33 documentos corresponden a la consulta.
Palabras contadas: comparative: 45, study: 880
Schweigmann, N. - Pietrokovsky, S. - Conti, O. - Escosteguy, M. - Bottazzi, V. - Solarz, N. - Wisnivesky-Colli, C.
Mem. Inst. Oswaldo Cruz 1997;92(2):151-152
1997
Temas: animal - animal disease - Argentina - article - Chagas disease - comparative study - male - opossum - parasitology - prevalence
Descripción: Fil:Schweigmann, N. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina.
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Brocklehurst, D. - Wider De Xifra, E.A. - Batlle, A.
Int. J. Biochem. 1980;12(5-6):791-793
1980
Temas: blood and hemopoietic system - erythrocyte - methodology - porphyria - uroporphyrinogen synthase - Acute Disease - Adult - Aged - Ammonia-Lyases - Chronic Disease
Descripción: 1. 1. This paper confirms the increase in sensitivity obtained for erythrocyte UIS measurement by pre-incubation of the red cells in a 0.2% Triton-X 100 solution containing 1 mmol/1 ZnSO4 and dithiothreitol as described by Piepkorn et al. (1978). 2. 2. To achieve optimal precision in this assay a substrate concentration of delta aminolaevulinic acid (ALA) of 1000nmol/ml is required. Interpretation of the results obtained by this method is discussed and its use in the detection of both latent and acute intermittent porphyria is demonstrated. Comparative studies were carried out by using the Batlle et al. (1978) method and a modification employing ALA as substrate. © 1980.
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Rossetti, M.V. - de Geralnik, A.A.J. - Kotler, M. - Fumagalli, S. - del C. Batlle, A.M.
Int. J. Biochem. 1980;12(5-6):761-767
1980
Temas: ammonia lyase - Ammonia Lyases - hydrolase - isomerase - multienzyme complex - animal - article - bird - cattle - comparative study
Descripción: 1. 1. Gel filtration on Sephadex G-100 and Sepharose 4B were used to redetermine the molecular weight (MW) of porphobilinogenase, deaminase and isomerase purified from different sources, and determine the MW of these enzymes purified from Eugtena gracilis. 2. 2. Results reported here, indicate that porphobilinogenase can be found, into three different molecular forms, tetramers, dimers and monomers according to the source organism. 3. 3. It is proposed that minimal functional structure of PBGase is a hybrid protomer of MW 25,000, composed by two different domains, in a ratio of 1 mol of deaminase, MW 20,000 to 1 mol of isomerase. MW 5000. 4. 4. A model explaining the occurrence of different MW species of PBGase in nature and the possible interconversion among the various forms is postulated. © 1980.
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Wainstok de Calmanovici, R. - Billi de Catabbi, S.C. - Aldonatti, C.A. - San Martin de Viale, L.C.
Int. J. Biochem. 1989;21(4):377-381
1989
Temas: 5 aminolevulinate synthase - aminolevulinic acid - heme - hexachlorobenzene - porphobilinogen - porphyrin - uroporphyrinogen decarboxylase - xenobiotic agent - animal cell - animal experiment
Descripción: 1. 1. The present work undertakes a comparative study on the hexachlorobenzene (HCB) porphyria induction in female rats of Wistar and CHBBTHOM strains. The purpose was to characterize the CHBBTHOM strain with respect to the haem metabolic pathway, its regulatory mechanisms and its response to foreign drugs. 2. 2. After 7 weeks of treatment it was observed that the hepatic porphyrins increased 140 times, ALA-synthase 4 times and PCL was 73% inhibited in the Wistar strain. 3. 3. On the other hand the animals of CHBBTHOM strain showed lesser alteration on these parameters; hepatic porphyrins increased only 3-fold, ALA-synthase 1.7-fold and PCL was only 22% inhibited. 4. 4. Total iron liver content was nearly equal in both strains of rats. 5. 5. The results obtained would indicate that the lower susceptibility of the CHBBTHOM strain to acquire porphyria does not seem to be due to either: (1) congenital alterations of any parameters of the haem metabolic pathway, since the behaviour of normal animals from both strains was similar; or (2) a lower hepatic iron content in such animals. 6. 6. These findings would suggest that the differential response to HCB to this strain would be looked for in another metabolic pathway, such as that involved in the metabolization process of the toxic. © 1989.
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Lobato, L. - Lizana, A. - Marquez, A. - Moreno, I. - Iemmi, C. - Campos, J. - Yzuel, M.J.
J. Eur. Opt. Soc. 2011;6:49
2011
Temas: Anamorphic phenomenon - Diffractive efficiency - Diffractive optical element - Global retardance - Lcos device - Density (optical) - Diffractive optical elements - Efficiency - Phase modulation - Anamorphic
Descripción: The diffractive efficiency of Liquid Crystal on Silicon (LCoS) displays can be greatly diminished by the appearance of temporal phase fluctuations in the reflected beam, depolarization effects and also because of phase modulation depths smaller than 2π. In order to maximize the efficiency of the Diffractive Optical Elements (DOEs) implemented in the LCoS device, the Minimum Euclidean Distance principle can be applied. However, not all the diffractive elements can be corrected in the same way due to the anamorphic and spatial frequency dependent phenomenon, which is related to the LCoS response, largely depending on the period and the spatial orientation of the generated DOE. Experimental evidence for the anamorphic and spatial frequency dependent phenomenon is provided in this paper, as well as a comparative study between the LCoS display response for binary gratings of different periods.
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Lavagnino, N. - Serra, F. - Arbiza, L. - Dopazo, H. - Hasson, E.
Evol. Bioinformatics 2011;2011(7):89-104
2011
Temas: Adaptation - Drosophila melanogaster species group - Evolutionary genomics - Insects - Olfactory behavior - arthropod life cycle stage - article - controlled study - Drosophila - Drosophila ananassae
Descripción: Abstract: Previous comparative genomic studies of genes involved in olfactory behavior in Drosophila focused only on particular gene families such as odorant receptor and/or odorant binding proteins. However, olfactory behavior has a complex genetic architecture that is orchestrated by many interacting genes. In this paper, we present a comparative genomic study of olfactory behavior in Drosophila including an extended set of genes known to affect olfactory behavior. We took advantage of the recent burst of whole genome sequences and the development of powerful statistical tools to analyze genomic data and test evolutionary and functional hypotheses of olfactory genes in the six species of the Drosophila melanogaster species group for which whole genome sequences are available. Our study reveals widespread purifying selection and limited incidence of positive selection on olfactory genes. We show that the pace of evolution of olfactory genes is mostly independent of the life cycle stage, and of the number of life cycle stages, in which they participate in olfaction. However, we detected a relationship between evolutionary rates and the position that the gene products occupy in the olfactory system, genes occupying central positions tend to be more constrained than peripheral genes. Finally, we demonstrate that specialization to one host does not seem to be associated with bursts of adaptive evolution in olfactory genes in D. sechellia and D. erecta, the two specialists species analyzed, but rather different lineages have idiosyncratic evolutionary histories in which both historical and ecological factors have been involved. © the author(s), publisher and licensee Libertas Academica Ltd.
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Cendra, P.G. - Segura, D. - Allinghi, A. - Cladera, J. - Vilardi, J.
Fla. Entomol. 2007;90(1):147-153
2007
Temas: Anastrepha fraterculus - Genetic control - Longevity - SIT - Survival - comparative study - fly - integrated approach - longevity - sterile release method
Descripción: The South American fruit fly Anastrepha fraterculus (Wiedemann) is one of the most destructive fruit pests in this region, infesting major fruit crops. Implementation of the sterile insect technique (SIT) as part of an area-wide integrated approach against this species requires information on the survival of mass-reared and sterilized insects in the field and their ability to mate with wild females. The survival rates in field cages of both non-irradiated and irradiated laboratory flies were compared with that of wild flies. Both types of laboratory flies survived longer than their wild counterparts over the 8 days under the experimental conditions. The irradiation dose (70 Gy) did not affect survival of the laboratory reared flies. Our results improve the prospect of integrating the SIT into the control of A. fraterculus populations in Argentina.
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Ostrowski de Nunez, M.
Mem. Inst. Oswaldo Cruz 1992;87(4):539-543
1992
Temas: animal - animal disease - Argentina - article - chicken - classification - comparative study - female - fish - fish disease
Descripción: The life cycle of Ascocotyle (Leighia) hadra n. sp. was experimentally reproduced, starting from cercariae from naturally infected Littoridina parchappei, collected from Los Ranchos stream, near Mercedes city, Buenos Aires Province, Argentina. Metacercariae were found encysted in the liver and mesentery of experimentally and naturally infected fishes Cnesterodon decemmaculatus and Jenynsia lineata. Adults were obtained experimentally in chicks and mice. The natural host is unknown. The new species is compared with Ascocotyle (Leighia) mcintoshi Price 1936 as described by Leigh, 1974, differing in behavior and morphology of cercarial, metacercarial and adult stages.
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de Ménorval, M.-A. - Mir, L.M. - Fernández, M.L. - Reigada, R.
PLoS ONE 2012;7(7)
2012
Temas: calcium ion - dimethyl sulfoxide - iodide - water - animal cell - article - calcium cell level - cell assay - cell membrane permeability - comparative study
Descripción: Dimethyl sulfoxide (DMSO) has been known to enhance cell membrane permeability of drugs or DNA. Molecular dynamics (MD) simulations with single-component lipid bilayers predicted the existence of three regimes of action of DMSO: membrane loosening, pore formation and bilayer collapse. We show here that these modes of action are also reproduced in the presence of cholesterol in the bilayer, and we provide a description at the atomic detail of the DMSO-mediated process of pore formation in cholesterol-containing lipid membranes. We also successfully explore the applicability of DMSO to promote plasma membrane permeability to water, calcium ions (Ca2+) and Yo-Pro-1 iodide (Yo-Pro-1) in living cell membranes. The experimental results on cells in culture can be easily explained according to the three expected regimes: in the presence of low doses of DMSO, the membrane of the cells exhibits undulations but no permeability increase can be detected, while at intermediate DMSO concentrations cells are permeabilized to water and calcium but not to larger molecules as Yo-Pro-1. These two behaviors can be associated to the MD-predicted consequences of the effects of the DMSO at low and intermediate DMSO concentrations. At larger DMSO concentrations, permeabilization is larger, as even Yo-Pro-1 can enter the cells as predicted by the DMSO-induced membrane-destructuring effects described in the MD simulations. © 2012 de Ménorval et al.
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Soto, I.M. - Hasson, E.R. - Manfrin, M.H.
Biol. J. Linn. Soc. 2008;95(4):655-665
2008
Temas: Cactus - Geometric morphometrics - Morphological evolution - Phenotypic plasticity - divergence - evolution - fly - host plant - morphometry - Neotropical region
Descripción: A central issue in evolutionary biology is to understand the mechanisms promoting morphological evolution during speciation. In a previous study, we showed that the Neotropical cactophilic sibling species Drosophila gouveai and Drosophila antonietae can be reared in media prepared with their presumptive natural host plants (Pilosocereus machrisis and Cereus hildmaniannus) and that egg to adult viability is not independent of the cactus host. In the present study, we investigate the effects of ecological and genetic factors on interspecific divergence in wing morphology, in relation to the pattern of wing venation and phenotypic plasticity in D. gouveai and D. antonietae, by means of the comparative analysis of isofemale lines reared in the two cactus hosts. The species differed significantly in wing size and shape, although specific differences were mainly localized in a particular portion of the wing. We detected significant variation in form among lines, which was not independent of the breeding cactus, suggesting the presence of genetic variation for phenotypic plasticity and wing shape variation in both species. We discuss the results considering the plausible role of host plant use in the evolutionary history of cactophilic Drosophila inhabiting the arid zones of South America. © 2008 The Linnean Society of London.
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Alexander, P. - De La Torre, A. - Llamedo, P. - Hierro, R. - Schmidt, T. - Haser, A. - Wickert, J.
Atmos. Meas. Tech. 2011;4(9):1777-1784
2011
Temas: air temperature - artifact - climatology - comparative study - COSMIC - decadal variation - digital mapping - filter - GPS - perturbation
Descripción: GPS radio occultation satellite data allowed to analyze in the last decade for the first time a large amount of atmospheric temperature profiles including both the troposphere and the stratosphere all over the globe. Wave amplitude enhancements have been systematically observed around tropopause levels, which are apparently due to artifacts generated by any digital filter used to isolate the wave components from these data. We present a new filtering method which can be equally applied to temperature or refractivity profiles. It was tested with synthetic temperature data based on NCEP reanalyes and observed wave climatologies and it was also statistically validated with GPS radio occultation profiles from the COSMIC mission. The suggested technique significantly reduces artificial enhancements around the tropopause, mainly at low latitudes, where a sharp lapse rate change usually exists. This represents an improvement in comparison to previous applications of standard filters. In addition it would allow the study of longer vertical wavelengths than previously done with other filtering procedures. © Author(s) 2011.
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Turjanski, P. - Olaiz, N. - Maglietti, F. - Michinski, S. - Suárez, C. - Molina, F.V. - Marshall, G.
PLoS ONE 2011;6(4)
2011
Temas: acidification - article - comparative study - controlled study - electrode - electrogenetherapy - electroporation - electrostimulation therapy - gene therapy - ion transport
Descripción: We present experimental measurements and theoretical predictions of ion transport in agar gels during reversible electroporation (ECT) for conditions typical to many clinical studies found in the literature, revealing the presence of pH fronts emerging from both electrodes. These results suggest that pH fronts are immediate and substantial. Since they might give rise to tissue necrosis, an unwanted condition in clinical applications of ECT as well as in irreversible electroporation (IRE) and in electrogenetherapy (EGT), it is important to quantify their extent and evolution. Here, a tracking technique is used to follow the space-time evolution of these pH fronts. It is found that they scale in time as t1/2 characteristic of a predominantly diffusive process. Comparing ECT pH fronts with those arising in electrotherapy (EChT), another treatment applying constant electric fields whose main goal is tissue necrosis, a striking result is observed: anodic acidification is larger in ECT than in EChT, suggesting that tissue necrosis could also be greater. Ways to minimize these adverse effects in ECT are suggested. © 2011 Turjanski et al.
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Gil, M. - De Marco, R.J.
J. Exp. Biol. 2005;208(4):671-680
2005
Temas: Apis mellifera - Associative learning - Honeybee - Olfactory conditioning - Trophallaxis - analysis of variance - animal - article - association - bee
Descripción: Early reports indicate that trophallaxis, i.e. the exchange of liquid food by mouth, may allow honeybees to assign nectar odours with predictive values to anticipate biological meaningful reward stimuli. Nevertheless, this type of learning has not been addressed directly. In the present study, pairs of animals were isolated to induce trophallaxis under controlled conditions and, afterwards, the honeybee proboscis extension reflex was used to investigate the possible role of trophallaxis in learning olfactory cues. The results demonstrate unambiguously that associative learning actually occurs by means of trophallaxis. Animals associate the odour (as the conditioned stimulus or CS) and the sucrose (as the unconditioned stimulus or US) present in the solution they receive through trophallaxis. Moreover, this particular kind of learning leads to long-term olfactory memories after a single learning trial, even when trophallaxis is brief. In addition, we found that the strength of association is clearly affected by CS and US intensity as well as the recent previous foraging experiences of the animals. Comparisons are presented among several features of the learning during trophallaxis and the classical conditioning of the proboscis extension reflex with restrained subjects. Finally, the relevance of learning through trophallaxis in the task of successful foraging is discussed.
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Villarreal, M.F. - Cerquetti, D. - Caruso, S. - Schwarcz López Aranguren, V. - Gerschcovich, E.R. - Frega, A.L. - Leiguarda, R.C.
PLoS ONE 2013;8(9)
2013
Temas: adult - anterior cingulate - article - BOLD signal - classification - comparative study - controlled study - creativity - electroencephalogram - female
Descripción: Previous studies of musical creativity suggest that this process involves multi-regional intra and interhemispheric interactions, particularly in the prefrontal cortex. However, the activity of the prefrontal cortex and that of the parieto-temporal regions, seems to depend on the domains of creativity that are evaluated and the task that is performed. In the field of music, only few studies have investigated the brain process of a creative task and none of them have investigated the effect of the level of creativity on the recruit networks. In this work we used magnetic resonance imaging to explore these issues by comparing the brain activities of subjects with higher creative abilities to those with lesser abilities, while the subjects improvised on different rhythmic fragments. We evaluated the products the subjects created during the fMRI scan using two musical parameters: fluidity and flexibility, and classified the subjects according to their punctuation. We examined the relation between brain activity and creativity level. Subjects with higher abilities generated their own creations based on modifications of the original rhythm with little adhesion to it. They showed activation in prefrontal regions of both hemispheres and the right insula. Subjects with lower abilities made only partial changes to the original musical patterns. In these subjects, activation was only observed in left unimodal areas. We demonstrated that the activations of prefrontal and paralimbic areas, such as the insula, are related to creativity level, which is related to a widespread integration of networks that are mainly associated with cognitive, motivational and emotional processes. © 2013 Villarreal et al.
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Salem, T. - Mazzella, A. - Barberini, M.L. - Wengier, D. - Motillo, V. - Parisi, G. - Muschietti, J.
J. Biol. Chem. 2011;286(6):4882-4891
2011
Temas: Amino acids - Enzymes - Fruits - Phosphorylation - Tubes (components) - Alanine substitution - Antagonistic effects - Comparative sequence analysis - Cytoplasmic juxtamembrane - Phosphorylation sites
Descripción: The tip-growing pollen tube is a useful model for studying polarized cell growth in plants. We previously characterized LePRK2, a pollen-specific receptor-like kinase from tomato (1). Here, we showed that LePRK2 is present as multiple phosphorylated isoforms in mature pollen membranes. Using comparative sequence analysis and phosphorylation site prediction programs, we identified two putative phosphorylation motifs in the cytoplasmic juxtamembrane (JM) domain. Site-directed mutagenesis in these motifs, followed by transient overexpression in tobacco pollen, showed that both motifs have opposite effects in regulating pollen tube length. Relative to LePRK2-eGFP pollen tubes, alanine substitutions in residues of motif I, Ser277/Ser279/ Ser282, resulted in longer pollen tubes, but alanine substitutions in motif II, Ser304/Ser307/Thr308, resulted in shorter tubes. In contrast, phosphomimicking aspartic substitutions at these residues gave reciprocal results, that is, shorter tubes with mutations in motif I and longer tubes with mutations in motif II. We conclude that the length of pollen tubes can be negatively and positively regulated by phosphorylation of residues in motif I and II respectively. We also showed that LePRK2-eGFP significantly decreased pollen tube length and increased pollen tube tip width, relative to eGFP tubes. The kinase activity of LePRK2 was relevant for this phenotype because tubes that expressed a mutation in a lysine essential for kinase activity showed the same length and width as the eGFP control. Taken together, these results suggest that LePRK2 may have a central role in pollen tube growth through regulation of its own phosphorylation status. © 2011 by The American Society for Biochemistry and Molecular Biology, Inc.
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Luquet, C.M. - Weihrauch, D. - Senek, M. - Towle, D.W.
J. Exp. Biol. 2005;208(19):3627-3636
2005
Temas: Arginine kinase - Crab - Gene expression - Gill - Na+/K+-ATPase - Na+/K+/2Cl - cotransporter - Quantitative PCR - V-type H+-ATPase - messenger RNA - primer DNA
Descripción: Using quantitative real-time PCR, the expression of mRNAs encoding three transport-related proteins and one putative housekeeping protein was analyzed in anterior and posterior gills of the euryhaline crab Chasmagnathus granulatus following transfer from isosmotic conditions (30‰ salinity) to either dilute (2‰) or concentrated (45‰) seawater. Modest changes were observed in the abundance of mRNAs encoding the housekeeping protein arginine kinase and the vacuolar-type H+-ATPase B-subunit, both of which were highly expressed under all conditions. By contrast, the expression of Na +/K+-ATPase α-subunit mRNA and Na+/K +/2Cl- cotransporter mRNA was strongly responsive to external salinity. During acclimation to dilute seawater, cotransporter mRNA increased 10-20-fold in posterior gills within the first 24 h while Na +/K+-ATPase α-subunit mRNA increased 35-55-fold. During acclimation to concentrated seawater, cotransporter mRNA increased 60-fold by 96 h and Na+/K+-ATPase α-subunit increased approximately 25-fold in posterior gills. Our results indicate a complex pattern of transcriptional regulation dependent upon the direction of salinity change and the developmental background of the gills.
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De Marco, R.J. - Gurevitz, J.M. - Menzel, R.
J. Exp. Biol. 2008;211(10):1635-1644
2008
Temas: Apis mellifera - Communication - Spatial information - Variability - Waggle dance - animal - animal communication - article - bee - comparative study
Descripción: A honeybee's waggle dance is an intriguing example of multisensory convergence, central processing and symbolic information transfer. It conveys to bees and human observers the position of a relatively small area at the endpoint of an average vector in a two-dimensional system of coordinates. This vector is often computed from a collection of waggle phases from the same or different dancers. The question remains, however, of how informative a small sample of waggle phases can be to the bees, and how the spatial information encoded in the dance is actually mapped to the followers' searches in the field. Certainly, it is the variability of a dancer's performance that initially defines the level of uncertainty that followers must cope with if they were to successfully decode information in the dance. Understanding how a dancer's behaviour is mapped to that of its followers initially relies on the analysis of both the accuracy and precision with which the dancer encodes spatial information in the dance. Here we describe within-individual variations in the encoding of the distance to and direction of a goal. We show that variations in the number of a dancer's wagging movements, a measure that correlates well with the distance to the goal, do not depend upon the dancer's travelled distance, meaning that there is a constant variance of wagging movements around the mean. We also show that the duration of the waggle phases and the angular dispersion and divergence of successive waggle phases co-vary with a dancer's orientation in space. Finally, using data from dances recorded through high-speed video techniques, we present the first analysis of the accuracy and precision with which an increasing number of waggle phases conveys spatial information to a human observer.
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Hermida, G.N. - Farías, A. - Fiorito, L.E.
Biocell 2002;26(3):347-355
2002
Temas: Amphibian - Electronic microscopic - Lung ultrastructure - Respiratory epithelium - Toad - animal tissue - article - cell ultrastructure - comparative anatomy - controlled study
Descripción: The lung of the toad, Melanophryniscus stelzneri stelzneri was studied using scanning and transmission electron microscopy. In M.s.stelzneri the parenchyma forms a polygonal network arrangement, therefore the parenchyma is edicular. These spaces are delimited by the interconnection of third order septa which are covered by respiratory epithelium. Small patches of ciliated epithelium without goblet cells appear irregularly distributed on the septa. The respiratory epithelium consists of one type of pneumocyte, which shows characteristics of both type I and type II alveolar cells of higher vertebrates. The pneumocytes are irregular in shape and possess attenuated cytoplasmic processes, which spread around the capillaries to form the outer layer of the air-blood barrier. These cells contain different types of cytoplasmic bodies: electron dense bodies, multivesicular bodies and lamellar bodies. Dense bodies are probably the precursors of lamellar bodies and the multivesicular bodies are incorporated into the latter. Neuroepithelial bodies appear randomly distributed over the septa. These bodies are separated from the lumen of the lung by thin cytoplasmic processes of neighbouring pneumocytes. The air-blood barrier consists of three layers: epithelium, interstitial space and endothelium. The relatively simple pulmonary structure of M.s.stelzneri is due to a lower degree of partitioning of the pulmonary lumen in comparison to the lung of other bufonid anurans, could be correlated with a well developed cutaneous and buccopharingeal respiration. The testing of this hypothesis awaits further studies.
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Panza, V. - Pighin, D. - Láinez, V. - Pollero, R.J. - Maldonado, S.
Biocell 2009;33(2):99-106
2009
Temas: Arecaceae - Fatty acids - Palm seeds - Recalcitrant behavior - Storage susceptibility - fatty acid - linoleic acid - lipid - oleic acid - palmitic acid
Descripción: Comparative studies on fatty acid and protein composition of the endosperm and embryo of palmito (Euterpe edulis Martius) were conducted using gas-liquid chromatography and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. On a dry weight basis, the embryo contained extremely lower amounts of lipids and proteins than did the endosperm, which was associated with the scarce lipid and protein bodies previously reported in axis and cotyledon. The fatty acid composition also exhibited differences between both tissues: (I) the fatty acid diversity was greater in embryo than in endosperm; (II) embryo and endosperm contained predominantly linoleic, palmitic, oleic and stearic acids even though the relative values were different for each tissue. As compared to other palm species, the higher fatty acid unsaturation in Euterpe edulis seed could be involved in the previously reported short longevity and recalcitrant behavior during storage. Proteins of both tissues were heterogeneous in molecular mass. Some proteins were tissue-specific, but other were common, among them a highly glycosylated protein which migrated at about 55 kDa. We hypothesize that the latter, also reported in all previously studied palm species, is one of the proteins characterizing the Arecaceae family.
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Iñón de Iannino, N. - Briones, G. - Kreiman, G. - Ugalde, R.
Cell. Mol. Biol. (Noisy-le-grand) 1996;42(5):617-629
1996
Temas: bacterial protein - beta glucan - cyclic beta(1 2)glucan - cyclic beta(1-2)glucan - glucan - glycopeptide - membrane protein - uridine diphosphate glucose - article - biosynthesis
Descripción: Three wild type strains of Rhizobium fredii, USDA 191, USDA 257 and HH 303, do not synthesize in vivo or in vitro beta(1-3), beta(1-6) cyclic glucans, all strains form in vitro and in vivo cyclic beta(1-2) glucans. Approximately 80% of the recovered R. fredii cellular cyclic beta(1-2) glucans were anionic and the substituent was identified as phosphoglycerol. Inner membranes prepared from these R. fredii strains have a beta(1-2) glucan-intermediate-protein with apparent molecular mass undistinguishable from Agrobacterium tumefaciens beta(1-2) glucan intermediate protein. Studies of the degree of polymerization of the oligosaccharides recovered from the protein-intermediate after short pulse incubations with UDP-14C-glucose suggested that the rate limiting step in the biosynthesis of cyclic glucan is cyclization. Kinetic studies revealed that the K(m) for UDP-glucose was 0.33 mM. No difference was detected between the K(m) for initiation/elongation and cyclization reactions. Nodulation studies of a ndvB R. fredii mutant with Mc Call and Peking soybean cultivars, revealed that beta(1-2) glucans do not seem to be required for normal nodule invasion of these soybean cultivars.
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