Qualitative and quantitative studies on DNA and RNA synthesis in Loxodes striatus nuclei

In this study the characteristics of the synthesis of DNA and RNA in the nuclei of Loxodes were investigated. Loxodes striatus is a primitive ciliate with 2 pairs of structurally differentiated diploid nuclei, the macro- and micronuclei. The macronuclei and differentiated morphologically into a clearly recoginzable central core and an outer zone. To determine DNA and RNA synthesis, individual organisms were analyzed by autoradiography after incubating groups of cells with a 3H-labeled precursor ([3H]thymidine for DNA and [3H]uridine for RNA). The following observations were made: (A) All portions of macro- and micronuclei appeared to contain DNA as judged by the localizations of incorporated [3H]thymidine. (B) The macro- and micronuclei did not synthesize DNA at the same time; moreover, the duration of DNA synthesis in the former was much longer than of the latter nucleus. (C) Replication of DNA in the inner core and outer zone of the macronucleus occurred at separate times with little if any overlap. (D) All of the detectable [3H]uridine incorporation was found in the macronucleus and none in the micronucleus. Within the macronucleus the central core was more heavily labeled. (E) The quantitative differences in the label of the different components synthesis can occur in adult macronuclei. The possible explantion of these results is discussed in the context of the nuclear evolution of ciliates and of recent information on nuclear differentiation.

The size distribution of Tetrahymena in relation to its position in the cell cycle

Tetrahymena size distribution during the cell cycle was analyzed by means of radioautography with the aid of a sonic-digitizer, and a computer. The study demonstrates that as the organism ages and passes through the various cell cycle phases the volume distribution of the organisms in each phase remains lognormal.

Fractionation of RNA from tetahymena by affinity chromatography on poly-U-Sepharose

Exponential growing Tetrahymena pyriformis organisms were labelled with (3H) uridine or (3H) adenosine. The labelled RNA was extracted and isolated by affinity chromatography on poly-uridylic-acid sepharose and further analysed by means of sucrose gradient centrifugation and RNase digestion. Experimental evidence proved the existence of RNase resistant poly adenylic-acid fragments in the RNA of Tetrahymena cells. This poly adenylic-acid segment has a sedimentation rate of 4-5 S and would be localised in the 10-12S region of the RNA which is probably the m-RNA.

Cytoplasmic DNA synthesis by cord blood cells of premature and full-term infants: an autoradiographic study

Cord blood cells from 8 full-term and 12 premature infants as well as blood leukocytes from 10 adults were incubated with 3H-thymidine and were subsequently exposed to autoradiographic emulsion for prolonged periods of 45 and 90 days. Cytoplasmic label -- which were interpreted as evidence of mitochondrial DNA synthesis -- was found in 1.7 per cent of lymphoid cells from adult blood, in 2.9 per cent and 4.5 per cent of lymphoid cells from full-term and premature infants, respectively. Statistical analysis of the data shows that the number of labelled cells is significantly larger in the blood of premature infants than in adults (p less than 0.01).

Cells in spontaneous DNA synthesis in cord blood of premature and full-term newborn infants. An autoradiographic study

Cord blood from 16 premature infants and 10 full-term infants, and blood from 10 healthy adults, was incubated for 30 minutes with tritiated thymidine, after which an autoradiographic study was made of spontaneously labeling cells. Apart from a varying number of erythroblasts, myelocytes, and an occasional blast cell, two main types of spontaneously labeling cells were observed: transitional cells and large lymphoid cells, previously shown to be phagocytic. Spontaneously labeling cells were 12 times more frequent in cord blood of premature and full-term infants than in the blood of adults. No transitional cells were seen in adult blood.