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Cortés A, Muñoz-Antoli C, Martín-Grau C, Esteban JG, Grencis RK, Toledo R. Differential alterations in the small intestine epithelial cell turnover during acute and chronic infection with Echinostoma caproni (Trematoda). Parasit Vectors 2015; 8:334. [PMID: 26082180 PMCID: PMC4482164 DOI: 10.1186/s13071-015-0948-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2015] [Accepted: 06/11/2015] [Indexed: 01/20/2023] Open
Abstract
Background The intestinal epithelium plays a multifactorial role in mucosal defense. In this sense, augmented epithelial cell turnover appears as a potential effector mechanism for the rejection of intestinal-dwelling helminths. Methods A BrdU pulse-chase experiment was conducted to investigate the infection-induced alterations on epithelial cell kinetics in hosts of high (mouse) and low (rat) compatibility with the intestinal trematode Echinostoma caproni. Results High levels of crypt-cell proliferation and tissue hyperplasia were observed in the ileum of infected mice, coinciding with the establishment of chronic infections. In contrast, the cell migration rate was about two times higher in the ileum of infected rats compared with controls, with no changes in tissue structure, indicating that an accelerated cell turnover is associated with worm expulsion. Conclusion Our results indicate that E. caproni infection induces a rapid renewal of the intestinal epithelium in the low compatible host that may impair the establishment of proper, stable host-parasite interactions, facilitating worm clearance.
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Affiliation(s)
- Alba Cortés
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain.
| | - Carla Muñoz-Antoli
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain.
| | - Carla Martín-Grau
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain.
| | - J Guillermo Esteban
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain.
| | - Richard K Grencis
- Faculty of Life Sciences, University of Manchester, Manchester, M13 9PT, UK.
| | - Rafael Toledo
- Departamento de Parasitología, Facultad de Farmacia, Universidad de Valencia, Av. Vicente Andrés Estellés s/n, 46100, Burjassot, Valencia, Spain.
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Lagapa JT, Oku Y, Kamiya M. Immunohistochemical characterization of cellular proliferation in small intestinal hyperplasia of rats with hepatic Strobilocercus fasciolaris infection. J Comp Pathol 2008; 139:34-9. [PMID: 18539293 DOI: 10.1016/j.jcpa.2008.04.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Revised: 04/11/2008] [Accepted: 04/14/2008] [Indexed: 01/16/2023]
Abstract
Rats infected with the larvae of Taenia taeniaeformis harbour the intermediate stage of the parasite Strobilocercus fasciolaris within the liver. Affected animals also develop gastric and intestinal hyperplasia. The pathogenesis of the gastric hyperplasia has been extensively investigated, but few studies have addressed the nature of the intestinal changes. This study characterizes the proliferation of small intestinal epithelial cells by immunohistochemical labelling for proliferating cell nuclear antigen (PCNA) and bromodeoxyuridine (BrdU) uptake. At 6 weeks post-infection (wpi) there was an increase in villous length but crypt depth was normal. At 9 wpi there was evidence of epithelial hyperplasia, increased villous length and crypt depth, and expansion of zones of epithelial proliferation. Immunohistochemical labelling indicated that an increase in the number of proliferating cells produced a greater number of progeny cells. Intestinal hyperplasia during experimental infection with T. taeniaeformis larvae is likely to be related to the associated gastropathy, although the mechanisms underlying both changes remain undefined.
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Affiliation(s)
- J T Lagapa
- Department of Medicine, Surgery and Zootechnics, College of Veterinary Medicine, Central Mindanao University, Musuan, Bukidnon 8710, Philippines.
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Lagapa J, Oku Y, Nonaka N, Kamiya M. Taenia taeniaeformis: Fate and proliferation of mucosal cells during gastric hyperplasia in larvae infected rats. Exp Parasitol 2008; 118:576-82. [DOI: 10.1016/j.exppara.2007.12.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2007] [Revised: 10/19/2007] [Accepted: 12/10/2007] [Indexed: 10/22/2022]
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Artis D. New weapons in the war on worms: identification of putative mechanisms of immune-mediated expulsion of gastrointestinal nematodes. Int J Parasitol 2006; 36:723-33. [PMID: 16620826 PMCID: PMC1800426 DOI: 10.1016/j.ijpara.2006.02.011] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2005] [Revised: 02/06/2006] [Accepted: 02/10/2006] [Indexed: 01/08/2023]
Abstract
Parasitic nematode infections of humans and livestock continue to impose a significant public health and economic burden worldwide. Murine models of intestinal nematode infection have proved to be relevant and tractable systems to define the cellular and molecular basis of how the host immune system regulates resistance and susceptibility to infection. While susceptibility to chronic infection is propagated by T helper cell type 1 cytokine responses (characterised by production of IL-12, IL-18 and interferon-gamma), immunity to intestinal-dwelling adult nematode worms is critically dependent on a type 2 cytokine response (controlled by CD4+T helper type 2 cells that secrete the cytokines IL-4, IL-5, IL-9 and IL-13). However, the immune effector mechanisms elicited by type 2 cytokines in the gut microenvironment that precipitate worm expulsion have remained elusive. This review focuses on new studies that implicate host intestinal epithelial cells as one of the dominant immune effector cells against this group of pathogens. Specifically, three recently identified type 2 cytokine-dependent pathways that could offer insights into the mechanisms of expulsion of parasitic nematodes will be discussed: (i) the intelectins, a new family of galactose-binding lectins implicated in innate immunity, (ii) the resistin-like molecules, a family of small cysteine-rich proteins expressed by multiple cell types, and (iii) cytokine regulation of intestinal epithelial cell turnover. Identifying how the mammalian immune response fights gastrointestinal nematode infections is providing new insights into host protective immunity. Harnessing these discoveries, coupled with identifying what the targets of these responses are within parasitic nematodes, offers promise in the design of a new generation of anti-parasitic drugs and vaccines.
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Affiliation(s)
- David Artis
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Rosenthal 207, 3800 Spruce Street, Philadelphia, PA 19104, USA.
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Lagapa JT, Konno K, Oku Y, Nonaka N, Ito M, Kamiya M. Gastric hyperplasia and parietal cell loss in Taenia taeniaeformis inoculated immunodeficient mice. Parasitol Int 2002; 51:81-9. [PMID: 11880230 DOI: 10.1016/s1383-5769(01)00108-8] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Immunodeficient mice were studied to determine their suitability as models in investigating the role of Taenia taeniaeformis larval products in the development of gastric hyperplasia. Recombinant active gene 2 (RAG2)-deficient and severe combined immune-deficient (SCID) mice were studied as candidate animal models. RAG2-deficient mice inoculated orally with T. taeniaeformis eggs developed gastric hyperplasia with alcian blue-periodic acid-Schiff-positive cell proliferation similar to those of rats. SCID mice inoculated with different doses and routes of T. taeniaeformis in vitro-hatched oncospheres and those orally inoculated with eggs resulted also in different degrees of gastric hyperplasia. Influence of inoculation forms of parasite, doses and routes of inoculation on initiation of hyperplastic gastropathy was suggested to be dependent on number and size of developed larvae. Both RAG2-deficient and SCID mice with hyperplastic mucosa were observed with significant loss of parietal cells. Apparent decrease in parietal cell number was observed in SCID mice at 2 weeks after intraperitoneal inoculation with oncospheres before hyperplastic lesions developed. Earliest occurrence of gastric hyperplasia in SCID mice was observed at 3 weeks after oral inoculation of in vitro-hatched oncospheres, sooner than orally inoculated rats. The results suggested that these immunodeficient mice could be used as animal models to study factors involved in T. taeniaeformis-induced gastric mucous cell hyperplasia.
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Affiliation(s)
- Jose Trinipil Lagapa
- Laboratory of Parasitology, Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo 060-0818, Japan
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Artis D, Potten CS, Else KJ, Finkelman FD, Grencis RK. Trichuris muris: host intestinal epithelial cell hyperproliferation during chronic infection is regulated by interferon-gamma. Exp Parasitol 1999; 92:144-53. [PMID: 10366539 DOI: 10.1006/expr.1999.4407] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic infection with the intestinal nematode Trichuris muris is associated with an inappropriate type 1 cytokine response (production of predominantly IFN-gamma), whereas resistance to infection requires the induction of a protective type 2 response with the production of interleukin (IL)-4, IL-5, IL-9, and IL-13. T. muris inhabits an intracellular niche within murine intestinal epithelial cells of the caecum and in common with other intestinal helminth infections is associated with gross morphological changes in gut architecture. The purpose of this study was to characterise cytokine production during chronic infection in AKR and severe-combined-immunodeficient (SCID) mice and investigate what effect the anti-parasite response had on epithelial cell proliferation and so regulation of intestinal pathology. Pulse labeling with tritiated thymidine is employed to generate a sensitive cell position-linked proliferation index of the intestinal epithelium at various times postinfection. Infection in AKR mice is characterized by a marked elevation in antigen specific IFN-gamma production from restimulated mesenteric lymph node cells and a significant increase in proliferation of pluripotent epithelial stem cells and transit cells within the crypts. Similarly, elevated IFN-gamma production was observed in the mesenteric lymph nodes and intestinal mucosa of infected SCID mice, with epithelial cell hyperproliferation and the development of crypt hyperplasia in the caecum. Critically, in vivo depletion of IFN-gamma during infection in SCID mice resulted in no significant increase in epithelial cell proliferation and effectively precluded the development of crypt hyperplasia without altering infection outcome. Taken together, the data provides the first detailed cell position linked analysis of epithelial dysregulation during chronic T. muris infection and identifies a critical role for IFN-gamma, either directly or indirectly, in regulation of epithelial cell proliferation during the chronic intestinal inflammation associated with infection.
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Affiliation(s)
- D Artis
- Immunology Research Group, School of Biological Sciences, University of Manchester, 3.239 Stopford Building, Manchester, M13 9PT, United Kingdom
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Konno K, Abella JA, Oku Y, Nonaka N, Kamiya M. Histopathology and physiopathology of gastric mucous hyperplasia in rats heavily infected with Taenia taeniaeformis. J Vet Med Sci 1999; 61:317-24. [PMID: 10342279 DOI: 10.1292/jvms.61.317] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Rats heavily infected with larval Taenia taeniaeformis show hyperplasia of the gastric mucosa accompanied by mucous cell proliferation, increase in the level of intragastric pH and hypergastrinemia. Sixty one rats were divided into 2 groups designed as infected (36 rats) and control (25 rats) group. These rats were examined with time course of the infection histopathologically and physiopathologically, during 14-112 days postinfection (DPI). In the infected rats, gastric mucosal hyperplasia began to be observed at 56 DPI, and the structural disturbance of zymogenic units in the corpus and mucous units in the antrum had increased with time. However, the degree of these changes in the antrum was weaker than those in the corpus. Alcianblue and/or PAS-positive cells increased in their numbers with time, and 4 types of cells other than typical surface mucous cell and mucous neck cell were observed by electron-microscopy. However, zymogenic and parietal cells decreased in their number after 56 DPI. Further, the infected rats showed changes in the serum concentration of alanine aminotransferase, aspartate aminotransferase, blood urea nitrogen, glucose and total protein. Some similarities with Menetrier's disease were discussed.
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Affiliation(s)
- K Konno
- Department of Disease Control, School of Veterinary Medicine, Hokkaido University, Japan
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Abella JA, Oku Y, Nonaka N, Ito M, Kamiya M. Role of host immune response in the occurrence of gastropathy in rats infected with larval Taenia taeniaeformis. J Vet Med Sci 1997; 59:1039-43. [PMID: 9409522 DOI: 10.1292/jvms.59.1039] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Decrease of spleen weight from peak to control levels together with a corresponding decline of serum IgG level at the onset of gastric hyperplasia in Taenia taeniaeformis-infected euthymic rats, may indicate that a form of down regulation of host immune response during the course of larval T. taeniaeformis infection could facilitate the occurrence of gastropathy in rats. Gastric hyperplasia developed in T. taeniaeformis-infected athymic nude rats, indicating that occurrence of gastropathy associated with larval T. taeniaeformis infection in the rat is T cell independent. Apparently, gastric hyperplasia appeared early in nude rats which suggests that absence of T cell-mediated response could have facilitated its early occurrence.
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Affiliation(s)
- J A Abella
- Department of Disease Control, Graduate School of Veterinary Medicine, Hokkaido University, Sapporo, Japan
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Abella JA, Oku Y, Konno K, Altamirano Z, Nonaka N, Kamiya M. Concomitant onset of hypergastrinemia, intragastric alkalinity and gastric hyperplasia, and numbers of antral G cells in Taenia taeniaeformis-infected rats. Parasitol Int 1997. [DOI: 10.1016/s1383-5769(97)00015-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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Abstract
The interactions between Khawia sinensis (Cestoda: Caryophyllidea), a pathogenic tapeworm of carp, and host leucocytes has been investigated in vitro by monitoring blastogenesis in pronephric, splenic and thymic lymphocytes and apoptosis of pronephric leucocytes. Both parasite homogenate and excretory/secretory (E/S) products were found to suppress lymphocyte blastogenesis at high concentrations (346.6-98.8 microg ml-1) whilst cell stimulation occurred at low concentrations (49.4-19.8 microg ml-1). This differential affect on leucocyte activity may not be associated with apoptosis in vitro as the parasite E/S products did not significantly affect programmed cell death as monitored by acridine orange and DNA analysis. The parasite effect on leucocyte activity is discussed and its relationship to host susceptibility is evaluated.
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Affiliation(s)
- N J Morley
- Parasitology Research Group, Centre for Applied Entomology and Parasitology, Department of Biological Sciences, Keele University, Keele, Staffordshire ST5 5BG, UK
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Dial EJ, Kao YC, Lichtenberger LM. Effects of 16,16-dimethyl prostaglandin E2 on glycoprotein and lipid synthesis of gastric epithelial cells grown in a primary culture. In Vitro Cell Dev Biol 1991; 27:39-46. [PMID: 2013552 DOI: 10.1007/bf02630893] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
We investigated the biosynthesis of phospholipid, neutral lipids, glycoproteins, and DNA in primary cultures of rat oxyntic mucosal cells. In addition, responses of these biosynthetic pathways to the gastric protective agent 16,16-dimethyl prostaglandin E2 (dmPGE2) were studied. Cultured gastric cells under control conditions synthesized glycoprotein in a linear manner over time. The cells responded to dmPGE2 with an increase in glycoprotein synthesis without an effect on DNA synthesis. Investigations of lipid synthesis showed that phospholipid was produced in a linear fashion by these cells, however, no effect of exogenously administered dmPGE2 on its rate of formation was discernible. In contrast, the incorporation of labeled palmitate into neutral lipids revealed that triglyceride biosynthesis was significantly increased by the addition of dmPGE2 to the culture medium, which could be further enhanced by the administration of the phosphodiesterase inhibitor, isobutyl methyl xanthine. Cyclic nucleotide involvement was further suggested by our finding that triglyceride synthesis in cultured gastric mucous cells could be increased a comparable amount by the addition of both dbcAMP and dbcGMP to the medium. The possible relationship between these biochemical alterations and the gastric protective action of dmPGE2 is discussed.
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Affiliation(s)
- E J Dial
- Department of Physiology and Cell Biology, University of Texas Medical School, Houston 77225
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Abstract
Gossypol, a natural biphenyl compound inhibits Taenia taeniaeformis metacestode development in vivo. In this paper, the direct effect of gossypol on metacestodes was examined. Within 24 hr of incubation at 37 degrees C in greater than or equal to 10(-5) M gossypol, shedding of the tegument from the surface of the metacestodes was observed. There was a significant decrease in [3H]thymidine uptake by T. taeniaeformis in greater than or equal to 10(-5)M gossypol. In addition, NADH lactate dehydrogenase activity of metacestodes was significantly inhibited in greater than or equal to 10(-5) M gossypol. Thus, gossypol has a direct inhibitory effect on T. taeniaeformis metacestodes in vitro.
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Affiliation(s)
- Y Rikihisa
- Department of Veterinary Pathobiology, College of Veterinary Medicine, Ohio State University, Columbus 43210
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Savin KW, Dopheide TA, Frenkel MJ, Wagland BM, Grant WN, Ward CW. Characterization, cloning and host-protective activity of a 30-kilodalton glycoprotein secreted by the parasitic stages of Trichostrongylus colubriformis. Mol Biochem Parasitol 1990; 41:167-76. [PMID: 2204828 DOI: 10.1016/0166-6851(90)90179-p] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
The helminth Trichostrongylus colubriformis is a parasitic nematode infecting the small intestine of sheep. We report the isolation and characterization of a 30-kDa glycoprotein capable of partially protecting guinea-pigs against the parasite. This glycoprotein is secreted by the L4 and adult parasitic stages of the worm. The sequence of three separate cDNA clones predicts the polypeptide to be about 15 kDa, with four N-linked carbohydrate chains and an internal disulphide bond. The clones also indicate the existence of sequence variability in this antigen. Limited sequence homology to a porcine intestinal peptide suggests an influence on host gut physiology.
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Affiliation(s)
- K W Savin
- CSIRO Division of Biotechnology, Parkville, Australia
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Burger CJ, Rikihisa Y, Lin YC. Taenia taeniaeformis: inhibition of mitogen induced proliferation and interleukin-2 production in rat splenocytes by larval in vitro product. Exp Parasitol 1986; 62:216-22. [PMID: 2943603 DOI: 10.1016/0014-4894(86)90026-3] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
Splenocytes from rats infected with Taenia taeniaeformis showed an early decreased proliferative response to the mitogen concanavalin A with larval growth. When larvae culture supernatant (in vitro product) was added to normal rat splenocytes, there was a decrease in the proliferative response to concanavalin A and phytohemagglutinin. The ability of infected rat splenocytes to produce interleukin-2 was decreased with larval growth. Addition of in vitro product to culture medium significantly depressed interleukin-2 production by normal as well as infected rat spleen cells. Culturing normal rat splenocytes with in vitro product for 3 days induced a suppressor cell population. When these cultured cells were admixed with fresh normal rat splenocytes plus concanavalin A, the proliferative response of the fresh cells was significantly reduced. The present results suggest that in vitro product secreted by larvae in hepatic cysts causes subversion of the cellular immune response in the host. Induction of a suppressor cell population could suppress interleukin-2 production which may lead to the inhibition of differentiation and proliferation of specific cytotoxic T lymphocytes.
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Rikihisa Y, Lin YC, Walton A. Taenia taeniaeformis: immunoperoxidase localization of metacestode culture product(s) in hyperplastic gastric mucosa. Exp Parasitol 1986; 61:134-7. [PMID: 3082661 DOI: 10.1016/0014-4894(86)90144-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Rats infected with the hepatic metacestode Taenia taeniaeformis develop an extraordinary gastric hyperplasia. Indirect immunoperoxidase staining localized larval in vitro excretory secretory product specifically in the supranuclear cytoplasm of the epithelial cells lining the pits and glands in the hyperplastic gastric mucosa. The accumulation of this substance in the stomach epithelial cells may be relevant to the gastric hyperplasia induced by tapeworm infection.
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Rikihisa Y, Lin YC, Fukaya T. Taenia taeniaeformis: inhibition of rat testosterone production by excretory-secretory product of the cultured metacestode. Exp Parasitol 1985; 59:390-7. [PMID: 3996527 DOI: 10.1016/0014-4894(85)90094-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
In 3- to 5-month-old male Sprague-Dawley rats infected with the hepatic metacestode, Taenia taeniaeformis, the serum testosterone level was significantly lower than in comparable uninfected controls. By transmission electron microscopy, testicular Leydig cells of infected rats had less smooth endoplasmic reticulum than control Leydig cells. Cultured metacestodes isolated from the hepatic cysts secreted or excreted substances into the incubation medium. The effect of the excretory-secretory product on testosterone concentration in the sera and testes of 15-day-old rats was examined. Subcutaneous injection of 50-200 micrograms of excretory-secretory product/0.1 ml saline/rat for 2 days significantly reduced human chorionic gonadotropin-stimulated serum and testicular testosterone concentrations. Furthermore, the effect of the excretory-secretory product on isolated rat Leydig cell testosterone production was examined. Rat Leydig cells produced testosterone in vitro and, in the presence of 50 IU human chorionic gonadotropin/ml incubation medium, they responded with approximately 100% increase in testosterone production. Addition of 2-10 micrograms excretory-secretory product protein/ml of culture medium significantly reduced the testosterone production by rat Leydig cells in vitro. These results indicate that excretory-secretory product of cultured T. taeniaeformis metacestodes has a direct inhibitory effect on Leydig cell testosterone production under stimulation with human chorionic gonadotropin.
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