A phylogenetic study ofSaxifraga sect.Saxifraga (Saxifragaceae) based on nrDNA ITS sequences

Parsimony analyses of 54 nrDNA ITS (Internal Transcribed Spacer) sequences ofSaxifraga sect.Saxifraga were performed. In addition to some unresolved clades, there is strong disagreement between the ITS phylogeny and previous classifications based primarily on morphology. The extensive cytological instability of sect.Saxifraga prevents previous cytotaxonomical results from resolving the incongruence between molecular and morphological data. Dissimilar topologies between chloroplast (matK) and nuclear (ITS) trees for eight species of sect.Saxifraga suggest that gene trees and the true species tree are not coincident. Recent and mid-term reticulation is proposed as an explanation for the incongruence between morphological, cytological, organellar, and nuclear data. Homogenization in multigene families, such as the ITS region, via concerted evolution may be the key to the interpretation of results based on ITS sequences within sect.Saxifraga. The use of organellar genes in a larger sample should help to determine whether extensive reticulation occurs in sect.Saxifraga, as has been documented in various genera of Saxifragaceae.     

Urinary excretion of digoxin-like immunoreactive factor and arginine-vasopressin in rats after several osmotic loads

Urinary digoxin-like immunoreactive factor (DLIF), arginine-vasopressin (AVP) and other urinary parameters were investigated under normal conditions and after the i.p. injection of the following solutions: distilled water, isotonic and hypertonic NaCl, NaHCO3, KCl and urea, at a rate of 3 ml/100 g body weight. The measurement of digoxin-like immunoreactivity by two different radioimmunoassays showed that DLIF was stimulated by all volume loads regardless of the presence or absence of osmolar compounds. This dissociation between DLIF and urinary sodium excretion suggests that DLIF may not constitute the natriuretic hormone. Moreover, a dissociation between DLIF and AVP excretion also were found, which speaks against the hypothesis of a common mechanism of stimulation for both substances.     

Biochemical characterization of the antioxidant system in the scallop Adamussium colbecki, a sentinel organism for monitoring the Antarctic environment

 The scallop Adamussium colbecki can be profitably used for monitoring Antarctic coastal environments but its utility would be increased if chemical analyses of pollutants were integrated with data on their biological effects. Since oxidative stress is a common pathway of toxicity induced by xenobiotics, a preliminary biochemical characterization was carried out on the antioxidant system of this species and baseline data collected for future assessment of the anthropogenic impact in this remote area. The digestive gland and gills were investigated for levels of glutathione and the activity of several glutathione-dependent and antioxidant enzymes: gluthathione reductase, EC 1.6.4.2; glyoxalase I, EC 4.4.1.5; glyoxalase II, EC 3.1.2.6; gluthathione S-transferases, EC 2.5.1.18; Se-dependent, EC 1.11.1.9 and Se-independent, EC 2.5.1.18 gluta-thione peroxidases; catalase, EC 1.11.1.6; and super-oxide dismutase, EC 1.15.1.1. The same enzymatic activities were measured for comparison in the Mediterranean molluscs Mytilus galloprovincialis and Pecten jacobaeus. Very high levels of glutathione S-transferases were found in the digestive gland of both species of scallop compared to mussels, suggesting the importance of different feeding behaviour among these molluscs. However, catalase activity, much higher in Adamussium colbecki than in the Mediterranean molluscs, may represent a biochemical adaptation to the Antarctic marine environment with high levels of dissolved oxygen. Enzymes from the Antarctic species appeared to be generally more active at low temperatures but, with a few exceptions, their activities increased at higher temperatures. Received: 20 March 1996/Accepted: 29 May 1996     

Microhabitat and morphometric variation of two Chaetophoracean (Chaetophorales, Chlorophyta) species in tropical streams of southeastern Brazil

Two populations of Chaetophora elegans (Roth) C. Agardh and two of Stigeoclonium helveticum Vischer were investigated for microhabitat characteristics and morphological variation in streams of São Paulo State, southeastern Brazil. Different patterns of microhabitat distribution were found between species investigated. Populations of C, elegans were distributed under relatively narrow microhabitat conditions (high irradiance, low depth, moderate to high current velocity, rocky substrata and lower values of niche width) and showing little morphometric variation (colony diameter, main axis cell size, and apical branch number), Stigeoclonium helveticum occurred under more diverse microhabitat conditions, revealed by lack of significant difference between sampling units with and without the alga and wider niche width, but also exhibited relatively narrow morphometric variation (plant length, main axis cell and ateral branch cell sizes). The narrow microhabitat conditions and smaller niche width of C. elegans can explain its low abundance (percentage cover) in streams from the area studied as well as in other regions of São Paulo State, In contrast, the wider variation of microhabitat conditions and the higher niche widths of S. helveticum suggest that this green alga is able to grow in a high number of stream ecosystems in the region investigated, ranging from undisturbed to highly disturbed habitats. Thus. the results suggest that S. helveticum is a generalist species.     

Anoxybacillus thermarum sp. nov., a novel thermophilic bacterium isolated from thermal mud in Euganean hot springs, Abano Terme, Italy

A novel aerobe thermophilic endospore-forming bacterium designated strain AF/04^T was isolated from thermal mud located in Euganean hot springs, Abano Terme, Padova, Italy. Strain AF/04^T was Gram-positive, motile, rod-shaped, occurring in pairs, or filamentous. The isolate grew between 55 and 67°C (optimum 65°C) and at pH 6.0–7.5 (optimum pH 7.2). The strain was aerobic and grew on maltose, trehalose, and sodium acetate as sole carbon sources. The G + C content of DNA was 53.5 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain AF/04^T falls within the genus Anoxybacillus. Levels of 16S rRNA gene sequence similarity between strain AF/04^T and the type strains of recognized Anoxybacillus species ranged from 95 to 99%. Chemotaxonomic data (major isoprenoid quinone–menaquinone-7; major fatty acid iso-C15:0 and anteiso-C17:0) supported the affiliation of strain AF/04^T to the genus Anoxybacillus. Based on phenotypic and chemotaxonomic characteristics, 16S rRNA gene sequence analysis and DNA–DNA hybridization data, it was proposed that strain AF/04^T (=DSM 17141^T = ATCC BAA 1156^T) should be placed in the genus Anoxybacillus as the type strain of a novel species, Anoxybacillus thermarum sp. nov.