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J I Ravdin

Publications and source records attributed to J I Ravdin.

At least 19 recordsLinked to original sources
PubMed1992

The Cleveland Veterans Affairs Medical Center firm system.

Hospital-based "firms" provide a means for combatting the fragmentation experienced by both patients and caregivers in the modern teaching hospital environment. A "firm" is an academic group practice that includes attending physicians, physician trainees, nurses, other staff, and patients. Each person's relationship with a firm lasts throughout his or her association with a particular institution. This article describes the firm system that was recently implemented on the Medical Service of the Cleveland VAMC. This system incorporates both inpatient and outpatient general medical services and provides for unbiased assignment of patients, physicians, and nurses.

Adult↗
PubMed1992

Human T-lymphocyte proliferation, lymphokine production, and amebicidal activity elicited by the galactose-inhibitable adherence protein of Entamoeba histolytica.

We studied human T-lymphocyte responses to the purified Entamoeba histolytica galactose-inhibitable adherence protein. Individuals having serum anti-adherence protein antibodies possess peripheral blood lymphocytes which demonstrate antigen-specific responses to the purified adherence protein (10 micrograms/ml) and whole soluble amebic antigen (100 micrograms/ml). This was determined by incorporation of [3H]thymidine (53,080 and 73,114 dpm, respectively) and by increased production of interleukin-2 and gamma interferon (42.0 and 67.5 U/ml, respectively) (P less than 0.05 for each in comparison with values for control lymphocyte responses). Lymphocytes from antiamebic antibody-positive subjects develop in vitro amebicidal activity only when incubated for 5 days with the purified adherence protein (P = 0.02). In conclusion, the E. histolytica galactose-inhibitable adherence protein elicits an in vitro amebicidal cell-mediated immune response, further supporting the potential for the use of this protein in a subunit amebiasis vaccine.

Animals↗
PubMed1992

Use of an enzyme-linked immunosorbent assay to detect anti-adherence protein antibodies in sera of patients with invasive amebiasis in Cairo, Egypt.

We used enzyme-linked immunosorbent assay (ELISA) to detect IgG antibodies to the Entamoeba histolytica galactose-inhibitable adherence protein in the sera of 50 uninfected controls, 50 cases with asymptomatic cyst passage, 100 patients with amebic colitis, and six patients with amebic liver abscess from Cairo, Egypt, and in 50 healthy controls from the United States. When the mean + 3 SD value above that of the controls from the United States was used as a criterion for a positive ELISA result, 100% of those with invasive amebiasis, 80% of those with asymptomatic infection, and 64% of the Egyptian controls had anti-adherence protein antibodies. However, when the mean + 2 SD value of Egyptian control sera (optical density = 0.094) was used as the criterion for positivity, 33 (89%) of 37 sera from individuals with invasive amebiasis having symptoms for at least one week were antibody positive, in contrast to only 12% of asymptomatic cyst passers (P < 0.01). In a highly endemic area such as Cairo, Egypt, detection of serum anti-adherence protein antibodies by ELISA may have greatest diagnostic use in patients with symptomatic invasive amebiasis of greater than one week duration.

Animals↗
PubMed1991

Mucin and nonmucin secretagogue activity of Entamoeba histolytica and cholera toxin in rat colon.

Depletion of colonic mucus occurs before invasion of the colonic mucosa by Entamoeba histolytica trophozoites. It is hypothesized that E. histolytica releases a mucus secretagogue; this was studied in a rat colonic loop model. In colonic loops exposed to live amebae, mucus secretion was quantitated by release of acid-precipitable [3H]glucosamine-labeled luminal glycoprotein and by specific immunoassay. Mucus secretion increased in dose-dependent fashion in response to greater than or equal to 1 X 10(5) trophozoites; cholera toxin (20 micrograms per loop), a known mucus secretagogue, elicited a similar response. Thin-section histological analysis of amebae and cholera toxin-exposed loops showed increased mucus release and streaming from mucosal goblet cells with cellular cavitation compared with control loops. Sepharose-4B chromatography of amebae and cholera toxin-stimulated glycoproteins demonstrated secretion of mucins and an 80%-90% increase in low-molecular-weight proteins. E. histolytica trophozoites and cholera toxin enhanced the secretion of preformed and newly synthesized mucin glycoproteins and stimulated colonic glycoprotein synthesis. The level of mucus secretion elicited by axenic E. histolytica strains correlated with their virulence in vivo and in vitro. The amebic secretagogue was released into the culture medium and was heat stable. Mucus secretagogue activity of E. histolytica may contribute to depletion or alteration of the protective mucus blanket, facilitating pathogenesis of invasive amebiasis.

Animals↗
PubMed1991

Protection of gerbils from amebic liver abscess by immunization with the galactose-specific adherence lectin of Entamoeba histolytica.

No protective antigens from Entamoeba histolytica have been previously defined. We tested the ability of the galactose-specific adherence lectin of E. histolytica to elicit a protective immune response in conjunction with Freund's incomplete and complete adjuvants. The gerbil (Meriones unguiculatus) model of an experimental amebic liver abscess was used. Gerbils were immunized intraperitoneally or subcutaneously with 10 micrograms of the affinity-purified lectin in complete Freund's adjuvant and then at 2 and 4 weeks with 10 micrograms of the lectin in incomplete Freund's adjuvant. All of the immunized animals developed antilectin antibody titers of greater than 1/1,024 as measured by a radioimmunoassay. The gerbil antilectin antibodies were shown by Western immunoblotting to be directed to the heavy subunit but not the light subunit of the lectin. Immune gerbil sera inhibited amebic adherence by 100% at a 1/10 dilution. Immune and control gerbils were challenged at 6 weeks by the intrahepatic injection of 5 x 10(5) E. histolytica trophozoites. Four independent trials demonstrated complete protection from amebic liver abscess formation in 67% of lectin-immunized gerbils. Unexpectedly, liver abscess weights were significantly higher in the gerbils that failed to become immune than in the control animals. Our results demonstrate that the galactose lectin is a protective antigen and provide an immune-animal model to study the mechanisms of protection and potential disease exacerbation conferred by the antilectin immune response.

Animals↗
PubMed1990

Association of serum antibodies to adherence lectin with invasive amebiasis and asymptomatic infection with pathogenic Entamoeba histolytica.

The recognition of the Entamoeba histolytica galactose-inhibitable adherence lectin by antibodies was studied using sera obtained from subjects in South Africa with an amebic liver abscess or asymptomatically pathogenic or nonpathogenic E. histolytica infection and from uninfected regional controls. In addition, sera from healthy American controls or Americans known to be infected with other parasites were studied. Of the 95 sera containing antibodies to total parasite protein, 95% demonstrated antibodies to the 170-kDa heavy subunit but not to the 35-kDa light lectin subunit. All sera (n = 253) were tested by ELISA for antibodies to lectin: 99% from liver abscess patients and all 4 from individuals asymptomatically infected with pathogenic E. histolytica were positive; all from the 40 healthy American controls and the 29 infected with other parasites were negative (P less than .01). The prevalence of serum anti-lectin antibodies was identical (25%) in asymptomatic South Africans with either a nonpathogenic infection or a negative stool culture for E. histolytica. Thus, the presence of serum antibodies to lectin seems to indicate current or prior invasive amebiasis or asymptomatic intestinal infection with pathogenic E. histolytica.

Amebiasis↗
PubMed1990

Suppression of T-lymphocyte responses to Entamoeba histolytica antigen by immune sera.

Lymphocytes from patients cured of amebic liver abscesses proliferate and produce gamma interferon upon incubation with soluble Entamoeba histolytica antigen: however, amebic liver abscesses exhibit a relentless progression without treatment. To determine whether suppressive factors are present in sera, we studied T-lymphocyte responses to total soluble E. histolytica antigen by using cells from five patients treated for amebic liver abscesses in the presence of 15 different immune sera and 10 control sera. In the presence of immune sera, E. histolytica antigen-induced lymphocyte proliferation decreased by 63% and production of gamma interferon was reduced by 93.2% (P less than 0.01). Immune sera had no effect on the mitogenic responses of patient lymphocytes to phytohemagglutinin or on the proliferative responses of control lymphocytes to phytohemagglutinin or tetanus toxoid. The suppressive activity of immune sera diminished as the time between therapy for amebic liver abscesses and serum collection increased (P less than 0.05). Suppressive activity did not correlate with the titers of serum anti-amebic antibody and was not affected when serum was absorbed with viable amebic trophozoites. In conclusion, soluble factors present in the sera of amebic liver abscess patients suppressed in vitro lymphocyte responses to E. histolytica antigen and may have contributed to the lack of development of effective in vivo cell-mediated immune responses following the onset of amebic liver abscesses.

Animals↗
PubMed1989

Subunit structure of the galactose and N-acetyl-D-galactosamine-inhibitable adherence lectin of Entamoeba histolytica.

The galactose and N-acetyl-D-galactosamine-inhibitable adherence lectin of Entamoeba histolytica is a cell surface protein which mediates parasite adherence to human colonic mucus, colonic epithelial cells, and other target cells. The amebic lectin was purified in 100-micrograms quantities from detergent-solubilized trophozoites by monoclonal antibody affinity chromatography. The adherence lectin was purified 500-fold as judged by radioimmunoassay. The nonreduced lectin had a molecular mass of 260 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis and an isoelectric point of pH 6.2. The amebic lectin reduced with beta-mercaptoethanol consisted of 170- and 35-kDa subunits. Both subunits could be labeled on the cell surface with 125I, and both were metabolically labeled with [3H]glucosamine. The amino termini of the subunits had unique amino acid sequences, and polyclonal antisera to the heavy subunit did not cross-react with the light subunit. The yield of phenylthiohydantoin derivatives from the second and third positions in the sequence of the heavy and light subunits gave a molar ratio of one 170- to one 35-kDa subunit. Antibodies directed to the heavy subunit inhibited amebic adherence to Chinese hamster ovary cells by 100%, suggesting that the heavy subunit is predominantly responsible for mediating amebic adherence.

Acetylgalactosamine↗
PubMed1989

Entamoeba histolytica: from adherence to enteropathy.

Entamoeba histolytica, a cause of invasive colitis or liver abscess, is responsible for substantial worldwide morbidity and mortality. An understanding of the biochemical basis for the parasite adherence and cytolytic activities and antiamebic host immune response mechanisms are prerequisites for vaccine development. The E. histolytica galactose (Gal) or N-acetyl-D-galactosamine (GalNAc) inhibitable adherence lectin mediates attachment of trophozoites to colonic mucins or mammalian target cells. Amebic cytolysis of target cells requires Gal/GalNAc-lectin-mediated adherence, parasite phospholipase A activity, and maintenance of an acid pH in amebic intracellular vesicles. Cytolytic activity is stimulated by phorbol esters (activators of protein kinase C) and results from an E. histolytica-mediated increase in free Ca++ within the target cell. The Gal/GalNAc adherence lectin is a highly conserved antigen that is universally recognized by human immune sera; patients cured of invasive amebiasis possess antigen-specific cell-mediated immunity effective in vitro against E. histolytica trophozoites. Promising vaccines include the purified adherence lectin, for eliciting an intestinal secretion of IgA antibody to lectin, and additional E. histolytica antigens, which elicit cell-mediated amebicidal responses.

Amebiasis↗
PubMed1989

Antigenic stability and immunodominance of the Gal/GalNAc adherence lectin of Entamoeba histolytica.

Immunoprecipitation of Entamoeba histolytica proteins was performed with the sera of patients recovered from amebic liver abscess and colitis. The patients' amebic infection had been acquired in diverse areas of the world. The amebic galactose and N-acetyl-D-galactosamine-inhibitable adherence lectin was the major amebic antigen immunoprecipitated. The adherence lectin was recognized by all of the patients' sera tested regardless of the site (liver abscess vs. colitis) or geographic region that the amebic infection had occurred.

Animals↗
PubMed1989

In vitro susceptibilities of Entamoeba histolytica to azithromycin, CP-63,956, erythromycin, and metronidazole.

Current therapy of Entamoeba histolytica infection requires use of multiple agents effective at different body sites, including the intestinal lumen, intestinal tissue, and liver. Azithromycin and CP-63,956, new extended-half-life macrolides which reach high levels in tissue, exhibit in vitro antiamebic activity at 18 or 48 h of incubation at concentrations comparable to that of erythromycin and slightly higher than that of metronidazole. Azithromycin and CP-63,956 have the potential to be useful therapeutic agents for all types of E. histolytica infection.

Animals↗
PubMed1989

Characterization of cell surface carbohydrate receptors for Entamoeba histolytica adherence lectin.

Binding and cytolysis of Chinese hamster ovary (CHO) cells by Entamoeba histolytica trophozoites is inhibitable by galactose (Gal) or N-acetyl-D-galactosamine (GalNAc). To better define the carbohydrate receptor for E. histolytica, we compared the binding and cytolytic target properties of 10 CHO glycosylation mutants. Each mutant expresses a uniquely altered array of N- and/or O-linked cell surface carbohydrates. Amebic adherence was reduced when lactosamine-containing N-linked carbohydrates were essentially absent (Lec1 mutant), almost undetectable when Gal and GalNAc residues were absent on both N- and O-linked carbohydrates (ldlD.Lec1 mutant), and enhanced for mutants with increased terminal Gal residues (Lec2 and Lec3). Parental CHO cells treated with neuraminidase to expose Gal residues behaved like Lec2 mutants. Binding of purified Gal or GalNAc lectin to parental, Lec1, ldlD.Lec1, and Lec2 mutant CHO cells corroborated the adherence results. The suitability of CHO cell mutants as targets for amebic cytolysis correlated with their glycosylation phenotype: the Lec1 mutants were less susceptible than parental CHO cells, the ldlD.Lec1 mutants were highly resistant, and the Lec2 mutants required higher concentrations of Gal for inhibition. The E. histolytica Gal or GalNAc adherence lectin bound preferentially to beta 1-6-branched, N-linked carbohydrates lacking terminal sialic acid or fucose residues. However, amebic lectin binding to either N- or O-linked cell surface carbohydrates was sufficient to initiate parasite cytolytic activity.

Acetylgalactosamine↗
PubMed1989

Amebiasis now.

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Amebiasis↗
PubMed1989

Chemoattractant activity of Entamoeba histolytica for human polymorphonuclear neutrophils.

The ability of axenic Entamoeba histolytica trophozoites and amoebic protein preparations to stimulate chemotaxis of human polymorphonuclear neutrophils (PMN) was evaluated. Virulent E. histolytica (strain HM1:IMSS) stimulated chemotaxis (delta distance = 0.55 +/- 0.02 mm, P less than 0.01 vs. control medium). Sonicated (100 micrograms protein/ml) or homogenized (500 micrograms protein/ml) virulent amoebae also significantly stimulated PMN chemotaxis, whereas preparations of the nonpathogenic "Entamoeba-like" Laredo strain did not stimulate chemotaxis. Preparations of subcellular fractions of E. histolytica demonstrated maximal stimulation of PMN chemotaxis existed in nonvesiculated membranes and the supernatant from plasma membranes.

Animals↗
PubMed1988

Binding and internalization of rat colonic mucins by the galactose/N-acetyl-D-galactosamine adherence lectin of Entamoeba histolytica.

Purified rat colonic mucins inhibit Entamoeba histolytica in vitro adherence to and lysis of colonic epithelial cells by binding to the amoebic galactose/N-acetyl-D-galactosamine (Gal/GalNAc)-inhibitable adherence lectin. We found that 125I-labeled mucins demonstrated saturable Gal-specific binding to E. histolytica trophozoites (strain HM1:IMSS), with 2.8 x 10(3) binding sites per amoeba and a dissociation constant of 8.20 x 10(-11) M-1. Inhibition of parasite protein synthesis completely abrogated mucin binding; elevation of amoebic vesicle pH with ammonium chloride (10 mM) had no effect. Surface-bound 125I-labeled mucins were rapidly internalized and released from amoebae without evidence of proteolytic degradation. Three avirulent HM1 clones contained immunoreactive Gal/GalNAc lectin molecules with high-affinity binding of 125I-labeled mucins but exhibited markedly reduced rates of uptake and exocytosis of bound mucins. High-affinity binding by the Gal/GalNAc adherence lectin was followed by rapid internalization and eventual release of the colonic mucins. Additionally, defects in lectin surface expression and endocytosis were found in the avirulent clones.

Animals↗