Trypanosoma cruzi: distribution of fluorescently labeled tubulin and actin in epimastigotes

Cytoskeletal components were visualized in epimastigote forms of Trypanosoma cruzi by double immunofluorescence microscopy using monospecific antibodies against tubulin and against actin. Intense staining of the flagellum and the edges of the cell body was observed when the cells were stained with anti-tubulin, reflecting the presence of the basal bodies, the flagellar axoneme and the subpellicular microtubules. A less intense staining was seen in the cell body of epimastigotes stained with anti-actin. However, an intense staining was observed with this antibody in the flagellum, in a pattern similar to that observed with anti-tubulin. It is suggested that the paraxial structure, which is formed by a complex array of 6-nm-thick microfilaments is composed, at least in part, of actin.     

Glucose transport in Entamoeba histolytica

That the uptake of glucose by the parasitic amoeba Entamoeba histolytica occurs by an equilibrative transport system is supported by the following observations. 1. The rate of glucose uptake is several orders of magnitude greater than the uptake by pinocytosis. 2. The uptake of glucose exhibits saturation kinetics, with K(m)=1.6mm and V(max.) ranging from 2 to 5mumol/min per ml of cells at 37 degrees C. 3. The glucose analogues 2-deoxyglucose, 3-O-methylglucose and d-xylose are transported by the glucose system although with much less affinity. Competitive inhibition was observed between pairs of substrates, with K(i) values for any sugar closely coincident with the corresponding K(m). 4. d-Xylose, a sugar not metabolized by the cells, equilibrated with 80% of the amoebal cell water. 5. Cells equilibrated with xylose exhibited countertransport of this sugar against its concentration gradient when another substrate was added to the medium. 6. Blocking of glycolysis by iodoacetate or F(-) has no immediate effect on transport. The presence of a glucose-transport system in E. histolytica contrasts with the situation found in the non-parasitic amoeba, where pinocytosis seems to be the only mechanism of solute uptake.     

The fine structure of the visual system of lycosa (Araneae: Lycosidae)

Summary The optic lobes of spiders contain a well differentiated synaptic region — the lame medullaire — in which the photoreceptor axon terminals synapse with the axons of the second order neurons.Each photoreceptor terminal has a very irregular outline and contains a great number of vesicles. It sends out collateral branches which end either in contact with other photoreceptor terminals or in contact with second order fibers. The second order fibers lie deeply recessed within folds of the photoreceptor terminal membrane. Frequently branches of the second order fibers can be seen as independent elements within the photoreceptor terminals. The synaptic loci are characterized by the presence of synaptic ribbons surrounded by cumuli of vesicles. These synaptic loci are always located at the intermembrane cleft between adjacent second order fibers.Synaptic structures have been found also within the second order fibers which in such cases appear as pre-synaptic elements in regard to the photoreceptor terminals.Research sponsored by the Air Force Office of Scientific Research, Office of Aerospace Research, United States Air Force, under AFOSR Grant Nr. 618-64.