PEDRO MANUEL FONSECA HERRERA - Academia.edu (original) (raw)

Papers by PEDRO MANUEL FONSECA HERRERA

Etic@net. Revista científica electrónica de Educación y Comunicación en la Sociedad del Conocimiento, 2015

Actualmente en la Universidad Autónoma de Yucatán a través de su Modelo Educativo para la Formaci... more Actualmente en la Universidad Autónoma de Yucatán a través de su Modelo Educativo para la Formación Integral (MEFI), comienza a darle importancia al aprendizaje a través de los entornos virtuales. El modelo tiene como propósito consolidar y desarrollar los nuevos entornos pedagógicos mediante la conformación de redes de educación abierta y a distancia. No menos importante el MEFI considera el rol del profesor como facilitador del aprendizaje y creador de las condiciones idóneas para el trabajo en entornos virtuales. Por tal motivo el presente trabajo pretende proponer un Modelo integral para la formación en entornos virtuales para los profesores de la Universidad Autónoma de Yucatán.

Tecné Episteme y Didaxis: TED, 2014

La formación y el desarrollo profesional del profesorado de ciencias experimentales A formação e ... more La formación y el desarrollo profesional del profesorado de ciencias experimentales A formação e o desenvolvimento profissional de professores de ciências experimentais

Trends Endocrinol Metab, 2011

El objetivo del siguiente artículo es, por una parte explicar las razones económicas por la que e... more El objetivo del siguiente artículo es, por una parte explicar las razones económicas por la que el mercado laboral maquilador, promueve en época de crecimiento la contratación de inmigrantes nacionales, por otra parte profundizar en el racismo entre mexicanos como efecto de esta inmigración y finalmente exponer como en las ciudades maquiladoras coexisten dos imaginarios urbanos, uno desde la cosmovisión de los residentes locales y otro desde la cosmovisión de los inmigrantes, que divide a la ciudad por medio de una frontera étnica cultural.

Este estudio buscó determinar factores o variables que sean económicas, eficientes y eficaces y q... more Este estudio buscó determinar factores o variables que sean económicas, eficientes y eficaces y que permitan modificar el clima laboral en las maquiladoras de Reynosa, en beneficio de la empresa y los trabajadores. La investigación fue de carácter mixto, estuvo dividida en dos momentos: la etapa cualitativa y la etapa cuantitativa. La cualitativa uso entrevistas a agentes claves y en la etapa cuantitativa se diseñó un cuestionario que se aplicó a una muestra de 20 ejecutivos para evaluar los factores que afectan el clima organizacional, estos son: reconocimiento, supervisión, espacio laboral, relación con los compañeros, seguridad laboral e ingresos. Se concluyó en la etapa cualitativa que el sistema de alimentación influye en el clima laboral; no obstante en la etapa cuantitativa los resultados estadísticos, basados en el coeficiente de Pearson no permitieron hacer la misma afirmación. Asimismo a nivel estadístico se determinó que el reconocimiento y la supervisión son factores que...

Current Opinion in Organ Transplantation, 2007

Purpose of review To summarize recent progress in understanding of the extrinsic and intrinsic si... more Purpose of review To summarize recent progress in understanding of the extrinsic and intrinsic signals directing pancreas development from early endoderm. Recent findings The pancreatic mesoderm was shown not only to play a permissive role in pancreas determination but also to control endocrine commitment and maturation through the interplay between Notch and fibroblast growth factor signaling. The requirement of Wnt (wingless-type)/ b-catenin signaling in the expansion of the acinar cell lineage, and the spatial-temporal specificity of PDX1 (pancreatic and duodenal homeobox) activity, which is needed for proper acinar development, were also demonstrated. A novel factor, IA1 (insulinoma-associated 1), was identified as an endocrine marker downstream of Ngn3 (neurogenin); MAFB (musculo-aponeurotic fibrosarcoma) was shown to be a marker of a-cell and b-cell precursors, and ARX (aristaless-related homeobox), a marker of a-cell progenitors, was revealed to directly antagonize PAX4 (paired homeobox) in determining a-cell and b-cell lineages. Summary Cell fate specification results from combined effects of extrinsic and intrinsic regulators and sensitivity of target cells to them, which vary depending on the precise stage of cell commitment or differentiation. Knowledge of the hierarchy of the different factors influencing pancreas development will aid in developing new cell therapies to treat diabetes.

Cancer research, Jan 15, 2003

The function of the predisposition gene to multiple endocrine neoplasia type 1 (MEN1) syndrome re... more The function of the predisposition gene to multiple endocrine neoplasia type 1 (MEN1) syndrome remains largely unknown. Previous studies demonstrated that null mutation of the Men1 gene caused mid-gestation lethality in mice, whereas heterozygous Men1 knockout mice developed multiple endocrine tumors late in life. To seek direct evidence on the causal role of menin in suppressing tumor development, we generated mice in which the Men1 gene was disrupted specifically in pancreatic beta cells. These mice began to develop hyperplastic islets at as early as 2 months of age and insulinomas at 6 months of age. The islet lesions exhibited features of multistage tumor progression, including beta-cell dedifferentiation, angiogenesis, and altered expression of both E-cadherin and beta-catenin. Additionally, disturbance of blood insulin and glucose levels correlated with tumor development, mimicking human MEN1 symptoms. Our data indicate that this strain of mice provides a powerful tool for the...

La cuestión de la identidad profesional: horizontes teóricos Resumen Este artículo teórico tiene ... more La cuestión de la identidad profesional: horizontes teóricos Resumen Este artículo teórico tiene el propósito de presentar la cuestión de la identidad profesional del profesor como una alternativa teórica a los trabajos tradicionales que se han realizado para conocer y caracterizar las necesidades de desarrollo profesional del docente universitario. En el escrito se hace referencia a la identidad en la posmodernidad; se muestran los diferentes esfuerzos en la literatura para la conceptuación de un concepto esquivo y difuso; se exponen las principales miradas teóricas reconocidas en la literatura; y en cuarto lugar, se presenta a modo de cierre los horizontes de estudio sobre la temática.

Journal of Nonverbal Behavior, 1999

Lipps (1907) presented a model of empathy which had an important influence on later formulations.... more Lipps (1907) presented a model of empathy which had an important influence on later formulations. According to Lipps, individuals tend to mimic an interaction partner's behavior, and this nonverbal mimicry induces—via a feedback process—the corresponding affective state in the observer. The resulting shared affect is believed to foster the understanding of the observed person's self. The present study tested this

Ciencia e Ingeniería …, 2011

RESUMEN Este artículo presenta el cálculo óptimo de las dimensiones de un robot paralelo tipo del... more RESUMEN Este artículo presenta el cálculo óptimo de las dimensiones de un robot paralelo tipo delta basado en el menor consumo de energía. También incluye la descripción de la plataforma experimental, y un análisis cinemático y dinámico. El algoritmo de ...

Trends in Endocrinology & Metabolism, 2011

Proceedings of the National Academy of Sciences, 2011

We combined multimodal imaging (bioluminescence, X-ray computed tomography, and PET), tomographic... more We combined multimodal imaging (bioluminescence, X-ray computed tomography, and PET), tomographic reconstruction of bioluminescent sources, and two unique, complementary models to evaluate three previously synthesized PET radiotracers thought to target pancreatic beta cells. The three radiotracers {[ 18 F]fluoropropyl-(+)-dihydrotetrabenazine ([ 18 F]FP-DTBZ), [ 18 F](+)-2-oxiranyl-3-isobutyl-9-(3-fluoropropoxy)-10-methoxy-2,3,4,6,7,11b-hexahydro-1H-pyrido[2,1-a]isoquinoline ( 18 F-AV-266), and (2 S ,3 R ,11b R )-9-(3-fluoropropoxy)-2-(hydroxymethyl)-3-isobutyl-10-methoxy-2,3,4,6,7,11b-hexahydro-1 H -pyrido[2,1- a ]isoquinolin-2-ol ( 18 F-AV-300)} bind vesicular monoamine transporter 2. Tomographic reconstruction of the bioluminescent signal in mice expressing luciferase only in pancreatic beta cells was used to delineate the pancreas and was coregistered with PET and X-ray computed tomography images. This strategy enabled unambiguous identification of the pancreas on PET images, pe...

Nature Genetics, 2006

The total mass of islets of Langerhans is reduced in individuals with type 2 diabetes 1 , possibl... more The total mass of islets of Langerhans is reduced in individuals with type 2 diabetes 1 , possibly contributing to the pathogenesis of this condition. Although the regulation of islet mass is complex, recent studies have suggested the importance of a signaling pathway that includes the insulin or insulin-like growth factor-1 receptors, insulin receptor substrate and phosphatidylinositol (PI) 3-kinase 2-4. 3-Phosphoinositidedependent protein kinase 1 (PDK1) is a serine-threonine kinase that mediates signaling downstream of PI 3-kinase. Here we show that mice that lack PDK1 specifically in pancreatic b cells (bPdk1-/mice) develop progressive hyperglycemia as a result of a loss of islet mass. The mice show reductions in islet density as well as in the number and size of b cells. Haploinsufficiency of the gene for the transcription factor Foxo1 resulted in a marked increase in the number, but not the size, of b cells and resulted in the restoration of glucose homeostasis in bPdk1-/mice. These results suggest that PDK1 is important in maintenance of pancreatic b cell mass and glucose homeostasis. Although recent studies have suggested the importance of a signaling pathway triggered by insulin or insulin-like growth factor-1 (IGF-1)

Journal of Clinical Investigation, 2002

Defective insulin secretion is a feature of type 2 diabetes that results from inadequate compensa... more Defective insulin secretion is a feature of type 2 diabetes that results from inadequate compensatory increase of β cell mass and impaired glucose-dependent insulin release. β cell proliferation and secretion are thought to be regulated by signaling through receptor tyrosine kinases. In this regard, we sought to examine the potential proliferative and/or antiapoptotic role of IGFs in β cells by tissuespecific conditional mutagenesis ablating type 1 IGF receptor (IGF1R) signaling. Unexpectedly, lack of functional IGF1R did not affect β cell mass, but resulted in age-dependent impairment of glucose tolerance, associated with a decrease of glucose-and arginine-dependent insulin release. These observations reveal a requirement of IGF1R-mediated signaling for insulin secretion.

Journal of Biological Chemistry, 2008

Insulin exocytosis is regulated in pancreatic ß-cells by a cascade of intracellular signals trans... more Insulin exocytosis is regulated in pancreatic ß-cells by a cascade of intracellular signals translating glucose levels into corresponding secretory responses. The mitochondrial enzyme glutamate dehydrogenase (GDH) is regarded as a major player in this process, although its abrogation has not been tested yet in animal models. Here, we generated transgenic mice, named ßGlud1 ؊/؊ , with ß-cell-specific GDH deletion. Our results show that GDH plays an essential role in the full development of the insulin secretory response. In situ pancreatic perfusion revealed that glucose-stimulated insulin secretion was reduced by 37% in ßGlud1 ؊/؊. Furthermore, isolated islets with either constitutive or acute adenovirus-mediated knockout of GDH showed a 49 and 38% reduction in glucose-induced insulin release, respectively. Adenovirus-mediated re-expression of GDH in ßGlud1 ؊/؊ islets fully restored glucose-induced insulin release. Thus, GDH appears to account for about 40% of glucose-stimulated insulin secretion and to lack redundant mechanisms. In ßGlud1 ؊/؊ mice, the reduced secretory capacity resulted in lower plasma insulin levels in response to both feeding and glucose load, while body weight gain was preserved. The results demonstrate that GDH is essential for the full development of the secretory response in ß-cells. However, maximal secretory capacity is not required for maintenance of glucose homeostasis in normo-caloric conditions.

Gastroenterology, 2010

BACKGROUND & AIMS: The tumor suppressor menin is recognized as a key regulator of pancreatic isle... more BACKGROUND & AIMS: The tumor suppressor menin is recognized as a key regulator of pancreatic islet development, proliferation, and ␤-cell function, whereas its role in ␣ cells remains poorly understood. The purpose of the current study was to address this issue in relation to islet tumor histogenesis. METHODS: We generated ␣ cell-specific Men1 mutant mice with Cre/loxP technology and carried out analyses of pancreatic lesions developed in the mutant mice during aging. RESULTS: We showed that, despite the ␣-cell specificity of the GluCre transgene, both glucagonomas and a large amount of insulinomas developed in mutant mice older than 6 months, accompanied by mixed islet tumors. Interestingly, the cells sharing characteristics of both ␣ and ␤ cells were identified shortly after the appearance of menin-deficient ␣ cells but well before the tumor onset. Using a genetic cell lineage tracing analysis, we demonstrated that insulinoma cells were directly derived from transdifferentiating glucagon-expressing cells. Furthermore, our data indicated that the expression of Pdx1, MafA, Pax4, and Ngn3 did not seem to be required for the initiation of this transdifferentiation. CONCLUSIONS: Our work shows cell transdifferentiation as a novel mechanism involved in islet tumor development and provides evidence showing that menin regulates the plasticity of differentiated pancreatic ␣ cells in vivo, shedding new light on the mechanisms of islet tumorigenesis.