The survival or degeneration of nuclei produced after meiosis in Paramecium caudatum depends upon their position in the cytoplasm. The surviving nucleus lies in the paroral region, which is the region around the cytostome. In this study, this was confirmed by quantitative measurements of the location of surviving nuclei in both stained and living conjugating cells. Observation of nuclear behavi...

The same dosage of ultraviolet (UV) radiation retards division of several protozoans more effectively when the light is intermittent than when it is continuous, and especially at temperatures of 25-35 degrees C. At lower temperatures the difference between the effects of intermittent and continuous radiations is less marked. Somewhat similar results were obtained with the ciliates Paramecium ca...

Cells of Paramecium caudatum, syngen 3 usually become sexually mature about 50 fissions after conjugation. In order to study the genetic mechanisms that control fission-department expression of maturity, an attempt was made to obtain early mature mutants by treatment with N-methyl-N'-nitro-N-nitrosoguanidine. A new cytoplasmic marker, erythromycin resistance, was used to eliminate nonconjugant ...

During the last few years, a considerable amount of work has been done on the hydrogen ion concentration of the blood in health and disease, as well as on its influence on the rate of multiplication of bacteria in artificial media. Whilst working in Dr. H. H. Dale's laboratory I noticed whilst testing the action of the cinchona alkaloids on Paramecium caudatum. that this ciliate was easily dest...

Little is known about the fate of lysosomal membrane in phagocytic cells. Because the age of the digestive vacuoles in Paramecium caudatum can be easily determined, we have been able to study the dynamic membrane events in the older vacuoles. Late in the phagolysosomal stage (DV-III) the vacuole membrane undergoes a burst of tubule formation. The tubules expand into vesicles which have characte...

Two types of Triton X-100 extracted model of Paramecium caudatum were prepared and effects of the ionic compositions of the reactivating medium on the swimming behaviour of the extracted models were examined. Type I, prepared by the method of Naitoh and Keneko, did not change swimming direction depending on the concentrations of Mg2+ and K+ in the reactivating medium. Type II, prepared by a dif...

The location and extent of local degeneration of cilia during sexual reproduction of Paramecium was studied using scanning electron microscopy to examine cells undergoing conjugation and autogamy. At some time during the mating reaction, but prior to conjugant pair formation, ciliary degeneration begins at the antero-ventral tip of cells and proceeds posteriorly along the suture. In the anterio...

Microtubule sliding was induced in axonemes obtained from isolated cilia of Paramecium caudatum when they were exposed to a reactivating solution containing ATP after mild treatment with trypsin. Over a very wide range of concentrations (1 nM-4 mM), Ca2+ in the reactivating solution had no effect on the proportion of axonemes that disintegrated as the result of microtubule sliding. Also, the ve...