DNA accumulation during oogenesis in the free-living nematode Panagrellus silusiae

Nuclear size and DNA content in host cells during first-generation schizogony of Eimeria zuernii

The response of intestinal host-cell nuclei of calves infected with Eimeria zuernii 6 and 8 days post-infection was examined using Feulgen-DNA microspectrophotometry. The results show that nuclear hypertrophy is dissociated from DNA replication. In the light of previous work (Fernando, Pasternak, Barrell & Stockdale, 1974) it is surmised that the specificity of infection of cells by E. zuernii is not stringent, with the major target being non-proliferative cells. At most, 20% of the first-generation schizonts develop within cells that would have had proliferative potential and as a result some non-scheduled DNA synthesis occurs.

Cytophotometric study of nuclear proteins during embryogenesis in two nematode species, Ascaris lumbricoides and Panagrellus silusiae

Patterns of nuclear protein changes during embryogenesis in two nematode systems: Ascaris lumbricoides and Panagrellus silusiae were examined microspectrophotometrically. In both species, development is accompanied by an extensive loss of basic nuclear protein as noted by the diminished intranuclear binding of both the Sakaguchi reagent and fluorodinitrobenzene chromophore. The alkaline fast green (pH 8.1) procedure stained both nuclear and cytoplasmic regions of interphase cells to a similar extent throughout embryogenesis. In cells at metaphase the chromosomes bound the fast green dye intensely while the cytoplasm continued to give a positive reaction. Relative Feulgen stainability of nuclei during embryonic development varied between species. In Ascaris, the one-celled stage nucleus was Feulgen-negative and the LI juvenile somatic nuclei yielded a mean Feulgen-DNA value which was considerably less than a postdiminution diploid DNA equivilent. In Panagrellus, the nuclei of one-celled stage embryos contain DNA in excess of a 4C quantity which subsequently is reduced during embryonic divisions. As in Ascaris the nuclei of Panagrellus LI juveniles give hypodiploid Feulgen-DNA values. The significance of these changes remains to be determined.

Cytophotometric analysis of basic nuclear proteins during gametogenesis in the free-living nematode Panagrellus silusiae

The cytochemical staining characteristics of basic nuclear proteins during gametogenesis in both sexes of the free-living nematode Panagrellus silusiae were monitored by absorption microspectrophotometry. During spermatogenesis, the levels of both of the nuclear-bound Sakaguchi and 1-fluoro-2, 4-dinitrobenzene (FDNB) reagents per Feulgen-DNA content increase prior to meiosis and subsequently drop off during spermiogenesis. During oogenesis, the amount of Sakaguchi-protein to DNA ratio rises slightly whereas the FDNB-protein to DNA ratio undergoes a meagre decline. Since the oocyte of Panagrellus accumulates DNA in excess of a 4C DNA equivalent, the relative constancy of the ratio of basic nuclear protein content to DNA amount during oogenesis signifies that these proteins are being continously produced during oocyte maturation. After treatment with alkaline fast green (pH 8.1) the cytoplasmic and nuclear regions of the gonocytes of both sexes yield such an intense reaction that microspectrophotometric measurements could not be taken. The basis of the cytoplasmic staining reaction to the fast green (pH 8.1) dye was not determined. The rapid, highly deterministic programme of embryogenesis in Panagrellus may require a substantial stockpiling of basic nuclear proteins during oogenesis.

Relative ribosomal RNA cistron multiplicity in oocytes and postembryonic stages of the eutelic nematode Panagrellus silusiae

The number of ribosomal RNA cistrons has been measured in the total DNA extracted from L2 juvenile and adult stages of the free-living nematode Panagrellus silusiae. Saturation hybridization studies with homologous rRNA indicate that both stages have about 275 ribosomal genes per haploid equivalent. Using homologous 125I-labelled rRNA for in situ hybridization, the mean number of silver grains per DNA content for oocyte, hypodermis and gut nuclei was similar. The mean DNA contents of maturing oocyte, hypodermis and gut nuclei are about 20C, 2C, and 10C respectively. We conclude that rDNA amplication alone is insufficient to account for the variation in DNA content of oocytes and that postembryonic development in this eutelic organism occurs without a significant differential increase in the number of ribosomal cistrons per worm.

An analysis of MP gene affected morphogenesis in Tetrahymena pyriformis, syngen 1, (Species 1) ciliates

The recessive mp gene in syngen 1 (Species 1) of Tetrahymena pyriformis results in a characteristic set of abnormalities of the adoral membranelles, commonly including some extra membranellar segments (Kaczanowski, '75). The abnormal pattern is produced in about 10% of dividing cells, compared to 80% of cells undergoing oral replacement. Thus the percentage of abnormal cells increases during prolonged stationary phase. Abnormal oral replacement arises primarily for a separation of two kinetosomal fields: the field of kinety no. 1 (the K-1 field), and the anterior field originating from the displaced undulating membrane. Both sites of proliferation appear also during wild type morphogenesis, but they fuse early to form one integrated field (Frankel, '69). The prolonged separation of the subfields in mp/mp cells results in a separate assembly of adoral membranelles; however, the independently developing membranelles of the two subfields are united later to produce a single oral apparatus. A single gene-dependent factor apparently alters some property of the cortical layer, which in turn is responsible for a reduced integrity of the oral replacement primordium.

Quantitation of nuclear DNA in Ascaris lumbricoides: DNA constancy and chromatin diminution

The DNA contents of nuclei during gametogenesis and embryogenesis inAscaris lumbricoideswere measured by Feulgen-microspectrophoto-metry. The variability in the mean value for the haploid amount of DNA in sperm from different males processed at different times was not significant when sperm cell samples were taken from the same region of the seminal vesicle. As the sperm mature, the extent of uptake of Feulgen dye decreases nonsystematically. A similar phenomenon occurs during embryogenesis, and as noted by others, primary oocytes in the terminal portion of the oviduct become Feulgen-negative. Feulgen-positive primary oocytes maintain a 4C DNA value without significant variation. Notwithstanding the differences in Feulgen-DNA values in certain types of nuclei, our evidence supports the view that inAscaris lumbricoidesthe amount of intraspecific DNA has a constant value between individual organisms and from one generation to the next. About 34% of the DNA of the zygote is lost through chromatin diminution at the third embryonic cleavage. This quantity represents 0·23 pg DNA per haploid equivalent.