Semipermeability of the Nuclear Membrane in the Intact Cell

Abstract

The osmotic properties of nuclei in intact cells were studied by injecting solutions into the cytoplasm of amphibian oocytes. Subsequent changes in nuclear volume were recorded photographically. The injection of solutions containing polyvinylpyrrolidone or bovine serum albumin caused changes in nuclear volume which were related to the colloid osmotic pressure of the solution injected. The concentration in which no significant nuclear volume change occurred (the isotonic range) was 1.0 to 1.5 per cent polyvinylpyrrolidone (2.0 to 3.75 X 10 -4 M). 2 per cent bovine serum albumin had no significant effect on nuclear volume, whereas 4 per cent caused a significant decrease. The significance of these findings is discussed in terms of the permeability characteristics of the nuclear membrane. I N T R O D U C T I O NIt has been known for some years that the cell nucleus behaves osmotically (Chumey, 1942). When whole ceils are placed in solutions of different salt concentrations, both the cell and nucleus are found to undergo changes in volume. If the nucleus is indeed an osmometer, and is thus surrounded by a semipermeable membrane, we must assume that some soluble component(s) of the cell does not freely penetrate the nuclear membrane (i.e. there is a physical or physiological impermeability to some soluble component(s)). One possible way to determine the nature of this soluble component(s) is to vary the concentration of specific components in the nuclear environment, and then note any changes in nuclear volume. This has been done in the case of amphibian oocytes by isolation of the large germinal vesicle nuclei in solutions of different composition (Callan, 1949;Goldstein and Harding, 1950). These studies indicated that ions or molecules of low molecular weight readily penetrate the nuclear membrane. Of the components tested, only protein and certain other substances of high molecular weight were found to exert an osmotic effect in this isoIated system.

Colloid osmotic parameterization and measurement of subcellular crowding

“…In the more typical cytoplasm of a frog oocyte, Harding and Feldherr took the creative approach of using the cell nucleus as a colloid osmometer (Harding and Feldherr, 1959). The nuclear envelope consists of a double lipid bilayer perforated by nuclear pores that are filled with a high concentration of phenylalanine-glycine-repeat peptides that interact to form a selective barrier (Schmidt and Görlich, 2016).…”

Nucleo‐cytoplasmic Interactions in the Achievement of Nuclear Synchrony in Dna Synthesis and Mitosis in Multinucleate Cells

“…Do these data on protein migration allow us to conclude that the genetic activity of the nucleus is controlled at least in part by the gain or loss of proteins? Merriam (1959) found that nuclei isolated from Chaetopterus eggs were permeable to bovine serum albumin although, in contrast, Harding & Feldherr (1959) showed that the nuclei of intact frog oocytes were impermeable to serum albumin and to other molecules of high molecular weight. They suggest, however, that during interphase the nuclear membrane presents a barrier to protein migration or diffusion which effectively eliminates any regulation by this means.…”

“…In a study of amphibian and avian erythrocytes Davies (1961) showed that there was an extension of the cytoplasmic material into the nucleus by way of the nuclear annuli. Merriam (1959) found that nuclei isolated from Chaetopterus eggs were permeable to bovine serum albumin although, in contrast, Harding & Feldherr (1959) showed that the nuclei of intact frog oocytes were impermeable to serum albumin and to other molecules of high molecular weight. In addition Loewenstein (1964) and Loewenstein, Kanno & Ito (1966) have demonstrated that a substantial electrical barrier exists between nucleus and cytoplasm.…”

A Comparative Study of Nucleocytoplasmic Interactions

“…This, however, is not consistent with the observation that the particles located within the cytoplasm were randomly distributed and were frequently in contact with the outer surface of the nuclear envelope . In addition, PVP remains osmotically active after being injected into the cytoplasm of immature frog oocytes (12) . This would not be the case if the PVP were removed from solution.…”