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1

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Saccharidic compounds as soil redox effectors and their influence on potential N2O production (1996)

Pidello, A. ; Menéndez, L. ; Perotti, E. B. R.

Springer

Biology and fertility of soils 23 (1996), S. 173-176

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ISSN: 1432-0789

Keywords: Denitrification ; Saccharide sources ; Redox conditions ; CO2:N2O ratio

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract Cellulose, xylan, and glucose were compared in waterlogged soil as modifying factors of the redox potential (Eh), of the quantity of reducing equivalents, and of the soil capacity to produce N2O and CO2. During the study period (168 h) soils supplied with glucose and xylan showed a higher Eh decrease than the control soil and the soil treated with cellulose. In samples taken after 0, 24, 48, and 168 h, the soils supplied with C showed a higher number of reducing equivalents than the control soil did. These quantities were not correlated with Eh values, nor with N2O production. N2O production was increased compared with the control soil over the entire experimental period in the glucose-amended soils but only after 48 h in the xylan-amended soils and not until 168 h in the cellulose-treated soils. The CO2:N2O ratio was consistently higher than the theoretical value of 2, suggesting that denitrification and CO2 production via fermentation occurred simultaneously. Moreover, this ratio was highly correlated with the Eh values. We conclude that more research is needed to explain the role of soil redox intensity (Eh) and capacity (quantity of redox species undergoing reduction) in the expression of soil denitrification-fermentation pathways.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00336059

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2

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Saccharidic compounds as soil redox effectors and their influence on potential N2O production (1996)

Pidello, A. ; Menéndez, L. ; Perotti, E. B. R.

Springer

Biology and fertility of soils 23 (1996), S. 173-176

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ISSN: 1432-0789

Keywords: Key words Denitrification ; Saccharide sources ; Redox conditions ; CO2:N2O ratio

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract Cellulose, xylan, and glucose were compared in waterlogged soil as modifying factors of the redox potential (Eh), of the quantity of reducing equivalents, and of the soil capacity to produce N2O and CO2. During the study period (168 h) soils supplied with glucose and xylan showed a higher Eh decrease than the control soil and the soil treated with cellulose. In samples taken after 0, 24, 48, and 168 h, the soils supplied with C showed a higher number of reducing equivalents than the control soil did. These quantities were not correlated with Eh values, nor with N2O production. N2O production was increased compared with the control soil over the entire experimental period in the glucose-amended soils but only after 48 h in the xylan-amended soils and not until 168 h in the cellulose-treated soils. The CO2:N2O ratio was consistently higher than the theoretical value of 2, suggesting that denitrification and CO2 production via fermentation occurred simultaneously. Moreover, this ratio was highly correlated with the Eh values. We conclude that more research is needed to explain the role of soil redox intensity (Eh) and capacity (quantity of redox species undergoing reduction) in the expression of soil denitrification-fermentation pathways.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00336059

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3

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Effect of addition of various carbon substrates on denitrification in a vertic Mollisol (1992)

Lescure, C. ; Menendez, L. ; Lensi, R. ; [et al.]

Springer

Biology and fertility of soils 13 (1992), S. 125-129

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ISSN: 1432-0789

Keywords: Denitrification ; Carbon substrate ; N2O formation ; Redox conditions ; Electron availability ; Microbial reduction

Source: Springer Online Journal Archives 1860-2000

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

Notes: Summary Glucose, acetate, malate, and citrate were added to an agricultural soil. The pe values (-log e-; calculated from the redox potential) obtained 30 min after the addition of C were not correlated with the theoretical reducing power nor with the theoretical total energy of the C compounds. By contrast the number of electron (e-) equivalents was correlated with pe7, indicating that the proton number affected the redox potential (Eh) measurement. After 24 h of incubation, denitrification rates followed the order citrate〉malate〉glucose and control. No N2O production was detected with acetate. Denitrification was not correlated with the theoretical reducing power of the added C compounds but was correlated with pe+pH. Similar numbers of e- equivalents were measured with all treatments. After 72 h of incubation, the order of the denitrification rates was malate〉citrate 〉acetate〉glucose and control. The Eh values (lower than after 24h) did not differ with treatment while the number of e- equivalents was influenced by the quality of the C source. This also demonstrates that the proton number affected the measured Eh. Our results suggest that the different C substrates did not directly influence the soil physicochemical and biological conditions through their degree of oxidation. Any effects appeared to be indirect, arising from the ability of the substrates to generate new metabolites, and consequently initiate different metabolic pathways that modified the soil physicochemical conditions, reducing power and microbial activity.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00336266

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4

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Azospirillum affects Eh and potential denitrification in a soil (1993)

Pidello, A. ; Menendez, L. ; Lensi, R.

Springer

Plant and soil 157 (1993), S. 31-34

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ISSN: 1573-5036

Keywords: Azospirillum brasilense ; denitrifying activity ; soil redox potential

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract The effect of inoculation withAzospirillum brasilense (strain 7001) on soil Eh under anaerobic conditions (N2 flux) was examined during 144 h at 26°C and 230 h at 18°C. The Eh values of the control (not inoculated) soil decreased to approximately 80 or 140 mV in both cases, whereas after 24 h of anaerobic incubation, the Eh of theAzospirillum-inoculated soil remained at higher values. After 144 and 230 h of anaerobic incubation, the denitrifying activity (measured in anaerobiosis with excess of e- acceptor and donor) in the inoculated soil was seven and three times lower respectively, than in the non-inoculated soil. This indicates thatAzospirillum may affect the soil Eh and consequently any highly Eh-dependent microbial activity, such as denitrification.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02390224

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5

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Azospirillum affects Eh and potential denitrification in a soil (1993)

Pidello, A. ; Menendez, L. ; Lensi, R.

Springer

Plant and soil 157 (1993), S. 31-34

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ISSN: 1573-5036

Keywords: Azospirillum brasilense ; denitrifying activity ; soil redox potential

Source: Springer Online Journal Archives 1860-2000

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

Notes: Abstract The effect of inoculation with Azospirillum brasilense (strain 7001) on soil Eh under anaerobic conditions (N2 flux) was examined during 144 h at 26°C and 230 h at 18°C. The Eh values of the control (not inoculated) soil decreased to approximately 80 or 140 mV in both cases, whereas after 24 h of anaerobic incubation, the Eh of the Azospirillum-inoculated soil remained at higher values. After 144 and 230 h of anaerobic incubation, the denitrifying activity (measured in anaerobiosis with excess of e- acceptor and donor) in the inoculated soil was seven and three times lower respectively, than in the non-inoculated soil. This indicates that Azospirillum may affect the soil Eh and consequently any highly Eh-dependent microbial activity, such as denitrification.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF00038745

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6

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Interaction among alfaxalone, pregnenolone sulfate, and two GABAA agonists on hippocampal slices (1996)

SanMartin, S. ; Andrés-Trelles, F. ; Menendez, L. ; [et al.]

Springer

Cellular and molecular neurobiology 16 (1996), S. 427-431

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ISSN: 1573-6830

Keywords: 3-amino propane sulphonic acid (3-APS) ; muscimol ; alfaxalone ; pregnenolone sulfate ; hippocampal slice ; mice

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary GABAA agonists do not respond to the same degree to allosteric modulators of the GABAA receptor complex such as benzodiazepines. We report there the effects of two steroids (alfaxalone and pregnenolone sulfate) on the inhibition induced by two GABAA agonists, 3-amino propane sulphonic acid (3-APS) and muscimol, on the extracellular evoked potentials obtained in CA1 of mice hippocampi. Alfaxalone (1µM) potentiates the effects of both agonists, although incubation times longer than 15 minutes are required to potentiate the inhibitory effect of muscimol. Lower doses of pregnenolone sulfate at shorter incubation periods are able to inhibit the effects produced by single doses of 3-APS as compared to muscimol (15µM during 5 minvs 30µM during 5 min). Our results confirm the possibility that there might be differences in the interaction between GABAA agonists and modulatory steroids.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02088108

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7

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Effects of Diethylstilbestrol on Mouse Hippocampal Evoked Potentials in Vitro (1999)

SanMartín, S. ; Gutiérrez, M. ; Menéndez, L. ; [et al.]

Springer

Cellular and molecular neurobiology 19 (1999), S. 691-703

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ISSN: 1573-6830

Keywords: diethylstilbestrol ; estrogens ; DAGO ; opiate receptors ; binding ; hippocampal evoked potentials ; hippocampal slices ; mouse

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract 1.Several steroids and related compounds can bind to central opiate receptors in whole-brain mouse homogenates. Among these drugs, the synthetic estrogen, diethylstilbestrol (DES), exhibits one of the highest affinities in binding experiments labeling opiate receptors with the nonselective opiate antagonist, [3H]diprenorphine. 2.In the search for a functional correlate to this biochemical finding, we have studied the effects of DES on the mouse hippocampal slice in vitro preparation. 3.Previously, binding studies were performed in hippocampal homogenates, labeling opiate receptors with [3H]diprenorphine or with the μ-selective opiate agonist, [3H]DAGO. DES inhibited [3H]diprenorphine and [3H]DAGO binding, the IC50 values obtained being (1.03 ± 0.16) × 10−5 and (1 ± 0.8) × 10−5 M, respectively. 4.In mice hippocampal slices, we measured the extracellular evoked potentials obtained in the CA1 pyramidal cell layer of the hippocampi and the field excitatory postsynaptic potentials (EPSP) obtained in the stratum radiatum. The presence of DES (10−5 M) induced an increase in the amplitude of the population spikes measured in the pyramidal layer without modifying the field EPSP. This effect is similar to that obtained in the presence of DAGO in this preparation. The effect produced by DES was not modified by the presence of the opiate competitive antagonist, naloxone (10−5 M), or by the opiate alkylating agent, β-chlornaltrexamine(10−5 M). Conversely, in the presence of the transcription inhibitor, actinomycin D (5 μg/ml), the effect produced by DES was inhibited. 5.Our results with DES support the general idea that estrogens increase central excitability. Although diethylstilbestrol can bind to opiate receptors in the hippocampus, the effect induced by this estrogen on hippocampal excitability seems unrelated to a direct action on opiate receptors, and an intracellular effect is suggested.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1006996805017

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