Inhibition of the synthesis of polyamines and macromolecules by 5′-methylthioadenosine and 5′-alkylthiotubercidins in BHK21 cells

5′-Methylthioadenosine and four 5′-alkylthiotubercidins were tested for their ability to inhibit polyamine synthesis in vitro and to decrease polyamine concentration and prevent growth of baby-hamster-kidney (BHK21) cells. 5′-Methylthioadenosine and 5′-methylthiotubercidin decreased the activity of spermidine synthase from brain to roughly the same extent, whereas brain spermine synthase was much more strongly inhibited by 5′-methylthioadenosine compared with 5′-methylthiotubercidin. These nucleoside derivatives also inhibited the growth of BHK21 cells and increased the concentration of putrescine. 5′-Methylthioadenosine decreased cellular spermine concentration, whereas 5′-methylthiotubercidin lowered the concentration of spermidine. The activities of ornithine decarboxylase and S-adenosylmethionine decarboxylase were enhanced in cells grown in the presence of 5′-methylthiotubercidin. The growth inhibition produced by these nucleoside derivatives was not reversed by exogenous spermidine or spermine. 5′-Ethylthiotubercidin, 5′-propylthiotubercidin and 5′-isopropylthiotubercidin did not appreciably inhibit spermidine or spermine synthase in vitro or decrease the cellular polyamine content, but effectively prevented the growth of BHK21 cells. All nucleoside derivatives at concentrations of 0.2–1 mm caused a rapid inhibition of protein synthesis. It is concluded that the growth inhibition produced by 5′-methylthioadenosine and 5′-alkylthiotubercidins was not primarily due to polyamine depletion but other target sites, for instance the cellular nucleotide pool, cell membranes etc. must be considered.     

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.     

THE ROLE OF STRESS HORMONES IN THE CONTROL OF GRANULOCYTE PRODUCTION

It has previously been indicated that the inhibitory power of the granulocytic chalone is not influenced by adrenalin. It is now shown that this is true both in absence and in presence of exogenous hydrocortisone. It is also shown that hydrocortisone itself does not cause significant inhibition of DNA synthesis in rat bone marrow cells in vitro, but that it does act to augment the inhibitory effect which the granulocytic chalone induces. It is suggested that the primary action of hydrocortisone may be on the cell membrane which changes the cell wall permeability to chalone, perhaps by reducing its rate of loss from the cells.     

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. Mature granulocytes contain, and presumably produce, the chalone which is also present in fresh normal serum. Thus, the inhibitor is both humoral and present within the same cell system on which it acts: the action of this chalone is target tissue specific as it only inhibits granulocytic precursor cells in normal rat bone marrow in vitro. Granulocytic chalone and antichalone were partly purified by gel filtration on Sephadex; the elution parameters suggested molecular weights of 4000 and 30,000–35,000, respectively. Granulocytic chalone was not separated from the erythrocytic chalone (present in fresh normal serum and in blood erythrocytes) on Sephadex; however, separation at the cellular level was easily achieved.     

Sagittal otolith growth patterns in regularly and irregularly spawning burbot,Lota lota,in northern Finland

Synopsis Sagittal otolith growth patterns were compared among three burbot,Lota lota, populations in northern Finland. Coastal burbot off Simo on the northern coast of the Bothnian Bay and lake burbot from Lake Kemijärvi represented populations with about 30% non-spawning adult individuals, while the river burbot from the River Kitinen spawned regularly. Irregular growth patterns i.e. crenulations on the dorsal edge of the sagitta and pointed extensions in the rostrum region and cloudy appearance of the sagittal otoliths, as observed by light, scanning and transmission microscopy, occurred significantly more often in the coastal and lake burbot than in the river burbot. This could not be explained by differences in age or size. Its possible relationship to supposed reproduction disorder is discussed.