Selective localization of lymphoblasts prepared from guinea pig intestinal lamina propria

The tissue localization patterns of radiolabeled dividing cells obtained from gut lamina propria (LP), mesenteric (MLN) and peripheral (PLN) lymph nodes, and Peyer's patches (PP) were studied in guinea pigs using an adoptive lymphocyte transfer method. Within 24 hr ¹²⁵I-deoxyuridine-labeled cells from donor LP and MLN, but not PLN, selectively localized in recipient gut and MLN. In contrast, donor PLN lymphoblasts returned to their sites of origin while labeled PP donor cells exhibited no specific tissue localization. These findings suggest that the gut LP, like the MLN, contains a population of cells which, unlike those in the PP and PLN, has the capacity to selectively localize in mucosal tissues. From this and other published work, we conclude that within the LP there is a population of cells at different stages of differentiation with a propensity to populate mucosae.     

Interaction of DNA with a porphyrin ligand: evidence for intercalation.

The porphyrin photosensitizer, meso-Tetra (4-N-methylpyridyl) porphine tetraperchlorate binds to calf thymus DNA by intercalation and by external electrostatic association. This was concluded from the results of measruements involving Scatchard analysis, viscometry, thermal denaturation, and circular dichroism.     

CELL PROLIFERATION IN THE ERYTHROID COMPARTMENT OF GUINEA-PIG BONE MARROW: STUDIES WITH 3H-THYMIDINE

Single and multiple injections of ³H-TdR have been used for measuring the rate of proliferation in morphologically defined cell populations of guinea-pig bone marrow that are committed to erythroid differentiation. The conclusions are based on the analysis of absolute cell numbers in the maturational compartments, the labeling and mitotic indices, labeled mitotic curves, pulse and chase grain counts over dividing and interphase cells, and on the rate of labeling during multiple, repeated injections of ³H-TdR. The average duration of S and the rate of cycling is similar in all maturational compartments of the erythron. The majority of cells progress to the next maturational compartment by the time they divide for the second time. All proerythroblasts and basophilic erythroblasts are in cycle. Polychromatic erythroblasts incapable of incorporating ³H-TdR reach the orthochromatic population in the span of 5–6 hr. The orthochromatic population is renewed every 20–24 hr. The number of divisions between the proerythroblast and orthochromatic erythroblast does not exceed four and some cells may undergo only two divisions during the maturation pathway. Cell input from a progenitor cell population contributes to the maintenance of the erythron. The kinetic behavior of progenitor cells is similar to that of proerythroblasts. By the time of their second division, progenitor cells may reach either the proerythroblast or basophilic erythroblast compartments. The kinetic behavior of basophilic transitional cells corresponds to the predicted behavior of the erythroblast progenitor cell pool. Several of the conclusions are based on the assumption that grain count halving is the result of cell division. In view of the evidence discussed, this assumption in the present studies seems justified.     

Stimulation of melanotic expression in a melanoma cell line by theophylline

Theophylline, a phosphodiesterase inhibitor, was found to be a potent stimulator of melanogenesis in the RPMI 3460 hamster melanoma cell line. This stimulation was greater than that caused by either dibutyryl cyclic AMP (db-cAMP) or another phosphodiesterase inhibitor, papaverine. Theophylline and db-cAMP treatments also produced strikingly different morphologies in the monolayered cells. The theophylline effect on melanogenesis was diminished by db-cAMP, whereas simultaneous treatment of cells with db-cAMP and papaverine produced greater stimulation of melanotic activity than either agent acting alone. Theophylline, therefore, may have phenotypic effects that are at least partially independent of phosphodiesterase inhibition. Theophylline stimulated melanin biosynthesis, as measured by rates of 2- [2-¹⁴C] thiouracil incorporation, and also caused an increase in the level of tyrosinase (EC 1.10.3.1) activity. This melanotic stimulation was prevented by the presence of cordycepin or cycloheximide. Theophylline inhibited DNA synthesis and mitosis in the melanoma cell cultures but stimulated protein synthesis. However, inhibition of proliferation and the first appearance of induced melanotic activity did not bear an immediate direct relationship to one another.