Growth,photosynthesis, and metabolism of sugar beet at an early stage of exposure to elevated CO<Subscript>2</Subscript>

The effects of CO₂ concentration (C _a) on growth, photosynthesis, and the activity of enzymes associated with the translocation and assimilation of CO₂ were studied in sugar beet (Beta vulgaris L. subsp. saccharifera, cv. Ramonskaya) plants. The plants were grown in controlled-climate chamber to the stage of 3–4 leaves and then used in experiments. Experimental plants were exposed in boxes to doubled C _a (700 µl/l, 2C plants), whereas control plants were kept in a chamber with ambient atmosphere (350 µl/l, 1C plants). As compared with 1C plants, in 3 and 8 days, the leaf area of 2C plants increased by 14 and 26%, respectively. The rate of their photosynthesis (P _n) measured in 3, 6, and 8 days increased by 85, 47, and 52%, respectively, whereas in normal air, the values of P _n in 2C plants were by 12, 19, and 15% lower than in 1C plants. After 8-day growth, the content of soluble carbohydrates in the leaves of 2C plants attained 7.2%, being by 80% greater than in 1C plants; the content of starch did not exceed 3%. The total content of chlorophylls a and b in the leaves of 2C plants was by 14% greater than in 1C plants, but their ratio was essentially the same. The level of protein in 2C plants was by 13.4% lower than in 1C plants. The activity and content of Rubisco in 1C and 2C plants were similar. As compared with 1C plants, in 2C plants the activity of soluble carbonic anhydrase (sCA) was lower by 34% in 3 days and by 18% in 8 days; the activity of carbonic anhydrase of membrane preparations (mCA), was lower by 24 and 77%, respectively. Catalase activity in 2C plants became by 8% lower than in 1C plants only after 8 days. A reduction in the photosynthetic ability of 2C plants in ambient atmosphere, a decrease in activity of sCA and, especially, of mCA observed together with invariable activity and content of Rubisco in the leaf extracts are interpreted as early symptoms of acclimation of young plants of sugar beet to elevated CO₂.Translated from Fiziologiya Rastenii, Vol. 52, No. 2, 2005, pp. 184–190.Original Russian Text Copyright © 2005 by Ignatova, Novichkova, Mudrik, Lyubimov, Ivanov, Romanova.This revised version was published online in April 2005 with a corrected cover date.     

Freshwater Crustacea (Cladocera,Copepoda) of Iceland: taxonomy,ecology, and biogeography

Of the many types of freshwater bodies across Iceland (e.g., lakes, springs, rivers, and ponds), greater effort has been invested in researching the freshwater Crustacea (Cladocera, Copepoda) of more permanent, larger, and deeper water bodies than on smaller or more ephemeral sites. To address this, we described the fauna of 12 shallow freshwater bodies distributed from the coast to the central highlands of Iceland. We identified 16 species in 11 genera belonging to six families of Cladocera, and 12 species in eight genera belonging to four families of Copepoda. Five of the species we identified (Alona werestschagini, Cyclops vicinus, Daphnia cristata, Diacyclops abyssicola, and Heterocope borealis) represent new distribution records for Iceland, increasing the number of species now known from this region to 34 Cladocera and 38 Copepoda taxa. Additionally, we discuss the taxonomy of some species with doubtful taxonomical status. Six crustacean taxocenes are described, each characterized by the dominance of different taxa, with bottom sediment characteristics best explaining species assemblage structure. We evaluated the relationships between Icelandic Cladocera and Copepoda faunas and those of the adjacent Svalbard, Faroe, and Shetland Islands, Greenland, and the mainland Norway. The taxonomic composition of the Icelandic fauna is dominated by widely distributed Holarctic, and secondarily Palaearctic and Nearctic species, and is more similar to the faunas of the major North Atlantic islands (64.2–71.8 % similarity) than it is to that of continental Norway.     

MedScan,a natural language processing engine for MEDLINE abstracts

MOTIVATION: The importance of extracting biomedical information from scientific publications is well recognized. A number of information extraction systems for the biomedical domain have been reported, but none of them have become widely used in practical applications. Most proposals to date make rather simplistic assumptions about the syntactic aspect of natural language. There is an urgent need for a system that has broad coverage and performs well in real-text applications. RESULTS: We present a general biomedical domain-oriented NLP engine called MedScan that efficiently processes sentences from MEDLINE abstracts and produces a set of regularized logical structures representing the meaning of each sentence. The engine utilizes a specially developed context-free grammar and lexicon. Preliminary evaluation of the system's performance, accuracy, and coverage exhibited encouraging results. Further approaches for increasing the coverage and reducing parsing ambiguity of the engine, as well as its application for information extraction are discussed.     

Physiological,biochemical, and fluorescence parameters of senescing sugar beet leaves in the vegetative phase of growth

The phase of vegetative growth of sugar beet (Beta vulgaris L., single-sprout form) was conditionally subdivided into four periods according to leaf number and size (including already withered leaves): (A) 8 ± 1 weeks after seedling emergence (wase) (5–7 leaves); (B) 11 ± 1 wase (10–12 leaves); (C) 14 wase (13–15 leaves); (D) 15 wase (15–18 leaves). It took each next leaf about 1 week to come into view. In the course of leaf senescence, palisade parenchyma became less ordered; cells, vacuoles, and intercellular spaces expanded; leaf area and thickness increased. Chloroplasts became swollen, starch grains (and later osmiophilic globules) accumulated and degraded. In every growth period, the highest levels of soluble carbohydrates (sCH), chlorophyll (Chl (a + b)), soluble protein, and the highest activities of rubisco and soluble carboanhydrase usually preceded the full leaf expansion. In unfolded leaves at the growth period B, the maximum values of biochemical characteristics were as a rule higher than at the growth periods A and C and especially D. The only exception was Chl (a + b) with its peak level somewhat increased with plant age. Occurrence of peak values of individual characteristics depended on plant growth period. These characteristics started diminishing asynchronously, with a minimum in old operational leaves. Only the sCH content in the leaves at the periods C and D was stable. Changes in quantum yield at PSII and nonphotochemical fluorescence quenching reflected the age-associated differences in biochemical characteristics. The results are discussed in the light of the idea that leaf senescence is a normal stage of development directly related to the changes in source-sink relations. Biochemically, this stage comprises the degradation of temporarily stored products and partial utilization of the breakdown products for maintenance of the growth of newly formed leaves and root.     

On fluoroquinolones treatment safety in children (clinical, morphological and catamnesis data)]

Results of prospective comparative investigation of monofluoroquinolones (ciprofloxacin, ofloxacin, pefloxacin) arthropathy are presented. The trial was performed at 144 children with mucoviscidosis (aged 0.5-16) and at 37 children with aplastic anemia (aged 1.75-15). Two groups differ by necessary antibacterials regimes and hence by different abilities for arthropathy development: patients with mucoviscidosis were treated with fluoroquinolones followed by repeated short courses in combination with other antibacterials; patients with aplastic anemia--were treated permanently for a long time with low doses as monotherapy for autoinfection prophylaxis. Analysis was performed on the base of catamnesis, year growth rate, postmortal morphological investigation of the right knee joint. It was shown that quinolone arthropathy development didn't depend on treatment duration, as it developed during the first three weeks of the fluoroquinolone use, but depended on the drug, patient age and nosology. Arthropathy has favourable prognosis and was fully resolved at the period from 7 days to 3 month according to the arthropathy form (arthrologic, arthritic). Quinolones arthropathy at the children has specific features, the main one is absence of cartilage damage confirmed by morphological analysis.     

Variability of key biochemical parameters in senescent leaves of sugar beet at nitrate deficiency and surplus accumulation of glucose

Parameters of sugar beet (Beta vulgaris L.) leaf senescence were investigated in the stage of vegetative growth in plants grown at normal nitrate level (N) or under its deficiency (DefN). Accelerated senescence was initiated by the 41-h-long exposure of leaf discs on the surface of water with alternating darkness and light. In plants grown at DefN, the number of leaves and their average area decreased; after the incubation of the discs from such leaves on water, the content of soluble carbohydrates (sCarb) and especially of glucose sharply increased as compared with normal level of nitrate (N), whereas the content of soluble protein (sProt) and Rubisco activity considerably decreased, which is characteristic of the negative hexokinase (HXK1) effect of glucose. The rate of a decrease in the content of sProt in the course of leaf senescence calculated for the leaf of each strorey was lower than the rate of a decrease in RuBisCO activity. A decrease in the content of sProt and RuBisCO activity in all the storeys of leaves grown at joint action of nitrate deficit (DefN) and incubation on water was on the average greater than in each of these treatments separately but less than the sum of these effects. The imperfection of the putative mechanism of signal transduction at DefN and excess glucose and their interaction in senescent sugar beet leaves is discussed as well as the opportunity to use the ratio between sCarb and sProt for the evaluation of the manifestation of the negative hexokinase effect of glucose.     

Formation and degradation of peroxisomes in yeasts

The formation, development and degradation of peroxisomes were studied directly in growing yeast-methylotrophs under the microscope using anoptral and phase contrast. The degradation of peroxisomes was caused by their degeneration and dislocation to the central vacuole of the yeast cell. A fluorescent-microscopic technique was elaborated for detecting selectively the crystals of catalase in the cells. As was shown by intravitam studies, electron microscopy and cytochemistry, peroxisomes are directly connected with the central vacuole of the cell, enzymes being transferred from the former into the latter. Experiments conducted with different cultures have demonstrated that the high activity of exocatalase is typical of methylotrophic yeast organisms. The highest activity that was exhibited for a long period of time was found in Torulopsis molischiana.     

Changes in trophic state and aquatic communities in high Arctic ponds in response to increasing goose populations

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Carbonic anhydrase in leaves during radish plant ontogeny and glucose effect

Radish (Raphanus sativus L.) plants were grown in a greenhouse in soil at natural illumination, temperature, and CO₂ concentration. A relationship between the activity of soluble carbonic anhydrase (sCA) and the content of soluble carbohydrates (sCH) was investigated depending on leaf position on the stem during plant development. Indices characterizing leaf ageing during the phase of vegetative growth (PVG) (in lower leaves as compared to upper ones) were a decrease in the rate of photosynthetic release of O₂, photosynthetic efficiency, quantum efficiency of photosystem II, and the content of chlorophylls a and b. During PVG and the phase of flower bud formation, the activity of sCA and the contents of sCH, soluble protein, and Glu were the greatest in young (topmost) leaves and declined in the leaves of middle and lower storeys. From the top to the middle leaves, a dependence of sCA activity on the content of Glu or other sCH (without Glu) was direct, whereas, from the middle and the lower leaves, it became inversed. During leaf ageing in vegetatively growing plants and in the phase of budding, the relation between sCA and a relative content of Glu (percent of the rest sCH) was similar to that described above and yielded broken lines, and, during flowering, an inverse relation was observed in the leaves of all three storeys with a low content content of Glu and a low sCA activity. In order to study a dependence of sCA activity on the levels of sCH and Glu during PVG, one half of the leaf was incubated in a thin layer of water at a light schedule: by 12 h of night/day/night + 3-h-long illumination (control material). Within the period of active growth of the hypocotyl up to the storage root formation, the sCA activity and the content of sCH in the leaves incubated in water (control) increased. During a later PVG, both characteristics declined with sCA activity reduced stronger. The rate of the photosynthetic O₂ release changed in accordance with the changes in sCA activity. Incubation of the other half of the same leaf in 20 mM Glu during early PVG brought about a considerable increase in sCA activity as compared with control material. During a later PVG and at a much greater Glu concentration (330 mM), its content in the leaves increased manifold; however, there were no significant changes in the activity of sCA, the content of protein or chlorophyll. It was concluded that the activity of sCA in the radish leaves during PVG was not regulated by the absolute content of sCH or Glu in the leaves but depended on endogenous factors associated with plant development.