Arginine vasopressin, circulation, and kidney during graded water immersion in humans

Ten normal males rested sitting upright at an air temperature of 28 degrees C for 5.5 h (control, C) and underwent 4 h of graded water immersion (WI) to the umbilicus (UI), to the chest (CI), and to the neck (NI), respectively (water temperature = 34.5 degrees C), on different experimental days. Plasma arginine vasopressin (PAVP) was suppressed during WI compared with C and maximally so during NI. However, there was no change in PAVP comparing CI with UI even though central venous pressure (CVP) increased. CVP increased during CI and NI compared with C but was unchanged during UI, whereas cardiac output (rebreathing method), stroke volume, and plasma volume increased to approximately the same level during all three steps of WI compared with C. Heart rate and total peripheral vascular resistance decreased during UI, CI, and NI. Systolic arterial pressure (SAP) and pulse pressure (PP) were increased gradually from prestudy related to the degree of WI. Also diuresis, natriuresis, kaliuresis, osmotic excretion, and clearance were increased gradually compared with C, whereas free water clearance (CH2O) gradually decreased. There were weak negative but statistically significant correlations between PAVP and CVP and between changes in PAVP from prestudy and corresponding changes in SAP and PP. Furthermore, a statistically significant and negative correlation between CH2O and natriuresis could be established. We conclude that graded immersion gradually increases central blood volume and decreases PAVP. However, not only cardiopulmonary mechanoreceptors but also arterial baroreceptors may play a role in AVP suppression during WI in humans. In hydropenic subjects the suppression of PAVP during WI is apparently not effective in counteracting the decrease in CH2O induced by increased solute excretion.     

Occurrence of Rotifera in the field under natural and intentionally-changed conditions

A comparison of population dynamics of rotifers under natural conditions with those under intentionally-changed ones was carried out at one Lake and five outdoor pools. In Lake Numasawa, dominant rotifers under natural conditions for the past two years were Polyarthra trigla vulgaris, Kellicottia longispina, Ploesoma truncatum, Asplanchna priodonta and Filinia longiseta. Keratella hiemalis, K. cochlearis, K. valga tropica, Brachionus caudatus and Ascomorpha saltans appeared sporadically. Three months after the start of circulation of part of the lake water by a water power plant no remarkable changes were observed as far as the seasonal and vertical distribution of dominant rotifers are concerned. In five pools with different kinds and ratios of covering by such macrophytes as Eichornia and Lemna or reed screen, three types of rotifer communities were found. Type I: Liliferotrocha sp., Brachionus calyciflorus, (B. budapestinensis), B. angularis, K. valga tropica, etc., in which both densities and frequencies were generally reduced in proportion to the ratio of covering either with macrophytes or reed screens. Type II: Filinia longiseta, Polyarthra trigla vulgaris, Asplanchnella sieboldi, etc. in which densities and frequencies were increased by covering either with macrophytes or reed screens. Type III: Trichocerca pusilla, B. quadridentatus, B. leydigi rotundus, Scaridium longicaudum, Euchlanis dilatata, Dicranophorus sp., etc, in which no precise correlation was found between occurrences of the Rotifers and ratio of covering.     

Hydrogen peroxide concentrations in leaves under natural conditions

While H2O2 has been implicated in numerous plant environmental responses, normal levels and variabilities are poorly established, and estimates of leaf tissue concentrations span more than three orders of magnitude, even in a single species under similar conditions. Here, leaf tissue H2O2 contents under natural conditions are reported after determining (i) that H2O2 in extracts was stable with time, (ii) that H2O2 added to the extract was recovered quantitatively, and (iii) that the H2O2 calibration curve was unaffected (or quantifiably affected) by the extract. The broad applicability of the protocol and variability in leaf concentrations were demonstrated using tissue collected from several habitats in association with three, more extensive, experiments. The first involved nychthemeral studies of the mangrove, Rhizophora mangle L. Lowest H2O2 levels occurred in the early morning and near sunset, with higher levels both at midday and at night. Second, using five temperate species in Spring, concentrations were compared on a warm, sunny day and a cool, cloudy day. Higher concentrations were found on the warm day for Aesculus glabra Willd., Glechoma hederacea L., Plantago major L., and Viola soraria Willd., while there were no differences in Quercus macrocarpa Michx. Finally, the effects of elevated CO2 and ozone were examined in soybean, Glycine max L. Pioneer 93B15 under Free Air gas Concentration Enrichment (FACE) conditions. Both supplements led to elevated H2O2. Overall, mean leaf, midday, and mid-summer H2O2 concentrations ranged from 0.67 micromol (gFW)(-1) in mangrove to 3.6 micromol (gFW)(-1) in A. glabra Willd. Greatest within-species differences were only 2.5-fold in any of the studies.     

Degradation of natural and synthetic polyesters under anaerobic conditions

Often, degradability under anaerobic conditions is desirable for plastics claimed to be biodegradable, e.g. in anaerobic biowaste treatment plants, landfills and in natural anaerobic sediments. The biodegradation of the natural polyesters poly(beta-hydroxybutyrate) (PHB), poly(beta-hydroxybutyrate-co-11.6%-beta-hydroxyvalerate) (PHBV) and the synthetic polyester poly(epsilon-caprolactone) (PCL) was studied in two anaerobic sludges and individual polyester degrading anaerobic strains were isolated, characterized and used for degradation experiments under controlled laboratory conditions. Incubation of PHB and PHBV films in two anaerobic sludges exhibited significant degradation in a time scale of 6-10 weeks monitored by weight loss and biogas formation. In contrast to aerobic conditions, PHB was degraded anaerobically more rapidly than the copolyester PHBV, when tested with either mixed cultures or a single strained isolate. PCL tends to degrade slower than the natural polyesters PHB and PHBV. Four PHB and PCL degrading isolates were taxonomically identified and are obviously new species belonging to the genus Clostridium group I. The depolymerizing enzyme systems of PHB and PCL degrading isolates are supposed to be different. Using one isolated strain in an optimized laboratory degradation test with PHB powder, the degradation time was drastically reduced compared to the degradation in sludges (2 days vs. 6-10 weeks).     

Silicification patterns in wheat leaves related to ontogeny and soil silicon availability under field conditions

Plant and Soil - Silicon (Si) accumulation is an important strategy for plant defense against biotic and abiotic stress. Solid amorphous silica (ASi) deposits have been found to protect plants...     

Activities of antioxidant system components and polyphenol oxidase in ontogeny of lawn grasses under megapolis conditions

The activities of antioxidants enzymes (peroxidase (POX) and catalase (CAT)), the contents of non-enzymatic antioxidants (vitamin C, carotenoids), and the activity of polyphenol oxidase (PPO) were studied in vegetative organs of red clover (Trifolium pratense L.) and meadow-fescue (Festuca pratensis Huds.) growing under city conditions. The plants of three ages (virginal (V), generative (G), and subsenyl (SS)) were analyzed. The highest POX and PPO activities were characteristic of G plants, whereas CAT was most active in V plants. The content of low-molecular-weight antioxidants depended on species specificity and developmental stage and also on environment pollution. The content of ascorbate (vitamin C) declined linearly with plant development. Medium pollution also reduced the ascorbate content in tested plant leaves and roots. In contrast, the content of carotenoids increased with the increased activity of anthropogenic factors. The highest content of the pigments was in G plants. At all developmental stages and in all habitats, meadow-fescue (tolerant species) was characterized by the lower content of studied compounds than red clover (sensitive species). Thus, anthropogenic medium pollution resulted in the peroxide group accumulation, POX and PPO activation, carotenoid accumulation, and the ascorbate content decline in the vegetative tissues during the entire ontogeny of tolerant and sensitive lawn plants.     

Pulmonary and bronchial blood circulation under conditions of changed gaseous environment

By means of ultrasonic method used in acute experiments on cats with closed chest under normal respiration the authors studied the blood flow in left low-lobar pulmonary artery and vein and in bronchial artery, as well as the blood pressure in pulmonary and femoral arteries in inhalation of next gaseous mixtures: 7.5% O2 in nitrogen; 30% O2; 3% CO2; 21% O2+ +79% He; 30% O2 + 67% He + 3% CO2. It was shown, that inhalation of the normoxic gaseous mixture, in which nitrogen is replaced by helium, did not call significant changes in pulmonary and systemic circulation. However, the presence of the helium in complicated gaseous mixture can change the reactivity of pulmonary and bronchial vessels to influence the components participating in these complicated gaseous mixtures.     

Fur-dependent detoxification of organic acids by rpoS mutants during prolonged incubation under aerobic, phosphate starvation conditions

The activity of amino acid-dependent acid resistance systems allows Escherichia coli to survive during prolonged incubation under phosphate (P_i) starvation conditions. We show in this work that rpoS-null mutants incubated in the absence of any amino acid survived during prolonged incubation under aerobic, P_i starvation conditions. Whereas rpoS⁺ cells incubated with glutamate excreted high levels of acetate, rpoS mutants grew on acetic acid. The characteristic metabolism of rpoS mutants required the activity of Fur (ferric uptake regulator) in order to decrease the synthesis of the small RNA RyhB that might otherwise inhibit the synthesis of iron-rich proteins. We propose that RpoS (σ^S) and the small RNA RyhB contribute to decrease the synthesis of iron-rich proteins required for the activity of the tricarboxylic acid (TCA) cycle, which redirects the metabolic flux toward the production of acetic acid at the onset of stationary phase in rpoS⁺ cells. In contrast, Fur activity, which represses ryhB, and the lack of RpoS activity allow a substantial activity of the TCA cycle to continue in stationary phase in rpoS mutants, which decreases the production of acetic acid and, eventually, allows growth on acetic acid and P_i excreted into the medium. These data may help explain the fact that a high frequency of E. coli rpoS mutants is found in nature.