University of Córdoba (Spain)

About: University of Córdoba (Spain) is a education organization based out in Cordova, Spain. It is known for research contribution in the topics: Population & Catalysis. The organization has 12006 authors who have published 22998 publications receiving 537842 citations. The organization is also known as: University of Córdoba (Spain) & Universidad de Córdoba.

Cytomegalovirus infection: a driving force in human T cell immunosenescence.

Abstract: The human immune system evolved to defend the organism against pathogens, but is clearly less well able to do so in the elderly, resulting in greater morbidity and mortality due to infectious disease in old people, and higher healthcare costs. Many age-associated immune alterations have been reported over the years, of which probably the changes in T cell immunity, often manifested dramatically as large clonal expansions of cells of limited antigen specificity together with a marked shrinkage of the T cell antigen receptor repertoire, are the most notable. It has recently emerged that the common herpesvirus, cytomegalovirus (CMV), which establishes persistent, life-long infection, usually asymptomatically, may well be the driving force behind clonal expansions and altered phenotypes and functions of CD8 cells seen in most old people. In those few who are not CMV-infected, another even more common herpesvirus, the Epstein-Barr virus, appears to have the same effect. These virus-driven changes are less marked in "successfully aged" centenarians, but most marked in people whom longitudinal studies have shown to be at higher risk of death, that is, those possessing an "immune risk profile" (IRP) characterized by an inverted CD4:8 ratio (caused by the accumulation primarily of CD8(+) CD28(-) cells). These findings support the hypothesis that persistent herpesviruses, especially CMV, act as chronic antigenic stressors and play a major causative role in immunosenescence and associated mortality.

Comparison of leaf construction costs in woody species with differing leaf life-spans in contrasting ecosystems

Abstract: ummary • The construction costs (CC) are reported of leaves from 162 wild woody species from 14 contrasting environments (desert to rain forest) and with different leaf life-spans. • Calorimetric methods were used to estimate the CC of deciduous, semideciduous and evergreen leaves. • Leaf CC showed a wide range (78%) between species, and deciduous species showed a slightly lower CC (6%) than both semideciduous and evergreen species. Mean leaf CC differed between ecosystems, with the highest and lowest CC in the tundra and rain forest, respectively. Leaf CC was positively correlated with lipid concentration. Leaf size (log) and specific leaf area (SLA, leaf area per leaf dry mass) were negatively correlated with leaf CC. Leaf CC did not show differences between different leaf life-spans or ecosystems when leaf size (log) or SLA were included as covariates. • The small differences in leaf CC among leaf life-span types and ecosystems (6% and 23%, respectively) suggest that SLA is more important in determining differences in the carbon balance between species than leaf CC. Leaf size is shown to be an important trait associated with other leaf characteristics. Abbreviations A, ash concentration; CC, construction cost per unit dry mass; CCA, construction cost per unit area; Eg, growth efficiency; Hc, ash free heat of combustion; N, nitrogen; SLA, specific leaf area.

Increasing day-length induces spring flushing of tropical dry forest trees in the absence of rain

Abstract: In many conspecific trees of >50 species highly synchronous bud break with low inter-annual variation was observed during the late dry season, around the spring equinox, in semideciduous tropical forests of Argentina, Costa Rica, Java and Thailand and in tropical savannas of Central Brazil. Bud break was 6 months out of phase between the northern and southern hemispheres and started about 1 month earlier in the subtropics than at lower latitudes. These observations indicate that "spring flushing", i.e., synchronous bud break around the spring equinox and weeks before the first rains of the wet season, is induced by an increase in photoperiod of 30 min or less. Spring flushing is common in semideciduous forests characterized by a 4–6 month dry season and annual rainfall of 800–1,500 mm, but rare in neotropical forests with a shorter dry season or lower annual precipitation. Establishment of new foliage shortly before the wet growing season is likely to optimize photosynthetic gain in tropical forests with a relatively short growing season.

Magnetic enhancement is linked to and precedes hematite formation in aerobic soil

Abstract: [1] Soil formation usually increases magnetic susceptibility, most often by increasing the concentrations of magnetite and maghemite, which are two ferrimagnetic iron oxides. Here we provide evidence that magnetic enhancement in aerobic soils not affected by detrital magnetic inputs or thermal transformation of other iron oxides is mostly due to the formation of maghemite, which is later transformed into hematite—the iron oxide that gives red color to soil. We show that the maghemite/hematite ratio is influenced by the particular environment and the degree of soil development, so it constitutes an effective tool for paleoenvironmental and planetary studies.