Alexandra von der Decken

Effect of Dietary Protein and Amino Acid Mixture on Protein Synthesis in vitro in Rat Liver

Rats received for 6 consecutive days a diet containing 20% of the protein under test, or an equivalent amount of amino acid mixture. Protein synthesis of liver ribosomes was determined by measuring th

Transcription of rat liver chromatin by Escherichia coli RNA polymerase: template properties after protein restriction.

Transcription was determined in liver chromatin from rats fed for 6 days, an optimal (20%) or suboptimal (3%) amount of high-quality protein. Transcription by Escherichia coli RNA polymerase (EC 2.7.7.6) was lower after prolonged incubation with chromatin from rats fed 3% as compared with 20% protein. Differences were detected in the transcripts of the two types of chromatin after analysis by sucrose density gradient centrifugation. But no measurable differences were found in the melting profiles at low ionic strength of the two chromatin preparations. Transcription per milligram chromatin DNA was 25-fold higher using E. coli RNA polymerase instead of rat liver RNA polymerase II. The use of UTP as radioactive precursor in the absence of ATP, GTP and CTP resulted in a low labelling of RNA. One [lambda32P]UTP nucleotide was incorporated/8 UMP nucleotides. The product obtained was sensitive to ribonuclease treatment. In the presence of ATP, GTP and CTP [lambda-32P]UTP nucleotide incorporation was reduced and that of UMP nucleotide was increased giving a ratio of 1:188.

Specific effects of protein deprivation on thymus and spleen; rates of protein synthesis in lymphocytes derived from thymus, spleen and bone marrow

Abstract Young adult male rats (body weight 90 g) were fed for 6 days a low protein (3% casein) diet and compared with rats fed a diet optimal in protein (20% casein). To study the dietary effects of protein, but not energy deficiency, intake of energy per unit body weight was kept constant. Wet weights and DNA content of thymus and spleen organs decreased in the low protein diet group. The in vitro incorporation of 14C-leucine into protein by isolated ribosomes was diminished in thymus by 22% and in spleen by 33% per mg of ribosomal RNA, and per mg of DNA by 43% in thymus and 48% in spleen. Lymphocytes were separated by Ficoll gradients. As compared with controls lymphocyte number from thymus decreased by 90%, that of spleen by 43% and of bone marrow by 20%. The rates of protein synthesis were significantly reduced after protein restriction in lymphocytes of the 3 organs. The strongest effects on the rates of protein synthesis were observed in bone marrow. Reduction in lymphocytes recovered was most pronounced in thymus. The results indicate that malnutrition by protein, but not energy deficiency, elicites specific effects on the 3 lymphocyte producing or containing organs studied.