Myc-induced T cell leukemia in transgenic zebrafish

The zebrafish is an attractive model organism for studying cancer development because of its genetic accessibility. Here we describe the induction of clonally derived T cell acute lymphoblastic leukemia in transgenic zebrafish expressing mouse c-myc under control of the zebrafish Rag2 promoter. Visualization of leukemic cells expressing a chimeric transgene encoding Myc fused to green fluorescent protein (GFP) revealed that leukemias arose in the thymus, spread locally into gill arches and retro-orbital soft tissue, and then disseminated into skeletal muscle and abdominal organs. Leukemic cells homed back to the thymus in irradiated fish transplanted with GFP-labeled leukemic lymphoblasts. This transgenic model provides a platform for drug screens and for genetic screens aimed at identifying mutations that suppress or enhance c-myc- induced carcinogenesis.     

Ancient DNA evidence for Old World origin of New World dogs

Mitochondrial DNA sequences isolated from ancient dog remains from Latin America and Alaska showed that native American dogs originated from multiple Old World lineages of dogs that accompanied late Pleistocene humans across the Bering Strait. One clade of dog sequences was unique to the New World, which is consistent with a period of geographic isolation. This unique clade was absent from a large sample of modern dogs, which implies that European colonists systematically discouraged the breeding of native American dogs.     

Taste pathways in rat brainstem

By means of a combination of electrophysiological and anatomical procedures, the projections of the anterior portion of the solitary nucleus were traced to the parabrachial nuclei in the pons, structures hitherto not considered to be included in the taste pathway. Responses to taste stimuli were recorded from this pontine area. Lesions in the pontine taste area resulted in degeneration of fibers reaching the lingual area in the thalamus.     

Bacteriophage structure: determination of head-tail symmetry mismatch for Caulobacter crescentus phage phiCbK

Electron micrographs of negatively stained bacteriophage [unknown]CbK have been analyzed by Fourier methods. Computer-calculated Fourier transforms that contain phase as well as magnitude information have established fivefold rotational symmetry for the head and threefold rotational symmetry for the tail. These results indicate that a symmetry match is not necessarily required between separate structural components of a bacteriophage.     

Development of disease and virus recovery in transgenic mice containing HIV proviral DNA

Transgenic mice containing intact copies of the human immunodeficiency virus (HIV) proviral DNA were constructed. Founder animals were not viremic for HIV and remained healthy during a 9-month observation period. After being mated with nontransgenic animals, one founder mouse (No. 13) gave rise to F1 progeny that developed a disease syndrome characterized by marked epidermal hyperplasia, lymphadenopathy, splenomegaly, pulmonary lymphoid infiltrates, growth retardation, and death by day 25 of life. Infectious HIV, indistinguishable from parental virus by immunoblot analysis, was recovered from the spleen, lymph nodes, and skin of five of five affected animals.     

Differential development of two classes of acetylcholine receptors in Xenopus muscle in culture

Physiological properties of acetylcholine receptors on muscle cells at very early stages of ontogeny were compared with those of cells at later stages. Two changes were observed that contributed to an overall shortening of the mean open time of single-channels. First, there was a shift in the relative proportions of two receptor types with different conductances and mean open times, such that the contribution of receptors with large conductance and short open time increased as development proceeded. Second, there was a sharp reduction in the mean open time of channels having small conductance, with no similar change in channels having large conductance.