Functional architecture of cortex revealed by optical imaging of intrinsic signals

Optical imaging of cortical activity offers several advantages over conventional electrophysiological and anatomical techniques. One can map a relatively large region, obtain successive maps to different stimuli in the same cortical area and follow variations in response over time. In the intact mammalian brain this imaging has been accomplished with the aid of voltage sensitive dyes. However, it has been known for many years that some intrinsic changes in the optical properties of the tissue are dependent on electrical or metabolic activity. Here we show that these changes can be used to study the functional architecture of cortex. Optical maps of whisker barrels in the rat and the orientation columns in the cat visual cortex, obtained by reflection measurements of the intrinsic signal, were confirmed with voltage sensitive dyes or by electrophysiological recordings. In addition, we describe an intrinsic signal originating from small arteries which can be used to investigate the communication between local neuronal activity and the microvasculature. One advantage of the method is that it is non-invasive and does not require dyes, a clear benefit for clinical applications.     

First identification of a trail pheromone of an army ant (Aenictus species)

Totally blind army ants carry out massive and highly organised foraging raids, apparently guided by chemical stimuli. Until now, this phenomenon has not been closely analysed. The existence of a trail pheromone in a postpygidial gland of anAenictus species has been demonstrated and the substances identified as methyl anthranilate and methyl nicotinate The pheromone consists of two parts: a primer effect, caused by methyl nicotinate, which prepares workers to follow trails, but is not itself followed, and a releaser effect, due to methyl anthranilate, which causes trail-following only in conjunction with the primer substance.     

Bcr encodes a GTPase-activating protein for p21rac

More than thirty small guanine nucleotide-binding proteins related to the ras-encoded oncoprotein, termed Ras or p21ras, are known. They regulate many fundamental processes in all eukaryotic cells, such as growth, vesicle traffic and cytoskeletal organization. GTPase-activating proteins (GAPs) accelerate the intrinsic rate of GTP hydrolysis of Ras-related proteins, leading to down-regulation of the active GTP-bound form. For p21ras, two GAP proteins are known, rasGAP and the neurofibromatosis (NF1) gene product. There is evidence that rasGAP may also be a target protein for regulation by Ras and be involved in downstream signalling. We have purified a GAP protein for p21rho, which is involved in the regulation of the actin cytoskeleton. Partial sequencing of rhoGAP reveals significant homology with the product of the bcr (breakpoint cluster region) gene, the translocation breakpoint in Philadelphia chromosome-positive chronic myeloid leukaemias. We show here that the carboxy-terminal domains of the bcr-encoded protein (Bcr) and of a Bcr-related protein, n-chimaerin, are both GAP proteins for the Ras-related GTP-binding protein, p21rac. This result suggest that Bcr could be a target for regulation by Rac and has important new implications for the role of bcr translocations in leukaemia.