Metastatic adenocarcinoma presenting as bilateral blindness.

A 71-year-old man had bilateral shallow retinal detachments. An extensive medical work-up was unrevealing. A "skinny-needle" biopsy of retrocrural lymph nodes under computed tomographic control supported a diagnosis of metastatic adenocarcinoma to his choroid.

Zwitterionic character of nucleotides: possible significance in the evolution of nucleic acids.

X-ray crystallography has shown that the free acids of adenosine 5'- and 3'-monophosphates and of cytidine 5'- and 3'-monophosphates exist as zwiterions in the solid state with protonation of the adenine base at the N(1) site and of the cytosine base at the corresponding site N(3) and the phosphate group negatively charged. In this paper, evidence is presented for the zwitterionic character of the free acids of the monomeric nucleotides guanosine 5'-monophosphate and inosine 5'-monophosphate with protonation of the base at the N(7) site of the imidazole moiety.