Browsing by Subject "Chickens"
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- ItemOpen AccessHypomelanosis in chickens(1994) Marco, Heather Gaile; Kidson, Susan HHypomelanosis, a severe reduction in pigmentation, is a widespread phenomenon which affects many different vertebrate species, including humans and chickens. The cause(s) of various forms of hypomelanosis is (are) not known. The aim of this study was to determine the cause of hypomelanosis in a breed of white chickens (White Plymouth Rock x Pile Game). It was hoped that this hypomelanotic breed may provide insight into the etiopathogenesis of certain human hypomelanotic disorders, such as vitiligo and albinism. To determine whether melanocytes are present in the hypomelanotic skin, two melanocyte-specific assays were carried out, in situ DOPA histochemistry and a sensitive radiometric assay for tyrosinase. The results show that active tyrosinase was present in 8, 9 and 10 day skins. However, unlike normal black skin, the level of tyrosinase did not increase with age, suggesting that the melanocytes either die or that they do not continue to synthesise tyrosinase. Ultrastructurally, these melanocytes appeared to be morphologically normal and they did not show signs of premature degeneration. Unlike black chick melanocytes, however, they contained very few premelanosomes and fully melanised melanosomes were never observed, suggesting that hypomelanosis results from the arrested development (melanisation) of melanosomes in vivo. Two different experiments were carried out to determine whether this blockage in melanogenesis is intrinsic in the melanocyte or whether it is caused by extrinsic environmental factors. The outcome of these studies were conflicting: 1) In culture, white chick neural crest cells produced pigment, suggesting that the melanocyte is not defective. However, ultrastructural examination of these cultured melanocytes showed that they contained a large proportion of partially melanised melanosomes. 2) Black chick neural crest cells migrated into white skin explants and contributed towards pigment in the developing feathers, suggesting that the white chick tissue environment is also not defective. The results hint that hypomelanosis in the white chicks is caused by the interaction of at least two genetic defects: an intrinsic mutation of the melanocyte, as well as an extrinsic mutation in the melanocyte environment that, in combination, exert an inhibitory influence on melanin synthesis. This study shows that, in situ, white chick melanocytes share some features with ty-pos albino melanocytes and may be representative of this pigmentary disorder. White Plymouth Rock x Pile Game chicks may also be useful as a model for the multi-faceted disorder, vitiligo.
- ItemOpen AccessMagnesium-dependent Association and Folding of Oligonucleosomes Reconstituted with Ubiquitinated H2A(2001) Jason, Laure J M; Moore, Susan C; Ausió, Juan; LINDSEY, GeorgeThe MgCl2-induced folding of defined 12-mer nucleosomal arrays, in which ubiquitinated histone H2A (uH2A) replaced H2A, was analyzed by quantitative agarose gel electrophoresis and analytical centrifugation. Both types of analysis showed that uH2A arrays attained a degree of compaction similar to that of control arrays in 2 mM MgCl2. These results indicate that attachment of ubiquitin to H2A has little effect on the ability of nucleosomal arrays to form higher order folded structures in the ionic conditions tested. In contrast, uH2A arrays were found to oligomerize at lower MgCl2 concentrations than control nucleosomal arrays, suggesting that histone ubiquitination may play a role in nucleosomal fiber association.
- ItemOpen AccessNon-lysosomal protein degrading systems in chicken skeleton muscle(1990) Arnold, Jane Elizabeth; Gevers, WielandIn an attempt to understand the roles played by the ubiquitin-dependent and calpain pathways in protein degradation in chicken skeletal muscles, biochemical studies were conducted on components of these two systems as well as their potential endogenous and exogenous substrates. ATP- and ubiquity tin-dependent breakdown of endogenous proteins (measured by tyrosine release) or exogenous proteins (measured by the appearance of trichloroacetic acid-soluble radiolabel after incubation with 125rlysozyme) took place in muscle extracts; the specific activities of these processes were significantly lower than those detected in rabbit reticulocytes. Conjugation of ubiquitin to a subset of endogenous proteins was detected by incubating muscle extracts (fraction II: depleted of ubiquitin by DEAE-cellulose chromatography) with 125rubiquitin and Mg2+-ATP, followed by analysis of the radiolabelled conjugates by one-dimensional polyacrylamide gel electrophoresis in the presence of sos, and autoradiography. Discrete conjugates were formed with apparent molecular weights between 30 -100 000, as well as a large number of undifferentiated entities of higher molecular weights. Conjugation of ubiquitin to the exogenous protein lysozyme was detected only when fresh, as opposed to previously frozen fraction II preparations were assayed: three bands were obtained, as opposed to the six ubiqui tin conjugates formed by reticulocyte extracts. The muscle system catalyzed the ubiquitination of partially purified myofibrillar proteins, principally myosin and possibly actin. Fractionation of the ubiquitin-activating enzymes into El and E2 on the one hand, and E3 on the other, permitted mixing experiments to be conducted by means of conjugation assays, and confirmed the low content of E3 in muscle as opposed to reticulocytes. Fraction II from muscle displayed ubiquitin conjugatedegrading activity but again this was less active than in reticulocytes. A number of other proteolytic activities, independent of ubiquitin, w~re also present. Isopeptidases, active on 125I-ubiquitin conjugates were strongly inhibited by sulphydryl alkylating agents such as N-ethylmaleimide. The overall picture of the ubiquitin pathway in muscle is one where many proteins may be converted into long-lived conjugates but not in all cases requiring the action of E3: some E3-dependent protein degradation undoubtably does occur in this physiologically basal system. Formation of a ubiquitin conjugate of the ubiquitinactivating enzyme (El) and some of the ubiquitin carrier proteins (E2 's) was detected during incubations of 125rubiqui tin and ATP lasting 2 hr or longer. Because treatment of such systems with NaOH, even at early times during the incubations, greatly enhanced the appearance of the same entities, the phenomenon appeared to be one of auto-, rather than E3-mediated ubiquitination. The bonds involved had properties compatible with their being peptidic in nature, and their formation occurred from ubiguitin thiolesters bound to El and E2. The protease inhibitor and alkylating agent, TLCK, when pre-incubated with fraction II for 2 hr before the addition of 125I-ubiquitin and ATP, greatly enhanced the subsequent auto-ubiqui tination of El in the absence of NaOH treatment, and caused the inhibition of it adenylate-forming and thiolester-transferring activities: thus, ubiquitin transfer to E2's and further to other acceptors was markedly impaired. Such an inactivation of El by TLCK may, in a manner analogous to that described in the thermolabile ts85 mutants (Finley et al., 1984), be the basis of the action of this agent to block the cell cycle in late G2 or early M phase (Schnebli & Haemmerli, 1974). TLCK-induced inactivating auto-ubiquitination of El may be an important tool for the study of ubiquitindependent processes which (apart from possible intrinsic protease activity), all appear to require the activity of this enzyme. The number of calpain species existing in chicken skeletal muscle is controversial with only one ( Ishiura et al. , I 1978) or three (Wolfe et al., 1985) species having been reported. When extracts of chicken skeletal muscle were applied to a DEAE-cellulose column and the bound protein eluted in a linear salt gradient, two calpain activities, separated from their endogenous inhibitors (calpastatins), were detected. The first eluting activity, "calpain I", was active at low ca2+ concentrations, was heat-labile and had a lower apparent molecular weight on gel filtration when compared with the later eluting activity which appeared to be a typical calpain II species. "Calpain I”. was not an autolytic product of calpain II but appeared to be derivea from a more heat-stable calpain I species. A proportion (up to 14%) of the calpains in crude muscle extracts was bound to membrane fractions in the presence of ca2+; this could be removed by EGTA treatment. In addition, membrane-bound fractions examined by 9el filtration contained calpain• forms of an apparent molecular · weight lower than that of calpain which had not been membraneassociated. Membrane binding of the calpains (especially of calpain II), may be important in physiological activation.
- ItemOpen AccessA novel glucagon-related peptide (GCRP) and its receptor GCRPR account for coevolution of their family members in vertebrates(Public Library of Science, 2013) Park, Cho Rong; Moon, Mi Jin; Park, Sumi; Kim, Dong-Kyu; Cho, Eun Bee; Millar, Robert Peter; Hwang, Jong-Ik; Seong, Jae YoungThe glucagon (GCG) peptide family consists of GCG, glucagon-like peptide 1 (GLP1), and GLP2, which are derived from a common GCG precursor, and the glucose-dependent insulinotropic polypeptide (GIP). These peptides interact with cognate receptors, GCGR, GLP1R, GLP2R, and GIPR, which belong to the secretin-like G protein-coupled receptor (GPCR) family. We used bioinformatics to identify genes encoding a novel GCG-related peptide (GCRP) and its cognate receptor, GCRPR. The GCRP and GCRPR genes were found in representative tetrapod taxa such as anole lizard, chicken, and Xenopus , and in teleosts including medaka, fugu, tetraodon, and stickleback. However, they were not present in mammals and zebrafish. Phylogenetic and genome synteny analyses showed that GCRP emerged through two rounds of whole genome duplication (2R) during early vertebrate evolution. GCRPR appears to have arisen by local tandem gene duplications from a common ancestor of GCRPR , GCGR , and GLP2R after 2R. Biochemical ligand-receptor interaction analyses revealed that GCRP had the highest affinity for GCRPR in comparison to other GCGR family members. Stimulation of chicken, Xenopus , and medaka GCRPRs activated Gα s -mediated signaling. In contrast to chicken and Xenopus GCRPRs, medaka GCRPR also induced Gα q/11 -mediated signaling. Chimeric peptides and receptors showed that the K 16 M 17 K 18 and G 16 Q 17 A 18 motifs in GCRP and GLP1, respectively, may at least in part contribute to specific recognition of their cognate receptors through interaction with the receptor core domain. In conclusion, we present novel data demonstrating that GCRP and GCRPR evolved through gene/genome duplications followed by specific modifications that conferred selective recognition to this ligand-receptor pair.
- ItemOpen AccessStructure and biological activity of avian hypothalamic luteinizing hormone-releasing hormone(1982) King, Judy A; Millar, Robert PIn 1971 Schally and co-workers (Schally et al., 1971) isolated gonadotropin-releasing hormone (now called luteinizing hormone-releasing hormone (LH-RH)) from sheep hypothalami and established that the hormone was a decapeptide with the amino acid sequence: pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂. The peptide was subsequently synthesised (Matsuo et al., 1971b) and shown to stimulate the release of gonadotropins (luteinizing hormone and follicle-stimulating hormone) in a wide range of mammalian species (Schally et al., 1973, 1976). With the exception of amphibians, nonmammalian vertebrates have a poor gonadotropin response to synthetic mammalian LH-RH (for reviews, see Ball, 1981; Jackson, 1981; King and Millar, 1981a). Since there is considerable molecular heterogeneity in the related neurohypophysial nonapeptide hormones (oxytocin-vasopressin) amongst vertebrates (Acher et al., 1972), we postulated that differences might exist in the structure of hypothalamic LH-RH in different vertebrate classes, Utilising a combination of regionspecific antisera and chromatographic techniques, we established that amphibian hypothalamic LH-RH is identical to the mammalian peptide while avian, reptilian, and piscine hypothalamic LH-RHs differ structurally in the region Gly⁶-Leu⁷-Arg⁸ (King and Millar, 1979a, 1980), We have now conducted further studies on avian hypothalamic LH-RH, which indicate that the arginine residue in position eight of mammalian LH-RH is substituted by glutamine in this vertebrate class. Purification of LH-RH from chicken hypothalami and determination of the amino acid composition have confirmed that the structure of avian LH-RH is: pGlu-His-Trp-Ser-Tyr-Gly-Leu-Gln-Pro-Gly-NH₂.
- ItemOpen AccessThe metabolic effects of a commercially available chicken peri-peri (African bird’s eye chilli) meal in overweight individuals(2017) Kroff, Jacolene; Hume, David J; Pienaar, Paula; Tucker, Ross; Lambert, Estelle V; Rae, Dale EAbstract A growing body of evidence suggests that capsaicin ingestion may lead to desirable metabolic outcomes; however, the results in humans are equivocal. Whether or not benefits may be gained from ingestion of capsaicin via a commercially available meal has not been determined. The objectives of this randomised, cross-over intervention study were to compare the 2 h postprandial effects of a standard commercially prepared meal containing chilli (HOT, 5·82 mg total capsaicinoids) with a similar meal with no chilli (CON, <1·0 mg total capsaicinoids) on resting energy expenditure, plasma insulin, glucose, serum high sensitivity C-reactive protein (hs-CRP) concentrations, core body temperature and forearm microvascular reactivity responses in overweight individuals. A total of thirty-four apparently healthy individuals (sixteen men and eighteen women) between 18 and 50 years of age, with a BMI >25 kg/m 2 and a waist circumference >94 cm (men) or 80 cm (women), were studied. Participants had normal glucose tolerance and were accustomed, but were not regular chilli eaters. A paired t test indicated that insulin AUC was smaller following the HOT meal ( P =0·002). Similarly, there was a tendency for glucose AUC to be reduced following the HOT meal ( P =0·056). No discernable effects of the HOT meal were observed on metabolic rate, core temperature, hs-CRP concentrations and endothelial-dependent microvascular reactivity. The results from this study indicate that a standard restaurant meal containing a relatively small dose of capsaicin delivered via African bird’s eye chilli, which is currently available to the public, results in lower postprandial insulin concentrations in overweight individuals, compared with the same meal without chilli.