Showing papers by "University of Buenos Aires published in 1991"
TL;DR: Liver and heart homogenates were subjected to in vitro oxidative stresses such as supplementation with organic hydroperoxide or with enzymatic systems generating superoxide anion or hydrogen peroxide and chemiluminescence was higher in the poststress samples than in the control ones.
426 citations
01 Jan 1991
213 citations
TL;DR: Shading treatments of 50% of the incident radiation were applied to the semidwarf wheat cultivar Leones INTA before and after anthesis in two field experiments in Argentina in 1987 and 1988, reducing biological yield, grain yield and number of grains/m2.
Abstract: Shading treatments of 50% of the incident radiation were applied to the semidwarf wheat cultivar Leones INTA before and after anthesis in two field experiments in Argentina in 1987 and 1988. The treatments reduced biological (above-ground dry matter) yield, grain yield and number of grains/m2. Number of grains/m2 was closely and linearly correlated with ear dry weight at anthesis and with the photothermal quotient, calculated from 20 days before to 10 days after anthesis. Grain yield was sink limited, and the shading treatments reduced sink strength. The contribution of preanthesis assimilates to grain yield was smaller in the shaded crops than in the unshaded controls; in unshaded crops, almost 40% of grain yield was contributed by preanthesis assimilates whilst in preanthesis shaded crops this contribution was negligible. The proportion of preanthesis assimilates contributed to the grain was closely related to the decrease in stem dry weight during grain filling. The effects of shading on main stems and tillers were the same.
207 citations
TL;DR: Findings indicate that benzodiazepines released in the septum, amygdala and hippocampus do indeed physiologically downregulate memory storage processes; moreover, Benzodiazepine release could be modulated by the anxiety and/or stress associated with each type of learning.
181 citations
TL;DR: The results suggest that in even-aged populations of LAI > 1 elongation growth is promoted by the low R:FR ratio and the reduced fluence rate, which may elicit morphological adaptations in the canopy before the onset of severe competition among neighbours for the resource of light.
Abstract: . We investigated the effects of photon fluence rate on internode elongation in fully de-etiolated plants growing under sunlight. Our goal was to find out whether perception by the stems of fluence rate changes related to canopy density may be involved in the modulation of internode growth in canopies formed by plants of similar stature (e.g. crop stands). Using Datura ferox L. and Sinapis alba L. seedlings growing under natural radiation, we found that internode elongation is promoted by localized shading. This effect was observed with internodes receiving light with a high (>0.9) or a low (0.3) red (R) to far-red (FR) photon ratio. Selective removal of the different wavebands from the light impinging on the internodes showed that part of the response to fluence rate is due to photons in the R + FR range. The blue (B) component, most likely acting through a specific photoreceptor, also inhibited elongation. However, changes in the fluence rate of B light did not have detectable effects on the response of the internodes to R:FR ratio. Fibre-optic studies and measurements with integrating-cylinder sensors in even-aged populations of seedlings showed that both the quality and quantity of radiation received by the stems are profoundly influenced by changes in canopy density. When density is very low (leaf area index = LAI ≥ 1) only the R:FR ratio is reduced, due to FR reflected from nearby leaves. In the LAI range of 1 to 2, though a large proportion of the leaf area is still receiving full sunlight, the photon fluence rate at the stem level drops dramatically. These results suggest that in even-aged populations of LAI > 1 elongation growth is promoted by the low R:FR ratio and the reduced fluence rate. Perception of these two factors at the stem level may elicit morphological adaptations in the canopy before the onset of severe competition among neighbours for the resource of light.
170 citations
TL;DR: Hydrogen peroxide metabolism in soybean embryonic axes during early inhibition appears to have the following main features: mitochondrial membranes are the most important source of cytosolic O2- and H2O2; and extracellular peroxidase located at the cell wall affords an enzymatic system able to use diffused H 2O2.
168 citations
TL;DR: In this article, the authors analyzed how two disturbance types (cattle grazing and large flooding) affected community diversity at two spatial scales (stand and patch) and three levels of species dominance in a grassland of the Flooding Pampa, Argentina.
Abstract: It is proposed that evaluations of disturbance effects upon community diversity will be influenced by two factors currently overlooked in models addressing disturbance-diversity relationships: (1) the spatial scale of inquiry, and (2) the level of the species abundance (dominance) hierarchy at which the search for diversity is done. We analyzed how two disturbance types—cattle grazing and large flooding—affected community diversity at two spatial scales (stand and patch) and three levels of species dominance in a grassland of the Flooding Pampa, Argentina. The effect of disturbance interaction was also examined. Species diversity at the stand scale was reduced by either grazing or flooding. Both disturbances decreased community spatial heterogeneity. At the patch scale, diversity declined with flooding but was enhanced by grazing. Flooding increased diversity under grazing conditions. However, stand diversity was highest in the undisturbed grassland; pattern diversity was the salient feature in this condition. The combination of disturbances yielded the highest patch-scale diversity; grazing increased richness whilst flooding enhanced evenness. Comparisons among grassland conditions appeared scale-dependent. Moreover the extent of disturbance effects varied with the level of dominance hierarchy considered. We point out the relevance of site history and initial conditions, encompassing the possibility of disturbances interaction, to the patters produced by disturbance events. Effects perceived at different spatial scales, or in species positioned at separate dominance levels, may parallel meaningful changes in the relative importance of factors controlling species coexistence and community organization.
167 citations
150 citations
TL;DR: Mitochondrial DNA, morphological and isoenzyme analyses show that substantial hybridization occurs between the two racial groups, and transecting regions populated by African- and European-derived honey bees in Argentina are described.
Abstract: IN the Neotropics, introduced European honey bees (Apis mellifera L.)1,2 have been largely supplanted by bees descended from an African race, A. m. scutellata Lepetier, which were introduced into Brazil in the 1950s. Recent restriction enzyme analyses indicate that mitochondrial DNA in some neotropical populations is almost entirely of African origin3,4, and these data have been cited as evidence for asymmetrical gene flow between African- and European-derived populations3,4. Evaluation of the nature of hybridization in the Neotropics is, however, confounded by possible population size advantages for the African-derived group5–7. As an alternative approach, genetic interactions can be studied in transition areas between zones ecologically and climatically adaptive for both racial groups. We describe here results of a survey transecting regions populated by African- and European-derived honey bees in Argentina. Mitochondrial DNA, morphological and isoenzyme analyses show that substantial hybridization occurs between the two racial groups.
141 citations
01 Jan 1991
TL;DR: A procedure which should fit many purposes reasonably well for robust regression estimators and the reluctance to use the straightforward inference based on asymptotics is proposed.
Abstract: Even if robust regression estimators have been around for nearly 20 years, they have not found widespread application. One obstacle is the diversity of estimator types and the necessary choices of tuning constants, combined with a lack of guidance for these decisions. While some participants of the IMA summer program have argued that these choices should always be made in view of the specific problem at hand, we propose a procedure which should fit many purposes reasonably well. A second obstacle is the lack of simple procedures for inference, or the reluctance to use the straightforward inference based on asymptotics.
136 citations
TL;DR: It seems that the genetic improvement produced important increases in harvest index, but it did not produce important changes in total biomass, and it is expected that further increases in grain yield will rely more on genetic gain than on technologic gain.
Abstract: The understanding of the changes produced by plant breeding on wheat grain yield and on its determinants, through the study of the behaviour of cultivars released at different times during the breeding process, could be a useful tool to define future selection criteria. The aim of this paper was to examine the genetic improvement effects on bread wheat grain yield potential and on its major physiological determinants in different countries. Generally, it seems that the genetic improvement produced important increases in harvest index, but it did not produce important changes in total biomass. The genetic gain in grain yield ranged from 0.58 g m-2 year-1 (India) to 5.84 g m-2 year-1 (Mexico); reflecting important differences among genetic improvement programmes. However, when the comparisons were made in relative values, the difference was much lower, ranging from 0.16% year-1 to 0.90% year-1, for the previously mentioned countries, respectively. Most of the regions showed relative genetic gains of around 0.45% year-1. Similar patterns of relative genetic gains in harvest index were found. Half of the total gain in grain yield in the past was due to genetic gain in grain yield potential. However, it is expected for the future, that further increases in grain yield will rely more on genetic gain than on technologic gain. Thus, a discussion about possible strategies in future breeding programmes of bread wheat is attempted throughout the paper. The changes in grain yield were mostly associated with changes in number of grains per m2 rather than with changes in individual grain weight. It appears that the source: sink ratio during the grain-filling period was very high in old cultivars, whereas the source: sink ratio in modern cultivars is more balanced. Further increases in number of grains m-2 could be compensated by a reduction in individual grain weight, if simultaneous improvement in source strength during grain-filling is not achieved. The crop attributes which have been changed together with the mentioned traits are discussed and alternative selection criteria are suggested.
TL;DR: The microheterogeneity found in the lipopeptidophosphoglycan glycan is described, using a combination of 1H and 31P NMR, fast atom bombardment mass spectrometry, methylation linkage analysis, and exoglycosidase sequencing.
TL;DR: Results indicate that time-dependent melatonin analgesia is sensitive to opioid or central-type BZP antagonism.
TL;DR: Cultured human peripheral blood mononuclear leucocytes (PBML) were able to synthesize indoleamines, including melatonin, and were also able to convert melatonin taken up from the incubation medium into N-acetyl-5-hydroxytryptamine (NAHT) and 5-hydosterone (5-HT).
Abstract: Cultured human peripheral blood mononuclear leucocytes (PBML) were able to synthesize indoleamines, including melatonin, and were also able to convert melatonin taken up from the incubation medium into N-acetyl-5-hydroxytryptamine (NAHT) and 5-hydroxytryptamine (5-HT). These compounds were analysed by h.p.l.c., and melatonin was additionally characterized by two-dimensional t.l.c., mass spectrometry and radioimmunoassay. Only hydroxyindoles were detected by h.p.l.c. in unstimulated PBML culture. Sustained stimulation by melatonin or interferon-gamma (IFN-gamma) increased markedly the basal production of 5-HT. IFN-gamma- or 5-HT-stimulated (but not resting) cells produced NAHT and melatonin. Furthermore, the addition of melatonin to the culture medium strongly enhanced NAHT and 5-HT production without affecting tryptophan hydroxylation, suggesting the possibility of direct or indirect transformation of melatonin into NAHT and 5-HT.
TL;DR: It is shown that the membership problem has single exponential sequential and polynomial parallel complexity for unmixed ideals.
TL;DR: Findings suggest that depression is the most important factor associated with the common problems of sleep disorder and pain among patients with PD.
Abstract: A consecutive series of patients with Parkinson’s disease (PD) were examined for the presence of sleep disturbances, pain, and depression. We found that patients with PD and major depression had significantly more sleep disturbances and severe pain than non-depressed patients with PD. Moreover, depression scores accounted for most of the variance in a stepwise regression analysis of the effect of numerous clinical variables on either sleep disorders or pain severity. These findings suggest that depression is the most important factor associated with the common problems of sleep disorder and pain among patients with PD.
TL;DR: Polyethylene bags proved to be promising containment systems for solid state cultivation for Aspergillus oryzae NRRL 2160 on solid substrates and casein and gluten were effective inducers.
Abstract: A number of culture conditions for protease production by Aspergillus oryzae NRRL 2160 on solid substrates were investigated. The pH of the medium and the substrate markedly affected protease production. High protease yield was obtained when the fungus was cultivated for 72-96 h on rice hulls: rice bran (7:3), at an initial pH of 7.0. Maximal protease production was achieved at an initial moisture content of 35-40%, corresponding to a water activity range of 0.982-0.986. Casein and gluten were effective inducers. Polyethylene bags proved to be promising containment systems for solid state cultivation.
TL;DR: In this paper, the Sierras Australes (Buenos Aires province, Argentina) form a sigmoidal foldbelt, about 150 km long, which is associated with cleavage, stretching lineation and kinematic indicators.
TL;DR: In this paper, the authors studied the large time behavior of positive solutions of the heat equation under the nonlinear boundary condition ∂u ∂ν = f(u), where η is the outward normal and f is non-decreasing with f (u) > 0 for u > 0.
TL;DR: The results suggest that the induction of heme oxygenase by phenylhydrazine and the diamide is preceded by an oxidative stress which very likely originates in the depletion of GSH.
TL;DR: Considering the percentage of asymmetric IgG molecules with antipaternal antigen specificity eluted from placenta and the possibility that they function as blocking antibodies, their participation in fetal protection is suggested.
TL;DR: The photomorphogenic control of hypocotyl extension growth was characterized in wild type (WT) and long hypocotyle (Ih) mutant seedlings of cucumber grown under natural radiation in outdoor and glasshouse experiments.
Abstract: The photomorphogenic control of hypocotyl extension growth was characterized in wild type (WT) and long hypocotyl (Ih) mutant seedlings of cucumber (Cucumis sativus L.) grown under natural radiation in outdoor and glasshouse experiments. Hypocotyl extension growth of WT plants was promoted by supplementing sunlight with far-red light during the photoperiod, by reducing the amount of blue light reaching either the whole shoot or the hypocotyl, and by reducing the amount of UV reaching the whole shoot.The Ih seedlings only responded to a reduction in UV-B levels. Both WT and Ih seedlings showed phototropic responses to the direction of blue light. Increasing degrees of vegetational shade promoted hypocotyl growth of WT plants. The Ih mutant showed no hypocotyl growth promotion by natural shade in glasshouse experiments (no UV-B, low water demand) and a reduced response (10-23% of the WT response, according to pretreatment conditions) in outdoor experiments (UV-B, high water demand).
TL;DR: This study supports the hypothesis of a causal association between the presence and number of infected dogs and increased levels of T. cruzi transmission to domestic T. infestans.
Abstract: The association between household seroreactivity to Trypanosoma cruzi in dogs and children and T. cruzi infection rates in domestic Triatoma infestons was investigated in 1988–1989 in the rural community of Arnama, north-west Argentina, where house spraying with residual pyrethroids was carried out in 1985. Three years after spraying, a greater reduction of the average T. cruzi prevalence rate in dogs (from 83% to 40%) than in children (from 48% to 30%) was accompanied by a substantial decrease in vector infection rates from 51%–63% to 21%. At a household level, in homes with or without seroreactive children, the percentage of infected T. infestons was 4·5–4·7 times higher when seroreactive dogs were present (27·1%–34·8%) than when they were not (5·8%–7·7%; stratified relative risk [RR] = 4·58). The contribution of seroreactive children to bug infection rates was not significant (RR = 1·29). The combined effect of both seroreactive dogs and seroreactive children fitted equally well with additive or multiplicative transmission models. Bug infection rates showed an increasing trend with the number of seroreactive dogs and an inverse association with the age of the youngest seroreactive dog. Our study supports the hypothesis of a causal association between the presence and number of infected dogs and increased levels of T. cruzi transmission to domestic T. infestons.
TL;DR: Serotonin inhibited in a concentration dependent way the LPS induced Tumor Necrosis Factor-α synthesis both, when added to the monocyte cultures from the beginning and when added together with the activating stimulus 8 hours before the end of the culture.
TL;DR: The results obtained in this particular group of patients demonstrated the effectiveness of IVIG treatment, and there was a significant fall in maternal anti‐D titers and intrauterine hemolysis after IVig treatment.
Abstract: The value of intravenous immunoglobulin (IVIG) in the treatment of 24 severely Rh-sensitized pregnant women was studied. IVIG was infused at a daily dose of 0.4 g/kg maternal body weight for 4-5 consecutive days, and was administered again 15-21 days later until delivery, depending on the evolution of the hemolytic disease. Our population was divided into 3 groups according to the time of onset of therapy: group 1 (n = 8), before 20 weeks' gestation; group 2 (n = 7), 20-28 weeks, and group 3 (n = 9), after 28 weeks. Initial mean anti-D level was significantly higher in group 1 (25.9 +/- 12.9 IU/ml) than in the other 2 groups, whose mean values were, however, higher than 10 IU/ml. Amniotic-fluid total bilirubin levels before the onset of therapy were pathologic, and in 55% of the cases they coincided with zone 3 of Liley's chart. Hydrops fetalis at the onset of treatment accounted for the only 3 fetal deaths in groups 1 and 2. None of the fetuses developed hydrops during treatment. Six of the 9 neonates in group 3 were depressed at birth (1-min Apgar below 7). However, at 5 min only 1 newborn showed an Apgar below 7. Mean birth weight was over 2,500 g in all the cases. Neonatal hematological condition in group 2 (50% of the babies required only phototherapy) was better than in the other 2 groups (transfusional therapy). There was a significant fall in maternal anti-D titers and intrauterine hemolysis after IVIG treatment.(ABSTRACT TRUNCATED AT 250 WORDS)
TL;DR: It is suggested that the change in the effect on gonadotrophin secretion of the activation of GABAA receptors which takes place during sexual maturation in the female rats is related to the central mechanisms involved in the onset of puberty.
TL;DR: Results lead to the inclusion of all species except C. talarum, within a complex called the mendocinus-group, and a new case of conservatism for chromosomal number in the genus Ctenomys is found in this group.
Abstract: Cytogenetic analysis was performed in six nominal taxa of the genus Ctenomys with a diploid number of 2n=47/48. The studied species were: C. australis (2n=48, FN=76); C. mendocinus (2n=47/48, FN=68/75/76); C. porteousi (2n=47/48, FN=71/72/73); C. azarae (2n=47, FN=71); C. sp. (‘chasiquensis’) (2n=47/48); and C. talarum (2n=48, FN=80). The first three species shared the whole complement, C. talarum shares with them 19 arms from a total of 43 (44%). In all species analyzed constitutive heterochromatin was detected in most short arms, and in several centromeres. Polymorphisms for several pairs involving the heterochromatic short arms together with a complex polymorphism of pair A1 were found in C. azarae, C. sp., C. mendocinus and C. porteousi. Intraindividual variation found in one specimen of C. porteousi involving heterochromatic arms is discussed. These results lead us to propose the inclusion of all species except C. talarum, within a complex called the mendocinus-group. A new case of conservatism for chromosomal number in the genus Ctenomys is found in this group.
TL;DR: The results indicate the existence of a time-dependency for melatonin activity on locomotor behavior similar to that known to occur for other effects of the hormone, and further support a link between melatonin and the activity of central type BZP receptors.
Journal Article•
TL;DR: It was found a highly significative correlation between malondialdehyde production and SOD activity, which could be used in bovine spermatozoa as a metabolic indicator of membrane integrity.
Abstract: SOD activity and susceptibility to peroxidation on spermatozoa from frozen and fresh bovine semen were determined either in presence or not of synthetic (BHA) or natural (vitamin E) antioxidants. In sperm suspensions incubated with vitamin E, SOD activity was higher than in the control samples and the ones treated with BHA. It was found a highly significative correlation between malondialdehyde production and SOD activity. SOD activity could be used in bovine spermatozoa as a metabolic indicator of membrane integrity.