Further observations on Calliacantha Leadbeater Choanoflagellata), with special reference to C. simplex sp. nov. from many parts of the world.

C. simplex is a new species with an unusually wide geographical range, occurring at sea temperatures as varied as 0 degrees C under ice at Pt Barrow or -1 degrees C in arctic Canada, to 22 degrees C on the equator at the Galapagos Islands. The morphology and range of variation are illustrated by means of light microscopy, transmission electron microscopy and scanning electron microscopy applied to dry whole mounts prepared in situ from freshly-gathered wild material. Among the diagnostic structural features, special interest attaches to the position of the anterior transverse costa which is located unusually far back in comparison with other members of the genus; it is also shown to be within and not outside the ring of four longitudinal costae building up the lorica chamber, although this feature can only be ascertained by scanning. The differences between this species and C. natans (type species of the genus) are shown to be greater and to involve more characters than could previously have been recognized, and some possible functional implications are discussed in a preliminary way.     

Measurement of Greenhouse Gas Flux from Agricultural Soils Using Static Chambers

Measurement of greenhouse gas (GHG) fluxes between the soil and the atmosphere, in both managed and unmanaged ecosystems, is critical to understanding the biogeochemical drivers of climate change and to the development and evaluation of GHG mitigation strategies based on modulation of landscape management practices. The static chamber-based method described here is based on trapping gases emitted from the soil surface within a chamber and collecting samples from the chamber headspace at regular intervals for analysis by gas chromatography. Change in gas concentration over time is used to calculate flux. This method can be utilized to measure landscape-based flux of carbon dioxide, nitrous oxide, and methane, and to estimate differences between treatments or explore system dynamics over seasons or years. Infrastructure requirements are modest, but a comprehensive experimental design is essential. This method is easily deployed in the field, conforms to established guidelines, and produces data suitable to large-scale GHG emissions studies.     

Hyperglycemia increases endothelial superoxide that impairs smooth muscle cell Na+-K+-ATPase activity

Nitric oxide (NO) plays an important role in the control of numerous vascular functions including basal Na+-K+-ATPase activity in arterial tissue. Hyperglycemia inhibits Na+-K+-ATPase activity in rabbit aorta, in part, through diminished bioactivity of NO. The precise mechanism(s) for such observations, however, are not yet clear. The purpose of this study was to examine the role of superoxide in modulating NO-mediated control of Na+-K+-ATPase in response to hyperglycemia. Rabbit aorta incubated with hyperglycemic glucose concentrations (44 mM) demonstrated a 50% reduction in Na+-K+-ATPase activity that was abrogated by superoxide dismutase. Hyperglycemia also produced a 50% increase in steady-state vascular superoxide measured by lucigenin-enhanced chemiluminescence that was closely associated with reduced Na+-K+-ATPase activity. Specifically, the hyperglycemia-induced increase in vascular superoxide was endothelium dependent, inhibited by L-arginine, and stimulated by N(omega)-nitro-L-arginine. Aldose reductase inhibition with zopolrestat also inhibited the hyperglycemia-induced increase in vascular superoxide. In each manipulation of vascular superoxide, a reciprocal change in Na+-K+-ATPase activity was observed. Finally, a commercially available preparation of Na+-K+-ATPase was inhibited by pyrogallol, a superoxide generator. These data suggest that hyperglycemia induces an increase in endothelial superoxide that inhibits the stimulatory effect of NO on vascular Na+-K+-ATPase activity.     

The enzymic defect and storage products in canine fucosidosis.

A marked deficiency of alpha-L-fucosidase and the accumulation of fucose-containing glycoasparagines were found in the brains of two English Springer spaniels suffering from a progressive nervous disorder. Both forms of alpha-L-fucosidase in normal brain, which are separable by ion-exchange chromatography, are absent from the affected animals. The storage products were characterized by t.l.c., gel filtration, g.l.c. and fast-atom-bombardment mass spectrometry. The postulated structures of the main components are: (formula; see text) The enzymic defect and nature of storage products justify designation of this disorder as canine fucosidosis.     

The site of VX2 tumor transplantation affects the development of hypercalcemia in rabbits

The relationship between plasma levels of 15-keto-13, 14-dihydro-prostaglandin E₂ (15K-H₂-PGE₂) and serum calcium levels was studied in nontumor-bearing rabbits and in rabbits bearing the VX₂ carcinoma intramuscularly and intra-abdominally. The plasma levels of 15K-H₂-PGE₂ in the two groups of tumor-bearing animals did not vary significantly but was several fold greater than in nontumor-bearing rabbits. Rabbits bearing the VX₂ carcinoma intramuscularly developed hypercalcemia between the second and third week after implantation of neoplastic tissue and remained hypercalcemic until they expired. The serum calcium levels in rabbits bearing the VX₂ carcinoma intra-abdominally did not vary significantly from those of nontumor-bearing rabbits. The differences in the serum calcium levels in rabbits bearing the VX₂ carcinoma at intramuscular and intra-abdominal implant sites may be related to different extents of metabolism by the lung and by the liver of prostaglandin E₂ or other cyclooxygense products of polyenoic fatty acids produced by the tumor.     

Molecular phylogeny of Amoebozoa and the evolutionary significance of the unikont Phalansterium

The taxonomic position of the uniciliate, unicentriolar zooflagellate Phalansterium is problematic; its distinctive ultrastructure with a pericentriolar microtubular cone placed it in its own order and suggested phenotypic closeness to the eukaryote cenancestor. We sequenced the 18S rRNA of a unicellular Phalansterium. Phylogenetic analysis shows that it belongs to Amoebozoa, decisively rejecting a postulated relationship with the cercozoan Spongomonas; Phalansterium groups with Varipodida ord. nov. (Gephyramoeba/Filamoeba) or occasionally Centramoebida emend. (Acanthamoebidae/Balamuthiidae fam. nov.), centrosomes of the latter suggesting flagellate ancestors. We also studied Phalansterium solitarium cyst ultrastructure; unlike previously studied P. solitarium, this strain has pentagonally symmetric walls like P. consociatum. We also sequenced 18S rRNA genes of further isolates of Hyperamoeba, an aerobic unicentriolar amoeboflagellate with conical microtubular skeleton; both group strongly with myxogastrid Mycetozoa. However, the four Hyperamoeba strains do not group together, suggesting that Hyperamoeba are polyphyletic derivatives of myxogastrids that lost fruiting bodies independently. We revise amoebozoan higher-level classification into seven classes, establishing Stelamoebea cl. nov. for Protosteliida emend. plus Dictyosteliida (biciliate former ‘protostelids’ comprise Parastelida ord. nov. within Myxogastrea), and new subphylum Protamoebae to embrace Variosea cl. nov. (Centramoebida, Phalansteriida, Varipodida), Lobosea emend., Breviatea cl. nov. for ‘Mastigamoeba invertens’ and relatives, and Discosea cl. nov. comprising Glycostylida ord. nov. (vannellids, vexilliferids, paramoebids, Multicilia), Dermamoebida ord. nov. (Thecamoebidae) and Himatismenida. We argue that the ancestral amoebozoan was probably unikont and that the cenancestral eukaryote may have been also.