Flavonoids are nearly ubiquitous in plants and are recognized as the pigments responsible for the colors of leaves, especially in autumn. They are rich in seeds, citrus fruits, olive oil, tea, and red wine. They are low molecular weight compounds composed of a three-ring structure with various substitutions. This basic structure is shared by tocopherols (vitamin E). Flavonoids can be subdivided according to the presence of an oxy group at position 4, a double bond between carbon atoms 2 and 3, or a hydroxyl group in position 3 of the C (middle) ring. These characteristics appear to also be required for best activity, especially antioxidant and antiproliferative, in the systems studied. The particular hydroxylation pattern of the B ring of the flavonoles increases their activities, especially in inhibition of mast cell secretion. Certain plants and spices containing flavonoids have been used for thousands of years in traditional Eastern medicine. In spite of the voluminous literature available, however, Western medicine has not yet used flavonoids therapeutically, even though their safety record is exceptional. Suggestions are made where such possibilities may be worth pursuing.

The Effects of Plant Flavonoids on Mammalian Cells:Implications for Inflammation, Heart Disease, and Cancer

"Embryogenesis is in some way a model system. It has always been distinguished by the exactitude even punctitio, of its anatomical descriptions. An experiment by one of the great masters of embryology could be made the text of a discourse on scientific method. But something is wrong, or has been wrong. There is no theory of development in the sense in which Mendelism is a theory that accounts for the results of breeding experiments. There has therefore been little sense of progression or timeliness about embryological research. Of many papers delivered at embryological meetings, however good they may be in themselves . . . one too often feels that they might have been delivered five years beforehand without making anyone much the wiser, or deferred for five years without making anyone conscious of a great loss" (1). This feeling of frustration so incisively conveyed by these considerations by P. Medawar, pervaded, in the forties, the field of experimental embryology which had been enthusiastically acclaimed in the mid-thirties, when the upper lip of the amphibian blastopore brought this area of research to the forefront of the biological stage. The side branch of experimental neuroembryology, which had stemmed out from the common tree and was entirely devoted to the study of the tropic interrelations between neuronal cell populations and between these and the innervated organs and tissues, was then in its initial vigorous growth phase. It in turn suffered from a sharp decrease in the enthusiasm that had inflamed the pioneers in this field, ever since R. G. Harrison delivered his celebrated lecture on this topic at the Royal Society in London in 1935 (2). Although the alternate "wax and wane" cycles are the rule rather than the exception in all fields of human endeavor, in that of biological sciences the "wane" is all too often indicative of a justified loss of faith in the rational and methodical approach that had at first raised so much hope. A brief account of the state-of-the-art of experimental neuroembryology in the

https://science.sciencemag.org/content/sci/237/4819/1154.full.pdf

The nerve growth factor 35 years later

Few nonphagocytic cells are known to generate reactive oxygen intermediates. Based on horseradish peroxidase-dependent, catalase-inhibitable oxidation of fluorescent scopoletin, seven human tumor cell lines constitutively elaborated H2O2 at rates (up to 0.5 nmol/10(4) cells/h) large enough that cumulative amounts at 4 h were comparable to the amount of H2O2 produced by phorbol ester-triggered neutrophils. Superoxide dismutase-inhibitable ferricytochrome c reduction was detectable at much lower rates. H2O2 production was inhibited by diphenyleneiodonium, a flavoprotein binder (concentration producing 50% inhibition, 0.3 microM), and diethyldithiocarbamate, a divalent cation chelator (concentration producing 50% inhibition, 3 microM), but not by cyanide or azide, inhibitors of electron transport, or by agents that inhibit xanthine oxidase, polyamine oxidase, or cytochrome P450. Cytochrome b559, present in human phagocytes and lymphocytes, was undetectable in these tumor cells by a sensitive spectrophotometric method. Mouse fibroblasts transfected with human tyrosinase complementary DNA made melanin, but not H2O2. Constitutive generation of large amounts of reactive oxygen intermediates, if it occurs in vivo, might contribute to the ability of some tumors to mutate, inhibit antiproteases, injure local tissues, and therefore promote tumor heterogeneity, invasion, and metastasis.

https://cancerres.aacrjournals.org/content/canres/51/3/794.full.pdf

Production of Large Amounts of Hydrogen Peroxide by Human Tumor Cells

Molecular themes in oncogenesis

The development and life-time of multicellular eukaryotic organisms represents a complex interplay of numerous proliferation and differentiation events that proceed in a highly ordered manner. As a prerequisite for those events, cells must respond to extracellular signals with a specific set of mechanisms that regulate or modulate gene expression. Between the signal and the gene, a system of rather different cellular components is assembled to guarantee a specific and successful process of signal transduction. Pathways of signal transduction, though differing remarkably in their complexity and in the use of cellular components, seem to obey certain principles which are evolutionarily conserved and ubiquitously distributed amongst living organisms. Extracellular signals, so-called ligands, either penetrate the cellular membrane or bind to the extracellular domain of receptors. Activated receptors as such, or in association with socalled transducers, are capable of activating effectors-either directly or by means of changing the amount or intracellular distribution of so-called second messengers. These second

/pdf/protein-kinase-c-isoenzymes-divergence-in-signal-1mikpzv06y.pdf

Protein kinase C isoenzymes: divergence in signal transduction?

https://febs.onlinelibrary.wiley.com/doi/pdf/10.1016/0014-5793%2886%2980428-8

Nerve growth factor induces mast cell degranulation without changing intracellular calcium levels

Expression of normal protein kinase C (PKC) isoenzymes in fibroblasts has been shown to alter growth regulation but has failed to induce complete transformation of the recipient cells. Here we report on a murine ultraviolet-induced fibrosarcoma cell line which has an unusual PKC subcellular distribution with 87% of the PKC activity associated with the membrane. We have cloned and sequenced the alpha-PKC complementary DNA from ultraviolet-induced-fibrosarcoma cells and from mouse Balb/c brain and found four point mutations in the fibrosarcoma PKC, of which three are in the highly conserved regulatory domain and one is in the conserved region of the catalytic domain. Expression of this mutant alpha-PKC gene in normal Balb/c 3T3 fibroblasts results in a fibrosarcoma-like PKC membrane localization and in cell transformation, as judged by their formation of dense foci, anchorage-independent growth and ability to induce solid tumours when inoculated into nude mice. By contast, transfectants expressing the normal alpha-PKC cDNA do not display a morphology typical of malignant transformed cells and fail to induce tumours in vivo. These findings demonstrate that point mutations in the primary structure of PKC modulate enzyme function and are responsible for inducing oncogenicity.

A mutant protein kinase C that can transform fibroblasts

Calcium permeability of basophil and mast cell membranes is stimulated on allergen binding to its specific membrane-bound IgE. This entry of Ca2+ ions into the cell triggers the degranulation and secretion process. Disodium cromoglycate (cromolyn DSCG), the disodium salt of 1,3-bis(-2-carboxychromon-5-yloxy)-2-hydroxypropane, inhibits the degranulation and release of anaphylactic mediators, and has found wide application in the treatment of allergic bronchial asthma. Accumulated evidence indicates that this inhibition takes place by blocking the calcium uptake. To localize its site of action, the drug has been covalently conjugated to fluorescent polyacrylamide and polyglutaraldehyde beads (0.7 and 0.2 microns in diameter, respectively). We show here that these drug-bead conjugates (DBC) do prevent the drug penetrating into the cell without reducing its ability to inhibit histamine release (Table 1). Furthermore, we show a specific Ca2+-dependent binding of the DBC to the membranes of rat peritoneal mast cells (RPMC) and basophils.

A binding site on mast cells and basophils for the anti-allergic drug cromolyn

Regulatory Effect of Phorbol Esters on Sphingosine Kinase in BALB/C 3T3 Fibroblasts (Variant A31): Demonstration of Cell Type-Specific Response - A Preliminary Note

Ca2+ channel opening has been proposed to be induced in the plasma membrane of mast cells and basophils upon crosslinking their Fc epsilon receptors. Here we report direct conductance measurements on planar lipid bilayers containing membrane components of rat basophils (RBL-2H3 line). These studies identify the Ca2+ channel-forming membrane component as the cromolyn binding protein [CBP, in which cromolyn is the anti-asthmatic drug 1,3-bis(2-carboxy-chromon-5-yloxy)-2-hydroxypropane]. Planar membranes were first formed from lipid vesicles containing unfractionated plasma membrane components prepared from RBL-2H3 cells. Conductance of these bilayers was induced by crosslinking IgE bound to the Fc epsilon receptors of this membrane by a specific polyvalent antigen. Channel conductance in the presence of only Ca2+ ions (2 mM) was 2 pS. When only sodium ions were present (150 mM), conductance was 10 pS. Upon addition of Ca2+ (2 mM) to the Na+ ion-containing solution, the conductance decreased from 10 pS to that of the Ca2+ ions--namely, 2pS. Open channel times were in the range of several hundred milliseconds. Conductance amplitudes and time characteristics were independent of the applied voltage. As our earlier studies revealed the essential role of the CBP in Ca2+ conductance of basophil membranes, we formed planar bilayers containing this isolated protein alone. Crosslinking of the CBP by a monoclonal antibody specific to it resulted in the appearance of channel conductances. All characteristics of these channels exhibited great similarity to those observed in planar membranes containing unfractionated RBL-2H3 membrane components. Moreover, in the latter membranes, the monoclonal anti-CBP antibody induced channel conductances that display an even closer similarity to those observed in membranes containing CBP alone. Conductances of both types of planar membranes, irrespective of the mode of activation used, were inhibited by cromolyn. Furthermore, the conductance induced in RBL membranes by polyvalent antigen was inhibited on dissociation of the crosslinked aggregates by a monovalent hapten. The detailed resemblance in channel behavior observed in experiments with the two types of planar bilayers provides compelling evidence that the CBP is the essential and sufficient component forming Ca2+ channels in basophil plasma membranes.

Nachman Mazurek

Papers

Nerve growth factor induces mast cell degranulation without changing intracellular calcium levels

A mutant protein kinase C that can transform fibroblasts

A binding site on mast cells and basophils for the anti-allergic drug cromolyn

Regulatory Effect of Phorbol Esters on Sphingosine Kinase in BALB/C 3T3 Fibroblasts (Variant A31): Demonstration of Cell Type-Specific Response - A Preliminary Note

The cromolyn binding protein constitutes the Ca2+ channel of basophils opening upon immunological stimulus