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[
WormBook,
2005]
C. elegans is a member of a group of nematodes called rhabditids, which encompasses a large number of ecologically and genetically diverse species. A new, preliminary phylogenetic analysis is presented for concatenated sequences of three nuclear genes for 48 rhabditid and diplogastrid species (including 10 Caenorhabditis species), as well as four species representing the outgroup. Although many relationships are well-resolved, more data are still needed to resolve some key relationships, particularly near the base of the rhabditid tree. There is high confidence for two major clades: (1) a clade comprising Mesorhabditis Parasitorhabditis, Pelodera, Teratorhabditis plus a few other species; (2) a large clade (Eurhabditis) comprising most of the remaining rhabditid genera, including Caenorhabditis and its sistergroup Protorhabditis-Prodontorhabditis-Diploscapter. Eurhabditis also contains the parasitic strongylids, the entomopathogenic Heterorhabditis, and the monophyletic group Oscheius which includes the satellite model organism O. tipulae. The relationships within Caenorhabditis are well resolved. The analysis also suggests that rhabditids include diplogastrids, to which the second satellite model organism Pristionchus pacificus belongs. Genetic disparity within Caenorhabditis is as great as that across vertebrates, suggesting Caenorhabditis lineages are quickly evolving, ancient, or both. The phylogenetic tree can be used to reconstruct evolutionary events within rhabditids. For instance, the reproductive mode changed multiple times from gonochorism to hermaphroditism, but only once from hermaphroditism to gonochorism. Complete retraction of the male tail tip, leading to a blunt, peloderan tail, evolved at least once. Reversions to unretracted tail tips occurred within both major rhabditid groups. The phylogeny also provides a guide to species which would be good candidates for future genome projects and comparative studies.
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Semin Nephrol,
2006]
The vacuolar H(+)-ATPase is a multisubunit protein consisting of a peripheral catalytic domain (V(1)) that binds and hydrolyzes adenosine triphosphate (ATP) and provides energy to pump H(+) through the transmembrane domain (V(0)) against a large gradient. This proton-translocating vacuolar H(+)-ATPase is present in both intracellular compartments and the plasma membrane of eukaryotic cells. Mutations in genes encoding kidney intercalated cell-specific V(0)
a4 and V(1) B1 subunits of the vacuolar H(+)-ATPase cause the syndrome of distal tubular renal acidosis. This review focuses on the function, regulation, and the role of vacuolar H(+)-ATPases in renal physiology. The localization of vacuolar H(+)-ATPases in the kidney, and their role in intracellular pH (pHi) regulation, transepithelial proton transport, and acid-base homeostasis are discussed.
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[
WormBook,
2007]
Heterorhabditis bacteriophora is an entomopathogenic nematode (EPN) mutually associated with the enteric bacterium, Photorhabdus luminescens, used globally for the biological control of insects. Much of the previous research concerning H. bacteriophora has dealt with applied aspects related to biological control. However, H. bacteriophora is an excellent model to investigate fundamental processes such as parasitism and mutualism in addition to its comparative value to Caenorhabditis elegans. In June 2005, H. bacteriophora was targeted by NHGRI for a high quality genome sequence. This chapter summarizes the biology of H. bacteriophora in common and distinct from C. elegans, as well as the status of the genome project.
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[
The Scientist,
1996]
Biologist H. Robert Horvitz discusses the genetics of cell death in the nematode C. elegans.
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[
Int J Parasitol,
2006]
Haemonchus contortus of small ruminants is a parasitic nematode of major socio-economic importance world-wide. While there is considerable knowledge of the morphological changes which take place during the life cycle of H. contortus, very little is understood about the molecular and biochemical processes which govern developmental changes in the parasite. Recent technological advances and the imminent genomic sequence for H. contortus provide unique opportunities to investigate the molecular basis of such processes in parasitic nematodes. This article reviews molecular and biochemical aspects of development in H. contortus, reports on some recent progress on signal transduction molecules in this parasite and emphasises the opportunities that new technologies and the free-living nematode, Caenorhabditis elegans, offer for investigating developmental aspects in H. contortus and related strongylid nematodes, also in relation to developing novel approaches for control.
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[
Parasitol Today,
1996]
Historically, peptidergic substances (in the form of neurosecretions) were linked to moulting in nematodes. More recently, there has been a renewal of interest in nematode neurobiology, initially triggered by studies demonstrating the localization of peptide immunoreactivities to the nervous system. Here, David Brownlee, Ian Fairweather, Lindy Holden-Dye and Robert Walker will review progress on the isolation of nematode neuropeptides and efforts to unravel their physiological actions and inactivation mechanisms. Future avenues for research are suggested and the potential exploitation of peptidergic pathways in future therapeutic strategies
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[
Annu Rev Microbiol,
1992]
Oxygenases that incorporate one or two atoms of dioxygen into substrates are found in many metabolic pathways. In this article, representative oxygenases, principally those found in bacterial pathways for the degradation of hydrocarbons, are reviewed. Monooxygenases, discussed in this chapter, incorporate one hydroxyl group into substrates. In this reaction, two atoms of dioxygen are reduced to one hydroxyl group and one H2O molecule by the concomitant oxidation of NAD(P)H. Dioxygenases catalyze the incorporation of two atoms of dioxygen into substrates. Two types of dioxygenases, aromatic-ring dioxygenases and aromatic-ring-cleavage dioxygenases, are discussed. The aromatic-ring dioxygenases incorporate two hydroxyl groups into aromatic substrates, and cis-diols are formed. This reaction also requires NAD(P)H as an electron donor. Aromatic-ring-cleavage dioxygenases incorporate two atoms of dioxygen into aromatic substrates, and the aromatic ring is cleaved. This reaction does not require an external reductant. All the oxygenases possess a cofactor, a transition metal, flavin or pteridine, that interacts with dioxygen. The concerted reactions between dioxygen and carbon in organic compounds are spin forbidden. The cofactor is used to overcome this restriction. For the oxygenases that require the NAD(P)H cofactor, the enzyme reaction is separated into two steps, the oxidation of NAD(P)H to generate two reducing equivalents, and the hydroxylation of substrates. Flavoprotein hydroxylases that catalyze the monohydroxylation of the aromatic ring carry out these two reactions on a single polypeptide chain. In other oxygenases, the NAD(P)H oxidation and a hydroxylation reaction are catalyzed by two separate polypeptides that are linked by a short electron-transport chain. Two reducing equivalents generated by the oxidation of NAD(P)H are transferred through the electron-transport chain to the cofactor on a hydroxylase component that they reduce. Dioxygen couples with the reduced cofactor and subsequently hydroxylates substrates. The electron-transport chains associated with oxygenases contain at least two redox centers. The first redox center is usually a flavin, while the second is an iron-sulfur cluster. The electron transport is initiated by a single two-electron transfer from NAD(P)H to a flavin, followed by two single-electron transfers from the flavin to an iron-sulfur cluster. The primary sequences of many oxygenases have been determined, and according to their sequence similarities, the oxygenases can be grouped into several protein families. Among proteins of the same family, the sequences in regions involved in cofactor binding are strongly conserved. Local sequence similarities are also observed among oxygenases from different families, primarily in regions involved in cofactor binding.
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Curr Opin Neurobiol,
1998]
Ion channels in the amiloride-sensitive Na+ channel/degenerin (NaC/DEG) family of cation channels have very diverse functions. They can be constitutively active (e.g. the epithelial Na+ channel), gated by a ligand (e.g. the peptide-gated channel FaNaC or H+-gated cation channels [ASICs]) or possibly activated by stretch (degenerins of Caenorhabditis elegans). Despite this functional diversity, the heterologous expressed channels share the following properties: permeability to Na+, inhibition by the diuretic amiloride and no voltage gating. This review will focus on recent advances in this ion channel family, with special emphasis on H+-gated cation channels.
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[
Can J Gastroenterol,
2000]
BACKGROUND: The rate of Helicobacter pylori resistance to antibiotics determines the cure rate of treatment regimens containing such antibiotics. AIMS: To review the literature to determine the rates of H pylori resistance to metronidazole and clarithromycin in Canada, and whether these rates vary in different regions of Canada. METHODS: The literature was reviewed extensively for the prevalence of antibiotic-resistant H pylori in Canada by searching MEDLINE from January 1980 to May 1999, as well as abstracts of the American Gastroenterology Association Digestive Disease Week, Canadian Digestive Disease Week and The European H pylori Study Group Meetings from January 1995 to May 1999. RESULTS: Eleven studies that estimated H pylori resistance to metronidazole resistance and nine that estimated resistance to clarithromycin in Canada were identified. Rates of resistance for metronidazole and clarithromycin varied from 11% to 48% and 0% to 12%, respectively. Studies that obtained their estimates using the E-test and those that did not clearly exclude patients who had undergone previous attempts at H pylori eradication had higher estimates of resistance, accounting for this variability in results. CONCLUSIONS: The prevalence of primary H pylori resistance in Canada appears to be 18% to 22% for metronidazole and less than 4% for clarithromycin. These rates appear to be consistent across the different regions studied in Canada, but many regions have not been studied.
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Cell Mol Life Sci,
2010]
The Caenorhabditis elegans one-cell embryo is a powerful system in which to study microtubule organization because this large cell assembles both meiotic and mitotic spindles within the same cytoplasm over the course of 1 h in a stereotypical manner. The fertilized oocyte assembles two consecutive acentrosomal meiotic spindles that function to reduce the replicated maternal diploid set of chromosomes to a single-copy haploid set. The resulting maternal DNA then unites with the paternal DNA to form a zygotic diploid complement, around which a centrosome-based mitotic spindle forms. The early C. elegans embryo is amenable to live-cell imaging and electron tomography, permitting a detailed structural comparison of the meiotic and mitotic modes of spindle assembly.