Cytoplasmic and nuclear basic protein synthesis during early sea urchin development

Chromatin topology during the transformation of the mouse sperm nucleus into pronucleus in vivo

Time relationships of sperm chromatin dispersion and sperm nucleoprotein replacement have been studied in vivo, by an in situ cytochemical approach. We used the Feulgen reaction to reveal DNA, which allow us to record both processes simultaneously, on the basis of the return after fertilization to haploid Feulgen values after sperm nucleoprotein replacement with somatic histones. We have shown that sperm nucleoprotein replacement occurs at around anaphase II, whereas sperm chromatin dispersion is massive between the anaphase and telophase II oocyte phases. The morphological pattern of sperm chromatin dispersion supports the idea that the process involves the whole sperm chromatin mass simultaneously, with the region located between the implantation fossa and the postacrosomial region the last to swell.

Histone binding to isolated rat liver nuclei

Calf thymus histone H3 bound irreversibly to the isolated rat liver nuclei. The rate and extent of binding was a function of the incubation period and the concentration of both H3 and nuclei, but independent of the temperature. The binding was saturable and was inhibited by simultaneous presence of various histones. Approximately 94% of the bound H3 was associated with nuclear membrane fraction.

A cytochemical study of nuclear changes in fertilized hamster eggs

Nucleoprotein changes during male and female pronuclear development have been examined in fertilized hamster eggs utilizing the ammoniacal silver reaction (ASR) at the light and ultrastructural levels of observation. Prior to its incorporation, the paternally derived chromatin was heavily laden with ASR product. Immediately upon gamete fusion the sperm nucleus underwent a dramatic increase in staining, suggesting an augmentation in the availability of reactive sites already present in the sperm nucleus or an accumulation of "new" reactive sites from the egg cytoplasm. With subsequent transformations of the sperm nucleus into a male pronucleus, there was a progressive reduction in ASR product associated with the paternal chromatin. Concomitantly, the condensed maternal chromosomes remaining in the zygote after the conclusion of meiosis dispersed and developed into a female pronucleus; these changes were accompanied by a progressive decrease in ASR staining. At the conclusion of pronuclear development, the morphologically similar male and female pronuclei were diffusely stained with the ASR. The increase in ASR staining of the sperm nucleus immediately following gamete fusion demonstrates a major effect of the egg cytoplasm on the paternal chromatin that, heretofore, has not been recognized. This augmentation and the following decrease in ASR staining may reflect changes in nucleoproteins during pronuclear development. Differences in nuclear staining are discussed in light of previous studies of nucleoprotein transitions at fertilization.

Nuclear protein changes in the maternally and paternally derived chromatin at fertilization

The proteins which become associated with the paternally derived chromatin during fertilization may be instrumental in its activation and in the dramatic structural metamorphosis of the sperm nucleus during pronuclear development. Proteins associated with sperm and zygote nuclei and male and female pronuclei of fertilized sea urchin eggs were analysed by polyacrylamide gel electrophoresis in order to examine nuclear protein changes in the paternally and maternally derived chromatin following insemination. Results demonstrate major changes in both the solubility characteristics and polypeptide profiles of sperm nuclei upon insemination. Evidence is presented which indicates that at fertilization the paternally derived chromatin acquires proteins of molecular weights greater than 80,000 and a nuclear protein composition similar to that of the female pronucleus. The nuclear proteins associated with zygote nuclei were compared to those of combined male and female pronuclei and showed many similarities and some differences. Several polypeptides were present in zygote nuclei which were not observed in pronuclear extracts.

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.

Incorporation of Arginine-3H into chromatin of mouse eggs shortly after sperm penetration

Mouse oocytes were fertilized in vitro in a complete cultivation medium enriched by L-arginine-5(3)H monohydrochloride. The oocytes were isolated four hours after insemination. The incorporation of this precursor, as detected by means of autoradiography, was significantly higher in swollen sperm heads and female chromosomes at anaphase/telophase of the second meiotic division than the incorporation into ooplasm.

Autoradiographic study of mouse spermatozoan arginine-rich nuclear protein in fertilization

General labeling of ripe mouse spermatozoa was obtained two weeks after six injections of L-arginine-5-3H monohydrochloride, administered within two days. Besides tail labeling a very intensive nuclear labeling was obtained. It is presumed that this nuclear labeling represents almost exclusively tritiated arginine incorporation into basic nuclear protein. Mouse oocytes were fertilized in vitro with such labeled spermatozoa. It was found that the nuclear label is lost very early during male pronucleus formation, probably concomitantly with sperm chromatin decondensation. This might indicate total loss of the basic spermatozoal nuclear protein before male genome activation.