Multiple single unit recording in the cortex of monkeys using independently moveable microelectrodes.

Simultaneous recording from multiple single neurones presents many technical difficulties. However, obtaining such data has many advantages, which make it highly worthwhile to overcome the technical problems. This report describes methods which we have developed to permit recordings in awake behaving monkeys using the 'Eckhorn' 16 electrode microdrive. Structural magnetic resonance images are collected to guide electrode placement. Head fixation is achieved using a specially designed headpiece, modified for the multiple electrode approach, and access to the cortex is provided via a novel recording chamber. Growth of scar tissue over the exposed dura mater is reduced using an anti-mitotic compound. Control of the microdrive is achieved by a computerised system which permits several experimenters to move different electrodes simultaneously, considerably reducing the load on an individual operator. Neurones are identified as pyramidal tract neurones by antidromic stimulation through chronically implanted electrodes; stimulus control is integrated into the computerised system. Finally, analysis of multiple single unit recordings requires accurate methods to correct for non-stationarity in unit firing. A novel technique for such correction is discussed.

Controlled adhesion and growth of long term glial and neuronal cultures on Parylene-c

This paper explores the long term development of networks of glia and neurons on patterns of Parylene-C on a SiO 2 substrate. We harvested glia and neurons from the Sprague-Dawley (P1-P7) rat hippocampus and utilized an established cell patterning technique in order to investigate cellular migration, over the course of 3 weeks. This work demonstrates that uncontrolled glial mitosis gradually disrupts cellular patterns that are established early during culture. This effect is not attributed to a loss of protein from the Parylene-C surface, as nitrogen levels on the substrate remain stable over 3 weeks. The inclusion of the anti-mitotic cytarabine (Ara-C) in the culture medium moderates glial division and thus, adequately preserves initial glial and neuronal conformity to underlying patterns. Neuronal apoptosis, often associated with the use of Ara-C, is mitigated by the addition of brain derived neurotrophic factor (BDNF). We believe that with the right combination of glial inhibitors and neuronal promoters, the Parylene-C based cell patterning method can generate structured, active neural networks that can be sustained and investigated over extended periods of time. To our knowledge this is the first report on the concurrent application of Ara-C and BDNF on patterned cell cultures. © 2011 Delivopoulos, Murray.

The need for winter in the switch to flowering.

Vernalization is the process whereby the floral transition is promoted through exposure of plants to long periods of cold temperature or winter. A requirement for vernalization aligns flowering with the seasons to ensure that their reproductive phase occurs in favorable conditions. The mitotic stability of vernalization, suggestive of an epigenetic mechanism, has intrigued researchers for many years. Genetic analysis of the vernalization requirement in Arabidopsis has identified key floral repressor genes, FRI and FLC. The action of these floral repressors is antagonized by vernalization and the activity of a set of genes grouped into the autonomous floral pathway. Analysis of the vernalization pathway has defined a series of epigenetic regulators crucial for "cellular-memory" of the cold signal, whereas the autonomous pathway appears to function in part through posttranscriptional mechanisms. The mechanism of the vernalization requirement, which is now being explored in a range of plant species, should uncover the evolutionary origins of this key agronomic trait.