PubMed Health⌕ Search

Biomedical subjects

K Chadee

Publications and source records attributed to K Chadee.

At least 73 records · Page 4Linked to original sources
PubMed1988

In vitro and in vivo studies of macrophage functions in amebiasis.

Experimental intrahepatic inoculation of the gerbil with Entamoeba histolytica trophozoites was used as a model of liver amebiasis to study the cellular immune response elicited by the parasite. It was shown that abscess-derived macrophages (5 to 20 days old) were deficient in their capacity to develop a respiratory burst, to secrete and express membrane-bound interleukin-1-like activity, and to kill E. histolytica trophozoites as well as to respond to lymphokines in vitro. However, macrophages isolated from the spleen and peritoneal cavities from the same infected animals were not significantly down regulated in these functions. Splenocytes from infected gerbils were shown to develop a strong responsiveness to amebic antigen, whereas their response to concanavalin A was suppressed. Crude E. histolytica extracts or conditioned medium down regulated murine BALB/c macrophage accessory and effector cell functions in vitro in a manner similar to abscess-derived macrophages, whereas crude extracts of the nonvirulent E. histolytica-like Laredo strain did not. Our results indicate that intrinsic or secreted products or both from E. histolytica are actively regulating macrophage functions at the abscess site and can possibly mediate other immunoregulatory mechanisms at distant targets.

Animals↗
PubMed1987

Entamoeba histolytica: chemoattractant activity for gerbil neutrophils in vivo and in vitro.

The kinetics of the host's cellular response in the peritoneal cavity of gerbils toward axenic pathogenic and nonpathogenic Entamoeba histolytica strains were examined. Amebae contained in diffusion chambers or free in the peritoneum elicited a neutrophilic response accompanied by decreased levels of macrophages and lymphocytes. Pathogenic amebae (IP:0682:1 strain) elicited a neutrophilic response greater than the nonpathogenic DKB and "entamoeba-like" Laredo amebae. The neutrophil eliciting factor was found in high levels in disrupted freeze-thawed amebae (53% elicited neutrophils vs 8% for control), glutaraldehyde fixed amebae (45%) and amebic membranes (65%), and low levels in conditioned amebic medium (15%) and the supernatant fraction of amebae (16%). The factor was heat stable to high temperature (100 C for 30 min) and at various pH (6 to 9). The neutrophil eliciting factor in amebic membranes was lowered following pretreatment for 30 min with 1% immune and nonimmune gerbil or human sera (34-48% lowered neutrophil response vs control), acidic pH (less than 3, 69%), proteolytic digestion [trypsin (68%) and alpha-chymotrypsin (72%), 100 micrograms/ml], and 2% Triton X-100 (75%). Peritoneal neutrophils isolated following stimulation with amebic membranes or thioglycollate medium demonstrated higher chemotaxis in vitro toward live pathogenic amebae and amebic membranes (IP:0682:1 strain) compared to either the supernatant fraction or the nonpathogenic DKB or Laredo amebae. The results of this study indicate that membrane bound proteins of pathogenic amebae are chemotactic for gerbil neutrophils which may be important in the pathogenesis and pathology of amebiasis.

Animals↗
PubMed1987

Rat and human colonic mucins bind to and inhibit adherence lectin of Entamoeba histolytica.

Establishment of adherence by Entamoeba histolytica is mediated by a 170-kD Gal/GalNAc inhibitable lectin and is required for cytolysis and phagocytosis of mammalian target cells. We studied the biochemical mechanisms of the in vitro interaction between rat and human colonic mucins and axenic E. histolytica trophozoites. Crude mucus prevented amebic adherence to Chinese hamster ovary (CHO) cells by up to 70%. Purification of the colonic mucins by Sepharose 4B chromatography, nuclease digestion, and cesium chloride gradient centrifugation resulted in a 1,000-fold enrichment of the inhibitory mucins. Purified rat mucin inhibited amebic adherence to and cytolysis of homologous rat colonic epithelial cells. Oxidation and enzymatic cleavage of rat mucin Gal and GalNAc residues completely abrogated mucin inhibition of amebic adherence. The binding of rat 125I-mucin to amebae was galactose specific, saturable, reversible, and pH dependent. A monoclonal antibody specific for the 170-kD amebic Gal/GalNAc lectin completely inhibited the binding of rat 125I-mucin. Rat mucin bound to Affigel affinity purified the amebic lectin from conditioned medium. Colonic mucin glycoproteins act as an important host defense by binding to the parasite's adherence lectin, thus preventing amebic attachment to and cytolysis of host epithelial cells.

Animals↗
PubMed1985

In vitro and in vivo interaction between trophozoites of Entamoeba histolytica and gerbil lymphoid cells.

The in vitro and in vivo antiamoebic cytotoxic effects of peritoneal exudate cells and mesenteric lymph node lymphocytes of gerbils with cecal amoebiasis or those immunized with amoebic extract were investigated. A differential effect of the lymphoid cells against trophozoites of nonpathogenic and pathogenic strains of Entamoeba histolytica was observed. Nonpathogenic amoebae were more susceptible to killing by lymphoid cells than pathogenic amoebae in vitro and in vivo in infected or immunized animals. These data suggest that during the course of cecal amoebiasis in gerbils, a differential stimulation or depletion of cytotoxic cells in the lymphoreticular tissues occurs, resulting in an impaired cell-mediated immune response.

Animals↗
PubMed1985

Entamoeba histolytica: early progressive pathology in the cecum of the gerbil (Meriones unguiculatus).

The early formation of amebic cecal lesions in the gerbil (Meriones unguiculatus) was studied sequentially from 1 to 10 days post-inoculation. The earliest response of the cecal mucosa towards trophozoites of Entamoeba histolytica was local release of interglandular and goblet cell mucin. Trophozoites adhered to the surface epithelium or were trapped in the luminal mucus in the absence of epithelial cell damage. Focal mucosal erosion occurred later, and was preceded by crypt hyperplasia, edema and hemorrhaging of the lamina propria. The interglandular epithelial cells were cytolysed or were sloughed off into the lumen. Amebic mucosal erosion was accompanied by trophozoite entry in the crypts, but rarely into the lamina propria. The inflammatory cellular infiltrate was diffuse, and neutrophils were found in the lumen in contact with trophozoites. The findings of this study suggest that trophozoites of E. histolytica do not actively penetrate or invade the interglandular epithelium, but rather, that amebae are permitted to invade as a result of the destruction of the epithelium. Mucus depletion and the mucosal inflammation, probably in response to the adsorption of amebic toxins, preceded epithelial erosions.

Amebiasis↗
PubMed1985

Entamoeba histolytica: electrophoretic isoenzyme patterns of strains and their virulence in the cecum of gerbils (Meriones unguiculatus).

Six strains of Entamoeba histolytica isolated from humans were characterized by their electrophoretic isoenzyme patterns and by virulence in the cecum of Mongolian gerbils (Meriones unguiculatus). Amebae from symptomatic cases of amebiasis were found to belong to zymodeme group II, whereas strains isolated from asymptomatic infections belonged to zymodeme groups I or V. Strains recently isolated from symptomatic cases of amebiasis were highly invasive in the cecum of gerbils. The most prominent pathologic changes present in these infections were the destruction of the interglandular epithelium, crypt hyperplasia and trophozoite invasion of the crypts and submucosa. Strains from asymptomatic carriers were of low or moderate invasiveness in the animal model. Two of the carrier strains expressing a zymodeme group I pattern caused diffuse or transient focal erosions of the interglandular epithelium in some animals. Trophozoites of carrier strains did not invade the crypts nor cause sloughing of the surface epithelium. Presence of colonic lesions was correlated with passage of motile trophozoites in the feces. The severity of histologically demonstrable lesions in the cecum of gerbils was positively correlated with the isoenzyme patterns characteristic of the more virulent amebic strains.

Animals↗
PubMed1985

Entamoeba histolytica: lymphoreticular changes in gerbils (Meriones unguiculatus) with experimentally induced cecal amebiasis.

Antibody responses and changes in the lymphoreticular tissues of gerbils with experimental cecal amebiasis were studied from 5 to 60 days PI. Changes in the cecum consisted of lymphoid follicle hyperplasia and depletion of lymphocytes, followed by follicle atrophy and histiocytosis. Mesenteric lymphadenopathy, and histologic alterations in the lymph nodes paralleled the progressive development of amebic cecal lesions. Early in the infection (5 to 10 days PI) mesenteric lymph nodes showed cortical follicle hyperplasia, blastogenesis in the paracortical areas (PCA) and intense lymphoblast and plasma cell activity in the medullary cords. At 20 to 30 days PI, the cortical follicles, the PCA and the medulla were depleted of lymphocytes and there was histiocytosis throughout the organ. At 60 days PI, lymphocyte repopulation took place in the PCA, and cortical follicles had active germinal centers. Spleen follicles did not increase in number as the infection progressed, but became hyperplastic. Antibody titers to ameba were low throughout the cecal infection but rose whenever amebic metastasis to the liver occurred. The results of this study indicate that lymphocytes from the submucosal lymphoid follicles and the draining lymph nodes may control the pathogenesis of the infection. Lymphoreticular tissue alterations could result from antigenic stimulation and migration of cells to the sites of infection.

Animals↗
PubMed1985

The pathology of experimentally induced cecal amebiasis in gerbils (Meriones unguiculatus). Liver changes and amebic liver abscess formation.

The pathogenesis of experimentally induced cecal amebiasis in gerbils (Meriones unguiculatus) was studied from 5 to 60 days after inoculation. Ulcerative lesions were noted 10 to 60 days after inoculation. The sequential development of lesions was asynchronous and progressed from destruction of the interglandular epithelium and of glandular crypt elements to loss of mucosa and formation of granulomatous lesions in the submucosa involving the muscularis mucosae. Pathologic changes in the liver correlated with the formation of ulcerative cecal lesions. Subacute hepatic changes showed lymphocytic portal infiltrate, Kupffer cell hyperplasia, multinucleated giant cells, granuloma formation, and sinusoidal mononuclear and granulocytic infiltrates. Metastatic amebic liver abscesses occurred as early as 10 days after inoculation, and small abscesses were found in the portal areas of the right liver lobe. The sequential development and pathologic manifestation of the infection and the usefulness of the gerbil for the study of human intestinal amebiasis are discussed.

Amebiasis↗
PubMed1984

Entamoeba histolytica: antibody responses and lymphoreticular changes in gerbils (Meriones unguiculatus) in response to experimental liver abscess and amebic extract infection.

Antibody responses and histological changes in hepatic lymph nodes and spleen of gerbils (Meriones unguiculatus) during the course of experimental hepatic amebiasis (5-60 days), or in those injected with extracts of Entamoeba histolytica, are described. Lymph node and spleen responses in infected animals paralleled the proliferation of the amebic liver abscess. However, spleen follicle responses were similar in animals that received low or high doses of the amebic extract and differed histologically from those with amebic liver abscess. Liver abscesses, up to 30 days postinfection (pi), doubled in weight between 10 and 15 and between 20 and 30 days pi. Early changes (10 days pi) in the lymphoreticular tissues were characterized by increased size and weight of the organs, hyperplastic follicles, and blastogenesis in the T-dependent areas. At 20 and 30 days pi, the size of spleen follicles increased and there was depletion of lymphocytes from the periarterial area (PAA), as well as gross extension of the red pulp, accompanied by extramedullary erythropoiesis and megakaryocytosis. The paracortical areas (PCA) of lymph nodes were depleted of lymphocytes and histiocytosis throughout the organ, and there was intense plasma cell activity in the medulla. At 60 days pi, lymphocyte repopulation was noted in the PCA and PAA; germinal centers were depleted of blast cells and the spleen red pulp had contracted. Antiamebic antibody titers were low throughout the infection. Changes in the cellularity of the lymphoid organs are discussed in relation to the proliferation of the amebic liver abscesses in infected animals and in those which were injected with the amebic extract.

Animals↗
PubMed1984

The Mongolian gerbil (Meriones unguiculatus) as an experimental host for Entamoeba histolytica.

Experimentally induced cecal and hepatic amebiasis was studied in the Mongolian gerbil (Meriones unguiculatus). Axenically cultivated Entamoeba histolytica trophozoites were inoculated into the cecum or the liver after laparotomy. Cecal infections were characterized by intense inflammation and distortion of the tissue. The intensity of the infection, measured by a standard method of scoring, was consistently high from 10 to 30 days postinoculation (p.i.). In tissue sections, disruption of the interglandular epithelium and presence of amebic ulcers and of large numbers of trophozoites were most noticeable 10 days p.i. In older infections there was cecal hypertrophy and crypt hyperplasia but only few amebae were seen. Amebic liver abscesses were well tolerated by gerbils and no mortality occurred. Growth of liver abscesses increased exponentially as the duration of the infection progressed from 5 to 30 days p.i. Liver abscesses were always confined to the inoculated liver lobe, and metastases did not occur. Early liver granulomas were discrete with well-defined walls. The abscesses had a fibrous wall and amebae were seen at their inner aspect. Older liver granulomas were coalesced, forming a single cavitary abscess with intense cellular infiltrate. Gerbils of all ages tested were equally susceptible to liver infections although larger abscesses were obtained in younger adult animals (60-80 days old). The Mongolian gerbil is proposed as a suitable animal model for experimental amebiasis because both the intestinal and hepatic aspects of the disease can be studied in it.

Animals↗
PubMed1984

The pathogenesis of experimentally induced amebic liver abscess in the gerbil (Meriones unguiculatus).

Sequential development and pathology of experimentally induced amebic liver abscess in the gerbil (Meriones unguiculatus) were studied from 1 to 60 days after inoculation. Early lesions were characterized by an acute inflammatory response, which became granulomatous at 5 days. Early granulomas were discrete, with well-defined fibrohistiocytic walls. Trophozoite dissemination as a result of fibrolysis of granuloma wall was confined to the liver parenchyma. The granulomatous cellular infiltrate (less than 20 days) was characterized by granulocytes and histiocytes; older granulomas (greater than 30 days) were composed of lymphocytic infiltrate, plasma cells, and a few granulocytes, and were characterized by the absence of epithelioid histiocytes. The degree of pathologic change adjacent to liver granulomas followed the sequential development of the amebic liver abscess. Severe changes observed were portal canal lymphocytic infiltration, the presence of foreign body giant cells, periportal fibrosis, proliferation of bile duct epithelium, and hepatocyte anisonucleosis and ballooning degeneration. The pathogenesis of the infection and the usefulness of the gerbil model for the study of human amebiasis are discussed.

Animals↗
PubMed1983

Helminth parasites of pine marten, Martes americana (Turton), from Manitoba, Canada.

Five species of helminths were recovered during a survey of 139 North American pine marten (Martes americana) from three areas of Manitoba: Alaria taxideae in 75 marten; Taenia sp. (cf. martis martis) in 16; Taenia mustelae in nine; Baylisascaris devosi in one; Trichinella sp. larvae in one. Taenia mustelae and Taenia sp. (cf. martis martis) were found in two different areas of the province, Taenia sp. (cf. martis martis) being isolated from the more northerly regions. Alaria taxideae, the most prevalent parasite in the survey, was common to all three areas. The intensity of infection and prevalence level of A. taxideae was significantly higher (P less than 0.05) in the southern region of this study. Altogether, male marten had a significantly higher intensity of A. taxideae compared to females, although there was no significant difference in prevalence level. When data for A. taxideae was combined for sexes and for regions a significantly higher prevalence level in young-of-the-year marten was noted compared to juveniles or adults, but no significant difference in intensities among the three age classes was found. No significant differences were detected in the prevalence of A. taxideae, Taenia sp. (cf. martis martis), or T. mustelae between sexes or among age classes from any of the three areas.

Age Factors↗
PubMed1983

Interbreeding and gene flow in the genus Trichinella.

Breeding experiments between isolates of Trichinella spiralis--Trichinella (pig; 43 degrees 00'N, 81 degrees 00'W; 1952), Trichinella (polar bear; 58 degrees 00'N, 95 degrees 00'W; 1976), and Trichinella (wolverine; 55 degrees 00'N, 100 degrees 00'W; 1979)--and T. spiralis var. pseudospiralis were undertaken. Results from breeding experiments differed, such as the inability of the strain isolated from pigs and T. spiralis var. pseudospiralis to breed. The pig isolate was capable of breeding with both arctic isolates (wolverine and polar bear) and the arctic isolates both were capable of breeding with T. spiralis var. pseudospiralis. These observations indicated that gene flow occurs between these isolates of Trichinella and suggests a latitudinal cline of variants but not distinct species. It is hypothesized that T. spiralis consists of a series of semispecies or incipient species in various stages of speciation.

Animals↗
PubMed1982

Designation and freezing resistance of isolates of Trichinella spiralis from wild carnivores.

A system to designate and define isolates of Trichinella spiralis is proposed. The designation gives the host from which the isolate was recovered, geographic origin, and year of recovery. Isolates of T. spiralis recovered from frozen muscles from four species of wild carnivores had low and different infectivity to laboratory mice. Viable larvae of T. spiralis were obtained from muscle samples of marten, wolverine, polar bear and arctic fox which had been frozen for 5, 6, 12 and 14 mo, respectively.

Animal Population Groups↗
PubMed1981

Chemical attraction in the absence of worm-mediated tactile behavior in Trichinella spiralis.

In vitro chemical attraction of Trichinella spiralis was studied using as migrators individual male or female worms. Both male and female worms exhibited a dose-dependent behavior at target doses of 20 to 80 worms, no significant differences in response at doses of 80 to 200 worms, and an inhibition of movement at doses of 200 to 400 worms. Single males were attracted less to a mixture of males and females as the source of pheromone than single males to a female source. Single females did not move significantly towards a mixture of males and females. Adult males and fourth-state, juvenile males were significantly attracted to fourth-stage females as the pheromone source. Fourth-stage males attracted adult females but not forth-stage juvenile females. Adult males and females and third-stage, juvenile males and females were not significantly attracted to a pheromone source from third-stage juvenile males and females. We postulate that the onset of pheromone production in T spiralis is during the fourth developmental stage.

Animals↗