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C M FELDHERR

Publications and source records attributed to C M FELDHERR.

7 recordsLinked to original sources
PubMed1965

THE EFFECT OF THE ELECTRON-OPAQUE PORE MATERIAL ON EXCHANGES THROUGH THE NUCLEAR ANNULI.

To investigate the extent to which the electron-opaque pore material can regulate nucleocytoplasmic exchanges which occur through the nuclear annuli, experiments were performed in which polyvinylpyrrolidone (PVP)-coated colloidal gold particles (25 to 170 A in diameter) were microinjected into the cytoplasm of amebas (Amoeba proteus). The cells were fixed at various times after injection and examined with the electron microscope in order to determine the location of the gold particles. High concentrations of gold were found associated with the pore material at specific points adjacent to and within the pores. It is tentatively suggested that such specific accumulations could be a means of selecting substances from the cytoplasm for transport through the pores. Particles were also scattered throughout the ground cytoplasm and nucleoplasm. A comparison of the diameters of particles located in these two regions showed that the ability of materials to penetrate the nuclear envelope is a function of their size. It was estimated that the maximum size of the particles able to enter the nucleus is approximately 125 to 145 A indiameter. The regulation of exchanges with regard to particle size is thought to be dependent on the specific organization of the electron-opaque pore material.

Amoeba↗
PubMed1962

The intracellular distribution of ferritin following microinjection.

Ferritin solutions were microinjected into the ground cytoplasm of intact amebae. At several time-intervals after injection the cells were fixed and the distribution of the protein in various organelles was studied with the aid of the electron microscope. Individual molecules of ferritin were found randomly dispersed throughout the ground cytoplasm and the ground nucleoplasm. Within the mitochondria, the ferritin was localized between the outer and inner membranes. Aggregates of ferritin were found in vacuoles, some of which could be identified as food vacuoles. The findings, which provide evidence for a rapid penetration of large molecules into the nucleus, the outer compartment of the mitochondria, and the digestive vacuoles, are discussed in relation to other reports on intracellular permeability.

Cell Nucleus↗
PubMed1962

The nuclear annuli as pathways for nucleocytoplasmic exchanges.

Colloidal gold particles, 25 to 55 A in diameter, which had been coated with polyvinylpyrrolidone, were microinjected into the ground cytoplasm of amebas (Chaos chaos). At time intervals of 1 minute, 2 minutes, 10 minutes, and 24 hours after injection the cells were fixed for electron microscopy. After 24 hours, gold particles were found in both the nuclei and the ground cytoplasm, the concentration being higher in the nuclei. Colloidal particles were also present in the nuclei after 10 minutes, but at this time interval the concentration did not appear to be greater than that in the ground cytoplasm. One and 2 minutes after injection, the gold particles were located almost exclusively in the ground cytoplasm; however, individual particles were often found within the annuli of the nuclear envelope, and were located specifically in the centers of these structures. The results suggest that at least some of the gold particles which enter the nuclei pass through the annuli, and that passage through these structures may be restricted to a central channel.

Cell Nucleus↗