Circadian rhythms identified in Caenorhabditis elegans by in vivo long-term monitoring of a bioluminescent reporter

Circadian rhythms are based on endogenous clocks that allow organisms to adjust their physiology and behavior by entrainment to the solar day and, in turn, to select the optimal times for most biological variables. Diverse model systems-including mice, flies, fungi, plants, and bacteria-have provided important insights into the mechanisms of circadian rhythmicity. However, the general principles that govern the circadian clock of Caenorhabditis elegans have remained largely elusive. Here we report robust molecular circadian rhythms in C elegans recorded with a bioluminescence assay in vivo and demonstrate the main features of the circadian system of the nematode. By constructing a luciferase-based reporter coupled to the promoter of the suppressor of activated let-60 Ras (sur-5) gene, we show in both population and single-nematode assays that C elegans expresses approximately 24-h rhythms that can be entrained by light/dark and temperature cycles. We provide evidence that these rhythms are temperature-compensated and can be re-entrained after phase changes of the synchronizing agents. In addition, we demonstrate that light and temperature sensing requires the photoreceptors LITE and GUR-3, and the cyclic nucleotide-gated channel subunit TAX-2. Our results shed light on C elegans circadian biology and demonstrate evolutionarily conserved features in the circadian system of the nematode

Análisis de imágenes cerebrales con FDG-PET en relación a una plantilla de estudios normales.

En esta tesis se desarrollaron dos algoritmos de registración de imágenes cerebrales obtenidas mediante Tomografía Computada (CT), PET (Tomografía por Emisión de Positrones) y RMN (Resonancia Magnética Nuclear). El primero de ellos usa registración rígida basada en cuaterniones y el segundo utiliza una registración deformable basada en B-Splines, ambos aplicando maximización de la función de información mutua. Los algoritmos fueron validados utilizando datos adquiridos en marco de la tesis: la registración rígida fue validada con fantomas con un error de 1.24 mm para registraciones de CT-RM (T1) y 1.57 mm para registraciones RM (T1)-PET, mientras que el algoritmo de registración deformable fue validado mediante imágenes de pacientes de PET con un error de 2.7 mm. Como parte de los objetivos del trabajo se generó y amplió una base de datos regional de estudios cerebrales con PET-FDG-F18 dentro del esquema de plantillas propuesto por el software SPM (Statistical Parametric Mapping). Esta plantilla regional fue exportada a la plataforma de visualización DICOM (Digital Imaging and Communication in Medicine) OsiriX ® para el análisis de casos patológicos. Se compararon 18 casos normales y 5 casos patológicos respecto de la plantilla generada. Los casos analizados coincidieron con el diagnóstico clínico, pudiendo analizarse patologías como Alzheimer, demencias frontotemporal y demencia de los cuerpos de Lewy. En el análisis estadístico de las imágenes con la plantillas se obtuvieron resultados concordantes con los hallazgos clínicos. Las diferentes técnicas de normalización de las imágenes permitieron realizar un análisis diferencial de los casos patológicos, aportando mayor información diagnóstica

Circadian Alterations in a Murine Model of Hypothalamic Glioma

The mammalian circadian system is controlled by a central oscillator located in the suprachiasmatic nuclei (SCN) of the hypothalamus, in which glia appears to play a prominent role. Gliomas originate from glial cells and are the primary brain tumors with the highest incidence and mortality. Optic pathway/hypothalamic gliomas account for 4–7% of all pediatric intracranial tumors. Given the anatomical location, which compromises both the circadian pacemaker and its photic input pathway, we decided to study whether the presence of gliomas in the hypothalamic region could alter circadian behavioral outputs. Athymic nude mice implanted with LN229 human glioma cells showed an increase in the endogenous period of the circadian clock, which was also less robust in terms of sustaining the free running period throughout 2 weeks of screening. We also found that implanted mice showed a slower resynchronization rate after an abrupt 6 h advance of the light-dark (LD) cycle, advanced phase angle, and a decreased direct effect of light in general activity (masking), indicating that hypothalamic tumors could also affect photic sensitivity of the circadian clock. Our work suggests that hypothalamic gliomas have a clear impact both on the endogenous pacemaking of the circadian system, as well as on the photic synchronization of the clock. These findings strongly suggest that the observation of altered circadian parameters in patients might be of relevance for glioma diagnosis

Relações de saúde e trabalho em assentamento rural do MST na região de fronteira Brasil-Paraguai Health and work relations in a rural settlement of the MST in the Brazil-Paraguay border region

Com o presente artigo, busca-se relatar e analisar as relações entre saúde e trabalho de pequenos produtores rurais do Movimento dos Trabalhadores Rurais Sem Terra (MST). Quanto à metodologia, adotou-se o aporte da investigação participativa e as bases da educação popular. O estudo realizado tornou possível uma compreensão de saúde e de trabalho mediante as narrativas dos trabalhadores e histórias relativas às lutas coletivas contra a exclusão e a violência no campo. Constataram-se importantes aspectos próprios a esse grupo populacional, como o sentido de conquista da propriedade da terra, os conflitos advindos da 'militância' e as diferenças de gênero e geração. Com base nos relatos, analisaram-se também os acidentes e os riscos relacionados à atividade de trabalho no assentamento rural, principalmente a exposição ao agrotóxico. Confirmaram-se, ainda, a solidariedade e a cooperação como valores importantes e como base de novas relações, um modo distinto de organização social coletiva do trabalho.<br>In this article, we aim to report on and analyze the relationship between health and work of small farmers of the Landless Workers Movement (MST). So far as the methodology is concerned, we used participatory research and the basics of popular education. The study allowed for an understanding of health and work based on the workers' narratives, stories relating to collective struggles against exclusion and violence in the countryside. Important aspects related to this population group as were discovered, such as, for example, the sense of conquest of land ownership, the conflicts arising from 'activism,' and the differences of gender and generations. From the reports that were provided, we also examined the accidents and risks related to work in the rural settlement, particularly exposure to pesticides. It was also found that solidarity and cooperation are important values, basic elements for new relations and a distinctive mode of social organization of collective