ABSTRACT
The in vitro excystation process in Giardia intestinalis was studied by transmission electron microscopy (TEM). Untreated cysts served as controls. The excystation process was monitored by examination of organisms after the in vitro induction and at several times during the incubation phase. The control cyts had a thick wall, made of microfibrils, that appeared not to contain any weak areas. The peritrophic space extended between the cyst wall and the organism peripherally, the space was delimited by a thin cytoplasmic layer, "the outer cytoplasmic envelope" that subtended the cyst wall. During the in vitro incubation, the trophozoite cytoplasm retracted from the wall; thus, the peritrophic space became progressively larger. The outer cytoplasmic envelope detached from the cyst wall, then broke up forming numerous small vesicles lodged between the wall and the organism. The tight arrangement of the wall microfibirils was lost. Electron-dense vacuoles appeared in the peripheral cytoplasm of the trophozoite. The organism emerged through the posterior end of the cyst, leaving behind the empty husk. Emergence was followed by cell division. The possible interrelationships of biochemical and mechanical factors affecting the process of excystation are discussed in light of the present TEM findings.
Subject(s)
Giardia/ultrastructure , Animals , Giardia/drug effects , In Vitro Techniques , Microscopy, Electron , Pepsin A/pharmacologyABSTRACT
The in vitro excystation of Giardia lamblia on cysts isolated from human feces was studied. After purification by sucrose gradient, cysts were incubated in a pepsin-acid solution, then placed in a modified HSP3 medium where excystation occurred within a few minutes. The excystation procedure was studied by continuous observations by light microscopy and sequential observations by scanning electron microscopy (SEM). The in vitro excystation was stopped at timed intervals during incubation by addition of a large amount of 1% glutaraldehyde. The excystation process began by the cyst wall opening at one pole. Flagella protruded rapidly, the parasite emerged progressively from the cyst envelope, posterior end first, the empty cyst collapsed and shrank. Although flagella emerging from the organism were distinguishable, the cell body had not yet shown all the morphological features of the G. lamblia trophozoite. A radical rearrangement of the organism occurred gradually: initially oval in shape, the parasite became round, then elongated, flattened, and underwent cytokinesis. The daughter trophozoites acquired their typical morphological features: the shape, the adhesive disc with the C-shaped structure distinctly visible on the ventral surface, and the definite placement of the flagella. These observations obtained on G. lamblia by SEM were comparable to those obtained with G. muris.
Subject(s)
Giardia/growth & development , Giardia/ultrastructure , Humans , Microscopy, Electron, ScanningABSTRACT
The in vitro excystation of Giardia intestinalis was studied to make the osmolarity (from 50 to 500 mosmol/l) and the components of growth medium (MCI saline solution, MCII glucose solution, MCIII nutritive solution) varying. The percentage of excystation, the viability and the generation time were determined. Excystation was observed in the saline solution between 100 to 450 mosmol/l after cyst acid pepsin incubation. The trophozoite viability was increased by glucose addition (60 min in MCI; 300 min in MCII). Only a rich medium (MCIII) permitted a generation time from 225 to 425 mosmol/l.
Subject(s)
Giardia/growth & development , Glucose/pharmacology , Sodium Chloride/pharmacology , Animals , Culture Media , Feces/parasitology , Giardia/drug effects , Giardia/embryology , Osmolar Concentration , Trophoblasts/drug effectsABSTRACT
10,000 faeces samples-from 9,120 adults and 880 children were examined to evaluate the faecal excretions. Giardia intestinalis was identified in 111 of those samples (84 adults and 27 children). A higher infection rate of G. Intestinalis was observed in child and male adult groups. Nitrogen excretion was evaluated and compared with fat excretion for the first time in the case of giardiasis. When malabsorption was obvious, both fat and nitrogen increased with generally moderate values. The malabsorption was much more frequent among children (88.9%) than among adults (26%) (p less than 0.001). These results could explain the fast settlement and the frequency of growth troubles in childhood. Giardiasis should be systematically and carefully investigated in a malabsorption in the person of a child.
Subject(s)
Feces/analysis , Giardiasis/metabolism , Lipid Metabolism , Nitrogen/metabolism , Adolescent , Adult , Aged , Child , Child, Preschool , Feces/parasitology , Female , Humans , Infant , Malabsorption Syndromes/metabolism , Male , Middle AgedABSTRACT
The fluorographic process for enhancement of the autoradiographic detection of beta-ray emitted by tritium has been successfully adapted to electron microscope autoradiography. An original scintillator plastic film helped to increase the detection yield of electrons up to 80% without alteration of the morphological aspect of the autoradiograms, and without increasing background fog or causing apparent loss of resolution.
