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F E Pittman

Publications and source records attributed to F E Pittman.

At least 19 recordsLinked to original sources
PubMed1986

Morphologic observations of experimental Campylobacter jejuni infection in the hamster intestinal tract.

The authors have developed a model for the diarrhea and intestinal lesions seen in Campylobacter jejuni enterocolitis by colonizing the hamster ileum and cecum with C jejuni. Erythematous inflammation of the ileum and cecum and distention of the cecum with fluid were observed at autopsy. The cecal mucosa appeared edematous. Epithelial abnormalities observed by light microscopy included focal edema, occasional hyperplasia, diffuse hyperemia, and infiltration of the lamina propria with leukocytes. C jejuni-like bacteria penetrated the epithelium and were seen in the lamina propria of infected animals but not in uninfected controls. Diverse microvillus lesions, including elongation, shortening, blebbing, and denudation, were seen by transmission electron microscopy. Occasional cytoplasmic aberrations included vacuoles, some containing C jejuni-like bacteria, swollen endoplasmic reticulum, and enlarged mitochondria. Campylobacter structures were vibrio and S-shaped types. Some C jejuni organisms had corrugated screwlike structures wrapped around their circumferences.

Animals↗
PubMed1985

Entamoeba histolytica: purification of cathepsin B.

A cytotoxic cysteine proteinase with a molecular weight of 16,000 was isolated from axenically grown trophozoites of Entamoeba histolytica. The enzyme was purified from frozen-thawed strain HM-1 by ion-exchange chromatography on DEAE-cellulose, organomercurial agarose affinity chromatography, and size-exclusion chromatography. The purified enzyme had proteinase activity that could be demonstrated on azocasein (pH 5), hemoglobin (pH 5), or carbobenzoxy-L-arginyl--L-arginyl-7-amino-4-trifluoromethylcoumarin++ + (Z-arg-arg-AFC), a substrate specific for cathepsin B. Enzyme activity was stable to high pH, but not to 40 C for 1 hr or 56 C for 0.5 hr. As typical of cysteine proteinases, inhibition of activity on Z-arg-arg-AFC by p-chloromercuribenzoate or mercury was reversed by free sulfhydryl groups. Both the proteinase and cytotoxic activities of the purified amoebal cathepsin B were inhibited by leupeptin and serum and activated by free sulfhydryl groups, supporting the hypothesis that both activities are characteristics of amoebal cathepsin B. Virulent strains of E. histolytica (HM-1 and Rahman) had significantly more cathepsin B activity per milligram protein than less virulent strains (HK-9, Laredo, and Huff). The correlation between higher levels of cathepsin B activity in strains with greater virulence could indicate a role for amoebal cathepsin B in the pathogenesis of amoebiasis.

Cathepsin B↗
PubMed1985

Experimental infection of hamsters with Campylobacter jejuni.

Campylobacter jejuni is a major cause of diarrhea and enterocolitis in humans and animals. A mammalian model has been developed for studying pathogenesis of the disease in hamsters by colonizing the ileum and cecum with C. jejuni via either oral intubation after purgation or direct surgical inoculation into the cecum. This colonization resulted in production of disease including diarrhea and intestinal lesions that resembles enterocolitis due to C. jejuni in humans and domestic animals. The mucosal lesions observed grossly at autopsy included erythema of the ileum and cecum and distention of the cecum with fluid. The cecal mucosa was edematous. Epithelial lesions observed by light microscopy included focal edema, occasional hyperplasia, diffuse hyperemia, and infiltration of the lamina propria with leukocytes. C. jejuni-like bacteria penetrated the epithelium and were observed within the lamina propria of infected animals but not in uninfected controls.

Animals↗
PubMed1984

Relationship of cytotoxins of axenically cultivated Entamoeba histolytica to virulence.

Clarified homogenates prepared from different strains of axenically reared Entamoeba histolytica were assayed for acid and neutral proteinase activity, cytotoxicity, and protein content. The homogenates of the more virulent strains contained more acid or neutral proteinase and more toxin units per 10(6) trophozoites. Toxicity and neutral proteinase activities had a similar pattern of distribution. The cytotoxicity of the gel-filtered proteins of the studied strains followed the same rank order as their reported virulence. The more virulent strains (HM-1 and Rahman) had significantly more neutral proteinase activity than less virulent strains (HK-9, Laredo and Huff). Purified extracts of HM-1 and Rahman strains contained more toxin per milligram of protein and exhibited a lower cytotoxicity end point than those of the less virulent strains. The most cytotoxic fraction of each strain had a molecular weight of approximately 24,000, and all cytotoxins were antigenically similar. A more virulent strain (HM-1) secreted more cytotoxic activity when incubated under tissue culture conditions than did a less virulent strain (HK-9). Cytotoxic material secreted by strain HM-1 during axenic growth had the same molecular weight as that isolated from trophozoites. The Entamoeba histolytica toxin studied may be a neutral proteinase that is present in greater quantities in more virulent strains, thus accounting for their greater cytotoxicity in vitro and invasiveness in vivo.

Animals↗
PubMed1984

Proteinase activities of Entamoeba histolytica cytotoxin.

The proteinase activity of the low molecular weight cytotoxin of Entamoeba histolytica was correlated with its cytotoxicity. Gel-filtered amebal toxin (mol wt 10-30,000) proteinase activities could be assayed on azocasein at pH 6 or on hemoglobin at pH 4.5. Proteinase activity was inhibited by serum fractions, thiol reagents, heavy metals, leupeptin, and antipain. The cytotoxic activity of gel-filtered amebal toxin was inhibited by serum fractions, leupeptin, and antipain. Increased proteinase and cytotoxic activity was produced by treatment with cysteine. These data support the action of a thiol proteinase in the production of cytopathic effects by gel-filtered amebal toxin in vitro. The cytotoxic and proteinase activities were further purified using a combination of column chromatography and preparative isoelectric focusing. Two low molecular weight cytotoxins with proteinase activity on both substrates were isolated. The major cytotoxin had an isoelectric point of 4.5 and a molecular weight of 22,000; the other cytotoxin had a basic isoelectric point. These substances may be cathepsin B-like proteinase and elastase or cathepsin G-like proteinases of E. histolytica. The major proteinase activity in the high molecular weight fraction was not cytotoxic. The isoelectric points of the high molecular weight proteinase activities corresponded to that of mammalian cathepsin D. The major cell rounding cytotoxic activity of E. histolytica extracts in vitro is probably due to the activity of a thiol-containing cathepsin B-like proteinase.

Caseins↗
PubMed1981

Inhibition of Entamoeba histolytica cytotoxin by alpha 1 antiprotease and alpha 2 macroglobulin.

We previously reported partial purification of a proteinaceous substance with cytotoxic and enterotoxic activity isolated from the soluble fraction of sonicated axenically cultivated Entamoeba histolytica trophozoites. Demonstration of cytotoxic activity of the preparation (amebal toxin) was dependent on removal of serum from the tissue culture assay system. The objective of the present study was to identify the factor(s) in non-immune sera responsible for producing in vitro inhibition of amebal toxin cytotoxicity on HeLa cells. Gel filtration of non-immune sera from adult humans or bovines demonstrated that two portions of the eluate had significant inhibitory against the toxin. A high molecular weight inhibitory fraction was identified as predominantly alpha-2 macroglobulin and a low molecular weight inhibitory fraction was identified as predominantly alpha-1 antiprotease. Preparative isoelectric focusing of human serum isolated inhibitory fractions containing these same alpha globulins. Alpha-2 macroglobulin was purified and alpha-1 antiprotease was partially purified from human serum by other methods and shown to have high inhibitory activity against the amebal cytotoxin. Substances that were inhibitory to the cytotoxic activity of the amebal toxin also mediated reattachment of toxin treated HeLa cells. We conclude that the characteristics of the serum inhibitors, especially their ability to reverse the cytotoxic effects of amebal toxin on HeLa cells, suggests that the amebal toxin has protease activity.

Animals↗
PubMed1980

Cimetidine-induced exfoliative dermatitis.

A 68-year-old woman developed exfoliative dermatitis while taking cimetidine for gastritis. She had no history of previous drug reactions, allergies, or skin disorders and had taken no other medications for three months. Although cimetidine is a relatively safe drug, severe reactions such as exfoliative dermatitis can occur.

Aged↗
PubMed1980

Tolazamide-induced cholestasis.

The sulfonylurea hypoglycemic agent tolazamide is thought to be a rare cause of jaundice and to exhibit no hepatic cross-sensitivity with other sulfonylurea compounds. We have described a patient who had self-limited cholestatic jaundice after treatment with chlorpropamide. Subsequent treatment with tolazamide resulted in recurrence of jaundice, which disappeared after cessation of treatment. Tolazamide may exhibit hepatic cross-sensitivity with chlorpropamide.

Chlorpropamide↗
PubMed1980

Sequential histopathology of cavitary liver abscess. Formation induced by axenically grown Entamoeba histolytica.

Multiple hamster liver passage of Entamoeba histolytica trophozoites with intervening recovery into axenic culture caused increased virulence as measured by increase in the size of the lesion produced. Lesions produced by amebae that had not been liver-passaged did not persist; however, multiply liver-passaged substrains produced large, fluid-filled abscesses one month to six weeks after inoculation. Six days after inoculation, lesions consisted of multiple granulomas, lymphocytes, and E histolytica trophozoites. Large, fluid-filled abscesses produced by liver-passaged substrains lacked the granulomatous appearance of the earlier lesions. The abscesses had a fibrous wall, with E histolytica trophozoites at the inner aspect. To our knowledge, the evolution of early granulomatous lesions into a cavitary abscess with features closely resembling those of human amebic abscess has not been reported previously in the experimental disease in the hamster.

Animals↗
PubMed1980

Further studies on a cytotoxin/enterotoxin from Entamoeba histolytica.

More virulent strains of Entamoeba histolytica contain more cytotoxic activity per trophozoite than do less virulent strains. Clarified sonicates of the more virulent strains are more cytotoxic than those of less virulent strains. The cytotoxins of all these strains are inhibited by specific immune IgG raised in rabbits or produced by natural human infection. Non-immune IgG's had no antitoxic activity. Serum fractions of non-immune serum containing alpha globulins (alpha 2 macroglobulin and alpha 1 antitrypsin) had a non-specific inhibitory effect on the cytotoxicity of the E. histolytica toxin. The positive correlation of strain cytotoxicity and the amount of toxin per trophozoite, with virulence suggests that the cytotoxin could play a role in production of human disease. The presence of immunoglobulins against the toxin in serum from a patient with clinical amebiasis indicates that the toxin is immunogenic in human infections and provides additional support for the relevance of E. histolytica cytotoxin to pathogenesis.

Cytotoxins↗
PubMed1980

Sequential histopathology of cavitary liver abscess formation induced by axenically grown Entamoeba histolytica.

Animal models of amebic hepatic abscess should parallel the human disease. Experimental amebic hepatic abscess in the hamster results in granulomatous lesions during the early period (six days) following inoculation. Hamster inoculated intrahepatically with axenically grown, non-liver passaged strains of Entamoeba histolytica revealed no evidence of lesions when sacrificed at later times. However, hamsters similarly inoculated with multiply liver passaged substrains were found to have large fluid-filled hepatic abscesses four to six weeks following inoculation. The histopathologic appearance of these lesions closely resembled that most often described in human amebic hepatic abscess. Production of amebic hepatic abscess in the hamster may provide a valuable animal model of this potentially fatal human disease and provide new information concerning both the pathogenesis and host response.

Animals↗
PubMed1979

Toxic megacolon.

Explore the source record for details and available documents.

Atropine↗
PubMed1979

Isolation of a cytotoxin-enterotoxin from Entamoeba histolytica.

A heat-labile material with cytotoxic and enterotoxic activities was isolated from axenically cultivated Entamoeba histolytica. The cytotoxin-enterotoxin was partially purified from the particulate-free supernatant of sonicated trophozoites by ammonium sulfate precipitation and gel filtration. Cytotoxic activity, assayed on monolayers of HeLa or BHK-21 cells, was restricted to proteins that eluted in the molecular weight range of 25,000--35,000 daltons. Cytotoxicity was demonstrated at protein concentrations as low as 2--4 microgram/ml, was heat-labile (75 C, 30 min), and was inhibited by specific immune IgG and by an undetermined factor in nonimmune serum. Enterotoxic activity of the partially purified toxin was demonstrated by induction of fluid secretion in ligated rabbit ileal loops. The cytotoxin-enterotoxin of E. histolytica may play an important role in the production of diarrhea and mucosal injury in amoebic colitis.

Animals↗
PubMed1979

Microscopic observations on the filopodia of Entamoeba histolytica.

Living Entamoeba histolytica trophozoites were examined by phase-contrast microscopy. Intact critical point dried trophozoites were examined by transmission electron microscopy at an accelerating voltage of 1000 kV (HVEM) and by scanning electron microscopy (SEM). Half and quarter micrometer thick sections of epoxy-embedded trophozoites were examined by HVEM. Many of the trophozoites of 2 strains examined had surface filopodia, 1 to over 100 micrometers in length. The cytoplasm of filopodia was continuous with the cytoplasm and bounded by surface plasmalemma bearing a glycocalyx. Structures called "surface-active lysosomes with trigger," "dendritic plasmalemmal extensions," and "extra-amebic vesicles" by previous investigators probably represent portions of filopodia demonstrated in the present study. Filopodia appear to be of frequent normal occurrence in E. histolytica and may function in: (a) endocytosis or pinocytosis; (b) exocytosis; (c) attachment to substratum; (d) penetration of tissue; (e) release of cytotoxic substances; or (f) contact cytolysis of host cells.

Animals↗
PubMed1979

Light and electron microscopic studies of antibiotic associated colitis in the hamster.

Lincomycin and its analogue, clindamycin, are capable of producing mild to severe colonic mucosal injury in humans (antibiotic associated colitis). Patients with the disorder may have severe diarrhoea, pseudomembranous plaques, confluent pseudomembranes, and/or a frank, diffuse haemorrhagic colitis. The present study was designed to assess the Golden Syrian hamster as an animal model for antibiotic associated colitis and to describe lesions seen in the animal model by light, transmission electron, and scanning electron microscopy. A colitis was produced in Golden Syrian hamsters by oral or parenteral administration of lincomycin, clindamycin, or N-demethyl clindamycin. Animals were killed at intervals and microscopic studies made of sequential morphological changes in the ileum, caecum, and colon. The microscopic lesions in the early stages of the disorder were abnormalities within the brush border, cellular oedema, and hyperaemia. Changes in the intracellular organelles were observed in more severely damaged epithelial cells. Epithelial hyperplasia resulted in the piling up of cells on the mucosal surfaces. In specimens with the most severe damage, complete loss of epithelium from the mucosal surface was observed. Pseudomembranous plaques were occasionally seen. Comparison of the clinical, gross, and histological features of the animal disease with the human disorder suggest that, although minor differences are present, the hamster model is suitable for experimental studies of antibiotic associated colitis.

Animals↗
PubMed1979

Partial purification of a toxin found in hamsters with antibiotic-associated colitis. Reversible binding of the toxin by cholestyramine.

A toxin with cytotoxic and enterotoxic activities was isolated from cecal contents of hamsters receiving lincomycin. The toxin was partially purified by ultracentrifugation, ultrafiltration, (NH4)2SO4 precipitation, and gel filtration. Cytotoxic activity, assayed on monolayers of HeLa cells, was restricted to material that eluted in the molecular weight range of 107,000 +/- 6,000 daltons. Cytotoxicity of crude AAC toxin could be demonstrated at concentrations as low as 0.04 microgram/ml. The toxin was heat labile (55 degrees-60 degrees C for 0.5 hr) and sensitive to trypsinization, acidification at pH 3, or alkalinization at pH 9. Cytotoxic activity was inhibited by Clostridium sordellii antitoxin. Enterotoxic activity of the crude toxin and the cytotoxic fraction from gel filtration was demonstrated by fluid secretion in ligated rabbit ileal loops. Studies were done in vitro with cholestyramine resin, vancomycin, or gentamicin to determine if the toxin was bound or denatured by these drugs. It was demonstrated that cholestyramine bound the toxin, significantly reducing its cytotoxicity. Reversible binding of the cytotoxic material was demonstrated by salt gradient elution. Neither vancomycin nor gentamicin had any effect on the in vitro cytotoxic activity of the toxin.

Ammonium Sulfate↗