Some Factors Inducing Formation of Metacyclic Stages of Trypanosoma cruzi

ABSTRACT Epimastigotes of Trypanosoma cruzi , Peru strain, incubated in Contreras'artificial triatomine urine transformed into metacyclic trypomastigotes within 48 h at 28° C when 10 mM L-proline or L-glutamate was added to the medium. Smaller numbers of metacyclic stages were induced in the presence of glucose or L-alanine. The L-leucine and L-isoleucine, 2 amino acids known to inhibit proline catabolism, inhibited proiine-induced metacyclogenesis. Cells gassed with 5% CO₂ showed significantly faster rates and higher levels of transformation than those not gassed, therefore indicating the additional importance of CO₂ for transformation.     

Fine structure, function and distribution of antennal sensilla in the saw-toothed grain beetle, Oryzaephilus surinamensis

ABSTRACT. Antennae of the saw-toothed grain beetle ( Oryzaephilus surinamensis L.) (Coleoptera: Silvanidae) were examined using scanning and transmission electron microscopy to determine the fine structure and distribution of sensilla. Seven morphologically different sensilla types are distinguished. Mechanoreceptor hairs account for over 68% of all sensilla. Mechanoreceptors are also found in conjunction with contact chemo-receptors; this dual function is demonstrated by electrophysiological recordings. Three different types of olfactory chemoreceptor are found, accounting for 26% of all sensilla, plus two sensilla types with possible hygro/thermo-receptor functions. Counts show the numbers of chemo-receptors to be small, though this many simply reflect the small size of these beetles.     

A Procedure for Comparing Growing and Non-growing Tetrahymena Cultures: Ribonucleotide Pools in Tetrahymena Starved for the Essential Amino Acid Histidine1

ABSTRACT A new starvation procedure permitted the study of early events in a protozoon's growth cycle. Growing cultures of Tetrahymena that differed from non-growing cultures by one variable were produced by adding histidine to cells deprived of that amino acid in an otherwise complete medium. Alterations of the nucleotide pools were examined in +His and in -His cultures in the period preceding RNA synthesis by cells in +His medium. High performance liquid chromatographic analysis provided a balance sheet for the difference in purine compounds in the two cultures. The change in rNTP levels occurred only when the cells were resuspended in a fresh medium and was not a function of cell density. These observations point to the presence of a factor(s) in the old medium that inhibits the energy charge increase in rNTP and in purine accumulation.     

Notes on the Distribution of Hyalophysa and Gymnodinioides on Crustacean Hosts in Coastal North Carolina and a Description of Hyalophysa trageri sp. n.

SYNOPSIS. Hyalophysa chattoni Bradbury, Hyalophysa Iwoffi Bradbury & Clamp, and Gymnodinioides inkystans Minkiewicz are found on species of palaemonids, astacurans, grapsid crabs, ocypodids, anomurans, and portunids in coastal North Carolina. Hyalophysa trageri sp. n. is described from species of Uca and Sesarma. Its life cycle is like that of other exuviotrophic apostomes. Hyalophysa trageri differs from other species in the genus in the pattern of its infraciliature and the shape of the macronucleus during the trophont stage.
In coastal North Carolina, H. chattoni is euryhaline and infests a great number of species. Hyalophysa Iwoffi is found in many locations on the freshwater shrimp Palaemonetes paludosus (Gibbes), and in one location on the crayfish Cambarus sp. Hyalophysa trageri is the most limited in range, being found only on semiterrestrial crabs. On some host species G. inkystans is found alone, but is sympatric with Hyalophysa on others.
Possible factors restricting the distribution of these apostomes are discussed. These include the structure of their encysted stages, salinity, and the behavior of their hosts.     

Chemoresponsiveness to cAMP and Folic Acid during Growth, Development, and Dedifferentiation in Dictyostelium discoideum

Chemoresponsiveness to cAMP and to folic acid are monitored in growing, developing, and dedifferentiating amebae of the cellular slime mold Dictyostelium discoideum . Two semiquantitative assays are employed, one measuring the directed movement of cells up a gradient of chemoattractant ('chemotaxis' assay) and the other measuring the outward spreading of cells in response to a chemical stimulant distributed equally throughout the substratum ('spreading' assay). Vegetative amebae possess relatively insignificant levels of chemotactic responsiveness to cAMP. Six h after the initiation of development, at approximately the same time as the onset of aggregation, cells rapidly acquire chemotactic responsiveness to cAMP. During 'erasure', a dedifferentiation induced by resuspending aggregating cells in fresh nutrient medium, chemotactic responsiveness to cAMP is lost just after the erasure event. By the same chemotactic assay, it is demonstrated that vegetative amebae possess a significant level of chemotactic responsiveness to folic acid. Two h after the initiation of development, cells completely lose chemotactic responsiveness to folic acid. During erasure, cells reacquire chemotactic responsiveness to folic acid at approximately the same time that they lose responsiveness to cAMP.
Dramatically different results are obtained by the spreading assay. When cells lose chemotactic responsiveness to folic acid early in development and when erasing cells lose chemotactic responsiveness to cAMP, they retain the spreading response to the two stimulants, respectively. The different results obtained for chemoreception employing the two assays are discussed in terms of molecular mechanisms, and a testable hypothesis is proposed for the possible roles of chemoresponsiveness and erasure in late morphogenesis.     

Temperature-Enhanced Osmotic Growth Requirement of Crithidia*†

SYNOPSIS. An osmotic growth requirement for the trypanosomatid Crithidia fasciculata became conspicuous at 32 C. Osmo-supportive compounds were surveyed at 28 vs. 33 C, in “low-osmotic” defined medium. Effective osmotic support was provided by many compounds, e.g., glycerophosphate, sorbitol, mannitol, glycerol, Na isethionate, glycine, arginine, KCl, NaCl, NH₄Cl, and K₂SO₄. The nonspecificity of the requirement was thus evident, but inactivity of the presumably poorly adsorbable pentaerythritol indicated that osmotic pressure was a likely but insufficient condition for satisfying the temperature-enhanced growth requirement most clearly expressed as a need for osmotic support. Fortification of the medium with a combination of glycerophosphate, glycine, glycerol, and Tween 80 permitted good growth at 35 C. Possible relations between the temperature-enhanced osmotic requirement cell membrane damage, and morphological phases of Trypanosoma and Leishmania are discussed.