Effect of blood sera from ischaemic and recirculated dogs on protein synthesis in vitro

A study was made of the effect on polypeptide synthesis in vitro of venous blood sera from dogs in which incomplete ischaemia had been induced by ligating the abdominal aorta and subsequent recirculation. Sera from the ischaemic animals had practically no effect on the incorporation of 14C-amino acids into the proteins, but sera obtained during the first minutes of recirculation reduced proteosynthesis by 24% as compared with the control. During subsequent 40 min recirculation this effect was lost. Separation of the sera on DEAE cellulose showed that the decrease in 14C-amino acid incorporation into protein in vitro was based on the temporary disappearance or inactivation of a substance normally present in the serum of control animals.     

Metabolism of 14C-amino acids in developing endosperm of corn

¹⁴C-Leucine and ¹⁴C-lysine were introduced into developing cornendosperm by injection into the shank below the ear or by directinjection into the endosperm. In contrast to the shank injectionexperiment, direct injection of the ¹⁴C-amino acids into theendosperm resulted in an unusual incorporation pattern. ¹ Present address: Centro de Energia Nuclear na Agriculture,E. S. A. L. Q,., Caixa Postal 96, Piracicaba, Est. S. Paulo,Brasil. (Received May 4, 1971; )     

The incorporation of microinjected 14C-amino acids into TCA insoluble fractions of the giant axon of the squid

Giant squid axons were microinjected with serine, valine and leucine-C¹⁴ under controlled electrophysiological conditions. These amino acids are incorporated into TCA insoluble fraction in the isolated axon. This incorporation is higher in the stimulated axons as compared to non-stimulated ones. By processing separately the axoplasm and axon sheath, it was found that the last one is responsible almost entirely for the observed incorporation. Through differential centrifugation of homogenates of microinjected axons was shown that the highest incorporation occurred in the 1500 × g sediment, which probably corresponds to membranes. The incorporation of amino acids in stimulated axons, is strongly inhibited by chloramphenicol and actinomycin D.     

Distribution of radioactivity of 14C-amino acids added to the medium in cells and metabolites in cultures of rumen fungi.

A mixture of L-(U-14C) amino acids was added to cultures of 11 strains of rumen anaerobic fungi belonging to Neocallimastix frontalis, Neocallimastix joyonii, Sphaeromonas communis and Piromonas communis. Fungi were grown in a complex medium with glucose for 4 days. The radioactivity was found in cellular protein (27.7-65.3% of the total radioactivity recovered), lactate (16.9-41.8%), volatile fatty acids (7.4-25.7%) and ethanol (4.6-10.5%). A small amount of radioactivity was recovered in lipids (0.2-1.8%) and CO2 (0.3-1.0%). The results suggest that the assimilation of amino acids by growing fungal cells was quantitatively comparable with their dissimilation to metabolites.     

Effects of salicylic acid on protein content and <Superscript>14</Superscript>C-amino acid incorporation into proteins of pea roots

Pea (Pisum sativum L.) root treatment with salicylic acid (SA) changed the content of some proteins and incorporation of ¹⁴C-amino acids into proteins. The analysis of changes in these indices allowed us to subdivide all proteins into the four groups: (1) most abundant SA-independent proteins; (2) SA-dependent proteins, which content and ¹⁴C-amino acids incorporation both increased; (3) SA-dependent proteins, which content and ¹⁴C-amino acids incorporation both decreased; and (4) SA-dependent proteins, which content was not essentially changed (referred earlier to SA-independent proteins) but ¹⁴C-amino acids incorporation into these proteins was strongly suppressed. It is very likely that proteolysis of the proteins referred to the fourth group is very low and even a strong inhibition of their synthesis (incorporation of ¹⁴C-amino acids) does not result in the substantial decrease in their contents. Some SA-dependent proteins were identified by means of modern methods of proteomics: phosphoglyceromutase, S-adenosylmethionine synthase 3, enolase, chalcone isomerase, nucleoside diphosphate kinase 1, and tioredoxin h.     

Schistosoma mansoni: incorporation and metabolism of protein amino acids in vitro

1. The amino acid composition of total proteins in six stages of the life cycle of Schistosoma mansoni was determined by routine autoanalysis of acid hydrolysates. Aspartate, glutamate and glycine were consistently the most abundant protein amino acids in all stages. 2. Incorporation of each of the protein amino acids into adult and egg proteins was determined using 72 hr cultures in complex media. Incorporation rates varied widely and there was no correlation between abundance in protein and the rate of incorporation. 3. Only five amino acids were interconverted to other amino acids which were themselves incorporated into worm and egg proteins (ala, arg, asp, gly, ser); of these only two (glu from ala and pro from arg) appeared to be of quantitative significance. Exogenous glucose yielded only three protein amino acids (ala, asp, glu). 4. The data are considered in the light of differences in egg and adult protein synthesis and with particular regard to potential chemotherapy at this level.