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  • 1
    Publication Date: 2022-05-25
    Description: © 2008 Salvador-Recatalà et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution License. The definitive version was published in BMC Physiology 8 (2008): 6, doi:10.1186/1472-6793-8-6.
    Description: The function of voltage-gated calcium (Cav) channels greatly depends on coupling to cytoplasmic accessory β subunits, which not only promote surface expression, but also modulate gating and kinetic properties of the α1 subunit. Schistosomes, parasitic platyhelminths that cause schistosomiasis, express two β subunit subtypes: a structurally conventional β subunit and a variant β subunit with unusual functional properties. We have previously characterized the functional properties of the variant Cavβ subunit. Here, we focus on the modulatory phenotype of the conventional Cavβ subunit (SmCavβ) using the human Cav2.3 channel as the substrate for SmCavβ and the whole-cell patch-clamp technique. The conventional Schistosoma mansoni Cavβ subunit markedly increases Cav2.3 currents, slows macroscopic inactivation and shifts steady state inactivation in the hyperpolarizing direction. However, currents produced by Cav2.3 in the presence of SmCavβ run-down to approximately 75% of their initial amplitudes within two minutes of establishing the whole-cell configuration. This suppressive effect was independent of Ca2+, but dependent on intracellular Mg2+-ATP. Additional experiments revealed that SmCavβ lends the Cav2.3/SmCavβ complex sensitivity to Na+ ions. A mutant version of the Cavβ subunit lacking the first forty-six amino acids, including a string of twenty-two acidic residues, no longer conferred sensitivity to intracellular Mg2+-ATP and Na+ ions, while continuing to show wild type modulation of current amplitude and inactivation of Cav2.3. The data presented in this article provide insights into novel mechanisms employed by platyhelminth Cavβ subunits to modulate voltage-gated Ca2+ currents that indicate interactions between the Ca2+ channel complex and chelated forms of ATP as well as Na+ ions. These results have potentially important implications for understanding previously unknown mechanisms by which platyhelminths and perhaps other organisms modulate Ca2+ currents in excitable cells.
    Description: This work was supported by NIH grant #s R01 AI-40522 and R01 AI-73660 to RMG and by NIH-NCRR grant # P41 RR001395 to the Biocurrents Research Center (BRC) at MBL.
    Repository Name: Woods Hole Open Access Server
    Type: Article
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  • 2
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2009. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Molecular and Biochemical Parasitology 167 (2009): 54-59, doi:10.1016/j.molbiopara.2009.04.007.
    Description: One potential physiological target for new antischistosomals is the parasite's system for excretion of wastes and xenobiotics. P-glycoprotein (Pgp), a member of the ATP-binding cassette superfamily of proteins, is an ATP-dependent efflux pump involved in transport of toxins and xenobiotics from cells. In vertebrates, increased expression of Pgp is associated with multidrug resistance in tumor cells. Pgp may also play a role in drug resistance in helminths. In this report, we examine the relationship between praziquantel (PZQ), the current drug of choice against schistosomiasis, and Pgp expression in Schistosoma mansoni. We show that levels of RNA for SMDR2, a Pgp homolog from S. mansoni, increase transiently in adult male worms following exposure to sublethal concentrations (100 - 500 nM) of PZQ. A corresponding, though delayed, increase in anti-Pgp immunoreactive protein expression occurs in adult males following exposure to PZQ. The level of anti-Pgp immunoreactivity in particular regions of adult worms also increases in response to PZQ. Adult worms from an Egyptian S. mansoni isolate with reduced sensitivity to PZQ express increased levels of SMDR2 RNA and anti-Pgp-immunoreactive protein, perhaps indicating a role for multidrug resistance proteins in development or maintenance of PZQ resistance.
    Description: SMM, RSK, WM, and RMG were supported by NIH grants R01 AI40522 and R01 AI 73660. RMG was also supported by the Neal Cornell Research Fund at the Marine Biological Laboratory. RMG and SMM were also supported in part by NIH/NSF Woods Hole Center for Oceans and Human Health grant WHOI-A100354/A100360. Support was also received from the NIH Biocurrents Research Center at MBL (P41 RR001395).
    Keywords: Schistosoma mansoni ; P-glycoprotein ; Multidrug resistance ; Praziquantel ; ABC transporter
    Repository Name: Woods Hole Open Access Server
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  • 3
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author, 2005. This is the author's version of the work. It is posted here by permission of Cambridge University Press for personal use, not for redistribution. The definitive version was published in Parasitology 131 (2005): S97-S108, doi:10.1017/S0031182005008346.
    Description: Transient changes in calcium (Ca2+) levels regulate a wide variety of cellular processes, and cells employ both intracellular and extracellular sources of Ca2+ for signaling. Praziquantel, the drug of choice against schistosomiasis, disrupts Ca2+ homeostasis in adult worms. This review will focus on voltage-gated Ca2+ channels, which regulate levels of intracellular Ca2+ by coupling membrane depolarization to entry of extracellular Ca2+. Ca2+ channels are members of the ion channel superfamily and represent essential components of neurons, muscles, and other excitable cells. Ca2+ channels are membrane protein complexes in which the pore-forming α1 subunit is modulated by auxiliary subunits such as β and α2δ. Schistosomes express two Ca2+ channel β subunit subtypes: a conventional subtype similar to β subunits found in other vertebrates and invertebrates; and a novel variant subtype with unusual structural and functional properties. The variant schistosome β subunit confers praziquantel sensitivity to an otherwise praziquantel-insensitive mammalian Ca2+ channel, implicating it as a mediator of praziquantel action.
    Description: RMG is supported by NIH grant #AI 40522, by the Woods Hole Center for Oceans and Human Health, and by the Neal Cornell Research Fund at the Marine Biological Laboratory.
    Repository Name: Woods Hole Open Access Server
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  • 4
    Publication Date: 2022-05-25
    Description: Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in International Journal for Parasitology 36 (2006): 625-632, doi:10.1016/j.ijpara.2006.02.002.
    Description: Voltage-gated calcium (Ca2+) channels provide the pathway for Ca2+ influxes that underlie Ca2+-dependent responses in muscles, nerves, and other excitable cells. They are also targets of a wide variety of drugs and toxins. Ca2+ channels are multisubunit protein complexes consisting of a pore-forming α1 subunit and other modulatory subunits, including the β subunit. Here, we review the structure and function of schistosome Ca2+ channel subunits, with particular emphasis on variant Ca2+ channel β subunits (Cavβvar) found in these parasites. In particular, we examine the role these β subunits may play in the action of praziquantel, the current drug of choice against schistosomiasis. We also present evidence that Cavβvar homologs are found in other praziquantel-sensitive platyhelminths such as the pork tapeworm, Taenia solium, and that these variant β subunits may thus represent a platyhelminth-specific gene family.
    Description: This work was supported by PAPIIT grant IN-221702 to MCJ. RMG is supported by NIH grant AI 40522 and by the Neal Cornell Research Fund at the Marine Biological Laboratory.
    Keywords: Calcium channels ; Praziquantel ; Schistosoma mansoni ; Taenia solium ; Platyhelminthes
    Repository Name: Woods Hole Open Access Server
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  • 5
    Publication Date: 2022-05-25
    Description: Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Experimental Parasitology 113 (2006): 130-133, doi:10.1016/j.exppara.2005.12.013.
    Description: Nitric oxide (NO) is synthesized enzymatically by nitric oxide synthase (NOS). Several groups have previously presented evidence for NOS activity and immunoreactivity in several parasitic platyhelminths, including schistosomes. Here, we use 4,5-diaminofluorescein-2 diacetate (DAF-2 DA), a fluorescent indicator of NO, to detect NO in living schistosomes. In adult worms, DAF-2 fluorescence is found selectively in epithelial-like cells. Fluorescence increases when worms are incubated in L-arginine, the precursor of NO synthesis, and decreases dramatically in the presence of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME), indicating that predicted NO release may be NOS-dependent, and that enzymatic NO signaling pathways may play an important role in schistosome physiology.
    Description: This work was supported by NIH grant NS 39103 and NSF grants 0304569 (LLM), and NIH grant AI 40522 and the Neal Cornell Research Fund at the Marine Biological Laboratory (RMG).
    Keywords: Nitric oxide ; Schistosomiasis ; Trematode
    Repository Name: Woods Hole Open Access Server
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  • 6
    ISSN: 1432-1432
    Keywords: Vitellogenin ; Vitellogenesis ; Phosvitin ; Lipovitellin ; Yolk ; Trinucleotide repeat ; Teleost ; Fundulus heteroclitus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have cloned and sequenced a cDNA encoding a vitellogenin (Vtg) from the mummichog, Fundulus heteroclitus, an estuarine teleost. We constructed a liver cDNA library against RNA from estrogen-treated male mummichogs. Five overlapping cDNA clones totalling 5,197 by were isolated through a combination of degenerate oligonucleotide probing of the library and PCR. The cDNA sequence contains a 5,112 by open reading frame. The predicted primary structure of the deduced 1,704-amino-acid protein is 30–40% identical to other documented chordate Vtgs, establishing this Vtg as a member of the ancient Vtg gene family. Of the previously reported chordate Vtg sequences (Xenopus laevis, Gallus domesticus, Ichthyomyzon unicuspis, and Acipenser transmontanus), all four act as precursor proteins to a yolk which is eventually rendered insoluble under physiological conditions, either as crystalline platelets or as noncrystalline granules. The yolk of F. heteroclitus, on the other hand, remains in a soluble state throughout oocyte growth. The putative F. heteroclitus Vtg contains a polyserine region with a relative serine composition that is 10–20% higher than that observed for the other Vtgs. The trinucleotide repeats encoding the characteristic polyserine tracts of the phosvitin region follow a previously reported trend: TCX codons on the 5′ end and AGY codons toward the 3′ end. Whether the difference in Vtg primary structure between F. heteroclitus and that of other chordates is responsible for the differences in yolk structure remains to be elucidated. As the first complete teleost Vtg to be reported, these data will aid in designing nucleotide and immunological probes for detecting Vtg as a reproductive status indicator in F. heteroclitus and other piscine species.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of comparative physiology 121 (1977), S. 289-305 
    ISSN: 1432-1351
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Low vitamin A rearing decreases sensitivity and eliminates the ultraviolet but not the blue sensitivity maximum in R1-6 inDrosophila, Calliphora andMusca (Figs. 2–4). Spectral adaptation functions for control and vitamin A deprived flies yielded derived stable metarhodopsin absorption spectra from spectral sensitivity. Metarhodopsin has a long wavelength maximum and also has an ultraviolet maximum especially in the normal vitamin A condition (Figs. 2–4). M-potentials (fast early-receptor-like potentials) were obtained (Fig. 1) from all three genera in normal vitamin A rearing and were used for spectral adaptation studies (Figs. 2–3); the latter data are approximate inverses of sensitivity based spectral adaptation data. Thus, sensitivity must reflect proportion of rhodopsin, with metarhodopsin being inert in receptor potential generation. Vitamin A effects on spectral functions were further investigated inDrosophila. Ultraviolet (370 nm) and visible (470 nm) sensitivities varied approximately linearly with dietary vitamin A dose (Fig. 5); 370 nm sensitivity decreased more than 470 nm sensitivity at lower doses. Increasing adaptation intensities of 370 and 470 nm caused parallel decreases in spectral sensitivity assayed at 370 and 470 nm in normal vitamin A flies (Fig. 6); the adapting intensities were sufficient to convert photopigment. These and previous results suggest that the two R1-6 spectral peaks are ultimately mediated by one rhodopsin. R1-6 rhabdomeres were structurally similar in high and low vitamin A flies but emitted a long wavelength fluorescence to ultraviolet excitation in high vitamin A flies only (Fig. 7). These results suggest some form of energy transfer; i.e., a carotenoid may capture ultraviolet quanta and transfer energy to rhodopsin via inductive resonance. Spectral adaptation data are consistent with a calculated high rhabdomeric optical density of ECL=0.26 (i.e., 45% of incident light is absorbed) derived from presently available data onDrosophila. Calculations show electro-retinographic sensitivity to be extremely high, perhaps measurable at less than one absorbed quantum per rhabdomere.
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  • 8
    Publication Date: 1998-07-01
    Print ISSN: 0141-1136
    Electronic ISSN: 1879-0291
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Elsevier
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  • 9
    Publication Date: 1998-07-01
    Print ISSN: 0141-1136
    Electronic ISSN: 1879-0291
    Topics: Biology , Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Published by Elsevier
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  • 10
    Publication Date: 2000-10-20
    Print ISSN: 0014-5793
    Electronic ISSN: 1873-3468
    Topics: Biology , Chemistry and Pharmacology
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