Browsing by Author "Marco, Heather G"

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    Open Access
    A single AKH neuropeptide activating three different fly AKH-receptors: an insecticide study via computational methods
    (2021) Abdulganiyyu, Ibrahim A; Jackson, Graham E; Marco, Heather G
    Flies are a widely distributed pest insect that poses a significant threat to food security. Flight is essential for the dispersal of the adult flies to find new food sources and ideal breeding spots. The supply of metabolic fuel to power the flight muscles of insects is regulated by adipokinetic hormones (AKHs). The fruit fly, Drosophila melanogaster, the flesh fly, Sarcophaga crassipalpis, and the oriental fruit fly, Bactrocera dorsalis all have the same AKH that is present in the blowfly, Phormia terraenovae; this AKH has the code-name Phote-HrTH. Binding of the AKH to the extracellular binding site of a G protein-coupled receptor causes its activation. In this thesis, the structure of Phote-HrTH in SDS micelle solution was determined using NMR restrained molecular dynamics. The peptide was found to bind to the micelle and be reasonably rigid, with an S 2 order parameter of 0.96. The translated protein sequence of the AKH receptor from the fruit fly, Drosophila melanogaster, the flesh fly, Sarcophaga crassipalpis, and the oriental fruit fly, Bactrocera dorsalis were used to construct two models for each receptor: Drome-AKHR, Sarcr-AKHR, and Bacdo-AKHR. It is proposed that these two models represent the active and inactive state of the receptor. The models based on the crystal structure of the β-2 adrenergic receptor were found to bind Phote-HrTH with a predicted binding free energy of –107 kJ mol–1 for Drome-AKHR, –102 kJ mol–1 for Sarcr-AKHR and –102 kJ mol–1 for Bacdo-AKHR. Under molecular dynamics simulation, in a POPC membrane, the β-2AR receptor-like complexes transformed to rhodopsin-like. The identification and characterisation of the ligand-binding site of each receptor provide novel information on ligand-receptor interactions, which could lead to the development of species-specific control substances to use discriminately against these pest flies.
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    Comparative genomic analysis of six Glossina genomes, vectors of African trypanosomes
    (2019-09-02) Attardo, Geoffrey M; Abd-Alla, Adly M M; Acosta-Serrano, Alvaro; Allen, James E; Bateta, Rosemary; Benoit, Joshua B; Bourtzis, Kostas; Caers, Jelle; Caljon, Guy; Christensen, Mikkel B; Farrow, David W; Friedrich, Markus; Hua-Van, Aurélie; Jennings, Emily C; Larkin, Denis M; Lawson, Daniel; Lehane, Michael J; Lenis, Vasileios P; Lowy-Gallego, Ernesto; Macharia, Rosaline W; Malacrida, Anna R; Marco, Heather G; Masiga, Daniel; Maslen, Gareth L; Matetovici, Irina; Meisel, Richard P; Meki, Irene; Michalkova, Veronika; Miller, Wolfgang J; Minx, Patrick; Mireji, Paul O; Ometto, Lino; Parker, Andrew G; Rio, Rita; Rose, Clair; Rosendale, Andrew J; Rota-Stabelli, Omar; Savini, Grazia; Schoofs, Liliane; Scolari, Francesca; Swain, Martin T; Takáč, Peter; Tomlinson, Chad; Tsiamis, George; Van Den Abbeele, Jan; Vigneron, Aurelien; Wang, Jingwen; Warren, Wesley C; Waterhouse, Robert M; Weirauch, Matthew T; Weiss, Brian L; Wilson, Richard K; Zhao, Xin; Aksoy, Serap
    Abstract Background Tsetse flies (Glossina sp.) are the vectors of human and animal trypanosomiasis throughout sub-Saharan Africa. Tsetse flies are distinguished from other Diptera by unique adaptations, including lactation and the birthing of live young (obligate viviparity), a vertebrate blood-specific diet by both sexes, and obligate bacterial symbiosis. This work describes the comparative analysis of six Glossina genomes representing three sub-genera: Morsitans (G. morsitans morsitans, G. pallidipes, G. austeni), Palpalis (G. palpalis, G. fuscipes), and Fusca (G. brevipalpis) which represent different habitats, host preferences, and vectorial capacity. Results Genomic analyses validate established evolutionary relationships and sub-genera. Syntenic analysis of Glossina relative to Drosophila melanogaster shows reduced structural conservation across the sex-linked X chromosome. Sex-linked scaffolds show increased rates of female-specific gene expression and lower evolutionary rates relative to autosome associated genes. Tsetse-specific genes are enriched in protease, odorant-binding, and helicase activities. Lactation-associated genes are conserved across all Glossina species while male seminal proteins are rapidly evolving. Olfactory and gustatory genes are reduced across the genus relative to other insects. Vision-associated Rhodopsin genes show conservation of motion detection/tracking functions and variance in the Rhodopsin detecting colors in the blue wavelength ranges. Conclusions Expanded genomic discoveries reveal the genetics underlying Glossina biology and provide a rich body of knowledge for basic science and disease control. They also provide insight into the evolutionary biology underlying novel adaptations and are relevant to applied aspects of vector control such as trap design and discovery of novel pest and disease control strategies.
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    Functional characterisation of the hypertrehalosaemic hormone from the Indian stick insect Carausius morosus: metabolic and myotropic studies
    (2017) Katali, Ottilie Kandiwapa Hasiike; Marco, Heather G; Gäde, Gerd
    Neuropeptides of the adipokinetic hormone/red pigment concentrating hormone (AKH/RPCH) family are well known as regulators for many physiological processes in insects, notably energy metabolism, and a possible role in myostimulation. The Indian stick insect Carausius morosus contains two members of this family, hypertrehalosaemic hormone I and II (Carmo-HrTH-I and -II). Both these are decapeptides and they differ only at position 8, where the tryptophan of Carmo-HrTH-I is C‐mannosylated. It is known that Carmo-HrTHs increase the carbohydrate (trehalose) concentration in the haemolymph via a G protein-coupled receptor. The current study seeks to identify which part of the HrTH amino acid sequence is necessary to interact with the receptor on the fat body of C. morosus to trigger a response (hypertrehalosaemia) eventually leading to the release of carbohydrates into the haemolymph. In addition, the role of Carmo-HrTHs in stimulating the heart rate through myostimulation was also investigated. Two biological assays were used to assess the potencies of various analogues, in comparison to that of the native peptides: (1) the carbohydrate-mobilizing assay assessed the increase in levels of carbohydrates; and (2) the semi-exposed heart assay assessed the increase in heart rates. The current study confirmed that both Carmo-HrTH-I and -II are capable of increasing the haemolymph carbohydrates in ligated stick insects. The results of the current study revealed, for the first time, that these peptides also similarly stimulate the heart rate of the stick insect. Thus, Carmo-HrTH-II was used as a lead peptide in the current study on which various naturally-occurring AKH peptides and systematically altered analogues were based. The selected naturally-occurring AKH peptides had a single or double amino acids replacement in comparison to Carmo-HrTH-II and some were octapeptides. Each systematically altered analogue of the native Carausius HrTH II had a single amino acid replaced with alanine. Additionally, two analogues that lacked the N-terminal pyroglutamate residue or had a free threonine acid at the C-terminus instead of an amide were also tested. The results showed that the N- or C- terminal modified analogues have no hypertrehalosaemic activity in C. morosus and are also incapable of increasing the heart rate of this insect as high as Carmo-HrTH-II. This suggests that the blocked termini are important features, for both peptide protection and receptor binding. The structural requirements of C. morosus receptor(s) for Carmo-HrTHs appear to be very specific. The receptor(s) do not accept octapeptides and only four out of the fourteen decapeptides elicited at least 46% of the biological activity as compared to the native peptide and the rest (ten) were not active. This implies that the HrTHs receptor (s) for C. morosus do not tolerate the replacement of most single amino acids. In the heart assay, known cardio-stimulatory peptides were applied to the semi-exposed heart of C. morosus to establish the potential extent of cardioexcitation. The results of this study revealed that crustacean cardioactive peptide and proctolin are capable of increasing the heart beat rate of the stick insect more than the AKH/RPCH peptides. It was also shown that the stick insect heart beat rate can be inhibited by octopamine. This is the first study to investigate, in detail, the importance of structural features of the hypertrehalosaemic hormones of the Phasmatodea insects, and is therefore an important contribution to designing environmentally friendly insect-specific pesticides.
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    The gonadotropin-releasing hormone (GnRH) system: a comparison between breeding and non-breeding naked mole rats (Heterocephalus glaber)
    (2010) Smith, Caitlin; Marco, Heather G; Gäde, Gerd
    Neuropeptides are well known to govern numerous biological functions and are found in all phyla studied to date. Probably the best known neuroendocrine system is the hypophyseal-portal system found in vertebrates, and one of the functions of this system is to mediate reproduction. Mammalian reproduction is controlled by a hormonal cascade which begins in distinct brain regions, namely the hypothalamus and the pituitary gland. Gonadotropin-releasing hormone (GnRH) is a neuropeptide typically produced in the hypothalamus. It is the key neuropeptide for initiating this cascade, and without it, reproduction cannot occur. Naked mole rats (Heterocephalus glaber) have a rigid social hierarchy. The "queen" is the most dominant female and is the only female who breeds. All aspects of reproduction are suppressed in other females in the colony: these "subordinates" are in a prepuberty-like state as they do not ovulate or display breeding behaviours. They are, however, not infertile, and are capable of rising to the breeding position. Since GnRH is the "master hormone" of reproduction, this study investigates its role in the socially-induced suppression of reproduction in female H. glaber. Brains of breeding (n = 7) and non-breeding (n = 5) female naked mole rats were compared to determine any differences in brain size, particularly in regions related to GnRH production. Noteworthy morphological and physiological transformations accompany the change from subordinate to dominant social status, including a significant increase in body length (Mann Whitney U test; p = 0.005, U = 0.000), body mass (Mann Whitney U test; p = 0.009, 1.000) and pituitary width and length (Mann Whitney U test; p = 0.028, U = 0.500 and p = 0.018, U = 0.000, respectively). Since little is known about the GnRH system in H. glaber, this study used immunocytochemistry to identify the distribution and abundance of GnRH neurons in the brains of both breeding and non-breeding females. GnRH neurons were found in the median eminence of the hypothalamus and in the anterior pituitary of both queens and subordinates, however in the brain of queen (n = 7) naked mole rats, there is a significantly larger area of immunoreactivity in comparison to the subordinate (n = 5) brain tissue (Mann Whitney U = 4.000, p = 0.030). This suggests that, in , subordinates, GnRH is inhibited at the level of production. The amino acid structure of the form of GnRH found in the brain of the naked mole rat is currently unknown, therefore a pilot study was carried out, using synthetic mammalian GnRH (mGnRH), mouse brain tissue and naked mole rat pituitaries and hypothalami, to examine and modify (where necessary) the methodologies used for neuropeptide extraction, purification and identification. A limited number of naked mole rats were available as source tissue (n = 4), therefore this study also tested whether it is possible to extract and purify an unknown neuropeptide from only a few mammalian samples. Training for reverse-phase liquid chromatography (RP-HPLC) was achieved by practicing the necessary methods with crude extracts prepared from stick insect (Carausius morosus) corpora cardiaca, which also served to compare vertebrate and invertebrate neuroendocrine systems. Synthetic mGnRH was used to demonstrate repeatability of the protocol and to set up suitable conditions for elution of mGnRH: mGnRH elutes at â 12 min when a solvent gradient of 32 % - 47 % B is applied. Synthetic mGnRH was also used to establish the amount of peptide required for accurate identification of GnRH by antigenicity tests (ELISA) and mass spectrometry. However, when extracts of mouse or naked mole rat brain matter were applied to this system, purification of GnRH was unconvincing as either there was insufficient material, or, some endogenous factor was masking the GnRH. Future studies would benefit from using molecular techniques as they require smaller amounts of source tissue. Alternatively, a larger amount of source tissue would be necessary in order to proceed with biochemical studies. While the impaired production of GnRH in subordinate naked mole rats seems to be linked to their prepuberty like state, it is unlikely that GnRH is the sole factor involved. Many other hormones (such as kisspeptin, gonadotropin-inhibiting hormone and neuropeptide Y) may influence GnRH and sexual maturity, and future studies would benefit from a multi-layered approach to investigate suppression of reproduction in naked mole rats.
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    In Silico Screening for Pesticide Candidates against the Desert Locust Schistocerca gregaria
    (Multidisciplinary Digital Publishing Institute, 2022-03-07) Jackson, Graham E; Gäde, Gerd; Marco, Heather G
    Adipokinetic hormone (AKH) is one of the most important metabolic neuropeptides in insects, with actions similar to glucagon in vertebrates. AKH regulates carbohydrate and fat metabolism by mobilizing trehalose and diacylglycerol into circulation from glycogen and triacylglycerol stores, respectively, in the fat body. The short peptide (8 to 10 amino acids long) exerts its function by binding to a rhodopsin-like G protein-coupled receptor located in the cell membrane of the fat body. The AKH receptor (AKHR) is, thus, a potential target for the development of novel specific (peptide) mimetics to control pest insects, such as locusts, which are feared for their prolific breeding, swarm-forming behavior and voracious appetite. Previously, we proposed a model of the interaction between the three endogenous AKHs of the desert locust, Schistocerca gregaria, and the cognate AKHR (Jackson et al., Peer J. 7, e7514, 2019). In the current study we have performed in silico screening of two databases (NCI Open 2012 library and Zinc20) to identify compounds which may fit the endogenous Schgr-AKH-II binding site on the AKHR of S. gregaria. In all, 354 compounds were found to fit the binding site with glide scores < −8. Using the glide scores and binding energies, 7 docked compounds were selected for molecular dynamic simulation in a phosphatidylcholine membrane. Of these 7 compounds, 4 had binding energies which would allow them to compete with Schgr-AKH-II for the receptor binding site and so are proposed as agonistic ligand candidates. One of the ligands, ZINC000257251537, was tested in a homospecific in vivo biological assay and found to have significant antagonistic activity.
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    Molecular biological studies on neuropeptides of the adipokinetic hormone/red pigment-concentrating hormone family and the neuroparsin family in the arthropod sister groups of insects and crustaceans
    (2012) Anders, Lance; G?de, Gerd; Marco, Heather G; Ingle, Robert
    This study describes the identification of three novel precursor transcripts which includes the adipokinetic hormone (AKH) / red pigment-concentrating hormone (RPCH) and the neuroparsin (NP) from the South African spiny lobster, Jasus lalandii, the RPCH and the RPCH receptor (RPCHR) from the water flea D. pulex and the NP from the southern green stinkbug, Nezara viridula. The study also investigates the localisation and expression profiles of the AKH/RPCH and NP transcripts within crustaceans and insects.
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    Neuropeptide hormones from the eyestalks of Jasus Lalandii
    (2000) Marco, Heather G; Gäde, Gerd; Cook, Peter; Brandt, Wolf F
    The X-organ sinus gland complex, situated in the eyestalks of decapod crustaceans, are known to be a source of a variety of neuropeptide hormones that regulate a number of diverse physiological processes. This neuroendocrine complex was investigated in 3 crustacean species, viz. the European shore crab Carcinus maellas, and 2 spiny lobster species Jasus lalandii and Panulirus homarus by means of tissue immunocytochemistry and an enzyme-linked immunosorbent assay (ELISA). Positive immunoreactions, associated with the X-organ - sinus gland system only, were obtained with antisera raised against crustacean hyperglycaemic hormone (cHH) of the American lobster (Homarus americanus), the Mexican crayfish (Procambarus bouvieri) and the edible crab (Cancer pagurus), as well as with antisera raised against vitellogenesis-inhibiting hormone (VIH) of the H. americanus and moult-inhibiting hormone (MIH) of C. pagurus. This is the first time that the immunolocalisation of these 3 hormones have been studied in a single crustacean species. The chief results of this comparative immunocytochemical study showed that (1) neuropeptide hormones of the shore crab and the 2 spiny lobster species were sufficiently homologous in primary structure to be recognised by the heterologous antisera, thus, an indication of conserved peptide structures across the species and infraorder boundaries; (2) preabsorbed complexes of purified peptides and antisera from the edible crab did not produce any immunoreactions in tissue immunocytochemistry, nor in ELISA, thus, indicating the specificity of the anti-cHH and anti-MIH sera; (3) the anti-VIH serum demonstrated the ability to bind epitopes on cHH and MIH peptides and is, thus, not a specific antiserum in this study; (4) there is co-localisation of cHH, MIH, VIH immunoreactivity in the eyestalk neuroendocrine complexes of all 3 species studied which suggests that the different peptide hormones can be synthesized in the same neuronal cell bodies. This co-localisation of neuropeptides in the eyestalk of J lalandii was confirmed by a double-staining immunoflourescence experiment, and finally (5) immunoreactivity of antisera raised against cHH of H. americanus and MIH of C. pagurus was associated with distinct and unique peak fractions, following reverse-phase high pressure liquid chromatographic (RP-HPLC) separation of sinus gland extracts from J. lalandii. A total of 6 neuropeptide hormones belonging to the cHH/MIH/VIH peptide family were isolated, functionally characterised and sequenced from extracts of sinus glands from the South African west coast rock lobster, Jasus lalandii. This is the first complete report on these peptides from any species belonging to the Palinuridae infraorder.
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    The nutritional effects of selected algae, prebiotics and commercial herbal feed additives on the growth rate and health of juvenile spotted grunter, Pomadasys commersonnii (Pisces: Haemulidae)
    (2017) Mbona, Anathi; Marco, Heather G; Fouche, Chris
    In the aquaculture of fish and shrimps, diets generally contain high levels of fish meal. Fish meal is a nutrient rich feed that contains essential amino acids and fatty acids, which are required to maintain optimum growth and health of an animal. It is traditionally used in aquaculture to promote feed efficiency, nutrient uptake and feed intake due to its high palatability and digestibility. Overexploitation of fisheries resources and the high growth rate of aquaculture industry, however, continues to put pressure on the supply of fish meal, thus increasing the demand and price of this sought-after product. The use of alternative ingredients to fish meal, therefore, remains a high priority for aquaculture nutrition. Hence, the aim of this was to investigate the physiological and developmental effects on juvenile spotted grunter, Pomadasys commersonnii, after supplementing fish meal with different feed additives for 12 weeks. One of the additives was then selected for further feeding at graded levels (increasing levels) for 8 weeks to ascertain whether fish meal could be replaced by higher amounts of the feed additive without negative consequences to the cultured spotted grunter.
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    Role and distribution of astaxanthin in spiny lobster, Jasus lalandii
    (2006) Matumba, Tshifhiwa Given; Marco, Heather G; Gäde, Gerd; Auerswald, L
    The occurance and distribution of astaxanthin in tissues of the spiny lobster, Jasus lalandii was investigated. The concentration of astaxanthin was quantified in the exoskeleton, haemolymph, muscles, gonads and hepatopancreas as well as in egg parcels from berried females during the moult as well as the reproductive cycles. Astaxanthin was the dominant carotenoid in all tissues, but small amounts of other carotenoids were detected. Exoskeleton, ovaries and extrude egg parcels had significantly higher astaxanthin concentration than haemolymp, muscles and hepatopancreas. This distribution of astaxanthin was found in both captive and free-living spiny lobsters. Free-living spiny lobsters generally had higher astaxanthin concentration than the captive spiny lobsters although the data is not statistically significant in all tissues investigated.