Differential effects of positive and negative proliferative stimuli on murine cytolytic and helper T-cell clones

Studies were performed to determine whether substances could be identified which exhibited differential regulatory effects--either positive or negative--on the growth of murine alloreactive cytolytic (Tc) and helper (Th) cloned T-cell lines. The following lines of evidence suggested that Tc and Th proliferate in response to the same growth factor (GF). (1) When GF-containing fluids from cultures of phorbol myristic acetate (PMA)-activated EL4 thymoma were fractionated by a variety of biochemical techniques. Tc and Th eluted together. (2) Absorption of GF-containing supernatants with either cloned Tc or cloned Th depleted GF activity for each to a similar extent, and GF eluted from either Tc or Th to which it had adsorbed supported the proliferation of Tc and Th equally well. (3) Lectin-depleted supernatants from cultures of concanavalin A (Con A)-activated Th stimulated the proliferation of Th as well as Tc. (4) Recombinant human interleukin (IL-2) supported the growth of Tc and Th with equal efficiency. On the other hand, the following observations indicated that Tc and Th differed in their responses to inhibitors of GF-driven proliferation. (1) Con A at greater than or equal to 0.3 micrograms/ml inhibited the GF-driven proliferation of each of three Th lines but not either of two Tc lines. To the contrary, Con A enhanced GF-dependent proliferation of Tc. (2) Like Con A, allogeneic splenocytes selectively depressed GF-driven proliferation of Th but not Tc. (3) A substance generated during the acid elution of GF from cells, possibly a modified fetal calf serum component, greatly reduced the GF-driven proliferation of Tc but not Th. These results suggest that differential control of the proliferation of Tc and Th in cellular immune responses may be achieved via negative regulatory signals and raise the possibility that substances which can selectively depress the proliferation of specific T-cell subsets might be found which would be of therapeutic value.     

Free amino Acid pools and enzymes in teratonia and habituated tobaceo tissue cultures

The free amino acid content of habituated (normal) and teratoma (abnormal) tobacco tissue cultured on white's medium were compared. Significant qualitative differences (twofold or more) were observed for serine, proline, alanine, leucine, phenylalanine, and lysine. There were qualitative differences in several unidentified ninhydrin sensitive compounds. One unknown which co-chromatographed with homo-serine was present in high concentrations (9.96 μmol/g dry weight) in habituated but was lacking in teratoma tissue, Isoenzymes of an esterase, acid phosphatase, and oxidase were demonstrated in both tissues. The distinct differences in the isoenzyme pattern of acid phosphatase suggests a differential regulatory capacity of certain phosphomonoester intermediates and P(1) . The invertase activity was higher in habituated tissue, implying a greater capacity to utilize the sole carbon source, socrose.     

IAN-bildung aus glucobrassicin: pH-Abhängigkeit und wachstumsphysiologische Bedeutung

Summary Indole auxin synthesis during enzymatic hydrolysis of glucobrassicin by myrosinase proved to be strictly dependent on pH. Neither IAN nor other indole compounds with auxin activity are synthesized at pH values higher than 5.2. An in vivo function of the indole glucosinolates as auxin precursors in Cruciferae is therefore of low probability.