Kerstin G. Eriksson

Angiostatin and endostatin inhibit endothelial cell migration in response to FGF and VEGF without interfering with specific intracellular signal transduction pathways.

The anti‐angiogenic agents angiostatin and endostatin have been shown to affect endothelial cell migration in a number of studies. We have examined the effect of these agents on intracellular signalling pathways known to regulate endothelial cell migration and proliferation/survival. Both agents inhibited fibroblast growth factor (FGF)‐, and vascular endothelial growth factor (VEGF)‐mediated migration of primary human microvascular endothelial cells and affected vascular formation in the embryoid body model. However, using phosphospecific antibodies we could not detect any effect of angiostatin or endostatin on phospholipase C‐γ (PLC‐γ), Akt/PKB, p44/42 mitogen‐activated protein kinase (MAPK), p38 MAPK and p21‐activated kinase (PAK) activity. Furthermore, using a glutathione S‐transferase (GST)‐PAK pull‐down assay, we could not detect any effect on Rac activity. We conclude that angiostatin and endostatin inhibit chemotaxis, without affecting intracellular signalling pathways known to regulate endothelial migration and proliferation/survival.

STUDIES ON MICROBIAL RNA. I. TRANSFER OF METHYL GROUPS FROM METHIONINE TO SOLUBLE RNA FROM ESCHERICHIA COLI.

Two partially purified enzyme preparations, one from yeast and one from Escherichia coli, have been used to study the transfer of methyl groups from methionine to soluble RNA (S-RNA) from E. coli. The reaction requires ATP and magnesium. The E. coli enzyme can incorporate methyl groups only into S-RNA from methionine-starved E. coli K12 W6 (a mutant with a deficient control of RNA synthesis). The yeast enzyme can methylate S-RNA from E. coli K12 in log phase as well as from methionine-starved cultures of W6. The methylation is not inhibited by periodate oxidation of the terminal adenosine residue in the S-RNA. The alkaline stability of the methylated S-RNA is clearly different from that of methionyl RNA. Methylated S-RNA has been degraded by snake venom enzymes as well as by alkaline hydrolysis. The digestion products have been examined by paper and anion exchange chromatography, respectively. In vitro, neither of the two enzymes can methylate purified ribosomal RNA (R-RNA). In vivo incorporation of methionine has, however, shown a significant methylation of both S-RNA and R-RNA. The composition of the methylated nucleosides obtained from R-RNA differs from that of S-RNA. Total RNA contains also smaller amounts of non-methylated RNA. Counter-current distribution of S-RNA has shown that the acceptors for the methyl groups can be separated from the acceptors for tyrosine.

Penicillin Induced Lysis in Escherichia coli

SUMMARY: The paper is a survey of the action of α-aminobenzylpenicillin (ampicillin) on Escherichia coli. The rate at which lysis was induced in exponentially growing organisms was studied for different concentrations of ampicillin, using pure D- and L-forms as well as a 6:4 mixture. The interpolated concentration of penicillin which gives lysis in one generation, the ‘LIOG value’, has been used for characterization of penicillin derivatives with twelve different side chains. These LIOG values were also used for characterization of some penicillin-resistant mutants. The lysis rate has been recorded for cultures of concentrations between 4 x 105 and 108 rods/ml, and found to be independent of the population density. The use of five different media showed that for a given ampicillin concentration the time to lysis was proportional to the growth rate. The addition of penicillinase to a culture growing with penicillin rescued the organisms as late as a few minutes before lysis. Synergistic effects on the lysis rates were found with 6-amino-penicillanic acid and two amino acids, which as residues are side chains, in two of the penicillins tested. Different models for penicillin action in E, coli are discussed.