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L Amaral

Publications and source records attributed to L Amaral.

57 records · Page 4Linked to original sources
PubMedDate not supplied

Effect of cortisol on the ultrastructure of normal, leukemic, and cultured human lymphocytes.

The effect of cortisol on the ultrastructure of normal, leukemic, and cultured human lymphocytes during a 2-hr incubation was investigated. The presence of 10(-5) M cortisol in the incubation medium produced in normal lymphocytes a variety of alterations in cytoplasmic organelles. Mitochondria were most affected and showed evidence of irreversible deterioration (formation of myelin figures). Occasional cells demonstrated an overt rearrangement of their cytoplasmic membranes resulting in a bizarre array of parallel cisternae-like structures. More commonly, the usually underdeveloped Golgi of normal lymphocytes became very pronounced in structure. All of these alterations were produced within 2 hr of incubation, but only in normal human lymphocytes. Under identical conditions, no evidence of ultrastructural changes were produced by cortisol in either lymphocytes from chronic lymphocytic leukemic patients, or those from the RPMI 1788 cell line.

Cell Line↗
PubMedDate not supplied

Effect of subminimal inhibitory concentrations of mecillinam on the synthesis of DNA, RNA, and protein of Salmonella typhimurium: a proposed mechanism of action.

Salmonellae alter their rod-like morphology to become large ovals within 3-5 hr after being exposed to concentrations of mecillinam below the minimal inhibitory concentration. Before this overt morphologic change occurs, synthesis of DNA increases, with a concomitant decrease in total protein synthesis. Incorporation of [3H]leucine into cell wall protein is markedly inhibited by mecillinam, whereas incorporation of leucine into soluble intracellular proteins is enchanced by the drug. Electrophoretic separation of stained, soluble intracellular proteins of salmonellae exposed to mecillinam indicates that as many as 15-20 individual groups of protein occur at higher concentrations in mecillinam-exposed salmonellae than in unexposed control organisms. These results suggest that, at low concentrations, mecillinam binds selectively to cell wall components, thereby interfering with the assembly of the cell wall during growth. This interference causes a buildup of newly synthesized soluble proteins that are normally involved in cell wall assembly. The weakening of the cell wall, combined with this buildup, causes the cell to assume a three-dimensional oval structure that is the result of equal hydrostatic pressure exerted by the medium.

Amdinocillin↗