ABSTRACT
The structure of the endogenous murine leukemia virus (MuLV) sequences of NIH/Swiss mice was analyzed by restriction endonuclease digestion, gel electrophoresis, and hybridization to an MuLV nucleic acid probe. Digestion of mouse DNA with certain restriction endonucleases revealed two classes of fragments. A large number of fragments (about 30) were present at a relatively low concentration, indicating that each derived from a sequence present once in the mouse genome. A smaller number of fragments (one to five) were present at a much higher concentration and must have resulted from sequences present multiple times in the mouse genome. These results indicated that the endogenous MuLV sequences represent a family of dispersed repetitive sequences. Hybridization of these same digested mouse DNAs to nucleic acid probes representing different portions of the MuLV genome allowed construction of a map of the sites where restriction endonucleases cleave the endogenous MuLV sequences. Several independent recombinant DNA clones of endogenous MuLV sequences have been isolated from C3H mice (Roblin et al., J. Virol. 43:113-126, 1982). Analysis of these sequences shows that they have the structure of MuLV proviruses. The sites at which restriction endonucleases cleave within these proviruses appeared to be similar or identical to the sites at which these nucleases cleaved within the MuLV sequences of NIH/Swiss mice. This identity was confirmed by parallel electrophoresis. We conclude that the apparently complex pattern of endogenous MuLV sequences of NIH/Swiss mice consists largely of only two kinds of provirus, each repeated multiple times at dispersed sites in the mouse genome.
Subject(s)
Genes, Viral , Leukemia Virus, Murine/genetics , Mice/microbiology , Recombination, Genetic , Animals , Base Sequence , DNA Restriction Enzymes , DNA, Recombinant , DNA, Viral , Mice/genetics , Moloney murine leukemia virus/genetics , Nucleic Acid Hybridization , Repetitive Sequences, Nucleic AcidABSTRACT
A quantitatively accurate map of the tonotopic organization of the anteroventral cochlear nucleus (AVCN) was derived from single unit recordings. Histologically localized single unit recordings from many animals were mapped onto a computerized atlas of the cochlear nucleus, and surfaces of constant characteristic frequency (CF) estimated with the aid of computer graphics. In anterior AVCN the surfaces of constant CF were found to be parallel planes, whereas in posterior AVCN they progressively deviated from this simple description. A further complication was noted in the most posterior portion of the AVCN where units with very different CF was found in close proximity. Comparison of the tonotopic map with descriptions of cellular organization shows conclusively that different CF ranges are dominant in the various cytoarchitectonic regions of the AVCN.
