Mechanisms of Action of Non-steroid Hormones in Animal Cells: Events in the Nucleus

1994 ◽  
pp. 197-213
Author(s):  
J.R.E. DAVIS ◽  
N. HOGGARD
Keyword(s):  
Steroid Hormones ◽  
Mechanisms Of Action ◽  
Animal Cells

Some Observations on the Cytological Effects of Antimitotic Poisons

1968 ◽  
Vol 17 (1) ◽  
pp. 182-184
Author(s):  
Pierre Dustin
Keyword(s):  
Chemical Structure ◽  
Complex Molecule ◽  
Mechanisms Of Action ◽  
Tubular Structures ◽  
Animal Cells ◽  
Inorganic Substances ◽  
Spindle Function ◽  
The Relationship ◽  
Cellular Destruction ◽  
Tubular Components

Recently discovered substances with antimitotic action fall in the two categories which have been defined since many years, i. e. spindle poisons and chromatin (or “radiomimetic”) poisons. The most recently studied are hydroxyurea — a powerful inhibitor of DNA synthesis — and the Vinca alcaloids — which destroy the tubular components of the spindle, bringing a prolonged arrest in metaphase.The mechanisms of action of many of these drugs remain most obscure. In the field of spindle-poisons, there has been no explanation sofar of the relationship between their chemical structure and cytological action. While it is known that minor changes in the chemical structure of colchicine can prevent its specific action on the spindle, the precise relation which appears to exist between this complex molecule and the spindle structures remains obscure. The same remark applies to the Vinca alcaloids. Progress is being made however in this field. The ultrastructural aspects of the spindle have been analysed by electron microscopy, and a precise definition in chemical terms of the spindle may be close. These observations have shown the similarity between the tubules of the spindle and other tubular structures of identifical size: the neurotubules. Some recent observations indicate that these may also be destroyed by colchicine, a fact which may be related to the well-known and severe neurotoxicity of this alcaloid. What remains to be explained is the fact that the most effective spindle poisons are molecules of the size and complexity of those of vinblastine, while simple inorganic substances (arsenicals, heavy metals) may exert identical if not so powerful effects on the spindle structures. Another point which needs further research is the cause of the extensive cellular destruction which follows, in animal cells, any prolonged inhibition of the spindle function. The chemotherapic actions of spindle poisons are most probably related, not only to the growth inhibiting effects of these drugs, but most of all to the cellular breakdown which is observed in cells when they have been kept for several hours in metaphase.

scholarly journals New Evidence of Similarity between Human and Plant Steroid Metabolism: 5α-Reductase Activity in Solanum malacoxylon

Endocrinology ◽  
2003 ◽  
Vol 144 (1) ◽  
pp. 220-229 ◽  
Author(s):  
Fabiana Rosati ◽  
Giovanna Danza ◽  
Antonio Guarna ◽  
Nicoletta Cini ◽  
Milvia Luisa Racchi ◽  
...  
Keyword(s):  
Steroid Hormones ◽  
Metabolic Pathways ◽  
Reductase Activity ◽  
Physiological Role ◽  
Mechanisms Of Action ◽  
Plant Tissues ◽  
Solanum Malacoxylon ◽  
New Evidence ◽  
Mammalian System

Abstract The physiological role of steroid hormones in humans is well known, and the metabolic pathway and mechanisms of action are almost completely elucidated. The role of plant steroid hormones, brassinosteroids, is less known, but an increasing amount of data on brassinosteroid biosynthesis is showing unexpected similarities between human and plant steroid metabolic pathways. Here we focus our attention on the enzyme 5α-reductase (5αR) for which a plant ortholog of the mammalian system, DET2, was recently described in Arabidopsis thaliana. We demonstrate that campestenone, the natural substrate of DET2, is reduced to 5α-campestanone by both human 5αR isozymes but with different affinities. Solanum malacoxylon, which is a calcinogenic plant very active in the biosynthesis of vitamin D-like molecules and sterols, was used to study 5αR activity. Leaves and calli were chosen as examples of differentiated and undifferentiated tissues, respectively. Two separate 5αR activities were found in calli and leaves of Solanum using campestenone as substrate. The use of progesterone allowed the detection of both activities in calli. Support for the existence of two 5αR isozymes in S. malacoxylon was provided by the differential actions of inhibitors of the human 5αR in calli and leaves. The evidence for the presence of two isozymes in different plant tissues extends the analogies between plant and mammalian steroid metabolic pathways.

scholarly journals New Insights into Cholesterol Functions: A Friend or an Enemy?

Nutrients ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1645 ◽  
Author(s):  
Zampelas ◽  
Magriplis
Keyword(s):  
Vitamin D ◽  
Bile Acids ◽  
Steroid Hormones ◽  
Cell Membranes ◽  
Animal Origin ◽  
Main Function ◽  
Animal Cells ◽  
Food Of Animal Origin

Cholesterol is a sterol synthesized by animal cells and is also a component of the diet, being present in food of animal origin. Its main function is to maintain the integrity and fluidity of cell membranes and to serve as a precursor for the synthesis of substances that are vital for the organism including steroid hormones, bile acids, and vitamin D [...]

Mechanisms of action of sex steroid hormones: Basic concepts and clinical correlations

Maturitas ◽  
1996 ◽  
Vol 23 ◽  
pp. S3-S12 ◽  
Author(s):  
Pentti Tuohimaa ◽  
Merja Bläuer ◽  
Susanna Pasanen ◽  
Satu Passinen ◽  
Anu Pekki ◽  
...  
Keyword(s):  
Steroid Hormones ◽  
Mechanisms Of Action ◽  
Sex Steroid Hormones ◽  
Sex Steroid ◽  
Clinical Correlations ◽  
Basic Concepts

scholarly journals Steroid signal transduction activated at the cell membrane: from plants to animals.

2002 ◽  
Vol 49 (3) ◽  
pp. 735-745 ◽  
Author(s):  
Ewa Marcinkowska ◽  
Antoni Wiedłocha
Keyword(s):  
Cell Surface ◽  
Steroid Hormones ◽  
Nuclear Receptors ◽  
Target Genes ◽  
Steroid Receptors ◽  
Transmembrane Protein ◽  
Steroid Receptor ◽  
Membrane Receptors ◽  
Protein Kinase Activity ◽  
Animal Cells

Steroid hormones in plants and in animals are very important for physiological and developmental regulation. In animals steroid hormones are recognized by nuclear receptors, which transcriptionally regulate specific target genes following binding of the ligand. In addition, numerous rapid effects generated by steroids appear to be mediated by a mechanism not depending on the activation of nuclear receptors. Although the existence of separate membrane receptors was postulated many years ago and hundreds of reports supporting this hypothesis have been published, no animal membrane steroid receptor has been cloned to date. Meanwhile, a plant steroid receptor from Arabidopsis thaliana has been identified and cloned. It is a transmembrane protein which specifically recognizes plant steroids (brassinosteroids) at the cell surface and has a serine/threonine protein kinase activity. It seems that plants have no intracellular steroid receptors, since there are no genes homologous to the family of animal nuclear steroid receptors in the genome of A. thaliana. Since the reason of the rapid responses to steroid hormones in animal cells still remains obscure we show in this article two possible explanations of this phenomenon. Using 1,25-dihydroxyvitamin D(3) as an example of animal steroid hormone, we review results of our and of other groups concordant with the hypothesis of membrane steroid receptors. We also review the results of experiments performed with ovarian hormones, that led their authors to the hypothesis explaining rapid steroid actions without distinct membrane steroid receptors. Finally, examples of polypeptide growth factor that similarly to steroids exhibit a dual mode of action, activating not only cell surface receptors, but also intracellular targets, are discussed.

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