News Scan Briefs; January 2006; Scientific American Magazine; by JR Minkel, Charles Q. Choi; 2 Page(s)
Telescopes will never peer inside a light-swallowing black hole, but they could soon reveal the event horizon, the surface beyond which a black hole traps light permanently. The horizon would absorb light originating from behind a black hole, creating a shadow visible at high enough resolution. Around the shadow would be a bright ring of focused light, like the corona in an eclipse. Astronomers recently acquired the sharpest image yet of the object presumed to be our galaxy's central black hole, thanks to the Very Long Base line Array, an 8,000-kilometer-wide system of 10 radio telescopes. Boosting such telescopes' resolution just four times should clarify the event horizon within the decade, according to a commentary published with the November 3, 2005, Nature.
The nucleus is not the only place where genetic instructions are pieced together. Messenger RNA, or mRNA, which conveys DNA instructions to the rest of the cell, is made of genetic sequences that, when spliced together properly, code for proteins. The many ways in which mRNA sequences can be woven back together help to create the body's vast diversity of proteins. Scientists thought that splicing took place only in the nucleus. Now, using fluorescent tags on splicing proteins in rat studies, molecular neurobiologist Jim Eberwine of the University of Pennsylvania and his colleagues have found that the process also occurs outside the nucleus--in particular, in dendrites, which are branches off neurons that help the cells receive electrical messages. Eberwine speculates that dendrites save mRNA in an unspliced form to ensure that the proteins they encode are not manufactured until needed. The findings appear in the November 15, 2005, Proceedings of the National Academy of Sciences USA.