Telomere dysfunction and evolution of intestinal carcinoma in mice and humans

Telomerase activation is a common feature of advanced human cancers and facilitates the malignant transformation of cultured human cells and in mice. These experimental observations are in accord with the presence of robust telomerase activity in more advanced stages of human colorectal carcinogenesis. However, the occurrence of colon carcinomas in telomerase RNA (Terc)-null, p53-mutant mice has revealed complex interactions between telomere dynamics, checkpoint responses and carcinogenesis. We therefore sought to determine whether telomere dysfunction exerts differential effects on cancer initiation versus progression of mouse and human intestinal neoplasia. In successive generations of ApcMin Terc-/- mice, progressive telomere dysfunction led to an increase in initiated lesions (microscopic adenomas), yet a significant decline in the multiplicity and size of macroscopic adenomas. That telomere dysfunction also contributes to human colorectal carcinogenesis is supported by the appearance of anaphase bridges (a correlate of telomere dysfunction) at the adenoma-early carcinoma transition, a transition recognized for marked chromosomal instability. Together, these data are consistent with a model in which telomere dysfunction promotes the chromosomal instability that drives early carcinogenesis, while telomerase activation restores genomic stability to a level permissive for tumor progression. We propose that early and transient telomere dysfunction is a major mechanism underlying chromosomal instability of human cancer.     

Vertebrate fauna of a radioactive leaching pond complex in southeastem Idaho

An inventory of the terrestrial vertebrate fauna and the seasonal occurrence of each species was determined for a man - made radioactive leaching pond complex in southeastern Idaho. Three reptile, 11 mammal, and 94 bird species were identified from February 1974 through January 1978. Fewest species were observed during the winter and most during the summer. Eight bird species nested at the pond complex, while 19 species of birds were common or seasonally abundant. It appears that the Test Reactor Area radioactive leaching pond complex is an important water source and provides habitat for some species of wildlife.     

Dscam2 mediates axonal tiling in the Drosophila visual system

Sensory processing centres in both the vertebrate and the invertebrate brain are often organized into reiterated columns, thus facilitating an internal topographic representation of the external world. Cells within each column are arranged in a stereotyped fashion and form precise patterns of synaptic connections within discrete layers. These connections are largely confined to a single column, thereby preserving the spatial information from the periphery. Other neurons integrate this information by connecting to multiple columns. Restricting axons to columns is conceptually similar to tiling. Axons and dendrites of neighbouring neurons of the same class use tiling to form complete, yet non-overlapping, receptive fields. It is thought that, at the molecular level, cell-surface proteins mediate tiling through contact-dependent repulsive interactions, but proteins serving this function have not yet been identified. Here we show that the immunoglobulin superfamily member Dscam2 restricts the connections formed by L1 lamina neurons to columns in the Drosophila visual system. Our data support a model in which Dscam2 homophilic interactions mediate repulsion between neurites of L1 cells in neighbouring columns. We propose that Dscam2 is a tiling receptor for L1 neurons.     

The effects of intracerebrally administered RNA,tubercidin and histones on learning in rats

Zusammenfassung RNA aus Hefe, RNA-Hydrolysat, Tubercidin und mit Lysin angereichertes Histon, i.c. oder i.p. injiziert, hatten keine Wirkung auf die Lernfähigkeit von Ratten. Intracerebral injiziertes¹⁴C-RNA verbreitete sich schnell über das ganze Gehirn und verschwand relativ schnell wieder. Nach i.p. Injection von¹⁴C-RNA konnte jedoch ein geringer Betrag von¹⁴C im cerebralen RNA gefunden werden.