bluuebunny/crossref_metadata_2025 huggingface dataset:
Functional and Physical Interaction of Diacylglycerol Kinase ζ with Protein Kinase Cα Is Required for Cerebellar Long-Term Depression
Authors: Lee Dongwon , Yamamoto Yukio , Kim Eunjoon , Tanaka-Yamamoto Keiko
Published: November 2015

The balance between positive and negative regulators required for synaptic plasticity must be well organized at synapses. Protein kinase Cα (PKCα) is a major mediator that triggers long-term depression (LTD) at synapses between parallel fibers and Purkinje cells in the cerebellum. However, the precise mechanisms involved in PKCα regulation are not clearly understood. Here, we analyzed the role of diacylglycerol kinase ζ (DGKζ), a kinase that physically interacts with PKCα as well as postsynaptic density protein 95 (PSD-95) family proteins and functionally suppresses PKCα by metabolizing diacylglycerol (DAG), in the regulation of cerebellar LTD. In Purkinje cells of DGKζ-deficient mice, LTD was impaired and PKCα was less localized in dendrites and synapses. This impaired LTD was rescued by virus-driven expression of wild-type DGKζ, but not by a kinase-dead mutant DGKζ or a mutant lacking the ability to localize at synapses, indicating that both the kinase activity and synaptic anchoring functions of DGKζ are necessary for LTD. In addition, experiments using another DGKζ mutant and immunoprecipitation analysis revealed an inverse regulatory mechanism, in which PKCα phosphorylates, inactivates, and then is released from DGKζ, is required for LTD. These results indicate that DGKζ is localized to synapses, through its interaction with PSD-95 family proteins, to promote synaptic localization of PKCα, but maintains PKCα in a minimally activated state by suppressing local DAG until its activation and release from DGKζ during LTD. Such local and reciprocal regulation of positive and negative regulators may contribute to the fine-tuning of synaptic signaling.

SIGNIFICANCE STATEMENTMany studies have identified signaling molecules that mediate long-term synaptic plasticity. In the basal state, the activities and concentrations of these signaling molecules must be maintained at low levels, yet be ready to be boosted, so that synapses can undergo synaptic plasticity only when they are stimulated. However, the mechanisms involved in creating such conditions are not well understood. Here, we show that diacylglycerol kinase ζ (DGKζ) creates optimal conditions for the induction of cerebellar long-term depression (LTD). DGKζ works by regulating localization and activity of protein kinase Cα (PKCα), an important mediator of LTD, so that PKCα effectively responds to the stimulation that triggers LTD.
Default Mode Dynamics for Global Functional Integration
Authors: Vatansever Deniz , Menon David K. , Manktelow Anne E. , Sahakian Barbara J. , Stamatakis Emmanuel A.
Published: November 2015

The default mode network (DMN) has been traditionally assumed to hinder behavioral performance in externally focused, goal-directed paradigms and to provide no active contribution to human cognition. However, recent evidence suggests greater DMN activity in an array of tasks, especially those that involve self-referential and memory-based processing. Although data that robustly demonstrate a comprehensive functional role for DMN remains relatively scarce, the global workspace framework, which implicates the DMN in global information integration for conscious processing, can potentially provide an explanation for the broad range of higher-order paradigms that report DMN involvement. We used graph theoretical measures to assess the contribution of the DMN to global functional connectivity dynamics in 22 healthy volunteers during an fMRI-basedn-back working-memory paradigm with parametric increases in difficulty. Our predominant finding is that brain modularity decreases with greater task demands, thus adapting a more global workspace configuration, in direct relation to increases in reaction times to correct responses. Flexible default mode regions dynamically switch community memberships and display significant changes in their nodal participation coefficient and strength, which may reflect the observed whole-brain changes in functional connectivity architecture. These findings have important implications for our understanding of healthy brain function, as they suggest a central role for the DMN in higher cognitive processing.

SIGNIFICANCE STATEMENTThe default mode network (DMN) has been shown to increase its activity during the absence of external stimulation, and hence was historically assumed to disengage during goal-directed tasks. Recent evidence, however, implicates the DMN in self-referential and memory-based processing. We provide robust evidence for this network's active contribution to working memory by revealing dynamic reconfiguration in its interactions with other networks and offer an explanation within the global workspace theoretical framework. These promising findings may help redefine our understanding of the exact DMN role in human cognition.
Structural Organization of the Corpus Callosum Predicts Attentional Shifts after Continuous Theta Burst Stimulation
Authors: Chechlacz Magdalena , Humphreys Glyn W. , Sotiropoulos Stamatios N. , Kennard Christopher , Cazzoli Dario
Published: November 2015

Repetitive transcranial magnetic stimulation (rTMS) applied over the right posterior parietal cortex (PPC) in healthy participants has been shown to trigger a significant rightward shift in the spatial allocation of visual attention, temporarily mimicking spatial deficits observed in neglect. In contrast, rTMS applied over the left PPC triggers a weaker or null attentional shift. However, large interindividual differences in responses to rTMS have been reported. Studies measuring changes in brain activation suggest that the effects of rTMS may depend on both interhemispheric and intrahemispheric interactions between cortical loci controlling visual attention. Here, we investigated whether variability in the structural organization of human white matter pathways subserving visual attention, as assessed by diffusion magnetic resonance imaging and tractography, could explain interindividual differences in the effects of rTMS. Most participants showed a rightward shift in the allocation of spatial attention after rTMS over the right intraparietal sulcus (IPS), but the size of this effect varied largely across participants. Conversely, rTMS over the left IPS resulted in strikingly opposed individual responses, with some participants responding with rightward and some with leftward attentional shifts. We demonstrate that microstructural and macrostructural variability within the corpus callosum, consistent with differential effects on cross-hemispheric interactions, predicts both the extent and the direction of the response to rTMS. Together, our findings suggest that the corpus callosum may have a dual inhibitory and excitatory function in maintaining the interhemispheric dynamics that underlie the allocation of spatial attention.

SIGNIFICANCE STATEMENTThe posterior parietal cortex (PPC) controls allocation of attention across left versus right visual fields. Damage to this area results in neglect, characterized by a lack of spatial awareness of the side of space contralateral to the brain injury. Transcranial magnetic stimulation over the PPC is used to study cognitive mechanisms of spatial attention and to examine the potential of this technique to treat neglect. However, large individual differences in behavioral responses to stimulation have been reported. We demonstrate that the variability in the structural organization of the corpus callosum accounts for these differences. Our findings suggest novel dual mechanism of the corpus callosum function in spatial attention and have broader implications for the use of stimulation in neglect rehabilitation.
Modulation of Saccade Vigor during Value-Based Decision Making
Authors: Reppert Thomas R. , Lempert Karolina M. , Glimcher Paul W. , Shadmehr Reza
Published: November 2015

During value-based decision-making, individuals consider the various options and select the one that provides the maximum subjective value. Although the brain integrates abstract information to compute and compare these values, the only behavioral outcome is often the decision itself. However, if the options are visual stimuli, during deliberation the brain moves the eyes from one stimulus to the other. Previous work suggests that saccade vigor, i.e., peak velocity as a function of amplitude, is greater if reward is associated with the visual stimulus. This raises the possibility that vigor during the free viewing of options may be influenced by the valuation of each option. Here, humans chose between a small, immediate monetary reward and a larger but delayed reward. As the deliberation began, vigor was similar for the saccades made to the two options but diverged 0.5 s before decision time, becoming greater for the preferred option. This difference in vigor increased as a function of the difference in the subjective values that the participant assigned to the delayed and immediate options. After the decision was made, participants continued to gaze at the options, but with reduced vigor, making it possible to infer timing of the decision from the sudden drop in vigor. Therefore, the subjective value that the brain assigned to a stimulus during decision-making affected the motor system via the vigor with which the eyes moved toward that stimulus.

SIGNIFICANCE STATEMENTWe find that, as individuals deliberate between two rewarding options and arrive at a decision, the vigor with which they make saccades to each option reflects a real-time evaluation of that option. With deliberation, saccade vigor diverges between the two options, becoming greater for the option that the individual will eventually choose. The results suggest a shared element between the network that assigns value to a stimulus during the process of decision-making and the network that controls vigor of movements toward that stimulus.
The Role of Motion Extrapolation in Amphibian Prey Capture
Authors: Borghuis Bart G. , Leonardo Anthony
Published: November 2015

Sensorimotor delays decouple behaviors from the events that drive them. The brain compensates for these delays with predictive mechanisms, but the efficacy and timescale over which these mechanisms operate remain poorly understood. Here, we assess how prediction is used to compensate for prey movement that occurs during visuomotor processing. We obtained high-speed video records of freely moving, tongue-projecting salamanders catching walking prey, emulating natural foraging conditions. We found that tongue projections were preceded by a rapid head turn lasting ∼130 ms. This motor lag, combined with the ∼100 ms phototransduction delay at photopic light levels, gave a ∼230 ms visuomotor response delay during which prey typically moved approximately one body length. Tongue projections, however, did not significantly lag prey position but were highly accurate instead. Angular errors in tongue projection accuracy were consistent with a linear extrapolation model that predicted prey position at the time of tongue contact using the average prey motion during a ∼175 ms period one visual latency before the head movement. The model explained successful strikes where the tongue hit the fly, and unsuccessful strikes where the fly turned and the tongue hit a phantom location consistent with the fly's earlier trajectory. The model parameters, obtained from the data, agree with the temporal integration and latency of retinal responses proposed to contribute to motion extrapolation. These results show that the salamander predicts future prey position and that prediction significantly improves prey capture success over a broad range of prey speeds and light levels.

SIGNIFICANCE STATEMENTNeural processing delays cause actions to lag behind the events that elicit them. To cope with these delays, the brain predicts what will happen in the future. While neural circuits in the retina and beyond have been suggested to participate in such predictions, few behaviors have been explored sufficiently to constrain circuit function. Here we show that salamanders aim their tongues by using extrapolation to estimate future prey position, thereby compensating for internal delays from both visual and motor processing. Predictions made just before a prey turn resulted in the tongue being projected to a position consistent with the prey's pre-turn trajectory. These results define the computations and operating regimen for neural circuits that predict target motion.
Limited value of cabergoline in Cushing's disease: a prospective study of a 6-week treatment in 20 patients
Authors: Burman Pia , Edén-Engström Britt , Ekman Bertil , Karlsson F Anders , Schwarcz Erik , Wahlberg Jeanette
Published: November 2015

Context and objective

The role of cabergoline in Cushing's disease (CD) remains controversial. The experience is limited to case reports and few open studies that report the effects determined after ≥1 month of treatment. In prolactinomas and dopamine-responsive GH-secreting tumours, effects of cabergoline are seen within days or weeks. Here, we searched for short-term effects of cabergoline in CD.

Design

Twenty patients (19 naïve and one recurrent) were included in a prospective study. Cabergoline was administered in increasing doses of 0.5–5 mg/week over 6 weeks.

Methods

Urinary free cortisol (UFC) 24 h, morning cortisol and ACTH, and salivary cortisol at 0800, 1600 and 2300 h were determined once weekly throughout. Diurnal curves (six samples) of serum cortisol were measured at start and end.

Results

At study end, the median cabergoline dose was 5 mg, range 2.5–5 mg/week. The prolactin levels, markers of compliance, were suppressed in all patients. During the treatment, hypercortisolism varied, gradual and dose-dependent reductions were not seen. Five patients had a >50% decrease of UFC, three had a >50% rise of UFC. Salivary cortisol at 2300 h showed a congruent >50% change with UFC in two of the five cases with decreased UFC, and in one of the three cases with increased UFC. One patient with decreases in both UFC and 2300 h salivary cortisol also had a reduction in diurnal serum cortisol during the course of the study.

Conclusions

Cabergoline seems to be of little value in the management of CD. Only one patient had a response-like pattern. Given the known variability of disease activity in CD, this might represent a chance finding.
Harmonic distortion in public low-voltage grids Comparison of the situation in Colombia and Germany
Authors: Blanco Castañeda Ana María , Meyer Jan , Pavas Fabio Andrés , Garzón Camilo Andrés , Romero Miguel Fernando , Schegner Peter
Published: November 2015

Current and voltage harmonic levels in LV grids depend not only on the harmonic emission of non-linear loads, but also on the characteristics of the grid and the voltage distortion of the upstream grid. Based on several measurements, it was found that Colombia and Germany have considerable differences in the current harmonic emission of electronic devices and voltage distortion in the LV-grids. These differences are the result of different regulation methodologies and the characteristics of the grid. Detail measurement campaigns are needed in both countries in order to verify the voltage and current harmonic levels, and to analyze the network efficiency and hosting capacity in terms of harmonics.
Auto-tuning of PV controllers to improve the speed response and stability of the P&O algorithm
Authors: Ortiz Valencia Paula Andrea , Ramos Paja Carlos Andrés
Published: November 2015

This paper proposes an auto-tuning control system to ensure a fast response of the photovoltaic (PV) voltage by reducing the perturbation time of a P&O algorithm. This solution accelerates the tracking of the maximum power point and, at the same time, guarantees the system stability, which increases the amount of energy produced by the PV system. The control system consists of three cascaded controllers: a P&O algorithm dynamically parameterized by the adaptive law in order to guarantee stability; an adaptive PI controller whose parameters are modified by the adaptive law, depending on the operating conditions, to reduce the settling time of the system as much as possible; and a sliding mode current controller to mitigate environmental and load perturbations and ensure global stability. The design of the new control structure is supported by mathematical analyses and validated with simulations performed in PSIM in order to demonstrate the robustness of the proposed solution.
Fault location in power distribution systems considering a dynamic load model
Authors: Cifuentes Chaves Harold Andres , Patiño Ipus Daniel Fernando , Mora Flórez Juan Jose
Published: November 2015

In the electrical power systems, load is one of the most difficult elements to be represented by an adequate mathematical model due to its complex composition and dynamic and non-deterministic behavior. Nowadays, static and dynamic load models have been developed for several studies such as voltage and transient stability, among others. However, on the issue of power quality, dynamic load models have not been taken into account in fault location. This paper presents a fault location technique based on sequence components, which considers static load models of constant impedance, constant current and constant power. Additionally, an exponential recovery dynamic load model, which is included in both the fault locator and the test system, is considered. This last model is included in order to consider the dynamic nature of the load and the performance of the fault locators under this situation. To demonstrate the adequate performance of the fault locator, tests on the IEEE 34 nodes test feeder are presented. According to the results, when the dynamic load model is considered in both the locator and the power system, performance is in an acceptable range.

 
El arte de la metáfora indígena
Authors: Ferro Luis E.
Published: November 2015

Para el mundo indígena, la memoria es palabra viva que se manifiesta en relatos que se construyen a través de las transfiguraciones de la metáfora. La metáfora es, por tanto, el eje y recurso narrativo para evocar el sentido de sus manifestaciones sociales y estéticas que nacen, ritualizan y explican con la oralidad sus propias experiencias vivenciales en el devenir del tiempo.
Petrographic analysis of Usulután and Rosales Zone Engraved ceramics from two Tempisque period (300 B.C. - 500 A.D.) sites on Culebra Bay, Costa Rica
Authors: Platz Lorelei
Published: November 2015

Como un estudio preliminar, el objetivo principal es determinar la composición de pasta de dos tipos de cerámica, el Usulután Negativo y el Rosales Esgrafiado, recuperados en los sitios Loma Corral 3 (G-776 LC3) y Manzanillo (G-430MZ) en la bahía de Culebra, Guanacaste. El análisis petrográfico de las cerámicas Usulután y Rosales Esgrafiado del período Tempisque (300 a.C.–500 d.C.) sugiere que los grupos en la bahía de Culebra estaban participando en el intercambio de cerámicas y las técnicas de manufactura. Las investigaciones más reciente han demostrado que Usulután fue manufacturado en Nicaragua, pues todavía hay una duda si fue manufacturando en Costa Rica
Assessment of knowledge of skin cancer prevention and its relation with sun exposure and photo protection amongst gym academy members on the south of Santa Catarina, Brazil
Authors: Fabris Mariana Rocha , Durães Edson Souza Machado , Martignago Beatriz Castellar de Faria , Blanco Luiz Felipe de Oliveira , Fabris Thiago Rocha
Published: November 2015

BACKGROUND: Skin cancer is the most frequent neoplasia in several parts of the world and also in Brazil. There is evidence of an increase in morbidity and mortality from skin cancer. Although the incidence of skin cancer is increasing, it is estimated that 45% of all preventable cancers worldwide are skin neoplasias. Several studies have emphasized the need for campaigns to encourage sun protection. OBJECTIVE: To assess the knowledge about skin cancer prevention and its association with sun exposure and photo protection in gym members. METHODS: We conducted a cross-sectional, descriptive and quantitative study during January to July 2009, including gym members of both sexes in the city of Criciuma. A self-administered questionnaire was used. The statistical analysis was conducted in a descriptive way in regards to the absolute and relative frequencies of the variables under study. RESULTS: Of the 317 questionnaires studied, 62% were from women and 38% from men. Skin types II and III predominated, and the average age was 27.6 years. 94.3% of the participants reported that they had heard about the risks of sun exposure, mostly in terms of skin cancer risk (80.8%). Most participants, especially women, reported some form of sun protective measure. CONCLUSION: The population studied, similar to that in other regions of Brazil and the world, is aware of the risks of excessive sun exposure and skin cancer prevention, but has not yet incorporated appropriate sun protection measures into their daily habits.
Localized scleroderma: assessment of the therapeutic response to phototherapy
Authors: Buense Roberta , Duarte Ida Alzira Gomes , Bouer Marcio
Published: November 2015

BACKGROUND: Scleroderma is a chronic autoimmune disease characterized by progressive connective tissue sclerosis and microcirculatory changes. Localized scleroderma is considered a limited disease. However, in some cases atrophic and deforming lesions may be observed that hinder the normal development. Literature reports indicate phototherapy as a therapeutic modality with favorable response in cutaneous forms of scleroderma. OBJECTIVES: This study had the purpose of assessing the phototherapy treatment for localized scleroderma. METHODS: Patients with localized scleroderma were selected for phototherapy treatment. They were classified according to the type of localized scleroderma and evolutive stage of the lesions. Clinical examination and skin ultrasound were used to demonstrate the results thus obtained. RESULTS: Some clinical improvement was observed after an average of 10 phototherapeutic sessions. All skin lesions were softer at clinical palpation with scores reduction upon pre and post treatment comparison. The ultrasound showed that most of the assessed lesions presented a decrease in dermal thickness, and only five maintained their previous measure. Treatment response was similar regardless of the type of phototherapeutic treatment employed. CONCLUSIONS: The proposed treatment was effective for all lesions, regardless of the phototherapeutic modality employed. The improvement was observed in all treated skin lesions and confirmed by clinical evaluation and skin ultrasound.
Sun exposure and sun protection habits in high school students from a city south of the country
Authors: Dupont Letícia , Pereira Denise Neves
Published: November 2015

BACKGROUND: Effective solar protection is an uncommon practice among young people, increasing the likelihood of sunburn, sunstroke and skin cancers. This fact is more significant in the south of Brazil, where the prevalence of white skinned population is larger, being more prone to sun damage. OBJECTIVES: To study the practices of sun exposure and sun protection in high school students from the city of Carlos Barbosa - RS. METHODS: Cross-sectional study involving 775 students, enrolled on the first half of 2010, who had signed the consent form. We used a non-identifiable, self-administered questionnaire, with questions about related topics. Statistical analysis was performed using Chi-square or Fisher exact and t-Student tests. The study was approved by the Research Ethics Committee under the number 2010-115H. RESULTS: Most students are exposed to the sun at the more critical periods, remaining exposed for more than an hour. Five hundred and seventy-six students (74,3%) reported using sunscreen, but less than 10% did it during all months of the year. Female teenagers are most likely to use sunscreen (p <0.001) and to spend less time exposed to sunlight (p <0.001). CONCLUSION: Most high school students from Carlos Barbosa had unsuitable sun exposure and sun protection habits, characterizing a high risk behavior for skin diseases. The existence of public programs for clarification of the risks to the population and the subsidization of sun protection products were suggested by these young people.
Association of acanthosis nigricans and skin tags with insulin resistance
Authors: Barbato Mariana Tremel , Criado Paulo Ricardo , Silva Ana Kris da , Averbeck Evelyne , Guerine Marina Bensen , Sá Naiana Bittencourt de
Published: November 2015

Insulin resistance is a metabolic disorder in which target cells fail to respond to normal levels of circulating insulin. Insulin resistance has been associated with presence of acanthosis nigricans and acrochordons. It is known that early diagnosis and early initial treatment are of paramount importance to prevent a series of future complications. These dermatoses may represent an easily identifiable sign of insulin resistance and non-insulin-dependent diabetes.
The Relevance of Burial to Evade Acorn Predation in an Oak Forest Affected by Habitat Loss and Land Use Changes
Authors: Ramos-Palacios Carlos Renato , Badano Ernesto I.
Published: November 2015

Seed burial was proposed as an effective mechanism to evade seed predation in continuous forests. However, the relevance of burial as a mechanism to evade seed predators may be compromised in fragmented forests intensely affected human activities because: (1) predators are usually concentrated within forests patches and this may elevate consumer pressure on seed banks at these habitats; and (2) fragmentation reduces seed production in remnant trees and this then decreases the availability of resources for seed consumers. Thus, seed predators within forest patches might be forced to consume buried seeds after seeds on the soil surface are depleted. Indeed, they may even explore the surrounding matrix habitat in search of food when seeds within the patches become scarce. This study assesses the relevance of burial as a mechanism to evade seed predators in a fragmented oak forest from central Mexico where human activities have generated four habitat types: the interior of remnant forest patches, their edges, the matrix habitat surrounding the patches, and an abandoned agricultural field in the neighborhoods of the fragmented forests. We experimentally assessed removal rates of acorns exposed on the soil surface and buried acorns in all these habitat types and compared them. Our results indicated that acorn burial may be an effective mechanism to evade predation in habitats strongly affected by human activities (e.g., the matrix surrounding the forest patches or the abandoned agricultural field), while it would have little relevance within forest patches.
Variación de la estructura y composición de comunidades de árboles y arbustos entre tipos de vegetación en la Cuenca de Cuitzeo, Michoacán
Authors: Maza-Villalobos Susana , Macedo-Santana Franceli , Rodríguez-Velázquez Jorge , Oyama Ken , Martínez-Ramos Miguel
Published: November 2015

Se analizó la variación estructural de comunidades de árboles y arbustos presentes en diferentes tipos de vegetación (matorral subtropical, bosque de encino, bosque mixto, bosque de pino y bosque de oyamel) a través de gradientes de altitud y profundidad del suelo en la Cuenca de Cuitzeo, Michoacán. La cuenca cubre 4,000 km2 y un ámbito altitudinal de 1,700 a 3,420 m s.n.m. En toda la cuenca se muestrearon 50 sitios de 1,000 m2 cada uno, registrándose un total de 4,941 plantas con diámetro a la altura del pecho ? 1 cm, que representaron 164 especies, 88 géneros y 47 familias. Las familias con más especies fueron Asteraceae (30; 18.4% del total de especies) y Fagaceae (16; 9.8%). Por arriba de los 2,500 m s.n.m. se encontraron los bosques de pino, oyamel y mixto (pino-encino); por debajo de 2,300 m s.n.m. se encontró el bosque de encino y el matorral subtropical. La densidad de plantas fue semejante entre los tipos de vegetación pero diferentes indicadores de la biomasa aumentaron con la altitud y la profundidad del suelo. El matorral subtropical y el bosque mixto fueron los más diversos en especies y el bosque de coníferas el menos diverso. Existió un elevado recambio de especies dentro y entre los tipos de vegetación (índice de similitud de Bray-Curtis, ámbito: 5.4% - 25.4%). La composición de especies varió notablemente asociada con la altitud y la profundidad del suelo. Se ofrecen lineamientos para la conservación del importante complejo vegetal presente en la Cuenca de Cuitzeo.
Calliandra ricoana (Leguminosae, Mimosoideae, tribe Ingeae): a new and critically endangered species from Chiapas, Mexico
Authors: Hernández Macias Héctor , Duno de Stefano Rodrigo , Gutierrez Celso , Carnevali Fernández-Concha Germán , Can Lilia A. , Pool Eliseo
Published: November 2015

Calliandra ricoana , a new species of Leguminosae (Mimosoideae, tribe Ingeae ) , from the state of Chiapas, Mexico is described and illustrated. Critical examination of C. ricoana in comparison with members of Calliandra section Androcallis , series Macrophyllae shows that it is morphologically similar and presumably closely related to C. macqueenii and C. trinervia var. arborea , but it can be distinguished from these and the other members of the series by a combination of characters, namely the arborescent habit, the relatively larger leaflets, the short peduncles, the homomorphic flowers, the longer corollas and the longer, exserted staminal tubes.
Conservation genetics of an endangered cycad, Dioon sonorense (Zamiaceae): implications from variation of chloroplast DNA
Authors: Gutiérrez-Ortega José Said , Kajita Tadashi , Molina-Freaner Francisco E.
Published: November 2015

The endemic species Dioon sonorense comprises the northernmost group of populations of Dioon , in Sonora, Mexico. Although it is endangered, only the southern populations are protected within a preservation area, while the remaining populations have not been taken into account in management plans or genealogical studies. Describing the intraspecific genealogy and the geographical structure of the genetic variation of D. sonorense may help in the identification of units for further conservation. Therefore, the main objective of this study was to describe the intraspecific genealogy of populations throughout the range of distribution of the endangered species D. sonorense , using haplotypes of the trnL-F spacer of the cpDNA. In addition, the levels of diversity of the employed molecular marker were estimated. Low levels of variability were recorded and at least two evolutionary units, corresponding to each haplotype, were identified as components of the species. The inclusion of northern populations into conservation programs is recommended. In order to integrate these findings to the genealogy of genus Dioon , trnL-F sequences of all the remaining species were merged and analyzed. An ancestral haplotype with wide distribution was detected in several species and one haplotype in D. sonorense was found shared with its sister species, D. tomasellii . This work represents a first attempt to reconcile a genealogical approach in the identification of important centers of genetic diversity of Mexican cycads.
Etnobotánica de la cultura teotihuacana
Authors: Vázquez-Alonso Mariana T. , Bye Robert , López-Mata Lauro , Pulido-Salas Ma. Teresa P. , McClung de Tapia Emily , Koch Stephen D.
Published: November 2015

El propósito de esta investigación fue obtener un listado de las plantas utilizadas por los antiguos habitantes de Teotihuacan prehispánico, a partir de la interpretación botánica y etnobotánica de registros arqueobotánicos e iconográficos. El registro resultante de plantas útiles para la cultura teotihuacana comprende 77 taxa y está basado en estudios publicados y reportes arqueológicos. Para conjuntar las evidencias de la presencia de las plantas con el contexto cultural se propuso un Índice de Importancia Cultural. Las evidencias directas son los restos arqueobotánicos identificados y el uso interpretado. Las evidencias indirectas son las representaciones en cerámica y mural, la necesidad de cultivar algunas especies y de importar otras. El maíz ( Zea mays L.) es la especie con mayor importancia cultural. Los taxa reportados y especies relacionadas se buscaron en dos fuentes posteriores que describieran sus usos: el Códice Florentino y estudios etnobotánicos contemporáneos. Ambas fuentes mencionan más usos para los taxa listados. El uso medicinal es el menos identi?cado en Teotihuacan (ocho taxa); sin embargo, de acuerdo con los usos contemporáneos, el 57% de las especies pudo ser medicinal. La lista obtenida con interpretación etnobotánica de las posibles especies útiles para la cultura teotihuacana es de 125, incluyendo 17 especies interpretadas como cultivadas en Teotihuacan y 108 aprovechadas que pertenecen a diferentes tipos de vegetación. Veintiocho de las plantas fueron domesticadas en México. Este listado sirve como un acercamiento para entender la relación de la cultura teotihuacana con la flora local y regional.
Análisis florístico de un bosque de Abies y el bosque mesófilo de montaña adyacente en Juanacatlán, Mascota, Jalisco, México
Authors: Guerrero-Hernández Ricardo , González-Gallegos Jesús Guadalupe , Castro-Castro Arturo
Published: November 2015

Se presenta el análisis florístico de un bosque de Abies y del bosque mesófilo de montaña adyacente, localizados al occidente de Jalisco, México. Se obtuvo una lista de plantas vasculares constituida por 80 familias, 195 géneros y 290 especies, con un índice de diversidad florística de 210.33 especies/km2, el cual es elevado al compararlo con el obtenido en otras áreas boscosas similares. Las familias más diversas por cantidad de especies son Asteraceae (46), Fabaceae (22) y Orchidaceae (18). La flora de la comunidad estudiada es similar a lo descrito para los bosques de oyamel en Nueva Galicia y a los bosques mesófilos de la Faja Volcánica Transmexicana. Cinco especies recolectadas en el área se encuentran bajo alguna categoría de riesgo dentro de la Norma Oficial Mexicana NOM-059-SEMARNAT-2010 ( Abies flinckii , Comarostaphylis discolor subsp. discolor , Juglans major var. glabrata , Ostrya virginiana y Tilia americana var. mexicana ). Los rodales de Abies flinckii son propuestos como área de conservación dado su carácter relictual.
Lianas of Mexico
Authors: Ibarra-Manríquez Guillermo , Rendón-Sandoval Francisco Javier , Cornejo-Tenorio Guadalupe , Carrillo-Reyes Pablo
Published: November 2015

Through an exhaustive literature review, field exploration and revision of herbaria, the presence of 861 native species of lianas in Mexico is documented, pertaining to 250 genera and 59 families. A total of 25.9 % ( n = 224) of the species and three genera are endemic to Mexico. The 15 most diverse families account for 80.1 % of the species and 85.7 % of endemics. The 18 richest genera comprise 38.1 % ( n = 328) of the species and approximately 50 % of the endemic. Chiapas is the state with the greatest diversity because it includes 65.4 % of the total species, whereas Oaxaca is the richest state in terms of endemism (49.6 %). Regardless of their area, the most diverse states are also notable for their endemism. The lianas found in only one state encompassed 16.5 and 26 % of the total number of species and endemics, respectively. Among the five recognized biomes in Mexico, the tropical humid forest and the tropical seasonally dry forest stand out for their number of species ( n = 692, 80.3 %) and number of endemics ( n = 134, 59.8 %), respectively. At the level of vegetation type, the tropical deciduous forest ranks first in both attributes. The number of lianas species decreased significantly with altitude. Our results demonstrate the importance of the contribution of lianas to the richness and endemism of Mexican flora and justify the development of initiatives to ensure their long-term conservation.
Florística y ecología de diatomeas bentónicas de la zona lacustre de Xochimilco-Tláhuac, México
Authors: Buendía-Flores Marisela , Tavera Rosaluz , Novelo Eberto
Published: November 2015

Se registraron 91 taxones de diatomeas bentónicas en varios sitios de la zona lacustre de Xochimilco-Tláhuac que representan un incremento de más de 50 % en el inventario florístico de diatomeas para esta zona. El estudio se basó en el análisis de 13 recolecciones con muestreos quincenales y mensuales durante la época seca y de lluvias, registrando simultáneamente varios factores ambientales que apoyaron un análisis comparativo para los cambios en la riqueza de especies entre recolecciones y sitios de estudio. Se elaboró una categorización ecológica que permitió asociar esta presencia con las condiciones ambientales propias de la zona lacustre, argumentando que las especies dominantes distinguen florísticamente una región, mientras que las frecuentes distinguen la flora local y las especies raras indican fragmentación del hábitat. La composición y riqueza de especies mostraron una relación evidente con los factores ambientales y resaltó la presencia de Nitzschia frustulum , Pseudostaurosira brevistriata , Fragilaria bidens , Rhoicosphenia abbreviata , Fragilariforma virescens , Staurosira construens , S. construens var. binodis , Staurosirella leptostauron y S. pinnata , las cuales son especies que típicamente se encuentran en los sedimentos de cuerpos de agua someros y eutróficos. La riqueza de especies estuvo estadísticamente correlacionada con la variación del sílice y el pH, lo que mostró que las diatomeas bentónicas pueden ser utilizadas como indicadores ecológicos para dar seguimiento a las condiciones ambientales de la zona lacustre de Xochimilco-Tláhuac.
Respuestas bioquímico-fisiológicas de especies de Agave a la restricción de humedad
Authors: Ramírez-Tobias Hugo Magdaleno , Peña-Valdivia Cecilia Beatriz , Aguirre Rogelio
Published: November 2015

En México se encuentra la mayor riqueza de especies de Agave , distribuidas en ambientes diversos. Para contribuir con el conocimiento en torno a las formas de tolerar las restricciones de humedad se evaluó el efecto de dos potenciales de agua (?) en el sustrato (-0.7 y -3.5 MPa) durante 14 meses, en invernadero, sobre el crecimiento, la distribución de biomasa, el grosor foliar y el contenido de prolina en dos especies del subgénero Littaea ( A. lechuguilla y A. striata ) y seis del subgénero Agave ( A. americana var. marginata , A. angustifolia subsp. tequilana , A. asperrima , A. cupreata , A. duranguesis y A. salmiana ), reconocidas por su importancia económica y ecológica. La menor disponibilidad de humedad inhibió la acumulación de biomasa en las ocho especies; no obstante, el crecimiento (número de hojas y cobertura de planta) pudo mantenerse en aquellas más adaptadas a la aridez o con límites de tolerancia ambiental más amplios como A. angustifolia subsp. tequilana , A. duranguensis , A. lechuguilla y A. salmiana . El ? limitante promovió mayor asignación de biomasa a la raíz a expensas de la de las hojas en algunas especies y la duplicación de la prolina radical en las especies del subgénero Agave . La modificación de la distribución de la biomasa y el incremento del contenido de prolina, como formas de tolerar la restricción de humedad, sólo se presentaron en algunas de las especies estudiadas. En contraste, el mantenimiento del grosor de la hoja (indicador de turgencia) fue una respuesta general al ? limitante. Las especies de Agave presentan respuestas fisiológicas y bioquímicas variadas, que reflejan su amplia tolerancia a condiciones ambientales adversas y explican la distribución ecológica amplia del género.
Nuevo registro de Pteridaceae para la península de Yucatán, México.
Authors: Gutiérrez-Báez Celso , Palacios-Ríos Mónica , Zamora-Crescencio Pedro , Ortiz-Díaz Juan Javier , Tun-Garrido Juan , Palma-Pech Geovani
Published: November 2015

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Riqueza y distribución de helechos y licófitos en el gradiente altitudinal del Cofre de Perote, centro de Veracruz, México
Authors: Carvajal-Hernández César I. , Krömer Thorsten
Published: November 2015

Se presenta el listado de las especies de helechos y licófitos registrados a lo largo del gradiente altitudinal (20-3,500 m s.n.m.) del Cofre de Perote, Veracruz, abarcando ambientes contrastantes y bosques con diferentes grados de perturbación, así como vegetación azonal. Se establecieron 15 a 25 parcelas de 20 × 20 m en ocho pisos altitudinales, separados por 500 m de altitud. En cada parcela, se registraron las especies terrestres y epífitas del sotobosque (hasta una altura aproximada de 8 m). En 135 parcelas, se registraron 140 especies y cuatro variedades de helechos (22 familias, 59 géneros), así como 11 especies de licófitos (dos familias, tres géneros), representando el 27,5 % de la pteridoflora de Veracruz. Dos especies del género Elaphoglossum ( E. pallidum , E. squarrosum ) y Polystichum muricatum , registradas a 2,500 m, son nuevos registros para el estado. El número de especies es contrastante en diferentes pisos altitudinales del gradiente y en las elevaciones medias con bosque mesófilo de montaña entre 1,500 y 2,500 m se presentan los valores máximos de riqueza. En los extremos superior e inferior del gradiente, caracterizado por bosque de coníferas y selva mediana subcaducifolia respectivamente, el número de especies disminuye. Se destaca la riqueza del bosque mesófilo y la pérdida de especies del mismo cuando existe una perturbación de origen antrópico. Además, la vegetación azonal en cañadas y al lado de ríos representa un reservorio importante de la pteridoflora, lo que resalta su valor para la conservación.
Heat shock effect in breaking physical dormancy in seeds of Lupinus elegans and L. rotundiflorus from Jalisco, Mexico
Authors: Robles-Díaz Erika , Jurado Enrique , Ruíz-Robles Mario , Yáñez-Espinosa Laura , Flores Joel
Published: November 2015

Most Lupinus spp. (Fabaceae) grow in pine and pine-oak forests with natural and induced fires, and their seeds have physical dormancy, which could be broken in response to appropriate environmental signals, such as high temperatures, humidity and fire. We applied heat treatments to break seed dormancy of L. elegans and L. rotundiflorus from the State of Jalisco, México, with different storage times (0, 1 and 2 yr for L. elegans and 0, 1, 2, 3 and 4 yr for L. rotundiflorus ). Seeds were immersed in boiling water for 5, 10, and 15 s and incubated in wet and dry sand at 100 °C, 120 °C, and 150 °C during 60 min and 90 min. Germination trials were set at 25 °C with 12 h of irradiance per day. For both species, no germination resulted after incubation at 120 °C and 150 °C. For L. rontundiflorus , germination was higher for seeds incubated in wet sand for 60 m than for those incubated for 90 m. After scarification with boiling water, fresh seeds of L. elegans , germinated more than those stored for 1 and 2 yr, whereas incubation in wet and dry sand resulted in higher germination for 1 and 2 yr old seeds than for fresh seeds. Fresh seeds of L. rotundiflorus showed higher germination than stored seeds across treatments. Our results may be useful for further studies to understand and predict ecological plant responses in Mexican forests.
Caracterización de las ectomicorrizas formadas por Laccaria trichodermophora y Suillus tomentosus en Pinus montezumae
Authors: Galindo-Flores Gema , Castillo-Guevara Citlalli , Campos-López Alberto , Lara Carlos
Published: November 2015

Las especies del género Pinus tienen una gran dependencia ecológica hacia la asociación ectomicorrízica. Sin embargo, a pesar de la importancia de la ectomicorriza en los ecosistemas forestales las descripciones morfológicas disponibles de estas asociaciones son escasas. En el presente trabajo se realizó la primera caracterización morfológica macroscópica y microscópica de las ectomicorrizas formadas por Laccaria trichodermophora y Suillus tomentosus en Pinus montezumae . La síntesis de las micorrizas estudiadas se efectuó mediante la inoculación con esporas en un sustrato estéril, bajo condiciones de invernadero. Laccaria trichodermophora presentó ramificación de tipo coraloide con un grosor del manto de 46.05 ?m; una longitud del sistema radical de 0.4 a 2.9 mm; sin rizomorfos. Suillus tomentosus presentó ramificación de tipo coraloide con un grosor del manto de 48.03 ?m; una longitud del sistema radical entre 0.4 a 1.6 mm; sin rizomorfos. La mayoría de las características descritas concuerdan con las publicadas para los géneros Suillus y Lacccaria . El conocimiento de la morfología permitirá hacer una mejor detección rápida en estudios in vitro y ex situ de la micorriza formada por hongos útiles para la producción de inoculantes con fines de manejo y conservación de sistemas forestales.
¿Es la disolución evolutiva de la tristilia un proceso frecuente?
Authors: Sosenski Paula , Fornoni Juan , Domínguez César A.
Published: November 2015

La tristilia es un polimorfismo floral reportado sólo en siete familias de angiospermas que se caracteriza por la presencia de tres morfos que difieren en la posición recíproca de los órganos sexuales. El mantenimiento del equilibrio en las frecuencias de los tres morfos en las poblaciones tristílicas es regulado por la selección dependiente de la frecuencia que opera a través de los flujos legítimos de polen, el sistema de incompatibilidad y la ausencia de diferencias en adecuación entre los morfos. Aunque teóricamente se ha considerado a la tristilia como un polimorfismo evolutivamente estable, en repetidas ocasiones se ha demostrado que su disolución a otros sistemas reproductivos como la distilia y el monomorfismo es muy común. A través de un enfoque indirecto que se basa en el análisis de la variación en las frecuencias de los morfos reportadas en las poblaciones de especies tristílicas, este trabajo evalúa y discute: (1) qué tan inestable es la tristilia, (2) si el patrón de variación en las frecuencias de los morfos concuerda con una hipótesis selectiva o de procesos azarosos y (3) los posibles mecanismos involucrados en la ruptura del equilibrio predicho. Los resultados sugieren que la disolución de la tristilia es un proceso frecuente que podría ser explicado por selección natural y/o procesos azarosos según el patrón de variación en las frecuencias de los morfos detectado entre las poblaciones de una especie. Sin embargo, se requieren un mayor número de estudios experimentales y comparativos para identificar los mecanismos responsables de la disolución del polimorfismo.
Pleopeltis (Polypodiaceae), a redefinition of the genus and nomenclatural novelties
Authors: Smith Alan , Tejero-Díez J. Daniel
Published: November 2015

Recent evidence from morphological, cytological, and gene sequencing studies has provided much additional evidence that the genus Pleopeltis (Polypodiaceae) requires redefinition to include other polypod genera and species with peltate scales on the leaf blades. Groups to be included are Polypodium subg. Marginaria (species treated in the group of Polypodium polypodioides (L.) Watt by Moran), and also including the Polypodium squamatum and Polypodium plebeium groups, Dicranoglossum , Microphlebodium , Neurodium , and Pseudocolysis . In this paper, we review all species of Polypodiaceae that we believe belong to Pleopeltis and make 35 species combinations, one varietal combination, and six hybrid combinations. In addition, three new names are necessary for species prevented from transfer because to do so results in homonymy. As redefined, Pleopeltis comprises ca. 90 species, mainly in the New World, but with two species and one hybrid in Africa, India, and Sri Lanka; it excludes Lepisorus in Asia and Africa, as well as many other especially simple-bladed Old World species once placed in Pleopeltis but now included in other Paleotropical genera, e.g., Lemmaphyllum , Leptochilus , and Selliguea . We provide a key to separate the American polypod genera, and address biogeographical data that derive from. In two appendices, we list previously accepted taxa of Pleopeltis for which combinations are already available, as well as salient synonymy