Mesoderm-inducing factor from bovine amniotic fluid: purification and N-terminal amino acid sequence determination.

Bovine amniotic fluid contains a protein capable of inducing mesoderm formation from animal cap cells isolated from Xenopus laevis embryos at the late blastula stage. The procedure for purification of this protein is described and includes the following steps: CM-cellulose cation-exchange chromatography, chromatography on hydroxylapatite, reverse-phase hplc, size exclusion hplc, and a second reverse-phase hplc. A partially purified preparation of a mesoderm-inducing factor with high mesoderm-inducing activity was thus obtained. SDS polyacrylamide gel electrophoresis with subsequent transfer of proteins onto Immobilon membrane was used to obtain the protein in pure form. The membrane was cut, the proteins eluted, and each fraction tested for mesoderm-inducing activity. The mesoderm-inducing activity corresponded to a protein of molecular mass 25 kDa (in nonreducing conditions) consisting of two identical polypeptides connected by disulphide bonds. The purified factor, at concentrations of 0.3-1 pmol ml-1, induced development of notochord and muscle cells and, at lower concentrations, mesenchyme and blood cells. The twenty N-terminal amino acid residues of the protein were sequenced and found to be identical to those of the N-terminus of the beta A-chain of inhibin and activin, known regulators of FSH secretion by pituitary cells. The beta A-chain is homologous with the transforming growth factor-beta family of proteins. On the basis of the estimated molecular mass of the mesoderm-inducing factor and its N-terminal sequence it is suggested that the protein is activin or a related protein.

[T-lymphocyte induced normalization of transformed malignant fibroblasts: lymphokine with normalization factor activity]. / Indutsirovannaia T-limfotsitami normalizatsiia transformirovannykh zlokachestvennykh fibroblastov: limfokin s aktivnost'iu faktora normalizatsii.

Normalizing influence of different lymphocyte populations and their soluble factors on L-929 transformed malignant fibroblasts (L cells) has been examined. It was demonstrated that splenic T-lymphocytes caused stable (heritable) normalization of receptor apparatus, biophysical and proliferative characteristics of L cells. Lymphokine with the activity of normalization factor (NF) was purified from 24-hour immunocyte conditioned medium. Stability of the normalization phenomenon was caused by NF induced synthesis of functionally analogous factor in L cells. The results obtained indicate the existence of non-cytotoxic mechanisms of tumour growth immunological control. The isolated lymphokine possessed also the activity of early embryonal cell differentiation factor. It is suggested that lymphokines with the activity of NF are physiological regulators of nonlymphoid cell differentiation.

[Detection of factors of differentiation in human malignant melanoma]. / Vyiavlenie faktorov differentsirovki v zlokachestvennykh melanomakh cheloveka.

Factors of differentiation (FD) have been detected and isolated from human melanomas cloned in nude mice as well as from amphibian embryos from neurula--early tail bud stage. It has been shown that each source contains two factors of differentiation--mesodermalizing (MF) and melanogenic (MgF). Biological activity of MF has been determined by its capacity to initiate in early embryonic multipotent cells the appearance of various cell types, normally arising from mesoderm. Biological activity of MgF have been determined by its capacity to initiate melanogenesis both in epithelial cells and in dermal melanophores of clawed toad. It has been shown that both factors, isolated from both sources are heterogeneous by their molecular weights. Mr values determined for MgF, isolated from both sources, are nearly identical whereas Mr values of MF from sources coincide partially. Resemblance of FD detected in remote representatives of animal kingdom suggest the high evolutionary conservatism of factors, which switch on cell differentiation.

[Dynamics of vitamin B12 (cyanocobalamin) sorption by silochrome C-120]. / Issledovanie dinamiki sorbtsii vitamina B12 (tsiankobalamina) silokhromom C-120.

Sorption of cyanocobalamin (vitamin B12) by silochrome C-120 of various graininess levels was studied under dynamic conditions. It was shown that the low-grained sorbent provided marked increasing of the cyanocobalamin sorption rate and enabled the use of the sorbent thin layers at high rates of the solution supply.