Biochemical composition of secretions from uropygial glands of steamer-ducks

Study of the secretions of the uropygial glands of the four species of steamer-duck (Tachyeres) revealed significant interspecific differences in the biochemical composition of the lipids and constituent fatty acids and alcohols. A canonical analysis of the fatty acids from monoester waxes provided an estimate of interspecific biochemical differentiation, but sexual differences in biochemistry, great intraspecific variation, and a lack of information concerning homologies and polarities of biochemical structures prevent confident chemophylogenetic inferences for the present.     

Ectoparasites, uropygial glands and hatching success in birds

The uropygial gland of birds secretes wax that is applied to the plumage, where the secretions are hypothesized to eliminate fungi and bacteria, thereby potentially providing important benefits in terms of plumage maintenance. We analyzed variation in size of the uropygial gland in 212 species of birds to determine the function and the ecological correlates of variation in gland size. Bird species with larger uropygial glands had more genera of chewing lice of the sub-order Amblycera, but not of the sub-order Ischnocera, and more feather mites. There was a fitness advantage associated with relatively large uropygial glands because such species had higher hatching success. These findings are consistent with the hypothesis that the uropygial gland functions to manage the community of microorganisms, and that certain taxa of chewing lice have diverged as a consequence of these defenses.     

House Sparrows Passer domesticus with larger uropygial glands show reduced feather wear

This study assesses whether uropygial gland size is related to improved feather quality. To address this question, I analysed the relationship between uropygial gland size and feather wear in the House Sparrow Passer domesticus. The results show that birds with larger uropygial glands had less worn feathers, suggesting that uropygial gland secretions improve feather resistance to abrasion.     

Cytological differentiation in the uropygial gland.

Ultrastructural changes were studied in the cells undergoing secretory differentiation in zone I of the tubules of the uropygial gland of White Plymouth Rock chickens. A layer of basal cells and four secretory stages are recognized as the cells migrate from the periphery to the lumen of tubules and progressively elaborate a secretion product. Basal cells, containing rough endoplasmic reticulum and free ribosomes, rest on the basement membrane and are the source from which secretory cells arise. Dilated perinuclear cisternae and the proliferation of smooth endoplasmic reticulum in the form of vesicles, invaginated sacs and cusp-shaped cisternae indicate the onset of lipgenesis in stage I cells. The perinuclear cisternae are more dilated and the endoplasmic reticulum is composed on saccules and cisternae in stage II cells. Stage III cells are characterized by concentric lamellae of endoplasmic reticulum surrounding secretory droplets. Dilated cisternae of endoplasmic reticulum and secretory droplets both contain a reticular substance. The perinuclear cisternae of stage III cells have returned to normal dimensions. Large mature lucent secretory droplets, lined with electron-dense material, fill the cytoplasm ostage IV cells which degenerate and release their secretory product into the tubule lumen. Spherical membrane-bound compartments containing a mottled substance of moderate electron density occur in basal cells and all subsequent secretory stages. These mottled bodies are surrounded by saccules of endoplasmic reticulum in stage II cells and are intimately associated with secretory droplets in stage III cells, but there is no evidence that they give rise to secretory droplets and their role in secretory differentiation is unknown.     

Enzymatic esterification of alkane-2,3-diols by the microsomes of the uropygial glands of ring-necked pheasants (Phasianus colchicus)

Extracts of uropygial glands of ring-necked pheasants (Phasianus colchicus) catalyzed diester formation from tritiated C₁₈ alkane-2,3-diol. Monoacylated diol was also tentatively identified in the enzymatic product. Subcellular fractionation showed that the esterifying activity was located mainly in the microsomal fraction. ATP and CoA were required for the esterification process, and this reaction was stimulated by Mg²⁺. Source of the acyl moieties for esterification was endogenous, and addition of exogenous fatty acid inhibited the reaction. When microsomes were treated with bovine serum albumin (BSA) in order to remove the endogenous source of acyl moieties, palmitoyl-CoA substituted for the ATP and CoA requirement. The pH optimum with ATP and CoA was between 6.0–9.0, while maximal rates of esterification were obtained with palmitoyl-CoA from pH 7.0 to 9.0. Borate ions stimulated esterification. The half maximal velocity was obtained with 2.0 × 10^?4, m diol, and 7.2 × 10^?5, m palmitoyl-CoA. Thiol reagents severely inhibited the esterification reaction with ATP and CoA, while much less inhibition was observed when palmitoyl-CoA was used. It is concluded that a microsomal acyl-CoA-diol transacylase catalyzes stepwise acylation of alkane-2,3-diols to give the diol diester which constitute the major component of the uropygial lipids of ring-necked pheasants.     

Purification and characterization of a fatty acyl-CoA hydrolase from the uropygial glands of Peking ducks (Anas domesticus)

In a previous communication the occurrence of a medium-chain acyl-CoA hydrolase designated thioesterase-B in the uropygial gland of mallard ducks was reported [L. Rogers, P. E. Kolattukudy, and M. J. de Renobales (1982) J. Biol. Chem. 257, 880-886]. In the present study, thioesterase-B was purified from the postmicrosomal supernatant of homogenized uropygial glands from Peking ducks (Anas domesticus). Most of the contaminating thioesterase activities were removed by ammonium sulfate fractionation. The 55% ammonium sulfate supernatant, containing thioesterase-B, was chromatographed on hydroxylapatite followed by gel filtration on Sephadex G-100. The remaining contaminants were removed by chromatofocusing followed by desalting on Sephadex G-75. This procedure gave a 26% yield with a nearly 200-fold purification. Gel filtration of the purified enzyme showed that the molecular weight of the native enzyme was 56,300, whereas sodium dodecyl sulfate-gel electrophoresis of components separated by chromatofocusing showed that the purified enzyme contained enzymatically active proteins of molecular weights 59,400, 58,300, 56,000, and 55,800. The four species differed slightly in pI (4.9, 4.7, 4.45, and 4.40) but they were kinetically and immunologically indistinguishable. All four had the same N-terminal sequence. The purified thioesterase preparation showed a pH optimum of 9.3 with C12-CoA but the pH optimum was dependent on the chain length of the acyl group. At pH 8.0, C10 was the preferred substrate with less activity on C12, C8, and C14. The enzymatic activity was stimulated by bovine serum albumin and was inhibited by p-hydroxymercuribenzoate. Involvement of active serine in catalysis was suggested by inhibition of the enzyme by diethylpyrocarbonate, diisopropylfluorophosphate and phenylmethylsulfonyl fluoride.     

Diesters of 3-hydroxy fatty acids produced by the uropygial glands of female mallards uniquely during the mating season

The uropygial gland secretions produced by female mallards (Anas platyrhynchos) throughout the year were analyzed by thin-layer chromatography and combined gas-liquid chromatography and mass spectrometry. Most of the year, the secretion was composed of wax esters. With the beginning of the mating season in the middle of March, a polar component appeared which became the dominant and sole component of the secretion through April and May and as the mating season ended in June, wax esters became the sole component of the secretion. The polar components were identified to be diesters of n-C8, n-C10, and n-C12 3-hydroxy acids with n-C16 and n-C18 alcohols and n-C6 to C16 even chain acids. Immediately after the diester-producing period the female uropygial glands produced very long chain wax esters composed of fatty acids longer than C12. By the end of August, shorter chain wax esters composed of C6 and C12 acids became the dominant components of the secretion and this composition, previously considered characteristic of mallards, remained constant until March. The observed disappearance of the short chain waxes during the postnuptial period is similar to that in males. The dramatic changes in the composition of the uropygial glands similar to those observed in the female mallards during the mating season have not yet been observed in any other species.     

Lipid biosynthesis in the sebaceous glands: synthesis of multibranched fatty acids from methylmalonyl-coenzyme A in cell-free preparations from the uropygial gland of goose.

Cell-free extracts from the uropygial gland of goose catalyzed the incorporation of malonyl-CoA and methylmalonyl-CoA into n- and multi-branched fatty acids, respectively, with NADPH as the preferred reductant. Methylmalonyl-CoA was shown to be incorporated almost exclusively into the acyl portion of wax esters by the cell-free extract while malonyl-CoA was incorporated into polar lipids and both the acyl and alcohol portions of the wax. The optimal pH for the synthesis of both n- and multibranched acids was 6.0. Apparent Km and Vmax for malonyl-CoA were 2 times 10- minus-4 M and 250 nmol per min per mg, respectively, while the Km and Vmax for methylmalonyl-CoA were 7.7 times 10- minus-4 M and 0.8 nmol per min per mg, respectively with 105,000g supernatant; but partial purification resulted in a tenfold decrease in Km values. The partially purified synthetase preparation catalyzed the formation of n-C16 acid (80%) and n-C18 acid (20%) from acetyl-CoA and malonyl-CoA. With the same synthetase preparation and the appropriate primer methylmalonyl-CoA was converted into 2,4,6,8-tetramethyldecanoic acid and 2,4,6,8-tetramethylundecanoic acid which were identified by radio gas-liquid chromatography and combined gas chromatography-mass spectrometry. Experiments with an equimolecular mixture of acetyl-CoA and propionyl-CoA showed that the synthetase preferred acetyl-CoA as a primer. Since malonyl-CoA is known to be rapidly decarboxylated in the gland, acetyl-CoA and methylmalonyl-CoA are expected to be the major primer and elongating agent, respectively, available in the gland and therefore 2,4,6,8-tetramethyldecanoic acid should be the major product. Combined gas-liquid chromatography and mass spectrometry demonstrated that this acid was in fact the major acid of the gland.     

Chemical composition of uropygial gland secretions of owls

The compositions of the uropygial gland secretions of the long-eared owl, eagle owl, and barn owl have been determined. The waxes of the first two owls, which are closely related, are composed of 2-alkyl-substituted fatty acids and n- or monomethyl-branched alcohols with even-numbered branching positions. In addition, some dimethyl-substituted alkanols were observed. In contrast to these waxes, the secretion of the barn owl is composed of 3-methyl- and 3,5-, 3,7-, 3,9-, 3,11-, 3,13-, and 3,15-dimethyl-branched fatty acids and n- as well as monomethyl-substituted alkanols branched at positions 2, 3, and 4. The mass spectra of esters of 2-alkyl-substituted fatty acids are discussed.     

Testosterone metabolism in the uropygial gland of the quail

The metabolism of testosterone in the uropygial gland of the quail principally results in the production of 17 alpha, 5 beta derivatives. Moreover, an unusually small amount of testosterone is converted to 5 alpha-dihydrotestosterone. These results question the role played by intracellular 5 alpha-reduction in the response of the gland to testosterone stimulation.     

Recessive inherited doubling of the chicken's uropygial gland papilla

A new mutation that causes doubling of the uropygial gland (oil gland) papilla is described, and data that demonstrate its inherited basis are presented. This condition, which has been given the name "double oil gland papilla," varies in its expression: some individuals show only an indention of the papilla tip, while others exhibit a complete cleavage of the papilla such that two completely separate papillae project from a single oil gland. The data presented show that a single autosomal recessive gene, dgp, is the main determinant of this trait, but that its expression may also be influenced by background genetic factors as well as sex. Males more frequently are of the extreme doubling expression while females more frequently express the milder indented phenotype. Approximately 4% of mutant females are classified as normal. A linkage test with the rose comb gene showed independent segregation.     

The chemical composition of uropygial gland secretions from ralliformes

The uropygial gland wax from rails contains ester waxes, triester waxes and triglycerides. The ester waxes are composed of mainly methyl-substituted fatty acids with predominantly n-alkanols. Methyl-branched alcohols are only found in minor amounts. The occurrence of 2,6,10- and 4,8,12-trimethyl-substituted acids can be used as chemotaxonomie markers. The triester waxes contain n-fatty acids, n-alkanols and alkyl-hydroxymalonic acids.