Dataset Information

Studies on the incorporation of [5-3H] uridine during activation and transformation of lymphocytes induced by phytohaemagglutinin. Dependence on the incorporation rate on uridine concentration at certain critical concentrations.

ABSTRACT: 1. Partially purified pig blood lymphocytes were stimulated to transform in culture with phytohaemagglutinin. Initial cell activation was assessed by measuring the increase of uridine incorporation into RNA induced by phytohaemagglutinin. The phytohaemagglutinin/serum ratio for this effect was similar to that required for transformation; however, no inhibition at high phytohaemagglutinin/serum ratios was found during cell activation. 2. Without replenishment of medium the pool of competitors with added uridine for incorporation fell to zero during 2 days of culture. At certain critical pool concentrations uridine itself could stimulate the rate of uridine incorporation. 3. Most of the tritium from [5-(3)H]uridine added at the initiation of culture had been incorporated into RNA by the end of the second day of culture; the subsequent loss of radioactivity preceded a fall in the total RNA content of cultures. 4. RNA was qualitatively examined on sucrose density gradients. In the first 30min. after the addition of phytohaemagglutinin, increased labelling occurred predominantly between the 28s and 4s regions of the gradients. On the second day of culture with phytohaemagglutinin mainly RNA sedimenting beyond the 28s region of gradients was labelled in 30min.

SUBMITTER: Forsdyke DR

PROVIDER: S-EPMC1198646 | biostudies-other | 1968 Mar

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:1. Rat lymph-node cells cultured in serum and medium 199 were activated to transform and proliferate by concanavalin A. Initial cell activation was assessed by measuring the enhanced radioactive labelling of cells with [(3)H]uridine produced by concanavalin A during the first 6h of culture. 2. In medium containing serum the degree of activation was dependent on the ratio of concanavalin A to non-diffusible serum macromolecules; however, cells could be activated to a normal extent in a medium containing only diffusible molecules. This indicates that certain serum macromolecules buffer cell receptor sites against reaction with concanavalin A. 3. At high concanavalin A concentrations labelling was depressed below that of control cultures without concanavalin A. This inhibition of labelling (i) occurred in calf serum, but not in homologous serum, (ii) was removed by pretreatment of serum with various complement inhibitors, and (iii) first appeared after 1h of culture following an initial phase of cell activation by concanavalin A. Cells pre-labelled with [(3)H]uridine slowly released the label into the culture medium; this rate of release was suddenly accelerated after 1h of culture with concanavalin A if complement was present. The results suggest that inhibition of labelling requires the sequential binding of concanavalin A and then complement to the cell surface. 4. Results from experiments in which calf serum was mixed in various proportions with calf serum which had been preheated to inactivate complement, suggest (i) a requirement for complement in stoicheiometric quantities dependent on the number of cells being inhibited, and (ii) that preheated serum can inactivate complement in unheated serum. 5. The proliferative response over 3 days of culture was assessed by measuring the enhanced labelling of cells with [(3)H]thymidine produced by concanavalin A. In preheated calf serum two types of inhibition were noted. (i) A progressive inhibition at high concanavalin A concentrations so that the optimum response was shifted to lower concanavalin A concentrations as the duration of culture was extended; it is suggested that this reflects the secretion of complement by cultured cells. (ii) An inhibition of the optimum response appearing late in the culture period at high cell concentrations; it is suggested that this is due to the exhaustion of medium nutrients in most actively growing cultures.

Dataset Information

Studies on the incorporation of [5-3H] uridine during activation and transformation of lymphocytes induced by phytohaemagglutinin. Dependence on the incorporation rate on uridine concentration at certain critical concentrations.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets