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Biomedical subjects

W R Farkas

Publications and source records attributed to W R Farkas.

45 records · Page 3Linked to original sources
PubMed1975

Effect of plumbous ion on messenger RNA.

The effects of Pb2+, a potent catalyst for the depolymerization of RNA have been studied on brome mosaic virus (BMV) RNA, rabbit globin m-RNA and polyuridylic acid. After exposure of these natural and synthetic messengers to a sufficiently high concentration of Pb2+, they all lost their ability to stimulate amino acid incorporation in cell-free protein-synthesizing systems. There were differences in the susceptibilities of the messengers; gloing the m-RNA for 40 min revealed that there was a threshold Pb2+ concentration below which no loss of m-RNA activity was observed. The threshold concentration was considerably greater than the Pb2+ concentration at which protein synthesis is inhibited in reticulocytes and overt symptoms of plumbism are observed. However, when m-RNA were incubated for an extended period (24 h), even with sub-threshold concentrations of Pb2+, there was destruction of messenger function and globin m-RNA was more susceptible than BMV-RNA. Also the susceptibility of m-RNA to Pb2+ is temperature-dependent, which would indicate that m-RNA, like t-RNA, exists as a population of molecules in different conformational states that are not readily interconvertible.

Animals↗
PubMed1975

The effects of plumbous ion on protein biosynthesis in reticulocytes.

Plumbous ion a potent inhibitor of hemoglobin synthesis by reticulocytes in vivo, is not as effective in inhibiting in vitro globin synthesizing systems prepared from these cells. The reticulocyte is considerably more sensitive to Pb2+ than are leukemic leukocytes, HeLa cells or bacteria. In fact, protein synthesis in leukemic leukocytes is actually stimulated by Pb2+. The synthesis of non-heme protein as well as hemoglobin is inhibited by Pb2+ in reticulocytes and the synthesis of alpha chains is inhibited to a greater degree tcids into reticulocytes. All of these observations are consistent with the biosynthesis of heme rather than any of the steps in protein biosynthesis being the locus for inhibition of hemoglobin synthesis by low levels of plumbous ion. Also, there is marked biological variations in the susceptibilities of reticulocytes from different rabbits to Pb2+.

Amino Acids↗
PubMedDate not supplied

Elevated urinary excretion of beta-aminoisobutyric acid and exposure to inorganic lead.

beta-Aminoisobutyric acid (beta-AIB), a normal degradation product of thymine, a constituent of DNA and, to a lesser extent, of transfer RNA, is excreted in low levels in human urine. We found that a group of iron workers occupationally exposed to inorganic lead excreted high levels of urinary beta-AIB. Elevated urinary excretion of beta-AIB was also observed in marmosets, Callithrix jacchus, that received lead acetate in drinking water. Our results suggest that increased urinary excretion of beta-AIB could stem from damage to DNA on exposure to lead.

Adult↗
PubMedDate not supplied

The absence of the diet-derived 7-deazapurine, queuine in artificial liquid diets.

Queuine is a derivative of guanine found in the transfer RNAs of most organisms including man. Higher mammals cannot synthesize queuine and must obtain it either from their diets or intestinal microflora. Tumor cells often contain much less queuine in their transfer RNAs than do normal cells. Cancer patients are frequently fed artificial liquid diets or are nourished by chemically defined intravenously administered liquids. In this report we present the results of our examination of five common artificial nutrition preparations obtained from a hospital pharmacy with respect to their content of queuine.

Animals↗