Antigenic transformations in Paramecium aurelia,variety 4, stock 51 under the influence of trypsin and chymotrypsin

Exposure of P. aurelia to trypsin and chymotrypsin results in the death of a large percentage of the population. Not all antigenic types are equally affected; antigen types 51B and 51E are most affected by exposure to trypsin, while antigen type 51B is most affected by the action of chymotrypsin. Type 51A does not transform when exposed to either trypsin or chymotrypsin, or after the animals have been removed from the enzyme preparations. Type 51B shows little transformations. Types 51C, 51D and 51E transform readily during and after exposure to these two enzymes. In every instance exposure to the enzymes, followed by growth at 20 °, 27 ° or 32 ° results in the transformation to more type 51A than growth at these temperatures alone. Exposure to chymotrypsin leads invariably to more transformation to type 51A than does exposure to trypsin. Exposure of type 51D to either trypsin or chymotrypsin gives rise to type 51J. The obtained results are analogous with those obtained by transformations, resulting from exposure to antiserum or exposure to different temperatures.     

Aerobic Respiration of Kappa Particles from Paramecium aurelia,Stock 51*

SYNOPSIS. Kappa particles from killer cultures of stock 51 Paramecium aurelia were purified and their respiration measured polarographically. The slight bacterial contaminations in the kappa preparations were not significant. Freshly collected kappa in dilute buffer at room temperature had an endogenous Q_O2 of 17.0 ± 1.6 μl/mg dry weight/hr (mean ± standard error). The Q_O2 decayed 50% in 5 hr. Among the sugars tested only glucose and sucrose increased the respiratory rate of kappa. The di- and tri-carboxylates of the tricarboxylic acid cycle stimulated the respiration of kappa. KCN, CO and 2-heptyl-4-hydroxyquinoline N-oxide (HOQNO) inhibited respiration. These findings ensure an organismic status for kappa and justify the belief that it is bacterial in origin.     

Mating Type Determination in Stock 51, Syngen 4 of Paramecium aurelia Grown in Axenic Culture*

SYNOPSIS. The use of axenic medium permits the study of mating type determination in stock 51 (sensitive) of syngen 4 of Paramecium aurelia. A high frequency of cytoplasmically bridged pairs was correlated with a high frequency of change of mating type following conjugation in axenic medium. The direction of change was predominantly from mating type VII to mating type VIII, suggesting a dominance of type VIII cytoplasm in the clones arising from a mixed cytoplasmic ancestry. No significant effect of either lower temperature or of N_aX₃ upon the pattern of mating type determination was found. The high frequency of cytoplasmic bridges between conjugants led to the formation of many double or higher multiplex clones.     

Allelic modulation in Paramecium aurelia heterozygotes. Study of G serotypes in syngen 1

Summary The systematic study of heterozygotes for the g locus controlling G serotype in Paramecium aurelia syngen 1, shows that a phenomenon of allelic exclusion exists. This phenomenon of exclusion happens either systematically, almost systematically or randomly, depending on the studied combination of alleles (Table 2). For a given combination of alleles, it is always the same allele which is excluded. Back-cross experiments indicate that the observed allelic modulation is not dependent upon a simple or classical type of regulatory system. It seems to be characteristic of a given allelic interaction.This phenomenon of allelic exclusion resembles the well-known phenomenon of mutual exclusion occurring between different loci which govern the surface antigens corresponding to the different serotypes of Paramecium aurelia. Both cases of exclusion (inter-allelic or intergenic) might involve an original mechanism of inter-regulation between proteins belonging to the same molecular family and fulfilling similar functions but under different physiological conditions.     

Subcellular Effects of Cytochalasin B and Dimethylsulfoxide on Paramecium aurelia*

SYNOPSIS. Paramecium aurelia syngen 4, stock 57 (sensitive) cultivated in Cerophyl infusion were exposed to cytochalasin B CB and dimethylsulfoxide (DMSO), the solvent for CB, to distinguish between the effects of these agents on a cellular system. DMSO significantly inhibited survival, fission rate, [³H]leucine incorporation, and cell size. CB-treated cells generally had slower division and poorer survival rates than cells exposed to the equivalent DMSO concentration, although the [3H]leucine incorporation was generally greater at the lower CB concentrations than for DMSO alone. As seen by electron microscopy and a new grycerination technic for observing polysomes, DMSO caused nuclear (nucleolar, chromatin) abnormalities as well as membrane degradation and polysomal breakdown; CB caused the formation of aberrant membrane structures and ribosomal tetramers, crystals, and tubes.     

The Nutrition of Paramecium aurelia, Stock 299

SYNOPSIS. Paramecium aurelia , stock 299 (symbiote-free) was cultivated in a synthetic medium consisting of amino acids, vitamins, purine and pyrimidine derivatives, fatty acids, stigmasterol, sodium acetate and salts. The medium supported the continued growth of this stock in serial subculture. Populations up to 17,000 organisms/ml were obtained in 9 or 10 days in the medium supplemented with a phospholipid. Synthetic 1-oleoyl-2-stearoyl-dl-phosphatidyl serine, phosphatidyl ethanolamine, phosphatidyl inositol, phosphatidyl serine and cephalin were comparable in growth-promoting activity. The nutritional need for each of the components of the medium was examined. The following were determined to be essential nutrilites for P. aurelia : arginine, glycine, histidine, isoleucine, leucine, lysine, methionine, phenylalanine, proline, threonine, tryptophan, tyrosine, valine, folic acid, nicotinamide, calcium pantothenate, pyridoxal, riboflavin, thiamine, DL-6-thioctic acid, guanosine, uridine (or cytidine), oleic acid, stigmasterol, calcium and magnesium. Serine replaced glycine for growth in the presence of thymidine. In the absence of thymidine, comparatively high levels of folic acid were required for optimal growth. Sodium acetate did not replace DL-6-thioctic acid. Populations were reduced in the absence of the non-essential amino acids, alanine, asparagine, aspartic acid and glutamic acid. These were restored to optimal levels by the addition of sodium acetate to the medium. Pyruvate was about as effective as acetate in this respect; glucose and certain other carbohydrates were not.