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1

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Response of field-grown bean (Phaseolus vulgaris L.) to Rhizobium inoculation and nitrogen fertilization in two Cerrados soils (2000)

Vargas, M. A. T. ; Mendes, Ieda C. ; Hungria, Mariangela

Springer

Biology and fertility of soils 32 (2000), S. 228-233

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ISSN: 1432-0789

Keywords: Key words Rhizobial competitiveness ; Inoculation ; Dinitrogen fixation ; Nodulation ; Phaseolus vulgaris

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract Most soils sown with field beans (Phaseolus vulgaris L.) contain indigenous rhizobia which might interfere with the establishment of inoculated strains. As a consequence, the benefits of bean inoculation are usually questioned, and the use of N fertilizer is gradually becoming a common practice. The present study had the objective of evaluating the effectiveness of inoculation and N fertilization in field soil with (site 1) and without (site 2) a previous bean-cropping history. At site 1, which had a rhizobial population of 7×102 cells g–1 soil, inoculation had no effect on nodulation or yield, whereas at site 2 (〈10 cells g–1 soil) inoculation increased nodulation, nodule occupancy by the inoculated strain and grain yield. N fertilizer decreased nodulation at both sites, but increased grain yield at site 1 but not at site 2, indicating that the response to inoculation and N fertilization depends on the cropping history. When bean was cultivated for the first time, indigenous populations of rhizobia were low and high yields were accomplished solely with seed inoculation, with no further response to N fertilizer. In contrast, previous cultivation of bean increases soil rhizobia, preventing nodule formation by inoculated strains, and N fertilizer may be necessary for maximum yields. A significant interaction effect between N fertilizer and inoculation was detected for serogroup distribution only at site 2, with N fertilizer decreasing nodule occupancy by the inoculated strain and increasing the occurrence of indigenous strains. Consequently, although no benefits were obtained by the combination of inoculation and N fertilizer, this practice may be feasible with the selection of appropriate N-tolerant strains from the indigenous rhizobial population.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003740000240

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2

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Nitrogen fixation capacity and nodule occupancy by Bradyrhizobium japonicum and B. elkanii strains (1998)

Hungria, M. ; Boddey, L. H. ; Santos, M. A. ; [et al.]

Springer

Biology and fertility of soils 27 (1998), S. 393-399

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ISSN: 1432-0789

Keywords: Key words Bradyrhizobium japonicum ; Bradyrhizobium elkanii ; Competitiveness ; Nitrogen fixation ; Soybean

Source: Springer Online Journal Archives 1860-2000

Topics: Biology , Geosciences , Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition

Notes: Abstract In a previous study soybean Bradyrhizobium strains, used in Brazilian studies and inoculants over the last 30 years, and strains adapted to the Brazilian Cerrados, a region frequently submitted to environmental and nutritional stresses, were analyzed for 32 morphological and physiological parameters in vivo and in vitro. A cluster analysis allowed the subdivision of these strains into species Bradyrhizobium japonicum, Bradyrhizobium elkanii and a mixed genotype. In this study, the bacteria were analyzed for nodulation, N2 fixation capacity, nodule occupancy and the ability to increase yield. The goal was to find a relationship between the strain groups and the symbiotic performance. Two strains of Brazilian B. japonicum showed higher rates of N2 fixation and nodule efficiency (mg of N mg–1 of nodules) under axenic conditions. These strains also showed greater yield increases in field experiments when compared to B. elkanii strains. However, no differences were detected between B. japonicum and B. elkanii strains when comparing nodule occupancy capacity. The adapted strains belonging to the serogroup B. elkanii SEMIA 566, most clustered in a mixed genotype, were more competitive than the parental strain, and some showed a higher capacity of N2 fixation. Some of the adapted strains, such as S-370 and S-372, have shown similar N2 fixation rates and nodulation competitiveness to two Brazilian strains of B. japonicum. This similarity demonstrates the possibility of enhancing N2 fixing ability, after local adaptation, even within B. elkanii species. Differences in the DNA profiles were also detected between the parental SEMIA 566 and the adapted strains by analyses with the ERIC and REP-PCR techniques. Consequently, genetic, morphological and physiological changes can be a result of adaptation of rhizobia to the soil. This variability can be used to select strains capable of increasing the contribution of N2 fixation to soybean nutrition.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s003740050449

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3

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Physiological Relevance of Pyroglutamate Aminopeptidase II (1989)

CHARLI, J. L. ; CRUZ, C. ; PONCE, G. ; [et al.]

Oxford, UK : Blackwell Publishing Ltd

Annals of the New York Academy of Sciences 553 (1989), S. 0

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ISSN: 1749-6632

Source: Blackwell Publishing Journal Backfiles 1879-2005

Topics: Natural Sciences in General

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1111/j.1749-6632.1989.tb54543.x

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4

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A novel cytoplasmic structure containing DNA networks in Entamoeba histolytica trophozoites (1997)

Orozco, E. ; Gharaibeh, R. ; Riverón, A. M. ; [et al.]

Springer

Molecular genetics and genomics 254 (1997), S. 250-257

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ISSN: 1617-4623

Keywords: Key words DNA networks ; Entamoeba histolytica ; DNA organization

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract We report here the presence of cytoplasmic DNA arranged in networks in the trophozoites of the human parasite Entamoeba histolytica. Cytoplasmic DNA was detected in live trophozoites in a structure that we called EhkO, using the fluorescent dye acridine orange, and by in situ hybridization to trophozoites with a rDNA probe. The EhkO was found in the axenically grown clones A, L6 (strain HM1:IMSS) and MAVax (strain MAV) and in the polyxenically grown clone MAVpx (strain MAV). Bacteria present in MAVpx did not cross hybridize with the DNA probe neither in in situ hybridization or in Southern blot experiments. Autoradiography of metabolically [3H]thymidine-labeled trophozoites showed the presence of EhkO, and an EhkO-enriched fraction, purified from a nuclei-free extract and examined by light microscopy, exhibited [3H]thymidine incorporation into this structure. DNA was purified from the EhkO and enriched nuclear fractions and analyzed by transmission electron microscopy. The EhkO fraction contained DNA networks resembling those of trypanosome kDNA, whereas nuclear DNA was present mainly as linear molecules and some circles. Our findings imply that E. histolytica may be taxonomically more closely related to the Trypanosomatidae than previously suspected.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/s004380050413

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5

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Multifactorial Modulation of TRH Metabolism (1998)

Joseph-Bravo, P. ; Uribe, R. M. ; Vargas, M. A. ; [et al.]

Springer

Cellular and molecular neurobiology 18 (1998), S. 231-247

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ISSN: 1573-6830

Keywords: thyrotropin releasing hormone (TRH) ; pryoglutamyl peptidase II ; paraventricular nucleus ; lactotroph ; convertases ; PC1 ; PC2 ; TRH mRNA ; neuroendocrine regulation ; glucocorticoids ; thyroid hormones ; suckling ; cold

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract 1. Thyrotropin releasing hormone (TRH), synthesized in the paraventricular nucleus of the hypothalamus (PVN), is released in response to physiological stimuli through medianeminence nerve terminals to control thyrotropin or prolactin secretion from the pituitary. 2. Several events participate in the metabolism of this neuropeptide: regulation of TRH biosynthesis and release as well as modulation of its inactivation by the target cell. 3. Upon a physiological stimulus such as cold stress or suckling, TRH is released and levels of TRH mRNA increase in a fast and transient manner in the PVN; a concomitant increase in cfos is observed only with cold exposure. 4. Hypothalamic cell cultures incubated with cAMP or phorbol esters show a rise in TRH mRNA levels; dexamethasone produces a further increase at short incubation times.TRH mRNA are thus controlled by transsynaptic and hormonal influences. 5. Once TRH is released, it is inactivated by a narrow specificity ectoenzyme, pyroglu-tamyl peptidase II (PPII). 6. In adenohypophysis, PPII is subject to stringent control: positive by thyroid hormones and negative by TRH; other hypothalamic factors such as dopamine and somatostatin also influence its activity. 7. These combined approaches suggest that TRH action is modulated in a coordinate fashion.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1022521020840

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6

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Polymerization by phase transfer catalysis. 12. Poly(ether-ester)s from (2,2-bis(1,4-phenyleneoxy)-propylidene)-diacetic acid and related diacids with diphenolsFor part 11, see ref. [14] (1991)

Tagle, L. H. ; Diaz, F. R. ; Vargas, M. A.

Weinheim : Wiley-Blackwell

Acta Polymerica 42 (1991), S. 398-402

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ISSN: 0323-7648

Keywords: Chemistry ; Polymer and Materials Science

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Physics

Description / Table of Contents: Aus 2,2-Bis(1,4-phenylenoxy)-propyliden-diessigsäure und ähnlichen Disäuren sowie Diphenolen wurden unter Verwendung verschiedener Ammonium- und Phosphoniumsalze als Phasentransfer-Katalysatoren Poly(ether-ester) synthetisiert. Die besten Ergebnisse wurden mit Benzyltriethylammoniumchlorid erzielt, das ein hydrophiler Katalysator ist, der die Hydrolyse der Polymerketten nicht beschleunigt. Auch andere Oniumsalze erwiesen sich als wirksame Phasentransfer-Katalysatoren. Die Polymere wurden mittels IR- und 1H-NMR-Spektroskopie sowie durch Elementaranalyse charakterisiert. Die Molmassen wurden durch Messung der Eigenviskosität ermittelt.

Notes: Poly(ether-ester)s from (2,2-bis(1,4-phenyleneoxy)-propylidene)-diacetic acid and related diacids with diphenols were synthesized using several ammonium and phosphonium salts as phase transfer catalysts. The best results were obtained with benzyltriethylammonium chloride, which is a hydrophilie catalyst that not promotes hydrolysis of the polymeric chains. Other onium salts also were effective as phase transfer catalysts. Polymers were characterized by IR and 1H-NMR spectroscopy and elemental analysis. Molecular weights were estimated by inherent viscosity measurements.

Additional Material: 6 Tab.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/actp.1991.010420813

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