Congruence of chloroplast- and nuclear-encoded DNA sequence variations used to assess species boundaries in the soil microalga Heterococcus (Stramenopiles, Xanthophyceae).

BackgroundHeterococcus is a microalgal genus of Xanthophyceae (Stramenopiles) that is common and widespread in soils, especially from cold regions. Species are characterized by extensively branched filaments produced when grown on agarized culture medium. Despite the large number of species described exclusively using light microscopic morphology, the assessment of species diversity is hampered by extensive morphological plasticity.ResultsTwo independent types of molecular data, the chloroplast-encoded psbA/rbcL spacer complemented by rbcL gene and the internal transcribed spacer 2 of the nuclear rDNA cistron (ITS2), congruently recovered a robust phylogenetic structure. With ITS2 considerable sequence and secondary structure divergence existed among the eight species, but a combined sequence and secondary structure phylogenetic analysis confined to helix II of ITS2 corroborated relationships as inferred from the rbcL gene phylogeny. Intra-genomic divergence of ITS2 sequences was revealed in many strains. The 'monophyletic species concept', appropriate for microalgae without known sexual reproduction, revealed eight different species. Species boundaries established using the molecular-based monophyletic species concept were more conservative than the traditional morphological species concept. Within a species, almost identical chloroplast marker sequences (genotypes) were repeatedly recovered from strains of different origins. At least two species had widespread geographical distributions; however, within a given species, genotypes recovered from Antarctic strains were distinct from those in temperate habitats. Furthermore, the sequence diversity may correspond to adaptation to different types of habitats or climates.ConclusionsWe established a method and a reference data base for the unambiguous identification of species of the common soil microalgal genus Heterococcus which uses DNA sequence variation in markers from plastid and nuclear genomes. The molecular data were more reliable and more conservative than morphological data

Scaled Chrysophyceae from Arkansas. II. The Genera Mallaomonas, Paraphysomonas and Spiniferomonas

This is the second paper of a floristic survey of the scaled Chrysophyceae of Arkansas and includes the following species: Mallomonax crassisquama, M. cratis var. Asmumdine, M. papillosa, M. caudata, M. heterospina, M. insignis, Paraph vsomonas vestita, P. imperforwa and Spiniferomonas conic

Acute Cholangitis: an Update in Management Based on Severity Assessment

Acute cholangitis (AC) is a biliary tract emergency which causes significant morbidity and mortality. The direct cause of death in AC is sepsis that leads to irreversible shock and multiple organ failure. The most common predisposition are bile duct stones and previous invasive manipulation of the biliary tree. Biliary infection and biliary obstruction are the two main factors in pathophysiology of AC. Gram-negative bacteria are isolated frequently from bile and blood culture in cholangitis. The most common cause of biliary obstruction is gallstone.The Charcot's triad which commonly has been used to diagnose AC is severely limited and the clinical presentation of the disease has wide spectrum ranging from mild symptoms to severe life-threatening disease. Thus, the use of the most updated Tokyo Guidelines (TG18) is imperative to diagnose the disease and to assess the severity. The TG18 diagnostic criteria is based on the presence of systemic inflammmation, cholestasis, and evidence on imaging studies of biliary tract. The prompt treatment is tailored according to severity assessed by TG18. Initial treatment includes sufficient fluid replacement, hemodynamic control, electrolyte compensation, intravenous antibiotic administration, and intravenous analgesic administration. The definitive treatment which related to the pathophysiology of the disease are biliary drainage and antibiotic administration

Scaled Chrysophyceae from Arkansas

An initial study of scaled chrysophytes from Arkansas is presented. Species include: Synura Petersenii f. Petersenii, S. spinosa f. spinosa, S. curtispina f. curtispina, S. curtispina f. reticulata, S. uvella, Mallomonas striata var. striata, M. pumilio var. pumilio, and Chrysosphaerella brevispina. Transmission electron micrographs of their siliceous scales are included

The DiskMass Survey. VIII. On the Relationship Between Disk Stability and Star Formation

We study the relationship between the stability level of late-type galaxy disks and their star-formation activity using integral-field gaseous and stellar kinematic data. Specifically, we compare the two-component (gas+stars) stability parameter from Romeo & Wiegert (Q_RW), incorporating stellar kinematic data for the first time, and the star-formation rate estimated from 21cm continuum emission. We determine the stability level of each disk probabilistically using a Bayesian analysis of our data and a simple dynamical model. Our method incorporates the shape of the stellar velocity ellipsoid (SVE) and yields robust SVE measurements for over 90% of our sample. Averaging over this subsample, we find a meridional shape of sigma_z/sigma_R = 0.51^{+0.36}_{-0.25} for the SVE and, at 1.5 disk scale lengths, a stability parameter of Q_RW = 2.0 +/- 0.9. We also find that the disk-averaged star-formation-rate surface density (Sigma-dot_e,*) is correlated with the disk-averaged gas and stellar mass surface densities (Sigma_e,g and Sigma_e,*) and anti-correlated with Q_RW. We show that an anti-correlation between Sigma-dot_e,* and Q_RW can be predicted using empirical scaling relations, such that this outcome is consistent with well-established statistical properties of star-forming galaxies. Interestingly, Sigma-dot_e,* is not correlated with the gas-only or star-only Toomre parameters, demonstrating the merit of calculating a multi-component stability parameter when comparing to star-formation activity. Finally, our results are consistent with the Ostriker et al. model of self-regulated star-formation, which predicts Sigma-dot_e,*/Sigma_e,g/sqrt(Sigma_e,*). Based on this and other theoretical expectations, we discuss the possibility of a physical link between disk stability level and star-formation rate in light of our empirical results.Comment: Accepted for publication in ApJ. 15 pages, 6 figures, 2 tables. An electronic version of Table 1 is available by request, or at http://www.astro.rug.nl/~westfall/research/dmVIII_table1.tx

Fourth Symposium on Chemical Evolution and the Origin and Evolution of Life

This symposium was held at the NASA Ames Research Center, Moffett Field, California, July 24-27, 1990. The NASA exobiology investigators reported their recent research findings. Scientific papers were presented in the following areas: cosmic evolution of biogenic compounds, prebiotic evolution (planetary and molecular), early evolution of life (biological and geochemical), evolution of advanced life, solar system exploration, and the Search for Extraterrestrial Intelligence (SETI)

Scaled Chrysophyceae From Lake Itasca Region. ll. Synura, Chrysophaerella, Spiniferomonas

Using electron microscopy, 49 plankton samples from the Lake Itasca region were examined for the silica-scaled chrysophycean genera Synura, Chrysosphaerella and Spiniferomonas. Twelve taxa were observed: five are new for Minnesota, and two of these, Synura multidenta and Synura petersenil f. asmundiae, are new reports for the continental United States

Real-time price discovery in stock, bond and foreign exchange markets

We characterize the response of U.S., German and British stock, bond and foreign exchange markets to real-time U.S. macroeconomic news. Our analysis is based on a unique data set of high-frequency futures returns for each of the markets. We find that news surprises produce conditional mean jumps; hence high-frequency stock, bond and exchange rate dynamics are linked to fundamentals. The details of the linkages are particularly intriguing as regards equity markets. We show that equity markets react differently to the same news depending on the state of the economy, with bad news having a positive impact during expansions and the traditionally-expected negative impact during recessions. We rationalize this by temporal variation in the competing "cash flow" and "discount rate" effects for equity valuation. This finding helps explain the time-varying correlation between stock and bond returns, and the relatively small equity market news effect when averaged across expansions and recessions. Lastly, relying on the pronounced heteroskedasticity in the high-frequency data, we document important contemporaneous linkages across all markets and countries over-and-above the direct news announcement effects. JEL Klassifikation: F3, F4, G1, C

CC199 Fall Potato Production Guide for Western Nebraska

EC199 discusses fall potato production quide for western Nebraska