Chapter 4 Induction of Synchronous Encystment (Differentiation) in Acanthamoeba sp.

Neff, Robert J.; Ray, Supriya; Benton, William; Wilborn, M.

doi:10.1016/s0091-679x(08)62086-5

Cited by 147 publications

(150 citation statements)

References 11 publications

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“…a T, trehalose ( (~,a); G, glucose; M, (l+4)a_ar-D glucopyranosyl linkage such as in maltose or higher oligomer thereof b Trehalose:cr-glucose:@glucose; Ratio 2:5:8; 'Weak intensity in the washed cells might be expected as a result of uptake from the growth medium by pinocytosis and phagocytosis, the characteristic nutritive mechanisms [5] for Acunthamoeba. Cellulose has been reported as a major consituent of the cyst [ 161, while glycogen is found in the trophozoite and is believed to be degraded to glucose prior to formation of cellulose in the cyst [17].…”

Section: Resultsmentioning

confidence: 99%

Observation by ¹³C NMR of metabolites in differentiating amoeba

et al. 1980

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Section: Resultsmentioning

confidence: 99%

Observation by ¹³C NMR of metabolites in differentiating amoeba

et al. 1980

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“…Culture Methods: Acanthamoeba castellanii (Neff strain) was cultured axenically as follows: 25-ml stock cultures of amebas were maintained in aerated tubes in a slightly modified optimal growth medium as described by Neffet al (5). Aliquots of stock solutions were transferred aseptically to 1 liter of growth medium in low-form culture flasks.…”

Section: Methodsmentioning

confidence: 99%

Acanthamoeba discriminates internally between digestible and indigestible particles.

Bowers¹,

Olszewski²

1983

The Journal of Cell Biology

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The capacity of Acanthamoeba to distinguish nutritive yeast particles from nonnutritive plastic beads during phagocytosis was investigated. When cells were allowed to phagocytose yeast to capacity, endocytosis stopped and subsequent presentation of particles (either yeast or beads) did not result in further uptake. By contrast, when cells were allowed to phagocytose plastic beads to capacity and a second dose of particles was presented (either yeast or beads), the cells exocytosed the internal particles and took up new ones. Yeast rendered indigestible by extensive chemical cross-linking were taken up at rates similar to those of untreated yeast, but, like beads, they were exocytosed when a second dose of particles was presented. The results show that an internal distinction is made between vacuoles containing yeast and vacuoles containing plastic beads, and they are consistent with the hypothesis that the presence within the vacuoles of material capable of being digested prevents exocytosis.Phagocytic uptake of panicles depends on a specific interaction at the cell surface which results in a localized stimulus for the cell to engulf the particle. In many cells this interaction can occur with a number of indigestible substances. For example, amebas will ingest silica, carbon particles, plastic beads, and other materials of no nutritive value (1, 2). Plastic beads, in fact, are valuable tools for studying the kinetics and mechanisms of endocytosis in a wide variety of cell types because they are indiscriminately engulfed by most cells. To understand better how cells control particle turnover rates and the related membrane recycling, we have studied how Acanthamoeba handles a nutritive particle, yeast, as compared with a nonnutritive particle, plastic bead.Acanthamoeba contains a vacuolar compartment that serves as its digestive system. This compartment is maintained by the cell at virtually constant volume and surface area under standard culture conditions (3). Nevertheless, considerable membrane flow occurs through the compartment because of endocytosis (3, 4). Membrane flow, as inferred from the rate of membrane ingestion by endocytosis, is rapid during pinocytosis (~9 surface equivalents/h) and close to zero in cells that have taken up particles to the limit of their capacity (that is, are saturated). When the cell is saturated with a digestible particle such as yeast, space for particle uptake gradually becomes available as digestion progresses and undigested residues are incorporated into defecation vacuoles to be expelled from the cell. In contrast, indigestible particles like plastic beads are ingested readily by the amebas, but cannot be reduced in volume. In the experiments reported here, in addition to testing turnover rates of different types of particles, we examined whether Acanthamoeba discriminates between inert and nutritive particles and whether they do so externally or internally. MATERIALS AND METHODSCulture Methods: Acanthamoeba castellanii (Neff strain) was cultured axenically as fol...

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“…Each were cultured in axenic medium at 32°C. 9 Flasks containing crowded amoebae were chilled at O°C for two minutes to detach the adherent amoebae from the flask, and spun at 400 rpm for five minutes. Amoebae were resuspended in either fresh axenic medium for maintenance in culture, or in tis sue culture medium for experimental use.…”

Section: Preparation Of Acanthamoebamentioning

confidence: 99%

In vitro corneal pathogenicity of Acanthamoeba

Larkin

Berry

Easty

1991

Eye

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SummaryThe comparative cytopathic effects of a keratitis and an environmental isolate of Acanthamoeba were studied on confluent monolayers of human and rabbit corneal cells grown in culture. The presence of cells in culture induced excystment of amoe bae to the active trophozoite form. Total destruction of cell monolayers was observed to be similar for both isolates, and dependent on incubation time and amoebic con centration. The relevance of these findings to human and experimental Acantha moeba keratitis is discussed.Acanthamoeba is a genus of free-living amoe bae which is ubiquitous in air, soil and aquatic environments. The active trophozoite form becomes a resilient cyst in unfavourable environmental conditions. Acanthamoeba is a cause of chronic granulomatous encephalitis, which occurs in immunocompromised hosts and is fatal. 1 Certain species cause chronic stromal keratitis, particularly in contact lens wearers whose lens solutions become contam inated by the amoeba. 2 The amoebae flourish in the corneal stroma, and a severe polymor phonuclear inflammatory response and cor neal thinning is observed in both human3 and experimental4 keratitis.In vitro studies of Acanthamoeba virulence have been performed on VERO cells5•6•7 a cell line derived from monkey kidney, or SIRC cells ,8 derived from rabbit cornea. These stud ies equated the speed with which the mamma lian cells were destroyed to virulence, and to pathogenicity in laboratory animals. 6 Isolated rabbit corneas, used as an in vitro model for amoebic infection, demonstrated a similar destructive effect by known pathogenic and non-pathogenic strains of amoebae.8Two questions have prompted this study.The first was raised by Garner, who ques tioned whether the corneal thinning is caused by the inflammatory response or the amoebae themselves.3 Can Acanthamoeba feed on cor neal cells? The second relates to the marked site-specificity of clinical Acanthamoeba infection: is corneal tissue unduly susceptible to amoebic infection? To answer these questions we studied the interaction of Acanthamoeba and cell cul tures. We first investigated whether Acantha moeba excysts in the presence of cultured cells, and whether a cytopathic effect (CPE) results. We then conducted a comparative investigation of the effect of amoebic tropho zoites on primary cultures of human and rab bit corneal cells, and on 3T3 alpha cells, a mouse fibroblast cell line. We contrasted the CPEs of Acanthamoeba spp. on these cells, and compared an environmental isolate with an isolate from an infected cornea. Materials and Methods Preparation of AcanthamoebaTwo strains of Acanthamoeba were used in these studies: an isolate from an infected cor nea, A. polyphaga (Davies), and a soil isolate

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Chapter 4 Induction of Synchronous Encystment (Differentiation) in Acanthamoeba sp.

Cited by 147 publications

References 11 publications

Observation by ¹³C NMR of metabolites in differentiating amoeba

Observation by ¹³C NMR of metabolites in differentiating amoeba

Acanthamoeba discriminates internally between digestible and indigestible particles.

In vitro corneal pathogenicity of Acanthamoeba

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Chapter 4 Induction of Synchronous Encystment (Differentiation) in Acanthamoeba sp.

Cited by 147 publications

References 11 publications

Observation by 13C NMR of metabolites in differentiating amoeba

Observation by 13C NMR of metabolites in differentiating amoeba

Acanthamoeba discriminates internally between digestible and indigestible particles.

In vitro corneal pathogenicity of Acanthamoeba

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Observation by ¹³C NMR of metabolites in differentiating amoeba

Observation by ¹³C NMR of metabolites in differentiating amoeba