F. Šorm

5-Azacytidine, a new, highly effective cancerostatic.

Die hohe bakteriostatische und cancerostatische Wirkung eines neuen Antimetaboliten, 5-Azacytidin, wird beschrieben.

Distribution of 5-methylcytosine in pyrimidine sequences of deoxyribonucleic acids.

Abstract Several samples of DNA from different mammalian organs and from wheat germ were degraded with Burton reagent and the location of derivatives of 5-methylcytosine in separate fractions of the hydrolysate was investigated. In mammalian DNAs 5-methylcytosine was found to occur almost exclusively in the fraction of solitary pyrimidine nucleotides and in the terminal groups of polypyrimidine series carrying monoesterified phosphorus on C-3′ of deoxyribose. The ratio of 5-methylcytosine to cytosine was nearly identical in these positions. In the DNA from wheat germ the highest degree of replacement occurred in similar positions, but a fairly high amount of 5-methylcytosine was found in the sequence MpT. The relation of these findings to earlier evidence obtained by enzymic degradation of DNA is discussed. It is concluded that the replacement of cytosine by 5-methylcytosine is determined by the nature of the nucleotide attached to C-3′ of deoxycytidine. The replacement occurs with highest probability in the sequence CpG; somewhat less probable is the replacement in the sequence CpT, whereas in the sequences CpM, CpC and CpA the substitution takes place only rarely, even in preparations with high overall content of 5-methylcytosine.

Covalent structure of bovine trypsinogen. The position of the remaining amides

Our recent paper concerning bovine trypsinogen1,2 presented a description of the primary structure of this protein, including the disulfide bridges. However, at that time an unequivocal assignment of all amino acid residues had not been made for several amino acid residues (positions 121, 177, 180). Thus it was not known whether these residues occurred in the form of acids or amides. The aspartic acid residue in position 151 has now been correctly determined as asparagine. The aim of the present communication was to remove all these uncertainties and to complete the investigation of the covalent structure of this protein. A preliminary report of this work was presented at the Third Federation Meeting of European Biochemical Societies3.

Incorporation of 5-Azacytidine into nucleic acids of Escherichia coli

Abstract The kinetics of incorporation of [14C]5-azacytidine into different species of nucleic acids have been investigated. 5-Azacytidine is incorporated into both RNA and DNA; if the incorporation is terminated by the addition of excess of cytidine, the rapidly-labeled RNA is transformed and the radioactivity is found in rRNA and tRNA. 20–30 % Cytidine is replaced by 5-azacytidine in RNA newly formed in its presence, and almost the same extent of replacement is found in DNA. A part of 5-azacytidine may be recovered from RNA by enzymic degradation. All species of RNA containing 5-azacytidine have normal sedimentation constants. RNA pulse-labeled in the presence of 5-azacytidine is capable of forming hybrids with homologous DNA. The synthesis of β-galactosidase is completely inhibited when 5-azacytidine is present during the synthesis of mRNA; if a messenger formed before its addition is utilized, little inhibition is observed.

Inhibition of protein synthesis by 5-azacytidine in Escherichia coli.

Abstract 1. 1. When 5-azacytidine is added to a culture of Escherichia coli induced to synthesize β-galactosidase, the synthesis of the enzyme slows down immediately and comes to complete rest about 12 min after the addition of the inhibitor. Upon addition of either cytidine or uridine, the synthesis of the enzyme is resumed at full or reduced speed, depending on the time of action of 5-azacytidine. 2. 2. Total protein synthesis is inhibited by 5-azacytidine to about 6 % of the control. Synthesis of RNA, as measured by pulse labelling with adenosine or uridine, is slightly inhibited. General inhibition of RNA synthesis is never observed. 3. 3. 5-Azacytidine does not inhibit the synthesis of DNA, as measured by incorporation of thymidine. Whereas in a normally growing culture the incorporation of thymidine soon ceases as a result of conversion of thymidine to thymine by thymidine phosphorylase, in the culture treated with 5-azacytidine the incorporation of thymidine proceeds indefinitely at a constant rate. The synthesis of inducible thymidine phosphorylase is inhibited by 5-azacytidine, whereas the action of the pre-formed enzyme is not affected. 4. 4. In a culture containing 5-azacytidine an unbalanced growth is observed, resulting from concurrent inhibition of protein synthesis, cessation of cell division and growth and continued synthesis of DNA. 5. 5. It is concluded that 5-azacytidine inhibits protein synthesis by selectively affecting the function of some species or portion of RNA essential for protein synthesis.

Natural and synthetic materials with insect hormones activity 8. Juvenile activity of the farnesane-type compounds on Galleria Mellonella

Abstract Farnesol, farnesyl ethers, farnesoate esters, and similar compounds act as potent analogues of juvenile hormone on several insect species (1,2,3). In tests on the larvae of Galleria mellonella , however, these chemicals displayed only very slight activities (unpublished observation). Their failure to induce a juvenilizing effect was puzzling since the larvae readily react to tiny amounts of Cecropia juvenile hormone (4,5) which is structurally related to farnesane-type sesquiterpenoids. Being stimulated by the contrast between the high activity of natural juvenile hormone (JH) and the negligible activity of farnesyl ethers and alkyl farnesoates, we started a detail investigation of the relation between the chemical structure and the juvenile hormone activity. This report describes the activity of compounds with the farnesane carbon skeleton but differing in the number of double bonds and the presence of halogen atom(s) or oxirane ring(s) in the molecule. It has been well established that there are great species specific differences in the activity of JH-analogues; e.g. the juvabione and related compounds act on Pyrrchocorids but not on other bugs (6). No attempts have been made, however, to examine whether similar differences do not exist also between successive developmental stages of a single species. Aiming to this goal, we employed in our tests both larvae and pupae of Galleria .

The biosynthesis of 6-azauracil riboside byEscherichia coli growing in the presence of 6-azauracil

Bei der Kultivierung vonE. coli in 6-azaurazilhaltigem Medium wird ein neuer Stoff akkumuliert, der als 6-Azaurazilribosid identifiziert wurde.

The anticancerous action of 6-azauracil (3,5-dioxo-2,3,4,5-tetrahydro-1,2,4-triazine)

Es wurde die kanzerostatische Wirkung des 6-Azauracils auf den Ehrlich-Aszites-Tumor beschrieben und mit der Wirkung des 6-Mercaptopurins verglichen.

Effect of 5-azacytidine on developing mouse embryo

5-Azacytidin wurde trächtigen Mäusen am 4.–6. und 11.–13. Tag verabreicht. Bei der ersten Gruppe zeigte sich eine völlige Resorption der Feutusse, während in der zweiten Gruppe hauptsächlich die Leber und das Nervengewebe geschädigt waren. In der ependymalen Zone werden die in Teilung befindlichen Zellen in der Metaphase gestoppt und unterliegen einer pyknotischen Degeneration.

The utilization of L-adenosine by mammalian tissues

Recently, we have been interested in a systematic study of the behaviour of L-nucleosides and nucleotides. These compounds, enantiomers of the naturally occurring nucleic acid components, are now easily accessible by unequivocal synthetic procedures [l-3] which eliminate any possibility of contamination by natural derivatives. On investigation of numerous enzymes and enzymatic systems in vitro it has been demonstrated [3,4] that the nucleotide derivatives of the L-ribo series are resistant towards many nucleolytic enzymes as determined by the mode of binding of the nucleoside residue to the enzyme molecule. This observation led us to investigate the biochemical properties of L-nucleosides in uivo. The experiments with bacterial cells showed that there is essentially no transport of L-ribonucleosides through the cell wall of the bacteria investigated [S] . Thereafter, we examined the possibility of L-nucleoside utilization in mammalian tissue systems in viva. In this paper we report the results obtained with L-adenosine applied intraperitoneally to mice.