Early estrogen treatment of female zebra finches masculinizes the brain pathway for learned vocalizations

Telencephalic nucleus HVC and its two efferent targets, RA and X, play essential roles in the production of complex, learned vocalizations in the male zebra finch. Normal females do not produce these learned vocalizations; HVC, RA, and X are small in volume, and HVC and RA are not synaptically connected. We have shown that estrogen treatment during development causes females to learn and produce male-like vocalization. This article describes the neural masculinization of these E2 females, replicating and extending the work of others. Female zebra finches were treated with 17β-estradiol (E2) at hatching, at 14–22 days of age, or as adults. In adulthood, the volumes of nucleus RA and area X were measured and the efferent projections of nucleus HVC examined using the anterograde tracer PHA-L. Early, sustained E2 treatment caused the greatest increase in the volume of RA and X, the innervation of RA and X by HVC axons, and the masculinization of auditory responses of cells in RA. Treatments that lasted for a shorter period or started later in development resulted in different patterns of partial brain masculinization. E2 treatment in adulthood had no effect on the volume of RA or X or their innervation by HVC. Bilateral lesions of the tracheosyringeal nerves or of HVC had the same effects on the male-typical vocalizations produced by E2 females as they do on the vocalizations produced by males. These results demonstrate that the neural masculinization of telencephalic nuclei induced by E2 treatment sets up a functional circuit in females similar to one in males that enables the learning and production of complex vocalizations.     

In vitro RNA editing-like activity in a mitochondrial extract from Leishmania tarentolae.

A mitochondrial extract from Leishmania tarentolae directs the incorporation of uridylate (U) residues within the pre-edited domain of synthetic cytochrome b (CYb) and NADH dehydrogenase subunit 7 mRNA. This has several characteristics of an in vitro RNA editing activity, but no direct evidence for involvement of guide RNAs was obtained. Inhibition by micrococcal nuclease suggests a requirement for some type of endogenous RNA. The limitation of internal U-incorporation to the pre-edited region in the CYb mRNA and the inhibition by deletion or substitution of both mRNA anchor sequences for CYb gRNA-I and -II could be consistent either with a gRNA-mediated process or a secondary structure-mediated process. A low level of incorporation of [alpha-32P]CTP occurs at the same sites as UTP. Internal U-incorporation activity is selectively inhibited by heterologous RNAs, suggesting an involvement of low affinity RNA-binding proteins which can be competed by the added RNA.     

Comparison of various ultraviolet sources for fluorescent detection of ethidium bromide-DNA complexes in polyacrylamide gels

Ultraviolet sources with output wavelengths of 254, 300, and 366 nm were compared for detection of ethidium bromide-DNA complexes in acrylamide gels. The 254- and 300-nm sources were both much more sensitive than the 366-nm source. The 254-nm source produced a great deal of photodamage, photonicking and photodimerization, and photobleaching, while the longer wavelength sources cause little damage or bleaching. The 300-nm source is clearly the most suitable source, providing high sensitivity and a relatively low amount of photodamage and photobleaching.