Population and Environmental Correlates of Maize Yields in Mesoamerica: a Test of Boserup’s Hypothesis in the Milpa

Using a sample of 40 sources reporting milpa and mucuna-intercropped maize yields in Mesoamerica, we test Boserup’s (1965) prediction that fallow is reduced as a result of growing population density. We further examine direct and indirect effects of population density on yield. We find only mixed support for Boserupian intensification. Fallow periods decrease slightly with increasing population density in this sample, but the relationship is weak. Controlling for other covariates, fallow-unadjusted maize yields first rise then fall with population density. Fallow-adjusted maize yields peak at 390 kg/ha/yr for low population densities (8 persons / km2) and decline to around 280 kg/ha/yr for the highest population densities observed in our dataset. Fallow practices do not appear to mediate the relationship between population density and yield. The multi-level modeling methods we adopt allow for data clustering, accurate estimates of group-level variation, and they generate conditional predictions, all features essential to the comparative study of prehistoric and contemporary agricultural yields

The Impact of Apolipoprotein E Allelic Variants on Alzheimer´s Disease

Alzheimer disease (AD) is a genetically and clinically complex neurodegenerative disease, often with decades-long preclinical and prodromal stages. In older adults, it is the most frequent form of dementia. Apolipoprotein E (ApoE) is a lipid-transport protein whose main function is to deliver lipids to cell-surface receptors. Carriers of the APOEε4 isoform of the gene are at higher risk than APOEε3 carriers (the predominant form in the average population) of developing sporadic AD. The genetic burden of homozygous APOEε4 status together with age are the two key risk factors in the late-onset variant of AD (LOAD). APOEε4 also increases brain amyloid-β pathology relative to other ApoE isoforms and appears to influence tau pathology. The mechanisms whereby ApoE4 protein expression affects neuronal cells is far from being understood; increased aggregation and/or hampering of amyloid-β peptide clearance, microglial cell dysregulation, alteration of glutamate-mediated excitatory neurotransmission, altered modulation of amyloid precursor protein (APP), loss of acetylcholine synthesizing enzymes, disruption of neurovascular regulation, dysregulation of signal transduction cascades and various other hypotheses have been invoked. This chapter critically discusses recent advances in our knowledge of the relationship between ApoE isoforms and AD from a molecular to a clinical standpoint, and reviews current strategies for using ApoE as a diagnostic tool and a therapeutic target, respectively.Fil: Serrano, Ezequiel Antonio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas; ArgentinaFil: Sanz, Pablo Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Barrantes, Francisco Jose. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones Biomédicas. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones Biomédicas; Argentin