National Autonomous University of Mexico

About: National Autonomous University of Mexico is a education organization based out in Mexico City, Distrito Federal, Mexico. It is known for research contribution in the topics: Population & Galaxy. The organization has 72868 authors who have published 127797 publications receiving 2285543 citations. The organization is also known as: UNAM & Universidad Nacional Autónoma de México.

Dopamine neuron activity before action initiation gates and invigorates future movements

Abstract: Deciding when and whether to move is critical for survival. Loss of dopamine neurons (DANs) of the substantia nigra pars compacta (SNc) in patients with Parkinson's disease causes deficits in movement initiation and slowness of movement. The role of DANs in self-paced movement has mostly been attributed to their tonic activity, whereas phasic changes in DAN activity have been linked to reward prediction. This model has recently been challenged by studies showing transient changes in DAN activity before or during self-paced movement initiation. Nevertheless, the necessity of this activity for spontaneous movement initiation has not been demonstrated, nor has its relation to initiation versus ongoing movement been described. Here we show that a large proportion of SNc DANs, which did not overlap with reward-responsive DANs, transiently increased their activity before self-paced movement initiation in mice. This activity was not action-specific, and was related to the vigour of future movements. Inhibition of DANs when mice were immobile reduced the probability and vigour of future movements. Conversely, brief activation of DANs when mice were immobile increased the probability and vigour of future movements. Manipulations of dopamine activity after movement initiation did not affect ongoing movements. Similar findings were observed for the initiation and execution of learned action sequences. These findings causally implicate DAN activity before movement initiation in the probability and vigour of future movements.

Polo-like kinases: structural variations lead to multiple functions

Abstract: Members of the polo-like kinase (PLK) family are crucial regulators of cell cycle progression, centriole duplication, mitosis, cytokinesis and the DNA damage response. PLKs undergo major changes in abundance, activity, localization and structure at different stages of the cell cycle. They interact with other proteins in a tightly controlled spatiotemporal manner as part of a network that coordinates key cell cycle events. Their essential roles are highlighted by the fact that alterations in PLK function are associated with cancers and other diseases. Recent knowledge gained from PLK crystal structures, evolution and interacting molecules offers important insights into the mechanisms that underlie their regulation and activity, and suggests novel functions unrelated to cell cycle control for this family of kinases.

Neuronal correlates of decision-making in secondary somatosensory cortex

Abstract: The ability to discriminate between two sequential stimuli requires evaluation of current sensory information in reference to stored information Where and how does this evaluation occur? We trained monkeys to compare two mechanical vibrations applied sequentially to the fingertips and to report which of the two had the higher frequency We recorded single neurons in secondary somatosensory cortex (S2) while the monkeys performed the task During the first stimulus period, the firing rate of S2 neurons encoded the stimulus frequency During the second stimulus period, however, some S2 neurons did not merely encode the stimulus frequency The responses of these neurons were a function of both the remembered (first) and current (second) stimulus Moreover, a few hundred milliseconds after the presentation of the second stimulus, these responses were correlated with the monkey's decision This suggests that some S2 neurons may combine past and present sensory information for decision-making

Observation of a large-scale anisotropy in the arrival directions of cosmic rays above 8 × 1018 eV

Abstract: Cosmic rays are atomic nuclei arriving from outer space that reach the highest energies observed in nature Clues to their origin come from studying the distribution of their arrival directions Using 3 × 10 4 cosmic rays with energies above 8 × 10 18 electron volts, recorded with the Pierre Auger Observatory from a total exposure of 76,800 km 2 sr year, we determined the existence of anisotropy in arrival directions The anisotropy, detected at more than a 52σ level of significance, can be described by a dipole with an amplitude of 65 − 09 + 13 percent toward right ascension α d = 100 ± 10 degrees and declination δ d = − 24 − 13 + 12 degrees That direction indicates an extragalactic origin for these ultrahigh-energy particles

Compilation and analysis of sigma(54)-dependent promoter sequences.

Abstract: Promoters recognized by the RNA-polymerase with the alternative sigma factor sigma(54) (Esigma54) are unique in having conserved positions around -24 and -12 nucleotides upstream from the transcriptional start site, instead of the typical -35 and -10 boxes. Here we compile 186 -24/-12 promoter sequences reported in the literature and generate an updated and extended consensus sequence. The use of the extended consensus increases the probability of identifying genuine -24/-12 promoters. The effect of several reported mutations at the -24/-12 elements on RNA-polymerase binding and promoter strength is discussed in the light of the updated consensus.