B Concentration (b + concentration)

Distribution by Scientific Domains


Selected Abstracts


Biochemical properties of the cell wall in the Arabidopsis mutant bor1-1 in relation to boron nutrition

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2003
Kyotaro Noguchi
Abstract We examined concentrations of boron (B) and dimerization of rhamnogalacturonan II (RG-II), a B-binding polysaccharide, in the cell wall of a low-B sensitive mutant of Arabidopsis thaliana, bor1-1, to investigate possible effects of the bor1-1 mutation on the biochemical form of pectins in the cell wall. In the bor1-1 mutant, B concentrations in the cell wall from shoots were lower than those in the wild type at low B supply, whereas they were similar at sufficient B supply. The amount of B present as borate ester of the RG-II dimer (dRG-II-B) in the bor1-1 mutant was lower than that in the wild type at low B supply. In the wild type, about 90,% of RG-II was present as dRG-II-B, both, at low and sufficient B supply. In the bor1-1 mutant, about 60,% of RG-II was in its monomeric form (mRG-II) at low B supply, whereas more than 85,% of it was present as dRG-II-B at sufficient B supply. However, similar as the wild type, mRG-II derived from the bor1-1 mutant was able to form dRG-II-B in vitro in the presence of borate and lead. Sugar composition of cell wall fractions was similar in both genotypes. These results suggest that the polysaccharide composition in the cell wall was not strongly affected by the bor1-1 mutation. The observed difference in dimerization of RG-II at low B supply is most likely due to a reduced B concentration in the shoots of the bor1-1 mutant. Biochemische Eigenschaften der Zellwände der Arabidopsis -Mutante bor1-1 bei unterschiedlicher Borernährung Um die Auswirkungen der bor1-1 -Mutation auf die biochemische Beschaffenheit von Zellwandpektinen zu verstehen, haben wir den Bor(B) -Gehalt und den Status des B-bindenden Polysaccharids Rhamnogalacturonan-II (RG-II) in den Zellwänden einer Arabidopsis thaliana -Mutante (bor1-1) untersucht. Diese Mutante reagiert empfindlich auf niedriges Borangebot. Bei niedriger Borversorgung waren die Borgehalte in der Zellwand des Sprosses der bor1-1 -Mutante niedriger als die des Wildtyps. Dagegen lagen die Borgehalte der bor1-1 -Mutante und des Wildtyps bei guter Borversorgung in einem ähnlichen Bereich. Der Boranteil, der im RG-II-Dimer (dRG-II-B) als Borester vorlag, war bei niedriger Borversorgung in der bor1-1 -Mutante geringer als im Wildtyp. Im Wildtyp lagen sowohl bei niedriger als auch bei hoher Borversorgung 90,% des RG-II als dRG-II-B vor. In der bor1-1- Mutante lagen dagegen bei niedriger Borversorgung 60,% des RG-II in monomerer Form (mRG-II) vor, während bei guter Borversorgung der Anteil von dRG-II-B 85,% ausmachte. Allerdings war mRG-II, das aus der bor1-1 -Mutante gewonnen wurde, fähig, in gleicher Weise wie beim Wildtyp in der Gegenwart von Borat und Bleiionen in vitro dRG-II-B zu bilden. Die Zuckerzusammensetzung der Zellwandfraktionen war in beiden Genotypen ähnlich. Diese Ergebnisse lassen vermuten, dass die Polysaccharidzusammensetzung in der Zellwand nicht gravierend von der bor1-1 -Mutation beeinflusst wurde. Der beobachtete Unterschied in der Dimerisierung von RG-II bei niedriger Borversorgung beruht wahrscheinlich auf dem geringeren Borgehalt im Spross der bor1-1 -Mutante. [source]


The mechanism of boron tolerance for maintenance of root growth in barley (Hordeum vulgare L.)

PLANT CELL & ENVIRONMENT, Issue 8 2007
EUN-YOUNG CHOI
ABSTRACT Cultivar differences in root elongation under B toxic conditions were observed in barley (Hordeum vulgare L.). A significant increase in the length and width of the root meristematic zone (RMZ) was observed in Sahara 3771 (B tolerant) when it was grown under excessive B concentration, compared to when grown at adequate B supply. This coincided with an increase in cell width and cell numbers in the meristematic zone (MZ), whereas a significant decrease in the length and no significant effect on the width of the MZ was observed in Clipper (B intolerant) when it was grown under excessive B supply. This was accompanied by a decrease in cell numbers, but an increase in the length and width of individual cells present along the MZ. Excessive B concentrations led to a significantly lower osmotic potential within the cell sap of the root tip in SloopVic (B tolerant) and Sahara 3771, while the opposite was observed in Clipper. Enhanced sugar levels in the root tips of SloopVic were observed between 48 and 96 h after excess B was applied. This coincided with an increase in the root elongation rate and with a 2.7-fold increase in sucrose level within mature leaf tissue. A significant decrease in reducing sugar levels was observed in the root tips of Clipper under excessive B concentrations. This coincided with significantly lower root elongation rates and lower sucrose levels in leaf tissues. Results indicate a B tolerance mechanism associated with a complex control of sucrose levels between leaf and root tip that assist in maintaining root growth under B toxicity. [source]


Relationship between boron and calcium in the N2 -fixing legume,rhizobia symbiosis

PLANT CELL & ENVIRONMENT, Issue 11 2003
M. REDONDO-NIETO
ABSTRACT Because boron (B) and calcium (Ca2+) seem to have a strong effect on legume nodulation and nitrogen fixation, rhizobial symbiosis with leguminous plants, grown under varying concentrations of both nutrients, was investigated. The study of early pre-infection events included the capacity of root exudates to induce nod genes, and the degree of adsorption of bacteria to the root surface. Both phenomena were inhibited by B deficiency, and increased by addition of Ca2+, resulting in an increase of the number of nodules. The infection and invasion steps were investigated by fluorescence microscopy in pea nodules harbouring a Rhizobium leguminosarum strain that constitutively expresses green fluorescent protein. High Ca2+ enhanced cell and tissue invasion by Rhizobium, which was highly inhibited after B deficiency. This was combined with an increased B concentration in nodules of plants grown on B-free medium and supplemented with high Ca2+ concentrations, and that can be attributed to an increased B import to the nodules. Histological examination of indeterminate (pea) and determinate (bean) nodules showed an altered nodule anatomy at low B content of the tissue. The moderate increase in nodular B due to additional Ca2+ was not sufficient to prevent the abnormal cell wall structure and the aberrant distribution of pectin polysaccharides in B-deficient treatments. Overall results indicate that the development of the symbiosis depends of the concentration of B and Ca2+, and that both nutrients are essential for nodule structure and function. [source]


Dyslipoproteinaemia in postmenopausal women with a history of eclampsia

BJOG : AN INTERNATIONAL JOURNAL OF OBSTETRICS & GYNAECOLOGY, Issue 6 2000
Carl A. Hubel Assistant Professor
Objective To test the hypothesis that postmenopausal women with a history of eclampsia manifest a more high risk lipid profile than postmenopausal women with a history of normal pregnancy. Setting The Department of Obstetrics and Gynaecology, National University Hospital, Reykjavik, Iceland, and the Magee-Womens Research Institute, Pittsburgh, Pennsylvania, USA. Participants Thirty Icelandic women with a history of eclampsia, aged between 50 and 67 years at the time of re-examination (cases) were individually matched for current age, and for age and parity at index pregnancy, to 30 unrelated Icelandic women with a history of normal pregnancy (controls). Methods The participating women completed a health and family history questionnaire and underwent a physical examination. Fasting plasma low density lipoprotein diameter, serum lipids, insulin, and glucose were measured. Results Mean low density lipoprotein size was significantly smaller and apolipoprotein B concentration was higher in women with prior eclampsia. The percentage of cases receiving blood pressure medication (33%) was significantly greater than controls (6.7%). Thirteen cases had had hypertensive complications in at least one other pregnancy (recurrent subgroup); postmenopausally, these women displayed significantly increased diastolic blood pressures, smaller-sized low density lipoprotein, increased apolipoprotein B, decreased high density lipoprotein2 (HDL2) cholesterol, and increased total cholesterol: HDL cholesterol ratio compared with their controls. Fourteen cases were normotensive in all other pregnancies (nonrecurrent); these showed no differences from their controls. Conclusions Dyslipoproteinaemia is more prevalent among postmenopausal women with prior eclampsia, especially with recurrent hypertension in pregnancy, than in postmenopausal women with prior normal pregnancies. [source]


Biochemical properties of the cell wall in the Arabidopsis mutant bor1-1 in relation to boron nutrition

JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2003
Kyotaro Noguchi
Abstract We examined concentrations of boron (B) and dimerization of rhamnogalacturonan II (RG-II), a B-binding polysaccharide, in the cell wall of a low-B sensitive mutant of Arabidopsis thaliana, bor1-1, to investigate possible effects of the bor1-1 mutation on the biochemical form of pectins in the cell wall. In the bor1-1 mutant, B concentrations in the cell wall from shoots were lower than those in the wild type at low B supply, whereas they were similar at sufficient B supply. The amount of B present as borate ester of the RG-II dimer (dRG-II-B) in the bor1-1 mutant was lower than that in the wild type at low B supply. In the wild type, about 90,% of RG-II was present as dRG-II-B, both, at low and sufficient B supply. In the bor1-1 mutant, about 60,% of RG-II was in its monomeric form (mRG-II) at low B supply, whereas more than 85,% of it was present as dRG-II-B at sufficient B supply. However, similar as the wild type, mRG-II derived from the bor1-1 mutant was able to form dRG-II-B in vitro in the presence of borate and lead. Sugar composition of cell wall fractions was similar in both genotypes. These results suggest that the polysaccharide composition in the cell wall was not strongly affected by the bor1-1 mutation. The observed difference in dimerization of RG-II at low B supply is most likely due to a reduced B concentration in the shoots of the bor1-1 mutant. Biochemische Eigenschaften der Zellwände der Arabidopsis -Mutante bor1-1 bei unterschiedlicher Borernährung Um die Auswirkungen der bor1-1 -Mutation auf die biochemische Beschaffenheit von Zellwandpektinen zu verstehen, haben wir den Bor(B) -Gehalt und den Status des B-bindenden Polysaccharids Rhamnogalacturonan-II (RG-II) in den Zellwänden einer Arabidopsis thaliana -Mutante (bor1-1) untersucht. Diese Mutante reagiert empfindlich auf niedriges Borangebot. Bei niedriger Borversorgung waren die Borgehalte in der Zellwand des Sprosses der bor1-1 -Mutante niedriger als die des Wildtyps. Dagegen lagen die Borgehalte der bor1-1 -Mutante und des Wildtyps bei guter Borversorgung in einem ähnlichen Bereich. Der Boranteil, der im RG-II-Dimer (dRG-II-B) als Borester vorlag, war bei niedriger Borversorgung in der bor1-1 -Mutante geringer als im Wildtyp. Im Wildtyp lagen sowohl bei niedriger als auch bei hoher Borversorgung 90,% des RG-II als dRG-II-B vor. In der bor1-1- Mutante lagen dagegen bei niedriger Borversorgung 60,% des RG-II in monomerer Form (mRG-II) vor, während bei guter Borversorgung der Anteil von dRG-II-B 85,% ausmachte. Allerdings war mRG-II, das aus der bor1-1 -Mutante gewonnen wurde, fähig, in gleicher Weise wie beim Wildtyp in der Gegenwart von Borat und Bleiionen in vitro dRG-II-B zu bilden. Die Zuckerzusammensetzung der Zellwandfraktionen war in beiden Genotypen ähnlich. Diese Ergebnisse lassen vermuten, dass die Polysaccharidzusammensetzung in der Zellwand nicht gravierend von der bor1-1 -Mutation beeinflusst wurde. Der beobachtete Unterschied in der Dimerisierung von RG-II bei niedriger Borversorgung beruht wahrscheinlich auf dem geringeren Borgehalt im Spross der bor1-1 -Mutante. [source]


Comparative pharmacodynamic interaction analysis of triple combinations of caspofungin and voriconazole or ravuconazole with subinhibitory concentrations of amphotericin B against Aspergillus spp.

MYCOSES, Issue 3 2010
Joanne P. Demchok
Summary Triple combination therapy with an antifungal triazole, echinocandin and amphotericin B (AmB) is used in some centres to treat refractory aspergillosis. The objective of this study was to investigate the effect of subinhibitory concentrations of AmB on the double combinations of caspofungin (CAS) + voriconazole (VOR) or ravuconazole (RAV) against Aspergillus fumigatus, Aspergillus flavus and Aspergillus terreus. Isolates were studied in triplicate against CAS/VOR and CAS/RAV combinations by chequerboard broth microdilution. AmB was added to each double combination at concentrations of 0, 0.1 and 0.2 ,g ml,1. The fractional inhibitory concentration (FIC) index was calculated for the double and triple combinations. Comparative analysis was performed by repeated measures analysis followed by Dunnett's post-test. The double combinations of CAS/RAV and CAS/VOR were synergistic or additive in most conditions. Addition of AmB to the double combinations resulted in increased FIC indices for A. fumigatus and A. flavus. By contrast, AmB increased the synergism of the double combinations decreasing FIC indices for A. terreus (P < 0.05). RAV and VOR displayed similar synergistic activity with CAS. The addition of sub-inhibitory amphotericin B concentrations reduced but did not eliminate the synergistic interaction between the echinocandin and triazole against A. fumigatus and A. flavus, while it increased the synergy against A. terreus. [source]


The mechanism of boron tolerance for maintenance of root growth in barley (Hordeum vulgare L.)

PLANT CELL & ENVIRONMENT, Issue 8 2007
EUN-YOUNG CHOI
ABSTRACT Cultivar differences in root elongation under B toxic conditions were observed in barley (Hordeum vulgare L.). A significant increase in the length and width of the root meristematic zone (RMZ) was observed in Sahara 3771 (B tolerant) when it was grown under excessive B concentration, compared to when grown at adequate B supply. This coincided with an increase in cell width and cell numbers in the meristematic zone (MZ), whereas a significant decrease in the length and no significant effect on the width of the MZ was observed in Clipper (B intolerant) when it was grown under excessive B supply. This was accompanied by a decrease in cell numbers, but an increase in the length and width of individual cells present along the MZ. Excessive B concentrations led to a significantly lower osmotic potential within the cell sap of the root tip in SloopVic (B tolerant) and Sahara 3771, while the opposite was observed in Clipper. Enhanced sugar levels in the root tips of SloopVic were observed between 48 and 96 h after excess B was applied. This coincided with an increase in the root elongation rate and with a 2.7-fold increase in sucrose level within mature leaf tissue. A significant decrease in reducing sugar levels was observed in the root tips of Clipper under excessive B concentrations. This coincided with significantly lower root elongation rates and lower sucrose levels in leaf tissues. Results indicate a B tolerance mechanism associated with a complex control of sucrose levels between leaf and root tip that assist in maintaining root growth under B toxicity. [source]