Transition on the entropic elasticity of DNA induced by intercalating molecules

We use optical tweezers to perform stretching experiments on DNA molecules when interacting with the drugs daunomycin and ethidium bromide, which intercalate the DNA molecule. These experiments are performed in the low-force regime from zero up to 2 pN. Our results show that the persistence length of the DNA-drug complexes increases strongly as the drug concentration increases up to some critical value. Above this critical value, the persistence length decreases abruptly and remains practically constant for larger drug concentrations. The contour length of the molecules increases monotonically and saturates as drugs concentration increases. Measured in- tercalants critical concentrations for the persistence length transition coincide with reported values for the helix-coil transition of DNA-drug complexes, obtained from sedimentation experiments.Comment: This experimental article shows and discuss a transition observed in the persistence length of DNA molecules when studied as a function of some intercalating drug concentrations, like daunomycin and ethidium bromide. It has 15 pages and 4 figures. The article presented here is in preprint forma

Altered sleep and EEG power in the P301S Tau transgenic mouse model

OBJECTIVE: Sleep disturbances are prevalent in human tauopathies yet despite the importance of sleep, little is known about its relationship with tau pathology. Here, we investigate this interaction by analyzing sleep and tau pathology throughout tauopathy disease progression in P301S human tau transgenic mice. METHODS: P301S and wild‐type mice were analyzed by electroencephalography (EEG)/electromyography at 3, 6, 9, and 11 months of age for sleep/wake time, EEG power, and homeostatic response. Cortical volume and tau pathology was also assessed by anti‐phospho‐tau AT8 staining. RESULTS: P301S tau mice had significantly decreased rapid eye movement (REM) sleep at 9 months of age and decreased REM and non‐REM (NREM) sleep as well as increased wakefulness at 11 months. Sleep loss was characterized by fewer wake, REM, and NREM bouts, increased wake bout duration, and decreased sleep bout duration. Decreased REM and NREM sleep was associated with increased brainstem tau pathology in the sublaterodorsal area and parafacial zone, respectively. P301S mice also showed increased EEG power at 6 and 9 months of age and decreased power at 11 months. Decreased EEG power was associated with decreased cortical volume. Despite sleep disturbances, P301S mice maintained homeostatic response to sleep deprivation. INTERPRETATION: Our results indicate that tau pathology is associated with sleep disturbances that worsen with age and these changes may be related to tau pathology in brainstem sleep regulating regions as well as neurodegeneration. Tau‐induced sleep changes could affect disease progression and be a marker for therapeutic efficacy in this and other tauopathy models

DNA-psoralen: single-molecule experiments and first principles calculations

The authors measure the persistence and contour lengths of DNA-psoralen complexes, as a function of psoralen concentration, for intercalated and crosslinked complexes. In both cases, the persistence length monotonically increases until a certain critical concentration is reached, above which it abruptly decreases and remains approximately constant. The contour length of the complexes exhibits no such discontinuous behavior. By fitting the relative increase of the contour length to the neighbor exclusion model, we obtain the exclusion number and the intrinsic intercalating constant of the psoralen-DNA interaction. Ab initio calculations are employed in order to provide an atomistic picture of these experimental findings.Comment: 9 pages, 4 figures in re-print format 3 pages, 4 figures in the published versio

Avaliação do período de floração e frutificação do BAG Ipecacuanha.

A ipecacuanha (Carapichea ipecacuanha (Brot.) L. Anderson Lorenzi, 2008) conhecida popularmente como ipeca e poaia, pertencente à família Rubiaceae é uma espécie medicinal de potencial econômico, onde sua raiz e obtida diretamente do extrativismo, sendo cada vez mais rara em seu habitat natural. O estudo da fenologia no Banco Ativo de Germoplasma (BAG) de Ipecacuanha da Embrapa Amazônia Oriental permitiu que a floração e frutificação desta espécie fossem avaliadas diariamente dentro do período de abril de 2009 à setembro de 2010. O BAG de Ipecacuanha apresentou floração de setembro de 2009 à setembro de 2010. Quanto à frutificação, apenas um acesso frutificou nos meses de março e agosto de 2010.PIBIC-2011

Multiple minute digitate hyperkeratosis affecting the face and folds: clinical, dermoscopic, and histological report of a familial case.

A case of a generalized non-follicular digitate keratosis classified as multiple minute digitate hyperkeratosis is described with suggestive clinical, dermoscopic, and histopathogical data. The patient was a 52-year-old Caucasian woman presenting a 6-year history of multiple asymptomatic skin-colored digitate lesions, 3 to 5 mm long and 1 to 2 mm wide, distributed on the forehead, neck, and extensor surface of the arms as well as in the inframammary folds, axillae, and lower limbs, especially on the popliteal fold. She reported having a 67-year-old sister and a 39-year-old niece with an identical eruption. Treatment with 15% glycolic acid (AHA) lotion and heliotherapy improved this disturbing eruption