ABSTRACT With the objective of evaluating the yield components and bromatological composition of three Megathyrsus maximus cultivars in Guayas area, Ecuador at different regrowth ages, the research was carried out, following a random block design with factorial arrangement (3x3) with five replications. The productivity (yields of total dry matter, leaves, stem and biomass), morphological components (plant height, length and width of leaves, number of leaves and stems) were studied; as well as the contents of DM, CP, NDF, ADF, ADL, cellulose (Cel), hemicellulose (Hcel), cellular content (CC), P, Ca, ash, OM, DMD, OMD, ME, LNE and the relations NDF-N and ADF-N at the ages of 21, 42 and 63 days. Analysis of variance was performed according to experimental design. The highest yields of DM and biomass were obtained in Tanzania at 63 days of regrowth (2.74 and 8.25 t/ha, respectively). The highest DM and biomass yields were obtained in Tanzania at 63 days of regrowth (4.18 and 12 t/ha, respectively). The CP and CC decreased with the maturity of the plant and the best values were obtained in Tanzania at 21 days of regrowth (15.67 and 62.16 %, respectively), while the components of the cell wall increased with age and Tanzania showed the best values. There was significant interaction between varieties and maturity (P <0.0001) for all indicators. It is concluded that the studied varieties show adequate productive performance under conditions of low rainfalls. The Tanzania and Tobiata cultivars are a good option to replace the food deficit during the dry period due to its higher proportion of leaves, better relations NDF-N and ADF-N that give it higher quality.

RESUMEN Con el objetivo de evaluar los componentes del rendimiento y composición bromatológica de tres cultivares de Megathyrsus maximus en la zona del Guayas, Ecuador a diferentes edades de rebrote, se desarrolló la investigación, siguiendo un diseño de bloque al azar con arreglo factorial (3x3) con cinco réplicas. Se estudiaron la productividad (rendimientos de materia seca total, hojas, tallo y biomasa), componentes morfológicos (altura de la planta, longitud y ancho de las hojas, así como número de hojas y tallos); los contenidos de MS, PB, FDN, FDA, LAD, celulosa (Cel), hemicelulosa (Hcel), contenido celular (CC), P, Ca, ceniza, MO, DMS, DMO, EM, ENL y las relaciones FND-N y FAD-N a las edades de 21, 42 y 63 días. Se realizó análisis de varianza según diseño experimental. Los mayores rendimientos de MS y de biomasa se obtuvieron en Tanzania a los 63 días de rebrote (2,74 y 8.25 t/ha, respectivamente). PB y el CC disminuyeron con la madurez de la planta y los mejores valores se obtuvieron en Tanzania y Común a los 21 días de rebrote (15.67 y 62.16%, respectivamente), mientras que los componentes de la pared celular se incrementaron con la edad y los mejores valores lo presentó Tanzania. Vale destacar que entre las variedades y madurez existió interacción significativa (P<0.0001) para todos los indicadores. Se concluye que las variedades estudiadas presentan adecuado comportamiento productivo en condiciones de escasas precipitaciones. Los cultivares Tanzania y Tobiatá constituyen una buena opción para suplir el déficit de alimento durante el período seco por su mayor proporción de hojas, mejores relaciones FND-N y FAD-N que le confieren mayor calidad.

Abstract Using a random block design with factorial arrangement (3x3) with five replications, the yields and quality of three Megathyrsus maximus cultivars (Common, Tanzania and Tobiata) and three regrowth ages (21, 42 and 63 days) were studied in the Empalme area, Ecuador. The yields of total dry matter, biomass, leaves and stems were determined, as well as the plant height, length and width of leaves, the contents of DM, CP, NDF, ADF, ADL, cellulose (Cel), hemicellulose ( Hcel), cellular content (CC), P, Ca, ash, OM, DMD, OMD, ME, FNE and relations leaf-stem, NDF-N and ADF-N. Analysis of variance was performed according to experimental design. There was significant interaction (P <0.0001) between the varieties and the regrowth age for all the studied indicators. The highest DM and biomass yields were obtained in Tanzania at 63 days of regrowth (4.18 and 12 t/ha, respectively). The CP and CC decreased with the maturity of the plant and the best values were obtained in Tanzania at 21 days of regrowth (12.56 and 64.40 %, respectively), while the components of the cell wall increased with age and Tanzania showed the best values. The results of this research showed the variability of the studied indicators determined by regrowth age and varieties, although the response patterns were similar for the varieties but with specific values for each of them. The best balance of the indicators was showed by Tanzania and the Common and Tobiata are not ruled out. Future studies of its use in the milk and beef production are recommended.

Resumen Mediante un diseño bloque al azar con arreglo factorial (3x3) con cinco réplicas se estudiaron los rendimientos y calidad de tres cultivares de Megathyrsus maximus (Común, Tanzania y Tobiatá) y tres edades de rebrote (21, 42 y 63 días) en la zona del Empalme, Ecuador. Se determinaron los rendimientos de materia seca total, biomasa, hojas y tallos, así como la altura de la planta, largo y ancho de las hojas, los contenidos de MS, PB, FDN, FDA, LAD, celulosa (Cel), hemicelulosa (Hcel), contenido celular (CC), P, Ca, ceniza, MO, DMS, DMO, EM, ENL y las relaciones hoja-tallo, FND-N y FAD-N. Se realizó análisis de varianza según diseño experimental. Hubo interacción significativa (P<0.0001) entre las variedades y la edad de rebrote para todos los indicadores estudiados. Los mayores rendimientos de MS y de biomasa se obtuvieron en Tanzania a los 63 días de rebrote (4,18 y 12 t/ha, respectivamente). La PB y el CC disminuyeron con la madurez de la planta y los mejores valores se obtuvieron en Tanzania a los 21 días de rebrote (12.56 y 64.40%, respectivamente), mientras que los componentes de la pared celular se incrementaron con la edad y los mejores valores lo presentó Tanzania. Los resultados de la presente investigación evidenciaron la variabilidad de los indicadores estudiados determinados por la edad de rebrote y las variedades, aunque los patrones de respuesta fueron similares para las variedades pero con valores específicos para cada una de ellas. El mejor balance de los indicadores lo presentó Tanzania y no se descartan a la Común y Tobiatá. Se recomiendan futuros estudios de su empleo en la producción de leche y carne bovina.

Proteína Tau desempenha um papel crucial na fisiopatologia da doença de Alzheimer, onde sua hiper-fosforilação promove agregação e desestabilização de microtúbulo. Tau submete-se a splicing alternativo que gera seis isoformas no cérebro humano, devido a inclusão/exclusão dos exons 2, 3 e 10. A desregulação do processo de splicing do exon tau 10 é suficiente para causar Taupatia e mostrou-se ser influenciado por peptídeos beta-amilóides, entretanto o splicing de outros exons é menos estudado. Nós estudamos os efeitos da beta-amiloide(42) no splicing alternativo de exons tau 2/3 e 6, usando células PC12 não tratadas ou estimuladas pelo fator de crescimento do nervo. A exposição de beta-amilóide levou processos celulares formados a retrair em células diferenciadas e alterou a expressão de exons 2/3 tanto em células indiferenciadas como diferenciadas. A expressão do exon 6 foi reprimida apenas em células indiferenciadas. Nossos resultados sugerem que beta-amilóide interfere com o processo de splicing de exons 2/3, favorecendo a sua exclusão e, portanto, a expressão de isoformas imaturas de tau que são menos eficientes em estabilizar microtúbulos e também podem ser mais propensas a hiper-fosforilação. O mecanismo molecular para essa interação amilóide-tau permanece a ser determinado, mas pode ter implicações potenciais para a compreensão dos processos neuropatológicos fundamentais na doença de Alzheimer.

Protein tau plays a pivotal role in the pathophysiology of Alzheimer's disease, where its hyperphos-phorylation promotes aggregation and microtubule destabilization. Tau undergoes alternative splicing which generates six isoforms in the human brain, due to inclusion/exclusion of exons 2, 3 and 10. Dysregulation of the splicing process of tau exon 10 is sufficient to cause tauopathy and has shown to be influenced by beta-amyloid peptides, but splicing of other exons is less studied. We studied the effects of beta-amyloid(42) in the alternative splicing of tau exons 2/3 and 6, using untreated and Nerve Growth Factor-induced PC12 cells. Beta-amyloid exposure caused formed cell processes to retract in differentiated cells and altered the expression of exons 2/3 in both undifferentiated and differentiated cells. Expression of exon 6 was repressed in undifferentiated cells only. Our results suggest that beta-amyloid interferes with the splicing process of exons 2/3, favoring their exclusion and thus the expression of immature tau isoforms that are less efficient in stabilizing microtubules and may also be more prone to hyperphosphorylation. The molecular mechanism for this amyloid-tau interaction remains to be determined, but may have potential implications for the understanding of the underlying neuropathological processes in Alzheimer's disease.

Embora a doença de Alzheimer seja um distúrbio do cérebro, uma série de alterações periféricas têm sido encontradas nesses pacientes; no entanto, pouco se sabe sobre como os genes envolvidos na fisiopatologia se expressam nas células periféricas, tais como em linfócitos durante o envelhecimento normal em comparação com o neuropatológico. Analisamos por RT-PCR a expressão dos genes de tau, da proteína precursora do amilóide, de nicastrin e da enzima de clivagem do sítio β da APP, em linfócitos de um pequeno grupo de pacientes com início tardio da Doença de Alzheimer, de um grupo de pacientes idosos que sofrem de doenças neuropsicológicas diferentes de Alzheimer, e de um grupo de indivíduos cognitivamente saudáveis, divididos em quatro grupos por idade. Também foram investigadas as correlações entre a expressão dos genes e os níveis de pressão arterial, glicose, colesterol total e triglicérides, como fatores de risco para doença de Alzheimer. Os resultados mostram a ausência de expressão de tau em linfócitos, a ausência de detecção da expressão do gene de nicastrina em pacientes com Alzheimer, e a correlação entre as condições médicas estudadas e a expressão gênica nos linfócitos. Acreditamos que a expressão de nicastrin em linfócitos deve ser considerada de interesse para análises em uma população mais ampla, para investigar se ela pode representar um potencial biomarcador para diferenciar a doença de Alzheimer de outros distúrbios neuropsicológicos.

Although Alzheimer's disease is a brain disorder, a number of peripheral alterations have been found in these patients; however, little is known about how the key genes involved in the pathophysiology express in peripheral cells such as lymphocytes during normal compared to neuropathological ageing. We analysed the expression of tau, of the amyloid precursor protein, of nicastrin and of the β-site APP cleaving enzyme genes by RT-PCR in lymphocytes from a small group of late-onset Alzheimer's disease patients, from aged patients suffering from neuropsychological conditions different from Alzheimer's and from cognitively healthy subjects divided in four groups by age. We also investigated correlations between gene expression and levels of blood pressure, glucose, total cholesterol and triglycerides as risk factors for Alzheimer's. Results show no tau expression in lymphocytes, a lack of detection of nicastrin expression in Alzheimer's patients and correlations between the medical conditions studied and gene expression in lymphocytes. We believe nicastrin gene expression in lymphocytes should be considered of interest for further analyses in a wider population to investigate whether it might represent a potential biomarker to differentiate Alzheimer's from other neuropsychological disorders.