Oxybenzone in sunscreen products.
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Benzophenones↗
Biomedical subjects
F A Anthony
Publications and source records attributed to F A Anthony.
Topical W-7 inhibits ultraviolet radiation-induced melanogenesis in Skh:HR2 pigmented hairless mice.
We studied the effect of N-(6-aminohexyl)-5-chloro-1-napthalenesulfonamide (W-7) on ultraviolet radiation (UVR)-induced melanogenesis (tanning) in Skh:HR2 pigmented hairless mice. Topically pretreated mice were exposed to subminimal edematogenic as well as edematogenic UVR doses to establish whether W-7-UVR-induced edema prophylaxis allows increased melanogenesis while preventing edema. Ultraviolet light-irradiated vehicle control animals developed visible tans; however, both W-7-treated groups failed to tan. Topical W-7 before UVR exposure inhibited UVR induction of dopa oxidase activity in melanocytes by 49% (P = 0.029) and inhibited UVR-induced deposition of melanin in the epidermis by 88% (P = 0.006). Topical W-7 blocked 23% of the UVR but this blockage could not account for the inhibition of dopa oxidase and melanization. We conclude that, in addition to preventing edema, W-7 inhibits UVR-induced melanogenesis, possibly by affecting Ca(2+)-calmodulin and/or protein kinase C-dependent processes.
Administration, Cutaneous↗
Attenuation of ultraviolet radiation-induced edema and erythema with topical calmodulin and protein kinase C inhibitors.
We treated Skh:HR1 hairless albino mice, NSA mice and hairless albino guinea pigs topically with N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W7) or trifluoperazine (TFP) before or after ultraviolet (UV) irradiation. When applied before irradiation, W7 and TFP prevented edema in Skh-1 mice and W7 prevented UV-induced edema in NSA mice in a dose-dependent manner. Preirradiation treatment with 2% W7 reduced erythema in guinea pigs by 50%. Epidermal histology of UVR-treated Skh-1 mice pretreated with W7 before UVR was similar to unirradiated mice. W7 did not reverse or prevent these UV-induced effects when applied after irradiation. Neither TFP nor W7 absorbed UV based on forward scattering absorbance spectra; we conclude that neither are physical or chemical sunscreens. These results suggest that calmodulin and/or protein kinase C-dependent events are involved in manifesting some of the effects of UV irradiation on skin.
Absorption↗
Calcium binding to tubulin.
Using flow dialysis, we found two classes of calcium-binding sites on tubulin: high-affinity binding sites (1.56 +/- 0.38 per tubulin dimer) with a dissociation constant of (4.86 +/- 0.12).10(-6) M and low-affinity binding sites (5.82 +/- 0.50 per tubulin dimer) with a dissociation constant of (6.4 +/- 0.4).10(-5) M. In the presence of 6.10(-5) M MgSO4, we found 0.64 +/- 0.18 calcium-binding sites per tubulin dimer with a dissociation constant of (4.7 +/- 0.5).10(-6) M and 1.2 +/- 0.2 sites per dimer with a dissociation constant of (3.5 +/- 0.4).10(-5) M. Under controlled conditions, trypsin and chymotrypsin selectively cleaved alpha- and beta-subunits, respectively, forming major fragments of 35 kDa and 20 kDa from the alpha-subunit, and major fragments of 31 kDa and 22 kDa from the beta-subunit. The high-affinity calcium-binding sites were detected in the carboxyl-terminal region of each tubulin subunit. Computer analysis of the subunit amino-acid sequences suggested possible locations of the putative calcium-binding sites.
Amino Acid Sequence↗
Quantitative subcellular localization of calmodulin-dependent phosphatase in chick forebrain.
Using a radioimmunoassay, we have measured the level of calmodulin-dependent phosphatase (calcineurin) in various subcellular fractions from chick forebrain. Our results revealed high levels of the enzyme in the cytoplasm and microsomes. A considerable amount was also observed in synaptosomes, where it was found exclusively in the synaptoplasm, comprising 0.32% of the total synaptoplasmic protein. Immunocytochemical localization of the phosphatase in isolated synaptosomes supported the biochemical finding. Phosphatase was not detected in nuclei, myelin, synaptic vesicles, and mitochondria. These results suggest that myelin basic protein and histone H1, widely used in biochemical characterization studies of the phosphatase, may not be physiological substrates, and that the cytoplasm, microsomes, and synaptoplasm may prove to be useful sources for the identification of physiological substrates.
Animals↗
Grasping for calcium binding sites in sodium channels with an EF hand.
Amino acid sequences near the carboxy terminal end of the Electrophorus electricus electric organ and rat brain sodium channel polypeptides were discovered to be putative EF hand calcium binding sites. This conclusion was made using the following criteria: the Tufty-Kretsinger and Szebenyi-Moffat EF hand tests, a computer generated analysis, the revised guidelines of Chou & Fasman, and sequence comparisons with other published EF hand calcium binding regions. These results suggest that the sodium channel may be a calcium binding protein.
Amino Acid Sequence↗
A spectrofluorimetric assay of calmodulin-dependent protein phosphatase using 4-methylumbelliferyl phosphate.
A continuous spectrofluorimetric assay of calmodulin-dependent phosphatase is described. The assay monitors the formation of a fluorescent 4-methylumbelliferone from the dephosphorylation of 4-methylumbelliferyl phosphate and detects as little as 1 pmol of 4-methylumbelliferone. The phosphatase shows a Km of 1.3 mM for the substrate and a Vmax of 100 nmol/mg/min.
Animals↗
Calcium-binding proteins in whole brain and synaptic subfractions.
At least 19 calcium-binding proteins were detected in avian brain subfraction using 45Ca2+ binding to proteins immobilized in polyacrylamide gels. Half of the 45Ca2+ binding proteins were observed in presynaptic cytoplasm. Two-dimensional gel electrophoresis of this material revealed at least 14 45Ca2+ binding polypeptides besides calmodulin. These proteins may be important in brain and nerve terminal function.
Animals↗
Optimal fixation of chick synaptosomes using different osmotic pressures.
Chick synaptosomes were found to remain intact following fixation in the presence of 0.2 M sucrose or 0.3 M sucrose. Increasing the sucrose concentration up to 0.4 M significantly decreased the number of intact synaptosomes; however, typical intrasynaptosomal organelles such as synaptic vesicles and mitochondria were visible in all preparations. This work suggests possibly important species differences in synaptosomal structure between chick and rat synaptosomes.
Animals↗
Improved detection of calcium-binding proteins in polyacrylamide gels.
We refined the method of Schibeci and Martonosi (1980a) to enhance detection of calcium-binding proteins in polyacrylamide gels using 45Ca2+. Our efforts have produced a method which is shorter, has 40-fold greater sensitivity over the previous method, and will detect 'EF hand'-containing calcium-binding proteins in polyacrylamide gels below the 0.5 microgram level. In addition, this method will detect at least one example from every described class of calcium-binding protein, including lectins and gamma-carboxyglutamic acid containing calcium-binding proteins. The method should be useful for detecting calcium-binding proteins which may trigger neurotransmitter release.
Calcium↗
Troponin is unlikely to occur in bovine and chick forebrain.
A search for the presence of troponin in brain reveals that troponin is below 0.00037% of total bovine brain soluble protein. Troponin levels were examined using G-actin-linked Sepharose affinity chromatography and 45Ca binding. The chromatographic and 45Ca binding experiments revealed the presence of several actin and calcium-binding proteins, none of which corresponded to any troponin subunit. In addition, troponin was not found in any chick brain subfraction analyzed, and the level of troponin in chick nerve ending cytoplasm enriched for troponin was less than 0.023%. Considering that substantial amounts of myosin and actin occur in brain, these findings indicate that troponin is not likely to be a regulator of putative brain actomyosin interactions. The significance of these results and their relation to proposed models for neurotransmitter release is discussed.
Animals↗
Psoralen-fatty acid adducts activate melanocyte protein kinase C: a proposed mechanism for melanogenesis induced by 8-methoxypsoralen and ultraviolet A light.
Diacylglycerol, a protein kinase C activator, induces and enhances melanogenesis in vitro and in vivo, providing evidence that melanogenesis may be a protein kinase C-mediated process. Melanogenesis is also induced by ultraviolet A radiation and potentiated by a combination of 8-methoxypsoralen and ultraviolet A radiation. We incubated cultured normal human melanocytes with 8-methoxypsoralen, irradiated the cells with ultraviolet A radiation, and detected formation of 8-methoxypsoralen-phospholipid photoadducts. The 8-methoxypsoralen-phospholipid photoadducts isolated from melanocytes were substrates for phospholipase A2 to generate 8-methoxypsoralen-fatty acid adducts. We found that 8-methoxypsoralen-fatty acid photoadducts prepared in vitro could be substituted for diacylglycerol to activate protein kinase C in a cell-free system. We propose that 8-methoxypsoralen-fatty acid adducts activate protein kinase C to potentiate ultraviolet A radiation-induced melanogenesis. This proposal links melanogenesis mediated by protein kinase C with that induced by a combination of 8-methoxypsoralen and ultraviolet A radiation.
Animals↗