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Biomedical subjects

J E Kay

Publications and source records attributed to J E Kay.

At least 55 records · Page 3Linked to original sources
PubMed1982

Inhibition of proliferation of a murine myeloma cell line and mitogen-stimulated B lymphocytes by the antibiotic amphotericin B (Fungizone).

Amphotericin B at the concentration normally used for routine suppression of fungal infection in tissue culture strongly inhibits the proliferation of NS1/1 myeloma cells and the LPS-induced activation of B lymphocytes from mouse spleen. The proliferation of T lymphocytes induced by concanavalin A (Con A) was less affected by the antibiotic, indicating that B-lymphocyte proliferation was preferentially inhibited. The unexpected sensitivity of B-lymphoid cells to amphotericin B precludes its use as an anti-fungal agent in the production of hybridomas from fusions between these cells.

Amphotericin B↗
PubMed1981

Amino acid transport in pig lymphocytes. Enhanced activity of transport system asc following mitogenic stimulation.

Changes in neutral amino acid transport activity caused by addition of phytohaemagglutinin-P to quiescent peripheral pig lymphocytes have been evaluated by measurements of 14C-labelled neutral and analogue amino acids under conditions approaching initial entry rates. Utilizing methylaminoisobutyric acid, the best model substrate of System A, we confirmed our previous report (Borghetti, A.F., Kay, J.E. and Wheeler, K.P. (1979) Biochem. J. 182, 27-32) on the absence of this transport system in quiescent cells and its emergence following stimulation. Furthermore, we demonstrated the presence in quiescent cells of an Na+-dependent transport system for neutral amino acids that has been characterized as System ASC by several criteria including intolerance to methylaminoisobutyric acid, strict Na+-dependence, the property of transtimulation and specificity for pertinent substrates such as alanine, serine, cysteine and threonine. Analysis of the relationship between influx and substrate concentration revealed that two independent saturable components contribute to entry of alanine in quiescent cells: a low affinity (Km = approximately 4 mM) and a high affinity (Km = approximately 0.2 mM) component. The high affinity component could be inhibited in a competitive way by serine, cysteine and threonine, but methylaminoisobutyric acid did not change appreciably its constants. The enhanced activity of alanine transport through the ASC system observed in activated cells resulted from a large increase in the capacity (V) of the high affinity component without any substantial change in the apparent affinity constant (Km).

Alanine↗
PubMed1981

Stability of polyadenylated mRNA in pig lymphocytes.

The stability of cytoplasmic poly(A)-containing mRNA in unstimulated pig lymphocytes has been determined by [3H]poly(U) hybridization after actinomycin D treatment. This approach has shown that the majority of the mRNA is much more unstable than has been suggested by earlier pulse-chase experiments, and has a half-life of between 1 and 2 h.

Animals↗
PubMed1979

Translational activity of messenger ribonucleic acid isolated from unstimulated and phytohaemagglutinin-activated lymphocytes.

Purified cytoplasmic poly(A)+ RNA isolated from unstimulated pig lymphocytes has the same ability to direct translation in a range of cell-free systems as the corresponding mRNA from 20h phytohaemagglutinin-activated lymphocytes. Additional methylation of the mRNA is not required for maximum protein synthesis in the wheat-germ cell-free system. Misleading results are obtained if the mRNA preparations used are not adequately purified, and a method suitable for routine assessment of the degree of purification achieved is described. Cell-free protein-synthesizing systems from unstimulated lymphocytes translate added lymphocyte mRNA with lower efficiency than do comparable systems from phytohaemagglutinin-activated lymphocytes, whatever the source of the mRNA used.

Animals↗
PubMed1979

Distribution of lymphocyte messenger RNA during stimulation by phytohaemagglutinin.

Additional of phytohaemagglutinin to cultured lymphocytes results in a progressive increase in the rate of protein synthesis of up to 7-10 times the initial rate after 20 h. Between 2 h and 12 h after the addition of mitogen, the increase in the rate of protein synthesis can be accounted for by the transfer of mRNA from messenger ribonucleoprotein complexes to polysomes. Between 12 h and 20 h the increase also reflects the accumulation of mRNA and ribosomes. However, the proportion of mRNA associated with ribosomes in unstimulated lymphocytes is unexpectedly high and paradoxically decreases during the first 2 h after mitogen addition, although the rate of protein synthesis increases. A mechanism involving mRNA selection is suggested.

Animals↗
PubMed1979

Enhanced transport of natural amino acids after activation of pig lymphocytes.

Na+-dependent uptake of the amino acids L-proline and L-methionine was greatly accelerated when pig lymphocytes were activated with phytohaemagglutinin or other mitogens. The increased influx was apparent after incubation with phytohaemagglutinin for 1 h, and reached a maximum after 24 h. The lymphocytes appear to possess at least three different transport systems for neutral amino acids with properties similar to, but not identical with, those described for other cells. The activity of a system resembling the A system of other cells was increased most dramatically after activation, its activity in unstimulated lymphocytes being extremely low or absent. A second Na+-dependent system, which has properties similar to those of the ASC system in other cells, but with a broader specificity for amino acids, was more active in unstimulated lymphocytes, and uptake by this system was also accelerated after incubation with phytohaemagglutinin. The activity of a third system, very similar to the L system in other cells, was increased to a much smaller extent after lymphocyte activation.

Amino Acids↗
PubMed1979

Enhanced stability of the Na+-dependent amino acid-transport system after lymphocyte activation.

The Na+-dependent transport system for the amino acid proline in unstimulated lymphocytes decays with a half-life of about 4 h when protein synthesis is inhibited by cycloheximide, but the system in mitogen-activated lymphocytes is more stable. However, the early increase in activity of this transport system after mitogen addition is not due to a direct effect on its stability, but is a secondary effect requiring protein synthesis.

Animals↗