Latvia. Lethaia, Vol. 45, pp. 356–370. The siliciclastic sequence of the Upper Devonian of Kurzeme, Western Latvia, is renowned for abundant vertebrate fossils, including the stem tetrapods Obruchevichthys gracilis and Ventastega curonica. During the first detailed taphonomic study of the vertebrate assemblage from the Ogre Formation cropping out at the Langsēde Cliff, Imula River, abundant vertebrate remains have been examined and identified as belonging to one psammosteid, two acanthodian and three sarcopterygian genera; the placoderm Bothriolepis maxima dominates the assemblage. Besides fully disarticulated placoderm and psammosteid plates, separate sarcopterygian scales and teeth, and acanthodian spines, partly articulated specimens including complete distal segments of Bothriolepis pectoral fins, Bothriolepis head shields and sarcopterygian lower jaws have been found. The size distribution of the placoderm bones demonstrates that the individuals within the assemblage are of approximately uniform age. Distinct zones have been traced within the horizontal distribution of the bones. These linear zones are almost perpendicular to the dominant dip azimuth of the cross‐beds and ripple‐laminae and most probably correspond to the depressions between subaqueous dunes. Concavity ratio varies significantly within the excavation area. The degree of fragmentation of the bones and disarticulation of the skeletons suggest that the carcasses were reworked and slightly transported before burial. Sedimentological data suggest deposition in a shallow marine environment under the influence of rapid currents. The fossiliferous bed consists of a basal bone conglomerate covered by a cross‐stratified sandstone with mud drapes, which is in turn overlain by ripple laminated sandstone, indicating the bones were buried by the gradual infilling of a tidal channel. All the Middle–Upper Devonian vertebrate bone‐beds from Latvia are associated with sandy to clayey deposits and have been formed in a sea‐coastal zone during rapid sedimentation episodes, but differ in fossil abundance and degree of preservation. □Agnathans, Devonian, facies analysis, fish, fossil assemblage, palaeoenvironment.     

Mechanochemical coupling in spin-labeled, active, isometric muscle

Observed effects of inorganic phosphate (P(i)) on active isometric muscle may provide the answer to one of the fundamental questions in muscle biophysics: how are the free energies of the chemical species in the myosin-catalyzed ATP hydrolysis (ATPase) reaction coupled to muscle force?. Pflugers Arch. 414:73-81) showed that active, isometric muscle force varies logarithmically with [P(i)]. Here, by simultaneously measuring electron paramagnetic resonance and the force of spin-labeled muscle fibers, we show that, in active, isometric muscle, the fraction of myosin heads in any given biochemical state is independent of both [P(i)] and force. These direct observations of mechanochemical coupling in muscle are immediately described by a muscle equation of state containing muscle force as a state variable. These results challenge the conventional assumption mechanochemical coupling is localized to individual myosin heads in muscle.     

Scats and den contents as indicators of the diet of stoats (Mustela erminea) in the Tasman Valley,South Canterbury,New Zealand

Stoats are significant predators of native fauna in New Zealand. They occur in many habitat types and consume a wide range of prey. The diet of stoats in the Tasman River, South Canterbury, was studied by analysis of scats and den contents. Analysis of 206 scats showed that stoats ate mainly lagomorphs, birds and invertebrates. Minor components included mice, lizards, fish and hedgehogs. Stoats ate more birds in spring than in autumn, and female stoats ate more invertebrates than did males. The contents of 219 dens collected in the same area at the same time provided further information. Birds and lagomorphs occurred at high frequency in dens, and other components were minor. Remains in dens were larger than in scats and allowed identification of many more prey items to species level. Den contents revealed a potentially substantial impact of stoats on threatened shorebirds locally; this impact was not detected by analysis of scats.     

Frequency of nosocomial infections as revealed by a prevalence survey

In 1984, a prevalence survey based on the methodology, definitions and criteria meeting the WHO requirements was carried out in the Czech Socialist Republic. This prevalence study on a total of 12,260 hospital patients revealed 751 active cases of nosocomial infection (NI). The conclusions emerging from an epidemiological analysis of the collected NI patient records were as follows: 60% of all infections were acquired on the surgical services, predominantly on the surgery service; 60% of those who developed NI were persons over 50 years of age; hospital-associated infections afflicted 366 males and 385 females; the ratio of infections acquired prior to hospital presentation to those originating while in hospital care was about 4:1, with a tendency to vary depending on type of hospital service; the urinary tract was the most frequent site of infection (25%), followed by surgical wounds (15%) and upper respiratory tract (13%); 17% of NI patients contracted the infection in spite of preventive doses of antimicrobials, 28% of NI patients received no antimicrobial prophylaxis; among the 78% (589 out of 751) of patients examined bacteriologically, 46% of infections were caused by Gram-negative rods, 19% by staphylococci, 7% by streptococci and 6% by Pseudomonas aeruginosa; 22% of NI patients were not examined for the pathogen. The prevalence survey methodology turned out to be useful as a tool for detecting the immediate magnitude of the NI problem, but can also be used as a control method.     

Evolutionary avenues for, and constraints on, the transmission of frog lung flukes (Haematoloechus spp.) in dragonfly second intermediate hosts

Metacercariae survival patterns and their distribution in second intermediate odonate hosts were examined for 4 species of frog lung flukes. Surveys of aquatic larvae and recently emerged teneral dragonflies and damselflies indicated that prevalence and mean abundance of Haematoloechus spp. metacercariae were significantly lower in teneral dragonflies than larval dragonflies, while there was no significant difference in prevalence or mean abundance of Haematoloechus spp. metacercariae among larval and teneral damselflies. Experimental infections of dragonflies indicated that metacercariae of Haematoloechus coloradensis and Haematoloechus complexus were located in the head, thorax, and branchial basket of dragonflies, whereas metacercariae of Haematoloechus longiplexus and Haematoloechus parviplexus were restricted to the branchial basket of these hosts. Metacercariae of H. coloradensis, H. complexus, and H. longiplexus infected the head, thorax, and abdomen of damselflies, but these insects were resistant to infection with H. parviplexus. Subsequent metamorphosis experiments on experimentally infected dragonflies indicated that most metacercariae of H. longiplexus were lost from the branchial basket during metamorphosis, but most metacercariae of H. coloradensis, H. complexus, and H. parviplexus survived dragonfly metamorphosis. These observations suggest that the observed ecological host specificity of H. longiplexus in semiterrestrial leopard frogs may be due to few metacercariae of H. longiplexus reaching these frogs in a terrestrial environment. Because of the uncertain validity of Haematoloechus varioplexus as a distinct species from its synonym H. parviplexus, their morphological characters were reevaluated. The morphological data on H. varioplexus and H. parviplexus indicate that they differ in their acetabulum length and width, ovary shape, testes length, and egg length and width. Experimental infections of plains leopard frogs, northern leopard frogs, and bullfrogs with worms from bullfrogs indicate that the synonymy of H. parviplexus with H. varioplexus is not warranted, and that these flukes are distinct species, i.e., H. parviplexus in bullfrogs and H. varioplexus in plains leopard frogs and northern leopard frogs.     

Biological effects of noble gases

Noble gases are known for their inertness. They do not react chemically with any element at normal temperature and pressure. Through that, some of them are known to be biologically active by their sedative, hypnotic and analgesic properties. Common inhalation anesthetics are characterized by some disadvantages (toxicity, decreased cardiac output, etc). Inhalation of xenon introduces anesthesia and has none of the above disadvantages, hence xenon seems to be the anesthetic gas of the future (with just one disadvantage - its cost). It is known that argon has similar anesthetic properties (under hyperbaric conditions), which is much cheaper and easily accessible. The question is if this could be used in clinical practice, in anesthesia of patients who undergo treatment in the hyperbaric chamber. Xenon was found to be organ-protective. Recent animal experiments indicated that xenon decreases infarction size after ischemic attack on brain or heart. The goal of our study is to check if hyperbaric argon has properties similar to those of xenon.