T. Rytömaa

CONTROL OF GRANULOCYTE PRODUCTION

In normal conditions the granulocytic cell population is prevented from excessive cell proliferation by a humoral mechanism based on a specific feedback inhibitor, granulocytic chalone. In conditions of acute functional demand a tissue‐specific stimulator, granulocytic antichalone, replaces chalone in rat serum.

ERYTHROCYTIC CHALONE, A TISSUE-SPECIFIC INHIBITOR OF CELL PROLIFERATION IN THE ERYTHRON

Control of the rate of cellular proliferation in the erythron seems to be mediated by a tissue‐specific mitotic inhibitor, termed the erythrocytic chalone. the function of this substance seems to be to prevent excessive proliferation of the erythrocyte precursor cells by means of a negative feedback and in terms of peripheral cell numbers.

Regression of Generalized Leukaemia in Rat Induced by the Granulocytic Chalone

Abstract It has been shown in this study that granulocytic chalone inhibits DNA synthesis in normal and leukaemic cells (chloroleukaemia in rat and chronic myeloid leukaemia in man), and that this inhibition is tissue specific to the granulocytic system. In contrast to this granulocytic chalone is not species specific either in respect to its origin or to its inhibitory action. The most important result of the present study is the demonstration that generalized leukaemia in rat (chloroleukaemia) can be completely and permanently cured by means of the granulocytic chalone. With the maximum dose used in this study the survival time was prolonged in all the treated rats and in 9 animals out of the 40 the leukaemia disappeared completely and permanently. The implication from the in vitro results with rat and man and from the in vivo results with rat is that cures of leukaemia may also be obtained on man.

THE CELL SPECIFIC EFFECT OF THE GRANULOCYTE CHALONE DEMONSTRATED WITH THE DIFFUSION CHAMBER TECHNIQUE

The granulocytic chalone is secreted by mature granulocytes and inhibits 3H‐thymidine incorporation of proliferating granulocytes in vitro. The effect and the cell line specificity of this chalone was assessed with the in vivo diffusion chamber culture technique. Tests were carried out on cultures from normal mouse bone marrow cells and mouse and rat blood leucocytes. The majority of the DNA synthesizing cells in marrow cultures were proliferating granulocytes. Macrophages and immunoblasts proliferated in rat leucocyte cultures, when the chambers had been carried for 5 days in host mice. Repeated chalone or control injections were given i.p. to the host mice during 6–7 hr prior to 3H‐thymidine injection. Isotope uptake of proliferative granulocytes was reduced by the chalone treatment. No such effect was found on the rat immunoblasts and macrophages. The viability of cultured cells was apparently not affected by the chalone treatment.

ROLE OF CHALONE IN GRANULOPOIESIS

Chaloiies are tissue-specific, species non-spccific regulator substances which are produced within the same tissue on which they act, and which inhibit cell proliferation in a reversible manner (Bullough & Rytomaa, 1965; Bullough, 1965). So far 12-13 different chalone systems have been described in the literature, but only a few have been studied in any detail; one of these is the graiiulocytic chalone. This article reviews the present state of knowlcdge of the chemical and biological characteristics of the granulocytic chalone.

Inhibition of Granulopoiesis by Endogenous Granulocyte Chalone Studied with the Diffusion Chamber Technique

Abstract This study showed that growth of granulocytes, both normal and leukaemic, is inhibited in a specific manner in diffusion chamber cultures carried by chloroma-bearing host rats (→ elevated granulocyte chalone content in the body). This inhibition could be demonstrated directly by a reduced formation of granulocytes and by measuring the 3H-thymidine uptake in the cells. Non-granulocytic cell lines (mastocytoma and HeLa cells) were not detectably inhibited when grown in identical conditions. The inhibition of granulocytic cells did not depend on a selective immunological reaction developed against granulocytic cells in the chloroma-bearing host rats.

The effect of early excision on bone-marrow cell growth in burned mice*

Summary Tritiated thymidine was used in vitro to study mouse bone-marrow cell proliferation at different intervals after severe burn injury. As observed before, strong inhibition was seen in bone-marrow cell production in the early post-burn period, which impairs host resistance to infections. When the wound area was excised early, the inhibition in bone-marrow cell production was totally eliminated. When the excision was made 2–4 hours post burn 3 H-TdR incorporation into the bone-marrow cells was even significantly increased. It is suggested that early removal of necrotic tissue can reduce deleterious antigenic materials and hence decrease general cell destruction and growth inhibition in the burned organism.

Regulation of maturation rate of mouse granulocytes.

Regenerating mouse bone marrow cells were cultured i.p. in diffusion chambers (DC) to study factors affecting the maturation rate of granulocyte precursors. One day after exposing 3‐day‐old DC cultures to 3H‐thymidine the cultures were harvested, and labelled proliferative and non‐proliferative granulocytes were counted in radioautographs. The relative maturation rate—defined as the fraction of proliferative precursors maturing into the non‐proliferative compartment per unit time—could be increased by different experimental procedures that inhibit cell production. Inhibition was obtained (a) by increasing culture cellularity; (b) by implanting DC into normal rats or rats with huge s.c. chloroma tumours rather than into mice; and (c) by treating the cells with leucocyte extracts (granulocyte chalone) during the last day of culture. Furthermore, a sudden inhibition of rapidly proliferating granulocytes by leucocyte extracts resulted in an increase (apparently transient) in the absolute number of labelled non‐proliferative granulocytes. Such an increase was not detected in experiments involving a stronger or sustained inhibition of granulopoiesis, evidently because the size of the precursor population had been markedly reduced.

Chalones: concepts and results.

Control of cell proliferation is executed, in part, by means of negative feedback, utilizing cell-line specific messenger substances called chalones. Although knowledge of chalone chemistry is still in its infancy, the reality of the concept can no longer be reasonably questioned. In particular, it has recently been shown that chalones are even capable of causing tumour regression both in animals and in man. In addition to overviewing the chalone concept, we show here that the chalone-induced tumour regression is readily explained in simple and plausible terms.

Proliferation kinetics of Shay chloroleukaemia cells grown in diffusion chambers in vivo.

The proliferation kinetics of Shay chloroleukaemia cells was studied by the labelled mitoses technique and some other methods. Detailed estimates of the phase durations of the cell cycle for proliferating cells were obtained using young, exponentially growing diffusion chamber cultures; estimates of kinetic parameters were also obtained for ‘old’ cultures and for local subcutaneous chloroma tumours. The results enabled determination of the growth fraction and the cell loss factor.