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Since the early 1960s, axenic culture and the development of procedures for the induction of encystation have made Acanthamoeba spp. superb experimental systems for studies of cell biology and differentiation. More recently, since their roles as human pathogens causing keratitis and encephalitis have become widely recognized, it has become urgent to understand the parameters that determine differentiation, as cysts are much more resistant to biocides than are the trophozoites. Viability of trophozoites of the soil amoeba Acanthamoeba castellanii (Neff), is conveniently measured by its ability to form plaques on a lawn of Escherichia coli. Use of confocal laser scanning microscopy with Calcofluor white, Congo Red or the anionic oxonol dye, DiBAC4(3) or flow cytometry with propidium iodide diacetate and fluorescein or oxonol provides more rapid assessment. For cysts, the plaque method is still the best, because dye exclusion does not necessarily indicate viability and therefore the plate count method has been used to study the sequence of development of biocide resistance during the differentiation process. After two hours, resistance to HCl was apparent. Polyhexamethylene biguanide, benzalkonium chloride, propamidine isethionate, pentamidine isethionate, dibromopropamine isethionate, and H2O2 and moist heat, all lost effectiveness at between 14 and 24 h after trophozoites were inoculated into encystation media. Chlorhexidine diacetate resistance was observed at between 24 and 36 h. The molecular biology and biochemistry of the modifications that underlie these changes are now being investigated.

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Background: Patients with radiation-induced xerostomia produce little or no saliva. Several studies have demonstrated the efficacy of systemic administration of pilocarpine hydrochloride in individuals with post-radiation xerostomia. However, analysis of pilocarpine lozenges for treatment of post-radiation xerostomia in patients with head and neck cancer has not been reported. Methods:The aim of this study was to quantify improvement in clinical symptoms and salivary function after treatment of post-radiation xerostomia with pilocarpine lozenges. In a double-blinded, placebo-controlled trial, 33 head and neck cancer patients were assigned randomly to receive Salagen® tablet, pilocarpine hydrochloride lozenge (3 or 5mg) or placebo lozenge every 10 days. At each visit, a subjective evaluation was undertaken through the use of visual analog scales before and at 180 minutes after treatment. Whole resting saliva was collected before and at 0, 30, 60, 90, 120, 150 and 180 minutes after treatment. Results:The percentage of patients with decreased feeling of oral dryness, sore mouth or speaking difficulties after taking 5-mg pilocarpine lozenge was greater than Salagen® or placebo. There were statistically significant increases in salivary production in pilocarpine treatment groups vs. placebo (P<0.05). Conclusion:The 5-mg pilocarpine lozenge produced the best clinical results, but further investigation with a larger group of patients is required.

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