Sexual difference in pattern of hormone accumulation in the brain of a songbird

After adult zebra finches (Poephila guttata) received injections of tritiated testosterone, fewer hormone-concentrating cells were found in females than in males in two brain regions involved in song: hyperstriatum ventrale pars caudale and magnocellular nucleus of the anterior neostriatum. In some other regions, no sexual difference was detected. It is, therefore, possible that sex differences in the sensitivity of specific neural populations to hormones underlie the striking anatomical dimorphism observed in neural regions controlling song.     

Living nautilus embryos: preliminary observations

Nautilus, long recognized as the most primitive living cephalopod, provides insight into molluscan evolution. Despite many attempts, embryos have not been observed until now. This report details the surface morphology and extraembryonic circulatory pattern. It was found that development, as in other extant cephalopods, is direct, without larval stages. There appears to be no embryonic protoconch associated with shell ontogeny.     

Regulation of blood and lymphatic vascular separation by signaling proteins SLP-76 and Syk

Lymphatic vessels develop from specialized endothelial cells in preexisting blood vessels, but the molecular signals that regulate this separation are unknown. Here we identify a failure to separate emerging lymphatic vessels from blood vessels in mice lacking the hematopoietic signaling protein SLP-76 or Syk. Blood-lymphatic connections lead to embryonic hemorrhage and arteriovenous shunting. Expression of slp-76 could not be detected in endothelial cells, and blood-filled lymphatics also arose in wild-type mice reconstituted with SLP-76-deficient bone marrow. These studies reveal a hematopoietic signaling pathway required for separation of the two major vascular networks in mammals.     

Evolution of block copolymer lithography to highly ordered square arrays

The manufacture of smaller, faster, more efficient microelectronic components is a major scientific and technological challenge, driven in part by a constant need for smaller lithographically defined features and patterns. Traditional self-assembling approaches based on block copolymer lithography spontaneously yield nanometer-sized hexagonal structures, but these features are not consistent with the industry-standard rectilinear coordinate system. We present a modular and hierarchical self-assembly strategy, combining supramolecular assembly of hydrogen-bonding units with controlled phase separation of diblock copolymers, for the generation of nanoscale square patterns. These square arrays will enable simplified addressability and circuit interconnection in integrated circuit manufacturing and nanotechnology.