Showing papers by "Nissi Varki published in 1987"

Developmental regulation of sialic acid modifications in rat and human colon.

Abstract: Using high-pressure liquid chromatography (HPLC) and gas-liquid chromatography/mass spectrometry (GLC/MS), we have confirmed the existence of several sialic acid modifications in the adult rat and human colon. The major O-acetylated sialic acid in both species is 9-O-acetyl-N-acetylneuraminic acid; N-glycolylneuraminic acid is a major component of the adult rat colon. Both of these major modifications were found to be developmentally regulated during the perinatal period in the rat. The N-glycolyl modification is present prenatally and disappears rapidly in the postnatal period. It reappears in the preweanling period, reaching levels at weaning comparable to those found prenatally. In contrast, the 9-O-acetyl modification is very low prenatally, and undergoes a marked increase shortly after birth in both the rat and human colon. The difference in the kinetics of appearance of the two modifications suggests that they are independently regulated. Regulation of these modifications seems to be influenced by exposure to bacterial by-products or environmental stimuli. The N-glycolyl modification in the rat colon reappeared at weaning, a time of major change in enteral colonic substances. Spontaneously aborted human fetuses, including three with intrauterine infection at 27, 33, and 35 wk of gestation, showed adult levels of O-acetylation in colonic tissue. Also, although O-acetylation in freshly isolated colon tumor specimens was only somewhat lower than that in the adult normal colon, all established colon cancer cell lines studied showed minimal O-acetylation.

Microscopic metastasis of a human lung carcinoma cell line in athymic nude mice: Isolation of a metastatic variant

Abstract: A human lung carcinoma cell line, UCP3, was carried as subcutaneous xenotransplants in athymic mice. Autopsies of these animals showed rare foci of microscopically visible metastases in the lungs and lymph nodes. There were no metastases to any of the other organs. A metastatic variant, 522, was established serendipitously in vitro as a continuous cell line by blind isolation of the pulmonary metastatic foci, at the time of autopsy, from the lungs of the animals that carried subcutaneous xenotransplants of the parental cell line. The parental UCP3 and the metastatic variant 522 were examined by karyotypic and isoenzyme analysis and shown to be human and related. The metastatic variant, 522, metastasizes spontaneously from subcutaneous sites (like the parental UCP3). However, it forms larger subcutaneous xenotransplants and forms more metastatic foci in the lungs of the animals than does the parental cell line. Comparisons of the cell surface glycolipids show many similarities and a few differences. This model system may now be used for further investigations into the processes of metastasis of this human neoplasm.