Encystation and expression of cyst antigens by Giardia lamblia in vitro
27 Feb 1987-Science (American Association for the Advancement of Science)-Vol. 235, Iss: 4792, pp 1040-1043
TL;DR: In these studies, encystation of Giardia lamblia in vitro was demonstrated by morphologic, immunologic, and biochemical criteria and will aid in understanding the differentiation of an important protozoan pathogen.
Abstract: The cyst form of Giardia lamblia is responsible for transmission of giardiasis, a common waterborne intestinal disease. In these studies, encystation of Giardia lamblia in vitro was demonstrated by morphologic, immunologic, and biochemical criteria. In the suckling mouse model, the jejunum was shown to be a major site of encystation of the parasite. Small intestinal factors were therefore tested as stimuli of encystation. An antiserum that reacted with cysts, but not with cultured trophozoites was raised in rabbits and used as a sensitive probe for differentiation in vitro. Cultured trophozoites that were exposed to bile salts showed a more than 20-fold increase in the number of oval, refractile cells that reacted strongly with anticyst antibodies, and in the expression of major cyst antigens. Exposure to primary bile salts resulted in higher levels of encystation than exposure to secondary bile salts. These studies will aid in understanding the differentiation of an important protozoan pathogen.
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TL;DR: A novel foam structure is presented, which exhibits a negative Poisson's ratio, and such a material expands laterally when stretched, in contrast to ordinary materials.
Abstract: A novel foam structure is presented, which exhibits a negative Poisson's ratio. Such a material expands laterally when stretched, in contrast to ordinary materials.
2,871 citations
TL;DR: The Giardia genome project promises to greatly increase the understanding of this interesting and enigmatic organism.
Abstract: Giardia lamblia is a common cause of diarrhea in humans and other mammals throughout the world. It can be distinguished from other Giardia species by light or electron microscopy. The two major genotypes of G. lamblia that infect humans are so different genetically and biologically that they may warrant separate species or subspecies designations. Trophozoites have nuclei and a well-developed cytoskeleton but lack mitochondria, peroxisomes, and the components of oxidative phosphorylation. They have an endomembrane system with at least some characteristics of the Golgi complex and encoplasmic reticulum, which becomes more extensive in encysting organisms. The primitive nature of the organelles and metabolism, as well as small-subunit rRNA phylogeny, has led to the proposal that Giardia spp. are among the most primitive eukaryotes. G. lamblia probably has a ploidy of 4 and a genome size of approximately 10 to 12 Mb divided among five chromosomes. Most genes have short 5′ and 3′ untranslated regions and promoter regions that are near the initiation codon. Trophozoites exhibit antigenic variation of an extensive repertoire of cysteine-rich variant-specific surface proteins. Expression is allele specific, and changes in expression from one vsp gene to another have not been associated with sequence alterations or gene rearrangements. The Giardia genome project promises to greatly increase our understanding of this interesting and enigmatic organism.
1,175 citations
TL;DR: The identification of antigens that play a role in acquired immunity has been difficult because of the occurrence of antigenic variation and because, Giardia being an ubiquitous organism, it is possible that the antigenic profiles of isolates from different geographic areas will vary.
Abstract: The intestinal protozoan Giardia duodenalis is a widespread opportunistic parasite of humans and animals. This parasite inhabits the upper part of the small intestine and has a direct life cycle. After ingestion of cysts, which are the infective stage, the trophozoites emerge from the cysts in the duodenum and attach to the small intestinal mucosa of the host. Since the migration of trophozoites from the lumen of the intestine into surrounding tissues is an unusual occurrence, the immune response to Giardia remains localized. The identification of antigens that play a role in acquired immunity has been difficult because of the occurrence of antigenic variation and because, Giardia being an ubiquituous organism, it is possible that the antigenic profiles of isolates from different geographic areas will vary. Innate-immunity mechanisms play a role in the control and/or severity of the infection. Both humoral and cell-mediated immune responses play a role in acquired immunity, but the mechanisms involved are unknown. A variety of serological assays have been used to detect circulating antibodies in serum. Because of the biological characteristics of the parasite and the lack of suitable antigens, the sensitivity of serological assays remains poor. On the other hand, detection of antigens in feces of infected patients has met with success. Commercial kits are available, and they are reported to be more sensitive than microscopic examination for the detection of giardiasis on a single specimen.
286 citations
TL;DR: The intention here is to give an up-to-date overview of Giardia and giardiasis and provide an insight into the enormous wealth of literature on the subject, as well as highlight the most important recent developments and unresolved questions.
Abstract: It is over 10 years since Meyer and Radulescu (1979) reviewed Giardia and giardiasis in Advances in Parasitology. In their introduction, they emphasized that "despite their ubiquity and antiquity, the Giardia have, until recently, been little studied". In the intervening years, Giardia has been extensively studied. The number of papers published has increased enormously, two books on the parasite have been produced (Erlandsen and Meyer, 1984; Meyer, 1990a), and an international conference on Giardia has been organized (Wallis and Hammond, 1988). Yet it is still very difficult to keep up with developments in this productive field of research and, despite all these research efforts, several fundamental questions concerning Giardia and giardiasis remain unresolved (Table 1), particularly with respect to the relationship of Giardia and disease, and the role of zoonotic transmission. Indeed, it is only recently that we have started to appreciate the clinical significance of Giardia infections in developing countries and among disadvantaged groups. Giardia is now recognized as one of the 10 major parasites of humans, being equal to ascariasis as a cause of death in the developing world (Warren, 1989; Meyer, 1990b). In developed countries, Giardia has the distinction of being the most commonly reported human intestinal parasite (Acha and Szyfres, 1987; Thompson et al., 1990a; Schantz, 1991). Regrettably, however, the range of drugs available to treat giardiasis is limited and their efficacy leaves much to be desired. There is an urgent need for new antigiardial agents, yet this search is hampered by our lack of understanding of many fundamental aspects of Giardia biochemistry and metabolism. In addition, although the application of molecular biological techniques to research on Giardia has revealed new avenues of investigation, it has also given rise to many new questions about this intriguing organism concerning its phylogenetic position, reproductive behaviour and genetic diversity.
To review Giardia and giardiasis in detail would require at least an entire volume of Advances in Parasitology. Such treatment in depth is not warranted at this time in view of the excellent book recently edited by Meyer (1990a). Our intention here is to give an up-to-date overview of Giardia and giardiasis and provide an insight into the enormous wealth of literature on the subject, as well as highlight the most important recent developments and unresolved questions.
262 citations
TL;DR: NO and arginine are defined as central components in a novel cross-talk between a luminal pathogen and host intestinal epithelium and G. lamblia is not simply a passive target for host-produced NO, but has strategies to evade this potential host defense.
Abstract: Giardia lamblia infection of the human small intestine is a common protozoan cause of diarrheal disease worldwide. Although infection is luminal and generally self-limiting, and secretory Abs are thought to be important in host defense, other defense mechanisms probably affect the duration of infection and the severity of symptoms. Because intestinal epithelial cells produce NO, and its stable end products, nitrite and nitrate, are detectable mainly on the apical side, we tested the hypothesis that NO production may constitute a host defense against G. lamblia. Several NO donors, but not their control compounds, inhibited giardial growth without affecting viability, suggesting that NO is cytostatic rather than cytotoxic for G. lamblia. NO donors also inhibited giardial differentiation induced by modeling crucial environmental factors, i. e., encystation induced by bile and alkaline pH, and excystation in response to gastric pH followed by alkaline pH and protease. Despite the potent antigiardial activity of NO, G. lamblia is not simply a passive target for host-produced NO, but has strategies to evade this potential host defense. Thus, in models of human intestinal epithelium, G. lamblia inhibited epithelial NO production by consuming arginine, the crucial substrate used by epithelial NO synthase to form NO. These studies define NO and arginine as central components in a novel cross-talk between a luminal pathogen and host intestinal epithelium.
235 citations
Cites background or methods from "Encystation and expression of cyst ..."
...For these experiments, trophozoites were exposed for 18 h to conditions that efficiently induce encystation in vitro (27, 36), and the number of ESVs was determined microscopically....
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...The latter is initiated when trophozoites are exposed to a slightly alkaline pH and bile (27, 36)....
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References
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TL;DR: Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products.
Abstract: Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products. Four major components of the head are cleaved during the process of assembly, apparently after the precursor proteins have assembled into some large intermediate structure.
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Journal Article•
TL;DR: Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products as mentioned in this paper.
Abstract: Using an improved method of gel electrophoresis, many hitherto unknown proteins have been found in bacteriophage T4 and some of these have been identified with specific gene products. Four major components of the head are cleaved during the process of assembly, apparently after the precursor proteins have assembled into some large intermediate structure.
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TL;DR: A method has been devised for the electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets that results in quantitative transfer of ribosomal proteins from gels containing urea.
Abstract: A method has been devised for the electrophoretic transfer of proteins from polyacrylamide gels to nitrocellulose sheets. The method results in quantitative transfer of ribosomal proteins from gels containing urea. For sodium dodecyl sulfate gels, the original band pattern was obtained with no loss of resolution, but the transfer was not quantitative. The method allows detection of proteins by autoradiography and is simpler than conventional procedures. The immobilized proteins were detectable by immunological procedures. All additional binding capacity on the nitrocellulose was blocked with excess protein; then a specific antibody was bound and, finally, a second antibody directed against the first antibody. The second antibody was either radioactively labeled or conjugated to fluorescein or to peroxidase. The specific protein was then detected by either autoradiography, under UV light, or by the peroxidase reaction product, respectively. In the latter case, as little as 100 pg of protein was clearly detectable. It is anticipated that the procedure will be applicable to analysis of a wide variety of proteins with specific reactions or ligands.
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TL;DR: Le milieu de Diamond TYI-S-33, utilise pour the culture axenique d'Entamoeba histolytica permet, apres addition de bile de bœuf, la culture axnique de G. lamblia.
Abstract: Le milieu de Diamond TYI-S-33, utilise pour la culture axenique d'Entamoeba histolytica permet, apres addition de bile de bœuf, la culture axenique de G. lamblia
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