Actinomycin D Act

When cells are exposed to doses of a water-soluble form of actinomycin D, Act D-mannitol (Sigma), at concentrations of O.l-l.O /i.g/ml (made from a 1 mg/ ml stock solution dissolved in distilled water) for times of 1-4 hr it is possible to obtain segregated nucleoli with fibrillar caps separated from granular regions (Fig. 7a). These optimally segregated nucleoli can then be fixed and prepared for fluorescence microscopy or immunoelectron microscopy in order to localize... 

Cycloheximide (CHI) infiltration of Cuscuta tissue was earlier shown to partially suppress the excision drop of PAL activity, suggesting a need for protein synthesis in the inactivation process [14]. The effects of CHI and actinomycin-D (Act-D) were therefore tested for their effects on both excision drop and BA + GAg-induced PAL activity increase. Table 4 shows that both inhibitors do suppress excision drop by about 85%, suggesting that de novo transcription and protein synthesis are required in the process. However, CHI or Act-D suppression of the PAL induction occasioned by use of BA + GA3 was almost complete. Thus, the increase of PAL activity on treatment with the hormones apparently involves de novo PAL synthesis. 

Table 4. Effect of cycloheximide (CHI) and actinomycin-D (Act-D) on excision drop or BA + GA,.-induction of PAL activity in segments from the 60-120 mm region...

An LC-MS-MS method for the simultaneous quantitative determination of actinomycin-D (Act-D) and vincristine (VCR), which are cytotoxic agents commonly used in the treatment of pediatric cancers. Following sohd-phase extraction, plasma samples are separated and analyzed using electrospray ionization (ESI). Lower limit of quantitation (LLOQ) for both Act-D and VCR 0.5 ng/ml. Analytical accuracy for detection of both Act-D and VCR <90%. Analytical precision, as estimated hy the coefficient of variation <6% for Act-D and <11% for VCR. Useful in clinical monitoring. 

Actlnomvcin D - Kinetic studies with actinomycin D (act-D) in transplanted leukemic mice showed that a single dose provided cytotoxic concentrations for up to 24 hours,The characteristics of act-D resistance in L5178Y cells show that alterations in membrane composition and conformation in the drug-resistant subline accounts for the observed changes in the permeability of this drug.91 Act-D enhances the toxicity of morphine by increasing brain permeability. ... 

Phenoxazines — The microbial phenoxazines like actinomycins are well-known antibiotics. Actinomycin D produced by Streptomyces anibioticus is an effective antineoplastic agent that inhibits nucleic acid synthesis. The main function of ommochromes is to act as screening pigments in the eyes of insects and other arthropods, as pattern pigments in the integument, and as excretion products of excess tryptophan. ... 

Fig. 3 Venn-diagram for selected compounds interacting with the key MDR-related ABC transporters. MDR-substrate anticancer agents. Abbreviations VCR vincristine, VP-16 etoposide, STER steroids, TAM tamoxiphen, TKI-INHIB tyrosin kinase inhibitors e.g. STI-571, DOX doxorubicine or adriamycin, DNR daunorubicin, EPIR epirubicin, MX mitoxantrone, TOPOT topotecan, iridotecan, BISANT bisanthrone, COLCH colchicin, ACT-D actinomycin D, MYTOM mytomycin, TX methotrexate, CPHAM cyclophosphamide, CHLB chlorambucil, CARM carmustine, LCV leucovorin, HUR hydroxy urea, CISPL cisplatin, TAXOL paclitaxel. (Reproduced from [4])...

Most of the important antitumor compounds used for chemotherapy of tumors are microbially-produced antibiotics. These include actinomycin D, mitomycin, bleomycins and the anthracyclines, daunorubicin and doxorubicin. The recent successful molecule, taxol (=paclitaxel), was discovered in plants but also is a fungal metabolite. It is approved for breast and ovarian cancer and is the only antitumor drug known to act by blocking depolymerization of microtubules. In addition, taxol promotes tubulin polymerization and inhibits rapidly dividing mammalian cancer cells. It also inhibits fungi such as Pythium, Phytopthora and Aphanomyces spp. by the same mechanism. ... 

DNA base pairs. When actinomycin D is present, DNA cannot act as a template for replication or transcription. 

In some experiments concerned with the mechanism by which tryptophan acted to improve hepatic protein synthesis after toxic injury, the ability of tryptophan to stimulate hepatic mRNA synthesis, nucleocytoplasmic translocation of RNA in vitro, and nuclear envelope nucleoside triphosphatase activity after hepatotoxic injury was measured.188 Nucleoside triphosphatase (Mg2+-dependent adenosine triphosphatase, EC 3.6.1.3.1) was assayed since it is present in mammalian liver nuclear envelopes,224 and there is evidence that this enzyme is involved in nucleocytoplasmic translocation of RNA.221 All of these parameters were elevated significantly by tryptophan after agents such as actinomycin D, cordycepin, ethionine, puromycin, and hypertonic NaCl demonstrated a curative effect by tryptophan, but not after tryptophan following CC14, NaF, and sparsomycin demonstrated no improvement with tryptophan. These findings emphasized the importance of the role that tryptophan plays in stimulating the availability of cytoplasmic... 

McKenzie, J. M., and Williamson, A., Experience with the bioassay of the long-acting thyroid stimulator. J. Clin. Endocrinol. Metab. 26, 518-526 (1966). McKenzie, J. M., Adiga, P. R., and Murthy, P. V. N., Effects of actinomycin-D, cycloheximide and puromycin on thyroid stimulation. Endocrinology 83, 1132-1139 (1968). 

Actinomycin D (Figure 26.4), is a transcriptional terminator that acts by binding to DNA. The tricyclic ring system (phenoxazone) intercalates between adjacent G-C base pairs, and the cyclic polypeptide arms fill the nearby narrow groove. 

The three eukaryotic RNA polymerases are distinguishable from one another by their differential sensitivity to the drag a-amanitin (the toxic principle of the mnshroom Amanita phalloides) which does not affect bacterial RNA polymerases. RNA polymerase II is very sensitive to a-amanitin, while RNA polymerase I is completely resistant. RNA polymerase III is moderately sensitive to this inhibitor. Mitochondria have yet another type of RNA polymerase, which is imaffected by a-amanitin bnt is sensitive to drags that inhibit bacterial RNA polymerase. A munber of antibiotics also act throngh their inhibition of transcription e.g., actinomycin D exerts its effect by binding to DNA templates, and it also blocks DNA replication. 

It is now recognized that DNA is also the target for the many other kinds of drugs that act by intercalation. These include the anti-cancer drugs dauno-rubicin, doxorubicin (adriamycin), actinomycin D, anthramycin, amsacrine, and ellipticine the anti-malarials mepacrine (quinacrine, atebrin) and chloro-quine and the anti-trypanosomal drugs ethidium and quinapyramine (more about these drugs in Section 10.3.5). 

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