Spin trapping: ESR parameters of spin adducts.

Trace levels of transition metals can participate in the metal-catalyzed Haber-Weiss reaction (superoxide-driven Fenton reaction) as well as catalyze the oxidation of ascorbate. Generally ascorbate is thought of as an excellent reducing agent; it is able to serve as a donor antioxidant in free radical-mediated oxidation processes. However, as a reducing agent it is also able to reduce redox-active metals such as copper and iron, thereby increasing the pro-oxidant chemistry of these metals. Thus ascorbate can serve as both a pro-oxidant and an antioxidant. In general, at low ascorbate concentrations, ascorbate is prone to be a pro-oxidant, and at high concentrations, it will tend to be an antioxidant. Hence there is a crossover effect. We propose that the "position" of this crossover effect is a function of the catalytic metal concentration. In this presentation, we discuss: (1) the role of catalytic metals in free radical-mediated oxidations; (2) ascorbate as both a pro-oxidant and an antioxidant; (3) catalytic metal catalysis of ascorbate oxidation; (4) use of ascorbate to determine adventitious catalytic metal concentrations; (5) use of ascorbate radical as a marker of oxidative stress; and (6) use of ascorbate and iron as free radical pro-oxidants in photodynamic therapy of cancer.

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Catalytic metals, ascorbate and free radicals: combinations to avoid.

Oocytes and their companion somatic cells maintain a close association throughout oogenesis and this association is essential for normal oocyte and follicular development. This review summarizes current concepts of the role of the somatic cells in the regulation of mammalian oocyte growth, the maintenance of meiotic arrest, the induction of oocyte maturation, and the acquisition of full embryonic developmental competence during oocyte maturation in vitro. Gap junctions appear to mediate these regulatory processes. The regulatory interaction of oocytes and somatic cells, however, is not unidirectional; the oocyte participates in the proliferation, development, and function of the follicular somatic cells. The oocyte secretes factors that enable the cumulus cells to synthesize hyaluronic acid and undergo cumulus expansion in response to hormonal stimulation. In addition, the oocyte produces factors that promote the proliferation of granulosa cells. These interactions in vitro do not appear to require the mediation of gap junctions. The oocyte also promotes the differentiation of granulosa cells into functional cumulus cells, but this function of the oocyte appears to require the continued presence and close association of the oocyte and granulosa cells. Therefore, oocytes and follicular somatic cells are interdependent for development and function.

Interactions between somatic cells and germ cells throughout mammalian oogenesis.

https://www.cell.com/cell/pdf/0092-8674(88)90060-8.pdf

cdc2 is a component of the M phase-specific histone H1 kinase: Evidence for identity with MPF

On the control of oocyte meiotic maturation and ovulation in Caenorhabditis elegans

INVESTIGATIONS of the mechanism of starfish spawning induced by injection of a water extract of radial nerves have shown that an active polypeptide acts on the ovary and induces the production of a second substance which is, in the true sense, a meiosis inducing factor as well as a spawning inducing factor1–7. The neural substance has therefore been renamed gonad stimulating substance (GSS), and the second substance, produced in the ovary, is meiosis inducing substance (MIS)5,7. Isolated ovarian fragments immersed in seawater containing MIS discharge their eggs4,5,7, while isolated oocytes with germinal vesicles treated with MIS mature4–7. The production of MIS by GSS has been demonstrated in isolated ovarian fragments of seven species of starfish, and it seems to be non-species specific among starfishes7. MIS is heat stable (100° C, 30 min) and is not a peptide5,6.

Isolation and indentification on meiosis inducing substance in starfish Asterias amurensis.

The mass spectra of fifteen metal acetylacetonates measured under the electron impact with 70 eV energies are reported. The acetylacetonates can be divided into three groups, A, B, and C, according to their stability in mass spectrometeric measurements. When the electronegativity of the central metal atom is 1.5—1.6, the complexes show abundant molecular ion peaks (group A); when the electronegativity is 1.6—1.8, no molecular ion appears and the M-L cations show as the highest mass (group B); when the electronegativity is greater than 1.8, there are no peaks arising from fragments containing the metal, only acetylacetone peaks being apparent (group C). Furthermore, the mass spectra of hexafluoroacetylacetone and its copper complex were also measured.

Mass Spectrometric Studies of Metal Acetylacetonates

The fragmentation of flavonoid compounds by electron impact has been studied and the following results described: 1) Chalcones gave the usual fragmentation pattern; however, 2′-hydroxy chalcones showed complex spectra according to the isomerization of chalcone to flavanone. 2) The fragmentation pathways of flavones were decided by comparison with many kinds of halogen-substituted flavones. 3) Isoflavone gave the M-1 ion as the base peak, and no loss of CO was observed.

Tadashi Kurokawa

Papers

Isolation and indentification on meiosis inducing substance in starfish Asterias amurensis.

Mass Spectrometric Studies of Metal Acetylacetonates

The Mass Spectra of Chalcones, Flavones and Isoflavones

Formation of polyprenyl phosphates by a cell-free enzyme of Micrococcus lysodeikticus.

Generation of free radicals and initiation of radical reactions in nitrones - Fe2+ - phosphate buffer systems.