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J Ilan

Publications and source records attributed to J Ilan.

104 records · Page 6Linked to original sources
PubMed1966

Effects of actinomycin D on nucleic acid metabolism and protein biosynthesis during metamorphosis of Tenebrio molitor L.

1. Injection of 0.16mug. of actinomycin D into pupae of the beetle Tenebrio molitor L. results in the development of modified adults in which the head and thorax are essentially adult while the abdomen and wings remain pupal-like. It is suggested that the messenger RNA for the development of head and thorax is present in the animal from the first day of pupation. 2. Injection of 0.16mug. of actinomycin D brings about 51-67% inhibition of labelled uridine incorporation into RNA. 3. When thymus DNA is mixed with actinomycin D before injection into pupae the latter develop into normal adults. This protection does not occur when DNA and actinomycin D are injected separately. 4. The inhibition of incorporation of labelled uridine into RNA by actinomycin is diminished to some extent when DNA and actinomycin D are injected separately and abolished if they are injected together. 5. Inhibition of RNA synthesis by actinomycin D in vitro is fully reversible. DNA or deoxyguanosine can reverse the effect of actinomycin D. 6. Incorporation of labelled glycine into protein is not affected by actinomycin D injection during the first 6 days of pupation. On the seventh day it becomes diminished in control pupae but this effect is prevented by actinomycin D. It is suggested that the template for protein synthesis is stable during the first 6 days of metamorphosis and that on the seventh day there is a qualitative change in the protein synthesized on the template.

Animals↗
PubMed1966

Effects of colchicine on nucleic acid metabolism during metamorphosis of Tenebrio molitor L. and in some mammalian tissues.

1. Administration of 10mug. of colchicine/pupa of the beetle Tenebrio molitor L. arrests its differentiation, the pupa remaining alive for 2-3 weeks. 2. The same concentration of colchicine inhibits DNA synthesis and stimulates RNA synthesis (as shown by incorporation into the nucleic acids of labelled adenine, labelled uridine and labelled thymidine). The effects of colchicine on nucleic acid metabolism are first detected 3 days after its administration to first-day pupae. 3. No effects of colchicine are seen on [1-(14)C]glycine incorporation into protein in vivo. 4. Relatively high concentrations of colchicine (e.g. 10mm) suppress incorporation of [8-(14)C]adenine into RNA in dorsal abdominal wall in vitro. Such concentrations have no effect on its incorporation into acid-soluble nucleotides. 5. Colchicine (1mm) suppresses incorporation of [8-(14)C]adenine into DNA to a greater extent than into RNA in various mammalian tissues in vitro (e.g. rat spleen, regenerating rat liver, rat embryo, guinea-pig intestinal mucosa, Ehrlich ascites cells). Colchicine (1mm) has no effect on the rate of respiration of, or on incorporation of radioactivity into acid-soluble nucleotides in, the mammalian tissues tested. 6. Further evidence indicates complex-formation between colchicine and DNA, and it is suggested that the effect of colchicine in suppressing DNA synthesis is due to its combination with the DNA primer (template).

Animals↗
PubMedDate not supplied

Potential triple helix-mediated inhibition of IGF-I gene expression significantly reduces tumorigenicity of glioblastoma in an animal model.

Oligonucleotide-directed triple helix formation is a powerful approach to block transcription of specific genes. Although the oligonucleotide triplex approach is efficient for inhibiting gene expression in cultured cells, suppression is transient. We developed an approach which inhibits insulin-like growth factor-I (IGF-I) expression following stable transfection of C6 rat glioblastoma cells with a plasmid from which an RNA is transcribed that codes for the third strand of a potential triple helix. We tested the ability of this expression vector to inhibit IGF-I gene expression in vitro as well as tumorigenesis in an animal. A dramatic reduction of IGF-I RNA and protein levels in cultured cells occurred following transfection of rat C6 cells with a eukaryotic expression plasmid encoding the oligopurine variant of the triple helix but not the oligopyrimidine or a control sequence. The cells transfected with the oligopurine variant displayed morphological changes, upregulation of major histocompatibility complex I, and increased expression of protease nexin I. Dramatic inhibition of tumor growth occurred in nude mice following injection of transfected C6 cells. To our knowledge, this is the first example of tumor growth inhibition in an animal model employing a triple helix approach.

Amyloid beta-Protein Precursor↗