A differential effect of L-serine on the incorporation of3H-deoxycytidine and3H-thymidine into DNA of rat thymocytes

Summary The addition of L-serine to short-term cultures of rat thymocytes stimulated the incorporation of³H-deoxycytidine into DNA, but simultaneously depressed the incorporation of³H-thymidine into DNA.This investigation was supported by NIH grants No. CA-10291 and T12CA8021 from the National Cancer Institute.     

Etude autoradiographique de l'incorporation de la thymidine-3H,de l'uridine-3H et de la phénylalanine-3H dans les chloroplastes deClivia miniata etBilbergia sp.

Summary Mature chloroplasts ofClivia miniata etBilbergia sp. show the intensive incorporation of thymidine³H into DNA and uridine³H into RNA. On the contrary, phenylalanine³H is mostly incorporated in the proplastids.     

Aufnahme von thymidin durch mastocytomzellenin vitro unter der einwirkung von podophyllumstoffen

Summary SP-G and SP-I, two podophyllum preparations with spindle poison activity, were tested for their effect on³H-thymidine incorporation into P-815 mastocytoma cellsin vitro. Concentrations which inhibited cell multiplication completely did not affect DNA-synthesis as measured by thymidine incorporation.     

Relationship between DNA and cholesterol synthesis in kidney after refeeding

Summary DNA and cholesterol synthesis were investigated in the kidneys of fasted-refed rats. Refeeding resulted in an increase in kidney DNA synthesis, as measured by³H-thymidine incorporation, starting at 72 h. The increase in DNA synthesis was accompanied by a stimulation of cholesterol synthesis, as measured by¹⁴C-acetate incorporation into cholesterol.     

Effect of sodium octanoate on leucine incorporation into protein of rat liver slices and of Yoshida ascites hepatoma cells

Summary 7.38×10^–4 M octanoate does not significantly modify leucine incorporation into protein of rat liver slices, while in hepatoma cells a 19% inhibition has been noted.3.69×10^–3 M octanoate reduces leucine incorporation to about the same extent (71–76%) in both liver slices and hepatoma cells.     

Serum cholinesterase: Function in lipoprotein metabolism

Summary Human serum beta-lipoproteins, isolated by percipitation with heparin-calcium mixture, showed cholinesterase activity. The enzyme activity was almost proportional to the lipoprotein concentration. Rats, treated with neostigmine, a cholinesterase inhibitor, showed a significant decrease in serum beta-lipoprotein and in the incorporation of H³-lysine into the lipoprotein compared to untreated controls. The decreased incorporation of H³-lysine into beta-lipoprotein was associated with increased labelling of alpha-lipoprotein. There was no significant difference in the labelling of pre-beta-lipoprotein. We propose that LDL is formed from VLDL in the presence of cholinesterase.We thank Dr C. J. Hutton for helpful discussions, Miss Patricia Fontaine for technical assistance, and Miss Patricia Candow and Mrs Barbara English for secretarial work. Supported by the Canadian Heart Foundation.     

In vitro effects of methionine-enkephalin,somatostatin and insulin on cultured gonadal cells of the snailHelix aspersa

Isolated snail gonadal cells were cultured in the presence of synthetic neuropeptides in order to determine the subsequent effect of these substances on gonadal synthetic activities. Gonadal cells were incubated for 24 h in concentrations of methionine-enkephalin, somatostatin and insulin ranging from 10^–4 M to 10^–9 M, in medium 199 supplemented with 6% Ultroser G. Synthesis of DNA and protein by the cultured cells were simultaneously estimated by measuring incorporation of³H thymidine and³⁵S methionine. The rate of labelled precursor incorporation was measured using the liquid scintillation technique. All substances tested exerted a dose-dependent effect. The synthetic activity of the cultured cells was highest when the concentration of the peptides added to the medium approximated the physiological levels. Methionine-enkephalin, somatostatin and insulin at 2×10^–8 M significantly increased³H thymidine incorporation, by 62%, 69% and 69% respectively, and protein synthesis by 42%, 57% and 57%, respectively. In the case of juvenile gonadal cultured cells, a similar increase in³H and³⁵S incorporation was registered for a 10^–7 M peptide concentration. Both lower and higher peptide concentrations inhibited³H thymidine and³⁵S methionine incorporation. Pharmacological studies suggest the existence of methionine-enkephalin and somatostatin-like receptors on snail gonadal cells. These results indicate that our gonadal cell culture model provides a useful tool for the study of the neuroendocrinological control of the activity of snail gonadal cells.     

Synthesis of L-[3-2H,18O]glycerol and its incorporation into the 4-methyl-5-hydroxyethyl thiazole moiety of thiamine byEscherichia coli

Summary L-[3-²H,¹⁸O]glycerol was prepared and fed toEscherichia coli in order to determine the origin of the oxygen atom in the biosynthesized thiazole moiety of thiamine. Measurement by GC-MS of the isotope incorporation into the thiazole from this substrate confirmed that the 2 hydrogens and the oxygen on the C-3 carbon of glycerol are incorporated directly into the thiazole.     

Kinetics of DNA repair synthesis in guinea-pig pancreatic slices following in vitro exposure to N-methyl-N-nitrosourethane

Summary In vitro exposure of guinea-pig pancreatic slices to NMUT resulted in an increase in hydroxyurea-insensitive³H-TdR incorporation into DNA; this represents DNA repair synthesis following NMUT-induced DNA damage. The kinetics of this hydroxyurea-insensitive³H-TdR incorporation suggest that the NMUT-induced DNA damage is largely repaired within 2 hours.Environmental Health Programs, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106 (USA). These studies were supported by National Cancer Institute (Bethesda, Md., USA). Contract No. N01-CP-23284. Technical assistance of MS.Mary Majdan is gratefully acknowledged.     

Influence of cyclic nucleotides on protein synthesis in vascular smooth muscle

Summary The incorporation of leucice-¹⁴C into protein in bovine mesenteric arteries was augmented by cyclic GMP (10^–3 M) and decreased by cyclic AMP (10^–3 M). There was no effect of 5 AMP (10^–3 M). The phosphodiesterase inhibiting drugs theophylline (10^–3 M) and papaverine (5×10^–5 g/ml) both decreased the leucine-¹⁴C incorporation.We are indebted to Mrs.Lena Burlin for hear assistance. Finacial support has been provided by the Swedish State Medical Research Council (No. 04X-101X-4498).     

Untersuchungen über den Wirkungsmechanismus von Procarbazin (Natulan®)

Summary The cytotoxic methylhydrazine derivative procarbazine or Natulan® has a marked influence on the synthesis of deoxyribonucleic acid in Ehrlich ascites carcinoma cells. The incorporation of³H-thymidine into DNA — measured by autoradiographic methods — is inhibited.     

Aberrant,canavanyl protein formation and the ability to tolerate or utilize L-canavanine

Summary L-Canavanine, 2-amino-4-(guanidinooxy)butyric acid, and L-arginine incorporation into de novo synthesized proteins was compared in six organisms. Utilizing L-[guanidinooxy¹⁴C]canavanine and L-[guanidino¹⁴C]arginine at substrate saturation, the canavanine to arginine incorporation ratio was determined in de, novo synthesized proteins.Caryedes brasiliensis andSternechus tuberculatus, canavanine utilizing insects;Canavalia ensiformis, a canavanine storing plant; and to a lesser extentHeliothis virescens, a canavanine resistant insect, failed to accumulate significant canavanyl proteins. By contrast,Manduca sexta, a canavanine-sensitive insect, andGlycine max, a canavanine free plant, readily incorporated canavanine into newly synthesized proteins. This study supports the contention that the incorporation of canavanine into proteins in place of arginine contributes significantly to canavanine's antimetabolic properties.     

Influence of progesterone on protein and RNA synthesis in cultured chick embryo liver cells.

Chick embryo liver primary cultures, when added with progesterone, exhibit, in comparison with the controls, a normal growth, a decline of both 3H-uridine uptake and incorporation into total RNA, a decline of 3H-leucine and 14C serine incorporation into the proteins. Progesterone is not able to stimulate phosvitin synthesis induction.     

Similarities between metallothionein and low molecular weight testicular cadmium-binding protein

Summary The incorporation of³⁵S-cysteine and³H-glutamic acid was studied in mouse hepatic and renal metallothionein and in testicular cadmium-binding protein of similar molecular weight. Preferential incorporation of³⁵S-cysteine over³H-glutamic acid was observed not only in hepatic and renal metallothionein, but also in testicular cadmium-binding protein. When the antigenic reactivity of these proteins was compared, all three proteins reacted with the metallothionein antibody. These similarities suggest that the low molecular weight testicular cadmium-binding protein is apparently metallothionein.     

35S-Sulphate incorporation into myelin sulphated mucopolysaccharides during rat brain development

Summary Rat brain myelin acid mucopolysaccharides (AMPS) incorporate 15%, 8%, 5.5% and 4% of tojtal associated³⁵S-sulphate, 14, 21, 30 and 75 days after birth, respectively. The course of³⁵S-sulphate incorporation into total rat brain mucopolysaccharides, as well in those from myelin, had a similar feature with peak on the 2nd week and a significant decrease on the 3rd and 4th week postnatally.     

Über den Einbau14C-markierter Aminosäuren in Zellkernfraktionen aus Meerschweinchenleberzellenin vitro

Summary The incorporation of¹⁴C-amino acids into ribonucleoproteid particles obtained by differential centrifugation of mechanically disintegrated liver cell nuclei was demonstratedin vitro. Nuclear supernatant revealed also very remarkable incorporation.     

Einbauunterschiede in den Zellschichten des Cortex nach Markierung mitd,l-Prolin-H3 bei der Maus

Summary Autoradiographic studies of the mouse brain following incorporation ofd,l-proline-H³ andl-histidine-H³ show a wide variation of the regional uptake ofd,l-proline into the cerebral nerve cells, in contrast tol-histidine. In the cerebral cortex proline is to be found only in the nerve cells of the lamina ganglionaris (V) and lamina multiformis/infima (VI/VII). Subsequent translocation of radioactivity is indicative of an axoplasmic flow of proline-labelled substances into the distal parts of the neuronal processes.

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Mit dankenswerter Unterstützung durch das Landesamt für Forschung Nordrhein-Westfalen.     

Effects of butyrate and insulin and their interaction on the DNA synthesis of rumen epithelial cells in culture

Summary Rumen epithelial cells (REC) were incubated in the presence of various concentrations of butyrate or insulin or with both of them, to obtain information on their effect on the DNA synthesis of cultured cells. The 24-h values of³H-thymidine incorporation into cellular DNA were measured in the presence of butyrate, insulin or butyrate plus insulin. While butyrate reduced DNA synthesis, insulin produced an increase over the control. Combined butyrate plus insulin treatment influenced the incorporation of label in accordance with the relative proportion of these two substances.     

Stimulation of the incorporation of3H-leucine into proteins by oestradiol in the foetal uterus of the guinea-pig

Summary Oestradiol treatment increases the incorporation of³H-leucine into acid insoluble proteins in the foetal guineapig uterus (50–65 days of gestation) 10 times above control values by 8 h and 20 times by 24 h after administration of oestradiol to the mother.     

Relationship between regeneration of cell surface glycoproteins in trypsin-treated chick embryo fibroblasts and cell adhesion to the substratum

Summary The ability of cells to adhere to a substratum was altered by treatment with trypsin but was restored after a 1.5-h culture. A concomitant incorporation of [³H] leucine and [⁴C] glucosamine in the trypsin-sensitive cell surface glycoproteins was observed and almost reached a plateau within 1.50 h following the treatment with trypsin.