Browning pigments

The last brown pigment to be considered is the Hon manganese brown. This is the deep brown associated with electrical porcelain insulators and with artware and bean pots. In many gla2es the presence of manganese wiH cause poor surface and unstable color. Hence, the use of this pigment is limited to dark colors on products where gla2e surface quaHty requHements are modest. 

The color of die iris may change because of an increase of the brown pigment and cause different eye coloration. This may be more noticeable in patients with blue, green, or gray brown or other light-colored eyes. 

Rat (Sprague- Dawley) 13 wk ad lib (F) Hemato Hepatic 3.8 M 0.8 (decreased hemoglobin) 23.4 M (granular brown pigment increased liver weight) Hoechst 1985a Technical... 

Solar lentigo are a macular area of brown pigmentation appearing after either acute or chronic sun exposure. The term solar lentigo is In younger patients solar lentigo are seen on preferred to senile lentigo, which is sometimes sim-exposed areas (Fig. i8.i). There is usually a... 

Chrome-magnesite brick, 6 495 Chrome Manganese Zinc Brown, pigment for plastics, 7 369t Chrome-mordant dyeing, 9 399 Chromenes... 

Iron Chromite Brown, pigment for plastics, 7 369t... 

Zinc-iron alloy plating, 9 831 Zinc iron chromite brown spinel formula and DCMA number, 7 348t Zinc Iron Chromite Brown pigment for plastics, 7 369t Zincite... 

Compound (25) parallels the acetoacetarylides of the monoazo yellow pigment series. Red and brown pigments, on the other hand, which are obtained with (26), find their counterpart in the corresponding Naphthol AS pigments. 

Rd stands for the usual substituents for diazo components (see, for instance, Sec. 2.6.1). However, it may also comprise additional carbonamide groups, connected via phenyl moieties. In commercially important pigments, A commonly represents a phenylene or a diphenylene group, and n is any number between 1 and 3. This general structure also covers orange and brown pigments. 

The reddish brown pigment is characterized by the following chemical structure ... 

Large amounts of iron are sequestered in substantia nigra and in locus coerulus as a neuromelanin-iron complex in dopaminergic neurons particularly in PD. Neuromelanin, a granular dark brown pigment, is produced in catecholaminergic neurons of the SN and... 

The initial products of the reactions between sugars and proteins may enter a cascade of reactions yielding fluorescence, browning, and polymerization of proteins ("cross-linking"). The brown pigments, so-called melanoidins, are polymers whose composition has not yet been established completely. Melanoidins bind calcium and may thus interfere with de- and remineralization in caries. 

Armstrong attributed the increased resistance of dentin matrix to proteolysis to the blockage of susceptible sites by covalently bound carbohydrate. Later it became clear that the Maillard reaction induces the formation of covalent bonds (cross-links) between protein molecules, accounting for such resistance as well. The presence of non-degradable matrix proteins inhibits mineral dissolution (Chapter 2). In addition, both brown pigments and cross-linked proteins inhibit the production of extracellular polysaccharides by cariogenic streptococci (Kobayashi et al., 1990). 

From carious enamel, a brown pigment-producing Actinomyces has been isolated (Hurst et al., 1948). Black caries lesions contained higher numbers of Actinomyces, Lactobacillus, and Veilonella (but not black pigmented Prevotella) than unstained lesions (Boue et al., 1987). 

Nordbo H, Eriksen HM and Rolla G (1979) Affinity of hydroxyapatite for furfural and a brown pigment formed by furfural and glycine. Scand J Dent Res 87, 395-397. 

Van Reenen JF (1955) The yellow-brown pigmentation of dental caries. A survey of the literature. J Dent Assoc S Afr 10, 262-267. 

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