Cortical parenchyma wall width regulates root metabolic cost and maize performance under suboptimal water availability.

We describe how increased root cortical parenchyma wall width (CPW) can improve tolerance to drought stress in maize by reducing the metabolic costs of soil exploration. Significant variation (1.0 to 5.0 µm) for CPW was observed in maize germplasm. The functional-structural model RootSlice predicts that increasing CPW from 2 to 4 µm is associated with ca. 15% reduction in root cortical cytoplasmic volume, respiration rate, and nitrogen content. Analysis of genotypes with contrasting CPW grown with and without water stress in the field confirms that increased CPW is correlated with ca. 32 to 42% decrease in root respiration. Under water stress in the field, increased CPW is correlated with 125% increased stomatal conductance, 325% increased leaf CO2 assimilation rate, 73 to 78% increased shoot biomass, and 92 to 108% increased yield. CPW was correlated with leaf mesophyll midrib parenchyma wall width, indicating pleiotropy. GWAS analysis identified candidate genes underlying CPW. OpenSimRoot modeling predicts that a reduction in root respiration due to increased CPW would also benefit maize growth under suboptimal nitrogen, which requires empirical testing. We propose CPW as a new phene that has utility under edaphic stress meriting further investigation.

Large root cortical cells and reduced cortical cell files improve growth under suboptimal nitrogen in silico.

Suboptimal nitrogen availability is a primary constraint to plant growth. We used OpenSimRoot, a functional-structural plant/soil model, to test the hypothesis that larger root cortical cell size (CCS), reduced cortical cell file number (CCFN), and their interactions with root cortical aerenchyma (RCA) and lateral root branching density (LRBD) are useful adaptations to suboptimal soil nitrogen availability in maize (Zea mays). Reduced CCFN increased shoot dry weight over 80%. Reduced respiration, reduced nitrogen content, and reduced root diameter accounted for 23%, 20%, and 33% of increased shoot biomass, respectively. Large CCS increased shoot biomass by 24% compared with small CCS. When simulated independently, reduced respiration and reduced nutrient content increased the shoot biomass by 14% and 3%, respectively. However, increased root diameter resulting from large CCS decreased shoot biomass by 4% due to an increase in root metabolic cost. Under moderate N stress, integrated phenotypes with reduced CCFN, large CCS, and high RCA improved shoot biomass in silt loam and loamy sand soils. In contrast, integrated phenotypes composed of reduced CCFN, large CCS, and reduced LRBD had the greatest growth in silt loam, while phenotypes with reduced CCFN, large CCS, and high LRBD were the best performers in loamy sands. Our results support the hypothesis that larger CCS, reduced CCFN, and their interactions with RCA and LRBD could increase nitrogen acquisition by reducing root respiration and root nutrient demand. Phene synergisms may exist between CCS, CCFN, and LRBD. CCS and CCFN merit consideration for breeding cereal crops with improved nitrogen acquisition, which is critical for global food security.

Domestication and lowland adaptation of coastal preceramic maize from Paredones, Peru.

Archaeological cobs from Paredones and Huaca Prieta (Peru) represent some of the oldest maize known to date, yet they present relevant phenotypic traits corresponding to domesticated maize. This contrasts with the earliest Mexican macro-specimens from Guila Naquitz and San Marcos, which are phenotypically intermediate for these traits, even though they date more recently in time. To gain insights into the origins of ancient Peruvian maize, we sequenced DNA from three Paredones specimens dating ~6700-5000 calibrated years before present (BP), conducting comparative analyses with two teosinte subspecies (Zea mays ssp. mexicana and parviglumis) and extant maize, that include highland and lowland landraces from Mesoamerica and South America. We show that Paredones maize originated from the same domestication event as Mexican maize and was domesticated by ~6700 BP, implying rapid dispersal followed by improvement. Paredones maize shows no relevant gene flow from mexicana, smaller than that observed in teosinte parviglumis. Thus, Paredones samples represent the only maize without confounding mexicana variation found to date. It also harbors significantly fewer alleles previously found to be adaptive to highlands, but not of alleles adaptive to lowlands, supporting a lowland migration route. Our overall results imply that Paredones maize originated in Mesoamerica, arrived in Peru without mexicana introgression through a rapid lowland migration route, and underwent improvements in both Mesoamerica and South America.

The plant we know today as maize or corn began its story 9,000 years ago in modern-day Mexico, when farmers of the Balsas River basin started to carefully breed its ancestor, the wild grass teosinte parviglumis. Recent discoveries suggest the crop may have started to travel to South America before its domestication was fully complete, leading to a complex history of semi-tamed lineages evolving in parallel in different regions. For example, 5,300-year-old corn specimens found in Tehuacán, in central Mexico, still genetically and morphologically resemble teosinte. Meanwhile, cobs harvested about 6,700 to 5,000 years ago on the northern coast of Peru ­ 3800km away from where maize was first domesticated ­ look like the ones we know today. Vallebueno-Estrada et al. aimed to explore the evolutionary history of this Peruvian maize, which was discovered at the archaeological coastal site of Paredones. To do so, they extracted and sequenced its genetic information, and compared these sequences with those from modern varieties of lowland and highland maize, as well as from teosinte parviglumis and teosinte mexicana. The analyses showed that the ancestor of the Paredones maize emerged from teosinte parviglumis like any other lineage, but that it was already domesticated when it started to spread South; by the time it was present in Peru 6,700 years ago, it was genetically closer to modern-day crops. This early departure is consistent with the fact that the Paredones specimens lacked teosinte mexicana genetic variants; this highland relative of lowland parviglumis is believed to have interbred with maize lineages from Central America more recently, when these were brought to higher altitudes. The presence of genetic marks tailored to low-elevation regions suggested that the Paredones maize lineage migrated through a coastal corridor connecting Central and South America, arriving in northern Peru about 2,500 years after first arising from teosinte parviglumis in Central America around 9,000 years ago. Under the care of rapidly developing Central Andean societies, the crop then evolved to adapt to its local conditions. Maize today has spread to all continents besides Antarctica; we produce more of it than wheat, rice or any other grain. How our modern varieties will adapt to the environmental constraints brought by climate change remains unclear. By peering into the history of maize, Vallebueno-Estrada et al. hope to find genetic variations which could inform new breeding strategies that improve the future of this crop.

Gradual domestication of root traits in the earliest maize from Tehuacán.

Efforts to understand the phenotypic transition that gave rise to maize from teosinte have mainly focused on the analysis of aerial organs, with little insights into possible domestication traits affecting the root system. Archeological excavations in San Marcos cave (Tehuacán, Mexico) yielded two well-preserved 5,300 to 4,970 calibrated y B.P. specimens (SM3 and SM11) corresponding to root stalks composed of at least five nodes with multiple nodal roots and, in case, a complete embryonic root system. To characterize in detail their architecture and anatomy, we used laser ablation tomography to reconstruct a three-dimensional segment of their nodal roots and a scutellar node, revealing exquisite preservation of the inner tissue and cell organization and providing reliable morphometric parameters for cellular characteristics of the stele and cortex. Whereas SM3 showed multiple cortical sclerenchyma typical of extant maize, the scutellar node of the SM11 embryonic root system completely lacked seminal roots, an attribute found in extant teosinte and in two specific maize mutants: root with undetectable meristem1 (rum1) and rootless concerning crown and seminal roots (rtcs). Ancient DNA sequences of SM10­a third San Marcos specimen of equivalent age to SM3 and SM11­revealed the presence of mutations in the transcribed sequence of both genes, offering the possibility for some of these mutations to be involved in the lack of seminal roots of the ancient specimens. Our results indicate that the root system of the earliest maize from Tehuacán resembled teosinte in traits important for maize drought adaptation.

Anatomicis network: una plataforma de software educativa basada en la nube para mejorar la enseñanza de la anatomía en la educación médica / Anatomicis network: a cloud-based educational software platformto enhance anatomy teaching in medical education

En este artículo, se describe una propuesta novedosa de plataforma de software educativa para mejorar la enseñanza de la anatomía en la educación médica. Con el fin de determinar la utilidad y el impacto de esta plataforma, se desarrollo una experiencia inter institucional entre los años 2016 y 2017, el cual involucró a las Universidades de Antofagasta, Playa Ancha, Austral y Católica de Chile. Los departamentos de anatomía que participaron en esta experiencia utilizaron la plataforma de software educativa para acceder a imágenes anatómicas 2D y 3D, videos y evaluaciones teórico prácticas multimodales en línea, pudiendo realizar con sus estudiantes pruebas de usabilidad. Este proyecto pretende aportar a la enseñanza de la anatomía en los diferentes departamentos de anatomía a lo largo del país.

In this article, we describe a novel proposal of an educational software platform to enhance the anatomy teaching in medical education. In order to determine the usefulness and impact of this platform, between 2016 and 2017, an inter-institutional experience was developed, which included the Universities of Antofagasta, Playa Ancha, Austral and Católica de Chile. The participation of anatomy departments in this experience, used the educational software platform to access 2D and 3D anatomical images and online multimodal practical-theoretical evaluations, being able to perform usability tests with their students. This project aims to improve teaching in the different anatomy departments throughout the country.

Dental gemination in a permanent mandibular central incisor: an uncommon dental anomaly / Geminación dental en un incisivo central mandibular permanente: una anomalía dental infrecuente

Gemination is an anomaly in size, shape, and structure of the teeth. The primary dentition is more frequently affected, but gemination may occur in permanent dentitions, usually in the maxillary-incisal region. In geminated teeth, incomplete development of two teeth from a single bud results in a larger tooth crown with a single root and canal. In this study, a gemination case in a male patient, 13-year-old, with an ancestry of Aymara, who visited a private clinic in Antofagasta, Chile, for a routine check is presented. On intra-oral clinical examination of the coronary anatomy, the tooth 4.1 was observed with a large crown, bifurcated in the center of incisal zone. In addition, a groove extending from the bifurcation to the cementoenamel junction was noted. Radiographic examination revealed the presence of a single root canal and a single root. The pulp cavity was separated in two cavities, in accordance with the division caused by the observed bifurcation. This report describes a unique case of dental gemination of mandibular permanent central incisor in a subject with Aymara ancestry and discusses the differential diagnosis and possible future treatment options anticipated for this particular case.

La geminación es una anomalía que afecta el tamaño, forma y estructura del diente. La dentición temporal es afectada con más frecuencia, pero puede ocurrir en la dentición permanente, generalmente en la región maxilar incisal. En los dientes geminados, el desarrollo incompleto de dos dientes desde un solo brote dentario resulta en una corona dentaria más grande, con una sola raíz y canal. En este artículo, se presenta un caso de geminación en un paciente de sexo masculino, de 13 años de edad con ascendencia Aymara observada durante un control de rutina. Al examen clínico intraoral, el diente 41 se observó con una gran corona, bifurcado en el centro de la zona incisal, junto a un surco que se extendió desde la bifurcación hasta la unión amelo-cementaria. El examen radiográfico reveló la presencia de una sola raíz y un canal único. La cavidad pulpar se separó en dos, según la división causada por la bifurcación coronaria. Este reporte muestra un caso infrecuente de geminación dental del incisivo central mandibular permanente en un sujeto de ascendencia Aymara, y se discute su diagnóstico diferencial y las opciones de tratamiento futuras previstas para este caso en particular.

Quality of life and memory after vagus nerve stimulator implantation for epilepsy.

OBJECTIVE: This prospective, case control study evaluates quality of life (QOL), depressive affect, and memory outcomes of epilepsy patients implanted with a vagus nerve stimulator (VNS). METHODS: Three groups of patients with epilepsy underwent assessment on two occasions: 1) patients with a VNS were tested before and 12 months after implantation (n = 16); 2) patients who underwent cerebral resective surgery were tested pre- and post-operatively (n = 10); and 3) patients under medical management (n = 9). Group means were compared on the QOLIE-89, Geriatric Depression Scale, Wechsler Memory Scale - III, and the Memory Observation Questionnaire. Secondary analyses calculated the reliable change index, providing information on change beyond measurement error and chance. RESULTS: Mean ratings of QOL, depression, and memory complaints and objective memory scores remained stable or improved in all the groups. The QOL improved more after cerebral resective surgery than VNS or medication controls, but the VNS and medication control groups did not differ. In the VNS group, QOL was not related to seizure reduction. The percentage of cases showing real change in memory was equivalent across groups, except in one of eight indices (i.e., verbal recognition memory). CONCLUSIONS: This first case controlled design found that vagus nerve stimulation as an adjunctive therapy for seizure control did not change QOL, depressive affect, or objective memory scores over one-year more so than medical management alone. We point out the need for larger case control, non-industry funded investigations.

Further examination of the psychometric properties of the comprehensive effects of alcohol questionnaire.

Although the expectancies component of the Comprehensive Effects of Alcohol Questionnaire has previously been shown to be factorially valid, the factor structure of its valuations component has not previously been examined. The aims of this paper were: (i) to replicate the factor structure of the expectancies items; (ii) to explore the factor structure of the valuations items; and (iii) to investigate the utility of using the Comprehensive Effects of Alcohol Questionnaire to predict drinking behavior. The questionnaire was administered to 1004 university students along with measures of quantity and frequency of alcohol consumption. Fromme, Stroot, and Kaplan's (1993) factor structure of the expectancies scales was replicated. The factor structures of the negative valuations scales were characterized by 2 rather than 3 factors. Negative expectancies improved upon the prediction of drinking quantity and frequency over-and-above positive expectancies, and valuations further improved prediction over-and-above expectancies. Theoretical and clinical implications are discussed.