Biomedical subjects
F E Pittman
Publications and source records attributed to F E Pittman.
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.
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.
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.
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.
Cytotoxic activity of a cell-free extract of Entamoeba histolytica.
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Effect of hamster liver passage on the virulence of axenically cultivated Entamoeba histolytica.
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Surface ultrastructure of Entamoeba histolytica; a study by high voltage transmission electron microscopy (HVTEM) and scanning electron microscopy (SEM).
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Cytotoxicity of a cell free extract of Entamoeba histolytica.
Previous attempts to demonstrate toxicity of cell-free extracts prepared from axenically cultivated E. histolytica have proved unsuccessful. We report here the successful production of cytopathic effect by cell-free extracts of two strains (HM-1 and HK-9) of E. histolytica in tissue culture monolayers. The cytotoxic effect demonstrated was sensitive to serum in the assay medium. Failure of past investigations to demonstrate cytotoxic activity may be explained by the presence of serum in the assay systems used.
Influence of mounting media on the fading of basic aniline dyes in epoxy embedded tissues.
A simple cytophotometric technique is used to quantitate stain fading of basic aniline dye-stained epoxy-embedded tissues mounted in six different commonly used mountants. Significant fading was detected with all six mountants, although rates varied. The lowest rate of fading was observed with immersion oil and the highest rate of fading with Canada balsam. No significant differences in fading rates of four synthetic mounting preparations were observed.
Tropical sprue in American servicemen following return from Vietnam.
Moderately severe tropical sprue was diagnosed in two American servicemen 15 and 19 months after return from Vietnam. Intestinal parasites were not demonstrated, and clinical, laboratory, and jejunal histological abnormalities returned to normal following treatment with tetracycline and folic acid in one patient and folic acid alone in the other. Neither patient was anemic, although one had hypersegmented polymorphonuclear leukocytes and both had macrocytosis and megaloblastic bone marrows. In each of these patients, diagnosis was delayed because of the failure to consider tropical sprue in the differential diagnosis of diarrhea and weight loss. The findings in these patients indicate that individuals from nonendemic areas who reside in Vietnam are at risk of developing overt tropical sprue.
Neurologic disease in patients with treated Whipple's disease.
Four patients with Whipple's disease which had responded to antibiotic therapy, later developed neurologic disease identical to that seen in patients with Whipple's disease who died without treatment. Dementia, myoclonus, ataxia, and supranuclear ophthalmoplegia were the main neurologic features. Restarting antibiotics has been followed by stabilization of disease in all four. Two have improved. In three, the previously diagnosed and treated Whipple's disease was not considered as a possible cause of the neurologic disease until the symptoms and signs were far advanced. It is advisable to periodically evaluate all patients with Whipple's disease, even after successful treatment. Signs of neurologic disease should be considered a possible recurrence of Whipple's disease and antibiotics restarted.
Letter: Transient Menetrier's disease.
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Letter: Antibiotic-associated colitis.
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Letter: Failure to diagnose amoebiasis.
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Letter: "Fecogram" to find swallowed radiopaque objects.
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IgA heavy chain disease. A case detected in the western hemisphere.
IgA heavy chain disease (alpha chain disease) was detected in a 46 year old South American (Colombian) of mixed Spanish and Indian (Mestizo) descent. The clinical course was characterized by severe malabsorption, initially thought to be a variant of tropical sprue. Jejunal mucosal biopsy revealed marked villous atrophy with heavy infiltration of the lamina propria by a single monotonous cell type which, by light microscopy, had the appearance of either a large, abnormal plasma cell or a small histiocyte. Electron microscopy of the biopsy specimen demonstrated the presence of abnormal plasma cells, lymphatic distention and abnormalities of surface epithelial cells. At autopsy a 6 by 3 cm mass was found in the right para-aortic area along with many firm 2 cm mesenteric and para-aortic lymph nodes. Histologic examination revealed the presence of a monotonous cell type similar to that found in the jejunal mucosal biopsy specimen.
Letter: Lomotil and antibiotic colitis.
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