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Biomedical subjects

E Meerovitch

Publications and source records attributed to E Meerovitch.

At least 37 records · Page 2Linked to original sources
PubMed1982

In vitro amoebicidal activity of immune cells.

The amoebicidal activity of peripheral blood lymphocytes and spleen and peritoneal cells from hamsters vaccinated against or protected from hepatic amoebiasis and from those with hepatic amoebiasis was investigated. Peripheral blood lymphocytes and peritoneal and spleen cells from vaccinated or protected animals can kill trophozoites of Entamoeba histolytica in vitro. In contrast, spleen cells from infected hamsters showed no significant cytotoxic effect on the parasite. These data suggest that cellular immunity plays an important role in host defense against hepatic amoebiasis.

Animals↗
PubMed1981

Cysticercus racemosus in an eosinophilic phlegmon in the brain.

Cysticercus racemosus in a tumour-like mass from the brain of a 30-year-old Canadian was identified by histological and specific immunofluorescent techniques. The patient possibly acquired the infection during her stay in India. She had a mild peripheral eosinophilia and complained of pounding headaches and convulsions. Examination of tissue sections revealed the larva enclosed in an eosinophilic phlegmon and the surrounding brain tissue infiltrated by histiocytes and eosinophils. Loss of microtriches and degenerative changes in the larva were apparent in areas with adherent eosinophils. With the appropriate reagents, both intracellular and interstitial specific immune complexes were detected in the biopsied tissue. The course of infection in the cystic and racemosus types of cysticercosis and the role of tissue eosinophilia in neurocysticercosis have been discussed.

Adult↗
PubMed1981

Effect of immunosuppression on the size and metastasis of amoebic liver abscesses in hamsters.

The effect of T-cell depletion on experimental hepatic amoebiasis in hamsters was investigated. Thymectomized and anti-T-cell (ATS) treated animals as well as sham-operated and unoperated controls were inoculated intrahepatically, following laparotomy, at 7 weeks of age with 1 x 10(5) axenic trophozoites of Entamoeba histolytica. In neonatally thymectomized hamsters the mean weight of the liver abscess 10 days post-inoculation was significantly greater than in neonatally sham-operated or unoperated controls, but there was no significant difference between these groups of animals in the size of metastatic foci to other organs. On the other hand, a combination of neonatal thymectomy and ATS treatment enhanced both the size of the primary abscess in the liver and the size of metastases to other sites. Adult thymectomy did not have a significant effect either on the size of the primary abscess or on metastatic dissemination of amoebae from the liver. Treatment of hamsters with ATS shortly before or after intrahepatic challenge increased significantly the size of the abscess, but similar treatment 2-3 weeks prior to challenge had no effect. These observations suggest that thymus-dependent cell-mediated immunity plays an important role in the host response to E. histolytica infection.

Animals↗
PubMed1981

Effect of splenectomy on the size of amoebic liver abscesses and metastatic foci in hamsters.

The role of the spleen in hepatic amoebiasis in hamsters was studied. In hamsters receiving an intrahepatic inoculation of 10(5) trophozoites of axenic Entamoeba histolytica at 7 or 14 days postsplenectomy, the mean weight of metastatic foci increased significantly when compared with sham-splenectomized or intact controls. In contrast, when both splenectomy and intrahepatic inoculation with amoebae were carried out at the same time, there was not only a significant increase in the mean weight of metastatic foci but also in the liver abscess. It is suggested that the spleen is important for host defense against E. histolytica infection, especially in the reduction in the degree of metastatic spread from the primary site.

Animals↗
PubMed1980

Protection against amebic liver abscess in hamsters by means of immunization with amebic antigen and some of its fractions.

Immunization of hamsters by intramuscular injections of an amebic extract and of two of its fractions, emulsified with complete Freund's adjuvant, resulted in protection against the development of amebic liver abscess, following intrahepatic inoculation of axenic trophozoites of Entamoeba histolytica such that Fraction I, Fraction II, and the whole antigen conferred protection to 18 out of 18, 4 out of 18, and 11 out of 18 hamsters, respectively. Splenomegaly was found to accompany the development of hepatic liver abscesses in this experimental system. There was a very high degree of correlation (r = 0.95) between the weights of the abscesses and the spleens. On the other hand, there was no correlation between the anti-amebic antibody titers (determined by the indirect hemagglutination test) and the development of the liver abscesses within the time-span of the experimental protocol used in this study.

Animals↗
PubMed1980

Physico-chemical factors affecting the behaviour and activity of Entamoeba histolytica.

Activity of individual trophozoites of several strains of axenic Entamoeba histolytica under different environmental conditions was measured by means of a newly devised method. Activity was found to be different between strains and corresponded to the degree of their pathogenicity. At low pH values amoebae moved further due to a straightening of their paths. A similar phenomenon was found in 1:50 cilution of pig bile. Bile was also found to induce an increase in the number of monopodial, "limax-like" forms in proportion to its concentration.

Culture Media↗
PubMed1980

Effect of Trichinella spiralis infection on the experimental amebic liver abscess in hamsters.

The development of experimental amebic liver abscess in hamsters was inhibited by a previous infection with the nematode parasite Trichinella spiralis, such that liver abscesses were present in 26% of hamsters with T. spiralis infection and in 80% of T. spiralis-free controls. The protective effect of T. spiralis infection is believed to be exerted through a non-specific activation of cellular immunity, with macrophages as probable effector cells.

Animals↗
PubMed1979

Studies on a morphologically distinct colchicine-resistance variant of Entamoeba sp.

Colchicine has a temperature-dependent cytotoxic effect on Entamoeba sp. (Laredo isolate) that is most apparent when the drug is applied during the initiation of cultures at a concentration of 7.5 mM or higher. Continued transfer of cultures in medium containing progressively increasing concentrations of colchicine has resulted in a variant that grows prolifically in the presence of colchicine (7.5 mM) with a generation time comparable to that of the parent stock, Comparison of a number of parameters of the 2 variants revealed that colchicine resistance was accompanied by a change in cell shape, a reduced membrane permeability, which could partially be overcome by the addition of dimethyl sulfoxide (DMSO), and a reduced tolerance to osmotic stress. However, the parent strain and resistant variant were equally susceptible to cycloheximide and puromycin suggesting that the acquired colchicine resistance may not be explained on the basis of an entirely unspecific generalized reduced ability for drug uptake. Colchicine resistance and altered structure were found to be stable over a long period of time. The possible interdependence of these 2 parameters and their relation to cell motility in Entamoeba sp. are discussed.

Animals↗
PubMed1979

Pathogenicity of axenically cultivated Entamoeba histolytica, strain 200:NIH, in the hamster.

Entamoeba histolytica strain 200:NIH cultured axenically for about 15 years produced lesions and abscesses in inbred adult hamsters following intrahepatic, intraperitoneal, and intradermal inoculation. These amebae, even in much higher doses, inoculated into the ceca of adult and young hamsters failed to produce lesions or to become established there. On the other hand, 200:NIH axenic amebae passaged through hamster liver (substrain 200:NIH-L) were able to become established and to produce lesions in the ceca of very young hamsters (1- and 3-week-old), the degree of pathogenicity appearing to be inversely proportional to age of the hamster.

Age Factors↗
PubMed1978

Restoration of virulence of axenically cultivated Entamoeba histolytica by cholesterol.

The lost pathogenicity of two strains of Entamoeba histolytica, one isolated in 1924 and the other in 1967, grown in axenic culture for the past 5 and 6 years respectively, was restored by supplementing the culture medium with cholesterol through a number of transfers. The number of passages in the cholesterol-supplemented medium, necessary to restore a certain degree of pathogenicity of the two strains in hamsters, was proportional to the total time of in vitro cultivation of the strain, and not just the time of cultivation under axenic conditions. Pathogenicity, once restored, persisted for a long time after cholesterol treatment was stopped.

Animals↗
PubMed1978

Behavior of axenic IP-106 strain of Entamoeba histolytica in the golden hamster.

Strain IP-106 of Entamoeba histolytica was isolated 12 yr ago from a case of amebic dysentery and has been maintained in axenic culture for the past 11 yr. Hamsters were inoculated intrahepatically, intraperitoneally, and intracecally with 6.5, 5.0, and 8.0 X 10(4) axenic trophozoites, respectively. With the first two routes of inoculation all the animals developed liver abscesses, and most developed amebic metastases to other sites. After intracecal inoculation only 3 out of 6 animals developed abscesses at the primary site and metastases to other sites. Most numerous metastases were obtained following intrahepatic inoculation. Intrahepatic inoculation with 1 and 2 X 10(4) axenic amebae resulted in an increase in the size of the liver abscess for a period of 2 wk and its apparent total resorption by day 17 post-inoculation, accompanied by a corresponding gain of body weight. With 4 and 6 X 10(4) amebae there was a steady increase of the size of the liver abscess and corresponding loss of body weight. High antiamebic indirect hemagglutination titers were observed only on day 17 post infection in animals inoculated with 2, 4, and 6 X 10(4) amebae. The extent of amebic metastases was roughly proportional to the size of the inoculum.

Animals↗
PubMed1978

The presence of liver auto-antibodies induced by Entamoeba histolytica in the sera from both naturally infected humans and immunized rabbits.

Auto-antibodies against normal human liver have been detected in the sera of humans with highly positive indirect hemagglutination (IHA) amebiasis titers and with clinically-proven amebic liver abscess. Sera of amebiasis patients and rabbits immunized with killed Entamoeba histolytica were tested for anti-amebic antibodies by the IHA test and for auto-antibodies by the complement fixation test, using the antigens prepared from extracts of human liver and rabbit liver. A direct correlation was found to exist between high anti-Entamoeba antibody titers and the presence of anti-liver antibody in the serum. It is proposed that, in addition to direct parasite damage to host tissue, immunological damage could result from the attachment of circulating antigen to the cell surfaces of host tissues such as the liver.

Adolescent↗
PubMed1978

Protective immunity and possible autoimmune regulation in amebiasis.

Hamsters were injected intradermally with axenic trophozoites of a pathogenic strain of Entamoeba histolytica, and controls similarly with culture medium. Localized lesions were produced in all animals injected with amebae. After the lesions healed all the animals were challenged intrahepatically with axenic amebae. Extensive liver abscesses were produced in all the controls, but a small abscess in only one of the vaccinated hamsters. In the protected animals the indirect hemagglutination antibody titers were high (I:512), while in the controls they ranged between 1:32 and 1:128. In the vaccinated hamster with the small abscess the IHA titer was 1:32. To investigate a possibility of autoimmune regulation in amebiasis, sera of hamsters with experimental amebic liver abscesses were acidified and tested by counter-current-immunoeletrophoresis against untreated autologous sera and amebic antigen. In most cases there was a direct correlation between the two titers. With human antisera in autologous systems there was reactivity against anti-amebic IgG antibodies. These experiments showed that autoimmune complexes may be present in cases of hepatic amebiasis. As in chronic hepatitis and some malignancies, it is possible that immune complexes have an immunoregulatory function in amebiasis.

Animals↗