Leprosy

Lehmann, C. F.

doi:10.1001/archderm.1938.01480080008002

Cited by 5 publications

(1 citation statement)

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“…Something should be said about another chemical, which is famous among embryologists for the fact that it inhibits the development ofchorda and produces strong microcephaly. This is the lithium ion, which has been studied in detail from the viewpoint of morphogenesis by Lehmann (1938), Pasteels (1945) and Hall (1942).…”

Section: Considerable Experimental Work Would Be Required In Ordermentioning

confidence: 99%

The biological role of ribonucleic acids

Brachet¹

1960

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Next to nothing was known a quarter of a century ago about the biological role and the intracellular localization of the nucleic acids. All that was well established was the existence of two different types of nucleic acids, which correspond to the deoxyribonucleic (DNA) and ribonucleic (RNA) acids of the present day. They were called, respectively, thymonucleic and zymonucleic acids, because purified preparations had only been obtained from thymus and yeast. It was erroneously believed that thymonucleic acid (DNA) is specific to animal cells and that yeast nucleic acid (RNA) is present only in plant cells. However RNA had been isolated from pancreas. A popular hypothesis was that DNA, which was known to contain both ortho-phosphoric acid and nitrogenous bases, might play the role of an intra-nuclear buffer. Such a role is certainly a minor one for the bearer of "genetic information"! One of the first important advances made in the field came from cytochemistry, when in 1924 Feulgen and Rossenbeck designed and utilized their well-known reaction for the detection of DNA. They were immediately able to demonstrate that thymonucleic acid (DNA) is specifically located in the cell nucleus, in plants as well as in animals. Progress on the role and localization of RNA was slower to come, because of the lack of specific cytochemical reactions comparable to the Feulgen tests. Indirect observations by Brachet (1933) strongly suggested, however, that animal cells may contain such References p. 50/54 RIBONUCLEIC ACIDS AND PROTEIN SYNTHESIS in RNA. Values up to 11.5% dry weight have been reported by Vendrely (1946). Work carried out in several different laboratories shows the existence of an excellent correlation between the synthesis of RNA and the synthesis of proteins, provided that the bacterial growth is studied during the logarithmic phase. For instance, Caldwell et al. (1950) found the RNA content of bacteria to be proportional to the growth rate, whatever the experimental conditions (changes in the nitrogen source of the culture medium, presence or absence of inhibitors, normal organisms or slow-growing mutants). Similar findings have been reported by Northrop (1953), Wade (1952) and Price (1952). An important study of Gale and Folkes (1953) shows that staphylococci synthesize proteins in the presence of glucose and amino acids. If purines and pyrimidines are added to this medium, nucleic acids are also synthesized. But the interesting fact is that if the medium contains no amino acids there is no nucleic acid synthesis, whereas the presence of purines and pyrimidines in the medium enhances protein synthesis. There thus exists a strong positive correlation between the nucleic acid content of the cells and the rate of protein synthesis. Gale and Folkes (1953) have also found that protein synthesis and RNA synthesis can be dissociated by the use of antibiotics. For instance, Chloromycetin, aureomycin, and terramycin all inhibit protein synthesis but increase nucleic acid synthesis. However, there is very good evidence (N...

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Section: Considerable Experimental Work Would Be Required In Ordermentioning

confidence: 99%