Browsing by Author "King, Judy A"

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    Evolution of the structure and function of vertebrate brain gonadotropin-releasing hormone
    (1986) Powell, R C; King, Judy A
    In this study, the structure and function of gonadotropin-releasing hormone (GnRH) in different vertebrate species, in the classes Aves, Reptilia and Pisces was investigated. Acetic acid extracts were subjected to gel filtration chromatography and semipreparative high performance liquid chromatography (HPLC) to partially purify the GnRHs. The GnRH immunoreactivity was then characterized by analytical HPLC, and by assaying HPLC fractions by radioimmunoassay with region-specific antisera generated against mammalian GnRH, Gln⁸-GnRH and Trp⁷,Leu⁸-GnRH and assessing luteinizing hormone (LH)-releasing activity of fractions in a chicken dispersed anterior pituitary cell bioassay. Five GnRH molecular forms have thusfar been structurally characterized in vertebrate brain. In mammals a GnRH with the structure pGlu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH₂ has been demonstrated in the hypothalamus (Matsuo et al., 1971; Burgus et al., 1972). Gln⁸-GnRH and His⁵,Trp⁷,Tyr⁸-GnRH were present in chicken hypothalamus (King and Millar, 1982a, 1982c; Miyamoto et al., 1983, 1984), Trp⁷,Leu⁸-GnRH in salmon brain (Sherwood et al., 1983) and Tyr³,Leu⁵,Glu⁶,Trp⁷,Lys⁸-GnRH in lamprey brain (Sherwood et al., 1986). In ostrich (Struthio camelus) hypothalamus two GnRHs with identical properties to Gln⁸-GnRH and His⁵,Trp⁷,Tyr⁸-GnRH have been demonstrated, as well as four other LR-releasing factors with different chromatographic and immunological properties to any of the known naturally-occurring GnRHs. Since Gln⁸-GnRH and His⁵,Trp⁷,Tyr⁸-GnRH were also present in chicken hypothalamus it appears likely that these two GnRHs occur in all birds. In alligator (Alligator mississippiensis) brain only two GnRHs were detected. These forms co-eluted with Gln⁸-GnRH and His⁵,Trp⁷,Tyr⁸-GnRH in two HPLC systems. They cross-reacted similarly to the two synthetic peptides with antisera directed against mammalian GnRH and Gln⁸-GnRH and released LH from chicken dispersed anterior pituitary cells in a similar manner to the synthetic peptides. The Archosaurs (alligators and crocodiles) are believed to be closely related to birds and therefore it seems likely that they should have identical GnRHs. In skink (Calcides ocellatus tiligugu) brain one GnRH, which co-eluted with His⁵,Trp⁷,Tyr⁸-GnRH, was demonstrated. Two other lizards (Cordylis nigra and Pordarcis s. sicula) have been studied (Powell et al., 1985; R.C. Powell, G. Ciarcia, V. Lance, R.P. Millar and J.A. King, submitted). In c. nigra four immunoreactive GnRHs were detected, two of which co-eluted released chicken LH similarly to, Trp⁷,Leu⁸-GnRH and with, and His⁵,Trp⁷,Tyr⁸-GnRH. In P. s. sicula a GnRH molecular form similar to Trp⁷,Leu⁸-GnRH occurred as well as two novel GnRHs. It thus appears that Gln⁸-GnRH does not occur in lower reptiles, but His⁵,Trp⁷,Tyr⁸-GnRH and/or Trp⁷,Leu⁸-GnRH do. His⁵,Trp⁷,Tyr⁸-GnRH appears to he a widespread GnRH, occurring in vertebrates as diverse as birds and elasmobranch fish. In dogfish (Poroderma africanum) brain seven factors, which stimulated release of LH from chicken dispersed anterior pituitary cells, were separated on analytical HPLC. Two of these factors were partially characterized as Trp⁷,Leu⁸-GnRH and His⁵,Trp⁷,Tyr⁸-GnRH. Three of the other forms cross-reacted with GnRH antisera, but appear to be novel GnRHs. In teleost (Coris julis) brain two GnRHs similar to Trp⁷,Leu⁸-GnRH and His⁵,Trp⁷,Tyr⁸-GnRH were present. These two GnRHs therefore appear to occur in both fish species studied. Trp⁷,Leu⁸-GnRH is widespread amongst teleost fish (Jackson and Pan, 1983; Sherwood et al., 1983; Breton et al., 1984; Sherwood et al., 1984; King and Millar, 1985). From these data it seems evident that the mammalian GnRH molecular form occurs only in mammals and amphibians, Gln⁸-GnRH in birds and higher reptiles, and Trp⁷,Leu⁸-GnRH in gnathostomes. His⁵,Trp⁷, Tyr⁸-GnRH appears to he present in numerous different vertebrates. Tyr³,Leu⁵,Glu⁶,Trp⁷,Lys⁸-GnRH has thus far only been detected in lamprey brain. A number of novel GnRHs, whose structures have not been elucidated are present.
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    High Molecular Weight (HMW): total adiponectin ratio is low in hiv-infected women receiving protease inhibitors
    (2014-12-16) Omar, Fierdoz; Dave, Joel A; King, Judy A; Levitt, Naomi S; Pillay, Tahir S
    Abstract Background At the time of the study, the HIV-treatment policy in South Africa included highly active antiretroviral therapy (HAART) regimens 1 (nucleotide reverse transcriptase inhibitors (NRTIs) only), and 2 (protease inhibitors (PI) and NRTIs). HAART is associated with the lipodystrophy syndrome, insulin resistance and reduced total adiponectin (TA) levels. The high molecular weight (HMW):TA ratio is a superior marker of insulin resistance. The aim of this study was to establish whether HMW:TA ratios are low in patients on PIs and whether they correlate with insulin resistance. Methods This was a cross-sectional study undertaken in an antiretroviral clinic at a tertiary hospital. The participants were 66 HIV-infected females: 22 were on regimen 2 (PI group), 22 on regimen 1 (non-PI) and 22 treatment naïve (TN), matched for BMI and age. Patients with a history of diabetes or impaired glucose tolerance were excluded. Serum adiponectin multimers were analysed using the AlpcoTM Adiponectin (Multimeric) enzyme immunoassay. Waist hip ratios (WHR), glucose and insulin levels were assessed, and HOMA-IR and QUICKI calculated. Data were analysed non-parametrically and multivariate analysis was performed. Results TA and HMW levels were lower in the treatment groups than in the TN group. HMW:TA was lower in the PI than in the non-PI and TN groups, and in the non-PI than in the TN groups. HMW:TA correlated negatively with waist, insulin and HOMA-IR, independently of BMI and duration of therapy. HOMA-IR and QUICKI did not differ among the groups. Conclusion HMW:TA is significantly decreased with HAART (particularly with PIs, but also with non-PIs) and may be a more sensitive marker of insulin resistance in these patients than conventional markers or HMW and total adiponectin individually.
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    The role of Ca²⁺ and cAMP in GnRH-stimulated LH release
    (1991) Wakefield, Ian Kurt; Davidson, James S; King, Judy A
    In this thesis a detailed study of the kinetics of GnRH-stimulated LH release was made. GnRH stimulated LH release in a biphasic manner. During the first 3 minutes of stimulation, there was a transient spike phase of release followed by plateau phase of lower amplitude. Both phases of release are largely dependent on extracellular Ca²⁺. The spike phase of release is dependent on Ca²⁺ entry via a receptor-operated Ca²⁺ channel (ROCC) (about 90%) and on the mobilization of intracellular Ca²⁺ stores. The role of ROCC were examined by using ruthenium red which inhibits both ROCC and voltage-sensitive Ca²⁺ channels (VSCC). VSCC are not involved in the spike phase of GnRH-stimulated LH release since D600 and nifedipine, inhibitors of VSCC, have no effect on the spike phase. The plateau phase of release is dependent on Ca²⁺ entry via VSCC (about 50%) and ROCC (about 50%). Forskolin, an activator of adenylate cyclase, was used to investigate the role of cAMP in LH release. Forskolin stimulated an increase in both LH release and cellular cAMP levels. GnRH was also able to elevate the cellular CAMP concentration. GnRH interacted synergistically with forskolin to stimulate LH release. The synergism between GnRH and forskolin was not due to an interaction at (1) the GnRH receptor, (2) the level of intracellular Ca²⁺ mobilization, or (3) inositol phosphate metabolism. However, forskolin was able to synergistically interact with secretagogues that increase the cytosolic Ca²⁺ concentration and activators of protein kinase C. This suggested that forskolin was interacting with GnRH at a site distal to the activation of the Ca²⁺ second messenger system and protein kinase C. The data suggest that the initial response to GnRH is largely Ca²⁺-dependent and that other second messengers, if active, play a minor role. cAMP is thought to play a modulatory role and may be involved in the maintenance of secretion.
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    Structure and biological activity of avian hypothalamic luteinizing hormone-releasing hormone
    (1982) King, Judy A; Millar, Robert P
    In 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.