The E. coli K-12 chromosome flanked by two IS10 sequences transposes

Summary Transposon are commonly found among prokaryotes and usually range up to 20 kilobases. In this study, we were interested to determine whether a larger DNA segment could transpose. We observed that the E. coli K-12 chromosome, 4,000 kilobases in size, when flanked by two IS10 sequences, could transpose to pACYC177 at a frequency of 10^-8 per cell per generation. We suggest that this transposition event occurs independently of the size and without duplication of the entire DNA sequence flanked by the IS10 elements.     

Studies on the production of indole-3-acetic acid with auxin-heterotrophic mutants derived from cultured crown gall cells

Mutants in the indole-3-acetic acid metabolism derived fromcultured crown gall cells were tested to see whether they couldutilize any one of eight indolic compounds in place of indole-3-aceticacid. Two auxin-heterotrophic mutant cell lines could not utilizeindolepyruvic acid, but growth recovered when there was a supplementof indole-3-acetic acid. Indoleacetonitril and indoleacetaldoximeinhibited the growth of mutant cell lines and their parentalcrown gall cells. Cultured crown gall cells may have synthesizedindole-3-acetic acid from tryptophan via indolepyruvic acidand indole-acetaldehyde, and also may be able to produce indole-3-aceticacid from tryptophan via tryptamine (Received May 6, 1980; )     

Spontaneous lesions in beagle dogs used in toxicity studies

Spontaneous histopathologic lesions were examined in 276 young beagle dogs (8 to 15 months old) used in toxicity studies. Mononuclear cell infiltration in the liver was observed with the highest incidence (more than 95%). Calcium deposition in the kidney, mononuclear cell infiltration in the salivary glands, pigmentation in the spleen, and cortical atrophy in the thymus were seen with relatively high incidences (more than 30%). The incidence of mononuclear cell infiltration in the gallbladder, vacuolization of the tubular epithelium in the kidney, and vacuolization of the zona glomerulosa cell in the adrenal gland showed differences between the sexes. No abnormalities were seen in the spinal cord, sternum, and femur. Although most lesions observed are considered to be age-related, several were considered to be due to congenital anomalies observed in some organs.